Integrated analysis of oxide nuclear fuel sintering

International Nuclear Information System (INIS)

Baranov, V.; Kuzmin, R.; Tenishev, A.; Timoshin, I.; Khlunov, A.; Ivanov, A.; Petrov, I.

2011-01-01

Dilatometric and thermal-gravimetric investigations have been carried out for the sintering process of oxide nuclear fuel in gaseous Ar - 8% H 2 atmosphere at temperatures up to 1600 0 C. The pressed compacts were fabricated under real production conditions of the OAO MSZ with application of two different technologies, so called 'dry' and 'wet' technologies. Effects of the grain size growth after the heating to different temperatures were observed. In order to investigate the effects produced by rate of heating on properties of sintered fuel pellets, the heating rates were varied from 1 to 8 0 C per minute. Time of isothermal overexposure at maximal temperature (1600 0 C) was about 8 hours. Real production conditions were imitated. The results showed that the sintering process of the fuel pellets produced by two technologies differs. The samples sintered under different heating rates were studied with application of scanning electronic microscopy analysis for determination of mean grain size. A simulation of heating profile for industrial furnaces was performed to reduce the beam cycles and estimate the effects of variation of the isothermal overexposure temperatures. Based on this data, an optimization of the sintering conditions was performed in operations terms of OAO MSZ. (authors)

Effect of process parameters on surface oxides on chromium-alloyed steel powder during sintering

International Nuclear Information System (INIS)

Chasoglou, D.; Hryha, E.; Nyborg, L.

2013-01-01

The use of chromium in the PM steel industry today puts high demands on the choice and control of the atmosphere during the sintering process due to its high affinity to oxygen. Particular attention is required in order to control the surface chemistry of the powder which in turn is the key factor for the successful sintering and production of PM parts. Different atmosphere compositions, heating rates and green densities were employed while performing sintering trials on water atomized steel powder pre-alloyed with 3 wt.% Cr in order to evaluate the effect on surface chemical reactions. Fracture surfaces of sintered samples were examined using high resolution scanning electron microscopy combined with X-ray microanalysis. The investigation was complemented with thermogravimetric (TG) studies. Reaction products in particulate form containing strong-oxide forming elements such as Cr, Si and Mn were formed during sintering for all conditions. Processing in vacuum results in intensive inter-particle neck development during the heating stage and consequently in the excessive enclosure of surface oxide which is reflected in less good final mechanical properties. Enhanced oxide reduction was observed in samples processed in hydrogen-containing atmospheres independent of the actual content in the range of 3–10 vol.%. An optimum heating rate was required for balancing reduction/oxidation processes. A simple model for the enclosure and growth of oxide inclusions during the sinter-neck development is proposed. The obtained results show that significant reduction of the oxygen content can be achieved by adjusting the atmosphere purity/composition. - Highlights: ► A local atmosphere microclimate is very important for sintering of PM steels. ► High risk of surface oxide enclosure between 800 and 1000 °C. ► Coalescence and agglomeration of enclosed oxides take place during sintering. ► The effect of different process parameters on the oxide reduction is examined. ► A

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.

Hot-pressed silicon nitride with various lanthanide oxides as sintering additives

Science.gov (United States)

Ueno, K.; Toibana, Y.

1984-01-01

The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.

Highly transparent Tb3Al5O12 magneto-optical ceramics sintered from co-precipitated powders with sintering aids

Science.gov (United States)

Dai, Jiawei; Pan, Yubai; Xie, Tengfei; Kou, Huamin; Li, Jiang

2018-04-01

Highly transparent terbium aluminum garnet (Tb3Al5O12, TAG) magneto-optical ceramics were fabricated from co-precipitated nanopowders with tetraethoxysilane (TEOS) as sintering aid by vacuum sintering combined with hot isostatic pressing (HIP) post-treatment. The ball milled TAG powder shows better dispersity than the as-synthesized powder, and its average particle size is about 80 nm. For the ceramic sample pre-sintered at 1720 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the in-line transmittance exceeds 76% in the region of 400-1580nm (except the absorption band), reaching a maximum value of 81.8% at the wavelength of 1390 nm. The microstructure of the TAG ceramic is homogeneous and its average grain size is approximately 19.7 μm. The Verdet constant of the sample is calculated to be -182.7 rad·T-1·m-1 at room temperature.

Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma

International Nuclear Information System (INIS)

Yar, Mazher Ahmed; Wahlberg, Sverker; Bergqvist, Hans; Salem, Hanadi G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

High purity W and W-0.9La 2 O 3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 o C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals.

Optimization of thorium oxalate precipitation conditions relative to thorium oxide sinterability

International Nuclear Information System (INIS)

White, G.D.; Bray, L.A.; Hart, P.E.

1980-01-01

The effect of thorium oxalate precipitation conditions on derived oxide sinterability was investigated with the objective of producing ThO 2 powder that could be sintered to high density without premilling. Precipitation conditions examined were temperature, digestion time and agitation method which were employed in a two-level factorial experimental design to delineate their effects. The two levels for each of the factors, respectively, were 10 0 C and 70 0 C, 15 min and 360 min, and mechanical stirrer and a homogenizer that imparted both mechanical and ultrasonic agitation. The ThO 2 derived from each of the precipitation trials was characterized with respect to morphology, surface area, and crystallite size as well as sinterability. Only precipitation temperature had a significant effect upon all the properties of the derived oxide powders

Manufacture of sintered bricks of high density from beryllium oxide

International Nuclear Information System (INIS)

Pointud, R.; Rispal, Ch.; Le Garec, M.

1959-01-01

Beryllium oxide bricks of nuclear purity 100 x 100 x 50 and 100 x 100 x 100 mm of very high density (between 2.85 and 3.00) are manufactured by sintering under pressure in graphite moulds at temperatures between 1,750 and 1,850 deg. C, and under a pressure of 150 kg/cm 2 . The physico-chemical state of the saw material is of considerable importance with regard to the success of the sintering operation. In addition, a study of the sintering of a BeO mixture with 3 to 5 per cent of boron introduced in the form of boric acid, boron carbide or elementary boron shows that high densities can only be obtained by sintering under pressure. For technical reasons of manufacture, only the mixture based on boron carbide is used. The sintering is carried out in graphite moulds at 1500 deg. C under 150 kg/cm 2 pressure, and bricks can be obtained with density between 2,85 and 2,90. Laboratory studies and the industrial manufacture of various sinters are described in detail. (author) [fr

Sintering of uranium oxide of high specific surface area

International Nuclear Information System (INIS)

Bel, Alain; Francois, Bernard; Delmas, Roger; Caillat, Roger

1959-01-01

The extent to which a uranium oxide powder deriving from ammonium uranate or uranium peroxide lends itself to the sintering process depends largely on its specific surface area. When this is greater than 5 m 2 / g there is an optimum temperature for sintering in hydrogen. This temperature becomes less as the specific area of the powder is greater. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 249, p. 1045-1047, sitting of 21 September 1959 [fr

Ferritic oxide dispersion strengthened alloys by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Allahar, Kerry N., E-mail: KerryAllahar@boisestate.edu [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Burns, Jatuporn [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Jaques, Brian [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Wu, Y.Q. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States); Charit, Indrajit [Department of Chemical and Materials Engineering, University of Idaho, McClure Hall Room 405D, Moscow, ID 83844 (United States); Cole, James [Idaho National Laboratory, Idaho Falls, ID 83401 (United States); Butt, Darryl P. [Materials and Science Engineering Department, Boise State University, 1910 University Blvd., Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Blvd., Idaho Falls, ID 83401 (United States)

2013-11-15

Spark plasma sintering (SPS) was used to consolidate a Fe–16Cr–3Al (wt.%) powder that was mechanically alloyed with Y{sub 2}O{sub 3} and Ti powders to produce 0.5 Y{sub 2}O{sub 3} and 0.5 Y{sub 2}O{sub 3}–1Ti powders. The effects of mechanical alloying and sintering conditions on the microstructure, relative density and hardness of the sintered oxide dispersion strengthened (ODS) alloys are presented. Scanning electron microscopy indicated a mixed fine-grain and coarse-grain microstructure that was attributed to recrystallization and grain growth during sintering. Analysis of the transmission electron microscopy (TEM) and atom probe tomography (APT) data identified Y–O and Y–O–Ti nanoclusters. Elemental ratios of these nanoclusters were consistent with that observed in hot-extruded ODS alloys. The influence of Ti was to refine the grains as well as the nanoclusters with there being greater number density and smaller sizes of the Y–O–Ti nanoclusters as compared to the Y–O nanoclusters. This resulted in the Ti-containing samples being harder than the Ti-free alloys. The hardness of the alloys with the Y–O–Ti nanoclusters was insensitive to sintering time while smaller hardness values were associated with longer sintering times for the alloys with the Y–O nanoclusters. Pressures greater than 80 MPa are recommended for improved densification as higher sintering temperatures and longer sintering times at 80 MPa did not improve the relative density beyond 97.5%.

The harmful effects of sintering aids in Pr:LuAG optical ceramic scintillator

Czech Academy of Sciences Publication Activity Database

Shen, Y.; Shi, Y.; Feng, X.; Pan, Y.; Li, J.; Zeng, J.-Y.; Nikl, Martin; Krasnikov, A.; Vedda, A.; Moretti, F.

2012-01-01

Roč. 95, č. 7 (2012), s. 2130-2132 ISSN 0002-7820 R&D Projects: GA MŠk LH12185 Institutional research plan: CEZ:AV0Z10100521 Keywords : scintillator * optical ceramics * sintering aids * luminescence Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.107, year: 2012

Sintering of beryllium oxide; Frittage de l'oxyde de beryllium

Energy Technology Data Exchange (ETDEWEB)

Caillat, R; Pointud, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1955-07-01

This study had for origin to find a process permitting to manufacture bricks of beryllium oxide of pure nuclear grade, with a density as elevated as possible and with standardized shape. The sintering under load was the technique kept for the manufacture of the bricks. Because of the important toxicity of the beryllium oxide, the general features for the preliminary study of the sintering, have been determined while using alumina. The obtained results will be able to act as general indication for ulterior studies with sintering under load. (M.B.) [French] Cette etude a eu pour origine la recherche d'un procede permettant de fabriquer industriellement des briques d'oxyde de beryllium nucleaireraent pures, de densite aussi elevee que possible et de forme standardisee. Le frittage sous charge fut la technique retenue pour la fabrication des briques. En raison de la grande toxicite de l'oxyde de beryllium, les caracteristiques generales du frittage, pour l'etude preliminaire, ont ete determine en utilisant de l'alumine. Les resultats obtenus pourront servir d'indication generale pour des etudes ulterieurs avec frittage sous charge. (M.B.)

Influence of sintering atmospheres on the aluminium sintering characteristics

International Nuclear Information System (INIS)

Mintzer, S.; Bermudez Belkys, S.

1993-01-01

This paper describes the aluminium powder (Al) cool compacted (at 95% from theoretical density) which was sintered at 903 K during 4 hours at different atmospheres; oxidizing (air), inert Argon (Ar), Nitrogen (N) and high vacuum. The results obtained show: a) porosity measurements; greater porosity when sintering in Ar and air. b) Metallographic and Scanning observations: many fine pores (< 1 μm) and pore lines distributed at random, at air sintering and greater pores distributed preferentially near the surface, in Ar and N atmospheres. c) Dimensional changes: tendency to contraction of the samples at N and vacuum sintering and expansion in Ar or air. d) Mechanical properties: greater strength and fluence stresses at air and N sintering. The analysis of the results is performed considering sintering modes in presence of an oxide layer and dropped inert gases. (Author)

Sintering of uranium dioxide pellets (UO2) in an oxidizing atmosphere (C O2)

International Nuclear Information System (INIS)

Santos, G.R.T.

1992-01-01

This work consists in the study of the sintering process of U O 2 pellets in an oxidizing atmosphere. Sintering tests were performed in an CO 2 atmosphere and the influence of temperature and time on the pellets density and microstructure were verified. The results obtained were compared to those from the conventional sintering process and its efficiency was confirmed. (author)

Effect of zinc oxide and boron oxide addition on the properties of yttrium-doped barium zirconate

International Nuclear Information System (INIS)

Andrade, Tiago Felipe

2011-01-01

BaZr 0.8 Y 0.2 O 3- δ protonic conductors, prepared by the ceramic route, were pressed and sintered with ZnO and B 2 O 3 sinter ing aids. The sintered pellets were analyzed by X-ray diffraction and impedance spectroscopy. Polished and thermally etched surfaces of the pellets were observed in a scanning probe microscope. The highest values of apparent density, 95%T.D., were obtained with 2 and 5 wt.% ZnO. The lowest value of electrical resistivity was obtained in BaZr 0.8 Y 0.2 O 3- δ compounds with 5 wt.% ZnO. Boron oxide and zinc oxide sinter ing aids were efficient to improve the apparent density as well as the electrical conductivity of BaZr 0.8 Y 0.2 O 3- δ protonic conductors. (author)

The role of the native oxide shell on the microwave sintering of copper metal powder compacts

International Nuclear Information System (INIS)

Mahmoud, Morsi M.; Link, Guido; Thumm, Manfred

2015-01-01

Highlights: • Thin oxide native layer had a critical role on microwave sintering of copper. • Explain why microwaves interact with copper powder differently than its bulk. • Abnormal expansion in copper is due to the plastic deformation and crack formation. • In-situ setup gives important insight about the microwave sintering of metals. • Microwave sintering is a promising candidate technology in powder metallurgy. - Abstract: Successful microwave sintering of several metal powders had been reported by many researchers with remarkable improvements in the materials properties and/or in the overall process. However, the concept behind microwave heating of metal powders has not been fully understood till now, as it is well known that bulk metals reflect microwaves. The progress of microwave sintering of copper metal powder compacts was investigated via combining both in-situ electrical resistivity and dilatometry measurements that give important information about microstructural changes with respect to the inter-particle electrical contacts during sintering. The sintering behavior of copper metal powders was depending on the type of the gas used, particle size, the initial green density, the soaking sintering time and the thin oxide layer on the particles surfaces. The thin copper oxide native layer (ceramics) that thermodynamically formed on the particles surfaces under normal handling and ambient environmental conditions had a very critical and important role in the microwave absorption and interaction, the sintering behavior and the microstructural changes. This finding could help to have a fundamental understanding of why MW’s interact with copper metal powder in a different way than its bulk at room temperature, i.e. why a given metal powder could be heated using microwaves while its bulk reflects it

Improved reaction sintered silicon nitride. [protective coatings to improve oxidation resistance

Science.gov (United States)

Baumgartner, H. R.

1978-01-01

Processing treatments were applied to as-nitrided reaction sintered silicon nitride (RSSN) with the purposes of improving strength after processing to above 350 MN/m2 and improving strength after oxidation exposure. The experimental approaches are divided into three broad classifications: sintering of surface-applied powders; impregnation of solution followed by further thermal processing; and infiltration of molten silicon and subsequent carburization or nitridation of the silicon. The impregnation of RSSN with solutions of aluminum nitrate and zirconyl chloride, followed by heating at 1400-1500 C in a nitrogen atmosphere containing silicon monoxide, improved RSSN strength and oxidation resistance. The room temperature bend strength of RSSN was increased nearly fifty percent above the untreated strength with mean absolute strengths up to 420 MN/m2. Strengths of treated samples that were measured after a 12 hour oxidation exposure in air were up to 90 percent of the original as-nitrided strength, as compared to retained strengths in the range of 35 to 60 percent for untreated RSSN after the same oxidation exposure.

Laser sintering of magnesia with nanoparticles of iron oxide and aluminum oxide

International Nuclear Information System (INIS)

García, L.V.; Mendivil, M.I.; Roy, T.K. Das; Castillo, G.A.; Shaji, S.

2015-01-01

Highlights: • Laser sintered MgO pellets with nanoparticles of Al 2 O 3 and Fe 2 O 3 . • Characterized these pellets by XRD, SEM and XPS. • Spinel formations were observed in both cases. • Changes in morphology and structure were analyzed. - Abstract: Nanoparticles of iron oxide (Fe 2 O 3 , 20–40 nm) and aluminum oxide (Al 2 O 3 , 50 nm) were mixed in different concentrations (3, 5 and 7 wt%) in a magnesium oxide (MgO) matrix. The mixture pellet was irradiated with 532 nm output from a Q-switched Nd:YAG laser using different laser fluence and translation speed for sintering. The refractory samples obtained were analyzed using X-ray diffraction technique, scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that the samples irradiated at translation speed of 110 μm/s and energy fluence of 1.7 J/cm 2 with a concentration of 5 and 7 wt% of Fe 2 O 3 presented the MgFe 2 O 4 spinel-type phase. With the addition of Al 2 O 3 nanoparticles, at a translation speed of 110 μm/s and energy fluence of 1.7 J/cm 2 , there were the formations of MgAl 2 O 4 spinel phase. The changes in morphologies and microstructure due to laser irradiation were analyzed

Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

Energy Technology Data Exchange (ETDEWEB)

Chen, I-Wei [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science & Engineering

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

Laser sintering of magnesia with nanoparticles of iron oxide and aluminum oxide

Energy Technology Data Exchange (ETDEWEB)

García, L.V.; Mendivil, M.I.; Roy, T.K. Das; Castillo, G.A. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66451 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66451 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

2015-05-01

Highlights: • Laser sintered MgO pellets with nanoparticles of Al{sub 2}O{sub 3} and Fe{sub 2}O{sub 3}. • Characterized these pellets by XRD, SEM and XPS. • Spinel formations were observed in both cases. • Changes in morphology and structure were analyzed. - Abstract: Nanoparticles of iron oxide (Fe{sub 2}O{sub 3}, 20–40 nm) and aluminum oxide (Al{sub 2}O{sub 3}, 50 nm) were mixed in different concentrations (3, 5 and 7 wt%) in a magnesium oxide (MgO) matrix. The mixture pellet was irradiated with 532 nm output from a Q-switched Nd:YAG laser using different laser fluence and translation speed for sintering. The refractory samples obtained were analyzed using X-ray diffraction technique, scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that the samples irradiated at translation speed of 110 μm/s and energy fluence of 1.7 J/cm{sup 2} with a concentration of 5 and 7 wt% of Fe{sub 2}O{sub 3} presented the MgFe{sub 2}O{sub 4} spinel-type phase. With the addition of Al{sub 2}O{sub 3} nanoparticles, at a translation speed of 110 μm/s and energy fluence of 1.7 J/cm{sup 2}, there were the formations of MgAl{sub 2}O{sub 4} spinel phase. The changes in morphologies and microstructure due to laser irradiation were analyzed.

Constrained Sintering in Fabrication of Solid Oxide Fuel Cells.

Science.gov (United States)

Lee, Hae-Weon; Park, Mansoo; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook

2016-08-09

Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs.

Formation of peripheral porosity regions around urania in zirconia-urania mixed oxide powder compact sintering

International Nuclear Information System (INIS)

Das, P.; Choudhury, R.

1992-01-01

Sintering studies of zirconia-urania mixed oxide powder compacts (in stages of 5% urania up to a maximum of 20% addition) were carried out at temperatures between 1000-1400deg C for various soaking periods. The formation of a peripheral porosity region around comparatively coarser urania particle was a characteristic feature in this mixed oxide sintered compact. At even a higher sintering temperature (1800deg C), where extensive solid solution formation takes place, this porosity region demarcates the solutionized particles from the host zirconia apparently acting as a discontinuity in the system. Relative shrinkage difference between the dissimilar particles probably contributes to the porosity regions around the minor second phase at a lower temperature while at higher temperature generation of 'Kirkendall porosity' may be responsible for such an effect. (orig.)

Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose

This thesis presents a fundamental study of the sintering of supported nanoparticles in relation to diesel oxidation catalysts. The sintering of supported nanoparticles is an important challenge in relation to this catalyst, as well as many other catalyst systems, and a fundamental understanding...... of Pt, Pd and bimetallic Pt-Pd nanoparticles supported on a flat and homogeneous Al2O3 or SiO2 surface. By using in situ TEM on the planar model catalysts it was possible to directly monitor the detailed dynamical changes of the individual nanoparticles during exposure to oxidizing conditions...

Constrained Sintering in Fabrication of Solid Oxide Fuel Cells

Science.gov (United States)

Lee, Hae-Weon; Park, Mansoo; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook

2016-01-01

Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs. PMID:28773795

Process for obtaining sintered conglomerates with a high density of rare earth oxides and actinides

International Nuclear Information System (INIS)

Pasto, A.E.

1974-01-01

The invention concerns a method to produce agglomerates of actinide and rare earth oxides possessing a cubic-monoclinic transformation in order to obtain high densities close to the theoretical density, and the articles produced by the method. The process is based on the use of a rare earth or actinide oxide, in particular Eu 2 O 3 , with a cubic-monoclinic phase transformation, the oxide being sintered by hot compression at a temperature 50 deg C to 100 deg C above the transformation temperature. The sintered agglomerates obtained can have a purity of at least 99.9% and a density of practically 100%. These agglomerates are suitable in particular for the formation of nuclear reactor control rods [fr

Cermet sintering on the oase of molybdenum, nickel, aluminium oxide in dry and wet hydrogen medium

International Nuclear Information System (INIS)

Fedotov, A.V.; Lutskaya, E.Eh.

1985-01-01

Cermet sintering on the base of molybdenum, nickel and aluminium oxide in dry and wer hydrogen medium is studied. It is stated that presence of water vapours permits to decrease sintering temperature of molybdenum containing cermets and to prepare dense nickeliferous cermets. Cermet density can he rather high at final stages of sintering that is probably conditioned by decrease of growth rate of corundum crystals. Pressing pressure activates cermet siptering at intermediate stages and it is low effective at finite stages of condensation. Constancy of relative reduction of void volume is preserved only at final stages of sintering

Evaluation of thermal properties of sintered beryllium oxide produced from Indian beryl ore

International Nuclear Information System (INIS)

Nair, Sathi R.; Ghanwat, S.J.; Patro, P.K.; Syambabu, M.; Mawal, N.E.; Mahata, T.; Sinha, P.K.

2014-01-01

Beryllium oxide (BeO) ceramics possess many interesting properties such as good thermal conductivity, high electrical resistivity, high chemical and thermal stability, low dielectric constant, low dielectric loss and low neutron absorption coefficient. These properties lead to its wide use in vacuum electronics technology, nuclear technology, microelectronics and photoelectron technology. The above properties depend on the purity of the material as well as density and microstructure of the sintered body. For high temperature application thermal conductivity and thermal expansion are two important parameters. In the present study, high purity fine BeO powder has been prepared by beryllate route starting with crude beryllium hydroxide. The powder has been sintered at 1550℃ and sintered samples have been evaluated for its thermal properties

Spark plasma sintering of tungsten-yttrium oxide composites from chemically synthesized nanopowders and microstructural characterization

International Nuclear Information System (INIS)

Yar, M.A.; Wahlberg, Sverker; Bergqvist, Hans; Salem, H.G.; Johnsson, Mats; Muhammed, Mamoun

2011-01-01

Nano-crystalline W-1%Y 2 O 3 (wt.%) powder was produced by a modified solution chemical reaction of ammonium paratungstate (APT) and yttrium nitrate. The precursor powder was found to consist of particles of bimodal morphology i.e. large APT-like particles up to 20 μm and rectangular yttrium containing ultrafine plates. After thermal processing tungsten crystals were evolved from W-O-Y plate like particles. spark plasma sintering (SPS) was used to consolidate the powder at 1100 and 1200 deg. C for different holding times in order to optimize the sintering conditions to yield high density but with reduced grain growth. Dispersion of yttrium oxide enhanced the sinterability of W powder with respect to lanthanum oxide. W-1%Y 2 O 3 composites with sub-micron grain size showed improved density and mechanical properties as compared to W-La 2 O 3 composites. Sample sintered in two steps showed improved density, due to longer holding time at lower temperature (900 deg. C) and less grain growth due to shorter holding time at higher temperature i.e. 1 min at 1100 deg. C.

Development and sintering of alumina based mixed oxide ceramic products for sensor applications in petroleum industries

Energy Technology Data Exchange (ETDEWEB)

Yadava, Y.P.; Muniz, L.B.; Aguiar, L.A.R.; Sanguinetti Ferreira, R.A. [Departamento de Engenharia Mecanica, Universidade Federal de Pernambuco, CEP 50741-530, Recife-PE (Brazil); Albino Aguiar, J. [Departamento de Fisica, Universidade Federal de Pernambuco, CEP 50670-901 Recife-PE (Brazil)

2005-07-01

In petroleum production, different types of sensors are required to monitor temperature, pressure, leakage of inflammable gases, etc. These sensors work in very hostile environmental conditions and frequently suffer from abrasion and corrosion problems. Presently perovskite oxide based ceramic materials are increasingly being used for such purposes, due to their highly inert behavior in hostile environment. In the present work, we have developed and characterized alumina based complex perovskite oxide ceramics, Ba{sub 2}AlSnO{sub 5.5}. These ceramics were prepared by solid state reaction process and produced in the form of circular discs by uniaxial pressure compaction technique. Green ceramic bodies were sintered at different sintering temperatures (1200 to 1500 deg. C) in air atmosphere. Structural and microstructural characteristics of sintered Ba{sub 2}AlMO{sub 5.5} were studied by XRD and SEM techniques. Mechanical properties were tested by Vickers microhardness tests. Ceramics sintered in the temperature range 1300 deg. C 1400 deg. C presented best results in terms of microstructural characteristics and mechanical performance. (authors)

Standard specification for sintered gadolinium oxide-uranium dioxide pellets

CERN Document Server

American Society for Testing and Materials. Philadelphia

2008-01-01

1.1 This specification is for finished sintered gadolinium oxide-uranium dioxide pellets for use in light-water reactors. It applies to gadolinium oxide-uranium dioxide pellets containing uranium of any 235U concentration and any concentration of gadolinium oxide. 1.2 This specification recognizes the presence of reprocessed uranium in the fuel cycle and consequently defines isotopic limits for gadolinium oxide-uranium dioxide pellets made from commercial grade UO2. Such commercial grade UO2 is defined so that, regarding fuel design and manufacture, the product is essentially equivalent to that made from unirradiated uranium. UO2 falling outside these limits cannot necessarily be regarded as equivalent and may thus need special provisions at the fuel fabrication plant or in the fuel design. 1.3 This specification does not include (1) provisions for preventing criticality accidents or (2) requirements for health and safety. Observance of this specification does not relieve the user of the obligation to be aw...

Pressureless sintering of whisker-toughened ceramic composites

Science.gov (United States)

Tiegs, T.N.

1993-05-04

A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

On the sintering kinetics in UO2

International Nuclear Information System (INIS)

Marajofsky, A.

1998-01-01

The fabrication process of UO 2 pellets from powders involve pressing and a sintering anneal at high temperature (1650 deg. C to 1750 deg. C) during two or more hours in a hydrogen atmosphere. An alternative method is the oxidative sintering, made at lower temperature (1000 deg. C to 1300 deg. C) in a CO 2 or CO/CO 2 atmosphere. The sintering phenomena consist in the densification of the material by a thermal treatment below the fusion point. For a compact made by pressing a powder, sintering is the process of annulation of the porosity present in the compact or pellet. Several theories describe the sintering phenomena dividing it in three stages, initial, intermediate and final: in all of them the densification is a continuous growing function of time. Nevertheless it has been experimentally reported that a reduction of the density occurs in the third step of the sintering. The phenomena has been called solarization. Solarization has been attributed to the effect of the evolved gases from additives or to the CO 2 atmosphere in oxidative sintering. Thus, it is convenient to distinguish between solarization in oxidative or reducing conditions. Reducing solarization is a consequence of the tendency towards equilibrium of intergranular pores. In oxidative sintering it occurs in the reducing anneal after the sintering and is due to the change in the lattice parameter. This work shows examples of both types of solarization and qualitative interpretation of this phenomena. Both situations show the need of strict control of the sintering and powder production conditions. (author)

Evaluation of marginal/internal fit of chrome-cobalt crowns: Direct laser metal sintering versus computer-aided design and computer-aided manufacturing.

Science.gov (United States)

Gunsoy, S; Ulusoy, M

2016-01-01

The purpose of this study was to evaluate the internal and marginal fit of chrome cobalt (Co-Cr) crowns were fabricated with laser sintering, computer-aided design (CAD) and computer-aided manufacturing, and conventional methods. Polyamide master and working models were designed and fabricated. The models were initially designed with a software application for three-dimensional (3D) CAD (Maya, Autodesk Inc.). All models were fabricated models were produced by a 3D printer (EOSINT P380 SLS, EOS). 128 1-unit Co-Cr fixed dental prostheses were fabricated with four different techniques: Conventional lost wax method, milled wax with lost-wax method (MWLW), direct laser metal sintering (DLMS), and milled Co-Cr (MCo-Cr). The cement film thickness of the marginal and internal gaps was measured by an observer using a stereomicroscope after taking digital photos in ×24. Best fit rates according to mean and standard deviations of all measurements was in DLMS both in premolar (65.84) and molar (58.38) models in μm. A significant difference was found DLMS and the rest of fabrication techniques (P 0.05). DMLS was best fitting fabrication techniques for single crown based on the results.The best fit was found in marginal; the larger gap was found in occlusal.All groups were within the clinically acceptable misfit range.

A study of emission property and microstructure of rare earth oxide-molybdenum cermet cathode materials made by spark plasma sintering

International Nuclear Information System (INIS)

Wang Jinshu; Li Hongyi; Yang Sa; Cui Ying; Zhou Meiling

2004-01-01

A fast sintering method, spark plasma sintering (SPS) was used for the synthesis of rare earth oxide-molybdenum cathode material. The secondary emission property, microstructure, and phase constitution of materials have been studied in this paper. The experimental results show that the maximum secondary emission coefficient of this material can be high to 3.84, much higher than that of rare earth oxide-molybdenum cathode made by traditional sintering method. The grain size is less than 1 μm and rare earth distributed evenly in the material. After the material was activated at 1600 deg. C, a 4 μm layer of rare earth oxide which leads to the high secondary emission coefficient of the material, is formed on the surface of the cathode

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...2018-03/24/2018 Sa. CONTRACT NUMBER Sb. GRANT NUMBER Sc. PROGRAM ELEMENT NUMBER Sd. PROJECT NUMBER Se. TASK NUMBER Sf. WORK UNIT NUMBER 8

Fabrication and scintillation properties of highly transparent Pr:LuAG ceramics using Sc,La-based isovalent sintering aids

Czech Academy of Sciences Publication Activity Database

Shen, Y.; Feng, X.; Babin, Vladimir; Nikl, Martin; Vedda, A.; Moretti, F.; Dell'Orto, E.; Pan, Y.; Li, J.; Zeng, Y.

2013-01-01

Roč. 39, č. 5 (2013), s. 5985-5990 ISSN 0272-8842 R&D Projects: GA MŠk LH12185; GA AV ČR KAN300100802 Institutional support: RVO:68378271 Keywords : Pr:LuAG transparent ceramics * isovalent sintering aids * scintillation Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.086, year: 2013

Laser sintering of copper nanoparticles

International Nuclear Information System (INIS)

Zenou, Michael; Saar, Amir; Ermak, Oleg; Kotler, Zvi

2014-01-01

Copper nanoparticle (NP) inks serve as an attractive potential replacement to silver NP inks in functional printing applications. However their tendency to rapidly oxidize has so far limited their wider use. In this work we have studied the conditions for laser sintering of Cu-NP inks in ambient conditions while avoiding oxidation. We have determined the regime for stable, low-resistivity copper (< ×3 bulk resistivity value) generation in terms of laser irradiance and exposure duration and have indicated the limits on fast processing. The role of pre-drying conditions on sintering outcome has also been studied. A method, based on spectral reflectivity measurements, was used for non-contact monitoring of the sintering process evolution. It also indicates preferred spectral regions for sintering. Finally, we illustrated how selective laser sintering can generate high-quality, fine line (<5 µm wide) and dense copper circuits. (paper)

Profile of yttrium segregation in BaCe0,9Y0,1O3-δ as function of sintering temperature

International Nuclear Information System (INIS)

Hosken, C.M.; Souza, D.P.F. de

2010-01-01

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 0,9 Y 0,1 O 3-δ 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)

Immobilization of Radioactive Rare Earth oxide Waste by Solid Phase Sintering

International Nuclear Information System (INIS)

Ahn, Byung Gil; Park, Hwan Seo; Kim, Hwan Young; Lee, Han Soo; Kim, In Tae

2010-01-01

In the pyroprocessing of spent nuclear fuels, LiCl-KCl waste salt containing radioactive rare earth chlorides are generated. The radioactive rare earth oxides are recovered by co-oxidative precipitation of rare earth elements. The powder phase of rare earth oxide waste must be immobilized to produce a monolithic wasteform suitable for storage and ultimate disposal. The immobilization of these waste developed in this study involves a solid state sintering of the waste with host borosilicate glass and zinc titanate based ceramic matrix (ZIT). And the rare-earth monazite which synthesised by reaction of ammonium di-hydrogen phosphate with the rare earth oxides waste, were immobilized with the borosilicate glass. It is shown that the developed ZIT ceramic wasteform is highly resistant the leaching process, high density and thermal conductivity.

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

KAUST Repository

Sun, Wenping; Shi, Zhen; Liu, Mingfei; Bi, Lei; Liu, Wei

2014-01-01

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

Sintered nuclear fuel compact and method for its production

International Nuclear Information System (INIS)

Peehs, M.; Dorr, W.

1988-01-01

This patent describes a method of producing a sintered nuclear fuel compact with which reactivity losses in a nuclear reactor having long fuel element cycles are avoided, which comprises, forming a compact of a mixture of powders containing at least one nuclear fuel oxide selected from the group consisting of UO/sub 2/, PuO/sub 2/, ThO/sub 2/, mixed oxide (U, Pu)O/sub 2/ and mixed oxide (U, Th)O/sub 2/, at least one neutron poison selected from the group consisting of UB/sub x/, where x=2; 4 and/or 12 and B/sub 4/C, and sintering the compact of the mixture of powders so that the neutron piston is embedded in a sintered matrix of the nuclear fuel oxide at a treatment temperature in a range from 1000 0 C to 1400 0 C in an oxidizing sintering atmosphere, and then heat treating the sintered compact in a reducing gas atmosphere

Metallographic preparation of sintered oxides, carbides and nitrides of uranium and plutonium

International Nuclear Information System (INIS)

Martin, A.; Arles, L.

1967-12-01

We describe the methods of polishing, attack and coloring used at the section of plutonium base ceramics studies. These methods have stood the test of experience on the uranium and plutonium carbides, nitrides and carbonitrides as well on the mixed uranium and plutonium oxides. These methods have been particularly adapted to fit to the low dense and sintered samples [fr

Guideline tests on the corrosion of sintered uranium oxide by lead and sodium about 450 deg. C

International Nuclear Information System (INIS)

Portnoff, A.; Pointud, R.

1958-05-01

Within the frame of the investigation of behaviour of a fuel element (such as UO 2 ) under irradiation, the authors report the study of the physical-chemical action of the coolant at different temperatures on the body to be irradiated. Thus, sintered uranium oxide has been submitted to corrosion by lead and by sodium during 250 hours at temperatures between 400 and 500 C. The physical characteristics of the UO 2 powder and of different sintered UO 2 pellets produced from this powder under different sintering processes are indicated, as well as the results of a spectrographic analysis of the sintered UO 2 . Corrosion devices, treatments and obtained results are reported for corrosion by lead and by sodium. In the latter case, extraction processes are discussed (using butyl alcohol, or melting in vaseline oil)

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

CERN Document Server

American Society for Testing and Materials. Philadelphia

2006-01-01

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

Flash sintering of ceramic materials

Science.gov (United States)

Dancer, C. E. J.

2016-10-01

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

Contribution to the study of the sintering of uranium oxide; Contribution a l'etude du frittage de l'oxyde d'uranium

Energy Technology Data Exchange (ETDEWEB)

Bel, A; Carteret, Y [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1958-07-01

The sintering ofnium oxide has been considered and the following factors have been particularly taken in consideration: - the particle size and the particles in shape of the initial powder, - the specific area of the initial powder, - the chemical composition of the oxide, - and the medium in which the sintering was carried out. A method of sintering uranium oxide on semi-industrial scale is presented. (author)Fren. [French] On xamine l'influence de differents facteurs sur le frittage de l'oxyde d'uranium. Sont particulierement prises en consideration: - la taille et la forme des grains de la poudre initiale, - la surface specifique de la poudre initiale, - la composition chimique de l'oxyde, - ainsi que la nature de l'atmosphere durant le frittage. D'autre part, une technique de frittage de l'oxyde d'uranium a l'echelle semi-industrielle est presentee. (auteur)

Effect of surface treatments on the bond strength between resin cement and differently sintered zirconium-oxide ceramics.

Science.gov (United States)

Yenisey, Murat; Dede, Doğu Ömür; Rona, Nergiz

2016-01-01

This study investigated the effects of surface treatments on bond strength between resin cement and differently sintered zirconium-oxide ceramics. 220 zirconium-oxide ceramic (Ceramill ZI) specimens were prepared, sintered in two different period (Short=Ss, Long=Ls) and divided into ten treatment groups as: GC, no treatment; GSil, silanized (ESPE-Sil); GSilPen, silane flame treatment (Silano-Pen); GSb, sandblasted; GSbSil, sandblasted+silanized; GSbCoSil, sandblasted+silica coated (CoJet)+silanized; GSbRoSil, sandblasted+silica coated (Rocatech-Plus)+silanized; GSbDSil, sandblasted+diamond particle abraded (Micron MDA)+silanized; GSbSilPen, sandblasted+silane flame treatment+silanized; GSbLSil, sandblasted+Er:Yag (Asclepion-MCL30) laser treated+silanized. The composite resin (Filtek Z-250) cylinders were cemented to the treated ceramic surfaces with a resin cement (Panavia F2.0). Shear bond strength test was performed after specimens were stored in water for 24h and thermo-cycled for 6000 cycles (5-55 °C). Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tamhane's multiple comparison test (α=0.05). According to the ANOVA, sintering time, surface treatments and their interaction were statistically significant (pzirconium-oxide ceramics. Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Sintering effect on material properties of electrochemical reactors used for removal of nitrogen oxides and soot particles emitted from diesel engines

DEFF Research Database (Denmark)

He, Zeming; Andersen, Kjeld Bøhm; Keel, Li

2010-01-01

In the present work, 12-layered electrochemical reactors (comprising five cells) with a novel configuration including supporting layer lanthanum strontium manganate (LSM)-yttria stabilised zirconia (YSZ), electrode layer LSM-gadolinia-doped cerium oxide (CGO) and electrolyte layer CGO were...... fabricated via the processes of slurry preparation, tape casting and lamination and sintering. The parameters of porosity, pore size, pore size distribution, shrinkage, flow rate of the sintered reactors and the electrical conductivities of the supporting layer and the electrode in the sintered reactors were...... characterised. The effect of sintering temperature on microstructures and properties of the sintered samples was discussed, and 1,250 °C was determined as the appropriate sintering temperature for reactor production based on the performance requirements for applications. Using the present ceramic processing...

