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Sample records for high temperature sintering

  1. Preparation of silicon carbide/carbon fiber composites through high-temperature spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Ehsan Ghasali

    2017-12-01

    Full Text Available This study discusses the potentials of spark plasma sintering (SPS integrated with high temperature process that can enable sintering of SiC/Cf composites without any sintering aids. The random distribution of carbon fibers was obtained through mixing composite components in ethanol by using a shaker mill for 10 min. The corresponding sintering process was carried out at 1900 and 2200 °C with 50 MPa pressure applied at maximum temperature. The results showed that 89 ± 0.9 and 97 ± 0.8% of the theoretical density can be obtained for sintering temperatures of 1900 and 2200 °C, respectively. The densification curves were plotted to monitor sintering behavior with punch displacement changes. The appropriate bonding between SiC particles and carbon fibers was detected using FE-SEM for sample which was sintered at 2200 °C. The clear maximum in hardness (2992 ± 33 Vickers, bending strength (427 ± 26 MPa and fracture toughness (4.2 ± 0.3 MPa m1/2 were identified for sample sintered at 2200 °C. XRD investigations supposed that SiC and carbon were the only crystalline phases in both sintered samples.

  2. Tribological and mechanical comparison of sintered and hipped PM212: High temperature self-lubricating composites

    Science.gov (United States)

    Dellacorte, Christopher; Sliney, Harold E.; Bogdanski, Michael S.

    1992-01-01

    Selected tribological, mechanical and thermophysical properties of two versions of PM212 (sintered and hot isostatically pressed, HIPped) are compared. PM212, a high temperature self-lubricating composite, contains 70 wt percent metal bonded chromium carbide, 15 wt percent CaF2/BaF2 eutectic and 15 wt percent silver. PM212 in the sintered form is about 80 percent dense and has previously been shown to have good tribological properties from room temperature to 850 C. Tribological results of a fully densified, HIPped version of PM212 are given. They are compared to sintered PM212. In addition, selected mechanical and thermophysical properties of both types of PM212 are discussed and related to the tribological similarities and differences between the two PM212 composites. In general, both composites display similar friction and wear properties. However, the fully dense PM212 HIPped composite exhibits slight lower friction and wear than sintered PM212. This may be attributed to its generally higher strength properties. The sintered version displays stable wear properties over a wide load range indicating its promise for use in a variety of applications. Based upon their properties, both the sintered and HIPped PM212 have potential as bearing and seal materials for advanced high temperature applications.

  3. Tribological and mechanical comparison of sintered and HIPped PM212 - High temperature self-lubricating composites

    Science.gov (United States)

    Dellacorte, Christopher; Sliney, Harold E.; Bogdanski, Michael S.

    1992-01-01

    Selected tribological, mechanical and thermophysical properties of two versions of PM212 (sintered and hot isostatically pressed, HIPped) are compared. PM212, a high temperature self-lubricating composite, contains 70 wt percent metal bonded chromium carbide, 15 wt percent CaF2/BaF2 eutectic and 15 wt percent silver. PM212 in the sintered form is about 80 percent dense and has previously been shown to have good tribological properties from room temperature to 850 C. Tribological results of a fully densified, HIPped version of PM212 are given. They are compared to sintered PM212. In addition, selected mechanical and thermophysical properties of both types of PM212 are discussed and related to the tribological similarities and differences between the two PM212 composites. In general, both composites display similar friction and wear properties. However, the fully dense PM212 HIPped composite exhibits slight lower friction and wear than sintered PM212. This may be attributed to its generally higher strength properties. The sintered version displays stable wear properties over a wide load range indicating its promise for use in a variety of applications. Based upon their properties, both the sintered and HIPped PM212 have potential as bearing and seal materials for advanced high temperature applications.

  4. Study on high temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics

    Directory of Open Access Journals (Sweden)

    Bai P.

    2009-01-01

    Full Text Available High temperature sintering processes of selective laser sintered Al2O3/ZrO2/TiC ceramics were studied. The effects of the sintering temperature and the sintering time on the relative density, strength and fracture toughness of Al2O3/ZrO2/TiC ceramics were investigated. The results showed that the sintering temperature and sintering time had a great effect on the relative density and the mechanical properties of Al2O3/ZrO2/TiC ceramics. The mechanical strength increased from 120MPa to 360MPa and KIC increased from 3.7 J/m2 to 6.9 J/m2 when the sintering temperature increased from 1400ºC to 1600ºC, however, the mechanical strength decreased rapidly from 370MPa to 330MPa and KIC decreased from 6.9 J/m2 to 6.1 J/m2 when the sintering time increased from 30min to 90min. Furthermore, the addition of TiC and ZrO2 in the Al2O3 matrix significantly improved mechanical strength and fracture toughness of the Al2O3 matrix ceramics.

  5. Matrix free fiber reinforced polymeric composites via high-temperature high-pressure sintering

    Science.gov (United States)

    Xu, Tao

    2004-11-01

    A novel manufacturing process called high-temperature high-pressure sintering was studied and explored. Solid fiber reinforced composites are produced by consolidating and compacting layers of polymeric fabrics near their melting temperature under high pressure. There is no need to use an additional matrix as a bonding material. Partial melting and recrystallization of the fibers effectively fuse the material together. The product is called a "matrix free" fiber reinforced composite and essentially a one-polymer composite in which the fiber and the matrix have the same chemical composition. Since the matrix is eliminated in the process, it is possible to achieve a high fiber volume fraction and light weight composite. Interfacial adhesion between fibers and matrix is very good due to the molecular continuity throughout the system and the material is thermally shapeable. Plain woven Spectra RTM cloth made of SpectraRTM fiber was used to comprehensively study the process. The intrinsic properties of the material demonstrate that matrix free SpectraRTM fiber reinforced composites have the potential to make ballistic shields such as body armor and helmets. The properties and structure of the original fiber and the cloth were carefully examined. Optimization of the processing conditions started with the probing of sintering temperatures by Differential Scanning Calorimetry. Coupled with the information from structural, morphological and mechanical investigations on the samples sintered at different processing conditions, the optimal processing windows were determined to ensure that the outstanding original properties of the fibers translate into high ballistic performance of the composites. Matrix free SpectraRTM composites exhibit excellent ballistic resistance in the V50 tests conducted by the US Army. In the research, process-structure-property relationship is established and correlations between various properties and structures are understood. Thorough knowledge is

  6. Effect of sintering time and temperature on properties of high pressure assisted WC/Co hard metal composite

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    Karimi, M.M.; Gomes, U.U.; Oliveira, M.P.; Filgueira, M. [Universidade Federal do Rio Grande do Norte (UFRN), RN (Brazil)

    2016-07-01

    Full text: WC/Co is widely used as cutting tools, because has a unique combination of high strength, hardness, toughness, and moderate stiffness, especially with fine grained WC and finely distributed cobalt. WC/Co powder mixture sinters by different methods such as vacuum sintering, microwave sintering and SPS. High pressure high temperature (HPHT) sintering is a proposed method that can results in better distribution of cobalt and avoid undesirable phases by using high pressure, high temperature and very low sintering time. In this study, a powder mixture of WC- 10 wt% Co was sintered by HPHT at 1500 to 1900 deg C under a pressure of 7.7 GPa for 2 and 3 minutes. Microstructural/structural analyses were performed by SEM/EDS and XRD. Hardness was also done to obtain the effect of sintering parameters. It was found that increasing sintering time in HPHT sintering method at a constant temperature can improve properties of WC/Co hard metal. It was also realized that both sintering temperature and time have effect on hardness and density. (author)

  7. Rheological properties of a reclaimed waste tire rubber through high-pressure high-temperature sintering

    Science.gov (United States)

    Ubaidillah, Yunus, N. A.; Aziz, S. A. A.; Wahab, N. A. A.; Mazlan, S. A.

    2017-01-01

    High-Pressure High-Temperature (HPHT) sintering method has successfully revulcanized waste tire rubber (WTR) without any additional virgin rubber. The crumb rubber cleaned from its fabric and metals was reclaimed by applying high pressure (25 MPa) and high temperature (200 °C) for an hour along with common vulcanization agents such as sulfur, zinc oxide, and stearic acid. Dynamic properties of reclaimed WTR were assessed through shear rheology test on MCR302 Rheometer, Anton Paar, Austria. The results indicated that under steady test, the yield stress occurred at 31 kPa at 5% linear viscoelastic limit. The storage modulus ranged from 0.6 to 0.7 MPa under excitation frequency of 0.1 to 100 Hz and 1% strain amplitude. Under ramp strain amplitude, the storage modulus showed Payne Effect phenomenon at 0.8 to 1 % strain amplitude and 1 Hz excitation frequency. In general, the resulted dynamic properties was comparable with non-reclaimed rubber based on a literature survey. The results confirmed that HPHT sintering method was capable of reclaiming 100% WTR without an additional virgin rubber and achieving acceptable dynamic properties.

  8. Thermoset recycling via high-pressure high-temperature sintering: Revisiting the effect of interchange chemistry

    Science.gov (United States)

    Morin, Jeremy Edward

    and between particles. The technique of high-pressure high-temperature sintering has worked on all types of thermoset materials. Typical mechanical properties for sintered SBR powder rubber are as follows: 1.3 MPa 100% Modulus, 12.0 MPa Tensile Strength and 300% Elongation at Break. The goal of this research is two-fold. First, to gain an understanding of the variables that control the process of high-pressure high-temperature sintering. Second, to study the factors governing the mechanism of fusion with the hope of controlling and exploiting this process so that tires can be recycled to produce high quality and high-value added products.

  9. Boron Carbide: Stabilization of Highly-Loaded Aqueous Suspensions, Pressureless Sintering, and Room Temperature Injection Molding

    Science.gov (United States)

    Diaz-Cano, Andres

    Boron carbide (B4C) is the third hardest material after diamond and cubic boron nitride. It's unique combination of properties makes B4C a highly valuable material. With hardness values around 35 MPa, a high melting point, 2450°C, density of 2.52 g/cm3, and high chemical inertness, boron carbide is used in severe wear components, like cutting tools and sandblasting nozzles, nuclear reactors' control rots, and finally and most common application, armor. Production of complex-shaped ceramic component is complex and represents many challenges. Present research presents a new and novel approach to produce complex-shaped B4C components. Proposed approach allows forming to be done at room temperatures and under very low forming pressures. Additives and binder concentrations are kept as low as possible, around 5Vol%, while ceramics loadings are maximized above 50Vol%. Given that proposed approach uses water as the main solvent, pieces drying is simple and environmentally safe. Optimized formulation allows rheological properties to be tailored and adjust to multiple processing approaches, including, injection molding, casting, and additive manufacturing. Boron carbide samples then were pressureless sintered. Due to the high covalent character of boron carbide, multiples sintering aids and techniques have been proposed in order to achieve high levels of densification. However, is not possible to define a clear sintering methodology based on literature. Thus, present research developed a comprehensive study on the effect of multiple sintering aids on the densification of boron carbide when pressureless sintered. Relative densities above 90% were achieved with values above 30MPa in hardness. Current research allows extending the uses and application of boron carbide, and other ceramic systems, by providing a new approach to produce complex-shaped components with competitive properties.

  10. Preparation of (Bi, Pb)-2223/Ag tapes by high temperature sintering and post-annealing process

    DEFF Research Database (Denmark)

    Hua, L.; Grivel, Jean-Claude; Andersen, L.G.

    2002-01-01

    A novel heat treatment process was developed to fabricate (Bi, Pb)-2223/Ag tapes with high critical current density (J(c)). The process can be divided into two parts: reformation and post-annealing. Tapes were first heated to the maximum temperature (830-860 degreesC) followed by slow cooling......-energy synchrotron XRD and SEM/EDX. Some process parameters e.g. sintering temperature. cooling rate. and post-annealing time were optimised. (C) 2002 Elsevier Science B.V. All rights reserved....

  11. Thermal insulation for high temperature microwave sintering operations and method thereof

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.; Morrow, Marvin S.

    1995-01-01

    Superior microwave transparent thermal insulations for high temperature microwave sintering operations were prepared. One embodiment of the thermal insulation comprises granules of boron nitride coated with a very thin layer of glassy carbon made by preparing a glassy carbon precursor and blending it with boron nitride powder to form a mixture. The blended mixture is granulated to form a grit which is dried and heated to form the granules of boron nitride coated with a glassy carbon. Alternatively, grains of glassy carbon are coated with boron nitride by blending a mixture of a slurry comprising boron nitride, boric acid binder, and methyl alcohol with glassy carbon grains to form a blended mixture. The blended mixture is dried to form grains of glassy carbon coated with boron nitride. In addition, a physical mixture of boron nitride powder and glassy carbon grains has also been shown to be an excellent thermal insulation material for microwave processing and sintering.

  12. Method of preparing thermal insulation for high temperature microwave sintering operations

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.; Morrow, Marvin S.

    1996-01-01

    Superior microwave transparent thermal insulations for high temperature microwave sintering operations were prepared. One embodiment of the thermal insulation comprises granules of boron nitride coated with a very thin layer of glassy carbon made by preparing a glassy carbon precursor and blending it with boron nitride powder to form a mixture. The blended mixture is granulated to form a grit which is dried and heated to form the granules of boron nitride coated with a glassy carbon. Alternatively, grains of glassy carbon are coated with boron nitride by blending a mixture of a slurry comprising boron nitride, boric acid binder, and methyl alcohol with glassy carbon grains to form a blended mixture. The blended mixture is dried to form grains of glassy carbon coated with boron nitride. In addition, a physical mixture of boron nitride powder and glassy carbon grains has also been shown to be an excellent thermal insulation material for microwave processing and sintering.

  13. Highly Conductive Cu-Cu Joint Formation by Low-Temperature Sintering of Formic Acid-Treated Cu Nanoparticles.

    Science.gov (United States)

    Liu, Jingdong; Chen, Hongtao; Ji, Hongjun; Li, Mingyu

    2016-12-07

    Highly conductive Cu-Cu interconnections of SiC die with Ti/Ni/Cu metallization and direct bonded copper substrate for high-power semiconductor devices are achieved by the low-temperature sintering of Cu nanoparticles with a formic acid treatment. The Cu-Cu joints formed via a long-range sintering process exhibited good electrical conductivity and high strength. When sintered at 260 °C, the Cu nanoparticle layer exhibited a low resistivity of 5.65 μΩ·cm and the joints displayed a high shear strength of 43.4 MPa. When sintered at 320 °C, the resistivity decreased to 3.16 μΩ·cm and the shear strength increased to 51.7 MPa. The microstructure analysis demonstrated that the formation of Cu-Cu joints was realized by metallurgical bonding at the contact interface between the Cu pad and the sintered Cu nanoparticle layer, and the densely sintered layer was composed of polycrystals with a size of hundreds of nanometers. In addition, high-density twins were found in the interior of the sintered layer, which contributed to the improvement of the performance of the Cu-Cu joints. This bonding technology is suitable for high-power devices operating under high temperatures.

  14. Recombination of atomic oxygen on sintered zirconia at high temperature in non-equilibrium air plasma

    Energy Technology Data Exchange (ETDEWEB)

    Balat-Pichelin, M., E-mail: marianne.balat@promes.cnrs.fr [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES-CNRS, UPR 8521, 7 rue du four solaire, 66120 Font-Romeu Odeillo (France); Passarelli, M.; Vesel, A. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES-CNRS, UPR 8521, 7 rue du four solaire, 66120 Font-Romeu Odeillo (France)

    2010-09-01

    High temperature ceramic materials are necessary for the design of primary heat shields for future re-usable space vehicles re-entering atmospheric planet at hypersonic velocity. During the re-entry phase on earth, one of the most important phenomena occurring on the heat shield is the recombination of atomic oxygen and this phenomenon is more or less catalyzed by the material of the heat shield. This paper presents some experimental results for the recombination coefficient of atomic oxygen {gamma} based on experiments performed on the MESOX facility using optical emission spectroscopy and actinometry techniques. Experimental results on the recombination coefficient are presented for three types of sintered ZrO{sub 2} in the temperature range 900-2500 K for 200 Pa total air pressure. These three zirconia ceramics differ essentially by the chemical nature of the sintering additives (Y{sub 2}O{sub 3}, CaO or MgO). A great different behavior of the recombination coefficient versus temperature is observed according to the crystalline structure of zirconia (monoclinic and tetragonal phases) and few influence of the additive is shown.

  15. Direct Selective Laser Sintering/Melting of High Density Alumina Powder Layers at Elevated Temperatures

    Science.gov (United States)

    Deckers, J.; Meyers, S.; Kruth, J. P.; Vleugels, J.

    Direct selective laser sintering (SLS) or selective laser melting (SLM) are additive manufacturing techniques that can be used to produce three-dimensional ceramic parts directly, without the need for a sacrificial binder. In this paper, a low laser energy density is applied to SLS/SLM high density powder layers of sub-micrometer alumina at elevated temperatures (up to 800̊C). In order to achieve this, a furnace was designed and built into a commercial SLS machine. This furnace was able to produce a homogeneously heated cylindrical zone with a height of 60 mm and a diameter of 32 mm. After optimizing the layer deposition and laser scanning parameters, two ceramic parts with a density up to 85% and grain sizes as low as 5 μm were successfully produced.

  16. Ultra-low temperature sintering of Cu@Ag core-shell nanoparticle paste by ultrasonic in air for high-temperature power device packaging.

    Science.gov (United States)

    Ji, Hongjun; Zhou, Junbo; Liang, Meng; Lu, Huajun; Li, Mingyu

    2018-03-01

    Sintering of low-cost Cu nanoparticles (NPs) for interconnection of chips to substrate at low temperature and in atmosphere conditions is difficult because they are prone to oxidation, but dramatically required in semiconductor industry. In the present work, we successfully synthesized Cu@Ag NPs paste, and they were successfully applied for joining Cu/Cu@Ag NPs paste/Cu firstly in air by the ultrasonic-assisted sintering (UAS) at a temperature of as low as 160 °C. Their sintered microstructures featuring with dense and crystallized cells are completely different from the traditional thermo-compression sintering (TCS). The optimized shear strength of the joints reached to 54.27 MPa, exhibiting one order of magnitude higher than TCS at the same temperature (180 °C) under the UAS. This ultra-low sintering temperature and high performance of the sintered joints were ascribed to ultrasonic effects. The ultrasonic vibrations have distinct effects on the metallurgical reactions of the joints, resulting in the contact and growth of Cu core and the stripping and connection of Ag shell, which contributes to the high shear strength. Thus, the UAS of Cu@Ag NPs paste has a great potential to be applied for high-temperature power device packaging. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Improved critical current densities in bulk FeSe superconductor using ball milled powders and high temperature sintering

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, M.; Furutani, K.; Murakami, M. [Graduate School of Science and Engineering, Superconducting Materials Laboratory, Shibaura Institute of Technology, Tokyo (Japan); Kumar, Dinesh; Rao, M.S. Ramachandra [Department of Physics, Nano Functional Materials Technology Centre and Materials Science Research Centre, Indian Institute of Technology Madras, Chennai (India); Koblischka, M.R. [Institute of Experimental Physics, Saarland University, Saarbruecken (Germany)

    2016-12-15

    The present study is investigating the effect of high temperature sintering combined with ball milled powders for the preparation of FeSe material via solid state sintering technique. The commercial powders of Fe (99.9% purity) and Se (99.9% purity) were mixed in a nominal ratio Fe:Se = 1:1 and thoroughly ground and ball-milled in a glove box during 6 h. Then, the powder mixture was pressed into pellets of 5 mm in diameter and 2 mm thickness using an uniaxial pressure of 100 MPa. The samples were sealed in quartz tubes and sintered at 600 C for 24 h. Then, the pellets were again thoroughly ground and ball-milled in the glove box and pressed into pellets, and the final sintering was performed at two different temperatures, namely at 900 C for 24 h and at 950 C for 24 h. X-ray diffraction results confirmed that both samples showed mainly of the β-FeSe with tetragonal structure. The temperature dependence of magnetization (M-T) curves revealed a sharp superconducting transition T{sub c,} {sub onset} = 8.16 K for the sample sintered at 900 C. Further, scanning electron microscopy observations proved that samples sintered at 900 C show a platelike grain structure with high density. As a result, improved irreversibility fields around 5 T and the critical current density (J{sub c}) values of 6252 A cm{sup -2} at 5 K and self-field are obtained. Furthermore, the normalized volume pinning force versus the reduced field plots indicated a peak position at 0.4 for the sample sintered at 900 C. Improved flux pinning and the high J{sub c} values are attributed to the textured microstructure of the material, produced by a combination of high temperature sintering and ball milling. (copyright 2016 The Authors. Phys. Status Solidi A published by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Design, microstructure, and high-temperature behavior of silicon nitride sintered with rate-earth oxides

    Energy Technology Data Exchange (ETDEWEB)

    Ciniculk, M.K. (California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering)

    1991-08-01

    The processing-microstructure-property relations of silicon nitride ceramics sintered with rare-earth oxide additives have been investigated with the aim of improving their high-temperature behavior. The additions of the oxides of Y, Sm, Gd, Dy, Er, or Yb were compositionally controlled to tailor the intergranular phase. The resulting microstructure consisted of {beta}-Si{sub 3}N{sub 4} grains and a crystalline secondary phase of RE{sub 2}Si{sub 2}O{sub 7}, with a thin residual amorphous phase present at grain boundaries. The lanthanide oxides were found to be as effective as Y{sub 2}O{sub 3} in densifying Si{sub 3}N{sub 4}, resulting in identical microstructures. The crystallization behavior of all six disilicates was similar, characterized by a limited nucleation and rapid growth mechanism resulting in large single crystals. Complete crystallization of the intergranular phase was obtained with the exception of a residual amorphous, observed at interfaces and believed to be rich in impurities, the cause of incomplete devitrification. The low resistance to oxidation of these materials was attributed to the minimization of amorphous phases via devitrification to disilicates, compatible with SiO{sub 2}, the oxidation product of Si{sub 3}N{sub 4}. The strength retention of these materials at 1300{degrees}C was found to be between 80% and 91% of room-temperature strength, due to crystallization of the secondary phase and a residual but refractory amorphous grain-boundary phase. The creep behavior was found to be strongly dependent on residual amorphous phase viscosity as well as on the oxidation behavior, as evidenced by the nonsteady-state creep rates of all materials. 122 refs., 51 figs., 12 tabs.

  19. The Influence of Sintering Temperature of Reactive Sintered (Ti, MoC-Ni Cermets

    Directory of Open Access Journals (Sweden)

    Marek Jõeleht

    2015-09-01

    Full Text Available Titanium-molybdenum carbide nickel cermets ((Ti, MoC-Ni were produced using high energy milling and reactive sintering process. Compared to conventional TiC-NiMo cermet sintering the parameters for reactive sintered cermets vary since additional processes are present such as carbide synthesis. Therefore, it is essential to acquire information about the suitable sintering regime for reactive sintered cermets. One of the key parameters is the final sintering temperature when the liquid binder Ni forms the final matrix and vacancies inside the material are removed. The influence of the final sintering temperature is analyzed by scanning electron microscopy. Mechanical properties of the material are characterized by transverse rupture strength, hardness and fracture toughness.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7179

  20. Mg 2+-doped GaN nanoparticles as blue-light emitters: a method to avoid sintering at high temperatures.

    Science.gov (United States)

    Mahalingam, Venkataramanan; Sudarsan, Vasanthakumaran; Munusamy, Prabhakaran; van Veggel, Frank C J M; Wang, Rui; Steckl, Andrew J; Raudsepp, Mati

    2008-01-01

    Bright blue-light emission at 410 nm is observed from Mg(2+)-doped GaN nanoparticles prepared by the nitridation of Ga(2)MgO(4) nanoparticles at 950 degrees C. The sintering of these nanoparticles during high-temperature nitridation was prevented by mixing the Ga(2)MgO(4) precursor nanoparticles with La(2)O(3) as an inert matrix before the nitridation process. The Mg(2+)-doped GaN nanoparticles were isolated from the matrix by etching with 10 % nitric acid. The Mg(2+)-doped GaN nanoparticles were characterized by photoluminescence, atomic force microscopy, X-ray diffraction, and IR analyses.

  1. 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.

  2. The effects of composition, temperature and sample size on the sintering of chem-prep high field varistors.

    Energy Technology Data Exchange (ETDEWEB)

    Garino, Terry J.

    2007-09-01

    The sintering behavior of Sandia chem-prep high field varistor materials was studied using techniques including in situ shrinkage measurements, optical and scanning electron microscopy and x-ray diffraction. A thorough literature review of phase behavior, sintering and microstructure in Bi{sub 2}O{sub 3}-ZnO varistor systems is included. The effects of Bi{sub 2}O{sub 3} content (from 0.25 to 0.56 mol%) and of sodium doping level (0 to 600 ppm) on the isothermal densification kinetics was determined between 650 and 825 C. At {ge} 750 C samples with {ge}0.41 mol% Bi{sub 2}O{sub 3} have very similar densification kinetics, whereas samples with {le}0.33 mol% begin to densify only after a period of hours at low temperatures. The effect of the sodium content was greatest at {approx}700 C for standard 0.56 mol% Bi{sub 2}O{sub 3} and was greater in samples with 0.30 mol% Bi{sub 2}O{sub 3} than for those with 0.56 mol%. Sintering experiments on samples of differing size and shape found that densification decreases and mass loss increases with increasing surface area to volume ratio. However, these two effects have different causes: the enhancement in densification as samples increase in size appears to be caused by a low oxygen internal atmosphere that develops whereas the mass loss is due to the evaporation of bismuth oxide. In situ XRD experiments showed that the bismuth is initially present as an oxycarbonate that transforms to metastable {beta}-Bi{sub 2}O{sub 3} by 400 C. At {approx}650 C, coincident with the onset of densification, the cubic binary phase, Bi{sub 38}ZnO{sub 58} forms and remains stable to >800 C, indicating that a eutectic liquid does not form during normal varistor sintering ({approx}730 C). Finally, the formation and morphology of bismuth oxide phase regions that form on the varistors surfaces during slow cooling were studied.

  3. Effect of sintering temperature on structural and electrical properties ...

    Indian Academy of Sciences (India)

    TECS

    energies decreased from 1⋅25–0⋅82 eV with increase in sintering temperature. Keywords. Ce0⋅9Gd0⋅1O1⋅95; IT–SOFC; XRD; SEM. 1. Introduction. Solid oxide fuel cells (SOFCs) are of two types based on their operating temperatures: high temperature SOFCs and low temperature or intermediate temperature SOFCs ( ...

  4. Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

    Science.gov (United States)

    Chen, Chang-hong; Feng, Ke-qin; Zhou, Yu; Zhou, Hong-ling

    2017-08-01

    Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060°C) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060°C. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000°C.

  5. Fast and low-temperature sintering of silver complex using oximes as a potential reducing agent for solution-processible, highly conductive electrodes

    Science.gov (United States)

    Yoo, Ji Hoon; Han, Dae Sang; Park, Su Bin; Chae, Jangwoo; Kim, Ji Man; Kwak, Jeonghun

    2014-11-01

    Highly conductive, solution-processed silver thin-films were obtained at a low sintering temperature of 100 °C in a short sintering time of 10 min by introducing oximes as a potential reductant for silver complex. The thermal properties and reducibility of three kinds of oximes, acetone oxime, 2-butanone oxime, and one dimethylglyoxime, were investigated as a reducing agent, and we found that the thermal decomposition product of oximes (ketones) accelerated the conversion of silver complex into highly conductive silver at low sintering temperature in a short time. Using the acetone oxime, the silver thin-film exhibited the lowest surface resistance (0.91 Ω sq-1) compared to those sing other oximes. The silver thin-film also showed a high reflectance of 97.8%, which is comparable to evaporated silver films. We also demonstrated inkjet printed silver patterns with the oxime-added silver complex inks.

  6. Fast and low-temperature sintering of silver complex using oximes as a potential reducing agent for solution-processible, highly conductive electrodes.

    Science.gov (United States)

    Yoo, Ji Hoon; Han, Dae Sang; Park, Su Bin; Chae, Jangwoo; Kim, Ji Man; Kwak, Jeonghun

    2014-11-21

    Highly conductive, solution-processed silver thin-films were obtained at a low sintering temperature of 100 °C in a short sintering time of 10 min by introducing oximes as a potential reductant for silver complex. The thermal properties and reducibility of three kinds of oximes, acetone oxime, 2-butanone oxime, and one dimethylglyoxime, were investigated as a reducing agent, and we found that the thermal decomposition product of oximes (ketones) accelerated the conversion of silver complex into highly conductive silver at low sintering temperature in a short time. Using the acetone oxime, the silver thin-film exhibited the lowest surface resistance (0.91 Ω sq(-1)) compared to those sing other oximes. The silver thin-film also showed a high reflectance of 97.8%, which is comparable to evaporated silver films. We also demonstrated inkjet printed silver patterns with the oxime-added silver complex inks.

  7. 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.

  8. Hydrothermal-Assisted Cold Sintering Process: A New Guidance for Low-Temperature Ceramic Sintering.

    Science.gov (United States)

    Guo, Hanzheng; Guo, Jing; Baker, Amanda; Randall, Clive A

    2016-08-17

    Sintering is a thermal treatment process that is generally applied to achieve dense bulk solids from particulate materials below the melting temperature. Conventional sintering of polycrystalline ceramics is prevalently performed at quite high temperatures, normally up to 1000 to 1200 °C for most ceramic materials, typically 50% to 75% of the melting temperatures. Here we present a new sintering route to achieve dense ceramics at extraordinarily low temperatures. This method is basically modified from the cold sintering process (CSP) we developed very recently by specifically incorporating the hydrothermal precursor solutions into the particles. BaTiO3 nano polycrystalline ceramics are exemplified for demonstration due to their technological importance and normally high processing temperature under conventional sintering routes. The presented technique could also be extended to a much broader range of material systems than previously demonstrated via a hydrothermal synthesis using water or volatile solutions. Such a methodology is of significant importance, because it provides a chemical roadmap for cost-effective inorganic processing that can enable broad practical applications.

  9. Coupling in-situ X-ray micro- and nano-tomography and discrete element method for investigating high temperature sintering of metal and ceramic powders

    Science.gov (United States)

    Yan, Zilin; Martin, Christophe L.; Bouvard, Didier; Jauffrès, David; Lhuissier, Pierre; Salvo, Luc; Olmos, Luis; Villanova, Julie; Guillon, Olivier

    2017-06-01

    The behaviour of various powder systems during high temperature sintering has been investigated by coupling X-ray microtomography and discrete element method (DEM). Both methods are particularly relevant to analyse particle interactions and porosity changes occurring during sintering. Two examples are presented. The first one deals with a copper powder including artificially created pores which sintering has been observed in situ at the European synchrotron and simulated by DEM. 3D images with a resolution of 1.5 μm have been taken at various times of the sintering cycle. The comparison of the real displacement of particle centers with the displacement derived from the mean field assumption demonstrates significant particle rearrangement in some regions of the sample. Although DEM simulation showed less rearrangement, it has been able to accurately predict the densification kinetics. The second example concerns multilayer ceramic capacitors (MLCCs) composed of hundreds of alternated metal electrode and ceramic dielectric layers. The observation of Ni-based MLCCs by synchrotron nanotomography at Argon National Laboratory with a spatial resolution between 10 and 50 nm allowed understanding the origin of heterogeneities formed in Ni layers during sintering. DEM simulations confirmed this analysis and provided clues for reducing these defects.

  10. Coupling in-situ X-ray micro- and nano-tomography and discrete element method for investigating high temperature sintering of metal and ceramic powders

    Directory of Open Access Journals (Sweden)

    Yan Zilin

    2017-01-01

    Full Text Available The behaviour of various powder systems during high temperature sintering has been investigated by coupling X-ray microtomography and discrete element method (DEM. Both methods are particularly relevant to analyse particle interactions and porosity changes occurring during sintering. Two examples are presented. The first one deals with a copper powder including artificially created pores which sintering has been observed in situ at the European synchrotron and simulated by DEM. 3D images with a resolution of 1.5 μm have been taken at various times of the sintering cycle. The comparison of the real displacement of particle centers with the displacement derived from the mean field assumption demonstrates significant particle rearrangement in some regions of the sample. Although DEM simulation showed less rearrangement, it has been able to accurately predict the densification kinetics. The second example concerns multilayer ceramic capacitors (MLCCs composed of hundreds of alternated metal electrode and ceramic dielectric layers. The observation of Ni-based MLCCs by synchrotron nanotomography at Argon National Laboratory with a spatial resolution between 10 and 50 nm allowed understanding the origin of heterogeneities formed in Ni layers during sintering. DEM simulations confirmed this analysis and provided clues for reducing these defects.

  11. [Determination of high temperature compressive strength and refractory degree of die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Kuang, X; Liao, Y; Chao, Y; Meng, Y

    1999-05-01

    The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the high temperature properties of the refractory die material compatible with slip casting core. To prepare three cylindrical specimens (phi 10 x 15 mm) and determine their compressive strength at 1000 degrees C: to make four specimens in flat-topped cone for determining the practical refractory degree by decreasing the pressing temperatures in a sequence of 1420, 1400, 1350 and 1100 degrees C. The compressive strength of this material was 17.8 MPa at 1000 degrees C. Its practical refractory degree was higher than 1100 degrees C. The high temperature properties of the refractory die material that we developed meet the demand of slip casting core of sintered powder.

  12. Low temperature sintering of fluorapatite glass-ceramics.

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. Effect of laser-induced temperature field on the characteristics of laser-sintered silver nanoparticle ink.

    Science.gov (United States)

    Lee, D G; Kim, D K; Moon, Y J; Moon, S-J

    2013-07-05

    Laser sintering of metal nanoparticles is a key technology for high-performance printed electronics fabricated on heat-sensitive substrates such as glass or plastic. Although laser-sintered electronic devices have been successfully fabricated, the role of the induced temperature field in the laser sintering process has not been reported thus far. In this work, the effect of temperature on the laser sintering process is described for the first time using a two-dimensional transient heat conduction equation for inkjet-printed silver nanoparticle ink. The in situ electrical resistance was measured to estimate the transient thermal conductivity and hence the temperature of the sintered ink during the laser sintering process. To verify the estimated laser sintering temperature, the morphology of furnace-sintered silver nanoparticle ink was compared with that of laser-sintered ink. The electrical characteristics and surface morphology of laser-sintered ink are found to be related to the process temperature.

  14. Mechanical Deformation of Sintered Porous Ag Die Attach at High Temperature and Its Size Effect for Wide-Bandgap Power Device Design

    Science.gov (United States)

    Chen, Chuantong; Nagao, Shijo; Zhang, Hao; Jiu, Jinting; Sugahara, Tohru; Suganuma, Katsuaki; Iwashige, Tomohito; Sugiura, Kazuhiko; Tsuruta, Kazuhiro

    2017-03-01

    The mechanical properties of sintered Ag paste with microporous structure have been investigated by tensile and shear tests, focusing on the temperature-dependent plastic deformation at various temperatures from 25°C to 300°C, corresponding to the target operating temperature range of emerging wide-bandgap semiconductor devices. Specimens were prepared by sintering hybrid Ag paste consisting of microflake and submicron spherical Ag particles, simulating a typical bonding process for power semiconductor die attach. Mechanical tests revealed that the unique microstructure caused a brittle-to-ductile transition at temperature of around 160°C, remarkably lower than that of bulk Ag. The obtained Young's modulus and shear modulus values indicate obvious softening with increasing temperature, together with a remarkable decrease in Poisson's ratio. These plastic behaviors at elevated temperature can be explained based on Coble creep in the microporous network structure. Fracture surfaces after tensile and shear tests indicated unique features on scanning electron microscopy, reflecting the variation in the ductile behavior with the test temperature. Furthermore, these temperature-dependent mechanical parameters were employed in three-dimensional finite-element analysis of the thermomechanical stress distribution in wide-bandgap semiconductor module structures including Ag paste die attach of different sizes. Detailed thermal stress analysis enabled precise evaluation of the packaging design for wide-bandgap semiconductor modules for use in high-temperature applications.

  15. Nanoporous gold synthesized by plasma-assisted inert gas condensation: room temperature sintering, nanoscale mechanical properties and stability against high energy electron irradiation

    Science.gov (United States)

    Weyrauch, S.; Wagner, C.; Suckfuell, C.; Lotnyk, A.; Knolle, W.; Gerlach, J. W.; Mayr, S. G.

    2018-02-01

    With a plasma assisted gas condensation system it is possible to achieve high-purity nanoporous Au (np-Au) structures with minimal contaminations and impurities. The structures consist of single Au-nanoparticles, which partially sintered together due to their high surface to volume ratio. Through electron microscopy investigations a porosity  >50% with ligament sizes between 20–30 nm was revealed. The elastic modulus of the np-Au was determined via peak force quantitative nanomechanical mapping and resulted in values of 7.5  ±  1.5 GPa. The presented structures partially sintered at room temperature, but proved to be stable to electron irradiation with energies of 7 MeV up to doses of 100 MGy. The electron irradiation stability opens the venue for electron assisted functionalization with biomolecules.

  16. 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.

  17. Foaming Glass Using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    Foam glass is a high added value product which contributes to waste recycling and energy efficiency through heat insulation. The foaming can be initiated by a chemical or physical process. Chemical foaming with aid of a foaming agent is the dominant industrial process. Physical foaming has two...... variations. One way is by saturation of glass melts with gas. The other involves sintering of powdered glass under a high gas pressure resulting in glass pellets with high pressure bubbles entrapped. Reheating the glass pellets above the glass transition temperature under ambient pressure allows the bubbles...

  18. Effects of sintering temperature on the density and porosity

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... perative. Hence the aim of this paper is to critically investi- gate the effects of sintering temperature on the density and porosity of salt bead preforms used in the liquid infiltration of aluminium for open cell foam manufac- turing. 2. Sintering Mechanism. Sintering occurs by atomic diffusion processes that.

  19. Effect of temperature on porosity of iron ore sinter with biochar derived from EFB

    Science.gov (United States)

    Purwanto, H.; Rozhan, A. N.; Zakiyuddin, A.; Mohamad, A. S.

    2018-01-01

    In this research, the replacement of fossil fuel energy (coke) with oil palm empty fruit bunch as a potential energy in sintering of iron ore was investigated. Carbon derived biomass has been produced by using oil palm empty fruit bunch by heat treatment process. In the present investigation, sintering process was carried out by heating the mixed iron ore and biochar at various temperatures. The apparent density and porosity for iron sinter show a significant increase and gradual decrement as the temperature increase, respectively. The porosity of iron sinter shows a gradual decrement from 950 °C to 1050 °C but up to 1150 °C it shows a significant decrement about 44%. Inferring to the micrograph, the agglomeration and assimilation of sinter at high temperature is better compared with low sintering temperature.

  20. All-inkjet-printed flexible electronics fabrication on a polymer substrate by low-temperature high-resolution selective laser sintering of metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Seung H [Department of Mechanical Engineering, University of California, 6177 Etcheverry Hall, Berkeley, CA 94720-1740 (United States); Pan Heng [Department of Mechanical Engineering, University of California, 6177 Etcheverry Hall, Berkeley, CA 94720-1740 (United States); Grigoropoulos, Costas P [Department of Mechanical Engineering, University of California, 6177 Etcheverry Hall, Berkeley, CA 94720-1740 (United States); Luscombe, Christine K [Department of Chemistry, University of California, Berkeley, CA 94720-1460 (United States); Frechet, Jean M J [Department of Chemistry, University of California, Berkeley, CA 94720-1460 (United States); Poulikakos, Dimos [Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, CH-8092 Zurich (Switzerland)

    2007-08-29

    All-printed electronics is the key technology to ultra-low-cost, large-area electronics. As a critical step in this direction, we demonstrate that laser sintering of inkjet-printed metal nanoparticles enables low-temperature metal deposition as well as high-resolution patterning to overcome the resolution limitation of the current inkjet direct writing processes. To demonstrate this process combined with the implementation of air-stable carboxylate-functionalized polythiophenes, high-resolution organic transistors were fabricated in ambient pressure and room temperature without utilizing any photolithographic steps or requiring a vacuum deposition process. Local thermal control of the laser sintering process could minimize the heat-affected zone and the thermal damage to the substrate and further enhance the resolution of the process. This local nanoparticle deposition and energy coupling enable an environmentally friendly and cost-effective process as well as a low-temperature manufacturing sequence to realize large-area, flexible electronics on polymer substrates.

  1. 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%.

  2. Numerical Simulation of Temperature Field in Selective Laser Sintering

    OpenAIRE

    Zhang, Jian; Li, Deying; Li, Jianyun; Zhao, Longzhi

    2010-01-01

    International audience; The laser sintering process of multi-component powder W/Cu is simulated by ANSYS software based on the factors of radiation, convection and thermal physical parameters on temperature. The laser power and scanning velocity which are the key process parameters to affect directly in sintering molding are studied in paper. The results show that when the scanning velocity is constant, the sintering depth is rising with the increase of laser power; In addition, when the lase...

  3. 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.

  4. Effects of sintering temperature on the density and porosity

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... Abstract. Effects of sintering temperature on the density and porosity of sodium chloride preforms for alu- minium foam manufacturing have been investigated. Cold pressed salt preforms were sintered at. 730Й, 760Й and 790Й and different times ranging between 6- 18 hours in a carbolite furnace at.

  5. Effects of Sintering Temperature on the Density And Porosity of ...

    African Journals Online (AJOL)

    Effects of sintering temperature on the density and porosity of sodium chloride preforms for alu- minium foam manufacturing have been investigated. Cold pressed salt preforms were sintered at 30, 760 and 790 and di erent times ranging between 6- 18 hours in a carbolite furnace at a heating rate of 5/minute. The Results of ...

  6. Bonding evolution with sintering temperature in low alloyed steels with chromium

    Directory of Open Access Journals (Sweden)

    Fuentes-Pacheco L.

    2009-01-01

    Full Text Available At present, high performance PM steels for automotive applications follow a processing route that comprises die compaction of water-atomized powder, followed by sintering and secondary treatments, and finishing operations. This study examines Cr-alloyed sintered steels with two level of alloying. In chromium-alloyed steels, the surface oxide on the powder is of critical importance for developing the bonding between the particles during sintering. Reduction of this oxide depends mainly on three factors: temperature, dew point of the atmosphere, and carbothermic reduction provided by the added graphite. The transformation of the initial surface oxide evolves sequence as temperature increases during sintering, depending on the oxide composition. Carbothermic reduction is supposed to be the controlling mechanism, even when sintering in hydrogen-containing atmospheres. The effect of carbothermic reduction can be monitored by investigating the behavior of the specimens under tensile testing, and studying the resultant fracture surfaces.

  7. Effect of Sintering Temperature on the Properties of Fused Silica Ceramics Prepared by Gelcasting

    Science.gov (United States)

    Wan, Wei; Huang, Chun-e.; Yang, Jian; Zeng, Jinzhen; Qiu, Tai

    2014-07-01

    Fused silica ceramics were fabricated by gelcasting, by use of a low-toxicity N' N-dimethylacrylamide gel system, and had excellent properties compared with those obtained by use of the low-toxicity 2-hydroxyethyl methacrylate and toxic acrylamide systems. The effect of sintering temperature on the microstructure, mechanical and dielectric properties, and thermal shock resistance of the fused silica ceramics was investigated. The results showed that sintering temperature has a critical effect. Use of an appropriate sintering temperature will promote densification and improve the strength, thermal shock resistance, and dielectric properties of fused silica ceramics. However, excessively high sintering temperature will greatly facilitate crystallization of amorphous silica and result in more cristobalite in the sample, which will cause deterioration of these properties. Fused silica ceramics sintered at 1275°C have the maximum flexural strength, as high as 81.32 MPa, but, simultaneously, a high coefficient of linear expansion (2.56 × 10-6/K at 800°C) and dramatically reduced residual flexural strength after thermal shock (600°C). Fused silica ceramics sintered at 1250°C have excellent properties, relatively high and similar flexural strength before (67.43 MPa) and after thermal shock (65.45 MPa), a dielectric constant of 3.34, and the lowest dielectric loss of 1.20 × 10-3 (at 1 MHz).

  8. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Science.gov (United States)

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  9. Monitoring of temperature profiles and surface morphologies during laser sintering of alumina ceramics

    Directory of Open Access Journals (Sweden)

    Bin Qian

    2014-06-01

    Full Text Available Additive manufacturing of alumina by laser is a delicate process and small changes of processing parameters might cause less controlled and understood consequences. The real-time monitoring of temperature profiles, spectrum profiles and surface morphologies were evaluated in off-axial set-up for controlling the laser sintering of alumina ceramics. The real-time spectrometer and pyrometer were used for rapid monitoring of the thermal stability during the laser sintering process. An active illumination imaging system successfully recorded the high temperature melt pool and surrounding area simultaneously. The captured images also showed how the defects form and progress during the laser sintering process. All of these real-time monitoring methods have shown a great potential for on-line quality control during laser sintering of ceramics.

  10. Effects of flux concentrations and sintering temperature on dental porcelain

    Science.gov (United States)

    Ghose, Polash; Gafur, Md. Abdul; Das, Sujan Kumar; Ranjan Chakraborty, Shyamal; Mohsin, Md.; Deb, Arun Kumar; Rakibul Qadir, Md.

    2014-02-01

    In this study, samples of dental porcelain bodies have been made by using the materials collected from selected deposits employing different mixing proportions of clay, quartz and feldspar. Dental porcelain ceramics have been successfully fabricated by using the sintering technique together with some Na2CO3 additive. The dental porcelain powder has been pressed into pellets at first and subsequently sintered at 700, 800, 900, 1000 and 1100 °C for 2 h. The physical and mechanical properties of the prepared samples have been investigated. The sintering behavior of the fired samples has been evaluated by bulk density, linear shrinkage, water absorption and apparent porosity measurements. This study includes the evaluation of the Vickers's microhardness by microhardness tester. Phase analysis and microstructural study have been performed by XRD and optical microscope respectively. Optical properties have been investigated using UV-visible spectroscopy. Influence of firing conditions on leucite formation, densification and microstructural development of the sintered samples has been investigated. It has been found that the choice of sintering temperature is one of the key factors in controlling leucite crystallization in dental porcelain ceramics. It has also been found that the flux concentration of material and the effect of temperature on preparation of dental porcelain contribute to the firing shrinkage and hardness, which has been found to increase with the increase of treatment temperature.

  11. Preparation and properties of low cement castable sintered at different temperatures

    Directory of Open Access Journals (Sweden)

    Sanja Martinović

    2009-12-01

    Full Text Available The low cement high alumina castable (LCC studied in this paper was synthesised, cured and then treated at different sintering temperatures. Since any inhomogeneity introduced during the castable preparation can remain inside the material degrading its properties and therefore the quality during service life, particular attention was given to the processing procedure in order to produce the material with the optimum characteristics. Composition of the castable regarding particle size distribution was adjusted according to the Andreassen’s packing model. The samples were sintered at 1100, 1300 and 1600°C for three hours. Influence of the different sintering temperatures on the castable properties is discussed. Compressive and flexural strengths were determined by destructive testing method, while the water immersion method was used for determination of the bulk density and the water absorption. Changes of elastic properties and microstructure (porosity were observed by the non-destructive testing methods, ultrasonic measurements and image analysis. Based on the results, it can be concluded that sintering temperature has strong influence on the properties of the LCC. Exceptionally good properties were obtained for the sample sintered at 1600°C, but it should be highlighted that the samples treated at 1100 and 1300°C were provided with good properties, too. This should not be neglected because of the energy saving importance, in cases where the material sintered at lower temperature satisfies the application requirements.

  12. Temperature-dependent thermal properties of spark plasma sintered alumina

    Directory of Open Access Journals (Sweden)

    Saheb Nouari

    2017-01-01

    Full Text Available In this work, we report temperature-dependent thermal properties of alumina powder and bulk alumina consolidated by spark plasma sintering method. The properties were measured between room temperature and 250ºC using a thermal constants analyzer. Alumina powder had very low thermal properties due to the presence of large pores and absence of bonding between its particles. Fully dense alumina with a relative density of 99.6 % was obtained at a sintering temperature of 1400°C and a holding time of 10 min. Thermal properties were found to mainly dependent on density. Thermal conductivity, thermal diffusivity, and specific heat of the fully dense alumina were 34.44 W/mK, 7.62 mm2s-1, and 1.22 J/gK, respectively, at room temperature. Thermal conductivity and thermal diffusivity decreased while specific heat increased with the increase in temperature from room temperature to 250ºC.

  13. 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.

  14. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  15. Low-Temperature Sintering Bonding Using Silver Nanoparticle Paste for Electronics Packaging

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2015-01-01

    Full Text Available Ag nanoparticles (NPs with about 40 nm diameter covered with 5–8 nm organic shell were prepared by chemical reduction reaction. The thermal characteristics of Ag nanoparticle (NP paste were measured by thermogravimetric analysis (TGA and differential scanning calorimetry (DSC. The low-temperature sintering bonding processes using Ag NP paste were carried out at the temperature range of 150–350°C for 5 min under the pressure of 3 MPa. The microstructures of the sintered joint and the fracture morphology were evaluated by scanning electron microscopy (SEM. The shear strength was used to evaluate the mechanical property of the sintered joint. TGA-DSC test showed that the Ag content is approximately 95.5 mass% in Ag NP paste. The average shear strength of the joint fabricated at 250°C for 5 min under the pressure of 3 MPa was about 28 MPa, which could meet the requirements of electronics packaging working at high temperature. The joint shear strength increased with the increase of the sintering temperature due to much denser sintered Ag NPs and more comprehensive metallurgical bonds formed in the joint.

  16. Room-Temperature and High-Temperature Tensile Mechanical Properties of TA15 Titanium Alloy and TiB Whisker-Reinforced TA15 Matrix Composites Fabricated by Vacuum Hot-Pressing Sintering.

    Science.gov (United States)

    Feng, Yangju; Zhang, Wencong; Zeng, Li; Cui, Guorong; Chen, Wenzhen

    2017-04-18

    In this paper, the microstructure, the room-temperature and high-temperature tensile mechanical properties of monolithic TA15 alloy and TiB whisker-reinforced TA15 titanium matrix composites (TiBw/TA15) fabricated by vacuum hot-pressing sintering were investigated. The microstructure results showed that there were no obvious differences in the microstructure between monolithic TA15 alloy and TiBw/TA15 composites, except whether or not the grain boundaries contained TiBw. After sintering, the matrix microstructure presented a typical Widmanstätten structure and the size of primary β grain was consistent with the size of spherical TA15 titanium metallic powders. This result demonstrated that TiBw was not the only factor limiting grain coarsening of the primary β grain. Moreover, the grain coarsening of α colonies was obvious, and high-angle grain boundaries (HAGBs) were distributed within the primary β grain. In addition, TiBw played an important role in the microstructure evolution. In the composites, TiBw were randomly distributed in the matrix and surrounded by a large number of low-angle grain boundaries (LAGBs). Globularization of α phase occurred prior, near the TiBw region, because TiBw provided the nucleation site for the equiaxed α phase. The room-temperature and high-temperature tensile results showed that TiBw distributed at the primary β grain boundaries can strengthen the grain boundary, but reduce the connectivity of the matrix. Therefore, compared to the monolithic TA15 alloy fabricated by the same process, the tensile strength of the composites increased, and the tensile elongation decreased. Moreover, with the addition of TiBw, the fracture mechanism was changed to a mixture of brittle fracture and ductile failure (composites) from ductile failure (monolithic TA15 alloy). The fracture surfaces of TiBw/TA15 composites were the grain boundaries of the primary β grain where the majority of TiB whiskers distributed, i.e., the surfaces of the

  17. Influence of Coke Ratio on the Sintering Behavior of High-Chromium Vanadium-Titanium Magnetite

    Directory of Open Access Journals (Sweden)

    Songtao Yang

    2017-06-01

    Full Text Available High-chromium vanadium and titanium magnetite (HCVTM sinter has poor properties. The coke ratio has an important effect on the behavior of HCVTM sintering as it affects the mineral phases in the high-chromium vanadium and titanium sinter (HCVTS via changing the sintering temperature and atmosphere. In this work, the sintering behavior of HCVTM mixed with varying coke ratios was investigated through sintering pot tests, X-ray diffraction (XRD, gas chromatographic analysis, and mineral phase analysis. The results show that, with the increase of the coke ratio from 4.0% to 6.0%, leading to the increase of the combustion ratio of the flue gas, the vertical sintering rate and sinter productivity decrease. Meanwhile, with the change of the coke ratio, the content of magnetite, silicate, and perovskite increase, while the hematite and calcium ferrite decrease. In addition, the tumble strength and reduction ability of HCVTS decrease, and its degradation strength increase. It was found that the appropriate coke ratio for the sintering process was 5.0 wt %.

  18. Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Jason Dale [Univ. of California, Berkeley, CA (United States)

    2007-01-01

    Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce0.9Gd0.1O1.95, and to evaluate whether they could be used to produce dense, constrained Ce0.9Gd0.1O1.95 films at temperatures below 1000 C. To find the optimal sintering aid, Ce0.9Gd0.1O1.95 was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li2O-Gd2O3-CeO2 liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.

  19. Record-low sintering-temperature (600 °C) of solid-oxide fuel cell electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Dasari, Hari Prasad, E-mail: energyhari@nitk.edu.in [High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Chemical Engineering Department, National Institute of Technology Karnataka, Mangalore 575025, Karnataka (India); Ahn, Kiyong; Park, Sun-Young; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Kim, Byung-Kook; Lee, Hae-Weon [High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Lee, Jong-Ho, E-mail: jongho@kist.re.kr [High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

    2016-07-05

    One of the major problems arising with Solid-Oxide Fuel Cell (SOFC) electrolyte is conventional sintering which requires a very high temperature (>1300 °C) to fully density the electrolyte material. In the present study, the sintering temperature of SOFC electrolyte is drastically decreased down to 600 °C. Combinational effects of particle size reduction, liquid-phase sintering mechanism and microwave sintering resulted in achieving full density in such a record-low sintering temperature. Gadolinium doped Ceria (GDC) nano-particles are synthesized by co-precipitation method, Lithium (Li), as an additional dopant, is used as liquid-phase sintering aid. Microwave sintering of this electrolyte material resulted in decreasing the sintering temperature to 600 °C. Micrographs obtained from Scanning/Transmission Electron Microscopy (SEM/TEM) clearly pointed a drastic growth in grain-size of Li-GDC sample (∼150 nm) than compared to GDC sample (<30 nm) showing the significance of Li addition. The sintered Li-GDC samples displayed an ionic conductivity of ∼1.00 × 10{sup −2} S cm{sup −1} at 600 °C in air and from the conductivity plots the activation energy is found to be 0.53 eV. - Highlights: • Sintering temperature is drastically decreased to 600 °C. • Key factors: Particle size reduction, liquid-phase and microwave sintering. • Nano-Li-GDC sample has ionic conductivity of ∼1.00 × 10{sup −2} S cm{sup −1} at 600 °C in air.

  20. Multilayer tape cast SOFC – Effect of anode sintering temperature

    DEFF Research Database (Denmark)

    Hauch, Anne; Birkl, Christoph; Brodersen, Karen

    2012-01-01

    be cost-efficient and simplify the half-cell manufacturing process. Fewer sintering steps (co-sintering), as well as fewer handling efforts, will be advantageous for up-scaled production. Previous reports have shown that our laboratory produces mechanically strong, high performing anode supported SOFC......Multilayer tape casting (MTC) is considered a promising, cost-efficient, up-scalable shaping process for production of planar anode supported solid oxide fuel cells (SOFC). Multilayer tape casting of the three layers comprising the half cell (anode support/active anode/electrolyte) can potentially...

  1. Fabrication mechanism of FeSe superconductors with high-energy ball milling aided sintering process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shengnan, E-mail: snzhang@c-nin.com [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China); Liu, Jixing [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China); School of Materials and Metallurgical, Northeast University, Shenyang, 110016 (China); Feng, Jianqing; Wang, Yao; Ma, Xiaobo; Li, Chengshan; Zhang, Pingxiang [Northwest Institute for Non-Ferrous Metal Research, 710016, Xi' an (China)

    2015-08-01

    FeSe Superconducting bulks with high content of superconducting PbO-type β-FeSe phase were prepared with high-energy ball milling (HEBM) aided sintering process. During this process, precursor powders with certain Fe/Se ratio were ball milled first then sintered. The influences of HEBM process as well as initial Fe/Se ratio on the phase evolution process were systematically discussed. With HEBM process and proper initial Fe/Se ratio, the formation of non-superconducting hexagonal δ-FeSe phase were effectively avoided. FeSe bulk with the critical temperature of 9.0 K was obtained through a simple one-step sintering process with lower sintering temperature. Meanwhile, the phase evolution mechanism of the HEBM precursor powders during sintering was deduced based on both the thermodynamic analysis and step-by-step sintering results. The key function of the HEBM process was to provide a high uniformity of chemical composition distribution, thus to successfully avoide the formation of intermediate product during sintering, including FeSe{sub 2} and Fe{sub 7}Se{sub 8}. Therefore, the fundamental principal for the synthesis of FeSe superconductors were concluded as: HEBM aided sintering process, with the sintering temperature of >635 °C and a slow cooling process. - Highlights: • A novel synthesis technique was developed for FeSe based superconductors. • FeSe bulks with high Tc and high β-FeSe phase content has been obtained. • Phase evolution process for the HEBM aided sintering process was proposed.

