WorldWideScience

Sample records for plasma sintering method

  1. W/steel joint fabrication using the pulse plasma sintering (PPS) method

    Energy Technology Data Exchange (ETDEWEB)

    Rosinski, Marcin, E-mail: ninmar@inmat.pw.edu.pl [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Kruszewski, Miroslaw J.; Michalski, Andrzej; Fortuna-Zalesna, Elzbieta; Ciupinski, Lukasz; Kurzydlowski, Krzysztof J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

    2011-10-15

    The paper presents application of pulse plasma sintering method (PPS), developed at the Faculty of the Materials Science and Engineering of Warsaw University of Technology. Unlike other electric-field assisted sintering methods, the PPS method employs pulse high-current electric discharges for heating and activating the material to be sintered. The phenomena, taking place during the high-current pulses, which heat the powder during the PPS treatment and activate the sintering process, are similar to those occurring in SPS technique. However, in PPS, thanks to much higher energy the pulse discharge, these phenomena run much more intensively. The aim of the present study was to fabricate by the PPS a joint between tungsten and Eurofer 97 steel. Because of the large difference in thermal expansion coefficients of the joined materials, stresses are induced at the joint interfaces. To reduce these stresses a thin interlayer was incorporated between the joined materials. Four different materials were tested. The experiments allowed to establish the optimal PPS sintering parameters. It was shown that the interlayers between W and Eurofer 97 steel fabricated at 1000 deg. C for 10 min were highly dense and no delamination at joint interfaces occurred. The results of the thermocycle tests proved a high strength of the joints produced by PPS.

  2. Synthesis of nonstoichiometric M-type barium ferrite nanobelt by spark plasma sintering method

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wenyu; ZHANG Qingjie; TANG Xinfeng; CHENG Haibin

    2005-01-01

    This study investigated the feasibility of ultrafast crystallization of M-type barium ferrite when the coprecipitation precursors in stoichiometric proportions as BaFe12O19, Fe(OH)3 and BaCO3 nanoparticles, had been heated by spark plasma sintering (SPS) process. The results show that SPS method may realize the ultrafast crystallization of M-type barium ferrite, absolutely prevent the crystallization of intermediate phase α-Fe2O3, and significantly decrease the crystallization temperature of M-type barium ferrite. The sintered samples obtained at 800℃ by sintering the precursors for 10 minutes are a kind of multiphase ferrites composed of major phase M-type barium ferrite and trace amount of BaFe0.24Fe0.76O2.88. It is discovered that M-type barium ferrites in the holes of the sintered samples are in nanobelt microstructure about 100-300 nm in width and several micrometers in length. These M-type barium ferrite nanobelts are non-stoichiometric and may be expressed as BaFe12+Xo19+1.5x (-4.77≤x≤6.50). Their composistions suggest completely random Fe-rich or Ba-rich domains.

  3. Fabrication And Properties Of Silver Based Multiwall Carbon Nanotube Composite Prepared By Spark Plasma Sintering Method

    Directory of Open Access Journals (Sweden)

    Lis M.

    2015-06-01

    Full Text Available The paper presents results of investigations of the obtained nanocomposite materials based on silver with addition of multiwall carbon nanotubes. The powder of carbon nanotubes content from 0.1 to 3 wt. % was produced by application of powder metallurgy methods, through mixing and high-energetic milling, and also chemical methods. Modification of carbon nanotubes included electroless deposition of silver particles on the carbon nanotube active surfaces and chemical reduction with strong reducing agent – sodium borohydride (NaBH4. The obtained powder mixtures were consolidated by SPS – Spark Plasma Sintering method. The formed composites were subjected to tests of relative density, electrical conductivity and electro-erosion properties. Detailed examinations of the structure with application of X-ray microanalysis, with consideration of carbon nanotubes distribution, were also carried out. The effect of manufacturing methods on properties of the obtained composites was observed.

  4. Development of Al2O3 electrospun fibers prepared by conventional sintering method or plasma assisted surface calcination

    Science.gov (United States)

    Mudra, E.; Streckova, M.; Pavlinak, D.; Medvecka, V.; Kovacik, D.; Kovalcikova, A.; Zubko, P.; Girman, V.; Dankova, Z.; Koval, V.; Duzsa, J.

    2017-09-01

    In this paper, the electrospinning method was used for preparation of α-Al2O3 microfibers from PAN/Al(NO3)3 precursor solution. The precursor fibers were thermally treated by conventional method in furnace or low-temperature plasma induced surface sintering method in ambient air. The four different temperatures of PAN/Al(NO3)3 precursors were chosen for formation of α-Al2O3 phase by conventional sintering way according to the transition features observed in the TG/DSC analysis. In comparison, the low-temperature plasma treatment at atmospheric pressure was used as an alternative sintering method at the exposure times of 5, 10 and 30 min. FTIR analysis was used for evaluation of residual polymer after plasma induced calcination and for studying the mechanism of polymer degradation. The polycrystalline alumina fibers arranged with the nanoparticles was created continuously throughout the whole volume of the sample. On the other side the low temperature approach, high density of reactive species and high power density of plasma generated at atmospheric pressure by used plasma source allowed rapid removal of polymer in preference from the surface of fibers leading to the formation of composite ceramic/polymer fibers. This plasma induced sintering of PAN/Al(NO3)3 can have obvious importance in industrial applications where the ceramic character of surface with higher toughness of the fibers are required.

  5. Methods of flash sintering

    Energy Technology Data Exchange (ETDEWEB)

    Raj, Rishi; Cologna, Marco; Francis, John S.

    2016-05-10

    This disclosure provides methods of flash sintering and compositions created by these methods. Methods for sintering multilayered bodies are provided in which a sintered body is produced in less than one minute. In one aspect, each layer is of a different composition, and may be constituted wholly from a ceramic or from a combination of ceramic and metallic particles. When the body includes a layer of an anode composition, a layer of an electrolyte composition and a layer of a cathode composition, the sintered body can be used to produce a solid oxide fuel cell.

  6. A method for sintering

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides a method for sintering, comprising in the following order the steps of: providing a body in the green state or in the pre-sintered state on a support; providing a load on at least one spacer on the support such that the load is located above said body in the green...

  7. Preparation and Microstructure of Porous ZrB2 Ceramics Using Reactive Spark Plasma Sintering Method

    Institute of Scientific and Technical Information of China (English)

    YUAN Huiping; LI Junguo; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    Zirconium oxide (ZrO2) and boron carbide (B4C) were added to ZrB2 raw powders to prepare ZrB2 porous ceramics by reactive spark plasma sintering (RSPS). The reactions between ZrO2 and B4C which produce ZrB2 and gas (such as CO and B2O3) result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB2 and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB2 to raw ZrB2 powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB2 are 0.185 and 0.222, respectivly. And dense ZrB2-SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB2-based ceramics.

  8. Plasma dynamic synthesis of ultradispersed zinc oxide and sintering ceramics on its basis by SPS method

    Science.gov (United States)

    Shanenkova, Yu; Sivkov, A.; Ivashutenko, A.; Shanenkov, I.; Firsov, K.

    2017-05-01

    Zinc oxide is a well-known semiconductor material having good electrical, optical and catalytic properties. It can be used in different areas from cosmetics to drug delivery and biosensors. The synthesis of nanosized zinc oxide is an urgent task for obtaining ZnO-based ceramics with enhanced physical properties. This work shows the possibility to implement the plasma dynamic synthesis of zinc oxide in one short-term process (less than 1 ms) using an electrodischarge zinc-containing plasma jet, flowing into oxygen atmosphere. It allows synthesizing a mono-crystalline powder with particle size distribution from tens to hundred nanometers. The synthesized powdered product is investigated using by X-Ray diffractometry (XRD), scanning electron microscopy and high-resolution transmission electron microscopy. According to XRD, the obtained product consists of hexagonal zinc oxide with lattice parameters a = b = 3.24982 Å, c = 5.20661 Å that is clearly confirmed by microscopy data. This powder was used to produce a bulk ceramics sample on its basis by spark plasma sintering. The influence of sintering parameters on the structure of the resulting sample was studied. The optimal parameters were found which allows obtaining the more dense ceramics with a better microstructure. It was also found that the absence of exposure time after reaching the working temperature and pressure allows decreasing the porosity of ceramics.

  9. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Directory of Open Access Journals (Sweden)

    Zorica Branković

    2016-12-01

    Full Text Available Bismuth ferrite, BiFeO3 (BFO, powder was synthesized by hydrothermal method from Bi(NO33·5 H2O and Fe(NO33·9 H2O as precursors. The synthesized powder was further sintered using spark plasma sintering (SPS. The sintering conditions were optimized in order to achieve high density, minimal amount of secondary phases and improved ferroelectric and magnetic properties. The optimal structure and properties were achieved after spark plasma sintering at 630 °C for 20 min, under uniaxial pressure of 90 MPa. The composition, microstructure, ferroelectric and magnetic properties of the SPS samples were characterized and compared to those of conventionally sintered ceramics obtained from the same powder. Although the samples sintered using conventional method showed slightly lower amount of secondary phases, the spark plasma sintered samples exhibited favourable microstructure and better ferroelectric properties.

  10. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink

    Energy Technology Data Exchange (ETDEWEB)

    Niittynen, Juha, E-mail: juha.niittynen@tut.fi [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland); Abbel, Robert [Holst Centre, High Tech Campus 31, 5656 AE Eindhoven (Netherlands); Mäntysalo, Matti [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland); Perelaer, Jolke; Schubert, Ulrich S. [Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich-Schiller-University Jena, Humboldtstrasse 10, D-07743 Jena (Germany); Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena, Humboldtstrasse 10, D-07743 Jena (Germany); Lupo, Donald [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland)

    2014-04-01

    In this contribution several alternative sintering methods are compared to traditional thermal sintering as high temperature and long process time of thermal sintering are increasing the costs of inkjet-printing and preventing the use of this technology in large scale manufacturing. Alternative sintering techniques are evaluated based on the electrical and mechanical performance they enable on inkjet-printed structures as well as their potential feasibility for large scale manufacturing. Photonic sintering was identified as the most promising alternative to thermal sintering. - Highlights: • Comparison of alternative sintering techniques for large-scale electronics manufacturing • Laser, plasma and photonic sintering of nanoparticle silver ink tested • Electrical and mechanical properties of sintered inks tested • Microstructure analysis used to explain the different electrical and mechanical properties • Photonic sintering identified as the most promising alternative technique.

  11. A Comparative Study on SiC-B4C-Si Cermet Prepared by Pressureless Sintering and Spark Plasma Sintering Methods

    Science.gov (United States)

    Sahani, P.; Karak, S. K.; Mishra, B.; Chakravarty, D.; Chaira, D.

    2016-06-01

    Silicon carbide (SiC)-boron carbide (B4C) based cermets were doped with 5, 10, and 20 wt pct Silicon (Si) and their sinterability and properties were investigated for conventional sintering at 2223 K (1950 °C) and spark plasma sintering (SPS) at 1623 K (1350 °C). An average particle size of ~3 µm was obtained after 10 hours of milling. There is an enhancement of Vickers microhardness in the 10 wt pct Si sample from 18.10 in conventional sintering to 27.80 GPa for SPS. The relative density, microhardness, and indentation fracture toughness of the composition SiC60(B4C)30Si10 fabricated by SPS are 98 pct, 27.80 GPa, and 3.8 MPa m1/2, respectively. The novelty of the present study is to tailor the wettability and ductility of the cermet by addition of Si into the SiC-B4C matrix. Better densification with improved properties is achieved for cermets consolidated by SPS at lower temperatures than conventional sintering.

  12. The Absence of Plasma in"Spark Plasma Sintering"

    Energy Technology Data Exchange (ETDEWEB)

    Hulbert, Dustin M.; Anders, Andre; Dudina, Dina V.; Andersson, Joakim; Jiang, Dongtao; Unuvar, Cosan; Anselmi-Tamburini, Umberto; Lavernia, Enrique J.; Mukherjee, Amiya K.

    2008-04-10

    Spark plasma sintering (SPS) is a remarkable method for synthesizing and consolidating a large variety of both novel and traditional materials. The process typically uses moderate uni-axial pressures (<100 MPa) in conjunction with a pulsing on-off DC current during operation. There are a number of mechanisms proposed to account for the enhanced sintering abilities of the SPS process. Of these mechanisms, the one most commonly put forth and the one that draws the most controversy involves the presence of momentary plasma generated between particles. This study employees three separate experimental methods in an attempt to determine the presence or absence of plasma during SPS. The methods employed include: in-situ atomic emission spectroscopy, direct visual observation and ultra-fast in-situ voltage measurements. It was found using these experimental techniques that no plasma is present during the SPS process. This result was confirmed using several different powders across a wide spectrum of SPS conditions.

  13. The Absence of Plasma in"Spark Plasma Sintering"

    Energy Technology Data Exchange (ETDEWEB)

    Hulbert, Dustin M.; Anders, Andre; Dudina, Dina V.; Andersson, Joakim; Jiang, Dongtao; Unuvar, Cosan; Anselmi-Tamburini, Umberto; Lavernia, Enrique J.; Mukherjee, Amiya K.

    2008-04-10

    Spark plasma sintering (SPS) is a remarkable method for synthesizing and consolidating a large variety of both novel and traditional materials. The process typically uses moderate uni-axial pressures (<100 MPa) in conjunction with a pulsing on-off DC current during operation. There are a number of mechanisms proposed to account for the enhanced sintering abilities of the SPS process. Of these mechanisms, the one most commonly put forth and the one that draws the most controversy involves the presence of momentary plasma generated between particles. This study employees three separate experimental methods in an attempt to determine the presence or absence of plasma during SPS. The methods employed include: in-situ atomic emission spectroscopy, direct visual observation and ultra-fast in-situ voltage measurements. It was found using these experimental techniques that no plasma is present during the SPS process. This result was confirmed using several different powders across a wide spectrum of SPS conditions.

  14. Thermoelectric and magnetic properties of Yb{sub 2}MgSi{sub 2} prepared by spark plasma sintering method

    Energy Technology Data Exchange (ETDEWEB)

    Kubouchi, M.; Hayashi, K.; Miyazaki, Y. [Tohoku University, Department of Applied Physics, Graduate School of Engineering, Sendai (Japan)

    2016-08-15

    An intermediate-valence compound, Yb{sub 2}MgSi{sub 2}, has been prepared using a spark plasma sintering method. The magnetic susceptibility and thermoelectric properties of Yb{sub 2}MgSi{sub 2} are measured in the temperature range from 5 to 300 K. From the magnetic susceptibility results, Yb valence of the Yb{sub 2}MgSi{sub 2} is evaluated. As compared with YbAl{sub 3}, which is one of the promising thermoelectric materials that can be used at low temperatures, Yb{sub 2}MgSi{sub 2} exhibits a lower absolute value of Seebeck coefficient, higher electrical resistivity, and lower thermal conductivity over the measured temperature range. A maximum dimensionless figure of merit, ZT, of 0.0018 is achieved at around 200 K. (orig.)

  15. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.

    2012-11-01

    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  16. Magnetic properties of ferrite-titanate nanostructured composites synthesized by the polyol method and consolidated by spark plasma sintering

    Science.gov (United States)

    Acevedo, Ulises; Gaudisson, Thomas; Ortega-Zempoalteca, Raul; Nowak, Sophie; Ammar, Souad; Valenzuela, Raul

    2013-05-01

    Multiferroic systems formed by a mixing of a ferroelectric phase and a ferrimagnetic phase are receiving significant attention because of their wide possibilities for tailoring properties. In this work, the magnetic properties of the cobalt ferrite-barium titanate system were investigated on samples prepared by an original combination of synthesis methods. Cobalt ferrite and barium titanate nanoparticles were synthesized separately by hydrolysis of the metal acetates in a polyol method. Both materials were mixed in a 1:1 ratio and consolidated by spark plasma sintering at 500 °C for 5 min. A high density nanostructured ceramic was obtained with grains smaller than 100 nm and a density about 80% of the theoretical value. Magnetic hysteresis loops showed a hard magnet behavior, with a coercive field larger than cobalt ferrite alone prepared under the same conditions. δM reversible magnetization plots exhibited dipolar interactions with a maximum at the coercive field. These results are interpreted in terms of an efficient mixing of the components, which strongly decreases the magnetic percolation in the composite by separating ferrite grains by titanate grains.

  17. Fabrication of 200 mm Diameter Sintering Body of Skutterudite Thermoelectric Material by Spark Plasma Sintering

    Science.gov (United States)

    Tomida, T.; Sumiyoshi, A.; Nie, G.; Ochi, T.; Suzuki, S.; Kikuchi, M.; Mukaiyama, K.; Guo, J. Q.

    2016-11-01

    Filled skutterudite is a promising material for thermoelectric power generation because its ZT value is relatively high. However, mass production of high-performance thermoelectric materials remains a challenge. This study focused on the sintering process of thermoelectric materials. Large-diameter n-type (Yb or La, Ca, Al, Ga, In)0.8(Co, Fe)4Sb12 skutterudite sintering bodies with a small thickness were successfully produced by the spark plasma sintering (SPS) method. When direct current flows through the thermoelectric sintering body during the SPS pulse, the Peltier effect causes a temperature difference within the sintering body. To eliminate the Peltier effect, an electrical insulating material was inserted between the punch (electrode) and the sintering body. In this way, an n-type La-filled skutterudite sample with a diameter of 200 mm, thickness of 21 mm, and weight of 5 kg was successfully produced. The thermoelectric properties and microstructures of the sample were almost the same throughout the whole sintering body, and the dimensionless figure of merit reached 1.0 at 773 K.

  18. Spark plasma sintering and spark plasma joining of refractory ceramics

    Science.gov (United States)

    Hoefer, Jeffrey Andrew

    Consolidation of refractory ceramics such as boron carbide (B4C) and silicon carbide (SiC) by conventional sintering techniques (pressure-less sintering, hot pressing, hot isostatic pressing etc.) can prove challenging due to the high temperatures required for sintering. Typically sintering additives are used in order to decrease sintering temperature, but at the sacrifice of purity. Typically B4C requires sintering temperatures above 2000°C without the use of additives, while SiC is generally considered not sinterable without additives, and requires temperatures above 2000°C even with additives. Spark Plasma Sintering (SPS) has emerged as a technology that can reduce the sintering temperature considerably compared to more conventional techniques. The simultaneous application of pressure, heat, and current can reduce sintering temperatures without the use of sintering aids to 1600°C and 2000°C for boron carbide and silicon carbide respectively. One shortcoming of SPS, however, is the difficulty in producing complex shapes. Therefore, for carbide materials such as B4C and SiC, which are difficult to machine, the ability to produce complex shapes is worthy of investigation. One means of creating complex shapes is by joining simple shapes. Joining of monolithic ceramics, in particular SiC, has been achieved, however in all cases an intermediate joining material is used (Ti foil, Silica Powder etc.). Joining of materials using SPS, or as it is called, Spark Plasma Joining, can eliminate the need for an intermediate joining material, producing a high purity and high strength joint. This study investigates SPS of 3 different B4C Powders, as well as SPS joining of simple shape monolithic SiC. Sintering parameters such as temperature, pressure, time, and heating rate are all considered. Influence of sintering parameters on density, grain size, mechanical strength, and joint quality is investigated in detail.

  19. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    OpenAIRE

    Theo Saunders; Salvatore Grasso; Reece, Michael J.

    2016-01-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 ...

  20. Master Sintering Surface: A practical approach to its construction and utilization for Spark Plasma Sintering prediction

    Directory of Open Access Journals (Sweden)

    Pouchly V.

    2012-01-01

    Full Text Available The sintering is a complex thermally activated process, thus any prediction of sintering behaviour is very welcome not only for industrial purposes. Presented paper shows the possibility of densification prediction based on concept of Master Sintering Surface (MSS for pressure assisted Spark Plasma Sintering (SPS. User friendly software for evaluation of the MSS is presented. The concept was used for densification prediction of alumina ceramics sintered by SPS.

  1. Plasma Nitriding of Low Alloy Sintered Steels

    Institute of Scientific and Technical Information of China (English)

    Shiva Mansoorzadeh; Fakhreddin Ashrafizadeh; Xiao-Ying Li; Tom Bell

    2004-01-01

    Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably.It was observed that monophase compound layer, γ, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.

  2. Spark Plasma Sintering of Ultracapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Curtis W. [CK Technologies, Camirillo, CA (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tucker, Dennis [NASA Johnson Space Center, Houston, TX (United States); Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cheng, Zhongyang [Auburn Univ., AL (United States)

    2016-01-01

    A solid-state ultracapacitor module to replace standard electrochemical batteries would achieve major performance gains and mass/volume reduction. This report summarizes a project to evaluate an alternative sintering process to produce a solid-state ultracapacitor to overcome the limitations of both the electrochemical batteries presently in use on spacecraft and of currently available electrochemical ultracapacitors. It will provide a robust energy storage device with higher reliability, wider working temperature range, longer lifetime, and less weight and volume than electrochemical batteries. As modern electronics decrease in size, more efficient and robust remote power is needed. Current state-of-the-art rechargeable batteries cannot be rapidly charged, contain harmful chemicals, and suffer from early wear-out mechanisms. Solid-state ultracapacitors are recyclable energy storage devices that offer the promise of higher power and a greater number of charge/discharge cycles than current rechargeable batteries. In addition, the theoretical energy density when compared to current electrochemical batteries indicates that a significant weight savings is possible. This is a project to develop a very high density solid-state ultracapacitor with giant permittivity and acceptable dielectric loss to overcome the energy-density barrier such that it will be a suitable replacement for batteries.

  3. Phase characterisation in spark plasma sintered TiPt alloy

    CSIR Research Space (South Africa)

    Chikosha, S

    2011-12-01

    Full Text Available The conclusions drawn from this presentation are that Spark Plasma Sintering (SPS) of equiatomic BE TiPt powder produces fully sintered specimens, with incomplete homogenisation. There is a need for improved furnace atmosphere control so...

  4. Plasma Synthesis and Sintering of Advanced Ceramics

    Science.gov (United States)

    1990-09-15

    glow discharge, corona discharge, RF or microwave discharge, etc.) and the electron concentration in the plasma are important. The efficiency of... corona discharge, and the low pressure capacitively or inductively coupled RF discharge. It is probable that a low pressure microwave discharge would also...Rhodes, "Agglomerate and Particle Size Effects on Sintering Yttria- Stabilized Zirconia ", J. Am. Ceram. Soc., 64 [1] 19-22 (1981). 4. T. S. Yeh and M

  5. Master sintering curves for UO{sub 2} and UO{sub 2}–SiC composite processed by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhichao [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Subhash, Ghatu, E-mail: subhash@ufl.edu [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Tulenko, James S. [Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2014-11-15

    Highlights: • Constructed master sintering curves for spark plasma sintering (SPS) of nuclear fuels. • Characterized sinterability of UO{sub 2} and UO{sub 2}–SiC powder compacts during SPS. • Determined activation energies for sintering of UO{sub 2} and UO{sub 2}–SiC composites by SPS. - Abstract: Master sintering curve (MSC) theory has been applied successfully to UO{sub 2} and UO{sub 2}–SiC composite ceramics processed using spark plasma sintering (SPS). By applying the constant heating rate method, where the powder compact was heated at a constant rate to a specified maximum temperature and then cooled naturally, the apparent activation energies for sintering have been determined to be 140 kJ/mol for UO{sub 2} and 420 kJ/mol for UO{sub 2}–SiC composite. The ability of the derived MSCs to control and predict final density in the sintered compact was demonstrated by additional experimental runs using the isothermal heating method, in which the powder is held for a specified time at the maximum sintering temperature. It is shown that the master sintering curve is an effective tool to characterize the densification and sinterability behavior of a given nuclear powder compact during spark plasma sintering. The reason for significantly lower activation energy in SPS processed UO{sub 2} pellets compared to conventional sintering has been rationalized on the basis of field activation in SPS process.

  6. Spray freeze granulation of submicron alumina and its sintering behavior via spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Liu Wei

    2015-01-01

    Full Text Available Spray freeze granulation is an improved method based on spray granulation, solving many limitations of spray granulation. In this work, spray freeze granulation of submicron alumina is performed to explore the possibility of industrial-scale production of dense alumina via spark plasma sintering. Powder pretreatment such as sedimentation and the selection of granules with the appropriate size are employed for the maximum use of the high qualified as-prepared granules and granule sliding, which would provide a guidance for the industrial-scale production. Debound granules were densified via SPS and the corresponding sintering behaviors such as the recorded shrinkage and shrinkage rate were discussed. The comparison of sintering behaviors between granulated and as-received powder are conducted to identify the role of spray freeze granulation in sinterability for dense alumina. The Vickers hardness (Hv and the fracture toughness (KIC of the freeze granulated body are higher than the corresponding properties of the as-received body due to the more homogenous microstructure with little agglomeration in the particle packing after freeze granulation.

  7. Synthesis and characterization of cBN/WCCo composites obtained by the pulse plasma sintering (PPS) method

    Energy Technology Data Exchange (ETDEWEB)

    Michalski, A; Rosinski, M; Plocinska, M; Szawlowski, J, E-mail: mihalski@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw (Poland)

    2011-10-29

    The cBN/cemented carbide containing 30vol% of cBN particles was produced using a mixture of a 6wt% Co added-WC powder, with a WC grain size of 0.4 {mu}m and a cBN powder with a grain size ranging from 4 to 40 {mu}m. The mixture was sintered to produce a plate, 20 mm in diameter, 3 mm thick. The sintering processes were conducted at temperature of 1100 deg. C under a load of 100 MPa. The phase composition, density, hardness and micro structure of the sintered parts thus obtained were examined. The fractures through the WCCo/cBN composite showed the cBN particles torn out from the cemented carbide matrix were only few, whereas most of them have cleaved along the fracture plane. This gives evidence that the bond at the WCCo/cBN interface is mechanically strong.

  8. Rapid sintering of anisotropic, nanograined Nd-Fe-B by flash-spark plasma sintering

    Science.gov (United States)

    Castle, Elinor; Sheridan, Richard; Grasso, Salvatore; Walton, Allan; Reece, Mike

    2016-11-01

    A Spark Plasma Sintering (SPS) furnace was used to Flash-Sinter (FS) Nd-Fe-Dy-Co-B-Ga melt spun permanent magnetic material. During the 10 s "Flash" process (heating rate 2660 K min-1), sample sintering (to theoretical density) and deformation (54% height reduction) occurred. This produced texturing and significant magnetic anisotropy, comparable to conventional die-upset magnets; yet with much greater coercivities (>1600 kA m-1) due to the nanoscale characteristics of the plate-like sintered grains. These preliminary results suggest that Flash-SPS could provide a new processing route for the mass production of highly anisotropic, nanocrystalline magnetic materials with high coercivity.

  9. Method of sintering materials with microwave radiation

    Science.gov (United States)

    Kimrey, Jr., Harold D.; Holcombe, Jr., Cressie E.; Dykes, Norman L.

    1994-01-01

    A method of sintering ceramic materials following: A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article.

  10. Chemically produced tungsten-praseodymium oxide composite sintered by spark plasma sintering

    Science.gov (United States)

    Ding, Xiao-Yu; Luo, Lai-Ma; Lu, Ze-Long; Luo, Guang-Nan; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

    2014-11-01

    Pr2O3 doped W composite were synthesized by a novel wet chemical method and spark plasma sintering. The grain size, relative density and the Vicker hardness HV0.2 of Pr2O3/W samples were 4 μm, 98.3% and 377.2, respectively. The tensile strength values of Pr2O3/W were higher than those of pure W. As the temperature rises from 25 °C to 800 °C, the conductivity of pure W and W-1 wt% Pr2O3 composites decreased with the same trend, was above 150 W/m K.

  11. Microstructural, phase transformation and magnetic properties of Ni-Mn-Ga alloy fabricated by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Tian Xiao-Hua; Sui Jie-He; Zhang Xin; Feng Xue; Cai Wei

    2011-01-01

    The microstructural, phase transformation and magnetic properties of Ni-Mn-Ga alloy fabricated using the spark plasma sintering method have been investigated. The results show that both the as-sintered and annealed sintered specimens exhibit typical martensitic transformation behaviours. The martensite of the sintered specimen after annealing exhibits a ferromagnetic nature. Moreover, study of the fracture surface indicates that the transgranular fracture contributes to the higher ductility of sintered Ni-Mn-Ga alloy. In addition, the transformation strain in sintered Ni-Mn-Gaalloy is studied for the first time.

  12. Reactive Spark Plasma Sintering: Successes and Challenges of Nanomaterial Synthesis

    Directory of Open Access Journals (Sweden)

    Dina V. Dudina

    2013-01-01

    Full Text Available Spark plasma sintering (SPS, initially developed as an advanced sintering technique for consolidating nanopowders into nanostructured bulk materials, has been recently looked at in much broader perspective and gained a strong reputation of a versatile method of solid state processing of metals, ceramics, and composites. The powders in the SPS-dies experience the action of pulsed electric current and uniaxial pressure; they are heated at very high rates unachievable in furnace heating and sintered within shorter times and at lower temperatures than in conventional methods. The principle of SPS and convenient design of the facilities make it attractive for conducting solid state synthesis. In this paper, based on our own results and the literature data, we analyze the microstructure formation of the products of chemical reactions occurring in the SPS in an attempt to formulate the requirements to the microstructure parameters of reactant mixtures and SPS conditions that should be fulfilled in order to produce a nanostructured material. We present successful syntheses of nanostructured ceramics and metal matrix composite with nanosized reinforcements in terms of microstructure stability and attractive properties of the materials and discuss the challenges of making a dense nanostructured material when reaction and densification do not coincide during the SPS. In the final part of the paper, we provide an outlook on the further uses of reactive SPS in the synthesis of nanostructured materials.

  13. Spark Plasma Sintering of Fuel Cermets for Nuclear Reactor Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang Zhong; Robert C. O' Brien; Steven D. Howe; Nathan D. Jerred; Kristopher Schwinn; Laura Sudderth; Joshua Hundley

    2011-11-01

    The feasibility of the fabrication of tungsten based nuclear fuel cermets via Spark Plasma Sintering (SPS) is investigated in this work. CeO2 is used to simulate fuel loadings of UO2 or Mixed-Oxide (MOX) fuels within tungsten-based cermets due to the similar properties of these materials. This study shows that after a short time sintering, greater than 90 % density can be achieved, which is suitable to possess good strength as well as the ability to contain fission products. The mechanical properties and the densities of the samples are also investigated as functions of the applied pressures during the sintering.

  14. Low temperature spark plasma sintering of YIG powders

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Garcia, L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Suarez, M., E-mail: m.suarez@cinn.e [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-07-16

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 {sup o}C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 {sup o}C leads to dense samples with minimal formation of YFeO{sub 3}, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  15. Effect of Current Pathways During Spark Plasma Sintering of an Aluminum Alloy Powder

    Science.gov (United States)

    Kellogg, Frank; McWilliams, Brandon; Cho, Kyu

    2016-12-01

    Spark plasma sintering has been a well-studied processing technique primarily for its very high cooling and heating rates. However, the underlying phenomenon driving the sintering behavior of powders under an electric field is still poorly understood. In this study, we look at the effect of changing current pathways through the powder bed by changing die materials, from conductive graphite to insulating boron nitride for sintering aluminum alloy 5083 powder. We found that the aluminum powder itself was insulating and that by changing the current paths, we had to find alternate processing methods to initiate sintering. Altering the current pathways led to faster temperature raises and faster melting (and potentially densification) of the aluminum powder. A flash sintering effect in metallic powders is observed in which the powder compact undergoes a rapid transition from electrically insulating to conducting at a temperature of 583 K (310 °C).

  16. Characterization of Green-Emitting Translucent Zinc Oxide Ceramics Prepared Via Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Mei [University of California; DeVito, David M [ORNL; Howe, Jane Y [ORNL; Yang, Xiaocheng [West Virginia University; Giles, Nancy C. [Air Force Institute of Technology; Neal, John S [ORNL; Munir, Zuhair [University of California

    2011-01-01

    Translucent, green-emitting zinc oxide (ZnO) bodies, 19 mm in diameter and 0.72 mm in thickness, have been prepared via spark plasma sintering method. The consolidation of ZnO powders was investigated over the temperature range of 550-1050 C and the pressure range of 55-530 MPa. Samples sintered at temperatures >850 C and pressures of {approx}120 MPa were translucent and had densities of {approx}100%. Samples sintered at 950 C and 130 MPa showed a higher maximum transmittance than the samples sintered at higher or lower temperatures or pressures, with an excellent in-line transmission of 70% in the IR region around 2330 nm. The dense ZnO ceramics exhibited a strong green emission and a weak ultraviolet emission, and the relative intensity of the green emission increased with increasing sintering temperature.

  17. TiO2 doped UO2 fuels sintered by spark plasma sintering

    Science.gov (United States)

    Yao, Tiankai; Scott, Spencer M.; Xin, Guoqing; Lian, Jie

    2016-02-01

    UO2 fuels doped with oxide additives Cr2O3 and TiO2 display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO2-doped UO2 fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The grain size can reach 80 μm by sintering at 1700 °C for 20 min, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric fuel pellets upon SPS process. Thermal-mechanical properties of the sintered doped fuel pellets including thermal conductivity and hardness are measured and compared with undoped fuel pellets. The enlarged grain size (80 μm) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grained UO2 fuel pellets to improve fuel performance.

  18. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink

    NARCIS (Netherlands)

    Niittynen, J.; Abbel, R.; Mäntysalo, M.; Perelaer, J.; Schubert, U.S.; Lupo, D.

    2014-01-01

    In this contribution several alternative sintering methods are compared to traditional thermal sintering as high temperature and long process time of thermal sintering are increasing the costs of inkjet-printing and preventing the use of this technology in large scale manufacturing. Alternative sint

  19. Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

    Science.gov (United States)

    Barnes, M. W.; Tucker, D. S.; Hone, L.; Cook, S.

    2017-01-01

    Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

  20. Structural, Mechanical and Tribological Properties of Spark Plasma Sintered Ti6Al4V Alloy

    Directory of Open Access Journals (Sweden)

    Mróz A.

    2016-06-01

    Full Text Available The influence of spark plasma sintering parameters on the structural, mechanical and tribological characteristics of the Ti6Al4V alloy, which is used as implant material in biomedical engineering, was investigated. The experimental data confirm that full density and attractive mechanical properties can be obtained using the spark plasma sintering method. Tribological tests, performed in dry conditions, allowed the authors to indicate the most suitable sintering parameters. The material characterized by the highest wear resistance was selected for further tribological testing in articulation with UHMWPE in simulated body fluids. Although the weight of the polymeric material articulating against the sintered Ti6Al4V was slightly higher compared to the UHMWPE articulating against the reference material (Ti6Al4V rod, the friction coefficient was lower.

  1. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    Science.gov (United States)

    Saunders, Theo; Grasso, Salvatore; Reece, Michael J.

    2016-06-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 °C. The best results were produced with pre-compacted samples (bars 1.8 mm thick) of pure B4C (discharge time 2s, current 4A) and SiC:B4C 50 wt% (3s at 6A), which were fully consolidated under a heating rate approaching 20000 °C/min. For the composite a cylindrical volume of 14 mm3 was sintered to full density with limited grain growth.

  2. Temperature Control in Spark Plasma Sintering: An FEM Approach

    Directory of Open Access Journals (Sweden)

    G. Molénat

    2010-01-01

    Full Text Available Powder consolidation assisted by pulsed current and uniaxial pressure, namely, Spark Plasma Sintering (SPS, is increasingly popular. One limitation however lies in the difficulty of controlling the sample temperature during compaction. The aim of this work is to present a computational method for the assembly temperature based on the finite elements method (FEM. Computed temperatures have been compared with experimental data for three different dies filled with three materials with different electrical conductivities (TiAl, SiC, Al2O3. The results obtained are encouraging: the difference between computed and experimental values is less than 5%. This allows thinking about this FEM approach as a predictive tool for selecting the right control temperatures in the SPS machine.

  3. Processing of bulk Al7075 alloy by spark plasma sintering

    Science.gov (United States)

    Málek, P.; Molnárová, O.; Cinert, J.; Lukáč, F.; Chráska, T.

    2017-02-01

    The main advantages of powder metallurgy processing route are the possibility to produce near-net-shape compacts and to minimize the finish machining and material loss. The main problem in particle consolidation process is to suppress porosity, to remove oxide layers, and to retain the microstructure of powder materials. Spark plasma sintering (SPS) combines concurrent uniaxial pressure and direct heating by a pulsed DC current. Sintering occurs at relatively low temperatures for a short time and does not influence significantly the microstructure in the interiors of original powder particles. The efficiency of SPS in producing compacts with low porosity might be dependent on the distribution of particle size in original powder material. The gas atomized Al7075 powder was sieved to several charges and then sintered by SPS. Microstructure of sintered compacts was studied by light and scanning electron microscopy. The phase composition was investigated using X-ray diffraction. The mechanical behaviour was tested by bending tests.

  4. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    Science.gov (United States)

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.

    2017-04-01

    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  5. THERMAL AND ELECTRIC FIELDS AT SPARK PLASMA SINTERING OF THERMOELECTRIC MATERIALS

    Directory of Open Access Journals (Sweden)

    L. P. Bulat

    2014-09-01

    Full Text Available Problem statement. Improvement of thermoelectric figure of merit is connected with the usage of nanostructured thermoelectric materials fabricated from powders by the spark plasma sintering (SPS method. Preservation of powder nanostructure during sintering is possible at optimum temperature modes of thermoelectrics fabrication. The choice of these modes becomes complicated because of anisotropic properties of semiconductor thermoelectric materials. The decision of the given problem by sintering process simulation demands the competent approach to the problem formulation, a correct specification of thermoelectric properties, the properties of materials forming working installation, and also corrects boundary conditions. The paper deals with the efficient model for sintering of thermoelectrics. Methods. Sintering process of the bismuth telluride thermoelectric material by means of SPS-511S installation is considered. Temperature dependences of electric and thermal conductivities of bismuth telluride, and also temperature dependences of installation elements materials are taken into account. It is shown that temperature distribution in the sample can be defined within the limits of a stationary problem. The simulation is carried out in the software product Comsol Multiphysics. Boundary conditions include convective heat exchange and also radiation under Stefan-Boltzmann law. Results. Computer simulation of electric and thermal processes at spark plasma sintering is carried out. Temperature and electric potential distributions in a sample are obtained at the sintering conditions. Determinative role of graphite compression mould in formation of the temperature field in samples is shown. The influence of geometrical sizes of a graphite compression mould on sintering conditions of nanostructured thermoelectrics is analyzed. Practical importance. The optimum sizes of a cylindrical compression mould for fabrication of volume homogeneous samples based on

  6. Consolidation of W–Ta composites: Hot isostatic pressing and spark and pulse plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dias, M., E-mail: marta.dias@itn.pt [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Guerreiro, F. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Correia, J.B. [LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); Galatanu, A. [National Institute of Materials Physics, Atomistilor 105 bis Bucharest-Magurele, 077125 Ilfov (Romania); Rosiński, M. [Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw (Poland); Monge, M.A.; Munoz, A. [Departamento de Física, Univerdidad Carlos III de Madrid, Avd. de la Universidad 30, 28911 Madrid (Spain); Alves, E. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Carvalho, P.A. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2015-10-15

    Highlights: • Consolidation of W–Ta composites using three techniques: HIP, SPS and PPS. • Comparison of consolidation methods in terms of W–Ta interdiffusion and densification. • Microstructure analysis in terms of oxides formation. - Abstract: Composites consisting of tantalum fiber/powder dispersed in a nanostructured W matrix have been consolidated by spark and pulse plasma sintering as well as by hot isostatic pressing. The microstructural observations revealed that the tungsten–tantalum fiber composites consolidated by hot isostatic pressing and pulse plasma sintering presented a continuous layer of Ta{sub 2}O{sub 5} phase at the W/Ta interfaces, while the samples consolidated by spark plasma sintering evidenced a Ta + Ta{sub 2}O{sub 5} eutectic mixture due to the higher temperature of this consolidation process. Similar results have been obtained for the tungsten–tantalum powder composites. A (W, Ta) solid solution was detected around the prior nanostructured W particles in tungsten–tantalum powder composites consolidated by spark and pulse plasma sintering. Higher densifications were obtained for composites consolidated by hot isostatic pressing and pulse plasma sintering.

  7. Lanthanide (Nd, Gd) compounds with garnet and monazite structures. Powders synthesis by "wet" chemistry to sintering ceramics by Spark Plasma Sintering

    Science.gov (United States)

    Potanina, Ekaterina; Golovkina, Ludmila; Orlova, Albina; Nokhrin, Aleksey; Boldin, Maksim; Sakharov, Nikita

    2016-05-01

    Complex oxide Y2.5Nd0.5Al5O12 with garnet structure and phosphates NdPO4 and GdPO4 with monazite structure were obtained by using precipitation methods. Ceramics Y2.5Nd0.5Al5O12 and NdPO4 were processed by Spark Plasma Sintering (SPS). Relative density more 98%, sintering time did not exceed 8 min, sintering temperature 1330-1390 °C. Leaching rates of elements from ceramics were 10-6-10-7 g/(cm2 d). The process of ceramics sintering has two-stage character: the first step of sintering-compaction process is related to the plastic flow of the material, the second step-to the process of grain boundary diffusion and grain growth.

  8. Tailored Net-Shape Powder Composites by Spark Plasma Sintering

    Science.gov (United States)

    Khaleghi, Evan Aryan

    This dissertation investigates the ability to produce net-shape and tailored composites in spark plasma sintering (SPS), with an analysis of how grain growth, densification, and mechanical properties are affected. Using alumina and four progressively anisotropic dies, we studied the impact of specimen shape on densification. We found specimen shape had an impact on overall densification, but no impact on localized properties. We expected areas of the specimen to densify differently, or have higher grain growth, based on current anisotropy in the specimen during sintering, and preliminary results indicated this, but further investigation showed this did not occur. Overall average grain size and porosity decreased as shape complexity increased. In Fe-V-C steel, we mechanical alloyed two rapidly solidified powders, and used spark sintering to retain the properties imparted during the rapid solidification. We noticed VC grains being produced during densification, which improved the final properties. We conducted spark plasma extrusion (SPE) of aluminum to understand the effect on microstructure. We found, through an analysis of the grain structure, that SPE did have a grain deformation potential, and grain size was severely decreased compared to conventional sintering. Dynamic recrystallization did not occur, due to the reduced temperatures we were able to extrude with SPS. Finally, we examined whether there were particular sintering conditions for SPS that reduced the complexity of the grain growth and porosity relationship to one similar to conventional sintering, of the form G = k G0 ε -1/. We found that although a reasonable case could be made for free sintering, as found in the literature, for hot-pressing and SPS the conditions required go against the common knowledge in grain growth and densification kinetics. We were able to fit our data very well to the model, but the correlated results do not make physical sense.

  9. Structure and Magnetic Properties of Sm2Fe17Nx Sintering Magnets Prepared by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN, α-Fe and N2. When sintering temperature was only above 200 ℃ under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase of α-Fe in the magnets.

  10. Transparent Yttrium Aluminium Garnet Obtained by Spark Plasma Sintering of Lyophilized Gels

    Directory of Open Access Journals (Sweden)

    M. Suárez

    2009-01-01

    Full Text Available Lyophilized YAG gel, synthesized by the coprecipitation technique, has been sintered to transparency by spark plasma sintering method at 1500∘C. Whereas conventionally dried gels show large agglomerates, over 1 μm, powders from lyophilized gels show no agglomeration with an average particle size below 100 nm. The absence of agglomerates affects on the optical properties of the sintered materials: conventionally dried powders are opaque after sintering, whereas 0.8 mm thick transparent YAG materials with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range have been obtained for the lyophilized gels.

  11. W/Cu composites produced by pulse plasma sintering technique (PPS)

    Energy Technology Data Exchange (ETDEWEB)

    Rosinski, M. [Association EURATOM-IPPLM, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Fortuna, E. [Association EURATOM-IPPLM, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)], E-mail: elaf@inmat.pw.edu.pl; Michalski, A.; Pakiela, Z.; Kurzydlowski, K.J. [Association EURATOM-IPPLM, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

    2007-10-15

    W-Cu composites of various compositions were produced using the pulse plasma sintering (PPS) technique which applies pulsed high electric discharges to heat the powders subjected to pressing. Because the arc discharges between the powder particles clean their surfaces and intensify diffusion processes, the sintering time is reduced to a few minutes. The powder preparation processes, milling, mixing and reduction before sintering, and the sintering conditions were optimized by undertaking detailed investigations of the microstructure of powders and composites. Room temperature tensile strength, using small samples, hardness and the coefficients of thermal expansion were measured. The results prove that by using the PPS method a high density material having 98% of the theoretical density can be fabricated. It has also been shown that the PPS device can be used to join the composite material to a tungsten plate.

  12. Spark Plasma Sintering Bulk Sm2 Fe17NxMagnets

    Institute of Scientific and Technical Information of China (English)

    Yue Ming; Zhang Dongtao; Ji Yongcheng; Zhang Jiuxing

    2004-01-01

    High performance Sm2Fe17Nx magnetic powders were fabricated by ball-milling method and were compacted using spark plasma sintering(SPS) technique.Effects of processing conditions on the magnetic properties and decomposition dynamic of the magnets were investigated.It is found that higher sintering temperature improves the densification of the magnets, while deteriorates their magnetic properties simultaneously due to the decomposition of the Sm2Fe17Nx.Sintering at lower temperature can preserve the crystal structure of Sm2Fe17Nx compound, while the powders cannot be consolidated into a fully dense compact.An increased compressive pressure leads to better magnetic properties and higher density for the magnet at the same sintering temperature.

  13. FEM Optimisation of Spark Plasma Sintering Furnace

    CERN Document Server

    Kellari, Demetrios Vasili

    2013-01-01

    Coupled electro-thermal FEM analysis has been carried out on a sintering furnace used to produce new materials for LHC collimators. The analysis showed there exist margins for improvement of the current process and equipment through minor changes. To optimise the design of the furnace several design changes have been proposed including: optimization of material selection using copper cooling plates, control of convection in cooling plates by lowering the water flow rate, modifying the electrode shape using unsymmetrical electrodes and upgrading the thermal shielding to make use of multilayer graphite shields. The results show that we have a significant improvement in temperature gradient on the plate, from 453 to 258 °C and a reduction in power requirement from 62 to 44 kW.

  14. Spark plasma sintering of Mn-Al-C hard magnets.

    Science.gov (United States)

    Pasko, A; LoBue, M; Fazakas, E; Varga, L K; Mazaleyrat, F

    2014-02-12

    Structural and magnetic characterization of isotropic Mn-Al-C bulk samples obtained by spark plasma sintering (SPS) is reported. This technique, to the best of our knowledge, has not been used for preparation of Mn-Al-based permanent magnets previously. Transformation from the parent -phase to the ferromagnetic τ-phase occurred on heating in the process of sintering. The phase constitution of the melt-spun precursors and consolidated samples was determined by x-ray diffraction. Magnetic hysteresis loops were recorded using a vibrating sample magnetometer. The compositional dependence of the coercivity, magnetization and density of the sintered materials is analysed. To combine good magnetic properties with proper densification, further optimization of the production parameters is necessary.

  15. Chemically produced tungsten–praseodymium oxide composite sintered by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Xiao-Yu [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Engineering Research Center of Powder Metallurgy of Anhui Province, Hefei 230009 (China); Lu, Ze-Long [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Engineering Research Center of Powder Metallurgy of Anhui Province, Hefei 230009 (China)

    2014-11-15

    Highlights: • Wet chemical method was used to prepare highly uniform Pr{sub 2}O{sub 3} doped W–Pr{sub 2}O{sub 3} powder. • The Pr{sub 2}O{sub 3} particles significantly refine the grain size of tungsten alloy. • The tensile strength of Pr{sub 2}O{sub 3}/W samples were higher than those of pure W samples. - Abstract: Pr{sub 2}O{sub 3} doped W composite were synthesized by a novel wet chemical method and spark plasma sintering. The grain size, relative density and the Vicker hardness HV{sub 0.2} of Pr{sub 2}O{sub 3}/W samples were 4 μm, 98.3% and 377.2, respectively. The tensile strength values of Pr{sub 2}O{sub 3}/W were higher than those of pure W. As the temperature rises from 25 °C to 800 °C, the conductivity of pure W and W–1 wt% Pr{sub 2}O{sub 3} composites decreased with the same trend, was above 150 W/m K.

  16. Unburned carbon behavior in sintered coal fly-ash bulk material by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Hasezaki, K.; Nakashita, A.; Kaneko, G.Y.; Kakuda, H. [Shimane University, Shimane (Japan). Dept. of Material Science

    2007-12-15

    Coal fly-ash bulk materials were prepared by spark plasma sintering (SPS). The as-received coal fly ash produced by Misumi Power Station (The Chugoku Flectric Power Co., Inc.), had an average particle size of 19 {mu}m and contained about 2% carbon from unburned coal. The sintering temperature was 1000{sup o}C for 10 min. The mass density of the sintered compact was 2.4 x 10{sup 3} kg/m{sup 3}. After three-point flexural testing of the compact, the average flexural strength and Young's modulus were 25.6 MPa and 23.0 GPa, respectively. From the flexural strength, the Weibull modulus was found to be m = 6.13, indicating that the compact was a typical ceramics. Fractographic examination indicated that in all specimens the fracture origin was located on the bottom surface and was not an intrinsic flaw. Vickers indentation test showed that the fracture toughness was 0.61 MPa.m{sup 0.5} and the calculated critical flaw size, c{sub 0}, was 0.18 mm. This c{sub 0} value was larger than that of the voids and unburned carbon on the fracture surface. It is noteworthy that the mechanical strength of the sintered compact was not affected by the voids and unburned carbon.

  17. Spark plasma sintering and microwave electromagnetic properties of MnFe{sub 2}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Penchal Reddy, M., E-mail: drlpenchal@gmail.com [Center for Advanced Materials, Qatar University, Doha 2713 (Qatar); Mohamed, A.M.A. [Center for Advanced Materials, Qatar University, Doha 2713 (Qatar); Department of Metallurgical and Materials Engineering, Faculty of Petroleum and Mining Engineering, Suez University, Suez 4372 (Egypt); Venkata Ramana, M. [Department of Physics, National Taiwan Normal University, Taipei 11677, Taiwan (China); Zhou, X.B.; Huang, Q. [Division of Functional Materials and Nanodevices, Ningbo Institute of Materials Technology and Engineering, Ningbo 315201 (China)

    2015-12-01

    MnFe{sub 2}O{sub 4} ferrite powder was synthesized by a facile one-pot hydrothermal route and then consolidated into dense nanostructured compacts by the spark plasma sintering (SPS) technique. The effect of sintering temperature, on densification, morphology, magnetic and microwave absorption properties was examined. Spark plasma sintering resulted in uniform microstructure, as well as maximum relative density of 98%. The magnetic analysis indicated that the MnFe{sub 2}O{sub 4} ferrite nanoparticles showed ferrimagnetic behavior. Moreover, the dielectric loss and magnetic loss properties of MnFe{sub 2}O{sub 4} ferrite nanoparticles were both enhanced due to its better dipole polarization, interfacial polarization and shape anisotropy. It is believed that such spark plasma sintered ceramic material will be applied widely in microwave absorbing area. - Highlights: • Successful synthesis of dense MnFe{sub 2}O{sub 4} ceramics using spark plasma sintering. • Lower temperature and shorter sintering time, compared to conventional methods. • Optimal sintering condition was achieved. • The magnetic properties of the sintered samples are sensitive to the density and microstructure.

  18. Microstructural development and mechanical properties of iron based cermets processed by pressureless and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Alvaredo, P. [Department of Materials Science and Engineering, IQMAAB, University Carlos III Madrid, Avda. de la Universidad, 30, 28911 Leganes (Spain); Gordo, E., E-mail: elena.gordo@uc3m.es [Department of Materials Science and Engineering, IQMAAB, University Carlos III Madrid, Avda. de la Universidad, 30, 28911 Leganes (Spain); Van der Biest, O.; Vanmeensel, K. [Katholieke Universiteit Leuven, Kasteelpark Arenberg, 44 3001 Heverlee (Belgium)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. Black-Right-Pointing-Pointer Influence of carbon content on the sintering mechanism and hardness. Black-Right-Pointing-Pointer The cermet phase diagram was calculated and permits to explain the microstructure. Black-Right-Pointing-Pointer SPS provides ferritic matrix and different carbide distribution than CPS samples. Black-Right-Pointing-Pointer Pressureless sintered samples contain retained austenite at room temperature. - Abstract: Iron-based cermets are an interesting class of metal-ceramic composites in which properties and the factors influencing them are to be explored. In this work the metal matrix contains Cr, W, Mo and V as alloying elements, and the hard phase is constituted by 50 vol% of titanium carbonitride (TiCN) particles. The work studies the influence of the C content and the processing method on the sinterability, microstructure and hardness of the developed cermet materials. For that purpose, cermet samples with different C content in the matrix (0 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%) were prepared by conventional pressureless sintering (CPS) and, in order to achieve finer microstructures and to reduce the sintering time, by spark plasma sintering (SPS). The density and hardness (HV30) of the processed materials was evaluated, while their phase composition and microstructure was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The equilibrium phase diagram of the composite material was calculated by ThermoCalc software in order to elucidate the influence of the carbon content on the obtained phases and developed microstructures.

  19. Pulse plasma sintering of a tungsten/steel divertor module

    Energy Technology Data Exchange (ETDEWEB)

    Kruszewski, Mirosław J., E-mail: m.kruszewski@inmat.pw.edu.pl; Ciupiński, Łukasz; Rosiński, Marcin; Michalski, Andrzej; Kurzydłowski, Krzysztof J.

    2013-10-15

    Highlights: • W/WL10 and WL10/steel joints were fabricated via pulse plasma sintering. • Fe interlayer successfully compensated thermal stresses at the WL10/steel joint. • Maximum temperature of a single stage sintering of the module was established. • Better accuracy in machining of W and WL10 elements is needed. -- Abstract: The paper presents the preliminary evaluation of the potential of a pulse plasma sintering (PPS) technique for the fabrication of a He-cooled modular divertor with a multiple-jet cooling module. In this work the W and WL10 elements were directly bonded by PPS. Examination of the microstructure revealed some minor defects at the interface, but the overall quality of the joint was good with no cracks or delamination being detected. To reduce the thermal stress gradient a thin transition layer of iron was used at the WL10/steel interface. In addition an attempt was made to fabricate the complete module by a single sintering process. The microstructures of the fabricated modules were examined and the findings were reported.

  20. The effect of sintering pressure on the microstructure and properties of a nanocrystalline magnesium alloy in spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ka Ram; Kim, Hye Sung; Kwon, Soon Hong; Hwang, Dae Youn [Pusan National University, Miryang (Korea, Republic of)

    2014-11-15

    Many studies have shown that particle boundaries in spark plasma sintering (SPS) can be easily removed by using a combination of sintering temperature and pressure. We already reported that a degassing treatment prior to sintering by SPS was a critical step to remove particle-particle boundaries effectively and to obtain a magnesium alloy having high strength and high ductility. In this study, the microstructural evolution and the mechanical properties of nanocrystalline Mg-6%Al alloys were investigated to determine the effect of sintering pressure combined with an appropriate degassing treatment.

  1. Synthesis and Sintering of Mg2Si Thermoelectric Generator by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    YANG Meijun; ZHANG Lianmeng; SHEN Qiang

    2008-01-01

    Raw Mg,Si powder were used to fabricate Mg2Si bulk thermoelectric generator by spark plasma sintering (SPS).The optimum parameters to synthesize pure Mg2Si powder were found to be 823 K,0 MPa,10 min with excessive content of 10wt% Mg from the stoichiometric Mg2Si.Mg2Si bulk was synthesized and densified simultaneously at low temperature (823 K) and high pressure (higher than 100 MPa) from the raw powder,but Mg,Si could not react completely,and the sample was not very dense with some microcracks on the surface.Then,Mg,Si powder reacted at 823 K,0 MPa,10 min in SPS chamber to form Mg2Si green compact,again sintered by SPS at 1023 K,20 MPa,5 min.The fabricated sample only contained MgESi phase with fully relative density.

  2. Processing of pure titanium containing titanium-based reinforcing ceramics additives using spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Mondiu Olayinka DUROWOJU

    2017-06-01

    Full Text Available The densification behaviour, microstructural changes and hardness characteristics during spark plasma sintering of CP-Ti reinforced with TiC, TiN, TiCN and TiB2 were investigated. Commercially pure Ti powders were dry mixed with varied amounts (2.5 and 5 wt. % of the ceramic additives using a T2F Turbula mixer for 5 h and at a speed of 49 rpm. The blended composite powders were then sintered using spark plasma sintering system (model HHPD-25 from FCT Germany at a heating rate of 100oC min-1, dwell time of 5 min and sintering temperature of 950ºC. The sintering of CP-Ti was used as a base study to select the proper spark plasma sintering temperature for full density. Densification was monitored through analysis of the recorded punch displacement and the measured density of the sintered samples using Archimedes method. High densities ranging from 97.8% for 5% TiB2 addition to 99.6% for 5% TiCN addition were achieved at a relatively low temperature of 950°C. Microstructural analyses show a uniform distribution of the additives and finer structure showing their inhibitive effect on grain growth. An improved hardness was observed in all the cases with highest values obtained with TiCN as a result of the combined effect of TiC and TiN. A change in the fracture mode from trans granular to intergranular was also observed.

  3. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    OpenAIRE

    Eugene A. Olevsky; Stephen M. Rolfing; Maximenko, Andrey L.

    2016-01-01

    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the f...

  4. Impact of sintering method on certain properties of titanium dioxide nanopowder materials

    Directory of Open Access Journals (Sweden)

    Porozova Svetlana E.

    2017-01-01

    Full Text Available Titanium dioxide nanopowder samples consolidated by method of cold uniaxial compaction at 200 MPa and conventionally sintered in air at 1300°С with isothermal tempering during 60 minutes or spark-plasma sintering at 1300°С and 30 MPа were studied using the method of light combination scattering spectroscopy (Raman spectroscopy and scanning electron microscopy. The samples were found to differ significantly in terms of color, density, phase composition and microstructure.

  5. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  6. Low temperature spark plasma sintering of TC4/HA composites

    Institute of Scientific and Technical Information of China (English)

    Huiliang Shao; Lei Cao; Daqian Sun; Zhankui Zhao

    2016-01-01

    Ti6Al4V/hydroxyapatite composites (TC4/HA) have been prepared by high energy ball milling and low temperature spark plasma sintering at 600 °C, 550 °C, 500 °C and 450 °C, respectively. The sintering temperature of the composites was sharply decreased as the result of the activation and surficial modification effects induced from high energy ball milling. The decomposition and reaction of hydro-xyapatite was successfully avoided, which offers the composites superior biocompatibility. The hydro-xyapatite in the composites was distributed in gap uniformly, and formed an ideal network structure. The lowest hardness, compressive strength and Young's modulus of the composites satisfy the requirements of human bone.

  7. Experimental investigations on the synthesis of W–Cu nanocomposite through spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Elsayed, Ayman, E-mail: aymanhamada@cmrdi.sci.eg [Central Metallurgical R& D Institute, Department of Powder Technology, P.O. Box 87, Helwan, Cairo 11421 (Egypt); Li, Wei [San Diego State University, College of Engineering, Department of Mechanical Engineering, 5500 Campanile Drive, San Diego, CA 92128-1326 (United States); El Kady, Omayma A. [Central Metallurgical R& D Institute, Department of Powder Technology, P.O. Box 87, Helwan, Cairo 11421 (Egypt); Daoush, Walid M. [Helwan University, Faculty of Industrial Education, Department of Production Technology, Cairo (Egypt); Olevsky, Eugene A.; German, Randall M. [San Diego State University, College of Engineering, Department of Mechanical Engineering, 5500 Campanile Drive, San Diego, CA 92128-1326 (United States)

    2015-08-05

    Highlights: • Tungsten–copper composites have been synthesized using SPS of nano powders. • Various preparation methods, namely mixing, milling and coating have been used. • Conventional compaction and sintering has also been used for comparison. • The composites by SPS have shown finer microstructure and better hardness. • Mixing has proven best preparation method with best physical/mechanical properties. - Abstract: Elemental powders of nanosized tungsten and chemically deposited nanosized copper were used for preparing tungsten/copper composites, which are used as electric contact components. A composite of 70 wt.%W/30 wt.%Cu (52 vol%W/48 vol%Cu) composition was prepared by three powder metallurgy techniques. Elemental mixing, mechanical milling and electroless Cu coating on tungsten particles were used for the synthesis. The obtained powder blends underwent consolidation by rapid hot pressing using the spark plasma sintering (SPS) route at 950 °C under vacuum and by conventional vacuum pressureless sintering for comparison. The elemental powders and the sintered composites were investigated by optical microscopy and SEM. Electrical conductivity, hardness, transverse rupture strength, and wear properties were measured. Results show that the synthesis of the composite by the investigated route yields good performance. Samples prepared by SPS have shown better mechanical properties than those prepared by compaction and sintering due to their fine microstructure.

  8. Spark Plasma Sintering and Densification Mechanisms of Antimony-Doped Tin Oxide Nanoceramics

    Directory of Open Access Journals (Sweden)

    Junyan Wu

    2013-01-01

    Full Text Available Densification of antimony-doped tin oxide (ATO ceramics without sintering aids is very difficult, due to the volatilization of SnO2, formation of deleterious phases above 1000°C, and poor sintering ability of ATO particles. In this paper, monodispersed ATO nanoparticles were synthesized via sol-gel method, and then ATO nanoceramics with high density were prepared by spark plasma sintering (SPS technology using the as-synthesized ATO nanoparticles without the addition of sintering aids. The effect of Sb doping content on the densification was investigated, and the densification mechanisms were explored. The results suggest that ATO nanoparticles derived from sol-gel method show good crystallinity with a crystal size of 5–20 nm and Sb is incorporated into the SnO2 crystal structure. When the SPS sintering temperature is 1000°C and the Sb doping content is 5 at.%, the density of ATO nanoceramics reaches a maximum value of 99.2%. Densification mechanisms are explored in detail.

  9. O2 plasma sintering study of TiO2 photoelectrodes in dye solar cells

    Science.gov (United States)

    Moraes, R. S.; Gonçalves, A. D.; Stegemann, C.; da Silva Sobrinho, A. S.; Miyakawa, W.; Massi, M.

    2017-08-01

    The development of more efficient photoelectrochemical solar cells has been, over the years, the subject of many scientific researches. In this paper a methodology was established to carry out the sintering process of nanoporous TiO2 layer by using plasma, which was compared with sintered layers made by the conventional sintering process in a furnace. The TiO2 commercial paste was spread by doctor-blading technique and subjected to different sintering processes. Porous layer samples were subjected to structural and morphological analyses. Then photoelectrodes dye-loading was measured by optical spectrophotometry. The quality of the layers under plasma sintering process in terms of weight loss and removal of organic compounds was evaluated by thermogravimetric analysis, mass spectrometry and FT-IR. The results showed that the plasma sintering process favors the adsorption of dye on the layer surface due to the creation of active states caused by O2 reactive plasma. Furthermore the O2 plasma process provides enough energy for removing organic compounds arising from the TiO2 paste and for providing nanoparticle sintering. Solar cells assembled with the plasma-sintered layers had a power conversion efficiency 20.1% higher than the obtained in solar cells sintered in a conventional furnace, proving the efficiency of the plasma sintering process.

  10. Full densification of inkjet-printed copper conductive tracks on a flexible substrate utilizing a hydrogen plasma sintering

    Science.gov (United States)

    Kwon, Young-Tae; Lee, Young-In; Kim, Seil; Lee, Kun-Jae; Choa, Yong-Ho

    2017-02-01

    Low temperature sintering techniques are crucial in developing flexible printed electronics. In this work, we demonstrate a novel hydrogen plasma sintering method that achieves a full reduction and densification of inkjet-printed patterns using a copper complex ion ink. After inkjet printing on polyethylene terephthalate (PET) substrates, both hydrogen plasma and conventional hydrogen thermal treatment were employed to compare the resulting microstructures, electrical properties and anti-oxidation behavior. The plasma treated pattern shows a fully densified microstructure with a resistivity of 3.23 μΩ cm, while the thermally treated pattern shows a relatively poor microstructure and high resistivity. In addition, the hydrogen plasma-treated copper pattern retains its electrical resistivity for one month without any significant decrease. This novel hydrogen plasma sintering technique could be used to produce conductive patterns with excellent electrical properties, allowing for highly reliable flexible printed electronics.

  11. Characterization of mechanically milled and spark plasma sintered Al2124-CNT nanocomposites

    Directory of Open Access Journals (Sweden)

    Saheb N.

    2015-01-01

    Full Text Available In the present work, ball milling and spark plasma sintering were used to develop Al2124-CNT nanocomposites. The effect of milling time on the grain size and lattice strain of the ball milled Al2124 alloy powder and the effect of sintering time and temperature on the grain size of the matrix in spark plasma sintered Al2124 alloy and CNT-reinforced Al2124 nanocomposites were investigated. The density and hardness of the developed materials were evaluated as functions of the sintering parameters. It was found that ball milling not only reduced the particle size of the Al2124 powder but also decreased the grain size of the α-aluminum phase to 50 nm and increased its lattice strain. A milling time of 6 hours was found to be the optimum time to reach a nanostructured α-aluminum matrix. The grain size of the α-aluminum phase in the sintered samples increased with increasing sintering temperature and time to reach maximum values at a sintering temperature of 500°C and a sintering time of 20 minutes. Although sintering led to grain growth, the grain size of the α-aluminium matrix remained in the nanometer range and did not exceed 150 nm. The relative density and hardness of the sintered samples increased with increasing sintering temperature and time to reach maximum values at a sintering temperature of 500°C and a sintering time of 20 minutes.

  12. Spark plasma sintering and porosity studies of uranium nitride

    Science.gov (United States)

    Johnson, Kyle D.; Wallenius, Janne; Jolkkonen, Mikael; Claisse, Antoine

    2016-05-01

    In this study, a number of samples of UN sintered by the SPS method have been fabricated, and highly pure samples ranging in density from 68% to 99.8%TD - corresponding to an absolute density of 14.25 g/cm3 out of a theoretical density of 14.28 g/cm3 - have been fabricated. By careful adjustment of the sintering parameters of temperature and applied pressure, the production of pellets of specific porosity may now be achieved between these ranges. The pore closure behaviour of the material has also been documented and compared to previous studies of similar materials, which demonstrates that full pore closure using these methods occurs near 97.5% of relative density.