Study and fabrication of solid oxide fuel cells through tape casting and co-sintering

International Nuclear Information System (INIS)

Grosjean, A.

2004-11-01

This work is dedicated to the devising of a low-cost fabrication process of solid oxide fuel cells (SOFC). Technical requirements impose the shaping method: stripe casting as well as the materials used: Yttria-stabilized zirconia (YSZ), nickel and lanthanum manganite doped with strontium (LSM). In order to comply with environmental requirements the developed process uses an aqueous barbotine solvent. We get electrodes and the electrolyte separately, the use of an absorbent drying process has enabled us to join 3 layers to form an elementary cell with great interfacial homogeneity. The resistance of the cell to sintering has been improved through the symmetrization of the deformations of the cell. In order to interpret the low electrical properties of the cell and its quick damaging, transmission microscopy studies have been performed. These studies have shown 2 facts. First, 2 isolating phases appear at the cathode (at the LSM/YSZ interface) because of a too high sintering temperature and secondly, a quick clustering of nickel grains appears during cell operation that leads to a local loss of the nickel grid percolation. This problem has been solved by increasing the size of nickel oxide grains from 0.5 μm to 3 μm) to stabilize the microstructure. The issue of the reactivity at the LSM/YSZ interfaces was tackled in 2 different ways, we have tried to lower the sintering temperature by using a zirconia nano-powder first and then by replacing zirconia in the electrolyte by gadolinium-doped ceria. The use of zirconia nano-powder has failed to decrease sintering temperature while preserving the electrolyte density and the use of ceria has triggered instabilities that have not yet been solved. Despite all these drawbacks, this process allows the fabrication of an excellent anode/electrolyte interface. (A.C.)

Mechanical characteristics of microwave sintered silicon carbide

Indian Academy of Sciences (India)

Unknown

sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered .... product, could be due to oxidation of SiC, e.g. 50% weight gain of a green SiC sample ... because, the charging current is 90° advanced in phase, ideally, with respect to the ...

Enhanced proton conductivity of yttrium-doped barium zirconate with sinterability in protonic ceramic fuel cells

International Nuclear Information System (INIS)

Park, Ka-Young; Seo, Yongho; Kim, Ki Buem; Song, Sun-Ju; Park, Byoungnam; Park, Jun-Young

2015-01-01

Highlights: • Report effects of ceramic processing methods on the electrical conductivity of BZY. • Present effects of sintering aids on the conductivity and density of BZY. • CuO is the most effective sintering aid for the BZY. • Polymer gelation is the most effective method in terms of conductivity of BZY. • Grain boundary conductivity of the polymer gelation BZY is higher than others. - Abstract: In this study, we report the effects of various ceramic processing methods with different sintering aids on the relative density, crystallinity, microstructure, and electrical conductivity of proton conducting BaZr 0.85 Y 0.15 O 3−δ (BZY) pellets in details. First, the BZY ceramic pellets are fabricated by the solid-state reactive sintering by adding diverse sintering aids including CuO, NiO, ZnO, SnO, MgO, and Al 2 O 3 . Among these, CuO is found to be the most effective sintering aid in terms of the sintering temperature and total conductivity. However, transition metals as sintering aids have detrimental effects on the electrical conductivity of the BZY electrolytes. Second, the BZY electrolytes have been synthesized by four different methods: the solid-state, combustion, hydrothermal, and polymer gelation methods. The BZY pellets synthesized by the polymer gelation method exhibit dense microstructure with a high relative density of 95.3%. Moreover, the electrical conductivity of the BZY pellets synthesized by the polymer gelation method is higher than those prepared by the solid-state methods under the same test conditions: 1.28 × 10 −2 S cm −1 (by the polymer gelation method) vs. 0.53 × 10 −2 S cm −1 by the solid-state method at 600 °C in wet 5% H 2 in Ar

Microwave processing of a dental ceramic used in computer-aided design/computer-aided manufacturing.

Science.gov (United States)

Pendola, Martin; Saha, Subrata

2015-01-01

Because of their favorable mechanical properties and natural esthetics, ceramics are widely used in restorative dentistry. The conventional ceramic sintering process required for their use is usually slow, however, and the equipment has an elevated energy consumption. Sintering processes that use microwaves have several advantages compared to regular sintering: shorter processing times, lower energy consumption, and the capacity for volumetric heating. The objective of this study was to test the mechanical properties of a dental ceramic used in computer-aided design/computer-aided manufacturing (CAD/CAM) after the specimens were processed with microwave hybrid sintering. Density, hardness, and bending strength were measured. When ceramic specimens were sintered with microwaves, the processing times were reduced and protocols were simplified. Hardness was improved almost 20% compared to regular sintering, and flexural strength measurements suggested that specimens were approximately 50% stronger than specimens sintered in a conventional system. Microwave hybrid sintering may preserve or improve the mechanical properties of dental ceramics designed for CAD/CAM processing systems, reducing processing and waiting times.

Current state of the Uranium dioxide sintering theory

International Nuclear Information System (INIS)

Baranov, V.; Devyatko, Y.; Tenishev, A.; Khlunov, A.; Khomyakov, O.

2011-01-01

The basic approaches to the description of the ceramics sintering phenomenon are considered. It is established that diffusive sintering models incorrectly describe an intermediate stage of this process. The physical model of sintering, considering the substance plastic flow of pressing under the influence of internal stress forces and capillary forces, as the basic mechanism defining the shrinkage of sintering oxide nuclear fuel, is offered. (authors)

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.

Two step sintering of zirconia-escandia-ceria

International Nuclear Information System (INIS)

Grosso, R.L.; Muccillo, E.N.S.

2011-01-01

Recent reports show that the ceramic system based on zirconia-scandia-ceria is a good candidate to act as solid electrolyte in solid oxide fuel cells operating at intermediate temperatures (600-800 °C). In this work, commercial ZrO_2 containing 10 mol% scandium oxide and 1 mol% cerium oxide was sintered by the two stage method. This technique was proposed to in order to obtain ceramic materials with high density along with fine grain sizes, because it avoids the grain growth occurring in the last stage of sintering. A number of experimental conditions were fully exploited by varying the dwell temperature (T_2) and the dwell time. The peak temperature (T_1) was chosen from linear shrinkage results. High (>98%) density values were obtained using this method. The medium grain size was evaluated for selected sintered samples. X-ray diffraction patterns reveal a secondary (rhombohedral) phase in sintered samples. The intensity of the secondary phase is a function of T_1 being small for relatively higher peak temperatures. (author)

Non-pressurized sintered silicon carbide with titanium carbide reinforcement

International Nuclear Information System (INIS)

Adler, J.

1992-01-01

A non-pressurized compression of SiC-TiC composite materials can be achieved via liquid phase sintering by the application of oxidic additives. Materials with TiC proportions up to 40% by volume of TiC and densities of 97 to 98% TD were produced at sintering temperatures around 1875 C. With SiC sintered in the liquid phase an increase of toughness at fracture of 80% compared with conventionally non-pressurized sintered SiC was achieved with B/C additive. No further increase could be achieved by the addition of TiC particles. However, the oxidation resistance at 1200 C was worsened. (orig.) [de

Accuracy evaluation of metal copings fabricated by computer-aided milling and direct metal laser sintering systems.

Science.gov (United States)

Park, Jong-Kyoung; Lee, Wan-Sun; Kim, Hae-Young; Kim, Woong-Chul; Kim, Ji-Hwan

2015-04-01

To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method. Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (α=.05), respectively. The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05). Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (<120 µm). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.

High temperature oxidation-sulfidation behavior of Cr-Al2O3 and Nb-Al2O3 composites densified by spark plasma sintering

International Nuclear Information System (INIS)

Saucedo-Acuna, R.A.; Monreal-Romero, H.; Martinez-Villafane, A.; Chacon-Nava, J.G.; Arce-Colunga, U.; Gaona-Tiburcio, C.; De la Torre, S.D.

2007-01-01

The high temperature oxidation-sulfidation behavior of Cr-Al 2 O 3 and Nb-Al 2 O 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 2 + 3.6%O 2 + N 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 2 O 3 and Nb-Al 2 O 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 2 O 3 layer immediately forms upon heating, whereas for the later pest disintegration was noted. Thus, under the same sintering conditions the Nb-Al 2 O 3 composites showed the highest weight gains. The oxidation products were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy

Mechanism of mechanochemical synthesis of complex oxides and the peculiarities of their nano-structurization determining sintering

Directory of Open Access Journals (Sweden)

Zyryanov V.V.

2005-01-01

Full Text Available A mechanism of superfast mechanosynthesis reaction for oxide systems is proposed on the base of a dynamics study. The threshold effect and linear dependence of the chemical response on the effective temperature of the reaction zone are established. Major factors are determined: molecular mass of reagents, enthalpy and difference of reagents in Mohs’s hardness, which also influence the composition of the primary product. Primary acts are characterized by a superfast roller mechanism of mass transfer with the formation of a transient dynamic state (D*. Secondary acts slowly approximate the composition of the product to the composition of the starting mixture by diffusion mass transfer in a deformation mixing regime with a contribution of a rotation (roller mechanism. The list of structure types for complex oxides derived by mechanosynthesis includes perovskites, fluorites, pyrochlors, sheelites, and some other ones. Powders of crystal products display multilevel structurization. In all studied complex oxides strong disordering of the “anti-glass” type was observed. The mechanism of sintering was studied in BaTiO3 powders of different origin and in metastable complex oxides derived by mechanosynthesis. The major contribution in shrinkage belongs to rearrangements of crystalline particles as a whole. Structure transformations accompany, as a rule, sintering of inhomogeneous powders derived by mechanosynthesis.

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.

Microstructure evolution of SiC sintered bodies activated by boron and carbon

International Nuclear Information System (INIS)

Gubernat, A.; Stobierski, L.

2003-01-01

Investigation on the role of sintering aids on densification of silicon carbide indicate that boron and carbon modify mass transport mechanisms. It leads to changes of microstructure of polycrystalline silicon carbide. In the present work the influence of varying proportions of sintering aids on the material microstructure was studied. The microstructural changes were related to the changes of the selected properties of the resulting materials. (author)

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

Effect of processing conditions on microstructural features in Mn–Si sintered steels

International Nuclear Information System (INIS)

Oro, Raquel; Hryha, Eduard; Campos, Mónica; Torralba, José M.

2014-01-01

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

Photoacoustic spectroscopy investigation of sintered zinc-tin-oxide ceramics

Directory of Open Access Journals (Sweden)

Ivetić Tamara B.

2007-01-01

Full Text Available In this paper the changes that occurred in differently activated ZnO-SnO2 and sintered samples were investigated using photoacoustic spectroscopy. ZnO and SnO2 powders, mixed in the molar ratio 2:1, were mechanically activated in a planetary ball mill for 10-160 min. The mixtures were pres­sed and isothermally sintered at 1300°C for two hours. X-ray diffraction analysis of the obtained sintered samples was performed in order to investigate changes of the phase composition and confirmed only the presence of a pure zinc stannate (Zn2SnO4 phase in all the sintered samples as a result of the solid state reaction and reaction sintering between the starting ZnO and SnO2 powders. The microstructure of the sintered sam­ples was examined by scanning electron microscopy and showed that mechanical activation leads to the formation of a structure with reduced particle size which accelerates spinel formation. Grain growth of the spinel phase slows down the densification process and together with the agglomerates formed during mechanical activation causes the appearance of a porous microstructure. The photoacoustic (PA phase and amplitude spectra of the sintered samples were recorded as a function of the chopped frequency of the laser beam used (red laser with a power of 25 mW, λ=632 nm in a thermal-transmission detection configuration. PA experimental data were analyzed using the Rosenzweig-Gersho thermal-piston model, which enabled determination of the thermal diffusivity, ZT (m2s-1, diffusion coefficient of the minority free carriers D (m2s-1 and the optical absorption coefficient (m-1. The detected differences of the measured thermal-electrical properties of the obtained Zn2SnO4 ceramics indicate changes in the material induced by the different preparation procedure of the starting powders before the sintering process.

SINTERING OF NASCENT CALCIUM OXIDE

Science.gov (United States)

The paper discusses the measurement of the sintering rate of CaO in a nitrogen atmosphere at temperatures of 700-1100 C. CaO prepared from ultrapure CaCO3 was compared with an impure CaO derived from limestone. Both materials yielded an initial surface area of 104 sq m/g. The rat...

Hydrothermal Cold Sintering

Science.gov (United States)

Kang, Xiaoyu

Solid state sintering transforms particle compact to a physically robust and dense polycrystalline monolith driven by reduction of surface energy and curvature. Since bulk diffusion is required for neck formation and pore elimination, sintering temperature about 2/3 of melting point is needed. It thus places limitations for materials synthesis and integration, and contributes to significant energy consumption in ceramic processing. Furthermore, since surface transport requires lower temperature than bulk processes, grain growth is often rapid and can be undesired for physical properties. For these reasons, several techniques have been developed including Liquid Phase Sintering (LPS), Hot Pressing (HP) and Field Assisted Sintering Technique (FAST), which introduce either viscous melt, external pressure or electric field to speed up densification rates at lower temperature. However, because of their inherent reliability on bulk diffusion, temperatures required are often too high for integrating polymers and non-noble metals. Reduction of sintering temperature below 400 °C would require a different densification mechanism that is based on surface transport with external forces to drive volume shrinkage. Densification method combining uniaxial pressure and solution under hydrothermal condition was first demonstrated by Kanahara's group at Kochi University in 1986 and was brought to our attention by the work of Kahari, etc, from University of Oulu on densification of Li2MoO 4 in 2015. This relatively new process showed promising ultra-low densification temperature below 300 °C, however little was known about its fundamental mechanism and scope of applications, which became the main focus of this dissertation. In this work, a uniaxial hydraulic press, a standard stainless steel 1/2 inch diameter die with heating band were utilized in densifying metal oxides. Applied pressure and sintering temperature were between 100 MPa and 700 MPa and from room temperature to 300 �

Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

Science.gov (United States)

Zhong, Zhi-Min; Goldsby, Jon C.

2005-01-01

Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the

Excimer laser sintering of indium tin oxide nanoparticles for fabricating thin films of variable thickness on flexible substrates

International Nuclear Information System (INIS)

Park, Taesoon; Kim, Dongsik

2015-01-01

Technology to fabricate electrically-conducting, transparent thin-film patterns on flexible substrates has possible applications in flexible electronics. In this work, a pulsed-laser sintering process applicable to indium tin oxide (ITO) thin-film fabrication on a substrate without thermal damage to the substrate was developed. A nanosecond pulsed laser was used to minimize thermal penetration into the substrate and to control the thickness of the sintered layer. ITO nanoparticles (NPs) of ~ 20 nm diameter were used to lower the process temperature by exploiting their low melting point. ITO thin film patterns were fabricated by first spin coating the NPs onto a surface, then sintering them using a KrF excimer laser. The sintered films were characterized using field emission scanning electron microscopy. The electrical resistivity and transparency of the film were measured by varying the process parameters. A single laser pulse could generate the polycrystalline structure (average grain size ~ 200 nm), reducing the electrical resistivity of the film by a factor of ~ 1000. The sintering process led to a minimum resistivity of 1.1 × 10 −4 Ω·m without losing the transparency of the film. The thickness of the sintered layer could be varied up to 150 nm by adjusting the laser fluence. Because the estimated thermal penetration depth in the ITO film was less than 200 nm, no thermal damage was observed in the substrate. This work suggests that the proposed process, combined with various particle deposition methods, can be an effective tool to form thin-film ITO patterns on flexible substrates. - Highlights: • Excimer laser sintering can fabricate ITO thin films on flexible substrates. • The laser pulse can form a polycrystalline structure without thermal damage. • The laser sintering process can reduce the electrical resistivity substantially. • The thickness of the sintered layer can be varied effectively

Excimer laser sintering of indium tin oxide nanoparticles for fabricating thin films of variable thickness on flexible substrates

Energy Technology Data Exchange (ETDEWEB)

Park, Taesoon; Kim, Dongsik, E-mail: dskim87@postech.ac.kr

2015-03-02

Technology to fabricate electrically-conducting, transparent thin-film patterns on flexible substrates has possible applications in flexible electronics. In this work, a pulsed-laser sintering process applicable to indium tin oxide (ITO) thin-film fabrication on a substrate without thermal damage to the substrate was developed. A nanosecond pulsed laser was used to minimize thermal penetration into the substrate and to control the thickness of the sintered layer. ITO nanoparticles (NPs) of ~ 20 nm diameter were used to lower the process temperature by exploiting their low melting point. ITO thin film patterns were fabricated by first spin coating the NPs onto a surface, then sintering them using a KrF excimer laser. The sintered films were characterized using field emission scanning electron microscopy. The electrical resistivity and transparency of the film were measured by varying the process parameters. A single laser pulse could generate the polycrystalline structure (average grain size ~ 200 nm), reducing the electrical resistivity of the film by a factor of ~ 1000. The sintering process led to a minimum resistivity of 1.1 × 10{sup −4} Ω·m without losing the transparency of the film. The thickness of the sintered layer could be varied up to 150 nm by adjusting the laser fluence. Because the estimated thermal penetration depth in the ITO film was less than 200 nm, no thermal damage was observed in the substrate. This work suggests that the proposed process, combined with various particle deposition methods, can be an effective tool to form thin-film ITO patterns on flexible substrates. - Highlights: • Excimer laser sintering can fabricate ITO thin films on flexible substrates. • The laser pulse can form a polycrystalline structure without thermal damage. • The laser sintering process can reduce the electrical resistivity substantially. • The thickness of the sintered layer can be varied effectively.

Solidification of HLLW into sintered ceramics

International Nuclear Information System (INIS)

O-Oka, K.; Ohta, T.; Masuda, S.; Tsunoda, N.

1979-01-01

Simulated HLLW from the PNC reprocessing plant at Tokai was solidified into sintered ceramics by normal sintering or hot-pressing with addition of some oxides. Among various ceramic products obtained so far, the most preferable was nepheline-type sintered solids formed with addition of SiO 2 and Al 2 O 3 to the simulated waste calcine. The solid shows advantageous properties in leach rate and mechanical strength, which suggest that the ceramic solids were prepared with additions of ZrO 2 or MnO 2 , and some of them showed good characteristics

Microstructures and mechanical properties of 9Cr oxide dispersion strengthened steel produced by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Xie, Rui [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); School of Metallurgy, Northeastern University, Shenyang 110819 (China); Lu, Zheng, E-mail: luz@atm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Lu, Chenyang; Li, Zhengyuan [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China); Ding, Xueyong [School of Metallurgy, Northeastern University, Shenyang 110819 (China); Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 110819 (China)

2017-02-15

Highlights: • A 9Cr-ODS steel was produced by mechanical alloying and spark plasma sintering. • Bimodal grain size distribution was observed. • Formation mechanism of bimodal grain size distribution was discussed. • The size and number density of nanoscale particles were obtained by SAXS and HRTEM. • The contribution of nano-sized particles to yield strength is dominating. - Abstract: 9Cr oxide dispersion strengthened (ODS) steel was fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). The nano-sized particles, grain size distribution and mechanical properties of 9Cr-ODS steel sintered at 950 °C were studied by synchrotron radiation small angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (HRTEM), electron backscatter diffraction (EBSD) and tensile experiment. The results showed that bimodal grain size distribution in the matrix is observed, which is attributed to the heterogeneous recrystallization process during the SPS. High-density nano-sized Y{sub 2}Ti{sub 2}O{sub 7} and some large oxides of Cr{sub 2}Mn(Ti)O{sub 4} are formed in 9Cr-ODS steel. The number density and average size of Y{sub 2}Ti{sub 2}O{sub 7} obtained from SAXS are 4.72 × 10{sup 22}/m{sup 3} and 4.4 nm, respectively. The yield strengths of 9Cr-ODS steel fabricated by SPS are compared with the typical 9Cr-ODS steel produced by HIP.

Microwave sintering of hydroxyapatite-based composites

International Nuclear Information System (INIS)

Fang, Y.; Roy, D.M.; Cheng, J.; Roy, R.; Agrawal, D.K.

1993-01-01

Composites of hydroxyapatite/partially stabilized zirconia (HAp/PSZ) and hydroxyapatite/silicon carbide whiskers (HAp/SiC) were sintered at 1100-1200 degrees C by microwave at 2.45 GHz. Characterization of the sintered composites was carried out by density, microstructure, phase composition, and fracture toughness measurements. The results show that although not yet fully densified, a much higher sintered density in the HAp/PSZ composite was achieved by microwave sintering than by conventional sintering at the same temperature. A relative density of 93% was achieved by 20 min. microwave processing at 1200 degrees C. Comparatively, 2 h conventional sintering of the same material at 1200 degrees C led to only 75.5% relative density. K IC of this microwave sintered HAp/PSZ of 93% density was found to be 3.88 MPa√m, which is 250% of the value for pure HAp of the same density. A further increase in K IC could be expected if full or nearly full densification was achieved. Sintering of PSZ particles in the HAp/PSZ composite was also observed in the microwave processed sample. Microwave sintering of HAp/SiC was not successful in the current study due to the oxidation of SiC in air at high temperature. 8 refs., 4 figs., 1 tab

Effect of sintering atmosphere on the hardness of ThO2

Science.gov (United States)

Baena, Angela; Cardinaels, Thomas; Van Eyken, Jelle; Puzzolante, Jean Louis; Binnemans, Koen; Verwerft, Marc

2016-08-01

The hardness and toughness of ThO2 sintered under reducing and oxidizing conditions has been investigated and, quite unexpectedly, a significant difference in hardness was observed for the entire range of porosities studied. Reducing conditions systematically yielded higher hardness values than oxidizing conditions. Extrapolated to zero porosity, the hardness for ThO2 is H0 = 10.5 ± 0.3 GPa for oxidizing conditions and H0 = 12.4 ± 0.7 GPa for reducing conditions. Toughness values have been derived from Vickers indentations; differences in toughness were insignificant and only a single value is proposed: KIC = 0.97 ± 0.12 MPa √m. The difference in hardness is attributed to the presence of point defects, also acting as color centers and causing grey coloration of ThO2 sintered under reducing conditions. Furthermore, and of interest for nuclear fuel production, is the finding that ThO2 sintered under reducing conditions is significantly easier to grind compared to material sintered under oxidizing conditions.

The influence of green microstructure and sintering parameters on precipitation process during copper-nickel-zinc ferrites sintering

International Nuclear Information System (INIS)

Barba, A.; Clausell, C.; Jarque, J. C.; Monzo, M.

2014-01-01

Microstructural changes that occur during heat treatment of copper-nickel-zinc ferrites have been studied. The process of precipitation of the two types of crystals that occur during the sintering process has been analyzed. It is found that this process depends on dry relative density of the press specimens and on the following sintering parameters: sintering temperature, sintering time and cooling rate of the thermal cycle. Crystal precipitates characterization have been done by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These techniques have allowed to determine the nature of these crystals, which in this case correspond to zinc and copper oxides. It has been used two chemical reactions to explain the bulk precipitation and subsequent re-dissolution of these crystal precipitates during sintering. (Author)

Mechanical characteristics of microwave sintered silicon carbide

Indian Academy of Sciences (India)

In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

Effect of sintering atmosphere on the hardness of ThO_2

International Nuclear Information System (INIS)

Baena, Angela; Cardinaels, Thomas; Van Eyken, Jelle; Puzzolante, Jean Louis; Binnemans, Koen; Verwerft, Marc

2016-01-01

The hardness and toughness of ThO_2 sintered under reducing and oxidizing conditions has been investigated and, quite unexpectedly, a significant difference in hardness was observed for the entire range of porosities studied. Reducing conditions systematically yielded higher hardness values than oxidizing conditions. Extrapolated to zero porosity, the hardness for ThO_2 is H_0 = 10.5 ± 0.3 GPa for oxidizing conditions and H_0 = 12.4 ± 0.7 GPa for reducing conditions. Toughness values have been derived from Vickers indentations; differences in toughness were insignificant and only a single value is proposed: K_I_C = 0.97 ± 0.12 MPa √m. The difference in hardness is attributed to the presence of point defects, also acting as color centers and causing grey coloration of ThO_2 sintered under reducing conditions. Furthermore, and of interest for nuclear fuel production, is the finding that ThO_2 sintered under reducing conditions is significantly easier to grind compared to material sintered under oxidizing conditions. - Highlights: • Reducing sintering conditions increase the hardness of polycrystalline ThO_2. • Systematic series of hardness versus porosity of ThO_2 were obtained. • Reducing sintering conditions improve grinding of ThO_2.

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

International Nuclear Information System (INIS)

Watanabe, Yuichi; Suemori, Kouji; Hoshino, Satoshi

2016-01-01

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 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 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 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.

Preparation of Nd–Fe–B sintered magnets from HDDR-processed powder

Energy Technology Data Exchange (ETDEWEB)

Takagi, Kenta, E-mail: k-takagi@aist.go.jp [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Akada, Misaho [Magnetic Materials R& D Center, Research Associations of Magnetic Materials for High-Efficiency Motors (MagHEM), Nagoya 463-8560 (Japan); Soda, Rikio; Ozaki, Kimihiro [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan)

2015-11-01

The electric-current sintering technique was used to fully densify hydrogenation–disproportionation–desorption–recombination (HDDR)-processed Nd–Fe–B powder at temperatures below the grain growth temperature in order to produce high-coercive bulk magnets. However, the sintered magnets exhibited anomalous coercivity reduction that depended on sintered density. Reheating examination of the sintered magnets revealed that the reduced coercivity was increased in proportion to the heating temperature, resulting in complete recovery of coercivity. As a result, the combination of electric-current sintering and post-annealing produced sintered magnets with a coercivity of 15 kOe. Scanning and transmission electron microscopy revealed no evidence that associated the anomalous coercivity reduction and recovery with grain boundary morphology. On the other hand, various HDDR powders with different particle sizes were sintered, and finer powders yielded lower coercivity after sintering, implying that the anomalous coercivity reduction was associated with particle surface oxides of the raw powder. - Highlights: • We conduct a sintering of HDDR-processed Nd–Fe–B powder without coercivity reduction. • Rapid current sintering allows densification of this powder without grain growth. • However, the sintered magnets show an anomalous coercivity reduction phenomenon. • It is found that post-annealing completely recovers the reduced coercivity. • The anomalous coercivity reduction would be due to surface oxide of the raw powder.

Effects of sintering atmosphere and initial particle size on sintering of gadolinia-doped ceria

International Nuclear Information System (INIS)

Batista, Rafael Morgado

2014-01-01

The effects of the sintering atmosphere and initial particle size on the sintering of ceria containing 10 mol% gadolinia (GdO 1.5 ) were systematically investigated. The main physical parameter was the specific surface area of the initial powders. Nanometric powders with three different specific surface areas were utilized, 210 m 2 /g, 36,2 m 2 /g e 7,4 m 2 /g. The influence on the densification, and micro structural evolution were evaluated. The starting sintering temperature was verified to decrease with increasing on the specific surface area of raw powders. The densification was accelerated for the materials with smaller particle size. Sintering paths for crystallite growth were obtained. Master sintering curves for gadolinium-doped ceria were constructed for all initial powders. A computational program was developed for this purpose. The results for apparent activation energy showed noticeable dependence with specific surface area. In this work, the apparent activation energy for densification increased with the initial particle size of powders. The evolution of the particle size distributions on non isothermal sintering was investigated by WPPM method. It was verified that the grain growth controlling mechanism on gadolinia doped ceria is the pore drag for initial stage and beginning of intermediate stage. The effects of the sintering atmosphere on the stoichiometry deviation of ceria, densification, microstructure evolution, and electrical conductivity were analyzed. Inert, oxidizing, and reducing atmospheres were utilized on this work. Deviations on ceria stoichiometry were verified on the bulk materials. The deviation verified was dependent of the specific surface area and sintering atmosphere. Higher reduction potential atmospheres increase Ce 3+ bulk concentration after sintering. Accelerated grain growth and lower electrical conductivities were verified when reduction reactions are significantly present on sintering. (author)

Pressure sintering and creep deformation: a joint modeling approach

International Nuclear Information System (INIS)

Notis, M.R.

1979-10-01

Work related to microchemical and microstructural aspects of the joint modeling of pressure sintering and creep in ceramic oxides is reported. Quantitative techniques for the microchemical analysis of ceramic oxides and for the examination of impurity segregation effects in polycrystalline ceramic materials were developed. This has included fundamental absorption corrections for the oxygen anion species as a function of foil thickness. The evolution in microstructure during the transition from intermediate stage to final stage densification during hot pressing of cobalt oxide and preliminary studies with doped oxides were studied. This work shows promise in using time-integrated microstructural effects to elucidate the role of impurities in the sintering of ceramic materials

Novel approaches for the in situ study of the sintering of nuclear oxide fuel materials and their surrogates

Energy Technology Data Exchange (ETDEWEB)

Clavier, Nicolas; Nkou Bouala, Galy Ingrid; Dacheux, Nicolas; Podor, Renaud [Montpellier Univ., Bagnols sur Ceze (France). ICSM - UMR 5257 CEA/CNRS/ENSCM; Lechelle, Jacques [CEA, DNE, DEC, SESC, LLCC, St-Paul lez Durance (France); Martinez, Julien [CEA, DEN, DTEC, SECA, LFC, Bagnols sur Ceze (France)

2017-07-01

Sintering is one of the key-points of the processing of ceramic materials. It is then of primary interest for the nuclear fuel cycle, in which it constitutes an important step in the fabrication of either UO{sub 2} or (U,Pu)O{sub 2} pellets used in current PWR reactors. The sintering of actinides oxides not only drives the final density and microstructure of the fuels, but also several characteristics that can impact significantly their behavior in the reactor. Dedicated tools are then needed to monitor the microstructure of such materials and forecast their evolution. In this frame, this paper presents the new potentialities offered by the use of environmental scanning electron microscope at high temperature (HT-ESEM) for the study of nuclear ceramics sintering. First, the results obtained from bulk pellets are detailed, either regarding original fundamental data at the grain level (such as grain boundaries and pores motion), or design of dedicated microstructures through the assessment of grain growth kinetics. Acquisition of sintering maps thanks to the combination of HT-ESEM observations and classical dilatometric measurements are also addressed. In a second part, observations undertaken at the 2-grain scale to monitor the first stage of sintering, dedicated to neck elaboration, are presented, and compared to the results currently provided by numerical models.

Method of sintering ceramic materials

Science.gov (United States)

Holcombe, Cressie E.; Dykes, Norman L.

1992-01-01

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

Nitric oxide synthase expression and apoptotic cell death in brains of AIDS and AIDS dementia patients

NARCIS (Netherlands)

Vincent, V. A.; de Groot, C. J.; Lucassen, P. J.; Portegies, P.; Troost, D.; Tilders, F. J.; van Dam, A. M.

1999-01-01

To determine the occurrence and cellular localization of inducible nitric oxide synthase (iNOS), NOS activity and its association with cell death in brains of AIDS and AIDS dementia complex (ADC) patients. Post-mortem cerebral cortex tissue of eight AIDS patients, eight ADC patients and eight

Effect of sintering atmosphere on the hardness of ThO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Baena, Angela; Cardinaels, Thomas [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Fuel Materials Group, Boeretang 200, B-2400, Mol (Belgium); KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001, Heverlee (Belgium); Van Eyken, Jelle; Puzzolante, Jean Louis [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Fuel Materials Group, Boeretang 200, B-2400, Mol (Belgium); Binnemans, Koen [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001, Heverlee (Belgium); Verwerft, Marc, E-mail: marc.verwerft@sckcen.be [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Fuel Materials Group, Boeretang 200, B-2400, Mol (Belgium)

2016-08-15

The hardness and toughness of ThO{sub 2} sintered under reducing and oxidizing conditions has been investigated and, quite unexpectedly, a significant difference in hardness was observed for the entire range of porosities studied. Reducing conditions systematically yielded higher hardness values than oxidizing conditions. Extrapolated to zero porosity, the hardness for ThO{sub 2} is H{sub 0} = 10.5 ± 0.3 GPa for oxidizing conditions and H{sub 0} = 12.4 ± 0.7 GPa for reducing conditions. Toughness values have been derived from Vickers indentations; differences in toughness were insignificant and only a single value is proposed: K{sub IC} = 0.97 ± 0.12 MPa √m. The difference in hardness is attributed to the presence of point defects, also acting as color centers and causing grey coloration of ThO{sub 2} sintered under reducing conditions. Furthermore, and of interest for nuclear fuel production, is the finding that ThO{sub 2} sintered under reducing conditions is significantly easier to grind compared to material sintered under oxidizing conditions. - Highlights: • Reducing sintering conditions increase the hardness of polycrystalline ThO{sub 2}. • Systematic series of hardness versus porosity of ThO{sub 2} were obtained. • Reducing sintering conditions improve grinding of ThO{sub 2}.

New materials through a variety of sintering methods

Science.gov (United States)

Jaworska, L.; Cyboroń, J.; Cygan, S.; Laszkiewicz-Łukasik, J.; Podsiadło, M.; Novak, P.; Holovenko, Y.

2018-03-01

New sintering techniques make it possible to obtain materials with special properties that are impossible to obtain by conventional sintering techniques. This issue is especially important for ceramic materials for application under extreme conditions. Following the tendency to limit critical materials in manufacturing processes, the use of W, Si, B, Co, Cr should be limited, also. One of the cheapest and widely available materials is aluminum oxide, which shows differences in phase composition, grain size, hardness, strain and fracture toughness of the same type of powder, sintered via various methods. In this paper the alumina was sintered using the conventional free sintering process, microwave sintering, Spark Plasma Sintering (SPS), high pressure-high temperature method (HP-HT) and High Pressure Spark Plasma Sintering (HP SPS). Phase composition analysis, by X-ray diffraction of the alumina materials sintered using various methods, was carried out. For the conventional sintering method, compacts are composed of α-Al2O3 and θ-Al2O3. For compacts sintered using SPS, microwave and HP-HT methods, χ-Al2O3 and γ-Al2O3 phases were additionally present. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. On the basis of images from scanning electron microscope quantitative analysis was performed to determine the degree of grain growth of alumina after sintering.

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.

Sintering of Synroc D

International Nuclear Information System (INIS)

Robinson, G.

1982-01-01

Sintering has been investigated as a method for the mineralization and densification of high-level nuclear defense waste powder. Studies have been conducted on Synroc D composite powder LS04. Optimal densification has been found to be highly dependent on the characteristics of the starting material. Powder subjected to milling, which was believed to reduce the level of agglomeration and possibly particle size, was found to densify better than powder not subjected to this milling. Densities of greater than 95% of theoretical could be achieved for samples sintered at 1150 to 1200 0 C. Mineralogy was found to be as expected for Synroc D for samples sintered in a CO 2 /CO atmosphere where the Fe +2 /Fe +3 ratio was maintained at 1.0 to 5.75. In a more oxidizing, pure CO 2 atmosphere a new phase, not previously identified in Synroc D, was found

Modeling sintering of multilayers under influence of gravity

DEFF Research Database (Denmark)

Frandsen, Henrik Lund; Olevsky, Eugene; Tadesse Molla, Tesfaye

2013-01-01

, which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod-Olevsky viscous sintering framework, the classical...... laminate theory and the elastic-viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant. © 2012 The American Ceramic Society....

Low temperature spark plasma sintering of YIG powders

International Nuclear Information System (INIS)

Fernandez-Garcia, L.; Suarez, M.; Menendez, J.L.

2010-01-01

A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 o C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 o C leads to dense samples with minimal formation of YFeO 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.

Densification of LSGM electrolytes using activated microwave sintering

Science.gov (United States)

Kesapragada, S. V.; Bhaduri, S. B.; Bhaduri, S.; Singh, P.

Lanthanum gallate doped with alkaline rare earths (LSGM) powders were densified using an activated microwave sintering process for developing a dense stable electrolyte layer for applications in intermediate temperature-solid oxide fuel cells (IT-SOFCs). Due to heat generation in situ, the process of sintering gets activated with faster kinetics compared to a conventional sintering process. The effect of various microwave process parameters on the microstructure and phase formation was studied. The sintered pellets were characterized using scanning electron microscopy-energy dispersive analysis (SEM-EDAX), and X-ray diffraction (XRD). The density of LSGM pellets microwave sintered at 1350 °C for 20 min is greater than 95% theoretical density with a fine grained microstructure (˜2-3 μm) and without the presence of other phase(s).

Studies on O/M ratio determination in uranium oxide, plutonium oxide and uranium-plutonium mixed oxide

International Nuclear Information System (INIS)

Sampath, S.; Chawla, K.L.

1975-01-01

Thermogravimetric studies were carried out in unsintered and sintered samples of uranium oxide, plutonium oxide and uranium-plutonium mixed oxide under different atmospheric conditions (air, argon and moist argon/hydrogen). Moisture loss was found to occur below 200 0 C for uranium dioxide samples, upto 700 0 C for sintered plutonium dioxide and negligible for sintered samples. The O/M ratios for non-stoichiometric uranium dioxide (sintered and unsintered), plutonium dioxide and mixed uranium and plutonium oxides (sintered) could be obtained with a precision of +- 0.002. Two reference states UOsub(2.000) and UOsub(2.656) were obtained for uranium dioxide and the reference state MOsub(2.000) was used for other cases. For unsintered plutonium dioxide samples, accurate O/M ratios could not be obtained of overlap of moisture loss with oxygen loss/gain. (author)

CALCIUM OXIDE SINTERING IN ATMOSPHERES CONTAINING WATER AND CARBON DIOXIDE

Science.gov (United States)

The paper gives results of measurements of the effects of water vapor and CO2 on the sintering rate of nascent CaO, as a function of partial pressure and temperature using CaO prepared by rapid decomposition of CaCO3 and CA(OH)2. Each gas strongly catalyzed the sintering process ...