  2. Room-Temperature Chemical Welding and Sintering of Metallic Nanostructures by Capillary Condensation.

    Science.gov (United States)

    Yoon, Sung-Soo; Khang, Dahl-Young

    2016-06-08

    Room-temperature welding and sintering of metal nanostructures, nanoparticles and nanowires, by capillary condensation of chemical vapors have successfully been demonstrated. Nanoscale gaps or capillaries that are abundant in layers of metal nanostructures have been found to be the preferred sites for the condensation of chemically oxidizing vapor, H2O2 in this work. The partial dissolution and resolidification at such nanogaps completes the welding/sintering of metal nanostructures within ∼10 min at room-temperature, while other parts of nanostructures remain almost intact due to negligible amount of condensation on there. The welded networks of Ag nanowires have shown much improved performances, such as high electrical conductivity, mechanical flexibility, optical transparency, and chemical stability. Chemically sintered layers of metal nanoparticles, such as Ag, Cu, Fe, Ni, and Co, have also shown orders of magnitude increase in electrical conductivity and improved environmental stability, compared to nontreated ones. Pertinent mechanisms involved in the chemical welding/sintering process have been discussed. Room-temperature welding and sintering of metal nanostructures demonstrated here may find widespread application in diverse fields, such as displays, deformable electronics, wearable heaters, and so forth.

  3. Impact of sintering temperature on the structural, electrical, and optical properties of doped ZnO nanoparticle-based discs

    Science.gov (United States)

    Sendi, Rabab Khalid; Mahmud, Shahrom

    2012-11-01

    In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to make high-density ZnO discs doped with Bi2O3 and Mn2O3 via the conventional ceramic processing method. Different sintering temperatures were found to have significant impacts on the ZnO discs, especially on enhancing grain growth even at a low sintering temperature of only 980 °C. The strong solid-state reaction during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles that promoted a strong surface reaction even at low sintering temperatures. Moreover, the sintering process also improved the grain crystallinity, as shown in the lowering of the intrinsic compressive stress based on the X-ray diffraction lattice constant and full-wave half-maximum data. The sintering temperatures also significantly influenced the electrical properties of the doped ZnO discs with a marked drop in the breakdown voltage from 330 V (sample at 980 °C) to 80 V (sample at 1380 °C). The resistivity also experienced a dramatic drop from 304.4 kΩ cm (sample at 980 °C) to 98.86 kΩ cm (sample at 1380 °C). The observed shift in the energy band-gap from a higher to a lower value may be attributed to the conversion of compressive stress to tensile stress with increasing sintering temperature. The Raman spectra indicate that the sintering temperatures and dopants in the discs had significant effects on the E2(high) phonon mode and ZnO crystal structures. Therefore, the sintering process can be used as a new technique for controlling the breakdown voltage of doped ZnO discs made from ZnO nanoparticles with improved structural and optical properties.

  4. The impact of sintering temperature on structural, morphological and thermoelectric properties of zinc titanate nanocrystals

    Science.gov (United States)

    Chandrasekaran, P.; Murugu thiruvalluvan, T. M. V.; Arivanandhan, M.; Jayakumari, T.; Anandan, P.

    2017-07-01

    The effect of sintering temperature and Ti:Zn ratio of precursor solutions on the structural, morphological and thermoelectric properties of Zinc titanate (TZO) nanocrystals have been investigated. TZO nanocrystals were synthesized by changing the molar ratio of precursors of Zn and Ti sources by sol-gel method. The synthesized materials were sintered at different temperatures and the formation of multi phases of TZO were analysed by x-ray diffraction studies. The morphological properties and composition of TZO samples were studied by FESEM, TEM and XPS analysis. The thermoelectric properties of the TZO have been studied by measuring the Seebeck coefficient of the materials at various temperature. It was observed that the Seebeck coefficient of TZO sample increases with increasing Zn content in the sample especially at high temperature.

  5. Conductive inks with a "built-in" mechanism that enables sintering at room temperature.

    Science.gov (United States)

    Grouchko, Michael; Kamyshny, Alexander; Mihailescu, Cristina Florentina; Anghel, Dan Florin; Magdassi, Shlomo

    2011-04-26

    At present there is no metallic ink that enables formation of conductive patterns at room temperature by a single printing step. Printing conductive features by metallic nanoparticle-based inks must be followed by sintering while heating to elevated temperatures, thus preventing their utilization on most plastic substrates used in plastic electronics. In this report we present a new silver nanoparticle-based conductive ink, having a built-in sintering mechanism, which is triggered during drying of the printed pattern. The nanoparticles that are stabilized by a polymer undergo self-sintering spontaneously, due to the presence of a destabilizing agent, which comes into action only during drying of the printed pattern. The destabilizing agent, which contains Cl(-) ions, causes detachment of the anchoring groups of the stabilizer from the nanoparticles' surface and thus enables their coalescence and sintering. It was found that the new metallic ink leads to very high conductivities, by a single printing step: up to 41% of the conductivity of bulk silver was achieved, the highest reported conductivity of a printed pattern that is obtained from nanoparticles at room temperature.

  6. Microwave assisted sintering of gadolinium doped barium cerate electrolyte for intermediate temperature solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arumugam Senthil, E-mail: senthu.ramp@gmail.com [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Balaji, Ramamoorthy [Department of Physics, PSG College of Technology, Coimbatore, 641 004, Tamilnadu (India); Jayakumar, Srinivasalu [Department of Physics, PSG Institute of Technology and Applied Research, Coimbatore, 641 062, Tamilnadu (India); Pradeep, Chandran [Department of Physics, Indian Institute of Technology, Madras, 600 036, Tamilnadu (India)

    2016-10-01

    In Solid Oxide Fuel Cell (SOFC), electrolyte plays a vital role to increase the energy conversion efficiency. The main hurdle of such electrolyte in fuel cell is its higher operating temperature (1000 °C) which results in design limitation and higher fabrication cost. In order to reduce the operating temperature of SOFC, a suitable electrolyte has been prepared through co-precipitation method followed by microwave sintering of solid ceramic. The calcination temperature for the as-prepared powder was identified using Differential Scanning Calorimetry. The crystal structure of the sample was found to exhibit its orthorhombic perovskite structure. The particle size was determined using High-Resolution Transmission Electron Microscope with uniform in shape and size, match with XRD results and confirmed from structural analysis. Thus, the sample prepared via co-precipitation method and the solid ceramic sintered through microwave can be a promising electrolyte for fuel cells operated at intermediate temperature. - Highlights: • To synthesis the composite electrolyte by chemical method and sinter using microwave. • To reduce the operating temperature of electrolyte for high ionic conductivity in SOFC's. • To study the phase purity and to develop nanocomposite at reduced temperature.

  7. The effect of various sintering temperature on used refractory towards its physical properties

    Science.gov (United States)

    Sudibyo; Wulandari, Y. R.; Amin, M.; Azhar

    2018-01-01

    The used magnesia refractory from the kiln of cement industry was successfully recycled to new refractory using Kaolin as an adhesive. In this work, the temperatures of sintering were varied from 1000°C to 1500°C. The result shows that the increment temperature effects in sintering process will enhance refractory physical properties such as bulk density, cold crushing strength or pressure strength and thermal conductivity. Meanwhile, the porosity was decreased as the increase of the sintering temperature.

  8. Magnetic properties of sintered high energy sm-co and nd-fe-b magnets

    Directory of Open Access Journals (Sweden)

    Talijan Nadežda M.

    2006-01-01

    Full Text Available Magnetic properties of permanent magnetic materials based on intermetallic compounds of Sm-Co and Nd-Fe-B are in direct dependence on the microstructure. In the first part of this paper, having in mind the importance of the regime of sintering and heat treatment to obtain the optimal magnetic structure, yet another approach in defining the most adequate technological parameters of the sintering process for applied heat treatment conditions was made. The goal of these investigations was to use the correlation that exists between sintering conditions (temperature and time and intensity of the diffraction peak of the (111 plane of the SmCo5 phase to optimize. In the second part a brief overview of high energy magnetic materials based on Nd-Fe-B is presented with special emphasis to the current research and development of high remanent nanocomposite magnetic materials based on Nd-Fe-B alloys with a reduced Nd content. Part of experimental results gained during research of the sintering process of SmCo5 magnetic materials were realized and published earlier. The scientific meeting devoted to the 60th anniversary of Frankel’s theory of sintering was an opportunity to show once more the importance and role of sintering in optimization of the magnetic microstructure of sintered Sm Co5 magnetic materials.

  9. Liquid Phase Sintering of Highly Alloyed Stainless Steel

    DEFF Research Database (Denmark)

    Mathiesen, Troels

    1996-01-01

    of boride to AISI 316L type steels have previously been studied, but were found to be sensitive to intergranular corrosion due to formation of intermetallic phases rich in chromium and molybdenum. In order to improve this system further, new investigations have focused on the use of higher alloyed stainless......Liquid phase sintering of stainless steel is usually applied to improve corrosion resistance by obtaining a material without an open pore system. The dense structure normally also give a higher strength when compared to conventional sintered steel. Liquid phase sintrering based on addition...... steel as base material. The stainless base powders were added different amounts and types of boride and sintered in hydrogen at different temperatures and times in a laboratory furnace. During sintering the outlet gas was analyzed and subsequently related to the obtained microstructure. Thermodynamic...

  10. Formation and texture of Bi-2223 phase during sintering in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X.Y.; Nagata, A.; Watanabe, K.; Nojima, T.; Sugawara, K.; Hanada, S.; Kamada, S

    2003-10-15

    The formation and texture of Bi-2223 phase during sintering in high magnetic fields were investigated. Samples contained in silver crucibles were sintered at different temperatures from 835 to 860 deg. C for 120 h in a vertical tube furnace installed in a solenoid-type superconducting magnet. A vertical magnetic field, H{sub a} of 10 T can be applied parallel to the long axis of the furnace. It has been found that the mixed structures of the Bi-2223 and the Bi-2212 grains with their c-axis parallel to the magnetic field are formed in samples sintered at 850-855 deg. C in 10 T magnetic field. Below 845 deg. C sintering in 10 T, a high proportion of Bi-2223 phase is obtained, however no preferred orientation is observed. It is suggested that a liquid phase is important for the formation of the textured structure in magnetic fields.

  11. Recent advances of high-pressure generation in a multianvil apparatus using sintered diamond anvils

    Directory of Open Access Journals (Sweden)

    Shuangmeng Zhai

    2011-01-01

    Full Text Available The tried and tested multianvil apparatus has been widely used for high-pressure and high-temperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limitation of materials, the attainable multianvil pressure is generally limited to about 30 GPa (corresponding to about 900 km of the depth in the Earth when tungsten carbide cubes are adopted as second-stage anvils. Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6–8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube (14 mm is now available. Recently, maximum attainable pressures reaching higher than 90 GPa (corresponding to about 2700 km of the depth in the Earth have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolution of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed.

  12. Thermal Conductivity of Foam Glasses Prepared using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    The increasing focus on better building insulation is important to lower energy consumption. Development of new and improved insulation materials can contribute to solving this problem. Foam glass has a good insulating effect due to its large gas volume (porosity >90 %). It can be produced...... with open or closed pores. If only open pores exist, air is the dominating medium for the insulating effect. However, closed pores make it possible to trap gases inside the foam. The gas can be introduced either chemically, through foaming agents, or physically, by gas compression-decompression at high...... temperatures. By introducing the gas physically it is possible to control composition of both the gas phase and the solid phase of the foam glass. In this work we have prepared foam glasses by physical foaming. Panel glass powder from obsolete televisions was first sintered under a gas pressure of 5-25 MPa...

  13. Effect of sintering temperature on magnetization and Mössbauer parameters of cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Grish, E-mail: grishphysics@gmail.com [Department of Physics, DSB Campus Kumaun University, Nainital 263002, Uttarakhand (India); Srivastava, R.C. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India); Reddy, V.R. [UGC-DAE CSR, Khandwa Road, DAVV Campus, Indore 452017, Madhya Pradesh (India); Agrawal, H.M. [Department of Physics, GB Pant University of Agriculture and Technology, Pantnagar, Uttarakhand (India)

    2017-04-01

    Nanoparticles of cobalt ferrite of different particle size were prepared using sol-gel method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Mössbauer spectroscopy techniques were employed for characterization of nanoparticles for structural and magnetic properties. The particle size and saturation magnetization increase with the increase of sintering temperature. The saturation magnetization increases from 53 to 85 emu/g as the sintering temperature increases from 300 to 900 °C. The remanence increases while the coercivity decreases slightly with the increase of sintering temperature. Mössbauer spectra show the ferrimagnetic nature of all the samples and the cation distribution strictly depends on the sintering temperature. The stoichiometry of the cobalt ferrite formed was estimated to be (Co{sup 2+}{sub x}Fe{sup 3+}{sub 1−x})[Co{sup 2+}{sub 1−x}Fe{sup 3+}{sub 1+x}]O{sub 4}, based on our Mössbauer analysis. The inverse spinel structure gradually transforms towards the normal spinel structure as the sintering temperature increases. - Highlights: • After 500 °C sintering the cobalt ferrite shows complete crystallization. • An inversion sintering temperature between 900 °C and 1200 °C is proposed where the Fe{sup +3} again starts migration from B site to A site. • Sintering temperature is one of the prime factors which effect the magnetization and cation distribution between two sites A and B.

  14. Diffusion of silver during sintering in high permittivity COG dielectrics

    NARCIS (Netherlands)

    Mikkenie, R.; Groen, W.A.; Drift, R. van der

    2010-01-01

    To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to

  15. Flash light sintered copper precursor/nanoparticle pattern with high electrical conductivity and low porosity for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Wan-Ho; Hwang, Hyun-Jun [Department of Mechanical Convergence Engineering, Hanyang University, 17 Haendang-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, 17 Haendang-Dong, Seongdong-Gu, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-04-01

    In this work, the hybrid copper inks with precursor and nanoparticles were fabricated and sintered via flash light irradiation to achieve highly conductive electrode pattern with low porosity. The hybrid copper ink was made of copper nanoparticles and various copper precursors (e.g., copper(II) chloride, copper(II) nitrate trihydrate, copper(II) sulfate pentahydrate and copper(II) trifluoroacetylacetonate). The printed hybrid copper inks were sintered at room temperature and under ambient conditions using an in-house flash light sintering system. The effects of copper precursor weight fraction and the flash light irradiation conditions (light energy and pulse duration) were investigated. Surfaces of the sintered hybrid copper patterns were analyzed using a scanning electron microscope. Also, spectroscopic characterization techniques such as Fourier transform infrared spectroscopy and X-ray diffraction were used to investigate the crystal phases of the flash light sintered copper precursors. High conductivity hybrid copper patterns (27.3 μΩ cm), which is comparable to the resistivity of bulk copper (1.68 μΩ cm) were obtained through flash light sintering at room temperature and under ambient conditions. - Highlights: • The hybrid copper inks with precursor and nanoparticles were fabricated. • The hybrid copper ink was sintered via flash light irradiation. • The resistivity of sintered hybrid copper ink was 27.3 μΩ cm. • Highly conductive copper film with low porosity could be achieved.

  16. The effect of sintering temperature on the properties of metakaolin artificial lightweight aggregate

    Science.gov (United States)

    Risdanareni, Puput; Ekaputri, Januarti Jaya; Triwulan

    2017-09-01

    This paper describes the effect of sintering temperature on the properties of metakaolin artificial lightweight aggregate (ALWA). Three types of sintering temperature applied in this research are 900°C, 1000°C and 1100°C, whereas ALWA without sintering treatment is used as data control. Properties of metakaolin ALWA investigated in this research are specific gravity, water absorption, physical appearance, porosity and aggregate impact value. Standard test used in this research is ASTM, AFNOR and British Standart. Based on the research results, it can be concluded that sintering temperature is greatly affect on the properties of metakaolin ALWA. Increased sintering temperatures can lead to decreased values of specific gravity, increased pore amount, increased aggregate impact value, increased water absorption values and change aggregate color to be more bright. Referring to the test results, sintering temperature not exceeding 900°C is recommended, as it provides good physical and mechanical properties to ALWA metakaolin. Further research on applying different method of sintering temperature and investigating the microstructure of ALWA metakaolin should be accomplished in order to improve the characteristic of ALWA metakaolin.

  17. Investigation of the sintering rate of snow with high-resolution penetration tests

    Science.gov (United States)

    Peinke, Isabel; Hagenmuller, Pascal; Chambon, Guillaume; Roulle, Jacques; Morin, Samuel

    2017-04-01

    Sintering in snow is very active due to a high homologous temperature and has a major effect on the evolution of the snow mechanical properties. We investigated the sintering rate of snow using high-resolution penetration tests performed with the Snow Micro Penetrometer (SMP) in a cold room at -10°C. To this end, we prepared several samples by sieving rounded grain snow with different sieve sizes (0.8, 1 and 1.6 mm) and conducted numerous SMP tests at different times during the first day of sintering. The SMP was modified such that only the measuring tip was in contact to the snow and we mounted three different tips with diameters of 4, 5 and 8 mm. The increase of the measured mean penetration resistance is shown to follow a power law whose exponent is defined as the sintering rate. The sintering rate mean value is about 0.25, which is consistent with values reported in the literature and it increases with specific surface area and depth. However, the sintering rate diminishes when SMP tip size increases, which is counterintuitive for a material property. An advanced analysis is thus required to extract relevant material properties, as the deflection at rupture, individual rupture force of bonds, and spatial intensity of rupture events, out of the SMP signal. A Poisson shot noise model [Löwe and Herwijnen 2012] was used, in which a depth-dependence of the parameters was assumed. The individual rupture force follows a power law with exponents around 0.3 with almost no dependency on the tip size. In comparison, the time evolution of intensity and deflection at rupture were negligible. This approach exploits the high-resolution of the SMP to give new insights on the sintering mechanisms in snow.

  18. Preparation of Ultrahigh Potential Gradient of ZnO Varistors by Rare-Earth Doping and Low-Temperature Sintering

    Directory of Open Access Journals (Sweden)

    Lei Ke

    2013-01-01

    Full Text Available The effects of rare-earth doping and low-temperature sintering on electrical properties of ZnO varistors were investigated. The potential gradient (E1mA of the ZnO varistors increased significantly to 2247.2 V/mm after doping 0.08 mol% of Y2O3 and sintering at 800°C for 2 h. The notable decrease of the grain size with the given experimental conditions was the origin for the increase in E1mA. During the process of high-temperature sintering, both the oxygen at the grain boundary interface and the neutralisation of the ions on the depletion layer were directly reduced, which caused the weight loss and the internal derangement of double Schottky barriers.

  19. Nickel and Copper-Free Sintered Structural Steels Containing Mn, Cr, Si, and Mo Developed for High Performance Applications

    Directory of Open Access Journals (Sweden)

    Cias A.

    2017-03-01

    Full Text Available In an attempt to study the sinterability of potential high-strength nickel-free sintered structural steels containing Mn, Cr, Si and Mo compacts were prepared based on sponge and water atomised iron powders and on Astaloy prealloyed powders. To these were admixed ferromanganese, ferroslicon, and graphite. The samples were sintered at temperatures 1120 and 1250°C in laboratory tube furnaces in hydrogen, hydrogen-nitrogen atmospheres with dew points better than -60°C or in nitrogen in a semiclosed container in a local microatmosphere. After sintering the samples were slowly cooled or sinterhardened. Generally resultant microstructures were inhomogeneous, consisted of pearlite/ bainite/martensite, but were characterised by an absence of oxide networks. Sintering studies performed over a range of compositions have shown that superior strength, ranging beyond 900 MPa, along with reasonable tensile elongation, can be achieved with these new steels.

  20. Low-temperature sintering of silica-boric acid-doped willemite and microwave dielectric properties

    Science.gov (United States)

    Ando, Minato; Ohsato, Hitoshi; Igimi, Daisuke; Higashida, Yutaka; Kan, Akinori; Suzuki, Sadahiko; Yasufuku, Yoshitoyo; Kagomiya, Isao

    2015-10-01

    Millimeter-wave wireless communications in a high-level information society have been expanding in terms of high-density data transfer and radar for pre-crash safety systems. For these communications, millimeter-wave dielectrics have been expected for the development of substrates with high quality factor (Qf), low dielectric constant (ɛr), and near-zero temperature coefficient of resonance frequency (TCf). We have been studying several silicates such as forsterite, willemite, diopside, wollastonite, and cordierite/indialite glass ceramics. In this study, the synthesis of willemite and low-temperature-sintered willemite for low temperature co-fired ceramics (LTCC) is examined. The raw materials used for preparing slurries in doctor blade tape casting are also analyzed.

  1. Effects of sintering temperatures on microstructure and wear resistance of iron-silica composite

    Science.gov (United States)

    Amir, Adibah; Mamat, Othman

    2015-07-01

    Ceramic particle reinforced into metal base matrix composite has been reported to produce higher strength and wear resistance than its alloys because the ceramic phases can strongly resist abrasion. In this study the iron matrix was reinforced with two compositions of 20 and 25 wt. % fine silica particles. The compacts were produced by using powder metallurgy fabrication technique and sintered at three sintering temperatures: 1000, 1100 and 1200°C. Effects of various sintering temperatures on microstructures and the composite's wear resistance were evaluated via optical and SEM microscopy. Both compositions were also subjected to ball-on-disk wear test. The results showed the reinforcement weight fraction of 20 wt.% of silica and sintering temperature at 1100°C exhibited better result, in all aspects. It possessed higher mechanical properties, it's microstructure revealed most intact reinforcing region and it displayed higher wear resistance during wear test.

  2. Tribological Behavior of Spark Plasma Sintered Aluminum-Graphene Composites at Room and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Sara Rengifo

    2017-01-01

    Full Text Available This study examines the role of Graphene nanoplatelets (GNPs as a solid lubricant additive to aluminum. Pure Al and Al-2 vol % GNP pellets are sintered by Spark Plasma Sintering (SPS. Their tribological properties are evaluated by a ball-on-disk tribometer at room temperature (RT and high temperature (200 °C. Al-2 vol % GNP composite displayed poor densification (91% and low hardness, resulting in poor wear resistance as compared to pure Al. However GNP addition resulted in a lower coefficient of friction (COF as compared to pure aluminum at both temperatures. The results demonstrated that GNPs contribute to reducing COF by forming a protective tribolayer. GNPs also play a unique role in reducing oxygen ingress at 200 °C. It is concluded that the packing density of a starting powder blend of Al-GNP needs to be improved by using irregular shaped aluminum powder mixed with both larger and smaller GNPs. This would result in greater densification and improve wear rate while maintaining low COF.

  3. The effect of sintering temperature on the structure and properties of corundum/mullite ceramics

    Directory of Open Access Journals (Sweden)

    Yu-Ming T.

    2015-01-01

    Full Text Available In this work, samples are prepared by adding secondary raw bauxite and some suitable amount pure silica. After dry pressing molding, using solid phase sintering method sinter them at 1380ºC,1410ºC,1440ºC,1410ºC,1500ºC,1530ºC, respectively. A performance of the material is characterized by using SEM and XRD, such as microscopic morphology, phase composition and the compressive strength, etc. Combining results of experiments, explore the mechanism of sintering temperature on the properties of ceramic materials.

  4. Effect of sintering temperature and heating mode on consolidation of ...

    Indian Academy of Sciences (India)

    Densification behaviour, phase transformation, microstructural evolution and hardness values of microwave sintered Al–7Zn–2·5Mg–1Cu ... study investigates densification behaviour, phase transfor- mation, microstructure development ... testing, flat dog-bone shaped specimens were prepared as per. MPIF specification 10.

  5. Effect of sintering temperature and time on the mechanical ...

    Indian Academy of Sciences (India)

    In the present study, Co–Cr–Mo/58S bioglass porous nano-composite samples were successfully produced using 30 wt% carbonate hydrogen ammonium and polyvinyl alcohol solution as space holder and binder, respectively. The cold compacted samples were heated at 175°C for 2 h and then were heated to sinter at ...

  6. Effect of Sintering Temperature on the Properties of Aluminium-Aluminium Oxide Composite Materials

    Directory of Open Access Journals (Sweden)

    Dewan Muhammad Nuruzzaman

    2016-12-01

    Full Text Available In this study, aluminium-aluminium oxide (Al-Al2O3 metal matrix composites of different weight percentage reinforcements of aluminium oxide were processed at different sintering temperatures. In order to prepare these composite specimens, conventional powder metallurgy (PM method was used. Three types specimens of different compositions such as 95%Al+5%Al2O3, 90%Al+10%Al2O3 and 85%Al+15%Al2O3 were prepared under 20 Ton compaction load. Then, all the specimens were sintered in a furnace at two different temperatures 550oC and 580oC. In each sintering process, two different heating cycles were used. After the sintering process, it was observed that undistorted flat specimens were successfully prepared for all the compositions. The effects of sintering temperature and weight fraction of aluminium oxide particulates on the density, hardness and microstructure of Al-Al2O3 composites were observed. It was found that density and hardness of the composite specimens were significantly influenced by sintering temperature and percentage aluminium oxide reinforcement. Furthermore, optical microscopy revealed that almost uniform distribution of aluminium oxide reinforcement within the aluminium matrix was achieved.

  7. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    Ultra high molecular weight polyethylene (UHMWPE) is a high performance polymer having low coefficient of friction, good abrasion resistance, good chemical resistance etc. It is used in shipbuilding, textile industries and also in biomedical applications. UHMWPE is processed by powder processing technique because of ...

  8. Effect of High Speed Sintering on the Properties of Zirconia Oxide Materials

    Science.gov (United States)

    2018-03-22

    12. REPORT TYPE 22/03/2018 Poster 4. TITLE AND SUBTITLE Effect of High-Speed Sintering on the Properties ofZirconia-Oxide Materials 6. AUTHOR(S...zirconia materials typically requires several hours of sintering. A new sintering furnace is available that reportedly sinters zirconia in...zirconia were also compared to a lithium- disilicate material , IPS e.max CAD (lvoclar Vivadent). IPS e.max CAD beams were crystallized in the CEREC

  9. Formation and texture of Bi-2223 phase during sintering in a temperature gradient

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X.Y.; Nagata, A.; Watanabe, K.; Nojima, T.; Sugawara, K.; Hanada, S.; Kamada, S

    2004-10-01

    The formation and texture of Bi-2223 phase during sintering in a temperature gradient were investigated. Co-precipitated powders with the composition of Bi:Pb:Sr:Ca:Cu=1.85:0.35:1.90:2.05:3.05 were used. Samples set on a silver holder were sintered at 850 deg. C for 120 h in a vertical tube furnace with a temperature gradient of 15 deg. C/cm installed in a solenoid-type superconducting magnet. A vertical magnetic field can be applied parallel to the long axis of the furnace. It has been found that the Bi-2223 grains with their c-axis parallel to the axial direction of the vertical tube furnace are formed not only on the surface, but also in the center of the sample sintered at 850 deg. C for 120 h in 15 deg. C/cm temperature gradient without magnetic field. Moreover, the sample sintered in the temperature gradient and in a 10 T magnetic field have a stronger c-axis alignment of Bi-2223 phase. It is suggested that both the temperature gradient and magnetic field during sintering are favorable for the c-axis alignment of Bi-2223 phase.

  10. An additive approach to low temperature zero pressure sintering of bismuth antimony telluride thermoelectric materials

    Science.gov (United States)

    Catlin, Glenn C.; Tripathi, Rajesh; Nunes, Geoffrey; Lynch, Philip B.; Jones, Howard D.; Schmitt, Devin C.

    2017-03-01

    This paper presents an additive-based approach to the formulation of thermoelectric materials suitable for screen printing. Such printing processes are a likely route to such thermoelectric applications as micro-generators for wireless sensor networks and medical devices, but require the development of materials that can be sintered at ambient pressure and low temperatures. Using a rapid screening process, we identify the eutectic combination of antimony and tellurium as an additive for bismuth-antimony-telluride that enables good thermoelectric performance without a high pressure step. An optimized composite of 15 weight percent Sb7.5Te92.5 in Bi0.5Sb1.5Te3 is scaled up and formulated into a screen-printable paste. Samples fabricated from this paste achieve a thermoelectric figure of merit (ZT) of 0.74 using a maximum processing temperature of 748 K and a total thermal processing budget of 12 K-hours.

  11. Cu ion ink for a flexible substrate and highly conductive patterning by intensive pulsed light sintering.

    Science.gov (United States)

    Wang, Byung-Yong; Yoo, Tae-Hee; Song, Yong-Won; Lim, Dae-Soon; Oh, Young-Jei

    2013-05-22

    Direct printing techniques that utilize nanoparticles to mitigate environmental pollution and reduce the processing time of the routing and formation of electrodes have received much attention lately. In particular, copper (Cu) nanoink using Cu nanoparticles offers high conductivity and can be prepared at low cost. However, it is difficult to produce homogeneous nanoparticles and ensure good dispersion within the ink. Moreover, Cu particles require a sintering process over an extended time at a high temperature due to high melting temperature of Cu. During this process, the nanoparticles oxidize quickly in air. To address these problems, the authors developed a Cu ion ink that is free of Cu particles or any other impurities. It consequently does not require separate dispersion stability. In addition, the developed ink is environmentally friendly and can be sintered even at low temperatures. The Cu ion ink was sintered on a flexible substrate using intense pulsed light (IPL), which facilitates large-area, high-speed calcination at room temperature and at atmospheric pressures. As the applied light energy increases, the Cu2O phase diminishes, leaving only the Cu phase. This is attributed to the influence of formic acid (HCOOH) on the Cu ion ink. Only the Cu phase was observed above 40 J cm(-2). The Cu-patterned film after sintering showed outstanding electrical resistivity in a range of 3.21-5.27 μΩ·cm at an IPL energy of 40-60 J cm(-2). A spiral-type micropattern with a line width of 160 μm on a PI substrate was formed without line bulges or coffee ring effects. The electrical resistivity was 5.27 μΩ·cm at an energy level of 40.6 J cm(-2).

  12. Large-Scale Synthesis of Silver Nanoparticles by Aqueous Reduction for Low-Temperature Sintering Bonding

    Directory of Open Access Journals (Sweden)

    Qiu Xiliang

    2014-01-01

    Full Text Available Silver nanoparticles with average diameter of 22.4 nm were prepared by aqueous reduction method for low-temperature sintering bonding application. The reaction temperature and PVP concentration, which are the influential factors of nanoparticle characteristics, were investigated during reduction process. In our research, monodispersity of nanoparticles was remarkably improved while unfavorable agglomeration was avoided with the AgNO3/PVP mass ratio of 1 : 4 at the reaction temperature 30°C. Besides, copper pads were successfully bonded using sintering paste employing fresh silver nanoparticles with diameter of 20~35 nm at 200°C. In addition, after morphology of the bonding joint was analysed by scanning electron microscope (SEM, the porous sintering characteristics were confirmed.

  13. Magnesia-zircon brick: Evolution of microstructure, properties and performance with increasing sintering temperature

    Directory of Open Access Journals (Sweden)

    Gao J.

    2013-01-01

    Full Text Available Depending on phase components and densification, Magnesia-Zircon brick varies in appearance from white to veined and then brown with increasing sintering temperature. Properties including bulk density, apparent porosity and hot modulus of rupture as well as performance embodied with creep resistance and refractoriness continue to improve with sustaining enhancement of sintering temperature. Exceptionally, cold crushing strength first increases then decreases with rising sintering temperature and a peak exists at 1550oC. Microstructural evolution suffers zircon decomposition companying by silica escape, forsterite formation, matrix solidification and zirconia coagulation, until a zirconia/forsterite composites belt tightly coating on magnesia aggregates. Excessive coagulation of zirconia caused by oversintering probably results in microcracks formation and defects enlargement thereby degrades cold crushing strength.

  14. Room temperature sintering of printer silver nanoparticle conductive ink

    Science.gov (United States)

    Corsino, Dianne C.; Balela, Mary Donnabelle L.

    2017-11-01

    Future electronics devices are not only smaller and thinner, but are also flexible, bendable and even wearable. This evolution in technology requires direct printing of patterns onto any substrate using conductive inks made of a dispersion of metallic nanoparticles. In this study, Cl- ions was used to induce spontaneous sintering of silver nanoparticles (Ag NPs). Ag NPs with an average diameter of 56 nm were synthesized by polyol method using silver nitrate (AgNO3) and ethylene glycol (EG) as precursor and solvent, respectively. Poly(vinyl pyrrolidone) was used as the capping agent. Water-based inks were formulated containing different Ag NP loading (10–25 wt %). Using 50 mM NaCl aqueous solution as the dispersing medium, an ink with 15 wt % Ag exhibited a sheet resistance of about 2.85 Ω/sq. This very low sheet resistance was attributed to sintering of Ag NPs, which was accompanied by an increase in average diameter of nanoparticles from 56 to 569 nm.

  15. Physico-chemical and environmental controls on siliceous sinter formation at the high-altitude El Tatio geothermal field, Chile

    Science.gov (United States)

    Nicolau, Constanza; Reich, Martin; Lynne, Bridget

    2014-08-01

    El Tatio geothermal field is located 4270 m above sea level in the Altiplano, northern Chile. Siliceous sinter deposits from El Tatio were studied to understand the influence of water chemistry and the extreme climatic conditions on their textures and mineralogy. The results of this study show that the mineralogy of El Tatio sinters include of opal-A and accessory minerals, such as halite, gypsum and cahnite (Ca4B2As2O12•4H2O), which precipitate by full evaporation of high arsenic, boron and calcium thermal waters. El Tatio sinters show a high degree of structural disorder, probably linked to cation incorporation into the silica structure and/or the occurrence of micro- to nano-scale accessory minerals. The high content of cations in the thermal waters is strongly tied to relatively high silica precipitation rates considering silica concentration in water (147-285 mg/l SiO2). Precipitation rate reach 2.5 kg/m2 per year based on in situ precipitation experiments. The particular environmental conditions of this high-altitude geothermal area that produce high water cooling rate and high evaporation rate, may also be responsible for the fast silica precipitation. Low environmental temperatures create freezing-related sinter textures (i.e., silica platelets and micro columns/ridges). Silicified microbial filaments are also characteristic of El Tatio sinters, and they are indicative of water temperature and hydrodynamic conditions at the moment of sinter formation. However, sinter textural interpretation in a high-altitude Andean context must be done carefully as specific relationships between microbial and hydrodynamic textures are found.

  16. Computer simulation of low-temperature composites sintering processes for additive technologies

    Science.gov (United States)

    Tovpinets, A. O.; Leytsin, V. N.; Dmitrieva, M. A.

    2017-12-01

    This is impact research of mixture raw components characteristics on the low-temperature composites structure formation during the sintering process. The obtained results showed that the structure determination of initial compacts obtained after thermal destruction of the polymer binder lets quantify the concentrations of main components and the refractory crystalline product of thermal destruction. Accounting for the distribution of thermal destruction refractory product allows us to refine the forecast of thermal stresses in the matrix of sintered composite. The presented results can be considered as a basis for optimization of initial compositions of multilayer low-temperature composites obtained by additive technologies.

  17. Solution combustion synthesis: Effect of calcination and sintering temperature on structural, dielectric and ferroelectric properties of five layer Aurivillius oxides

    Science.gov (United States)

    Dubey, Shivangi; Subohi, Oroosa; Kurchania, Rajnish

    2017-09-01

    The effect of calcination temperature on phase formation and sintering temperature on structural, dielectric, electrical and ferroelectric properties of Ba2Bi4Ti5O18 (BBT), Pb2Bi4Ti5O18 (PBT) and Sr2Bi4Ti5O18 (SBT) ceramics prepared by solution combustion route using glycine as a fuel are investigated in this paper. Calcination temperature was optimized at 650 °C for BBT and 750 °C for SBT and PBT, at which these compounds showed pure phase formation. It was observed that density and grain size of the sintered pellets increases with increasing sintering temperature. The dielectric constant was found to be dependent on grain size and density. Transition temperature, activation energy and remnant polarization were found to increase with an increase in sintering temperature. Porosity and conductivity decreases with an increase in the sintering temperature. Thus improving the dielectric, electrical and ferroelectric properties of five layered Aurivillius oxides.

  18. Improvement of the electrochromic response of a low-temperature sintered dye-modified porous electrode using low-resistivity indium tin oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Yuichi, E-mail: yuichi.watanabe@aist.go.jp; Suemori, Kouji; Hoshino, Satoshi [Flexible Electronics Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)

    2016-06-15

    An indium tin oxide (ITO) nanoparticle-based porous electrode sintered at low temperatures was investigated as a transparent electrode for electrochromic displays (ECDs). The electrochromic (EC) response of the dye-modified ITO porous electrode sintered at 150 °C, which exhibited a generally low resistivity, was markedly superior to that of a conventional dye-modified TiO{sub 2} porous electrode sintered at the same temperature. Moreover, the EC characteristics of the dye-modified ITO porous electrode sintered at 150 °C were better than those of the high-temperature (450 °C) sintered conventional dye-modified TiO{sub 2} porous electrode. These improvements in the EC characteristics of the dye-modified ITO porous electrode are attributed to its lower resistivity than that of the TiO{sub 2} porous electrodes. In addition to its sufficiently low resistivity attained under the sintering conditions required for flexible ECD applications, the ITO porous film had superior visible-light transparency and dye adsorption capabilities. We conclude that the process temperature, resistivity, optical transmittance, and dye adsorption capability of the ITO porous electrode make it a promising transparent porous electrode for flexible ECD applications.

  19. Highly conductive copper nano/microparticles ink via flash light sintering for printed electronics.

    Science.gov (United States)

    Joo, Sung-Jun; Hwang, Hyun-Jun; Kim, Hak-Sung

    2014-07-04

    In this study, the size effect of copper particles on the flash light sintering of copper (Cu) ink was investigated using Cu nanoparticles (20-50 nm diameter) and microparticles (2 μm diameter). Also, the mixed Cu nano-/micro-inks were fabricated, and the synergetic effects between the Cu nano-ink and micro-ink on flash light sintering were assessed. The ratio of nanoparticles to microparticles in Cu ink and the several flash light irradiation conditions (irradiation energy density, pulse number, on-time, and off-time) were optimized to obtain high conductivity of Cu films. In order to precisely monitor the milliseconds-long flash light sintering process, in situ monitoring of electrical resistance and temperature changes of Cu films was conducted during the flash light irradiation using a real-time Wheatstone bridge electrical circuit, thermocouple-based circuit, and a high-rate data acquisition system. Also, several microscopic and spectroscopic characterization techniques such as scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the flash light sintered Cu nano-/micro-films. In addition, the sheet resistance of Cu film was measured using a four-point probe method. This work revealed that the optimal ratio of nanoparticles to microparticles is 50:50 wt%, and the optimally fabricated and flash light sintered Cu nano-/micro-ink films have the lowest resistivity (80 μΩ cm) among nano-ink, micro-ink, or nano-micro mixed films.

  20. Sintering Temperature and Deposition Orientation Effects on Mechanical, PhysicalProperties and Geometric Distortion of Cu–Ni Single and Multi Material Indirect Sintering Products

    Directory of Open Access Journals (Sweden)

    EkoSutarto

    2012-08-01

    Full Text Available Development of multi material mechanical parts is constantly undertaken to increase functional aspectsas well as life cycle.One example is the use of bimaterial which is widely used as a temperature contactor. This paper presents mechanical, physical properties and geometric distortion of Cu-Ni indirect sintering products used to develop Cu-Ni bimaterial products. The experiment was executed with the following method: firstly, Cu and/or Ni powders were deposited into cast iron powder as the supporting powder. Secondly, it was heated in a furnace with varying temperatures of 870C, 900C and 930C with a holding time of four hours. Lastly, deposition orientation was varied to observe the effect on the occurence of shrinkage.To initiate the multi materials sintering process, single material sintering was performed to observe the physical and mechanical properties. Based onprevious work, multi material sintering of Cu and Ni powders was conducted. The experiment results showed that the geometric distortion of the sintering products was influenced by deposition orientation. The Cu and Ni products shrinkage were 49% and 35.33%, respectively. Although the melting temperature of Cu and Ni is close, the binding mechanism of the sintered product did not occur. The significant difference of shrinkage levelswas the main factor for the binding mechanism failure between Cu and Ni materials.

  1. Microstructure characteristics of high borated stainless steel fabricated by hot-pressing sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Xuan; Wang, Mingjia, E-mail: mingjiawangysu@126.com; Zhao, Hongchang

    2016-04-25

    The present study investigated the microstructure of powder metallurgy (P/M) high borated stainless steel through hot-pressing sintering in a temperature range of 1000–1150 °C within 30 min under 30 MPa. Microstructure and phase examinations were carried out by applying scanning electron microscope, electron backscatter diffraction and X-ray diffraction analysis. The results of as-atomized powders demonstrated that many powders kept egg-type structure with an austenite outer layer and the eutectic borides were much finer than those in traditional cast products. Microstructure studies revealed that borides suffered Ostwald ripening and were significantly influenced by the sintering temperature. Orientation maps indicated that the inter-particle contact areas consisted of equiaxed grains and the regions consisting of large elongated grains partly inherited the microstructure characteristics of as-atomized powder particles. Furthermore, the mechanisms governing the morphological changes in microstructure were discussed. - Highlights: • Near-complete densification could be obtained through hot-pressing sintering. • There was no phase transformation and present phases were M{sub 2}B and austenite. • Borides suffered Ostwald ripening and were significantly influenced by temperature. • Inter-particle contact areas consisted of equiaxed grains for recrystallization. • Deformation-free zones exhibited elongated grains for dendritic arms coarsening.

  2. 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

    A rapid method for the synthesis of Ca3Co4O9+δpowder is introduced. The procedure is a modification of the conventional citric-nitrate sol–gelmethod where an auto-combustion process is initiated by a controlled thermal oxidation–reduction reaction. The resulting powders inherit theadvantages...... 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...

  3. Effect of Sintering Temperature and Applied Load on Anode-Supported Electrodes for SOFC Application

    Directory of Open Access Journals (Sweden)

    Xuan-Vien Nguyen

    2016-08-01

    Full Text Available Anode-supported cells are prepared by a sequence of hot pressing and co-sintering processes for solid oxide fuel cell (SOFC applications. Commercially available porous anode tape (NiO/YSZ = 50 wt %/50 wt %, anode tape (NiO/YSZ = 30 wt %/70 wt %, and YSZ are used as the anode substrate, anode functional layer, and electrolyte layer, respectively. After hot pressing, the stacked layers are then sintered at different temperatures (1250 °C, 1350 °C, 1400 °C and 1450 °C for 5 h in air. Different compressive loads are applied during the sintering process. An (La,SrMnO3 (LSM paste is coated on the post-sintered anode-supported electrolyte surface as the cathode, and sintered at different temperatures (1100 °C, 1150 °C, 1200 °C and 1250 °C for 2 h in air to generate anode-supported cells with dimensions of 60 × 60 mm2 (active reaction area of 50 × 50 mm2. SEM is used to investigate the anode structure of the anode-supported cells. In addition, confocal laser scanning microscopy is used to investigate the roughness of the cathode surfaces. At sintering temperatures of 1400 °C and 1450 °C, there is significant grain growth in the anode. Furthermore, the surface of the cathode is smoother at a firing temperature of 1200 °C. It is also found that the optimal compressive load of 1742 Pa led to a flatness of 168 µm/6 cm and a deformation of 0.72%. The open circuit voltage and power density of the anode-supported cell at 750 °C were 1.0 V and 178 mW·cm−2, respectively.

  4. Low temperature sintering of MgCuZn ferrite and its electrical and ...

    Indian Academy of Sciences (India)

    cm was obtained for the ferrite with 12 mol% Cu at relatively low sintering temperature (910°C). The magnetic properties of the ferrites also improved by the Cu substitution. The chip inductors made of the ferrite fired at 910 C with 12 mol% Cu ...

  5. Sintering temperature and atmosphere modulated evolution of structure and luminescence of 2CaO-P2O5-B2O3

    DEFF Research Database (Denmark)

    Zhu, C. F.; Wang, J.; Ren, X. R.

    2014-01-01

    Europium doped 2CaO-P2O5-B2O3 phosphors prepared via high temperature solid state reactions are reported. The evolution of luminescence and structure of the phosphors induced by variation of sintering temperature and atmosphere is investigated using photoluminescence spectra and X-ray diffraction...

  6. Effect of sintering temperature on the optical properties of BiFeO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Jalandhara, Devender, E-mail: devj713@gmail.com; Singh, Gurdhir; Yadav, Kamlesh, E-mail: kamlesh.yadav001@gmail.com [Centre for Physical Sciences, Central University of Punjab, Bathinda-151001 (India)

    2016-05-06

    BiFeO{sub 3} is a multiferroic material which exhibits excellent optical properties. BiFeO{sub 3} nanoparticles are synthesized by using sol-gel method. The prepared samples are sintered at 500°C, 600°C, 700°C, 800°C and 850°C. In this paper, the effect of sintering temperature on the optical properties in BiFeO{sub 3} nanoparticles is studied. Field emission electron microscopy (FESEM) images show that particles are nearly spherical in shape. It is found that the particles size increases from 37 nm to 51 nm with increasing the sintering temperature. FESEM images also reveal a homogenous size distribution of nanoparticles. All the functional groups are indexed in the Fourier transform infrared spectroscopy (FTIR) spectra. It is found that Fe-O stretching peaks are appeared in the wave number range 447 and 507 cm{sup −1}. The value of energy band gap are found 2.14, 2.26, 2.30, 2.36, and 2.54 eV for the samples sintered at 500°C, 600°C, 700°C, 800°C and 850°C respectively. Thus, the increase in band gap with increasing temperature has been observed. The present samples can be used as photo-catalyst, in non-volatile memories and to make spintronics devices.

  7. High resolution laser micro sintering / melting using q-switched and high brilliant laser radiation

    Science.gov (United States)

    Exner, H.; Streek, A.

    2015-03-01

    Since the discovery of selective laser sintering/melting, numerous modifications have been made to upgrade or customize this technology for industrial purposes. Laser micro sintering (LMS) is one of those modifications: Powders with particles in the range of a few micrometers are used to obtain products with highly resolved structures. Pulses of a q-switched laser had been considered necessary in order to generate sinter layers from the micrometer scaled metal powders. LMS has been applied with powders from metals as well as from ceramic and cermet feedstock's to generate micro parts. Recent technological progress and the application of high brilliant continuous laser radiation have now allowed an efficient laser sintering/melting of micrometer scaled metal powders. Thereby it is remarkable that thin sinter layers are generated using high continuous laser power. The principles of the process, the state of the art in LMS concerning its advantages and limitations and furthermore the latest results of the recent development of this technology will be presented. Laser Micro Sintering / Laser Micro Melting (LMM) offer a vision for a new dimension of additive fabrication of miniature and precise parts also with application potential in all engineering fields.

  8. Green Compact Temperature Evolution during Current-Activated Tip-Based Sintering (CATS of Nickel

    Directory of Open Access Journals (Sweden)

    Khaled Morsi

    2013-04-01

    Full Text Available Current-activated tip-based sintering (CATS is a novel process where spark plasma sintering conditions are applied through an electrically conducting tip on a locally controlled area on a green powder compact/bed. The localization of electric current in CATS allows for unique temporal and spatial current and temperature distributions within the tip and powder compact. In this paper, special experimental setups were used to monitor the temperature profiles in the tip and at multiple locations on the surface of nickel powder compacts. A variation in the initial green density was found to have a significant effect on the maximum temperature in the tip as well as the temperature distribution across the powder compact. In general, the lowest green density specimens displayed the best conditions for localized densification. The concept of effective current density is introduced and results are discussed in relation to the densification parameter.

  9. Low temperature sintering of MgCuZn ferrite and its electrical and ...

    Indian Academy of Sciences (India)

    Unknown

    The effect of Cu substitution on the properties of MgZn ferrites was also investigated and it was found that the densification of MgCuZn ... rate of 4°C/h. Then, the temperature was raised to the firing temperature at the rate of 20°C/h. After sintering the samples were cooled at the rate of 20°C/h up to 300°C and at this stage the ...

  10. Pengaruh Variasi Kecepatan Stiring & Temperatur Sintering Terhadap Perubahan Struktur Mikro & Fase Material Sensor Gas Tio2

    Directory of Open Access Journals (Sweden)

    Della Dewi Ratnasari

    2014-03-01

    Full Text Available Penelitian material untuk sensor gas ini menggunakan bahan dasar TiO2 dan zat pelarut H2SO4 pekat 98% . Metode pembentuk sol-gel dilakukan dengan sampel di stiring menggunakan magnetic stirrer selama 2,5 jam, kecepatan 600, 700 dan 800 rpm dengan temperatur 200 º C hingga terbentuk gel. Drying dilakukan selama 1 jam dengan temperatur 350 º C, proses kalsinasi selama 1 jam temperatur 500 ºC. Proses selanjutnya serbuk TiO2 dikompaksi dengan tekanan 200 bar agar terbentuk padatan / pellet. Sintering dilakukan pada temperatur 700 ºC selama 1 jam. Karakterisasi material dilakukan dengan alat uji Scanning Electron microscope (SEM dan X-ray diffraction (XRD untuk menganalisa perubahan struktur mikro & fase material keramik TiO2. Berdasarkan hasil pengujian difraksi sinar–x (XRD, variasi stiring 600 rpm, 700 rpm & 800 rpm telah merubah fase anatase (raw material menjadi unstabil fase orthohombik (TiOSO4. Sintering pada temperatur 700 ͦ C telah menyebabkan unstabil fase TiOSO4 menjadi stabil fase TiO2 anatase. Sintesa sol-gel stiring 700 rpm dan 800 rpm dilanjutkan sintering 700 ͦ C menyebabkan reduksi kation Titanium. Berdasarkan hasil SEM, proses sol-gel dapat mereduksi raw material menjadi 130 nm pada kecepatan stiring 700 rpm temperatur operasi 200 ͦ C selama 150 menit.

  11. Identification of Industrial Furnace Temperature for Sintering Process in Nuclear Fuel Fabrication Using NARX Neural Networks

    Directory of Open Access Journals (Sweden)

    Dede Sutarya

    2014-01-01

    Full Text Available Nonlinear system identification is becoming an important tool which can be used to improve control performance and achieve robust fault-tolerant behavior. Among the different nonlinear identification techniques, methods based on neural network model are gradually becoming established not only in the academia, but also in industrial application. An identification scheme of nonlinear systems for sintering furnace temperature in nuclear fuel fabrication using neural network autoregressive with exogenous inputs (NNARX model investigated in this paper. The main contribution of this paper is to identify the appropriate model and structure to be applied in control temperature in the sintering process in nuclear fuel fabrication, that is, a nonlinear dynamical system. Satisfactory agreement between identified and experimental data is found with normalized sum square error 1.9e-03 for heating step and 6.3859e-08 for soaking step. That result shows the model successfully predict the evolution of the temperature in the furnace.

  12. Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

    Science.gov (United States)

    Varghese, Jobin; Vahera, Timo; Ohsato, Hitoshi; Iwata, Makoto; Jantunen, Heli

    2017-10-01

    In this paper, a novel low-temperature sintering substrate for low temperature co-fired ceramic applications based on indialite/cordierite glass ceramics with Bi2O3 as a sintering aid showing low permittivity (εr) and ultralow dielectric loss (tan δ) is described. The fine powder of indialite was prepared by the crystallization of cordierite glass at 1000 °C/1 h. The optimized sintering temperature was 900 °C with 10 wt % Bi2O3 addition. The relative density achieved was 97%, and εr and tan δ were 6.10 and 0.0001 at 1 MHz, respectively. The composition also showed a moderately low temperature coefficient of relative permittivity of 118 ppm/°C at 1 MHz. The obtained linear coefficient of thermal expansion was 3.5 ppm/°C in the measured temperature range of 100 to 600 °C. The decreasing trend in dielectric loss, the low relative permittivity at 1 MHz, and the low thermal expansion of the newly developed composition make it an ideal choice for radio frequency applications.

  13. Influence of Basicity on High-Chromium Vanadium-Titanium Magnetite Sinter Properties, Productivity, and Mineralogy

    Science.gov (United States)

    Zhou, Mi; Yang, Songtao; Jiang, Tao; Xue, Xiangxin

    2015-05-01

    The effect of basicity on high-chromium vanadium-titanium magnetite (V-Ti-Cr) sintering was studied via sintering pot tests. The sinter rate, yield, and productivity were calculated before determining sinter strength (TI) and reduction degradation index (RDI). Furthermore, the effect of basicity on V-Ti-Cr sinter mineralogy was clarified using metallographic microscopy, x-ray diffraction, and scanning electron microscopy-energy-dispersive x-ray spectroscopy. The results indicate that increasing basicity quickly increases the sintering rate from 25.4 mm min-1 to 28.9 mm min-1, yield from 75.3% to 87.2%, TI from 55.4% to 64.8%, and productivity from 1.83 t (m2 h)-1 to 1.94 t (m2 h)-1 before experiencing a slight drop. The V-Ti-Cr sinter shows complex mineral composition, with main mineral phases such as magnetite, hematite, silicate (dicalcium silicate, Ca-Fe olivine, glass), calcium and aluminum silico-ferrite (SFCA/SFCAI) and perovskite. Perovskite is notable because it lowers the V-Ti sinter strength and RDI. The well intergrowths between magnetite and SFCA/SFCAI, and the decrease in perovskite and secondary skeletal hematite are the key for improving TI and RDI. Finally, a comprehensive index was calculated, and the optimal V-Ti-Cr sinter basicity also for industrial application was 2.55.

  14. EFFECT OF SINTERING TEMPERATURE ON MICROSTRUCTURE AND IN-VITRO BEHAVIOR OF BIOACTIVE GLASS-CERAMICS

    Directory of Open Access Journals (Sweden)

    Hashmi M. U.

    2013-12-01

    Full Text Available In this work, powders of the composition (CaO 46- SiO2 34- P2O5 14.5- MgO 4- CaF2 1- MgF2 0.5 (wt. % were thoroughly mixed and melted in a muffle furnace. The melt was quenched in water to form glass. Three glass-ceramics were prepared by sintering glass samples at three different temperatures 850, 900 and 950°C according to the exothermal peaks of DTA. The DTA peaks correspond to the bioactive crystalline phases hydroxyapatite (HA and wollastonite as confirmed by the XRD data. Study of diameter-shrinkage co-efficient and bulk-density of samples revealed higher densification rate for the range 900 - 950°C than that for the range 850 - 900°C.SEM and optical microscope results illustrated a tendency towards closely packed structure and increasing grain size with the increase of sintering temperature. The samples were immersed in SBF for 30 days at room temperature for in-vitro evaluation.EDS analysis, showing the presence of carbon (C along with calcium (Ca and phosphorus (P suggests the formation of hydroxycarbonate-apatite (HCA phase that indicates the bioactivity of the material which increases with the increase of sintering temperature.

  15. Effect of fluxing additive on sintering temperature, microstructure and ...

    Indian Academy of Sciences (India)

    The persistence of various phase(s) at higher temperatures in the flux-added materials indicated that the phase transitions occurred relatively slowly. A decrease in dielectric constant of Li2O-added BaTiO3 in comparison to pure BaTiO3 may be due to the diminished dielectric polarizability of Li+ in comparison to Ba2+.

  16. Effect of fluxing additive on sintering temperature, microstructure and ...

    Indian Academy of Sciences (India)

    doping have been described and discussed. Additionally, in situ Raman spectroscopy has been used for the first time to investigate and compare the phase transition temperatures of pure and Li2CO3-added BaTiO3. 2. Experimental. Batches (50g) of GPR grade TiO2 and BaCO3 (Aldrich. Chemicals Company Inc.) powder ...

  17. Pengaruh Variasi Temperatur Sintering terhadap Umur Tanur pada Industri Kerajinan Gong di Gianyar

    Directory of Open Access Journals (Sweden)

    Gede Widayana

    2015-01-01

    Full Text Available Keramik merupakan salah satu kerajinan tradisional yang telah ada sejak berabad-abad lalu. Salah satu jenisnya adalah tanur krus grafit yang banyak digunakan pada industri-industri pengecoran terutama untuk mencairkan logam. Dalam penggunaannya tanur krus grafit ini mengalami keretakan setelah pemakaian 5 atau 6 kali. Hal ini disebabkan karena material yang dipakai tidak memenuhi standar dan proses yang dilakukan masih belum sempurna.Penelitian ini dilakukan dengan merubah komposisi material yaitu terdiri dari fraksi halus 30%, fraksi kasar 40% dan clay 30% dan memakai proses sintering pada temperature 1000°C dan 1100°C  untuk meningkatkan kekuatan tanur sehingga diharapkan dapat memperpanjang umur tanur. Hasil penelitian menunjukan bahwa pada temperature sintering 1100°C mendapatkan berat jenis, nilai porositas dan nilai abrasi yang lebih baik pada tanur sehingga umur tanur dapat diperpanjang hingga lebih dari 10 kali pakai.