  13. Plasma sintering of Fe-NbC composites

    Energy Technology Data Exchange (ETDEWEB)

    Paulo, D.S.; Martinelli, A.E.; Alves, C. Jr.; Assuncao, C.A.M.; Tavora, M.P. [Univ. Federal do Rio Grande do Norte, Programa de Doutorado em Ciencia e Engenharia de Materiais, Campus, Natal, RN (Brazil); Echude-Silva, J.H. [Univ. Federal da Paraiba, Dept. de Engenharia Mecanica, Joao Pessoa, PB (Brazil)

    2003-07-01

    Ferrous alloys have been reinforced by particle dispersion using hard ceramics such as niobium carbide, tantalum carbide, or titanium carbide. The resulting composites have a number of potential applications in the ceramic and textile fields where abrasion plays an important role. Their cost-efficient production allows them to exceed the capabilities of conventional non-reinforced tool steels. The present study presents some of the results obtained sintering Fe-NbC composites either in a resistive oven or in a d.c. plasma furnace. Final densities of approximately 95% TD were obtained in the latter atmosphere at temperatures as low as 750 C. Dilatometric studies carried out in resistive furnace indicated that this composite did not show significant densification below 1240 C in the presence of a liquid phase formed by the addition of small amounts of Fe{sub 3}P. The differences between conventional and plasma sintering are discussed herein along with the effect on the microstructure of the composite. (orig.)

  14. Dynamic compressive and tensile strengths of spark plasma sintered alumina

    Science.gov (United States)

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M. P.; Frage, N.

    2014-06-01

    Fully dense submicron grain size alumina samples were manufactured from alumina nano-powder using Spark Plasma Sintering and tested in two kinds of VISAR-instrumented planar impact tests. In the first kind, samples were loaded by 1-mm tungsten impactors, accelerated to a velocity of about 1 km/s. These tests were aimed at studying the Hugoniot elastic limit (HEL) of Spark Plasma Sintering (SPS)-processed alumina and the decay, with propagation distance, of the elastic precursor wave. In the tests of the second kind, alumina samples of 3-mm thickness were loaded by 1-mm copper impactors accelerated to 100-1000 m/s. These tests were aimed at studying the dynamic tensile (spall) strength of the alumina specimens. The tensile fracture of the un-alloyed alumina shows a monotonic decline of the spall strength with the amplitude of the loading stress pulse. Analysis of the decay of the elastic precursor wave allowed determining the rate of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of the shock-induced inelastic deformation and to clarify the mechanisms responsible for the deformation. The 1-% addition of Cr2O3 decreases the HEL of the SPS-processed alumina by 5-% and its spall strength by 50% but barely affects its static properties.

  15. Effect of sintering on the relative density of Cr-coated diamond/Cu composites prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Wei Cui; Hui Xu; Jian-hao Chen; Shu-bin Ren; Xin-bo He; Xuan-hui Qu

    2016-01-01

    Cr-coated diamond/Cu composites were prepared by spark plasma sintering. The effects of sintering pressure, sintering tempera-ture, sintering duration, and Cu powder particle size on the relative density and thermal conductivity of the composites were investigated in this paper. The influence of these parameters on the properties and microstructures of the composites was also discussed. The results show that the relative density of Cr-coated diamond/Cu reaches ~100% when the composite is gradually compressed to 30 MPa during the heating process. The densification temperature increases from 880 to 915°C when the diamond content is increased from 45vol% to 60vol%. The densification temperature does not increase further when the content reaches 65vol%. Cu powder particles in larger size are beneficial for in-creasing the relative density of the composite.

  16. Joining of beta-SiC by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Grasso, Salvatore [Queen Mary, University of London; Tatarko, Peter [Institute of Physics of Materials, Academy of Sciences of the Czech Republic; Rizzo, S. [Politecnico di Torino; Porwal, Harshit [Queen Mary, University of London; Hu, Chunfeng [Ningbo Institute of Materials Technology & Engineering; Katoh, Yutai [ORNL; Salvo, M [Politecnico di Torino; Reece, Michael John [University of London; Ferraris, Monica [Politecnico di Torino

    2014-01-01

    Spark plasma sintering (SPS) was employed to join monolithic -SiC with or without titanium as intermediate joining material. Both the localizedand rapid heating contributed to the inherent energy saving of electric current assisted joining technique. The effects of uniaxial pressure and surfacepreparation were analyzed independently with respect to the flexural strength and the morphology of the joints. In particular samples polisheddown to 1 m and joined at 1900 C for 5 min achieved the strength of the as received material. The failure occurred outside the joining interface,confirming the optimum quality of the joint. Pressure in combination with surface preparation was necessary to achieve perfect adhesion and porefree direct joining of SiC. The use of Ti foil as a joining material and pressure allowed joining of unpolished SiC.

  17. Oxidation behavior of plasma sintered beryllium–titanium intermetallic compounds as an advanced neutron multiplier

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Hwan, E-mail: kim.jaehwan@jaea.go.jp; Nakamichi, Masaru

    2013-07-15

    Beryllium intermetallic compounds (beryllides) such as Be{sub 12}Ti are very promising candidates for advanced neutron multiplier materials in a demonstration fusion power reactor (DEMO). However, beryllides are too brittle to be fabricated either into pebble-type or rod-type shapes via conventional methods (i.e. arc melting and hot isostatic pressing). We have proposed a plasma sintering technique as a new method for beryllide fabrication, and our studies on the properties of plasma sintered beryllides are ongoing. In the present work, the oxidation properties of plasma sintered beryllides were investigated at 1273 K for 24 h in a dry air atmosphere to evaluate the high temperature properties of this material. Thermal gravimetry measurements indicate that specimens with larger fractions of Be{sub 12}Ti phase corresponding to samples that have been sintered for longer time periods, exhibit superior oxidation properties. Our evaluation of the oxidation behavior of each phase in our beryllide samples is as follows: Be{sub 12}Ti and Be{sub 17}Ti{sub 2} both have good oxidation resistance, owing to the formation of dense and protective scales, while the Be and Be{sub 2}Ti phases are mainly responsible for thermal-gravimetry (TG) weight gains, which is indicative of severe oxidation. We attribute the degradation in oxidation resistance specifically to Be{sub 2}Ti that transforms into TiO{sub 2}, and also find this phase to be the cause of deterioration in the mechanical properties of samples, owing to cracks near Be{sub 2}Ti phase conglomerates.

  18. Corrosion behaviors of NdFeB magnets prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Tao Li; Ming Yue; Aizhi Sun; Baoqin Qiu; Yaofu Xiao; Jiuxing Zhang

    2004-01-01

    The spark plasma sintering (SPS) technique was introduced into the field of NdFeB preparation due to its own advantages.High property NdFeB magnets with fine grains were prepared by SPS method. The corrosion behaviors of SPS NdFeB were studied by electrochemical measurements and 92% RH hyther tests at 353 K. The results were compared with those of the traditional sintered NdFeB magnets. It shows that both the SPS NdFeB and the traditional sintered NdFeB have good corrosion resistance in alkaline environment due to surface passivation; while, the fine grain microstructure of SPS NdFeB results in a more homogeneous phase composition distribution and thus reduces the electrochemical inhomogenity between the ferromagnetic phase and the Nd-rich intergranular phase in the magnet. Therefore, the SPS NdFeB exhibits better corrosion resistance than the traditional sintered NdFeB in neutral and weak acidic environment.

  19. Mechanochemical synthesis and spark plasma sintering of the cerium silicides

    Energy Technology Data Exchange (ETDEWEB)

    Alanko, Gordon A.; Jaques, Brian; Bateman, Allyssa [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Butt, Darryl P., E-mail: darrylbutt@boisestate.edu [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Boulevard, Idaho Falls, ID 83401 (United States)

    2014-12-15

    Highlights: • Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−x} and CeSi{sub 2} were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−y}, and CeSi{sub 2−x}, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce{sub 5}Si{sub 4} was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides.

  20. Elaboration of translucent ZnO ceramics by spark plasma sintering under low temperature

    Science.gov (United States)

    Lin, Debao; Fan, Lingcong; Shi, Ying; Xie, Jianjun; Lei, Fang; Ren, Dudi

    2017-09-01

    ZnO is considered to be a potential ultrafast scintillator. In this work, nanosized ZnO powders were synthesized via thermal decomposition of precursors prepared by indirect-precipitation method from zinc nitrate and urea in aqueous solutions. The resultant single phased ZnO powder calcined at 600 °C for 2 h had a primary grain size of 66.0 nm with good dispersity showing excellent sinterability. Translucent ZnO ceramic with a relative density of 99.2% was fabricated successfully by spark plasma sintering at 850 °C for 10 min under the pressure of 80 MPa. The obtained ZnO ceramic exhibited fully dense and homogenous microstructure with average grain size of ∼1 μm, leading to an in-line optical transmission of 11.8% at a wavelength of 950 nm.

  1. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    Science.gov (United States)

    Olevsky, Eugene A.; Rolfing, Stephen M.; Maximenko, Andrey L.

    2016-09-01

    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the flash sintering process through the application of the external pressure. The effectiveness of the developed FHP technique is demonstrated by the few seconds-long consolidation of SiC powder in an industrial spark plasma sintering device. Specially designed sacrificial dies heat the pre-compacted SiC powder specimens to a critical temperature before applying any voltage to the powder volume and allowing the electrode-punches of the SPS device setup to contact the specimens and pass electric current through them under elevated temperatures. The experimental results demonstrate that flash sintering phenomena can be realized using conventional SPS devices. The usage of hybrid heating SPS devices is pointed out as the mainstream direction for the future studies and utilization of the new flash hot pressing (ultra-rapid spark plasma sintering) technique.

  2. Interaction of non-equilibrium oxygen plasma with sintered graphite

    Science.gov (United States)

    Cvelbar, Uroš

    2013-03-01

    Samples made from sintered graphite with grain size of about 10 μm were exposed to highly non-equilibrium oxygen plasma created in a borosilicate glass tube by an electrodeless RF discharge. The density of charged particles was about 7 × 1015 m-3 and the neutral oxygen atom density 6 × 1021 m-3. The sample temperature was determined by a calibrated IR detector while the surface modifications were quantified by XPS and water drop techniques. The sample surface was rapidly saturated with carbonyl groups. Prolonged treatment of samples caused a decrease in concentration of the groups what was explained by thermal destruction. Therefore, the created functional groups were temperature dependent. The heating of samples resulted in extensive chemical interaction between the O atoms and samples what was best monitored by decreasing of the O atom density with increasing sample temperature. The saturation with functional groups could be restored only after cooling down of the samples and repeated short plasma treatment at low temperature.

  3. Characterization of plasma nitrided layers produced on sintered iron

    Directory of Open Access Journals (Sweden)

    Marcos Alves Fontes

    2014-07-01

    Full Text Available Plasma nitriding is a thermo-physical-chemical treatment process, which promotes surface hardening, caused by interstitial diffusion of atomic nitrogen into metallic alloys. In this work, this process was employed in the surface modification of a sintered ferrous alloy. Scanning electron microscopy (SEM, X-ray diffraction (XRD analyses, and wear and microhardness tests were performed on the samples submitted to ferrox treatment and plasma nitriding carried out under different conditions of time and temperature. The results showed that the nitride layer thickness is higher for all nitrided samples than for ferrox treated samples, and this layer thickness increases with nitriding time and temperature, and temperature is a more significant variable. The XRD analysis showed that the nitrided layer, for all samples, near the surface consists in a mixture of γ′-Fe4N and ɛ-Fe3N phases. Both wear resistance and microhardness increase with nitriding time and temperature, and temperature influences both the characteristics the most.

  4. Method to Determine Maximum Allowable Sinterable Silver Interconnect Size

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, A. A.; Modugno, M. C.; Waters, S. B.; DeVoto, D. J.; Paret, P. P.

    2016-05-01

    The use of sintered-silver for large-area interconnection is attractive for some large-area bonding applications in power electronics such as the bonding of metal-clad, electrically-insulating substrates to heat sinks. Arrays of different pad sizes and pad shapes have been considered for such large area bonding; however, rather than arbitrarily choosing their size, it is desirable to use the largest size possible where the onset of interconnect delamination does not occur. If that is achieved, then sintered-silver's high thermal and electrical conductivities can be fully taken advantage of. Toward achieving this, a simple and inexpensive proof test is described to identify the largest achievable interconnect size with sinterable silver. The method's objective is to purposely initiate failure or delamination. Copper and invar (a ferrous-nickel alloy whose coefficient of thermal expansion (CTE) is similar to that of silicon or silicon carbide) disks were used in this study and sinterable silver was used to bond them. As a consequence of the method's execution, delamination occurred in some samples during cooling from the 250 degrees C sintering temperature to room temperature and bonding temperature and from thermal cycling in others. These occurrences and their interpretations highlight the method's utility, and the herein described results are used to speculate how sintered-silver bonding will work with other material combinations.

  5. The Densification of Cu/Ti System by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jinyong; TAN Tianya; FU Zhengyi; WANG Weimin

    2005-01-01

    In order to unclose the dynamics of SPS densification, a special sintering sample (Cu/Ti wires compact) was designed. Characters of the shrinkage rates during sintering process and microstructures of products fabricated by the spark plasma sintering(SPS) and hot-press sintering were investigated. The experimental results reveal that a higher temperature field is formed at the connected area and conductive net of the compact. These high-temperature parts deformed more easily than other parts, which is believed to be the main cause of SPS fast densification, according to a hard-core and soft-hell material model.

  6. Dynamic yield and tensile strengths of spark plasma sintered alumina

    Science.gov (United States)

    Girlitsky, I.; Zaretsky, E.; Kalabukhov, S.; Dariel, M.; Frage, N.

    2014-05-01

    Fully dense alumina samples with 0.6 μm grain size were produced from alumina powder using Spark Plasma Sintering and tested in two types of VISAR-instrumented planar impact tests. In the tests of the first type the samples of 0.28 to 6-mm thickness were loaded by 1-mm tungsten impactors accelerated up to a velocity of about 1 km/s. These tests were aimed to study the Hugoniot elastic limit (HEL) of the SPS-processed alumina and the decay of the elastic precursor wave with propagation distance. In the second type of test the samples of ~3-mm thickness were loaded by 1-mm copper impactors accelerated up to velocities 100-1000 m/s. These tests were aimed to study the dynamic tensile (spall) strength of the alumina. The data on tensile fracture of the alumina demonstrate a monotonic decline of the spall strength with the amplitude of the loading stress pulse. The data on the decay of the elastic precursor wave allows for determining the rates of the irreversible (inelastic) strains in the SPS-processed alumina at the initial stages of shock-induced inelastic deformation and, thus, to derive some conclusions concerning the mechanisms responsible of the deformation.

  7. Fabrication of W–1 wt.% TiC composites by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Xiao-Yu [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province, Hefei 230009 (China); Chen, Hong-Yu [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhu, Xiao-Yong; Zan, Xiang; Cheng, Ji-Gui [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province, Hefei 230009 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Laboratories of Nonferrous Metal Material and Processing Engineering of Anhui Province, Hefei 230009 (China)

    2015-03-15

    Graphical abstract: - Highlights: • TiC/W nanoparticles with core–shell structure were produced by chemical method. • TiC particles were dispersed in the tungsten grains and grain boundaries. • The grain size and relative density of W–TiC composite were 3 μm and 98.6%, respectively. - Abstract: TiC/W ultra-fine powders were produced by one-step activation and chemical reduction process. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The grain size, relative density and the Vicker hardness HV{sub 0.2} of the bulk sample fabricated by SPS were 3 μm, 98.6% and 471, respectively. The reduced Young's elastic modulus of the sintered W–1 wt.% TiC composites was 382.7 GPa. As the temperature rises from room temperature (RT) to 1100 K, the thermal conductivity of pure W and W–1 wt.% TiC composites decreased with the same trend. However, the thermal conductivity of the samples was both above 120 W/m K at RT.

  8. Production of dispersed nanometer sized YAG powders from alkoxide, nitrate and chloride precursors and spark plasma sintering to transparency

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, M., E-mail: m.suarez@cinn.e [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fernandez, A. [Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L.; Torrecillas, R. [Departamento de Materiales Nanoestructurados, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN), Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-03-18

    Yttrium aluminum garnet (YAG) was synthesized from different starting materials, i.e., alkoxide, nitrate and chloride precursors. The conversion steps from the precursors to crystalline YAG were studied by Raman spectroscopy. Dispersed YAG powders were formed at a relatively low temperature, around 800 {sup o}C by the chlorides route, whereas alkoxide precursors needed firing over 900 {sup o}C and nitrates even over 1100 {sup o}C. Lyophilized YAG gel was sintered to transparency by the spark plasma sintering method at 1500 {sup o}C with in-line transmittances close to 60% at 680 nm and over 80% in the infrared range.

  9. Nanocompósitos de Al2O3-SiC sinterizados por "spark plasma sintering" (SPS Al2O3-SiC nanocomposites sintered by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    V. Trombini

    2008-09-01

    Full Text Available O nanocompósito (alumina-carbeto de silício vem sendo estudado extensivamente em função do resultados promissores encontrados quanto a propriedades mecâncias. Usualmente o processamento desse material envolve um alto custo, pois para a obtenção de materiais densos é necessária a utilização de prensagem a quente. Uma alternativa mais recente para a sinterização de cerâmicas nanocristalinas é a sinterização por plasma (Spark Plasma Sintering - SPS. Nesse trabalho, pós de alumina contendo 5%vol de inclusões de SiC foram sinterizados por SPS em temperaturas variando de 1500 a 1600 °C usando diferentes tempos de patamar. Os corpos de prova foram analisados por meio da determinação da densidade aparente, microscopia eletrônica de varredura e microdureza Vickers. Os resultados mostraram que as melhores condições para a obtenção de uma microestrutura com tamanho de grãos próximos ao tamanho das partículas do pó inicial foi com temperatura de 1500 °C e tempo de patamar 7 min.(Alumina-silicon carbide nanocomposite has been extensivelly studied due to its promising results regarding its mechanical properties. The processing of this material usually involves high cost, once the use of hot pressing is necessary for obtaining dense materials. A more recent alternative for sintering nanocrystalline ceramics is the Spark Plasma Sintering - SPS. In this work alumina powders with 5%vol SiC inclusions were sintered using the SPS method at temperatures varying from 1500 to 1600 °C, using different holding times. The effect of temperature and hold time on density and microstructure was investigated. The best results in microestucture and microhardness measurements were shown at 1500 °C and time of landing of 7 min.

  10. Comparative study of β-Si3N4 powders prepared by SHS sintered by spark plasma sintering and hot pressing

    Institute of Scientific and Technical Information of China (English)

    Ling Bai; Xiaodong Mao; Weiping Shen; Changchun Ge

    2007-01-01

    β-Si3N4 powders prepared by self-propagating high-temperature synthesis (SHS) with additions of Y2O3 and Al2O3 were sintered by spark plasma sintering (SPS). The densification, microstructure, and mechanical properties of Si3N4 ceramics prepared using this method were compared with those obtained by hot pressing process. Well densified Si3N4 ceramics with finer and homogeneous microstructure and better mechanical properties were obtained in the case of the SPS technique at 200℃ lower than that of hot pressing. The microhardness is 15.72 GPa, the bending strength is 716.46 MPa, and the fracture toughness is 7.03 MPa.m1/2.

  11. Flash sintering of ceramic materials

    OpenAIRE

    Dancer, C. E. J.

    2016-01-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sint...

  12. Fabrication and characterization of spark plasma sintered Ce:LuAG ceramic for scintillation application

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S. Arun; Senthilselvan, J., E-mail: jsselvan@hotmail.com [Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai–600 025, Tamil Nadu (India)

    2016-05-23

    Rare earth Cerium doped Lutetium Aluminum Garnet (Ce:LuAG) ceramics are widely used as phosphor material in medical imaging and high-energy physics. Due to its technological importance, an attempt has been made to fabricate Ce:LuAG ceramics by using spark plasma sintering (SPS) technique. XRD patterns of SPS sintered Ce:LuAG ceramics reveals a mixed LuAG and CeO{sub 2} (antisite defect) phases. The microstructures of SPS sintered Ce:LuAG ceramics shows limited densification, inappropriate compaction of particles and existence of residual pores, voids between the grain boundaries affects the transparency of Ce:LuAG ceramics. Relative density and hardness of post sintered Ce:LuAG ceramic is also determined. The effect of Ce{sup 3+} doping concentration and sintering temperature on optical luminescence behavior of Ce:LuAG ceramic is presented.

  13. Spark Plasma Sintering Properties of Ultrafine Ti ( C,N)-based Cermet

    Institute of Scientific and Technical Information of China (English)

    FENG Ping; XIONG Wei-hao; ZHENG Yong; YU Li-xin; XIA Yang-hua

    2004-01-01

    Ultrafine Ti( C, N )-based cermet was sintered by SPS from 1050℃ to 1450℃ and its sintering properties, such as porosity, mechanical properties and phase transformation, were investigated by optical mi-croscopy (OM), scanning electron microscopy (SEM), X- ray diffraction (XRD), and differential scanning calo-rimeter (DSC). It is found that the spark plasma sintering properties of Ti( C, N )-based cermet differ from thoseof conventional vacuum sintering. The liquid phase appearance is at least lower by 150℃ than that in vacuum sin-tering. The porosity decreases sharply below 1 200℃ and reaches minimum at 1 200℃ , and afterwards it almostkeeps invariable and no longer increases. SPS remarkably accelerates the phase transformation of Ti( C, N )-basedcermet and it has a powerful ability to remove oxides in Ti( C, N )-based cermets. Above 1 3502 ,denitrificationoccurred. Fresh graphite phase formed above 1 430℃ . Both the porosity and graphite are responsible for the poor TRS.

  14. Fabrication and characterization of spark plasma sintered Ce:LuAG ceramic for scintillation application

    Science.gov (United States)

    Kumar, S. Arun; Senthilselvan, J.

    2016-05-01

    Rare earth Cerium doped Lutetium Aluminum Garnet (Ce:LuAG) ceramics are widely used as phosphor material in medical imaging and high-energy physics. Due to its technological importance, an attempt has been made to fabricate Ce:LuAG ceramics by using spark plasma sintering (SPS) technique. XRD patterns of SPS sintered Ce:LuAG ceramics reveals a mixed LuAG and CeO2 (antisite defect) phases. The microstructures of SPS sintered Ce:LuAG ceramics shows limited densification, inappropriate compaction of particles and existence of residual pores, voids between the grain boundaries affects the transparency of Ce:LuAG ceramics. Relative density and hardness of post sintered Ce:LuAG ceramic is also determined. The effect of Ce3+ doping concentration and sintering temperature on optical luminescence behavior of Ce:LuAG ceramic is presented.

  15. Evaluation of microwave plasma sintering for the fabrication of dye sensitized solar cell (DSSC) electrodes.

    Science.gov (United States)

    Dembele, A; Rahman, M; MacElroy, J M D; Dowling, D P

    2012-06-01

    Dye-sensitized solar cells (DSSCs) have demonstrated considerable potential due to their solar energy conversion efficiency and their fabrication from relatively low cost materials. Titanium dioxide (TiO2) nanoparticles are widely used in the fabrication of the DSSC electrodes. There is a considerable energy requirement however required for the sintering of the TiO2 particles during the fabrication of the mesoporous electrodes. This study investigates the use of microwave (MW) plasma treatments as a rapid, energy efficient processing technique for the sintering of the metal oxide particles. A comparison is made with conventional furnace treatments for the sintering of TiO2 nanoparticles (Degussa P25), deposited onto fluorine doped tin oxide (FTO) coated glass substrates. Subsequent to the TiO2 sintering, ruthenium based dye (N719) adsorption studies were carried out for coatings heated using both sintering techniques. Based on UV/Vis absorption spectra measurements of 5 mins plasma and 30 mins furnace sintering, it was observed that both sintering techniques exhibited similar levels of dye adsorption. A decrease in the level of dye adsorption was observed for the TiO2 coatings sintered for longer periods (up to 10 mins in this study). This change with longer plasma treatment times was associated with rutile grain growth and a decrease in surface roughness, possibly due to a densification of the mesoporous structure. The effect of TiO2 coating plasma treatment times on the conversion efficiency of the dye sensitised electrodes was also evaluated. Plasma treatments of 5 mins were found to yield the highest conversion efficiency of 6.4%.

  16. Recent Trends in Newly Developed Plasma-Sprayed and Sintered Coatings for Implant Applications

    Science.gov (United States)

    Bsat, Suzan; Speirs, Andrew; Huang, Xiao

    2016-08-01

    The current paper aims to review recent trends (2011 to 2015) in newly developed plasma-sprayed and sintered coatings for implant applications. Recent developments in plasma-sprayed and sintered coatings have focused on improving biological performance, bacterial growth resistance, and mechanical properties, predominantly of HA and glass ceramics. The majority of these improvements are attributed to the addition of dopants. To improve biological performance, trace elements, such as Zn and Mg, both of which are found in bone, were added to replicate the functions they provide for the skeletal system. Though bacterial growth resistance is traditionally improved by Ag dopant, the addition of new dopants such as CeO2 and Zn were explored as well. Great effort has also been made to improve coating adherence and reduce stresses by minimizing coefficient of thermal expansion mismatch between the coating and substrate through the addition of elements such as Zn and Mg or the inclusion of a buffer layer. For sintering process in particular, there was an emphasis on reducing sintering temperature through modification of 45S5 Bioglass. New plasma spray and sintering technologies aimed at reducing high-temperature exposure are briefly introduced as well. These include microplasma spray and spark plasma sintering.

  17. Post-treatment of Plasma-Sprayed Amorphous Ceramic Coatings by Spark Plasma Sintering

    Science.gov (United States)

    Chraska, T.; Pala, Z.; Mušálek, R.; Medřický, J.; Vilémová, M.

    2015-04-01

    Alumina-zirconia ceramic material has been plasma sprayed using a water-stabilized plasma torch to produce free standing coatings. The as-sprayed coatings have very low porosity and are mostly amorphous. The amorphous material crystallizes at temperatures above 900 °C. A spark plasma sintering apparatus has been used to heat the as-sprayed samples to temperatures above 900 °C to induce crystallization, while at the same time, a uniaxial pressure of 80 MPa has been applied to their surface. After such post-treatment, the ceramic samples are crystalline and have very low open porosity. The post-treated material exhibits high hardness and significantly increased flexural strength. The post-treated samples have a microstructure that is best described as nanocomposite with the very small crystallites embedded in an amorphous matrix.

  18. The potential of rapid cooling spark plasma sintering for metallic materials

    Directory of Open Access Journals (Sweden)

    Faming Zhang

    2013-05-01

    Full Text Available Spark plasma sintering (SPS is a remarkable technique for consolidating a large variety of advanced materials with rapid heating rates. However, adjusting the cooling rates has so far faced limitations. This communication discusses the potentials of SPS integrated with a novel gas quenching system that can allow metallic materials to be sintered and rapidly quenched directly after the sintering step, saving energy and costs. Results on numerical simulations of rapid cooling-SPS and the mechanical properties and microstructures of Ti6Al4V alloy are discussed; exhibiting the feasibility of this rapid cooling SPS technique and the major implications for the field of SPS and metallic powder consolidation.

  19. Spark Plasma Sintering of high-strength ultrafine-grained tungsten carbide

    Science.gov (United States)

    Nokhrin, A. V.; Chuvil'deev, V. N.; Blagoveshchenskiy, Yu V.; Boldin, M. S.; Sakharov, N. V.; Isaeva, N. V.; Popov, A. A.; Lantcev, E. A.; Belkin, O. A.; Smirnova, E. S.

    2017-07-01

    The paper dwells on the research conducted into high-rate consolidation of pure tungsten carbide nanopowders using the Spark Plasma Sintering. Studies included the effect that the original size of WC nanoparticles and their preparation modes have on density, structure parameters, and mechanical properties of tungsten carbide. It has been found that materials that show abnormal grain growth during sintering have lower values of sintering activation energy as compared to materials the structure of which is more stable during high-rate heating. A qualitative model is proposed that explains this effect through the dependence of the grain boundary diffusion coefficient on the grain boundary migration rate.

  20. Elaboration and thermomechanical characterization of W/Cu functionally graded materials produced by Spark Plasma Sintering for plasma facing components

    Energy Technology Data Exchange (ETDEWEB)

    Autissier, E., E-mail: manu.autissier@orange.fr [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Richou, M. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Minier, L. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-UB, 9 Av. Alain Savary, BP 47870, 21078 Dijon Cedex (France); Gardarein, J.-L. [Aix Marseille Univ, IUSTI, UMR CNRS 7343, F-13453 Marseille (France); Bernard, F. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-UB, 9 Av. Alain Savary, BP 47870, 21078 Dijon Cedex (France)

    2015-10-15

    Highlights: • Different W-Cu powders were sintered by Spark Plasma Sintering. • The relative density increase with the temperature and Cu concentration. • Thermal conductivity of W-Cu samples has been measured in function of density. • Assembly of a three-layer W-Cu between a W block and a CuCrZr block was realized. • 40 min is the minimum time to complete bonding between W and W{sub 80}Cu{sub 20}. - Abstract: The assembly of W block with a CuCrZr block has been produced by adding compliant W-Cu layers. Firstly, three W-Cu powders (W{sub 80}Cu{sub 20}, W{sub 60}Cu{sub 40} and W{sub 40}Cu{sub 60}) were sintered by spark plasma sintering (SPS) to investigate the influences of sintering temperature and pressure on relative density and microstructure. The experimental results indicated that the relative density increases with temperature and Cu concentration, achieving a value of 94.1% for the W{sub 40}Cu{sub 60} sample sintered at 1000 °C and a value of 83.1% for the W{sub 80}Cu{sub 20} sample sintered at the same temperature. Then, a three-layer W-Cu assembly between a W block and a CuCrZr block was fabricated using similar sintering conditions to the W-Cu powders. The sintering temperature was limited at 1000 °C due to the CuCrZr melting temperature (1083 °C). The experimental results indicated that loading time, when the right sintering temperature and pressure are applied, is the most important parameter.

  1. Reactive Spark Plasma Sintering (SPS) of Nitride Reinforced Titanium Alloy Composites (Postprint)

    Science.gov (United States)

    2014-08-15

    ies on in situ alloying and reactions during the SPS process. A recent study on SPS processing of hafnium carbide (HfC) starting from a blend of...AFRL-RX-WP-JA-2014-0177 REACTIVE SPARK PLASMA SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) Jaimie S...SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  2. Comparative study of the fabrication of ultrafine Ti(C,N)-based cermets by spark plasma sintering and conventional vacuum sintering

    Institute of Scientific and Technical Information of China (English)

    LEI Yan; XIONG Weihao; LIANG Zaiguo; FENG Ping; WANG Zhiwu

    2005-01-01

    Spark plasma sintering (SPS) and conventional vacuum sintering (VS) were employed to fabricate ultrafine Ti(C,N)-based cermets. The shrinkage behavior, microstructure, and porosity and mechanical properties of the samples fabricated by SPS were compared with those of the samples sintered by VS using optical microscopy, scanning electron microscopy, universal testing machine, and rockwell tester. The results are as follows: (1) The shrinkage process occurred mainly in the range of 1000-1300℃ during the VS process, and only a 0.2% linear shrinkage ratio appeared below 800℃;during the SPS process, a 60% dimensional change occurred below 800℃ as a result of pressure action. (2) By utilizing the SPS technique, it is difficult for obtaining fully dense Ti(C,N)-based cermets. Due to the much existence of pores and uncombined carbon, the mechanical properties of the sintered samples by SPS are inferior to sintered ones by VS. (3) grain size of the samples sintered by SPS is still below 0.5 μm, but not by VS; because of low sintering temperature, there are no typical core/rim structures formed in the sintered samples by SPS 1; the main microstructures of the sintered samples by SPS2 are a white core/grey shell structure, whereas by VS show a typical black core/grey shell structure.

  3. Microstructure and mechanical properties of spark plasma sintered Ti-Mo alloys for dental applications

    Institute of Scientific and Technical Information of China (English)

    Xin Lu; Bo Sun; Teng-fei Zhao; Lu-ning Wang; Cheng-cheng Liu; Xuan-hui Qu

    2014-01-01

    Ti-Mo alloys with various Mo contents from 6wt%to 14wt%were processed by spark plasma sintering based on elemental pow-ders. The influence of sintering temperature and Mo content on the microstructure and mechanical properties of the resulting alloys were in-vestigated. For each Mo concentration, the optimum sintering temperature was determined, resulting in a fully dense and uniform micro-structure of the alloy. The optimized sintering temperature gradually increases in the range of 1100-1300°C with the increase in Mo content. The microstructure of the Ti-(6-12)Mo alloy consists of acicularαphase surrounded by equiaxed grains ofβphase, while the Ti-14Mo al-loy only contains singleβphase. A small amount of fineαlath precipitated fromβphase contributes to the improvement in strength and hardness of the alloys. Under the sintering condition at 1250°C, the Ti-12Mo alloy is found to possess superior mechanical properties with the Vickers hardness of Hv 472, the compressive yield strength of 2182 MPa, the compression rate of 32.7%, and the elastic modulus of 72.1 GPa. These results demonstrate that Ti-Mo alloys fabricated via spark plasma sintering are indeed a perspective candidate alloy for dental applications.

  4. Spark plasma sintering of mechanically alloyed in situ copper-niobium carbide composite

    Energy Technology Data Exchange (ETDEWEB)

    Long, B.D. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Othman, R. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Umemoto, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Zuhailawati, H., E-mail: zuhaila@eng.usm.m [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia)

    2010-09-03

    A Cu-NbC composite with high electrical conductivity and high microhardness was synthesized by mechanical alloying and densified using spark plasma sintering (SPS). Mixtures of Cu-NbC powders corresponding to volume fractions of 1, 5, 15 and 25 vol% NbC were milled in a high energy planetary mill under argon atmosphere for 30 h using ethanol as process control agent. The Cu-NbC as-milled powder was sintered using spark plasma sintering temperatures between 900 and 1000 {sup o}C. X-ray diffraction investigation showed that NbC started to form in the copper matrix during ball milling and the reaction between Nb and C was completed after 10 min of SPS sintering. Electrical conductivity and density of the Cu-15 vol% NbC composite increased with increasing sintering temperature. The results showed the superior properties of SPS-prepared Cu-NbC composite: electrical conductivity is almost 4 times higher and microhardness is 3.5 times higher than with normal sintering. A highest density of 98% and electrical conductivity of 45.6% IACS were obtained in the Cu-1 vol% NbC composite. The highest microhardness of 452.9 Hv was achieved in the Cu-25 vol% NbC composite.

  5. Effects of spark plasma sintering conditions on the anisotropic thermoelectric properties of bismuth antimony telluride

    DEFF Research Database (Denmark)

    Han, Li; Hegelund Spangsdorf, Steeven; Van Nong, Ngo

    2016-01-01

    Bismuth antimony telluride (BixSb2-xTe3, 0.4 Sb1.6Te3 samples were prepared under various conditions (temperature, holding time, and ramp......-rate) using spark plasma sintering (SPS). The effects of SPS conditions on the anisotropic thermoelectric properties and microstructure evolutions were systematically investigated. The change of sintering temperature showed stronger influence than other sintering parameters to the resulting thermoelectric...... properties. Samples sintered over the temperature range between 653 K and 773 K showed significant differences in the degrees of orientations. The change was mainly caused by grain growth and re-orientation. Despite of the anisotropy, zT value as high as 1.2 to 1.3 was achieved over the temperature range...

  6. Porous copper template from partially spark plasma-sintered Cu–Zn aggregate via dezincification

    Indian Academy of Sciences (India)

    M Mandal; D Singh; Gouthama; B S Murty; S Sangal; K Mondal

    2014-06-01

    Present work deals with the preparation of spark plasma-sintered Cu–Zn aggregate (5, 10 and 20 wt% Zn) with interfacial bonding only starting from elemental powders of Cu and Zn (99.9% purity) and subsequently making of porous template of Cu by dezincification. Sintering is done so as to achieve only interfacial bonding with the aim to maintain maximum potential difference between the Cu and Zn particles during dezincification process in various solutions, viz. 1 N HCl and 3.5 wt% NaCl solutions. X-ray diffraction, optical microscopy and SEM–EDS are carried out to examine microstructural evolution and subsequent changes in hardness with sintering temperatures and different Zn percentages. Dezincification and pore formation are conducted on sintered 0.5 mm thick 12 mm diameter disc samples. The size, distribution and nature of pores in porous templates of Cu are then investigated using optical microscopy and SEM–EDS analysis.

  7. Welding of titanium and nickel alloy by combination of explosive welding and spark plasma sintering technologies

    Energy Technology Data Exchange (ETDEWEB)

    Malyutina, Yu. N., E-mail: iuliiamaliutina@gmail.com; Bataev, A. A., E-mail: bataev@adm.nstu.ru; Shevtsova, L. I., E-mail: edeliya2010@mail.ru [Novosibirsk State Technical University, Novosibirsk, 630073 (Russian Federation); Mali, V. I., E-mail: vmali@mail.ru; Anisimov, A. G., E-mail: anis@hydro.nsc.ru [Lavrentyev Institute of Hydrodynamics SB RAS, Novosibirsk, 630090 (Russian Federation)

    2015-10-27

    A possibility of titanium and nickel-based alloys composite materials formation using combination of explosive welding and spark plasma sintering technologies was demonstrated in the current research. An employment of interlayer consisting of copper and tantalum thin plates makes possible to eliminate a contact between metallurgical incompatible titanium and nickel that are susceptible to intermetallic compounds formation during their interaction. By the following spark plasma sintering process the bonding has been received between titanium and titanium alloy VT20 through the thin powder layer of pure titanium that is distinguished by low defectiveness and fine dispersive structure.

  8. Welding of titanium and nickel alloy by combination of explosive welding and spark plasma sintering technologies

    Science.gov (United States)

    Malyutina, Yu. N.; Bataev, A. A.; Mali, V. I.; Anisimov, A. G.; Shevtsova, L. I.

    2015-10-01

    A possibility of titanium and nickel-based alloys composite materials formation using combination of explosive welding and spark plasma sintering technologies was demonstrated in the current research. An employment of interlayer consisting of copper and tantalum thin plates makes possible to eliminate a contact between metallurgical incompatible titanium and nickel that are susceptible to intermetallic compounds formation during their interaction. By the following spark plasma sintering process the bonding has been received between titanium and titanium alloy VT20 through the thin powder layer of pure titanium that is distinguished by low defectiveness and fine dispersive structure.

  9. Plasma sintering of unalloyed iron: a study of surface porosity

    Directory of Open Access Journals (Sweden)

    Lourenço Jorge Magner

    2004-01-01

    Full Text Available Samples of unalloyed iron powder were compacted and sintered in an abnormal glow discharge, generated in a gas mixture of 80% Ar + 20% H2 by using a pulsed power source. The samples were placed on a holder, acting as the discharge cathode, and were heated by the bombardment of ions, strongly accelerated in the cathode sheath. Sintering was performed at temperatures of 1173, 1273 and 1373 K for 30 min, varying the voltage applied to the cathode from 400 to 700 V and pressure ranging from 470 to 2650 Pa. It is shown that the kinetic energy of ions striking the sample surface increased approximately three times, when the voltage changed from 400 to 700 V, with a corresponding reduction of surface porosity. The surface sealing is related to the ion bombardment, which produced a high mobility of surface atoms and consequent enhanced diffusion as well as sputtering and condensation on the concave surface, resulting in an activation of surface sintering.

  10. Enhanced thermoelectric performance of spark plasma sintered copper-deficient nanostructured copper selenide

    Science.gov (United States)

    Tyagi, Kriti; Gahtori, Bhasker; Bathula, Sivaiah; Jayasimhadri, M.; Singh, Niraj Kumar; Sharma, Sakshi; Haranath, D.; Srivastava, A. K.; Dhar, Ajay

    2015-06-01

    We report the thermoelectric properties of nanostructured Cu-deficient Cu2Se, which was synthesized by high energy ball milling followed by spark plasma sintering. Our method obtained a significant enhancement in the thermoelectric figure of merit (ZT), i.e., ~1.4 at 973 K, which was ~30% higher than its bulk counterpart. This enhancement in the thermoelectric performance was due mainly to a significant reduction in the lattice thermal conductivity, which was attributed to enhanced phonon scattering at various length scales by nanoscale defects as well as abundant nanograin boundaries. The nanoscale defects were characterized by transmission electron microscopy of the nanostructured Cu2-xSe samples, which formed the basis of the ZT enhancement.

  11. Spark plasma sintering and thermal conductivity of carbon nanotube bulk materials

    Science.gov (United States)

    Zhang, H. L.; Li, J.-F.; Yao, K. F.; Chen, L. D.

    2005-06-01

    Carbon nanotube (CNT) bulk samples were fabricated by spark plasma sintering (SPS), which, as a rapid consolidation technique, preserved the phase structure and diameter of cylindrical tubules of the CNTs even at high temperatures of up to 2000°C. The thermal conductivity of the resultant bulk samples was measured by the conventional laser-flash method, and the corresponding thermal conductivity was found to be as low as 4.2W/m/K at room temperature. This low thermal conductivity of the CNT bulk materials was explained on the basis of multiple physical elements including intensive tube-tube interactions. CNT bulk materials may find potential applications as thermoelectric materials that require low thermal conductivity, but high electrical conductivity.

  12. Spark plasma sintering and mechanical properties of zirconium micro-alloyed tungsten

    Science.gov (United States)

    Xie, Z. M.; Liu, R.; Fang, Q. F.; Zhou, Y.; Wang, X. P.; Liu, C. S.

    2014-01-01

    Dense pure tungsten and W-(0.1, 0.2, 0.5, 1.0) wt% Zr alloys were fabricated through spark plasma sintering method. The relative density of all the samples was about 97%. The FESEM and TEM analysis, tensile tests and Vickers micro-hardness measurements were exploited to characterize these samples. It is found that Zr could capture impurity oxygen in tungsten and form nanometer scaled ZrO2 particles. With the increase of Zr addition from 0 to 0.2 wt%, the room-temperature fracture strength increased from 154 MPa to 265 MPa, and the fracture energy density elevated from 3.73 × 104 J/m3 to 9.22 × 104 J/m3. However, more Zr addition would increase the size of Zr-O particles and significantly decrease the fracture strength and toughness of tungsten.

  13. Characterization of Sintered and Sintered/Plasma-Nitrided Fe-1.5% Mo Alloy by SEM, X-Ray Diffraction and Electrochemical Techniques

    Directory of Open Access Journals (Sweden)

    Alves Neto José de Pinho

    2002-01-01

    Full Text Available Electrochemical experiments together with SEM and X-Ray techniques were carried out in order to evaluate the corrosion resistance, to analyze the surface condition and to characterize the nitride layer of the sintered and sintered/plasma-nitrided Fe-1.5% Mo alloy in Mg(NO32 0.5mol.L-1 solution (pH 7.0. The sintered/plasma-nitrided samples presented a higher corrosion resistance, indicating that the surface treatment improved the electrochemical properties of the sintered material. In addition, the nitride layer formed at 500 °C showed better corrosion resistance that the layers formed at higher temperatures. This difference can be ascribed to the nitrogen content in the nitride layer, which at 500°C is higher due to the formation of a phase rich in nitrogen (epsilon phase while at higher temperatures a phase poor in nitrogen (gamma' phase is formed.

  14. Effect of particle size on the polycrystalline CeB6 cathode prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    BAO Lihong; ZHANG Jiuxing; ZHOU Shenlin

    2011-01-01

    The full densification polycrystalline cerium hexaboride (CeB6) cathode material was prepared by using the spark plasma sintering (SPS) method in an oxygen free system. The starting precursor nanopowders with an average grain size of 50 nm were prepared by high-energy ball milling. The ball-milled nanopowder was fully densified at 1550 ℃ under 50 MPa, which was about 350 ℃ lower than the conventional hot-pressing method and it was also lower than that of coarse powder under the same sintering condition. The mechanical properties of nanopowder sintered samples were significantly better than that of coarse powder, e.g., the flexural strength and Vickers hardness were 211% and 51% higher than that of coarse powder, respectively. The electron backscattered diffraction (EBSD) result showed that the (100) fiber texture could be fabricated by the ball-milled nanopowder sintered at 1550 ℃ and the thermionic emission current density was measured to be 16.04 A/cm2 at a cathode temperature of 1873 K.

  15. Optimisation of Sintering Factors of Titanium Foams Using Taguchi Method

    Directory of Open Access Journals (Sweden)

    S. Ahmad

    2010-06-01

    Full Text Available Metal foams have the potential to be used in the production of bipolar plates in Polymer Electron Membrane Fuel Cells (PEMFC. In this paper, pure titanium was used to prepare titanium foam using the slurry method. The electrical conductivity is the most important parameter to be considered in the production of good bipolar plates. To achieve a high conductivity of the titanium foam, the effects of various parameters including temperature, time profile and composition have to be characterised and optimised. This paper reports the use of the Taguchi method in optimising the processing parameters of pure titanium foams. The effects of four sintering factors, namely, composition, sintering temperature, heating rate and soaking time on the electrical conductivity has been studied. The titanium slurry was prepared by mixing titanium alloy powder, polyethylene glycol (PEG, methylcellulose and water. Polyurethane (PU foams were then impregnated into the slurry and later dried at room temperature. These were next sintered in a high temperature vacuum furnace. The various factors were assigned to an L9 orthogonal array. From the Analysis of Variance (ANOVA, the composition of titanium powder has the highest percentage of contribution (24.51 to the electrical conductivity followed by the heating rate (10.29. The optimum electrical conductivity was found to be 1336.227 ± 240.61 S/cm-1 for this titanium foam. It was achieved with a 70% composition of titanium, sintering temperature of 1200oC, a heating rate of 0.5oC/min and 2 hours soaking time. Confirmatory experiments have produced results that lay within the 90% confidence interval.

  16. Optical and biological properties of transparent nanocrystalline hydroxyapatite obtained through spark plasma sintering.

    Science.gov (United States)

    Li, Zhong; Thompson, Brianna C; Dong, Zhili; Khor, Khiam Aik

    2016-12-01

    Transparent bioceramics have attracted a large amount of research interest as they facilitate direct observation of biointerfacial reactions. Thus far, attempts to achieve transparent hydroxyapatite have been focused on augmenting the sintering pressure and/or extending the sintering duration. This study aims at fabricating transparent HA using a direct and fast spark plasma sintering process with appropriate starting powder and moderate sintering pressure. Three types of raw powder, namely micro-spheres, nano-rods and nano-spheres, were sintered to investigate the optical and biological properties of the compacted pellets. It was found that in terms of transparency, the micro-sphere pellet sintered at 1000°C stood out with an in-line transmittance as high as 84% achieved at 1300nm for a 2mm thick sample. In addition, pellets fabricated from micro-spheres demonstrated the highest cell viability in in vitro biological tests with L929 cells. Living cells cultured on a transparent micro-sphere pellet could be directly and clearly observed by light microscopy. It is thus concluded that the micro-sphere powder is the most desirable raw material to manufacture transparent hydroxyapatite because it could enable dense pellets with notably high transparency and outstanding in vitro biocompatibility to be readily obtained.

  17. Preparing Magnetocaloric LaFeSi Uniform Microstructures by Spark Plasma Sintering

    DEFF Research Database (Denmark)

    Vicente, N.; Ocanã, J.; Neves Bez, Henrique

    2014-01-01

    Spark Plasma Sintering (SPS) of LaFeSi alloy powders was conducted to prepare magnetocaloric La-Fe-Si-based uniform microstructures. Two electrically insulating discs made of alumina were interposed between the punches and powder sample inhibiting the flow of electric current across the powder......’s microhardness by means of ANOVA statistics....

  18. High thermoelectric performance of reduced lanthanide molybdenum oxides densified by spark plasma sintering

    DEFF Research Database (Denmark)

    Xu, Jianxiao Jackie; Sonne, Monica; Yanangiya, Shun-ichi

    2010-01-01

    Four highly reduced molybdenum oxides LnMo8O14 (Ln = La, Ce, Nd and Sm) containing bicapped Mo8 clusters were synthesized via solid state reaction followed by spark plasma sintering. The thermoelectric properties were investigated, and NdMo8O14 exhibits the best performance with the maximum power...

  19. Spark plasma-sintered Sn-based intermetallic alloys and their Li-storage studies

    CSIR Research Space (South Africa)

    Nithyadharseni, P

    2016-06-01

    Full Text Available In the present study, SnSb, SnSb/Fe, SnSb/Co, and SnSb/Ni alloy powders processed by co-precipitation were subjected to spark plasma-sintering (SPS) at 400 °C for 5 min. The compacts were structurally and morphologically characterized by X...

  20. The phase analysis of spark plasma sintered MgB2 after ball milling.

    Science.gov (United States)

    Kang, Deuk-Kyun; Kim, Dong-Woong; Kim, Cheol-Jin; Ahn, In-Shup

    2010-01-01

    Mg and amorphous B powders below 10 and 3 micro meter were used as raw materials, and mixed by planetary-mill for 9 hours at argon atmosphere. MgB2 bulk was fabricated at the various temperatures by Spark Plasma Sintering. In the sintering process, mixed powders were sintered in graphite mold, at the pressure of 55 Mpa. The fabricated MgB2 samples were evaluated with XRD, EDS, FE-SEM, PPMS. MgB2, MgO and Fe phases were observed from XRD result. In the results, MgO and Fe were impurity which may affect superconducting properties of MgB2 samples, and it's distribution could be confirmed from EDS mapping result. In order to confirm the formation of MgB2 phase, DTA was used as heating rate of 10 degrees C/min at Ar atmosphere from room temperature to 1200 degrees C. In the PPMS result, the Tc (critical temperature) was about 21 K, and the density of spark plasma sintered samples increased to 1.87 g/cm3 by increasing sintering temperature.

  1. The Effect of Processing Parameters on the Performance of Spark Plasma Sintered cBN-WC-Co Composites

    Science.gov (United States)

    Mao, Cong; Zhang, Mingjun; Zhang, Jian; Tang, Kun; Gan, Hangyu; Zhang, Gaofeng

    2015-12-01

    Cubic boron nitride (cBN) particles were mixed into superfine tungsten carbide (WC), and then cBN-WC-cobalt (Co) composites were prepared using spark plasma sintering method. The influence of the processing parameters on the microstructures and the mechanical properties of the cBN-WC-Co composites were investigated. The results indicated that the cBN particles arranged uniformly and had an excellent adhesion with WC matrix. There was no evidence of phase transformation from cBN to hBN. With the increasing of the sintering temperature, the liquid-phase Co was increased and entered the micro-pores between WC and cBN particles easily. Correspondingly, the density, the flexural strength, and the hardness of the cBN-WC-Co composites also increased. With the further increasing of the sintering temperature, WC grains grew leading to the reduction of the hardness. Therefore, the hardness of the samples increased to a maximum value of 2978 HV at 1250 °C, and then decreased with the sintering temperature. The experimental results also showed that the density, the flexural strength, and the hardness of cBN-WC-Co composites increased with the holding time, whereas the hardness presented a decreasing tendency when the holding time exceeded 7 min.

  2. Mechanical characterization of cemented carbide WC-6Co (%wt) manufactured by SPS (Spark Plasma Sintering; Caracterizacao mecanica de metal duro WC-6Co (%massa) sinterizado via SPS (Spark Plasma Sintering)

    Energy Technology Data Exchange (ETDEWEB)

    Boidi, G.; Tertuliano, A.J.; Machado, I.F., E-mail: guido.boidi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Departamento de Engenharia Mecatronica e Sistemas Mecanicos; Rodrigues, D. [BRATS- Filtros Sinterizados e Pos Metalicos, Cajamar, SP (Brazil)

    2016-07-01

    This work aimed to manufacture cemented carbide (WC-6%wtCo) obtained by SPS (Spark Plasma Sintering) process and to carry out the mechanical characterization by hardness and fracture toughness. The material was consolidated at 1100 deg C for different holding times (1 min, 5 min, 10 min), in order to evaluate the densification. A reference sample was also used to be compared to SPS. Optical and scanning electron microscopy were carried out to characterize the microstructural features of the samples and mechanical properties were obtained by hardness measurements (micro and macro) and instrumented indentation. The fracture toughness was calculated with the method of Palmqvist. Best results were found in the material sintered by SPS for 10 minutes of holding time, in which 97% of relative density and about 1600 HV{sub 10} was reached. (author)

  3. The effect of temperature on the in situ synthesis–sintering and mechanical properties of MoSi{sub 2} prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kermani, Milad, E-mail: miladkermani.mk@gmail.com; Razavi, Mansour; Rahimipour, Mohammad Reza; Zakeri, Mohammad

    2014-02-05

    Highlights: • MoSi{sub 2} synthesized and sintered by using SPS. • Internal heat generation as the elemental powders react during sintering leads to an additional short high temperature excursion. • Effect of temperature and holding time on mechanical properties investigated. -- Abstract: In this research, dense MoSi{sub 2} was fabricated using of spark plasma sintering. Mo and Si powders according to MoSi{sub 2} stoichiometry ratio was mixed by a high energy ball mill for 1 h. The milled powders were compacted into green body by using 200 MPa uniaxial pressure. Then the samples were synthesized and sintered in one step by using spark plasma sintering apparatus at temperature from 1273 to 1573 K. X-ray diffraction results showed that at 1273 K there is no reaction between Mo and Si. By increasing temperature to 1373 K the reaction between Mo and Si was took place. Also, the effect of temperature and holding time on the in situ synthesis–sintering, density and mechanical properties was also investigated.

  4. Zirconium carbonitride pellets by internal sol gel and spark plasma sintering as inert matrix fuel material

    Science.gov (United States)

    Hedberg, Marcus; Cologna, Marco; Cambriani, Andrea; Somers, Joseph; Ekberg, Christian

    2016-10-01

    Inert matrix fuel is a fuel type where the fissile material is blended with a solid diluent material. In this work zirconium carbonitride microspheres have been produced by internal sol gel technique, followed by carbothermal reduction. Material nitride purities in the produced materials ranged from Zr(N0.45C0.55) to Zr(N0.74C0.26) as determined by X-ray diffraction and application of Vegard's law. The zirconium carbonitride microspheres have been pelletized by spark plasma sintering (SPS) and by conventional cold pressing and sintering. In all SPS experiments cohesive pellets were formed. Maximum final density reached by SPS at 1700 °C was 87% theoretical density (TD) compared to 53% TD in conventional sintering at 1700 °C. Pore sizes in all the produced pellets were in the μm scale and no density gradients could be observed by computer tomography.

  5. Activation of mass transfer processes at spark plasma sintering of zirconium dioxide

    Science.gov (United States)

    Akarachkin, S. A.; Ivashutenko, A. S.; Martyushev, N. V.

    2016-04-01

    The paper presents the results of numerical simulation of thermal and electric fields' distribution in the graphite moulding tool and in the sintered sample of ZrO2-4%Y2O3 in the course of spark plasma sintering (SPS). The reduction of SPS duration is accounted for the largeness of specific thermal flux towards the sample surface, emitted by the graphite moulding tool. The impact of the electric field on the sample structure leads to emergence of the polarizing processes forcing zirconium ions to shift from lattice sites, which is able to reduce the required value of thermal energy necessary for initiation of a diffusion process. The axial pressure at high temperatures of sintering can lead to plastic deformation of the powder particles.

  6. On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x

    Science.gov (United States)

    Tyrpekl, Vaclav; Naji, Mohamed; Holzhäuser, Michael; Freis, Daniel; Prieur, Damien; Martin, Philippe; Cremer, Bert; Murray-Farthing, Mairead; Cologna, Marco

    2017-04-01

    The electric field has a large effect on the stoichiometry and grain growth of UO2+x during Spark Plasma Sintering. UO2+x is gradually reduced to UO2.00 as a function of sintering temperature and time. A gradient in the oxidation state within the pellets is observed in intermediate conditions. The shape of the gradient depends unequivocally on the direction of the electrical field. The positive surface of the pellet shows a higher oxidation state compared to the negative one. An area with larger grain size is found close to the positive electrode, but not in contact with it. We interpret these findings with the redistribution of defects under an electric field, which affect the stoichiometry of UO2+x and thus the cation diffusivity. The results bear implications for understanding the electric field assisted sintering of UO2 and non-stoichiometric oxides in general.

  7. Microstructure and Thermoelectric Properties of Bulk Cobalt Antimonide (CoSb3) Skutterudites Obtained by Pulse Plasma Sintering

    Science.gov (United States)

    Kruszewski, M. J.; Zybała, R.; Ciupiński, Ł.; Chmielewski, M.; Adamczyk-Cieślak, B.; Michalski, A.; Rajska, M.; Kurzydłowski, K. J.

    2016-03-01

    The use of the pulse plasma sintering technique for CoSb3 thermoelectric material consolidation is reported in this work. The influence of sintering temperature on the microstructure and material properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity has been investigated. It is shown that, for samples fabricated at 923 K and 973 K, there were no significant differences in the average grain size or final phase composition. In both cases, a fine-grained polycrystalline structure of the compacts with density nearly equal to the theoretical value was achieved. Both samples were composed almost uniquely of CoSb3 phase. The measured thermoelectric parameters such as the Seebeck coefficient, electrical, and thermal conductivity showed similar dependence on temperature. For both samples, the Seebeck coefficient was negative at room temperature and showed a transition from n- to p-type conduction over the temperature range of 400 K to 460 K. The measured minimum thermal conductivity values, 4 W m-1 K-1 to 5 W m-1 K-1 at 723 K, are typical for undoped bulk CoSb3. A maximum ZT value of 0.08 at 623 K was obtained for the sample consolidated at 923 K for 5 min. The results of this work are very promising from the point of view of use of pulse plasma sintering as an alternative method for fabrication of a broad range of thermoelectric materials in the future.

  8. Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Roman-Manso, B.; Pablos, A. de; Belmonte, M.; Osendi, M. I.; Miranzo, P.

    2014-04-01

    Concentrated ceramic inks based on (SiC) powders, with different amounts of Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3} as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique. The densification of the as-produced 3D structures, previously heat treated in air at 600 degree centigrade for the organics burn-out, is achieved with a Spark Plasma Sintering (SPS) furnace. The effects of the amount of sintering additives (7 - 20 wt. %) and the size of the SiC powders (50 nm and 0.5 {mu}m) on the processing of the inks, microstructure, hardness and elastic modulus of the sintered scaffolds, are studied. The use of nano-sized (SiC) powders significantly restricts the attainable maximum solids volume fraction of the ink (0.32 compared to 0.44 of the submicron-sized powders-based ink), involving a much larger porosity of the green ceramic bodies. Furthermore, reduced amounts of additives improve the mechanical properties of the ceramic skeleton; particularly, the stiffness. The grain size and specific surface area of the starting powders, the ink solids content, green porosity, amount of sintering additives and SPS temperatures are the main parameters to be taken into account for the production of these SiC cellular ceramics. (Author)

  9. Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

    Directory of Open Access Journals (Sweden)

    Michalski B.

    2013-01-01

    Full Text Available In this study the SPS method was applied for low RE content (8,5% at. and high RE content (13,5 % at. MQ powders. The powders were sintered in a wide range of temperature, for 5 min., under pressure of 35 MPa. The low RE content grade, densified reluctantly and gained the density close to the theoretical value only for 850 °C. The coercivity decreased gradually with increasing sintering temperature. On the other hand, the densification of the higher RE content grade powder occurred much easier and the coercivity, close to the theoretical value, was achieved already at 650 °C. The coercivity of this material also decreased with increasing sintering temperature. Microstructural studies revealed that the SPS sintering process leads to partial decomposition of the Nd2Fe14B phase. The proportion of the RE-rich and iron phases increases parallel to the increasing sintering temperature. On the basis of the current results one can conclude that fabrication of high density MQ powders based magnets by the SPS method is possible, however the powders having higher RE content should be used for this purpose and the sintering temperature as low as possible, related to density, should be kept.

  10. Approximation of mechanical properties of sintered materials with discrete element method

    Science.gov (United States)

    Dosta, Maksym; Besler, Robert; Ziehdorn, Christian; Janßen, Rolf; Heinrich, Stefan

    2017-06-01

    Sintering process is a key step in ceramic processing, which has strong influence on quality of final product. The final shape, microstructure and mechanical properties, e.g. density, heat conductivity, strength and hardness are depending on the sintering process. In order to characterize mechanical properties of sintered materials, in this contribution we present a microscale modelling approach. This approach consists of three different stages: simulation of the sintering process, transition to final structure and modelling of mechanical behaviour of sintered material with discrete element method (DEM). To validate the proposed simulation approach and to investigate products with varied internal structures alumina powder has been experimentally sintered at different temperatures. The comparison has shown that simulation results are in a very good agreement with experimental data and that the novel strategy can be effectively used for modelling of sintering process.

  11. Observation of Curie transition during spark plasma sintering of ferromagnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar Mani, Mahesh [Wolfson Centre for Magnetics, Cardiff School of Engineering, Cardiff University (United Kingdom); Viola, Giuseppe [School of Engineering and Materials Science, Queen Mary University of London (United Kingdom); Nanoforce Technology Ltd., London (United Kingdom); Hall, Jeremy P. [Wolfson Centre for Magnetics, Cardiff School of Engineering, Cardiff University (United Kingdom); Grasso, Salvatore; Reece, Mike J. [School of Engineering and Materials Science, Queen Mary University of London (United Kingdom); Nanoforce Technology Ltd., London (United Kingdom)

    2015-05-15

    The possibility of employing the ferromagnetic–paramagnetic phase transitions of magnetic materials to calibrate temperature during spark plasma sintering (SPS) was investigated using pure Fe and Fe–50Co alloy. A sharp and repeatable change was observed in the electrical current profile at the Curie temperature (T{sub c}) during both sintering and reheating of the sintered samples. Under a pulsed DC current, an abrupt change in the electrical resistance was observed at T{sub c} due to the sudden changes in the permeability and in turn, the skin depth during heating and cooling. These effects can be used to obtain a more accurate in-situ measurement of the sample temperature than the one provided by the pyrometers that are normally used for SPS processing. The temperature measured using a pyrometer was found to be significantly lower (up to 70 °C) than the actual temperature of the specimen. - Highlights: • Calibration of temperature during spark plasma sintering (SPS) remains a big challenge. • Temperature measured by non-contact pyrometers in SPS is not accurate. • Ferromagnetic materials exhibit abrupt change in permeability at Curie temperature (T{sub c}). • Iron and Fe–Co alloy showed sharp and reproducible changes in SPS electric current profiles at T{sub c}. • Ferromagnetic materials can be successfully used to calibrate pyrometers in SPS.

  12. Nanocompósitos de Al2O3-SiC sinterizados por "spark plasma sintering" (SPS) Al2O3-SiC nanocomposites sintered by spark plasma sintering

    OpenAIRE

    Trombini,V.; Pallone,E. M. J. A.; Munir, Z.A.; Tomasi, R.

    2008-01-01

    O nanocompósito (alumina-carbeto de silício) vem sendo estudado extensivamente em função do resultados promissores encontrados quanto a propriedades mecâncias. Usualmente o processamento desse material envolve um alto custo, pois para a obtenção de materiais densos é necessária a utilização de prensagem a quente. Uma alternativa mais recente para a sinterização de cerâmicas nanocristalinas é a sinterização por plasma (Spark Plasma Sintering - SPS). Nesse trabalho, pós de alumina contendo 5%vo...

  13. Suppressing pore-boundary separation during spark plasma sintering of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jing; Zhang, Junzhan [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden); Liu, Wei [School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China); Shen, Zhijian, E-mail: shen@mmk.su.se [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden); School of Materials Science and Engineering, Tsinghua University, 100084 Beijing (China)

    2013-07-15

    A tungsten powder with bimodal particle size distribution is consolidated by spark plasma sintering (SPS). Effects are made for understanding the densification and grain growth mechanisms and their relations to the SPS processing parameters. By holding the sample at an intermediate temperature, i.e., 1200 °C for 5 min, where the densification is enhanced by particle close packing, the pore-boundary separation that yields the formation of entrapped pores inside individual grains at final stage of sintering is suppressed. This optimization of the SPS process is beneficial for preparing fine grained bulk tungsten with homogeneous microstructure from the powders produced in industrial-scale. The prepared tungsten with minimized porosity appears a potential candidate for plasma-facing materials in the divertor region in the International Thermonuclear Experimental Reactor (ITER)

  14. Heat treatment process of new NdFeB magnet prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    李涛; 岳明; 张久兴; 王公平; 肖耀福; 王润

    2003-01-01

    In recent years, spark plasma sintering technique(SPS) has been a focus in the field of material preparation due to its advantages. SPS technique is first introduced for preparation of high quality NdFeB magnets. The effects of heat treatment process on the magnetic properties of SPS NdFeB magnet were investigated. Meanwhile, the effects of heat treatment process on the microstructure, tropism and dimensional precision of the SPS NdFeB magnets were also studied. The high quality NdFeB magnets with fine grains were prepared under proper heat treatment process. The results show that the magnetic properties of SPS NdFeB can be further improved through proper heat treatment process. Meanwhile, the experiment also demonstrates that it is feasible to prepare near-net-shape NdFeB magnets with fine grains and high magnetic property by spark plasma sintering.

  15. Spark Plasma Sintering and Multi-scale Characterization of Mesoporous Silica Disks

    Science.gov (United States)

    Maheshwari, Harsh

    Oil from shale and tight formations has helped the United States produce close to 10 million barrels of oil per day, a 40-year high. Well characterized sintered nano materials will serve as calibration materials for understanding important thermodynamic and flow properties of fluids in similar formations. To this effect, sintered mesoporous silica monoliths containing micro- and nano-porosity are characterized across multiple length scales at various processing temperatures using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers hardness tests, and Brunauer-Emmett-Teller (BET) gas adsorption measurements. Results show that the mesoporosity in raw SBA-15 silica powders can be retained during spark-plasma sintering (SPS) up to 850 ºC which is lower than those achieved by conventional sintering techniques (>1050 ºC). Details of micro- and meso-porosity were revealed by studying the internal structure through SEM and in-situ TEM tomography of the sintered specimens in comparison to the pristine silica powder. The microporosity is retained up to 950°C under the same pressure, and the degree of microporosity increases when the mesopores collapse due to individual nanoparticle shrinkage. In situ TEM characterization of mesoporosity in the absence of applied pressure reveal pore collapse above 1050°C, which is considerably above the temperatures observed under applied pressures during SPS processing. The degree of microporosity, obtained under different processing conditions, is correlated to the mechanical properties, available surface area and pore morphology. In spite of the unique synthesis process, sintered mesoporous silica satisfies the Ryshkewitch relationship -- the correlation of mechanical properties to porosity. Subsequently, in-situ TEM nanoindentation was conducted to investigate the mechanical properties of individual mesoporous silica nanoparticles. The ability to control the micro- and meso-porosity of these

  16. Structure and properties of nanocrystalline rare earth bulks prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    卢年端; 宋晓艳; 刘雪梅; 张久兴

    2009-01-01

    A series of rare earth bulks with the ultrafine nanocrystalline structure were prepared by applying an "oxygen-free" (an environmental oxygen concentration less than 0.5 ppm) in-situ synthesis system, where the inert-gas condensation was combined with the spark plasma sintering technology into an entirely closed system. The thermal and mechanical properties of the prepared ultrafine nanocrystalline bulks were characterized and compared with those of the raw polycrystalline bulks. It was found that the speci...