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.

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.

Synthesis strategies for improving the performance of doped-BaZrO 3 materials in solid oxide fuel cell applications

KAUST Repository

Bi, Lei

2013-08-07

Solid oxide fuel cells (SOFCs) offer an efficient energy conversion technology for alleviating current energy problems. High temperature proton-conducting (HTPC) oxides are promising electrolytes for this technology, since their activation energy is lower than that of conventional oxygen-ion conductors, enabling the operating temperature reduction at 600 °C. Among HTPC oxides, doped BaZrO3 materials possess high chemical stability, needed for practical applications. Though, poor sinterability and the resulting large volume of highly resistive grain boundaries hindered their deployment for many years. Nonetheless, the recently demonstrated high proton conductivity of the bulk revived the attention on doped BaZrO3, stimulating research on solving the sintering issues. The proper selection of dopants and sintering aids was demonstrated to be successful for improving the BaZrO3 electrolyte sinterability. We here briefly review the synthesis strategies proposed for preparing BaZrO3-based nanostructured powders for electrolyte and electrodes, with the aim to improve the SOFC performance. © Materials Research Society 2013.

Synthesis by spark plasma sintering of a novel protonic/electronic conductor composite: BaCe0.2Zr0.7Y0.1O3−δ /Sr0.95Ti0.9Nb0.1O3−δ (BCZY27/STN95)

DEFF Research Database (Denmark)

Fish, Jason; Ricote, Sandrine; Lenrick, Filip

2013-01-01

and sintered conventionally (CS) at 1350–1500 °C, as well as by spark plasma sintering (SPS) at 1300–1350 °C. CS samples were porous and exhibited high degrees of inter-phase reaction. Nickel oxide sintering aids did not improve CS sample density. In contrast, samples made by SPS were significantly denser (>95...... of these regions with high-resolution transmission electron microscopy and selective area electron diffraction. We thus suggest that these phases are present as independent grains in the bulk. It is believed these secondary phases inhibit electronic conductivity in the composite....

Influence of spark plasma sintering conditions on the sintering and functional properties of an ultra-fine grained 316L stainless steel obtained from ball-milled powder

Energy Technology Data Exchange (ETDEWEB)

Keller, C., E-mail: clement.keller@insa-rouen.fr [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Tabalaiev, K.; Marnier, G. [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Noudem, J. [Laboratoire de Cristallographie des Matériaux, CNRS-UMR 6508, Université de Caen, ENSICAEN, 7 bd du Maréchal Juin, 14050 Caen (France); Sauvage, X. [Groupe de Physique des Matériaux, CNRS-UMR 6634, Université de Rouen, INSA de Rouen, Avenue de l' Université, 76800 Saint-Etienne du Rouvray (France); Hug, E. [Laboratoire de Cristallographie des Matériaux, CNRS-UMR 6508, Université de Caen, ENSICAEN, 7 bd du Maréchal Juin, 14050 Caen (France)

2016-05-17

In this work, 316L samples with submicrometric grain size were sintered by spark plasma sintering. To this aim, 316L powder was first ball-milled with different conditions to obtain nanostructured powder. The process control agent quantity and milling time were varied to check their influence on the crystallite size of milled powder. Samples were then sintered by spark plasma sintering using different sets of sintering parameters (temperature, dwell time and pressure). For each sample, grain size and density were systematically measured in order to investigate the influence of the sintering process on these two key microstructure parameters. Results show that suitable ball-milling and subsequent sintering can be employed to obtain austenitic stainless steel samples with grain sizes in the nanometer range with porosity lower than 3%. However, ball-milling and subsequent sintering enhance chromium carbides formation at the sample surface in addition to intragranular and intergranular oxides in the sample as revealed by X-ray diffraction and transmission electron microscopy. It has been shown that using Boron nitride together with graphite foils to protect the mold from powder welding prevent such carbide formation. For mechanical properties, results show that the grain size refinement strongly increases the hardness of the samples without deviation from Hall-Petch relationship despite the oxides formation. For corrosion resistance, grain sizes lower than a few micrometers involve a strong decrease in the pitting potential and a strong increase in passivation current. As a consequence, spark plasma sintering can be considered as a promising tool for ultra-fine grained austenitic stainless steel.

Fabrication of aluminum nitride crucibles for molten salt and plutonium compatibility studies

International Nuclear Information System (INIS)

Phillips, J.A.

1991-01-01

The overall objective of this research was to fabricate a calcium oxide sinter-aided aluminum nitride crucible and determine the compatibility of this crucible with molten chloride salts and plutonium metal in the DOR process. Calcium oxide sinter-aided aluminum nitride was preferred over yttrium oxide sinter-aided aluminum nitride because of (1) the presence of calcium chloride, calcium oxide, and calcium metal in the molten salts utilized in the DOR process, and (2) the higher volatility of the secondary phases formed compared with phases resulting from the addition of yttrium oxide during the aluminum nitride sintering process. The calcium oxide system may yield a higher purity crystal structure with fewer secondary phases present than in the yttrium oxide system. The secondary phases that are present in the grain boundaries may be unreactive with the calcium chloride salt due to the presence of calcium in the secondary phases

Characteristics Of The Porous Body Sintered By Nano-Sized Fe-Cr-Al Alloy Powder

Directory of Open Access Journals (Sweden)

Lee Su-In

2015-06-01

Full Text Available Porous metal with uniform honeycomb structure was successfully produced by sintering using Fe-Cr-Al nano powder, which was prepared by the pulsed wire evaporation (PWE in ethanol. Its process consisted of the several steps; 1 coating on the surface of polyurethane sponge with the liquid droplets generated from the ethanol-based slurry where the Fe-Cr-Al nano powders were uniformly dispersed, 2 heat treatment of debinding to remove the polyurethane sponge and 3 sintering of the porous green body formed by Fe-Cr-Al nano powders. The strut thickness of porous Fe-Cr-Al was increased by the increase of spraying times in ESP step. Also, The shrinkages and the oxidation resistance of the sintered porous body was increased with increase of sintering temperature. The optimal sintering temperature was shown to 1450°C in views to maximize the oxidation resistance and sinterability.

Effects of pressure and temperature on sintering of Cr-doped Al2O3 by pulsed electric current sintering process

Science.gov (United States)

Dang, K. Q.; Nanko, M.

2011-03-01

The aluminium oxide crystal, Al2O3, which contains a small amount of chromium, Cr, is called ruby. Pulsed electric current sintering (PECS) was applied to sinter ruby polycrystals. Cr2O3-Al2O3 powder mixture prepared by drying an aqueous slurry containing amounts of Al2O3 and Cr(NO3)3 was consolidated by PECS process. The PECS process was performed in vacuum at sintering temperature raging from 1100 to 1300°C with heating rate of 2 K/min under applied uniaxial pressure varied from 40 to 100 MPa. This study found that highly densified and transparent Cr-doped Al2O3 can be obtained by the PECS process with the high applied pressure at sintering temperature of 1200°C.

Thermoelectric Properties of Hot-Pressed and PECS-Sintered Magnesium-Doped Copper Aluminum Oxide

Science.gov (United States)

Liu, Chang; Morelli, Donald T.

2011-05-01

Copper aluminum oxide (CuAlO2) is considered as a potential candidate for thermoelectric applications. Partially magnesium-doped CuAlO2 bulk pellets were fabricated using solid-state reactions, hot-pressing, and pulsed electric current sintering (PECS) techniques. X-ray diffraction and scanning electron microscopy were adopted for structural analysis. High-temperature transport property measurements were performed on hot-pressed samples. Electrical conductivity increased with Mg doping before secondary phases became significant, while the Seebeck coefficient displayed the opposite trend. Thermal conductivity was consistently reduced as the Mg concentration increased. Effects of Mg doping, preparation conditions, and future modification on this material's properties are discussed.

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

Energy Technology Data Exchange (ETDEWEB)

Potanina, Ekaterina, E-mail: ekaterina.potanina@list.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Golovkina, Ludmila, E-mail: golovkina_lyudmila@mail.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Orlova, Albina, E-mail: albina.orlova@inbox.ru [Department of Solid State Chemistry, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 2, 603950 Nizhny Novgorod (Russian Federation); Nokhrin, Aleksey, E-mail: nokhrin@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation); Boldin, Maksim, E-mail: boldin@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation); Sakharov, Nikita, E-mail: nvsaharov@nifti.unn.ru [Research Institute of Physics and Technology, Lobachevsky State University of Nizhni Novgorod, National Research University, 23 Prospekt Gagarina, BLDG 3, 603950 Nizhny Novgorod (Russian Federation)

2016-05-15

Complex oxide Y{sub 2.5}Nd{sub 0.5}Al{sub 5}O{sub 12} with garnet structure and phosphates NdPO{sub 4} and GdPO{sub 4} with monazite structure were obtained by using precipitation methods. Ceramics Y{sub 2.5}Nd{sub 0.5}Al{sub 5}O{sub 12} and NdPO{sub 4} were processed by Spark Plasma Sintering (SPS). Relative density more 98%, sintering time did not exceed 8 min, sintering temperature 1330–1390 °C. Leaching rates of elements from ceramics were 10{sup −6}–10{sup −7} g/(cm{sup 2} d). The process of ceramics sintering has two-stage character: the first step of sintering-compaction process is related to the plastic flow of the material, the second step–to the process of grain boundary diffusion and grain growth. - Highlights: • Powders were obtained by precipitation (sol–gel) method. • Ceramics were sintering by Spark Plasma Sintering method (ρ{sub rel} > 98%); shrinkage time does not exceed 8 min. • The process of ceramics sintering has two-stage character.

Effect of rare earth oxide addition on microstructures of ultra-fine WC-Co particulate reinforced Cu matrix composites prepared by direct laser sintering

International Nuclear Information System (INIS)

Gu Dongdong; Shen Yifu; Zhao Long; Xiao Jun; Wu Peng; Zhu Yongbing

2007-01-01

This paper presents a detailed investigation into the influence of the rare earth (RE) oxide (La 2 O 3 ) addition upon the densification and the resultant microstructural characteristics of the submicron WC-Co particulate reinforced Cu matrix composites prepared by direct laser sintering. It is found that the relative density of the laser sintered sample with 1 wt.% La 2 O 3 addition increased by 11.5% as compared with the sample without RE addition. The addition of RE element favored the microstructural refinement and improved the particulate dispersion homogeneity and the particulate/matrix interfacial coherence. The metallurgical functions of the RE element in improving the sinterability were also addressed. It shows that due to the unique properties of RE element such as high surface activity and large atomic radius, the addition of trace RE element can decrease the surface tension of the melt, resist the grain growth coarsening and increase the heterogeneous nucleation rate during laser sintering

Improved Modeling Approaches for Constrained Sintering of Bi-Layered Porous Structures

DEFF Research Database (Denmark)

Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Esposito, Vincenzo

2012-01-01

Shape instabilities during constrained sintering experiment of bi-layer porous and dense cerium gadolinium oxide (CGO) structures have been analyzed. An analytical and a numerical model based on the continuum theory of sintering has been implemented to describe the evolution of bow and densificat...

Low-cost optical fabrication of flexible copper electrode via laser-induced reductive sintering and adhesive transfer

Science.gov (United States)

Back, Seunghyun; Kang, Bongchul

2018-02-01

Fabricating copper electrodes on heat-sensitive polymer films in air is highly challenging owing to the need of expensive copper nanoparticles, rapid oxidation of precursor during sintering, and limitation of sintering temperature to prevent the thermal damage of the polymer film. A laser-induced hybrid process of reductive sintering and adhesive transfer is demonstrated to cost-effectively fabricate copper electrode on a polyethylene film with a thermal resistance below 100 °C. A laser-induced reductive sintering process directly fabricates a high-conductive copper electrode onto a glass donor from copper oxide nanoparticle solution via photo-thermochemical reduction and agglomeration of copper oxide nanoparticles. The sintered copper patterns were transferred in parallel to a heat-sensitive polyethylene film through self-selective surface adhesion of the film, which was generated by the selective laser absorption of the copper pattern. The method reported here could become one of the most important manufacturing technologies for fabricating low-cost wearable and disposable electronics.

Development of a Sinter/HIP process for the superalloy Udimet 700 with investigations of the influence of the sinteratmosphere

International Nuclear Information System (INIS)

Wenning, L.

1991-03-01

The oxidation free treatment of reactive metalpowders like the nickel base alloy Udimet 700 demands sufficient oxygen free sinteratmospheres in nowadays sinter-HIP plants are not reachable. The reported work deals with the development of a sinter-HIP process which enables a sufficient low partial pressure of oxygen by scavenging the Udimet 700 powder packings with argon during vacuum sintering. By this the sinter hindering oxidation is avoided. Intensive investigations of the sinteratmosphere with a mass spectrometer and a zirconium oxide probe verify the reduction of the oxygen content of the residual gas atmosphere reached with different processes. In a second part the applicability of the scavenging gas process during the capsule free sinter-HIP treatment of metall injection moulded (MIM) samples is shown. (orig.) [de

Phenomenological model of sintering of oxide nuclear fuel with doping admixtures

Science.gov (United States)

Baranov, V. G.; Devyatko, Yu. N.; Tenishev, A. V.; Khomyakov, O. V.

2015-12-01

It is shown that a change in the linear dimension of compacted UO2 in the sintering process is associated with its plastic yielding under the action of the forces of residual stress and capillary forces. From the curves of sintering of a fuel with doping admixtures in various gaseous media, its rate of creep is reduced.

Sintering and densification; new techniques: sinter forging

International Nuclear Information System (INIS)

Winnubst, A.J.A.

1998-01-01

In this chapter pressure assisted sintering methods will be described. Attention will mainly be paid to sinter forging as a die-wall free uniaxial pressure sintering technique, where large creep strains are possible. Sinter forging is an effective tool to reduce sintering temperature and time and to obtain a nearly theoretically dense ceramic. In this way grain size in tetragonal zirconia ceramics can be reduced down to 100 nm. Another important phenomenon is the reduction of the number density and size of cracks and flaws resulting in higher strength and improved reliability, which is of utmost importance for engineering ceramics. The creep deformation during sinter forging causes a rearrangement of the grains resulting in a reduction of interatomic spaces between grains, while grain boundary (glassy) phases can be removed. The toughness and in some cases the wear resistance is enhanced after sinter forging as a result of the grain-boundary-morphology improvement. (orig.)

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Directory of Open Access Journals (Sweden)

Pieczonka T.

2017-06-01

Full Text Available Aluminium oxide layer on aluminium particles cannot be avoided. However, to make the metal-metal contacts possible, this sintering barrier has to be overcome in some way, necessarily to form sintering necks and their development. It is postulated that the disruption of alumina layer under sintering conditions may originate physically and chemically. Additionally, to sinter successfully non alloyed aluminium powder in nitrogen, the operation of both types mechanism is required. It is to be noted that metallic aluminium surface has to be available to initiate reactions between aluminium and the sintering atmosphere, i.e. mechanical disruption of alumina film precedes the chemical reactions, and only then chemically induced mechanisms may develop. Dilatometry, gravimetric and differential thermal analyses, and microstructure investigations were used to study the sintering response of aluminium at 620°C in nitrogen, which is the only sintering atmosphere producing shrinkage.

Solidification of high level liquid waste (HLLW) into ceramics by sintering process

International Nuclear Information System (INIS)

Masuda, Sumio; Oguino, Naohiko; Tsunoda, Naomi; O-oka, Kazuo; Ohta, Takao.

1979-01-01

One of the alternatives to vitrified solid which is acceptable and well characterized for storing radioactive HLLW with desirable long-term stability is ceramics. On the other hand, the solidification process of highly radioactive wastes should be simple and suitable for continuous production. On the above described basis, the authors have made preliminary study on the production of sintered ceramics by the addition of several oxides to HLLW. The simulated waste and additive oxides were pressed in a mold to make the preforms of 50 mm diameter and 10 to 15 mm thick. The preforms were then normally sintered at temperature from 1000 to 1400 deg C for 2 to 4 hours. The characterization of the sintered solids revealed the following facts. (1) X-ray diffraction analysis showed that the expected crystals were formed by normal-sintering as well as by hot-pressing. (2) The bulk density of the ceramics by normal-sintering was around 90 to 95% of the assumed theoretical values. (3) The leach-rate of the solids was affected by the bulk density. (4) Other properties of the solids, such as thermal expansion or thermal conductivity, are dominantly determined by those of main crystals in the solids. Sintering process is generally simple and productive as far as normal sintering is concerned. However, hot-pressing is an intermittent and time consuming process. From this fact, the authors intended to adopt the normal sintering process for the ceramic solidification of high level liquid wastes. (Wakatsuki, Y.)

Effect of grain size on the hardness and reactivity of plasma-sintered beryllium

International Nuclear Information System (INIS)

Kim, Jae-Hwan; Nakamichi, Masaru

2014-01-01

Beryllium and its intermetallic compounds have attracted great attention as promising neutron multipliers in fusion reactors. In this study, mechanical and chemical properties of fabricated plasma-sintered beryllium (PS-Be) with different grain-sizes are investigated. Density and hardness analysis results of the fabricated PS-Be samples infer that a smaller grain size in the sintered Be indicates higher porosity and hardness. Sintered Be with a large grain size exhibits better resistance toward oxidation at 1273 K in dry air and at 1073 K in Ar/1% H 2 O, since oxidation at the grain boundaries of the determines the rate. In contrast, at 1273 K in Ar/1% H 2 O, a catastrophic oxidation is indicated by the increase of weight of the samples and the generation of H 2 from the bulk Be

Spark plasma sintering of pure and doped tungsten as plasma facing material

Science.gov (United States)

Autissier, E.; Richou, M.; Minier, L.; Naimi, F.; Pintsuk, G.; Bernard, F.

2014-04-01

In the current water cooled divertor concept, tungsten is an armour material and CuCrZr is a structural material. In this work, a fabrication route via a powder metallurgy process such as spark plasma sintering is proposed to fully control the microstructure of W and W composites. The effect of chemical composition (additives) and the powder grain size was investigated. To reduce the sintering temperature, W powders doped with a nano-oxide dispersion of Y2O3 are used. Consequently, the sintering temperature for W-oxide dispersed strengthened (1800 °C) is lower than for pure W powder. Edge localized mode tests were performed on pure W and compared to other preparation techniques and showed promising results.

Sintering and Electrical Characterization of La and Nb Co‐doped SrTiO3 Electrode Materials for Solid Oxide Cell Applications

DEFF Research Database (Denmark)

Sudireddy, Bhaskar Reddy; Agersted, Karsten

2014-01-01

Single‐phase lanthanum and niobium co‐doped strontium titanate (Sr1–3x/2LaxTi0.9Nb0.1O3; x = 0–0.02) ceramics were prepared. Dilatometry in reducing atmosphere showed an increase in the sintering rate and sintered density with an increase in La amount. Microscopy of fractured surfaces of sintered...... samples showed that the average grain size increased drastically in reducing conditions with increasing La content (and associated A‐site vacancies). By incorporating 2 mol.% La, the electronic conductivity significantly improved from 80 to 135 S cm−1 at 1,000 °C, and even larger improvements were...... observed at lower temperatures. These observations demonstrate the flexibility in tailoring the microstructure and electronic transport properties by doping small amounts of La into the Nb‐doped SrTiO3 and show that Sr1–3x/2LaxTi0.9Nb0.1O3 is a potential electrode material for solid oxide cells....

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)

Surface phenomena during the early stages of sintering in steels modified with Fe–Mn–Si–C master alloys

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); 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); Hryha, Eduard, E-mail: hryha@chalmers.se [Department of Materials and Manufacturing Technology, Chalmers University of Technology, Rännvägen 2A, SE-41296 Gothenburg (Sweden); Torralba, José Manuel, 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); Nyborg, Lars, E-mail: lars.nyborg@chalmers.se [Department of Materials and Manufacturing Technology, Chalmers University of Technology, Rännvägen 2A, SE-41296 Gothenburg (Sweden)

2013-12-15

The characteristics of the metallic powder surface play a critical role in the development of strong bonds between particles during sintering, especially when introducing elements with a high affinity for oxygen. In this study, Mn and Si have been combined in a Fe–Mn–Si–C master alloy powder in order to reduce their chemical activity and prevent oxidation during the heating stage of the sintering process. However, when this master alloy powder is mixed with an iron base powder, differences in chemical activity between both components can lead to an oxygen transfer from the iron base powder to the surface of the master alloy particles. The present research is focused on studying the evolution of the master alloy particle surface during the early stages of sintering. Surface characterization by X-ray Photoelectron Spectroscopy (XPS) shows that the master alloy powder surface is mostly covered by a thin easily reducible iron oxide layer (∼ 1 nm). Mn–Si particulate oxides are found as inclusions in specific areas of the surface. Evolution of oxides during sintering was studied on green compacts containing iron powder, graphite and Fe–Mn–Si–C master alloy powder that were heat treated in vacuum (10{sup −6} mbar) at different temperatures (from 400, 600, 800 to 1000 °C) and analyzed by means of XPS. Vacuum sintering provides the necessary conditions to remove manganese and silicon oxides from the powder surface in the range of temperatures between 600 °C and 1000 °C. When sintering in vacuum, since the gaseous products from reduction processes are continuously eliminated, oxidation of master alloy particles due to oxygen transfer through the atmosphere is minimized. - Highlights: • Mn and Si were introduced in sintered steels using a master alloy powder. • Surface of the master alloy is mainly covered by an easily reducible iron oxide. • Temperature ranges for oxidation/reduction are identified. • Vacuum conditions avoid oxygen transfer to

Sintering Theory and Practice

Science.gov (United States)

German, Randall M.

1996-01-01

process all around us--in manufactured objects from metals, ceramics, polymers, and many compounds. From a vast professional literature, Sintering Theory and Practice emerges as the only comprehensive, systematic, and self-contained volume on the subject. Covering all aspects of sintering as a processing topic, including materials, processes, theories, and the overall state of the art, the book Offers numerous examples, illustrations, and tables that detail actual processing cycles, and that stress existing knowledge in the field Uses the specifics of various consolidation cycles to illustrate the basics Leads the reader from the fundamentals to advanced topics, without getting bogged down in various mathematical disputes over treatments and measurements Supports the discussion with critically selected references from thousands of sources Examines the sintering behavior of a wide variety of engineered materials--metals, alloys, oxide ceramics, composites, carbides, intermetallics, glasses, and polymers Guides the reader through the sintering processes for several important industrial materials and demonstrates how to control these processes effectively and improve present techniques Provides a helpful reference for specific information on materials, processing problems, and concepts For practitioners and researchers in ceramics, powder metallurgy, and other areas, and for students and faculty in materials science and engineering, this book provides the know-how and understanding crucial to many industrial operations, offers many ideas for further research, and suggests future applications of this important technology. This book offers an unprecedented opportunity to explore sintering in both practical and theoretical terms, whether at the lab or in real-world applications, and to acquire a broad, yet thorough, understanding of this important technology.

Simulated UO{sub 2} fuel containing CsI by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Wangle, T. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, Praha 1, 115 19 (Czech Republic); Tyrpekl, V. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Cologna, M., E-mail: marco.cologna@ec.europa.eu [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany); Somers, J. [European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, 76125 Karlsruhe (Germany)

2015-11-15

Herein, an innovative preparation procedure has been deployed enabling, for the first time, the incorporation of volatile fission product simulant into highly dense nuclear fuel pellets. Highly volatile fission products were embedded in a dense UO{sub 2} matrix in the form of CsI by simply mixing starting materials and consolidation in a Spark Plasma Sintering step at 1000 °C with a 5 min dwell time. CsI particles were evenly distributed throughout the pellet and were located at the grain boundaries. The sintering rate is dependent on the O/U ratio of the powder. Addition of CsI also acts as a sintering aid, reducing the temperature of maximum densification. - Highlights: • A new method was developed to incorporation of volatile fission products simulants into dense nuclear fuel pellets. • CsI doped UO{sub 2} pellets were synthetized for the first time, by Spark Plasma Sintering. • The sintering rate in Spark Plasma Sintering is dependent on the O/U ratio of UO{sub 2+x}.

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.

Effect of Al2O3 on the sintering of garnet-type Li6.5La3Zr1.5Ta0.5O12

Energy Technology Data Exchange (ETDEWEB)

Wang, Yuxing; Yan, Pengfei; Xiao, Jie; Lu, Xiaochuan; Zhang, Ji-Guang; Sprenkle, Vincent L.

2016-10-01

It is widely recognized that Al plays a dual role in the fabrication of garnet-type solid electrolytes, i.e., as a dopant that stabilizes the cubic structure and a sintering aid that facilitates the densification. However, the sintering effect of Al2O3 has not been well understood so far because Al is typically “unintentionally” introduced into the sample from the crucible during the fabrication process. In this study, we have investigated the sintering effect of Al on the phase composition, microstructure, and ionic conductivity of Li6.5La3Zr1.5Ta0.5O12 by using an Al-free crucible and intentionally adding various amounts of γ-Al2O3. It was found that the densification of Li6.5La3Zr1.5Ta0.5O12 occurred via liquid-phase sintering, with evidence of morphology change among different compositions. Among all of the compositions, samples with 0.05 mol of Al per unit formula of garnet oxide (i.e., 0.3 wt% Al2O3) exhibited the optimal microstructure and the highest total ionic conductivity of 5 10-4 S cm-1 at room temperature.

Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

Science.gov (United States)

Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

2014-01-01

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

Characterization and Electrical Response to Humidity of Sintered Polymeric Electrospun Fibers of Vanadium Oxide-({TiO}_{{2}} /{WO}_{{3}} )

Science.gov (United States)

Araújo, E. S.; Libardi, J.; Faia, P. M.; de Oliveira, H. P.

2018-02-01

Metal oxide composites have attracted much consideration due to their promising applications in humidity sensors in response to the physical and chemical property modifications of the resulting materials. This work focused on the preparation, microstructural characterization and analysis of humidity-dependent electrical properties of undoped and vanadium oxide (V2O5)-doped titanium oxide/tungsten oxide (TiO2/WO3) sintered ceramic films obtained by electrospinning. The electrical properties were investigated by impedance spectroscopy (400 Hz-40 MHz) as a function of relative humidity (RH). The results revealed a typical transition in the transport mechanisms controlled by the appropriated doping level of V2O5, which introduces important advantages to RH detection due to the atomic substitution of titanium by vanadium atoms in highly doped structures. These aspects are directly related to the microstructure modification and structure fabrication procedure.

Heterojunction p-Cu2O/ZnO-n solar cell fabricated by spark plasma sintering

Directory of Open Access Journals (Sweden)

Christophe Tenailleau

2017-09-01

Full Text Available Abstract Cuprous oxide and zinc oxide nanoparticles were prepared at room temperature by inorganic polycondensation. X-ray diffraction (XRD analyses show that the oxide phases formed are pure and well crystallized. The spark plasma sintering (SPS technique was successfully used to prepare dense nanoceramics with superimposed layers of Cu2O and ZnO nanopowders. Sintering conditions were optimized to densify the ceramics without phase transformation or diffusion. These ceramics were also characterized by XRD and scanning electron microscopy (SEM, as well as X-ray computed tomography (XCT. SEM and XCT showed that nanograins are preserved after SPS throughout both oxide materials, while a smaller layer (~20 µm of pure oxide phase with larger grains is formed in between Cu2O and ZnO during the sintering process. The SPS technique results in high material density, with the absence of porosity and cracks, homogenous distribution, and a good phase separation. This is the first time that such as-prepared dense oxide-based heterojunction exhibits a photovoltaic effect under illumination opening a new route for preparing solar cells.

Nd-Fe-B sintered magnets fabrication by using atomized powders

International Nuclear Information System (INIS)

Goto, R; Sugimoto, S; Matsuura, M; Tezuka, N; Une, Y; Sagawa, M

2011-01-01

Nd-Fe-B sintered magnets are required to achieve high coercivity for improvement of their thermal stability. Dy is added to increase coercivity, however, this element decrease magnetization and energy products. Therefore, Dy-lean Nd-Fe-B sintered magnets with high coercivity are strongly demanded. To increase coercivity, it is necessary that microstructure of sintered magnets is consisted of both fine main phase particles and homogeneously distributed Nd-rich phases around the main phase. To meet those requirements, Nd-Fe-B atomized powders were applied to the fabrication process of sintered magnets. Comparing with the case of using strip casting (SC) alloys, jet-milled powders from atomized powders show homogeneous distribution of Nd-rich phase. After optimized thermal treatment, coercivities of sintered magnets from atomized powders and SC alloys reach 1050 kA·m-1 and 1220 kA·m-1, respectively. This difference in coercivity was due to initial oxygen concentration of starting materials. Consequently, Nd-rich phases became oxides with high melting points, and did not melt and spread during sintering and annealing.

Morphological analysis and modelling of sintering and of sintered materials

International Nuclear Information System (INIS)

Jernot, Jean-Paul

1982-01-01

This research thesis addresses the study of solid phase sintering of metallic powders, and aims at describing as precisely as possible the different involved matter transport mechanisms, first by using a thermodynamic approach to sintering. Sintering diagrams are also used to determine prevailing mechanisms. The microstructure of sintered materials has been studied by using image quantitative analysis, thus by using a morphological approach to sintering. Morphological parameters allow, on the one hand, the evolution of powders during sintering to be followed, and, on the other hand, sintered products to be correctly characterised. Moreover, the author reports the study of the evolution of some physical properties of sintered materials with respect to their microstructure parameters. This leads to the development of a modelling of the behaviour of these materials [fr

Two-step sintering of ultrafine-grained barium cerate proton conducting ceramics

International Nuclear Information System (INIS)

Wang, Siwei; Zhang, Lei; Zhang, Lingling; Brinkman, Kyle; Chen, Fanglin

2013-01-01

Ultra-fine grained dense BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) ceramics have been successfully prepared via a two-step sintering method. Co-precipitation method has been adopted to prepare nano-sized BZCYYb precursors with an average particle size of 30 nm. By controlling the sintering profile, an average grain size of 184 nm was obtained for dense BZCYYb ceramics via the two-step sintering method, compared to 445 nm for the conventional sintered samples. The two-step sintered BZCYYb samples showed less impurity and an enhanced electrical conductivity compared with the conventional sintered ones. Further, the two-step sintering method was applied to fabricate anode supported solid oxide fuel cells (SOFCs) using BZCYYb as the electrolyte, resulting in dense ultrafine-grained electrolyte membranes and porous anode substrates with fine particles. Due to the reduced ohmic as well as polarization resistances, the maximum power output of the cells fabricated from the two-step sintering method reached 349 mW m −2 at 700 °C, significantly improved from 172 mW cm −2 for the conventional sintered cells, suggesting that two-step sintering method is very promising for optimizing the microstructure and thus enhancing the electrochemical performances for barium cerate based proton-conducting SOFCs.

Study on the characteristics and sinterability of DUPIC powder by using simulated fuel

International Nuclear Information System (INIS)

Lee, Jae-Won; Lee, Jung-Won; Kim, Jong-Ho; Yim, Sung-Paal; Lee, Young-Woo; Yang, Myung-Seung

2002-01-01

The sinterability of the OREOX (oxidation and reduction of oxide fuels) powder was investigated in terms of the number of the OREOX cycles and milling time using simulated spent fuel of an equivalent burnup of 35,000 MWD/MTU. Wet milled powder was prepared and sintered to compare the morphology and sinterability with the dry milled powder. Powders having a medium particle size of less than 1μm were obtained by dry milling of OREOX powders regardless of the number of cycles. The specific surface area of the simulated DUPIC powder was governed by the number of OREOX cycles rather than by milling time. The sound pellets with a sintered density of higher than 95% TD and average grain size of larger than 8μm were obtained with the dry milled powder after 1 cycle of OREOX treatment. The powders prepared by dry milling for a short time and wet milling for a long time after 3 cycles of OREOX treatment also produced pellets with a sintered density of higher than 95% TD and average grain size of larger than 8μm. (author)

Influence of sintering temperature on the properties of pulsed electric current sintered hybrid coreshell powders

Czech Academy of Sciences Publication Activity Database

Mahmed, N.; Larismaa, J.; Heczko, Oleg; Cura, M.E.; Hannula, S.-P.

2013-01-01

Roč. 33, č. 12 (2013), s. 2233-2239 ISSN 0955-2219 R&D Projects: GA ČR(CZ) GAP107/11/0391 Institutional support: RVO:68378271 Keywords : sintering * silver * iron oxide * SiO 2 * phase transformation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.307, year: 2013 http://dx.doi.org/10.1016/j.jeurceramsoc.2012.12.023

Effect of MoSi2 addition and particle size of SiC on pressureless sintering behavior and mechanical properties of ZrB2–SiC–MoSi2 composites

Directory of Open Access Journals (Sweden)

Mehri Mashhadi

2016-07-01

Full Text Available In the present paper, ZrB2–SiC–MoSi2 composites were prepared by pressureless sintering at temperatures of 2050, 2100 and 2150 °C for 1 h under argon atmosphere. In order to prepare composite samples, ZrB2 powder was milled for 2 h, then the reinforcing particles including of micron and nano-sized SiC powder were added. MoSi2 was added to ZrB2 from 0 to 5 wt.% as sintering aid. The mixtures were formed and, after the pyrolysis, they were sintered. Densification, microstructure and mechanical properties of ZrB2–SiC composites were investigated. The shrinkage of samples was measured, and the microstructure of samples was examined using scanning electron microscopy (SEM, equipped with EDS spectroscopy. In order to examine the oxidation behavior, the samples were heat treated at 1500 °C in air and then their weight changes were measured. Room temperature mechanical properties were examined. Mass fraction of MoSi2, particle size of SiC powder and sintering temperature have a great effect on relative density, porosity, shrinkage, hardness, fracture toughness, oxidation resistance and microstructure of these composites. The highest relative density, hardness, fracture toughness and weight changes of 98.7%, 16.17 GPa, 3 MPa m1/2 and 0.28%, respectively, were obtained in ZrB2–10 wt.%SiCnano–4 wt.%MoSi2 composites sintered at 2150 °C.

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...... to expand. After heat-treatment foam glass can be obtained with porosities of 80–90 %. In this study we conduct physical foaming of cathode ray tube (CRT) panel glass by sintering under high pressure (5-25 MPa) using helium, nitrogen, or argon at 640 °C (~108 Pa s). Reheating a sample in a heating...... 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...

Correction of facial and mandibular asymmetry using a computer aided design/computer aided manufacturing prefabricated titanium implant.

Science.gov (United States)

Watson, Jason; Hatamleh, Muhanad; Alwahadni, Ahed; Srinivasan, Dilip

2014-05-01

Patients with significant craniofacial asymmetry may have functional problems associated with their occlusion and aesthetic concerns related to the imbalance in soft and hard tissue profiles. This report details a case of facial asymmetry secondary to left mandible angle deficiency due to undergoing previous radiotherapy. We describe the correction of the bony deformity using computer aided design/computer aided manufacturing custom-made titanium onlay using novel direct metal laser sintering. The direct metal laser sintering onlay proved a very accurate operative fit and showed a good aesthetic correction of the bony defect with no reported complications postoperatively. It is a useful low-morbidity technique, and there is no resorption or associated donor-site complications.

Determination of oxygen to metal ratio for varying UO2 content in sintered (U,Th)O2 pellet by oxidation-reduction method using thermo-gravimetric analyser

International Nuclear Information System (INIS)

Mahanty, B.N.; Khan, F.A.; Karande, A.P.; Prakash, A.; Afzal, Md.; Panakkal, J.P.

2009-01-01

Experiments were carried out to determine oxygen to metal ratio in 4%, 6%, 10%, 20%, 50% and 80% UO 2 in sintered (U, Th) O 2 pellets by oxidation-reduction method using thermo gravimetric analyser. (author)

Sintering process of Eu doped luminescent glass prepared from porous glass

International Nuclear Information System (INIS)

Akai, T; Murakami, M; Yamashita, M; Okajima, T; Umesaki, N

2011-01-01

Eu doped high silica glass prepared by sintering porous glass exhibits blue luminescence with high quantum efficiency. In this work, we studied effects of sintering temperature on valance state of europium ion. To investigate a change of valance state of Eu, X-ray absorption near edge structure (XANES) spectroscopy measurements were carried out. Intensity of blue emission at around 430nm drastically increases when the sintering temperature is above 1000 deg. C. From XANES spectra, it is found that almost all the Eu exist as Eu 3+ in a samples sintered below 900 deg. C, while more than 70% of Eu exist as Eu 2+ in the sample sintered at 1050 deg. C and 1100 deg. C. The drastic change of oxidation state of europium ion between 900 and 1050 deg. C is discussed in relation to the structural change probed by infrared (IR) spectroscopy.

Sintering of MSW fly ash for reuse as a concrete aggregate.

Science.gov (United States)

Mangialardi, T

2001-10-12

The sintering process of municipal solid waste (MSW) fly ash was investigated in order to manufacture sintered products for reuse as concrete aggregates. Four types of fly ash resulting from different Italian MSW incineration plants were tested in this study. A modification of the chemical composition of MSW fly ash--through a preliminary four-stage washing treatment of this material with water--was attempted to improve the chemical and mechanical characteristics of sintered products.The sintering treatment of untreated or washed fly ash was performed on cylindrical compact specimens (15 mm in diameter and 20mm in height) at different compact pressures, sintering temperatures and times.The sintering process of untreated MSW fly ashes proved to be ineffective for manufacturing sintered products for reuse as a construction material, because of the adverse chemical characteristics of these fly ashes in terms of sulfate, chloride, and vitrifying oxide contents.A preliminary washing treatment of MSW fly ash with water greatly improved the chemical and mechanical characteristics of sintered products and, for all the types of fly ash tested, the sintered products satisfied the Italian requirements for normal weight aggregates for use in concretes having a specified strength not greater than 12 and 15N/mm(2), when measured on cylindrical and cubic specimens, respectively.A compact pressure of 28 N/mm(2), a sintering temperature of 1140 degrees C, and a sintering time of 60 min were the best operating conditions for manufacturing sintered products of washed MSW fly ash.