  18. 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

  19. Initial stage sintering of polymer particles – Experiments and modelling of size-, temperature- and time-dependent contacts

    Directory of Open Access Journals (Sweden)

    Fuchs Regina

    2017-01-01

    Full Text Available The early-stage sintering of thin layers of micron-sized polystyrene (PS particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C, is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (rcrit ~ 1 μm below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than rcrit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.

  20. Lightweight High-Temperature Thermal Insulation

    Science.gov (United States)

    Wagner, W. R.; Fasheh, J. I.

    1985-01-01

    Fine Ni/Cr fibers sintered into corrosion-resistant, fireproof batt. Possible applications include stoves, furnaces, safes, fire clothing, draperies in public buildings, wall firebreaks, airplane walls, and jetengine components. New insulation takes advantage of some of same properties of nickel/chromium alloy useful in heating elements in toasters, namely, corrosion and oxidation resistance even at high temperatures.

  1. Effects of Milling Atmosphere and Increasing Sintering Temperature on the Magnetic Properties of Nanocrystalline Ni0.36Zn0.64Fe2O4

    Directory of Open Access Journals (Sweden)

    Abdollah Hajalilou

    2015-01-01

    Full Text Available Nanocrystalline Ni0.36Zn0.64Fe2O4 was synthesized by milling a powder mixture of Zn, NiO, and Fe2O3 in a high-energy ball mill for 30 h under three different atmospheres of air, argon, and oxygen. After sintering the 30 h milled samples at 500°C, the XRD patterns suggested the formation of a single phase of Ni-Zn ferrite. The XRD results indicated the average crystallite sizes to be 15, 14, and 16 nm, respectively, for the 30 h milled samples in air, argon, and oxygen atmospheres sintered at 500°C. From the FeSEM micrographs, the average grain sizes of the mentioned samples were 83, 75, and 105 nm, respectively, which grew to 284, 243, and 302 nm after sintering to 900°C. A density of all the samples increased while a porosity decreased by elevating sintering temperature. The parallel evolution of changes in magnetic properties, due to microstructural variations with changes in the milling atmosphere and sintering temperature in the rage of 500–900°C with 100°C increments, is also studied in this work.

  2. Sintering behavior of doped ZnO powders for high field varistors

    Energy Technology Data Exchange (ETDEWEB)

    Ghirlanda, M.

    1990-08-01

    The sintering of ZnO varistor precursor powders, doped with Co, Mn and different concentrations of Bi and Al, is investigated and discussed in relation with sintering models. One purpose of the present study is to provide information valuable for the fabrication of high field varistors. As the fundamental parameter of these electronic components is the breakdown voltage per unit of thickness, which is determined by the number of grain boundaries per linear dimension, the grain size and the sintered density are crucial variables, and the sintering is a central step in the manufacturing of such varistors. Sintering experiments performed at constant heating rate in a loading dilatometer provide data on the densification and creep of the compacted powders. Another goal of the present study is to provide an experimental basis for the interpretation of the evolution of the ratio between densification rate and creep rate in terms of competition between densification and microstructure coarsening. This is accomplished by taking advantage of the variety of sintering behaviors that takes place in the system ZnO-Bi-Al: the comparison of these behaviors allows us to correlate the macroscopic sintering parameters to the evolution of the microstructure. It results that, while in non-doped powders densification and coarsening develop in a balanced way, resulting in the constancy of the ratio between densification rate and creep rate, the effect of the dopants on the sintering kinetics alters such a balance, leading this ratio to vary. 17 figs.

  3. 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.

  4. Thermoplastic Elastomer Part Color as Function of Temperature Histories and Oxygen Atmosphere During Selective Laser Sintering

    Science.gov (United States)

    Kummert, C.; Josupeit, S.; Schmid, H.-J.

    2017-11-01

    The influence of selective laser sintering (SLS) parameters on PA12 part properties is well known, but research on other materials is rare. One alternative material is a thermoplastic elastomer (TPE) called PrimePart ST that is more elastic and shows a distinct SLS processing behavior. It undergoes a three-dimensional temperature distribution during the SLS process within the TPE part cake. To examine this further, a temperature measurement system that allows temperature measurements inside the part cake is applied to TPE in the present work. Position-dependent temperature histories are directly correlated with the color and mechanical properties of built parts and are in very good agreement with artificial heat treatment in a furnace. Furthermore, it is clearly shown that the yellowish discoloration of parts in different intensities is not only temperature dependent but also influenced by the residual oxygen content in the process atmosphere. Nevertheless, the discoloration has no influence on the mechanical part properties.

  5. Effect of sintering temperature on physical properties & hardness of CoCrMo alloys fabricated by metal injection moulding process

    Science.gov (United States)

    Ridhwan Abdullah, Ahmad; Aidah Nabihah Dandang, Nur; Zalikha Khalil, Nur; Harun, Wan Sharuzi Wan

    2017-10-01

    Metal Injection Moulding (MIM) process is one of the Powder Metallurgy manufacturing techniques utilised to produce Cobalt Chromium Molybdenum (CoCrMo) compacts. The objective of this study is to determine physical properties and hardness of CoCrMo alloy compact sintered at three different sintering temperature at the similar soaking time. At the beginning, sample were fabricated by using Injection Moulding machine. Cobalt Chrome Molybdenum (CoCrMo) metal powder was selected for this study. A morphological study was conducted using optical microscope (OM) and micro-Vickers hardness testing. From the result obtained, it shows upward trend either on the hardness or physical properties of the samples. CoCrMo sintered compact become harder and volume of pores on surface become less due to the increase on sintering temperature. However, effect of increasing sintering temperature shows significant shrinkage of the sample, beginning losses in dimensional accuracy. It is discovered that a little change in sintering temperature gives significant impact on the microstructure, physical, mechanical of the alloy.

  6. 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

    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 Zn......O particles and microstructure evolutions at different sintering temperatures were investigated by the simulation of the self-Joule-heating effect of the individual particles.......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...

  7. 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

    densities and higher electronic conductivity than the sample sintered at 1073 K. These results were supported by the solid-state reaction completion rate, which suggested that sintering temperature above 1223 K would be preferable for complete solid-state reaction of the samples. The sintering mechanism...... of ZnO particles and microstructure evolution at different sintering temperatures were investigated by simulation of the self-Joule-heating effect of the individual particles.......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...

  8. Effect of neodymium substitutions on electromagnetic properties in low temperature sintered NiCuZn ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Wu, C.P., E-mail: itria20161@itri.org.tw; Tung, M.J.; Ko, W.S.; Wang, Y.P.; Tong, S.Y.; Yang, M.D.

    2015-11-01

    Nd{sup 3+} ions substituted Ni{sub 0.37}Cu{sub 0.14}Zn{sub 0.52}Fe{sub 2}O{sub 4} (Nd{sup 3+} ions content=0, 0.01, 0.04, 0.6, 1.5 wt%) were prepared by the usual standard ceramic method at 1030 °C sintering temperature, and the composition dependence of the physical and magnetic properties has been investigated. SEM micrographs and EDX analysis revealed that it is no obvious impurities up to Nd{sup 3+} ions content wt%=0.04. For higher Nd{sup 3+} ions content samples (0.6 and 1.5 wt%), there are two kind of impurities Cu-rich and Nd-rich iron oxide phase. The saturation magnetization of the 0.01 wt% Nd{sup 3+}ions content sample is higher as result of that the A–B sites distance and YK-angles are shorter and smaller. The saturation magnetization of 0.04–1.5 wt% Nd{sup 3+} ion content sample are reduced, since the total magnetic moments of the AB site are decreased. For the 0.6 wt% sample, the Curie temperature increasing is as result of the Cu-rich iron oxide separating out. The maximum enhancements of permeability μ′ are improved to 11.2% (0.04 wt%) and 29.2% (0.6 wt%) at the 6.7 and 13.8 MHz, respectively. However, it is notice that small amount substitutions of Nd{sup 3+} increase the high frequency electromagnetic characteristics, can be applied to NFC technology and WPT technologies.

  9. High Rate Plastic Deformation and Failure of Tungsten-Sintered Metals

    National Research Council Canada - National Science Library

    Bjerke, Todd

    2004-01-01

    The competition between plastic deformation and brittle fracture during high rate loading of a tungsten-sintered metal is examined through impact experiments, post-experiment microscopy, and numerical simulation...

  10. Investigation on Thermocompression Bonding Using Lead Free Sinterable Paste and High Lead Solder Paste for Power QFN Application

    Directory of Open Access Journals (Sweden)

    Chandrakasan Gunaseelan

    2016-01-01

    Full Text Available Persistently growing Power QFN packages are used in various fields especially micro-electronics, aerospace, oil and gas as well. However, the particular industries is pushing forward to reduce the use of hazardous materials in the process of manufacturing and assemblies. Thermo-compression die-attach layer is perceived to be the most critical element in power QFN packages as the increase in operating temperature requires new materials with suitable thermo-chemical properties also with suitable melting points of next generation lead free die attachment material. In this situation, Hi-lead solder (RM218: Pb92.5Sn5Ag2.5 which known as high temperature material is widely being used in most semiconductor assembly for die attach, yet it deduce few reliability challenges like solder voids, the clip tilt performance and also solder splash which has been considered as major quality issue in assembly of Power QFN packages (FET die, IC die and clip attach. As a solution, sintering epoxy paste (SPC073-3: Sn96.5/Ag3/Cu0.5 is being considered as a replacement. In this case, sintering epoxy paste demonstrating excellent electrical and thermal performance for Power QFN packages which is known to be demanded in market. Thus, this study investigates the differential pastes sintering paste and also solder paste, in order to identify best die attachment material to be used in thermo-compression bonding method. Therefore, the shear strength was resulting good indication where the sintering paste was recorded 2.4 Kg/mm meanwhile the solder paste was recorded 0Kg/mm at peak temperature of 260°C. Besides of that, the pot life seems promising as the sintering paste seems to have constant viscosity of 100Pa*s throughout the 48 hours tested while, high lead solder paste records viscosity from 100Pa*s marginally increase as the time increase which effects the inconsistency of pot life. Last but not least, the voids mechanisms proves sintering epoxy paste has the same

  11. Low-temperature sintering and phase changes in chromite interconnect materials

    Energy Technology Data Exchange (ETDEWEB)

    Chick, L.A.; Armstrong, T.R.; McCready, D.E.; Coffey, G.W.; Maupin, G.D.; Bates, J.L.

    1993-05-01

    Sintering shrinkage curves and phase changes were compared for calcium-substituted lanthanum chromates with either slight Asite enrichment or depletion. Of the former type, La{sub 0.7}Ca{sub 0.31},CrO{sub 3} that was synthesized by the glycine-nitrate method sintered to high density in air at 1250C, exhibiting two rapid-shrinkage events. Weight loss measurements corroborated XRD data showing that, prior to densiflcation, over half the Ca resided in non-perovskite phases, including CaCrO{sub 4}. In the La{sub 0.7}Ca{sub 0.31}CrO{sub 3}, densification was closely associated with re-dissolution of the Ca into the perovskite.

  12. Low-temperature sintering and phase changes in chromite interconnect materials

    Energy Technology Data Exchange (ETDEWEB)

    Chick, L.A.; Armstrong, T.R.; McCready, D.E.; Coffey, G.W.; Maupin, G.D.; Bates, J.L.

    1993-05-01

    Sintering shrinkage curves and phase changes were compared for calcium-substituted lanthanum chromates with either slight Asite enrichment or depletion. Of the former type, La[sub 0.7]Ca[sub 0.31],CrO[sub 3] that was synthesized by the glycine-nitrate method sintered to high density in air at 1250C, exhibiting two rapid-shrinkage events. Weight loss measurements corroborated XRD data showing that, prior to densiflcation, over half the Ca resided in non-perovskite phases, including CaCrO[sub 4]. In the La[sub 0.7]Ca[sub 0.31]CrO[sub 3], densification was closely associated with re-dissolution of the Ca into the perovskite.

  13. Synthesis of highly sinterable Yb: SrF2 nanopowders for transparent ceramics

    Science.gov (United States)

    Li, Weiwei; Huang, Haijun; Mei, Bingchu; Song, Jinghong

    2018-01-01

    In this paper, ytterbium doped strontium fluoride (Yb: SrF2) nanoparticles were synthesized by direct precipitation method. High-speed centrifugation was used to separate high sintering activity of nanopowders from powders with hard aggregated and large size. Using powders at different parts of the centrifugal tube as starting powders, Yb: SrF2 transparent ceramics was fabricated by hot pressed (HP) method for the first time. Effects of morphology and particle size on the sinterability of Yb: SrF2 nanopowders were investigated. The transmittance reached 77% at the wavelength of 1200 nm and pores stilled remained in the ceramics. The spectroscopic and thermal properties of Yb: SrF2 transparent ceramics were also investigated. This paper provides an effective way to obtain well dispersed and high sinterability nanoparticles for SrF2 ceramics sintering.

  14. Effect of different sintering temperature on fly ash based geopolymer artificial aggregate

    Science.gov (United States)

    Abdullah, Alida; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Tahir, Muhammad Faheem Mohd

    2017-04-01

    This research was conducted to study the mechanical and morphology of fly ash based geopolymer as artificial aggregate at different sintering temperature. The raw material that are used is fly ash, sodium hydroxide, sodium silicate, geopolymer artificial aggregate, Ordinary Portland Cement (OPC), coarse aggregate and fine aggregate. The research starts with the preparation of geopolymer artificial aggregate. Then, geopolymer artificial aggregate will be sintered at six difference temperature that is 400°C, 500°C, 600°C, 700°C, 800°C and 900°C to known at which temperature the geopolymer artificial aggregate will become a lightweight aggregate. In order to characterize the geopolymer artificial aggregate the X-ray Diffraction (XRD) and X-Ray Fluorescence (XRF) was done. The testing and analyses involve for the artificial aggregate is aggregate impact test, specific gravity test and Scanning Electron Microscopy (SEM). After that the process will proceed to produce concrete with two type of different aggregate that is course aggregate and geopolymer artificial aggregate. The testing for concrete is compressive strength test, water absorption test and density test. The result obtained will be compared and analyse.

  15. Industrial symbiosis: high purity recovery of metals from Waelz sintering waste by aqueous SO2 solution.

    Science.gov (United States)

    Copur, Mehmet; Pekdemir, Turgay; Colak, Sabri; Künkül, Asim

    2007-10-22

    Sintering operation in the production of Zn, Cd, and Pb by Waelz process produces a powdery waste containing mainly (about 70%) ZnO, CdO, and PbO. The waste may be referred to as Waelz sintering waste (WSW). The aim of this study is to develop a process for the separation and recovery of the metals from WSW with high purities. The process is based on the dissolution of the WSW in aqueous SO2 solution. The research reported here concentrated on the effect of some important operational parameters on dissolution process. The parameters investigated and their ranges were as follows: SO(2) gas flow rate (V); 38-590 ml/min, stirring speed (W); 100-1000 rpm, reaction temperature (T); 13-60 degrees C, reaction time (t); 1-16 min, and solid-liquid ratio (S/L); 0.1-0.5 g/ml. The results showed that the dissolution rate increased with increasing W, V, and S/L and decreasing T. The best dissolution conditions were found to be V=325 ml/min, W=600 rpm, t=6 min, T=21 degrees C, and S/L=0.1g/ml. Separation of Zn from Cd involved precipitation of ZnSO3 from a mixture solution. The best pH level for the precipitation was observed to be 6.

  16. Influence of high sintering pressure on the microhardness and wear resistance of diamond powder and silicon carbide-based composites

    Directory of Open Access Journals (Sweden)

    Osipov Oleksandr Sergueevitch

    2004-01-01

    Full Text Available The work reported on here involved the development of several samples of "diamond-SiC" composite produced under sintering pressures of up to 9.0 GPa at temperatures of up to 1973 7K. The average size of the diamond micropowder crystals used was 40/28 µm. The sintering process was carried out in a 2500-ton hydraulic press equipped with an anvil-type high-pressure device having a toroidal work surface and a central concavity diameter of 20 mm. The microhardness and wear resistance of the samples were found to be dependent on the sintering pressure. The experimental results indicated that the maximum microhardness and minimum wear resistance coefficients of each compact were attained when the pressure applied during sintering exceeded 6.5 GPa. Based on the established values of pressure, this study served to identify the types of devices applicable for the manufacture of composite material inserts for a variety of rock drilling applications.

  17. Complexity of the relationships between the sintering-temperature-dependent grain size, airborne-particle abrasion, ageing and strength of 3Y-TZP ceramics.

    Science.gov (United States)

    Cotič, Jasna; Jevnikar, Peter; Kocjan, Andraž; Kosmač, Tomaž

    2016-04-01

    This study was designed to explore the complex relationships between the sintering-temperature-dependent grain size, airborne-particle abrasion, ageing and strength of 3Y-TZP ceramics. Biomedical grade 3Y-TZP powder was used to fabricate 180 discs. Half of them were sintered at 1400°C for 2h and half at 1500°C for 2h. A total of 18 groups of 10 were formed and subjected to the fully crossed experimental protocol of airborne-particle abrasion with Al2O3 at 2.5bar (no abrasion, 50μm, 110μm) and accelerated ageing at 134°C (no ageing, 12h, 48h). The relative amount of monoclinic phase was determined with XRD. The biaxial flexural strength was measured and statistically analyzed using the three-way ANOVA followed by predetermined contrasts and Tukey's HSD test (α=0.05). The low-temperature-sintered, fine-grained ceramic exhibited an excellent ageing resistance, while the high-temperature-sintered, coarse-grained ceramic experienced a higher surface strengthening and a substantially improved ageing resistance with respect to the airborne-particle abrasion. The overall performance of this material was superior. Our results show that the sintering temperature has a minor effect on the flexural strength, but it plays a crucial role in the surface strengthening and the ageing behaviour of 3Y-TZP dental ceramics. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  18. The microwave effects on the properties of alumina at high frequencies of microwave sintering

    Energy Technology Data Exchange (ETDEWEB)

    Sudiana, I. Nyoman, E-mail: sudiana75@yahoo.com; Ngkoimani, La Ode; Usman, Ida [Department of Physics, Faculty of Mathematic and Natural Science, Halu Oleo University, Kampus Bumi Tridharma Anduonohu, Kendari 93232 (Indonesia); Mitsudo, Seitaro; Sako, Katsuhide; Inagaki, Shunsuke [Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui-shi 910-8507 (Japan); Aripin, H. [Center for Material Processing and Renewable Energy, Faculty of Learning Teacher and Education Science, Siliwangi University, Jl. Siliwangi 24 Tasikmalaya 46115, West Java (Indonesia)

    2016-03-11

    Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materials by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.

  19. Effects of helium and deuterium irradiation on SPS sintered W–Ta composites at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mateus, R., E-mail: rmateus@ipfn.ist.utl.pt [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Dias, M. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Lopes, J. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); ISEL, Instituto Superior de Engenharia de Lisboa, Rua Conselheiro Emídio Navarro, 1, 1959-007 Lisboa (Portugal); Rocha, J.; Catarino, N.; Franco, N. [ITN, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém (Portugal); Livramento, V. [Associação Euratom/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 1649-038 Lisboa (Portugal); and others

    2013-11-15

    Energetic He{sup +} and D{sup +} ions were implanted into different W–Ta composites in order to investigate their stability under helium and deuterium irradiation. The results were compared with morphological and chemical modifications arising from exposure of pure W and Ta. Special attention was given to tantalum hydride (Ta{sub 2}H) formation due to its implications for tritium inventory. Three W–Ta composites with 10 and 20 at.% Ta were prepared from elemental W powder and Ta fibre or powder through low-energy ball milling in argon atmosphere. Spark plasma sintering (SPS) was used as the consolidation process in the temperature range from 1473 to 1873 K. The results obtained from pure elemental samples and composites are similar. However, Ta{sub 2}H is easily formed in pure Ta by using a pre-implantation stage of He{sup +}, whereas in W–Ta composites the same reaction is clearly reduced, and it can be inhibited by controlling the sintering temperature.

  20. The effect of temperature on the electrical properties of inkjet-printed silver nanoparticle ink during electrical sintering.

    Science.gov (United States)

    Moon, Seung-Jae

    2013-09-01

    In this work, the thermal behavior of ink-jet-printed nanoparticle ink during electrical sintering was demonstrated. The ink consisting of silver nanoparticles approximately 50 nm in size and 34 wt% was used. Constant currents of 0.11, 0.22, and 0.31 A were applied to Joule-heat the inkjet-printed silver nanoparticles. During the sintering process, in-situ voltage and current measurements were taken to calculate the heat source and thermal conductivity. In order to estimate the temperature during the electrical sintering process, numerical modeling of the two-dimensional heat conduction equation was adopted. Thermal conductivity was obtained from the in-situ electrical conductivity measurement and coupled to the numerical model using the Wiedemann Franz law. From these numerical modeling results, the relationship between the specific resistance of the ink and the temperature was determined. During the electrical sintering process, the specific resistance of the ink was strongly related to the sintering temperature. The specific resistance of the ink decreases as the process temperature rises.

  1. Fabrication of Bi2223 bulks with high critical current properties sintered in Ag tubes

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Yasuaki, E-mail: ytakeda@g.ecc.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Shimoyama, Jun-ichi; Motoki, Takanori [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258 (Japan); Kishio, Kohji [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakashima, Takayoshi; Kagiyama, Tomohiro; Kobayashi, Shin-ichi; Hayashi, Kazuhiko [Sumitomo Electric Industries, Ltd. 1-1-3 Shimaya, Konohana-ku, Osaka 554-0024 (Japan)

    2017-03-15

    Highlights: • Fabrication conditions of Bi2223 bulks was reconsidered in terms of high J{sub c}. • Pressure of uniaxial pressing and heat treatment conditions were investigated. • The best sample showed higher J{sub c} than that of practically used Bi2223 bulks. - Abstract: Randomly grain oriented Bi2223 sintered bulks are one of the representative superconducting materials having weak-link problem due to very short coherence length particularly along the c-axis, resulting in poor intergrain J{sub c} properties. In our previous studies, sintering and/or post-annealing under moderately reducing atmospheres were found to be effective for improving grain coupling in Bi2223 sintered bulks. Further optimizations of the synthesis process for Bi2223 sintered bulks were attempted in the present study to enhance their intergrain J{sub c}. Effects of applied pressure of uniaxial pressing and sintering conditions on microstructure and superconducting properties have been systematically investigated. The best sample showed intergrain J{sub c} of 2.0 kA cm{sup −2} at 77 K and 8.2 kA cm{sup −2} at 20 K, while its relative density was low ∼65%. These values are quite high as for a randomly oriented sintered bulk of cuprate superconductors.

  2. Simulation of temperature distribution for large sized ceramic substrates in vertical type sintering furnace; Tategata denkiro shosei deno ogata seramikkusu kiban no ondo bunpu shumyureshon

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, M.; Ami, N.; Hirasawa, S. [Hitachi, Ltd., Tokyo (Japan)

    2000-01-01

    The temperature distribution in large sized ceramic substrates at 1600 degree C sintered by vertical type furnace was simulated by using a model of heat conduction and radiation heat transfer. The temperature distribution at the center of each ceramic substrate is larger than that in each ceramic substrate at steady state in the case of 3 substrates were fired. The temperature distribution becomes narrow by using a high thermal conductivity material setter or inserting heat insulating material between the bottom setter and the furnace floor. The temperature distribution in each ceramic substrate is closely related to the distance between the surface of the ceramic substrate and the bottom of the upper setter. (author)

  3. The Influence of Sintering Method on Kaolin-Based Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene as Binder

    Science.gov (United States)

    Romisuhani, A.; AlBakri, M. M.; Kamarudin, H.; Andrei, S. V.

    2017-11-01

    The influence of sintering method on kaolin-based geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene as binder were studied. Geopolymer were formed at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. 12 M of sodium hydroxide solution were mixed with sodium silicate at a ratio of 0.24 to form alkaline activator. Powder metallurgy technique were used in order to produce kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene. The samples were heated at temperature of 1200 °C with two different sintering method which are conventional method and two-step sintering method. The strength and density were tested.

  4. Enhancing Low-Temperature and Pressureless Sintering of Micron Silver Paste Based on an Ether-Type Solvent

    Science.gov (United States)

    Zhang, Hao; Li, Wanli; Gao, Yue; Zhang, Hao; Jiu, Jinting; Suganuma, Katsuaki

    2017-08-01

    Micron silver paste enables a low-temperature and pressureless sintering process by using an ether-type solvent CELTOL-IA (C x H y O z , x > 10, boiling point of approximately 200°C) for the die attachment of high-powered devices. The conductive patterns formed by the silver paste had a low electrical resistivity of 8.45 μΩ cm at 180°C. The paste also achieved a high bonding strength above 30 MPa at 180°C without the assistance of pressures. These superior performance indicators result from the favorable removal of the solvent, its thermal behavior, and its good wetting on the silver layer. The results suggest that the micron silver paste with a suitable solvent can promote the further spreading of next-generation power devices owing to its marked cost advantage and excellent performance.

  5. Nonvacuum, maskless fabrication of a flexible metal grid transparent conductor by low-temperature selective laser sintering of nanoparticle ink.

    Science.gov (United States)

    Hong, Sukjoon; Yeo, Junyeob; Kim, Gunho; Kim, Dongkyu; Lee, Habeom; Kwon, Jinhyeong; Lee, Hyungman; Lee, Phillip; Ko, Seung Hwan

    2013-06-25

    We introduce a facile approach to fabricate a metallic grid transparent conductor on a flexible substrate using selective laser sintering of metal nanoparticle ink. The metallic grid transparent conductors with high transmittance (>85%) and low sheet resistance (30 Ω/sq) are readily produced on glass and polymer substrates at large scale without any vacuum or high-temperature environment. Being a maskless direct writing method, the shape and the parameters of the grid can be easily changed by CAD data. The resultant metallic grid also showed a superior stability in terms of adhesion and bending. This transparent conductor is further applied to the touch screen panel, and it is confirmed that the final device operates firmly under continuous mechanical stress.

  6. Influence of Sintering Temperature on the Microstructure and Property of Low-cost Ceramic Proppants Prepared by Adding Purple Sands

    Science.gov (United States)

    Ma, H. Q.; Tian, Y. M.; Li, G. M.; Wang, K. Y.; Zhou, Y.; Bai, P. B.

    2017-09-01

    High-strength corundum-mullite based ceramic proppants have been fabricated from 2nd bauxite (62.3wt%Al2O3) and purple sands, which were used as main raw materials by solid sintering method, combined with the additive of feldspar and pyrolusite powder. The phase analysis was studied by X-ray diffraction (XRD) and the morphology of specimen was observed by the scanning electron microscopy (SEM). The result showed that the additive of feldspar was beneficial to the formation of internal liquid phase of sample with the sintering temperature increasing, which reduced the pores and promoted the densification of sample. Meanwhile the proper liquid phase resulted in the growth of mullite and promoted the close integration of mullite and corundum, forming the network structure of needle-like mullite. Ultimately the proppants exhibited the optimal performance at 1450 °C with bulk density of 1.59 g/cm3, apparent density of 3.11 g/cm3 and the lowest breakage ratio of 3.76% under 52 MPa pressure.

  7. Microstructural characteristics of low-temperature (1400°C sintered MgO obtained from seawater

    Directory of Open Access Journals (Sweden)

    Jakić Jelena

    2017-01-01

    Full Text Available The purpose of this study was to investigate the influence of a rinsing of Mg(OH2 precipitated from seawater by substoichiometric precipitation (80% precipitation and the addition of TiO2 on microstructural characteristics of the MgO obtained by sintering at low temperature (1400°C. The results of examination indicate that the method of rinsing of the magnesium hydroxide precipitate in the technological process of obtaining MgO from seawater significantly affects the chemical composition of samples, primarily with regard to the CaO and B2O3 content. The samples were doped with TiO2 to improve the evaporation of B2O3 and sintering of MgO samples that were characterized by XRD and SEM/EDS. These techniques confirmed the high purity of MgO samples obtained and the formation of secondary compounds in very small quantities that have a positive effect on the densification.

  8. Temperature modeling for analysis and design of the sintering furnance in HTR fuel type of ball

    Energy Technology Data Exchange (ETDEWEB)

    Saragi, Elfrida [Computational Division, Centre for Nuclear Informatic Development, National Nuclear Energy Agency, Serpong 15310 (Indonesia); Setiadji, Moch [PTAPB - National Nuclear Energy Agency, Yogyakarta 1008 (Indonesia)

    2013-09-09

    One of the factors that determine the safety of the operation of the sintering furnace fuel HTR ball is the temperature distribution in the ceramic tube furnace. The temperature distribution must be determined at design stage. The tube has a temperature of 1600 °C at one end and about 40 °C at the other end. The outside of the tube was cooled by air through natural convection. The tube is a furnace ceramic tube which its geometry are 0.08, 0.09 and 0.5 m correspondingly for the inner tube diameter, outer tube diameter and tube length. The temperature distribution of the tube is determined by the natural convection coefficient (NCF), which is difficult to be calculated manually. The determination of NCF includes the Grasshoff, Prandtl, and Nusselt numbers which is a function of the temperature difference between the surrounding air with the ceramic tube. If the temperature vary along the tube, the complexity of the calculations increases. Thus the proposed modeling was performed to determine the temperature distribution along the tube and heat transfer coefficient using a self-developed software which permit the design process easier.

  9. Melt-Pool Temperature and Size Measurement During Direct Laser Sintering

    Energy Technology Data Exchange (ETDEWEB)

    List, III, Frederick Alyious [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Dinwiddie, Ralph Barton [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Carver, Keith [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gockel, Joy E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    Additive manufacturing has demonstrated the ability to fabricate complex geometries and components not possible with conventional casting and machining. In many cases, industry has demonstrated the ability to fabricate complex geometries with improved efficiency and performance. However, qualification and certification of processes is challenging, leaving companies to focus on certification of material though design allowable based approaches. This significantly reduces the business case for additive manufacturing. Therefore, real time monitoring of the melt pool can be used to detect the development of flaws, such as porosity or un-sintered powder and aid in the certification process. Characteristics of the melt pool in the Direct Laser Sintering (DLS) process is also of great interest to modelers who are developing simulation models needed to improve and perfect the DLS process. Such models could provide a means to rapidly develop the optimum processing parameters for new alloy powders and optimize processing parameters for specific part geometries. Stratonics’ ThermaViz system will be integrated with the Renishaw DLS system in order to demonstrate its ability to measure melt pool size, shape and temperature. These results will be compared with data from an existing IR camera to determine the best approach for the determination of these critical parameters.

  10. Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

    Science.gov (United States)

    Leenakul, Wilaiwan; Tunkasiri, Tawee; Tongsiri, Natee; Pengpat, Kamonpan; Ruangsuriya, Jetsada

    2016-04-01

    45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Fabrication of Conductive Copper Films on Flexible Polymer Substrates by Low-Temperature Sintering of Composite Cu Ink in Air.

    Science.gov (United States)

    Kanzaki, Mai; Kawaguchi, Yuki; Kawasaki, Hideya

    2017-06-21

    The development of a thermal sintering method for Cu-based inks under an air atmosphere could greatly expand their application for printed electronics. However, it is well-known that Cu-based inks cannot produce conductive Cu films when sintered at low temperatures in air because Cu readily oxidizes under such conditions. In this study, we have successfully demonstrated air atmosphere sintering at low temperatures (less than 150 °C) via a simple hot plate heat treatment for producing conductive Cu films on flexible polymer substrates, using a novel Cu-based composite ink with sub-10 nm Cu nanoparticles protected with 1-amino-2-propanol with micrometer-sized Cu particles and submicrometer-sized Cu particles; oxalic acid was also added to prevent the oxidation of the Cu during sintering. The Cu films showed a minimum resistivity of 5.5 × 10-5 Ω·cm when sintered in air at 150 °C for a very short period of 10 s. To the best of our knowledge, this is the first report of sintering of Cu-based inks in air at less than 150 °C. Another novel property of the present Cu-based composite ink is the lowest reported resistivity at 80 °C under N2 flow (5.3 × 10-5 Ω·cm at 80 °C and 8.4 × 10-6 Ω·cm at 120 °C). This fast, efficient, and inexpensive technology for thermal sintering in ambient air using composite inks could be a commercially viable method for fabricating printed electronics on flexible substrates.

  12. 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.

  13. UV-Sintered Low-Temperature Solution-Processed SnO2as Robust Electron Transport Layer for Efficient Planar Heterojunction Perovskite Solar Cells.

    Science.gov (United States)

    Huang, Like; Sun, Xiaoxiang; Li, Chang; Xu, Jie; Xu, Rui; Du, Yangyang; Ni, Jian; Cai, Hongkun; Li, Juan; Hu, Ziyang; Zhang, Jianjun

    2017-07-05

    Recently, low temperature solution-processed tin oxide (SnO 2 ) as a versatile electron transport layer (ETL) for efficient and robust planar heterojunction (PH) perovskite solar cells (PSCs) has attracted particular attention due to its outstanding properties such as high optical transparency, high electron mobility, and suitable band alignment. However, for most of the reported works, an annealing temperature of 180 °C is generally required. This temperature is reluctantly considered to be a low temperature, especially with respect to the flexible application where 180 °C is still too high for the polyethylene terephthalate flexible substrate to bear. In this contribution, low temperature (about 70 °C) UV/ozone treatment was applied to in situ synthesis of SnO 2 films deposited on the fluorine-doped tin oxide substrate as ETL. This method is a facile photochemical treatment which is simple to operate and can easily eliminate the organic components. Accordingly, PH PSCs with UV-sintered SnO 2 films as ETL were successfully fabricated for the first time. The device exhibited excellent photovoltaic performance as high as 16.21%, which is even higher than the value (11.49%) reported for a counterpart device with solution-processed and high temperature annealed SnO 2 films as ETL. These low temperature solution-processed and UV-sintered SnO 2 films are suitable for the low-cost, large yield solution process on a flexible substrate for optoelectronic devices.

  14. 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)

  15. Photonic flash sintering of silver nanoparticle inks: a fast and convenient method for the preparation of highly conductive structures on foil

    NARCIS (Netherlands)

    Abbel, R.J.; Lammeren, T.J. van; Hendriks, R.; Ploegmakers, J.J.; Rubingh, J.E.J.M.; Meinders, E.R.; Groen, W.A.

    2012-01-01

    Silver nanoparticle inks printed on temperature-sensitive substrates can be converted into structures with high electrical conductivities within fractions of a second by photonic flash sintering. The key principle is the selective heating of the ink by the absorption of strongly focused pulsed light

  16. Effect of sintering temperature on micro structural and impedance spectroscopic properties of Ni0.5Zn0.5Fe2O4 nano ferrite

    Science.gov (United States)

    Venkatesh, Davuluri; Ramesh, K. V.; Sastry, C. V. S. S.

    2017-07-01

    Ni-Zn nanoferrite Ni0.5Zn0.5Fe2O4 is prepared by citrate gel auto combustion method and sintered at various temperatures 800, 900, 1000, 1100 and 1200°C. The room temperature x-ray diffraction conforms that the single phase spinel structure is formed. Crystallite size and density were increased with increasing of sintering temperature. From Raman spectroscopy all sintered samples are single phase with cubic spinel structure belong to Fd3m space group. From surface morphology studies it is clearly observed that the particle size increased with increasing of sintering temperature. Impedance spectroscopy revel that increasing of conductivity is due to grain resistance is decreased with increasing of sintering temperature. Cole-Cole plots are studied from impedance data. The electrical modulus analysis shows that non-Debye nature of Ni0.5Zn0.5Fe2O4 ferrite.

  17. Electrical conductivity of titanium pyrophosphate between 100 and 400 °C: effect of sintering temperature and phosphorus content

    DEFF Research Database (Denmark)

    Lapina, Alberto; Chatzichristodoulou, Christodoulos; Hallinder, Jonathan

    2014-01-01

    The synthesis of titanium pyrophosphate is carried out, and the material is sintered at different temperatures between 370 and 970 °C. Yttrium is added during the synthesis to act as acceptor dopant, but it is mainly present in the material in secondary phases. The conductivity is studied systema...

  18. Design and fabrication of sintered Nd-Fe-B magnets with a low temperature coefficient of intrinsic coercivity

    Directory of Open Access Journals (Sweden)

    Cui X.G.

    2009-01-01

    Full Text Available To decrease the temperature coefficients of sintered Nd-Fe-B magnets, the influencing factors on temperature coefficients, especially the reversible temperature coefficient β of intrinsic coercivity Hcj, were analyzed. The results showed that the absolute value of β decreased with increasing Hcj and also the ratio of microstructure parameter c to Neff, indicating that the increase of magnetocrystalline anisotropy field HA and c/Neff can effectively decrease the absolute value of β. On the basis of this analysis, a sintered Nd-Fe-B magnet with a low temperature coefficient of Hcj was fabricated through composition design, and the value of β was only -0.385%/ºC in the temperature interval of 20-150ºC.

  19. Effect of Sintering Temperature on the Microstructure and Mechanical Properties of Low-Cost Light-Weight Proppant Ceramics

    Science.gov (United States)

    Wang, K. Y.; Wang, H. J.; Zhou, Y.; Wu, Y. Q.; Li, G. M.; Tian, Y. M.

    2017-09-01

    In this paper, the low-cost light-weight proppant ceramics were prepared with the solid wastes of coal gangue as the raw materials, and the effect of sintering temperature on the apparent porosity, bulk density, bending strength, microstructure and phase composition were investigated. The results showed that the ceramics, sintered at 1350°C, has the best performance with the bending strength of 85MPa, bulk density of 2.7 g/cm3 and apparent porosity of 18%. These properties of ceramics were very close to that of the bauxite-sintered, and thus the gangue were very probably selected for the preparation of proppants that involved in the exploitation of coalbed methane.

  20. Highly coke-resistant ni nanoparticle catalysts with minimal sintering in dry reforming of methane.

    Science.gov (United States)

    Han, Joung Woo; Kim, Chanyeon; Park, Jun Seong; Lee, Hyunjoo

    2014-02-01

    Nickel catalysts are typically used for hydrogen production by reforming reactions. Reforming methane with carbon dioxide, called dry reforming of methane (DRM), is a good way to produce hydrogen or syngas (a mixture of hydrogen and carbon monoxide) from two notable greenhouse gases. However, Ni catalysts used for DRM suffer from severe coke deposition. It has been known that small Ni nanoparticles are advantageous to reduce coke formation, but the high reaction temperature of DRM (800 °C) inevitably induces aggregation of the nanoparticles, leading to severe coke formation and degraded activity. Here, we develop highly coke-resistant Ni catalysts by immobilizing premade Ni nanoparticles of 5.2 nm in size onto functionalized silica supports, and then coating the Ni/SiO2 catalyst with silica overlayers. The silica overlayers enable the transfer of reactants and products while preventing aggregation of the Ni nanoparticles. The silica-coated Ni catalysts operate stably for 170 h without any degradation in activity. No carbon deposition was observed by temperature programmed oxidation (TPO), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The Ni catalysts without silica coating show severe sintering after DRM reaction, and the formation of filamentous carbon was observed. The coke-resistant Ni catalyst is potentially useful in various hydrocarbon transformations. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Low-Temperature Sintering of AlN Ceramics by Sm2O3-Y2O3-CaO Sintering Additives Formed via Decomposition of Nitrate Solutions

    Science.gov (United States)

    Zhan, Jun; Cao, Ye; Zhang, Hao; Guo, Jun; Zhang, Jianhua; Geng, Chunlei; Shi, Changdong; Cui, Song; Tang, Wenming

    2017-01-01

    The Sm, Y and Ca anhydrous nitrates were mixed with the AlN powder in ethanol and then decomposed into the Sm2O3-Y2O3-CaO sintering additives via calcining. Low-temperature sintering of the AlN ceramics was carried out at temperature range from 1675 to 1750 °C. Effects of the composition and adding amount of the sintering additives on the phases, microstructures and properties of the AlN ceramics were investigated. During sintering the AlN ceramics, main secondary phases of CaYAl3O7 and CaSmAl3O7 form. The relative density, bending strength and thermal conductivity of the AlN ceramics increase with the increase in the rare-earth oxides in them. The thermal conductivity of the sintered AlN ceramics is also greatly affected by the distribution of the secondary phases. As sintered at 1750 °C, the AlN ceramics by adding the sintering additives of 2 wt.% Sm2O3, 2 wt.% Y2O3 and 1 wt.% CaO formed via decomposition of their nitrates is fully dense and have the optimal bending strength and thermal conductivity of 402.1 MPa and 153.7 W/(m K), respectively.

  2. Effects of sintering temperature on morphology and mechanical characteristics of 3D printed porous titanium used as dental implant.

    Science.gov (United States)

    Gagg, Graham; Ghassemieh, Elaheh; Wiria, Florencia Edith

    2013-10-01

    Porous titanium samples were manufactured using the 3D printing and sintering method in order to determine the effects of final sintering temperature on morphology and mechanical properties. Cylindrical samples were printed and split into groups according to a final sintering temperature (FST). Irregular geometry samples were also printed and split into groups according to their FST. The cylindrical samples were used to determine part shrinkage, in compressive tests to provide stress-strain data, in microCT scans to provide internal morphology data and for optical microscopy to determine surface morphology. All of the samples were used in microhardness testing to establish the hardness. Below 1100 °C FST, shrinkage was in the region of 20% but increased to approximately 30% by a FST of 1300 °C. Porosity varied from a maximum of approximately 65% at the surface to the region of 30% internally. Between 97 and 99% of the internal porosity is interconnected. Average pore size varied between 24 μm at the surface and 19 μm internally. Sample hardness increased to in excess of 300 HV0.05 with increasing FST while samples with an FST of below 1250 °C produced an elastic-brittle stress/strain curve and samples above this displayed elastic-plastic behaviour. Yield strength increased significantly through the range of sintering temperatures while the Young's modulus remained fairly consistent. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. 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.

  4. Structural and optical properties of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} nano ferrites: Effect of sintering temperature

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Prashant, E-mail: prashant007thakur@gmail.com; Sharma, Rohit; Sharma, Vineet, E-mail: vineet.sharma@juiit.ac.in; Sharma, Pankaj, E-mail: pankaj.sharma@juit.ac.in

    2017-06-01

    Mn-Zn ferrites have shown various remarkable applications e.g. in magnetic amplifiers, power transformers and electromagnetic interference etc. due to their high initial permeability. Mn–Zn ferrite powder (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) has been prepared by the co-precipitation method and subsequently sintered at three different temperatures i.e. 973 K, 1173 K, 1373 K. Optical properties have been correlated with the structural properties. For structural properties X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) have been employed. It has been observed that there is an increase in crystallite size with sintering from 973 K to 1373 K and FTIR confirms the formation of bond between metal ion and oxygen ion at the octahedral site and tetrahedral site. A red shift has been confirmed from UV–visible absorption spectra and photoluminescence spectra have been reported with an increase in sintering temperature. - Graphical abstract: Mn–Zn ferrite powder (Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) has been prepared by the co-precipitation method and subsequently sintered at three different temperatures i.e. 973 K, 1173 K, 1373 K. A red shift has been confirmed from UV–visible absorption spectra and photoluminescence spectra have been reported with an increase in sintering temperature. - Highlights: • Nanoparticles of Mn{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4} have been prepared by the co-precipitation method. • There is an increase in crystallite size with sintering from 973 K to 1373 K. • A red shift is found in UV–visible and PL spectra with an increase in sintering temperature.

  5. Effect of sintering temperature on the microstructure and ionic conductivity of Ce0.8Sm0.1Ba0.1O2-δ electrolyte

    Directory of Open Access Journals (Sweden)

    Mustafa Anwar

    2017-03-01

    Full Text Available This study investigated the effects of sintering temperature on the microstructure and ionic conductivity of codoped ceria electrolyte with barium and samarium as dopants. The electrolyte (Ce0.8Sm0.1Ba0.1O2-δ powder was synthesized using the citric acid-nitrate combustion method and calcined at 900 °C for 5 h. The calcined electrolyte exhibited a cubic fluorite crystal structure with some impurity phases. The calcined powder was then pressed into cylindrical pellets using uniaxial die-pressing. The pellets were sintered at three different temperatures, i.e., 1200, 1300 and 1400 °C for 5 h. Microstructural analysis of the pellets showed that the average grain size increased with the increase in sintering temperature. The sintered densities of the pellets were measured by Archimedes’ method, and the relative density values were within the range of 78 %TD to 87 %TD as the sintering temperature increased from 1200 to 1400 °C. Electrochemical impedance spectroscopy analysis showed that conductivity increased with the increase in sintering temperature, but no considerable change in conductivity was observed for the pellets sintered at 1300 and 1400 °C. The results revealed that the electrolyte pellet sintered at 1300 °C exhibited the ionic conductivity of 0.005 S/cm with lowest activation energy of 0.7275 eV.

  6. 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...

  7. Printed highly conductive Cu films with strong adhesion enabled by low-energy photonic sintering on low-Tg flexible plastic substrate

    Science.gov (United States)

    Wu, Xinzhou; Shao, Shuangshuang; Chen, Zheng; Cui, Zheng

    2017-01-01

    Copper (Cu) films and circuits were fabricated by screen-printing Cu nanoink on low-Tg (glass transition temperature) flexible plastic substrates (PEN and PET) instead of widely used high-Tg polyimide (PI) substrate. Photonic sintering of printed Cu films was carried out using intensive pulsed light (IPL). Low resistivities of 28 μΩ · cm on PEN and 44 μΩ · cm on PET were obtained without damaging the substrates. The sintered Cu films exhibited strong adhesion to PEN and PET substrates, with measured adhesion strength of 5B by the ASTM D3359 international standard, whereas the top part of the copper film on the PI substrate was stripped off during the adhesion test. The sintered Cu films also showed excellent stability in harsh conditions and mechanical flexibility in rolling tests. The underlying mechanisms of the high conductivity and strong adhesion on PEN and PET substrates with low-energy IPL sintering were investigated. Simple circuits and radio frequency identification antennas were made by screen-printing Cu nanoink and IPL sintering, demonstrating the technique’s feasibility for practical applications.

  8. Effect of sintering temperature and the particle size on the structural and magnetic properties of nanocrystalline Li{sub 0.5}Fe{sub 2.5}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Shirsath, Sagar E., E-mail: shirsathsagar@hotmail.com [Department of Physics, Vivekanand College, Aurangabad 431004 (MS) (India); Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (MS) (India); Kadam, R.H. [Materials Science Research Laboratory, Shrikrishna Mahavidyalaya Gunjoti, Osmanabad (MS) (India); Gaikwad, Anil S. [Department of Physics, Vivekanand College, Aurangabad 431004 (MS) (India); Ghasemi, Ali [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Morisako, Akimitsu [Spin Device Technology Center, Faculty of Engineering, Shinshu University, Nagano (Japan)

    2011-12-15

    Sintering temperature and particle size dependent structural and magnetic properties of lithium ferrite (Li{sub 0.5}Fe{sub 2.5}O{sub 4}) were synthesized and sintered at four different temperatures ranging from 875 to 1475 K in the step of 200 K. The sample sintered at 875 K was also treated for four different sintering times ranging from 4 to 16 h. Samples sintered at 1475 K have the cubic spinel structure with a small amount of {alpha}-Fe{sub 2}O{sub 3} (hematite) and {gamma}-Fe{sub 2}O{sub 3} (maghemite). The samples sintered at{<=}1275 K do not show hematite and maghemite phases and the crystals form the single phase spinel structure with the cation ordering on octahedral sites. Particle size of lithium ferrite is in the range of 13-45 nm, and is depend on the sintering temperature and sintering time. The saturation magnetization increased from 45 to 76 emu/g and coercivity decreases from 151 to 139 Oe with an increase in particle size. Magnetization temperature curve recorded in ZFC and FC modes in an external magnetic field of 100 Oe. Typical blocking effects are observed below about 244 K. The dielectric constant increases with an increase in sintering temperature and particle size. - Highlights: > Lithium ferrite with heat treatment. > Structure changes from disordered system to ordered system. > Magnetization increases with sintering temperature. > Blocking temperature increases with sintering temperature. > Coercivity decreases with sintering temperature.

  9. The use of Spark Plasma Sintering method for high-rate diffusion welding of high-strength UFG titanium alloys

    Science.gov (United States)

    Nokhrin, A. V.; Chuvil'deev, V. N.; Boldin, M. S.; Piskunov, A. V.; Kozlova, N. A.; Chegurov, M. K.; Popov, A. A.; Lantcev, E. A.; Kopylov, V. I.; Tabachkova, N. Yu

    2017-07-01

    The article provides an example of applying the technology of spark plasma sintering (SPS) to ensure high-rate diffusion welding of high-strength ultra-fine-grained UFG titanium alloys. Weld seams produced from Ti-5Al-2V UFG titanium alloy and obtained through SPS are characterized by high density, hardness and corrosion resistance.

  10. Microstructure and mechanical properties of nanocrystalline high strength Al-Mg-Si (AA6061) alloy by high energy ball milling and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Jatinkumar Kumar [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Sivaprahasam, D. [International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad 500005 (India); Seetharama Raju, K. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Subramanya Sarma, V., E-mail: vsarma@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2009-12-15

    In the present paper, the microstructure and mechanical properties of nanostructured Al-Mg-Si based AA6061 alloy obtained by high energy ball milling and spark plasma sintering were reported. Gas atomized microcrystalline powder of AA6061 alloy was ball milled under wet condition at room temperature to obtain nanocrystalline powder with grain size of {approx}30 nm. The nanocrystalline powder was consolidated to fully dense compacts by spark plasma sintering (SPS) at 500 deg. C. The grain size after SPS consolidation was found to be {approx}85 nm. The resultant SPS compacts exhibited microhardness of 190-200 HV{sub 100g}, compressive strength of {approx}800 MPa and strain to fracture of {approx}15%.

  11. 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.

  12. Effect of sintering temperatures and screen printing types on TiO{sub 2} layers in DSSC applications

    Energy Technology Data Exchange (ETDEWEB)

    Supriyanto, Agus; Furqoni, Lutfi; Nurosyid, Fahru, E-mail: nurosyid@yahoo.com; Suryana, Risa [Department of Physics, Faculty of Mathematics and Natural Sciences, Sebel as Maret University Jl. Ir. Sutami 36A Kentingan Surakarta 57126 (Indonesia); Hidayat, Jojo [Research Center for Electronics and Telecommunication, Indonesian Institute of Sciences (PPET-LIPI) Kampus LIPI Gd. 20 Jl. Sangkuriang Bandung (Indonesia)

    2016-03-29

    Dye-Sensitized Solar Cell (DSSC) is a candidate solar cell, which has a big potential in the future due to its eco-friendly material. This research is conducted to study the effect of sintering temperature and the type of screen-printing toward the characteristics of TiO{sub 2} layer as a working electrode in DSSC. TiO{sub 2} layers were fabricated using a screen-printing method with a mesh size of T-49, T-55, and T-61. TiO{sub 2} layers were sintered at temperatures of 600°C and 650°C for 60 min. DSSC structure was composed of TiO{sub 2} as semiconductors, ruthenium complex as dyes, and carbon as counter electrodes. The morphology of TiO{sub 2} layer was observed by using Nikon E2 Digital Camera Microscopy. The efficiencies of DSSC were calculated from the I-V curves. The highest efficiency is 0.015% at TiO{sub 2} layer fabricated with screen type T-61 and at a sintering temperature of 650°C.

  13. Tough yttria-stabilized zirconia ceramic by low-temperature spark plasma sintering of long-term stored nanopowders.

    Science.gov (United States)

    Bezdorozhev, Oleksii; Borodianska, Hanna; Sakka, Yoshio; Vasylkiv, Oleg

    2011-09-01

    Weakly agglomerated 1.75 and 3 mol% yttria stabilized zirconia nanopowders were used in this study after six years of storage in vacuum-processed plastic containers. The proper storage conditions of the Y-TZP nanopowders avoided the hard agglomeration. Untreated and bead-milled nanopowders were used to obtain dense ceramics by slip casting and subsequent low-temperature sintering. Fully dense nanostructured 1.75Y-TZP and 3Y-YZP ceramics with and without doping of 1 wt% Al2O3 were produced by an optimized spark plasma sintering (SPS) technique at the temperatures of 1050-1150 degrees C at a pressure of 100 MPa. The SPS has revealed the clear advantage of consolidation of the weakly agglomerated nanopowders without preliminary deagglomeration. The Vickers hardness of both the low-temperature and spark plasma sintered samples was found to lie in the range of 10.98-13.71 GPa. A maximum fracture toughness of 15.7 MPa m(1/2) (average 14.23 MPa m(1/2)) was achieved by SPS of the 1.75Y-TZP ceramic doped with 1 wt% Al2O3 whereas the toughness of the 3Y-TZP ceramics with and without alumina doping was found to vary between 3.55 and 5.5 MPa m(1/2).

  14. Effect of sintering temperature on the structural, dielectric and magnetic properties of Ni0.4Zn0.2Mn0.4Fe2O4 potential for radar absorbing

    Science.gov (United States)

    Praveena, K.; Sadhana, K.; Matteppanavar, S.; Liu, Hsiang-Lin

    2017-02-01

    Ni0.4Zn0.2Mn0.4Fe2O4 nanopowders were prepared by sol-gel auto-combustion method, densified at different temperatures 400-700 °C/4 h using conventional sintering method. The grain sizes of all the samples vary between 18 nm and 30 nm. The hysteresis loops show high saturation magnetization and low coercivity, indicating magnetically soft behaviour of the material. The real and imaginary parts of permittivity is almost constant upto 1 GHz and increases with further increase of frequency. The permeability is ruled by Snoek's law, the values of μ‧ increases with increase of temperature and the resonance frequency increases with an increase of temperature. The reflection coefficient is however increasing with sintering temperature and the maximum loss is observed in the range of 100 MHz-1 GHz. Sample sintered at 700 °C has shown maximum reflection loss and this loss occurs due to absorption, destructive interference and multiple internal reflections in the sample. Quality factor is constant upto 380 MHz and increases with frequency for all the samples sintered at different temperatures. The TC for all the samples is above 230 °C. The room temperature EPR spectra confirm the oxidation state of Fe3+. The g-factor is in the range of 2.

  15. Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

    Science.gov (United States)

    Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

    2004-01-01

    Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

  16. Up-cycling waste glass to minimal water adsorption/absorption lightweight aggregate by rapid low temperature sintering: optimization by dual process-mixture response surface methodology.

    Science.gov (United States)

    Velis, Costas A; Franco-Salinas, Claudia; O'Sullivan, Catherine; Najorka, Jens; Boccaccini, Aldo R; Cheeseman, Christopher R

    2014-07-01

    Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows.

  17. Review - Fabrication of crystal-oriented barium-bismuth titanate ceramics in high magnetic field and subsequent reaction sintering

    Directory of Open Access Journals (Sweden)

    Satoshi Tanaka, Yusuke Tomita, Ryoichi Furushima, Hiroyuki Shimizu, Yutaka Doshida and Keizo Uematsu

    2009-01-01

    Full Text Available High magnetic field was applied to fabricate novel lead-free piezoelectric ceramics with a textured structure. A compact of crystallographically oriented grains was prepared by dry forming in a high magnetic field from a mixed slurry of bismuth titanate and barium titanate powders. Bismuth titanate particles with a size of about 1 μ m were used as the host material. In the forming process, the slurry was poured into a mold and set in a magnetic field of 10 T until completely dried. Bismuth titanate particles were highly oriented in the slurry under the magnetic field. The dried powder compact consisted of highly oriented bismuth titanate particles and randomly oriented barium titanate particles. Barium bismuth titanate ceramics with a- and b-axis orientations were successfully produced from the dried compact by sintering at temperatures above 1100 ° C.

  18. Evaluation of Sintering Behavior of Premix Al-Zn-Mg-Cu Alloy Powder

    OpenAIRE

    Haris Rudianto; Gwang Joo Jang; Sang Sun Yang; Yong Jin Kim,; Ivo Dlouhy

    2015-01-01

    Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. For...

  19. High temperature measuring device

    Science.gov (United States)

    Tokarz, Richard D.

    1983-01-01

    A temperature measuring device for very high design temperatures (to 2,000.degree. C.). The device comprises a homogenous base structure preferably in the form of a sphere or cylinder. The base structure contains a large number of individual walled cells. The base structure has a decreasing coefficient of elasticity within the temperature range being monitored. A predetermined quantity of inert gas is confined within each cell. The cells are dimensionally stable at the normal working temperature of the device. Increases in gaseous pressure within the cells will permanently deform the cell walls at temperatures within the high temperature range to be measured. Such deformation can be correlated to temperature by calibrating similarly constructed devices under known time and temperature conditions.