  17. Microstructural and Mechanical Characterization of Ti-12Mo-6Zr Biomaterials Fabricated by Spark Plasma Sintering

    Science.gov (United States)

    Daoush, Walid Mohamed Rashad Mohamed; Park, Hee Sup; Inam, Fawad; Lim, Byung Kyu; Hong, Soon Hyung

    2015-03-01

    Ti-12Mo-6Zr/Al2O3 (titanium biomaterial) was prepared by a powder metallurgy route using Spark Plasma Sintering (SPS). Ti, Mo, and Zr powders were mixed by wet milling with different content of alumina nanoparticles (up to 5 wt pct) as an oxide dispersion strengthening phase. Composite powder mixtures were SPSed at 1273 K (1000 °C) followed by heat treatment and quenching. Composite powders, sintered materials, and heat-treated materials were examined using optical and high-resolution electronic microscopy (scanning and transmission) and X-ray diffraction to characterize particle size, surface morphology, and phase identifications for each composition. All sintered materials were evaluated by measuring density, Vickers hardness, and tensile properties. Fully dense sintered materials were produced by SPS and mechanical properties were found to be improved by subsequent heat treatment. The tensile properties as well as the hardness were increased by increasing the content of Al2O3 nanoparticles in the Ti-12Mo-6Zr matrix.

  18. Mechanical properties of high dense coal fly-ash bulk materials by plasma spark sintering (SPS)

    Energy Technology Data Exchange (ETDEWEB)

    Kaneko, G.; Hasezaki, K.; Nakashita, A.; Kakuda, H. [Shimane University, Shimane (Japan). Dept. of Material Science

    2008-10-15

    Coal fly-ash bulk materials were prepared by spark plasma sintering (SPS). The as-received coal fly ash produced by Misumi Power Station (The Chugoku Electric Power Co. Inc.), had an average particle size of 19 mm and contained about 2% carbon from unburned coal. The sintering temperature was 1273 K for 10 min. The mass density of the sintered compact was 2.4 x 103 kg/m{sup 3}. After three-point flexural testing of the compact, the average flexural strength and Young's modulus were 25.6 MPa and 23.0 GPa, respectively. From the flexural strength, the Weibull modulus was found to be m = 6.13, indicating that the compact was a typical ceramics. Fractographic examination indicated that in all specimens the fracture origin was located on the bottom surface and was not an intrinsic flaw. Vickers indentation test showed that the fracture toughness was 0.61 MPa.m{sup 0.5} and the calculated critical flaw size c{sub 0}, was 0.18 mm. This c{sub 0} value was larger than that of the voids and the unburned carbon at the fracture surface. It is noteworthy that the mechanical strength of the sintered compact was not affected by the voids and unburned carbon.

  19. Nanostructured Al-ZrAl{sub 3} materials consolidated via spark plasma sintering: Evaluation of their mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, C.; Belzunce, F.J.; Betegon, C. [Escuela Politecnica de Ingenieria (University of Oviedo), Campus Universitario, 33203 Gijon (Spain); Goyos, L. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN-CSIC-UNIOVI-PA), Consejo Superior de Investigaciones Cientificas-Universidad de Oviedo-Principado de Asturias, Parque Tecnologico de Asturias, Llanera (Spain); Diaz, L.A., E-mail: la.diaz@cinn.es [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN-CSIC-UNIOVI-PA), Consejo Superior de Investigaciones Cientificas-Universidad de Oviedo-Principado de Asturias, Parque Tecnologico de Asturias, Llanera (Spain); Torrecillas, R. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN-CSIC-UNIOVI-PA), Consejo Superior de Investigaciones Cientificas-Universidad de Oviedo-Principado de Asturias, Parque Tecnologico de Asturias, Llanera (Spain)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer A surface modification of aluminium powders was carried out by means of a colloidal process. Black-Right-Pointing-Pointer These powders were consolidated and sintered by spark plasma sintering. Black-Right-Pointing-Pointer Regarding the dwell time at the sintering temperature (625 Degree-Sign C), ZrAl{sub 3} intermetallic crystallizes. Black-Right-Pointing-Pointer The mechanical behaviour of this reinforcement was evaluated by Small Punch Test. - Abstract: Aluminium based nanostructured materials with additions of 0.5, 1 and 1.5 wt.% of zirconium have been produced and sintered using the spark plasma sintering technique in order to promote the nucleation of ZrAl{sub 3} platelets. The mechanical behaviour of all these nanocomposites was determined by means of the Small Punch Test. Zirconium additions significantly decrease the mechanical properties of these products when sintering time at the sintering temperature (625 Degree-Sign C) is short (3 min). Nevertheless, when the sintering time increases to 1 h (intermetallic crystallization), the zirconium additions show the expected effect: the stiffness and the yield strength increase while ductility and toughness decrease. The maximum load increases until a 0.5 wt.% Zr is attained and suddenly drops when the Zr content surpasses 1 wt.%.

  20. Plasma debinding and pre-sintering of injected parts

    Directory of Open Access Journals (Sweden)

    Santos Maria Antônia dos

    2004-01-01

    Full Text Available Results of polypropylene removal in injected metallic parts by using plasma technology are presented. The samples were injected with 55.18% Vol. of unalloyed iron powder, 23.57% Vol. of paraffin and 21.25% Vol. of polypropylene. The paraffin was previously removed in hexane bath, followed by a treatment in abnormal glow discharge of argon and hydrogen for the removal of the polypropylene. The electric discharge was generated in two configurations: a confined anode-cathode with the samples placed on the anode and a confined grid (anode-cathode system with the sample placed on a holder at floating potential inside the grid. In the first geometry, electrons bombarded the sample surface, while in the second, they are collected by the grid. The samples were characterized by mass loss measurements and scanning electron microscopy. The results showed that the hydrogen discharge was more efficient for both configurations, which is attributed to the high reactivity of hydrogen atoms produced in the discharge. In addition, when plasma debinding was performed at 400 ºC for 10 min, by using the confined anode-cathode configuration, the polypropylene removal was total, while in the confined grid (anode-cathode geometry the removal was approximately 32%. The higher polypropylene removing observed in the anode-cathode configuration is attributed to electron bombardment of the surface of the sample.

  1. 78 FR 42974 - Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same...

    Science.gov (United States)

    2013-07-18

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same... the sale within the United States after importation of certain sintered rare earth magnets, methods...

  2. Indentation strength of silicon nitride ceramics processed by spark plasma sintering technique

    Energy Technology Data Exchange (ETDEWEB)

    Azeggagh, N. [Université de Lyon, INSA-Lyon, LaMCoS CNRS UMR5259, F-69621 Villeurbanne (France); Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Tohoku University, 6-6-11, Aza-Aoba, Aramaki, Aobaku, Sendai 980-8579 (Japan); Joly-Pottuz, L., E-mail: lucile.joly-pottuz@insa-lyon.fr [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Chevalier, J. [Université de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, F-69621 Villeurbanne (France); Omori, M.; Hashida, T. [Tohoku University, 6-6-11, Aza-Aoba, Aramaki, Aobaku, Sendai 980-8579 (Japan); Nélias, D. [Université de Lyon, INSA-Lyon, LaMCoS CNRS UMR5259, F-69621 Villeurbanne (France)

    2015-09-17

    We investigated the influence of the microstructure on the true stress–strain curve of silicon nitride based ceramics. The materials were processed by spark plasma sintering technique. Si{sub 3}N{sub 4} with fine, average and coarse microstructures were obtained. Load versus displacement curves (P–h) were obtained by means of instrumented indentation technique using diamond coni-spherical tip. The experimental data were coupled with a minimization method based on the Levenberg–Marquardt algorithm and the non-linear part of the mechanical response was identified. Based on the obtained stress–strain curves, rolling contact simulations were performed. In addition, the nature of Hertzian contact damage was examined in the material with coarse microstructure using diamond indenters of radii 0.2 and 1 mm. The surface damage was observed under optical microscopy while Focused Ion Beam Sectioning technique permitted to image the subsurface damage. An evident size effect was noticed: fracture consisting of classical ring cracks dominated at large scale while distributed microcracks beneath the indent dominated at small scale.

  3. Severe reduction of Ni–Zn ferrites during consolidation by Spark Plasma Sintering (SPS)

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, Raul, E-mail: monjaras@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Gaudisson, Thomas; Ammar, Souad [ITODYS, Université Paris-Diderot, PRES Sorbonne Paris Cité, CNRS-UMR-7086, 75205 Paris (France)

    2016-02-15

    NiZn ferrites of composition Zn{sub 0.7}Ni{sub 0.3}Fe{sub 2}O{sub 4} were synthesized by the polyol method and subsequently consolidated into fine grain, high density ceramics by means of Spark Plasma Sintering at 600 °C for 10 min, under vacuum and applying a uniaxial pressure of 80 MPa. Their saturation magnetization at room temperature exhibited a value far larger (~71 emu/g) than the value corresponding to the bulk ferrite (~50 emu/g), and their Curie point showed also an increase of about 210 K, as compared with the bulk value. These results, together with the presence of a small amount of metallic Ni, are interpreted in terms of a departure of Ni from the spinel phase and an associated reduction of ferric to ferrous cations to compensate for Ni loss. - Highlights: • Nanostructured ferrites are obtained at 600°C by 10 min. • Magnetic properties change significantly. • These changes are due to reductive conditions in SPS. • Metallic Ni precipitated from the spinel and are replaced by ferrous ions. • This leads to an increase in Ms and Tc.

  4. Localized Overheating Phenomena and Optimization of Spark-Plasma Sintering Tooling Design

    Directory of Open Access Journals (Sweden)

    Darold G. Martin

    2013-06-01

    Full Text Available The present paper shows the application of a three-dimensional coupled electrical, thermal, mechanical finite element macro-scale modeling framework of Spark Plasma Sintering (SPS to an actual problem of SPS tooling overheating, encountered during SPS experimentation. The overheating phenomenon is analyzed by varying the geometry of the tooling that exhibits the problem, namely by modeling various tooling configurations involving sequences of disk-shape spacers with step-wise increasing radii. The analysis is conducted by means of finite element simulations, intended to obtain temperature spatial distributions in the graphite press-forms, including punches, dies, and spacers; to identify the temperature peaks and their respective timing, and to propose a more suitable SPS tooling configuration with the avoidance of the overheating as a final aim. Electric currents-based Joule heating, heat transfer, mechanical conditions, and densification are imbedded in the model, utilizing the finite-element software COMSOL™, which possesses a distinguishing ability of coupling multiple physics. Thereby the implementation of a finite element method applicable to a broad range of SPS procedures is carried out, together with the more specific optimization of the SPS tooling design when dealing with excessive heating phenomena.

  5. Synthesis of dense yttrium-stabilised hafnia pellets for nuclear applications by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Tyrpekl, Vaclav, E-mail: vaclav.tyrpekl@ec.europa.eu [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Holzhäuser, Michael; Hein, Herwin; Vigier, Jean-Francois; Somers, Joseph [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Svora, Petr [Institute of Inorganic Chemistry AS CR, v.v.i, Husinec-Rez 1001, 250 68 Rez (Czech Republic)

    2014-11-15

    Graphical abstract: Densification of HfO{sub 2}–Y{sub 2}O{sub 3} micro-beads by Spark Plasma Sintering High density pellets with homogenous distribution of Hf and Y serve as neutron absorbers. - Abstract: Dense yttrium–stabilised hafnia pellets (91.35 wt.% HfO{sub 2} and 8.65 wt.% Y{sub 2}O{sub 3}) were prepared by spark plasma sintering consolidation of micro-beads synthesised by the “external gelation” sol–gel technique. This technique allows a preparation of HfO{sub 2}–Y{sub 2}O{sub 3} beads with homogenous yttria–hafnia solid solution. A sintering time of 5 min at 1600 °C was sufficient to produce high density pellets (over 90% of the theoretical density) with significant reproducibility. The pellets have been machined in a lathe to the correct dimensions for use as neutron absorbers in an experimental test irradiation in the High Flux Reactor (HFR) in Petten, Holland, in order to investigate the safety of americium based nuclear fuels.

  6. Properties of sintered glass-ceramics prepared from plasma vitrified air pollution control residues.

    Science.gov (United States)

    Roether, J A; Daniel, D J; Rani, D Amutha; Deegan, D E; Cheeseman, C R; Boccaccini, A R

    2010-01-15

    Air pollution control (APC) residues, obtained from a major UK energy from waste (EfW) plant, processing municipal solid waste, have been blended with silica and alumina and melted using DC plasma arc technology. The glass produced was crushed, milled, uni-axially pressed and sintered at temperatures between 750 and 1150 degrees C, and the glass-ceramics formed were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties assessed included Vickers's hardness, flexural strength, Young's modulus and thermal shock resistance. The optimum sintering temperature was found to be 950 degrees C. This produced a glass-ceramic with high density (approximately 2.58 g/cm(3)), minimum water absorption (approximately 2%) and relatively high mechanical strength (approximately 81+/-4 MPa). Thermal shock testing showed that 950 degrees C sintered samples could withstand a 700 degrees C quench in water without micro-cracking. The research demonstrates that glass-ceramics can be readily formed from DC plasma treated APC residues and that these have comparable properties to marble and porcelain. This novel approach represents a technically and commercially viable treatment option for APC residues that allow the beneficial reuse of this problematic waste.

  7. Dynamic Fracture Toughness of TaC/CNTs/SiC CMCs Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Qiaoyun Xie

    2015-01-01

    Full Text Available This study focuses on the fracture toughness of TaC and carbon nanotubes (CNTs reinforced SiC ceramic matrix composites (CMCs, prepared by spark plasma sintering (SPS technique. A high densification of 98.4% was achieved under the sintering parameter of 133°C/min, 1800°C, and 90 MPa pressure. Vickers indentation was employed to measure the indentation toughness on the polished surface of ceramic samples, SEM was applied to directly observe the crack propagation after indentation, and split Hopkinson pressure bar (SHPB was developed to determine the dynamic fracture toughness within the ceramic samples subjected to an impact in a three-point bending configuration.

  8. Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Wen-ming Tian; Song-mei Li; Bo Wang; Xin Chen; Jian-hua Liu; Mei Yu

    2016-01-01

    Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sinter-ing (SPS). The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide (Al4C3) is not formed during SPS processing. Further addition of graphene (above 1wt%) results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

  9. Spark Plasma Sintering of Low Alloy Steel Modified with Silicon Carbide

    Directory of Open Access Journals (Sweden)

    Hebda M.

    2016-06-01

    Full Text Available The influence of adding different amounts of silicon carbide on the properties (density, transverse rupture strength, microhardness and corrosion resistance and microstructure of low alloy steel was investigated. Samples were prepared by mechanical alloying (MA process and sintered by spark plasma sintering (SPS technique. After the SPS process, half of each of obtained samples was heat-treated in a vacuum furnace. The results show that the high-density materials have been achieved. Homogeneous and fine microstructure was obtained. The heat treatment that followed the SPS process resulted in an increase in the mechanical and plastic properties of samples with the addition 1wt. % of silicon carbide. The investigated compositions containing 1 wt.% of SiC had better corrosion resistance than samples with 3 wt.% of silicon carbide addition. Moreover, corrosion resistance of the samples with 1 wt.% of SiC can further be improved by applying heat treatment.

  10. Ultrafine WC-Ni cemented carbides fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rong Huiyong [School of Engineering and Technology, China University of Geosciences at Beijing, Beijing 100083 (China); Peng Zhijian, E-mail: pengzhijian@cugb.edu.cn [School of Engineering and Technology, China University of Geosciences at Beijing, Beijing 100083 (China); Ren Xiaoyong; Peng Ying; Wang Chengbiao; Fu Zhiqiang [School of Engineering and Technology, China University of Geosciences at Beijing, Beijing 100083 (China); Qi Longhao; Miao Hezhuo [State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Ultrafine WC-Ni cemented carbides with average WC grain size of about 330 nm prepared by combination of sparking plasma sintering and grain growth inhibitors. Black-Right-Pointing-Pointer Very short mean free path of about 22 nm for crack in metal binder of the obtained materials. Black-Right-Pointing-Pointer Higher hardness than those of WC-Co cemented carbide counterparts sintered by rapid sintering. Black-Right-Pointing-Pointer Observation of fracture along metal binder and no carbon-carbon fracture face. - Abstract: With VC and TaC as WC grain growth inhibitors, ultrafine WC-Ni cemented carbides with different fractions (6-10 wt%) of binder metal nickel were fabricated by utilizing high energy milling together with spark plasma sintering. In the obtained samples, only WC and Ni phases were detected in X-ray diffraction limit. The microstructure of the specimens was examined on fractural, polished, and polished/etched surfaces by scanning electron microscopy, and the results revealed that the average WC grain size of the WC-Ni cemented carbides was about 330 nm, and there were lots of micro-pores in the samples. The relative density of the samples was all higher than 92%. But the measurement of hardness and flexural strength indicated that the existence of micro-pores had no significant influence on the performance of the obtained materials. On the basis of observation on the micro-fracture surface of the samples, it was found that fractures occurred along the binder metal, and the obtained ultrafine WC-Ni cemented carbides showed a very short binder mean free path (about 22 nm), thus resulting in excellent performance in mechanical strength.

  11. The Influence of Spark Plasma Sintering Temperature on the Microstructure and Thermoelectric Properties of Al,Ga Dual-Doped ZnO

    DEFF Research Database (Denmark)

    Han, Li; Le, Thanh Hung; Van Nong, Ngo

    2013-01-01

    ZnO dual-doped with Al and Ga was prepared by spark plasma sintering using different sintering temperatures. The microstructural evolution and thermoelectric properties of the samples were investigated in detail. The samples obtained with sintering temperature above 1223 K had higher relative...

  12. The Influence of Spark Plasma Sintering Temperature on the Microstructure and the Thermoelectric Properties of Al, Ga dually-doped ZnO

    DEFF Research Database (Denmark)

    Han, Li; Le, Thanh Hung; Van Nong, Ngo;

    2012-01-01

    Al, Ga dually-doped ZnO was prepared by spark plasma sintering with different sintering temperatures. The microstructural evolution and thermoelectric properties of the samples were investigated in detail. The samples with a sintering temperature above 1223K obtained higher relative densities...... and better electrical properties compared with the sample sintered at 1073K. These results were supported by solid-state-reaction completion rate which suggested that the sintering temperature above 1223K would be preferable for the complete solid state reaction of the samples. The sintering mechanism of ZnO...

  13. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    Science.gov (United States)

    Watanabe, Yoshimi; Shibuya, Masafumi; Sato, Hisashi

    2013-03-01

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  14. Prediction of heating rate controlled viscous flow activation energy during spark plasma sintering of amorphous alloy powders

    Science.gov (United States)

    Paul, Tanaji; Harimkar, Sandip P.

    2017-07-01

    The viscous flow behavior of Fe-based amorphous alloy powder during isochronal spark plasma sintering was analyzed under the integrated theoretical background of the Arrhenius and directional structural relaxation models. A relationship between viscous flow activation energy and heating rate was derived. An extension of the pertinent analysis to Ti-based amorphous alloys confirmed the broad applicability of such a relationship for predicting the activation energy for sintering below the glass transition temperature (T g) of the amorphous alloy powders.

  15. Formation of High Temperature Compounds in W-C-B System by Reactive Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Janis Grabis

    2015-09-01

    Full Text Available The formation of high temperature composites in W-C-Bsystem from fine-grained powders in dependence on the ratio of components byusing reactive spark plasma sintering was studied. The mixture of W2Cand C nanoparticles was used as tungsten and carbon precursors. The W2Cand carbon mixture with different ratio of components was prepared by reductionof WO3 in presence of CH4 in nitrogen inductively coupledplasma. The specific surface area of the mixture was in the range of 36–42 m2/gin dependence on the content of carbon. The W2C and carbon particleswere mixed mechanically with amorphous boron and densified using the sparkplasma sintering technique at 1500–1700 oC and pressure of 30 MPafor 4 minutes. The sintered bodies contained WB2 and B4Cphases. The ratio of phase depends on the content of the components in the rawmixture.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7352

  16. Ceramic-intermetallic composites produced by mechanical alloying and spark plasma sintering

    CERN Document Server

    Cabanas-Moreno, J G; Martínez-Sanchez, R; Delgado-Gutierrez, O; Palacios-Gomez, J; Umemoto, M

    1998-01-01

    Nano-and microcomposites of intermetallic (Co/sub 3/Ti, AlCo/sub 2 /Ti) and ceramic (TiN, Ti(C, N), Al/sub 2/O/sub 3/) phases have been produced by spark plasma sintering (SPS) of powders resulting from mechanical alloying of Al-Co-Ti elemental powder mixtures. The mechanically alloyed powders consisted of mixtures of nanocrystalline and amorphous phases which, on sintering, transformed into complex microstructures of the intermetallic and ceramic phases. For Al contents lower than about 30 at% in the original powder mixtures, the use of SPS led to porosities of 1-2% in the sintered compacts and hardness values as high as ~1700 kg/mm/sup 2/; in these cases, the composite matrix was TiN and Ti(C, N), with the Al/sub 2/O/sub 3/ phase found as finely dispersed particles in the matrix and the Co /sub 3/Ti and AlCo/sub 2/Ti phases as interdispersed grains. (19 refs).

  17. 77 FR 51046 - Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same; Notice...

    Science.gov (United States)

    2012-08-23

    ... COMMISSION Certain Sintered Rare Earth Magnets, Methods of Making Same and Products Containing Same; Notice... Trade Commission has received a complaint entitled Certain Sintered Rare Earth Magnets, Methods of... United States after importation of certain sintered rare earth magnets, methods of making same...

  18. Surprising synthesis of nanodiamond from single-walled carbon nanotubes by the spark plasma sintering process

    Science.gov (United States)

    Mirzaei, Ali; Ham, Heon; Na, Han Gil; Kwon, Yong Jung; Kang, Sung Yong; Choi, Myung Sik; Bang, Jae Hoon; Park, No-Hyung; Kang, Inpil; Kim, Hyoun Woo

    2016-10-01

    Nanodiamond (ND) was successfully synthesized using single-walled carbon nanotubes (SWCNTs) as a pure solid carbon source by means of a spark plasma sintering process. Raman spectra and X-ray diffraction patterns revealed the generation of the cubic diamond phase by means of the SPS process. Lattice-resolved TEM images confirmed that diamond nanoparticles with a diameter of about ˜10 nm existed in the products. The NDs were generated mainly through the gas-phase nucleation of carbon atoms evaporated from the SWCNTs. [Figure not available: see fulltext.

  19. Microstructure and mechanical properties of ZrO2 (Y2O3)-Al2O3 nanocomposites prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Shufeng Li; Hiroshi Izui; Michiharu Okano; Weihua Zhang; Taku Watanabe

    2012-01-01

    Zirconia (yttria)-alumina ceramic nanocomposites were fabricated from different powders by spark plasma sintering (SPS).One powder was a commercially available nanocomposite powder TZP-3Y2OA,consisting of 3 mol% yttria-stabilized zirconia (3-YSZ) reinforced with 20 wt% alumina,and the other,used as a comparison,was a conventional mechanically mixed powder 3YSZ-20A,a blend made of 3 mol% yttria-stabilized zirconia powder ZrO2 (3Y) and 20 wt% α-alumina powder.The effect of the sintering temperature on the densification,the sintering behavior,the mechanical properties and the microstructure of the composites was investigated.The results showed that the density increased with increasing sintering temperature,and thus,the mechanical properties were strengthened because of the increased densification.The nanocomposite powder TZP-3Y20A was easily sintered,and good mechanical properties were achieved as compared with the powder from the conventional mechanically mixed method,the maximum flexural strength and fracture toughness of which were 967 MPa and 5.27 MPa m1/2,respectively.

  20. Spark plasma sintering synthesis of porous nanocrystalline titanium alloys for biomedical applications.

    Science.gov (United States)

    Nicula, R; Lüthen, F; Stir, M; Nebe, B; Burkel, E

    2007-11-01

    The reason for the extended use of titanium and its alloys as implant biomaterials stems from their lower elastic modulus, their superior biocompatibility and improved corrosion resistance compared to the more conventional stainless steel and cobalt-based alloys [Niinomi, M., Hattori, T., Niwa, S., 2004. Material characteristics and biocompatibility of low rigidity titanium alloys for biomedical applications. In: Jaszemski, M.J., Trantolo, D.J., Lewandrowski, K.U., Hasirci, V., Altobelli, D.E., Wise, D.L. (Eds.), Biomaterials in Orthopedics. Marcel Dekker Inc., New York, pp. 41-62]. Nanostructured titanium-based biomaterials with tailored porosity are important for cell-adhesion, viability, differentiation and growth. Newer technologies like foaming or low-density core processing were recently used for the surface modification of titanium alloy implant bodies to stimulate bone in-growth and improve osseointegration and cell-adhesion, which in turn play a key role in the acceptance of the implants. We here report preliminary results concerning the synthesis of mesoporous titanium alloy bodies by spark plasma sintering. Nanocrystalline cp Ti, Ti-6Al-4V, Ti-Al-V-Cr and Ti-Mn-V-Cr-Al alloy powders were prepared by high-energy wet-milling and sintered to either full-density (cp Ti, Ti-Al-V) or uniform porous (Ti-Al-V-Cr, Ti-Mn-V-Cr-Al) bulk specimens by field-assisted spark plasma sintering (FAST/SPS). Cellular interactions with the porous titanium alloy surfaces were tested with osteoblast-like human MG-63 cells. Cell morphology was investigated by scanning electron microscopy (SEM). The SEM analysis results were correlated with the alloy chemistry and the topographic features of the surface, namely porosity and roughness.

  1. Simulation of coagulation and sintering of nano-structured particles using the moment method.

    Science.gov (United States)

    Park, Young-Kwon; Jung, Sang-Chul; Park, Sung Hoon

    2011-02-01

    In this study, a new method of simulating sintering of nano-structured particles in the frame of the moment method was developed. Simultaneous coagulation and sintering was simulated using the developed method and the results were compared with a more accurate numerical model. Good agreement was obtained between the model outputs while the new model was shown to be much more time-efficient.

  2. Development of low-power loss Mn–Zn ferrites using microwave sintering method

    Indian Academy of Sciences (India)

    S R Murthy

    2003-08-01

    Microwave sintering (MS) method has been successfully used for densifying Mn–Zn ferrites used for high frequency applications. This method needs only a short time to obtain high density when compared to conventionally sintered (CS) Mn–Zn ferrites. The lowest power loss was also achieved at 100 kHz and 200 mT condition for the microwave sintered samples. Conductor-embedded ferrite transformers were constructed using CS and MS samples and output power, efficiency, and surface rise of temperature were measured at sinusoidal voltage of 25 V with frequency, 1 MHz. The efficiency and surface rise of temperature of transformer were found to be high and low, respectively.

  3. Nanoclay/Polymer Composite Powders for Use in Laser Sintering Applications: Effects of Nanoclay Plasma Treatment

    Science.gov (United States)

    Almansoori, Alaa; Majewski, Candice; Rodenburg, Cornelia

    2017-06-01

    Plasma-etched nanoclay-reinforced Polyamide 12 (PA12) powder is prepared with its intended use in selective laser sintering (LS) applications. To replicate the LS process we present a downward heat sintering (DHS) process, carried out in a hot press, to fabricate tensile test specimens from the composite powders. The DHS parameters are optimized through hot stage microscopy, which reveal that the etched clay (EC)-based PA12 (EC/PA12) nanocomposite powder melts at a temperature 2°C higher than that of neat PA12, and 1-3°C lower than that of the nonetched clay-based nanocompsite (NEC/PA12 composite). We show that these temperature differences are critical to successful LS. The distribution of EC and NEC onto PA12 is investigated by scanning electron microscopy (SEM). SEM images show clearly that the plasma treatment prevents the micron-scale aggregation of the nanoclay, resulting in an improved elastic modulus of EC/PA12 when compared with neat PA12 and NEC/PA12. Moreover, the reduction in elongation at break for EC/PA12 is less pronounced than for NEC/PA12.

  4. A Modified Porous Titanium Sheet Prepared by Plasma-Activated Sintering for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Yukimichi Tamaki

    2010-01-01

    Full Text Available This study aimed to develop a contamination-free porous titanium scaffold by a plasma-activated sintering within an originally developed TiN-coated graphite mold. The surface of porous titanium sheet with or without a coated graphite mold was characterized. The cell adhesion property of porous titanium sheet was also evaluated in this study. The peak of TiC was detected on the titanium sheet processed with the graphite mold without a TiN coating. Since the titanium fiber elements were directly in contact with the carbon graphite mold during processing, surface contamination was unavoidable event in this condition. The TiC peak was not detectable on the titanium sheet processed within the TiN-coated carbon graphite mold. This modified plasma-activated sintering with the TiN-coated graphite mold would be useful to fabricate a contamination-free titanium sheet. The number of adherent cells on the modified titanium sheet was greater than that of the bare titanium plate. Stress fiber formation and the extension of the cells were observed on the titanium sheets. This modified titanium sheet is expected to be a new tissue engineering material in orthopedic bone repair.

  5. Biocompatibility assessment of spark plasma-sintered alumina-titanium cermets.

    Science.gov (United States)

    Guzman, Rodrigo; Fernandez-García, Elisa; Gutierrez-Gonzalez, Carlos F; Fernandez, Adolfo; Lopez-Lacomba, Jose Luis; Lopez-Esteban, Sonia

    2016-01-01

    Alumina-titanium materials (cermets) of enhanced mechanical properties have been lately developed. In this work, physical properties such as electrical conductivity and the crystalline phases in the bulk material are evaluated. As these new cermets manufactured by spark plasma sintering may have potential application for hard tissue replacements, their biocompatibility needs to be evaluated. Thus, this research aims to study the cytocompatibility of a novel alumina-titanium (25 vol. % Ti) cermet compared to its pure counterpart, the spark plasma sintered alumina. The influence of the particular surface properties (chemical composition, roughness and wettability) on the pre-osteoblastic cell response is also analyzed. The material electrical resistance revealed that this cermet may be machined to any shape by electroerosion. The investigated specimens had a slightly undulated topography, with a roughness pattern that had similar morphology in all orientations (isotropic roughness) and a sub-micrometric average roughness. Differences in skewness that implied valley-like structures in the cermet and predominance of peaks in alumina were found. The cermet presented a higher surface hydrophilicity than alumina. Any cytotoxicity risk associated with the new materials or with the innovative manufacturing methodology was rejected. Proliferation and early-differentiation stages of osteoblasts were statistically improved on the composite. Thus, our results suggest that this new multifunctional cermet could improve current alumina-based biomedical devices for applications such as hip joint replacements.

  6. The effect of Mo on the characteristics of a plasma nitrided layer of sintered iron

    Science.gov (United States)

    Bendo, T.; Maliska, A. M.; Acuña, J. J. S.; Binder, C.; Hammes, G.; Consoni, D. R.; Klein, A. N.

    2016-02-01

    Samples of PM (powder metallurgy) plain iron were superficially enriched with Mo during a sintering process using a DC discharge. The Mo atoms from the cathode produced an enriched layer of approximately 15-20 μm thick, and it was enriched with up to 2.0 at.% Mo. Subsequently, the samples were plasma nitrided in a gas mixture (N2/H2) at different temperatures and nitrogen concentrations. The effect of the molybdenum on the plasma nitrided layer of sintered iron was investigated. Abnormal nitride morphologies that developed in the surface layer were observed. The presence of Mo that was substitutionally dissolved in ferrite influences the nucleation and growth of the iron-nitride compound layer. The microstructure and (local) composition changes of the layers were investigated using scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and glow discharge optical emission spectroscopy (GDOES) analyses. To evaluate the mechanical properties, Vickers microhardness tests were conducted along the sample cross-sections. According to the nitriding conditions, submicroscopic fcc Mo2N-type nitrides that are coherent with the α-Fe matrix develop, as confirmed by the TEM analysis and by the broadening of the diffraction lines in the X-ray diffractogram. Molybdenum nitrides, γ-Mo2N, with an fcc structure and sphere-like shapes were observed on the sample surface where the Mo concentrations were higher.

  7. Carbon nanotubes/hydroxyapatite nanocomposites fabricated by spark plasma sintering for bonegraft applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang Wei, E-mail: Yuhe740442@hotmail.com [School of Stomatology, China Medical University, ShenYang (China); Zhu Yuhe [School of Stomatology, China Medical University, ShenYang (China); Watari, Fumio [Gaduate School of Dental Medicine, Hokkaido University, Sapporo (Japan); Liao, Susan [School of Materials Science and Engineering, Nanyang Technological University (Singapore); Yokoyama, Atsuro [Gaduate School of Dental Medicine, Hokkaido University, Sapporo (Japan); Omori, Mamoru [Institute for Materials Research, Tohoku University, Sendai (Japan); Ai Hongjun [School of Stomatology, China Medical University, ShenYang (China); Cui Fuzhai [Department of Materials Science and Engineering, Tsinghua University, Beijing (China)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer Multi-wall carbon nanotubes/hydroxyapatite (MWCNTs/HA) composites with 20%, 40% and 60% HA were fabricated successfully by spark plasma sintering (SPS). Black-Right-Pointing-Pointer MWCNTs/HA composites kept the nanostructure of MWCNTs after SPS treatment. Black-Right-Pointing-Pointer The in vivo reaction of four weeks showed that the MWCNTs/HA composites possessed better osseointegration compared to pure MWCNTs. - Abstract: Multi-wall carbon nanotubes/hydroxyapatite (MWCNTs/HA) composites with 20%, 40% and 60% HA were successfully fabricated at 1200 Degree-Sign C and 120 MPa by spark plasma sintering (SPS). Scanning electron microscope (SEM) observations showed that MWCNTs/HA composites kept the nanostructure of MWCNTs after SPS treatment. The bulk density of the MWCNTs/HA composites was increased by the addition of HA. However, the Vickers hardness, porosity, Young's modulus, flexure strength and compression strength of the MWCNTs/HA composites were decreased with increasing content of HA. To test their biocompatibility, the MWCNTs/40% HA composites were inserted into rat femur. The in vivo reaction of four weeks showed that the composites possessed better osseointegration compared to pure MWCNTs. The results indicated that the MWCNTs/HA composites have potential for a wide variety of bonegraft applications in the future.

  8. Characterization of phase transformation and microstructure of nano hard phase Ti(C,N)-based cermet by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    丰平; 熊惟皓; 李鹏; 余新; 夏阳华

    2004-01-01

    By means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), the process of densification, the characterization of phase transformation and the microstructure for spark plasma sintering (SPS) nano hard phase Ti(C,N)-based cermet were investigated. It is found that the spark plasma sintering (SPS) enables the nano hard phase Ti(C,N)-based cermet to densify rapidly, however, the full densification of the sintered samples can not be obtained. The rate of phase transformation is significantly quick.When being sintered at 1 200 ℃ for 8 min, Mo2C is completely dissolved, and TiN dissolves into TiC entirely and disappears. Above 1 200 ℃, Ti(C,N) begins to decompose and the atoms of C and N separate from Ti(C,N) resulting in the generation of N2 and the graphite. Due to the denitrification and the graphitization, the density and the hardness of sintered samples are rather low. The distribution of grain size of the sample sintered at 1 350 ℃ covers a wide range of 90 - 500 nm, and most of the grain size are about 200 nm. The hard phase is not of typical core-rim structure. Oxides on the surface of particles can not be fully removed and present in sample as titanium oxide TiO2.Graphite exists in band-like shape.

  9. PROCESSING OF ZIRCONIA AND CALCIUM ALUMINATE CEMENT MIXTURES BY SPARK PLASMA SINTERING

    Directory of Open Access Journals (Sweden)

    Y. L. Bruni

    2015-12-01

    Full Text Available Spark Plasma sintering (SPS was applied for the densification of Calcia stabilized ZrO2 based composites obtained from mixtures of pure zirconia (m-ZrO2 and calcium aluminate cement (HAC. Two commercial powders of pure zirconia were employed as reactants. One of these powders had a coarse mean particle size (d50 = 8 μm and the other was a submicrometer sized power (d50 = 0.44 μm. Several compositions containing different proportions of HAC (5 to 30 mol. % CaO in ZrO2 were sintered by SPS at temperatures between 1200 and 1400ºC under a pressure of 100 MPa during 10 min. The effect of processing conditions on phase composition, densification, microstructure and Vickers hardness of the obtained composites was examined. SPS significantly enhanced the densification in both type of composites (relative density > 93 % as compared to those previously produced by conventional sintering. Composites with low CaO content consisted of mixtures of c-ZrO2, (Ca0.15Zr0.85O1.85, unreacted m-ZrO2 and calcium dialuminate (CaAl4O7 or CA2. The highest hardness was determined for composites sintered at 1400ºC being related to the maximum relative density (~ 99 %. High densification of composites with 30 mol. % CaO composed by similar proportions of CaAl4O7 and c-ZrO2 were obtained even at 1200ºC but led to a slightly lower hardness. In general, the use of the finer m-ZrO2 powder contributed to increase both the c-ZrO2 content and densification of composite sintered at a relatively lower temperature. For these composites, best hardness (Hv near to 10 GPa resulted when the microstructure consisted of a fine grained ZrO2 matrix surrounding the dispersed CaAl4O7 grains instead of large interconnection between grains of both phases existed.

  10. Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    GUO Xing-zhong; YANG Hui

    2005-01-01

    Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 860 ℃ with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging'.

  11. Thermoelectric and mechanical properties of melt spun and spark plasma sintered n-type Yb- and Ba-filled skutterudites

    Energy Technology Data Exchange (ETDEWEB)

    Salvador, James R., E-mail: James.salvador@gm.com [General Motors Research and Development Center, 30500 Mound Road, Warren, MI 48090 (United States); Waldo, Richard A.; Wong, Curtis A. [General Motors Research and Development Center, 30500 Mound Road, Warren, MI 48090 (United States); Tessema, Misle [Optimal Inc., 14492 Sheldon Road, Suite 300, Plymouth, MI 48170 (United States); Brown, David N.; Miller, David J. [Molycorp Inc. Research and Development Center, 61 Science Park Road, 01-17 Galen, Singapore 117252 (Singapore); Wang, Hsin; Wereszczak, Andrew A.; Cai, Wei [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2013-10-01

    Highlights: • N-type double filled skutterudites can be formed by a combination of melt spinning and spark plasma sintering, obviating annealing steps. • The consolidated billets have thermoelectric properties that are comparable to those produced using more time and energy intensive powder metallurgical methods. • We demonstrate that the here described preparation route is scalable to 80 g billets as evidenced by the comparable nature of the transport properties of specimens cuts from large samples to those of smaller lab-scale specimens. -- Abstract: Here we present thermoelectric and mechanical properties of n-type filled-skutterudites produced by a combination of melt spinning of pre-melted charges with subsequent consolidation by spark plasma sintering, a process we refer to as MS-SPS. This combination of processing steps leads to phase-pure n-type filled-skutterudites and obviates more energy and time intensive annealing steps. We show that both the thermoelectric properties and the tensile fracture strength compare favorably to materials made by traditional methods. The process is scalable to at least 80 g billets, such that the transport properties measured on test bars harvested from these larger billets compare favorably to those measured on lab-scale billets (5 g total billet mass). ZT values approaching 1.1 at 750 K were observed in materials made by MS-SPS. In addition, the tensile fracture strength of test bars cut from an 80 g billet is ∼128 MPa at room temperature and decreases with increasing temperature. Fractography of the test bars reveals that the majority failed due to surface and edge flaws with few failures due to volume type flaws. This indicates that the powder metallurgical methods employed to produce these samples is mature.

  12. Reactive Spark Plasma Sintering and Mechanical Properties of Zirconium Diboride–Titanium Diboride Ultrahigh Temperature Ceramic Solid Solutions

    Directory of Open Access Journals (Sweden)

    Karthiselva N. S.

    2016-09-01

    Full Text Available Ultrahigh temperature ceramics (UHTCs such as diborides of zirconium, hafnium tantalum and their composites are considered to be the candidate materials for thermal protection systems of hypersonic vehicles due to their exceptional combination of physical, chemical and mechanical properties. A composite of ZrB2-TiB2 is expected to have better properties. In this study, an attempt has been made to fabricate ZrB2-TiB2 ceramics using mechanically activated elemental powders followed by reactive spark plasma sintering (RSPS at 1400 °C. Microstructure and phase analysis was carried out using X-ray diffractometer (XRD and electron microscopy to understand microstructure evolution. Fracture toughness and hardness were evaluated using indentation methods. Nanoindentation was used to measure elastic modulus. Compressive strength of the composites has been reported.

  13. Magnetic and structural properties of spark plasma sintered nanocrystalline NdFeB-powders

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2015-10-15

    Near-stoichiometric NdFeB melt-spun ribbons have been subjected to spark plasma sintering varying the process temperature T{sub SPS} and pressure p{sub SPS} between 600 and 800 °C and 50–300 MPa, respectively. Produced bulk magnets were analyzed regarding microstructure and magnetic properties. For all samples the intrinsic coercivity H{sub c,J} gradually decreases with increasing sintering temperature and pressure, while residual induction B{sub r} increases simultaneously with sample density. Densities close to the theoretical limit were achieved for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. With increasing T{sub SPS} precipitations of Nd-rich and Fe-rich phases have been observed as a result of a decomposition of the hard magnetic Nd{sub 2}Fe{sub 14}B phase. Under optimum sintering conditions of p{sub SPS}=300 MPa and T{sub SPS}=650 °C high-density bulk magnets with H{sub c,J}=652 kA/m, B{sub r}=0.86 T and (BH){sub max}=106 kJ/m{sup 3} have been produced. - Highlights: • Consolidation close to the theoretical density for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. • Highest (BH){sub max} of 106 kJ/m{sup 3} for p{sub SPS}=300 MPa and T{sub SPS}=650 °C with 98% theo. • H{sub c,J} gradually decreases with increasing T{sub SPS}, while B{sub r} increases simultaneously with. • With increasing T{sub SPS}, Nd- and Fe-rich precipitations are observed. • Reduction in t{sub SPS} is economic but does not increase (BH){sub max} significantly.

  14. The effect of Mo on the characteristics of a plasma nitrided layer of sintered iron

    Energy Technology Data Exchange (ETDEWEB)

    Bendo, T., E-mail: tatiana.bendo@labmat.ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil); Maliska, A.M., E-mail: a.maliska@ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil); Acuña, J.J.S., E-mail: Javier.acuna@ufabc.edu.br [UFABC – Universidade Federal do ABC, Centro de Ciências Nat. e Humanas, R. Sta. Adélia 166, 09210170, Santo André, SP (Brazil); Binder, C., E-mail: Cristiano.binder@labmat.ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil); Hammes, G., E-mail: gisele.hammes@labmat.ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil); Consoni, D.R., E-mail: deise.r.c@labmat.ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil); Klein, A.N., E-mail: a.n.klein@labmat.ufsc.br [UFSC – LabMat - Laboratório de Materiais, Bloco B – Eng. Mecânica, 88040900, Florianópolis, SC (Brazil)

    2016-02-15

    Graphical abstract: - Highlights: • Microstructure of the white layer formed on nitrided Fe-Mo. • Plasma nitriding. • Nitriding of the Fe-Mo alloys. • Morphology of the hererogeneous Fe-Mo-N nitrides. • Morphology and constitution of the compound layer formed on Fe-Mo alloy. - Abstract: Samples of PM (powder metallurgy) plain iron were superficially enriched with Mo during a sintering process using a DC discharge. The Mo atoms from the cathode produced an enriched layer of approximately 15–20 μm thick, and it was enriched with up to 2.0 at.% Mo. Subsequently, the samples were plasma nitrided in a gas mixture (N{sub 2}/H{sub 2}) at different temperatures and nitrogen concentrations. The effect of the molybdenum on the plasma nitrided layer of sintered iron was investigated. Abnormal nitride morphologies that developed in the surface layer were observed. The presence of Mo that was substitutionally dissolved in ferrite influences the nucleation and growth of the iron-nitride compound layer. The microstructure and (local) composition changes of the layers were investigated using scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and glow discharge optical emission spectroscopy (GDOES) analyses. To evaluate the mechanical properties, Vickers microhardness tests were conducted along the sample cross-sections. According to the nitriding conditions, submicroscopic fcc Mo{sub 2}N-type nitrides that are coherent with the α-Fe matrix develop, as confirmed by the TEM analysis and by the broadening of the diffraction lines in the X-ray diffractogram. Molybdenum nitrides, γ-Mo{sub 2}N, with an fcc structure and sphere-like shapes were observed on the sample surface where the Mo concentrations were higher.

  15. Spark Plasma Sintering of Commercial Zirconium Carbide Powders: Densification Behavior and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Xialu Wei

    2015-09-01

    Full Text Available Commercial zirconium carbide (ZrC powder is consolidated by Spark Plasma Sintering (SPS. Processing temperatures range from 1650 to 2100 °C. Specimens with various density levels are obtained when performing single-die SPS at different temperatures. Besides the single-die tooling setup, a double-die tooling setup is employed to largely increase the actual applied pressure to achieve higher densification in a shorter processing time. In order to describe the densification mechanism of ZrC powder under SPS conditions, a power-law creep constitutive equation is utilized, whose coefficients are determined by the inverse regression of the obtained experimental data. The densification of the selected ZrC powder is shown to be likely associated with grain boundary sliding and dislocation glide controlled creep. Transverse rupture strength and microhardness of sintered specimens are measured to be up to 380 MPa and 24 GPa, respectively. Mechanical properties are correlated with specimens’ average grain size and relative density to elucidate the co-factor dependencies.

  16. Microstructure-Wear Resistance Correlation and Wear Mechanisms of Spark Plasma Sintered Cu-Pb Nanocomposites

    Science.gov (United States)

    Sharma, Amit Siddharth; Biswas, Krishanu; Basu, Bikramjit

    2014-01-01

    The dispersion of a softer phase in a metallic matrix reduces the coefficient of friction (COF), often at the expense of an increased wear rate at the tribological contact. To address this issue, unlubricated fretting wear tests were performed on spark plasma sintered Cu-Pb nanocomposites against bearing steel. The sintering temperature and the Pb content as well as the fretting parameters were judiciously selected and varied to investigate the role of microstructure (grain size, second-phase content) on the wear resistance properties of Cu-Pb nanocomposites. A combination of the lowest wear rate (~1.5 × 10-6 mm3/Nm) and a modest COF (~0.4) was achieved for Cu-15 wt pct Pb nanocomposites. The lower wear rate of Cu-Pb nanocomposites with respect to unreinforced Cu is attributed to high hardness (~2 to 3.5 GPa) of the matrix, Cu2O/Fe2O3-rich oxide layer formation at tribological interface, and exuding of softer Pb particles. The wear properties are discussed in reference to the characteristics of transfer layer on worn surface as well as subsurface damage probed using focused ion beam microscopy. Interestingly, the flash temperature has been found to have insignificant effect on the observed oxidative wear, and alternative mechanisms are proposed. Importantly, the wear resistance properties of the nanocomposites reveal a weak Hall-Petch-like relationship with grain size of nanocrystalline Cu.

  17. Microstructure and Electrical Properties of AZO/Graphene Nanosheets Fabricated by Spark Plasma Sintering.

    Science.gov (United States)

    Yang, Shuang; Chen, Fei; Shen, Qiang; Lavernia, Enrique J; Zhang, Lianmeng

    2016-07-29

    In this study we report on the sintering behavior, microstructure and electrical properties of Al-doped ZnO ceramics containing 0-0.2 wt. % graphene sheets (AZO-GNSs) and processed using spark plasma sintering (SPS). Our results show that the addition of <0.25 wt. % GNSs enhances both the relative density and the electrical resistivity of AZO ceramics. In terms of the microstructure, the GNSs are distributed at grain boundaries. In addition, the GNSs are also present between ZnO and secondary phases (e.g., ZnAl₂O₄) and likely contribute to the measured enhancement of Hall mobility (up to 105.1 cm²·V(-1)·s(-1)) in these AZO ceramics. The minimum resistivity of the AZO-GNS composite ceramics is 3.1 × 10(-4) Ω·cm which compares favorably to the value of AZO ceramics which typically have a resistivity of 1.7 × 10(-3) Ω·cm.

  18. Spark Plasma Sintering constrained process parameters of sintered silver paste for connection in power electronic modules: Microstructure, mechanical and thermal properties

    Energy Technology Data Exchange (ETDEWEB)

    Alayli, N. [Université Paris 13, Sorbonne Paris Cité, Laboratoire des Sciences des Procédés et des Matériaux, Centre National de la Recherche Scientifique, Unité Propre de Recherche 3407, 99 avenue Jean Baptiste Clément, F-93430 Villetaneuse (France); Université de Versailles-Saint-Quentin-en-Yvelines, Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, Centre National de la Recherche Scientifique/INSU, Laboratoire Atmosphères Milieux Observations Spatiales-IPSL, Quartier des Garennes, 11 Boulevard d' Alembert, F-78280 Guyancourt (France); Schoenstein, F., E-mail: frederic.schoenstein@univ-paris13.fr [Université Paris 13, Sorbonne Paris Cité, Laboratoire des Sciences des Procédés et des Matériaux, Centre National de la Recherche Scientifique, Unité Propre de Recherche 3407, 99 avenue Jean Baptiste Clément, F-93430 Villetaneuse (France); Girard, A. [Office National d' Étude et de Recherches Aérospatiales, Laboratoire d' Étude des Microstructures, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 104, 29 avenue de la Division Leclerc, F-92322 Châtillon (France); and others

    2014-11-14

    Processing parameters of Spark Plasma Sintering (SPS) technique were constrained to process nano sized silver particles bound in a paste for interconnection in power electronic devices. A novel strategy combining debinding step and consolidation processes (SPS) in order to elaborate nano-structured silver bulk material is investigated. Optimum parameters were sought for industrial power electronics packaging from the microstructural and morphological properties of the sintered material. The latter was studied by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) to determine the density and the grain size of crystallites. Two types of samples, termed S1 (bulk) and S2 (multilayer) were elaborated and characterized. They are homogeneous with a low degree of porosity and a good adhesion to the substrate and the process parameters are compatible with industrial constraints. As the experimental results show, the mean crystallite size is between 60 nm and 790 nm with a density between 50% and 92% resulting in mechanical and thermal properties that are better than that of lead free solder. The best SPS sintering parameters, the applied pressure, the temperature and the processing time were determined as being 3 MPa, 300 °C and 1 min respectively when the desizing time of the preprocessing step was kept below 5 min at 150 °C. Using these processing parameters, acceptable for automotive packaging industry, a semi-conductor power chip was successfully connected to a metalized substrate by sintered silver with thermal and electrical properties better than those of current solders and with thermomechanical properties allowing absorption of thermoplastic stresses. - Highlights: • The sintered silver joints have nanometric structure. • The grain growth was controlled by the SPS sintering parameters. • New connection material improve thermal and electrical properties of current solders. • Interconnection's plastic strain can absorb thermo

  19. Spark plasma sintering of tantalum carbide and graphene reinforced tantalum carbide composites

    Science.gov (United States)

    Kalluri, Ajith Kumar

    Tantalum carbide (TaC), an ultra-high temperature ceramic (UHTC), is well known for its exceptional properties such as high hardness (15-19 GPa), melting point (3950 °C), elastic modulus (537 GPa), chemical resistance, and thermal shock resistance. To make TaC to be the future material for hypersonic vehicles, it is required to improve its thermal conductivity, strength, and fracture toughness. Researchers have previously reinforced TaC ceramic with carbides of silicon and boron as well as carbon nanotubes (CNTs), however, these reinforcements either undergo chemical changes or induce defects in the matrix during processing. In addition, these reinforcements exhibit a very minimal improvement in the properties. In the present work, we attempted to improve TaC fracture toughness by reinforcing with graphene nano-platelets (GNPs) and processing through spark plasma sintering at high temperature of 2000 °C, pressure of 70 MPa, and soaking time of 10 min. In addition, we investigated the active densification mechanism during SPS of TaC powder and the effect of ball milling time on mechanical properties of sintered TaC. A relative density of >96% was achieved using SPS of monolithic TaC (<3 μm). Ball milling improved the sintering kinetics and improved the mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness). Activation energy (100 kJ/mol) and stress exponent (1.2) were obtained using the analytical model developed for power-law creep. Grain boundary sliding is proposed as active densification mechanism based on these calculations. Reinforcing GNPs (2-6 vol.% ) in the TaC matrix improved relative density (99.8% for TaC-6 vol.% GNP). Also ˜150% and ˜180% increase in flexural strength and fracture toughness, respectively, was observed for TaC-6 vol.% GNP composite. The significant improvement in these properties is attributed to improved densification and toughening mechanisms such as sheet pull-out and crack

  20. Spark plasma sintered Sm(2)Co(17)-FeCo nanocomposite permanent magnets synthesized by high energy ball milling.

    Science.gov (United States)

    Sreenivasulu, G; Gopalan, R; Chandrasekaran, V; Markandeyulu, G; Suresh, K G; Murty, B S

    2008-08-20

    Nanocomposite Sm(2)Co(17)-5 wt% FeCo magnets were synthesized by high energy ball milling followed by consolidation into bulk shape by the spark plasma sintering technique. The evolution of magnetic properties was systematically investigated in milled powders as well as in spark plasma sintered samples. A high energy product of 10.2 MGOe and the other magnetic properties of M(s) = 107 emu g(-1), M(r) = 59 emu g(-1), M(r)/M(s) = 0.55 and H(c) = 6.4 kOe were achieved in a 5 h milled and spark plasma sintered Sm(2)Co(17)-5 wt% FeCo nanocomposite magnet. The spark plasma sintering was carried out at 700 °C for 5 min with a pressure of 70 MPa. The nanocomposite showed a higher Curie temperature of 955 °C for the Sm(2)Co(17) phase in comparison to its bulk Curie temperature for the Sm(2)Co(17) phase (920 °C). This higher Curie temperature can improve the performance of the magnet at higher temperatures.

  1. Flash sintering of ceramic materials

    Science.gov (United States)

    Dancer, C. E. J.

    2016-10-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

  2. Plasma preparation and low-temperature sintering of spherical TiC-Fe composite powder

    Institute of Scientific and Technical Information of China (English)

    Jian-jun Wang; Jun-jie Hao; Zhi-meng Guo; Song Wang

    2015-01-01

    A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced us-ing a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense struc-ture, and the fine sub-micron TiC particles were homogeneously distributed in theα-Fe matrix. A TiC–Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature;the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

  3. Thermodynamics analysis of diffusion in spark plasma sintering welding Cr3C2 and Ni

    Science.gov (United States)

    Zhang, Fan; Zhang, Jinyong; Leng, Xiaoxuan; Lei, Liwen; Fu, Zhengyi

    2017-03-01

    Spark plasma sintering (SPS) welding of chromium carbide (Cr3C2) and nickel (Ni) was used to investigate the atomic diffusion caused by bypassing current. It was found that the diffusion coefficient with bypassing current was enhanced by almost 3.57 times over that without bypassing current. Different from the previous researches, the thermodynamics analysis conducted herein showed that the enhancement included a current direction-independent part besides the known current direction-dependent part. A local temperature gradient (LTG) model was proposed to explain the current direction-independent effect. Assuming that the LTG was mainly due to the interfacial electric resistance causing heterogeneous Joule heating, the theoretical results were in good agreement with the experimental results both in the present and previous studies. This new LTG model provides a reasonable physical meaning for the low-temperature advantage of SPS welding and should be useful in a wide range of applications.

  4. Relaxation and pinning in spark-plasma sintered MgB2 superconductor

    Science.gov (United States)

    Jirsa, M.; Rames, M.; Koblischka, M. R.; Koblischka-Veneva, A.; Berger, K.; Douine, B.

    2016-02-01

    The model of thermally activated relaxation developed and successfully tested on high-T c superconductors (Jirsa et al 2004 Phys. Rev. B 70 0245251) was applied to magnetic data of a bulk spark-plasma sintered MgB2 sample to elucidate its magnetic relaxation behavior. MgB2 and the related borides form a superconductor class lying between classical and high-T c superconductors. In accord with this classification, the relaxation phenomena were found to be about ten times weaker than in cuprates. Vortex pinning analyzed in terms of the field dependence of the pinning force density indicates a combined pinning by normal point-like defects and by grain surfaces. An additional mode of pinning at rather high magnetic fields (of still unknown origin) was observed.

  5. Tantalum-Tungsten Oxide Thermite Composite Prepared by Sol-Gel Synthesis and Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, O; Kuntz, J; Gash, A; Munir, Z

    2009-02-13

    Energetic composite powders consisting of sol-gel derived nanostructured tungsten oxide were produced with various amounts of micrometer-scale tantalum fuel metal. Such energetic composite powders were ignition tested and results show that the powders are not sensitive to friction, spark and/or impact ignition. Initial consolidation experiments, using the High Pressure Spark Plasma Sintering (HPSPS) technique, on the sol-gel derived nanostructured tungsten oxide produced samples with higher relative density than can be achieved with commercially available tungsten oxide. The sol-gel derived nanostructured tungsten oxide with immobilized tantalum fuel metal (Ta - WO{sub 3}) energetic composite was consolidated to a density of 9.17 g.cm{sup -3} or 93% relative density. In addition those parts were consolidated without significant pre-reaction of the constituents, thus the sample retained its stored chemical energy.

  6. Preparation of Ti3SiC2 with Aluminum by Means of Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Polycrystalline bulk Ti3SiC2 material with a high purity and density was fabricated by spark plasma sintering from the elemental powder mixture with starting composition of Ti3Si1-xAlxC2,where x=0.05-0.2.X-ray diffraction patterns and scanning electron microscopy photographs of the fully dense samples show that a proper addition of aluminum promotes the formation,and accelerates the crystal growth rate of Ti3SiC2,consequently results in a high purity of the prepared samples.The synthesized Ti3SiC2 is in plane-shape with a size of about 10-25μm in the elongated dimension.Solid solution of aluminum decreases the thermal stability of Ti3SiC2,and lowers the temperature of Ti3SiC2 decomposeing to be 1300 ℃.

  7. Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

    Directory of Open Access Journals (Sweden)

    Román-Manso, B.

    2014-04-01

    Full Text Available Concentrated ceramic inks based on β-SiC powders, with different amounts of Y2O3 and Al2O3 as sintering aids, are developed for the adequate production of SiC scaffolds, with different patterned morphologies, by the Robocasting technique. The densifi cation of the as-produced 3D structures, previously heat treated in air at 600 ºC for the organics burn-out, is achieved with a Spark Plasma Sintering (SPS furnace. The effects of the amount of sintering additives (7 - 20 wt. % and the size of the SiC powders (50 nm and 0.5 μm on the processing of the inks, microstructure, hardness and elastic modulus of the sintered scaffolds, are studied. The use of nano-sized β-SiC powders significantly restricts the attainable maximum solids volume fraction of the ink (0.32 compared to 0.44 of the submicron-sized powders-based ink, involving a much larger porosity of the green ceramic bodies. Furthermore, reduced amounts of additives improve the mechanical properties of the ceramic skeleton; particularly, the stiffness. The grain size and specific surface area of the starting powders, the ink solids content, green porosity, amount of sintering additives and SPS temperatures are the main parameters to be taken into account for the production of these SiC cellular ceramics.Se han fabricado andamiajes de carburo de silicio (SiC usando la técnica de “Robocasting”, a partir de tintas cerámicas conteniendo β-SiC y distintas cantidades de Y2O3 and Al2O3, como aditivos de sinterización. La densificación de las estructuras tridimensionales, previamente calcinadas a 600 ºC para eliminar los aditivos orgánicos, se realizó en un horno de “Spark Plasma Sintering” (SPS. Se analizó el efecto de la cantidad de aditivos de sinterización (7-20 % en peso y del tamaño de partícula inicial del polvo de SiC (50 nm y 0.5 μm en el procesado de las tintas, en la microestructura, la dureza y el módulo elástico de las estructuras sinterizadas. El uso de polvo

  8. Densification of silicon and zirconium carbides by a new process: spark plasma sintering; Densification des carbures de silicium et de zirconium par un procede innovant: le spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Guillard, F

    2006-12-15

    Materials research for suitable utilization in 4. generation nuclear plants needs new ways to densify testing components. Two carbides, silicon and zirconium carbide seems to be the most suitable choice due to their mechanical, thermal and neutron-transparency properties against next nuclear plant specifications. Nevertheless one main difficulty remains, which is densifying them even at high temperature. Spark Plasma Sintering a new metal-, ceramic- and composite-sintering process has been used to densify both SiC and ZrC. Understanding bases of mass transport mechanisms in SPS have been studied. Composites and interfaces have been processed and analyzed. This manuscript reports original results on SiC and ZrC ceramics sintered with commercial powder started, without additives. (author)

  9. Spark plasma sintering and mechanical properties of $ZrO_{2} (Y_{2}O_{3})-Al_{2}O_{3}$ composites

    CERN Document Server

    Jin Sheng H; Dalla Torre, S; Miyamoto, H; Miyamoto, K

    2000-01-01

    Spark plasma sintering (SPS) was conducted on nanocrystalline ZrO/sub 2/(Y/sub 2/O/sub 3/)-20 mol% Al/sub 2/O/sub 3/ powder at a heat rate of 600 degrees C/min with a short holding time. Full density was obtained at sintering temperatures >1300 degrees C. Considerable grain growth occurred relative to the initial powder particles, but smaller grain size and higher density can be obtained as compared to hot-pressing. High flexural strength and fracture toughness were also achieved for the SPS-resulted composite. (8 refs).

  10. Effect of Composition on Mechanical Properties of Mullite-WC Nano Composites Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    H. Rajaei

    2016-12-01

    Full Text Available Mullite-WC composites were prepared from Mullite and WC powders by spark plasma sintering at 1400 °C for a holding time of 180 s under 30 MPa. Microstructure, strength, and hardness of the mullite-WC composites were studied. The mullite-WC composite containing 5-20 wt% WC reached over 94 % theoretical density. The strength and Vickers hardness of mullite-(10 wt% WC sintered composite reached maximum values of 298 MPa, and 1589 HV, respectively demonstrating that the introduction of WC significantly enhances the mechanical properties of the mullite matrix.

  11. Sintering of ZrC by hot isostatic pressing (HIP) and spark plasma sintering (SPS). Effect of impurities

    Energy Technology Data Exchange (ETDEWEB)

    Allemand, Alexandre [CEA Saclay, DRT/DTEN/S3ME/LTMEx, 91191 Gif-sur-Yvette (France); Le Flem - Dormeval, Marion [CEA Saclay, DEN/DMN/SRMA/LA2M, 91191 Gif-sur-Yvette (France); Guillard, Francois [CNRS-CEMES-CMI, 29 rue J.Marving, 31000 Toulouse (France)

    2005-07-01

    Carbides are generally used as structural materials for high temperature applications. Particularly, ZrC because of low activation, neutronic transparency, cubic structure (isotropic behaviour) and good thermal conductivity, is one of the candidates under consideration for structural materials in the core of new high temperature nuclear reactors (Generation IV). Just a few studies about densification of monolithic ZrC exist. They mainly involve natural sintering or hot pressing at high temperature (until 2700 deg. C). Unfortunately those processes induce grain growth and do not lead to fully densified ZrC. The aim of this study is to compare the characteristics and the properties of ZrC sintered by HIP and by SPS. Fully dense ZrC can be reached either by HIP or by SPS, grain size being more or less controlled. Microstructural observations and mechanical testing of several ZrC grades shows that powder impurities play an important role in the quality of the grain boundaries and consequently in the mechanical properties. In particular, the porosity falls from 17% to 3 % just by reducing the free carbon content in starting ZrC powder. The densification process of dense monolithic ZrC was improved by combining a HIP at 1600 deg. C (titanium canning) followed by a post-HIP at 1900 deg. C (no canning required). Four-point bending tests are in progress to confirm the improvement of fracture strength. (authors)

  12. Synthesis and Characterization of Diamond-vitrified Bond Sintered Composite By Spray-drying Method

    Directory of Open Access Journals (Sweden)

    HAO Su-ye

    2016-08-01

    Full Text Available Based on the diamond and inorganic sol, spray-drying method was used to prepare diamond-vitrified bond composite powders and then the bulk samples were obtained after pressing and sintering the powders. The surface morphology and particle size distribution of the composite powders were examined by scanning electron microscope and laser particle size analyzer,the sintering temperature of the composites was selected with the aid of the comprehensive thermal analysis instrument,the bending strength, fracture morphology and crystal phases of sintered samples prepared by spray-drying method and melting method were characterized by motorized bending tester, scanning electron microscope and X-ray diffraction, respectively. The results show that the composite powders prepared by spray-drying are spherical,which is beneficial to mould forming. Their wide size distribution helps to improve the density of diamond-vitrified bond green body. The sintering temperature of the composites is 820℃.The bonding and wrapping of diamond can be realized at this temperature. With the increase of bond content, the bending strength of sintered samples prepared by two methods increases and porosity decreases. When the vitrified bond content is 32%(mass fraction, the microstructure of samples prepared by spray-drying is uniform and is easy to be crystallized, and the bending strength and porosity are 99.46MPa and 38.55%;while for samples obtained from melting method, the corresponding figures are 72.42MPa and 39.89%.

  13. Influence of mechanical alloying time on the properties of Fe3Al intermetallics prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Chengchang Jia; Qing He; Jie Meng; Lina Guo

    2007-01-01

    The Fe3Al-based intermetallics were prepared by mechanical alloying and spark plasma sintering (SPS), and the influence of milling time on the properties of materials was investigated. The phase identification was investigated by X-ray, and the surface morphology and fractography were observed by scanning electron microscope (SEM). The mechanical properties such as bending strength, strain, and microhardness were tested. The results show that Fe reacts with Al completely to form Fe3Al during short SPS processing time. The relative densities of the sintered samples were nearly 100%. The mechanical properties of the sintered samples can be improved along with the milling time. The representative values are the bend strength of 1327 MPa and the microhardness of 434.

  14. Dry Sliding Wear Behavior of Spark Plasma Sintered Fe-Based Bulk Metallic Glass/Graphite Composites

    Directory of Open Access Journals (Sweden)

    Xiulin Ji

    2016-09-01

    Full Text Available Bulk metallic glass (BMG and BMG-graphite composites were fabricated using spark plasma sintering at the sintering temperature of 575 °C and holding time of 15 min. The sintered composites exhibited partial crystallization and the presence of distributed porosity and graphite particles. The effect of graphite reinforcement on the tribological properties of the BMG/graphite composites was investigated using dry ball-on-disc sliding wear tests. The reinforcement of graphite resulted in a reduction in both the wear rate and the coefficient of friction as compared to monolithic BMG samples. The wear surfaces of BMG/graphite composites showed regions of localized wear loss due to microcracking and fracture, as was also the case with the regions covered with graphite-rich protective film due to smearing of pulled off graphite particles.