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)

Predicting sintering deformation of ceramic film constrained by rigid substrate using anisotropic constitutive law

International Nuclear Information System (INIS)

Li Fan; Pan Jingzhe; Guillon, Olivier; Cocks, Alan

2010-01-01

Sintering of ceramic films on a solid substrate is an important technology for fabricating a range of products, including solid oxide fuel cells, micro-electronic PZT films and protective coatings. There is clear evidence that the constrained sintering process is anisotropic in nature. This paper presents a study of the constrained sintering deformation using an anisotropic constitutive law. The state of the material is described using the sintering strains rather than the relative density. In the limiting case of free sintering, the constitutive law reduces to a conventional isotropic constitutive law. The anisotropic constitutive law is used to calculate sintering deformation of a constrained film bonded to a rigid substrate and the compressive stress required in a sinter-forging experiment to achieve zero lateral shrinkage. The results are compared with experimental data in the literature. It is shown that the anisotropic constitutive law can capture the behaviour of the materials observed in the sintering experiments.

Study of nano-metric silicon carbide powder sintering. Application to fibers processing

International Nuclear Information System (INIS)

Malinge, A.

2011-01-01

Silicon carbide ceramic matrix composites (SiCf/SiCm) are of interest for high temperature applications in aerospace or nuclear components for their relatively high thermal conductivity and low activation under neutron irradiation. While most of silicon carbide fibers are obtained through the pyrolysis of a poly-carbo-silane precursor, sintering of silicon carbide nano-powders seems to be a promising route to explore. For this reason, pressureless sintering of SiC has been studied. Following the identification of appropriate sintering aids for the densification, optimization of the microstructure has been achieved through (i) the analysis of the influence of operating parameters and (ii) the control of the SiC β a SiC α phase transition. Green fibers have been obtained by two different processes involving the extrusion of SiC powder dispersion in polymer solution or the coagulation of a water-soluble polymer containing ceramic particles. Sintering of these green fibers led to fibers of around fifty microns in diameter. (author) [fr

A constitutive model and numerical simulation of sintering processes at macroscopic level

Science.gov (United States)

Wawrzyk, Krzysztof; Kowalczyk, Piotr; Nosewicz, Szymon; Rojek, Jerzy

2018-01-01

This paper presents modelling of both single and double-phase powder sintering processes at the macroscopic level. In particular, its constitutive formulation, numerical implementation and numerical tests are described. The macroscopic constitutive model is based on the assumption that the sintered material is a continuous medium. The parameters of the constitutive model for material under sintering are determined by simulation of sintering at the microscopic level using a micro-scale model. Numerical tests were carried out for a cylindrical specimen under hydrostatic and uniaxial pressure. Results of macroscopic analysis are compared against the microscopic model results. Moreover, numerical simulations are validated by comparison with experimental results. The simulations and preparation of the model are carried out by Abaqus FEA - a software for finite element analysis and computer-aided engineering. A mechanical model is defined by the user procedure "Vumat" which is developed by the first author in Fortran programming language. Modelling presented in the paper can be used to optimize and to better understand the process.

Microwave Sintering of Ceramic Materials for Industrial Application Final Report CRADA No. TC-1116-95

Energy Technology Data Exchange (ETDEWEB)

Caplan, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tandon, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Callis, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-10-19

The goal of this project was to develop the commercial capability in the US to sinter alumina oxide ceramic parts for the semiconductor manufacturing equipment industry. We planned to use the millimeter microwave (30 GHz) sintering system first developed by IAP in Russia.

Co-sintering of CGO/NIO-CGO bilayers for solid oxide fuel cell

International Nuclear Information System (INIS)

Neto, P.P.B.; Grilo, J.P.F.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M.

2012-01-01

Reducing the operating temperature of solid oxide fuel cells (SOFC) for the range between 500 and 700°C is one of the challenges which more has aroused the interest of research in SOFC in recent years. In this context, the bilayer anode/electrolyte composed of a porous support based on Ni-doped ceria (anode) and a ceria doped gadolinia (CGO) electrolyte, presents itself as one of the half-cell configurations of the most interest towards the production of electricity in the operating logic of a SOFC. In this work, CGO films were successfully prepared on NiO-CGO substrates using the resources of the screen-printing technique. The bi-layers were co-sintered between 1350 and 1450 ° C for 4 h and then characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). The results showed good adhesion at the film/substrate interface and no cracks in the films. (author)

Role of Cu During Sintering of Fe0.96Cu0.04 Nanoparticles

Science.gov (United States)

Sivaprahasam, D.; Sriramamurthy, A. M.; Bysakh, S.; Sundararajan, G.; Chattopadhyay, K.

2018-04-01

Nanoparticle agglomerates of passivated Fe ( n-Fe) and Fe0.96Cu0.04 ( n-Fe0.96Cu0.04), synthesized through the levitational gas condensation (LGC) process, were compacted and sintered using the conventional powder metallurgy method. The n-Fe0.96Cu0.04 agglomerates produced lower green density than n-Fe, and when compacted under pressure beyond 200 MPa, they underwent lateral cracking during ejection attributed to the presence of a passive oxide layer. Sintering under dynamic hydrogen atmosphere can produce a higher density of compact in n-Fe0.96Cu0.04 in comparison to n-Fe. Both the results of dilatometry and thermogravimetric (TG) measurements of the samples under flowing hydrogen revealed enhancement of the sintering process as soon as the reduction of oxide layers could be accomplished. The shrinkage rate of n-Fe0.96Cu0.04 reached a value three times higher than n-Fe at a low temperature of 723 K (450 °C) during heating. This enhanced shrinkage rate was the manifestation of accumulation of Cu at the surface of the particles. The formation of a thin-surface melted layer enriched with copper during heating to isothermal holding facilitated as a medium of transport for diffusion of the elements. The compacts produced by sintering at 773 K (500 °C), with relative density 82 pct, were found to be unstable and oxidized instantly when exposed to ambient atmosphere. The stable compacts of density more than 92 pct with 300- to 450-nm grain size could only be produced when sintering was carried out at 973 K (700 °C) and beyond. The 0.22 wt pct residual oxygen obtained in the sintered compact is similar to what is used for conventional ferrous powder metallurgy products.

Phase identification and morphology study of hematite (Fe2O3) with sintering time varitions

Science.gov (United States)

Yazirin, Cepi; Puspitasari, Poppy; Sasongko, Muhammad Ilman Nur; Tsamroh, Dewi Izzatus; Risdanareni, Puput

2017-09-01

Iron oxide has been the interest of many studies due to its applications in various scientific and industrial fields including in environment, corrosion, soil science, and exhaust emissions. Iron oxide (Fe2O3) has potential applications in catalytic reactions in electronic devices such as semiconductors, paint formulations, and lithium rechargeable batteries. Fe2O3 can be synthesized through the process of stirring, decomposition of organic iron, sol-gel, combustion, and evaporating solvents. Most of the methods used involve several steps and take a long time. The aim of this research was to investigate the phase and morphology characterization of iron oxide (Fe2O3) powder with solvent ethylene glycol after being sintered for 1 hour, 2 hours and 3 hours. The characterization tools utilized were XRD, SEM-EDX, and FTIR. The results of XRD analysis showed that the Fe2O3 sintered for 1 hour had the smallest crystallite size with a diameter of 21.05 nm. In the XRD test, the beam of X-ray was shot directly at the grain being tested. The results of SEM analysis showed thatthe Fe2O3 sintered for 1 hour produced the best result due to its crystallite size of 12.36 nm and hada shape of homogeneous nanosphere; the duration of sintering indeed had a great influence on the grain size of iron oxide (Fe2O3). In addition, the results of the elemental composition analysis indicate that the longer the sintering process, the higher the concentration of O but the lower the Fe.

Ash chemistry and sintering, verification of the mechanisms

Energy Technology Data Exchange (ETDEWEB)

Hupa, M.; Skrifvars, B.J. [Aabo Akademi, Turku (Finland)

1996-12-01

In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). In one part of study the melting behavior was calculated for ten biomass ashes and compared with lab measurements of sintering tendencies. The comparison showed that the T{sub 15} temperatures, i.e. those temperatures at which the ashes contained 15 % molten phase, correlated fairly well with the temperature at which the sintering measurements detected sintering. This suggests that partial melting can be predicted fairly accurate for some ashes already with the today existing thermodynamic calculation routines. In some cases, however the melting calculations did not correlate with the detected sintering temperatures. In a second part detailed measurements on ash behavior was conducted both in a semi full scale CFB and a lab scale FBC. Ashes and deposits were collected and analyzed in several different ways. These analyses show that the ash chemistry shifts radically when the fuel is shifted. Fuels with silicate based ashes behaved totally different than those with an oxide or salt based ash. The chemistry was also affected by fuel blending. The ultimate goal has been to be able to predict the ash thermal behavior during biomass thermal conversion, using the fuel and ash elemental analyses and a few operational key parameters as the only input data. This goal has not yet today been achieved. (author)

Study on the isothermal oxidation behavior in air of Ti3AlC2 sintered by hot pressing

Institute of Scientific and Technical Information of China (English)

XU Xuewen; LI Yangxian; MEI Bingchu; ZHU Jiaoqun; LIU Heyan; QU Jingping

2006-01-01

The isothermal oxidation behavior at 900―1300℃ for 20 h in air of bulk Ti3AlC2 with 2.8 wt% TiC sintered by means of hot pressing was investigated in the work. The isothermal oxidation behavior generally followed a parabolic rate law. The parabolic rate constants increased from 1.39×10-10 kg2·m-4·s-1 at 900℃ to 5.56×10-9 kg2·m-4·s-1 at 1300℃. The calculated activation energy was 136.45 kJ/mol. It was demonstrated that Ti3AlC2 had excellent oxidation resistance due to the continuous, dense and adhesive protect scales consisted of a mass of α-Al2O3 and a little of TiO2 and/or Al2TiO5. In principle, the oxide scale was grown by the inward diffusion of O2- and the outward diffusion of Ti4+ and Al3+. The rapid outward diffusion of cations usually resulted in the formation of cracks, gaps, and holes.

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

Science.gov (United States)

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

2017-01-01

The electric field has a large effect on the stoichiometry and grain growth of UO2+x during Spark Plasma Sintering. UO2+x is gradually reduced to UO2.00 as a function of sintering temperature and time. A gradient in the oxidation state within the pellets is observed in intermediate conditions. The shape of the gradient depends unequivocally on the direction of the electrical field. The positive surface of the pellet shows a higher oxidation state compared to the negative one. An area with larger grain size is found close to the positive electrode, but not in contact with it. We interpret these findings with the redistribution of defects under an electric field, which affect the stoichiometry of UO2+x and thus the cation diffusivity. The results bear implications for understanding the electric field assisted sintering of UO2 and non-stoichiometric oxides in general. PMID:28422164

Patient satisfaction with laser-sintered removable partial dentures: A crossover pilot clinical trial.

Science.gov (United States)

Almufleh, Balqees; Emami, Elham; Alageel, Omar; de Melo, Fabiana; Seng, Francois; Caron, Eric; Nader, Samer Abi; Al-Hashedi, Ashwaq; Albuquerque, Rubens; Feine, Jocelyne; Tamimi, Faleh

2018-04-01

Clinical data regarding newly introduced laser-sintered removable partial dentures (RPDs) are needed before this technique can be recommended. Currently, only a few clinical reports have been published, with no clinical studies. This clinical trial compared short-term satisfaction in patients wearing RPDs fabricated with conventional or computer-aided design and computer-aided manufacturing (CAD-CAM) laser-sintering technology. Twelve participants with partial edentulism were enrolled in this pilot crossover double-blinded clinical trial. Participants were randomly assigned to wear cast or CAD-CAM laser-sintered RPDs for alternate periods of 30 days. The outcome of interest was patient satisfaction as measured using the McGill Denture Satisfaction Instrument. Assessments was conducted at 1, 2, and 4 weeks. The participant's preference in regard to the type of prosthesis was assessed at the final evaluation. The linear mixed effects regression models for repeated measures were used to analyze the data, using the intention-to-treat principle. To assess the robustness of potential, incomplete adherence, sensitivity analyses were conducted. Statistically significant differences were found in patients' satisfaction between the 2 methods of RPD fabrication. Participants were significantly more satisfied with laser-sintered prostheses than cast prostheses in regard to general satisfaction, ability to speak, ability to clean, comfort, ability to masticate, masticatory efficiency, and oral condition (Premovable partial dentures may lead to better outcomes in terms of patient satisfaction in the short term. The conclusion from this pilot study requires confirmation by a larger randomized controlled trial. ClinicalTrials.gov. A study about patient satisfaction with laser-sintered removable partial dentures; NCT02769715. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Assessment of consolidation of oxide dispersion strengthened ferritic steels by spark plasma sintering: from laboratory scale to industrial products

International Nuclear Information System (INIS)

Boulnat, X.; Fabregue, D.; Perez, M.; Urvoy, S.; Hamon, D.; Carlan, Y. de

2014-01-01

Oxide dispersion strengthened steels are new generation alloys that are usually processed by hot isostatic pressing (HIP). In this study, spark plasma sintering (SPS) was studied as an alternative consolidation technique. The influence of the processing parameters on the microstructure was quantified. The homogeneity of the SPSed materials was characterised by electron microprobe and microhardness. A combination of limited grain growth and minimised porosity can be achieved on semi-industrial compact. Excellent tensile properties were obtained compared to the literature. (authors)

Pressureless sintering of dense Si3N4 and Si3N4/SiC composites with nitrate additives

International Nuclear Information System (INIS)

Kim, J.Y.; Iseki, Takayoshi; Yano, Toyohiko

1996-01-01

The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si 3 N 4 and a Si 3 N 4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si 3 N 4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si 3 N 4 particles milled with oxide additives. Monolithic Si 3 N 4 could be sintered to 94% of theoretical density (TD) at 1,500 C with nitrate additives. The sintering temperature was about 100 C lower than the case with oxide additives. After pressureless sintering at 1,750 C for 2 h in N 2 , the bulk density of a Si 3 N 4 /20 wt% SiC composite reached 95% TD with nitrate additives

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.

Microstructural designs of spark-plasma sintered silicon carbide ceramic scaffolds

Energy Technology Data Exchange (ETDEWEB)

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

2014-04-01

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

Preparation of a sinterable beryllium oxide through decomposition of beryllium hydroxide (1963); Preparation d'un oxyde de beryllium frittable par decomposition de l'hydiloxyde (1963)

Energy Technology Data Exchange (ETDEWEB)

Bernier, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

In the course of the present study, we have attempted to precise the factors which among the ones effective in the course of the preparation of the beryllium hydroxide and oxide and during the sintering have an influence on the final result: the density and homogeneity of the sintered body. Of the several varieties of hydroxides precipitated from a sulfate solution the {beta}-hydroxide only is always contaminated with beryllium sulfate and cannot be purified even by thorough washing. We noticed that those varieties of the hydroxide (gel, {alpha}, {beta}) have different decomposition rates; this behaviour is used to identify and even to dose the different species in ({alpha}, {beta}) mixtures. The various hydroxides transmit to the resulting oxides the shape they had when precipitated. Accordingly the history of the oxide is revealed by its behaviour during its fabrication and sintering. By comparing the results of the sintering operation with the various measurements performed on the oxide powders we are led to the conclusion that an oxide obtained from beryllium hydroxide is sinterable under vacuum if the following conditions are fulfilled: the particle size must lie between 0.1 and 0.2 {mu} and the BeSO{sub 4} content of the powder must be less than 0.25 per cent wt (expressed as SO{sub 3}/BeO). The best fitting is obtained with the oxide issued from an {alpha}-hydroxide precipitated as very small aggregates and with a low sulfur-content. We have observed that this is also the case for the oxide obtained by direct calcination of beryllium sulfate. (author) [French] Au cours de cette etude, nous avons cherche a preciser les facteurs qui, intervenant tout au long de la preparation de l'hydroxyde, puis de l'oxyde de beryllium et enfin du frittage, peuvent avoir une influence sur le resultat final: la densite et l'homogeneite du fritte. Parmi tous les hydroxydes precipites d'une solution de sulfate, seul l'hydroxyde {beta} est toujours fortement pollue par le sulfate

Sinterability and conductivity of barium doped aluminium lanthanum oxyapatite La{sub 9.5}Ba{sub 0.5}Si{sub 5.5}Al{sub 0.5}O{sub 26.5} electrolyte of solid oxide fuel cells

Energy Technology Data Exchange (ETDEWEB)

Cao Xiaoguo [Faculty of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, Guangdong (China); Jiang Sanping, E-mail: s.jiang@curtin.edu.au [Fuels and Energy Technology Institute and Department of Chemical Engineering, Curtin University, Perth, WA 6102 (Australia)

2012-05-15

Highlights: Black-Right-Pointing-Pointer Ba doping enhances the sintering and densification properties of aluminium lanthanum apatite. Black-Right-Pointing-Pointer Ba doping improves the oxide conductivity of aluminium lanthanum apatite. Black-Right-Pointing-Pointer The enhancement of Ba doping is mainly due to the significantly reduced grain boundary resistance of the aluminium lanthanum apatite. - Abstract: Apatite ceramics are interesting alternative solid oxide fuel cells (SOFCs) electrolytes because of their open structure for the transportation of oxide ions and their good chemical stability. This study reports the influence of barium doping on the microstructure, sinterability and oxide conductivity properties of the aluminium lanthanum oxyapatite La{sub 9.5}Ba{sub 0.5}Si{sub 5.5}Al{sub 0.5}O{sub 26.5}. SEM results show that lanthanum substitution with barium improves the sinterability of apatite ceramics. The barium doping also enhances the conductivity of the aluminium lanthanum silicates. The oxygen ion conductivity of La{sub 9.5}Ba{sub 0.5}Si{sub 5.5}Al{sub 0.5}O{sub 26.5} sintered at 1600 Degree-Sign C is 2.21 Multiplication-Sign 10{sup -2} S cm{sup -1} at 800 Degree-Sign C, higher than 9.81 Multiplication-Sign 10{sup -3} S cm{sup -1} of La{sub 10}Si{sub 5}AlO{sub 26.5} sample prepared under the same conditions. The results in the present study demonstrate that doping Ba on the La site for aluminium lanthanum oxyapatite reduces the sintering temperature and improves the ion conductivity. The enhancement of Ba dopant is mainly on the improvement of the densification and thus substantially reduced grain boundary resistance of aluminium lanthanum oxyapatite particularly at low temperatures.

Special metallurgy - the electrical butt-welding by flashing of sintered magnesium-magnesium oxide composites (1963)

International Nuclear Information System (INIS)

Charleux, J.

1963-01-01

Electrical resistance welding has become quite important since World War II because of the need of a high yield in aeronautical production. Progress has been due in particular to the improvements made in electronically controlled apparatus making possible the automatic control of welding. For the butt-welding of sections requiring either a high production rate or a high quality weld, the flash butt-welding system has been very much developed these last few years. The use of this welding method is of great importance in the field of the bonding of oxidisable metals such as magnesium or aluminium and its alloys, because the welded joint is free from oxides. This study consists of general considerations on the flash-welding process with regard to temperature distribution in the parts during welding, and to electrical phenomena connected with flashing. Besides this general or theoretical section, we have applied the welding process to the bonding of sintered magnesium, a magnesium-magnesium oxide composite, whose use as a structural element in nuclear reactors is considered. (author) [fr

SnO2*CoO ceramic obtained by microwave sintering

International Nuclear Information System (INIS)

Bordignon, M.A.N; Moura, F.; Zaghete, M.A.; Varela, J.A.; Perazolli, L.

2009-01-01

This work consists in the sintering study of CoO doped SnO 2 using microwave sintering oven and silicon carbide as a susceptor. The powders were obtained by dry oxides mixture and conformed in cylindrical shapes with 6mmx8mm and green density to 60%. Then the compacts were sintering up to 1.050 deg C, using heating rate of 50 deg C/min and isotherm up to 30min. The densities obtained were above 95% for both techniques. It was observed that occurred a temperature reducing of 400 deg C and time reducing of 210min to obtain the same densities, when was used the microwave oven without the phenomena of thermal runaway. So the sintered compacts were accomplished using DRX and SEM. It was made the electrical characterization (current x voltage) and it was found to have great potential in the production of dense ceramic-based SnO 2 with low resistivity to obtain electro-ceramic devices. (author)

3Y-TZP/Si2N2O composite obtained by pressureless sintering

International Nuclear Information System (INIS)

Santos, Carlos Augusto Xavier

2006-01-01

Zirconia 3YTZP presents excellent properties at room temperature. These properties decrease as the temperature increases because high temperature acts negatively over the stress induced transformation toughening in the matrix. The addition of Si 3 N 4 and SiC in a Y-TZP matrix is very interesting because leads to formation of silicon oxynitride and it increases the mechanical properties like toughness and hardness. Certainly the mechanical properties increment is limited by several difficulties which have appeared during processing and heating of these materials. This paper studies the Y-TZP/Si 2 N 2 0 pressureless sintered composite, under different temperatures, showing the behavior of 20 vol %Si 3 N 4 -SiC when added in YTZP matrix and heated under no pressure system. Al 2 O 3 and Y 2 O 3 were used as sintering aids. The mixture was milled and molded by cold isostatic pressure. Samples were heated at 1500 deg, 1600 deg and 17000 deg C x 2h without pressure under atmospheric conditions using Si 3 N 4 bed-powder. Samples were characterized by XRD and density, hardness, toughness, bending strength were measured. The structure of the material was observed in SEMITEM/EPMA to verify the distribution and composition of the materials in the composite and the contact between filler surface and the matrix. The formation of SiON 2 was observed in the sintered material due to reaction between both nitride and carbide with Y - TZP matrix. Furthermore the material showed an increment of both hardness and toughness as temperature increases. The samples presented considerable resistance to oxidation below 1000 deg C. (author)

Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

International Nuclear Information System (INIS)

Wang, G.P.; Liu, W.Q.; Huang, Y.L.; Ma, S.C.; Zhong, Z.C.

2014-01-01

Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively

Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Wang, G.P., E-mail: wgp@jxnu.edu.cn [College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022 (China); Liu, W.Q. [Key Laboratory of Advanced Functional Materials Science and Engineering, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Huang, Y.L.; Ma, S.C.; Zhong, Z.C. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

2014-01-15

Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively.

Lanthana-bearing nanostructured ferritic steels via spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Pasebani, Somayeh [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Charit, Indrajit, E-mail: icharit@uidaho.edu [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Wu, Yaqiao; Burns, Jatuporn; Allahar, Kerry N.; Butt, Darryl P. [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Cole, James I. [Idaho National Laboratory, Idaho Falls, ID 83401 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Alsagabi, Sultan F. [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States)

2016-03-15

A lanthana-containing nanostructured ferritic steel (NFS) was processed via mechanical alloying (MA) of Fe-14Cr-1Ti-0.3Mo-0.5La{sub 2}O{sub 3} (wt.%) and consolidated via spark plasma sintering (SPS). In order to study the consolidation behavior via SPS, sintering temperature and dwell time were correlated with microstructure, density, microhardness and shear yield strength of the sintered specimens. A bimodal grain size distribution including both micron-sized and nano-sized grains was observed in the microstructure of specimens sintered at 850, 950 and1050 °C for 45 min. Significant densification occurred at temperatures greater than 950 °C with a relative density higher than 98%. A variety of nanoparticles, some enriched in Fe and Cr oxides and copious nanoparticles smaller than 10 nm with faceted morphology and enriched in La and Ti oxides were observed. After SPS at 950 °C, the number density of Cr–Ti–La–O-enriched nanoclusters with an average radius of 1.5 nm was estimated to be 1.2 × 10{sup 24} m{sup −3}. The La + Ti:O ratio was close to 1 after SPS at 950 and 1050 °C; however, the number density of nanoclusters decreased at 1050 °C. With SPS above 950 °C, the density improved but the microhardness and shear yield strength decreased due to partial coarsening of the grains and nanoparticles.

Thulium oxide fuel characterization study: Part 3, Procedures

International Nuclear Information System (INIS)

Nelson, C.A.; Anderson, R.W.; Talbot, M.; Bierds, W.

1970-06-01

Procedures are presented for the following: Tm 2 O 3 -Yb 2 O 3 pseudo - binary phase diagram tests; compatibility tests; thulium-170 oxide dose rate measurements; preparation of Tm 2 O 3 wafers; SRL thulium and/or ytterbium oxide powder reprocessing for sintering; cold pressing and sintering thulium oxide wafers; preparation of thulium and/or ytterbium oxide powder via precipitation with oxalic acid, ammonium oxalate, urea and methyl oxalate; determination of the total surface area of rare earth oxide powders; determining oxygen in thulia - thulia/ytterbia for the purpose of determining metal-to-oxygen ratios; and determination of the impact resistance to fines generation of sintered rare earth oxide

Laser Surface Treatment of Sintered Alumina

Science.gov (United States)

Hagemann, R.; Noelke, C.; Kaierle, S.; Wesling, V.

Sintered alumina ceramics are used as refractory materials for industrial aluminum furnaces. In this environment the ceramic surface is in permanent contact with molten aluminum resulting in deposition of oxidic material on its surface. Consequently, a lower volume capacity as well as thermal efficiency of the furnaces follows. To reduce oxidic adherence of the ceramic material, two laser-based surface treatment processes were investigated: a powder- based single-step laser cladding and a laser surface remelting. Main objective is to achieve an improved surface quality of the ceramic material considering the industrial requirements as a high process speed.

Effects of additives on the sintering of UO2.Gd2O3 nuclear fuel

International Nuclear Information System (INIS)

Pagano Junior, Luciano

2009-01-01

The addition of 0.5wt% TiO 2 , Nb 2 O 5 , SiO 2 , Fe 2 O 3 and Al(OH) 3 in the UO 2 ·7%Gd 2 O 3 nuclear fuel and the effect on its sintering kinetics under a 99.999% H 2 atmosphere were investigated by stepwise isothermal dilatometry. This fuel, used as burnable poison in nuclear power plants, presents a diffusion barrier around 1573 K that impairs densification. The aid of the sintering additives TiO 2 , Al(OH) 3 , Nb 2 O 5 and Fe 2 O 3 turned out to be effective to obtain the required final density, unlike the effect observed for the SiO 2 -doped composition. The activation energy for the intermediate sintering stage was calculated by stepwise isothermal dilatometry method and a positive correlation with the sintered body density was found. The method was valid for part of the intermediate sintering stage, in the range from 1200 K to 1700 K for the doped compositions and with no additive, except for the SiO 2 -doped one, whose validity range was between 1500 K and 1900 K. The energy-density correlation was not valid for the SiO 2 -doped composition, whose effect was to reduce the final density. This anomalous behavior may be attributed to the intense loss of Si mass, probably due to lower oxides volatilization, during the initial sintering stage at temperatures lower than 1173 K. Similar loss, but no so intense, was observed for the Al(OH) 3 -doped composition in the temperature interval from 1173 K to 1573 K. The Si concentration decrease to residual values of dozens of parts per million may explain its anomalous behavior. The positive correlation between activation energy and sintered body density may be explained by the inhibitor role played by the TiO 2 , Nb 2 O 5 , Fe 2 O 3 and Al(OH) 3 additives on the diffusion mechanisms that enhance the coarsening regime. As a consequence, the densification mechanisms are favored in the competition for the surface free energy. The coarsening-densification transition temperature model, originally suggested for the UO 2

Optimization of the sintering atmosphere for high-density hydroxyapatite–carbon nanotube composites

Science.gov (United States)

White, Ashley A.; Kinloch, Ian A.; Windle, Alan H.; Best, Serena M.

2010-01-01

Hydroxyapatite–carbon nanotube (HA–CNT) composites have the potential for improved mechanical properties over HA for use in bone graft applications. Finding an appropriate sintering atmosphere for this composite presents a dilemma, as HA requires water in the sintering atmosphere to remain phase pure and well hydroxylated, yet CNTs oxidize at the high temperatures required for sintering. The purpose of this study was to optimize the atmosphere for sintering these composites. While the reaction between carbon and water to form carbon monoxide and hydrogen at high temperatures (known as the ‘water–gas reaction’) would seem to present a problem for sintering these composites, Le Chatelier's principle suggests this reaction can be suppressed by increasing the concentration of carbon monoxide and hydrogen relative to the concentration of carbon and water, so as to retain the CNTs and keep the HA's structure intact. Eight sintering atmospheres were investigated, including standard atmospheres (such as air and wet Ar), as well as atmospheres based on the water–gas reaction. It was found that sintering in an atmosphere of carbon monoxide and hydrogen, with a small amount of water added, resulted in an optimal combination of phase purity, hydroxylation, CNT retention and density. PMID:20573629

Liquid phase sintered superconducting cermet

International Nuclear Information System (INIS)

Ray, S.P.

1990-01-01

This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

Age hardening of a sintered Al-Cu-Mg-Si-(Sn) alloy

International Nuclear Information System (INIS)

Kent, D.; Schaffer, G.B.; Drennan, J.

2005-01-01

The age hardening response of a sintered Al-3.8 wt% Cu-1.0 wt% Mg-0.70 wt% Si alloy with and without 0.1 wt% Sn was investigated. The sequence of precipitation was characterised using transmission electron microscopy. The ageing response of the sintered Al-Cu-Mg-Si-(Sn) alloy is similar to that of cognate wrought 2xxx series alloys. Peak hardness was associated with a fine, uniform dispersion of lath shaped precipitates, believed to be either the β'or Q' phase, oriented along α directions and θ' plates lying on {0 0 1} α planes. Natural ageing also resulted in comparable behaviour to that observed in wrought alloys. Porosity in the powder metallurgy alloys did not significantly affect the kinetics of precipitation during artificial ageing. Trace levels of tin, used to aid sintering, slightly reduced the hardening response of the alloy. However, this was compensated for by significant improvements in density and hardness

Superior sinterability of nano-crystalline gadolinium doped ceria powders synthesized by co-precipitation method

International Nuclear Information System (INIS)

Hari Prasad, D.; Kim, H.-R.; Park, J.-S.; Son, J.-W.; Kim, B.-K.; Lee, H.-W.; Lee, J.-H.

2010-01-01

Reduced sintering temperature of doped ceria can greatly simplify the fabrication process of solid oxide fuel cells (SOFCs) by utilizing the co-firing of all cell components with a single step. In the present study, nano-crystalline gadolinium doped ceria (GDC) powders of high sinterability at lower sintering temperature has been synthesized by co-precipitation at room temperature. The successful synthesis of nano-crystalline GDC was confirmed by XRD, TEM and Raman spectroscopy analysis. Dilatometry studies showed that GDC prepared by this method can be fully densified (97% relative density) at a sintering temperature of 950 o C which is fairly lower than ever before. It has also been found that the sintered samples have a higher ionic conductivity of 1.64 x 10 -2 S cm -1 at 600 o C which is suitable for the intermediate temperature SOFC application.

Sinterability and microstructure evolution during sintering of ferrous powder mixtures

Directory of Open Access Journals (Sweden)

Kétner Bendo Demétrio

2013-01-01

Full Text Available The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%, in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

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.

Sintering of nonstoichiometric UO2

International Nuclear Information System (INIS)

Susnik, D.; Holc, J.

1983-01-01

Activated sintering of UO 2 pellets at 1100 deg C is described. In CO 2 atmosphere is UO 2 is nonstoichiometric and pellets from active UO 2 powders sinter at 900 deg C to high density. At 1100 deg C the final sintered density is practically achieved at heating on sintering temperature. After reduction and cooling in H 2 atmosphere which is followed sintering in CO 2 the structure is identical to the structured UO 2 pellets sintered at high temperature in H 2 . Density of activated sintered UO 2 pellets is stable, even after additional sintering at 1800 deg C. (author)

Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

Directory of Open Access Journals (Sweden)

Changzhou Yu

2017-02-01

Full Text Available Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P. titanium in a graphite furnace backfilled with argon and studied the effects of common contaminants (C, O, N on sintering densification of titanium. It is found that on the surface of the as-sintered titanium, a severely contaminated porous scale was formed and identified as titanium oxycarbonitride. Despite the porous surface, the sintered density in the sample interiors increased with increasing sintering temperature and holding time. Tensile specimens cut from different positions within a large sintered cylinder reveal different tensile properties, strongly dependent on the impurity level mainly carbon and oxygen. Depending on where the specimen is taken from the sintered compact, ultimate tensile strength varied from 300 to 580 MPa. An average tensile elongation of 5% to 7% was observed. Largely depending on the interstitial contents, the fracture modes from typical brittle intergranular fracture to typical ductile fracture.

Cr2O3-doped MOX fuel: doping and sintering atmosphere optimization

International Nuclear Information System (INIS)

Thomas, R.

2013-01-01

Optimal use of the Mixed Oxide (U,Pu)O 2 nuclear fuel in pressurized water reactors is mainly limited by the behavior of gaseous fission produced during irradiation. Within the MOX microstructure, the probability of fission gas release is increased by the presence of rich localized plutonium areas exhibiting a higher local burn-up. A solution consists in optimizing plutonium distribution within the industrial product and promoting the crystalline growth of the fuel grains. For this purpose, addition of chromium sesquioxide during the manufacturing process is currently considered. A previous thesis has shown that the best results are obtained for a Cr addition slightly greater than the solubility limit of Cr in (U,Pu)O 2 . In order to explain the enhanced plutonium homogeneity, the author highlighted the formation of PuCrO 3 precipitates at grain boundaries. A sintering model under reducing atmosphere, with chromium addition, was proposed. However, several points have to be more thoroughly investigated, especially regarding the solubility limit of chromium, as well as the optimal conditions of PuCrO 3 precipitates formation. In a first part, speciation of solubilized and precipitated chromium in the mixed oxide (U,Pu)O 2 is studied using electron probe microanalysis (EPMA) and X-ray absorption spectroscopy (XAS). It was shown that the oxidation state and the environment of soluble chromium within the (U,Pu)O 2 matrix do not depend on the oxygen partial pressure during sintering, neither on the plutonium content of the mixed oxide. However, both chemical nature of the precipitates and chromium solubility depend on the thermodynamic variable and on the plutonium content.Based on these results, a chromium solubility model in the mixed oxide (U,Pu)O 2-x was built using the law of mass action governing solubility equilibrium. This model is described as a function of the plutonium content (y) of the solid solution (U 1-y Pu y )O 2-x (y = 0,11; 0,275 et 1) and in the

Preparation and sintering of Zr(C,N,O) phases

International Nuclear Information System (INIS)

Tamborenea, S.; Mazzoni, A.D.; Aglietti, E.F.

2003-01-01

The Zr(C,O,N) compounds form a great mono-phase zone belonging to the pseudoternary ZrO-ZrN-ZrC system.Theses phases have cubic crystalline structure with a o parameter depending on the C, O 2 and N 2 content.These phases have many potential applications in the manufacture of ceramic pieces utilizable as electronic conductors.The Zr (C,O,N) phases can be obtained from ZrO 2 by carbonitriding reactions: that is carbothermal reduction and simultaneous nitriding.In this work a series of experiences of carbonitriding of zirconia under different conditions (temperatures between 1400 and 1600degC, times of 120 min, carbon content between 20 and 40%) in order to obtain suitable powders to be sintered.The XRD analysis shows the Zr(C,O,N) as the main products and β -ZrON as the only secondary product in proportions depending on the obtaining conditions.The variables employed were the C content and the reaction temperature.The Zr(C,O,N) content varies between 40 and 90% and tends to increase with the temperature and the carbon content whereas the β -ZrON phase varies between the 40 and 10 % decreasing its proportion with temperature and the carbon content.The oxidation resistance of these phases was studied by DTA-TG tests in air.Results show complete oxidation reaction at ∼500degC in air.The sintering of these materials was made on disks obtained by pressing of powders of Zr(C,N,O) contents higher than 90%.Sintering was performed in nitrogen atmosphere and temperatures between 1450 and 1620degC.Disks were characterized by pycnometry and Hg volumeter.The densities obtained were between 5 and 6,6g/cm 3 with a tendency to increase with the Zr(C,N,O) phase content, the temperature and the sintering time.Sintered disks were characterized by dilatometry in N 2

Transparent Lu 2 O 3 :Eu ceramics by sinter and HIP optimization

Science.gov (United States)

Seeley, Z. M.; Kuntz, J. D.; Cherepy, N. J.; Payne, S. A.

2011-09-01

Evolution of porosity and microstructure was observed during densification of lutetium oxide ceramics doped with europium (Lu 2O 3:Eu) fabricated via vacuum sintering and hot isostatic pressing (HIP'ing). Nano-scale starting powder was uniaxially pressed and sintered under high vacuum at temperatures between 1575 and 1850 °C to obtain densities ranging between 94% and 99%, respectively. Sintered compacts were then subjected to 200 MPa argon gas at 1850 °C to reach full density. Vacuum sintering above 1650 °C led to rapid grain growth prior to densification, rendering the pores immobile. Sintering between 1600 and 1650 °C resulted in closed porosity yet a fine grain size to allow the pores to remain mobile during the subsequent HIP'ing step, resulting in a fully-dense highly transparent ceramic without the need for subsequent air anneal. Light yield performance was measured and Lu 2O 3:Eu showed ˜4 times higher light yield than commercially used scintillating glass indicating that this material has the potential to improve the performance of high energy radiography devices.

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

Effect of coating density on oxidation resistance and Cr vaporization from solid oxide fuel cell interconnects

Science.gov (United States)

Talic, Belma; Falk-Windisch, Hannes; Venkatachalam, Vinothini; Hendriksen, Peter Vang; Wiik, Kjell; Lein, Hilde Lea

2017-06-01

Manganese cobalt spinel oxides are promising materials for protective coatings for solid oxide fuel cell (SOFC) interconnects. To achieve high density such coatings are often sintered in a two-step procedure, involving heat treatment first in reducing and then in oxidizing atmospheres. Sintering the coating inside the SOFC stack during heating would reduce production costs, but may result in a lower coating density. The importance of coating density is here assessed by characterization of the oxidation kinetics and Cr evaporation of Crofer 22 APU with MnCo1.7Fe0.3O4 spinel coatings of different density. The coating density is shown to have minor influence on the long-term oxidation behavior in air at 800 °C, evaluated over 5000 h. Sintering the spinel coating in air at 900 °C, equivalent to an in-situ heat treatment, leads to an 88% reduction of the Cr evaporation rate of Crofer 22 APU in air-3% H2O at 800 °C. The air sintered spinel coating is initially highly porous, however, densifies with time in interaction with the alloy. A two-step reduction and re-oxidation heat treatment results in a denser coating, which reduces Cr evaporation by 97%.