  20. Improvement of strength of carbon nanotube-dispersed Si3N4 ceramics by bead milling and adding lower-temperature sintering aids

    Directory of Open Access Journals (Sweden)

    Mitsuaki Matsuoka

    2014-09-01

    Full Text Available Studies on the dispersion of carbon nanotubes (CNTs in silicon nitride (Si3N4 ceramics to provide the latter with electrical conductivity have been carried out in recent years. The density and the strength of Si3N4 ceramics were degraded, however, because the CNTs prevented Si3N4 from densifying. The CNTs disappeared after firing at high temperatures owing to the reaction between CNTs and Si3N4 or SiO2, or both Si3N4 and SiO2. In order to improve the density and suppress the reaction, sintering aids for lower-temperature densification of Si3N4 are needed. In this study, we added HfO2 as a sintering aid to a Si3N4–Y2O3–Al2O3–AlN–TiO2 system to fabricate CNT-dispersed Si3N4 ceramics at lower temperatures. Furthermore, bead milling was applied to disperse the CNTs homogeneously. Agglomerates of CNTs were pulverized by bead milling without obvious changes in morphology to eliminate larger fracture origins in CNT-dispersed ceramics. As a result of both the addition of HfO2 and bead milling, we successfully fabricated dense CNT-dispersed Si3N4 ceramics with high strength and electrical conductivity.

  1. High temperature behaviour of a zircon ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Carbonneau, X.; Olagnon, C.; Fantozzi, G. [INSA, Villeurbanne (France). GEMMPM; Hamidouche, M. [Lab. Science des Materiaux, Univ. de Setif (Algeria); Torrecillas, R. [Inst. Nacional del Carbon, Oviedo (Spain)

    1997-12-31

    The high temperature properties of a sintered zircon material has been tested up to 1200 C. A significant creep rate is observed, mainly attributed to the presence of glassy phase. The sub-critical crack growth measured in double torsion showed that above 1000 C, the crack velocity is reduced either by stress relaxation or by crack healing. The thermal shock analysis under a heat exchange coefficient of 600 W/m{sup 2}/K showed a regular decrease rather that a sudden fall off of properties. (orig.) 3 refs.

  2. The effect of build orientation and surface modification on mechanical properties of high speed sintered parts

    Science.gov (United States)

    Ellis, Adam; Brown, Ryan; Hopkinson, Neil

    2015-09-01

    High speed sintering is a novel additive manufacturing technology that uses inkjet printing and infra-red energy to selectively sinter polymeric powder. The research presented here investigates the effect of build orientation on dimensional accuracy, density, mechanical properties and surface roughness of high speed sintered parts. Tensile specimens were built through seven different angles between and including the XY (horizontal) and ZY (vertical) planes and analysed. The effect of the PUSh™ process was also investigated across this range of build orientations. The results show that build orientation does infuence the properties of the parts. A number of mechanical properties showed a relationship with build orientation. Density was seen to decrease as the angle increased from XY towards ZY. This increase in angle was shown to increase surface roughness while ultimate tensile strength and elongation at break decreased. At all build orientations, the PUSh™ process significantly reduces surface roughness, mildly increases part density and had a small effect on ultimate tensile strength whilst showing a small but consistent increase in elongation at break.

  3. Low-Temperature Sintering and Microwave Dielectric Properties of Zn2SiO4 Ceramic Added with Crystalline Zinc Borate

    Science.gov (United States)

    Chaware, Varsha; Deshmukh, Ravindra; Sarode, Chetan; Gokhale, Suresh; Phatak, Girish

    2015-07-01

    The physical and dielectric properties of composites of known microwave materials, Zn2SiO4 and Zn3B2O6, prepared by solid-state reaction, were investigated with the purpose of developing a low-loss dielectric material for low-temperature co-fired ceramic applications. An off-stoichiometric phase of Zn2SiO4 with extra SiO2 was used to avoid the occurrence of unreacted ZnO. During sintering, zinc borate was found to partially react with residual SiO2 to form Zn2SiO4. The residual zinc borate was converted to a boron-rich glassy phase which helped to reduce the sintering temperature of the composite. Good relative sintering density (>90%) at temperatures below the melting temperature of zinc borate is indicative of a sintering mechanism of diffusion-based mass transfer. Composites containing 15 wt.% zinc borate, 2.5 wt.% lithium carbonate and 20 wt.% zinc borate in zinc silicate had dielectric constants of 6.8 and 6.1, quality factors (Q×f) of 48,800 and 94,300 GHz when sintered at 900°C and 950°C, respectively. These quality factor results are close to the best values reported for zinc silicate at these sintering temperatures.

  4. The effect of sintering temperature on electrical characteristics of Fe2TiO5/Nb2O5 ceramics for NTC thermistor

    Science.gov (United States)

    Wiendartun, Risdiana, Fitrilawati, Siregar, R. E.

    2016-02-01

    A study on the fabrication of Iron Titanium Oxide (Fe2TiO5) ceramics for negative temperature coefficient (NTC) thermistors has been carried out, in order to know the effect of sintering temperature on the electrical characteristic of 1.0 % mole Nb2O5 doped Fe2TiO5 ceramics.These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and Nb2O5 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1000 °C, 1100 °C and 1200 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD spectra showed that the crystal structure of all ceramics of Fe2TiO5 made at various sintering temperatures are orthorhombic. The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical resistances data that was measured at temperature 30-300 °C, it is found that the value of thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT) decreases with respect to the increasing of sintering temperature. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 6394-6959 K). This can be applied as temperature sensor, and will fulfill the market requirement.

  5. Highly durable Cu-based electrodes from a printable nanoparticle mixture ink: flash-light-sintered, kinetically-controlled microstructure.

    Science.gov (United States)

    Park, Hye Jin; Jo, Yejin; Cho, Min Kyung; Young Woo, Jeong; Kim, Dojin; Lee, Su Yeon; Choi, Youngmin; Jeong, Sunho

    2018-02-07

    Recently, printable nanomaterials have drawn tremendous attention for low-cost, large-area electronics applications. In particular, metallic nanoparticles that can facilitate the formation of highly functioning electrodes are indispensable constituent nanomaterials. In this paper, we propose printable mixed inks comprising multicomponent ingredients of Cu, Ni and Cu/Cu10Sn3 core/shell nanoparticles. It is clearly revealed that a characteristic morphology appropriate to highly conductive and durable Cu-based electrodes can be derived easily in a timescale of about 1 ms through an instantaneous flash-light-sintering process, resulting in a resistivity of 49 μΩ cm and normalized resistance variation of around 1 (after 28 days under a harsh environment of 85 °C temperature and 85% humidity). In addition, it is demonstrated that highly functioning electrodes can be formed on thermally vulnerable polyethylene terephthalate (PET) substrates by incorporating an ultrathin optical/thermal plasmonic barrier layer.

  6. Effects of sintering temperature on the corrosion behavior of AZ31 alloy with Ca–P sol–gel coating

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Bo [School of Materials Science and Engineering, Liaoning University of Technology, Jinzhou, Liaoning Province, 121001 (China); Shi, Ping, E-mail: p_shi@sohu.com [School of Materials Science and Engineering, Liaoning University of Technology, Jinzhou, Liaoning Province, 121001 (China); Wei, Donghua [School of Materials Science and Engineering, Liaoning University of Technology, Jinzhou, Liaoning Province, 121001 (China); E, Shanshan [School of Mathematics and Physics, Bohai University, Jinzhou, Liaoning Province, 121013 (China); Li, Qiang; Chen, Yang [School of Materials Science and Engineering, Liaoning University of Technology, Jinzhou, Liaoning Province, 121001 (China)

    2016-04-25

    To slow down the initial biodegradation rate of magnesium alloy, calcium phosphate (Ca–P) coatings were prepared on AZ31 magnesium alloy by a sol–gel technique. To study the effects of sintering temperature on microstructure, bonding strength and corrosion behavior of the coatings, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and an adhesive strength test were used to characterize the coatings. The corrosion resistance of the coatings was investigated by immersion test and electrochemical corrosion techniques in simulated body fluid (SBF) solution. It shows that the sol–gel coatings consist of Ca{sub 2}P{sub 2}O{sub 7}, mixture of Ca{sub 2}P{sub 2}O{sub 7}, Ca{sub 3}(PO{sub 4}){sub 2} and hydroxyapatite, and hydroxyapatite, by sintering respectively at 300 °C, 400 °C and 500 °C. There are major cracks on the coatings. The crack area portion on the coating and the bonding strength at the interface between the calcium phosphate coating and the bare AZ31 increases, and the corrosion resistance of the coated AZ31 in SBF decreases with increasing sintering temperatures from 300 °C to 500 °C. Based on our investigations, the corrosion resistance of the coated AZ31 in SBF depends mainly on the crack area portion on the coatings, rather than on the coating phase stability. - Highlights: • Ca–P coating was prepared on AZ31 alloy by a sol–gel technique. • Crack area portion in the coating increases with temperatures. • Bonding strength between Ca–P coating and substrate increases with temperatures. • Corrosion resistance of the coated AZ31 in SBF decreases with temperatures. • Corrosion resistance of the coated AZ31 depends mainly on the crack area portion.

  7. Effect of sintering temperature on structural and optical properties of indium(III) oxide nanoparticles prepared with Triton X-100 by hydrothermal method

    Science.gov (United States)

    Selvakumar, D.; Dharmaraj, N.; Kadirvelu, K.; Kumar, N. S.; Padaki, V. C.

    2014-12-01

    Indium(III) hydroxide (In(OH)3) powders prepared via Triton X-100 mediated hydrothermal method was sintered at different temperatures (400, 500 and 600 °C) to yield indium(III) oxide nanoparticles (In2O3 NPs). Thermal studies of In(OH)3 confirmed complete conversion to In2O3 around 400 °C. Powder X-ray diffraction (XRD) pattern of sintered In2O3 nanoparticles revealed the formation of phase pure cubic In2O3. The crystallite size of In2O3 NPs was increased from 12 to 26 nm upon increasing the sintering temperature from 400 °C to 600 °C, while the percentage crystallinity was increased up to 90% after sintering at 600 °C. A red shift in the band gap energy was observed with increasing sintering temperature due to the larger size of sintered In2O3 NPs. Room temperature photoluminescence spectra of the indium oxide nanoparticles showed both near band and excitonic emission of In2O3 due to oxygen vacancies.

  8. Effect of sintering temperature on structural and optical properties of indium(III) oxide nanoparticles prepared with Triton X-100 by hydrothermal method.

    Science.gov (United States)

    Selvakumar, D; Dharmaraj, N; Kadirvelu, K; Kumar, N S; Padaki, V C

    2014-12-10

    Indium(III) hydroxide (In(OH)3) powders prepared via Triton X-100 mediated hydrothermal method was sintered at different temperatures (400, 500 and 600°C) to yield indium(III) oxide nanoparticles (In2O3 NPs). Thermal studies of In(OH)3 confirmed complete conversion to In2O3 around 400°C. Powder X-ray diffraction (XRD) pattern of sintered In2O3 nanoparticles revealed the formation of phase pure cubic In2O3. The crystallite size of In2O3 NPs was increased from 12 to 26nm upon increasing the sintering temperature from 400°C to 600°C, while the percentage crystallinity was increased up to 90% after sintering at 600°C. A red shift in the band gap energy was observed with increasing sintering temperature due to the larger size of sintered In2O3 NPs. Room temperature photoluminescence spectra of the indium oxide nanoparticles showed both near band and excitonic emission of In2O3 due to oxygen vacancies. Copyright © 2014. Published by Elsevier B.V.

  9. Effect of sintering temperature on mechanical behaviour and bioactivity of sol-gel synthesized bioglass-ceramics using rice husk ash as a silica source

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, J.P., E-mail: jyotiprakash_nitrkl@rediffmail.com [Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Bera, J., E-mail: bera@rediffmail.com [Department of Ceramic Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India)

    2010-11-01

    Bioglass-ceramics with SiO{sub 2}-Na{sub 2}O-CaO composition was prepared by sol-gel method using rice husk ash as a silica source. Material was sintered at different temperatures ranging from 900 to 1050 deg. C for 2 h. Phase-formation behaviour, densification characteristics, and mechanical strength of glass-ceramics were investigated. The material sintered at 1000 deg. C showed a good mechanical strength. Mechanical properties were correlated with microstructural features. Both in vitro bioactivity and biodegradability of sintered material were investigated by incubating in simulated body fluid and Tris buffer solution, respectively. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to investigate the surface deposition during body fluid incubation. Both bioactivity and degradability decreased with increase in sintering temperature.

  10. Effect of sintering temperature on mechanical behaviour and bioactivity of sol-gel synthesized bioglass-ceramics using rice husk ash as a silica source

    Science.gov (United States)

    Nayak, J. P.; Bera, J.

    2010-11-01

    Bioglass-ceramics with SiO2-Na2O-CaO composition was prepared by sol-gel method using rice husk ash as a silica source. Material was sintered at different temperatures ranging from 900 to 1050 °C for 2 h. Phase-formation behaviour, densification characteristics, and mechanical strength of glass-ceramics were investigated. The material sintered at 1000 °C showed a good mechanical strength. Mechanical properties were correlated with microstructural features. Both in vitro bioactivity and biodegradability of sintered material were investigated by incubating in simulated body fluid and Tris buffer solution, respectively. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to investigate the surface deposition during body fluid incubation. Both bioactivity and degradability decreased with increase in sintering temperature.

  11. Laser-high-speed-DSC: Process-oriented Thermal Analysis of PA 12 in Selective Laser Sintering

    Science.gov (United States)

    Lanzl, Lydia; Wudy, Katrin; Drexler, Maximilian; Drummer, Dietmar

    In the Selective Laser Sintering process very high heating rates occur due to the melting of the material by a laser. Extreme scanning rates could not be measured by conventional thermal analysis methods, since typical heating rates for DSC (differential scanning calorimetry) are between 5-20K min-1. By using a Laser-High-Speed-DSC, a self-developed combination of a Flash-DSC and a fitted laser head, the sample is directly heated by a CO2 laser like in the SLS process. These experiments allow a process-oriented thermal analyzation of the material. In this paper, the set-up and function of this new measuring method is introduced. Furthermore, the reliability of the measurements is evaluated by statistical design of experiment methods. By using this new measuring method, the time-dependent melting behavior of the polymer can be analyzed. Moreover, sample temperatures and heating rates dependent on laser exposure times can be quantified.

  12. Thermal Behavior of Ag Micro/Nano Wires Formed by Low-Temperature Sintering of Ag Nanoparticles

    Science.gov (United States)

    Wang, Wen; Zhong, Yinghui; Li, Dongxue; Wang, Pan; Cai, Yuwei; Duan, Zhiyong

    2015-12-01

    Ag nanoparticles of 30 nm size were deposited onto a Si substrate to form Ag microwires. The nanoparticles were transformed into continuous Ag wires with low-temperature heat treatment at temperatures not higher than 200°C. The morphology, electrical properties, and interface of the sintered Ag nanoparticle wires are described. It is shown that the neck between the nanoparticles begins to form at 150°C, and obvious metallization was found at 170°C. The changes of the crystal structure of the Ag wires at different sintering temperatures were analyzed by x-ray diffractometry. The grain boundary resistance decreased as the crystal grain size increased above 130 nm. The corresponding resistivity of the microstructure is close to that of the bulk. Through the comparison between the Mayadas-Shatzkes's model and experimental data, the range of the grain boundary reflection coefficient C at different temperatures is obtained. This research lays the foundation for the study of nanoimprint lithography with a pseudoplastic metal nanoparticle fluid.

  13. Profile of yttrium segregation in BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} as function of sintering temperature; Perfil da segregacao do itrio em BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} em funcao da temperatura de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Hosken, C.M.; Souza, D.P.F. de, E-mail: camila.hosken@gmail.co [Universidade Federal de Sao Carlos (LAPCEC/UFSCar), SP (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais. Lab. de Preparacao e Caracterizacao Eletrica em Ceramicas

    2010-07-01

    Researches on solid oxide fuel cells indicate barium cerate perovskite as a very attractive material for using as electrolyte due to its high protonic conductivity. The objective of this work is investigate the yttrium segregation during sintering of BaCe{sub 0,9}Y{sub 0,1}O{sub 3-{delta}} doped with Zn O as a sintering aid. The powders were prepared by citrate process. Powders were isostatic pressed into pellets and sintered in air at 1200, 1275, 1325 and 1400 deg C. The samples were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy. Secondary phase containing Yttrium and Cerium was detected as sintering temperature increased. Increase of the lattice parameter and activation energy for electrical conductivity were also detected on samples sintered at 1400 deg C. (author)

  14. Effects of the sintering temperature on the flux-pinning mechanism and the activation energy of malic-acid doped MgB2

    Directory of Open Access Journals (Sweden)

    J Peleckis

    2012-12-01

    Full Text Available   The flux-pinning mechanism and activation energy of 10 wt % malic acid-doped MgB2 were investigated by measuring of the critical current density and resistivity as a function of magnetic field and temperature. A crossover field, Bsb, was observed from the single vortex to the small vortex bundle pinning regime. For the sintered sample, the temperature dependence of Bsb(T at low temperature is in good agreement with the δℓ pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation. The activation energy was decreased by increasing the magnetic field and increased by increasing sintering temperature.

  15. High temperature battery. Hochtemperaturbatterie

    Energy Technology Data Exchange (ETDEWEB)

    Bulling, M.

    1992-06-04

    To prevent heat losses of a high temperature battery, it is proposed to make the incoming current leads in the area of their penetration through the double-walled insulating housing as thermal throttle, particularly spiral ones.

  16. Sintering temperature and atmosphere modulated evolution of structure and luminescence of 2CaO–P{sub 2}O{sub 5}–B{sub 2}O{sub 3}: Eu phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chaofeng, E-mail: chaofengzhu@gmail.com [Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics of Shandong Province, Shandong Polytechnic University, Jinan 250353 (China); Key Laboratory of Amorphous and Polycrystalline Materials in Universities of Shandong, Shandong Polytechnic University, Jinan 250353 (China); Wang, Jia [Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics of Shandong Province, Shandong Polytechnic University, Jinan 250353 (China); Ren, Xiaorong [Instrumental Analysis Center, Shandong Polytechnic University, Jinan 250353 (China); Zhang, Yanfei; Liu, Shujiang; Shen, Jianxing [Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics of Shandong Province, Shandong Polytechnic University, Jinan 250353 (China); Yue, Yuanzheng, E-mail: yy@bio.aau.dk [Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics of Shandong Province, Shandong Polytechnic University, Jinan 250353 (China); Section of Chemistry, Aalborg University, Aalborg DK-9000 (Denmark)

    2014-01-15

    Europium doped 2CaO–P{sub 2}O{sub 5}–B{sub 2}O{sub 3} phosphors prepared via high temperature solid state reactions are reported. The evolution of luminescence and structure of the phosphors induced by variation of sintering temperature and atmosphere is investigated using photoluminescence spectra and X-ray diffraction techniques. We found that the optical performance and structure of the phosphors are sensitive to the sintering temperature and atmosphere. The luminescence intensity due to {sup 5}D{sub 0}→{sup 7}F{sub 2} transition of Eu{sup 3+} is decreased with increasing sintering temperature. CaBPO{sub 5} and BPO{sub 4} crystals co-exist in the as-prepared phosphors and the relative content of these two phases is dependent on sintering temperature. CaBPO{sub 5} crystal favors the transition of {sup 5}D{sub 0}→{sup 7}F{sub 1} of Eu{sup 3+} ions, while BPO{sub 4} enhances the emission of 612 nm. This study gives insight into the correlation between optical properties and structure of the as-prepared phosphors. The phosphors reported here are good candidates for light emitting diode applications. -- Highlights: • Eu doped 2CaO–P{sub 2}O{sub 5}–B{sub 2}O{sub 3} phosphors for LED applications are studied. • Effect of sintering conditions on optical property and structure is examined. • CaBPO{sub 5} favors the transition of {sup 5}D{sub 0}→{sup 7}F{sub 1} of Eu{sup 3+} in the investigated phosphors. • BPO{sub 4} enhances the emission of 612 nm of the phosphor.

  17. High temperature structural silicides

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.

    1997-03-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi{sub 2}-based materials, which are borderline ceramic-intermetallic compounds. MoSi{sub 2} single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi{sub 2} possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi{sub 2}-Si{sub 3}N{sub 4} composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi{sub 2}-based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing.

  18. High-temperature superconductors

    CERN Document Server

    Saxena, Ajay Kumar

    2010-01-01

    The present book aims at describing the phenomenon of superconductivity and high-temperature superconductors discovered by Bednorz and Muller in 1986. The book covers the superconductivity phenomenon, structure of high-Tc superconductors, critical currents, synthesis routes for high Tc materials, superconductivity in cuprates, the proximity effect and SQUIDs, theories of superconductivity and applications of superconductors.

  19. Evaluation of Sintering Behavior of Premix Al-Zn-Mg-Cu Alloy Powder

    Directory of Open Access Journals (Sweden)

    Haris Rudianto

    2015-01-01

    Full Text Available Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. Formation of liquid phase seems to support achieving high sintering density. Optimum mechanical properties also were obtained under those conditions. T6 heat treatment was done to improve the mechanical properties by formation of precipitation strengthening, and MgZn2 appears to be dominant strengthening precipitate. X-ray diffraction, optical microscopy, and SEM-EDS were used to characterize powder, and sintered and heat treated samples.

  20. High Temperature Electrolysis

    DEFF Research Database (Denmark)

    Elder, Rachael; Cumming, Denis; Mogensen, Mogens Bjerg

    2015-01-01

    High temperature electrolysis of carbon dioxide, or co-electrolysis of carbon dioxide and steam, has a great potential for carbon dioxide utilisation. A solid oxide electrolysis cell (SOEC), operating between 500 and 900. °C, is used to reduce carbon dioxide to carbon monoxide. If steam is also...... input to the cell then hydrogen is produced giving syngas. This syngas can then be further reacted to form hydrocarbon fuels and chemicals. Operating at high temperature gives much higher efficiencies than can be achieved with low temperature electrolysis. Current state of the art SOECs utilise a dense...

  1. Colloidal Nanocrystal-Based BaTiO3Xerogels as Green Bodies: Effect of Drying and Sintering at Low Temperatures on Pore Structure and Microstructures.

    Science.gov (United States)

    Rechberger, Felix; Mercandetti, Cristina; Tervoort, Elena; Niederberger, Markus

    2017-01-10

    Although aerogels prepared by the colloidal assembly of nanoparticles are a rapidly emerging class of highly porous and low-density materials, their ambient dried counterparts, namely xerogels, have hardly been explored. Here we report the use of nanoparticle-based BaTiO 3 xerogels as green bodies, which provide a versatile route to ceramic materials under the minimization of organic additives with a significant reduction of the calcination temperature compared to that of conventional powder sintering. The structural changes of the xerogels are investigated during ambient drying by carefully analyzing the microstructure at different drying stages. For this purpose, the shrinkage was arrested by a supercritical drying step under full preservation of the intermediate microstructure, giving unprecedented insight into the structural changes during ambient drying of a nanoparticle-based gel. In a first step, the large macropores shrink because of capillary forces, followed by the collapse of residual mesopores until a dense xerogel is obtained. The whole process is accompanied by a volume shrinkage of 97% and a drop in surface area from 300 to 220 m 2 g -1 . Finally, the xerogels are sintered, causing another shrinkage of up to 8% with a slight increase in the average pore and crystal sizes. At temperatures higher than 700 °C, an unexpected phase transition to BaTi 2 O 5 is observed.

  2. 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.

  3. Drastic decrease of Ba(Zn1/3Ta2/3O3 sintering temperature by lithium salts and glass phase addition

    Directory of Open Access Journals (Sweden)

    Marinel, S.

    2011-04-01

    Full Text Available The complex perovskite oxide Ba(Zn1/3Ta2/3O3 (BZT has been studied for its attractive dielectric properties which make this material interesting for applications such as multilayer ceramics capacitors or hyperfrequency resonators. Nevertheless, BZT ceramic requires high temperature to be correctly sintered (≅1450°C, that is too high to envisage a silver co-sintering (Tf(Ag = 961°C. For this reason, the lowering of the sintering temperature of BZT by glass phase’s additions has been investigated. This material is sinterable at low temperature with combined glass phase –lithium salt additions, and exhibits, at 1MHz very low dielectric losses combined with relatively high dielectric constant and a good stability of this later versus temperature. The 5 wt% of ZnO-SiO2-B2O3 glass phase and 1 wt% of LiF added BZT sample sintered at 900°C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant εr of 32, low dielectrics losses (tan (δ-3 and a temperature coefficient of permittivity τε of -10ppm/°C. Their good dielectric properties and their compatibility with silver electrodes, make these ceramics suitable for L.T.C.C applications.Se ha estudiado el óxido complejo con estructura tipo perovskita Ba (Zn1/3Ta2/3 O3 (BZT. Sus atractivas propiedades dieléctricas le hacen muy interesante para aplicaciones como condensadores cerámicos multicapa o resonadores de microondas. No obstante, los cerámicos de BZT requieren temperaturas de sinterización superiores a 1450 ° C, que es muy alta para abordar un proceso de co-sinterización con electrodos de plata (Tf (Ag = 961 ° C. Para ello, se ha estudiado la bajada de la temperatura de sinterización del BZT mediante la adición de una fase vítrea. La suma combinada de la fase vítrea y la sal de litio lleva la sinterización de este material a temperaturas bajas. Las propiedades dieléctricas presentan pérdidas muy bajas, constante diel

  4. High Temperature QCD

    CERN Document Server

    Lombardo, M P

    2012-01-01

    I review recent results on QCD at high temperature on a lattice. Steady progress with staggered fermions and Wilson type fermions allow a quantitative description of hot QCD whose accuracy in many cases parallels that of zero temperature studies. Simulations with chiral quarks are coming of age, and togheter with theoretical developments trigger interesting developments in the analysis of the critical region. Issues related with the universality class of the chiral transition and the fate of the axial symmetry are discussed in the light of new numerical and analytical results. Transport coefficients and analysis of bottomonium spectra compare well with results of heavy ion collisions at RHIC and LHC. Model field theories, lattice simulations and high temperature systematic expansions help building a coherent picture of the high temperature phase of QCD. The (strongly coupled) Quark Gluon Plasma is heavily investigated, and asserts its role as an inspiring theoretical laboratory.

  5. Effect of low temperature in-situ sintering on the impedance and the performance of intermediate temperature solid oxide fuel cell cathodes

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Hjalmarsson, Per; Hansen, Martin Hangaard

    2014-01-01

    frequency slope of the characteristic Gerischer impedance response of porous mixed ionic and electronically conducting (MIEC) cathodes. In contrast to LSCF, the LSC-based cathodes showed excellent sintering capabilities, electronic conductivity and performance. Scanning electron microscopy investigations......The effect of in-situ sintering temperature and time on the electronic conductivity, impedance and performance of IT-SOFC cathodes were studied. The studied cathodes were for comparison (La0.6Sr0.4)0.99CoO3 (LSC), (La0.6Sr0.4)0.99CoO3:Ce0.9Gd0.1O1.95 (LSC:CGO), La0.58Sr0.4Co0.2Fe0.8O3 (LSCF) and La...

  6. Highly efficient high temperature electrolysis

    DEFF Research Database (Denmark)

    Hauch, Anne; Ebbesen, Sune; Jensen, Søren Højgaard

    2008-01-01

    High temperature electrolysis of water and steam may provide an efficient, cost effective and environmentally friendly production of H-2 Using electricity produced from sustainable, non-fossil energy sources. To achieve cost competitive electrolysis cells that are both high performing i.e. minimum...... electrolysis is favourable from a thermodynamic point of view, because a part of the required energy can be supplied as thermal heat, and the activation barrier is lowered increasing the H-2 production rate. Only two types of cells operating at high temperature (above 200 degrees C) have been described...... electrolysis using SOECs is competitive to H-2 production from fossil fuels at electricity prices below 0.02-0.03 is an element of per kWh. Though promising SOEC results on H-2 production have been reported a substantial R&D is still required to obtain inexpensive, high performing and long-term stable...

  7. Electromagnetic properties of low-temperature-sintered Ba{sub 3}Co{sub 2-x}Zn{sub x}Fe{sub 24}O{sub 41} ferrites prepared by solid state reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiaohui E-mail: wxh@tsinghua.edu.cn; Li Longtu; Su Shuiyuan; Yue Zhenxing

    2004-09-01

    Hexagonal ferrites Ba{sub 3}Co{sub 2-x}Zn{sub x}Fe{sub 24}O{sub 41} (X=0-2.0) were prepared by a solid state reaction method. The influences of Zn content (X) on the Z-type phase formation temperature and specific saturation magnetization were investigated. With a small amount of sintering aids, highly dense hexaferrite ceramics with fine-grained microstructure were obtained after sintering at a relatively low temperature below 900 deg. C. The hexaferrite ceramics show excellent high-frequency properties such as high initial permeability up to 10, high cut-off frequency over 1.1 GHz and good DC resistivity more than 10{sup 9} {omega} cm.

  8. Comprehensive study on effect of sintering temperature on the physical, structural and optical properties of Er3+ doped ZnO-GSLS glasses

    Science.gov (United States)

    Rashid, Siti Syuhaida Abdul; Aziz, Sidek Hj. Ab; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd; Mohamed, Nurzilla

    The Er3+ doped zinc soda lime silica (ZnO-GSLS) glass system was prepared by the conventional melt-quenching technique using waste green soda lime silica (GSLS) glass, zinc oxide (ZnO) and erbium oxide (Er2O3) powder as starting materials. Er3+ doped willemite based glass-ceramics (Zn2SiO4:Er3+) were derived from this precursor glass by a controlled sintering process. The effect of sintering temperature on the density and linear shrinkage of the sample was investigated. XRD analysis revealed the presence of thermodynamically stable zinc orthosilicate (α-Zn2SiO4) phase at sintering temperatures above 700 °C. FESEM image shows the presence of densely packed grains as the sintering temperature increase. FTIR spectroscopy was used to observe the structural of SiO4 and ZnO4 groups in the formation of willemite phase evolution. The UV-Vis absorption spectra reveals four peaks centered at excitation of electron from ground state 4I15/2 to 4G11/2 (∼363 nm),4F7/2 (∼488 nm), 2H11/2 (∼523 nm), and 4F9/2 (∼652 nm). PL spectroscopy measurements were performed at room temperature using 385 nm excitation wavelengths. Enhancement of the Er3+ luminescence was observed with the progression of sintering temperature.

  9. Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications.

    Science.gov (United States)

    Kwon, Jinhyeong; Cho, Hyunmin; Eom, Hyeonjin; Lee, Habeom; Suh, Young Duk; Moon, Hyunjin; Shin, Jaeho; Hong, Sukjoon; Ko, Seung Hwan

    2016-05-11

    Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications.

  10. High temperature superconducting materials

    Energy Technology Data Exchange (ETDEWEB)

    Alario-Franco, M.A. [Universidad Complutense de Madrid (Spain). Facultad de Ciencias Quimicas

    1995-02-01

    The perovskite structure is the basis of all known high-temperature superconducting materials. Many of the most successful (highest T{sub c}) materials are based on mercury and thallium phases but, due to the high toxicity of the component compounds effort has been invested in the substitution of these elements with silver. Progress is reviewed. (orig.)

  11. Synthesis, Characterization, and Low Temperature Sintering of Nanostructured BaWO4 for Optical and LTCC Applications

    Directory of Open Access Journals (Sweden)

    S. Vidya

    2013-01-01

    Full Text Available Synthesis of nano-BaWO4 by a modified combustion technique and its suitability for various applications are reported. The structure and phase purity of the sample analyzed by X-ray diffraction, Fourier transform Raman, and infrared spectroscopy show that the sample is phase pure with tetragonal structure. The particle size from the transmission electron microscopy is 22 nm. The basic optical properties and optical constants of the nano BaWO4 are studied using UV-visible absorption spectroscopy which showed that the material is a wide band gap semiconductor with band gap of 4.1 eV. The sample shows poor transmittance in ultraviolet region while maximum in visible-near infrared regions. The photoluminescence spectra show intense emission in blue region. The sample is sintered at low temperature of 810°C, without any sintering aid. Surface morphology of the sample is analyzed by scanning electron microscopy. The dielectric constant and loss factor measured at 5 MHz are 9 and 1.56×10-3. The temperature coefficient of dielectric constant is −22 ppm/°C. The experimental results obtained in the present work claim the potential use of nano BaWO4 as UV filters, transparent films for window layers on solar cells, antireflection coatings, scintillators, detectors, and for LTCC applications.

  12. Effect of sintering temperature and boron carbide content on the wear behavior of hot pressed diamond cutting segments

    Directory of Open Access Journals (Sweden)

    Islak S.

    2015-01-01

    Full Text Available The aim of this study was to investigate the effect of sintering temperature and boron carbide content on wear behavior of diamond cutting segments. For this purpose, the segments contained 2, 5 and 10 wt.% B4C were prepared by hot pressing process carried out under a pressure of 35 MPa, at 600, 650 and 700 °C for 3 minutes. The transverse rupture strength (TRS of the segments was assessed using a three-point bending test. Ankara andesite stone was cut to examine the wear behavior of segments with boron carbide. Microstructure, surfaces of wear and fracture of segments were determined by scanning electron microscopy (SEM-EDS, and X-ray diffraction (XRD analysis. As a result, the wear rate decreased significantly in the 0-5 wt.% B4C contents, while it increased in the 5-10 wt.% B4C contents. With increase in sintering temperature, the wear rate decreased due to the hard matrix.

  13. [Determination of normal temperature properties of refractory die material compatible with slip casting core of sintered titanium powder].

    Science.gov (United States)

    Kuang, X; Liao, Y; Chao, Y; Wang, H

    1999-05-01

    The refractory die is the precondition for developing slip casting core of sintered powder. This study is to determine the normal temperature properties of the refractory die material compatible with slip casting core. to mix the die material at five different ratios (8/1, 7.5/1, 7/1, 6.5/1, and 6/1) and measure their solidification time with self-manufactured Vicker's needle; to prepare five cylindrical specimens (phi 10 x 15 mm) in different drying time for determining their compressive strength, and then to let another five specimens fire at 1000 degrees C four times for measuring the residual compressive strength at room temperature. The setting time was 16.25 minutes (7.5/1), and the lower the powder-liquid ratio, the longer the setting time. The normal compressive strength was 25.32 MPa (drying 24 hours), while the longer the drying time, the higher the compressive strength achieved (P slip casting core of sintered powder.

  14. Low-temperature preparation by polymeric complex solution synthesis of Cu-Gd-doped ceria cermets for solid oxide fuel cells anodes: Sinterability, microstructures and electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Tartaj, J.; Moure, A. [Instituto de Ceramica y Vidrio (CSIC), Electroceramics Department, Kelsen 5, 28049 Madrid (Spain); Gil, V. [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC, Pedro Cerbuna 12, E-50009 Zaragoza (Spain)

    2010-05-01

    A homogeneous dispersion of fine CuO in a gadolinia-doped ceria (CGO) ceramic matrix by the polymeric organic complex solution method has been achieved. Highly sinterable powders were prepared by this method after calcining the precursor at 600 C and attrition milled. The powders consist of individual particles of few tens of nanometer in size with a low agglomeration state. The isopressed compacts were sintered in air at 1000 C and reducing in N{sub 2} 90%-H{sub 2} 10% atmosphere to form Cu-CGO cermets. The microstructures showed a uniform distribution of porous metallic Cu particles surrounded by microporous spaces. The influence of Cu content in Cu-CGO cermets on the electrode performance has been investigated in order to create the most suitable microstructure. The electrical properties of Cu-CGO cermets have been also studied using impedance spectroscopy, in the temperature range form 150 to about 700 C in argon atmosphere. These measurements determined a high value of electrical conductivity at 700 C, similar to that corresponded to pure metallic cupper. (author)

  15. Effect of compaction load and sintering temperature on the mechanical properties of the Al-SiC nano-composite materials

    Science.gov (United States)

    Iqbal, AKM Asif; Lim, Mei Jing; Nuruzzaman, Dewan Muhammad

    2017-12-01

    The development of metal matrix composites (MMCs) has set the stage for a new revolution in materials. In this research, Al matrix composites reinforced with SiC nanoparticles were fabricated by a powder metallurgy process and the effects of compaction load and sintering temperature on the mechanical properties of the Al-SiC nano-composite was investigated. The samples were prepared with two different compaction loads, 100 kN and 200 kN, and two different sintering temperatures, 550 °C and 600 °C. Subsequently, their mechanical testing was carried out. The density and hardness of the samples were investigated. The microstructure of the nano-composite was examined by optical microscope. The results showed that the higher compaction load and higher sintering temperature significantly increased the density and hardness of the nano-composite materials.

  16. High temperature storage loop :

    Energy Technology Data Exchange (ETDEWEB)

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  17. High temperature superconductivity: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Bedell, K.S.; Coffey, D. (Los Alamos National Lab., NM (USA)); Meltzer, D.E. (Florida Univ., Gainesville, FL (USA)); Pines, D. (Illinois Univ., Urbana, IL (USA)); Schrieffer, J.R. (California Univ., Santa Barbara, CA (USA)) (eds.)

    1990-01-01

    This book is the result of a symposium at Los Alamos in 1989 on High Temperature Superconductivity. The topics covered include: phenomenology, quantum spin liquids, spin space fluctuations in the insulating and metallic phases, normal state properties, and numerical studies and simulations. (JF)

  18. Life at High Temperatures

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 9. Life at High Temperatures. Ramesh Maheshwari. General Article Volume 10 Issue 9 September 2005 pp 23-36. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/010/09/0023-0036. Keywords.

  19. Effect of citric acid dosage and sintered temperature on the composition, morphology and electrochemical properties of lithium vanadium oxide prepared by a sol-gel method

    Science.gov (United States)

    Zhong, C. R.; Su, X. J.; Hou, G. L.; Liu, Z. H.; Yu, F. S.; Bi, S.; Li, H.

    2017-03-01

    A lithium vanadium oxide cathode material was synthesized via sol-gel processing using citric acid as the chelating agent. Different dosage of citric acid and sintered temperature were introduced to investigate their effects on the products composition, morphology and electrochemical properties. The results showed that the V2O3 yield was inhibited and the crystallization of grain was accelerated with the increasing dosage of citric acid. Furthermore, V2O3 was oxidized to LiV3O8 and Li0.3V2O5 with the increase of sintered temperature.

  20. Influences of composition of starting powders and sintering temperature on the pore size distribution of porous corundum-mullite ceramics

    Directory of Open Access Journals (Sweden)

    Shujing Li

    2005-01-01

    Full Text Available Porous corundum-mullite ceramics were prepared by an in-situ decomposition pore-forming technique. Starting powders were mixtures of milled Al(OH3 and microsilica and were formed into oblong samples with a length of 100mm and a square cross-section with edge size of 20mm. The samples were heated at 1300°C, 1400°C, 1500°C or 1600°C for 3h in air atmosphere, respectively. Apparent porosity was detected by Archimedes’ Principle with water as a medium. Pore size distribution and the volume percentage of micropores were measured by mercury intrusion porosimetry. The results show that the pore morphology parameters in the samples depend on four factors: particle size distribution of starting powders, decomposition of Al(OH3, the expansion caused by mullite and sintering. The optimum mode which has a higher apparent porosity up to 42.3%, well-distributed pores and more microsize pores up to 16.3% is sample No.3 and the most apposite sintering temperature of this sample is 1500°C.

  1. High temperature future

    Energy Technology Data Exchange (ETDEWEB)

    Sheinkopf, K. [Solar Energy Research and Education Foundation, Washington, DC (United States)

    1994-09-01

    During the past few years, there have been dramatic accomplishments and success of high temperature solar thermal systems and significant development of these systems. High temperature technologies, about 500 F and higher, such as dish engines, troughs, central receiver power towers and solar process heat systems, have been tested, demonstrated and used in an array of applications, including many cost-effective utility bulk power production and demand side supply projects in the United States. Large systems provide power and hot water to prisons, schools, nursing homes and other institutions. Joint ventures with industry, utility projects, laboratory design assistance and other activities are building a solid industry of US solar thermal systems ready for use today.

  2. EFFECTS OF SINTERING TEMPERATURE ON THE PERFORMANCE OF SrSc0.1Co0.9O3-δOXYGEN SEMIPERMEABLE MEMBRANE

    Directory of Open Access Journals (Sweden)

    P. Zeng

    2015-09-01

    Full Text Available AbstractOur study investigates the influence of sintering temperature on the microstructure (grain size distribution, grain boundary length, electrical conductivity, and oxygen permeation properties of permeation membranes. For this purpose, SrSc0.1Co0.9O3-δ samples with different microstructures were prepared by varying the sintering temperature from 1100 to 1250 ˚C. The average grain sizes were gradually increased, thus the grain boundary lengths decreased with increased sintering temperatures. The influence of the ceramic microstructure on total electrical conductivity was found to be negligible. The oxygen transport properties of the samples were characterized by permeation measurements as a function of temperature in an air/helium oxygen partial pressure gradient. The decrease of the sintering temperature, meaning a decrease of grain size and thus the increase of grain boundary length, leads to an enhanced oxygen permeation flux and a reduced activation energy. This implies that oxygen exchange and transport in the SrSc0.1Co0.9O3-δ membranes occur more rapidly along grain boundaries than in the grain bulk.

  3. 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.

  4. Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Sazzad Hossain; Mian, Ahsan, E-mail: ahsan.mian@wright.edu; Srinivasan, Raghavan [Department of Mechanical and Materials Engineering, Wright State University, Dayton, Ohio 45435 (United States)

    2016-07-12

    In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

  5. High-performance direct conversion X-ray detectors based on sintered hybrid lead triiodide perovskite wafers

    Science.gov (United States)

    Shrestha, Shreetu; Fischer, René; Matt, Gebhard J.; Feldner, Patrick; Michel, Thilo; Osvet, Andres; Levchuk, Ievgen; Merle, Benoit; Golkar, Saeedeh; Chen, Haiwei; Tedde, Sandro F.; Schmidt, Oliver; Hock, Rainer; Rührig, Manfred; Göken, Mathias; Heiss, Wolfgang; Anton, Gisela; Brabec, Christoph J.

    2017-07-01

    Lead halide perovskite semiconductors are in general known to have an inherently high X-ray absorption cross-section and a significantly higher carrier mobility than any other low-temperature solution-processed semiconductor. So far, the processing of several-hundred-micrometres-thick high-quality crystalline perovskite films over a large area has been unresolved for efficient X-ray detection. In this Article, we present a mechanical sintering process to fabricate polycrystalline methyl ammonium lead triiodide perovskite (MAPbI3) wafers with millimetre thickness and well-defined crystallinity. Benchmarking of the MAPbI3 wafers against state-of-the-art CdTe detectors reveals competitive conversion efficiencies of 2,527 µC Gyair-1 cm-2 under 70 kVp X-ray exposure. The high ambipolar mobility-lifetime product of 2 × 10-4 cm2 V-1 is suggested to be responsible for this exceptionally high sensitivity. Our findings inform a new generation of highly efficient and low-cost X-ray detectors based on perovskite wafers.

  6. High Temperature Piezoelectric Drill

    Science.gov (United States)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

    2012-01-01

    Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

  7. High temperature materials and mechanisms

    CERN Document Server

    2014-01-01

    The use of high-temperature materials in current and future applications, including silicone materials for handling hot foods and metal alloys for developing high-speed aircraft and spacecraft systems, has generated a growing interest in high-temperature technologies. High Temperature Materials and Mechanisms explores a broad range of issues related to high-temperature materials and mechanisms that operate in harsh conditions. While some applications involve the use of materials at high temperatures, others require materials processed at high temperatures for use at room temperature. High-temperature materials must also be resistant to related causes of damage, such as oxidation and corrosion, which are accelerated with increased temperatures. This book examines high-temperature materials and mechanisms from many angles. It covers the topics of processes, materials characterization methods, and the nondestructive evaluation and health monitoring of high-temperature materials and structures. It describes the ...

  8. Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

    Science.gov (United States)

    Almasri, Karima Amer; Sidek, Hj. Ab Aziz; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd

    The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3) based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF) and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM), Fourier transforms infrared reflection spectroscopy (FTIR), and X-ray diffraction (XRD). The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature.

  9. High Temperature Integrated Thermoelectric Ststem and Materials

    Energy Technology Data Exchange (ETDEWEB)

    Mike S. H. Chu

    2011-06-06

    The final goal of this project is to produce, by the end of Phase II, an all ceramic high temperature thermoelectric module. Such a module design integrates oxide ceramic n-type, oxide ceramic p-type materials as thermoelectric legs and oxide ceramic conductive material as metalizing connection between n-type and p-type legs. The benefits of this all ceramic module are that it can function at higher temperatures (> 700 C), it is mechanically and functionally more reliable and it can be scaled up to production at lower cost. With this all ceramic module, millions of dollars in savings or in new opportunities recovering waste heat from high temperature processes could be made available. A very attractive application will be to convert exhaust heat from a vehicle to reusable electric energy by a thermoelectric generator (TEG). Phase I activities were focused on evaluating potential n-type and p-type oxide compositions as the thermoelectric legs. More than 40 oxide ceramic powder compositions were made and studied in the laboratory. The compositions were divided into 6 groups representing different material systems. Basic ceramic properties and thermoelectric properties of discs sintered from these powders were measured. Powders with different particles sizes were made to evaluate the effects of particle size reduction on thermoelectric properties. Several powders were submitted to a leading thermoelectric company for complete thermoelectric evaluation. Initial evaluation showed that when samples were sintered by conventional method, they had reasonable values of Seebeck coefficient but very low values of electrical conductivity. Therefore, their power factors (PF) and figure of merits (ZT) were too low to be useful for high temperature thermoelectric applications. An unconventional sintering method, Spark Plasma Sintering (SPS) was determined to produce better thermoelectric properties. Particle size reduction of powders also was found to have some positive benefits

  10. High temperature superconductors

    CERN Document Server

    Paranthaman, Parans

    2010-01-01

    This essential reference provides the most comprehensive presentation of the state of the art in the field of high temperature superconductors. This growing field of research and applications is currently being supported by numerous governmental and industrial initiatives in the United States, Asia and Europe to overcome grid energy distribution issues. The technology is particularly intended for densely populated areas. It is now being commercialized for power-delivery devices, such as power transmission lines and cables, motors and generators. Applications in electric utilities include current limiters, long transmission lines and energy-storage devices that will help industries avoid dips in electric power.

  11. Modeling the mechanical behavior of ceramic and heterophase structures manufactured using selective laser sintering and spark plasma sintering

    Science.gov (United States)

    Skripnyak, Vladimir A.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.; Vaganova, Irina K.

    A model for predicting mechanical properties of ultra-high temperature ceramics and composites manufactured by selective laser sintering (SLS) and spark plasma sintering (SPS) under shock loading is presented. The model takes into account the porous structure, the specific volume and average sizes of phases, and the temperature of sintering. Residual stresses in ceramic composites reinforced with particles of refractory borides, carbides and nitrides after SLS or SPS were calculated. It is shown that the spall strength of diboride-zirconium matrix composites can be increased by the decreasing of porosity and the introduction of inclusions of specially selected refractory strengthening phases.

  12. Effect of Co3O4 doping and sintering temperature on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

    Science.gov (United States)

    Ghazali, Mohd Sabri Mohd; Abdullah, Wan Rafizah Wan; Zakaria, Azmi; Zulkifli, Muhamad Azman; Zaid, Mohd Hafiz Mohd; Rizwan, Zahid

    2017-09-01

    It is necessary to investigate the electronic states of ceramic based ZnO vasristor and effect of doped impurities at different concentration. Band gap (Eg) of the ceramic (99-x) mol% ZnO+0.5 mol% Bi2O3+0.5 mol% TiO2+ xCo3O4 where x = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples were prepared via solid-state route and sintered at the sintering temperature at 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of Co3O4, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.368 ± 0.002 and 2.352 ± 0.001 eV at 0.8 mol% Co3O4 for 45 and 90 min sintering time; respectively. XRD analysis indicates that two main phases existed at all concentrations which are ZnO and secondary phases, Bi12TiO20, Zn2Ti3O8, ZnCo2O4 and Co3Ti3O. Relative density decreases with the addition of Co3O4 compared to that of undoped at all doping level. When Co3O4 is added in the ceramics, relative density increases with the increase of doping level at both 45 and 90 min sintering time. The variation of sintering temperatures and XRD findings of steepness factor are correlated with the UV-Vis spectrophotometer results of based ZnO varistor doped with Co3O4 due to the growth of interface states.

  13. Sintering of HDH Ti Powder

    Directory of Open Access Journals (Sweden)

    Kováčik Jaroslav

    2014-12-01

    Full Text Available Titanium powders prepared by hydro-dehydration process (HDH powder were pressure less sintered in vacuum oven at different temperatures, time and green density. The sintering properties of powders of two particle sizes - 30 and 150 microns were investigated. The usual powder metallurgical (PM results were observed, i.e., decreasing final porosity with increasing sintering temperature and time at constant heating rate. Higher green density leading to higher final density for both powder sizes was also observed. The obtained results will be used as comparative material for future sintering experiments of Ti based composites.

  14. Effect of high pressure sintering and annealing on microstructure and thermoelectric properties of nanocrystalline Bi2Te2.7Se0.3 doped with Gd

    Directory of Open Access Journals (Sweden)

    Ping Zou

    2014-06-01

    Full Text Available Bi2Te2.7Se0.3 of high performance doped with Gd bulk materials was prepared by a high pressure (6.0 GPa sintering (HPS method at 593 K, 633 K, 673 K and 693 K. The sample was then annealed for 36 h in a vacuum at 633 K. The phase composition, crystal structure and morphology of the sample were analyzed by X-ray diffraction and scanning electron microscopy. The electric conductivity, Seebeck coefficient, and thermal conductivity aspects of the sample were measured from 298 K to 473 K. The results show that high pressure sintering and the doping with Gd has a great effect on the crystal structure and the thermoelectric properties of the samples. The samples are consisted of nanoparticles before and after annealing, and these nanostructures have good stability at high temperature. HPS together with annealing can improve the TE properties of the sample by decreasing the thermal conductivity of the sample with nanostructures. The maximum ZT value of 0.74 was obtained at 423 K for the sample, which was sintered at 673 K and then annealed at 633 K for 36 h. Compared with the zone melting sample, it was increased by 85% at 423 K. Hence the temperature of the maximum of figure of merit was increased. The results can be applied to the field of thermoelectric power generation materials.

  15. Mn doping effect on optical and ESR studies of Zn{sub 1-x}Mn{sub x}O compound sintered at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Mahule, T.; Srinivasu, V. V. [Department of Physics, CSET, University of South Africa, Johannesburg, 1710 (South Africa); Das, J., E-mail: jayashree304@gmail.com [Department of Physics, CSET, University of South Africa, Johannesburg, 1710 (South Africa); Department of Physics, Silicon Institute of Technology, Bhubaneswar, 751024, Odisha (India)

    2016-05-06

    Polycrystalline bulk samples of Zn{sub 1-x}Mn{sub x}O with x=0.02, 0.04, 0.05 and sintered at different temperatures (500 °C & 800 °C) were studied to investigate the doping effect on the structural, optical properties and spin dynamics in ZnO system. The crystallite size was seen to decrease with no significant change in other structural parameters. FTIR study showed a small effect on the Zn-O stretching bond and other bonds due to presence of Mn. Calculation from UV-Vis spectra showed increase in the optical band gap in the low temperature sintered samples due to Mn doping. In the PL spectra, the UV emission seen to dominate for the 500 °C sintered sample, for 800 °C sample the visible emission dominate indicating increase in non-radiative emission. ESR signals obtained from the microwave absorption shows ferromagnetic signal for the low temperature sintered sample only with a g value of 2.004 for the 2% Mn doped sample. The number of spin participation for resonance is calculated from the ESR signal, which supports the magnetic behaviour of this particular sample.

  16. 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.

  17. Effects of B2O3 content and sintering temperature on crystallization and microstructure of CBS glass-ceramic coatings

    Science.gov (United States)

    Li, Pengyang; Wang, Shubin; Liu, Jianggao; Feng, Mengjie; Yang, Xinwang

    2015-11-01

    Borosilicate glass-ceramics precursors with varying compositional ratios in the CaO-SiO2-B2O3 (CBS) system were synthesized by sol-gel method. The precursors were calcined at 1200 °C for 2 h to form glass powders. The glass-ceramics were prepared by overlaying glass slurries on the substrates before sintering at different temperatures. The as-prepared glasses and glass-ceramics were characterized by differential scanning calorimetry and X-ray diffraction. The crystallization activation energies (Ec) were calculated using the Kissinger method from DSC results. The morphology and crystallization behavior of the glass-ceramics were monitored by scanning electron microscopy. Both glass transition and crystallization temperatures decreased, however, the metastable zone increased. The Ec values of CBS glasses and glass-ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B2O3 content, whereas that of the calcined G3 glass was 104.9 kJ/mol. Finally, the coatings were prepared at a low temperature (700 °C). The crystals that grew on the surface of multilayer coatings demonstrated heterogeneous surface nucleation and crystallization after heat-treatment from 700 °C to 850 °C for 4 h.

  18. High Temperature Aquifer Storage

    Science.gov (United States)

    Ueckert, Martina; Niessner, Reinhard; Baumann, Thomas

    2016-04-01

    Combined heat and power generation (CHP) is highly efficient because excess heat is used for heating and/or process energy. However, the demand of heat energy varies considerably throughout the year while the demand for electrical energy is rather constant. It seems economically and ecologically highly beneficial for municipalities and large power consumers such as manufacturing plants to store excess heat in groundwater aquifers and to recuperate this energy at times of higher demand. Within the project High Temperature Aquifer Storage, scientists investigate storage and recuperation of excess heat energy into the bavarian Malm aquifer. Apart from high transmissivity and favorable pressure gradients, the hydrochemical conditions are crucial for long-term operation. An enormous technical challenge is the disruption of the carbonate equilibrium - modeling results indicated a carbonate precipitation of 10 - 50 kg/d in the heat exchangers. The test included five injection pulses of hot water (60 °C up to 110 °C) and four tracer pulses, each consisting of a reactive and a conservative fluorescent dye, into a depth of about 300 m b.s.l. resp. 470 m b.s.l. Injection and production rates were 15 L/s. To achieve the desired water temperatures, about 4 TJ of heat energy were necessary. Electrical conductivity, pH and temperature were recorded at a bypass where also samples were taken. A laboratory container at the drilling site was equipped for analysing the concentration of the dyes and the major cations at sampling intervals of down to 15 minutes. Additional water samples were taken and analysed in the laboratory. The disassembled heat exchanger prooved that precipitation was successfully prevented by adding CO2 to the water before heating. Nevertheless, hydrochemical data proved both, dissolution and precipitation processes in the aquifer. This was also suggested by the hydrochemical modelling with PhreeqC and is traced back to mixture dissolution and changing

  19. Sintering temperature effect on electric transport properties and magnetoresistance of La{sub 0.67}Ca{sub 0.33}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Ramadhan, M. R.; Kurniawan, B., E-mail: bkuru07@gmail.com; Manaf, A.; Pratama, R. [Department of Physics, FMIPA, Universitas Indonesia, Kampus UI Depok (Indonesia); Nanto, D. [Department of Physics Education, Syarif Hidayatullah State Islamic University, Jakarta 15412 (Indonesia); Saptari, S. A. [Faculty of Science and Technology, Syarif Hidayatullah State Islamic University, Jakarta 15412 (Indonesia); Imaduddin, A. [Research Center of Metallurgy and Material, Indonesian Institute of Sciences, Gd 470 Kawasan Puspitek, Serpong, Tangerang Selatan 15314 (Indonesia)

    2016-04-19

    A compound of La{sub 0.67}Ca{sub 0.33}MnO{sub 3} (LCMO) is known as a famous colossal magnetoresistance material. Many studies have been carried in order to get more information about the electric and magnetic characteristic of the sample. The effect of two different sintering temperatures on manganite material La{sub 0.67}Ca{sub 0.33}MnO{sub 3} (LCMO) which prepared by solid state reaction, has been investigated in order to find the relations between the sintering temperature and the manganite’s electric transport properties. Characterization using X-Ray Diffractometer shows that the two samples have a single phase pattern. However, from the resistivity measurement both samples show a different value, but similar behavior. The resistivity reach maximum value in specific temperature T{sub p}, before it decreases once again to its lowest value in low temperature region.

  20. Second report on sintering diagrams

    Energy Technology Data Exchange (ETDEWEB)

    Swinkels, F.B.; Ashby, M.F.