  15. Densification, microstructure, and fracture behavior of TiC/Si3N4 composites by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    BAI Ling; GE Changchun; SHEN Weiping; MAO Xiaodong; ZHANG Ke

    2008-01-01

    TiC/Si3N4 composites were prepared using the β-Si3N4 powder synthesized by self-propagating high-temperature synthesis (SHS) and 35 wt.% TiC by spark plasma sintering. Y2O3 and A12O3 were added as sintering additives. The almost full sintered density and the highest fracture toughness (8.48 MPa·m1/2) values of Si3N4-based ceramics could be achieved at 1550℃. No interfacial interactions were noticeable between TiC and Si3N4. The toughening mechanisms in TiC/Si3N4 composites were attributed to crack deflection, microcrack toughening, and crack impedance by the periodic compressive stress in the Si3N4 matrix. However, increasing microcracks easily led to excessive connection of microcracks, which would not be beneficial to the strength.

  16. Ti3SiC2-Cu composites by mechanical milling and spark plasma sintering: Possible microstructure formation scenarios

    Science.gov (United States)

    Dudina, Dina V.; Mali, Vyacheslav I.; Anisimov, Alexander G.; Bulina, Natalia V.; Korchagin, Michail A.; Lomovsky, Oleg I.; Bataev, Ivan A.; Bataev, Vladimir A.

    2013-11-01

    We present several possible microstructure development scenarios in Ti3SiC2-Cu composites during mechanical milling and Spark Plasma Sintering (SPS). We have studied the effect of in situ consolidation during milling of Ti3SiC2 and Cu powders and melting of the Cu matrix during the SPS on the hardness and electrical conductivity of the sintered materials. Under low-energy milling, (3-5) vol.%Ti3SiC2-Cu composite particles of platelet morphology formed, which could be easily SPS-ed to 92-95% relative density. Under high-energy milling, millimeter-scale (3-5) vol.%Ti3SiC2-Cu granules formed as a result of in situ consolidation and presented a challenge to be sintered into a bulk fully dense sample; the corresponding SPS-ed compacts demonstrated a finer-grained Cu matrix and more significant levels of hardening compared to composites of the same composition processed by low-energy milling. The 3 vol.% Ti3SiC2-Cu in situ consolidated and Spark Plasma Sintered granules showed an extremely high hardness of 227 HV. High electrical conductivity of the Ti3SiC2-Cu composites sintered from the granules was an indication of efficient sintering of the granules to each other. Partial melting of the Cu matrix, if induced during the SPS, compromised the phase stability and uniformity of the microstructure of the Ti3SiC2-Cu composites and thus it is not to be suggested as a pathway to enhanced densification in this system.

  17. Effect of Processing on Mechanically Alloyed and Spark Plasma Sintered Al-Al2O3 Nanocomposites

    Directory of Open Access Journals (Sweden)

    Nouari Saheb

    2015-01-01

    Full Text Available Metal matrix nanocomposites are advanced materials developed using ceramic nanoreinforcements and nanocrystalline metal matrices. These composites have outstanding properties and high potential for large number of functional and structural applications. In this work, nanocrystalline aluminium and Al-Al2O3 nanocomposites were synthesised using mechanical alloying and consolidated through spark plasma sintering technique. Scanning electron microscopy, X-ray diffraction, and mapping were used to characterize the powders and sintered samples. Density and hardness of sintered samples were measured using densimeter and hardness tester, respectively. It was found that milling of pure aluminium for 24 h reduced its crystallite size to less than 100 nm. For Al-Al2O3 nanocomposites, milling for 24 h decreased the crystallite size of the aluminium phase and resulted in uniform dispersion of the reinforcement. Sintering of the synthesised powders led to grain growth. Al2O3 contributed to growth inhibition when samples were sintered for 20 minutes and improved the hardness but reduced densification. The Al-10 vol.%  Al2O3 nanocomposite had the highest Vickers hardness value of 1460 MPa.

  18. Fast plasma sintering delivers functional graded materials components with macroporous structures and osseointegration properties.

    Science.gov (United States)

    Godoy, R F; Coathup, M J; Blunn, G W; Alves, A L; Robotti, P; Goodship, A E

    2016-04-13

    We explored the osseointegration potential of two macroporous titanium surfaces obtained using fast plasma sintering (FPS): Ti macroporous structures with 400-600 µmØ pores (TiMac400) and 850-1000 µmØ pores (TiMac850). They were compared against two surfaces currently in clinical use: Ti-Growth® and air plasma spray (Ti-Y367). Each surface was tested, once placed over a Ti-alloy and once onto a CoCr bulk substrate. Implants were placed in medial femoral condyles in 24 sheep. Samples were explanted at four and eight weeks after surgery. Push-out loads were measured using a material-testing system. Bone contact and ingrowth were assessed by histomorphometry and SEM and EDX analyses. Histology showed early osseointegration for all the surfaces tested. At 8 weeks, TiMac400, TiMac850 and Ti-Growth® showed deep bone ingrowth and extended colonisation with newly formed bone. The mechanical push-out force was equal in all tested surfaces. Plasma spray surfaces showed greater bone-implant contact and higher level of pores colonisation with new bone than FPS produced surfaces. However, the void pore area in FPS specimens was significantly higher, yet the FPS porous surfaces allowed a deeper osseointegration of bone to implant. FPS manufactured specimens showed similar osseointegration potential to the plasma spray surfaces for orthopaedic implants. FPS is a useful technology for manufacturing macroporous titanium surfaces. Furthermore, its capability to combine two implantable materials, using bulk CoCr with macroporous titanium surfaces, could be of interest as it enables designers to conceive and manufacture innovative components. FPS delivers functional graded materials components with macroporous structures optimised for osseointegration.

  19. Solar furnace sintering of ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhilinska, N.; Zalite, I.; Korb, G.; Angerer, P.; Rodriguez, J.; Martinez, D.

    2004-07-01

    This paper reports on the current status of application of solar furnace for sintering of TiCN, TiO2 and Al2O3 nano powders with the specific surface area of 30-50 m''2/g and average particle size of 30-50 nm. The powders have been prepared by the plasma chemical synthesis and other methods. This work relates to innovative methods of sintering in the solar furnace at Plataforma Solar de Almeria and the Spark Plasma Sintering (SPS). The influence of sintering temperature, sintering time and heating rate on the densification behaviour of the nanopowders was investigated. The results were compared with the data obtained using commercial powders. (Author) 4 refs.

  20. Low-temperature plasma nitriding of sintered PIM 316L austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Aecio Fernando; Scheuer, Cristiano Jose; Joanidis, Ioanis Labhardt; Cardoso, Rodrigo Perito; Mafra, Marcio; Klein, Aloisio Nelmo; Brunatto, Silvio Francisco, E-mail: brunatto@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Engenharia Mecanica. Grupo de Tecnologia de Fabricacao Assistida pro Plasma e Metalurgia do Po

    2014-08-15

    This work reports experimental results on sintered PIM 316L stainless steel low-temperature plasma nitriding. The effect of treatment temperature and time on process kinetics, microstructure and surface characteristics of the nitrided samples were investigated. Nitriding was carried out at temperatures of 350, 380, 410 and 440 °C , and times of 4, 8 and 16 h, using a gas mixture composed by 60% N2 + 20% H2 + 20% Ar, at a gas flow rate of 5.00 X 10{sup 6} Nm{sup 3-1}, and a pressure of 800 Pa. The treated samples were characterized by scanning electron microscopy, X-ray diffractometry and microhardness measurements. Results indicate that low-temperature plasma nitriding is a diffusion controlled process. The calculated activation energy for nitrided layer growth was 111.4 kJmol{sup -1}. Apparently precipitation-free layers were produced in this study. It was also observed that the higher the treatment temperature and time the higher is the obtained surface hardness. Hardness up to 1343 HV{sub 0.025} was verified for samples nitrided at 440 °C. Finally, the characterization of the treated surface indicates the formation of cracks, which were observed in regions adjacent to the original pores after the treatment. (author)

  1. Towards low-friction and wear-resistant plasma sintering dies via plasma surface co-alloying CM247 nickel alloy with V/Ag and N

    Directory of Open Access Journals (Sweden)

    Zhang Zhenxue

    2015-01-01

    Full Text Available Nickel based superalloys have good oxidation and creep resistance and hence they can function under high mechanical stress and high temperatures. However, their undesirable tribological behaviour is the major technical barrier to the challenging high-temperature, lubricant-free plasma sintering tool application. In this study, nickel based CM247 superalloy surfaces were co-alloyed using innovative active screen plasma technology with both interstitial element (e.g. N and substitutional alloying elements (e.g. V and Ag to provide a synergy effect to enhance its tribological properties. The tribological behaviour of the plasma co-alloyed CM247 superalloy surfaces were fully evaluated using reciprocal and pin-on-disc tribometers at temperatures from room temperature to 600 ∘C. The experimental results demonstrate that the co-alloyed surface with N, Ag and V can effectively lower the friction coefficient, which is expected to help demoulding during lubricant-free plasma sintering.

  2. Towards low-friction and wear-resistant plasma sintering dies via plasma surface co-alloying CM247 nickel alloy with V/Ag and N

    OpenAIRE

    Zhang Zhenxue; Li Xiaoying; Dong Hanshan; Sánchez Eluxka Almandoz; Fuentes Gonzalo García; Qin Yi

    2015-01-01

    Nickel based superalloys have good oxidation and creep resistance and hence they can function under high mechanical stress and high temperatures. However, their undesirable tribological behaviour is the major technical barrier to the challenging high-temperature, lubricant-free plasma sintering tool application. In this study, nickel based CM247 superalloy surfaces were co-alloyed using innovative active screen plasma technology with both interstitial element (e.g. N) and substitutional alloy...

  3. Comparison the fitness of zirconia ceramic crown sintered by microwave sintering method and conventional sintering method%微波烧结和常规烧结氧化锆全瓷冠适合性的比较

    Institute of Scientific and Technical Information of China (English)

    吴丽艳; 苏晓晖; 王磊; 韦赞军

    2014-01-01

    Objective:To study the effect of different sintering method on the marginal and internal adaptation of Cercon zirconia crowns. Method:A first premolar teeth was prepared and replicated in to ten resin castes. The units were randomly assigned to two groups and the crowns were made by CAD/CAM system. Group one was sintered by manufacturers recommend conventional second-time sintering process. Group two was sintered by microwave second-time sintering process. All crowns adhered to the corresponding dies and compare their adaption through statistical analysis. Result:Marginal fit and axial plane of zirconia ceramic crowns sintered by two methods have no significant differences (P>0.05). Shoulder suitability and occlusal surface have significant differences (P <0.05).Conclusion:Microwave sintered Cercon zirconia crowns appeared to have clinically acceptable marginal fit.%目的:研究微波烧结工艺制作的Cercon氧化锆全瓷冠适合性。方法:选取1颗完好的离体前磨牙行全瓷冠牙体预备,双重印模法取模,翻制10个相同的环氧树脂代型,将代型随机分为2组,利用CAD/CAM制作Cercon全瓷冠后,分别用微波二次烧结和常规二次烧结,将制得的全瓷冠粘接、包埋、切割后利用扫描电镜(SEM)测量冠适合性。结果:两种烧结方法制作的冠的边缘间隙和轴面间隙差异均无统计学意义(P>0.05),肩台间隙和牙合面间隙差异均有统计学意义(P<0.05)。结论:利用微波二次烧结制作的Cercon全瓷冠具有与常规烧结氧化锆相似的冠边缘适合性,在临床的接受范围内。

  4. The effect of alloying method on the structure and properties of sintered stainless steel

    Directory of Open Access Journals (Sweden)

    Dudek A.

    2017-03-01

    Full Text Available Sintered duplex stainless steels (SDSSs appear to be very interesting and promising materials that can be used in many industrial sectors. Ferrite improves material strength while austenite increases hardness and corrosion resistance. This study proposes a method to improve functional properties (e.g. hardness and wear resistance by means of alloying the surface of the sintered duplex steel with Cr3C2 + 10% NiAl powder. The results of optical microscope metallography, SEM/EDX, XRD analysis and microhardness and wear resistance measurements are also presented. The surface alloying with Cr3C2 is a manufacturing method of surface layer hardening in sintered stainless steels and modification of surface layer properties such as hardness and coefficient of friction.

  5. Thermoelectric transport properties of polycrystalline titanium diselenide co-intercalated with nickel and titanium using spark plasma sintering

    DEFF Research Database (Denmark)

    Holgate, Tim; Zhu, S.; Zhou, M.

    2013-01-01

    Polycrystalline samples of nickel intercalated (0–5%) TiSe2 were attempted via solid-state reaction in evacuated quartz tubes followed by densification using a spark plasma sintering process. X-ray diffraction data indicated that mixed NiSe2 and TiSe2 phases were present after initial synthesis...... by solid-state reaction, but a pure TiSe2 phase was present after the spark plasma sintering. While EPMA data reveals the stoichiometry to be near 1:1.8 (Ti:Se) for all samples, comparisons of the measured bulk densities to the theoretical densities suggest that the off stoichiometry is a result of the co-intercalation......, stoichiometric TiSe2. The effects of the co-intercalation of both Ni and Ti in TiSe2 on the structural, thermal, and electrical properties are discussed herein....

  6. Comparison of Reactive and Non-Reactive Spark Plasma Sintering Routes for the Fabrication of Monolithic and Composite Ultra High Temperature Ceramics (UHTC Materials

    Directory of Open Access Journals (Sweden)

    Roberto Orrù

    2013-04-01

    Full Text Available A wider utilization of ultra high temperature ceramics (UHTC materials strongly depends on the availability of efficient techniques for their fabrication as dense bodies. Based on recent results reported in the literature, it is possible to state that Spark Plasma Sintering (SPS technology offers a useful contribution in this direction. Along these lines, the use of two different SPS-based processing routes for the preparation of massive UHTCs is examined in this work. One method, the so-called reactive SPS (R-SPS, consists of the synthesis and densification of the material in a single step. Alternatively, the ceramic powders are first synthesized by Self-propagating High-temperature Synthesis (SHS and then sintered by SPS. The obtained results evidenced that R-SPS method is preferable for the preparation of dense monolithic products, while the sintering of SHS powders requires relatively milder conditions when considering binary composites. The different kinetic mechanisms involved during R-SPS of the monolithic and composite systems, i.e., combustion-like or gradual solid-diffusion, respectively, provides a possible explanation. An important role is also played by the SHS process, particularly for the preparation of composite powders, since stronger interfaces are established between the ceramic constituents formed in situ, thus favoring diffusion processes during the subsequent SPS step.

  7. Microstructure and mechanical strength of near- and sub-micrometre grain size copper prepared by spark plasma sintering

    DEFF Research Database (Denmark)

    Zhu, K. N.; Godfrey, A.; Hansen, Niels

    2017-01-01

    Spark plasma sintering (SPS) has been used to prepare fully dense samples of copper in a fully recrystallized condition with grain sizes in the near- and sub-micrometre regime. Two synthesis routes have been investigated to achieve grain size control: (i) SPS at different temperatures from 800 to...... been probed using hardness measurements and tensile testing, revealing an enhanced strength for samples with grain sizes less than ≈ 1 μm....

  8. Influence of sintering temperature on the thermoelectric properties of Ba8Ga16Si30 clathrate treated by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Li-hua Liu; Feng Li; Ning Chen; Hong-mei Qiu; Guo-hui Cao; Yang Li

    2015-01-01

    A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750°C. Lattice contraction recurred when the SPS temperature was further increased in the range of 750–1000°C. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800°C. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT–T curve.

  9. Optimization of mechanical alloying and spark-plasma sintering regimes to obtain ferrite–martensitic ODS steel

    Directory of Open Access Journals (Sweden)

    M.S. Staltsov

    2016-12-01

    Full Text Available The results of structure investigation, distribution uniformity of dispersed particles of Y2O3, porosity and density of the ferritic/martensitic reactor steel EP-450 (0.12C–13Cr–2Mo–Nb–V–B, wt% produced by spark-plasma sintering (SPS are presented. More than 140 samples were produced using different combinations of mechanical alloying (time, speed of attritor rotation and SPS parameters (temperature, speed of reaching preset temperature, pressure and time of exposure under pressure, concentration of strengthening particles. It is determined that the absence of strengthening Y2O3 nano-particles in local volumes of sintered specimens is connected with the imperfection of mechanical alloying, namely, the formation of agglomerates of matrix steel powder containing no oxide nano-particles. It has been determined that the time of mechanical alloying should not exceed 30h to provide minimum powder agglomeration, uniform distribution of Y2O3 particles in the powder mixture and minimum porosity of sintered samples. Spark-plasma sintering should be performed at the lowest possible temperature. As a result it was found that samples with 99% theoretical density can be obtained using the following optimized SPS-parameters: sintering temperature is 1098÷1163K; speed for reaching the preset temperature is >573K/min; load is 70÷80MPa; time of exposure under pressure – either without isothermal exposure, or exposure during ≥3min; optimum quantity of Y2O3 is 0.2÷0.5wt%.

  10. Strength and failure behaviour of spark plasma sintered steel-zirconia composites under compressive Loading

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, L.; Decker, S.; Ehinger, D. [Institute of Materials Engineering, TU Bergakademie Freiberg (Germany); Ohser-Wiedemann, R.; Martin, S.; Martin, U.; Seifert, H.J. [Institute of Materials Science, TU Bergakademie Freiberg (Germany)

    2011-09-15

    Several composites, consisting of a metastable austenitic steel matrix and varying amounts of MgO partially stabilized zirconia particles (Mg-PSZ), were produced through spark plasma sintering (SPS). Compression tests were carried out at room temperature in a wide range of strain rate (4 . 10{sup -4} s{sup -1}, 2 . 10{sup -3} s{sup -1}, 10{sup -1} s{sup -1}, 1 s{sup -1}, 10{sup 2} s{sup -1}). In conjunction with subsequent microstructural investigations, the mechanical material behaviour was clarified. All composites showed a good ductility and a high strength. The strength increased with an increase of the ceramic content and with higher strain rates. Both, the martensitic transformation of the steel matrix and of the ceramic particles, could be proved at all strain rates. In this study no significant influence of the strain rate on the amount of transformed ceramic could be detected while the steel matrix showed less {alpha}'-martensite after compression at rising strain rates. Local material failure occurred around 0.3 true compressive strain depending on the applied strain rate and the amount of the Mg-PSZ powder. The main reason for the damage is the relatively weak ceramic-ceramic interface within the ceramic clusters. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Spark Plasma Sintering of a Gas Atomized Al7075 Alloy: Microstructure and Properties

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    Orsolya Molnárová

    2016-12-01

    Full Text Available The powder of an Al7075 alloy was prepared by gas atomization. A combination of cellular, columnar, and equiaxed dendritic-like morphology was observed in individual powder particles with continuous layers of intermetallic phases along boundaries. The cells are separated predominantly by high-angle boundaries, the areas with dendritic-like morphology usually have a similar crystallographic orientation. Spark plasma sintering resulted in a fully dense material with a microstructure similar to that of the powder material. The continuous layers of intermetallic phases are replaced by individual particles located along internal boundaries, coarse particles are formed at the surface of original powder particles. Microhardness measurements revealed both artificial and natural ageing behavior similar to that observed in ingot metallurgy material. The minimum microhardness of 81 HV, observed in the sample annealed at 300 °C, reflects the presence of coarse particles. The peak microhardness of 160 HV was observed in the sample annealed at 500 °C and then aged at room temperature. Compression tests confirmed high strength combined with sufficient plasticity. Annealing even at 500 °C does not significantly influence the distribution of grain sizes—about 45% of the area is occupied by grains with the size below 10 µm.

  12. Consolidation of B4C-TaB2 eutectic composites by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Dmytro Demirskyi

    2015-12-01

    Full Text Available The in situ synthesis/consolidation of B4C-TaB2 eutectic composites by spark plasma sintering (SPS is reported. The microstructure–property relations were determined for composites with the B4C-TaB2 eutectic composition as functions of TaB2 content, and TaB2-TaB2 interlamellar spacing. A clear maximum in fracture toughness was identified (∼4.5 MPa m1/2 for eutectic composites with interlamellar spacing between 0.9 and 1.1 μm. The composites with the hypereutectic composition of 40 mol.% TaB2 obtained by SPS exhibited lower Vickers hardness (25–26 GPa but higher indentation fracture toughness (up to 4.9 MPa m1/2 than eutectic composites with 30–35 mol.% of TaB2.

  13. Nanocrystalline Al7075 + 1 wt % Zr Alloy Prepared Using Mechanical Milling and Spark Plasma Sintering.

    Science.gov (United States)

    Molnárová, Orsolya; Málek, Přemysl; Veselý, Jozef; Šlapáková, Michaela; Minárik, Peter; Lukáč, František; Chráska, Tomáš; Novák, Pavel; Průša, Filip

    2017-09-20

    The microstructure, phase composition, and microhardness of both gas-atomized and mechanically milled powders of the Al7075 + 1 wt % Zr alloy were investigated. The gas-atomized powder exhibited a cellular microstructure (grain size of a few µm) with layers of intermetallic phases along the cell boundaries. Mechanical milling (400 revolutions per minute (RPM)/8 h) resulted in a grain size reduction to the nanocrystalline range (20 to 100 nm) along with the dissolution of the intermetallic phases. Milling led to an increase in the powder's microhardness from 97 to 343 HV. Compacts prepared by spark plasma sintering (SPS) exhibited negligible porosity. The grain size of the originally gas-atomized material was retained, but the continuous layers of intermetallic phases were replaced by individual particles. Recrystallization led to a grain size increase to 365 nm in the SPS compact prepared from the originally milled powder. Small precipitates of the Al₃Zr phase were observed in the SPS compacts, and they are believed to be responsible for the retainment of the sub-microcrystalline microstructure during SPS. A more intensive precipitation in this SPS compact can be attributed to a faster diffusion due to a high density of dislocations and grain boundaries in the milled powder.

  14. Nanocrystalline Al7075 + 1 wt % Zr Alloy Prepared Using Mechanical Milling and Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Orsolya Molnárová

    2017-09-01

    Full Text Available The microstructure, phase composition, and microhardness of both gas-atomized and mechanically milled powders of the Al7075 + 1 wt % Zr alloy were investigated. The gas-atomized powder exhibited a cellular microstructure (grain size of a few µm with layers of intermetallic phases along the cell boundaries. Mechanical milling (400 revolutions per minute (RPM/8 h resulted in a grain size reduction to the nanocrystalline range (20 to 100 nm along with the dissolution of the intermetallic phases. Milling led to an increase in the powder’s microhardness from 97 to 343 HV. Compacts prepared by spark plasma sintering (SPS exhibited negligible porosity. The grain size of the originally gas-atomized material was retained, but the continuous layers of intermetallic phases were replaced by individual particles. Recrystallization led to a grain size increase to 365 nm in the SPS compact prepared from the originally milled powder. Small precipitates of the Al3Zr phase were observed in the SPS compacts, and they are believed to be responsible for the retainment of the sub-microcrystalline microstructure during SPS. A more intensive precipitation in this SPS compact can be attributed to a faster diffusion due to a high density of dislocations and grain boundaries in the milled powder.

  15. Ultrafine grained high density manganese zinc ferrite produced using polyol process assisted by Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gaudisson, T.; Beji, Z.; Herbst, F.; Nowak, S. [ITODYS, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR-7086, 75205 Paris (France); Ammar, S., E-mail: ammarmer@univ-paris-diderot.fr [ITODYS, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR-7086, 75205 Paris (France); Valenzuela, R. [D2MC, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, 04510 Ciudad de Mexico (Mexico)

    2015-08-01

    We report the synthesis of Mn–Zn ferrite (MZFO) nanoparticles (NPs) by the polyol process and their consolidation by Spark Plasma Sintering (SPS) technique at relatively low temperature and short time, namely 500 °C for 10 min. NPs were obtained as perfectly epitaxied aggregated nanoclusters forming a kind of spherical pseudo-single-crystals of about 40 nm in size. The results on NPs consolidation by SPS underlined the importance of this clustering on the grain growth mechanism. Grain growth proceeds by coalescing nanocrystalline aggregates into single grain of almost the same average size, thus leading to a high density ceramic. Due to magnetic exchange interactions between grains, the produced ceramic does not exhibit thermal relaxation whereas their precursor polyol-made NPs are superparamagnetic. - Highlights: • Textured Mn–Zn ferrite nano-aggregates were produced in polyol. • Dense ceramic was obtained by SPS starting from these particles at 500 °C for 10 min. • The grain growth was driven by coalescence leading to nanometer-sized grains. • The 300 K-magnetic properties of the ceramic are typical of a soft magnet. • Its magnetization is very close to that of bulk despite its ultrafine grain size.

  16. Biomimetic apatite-based composite materials obtained by spark plasma sintering (SPS): physicochemical and mechanical characterizations.

    Science.gov (United States)

    Brouillet, Fabien; Laurencin, Danielle; Grossin, David; Drouet, Christophe; Estournes, Claude; Chevallier, Geoffroy; Rey, Christian

    2015-08-01

    Nanocrystalline calcium phosphate apatites are biomimetic compounds analogous to bone mineral and are at the origin of the bioactivity of most biomaterials used as bone substitutes. Their unique surface reactivity originates from the presence of a hydrated layer containing labile ions (mostly divalent ones). So the setup of 3D biocompatible apatite-based bioceramics exhibiting a high reactivity requests the development of «low» temperature consolidation processes such as spark plasma sintering (SPS), in order to preserve the characteristics of the hydrated nanocrystals. However, mechanical performances may still need to be improved for such nanocrystalline apatite bioceramics, especially in view of load-bearing applications. The reinforcement by association with biopolymers represents an appealing approach, while preserving the advantageous biological properties of biomimetic apatites. Herein, we report the preparation of composites based on biomimetic apatite associated with various quantities of microcrystalline cellulose (MCC, 1-20 wt%), a natural fibrous polymer. The SPS-consolidated composites were analyzed from both physicochemical (X-ray diffraction, Fourier transform infrared, solid state NMR) and mechanical (Brazilian test) viewpoints. The preservation of the physicochemical characteristics of apatite and cellulose in the final material was observed. Mechanical properties of the composite materials were found to be directly related to the polymer/apatite ratios and a maximum crushing strength was reached for 10 wt% of MCC.

  17. Microscopy of Alloy Formation on Arc Plasma Sintered Oxide Dispersion Strengthen (ODS) Steel

    Science.gov (United States)

    Bandriyana, B.; Sujatno, A.; Salam, R.; Dimyati, A.; Untoro, P.

    2017-07-01

    The oxide dispersed strengthened (ODS) alloys steel developed as structure material for nuclear power plants (NPP) has good resistant against creep due to their unique microstructure. Microscopy investigation on the microstructure formation during alloying process especially at the early stages was carried out to study the correlation between structure and property of ODS alloys. This was possible thanks to the arc plasma sintering (APS) device which can simulate the time dependent alloying processes. The ODS sample with composition of 88 wt.% Fe and 12 wt.% Cr powder dispersed with 1 wt.% ZrO2 nano powder was mixed in a high energy milling, isostatic compressed to form sample coins and then alloyed in APS. The Scanning Electron Microscope (SEM) with X-ray Diffraction Spectroscopy (EDX) line scan and mapping was used to characterize the microstructure and elemental composition distribution of the samples. The alloying process with unification of each Fe and Cr phase continued by the alloying formation of Fe-Cr by inter-diffusion of both Fe and Cr and followed by the improvement of the mechanical properties of hardness.

  18. High temperature Oxidation of ODS alloy with zirconia dispersions synthesized using Arc Plasma Sintering

    Science.gov (United States)

    Bandriyana; Sujatno, A.; Salam, R.; Sugeng, B.; Dimyati, A.

    2017-02-01

    Microstructure formation and oxidation behaviour of the Oxide Dispersion Strengthened (ODS) steels for application as structure material in Nuclear Power Plant was investigated. A mixture composed of Fe and 12 wt. % Cr powder with addition of 0.5 and 1 wt.% ZrO2 particles was milled and isostatic pressed to form a sample coin. The coin was then consolidated in the Arc Plasma Sintering (APS) for 4 minutes. The samples were subjected to the high temperature oxidation test in the Magnetic Suspension Balance (MSB). The oxidation test was carried out at 700°C for 6 hours to evaluate the oxide growth in the early stage of it formation by extraction the mass gain curve. The Scanning Electron Microscope (SEM) imaging and X-ray Diffraction Spectroscopy (EDX) elemental mapping were performed to study the microstructure change and compositional distribution. SEM and EDX observation revealed the time dependent development of the Fe-Cr-phases during consolidation. The oxidation rate behaviour of the samples followed the parabolic rate characteristic for inward oxidation process driven by oxygen inward diffusion through the oxide scale with the maximum weight gain around of 60 g/m2. The oxidation resistance was strongly affected by the formation of the oxide protective layer on the surface. In so far, addition of zirconia particles has played no significant role to the oxidation behaviour.

  19. Effect of Sintering Temperature on Electrical Properties of Chip on Glass Module with Direct Printing Method

    Science.gov (United States)

    Lee, Young-Chul; Kim, Yongil; Jung, Seung-Boo

    2012-09-01

    In order to apply the direct printing method to the fabrication of chip on glass (COG) modules, we examined that the effect of the sintering temperature on the electrical properties of a COG module with direct printing method. Firstly, we fabricated an Ag conductive circuit on a glass substrate by the screen-printing method. To investigate its the effect on the electrical properties of the circuit, it was sintered at various temperatures, such as 150, 200, 250, and 300 °C for 30 min. Subsequently, we conducted Au electro-plating for the fabrication of a Si dummy chip. Finally, the flip-chip bonding process was conducted using anisotropic conductive film (ACF). The printed Ag circuits were well formed on the quartz substrate without any shorts or remarkable changes compared with the initial design. The electrical properties of the printed Ag circuits improved with increasing sintering temperature. The conductive particles in the ACF were well deformed in between the Au bumps and printed Ag pads after the bonding process. The four-point probe method was employed to measure the connection resistance of the joints constructed with the Au bumps on the Si chip and printed Ag circuit on the quartz substrate. The resistances of the interconnections drastically decreased with increasing sintering temperature, i.e., subsequently converged from 11.8 Ω to 7.36 mΩ.

  20. Spark Plasma Sintered Si3N4/TiN Nanocomposites Obtained by a Colloidal Processing Route

    Directory of Open Access Journals (Sweden)

    L. A. Díaz

    2016-01-01

    Full Text Available Ceramic Si3N4/TiN (22 vol% nanocomposites have been obtained by Spark Plasma Sintering (SPS. Our colloidal processing route allows obtaining dispersed nanoparticles of TiN smaller than 50 nm avoiding the presence of agglomerates. The nanostructured starting powders were obtained by using a colloidal method where commercial Si3N4 submicrometer particles were coated with anatase TiO2 nanocrystals. A later nitridation process led to the formation of TiN nanoparticles on the surface of Si3N4. A second set of powders was prepared by doping the above defined powders with yttrium and aluminium precursors using also a colloidal method as sources of alumina and yttria. After thermal nitridation and SPS treatment, it has been found that the addition of oxides dopants improves the mechanical performance (KIC, σf but increases the electrical resistivity and significantly reduces the hardness. This is due to the formation of a continuous insulating glassy phase that totally envelops the conductive TiN nanoparticles, avoiding the percolative contact between them. The combination of colloidal processing route and SPS allows the designing of tailor-made free glassy phase Si3N4/TiN nanocomposites with controlled microstructure. The microstructural features and the thermoelectrical and mechanical properties of both kinds of dense SPSed compacts are discussed in this work.

  1. Fabrication of Ni-Ti Alloy by Self-Propagating High-Temperature Synthesis and Spark Plasma Sintering Technique

    Science.gov (United States)

    Salvetr, Pavel; Kubatík, Tomáš František; Pignol, Damien; Novák, Pavel

    2017-04-01

    This work is focused on the possibilities of preparing Ni-Ti46 wt pct alloy by powder metallurgy methods. The self-propagating high-temperature synthesis (SHS) and combination of SHS reaction, milling, and spark plasma sintering consolidation (SPS) are explored. The aim of this work is the development of preparation method with the lowest amount of undesirable phases (mainly Ti2Ni phase). The SHS with high heating rate (approx. 200 and 300 K min-1) was applied. Because the SHS product is very porous, it was milled in vibratory disk milling and consolidated by SPS technique at temperatures of 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C). The microstructures of samples prepared by SHS reaction and combination of SHS reaction, milling, and SPS consolidation are compared. The changes in microstructure with increasing temperature of SPS consolidation are observed. Mechanical properties are tested by hardness measurement. The way to reduce the amount of Ti2Ni phase in structure is leaching of powder in 35 pct hydrochloric acid before SPS consolidation.

  2. Effect of Spark-Plasma-Sintering Conditions on Tensile Properties of Aluminum Matrix Composites Reinforced with Multiwalled Carbon Nanotubes (MWCNTs)

    Science.gov (United States)

    Chen, B.; Imai, H.; Umeda, J.; Takahashi, M.; Kondoh, K.

    2017-02-01

    In this study, aluminum (Al) matrix composites containing 2 wt.% multiwalled carbon nanotubes (CNTs) were fabricated by powder metallurgy using high-energy ball milling (HEBM), spark plasma sintering (SPS), and subsequent hot extrusion. The effect of SPS conditions on the tensile properties of CNT/Al composites was investigated. The results showed that composites with well-dispersed CNTs and nearly full-density CNT/Al can be obtained. During HEBM, CNTs were shortened, inserted into welded Al powder particles, bonded to Al, and still stable without CNT-Al reaction. After consolidation, Al4C3 phases formed in composites under different sintering conditions. With the increase of sintering temperature and holding time, the strength decreased. Conversely, the ductility and toughness noticeably increased. As a result, a good balance between strength (367 MPa in ultimate tensile strength) and ductility (13% in elongation) was achieved in the as-extruded CNT/Al composite sintered at 630°C with a holding time of 300 min.

  3. Synthesis of Vanadium-Vanadium Carbide in-situ nanocomposites by high energy ball milling and spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Krishnan Vinoadh Kumar

    2016-01-01

    Full Text Available In the present work, Vanadium-Vanadium Carbide (V-V2C in-situ nanocomposites were synthesized by mechanically milling vanadium powders with 0.5 wt.% stearic acid. Milled powders were consolidated using spark plasma sintering at 1150, 1250 and 1350°C for 10 min. Phase and morphology of the milled powders were studied using X-ray diffraction and scanning electron microscopy. X-ray diffraction analysis of 10 h milled powder shows the evolution of amorphous phase. Energy dispersive X-ray spectroscopy studies on milled powder shows the presence of carbon, which could be due to the decomposition of stearic acid during milling. Degree of crystallinity of milled powder was confirmed using the selective area electron diffraction pattern. X-ray diffraction analysis of sintered samples indicate sharp peaks from vanadium and vanadium carbide (V2C, endorsing amorphous to nanocrystalline transformation. Micro-hardness value of sintered samples increases with increasing sintering temperature.

  4. Orientation distribution in Bi{sub 2}Te{sub 3}-based compound prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.T.; Kim, Y.H. [System Engineering Team, Korea Inst. of Industrial Technology, Ibjang-Myun, Chonan, ChungNam (Korea); Lim, C.H.; Cho, D.C.; Lee, Y.S.; Lee, C.H. [Dept. of Metallurgical Engineering, Coll. of Engineering, Inha Univ., Nam-Gu, Inchon (Korea)

    2005-07-01

    P-type Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} compounds doped with 3wt.% Te were fabricated by spark plasma sintering after mixing large powders(P{sub L}) and small powders(P{sub S}). We could obtained the highest figure of merit(Z{sub C}) of 2.89 x 10{sup -3}/K in sintered compound mixed to P{sub L}:P{sub S}=80:20. This resulted from the increase of orientation by large powders(P{sub S}) and the reduce of pores by small powders. The figure of merit(Z{sub C}) of the sintered compound using only small powders(P{sub S}) showed lower value of 2.67 x 10{sup -3}/K compared with that of sintered compound mixed to P{sub L}:P{sub S}=80:20 due to the increase of electrical resistivity. (orig.)

  5. Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

    Science.gov (United States)

    Scott, Spencer M.; Yao, Tiankai; Lu, Fengyuan; Xin, Guoqing; Zhu, Weiguang; Lian, Jie

    2017-03-01

    High-energy ball milling was used to synthesize Th1-xLaxO2-0.5x (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO2 powders. Dense La-doped ThO2 pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO2 pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C.

  6. Fabrication Of Zn4Sb3 Alloys By A Combination Of Gas-Atomization And Spark Plasma Sintering Processes

    Directory of Open Access Journals (Sweden)

    Dharmaiah P.

    2015-06-01

    Full Text Available In this study, single phase polycrystalline Zn4Sb3 as well as 11 at.% Zn-rich Zn4Sb3 alloy having ε-Zn4Sb3 (majority phase and Zn (minority phase phases bulk samples produced by gas-atomization and subsequently consolidated by spark plasma sintering (SPS process. The crystal structures were analyzed by X-ray diffraction (XRD and cross-sectional microstructure were observed by the scanning electron microscopy (SEM. The internal grain microstructure of 11at.% Zn-rich Zn4Sb3 powders shows lamellar structure. Relative density, Vickers hardness and crack lengths were measured to investigate the effect of sintering temperature of Zn4Sb3 samples which are sintered at 653, 673 and 693 K. Relative density of the single phase bulk Zn4Sb3 sample reached to 99.2% of its theoretical density. The micro Vickers hardness of three different sintering temperatures were found around 2.17 – 2.236 GPa.

  7. Magnetic properties of LiZnCu ferrite synthesized by the microwave sintering method

    Energy Technology Data Exchange (ETDEWEB)

    Khot, Sujata S., E-mail: sujataskhot@rediffmail.com [D.B.J. College, Chiplun, Maharashtra (India); Smt. Chandibai Himathmal Mansukhani College, Ulhasnagar, Maharashtra (India); Shinde, Neelam S., E-mail: neelamshinde1976@gmail.com [D.B.J. College, Chiplun, Maharashtra (India); Smt. Chandibai Himathmal Mansukhani College, Ulhasnagar, Maharashtra (India); Basavaiah, Nathani, E-mail: bas@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel 410218, Maharashtra (India); Watawe, Shrikant C., E-mail: shrikantwatawe@yahoo.com [P.D.Karkhanis College, Ambernath (East), Maharashtra (India); Vaidya, Milind M., E-mail: milind_chm@yahoo.co.in [Vedanta College of Management and Information Technology, Vitthalvadi (West), Maharashtra (India)

    2015-01-15

    Lithium ferrites have attracted considerable attention because they have been used as replacements for garnets due to their low cost. A series of polycrystalline ferrite samples were prepared with the composition of Li{sub X}Zn{sub (0.6−2X)}Cu{sub 0.4}Fe{sub 2}O{sub 4}(X=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at chemical reaction temperature 150 °C by sintering with microwave assisted combustion method. The characterization shows the formation of single phase cubic structure when carried out by using the X-rays technique and I–R technique. Magnetization parameters such as saturation magnetization, coercivity, magnetic moment were calculated by using the Hysteresis graph. The Curie temperature obtained using the susceptibility data are found to be in the range 350–700 °C. Anhysteric remanent magnetization is used for estimating the grain size and domain structure of the composition. An attempt has been made to synthesis the nano-particles at lower reaction temperature by using non-conventional microwave sintering method. The advantage of this method is its lower sintering temperature and time compared to the conventional ceramic technique and direct formation of nano-ferrites without ball-milling. - Highlights: • Single spinel phases of LiZnCu ferrite are studied. • Different sized particles, ranging 43–63 nm were formed by using microwave sintering method. • The substitution of Zn{sup 2+} ions alters the domain structure from SD to MD and then to SP. • SD particle have higher ARM intensities per unit mass compared to MD particles. • A combination of lower chemical reaction temperature with microwave sintering could be useful for obtaining nano-ferrites.

  8. Magnetic properties of lithium zinc ferrites synthesized by microwave sintered method

    Science.gov (United States)

    Yang, Qinghui; Zhang, Huaiwu; Wen, Qiye; Liu, Yingli; Yang, Xuwen

    2016-05-01

    In this paper, a series of polycrystalline ferrite samples were prepared with the composition of Zn0.1Li0.525-xTi0.15MgxFe2.225-0.5xO4 (LiZn) (x=0, 0.05, 0.10, 0.15 and 0.20) using both microwave sintering (MS) and conventional sintering (CS) technologies, respectively. The sintering time and temperature were 22 hours and 1000°C for the CS process, and 2 hours and 880°C for the MS process. Experiments showed that the MS treated LiZn ferrites exhibited more excellent magnetic properties and denser, more uniform micro-structures comparing with the ones treated by CS method. For the LiZn ferrite (x=0.1) sintered at 880°C using MS, the saturation magnetic induction (Bs) is 242.3 mT, the coercive force (Hc) is 135 A/m, the square ratio (Br/Bs) is 0.87 and the ferromagnetic resonance line-width (Δ H) is 143.2 Oe. These results represented very good properties for an X-band phase shifter material and indicated that the MS method is a potentially important technique for fabricating low temperature co-fired ceramics (LTCC).

  9. Magnetic properties of lithium zinc ferrites synthesized by microwave sintered method

    Directory of Open Access Journals (Sweden)

    Qinghui Yang

    2016-05-01

    Full Text Available In this paper, a series of polycrystalline ferrite samples were prepared with the composition of Zn0.1Li0.525-xTi0.15MgxFe2.225-0.5xO4 (LiZn (x=0, 0.05, 0.10, 0.15 and 0.20 using both microwave sintering (MS and conventional sintering (CS technologies, respectively. The sintering time and temperature were 22 hours and 1000°C for the CS process, and 2 hours and 880°C for the MS process. Experiments showed that the MS treated LiZn ferrites exhibited more excellent magnetic properties and denser, more uniform micro-structures comparing with the ones treated by CS method. For the LiZn ferrite (x=0.1 sintered at 880°C using MS, the saturation magnetic induction (Bs is 242.3 mT, the coercive force (Hc is 135 A/m, the square ratio (Br/Bs is 0.87 and the ferromagnetic resonance line-width (Δ H is 143.2 Oe. These results represented very good properties for an X-band phase shifter material and indicated that the MS method is a potentially important technique for fabricating low temperature co-fired ceramics (LTCC.

  10. The Verwey transition in nanostructured magnetite produced by a combination of chimie douce and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gaudisson, T.; Nowak, S.; Ammar, S. [ITODYS, Université Paris Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086, 75205 Paris Cedex (France); Vázquez-Victorio, G.; Valenzuela, R., E-mail: raulvale@yahoo.com [Depto Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Mexico 04510 (Mexico); Bañobre-López, M.; Rivas, J. [International Iberian Nanotechnology Laboratory, 4715-310 Braga (Portugal); Mazaleyrat, F. [SATIE, ENS Cachan, CNRS, UniverSud, F-94230 Cachan (France)

    2014-05-07

    Magnetite nanoparticles about 10 nm sized were synthesized by the polyol method. Zero-field-cooled (ZFC)-FC measurements showed a blocking temperature ∼170 K and the absence of the Verwey transition. They were subsequently consolidated by spark plasma sintering at 750 °C for 15 min, leading to a high density (92% of the theoretical density), solid body, with grains in the 150 nm range. X-ray diffraction patterns exhibited a spinel single phase with cell parameters corresponding to the magnetite structure. Magnetic measurements showed a decrease of coercivity from 685 Oe (54.5 kA/m) at 118 K to 90 Oe (7.2 kA/m) at 139 K. ZFC measurements at 25 Oe presented a three-fold magnetization increase as temperature increased; a small transition between 116 and 117.5 K, followed by a larger one from 117.6 to 124 K. The first transition can be associated with a complex crystallographic transition and delocalization of Fe{sup 2+}-Fe{sup 3+}, while the second one can be attributed to spin reorientation due to the magnetocrystalline anisotropy constant (K{sub 1}) change of sign as previously observed only in magnetite single crystals.

  11. The Verwey transition in nanostructured magnetite produced by a combination of chimie douce and spark plasma sintering

    Science.gov (United States)

    Gaudisson, T.; Vázquez-Victorio, G.; Bañobre-López, M.; Nowak, S.; Rivas, J.; Ammar, S.; Mazaleyrat, F.; Valenzuela, R.

    2014-05-01

    Magnetite nanoparticles about 10 nm sized were synthesized by the polyol method. Zero-field-cooled (ZFC)-FC measurements showed a blocking temperature ˜170 K and the absence of the Verwey transition. They were subsequently consolidated by spark plasma sintering at 750 °C for 15 min, leading to a high density (92% of the theoretical density), solid body, with grains in the 150 nm range. X-ray diffraction patterns exhibited a spinel single phase with cell parameters corresponding to the magnetite structure. Magnetic measurements showed a decrease of coercivity from 685 Oe (54.5 kA/m) at 118 K to 90 Oe (7.2 kA/m) at 139 K. ZFC measurements at 25 Oe presented a three-fold magnetization increase as temperature increased; a small transition between 116 and 117.5 K, followed by a larger one from 117.6 to 124 K. The first transition can be associated with a complex crystallographic transition and delocalization of Fe2+-Fe3+, while the second one can be attributed to spin reorientation due to the magnetocrystalline anisotropy constant (K1) change of sign as previously observed only in magnetite single crystals.

  12. The spatial distribution of temperature and oxygen deficiency in spark-plasma sintered superconducting Bi-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Govea-Alcaide, E.; Pérez-Fernández, J.E. [Departamento de Ciencias Básicas, Facultad de Ciencias Técnicas, Universidad de Granma, Apdo. 21, P.O. Box 85100, Bayamo (Cuba); Machado, I.F. [Departamento de Engenharia Mecatrônica e Sistemas Mecânicos, Escola Politécnica, Universidade de São Paulo, 05508-900 São Paulo, SP (Brazil); Jardim, R.F., E-mail: rjardim@if.usp.br [Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP (Brazil)

    2014-12-15

    Pre-reacted powders of (Bi–Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+δ} (Bi-2223) were consolidated by using the spark plasma sintering (SPS) technique under vacuum and at different consolidate temperatures T{sub D}. X-ray diffraction patterns revealed that the dominant phase in all SPS samples is the Bi-2223 phase, but traces of the Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 10+x} (Bi-2212) phase were identified. We have found that the transport properties of SPS samples depend on their oxygen content because the SPS process is performed under vacuum. Simulations by using the finite element method (FEM) were performed for determining the actual temperature in which powders are consolidated. From these results we have inferred that SPS samples are oxygen deficient and such a deficiency is more marked near the grain boundaries, suggesting the occurrence of grains with core–shell morphology. We also argued that the width of the shell depends on the consolidation temperature, a feature corroborated by the FEM simulations.

  13. Corrosion Behavior and Strength of Dissimilar Bonding Material between Ti and Mg Alloys Fabricated by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Patchara Pripanapong

    2016-08-01

    Full Text Available Ti and solution treated Mg alloys such as AZ31B (ST, AZ61 (ST, AZ80 (ST and AZ91 (ST were successfully bonded at 475 °C by spark plasma sintering, which is a promising new method in welding field. The formation of Ti3Al intermetallic compound was found to be an important factor in controlling the bonding strength and galvanic corrosion resistance of dissimilar materials. The maximum bonding strength and bonding efficiency at 193 MPa and 96% were obtained from Ti/AZ91 (ST, in which a thick and uniform nano-level Ti3Al layer was observed. This sample also shows the highest galvanic corrosion resistance with a measured galvanic width and depth of 281 and 19 µm, respectively. The corrosion resistance of the matrix on Mg alloy side was controlled by its Al content. AZ91 (ST exhibited the highest corrosion resistance considered from its corrode surface after corrosion test in Kroll’s etchant. The effect of Al content in Mg alloy on bonding strength and corrosion behavior of Ti/Mg alloy (ST dissimilar materials is discussed in this work.

  14. Electrochemical properties of the passive film on bulk Zr-Fe-Cr intermetallic fabricated by spark plasma sintering

    Science.gov (United States)

    Bai, Yakui; Ling, Yunhan; Lai, Wensheng; Xing, Shupei; Ma, Wen

    2016-12-01

    Although Zr-based second phase particles (SPPs) are important factors influencing corrosion resistance of zircaloy cladding materials, the corrosion behavior of SPPs has not been investigated by means of electrochemical method so far. In order to clarify the role of SPPs commonly existed in zircaloy, bulk Zr-based intermetallics were firstly fabricated by spark plasma sintering (SPS) at temperatures 1373 K and an applied pressure of 60 MPa in this work. Both the natural passive film on surface and oxidation behavior of intermetallic has been investigated in this work. X-ray diffraction (XRD) pattern showed that as-prepared intermetallic of crystal structure belongs to Laves phase with AB2 type. Electrochemical measurement of passive film on surface of bulk Zr-based intermetallic exhibited significant difference with that of zirconium. Potentiodynamic measurements results revealed that intermetallic exhibited higher corrosion potential and lower corrosion current density than that of pure zirconium, implying that Zr-based second phase will act as cathode when they are included in zirconium matrix. Meanwhile, significant improvement of Zr-Fe-Cr intermetallic on the water chemistry corrosion resistance was demonstrated comparing with Zr-Fe and Zr-Cr binary intermetallics.

  15. Fabrication of Tungsten-Rhenium Cladding materials via Spark Plasma Sintering for Ultra High Temperature Reactor Applications

    Energy Technology Data Exchange (ETDEWEB)

    Charit, Indrajit; Butt, Darryl; Frary, Megan; Carroll, Mark

    2012-11-05

    This research will develop an optimized, cost-effective method for producing high-purity tungsten-rhenium alloyed fuel clad forms that are crucial for the development of a very high-temperature nuclear reactor. The study will provide critical insight into the fundamental behavior (processing-microstructure- property correlations) of W-Re alloys made using this new fabrication process comprising high-energy ball milling (HEBM) and spark plasma sintering (SPS). A broader goal is to re-establish the U.S. lead in the research field of refractory alloys, such as W-Re systems, with potential applications in very high-temperature nuclear reactors. An essential long-term goal for nuclear power is to develop the capability of operating nuclear reactors at temperatures in excess of 1,000K. This capability has applications in space exploration and some special terrestrial uses where high temperatures are needed in certain chemical or reforming processes. Refractory alloys have been identified as being capable of withstanding temperatures in excess of 1,000K and are considered critical for the development of ultra hightemperature reactors. Tungsten alloys are known to possess extraordinary properties, such as excellent high-temperature capability, including the ability to resist leakage of fissile materials when used as a fuel clad. However, there are difficulties with the development of refractory alloys: 1) lack of basic experimental data on thermodynamics and mechanical and physical properties, and 2) challenges associated with processing these alloys.

  16. Microstructure and mechanical properties of Al-Si-Ni-Ce alloys prepared by gas-atomization spark plasma sintering and hot-extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, E.R. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Hui, X.D., E-mail: xdhui@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Wang, S.S.; Zhao, Y.F.; Chen, G.L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2011-07-15

    Highlights: {yields} There are distinct microstructures in the as-atomized powders with different size. {yields} The morphology of Al{sub 11}Ce{sub 3} crystals is related to the Ni content. {yields} Tiny Al{sub 3}Ni precipitated from the supersaturated matrix after SPS process. {yields} Hot-extrusion leads to the improved microstructures. {yields} This kind of alloy exhibits high comprehensive mechanical properties. - Abstract: Al-Si-Ni-Ce alloys with the composition of Al{sub 78.5}Si{sub 19}Ni{sub 2}Ce{sub 0.5}, Al{sub 76}Si{sub 19}Ni{sub 4}Ce{sub 1} and Al{sub 73}Si{sub 19}Ni{sub 7}Ce{sub 1} were atomized and then sintered by using spark plasma method. The microstructure of the as-atomized powders, sintered and hot-extruded samples was analyzed. The influences of granularity and sintering parameters including time and temperature on the density of sintered alloy were also discussed. It is shown that the atomized powders are composed of Si, Al{sub 11}Ce{sub 3}, Al{sub 3}Ni and alpha Al. Tiny Al{sub 3}Ni particles precipitate from supersaturated matrix near the powder boundaries during SPS. Hot-extrusion process leads to the layer structure and more homogeneous distribution of precipitates. These alloys exhibit high comprehensive mechanical properties with combination of high Vicker's micro-hardness, moderate tensile properties and elongation, which provide a novel kind of promising engineering materials.

  17. Study on synthesis of titanium carbide bulk by spark plasma sintering%放电等离子烧结制备碳化钛块材研究

    Institute of Scientific and Technical Information of China (English)

    陈灿坤; 刘少存; 张洋; 胡文涛; 向建勇; 温福昇; 王鹏; 王海涛; 柳忠元

    2012-01-01

    利用放电等离子烧结(SPS)对碳化钛(TiC)/氢化钛(TiH2)混合粉末进行烧结以制备块材.利用X射线衍射(XRD)并结合Rietveld精修法对块材进行定性与结构分析;借助扫描电子显微镜(SEM)对块材断面微观形貌进行观察;测试了块材硬度并探讨SPS技术制备TiC块材的致密化过程与反应机理.结果表明:混合粉末经SPS烧结,获得了高度致密的TiC块材;与传统烧结方法比较,SPS技术更具低温快速性.%In this work, the blended powders of titanium carbide (TiC) /titanium hydride (TiH2) are sintered by spark plasma sintering (SPS) in order to prepare TiC bulk. The qualitive and structural analysis are realized by X-ray diffraction (XRD) combined with Rietveld refinement. Furthermore, the micrographs of the fracture surface is characterized by scanning electron microscopy (SEM). Then, the hardness is measured and the densification and reactive mechanism of TiC bulk prepared by SPS technology are discussed. The results show that the TiC bulk with good densification is prepared by SPS with the starting materials of blended powders.Compared with traditional sintering methods.the SPS technology is of lower sintering temperature and less time.

  18. Mechanical properties and microstructure of Fe3Al intermetallics fabricated by mechanical alloying and spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    HE Qing; JIA Cheng-chang; MENG Jie

    2006-01-01

    Fabrication technology and mechanical properties of the Fe3Al based alloys were studied by spark plasma sintering from elemental powders (Fe-30Al, volume fraction, %) and mechanically alloying powders. The mechanically alloying powders were processed by the high-energy ball milling the elemental mixture powders with the milling time of 5, 8 and 10 min, respectively. The spark plasma sintering process was performed under the pressure of 50 MPa at 1 050 ℃ for 5 min. The phase identification by X-ray diffraction presents the Fe reacts with Al completely during the processing time. The samples are nearly full density (e.g. the relative density of sinter of raw powder is 99%). The microstructure was observed by TEM. The mechanical properties were tested by three-point bending at room temperature in air. The results show that the mechanical properties are better (e.g. bend strength of 1 500 MPa ) than those of the ordinary Fe3Al casting.

  19. NCSX Plasma Heating Methods

    Energy Technology Data Exchange (ETDEWEB)

    H.W. Kugel; D. Spong; R. Majeski; M. Zarnstorff

    2003-02-28

    The NCSX (National Compact Stellarator Experiment) has been designed to accommodate a variety of heating systems, including ohmic heating, neutral-beam injection, and radio-frequency. Neutral beams will provide one of the primary heating methods for NCSX. In addition to plasma heating, beams are also expected to provide a means for external control over the level of toroidal plasma rotation velocity and its profile. The plan is to provide 3 MW of 50 keV balanced neutral-beam tangential injection with pulse lengths of 500 msec for initial experiments, and to be upgradeable to pulse lengths of 1.5 sec. Subsequent upgrades will add 3 MW of neutral-beam injection. This Chapter discusses the NCSX neutral-beam injection requirements and design issues, and shows how these are provided by the candidate PBX-M (Princeton Beta Experiment-Modification) neutral-beam injection system. In addition, estimations are given for beam-heating efficiencies, scaling of heating efficiency with machine size an d magnetic field level, parameter studies of the optimum beam-injection tangency radius and toroidal injection location, and loss patterns of beam ions on the vacuum chamber wall to assist placement of wall armor and for minimizing the generation of impurities by the energetic beam ions. Finally, subsequent upgrades could add an additional 6 MW of radio-frequency heating by mode-conversion ion-Bernstein wave (MCIBW) heating, and if desired as possible future upgrades, the design also will accommodate high-harmonic fast-wave and electron-cyclotron heating. The initial MCIBW heating technique and the design of the radio-frequency system lend themselves to current drive, so that if current drive became desirable for any reason only minor modifications to the heating system described here would be needed. The radio-frequency system will also be capable of localized ion heating (bulk or tail), and possibly ion-Bernstein-wave-generated sheared flows.

  20. NCSX Plasma Heating Methods

    Energy Technology Data Exchange (ETDEWEB)

    Kugel, H. W.; Spong, D.; Majeski, R.; Zarnstorff, M.

    2008-01-18

    The National Compact Stellarator Experiment (NCSX) has been designed to accommodate a variety of heating systems, including ohmic heating, neutral beam injection, and radio-frequency (rf). Neutral beams will provide one of the primary heating methods for NCSX. In addition to plasma heating, neutral beams are also expected to provide a means for external control over the level of toroidal plasma rotation velocity and its profile. The experimental plan requires 3 MW of 50-keV balanced neutral beam tangential injection with pulse lengths of 500 ms for initial experiments, to be upgradeable to pulse lengths of 1.5 s. Subsequent upgrades will add 3MW of neutral beam injection (NBI). This paper discusses the NCSX NBI requirements and design issues and shows how these are provided by the candidate PBX-M NBI system. In addition, estimations are given for beam heating efficiencies, scaling of heating efficiency with machine size and magnetic field level, parameter studies of the optimum beam injection tangency radius and toroidal injection location, and loss patterns of beam ions on the vacuum chamber wall to assist placement of wall armor and for minimizing the generation of impurities by the energetic beam ions. Finally, subsequent upgrades could add an additional 6 MW of rf heating by mode conversion ion Bernstein wave (MCIBW) heating, and if desired as possible future upgrades, the design also will accommodate high-harmonic fast-wave and electron cyclotron heating. The initial MCIBW heating technique and the design of the rf system lend themselves to current drive, so if current drive became desirable for any reason, only minor modifications to the heating system described here would be needed. The rf system will also be capable of localized ion heating (bulk or tail), and possiblyIBW-generated sheared flows.

  1. Can the use of pulsed direct current induce oscillation in the applied pressure during spark plasma sintering?

    Directory of Open Access Journals (Sweden)

    David Salamon, Mirva Eriksson, Mats Nygren and Zhijian Shen

    2012-01-01

    Full Text Available The spark plasma sintering (SPS process is known for its rapid densification of metals and ceramics. The mechanism behind this rapid densification has been discussed during the last few decades and is yet uncertain. During our SPS experiments we noticed oscillations in the applied pressure, related to a change in electric current. In this study, we investigated the effect of pulsed electrical current on the applied mechanical pressure and related changes in temperature. We eliminated the effect of sample shrinkage in the SPS setup and used a transparent quartz die allowing direct observation of the sample. We found that the use of pulsed direct electric current in our apparatus induces pressure oscillations with the amplitude depending on the current density. While sintering Ti samples we observed temperature oscillations resulting from pressure oscillations, which we attribute to magnetic forces generated within the SPS apparatus. The described current–pressure–temperature relations might increase understanding of the SPS process.

  2. Structure and strength of aluminum with sub-micrometer/micrometer grain size prepared by spark plasma sintering

    DEFF Research Database (Denmark)

    Le, G.M.; Godfrey, A.; Hansen, Niels

    2013-01-01

    A spark plasma sintering (SPS) technique has been applied to prepare fully dense Al samples from Al powder. By applying a sintering temperature of 600°C and a loading pressure of 50MPa, fully recrystallized samples of nearly 100% density with average grain sizes of 5.2μm, 1.3μm and 0.8μm have been...... the initial powder particle size. The SPS samples show higher strength than Al samples with an identical grain size prepared using thermo-mechanical processing, and a better strength-ductility combination, with the 1.3μm grain size sample showing a yield strength (σ0.2%) of 140MPa and a uniform elongation...

  3. Stable solidification of cesium with an allophane additive by a pressing/sintering method

    Science.gov (United States)

    Zhang, Xiaoxia; Wu, Yan; Wei, Yuezhou; Mimura, Hitoshi; Matsukura, Minoru

    2017-03-01

    Pyrolysis of AMP/SiO2 adsorbed Cs (AMP-Cs/SiO2) occurred at > 400 °C sintering temperature, and Cs immobilisation decreased from 100% to 40% after sintering at 1200 °C. To safely dispose radioactive Cs, allophane was immobilized with AMP-Cs/SiO2 to prepare a stable form by using a pressing/sintering method. The structure of AMP-Cs/SiO2 collapsed, and cesium aluminosilicate formed more easily under conditions of higher sintering temperature (>800 °C) or increasing mixing ratio of allophane (mass ratio = 1:3 AMP-Cs/SiO2-allophane). The decomposition products of AMP-Cs/SiO2 were Cs2O, MoO3 and P2O5 at 1200 °C. Cs2O volatilisation was depressed by allophane addition, and a stable immobilisation phase of Cs4Al4Si20O48 formed. An immobilisation ratio of Cs of approximately 100% was maintained. The leachability of Cs for AMP-Cs/SiO2-allophane (1:3, 1200 °C) in distilled water at 25 °C and 90 °C for 15 days was estimated as 0.174% and 1.55%, respectively.

  4. Fabrication, characterization, and mechanical properties of spark plasma sintered Al–BN nanoparticle composites

    Energy Technology Data Exchange (ETDEWEB)

    Firestein, Konstantin L., E-mail: kosty@firestein.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Steinman, Alexander E.; Golovin, Igor S. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Cifre, Joan [Universitat de les Illes Balears, Ctra. de Valldemossa, km. 7.5, E-07122 Palma de Mallorca (Spain); Obraztsova, Ekaterina A.; Matveev, Andrei T.; Kovalskii, Andrey M. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Lebedev, Oleg I. [CRISMAT, UMR 6508, CNRS-ENSICAEN, 6Bd Marechal Juin, 14050 Caen (France); Shtansky, Dmitry V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Golberg, Dmitri, E-mail: golberg.dmitri@nims.go.jp [World Premier International Center for Materials Nanoarchitectonics (WPI-MANA) National Institute for Materials Science (NIMS), Namiki 1, Tsukuba, Ibaraki 3050044 (Japan)

    2015-08-26

    Fabrication of high strength yet light and low cost composite materials with good mechanical properties at room and elevated temperatures is a challenge that metallurgy and materials science communities are facing for many years, and no “dream material” has been developed so far. The primary goal of this study was to fabricate, characterize, and to carry out tensile tests on Al-based composite materials strengthened with commercially-available BN nanoparticles (BNNPs). The composites were fabricated by spark plasma sintering (SPS) technique. The structures of powder mixtures and composite materials, as well as their fracture surfaces, were studied by scanning and transmission electron microscopy. The influence of BNNPs content (0.5, 1.5, 3, 4.5, 6, and 7.5 wt%) and holding times (5, 60, and 300 min) at 600 °C during SPS on the tensile strength was investigated. A maximum increase in strength was observed for Al-based composites with 4.5 wt% of BNNPs. The sample demonstrated a 50% increase in tensile strength compared with pristine Al. Although the tensile tests performed at 300 °C revealed that the tensile strength became 20% lower than the strength at room temperature, it was, however, still 75% higher compared with that of the pure Al at 300 °C. In addition, at 300 °C the Al–BNNPs composites demonstrated a much higher value of yield stress, about 115 MPa, which is 190% higher than that of pure Al at the same temperature. The damping properties of Al–BNNPs composites were evaluated by temperature dependent internal friction (TDIF) measurements. The obtained results are discussed based on structural analysis and the TDIF data.

  5. Spark plasma sintered bismuth telluride-based thermoelectric materials incorporating dispersed boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Williams, H.R., E-mail: hugo.williams@leicester.ac.uk [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Ambrosi, R.M. [Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Chen, K. [School of Engineering and Materials Science, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom); Friedman, U. [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Ning, H.; Reece, M.J. [School of Engineering and Materials Science, Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom); Robbins, M.C.; Simpson, K. [European Thermodynamics Ltd., 8 Priory Business Park, Wistow Road, Kibworth LE8 0R (United Kingdom); Stephenson, K. [European Space Agency, ESTEC TEC-EP, Keplerlaan 1, 2201AZ Noordwijk (Netherlands)

    2015-03-25

    Highlights: • Nano-B{sub 4}C reinforced Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} p-type thermoelectric produced by SPS. • Addition of B{sub 4}C up to 0.2 vol% to SPS’d material has little effect on zT. • Vickers hardness improved by 27% by adding 0.2 vol% B{sub 4}C. • Fracture toughness of SPS material: K{sub IC} = 0.80 MPa m{sup 1/2} by SEVNB. • Mechanical properties much better than commercial directionally solidified material. - Abstract: The mechanical properties of bismuth telluride based thermoelectric materials have received much less attention in the literature than their thermoelectric properties. Polycrystalline p-type Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} materials were produced from powder using spark plasma sintering (SPS). The effects of nano-B{sub 4}C addition on the thermoelectric performance, Vickers hardness and fracture toughness were measured. Addition of 0.2 vol% B{sub 4}C was found to have little effect on zT but increased hardness by approximately 27% when compared to polycrystalline material without B{sub 4}C. The K{sub IC} fracture toughness of these compositions was measured as 0.80 MPa m{sup 1/2} by Single-Edge V-Notched Beam (SEVNB). The machinability of polycrystalline materials produced by SPS was significantly better than commercially available directionally solidified materials because the latter is limited by cleavage along the crystallographic plane parallel to the direction of solidification.

  6. Preparation of Bulk Graphene Nanoplatelets by Spark Plasma Sintering — Electrical and Thermal Properties

    Science.gov (United States)

    Prasad, Mattipally; Rao, Tata N.; Prasad, P. S. R.; Babu, D. Suresh

    2016-10-01

    Consolidation of graphene nanoplatelets (GNPs) by spark plasma sintering (SPS) to study the feasibility of its structure retention at extreme temperature and pressure conditions. Structural characterization of the GNP powder and pellet were carried out by Micro-Raman, SEM, and TEM. HT-XRD. A.C. and D.C. conductivity of GNP pellet is carried out at room temperature. GNPs survived its structure in the SPS processing at an extreme temperature of 1850∘C and uni-axial pressure 60MPa, vacuum at 2.5-3.2 × 10-3 Torr. Our study shows the potential for GNPs to be successfully used as a reinforcing in ceramic matrix composites using SPS. The diffraction has been accurately calibrated to waterfall the shift in 2θ values at elevated temperatures. The corrected lattice parameter data have been used to estimate the instantaneous and mean thermal expansion coefficients as a function of temperature. The lattice parameters “a” and “c” for powder and pellet GNP is found to be 0.2456(1)nm and 0.6700(2)nm, respectively. The thermal expansivity of GNP powder and pellet along “a”- and “c”-axis are found to be 22.6×10-6K-1, 13.01×10-6K-1 and 15.11×10-6K-1, 10.44×10-6K-1, respectively. Electrical conductivity of GNP pellet is found to be 5700S/m.