Evaluation of dilatometric techniques for studies of sintering kinetics

International Nuclear Information System (INIS)

El-Sayed Ali, M.; Toft Soerensen, O.

1985-04-01

The kinetics of the initial sintering stage of CeO 2 is evaluated by three different techniques: constant heating rate dilatometry, constant shrinkage rate dilatometry and a new technique recently introduced by the authors called Stepwise Isothermal Dilatometry (SID). Comparative measurements with these techniques showed that too high activation energies were obtained with the two first techniques, both of which can be termed as nonisothermal, whereas activation energies comparable to those reported for cation diffusion in other fluorite oxides were obtained with the latter technique. Of the three techniques SID is thus considered to be the most accurate for studies of the sintering kinetics. In contrast to the two nonisothermal techniques SID has the further advantage that both the controlling mechanism and its activation energy can be determined in a single experiment. From the SID-measurement it was concluded that the initial sintering stage of CeO 2 is controlled by grain-boundary diffusion. (author)

Low-temperature sintering and electrical properties of strontium- and magnesium-doped lanthanum gallate with V2O5 additive

Science.gov (United States)

Ha, Sang Bu; Cho, Yoon Ho; Ji, Ho-Il; Lee, Jong-Ho; Kang, Yun Chan; Lee, Jong-Heun

2011-03-01

The effects of a V2O5 additive on the low-temperature sintering and ionic conductivity of strontium- and magnesium-doped lanthanum gallate (LSGM: La0.8Sr0.2Ga0.8Mg0.2O2.8) are studied. The LSGM powders prepared by the glycine nitrate method are mixed with 0.5-2 at.% of VO5/2 and then sintered at 1100-1400 °C in air for 4 h. The apparent density and phase purity of the LSGM specimens are increased with increasing sintering temperature and VO5/2 concentration due to the enhanced sintering and mass transfer via the intergranular liquid phase. The 1 at.% VO5/2-doped LSGM specimen sintered at 1300 °C exhibits a high oxide ion conductivity of ∼0.027 S cm-1 at 700 °C over a wide range of oxygen partial pressure (PO2 =10-27 - 1 atm), thereby demonstrating its potential as a useful electrolyte for anode-supported solid oxide fuel cells (SOFCs) without the requirement for any buffer layer between the electrolyte and anode.

Thermal diffusivity of alumina-zirconia sintered with niobium additions

International Nuclear Information System (INIS)

Santos, W.N. dos; Paulin Filho, P.I.; Taylor, R.

1994-01-01

The effect of niobium oxide addition on the alumina-zirconia thermal diffusivity was investigated from 100 0 C to 1000 0 C by the laser flash method. It was observed that 4 to 6% addition of niobium oxide increases the thermal diffusivity when samples were sintered at 1450 0 C. This effect was due to elimination of porosity by formation of liquid please above 1420 0 C in the Al 2 O 3 - Nb 2 O 5 system. (author). 7 refs., 3 figs

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.

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

Science.gov (United States)

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

2017-07-01

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

Effects of sintering atmosphere and initial particle size on sintering of gadolinia-doped ceria; Efeitos da atmosfera de sinterizacao e do tamanho de particula na sinterizacao da ceria-gadolinia

Energy Technology Data Exchange (ETDEWEB)

Batista, Rafael Morgado

2014-07-01

The effects of the sintering atmosphere and initial particle size on the sintering of ceria containing 10 mol% gadolinia (GdO{sub 1.5}) were systematically investigated. The main physical parameter was the specific surface area of the initial powders. Nanometric powders with three different specific surface areas were utilized, 210 m{sup 2}/g, 36,2 m{sup 2}/g e 7,4 m{sup 2}/g. The influence on the densification, and micro structural evolution were evaluated. The starting sintering temperature was verified to decrease with increasing on the specific surface area of raw powders. The densification was accelerated for the materials with smaller particle size. Sintering paths for crystallite growth were obtained. Master sintering curves for gadolinium-doped ceria were constructed for all initial powders. A computational program was developed for this purpose. The results for apparent activation energy showed noticeable dependence with specific surface area. In this work, the apparent activation energy for densification increased with the initial particle size of powders. The evolution of the particle size distributions on non isothermal sintering was investigated by WPPM method. It was verified that the grain growth controlling mechanism on gadolinia doped ceria is the pore drag for initial stage and beginning of intermediate stage. The effects of the sintering atmosphere on the stoichiometry deviation of ceria, densification, microstructure evolution, and electrical conductivity were analyzed. Inert, oxidizing, and reducing atmospheres were utilized on this work. Deviations on ceria stoichiometry were verified on the bulk materials. The deviation verified was dependent of the specific surface area and sintering atmosphere. Higher reduction potential atmospheres increase Ce{sup 3+} bulk concentration after sintering. Accelerated grain growth and lower electrical conductivities were verified when reduction reactions are significantly present on sintering. (author)

High-level radioactive waste fixation in sintered vitreous matrix

International Nuclear Information System (INIS)

Russo, D.O.; Messi de Bernasconi, N.; Audero, M.A.

1987-01-01

The safe storage of high-level wastes from fuel elements reprocessing includes, as a first step, the fixation of the same in materials having a good resistance to the leaching in aqueous medium, such as borosilicate glass. As an alternative to the usual method of the molten glasses, a procedure for the sintering of a powdered glass and waste mixture at lower temperatures (600-700 deg C) has been developed, which minimizes the volatilization of active compounds during the process. Two glasses matrices of different composition and characteristics were used, to which the simulated wastes were added in the ratio of a 10% in weight of oxides. Two sintering techniques were employed 1: cold pressing and further sintering; 2: hot pressing and sintering under pressure. The densities were measured, the microstructure of the samples was analyzed and leaching essays were made in distilled water. The pellet's microstructure was observed by means of optical microscopy, by reflection in polished samples and by transparency in thin slices. The presence of crystalline compounds was analyzed by means of x rays and electron microprobe. The results have shown the convenience to continue with hot pressing essays, because a denser product with a higher resistance to the leaching is thus obtained. (M.E.L.) [es

CRITIC-I: Instrumented lithium oxide irradiation: Part 1, Lithium oxide fabrication and characteristics

International Nuclear Information System (INIS)

Applegate, D.S.; Poeppel, R.B.

1987-06-01

Fine-grained, sinterable lithium oxide powder was prepared by high-temperature vacuum calcination of molten lithium carbonate. The product was ball milled, cold pressed, and fired in an oxygen atmosphere. The fired density, grain size, and surface roughness varied widely with firing schedule. Most variations were attributed to moisture content. Rings of high-density, sintered lithium oxide will be used in an in-reactor experiment to measure tritium release. 2 refs., 8 figs., 1 tab

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

Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

Science.gov (United States)

Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

2017-07-01

The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

[Effect of repeated sintering and variations in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers].

Science.gov (United States)

Cui, Huang; Jia, Yu; Shaofeng, Meng; Biyun, Gao

2017-08-01

Objective The aim of this study is to evaluate the effect of repeated sintering and variation in thickness on the color and microstructure of dental lithium disilicate-based glass ceramic veneers. Methods A total of 24 computer aided design and computer aided manufacturing (CAD/CAM) veneers was fabricated using the IPS e.max-CAD LS2 and then randomly divided into four groups (S0, S1, S2, S3; n=6). Each group was sintered 0, 1, 2, 3 times individually according to the manufacturer's recommendation. The color parameters (L, C, H, a, b values) of all the specimens were measured by a Vita easyshade dental colorimeter. The results were statistically analyzed using the SAS 9.1.3 software for MANOVA and LSD. Subsequently, the microstructures of the intersecting surfaces of the specimens were observed by scanning electron microscopy (SEM). Results After repeated sintering, the L value significantly decreased (P<0.05). For the C and b values, statistical differences were observed among the groups except between S2 and S3. SEM results showed that the interlocking microstructures of rod-shaped Li₂Si₂O₅ crystals became more compact when the number of sintering times was increased. Conclusion Repeated sintering exhibited significant influence on the color of the IPS e.max-CAD LS2 veneers.

Compactibility of Al/Al2O3 Isotropic Composite with Variation of Holding Time Sintering.

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Eddy S Siradj

2008-11-01

Full Text Available The requirement of component with structural ability, light weight and also strength is increasing base on Metal Matrix Composites (MMCs by aluminum as matrix (AMCs. A structural ability is connected to composites compactibility which is depend on quality of interfacial bounding. Powder metallurgy is one of method to produce composite with powder mixing, compacting and sintering. Volume fractions reinforced and sintering time can influence composites compactibility. Volume fractions reinforced variable can produce different reinforcement effect. Beside that, on sintering enables the formation of new phase during sintering time. In this research, Al/Al2O3 isotropic composites are made with aluminum as matrix and alumina (Al2O3 as reinforced. Volume fraction reinforced used 10%. 20%. 30% and 40%. Sintering temperature and compaction pressure are each 600oC and 15 kN. The tests that applied are compression and metallographic test. The result that obtained is optimum compactibility of Al/Al2O3 composite reached at holding time 2 hour. During sintering, new phase can occur that is aluminum oxides (alumina, with unstable properties. The best volume fraction reinforced and holding time sintering are 40% and 2 hours.

"A New Class of Creep Resistant Oxide/Oxide Ceramic Matrix Composites"

Energy Technology Data Exchange (ETDEWEB)

Dr. Mohit Jain, Dr. Ganesh Skandan, Prof. Roger Cannon, Rutgers University

2007-03-30

Despite recent progress in the development of SiC-SiC ceramic matrix composites (CMCs), their application in industrial gas turbines for distributed energy (DE) systems has been limited. The poor oxidation resistance of the non-oxide ceramics warrants the use of envrionmental barrier coatings (EBCs), which in turn lead to issues pertaining to life expectancy of the coatings. On the other hand, oxide/oxide CMCs are potential replacements, but their use has been limited until now due to the poor creep resistance at high temperatures, particularly above 1200 oC: the lack of a creep resistant matrix has been a major limiting factor. Using yttrium aluminum garnet (YAG) as the matrix material system, we have advanced the state-of-the-art in oxide/oxide CMCs by introducing innovations in both the structure and composition of the matrix material, thereby leading to high temperature matrix creep properties not achieved until now. An array of YAG-based powders with a unique set of particle characteristics were produced in-house and sintered to full density and compressive creep data was obtained. Aided in part by the composition and the microstructure, the creep rates were found to be two orders of magnitude smaller than the most creep resistant oxide fiber available commercially. Even after accounting for porosity and a smaller matrix grain size in a practical CMC component, the YAG-based matrix material was found to creep slower than the most creep resistant oxide fiber available commercially.

Science of sintering

International Nuclear Information System (INIS)

Kuczynski, G.

1977-01-01

Although the methods of integration of materials by sintering, have been used since the early history of humanity, the actual understanding of the process involved came only in the last three decades. As in the most human endeavors, the art preceded theory. The comprehension of the elementary processes occuring during sintering comes from the studies of model system. Although the elementary processes occuring during sintering are today quite well understood, the problem of shrinkage of a powder compact which was at the origin of Sintering Science is still far from solved. This is due to the complexity of the internal geometry of the compacts. The recent attempts to apply statistics to this problem, seem to offer some promise

Effect of the sintering temperature and time on phase assemblage and electrical conductivity of zirconia-scandia-ceria

International Nuclear Information System (INIS)

Grosso, R.L.; Muccillo, E.N.S.

2012-01-01

ZrO 2 -based solid electrolytes have been extensively studied over the last decades for application in solid oxide fuel cells (SOFCs). Zirconia containing scandia and ceria solid electrolyte is a potential candidate in SOFCs operating at intermediate temperatures (600 - 800 deg C). In this work, commercial ZrO 2 containing 10 mol% Sc 2 O 3 and 1 mol% CeO 2 was sintered by the conventional and two-step methods. Several sintering conditions were evaluated by varying the temperature as well as the residence time. High values of sintered density (> 98%) were obtained. A careful selection of the sintering conditions is necessary in order to obtain a single cubic phase, as revealed by X-ray diffraction results. The grain growth can be controlled in specimens sintered by the two-step method. The electrical conductivity show similar behavior for the grain component independent on the sintering method. (author)

A study on some properties of sintered stainless steel powder compacts with sintering conditions

International Nuclear Information System (INIS)

Lee, Bang Sik; Kim, Kwan Hyu; Lee, Doh Jae; Choi, Dap Chun

1986-01-01

Sintered specimens for the mechanical and corrosion tests were prepared from 316L, 410L and 434L stainless steel powder compacts with green densities in the range of 6.2∼7.0g/cm 3 . The experimental variables studied were green density, sintering atmosphere, temperature and time, type of lubricant used and cooling rate after sintering operation. Mechanical properties of green compacts and sintered specimens were evaluated. The corrosion tests were performed by potentiodynamic anodic polarization technique. Mechanical properties were very sensitive to the sintering atmosphere; sintering in dissociated ammonia resulted in the strengthing but embrittlement of sintered 316L, 410L and 434L strainless steel powder compacts. Their corrosion resistance was also decreased. The tensile strength was increased with increases in sintering time and temperature while the decreases in the yield strength were observed. The tensile properties of green compacts were shown to closely related to the green density. Addition of 1% acrawax as a lubricant was appeared to be most effective for the improvement of green strength. (Author)

Study of the oxide reduction and interstitial contents during sintering of different plain carbon steels by in situ mass spectrometry in nitrogen atmosphere

International Nuclear Information System (INIS)

Momeni, Mohammad; Gierl, Christian; Danninger, Herbert

2011-01-01

Highlights: → Degassing phenomenon was studied in plain steels with different iron base powders. → The integrated area below the MS m12 graph can be used as an indicator of formed CO. → The integrated area is an indicator for in situ carbon loss in the specimen. → Carbon loss and area below the m12 graph can be correlated. - Abstract: Reduction of oxides covering powder particles is an important process during sintering and a prerequisite to form sintering contacts in PM parts. In the present research, degassing and reduction phenomena during sintering of plain carbon steels prepared from different atomised and sponge iron powders were studied by mass spectrometry (MS) in the dilatometer under protective N 2 atmosphere. Interstitial constituents were measured by carbon and oxygen analysis. According to the results, the major part of CO 2 is formed during carbothermic reduction of surface oxides in the low to moderate temperature range ( 600 deg. C, the main product of carbothermic reduction is CO and not CO 2 , but the former cannot be detected by MS in N 2 atmosphere. Signals m44 (CO 2 ) and m12 (C) were however found to be reliable indicators for CO. Similar intensity of mass 12 signals for both ASC and SC up to 1000 deg. C is consistent with equal carbon loss through carbothermic reaction. The integrated areas below the MS signal graphs, and thus the areas of the different degassing peaks obtained in the MS, were used as at least semi-quantitative estimation of the amount of gases formed, bearing in mind that MS is not really a quantitative analytical tool. Although a clearly defined relationship is not visible between oxygen loss and area below the m16 graph, the area for m12 can be used as an indicator for in situ carbon loss in the specimen. Increasing integrated areas for m12 and 16 between 800 and 1300 deg. C with only marginal enhancement of m44 indicates that the major part of oxides are removed as CO, in agreement with Boudouard equilibrium, at

Manufacture of sintered bricks of high density from beryllium oxide; Fabrication de frittes de forte densite a base d'oxyde de beryllium

Energy Technology Data Exchange (ETDEWEB)

Pointud, R; Rispal, Ch; Le Garec, M [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1959-07-01

Beryllium oxide bricks of nuclear purity 100 x 100 x 50 and 100 x 100 x 100 mm of very high density (between 2.85 and 3.00) are manufactured by sintering under pressure in graphite moulds at temperatures between 1,750 and 1,850 deg. C, and under a pressure of 150 kg/cm{sup 2}. The physico-chemical state of the saw material is of considerable importance with regard to the success of the sintering operation. In addition, a study of the sintering of a BeO mixture with 3 to 5 per cent of boron introduced in the form of boric acid, boron carbide or elementary boron shows that high densities can only be obtained by sintering under pressure. For technical reasons of manufacture, only the mixture based on boron carbide is used. The sintering is carried out in graphite moulds at 1500 deg. C under 150 kg/cm{sup 2} pressure, and bricks can be obtained with density between 2,85 and 2,90. Laboratory studies and the industrial manufacture of various sinters are described in detail. (author) [French] La fabrication de briques d'oxyde de beryllium de purete nucleaire de 100 x 100 x 50 et de 100 x 100 x 100 mm de densite tres elevee (comprise entre 2.85 et 3.00) est realisee par frittage sous charge dans des moules en graphite entre 1750 et 1850 deg. C, sous 150 kg/cm{sup 2} de pression. L'etat physico-chimique de la matiere premiere a une importance considerable quant au succes de l'operation de frittage. Par ailleurs, l'etude du frittage du mixte BeO a 3 et 5 pour cent de bore element introduit sous forme d'anhydride borique, soit de carbure de bore ou de bore element, montre que seul le frittage sous charge permet d'obtenir des densites elevees. Pour des raisons techniques de fabrication seul le mixte a base de carbure de bore est retenu. Le frittage s'opere dans des moules de graphite a 1500 deg. C sous 150 kg/cm{sup 2} de pression et permet d'obtenir des briques de densite comprise entre 2.85 et 2.90. Les etudes de laboratoire et la fabrication industrielle des differents

The dimensional accuracy of the sintered billets

Directory of Open Access Journals (Sweden)

Чингиз Ариф оглы Алиев

2016-01-01

Full Text Available The article presents the results of assessing the impact of the behaviour stability of the components included in the compositions and process parameters of their production, on the dimensional accuracy of workpieces. It was found that by increasing the amount of oxide in the composition is greater compaction of the sintered billet in the process of heat treatment. This also increases the density of all components of the composition

Mineral Phases and Release Behaviors of As in the Process of Sintering Residues Containing As at High Temperature

Directory of Open Access Journals (Sweden)

Xingrun Wang

2014-01-01

Full Text Available To investigate the effect of sintering temperature and sintering time on arsenic volatility and arsenic leaching in the sinter, we carried out experimental works and studied the structural changes of mineral phases and microstructure observation of the sinter at different sintering temperatures. Raw materials were shaped under the pressure of 10 MPa and sintered at 1000~1350°C for 45 min with air flow rate of 2000 mL/min. The results showed that different sintering temperatures and different sintering times had little impact on the volatilization of arsenic, and the arsenic fixed rate remained above 90%; however, both factors greatly influenced the leaching concentration of arsenic. Considering the product’s environmental safety, the best sintering temperature was 1200°C and the best sintering time was 45 min. When sintering temperature was lower than 1000°C, FeAsS was oxidized into calcium, aluminum, and iron arsenide, mainly Ca3(AsO42 and AlAsO4, and the arsenic leaching was high. When it increased to 1200°C, arsenic was surrounded by a glass matrix and became chemically bonded inside the matrix, which lead to significantly lower arsenic leaching.

Effect of B2O3 and P2O5 on fluorosilicic mica glass-ceramic sintering process

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Wu S.

2010-01-01

Full Text Available To study the effect of B2O3 and P2O5 on fluorosilicic mica glass-ceramic sintering process, six sets of K2O-MgO-SiO2-F glasses were prepared by using B2O3 and P2O5 as sintering aid, respectively. Green bodies of the glass powder were formed by gel casting and sintered at 800, 850, 900, 950, 1000oC for 6 hours, resectively. The sintering and crystallization behavior were studied by thermal shrinkage , X-ray diffraction and SEM. The results showed that the shrinkage rate of the glass with 2wt% B2O3 and P2O5 was highest, while the rate of the glass with 5wt% P2O5 was lowest. An additional crystal other than fluorosilicic mica was precipitated in the glass ceramics generated by sintering of glass powder. The present results confirmed that the glass powder of pure K2O-MgO-SiO2-Fsystem had poor sinterability, while glass powder with minor addition of P2O5 and/or B2O3 showed good sinterability. This result was also verified by SEM.

Geometrical and electrical properties of NTC polycrystalline thermistors vs. Changes of sintering parameters

Directory of Open Access Journals (Sweden)

Savić S.M.

2006-01-01

Full Text Available NTC thermistor powder was made of a Mn, Ni, Fe and Co oxide mixture calcinated at 1050°C / 60 min. The powder was milled in a ball mill down to an average particle diameter of 0.9 μm. Small disc shaped pills of the powder obtained were made by pressing with a pressure of 2.5 MPa. The pills were sintered in the temperature range of 900-1400 °C for 30-240 min. The volume and specific volume resistivity change were measured as a function of sintering conditions. Microstructure development was observed using a SEM microscope. Using the results obtained, optimization of sintering parameters was performed in order to determine optimal electrical properties of the selected thermistor composition.

Technological parameter effect on properties of sintered hard-magnetic type Nd-Fe-B materials

International Nuclear Information System (INIS)

Rastegaev, V.S.; Stepanova, G.I.; Gudim, Z.Yu.

1989-01-01

The effect of each technological operation on manufacturing hard magnets from Nd-Fe-B alloys on properties of sintered permanent magnets is studied. It is noted that violation of the metting regime can result in burn-up of boron and rare earths, and violation of the grinding mode-formation of nonmagnetic powder fractions, etc. Special attention is paid to material protection against oxidation by introducing passivating additions and creating of particular conditions for alloy sintering and heat treatment

Kinetics of UO2 sintering

International Nuclear Information System (INIS)

Ristic, M.M.

1962-01-01

Detailed conclusions related to the UO 2 sintering can be drawn from investigating the kinetics of the sintering process. This report gives an thorough analysis of the the data concerned with sintering available in the literature taking into account the Jander and Arrhenius laws. This analysis completes the study of influence of the O/U ratio and the atmosphere on the sintering. Results presented are fundamentals of future theoretical and experimental work related to characterisation of the UO 2 sintering process

Method for hot pressing beryllium oxide articles

Science.gov (United States)

Ballard, Ambrose H.; Godfrey, Jr., Thomas G.; Mowery, Erb H.

1988-01-01

The hot pressing of beryllium oxide powder into high density compacts with little or no density gradients is achieved by employing a homogeneous blend of beryllium oxide powder with a lithium oxide sintering agent. The lithium oxide sintering agent is uniformly dispersed throughout the beryllium oxide powder by mixing lithium hydroxide in an aqueous solution with beryllium oxide powder. The lithium hydroxide is converted in situ to lithium carbonate by contacting or flooding the beryllium oxide-lithium hydroxide blend with a stream of carbon dioxide. The lithium carbonate is converted to lithium oxide while remaining fixed to the beryllium oxide particles during the hot pressing step to assure uniform density throughout the compact.

Influences of chemical packing and the chemical composition in porcelain sintering: from theory to practice

International Nuclear Information System (INIS)

Conceicao, E.S.; Gouvea, D.; Romano, R.C.O.; Pileggi, R.G.

2011-01-01

Studies have been conducted using the size distribution particles as a tool to obtain maximum packing in porcelain bodies. However, little attention has been given for the maximum size of particles and its effect in the sintering. While some particles are relatively large (63 μ m) for some oxides in the porcelain composition, they could compromise the sintering if a liquid phase is formed during heat processing. In this work, a comparative analysis showed that compositions with a maximum green packing density does not always lead to a maximum final densification in sintering if there is no control of the maximum size of the particles. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-10-15

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

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.

Multi-metallic anodes for solid oxide fuel cell applications

International Nuclear Information System (INIS)

Restivo, T.A. Guisard; Mello-Castanho, S.R.H.; Leite, D. Will

2009-01-01

A new method for direct preparation of materials for solid oxide fuel cell anode - Ni- YSZ cermets - based on mechanical alloying (MA) of the original powders is developed, allowing to admix homogeneously any component. Additive metals are selected from thermodynamic criteria, leading to compacts consolidation through sintering by activated surface (SAS). The combined process MA-SSA can reduce the sintering temperature by 300 deg C, yielding porous anodes. Densification mechanisms are discussed from quasi-isothermal sintering kinetics results. Doping with Ag, W, Cu, Mo, Nb, Ta, in descending order, promotes the densification of pellets through liquid phase sintering and evaporation of metals and oxides, which allow reducing the sintering temperature. Powders and pellets characterization by electronic microscopy and X-ray diffraction completes the result analyses. (author)

Study of the sintering process and the formation of a (Th, U) O2 solid solution

International Nuclear Information System (INIS)

Tomasi, Roberto

1979-01-01

The effect of some variables in the (Th, U) O 2 sintering process and solid solution formation was studied. ThO 2 , U 3 O 8 and UO 2 powder were prepared. The ThO 2 powders were obtained by calcination of thorium at 500 and 750 deg C; the U 3 O 8 powders were derived from the calcination of ADU at 660 and 750 deg C; the UO 2 powder were prepared from ADU and from ATCU. The different characteristics of these materials were determined by measurements of surface area, by scanning electron microscopy, tap density tests, X-ray diffractometry and by measurements of the O/U ratios. The oxide mixtures were chosen in order to produce a final composition with 10 w/o of UO 2 . A mixture of thorium oxalate and ADU was also prepared by calcining these salts in air at 700 deg C, in order to obtain certain amount of solid solution prior to sintering. The sintering operations were developed in an argon atmosphere at temperatures between 1400 and 1700 deg C, during interval varying from 1 to 4 hours. The effect of the mixture characteristics on the sintering process and solid solution formation were studied considering the results of densification, microstructure development and X-ray diffractometry. The ThO 2 powder characteristics have a main effect on the mixtures compactability and sinterability, the higher calcining temperatures increasing the green density, but decreasing the final density of the sintered pellets. In the sintering of mixtures containing U 3 O 3 , this oxide is reduced to UO 2 and it is possible to obtain pellets with density and microstructures similar to those produced from mixtures containing UO 2 . But if oxygen in excess is present during sintering, the process is affected, occurring exaggerated grain growth. The densification results were related to the Coble's kinetics equation for second stage of sintering, valid for bulk diffusion, grain boundary acting as vacancy sinks. The sintering activation energy is independent from the powder starting

Processing and microstructure characterisation of oxide dispersion strengthened Fe–14Cr–0.4Ti–0.25Y2O3 ferritic steels fabricated by spark plasma sintering

International Nuclear Information System (INIS)

Zhang, Hongtao; Huang, Yina; Ning, Huanpo; Williams, Ceri A.; London, Andrew J.; Dawson, Karl; Hong, Zuliang; Gorley, Michael J.; Grovenor, Chris R.M.; Tatlock, Gordon J.; Roberts, Steve G.; Reece, Michael J.; Yan, Haixue; Grant, Patrick S.

2015-01-01

Highlights: • Nanostructured ODS steels were successfully produced by SPS. • Presence of Y 2 Ti 2 O 7 nanoclusters was confirmed by synchrotron XRD and microscopy. • The chemistry of nanoclusters tested by ATP indicated they are Y–Ti–O oxides. - Abstract: Ferritic steels strengthened with Ti–Y–O nanoclusters are leading candidates for fission and fusion reactor components. A Fe–14Cr–0.4Ti + 0.25Y 2 O 3 (14YT) alloy was fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). The densification of the 14YT alloys significantly improved with an increase in the sintering temperature. Scanning electron microscopy and electron backscatter diffraction revealed that 14YT SPS-sintered at 1150 °C under 50 MPa for 5 min had a high density (99.6%), a random grain orientation and a bimodal grain size distribution (<500 nm and 1–20 μm). Synchrotron X-ray diffraction patterns showed bcc ferrite, Y 2 Ti 2 O 7 , FeO, and chromium carbides, while transmission electron microscopy and atom probe tomography showed uniformly dispersed Y 2 Ti 2 O 7 nanoclusters of <5 nm diameter and number density of 1.04 × 10 23 m −3 . Due to the very much shorter consolidation times and lower pressures used in SPS compared with the more usual hot isostatic pressing routes, SPS is shown to be a cost-effective technique for oxide dispersion strengthened (ODS) alloy manufacturing with microstructural features consistent with the best-performing ODS alloys

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.

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

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Pouchly V.

2012-01-01

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

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

NARCIS (Netherlands)

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

2014-01-01

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

Method to produce sintered carriers for electrodes of galvanic elements

Energy Technology Data Exchange (ETDEWEB)

Jost, E M

1978-03-24

Carrier plates of precisely uniform thickness can be produced according to the invention by firstly thickening a solution of polyethylene oxide and (preferably) methanol by adding water and then, by adding nickel powder, obtaining an essentially homogeneous suspension of considerable viscosity. This slurry is coated on both sides of a nickel grid, dried and sintered.

Sol-gel synthesis of lithium metatitanate as tritium breeding material under different sintering conditions

Science.gov (United States)

Lu, Wei; Wang, Jing; Pu, Wenjing; Li, Kaiping; Ma, Shubing; Wang, Weihua

2018-04-01

Lithium metatitanate (Li2TiO3) is a promising tritium breeding material candidate for solid blanket of D-T fusion reactors, due to its high mechanical strength, chemical stability, and tritium release rate. In this paper, Li2TiO3 powder with homogeneous crystal structure is synthesized by sol-gel method. The chemical reactions in gel thermal cracking and sintering process are studied by thermo gravimetric/differential scanning calorimetry (TG-DSC). The relationship between the sintering condition and the particle/grain size is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results show that below 673 K the gel precursor is completely decomposed and Li2TiO3 phase initially forms. The LiTiO2 by-product formed under the reductive atmosphere in muffle furnace, could be oxidized continually to Li2TiO3 at higher sintering temperature (≥1273 K) for longer sintering time (≥10 h). Both grain and particle sizes rely on a linear growth with the increase of sintering time at 1273 K. Over 1473 K, significant agglomerations exist among particles. The optimal sintering condition is selected as 1273 K for 10 h, for the purer Li2TiO3 phase (>99%), smaller grain and particle size.

Effect of two-stage sintering process on microstructure and mechanical properties of ODS tungsten heavy alloy

Energy Technology Data Exchange (ETDEWEB)

Lee, Kyong H. [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-gu, Taejon 305-701 (Korea, Republic of); Cha, Seung I. [International Center for Young Scientists, National Institute for Materials Science 1-1, Namiki, Tsukuba 305-0044 (Japan); Ryu, Ho J. [DUPIC, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yusong-gu, Taejon 305-353 (Korea, Republic of); Hong, Soon H. [Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-gu, Taejon 305-701 (Korea, Republic of)], E-mail: shhong@kaist.ac.kr

2007-06-15

Oxide dispersion strengthened (ODS) tungsten heavy alloys have been considered as promising candidates for advanced kinetic energy penetrator due to their characteristic fracture mode compared to conventional tungsten heavy alloy. In order to obtain high relative density, the ODS tungsten heavy alloy needs to be sintered at higher temperature for longer time, however, induces growth of tungsten grains. Therefore, it is very difficult to obtain controlled microstructure of ODS tungsten heavy alloy having fine tungsten grains with full densification. In this study, two-stage sintering process, consisted of primary solid-state sintering and followed by secondary liquid phase sintering, was introduced for ODS tungsten heavy alloys. The mechanically alloyed 94W-4.56Ni-1.14Fe-0.3Y{sub 2}O{sub 3} powders are solid-state sintered at 1300-1450 deg. C for 1 h in hydrogen atmosphere, and followed by liquid phase sintering temperature at 1465-1485 deg. C for 0-60 min. The microstructure of ODS tungsten heavy alloys showed high relative density above 97%, with contiguous tungsten grains after primary solid-state sintering. The microstructure of solid-state sintered ODS tungsten heavy alloy was changed into spherical tungsten grains embedded in W-Ni-Fe matrix during secondary liquid phase sintering. The two-stage sintered ODS tungsten heavy alloy from mechanically alloyed powders showed finer microstructure and higher mechanical properties than conventional liquid phase sintered alloy. The mechanical properties of ODS tungsten heavy alloys are dependent on the microstructural parameters such as tungsten grain size, matrix volume fraction and tungsten/tungsten contiguity, which can be controlled through the two-stage sintering process.

Bioactivity and mineralization of hydroxyapatite with bioglass as sintering aid and bioceramics with Na3Ca6(PO4)5 and Ca5(PO4)2SiO4 in a silicate matrix

International Nuclear Information System (INIS)

Demirkiran, Hande; Mohandas, Arunesh; Dohi, Motokazi; Fuentes, Alonso; Nguyen, Kytai; Aswath, Pranesh

2010-01-01

Hydroxyapatite and Bioglass-45S5 were sintered together creating new ceramic compositions that yielded increased apatite deposition and osteoblast differentiation and proliferation in vitro compared to hydroxyapatite. The sintered products characterized by X-ray diffraction, revealed hydroxyapatite as the main phase when small quantities (1, 2.5 and 5 wt.%) of bioglass was added. Bioglass behaved as a sintering aid with β-TCP (Ca 3 (PO 4 ) 2 ) being the minor phase. The amount of β-TCP increased with the amount of bioglass added. In compositions with larger additions of bioglass (10 and 25 wt.%), new phases with compositions of calcium phosphate silicate (Ca 5 (PO 4 ) 2 SiO 4 ) and sodium calcium phosphate (Na 3 Ca 6 (PO 4 ) 5 ) were formed respectively within amorphous silicate matrices. In vitro cell culture studies of the ceramic compositions were examined using bone marrow stromal cell (BMSC). Cell proliferation and differentiation of bone marrow stromal cells into osteoblasts were determined by Pico Green DNA assays and alkaline phosphatase (ALP) activity, respectively. All hydroxyapatite-bioglass co-sintered ceramics exhibited larger cell proliferation compared to pure hydroxyapatite samples. After 6 days in cell culture, the ceramic with Ca 5 (PO 4 ) 3 SiO 4 in a silicate matrix formed by reacting hydroxyapatite with 10 wt.% bioglass exhibited the maximum proliferation of the BMSC's. The ALP activity was found to be largest in the ceramic with Na 3 Ca 6 (PO 4 ) 5 embedded in a silicate matrix synthesized by reacting hydroxyapatite with 25 wt.% bioglass.

The influence of green microstructure and sintering parameters on precipitation process during copper-nickel-zinc ferrites sintering

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Barba, Antonio

2014-04-01

Full Text Available Microstructural changes that occur during heat treatment of copper-nickel-zinc ferrites have been studied. The process of precipitation of the two types of crystals that occur during the sintering process has been analyzed. It is found that this process depends on dry relative density of the press specimens and on the following sintering parameters: sintering temperature, sintering time and cooling rate of the thermal cycle. Crystal precipitates characterization have been done by scanning electron microscopy (SEM, energy-dispersive X-ray (EDX analysis, X-ray diffraction (XRD, and X-ray photoelectron spectroscopy (XPS. These techniques have allowed to determine the nature of these crystals, which in this case correspond to zinc and copper oxides. It has been used two chemical reactions to explain the bulk precipitation and subsequent re-dissolution of these crystal precipitates during sintering.En este trabajo se han estudiado los cambios microestructurales que se producen durante el tratamiento térmico de las ferritas de cobre-níquel-cinc y se ha analizado el proceso de precipitación de los dos tipos de cristales que aparecen durante el proceso de sinterización. Se ha encontrado que este proceso depende de la densidad relativa en seco de las muestras compactadas y de las siguientes variables de la etapa de sinterización: temperatura y tiempo de sinterización y velocidad de enfriamiento. La caracterización de los cristales precipitados se ha realizado por microscopía electrónica de barrido (MEB, microanálisis por dispersión de energía de rayos X (EDX, difracción de rayos X (DRX, y espectroscopía de fotoelectrones de rayos X (XPS. Estas técnicas han permitido determinar la naturaleza de estos cristales, que en este caso corresponden a los óxidos de cinc y de cobre. Se han propuesto dos reacciones químicas que permiten explicar el proceso de precipitación y la posterior re-disolución de estos cristales precipitados durante la

Preparation and Characterization of TiB2-(Supra-Nano-Dual-Phase High-Entropy Alloy Cermet by Spark Plasma Sintering

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Shulei Zhang

2018-01-01

Full Text Available This paper introduces the preparation method and characterization results of TiB2 ceramics with CoCrFeNiAl high-entropy alloy (HEA as a sintering aid by Spark Plasma Sintering (SPS. Good wettability between HEA and TiB2 was proved by the sessile drop method, indicating promising prospects for this composite. The sintering results showed that the addition of HEA could dramatically promote the sinterability of TiB2. TiB2-5 wt. % HEA dense ceramics prepared at the optimal temperature of 1650 °C showed fine morphology without formation of brittle phases. The liquid phase in the ceramics was highly consistent with the so-called “supra-nano-dual-phase materials (SNDPM”, with near-ideal strength. This study represents the first time that a ceramic-SNDPM composite has been fabricated since the invention of such structures.

Production of pure sintered alumina

International Nuclear Information System (INIS)

Rocha, J.C. da; Huebner, H.W.

1982-01-01

With the aim of optimizing the sintering parameters, the strength of a large number of alumina samples was determined which were produced under widely varying sintering conditions and with different amounts of MgO content. The strength as a function of sintering time or temperature was found to go through a maximum. With increasing time, this maximum is shifted to lower temperatures, and with decreasing temperature to longer times. Data pairs of sintering times and temperatures which yeld the strength maximum were determined. The value of the strength at the maximum remains unchanged. The strength is high (= 400 MN/m 2 , at a grain size of 3 um and a porosity of 2 per cent) and comparable to foreign aluminas produced for commercial purposes, or even higher. The increase in the sintering time from 1 h to 16 h permits a reduction of the sintering temperature from 1600 to 1450 0 C without losing strength. The practical importance of this fact for a production of sintered alumina on a large scale is emphasized. (Author) [pt

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

Energy Technology Data Exchange (ETDEWEB)

McKenzie, E.J.; Brown, K.L.; Campbell, K.A. [University of Auckland (New Zealand). Dept. of Geology; Cady, S.L. [Portland State University, Portland, OR (United States). Dept. of Geology

2001-08-01

As part of a pilot study investigating the role of microorganisms in the immobilisation ol As, Sb, B, Tl and Ug, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92-94{sup o}C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and TI were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92-94{sup o}C) ends of the terrestrial thermal spring ecosystems studied. (author)

Kinetics of sintering of uranium dioxide

International Nuclear Information System (INIS)

Soni, N.C.; Moorthy, V.K.