    1980-04-01

    Sintering-mechanism diagrams are diagrams with axes of neck-size or density, and temperature, which identify the fields of dominance of each of the several mechanisms which contribute to sintering, and show the rate or extent of sintering that all the mechanisms, acting together, produce. The present paper incorporates certain new ideas about sintering into the diagrams: the coupling of boundary diffusion and surface diffusion; new criteria for the stages of sintering; and an approximate treatment of particle rearrangement. Diagrams showing how both the neck size and the density of compacts of wires and of spheres change with time and temperature are developed. Their use is illustrated by an analysis of a large body of sintering data for both wires and spheres of Ag, Cu, Ni, Fe, W, NaCl and Stainless Steel.

  1. INFLUENCE OF SINTERING TEMPERATURE ON THE POLARIZATION RESISTANCE OF LaO20.6SrO20.4CoO20.2FeO20.8O3-δ - SDC CARBONATE COMPOSITE CATHODE

    Directory of Open Access Journals (Sweden)

    Nurul Akidah Baharuddin

    2016-05-01

    Full Text Available The effects of sintering temperature of an LSCF-samarium-doped ceria carbonate (SDCC cathode composite film on its polarization resistance (Rp were evaluated in this study. An LSCF-SDCC composite cathode was prepared for cathode film development by electrophoretic deposition (EPD. The LSCF-SDCC composite cathode was prepared at 50:50 weight percentage ratio. An EPD suspension which is based on an organic aqueous solution was used, and a mixture of ethanol and deionized water was used as medium with poly diallyl dimethyl ammonium chloride (PDADMAC as a dispersing agent. SDCC substrate was used, and EPD was performed on both sides. A symmetrical cell with cathode composite LSCF-SDCC films on both sides of the substrate was subjected to sintering at five different temperatures (from 550°C to 750°C. A symmetrical cell was painted using silver paste before undergoing electrochemical performance test (air condition, in which the impedance, Z data, was measured. The effects of sintering temperature change on element content and film porosity were first investigated by energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, and J-image analysis. Ceramic-based cathode LSCF-SDCC that was sintered at 600°C exhibited the lowest Rp at a value of 0.68 Ω when operated at 650°C. This study proved that EPD has potential in developing IT-LT solid oxide fuel cell cathode components with high electrochemical performance in terms of Rp values.

  2. Influence of Sintering Temperature on Pore Structure and Electrical properties of Technologically Modified MgO-Al2O3 Ceramics

    Directory of Open Access Journals (Sweden)

    Halyna Klym

    2015-03-01

    Full Text Available Technologically modified spinel ceramics are prepared from Al2O3 and 4MgCO3×Mg(OH2×5H2O powders at 1200, 1300 and 1400 oC. The influence of sintering temperature on porous structure and exploitation properties of obtained humidity-sensitive MgO-Al2O3 ceramics are studied. It is shown that increasing of preparing temperature from 1200 to 1400 oC result in transformation of pore size distribution in ceramics from tri- to bi-modal including the open macro- and mesopores with sizes from tem to hundreds nm and nanopores until to a few nm. The studied ceramic elements with electrical resistances ~ 10-2-102 MОhm are high humidity sensitive in the region of 30-95 % with minimal hysteresis in adsorption-desorption cycles. It is established that increasing of humidity sensitivity in ceramics are related to achievement near to optimum pore size distribution and quantity of pores in the all regions. Prolonged degradation transformation in ceramics at higher temperature and relative humidity result in lose sensitivity up to 40-50 %.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5189

  3. High Temperature Hybrid Elastomers

    Science.gov (United States)

    Drake, Kerry Anthony

    Conventional high temperature elastomers are produced by chain polymerization of olefinic or fluorinated olefinic monomers. Ultimate thermal stabilities are limited by backbone bond strengths, lower thermal stability of cross-link sites relative to backbone bonds, and depolymerization or "unzipping" at high temperatures. In order to develop elastomers with enhanced thermal stability, hybrid thermally cross-linkable polymers that consisted only of organic-inorganic and aromatic bonds were synthesized and evaluated. The addition of phenylethynyl or phenylacetylinic functional groups to these polymers resulted in conversion of the polymers into high temperature elastomers when cross-linked by thermal curing. Polyphenyoxydiphenylsilanes were synthesized via several different condensation reactions. Results of these synthetic reactions, which utilized both hydroquinone and biphenol as monomers, were systematically evaluated to determine the optimal synthetic conditions for subsequent endcapping reactions. It was determined that dichlorodiphenylsilane condensations with biphenol in toluene or THF were best suited for this work. Use of excess dichlorodiphenylsilane yielded polymers of appropriate molecular weights with terminal reactive chlorosilane groups that could be utilized for coupling with phenylethynyl reagents in a subsequent reaction. Two new synthetic routes were developed to endcap biphenoxysilanes with ethynyl containing substituents, to yield polymers with cross-linkable end groups. Endcapping by lithiumphenylacetylide and 4[(4-fluorophenylethynyl))phenol yielded two new polymers that could be thermally cross-linked on heating above 300 °C. Successful endcapping was verified chemically by 13C NMR, FTIR and Raman analysis. Exothermic peaks consistent with ethynyl curing reactions were observed in endcapped polymers by DSC. A new diacetylinic polymer was prepared through reaction of 4,4'-buta-1,3-diyne-1,4-diyldiphenol and dichlorodiphenylsilane. This

  4. Effect of Sintering Temperature to Physical, Magnetic Properties and Crystal Structure on Permanent Magnet BaFe12O19 Prepared From Mill Scale

    Science.gov (United States)

    Ramlan; Muljadi; Sardjono, Priyo; Gulo, Fakhili; Setiabudidaya, Dedi

    2017-07-01

    Permanent magnet of Barium hexa Ferrite with formula BaFe12O19 has been made by metallurgy powder method from raw materials : Barium carbonate (BaCO3 E-merck) and Iron Oxide (Fe2O3 from mill scale). Both of raw materials have been mixed with stoichiometry composition by using a ball mill for 24 hours. The fine powder obtained from milling process was formed by using a hydraulic press at pressure 50 MPa and continued with sintering process. The sintering temperature was varied : 1150°C, 1200°C, 1250°C and 1300°C with holding time for 1 hour. The sintered samples were characterized such as : physical properties (bulk density, porosity and shrinkage), magnetic properties (flux density, remanence, coercivity and magnetic saturation) by using VSM and crystal structure by using XRD. According characterization results show that the crystal structure of BaFe12O19 does not change after sintering process, but the grain size tends to increase. The optimum condition is achieved at temperature 1250°C, and at this condition, the sample has characterization such as : bulk density = 4.35 g/cm3, porosity = 1.03% and firing shrinkage = 11.63%, flux density = 681.1 Gauss, remanence (σr) = 20.78 emu/g, coercivity (Hc) = 2058 Oe and magnetic saturation (σs) 45.16 emu/g.

  5. Effect of sintering temperature on the morphology and mechanical properties of PTFE membranes as a base substrate for proton exchange membrane

    Directory of Open Access Journals (Sweden)

    Nor Aida Zubir

    2002-11-01

    Full Text Available This paper reports the development of PTFE membranes as the base substrates for producing proton exchange membrane by using radiation-grafting technique. An aqueous dispersion of PTFE, which includes sodium benzoate, is cast in order to form suitable membranes. The casting was done by usinga pneumatically controlled flat sheet membrane-casting machine. The membrane is then sintered to fuse the polymer particles and cooled. After cooling process, the salt crystals are leached from the membrane by dissolution in hot bath to leave a microporous structure, which is suitable for such uses as a filtration membrane or as a base substrate for radiation grafted membrane in PEMFC. The effects of sintering temperature on the membrane morphology and tensile strength were investigated at 350oC and 385oC by using scanning electron microscopy (SEM and EX 20, respectively. The pore size and total void space are significantly smaller at higher sintering temperature employed with an average pore diameter of 11.78 nm. The tensile strength and tensile strain of sintered PTFE membrane at 385oC are approximately 19.02 + 1.46 MPa and 351.04 + 23.13 %, respectively. These results were indicated at 385oC, which represents significant improvements in tensile strength and tensile strain, which are nearly twice those at 350oC.

  6. Room temperature synthesis of a copper ink for the intense pulsed light sintering of conductive copper films.

    Science.gov (United States)

    Dharmadasa, Ruvini; Jha, Menaka; Amos, Delaina A; Druffel, Thad

    2013-12-26

    Conducting films are becoming increasingly important for the printed electronics industry with applications in various technologies including antennas, RFID tags, photovoltaics, flexible electronics, and displays. To date, expensive noble metals have been utilized in these conductive films, which ultimately increases the cost. In the present work, more economically viable copper based conducting films have been developed for both glass and flexible PET substrates, using copper and copper oxide nanoparticles. The copper nanoparticles (with copper(I) oxide impurity) are synthesized by using a simple copper reduction method in the presence of Tergitol as a capping agent. Various factors such as solvent, pH, and reductant concentration have been explored in detail and optimized in order to produce a nanoparticle ink at room temperature. Second, the ink obtained at room temperature was used to fabricate conducting films by intense pulse light sintering of the deposited films. These conducting films had sheet resistances as low as 0.12 Ω/□ over areas up to 10 cm(2) with a thickness of 8 μm.

  7. Characterization of high-current, high-temperature superconductor current lead elements

    Energy Technology Data Exchange (ETDEWEB)

    Niemann, R.C.; Evans, D.J.; Fisher, B.L. [Argonne National Lab., IL (United States); Brockenborough, W.E.; Roberts, P.R.; Rodenbush, A.J. [American Superconductor Corp., Westborough, MA (United States)

    1996-08-01

    The refrigeration loads of current leads for superconducting magnets can be significantly reduced by using high-temperature superconductor (HTS) leads. An HTS conductor type that is well suited for this application is a laminated sintered stack of HTS powder-in-tube (PIT) tapes. The superconducting elements are normally characterized by their manufacturer by measuring critical currents at 77 K in self field. Additional characterization, which correlates electrical performance at 77 K and at lower temperatures with applied magnetic fields, provides the current lead designer and conductor element manufacturer with critical information. For HTS conductor elements comprising a laminated and sintered stack of Bi-2223 PIT tapes having an alloyed Ag sheath, this characterization uses variable applied fields and operating temperatures.

  8. Tuning Ce distribution for high performanced Nd-Ce-Fe-B sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Xiaodong [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); Guo, Shuai; Chen, Kan; Chen, Renjie; Lee, Don [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China); You, Caiyin, E-mail: caiyinyou@xaut.edu.cn [School of Materials Science and Engineering, Xi’an University of Technology, Xi’an 710048 (China); Yan, Aru, E-mail: aruyan@nimte.ac.cn [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201 (China)

    2016-12-01

    A dual-alloy method was applied to tune the distribution of Ce for enhancing the performance of Nd-Ce-Fe-B sintered magnets with a nominal composition of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B. In comparison to the single alloy of (Nd{sub 0.75}Ce{sub 0.25}){sub 30.5}Fe{sub bal}Al{sub 0.1}Cu{sub 0.1}B, the coercivity was enhanced from 10.3 kOe to 12.1 kOe and the remanence was increased from 13.1 kG to 13.3 kG for the magnets with a dual-alloy method. In addition, the remanence temperature coefficient α and coercivity temperature coefficient β were also slightly improved for the magnet with the dual alloys. The results of microstructure characterizations show the uniform distribution of Ce for the magnet with a single alloy, and the coexistence of the Ce-rich and Ce-lean regions for the magnet with the dual alloys. In combinations with the nucleation of reversal domains and magnetic recoil curves, the property enhancement of magnets with a dual-alloy method was well explained. - Highlights: • Improved magnetic properties were obtained in dual-alloy magnet. • This is due to the tuning of Ce distribution and the change in microstructure. • The magnetic hardening effect can be observed in dual-alloy magnet.

  9. Effect of the sintering temperature on the photocatalytic activity of ZnO+Zn{sub 2}TiO{sub 4} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mayen-Hernandez, S.A.; Torres-Delgado, G.; Castanedo-Perez, R.; Marquez Marin, J. [Centro de Investigacion y de Estudios Avanzados del I. PN, Unidad Queretaro. AP. 1-798, Queretaro, Qro. 76001 (Mexico); Gutierrez-Villarreal, M. [Centro de Investigacion en Quimica Aplicada Boulevard Enrique Reyna No.140. Saltillo Coah., 25100 (Mexico); Zelaya-Angel, O. [Depto. de Fisica, Centro de Investigacion y de Estudios Avanzados del I.P.N. AP 14-740, Mexico 07360 DF (Mexico)

    2007-09-22

    ZnO+Zn{sub 2}TiO{sub 4} thin films were obtained by the sol-gel method, the precursor solutions were prepared using two Ti/Zn ratios: 0.49 and 0.69. The films were deposited on glass slide substrates and sintered at temperatures in the 200-600 C range in increments of 50 C, with the goal of studying the dependence of the photocatalytic activity (PA) on the annealing temperature. The films were characterized by X-ray diffraction and UV-Vis spectroscopy. The PA was evaluated by measuring the UV-Vis absorption spectra of the methylene blue in aqueous solution before and after photobleaching, using the Lambert-Beer's principle. The higher photocatalytic activities were obtained from the films with sintering temperature around 450 C, for both Ti/Zn ratios studied. (author)

  10. Effect of sintering temperature on the structural and electrical properties of Zn{sub 0.95}Cr{sub 0.05}O

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Zalak; Gadani, Keval; Boricha, Hetal; Pandya, D. D.; Solanki, P. S.; Shah, N. A., E-mail: snikesh@yahoo.com [Department of Physics, Saurashtra University, Rajkot – 360 005 (India); Dhruv, Davit [Department of Physics, Saurashtra University, Rajkot – 360 005 (India); V.V.P. Engineering College, Gujarat Technological University, Rajkot – 360 005 (India)

    2016-05-06

    In this communication, we report the results of the studies on the sintering temperature dependent structural properties and dielectric behavior of 5% Cr doped Zn{sub 0.95}Cr{sub 0.05}O samples synthesized by cost effective sol-gel technique. Crystallographic orientations, crystallinity and crystallite size (CS) have been understood by performing X-ray diffraction (XRD) measurement at room temperature. Values of CS have been further verified by carrying out Williamson – Hall (W-H) plot analysis and the difference between the CS from XRD and W-H analyses has been discussed. Dielectric behavior has been studied and its dependence on the sintering temperature has been understood in the light of crystallite size, crystal boundary density and oxygen vacancies induced possible conductivity in the samples.

  11. Low temperature synthesis and sintering behaviour of Gd-doped ceria nanosized powders: comparison between two synthesis procedures

    Directory of Open Access Journals (Sweden)

    Tartaj, J.

    2009-04-01

    Full Text Available Two different routes of synthesis of Ce0.9Gd0.1O1.95 (CGO nanopowders are presented; the ethylene glycol-metal nitrate polymerized complex solution method and the precipitation technique using ammonia as the precipitant agent. The powders characteristics were examined by X-ray diffraction (XRD, transmission electron microscopy (TEM, Brunauer-Emmett-Teller (BET surface area and simultaneous thermogravimetric and differential thermal analysis (TG/DTA. Scanning electron microscopy (SEM observations were used to determine the agglomeration degree of the powders, and the uniformity of the green compacts. The Hg-porosimetry results were used to investigate the pore size. The densification process was studied by constant heating rate dilatometry and isothermal sintering at different temperatures. Microstructural development of each sample at different sintering temperatures and times was followed by SEM.

    Se presentan dos diferentes rutas de síntesis de nanopolvos de Ce0.9Gd0.1O1.95 (CGO: precipitación de hidróxidos, a partir de soluciones de nitratos utilizando amonia como agente precipitante y formación de complejos polimerizados etilene-glicol nitratos metálicos. Las características de los polvos se determinaron por DRX, microscopía de transmisión (TEM, superficie específica por Brunauer-Emmett-Teller (BET, y ensayos de ATD/ATG. El grado de aglomeración de los nanopolvos y la uniformidad de los compactos en verde se ha observado por Microscopía electrónica de barrido, (SEM. El tamaño de poro de los compactos en verde se ha medido mediante porosimetría de Hg. El comportamiento a la sinterización se ha evaluado por dilatometría a velocidad de calentamiento constante y por sinterización isoterma a diferentes temperaturas. La evolución microestructural se ha seguido por SEM.

  12. High Temperature Thermoelectric Properties of ZnO Based Materials

    DEFF Research Database (Denmark)

    Han, Li

    This thesis investigated the high temperature thermoelectric properties of ZnO based materials. The investigation first focused on the doping mechanisms of Al-doped ZnO, and then the influence of spark plasma sintering conditions on the thermoelectric properties of Al, Ga-dually doped ZnO....... Following that, the nanostructuring effect for Al-doped ZnO was systematically investigated using samples with different microstructure morphologies. At last, the newly developed ZnCdO materials with superior thermoelectric properties and thermal stability were introduced as promising substitutions...... for conventional ZnO materials. For Al-doped ZnO, α- and γ-Al2O3 were selectively used as dopants in order to understand the doping mechanism of each phase and their effects on the thermoelectric properties. The samples were prepared by the spark plasma sintering technique from precursors calcined at various...

  13. HIGH TEMPERATURE VACUUM MIXER

    Directory of Open Access Journals (Sweden)

    E. D. Chertov

    2015-01-01

    Full Text Available The work is devoted to the creation of a new type of mixer to produce homogeneous mixtures of dissimilar materials applied to recycling of housing and communal services waste. The article describes the design of a dual-chamber device of the original high-temperature vacuum mixer, there investigated the processes occurring in the chambers of such devices. The results of theoretical and experimental research of the process of mixing recycled polyethylene with a mixture of "grinded food waste – Eco wool” are presented. The problem of the optimum choice of bending the curvilinear blades in the working volume of the seal, which is achieved by setting their profile in the form of involute arc of several circles of different radii, is examined . The dependences, allowing to define the limits of the changes of the main mode parameters the angular velocity of rotation of the working body of the mixer using two ways of setting the profile of the curvilinear blade mixer are obtained. Represented design of the mixer is proposed to use for a wide range of tasks associated with the mixing of the components with a strongly pronounced difference of physic al chemical properties and, in particular, in the production of composites out of housing and communal services waste.

  14. Performance and Reliability of Bonded Interfaces for High-temperature Packaging: Annual Progress Report

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, Douglas J. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-10-19

    As maximum device temperatures approach 200 °Celsius, continuous operation, sintered silver materials promise to maintain bonds at these high temperatures without excessive degradation rates. A detailed characterization of the thermal performance and reliability of sintered silver materials and processes has been initiated for the next year. Future steps in crack modeling include efforts to simulate crack propagation directly using the extended finite element method (X-FEM), a numerical technique that uses the partition of unity method for modeling discontinuities such as cracks in a system.

  15. Selection of optimal sintering temperature of K0.5Na0.5NbO3 ceramics for electromechanical applications

    Directory of Open Access Journals (Sweden)

    Gaurav Vats

    2014-03-01

    Full Text Available This paper has considered the selection of the optimal processing parameter (sintering temperature leading to best possible properties of K0.5Na0.5NbO3 (KNN for electromechanical applications. Vital piezoelectric properties for such applications include the piezoelectric coupling coefficient (kp, piezoelectric coefficient (d31, Curie temperature (Tc, remanent polarization (Pr, coercive field (Ec, density (ρ, elastic compliance (S11E and S12E and dielectric loss (tan δ. The weights and priority of these physical properties for KNN are calculated using the modified digital logic (MDL method. The priority order of these properties used for the selection of optimal processing parameters is as d31>tan δ>S11E=S12E>Tc=Pr>ρ>kp>Ec. The weights obtained using MDL are further incorporated with analytic hierarchy process (AHP and VlseKriterijumska Optimisacija I Kompromisno Resenje (VIKOR in order to determine the optimal sintering temperature for KNN. Both methods suggest that 1080 °C and 1120 °C are the most and least desirable sintering temperatures, respectively. Finally, sensitivity analysis is performed for the robustness of our results and prediction of most influential parameter in terms of sensitivity. tan δ is found to be the most sensitive property for alteration in the present ranking.

  16. Selective laser sintering of ultra high molecular weight polyethylene for clinical applications.

    Science.gov (United States)

    Rimell, J T; Marquis, P M

    2000-01-01

    Rapid prototyping is a relatively new technology, which although prominent in the engineering industry is only just starting to make an impact in the medical field. Its current medical uses are mainly confined to surgical planning and teaching, but the technology also has the potential to allow for patient-tailored prostheses. The work reported here describes the application of a simplified selective laser sintering apparatus with ultra high molecular weight polyethylene (UHMWPE). The morphology and chemistry of the starting powders and lased material have been characterized using Fourier Transform Infra Red spectroscopy and a combination of light and scanning electron microscopy. It was found that solid linear continuous bodies could be formed, but material shrinkage caused problems when trying to form sheet-like structures. The porosity of the formed material was also a concern. The material exposed to the laser beam was shown to have undergone degradation in terms of chain scission, cross-linking, and oxidation. It has been concluded that to apply this technology to the fabrication of UHMWPE devices requires the development of improved starting powders, in particular with increased density. Copyright 2000 John Wiley & Sons, Inc.

  17. Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3–Al2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Denghao Li

    2014-06-01

    Full Text Available CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior, microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from 1250 °C to 1050 °C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3 ceramic sintered at 1100 °C presented good microwave dielectric properties of εr=7.27, Q×f=16,850 GHz and τf=−39.53 ppm/°C, which is much better than those of pure CaSiO3 ceramic sintered at 1340 oC (Q×f=13,109 GHz. The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.

  18. Effects of Sb2O3 on the Mechanical Properties of the Borosilicate Foam Glasses Sintered at Low Temperature

    Directory of Open Access Journals (Sweden)

    Chenxi Zhai

    2014-01-01

    Full Text Available The physical properties and microstructure of a new kind of borosilicate foam glasses with different Sb2O3 doping content are comprehensively investigated. The experimental results show that appropriate addition of Sb2O3 has positive impact on the bulk porosity and compressive strength of the foam glass. It is more suitable in this work to introduce 0.9 wt.% Sb2O3 into the Na2O-K2O-B2O3-Al2O3-SiO2 basic foam glass component and sinter at 775°C. And the obtained foam glasses present much more uniform microstructure, large pore size, and smooth cell walls, which bring them with better performance including a lower bulk density, low water absorption, and an appreciable compressive strength. The microstructure analysis indicates that, with the increase of the content of Sb2O3 additives, the cell size tends to increase at first and then decreases. Larger amounts of Sb2O3 do not change the crystalline phase of foam glass but increase its vitrification. It is meaningful to prepare the foam glass at a relatively low temperature for reducing the heat energy consumption.

  19. The Effects of High Al2O3 on the Metallurgical Properties of Sinter

    Science.gov (United States)

    Yu, Wen-tao; Zuo, Hai-bin; Zhang, Jian-liang; Zhang, Tao

    Sintering-pot tests and metallurgical performances of sinter with 4 kind of different Al2O3 contents are experimented in this paper. Results show: when the Al2O3 contents increase from 2.0% to 3.5%, acicular calcium ferrites in mine phase will be gradually replaced by plate-like iron calcium. The increase of Al2O3 contents will lead to the addition of liquid viscosity and the reduction of permeability of sinter bed. Sintering time will be prolonged. The rate of yield is stable basically but production is low; besides, the increase of liquid viscosity will decrease of drum strength. The change of permeability of the material layer will make RDI+3.15 decrease first and then increase when Al2O3 contents changed from 2.0% to 3.5%. RI of sinter shows a contrary trend because many open voids are formed by deterioration of liquidity first and then pores closed.

  20. Advances in high temperature chemistry

    CERN Document Server

    Eyring, Leroy

    1969-01-01

    Advances in High Temperature Chemistry, Volume 2 covers the advances in the knowledge of the high temperature behavior of materials and the complex and unfamiliar characteristics of matter at high temperature. The book discusses the dissociation energies and free energy functions of gaseous monoxides; the matrix-isolation technique applied to high temperature molecules; and the main features, the techniques for the production, detection, and diagnosis, and the applications of molecular beams in high temperatures. The text also describes the chemical research in streaming thermal plasmas, as w

  1. Effects of La{sub 2}O{sub 3}-doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Hong Wei; Chang, Chun Rui [College of Science, North China University of Science and Technology, Hebei Province (China); Li, Yuan Liang [Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, North China University of Science and Technology, Hebei Province (China); Yan, Chun Liang [Analysis and Testing Center, North China University of Science and Technology, Hebei Province (China)

    2016-03-15

    Using BaCO{sub 3}, SrCO{sub 3} and TiO{sub 2}, et al as crude materials, La{sub 2}O{sub 3} as dopant, Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} (BST) Ceramics of perovskite structure were prepared by solid state reaction method. We investigated the effects of La{sub 2}O{sub 3} -doping and sintering temperature on the dielectric properties of BaSrTiO{sub 3} ceramics. The experiment results show that: The amount of La{sub 2}O{sub 3} can increase the dielectric constant of the sample, with the doping amount increasing, the dielectric constant increases. The sintering temperature has also significant impact on the dielectric properties. The dielectric constant of the sample reaches its highest point at 1280 °C. (author)

  2. High-Temperature Piezoelectric Sensing

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2013-12-01

    Full Text Available Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  3. Sintering and electrical properties of strontium-doped lanthanum manganite

    Energy Technology Data Exchange (ETDEWEB)

    Tarrago, Diego Pereira; Sousa, Vania Caldas de [Universidade Federal do Rio Grande do Sul (LABIOMAT/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Biomateriais], Email: dptarrago@gmail.com; Moreno Buriel, Berta; Chinarro Martini, Eva; Jurado Egea, Jose Ramon [Consejo Superior de Investigaciones Cientificas (ICV/CSIC), Madrid (Spain). Inst. de Ceramica y Vidrio; Malfatti, Celia de Fraga [Universidade Federal do Rio Grande do Sul (LAPEC/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Pesquisa em Corrosao

    2010-07-01

    Lanthanum strontium manganites (LSM) are potential materials for cathode applications in solid oxide fuel cells (SOFC) due to their good catalytic activity, chemical stability and compatibility with electrolyte materials in high temperatures. The sinterability of single phase La{sub 1-x}Sr{sub x}Mn{sub O3} (x=0.18) perovskite powders and the electrical properties of the resulting samples are analyzed in this study. Using a heating microscope, the powders were pressed and sintered at different pressures and temperatures, resulting in an open porosity of 33.36% when compacted at 125 MPa and sintered at 1200 degree C. Top and cross-section s canning electron microscopy (SEM) micrographs revealed interconnected pores in the sintered body and, hence, a suitable microstructure for the application. The activation energy for conductance was 0.04 eV and the tested LSM bulk started to exhibit adequate electrical properties at about 500 degree C. (author)

  4. Two-step flash light sintering of copper nanoparticle ink to remove substrate warping

    Energy Technology Data Exchange (ETDEWEB)

    Ryu, Chung-Hyeon; Joo, Sung-Jun [Department of Mechanical Convergence 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)

    2016-10-30

    Highlights: • We performed the two-step flash light sintering for copper nanoparticle ink to remove substrate warping. • 12 J/cm{sup 2} of preheating and 7 J/cm{sup 2} of main sintering energies were determined as optimum conditions to sinter the copper nanoparticle ink. • The resistivity of two-step sintered copper nanoparticle ink was 3.81 μΩ cm with 5B adhesion level, 2.3 times greater than that of bulk copper. • The two-step sintered case showed a high conductivity without any substrate warping. - Abstract: A two-step flash light sintering process was devised to reduce the warping of polymer substrates during the sintering of copper nanoparticle ink. To determine the optimum sintering conditions of the copper nanoparticle ink, the flash light irradiation conditions (pulse power, pulse number, on-time, and off-time) were varied and optimized. In order to monitor the flash light sintering process, in situ resistance and temperature monitoring of copper nanoink were conducted during the flash light sintering process. Also, a transient heat transfer analysis was performed by using the finite-element program ABAQUS to predict the temperature changes of copper nanoink and polymer substrate. The microstructures of the sintered copper nanoink films were analyzed by scanning electron microscopy. Additionally, an X-ray diffraction and Fourier transform infrared spectroscopy were used to characterize the crystal phase change of the sintered copper nanoparticles. The resulting two-step flash light sintered copper nanoink films exhibited a low resistivity (3.81 μΩ cm, 2.3 times of that of bulk copper) and 5B level of adhesion strength without warping of the polymer substrate.

  5. High temperature superconductor accelerator magnets

    NARCIS (Netherlands)

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and

  6. Life at High Temperatures

    Indian Academy of Sciences (India)

    2005-09-15

    Sep 15, 2005 ... or more in the vicinity of geothermal vents in the deep sea and the plant Tidestromia oblongifolia (Amaranthaceae) found in Death. Valley in California, where the hottest temperature on earth ever recorded during 43 consecutive days in 1917 was >48 °C. (Guinness Book of W orId Records, 1999).

  7. Modelling of Mechanical Behavior at High Strain Rate of Ti-6al-4v Manufactured By Means of Direct Metal Laser Sintering Technique

    Science.gov (United States)

    Iannitti, Gianluca; Bonora, Nicola; Gentile, Domenico; Ruggiero, Andrew; Testa, Gabriel; Gubbioni, Simone

    2017-06-01

    In this work, the mechanical behavior of Ti-6Al-4V obtained by additive manufacturing technique was investigated, also considering the build direction. Dog-bone shaped specimens and Taylor cylinders were machined from rods manufactured by means of the EOSSINT M2 80 machine, based on Direct Metal Laser Sintering technique. Tensile tests were performed at strain rate ranging from 5E-4 s-1 to 1000 s-1 using an Instron electromechanical machine for quasistatic tests and a Direct-Tension Split Hopkinson Bar for dynamic tests. The mechanical strength of the material was described by a Johnson-Cook model modified to account for stress saturation occurring at high strain. Taylor cylinder tests and their corresponding numerical simulations were carried out in order to validate the constitutive model under a complex deformation path, high strain rates, and high temperatures.

  8. Performance and Reliability of Bonded Interfaces for High-Temperature Packaging

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, Douglas

    2016-06-08

    This is a technical review of the DOE VTO EDT project EDT063, Performance and Reliability of Bonded Interfaces for High-Temperature Packaging. A procedure for analyzing the reliability of sintered-silver through experimental thermal cycling and crack propagation modeling has been outlined and results have been presented.

  9. High sintering resistance of size-selected platinum cluster catalysts by suppressed ostwald ripening

    DEFF Research Database (Denmark)

    Wettergren, Kristina; Schweinberger, Florian F.; Deiana, Davide

    2014-01-01

    on different supports exhibit remarkable intrinsic sintering resistance even under reaction conditions. The observed stability is related to suppression of Ostwald ripening by elimination of its main driving force via size-selection. This study thus constitutes a general blueprint for the rational design...

  10. High-temperature-pressure polymerized resin-infiltrated ceramic networks.

    Science.gov (United States)

    Nguyen, J F; Ruse, D; Phan, A C; Sadoun, M J

    2014-01-01

    The aim of this study was to produce composite blocks (CB) for CAD/CAM applications by high-temperature-pressure (HT/HP) polymerization of resin-infiltrated glass-ceramic networks. The effect of network sintering and the absence/presence of initiator was investigated. Mechanical properties were determined and compared with those of Paradigm MZ100 (3M ESPE) blocks and HT/HP polymerized experimental "classic" CB, in which the filler had been incorporated by conventional mixing. The networks were made from glass-ceramic powder (VITA Zahnfabrik) formed by slip casting and were either sintered or not. They were silanized, infiltrated by urethane dimethacrylate, with or without initiator, and polymerized under HT/HP (300 MPa, 180°C) to obtain resin-infiltrated glass-ceramic network (RIGCN) CB. HT/HP polymerized CB were also made from an experimental "classic" composite. Flexural strength (σf), fracture toughness (KIC), and Vickers hardness were determined and analyzed by one- or two-way analysis of variance (ANOVA), Scheffé multiple-means comparisons (α = 0.05), and Weibull statistics (for σf). Fractured surfaces were characterized with scanning electron microscopy. The mechanical properties of RIGCN CB were significantly higher. Sintering induced significant increases in σf and hardness, while the initiator significantly decreased hardness. The results suggested that RIGCN and HT/HP polymerization could be used to obtain CB with superior mechanical properties, suitable for CAD/CAM applications.

  11. Effects of B{sub 2}O{sub 3} content and sintering temperature on crystallization and microstructure of CBS glass–ceramic coatings

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pengyang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Wang, Shubin, E-mail: shubinwang@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials and Engneering, Beihang University, Beijing 100191 (China); Liu, Jianggao; Feng, Mengjie; Yang, Xinwang [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-11-30

    Graphical abstract: (a) TEM photogram of CG3 sintered at 800 °C, crystals are obvious; (b) the XRD patterns of CG3 glass samples sintered at various temperatures; (c) SEM photogram of CG3 sintered at 800 °C; (d) Kissinger, Augis–Bennett and Ozawa kinetics plots of CG3 glass samples. - Highlights: • Combining sol–gel method with direct sintering method to reduce the temperature of coatings formation. • Characterizing CaO–SiO{sub 2}–B{sub 2}O{sub 3} glass–ceramic coatings on porous substrates. • Surface crystallization of CBS glass–ceramic coatings: nucleation and kinetics. • Activation energies for crystal growth in CBS glass–ceramics with different contents of B{sub 2}O{sub 3}. - Abstract: Borosilicate glass–ceramics precursors with varying compositional ratios in the CaO–SiO{sub 2}–B{sub 2}O{sub 3} (CBS) system were synthesized by sol–gel method. The precursors were calcined at 1200 °C for 2 h to form glass powders. The glass–ceramics were prepared by overlaying glass slurries on the substrates before sintering at different temperatures. The as-prepared glasses and glass–ceramics were characterized by differential scanning calorimetry and X-ray diffraction. The crystallization activation energies (E{sub c}) were calculated using the Kissinger method from DSC results. The morphology and crystallization behavior of the glass–ceramics were monitored by scanning electron microscopy. Both glass transition and crystallization temperatures decreased, however, the metastable zone increased. The E{sub c} values of CBS glasses and glass–ceramics were 254.1, 173.2 and 164.4 kJ/mol with increasing B{sub 2}O{sub 3} content, whereas that of the calcined G3 glass was 104.9 kJ/mol. Finally, the coatings were prepared at a low temperature (700 °C). The crystals that grew on the surface of multilayer coatings demonstrated heterogeneous surface nucleation and crystallization after heat-treatment from 700 °C to 850 °C for 4 h.

  12. Improvement of mechanical strength of sintered Mo alloyed steel by optimization of sintering and cold-forging processes with densification

    Science.gov (United States)

    Kamakoshi, Y.; Shohji, I.; Inoue, Y.; Fukuda, S.

    2017-10-01

    Powder metallurgy (P/M) materials have been expected to be spread in automotive industry. Generally, since sintered materials using P/M ones contain many pores and voids, mechanical properties of them are inferior to those of conventional wrought materials. To improve mechanical properties of the sintered materials, densification is effective. The aim of this study is to improve mechanical strength of sintered Mo-alloyed steel by optimizing conditions in sintering and cold-forging processes. Mo-alloyed steel powder was compacted. Then, pre-sintering (PS) using a vacuum sintering furnace was conducted. Subsequently, coldforging (CF) by a backward extrusion method was conducted to the pre-sintered specimen. Moreover, the cold-forged specimen was heat treated by carburizing, tempering and quenching (CQT). Afterwards, mechanical properties were investigated. As a result, it was found that the density of the PS specimen is required to be more than 7.4 Mg/m3 to strengthen the specimen by heat treatment after CF. Furthermore, density and the microstructure of the PS specimen are most important factors to make the high density and strength material by CF. At the CF load of 1200 kN, the maximum density ratio reached approximately 99% by the use of the PS specimen with proper density and microstructure. At the CF load of 900 kN, although density ratio was high like more than 97.8%, transverse rupture strength decreased sharply. Since densification caused high shear stress and stress concentration in the surface layer, microcracks occurred by the damages of inter-particle sintered connection of the surface layer. On the contrary, in case of the CF load of 1200 kN, ultra-densification of the surface layer occurred by a sufficient plastic flow. Such sufficient compressed specimens regenerated the sintered connections by high temperature heat treatment and thus the high strength densified material was obtained. These processes can be applicable to near net shape manufacturing

  13. High temperature materials; Materiaux a hautes temperatures

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-07-01

    The aim of this workshop is to share the needs of high temperature and nuclear fuel materials for future nuclear systems, to take stock of the status of researches in this domain and to propose some cooperation works between the different research organisations. The future nuclear systems are the very high temperature (850 to 1200 deg. C) gas cooled reactors (GCR) and the molten salt reactors (MSR). These systems include not only the reactor but also the fabrication and reprocessing of the spent fuel. This document brings together the transparencies of 13 communications among the 25 given at the workshop: 1) characteristics and needs of future systems: specifications, materials and fuel needs for fast spectrum GCR and very high temperature GCR; 2) high temperature materials out of neutron flux: thermal barriers: materials, resistance, lifetimes; nickel-base metal alloys: status of knowledge, mechanical behaviour, possible applications; corrosion linked with the gas coolant: knowledge and problems to be solved; super-alloys for turbines: alloys for blades and discs; corrosion linked with MSR: knowledge and problems to be solved; 3) materials for reactor core structure: nuclear graphite and carbon; fuel assembly structure materials of the GCR with fast neutron spectrum: status of knowledge and ceramics and cermets needs; silicon carbide as fuel confinement material, study of irradiation induced defects; migration of fission products, I and Cs in SiC; 4) materials for hydrogen production: status of the knowledge and needs for the thermochemical cycle; 5) technologies: GCR components and the associated material needs: compact exchangers, pumps, turbines; MSR components: valves, exchangers, pumps. (J.S.)

  14. Low temperature sintering of inkjet printed metal precursor inks for organic electronic applications

    NARCIS (Netherlands)

    Perelaer, J.; Wunscher, S.; Franziska, M.W.; Abbel, R.; Grouchko, M.; Magdassi, S.; Ulrich, S.S.

    2013-01-01

    As a nascent technology that developed during the last decades from only printing text and graphics into an important scientific research tool for R&D, inkjet printers are nowadays used as a highly reproducible non-contact patterning tool. In contrast to non-digital patterning tools, inkjet printing

  15. High Temperature Superconductor Machine Prototype

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2011-01-01

    A versatile testing platform for a High Temperature Superconductor (HTS) machine has been constructed. The stationary HTS field winding can carry up to 10 coils and it is operated at a temperature of 77K. The rotating armature is at room temperature. Test results and performance for the HTS field...

  16. Production of High-Purity Anhydrous Nickel(II) Perrhenate for Tungsten-Based Sintered Heavy Alloys.

    Science.gov (United States)

    Leszczyńska-Sejda, Katarzyna; Benke, Grzegorz; Kopyto, Dorota; Majewski, Tomasz; Drzazga, Michał

    2017-04-24

    This paper presents a method for the production of high-purity anhydrous nickel(II) perrhenate. The method comprises sorption of nickel(II) ions from aqueous nickel(II) nitrate solutions, using strongly acidic C160 cation exchange resin, and subsequent elution of sorbed nickel(II) ions using concentrated perrhenic acid solutions. After the neutralization of the resulting rhenium-nickel solutions, hydrated nickel(II) perrhenate is then separated and then dried at 160 °C to obtain the anhydrous form. The resulting compound is reduced in an atmosphere of dissociated ammonia in order to produce a Re-Ni alloy powder. This study provides information on the selected properties of the resulting Re-Ni powder. This powder was used as a starting material for the production of 77W-20Re-3Ni heavy alloys. Microstructure examination results and selected properties of the produced sintered heavy alloys were compared to sintered alloys produced using elemental W, Re, and Ni powders. This study showed that the application of anhydrous nickel(II) perrhenate in the production of 77W-20Re-3Ni results in better properties of the sintered alloys compared to those made from elemental powders.

  17. Production of High-Purity Anhydrous Nickel(II Perrhenate for Tungsten-Based Sintered Heavy Alloys

    Directory of Open Access Journals (Sweden)

    Katarzyna Leszczyńska-Sejda

    2017-04-01

    Full Text Available This paper presents a method for the production of high-purity anhydrous nickel(II perrhenate. The method comprises sorption of nickel(II ions from aqueous nickel(II nitrate solutions, using strongly acidic C160 cation exchange resin, and subsequent elution of sorbed nickel(II ions using concentrated perrhenic acid solutions. After the neutralization of the resulting rhenium-nickel solutions, hydrated nickel(II perrhenate is then separated and then dried at 160 °C to obtain the anhydrous form. The resulting compound is reduced in an atmosphere of dissociated ammonia in order to produce a Re-Ni alloy powder. This study provides information on the selected properties of the resulting Re-Ni powder. This powder was used as a starting material for the production of 77W-20Re-3Ni heavy alloys. Microstructure examination results and selected properties of the produced sintered heavy alloys were compared to sintered alloys produced using elemental W, Re, and Ni powders. This study showed that the application of anhydrous nickel(II perrhenate in the production of 77W-20Re-3Ni results in better properties of the sintered alloys compared to those made from elemental powders.

  18. Effect of the cBN content and sintering temperature on the transverse rupture strength and hardness of cBn/diamond cutting tools

    Directory of Open Access Journals (Sweden)

    Kır Durmuş

    2012-01-01

    Full Text Available The aim of this work was to investigate the effect of cBN content and sintering temperature on the transverse rupture strength (TRS of cBN/diamond cutting tools produced by hot pressing. The segments containing different cBN content were manufactured under 35 MPa pressure at 600, 650 and 700°C with a 3 minutes sintering time. The TRS of segments were determined using three-point bending test. Microstructure and phase composition of fracture surface of segments were determined by scanning electron microscopy (SEM, and X-ray diffraction (XRD analysis. The obtained results show that the TRS of the segments with cBN were higher than that of the segments with diamond.

  19. Sintering Behavior, Microstructure, and Mechanical Properties: A Comparison among Pressureless Sintered Ultra-Refractory Carbides

    Directory of Open Access Journals (Sweden)

    Laura Silvestroni

    2010-01-01

    Full Text Available Nearly fully dense carbides of zirconium, hafnium, and tantalum were obtained by pressureless sintering at 1950°C with the addition of 5–20 vol% of MoSi2. Increasing the amount of sintering aid, the final density increased too, thanks to the formation of small amounts of liquid phase constituted by M-Mo-Si-O-C, where M is either Zr, Hf, or Ta. The matrices of the composites obtained with the standard procedure showed faceted squared grains; when an ultrasonication step was introduced in the powder treatment, the grains were more rounded and no exaggerated grains growth occurred. Other secondary phases observed in the microstructure were SiC and mixed silicides of the transition metals. Among the three carbides prepared by pressurless sintering, TaC-based composites had the highest mechanical properties at room temperature (strength 590 MPa, Young's modulus 480 GPa, toughness 3.8 MPa·m1/2. HfC-based materials showed the highest sinterability (in terms of final density versus amount of sintering aid and the highest high-temperature strength (300 MPa at 1500  °C.

  20. The Effect of Sintering Temperature on The Rolled Silver-Sheathed Monofilament Bi,Pb-Sr-Ca-Cu-O Superconducting Wire

    Science.gov (United States)

    Hendrik; Sebleku, P.; Siswayanti, B.; Pramono, A. W.

    2017-05-01

    The manufacture of high critical temperature (Tc) Bi, Pb-Sr-Ca-Cu-O (HTS BPSCCO) superconductor wire fabricated by power-in-tube (PIT) is a multi-step process. The main difficulty is that the value of Tc superconductor wire determined by various factors for each step. The objective of this research is to investigate the effect of sintering parameters on the properties of final rolled material. The fabrication process of 1 m rolled-silver sheath monofilament superconductor BPSCCO wire using mechanical deformation process including rolling and drawing has been carried out. The pure silver powders were melted and formed into pure silver (Ag) tube. The tube was 10 mm in diameter with a sheath material: superconductor powders ratio of about 6 : 1. Starting powders, containing the nominal composition of Bi2-Sr2-Cam-1-Cum-Oy, were inserted into the pure silver tube and rolled until it reached a diameter of 4 mm. A typical area reduction ratio of about 5% per step has been proposed to prevent microcracking during the cold-drawing process. The process of rolling of the silver tube was subsequently repeated to obtain three samples and then followed by heat-treated at 820 °C, 840 °C, and 860 °C, respectively. The surface morphology was analyzed by using SEM; the crystal structure was studied by using X-RD, whereas the superconductivity was investigated by using temperature dependence resistivity measurement by using four-point probe technique. SEM images showed the porosity of the cross-sectional surface of the samples. The sample with low heating temperature showed porosity more than the one with high temperature. The value of critical temperature (Tc) of the sample with a dwelling time of heating of 8 hours is 70 K. At above 70 K, it shows the behavior of conductor properties. However, the porosity increased as the heating time increased up to 24 hours. The critical temperature was difficult to be identified due to its porosity. According to XRD results, the Bi-2212

  1. High-Temperature Superconductors

    CERN Document Server

    Saxena, Ajay Kumar

    2012-01-01

    This book presents the current knowledge about superconductivity in high Tc cuprate superconductors. There is a large scientific interest and great potential for technological applications. The book discusses all the aspects related to all families of cuprate superconductors discovered so far. Beginning with the phenomenon of superconductivity, the book covers: the structure of cuprate HTSCs, critical currents, flux pinning, synthesis of HTSCs, proximity effect and SQUIDs, possible applications of high Tc superconductors and theories of superconductivity. Though a high Tc theory is still awaited, this book describes the present scenario and BCS and RVB theories. The second edition was  significantly extended by including film-substrate lattice matching and buffer layer considerations in thin film HTSCs, brick-wall microstructure in the epitaxial films, electronic structure of the CuO2 layer in cuprates, s-wave and d-wave coupling in HTSCs and possible scenarios of theories of high Tc superconductivity.

  2. High Temperature Electrostrictive Ceramics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS Technologies proposes to develop high temperature electrostrictors from bismuth-based ferroelectrics. These materials will exhibit high strain and low loss in...

  3. High Temperature Surface Interactions

    Science.gov (United States)

    1989-11-01

    oxidation rate of "pure SiC* in air (from compilation of data by Schlichting6). For T < 14001C, partial cristobalite formation; T > 1400"C, decreased...aluminium content is high enough, the beta phase percolates and contains a dispersion of -- Ni particles. Such a tructure is certainly less favourable

  4. Spark plasma sintering of titanium aluminide intermetallics and its composites

    Science.gov (United States)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  5. Sintering of bulk high- Tc superconductors: Y-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K.C.; Chen, N.; Lanagan, M.T.; Wu, W.; Singh, J.P.; Olson, R.A.; Routbort, J.L.; Poeppel, R.B.

    1992-05-01

    Sintering of bulk YBa{sub 2}Cu{sub 3}O{sub x} (123) samples has been conducted from 850 to 1010{degrees}C in oxygen partial pressures (P{sub O2}) of 2.5 {times} 10{sup 2} to 10{sup 5} Pa. The final grain sizes of the samples were controlled by selective use of (1) liquid phases and (2) partial decomposition of the 123 phase by sintering in a P{sub O2} that was lower than the minimum needed for 123 stability. In nearly fully dense samples, it was found that the grain size could range from about 1 to 500 {mu}m, depending on the processing conditions.

  6. Sintering of bulk high-{Tc} superconductors: Y-Ba-Cu-O

    Energy Technology Data Exchange (ETDEWEB)

    Goretta, K.C.; Chen, N.; Lanagan, M.T.; Wu, W.; Singh, J.P.; Olson, R.A.; Routbort, J.L.; Poeppel, R.B.

    1992-05-01

    Sintering of bulk YBa{sub 2}Cu{sub 3}O{sub x} (123) samples has been conducted from 850 to 1010{degrees}C in oxygen partial pressures (P{sub O2}) of 2.5 {times} 10{sup 2} to 10{sup 5} Pa. The final grain sizes of the samples were controlled by selective use of (1) liquid phases and (2) partial decomposition of the 123 phase by sintering in a P{sub O2} that was lower than the minimum needed for 123 stability. In nearly fully dense samples, it was found that the grain size could range from about 1 to 500 {mu}m, depending on the processing conditions.

  7. Effects of different sintering temperature and Nb{sub 2}O{sub 5} content on structural and magnetic properties of Z-type hexaferrites

    Energy Technology Data Exchange (ETDEWEB)

    Jia Lijun [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)]. E-mail: jlj@uestc.edu.cn; Zhang Huaiwu [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zhong Zhiyong [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Liu Yingli [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2007-03-15

    Nb-doped Z-type hexaferrites (Ba{sub 3}(Co{sub 0.4}Zn{sub 0.6}){sub 2}Fe{sub 24}O{sub 41}) with composition of Ba{sub 3}(Co{sub 0.4}Zn{sub 0.6}){sub 2}Fe{sub 24}O{sub 41}+x Nb{sub 2}O{sub 5} (where x=0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 1.6 and 2.0 wt%) were prepared by a solid-state reaction method. The effects of different sintering temperature (T {sub s}) and Nb{sub 2}O{sub 5} content on the sintering behaviors, phase composing, microstructure, and magnetic properties of the samples were investigated. The results from X-ray diffraction and scanning electron microscopy show that as the amount of Nb{sub 2}O{sub 5} additive increases, the major phase changes to Z-phase, Simultaneously, M-phase and a small amount of niobate phase appear. The Nb{sub 2}O{sub 5} additive promotes the grain growth as reaction center at lower sintering temperature (1220 deg. C), but at higher temperature (1260 deg. C), niobate phase separated out in grain boundaries as secondary phase will restrain abnormal grain growth, so closed pores in grains are not formed. The Nb{sub 2}O{sub 5} additive can enhance densification, improve initial permeability of hexaferrites by increasing the grain growth of hexaferrite and the displacement of ions in the sintering process due to the aberration and activation of crystal lattice, which is accompanied by the solubility of Nb{sup 5+} in the hexaferrites. A relative density of 96%, maximum initial permeability (32-33), minimum coercivity (454-455 A/m) and resonance frequency above 400 MHz were obtained for the sample with 0.8 wt% Nb{sub 2}O{sub 5} sintered at 1260 deg. C for 6 h.

  8. Amino Acids Aided Sintering for the Formation of Highly Porous FeAl Intermetallic Alloys.

    Science.gov (United States)

    Karczewski, Krzysztof; Stepniowski, Wojciech J; Salerno, Marco

    2017-07-04

    Fabrication of metallic foams by sintering metal powders mixed with thermally degradable compounds is of interest for numerous applications. Compounds releasing gaseous nitrogen, minimizing interactions between the formed gases and metallic foam by diluting other combustion products, were applied. Cysteine and phenylalanine, were used as gas releasing agents during the sintering of elemental Fe and Al powders in order to obtain metallic foams. Characterization was carried out by optical microscopy with image analysis, scanning electron microscopy with energy dispersive spectroscopy, and gas permeability tests. Porosity of the foams was up to 42 ± 3% and 46 ± 2% for sintering conducted with 5 wt % cysteine and phenylalanine, respectively. Chemical analyses of the formed foams revealed that the oxygen content was below 0.14 wt % and the carbon content was below 0.3 wt %. Therefore, no brittle phases could be formed that would spoil the mechanical stability of the FeAl intermetallic foams. The gas permeability tests revealed that only the foams formed in the presence of cysteine have enough interconnections between the pores, thanks to the improved air flow through the porous materials. The foams formed with cysteine can be applied as filters and industrial catalysts.

  9. Influence of sintering temperature and oxygen annealing on transport properties of La{sub 0.67}Ca{sub 0.33}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Rahul; Dogra, Anjana; Srivastava, A K; Awana, V P S; Kotnala, R K; Kishan, H [National Physical Laboratory, Dr K S Krishnan Marg, New Delhi-110012 (India); Bhalla, G L, E-mail: awana@mail.nplindia.ernet.i [Department of Physics and Astrophysics, Delhi University, New Delhi-110007 (India)

    2009-01-21

    We investigate the influence of sintering temperature and annealing conditions on the transport properties of La{sub 0.67}Ca{sub 0.33}MnO{sub 3} (LCMO) samples prepared by the solid-state reaction method. In the plot of resistance as a function of temperature, R(T), we observe two peaks for air-annealed samples, which is attributed to the inhomogeneous distribution of oxygen-whereas the sample annealed in oxygen shows only a single peak, which is explained on the basis of homogeneous distribution of oxygen and grain connectivity. The sharpness in the transition peak is described in terms of the temperature coefficient of resistance, which is calculated using R(T) data. We present and compare here the results of structural, transport and magnetic measurements of LCMO prepared at different sintering temperatures as well as under different annealing conditions. The results of the compound are mainly discussed in terms of grain growth and the grain boundaries.

  10. Recycling of mill scale in sintering process

    Directory of Open Access Journals (Sweden)

    El-Hussiny N.A.

    2011-01-01

    Full Text Available This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

  11. Two steps sintering alumina doped with niobia; Sinterizacao em duas etapas de alumina aditivada com niobia

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, L.B.; Hatzfeld, J.; Heck, M.; Pokorny, A.; Bergmann, C.P., E-mail: lucas.gomes@ufrgs.br [Universidade Federal do Rio Grande do Sul (LACER/UFRGS) Porto Alegre, RS (Brazil). Laboratorio de Materiais Ceramicos

    2014-07-01

    In this work, high surface area commercial alumina was doped with niobia and sintered in two steps in order to obtain dense materials with lower processing temperatures. The powders were milled and uniaxially pressed (200 MPa). The first step of sintering took place at 1100°C for 3, 6, 9 and 12 hours, followed by the second step at 1350°C for 3 hours. The relative density, porosity and water absorption of the samples were determined by the Archimedes method. The crystalline phases were analyzed by X-ray Diffraction (XRD) and the morphology of the samples after sintering, evaluated by Scanning Electron Microscopy (SEM). The results indicate that the use of niobia combined with the two steps sintering promotes an increase in the density of the material, even at lower sintering temperatures. (author)

  12. (Krauss) at constant high temperatures

    African Journals Online (AJOL)

    Snail Research Unit of the SAMRC and Department of Zoology, Potchefstroom University for CHE,. Potchefstroom. The survival of the freshwater snail species Bulinus africanus, Bulinus g/obosus and Biompha/aria pfeifferi at extreme high temperatures was experimentally investigated. Snails were exposed to temperatures ...

  13. HIGH TEMPERATURE POLYMER FUEL CELLS

    DEFF Research Database (Denmark)

    Jensen, Jens Oluf; Qingfeng, Li; He, Ronghuan

    2003-01-01

    This paper will report recent results from our group on polymer fuel cells (PEMFC) based on the temperature resistant polymer polybenzimidazole (PBI), which allow working temperatures up to 200°C. The membrane has a water drag number near zero and need no water management at all. The high working...

  14. Mechanical strength and thermophysical properties of PM212: A high temperature self-lubricating powder metallurgy composite

    Science.gov (United States)

    Edwards, Phillip M.; Sliney, Harold E.; Dellacorte, Christopher; Whittenberger, J. Daniel; Martineau, Robert R.

    1990-01-01

    A powder metallurgy composite, PM212, composed of metal bonded chromium carbide and solid lubricants is shown to be self-lubricating to a maximum application temperature of 900 C. The high temperature compressive strength, tensile strength, thermal expansion and thermal conductivity data needed to design PM212 sliding contact bearings and seals are reported for sintered and isostatically pressed (HIPed) versions of PM212. Other properties presented are room temperature density, hardness, and elastic modulus. In general, both versions appear to have adequate strength to be considered as sliding contact bearing materials, but the HIPed version, which is fully dense, is much stronger than the sintered version which contains about 20 percent pore volume. The sintered material is less costly to make, but the HIPed version is better where high compressive strength is important.

  15. High Temperature Bell Motor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The National Research Council (NRC) has identified the need for motors and actuators that can operate in extreme high and low temperature environments as a technical...

  16. High Temperature Materials Laboratory (HTML)

    Data.gov (United States)

    Federal Laboratory Consortium — The six user centers in the High Temperature Materials Laboratory (HTML), a DOE User Facility, are dedicated to solving materials problems that limit the efficiency...

  17. Multi-pulse flash light sintering of bimodal Cu nanoparticle-ink for highly conductive printed Cu electrodes

    Science.gov (United States)

    Yu, Myeong-Hyeon; Joo, Sung-Jun; Kim, Hak-Sung

    2017-05-01

    In this work, bimodal Cu nano-inks composed of two different sizes of Cu nanoparticles (NPs) (40 and 100 nm in diameter) were successfully sintered with a multi-pulse flashlight sintering technique. Bimodal Cu nano-inks were fabricated and printed with various mixing ratios and subsequently sintered by a flash light sintering method. The effects of the flashlight sintering conditions, including irradiation energy and pulse number, were investigated to optimize the sintering conditions. A detailed mechanism of the sintering of bimodal Cu nano-ink was also studied via real-time resistance measurement during the sintering process. The sintered Cu nano-ink films were characterized using x-ray photoelectron spectroscopy and scanning electron microscopy. From these results, it was found that the optimal ratio of 40-100 nm NPs was found to be 25:75 wt%, and the optimal multi-pulse flash light sintering condition (irradiation energy: 6 J cm-2, and pulse duration: 1 ms, off-time: 4 ms, and pulse number: 5) was found. The optimally sintered Cu nano-ink film exhibited the lowest resistivity of 5.68 μΩ cm and 5B adhesion level.