  7. Microstructure Evolution in Nano-reinforced Ferritic Steel Processed By Mechanical Alloying and Spark Plasma Sintering

    Science.gov (United States)

    Boulnat, Xavier; Perez, Michel; Fabregue, Damien; Douillard, Thierry; Mathon, Marie-Hélène; de Carlan, Yann

    2013-11-01

    Oxide-dispersion strengthened ferritic steel was produced by high-energy attrition, leading to a complex nanostructure with deformed ferritic grains. After mechanical alloying, the powder was then consolidated by spark plasma sintering (SPS) using various thermo-mechanical treatments. Hot isostatic pressing (HIP) was also performed on the same powder for comparison. Above 1123 K (850 °C), SPS consolidation-induced heterogeneous microstructure composed of ultra-fine-grained regions surrounded by larger grains. Spatial distribution of the stored energy was measured in the bimodal microstructure using the Kernel average misorientation. In contrary to large recrystallized grains, ultra-fine grains are still substructured with low-angle grain boundaries. The precipitation kinetics of the nano-oxides during consolidation was determined by small-angle neutron scattering. Precipitation mainly occurred during the heating stage, leading to a high density of nanoclusters that are of prime importance for the mechanical properties. Other coarser titanium-enriched oxides were also detected. The multiscale characterization allowed us to understand and model the evolution of the complex microstructure. An analytical evaluation of the contributing mechanisms explains the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Then, the thermal stability of coherent nano-oxides is responsible for effective grain boundary pinning in recovered regions where the driving pressure for recrystallization is lowered. This scenario is confirmed in both SPSed and HIPed materials.

  8. Spark Plasma Sintering of α/β Si3N4 Ceramics with MgO-Al2O3 and MgO-Y2O3 as Sintering Additives

    Science.gov (United States)

    Yu, F. L.; Bai, Y.; Han, P. D.; Shi, Q. L.; Ni, S.; Wu, J. H.

    2016-12-01

    In the present work, the α/β Si3N4 ceramics were fabricated by spark plasma sintering (SPS) at 1400-1500 °C for 6 min with 3wt.%MgO + 5wt.%Al2O3 and 3wt.%MgO + 5wt.%Y2O3 as sintering additives. The results showed that the phase composition, microstructure and mechanical properties of α/β Si3N4 ceramics were highly dependent on the type of sintering additive. The incomplete phase transformation from α to β occurred in the presence of an oxynitride (Mg-Al(Y)-Si-O-N) liquid phase. Compared with MgO-Al2O3, MgO-Y2O3 can significantly improve the β conversion rate of as-sintered α/β Si3N4 ceramics. And the as-sintered ceramics using MgO + Al2O3 as sintering additives had higher mechanical properties.

  9. Plasma and microwave flash sintering of a tailored silver nanoparticle ink, yielding 60% bulk conductivity on cost-effective polymer foils.

    Science.gov (United States)

    Perelaer, Jolke; Jani, Robin; Grouchko, Michael; Kamyshny, Alexander; Magdassi, Shlomo; Schubert, Ulrich S

    2012-08-02

    A combination of plasma and microwave flash sintering is used to sinter an inkjet-printed and tailored silver nanoparticle formulation. By using two sintering techniques sequentially, the obtained conductivity is 60%, while keeping the processing temperature well below the glass transition temperature (T(g)) of the used polymer substrate. This approach leads to highly conductive features on cost-effective polymer substrates in relatively short times, which are compatible with roll-to-roll (R2R) production. An electroluminescence device is prepared as an example. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Computational Methods in Plasma Physics

    CERN Document Server

    Jardin, Stephen

    2010-01-01

    Assuming no prior knowledge of plasma physics or numerical methods, Computational Methods in Plasma Physics covers the computational mathematics and techniques needed to simulate magnetically confined plasmas in modern magnetic fusion experiments and future magnetic fusion reactors. Largely self-contained, the text presents the basic concepts necessary for the numerical solution of partial differential equations. Along with discussing numerical stability and accuracy, the author explores many of the algorithms used today in enough depth so that readers can analyze their stability, efficiency,

  11. SinterHab

    Science.gov (United States)

    Rousek, Tomáš; Eriksson, Katarina; Doule, Ondřej

    2012-05-01

    This project describes a design study for a core module on a Lunar South Pole outpost, constructed by 3D printing technology with the use of in-situ resources and equipped with a bio-regenerative life support system. The module would be a hybrid of deployable (CLASS II) and in-situ built (CLASS III) structures. It would combine deployable membrane structures and pre-integrated rigid elements with a sintered regolith shell for enhanced radiation and micrometeorite shielding. The closed loop ecological system would support a sustainable presence on the Moon with particular focus on research activities. The core module accommodates from four to eight people, and provides laboratories as a test bed for development of new lunar technologies directly in the environment where they will be used. SinterHab also includes an experimental garden for development of new bio-regenerative life support system elements. The project explores these various concepts from an architectural point-of-view particularly, as they constitute the building, construction and interior elements. The construction method for SinterHab is based on 3D printing by sintering of the lunar regolith. Sinterator robotics 3D printing technology proposed by NASA JPL enables construction of future generations of large lunar settlements with little imported material and the use of solar energy. The regolith is processed, placed and sintered by the Sinterator robotics system which combines the NASA ATHLETE and the Chariot remotely controlled rovers. Microwave sintering creates a rigid structure in the form of walls, vaults and other architectural elements. The interior is coated with a layer of inflatable membranes inspired by the TransHab project. The life-support system is mainly bio-regenerative and several parts of the system are intrinsically multifunctional and serve more than one purpose. The plants for food production are also an efficient part of atmosphere revitalization and water treatment. Moreover

  12. Sintering, camber development of layer composites and a new method to eliminate or decrease camber

    Indian Academy of Sciences (India)

    Xiangchun Liu

    2014-02-01

    Zinc–magnesium titanate dielectrics/nickel–zinc–copper ferrite layer composites were prepared by tape-casting technique combined with a uniaxial pressure shaping technique. The sintering and camber development of the composites were investigated. The results show that the difference of shrinkage in the later stages of sintering is the main cause of camber distortion. To eliminate or decrease the camber, a new method semi-fixed uniaxial pressure technique (SUP) was proposed. This method uses uniaxial pressures by which different radial densities can be introduced when one layer's edge is clamped and the other is free while laminating two different layers. The results obviously show that the SUP technique can decrease the camber and the camber curvature shows an inverse quadratic dependence on the applied pressure.

  13. Spark plasma sintering of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Yadhukulakrishnan, Govindaraajan B.; Rahman, Arif; Karumuri, Sriharsha [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Stackpoole, Margaret M. [ELORET Corporation, Moffett Field, CA 94035 (United States); Kalkan, A. Kaan; Singh, Raman P. [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States); Harimkar, Sandip P., E-mail: sandip.harimkar@okstate.edu [School of Mechanical and Aerospace Engineering Oklahoma State University, Stillwater, OK 74078 (United States)

    2012-08-30

    Highlights: Black-Right-Pointing-Pointer Dense SiC and carbon nanotube reinforced ZrB{sub 2} composites were spark plasma sintered. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement favored the densification of ZrB{sub 2} composites. Black-Right-Pointing-Pointer SiC and carbon nanotube reinforcement resulted in toughening of ZrB{sub 2} composites. Black-Right-Pointing-Pointer Carbon nanotubes were retained in the spark plasma sintered ZrB{sub 2} composites. - Abstract: In this paper spark plasma sintering (SPS) of silicon carbide and multi-walled carbon nanotube reinforced zirconium diboride ultra-high temperature ceramic matrix composites is reported. Systematic investigations on the effect of reinforcement type (SiC and CNTs) and content (10-40 vol.% SiC and 2-6 vol.% CNTs) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are presented. With the similar SPS processing parameters (1900 Degree-Sign C, 70 MPa pressure, and 15 min soaking time), near-full densification (>99% relative density) was achieved with 10-40% SiC (in ZrB{sub 2}-SiC) and 4-6% CNT (in ZrB{sub 2}-CNT) reinforced composites. The SiC and CNT reinforcement further improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB{sub 2}-SiC composites, and CNT pull-outs and crack deflection in ZrB{sub 2}-CNT composites.

  14. Thermoelectric transport properties of polycrystalline titanium diselenide co-intercalated with nickel and titanium using spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Holgate, T.C. [Department of Energy Storage and Conversion, Technical University of Denmark, Riso Campus, 4000 Roskilde (Denmark); Zhu, S.; Zhou, M. [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States); Bangarigadu-Sanasy, S.; Kleinke, H. [Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); He, J. [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States); Tritt, T.M., E-mail: ttritt@clemson.edu [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States)

    2013-01-15

    Polycrystalline samples of nickel intercalated (0-5%) TiSe{sub 2} were attempted via solid-state reaction in evacuated quartz tubes followed by densification using a spark plasma sintering process. X-ray diffraction data indicated that mixed NiSe{sub 2} and TiSe{sub 2} phases were present after initial synthesis by solid-state reaction, but a pure TiSe{sub 2} phase was present after the spark plasma sintering. While EPMA data reveals the stoichiometry to be near 1:1.8 (Ti:Se) for all samples, comparisons of the measured bulk densities to the theoretical densities suggest that the off stoichiometry is a result of the co-intercalation of both Ni and Ti rather than Se vacancies. Due to the presence of excess Ti (0.085-0.130 per formula) in the van der Waals gap of all the samples, the sensitive electron-hole balance is offset by the additional Ti-3d electrons, leading to an increase in the thermopower (n-type) over pristine, stoichiometric TiSe{sub 2}. The effects of the co-intercalation of both Ni and Ti in TiSe{sub 2} on the structural, thermal, and electrical properties are discussed herein. - Graphical abstract: Co-intercalation of nickel and excess titanium into the van der Waals gap of TiSe{sub 2} via solid state synthesis followed by spark plasma sintering results in a systematic shift in the ratio of hole and electron carrier concentration, which is close to unity for pristine TiSe{sub 2}. This directly affects the electrical transport properties, and as the structural disorder induced by intercalation suppresses the lattice thermal conductivity, co-intercalation is an effective route to enhance the thermoelectric properties of transition metal diselenides. Highlights: Black-Right-Pointing-Pointer Single phase bulk Ni and Ti co-intercalated TiSe{sub 2} samples prepared by spark plasma sintering. Black-Right-Pointing-Pointer Density and X-ray diffraction suggest that the Ni and excess Ti are ordered in the Van der Waals gap. Black-Right-Pointing-Pointer Co

  15. The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

    Science.gov (United States)

    Aldica, G.; Burdusel, M.; Popa, S.; Enculescu, M.; Pasuk, I.; Badica, P.

    2015-12-01

    Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 °C/min were used. Samples have high density, above 95%. The onset critical temperature Tc, is about 38.8 K. There is an optimum heating rate of ∼100 °C/min to maximize the critical current density Jc0, the irreversibility field Hirr, the product (Jc0 x μ0Hirr), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries.

  16. Spark Plasma Sintering of Dielectric Ceramics Zr0.8Sn0.2TiO4

    Directory of Open Access Journals (Sweden)

    Pavel CTIBOR

    2016-09-01

    Full Text Available Zirconium-tin titanate ceramics (Zr,SnTiO4 was prepared by spark plasma sintering (SPS technique. Resulting samples, low-height cylinders, were subjected to microstructural observations, immersion measurements of density and porosity and X-ray diffraction phase analysis. Dielectric parameters – relative permittivity and loss factor – were tested in the frequency range from 80 Hz to 1 MHz and volume DC resistivity at 100 volts.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.8767

  17. Forming method of micro heat pipe with compound structure of sintered wick on grooved substrate

    Science.gov (United States)

    Li, Xibing; Li, Mingjian; Li, Ming; Wu, Ruchen; Wan, Yingsi; Cheng, Tian

    2016-03-01

    Micro heat pipes (MHPs) with excellent heat transfer performance have been the ideal radiating components to meet increasingly higher requirements posed by high heat-flux products. Based on MHPs' working principle, this study deduced capillary limit of a novel MHP with compound structure of sintered wick on grooved substrate, and probed into its forming mechanism: first, high-speed oil-filled spinning was applied to fabricating micro grooves, with optimal spinning and drawing speeds determined; then a mini-type vibration machine was used to help fill copper powders fast and uniformly, with appropriate sintering temperature and time fixed; the manufacturing method that integrates vacuum-pumping-cold-welding with secondary-degassing-cold-welding to increase vacuumizing efficiency. The results of experiments on its heat transfer performance show that the MHPs with sintered-wick-on-grooved-substrate structure fabricated through the proposed forming method can not only acquire much better heat transfer performance, but have advantages such as higher productivity and lower cost.

  18. A method to rapidly determine the sintering process parameters of powder metallurgy by real-time resistivity monitoring

    Science.gov (United States)

    Xiao, Zhen; Liu, Huanchao; Geng, Haoran; Leng, Jinfeng

    2016-10-01

    A new method, which is called the resistivity method, is applied in this paper to explore the optimum sintering parameters of powder metallurgy (PM) since general methods are always labor-intensive and time-consuming. This method can probe the resistivity of the powder metallurgy samples in real-time during the sintering process, to quickly estimate the change of the relative density, which consequently determine the properties of the sintered item. As an example, in this paper, copper/tungsten carbide (Cu/WC) composites and pure aluminum (Al) powder compacts are experimentally considered. As a result, for the Cu/WC composites, the highest value of relative density appeared at the holding time of 50 min where the sample has the lowest resistivity. For the Al compacts, the optimum sintering temperature is 450 °C, and the longer the holding time the better.

  19. Spark plasma sintering of silicon carbide, multi-walled carbon nanotube and graphene reinforced zirconium diboride ceramic composite

    Science.gov (United States)

    Balaraman Yadhukulakrishnan, Govindaraajan

    Scope and Method of Study: Space vehicles re-entering the earth's atmosphere experience very high temperatures due to aerodynamic heating. Ultra-high temperature ceramics (UHTC) with melting point higher than 3200°C are promising materials for thermal protection systems of such space vehicles re-entering the earth's atmosphere. Among several UHTC systems ZrB2 based ceramic composites are particularly important for thermal protection systems due to their better mechanical and thermoelectric properties and high oxidation resistance. In this study spark plasma sintering of SiC, carbon nanotubes (CNT) and graphene nano platelets (GNP) reinforced ZrB2 ultra-high temperature ceramic matrix composites is reported. Findings and Conclusions: Systematic investigations on the effect of reinforcement type (SiC, CNTs and GNP) and content (10-40 vol.% SiC, 2-6 vol.% CNTs and 2-6 vol.% GNP) on densification behavior, microstructure development, and mechanical properties (microhardness, bi-axial flexural strength, and indentation fracture toughness) are reported. With the similar SPS parameters near-full densification (>99% relative density) was achieved with 10-40 vol.% SiC, 4-6 vol.% CNT reinforced composites. Highly dense composites were obtained in 4-6 vol.% GNP reinforced composites. The SiC, CNT and GNP reinforcement improved the indentation fracture toughness of the composites through a range of toughening mechanisms, including particle shearing, crack deflection at the particle-matrix interface, and grain pull-outs for ZrB2-SiC composites, CNT pull-outs and crack deflection in ZrB2-CNT composites and crack deflection, crack bridging and GNP sheet pull-out for ZrB2 -GNP composites.

  20. Comparative analysis of oxidation methods of reaction-sintered silicon carbide for optimization of oxidation-assisted polishing.

    Science.gov (United States)

    Shen, Xinmin; Dai, Yifan; Deng, Hui; Guan, Chaoliang; Yamamura, Kazuya

    2013-11-04

    Combination of the oxidation of reaction-sintered silicon carbide (RS-SiC) and the polishing of the oxide is an effective way of machining RS-SiC. In this study, anodic oxidation, thermal oxidation, and plasma oxidation were respectively conducted to obtain oxides on RS-SiC surfaces. By performing scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) analysis and scanning white light interferometry (SWLI) measurement, the oxidation behavior of these oxidation methods was compared. Through ceria slurry polishing, the polishing properties of the oxides were evaluated. Analysis of the oxygen element on polished surfaces by SEM-EDX was conducted to evaluate the remaining oxide. By analyzing the three oxidation methods with corresponding polishing process on the basis of schematic diagrams, suitable application conditions for these methods were clarified. Anodic oxidation with simultaneous polishing is suitable for the rapid figuring of RS-SiC with a high material removal rate; polishing of a thermally oxidized surface is suitable for machining RS-SiC mirrors with complex shapes; combination of plasma oxidation and polishing is suitable for the fine finishing of RS-SiC with excellent surface roughness. These oxidation methods are expected to improve the machining of RS-SiC substrates and promote the application of RS-SiC products in the fields of optics, molds, and ceramics.

  1. Influence of spark plasma sintering and baghdadite powder on mechanical properties of hydroxyapatite

    NARCIS (Netherlands)

    Khandan, A.; Karamian, E.; Mehdikhani-Nahrkhalaji, M.; Mirmohammadi, H.; Farzadi, A.; Ozada, N.; Heidarshenas, B.; Zamani, K.

    2015-01-01

    Since hydroxyapatite-based materials have similar composition and crystallinity as natural calcified tissues, can be used for bone/tissue engineering. In the present study a novel nanocomposite based on bioceramics such as Natural Hydroxyapatite (NHA) and Baghdadite (BAG), was sintered by spark plas

  2. Plasma sintering of ferritic steel reinforced with niobium carbide prepared by high energy milling; Sinterizacao a plasma de aco ferritico reforcado com carbeto de niobio preparado por moagem de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Silva Junior, J.F. da; Almeida, E.O.; Gomes, U.U.; Alves Junior, C.; Messias, A.P. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil). Lab. de Materiais Ceramicos e Metais Especiais; Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil). Lab. de Processamento de Materiais por Plasma

    2010-07-01

    Plasma is an ionized gas where ions are accelerated from anode to cathode surface, where the sample is placed. There are a lot of collisions on cathode surface by ions heating and sintering the sample. High energy milling (HEM) is often used to produce composite particles to be used on powder metallurgy. These particles can exhibit fine particles and high phase dispersion. This present work aim to study ferritic steels reinforced with 3%NbC prepared by HEM and sintered on plasma furnace. Ferritic steel and NbC powders were milled during 5 hours and characterized by SEM, XRD and laser scattering. Then, these composite powders were compacted in a cylindrical steel die and then sintered in a plasma furnace. Vickers microhardness tests and SEM and XRD analysis were performed on sintered samples. (author)

  3. Thermal Diffusivity of Sintered Steels with Flash Method at Ambient Temperature

    Science.gov (United States)

    Bocchini, G. F.; Bovesecchi, G.; Coppa, P.; Corasaniti, S.; Montanari, R.; Varone, A.

    2016-04-01

    Due to lack of reliable thermal diffusivity data of sintered steels in literature, experimental investigations were conducted on samples made of different powder types (based on prealloyed, or diffusion-bonded, or admixed powders) and under different process conditions. So the influence of pressing pressure and sintering temperature on thermal diffusivity was established. Thermal diffusivity was measured using the "flash method": a sample in the shape of a slab is irradiated with a light pulse on one of the two surfaces, and temperature of the other surface is detected by an ambient temperature pyrometer. The value of the thermal diffusivity is obtained by a least squares regression on the entire trend of the temperature vs. time using the analytical solution of the heat conduction as regression model. Results show the increase of the thermal diffusivity with increasing density. This outcome can be explained from the mutual effect of thermal conductivity and density on thermal diffusivity in porous media. The experimental results have also permitted to verify the influence of the composition of the sintered materials and carbon contents on thermal diffusivity.

  4. Sintering in Laser Sintering

    Science.gov (United States)

    Bourell, David L.

    2016-03-01

    Laser sintering is a popular additive manufacturing technology, particularly for service parts. Invented by C. Deckard in the mid-1980s, the approach of using a laser to densify a powder bed selectively has been extensively researched and has been applied to metals, ceramics, polymers and composites. In the traditional powder-metallurgical sense, sintering involves solid-state atomic transport resulting in neck formation and eventual densification in a powder mass. The use of the term "sintering" as a descriptive term for the powder-bed additive manufacturing process has been problematical to the technical community, because the predominant densification mechanism has been shown for most applications to be melting and reflow. The term has perpetuated as a name for the additive manufacturing process, at least for polymers. The technical term "sintering" is accurately associated with laser sintering insofar as powder pre-processing and part post-processing are concerned. It may also be used to describe formation of "part cake". This paper describes the circumstances surrounding the coining of the term, "laser sintering" and provides some examples of how sintering is used in pre- and post-processing.

  5. The influence of heating rate on superconducting characteristics of MgB{sub 2} obtained by spark plasma sintering technique

    Energy Technology Data Exchange (ETDEWEB)

    Aldica, G. [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele (Romania); Burdusel, M. [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele (Romania); Faculty of Materials Science and Engineering, University ’Politehnica’ of Bucharest, Splaiul Independentei 313, 060042 Bucharest (Romania); Popa, S.; Enculescu, M.; Pasuk, I. [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele (Romania); Badica, P., E-mail: badica2003@yahoo.com [National Institute of Materials Physics, Atomistilor 105bis, 077125 Magurele (Romania)

    2015-12-15

    Highlights: • MgB{sub 2} was obtained by ex-situ spark plasma sintering for different heating rates. • Heating rates were 20–475 °C/min: the optimum heating rate is ∼100 °C/min. • For 100 °C/min, J{sub c0}, H{sub irr} and (J{sub c0} x μ{sub 0}H{sub irr}) have maximum values. • For 100 °C/min, macro flux jumps are partially suppressed at 5 K. • Grain boundaries are modified depending on the heating rate. - Abstract: Superconducting bulks of MgB{sub 2} were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 °C/min were used. Samples have high density, above 95%. The onset critical temperature T{sub c}, is about 38.8 K. There is an optimum heating rate of ∼100 °C/min to maximize the critical current density J{sub c0}, the irreversibility field H{sub irr}, the product (J{sub c0} x μ{sub 0}H{sub irr}), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries.

  6. Microstructure and mechanical behavior of ODS and non-ODS Fe–14Cr model alloys produced by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.A.; Castro, V. de [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Leguey, T., E-mail: leguey@fis.uc3m.es [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain); Muñoz, A.; Pareja, R. [Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés (Spain)

    2013-05-15

    In this work the spark plasma sintering (SPS) technique has been explored as an alternative consolidation route for producing ultra-fine grained Fe–14Cr model alloys containing a dispersion of oxide nanoparticles. Elemental powders of Fe and Cr, and nanosized Y{sub 2}O{sub 3} powder have been mechanically alloyed in a planetary ball mill and rapidly sintered in a spark plasma furnace. Two alloys, with nominal compositions Fe–14%Cr and Fe–14%Cr–0.3%Y{sub 2}O{sub 3} (wt.%), have been fabricated and their microstructure and mechanical properties investigated. The results have been compared with those obtained for other powder metallurgy processed alloys of the same composition but consolidated by hot isostatic pressing. The SPS technique under the present conditions has produced Fe–14Cr materials that apparently exhibit different microstructures yielding inferior mechanical properties than the counterpart material consolidated by hot isostatic pressing. Although the presence of a dispersion of Y-rich particles is evident, the oxide dispersion strengthened (ODS) Fe–14Cr alloy consolidated by SPS exhibits poor tensile properties. The extensive decoration of the powder particle surfaces with Cr-rich precipitates and the residual porosity appear to be responsible for the impaired properties of this ODS alloy consolidated by SPS.

  7. Electric and mechanical performances of Bi0.5Sb1.5Te3 prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    XIAO Bo; CHEN Hui; WU Borong; ZHU Lei; LIU Mingyi; JIAN Xuyu; LI Lin

    2006-01-01

    Thermoelectric (TE) materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi2Te3 and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering (SPS) on electric performance of Bi0.5Sb1.5Te3 thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800, the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature (from 300 to 500 ℃) and pressure(from 30 to 60 MPa), and the density and mechanical strength of Bi0.5Sb1.5Te3 thermoelectric material increase, too.

  8. The effect of heating rate and composition on the properties of spark plasma sintered zirconium diboride based composites

    Energy Technology Data Exchange (ETDEWEB)

    Snyder, Alexandra; Bo Zhenyu [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Hodson, Stephen; Fisher, Timothy [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States); Stanciu, Lia, E-mail: lstanciu@purdue.edu [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer We investigated the effect of heating rate on spark plasma sintering of ZrB{sub 2}-SiC-ZrC composites. Black-Right-Pointing-Pointer Adding SiC up to 10 wt.% had a positive effect on densification and strength. Black-Right-Pointing-Pointer Increasing heating rate promoted densification and retarded grain growth when SiC and ZrC content was above 15 wt.%, respectively. Black-Right-Pointing-Pointer Increasing heating rate had a slight negative effect on densification when SiC and ZrC content was at 10%, respectively. - Abstract: Five different compositions of ZrB{sub 2}-SiC-ZrC were prepared and then processed by spark plasma sintering (SPS) to a maximum temperature of 2000 Degree-Sign C, with heating rates of 100 Degree-Sign C/min and 200 Degree-Sign C/min. Grain size, density, Rockwell hardness, flexural strength, and thermal conductivity were evaluated for the processed composites. Adding SiC up to 10 wt.% had a positive effect on densification and strength. Increasing the heating rate promoted densification and less overall grain growth for samples with SiC and ZrC above 15 wt.% each, and had a slight negative effect on densification when these values were at 10%.

  9. Taguchi Analysis on the Effect of Process Parameters on Densification During Spark Plasma Sintering of HfB2-20SiC (Preprint)

    Science.gov (United States)

    2011-11-01

    pressing and spark plasma sintering. J Alloys Compd 2007; 428:197–05. 2. Van Wie D.M., Drewry Jr. D.G., King D.E., Hudson C.M. The hypersonic environment...spark plasma sintering of HfB2/SiC and HfB2/HfC/SiC composite powders obtained by self-propagating high-temperature synthesis. J Alloys Compd 2009...2008; 91:10:3448-50. 9. Carmen M Carney. Oxidation resistance of hafnium diboride—silicon carbide from 1400 to 2000 °C. J Mater Sci 2009; 44:20:5673-81

  10. Effects of Synthesis and Spark Plasma Sintering Conditions on the Thermoelectric Properties of Ca3Co4O9+δ

    DEFF Research Database (Denmark)

    Wu, NingYu; Holgate, Tim; Van Nong, Ngo

    2013-01-01

    Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density, and therm......Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density......, and thermoelectric transport properties. High power factors of about 400 μW/m·K2 and 465 μW/m·K2 (at 800°C) were measured for SS and SG samples, respectively. The improved thermoelectric performance of the SG sample is believed to originate from the smaller particle sizes and better grain alignment. The SG method...

  11. Low-temperature sintering method for NiCuZn ferrite and effect of Mn addition on electromagnetic properties

    Institute of Scientific and Technical Information of China (English)

    JU Dong-ying; BIAN Pei

    2006-01-01

    Low temperature sintering NiCuZn ferrite was employed at most cases due to its co-firability with Ag (below 960 ℃). The NiCuZn ferrite sintered body with high-strength and high-frequency magnetic properties was fabricated. Firstly,NiCuZn ferrite powder was synthesized under CO2 atmosphere at 500 ℃ from the mixed doxalate synthesized by liquid phase precipitation method. Then a small amount of boric acid (H3BO3) was added to the powder,and the NiCuZn ferrite powder compact was prepared with Newton press and CIP methods. Finally,NiCuZn ferrite sintered body was fabricated by sintering at 900 ℃ under CO2 atmosphere. The minimum sintering temperature (800 ℃) was determined by the study of high temperature shrinkage. By this method,NiCuZn ferrite sintered body with 0.5% (mass fraction) boric acid was obtained,which has the bending strength of 340 MPa. The effect of various Mn addition on electromagnetic properties were studied.

  12. The effects of composition and sintering temperature on the silica foam fabricated by slurry method

    Science.gov (United States)

    Baharom, Syazwani; Ahmad, Sufizar; Taib, Hariati; Muda, Rizamarhaiza

    2016-07-01

    Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO2) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO2 were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO2 that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO2 ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO2 ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO2 ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm3 up to 0.75 g/cm3, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

  13. The effects of composition and sintering temperature on the silica foam fabricated by slurry method

    Energy Technology Data Exchange (ETDEWEB)

    Baharom, Syazwani, E-mail: hd140001@siswa.uthm.edu.my; Ahmad, Sufizar, E-mail: sufizar@uthm.edu.my; Taib, Hariati, E-mail: hariati@uthm.edu.my; Muda, Rizamarhaiza, E-mail: hd130013@siswa.uthm.edu.my [Department of Material and Design Engineering, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat, Johor (Malaysia)

    2016-07-19

    Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO{sub 2}) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO{sub 2} were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO{sub 2} that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO{sub 2} ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO{sub 2} ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO{sub 2} ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm{sup 3} up to 0.75 g/cm{sup 3}, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

  14. Standard test methods for analysis of sintered gadolinium oxide-uranium dioxide pellets

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 These test methods cover procedures for the analysis of sintered gadolinium oxide-uranium dioxide pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Section Carbon (Total) by Direct CombustionThermal Conductivity Method C1408 Test Method for Carbon (Total) in Uranium Oxide Powders and Pellets By Direct Combustion-Infrared Detection Method Chlorine and Fluorine by Pyrohydrolysis Ion-Selective Electrode Method C1502 Test Method for Determination of Total Chlorine and Fluorine in Uranium Dioxide and Gadolinium Oxide Gadolinia Content by Energy-Dispersive X-Ray Spectrometry C1456 Test Method for Determination of Uranium or Gadolinium, or Both, in Gadolinium Oxide-Uranium Oxide Pellets or by X-Ray Fluorescence (XRF) Hydrogen by Inert Gas Fusion C1457 Test Method for Determination of Total Hydrogen Content of Uranium Oxide Powders and Pellets by Carrier Gas Extraction Isotopic Uranium Composition by Multiple-Filament Surface-Ioni...

  15. Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry.

    Science.gov (United States)

    Kanický, V; Otruba, V; Mermet, J M

    2001-12-01

    Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.

  16. SiC whisker reinforced MoSi2 composite prepared by spark plasma sintering from COSHS-ed powder

    Institute of Scientific and Technical Information of China (English)

    XU Jian-guang; ZHANG Hou-an; JIANG Guo-jian; ZHANG Bao-lin; LI Wen-lan

    2006-01-01

    SiC whisker reinforced MoSi2 composite powder was synthesized by a novel process,referred to the literature as chemical oven self-propagating high temperature synthesis(COSHS). The as-prepared SiCw/MoSi2 composite powder was rapidly sintered by spark plasma sintering(SPS) process. The sintering temperature and pressure were 1 723 K at heating rate of 100 K/min and 40 MPa,respectively. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite are 95% and 99.3%,respectively. SEM micrographs of SiCw/MoSi2 composite show that SiC whiskers homogeneously distribute in MoSi2 matrix. The composite containing SiC whisker has higher Vicker hardness than monolithic MoSi2. Especially the room-temperature fracture toughness of the composite is higher than that of MoSi2,from 3.6 MPa -m1/2 for MoSi2 to 7.7 MPa-m1/2 for composite with 15% SiC(volume fraction),increased by 113.9%. The morphology of propagation of crack and fractured surface of composite reveal the mechnaism to improve fracture toughness of MoSi2 matrix. The results show that the in-situ SiCw/MoSi2 composite powder prepared by COSHS technique can be successfully sinterded through SPS process and significant improvement of low temperature fracture toughness can be achieved.

  17. Study of Thermal Fatigue Resistance of a Composite Coating Made by a Vacuum Fusion Sintering Method

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Thermal fatigue behavior of a Ni-base alloy chromium carbide composite coating made by a vacuum fusion sintering method are discussed. Results show that thermal fatigue behavior is associated with cyclic upper temperature and coating thickness. As the thickness of the coating decreases, the thermal fatigue resistance increases. The thermal fatigue resistance cuts down with the thermal cyclic upper temperature rising. The crack growth rate decreases with the increase in cyclic number until crack arrests. Thermal fatigue failure was not found along the interface of the coating/matrix. The tract of thermal fatigue crack cracks along the interfaces of phases.

  18. Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation

    Directory of Open Access Journals (Sweden)

    Dimos Paraskevas

    2014-08-01

    Full Text Available Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS is proposed in this paper as a novel solid-state recycling technique. The objective is two-fold: (I to prove the technical feasibility of this approach; and (II to characterize the recycled samples. Aluminum (Al alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach.

  19. Alumina-carbon nanofibers nanocomposites obtained by spark plasma sintering for proton exchange membrane fuel cell bipolar plates

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, A.; Torrecillas, R. [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) Consejo Superior de Investigaciones Cientificas, Universidad de Oviedo, Principado de Asturias, Parque Tecnologico de Asturias, Llanera Asturias (Spain); Rocha, V.G.; Fernandez, A. [ITMA Materials Technology, Parque Tecnologico de Asturias, Llanera Asturias (Spain)

    2012-08-15

    There is an increasing demand of multifunctional materials for a wide variety of technological developments. Bipolar plates for proton exchange membrane fuel cells are an example of complex functionality components that must show among other properties high mechanical strength, electrical, and thermal conductivity. The present research explored the possibility of using alumina-carbon nanofibers (CNFs) nanocomposites for this purpose. In this study, it was studied for the first time the whole range of powder compositions in this system. Homogeneous powders mixtures were prepared and subsequently sintered by spark plasma sintering. The materials obtained were thoroughly characterized and compared in terms of properties required to be used as bipolar plates. The control on material microstructure and composition allows designing materials where mechanical or electrical performances are enhanced. A 50/50 vol.% alumina-CNFs composite appears to be a very promising material for this kind of application. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Investigation of microstructure and irradiation behavior of W–Nb/Ti composites prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing-Bo [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Zhao, Mei-Ling [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Xu, Qiu [Research Reactor Institute, Kyoto University, Osaka-Fu 590-0494 (Japan); Zan, Xiang [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China)

    2016-11-15

    W–Nb/Ti composites were prepared by machine milling and spark plasma sintering. Field–emission scanning electron microscopy, high–resolution transmission electron microscopy, and X-ray diffraction analyses were used to characterize the samples. Thermal desorption spectroscopy (TDS) was used to measure the deuterium retention after only deuterium irradiation. The deuterium retention in W–4wt%Ti–wt1%Nb was lower than that in pure W (D{sub 2}{sup +} flux ∼10{sup 22} ions/(m{sup 2} s), ion energy ∼5 keV), Nb and Ti will improve the deuterium irradiation resistance of tungsten composite. In addition, transgranular and intergranular fractures were observed on the surface of the W–4 wt% Ti–1 wt% Nb composite. A Ti{sub (X)}W{sub (1−X)} solid solution was formed during sintering. The maximum tensile strength (410.53 MPa) was detected in the W–4wt%Ti–1wt%Nb composite at 600 °C.

  1. Characterization of In-Situ Cu–TiH2–C and Cu–Ti–C Nanocomposites Produced by Mechanical Milling and Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Nguyen Thi Hoang Oanh

    2017-03-01

    Full Text Available This study focuses on the fabrication and microstructural investigation of Cu–TiH2–C and Cu–Ti–C nanocomposites with different volume fractions (10% and 20% of TiC. Two mixtures of powders were ball milled for 10 h, consequently consolidated by spark plasma sintering (SPS at 900 and 1000 °C producing bulk materials with relative densities of 95–97%. The evolution process of TiC formation during sintering process was studied by using X-ray diffraction (XRD, scanning electron microscopy (SEM, and high resolution transmission electron microscopy (HRTEM. XRD patterns of composites present only Cu and TiC phases, no residual Ti phase can be detected. TEM images of composites with (10 vol % TiC sintered at 900 °C show TiC nanoparticles about 10–30 nm precipitated in copper matrix, most of Ti and C dissolved in the composite matrix. At the higher sintering temperature of 1000 °C, more TiC precipitates from Cu–TiH2–C than those of Cu–Ti–C composite, particle size ranges from 10 to 20 nm. The hardness of both nanocomposites also increased with increasing sintering temperature. The highest hardness values of Cu–TiH2–C and Cu–Ti–C nanocomposites sintered at 1000 °C are 314 and 306 HV, respectively.

  2. Microstructure, thermal properties, and corrosion behaviors of FeSiBAlNi alloy fabricated by mechanical alloying and spark plasma sintering

    Science.gov (United States)

    Wang, Hong-lei; Gao, Tai-xiu; Niu, Jia-zheng; Shi, Pei-jian; Xu, Jing; Wang, Yan

    2016-01-01

    An equiatomic FeSiBAlNi amorphous high-entropy alloy (HEA) was fabricated by mechanical alloying (MA). A fully amorphous phase was obtained in the FeSiBAlNi HEA after 240 h of MA. The bulk FeSiBAlNi samples were sintered by spark plasma sintering (SPS) at 520 and 1080°C under a pressure of 80 MPa. The sample sintered at 520°C exhibited an amorphous composite structure comprising solid-solution phases (body-centered cubic (bcc) and face-centered cubic (fcc) phases). When the as-milled amorphous HEA was consolidated at 1080°C, another fcc phase appeared and the amorphous phase disappeared. The sample sintered by SPS at 1080°C exhibited a slightly higher melting temperature compared with those of the as-milled alloy and the bulk sample sintered at 520°C. The corrosion behaviors of the as-sintered samples were investigated by potentiodynamic polarization measurements and immersion tests in seawater solution. The results showed that the HEA obtained by SPS at 1080°C exhibited better corrosion resistance than that obtained by SPS at 520°C.

  3. Microstructure, thermal properties, and corrosion behaviors of FeSiBAlNi alloy fabricated by mechanical alloying and spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Hong-lei Wang; Tai-xiu Gao; Jia-zheng Niu; Pei-jian Shi; Jing Xu; Yan Wang

    2016-01-01

    An equiatomic FeSiBAlNi amorphous high-entropy alloy (HEA) was fabricated by mechanical alloying (MA). A fully amorphous phase was obtained in the FeSiBAlNi HEA after 240 h of MA. The bulk FeSiBAlNi samples were sintered by spark plasma sintering (SPS) at 520 and 1080°C under a pressure of 80 MPa. The sample sintered at 520°C exhibited an amorphous composite structure comprising solid-solution phases (body-centered cubic (bcc) and face-centered cubic (fcc) phases). When the as-milled amorphous HEA was consoli-dated at 1080°C, another fcc phase appeared and the amorphous phase disappeared. The sample sintered by SPS at 1080°C exhibited a slightly higher melting temperature compared with those of the as-milled alloy and the bulk sample sintered at 520°C. The corrosion behav-iors of the as-sintered samples were investigated by potentiodynamic polarization measurements and immersion tests in seawater solution. The results showed that the HEA obtained by SPS at 1080°C exhibited better corrosion resistance than that obtained by SPS at 520°C.

  4. A study of the method of making dental prosthetic appliances by sintered titanium alloys: effect of copper powder content on properties of sintered titanium alloy.

    Science.gov (United States)

    Oda, Y; Nakanishi, K; Sumii, T

    1990-02-01

    The effects of added copper powder to the properties of the sintered titanium alloys were investigated by measuring the compressive strength and densities of the green and sintered compacts, the thermal expansion curves and dimensional changes in the sintered compacts, and the accuracy of the crown-type restorations. The compressive strengths of green compacts ranged from 55 to 75 MPa. The expansion of green compacts increased with increased copper content. The sintered density was lower than the green density. The compressive yield strength of sintered compacts ranged from 260 MPa to 410 MPa. The sintered compacts expanded from 0.35% to 1.03% and the expansion increased with increased copper content. The dimensional accuracy of crown-type restorations showed the same dimensional change tendencies as did the sintered compacts. These results showed that the fit and the strength of sintered titanium alloy restorations could be improved.

  5. The Kinetics, Stability and Thermal Contact Resistance of Nickel-Ca3Co4O9 Interfaces Formed by Spark Plasma Sintering

    DEFF Research Database (Denmark)

    Holgate, Tim; Wu, NingYu; Søndergaard, M.

    2012-01-01

    (Ca3Co4O9) have been formed directly by spark plasma sintering (SPS). An intermediate NiO phase is formed during the SPS processes, which grows during post heating with Co entering from the cobaltate side to form a graded Ni1-xCoxO interfacial layer. The electrical and thermal transport across...

  6. The effect of mechanical alloying on microstructure and mechanical properties of MoSi{sub 2} prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kermani, Milad, E-mail: miladkermani.mk@gmail.com; Razavi, Mansour; Rahimipour, Mohammad Reza; Zakeri, Mohammad

    2014-04-01

    Highlights: • Powders of Mo and Si according to MoSi{sub 2} stoichiometry were mechanically alloyed. • The as milled powder mixture was sintered using spark plasma sintering. • We investigated the microstructure and mechanical properties of samples. - Abstract: In this research the effect of mechanical alloying on the in situ synthesis–sintering behavior and mechanical properties of MoSi{sub 2} has been investigated. The Mo and Si powders according to MoSi{sub 2} stoichiometric composition were mechanically alloyed at different times. Then, the powders were subjected to spark plasma sintering process for preparing monolithic MoSi{sub 2}. X-ray diffraction pattern of the sintered samples showed that by increasing the mechanical alloying time, Mo{sub 5}Si{sub 3} has been formed. It seems that the formation of Mo{sub 5}Si{sub 3} is due to the effect of mechanical alloying on microstructure and thermodynamic condition of the reaction.

  7. Optimization of vortex pinning at grain boundaries on ex-situ MgB2 bulks synthesized by spark plasma sintering

    Science.gov (United States)

    Naito, Tomoyuki; Endo, Yuri; Fujishiro, Hiroyuki

    2017-09-01

    Grain boundaries are well known to be the predominant pinning centers in MgB2 superconductors. To study the effects of grain boundaries on the trapped field properties of MgB2 bulk, we prepared MgB2 bulks by a spark plasma sintering method using a ball-milled starting powder. The trapped field was maximized for the bulk made from the ball-milled powder with crystallite size, τ, of 27 nm; the highest trapped field, {B}{{T}}, of 2.3 T achieved at 19.3 K was 1.2 times larger than that of the bulk made from the non ball-milled powder (τ = 50 nm). The degradation of the trapped field for the bulk from finer powder (τ = 6 nm) originated mainly from the lowered {T}{{c}}. The critical current density, {J}{{c}}, and the pinning force density, {F}{{p}}, were also maximized for the bulk from τ = 27 nm. The competition between the increase of the numerical density of grain boundaries and the degradation of superconductivity determined the vortex pinning properties for the MgB2 bulks with mechanically refined grains. The scaling analysis for the pinning force density suggested that the change in the dimension of the dominant pinning source from 2D (surface) to 0D (point) was induced by grain refining. Although the nanometric impurity particles such as MgB4, MgO and Mg-B-O were created in the bulk during both ball-milling and spark plasma sintering processes, we considered the point-contact between the refined grains was the predominant point pinning source.

  8. Zirconia-Based Powders Produced by Plasma-Spray Pyrolisys and Properties of Sintered Ceramics

    Science.gov (United States)

    Kulkov, S. N.; Buyakova, S.; Gömze, L. A.

    2017-01-01

    It have been studied zirconia-based powders and sintered ceramic. It was shown that in the porous structure of zirconia-based ceramics there is a critical value of porosity the material divides into two sub-systems, being variously deformable under external loading. It have been shown that m-phase in ZrO2 is formed due to increase in the microdistortion level which destabilizes the nanocrystalline t phase. It has been found out the correlation between the sizes of crystallites and porosity, which associated with transition of the isolated porous structure to the continuous one and the porosity of 20%, corresponds to the first percolation threshold.

  9. Temperature dependence of magnetic behaviour in very fine grained, spark plasma sintered NiCuZn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadi, Behzad; Zehani, Karim; LoBue, Martino; Loyau, Vincent; Mazaleyrat, Frederic [SATIE, ENS Cachan, CNRS, UniverSud 61, avenue du President Wilson, F-94230 Cachan (France)

    2012-04-01

    Recently, using spark plasma sintering technique, a family of very fine grained, fully dense NiCuZn ferrites have been produced, which show constant permeability up to several 10 MHz. These ferrites can be used for filtering purposes in high frequency applications where a wide frequency band is required. In this paper, we study the magnetization processes taking place in these nano grained materials, in the frequency interval of 100 kHz to 5 MHz. Using a fluxmetric hysteresis graph, permeability, loss, and BH loops are measured at different temperatures, from -5 deg. C to 110 deg. C. Results are compared to the behavior of micrometric grain size ferrites, which are commonly used for power electronic and high frequency applications.

  10. Effect of particle size on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    CHU Ke; JIA Chengchang; LIANG Xuebing; CHEN Hui; GAO Wenjia

    2009-01-01

    Spark plasma sintering (SPS) was used to fabricate Al/diamond composites. The influence of diamond particle size on the microstrueture and thermal conductivity (TC) of composites was investigated by combining experimental results with model prediction. The results show that both composites with 40 μm particles and 70 μm particles exhibit high density and good TC, and the composite with 70 μm particles indi-cates an excellent TC of 325 W·m~(-1)·K~(-1). Their TCs lay between the theoretical estimated bounds. In contrast, the composite with 100 μm particles demonstrates low density as well as poor TC due to its high porosity and weak interfacial bonding. Its TC is even considerably less than the lower bound of the predicted value. Using larger diamond particles can further enhance thermal conductive performance only based on the premise that highly dense composites of strong interfacial bonding can be obtained.

  11. Synthesis of Ti3SiC2 by spark plasma sintering(SPS) of elemental powders

    Institute of Scientific and Technical Information of China (English)

    朱教群; 梅炳初; 何利萍; 陈艳林

    2003-01-01

    Ti3 SiC2 materials have been fabricated by spark plasma sintering of the elemental powders with the addi-tion of Al. At the heating rate of 80 ℃/min and under the pressure of 30 MPa, the ideal synthesis temperature ofTi3 SiC2 is in the range of 1 150 - 1250 ℃. The addition of Al is in favor of the formation of Ti3 SiC2. The synthesizedcompound has the molecular of Ti3 Si0.8 Al0.2 C2 and lattice parameters of a = 0.306 9 nm, c= 1.767 0 nm. Its grain isplane-shape with a size of about 50μm in the elongated dimension. The prepared material has Vickers hardness of 3.5 - 5.5 GPa(at 1 N and 15 s) and is as readily machinable as graphite's.

  12. The Manufacturing of High Porosity Iron with an Ultra-Fine Microstructure via Free Pressureless Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Guodong Cui

    2016-06-01

    Full Text Available High porosity (>40 vol % iron specimens with micro- and nanoscale isotropic pores were fabricated by carrying out free pressureless spark plasma sintering (FPSPS of submicron hollow Fe–N powders at 750 °C. Ultra-fine porous microstructures are obtained by imposing high heating rates during the preparation process. This specially designed approach not only avoids the extra procedures of adding and removing space holders during the formation of porous structures, but also triggers the continued phase transitions of the Fe–N system at relatively lower processing temperatures. The compressive strength and energy absorption characteristics of the FPSPS processed specimens are examined here to be correspondingly improved as a result of the refined microstructure.

  13. Photoconductivity induced by nanoparticle segregated grain-boundary in spark plasma sintered BiFeO3

    Science.gov (United States)

    Nandy, Subhajit; Mocherla, Pavana S. V.; Sudakar, C.

    2017-05-01

    Photoconductivity studies on spark plasma sintered BiFeO3 samples with two contrasting morphologies, viz., nanoparticle-segregated grain boundary (BFO-AP) and clean grain boundary (BFO-AA), show that their photo-response is largely influenced by the grain boundary defects. Impedance analyses at 300 K and 573 K clearly demarcate the contributions from grain, grain-boundary, and the nanoparticle-segregated grain-boundary conductivities. I-V characteristics under 1 sun illumination show one order of higher conductivity for BFO-AP, whereas conductivity decreases for BFO-AA sample. Larger photocurrent in BFO-AP is attributed to the extra conduction path provided by oxygen vacancies on the nanoparticle surfaces residing at the grain boundaries. Creation of photo-induced traps under illumination and the absence of surface conduction channels in BFO-AA are surmised to result in a decreased conductivity on illumination.

  14. Enhanced magnetic properties in Nd-Fe-B magnets prepared by spark plasma sintering via die-upsetting process

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHU Linhua; LI Jun; LIU Ying

    2011-01-01

    The magnetic properties and microstructure of Nd-Fe-B magnets prepared by spark plasma sintering with different die-upsetting processes were investigated.The results showed that the optimum magnetic properties of die-upset Nd-Fe-B magnets were obtained at 680 ℃ when the die-upset level was 60%,and the degree of magnetic alignment was 0.84.The microstructures showed that the coarse grains occurred predominantly within certain areas,and abnormal grain growth was not observed within the major areas of well-aligned grains.There existed many small spherical grains,which stacked together and were not aligned during die upsetting when the deformation temperature was 650 ℃.These small spherical grains grew up,and were aligned when the deformation temperature increased from 650 to 680 ℃,which could improve the crystallographic alignment of die-upset Nd-Fe-B magnets.

  15. Mechanism analysis on finishing of reaction-sintered silicon carbide by combination of water vapor plasma oxidation and ceria slurry polishing

    Science.gov (United States)

    Shen, Xinmin; Tu, Qunzhang; Deng, Hui; Jiang, Guoliang; Yamamura, Kazuya

    2015-05-01

    Reaction-sintered silicon carbide (RS-SiC), which is considered as a promising mirror material for space telescope systems, requires a high surface property. An ultrasmooth surface with a Ra surface roughness of 0.480 nm was obtained after water vapor plasma oxidation for 90 min followed by ceria slurry polishing for 40 min. The oxidation process of RS-SiC by water vapor plasma was analyzed based on the Deal-Grove model, and the theoretical calculation results are consistent with the measured data obtained by scanning white light interferometer (SWLI), scanning electron microscopy/energy-dispersive x-ray, and atomic force microscope. The polishing process of oxidized RS-SiC by ceria slurry was investigated according to the Preston equation, which would theoretically forecast the evolutions of RS-SiC surfaces along with the increasing of polishing time, and it was experimentally verified by comparing the surface roughnesses obtained by SWLI and the surface morphologies obtained by SEM. The mechanism analysis on the finishing of RS-SiC would be effective for the optimization of water vapor plasma oxidation parameters and ceria slurry polishing parameters, which will promote the application of RS-SiC substrates by improving the surface property obtained by the oxidation-assisted polishing method.

  16. Interface evolution and shear strength of Al/Ti bi-metals processed by a spark plasma sintering (SPS) apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Miriyev, Aslan, E-mail: aslan.miriyev@columbia.edu [Department of Mechanical Engineering, Columbia University in the City of New York, 500 W. 120th St., Mudd 220, New York, NY 10027 (United States); Levy, Asaf; Kalabukhov, Sergey; Frage, Nachum [Department of Materials Engineering, Ben-Gurion University of the Negev, P.O.B. 653, Beer Sheva 8410501 (Israel)

    2016-09-05

    Microstructural evolution of the Al/Ti bi-metal interface during heat treatment in a spark plasma sintering (SPS) apparatus was investigated under various conditions for the first time. A mechanism of interfacial layer growth was suggested based on the results of SEM, TEM and X-ray diffraction analysis. A continuous TiAl{sub 3} intermetallic layer was formed at the Al/Ti interface even after a processing time as short as about a minute. The TiAl{sub 3} layer grew mainly into the Ti part, while only a few individual grains grew into the Al part. Evolution of the interlayer was determined by Al diffusion through the (TiAl{sub 3}/TiAl{sub 3}) grain boundary. The activation energy of the process was 140 kJ/mol. The shear strength of the interface in the Al/Ti bi-metal was determined after various heat treatments. The shear strength of the bi-metal was limited by the properties of aluminum, with no effect of interlayer thickness or current mode and pulse pattern of the SPS treatment being detected. - Highlights: • Spark plasma sintering apparatus was used for heat treatment of Al/Ti bi-metals. • Microstructural evolution of Al/Ti interface during SPS treatment was investigated. • A continuous TiAl{sub 3} intermetallic layer was formed at the Al/Ti interface. • The bi-metal shear strength was limited by the properties of pure aluminum. • No effect of TiAl{sub 3} thickness or SPS current mode and pulse pattern was detected.

  17. Microstructure and mechanical properties of air atomized aluminum powder consolidated via spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Sweet, G.A. [Dalhousie University, Department of Process Engineering and Applied Science, 1360 Barrington Street, Halifax, Nova Scotia, Canada B3J 1Z1 (Canada); Brochu, M. [McGill University, Mining and Materials Engineering Department, 3610 University Street, Montreal, Quebec, Canada H3A 0C5 (Canada); Hexemer, R.L.; Donaldson, I.W. [GKN Sinter Metals LLC, 3300 University Drive, Auburn Hills 48326 (United States); Bishop, D.P., E-mail: Paul.Bishop@dal.ca [Dalhousie University, Department of Process Engineering and Applied Science, 1360 Barrington Street, Halifax, Nova Scotia, Canada B3J 1Z1 (Canada)

    2014-07-01

    Two air atomized aluminum powders, one of commercial purity and the other magnesium-doped (0.4 wt%), were processed by SPS and conventional PM means. An investigation of SPS processing parameters and their effect on sinter quality were investigated. A comparison with conventionally processed PM counterparts was also conducted. Applied pressure and ultimate processing temperature bore the greatest influence on processing, while heating rate and hold time showed a minor effect. Full density specimens were achieved for both powders under select processing conditions. To compliment this, large (80 mm) and small (20 mm) diameter samples were made to observe possible up-scaling effects, as well as tensile properties. Large samples were successfully processed, albeit with somewhat inferior densities to the smaller counterparts presumably due to the temperature inhomogeneity during processing. An investigation of tensile properties for SPS samples exhibited extensive ductility (∼30%) at high sintering temperatures, while lower temperature SPS samples as well as all PM processed samples exhibited a brittle nature. The measurement of residual oxygen and hydrogen contents showed a significant elimination of both species in SPS samples under certain processing parameters when compared to conventional PM equivalents.

  18. Preliminary study on atmospheric-pressure plasma-based chemical dry figuring and finishing of reaction-sintered silicon carbide

    Science.gov (United States)

    Shen, Xinmin; Deng, Hui; Zhang, Xiaonan; Peng, Kang; Yamamura, Kazuya

    2016-10-01

    Reaction-sintered silicon carbide (RS-SiC) is a research focus in the field of optical manufacturing. Atmospheric-pressure plasma-based chemical dry figuring and finishing, which consist of plasma chemical vaporization machining (PCVM) and plasma-assisted polishing (PAP), were applied to improve material removal rate (MRR) in rapid figuring and ameliorate surface quality in fine finishing. Through observing the processed RS-SiC sample in PCVM by scanning white-light interferometer (SWLI), the calculated peak-MRR and volume-MRR were 0.533 μm/min and 2.78×10-3 mm3/min, respectively. The comparisons of surface roughness and morphology of the RS-SiC samples before and after PCVM were obtained by the scanning electron microscope and atomic force microscope. It could be found that the processed RS-SiC surface was deteriorated with surface roughness rms 382.116 nm. The evaluations of surface quality of the processed RS-SiC sample in PAP corresponding to different collocations of autorotation speed and revolution speed were obtained by SWLI measurement. The optimal surface roughness rms of the processed RS-SiC sample in PAP was 2.186 nm. There were no subsurface damages, scratches, or residual stresses on the processed sample in PAP. The results indicate that parameters in PAP should be strictly selected, and the optimal parameters can simultaneously obtain high MRR and smooth surface.

  19. Mechanical alloying and sintering of aluminum reinforced with SiC nanopowders produced by plasma-enhanced chemical-vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Costa, J.; Fort, J.; Roura, P. [GRM, Dept. de Enginyeria Industrial, Universitat de Girona (Spain); Froyen, L. [MTM Katholieke Universiteit Leuven (Belgium); Viera, G.; Bertran, E. [FEMAN, Dept. Fisica Aplicada i Optica, Universitat de Barcelona (Spain)

    2000-07-01

    Nanometric powders of stoichiometric SiC have been synthesised by plasma-enhanced chemical-vapour deposition. These are constituted by amorphous particles with diameters ranging from 10 to 100 nm. Due to their high hydrogen content, a heat treatment at 900 C was needed to prevent spontaneous oxidation. The stabilized SiC powder was mechanically alloyed with aluminum particles of 40 {mu}m in diameter and the alloy was formed by hot isostatic sintering. The SiC content ranged from 0 to 5% in weight. A detailed analysis of the alloyed powder microstructure is presented as well as preliminary results concerning the mechanical properties after sintering. (orig.)

  20. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

    Full Text Available The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions and different atmospheres (i.e., defect chemistry on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT.

  1. Development of an Innovative High-Thermal Conductivity UO2 Ceramic Composites Fuel Pellets with Carbon Nano-Tubes Using Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Subhash, Ghatu [Univ. of Florida, Gainesville, FL (United States); Wu, Kuang-Hsi [Florida International Univ. (FIU), Miami, FL (United States); Tulenko, James [Univ. of Florida, Gainesville, FL (United States)

    2014-03-10

    Uranium dioxide (UO2) is the most common fuel material in commercial nuclear power reactors. Despite its numerous advantages such as high melting point, good high-temperature stability, good chemical compatibility with cladding and coolant, and resistance to radiation, it suffers from low thermal conductivity that can result in large temperature gradients within the UO2 fuel pellet, causing it to crack and release fission gases. Thermal swelling of the pellets also limits the lifetime of UO2 fuel in the reactor. To mitigate these problems, we propose to develop novel UO2 fuel with uniformly distributed carbon nanotubes (CNTs) that can provide high-conductivity thermal pathways and can eliminate fuel cracking and fission gas release due to high temperatures. CNTs have been investigated extensively for the past decade to explore their unique physical properties and many potential applications. CNTs have high thermal conductivity (6600 W/mK for an individual single- walled CNT and >3000 W/mK for an individual multi-walled CNT) and high temperature stability up to 2800°C in vacuum and about 750°C in air. These properties make them attractive candidates in preparing nano-composites with new functional properties. The objective of the proposed research is to develop high thermal conductivity of UO2–CNT composites without affecting the neutronic property of UO2 significantly. The concept of this goal is to utilize a rapid sintering method (5–15 min) called spark plasma sintering (SPS) in which a mixture of CNTs and UO2 powder are used to make composites with different volume fractions of CNTs. Incorporation of these nanoscale materials plays a fundamentally critical role in controlling the performance and stability of UO2 fuel. We will use a novel in situ growth process to grow CNTs on UO2 particles for rapid sintering and develop UO2-CNT composites. This method is expected to provide a uniform distribution of CNTs at various volume fractions so that a high

  2. A novel sintering method to obtain fully dense gadolinia doped ceria by applying a direct current

    Science.gov (United States)

    Hao, Xiaoming; Liu, Yajie; Wang, Zhenhua; Qiao, Jinshuo; Sun, Kening

    2012-07-01

    A fully dense Ce0.8Gd0.2O1.9 (gadolinia doped ceria, GDC) is obtained by a novel using a sintering technique for several seconds at 545 °C by applying a direct current (DC) electrical field of 70 V cm-1. The onset applied field value of this phenomenon is 20 V cm-1, and the volume specific power dissipation for the onset of flash sintering is about ∼10 mW mm-3. Through contrast with the shrinkage strain of the conventional sintering as well as scanning electron microscopy (SEM) analysis, we conclude that GDC specimens are sintered to fully density under various applied fields. In addition, we demonstrate that the grain size of GDC is decreasing with the increase of applied field and the decrease of sintering temperature. Through calculation, we find that sintering of GDC can be explained by the Joule heating from the applied electrical field.

  3. Crystal structure, microstructure, and thermoelectric properties of GeSb{sub 6}Te{sub 10} prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kosuga, Atsuko, E-mail: a-kosuga@21c.osakafu-u.ac.jp [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Nakai, Kazuki [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Matsuzawa, Mie; Fujii, Yousuke [Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570 (Japan); Funahashi, Ryoji [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, Ikeda 563-8577 (Japan); Tachizawa, Takuya; Kubota, Yoshiki [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Kifune, Kouichi [Department of Physical Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531 (Japan); Faculty of Engineering, Hiroshima Institute of Technology, Hiroshima 731-5193 (Japan)

    2015-01-05

    Highlights: • Spark plasma sintering effects on GeSb{sub 6}Te{sub 10} properties are described. • Sintered GeSb{sub 6}Te{sub 10} contains homologous GeSb{sub 6}Te{sub 10} and Sb{sub 2}Te{sub 3} tetradymite structures. • Spark plasma sintering causes elemental compositional deviations from GeSb{sub 6}Te{sub 10}. • SPS-consolidated and melt-prepared samples have similar ZT{sub max} values. • Spark plasma sintering significantly changes crystal structure and microstructure. - Abstract: We report the effects of spark plasma sintering (SPS) and subsequent annealing on the crystal structure, microstructure, and thermoelectric properties of polycrystalline GeSb{sub 6}Te{sub 10}. GeSb{sub 6}Te{sub 10} consolidated using SPS consisted of a mixture of GeSb{sub 6}Te{sub 10}-type homologous and Sb{sub 2}Te{sub 3}-type tetradymite structures, whereas the sample prepared by melting had a single homologous structure. SPS produced small amounts of Ge-rich precipitates with a few micrometers in size. Even excluding these precipitates, the elemental compositional deviation from the nominal composition was wider than that for the sample prepared by melting. This implies that SPS promoted atomic diffusion and rearrangement of elements, leading to a substantial change in the crystal structure and elemental distribution of GeSb{sub 6}Te{sub 10}. SPS improved the power factor but also increased the thermal conductivity, as a result of the increased electrical conductivity, yielding a maximum dimensionless figure of merit, ZT{sub max}, of 0.33 at 710 K, which is similar to the value for the sample prepared by melting (0.39 at 710 K)

  4. Tunable thermoelectric transport properties of Cu0.008Bi2Te2.7Se0.3 via control of the spark plasma sintering conditions

    Science.gov (United States)

    Moon, Seung Pil; Ahn, Yeon Sik; Kim, Tae Wan; Choi, Soon-Mok; Park, Hee Jung; Kim, Sung Wng; Lee, Kyu Hyoung

    2016-09-01

    Polycrystalline bulks of n-type Cu0.008Bi2Te2.7Se0.3 were prepared to investigate the controllability of its thermoelectric transport properties by using the compaction conditions of spark plasma sintering (SPS). The 00 l crystal orientation to the press direction of the SPSed bulks was easily improved by increasing the applied pressure at 500 °C. The thermoelectric figure of merit, ZT values (0.72 - 0.75 at 300 K), of all samples were almost the same, however, both the electronic and the thermal transport properties could be tuned significantly by adjusting the sintering pressure. This result highlights the feasibility of using pressure-induced sintering as a fabrication technology for Bi2Te3-based polycrystalline bulks with high mechanical reliability, which is an effective means of optimizing the electrical and the thermal conductivities for maximizing the efficiencies of the thermoelectric cooling and the power generation modules.

  5. Sintering of calcium phosphate bioceramics.

    Science.gov (United States)

    Champion, E

    2013-04-01

    Calcium phosphate ceramics have become of prime importance for biological applications in the field of bone tissue engineering. This paper reviews the sintering behaviour of these bioceramics. Conventional pressureless sintering of hydroxyapatite, Ca10(PO4)6(OH)2, a reference compound, has been extensively studied. Its physico-chemistry is detailed. It can be seen as a competition between two thermally activated phenomena that proceed by solid-state diffusion of matter: densification and grain growth. Usually, the objective is to promote the first and prevent the second. Literature data are analysed from sintering maps (i.e. grain growth vs. densification). Sintering trajectories of hydroxyapatite produced by conventional pressureless sintering and non-conventional techniques, including two-step sintering, liquid phase sintering, hot pressing, hot isostatic pressing, ultrahigh pressure, microwave and spark plasma sintering, are presented. Whatever the sintering technique may be, grain growth occurs mainly during the last step of sintering, when the relative bulk density reaches 95% of the maximum value. Though often considered very advantageous, most assisted sintering techniques do not appear very superior to conventional pressureless sintering. Sintering of tricalcium phosphate or biphasic calcium phosphates is also discussed. The chemical composition of calcium phosphate influences the behaviour. Similarly, ionic substitutions in hydroxyapatite or in tricalcium phosphate create lattice defects that modify the sintering rate. Depending on their nature, they can either accelerate or slow down the sintering rate. The thermal stability of compounds at the sintering temperature must also be taken into account. Controlled atmospheres may be required to prevent thermal decomposition, and flash sintering techniques, which allow consolidation at low temperature, can be helpful.

  6. Relevance of the choice of spark plasma sintering parameters in obtaining a suitable microstructure for iodine-bearing apatite designed for the conditioning of I-129

    Energy Technology Data Exchange (ETDEWEB)

    Campayo, L., E-mail: lionel.campayo@cea.fr [CEA, DEN, DTCD/SECM/LDMC – Marcoule, F-30207 Bagnols-sur-Cèze (France); Le Gallet, S. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-UB, 9 Av. Alain Savary, BP 47870, 21078 Dijon Cedex (France); Perret, D.; Courtois, E. [CEA, DEN, DTCD/SECM/LDMC – Marcoule, F-30207 Bagnols-sur-Cèze (France); Cau Dit Coumes, C. [CEA, DEN, DTCD/SPDE/LP2C – Marcoule, F-30207 Bagnols-sur-Cèze (France); Grin, Yu. [Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden (Germany); Bernard, F. [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-UB, 9 Av. Alain Savary, BP 47870, 21078 Dijon Cedex (France)

    2015-02-15

    Highlights: • Modeling of reactive sintering by SPS of an iodoapatite for waste immobilization. • Use of a statistical approach to surmount the complexity of the process. • The supposed most resistant microstructure towards leaching is obtained at 450 °C. • Pressure has no influence in the liquid sintering regime. - Abstract: The high chemical durability of iodine-bearing apatite phases makes them potentially attractive for immobilizing radioactive iodine. Reactive spark plasma sintering provides a dense ceramic as a wasteform. A design-of-experiments (DOE) approach was adopted to identify the main process/material parameters and their first order interactions in order to specify experimental conditions guaranteeing complete reaction, relative density of the wasteform exceeding 92% and the largest possible grain size. For a disposal of the wasteform in a deep geological repository, these characteristics allow minimization of the iodine release by contact with groundwater. It was found that sintering at a temperature of 450 °C with an initial specific surface area of 3.3 m{sup 2} g{sup −1} for the powder reactants is sufficient in itself to achieve the targeted characteristics of the wasteform. However, this relies on a liquid sintering regime the efficiency of which can be limited by the lead iodide initial content in the mix as well as by its particle size.