1978-01-01

The kinetics of sintering of UO 2 powders derived from ADU route and calcined at different temperatures was studied. The activation energy for sintering was found to depend on the calcination temperature, the density chosen and the sintering temperature range. The motive force for sintering is the excess free energy in the particle system. This exists in the powder compact in the form of surface energy and the excess lattice energy due to defects. The defects which can be eliminated at the operating temperature are responsible for the mobility and hence sintering. This concept of the motive force for sintering has been used to explain the difference in the activation energies observed in the present study. This would also explain phenomena such as attainment of limiting density, presence of optimum sintering temperature and the influence of calcination treatments on the sintering behaviour of powders. (author)

Low-Cost Manufacturing of Bioresorbable Conductors by Evaporation-Condensation-Mediated Laser Printing and Sintering of Zn Nanoparticles.

Science.gov (United States)

Shou, Wan; Mahajan, Bikram K; Ludwig, Brandon; Yu, Xiaowei; Staggs, Joshua; Huang, Xian; Pan, Heng

2017-07-01

Currently, bioresorbable electronic devices are predominantly fabricated by complex and expensive vacuum-based integrated circuit (IC) processes. Here, a low-cost manufacturing approach for bioresorbable conductors on bioresorbable polymer substrates by evaporation-condensation-mediated laser printing and sintering of Zn nanoparticle is reported. Laser sintering of Zn nanoparticles has been technically difficult due to the surface oxide on nanoparticles. To circumvent the surface oxide, a novel approach is discovered to print and sinter Zn nanoparticle facilitated by evaporation-condensation in confined domains. The printing process can be performed on low-temperature substrates in ambient environment allowing easy integration on a roll-to-roll platform for economical manufacturing of bioresorbable electronics. The fabricated Zn conductors show excellent electrical conductivity (≈1.124 × 10 6 S m -1 ), mechanical durability, and water dissolvability. Successful demonstration of strain gauges confirms the potential application in various environmentally friendly sensors and circuits. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study of pore closure during pressure-less sintering of advanced oxide ceramics

Czech Academy of Sciences Publication Activity Database

Spusta, T.; Svoboda, Jiří; Maca, K.

2016-01-01

Roč. 115, AUG (2016), s. 347-353 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA15-06390S Institutional support: RVO:68081723 Keywords : Ceramic material * Sintering * Porosity * Modelling * Hot isostatic pressing Subject RIV: BJ - Thermodynamics Impact factor: 5.301, year: 2016

Effects of AlN on the densification and mechanical properties of pressureless-sintered SiC ceramics

Directory of Open Access Journals (Sweden)

Qisong Li

2016-02-01

Full Text Available In the present work, SiC ceramics was fabricated with AlN using B4C and C as sintering aids by a solid-state pressureless-sintered method. The effects of AlN contents on the densification, mechanical properties, phase compositions, and microstructure evolutions of as-obtained SiC ceramics were thoroughly investigated. AlN was found to promote further densification of the SiC ceramics due to its evaporation over 1800 °C, transportation, and solidification in the pores resulted from SiC grain coarsening. The highest relative density of 99.65% was achieved for SiC sample with 15.0 wt% AlN by the pressureless-sintered method at 2130 °C for 1 h in Ar atmosphere. Furthermore, the fracture mechanism for SiC ceramics containing AlN tended to transfer from single transgranular fracture mode to both transgranular fracture and intergranular fracture modes when the sample with 30.0 wt% AlN sintered at 1900 °C for 1 h in Ar. Also, SiC ceramics with 30.0 wt% AlN exhibited the highest fracture toughness of 5.23 MPa m1/2 when sintered at 1900 °C.

Effect of additives in sintering UO2-7wt%Gd2O3 fuel pellets

International Nuclear Information System (INIS)

Santos, L.R.; Riella, H.G.

2009-01-01

Gadolinium has been used as burnable poison for reactivity control in modern PWRs. The incorporation of Gd 2 O 3 powder directly into the UO 2 powder enables longer fuel cycles and optimized fuel utilization. Nevertheless, processing by this method leads to difficulties while obtaining sintered pellets with the minimum required density. The process for manufacturing UO 2 - Gd 2 O 3 generates scraps that should be reused. The main scraps are green and sintered pellets, which must be calcined to U 3 O 8 to return to the fabrication process. Also, the incorporation of Gd 2 O 3 in UO 2 requires the use of an additive to improve the sintering process, in order to achieve the physical properties specified for the mixed fuel, mainly density and microstructure. This paper describes the effect of the addition of fabrication scraps on the properties of the UO 2 -Gd 2 O 3 fuel. Aluminum hydroxide Al(OH) 3 was also incorporated to the fuel as a sintering aid. The results shown that the use of 2000 ppm of Al(OH) 3 as additive allow to fabricate good pellets with up to 10 wt% of recycled scraps. (author)

Sintering and thermal ageing studies of zirconia - yttria ceramics by impedance spectroscopy

International Nuclear Information System (INIS)

Florio, Daniel Zanetti de

1998-01-01

ZrO 2 :8 mol %Y 2 O 3 solid electrolyte ceramic pellets have been prepared with powders of three different origins: a Nissan (Japan) commercial powder, a powder obtained by the coprecipitation technique at IPEN, and the mixing of powder oxides (ZrO 2 produced at a Pilot Plant at IPEN and 99.9% pure Y 2 O 3 of USA origin). These starting powders have been analysed by the following techniques: X-ray fluorescence for yttrium content, X-ray diffraction for structural phase content, sedimentation for particle size distribution, gas adsorption (BET) for surface area determination, and transmission electron microscopy for average particle size determination. Pressed ceramic pellets have been analysed by dilatometry to evaluate the sintering stages. Sintered pellets have been characterized by X-ray diffraction for phase analysis and scanning electron microscopy for grain morphology analysis. Impedance spectroscopy analysis have been carried out to follow thermal ageing of zirconia-yttria solid electrolyte at 600 deg C, the working temperature of permanent oxygen sensor, and to study sintering kinetics. The main results show that ageing at 600 deg C decreases the emf sensor response in the first 100 h to a steady value. Moreover, sintering studies by impedance spectroscopy allowed for finding correlations between electrical parameters, sintering kinetics and grain growth mechanisms. (author)

Effect of the sintering method on microstructure and thermal and mechanical properties of zirconium oxophosphate ceramics Zr2O(PO4)2

Science.gov (United States)

Bregiroux, Damien; Cedelle, Julie; Ranc, Isabelle; Barreteau, Céline; Mata Osoro, Gustavo; Wallez, Gilles

2017-12-01

Due to an ultra-low thermal expansion, Zr2O(PO4)2 could find many applications as a thermal shock resistant material. To this end, ceramic processing is a key step in order to reach best properties. In this work, Zr2O(PO4)2 was sintered by conventional sintering and by the spark plasma sintering technique (SPS) with and without additive. Samples made by conventional sintering with ZnO as sintering aid have a maximum relative density of around 92%. Microstructure is composed of large grains and microcracks can be observed. When doped with 5 wt. % of MgO, samples can be densified by SPS up to 99.6% of the relative density and the grain size maintained between 0.5 and 1.5 μm. Thermal conductivity and Vickers microhardness were investigated as a function of the microstructure. Best values were obtained for the ceramic doped with 5 wt.% MgO and sintered by SPS, thanks to a fine microstructure and a small amount of residual microcracks.

Effect of Co3O4 addition on densification of 8 mil% Yttria stabilized zirconia

International Nuclear Information System (INIS)

Grilo, J.P.F.; Neto, P.P.B.; Souza, G.L.; Macedo, D.A.; Paskocimas, C.A.; Nascimento, R.M.

2012-01-01

8 mol% Yttria stabilized zirconia (8YSZ) is the most common material used as electrolyte in solid oxide fuel cells (SOFC). In recent years, many research efforts have been focused on trying to reduce its sintering temperature with a view of the possibility of co-sintering of the anode/electrolyte interface. In this context, the use of sintering aids is a major technological routes used to enhance the densification of YSZ. In this work, Co 3 O 4 powders obtained by the Pechini method were used as sintering aids for 8YSZ. The effect of the addition of Co 3 O 4' (between 0.075 and 1 wt.%) in the densification of 8YSZ was investigated by X-ray diffraction, electron microscopy and density measurements. The results indicated that the optimum temperature sintering decreases with increasing content of Co 3 O 4 . The best content of the sintering aid was 0.25 wt.%, for this content was obtained value of relative density above 90% after sintering at temperatures as low as 1350 deg C. (author)

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.

Strain-enhanced sintering of iron powders

Energy Technology Data Exchange (ETDEWEB)

Amador, D.R.; Torralba, J.M. [Universidad Carlos III de Madrid, Departamento de Ciencias de Materiales e Ingenieria Metalurgica, Leganes, Madrid (Spain); Monge, M.A.; Pareja, R. [Universidad Carlos III de Madrid, Departamento de Fisica, Madrid (Spain)

2005-02-01

Sintering of ball-milled and un-milled Fe powders has been investigated using dilatometry, X-ray, density, and positron annihilation techniques. A considerable sintering enhancement is found in milled powders showing apparent activation energies that range between 0.44 and 0.80 eV/at. The positron annihilation results, combined with the evolution of the shrinkage rate with sintering temperature, indicate generation of lattice defects during the sintering process of milled and un-milled powders. The sintering enhancement is attributed to pipe diffusion along the core of moving dislocations in the presence of the vacancy excess produced by plastic deformation. Positron annihilation results do not reveal the presence of sintering-induced defects in un-milled powders sintered above 1200 K, the apparent activation energy being in good agreement with that for grain-boundary diffusion in {gamma}-Fe. (orig.)

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

International Nuclear Information System (INIS)

Xu, J.L.; Xiao, Q.F.; Mei, D.D.; Zhong, Z.C.; Tong, Y.X.; Zheng, Y.F.; Li, L.

2017-01-01

Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO 2 and a few amorphous Fe 2 O 3 and Nd 2 O 3 . The amorphous SiO 2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

Solid-state sintering of tungsten heavy alloys

International Nuclear Information System (INIS)

Gurwell, W.E.

1994-10-01

Solid-state sintering is a technologically important step in the fabrication of tungsten heavy alloys. This work addresses practical variables affecting the sinterability: powder particle size, powder mixing, and sintering temperature and time. Compositions containing 1 to 10 micrometer (μM) tungsten (W) powders can be fully densified at temperatures near the matrix solidus. Blending with an intensifier bar provided good dispersion of elemental powders and good as-sintered mechanical properties under adequate sintering conditions. Additional ball milling increases powder bulk density which primarily benefits mold and die filling. Although fine, 1 μm W powder blends have high sinterability, higher as-sintered ductilities are reached in shorter sintering times with coarser, 5 μm W powder blends; 10μm W powder blends promise the highest as-sintered ductilities due to their coarse microstructural W

Influence of the starch content and sintering temperature on the processing of porous zirconia substrates

International Nuclear Information System (INIS)

Albano, Maria P; Garrido, Liliana B

2008-01-01

Porous ceramics are used as electrodes in fuel cells, separators in batteries, filters, etc. Thin porous substrates of zirconium stabilized with yttrium oxide (ZSY) are used as anodes in solid oxide fuel cells. One way to obtain a porous band is to mix starch particles during the preparation stage of the ZSY suspension. The starch burns during the removal of the binder and leaves stable pores that are not eliminated in the subsequent sintering stage. This work used the band pouring process to produce porous bands of ZSY with porosities of 29% to 53% using starch as a transitory additive. Concentrated aqueous suspensions of ZSY were prepared with different contents of starch and of an acrylic latex binder. The influence of the fraction of starch volume and of the temperature on the sintering behavior and on the final micro structure of the bands was studied. The total porosity of the bands was higher than the fractions in volume of added starch, due to the presence of closed porosity in the matrix. The deviations compared to the porosity predicted based on the fractions in the volume of starch, were greater as the starch content increased. The percentage of open porosity in the sintered bands depended on the fraction in the volume of added starch and on the sintering temperature. When the fraction in volume of starch increased from 17.6% to 37.8% a gradual increase occurred in the opening of the porous structure. The contraction of the bands during sintering at a given temperature correlated with the density of the packing of ZSY (au)

Alumina-zirconium ceramics synthesis by selective laser sintering/melting

International Nuclear Information System (INIS)

Shishkovsky, I.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

2007-01-01

In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al 2 O 3 . By applying finely dispersed Y 2 O 3 powder inclusions, the type of the ceramic structure is significantly changed

A comparative approach to synthesis and sintering of alumina/yttria nanocomposite powders using different precipitants

Energy Technology Data Exchange (ETDEWEB)

Kafili, G. [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Movahedi, B., E-mail: b.movahedi@ast.ui.ac.ir [Department of Nanotechnology Engineering, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, 81746-73441 (Iran, Islamic Republic of); Milani, M. [Faculty of Advanced Materials and Renewable Energy Research Center, Tehran (Iran, Islamic Republic of)

2016-11-01

Alumina/yttria nanocomposite powder as an yttrium aluminum garnet (YAG) precursor was synthesized via partial wet route using urea and ammonium hydrogen carbonate (AHC) as precipitants, respectively. The products were characterized using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectroscopy. The use of urea produced very tiny spherical Y-compounds with chemical composition of Y{sub 2}(CO{sub 3}){sub 3}·nH{sub 2}O, which were attracted to the surface of alumina nanoparticles and consequently, a core-shell structure was obtained. The use of ammonium hydrogen carbonate produced sheets of Y-compounds with chemical composition of Y(OH)CO{sub 3} covering the alumina nanoparticles. A fine-grained YAG ceramic (about 500 nm), presenting a non-negligible transparency (45% RIT at IR range) was obtained by the spark plasma sintering (SPS) of alumina-yttria nanocomposite synthesized in the urea system. This amount of transmission was obtained by only the sintering of the powder specimen without any colloidal forming process before sintering or adding any sintering aids or dopant elements. However, by spark plasma sintering of alumina-yttria nanocomposite powder synthesized in AHC system, an opaque YAG ceramic with an average grain size of 1.2 μm was obtained. - Highlights: • Urea proved to be an appropriate precipitant for obtaining a core-shell alumina/yttria nanocomposite. • Alumina/yttria nanocomposite powders with more appropriate morphology and highly sinterability. • A fine-grained YAG ceramic was obtained by SPS of alumina-yttria nanocomposite.

Sintering of MnCo2O4 coatings prepared by electrophoretic deposition

DEFF Research Database (Denmark)

Bobruk, M.; Molin, Sebastian; Chen, Ming

2018-01-01

Sintering of MnCo2O4 coatings prepared by electrophoretic deposition on steel substrates has been studied in air and in reducing-oxidizing atmosphere. Effect of temperature and pO2 on the resulting coating density was evaluated from scanning electron microscopy images of polished cross sections...

Studying hardness, workability and minimum bending radius in selectively laser-sintered Ti–6Al–4V alloy samples

Science.gov (United States)

Galkina, N. V.; Nosova, Y. A.; Balyakin, A. V.

2018-03-01

This research is relevant as it tries to improve the mechanical and service performance of the Ti–6Al–4V titanium alloy obtained by selective laser sintering. For that purpose, sintered samples were annealed at 750 and 850°C for an hour. Sintered and annealed samples were tested for hardness, workability and microstructure. It was found that incomplete annealing of selectively laser-sintered Ti–6Al–4V samples results in an insignificant reduction in hardness and ductility. Sintered and incompletely annealed samples had a hardness of 32..33 HRC, which is lower than the value of annealed parts specified in standards. Complete annealing at temperature 850°C reduces the hardness to 25 HRC and ductility by 15...20%. Incomplete annealing lowers the ductility factor from 0.08 to 0.06. Complete annealing lowers that value to 0.025. Complete annealing probably results in the embrittlement of sintered samples, perhaps due to their oxidation and hydrogenation in the air. Optical metallography showed lateral fractures in both sintered and annealed samples, which might be the reason why they had lower hardness and ductility.

Inversion defects in MgAl2O4 elaborated by pressureless sintering, pressureless sintering plus hot isostatic pressing, and spark plasma sintering

International Nuclear Information System (INIS)

Mussi, A.; Granger, G. Bernard; Addad, A.; Benameur, N.; Beclin, F.; Bataille, A.

2009-01-01

The distribution of inversion defects of Al was investigated in dense magnesium-aluminate spinel elaborated by pressureless sintering, pressureless sintering plus hot isostatic pressing, and spark plasma sintering. This study was conducted by energy electron loss spectroscopy analyses and more particularly by energy loss near edge structure investigations of the Al-L 2,3 edge. Several aspects are discussed with the purpose of understanding why charged defects dispersal reveals a special configuration.

The effect of Cu addition and milling contaminations on the microstructure evolution of ball milled Al-Pb alloy during sintering

International Nuclear Information System (INIS)

Zhu, M.; Ouyang, L.Z.; Wu, Z.F.; Zeng, M.Q.; Li, Y.Y.; Zou, J.

2006-01-01

Al-10 wt.%Pb and Al-10 wt.%Pb-x wt.%Cu (x = 0-7.0) bulk alloys were prepared by sintering the mechanically alloyed powders at various temperatures. The microstructure changes of the as consolidated powders in the course of sintering were analyzed by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction analysis and transmission electron microscopy. It has been found that, with respect to the Al-10 wt.%Pb-x wt.%Cu alloy, CuAl 2 and Cu 9 Al 4 phases formed in the milling process, and the amount of CuAl 2 phase increased while the Cu 9 Al 4 phase disappeared gradually in the sintering process. In both Al-10 wt.%Pb and Al-10 wt.%Pb-x wt.%Cu alloys, the sintering process results in the coarsening of Pb phase and the growth rate of Pb phase fulfills the Lifshitz-Slyozov-Wagner equation even though the size of the Pb phase was in nanometer range. The Pb particle exhibits cuboctahedral morphology and has a cubic to cubic orientation relationship with the Al matrix. The addition of Cu strongly depressed the growth rate of Pb. Contamination induced by milling has apparent influence on the microstructure of the sintered alloys. Al 7 Cu 2 Fe and aluminium oxide phases were identified in the sintered alloys. The cuboctahedral morphology of Pb particles was broken up by the presence of the oxide phase

Comparison of Ti(C,N)-based cermets processed by hot-pressing sintering and conventional pressureless sintering

International Nuclear Information System (INIS)

Xu, Qingzhong; Ai, Xing; Zhao, Jun; Qin, Weizhen; Wang, Yintao; Gong, Feng

2015-01-01

Highlights: • The HP sintered Ti(C,N)-based cermets exhibit high hardness with fine grain size. • The PLS sintered cermets possess high mechanical properties with low porosity. • The applied pressure can rearrange particles and contribute to grain refinement. • The heating rate can greatly affect the solid and liquid phase sintering of cermets. - Abstract: A suitable sintering method is important to obtain the Ti(C,N)-based cermets with superior properties. In this paper, Ti(C,N)-based cermets were fabricated by hot-pressing sintering (HP) and conventional pressureless sintering (PLS) technology, respectively, to investigate the influence of different sintering methods on the microstructure and mechanical properties of cermets materials. The microstructure, fracture morphology, indention cracks and phase composition were observed and detected using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The transverse rupture strength (TRS), Vickers hardness (HV) and fracture toughness (K IC ) were also measured. The results reveal that all of the Ti(C,N)-based cermets exhibit core–rim microstructures with black cores, white cores and grey rims embedded into metal binder phases. The grain size of the samples fabricated by HP is much finer and the structure is more compact than those fabricated by PLS, while there exist pores in the HP sintered samples. The sintering process has no influence on the phase composition of cermets, but affects the phase content and crystallinity. The samples fabricated by PLS present higher transverse rupture strength, fracture toughness and density than samples fabricated by HP. However, the HP sintered samples possess a higher hardness

Expeditious low-temperature sintering of copper nanoparticles with thin defective carbon shells

Science.gov (United States)

Kim, Changkyu; Lee, Gyoungja; Rhee, Changkyu; Lee, Minku

2015-04-01

The realization of air-stable nanoparticles, well-formulated nanoinks, and conductive patterns based on copper is a great challenge in low-cost and large-area flexible printed electronics. This work reports the synthesis of a conductively interconnected copper structure via thermal sintering of copper inks at a low temperature for a short period of time, with the help of thin defective carbon shells coated onto the copper nanoparticles. Air-stable copper/carbon core/shell nanoparticles (typical size ~23 nm, shell thickness ~1.0 nm) are prepared by means of an electric explosion of wires. Gaseous oxidation of the carbon shells with a defective structure occurs at 180 °C, impacting the choice of organic solvents as well as the sintering conditions to create a crucial neck formation. Isothermal oxidation and reduction treatment at 200 °C for only about 10 min yields an oxide-free copper network structure with an electrical resistivity of 25.1 μΩ cm (14.0 μΩ cm at 250 °C). Finally, conductive copper line patterns are achieved down to a 50 μm width with an excellent printing resolution (standard deviation ~4.0%) onto a polyimide substrate using screen printing of the optimized inks.The realization of air-stable nanoparticles, well-formulated nanoinks, and conductive patterns based on copper is a great challenge in low-cost and large-area flexible printed electronics. This work reports the synthesis of a conductively interconnected copper structure via thermal sintering of copper inks at a low temperature for a short period of time, with the help of thin defective carbon shells coated onto the copper nanoparticles. Air-stable copper/carbon core/shell nanoparticles (typical size ~23 nm, shell thickness ~1.0 nm) are prepared by means of an electric explosion of wires. Gaseous oxidation of the carbon shells with a defective structure occurs at 180 °C, impacting the choice of organic solvents as well as the sintering conditions to create a crucial neck formation

Production of sintered alumina from powder; optimization of the sinterized parameters for the maximum mechanical resistence

International Nuclear Information System (INIS)

Rocha, J.C. da.

1981-02-01

Pure, sinterized alumina and the optimization of the parameters of sinterization in order to obtain the highest mechanical resistence are discussed. Test materials are sinterized from a fine powder of pure alumina (Al 2 O 3 ), α phase, at different temperatures and times, in air. The microstructures are analysed concerning porosity and grain size. Depending on the temperature or the time of sinterization, there is a maximum for the mechanical resistence. (A.R.H.) [pt

Microstructural comparison of effects of hafnium and titanium additions in spark-plasma-sintered Fe-based oxide-dispersion strengthened alloys

Energy Technology Data Exchange (ETDEWEB)

Huang, Yina, E-mail: huangyina1981@hotmail.com [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); School of Electronic Science & Applied Physics, Hefei University of Technology, Hefei, Anhui 230009 (China); Zhang, Hongtao [Department of Materials, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Auger, Maria A.; Hong, Zuliang [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Ning, Huanpo [School of Engineering of Materials Science, Queen Mary University of London, London, E1 4NS (United Kingdom); Nanoforce Technology Ltd, London, E1 4NS (United Kingdom); Gorley, Michael J. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom); Grant, Patrick S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Reece, Michael J.; Yan, Haixue [School of Engineering of Materials Science, Queen Mary University of London, London, E1 4NS (United Kingdom); Nanoforce Technology Ltd, London, E1 4NS (United Kingdom); Roberts, Steve G. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom)

2017-04-15

Two oxide dispersion strengthened alloys: 14Cr-0.25Y{sub 2}O{sub 3}-0.22Hf (wt.%) and Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.4Ti (wt.%) were fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). Electron backscatter diffraction showed grain sizes in the range 0.5–15 μm in both alloys. Transmission electron microscopy and scanning transmission electron microscopy showed a homogeneous distribution of nano-oxides precipitated during SPS. Using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography, several different oxide phases were found in both alloys, but the majority of dispersoids were Y-Hf-O type in Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.22Hf and Y-Ti-O type in Fe-14Cr-0.25Y{sub 2}O{sub 3}-0.4Ti. There were a variety of orientation relationships between the different dispersoids and the ferritic matrix. Both alloys had dispersoid densities of ∼10{sup 23}/m{sup 3}, with average diameters of 4.3 nm and 3.5 nm in the 0.22Hf and 0.4Ti containing alloys, respectively. Per atom added, Hf (0.07 at.%) is suggested to be more potent than Ti (0.46 at.%) in refining the nano-oxides.

Guideline tests on the corrosion of sintered uranium oxide by lead and sodium about 450 deg. C; Essais d'orientation sur la corrosion de l'oxyde d'uranium fritte par le plomb et le sodium aux environs de 450 deg. C

Energy Technology Data Exchange (ETDEWEB)

Portnoff, A.; Pointud, R.

1958-05-15

Within the frame of the investigation of behaviour of a fuel element (such as UO{sub 2}) under irradiation, the authors report the study of the physical-chemical action of the coolant at different temperatures on the body to be irradiated. Thus, sintered uranium oxide has been submitted to corrosion by lead and by sodium during 250 hours at temperatures between 400 and 500 C. The physical characteristics of the UO{sub 2} powder and of different sintered UO{sub 2} pellets produced from this powder under different sintering processes are indicated, as well as the results of a spectrographic analysis of the sintered UO{sub 2}. Corrosion devices, treatments and obtained results are reported for corrosion by lead and by sodium. In the latter case, extraction processes are discussed (using butyl alcohol, or melting in vaseline oil)

Analysis of wear in organic and sintered friction materials used in small wind energy converters

Directory of Open Access Journals (Sweden)

Jorge Alberto Lewis Esswein Junior

2008-09-01

Full Text Available Wind energy converters of small size used in isolated units to generate electrical energy must present low maintenance cost to such facilities economically viable. The aspect to be analyzed in cost reduction is the brake system, since in isolated systems the use of brake is more frequent reducing the brake pads life time. This study aims at analyzing the wear behavior of some materials used in brake pads. An organic material was analyzed comparing it with a commercial brake pad, and the sintered material was developed and tested. The materials behaviors were evaluated in both wear and friction coefficient. The sintered samples were made by powder metallurgy. The composition was compacted at 550 MPa and sintered in a furnace with controlled atmosphere to avoid oxidation. Despite the different compositions of the two types of materials, they presented a very similar wear; however, the sintered material presented a higher friction coefficient. An adjustment in the braking system of the wind generator might be proposed to use the sintered brake pad, due to its higher friction coefficient. Consequently, the braking action becomes lower, reducing the wear rate of the material.

Mixed oxide fuel pellet and manufacturing method thereof

International Nuclear Information System (INIS)

Yuda, Ryoichi; Ito, Ken-ichi; Masuda, Hiroshi.

1993-01-01

In a method of manufacturing nuclear fuel pellets which comprises compression molding a mixed oxide powder containing UO 2 and PuO 2 followed by sintering, a sintering agent having a composition comprising about 40 to 80 wt% of SiO 2 and the balance of Al 2 O 3 is mixed to a mixed oxide at a ratio of about 40ppm to about 0.5 wt% based on the total amount of the mixed oxide and the sintering agent, to prepare a mixture. The mixture is molded into a compression product and then sintered at a weakly acidic atmosphere at a temperature of about 1500degC to 1800degC. With such procedures, the sintering agent forms an eutectic product of a single liquid phase, PuO 2 is dispersed over the entire region of the pellet by way of the liquid phase, formation of a solid solution phase is promoted to annihilate a free PuO 2 phase. Further, growth of crystal grains is promoted. Accordingly, since the MOX fuel pellets prepared according to the present invention have a uniform solid solution state, and no free PuO 2 phase remains, increase of FP gas emission due to local nuclear fission of Pu can be avoided. (T.M.)

Room Temperature Electrochemical Sintering of Zn Microparticles and Its Use in Printable Conducting Inks for Bioresorbable Electronics.

Science.gov (United States)

Lee, Yoon Kyeung; Kim, Jeonghyun; Kim, Yerim; Kwak, Jean Won; Yoon, Younghee; Rogers, John A

2017-10-01

This study describes a conductive ink formulation that exploits electrochemical sintering of Zn microparticles in aqueous solutions at room temperature. This material system has relevance to emerging classes of biologically and environmentally degradable electronic devices. The sintering process involves dissolution of a surface passivation layer of zinc oxide in CH 3 COOH/H 2 O and subsequent self-exchange of Zn and Zn 2+ at the Zn/H 2 O interface. The chemical specificity associated with the Zn metal and the CH 3 COOH/H 2 O solution is critically important, as revealed by studies of other material combinations. The resulting electrochemistry establishes the basis for a remarkably simple procedure for printing highly conductive (3 × 10 5 S m -1 ) features in degradable materials at ambient conditions over large areas, with key advantages over strategies based on liquid phase (fusion) sintering that requires both oxide-free metal surfaces and high temperature conditions. Demonstrations include printed magnetic loop antennas for near-field communication devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, vacuum sintering and dielectric characterization of zirconia (t-ZrO2) nanopowder

International Nuclear Information System (INIS)

Pazhani, R.; Padma Kumar, H.; Varghese, Angeo; Moses Ezhil Raj, A.; Solomon, Sam; Thomas, J.K.

2011-01-01

Highlights: → A single step auto-igniting combustion synthesis was employed for the preparation of nanocrystalline ZrO 2 . → Detailed structural analysis was carried out using XRD and FT-IR techniques. → Micro strain analysis of the asprepared nanocrystalline ZrO 2 was carried out. → A sintered density of above 98% of the theoretical value was obtained using vacuum sintering techniques. → The dielectric properties of vacuum sintered ZrO 2 were measured for a frequency range from 10 KHz to 10 MHz. - Abstract: Phase pure zirconium oxide powders have been synthesized using the single step auto-ignition combustion method, the particles were nanometer sized (20 nm) and the size distribution was very narrow (3.4 nm). Systematic structural characterization revealed the t-ZrO 2 and indexed for its tetragonal structure (a = 3.5975 A and c = 5.1649 A). Calculated microstrain in most of the plane indicated the presence of compressive stress (65-288 MPa) along various planes of the particles. Observed space group (P4 2 /nmc) revealed the presence of cations in the 8e positions (0.75, 0.25, 0.75) and the anions in the 16 h positions (0.25, 0.25, 0.4534). The metal-oxide (Zr-O) band observed at the low wavenumber region further confirmed the phase purity of the as-prepared ZrO 2 nanopowders. Peaks at the binding energy positions 2.042 and 0.525 keV in the energy dispersive X-ray spectrum revealed oxygen deficient zirconia. The particle size estimated by TEM was in good agreement with the results obtained through X-ray line broadening (20.81 nm) measurements. The nanopowders were sintered to above 98% of the theoretical density by using vacuum sintering technique at a relatively low temperature of 1300 deg. C. Stable tetragonal ZrO 2 experimentally yield the permittivity value of about 28 at 10 MHz.

Effect of carbon and titanium carbide on sintering behaviour of zirconium diboride

International Nuclear Information System (INIS)

Mishra, S.K.; Pathak, L.C.

2008-01-01

Systematic sintering studies on the ZrB 2 powder were carried out with the addition of carbon (C) in the range of 0 2 . The addition of C also found to inhibit the grain size and fine grained ZrB 2 -C composite could be obtained with high densification. The increased densification with the C addition was due to removal of oxygen impurities on the ZrB 2 powder surfaces that prevented the commonly observed exaggerated grain growth through evaporation condensation of oxide phases during sintering of boride ceramics. At higher percentages of C addition, the densification rates decreased due to increased volume fraction of second phase that acted as diffusion barrier

Oxide ceramics

International Nuclear Information System (INIS)

Ryshkewitch, E.; Richerson, D.W.

1985-01-01

The book explores single-phase ceramic oxide systems from the standpoint of physical chemistry and technology. This second edition also focuses on advances in technology since publication of the original edition. These include improvements in raw materials and forming and sintering techniques, and the major role that oxide ceramics have had in development of advanced products and processes. The text is divided into five major sections: general fundamentals of oxide ceramics, advances in aluminum oxide technology, advances in zirconia technology, and advances in beryllium oxide technology

Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings.

Science.gov (United States)

Kim, Myung-Joo; Choi, Yun-Jung; Kim, Seong-Kyun; Heo, Seong-Joo; Koak, Jai-Young

2017-01-23

Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe's test, and Pearson's correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps ( p marginal discrepancy and the internal gap variables ( r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.

Status of Research on Selective Laser Sintering of Nanomaterials for Flexible Electronics Fabrication

International Nuclear Information System (INIS)

Ko, Seung Hwan

2011-01-01

A plastic-compatible low-temperature metal deposition and patterning process is essential for the fabrication of flexible electronics because they are usually built on a heat-sensitive flexible substrate, for example plastic, fabric, paper, or metal foil. There is considerable interest in solution-processible metal nanoparticle ink deposition and patterning by selective laser sintering. It provides flexible electronics fabrication without the use of conventional photolithography or vacuum deposition techniques. We summarize our recent progress on the selective laser sintering of metals and metal oxide nanoparticles on a polymer substrate to realize flexible electronics such as flexible displays and flexible solar cells. Future research directions are also discussed

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.

Preparation and characterization of amorphous SiO{sub 2} coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

Energy Technology Data Exchange (ETDEWEB)

Xu, J.L., E-mail: jlxu@nchu.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Xiao, Q.F.; Mei, D.D. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Zhong, Z.C., E-mail: zzhong2014@sina.com [The Institute for Rare Earth Magnetic Materials and Devices, Jiangxi University of Science and Technology, Ganzhou 341000 (China); Tong, Y.X. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Li, L. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China)

2017-03-15

Amorphous SiO{sub 2} coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO{sub 2} and a few amorphous Fe{sub 2}O{sub 3} and Nd{sub 2}O{sub 3}. The amorphous SiO{sub 2} coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO{sub 2} coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

Development of microstructure during sintering and aluminium exposure of titanium diboride ceramics

Energy Technology Data Exchange (ETDEWEB)

Pettersen, Gunnar

1997-12-31

In the production of aluminium, much less energy need be consumed if an inert, wetted cathode is present in the electrolysis cell. Titanium diboride, TiB{sub 2}, is easily wetted and does not readily dissolve in liquid aluminium, but it degrades, probably because aluminium penetrates into it during electrolysis. This degradation is linked to impurities present in the TiB{sub 2} after sintering. This thesis studies the sintering process and how aluminium penetrates into the material. High-purity, high-density TiB{sub 2} compacts were made by hot pressing at 50 MPa in an argon atmosphere at 1790-1960 {sup o}C. Samples were made with different impurity additions. These samples were exposed to liquid aluminium at 980 {sup o}C for 24 hours. All samples were penetrated, but the amount and appearance depended on the sintering aid used. Unlike the other samples, pure TiB{sub 2} was easily penetrated by metallic aluminium because of the open porosity and microcracks of this material. Grain boundary penetration was common among the samples. Differences in penetration behaviour between grain boundaries are probably due to differences in grain boundary energy. But no relation to segregants or boundary misorientation was found. The orientation of grain boundary planes and de-wetting of thin films upon cooling may explain the observed microstructure development. The samples sintered with Ti addition suffered extensive penetration despite their high densities. The grain boundaries of these samples became faceted and contained thicker films of metallic aluminium, presumably because of increased solubility due to iron segregations. All secondary phases present in the grain junctions after sintering, except from the B{sub 4}C phase, reacted with the penetrated aluminium. This did not cause swelling and cracking, as has been suggested by other authors. 101 refs., 48 figs., 7 tabs.

Optimisation of Copper Oxide Impregnation on Carbonised Oil Palm Empty Fruit Bunch for Nitric Oxide Removal using Response Surface Methodology

Science.gov (United States)

Ahmad, Norhidayah; Yong, Sing Hung; Ibrahim, Naimah; Ali, Umi Fazara Md; Ridwan, Fahmi Muhammad; Ahmad, Razi

2018-03-01

Oil palm empty fruit bunch (EFB) was successfully modified with phosphoric acid hydration followed by impregnation with copper oxide (CuO) to synthesize CuO modified catalytic carbon (CuO/EFBC) for low-temperature removal of nitric oxide (NO) from gas streams. CuO impregnation was optimised through response surface methodology (RSM) using Box-Behnken Design (BBD) in terms of metal loading (5-20%), sintering temperature (200-800˚C) and sintering time (2-6 hours). The model response for the variables was NO adsorption capacity, which was obtained from an up-flow column adsorption experiment with 100 mL/min flow of 500 ppm NO/He at different operating conditions. The optimum operating variables suggested by the model were 20% metal loading, 200˚C sintering temperature and 6 hours sintering time. A good agreement (R2 = 0.9625) was achieved between the experimental data and model prediction. ANOVA analysis indicated that the model terms (metal loading and sintering temperature) are significant (Prob.>F less than 0.05).

Optimisation of Copper Oxide Impregnation on Carbonised Oil Palm Empty Fruit Bunch for Nitric Oxide Removal using Response Surface Methodology

Directory of Open Access Journals (Sweden)

Ahmad Norhidayah

2018-01-01

Full Text Available Oil palm empty fruit bunch (EFB was successfully modified with phosphoric acid hydration followed by impregnation with copper oxide (CuO to synthesize CuO modified catalytic carbon (CuO/EFBC for low-temperature removal of nitric oxide (NO from gas streams. CuO impregnation was optimised through response surface methodology (RSM using Box-Behnken Design (BBD in terms of metal loading (5-20%, sintering temperature (200-800˚C and sintering time (2-6 hours. The model response for the variables was NO adsorption capacity, which was obtained from an up-flow column adsorption experiment with 100 mL/min flow of 500 ppm NO/He at different operating conditions. The optimum operating variables suggested by the model were 20% metal loading, 200˚C sintering temperature and 6 hours sintering time. A good agreement (R2 = 0.9625 was achieved between the experimental data and model prediction. ANOVA analysis indicated that the model terms (metal loading and sintering temperature are significant (Prob.>F less than 0.05.

Tungsten and molybdenum with oxide dispersion, production and properties

International Nuclear Information System (INIS)

Haerdtle, S.; Schmidberger, R.