  18. Influences of sintering temperature on low-cost carbon paste based counter electrodes for dye-sensitized solar cells

    Science.gov (United States)

    Huang, Chun-Ying; Lin, Guan-You; Lin, Pei-Te; Chen, Jhih-Wei; Chen, Chia-Hao; Shih-Sen Chien, Forest

    2017-08-01

    In this paper we have demonstrated the photovoltaic performance of dye-sensitized solar cells with low-cost carbon paste (CP) based counter electrodes. With sintering CP at 300 °C, the overall conversion efficiency of cells can reach 4.9%, which is comparable to 5.7% of the cells with counter electrode of platinum. After sintering, crystalline quality of CP was improved, resulting in the decrease of series resistance of cells and the increase of the work function of CP. We also showed that the reduction rate of triiodide is significantly enhanced due to the increase of surface area of CP and the energy matching between the reduction potential of triiodide and the work function of CP.

  19. Sintering behavior of LZSA glass-ceramics

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2009-06-01

    Full Text Available The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3 shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter. Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.

  20. Surprising formation of a rhodochrosite-like (MnCO3) phase on Co-Zn-Mn sintered spinels upon storage at room temperature and ambient air

    Science.gov (United States)

    Casaletto, Maria Pia; Fierro, Giuseppe

    2017-11-01

    A detailed XPS investigation, supported by XRD analysis, was performed on Co-Zn-Mn oxide-based spinels as a function of cobalt concentration and calcination temperature (723 and 973 K). Results revealed for the first time that a recarbonation occurred under ambient conditions but only for the Co-containing materials calcined at 973 K. Indeed, such effect was not observed for the homologous preparations at 723 K. This evidence was quite surprising because the solids calcined at 973 K, for which a sintering occurred as reflected by the low surface areas, were supposed to be almost inert under ambient conditions. Such an intriguing recarbonation chemistry, leading even to a bulky rhodochrosite-like (MnCO3) phase in the cobalt most enriched samples, arises from the combined effect of the calcination treatment at high temperature and the presence of cobalt ions. The spinels calcined at higher temperature are characterized by a high surface defectivity, due to anionic vacancies produced by a partial self-reduction of a fraction of Mn3+ ions that occurs only at 973 K but not at 723 K. Consequently, the presence of anionic vacancies and the incomplete coordination of the outermost layers promoted a higher reactivity of the solids calcined at 973 K with CO2 and moisture from ambient air. However, a carbonate phase was absent in the sample at 973 K with no cobalt. This suggests that the presence of cobalt is another crucial factor for the recarbonation process to take place. Cobalt ions appear to play a catalytic role. An attempt is made to provide a reasonable explanation of this intriguing recarbonation chemistry, trying to shed some more light on the rather complex chemistry behind the attack of moisture and CO2 to oxide solid surfaces. These results, as a whole, may provide new insight on phenomena observed in the case of some Mn-based catalysts, as the severe deactivation by traces of moisture occurring in hopcalite during CO oxidation at RT. They may also give an

  1. Effect of changes in sintering parameters on monolithic translucent zirconia.

    Science.gov (United States)

    Ebeid, Kamal; Wille, Sebastian; Hamdy, Amina; Salah, Tarek; El-Etreby, Amr; Kern, Matthias

    2014-12-01

    Aim of this study was to evaluate the effect of different sintering parameters on color reproduction, translucency and biaxial flexural strength of monolithic zirconia. Translucent zirconia discs having 15mm diameter, 1mm thickness, and shade A3 were milled and divided according to the sintering temperatures (1460°C, 1530°C, and 1600°C) into three groups (n=30). Each group was later divided into three subgroups (n=10) according to the sintering holding time (1, 2, and 4h). Easyshade spectrophotometer (Vita, Bad Säckingen, Germany) was used to obtain the ΔE between the specimens and the shade A3. Mean ΔE values below 3.0 were considered "clinically imperceptible", ΔE values between 3.0 and 5.0 were considered "clinically acceptable" and ΔE values above 5.0 were considered "clinically unacceptable". Contrast ratio (CR) was obtained after comparing the reflectance of light through the specimens over black and white background. Biaxial flexural strength was tested using the piston-on-three balls technique in a universal testing machine. Mean ΔE results ranged from 4.4 to 2.2. Statistically significant decrease in the Delta E was observed as the sintering time and temperature increased. CR decreased from 0.75 to 0.68 as the sintering time and temperature increased. No significant change in the biaxial flexural strength was observed. Sintering zirconia using long cycles and high temperatures will result in reduction of ΔE and CR. Biaxial flexural strength is not affected by changes in the evaluated sintering parameters. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Synthesis, microstructure and magnetic properties of nanocrystalline MgFe2O4 particles: Effect of mixture of fuels and sintering temperature

    Directory of Open Access Journals (Sweden)

    Osereme Ehi-Eromosele Cyril

    2016-01-01

    Full Text Available The present article reports the results of studies related to the synthesis of MgFe2O4 nanocomposite powder by solution combustion process using mixture of fuels containing urea (U and ammonium acetate (AA. The effect of mixture of fuel and sintering temperature on phase formation, structural, morphological and magnetic properties of MgFe2O4 particles were investigated by X-ray diffraction (XRD, thermogravimetric analysis (TGA, Raman spectroscopy, scanning electron microscopy (SEM, energy dispersive absorption x-ray (EDAX and vibrating sample magnetometer (VSM. Thermodynamic modeling of the combustion reaction shows that by using a mixture of urea and ammonium acetate fuels, the adiabatic flame temperature (Tad, exothermicity and amount of gases produced during the combustion process as well as product characteristics could be controlled. The use of mixture of fuels (U and AA in the synthesis of MgFe2O4 was found to produce ferrites with finer agglomerates, higher crystallinity, higher magnetic properties and smaller crystallite sizes than when only urea was used. It was found that only samples prepared with a mixture of fuels (0.5U + 0.5AA and sintered at 900oC for 2 h produced pure ferrite spinel phase while the auto-combusted and powders sintered at 600oC for 2 h had secondary phases. Apart from giving detailed information about the structural order of the samples, Raman spectroscopy also confirmed that MgFe2O4 is a mixed spinel ferrite.

  3. Laser sintering of Cu-Zr-ZrB2 composite

    Science.gov (United States)

    Stašić, J.; Trtica, M.; Rajković, V.; Ružić, J.; Božić, D.

    2014-12-01

    Cu-4.1Zr-1.1B (wt%) composite has been synthesized by mechanical alloying, cold pressing of mechanically alloyed powders and, for the first time in literature, sintering by laser irradiation (pulsed, millisecond Nd:YAG laser was employed) in nitrogen atmosphere. The influence of different sintering parameters on the properties of laser-sintered materials was investigated. Microstructural changes during laser sintering were studied using scanning electron microscopy and X-ray diffraction. Rapidly solidified structure, as well as the presence of ZrB2 particles and metastable CuZr phase, which are a product of laser sintering, affected higher degree of copper matrix hardening which was retained up to high temperatures. In general, laser sintering of Cu-4.1Zr-1.1B (wt%) green compact using the parameters: laser frequency 3 Hz, laser pulse duration 8 ms, pulse energy ∼19 J, number of scans 4 yields the optimum combination of high density, microhardness and electrical conductivity.

  4. Influence of sintering temperature in red ceramic with addition of mill scale; Influencia da temperatura de sinterizacao em ceramica vermelha com adicao de carepa/residuo de laminacao

    Energy Technology Data Exchange (ETDEWEB)

    Arnt, A.B.C.; Rocha, M.R.; Bernardin, A.M.; Meller, J.G., E-mail: anb@unesc.ne [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Engenharia de Materiais. Lab. de Fenomenos de Superficies e Tratamentos Termicos

    2010-07-01

    This study aimed to evaluate the influence of sintering temperature in a red ceramic body with the addition of mill scale. This residue consists of oxides of iron had to replace the function of pigments used in ceramic materials. After chemical characterization, by X-ray diffraction, X-ray fluorescence and scanning electron microscopy, this residue was added at a rate of 5% in commercial ceramic past. The formulations were subjected to different burn temperatures of around 950 deg C, 1000 deg C and 1200 deg C. The formulations were evaluated for physical loss to fire, linear firing shrinkage, water absorption and flexural strength by 3 and intensity of tone. The results indicate that the different firing temperatures influence the strength and stability of tone in the formulations tested. (author)

  5. Temperature optimization of high con

    Directory of Open Access Journals (Sweden)

    M. Sabry

    2016-06-01

    Full Text Available Active cooling is essential for solar cells operating under high optical concentration ratios. A system comprises four solar cells that are in thermal contact on top of a copper tube is proposed. Water is flowing inside the tube in order to reduce solar cells temperature for increasing their performance. Computational Fluid Dynamics (CFD simulation of such system has been performed in order to investigate the effect of water flow rate, tube internal diameter, and convective heat transfer coefficient on the temperature of the solar cells. It is found that increasing convective heat transfer coefficient has a significant effect on reducing solar cells temperatures operating at low flow rates and high optical concentration ratios. Also, a further increase of water flow rate has no effect on reducing cells temperatures.

  6. RPC operation at high temperature

    CERN Document Server

    Aielli, G; Cardarelli, R; Di Ciaccio, A; Di Stante, L; Liberti, B; Paoloni, A; Pastori, E; Santonico, R

    2003-01-01

    The resistive electrodes of RPCs utilised in several current experiments (ATLAS, CMS, ALICE, BABAR and ARGO) are made of phenolic /melaminic polymers, with room temperature resistivities ranging from 10**1**0 Omega cm, for high rate operation in avalanche mode, to 5 multiplied by 10**1**1 Omega cm, for streamer mode operation at low rate. The resistivity has however a strong temperature dependence, decreasing exponentially with increasing temperature. We have tested several RPCs with different electrode resistivities in avalanche as well as in streamer mode operation. The behaviours of the operating current and of the counting rate have been studied at different temperatures. Long-term operation has also been studied at T = 45 degree C and 35 degree C, respectively, for high and low resistivity electrodes RPCs.

  7. HIgh Temperature Photocatalysis over Semiconductors

    Science.gov (United States)

    Westrich, Thomas A.

    Due in large part to in prevalence of solar energy, increasing demand of energy production (from all sources), and the uncertain future of petroleum energy feedstocks, solar energy harvesting and other photochemical systems will play a major role in the developing energy market. This dissertation focuses on a novel photochemical reaction process: high temperature photocatalysis (i.e., photocatalysis conducted above ambient temperatures, T ≥ 100°C). The overarching hypothesis of this process is that photo-generated charge carriers are able to constructively participate in thermo-catalytic chemical reactions, thereby increasing catalytic rates at one temperature, or maintaining catalytic rates at lower temperatures. The photocatalytic oxidation of carbon deposits in an operational hydrocarbon reformer is one envisioned application of high temperature photocatalysis. Carbon build-up during hydrocarbon reforming results in catalyst deactivation, in the worst cases, this was shown to happen in a period of minutes with a liquid hydrocarbon. In the presence of steam, oxygen, and above-ambient temperatures, carbonaceous deposits were photocatalytically oxidized over very long periods (t ≥ 24 hours). This initial experiment exemplified the necessity of a fundamental assessment of high temperature photocatalytic activity. Fundamental understanding of the mechanisms that affect photocatalytic activity as a function of temperatures was achieved using an ethylene photocatalytic oxidation probe reaction. Maximum ethylene photocatalytic oxidation rates were observed between 100 °C and 200 °C; the maximum photocatalytic rates were approximately a factor of 2 larger than photocatalytic rates at ambient temperatures. The loss of photocatalytic activity at temperatures above 200 °C is due to a non-radiative multi-phonon recombination mechanism. Further, it was shown that the fundamental rate of recombination (as a function of temperature) can be effectively modeled as a

  8. Moire interferometry at high temperatures

    Science.gov (United States)

    Wu, Jau-Je

    1992-01-01

    The objective of this study was to provide an optical technique allowing full-field in-plane deformation measurements at high temperature by using high-sensitivity moire interferometry. This was achieved by a new approach of performing deformation measurements at high temperatures in a vacuum oven using an achromatic interferometer. The moire system setup was designed with particular consideration for the stability, compactness, flexibility, and ease of control. A vacuum testing environment was provided to minimize the instability of the patterns by protecting the optical instruments from the thermal convection currents. Also, a preparation procedure for the high-temperature specimen grating was developed with the use of the plasma-etched technique. Gold was used as a metallic layer in this procedure. This method was demonstrated on a ceramic block, metal/matrix composite, and quartz. Thermal deformation of a quartz specimen was successfully measured in vacuum at 980 degrees Celsius, with the sensitivity of 417 nm per fringe. The stable and well-defined interference patterns confirmed the feasibility of the developments, including the high-temperature moire system and high-temperature specimen grating. The moire system was demonstrated to be vibration-insensitive. Also, the contrast of interference fringes at high temperature was enhanced by means of a spatial filter and a narrow band interference filter to minimize the background noise from the flow of the specimen and heater. The system was verified by a free thermal expansion test of an aluminum block. Good agreement demonstrated the validity of the optical design. The measurements of thermal deformation mismatch were performed on a graphite/epoxy composite, a metal/matrix composite equipped with an optical fiber, and a cutting tool bit. A high-resolution data-reduction technique was used to measure the strain distribution of the cutting tool bit.

  9. High temperature superconductor accelerator magnets

    OpenAIRE

    van Nugteren, J.

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding 20T. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is ...

  10. High Temperature Superconductor Accelerator Magnets

    OpenAIRE

    Van Nugteren, Jeroen; ten Kate, Herman; de Rijk, Gijs; Dhalle, Marc

    2016-01-01

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet ...

  11. Solution spinning of high-? oxide superconductors: part VII. The effect of polyvinyl alcohol spinning medium on the sintering of ? superconducting filaments

    Science.gov (United States)

    Tomita, Hisayo; Goto, Tomoko; Takahashi, Kiyohisa

    1996-05-01

    As basic research for the solution spinning of high-0953-2048/9/5/005/img8 oxide superconductor, the effect of poly(vinyl alcohol) (PVA) spinning medium on the sintering of 0953-2048/9/5/005/img9 filament was examined. A precursor filament was produced by dry-spinning starting from a homogeneous aqueous PVA solution of Y, Ba and Cu acetates. The as-drawn filament was pyrolysed to remove volatile components and sintered to generate a superconducting phase. The degree of polymerization (DP) of PVA and the content of acetates in the precursor filament affected the 0953-2048/9/5/005/img10 of the sintered filament. Although most filaments exhibited high 0953-2048/9/5/005/img10 greater than 0953-2048/9/5/005/img12 at 77 K and 0 T, superconductivity above 77 K was not observed for the filament spun from PVA solution of DP=2450 with [acetates]/[PVA]=2 and sintered at 900 and 0953-2048/9/5/005/img13C for 15 min. The filament had a dense structure due to liquid phase sintering. The filament with high 0953-2048/9/5/005/img10 had a skin - core structure, and the highest 0953-2048/9/5/005/img10 of 0953-2048/9/5/005/img16 at 77 K and 0 T was attained for the filament from DP=3500 with [acetates]/[PVA]=4.

  12. Sintering Inhibition of Silver Nanoparticle Films via AgCl Nanocrystal Formation.

    Science.gov (United States)

    Öhlund, Thomas; Hummelgård, Magnus; Olin, Håkan

    2017-08-17

    Electrically conductive films are key components in most printed and flexible electronics applications. For the solution processing of conductive films, inks containing silver nanoparticles (AgNPs) remain important because of their relatively easy processing and generally low resistivity after a sintering procedure. Because the commonly used, moderate sintering temperatures of 150-300 °C are still too high for most low-cost flexible substrates, expanding the knowledge of surface-ink interactions that affect the sintering temperature is desirable. It is known that chloride ions can assist the sintering of AgNP films by displacing capping agents on the surfaces of AgNPs. However, very little is known about other possible Cl-AgNP interactions that affect the resistivity and no interaction having the opposite effect (sintering inhibition) has been identified before. Here we identify such a Cl-AgNP interaction giving sintering inhibition and find that the mechanism involves the formation of AgCl nanocrystals within the AgNP film. The AgCl formation was observed after inkjet-printing of AgNP inks with polyvinylpyrrolidone (PVP) as the capping agent onto papers with quick-absorbing coatings containing 0.3 wt % KCl. Our findings show that chloride can have opposite roles during sintering, either assisting or inhibiting the sintering depending on the prevalence of AgCl formation. The prevalence of AgCl formation depends on the absorption properties and the capping agent.

  13. All-photonic drying and sintering process via flash white light combined with deep-UV and near-infrared irradiation for highly conductive copper nano-ink.

    Science.gov (United States)

    Hwang, Hyun-Jun; Oh, Kyung-Hwan; Kim, Hak-Sung

    2016-01-25

    We developed an ultra-high speed photonic sintering method involving flash white light (FWL) combined with near infrared (NIR) and deep UV light irradiation to produce highly conductive copper nano-ink film. Flash white light irradiation energy and the power of NIR/deep UV were optimized to obtain high conductivity Cu films. Several microscopic and spectroscopic characterization techniques such as scanning electron microscopy (SEM), a x-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy were employed to characterize the Cu nano-films. Optimally sintered Cu nano-ink films produced using a deep UV-assisted flash white light sintering technique had the lowest resistivity (7.62 μΩ·cm), which was only 4.5-fold higher than that of bulk Cu film (1.68 μΩ•cm).

  14. 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 .

  15. High-Temperature Optical Sensor

    Science.gov (United States)

    Adamovsky, Grigory; Juergens, Jeffrey R.; Varga, Donald J.; Floyd, Bertram M.

    2010-01-01

    A high-temperature optical sensor (see Figure 1) has been developed that can operate at temperatures up to 1,000 C. The sensor development process consists of two parts: packaging of a fiber Bragg grating into a housing that allows a more sturdy thermally stable device, and a technological process to which the device is subjected to in order to meet environmental requirements of several hundred C. This technology uses a newly discovered phenomenon of the formation of thermally stable secondary Bragg gratings in communication-grade fibers at high temperatures to construct robust, optical, high-temperature sensors. Testing and performance evaluation (see Figure 2) of packaged sensors demonstrated operability of the devices at 1,000 C for several hundred hours, and during numerous thermal cycling from 400 to 800 C with different heating rates. The technology significantly extends applicability of optical sensors to high-temperature environments including ground testing of engines, flight propulsion control, thermal protection monitoring of launch vehicles, etc. It may also find applications in such non-aerospace arenas as monitoring of nuclear reactors, furnaces, chemical processes, and other hightemperature environments where other measurement techniques are either unreliable, dangerous, undesirable, or unavailable.

  16. Influence of vacuum sintering on microstructure and magnetic properties of magnetostrictive cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Nlebedim, I.C.; Ranvah, N; Williams, P.I.; Melikhov, Y; Anayi, F; Snyder, J.E.; Moses, A.J. [Wolfson Centre for Magnetics, School of Engineering, Cardiff University, Cardiff CF24 3AA (United Kingdom); Jiles, D.C. [Wolfson Centre for Magnetics, School of Engineering, Cardiff University, Cardiff CF24 3AA (United Kingdom)], E-mail: jilesd@cf.ac.uk

    2009-09-15

    Differences in the microstructure and magnetic properties of highly magnetostrictive cobalt ferrite resulting from the effects of different vacuum sintering temperatures and times have been investigated. A vacuum environment was chosen to allow direct comparison of results with air-sintered samples which are more often reported in the literature. It was found that vacuum sintering resulted in the development of a solid solution second phase with composition Co{sub 1-x}Fe{sub x}O{sub 4} (x{approx}0.33). There was a decrease in magnetostriction as a result of the formation of the second phase. Furthermore, differences in sintering temperatures were found to have a greater effect on the magnetostriction than differences in sintering times. It was found that the first order cubic anisotropy coefficient initially increased with both sintering temperature and time, before peaking and decreasing to its lowest measured value. The lowest anisotropy was therefore achieved with samples sintered at higher temperatures and longer times.

  17. Solute strengthening at high temperatures

    Science.gov (United States)

    Leyson, G. P. M.; Curtin, W. A.

    2016-08-01

    The high temperature behavior of solute strengthening has previously been treated approximately using various scaling arguments, resulting in logarithmic and power-law scalings for the stress-dependent energy barrier Δ E(τ ) versus stress τ. Here, a parameter-free solute strengthening model is extended to high temperatures/low stresses without any a priori assumptions on the functional form of Δ E(τ ) . The new model predicts that the well-established low-temperature, with energy barrier Δ {{E}\\text{b}} and zero temperature flow stress {τy0} , transitions to a near-logarithmic form for stresses in the regime 0.2intermediate-temperature and the associated transition for the activation volume. Overall, the present analysis unifies the different qualitative models in the literature and, when coupled with the previous parameter-free solute strengthening model, provides a single predictive model for solute strengthening as a function of composition, temperature, and strain rate over the full range of practical utility.

  18. High temperature superconductor current leads

    Science.gov (United States)

    Hull, John R.; Poeppel, Roger B.

    1995-01-01

    An electrical lead having one end for connection to an apparatus in a cryogenic environment and the other end for connection to an apparatus outside the cryogenic environment. The electrical lead includes a high temperature superconductor wire and an electrically conductive material distributed therein, where the conductive material is present at the one end of the lead at a concentration in the range of from 0 to about 3% by volume, and at the other end of the lead at a concentration of less than about 20% by volume. Various embodiments are shown for groups of high temperature superconductor wires and sheaths.

  19. High temperature corrosion in gasifiers

    Directory of Open Access Journals (Sweden)

    Wate Bakker

    2004-03-01

    Full Text Available Several commercial scale coal gasification combined cycle power plants have been built and successfully operated during the last 5-10 years. Supporting research on materials of construction has been carried out for the last 20 years by EPRI and others. Emphasis was on metallic alloys for heat exchangers and other components in contact with hot corrosive gases at high temperatures. In this paper major high temperature corrosion mechanisms, materials performance in presently operating gasifiers and future research needs will be discussed.

  20. Sol-gel synthesis of carbon based materials reinforced ultra high temperature ceramic composites

    OpenAIRE

    Wang, Xiaojing

    2017-01-01

    This Ph.D. research is based on the development of novel sol-gel techniques for synthesis of nanostructured ultra high temperature ceramics (UHTCs) and subsequent spark plasma sintering (SPS) for densifying the UHTC composites. The liquid nature of the sol-gel process offers advantages such as high purity and ability for mixing and infiltration, and thus it can overcome some shortcomings of the conventional power processing of ceramics. SPS delivers microstructures with good density and fine ...

  1. Nonlinear plasmonics at high temperatures

    Science.gov (United States)

    Sivan, Yonatan; Chu, Shi-Wei

    2017-01-01

    We solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense continuous wave (CW) illumination. Unlike previous studies, we rely on experimentally-measured data for metal permittivity for increasing temperature and for the visible spectral range. We show that the thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear model for the temperature and field distribution and, thus, can explain qualitatively the strong nonlinear scattering from such configurations observed experimentally. We also show that the incompleteness of existing data of the temperature dependence of the thermal properties of the system prevents reaching a quantitative agreement between the measured and calculated scattering data. This modeling approach is essential for the identification of the underlying physical mechanism responsible for the thermo-optical nonlinearity of the metal and should be adopted in all applications of high-temperature nonlinear plasmonics, especially for refractory metals, for both CW and pulsed illumination.

  2. Nonlinear plasmonics at high temperatures

    Directory of Open Access Journals (Sweden)

    Sivan Yonatan

    2016-10-01

    Full Text Available We solve the Maxwell and heat equations self-consistently for metal nanoparticles under intense continuous wave (CW illumination. Unlike previous studies, we rely on experimentally-measured data for metal permittivity for increasing temperature and for the visible spectral range. We show that the thermal nonlinearity of the metal can lead to substantial deviations from the predictions of the linear model for the temperature and field distribution and, thus, can explain qualitatively the strong nonlinear scattering from such configurations observed experimentally. We also show that the incompleteness of existing data of the temperature dependence of the thermal properties of the system prevents reaching a quantitative agreement between the measured and calculated scattering data. This modeling approach is essential for the identification of the underlying physical mechanism responsible for the thermo-optical nonlinearity of the metal and should be adopted in all applications of high-temperature nonlinear plasmonics, especially for refractory metals, for both CW and pulsed illumination.

  3. An easily sintered, chemically stable, barium zirconate-based proton conductor for high-performance proton-conducting solid oxide fuel cells

    KAUST Repository

    Sun, Wenping

    2014-07-25

    Yttrium and indium co-doped barium zirconate is investigated to develop a chemically stable and sintering active proton conductor for solid oxide fuel cells (SOFCs). BaZr0.8Y0.2-xInxO3- δ possesses a pure cubic perovskite structure. The sintering activity of BaZr0.8Y0.2-xInxO3- δ increases significantly with In concentration. BaZr0.8Y0.15In0.05O3- δ (BZYI5) exhibits the highest total electrical conductivity among the sintered oxides. BZYI5 also retains high chemical stability against CO2, vapor, and reduction of H2. The good sintering activity, high conductivity, and chemical stability of BZYI5 facilitate the fabrication of durable SOFCs based on a highly conductive BZYI5 electrolyte film by cost-effective ceramic processes. Fully dense BZYI5 electrolyte film is successfully prepared on the anode substrate by a facile drop-coating technique followed by co-firing at 1400 °C for 5 h in air. The BZYI5 film exhibits one of the highest conductivity among the BaZrO3-based electrolyte films with various sintering aids. BZYI5-based single cells output very encouraging and by far the highest peak power density for BaZrO3-based proton-conducting SOFCs, reaching as high as 379 mW cm-2 at 700 °C. The results demonstrate that Y and In co-doping is an effective strategy for exploring sintering active and chemically stable BaZrO3-based proton conductors for high performance proton-conducting SOFCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. 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.

  5. Processing temperature tuned interfacial microstructure and protonic and oxide ionic conductivities of well-sintered Sm0.2Ce0.8O1.9- Na2CO3 nanocomposite electrolytes for intermediate temperature solid oxide fuel cells

    Science.gov (United States)

    Li, Chuanming; Zeng, Yanwei; Wang, Zhentao; Ye, Zhupeng; Zhang, Yuan

    2017-08-01

    Well-sintered SDC-NC (Sm0.2Ce0.8O1.9-Na2CO3) nanocomposites have been prepared through a rare-earth/sodium complex carbonate precipitation, powder prefirings at the temperatures 400, 500 and 600 °C and sintering at 800 °C. Their sintering performances, phase components and microstructures have been characterized by Archimedean method, XRD and FESEM techniques. In particular, the influence of the interfacial interactions between the phases of SDC and NC on the microstructures and electrical conductivities of SDC-NC nanocomposites have been investigated by AC impedance and Raman spectroscopies. It has been found that on the basis of the fitting analysis of AC impedance data, the oxide ionic and protonic conductivities of interfacial and non-interfacial phases in the SDC-NC nanocomposites are found to be strongly dependent upon their prefiring temperatures with the sample of SN-600 showing the highest values of 73.2/33.7 and 51.1/105.4 μS/cm at 300 °C, respectively. The single cell based on the electrolyte of SN-600 presents an OCV of 0.992 V and peak power density of 421 mW/cm2 at 550 °C. The interfacial interactions between the phases of SDC and NC inside SDC-NC nanocomposites are considered responsible for their differences in microstructure and electrical conductivity.

  6. Chemistry of high temperature superconductors

    CERN Document Server

    1991-01-01

    This review volume contains the most up-to-date articles on the chemical aspects of high temperature oxide superconductors. These articles are written by some of the leading scientists in the field and includes a comprehensive list of references. This is an essential volume for researchers working in the fields of ceramics, materials science and chemistry.

  7. High temperature component life assessment

    CERN Document Server

    Webster, G A

    1994-01-01

    The aim of this book is to investigate and explain the rapid advances in the characterization of high temperature crack growth behaviour which have been made in recent years, with reference to industrial applications. Complicated mathematics has been minimized with the emphasis placed instead on finding solutions using simplified procedures without the need for complex numerical analysis.

  8. Properties of high temperature SQUIDS

    Energy Technology Data Exchange (ETDEWEB)

    Falco, C. M.; Wu, C. T.

    1978-01-01

    A review is given of the present status of weak links and dc and rf biased SQUIDs made with high temperature superconductors. A method for producing reliable, reproducible devices using Nb/sub 3/Sn is outlined, and comments are made on directions future work should take.

  9. High-temperature flooding injury

    Science.gov (United States)

    This problem, also called scald, is most serious in the hot desert valleys of the southwestern United States, subtropical regions in eastern Australia, and western Asia and northern Africa (Middle East) where fields are established and irrigated under high temperatures. The disorder also occurs to...

  10. High temperature thermoelectric energy conversion

    Science.gov (United States)

    Wood, Charles

    1987-01-01

    The theory and current status of materials research for high-temperature thermoelectric energy conversion are reviewed. Semiconductors are shown to be the preferred class of materials for this application. Optimization of the figure of merit of both broadband and narrow-band semiconductors is discussed as a function of temperature. Phonon scattering mechanisms are discussed, and basic material guidelines are given for reduction of thermal conductivity. Two general classes of materials show promise for high temperature figure of merit (Z) values, namely the rare earth chalcogenides and the boron-rich borides. The electronic transport properties of the rare earth chalcogenides are explicable on the basis of degenerate or partially degenerate n-type semiconductors. Boron and boron-rich borides exhibit p-type hopping conductivity, with detailed explanations proposed for the transport differing from compound to compound. Some discussion is presented on the reasons for the low thermal conductivities in these materials. Also, ZTs greater than one appear to have been realized at high temperature in many of these compounds.

  11. High temperature, high power piezoelectric composite transducers.

    Science.gov (United States)

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, Stewart

    2014-08-08

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

  12. High Temperature Composite Heat Exchangers

    Science.gov (United States)

    Eckel, Andrew J.; Jaskowiak, Martha H.

    2002-01-01

    High temperature composite heat exchangers are an enabling technology for a number of aeropropulsion applications. They offer the potential for mass reductions of greater than fifty percent over traditional metallics designs and enable vehicle and engine designs. Since they offer the ability to operate at significantly higher operating temperatures, they facilitate operation at reduced coolant flows and make possible temporary uncooled operation in temperature regimes, such as experienced during vehicle reentry, where traditional heat exchangers require coolant flow. This reduction in coolant requirements can translate into enhanced range or system payload. A brief review of the approaches and challengers to exploiting this important technology are presented, along with a status of recent government-funded projects.

  13. 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.

  14. 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.

  15. Summary: High Temperature Downhole Motor

    Energy Technology Data Exchange (ETDEWEB)

    Raymond, David W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    Directional drilling can be used to enable multi-lateral completions from a single well pad to improve well productivity and decrease environmental impact. Downhole rotation is typically developed with a motor in the Bottom Hole Assembly (BHA) that develops drilling power (speed and torque) necessary to drive rock reduction mechanisms (i.e., the bit) apart from the rotation developed by the surface rig. Historically, wellbore deviation has been introduced by a “bent-sub,” located in the BHA, that introduces a small angular deviation, typically less than 3 degrees, to allow the bit to drill off-axis with orientation of the BHA controlled at the surface. The development of a high temperature downhole motor would allow reliable use of bent subs for geothermal directional drilling. Sandia National Laboratories is pursuing the development of a high temperature motor that will operate on either drilling fluid (water-based mud) or compressed air to enable drilling high temperature, high strength, fractured rock. The project consists of designing a power section based upon geothermal drilling requirements; modeling and analysis of potential solutions; and design, development and testing of prototype hardware to validate the concept. Drilling costs contribute substantially to geothermal electricity production costs. The present development will result in more reliable access to deep, hot geothermal resources and allow preferential wellbore trajectories to be achieved. This will enable development of geothermal wells with multi-lateral completions resulting in improved geothermal resource recovery, decreased environmental impact and enhanced well construction economics.

  16. High temperature two component explosive

    Science.gov (United States)

    Mars, James E.; Poole, Donald R.; Schmidt, Eckart W.; Wang, Charles

    1981-01-01

    A two component, high temperature, thermally stable explosive composition comprises a liquid or low melting oxidizer and a liquid or low melting organic fuel. The oxidizer and fuel in admixture are incapable of substantial spontaneous exothermic reaction at temperatures on the order of 475.degree. K. At temperatures on the order of 475.degree. K., the oxidizer and fuel in admixture have an activation energy of at least about 40 kcal/mol. As a result of the high activation energy, the preferred explosive compositions are nondetonable as solids at ambient temperature, and become detonable only when heated beyond the melting point. Preferable oxidizers are selected from alkali or alkaline earth metal nitrates, nitrites, perchlorates, and/or mixtures thereof. Preferred fuels are organic compounds having polar hydrophilic groups. The most preferred fuels are guanidinium nitrate, acetamide and mixtures of the two. Most preferred oxidizers are eutectic mixtures of lithium nitrate, potassium nitrate and sodium nitrate, of sodium nitrite, sodium nitrate and potassium nitrate, and of potassium nitrate, calcium nitrate and sodium nitrate.

  17. Low-Temperature Sintering Behavior and Dielectric Properties of Li2O-Nb2O5-TiO2 Ceramics with Li-B-Si-O Glass

    Science.gov (United States)

    Li, Enzhu; Zhang, Peng; Mi, Yuean; Wang, Jing; Yuan, Ying; Zhou, Xiaohua

    2015-11-01

    This paper reports an investigation of the low-temperature sintering behaviors, microstructures, and microwave dielectric properties of Li1.0Nb0.6Ti0.5O3 (LNT) ceramics fired with addition of different amounts of Li2O-B2O3-SiO2 (LBS) glass. The results suggest that addition of LBS glass can effectively reduce the sintering temperature of LNT ceramic from 1100°C to 900°C without detriment of its microwave dielectric properties. However, addition of excess LBS glass leads to rapid grain growth and therefore decreases the density and microwave dielectric properties of the LNT ceramic. Optimized specimens with 1.0 wt.% LBS glass sintered at 900°C possessed excellent microwave dielectric properties of ɛ r ≈ 66.17, Q × f ≈ 5170 GHz ( f = 4.32 GHz), and τ f ≈ 19.2 ppm/°C.

  18. High temperature structural sandwich panels

    Science.gov (United States)

    Papakonstantinou, Christos G.

    High strength composites are being used for making lightweight structural panels that are being employed in aerospace, naval and automotive structures. Recently, there is renewed interest in use of these panels. The major problem of most commercial available sandwich panels is the fire resistance. A recently developed inorganic matrix is investigated for use in cases where fire and high temperature resistance are necessary. The focus of this dissertation is the development of a fireproof composite structural system. Sandwich panels made with polysialate matrices have an excellent potential for use in applications where exposure to high temperatures or fire is a concern. Commercial available sandwich panels will soften and lose nearly all of their compressive strength temperatures lower than 400°C. This dissertation consists of the state of the art, the experimental investigation and the analytical modeling. The state of the art covers the performance of existing high temperature composites, sandwich panels and reinforced concrete beams strengthened with Fiber Reinforced Polymers (FRP). The experimental part consists of four major components: (i) Development of a fireproof syntactic foam with maximum specific strength, (ii) Development of a lightweight syntactic foam based on polystyrene spheres, (iii) Development of the composite system for the skins. The variables are the skin thickness, modulus of elasticity of skin and high temperature resistance, and (iv) Experimental evaluation of the flexural behavior of sandwich panels. Analytical modeling consists of a model for the flexural behavior of lightweight sandwich panels, and a model for deflection calculations of reinforced concrete beams strengthened with FRP subjected to fatigue loading. The experimental and analytical results show that sandwich panels made with polysialate matrices and ceramic spheres do not lose their load bearing capability during severe fire exposure, where temperatures reach several

  19. High Temperature Heat Exchanger Project

    Energy Technology Data Exchange (ETDEWEB)

    Anthony E. Hechanova, Ph.D.

    2008-09-30

    The UNLV Research Foundation assembled a research consortium for high temperature heat exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature heat exchanger componets in hydrogen production processes and design and perform prototypical testing of heat exchangers. The initial research of the consortium focused on the intermediate heat exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These heat exchanger components were deemed the most challenging from a materials performance and compatibility perspective

  20. Motor for High Temperature Applications

    Science.gov (United States)

    Roopnarine (Inventor)

    2013-01-01

    A high temperature motor has a stator with poles formed by wire windings, and a rotor with magnetic poles on a rotor shaft positioned coaxially within the stator. The stator and rotor are built up from stacks of magnetic-alloy laminations. The stator windings are made of high temperature magnet wire insulated with a vitreous enamel film, and the wire windings are bonded together with ceramic binder. A thin-walled cylinder is positioned coaxially between the rotor and the stator to prevent debris from the stator windings from reaching the rotor. The stator windings are wound on wire spools made of ceramic, thereby avoiding need for mica insulation and epoxy/adhesive. The stator and rotor are encased in a stator housing with rear and front end caps, and rear and front bearings for the rotor shaft are mounted on external sides of the end caps to keep debris from the motor migrating into the bearings' races.

  1. Effect of Mg doping and sintering temperature on structural and morphological properties of samarium-doped ceria for IT-SOFC electrolyte

    Science.gov (United States)

    Ahmad, Syed Ismail; Mohammed, Tasneem; Bahafi, Amal; Suresh, Madireddy Buchi

    2017-06-01

    Samples of Sm and Mg co-doped ceria electrolyte of Ce1- x Sm x- y Mg y O2- δ ( x = 0.2; y = 0.00, 0.05, 0.1, 0.15, and 0.175) were synthesized by sol-gel process. The prepared samples were sintered at 1100 and 1400 °C for 4 h. The bulk densities were measured by Archimedes method. XRD measurements indicate that the synthesized samples were in single-phase cubic fluorite structure (space group Fm3m). The cell parameters decrease with the concentration of Mg, and 2 θ values slightly shift towards right. The particle sizes obtained were between 7.14 and 17.44 nm. The sintered sample achieved 95% of theoretical density. FTIR spectra of samples sintered at 1400 °C indicates weak interactions between 3550-3400 cm-1 and 1600-1300 cm-1 are attributed to O-H stretching modes and strong bonds 850-450 cm-1 are assigned to characteristic Ce-O vibrations. The surface morphology and chemical composition were analyzed by SEM and EDS, SEM micrographs show spherical faceted grains, and the samples were crack free, dense material with some pores on surface which are inconsistent with density results. The average grain size obtained was 0.5 μm. Particle size obtained by TEM was in agreement with that obtained by XRD. The high-density ceria co-doped ceramic can be used as electrolyte in SOFC.

  2. Very High Temperature Sound Absorption Coating Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Phase I demonstrated experimentally a very high temperature acoustically absorbing coating for ducted acoustics applications. High temperature survivability at 3500...

  3. Sintering behavior in zirconium phosphate bonded silicon nitride porous ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen Fei [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Shen Qiang [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)], E-mail: sqqf@263.net; Schoenung, Julie M. [Department of Chemical Engineering and Materials Science, University of California Davis, CA 95616 (United States); Zhang Lianmeng [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2008-12-15

    A new method for preparing high bending strength porous silicon nitride ceramics with controlled porosity has been developed by using a pressureless sintering technique with zirconium phosphate (ZrP{sub 2}O{sub 7}) as a binder phase. The sintering behavior in these porous ceramics is investigated in this study by using XRD, SEM, and HRTEM analysis. The results show that the sintering process can be divided into two stages: one is at temperatures below 250 deg. C, during which ZrO{sub 2} can react completely with H{sub 3}PO{sub 4} to form ZrP{sub 2}O{sub 7}, and a ZrP{sub 2}O{sub 7} bonded Si{sub 3}N{sub 4} porous structure is formed; the other is at temperatures above 250 deg. C, at which solid state sintering of the ZrP{sub 2}O{sub 7} dominates and a continuous open porosity network is obtained. The effect of the ZrP{sub 2}O{sub 7} binder content on sintering behavior, porosity and mechanical properties is also investigated.

  4. Nanoscale high-temperature superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, P.; Wei, J.Y.T.; Ananth, V.; Morales, P.; Skocpol, W

    2004-08-01

    We discuss the exciting prospects of studying high-temperature superconductivity in the nanometer scale from the perspective of experiments, theory and simulation. In addition to enabling studies of novel quantum phases in an unexplored regime of system dimensions and parameters, nanoscale high-temperature superconducting structures will allow exploration of fundamental mechanisms with unprecedented insight. The prospects include, spin-charge separation, detection of electron fractionalization via novel excitations such as vison, stripe states and their dynamics, preformed cooper pairs or bose-condensation in the underdoped regime, and other quantum-ordered states. Towards this initiative, we present the successful development of a novel nanofabrication technique for the epitaxial growth of nanoscale cuprates. Combining the techniques of e-beam lithography and nanomachining, we have been able to fabricate the first generation of high-temperature superconducting nanoscale devices, including Y-junctions, four-probe wires and rings. Their initial transport characterization and scanning tunneling microscopy reveal the integrity of the crystal structure, grown on nanometer scale lateral dimensions. Here, we present atomic force micrographs and electrical characterization of a few nanoscale YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) samples.

  5. Characteristics of 14Cr-ODS ferritic alloy fabricated by mechanically alloying and microwave sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhenhua, Yao [State Key Laboratory of Materia Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Weihao, Xiong, E-mail: whxiong@mail.hust.edu.cn [State Key Laboratory of Materia Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Bin, Huang; Qingqing, Yang [State Key Laboratory of Materia Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Jiang, Jianjun [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2015-06-15

    14Cr-ODS ferritic alloys were fabricated by microwave sintering and conventional vacuum sintering. The results showed that the sintering time could be reduced and the sintering temperature could be decreased effectively by adoption of microwave sintering. The tensile strength of the alloy microwave sintered at 1250 °C and the alloy vacuum sintered at 1350 °C were 691.4 MPa and 521.5 MPa respectively. The superior strength of microwave sintered one would be attributed to finer grain size, which was resulted from the shorter sintering time and lower sintering temperature. The elongation of microwave sintered alloy was worse than that of the vacuum sintering one. Nano-oxide precipitates were dispersed homogeneously in the Fe-based matrix, and their size was mostly ranged from several nm to more than 20 nm.

  6. The master sintering curve for pressure-less sintering of TiO2

    Directory of Open Access Journals (Sweden)

    Li D.

    2007-01-01

    Full Text Available A Master Sintering Curve (MSC for rutile TiO2 was constructed for Pressure-less sintering using constant heating rate dilatometry data based on the combined-stage sintering model. Construction of the master sintering curve is described and the validation is proved with rutile TiO2 under different thermal histories. The concept of master sintering can be used to predict the sintering shrinkage and final density and calculate the activation energy, and a value of 105 KJ/mol for TiO2 was obtained. With one temperature dependent parameter determined experimentally, it became possible to describe accurately the densification behavior of TiO2 from the initial to final stages of sintering. .

  7. The agglomeration, coalescence and sliding of nanoparticles, leading to the rapid sintering of zirconia nanoceramics.

    Science.gov (United States)

    Kocjan, Andraž; Logar, Manca; Shen, Zhijian

    2017-05-31

    Conventional sintering is a time- and energy-consuming process used for the densification of consolidated particles facilitated by atomic diffusion at high temperatures. Nanoparticles, with their increased surface free energy, can promote sintering; however, size reduction also promotes agglomeration, so hampering particle packing and complete densification. Here we show how the ordered agglomeration of zirconia primary crystallites into secondary particle assemblies ensures their homogeneous packing, while also preserving the high surface energy to higher temperatures, increasing the sintering activity. When exposed to intense electromagnetic radiation, providing rapid heating, the assembled crystallites are subjected to further agglomeration, coalescence and sliding, leading to rapid densification in the absence of extensive diffusional processes, cancelling out the grain growth during the initial sintering stages and providing a zirconia nanoceramic in only 2 minutes at 1300 °C.

  8. Preparation of high-performance ultrafine-grained AISI 304L stainless steel under high temperature and pressure

    Directory of Open Access Journals (Sweden)

    Peng Wang

    2016-08-01

    Full Text Available Bulk ultra-fine grained (UFG AISI 304L stainless steel with excellent mechanical properties was prepared by a high-temperature and high-pressure (HTHP method using nanocrystalline AISI 304L stainless steel powders obtained from ball milling. Samples were sintered in high-pressure conditions using the highest martensite content of AISI 304L stainless steel powders milled for 25 h. Analyses of phase composition and grain size were accomplished by X-ray diffraction and Rietveld refinement. By comparing the reverse martensite transformation under vacuum and HTHP treat, we consider that pressure can effectively promote the change in the process of transformation. Compared with the solid-solution-treated 304L, the hardness and yield strength of the samples sintered under HTHP are considerably higher. This method of preparation of UFG bulk stainless steel may be widely popularised and used to obtain UFG metallic materials with good comprehensive performance.

  9. 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).

  10. Sintering and annealing effects on undoped yttria transparent ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Letue, Laetitia; Petit, Johan, E-mail: johan.petit@onera.fr; Ritti, Marie-Hélène; Lalanne, Sylvie; Landais, Stéphane

    2017-06-15

    Transparent yttrium oxide (Y{sub 2}O{sub 3}) ceramics were processed by several densifications steps without any doping species. The green bodies were obtained by the aqueous way and sintered at high temperature under vacuum and then under high pressure. We studied the effects of different sintering cycles and air annealing at different steps of the process on the density and the grain growth. We also focused on the reaction between yttria ceramics and BN-coated graphite crucible which occurs during HIP. We noted that a low heating rate and two annealing steps are necessary to improve our samples’ transparency. - Highlights: • The quality of transparent ceramics is compared with the tested process parameters. • Air annealing is critical when using a carbon environment in the process. • Intra-granular pores, and so the final transparency, are directly linked to the sintering heating rates.

  11. Synthesis and Sintering of ZnO Nanopowders

    Directory of Open Access Journals (Sweden)

    Anne Aimable

    2017-05-01

    Full Text Available Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders’ nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv50~60 nm, easily redispersable by using a continuous Segmented Flow Tubular Reactor (SFTR, which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a “scale-out” concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 °C and 1100 °C, and Spark Plasma Sintering (SPS at 900 °C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 °C, while also limiting the grain growth, thus leading to a nanostructured material.

  12. 3D Online Submicron Scale Observation of Mixed Metal Powder's Microstructure Evolution in High Temperature and Microwave Compound Fields

    Directory of Open Access Journals (Sweden)

    Dan Kang

    2014-01-01

    Full Text Available In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT technique; the spatial resolution was enhanced to 0.37 μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  13. 3D online submicron scale observation of mixed metal powder's microstructure evolution in high temperature and microwave compound fields.

    Science.gov (United States)

    Kang, Dan; Xu, Feng; Hu, Xiao-fang; Dong, Bo; Xiao, Yu; Xiao, Ti-qiao

    2014-01-01

    In order to study the influence on the mechanical properties caused by microstructure evolution of metal powder in extreme environment, 3D real-time observation of the microstructure evolution of Al-Ti mixed powder in high temperature and microwave compound fields was realized by using synchrotron radiation computerized topography (SR-CT) technique; the spatial resolution was enhanced to 0.37  μm/pixel through the designed equipment and the introduction of excellent reconstruction method for the first time. The process of microstructure evolution during sintering was clearly distinguished from 2D and 3D reconstructed images. Typical sintering parameters such as sintering neck size, porosity, and particle size of the sample were presented for quantitative analysis of the influence on the mechanical properties and the sintering kinetics during microwave sintering. The neck size-time curve was obtained and the neck growth exponent was 7.3, which indicated that surface diffusion was the main diffusion mechanism; the reason was the eddy current loss induced by the external microwave fields providing an additional driving force for mass diffusion on the particle surface. From the reconstructed images and the curve of porosity and average particle size versus temperature, it was believed that the presence of liquid phase aluminum accelerated the densification and particle growth.

  14. Report on in-situ studies of flash sintering of uranium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, Alicia Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-01-24

    Flash sintering is a novel type of field assisted sintering that uses an electric field and current to provide densification of materials on very short time scales. The potential for field assisted sintering techniques to be used in producing nuclear fuel is gaining recognition due to the potential economic benefits and improvements in material properties. The flash sintering behavior has so far been linked to applied and material parameters, but the underlying mechanisms active during flash sintering have yet to be identified. This report summarizes the efforts to investigate flash sintering of uranium dioxide using dilatometer studies at Los Alamos National Laboratory and two separate sets of in-situ studies at Brookhaven National Laboratory’s NSLS-II XPD-1 beamline. The purpose of the dilatometer studies was to understand individual parameter (applied and material) effects on the flash behavior and the purpose of the in-situ studies was to better understand the mechanisms active during flash sintering. As far as applied parameters, it was found that stoichiometry, or oxygen-to-metal ratio, has a significant effect on the flash behavior (time to flash and speed of flash). Composite systems were found to have degraded sintering behavior relative to pure UO2. The critical field studies are complete for UO2.00 and will be analyzed against an existing model for comparison. The in-situ studies showed that the strength of the field and current are directly related to the sample temperature, with temperature-driven phase changes occurring at high values. The existence of an ‘incubation time’ has been questioned, due to a continuous change in lattice parameter values from the moment that the field is applied. Some results from the in-situ experiments, which should provide evidence regarding ion migration, are still being analyzed. Some preliminary conclusions can be made from these results with regard to using field assisted sintering to

  15. High temperature PEM fuel cells

    Science.gov (United States)

    Zhang, Jianlu; Xie, Zhong; Zhang, Jiujun; Tang, Yanghua; Song, Chaojie; Navessin, Titichai; Shi, Zhiqing; Song, Datong; Wang, Haijiang; Wilkinson, David P.; Liu, Zhong-Sheng; Holdcroft, Steven

    There are several compelling technological and commercial reasons for operating H 2/air PEM fuel cells at temperatures above 100 °C. Rates of electrochemical kinetics are enhanced, water management and cooling is simplified, useful waste heat can be recovered, and lower quality reformed hydrogen may be used as the fuel. This review paper provides a concise review of high temperature PEM fuel cells (HT-PEMFCs) from the perspective of HT-specific materials, designs, and testing/diagnostics. The review describes the motivation for HT-PEMFC development, the technology gaps, and recent advances. HT-membrane development accounts for ∼90% of the published research in the field of HT-PEMFCs. Despite this, the status of membrane development for high temperature/low humidity operation is less than satisfactory. A weakness in the development of HT-PEMFC technology is the deficiency in HT-specific fuel cell architectures, test station designs, and testing protocols, and an understanding of the underlying fundamental principles behind these areas. The development of HT-specific PEMFC designs is of key importance that may help mitigate issues of membrane dehydration and MEA degradation.

  16. Sintering characteristics of nano-ceramic coatings

    NARCIS (Netherlands)

    De Hosson, JTM; Popma, R

    2003-01-01

    This paper concentrates on sintering characteristics of nano-sized ceramic SiO2 particles. The sintering process is studied as a function of temperature using a conventional furnace and using a laser beam. The underlying idea is to combine the nanoceramic sol-gel concept with inkjet technology and

  17. Temperature uniformity mapping in a high pressure high temperature reactor using a temperature sensitive indicator

    NARCIS (Netherlands)

    Grauwet, T.; Plancken, van der I.; Vervoort, L.; Matser, A.M.; Hendrickx, M.; Loey, van A.

    2011-01-01

    Recently, the first prototype ovomucoid-based pressure–temperature–time indicator (pTTI) for high pressure high temperature (HPHT) processing was described. However, for temperature uniformity mapping of high pressure (HP) vessels under HPHT sterilization conditions, this prototype needs to be

  18. Liquid phase sintered SiC. Processing and transformation controlled microstructure tailoring

    Directory of Open Access Journals (Sweden)

    V.A. Izhevskyi

    2000-10-01

    Full Text Available Microstructure development and phase formation processes during sintering of silicon carbide based materials with AlN-Y2O3, AlN-Yb2O3, and AlN-La2O3 sintering additives were investigated. Densification of the materials occurred by liquid-phase sintering mechanism. Proportion of alpha- and beta-SiC powders in the initial mixtures was a variable parameter, while the molar ratio of AlN/RE2O3, and the total amount of additives (10 vol. % were kept constant. Shrinkage behavior during sintering in interrelation with the starting composition of the material and the sintering atmosphere was investigated by high temperature dilatometry. Kinetics of b-SiC to a-SiC phase transformation during post-sintering heat treatment at temperatures 1900-1950 °C was studied, the degree of phase transformation being determined by quantitative x-ray analysis using internal standard technique. Evolution of microstructure resulting from beta-SiC to alpha-SiC transformation was followed up by scanning electron microscopy on polished and chemically etched samples. Transformation-controlled grain growth mechanism similar to the one observed for silicon nitride based ceramics was established. Possibility of in-situ platelet reinforced dense SiC-based ceramics fabrication with improved mechanical properties by means of sintering was shown.

  19. Electric and thermal properties of wood charcoal made by spark plasma sintering; Hoden shoketsuho ni yori chosei sareta mokutan no denkiteki/netsuteki seishitsu

    Energy Technology Data Exchange (ETDEWEB)

    Yamane, K.; Okudo, H. [Shinmoywa Industries Ltd., Hyogo (Japan). Developmest Center; Ishihara, S. [Kyoto Univ. (Japan)

    1998-05-15

    In conventional, most of wood charcoal is used as the materials for improving qualities of fuels or soils, while the thermal conversion to carbon functional materials using wood materials as raw materials is paid attention now due to more and more demand for the uses to increase the added values. In this study, it is confirmed that various desired carbides can be prepared by controlling and sintering wood charcoal at various temperatures. Further, the bulk density, electrical resistance and thermal constants of sintered Sugi carbide are clarified. It is also clarified that when spark plasma sintering method is applied to high-temperature sintering of charcoal powder, the temperature rises rapidly, and calcination/sintering can be carried out at temperature of 1000 to 2700degC within a very short period of time as 5 minutes. Thus sintered charcoal is superior in bulk density, heat conductivity and volume resistivity to the carbide sintered in a high temperature electric furnace of indirect heating type or glass-like carbon made from thermosetting synthetic resin. Additionally, the existence of graphitized structure in the sintered charcoal is suggested. 19 refs., 8 figs., 2 tabs.

  20. Nondestructive evaluation of sintered ceramics

    Science.gov (United States)

    Baaklini, George Y.; Klima, Stanley J.; Sanders, William A.

    1988-01-01

    Radiography and several acoustic and thermoacoustic microscopy techniques are investigated for application to structural ceramics for advanced heat engines. A comparison is made of the results obtained from the use of scanning acoustic microscopy (SAM), scanning laser acoustic microscopy (SLAM), and thermoacoustic microscopy (TAM). These techniques are evaluated on research samples of green and sintered monolithic silicon nitrides and silicon carbides in the form of modulus-of-rupture (MOR) bars containing deliberately introduced flaws. Strengths and limitations of the techniques are described, with the emphasis being on statistics of detectability of flaws that constitute potential fracture origins. Further, it is shown that radiographic evaluation and guidance helped develop uniform high-density Si3N4 MOR bars with improved four-point flexural strength (875, 544, and 462 MPa at room temperature, 1200 C, 1370 C, respectively) and reduced scatter in bend strength.

  1. All-photonic drying and sintering process via flash white light combined with deep-UV and near-infrared irradiation for highly conductive copper nano-ink

    OpenAIRE

    Hwang, Hyun-Jun; Oh, Kyung-Hwan; Kim, Hak-Sung

    2016-01-01

    We developed an ultra-high speed photonic sintering method involving flash white light (FWL) combined with near infrared (NIR) and deep UV light irradiation to produce highly conductive copper nano-ink film. Flash white light irradiation energy and the power of NIR/deep UV were optimized to obtain high conductivity Cu films. Several microscopic and spectroscopic characterization techniques such as scanning electron microscopy (SEM), a x-ray diffraction (XRD), and Fourier-transform infrared (F...