  7. Spark Plasma Sintering of Load-Bearing Iron-Carbon Nanotube-Tricalcium Phosphate CerMets for Orthopaedic Applications

    Science.gov (United States)

    Montufar, Edgar B.; Horynová, Miroslava; Casas-Luna, Mariano; Diaz-de-la-Torre, Sebastián; Celko, Ladislav; Klakurková, Lenka; Spotz, Zdenek; Diéguez-Trejo, Guillermo; Fohlerová, Zdenka; Dvorak, Karel; Zikmund, Tomáš; Kaiser, Jozef

    2016-04-01

    Recently, ceramic-metallic composite materials (CerMets) have been investigated for orthopaedic applications with promising results. This first generation of bio-CerMets combine the bioactivity of hydroxyapatite with the mechanical stability of titanium to fabricate bioactive, tough and biomechanically more biocompatible osteosynthetic devices. Nonetheless, these first CerMets are not biodegradable materials and a second surgery is required to remove the implant after bone healing. The present work aims to develop the next generation bio-CerMets, which are potential biodegradable materials. The process to produce the new biodegradable CerMet consisted of mixing powder of soluble and osteoconductive alpha tricalcium phosphate with biocompatible and biodegradable iron with consolidation through spark plasma sintering (SPS). The microstructure, composition and mechanical strength of the new CerMet were studied by metallography, x-ray diffraction and diametral tensile strength tests, respectively. The results show that SPS produces CerMet with higher mechanical performance (120 MPa) than the ceramic component alone (29 MPa) and similar mechanical strength to the pure metallic component (129 MPa). Nonetheless, although a short sintering time (10 min) was used, partial transformation of the alpha tricalcium phosphate into its allotropic and slightly less soluble beta phase was observed. Cell adhesion tests show that osteoblasts are able to attach to the CerMet surface, presenting spread morphology regardless of the component of the material with which they are in contact. However, the degradation process restricted to the small volume of the cell culture well quickly reduces the osteoblast viability.

  8. High coercivity, anisotropic, heavy rare earth-free Nd-Fe-B by Flash Spark Plasma Sintering.

    Science.gov (United States)

    Castle, Elinor; Sheridan, Richard; Zhou, Wei; Grasso, Salvatore; Walton, Allan; Reece, Michael J

    2017-09-11

    In the drive to reduce the critical Heavy Rare Earth (HRE) content of magnets for green technologies, HRE-free Nd-Fe-B has become an attractive option. HRE is added to Nd-Fe-B to enhance the high temperature performance of the magnets. To produce similar high temperature properties without HRE, a crystallographically textured nanoscale grain structure is ideal; and this conventionally requires expensive "die upset" processing routes. Here, a Flash Spark Plasma Sintering (FSPS) process has been applied to a Dy-free Nd30.0Fe61.8Co5.8Ga0.6Al0.1B0.9 melt spun powder (MQU-F, neo Magnequench). Rapid sinter-forging of a green compact to near theoretical density was achieved during the 10 s process, and therefore represents a quick and efficient means of producing die-upset Nd-Fe-B material. The microstructure of the FSPS samples was investigated by SEM and TEM imaging, and the observations were used to guide the optimisation of the process. The most optimal sample is compared directly to commercially die-upset forged (MQIII-F) material made from the same MQU-F powder. It is shown that the grain size of the FSPS material is halved in comparison to the MQIII-F material, leading to a 14% increase in coercivity (1438 kA m(-1)) and matched remanence (1.16 T) giving a BHmax of 230 kJ m(-3).

  9. Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe2O4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900 ℃ for 2 h has an average diameter of 60~90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

  10. Structure properties and sintering densification of Gd2Zr2O7 nanoparticles prepared via different acid combustion methods

    Institute of Scientific and Technical Information of China (English)

    马雷; 马伟民; 孙旭东; 刘佳男; 纪连永; 宋晗

    2015-01-01

    Gadolinium zirconate (Gd2Zr2O7) nanocrystals were prepared via two different combustion methods:citric acid combus-tion (CAC) and stearic acid combustion (SAC). The effects of the different preparation methods on the phase composition, micro-topography, and sintering densification of the resulting Gd2Zr2O7 nanopowders were investigated by thermal-gravimetric and differ-ential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission elec-tron microscopy (TEM) techniques. The results indicated that both methods could produce Gd2Zr2O7 nanopowders with an excellent defective fluorite structure. The reaction time was reduced by the SAC method, compared with the CAC method. The nanopowders synthesized by the two methods were different in grain size distribution. The resulting nanoparticle diameter was about 50 nm for CAC and 10 nm for SAC. After vacuum sintering, the sintered bodies also had a different relative density of about 93%and 98%, respectively. Thus the preparation of Gd2Zr2O7 nanopowders by SAC was the first choice to achieve the desired sintering densifi-cation.

  11. Fabrication of Ce3+ doped Gd3Ga3Al2O12 ceramics by reactive sintering method

    Science.gov (United States)

    Ye, Yong; Liu, Peng; Yan, Dongyue; Xu, Xiaodong; Zhang, Jian

    2017-09-01

    Ce3+ doped Gd3Ga3Al2O12 (Ce:GGAG) ceramics were fabricated by solid state reactive sintering method in this study. The ceramics were pre-sintered in normal muffle furnace in air at various temperature range from 1410 °C to 1550 °C for 10 h and post-treated by hot isostatic press at 1400 °C/2 h in 200 MPa Ar. The phase and microstructure evolution of Ce: GGAG samples during the densification process were investigated by X-ray diffraction and scanning electron microscope. Pure GGAG phase appeared with the temperature increased to 1200 °C. The fully dense and translucent GGAG ceramics were fabricated by pre-sintering at 1450 °C and followed by HIP treatment.

  12. High hardness BaCb-(BxOy/BN) composites with 3D mesh-like fine grain-boundary structure by reactive spark plasma sintering.

    Science.gov (United States)

    Vasylkiv, Oleg; Borodianska, Hanna; Badica, Petre; Grasso, Salvatore; Sakka, Yoshio; Tok, Alfred; Su, Liap Tat; Bosman, Michael; Ma, Jan

    2012-02-01

    Boron carbide B4C powders were subject to reactive spark plasma sintering (also known as field assisted sintering, pulsed current sintering or plasma assisted sintering) under nitrogen atmosphere. For an optimum hexagonal BN (h-BN) content estimated from X-ray diffraction measurements at approximately 0.4 wt%, the as-prepared BaCb-(BxOy/BN) ceramic shows values of Berkovich and Vickers hardness of 56.7 +/- 3.1 GPa and 39.3 +/- 7.6 GPa, respectively. These values are higher than for the vacuum SPS processed B4C pristine sample and the h-BN -mechanically-added samples. XRD and electronic microscopy data suggest that in the samples produced by reactive SPS in N2 atmosphere, and containing an estimated amount of 0.3-1.5% h-BN, the crystallite size of the boron carbide grains is decreasing with the increasing amount of N2, while for the newly formed lamellar h-BN the crystallite size is almost constant (approximately 30-50 nm). BN is located at the grain boundaries between the boron carbide grains and it is wrapped and intercalated by a thin layer of boron oxide. BxOy/BN forms a fine and continuous 3D mesh-like structure that is a possible reason for good mechanical properties.

  13. Enhanced ferroelectricity and magnetoelectricity in 0.75BaTiO3-0.25BaFe12O19 by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Adiraj Srinivas

    2013-03-01

    Full Text Available Spark Plasma Sintering (SPS technique was employed to synthesize 0.75BaTiO3-0.25BaFe12O19 composite. X-ray diffraction studies revealed that the composite consisted of both BaTiO3 (ferroelectric phase andBaFe12O19 (ferrimagnetic phase, respectively. The SPS treated sample showed improved ferroelectric nature when compared to conventional sintered (CS sample. Transformation from hard to soft magnetic nature was envisaged by magnetization measurements for SPS sample. A slim hysteresis loop was recorded with a low coercivity values (390 Oe when compared to CS sample (3900 Oe. Mossbauer spectroscopy analysis indicated that the existence of a partial amount of γ-Fe2O3 phase in the lattice, giving rise to soft magnetic nature. The SPS sample showed slightly higher value of magnetoelectric output of 2.95 mV/cm at 3 kOe magnetic field when compared to the CS sample (1.45 mV/cm at 3 kOe. The present investigation compares the spark plasma sintered sample with the conventional sintered sample.

  14. Preparation of fine-grained tungsten heavy alloys by spark plasma sintered W–7Ni–3Fe composite powders with different ball milling time

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.P., E-mail: dpxiang@hainu.edu.cn [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Ding, L. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); Li, Y.Y.; Chen, G.B. [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Zhao, Y.W. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China)

    2013-06-15

    Highlights: ► We fabricate fine-grained W–7Ni–3Fe alloys using HEBM assisted SPS method. ► The γ-(Ni, Fe, W) phase is not observed in HEBM raw powders. ► The density of the WHAs gradually decreased with increasing HEBM time. ► The hardness and bending strength of the WHAs show different trends of variation. ► The intergranular fracture was the main bending fracture mode of the WHAs. -- Abstract: The fine-grained tungsten heavy alloys (WHAs) with grain size of about 1–3 μm were successfully prepared by spark plasma sintered W–7Ni–3Fe composite powders with different high-energy ball milling (HEBM) time. This study analyzes the effects of HEBM time not only on the composite powders but on the microstructure and mechanical properties of WHAs. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the microstructure and phase evolution rules of powders and alloys, respectively. The γ-(Ni, Fe, W) is not observed in XRD patterns of the ball milled powders. With prolonging HEBM time, the W phase diffraction peak becomes increasingly wider, and its intensity continues to decline. However, the completely amorphous structures are not formed even after HEBM 40 h. The relative density of the WHAs prepared by HEBM assisted SPS technique decreases gradually with increasing the ball milling time. For the WHAs sintered in 1150 °C for 8 min, the W grains grow finer and the content of the γ-(Ni, Fe, W) binding phase greatly increases with prolonging the HEBM time. Meanwhile, over 5 h of HEBM time, the bending strength continuously decreases and the hardness slightly increases. The intergranular fracture of the W grains is the main bending fracture mode in all the WHAs. The microporous of different sizes are distributed on the bending fracture and progressively increased with prolonging the ball milling time.

  15. In vitro degradation and biocompatibility of Fe–Pd and Fe–Pt composites fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Huang, T. [State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Cheng, J. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

    2014-02-01

    In order to obtain biodegradable Fe-based materials with similar mechanical properties as 316L stainless steel and faster degradation rate than pure iron, Fe-5 wt.%Pd and Fe-5 wt.%Pt composites were prepared by spark plasma sintering with powders of pure Fe and Pd/Pt, respectively. The grain size of Fe-5 wt.%Pd and Fe-5 wt.%Pt composites was much smaller than that of as-cast pure iron. The metallic elements Pd and Pt were uniformly distributed in the matrix and the mechanical properties of these materials were improved. Uniform corrosion of Fe–Pd and Fe–Pt composites was observed in both electrochemical tests and immersion tests, and the degradation rates of Fe–Pd and Fe–Pt composites were much faster than that of pure iron. It was found that viabilities of mouse fibroblast L-929 cells and human umbilical vein endothelial cells (ECV304) cultured in extraction mediums of Fe–Pd and Fe–Pt composites were close to that of pure iron. After 4 days' culture, the viabilities of L-929 and ECV304 cells in extraction medium of experimental materials were about 80%. The result of direct contact cytotoxicity also indicated that experimental materials exhibited no inhibition on vascular endothelial process. Meanwhile, iron ions released from experimental materials could inhibit proliferation of vascular smooth muscle cells (VSMC), which may be beneficial for hindering vascular restenosis. Furthermore, compared with that of as-cast pure iron, the hemolysis rates of Fe–Pd and Fe–Pt composites were slightly higher, but still within the range of 5%, which is the criteria for good blood compatibility. The numbers of platelet adhered on the surface of Fe–Pd and Fe–Pt composites were lower than that of pure iron, and the morphology of platelets kept spherical. To sum up, the Fe-5wt.%Pd and Fe-5wt.%Pt composites exhibited good mechanical properties and degradation behavior, closely approaching the requirements for biodegradable metallic stents. - Highlights:

  16. Fabrication of 13Cr-2Mo Ferritic/Martensitic Oxide-Dispersion-Strengthened Steel Components by Mechanical Alloying and Spark-Plasma Sintering

    Science.gov (United States)

    Bogachev, I.; Grigoryev, E.; Khasanov, O. L.; Olevsky, E.

    2014-06-01

    The outcomes of the mechanical alloying of 13Cr-2Mo ferritic/martensitic steel and yttria (oxide-dispersion-strengthened steel) powders in a ball mill are reported in terms of the powder particle size and morphology evolution. The optimal ball mill rotation speed and the milling time are discussed. The densification kinetics of the mechanically alloyed powder during the process of spark-plasma sintering is analyzed. An optimal set of the compaction processing parameters, including the maximum temperature, the dwell time, and the heating rate, is determined. The specifics of the densification are discussed in terms of the impact of major spark-plasma sintering parameters as well as the possible phase transformations occurring during compaction processing.

  17. Enhanced Homogenization of Vanadium in Spark Plasma Sintering of Ti-10V-2Fe-3Al Alloy from Titanium and V-Fe-Al Master Alloy Powder Blends

    Science.gov (United States)

    Yang, Y. F.; Imai, H.; Kondoh, K.; Qian, M.

    2017-02-01

    Strong and ductile powder metallurgy (PM) Ti-10V-2Fe-3Al alloy has been fabricated by spark plasma sintering (SPS) of titanium and V-Fe-Al master alloy powder blends at 1100°C for 30 min under 30 MPa. The homogenization of vanadium, which dictates the realization of a uniform microstructure of the Ti-10V-2Fe-3Al alloy, was markedly accelerated by SPS. The mechanism is attributed to the intensive Joule heating effect produced by the direct current passing through the electric conducting powder blends, rather than through spark plasma discharge, because homogenization occurred mainly after near full identification had been achieved. The chemical and microstructural homogeneity ensured the achievement of excellent tensile properties of PM Ti-10V-2Fe-3Al in the as-sintered state, with tensile strength >1250 MPa and elongation >10%.

  18. Enhancing Thermoelectric Properties of Si80Ge20 Alloys Utilizing the Decomposition of NaBH4 in the Spark Plasma Sintering Process

    Directory of Open Access Journals (Sweden)

    Ali Lahwal

    2015-09-01

    Full Text Available The thermoelectric properties of spark plasma sintered, ball-milled, p-type Si80Ge20-(NaBH4x (x = 0.7,1.7 and 2.7, and Si80Ge20B1.7-y-(NaBH4y (y = 0.2 and 0.7 samples have been investigated from 30 K to 1100 K. These samples were prepared by spark plasma sintering of an admixture of Si, Ge, B and NaBH4 powders. In particular, the degasing process during the spark plasma sintering process, the combined results of X-ray powder diffraction, Raman spectroscopy, Hall coefficient, electrical resistivity, and Seebeck coefficient measurements indicated that NaBH4 decomposed into Na, B, Na2B29, and H2 during the spark plasma sintering process; Na and B were doped into the SiGe lattice, resulting in favorable changes in the carrier concentration and the power factor. In addition, the ball milling process and the formation of Na2B29 nanoparticles resulted in stronger grain boundary scattering of heat-carrying phonons, leading to a reduced lattice thermal conductivity. As a result, a significant improvement in the figure of merit ZT (60% was attained in p-type Si80Ge20-(NaBH41.7 and Si80Ge20-B1.5(NaBH40.7 at 1100 K as compared to the p-type B-doped Si80Ge20 material used in the NASA’s radioactive thermoelectric generators. This single-step “doping-nanostructuring” procedure can possibly be applied to other thermoelectric materials.

  19. Preparation of SiC–MgAl2O4–Y3Al5O12-MWCNTs nanocomposites by spark plasma sintering

    Science.gov (United States)

    Zharikov, E. V.; Kapustin, V. V.; Faikov, P. P.; Popova, N. A.; Barmin, A. A.; Ivanov, A. V.; Rizakhanov, R. N.

    2017-02-01

    Fabrication a composite materials based on silicon carbide (SiC) reinforced with multi-walled carbon nanotubes (MWCNTs) with addition of magnesium alumina spinel MgAl2O4, and yttrium aluminum garnet Y3Al5O12 by spark plasma sintering are presented. Two series of composites differing by the particle size of starting SiC were prepared. Mechanical characteristics of composites including microhardness, fracture toughness and flexural strength are determined.

  20. Structural characteristics and magnetic properties of bulk nanocrystalline Fe_(84)Zr_2Nb_4B_(10) alloy prepared by mechanical alloying and spark plasma sintering consolidation

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Magnetic properties of Fe84Zr2Nb4B10 sample were investigated. The sample was produced from nanocrystalline powders made by the mechanical alloying (MA) and consolidation using the spark plasma sintering (SPS) technique. Effects of milling time on phase transformation, structural characteristics, and magnetic properties of powders were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and physical property measure system (PPMS), respectively. Results show that nanostructured α-Fe supe...

  1. Comparison of ZrB{sub 2}-ZrC-SiC composites fabricated by spark plasma sintering and hot-pressing

    Energy Technology Data Exchange (ETDEWEB)

    Medri, V.; Monteverde, F.; Balbo, A.; Bellosi, A. [National Research Council - Institute of Science and Technology for Ceramics, Via Granarolo 64, I-48018, Faenza (Italy)

    2005-03-01

    Ultra-high temperature ceramics (UHTCs) exhibit a number of properties (thermal and chemical stability, high strength and hardness, ablation/oxidation and thermal shock resistance) for sustained use in the extreme environments experienced by re-entry space vehicles. The spark plasma sintering (SPS) was considered as a new processible fast approach to develop structural ceramics with improved ultra-high temperature capabilities. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  2. Effects of adding alumina to the nickel-zirconia anode materials for solid oxide fuel cells and a two-step sintering method for half-cells

    Science.gov (United States)

    Song, Xiao; Dong, Xiaolei; Li, Ming; Wang, Haiqian

    2016-03-01

    The co-sintering process of half-cells has an important effect on the flatness and performance of solid oxide fuel cells. In this study, we report a two-step sintering method to fabricate flat three-layer half-cells. The first sintering step is a freestanding sintering process at a low temperature (1280 °C). The second sintering step is a constrained sintering process at 1400 °C. The shrinkage of the anode support layer (ASL) and the curvature of the half-cell can be adjusted by adding Al2O3 into the ASL in the first sintering step. Effects of Al2O3 addition on the NiO-YSZ anode material are also studied. We find that NiO reacts with Al2O3 to form NiAl2O4 spinel at the early sintering stage. This reaction transiently promotes the grain growth of NiO. Once the reaction terminates and the NiAl2O4 spinel is formed, the grain growth of NiO will be suppressed, even at higher sintering temperatures. Our results indicate that by a proper amount (approximately 0.2 wt%) of Al2O3 addition, smaller NiO grains can be obtained while the side effects of NiAl2O4 are negligible, which is favorable to increase the conductivity and stability of the ASL, and can enhance the performance of SOFC.

  3. The effects of an electric field on the sintering of ceramics

    Science.gov (United States)

    Luitjohan, Kara Eileen

    Sintering is a method used to condense a solid powder material into a single solid mass allowing for the production of metal or ceramic parts. Different sintering techniques involve the manipulation of different processing variables. To fully exploit the processing variables, how they affect the sintering process must be fully understood. One such processing variable is an applied electric field, utilized in spark plasma sintering and flash sintering. Both techniques allow for densification to occur at lower temperatures and in shorter times when compared to other sintering techniques. Though various theories exist in literature for how the electric field affects the sintering process, not one has been universally agreed upon. In this work, the sintering of zinc oxide was characterized to determine its response to an electric field. Samples were sintered in a modified tube furnace under various strengths of an applied electric field ranging up to 112 V/cm. After sintering, densities and grain sizes were analyzed. For applied fields up to 112 V/cm, there was no change in the final density or final grain size with respect to the strength of the applied field. It can be concluded that while the field does not affect the final density and final grain size, it does affect when the material reaches those values during the sintering process. With increasing field strengths, less time and lower temperatures are required to reach final density and final grain size. Before the advantages of spark plasma sintering or flash sintering can be applied at the industrial level, more work is still needed to determine the specific effects of an electric field on the sintering of ceramic materials.

  4. Influence of TiN nanoparticles on the microstructure and properties of W matrix materials prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shuang [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Engineering Research Center of Powder Metallurgy of Anhui Province, Hefei 230009 (China); Tan, Xiao-Yue [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zan, Xiang; Cheng, Ji-Gui; Zhu, Xiao-Yong; Wu, Yu-Cheng [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Engineering Research Center of Powder Metallurgy of Anhui Province, Hefei 230009 (China)

    2014-11-15

    Highlights: • Effect of TiN on microstructure and properties of composites were studied. • TiN particles exist in the grain interior and at the grain boundary. • The tensile strength reached 180 MPa when the content of TiN was 2 wt.%. - Abstract: W–(0.5, 1, 2, 4) wt.% TiN composite powders were formed by mechanical alloying for 5 h and sintered by spark plasma at 1800 °C. The effect of TiN nanoparticle content on the microstructure and properties of the composites were investigated by scanning electron microscopy, transmission electron microscopy, tensile test, microhardness test, and thermal conductivity test. With the addition of TiN ranging from 0.5 wt.% to 4 wt.%, SEM analysis results showed that TiN was distributed homogeneously and W grains were refined by TiN. The fracturing of pure W was intergranular, whereas cleavage fracture appeared in the W–TiN composites and increased with increased TiN content. The density was found to initially increase and then decrease with increased TiN content. The same trend was observed for the thermal conductivity. Microhardness increased with increased TiN content. The tensile strength reached 180 MPa when the content of TiN was 2 wt.%. Furthermore, the mechanical properties of 2 wt.% exceeded those of other alloys at different TiN weight percentages.

  5. Investigation on 316L/W functionally graded materials fabricated by mechanical alloying and spark plasma sintering

    Science.gov (United States)

    Tan, Chao; Wang, Guoyu; Ji, Lina; Tong, Yangang; Duan, Xuan-Ming

    2016-02-01

    316L-W (Tungsten) composite materials were fabricated by spark plasma sintering (SPS) of mechanically alloyed 316L-W powders for the development of functionally graded materials (FGMs). The effect of milling parameters on the morphology of the blended 316L/W powders and its subsequent effect on the transition between 316L and W particles during the SPS process were investigated. Samples were characterized by SEM, EDS and XRD analyses. The results so obtained show that with the increase of milling time, the mechanically activated W powder particles become thinner and smoother, with some broken fragments aggregated or inserted in the severely deformed 316L particles. A further SPS process under the conditions of 1050 °C × 45.5 MPa × 5 min leads to the densification of the powder compact and the formation of a distinguishable gray belt surrounding the retained W particles. Such a belt, which has a width of about 2-8 μm depending on different milling parameters and mainly contains Fe7W6, Fe3W3C and Fe2W phases, is bound to be a transitional region between the retained W particles and the 316L matrix. This favorable behavior with regards to the formation of a transitional belt, is accompanied by a substantial increase in the hardness values of the composite.

  6. Zirconium Carbide Produced by Spark Plasma Sintering and Hot Pressing: Densification Kinetics, Grain Growth, and Thermal Properties

    Directory of Open Access Journals (Sweden)

    Xialu Wei

    2016-07-01

    Full Text Available Spark plasma sintering (SPS has been employed to consolidate a micron-sized zirconium carbide (ZrC powder. ZrC pellets with a variety of relative densities are obtained under different processing parameters. The densification kinetics of ZrC powders subjected to conventional hot pressing and SPS are comparatively studied by applying similar heating and loading profiles. Due to the lack of electric current assistance, the conventional hot pressing appears to impose lower strain rate sensitivity and higher activation energy values than those which correspond to the SPS processing. A finite element simulation is used to analyze the temperature evolution within the volume of ZrC specimens subjected to SPS. The control mechanism for grain growth during the final SPS stage is studied via a recently modified model, in which the grain growth rate dependence on porosity is incorporated. The constant pressure specific heat and thermal conductivity of the SPS-processed ZrC are determined to be higher than those reported for the hot-pressed ZrC and the benefits of applying SPS are indicated accordingly.

  7. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  8. Optically- and thermally-stimulated luminescences of Ce-doped SiO2 glasses prepared by spark plasma sintering

    Science.gov (United States)

    Okada, Go; Kasap, Safa; Yanagida, Takayuki

    2016-11-01

    Rare-earth doped phosphors have been used in many applications including radiation measurements. In the latter applications, the radiation photons are converted to light so that we can indirectly detect the radiation using a conventional photodetector. In this work, we have prepared and characterized a Ce-doped SiO2 glass for dosimeter applications. Unlike conventional techniques such as sol-gel synthesis, the sample was prepared by spark plasma sintering. Although the PL emission seems to be only from the Ce3+ ions in the structure, due to the X-ray induced luminescence, we have also observed optically-stimulated luminescence (OSL), and thermally-stimulated luminescence (TSL), owing to a pair of silylenes and a set of dioxasilirane and silylene in addition to Ce3+. We have measured the detector response vs irradiation dose for both the OSL and TSL. The detector response in both cases is linear over the dose range from at least 1 mGy to 2 Gy. Particularly, the sensitivity of TSL is so high that it should be considered to be a good candidate for practical applications.

  9. Magnetic features of Fe-Cr-Co alloys with tailoring chromium content fabricated by spark plasma sintering

    Science.gov (United States)

    Rastabi, Reza Amini; Ghasemi, Ali; Tavoosi, Majid; Ramazani, Mazaher

    2017-03-01

    Structural and magnetic characterization of Fe-Cr-Co alloys during milling, annealing and consolidation processes was the goal of this study. In this regards, different powder mixtures of Fe80-xCrxCo20 (15≤x≤35) were mechanically milled in a planetary ball mill and then were consolidated by spark plasma sintering (SPS). The produced samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). According to achieved results, the structure of as-milled samples in different compositions consists of single α phase solid solution with coercivity and saturation of magnetization in the range of 110-200 Oe and 150-220 emu/g, respectively. The magnetic properties of consolidated samples depend on the kinds of formed precipitates in microstructure and the maximum values of coercive force and saturation of magnetization obtained in Fe55Cr25Co20 magnetic (with single α phase) alloy were 107 Oe and Ms 172 emu/g, respectively. In fact, the formation of non-magnetic σ and γ phases has a destructive effect on magnetic properties of consolidated samples with higher Cr content. Since such magnet requires less cobalt, and contains similar magnetic feature with superior ductility compare to the AlNiCo 5, it could be considered as a promising candidate for employing instead of AlNiCo 5.

  10. Fabricating fine-grained tungsten heavy alloy by spark plasma sintering of low-energy ball-milled W–2Mo–7Ni–3Fe powders

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.P., E-mail: dpxiang@hainu.edu.cn [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Ding, L. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); Li, Y.Y. [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Chen, X.Y.; Zhang, T.M. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China)

    2013-08-20

    Fine-grained W–2Mo–7Ni–3Fe heavy alloys were fabricated by low-energy ball milling (LEBM)-assisted spark plasma sintering at a temperature range of 1000–1250 °C. The effects of sintering temperature on the phase evolution, microstructural characteristics, and mechanical properties of the alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), hardness testing, and universal testing. The XRD results show that small intermetallic compounds, such as NiW and Ni{sub 2}W{sub 4}C, form in the alloys. The W–2Mo–7Ni–3Fe alloys are characterized by white W grains, a gray W-rich microstructure that contains Mo, and a black γ–(Ni, Fe, W, Mo) binding phase. The X-ray energy dispersive analysis (EDS) shows that the Mo, Ni, and Fe that form a solid solution with W in the gray structure gradually decrease with increasing temperature. The hardness and bending strength of the alloys initially increase and then decrease with rising sintering temperature. Moreover, the alloys sintered at different temperatures exhibit dissimilar bending fracture modes.

  11. Low temperature plasma technology methods and applications

    CERN Document Server

    Chu, Paul K

    2013-01-01

    Written by a team of pioneering scientists from around the world, Low Temperature Plasma Technology: Methods and Applications brings together recent technological advances and research in the rapidly growing field of low temperature plasmas. The book provides a comprehensive overview of related phenomena such as plasma bullets, plasma penetration into biofilms, discharge-mode transition of atmospheric pressure plasmas, and self-organization of microdischarges. It describes relevant technology and diagnostics, including nanosecond pulsed discharge, cavity ringdown spectroscopy, and laser-induce

  12. Characterization and processing of sintered products from Nano-crystalline powders generated by the RTDS method

    Energy Technology Data Exchange (ETDEWEB)

    Darab, J.G.; Buehler, M.F.; Linehan, J.C.; Matson, D.W.

    1993-08-01

    Large quantities of nano-crystalline zirconium oxide/oxyhydroxide and nickel-chromium oxide/oxyhydroxide particles agglomerated and sieved into +320/{minus}200 mesh powders have been produced using the rapid thermal decomposition of solutes (RTDS) method. Green compacts (approximately 40% theoretical density) prepared by cold-pressing the RTDS powders at pressures of 140-280-MPa were heated to form dense (86--91% theoretical density) ZrO{sub 2} or Ni{sub 50}Cr{sub 50}components. Dimensional changes in the compacts during heating were used to extract information about the sintering kinetics in these systems. At 800C, grain-boundary diffusion coupled with some surface diffusion are the dominant mechanisms contributing toward the observed densification in the ZrO{sub 2} system. The mechanism-independent activation energy for densification was determined to be 81-kJ/mol for the ZrO{sub 2} system and 56-kj/mol for the NiCr system.

  13. Using multi-walled carbon nanotubes in spark plasma sintered Pb(Zr0.47Ti0.53)O3 ceramics for tailoring dielectric and tunability properties

    Science.gov (United States)

    Ciomaga, Cristina E.; Padurariu, Leontin; Curecheriu, Lavinia P.; Lupu, Nicoleta; Lisiecki, Isabelle; Deluca, Marco; Tascu, Sorin; Galassi, Carmen; Mitoseriu, Liliana

    2014-10-01

    The addition of small amounts (below 0.1 wt. %) of multi-walled carbon nanotubes (MWCNTs) to Pb(Zr0.47Ti0.53)O3 (PZT) ceramics prepared by spark plasma sintering is proposed as a method of tailoring the electrical properties, which are expected to be modified with respect to the pure PZT, both as result of the presence of 1-D conductive fillers in the ceramic product and via the microstructural modifications of ceramics induced during the sintering. The addition of even small amounts of carbon nanotubes strongly reduced the sinterability of PZT ceramics and resulted in the porous and fine-grained microstructures (relative density of 73% for a MWCNT addition of 0.5 vol. % by comparison with 91% in the pure PZT, produced in the same conditions). A monotonous decrease of permittivity with increasing the MWCNT level from ˜830 in pure PZT to ˜627 for x = 0.5 vol. %, at a fixed frequency f = 1kHz, and low dielectric losses below 2% have been observed. Tunability increases with respect to the values of dense PZT for small concentration of MWCNT as high as 0.0625 vol. % and then monotonically decreases for higher additions. Calculations by finite element modeling demonstrated that by addition of 1-D conductive fillers with compositions below the percolation limits to porous microstructures, the major role in changing the electrical properties via local field modification is related to the induced porosity rather than to the influence of the small amounts of MWCNTs survived after sintering and post-annealing treatment. The reduced permittivity with about 14% combined with low losses and higher tunability than in the pure PZT ceramics obtained at reasonable fields, makes the idea of using the addition of MWCNTs to ferroelectric ceramics an interesting approach in searching new structures for tunability properties.

  14. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    Science.gov (United States)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  15. Spark-plasma-sintering magnetic field assisted compaction of Co{sub 80}Ni{sub 20} nanowires for anisotropic ferromagnetic bulk materials

    Energy Technology Data Exchange (ETDEWEB)

    Ouar, Nassima; Schoenstein, Frédéric; Mercone, Silvana; Farhat, Samir; Jouini, Noureddine [Laboratoire des Sciences des Procédés et des Matériaux, CNRS, LSPM—UPR 3407, Université Paris 13, Sorbonne-Paris-Cité, 99 Avenue J.-B. Clément, 93430 Villetaneuse (France); Villeroy, Benjamin [Institut de Chimie et des Matériaux Paris Est, CNRS, ICMPE—UMR 7182, Equipe de Chimie Métallurgique des Terres Rares, 2-8 rue Henri Dunant, 94320 Thiais Cedex (France); Leridon, Brigitte [Laboratoire de Physique et d’Étude des Matériaux, LPEM, ESPCI-ParisTech, CNRS, UPMC, 10 rue Vauquelin, F-75231 Paris Cedex 5 (France)

    2013-10-28

    We developed a two-step process showing the way for sintering anisotropic nanostructured bulk ferromagnetic materials. A new reactor has been optimized allowing the synthesis of several grams per batch of nanopowders via a polyol soft chemistry route. The feasibility of the scale-up has been successfully demonstrated for Co{sub 80}Ni{sub 20} nanowires and a massic yield of ∼97% was obtained. The thus obtained nanowires show an average diameter of ∼6 nm and a length of ∼270 nm. A new bottom-up strategy allowed us to compact the powder into a bulk nanostructured system. We used a spark-plasma-sintering technique under uniaxial compression and low temperature assisted by a permanent magnetic field of 1 T. A macroscopic pellet of partially aligned nanowire arrays has been easily obtained. This showed optimized coercive properties along the direction of the magnetic field applied during compaction (i.e., the nanowires' direction)

  16. In vitro cell-biological performance and structural characterization of selective laser sintered and plasma surface functionalized polycaprolactone scaffolds for bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Van Bael, Simon, E-mail: simon.vanbael@mech.kuleuven.be [Department of Mechanical Engineering, Division of Production Engineering, Machine Design and Automation, Katholieke Universiteit Leuven, Celestijnenlaan 300b, 3001 Leuven (Belgium); Department of Mechanical Engineering, Division of Biomechanics and Engineering Design, Katholieke Universiteit Leuven, Celestijnenlaan 300c, bus 2419, 3001 Heverlee (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Herestraat 49, bus 813, 3000 Leuven (Belgium); Desmet, Tim [Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4 Bis, Ghent, 9000 (Belgium); Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering, Ghent University, Jozef Plateaustraat 22, 9000 Ghent (Belgium); Chai, Yoke Chin [Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Herestraat 49, bus 813, 3000 Leuven (Belgium); Pyka, Gregory [Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Herestraat 49, bus 813, 3000 Leuven (Belgium); Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, bus 2450, 3001 Leuven (Belgium); Dubruel, Peter [Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4 Bis, Ghent, 9000 (Belgium); Research Unit Plasma Technology (RUPT), Department of Applied Physics, Faculty of Engineering, Ghent University, Jozef Plateaustraat 22, 9000 Ghent (Belgium); Kruth, Jean-Pierre [Department of Mechanical Engineering, Division of Production Engineering, Machine Design and Automation, Katholieke Universiteit Leuven, Celestijnenlaan 300b, 3001 Leuven (Belgium); Schrooten, Jan [Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Herestraat 49, bus 813, 3000 Leuven (Belgium)

    2013-08-01

    In the present study a structural characterization and in vitro cell-biological evaluation was performed on polycaprolactone (PCL) scaffolds that were produced by the additive manufacturing technique selective laser sintering (SLS), followed by a plasma-based surface modification technique, either non-thermal oxygen plasma or double protein coating, to functionalize the PCL scaffold surfaces. In the first part of this study pore morphology by means of 2D optical microscopy, surface chemistry by means of hydrophilicity measurement and X-ray photoelectron spectroscopy, strut surface roughness by means of 3D micro-computed tomography (CT) imaging and scaffold mechanical properties by means of compression testing were evaluated before and after the surface modifications. The results showed that both surface modifications increased the PCL scaffold hydrophilicity without altering the morphological and mechanical properties. In the second part of this study the in vitro cell proliferation and differentiation of human osteoprogenitor cells, over 14 days of culture in osteogenic and growth medium were investigated. The O{sub 2} plasma modification gave rise to a significant lower in vitro cell proliferation compared to the untreated and double protein coated scaffolds. Furthermore the double protein coating increased in vitro cell metabolic activity and cell differentiation compared to the untreated and O{sub 2} plasma PCL scaffolds when OM was used. - Highlights: • Polycaprolactone scaffolds are produced with selective laser sintering. • 2 types of plasma based surface functionalization were applied. • Plasma had no significant effect on strut roughness and pore morphology. • Plasma improved surface hydrophilicity. • In vitro cell differentiation increased with plasma protein coated functionalization.

  17. Microstructure and Mechanical Performance of Cu-SnO2-rGO based Composites Prepared by Plasma Activated Sintering

    Institute of Scientific and Technical Information of China (English)

    LUO Guoqiang; HUANG Jing; JIN Zhipeng; LI Meijuan; JIANG Xiaojuan; SHEN Qiang; ZHANG Lianmeng

    2015-01-01

    A novel chemical technique combined with unique plasma activated sintering (PAS) was utilized to prepare consolidated copper matrix composites (CMCs) by adding Cu-SnO2-rGO layered micro powders as reinforced fillers into Cu matrix. The repeating Cu-SnO2-rGO structure was composed of inner dispersed reduced graphene oxide (rGO), SnO2 as intermedia and outer Cu coating. SnO2 was introduced to the surface of rGO sheets in order to prevent the graphene aggregation with SnO2 serving as spacer and to provide enough active sites for subsequent Cu deposition. This process can guarantee rGO sheets to sufifciently disperse and Cu nanoparticles to tightly and uniformly anchor on each layer of rGO by means of the SnO2 active sites as well as strictly control the reduction speed of Cu2+. The complete cover of Cu nanoparticles on rGO sheets thoroughly avoids direct contact among rGO layers. Hence, the repeating structure can simultaneously solve the wettability problem between rGO and Cu matrix as well as improve the bonding strength between rGO and Cu matrix at the well-bonded Cu-SnO2-rGO interface. The isolated rGO can effectively hinder the glide of dislocation at Cu-rGO interface and support the applied loads. Finally, the compressive strength of CMCs was enhanced when the strengthening efifciency reached up to 41.

  18. Si1-xGex crystal growth by the floating zone method starting from SPS sintered feed rods - A segregation study

    Science.gov (United States)

    Wagner, A. C.; Cröll, A.; Hillebrecht, H.

    2016-08-01

    The availability of suitable feed rods for Si-Ge bulk crystal growth is known to be a limiting factor in floating zone growth and other growth techniques. In this work, three Si-rich SiGe single crystals were crystallized by an optical floating zone technique in a double ellipsoid mirror furnace. The feed rods were prepared by pre-synthesis in the Spark Plasma Sintering (SPS) process starting with powders of different compositions. In a detailed section the preparation method of consolidation by mechanical alloyed powders to feed rods will be given. Results from two growth experiments starting with uniform compositions with 11 at% and 20 at% germanium as well as a zone leveling experiment with a segmented feed rod consisting of a starting zone with 32 at% Ge will be discussed. The latter experiment resulted in a crystal with nearly no axial segregation.

  19. Approach of the spark plasma sintering mechanism in Zr{sub 57}Cu{sub 20}Al{sub 10}Ni{sub 8}Ti{sub 5} metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Sophie [ICMPE, CNRS UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais (France); Perriere, Loic, E-mail: perriere@icmpe.cnrs.fr [ICMPE, CNRS UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais (France); Dembinski, Lucas [LERMPS, Universite de Technologie de Belfort-Montbeliard, 90010 Belfort (France); Tusseau-Nenez, Sandrine; Champion, Yannick [ICMPE, CNRS UMR 7182, 2-8 rue Henri Dunant, 94320 Thiais (France)

    2011-01-21

    Research highlights: > SPS allows manufacturing bulk parts from metallic glass powders. > Regarding the sintering conditions, SPSed samples exhibit mechanical properties similar to the quenched BMG. > Sintering of MG by SPS is likely divided into two steps: first, over-heating at particles necks leads to partial devitrification and consolidation; second, viscous flow of the metallic glass is reached and total densification is fulfilled. - Abstract: Spark plasma sintering (SPS) was used to sinter gas-atomized Zr{sub 57}Cu{sub 20}Al{sub 10}Ni{sub 8}Ti{sub 5} amorphous powder. Systematic analyses were performed to study particle size and annealing time effects on the parts structure and properties. Partial devitrification and particles welding were observed and correlated to particle size and thermal conditions. Mechanical testing, through compression and micro-hardness, reveals that the sintered parts show strength similar to a quenched bulk metallic glass and damaging before failure. However, the pulsed current input does not seem the most relevant way to sinter amorphous powders: during the sintering initial stages (when necks are small), excessive over-heating is generated in the vicinity of particles necks, and is responsible for partial devitrification; further current input at large necks leads to complete densification. Effects of the stress, the thermo- and electro-transports on the sintering are evaluated to provide a better understanding of the SPS mechanisms of densification of metallic glasses.

  20. Preparation of Functionally Graded Materials (FGMs) Using Coal Fly Ash and NiCr-Based Alloy Powder by Spark Plasma Sintering (SPS)

    Science.gov (United States)

    Kaneko, Gen-yo; Kitagawa, Hiroyuki; Hasezaki, Kazuhiro; Ito, Yuji; Kakuda, Hideaki

    2008-02-01

    Functionally Graded Materials (FGMs) were prepared by spark plasma sintering (SPS) using coal fly ash and NiCr alloy powder. The coal fly ash was produced by the Misumi Coal Thermal Power Station (Chugoku Electric Power Co., Inc.), with 80 wt% nickel and 20 wt% chromium (Fukuda Metal Foil & Powder Co., Ltd.) used as source materials. The sintering temperature in the graphite die was 1000 °C. X-ray diffraction patterns of the sintered coal fly ash materials indicated that mullite (3Al2O3ṡ2SiO2) and silica (SiO2) phases were predominant. Direct joining of coal fly ash and NiCr causes fracture at the interface. This is due to the mismatch in the thermal expansion coefficients (CTE). A crack in the FGM was observed between the two layers with a CTE difference of over 4.86×10-6 K-1, while a crack in the FGM was difficult to detect when the CTE difference was less than 2.77×10-6 K-1.

  1. TiC0.5N0.5-Based Cermets with Varied Amounts of Si3N4 Nanopowders Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Changchun Lv

    2015-01-01

    Full Text Available TiCN-based cermets with varied fractions of Si3N4 nanopowder (0–5 wt.% were prepared by spark plasma sintering. The microstructural and mechanical properties of these cermets were investigated. In general, with increasing addition amount of Si3N4 nanopowder the relative density as well as mechanical properties of the as-prepared TiCN cermets increased first and then decreased. The samples containing 2 wt.% Si3N4 nanopowder presented the best performance with the relative density of about 98%, bending strength of 1000 MPa, and Vickers microhardness of about 1810 HV10.

  2. Optimization of p-type Segmented Bi2Te3/CoSb3 Thermoelectric Material Prepared by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; TANG Xinfeng; LIU Haiqiang; YANG Xiuli; ZHANG Qingjie

    2006-01-01

    A kind of p- type segmented Bi2 Te3/ CoSb3 thermoelectric material was prepared by spark plasma sintering( SPS ). When the segmented materials were used at the temperature ranging from 300 K to 800 K, the junction temperature was optimized, which is about 500 K, and the corresponding length ratio of CoSb3 to Bi2 Te3 is about 15:2. The measured maximum power output of segmented materials is about 320 W·m-2, which is about 1.8 times as high as that of monolithic material CoSb3 under the same measuring conditions.

  3. On the microstructural and magnetic properties of fine-grained CoFe2O4 ceramics produced by combining polyol process and spark plasma sintering

    Science.gov (United States)

    Gaudisson, T.; Artus, M.; Acevedo, U.; Herbst, F.; Nowak, S.; Valenzuela, R.; Ammar, S.

    2014-12-01

    Starting from polyol-made CoFe2O4 ferrite nanoparticles of different aggregation states, high-density fine-grained ceramics were produced using Spark Plasma Sintering technique at 600 and 500 °C, under vacuum and applying a uniaxial pressure of more than 80 MPa. The grain growth of thus produced ceramics appears to be proportional to the temperature plateau and inversely proportional to the aggregation state of the initial powders. Average grain sizes ranging between about 50 and 350 nm were obtained. In all the cases, magnetic measurements evidenced a ferrimagnetic behavior at room temperature with non-zero coercivity, while their starting powders exhibited superparamagnetic features.

  4. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Hola, Marketa [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Otruba, Vitezslav [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Kanicky, Viktor [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic)]. E-mail: viktork@chemi.muni.cz

    2006-05-15

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm{sup 3}) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between {+-} 3% and {+-} 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed

  5. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Holá, Markéta; Otruba, Vítězslav; Kanický, Viktor

    2006-05-01

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm 3) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between ± 3% and ± 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed. The

  6. Effects of hydrogen reduction on the thermoelectric properties of spark-plasma-sintered Bi{sub 2}Te{sub 3}-based compounds

    Energy Technology Data Exchange (ETDEWEB)

    Lim, C. H.; Cho, D. C.; Lee, Y. S.; Lee, C. H. [Inha University, Incheon (Korea, Republic of); Kim, K. T.; Lee, D. M. [Korea Institute of Industrial Technology, Chonan (Korea, Republic of)

    2005-04-15

    The n-type Bi{sub 2}Te{sub 2.7}Se{sub 0.3} and p-type Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} compounds were fabricated by using a spark plasma sintering technique after ball-milling a solidified ingot. Both the n-type and the p-type ingots exhibited low oxygen concentrations of 0.035 at.%. After pulverizing, the oxygen concentrations of both the n-type and the p-type powders considerably increased up to 1.836 at.% and 1.520 at.%, respectively. Due to hydrogen reduction, the oxygen concentrations of the n-type and the p-type powders decreased to 0.196 at.% and 0.234 at.%, respectively. The figure-of{sub m}erit Z of the sintered n-type compounds by using hydrogen-reduced powders was found to be remarkably improved up to 2.37 x 10{sup -3} K{sup -1}, compared with that of sintered n-type compounds by using non-reduced powders (1.32 x 10{sup -3} K{sup -1}) because of the removal of oxygen, which acted as a donor. However, the figure-of-merit Z of the sintered p-type compounds by using hydrogen-reduced powders somewhat increased from 2.72 x 10{sup -3} K{sup -1} to 3.09 x 10{sup -3} K{sup -1}. The p-type thermoelectric compounds are believed to be not significantly affected by hydrogen reduction.

  7. Conversion of Methane by Dielectric-barrier Discharge Plasma Method-Comparison with Microwave Plasma Method

    National Research Council Canada - National Science Library

    Konno, Katsuya; Kobayashi, Motoki; Onoe, Kaoru; Yamaguchi, Tatsuaki

    2010-01-01

      Methane conversion by the dielectric-barrier discharge plasma method (DBD) was compared with our previous findings for the microwave plasma method (MW). The power (Pw), initial pressure (P0) and flow rate (F0...

  8. Functional properties of Sm{sub 2}NiMnO{sub 6} multiferroic ceramics prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Gheorghiu, Felicia, E-mail: felicia.gheorghiu@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); RAMTECH Centre, Interdisciplinary Research Department-Field Science, “Al. I. Cuza” Univ., Blvd. Carol I, Nr. 11, 700506 Iasi (Romania); Curecheriu, Lavinia [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Lisiecki, Isabelle [CNRS, Univ Paris 06, UMR 7070, LM2N, bât. F, B.P. 52, 4 place Jussieu, Paris F-75231, Cedex 05 (France); Beaunier, Patricia [UPMC, Univ Paris 06, UMR 7197, LRS, Le Raphaël, 3 rue Galilée, 94200 Ivry (France); Feraru, Simona; Palamaru, Mircea N. [Faculty of Chemistry, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania); Musteata, Valentina [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41A, 700487 Iasi (Romania); Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 700050 Iasi (Romania); Mitoseriu, Liliana, E-mail: lmtsr@uaic.ro [Dielectrics, Ferroelectrics & Multiferroics Group, Department of Physics, “Al. I. Cuza” Univ., 11 Blvd. Carol I, 700506 Iasi (Romania)

    2015-11-15

    In the present work, it was reported for the first time the new synthesis of Sm{sub 2}NiMnO{sub 6} double perovskite oxides by sol–gel auto-combustion method. The Rietveld analysis of the X-ray ceramics diffraction pattern recorded at room temperature for Sm{sub 2}NiMnO{sub 6} ceramics sintered at 1000 °C/5 min from powders obtained at 700 °C/7 h confirm the formation of the double perovskite with a monoclinic structure and the space group P2{sub 1}/n. The HRTEM analysis shows clear lattice fringes that confirm a high crystallinity level of the material corresponding to the monoclinic structure. The non-linear dielectric character was checked for the first time in Sm{sub 2}NiMnO{sub 6} double perovskite and the results reveals a strong nonlinearity and a small hysteretic behaviour. The present structural, magnetic and dielectric data make the Sm{sub 2}NiMnO{sub 6} system due to its multiferroic character a promising candidate to different modern electronic devices applications. - Highlights: • The Sm{sub 2}NiMnO{sub 6} double perovskite were prepared by sol–gel auto-combustion method. • The Rietveld and HRTEM analysis confirm a double perovskite monoclinic structure. • The non-linear character reveals a strong nonlinearity. • The magnetic transitions indicate a change in the spin ordering. • The Sm{sub 2}NiMnO{sub 6} system is a promising multiferroic candidate to modern applications.

  9. PLATYNG OF WEAR RESISTANT SURFACE LAYERS BY THE METHOD - LASER SINTERING

    Directory of Open Access Journals (Sweden)

    CIOFU Florin

    2012-05-01

    Full Text Available The essence of process for production of metal powders by aggregation is the formation and sintering operations that cause growth and stabilization of the contact surfaces, together with connections interatomic cohesion between particles. A body of metal powders is a thermodynamically unstable state due to the smoothness powder, grains surface roughness, form, degree of hardening in deformed areas, surface defects at grain polycrystalline networks (vacations, dislocations, etc.

  10. Effect of Particle Size on the Solid-Phase Sintered Polycrystalline La0.6Eu0.4B6 Cathode Prepared by Spark Plasma Sintering%粉末粒度对SPS固相烧结La0.6Eu0.4B6阴极材料的影响

    Institute of Scientific and Technical Information of China (English)

    张宁; 张久兴; 包黎红; 魏永峰; 李晓娜

    2013-01-01

    The La0.6Eu0.4B6 nanopowders were prepared by high-energy ball milling, and then the ball-milled nanopowder were used to prepare the high-density La0.6Eu0.4B6 polycrystalline bulks by spark plasma sintering (SPS). The influence of sintering temperature and pressure on the sample density and mechanical properties were investigated. The results show that this method reduces the sintering temperature more effectively than the conventional hot-pressing method. The sample density, Vickers hardness and flexural strength are 4.71 g/cm3, 23.37 GPa, and 295.14 MPa, respectively, which are also higher than those of conventional hot-pressing methods. The thermionic emission results show that when the cathode temperature is 1873 K, the maximum emission current density of La0.6Eu0.4B6 is 33.74 A/cm2. Under the same sintering condition, the Vickers hardness, flexural strength and thermionic emission current density of ball-milled nanopowder are increased by 28%, 58% and 32% compared with coarse-powder-sintered sample. These results indicate that refining the powder grain size to nano level is beneficial for reducing the sintering temperature and promoting the thermionic emission and mechanical properties.%采用高能球磨法制备出La0 6Eu0.4B6纳米粉体,将球磨后的纳米粉进行放电等离子(SPS)烧结,制备出了高致密的La0.6Eu0.4B6多晶块体材料.系统研究了烧结温度、烧结压力对样品致密度和力学性能的影响.结果表明,该方法与传统热压烧结方法相比有效降低了烧结温度,制备出的样品密度、维氏硬度和抗弯强度分别达到4.71 g/cm3、23.37 GPa和295.14MPa,这些值均高于传统热压烧结方法.热电子发射结果表明,当阴极温度为1873 K时,最大发射电流密度为33.74 A/cm2.实验过程中还发现,在相同烧结工艺下,球磨纳米粉与粗粉相比,维氏硬度、抗弯强度和热电子发射电流密度分别提高了28%、58%和32%.因此,在固相烧结过程中,粉末

  11. Effect of SiC Nanowhisker on the Microstructure and Mechanical Properties of WC-Ni Cemented Carbide Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Xiaoyong Ren

    2014-01-01

    Full Text Available Ultrafine tungsten carbide-nickel (WC-Ni cemented carbides with varied fractions of silicon carbide (SiC nanowhisker (0–3.75 wt.% were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC and tantalum carbide (TaC as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  12. Li{sub 3-x}M{sub x}N (M = Co, Ni) synthesized by Spark Plasma Sintering for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Junxian, E-mail: junxian@icmpe.cnrs.fr [Chimie Metallurgie des Terres Rares, ICMPE-UMR 7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais (France); Cerny, Radovan [Laboratory of Crystallography, University of Geneva, 24 quai Ernest-Ansermet, Geneva (Switzerland); Villeroy, Benjamin; Godart, Claude [Chimie Metallurgie des Terres Rares, ICMPE-UMR 7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais (France); Chandra, Dhanesh [University of Nevada, Reno (United States); Latroche, Michel [Chimie Metallurgie des Terres Rares, ICMPE-UMR 7182, CNRS, 2-8 rue Henri Dunant, 94320 Thiais (France)

    2011-09-15

    Research highlights: > Anion substitution in light hydrides (amides) is realized experimentally. > The compounds have been synthesized by in-situ Spark plasma Sintering. > The structural characterization has been done by synchrotron powder diffraction. - Abstract: Lithium nitride has recently emerged as a promising material for hydrogen storage. The hydrogen storage capacity reaches 10.2 wt% H by the formation of compounds, such as imides, amides, and others. Hydrogenation of lithium nitride is highly exothermic, and thus desorbing hydrogen from these compounds requires high temperature and cannot be used for reversible hydrogen storage. Ab initio calculations predict that partial substitution of Li by transition metals like Cu or Ni can reduce the reaction enthalpy between amide and imide. In this work, we present the synthesis of the ternary system Li{sub 3-x}M{sub x}N (M = Co or Ni) by Spark Plasma Sintering (SPS). The samples are hydrogenated at 255 deg. C by solid gas reaction. The sample crystal structures have been analyzed by synchrotron X-ray powder diffraction using a high resolution powder diffractometer. The structural models for Co and Ni-substituted Li{sub 3}N have been confirmed. The effect of the substitution on the phase formation upon hydrogenation has been investigated at various metal and hydrogen concentration. Different behaviors are observed depending on the nature of M.

  13. Effect of doped niobium on the microstructure and properties of W–Nb/TiC composites prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Lai-Ma, E-mail: luolaima@126.com [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Chen, Jing-Bo; Chen, Hong-Yu [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Luo, Guang-Nan [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhu, Xiao-Yong; Cheng, Ji-Gui; Zan, Xiang [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China); Wu, Yu-Cheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); National–Local Joint Engineering Research Centre of Nonferrous Metals and Processing Technology, Hefei 230009 (China)

    2015-01-15

    Highlights: • W–Nb/TiC composites were synthesized by machine milling and spark plasma sintering. • Effect of Nb on the microstructure and properties of W–TiC were investigated. • The performance of W–1 wt%Nb–1 wt%TiC was better than that of W–1 wt%TiC. - Abstract: W–1 wt%Nb/TiC composites were prepared by mechanical milling and spark plasma sintering. Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and thermal conductivity analyses were used to characterize the samples. Results showed that niobium carbide (NbC) formed in the composites. The relative density of the composites has been improved after adding Nb into W–1 wt%TiC. The tensile strength increased as well because Nb has high affinity for impurities such as O, C, and N and can form with these elements hard compounds. The thermal conductivity of W–1 wt%Nb/TiC was also improved, in comparison with that of W–1 wt%TiC.

  14. Effect of SiC nanowhisker on the microstructure and mechanical properties of WC-Ni cemented carbide prepared by spark plasma sintering.

    Science.gov (United States)

    Ren, Xiaoyong; Peng, Zhijian; Fu, Zhiqiang; Wang, Chengbiao

    2014-01-01

    Ultrafine tungsten carbide-nickel (WC-Ni) cemented carbides with varied fractions of silicon carbide (SiC) nanowhisker (0-3.75 wt.%) were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC) and tantalum carbide (TaC) as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS) Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  15. Relación entre los mecanismos de difusión atómica y las propiedades ópticas en la sinterización por Spark Plasma Sintering (SPS de la alúmina.

    Directory of Open Access Journals (Sweden)

    Torrecillas, R.

    2009-12-01

    Full Text Available The control of the sintering parameters during spark plasma sintering (SPS of polycrystalline alumina allows modifying the contribution due to the different atomic diffusion mechanisms. Thus, changing the heating rate as a function of the sintering stage allows tailoring sintering cycles that optimize the final density of the material with a minimal grain growth. It is shown in this work how by using two heating rates, 100 and 4ºC/min, allows obtaining a polycrystalline transparent alumina with a higher real in-line transmittance than that obtained with constant heating rates sintering cycles.

    El control de los parámetros de sinterización de la alúmina policristalina por spark plasma sintering (SPS permite modificar la contribución de los diferentes mecanismos de difusión atómica. Así, variar la rampa de calentamiento en función de la etapa de sinterización permite diseñar ciclos de sinterización que optimizan la densidad final del material con un mínimo crecimiento de grano. En este trabajo se demuestra cómo empleando dos velocidades, 100 y 4ºC/min, es posible obtener una alúmina policristalina con una transmitancia real en línea superior a la obtenida en ciclos con rampas constantes.

  16. Effect of heat treatment on the optical properties of perovskite BaZr0.5Ce0.3Y0.2O3-δ ceramic prepared by spark plasma sintering

    Science.gov (United States)

    Xing, Bohang; Cheng, Zhi; Wang, Cao; Zhao, Zhe

    2017-09-01

    The effect of heat treatment on the in-line transmittance of BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) ceramics prepared by spark plasma sintering method was investigated. The loss of Ba in transparent BZCY532 ceramics is the key reason for the loss of transmittance during the annealing process. This problem can be effectively alleviated by using a powder bed of BZCY532. Heat treatment atmospheres, wet air and dry air, were also found to be critical for obtaining high quality transparent ceramics. A highly transparent BZCY532 ceramic with the in-line transmittance (Tin) of 71.4% at 2000 nm can be obtained by using SPS method followed by an annealing in powder bed at 1500 °C in wet air.

  17. Bivariate Extension of the Quadrature Method of Moments for Modeling Simultaneous Coagulation and Sintering of Particle Populations.

    Science.gov (United States)

    Wright, Douglas L.; McGraw, Robert; Rosner, Daniel E.

    2001-04-15

    We extendthe application of moment methods to multivariate suspended particle population problems-those for which size alone is insufficient to specify the state of a particle in the population. Specifically, a bivariate extension of the quadrature method of moments (QMOM) (R. McGraw, Aerosol Sci. Technol. 27, 255 (1997)) is presented for efficiently modeling the dynamics of a population of inorganic nanoparticles undergoing simultaneous coagulation and particle sintering. Continuum regime calculations are presented for the Koch-Friedlander-Tandon-Rosner model, which includes coagulation by Brownian diffusion (evaluated for particle fractal dimensions, D(f), in the range 1.8-3) and simultaneous sintering of the resulting aggregates (P. Tandon and D. E. Rosner, J. Colloid Interface Sci. 213, 273 (1999)). For evaluation purposes, and to demonstrate the computational efficiency of the bivariate QMOM, benchmark calculations are carried out using a high-resolution discrete method to evolve the particle distribution function n(nu, a) for short to intermediate times (where nu and a are particle volume and surface area, respectively). Time evolution of a selected set of 36 low-order mixed moments is obtained by integration of the full bivariate distribution and compared with the corresponding moments obtained directly using two different extensions of the QMOM. With the more extensive treatment, errors of less than 1% are obtained over substantial aerosol evolution, while requiring only a few minutes (rather than days) of CPU time. Longer time QMOM simulations lend support to the earlier finding of a self-preserving limit for the dimensionless joint (nu, a) particle distribution function under simultaneous coagulation and sintering (Tandon and Rosner, 1999; D. E. Rosner and S. Yu, AIChE J., 47 (2001)). We demonstrate that, even in the bivariate case, it is possible to use the QMOM to rapidly model the approach to asymptotic behavior, allowing an immediate assessment of

  18. Decrease of sintering temperature by CuO doping of the 0.8Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.2PbTiO{sub 3} ceramics prepared by reaction-sintering method

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Bijun [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu (China); Key Laboratory of New Energy Engineering, Changzhou University, Changzhou, Jiangsu (China); Jiang, Na; Ding, Chenlu; Du, Qingbo [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu (China); Ding, Jianning [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu (China); Key Laboratory of New Energy Engineering, Changzhou University, Changzhou, Jiangsu (China); Jiangsu University, Zhenjiang, Jiangsu (China)

    2012-02-15

    CuO-doped 0.8Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.2PbTiO{sub 3} (0.8PMN-0.2PT) ceramics were prepared by the reaction-sintering method. X-ray diffraction (XRD) measurement, scanning electron microscopy (SEM) observation and density measurement confirmed that the CuO-doped 0.8PMN-0.2PT ceramics prepared by the reaction-sintering method with the addition of up to 5 mol% CuO and sintered over a wide sintering temperature range exhibit pure rhombohedral perovskite structure, rather homogeneous micromorphology and high relative density. As compared to the undoped 0.8PMN-0.2PT ceramics prepared by the same method, CuO proves to be an effective sintering aid, which can greatly decrease the sintering temperature of the 0.8PMN-0.2PT ceramics prepared by the reaction-sintering method, where high relative density can be obtained and the electrical properties are not deteriorated or improved of the synthesized 0.8PMN-0.2PT ceramics. The CuO doping content and sintering temperature exert great influences on the crystal structure, density and electrical properties of the 0.8PMN-0.2PT ceramics prepared by the reaction-sintering method. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, E N; Krotova, L I; Minaev, N V; Minaeva, S A; Mironov, A V; Popov, V K [Institute on Laser and Information Technologies of the Russian Academy of Sciencies, Troitsk, Moscow (Russian Federation); Bagratashvili, V N [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-11-30

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 – 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering. (interaction of laser radiation with matter. laser plasma)

  20. Influence of pulsed d. c. -glow-discharge on the phase constitution of nitride layers during plasma nitrocarburizing of sintered materials

    Energy Technology Data Exchange (ETDEWEB)

    Rie, K.T.; Schnatbaum, F. (Inst. fuer Oberflaechentechnik und Plasmatechnische Werkstoffentwicklung, Technische Univ. Braunschweig (Germany))

    1991-07-07

    In the past it was shown that plasma diffusion treatment of sintered materials has several advantages over conventional processes such as gas or salt bath nitriding and nitrocarburizing. The large number of parameters in plasma diffusion treatment allows close control of the process so that surface layers with defined microstructures and properties can be obtained. Durig plasma diffusion treatment the phase constitution of the nitride compound layer can be influenced by varying the gas mixture. By using a pulsed d.c. glow discharge the phase constitution and the microstructure of the compound layer can be influenced by varying the pulse duration and pulse repetition time. The number of micropores in the compound layer can be reduced in a pulsed d.c. glow discharge by pulsing the plasma, i.e. by reducing the plasma power. The phase constitution can be influenced by the pulse duration and pulse repetition time. With short pulse duration and long pulse repetition time the formation of Fe{sub 3}C in the compound layer can be suppressed. The amount of {gamma}' and {epsilon} phase present can be influenced. (orig.).

  1. Production of Al2O3–SiC nano-composites by spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Mansour Razavi

    2017-07-01

    Full Text Available In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600 °C for 10 min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5 h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329 MPa, respectively, in Al2O3–20 wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale.

  2. Preparation of Gd2O2S:Pr Scintillation Ceramics by Pressureless Reaction Sintering Method

    Institute of Scientific and Technical Information of China (English)

    Jingbao Lian; Xudong Sun; Tie Gao; Qiang Li; Xiaodong Li; Zhigang Liu

    2009-01-01

    Fabrication of Gd2O2S:Pr scintillation ceramics by pressureless reaction sintering was investigated. The 2Gd2O3.(Gd,Pr)2(SO4)3.mH2O precursor was made by hydrotherrnal reaction using commercially available Gd2O3, Pr6O11 and H2SO4 as the starting materials. Then single phase Gd2O2SO4:Pr powder was obtained by calcining the precursor at 750℃ for 2 h. The Gd2O2SO4:Pr powder compacts can be sintered to single phase Gd2O2S:Pr ceramics with a relative density of 99% and mean grain size of 30 μm at 1750℃ for 2 h in flowing hydrogen atmosphere. Densification and microstructural development of the Gd2O2S:Pr ceramics were examined. Luminescence spectra of the Gd2O2S:Pr ceramic under 309 nm UV excitation and X-ray excitation show a green emission at 511 nm as the most prominent peak, which corresponds to the 3P0-ZH4 transition of Pr3+ ions.

  3. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    S Mandal; A Seal; S K Dalui; A K Dey; S Ghatak; A K Mukhopadhyay

    2001-04-01

    The present work deals with the sintering of SiC with a low melting additive by microwave technique. The mechanical characteristics of the products were compared with that of conventionally sintered products. The failure stress of the microwave sintered products, in biaxial flexure, was superior to that of the products made by conventional sintering route in ambient condition. In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

  4. Comparative evaluation of electrical conductivity of hydroxyapatite ceramics densified through ramp and hold, spark plasma and post sinter Hot Isostatic Pressing routes.

    Science.gov (United States)

    Buchi Suresh, M; Biswas, P; Mahender, V; Johnson, Roy

    2017-01-01

    Hydroxyapatite ceramics synthesized through sonochemical route were processed and densified through ramp & hold (R&H) and Spark Plasma Sintering (SPS) routes. The effect of processing route on the relative density and electrical conductivity were studied. Further, the samples were Hot Isostatically Pressed (HIP) under argon pressure at elevated temperature to further densify the sample. All these samples processed under different conditions were characterized by X-ray diffraction, Scanning Electron Microscopy and AC Conductivity. The samples have exhibited hydroxyapatite phase; however, microstructures exhibited distinctly different grain morphologies and grain sizes. AC impedance spectroscopic measurement was carried out on hydroxyapatite samples processed through different routes and the corresponding spectra were analyzed by the analogy to equivalent circuit involving resistors and capacitors. SPS sintered sample after HIPing has exhibited the highest conductivity. This can be attributed to the higher density in combination with finer grain sizes. Activation energy based on Arrhenius equation is calculated and the prominent conduction mechanism is proposed. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Phase and Microstructural Correlation of Spark Plasma Sintered HfB2-ZrB2 Based Ultra-High Temperature Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Ambreen Nisar

    2017-07-01

    Full Text Available The refractory diborides (HfB2 and ZrB2 are considered as promising ultra-high temperature ceramic (UHTCs where low damage tolerance limits their application for the thermal protection system in re-entry vehicles. In this regard, SiC and CNT have been synergistically added as the sintering aids and toughening agents in the spark plasma sintered (SPS HfB2-ZrB2 system. Herein, a novel equimolar composition of HfB2 and ZrB2 has shown to form a solid-solution which then allows compositional tailoring of mechanical properties (such as hardness, elastic modulus, and fracture toughness. The hardness of the processed composite is higher than the individual phase hardness up to 1.5 times, insinuating the synergy of SiC and CNT reinforcement in HfB2-ZrB2 composites. The enhanced fracture toughness of CNT reinforced composite (up to a 196% increment surpassing that of the parent materials (ZrB2/HfB2-SiC is attributed to the synergy of solid solution formation and enhanced densification (~99.5%. In addition, the reduction in the analytically quantified interfacial residual tensile stress with SiC and CNT reinforcements contribute to the enhancement in the fracture toughness of HfB2-ZrB2-SiC-CNT composites, mandatory for aerospace applications.