1989-01-01

By the reaction spray process metal powders with dispersed metal oxides can be produced in one step. The systems investigated here are tungsten and molybdenum with 0,5% resp. 5% La 2 O 3 , Y 2 O 3 and ZrO 2 . The oxides with diameters below 0,5μm are finely dispersed within the metal powder particles. The sinterability of the powders depends on the oxide content. Maximum density at an oxide content of 0,5% is about 96% at a sintering temperature of 1600 0 C. The type of oxide influences the densification versus temperature but not the final density. 5 refs., 11 figs. (Author)

Fabrication of Cr-doped UO2 Fuel Pellet using Liquid Phase Sintering

International Nuclear Information System (INIS)

Kim, Dong Joo; Yang, Jae Ho; Kim, Keon Sik; Rhee, Young Woo; Kim, Jong Hun; Oh, Jang Soo; Koo, Yang Hyun

2013-01-01

An enhancement of the thermal conductivity of a pellet can be obtained by the addition of a higher thermal conductive material in the pellet. In addition, the resistance to the PCI can be increased through a plasticity increase of the pellet. Thermal conductivity of ceramic materials is generally lower than that of metallic materials. The thermal conductivity of uranium oxide which is a typical ceramic material is low as well. The steep temperature gradient in the fuel pellet results from the low thermal conductivity. Therefore, the thermal conductivity improvement of a nuclear fuel pellet can enhance the fuel performance in various aspects. The lower centerline temperature of a fuel pellet affects the enhancement of fuel safety as well as fuel pellet integrity during nuclear reactor operation. Besides, the nuclear reactor power can be uprated due to the higher safety margin. So, many researches to enhance the thermal conductivity of nuclear fuel pellet have been performed in various ways. To improve the thermal conductivity of UO 2 pellet, an appropriate arrangement of the high thermal conductive material in UO 2 matrix is one of the various methods. We intended to control a placement of chromium as the high thermal conductive material. The metallic chromium and chromium oxide were arranged in a grain boundary of UO 2 using a liquid phase sintering method. The liquid phase sintering of Cr-doped UO 2 pellet could be adjusted using a control of an oxygen potential in sintering atmosphere

Investigation of the sintering mechanisms for (U,Am)O{sub 2} pellets obtained by CRMP process

Energy Technology Data Exchange (ETDEWEB)

Caisso, M. [CEA, Centre de Marcoule, DEN, DTEC/SECA/LFC, F-30207 Bagnols-sur-Ceze (France); CEA, Centre de Marcole, DEN, DRCP/SERA/LCAR, F-30207 Bagnols-sur-Ceze (France); Institut Europeen des Membranes, UMR 5635 CNRS-ENSCM-UM, CC047, Campus Triolet, Universite de Montpellier, F-34095 Montpellier Cedex 5 (France); Boulesteix, R.; Maitre, A. [SPCTS, UMR 7315 CNRS-Universite de Limoges-ENSCI, Centre Europeen de la Ceramique, 12 Rue Atlantis, F-87068 Limoges (France); Picart, S.; Delahaye, T. [CEA, Centre de Marcole, DEN, DRCP/SERA/LCAR, F-30207 Bagnols-sur-Ceze Cedex (France); Ayral, A. [Institut Europeen des Membranes, UMR 5635 CNRS-ENSCM-UM, CC047, Campus Triolet Universite de Montpellier, F-34095 Montpellier Cedex 5 (France)

2016-07-01

The use of CRMP (Calcined Resin Microsphere Pelletization) process for AmBB (Americium Bearing Blankets) fabrication is today a key research axis in americium transmutation domain, where its very high activity requires minimization of powder dissemination. In this aim, the use of oxide microspheres as compaction precursors is a promising clean alternative to powder metallurgy. Understanding the different steps of densification during CRMP pellet sintering thus appears as fundamental to obtain final materials with the specific features required for AmBB. The densification curve recorded in dynamic conditions shows different sintering steps. A first decrease of shrinkage rate happens at low temperature, around 1100 K. This phenomenon is not normally observed in the sintering of conventional powders. Chemical and microstructural studies were performed on (U,Am)O{sub 2} and also on (Ce,Gd)O{sub 2} surrogate compound to highlight the causes of this low-temperature sintering step. Multi-scale reorganization finally appears as the sole explanation, through the sintering of nano-metric aggregate present in the green pellet and related to the morphology of the starting microspheres employed as pelletization precursors. (authors)

Studies on frequency dependent electrical and dielectric properties of sintered zinc oxide pellets: effects of Al-doping

Science.gov (United States)

Tewari, S.; Ghosh, A.; Bhattacharjee, A.

2016-11-01

Sintered pellets of zinc oxide (ZnO), both undoped and Al-doped are prepared through a chemical process. Dopant concentration of Aluminium in ZnO [Al/Zn in weight percentage (wt%)] is varied from 0 to 3 wt%. After synthesis structural characterisation of the samples are performed with XRD and SEM-EDAX which confirm that all the samples are of ZnO having polycrystalline nature with particle size from 108.6 to 116 nm. Frequency dependent properties like a.c. conductivity, capacitance, impedance and phase angle are measured in the frequency range 10 Hz to 100 kHz as a function of temperature (in the range 25-150 °C). Nature of a.c. conductivity in these samples indicates hopping type of conduction arising from localised defect states. The frequency and temperature dependent properties under study are found to be as per correlated barrier hoping model. Dielectric and impedance properties studied in the samples indicate distributed relaxation, showing decrease of relaxation time with temperature.

Study and fabrication of solid oxide fuel cells through tape casting and co-sintering; Etude et realisation par coulage en bande et co-frittage de cellules de pile a combustible a oxydes solides

Energy Technology Data Exchange (ETDEWEB)

Grosjean, A

2004-11-15

This work is dedicated to the devising of a low-cost fabrication process of solid oxide fuel cells (SOFC). Technical requirements impose the shaping method: stripe casting as well as the materials used: Yttria-stabilized zirconia (YSZ), nickel and lanthanum manganite doped with strontium (LSM). In order to comply with environmental requirements the developed process uses an aqueous barbotine solvent. We get electrodes and the electrolyte separately, the use of an absorbent drying process has enabled us to join 3 layers to form an elementary cell with great interfacial homogeneity. The resistance of the cell to sintering has been improved through the symmetrization of the deformations of the cell. In order to interpret the low electrical properties of the cell and its quick damaging, transmission microscopy studies have been performed. These studies have shown 2 facts. First, 2 isolating phases appear at the cathode (at the LSM/YSZ interface) because of a too high sintering temperature and secondly, a quick clustering of nickel grains appears during cell operation that leads to a local loss of the nickel grid percolation. This problem has been solved by increasing the size of nickel oxide grains from 0.5 {mu}m to 3 {mu}m) to stabilize the microstructure. The issue of the reactivity at the LSM/YSZ interfaces was tackled in 2 different ways, we have tried to lower the sintering temperature by using a zirconia nano-powder first and then by replacing zirconia in the electrolyte by gadolinium-doped ceria. The use of zirconia nano-powder has failed to decrease sintering temperature while preserving the electrolyte density and the use of ceria has triggered instabilities that have not yet been solved. Despite all these drawbacks, this process allows the fabrication of an excellent anode/electrolyte interface. (A.C.)

Effect Of SiC Particles On Sinterability Of Al-Zn-Mg-Cu P/M Alloy

Directory of Open Access Journals (Sweden)

Rudianto H.

2015-06-01

Full Text Available Premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder was analyzed as matrix in this research. Gas atomized powder Al-9Si with 20% volume fraction of SiC particles was used as reinforcement and added into the alloy with varied concentration. Mix powders were compacted by dual action press with compaction pressure of 700 MPa. High volume fraction of SiC particles gave lower green density due to resistance of SiC particles to plastic deformation during compaction process and resulted voids between particles and this might reduce sinterability of this mix powder. Sintering was carried out under ultra high purity nitrogen gas from 565°-580°C for 1 hour. High content of premix Al-5.5Zn-2.5Mg-0.5Cu alloy powder gave better sintering density and reached up to 98% relative. Void between particles, oxide layer on aluminum powder and lower wettability between matrix and reinforcement particles lead to uncompleted liquid phase sintering, and resulted on lower sintering density and mechanical properties on powder with high content of SiC particles. Mix powder with wt90% of Alumix 431D and wt10% of Al-9Si-vf20SiC powder gave higher tensile strength compare to another mix powder for 270 MPa. From chemical compositions, sintering precipitates might form after sintering such as MgZn2, CuAl2 and Mg2Si. X-ray diffraction, DSC-TGA, and SEM were used to characterize these materials.

Influence of sintering temperature on mechanical properties of spark plasma sintered pre-alloyed Ti-6Al-4 V powder

Energy Technology Data Exchange (ETDEWEB)

Muthuchamy, A.; Patel, Paridh; Rajadurai, M. [VIT Univ., Vellore, Tamil Nadu (India); Chaurisiya, Jitendar K. [NIT, Suratkal (India); Annamalai, A. Raja [VIT Univ., Vellore, Tamil Nadu (India). Centre for Innovative Manufacturing Research

2018-04-01

Spark plasma sintering provides faster heating that can create fully, or near fully, dense samples without significant grain growth. In this study, pre-alloyed Ti-6Al-4 V powder compact samples produced through field assisted sintering in a spark plasma sintering machine are compared as a function of consolidation temperature. The effect of sintering temperature on the densification mechanism, microstructural evolution and mechanical properties of spark plasma sintered Ti-6Al-4 V alloy compacts was investigated in detail. The compact, sintered at 1100 C, exhibited near net density, highest hardness and strength as compared to the other compacts processed at a temperature lower than 1100 C.

Mechanical properties' improvement of a tricalcium phosphate scaffold with poly-l-lactic acid in selective laser sintering

International Nuclear Information System (INIS)

Liu, Defu; Zhuang, Jingyu; Shuai, Cijun; Peng, Shuping

2013-01-01

To improve the mechanical properties of a scaffold fabricated via selective laser sintering (SLS), a small amount (0.5–3 wt%) of poly-l-lactic acid (PLLA) is added to the β-tricalcium phosphate (β-TCP) powder. The fracture toughness of the scaffold prepared with the mixture powder containing 1 wt% PLLA increases by 18.18% and the compressive strength increases by 4.45% compared to the scaffold prepared from the β-TCP powder. The strengthening and toughening is related to the enhancement of β-TCP sintering characteristics via introducing a transient liquid phase in SLS. Moreover, the microcracks caused by the volume expansion due to the β–α phase transformation of TCP are reduced because of the PLLA inhibition function on the phase transformation. However, PLLA additive above 1 wt% would lead to a PLLA residue which will decrease the mechanical properties. The experimental results show that PLLA is an effective sintering aid to improve the mechanical properties of a TCP scaffold. (paper)

Analysis of the conductivity of commercial easy sintering grade 3 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} materials

Energy Technology Data Exchange (ETDEWEB)

Badwal, Sukhvinder P.S.; Ciacchi, Fabio T.; Giampietro, Kristine M. [CSIRO, Manufacturing and Infrastructure Technology, Private Bag 33, Clayton South 3169, Victoria (Australia)

2005-01-14

Fine grain zirconia-yttria materials are required for enhanced performance in solid oxide fuel cells and related devices and in applications requiring good thermo-mechanical properties. Materials with about 3 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} composition are good electrolyte materials for solid oxide fuel cell, ceramic membrane oxygen separation and a number of related devices because of their superior mechanical properties and ease of fabrication into thin self-supporting structures in comparison with a material in the 8-10 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} composition range. In this study, sintering behaviour, impedance studies, four-probe DC conductivity measurements and microstructure analysis has been performed on various easy sintering grade materials from two commercial powder suppliers. These materials achieve near theoretical density at sintering temperatures as low as 1350-1400C. For direct comparison of the conductivity and impedance behaviour in easy sintering grade materials, several other 3 mol% Y{sub 2}O{sub 3}-ZrO{sub 2} powders were also investigated. The total ionic conductivity at 850C in easy sintering grade materials is comparable with normal-grade commercial materials of similar composition despite a slightly higher grain boundary impedance at lower temperatures (below circa 450C). There were no obvious differences in the grain boundary thickness, calculated from the impedance data, of normal and easy sintering grade materials.

Laser sintering of metal powders on top of sintered layers under multiple-line laser scanning

International Nuclear Information System (INIS)

Xiao Bin; Zhang Yuwen

2007-01-01

A three-dimensional numerical model for multiple-line sintering of loose powders on top of multiple sintered layers under the irradiation of a moving Gaussian laser beam is carried out. The overlaps between vertically deposited layers and adjacent lines which strengthen bonding are taken into account. The energy equation is formulated using the temperature transforming model and solved by the finite volume method. The effects of the number of the existing sintered layers, porosity and initial temperature coupled with the optimal combination laser intensity and scanning velocity are presented. The results show that the liquid pool moves slightly towards the negative scanning direction and the shape of the liquid pool becomes shallower with higher scanning velocity. A higher laser intensity is needed to achieve the required overlaps when the number of the existing sintered layers increases. Increasing porosity or initial temperature enhances the sintering process and thus less intensity is needed for the overlap requirement

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.

Sintered indium-tin oxide particles induce pro-inflammatory responses in vitro, in part through inflammasome activation.

Directory of Open Access Journals (Sweden)

Melissa A Badding

Full Text Available Indium-tin oxide (ITO is used to make transparent conductive coatings for touch-screen and liquid crystal display electronics. As the demand for consumer electronics continues to increase, so does the concern for occupational exposures to particles containing these potentially toxic metal oxides. Indium-containing particles have been shown to be cytotoxic in cultured cells and pro-inflammatory in pulmonary animal models. In humans, pulmonary alveolar proteinosis and fibrotic interstitial lung disease have been observed in ITO facility workers. However, which ITO production materials may be the most toxic to workers and how they initiate pulmonary inflammation remain poorly understood. Here we examined four different particle samples collected from an ITO production facility for their ability to induce pro-inflammatory responses in vitro. Tin oxide, sintered ITO (SITO, and ventilation dust particles activated nuclear factor kappa B (NFκB within 3 h of treatment. However, only SITO induced robust cytokine production (IL-1β, IL-6, TNFα, and IL-8 within 24 h in both RAW 264.7 mouse macrophages and BEAS-2B human bronchial epithelial cells. Our lab and others have previously demonstrated SITO-induced cytotoxicity as well. These findings suggest that SITO particles activate the NLRP3 inflammasome, which has been implicated in several immune-mediated diseases via its ability to induce IL-1β release and cause subsequent cell death. Inflammasome activation by SITO was confirmed, but it required the presence of endotoxin. Further, a phagocytosis assay revealed that pre-uptake of SITO or ventilation dust impaired proper macrophage phagocytosis of E. coli. Our results suggest that adverse inflammatory responses to SITO particles by both macrophage and epithelial cells may initiate and propagate indium lung disease. These findings will provide a better understanding of the molecular mechanisms behind an emerging occupational health issue.

Studies on the sintering of copper powder compacts

International Nuclear Information System (INIS)

Elmasry, M.A.A.; Abadir, M.F.; Mahdy, A.N.; Elkinawy, W.S.

1995-01-01

Solid state sintering behavior of cylindrical compacts, (1 cm diameter and 1 cm height), made of copper powder was studied within a range of compacting pressure of 75 up to 300 MPa, sintering temperature of 600 up to to 900 degree C, and sintering time of 5 up to 60 min in a reducing atmosphere composed of H2 and N 2 gases with a volumetric ratio 3:1. The green and the sintered densities were found to to increase with the compacting pressure. Higher sintering temperature, and time favour increased sintered density. probable mechanisms during the initial stage of sintering were disclosed. It was found that low pressures cause dilation of closed pores, and vice versa. At low pressures and temperatures the surface diffusion mechanism is favoured, While high temperatures favour lattice diffusion mechanism. at high pressures, the lattice diffusion mechanism is suppressed while surface diffusion predominates. Density and hence shrinkage were also found to increase with the increase of sintering time, While its rate increases with the increase of sintering temperature. the influence of sintering conditions on the hardness of the compacts was studied. An increase in hardness, When higher compacting pressures and higher sintering temperatures were adopted, has bee obtained. 11 figs

Multiple recycling of NdFeB-type sintered magnets

Energy Technology Data Exchange (ETDEWEB)

Zakotnik, M. [Department of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)], E-mail: miha.zakotnik@gmail.com; Harris, I.R.; Williams, A.J. [Department of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2009-02-05

Some fully dense, sintered NdFeB-type magnets (employed in VCM disc drives) have been subjected to a recycling process using the hydrogen decrepitation (HD) process. After a brief milling treatment, the powder was aligned, pressed and re-sintered and this procedure was repeated four times with a progressive fall in the density and in the magnetic properties. The chemical analysis indicated that this was due to the progressive oxidation of the Nd-rich material and to some Nd loss by evaporation. The procedure was then repeated but with the addition (blending) of a fine powder of neodymium hydride after the first cycle. It was found that the addition of 1 at.% of neodymium at each stage was sufficient to maintain the density and the magnetic properties of the recycled magnets up to and including the 4th cycle. Inductively coupled plasma (ICP) and metallographic analysis indicated that the neodymium hydride additions compensated for the neodymium loss due to evaporation and to oxidation so that the proportion of Nd-rich material remained approximately constant. The additional amount of Nd{sub 2}O{sub 3} in the blended recycled magnets appeared to inhibit grain growth on the 3rd and 4th cycles when compared to that of the unblended magnets. The next challenge is to see if the process can be scaled-up to an industrial scale.

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.

Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings

Directory of Open Access Journals (Sweden)

Myung-Joo Kim

2017-01-01

Full Text Available Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance, a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05. The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654, except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.

Modeling the microstructural evolution during constrained sintering

DEFF Research Database (Denmark)

Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...... to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number...

Master sintering curves of two different alumina powder compacts

Directory of Open Access Journals (Sweden)

Vaclav Pouchly

2009-12-01

Full Text Available Concept of Master Sintering Curve is a strong tool for optimizing sintering schedule. The sintering behaviour can be predicted, and sintering activation energy can be calculated with the help of few dilatometric measurements. In this paper an automatic procedure was used to calculate Master Sintering Curves of two different alumina compacts. The sintering activation energies were determined as 640 kJ/mol for alumina with particle size of 240 nm, respective 770 kJ/mol for alumina with particle size of 110 nm. The possibility to predict sintering behaviour with the help of Master Sintering Curve was verified.

Residual stresses in a co-sintered SOC half-cell during post-sintering cooling

DEFF Research Database (Denmark)

Charlas, Benoit; Chatzichristodoulou, Christodoulos; Brodersen, Karen

2014-01-01

.e. the reference temperature (Tref) or the strain difference based on the curvature. This approximation gives good results for bilayers with a defined cooling temperature profile, where the curvature of the bilayer defines a unique balance between the two unknown residual stress states in the two layers......Due to the thermal expansion mismatch between the layers of a Solid Oxide Cell, residual stresses (thermal stresses) develop during the cooling after sintering. Residual stresses can induce cell curvature for asymmetric cells but more importantly they also result in more fragile cells. Depending...... on the loading conditions, the additional stress needed to break the cells can indeed be smaller due to the initial thermo-mechanical stress state. The residual stresses can for a bilayer cell be approximated by estimating the temperature at which elastic stresses start to build up during the cooling, i...

HAp physical investigation - the effect of sintering temperature

International Nuclear Information System (INIS)

Mohd Reusmaazran Yusof; Idris Besar; Rusnah Mustaffa; Cik Rohaida Che Hak

2004-01-01

The paper presents the effect of sintering temperature on the physical properties of porous hydroxyapatite (HAp). In this study, the HAp was prepared using polymeric sponge techniques with different binder concentration. The sintering process was carried out in air for temperature ranging from 1200 degree C to 1600 degree C. Different physical properties namely density and porosity were observed at different sintering temperatures. The HAp prepared with higher PVP binder showed a slightly decreased in apparent density with increasing sintering temperature, while those HAp prepared with lower PVP showed a slightly increase in apparent density with increasing sintering temperature. The total porosity was found to be approximately constant in the whole sintering temperature range. However, closed porosity decreases with increasing sintering temperature for HAp prepared by lower binder concentration. On the other hand, the HAp prepared by higher binder concentration HAp showed increasing closed porosity with increasing sintering temperature. Other features such as the influence of sintering temperatures on grain and strut also be presented in this paper. (Author)

Fractographical characterization of hot pressed and pressureless sintered AlN-doped ZrB{sub 2}–SiC composites

Energy Technology Data Exchange (ETDEWEB)

Ahmadi, Zohre [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Nayebi, Behzad [School of Materials and Metallurgy Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Young Researchers and Elite Club, Khorramabad Branch, Islamic Azad University, Khorramabad (Iran, Islamic Republic of); Shahedi Asl, Mehdi [Department of Mechanical Engineering, University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Ghassemi Kakroudi, Mahdi, E-mail: mg_kakroudi@tabrizu.ac.ir [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

2015-12-15

In this paper, ZrB{sub 2}–SiC composites doped with 0–5 wt.% AlN were prepared by a low pressure hot pressing as well as a pressureless sintering methods at 1900 °C for 2 h. The influence of aluminum nitride addition on the sinterability and microstructure development of such ceramic composites was studied by a fractographical approach. The results revealed that only 1 wt.% AlN can aid the densification process of the hot pressed ceramic composite via the liquid phase sintering mechanism due to the formation of nano-scale metakaolinite spinel layers. In the pressureless sintering method, adding more AlN can increase the formation of gaseous products which raised the amount of porosities in the final microstructure. The formation of nano-graphite phase in the hot pressing process, the formation of Al{sub 2}OC in the pressureless sintering process, and the formation of BN in the both processes were disclosed by X-ray diffraction, SEM and TEM analyses. - Highlights: • The effect of AlN addition on densification of ZrB{sub 2}–SiC composites was studied. • AlN promotes the densification in hot pressed samples by liquid phase formation. • A fully dense composite was obtained by adding 1 wt.% AlN in hot pressing process. • In pressureless sintering, more AlN content intensifies the formation of porosities.

Low temperature solid oxide electrolytes (LT-SOE): A review

Science.gov (United States)

Singh, B.; Ghosh, S.; Aich, S.; Roy, B.

2017-01-01

Low temperature solid oxide fuel cell (LT-SOFC) can be a source of power for vehicles, online grid, and at the same time reduce system cost, offer high reliability, and fast start-up. A huge amount of research work, as evident from the literature has been conducted for the enhancement of the ionic conductivity of LT electrolytes in the last few years. The basic conduction mechanisms, advantages and disadvantages of different LT oxide ion conducting electrolytes {BIMEVOX systems, bilayer systems including doped cerium oxide/stabilised bismuth oxide and YSZ/DCO}, mixed ion conducting electrolytes {doped cerium oxides/alkali metal carbonate composites}, and proton conducting electrolytes {doped and undoped BaCeO3, BaZrO3, etc.} are discussed here based on the recent research articles. Effect of various material aspects (composition, doping, layer thickness, etc.), fabrication methods (to achieve different microstructures and particle size), design related strategies (interlayer, sintering aid etc.), characterization temperature & environment on the conductivity of the electrolytes and performance of the fuel cells made from these electrolytes are shown in tabular form and discussed. The conductivity of the electrolytes and performance of the corresponding fuel cells are compared. Other applications of the electrolytes are mentioned. A few considerations regarding the future prospects are pointed.

Nano-composite powders Ag-SnO2 prepared by reactive milling sintering and microstructural evolution

International Nuclear Information System (INIS)

Lorrain, Nathalie

2000-01-01

This work aims at controlling the synthesis and the sintering of nano-composite powders Ag-SnO 2 in order to obtain a dense and nano-structured material for electrical contact as a substitute of the toxic compound Ag - CdO. The powder is prepared by reactive milling from silver oxide (Ag 2 O) and silver bronze (Ag 3 Sn) powders. This process leads to a fine dispersion of silver and tin oxide nanometer sized particles. We first studied the mechanisms of reaction promoted by milling in vacuum and in air. A two-stage oxidation of tin in Ag 3 Sn occurs: during forced contact with Ag 2 O, tin oxidises in SnO, then in SnO 2 . In air, gaseous oxygen also participates to the oxidation of tin in SnO 2 but the reaction is slower because of the formation of silver carbonates from a reaction of Ag 2 O with CO 2 .Then the sintering behaviour of the nano-composite powder as a function of the compacting pressure and of the heating rate has been studied. We show: (i) a diffusion of pure silver towards porosity and free surfaces (exo-diffusion) which destroys the nano-structure and (ii) a severe de-densification. We show that the origin of these phenomena is due to carbonates on to the Ag 2 O starting powder, which are incorporated, in the milled Ag-SnO 2 powder in course of milling; during sintering, decomposition gases generate internal stresses. Low stresses lead to a diffusional creep with exo-diffusion whereas high stresses induce an intensive de-densification by local plastic deformation but no exo-diffusion. A modelling shows that exo-diffusion is limited by heating very quickly a strongly compacted powder that contains a high quantity of carbonates. The experimental results confirm the predictions of the model. Finally, we propose solutions allowing a full densification and a process for decreasing the tin oxide concentration. (author) [fr

High-Pressure Spark Plasma Sintering (HP SPS): A Promising and Reliable Method for Preparing Ti-Al-Si Alloys.

Science.gov (United States)

Knaislová, Anna; Novák, Pavel; Cygan, Sławomir; Jaworska, Lucyna; Cabibbo, Marcello

2017-04-27

Ti-Al-Si alloys are prospective material for high-temperature applications. Due to low density, good mechanical properties, and oxidation resistance, these intermetallic alloys can be used in the aerospace and automobile industries. Ti-Al-Si alloys were prepared by powder metallurgy using reactive sintering, milling, and spark plasma sintering. One of the novel SPS techniques is high-pressure spark plasma sintering (HP SPS), which was tested in this work and applied to a Ti-10Al-20Si intermetallic alloy using a pressure of 6 GPa and temperatures ranging from 1318 K (1045 °C) to 1597 K (1324 °C). The low-porosity consolidated samples consist of Ti₅Si₃ silicides in an aluminide (TiAl) matrix. The hardness varied between 720 and 892 HV 5.

Characterization and sintering of niobium-ATR alumina

International Nuclear Information System (INIS)

Sibuya, N.H.; Iwasaki, H.; Suzuki, C.K.; Pinatti, D.G.

1987-01-01

In the niobium aluminothermy a slag is produced, composed mostly of alumina and other compounds such as niobium oxide and silica. The phase composition of this ATR alumina was characterized by X-ray powder diffractometry, and afterwards this alumina was subjected to leaching processes. It was noticed that the original content of 70% α-alumina in slag rose to 95% after the calcination. ATR alumina (leached and calcined, and without any treatment) was used to make pressed bodies which were fired in air at 1200 to 1400 0 C for 1 to 10,5 hours; and in vacuum at 1550 to 1800$0C for 2 hours. Characterization was done by density measurements, X-ray diffractometry and ultrasonic analysis. Ultrasonic analysis of some vacuum fired bodies showed londitudinal velocities close to the value found in literature. Correlation of several techniques measurements disclosed the niobium oxide interference in sintering. (Author) [pt

Brush-Painting and Photonic Sintering of Copper Oxide and Silver Inks on Wood and Cardboard Substrates to Form Antennas for UHF RFID Tags

Directory of Open Access Journals (Sweden)

Erja Sipilä

2016-01-01

Full Text Available Additive deposition of inks with metallic inclusions provides compelling means to embed electronics into versatile structures. The need to integrate electronics into environmentally friendly components and structures increases dramatically together with the increasing popularity of the Internet of Things. We demonstrate a novel brush-painting method for depositing copper oxide and silver inks directly on wood and cardboard substrates and discuss the optimization of the photonic sintering process parameters for both materials. The optimized parameters were utilized to manufacture passive ultra high frequency (UHF radio frequency identification (RFID tag antennas. The results from wireless testing show that the RFID tags based on the copper oxide and silver ink antennas on wood substrate are readable from ranges of 8.5 and 11 meters, respectively, and on cardboard substrate from read ranges of 8.5 and 12 meters, respectively. These results are well sufficient for many future wireless applications requiring remote identification with RFID.

A new UO2 sintering technology for the recycling of defective fuel pellets

International Nuclear Information System (INIS)

Song, K. W.; Kim, K. S.; Jeong, Y. H.

1998-01-01

A new UO 2 sintering technology to recycle defective UO 2 pellets has been developed. The defective UO 2 pellets were oxidized in an air to produce U 3 O 8 powder, and the U 3 O 8 powder was mixed with fresh AUC-UO 2 powder in the range of 10 to 100 wt%. Nb 2 O 5 and TiO 2 are added to the mixed powder. The mixed powder was pressed and sintered at 1680 deg C for 4 hours in hydrogen. The density of UO 2 pellets without sintering agents decreased linearly with the U 3 O 8 content at the rate of 0.2 %TD per 1 wt% U 3 O 8 , and the density was below 93.5 %TD at the U 3 O 8 contents above 10 wt%. However, the mixed UO 2 and U 3 O 8 powder containing Nb 2 O 5 (≥0.3 wt%) and TiO 2 (≥0.1 wt%) yielded a sintered density above 94 %TD in all ranges of U 3 O 8 contents. It was found that higher mixing ratios of U 3 O 8 to UO 2 powder did not affect the grain size of UO 2 pellets under the addition of Nb 2 O 5 , but decreased the grain size of UO 2 pellets under the addition of TiO 2 . The doped UO 2 pellets have grain sizes larger than 20 μm, and have small density gain after re-sintering test, owing to large pores. Therefore, the sintering agents such as Nb 2 O 5 and TiO 2 can make highly densified UO 2 pellets from the powder comprising a large amount of U 3 O 8 powder

Reaction behavior of SO2 in the sintering process with flue gas recirculation.

Science.gov (United States)

Yu, Zhi-Yuan; Fan, Xiao-Hui; Gan, Min; Chen, Xu-Ling; Chen, Qiang; Huang, Yun-Song

2016-07-01

The primary goal of this paper is to reveal the reaction behavior of SO2 in the sinter zone, combustion zone, drying-preheating zone, and over-wet zone during flue gas recirculation (FGR) technique. The results showed that SO2 retention in the sinter zone was associated with free-CaO in the form of CaSO3/CaSO4, and the SO2 adsorption reached a maximum under 900ºC. SO2 in the flue gas came almost from the combustion zone. One reaction behavior was the oxidation of sulfur in the sintering mix when the temperature was between 800 and 1000ºC; the other behavior was the decomposition of sulfite/sulfate when the temperature was over 1000ºC. However, the SO2 adsorption in the sintering bed mainly occurred in the drying-preheating zone, adsorbed by CaCO3, Ca(OH)2, and CaO. When the SO2 adsorption reaction in the drying-preheating zone reached equilibrium, the excess SO2 gas continued to migrate to the over-wet zone and was then absorbed by Ca(OH)2 and H2O. The emission rising point of SO2 moved forward in combustion zone, and the concentration of SO2 emissions significantly increased in the case of flue gas recirculation (FGR) technique. Aiming for the reuse of the sensible heat and a reduction in exhaust gas emission, the FGR technique is proposed in the iron ore sintering process. When using the FGR technique, SO2 emission in exhaust gas gets changed. In practice, the application of the FGR technique in a sinter plant should be cooperative with the flue gas desulfurization (FGD) technique. Thus, it is necessary to study the influence of the FGR technique on SO2 emissions because it will directly influence the demand and design of the FGD system.

Sintering of composite

International Nuclear Information System (INIS)

Bordia, R.K.; Scherer, G.W.

1988-01-01

Several constitutive laws have been used in the literature to predict the response of sintering bodies under external and internal stress fields. These analyses are based on the assumptions of linear and isotropic behavior. The authors provide a critical examination of these equations and show that some of the available constitutive laws predict a negative Poisson's ratio. These laws have been used to analyze sintering of ceramic matrix composites with rigid inclusions and predict large values of the internal stresses and significant retardation of the densification of composites. Since a negative value of Poisson's ratio has never been observed in sinter - forging experiments, the authors conclude that either the stresses are small (as predicted by the constitutive laws with positive Poisson's ratio) or the basic assumption of linearity and isotropy used in all the analyses is incorrect. Finally, the authors discuss some phenomena that could be important in understanding the densification of ceramic matrix composites

Influence of surface topography on the surface durability of steam oxidised sintered iron

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José Daniel Biasoli de Mello

2005-06-01

Full Text Available Durability of surfaces has been reported as the main factor affecting tribological behavior of steam oxidised sintered iron. The presence of surface pores and their negative influence on load bearing capacity, suggest that surface topography might play an important role on the durability of the oxide layer. In this paper, the influence of compaction pressure and powder grade on surface topography, and as a consequence, its effect on the tribological behavior of steam oxidised sintered iron has been analysed. Specimens prepared from atomised iron powders with different sizes were compacted using 4 different pressures, sintered, and then subjected to steam treatment. Tribological characterisation was carried out in a reciprocating sliding wear test. Although the processing parameters affected the surface topography to a considerable extent, the main influence may be attributed to powder grade. A strong influence of surface topography on the durability distance, evaluated in terms of the evolution of contact resistance with total sliding distance, has been highlighted. Surfaces which were smoother and had high load-carrying capacity were always associated with a higher durability distance.

Corrosion of beryllium oxide

International Nuclear Information System (INIS)

Elston, J.; Caillat, R.

1958-01-01

Data are reported on the volatilization rate of beryllium oxide in moist air depending on temperature and water vapour concentration. They are concerned with powder samples or sintered shapes of various densities. For sintered samples, the volatilization rate is very low under the following conditions: - temperature: 1300 deg. C, - water vapour concentration in moist air: 25 g/m 3 , - flow rate: 12 I/hour corresponding to a speed of 40 m/hour on the surface of the sample. For calcinated powders (1300 deg. C), grain growth has been observed under a stream of moist air at 1100 deg. C. For instance, grain size changes from 0,5 to at least 2 microns after 500 hours of exposure at this temperature. Furthermore, results data are reported on corrosion of sintered beryllium oxide in pressurized water. At 250 deg. C, under a pressure of 40 kg/cm 2 water is very slightly corrosive; however, internal strains are revealed. Finally, some features on the corrosion in liquid sodium are exposed. (author) [fr

Reduction of surface erosion caused by helium blistering in sintered beryllium and sintered aluminum powder

International Nuclear Information System (INIS)

Das, S.K.; Kaminsky, M.

1976-01-01

Studies have been conducted to find materials with microstructures which minimize the formation of blisters. A promising class of materials appears to be sintered metal powder with small average grain sizes and low atomic number Z. Studies of the surface erosion of sintered aluminum powder (SAP 895) and of aluminum held at 400 0 C due to blistering by 100 keV helium ions have been conducted and the results are compared to those obtained earlier for room temperature irradiation. A significant reduction of the erosion rate in SAP 895 in comparison to annealed aluminum and SAP 930 is observed. In addition results on the blistering of sintered beryllium powder (type I) irradiated at room temperature and 600 0 C by 100 keV helium ions are given. These results will be compared with those reported recently for vacuum cast beryllium foil and a foil of sintered beryllium powder (type II) which was fabricated differently, than type I. For room temperature irradiation only a few blisters could be observed in sintered beryllium powder type I and type II and they are smaller in size and in number than in vacuum cast beryllium. For irradiation at 600 0 C large scale exfoliation of blisters was observed for vacuum cast beryllium but much less exfoliation was seen for sintered beryllium powder, type I, and type II. The results show a reduction in erosion rate cast beryllium, for both room temperature and 600 0 C

Effect of Sintering Temperature on Microstructure, Chemical Stability, and Electrical Properties of Transition Metal or Yb-Doped BaZr{sub 0.1}Ce{sub 0.7}Y{sub 0.1}M{sub 0.1}O{sub 3−δ} (M = Fe, Ni, Co, and Yb)

Energy Technology Data Exchange (ETDEWEB)

Mirfakhraei, Behzad; Ramezanipour, Farshid; Paulson, Scott; Birss, Viola; Thangadurai, Venkataraman, E-mail: vthangad@ucalgary.ca [Department of Chemistry, University of Calgary, Calgary, AB (Canada)

2014-03-13

Perovskite-type BaZr{sub 0.1}Ce{sub 0.7}Y{sub 0.1}M{sub 0.1}O{sub 3−δ} (M = Fe, Ni, Co, and Yb) (BZCY-M) oxides were synthesized using the conventional solid-state reaction method at 1350–1550°C in air in order to investigate the effect of dopants on sintering, crystal structure, chemical stability under CO{sub 2} and H{sub 2}S, 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 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{sup −3} S cm{sup −1} at 600°C in wet H{sub 2} with an activation energy of 0.36 and 0.41 eV, respectively. Scanning electron microscope and energy-dispersive X-ray analysis 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°C, 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°C. The Fe, Co, and Ni-doped BZCY-M samples synthesized at 1350°C show stability in 30 ppm H{sub 2}S/H{sub 2} at 800°C, and increasing the firing temperature to 1550°C, enhanced the chemical stability in CO{sub 2}/N{sub 2} (1:2) at 25–900°C. The BZCY-Co and BZCY-Ni compounds with high conductivity in wet H{sub 2} could be considered as possible anodes for intermediate temperature solid oxide fuel cells.

Science of sintering and its future

International Nuclear Information System (INIS)

Ristic, M.M.

1975-01-01

Some new books published by M.Yu. Baljshin, V.A. Ivensen, V.V. Skorohod and others are characterized by the wish to give a complete approach to the problems of sintering theory. Bearing just this in mind while writing the book ''An Essay on the Generalization of Sintering Theory'' (G.V.Samsonov, M.M. Ristic with the collaborators) an idea was born: to ask the most eminent scientists in this field to present their own opinions on the theme ''The Science of Sintering and Modern Views on its Future''. There were formed 18 questions, given in the appendix to be answered. The received answers were presented in 10 chapters of this book. The fourth part of the book consists of papers of eminent scientists engaged in the field of sintering science (some of which were published here for the first time). This material is published in the book with the consent of the authors and these original contributions provide a more profound knowledge of sintering. The initial idea, that the book should have a monograph character and in which the answers would serve as some data on the latest notions of the science of sintering, was somewhat changed since the original opinions of individual scientists are given in the book and these, are sometimes very contradictory. This, in fact, gives the book a special charm because the unsolved problems in the science of sintering are most evidently stressed in this way

Factors Affecting the Sintering of UO2 Pellets

International Nuclear Information System (INIS)

El-Hakim, E.; Afifi, Y.K.