  2. Study of phase development in alumina-spodumene ceramics by high temperature neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Gan, B.K. [University of Technology, Sydney, NSW (Australia). Microstructural Analysis Unit; Latella, B.A.; Hunter, B.A. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); O`Connor, B.H. [Curtin University of Technology, Perth, WA (Australia). Department of Applied Physics

    1999-12-01

    Full text: Melting and crystallisation of minor phases are important in many material systems which contain impurities and/or grain boundary liquid phases. Grain boundary glassy phases are generally not thermodynamically stable, and can devitrify during the sintering process or from other high temperature exposure. Characterising the minor phase assemblage in these types of materials has implications in processing, microstructural design and in-service use, particularly fluctuating thermal environments. An in situ high temperature neutron diffraction (ND) technique was used to follow the phase dynamics on sintering an alumina-spodumene ceramic as well as the crystallisation kinetics of the evolving crystalline phase in real time. The main benefit of using ND analysis in the present work is that it provides bulk specimen character of the material which is important in quantitatively extracting phase composition information. Likewise, most diffraction measurements are conducted with ambient or static temperature data, collected after specimens have been heat-treated and then cooled. Such data may yield misleading information particularly in relation to non-equilibrium phases. Hence dynamic measurements are clearly preferable as a direct means of confirming sintering processes. ND measurements were performed using the High Flux Australian Reactor (HIFAR) neutron source operated by the Australian Nuclear Science and Technology Organisation (ANSTO) at Lucas Heights, NSW, Australia. The ND patterns collected on heating the compacts provided relevant information for optimising materials processing and sintering protocols. Similarly, the ND patterns collected for three specific cooling schemes yielded significant details of evolution and crystallisation of the minor phase. The principal aim was to demonstrate the fundamental influence of the minor crystalline phase (and hence glassy phase) on properties and to manipulate and tailor the phase structure by controlled

  3. High Temperature Radio Frequency Loads

    CERN Document Server

    Federmann, S; Grudiev, A; Montesinos, E; Syratchev, I

    2011-01-01

    In the context of energy saving and recovery requirements the design of reliable and robust RF power loads which permit a high outlet temperature and high pressure of the cooling water is desirable. Cooling water arriving at the outlet withmore than 150 ◦C and high pressure has a higher value than water with 50 ◦C under low pressure. Conventional RF power loads containing dielectric and magnetic materials as well as sensitive ceramic windows usually do not permit going much higher than 90 ◦C. Here we present and discuss several design concepts for "metal only" RF high power loads. One concept is the application of magnetic steel corrugated waveguides near cutoff – this concept could find practical use above several GHz. Another solution are resonant structures made of steel to be installed in large waveguides for frequencies of 500 MHz or lower. Similar resonant structures above 100 MHz taking advantage of the rather high losses of normal steel may also be used in coaxial line geometries with large di...

  4. Influence of yttria surface modification on high temperature corrosion of porous Ni22Cr alloy

    DEFF Research Database (Denmark)

    Karczewski, Jakub; Dunst, Katarzyna; Jasinski, Piotr

    2017-01-01

    Protective coatings for porous alloys for high temperature use are relatively new materials. Their main drawback is high temperature corrosion. In this work protective coatings based the on Y-precursor infiltrated into the sintered Ni22Cr alloys are studied at 700°C. Effects of the amount...... of the protective phase on the resulting corrosion properties are evaluated in air and humidified hydrogen. Weight gain of the samples, their open porosities and microstructures are analyzed and compared. Results show, that by the addition of even a minor amount of the Y-precursor corrosion rates can be decreased...

  5. High-Temperature Proton-Conducting Ceramics Developed

    Science.gov (United States)

    Sayir, Ali; Dynys, Frederick W.; Berger, M. H.

    2005-01-01

    High-temperature protonic conductors (HTPC) are needed for hydrogen separation, hydrogen sensors, fuel cells, and hydrogen production from fossil fuels. The HTPC materials for hydrogen separation at high temperatures are foreseen to be metal oxides with the perovskite structure A(sup 2+)B(sup 4+)C(sup 2-, sub 3) and with the trivalent cation (M(sup 3+)) substitution at the B(sup 4+)-site to introduce oxygen vacancies. The high affinity for hydrogen ions (H(sup +)) is advantageous for protonic transport, but it increases the reactivity toward water (H2O) and carbon dioxide (CO2), which can lead to premature membrane failure. In addition, there are considerable technological challenges related to the processing of HTPC materials. The high melting point and multi-cation chemistry of HTPC materials creates difficulties in in achieving high-density, single-phase membranes by solid-state sintering. The presence of secondary phases and grain-boundary interfaces are detrimental to the protonic conduction and environmental stability of polycrystalline HTPC materials.

  6. Advances in High Temperature Materials for Additive Manufacturing

    Science.gov (United States)

    Nordin, Nurul Amira Binti; Johar, Muhammad Akmal Bin; Ibrahim, Mohd Halim Irwan Bin; Marwah, Omar Mohd Faizan bin

    2017-08-01

    In today’s technology, additive manufacturing has evolved over the year that commonly known as 3D printing. Currently, additive manufacturing have been applied for many industries such as for automotive, aerospace, medical and other commercial product. The technologies are supported by materials for the manufacturing process to produce high quality product. Plus, additive manufacturing technologies has been growth from the lowest to moderate and high technology to fulfil manufacturing industries obligation. Initially from simple 3D printing such as fused deposition modelling (FDM), poly-jet, inkjet printing, to selective laser sintering (SLS), and electron beam melting (EBM). However, the high technology of additive manufacturing nowadays really needs high investment to carry out the process for fine products. There are three foremost type of material which is polymer, metal and ceramic used for additive manufacturing application, and mostly they were in the form of wire feedstock or powder. In circumstance, it is crucial to recognize the characteristics of each type of materials used in order to understand the behaviours of the materials on high temperature application via additive manufacturing. Therefore, this review aims to provide excessive inquiry and gather the necessary information for further research on additive material materials for high temperature application. This paper also proposed a new material based on powder glass, which comes from recycled tempered glass from automotive industry, having a huge potential to be applied for high temperature application. The technique proposed for additive manufacturing will minimize some cost of modelling with same quality of products compare to the others advanced technology used for high temperature application.

  7. High Temperature Superconductor Accelerator Magnets

    CERN Document Server

    AUTHOR|(CDS)2079328; de Rijk, Gijs; Dhalle, Marc

    2016-11-10

    For future particle accelerators bending dipoles are considered with magnetic fields exceeding $20T$. This can only be achieved using high temperature superconductors (HTS). These exhibit different properties from classical low temperature superconductors and still require significant research and development before they can be applied in a practical accelerator magnet. In order to study HTS in detail, a five tesla demonstrator magnet named Feather-M2 is designed and constructed. The magnet is based on ReBCO coated conductor, which is assembled into a $10kA$ class Roebel cable. A new and optimized Aligned Block layout is used, which takes advantage of the anisotropy of the conductor. This is achieved by providing local alignment of the Roebel cable in the coil windings with the magnetic field lines. A new Network Model capable of analyzing transient electro-magnetic and thermal phenomena in coated conductor cables and coils is developed. This model is necessary to solve critical issues in coated conductor ac...

  8. Faraday imaging at high temperatures

    Science.gov (United States)

    Hackel, Lloyd A.; Reichert, Patrick

    1997-01-01

    A Faraday filter rejects background light from self-luminous thermal objects, but transmits laser light at the passband wavelength, thus providing an ultra-narrow optical bandpass filter. The filter preserves images so a camera looking through a Faraday filter at a hot target illuminated by a laser will not see the thermal radiation but will see the laser radiation. Faraday filters are useful for monitoring or inspecting the uranium separator chamber in an atomic vapor laser isotope separation process. Other uses include viewing welds, furnaces, plasma jets, combustion chambers, and other high temperature objects. These filters are can be produced at many discrete wavelengths. A Faraday filter consists of a pair of crossed polarizers on either side of a heated vapor cell mounted inside a solenoid.

  9. Processing of bulk Bi-2223 high-temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2005-12-01

    Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

  10. High temperature autoclave vacuum seals

    Science.gov (United States)

    Hoffman, J. R.; Simpson, W. G.; Walker, H. M.

    1971-01-01

    Aluminum sheet forms effective sealing film at temperatures up to 728 K. Soft aluminum wire rings provide positive seal between foil and platen. For applications at temperatures above aluminum's service temperature, stainless steel is used as film material and copper wire as sealant.

  11. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    Science.gov (United States)

    Gephart, Sean

    The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques. This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering. The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4 x 4 x 0.315 inches3 (101.6 x 101.6 x 8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered

  12. High temperature Hexoloy{trademark} SX silicon carbide. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, G.V.; Lau, S.K.; Storm, R.S. [Carborundum Co., Niagara Falls, NY (United States)

    1994-09-01

    HEXOLOY{reg_sign} SX-SiC, fabricated with Y and Al containing compounds as sintering aids, has been shown to possess significantly improved strength and toughness over HEXOLOY{reg_sign}SA-SiC. This study was undertaken to establish and benchmark the complete mechanical property database of a first generation material, followed by a process optimization task to further improve the properties. Mechanical characterization on the first generation material indicated that silicon-rich pools, presumably formed as a reaction product during sintering, controlled the strength from room temperature to 1,232 C. At 1,370 C in air, the material was failing due to a glass-phase formation at the surface. This glass-phase formation was attributed to the reaction of yttrium aluminates, which exist as a second phase in the material, with the ambient. This process was determined to be a time-dependent one that leads to slow crack growth. Fatigue experiments clearly indicated that the slow crack growth driven by the reaction occurred only at temperatures >1,300 C, above the melting point of the glass phase. Process optimization tasks conducted included the selection of the best SiC powder source, studies on mixing/milling conditions for SiC powder with the sintering aids, and a designed experiment involving a range of sintering and post-treatment conditions. The optimization study conducted on the densification variables indicated that lower sintering temperatures and higher post-treatment pressures reduce the Si-rich pool formation, thereby improving the room-temperature strength. In addition, it was also determined that furnacing configuration and atmosphere were critical in controlling the Si-rich formation.

  13. High Temperature Solid Lubricant Coating for High Temperature Wear Applications

    Science.gov (United States)

    DellaCorte, Christopher (Inventor); Edmonds, Brian J (Inventor)

    2014-01-01

    A self-lubricating, friction and wear reducing composite useful over a wide temperature range is described herein. The composite includes metal bonded chromium oxide dispersed in a metal binder having a substantial amount of nickel. The composite contains a fluoride of at least one Group I, Group II, or rare earth metal, and optionally a low temperature lubricant metal.

  14. Microstructural evaluation of the NbC-20Ni cemented carbides during sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, D. [BRATS Sintered Filters and Metallic Powders, Cajamar, SP (Brazil); Cannizza, E. [EHT Cannizza Consultoria Em Engenharia Ltda, Sao Paulo, SP (Brazil)

    2016-07-01

    Full text: Fine carbides in a metallic matrix (binder) form the microstructure of the cemented carbides. Grain size and binder content are the main variables to adjust hardness and toughness. These products are produced by Powder Metallurgy, and traditional route involves mixing carbides with binder by high energy milling, pressing and sintering. During sintering, a liquid phase promotes densification, and a final relative density higher than 99% is expected. Sintering is carried out at high temperatures, and dissolution of the carbides changes the chemical composition of the binder. To control grain growth of the main carbide, which reduces hardness, small quantities of secondary carbides are used. These additives limit dissolution and precipitation of the main carbides reducing the final grain size. This paper focused the structural and chemical evolution during sintering using NbC-20Ni cermets. Mixtures of very fine NbC carbides and carbonyl Ni powders were produce by intense milling. These mixtures were pressed using uniaxial pressures from 50 to 200MPa. Shrinkage was evaluated using dilatometric measurements under an atmosphere of dynamic argon. Samples were also sintered under vacuum in high temperature industrial furnace. The sintered samples were characterized in terms of density hardness, toughness and microstructure. DRX was the main tool used to evaluate the structural evolution of the binder. In situ chemical analysis helped to understand the dissolution mechanisms. (author)

  15. Influence of Cr2O3 additive and sintering temperature on the structural characteristics and piezoelectric properties of Bi4Ti2.95W0.05O12.05 Aurivillius ceramics

    Directory of Open Access Journals (Sweden)

    Yu Chen

    2016-12-01

    Full Text Available In this paper, Cr2O3 (0–0.4 wt% as an additive was added into Bi4Ti2.95W0.05O12.05 (BITW for preparing a kind of W/Cr co-doped BIT (BITW-yCr Aurivillius ceramics, both W6+ and Cr3+ are considered to substitute Ti4+ in the [TiO6] octahedron of BIT. Besides the orthorhombic Bi4Ti3O12 as the major phase, BITW-yCr ceramics also contain the cubic Bi2Ti2O7 as the second phase which was formed due to the doping effect of WO3, but its formation could be depressed by the addition of less Cr2O3. Additionally, the cell parameters of BITW ceramics are also changed by the incorporation of Cr2O3, as the distortion degree of the orthorhombic structure (a/b increases firstly and then decreases with its addtional amount (y. On the other hand, the grain growth of BITW-yCr ceramics is mainly controlled by the sintering process, there a higher sintering temperature results in a larger grain size. In comparison to BIT ceramics, BITW-yCr ceramics with less Cr-addition (y=0–0.2 require a higher sintering temperature to attain the best dense state, moreover, as y increases, the sintering temperature to gain the highest piezoelectric activity also increases. Finally, BITW-0.2Cr which was sintered at 1150 °C exhibits a higher piezoelectric activity than the others, which could be attributed to its larger orthorhombic distortion and larger grain size, its ideal piezoelectric constant (d33=28 pC/N provides it with great applying potentiality.

  16. Evaluation of Foaming Behavior of Glass Melts by High-Temperature Microscopy

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    2016-01-01

    Optical monitoring techniques can record in situ the size of glass samples during a dynamic heating process. This allowed us to study sintering and expansion rate of panel glass from cathode ray tube using MnO2 as foaming agent. We show the maximum expansion rate of glass melt foaming (in situ...... value) correlates to 50% closed porosity and we define a universal temperature window for foaming glass melts based on the sintering-expansion curves obtained with a heating microscope. The sample size obtained at the maximum expansion rate can be used to quickly evaluate various foaming parameters...... such as type and concentration of foaming agent, glass composition and particle size to obtain foam glass with high porosity and closed pores. Using this approach we show that the foaming of bottle glass is preferentially conducted at a SiC concentration of 1‒4 wt%....

  17. Development of Sintered Si3N4 for High Performance Thermomechanical Applications.

    Science.gov (United States)

    1984-01-01

    oxidized surface revealed the presence of Y2 Si2O7 and Y2 0Si18 N40 1 2 in addition to 8- Si 3N and a very large a- cristobalite peak. XAFS revealed that...of YF 3 lowered the temperature at which conversion from alpha to beta was complete at less than 1800 0 C. It appears that the LiAI,0 8 tends to...stabilize the alpha phase whereas the presence of YF 3 tends to enhance the conversion to beta . B. Properties A test bar (0.8 x 0.8 x 5.8 cm before firing

  18. 3D printed high performance strain sensors for high temperature applications

    Science.gov (United States)

    Rahman, Md Taibur; Moser, Russell; Zbib, Hussein M.; Ramana, C. V.; Panat, Rahul

    2018-01-01

    Realization of high temperature physical measurement sensors, which are needed in many of the current and emerging technologies, is challenging due to the degradation of their electrical stability by drift currents, material oxidation, thermal strain, and creep. In this paper, for the first time, we demonstrate that 3D printed sensors show a metamaterial-like behavior, resulting in superior performance such as high sensitivity, low thermal strain, and enhanced thermal stability. The sensors were fabricated using silver (Ag) nanoparticles (NPs), using an advanced Aerosol Jet based additive printing method followed by thermal sintering. The sensors were tested under cyclic strain up to a temperature of 500 °C and showed a gauge factor of 3.15 ± 0.086, which is about 57% higher than that of those available commercially. The sensor thermal strain was also an order of magnitude lower than that of commercial gages for operation up to a temperature of 500 °C. An analytical model was developed to account for the enhanced performance of such printed sensors based on enhanced lateral contraction of the NP films due to the porosity, a behavior akin to cellular metamaterials. The results demonstrate the potential of 3D printing technology as a pathway to realize highly stable and high-performance sensors for high temperature applications.

  19. Sintering behaviour and mechanical properties of Cr3C2–NiCr ...

    Indian Academy of Sciences (India)

    Abstract. Cr3C2–NiCr cermets are used as metal cutting tools due to their relatively high hardness and low sin- tering temperatures. In this study, a powder mixture consisting of 75 wt% Cr3C2–25 wt% NiCr was sintered at four different temperatures and characterized for its microstructure and mechanical properties.

  20. Photonic Flash Sintering of Ink-Jet-Printed Back Electrodes for Organic Photovoltaic Applications.

    Science.gov (United States)

    Polino, Giuseppina; Shanmugam, Santhosh; Bex, Guy J P; Abbel, Robert; Brunetti, Francesca; Di Carlo, Aldo; Andriessen, Ronn; Galagan, Yulia

    2016-01-27

    A study of the photonic flash sintering of a silver nanoparticle ink printed as the back electrode for organic solar cells is presented. A number of sintering settings with different intensities and pulse durations have been tested on both full-area and grid-based silver electrodes, using the complete emission spectrum of the flash lamps from UV-A to NIR. However, none of these settings was able to produce functional devices with performances comparable to those of reference cells prepared using thermally sintered ink. Different degradation mechanisms were detected in the devices with a flash-sintered back electrode. The P3HT:PCBM photoactive layer appears to be highly heat-sensitive and turned out to be severely damaged by the high temperatures generated in the silver layer during the sintering. In addition, UV-induced photochemical degradation of the functional materials was identified as another possible source of performance deterioration in the devices with grid-based electrodes. Reducing the light intensity does not provide a proper solution because in this case the Ag electrode is not sintered sufficiently. For both types of devices, with full-area and grid-based electrodes, these problems could be solved by excluding the short wavelength contribution from the flash light spectrum using a filter. Optimized sintering parameters allowed manufacture of OPV devices with performance equal to those of the reference devices. Photonic flash sintering of the top electrode in organic solar cells was demonstrated for the first time. It reveals the great potential of this sintering method for the future roll-to-roll manufacturing of organic solar cells from solution.

  1. High-temperature borehole instrumentation

    Science.gov (United States)

    Dennis, B. R.; Koczan, S. P.; Stephani, E. L.

    1985-10-01

    A new method of extracting natural heat from the Earth's crust was invented at the Los Alamos National Laboratory in 1970. It uses fluid pressures (hydraulic fracturing) to produce cracks that connect two boreholes drilled into hot rock formations of low initial permeability. Pressurized water is then circulated through this connected underground loop to extract heat from the rock and bring it to the surface. The creation of the fracture reservior began with drilling boreholes deep within the Precambrian basement rock at the Fenton Hill Test Site. Hydraulic fracturing, flow testing, and well-completion operations required unique wellbore measurements using downhole instrumentation systems that would survive the very high borehole temperatures, 320(0)C (610(0)F). These instruments were not available in the oil and gas industrial complex, so the Los Alamos National Laboratory initiated an intense program upgrading existing technology where applicable, subcontracting materials and equipment development to industrial manufactures, and using the Laboratory resources to develop the necessary downhole instruments to meet programmatic schedules.

  2. High Temperature Superconducting Underground Cable

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, Roger, A.

    2010-02-28

    The purpose of this Project was to design, build, install and demonstrate the technical feasibility of an underground high temperature superconducting (HTS) power cable installed between two utility substations. In the first phase two HTS cables, 320 m and 30 m in length, were constructed using 1st generation BSCCO wire. The two 34.5 kV, 800 Arms, 48 MVA sections were connected together using a superconducting joint in an underground vault. In the second phase the 30 m BSCCO cable was replaced by one constructed with 2nd generation YBCO wire. 2nd generation wire is needed for commercialization because of inherent cost and performance benefits. Primary objectives of the Project were to build and operate an HTS cable system which demonstrates significant progress towards commercial progress and addresses real world utility concerns such as installation, maintenance, reliability and compatibility with the existing grid. Four key technical areas addressed were the HTS cable and terminations (where the cable connects to the grid), cryogenic refrigeration system, underground cable-to-cable joint (needed for replacement of cable sections) and cost-effective 2nd generation HTS wire. This was the world’s first installation and operation of an HTS cable underground, between two utility substations as well as the first to demonstrate a cable-to-cable joint, remote monitoring system and 2nd generation HTS.

  3. In situ high temperature study of ZrO 2 ball-milled to nanometer sizes

    Science.gov (United States)

    Gajović, A.; Furić, K.; Štefanić, G.; Musić, S.

    2005-06-01

    Nanostructured ZrO 2 was prepared by high-energy ball-milling under different conditions and sintered at high temperatures. Structural and microstructural changes during the ball-milling were monitored using Raman spectroscopy (RS), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The sintering process was monitored in situ at high temperature (300-1400 °C) by RS and XRD. The results of RS showed that the ball-milling had little or no influence on the transition from the starting monoclinic ZrO 2 to the high-temperature tetragonal ZrO 2. It was concluded that a partial transition from monoclinic to tetragonal polymorph, observed in some earlier ball-milling experiments, can be attributed to the stabilizing influence of impurities introduced due to the wearing of the milling media. In the present experiment ZrO 2 ball-milling assembly was used, which reduced the influence of an additional material. The results of the line broadening analysis, performed using Rietveld refinements of the ball-milling products with powder-to-ball weight ratio ( R) 1:10, indicated a decrease in the crystallite size and an increase in the microstrains with an increase in the ball-milling time up to 3 h. Further increase in the ball-milling time up to 10 h had a very small influence on the size and strain of the obtained m-ZrO 2 products. A difference between the results of in situ RS and XRD analysis of the samples subjected to prolonged ball-milling was attributed to the chemical and microstractural differences between the surface and the bulk of the ZrO 2 particles during the sintering at high temperatures.

  4. High Temperature Chemistry at NASA: Hot Topics

    Science.gov (United States)

    Jacobson, Nathan S.

    2014-01-01

    High Temperature issues in aircraft engines Hot section: Ni and Co based Superalloys Oxidation and Corrosion (Durability) at high temperatures. Thermal protection system (TPS) and RCC (Reinforced Carbon-Carbon) on the Space Shuttle Orbiter. High temperatures in other worlds: Planets close to their stars.

  5. Interfacial reactions and wetting in Al-Mg sintered by powder metallurgy process

    Energy Technology Data Exchange (ETDEWEB)

    Faisal, Heny, E-mail: faisal@physics.its.ac.id; Darminto,; Triwikantoro,; Zainuri, M. [Physics Department, Math and Science Faculty, Institute of Technology Sepuluh Nopember (ITS) Jl. Arief Rahman Hakim, Surabaya 60111 (Indonesia)

    2016-04-19

    Was conducted to analyze the effect of temperature variation on the bonding interface sintered composite Al-Mg and analyze the effect of variations of the density and hardness sinter. Research carried out by the base material powders of Al, Mg powder and solvent n-butanol. The method used in this study is a powder metallurgy, with a composition of 60% volume fraction of Al - 40% Mg. Al-Mg mixing with n-butanol for 1 hour at 500 rpm. Then the emphasis (cold comression) with a size of 1.4 cm in diameter dies and height of 2.8 cm, is pressed with a force of 20 MPa and held for 15 minutes. After the sample into pellets, then sintered at various temperatures 300 °C, 350 °C, 400 °C and 450 °C. Characterization is done by using the testing green density, sintered density, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), vickers microhardness, and press test. XRD data analysis done by using X’Pert High Score Plus (HSP) to determine whether there is a new phase is formed. Test results show that the sintered density increasing sintering temperature, the resulting density is also increasing (shrinkage). However, at a temperature of 450 °C decreased (swelling). With the increased sinter density, interfacial bonding getting Kuta and more compact so that its hardness is also increased. From the test results of SEM / EDX, there Mg into Al in the border area. At temperatures of 300 °C, 350 °C, 400 °C, the phase formed is Al, Mg and MgO. While phase is formed at a temperature of 450 °C is aluminum magnesium (Al{sub 3}Mg{sub 2}), Aluminum Magnesium Zinc (AlMg{sub 2}Zn).

  6. High temperature vapors science and technology

    CERN Document Server

    Hastie, John

    2012-01-01

    High Temperature Vapors: Science and Technology focuses on the relationship of the basic science of high-temperature vapors to some areas of discernible practical importance in modern science and technology. The major high-temperature problem areas selected for discussion include chemical vapor transport and deposition; the vapor phase aspects of corrosion, combustion, and energy systems; and extraterrestrial high-temperature species. This book is comprised of seven chapters and begins with an introduction to the nature of the high-temperature vapor state, the scope and literature of high-temp

  7. High temperature reflectance of hyperpure slip cast silica. [for Outer Planet Entry Probe reflective heat shields

    Science.gov (United States)

    Dillow, C. F.; Schmitt, R. J.; Blome, J. C.

    1976-01-01

    An experimental program to optically characterize hyperpure slip cast silica at elevated temperatures is described. This sintered ceramic material is being used in the development of a reflective heat shield for the Outer Planet Entry Probe. A unique high temperature integrating sphere reflectometer is described and reflectance data in the spectral range 0.23-2.3 micron are presented at temperatures up to 1427 C in air and helium environments. Kubelka-Munk (K-M) scattering and absorptance coefficients (K and S), using the Reichman extension of the K-M theory, are presented as is a unique method of obtaining K and S from the Reichman equations using only reflectance data. The hyperpure slip cast silica material was found to retain its high diffuse reflectance at temperatures up to 1204 C, with slight degradation occurring at higher temperatures.

  8. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency.

    Science.gov (United States)

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-02-03

    Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time.

  9. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

    Science.gov (United States)

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-02-01

    Stereocomplexation between enantiomeric poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time.

  10. Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

    Science.gov (United States)

    Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

    2016-01-01

    Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240–260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180–210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time. PMID:26837848

  11. Pengaruh Variasi pH dan Temperatur Sintering Terhadap Nilai Sensitivitas Material TiO2 Sebagai Sensor Gas CO

    Directory of Open Access Journals (Sweden)

    Ika Silviana Widianti

    2015-03-01

    Full Text Available Telah dilakukan berbagai macam pengupayaan untuk mengoptimalkan potensi Titanium dioksida (TiO2 sebagai sensor gas, mengingat TiO2 merupakan semikonduktor metal oksida. Pada penelitian ini digunakan TiO2 dalam bentuk serbuk, dengan pelarutnya H2SO4 yang diencerkan dengan air distilasi sehingga terbentuk variasi pH 1, 3, dan 5. Metode sol-gel dilakukan dengan perendaman dan dilanjutkan stiring selama 2,5 jam, kecepatan 700 rpm, dan temperatur 200ºC . Drying dilakukan selama 2 jam pada temperatur 350ºC, selanjutnya serbuk dikompaksi pada tekanan 200 bar agar terbentuk pellet. Pelet kemudian disintering pada temperatur 700,800, dan 900ºC selama 1 jam. Karakterisasi material dilakukan dengan Scanning Electron Microscope (SEM dan X-Ray Diffraction (XRD. Sedangkan untuk luas permukaan spesifik sampel TiO2 diuji dengan BET Analyser. Morfologi TiO2 yang dihasilkan dari proses sol-gel berbentuk bulat (spherical dan memiliki fase stabil anatase. Nilai sensitivitas didapatkan dari pengujian pada temperatur operasi 100ºC dan variasi volume gas CO 5L, 12,5L, 25L. Respon tercepat adalah material TiO2 pH 3 yang disinter dengan temperatur 900ºC, serta memiliki ukuran pori 50,83 nm

  12. Highly improved reliability of amber light emitting diode with Ca -α-SiAlON phosphor in glass formed by gas pressure sintering for automotive applications.

    Science.gov (United States)

    Yoon, Chang-Bun; Kim, Sanghyun; Choi, Sung-Woo; Yoon, Chulsoo; Ahn, Sang Hyeon; Chung, Woon Jin

    2016-04-01

    Phosphor in glass (PiG) with 40 wt% of Ca-α-SiAlON phosphor and 60 wt% of Pb-free silicate glass was synthesized and mounted on a high-power blue LED to make an amber LED for automotive applications. Gas pressure sintering was applied after the conventional sintering process was used to achieve fully dense PiG plates. Changes in photoluminescence spectra and color coordination were inspected by varying the thickness of the plates that were mounted after optical polishing and machining. A trade-off between luminous flux and color purity was observed. The commercial feasibility of amber PiG packaged LED, which can satisfy international regulations for automotive components, was successfully demonstrated by examining the practical reliability under 85% humidity at an 85°C condition.

  13. Sintering of catalytic nanoparticles: particle migration or Ostwald ripening?

    Science.gov (United States)

    Hansen, Thomas W; Delariva, Andrew T; Challa, Sivakumar R; Datye, Abhaya K

    2013-08-20

    Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. This is especially true for high temperature catalytic processes, such as steam reforming, automotive exhaust treatment, or catalytic combustion. With dwindling supplies of precious metals and increasing demand, fundamental understanding of catalyst sintering is very important for achieving clean energy and a clean environment, and for efficient chemical conversion processes with atom selectivity. Scientists have proposed two mechanisms for sintering of nanoparticles: particle migration and coalescence (PMC) and Ostwald ripening (OR). PMC involves the mobility of particles in a Brownian-like motion on the support surface, with subsequent coalescence leading to nanoparticle growth. In contrast, OR involves the migration of adatoms or mobile molecular species, driven by differences in free energy and local adatom concentrations on the support surface. In this Account, we divide the process of sintering into three phases. Phase I involves rapid loss in catalyst activity (or surface area), phase II is where sintering slows down, and phase III is where the catalyst may reach a stable performance. Much of the previous work is based on inferences from catalysts that were observed before and after long term treatments. While the general phenomena can be captured correctly, the mechanisms cannot be determined. Advancements in the techniques of in situ TEM allow us to observe catalysts at elevated temperatures under working conditions. We review recent evidence obtained via in situ methods to determine the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that

  14. Measurement of thermodynamic temperature of high temperature fixed points

    Energy Technology Data Exchange (ETDEWEB)

    Gavrilov, V. R.; Khlevnoy, B. B.; Otryaskin, D. A.; Grigorieva, I. A.; Samoylov, M. L.; Sapritsky, V. I. [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), 46 Ozernaya St., Moscow 119361 (Russian Federation)

    2013-09-11

    The paper is devoted to VNIIOFI's measurements of thermodynamic temperature of the high temperature fixed points Co-C, Pt-C and Re-C within the scope of the international project coordinated by the Consultative Committee for Thermometry working group 5 'Radiation Thermometry'. The melting temperatures of the fixed points were measured by a radiance mode radiation thermometer calibrated against a filter radiometer with known irradiance spectral responsivity via a high temperature black body. This paper describes the facility used for the measurements, the results and estimated uncertainties.

  15. Measurement of thermodynamic temperature of high temperature fixed points

    Science.gov (United States)

    Gavrilov, V. R.; Khlevnoy, B. B.; Otryaskin, D. A.; Grigorieva, I. A.; Samoylov, M. L.; Sapritsky, V. I.

    2013-09-01

    The paper is devoted to VNIIOFI's measurements of thermodynamic temperature of the high temperature fixed points Co-C, Pt-C and Re-C within the scope of the international project coordinated by the Consultative Committee for Thermometry working group 5 "Radiation Thermometry". The melting temperatures of the fixed points were measured by a radiance mode radiation thermometer calibrated against a filter radiometer with known irradiance spectral responsivity via a high temperature black body. This paper describes the facility used for the measurements, the results and estimated uncertainties.

  16. Low temperature sintering and microwave dielectric properties of BaZn2Ti4O11 ceramics with Li2O-B2O3-SiO2 glass

    Science.gov (United States)

    Duan, S. X.; Li, E. Z.; Chen, Y. W.; Tang, B.; Yuan, Y.; Zhang, S. R.

    2017-02-01

    The effects of Li2O-B2O3-SiO2 glass (LBS) on the sintering behavior, phase evolution, microstructure and microwave dielectric properties of the BaZn2Ti4O11 ceramic were studied in detail. The results show that LBS significantly lowers the sintering temperature of the BaZn2Ti4O11 ceramic from 1200 °C to 850 °C. Small amount of LBS promotes the sintering process of the BaZn2Ti4O11 ceramic and obtains excellent microwave dielectric properties. However, excessive LBS addition leads to the change of phase and growth of abnormal grain, destroying the compact microstructure and deteriorating the microwave dielectric properties of the BaZn2Ti4O11 ceramic. BaZn2Ti4O11 ceramic with 4∼6 wt.% LBS can be well sintered at 850 °C and shows excellent microwave dielectric properties: ɛr = 22.95∼24.92, Q×f = 27181∼31301 GHz.

  17. Studies of nonlinear electrodynamics of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Quan-Chiu H.

    1991-08-01

    Nonlinear electrodynamics of high-{Tc} superconductors are studied both theoretically and experimentally. For powdered samples, a novel model is presented in which the metallographically observed superconducting grains in the powder are modeled as superconducting current loops of various areas with weak links. Surprising harmonic generation behavior in an arc field, H{sub 1} cos({omega}t), is predicted by the model; the power at high harmonics show sharp dips almost periodic in a superposing dc magnetic field, revealing flux quantization in the prototype loops in the model. Such oscillation of the harmonic power in dc magnetic field P{sub nf}(H{sub dc}), is indeed experimentally observed in powdered YBa{sub 2}Cu{sub 3}O{sub 7}. Other experimental aspects also agree with model predictions. For bulk sintered cylindrical samples, a generalized critical state model is presented. In this model, the nonlinear electrodynamics are due to flux-pinning, somewhat similar to low-temperature type-II superconductors, but with a more generalized critical current densities' dependence on magnetic field -- J{sub c}(H){approximately}H{sub local}{sup -{beta}}, with {beta} being an adjustable parameter. Experiments in ac and dc magnetic fields on a sintered cylindrical rod of YBa{sub 2}Cu{sub 3}O{sub 7} yield unambiguous evidence of independent inter- and intragranular contributions to the complex harmonic permeability {tilde {mu}}{sub n} = {mu}{prime}{sub n} -i{mu}{double prime}{sub n}. Temperature- dependence measurements reveal that, while the intragranular supercurrents disappear at {Tc}{ge}91.2 K, the intergranular supercurrents disappear at T{ge}86.6 K. This result is, to our knowledge, the first clear measurement of the phase-locking temperature of the 3-D matrix formed by YBa{sub 2}Cu{sub 3}O{sub 7} grains, which are in electrical contact with one another through weak links.

  18. Studies of nonlinear electrodynamics of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Quan-Chiu H. [Univ. of California, Berkeley, CA (United States)

    1991-08-01

    Nonlinear electrodynamics of high-Tc superconductors are studied both theoretically and experimentally. For powdered samples, a novel model is presented in which the metallographically observed superconducting grains in the powder are modeled as superconducting current loops of various areas with weak links. Surprising harmonic generation behavior in an arc field, H1 cos(ωt), is predicted by the model; the power at high harmonics show sharp dips almost periodic in a superposing dc magnetic field, revealing flux quantization in the prototype loops in the model. Such oscillation of the harmonic power in dc magnetic field Pnf(Hdc), is indeed experimentally observed in powdered YBa2Cu3O7. Other experimental aspects also agree with model predictions. For bulk sintered cylindrical samples, a generalized critical state model is presented. In this model, the nonlinear electrodynamics are due to flux-pinning, somewhat similar to low-temperature type-II superconductors, but with a more generalized critical current densities` dependence on magnetic field -- Jc(H)~H$β\\atop{local}$, with β being an adjustable parameter. Experiments in ac and dc magnetic fields on a sintered cylindrical rod of YBa2Cu3O7 yield unambiguous evidence of independent inter- and intragranular contributions to the complex harmonic permeability$\\tilde{μ}$n = μ'n -iμ''n. Temperature- dependence measurements reveal that, while the intragranular supercurrents disappear at Tc≥91.2 K, the intergranular supercurrents disappear at T≥86.6 K. This result is, to our knowledge, the first clear measurement of the phase-locking temperature of the 3-D matrix formed by YBa2Cu3O7 grains, which are in electrical contact with one another through weak links.

  19. Temperature and high pressure effects on the structural features of catalytic nanocomposites oxides by Raman spectroscopy

    Science.gov (United States)

    da Silva, Antonio N.; Pinto, Raffael C. F.; Freire, Paulo T. C.; Junior, Jose Alves L.; Oliveira, Alcineia C.; Filho, Josué M.

    2015-03-01

    Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600 °C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10 GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15 GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied.

  20. Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

    Science.gov (United States)

    Pan, Minqiang; Zhong, Yujian

    2018-01-01

    Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

  1. Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

    Science.gov (United States)

    Pan, Minqiang; Zhong, Yujian

    2017-07-01

    Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

  2. (Krauss) at constant high temperatures

    African Journals Online (AJOL)

    A number of opinions are held on the relative importance of the various physical ... optimum as well as extreme temperatures on vital functions such as survival, egg ..... solids on the biology of certain freshwater molluscs. D .Sc. thesis,. Potch.

  3. Reaction of Unalloyed and Cr-Mo Alloyed Steels with Nitrogen from the Sintering Atmosphere

    Science.gov (United States)

    Dlapka, Magdalena; Gierl-Mayer, Christian; Calderon, Raquel de Oro; Danninger, Herbert; Bengtsson, Sven; Dudrova, Eva

    2016-12-01

    Nitrogen is usually regarded as an inert sintering atmosphere for PM steels; however, this cannot be taken for granted in particular for steels alloyed with nitride forming elements. Among those elements, chromium has become more and more important as an alloying element in sintered low alloy structural steels in the last decade due to the moderate alloying cost and the excellent mechanical properties obtainable, in particular when sinter hardening is applied. The high affinity of Cr to oxygen and the possible ways to overcome related problems have been the subject of numerous studies, while the fact that chromium is also a fairly strong nitride forming element has largely been neglected at least for low alloy steel grades, although frequently used materials like steels from Cr and Cr-Mo prealloyed powders are commonly sintered in atmospheres consisting mainly of nitrogen. In the present study, nitrogen pickup during sintering at different temperatures and for varying times has been studied for Cr-Mo prealloyed steel grades as well as for unalloyed carbon steel. Also the effect of the cooling rate and its influence on the properties, of the microstructure and the composition have been investigated. It showed that the main nitrogen uptake occurs not during isothermal sintering but rather during cooling. It could be demonstrated that a critical temperature range exists within which the investigated CrM-based steel is particularly sensitive to nitrogen pickup.

  4. High temperature superconducting fault current limiter

    Science.gov (United States)

    Hull, John R.

    1997-01-01

    A fault current limiter (10) for an electrical circuit (14). The fault current limiter (10) includes a high temperature superconductor (12) in the electrical circuit (14). The high temperature superconductor (12) is cooled below its critical temperature to maintain the superconducting electrical properties during operation as the fault current limiter (10).

  5. Technological Evolution of High Temperature Superconductors

    Science.gov (United States)

    2015-12-01

    TEMPERATURE SUPERCONDUCTORS by Jordan R. White December 2015 Thesis Advisor: Clifford Whitcomb Co-Advisor: Fotis Papoulias THIS PAGE INTENTIONALLY...AND SUBTITLE TECHNOLOGICAL EVOLUTION OF HIGH TEMPERATURE SUPERCONDUCTORS 5. FUNDING NUMBERS 6. AUTHOR(S) Jordan R. White 7. PERFORMING ORGANIZATION...trends. 14. SUBJECT TERMS electric ships, high temperature superconductor , HTS 15. NUMBER OF PAGES 111 16. PRICE CODE 17. SECURITY CLASSIFICATION

  6. Sintered powder cores of high Bs and low coreloss Fe84.3Si4B8P3Cu0.7 nano-crystalline alloy

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2013-06-01

    Full Text Available Nano-crystalline Fe-rich Fe84.3Si4B8P3Cu0.7 alloy ribbon with saturation magnetic flux density (Bs close to Si-steel exhibits much lower core loss (Wt than Si-Steels. Low glass forming ability of this alloy limits fabrication of magnetic cores only to stack/wound types. Here, we report on fabrication, structural, thermal and magnetic properties of bulk Fe84.3Si4B8P3Cu0.7 cores. Partially crystallized ribbons (obtained after salt-bath annealing treatment were crushed into powdered form (by ball milling, and were compacted to high-density (∼88% bulk cores by spark plasma sintering (SPS. Nano-crystalline structure (consisting of α-Fe grain in remaining amorphous matrix similar to wound ribbon cores is preserved in the compacted cores. At 50 Hz, cores sintered at Ts = 680 K show Wt 1 kHz. A trade-off between porosity and electrical resistivity is necessary to get low Wt at higher f. In the f range of ∼1 to 100 kHz, we have shown that the cores mixed with SiO2 exhibit much lower Wt than Fe-powder cores, non-oriented Si-steel sheets and commercially available sintered cores. We believe our core material is very promising to make power electronics/electrical devices much more energy-efficient.

  7. Microstructural and hardness characterisation of sintered low alloyed steel

    OpenAIRE

    Yilmaz, R.; M.R. Ekici

    2008-01-01

    Purpose: The purpose of the present study is to produce low ally PM steel without any addition and with addition of ferro-boron addition by conventional PM manufacturing route at the different sintering temperature.Design/methodology/approach: Fe-Ni-Cu-Mo-C sintered steel containing 0.5 percent ferro-boron addition was used in this study. The compacts were prepared by powder metallurgy method involving powder mixing, cold pressing at 700 MPa pressure and sintering at temperatur...

  8. Deep Trek High Temperature Electronics Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce Ohme

    2007-07-31

    This report summarizes technical progress achieved during the cooperative research agreement between Honeywell and U.S. Department of Energy to develop high-temperature electronics. Objects of this development included Silicon-on-Insulator (SOI) wafer process development for high temperature, supporting design tools and libraries, and high temperature integrated circuit component development including FPGA, EEPROM, high-resolution A-to-D converter, and a precision amplifier.

  9. 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)

  10. Spark plasma sintering of alumina nanopowders produced by electrical explosion of wires

    OpenAIRE

    An, Vladimir; Khasanov, Alexey; de Izarra, Charles

    2015-01-01

    Alumina nanopowders produced by electrical explosion of wires were sintered using the spark plasma sintering technique. The results of XRD analysis show that the main phase in the compacted nanopowders is ?-Al2O3. According to the SEM observations, the sintered alumina nanopowder consists of micron-sized faceted grains and nano-sized necked grains. The increase in sintering temperature resulted in a higher density of the sintered powders: from 78.44 to 98.21?% of theoretical density.

  11. Ultra high temperature ceramics for hypersonic vehicle applications.

    Energy Technology Data Exchange (ETDEWEB)

    Tandon, Rajan; Dumm, Hans Peter; Corral, Erica L.; Loehman, Ronald E.; Kotula, Paul Gabriel

    2006-01-01

    HfB{sub 2} and ZrB{sub 2} are of interest for thermal protection materials because of favorable thermal stability, mechanical properties, and oxidation resistance. We have made dense diboride ceramics with 2 to 20 % SiC by hot pressing at 2000 C and 5000 psi. High-resolution transmission electron microscopy (TEM) shows very thin grain boundary phases that suggest liquid phase sintering. Fracture toughness measurements give RT values of 4 to 6 MPam{sup 1/2}. Four-pt flexure strengths measured in air up to 1450 C were as high as 450-500 MPa. Thermal diffusivities were measured to 2000 C for ZrB{sub 2} and HfB{sub 2} ceramics with SiC contents from 2 to 20%. Thermal conductivities were calculated from thermal diffusivities and measured heat capacities. Thermal diffusivities were modeled using different two-phase composite models. These materials exhibit excellent high temperature properties and are attractive for further development for thermal protection systems.

  12. Sintering of polydisperse viscous droplets

    Science.gov (United States)

    Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Dingwell, Donald B.

    2017-03-01

    Sintering—or coalescence—of compacts of viscous droplets is driven by the interfacial tension between the droplets and the interstitial gas phase. The process, which occurs in a range of industrial and natural settings, such as the manufacture of ceramics and the welding of volcanic ash, causes the compact to densify, to become stronger, and to become less permeable. We investigate the role of droplet polydispersivity in sintering dynamics by conducting experiments in which populations of glass spheres with different size distributions are heated to temperatures above the glass transition interval. We quantify the progress of sintering by tracking changes in porosity with time. The sintering dynamics is modeled by treating the system as a random distribution of interstitial gas bubbles shrinking under the action of interfacial tension only. We identify the scaling between the polydispersivity of the initial droplets and the dynamics of bulk densification. The framework that we develop allows the sintering dynamics of arbitrary polydisperse populations of droplets to be predicted if the initial droplet (or particle) size distribution is known.

  13. Novel Routes for Sintering of Ultra-high Temperature Ceramics and their Properties

    Science.gov (United States)

    2014-10-31

    low thermal expansion is needed for many insulation materials, as well as parts of nuclear reactors. Due to the similarity of physico-chemical...J. Materials Sci. – 2003. – Vol. 38. – P. 1413-1423. 22. E.V. Tsipis, V.V. Kharton, I.A. Bashmakov, E.N. Naumovich, J.R. Frade, Cellulose -precursor

  14. Novel Routes for Sintering of Ultra-high Temperature Ceramics and their Properties

    Science.gov (United States)

    2014-10-31

    its transformation into lower carbides. According to the equilibrium diagram Cr – C it means a transition of chromium carbide in much fusible states...presented tetrahedron there are fusible quadruple eutectics, apart from highlighted ternary eutectics. Thorough analysis of phase interactions is not

  15. MECHANICAL TESTING OF SINTERED MATERIALS

    Directory of Open Access Journals (Sweden)

    Cristina IONICI

    2011-07-01

    Full Text Available Alloying elements have an important affect upon the mechanical properties of the Sintered Materials.Compression tests show that the cupper based material obtains high results in cryogenic environments.Testsreveal the weak resistance of materials that contain 0,8% C, due to a poor classification and a inhomogenousmetallographycal structure.

  16. 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.

  17. Sintering studies on iron-carbon-copper compacts

    Directory of Open Access Journals (Sweden)

    Perianayagam Philomen-D-Anand Raj

    2016-01-01

    Full Text Available Sintered Iron-Carbon-Copper parts are among the most widely used powder metallurgy product in automobile. In this paper, studies have been carried out to find out the sintering characteristics of iron-carbon-copper compacts when sintered in nitrogen atmosphere. The effects of various processing parameters on the sintering characteristics were studied. The various processing parameters considered were compaction pressure, green density and sintering temperature. The sintering characteristics determined were sintered density, porosity, dimensional change, micro hardness and radial crush strength. The results obtained have been discussed on the basis of micro structural observations. The characteristics of SEM fractography were also used to determine the mechanism of fracture. The fracture energy is strongly dependent on density of the compact.

  18. Thermoelastic properties of minerals at high temperature

    Indian Academy of Sciences (India)

    under high temperatures and calculated the second-order elastic constant (Cij ) and bulk modulus. (KT) of the above minerals, in two cases first by taking Anderson–Gruneisen parameter (δT) as temperature-independent and then by treating δT as temperature-dependent parameter. The results obtained when δT is ...

  19. High Temperature Capacitors for Venus Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this SBIR program, TRS Technologies has developed several new dielectrics for high temperature applications including signal conditioning, filtering and energy...

  20. Advances in high temperature chemistry 1

    CERN Document Server

    Eyring, Leroy

    2013-01-01

    Advances in High Temperature Chemistry, Volume 1 describes the complexities and special and changing characteristics of high temperature chemistry. After providing a brief definition of high temperature chemistry, this nine-chapter book goes on describing the experiments and calculations of diatomic transition metal molecules, as well as the advances in applied wave mechanics that may contribute to an understanding of the bonding, structure, and spectra of the molecules of high temperature interest. The next chapter provides a summary of gaseous ternary compounds of the alkali metals used in

  1. High temperature phase equilibria and phase diagrams

    CERN Document Server

    Kuo, Chu-Kun; Yan, Dong-Sheng

    2013-01-01

    High temperature phase equilibria studies play an increasingly important role in materials science and engineering. It is especially significant in the research into the properties of the material and the ways in which they can be improved. This is achieved by observing equilibrium and by examining the phase relationships at high temperature. The study of high temperature phase diagrams of nonmetallic systems began in the early 1900s when silica and mineral systems containing silica were focussed upon. Since then technical ceramics emerged and more emphasis has been placed on high temperature

  2. High-Temperature Test Technology

    Science.gov (United States)

    1987-03-01

    Do any of your facilities have vacuum test capability? YesO No~l If yes, What is the minimum vacuum chamber pressure? What is the maximum allowable...available? YesO N[-- If "yes," please Indicate the following: Vaporizer Superheater Capacity Capacity Max Temperature LH2 LN2 Are gaseous hydrogen...personnel safety? 5. Does the facility have radiant heating capability? YesO NoF- If "yes," please provide the following information: Lamp types Tungsten

  3. Thermodynamics of High Temperature Materials.

    Science.gov (United States)

    1985-03-15

    temperatures In the present range have also been obtained by Krauss and Warncke [8] and by Vollmer et al. [9], using adiabatic calorimetry, and by Kollie [10...value for heat capacity. The electrical resistivity results reported by Kollie [10] and by Powell et al. [13] are respectively about 1 and 1.5% lower...extensive annealing of the specimens used in the measurements: the specimen (>99.89% pure) used by Kollie was annealed at 1100 K for 24 h and Laubitz et al

  4. Study of the sintering behavior of fine, ultrafine and nanocrystalline WC-CO mixtures obtained by high energy milling; Estudio del comportamiento durante la sinterizacion de mezclas WC-Co finas, ultrafinas y nanocristalinas obtenidas por molienda de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Salvador, M. D.; Bonache, V.; Amigo, V.; Busquets, D.

    2008-07-01

    In this work the sintering behaviour of fine, ultrafine and nanocrystalline WC-12Co mixtures obtained by high energy milling, as well commercial nano powders, have been studied, in order to evaluate the effect of the particle size and the powder processing, in the densification, microstructural development and mechanical properties of the final product. The consolidation of the mixtures has been made by uniaxial pressing and sintering in vacuum, and by hot isostatic pressing. The sintered materials have been evaluated by measures of density, hardness and indentation fracture toughness, and micro structurally characterized by optical microscopy and scanning and transmission electronic microscopy (SEM and TEM). The results show the improvements in resistant behaviour of the materials obtained from nanocrystalline powders, in spite of the grain growth experienced during the sintering. The best results were obtained for the milling nanocrystalline material, which presents values of hardness higher than 180 HV. (Author) 46 refs.

  5. Morphology and phase identification of micron to nanosized manganese oxide (MnO) with variations in sintering time

    Science.gov (United States)

    Sasongko, Muhammad Ilman Nur; Puspitasari, Poppy; Yazirin, Cepi; Tsamroh, Dewi Izzatus; Risdanareni, Puput

    2017-09-01

    Manganese oxide (MnO) occurs in many rock types and may take the form of minerals. MnO has its drawbacks, namely highly reactive oxidizing species classified as dangerous and explosive at temperatures above 55 °C. Despite this,MnO has excellent magnetic, electrochemical, and conductivity properties, which should be reduced to nano-size to maximize their use and improve the properties of MnO. Phase and morphology characterization of powder this research aims to reduce the grain size of the MnO from micro to nano using the sol-gel method with various sintering times. Sol-gel is a simple synthesis method that has been proven capable of synthesizing a wide variety of micro-sized oxide materials into nano. Sintering time is a technique performed in the synthesis process to dry the material to a temperature above the normal temperature. The temperature used for sintering starting from 600 °C to 1000 °C. Characterizations were done using XRD, SEM, EDX, and FTIR machines. The sintering processes in this study used a temperature of 600 °C with different sintering periods of 30, 60 and 90 minutes. The XRD characterization with a 30-minute sintering time resulted in the smallest MnO in the form crystalline powder of 47.3 nm. The highest intensity (degree of crystallinity) found in MnO sintered for 90 minutes. The results of the morphological characterization of SEM showed a morphological change in MnO from micro-sized triangular to nano-sized spherical shape. The EDX characterization results indicated that the 30-minute sintering caused the lowest change in Mn and the highest change in O. The results of FTIR characterization showed a shift in C-H and Mn-O followed by an increase in the group of N-H, C=O and Mn-O.

  6. Effect of processing conditions on microstructural features in Mn–Si sintered steels

    Energy Technology Data Exchange (ETDEWEB)

    Oro, Raquel, E-mail: raqueld@chalmers.se [Department of Materials and Manufacturing Technology, Chalmers University of Technology, Rännvägen 2A, SE-41296 Gothenburg (Sweden); Hryha, Eduard, E-mail: hryha@chalmers.se [Department of Materials and Manufacturing Technology, Chalmers University of Technology, Rännvägen 2A, SE-41296 Gothenburg (Sweden); Campos, Mónica, E-mail: campos@ing.uc3m.es [Department of Materials Science and Engineering, IAAB, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés, Madrid (Spain); Torralba, José M., E-mail: torralba@ing.uc3m.es [Department of Materials Science and Engineering, IAAB, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés, Madrid (Spain); IMDEA Materials Institute, c/Eric Kandel, 2, 28906 Getafe, Madrid (Spain)

    2014-09-15

    Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe–Mn–Si–C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties. Chemical analyses, metallography and fractography studies combined with X-ray photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces. The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn–Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly the final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles. - Highlights: • Oxide distribution in steels containing oxidation-sensitive elements • Mn, Si introduced in a master alloy powder, mixed with a base iron powder • Selective oxidation of Mn and Si on iron grain boundaries • Decohesive fracture caused by degradation of grain

  7. Interpretation of Frenkel’s theory of sintering considering evolution of activated pores: III. Determination of equilibrium sintering time

    Directory of Open Access Journals (Sweden)

    Yu C.L.

    2015-01-01

    Full Text Available In this article, the Frenkel’s theory of liquid-phase sintering was interpreted regarding pores as the activated volume. The mathematical model established by Nikolić et al. was used to infer the equilibrium sintering time at varied sintering temperatures during the isothermal sintering of codierite glass by Giess et al. Through the calculation, the equilibrium time at 800ºC, 820ºC, 840ºC and 860ºC is inferred to be 7014.42mins, 1569.65mins, 368.92mins and 114.61mins, respectively. The equilibrium time decreases as the temperature increases. And the theoretical value is in good accordance with the experimental results. Thus, the model established by Nikolić et al. can be applied successfully to predict the equilibrium sintering time of the cordierite glass at varied temperatures during isothermal sintering.

  8. Investigations into High Temperature Components and Packaging

    Energy Technology Data Exchange (ETDEWEB)

    Marlino, L.D.; Seiber, L.E.; Scudiere, M.B.; M.S. Chinthavali, M.S.; McCluskey, F.P.

    2007-12-31

    The purpose of this report is to document the work that was performed at the Oak Ridge National Laboratory (ORNL) in support of the development of high temperature power electronics and components with monies remaining from the Semikron High Temperature Inverter Project managed by the National Energy Technology Laboratory (NETL). High temperature electronic components are needed to allow inverters to operate in more extreme operating conditions as required in advanced traction drive applications. The trend to try to eliminate secondary cooling loops and utilize the internal combustion (IC) cooling system, which operates with approximately 105 C water/ethylene glycol coolant at the output of the radiator, is necessary to further reduce vehicle costs and weight. The activity documented in this report includes development and testing of high temperature components, activities in support of high temperature testing, an assessment of several component packaging methods, and how elevated operating temperatures would impact their reliability. This report is organized with testing of new high temperature capacitors in Section 2 and testing of new 150 C junction temperature trench insulated gate bipolar transistor (IGBTs) in Section 3. Section 4 addresses some operational OPAL-GT information, which was necessary for developing module level tests. Section 5 summarizes calibration of equipment needed for the high temperature testing. Section 6 details some additional work that was funded on silicon carbide (SiC) device testing for high temperature use, and Section 7 is the complete text of a report funded from this effort summarizing packaging methods and their reliability issues for use in high temperature power electronics. Components were tested to evaluate the performance characteristics of the component at different operating temperatures. The temperature of the component is determined by the ambient temperature (i.e., temperature surrounding the device) plus the

  9. On the Mechanism of Microwave Flash Sintering of Ceramics

    Directory of Open Access Journals (Sweden)

    Yury V. Bykov

    2016-08-01

    Full Text Available The results of a study of ultra-rapid (flash sintering of oxide ceramic materials under microwave heating with high absorbed power per unit volume of material (10–500 W/cm3 are presented. Ceramic samples of various compositions—Al2O3; Y2O3; MgAl2O4; and Yb(LaO2O3—were sintered using a 24 GHz gyrotron system to a density above 0.98–0.99 of the theoretical value in 0.5–5 min without isothermal hold. An analysis of the experimental data (microwave power; heating and cooling rates along with microstructure characterization provided an insight into the mechanism of flash sintering. Flash sintering occurs when the processing conditions—including the temperature of the sample; the properties of thermal insulation; and the intensity of microwave radiation—facilitate the development of thermal runaway due to an Arrhenius-type dependency of the material’s effective conductivity on temperature. The proper control over the thermal runaway effect is provided by fast regulation of the microwave power. The elevated concentration of defects and impurities in the boundary regions of the grains leads to localized preferential absorption of microwave radiation and results in grain boundary softening/pre-melting. The rapid densification of the granular medium with a reduced viscosity of the grain boundary phase occurs via rotation and sliding of the grains which accommodate their shape due to fast diffusion mass transport through the (quasi-liquid phase. The same mechanism based on a thermal runaway under volumetric heating can be relevant for the effect of flash sintering of various oxide ceramics under a dc/ac voltage applied to the sample.