  6. Improvement of the mechanical properties of spark plasma sintered hap bioceramics by decreasing the grain size and by adding multi-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Veljović Đ.

    2013-01-01

    Full Text Available Composites based on HAP and oxidized multi-walled carbon nanotubes (o-MWCNT and monophase HAP materials were processed by spark plasma sintering. Starting from stoichiometric nano-sized HAP powder, monophase bioceramics were obtained with a density close to the theoretical one and with an average grain size of several hundred nanometers to micron dimensions. It was shown that decreasing the sintering temperature resulted in a decrease of the grain size, which affected an increase in the fracture toughness and hardness. The fracture toughness of an HAP/ o-MWCNT bioceramic processed at 900°C for only 5 min was 30 % higher than that of monophase HAP materials obtained under the same conditions. The addition of MWCNT during SPS processing of HAP materials caused a decrease in the grain size to the nano-dimension, which was one of the reasons for the improved mechanical properties. [Projekat Ministarstva nauke Republike Srbije, br. III45019 i FP7-REGPOT-2009-1 NANOTECH FTM, Grant Agreement Number: 245916

  7. Nickel-graphite composites of variable architecture by graphitization-accompanied spark plasma sintering and hot pressing and their response to phase separation

    Directory of Open Access Journals (Sweden)

    Dudina D.V.

    2015-01-01

    Full Text Available We report the formation and phase separation response of nickel-graphite composites with variable-architecture phases by graphitization-accompanied consolidation via Spark Plasma Sintering and hot pressing. It was shown that the application of pressure during consolidation is crucial for the occurrence of graphitization and formation of 3D graphite structures. We evaluated the suitability of the synthesized composites as precursors for making porous structures. Nickel behaved as a space holder with the particle size and spatial distribution changing during consolidation with the temperature and determining the structure of porous graphite formed by phase separation by dissolution in HCl. The response of the consolidated Ni-Cgr to separation of carbon by its burnout in air was studied. The result of the carbon removal was either the formation of a dense and continuous NiO film on the surface of the compacts or oxidation through the compact thickness. The choice between these two options depended on the density of the compacts and on the presence of carbon dissolved in nickel. It was found that during the burnout of graphite from Ni-Cgr composites, sintering, rather than formation of pores, dominated.

  8. Sintering Theory and Practice

    Science.gov (United States)

    German, Randall M.

    1996-01-01

    Although sintering is an essential process in the manufacture of ceramics and certain metals, as well as several other industrial operations, until now, no single book has treated both the background theory and the practical application of this complex and often delicate procedure. In Sintering Theory and Practice, leading researcher and materials engineer Randall M. German presents a comprehensive treatment of this subject that will be of great use to manufacturers and scientists alike. This practical guide to sintering considers the fact that while the bonding process improves strength and other engineering properties of the compacted material, inappropriate methods of control may lead to cracking, distortion, and other defects. It provides a working knowledge of sintering, and shows how to avoid problems while accounting for variables such as particle size, maximum temperature, time at that temperature, and other problems that may cause changes in processing. The book describes the fundamental atomic events that govern the transformation from particles to solid, covers all forms of the sintering process, and provides a summary of many actual production cycles. Building from the ground up, it begins with definitions and progresses to measurement techniques, easing the transition, especially for students, into advanced topics such as single-phase solid-state sintering, microstructure changes, the complications of mixed particles, and pressure-assisted sintering. German draws on some six thousand references to provide a coherent and lucid treatment of the subject, making scientific principles and practical applications accessible to both students and professionals. In the process, he also points out and avoids the pitfalls found in various competing theories, concepts, and mathematical disputes within the field. A unique opportunity to discover what sintering is all about--both in theory and in practice What is sintering? We see the end product of this thermal

  9. THE EFFECT OF Mo ADDITION ON COERCIVITY OF NdFeB SINTERED MAGNET PREPARED BY BLENDING METHOD

    Institute of Scientific and Technical Information of China (English)

    J.Q.Zhou; M.G. Zhang

    2005-01-01

    Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of NdFeB magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-granular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the Nd22Fe71B/Mo sintered magnet, and its magnetic properties and microstructures are investigated. The results show that by adding 1.5% (mass fraction) Mo, the intrinsic coercivity Hc of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free Nd-Fe-B magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the NdFeB magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and Nd-rich phase, thus resulting in the precipitation of fine second main phase (Nd2Fe14-xMoxB) from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity.

  10. Pulsed Plasma Methods in Materials Processing

    Science.gov (United States)

    Rej, D. J.

    1996-05-01

    Plasmas are routinely used to synthesize advanced materials, because of their ability to produce reactant species that enable a wide variety of chemical reactions. For example, in microelectronics manufacturing, plasmas are used to etch, clean, ash photoresist, implant, deposit, polymerize, and metalize. The use of pulsed power may extend the utility of plasma processing. Pulsed devices such as coaxial plasma guns, cathodic arcs, pseudosparks have been employed to synthesize materials ranging from novel steel alloys and high-temperature superconductors to diamond coatings. In this talk, we will highlight plasma immersion ion implantation and deposition, methods that improve conventional steady-state chemical and physical vapor deposition techniques. Pulsed power enables energetic ion bombardment before plasma deposition to promote better film adhesion through the formation of a graded interface. Ion bombardment during deposition reduces residual stress in the deposited film, thereby enabling formation of thick layers. Also, pulsed plasma sources have advantages over steady-state devices in that they conserve electrical power and can produce high-density, fully-dissociated plasmas. As an example, we will review recent experiments on the formation of adherent diamond-like carbon films deposited onto relatively large batches of automotive components.

  11. Kinetics, Stability, and Thermal Contact Resistance of Nickel–Ca3Co4O9 Interfaces Formed by Spark Plasma Sintering

    DEFF Research Database (Denmark)

    Holgate, Tim; Wu, NingYu; Søndergaard, M.;

    2013-01-01

    3Co4O9) have been formed directly by spark plasma sintering (SPS). An intermediate NiO phase is formed during the SPS processes, which grows during post-heating with Co entering from the cobaltate side to form a graded Ni1xCoxO interfacial layer. The electrical and thermal transport across...

  12. High temperature thermoelectric properties of Ca3Co4O9+δ by auto-combustion synthesis and spark plasma sintering

    DEFF Research Database (Denmark)

    Wu, NingYu; Holgate, Tim; Van Nong, Ngo

    2014-01-01

    of a wet chemical synthesis, such as morphological and compositional homogeneity, and fine, well-defined particle sizes comingfrom the controlled nature of the auto-combustion. Optimized spark plasma sintering (SPS) processing conditions were determined and used tofabricate dense and highly c-axis oriented...

  13. HRTEM and Nanoindentation Studies of Bulk WC Nanocrystalline Materials Prepared by Spark Plasma Sintering of Ball-Milled Powders

    Science.gov (United States)

    Sherif El-Eskandarany, M.; Al-Hazza, Abdulsalam; Al-Hajji, L. A.

    2017-01-01

    In the present work, mechanical milling technique using a high-energy ball mill was employed for preparing of nanoscaled WC grains powders with an average grain size of 7 nm in diameters of WC. The present study demonstrates a successful consolidation process achieved at 1250 °C for sintering of ball-milled WC powders into full dense bulk buttons (above 99.6%), using SPS technique. The as-consolidated WC bulk nanocrystalline buttons revealed high hardness value ( 24 GPa) with low elastic modulus ( 332 GPa). Moreover, they possessed a high fracture toughness (15 MPa m1/2) that has never been reported for pure WC.

  14. Sintering time effect on thermal diffusivity in BSSCO doped with Sm at low temperatures as revealed by flash method

    Science.gov (United States)

    Haydari, M.; Moksin, Mohd Maarof; Yunus, W. Mahmood M.; Grozescu, Ionel Valeriu; Hamadneh, I.; Halim, S. A.

    2004-10-01

    We report the effect of sintering time on thermal diffusivity of BSCCO (Bi-Pb-Sr-Ca-Cu-O) superconductors doped with Sm with different concentration. The superconductor samples were sintered for 24, 48 and 100 hours respectively at 850 Celsius. Thermal diffusivity measurement was carried out at 80 - 300 K by using photoflash technique. The sintering time was found indirectly affect the thermal diffusivity in the way it influenced the grain size and grain alignment.

  15. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

    Science.gov (United States)

    Badica, P.; Burdusel, M.; Popa, S.; Pasuk, I.; Ivan, I.; Borodianska, H.; Vasylkiv, O.; Kuncser, A.; Ionescu, A. M.; Miu, L.; Aldica, G.

    2016-10-01

    High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N2) atmosphere for different heating rates (10, 20 and 100 °C min-1) and compared with reference samples processed in vacuum and Ar. N2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N2 with a heating rate of 100 °C min-1. At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

  16. Data on the impact of increasing the W amount on the mass density and compressive properties of Ni-W alloys processed by spark plasma sintering.

    Science.gov (United States)

    Sadat, T; Hocini, A; Lilensten, L; Faurie, D; Tingaud, D; Dirras, G

    2016-06-01

    Bulk Ni-W alloys having composite-like microstructures are processed by spark plasma sintering (SPS) route of Ni and W powder blends as reported in a recent study of Sadat et al. (2016) (DOI of original article: doi:10.1016/j.matdes.2015.10.083) [1]. The present dataset deals with determination of mass density and evaluation of room temperature compressive mechanical properties as function of the amount of W (%wt. basis). The presented data concern: (i) measurement of the mass of each investigated Ni-W alloy which is subsequently used to compute the mass density of the alloy and (ii) the raw (stress (MPa) and strain ([Formula: see text])) data, which can be subsequently used for stress/ strain plots.

  17. Data on the impact of increasing the W amount on the mass density and compressive properties of Ni–W alloys processed by spark plasma sintering

    Science.gov (United States)

    Sadat, T.; Hocini, A.; Lilensten, L.; Faurie, D.; Tingaud, D.; Dirras, G.

    2016-01-01

    Bulk Ni–W alloys having composite-like microstructures are processed by spark plasma sintering (SPS) route of Ni and W powder blends as reported in a recent study of Sadat et al. (2016) (DOI of original article: doi:10.1016/j.matdes.2015.10.083) [1]. The present dataset deals with determination of mass density and evaluation of room temperature compressive mechanical properties as function of the amount of W (%wt. basis). The presented data concern: (i) measurement of the mass of each investigated Ni–W alloy which is subsequently used to compute the mass density of the alloy and (ii) the raw (stress (MPa) and strain (ΔLL0)) data, which can be subsequently used for stress/ strain plots. PMID:27158658

  18. On the Densification Behavior of (0.2, 0.5, and 1 Wt Pct) CNT-YSZ Ceramic Composites Processed via Spark Plasma Sintering

    Science.gov (United States)

    Karanam, Abhinav; Bichler, Lukas; Fong, Randy

    2015-08-01

    Yttria-Stabilized Zirconia (YSZ) is a promising thermal insulating ceramic for high temperature applications due to its stability and chemical inertness. As was demonstrated with other technical ceramics ( e.g., Alumina), addition of Single-Wall Carbon Nanotubes (CNTs) to a ceramic matrix may significantly enhance its mechanical properties. In this work, 8 mol pct YSZ with 0.2, 0.5, and 1 wt pct CNT composites were fabricated via the spark plasma sintering process. The densification, Vicker's microhardness, specific gravity, and microstructure evolution of the composites were investigated. The results suggest that the addition of CNTs to YSZ hindered densification and grain growth during SPS processing leading to inhomogeneous grain size distribution. However, the CNTs had a profound impact on the hardness of the composite ceramics, with an increase from 697 HV (YSZ) to 1195 HV (1 wt pctCNT-YSZ).

  19. The Structure and Mechanical Properties of High-Strength Bulk Ultrafine-Grained Cobalt Prepared Using High-Energy Ball Milling in Combination with Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Ivo Marek

    2016-05-01

    Full Text Available In this study, bulk ultrafine-grained and micro-crystalline cobalt was prepared using a combination of high-energy ball milling and subsequent spark plasma sintering. The average grain sizes of the ultrafine-grained and micro-crystalline materials were 200 nm and 1 μm, respectively. Mechanical properties such as the compressive yield strength, the ultimate compressive strength, the maximum compressive deformation and the Vickers hardness were studied and compared with those of a coarse-grained as-cast cobalt reference sample. The bulk ultrafine-grained sample showed an ultra-high compressive yield strength that was greater than 1 GPa, which is discussed with respect to the preparation technique and a structural investigation.

  20. Thermal Stress Calculation and Fabrication of 6063 Al/60SiC-35Al-5Si Graded Materials by Spark Plasma Sintering

    Science.gov (United States)

    Dongming, Zhang; Lianmeng, Zhang; Xiaofeng, Gu; Fei, Chen

    2008-02-01

    The high intensity of thermal stress was generated during fabrication of 6063 aluminum/60SiC-35Al-5Si double-layer material. In order to decrease the thermal stress, graded materials of Al/60SiC-35Al-5Si was fabricated by spark plasma sintering. The CTE in the graded layer was controlled by SiC fraction and particle sizes. The calculation results indicate that the net stress of more than 800 MPa was generated in the double-layer materials, but it decreased to 170 MPa or less in the graded materials. So the stability can be guaranteed in the graded composites. The graded layers also have the potential for high thermal conductivity, more than 180W/Mk for every layer, which satisfies the application.

  1. Influence of electric current on microstructure evolution in Ti/Al and Ti/TiAl{sub 3} during spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Y. [Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States); Haley, J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616-5294 (United States); Kulkarni, K. [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, UP (India); Aindow, M. [Department of Materials Science and Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States); Lavernia, E.J., E-mail: lavernia@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616-5294 (United States); Department of Chemical Engineering and Materials Science, University of California, Irvine, CA 92697-2575 (United States)

    2015-11-05

    The synthesis of γ-TiAl from elemental metals via solid-state reactive diffusion processing routes involves multiple reaction steps with the formation of various intermediate intermetallic compounds, starting with TiAl{sub 3} because this phase is favored kinetically. To understand the processes by which the TiAl{sub 3} intermediate is eliminated during synthesis of γ-TiAl alloy via spark plasma sintering (SPS), the reaction between Ti and TiAl{sub 3} during SPS was studied with emphasis on the effects of the applied electric current and starting TiAl{sub 3} microstructure on the reaction kinetics and the underlying diffusion mechanisms. The intermediate intermetallic phases Ti{sub 3}Al, TiAl and TiAl{sub 2} were formed between the Ti and TiAl{sub 3} upon SPS processing at 900 °C. The applied electric current did not alter the character of the phases formation in the Ti/TiAl{sub 3} system, but thermodynamic calculations suggest that the activation energy for the nucleation of TiAl{sub 2} is reduced significantly with an electric current flowing. Moreover, the kinetics of the reactions between Ti and TiAl{sub 3} were enhanced when the starting TiAl{sub 3} microstructure was refined. The electric field also had a more significant influence on the grain growth kinetics for TiAl{sub 2} and TiAl in powder blend compacts with refined microstructures. - Highlights: • Reaction between Ti and TiAl{sub 3} during spark plasma sintering was studied. • Refined starting TiAl{sub 3} microstructure enhanced the reactions kinetics. • The nucleation barrier of TiAl{sub 2} was reduced by the applied electric field. • The applied electric field restrained the grain growth of TiAl and TiAl{sub 2}.

  2. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    A mesoscale numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element method for calculating stresses. The sintering behavior of a sample constrained by a rigid substrate ...

  3. Sintering of nano sized powders on the basis of silicon nitride in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Zhilinska, N.; Zalite, I.; Grabis, J.; Rodriguez, J.; Martinez, D.

    2003-07-01

    A study of the sintering of Si{sub 3}N{sub 4}-Y{sub 2}O{sub 3}-Al{sub 2}O{sub 3} and Si{sub 3}N{sub 4}-AIN-Al{sub 2}O{sub 3}-Y{sub 2}O{sub 3} ({alpha}/{beta}-SiAION) nano powders with the specific surface area of 65-70 m''2/g and average particle size of 30-35 nm is reported. The powders have been prepared by the plasma chemical synthesis. This work relates to an innovative method of sintering in the solar furnace at Plataforma Solar de Almeria. The influence of sintering temperature, sintering time and heating rate on the densification behaviour of the plasma synthesized powder compositions was investigated. The results were compared with the data obtained using commercial powder. (Author) 3 refs.

  4. Spectral Methods in Numerical Plasma Simulation

    DEFF Research Database (Denmark)

    Coutsias, E.A.; Hansen, F.R.; Huld, T.;

    1989-01-01

    An introduction is given to the use of spectral methods in numerical plasma simulation. As examples of the use of spectral methods, solutions to the two-dimensional Euler equations in both a simple, doubly periodic region, and on an annulus will be shown. In the first case, the solution is expanded...

  5. Properties of sintered Al2O3-Cr composites depending on the method of preparation of the powder mixture

    Directory of Open Access Journals (Sweden)

    Chmielewski M.

    2006-01-01

    Full Text Available Continuous progress in modern science and industry depends on the availability of new effective devices and materials. New generation materials should be characterized by a specified combination of properties which sometimes exclude one another. Al2O3-Cr composites belong to this group of materials. This study is concerned with the effect of the method of preparation of the starting powders upon the properties of sintered Al2O3-Cr composites. The composites were produced using powder mixtures with various volumetric shares of the starting powders (from 25 to 75vol.%. The mixtures were prepared by conventional mechanical mixing in a ball-mill or by mechanical alloying in a high-energy mill of the attritor type. It has been found that with mechanically alloyed powders the Al2O3-Cr composites have better bending strength, hardness and frictional wear resistance.

  6. Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

    Directory of Open Access Journals (Sweden)

    Manoj Gupta

    2013-05-01

    Full Text Available In this study, magnesium composites with nano-size boron nitride (BN particulates of varying contents were synthesized using the powder metallurgy (PM technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture.

  7. Thermoelectric Properties of Fe1+y Te Prepared by a High Pressure Sintering Method

    Science.gov (United States)

    Di, Jiaxin; Li, Hong-Tao; Xu, Gui-Ying

    2016-11-01

    Enhancing thermoelectric properties by utilizing topological properties of topological insulators has attracted increasing attention. Here, powder metallurgy technology combined with high pressure sintering (HPS) was used to prepare Fe1+y Te (y = 0.1, 0.15, 0.1978, 0.22) alloys at 1173 K. The prepared products were identified by x-ray diffraction, and their microstructures were examined by field-emission scanning electron microscopy (FE-SEM). Electric conductivities (σ) and Seebeck coefficient (S) were measured in the temperature range of 303-623 K. The influence of variation in Fe content on thermoelectric properties was studied. The experimental results show that all HPS samples are nanometer composites consisting of Fe3Te2 and FeTe2. Fe1+y Te have electrical charges on the boundaries of topological insulators, which have the potential to be studied in the future. The Fe1+y Te with y = 0.1 shows the best thermoelectric properties at room temperature.

  8. Fabrication of high thermal conductive Al-cBN ceramic sinters by high temperature high pressure method

    Science.gov (United States)

    Wang, P. F.; Li, Zh. H.; Zhu, Y. M.

    2011-05-01

    Al-cBN ceramic sinters were fabricated by sintering micro-powder mixture of Al and cBN under high temperature and high pressure condition. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) elemental mapping analyses and laser flashing thermal conductivity measurements were performed to investigate the sintering properties and thermal conductivity of the Al-cBN ceramic sinters. XRD analysis revealed these Al-cBN ceramic sinters were composed of a large portion of cBN and of a small portion of AlN, and very little amount of AlB 12 and hBN. Formation of boundary phase resulted in the rapid densification of the sinters, as well as the increase of their relative density with increasing Al additions. The Al-cBN ceramic sinters have a maximum thermal conductivity of about 1.94 W/cm K at room temperature and a much higher value of about 2.04 W/cm K at 200 °C. Their high thermal conductivity over that of AlN-hBN composites promise Al-cBN ceramic sinters favorite candidates as high efficiency heat sink materials for wide band gap semiconductors.

  9. Preparation of dense nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic by microwave plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhen Qiang [Nano-Science and Nano-Technology Research Center, School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)]. E-mail: qzhen@staff.shu.edu.cn; Vannier, Rose Noelle [Laboratoire de Cristallochimie et Physicochimie du Solide, UPRESA-CNRS 8012 ENSCL-USTL, BP 108, 59652 Villeneuve d' Ascq Cedex (France); Kale, Girish M. [Institute for Materials Research, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2007-01-25

    Processing of nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic having high density has been investigated and reported in this paper. Nanopowders of mixed bismuth oxide, hafnia and yttrium oxide have been prepared by a reverse titration chemical coprecipitation from Bi{sup 3+}, Hf{sup 4+} and Y{sup 3+} containing aqueous solution. The high density, nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic has been synthesized by microwave plasma sintering. The XRD results of grain growth behavior indicates that growth of both {delta}-Bi{sub 2}O{sub 3} and c-HfO{sub 2} crystallites obeys the parabolic rate law, expressed as (D-D {sub 0}){sup 2} = Kt, during sintering process. After sintering at 700 deg. C for 60 min, the relative density of the samples sintered by microwave plasma has been found to be greater than 97%, and the samples exhibit considerably finer microstructure with an average size between 60 and 70 nm and equiaxed morphology and better density comparing with that of samples sintered by conventional pressureless sintering. In addition, mechanical properties of nanocrystalline Bi{sub 2}O{sub 3}-HfO{sub 2}-Y{sub 2}O{sub 3} ceramic has been improved greatly compareing with nanocrystalline Bi{sub 2}O{sub 3}-Y{sub 2}O{sub 3} ceramic.

  10. Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sang-Soon [Center for Electronic Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Ju-Heon [High Temp. Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Kwon, Beomjin; Kim, Seong Keun [Center for Electronic Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Park, Hyung-Ho [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Ki-Suk; Baik, Jeong Min [School of Materials and Science Engineering, UNIST, Ulsan 689-798 (Korea, Republic of); KIST-UNIST Ulsan Center for Convergent Materials, UNIST, Ulsan 689-798 (Korea, Republic of); Choi, Won Jun [Center for Opto-Electronic Materials and Devices, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Kim, Dong-Ik [High Temp. Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Hyun, Dow-Bin; Kim, Jin-Sang [Center for Electronic Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Baek, Seung-Hyub, E-mail: shbaek77@kist.re.kr [Center for Electronic Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); KIST-UNIST Ulsan Center for Convergent Materials, UNIST, Ulsan 689-798 (Korea, Republic of); Department of Nanomaterials Science and Technology, Korea University of Science and Technology, Daejeon, 305-333 (Korea, Republic of)

    2016-09-05

    As a field-assisted technique, spark plasma sintering (SPS) enables densification of specimens in a very short period of time compared to other sintering techniques. For high performance thermoelectric material synthesis, SPS is widely used to fabricate nanograin-structured thermoelectric materials by rapidly densifying the nanopowders suppressing grain growth. However, the microstructural evolution behavior of thermoelectric materials by SPS, another important process during sintering, has been rarely studied. Here, we explore SPS as a tool to control the microstructure by long-time SPS. Using p-type (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3} thermoelectric materials as a model system, we systematically vary SPS temperature and time to understand the correlations between SPS conditions, microstructural evolution, and the thermoelectric properties. Our results show that the relatively low eutectic temperature (∼420 °C) and the existence of volatile tellurium (Te) are critical factors to determine both microstructure and thermoelectric property. In the liquid-phase sintering regime, rapid evaporation of Te leads to a strong dependence of thermoelectric property on SPS time. On the other hand, in the solid-phase sintering regime, there is a weak dependence on SPS time. The optimum thermoelectric figure-of-merit (Z) of 2.93 × 10{sup −3}/K is achieved by SPS at 500 °C for 30 min. Our results will provide an insight on the optimization of SPS conditions for materials containing volatile elements with low eutectic temperature. - Highlights: • Spark plasma sintering (SPS) is used to synthesize the thermoelectric (Bi{sub 0.25}Sb{sub 0.75}){sub 2}Te{sub 3}. • Liquid phase and volatile element are a key for the microstructure and thermoelectric property. • Thermoelectric figure-of-merit of 2.9 × 10{sup −3}/K is achieved at 500 °C for 30 min.

  11. Chemometric study of the sinter mixtures used in sinter plants in Poland

    Directory of Open Access Journals (Sweden)

    A. Smoliński

    2015-01-01

    Full Text Available The main goal of the study was the analysis of chemical parameters of sinter mixtures used in sinter plants in Poland. For this purpose the chemometric method was used, in this case hierarchical clustering analysis. This method allowed to examine the similarities and differences between the studied sinter mixtures.

  12. Si3N4-TiN nanocomposite by nitration of TiSi2 and consolidation by hot pressing and spark plasma sintering.

    Science.gov (United States)

    Borodianska, Hanna; Krushinskaya, Larisa; Makarenko, Galina; Sakka, Yoshio; Uvarova, Irina; Vasylkiv, Oleg

    2009-11-01

    Homogeneous nanostructured Si3N4-TiN composite powder was obtained by nitration of a TiSi2 powder precursor in a nitrogen flow. Mechanoactivation of titanium disilicide increases the nitration rate and reduces the temperature of formation of the Si3N4 and TiN. The properties of hot pressing (HP) and spark plasma sintering (SPS) of the nanostructured Si3N4-TiN composite with Y2O3 and Al2O3 additives have been studied. In the case of the HP-prepared composite the processing conditions are sufficient to form a stable, equilibrated grain boundary framework. The SPS consolidation is extremely rapid, low-temperature process and the sintering temperature was 300-400 degrees C lower than that of the hot pressing temperature. As a result the grain boundary framework was underdeveloped. Post-sintering anneal of the SPS-prepared samples caused significant improvement of their mechanical properties. The SPS and HP-derived Si3N4-40 mass% TiN-6 mass% Y2O3-2 mass% Al2O3 nano-composite of 98.4% and 98.9% of relative density demonstrate the Vickers hardness values of 13.2 and 13.7 GPa, respectively. The grains of Si3N4 and TiN were much finer in the case of the SPS-derived ceramic composite. However, the better development of the grain boundary framework in the case of the higher temperature HP treatment in comparison to the SPS significantly reduced the advantage of nanocrystallinity. In both cases the fracture toughness was comparable even after the improvement of grain boundary framework during the SPS consolidation. The K(1c), of 7.83 MPax m(1/2) of the sample prepared according to the best SPS regime is also comparable to K(1c) of 8.30 MPa x m(1/2) of much coarser hot pressed ceramic with very similar relative density.

  13. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number......A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...

  14. Interfacial behavior of Fe76Si9B10P5/Zn0.5Ni0.5Fe2O4 amorphous soft magnetic composite during spark plasma sintering process

    Directory of Open Access Journals (Sweden)

    Zhankui Zhao

    2016-02-01

    Full Text Available Fe76Si9B10P5/Zn0.5Ni0.5Fe2O4 amorphous composite with micro-cellular structure and high electrical resistivity was prepared by spark plasma sintering (SPS at 487 °C. XRD and SEM results showed that the Fe76Si9B10P5 alloy powders remained the amorphous state and the composite was dense. A fusion zone at interface of Fe76Si9B10P5 cell body and Zn0.5Ni0.5Fe2O4 cell wall was observed by TEM, which also indicates the formation of local high temperature. The interface bonding based on the formation of local high temperature in SPS process was observed. It is believed that the tip effect of Zn0.5Ni0.5Fe2O4 nanoparticles promotes the local discharging and plasmas creation in the gaps, and the discharging energy forms an instantaneous local high temperature to complete the local sintering and the densification of Zn0.5Ni0.5Fe2O4 particles at a low nominal sinter temperature. Simultaneously, the local high temperature stimulates the adjacent gaps discharging, thus facilitate the continuous formation of new discharging path. Finally, sintering and densification of the amorphous composite is complete.

  15. Plasma processing methods for hydrogen production

    Science.gov (United States)

    Mizeraczyk, Jerzy; Jasiński, Mariusz

    2016-08-01

    In the future a transfer from the fossil fuel-based economy to hydrogen-based economy is expected. Therefore the development of systems for efficient H2 production becomes important. The several conventional methods of mass-scale (or central) H2 production (methane, natural gas and higher hydrocarbons reforming, coal gasification reforming) are well developed and their costs of H2 production are acceptable. However, due to the H2 transport and storage problems the small-scale (distributed) technologies for H2 production are demanded. However, these new technologies have to meet the requirement of producing H2 at a production cost of (1-2)/kg(H2) (or 60 g(H2)/kWh) by 2020 (the U.S. Department of Energy's target). Recently several plasma methods have been proposed for the small-scale H2 production. The most promising plasmas for this purpose seems to be those generated by gliding, plasmatron and nozzle arcs, and microwave discharges. In this paper plasma methods proposed for H2 production are briefly described and critically evaluated from the view point of H2 production efficiency. The paper is aiming at answering a question if any plasma method for the small-scale H2 production approaches such challenges as the production energy yield of 60 g(H2)/kWh, high production rate, high reliability and low investment cost. Contribution to the topical issue "6th Central European Symposium on Plasma Chemistry (CESPC-6)", edited by Nicolas Gherardi, Ester Marotta and Cristina Paradisi

  16. Photoelectrochemical properties of mesoporous NiO x deposited on technical FTO via nanopowder sintering in conventional and plasma atmospheres.

    Science.gov (United States)

    Awais, Muhammad; Dowling, Denis D; Decker, Franco; Dini, Danilo

    2015-01-01

    Nanoporous nickel oxide (NiO x ) has been deposited with two different procedures of sintering (CS and RDS). Both samples display solid state oxidation at about 3.1 V vs Li+/Li. Upon sensitization of CS/RDS NiO x with erythrosine b (ERY), nickel oxide oxidation occurs at the same potential. Impedance spectroscopy revealed a higher charge transfer resistance for ERY-sensitized RDS NiO x with respect to sensitized CS NiO x . This was due to the chemisorption of a larger amount of ERY on RDS with respect to CS NiO x . Upon illumination the photoinduced charge transfer between ERY layer and NiO x could be observed only with oxidized CS. Photoelectrochemical effects of sensitized RDS NiO x were evidenced upon oxide reduction. With the addition of iodine RDS NiOx electrodes could give the reduction iodine → iodide in addition to the reduction of RDS NiO x . p-type dye sensitized solar cells were assembled with RDS NiO x photocathodes sensitized either by ERY or Fast Green. Resulting overall efficiencies ranged between 0.02 and 0.04 % upon irradiation with solar spectrum simulator (I in: 0.1 W cm(-2)).

  17. Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe{sub 11.6}Si{sub 1.4}

    Energy Technology Data Exchange (ETDEWEB)

    Shamba, P.; Morley, N.A.; Reaney, I.M.; Rainforth, W.M. [University of Sheffield, Department of Materials Science and Engineering, Sheffield (United Kingdom); Cespedes, O. [University of Leeds, School of Physics and Astronomy, Leeds (United Kingdom)

    2016-08-15

    LaFe{sub 11.6}Si{sub 1.4} alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe{sub 11.6}Si{sub 1.4} alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (ΔS{sub M}) for the arc-melted LaFe{sub 11.6}Si{sub 1.4} compound, obtained for a field change of 5 - 0T (decreasing field), was estimated to be 19.6 J kg{sup -1} K{sup -1}. The effective RCP at 5T of the arc-melted LaFe{sub 11.6}Si{sub 1.4} compound was determined to be 360 J kg{sup -1} which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe{sub 11.6}Si{sub 1.4} compound was observed. The ΔS{sub M}, obtained for a field change of 5 - 0T (decreasing field), for the SPS LaFe{sub 11.6}Si{sub 1.4} compound decreases to 7.4 J kg{sup -1} K{sup -1}. The T{sub C} also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe{sub 11.6}Si{sub 1.4} compound spreads over a larger temperature range with the RCP value at 5T reaching 288 J kg{sup -1} corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe{sub 11.6}Si{sub 1.4} compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe{sub 11.6}Si{sub 1.4} compounds in low-field magnetic refrigeration applications. (orig.)

  18. Effect of powder reactivity on fabrication and properties of NiAl/Al{sub 2}O{sub 3} composite coated on cast iron using spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Beyhaghi, Maryam [Department of Metallurgical and Materials Engineering, Ferdowsi University of Mashhad, 91775-1111 Mashhad (Iran, Islamic Republic of); Kiani-Rashid, Ali-Reza, E-mail: kianirashid@um.ac.ir [Department of Metallurgical and Materials Engineering, Ferdowsi University of Mashhad, 91775-1111 Mashhad (Iran, Islamic Republic of); Kashefi, Mehrdad; Khaki, Jalil Vahdati [Department of Metallurgical and Materials Engineering, Ferdowsi University of Mashhad, 91775-1111 Mashhad (Iran, Islamic Republic of); Jonsson, Stefan [Department of Materials Science and Engineering, Royal institute of Technology, SE-10044 Stockholm (Sweden)

    2015-07-30

    Highlights: • Obtaining mechanically activated and reacted powders by different ball milling time of Ni, Al and NiO. • Fabrication of dense NiAl/Al{sub 2}O{sub 3} composite coatings by spark plasma sintering of both reacted and reactive powder mixtures. • Investigation on phase evolution in diffusion bond layer at coating-substrate interface of samples. • Study on influence of powder ball milling time on microstructure, Vickers hardness and scratch hardness of coatings. • Achieving good adhesion of coating to substrate and clean interface between substrate and coating in samples. - Abstract: Powder mixtures of Ni, NiO and Al are ball milled for 1 and 10 h. X-ray diffractometry and differential thermal analysis show that while ball milling for 1 h produced mechanically activated powder; 10 h ball milling produced NiAl and Al{sub 2}O{sub 3} phases. Dense NiAl/Al{sub 2}O{sub 3} composite coatings are formed on gray cast iron substrate by spark plasma sintering (SPS) technique. The effect of powder reactivity on microstructure, hardness and scratch hardness of NiAl/Al{sub 2}O{sub 3} coatings after SPS is discussed. Results show that in the coating sample made of mechanically activated powder in situ synthesis of NiAl/Al{sub 2}O{sub 3} composite coating is fulfilled and a thicker well-formed diffusion bond layer at the interface between coating and substrate is observed. The diffusion of elements across the bond layers and phase evolution in the bond layers were investigated. No pores or cracks were observed at the interface between coating layer and substrate in any of samples. Higher Vickers hardness and scratch hardness values in coating made of 10 h ball milled powder than in coating fabricated from 1 h ball milled powder are attributed to better dispersion of Al{sub 2}O{sub 3} reinforcement particles in NiAl matrix and nano-crystalline structure of NiAl matrix. Scratched surface of coatings did not reveal any cracking or spallation at coating

  19. Optimization of magnetocaloric properties of arc-melted and spark plasma-sintered LaFe11.6Si1.4

    Science.gov (United States)

    Shamba, P.; Morley, N. A.; Cespedes, O.; Reaney, I. M.; Rainforth, W. M.

    2016-08-01

    LaFe11.6Si1.4 alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe11.6Si1.4 alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (Δ S M) for the arc-melted LaFe11.6Si1.4 compound, obtained for a field change of 5 - 0 T (decreasing field), was estimated to be 19.6 J kg-1 K-1. The effective RCP at 5 T of the arc-melted LaFe11.6Si1.4 compound was determined to be 360 J kg-1 which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe11.6Si1.4 compound was observed. The Δ S M, obtained for a field change of 5 - 0 T (decreasing field), for the SPS LaFe11.6Si1.4 compound decreases to 7.4 J kg-1 K-1. The T C also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe11.6Si1.4 compound spreads over a larger temperature range with the RCP value at 5 T reaching 288 J kg-1 corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe11.6Si1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe11.6Si1.4 compounds in low-field magnetic refrigeration applications.

  20. Report on in-situ studies of flash sintering of uranium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, Alicia Marie [MST-8: MATERIALS SCIENCE IN RADIATION & DYNAMICS EXTREMES

    2017-01-24

    fabricate nuclear fuel. First, the pure UO2-based system shows promising behavior with flash sintering, but composite systems are likely to show better sintering behavior with spark plasma sintering. Efforts to develop these methods should therefore be tailored towards the likelihood of success. Additionally, modeling is a rapidly developing aspect of current flash sintering research and should be used in parallel with experiments. Ultimately, ongoing flash sintering studies on various materials, like those summarized in this report, are rapidly contributing to the feasibility of controlling this method for use in the future.

  1. Accelerated simulation methods for plasma kinetics

    Science.gov (United States)

    Caflisch, Russel

    2016-11-01

    Collisional kinetics is a multiscale phenomenon due to the disparity between the continuum (fluid) and the collisional (particle) length scales. This paper describes a class of simulation methods for gases and plasmas, and acceleration techniques for improving their speed and accuracy. Starting from the Landau-Fokker-Planck equation for plasmas, the focus will be on a binary collision model that is solved using a Direct Simulation Monte Carlo (DSMC) method. Acceleration of this method is achieved by coupling the particle method to a continuum fluid description. The velocity distribution function f is represented as a combination of a Maxwellian M (the thermal component) and a set of discrete particles fp (the kinetic component). For systems that are close to (local) equilibrium, this reduces the number N of simulated particles that are required to represent f for a given level of accuracy. We present two methods for exploiting this representation. In the first method, equilibration of particles in fp, as well as disequilibration of particles from M, due to the collision process, is represented by a thermalization/dethermalization step that employs an entropy criterion. Efficiency of the representation is greatly increased by inclusion of particles with negative weights. This significantly complicates the simulation, but the second method is a tractable approach for negatively weighted particles. The accelerated simulation method is compared with standard PIC-DSMC method for both spatially homogeneous problems such as a bump-on-tail and inhomogeneous problems such as nonlinear Landau damping.

  2. Signal processing methods for MFE plasma diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Candy, J.V.; Casper, T.; Kane, R.

    1985-02-01

    The application of various signal processing methods to extract energy storage information from plasma diamagnetism sensors occurring during physics experiments on the Tandom Mirror Experiment-Upgrade (TMX-U) is discussed. We show how these processing techniques can be used to decrease the uncertainty in the corresponding sensor measurements. The algorithms suggested are implemented using SIG, an interactive signal processing package developed at LLNL.

  3. Microstructural aspects of in-situ TiB reinforced Ti-6Al-4V composite processed by spark plasma sintering%放电等离子烧结法制备原位TiB增强Ti-6Al-4V复合材料的显微组织特征

    Institute of Scientific and Technical Information of China (English)

    Saeid GHESMATITABRIZI; Abolfazl BABAKHANI; Seyed Abdolkarim SAJJADI; 吕维洁

    2015-01-01

    钛基复合材料在运输和航空工业领域具有广泛的应用.以Ti-6Al-4V和B4C为原料分别采用冷压-真空烧结和放电等离子烧结两种方法制备TiB晶须增强钛基复合材料.考察不同复合材料TiB晶须的分布、大小以及长径比,研究放电等离子烧结温度对TiB晶须增强钛基复合材料的影响.光学显微镜(OM),扫描电镜(SEM)以及EDS分析结果表明:将放电等离子烧结温度从900 °C升高到1100 °C可以使TiB晶须原位自生反应完全,同时减少材料的孔隙含量.%Titanium-matrix composites have important and wide applications in the transport and aerospace industries. The current research was focused on powder metallurgy processing of in-situ reinforced titanium-matrix composite with TiB whiskers. The Ti-6Al-4V alloy and B4C additive powders were used as raw materials. Two different consolidation techniques, namely press-and-sintering and spark plasma sintering, were selected. It was observed that in-situ TiB whiskers were formed during sintering in both methods. The changes in size, aspect ratio and distribution of in-situ whiskers in different composite samples were monitored. The effect of spark plasma sintering temperature on the synthesis of in-situ whiskers was also investigated. Based on the microstructural observations (optical microscopy and scanning electron microscopy) and the energy dispersive spectroscopy analysis, it was concluded that increasing the spark plasma sintering temperature from 900 to 1100 °C would lead to the complete formation of in-situ TiB whiskers and reduced porosity content.

  4. Effect of Spark Plasma Sintering on the Structure and Properties of Ti1−xZrxNiSn Half-Heusler Alloys

    Directory of Open Access Journals (Sweden)

    Ruth A. Downie

    2014-10-01

    Full Text Available XNiSn (X = Ti, Zr and Hf half-Heusler alloys have promising thermoelectric properties and are attracting enormous interest for use in waste heat recovery. In particular, multiphase behaviour has been linked to reduced lattice thermal conductivities, which enables improved energy conversion efficiencies. This manuscript describes the impact of spark plasma sintering (SPS on the phase distributions and thermoelectric properties of Ti0.5Zr0.5NiSn based half-Heuslers. Rietveld analysis reveals small changes in composition, while measurement of the Seebeck coefficient and electrical resistivities reveals that all SPS treated samples are electron doped compared to the as-prepared samples. The lattice thermal conductivities fall between 4 W·m−1·K−1 at 350 K and 3 W·m−1·K−1 at 740 K. A maximum ZT = 0.7 at 740 K is observed in a sample with nominal Ti0.5Zr0.5NiSn composition.

  5. Microstructural comparison of effects of hafnium and titanium additions in spark-plasma-sintered Fe-based oxide-dispersion strengthened alloys

    Science.gov (United States)

    Huang, Yina; Zhang, Hongtao; Auger, Maria A.; Hong, Zuliang; Ning, Huanpo; Gorley, Michael J.; Grant, Patrick S.; Reece, Michael J.; Yan, Haixue; Roberts, Steve G.

    2017-04-01

    Two oxide dispersion strengthened alloys: 14Cr-0.25Y2O3-0.22Hf (wt.%) and Fe-14Cr-0.25Y2O3-0.4Ti (wt.%) were fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). Electron backscatter diffraction showed grain sizes in the range 0.5-15 μm in both alloys. Transmission electron microscopy and scanning transmission electron microscopy showed a homogeneous distribution of nano-oxides precipitated during SPS. Using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography, several different oxide phases were found in both alloys, but the majority of dispersoids were Y-Hf-O type in Fe-14Cr-0.25Y2O3-0.22Hf and Y-Ti-O type in Fe-14Cr-0.25Y2O3-0.4Ti. There were a variety of orientation relationships between the different dispersoids and the ferritic matrix. Both alloys had dispersoid densities of ∼1023/m3, with average diameters of 4.3 nm and 3.5 nm in the 0.22Hf and 0.4Ti containing alloys, respectively. Per atom added, Hf (0.07 at.%) is suggested to be more potent than Ti (0.46 at.%) in refining the nano-oxides.

  6. A methodology to investigate the intrinsic effect of the pulsed electric current during the spark plasma sintering of electrically conductive powders.

    Science.gov (United States)

    Locci, Antonio Mario; Cincotti, Alberto; Todde, Sara; Orrù, Roberto; Cao, Giacomo

    2010-08-01

    A novel methodology is proposed for investigating the effect of the pulsed electric current during the spark plasma sintering (SPS) of electrically conductive powders without potential misinterpretation of experimental results. First, ensemble configurations (geometry, size and material of the powder sample, die, plunger and spacers) are identified where the electric current is forced to flow only through either the sample or the die, so that the sample is heated either through the Joule effect or by thermal conduction, respectively. These ensemble configurations are selected using a recently proposed mathematical model of an SPS apparatus, which, once suitably modified, makes it possible to carry out detailed electrical and thermal analysis. Next, SPS experiments are conducted using the ensemble configurations theoretically identified. Using aluminum powders as a case study, we find that the temporal profiles of sample shrinkage, which indicate densification behavior, as well as the final density of the sample are clearly different when the electric current flows only through the sample or through the die containing it, whereas the temperature cycle and mechanical load are the same in both cases.

  7. A methodology to investigate the intrinsic effect of the pulsed electric current during the spark plasma sintering of electrically conductive powders

    Directory of Open Access Journals (Sweden)

    Antonio Mario Locci, Alberto Cincotti, Sara Todde, Roberto Orrù and Giacomo Cao

    2010-01-01

    Full Text Available A novel methodology is proposed for investigating the effect of the pulsed electric current during the spark plasma sintering (SPS of electrically conductive powders without potential misinterpretation of experimental results. First, ensemble configurations (geometry, size and material of the powder sample, die, plunger and spacers are identified where the electric current is forced to flow only through either the sample or the die, so that the sample is heated either through the Joule effect or by thermal conduction, respectively. These ensemble configurations are selected using a recently proposed mathematical model of an SPS apparatus, which, once suitably modified, makes it possible to carry out detailed electrical and thermal analysis. Next, SPS experiments are conducted using the ensemble configurations theoretically identified. Using aluminum powders as a case study, we find that the temporal profiles of sample shrinkage, which indicate densification behavior, as well as the final density of the sample are clearly different when the electric current flows only through the sample or through the die containing it, whereas the temperature cycle and mechanical load are the same in both cases.

  8. Influence of Ni nanoparticle addition and spark plasma sintering on the TiNiSn–Ni system: Structure, microstructure, and thermoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Birkel, Christina S.; Douglas, Jason E.; Lettiere, Bethany R.; Seward, Gareth; Zhang, Yichi; Pollock, Tresa M.; Seshadri, Ram; Stucky, Galen D.

    2013-12-01

    The electronic and thermal properties of thermoelectric materials are highly dependent on their microstructure and therefore on the preparation conditions, including the initial synthesis and, if applicable, densification of the obtained powders. Introduction of secondary phases on the nano- and/or microscale is widely used to improve the thermoelectric figure of merit by reduction of the thermal conductivity. In order to understand the effect of the preparation technique on structure and properties, we have studied the thermoelectric properties of the well-known half-Heusler TiNiSn with addition of a small amount of nickel nanoparticles. The different parameters are the initial synthesis (levitation melting and microwave heating), the amount of nickel nanoparticles added and the exact pressing profile using spark plasma sintering. The resulting materials have been characterized by synchrotron X-ray diffraction and microprobe measurements and their thermoelectric properties are investigated. We found the lowest (lattice) thermal conductivity in samples with full-Heusler TiNi2Sn and Ni3Sn4 as secondary phases.

  9. Preparation of In2O3-Sr2RuErO6 Composite Ceramics by the Spark Plasma Sintering and Their Thermoelectric Performance

    Institute of Scientific and Technical Information of China (English)

    Bo Cheng; Yuanhua Lin; Jinle Lan; Yong Liu; Cewen Nan

    2011-01-01

    In1.94Zn0.03Ge0.03O3 and Sr2RuErO6 composite ceramics have been prepared by the spark plasma sintering (SPS) technique. Microstructure studies show that the Sr2RuErO6 phases are randomly dispersed in the ln1.94Zn0.03Ge0.03O3 matrix. The results show that the Seebeck coefficient increases with increasing the amount of Sr2RuErO6, while the thermal conductivity of the composite samples is lower than that of the In1.94Zn0.03Ge0.03O3 ceramic. The thermal conductivity of the 7 vol.% Sr2RuErO6 sample can decrease to 2.15 W·m-1·K-1 at 973 K, and the evaluated maximum ZT value is 0.23 for 3 vol.% Sr2RuErO6 samples at 973 K, which makes them promising materials for the thermoelectric devices.

  10. Bone Tissue Engineering with Adipose-Derived Stem Cells in Bioactive Composites of Laser-Sintered Porous Polycaprolactone Scaffolds and Platelet-Rich Plasma

    Directory of Open Access Journals (Sweden)

    Han-Tsung Liao

    2013-10-01

    Full Text Available Three-dimensional porous polycaprolactone (PCL scaffolds with consistent inter-pore channels, 83% porosity and 300–400 μm pore size were fabricated via selective laser sintering. The PCL scaffold was combined with platelet-rich plasma (PRP to form a bioactive composite and studied for potential application in bone tissue engineering using porcine adipose-derived stem cells (PASCs. The PCL/PRP/PASCs construct showed enhanced cell seeding efficiency and synergistically increased the differentiation capability of PASCs in osteogenic medium toward the osteoblast lineage, judging from elevated alkaline phosphatase activity and up-regulated osteogenic genes expression. For in vivo study, a 3 cm × 3 cm mandible defect was created in pigs and reconstructed by implanting acellular PCL scaffolds or PCL/PRP/PASCs constructs. Both groups showed new bone formation, however, the new bone volume was 5.1 times higher for PCL/PRP/PASCs 6 months post-operation. The bone density was less and loose in the acellular PCL group and the Young’s modulus was only 29% of normal bone. In contrast, continued and compact bone formation was found in PCL/PRP/PASCs and the Young’s modulus was 81% that of normal bone. Masson’s trichrome stain, immunohistochemical analysis of osteocalcin and collagen type I also confirmed new bone formation.

  11. Sintering Behavior and Microwave Dielectric Properties of MgTiO3 Ceramics Doped with B2O3 by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    Huanping Wang; Qinghua Yang; Denghao Li; Lihui Huang; Shilong Zhao; Shiqing Xu

    2012-01-01

    The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg(NO3)2-6H2O, Ti(C4H9O)4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 ℃ and the derived particle sizes of powders were 20-30 nm, 30-40 nm, 40-60 nm, 60-90 nm, 90-120 nm and 120-150 nm, respectively. The nanoparticles with the size of 30-60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20-30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B203 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTi03 lattice and resulted in the formation of (MgTi)2(BO3)O phase. The B203-doped MgTiO3 ceramic sintered at 1100℃ and prepared from the nanoparticles of 40-60 nm had compact structure and exhibited good microwave dielectric properties: εr=17.63, Q x f=33,768 GHz and Tf=-48X 10-6 ℃-1.

  12. Microwave sintering studies on low loss (Zn, Mg)TiO3 dielectric resonator materials.

    Science.gov (United States)

    Sirugudu, Roopas Kiran; Vemuri, Rama Krishna Murthy; Murty, B S

    2013-01-01

    Low dielectric loss Zn07Mg0.3TiO3 and MgTiO3 microwave dielectric resonators were prepared by the conventional solid state reaction method. The microwave interaction with these materials has been studied using both single-mode and multimode microwave furnaces operating at a frequency of 2.45 GHz. Microwave sintering could be achieved using a multimode microwave furnace only, whereas, interaction with a single-mode furnace showed plasma generation. Phase formation was observed by X-ray diffraction. Microwave dielectric characteristics such as dielectric constant (epsilon'), quality factor (Q x f) and temperature coefficient of resonant frequency (tauf) of microwave sintered samples were measured using a vector network analyzer and compared with conventional sintered ones. Microstructure of all the conventional and microwave sintered samples was observed using high resolution scanning electron microscope. Although epsilon' and tauf of the conventional and microwave sintered samples are found to be comparable, the quality factor (the vital characteristic of dielectric resonators) of microwave sintered samples are observed to be much lower than those obtained by conventional sintering. The difference in these values is discussed with respect to the grain size.

  13. Relativistic mirrors in laser plasmas (analytical methods)

    Science.gov (United States)

    Bulanov, S. V.; Esirkepov, T. Zh; Kando, M.; Koga, J.

    2016-10-01

    Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort x-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. We present an overview of theoretical methods used to describe relativistic flying, accelerating, oscillating mirrors emerging in intense laser-plasma interactions.

  14. High temperature oxidation-sulfidation behavior of Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composites densified by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Saucedo-Acuna, R.A. [Instituto e Ingenieria y Tecnologia, Universidad Autonoma de Cd. Juarez, Av. Del Charro 450 Norte, Col. Partido Romero, C.P. 32310, Cd. Juarez, Chihuahua (Mexico); Monreal-Romero, H.; Martinez-Villafane, A. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); Chacon-Nava, J.G. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico)], E-mail: jose.chacon@cimav.edu.mx; Arce-Colunga, U. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); Universidad Autonoma de Tamaulipas, Matamoros 8 y 9 Col. Centro C.P. 87110, Cd. Victoria, Tamaulipas (Mexico); Gaona-Tiburcio, C. [Centro de Investigacion en Materiales Avanzados, Departamento de Fisica de Materiales, Miguel de Cervantes 120, Complejo Industrial Chihuahua, C.P. 31109, Chihuahua (Mexico); De la Torre, S.D. [Centro de Investigacion e Innovacion Tecnologica (CIITEC)-IPN, D.F. Mexico (Mexico)

    2007-12-15

    The high temperature oxidation-sulfidation behavior of Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composites prepared by mechanical alloying (MA) and spark plasma sintering (SPS) has been studied. These composite powders have a particular metal-ceramic interpenetrating network and excellent mechanical properties. Oxidation-sulfidation tests were carried out at 900 deg. C, in a 2.5%SO{sub 2} + 3.6%O{sub 2} + N{sub 2}(balance) atmosphere for 48 h. The results revealed the influence of the sintering conditions on the specimens corrosion resistance, i.e. the Cr-Al{sub 2}O{sub 3} and Nb-Al{sub 2}O{sub 3} composite sintered at 1310 deg. C/4 min showed better corrosion resistance (lower weight gains) compared with those found for the 1440 deg. C/5 min conditions. For the former composite, a protective Cr{sub 2}O{sub 3} layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb-Al{sub 2}O{sub 3} composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy.

  15. Comparison of initial permeability of MgCuZn ferrites sintered by both conventional and microwave methods

    Energy Technology Data Exchange (ETDEWEB)

    Madhuri, W; Penchal Reddy, M; Rammanohar Reddy, N; Siva Kumar, K V [Ceramic Composite Materials Laboratory, Department of Physics, Sri Krishnadevaraya University, Anantapur-515 003 (India); Murthy, V R K, E-mail: sivakumar.sivani@gmail.co [Microwave Laboratory, Department of Physics, Indian Institute of Technology, Chennai-600 036 (India)

    2009-08-21

    NiCuZn ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like low magnetostriction, environmental stability, low stress sensitivity and low cost. In view of this, a series of non-stoichiometric MgCuZn ferrites (Mg{sub 0.5-x}Cu{sub x}Zn{sub 0.5}Fe{sub 1.9}O{sub 4-{delta}} with x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25) have been successfully synthesized by both conventional and microwave sintering techniques. The non-stoichiometry was intentionally introduced into the ferrites to ensure high resistivity of the samples. X-ray diffraction patterns confirm the single phase spinel structure in both cases. The elemental composition of these ferrites was analysed by energy-dispersive x-ray spectrometry. The samples sintered by the microwave technique were found to be denser than the conventionally sintered samples. The initial permeability of MgCuZn ferrites was studied with an increase in copper concentration from x = 0.0 to 0.25. The temperature variation of the initial permeability of these samples was carried out from 30 {sup 0}C to 150 {sup 0}C. The results are discussed in the light of microstructure variations of the conventionally and microwave sintered samples. The phenomena involved in microwave sintering are also discussed.

  16. Plasma methods of obtainment of multifunctional composite materials, dispersion-hardened by nanoparticles

    Science.gov (United States)

    Sizonenko, O. N.; Grigoryev, E. G.; Zaichenko, A. D.; Pristash, N. S.; Torpakov, A. S.; Lipyan, Ye V.; Tregub, V. A.; Zholnin, A. G.; Yudin, A. V.; Kovalenko, A. A.

    2016-04-01

    The new approach in developed plasma methods consists in that dispersionhardening additives (TiC, TiB2 in particular) are not mechanically added to powder mixture as additional component, as in conventional methods, but are instead synthesized during high voltage electric discharges (HVED) in disperse system “hydrocarbon liquid - powder” preservation of ultrafine structure is ensured due to use of spark plasma sintering (SPS) as a consolidation method. HVED in disperse system “hydrocarbon liquid - powder” due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10-6 to 10-7 m) and nanosized (from 10-7 to 10-9 m) composite powders of hardening phases. SPS is the passage of pulsed current (superposition of direct and alternating current) through powder with the simultaneous mechanical compressing. The formation of plasma is initiated in gaseous phase that fills gaps between particles. SPS allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10 - 20%), hardness and wear-resistance (by 30 - 60%) of obtained materials.

  17. Magnetic properties of lithium zinc ferrites synthesized by microwave sintered method

    National Research Council Canada - National Science Library

    Yang, Qinghui; Zhang, Huaiwu; Wen, Qiye; Liu, Yingli; Yang, Xuwen

    2016-01-01

    ...°C for the MS process. Experiments showed that the MS treated LiZn ferrites exhibited more excellent magnetic properties and denser, more uniform micro-structures comparing with the ones treated by CS method...

  18. Kinetic of sintering of polyethilene glycol and lanthanum dopped aluminum oxide obtained by the sol-gel method

    Directory of Open Access Journals (Sweden)

    Novaković Tatjana B.

    2011-01-01

    Full Text Available Sintering and crystallization of low-density polyethylene glycol (PEG and lanthanum, La(III-doped Al2O3 aerogels prepared from aluminum isopropoxide were investigated. The sintering behavior of non-doped and doped aerogels was examined by following the change of specific surface area with isothermal heat-treatment. The specific surface area and crystalline phases of non-doped and PEG+La(III-doped aerogels were determined, and the effects of dopants on the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal sintering experiments showed that the sintering mechanism of non-doped and PEG+La(III-doped Al2O3 aerogels is surface diffusion. The specific surface areas of alumina samples decrease rapidly during the initial period of sintering, and more slowly with prolonged sintering time. The change of the porous structure is correlated with the phase transformation of γ-Al2O3 during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3 aerogels came to about 20 m2g-1 with heat-treatment at 1100°C because of crystallization of α-Al2O3 after densification. In the case of heattreatment at 1200°C, the largest surface area was observed for PEG+La(III doped Al2O3 aerogels and the XRD pattern showed only low ordered θ-Al2O3. These indicate that the addition of PEG+La(III to boehmite sol prevents Al2O3 aerogels from sintering and crystallizing to the α-Al2O3 phase. Even after 20 h at 1000°C, PEG+La (III-doped alumina samples maintain a rather good specific surface area (108 m2 g-1 in comparison to the non-doped, containing mainly θ-Al2O3 and minor amounts of δ-Al2O3. Aluminum-oxides with these structural and textural properties are widely used as a coatings and catalyst supports in the field of various catalysis.

  19. Pulsed Plasma Lubrication Device and Method

    Science.gov (United States)

    Hofer, Richard R. (Inventor); Bickler, Donald B. (Inventor); D'Agostino, Saverio A. (Inventor)

    2016-01-01

    Disclosed herein is a lubrication device comprising a solid lubricant disposed between and in contact with a first electrode and a second electrode dimensioned and arranged such that application of an electric potential between the first electrode and the second electrode sufficient to produce an electric arc between the first electrode and the second electrode to produce a plasma in an ambient atmosphere at an ambient pressure which vaporizes at least a portion of the solid lubricant to produce a vapor stream comprising the solid lubricant. Methods to lubricate a surface utilizing the lubrication device in-situ are also disclosed.

  20. Synthesis and characterization of the NiFe{sub 2}O{sub 4}/Ni{sub 3}Fe nanocomposite powder and compacts obtained by mechanical milling and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Marinca, T.F.; Neamţu, B.V.; Popa, F.; Tarţa, V.F. [Materials Sciences and Engineering Department, Technical University of Cluj-Napoca, 103-105, Muncii Avenue, 400641 Cluj-Napoca (Romania); Pascuta, P. [Physics and Chemistry Department, Technical University of Cluj-Napoca, 103-105 Muncii Avenue, 400641 Cluj-Napoca (Romania); Takacs, A.F. [Faculty of Physics, Babeş-Bolyai University, 1 Mihail Kogălniceanu, 400084 Cluj-Napoca (Romania); Chicinaş, I., E-mail: Ionel.Chicinas@stm.utcluj.ro [Materials Sciences and Engineering Department, Technical University of Cluj-Napoca, 103-105, Muncii Avenue, 400641 Cluj-Napoca (Romania)

    2013-11-15

    Nanocomposite powder and compacts of NiFe{sub 2}O{sub 4}/Ni{sub 3}Fe type were synthesized using mechanical milling and spark plasma sintering (SPS) techniques. The samples have been investigated by X-ray diffraction (XRD), laser particles size analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The nanocomposite powder was obtained by mechanical milling in a high planetary ball mill of nanocrystalline NiFe{sub 2}O{sub 4} and nanocrystalline Ni{sub 3}Fe powders. The nanocomposite powder consists from Ni{sub 3}Fe particles covered at the surface with a layer of NiFe{sub 2}O{sub 4} fine particles and NiFe{sub 2}O{sub 4} particles. The nanocomposite particles have the median diameter d{sub 50} of 1.6 μm. The sintering in 400–600 °C temperature range preserve the nanocomposite phases but lead to a high porosity. The nanocomposite compacts consist in Ni{sub 3}Fe clusters surrounded by NiFe{sub 2}O{sub 4}. A sintering temperature of 800 °C leads to a good density for the nanocomposite compacts and to the new phase formation. The new phase is a wustite type (Fe{sub 1−x}Ni{sub x}O) and is formed at the metal/ceramic interface. A change in the Ni/Fe ratio, in the spinel structure, was evidenced during sintering. Sintering at a temperature of 800 °C, leads to the formation of a mixed iron–nickel ferrite with a very small amount of nickel, Ni{sub 1−x}Fe{sub x}Fe{sub 2}O{sub 4}.

  1. Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul A. Lessing

    2012-03-01

    Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi{sub x} (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages (high thermal conductivity, very high melting point, and high density) of nitride fuel have long been recognized. The sodium cooled BR-10 reactor in Russia operated for 18 years on uranium nitride fuel (UN was used as the driver fuel for two core loads). However, the potential advantages (large power up-grade, increased cycle lengths, possible high burn-ups) as a Light Water Reactor (LWR) fuel are offset by uranium nitride's extremely low oxidation resistance (UN powders oxidize in air and UN pellets decompose in hot water). Innovative research is proposed to solve this problem and thereby provide an accident tolerant LWR fuel that would resist water leaks and high temperature steam oxidation/spalling during an accident. It is proposed that we investigate two methods to increase the oxidation resistance of UN: (1) Addition of USi{sub x} (e.g. U{sub 3}Si{sub 2}) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with compounds (followed by densification via Spark Plasma Sintering) that will greatly increase oxidation resistance.

  2. Fundamentals of Sintering Dolomite

    Institute of Scientific and Technical Information of China (English)

    LIMaoqiang

    1996-01-01

    The difficulties in sintering of dolomite rise form the low mutual diffusibilites of Ca2+ in MgO and Mg2+ in CaO ,and from unique pore and agglomerate structures formed after calcination of dolomite.These microstructures in decompsoed dolomite play a great role in inhibition of densification during sintering.The measures ,which can destroy these stuctures,such as hydration or isostatic pressing after calcination of dolomite,result in increasing the sintered density and reducting the sintering temperature,Addition of ome oxide such as Fe2O3,ater the sintering mechanism from solid state sintering to liquid phase sintering,therefore,dense dolomite ody can be obtained at relatively low sintering temperature,Com-minution of dolomite before its calcination can lower the sintering temperature and enhance the sinterd ensity due to increasing both the quantity and homogeneity of Fe2O3 in dolomite.

  3. Sintering unalloyed titanium in DC electrical abnormal glow discharge

    Directory of Open Access Journals (Sweden)

    Allan Seeber

    2010-03-01

    Full Text Available Powder metallurgy is widely used in the manufacture of components that have complex geometry. The good dimensional control, reduction in manufacturing steps and operating costs which has favored the use of this technique for manufacturing of titanium alloys components. However, the high affinity of this material with oxygen hinders strongly the sintering process. For this, the sintering associated with plasma technology can be considered an alternative technique for the processing of this material. The strict control of sintering atmosphere performed at low pressures and the reactive species present in the plasma environment can help to improve the sintering of this material. The results presented in this paper show a good correlation between the parameters used for the compaction of the samples and the microstructure develop during the plasma sintering of samples. The microstructure of the plasma assisted samples is also affected by the particular configuration used in the plasma reactor.

  4. Effect of mechanical activation on cordierite synthesis through solid-state sintering method

    Indian Academy of Sciences (India)

    S K Nath; Sanjay Kumar; Rakesh Kumar

    2014-10-01

    Synthesis of cordierite (5SiO2.2MgO.2Al2O3) has attracted special attention from researchers for its special characteristics. Most common method of cordierite preparation is solid-state reaction using source of alumina, silica and magnesia, which requires temperature of 1350 °C or above. This study deals with the effect of mechanical activation on cordierite synthesis at lower temperature. Talc, kaolinite clay and alumina powder were taken as precursor materials and the batches were formulated on the basis of stoichometric cordierite formation. Particle size distribution (PSD) was measured to get the distribution pattern of milled powder. Pellets were prepared by compaction of dried milled powders and fired at 1200 °C temperature. X-ray diffraction (XRD) technique was used to characterize crystalline phases. Microstructural analysis was done under scanning electron microscope (SEM). It was observed that properties were improved with milling time. Dense and uniform microstructures were formed when samples were milled for 45 and 60 min.

  5. Enhanced thermionic emission properties in textured two-phase LaB{sub 6}–BaB{sub 6} system prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Shen Lin, E-mail: shenlinz@sina.com [College of Mathematics and Physics, Jinggangshan University, Jian 343409 (China); Shanghai Key Laboratory of Special Artificial Microstructure and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Jiu Xing, E-mail: zjiuxing@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Bao, Li Hong [Inner Mongolia Key Laboratory for Physics and Chemistry of Functional Materials, Inner Mongolia Normal University, Hohhot 010022 (China); Yu, Xiao Guang; Hu, Qiang Lin; Hu, Dong Qiang [College of Mathematics and Physics, Jinggangshan University, Jian 343409 (China)

    2014-10-25

    Graphical abstract: Room temperature XRD patterns of the nominal composition (La{sub 0.6}Ba{sub 0.4})B{sub 6} synthesized by SPS at 1400 °C for 5 min under 50 MPa. The XRD patterns reveal that the (La{sub 0.6}Ba{sub 0.4})B{sub 6} is a two-phase mixture of LaB{sub 6} and BaB{sub 6}. The inset is a macroscopic picture of the obtained (La{sub 0.6}Ba{sub 0.4})B{sub 6}. - Highlights: • (La{sub 0.6}Ba{sub 0.4})B{sub 6} has been successfully prepared by spark plasma sintering. • The obtained (La{sub 0.6}Ba{sub 0.4})B{sub 6} compound is a two-phase mixture of LaB{sub 6} and BaB{sub 6}. • The (0 0 1) texture is favorable for the decrease of work function. • The addition of BaB{sub 6} to LaB{sub 6} improves the electron emission performance. • (La{sub 0.6}Ba{sub 0.4})B{sub 6} is shown to be promising candidate for cathode applications. - Abstract: Structure, crystallographic orientation, and thermionic emission properties of the two-phase LaB{sub 6}–BaB{sub 6} system fabricated by a combined process of evaporation–condensation and spark plasma sintering (SPS) were investigated systematically. The powder X-ray diffraction (XRD) reveals that the obtained nominal composition (La{sub 0.6}Ba{sub 0.4})B{sub 6} compound exhibits coexistence of two isostructural phases of LaB{sub 6} and BaB{sub 6}. The electron backscatter diffraction (EBSD) confirms that the surface of the (La{sub 0.6}Ba{sub 0.4})B{sub 6} forms a clear (0 0 1) texture, which favors reduction in work function. Thermionic emission properties were measured in the temperature range between 1500 and 1873 K. The results indicated that the (La{sub 0.6}Ba{sub 0.4})B{sub 6} emitter displayed a low work function of 1.95 eV, and a high zero field emission current density of 10 A cm{sup −2} at 1773 K. Compared to the reported LaB{sub 6} and (La{sub 0.6}Sm{sub 0.4})B{sub 6} prepared for identical synthesis conditions, (La{sub 0.6}Ba{sub 0.4})B{sub 6} is shown to have the most excellent thermionic emission

  6. Mechanical properties of ZrB2- and HfB2-based ultra-high temperature ceramics fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zapata-Solvas, E. [Imperial College, London; Jayaseelan, D. [Imperial College, London; Lin, Hua-Tay [ORNL; Brown, P. [DSTL, Porton Down, Salisbury, Wiltshire, UK; Lee, W.E. [Imperial College, London

    2013-01-01

    Flexural strengths at room temperature, at 1400 C in air and at room temperature after 1 h oxidation at 1400 C were determined for ZrB2- and HfB2-based ultra-high temperature ceramics (UHTCs). Defects caused by electrical discharge machining (EDM) lowered measured strengths significantly and were used to calculate fracture toughness via a fracture mechanics approach. ZrB2 with 20 vol.% SiC had room temperature strength of 700 90 MPa, fracture toughness of 6.4 0.6 MPa, Vickers hardness at 9.8 N load of 21.1 0.6 GPa, 1400 C strength of 400 30 MPa and room temperature strength after 1 h oxidation at 1400 C of 678 15 MPa with an oxide layer thickness of 45 5 m. HfB2 with 20 vol.% SiC showed room temperature strength of 620 50 MPa, fracture toughness of 5.0 0.4 MPa, Vickers hardness at 9.8 N load of 27.0 0.6 GPa, 1400 C strength of 590 150 MPa and room temperature strength after 1 h oxidation at 1400 C of 660 25 MPa with an oxide layer thickness of 12 1 m. 2 wt.% La2O3 addition to UHTCs slightly reduced mechanical performance while increasing tolerance to property degradation after oxidation and effectively aided internal stress relaxation during spark plasma sintering (SPS) cooling, as quantified by X-ray diffraction (XRD). Slow crack growth was suggested as the failure mechanism at high temperatures as a consequence of sharp cracks formation during oxidation.

  7. Impact of yttria stabilized zirconia nanoinclusions on the thermal conductivity of n-type Si80Ge20 alloys prepared by spark plasma sintering

    Science.gov (United States)

    Lahwal, Ali; Bhattacharya, S.; He, Jian; Wu, Di; Peterson, A.; Poon, S. J.; Williams, L.; Dehkordi, A. Mehdizadeh; Tritt, T. M.

    2015-04-01

    Nanocomposites have become a new paradigm for thermoelectric research in recent years and have resulted in the reduction of thermal conductivity via the nano-inclusion and grain boundary scattering. In this work, we report the preparation and thermoelectric study of SiGe-yttria stabilized zirconia (YSZ) nanocomposites prepared by Spark Plasma Sintering (SPS). We experimentally investigated the reduction of lattice thermal conductivity (κL) in the temperature range (30-800 K) of n-type Si80Ge20P2 alloys with the incorporation of YSZ nanoparticles (20-40 nm diameter) into the Si-Ge matrix. These samples synthesized by using the SPS technique were found to have densities > 95% of the theoretical density. The thermal conductivity, at both low and high temperatures, was measured by steady state and laser flash techniques, respectively. At room temperature, we observed approximately a 50% reduction in the lattice thermal conductivity as result of adding 10% YSZ by volume to the Si80Ge20P2 host matrix. A phenomenological model developed by Callaway was used to corroborate both the temperature dependence and reduction of κ L over the measured temperature range (30-800 K) of both Si80Ge20P2 and Si80Ge20P2 + YSZ samples. The observed κL is discussed and interpreted in terms of various phonon scattering mechanisms such as alloy disorder, the Umklapp phonon scattering, and boundary scattering. In addition, a contribution from the phonon scattering by YSZ nanoparticles was further included to account for the κL of Si80Ge20P2 + YSZ sample. The theoretical calculations are in reasonably good agreement with the experimental results for both the Si80Ge20P2 and Si80Ge20P2 + YSZ alloys.

  8. Microstructures and mechanical properties of bulk nanocrystalline Fe–Al–C alloys made by mechanically alloying with subsequent spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Yoritoshi Minamino, Yuichiro Koizumi, Nobuhiro Tsuji, Naoko Hirohata, Kiyoshi Mizuuchi and Yoshihira Ohkanda

    2004-01-01

    Full Text Available The microstructure and superior mechanical properties of bulk nanocrystalline Fe–Al–C alloys made by mechanically alloying (MA with subsequent spark plasma sintering (SPS were investigated. Three kinds of nanocrystalline Fe–24 at% Al–X at%C (X=1,2,4 alloy powder were produced by MA from iron and aluminum powder with addition of methanol, and were subsequently consolidated at 1073–1273 K under 64 MPa by SPS. These compacts have the relative densities of 99.97% (1 at%C to 99.5% (4 at%C. The structure of compacts with 1at%C is composed of grains of Fe3Al of 1.5 μm in diameter and nano κ-carbides (Fe3AlC0.5 precipitates, while those of compacts with 2 and 4 at%C are composed of nanocrystalline Fe3Al of about 80 nm in diameter, nano κ-carbides and small amount of large α-grains of about 1 μm in diameter. These structures maintain the nanostructure even at 973 K, that is, they have the good thermal stability. The mechanical properties of these compacts were measured by compression tests at room temperature (RT to 973 K in vacuum. The compacts with 1 and 2 at%C of this work perform the superior mechanical properties (e.g. yield strength of 2150 MPa and rupture strain of 0.14 for compact with 2 at%C at R.T. when compared with the ordinary Fe3Al casting (e.g. the yield strength of 380 MPa and rupture strain of 0.12.

  9. Synthesis and electrical field-assisted sintering behaviour of yttria-stabilized tetragonal ZrO$_2$ nanopowders by polyacrylamide gel method

    Indian Academy of Sciences (India)

    XINGHUA SU; BENPAN WANG; JIE ZHOU; HAOYU SUN

    2016-06-01

    The tetragonal ZrO$_2$ nanopowders stabilized with 3 mol% Y$_2$O$_3$ (3YSZ) were synthesized using a polyacrylamide gel method. The mean particle size of the 3YSZ nanopowders was found to decrease with increasing molecular ratio of monomer to the precursor salt. The 3YSZ nanopowders with mean particle size of 12 nm can be densified in 1 h at 800$^{\\circ}$C, by the application of a d.c. electrical field. Under a constant d.c. electrical field, the current density through the specimen of 3YSZ rose rapidly when the temperature increased to a certain value. In the sintering process, the current density was restricted when the sharp increase occurred. By limiting current density to different values for one hour, it was found that current density was the most important factor in electrical field assisted sintering process. The grain size of 3YSZ bulk increased with the enhanced current density. The stable stageof electrical field-assisted sintering process can be explained by Joule heating. Corresponding real temperature of specimens is estimated by applying black body radiation theory.

  10. Autonomous Method and System for Minimizing the Magnitude of Plasma Discharge Current Oscillations in a Hall Effect Plasma Device

    Science.gov (United States)

    Hruby, Vladimir (Inventor); Demmons, Nathaniel (Inventor); Ehrbar, Eric (Inventor); Pote, Bruce (Inventor); Rosenblad, Nathan (Inventor)

    2014-01-01

    An autonomous method for minimizing the magnitude of plasma discharge current oscillations in a Hall effect plasma device includes iteratively measuring plasma discharge current oscillations of the plasma device and iteratively adjusting the magnet current delivered to the plasma device in response to measured plasma discharge current oscillations to reduce the magnitude of the plasma discharge current oscillations.

  11. CHAPTER 7. BERYLLIUM ANALYSIS BY NON-PLASMA BASED METHODS

    Energy Technology Data Exchange (ETDEWEB)

    Ekechukwu, A

    2009-04-20

    The most common method of analysis for beryllium is inductively coupled plasma atomic emission spectrometry (ICP-AES). This method, along with inductively coupled plasma mass spectrometry (ICP-MS), is discussed in Chapter 6. However, other methods exist and have been used for different applications. These methods include spectroscopic, chromatographic, colorimetric, and electrochemical. This chapter provides an overview of beryllium analysis methods other than plasma spectrometry (inductively coupled plasma atomic emission spectrometry or mass spectrometry). The basic methods, detection limits and interferences are described. Specific applications from the literature are also presented.

  12. Synthesis of lead-free piezoelectric powders by ultrasonic-assisted hydrothermal method and properties of sintered (K0.48Na0.52)NBO3 ceramics.

    Science.gov (United States)

    Isobe, Gaku; Maeda, Takafumi; Bornmann, Peter; Hemsel, Tobias; Morita, Takeshi

    2014-02-01

    (K,Na)NbO3 ceramics have attracted much attention as lead-free piezoelectric materials with high piezoelectric properties. High-quality (K,Na)NbO3 ceramics can be sintered using KNbO3 and NaNbO3 powders synthesized by a hydrothermal method. In this study, to enhance the quality factor of the ceramics, high-power ultrasonic irradiation was employed during the hydrothermal method, which led to a reduction in the particle size of the resultant powders.

  13. Sintered pellets: A simple and cost effective method to predict the performance of GGAG:Ce single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Fang, E-mail: fmeng2@vols.utk.edu [Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Scintillation Materials Research Center, University of Tennessee, Knoxville, TN 37996 (United States); Koschan, Merry [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN 37996 (United States); Melcher, Charles L. [Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Scintillation Materials Research Center, University of Tennessee, Knoxville, TN 37996 (United States); Cohen, Peter [Siemens Medical Solutions Molecular Imaging, Knoxville, TN 37932 (United States)

    2015-03-15

    Highlights: • Sintered pellets were firstly used to predict the performance of single crystals. • Similar properties between sintered pellets and single crystals were investigated. • B and Ba increase luminescence intensity in pellets and light yield in crystals. • Ca shortens photoluminescence decay in pellets and scintillation decay in crystals. - Abstract: Polycrystalline Gd{sub 3}Ga{sub 3}Al{sub 2}O{sub 12}:Ce (GGAG:Ce) pellets with various codopants were prepared via solid-state synthesis and characterized by X-ray diffraction, radioluminescence (RL), photoluminescence (PL), reflectivity and PL decay measurements. GGAG:Ce pellets codoped with B and Ba were found to have higher RL intensity than pellets with other codopants, while Ca codoping improved the decay time but reduced the RL intensity. These results were strongly correlated with the performance of these codopants in GGAG:Ce single crystals. The light yield of the single crystals codoped with B or Ba was ∼15% higher than the light yield of the GGAG:Ce crystal without codoping, while Ca codoping in single crystals resulted in lower light yield but shorter scintillation decay time (43 ns vs. 56 ns). The consistent performance of these codopants in both matrix forms indicates that sintering pellets may be used as a simple cost effective technique to evaluate compositions for likely single crystal scintillator performance.

  14. Numerical Simulation of Plasma Antenna with FDTD Method

    Institute of Scientific and Technical Information of China (English)

    LIANG Chao; XU Yue-Min; WANG Zhi-Jiang

    2008-01-01

    We adopt cylindrical-coordinate FDTD algorithm to simulate and analyse a 0.4-m-long column configuration plasma antenna. FDTD method is useful for solving electromagnetic problems, especially when wave characteristics and plasma properties are self-consistently related to each other. Focus on the frequency from 75 MHz to 400 MHz, the input impedance and radiation efficiency of plasma antennas are computed. Numerical results show that, different from copper antenna, the characteristics of plasma antenna vary simultaneously with plasma frequency and collision frequency. The property can be used to construct dynamically reconfigurable antenna.The investigation is meaningful and instructional for the optimization of plasma antenna design.

  15. Improvement of magnetic hysteresis loss, corrosion resistance and compressive strength through spark plasma sintering magnetocaloric LaFe11.65Si1.35/Cu core-shell powders

    Directory of Open Access Journals (Sweden)

    Caiyin You

    2016-05-01

    Full Text Available LaFe11.65Si1.35/Cu core-shell powders were achieved by self-designed magnetron sputtering system, which presents a better solidification during spark plasma sintering in comparison to the naked LaFe11.65Si1.35 powders. Much higher compressive strength, lower corrosion current density and magnetic hysteresis losses are achieved for the sintered sample of LaFe11.65Si1.35/Cu core-shell powders without significant decrease of the magnetic entropy change. The compressive strength, corrosion current density and maximum magnetic hysteresis losses are 105.6 MPa/16.8 MPa, 1.08 × 10−3A/cm2/3.03 × 10−3 A/cm2 and 1.33 J/kg/2.71 J/kg, respectively for the sintered samples of core-shell structured/naked powders. The technique of fabricating the core-shell structured powders demonstrated here is also applicable for other types of functional powders.

  16. Applied Pressure on Altering the Nano-Crystallization Behavior of Al86Ni6Y4.5Co2La1.5 Metallic Glass Powder during Spark Plasma Sintering and Its Effect on Powder Consolidation

    Directory of Open Access Journals (Sweden)

    X. P. Li

    2013-01-01

    Full Text Available Metallic glass powder of the composition Al86Ni6Y4.5Co2La1.5 was consolidated into 10 mm diameter samples by spark plasma sintering (SPS at different temperatures under an applied pressure of 200 MPa or 600 MPa. The heating rate and isothermal holding time were fixed at 40°C/min and 2 min, respectively. Fully dense bulk metallic glasses (BMGs free of particle-particle interface oxides and nano-crystallization were fabricated under 600 MPa. In contrast, residual oxides were detected at particle-particle interfaces (enriched in both Al and O when fabricated under a pressure of 200 MPa, indicating the incomplete removal of the oxide surface layers during SPS at a low pressure. Transmission electron microscopy (TEM revealed noticeable nano-crystallization of face-centered cubic (fcc Al close to such interfaces. Applying a high pressure played a key role in facilitating the removal of the oxide surface layers and therefore full densification of the Al86Ni6Y4.5Co2La1.5 metallic glass powder without nano-crystallization. It is proposed that applied high pressure, as an external force, assisted in the breakdown of surface oxide layers that enveloped the powder particles in the early stage of sintering. This, together with the electrical discharge during SPS, may have benefitted the viscous flow of metallic glasses during sintering.

  17. Melting and Sintering of Ashes

    DEFF Research Database (Denmark)

    Hansen, Lone Aslaug

    1997-01-01

    The thesis contains an experimental study of the fusion and sintering of ashes collected during straw and coal/straw co-firing.A laboratory technique for quantitative determination of ash fusion has been developed based on Simultaneous Thermal Analysis (STA). By means of this method the fraction...... of melt in the investigated ashes has been determined as a function of temperature. Ash fusion results have been correlated to the chemical and mineralogical composition of the ashes, to results from a standard ash fusion test and to results from sintering experiments. Furthermore, the ash fusion results......-firing, the model only had a qualitative agreement with the measured ash deposit formation rates.Sintering measurements were carried out by means of compression strength testing of ash pellets. This method showed to not be applicable for the salt rich fly ash derived from straw combustion. For the fly ashes...

  18. Some features of sintering of tungsten powders

    Directory of Open Access Journals (Sweden)

    Andreiev Igor Viktorovich

    2016-01-01

    Full Text Available A method of activating the sintering process for tungsten powders using a closed reaction space and hydrogen, steam-saturated water was observed. This sintering process is allowed to activate super coarse-grained (1000μm tungsten powder sat relatively low temperatures (1000-1200°C.

  19. Asymptotic-Preserving methods and multiscale models for plasma physics

    CERN Document Server

    Degond, Pierre

    2016-01-01

    The purpose of the present paper is to provide an overview of Asymptotic-Preserving methods for multiscale plasma simulations by addressing three singular perturbation problems. First, the quasi-neutral limit of fluid and kinetic models is investigated in the framework of non magnetized as well as magnetized plasmas. Second, the drift limit for fluid descriptions of thermal plasmas under large magnetic fields is addressed. Finally efficient numerical resolutions of anisotropic elliptic or diffusion equations arising in magnetized plasma simulation are reviewed.

  20. Electrical Grain Boundary Characteristics of Dense Cubic Li 7-3xAlxLa3Zr2O7 (x = 0.05 - 0.3) Prepared by Spark Plasma Sintering

    Science.gov (United States)

    Ibbotson, Matthew Gianni Equi

    In an effort to measure the electrical grain boundary characteristics of fully dense (˜99%) cubic Li 7-3xAlxLa3Zr 2O12 (x = 0.05 - 0.3), small grain size samples of 1 - 2mum were made using the Spark Plasma Sintering (SPS) method. The large internal interfacial area of SPS samples increased the grain boundary contribution to the total resistance to separate typically overlapping bulk and grain boundary impedance responses, supporting grain boundary conductivity (sigma GB) measurements. sigmaGBwas on average two orders of magnitude lower than the bulk conductivity (sigmabulk), indicating the grain boundaries of this material are resistive to Li+ transport, despite literature reports of low grain boundary resistance. sigmaGB = 3.8x10-7 +/- 11%, 7.9x10-7 +/- 11%, and 4.8x10-7 +/- 27% S/cm at 250C with corresponding EaGB = 0.44 +/- 3%, 0.49 +/- 4%, 0.46 +/- 2% eV, for 5, 20, and 30mol%Al 3+ LLZO, respectively. The electrical grain boundary thickness (delta GB) calculated using the Brick Layer Model decreased monotonically with aluminum concentration (CAl3+) to indicate a possible space-charge effect on sigmaGB, and was deltaGB = 10.2 +/- 18% , 9.9 +/- 12% , 6.0 +/- 20% nm for 5, 20, and 30mol%Al LLZO, respectively. Non-linear behavior of sigmaGB with CAl3+ was discussed in terms of competing space-charge and impurity segregation effects that simultaneously influence lithium conduction in the electrical GB. Optimum sigmaGB and sigmabulk of 7.9x10-7 +/- 11% and 4.6x10-4 +/- 4% S/cm at 250C, respectively, were found to coincide at CAl3+ = 20mol%, the critical aluminum dopant concentration for cubic LLZO phase stability.

  1. Laser sintering of conductive carbon paste on plastic substrate

    Science.gov (United States)

    Kinzel, Edward C.; Kelkar, Rohan; Xu, Xianfan

    2010-02-01

    This work investigates fabrication of functional conductive carbon paste onto a plastic substrate using a laser. The method allows simultaneous sintering, patterning, and functionalization of the carbon paste. Experiments are carried out to optimize the laser processing parameters. It is shown that sheet resistance values obtained by laser sintering are close to the one specified by the manufacturer using conventional sintering method. Additionally, a heat transfer analysis using numerical methods is conducted to understand the relationship between the temperature during sintering and the sheet resistance values of sintered carbon wires. The process developed in this work has the potential of producing carbon-based electronic components on low cost plastic substrates.

  2. Bonding of TRIP-Steel/Al2O3-(3Y-TZP Composites and (3Y-TZP Ceramic by a Spark Plasma Sintering (SPS Apparatus

    Directory of Open Access Journals (Sweden)

    Aslan Miriyev

    2016-07-01

    Full Text Available A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening.

  3. Bonding of TRIP-Steel/Al₂O₃-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus.

    Science.gov (United States)

    Miriyev, Aslan; Grützner, Steffen; Krüger, Lutz; Kalabukhov, Sergey; Frage, Nachum

    2016-07-09

    A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y)-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al₂O₃ and 40 vol % (3Y)-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050-1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer's fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening.

  4. Bonding of TRIP-Steel/Al2O3-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus

    Science.gov (United States)

    Miriyev, Aslan; Grützner, Steffen; Krüger, Lutz; Kalabukhov, Sergey; Frage, Nachum

    2016-01-01

    A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y)-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y)-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening. PMID:28773680

  5. A comparative study of conventionally sintered and microwave sintered nickel zinc ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Rekha [Electroceramics Research Lab, GVM Girls College, Sonepat-131001, India and School of Physics and Materials Science, Thapar University, Patiala-147004 (India); Juneja, J. K. [Department of Physics, Hindu College, Sonepat-131001 (India); Raina, K. K. [School of Physics and Materials Science, Thapar University, Patiala-147004 (India); Kotnala, R. K. [National Physical Laboratory, New Delhi -110012 (India); Prakash, Chandra, E-mail: cprakash2014@gmail.com [Solid State Physics Laboratory, Timarpur, Delhi - 110054 (India)

    2014-04-24

    For the present work, nickel zinc ferrite having compositional formula Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} was synthesized by conventional solid state method and sintered in conventional and microwave furnaces. Pellets were sintered with very short soaking time of 10 min at 1150 °C in microwave furnace whereas 4 hrs of soaking time was selected for conventional sintering at 1200 °C. Phase formation was confirmed by X-ray diffraction analysis technique. Scanning electron micrographs were taken for microstructural study. Dielectric properties were studied as a function of temperature. To study magnetic behavior, M-H hysteresis loops were recorded for both samples. It is observed that microwave sintered sample could obtain comparable properties to the conventionally sintered one in lesser soaking time at lower sintering temperature.

  6. Aqueous Plasma Pharmacy: Preparation Methods, Chemistry, and Therapeutic Applications

    Science.gov (United States)

    Joslin, Jessica M.; McCall, James R.; Bzdek, Justin P.; Johnson, Derek C.; Hybertson, Brooks M.

    2017-01-01

    Plasma pharmacy is a subset of the broader field of plasma medicine. Although not strictly defined, the term aqueous plasma pharmacy (APP) is used to refer to the generation and distribution of reactive plasma-generated species in an aqueous solution followed by subsequent administration for therapeutic benefits. APP attempts to harness the therapeutic effects of plasma-generated oxidant species within aqueous solution in various applications, such as disinfectant solutions, cell proliferation related to wound healing, and cancer treatment. The subsequent use of plasma-generated solutions in the APP approach facilitates the delivery of reactive plasma species to internal locations within the body. Although significant efforts in the field of plasma medicine have concentrated on employing direct plasma plume exposure to cells or tissues, here we focus specifically on plasma discharge in aqueous solution to render the solution biologically active for subsequent application. Methods of plasma discharge in solution are reviewed, along with aqueous plasma chemistry and the applications for APP. The future of the field also is discussed regarding necessary research efforts that will enable commercialization for clinical deployment. PMID:28428835

  7. Methods for characterising microphysical processes in plasmas

    CERN Document Server

    de Wit, T Dudok; Furno, I; Sorriso-Valvo, L; Zimbardo, G

    2013-01-01

    Advanced spectral and statistical data analysis techniques have greatly contributed to shaping our understanding of microphysical processes in plasmas. We review some of the main techniques that allow for characterising fluctuation phenomena in geospace and in laboratory plasma observations. Special emphasis is given to the commonalities between different disciplines, which have witnessed the development of similar tools, often with differing terminologies. The review is phrased in terms of few important concepts: self-similarity, deviation from self-similarity (i.e. intermittency and coherent structures), wave-turbulence, and anomalous transport.

  8. Liquid Phase Sintering (LPS) and Dielectric Constant of α-Silicon Nitride Ceramic

    Institute of Scientific and Technical Information of China (English)

    CHEN Changlian; CHEN Fei; SHEN Qiang; ZHANG Lianmeng; YAN Faqiang

    2006-01-01

    The spark plasma sintering (SPS) was applied to prepare α-Si3N4 ceramics of different densities with magnesia, silicon dioxide, alumina as the sintering aids. The mechanism of liquid phase sintering (LPS) was discussed and the factors influencing the density of the prepared samples were analyzed. The dielectric constant of sintered samples was tested. The experimental results show that the density can be controlled from 2.48 g/cm3 to 3.09 g/cm3 while the content of the sintering aids and the sintering temperature alter and the dielectric constant is closely dependent on the density of obtained samples.

  9. The usability of ark clam shell (Anadara granosa) as calcium precursor to produce hydroxyapatite nanoparticle via wet chemical precipitate method in various sintering temperature.

    Science.gov (United States)

    Khiri, Mohammad Zulhasif Ahmad; Matori, Khamirul Amin; Zainuddin, Norhazlin; Abdullah, Che Azurahanim Che; Alassan, Zarifah Nadakkavil; Baharuddin, Nur Fadilah; Zaid, Mohd Hafiz Mohd

    2016-01-01

    This paper reported the uses of ark clam shell calcium precursor in order to form hydroxyapatite (HA) via the wet chemical precipitation method. The main objective of this research is to acquire better understanding regarding the effect of sintering temperature in the fabrication of HA. Throughout experiment, the ratio of Ca:P were constantly controlled, between 1.67 and 2.00. The formation of HA at these ratio was confirmed by means of energy-dispersive X-ray spectroscopy analysis. In addition, the effect of sintering temperature on the formation of HA was observed using X-ray diffraction analysis, while the structural and morphology was determined by means of field emission scanning electron microscopy. The formation of HA nanoparticle was recorded (~35-69 nm) in the form of as-synthesize HA powder. The bonding compound appeared in the formation of HA was carried out using Fourier transform infrared spectroscopy such as biomaterials that are expected to find potential applications in orthopedic and biomedical industries .

  10. Plasma actuator electron density measurement using microwave perturbation method

    Energy Technology Data Exchange (ETDEWEB)

    Mirhosseini, Farid; Colpitts, Bruce [Electrical and Computer Engineering, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)

    2014-07-21

    A cylindrical dielectric barrier discharge plasma under five different pressures is generated in an evacuated glass tube. This plasma volume is located at the center of a rectangular copper waveguide cavity, where the electric field is maximum for the first mode and the magnetic field is very close to zero. The microwave perturbation method is used to measure electron density and plasma frequency for these five pressures. Simulations by a commercial microwave simulator are comparable to the experimental results.

  11. Plasma confinement system and methods for use

    Energy Technology Data Exchange (ETDEWEB)

    Jarboe, Thomas R.; Sutherland, Derek

    2017-09-05

    A plasma confinement system is provided that includes a confinement chamber that includes one or more enclosures of respective helicity injectors. The one or more enclosures are coupled to ports at an outer radius of the confinement chamber. The system further includes one or more conductive coils aligned substantially parallel to the one or more enclosures and a further set of one or more conductive coils respectively surrounding portions of the one or more enclosures. Currents may be provided to the sets of conductive coils to energize a gas within the confinement chamber into a plasma. Further, a heat-exchange system is provided that includes an inner wall, an intermediate wall, an outer wall, and pipe sections configured to carry coolant through cavities formed by the walls.

  12. Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y{sub 2}O{sub 3} ferritic steels fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongtao, E-mail: h.zhang3@lboro.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Department of Materials, Loughborough University, Leicester LE11 3TU (United Kingdom); Huang, Yina [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Ning, Huanpo [School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS (United Kingdom); Nanoforce Technology Ltd, London E1 4NS (United Kingdom); Williams, Ceri A.; London, Andrew J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Dawson, Karl [Centre for Materials and Structures, University of Liverpool, Liverpool L69 3GH (United Kingdom); Hong, Zuliang [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Gorley, Michael J. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Grovenor, Chris R.M. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Tatlock, Gordon J. [Centre for Materials and Structures, University of Liverpool, Liverpool L69 3GH (United Kingdom); Roberts, Steve G. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Reece, Michael J.; Yan, Haixue [School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS (United Kingdom); Nanoforce Technology Ltd, London E1 4NS (United Kingdom); Grant, Patrick S. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-09-15

    Highlights: • Nanostructured ODS steels were successfully produced by SPS. • Presence of Y{sub 2}Ti{sub 2}O{sub 7} nanoclusters was confirmed by synchrotron XRD and microscopy. • The chemistry of nanoclusters tested by ATP indicated they are Y–Ti–O oxides. - Abstract: Ferritic steels strengthened with Ti–Y–O nanoclusters are leading candidates for fission and fusion reactor components. A Fe–14Cr–0.4Ti + 0.25Y{sub 2}O{sub 3} (14YT) alloy was fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). The densification of the 14YT alloys significantly improved with an increase in the sintering temperature. Scanning electron microscopy and electron backscatter diffraction revealed that 14YT SPS-sintered at 1150 °C under 50 MPa for 5 min had a high density (99.6%), a random grain orientation and a bimodal grain size distribution (<500 nm and 1–20 μm). Synchrotron X-ray diffraction patterns showed bcc ferrite, Y{sub 2}Ti{sub 2}O{sub 7}, FeO, and chromium carbides, while transmission electron microscopy and atom probe tomography showed uniformly dispersed Y{sub 2}Ti{sub 2}O{sub 7} nanoclusters of <5 nm diameter and number density of 1.04 × 10{sup 23} m{sup −3}. Due to the very much shorter consolidation times and lower pressures used in SPS compared with the more usual hot isostatic pressing routes, SPS is shown to be a cost-effective technique for oxide dispersion strengthened (ODS) alloy manufacturing with microstructural features consistent with the best-performing ODS alloys.

  13. Effects of dopants on the synthesis of Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-PbTiO{sub 3} ceramics by the reaction-sintering method

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Bijun; Ding, Chenlu; Wu, Jian; Du, Qingbo [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Ding, Jianning [School of Materials Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Key Laboratory of New Energy Engineering, Changzhou University, Changzhou, Jiangsu 213164 (China); Jiangsu University, Zhenjiang, Jiangsu 212013 (China)

    2011-07-15

    Sintering aid-doped 0.8Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.2PbTiO{sub 3} (0.8PMN-0.2PT) relaxor-based ferroelectric ceramics were prepared by the reaction-sintering method. X-ray diffraction (XRD) measurement, SEM observation, and density measurement confirmed that the Li{sub 2}CO{sub 3}- and CuO-doped 0.8PMN-0.2PT ceramics exhibit pure rhombohedral perovskite structure, rather homogenous micromorphology and high relative density. As compared to the undoped 0.8PMN-0.2PT ceramics, the Li{sub 2}CO{sub 3}- and CuO-doped 0.8PMN-0.2PT ceramics exhibit enhanced dielectric diffused and frequency dispersion, improved ferroelectric property, and piezoelectric property, while as the sintering temperature is decreased greatly. Therefore, Li{sub 2}CO{sub 3} and CuO are effective sintering aids for the PMN-PT ceramics prepared by the reaction-sintering method, which exhibit promising applications in the electronic ceramic industries. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Models of current sintering

    Science.gov (United States)

    Angst, Sebastian; Engelke, Lukas; Winterer, Markus; Wolf, Dietrich E.

    2017-06-01

    Densification of (semi-)conducting particle agglomerates with the help of an electrical current is much faster and more energy efficient than traditional thermal sintering or powder compression. Therefore, this method becomes more and more common among experimentalists, engineers, and in industry. The mechanisms at work at the particle scale are highly complex because of the mutual feedback between current and pore structure. This paper extends previous modelling approaches in order to study mixtures of particles of two different materials. In addition to the delivery of Joule heat throughout the sample, especially in current bottlenecks, thermoelectric effects must be taken into account. They lead to segregation or spatial correlations in the particle arrangement. Various model extensions are possible and will be discussed.

  15. Spark plasma sintering of Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x} monolithic ceramics obtained by mechanically induced self-sustaining reaction

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, Amparo, E-mail: aborrell@upvnet.upv.es [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Salvador, Maria Dolores [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garcia-Rocha, Victoria [ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Fernandez, Adolfo [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Chicardi, Ernesto; Gotor, Francisco J. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Calle Americo Vespucio 49, 41092 Sevilla (Spain)

    2012-05-01

    Nanometer-sized titanium-niobium carbonitride powders (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with different Ti/Nb atomic ratios were obtained by a mechanically induced self-sustaining reaction, and sintered by spark plasma sintering technique at 1500 Degree-Sign C for 1 min in a vacuum atmosphere. Mechanical properties such as hardness and Young's modulus were determined by nanoindentation technique and friction and wear coefficients assessed by ball-on-disk testing using alumina ball in dry sliding conditions. The fracture surface and wear tracks of samples were examined by scanning electron microscopy. Results showed that it is possible to obtain dense monolithic ceramics from the solid solution (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti{sub 0.3}Nb{sub 0.7}C{sub 0.5}N{sub 0.5} ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa.

  16. Relativistic Mirrors in Laser Plasmas (Analytical Methods)

    CERN Document Server

    Bulanov, Sergei V; Kando, Masaki; Koga, James K

    2016-01-01

    Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort X-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role.

  17. Apparatus and method for plasma processing of SRF cavities

    CERN Document Server

    Upadhyay, J; Peshl, J; Bašović, M; Popović, S; Valente-Feliciano, A -M; Phillips, L; Vuškovića, L

    2015-01-01

    An apparatus and a method are described for plasma etching of the inner surface of superconducting radio frequency (SRF) cavities. Accelerator SRF cavities are formed into a variable-diameter cylindrical structure made of bulk niobium, for resonant generation of the particle accelerating field. The etch rate non-uniformity due to depletion of the radicals has been overcome by the simultaneous movement of the gas flow inlet and the inner electrode. An effective shape of the inner electrode to reduce the plasma asymmetry for the coaxial cylindrical rf plasma reactor is determined and implemented in the cavity processing method. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise way to establish segmented plasma columns. The test structure was a pillbox cavity made of steel of similar dimension to the standard SRF cavity. This was adopted to experimentally verify the plasma surface reaction on cylindrical structures with variable diameter using the segment...

  18. Research on Degradation of Dye Acid Red B by Sr2FeMoO6 Synthesized by Microwave Sintering Method

    Directory of Open Access Journals (Sweden)

    Yong-Qing Zhai

    2012-01-01

    Full Text Available Double perovskite Sr2FeMoO6 was synthesized rapidly by microwave sintering method. The crystal structure of the sample was investigated by XRD. It shows that the as-synthesized sample is Sr2FeMoO6 with tetragonal crystal structure and I4/mmm space group. The test of electrical transport properties shows that the sample exhibits typical semiconductor behavior in the temperature range of 80~300 K. The influence of the dosage of the sample, light irradiation sources, and time on the efficiency of degradation have been studied. The results show Sr2FeMoO6 exhibits excellent degradation activity for dye Acid Red B, the decolorization rate is close to 100% under proper conditions. Meanwhile, a mechanism related to the process of degradation is proposed.

  19. In-liquid plasma devices and methods of use thereof

    KAUST Repository

    Cha, Min Suk

    2017-08-10

    Devices and methods for generating a plasma in a liquid are provided. A low- dielectric material can be placed in contact with the liquid to form an interface a distance from an anode. A voltage can be applied across the anode and a cathode submerged in the liquid to produce the plasma. A variety of devices are provided, including for continuous operation. The devices and methods can be used to generate a plasma in a variety of liquids, for example for water treatment, hydrocarbon reformation, or synthesis of nanomaterial.

  20. Transparent La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} ceramics obtained by combustion method and vacuum sintering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhengjuan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhou, Guohong, E-mail: sic_zhough@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Qin, Xianpeng; Yang, Yan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang, Guangjun [SCHOTT Glass Technologies (Suzhou) Co. Ltd., Suzhou 215009 (China); Menke, Yvonne [Schott AG, Corporate Research and Technology Development, Hattenbergstrasse 10, 55122 Mainz (Germany); Wang, Shiwei, E-mail: swwang51@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2014-02-05

    Highlights: • Combustion method and vacuum sintering were used to fabricate La{sub 2-x}Gd{sub x}Zr{sub 2}O{sub 7}. • The lattice parameters decreased with the increase of Gd{sup 3+} concent(x). • The absorption edge of the transmittance curves shifted to UV region from 0.4-2.0. • All the ceramics have high n (2.08), making them candidate for optical lens. • With the increase of x, the effective atomic number and density increased. -- Abstract: Transparent La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} (x = 0–2.0) ceramics were prepared via vacuum sintering from nanometric powders synthesized by a simple combustion method. The changes of phase composition, morphology and in-line transmittance of the resulting ceramics with Gd{sup 3+} content’s variation were investigated. With the increase of Gd{sup 3+} content, the samples keep the pyrochlore structure, but the X-ray diffraction peaks of the powders and ceramics shift to higher angle as the lattice parameters become smaller. All the ceramics are transparent with high in-line transmittance and high refractive index (2.08 @ 632.8 nm, x = 0.4–1.6). These results indicate that La{sub 2−x}Gd{sub x}Zr{sub 2}O{sub 7} ceramics might be used as optical lens. Moreover, with the increase of Gd{sup 3+} content, the effective atomic number and density of the ceramics increase, therefore making them promising host candidates for scintillators.

  1. Sintering and microstructural evolution of Si{sub 3}N{sub 4}-La{sub 2}O{sub 3}-Y{sub 2}O{sub 3} system from different powder processing methods

    Energy Technology Data Exchange (ETDEWEB)

    Monteverde, F.; Bellosi, A. [Consiglio Nazionale delle Ricerche, Faenza (Italy). Lab. di Ricerche Tecnologiche per la Ceramica

    1997-12-31

    The effects of different powder processing routes for the addition of sintering aids (La{sub 2}O{sub 3}+Y{sub 2}O{sub 3} in amounts 3+3 and 2+2 wt%) in Si{sub 3}N{sub 4}-based mixtures on sintering behaviour and microstructure of hot-pressed dense samples were evaluated and compared. The investigated powder processing methods were: ultrasonic- or attritor-mixing and chemical precipitation. Densification, microstructural features (grain size and shape) and grain boundary phases were found to depend on the powder processing as well as the amount of the additives. (orig.) 9 refs.

  2. Microwave sintered nanocomposite electrodes for solid oxide fuel cells.

    Science.gov (United States)

    Raza, Rizwan; Zhu, Bin

    2011-06-01

    Microwave sintering is a very interesting subject, which provides an alternative method to overcome problems faced with conventional sintering. This process is very efficient and only requires a few minutes. In this paper, nanocomposite electrodes (Cu0.15Ni0.85-GDC) were sintered at 700 degrees C for 10 mins in a single mode 2.45 GHz microwave oven by the solid state reaction method. The composition influence and the sintering methods on the as-obtained powder were characterized by XRD, SEM and TEM. It was observed that excellent sintering took place. Excellent fuel cell performance was achieved with microwave sintering compared tosamples sintered using conventional sintering. Electrochemical analysis was carried out using AC Impedance technique. This paper reports a new approach to develop a microwave sintered based nanocomposite material, which is more efficient on time and energy. This method can gain significant economical benefits compared to conventional sintered materials for applications in low temperature solid oxide fuel cells (LTSOFC).

  3. Synthesis, Sintering, and Electrical Properties of BaCe0.9−xZrxY0.1O3−δ

    DEFF Research Database (Denmark)

    Ricote, S.; Caboche, G.; Estournes, C.

    2008-01-01

    BaCe0.9-xZrxY0.1O3-delta powders were synthesized by a solid-state reaction. Different contents of cerium and zirconium were studied. Pellets were sintered using either conventional sintering in air at 1700 degrees C or the Spark Plasma Sintering (SPS) technique. The density of the samples sintered...

  4. Sintering process and grain growth of Mn-Zn ferrite nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; CUI Yinfang; WANG Yongming; HAO Shunli; LIU Chunjing

    2006-01-01

    The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.

  5. Preparation of nanostructured La{sub 0.7}Ca{sub 0.3−x}Ba{sub x}MnO{sub 3} ceramics by a combined sol–gel and spark plasma sintering route and resulting magnetocaloric properties

    Energy Technology Data Exchange (ETDEWEB)

    Ayadi, F.; Regaieg, Y. [Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue J.-A. de Baïf, 75205 Paris Cedex 13 (France); Faculté des Sciences de Sfax, Université de Sfax, LPM, B.P 1171, 3000 Sfax (Tunisia); Cheikhrouhou-Koubaa, W.; Koubaa, M.; Cheikhrouhou, A. [Faculté des Sciences de Sfax, Université de Sfax, LPM, B.P 1171, 3000 Sfax (Tunisia); Lecoq, H.; Nowak, S.; Ammar, S. [Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue J.-A. de Baïf, 75205 Paris Cedex 13 (France); Sicard, L., E-mail: lorette.sicard@univ-paris-diderot.fr [Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086 CNRS, 15 rue J.-A. de Baïf, 75205 Paris Cedex 13 (France)

    2015-05-01

    This work proposes an original, easy to achieve and inexpensive route to synthesize manganite ceramics for magnetic refrigeration, combining sol–gel chemistry to Spark Plasma Sintering (SPS). The target La{sub 0.7}Ca{sub 0.3−x}Ba{sub x}MnO{sub 3} (x=0, 0.1, 0.2) compounds are obtained as single phases which crystallize in the orthorhombic structure (Pnma space group). SPS allows a quick sintering at a relatively low temperature (700 °C in this work) compared to the conventional solid state method (≥1100 °C), leading to densified ultrafine grained pellets (85% of compactness). Magnetic studies show that Ba substitution does not affect significantly the relative cooling power (RCP) of these manganites, while it increases their Curie temperature (T{sub C}) by several tens of degrees. Typically, RCP values ranging between 267 and 270 J/kg (for a magnetic field change of 5 T) and T{sub C} between 205 and 245 K were measured when x was increased from 0 to 0.2, respectively. These results combined to the fact that the synthesis route is economically advantageous makes the obtained ceramics interesting as active refrigerants for magnetic refrigeration technology below room temperature. - Highlights: • Nanostructured La{sub 0.7}Ca{sub 0.3−x}Ba{sub x}MnO{sub 3} ceramics were obtained as single phase. • An original and low cost method was developed combining sol–gel chemistry and SPS. • The method can be extended to prepare most dense nanostructured oxides. • Our ceramics have higher RCP than those obtained by the solid state method. • The optimum temperature of the magnetocaloric effect is tunable with Ba content.

  6. Sintered Superhard Materials

    Science.gov (United States)

    Wentorf, R. H.; Devries, R. C.; Bundy, F. P.

    1980-05-01

    Diamond or cubic boron nitride particles can be sintered into strong masses at high temperatures and very high pressures at which these crystalline forms are stable. Most of the desirable physical properties of the sintered masses, such as hardness and thermal conductivity, approach those of large single crystals; their resistance to wear and catastrophic splitting is superior. The sintered masses are produced on a commercial scale and are increasingly used as cutting tools on hard or abrasive materials, as wire-drawing dies, in rock drills, and in special high-pressure apparatus.

  7. Analytical method for thermal stress analysis of plasma facing materials

    Science.gov (United States)

    You, J. H.; Bolt, H.

    2001-10-01

    The thermo-mechanical response of plasma facing materials (PFMs) to heat loads from the fusion plasma is one of the crucial issues in fusion technology. In this work, a fully analytical description of the thermal stress distribution in armour tiles of plasma facing components is presented which is expected to occur under typical high heat flux (HHF) loads. The method of stress superposition is applied considering the temperature gradient and thermal expansion mismatch. Several combinations of PFMs and heat sink metals are analysed and compared. In the framework of the present theoretical model, plastic flow and the effect of residual stress can be quantitatively assessed. Possible failure features are discussed.

  8. Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

    Science.gov (United States)

    Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

    2013-09-17

    Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

  9. Applications of Symmetry Methods to the Theory of Plasma Physics

    OpenAIRE

    Giampaolo Cicogna; Francesco Ceccherini; Francesco Pegoraro

    2006-01-01

    The theory of plasma physics offers a number of nontrivial examples of partial differential equations, which can be successfully treated with symmetry methods. We propose three different examples which may illustrate the reciprocal advantage of this "interaction" between plasma physics and symmetry techniques. The examples include, in particular, the complete symmetry analysis of system of two PDE's, with the determination of some conditional and partial symmetries, the construction of group-...

  10. Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

    Science.gov (United States)

    Tran, Tien Bich

    As the main inorganic component of bone, hydroxyapatite (HA, Ca 10(PO4)6(OH)2) should be an ideal candidate in biomaterials selection. When grain sizes are in the nanometric regime, protein adsorption and cell adhesion are enhanced, while strength, hardness, and wear resistance are improved. Unfortunately, low phase stability, poor sinterability, and a tendency towards exaggerated grain coarsening challenge full densification of nanocrystalline hydroxyapatite by conventional sintering methods. The field-assisted sintering technique (FAST) has successfully consolidated a variety of nanocrystalline metals and ceramics in dramatically reduced times. The sintering enhancements observed during FAST can be attributed to thermal and athermal effects. The rapid heating rates (up to ˜1000ºC/min) afforded by FAST contribute a significant thermal effect. Since fast heating rates reduce powder exposure to sub-sintering temperatures, non-densifying surface diffusion is limited. The athermal effects of FAST are less well understood and can include plasma generation, dielectric breakdown, particle surface cleaning, grain boundary pinning, and space charge effects. Applying the field-assisted sintering technique to nanocrystalline hydroxyapatite yielded surprising results. Deviations from conventional densification behavior were observed, with dehydroxylation identified as the most deleterious process to densification as well as mechanical and biological performance. Since hydroxyapatite is not a stable phase at high temperatures and low water partial pressure atmospheres, desintering due to dehydroxylation-related pore formation became apparent during Stage III sintering. In fact, the degree of desintering and pore formation increased with the extent of Stage III sintering and grain growth. The atomic rearrangements taking place during grain boundary migration are believed to favor the formation of more-stable oxyapatite through hydroxyapatite dehydroxylation. This behavior was

  11. A viscometric method of measuring plasma fibrinogen concentrations.

    OpenAIRE

    Ernst, E.; Resch, K L; Saradeth, T.; A. Maier; Matrai, A

    1992-01-01

    A technique based on deducing the viscosity of serum from that of plasma was compared with the commonly used Clauss method. The two methods correlated closely (r = 0.914). The reproducibility of the viscometric method was slightly poorer than the Clauss technique at low fibrinogen concentrations, equal to that at medium fibrinogen concentrations, and marginally better at high concentrations. Fibrinogen can therefore be measured reasonably accurately with the viscometric method, and can be rec...

  12. Research on Radiation Characteristic of Plasma Antenna through FDTD Method

    Directory of Open Access Journals (Sweden)

    Jianming Zhou

    2014-01-01

    Full Text Available The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML. Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

  13. Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jardin, S C

    2010-09-28

    Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.

  14. The Gaussian radial basis function method for plasma kinetic theory

    Energy Technology Data Exchange (ETDEWEB)

    Hirvijoki, E., E-mail: eero.hirvijoki@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Candy, J.; Belli, E. [General Atomics, PO Box 85608, San Diego, CA 92186-5608 (United States); Embréus, O. [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2015-10-30

    Description of a magnetized plasma involves the Vlasov equation supplemented with the non-linear Fokker–Planck collision operator. For non-Maxwellian distributions, the collision operator, however, is difficult to compute. In this Letter, we introduce Gaussian Radial Basis Functions (RBFs) to discretize the velocity space of the entire kinetic system, and give the corresponding analytical expressions for the Vlasov and collision operator. Outlining the general theory, we also highlight the connection to plasma fluid theories, and give 2D and 3D numerical solutions of the non-linear Fokker–Planck equation. Applications are anticipated in both astrophysical and laboratory plasmas. - Highlights: • A radically new method to address the velocity space discretization of the non-linear kinetic equation of plasmas. • Elegant and physically intuitive, flexible and mesh-free. • Demonstration of numerical solution of both 2-D and 3-D non-linear Fokker–Planck relaxation problem.

  15. Transport properties of multicomponent thermal plasmas: Grad method versus Chapman-Enskog method

    Energy Technology Data Exchange (ETDEWEB)

    Porytsky, P. [Institute for Nuclear Research, 03680 Kyiv (Ukraine); Krivtsun, I.; Demchenko, V. [Paton Welding Institute, 03680 Kyiv (Ukraine); Reisgen, U.; Mokrov, O.; Zabirov, A. [RWTH Aachen University, ISF-Welding and Joining Institute, 52062 Aachen (Germany); Gorchakov, S.; Timofeev, A.; Uhrlandt, D. [Leibniz Institute for Plasma Science and Technology (INP Greifswald), 17489 Greifswald (Germany)

    2013-02-15

    Transport properties (thermal conductivity, viscosity, and electrical conductivity) for multicomponent Ar-Fe thermal plasmas at atmospheric pressure have been determined by means of two different methods. The transport coefficients set based on Grad's method is compared with the data obtained when using the Chapman-Enskog's method. Results from both applied methods are in good agreement. It is shown that the Grad method is suitable for the determination of transport properties of the thermal plasmas.

  16. Grain size effect on the giant dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} nanoceramics prepared by mechanosynthesis and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Mohamad M., E-mail: mmohamad@kfu.edu.sa [Department of Physics, College of Science, King Faisal University, Al-Ahsaa 31982 (Saudi Arabia); Department of Physics, Faculty of Science, Assiut University in the New Valley, El-Kharga 72511 (Egypt); Yamada, Koji [Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575 (Japan)

    2014-04-21

    In the present work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) nanoceramics with different grain sizes were prepared by spark plasma sintering (SPS) at different temperatures (SPS-800, SPS-900, SPS-975, and SPS-1050) of the mechanosynthesized nano-powder. Structural and microstructural properties were studied by XRD and field-emission scanning electron microscope measurements. The grain size of CCTO nanoceramics increases from 80 nm to ∼200 nm for the ceramics sintered at 800 °C and 975 °C, respectively. Further increase of SPS temperature to 1050 °C leads to micro-sized ceramics of 2–3 μm. The electrical and dielectric properties of the investigated ceramics were studied by impedance spectroscopy. Giant dielectric constant was observed in CCTO nanoceramics. The dielectric constant increases with increasing the grain size of the nanoceramics with values of 8.3 × 10{sup 3}, 2.4 × 10{sup 4}, and 3.2 × 10{sup 4} for SPS-800, SPS-900, and SPS-975, respectively. For the micro-sized SPS-1050 ceramics, the dielectric constant dropped to 2.14 × 10{sup 4}. The dielectric behavior is interpreted within the internal barrier layer capacitance picture due to the electrical inhomogeneity of the ceramics. Besides the resistive grain boundaries that are usually observed in CCTO ceramics, domain boundaries appear as a second source of internal layers in the current nanoceramics.

  17. Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

    Science.gov (United States)

    Liu, Dong-hui; Liu, Hao; Zhang, Jian-liang; Liu, Zheng-jian; Xue, Xun; Wang, Guang-wei; Kang, Qing-feng

    2017-09-01

    The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Δ T) and the softening start temperature ( T 10%) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO·SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

  18. Plasma synthesis of nanostructures for improved thermoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Petermann, Nils; Hecht, Christian; Schulz, Christof; Wiggers, Hartmut [Institut fuer Verbrennung und Gasdynamik, Universitaet Duisburg-Essen, 47058 Duisburg (Germany); Stein, Niklas; Schierning, Gabi; Theissmann, Ralf [Nanostrukturtechnik, Universitaet Duisburg-Essen, 47058 Duisburg (Germany); Stoib, Benedikt; Brandt, Martin S, E-mail: hartmut.wiggers@uni-due.de [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 3, 85748 Garching (Germany)

    2011-05-04

    The utilization of silicon-based materials for thermoelectrics is studied with respect to the synthesis and processing of doped silicon nanoparticles from gas phase plasma synthesis. It is found that plasma synthesis enables the formation of spherical, highly crystalline and soft-agglomerated materials. We discuss the requirements for the formation of dense sintered bodies, while keeping the crystallite size small. Small particles a few tens of nanometres and below that are easily achievable from plasma synthesis, and a weak surface oxidation, both lead to a pronounced sinter activity about 350 K below the temperature usually needed for the successful densification of silicon. The thermoelectric properties of our sintered materials are comparable to the best results found for nanocrystalline silicon prepared by methods other than plasma synthesis.

  19. Fabrication of Ti-based composites based on bulk amorphous alloys by spark plasma sintering and crystallization of amorphous phase%放电等离子烧结-非晶晶化法合成钛基块状非晶复合材料

    Institute of Scientific and Technical Information of China (English)

    李元元; 杨超; 李小强; 陈友

    2011-01-01

    In order to circumvent low plasticity of bulk amorphous alloys (BAAs), a material forming method by coupling spark plasma sintering with crystallization of amorphous phase, fabricating composites based on BAAs (CBBAAs) with excellent mechanical property was reviewed systematically. By appropriate annealing of sintered BAAs prepared from spark plasma sintering in the supercooled liquid region of a mechanically alloyed amorphous powder, crystallized ductile β-Ti phase with controllable grain size, phase morphology and distribution can precipitate from the amorphous phase, and therefore, CBBAAs with a matrix of amorphous phase or crystallized β-Ti phase were obtained. The effect of different additions or substitute elements on the particle size, thermal property and microstructure of TiNbCuNiAl amorphous powder, and the influence of different sintering parameters on the microstructure and mechanical property of fabricated CBBAAs were investigated. The theoretical bases of fabricating crystallized phase-containing CBBAAs, and nucleation and growth mechanism of crystalline phase during the crystallization process were elucidated. The facture mechanism of fabricated CBBAAs under stress was explained based on a proposed "Developed hard-soft model". The results provide a promising method for fabricating large-sized crystallized phase-containing bulk composites with excellent mechanical property by powder metallurgy.%鉴于块状非晶合金(BAAs)的低塑性特征,回顾了利用放电等离子烧结-非晶晶化法制备高性能块状材料的成形技术,即先机械合金化制备钛基多组元非晶合金粉末,然后利用放电等离子烧结在粉末的过冷液相区固结非晶粉末,再利用非晶晶化法使烧结的非晶块体在随后的烧结和热处理过程中晶化析出-Ti延性相,控制延性相的形貌、尺度和分布,合成以非晶相或β-Ti晶化相为基体的钛基块状非晶复合材料(CBBAAs),研究不同添加或替换组元对TiNb

  20. A novel method based on selective laser sintering for preparing high-performance carbon fibres/polyamide12/epoxy ternary composites.

    Science.gov (United States)

    Zhu, Wei; Yan, Chunze; Shi, Yunsong; Wen, Shifeng; Liu, Jie; Wei, Qingsong; Shi, Yusheng

    2016-09-21

    A novel method based on selective laser sintering (SLS) process is proposed for the first time to prepare complex and high-performance carbon fibres/polyamide12/epoxy (CF/PA12/EP) ternary composites. The procedures are briefly described as follows: prepare polyamide12 (PA12) coated carbon fibre (CF) composite powder; build porous green parts by SLS; infiltrate the green parts with high-performance thermosetting epoxy (EP) resin; and finally cure the resin at high temperature. The obtained composites are a ternary composite system consisting of the matrix of novolac EP resin, the reinforcement of CFs and the transition thin layer of PA12 with a thickness of 595 nm. The SEM images and micro-CT analysis prove that the ternary system is a three-dimensional co-continuous structure and the reinforcement of CFs are well dispersed in the matrix of EP with the volume fraction of 31%. Mechanical tests show that the composites fabricated by this method yield an ultimate tensile strength of 101.03 MPa and a flexural strength of 153.43 MPa, which are higher than those of most of the previously reported SLS materials. Therefore, the process proposed in this paper shows great potential for manufacturing complex, lightweight and high-performance CF reinforced composite components in aerospace, automotive industries and other areas.

  1. A novel method based on selective laser sintering for preparing high-performance carbon fibres/polyamide12/epoxy ternary composites

    Science.gov (United States)

    Zhu, Wei; Yan, Chunze; Shi, Yunsong; Wen, Shifeng; Liu, Jie; Wei, Qingsong; Shi, Yusheng

    2016-09-01

    A novel method based on selective laser sintering (SLS) process is proposed for the first time to prepare complex and high-performance carbon fibres/polyamide12/epoxy (CF/PA12/EP) ternary composites. The procedures are briefly described as follows: prepare polyamide12 (PA12) coated carbon fibre (CF) composite powder; build porous green parts by SLS; infiltrate the green parts with high-performance thermosetting epoxy (EP) resin; and finally cure the resin at high temperature. The obtained composites are a ternary composite system consisting of the matrix of novolac EP resin, the reinforcement of CFs and the transition thin layer of PA12 with a thickness of 595 nm. The SEM images and micro-CT analysis prove that the ternary system is a three-dimensional co-continuous structure and the reinforcement of CFs are well dispersed in the matrix of EP with the volume fraction of 31%. Mechanical tests show that the composites fabricated by this method yield an ultimate tensile strength of 101.03 MPa and a flexural strength of 153.43 MPa, which are higher than those of most of the previously reported SLS materials. Therefore, the process proposed in this paper shows great potential for manufacturing complex, lightweight and high-performance CF reinforced composite components in aerospace, automotive industries and other areas.

  2. A novel method based on selective laser sintering for preparing high-performance carbon fibres/polyamide12/epoxy ternary composites

    Science.gov (United States)

    Zhu, Wei; Yan, Chunze; Shi, Yunsong; Wen, Shifeng; Liu, Jie; Wei, Qingsong; Shi, Yusheng

    2016-01-01

    A novel method based on selective laser sintering (SLS) process is proposed for the first time to prepare complex and high-performance carbon fibres/polyamide12/epoxy (CF/PA12/EP) ternary composites. The procedures are briefly described as follows: prepare polyamide12 (PA12) coated carbon fibre (CF) composite powder; build porous green parts by SLS; infiltrate the green parts with high-performance thermosetting epoxy (EP) resin; and finally cure the resin at high temperature. The obtained composites are a ternary composite system consisting of the matrix of novolac EP resin, the reinforcement of CFs and the transition thin layer of PA12 with a thickness of 595 nm. The SEM images and micro-CT analysis prove that the ternary system is a three-dimensional co-continuous structure and the reinforcement of CFs are well dispersed in the matrix of EP with the volume fraction of 31%. Mechanical tests show that the composites fabricated by this method yield an ultimate tensile strength of 101.03 MPa and a flexural strength of 153.43 MPa, which are higher than those of most of the previously reported SLS materials. Therefore, the process proposed in this paper shows great potential for manufacturing complex, lightweight and high-performance CF reinforced composite components in aerospace, automotive industries and other areas. PMID:27650254

  3. Selective laser sintering mechanism of polymer-coated molybdenum powder

    Institute of Scientific and Technical Information of China (English)

    BAI Pei-kang; WANG Wen-feng

    2007-01-01

    A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine (HLRP-350I). The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting /solidification when the temperature is above 160 ℃.

  4. Two-step flash light sintering process for enhanced adhesion between copper complex ion/silane ink and a flexible substrate

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Eun-Beom; Joo, Sung-Jun [Department of Mechanical Convergence Engineering, Hanyang University, Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Ahn, Heejoon [Department of Organic and Nano Engineering, Hanyang University, Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Hak-Sung, E-mail: kima@hanyang.ac.kr [Department of Mechanical Convergence Engineering, Hanyang University, Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2016-03-31

    A copper complex ion ink (including copper nanoparticles, a copper precursor and a silane coupling agent) was synthesized to enhance the adhesion between the copper pattern and a polyimide (PI) substrate. Oxygen plasma treatment was performed on the polyimide substrate to initiate a chemical reaction between the complex ion ink and the polyimide. Then, a two-step flash light sintering method (consisting of preheating and main sintering) was used to sinter the copper complex ion ink. The copper complex ion patterns were characterized as a function of the weight fraction of silane coupling agent using scanning electron microscopy (SEM), a four-point probe method and adhesion testing. In addition, a bending fatigue test was performed to evaluate the reliability of the conductive copper pattern under cyclic bending. The copper pattern fabricated with copper complex ion ink containing 3 wt% silane coupling agent exhibited the highest adhesion level (5B), the lowest resistivity (7.6 μΩ·cm) and a low resistance change (18%) after the bending fatigue test. The two-step sintering method used to enhance the adhesion between the copper complex ion ink and polyimide substrate was also studied using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). - Highlights: • The copper complex ion ink with copper nanoparticles and copper precursor was fabricated. • The copper complex ion ink was sintered by two-step flash light sintering method. • The sintered copper pattern exhibited the highest adhesion level (5B). • The resistivity of sintered copper pattern was 7.6 μΩ·cm.

  5. Preliminary characterization of interlayer for Be/Cu sintered compacts

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, N.; Kawamura, H. [Oarai Research Establishment, Ibaraki-ken (Japan)

    1995-09-01

    At present, beryllium is under consideration as a main candidate material for plasma facing components of ITER, because of its many advantages such as low Z, high thermal conductivity, low tritium retention, low activation and so on. Among the different divertor design options, the duplex structure where the beryllium armor is bonded with heat sink structural materials (DS-copper, Cu-Cr-Zr and so on) is under consideration. And plasma facing components will be exposed to high heat load and high neutron flux generated by the plasma. Therefore, it is necessary to develop the reliable bonding technologies between beryllium and heat sink structural materials in order to fabricate plasma facing components which can resist those. Then, we started the bonding technology development of beryllium and copper alloy with FGM (functional gradient material) in order to reduce thermal stress due to the difference of thermal expansion between beryllium and copper alloy. As the interlayers for FGM, eleven kinds of sintered compacts in which the mixing ratio of beryllium powder and oxygen free copper powder is different, were fabricated by the hot press/HIP method. The dimension of each compact is 8mm in diameter, 2mm in thickness. Then, thermal diffusivity and specific heat of these compacts were measured by laser flash method, and thermal conductivity was calculated from those values. From metalographical observation, it became clear that the sintered compacts of mixture of beryllium powder and copper powder contain residual beryllium, copper and two kinds of intermetallic compounds, Be{sub 2}Cu({delta}) and BeCu({gamma}). From the results of thermal characterization, thermal diffusivity of interlayers increased with increase of copper containing ratio. And, specific heat gradually decreased with increase of copper containing ratio.

  6. Alternative modeling methods for plasma-based Rf ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Veitzer, Seth A., E-mail: veitzer@txcorp.com; Kundrapu, Madhusudhan, E-mail: madhusnk@txcorp.com; Stoltz, Peter H., E-mail: phstoltz@txcorp.com; Beckwith, Kristian R. C., E-mail: beckwith@txcorp.com [Tech-X Corporation, Boulder, Colorado 80303 (United States)

    2016-02-15

    Rf-driven ion sources for accelerators and many industrial applications benefit from detailed numerical modeling and simulation of plasma characteristics. For instance, modeling of the Spallation Neutron Source (SNS) internal antenna H{sup −} source has indicated that a large plasma velocity is induced near bends in the antenna where structural failures are often observed. This could lead to improved designs and ion source performance based on simulation and modeling. However, there are significant separations of time and spatial scales inherent to Rf-driven plasma ion sources, which makes it difficult to model ion sources with explicit, kinetic Particle-In-Cell (PIC) simulation codes. In particular, if both electron and ion motions are to be explicitly modeled, then the simulation time step must be very small, and total simulation times must be large enough to capture the evolution of the plasma ions, as well as extending over many Rf periods. Additional physics processes such as plasma chemistry and surface effects such as secondary electron emission increase the computational requirements in such a way that even fully parallel explicit PIC models cannot be used. One alternative method is to develop fluid-based codes coupled with electromagnetics in order to model ion sources. Time-domain fluid models can simulate plasma evolution, plasma chemistry, and surface physics models with reasonable computational resources by not explicitly resolving electron motions, which thereby leads to an increase in the time step. This is achieved by solving fluid motions coupled with electromagnetics using reduced-physics models, such as single-temperature magnetohydrodynamics (MHD), extended, gas dynamic, and Hall MHD, and two-fluid MHD models. We show recent results on modeling the internal antenna H{sup −} ion source for the SNS at Oak Ridge National Laboratory using the fluid plasma modeling code USim. We compare demonstrate plasma temperature equilibration in two

  7. Alternative modeling methods for plasma-based Rf ion sources

    Science.gov (United States)

    Veitzer, Seth A.; Kundrapu, Madhusudhan; Stoltz, Peter H.; Beckwith, Kristian R. C.

    2016-02-01

    Rf-driven ion sources for accelerators and many industrial applications benefit from detailed numerical modeling and simulation of plasma characteristics. For instance, modeling of the Spallation Neutron Source (SNS) internal antenna H- source has indicated that a large plasma velocity is induced near bends in the antenna where structural failures are often observed. This could lead to improved designs and ion source performance based on simulation and modeling. However, there are significant separations of time and spatial scales inherent to Rf-driven plasma ion sources, which makes it difficult to model ion sources with explicit, kinetic Particle-In-Cell (PIC) simulation codes. In particular, if both electron and ion motions are to be explicitly modeled, then the simulation time step must be very small, and total simulation times must be large enough to capture the evolution of the plasma ions, as well as extending over many Rf periods. Additional physics processes such as plasma chemistry and surface effects such as secondary electron emission increase the computational requirements in such a way that even fully parallel explicit PIC models cannot be used. One alternative method is to develop fluid-based codes coupled with electromagnetics in order to model ion sources. Time-domain fluid models can simulate plasma evolution, plasma chemistry, and surface physics models with reasonable computational resources by not explicitly resolving electron motions, which thereby leads to an increase in the time step. This is achieved by solving fluid motions coupled with electromagnetics using reduced-physics models, such as single-temperature magnetohydrodynamics (MHD), extended, gas dynamic, and Hall MHD, and two-fluid MHD models. We show recent results on modeling the internal antenna H- ion source for the SNS at Oak Ridge National Laboratory using the fluid plasma modeling code USim. We compare demonstrate plasma temperature equilibration in two-temperature MHD models

  8. Inkjet printed paper based frequency selective surfaces and skin mounted RFID tags: The interrelation between silver nanoparticle ink, paper substrate and low temperature sintering technique

    NARCIS (Netherlands)

    Sanchez-Romaguera, V.; Wünscher, S.; Turki, B.M.; Abbel, R.; Barbosa, S.; Tate, D.J.; Oyeka, D.; Batchelor, J.C.; Parker, E.A.; Schubert, U.S.; Yeates, S.G.

    2015-01-01

    Inkjet printing of functional frequency selective surfaces (FSS) and radio frequency identification (RFID) tags on commercial paper substrates using silver nanoparticle inks sintered using low temperature thermal, plasma and photonic techniques is reported. Printed and sintered FSS devices demonstra

  9. Applications of Symmetry Methods to the Theory of Plasma Physics

    Directory of Open Access Journals (Sweden)

    Giampaolo Cicogna

    2006-02-01

    Full Text Available The theory of plasma physics offers a number of nontrivial examples of partial differential equations, which can be successfully treated with symmetry methods. We propose three different examples which may illustrate the reciprocal advantage of this "interaction" between plasma physics and symmetry techniques. The examples include, in particular, the complete symmetry analysis of system of two PDE's, with the determination of some conditional and partial symmetries, the construction of group-invariant solutions, and the symmetry classification of a nonlinear PDE.

  10. A divertor plasma configuration design method for tokamaks

    Science.gov (United States)

    Guo, Yong; Xiao, Bing-Jia; Liu, Lei; Yang, Fei; Wang, Yuehang; Qiu, Qinglai

    2016-11-01

    The efficient and safe operation of large fusion devices strongly relies on the plasma configuration inside the vacuum chamber. It is important to construct the proper plasma equilibrium with a desired plasma configuration. In order to construct the target configuration, a shape constraint module has been developed in the tokamak simulation code (TSC), which controls the poloidal flux and the magnetic field at several defined control points. It is used to construct the double null, lower single null, and quasi-snowflake configurations for the required target shape and calculate the required PF coils current.