  10. Weibull strength variations between room temperature and high temperature Ni-3YSZ half-cells

    DEFF Research Database (Denmark)

    Curran, Declan; Frandsen, Henrik Lund; Hendriksen, Peter Vang

    2013-01-01

    efficiency, increased degradation and/or the complete termination of a functioning stack. This paper investigates the effects of temperature on the mechanical strength of 3% yttria-stabilised zirconia half-cells. Strength was measured using a four-point bend method at room temperature and at 600°C, 700°C...... and 800°C in a reducing atmosphere. The strength of an as sintered half-cell was also measured at room temperature for comparison. Weibull analysis was performed on large sample sets of 30 for statistical viability. The Weibull strength and elastic modulus of the room temperature tested reduced samples...... show a decrease of approximately 33% and 51% respectively, when compared to the oxidized samples tested at room temperature. When tested at elevated temperatures both Weibull strength and elastic modulus decrease further when compared to the room temperature reduced samples. However these further...

  11. High temperature skin friction measurement

    Science.gov (United States)

    Tcheng, Ping; Holmes, Harlan K.; Supplee, Frank H., Jr.

    1989-01-01

    Skin friction measurement in the NASA Langley hypersonic propulsion facility is described. The sensor configuration utilized an existing balance, modified to provide thermal isolation and an increased standoff distance. For test run times of about 20 sec and ambient-air cooling of the test section and balance, the modified balance performed satisfactorily, even when it was subjected to acoustic and structural vibration. The balance is an inertially balanced closed-loop servo system where the current to a moving-coil motor needed to restore or null the output from the position sensor is a measure of the force or skin friction tending to displace the moving element. The accuracy of the sensor is directly affected by the position sensor in the feedback loop, in this case a linear-variable differential transformer which has proven to be influenced by temperature gradients.

  12. Hydraulic and Physical properties of modern sinter deposits: El Tatio, Atacama

    Science.gov (United States)

    Munoz Saez, C.; Saltiel, S.; Manga, M.; Nguyen, C. T.; Gonnermann, H. M.

    2015-12-01

    Sinters are sedimentary, siliceous deposits, and are common in geothermal areas. Formation occurs in two steps. Hot water circulates underground, and dissolves silica from the host rock. Silica then precipitates at the surface as water is discharged from hot springs. Extensive sinter formations are linked to up-flow areas of fluids originated in high temperature (>175 °C) reservoirs. Sinter samples provide a guide for geothermal and epithermal ore deposit exploration. Fluid geochemistry, microbial communities, and environmental conditions of deposition determine the texture of sinter. To better understand the water balance in geothermal systems, and interpret geophysical observations, we studied 21 samples of modern geyserite sinter deposits (<10,000 years) from an active geothermal field located in the north of Chile, El Tatio. We measured the physical properties (hydraulic, seismic, and electrical), and internal micro-structure (using X-Ray micro- tomography). The pore structure, and thus hydraulic and physical properties, are controlled by the distribution of microbial matter. Based on velocity-porosity relationships, permeability-porosity scaling, and image analysis of the 3D pore structure, we find that the sinter more closely resembles vesicular volcanic rocks than clastic sedimentary rocks.

  13. Selective Surface Sintering Using a Laser-Induced Breakdown Spectroscopy System

    Directory of Open Access Journals (Sweden)

    H. Jull

    2017-01-01

    Full Text Available Titanium metal injection molding allows creation of complex metal parts that are lightweight and biocompatible with reduced cost in comparison with machining titanium. Laser-induced breakdown spectroscopy (LIBS can be used to create plasma on the surface of a sample to analyze its elemental composition. Repetitive ablation on the same site has been shown to create differences from the original sample. This study investigates the potential of LIBS for selective surface sintering of injection-molded titanium metal. The temperature created throughout the LIBS process on the surface of the injection-molded titanium is high enough to fuse together the titanium particles. Using the ratio of the Ti II 282.81 nm and the C I 247.86 nm lines, the effectiveness of repetitive plasma formation to produce sintering can be monitored during the process. Energy-dispersive X-ray spectroscopy on the ablation craters confirms sintering through the reduction in carbon from 20.29 Wt.% to 2.13 Wt.%. Scanning electron microscope images confirm sintering. A conventional LIBS system, with a fixed distance, investigated laser parameters on injection-molded and injection-sintered titanium. To prove the feasibility of using this technique on a production line, a second LIBS system, with an autofocus and 3-axis translation stage, successfully sintered a sample with a nonplanar surface.

  14. High Temperature Solid State Lithium Battery Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Reliable energy systems with high energy density capable of operating at high temperatures, pressures and radiation levels are needed for certain NASA missions....

  15. Copper Alloy For High-Temperature Uses

    Science.gov (United States)

    Dreshfield, Robert L.; Ellis, David L.; Michal, Gary

    1994-01-01

    Alloy of Cu/8Cr/4Nb (numbers indicate parts by atom percent) improved over older high-temperature copper-based alloys in that it offers enhanced high temperature strength, resistance to creep, and ductility while retaining most of thermal conductivity of pure copper; in addition, alloy does not become embrittled upon exposure to hydrogen at temperatures as high as 705 degrees C. Designed for use in presence of high heat fluxes and active cooling; for example, in heat exchangers in advanced aircraft and spacecraft engines, and other high-temperature applications in which there is need for such material. High conductivity and hardness of alloy exploited in welding electrodes and in high-voltage and high-current switches and other applications in which wear poses design problem.

  16. Lightweight, High-Temperature Radiator Panels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Lightweight, high-temperature radiators are needed for future, high-efficiency power conversion systems for Nuclear Electric Propulsion (NEP). Creare has developed...

  17. High Temperature Rechargeable Battery Development Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This small business innovation research is intended to develop and proof the concept of a highly efficient, high temperature rechargeable battery for supporting...

  18. High temperature sensor/microphone development for active noise control

    Science.gov (United States)

    Shrout, Thomas R.

    1993-01-01

    The industrial and scientific communities have shown genuine interest in electronic systems which can operate at high temperatures, among which are sensors to monitor noise, vibration, and acoustic emissions. Acoustic sensing can be accomplished by a wide variety of commercially available devices, including: simple piezoelectric sensors, accelerometers, strain gauges, proximity sensors, and fiber optics. Of the several sensing mechanisms investigated, piezoelectrics were found to be the most prevalent, because of their simplicity of design and application and, because of their high sensitivity over broad ranges of frequencies and temperature. Numerous piezoelectric materials are used in acoustic sensors today; but maximum use temperatures are imposed by their transition temperatures (T(sub c)) and by their resistivity. Lithium niobate, in single crystal form, has the highest operating temperature of any commercially available material, 650 C; but that is not high enough for future requirements. Only two piezoelectric materials show potential for use at 1000 C; AlN thin film reported to be piezoactive at 1150 C, and perovskite layer structure (PLS) materials, which possess among the highest T(sub c) (greater than 1500 C) reported for ferroelectrics. A ceramic PLS composition was chosen. The solid solution composition, 80% strontium niobate (SN) and 20% strontium tantalate (STa), with a T(sub c) approximately 1160 C, was hot forged, a process which concurrently sinters and renders the plate-like grains into a highly oriented configuration to enhance piezo properties. Poled samples of this composition showed coupling (k33) approximately 6 and piezoelectric strain constant (d33) approximately 3. Piezoactivity was seen at 1125 C, the highest temperature measurement reported for a ferroelectric ceramic. The high temperature piezoelectric responses of this, and similar PLS materials, opens the possibility of their use in electronic devices operating at temperatures up to

  19. 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.

  20. Enhanced Sintering of TiNi Shape Memory Foams under Mg Vapor Atmosphere

    Science.gov (United States)

    Aydoğmuş, Tarik; Bor, Şakir

    2012-12-01

    TiNi alloy foams are promising candidates for biomaterials to be used as artificial orthopedic implant materials for bone replacement applications in biomedical sector. However, certain problems exist in their processing routes, such as formation of unwanted secondary intermetallic phases leading to brittleness and deterioration of shape memory and superelasticity characteristics; and the contamination during processing resulting in oxides and carbonitrides which affect mechanical properties negatively. Moreover, the eutectic reaction present in Ti-Ni binary system at 1391 K (1118 °C) prevents employment of higher sintering temperatures (and higher mechanical properties) even when equiatomic prealloyed powders are used because of Ni enrichment of TiNi matrix as a result of oxidation. It is essential to prevent oxidation of TiNi powders during processing for high-temperature (>1391 K i.e., 1118 °C) sintering practices. In the current study, magnesium powders were used as space holder material to produce TiNi foams with the porosities in the range of 40 to 65 pct. It has been found that magnesium prevents secondary phase formation and contamination. It also prevents liquid phase formation while enabling employment of higher sintering temperatures by two-step sintering processing: holding the sample at 1373 K (1100 °C) for 30 minutes, and subsequently sintering at temperatures higher than the eutectic temperature, 1391 K (1118 °C). By this procedure, magnesium may allow sintering up to temperatures close to the melting point of TiNi. TiNi foams produced with porosities in the range of 40 to 55 pct were found to be acceptable as implant materials in the light of their favorable mechanical properties.

  1. Ageing sintered silver: Relationship between tensile behavior, mechanical properties and the nanoporous structure evolution

    Energy Technology Data Exchange (ETDEWEB)

    Gadaud, Pascal; Caccuri, Vincenzo; Bertheau, Denis [Institut Pprime, Dept. Phys. Mech. Mat., UPR CNRS 3346, ENSMA, Université de Poitiers, 1 av. Clément Ader, Téléport 2, 86961 Futuroscope – Chasseneuil (France); Carr, James [HMXIF, Materials Science Centre, The University of Manchester, M13 9PL (United Kingdom); Milhet, Xavier, E-mail: xavier.milhet@ensma.fr [Institut Pprime, Dept. Phys. Mech. Mat., UPR CNRS 3346, ENSMA, Université de Poitiers, 1 av. Clément Ader, Téléport 2, 86961 Futuroscope – Chasseneuil (France)

    2016-07-04

    Silver pastes sintering is a potential candidate for die bonding in power electronic modules. The joints, obtained by sintering, exhibit a significant pore fraction thus reducing the density of the material compared to bulk silver. This was shown to alter drastically the mechanical properties (Young's modulus, yield strength and ultimate tensile stress) at room temperature. While careful analysis of the microstructure has been reported for the as-sintered material, little is known about its quantitative evolution (pores and grains) during thermal ageing. To address this issue, sintered bulk specimens and sintered joints were aged either under isothermal conditions (125 °C up to 1500 h) or under thermal cycling (between −40 °C/+125 °C with 30 min dwell time at each temperature for 2400 cycles). Under these conditions, it is shown that the density of the material does not change but the sub-micron porosity evolves towards a broader size distribution, consistent with Oswald ripening. It is also shown that only the step at 125 °C during the non-isothermal ageing is responsible for the microstructure evolution: isothermal ageing at high temperature can be regarded as a useful tool to perform accelerated ageing tests. Tensile properties are investigated as both a function of ageing time and a function of density. It is shown that the elastic properties do not evolve with the ageing time unlike the plastic properties. This is discussed as a function of the material microstructure evolution.

  2. Effects of particle size and forming pressure on pore properties of Fe-Cr-Al porous metal by pressureless sintering

    Science.gov (United States)

    Koo, Bon-Uk; Yi, Yujeong; Lee, Minjeong; Kim, Byoung-Kee

    2017-03-01

    With increased hydrogen consumption in ammonia production, refining and synthesis, fuel cells and vehicle industries, development of the material components related to hydrogen production is becoming an important factor in industry growth. Porous metals for fabrication of hydrogen are commonly known for their relative excellence in terms of large area, lightness, lower heat capacity, high toughness, and permeability. Fe-Cr-Al alloys not only have high corrosion resistance, heat resistance, and chemical stability but also ductility, excellent mechanical properties. In order to control powder size and sintering temperature effects of Fe-Cr-Al porous metal fabrication, Fe-Cr-Al powder was classified into 25-35 μm, 35-45 μm, 45-75 μm using an auto shaking sieve machine and then classified Fe-Cr-Al powders were pressed into disk shapes using a uniaxial press machine and CIP. The pelletized Fe-Cr-Al specimens were sintered at various temperatures in high vacuum. Properties such as pore size, porosity, and air permeability were evaluated using perm-porosimetry. Microstructure and phase changes were observed with SEM and XRD. Porosity and relative density were proportionated to increasing sintering temperature. With sufficient sintering at increasing temperatures, the pore size is expected to be gradually reduced. Porosity decreased with increasing sintering temperature and gradually increased necking of the powder.

  3. The flavoured BFSS model at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Asano, Yuhma; Filev, Veselin G. [School of Theoretical Physics, Dublin Institute for Advanced Studies,10 Burlington Road, Dublin 4 (Ireland); Kováčik, Samuel [School of Theoretical Physics, Dublin Institute for Advanced Studies,10 Burlington Road, Dublin 4 (Ireland); Faculty of Mathematics, Physics and Informatics,Comenius University Bratislava, Mlynská dolina, Bratislava, 842 48 (Slovakia); O’Connor, Denjoe [School of Theoretical Physics, Dublin Institute for Advanced Studies,10 Burlington Road, Dublin 4 (Ireland)

    2017-01-25

    We study the high-temperature series expansion of the Berkooz-Douglas matrix model, which describes the D0/D4-brane system. At high temperature the model is weakly coupled and we develop the series to second order. We check our results against the high-temperature regime of the bosonic model (without fermions) and find excellent agreement. We track the temperature dependence of the bosonic model and find backreaction of the fundamental fields lifts the zero-temperature adjoint mass degeneracy. In the low-temperature phase the system is well described by a gaussian model with three masses m{sub A}{sup t}=1.964±0.003, m{sub A}{sup l}=2.001±0.003 and m{sub f}=1.463±0.001, the adjoint longitudinal and transverse masses and the mass of the fundamental fields respectively.

  4. Vacuum-sintered body of a novel apatite for artificial bone

    Science.gov (United States)

    Tamura, Kenichi; Fujita, Tatsushi; Morisaki, Yuriko

    2013-12-01

    We produced regenerative artificial bone material and bone parts using vacuum-sintered bodies of a novel apatite called "Titanium medical apatite (TMA®)" for biomedical applications. TMA was formed by chemically connecting a Ti oxide molecule with the reactive [Ca10(PO4)6] group of Hydroxyapatite (HAp). The TMA powders were kneaded with distilled water, and solid cylinders of compacted TMA were made by compression molding at 10 MPa using a stainless-steel vessel. The TMA compacts were dried and then sintered in vacuum (about 10-3 Pa) or in air using a resistance heating furnace in the temperature range 1073-1773 K. TMA compacts were sintered at temperatures greater than 1073 K, thus resulting in recrystallization. The TMA compact bodies sintered in the range 1273-1773 K were converted into mixtures composed of three crystalline materials: α-TCP (tricalcium phosphate), β-TCP, and Perovskite-CaTiO3. The Perovskite crystals were stable and hard. In vacuum-sintering, the Perovskite crystals were transformed into fibers (approximately 1 µm in diameter × 8 µm in length), and the fiber distribution was uniform in various directions. We refer to the TMA vacuum-sintered bodies as a "reinforced composite material with Perovskite crystal fibers." However, in atmospheric sintering, the Perovskite crystals were of various sizes and were irregularly distributed as a result of the effect of oxygen. After sintering temperature at 1573 K, the following results were obtained: the obtained TMA vacuum-sintered bodies (1) were white, (2) had a density of approximately 2300 kg/m3 (corresponding to that of a compact bone or a tooth), and had a thermal conductivity of approximately 31.3 W/(m·K) (corresponding to those of metal or ceramic implants). Further, it was possible to cut the TMA bodies into various forms with a cutting machine. An implant made of TMA and inserted into a rabbit jaw bone was covered by new bone tissues after just one month because of the high

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

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Young-Tae [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Lee, Young-In [Department of Materials Science and Engineering, Seoul National University of Science and Technology, Seoul 01811 (Korea, Republic of); Kim, Seil [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of); Lee, Kun-Jae [Department of Energy Engineering, Dankook University, Cheonan 31116 (Korea, Republic of); Choa, Yong-Ho, E-mail: choa15@hanyang.ac.kr [Department of Fusion Chemical Engineering, Hanyang University, Ansan 15588 (Korea, Republic of)

    2017-02-28

    Highlights: • Hydrogen thermally- and plasma- treatments are applied to reduce and sinter the inkjet-printed copper patterns at low temperature. • Plasma sintered Cu patterns have fully densified microstructure with the resistivity of 3.23 μW cm. • Cu conductive track with dense microstructure remains its electrical resistivity after 1 month. • Thermal sintered Cu patterns show a relatively poor microstructure and high resistivity. - Abstract: 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.

  6. Laser Sintered Calcium Phosphate Bone

    National Research Council Canada - National Science Library

    Vail, Neil

    1999-01-01

    ...) technology selective laser sintering (SLS). BME has successfully implemented a pilot facility to fabricate calcium phosphate implants using anatomical data coupled with the selective laser sintering process...

  7. Application of High Temperature Superconductors to Accelerators

    CERN Document Server

    Ballarino, A

    2000-01-01

    Since the discovery of high temperature superconductivity, a large effort has been made by the scientific community to investigate this field towards a possible application of the new oxide superconductors to different devices like SMES, magnetic bearings, flywheels energy storage, magnetic shielding, transmission cables, fault current limiters, etc. However, all present day large scale applications using superconductivity in accelerator technology are based on conventional materials operating at liquid helium temperatures. Poor mechanical properties, low critical current density and sensitivity to the magnetic field at high temperature are the key parameters whose improvement is essential for a large scale application of high temperature superconductors to such devices. Current leads, used for transferring currents from the power converters, working at room temperature, into the liquid helium environment, where the magnets are operating, represent an immediate application of the emerging technology of high t...

  8. Effect of Sintering Temperature on Microstructure, Chemical Stability and Electrical Properties of Transition Metal or Yb-Doped BaZr0.1Ce0.7Y0.1M0.1O3-δ (M = Fe, Ni, Co and Yb

    Directory of Open Access Journals (Sweden)

    Behzad eMirfakhraei

    2014-03-01

    Full Text Available Perovskite-type BaZr0.1Ce0.7Y0.1M0.1O3-δ (M = Fe, Ni, Co and Yb (BZCY-M oxides were synthesized using the conventional solid-state reaction method at 1350-1550 oC in air in order to investigate the effect of dopants on sintering, crystal structure, chemical stability under CO2 and H2S, and electrical transport properties. The formation of the single-phase perovskite-type structure with an orthorhombic space group Imam was confirmed by Rietveld refinement using powder X-ray diffraction (PXRD for the Fe, Co, Ni and Yb-doped samples. The BZCY-Co and BZCY-Ni oxides show a total electrical conductivity of 0.01 and 8 × 10-3 Scm-1 at 600 oC in wet H2 with an activation energy of 0.36 and 0.41 eV, respectively. Scanning electron microscopy (SEM and energy-dispersive X-ray analysis (EDX revealed Ba and Co rich secondary phase at the grain-boundaries, which may explain the enhancement in the total conductivity of the BZCY-Co. However, ex-solution of Ni at higher sintering temperatures, especially at 1550 oC, decreases the total conductivity of the BZCY-Ni material. The Co and Ni dopants act as a sintering aid and form dense pellets at a lower sintering temperature of 1250 oC. The Fe, Co and Ni-doped BZCY-M samples synthesized at 1350 oC show stability in 30 ppm H2S/H2 at 800 oC, and increasing the firing temperature to 1550 oC, enhanced the chemical stability in CO2 / N2 (1: 2 at 25-900 oC. The BZCY-Co and Ni compounds with high conductivity in wet H2 could be considered as possible anodes for intermediate temperature solid oxide fuel cells (IT-SOFCs.

  9. 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...... have been employed in a simple model for prediction of ash deposit formation, the results of which have been compared to ash deposition formation rates measured at the respective boilers.The ash fusion results were found to directly reflect the ash compositional data:a) Fly ashes and deposits from...

  10. Models of current sintering

    Directory of Open Access Journals (Sweden)

    Angst Sebastian

    2017-01-01

    Full Text Available 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.

  11. Dynamic Model of High Temperature PEM Fuel Cell Stack Temperature

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen

    2007-01-01

    The present work involves the development of a model for predicting the dynamic temperature of a high temperature PEM (HTPEM) fuel cell stack. The model is developed to test different thermal control strategies before implementing them in the actual system. The test system consists of a prototype...... cathode air cooled 30 cell HTPEM fuel cell stack developed at the Institute of Energy Technology at Aalborg University. This fuel cell stack uses PEMEAS Celtec P-1000 membranes, runs on pure hydrogen in a dead end anode configuration with a purge valve. The cooling of the stack is managed by running...... the stack at a high stoichiometric air flow. This is possible because of the PBI fuel cell membranes used, and the very low pressure drop in the stack. The model consists of a discrete thermal model dividing the stack into three parts: inlet, middle and end and predicting the temperatures in these three...

  12. High-temperature heat-pump fluids

    Science.gov (United States)

    Bertinat, M. P.

    1988-05-01

    Heat pumps could be immensely useful in many industrial processes, but standard working fluids are unsuitable for the high temperatures involved. The ideal high-temperature heat-pump fluid should have a high (but not too high) critical temperature, a moderate critical pressure ( approximately=5.0 MPa) and a low (but not too low) boiling point. There are many organic fluids that do meet the above thermodynamic criteria The author's list of 250 contained dozens of them including many of the common laboratory solvents such as ethanol, ether and especially acetone. Unfortunately most of them are highly flammable. The ideal work fluid for high-temperature heat pumps will probably always remain elusive and water, despite its drawbacks will continue to be the best choice in most applications

  13. Silver Ink Formulations for Sinter-free Printing of Conductive Films.

    Science.gov (United States)

    Black, Kate; Singh, Jetinder; Mehta, Danielle; Sung, Sarah; Sutcliffe, Christopher J; Chalker, Paul R

    2016-02-09

    Inkjet printing offers an attractive method for the deposition of metal interconnects in electronic systems and enables a low-cost, environmentally friendly route to manufacture. However, virtually all current metal inkjet processes require post-deposition sintering treatments to achieve the optimum electrical conductivity, because the growth mechanism involves coalescence of discrete nanoparticles. A manufacturing process that reduces the number of steps by directly printing silver, removing the need to sinter the printed metal, would be highly advantageous. Here we describe a, sinter-free process that results in the direct printing of crystalline silver. This process exploits the chemistries developed for Atomic Layer Deposition (ALD), to form the basis of a new ink formulation, which we term; Reactive Organometallic inks (ROM). These ROM ink formulations are capable of depositing low temperature, high conductivity metal films, without the need for subsequent sintering treatments. To reduce the temperature for direct formation of metallic Ag, we have added an alcohol as a catalytic reducing agent to dissociate the organometallic component. Silver films printed from our novel ROM ink, on a glass substrate at 120 °C, are electrically conductive with a typical resistivity as low as 39.2% that of bulk silver, without the need for sintering.

  14. Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

    OpenAIRE

    MARCHI, J.; J.C. Bressiani; Bressiani,A. H. A.

    2001-01-01

    Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polis...

  15. Sintering behaviour and mechanical properties of Cr3C2–NiCr ...

    Indian Academy of Sciences (India)

    Cr3C2–NiCr cermets are used as metal cutting tools due to their relatively high hardness and low sintering temperatures. In this study, a powder mixture consisting of 75 wt% ... Author Affiliations. A Özer1 Y K Tür1. Department of Material Science and Engineering, Gebze Institute of Technology, Gebze, Kocaeli, Turkey ...

  16. Sandia_HighTemperatureComponentEvaluation_2015

    Energy Technology Data Exchange (ETDEWEB)

    Cashion, Avery T. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    The objective of this project is to perform independent evaluation of high temperature components to determine their suitability for use in high temperature geothermal tools. Development of high temperature components has been increasing rapidly due to demand from the high temperature oil and gas exploration and aerospace industries. Many of these new components are at the late prototype or first production stage of development and could benefit from third party evaluation of functionality and lifetime at elevated temperatures. In addition to independent testing of new components, this project recognizes that there is a paucity of commercial-off-the-shelf COTS components rated for geothermal temperatures. As such, high-temperature circuit designers often must dedicate considerable time and resources to determine if a component exists that they may be able to knead performance out of to meet their requirements. This project aids tool developers by characterization of select COTS component performances beyond published temperature specifications. The process for selecting components includes public announcements of project intent (e.g., FedBizOps), direct discussions with candidate manufacturers,and coordination with other DOE funded programs.

  17. Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Chen, I-Wei

    2018-02-02

    Solid oxide fuel cells and solid oxide electrolysis cells rely on solid electrolytes in which a large ionic current dominates. This project was initiated to investigate microstructural changes in such devices under electrochemical forces, because nominally insignificant processes may couple to the large ionic current to yield non-equilibrium phenomena that alter the microstructure. Our studies had focused on yttria-stabilized cubic zirconia (YSZ) widely used in these devices. The experiments have revealed enhanced grain growth at higher temperatures, pore and gas bubble migration at all temperatures, and the latter also lead to enhanced sintering of highly porous ceramics into fully dense ceramics at unprecedentedly low temperatures. These results have shed light on kinetic processes that fall completely outside the realm of classical ceramic processing. Other fast-oxygen oxide ceramics closely related to, and often used in conjunction with zirconia ceramics, have also be investigated, as are closely related scientific problems in zirconia ceramics. These include crystal structures, defects, diffusion kinetics, oxygen potentials, low temperature sintering, flash sintering, and coarsening theory, and all have resulted in greater clarity in scientific understanding. The knowledge is leveraged to provide new insight to electrode kinetics and near-electrode mixed conductivity and to new materials. In the following areas, our research has resulted in completely new knowledge that defines the state-of-the-art of the field. (a) Electrical current driven non-equilibrium phenomena, (b) Enhanced grain growth under electrochemically reducing conditions, (c) Development of oxygen potential polarization in electrically loaded electrolyte, (d) Low temperature sintering and grain growth, and (e) Structure, defects and cation kinetics of fluorite-structured oxides. Our research has also contributed to synthesis of new energy-relevant electrochemical materials and new understanding

  18. Aeronautical applications of high-temperature superconductors

    Science.gov (United States)

    Turney, George E.; Luidens, Roger W.; Uherka, Kenneth; Hull, John

    1989-01-01

    The successful development of high-temperature superconductors (HTS) could have a major impact on future aeronautical propulsion and aeronautical flight vehicle systems. A preliminary examination of the potential application of HTS for aeronautics indicates that significant benefits may be realized through the development and implementation of these newly discovered materials. Applications of high-temperature superconductors (currently substantiated at 95 k) were envisioned for several classes of aeronautical systems, including subsonic and supersonic transports, hypersonic aircraft, V/STOL aircraft, rotorcraft, and solar, microwave and laser powered aircraft. Introduced and described are the particular applications and potential benefits of high-temperature superconductors as related to aeronautics and/or aeronautical systems.

  19. Symposium on high temperature and materials chemistry

    Energy Technology Data Exchange (ETDEWEB)

    1989-10-01

    This volume contains the written proceedings of the Symposium on High Temperature and Materials Chemistry held in Berkeley, California on October 24--25, 1989. The Symposium was sponsored by the Materials and Chemical Sciences Division of Lawrence Berkeley Laboratory and by the College of Chemistry of the University of California at Berkeley to discuss directions, trends, and accomplishments in the field of high temperature and materials chemistry. Its purpose was to provide a snapshot of high temperature and materials chemistry and, in so doing, to define status and directions.

  20. Silicon Carbide Nanotube Oxidation at High Temperatures

    Science.gov (United States)

    Ahlborg, Nadia; Zhu, Dongming

    2012-01-01

    Silicon Carbide Nanotubes (SiCNTs) have high mechanical strength and also have many potential functional applications. In this study, SiCNTs were investigated for use in strengthening high temperature silicate and oxide materials for high performance ceramic nanocomposites and environmental barrier coating bond coats. The high · temperature oxidation behavior of the nanotubes was of particular interest. The SiCNTs were synthesized by a direct reactive conversion process of multiwall carbon nanotubes and silicon at high temperature. Thermogravimetric analysis (TGA) was used to study the oxidation kinetics of SiCNTs at temperatures ranging from 800degC to1300degC. The specific oxidation mechanisms were also investigated.

  1. Low temperature sintering and microwave dielectric properties of MnZrNb{sub 2}O{sub 8} ceramics with H{sub 3}BO{sub 3} addition

    Energy Technology Data Exchange (ETDEWEB)

    Bi, J.X.; Xing, C.F.; Yang, C.H.; Wu, H.T., E-mail: mse_wuht@ujn.edu.cn; Jiang, X.S.

    2016-08-15

    The effects of H{sub 3}BO{sub 3} additions on sintering characteristic, phase composition, microstructure and microwave dielectric properties of MnZrNb{sub 2}O{sub 8} ceramics were investigated. The MnZrNb{sub 2}O{sub 8} ceramics were prepared by the solid-state method. The phase composition, microstructure and elemental composition of the ceramics were studied using X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive Analysis. Only a single-phase MnZrNb{sub 2}O{sub 8} was formed in MnZrNb{sub 2}O{sub 8} ceramics with H{sub 3}BO{sub 3} addition. A small amount of H{sub 3}BO{sub 3} successfully reduced the sintering temperature of MnZrNb{sub 2}O{sub 8} ceramics from 1250 to 1200 °C without much degradation of the microwave dielectric properties. In addition, the τ{sub f} values were shifted to positive direction with the increase of H{sub 3}BO{sub 3} contents. Typically, the MnZrNb{sub 2}O{sub 8} ceramic with 1 wt% H{sub 3}BO{sub 3} sintered at 1250 °C for 4 h exhibited excellent microwave dielectric properties with ε{sub r} = 25.80, Q·f = 28,419 GHz and τ{sub f} = −8.4 ppm/°C. - Highlights: • Addition of H{sub 3}BO{sub 3} reduced the sintering temperature of MnZrNb{sub 2}O{sub 8} ceramics. • The τ{sub f} values were shifted to positive direction with the H{sub 3}BO{sub 3} addition. • The MnZrNb{sub 2}O{sub 8} ceramic with 1 wt% H{sub 3}BO{sub 3} was obtained sintered at 1250 °C for 4 h. • The microwave properties were ε{sub r} = 25.80, Q·f = 28,419 GHz and τ{sub f} = −8.4 ppm/°C.

  2. 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.

  3. High temperature spectral gamma well logging

    Energy Technology Data Exchange (ETDEWEB)

    Normann, R.A.; Henfling, J.A.

    1997-01-01

    A high temperature spectral gamma tool has been designed and built for use in small-diameter geothermal exploration wells. Several engineering judgments are discussed regarding operating parameters, well model selection, and signal processing. An actual well log at elevated temperatures is given with spectral gamma reading showing repeatability.

  4. Microstructural optimization of solid-state sintered silicon carbide

    Science.gov (United States)

    Vargas-Gonzalez, Lionel R.

    Silicon carbide armor, manufactured through solid-state sintering, liquid-phase sintering, and hot-pressing, is being used by the United States Armed Forces for personal and vehicle protection. There is a lack of consensus, however, on which process results in the best-performing ballistic armor. Previous studies have shown that hot-pressed ceramics processed with secondary oxide and/or rare earth oxides, which exhibit high fracture toughness, perform well in handling and under ballistic impact. This high toughness is due to the intergranular nature of the fracture, creating a tortuous path for cracks and facilitating crack deflection and bridging. However, it has also been shown that higher-hardness sintered SiC materials might perform similarly or better to hot-pressed armor, in spite of the large fracture toughness deficit, if the microstructure (density, grain size, purity) of these materials are improved. In this work, the development of theoretically-dense, clean grain boundary, high hardness solid-state sintered silicon carbide (SiC) armor was pursued. Boron carbide and graphite (added as phenolic resin to ensure the carbon is finely dispersed throughout the microstructure) were used as the sintering aids. SiC batches between 0.25--4.00 wt.% carbon were mixed and spray dried. Cylindrical pellets were pressed at 13.7 MPa, cold-isostatically pressed (CIP) at 344 MPa, sintered under varying sintering soaking temperatures and heating rates, and varying post hot-isostatic pressing (HIP) parameters. Carbon additive amounts between 2.0--2.5 wt.% (based on the resin source), a 0.36 wt.% B4C addition, and a 2050°C sintering soak yielded parts with high sintering densities (˜95.5--96.5%) and a fine, equiaxed microstructure (d50 = 2.525 mum). A slow ramp rate (10°C/min) prevented any occurrence of abnormal grain growth. Post-HIPing at 1900°C removed the remaining closed porosity to yield a theoretically-dense part (3.175 g/cm3, according to rule of mixtures). These

  5. Investigation of mechanical properties based on grain growth and microstructure evolution of alumina ceramics during two step sintering process

    Science.gov (United States)

    Khan, U. A.; Hussain, A.; Shah, M.; Shuaib, M.; Qayyum, F.

    2016-08-01

    Alumina ceramics having small grain size and high density yield good mechanical properties, which are required in most mechanical applications. Two Step Sintering (TSS) is used to develop dense alumina ceramics. In this research work the effect of sintering temperatures on microstructure and density of the alumina specimens developed by using TSS has been investigated. It has been observed that TSS is more efficient in controlling grain growth and increasing the density as compared to One Step Sintering (OSS) of alumina. Scanning electron micrographs of sintered alumina specimens have been compared. It has been observed that TSS proves to be a better technique for increasing density and controlling grain growth of alumina ceramics than OSS. More relative density, hardness, fracture toughness and small grain size was achieved by using TSS over OSS technique.

  6. Effects of bonding temperature on microstructure, fracture behavior and joint strength of Ag nanoporous bonding for high temperature die attach

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Su, E-mail: mskim927@gmail.com [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Nishikawa, Hiroshi [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2015-10-01

    Ag nanoparticle sintering has received much attention as an alternative joining method to lead-based soldering for high temperature electronic applications. However, there are still certain issues with this method, such as difficulties of in controlling the joining layer thickness and the occurrence of unexpected voids resulting from solvent evaporation. In this study, the effect of bonding temperature (200–400 °C) and environment (air and N{sub 2}) on the joint strength of Ag nanoporous bonding (NPB) on electroless nickel/immersion gold finished Cu disks was investigated. A nanoporous Ag sheet fabricated using dealloying method from an Al–Ag precursor was adopted as the insert material. The NPB was conducted at various temperatures (200–400 °C) for 30 min at a pressure of 20 MPa in both air and N{sub 2} environments. The joint strength of NPB was closely related with the microstructure of the Ag layer and the fracture mode of the joint, and increased with increasing bonding temperature through the formation of strong interface and a coarsened Ag layer. The effect of the bonding environment was not significant, except in the case of bonding temperature of 400 °C.

  7. New Oxide Materials for an Ultra High Temperature Environment

    Energy Technology Data Exchange (ETDEWEB)

    Perepezko, John H. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Materials Science and Engineering

    2017-11-13

    In this project, a new oxide material, Hf6Ta2O17 has been successfully synthesized by the controlled oxidization of Hf-Ta alloys. This oxide exhibits good oxidation resistance, high temperature phase stability up to more than 2000°C, low thermal conductivity and thus could serve as a component or a coating material in an ultrahigh temperature environment. We have examined the microstructure evolution and phase formation sequence during the oxidation exposure of Hf-Ta alloys at 1500°C and identified that the oxidation of a Hf-26.7atomic %Ta alloy leads to the formation of a single phase adherent Hf6Ta2O17 with a complex atomic structure i.e. superstructure. The overall reactive diffusion pathway is consistent with the calculated Hf-Ta-O ternary phase diagram. Besides the synthesis of Hf6Ta2O17 superstructure by oxidizing Hf-Ta alloys, we have also developed a synthesis method based upon the reactive sintering of the correct ratios of mixed powders of HfO2 and Ta2O5 and verified the low thermal conductivity of Hf6Ta2O17 superstructure on these samples. We have completed a preliminary analysis of the oxidation kinetics for Hf6Ta2O17, which shows an initial parabolic oxidation kinetics.

  8. Novel High Temperature Strain Gauge Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced high-temperature sensor technology and bonding methods are of great interests in designing and developing advanced future aircraft. Current state-of-the-art...

  9. High Temperature Fiberoptic Thermal Imaging System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase 1 program will fabricate and demonstrate a small diameter single fiber endoscope that can perform high temperature thermal imaging in a jet engine...

  10. High Temperature Capacitors for Venus Exploration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High temperature power electronics have become a vital aspect of future designs for power converters in spacecraft, battle zone electric power, satellite power...

  11. Ion Based High-Temperature Pressure Sensor

    National Research Council Canada - National Science Library

    Zdenek, Jeffrey S; Anthenien, Ralph A

    2004-01-01

    .... The environment encountered in such engines necessitates high temperature and durable (vibration resistant) devices. Traditional pressure sensors can be used, however thermal insulating materials must be used to protect the diaphragm...

  12. NASA High Operating Temperature Technology Program Overview

    Science.gov (United States)

    Nguyen, Q. V.; Hunter, G. W.

    2017-11-01

    NASA’s Planetary Science Division has begun the High Operating Temperature Technology (HOTTech) program to address Venus surface technology challenges by investing in new technology development. This presentation reviews this HOTTech program.

  13. Panel report on high temperature ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Nolet, T C [ed.

    1979-01-01

    Fundamental research is reported concerning high temperature ceramics for application in turbines, engines, batteries, gasifiers, MHD, fuel cells, heat exchangers, and hot wall combustors. Ceramics microstructure and behavior are included. (FS)

  14. Solution spinning of high-T{sub c} oxide superconductors: part VII. The effect of polyvinyl alcohol spinning medium on the sintering of YBa{sub 2}Cu{sub 3}O{sub x} superconducting filaments

    Energy Technology Data Exchange (ETDEWEB)

    Tomita, Hisayo [Suzuka Junior College, 1250 Shono, Suzuka, Mie 513 (Japan); Goto, Tomoko; Takahashi, Kiyohisa [Department of Material Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466 (Japan)

    1996-05-01

    As basic research for the solution spinning of high-T{sub c} oxide superconductor, the effect of poly(vinyl alcohol) (PVA) spinning medium on the sintering of YBa{sub 2}Cu{sub 3}O{sub x} filament was examined. A precursor filament was produced by dry-spinning starting from a homogeneous aqueous PVA solution of Y, Ba and Cu acetates. The as-drawn filament was pyrolysed to remove volatile components and sintered to generate a superconducting phase. The degree of polymerization (DP) of PVA and the content of acetates in the precursor filament affected the J{sub c} of the sintered filament. Although most filaments exhibited high J{sub c} greater than 10{sup 3} A cm{sup -3} at 77 K and 0 T, superconductivity above 77 K was not observed for the filament spun from PVA solution of DP=2450 with [acetates]/[PVA]=2 and sintered at 900 and 920{sup 0}C for 15 min. The filament had a dense structure due to liquid phase sintering. The filament with high J{sub c} had a skin-core structure, and the highest J{sub c} of 4.3x10{sup 3} A cm{sup -2} at 77 K and 0 T was attained for the filament from DP=3500 with [acetates]/[PVA]=4. (author)

  15. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  16. Mechanical Proprieties of Steel at High Temperatures

    Directory of Open Access Journals (Sweden)

    Ana-Diana Ancaş

    2005-01-01

    Full Text Available The experimental test results obtained in the study of steel mechanical proprieties variation in case of high temperatures (fire are presented. The proprieties are referring to: Young’s modulus, E, the elastic limit, σe, and the characteristic diagram of the material (the rotation stress-strain. Theoretical laws that the model the steel behaviour at high temperature have been elaborated based on the most significant studies presented in the literature.

  17. High temperature superconductors and other superfluids

    CERN Document Server

    Alexandrov, A S

    2017-01-01

    Written by eminent researchers in the field, this text describes the theory of superconductivity and superfluidity starting from liquid helium and a charged Bose-gas. It also discusses the modern bipolaron theory of strongly coupled superconductors, which explains the basic physical properties of high-temperature superconductors. This book will be of interest to fourth year graduate and postgraduate students, specialist libraries, information centres and chemists working in high-temperature superconductivity.

  18. Spark plasma sintering of MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite thermistor ceramics and a comparison investigation with conventional sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bo; Zhao, Qing [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Chang, Aimin, E-mail: changam@ms.xjb.ac.cn [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Wu, Yiquan, E-mail: wuy@alfred.edu [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, NY 14802 (United States); Li, Hongyi [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics & Chemistry of CAS, Urumqi 830011 (China); Product Quality Supervision and Inspection Institute of Xinjiang Uygur Autonomous Region, Urumqi 830013 (China)

    2016-08-05

    The microstructure and negative temperature coefficient (NTC) electrical properties of the MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite ceramics prepared by spark plasma sintering (SPS) were investigated. The effects of SPS and conventional sintering (CS) on electrical properties and high temperature aging characteristics of 0.6MgAl{sub 2}O{sub 4}–0.4LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} ceramics were comparatively studied. X-ray diffraction (XRD) results showed both SPS- and CS-sintered ceramics were indexed to be cubic spinel MgAl{sub 2}O{sub 4} phase and orthorhombic perovskite LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} phase isomorphic to LaCrO{sub 3}. Microstructural study reveled that SPS-sintered specimens had a higher relative density more than 96%. The electrical properties of the SPS-sintered NTC thermistors could be adjusted by changing MgAl{sub 2}O{sub 4} content and sintering temperature. The SPS-sintered samples possessed a higher resistivity than that from conventionally sintered ceramics. The reasons for the increase of resistivity in the SPS-sintered samples, and the aging mechanism of the thermistor ceramics were investigated through applying the defect chemistry theory. - Highlights: • MgAl{sub 2}O{sub 4}–LaCr{sub 0.5}Mn{sub 0.5}O{sub 3} composite ceramics have been successfully fabricated by SPS. • Comparison investigation has been performed on the SPS- and CS-sintered ceramics. • The NTC electrical properties of these composite ceramics have been investigated. • The aging mechanism of the thermistor ceramics has been investigated.

  19. Laser Plasma Coupling for High Temperature Hohlraums

    Energy Technology Data Exchange (ETDEWEB)

    Kruer, W.

    1999-11-04

    Simple scaling models indicate that quite high radiation temperatures can be achieved in hohlraums driven with the National Ignition Facility. A scaling estimate for the radiation temperature versus pulse duration for different size NIF hohlraums is shown in Figure 1. Note that a radiation temperature of about 650 ev is projected for a so-called scale 1 hohlraum (length 2.6mm, diameter 1.6mm). With such high temperature hohlraums, for example, opacity experiments could be carried out using more relevant high Z materials rather than low Z surrogates. These projections of high temperature hohlraums are uncertain, since the scaling model does not allow for the very strongly-driven laser plasma coupling physics. Lasnex calculations have been carried out to estimate the plasma and irradiation conditions in a scale 1 hohlraum driven by NIF. Linear instability gains as high as exp(100) have been found for stimulated Brillouin scattering, and other laser-driven instabilities are also far above their thresholds. More understanding of the very strongly-driven coupling physics is clearly needed in order to more realistically assess and improve the prospects for high temperature hohlraums. Not surprisingly, this regime has been avoided for inertial fusion applications and so is relatively unexplored.

  20. Electrons and Phonons in High Temperature Superconductors

    Directory of Open Access Journals (Sweden)

    Anu Singh

    2013-01-01

    Full Text Available The defect-induced anharmonic phonon-electron problem in high-temperature superconductors has been investigated with the help of double time thermodynamic electron and phonon Green’s function theory using a comprehensive Hamiltonian which includes the contribution due to unperturbed electrons and phonons, anharmonic phonons, impurities, and interactions of electrons and phonons. This formulation enables one to resolve the problem of electronic heat transport and equilibrium phenomenon in high-temperature superconductors in an amicable way. The problem of electronic heat capacity and electron-phonon problem has been taken up with special reference to the anharmonicity, defect concentration electron-phonon coupling, and temperature dependence.

  1. Phase transformations during sintering of mechanically alloyed TiPt

    CSIR Research Space (South Africa)

    Nxumalo, S

    2010-10-01

    Full Text Available of Mining and Metallurgy Advanced Metals Initiative Light Metals Conference 2010 S Nxumalo, H K Chikwanda and C Machio Page 306 PHASE TRANSFORMATIONS DURING SINTERING OF MECHANICALLY ALLOYED TIPT S Nxumalo, H K Chikwanda and C Machio.... It undergoes a transformation from high temperature β-TiPt to low temperature α- TiPt as shown in the phase diagram when slow cooling conditions are used7. However, when non equilibrium conditions of cooling are used such quenching (fast cooling) β...

  2. 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.

  3. Strain rate dependency of laser sintered polyamide 12

    Directory of Open Access Journals (Sweden)

    Cook J.E.T.

    2015-01-01

    Full Text Available Parts processed by Additive Manufacturing can now be found across a wide range of applications, such as those in the aerospace and automotive industry in which the mechanical response must be optimised. Many of these applications are subjected to high rate or impact loading, yet it is believed that there is no prior research on the strain rate dependence in these materials. This research investigates the effect of strain rate and laser energy density on laser sintered polyamide 12. In the study presented here, parts produced using four different laser sintered energy densities were exposed to uniaxial compression tests at strain rates ranging from 10−3 to 10+3 s−1 at room temperature, and the dependence on these parameters is presented.

  4. Strain rate dependency of laser sintered polyamide 12

    Science.gov (United States)

    Cook, J. E. T.; Goodridge, R. D.; Siviour, C. R.

    2015-09-01

    Parts processed by Additive Manufacturing can now be found across a wide range of applications, such as those in the aerospace and automotive industry in which the mechanical response must be optimised. Many of these applications are subjected to high rate or impact loading, yet it is believed that there is no prior research on the strain rate dependence in these materials. This research investigates the effect of strain rate and laser energy density on laser sintered polyamide 12. In the study presented here, parts produced using four different laser sintered energy densities were exposed to uniaxial compression tests at strain rates ranging from 10-3 to 10+3 s-1 at room temperature, and the dependence on these parameters is presented.

  5. Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

    Directory of Open Access Journals (Sweden)

    J. Marchi

    2001-10-01

    Full Text Available Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polished/etched samples was carried out with help of scanning electron microscopy. Silicon carbide ceramics with more than 90% of the theoretical density were obtained by pressureless sintering if a suitable proportion of the additives is used.

  6. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  7. Neutron experiments on high-temperature superconductors

    Science.gov (United States)

    Mook, H. A., Jr.

    1989-12-01

    This report details the trip to the ILL to perform neutron scattering research on high-temperature superconductivity. The trip was very successful because of the excellent users' facilities available at the ILL. The data we accumulated were of high quality and will make an impact on our understanding of high-temperature superconductivity. However, we cannot continue to run a research program in this field with the limited beam time available at the ILL. To make substantial progress in this field, we must restart the High Flux Isotope Reactor.

  8. High Temperature, Wireless Seismometer Sensor for Venus

    Science.gov (United States)

    Ponchak, George E.; Scardelletti, Maximilian C.; Taylor, Brandt; Beard, Steve; Meredith, Roger D.; Beheim, Glenn M.; Hunter Gary W.; Kiefer, Walter S.

    2012-01-01

    Space agency mission plans state the need to measure the seismic activity on Venus. Because of the high temperature on Venus (462? C average surface temperature) and the difficulty in placing and wiring multiple sensors using robots, a high temperature, wireless sensor using a wide bandgap semiconductor is an attractive option. This paper presents the description and proof of concept measurements of a high temperature, wireless seismometer sensor for Venus. A variation in inductance of a coil caused by the movement of an aluminum probe held in the coil and attached to a balanced leaf-spring seismometer causes a variation of 700 Hz in the transmitted signal from the oscillator/sensor system at 426? C. This result indicates that the concept may be used on Venus.

  9. Sintering of bi-layered porous structures: Stress development and shape evolution

    DEFF Research Database (Denmark)

    Ni, De Wei; Esposito, Vincenzo; Ramousse, Severine

    viscosity of layers was determined as a function of temperature and density using a vertical sintering approach. The distortion in the bi-layer configurations was experimentally recorded and compared with the analytical calculations. The sintering mismatch stress was calculated from both the camber......Ce0.9Gd0.1O1.95 (CGO) and (La, Sr)MnO3 (LSM) are electro-ceramics materials with high potential for several electrochemical applications such as solid Oxide Fuel Cell (SOFC), gas separation membranes, and flue gas purification application. In the latter case, these materials are shaped as thick...

  10. High-temperature granulites and supercontinents

    Directory of Open Access Journals (Sweden)

    J.L.R. Touret

    2016-01-01

    Full Text Available The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature (P-T conditions of (ultra high-temperature granulites and magmatic rocks are similar. Continents grow laterally, by magmatic activity above oceanic subduction zones (high-pressure metamorphic setting, and vertically by accumulation of mantle-derived magmas at the base of the crust (high-temperature metamorphic setting. Both events are separated from each other in time; the vertical accretion postdating lateral growth by several tens of millions of years. Fluid inclusion data indicate that during the high-temperature metamorphic episode the granulite lower crust is invaded by large amounts of low H2O-activity fluids including high-density CO2 and concentrated saline solutions (brines. These fluids are expelled from the lower crust to higher crustal levels at the end of the high-grade metamorphic event. The final amalgamation of supercontinents corresponds to episodes of ultra-high temperature metamorphism involving large-scale accumulation of these low-water activity fluids in the lower crust. This accumulation causes tectonic instability, which together with the heat input from the sub-continental lithospheric mantle, leads to the disruption of supercontinents. Thus, the fragmentation of a supercontinent is already programmed at the time of its amalgamation.

  11. Effects of sintering on microstructure and dielectric response in ...

    Indian Academy of Sciences (India)

    Abstract. Effects of sintering on pore morphology and dielectric response have been investigated. Pore structure has been probed by small angle neutron scattering (SANS). It has been observed that the size distribution becomes less polydisperse with a slight modification in the distribution as sintering temperature is ...

  12. HIGH TEMPERATURE HIGH PRESSURE THERMODYNAMIC MEASUREMENTS FOR COAL MODEL COMPOUNDS

    Energy Technology Data Exchange (ETDEWEB)

    Vinayak N. Kabadi

    1999-02-20

    It is well known that the fluid phase equilibria can be represented by a number of {gamma}-models , but unfortunately most of them do not function well under high temperature. In this calculation, we mainly investigate the performance of UNIQUAC and NRTL models under high temperature, using temperature dependent parameters rather than using the original formulas. the other feature of this calculation is that we try to relate the excess Gibbs energy G{sup E}and enthalpy of mixing H{sup E}simultaneously. In other words, we will use the high temperature and pressure G{sup E} and H{sup E}data to regress the temperature dependant parameters to find out which model and what kind of temperature dependant parameters should be used.

  13. Temperature and high pressure effects on the structural features of catalytic nanocomposites oxides by Raman spectroscopy.

    Science.gov (United States)

    da Silva, Antonio N; Pinto, Raffael C F; Freire, Paulo T C; Junior, Jose Alves L; Oliveira, Alcineia C; Filho, Josué M

    2015-03-05

    Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600°C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Electro sinter forging of titanium disks

    DEFF Research Database (Denmark)

    Cannella, Emanuele; Nielsen, Chris Valentin; Bay, Niels Oluf

    Electro sinter forging (ESF) is a new sintering process based on the principle of electrical Joule heating. In the present work, middle frequency direct current (MFDC) was flowing through the powder compact, which was under mechanical pressure. The main parameters are the high electrical current......, up to 10 kA, and the low voltage, 1-2 V, resulting in heat generation in the powder. Figure 1 shows the experimental setup. The punches were made of a conductive material; namely a copper alloy. The die, which has to be electrically insulating, was made of alumina. The ESF process takes 3-4s...... including the following phases: (i) feeding of powder (ii) pre-compaction (iii) heating by electrical current during 100-200ms (iv) cooling (v) ejection. Figure 2 shows an example of measured pressure and current during sintering of the sample shown in Figure 3. As compared to conventional sintering [1...

  15. Effect of additives in reducing ash sintering and slagging in biomass combustion applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liang

    2012-07-01

    The objective of this study was to investigate sintering and slagging behaviors of biofuels during combustion processes. Biofuels tested are derived from the agricultural sector, wood and furniture industry as well as from municipal sewage sludge. It was also the aim to test and evaluate additives that can prevent and abate biomass ash sintering by conducting laboratory and industrial scale tests. Sintering characteristics of sewage sludge ashes at elevated temperatures were investigated by means of different laboratory methods. Utilizing of phosphorus participation agents Al2(SO4)3 or Fe2(SO4)3 caused substantially high contents of aluminum or iron in the studied sewage sludge ashes, respectively. High initial melting temperatures over 1100 degrees C and low sintering tendencies were observed from the sewage sludge ashes rich in aluminum. It was related to presence and formation of the inert mineral phases such as aluminum oxide, quartz and calcium aluminum silicates in the aluminum rich sewage sludge ashes at elevated temperatures. A low melting temperature, about 994 degree C, was detected from the iron rich sewage sludge ash. Severe sintering of this sewage sludge ash was mainly due to generation of low temperature melting iron silicates, as results of interaction and re-assemblage of hematite (Fe2O3), quartz (SiO2) and alkali feldspars under heating. Fusion behaviors of corn cob ashes under rising temperatures were characterized. The work revealed that chemical compositions of corn cob ashes are dominated by potassium, silicon, chlorine and phosphorus. However, the relative concentrations of these principal elements are considerably different for three studied corn cob ashes, which have major influence on ash transformation reactions and sintering tendencies. Compared with the other two, the chemical composition of the Waimanalo corn cob (WCob) was characterized with the highest K/Cl, Si/(Ca+Mg) and (Si+P+K)/(Ca+Mg) molar ratios, which was favorable for

  16. Low Temperature Heating and High Temperature Cooling in Buildings

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk

    , a single-family house designed for plus-energy targets and equipped with a radiant water-based floor heating and cooling system was studied by means of full-scale measurements, dynamic building simulations and thermodynamic evaluation tools. Thermal indoor environment and energy performance of the house......A heating and cooling system could be divided into three parts: terminal units (emission system), distribution system, and heating and cooling plant (generation system). The choice of terminal unit directly affects the energy performance, and the indoor environment in that space. Therefore......, a holistic system evaluation is necessary to ensure an optimal indoor environment for the occupants and to achieve energy efficiency simultaneously. Low temperature heating and high temperature cooling systems are one of the possible approaches to heat or cool indoor spaces in buildings. In this thesis...

  17. Effect of the quantity of carbonate components and sintering parameters on the quality of hydrothermally synthesized carbonate hydroxyapatite

    Science.gov (United States)

    Ruddyard, A. A.; Soejoko, D. S.; Nurlely

    2017-07-01

    Carbonated hydroxyapatite is a biomaterial with high biocompatibility with human bone, moreso than regular hydroxyapatite, making it an acceptable synthetic bone graft material. The purpose of this research is to study the effect of sintering temperature and time on carbonated hydroxyapatite samples synthesized using a hydrothermal method with CaCO3 as one of its components. The samples are then characterized using Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, and Scanning Electron Microscope. Infrared (IR) spectra showed that the CO3 content in each sample is proportional to the amount of CaCO3 used during synthesis. X-Ray Diffraction (XRD) patterns showed an increase in apatite content and a decrease in calcite content as sintering temperature and time increases, with temperature increases having a stronger effect on the samples than time increases. Calcite disappears completely after sintering at 900 °C for 2 hours.

  18. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

    Science.gov (United States)

    Kolte, Jayant; Salame, Paresh H.; Daryapurkar, A. S.; Gopalan, P.

    2015-09-01

    In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ¯ ≈ 10 n m ). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ˜1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher's power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (˜180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS) we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC) leading to high dielectric constant in microwave sintered BFO.

  19. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3, synthesized by microwave sintering

    Directory of Open Access Journals (Sweden)

    Jayant Kolte

    2015-09-01

    Full Text Available In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ̄   ≈ 10   n m . Microwave sintering resulted in reducing the sintering time substantially (by 1h, and has resulted in submicron sized grains and high resistivity ∼1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher’s power law behavior, suggesting correlated barrier hopping (CBH mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (∼180 °C indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC leading to high dielectric constant in microwave sintered BFO.

  20. Spark Plasma Sintered AlN-BN Composites and Its Thermal Conductivity

    NARCIS (Netherlands)

    Zhao Haiyang, [No Value; Wang Weimin, [No Value; Wang Hao, [No Value; Fu Zhengyi, [No Value

    2008-01-01

    A series of samples of hexagonal boron nitride-aluminum nitride ceramic composites with different amounts of CaF(2) as sintering aid were prepared by spark plasma sintered at 1700-1850 degrees C for 5 min. The addition of CaF(2) effectively lowered the sintering temperature and promoted the