1999-01-01

Sintering of UO 2 pellets is affected by many parameters such as; UO 2 powder parameters, the conditions followed for preparing the green UO 2 pellets and the sintering scheme(heating and cooling rate, soaking time and temperature). The aim of this work is to study the effect of some these parameters on the characteristics of the sintered UO 2 pellets were qualified according to the technical specifications of Candu fuel. Pressed green pellets at different pressing force (15 to 50 k N) were sintered at 1650 ±20 degree for two hours to study the effect of pressing force on the sintered pellets characteristics; visual inspection, pellet dimensions, density and shrinkage ratio. Compacted green pellets at a pressing force of 48 k N were sintered at different sintering temperature (1600± 20 degree, 1650 ±20 degree, 1700± 20 degree) for two hours to study the effect of sintering temperature on the sintered pellets characteristics. The effect of the heating rate (200,300 and 400 degree per hour) on the sintered pellets characteristics was also investigated. It was found that the pressing force used to compact the green pellets had an effect on the density of the sintered pellets. Pellets pressed at 15 k N have a density of 10.3 g/cm 3 while, those pressed at 50 k N have a density of 10.6 g/cm 3. It was observed that increasing the heating rate to 400 degree /h lead to cracked pellets

Rapid immobilization of simulated radioactive soil waste by microwave sintering.

Science.gov (United States)

Zhang, Shuai; Shu, Xiaoyan; Chen, Shunzhang; Yang, Huimin; Hou, Chenxi; Mao, Xueli; Chi, Fangting; Song, Mianxin; Lu, Xirui

2017-09-05

A rapid and efficient method is particularly necessary in the timely disposal of seriously radioactive contaminated soil. In this paper, a series of simulated radioactive soil waste containing different contents of neodymium oxide (3-25wt.%) has been successfully vitrified by microwave sintering at 1300°C for 30min. The microstructures, morphology, element distribution, density and chemical durability of as obtained vitrified forms have been analyzed. The results show that the amorphous structure, homogeneous element distribution, and regular density improvement are well kept, except slight cracks emerge on the magnified surface for the 25wt.% Nd 2 O 3 -containing sample. Moreover, all the vitrified forms exhibit excellent chemical durability, and the leaching rates of Nd are kept as ∼10 -4 -10 -6 g/(m 2 day) within 42days. This demonstrates a potential application of microwave sintering in radioactive contaminated soil disposal. Copyright © 2017 Elsevier B.V. All rights reserved.

Sintering behavior, microstructure and properties of TiC-FeCr hard alloy

Institute of Scientific and Technical Information of China (English)

Farid Akhtar; Shiju Guo; Jawid Askari; Jianjun Tian

2007-01-01

TiC based cermets were produced with FeCr,as a binder,by conventional P/M (powder metallurgy) to near ＞97% of the theoretical density.Sintering temperature significantly affects the mechanical properties of the composite.The sintering temperature of＞1360 ℃ caused severe chemical reaction between TiC particles and the binder phase.In the TiC-FeCr cermets,the mechanical properties did not vary linearly with the carbide content.Optimum mechanical properties were found in the composite containing 57wt%TiC reinforcement,when sintered at 1360 ℃ for 1 h.Use of carbon as an additive enhanced the mechanical properties of the composites.Cermets containing carbon as an additive with 49wt% TiC exhibited attractive mechanical properties.The microstructure of the developed composite contained less or no debonding,representing good wettability of the binder with TiC particles.Homogeneous distribution of the TiC particles ensured the presence of isotropic mechanical properties and homogeneous distribution of stresses in the composite.Preliminary experiments for evaluation of the oxidation resistance of FeCr bonded TiC cermets indicate that they are more resistant than WC-Co hardmetals.

Modeling of sintering of functionally gradated materials

International Nuclear Information System (INIS)

Gasik, M.; Zhang, B.

2001-01-01

The functionally gradated materials (FGMs) are distinguished from isotropic materials by gradients of composition, phase distribution, porosity, and related properties. For FGMs made by powder metallurgy, sintering control is one of the most important factors. In this study sintering process of FGMs is modeled and simulated with a computer. A new modeling approach was used to formulate equation systems and the model for sintering of gradated hard metals, coupled with heat transfer and grain growth. A FEM module was developed to simulate FGM sintering in conventional, microwave and hybrid conditions, to calculate density, stress and temperature distribution. Behavior of gradated WC-Co hardmetal plate and cone specimens was simulated for various conditions, such as mean particle size, green density distribution and cobalt gradation parameter. The results show that the deformation behavior and stress history of graded powder compacts during heating, sintering and cooling could be predicted for optimization of sintering process. (author)

Properties, structure and machnining capabilities sintered corundum abrasives

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Cz.J. Niżankowski

2010-07-01

Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

Determination of rare earth elements, hafnium and cadmium in sintered pellets of mixed thorium and uranium oxides by neutron activation

International Nuclear Information System (INIS)

Cardoso, S.N.M.

1987-01-01

This work shows the development of a method for determination of the rare-earth elements (Eu, Sm, Dy and Gd), Hf and Cd contents in sinterized U and Th mixed oxides by neutron activation analysis. The sample is dissolved in nitric/fluoridric (0,1% HF) medium, to dryness and redissolved in 6N HCl solution. The Hf is extracted into organic phase (0,5 M TTA/benzene), irradiated and analysed through 181 Hf isotope energy peak. The aqueous phase is treated with NH 4 OH for the precipitation of hidroxides. Then, these are dissolved in 6N HNO 3 solution. The extraction of U and Th is made in two steps, one with TBP/CCl 4 and another with 0,5 M TTA/C 6 H 6 . Then the rare-earth elements and Cd are irradiated and determined by gamma spectrometry. (author) [pt

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

Science.gov (United States)

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

2017-02-01

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

Effect of sintering temperature on structure of C-B4C-SiC composites with silicon additive

International Nuclear Information System (INIS)

Wu Lijun; Academia Sinica, Shenyang; Huang Qizhong; Yang Qiaoqin; Zhao Lihu; Xu Zhongyu

1996-01-01

Carbon materials possess good electric conductivity, heat conductivity, corrosion-resistance, self-lubrication and hot-shocking resistance, and are easily machined. However, they have low mechanical strength, and are easily oxidized in air at high temperature. On the contrary, ceramic materials have high mechanical strength and hardness, and have good wear-resistance and oxidation-resistance. However, they have the shortages of poor thermal-shock resistance lubrication, and are difficult to machine. Therefore, carbon/ceramic composites with the advantages of both carbon and ceramic materials have been widely studied in the recent years. Huang prepared C-B 4 C-SiC composites with the free sintering method and the hot pressing method, and studied the effects of Si, Al, Al 2 O 3 , Ni and Ti additives on the properties of the composites. The results showed that these additives could improve the properties of the composites. Zhao et al. studies the structure of C-B 4 C-SiC composites with Si additive sintered at 2,000 C and found two c-center monoclinic phases. In this paper, the authors discussed the effect of the sintering temperature on the structure of C-B 4 C-SiC composites with Si additive by means of transmission electron microscope (TEM) and x-ray diffractometer (XRD)

Master sintering curve: A practical approach to its construction

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Pouchly V.

2010-01-01

Full Text Available The concept of a Master Sintering Curve (MSC is a strong tool for optimizing the sintering process. However, constructing the MSC from sintering data involves complicated and time-consuming calculations. A practical method for the construction of a MSC is presented in the paper. With the help of a few dilatometric sintering experiments the newly developed software calculates the MSC and finds the optimal activation energy of a given material. The software, which also enables sintering prediction, was verified by sintering tetragonal and cubic zirconia, and alumina of two different particle sizes.

Lutetium oxide-based transparent ceramic scintillators

Science.gov (United States)

Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

2016-01-19

In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

Two-dimensional simulation of sintering process

International Nuclear Information System (INIS)

Vasconcelos, Vanderley de; Pinto, Lucio Carlos Martins; Vasconcelos, Wander L.

1996-01-01

The results of two-dimensional simulations are directly applied to systems in which one of the dimensions is much smaller than the others, and to sections of three dimensional models. Moreover, these simulations are the first step of the analysis of more complex three-dimensional systems. In this work, two basic features of the sintering process are studied: the types of particle size distributions related to the powder production processes and the evolution of geometric parameters of the resultant microstructures during the solid-state sintering. Random packing of equal spheres is considered in the sintering simulation. The packing algorithm does not take into account the interactive forces between the particles. The used sintering algorithm causes the densification of the particle set. (author)

Three-dimensional simulation of viscous-flow agglomerate sintering.

Science.gov (United States)

Kirchhof, M J; Schmid, H -J; Peukert, W

2009-08-01

The viscous-flow sintering of different agglomerate particle morphologies is studied by three-dimensional computer simulations based on the concept of fractional volume of fluid. For a fundamental understanding of particle sintering characteristics, the neck growth kinetics in agglomerate chains and in doublets consisting of differently sized primary particles is investigated. Results show that different sintering contacts in agglomerates even during the first stages are not completely independent from each other, even though differences are small. The neck growth kinetics of differently sized primary particles is determined by the smaller one up to a size difference by a factor of approximately 2, whereas for larger size differences, the kinetics becomes faster. In particular, the agglomerate sintering kinetics is investigated for particle chains of different lengths and for different particle morphologies each having ten primary particles and nine initial sintering contacts. For agglomerate chains, the kinetics approximately can be normalized by using the radius of the fully coalesced sphere. In general, different agglomerate morphologies show equal kinetics during the first sintering stages, whereas during advanced stages, compact morphologies show significantly faster sintering progress than more open morphologies. Hence, the overall kinetics cannot be described by simply using constant morphology correction factors such as fractal dimension or mean coordination number which are used in common sintering models. However, for the first stages of viscous-flow agglomerate sintering, which are the most important for many particle processes, a sintering equation is presented. Although we use agglomerates consisting of spherical primary particles, our methodology can be applied to other aggregate geometries as well.

Sintered ceramics having controlled density and porosity

International Nuclear Information System (INIS)

Brassfield, H.C.; DeHollander, W.R.; Nivas, Y.

1980-01-01

A new method was developed for sintering ceramic uranium dioxide powders, in which ammonium oxalate is admixed with the powder prior to being pressed into a cylindrical green body, so that the end-point density of the final nuclear-reactor fuel product can be controlled. When the green body is heated, the ammonium oxalate decomposes and leaves discrete porosity in the sintered body, which corresponds to the ammonium oxalate regions in the green body. Thus the end-point density of the sintered body is a function of the amount of ammonium oxalate added. The final density of the sintered product is about 90-97% of the theoretical. The addition of ammonium oxalate also allows control of the pore size and distribution throughout the fuel. The process leaves substantially no impurities in the sintered strucuture. (DN)

Two steps sintering alumina doped with niobia

International Nuclear Information System (INIS)

Gomes, L.B.; Hatzfeld, J.; Heck, M.; Pokorny, A.; Bergmann, C.P.

2014-01-01

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)

Freeform Fabrication of Magnetophotonic Crystals with Diamond Lattices of Oxide and Metallic Glasses for Terahertz Wave Control by Micro Patterning Stereolithography and Low Temperature Sintering

Directory of Open Access Journals (Sweden)

Maasa Nakano

2013-04-01

Full Text Available Micrometer order magnetophotonic crystals with periodic arranged metallic glass and oxide glass composite materials were fabricated by stereolithographic method to reflect electromagnetic waves in terahertz frequency ranges through Bragg diffraction. In the fabrication process, the photo sensitive acrylic resin paste mixed with micrometer sized metallic glass of Fe72B14.4Si9.6Nb4 and oxide glass of B2O3·Bi2O3 particles was spread on a metal substrate, and cross sectional images of ultra violet ray were exposed. Through the layer by layer stacking, micro lattice structures with a diamond type periodic arrangement were successfully formed. The composite structures could be obtained through the dewaxing and sintering process with the lower temperature under the transition point of metallic glass. Transmission spectra of the terahertz waves through the magnetophotonic crystals were measured by using a terahertz time domain spectroscopy.

Effect of K3PO4 addition as sintering inhibitor during calcination of Y2O3 nanoparticles

Science.gov (United States)

Soga, K.; Okumura, Y.; Tsuji, K.; Venkatachalam, N.

2009-11-01

Erbium-doped yttrium oxide nanoparticle is one of the most important for fluorescence bioimaging under near infrared excitation. Particle size of it below 100 nm is an important requirement for a cellular bioimaging. However, the synthesis with such small particles is difficult at the calcination temperature above 1200 °C due to the sintering and crystal growth of the particles. In this study, yttrium oxide nanoparticles with average size of 30 nm were successfully synthesized by using K3PO4 as a sintering inhibitor during the calcination. A single phase of cubic Y2O3 as the resultant material was confirmed by XRD, which was also confirmed to emit a bright upconversion emission under 980-nm excitation. Improvement of chemical durability due to the introduction of phosphate group on the surface of the Y2O3 particles is also reported.

Sintering and microstructure of ice: a review

International Nuclear Information System (INIS)

Blackford, Jane R

2007-01-01

Sintering of ice is driven by the thermodynamic requirement to decrease surface energy. The structural morphology of ice in nature has many forms-from snowflakes to glaciers. These forms and their evolution depend critically on the balance between the thermodynamic and kinetic factors involved. Ice is a crystalline material so scientific understanding and approaches from more conventional materials can be applied to ice. The early models of solid state ice sintering are based on power law models originally developed in metallurgy. For pressure sintering of ice, these are based on work on hot isostatic pressing of metals and ceramics. Recent advances in recognizing the grain boundary groove geometry between sintering ice particles require models that use new approaches in materials science. The newer models of sintering in materials science are beginning to incorporate more realistic processing conditions and microstructural complexity, and so there is much to be gained from applying these to ice in the future. The vapour pressure of ice is high, which causes it to sublime readily. The main mechanism for isothermal sintering of ice particles is by vapour diffusion; however other transport mechanisms certainly contribute. Plastic deformation with power law creep combined with recrystallization become important mechanisms in sintering with external pressure. Modern experimental techniques, low temperature scanning electron microscopy and x-ray tomography, are providing new insights into the evolution of microstructures in ice. Sintering in the presence of a small volume fraction of the liquid phase causes much higher bond growth rates. This may be important in natural snow which contains impurities that form a liquid phase. Knowledge of ice microstructure and sintering is beneficial in understanding mechanical behaviour in ice friction and the stability of snow slopes prone to avalanches. (topical review)

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.

Sintered cobalt-rare earth intermetallic product

International Nuclear Information System (INIS)

Benz, M.C.

1975-01-01

A process is described for preparing novel sintered cobalt--rare earth intermetallic products which can be magnetized to form permanent magnets having stable improved magnetic properties. A cobalt--rare earth metal alloy is formed having a composition which at sintering temperature falls outside the composition covered by the single Co 5 R intermetallic phase on the rare earth richer side. The alloy contains a major amount of the Co 5 R intermetallic phase and a second solid CoR phase which is richer in rare earth metal content than the Co 5 R phase. The specific cobalt and rare earth metal content of the alloy is substantially the same as that desired in the sintered product. The alloy, in particulate form, is pressed into compacts and sintered to the desired density. The sintered product is comprised of a major amount of the Co 5 R solid intermetallic phase and up to about 35 percent of the product of the second solid CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase

Sintering-alkaline processing of borosilicate ores of Tajikistan

International Nuclear Information System (INIS)

Nazarov, F.A.

2018-01-01

The aim of the work is to study the processes of decomposition of boron-containing ore by sintering with NaOH, finding the optimal parameters of the decomposition process, studying the kinetics of processes and developing the technological foundations for ore processing. The processes of borosilicate ore processing were studied by sintering with NaOH. Possible mechanisms of chemical reactions of the process of sintering-alkaline decomposition of boron-containing ore are established, the results of which are substantiated by physicochemical methods of analysis. A principal technological scheme for processing of borosilicate ores by a sintering-alkaline method has been developed. In the first chapter, data on alkaline and caking processes for processing boron-containing and aluminium comprising raw materials are available in the literature. Based on this, the directions of our own research are outlined. The second chapter is devoted to the study of the chemical and mineralogical compositions of borosilicate ores and their concentrates with the help of X-ray phase and chemical analysis methods, the stoichiometric calculation of the formation of aluminum, iron, and boron salts has been carried out, and a thermodynamic analysis of the processes of sintering borosilicate ores with alkali has been considered. The third chapter presents the results of a study of sintering-alkaline method of processing of initial borosilicate ore of the Ak-Arkhar Deposit and its concentrate without calcination and after calcination. The kinetics of sintering of borosilicate ores with sodium hydroxide was studied. The optimal conditions of borosilicate ore sintering before and after the preliminary calcination with alkali were determined. Optimal parameters of the sintering process have been found: sintering temperature 800-8500 deg C, duration of the process - 60 minutes, mass ratio of NaOH to raw materials 2: 1. The conditions for sintering of borosilicate concentrate with alkali have been

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.

Sintered-to-size FBR fuel

International Nuclear Information System (INIS)

Rasmussen, D.E.; Schaus, P.S.

1984-04-01

Fabrication of sintered-to-size PuO 2 -UO 2 fuel pellets was completed for testing of proposed FBR product specifications. Approximately 6000 pellets were fabricated to two nominal diameters and two densities by cold pressing and sintering to size. Process control and correlation between test and production batches are discussed

Influence of sintering parameters in the ferroelectric properties os strontium bismuth tantalate samples obtained by oxide mixture

International Nuclear Information System (INIS)

Souza, R.R. de; Pereira, A.S.; Sousa, V.C.; Egea, J.R.J.

2012-01-01

The family of compounds layered-type perovskite, know as Aurivilius presents great alternative not only by the absence of lead in the composition, but because the polarization retention, replacing PZT in FeRAM devices. The strontium bismuth tantalate (SrBi 2 Ta 2 O 9 ) or SBT is ferroelectric material that has attracted considerable interest, since it has high fatigue resistance, supporting high hysteresis loops, with the change in polarization.Checking polarization and depolarization currents stimulated by temperature it is possible to obtain, for example, information about the nature of charges and about the activation energy for the process of dielectric relaxation. For analysis of ferroelectric properties of this compound, it is essential to obtain specimens with a relative density around 95%. Thus, it is important the optimization of the sintering process in order to obtain a ceramic body with a high densification. The influence of sintering parameters to obtain SrBi 2 Ta 2 O 9 in the polarization properties and in the microstructure of sintered samples was investigated by thermostimulated currents and electronic microscopy, respectively. Results show that variation of these parameters may cause changes in the ferroelectric properties of the material. (author)

Sintering of a class F fly ash

Energy Technology Data Exchange (ETDEWEB)

Joseph J. Biernacki; Anil K. Vazrala; H. Wayne Leimer [Tennessee Technological University, Cookeville, TN (United States). Department of Chemical Engineering

2008-05-15

The sinterability of a class F fly ash was investigated as a function of processing conditions including sintering temperature (1050-1200{sup o}C) and sintering time (0-90 min). Density, shrinkage, splitting tensile strength, water absorption and residual loss on ignition (RLOI) were evaluated as measures of sintering efficiency. Scanning electron microscopy (SEM), X-ray microanalysis and X-ray diffraction was used to examine microstructure and phase development due to processing. The results show that premature densification can inhibit complete carbon removal and that carbon combustion is influenced by both internal and external mass transfer conditions. 18 refs., 10 figs., 1 tab.

Sintering of nano crystalline o silicon carbide doping with

Indian Academy of Sciences (India)

Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by ...

Monitoring Sintering Burn-Through Point Using Infrared Thermography

Directory of Open Access Journals (Sweden)

Francisco G. Bulnes

2013-08-01

Full Text Available Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burnthrough point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

The quantitative characterization of sintering of urania powders

International Nuclear Information System (INIS)

Das, P.; Kulkarni, U.D.

1981-01-01

This paper presents a unified approach towards characterization of the sintering behaviour of UO 2 powders in terms of their extrinsic properties. Empirical equations connecting the sintering index with various powder parameters have been set up. The influence of various powder parameters, either individually or as dimensionless/dimensional groups, on the sintering behaviour has been studied. The relative importance of these factors has also been analysed. A good polynomial fit has been obtained for variation of sintering index with some of the powder parameters and dimensionless/dimensional groups. The equations are expected to provide a good basis for assessing the sinterability of UO 2 powders. (Auth.)

Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields

Energy Technology Data Exchange (ETDEWEB)

Lisenker, Ilya; Stoldt, Conrad R., E-mail: stoldt@colorado.edu [Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO (United States)

2016-03-31

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 Li{sub 1.5}Al{sub 0.5}Ge{sub 1.5}(PO{sub 4}){sub 3} was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, 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 X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy 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 h 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.

Effects of surrounding powder in sintering process on the properties of Sb and Mn- doped barium-strontium titanate PTCR ceramics

Directory of Open Access Journals (Sweden)

Pornsuda Bomlai

2006-05-01

Full Text Available In this research, the effects of surrounding powder used during sintering of Sb and Mn doped bariumstrontium titanate (BST ceramics were studied. The ceramic samples were prepared by a conventional mixed-oxide method and placed on different powders during sintering. Phase formation, microstructure and PTCR behavior of the samples were then observed. Microstructures and PTCR behavior varied with the type of surrounding powder, whereas the crystal structure did not change. The surrounding powder has more effects on the shape of the grain than on the size. The grain size of samples was in the range of 5-20 μm. The most uniform grain size and the highest increase of the ratio of ρmax/ρRT were found to be about 106 for samples which had been sintered on Sb-doped BST powder. This value was an order of magnitude greater than for samples sintered on a powder of the equivalent composition to that of the sample pellet.

Microwave sintering of nano size powder β-TCP bioceramics

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Mirhadi B.

2014-01-01

Full Text Available A nano sized beta tricalcium phosphate (β-TCP powder was conventional sintered (CS and microwave sintered (MW, in order to obtain dense β-TCP ceramics. In this work the effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on tricalcium phosphate (TCP was investigated by SEM (scanning electron microscopyand XRD(X-ray diffraction and then compared with conventional sintered samples. Nano-size β-TCP powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and diammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of submicrometre β-TCP powder in situ. The β-TCP samples microwave (MW sintered for 15 min at 1100°C, with average grain size of 3μm, showed better densification, higher density and certainly higher hardness than samples conventionally sintered for 2 h at the same temperature. By comparing sintered and MW sintered β-TCP samples, it was concluded that MW sintered β-TCP samples have superior mechanical properties.

Sintering of B4C powder obtained by a modified carbo-thermal reaction

International Nuclear Information System (INIS)

Rocha, R.M.; Kazumi, M.H.; Goncalves, D.P.; Melo, F.C.L.

2005-01-01

Boron carbide is one of the hardest materials and a highly refractory material that is of great interest for structural, electronic and nuclear applications. B 4 C is commercially manufactured by the carbo-thermal reduction of a mixture of boron oxide (B 2 O 3 ) in an batch electric arc furnace process. However the carbo-thermal reaction on the stoichiometric starting composition results an excess carbon residue because of the boron loss in the form of B 2 O 2 . Thus, a modified carbo-thermal reaction is applied with an excess B 2 O 3 to compensate the loss and to obtain stoichiometric powders. The aim of this work is to study the sinterability of this powder with the lower carbon residue acting as sintering additive. Pressureless sintering in the temperatures of 1900 deg. C/30 min and 2100 deg. C/30 min in argon atmosphere were applied. The synthesized powders were analysed by XRD and SEM. Density of 94% of theoretical density was achieved for sample prepared with the powder obtained with 50% B 2 O 3 excess synthesized at 1700 deg. C/15 min. (authors)

Effect of sintering conditions on the microstructural and mechanical characteristics of porous magnesium materials prepared by powder metallurgy.

Science.gov (United States)

Čapek, Jaroslav; Vojtěch, Dalibor

2014-02-01

There has recently been an increased demand for porous magnesium materials in many applications, especially in the medical field. Powder metallurgy appears to be a promising approach for the preparation of such materials. Many works have dealt with the preparation of porous magnesium; however, the effect of sintering conditions on material properties has rarely been investigated. In this work, we investigated porous magnesium samples that were prepared by powder metallurgy using ammonium bicarbonate spacer particles. The effects of the purity of the argon atmosphere and sintering time on the microstructure (SEM, EDX and XRD) and mechanical behaviour (universal loading machine and Vickers hardness tester) of porous magnesium were studied. The porosities of the prepared samples ranged from 24 to 29 vol.% depending on the sintering conditions. The purity of atmosphere played a significant role when the sintering time exceeded 6h. Under a gettered argon atmosphere, a prolonged sintering time enhanced diffusion connections between magnesium particles and improved the mechanical properties of the samples, whereas under a technical argon atmosphere, oxidation at the particle surfaces caused deterioration in the mechanical properties of the samples. These results suggest that a refined atmosphere is required to improve the mechanical properties of porous magnesium. © 2013.

Effect of rigid inclusions on sintering

International Nuclear Information System (INIS)

Rahaman, M.N.; De Jonghe, L.C.

1988-01-01

The predictions of recent theoretical studies on the effect of inert, rigid inclusions on the sintering of ceramic powder matrices are examined and compared with experimental data. The densification of glass matrix composites with inclusion volume fractions of ≤0.15 can be adequately explained by Scherer's theory for viscous sintering with rigid inclusions. Inclusions cause a vast reduction in the densification rates of polycrystalline matrix composites even at low inclusion volume fractions. Models put forward to explain the sintering of polycrystalline matrix composites are discussed

Low temperature sintering of fluorapatite glass-ceramics

Science.gov (United States)

Denry, Isabelle; Holloway, Julie A.

2014-01-01

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. 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. 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. Disc-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. 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. PMID:24252652

A finite difference model of the iron ore sinter process

OpenAIRE

Muller, J.; de Vries, T.L.; Dippenaar, B.A.; Vreugdenburg, J.C.

2015-01-01

Iron ore fines are agglomerated to produce sinter, which is an important feed material for blast furnaces worldwide. A model of the iron ore sintering process has been developed with the objective of being representative of the sinter pot test, the standard laboratory process in which the behaviour of specific sinter feed mixtures is evaluated. The model aims to predict sinter quality, including chemical quality and physical strength, as well as key sinter process performance parameters such ...

Vacuum-Free, Maskless Patterning of Ni Electrodes by Laser Reductive Sintering of NiO Nanoparticle Ink and Its Application to Transparent Conductors

KAUST Repository

Lee, Daeho

2014-10-28

© 2014 American Chemical Society. We introduce a method for direct patterning of Ni electrodes through selective laser direct writing (LDW) of NiO nanoparticle (NP) ink. High-resolution Ni patterns are generated from NiO NP thin films by a vacuum-free, lithography-free, and solution-processable route. In particular, a continuous wave laser is used for the LDW reductive sintering of the metal oxide under ambient conditions with the aid of reducing agents in the ink solvent. Thin (∼40 nm) Ni electrodes of glossy metallic surfaces with smooth morphology and excellent edge definition can be fabricated. By applying this method, we demonstrate a high transmittance (>87%), electrically conducting panel for a touch screen panel application. The resistivity of the Ni electrode is less than an order of magnitude higher compared to that of the bulk Ni. Mechanical bending test, tape-pull test, and ultrasonic bath test confirm the robust adhesion of the electrodes on glass and polymer substrates.

Vacuum-free, maskless patterning of Ni electrodes by laser reductive sintering of NiO nanoparticle ink and its application to transparent conductors.

Science.gov (United States)

Lee, Daeho; Paeng, Dongwoo; Park, Hee K; Grigoropoulos, Costas P

2014-10-28

We introduce a method for direct patterning of Ni electrodes through selective laser direct writing (LDW) of NiO nanoparticle (NP) ink. High-resolution Ni patterns are generated from NiO NP thin films by a vacuum-free, lithography-free, and solution-processable route. In particular, a continuous wave laser is used for the LDW reductive sintering of the metal oxide under ambient conditions with the aid of reducing agents in the ink solvent. Thin (∼ 40 nm) Ni electrodes of glossy metallic surfaces with smooth morphology and excellent edge definition can be fabricated. By applying this method, we demonstrate a high transmittance (>87%), electrically conducting panel for a touch screen panel application. The resistivity of the Ni electrode is less than an order of magnitude higher compared to that of the bulk Ni. Mechanical bending test, tape-pull test, and ultrasonic bath test confirm the robust adhesion of the electrodes on glass and polymer substrates.

Study of scrap recovery for mixed oxide pellet by means of UO2+5wt.%CeO2

International Nuclear Information System (INIS)

Joung, Chang Young; Kim, Si Hyung; Kim, Han Soo; Lee, Yong Woo

2000-01-01

The recovery method of scrap powder was established using UO 2 -5wt.%CeO 2 powder in the way of of technology development of scrap recovery and recycle in the mixed oxide pellet fabrication process. And pellet density and microstructure, which depend on quantity of scrap, powder treatment method, and sintering condition, was analyzed. As a result of oxidation of sintered pellet in the air the powdering at below 400 degrees C occurred smoothly, and at above 400 degrees C powdering process was not proceeding well as temperature increased and powder particle size grew bigger. M 3 O 8 scrap powder which was powdered through oxidation method was added to UO 2 -5wt.%CeO 2 mixed powder. The results after the powder was treated by means of mixing, crushing, attrition milling, pelletizing, and sintering showed that its density and grain size in the case of reductive sintering decreased as scrap addition increased, but the result in the case of crushing showed increase in grain size. In attrition milling case both density and grain size showed the tendency of increase, particularly grain size grew up to 12 μm. In the oxidative sintering with scrap added mixed powder sintering was accelerated under the oxygen environment and the effect of powder treatment showed the tendency of relatively decreasing. (Hong, J. S.)

Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O3 lead-free ceramics

International Nuclear Information System (INIS)

Chen, Xiaoming; Ruan, Xuezheng; Zhao, Kunyun; He, Xueqing; Zeng, Jiangtao; Li, Yongsheng; Zheng, Liaoying; Park, Chul Hong; Li, Guorong

2015-01-01

Highlights: • Li-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d 33 (512 pC/N) and a planar electromechanical coupling factor k p (0.49), which have the characteristics of soft Pb(Zr,Ti)O 3 (PZT) piezoceramic, on the other hand, the mechanical quality factor Q m is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature

Design of sintering-stable heterogeneous catalysts

DEFF Research Database (Denmark)

Gallas-Hulin, Agata

One of the major issues in the use of metal nanoparticles in heterogeneous catalysis is sintering. Sintering occurs at elevated temperatures because of increased mobility of nanoparticles, leading to their agglomeration and, as a consequence, to the deactivation of the catalyst. It is an emerging...... problem especially for the noble metals-based catalysis. These metals being expensive and scarce, it is worth developing catalyst systems which preserve their activity over time. Encapsulation of nanoparticles inside zeolites is one of the ways to prevent sintering. Entrapment of nanoparticles inside...

Cinética de sinterização para sistemas à base de SnO2 por taxa de aquecimento constante Sintering kinetics for SnO2-based systems by constant heating rate

Directory of Open Access Journals (Sweden)

S. M. Tebcheran

2003-04-01

in small concentrations as densifying aids for this oxide. In the present study the sintering kinetics of tin oxide was studied considering the effect of sintering atmosphere and of the MnO2 concentration. SnO2-MnO2 systems were prepared from the polymeric precursors method and the obtained powders were characterized by surface area by the BET method. SnO2 powders with varied MnO2 concentrations were pressed in cylindrical shape, and sintered in a dilatometer furnace with constant heating rate and controlled atmospheres. Sintered samples were characterized by scanning electron microscopy. The influence of atmosphere (argon, air or CO2 as well as of the MnO2 concentrations on the sintering kinetics was determined. The kinetics data of linear shrinkage were analyzed in terms of kinetic models for the initial stage of sintering (Woolfrey and Bannister as well as for the global sintering (Su e Johnson allowing the determination of the apparent activation energy. Following the determination of the master sintering curve the apparent activation energy of all sintering process were determined as well as its dependence with the atmosphere and manganese concentrations. Based on these values and on the n exponent, determined by the classical grain growth equation, it was concluded that the most probable sintering mechanism is grain boundary diffusion with surface redistribution controlling the kinetics.

Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

Energy Technology Data Exchange (ETDEWEB)

Zaiou, S.; Harabi, A.; Harabi, E.; Guechi, A.; Karboua, N.; Benhassine, M.-T.; Zouai, S.; Guerfa, F., E-mail: Zaiou_21@yahoo.fr, E-mail: harabi52@gmail.com, E-mail: semouni84@gmail.com, E-mail: guechia@yahoo.fr, E-mail: kanour17@yahoo.fr, E-mail: mtb25dz@gmail.com, E-mail: zouaisouheila@yahoo.fr, E-mail: guerfatiha@gmail.com [Ceramics Lab., Faculty of Exact Science, Physics Department, Mentouri University of Constantine (Algeria)

2016-10-15

In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO{sub 3} is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm{sup 3} ). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. (author)

Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

Directory of Open Access Journals (Sweden)

S. Zaiou

Full Text Available Abstract In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type and 20 wt% calcium oxide extracted from CaCO3 is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm3. Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy.

Sintering of anorthite based ceramics prepared from kaolin DD2 and calcite

International Nuclear Information System (INIS)

Zaiou, S.; Harabi, A.; Harabi, E.; Guechi, A.; Karboua, N.; Benhassine, M.-T.; Zouai, S.; Guerfa, F.

2016-01-01

In this work, the preparation of anorthite based ceramics using a modified milling system and 80 wt% kaolin (DD2 type) and 20 wt% calcium oxide extracted from CaCO 3 is shown. The choice of these raw materials was dictated by their natural abundance. Previous studies have shown that a simple and vibratory multidirectional milling system using a bimodal distribution of highly resistant ceramics can be successfully used for obtaining fine powders. The prepared samples were sintered at different temperatures ranging between 800 and 1100 °C. It has been found that the relative density of samples sintered at 900 °C for 1 h with a heating rate of 5 °C/min was about 96% of the theoretical density of anorthite (2.75 g/cm 3 ). Finally, the prepared samples were also characterized by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. (author)

Development of iodine waste forms using low-temperature sintering glass

International Nuclear Information System (INIS)

Krumhansl, James Lee; Nenoff, Tina Maria; Garino, Terry J.; Rademacher, David

2010-01-01

This presentation will describe our recent work on the use of low temperature-sintering glass powders mixed with either AgI or AgI-zeolite to produce a stable waste form. Radioactive iodine ( 129 I, half-life of 1.6 x 10 7 years) is generated in the nuclear fuel cycle and is of particular concern due to its extremely long half-life and its effects on human health. As part of the DOE/NE Advanced Fuel Cycle Initiative (AFCI), the separation of 129 I from spent fuel during fuel reprocessing is being studied. In the spent fuel reprocessing scheme under consideration, the iodine is released in gaseous form and collected using Ag-loaded zeolites, to form AgI. Although AgI has extremely low solubility in water, it has a relatively high vapor pressure at moderate temperatures (>550 C), thus limiting the thermal processing. Because of this, immobilization using borosilicate glass is not feasible. Therefore, a bismuth oxide-based glasses are being studied due to the low solubility of bismuth oxide in aqueous solution at pH > 7. These waste forms were processed at 500 C, where AgI volatility is low but the glass powder is able to first densify by viscous sintering and then crystallize. Since the glass is not melted, a more chemically stable glass can be used. The AgI-glass mixture was found to have high iodine leach resistance in these initial studies.

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.

Bioactivity and mineralization of hydroxyapatite with bioglass as sintering aid and bioceramics with Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} and Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4} in a silicate matrix

Energy Technology Data Exchange (ETDEWEB)

Demirkiran, Hande [Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX 76019 (United States); Mohandas, Arunesh; Dohi, Motokazi; Fuentes, Alonso; Nguyen, Kytai [Bioengineering Department, University of Texas at Arlington, Arlington, TX 76019 (United States); Aswath, Pranesh, E-mail: aswath@uta.edu [Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX 76019 (United States)

2010-01-30

Hydroxyapatite and Bioglass-45S5 were sintered together creating new ceramic compositions that yielded increased apatite deposition and osteoblast differentiation and proliferation in vitro compared to hydroxyapatite. The sintered products characterized by X-ray diffraction, revealed hydroxyapatite as the main phase when small quantities (1, 2.5 and 5 wt.%) of bioglass was added. Bioglass behaved as a sintering aid with {beta}-TCP (Ca{sub 3}(PO{sub 4}){sub 2}) being the minor phase. The amount of {beta}-TCP increased with the amount of bioglass added. In compositions with larger additions of bioglass (10 and 25 wt.%), new phases with compositions of calcium phosphate silicate (Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4}) and sodium calcium phosphate (Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5}) were formed respectively within amorphous silicate matrices. In vitro cell culture studies of the ceramic compositions were examined using bone marrow stromal cell (BMSC). Cell proliferation and differentiation of bone marrow stromal cells into osteoblasts were determined by Pico Green DNA assays and alkaline phosphatase (ALP) activity, respectively. All hydroxyapatite-bioglass co-sintered ceramics exhibited larger cell proliferation compared to pure hydroxyapatite samples. After 6 days in cell culture, the ceramic with Ca{sub 5}(PO{sub 4}){sub 3}SiO{sub 4} in a silicate matrix formed by reacting hydroxyapatite with 10 wt.% bioglass exhibited the maximum proliferation of the BMSC's. The ALP activity was found to be largest in the ceramic with Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} embedded in a silicate matrix synthesized by reacting hydroxyapatite with 25 wt.% bioglass.

Final Report on Initial Samples Supplied by LLNL for Task 3.3 Binder Burnout and Sintering Schedule Optimisation

Energy Technology Data Exchange (ETDEWEB)

Walls, P

1999-01-04

Sixteen of the twenty-one samples have been investigated using the scanning laser dilatometer. This includes all three types of samples with different preparation routes and organic content. Cracks were observed in all samples, even those only heated to 300 C. It was concluded that the cracking was occurring in the early part of the heat treatment before the samples reached 300 C. Increase in the rate of dilation of the samples occurred above 170 C which coincided with the decomposition of the binder/wax additives as determined by differential thermal analysis. A comparison was made with SYNROC C material (Powder Run 143), samples of which had been CIPed and green machined to a similar diameter and thickness as the 089mm SRTC pucks. These samples contained neither binder nor other organic processing aids and had been kept in the same desiccator as the SRTC samples. The CIPed Synroc C samples sintered to high density with zero cracks. As the cracks made up only a small contribution to the change in diameter of the sample compared to the sintering shrinkage, useful information could still be gained from the runs. The sintering curves showed that there was much greater shrinkage of the Type III samples containing only the 5% PEG binder compared to the Type I which contained polyolefin wax as processing aid. Slight changes in gradient of the sintering curve were observed, however, due to the masking effect of the cracking, full analysis of the sintering kinetics cannot be conducted. Even heating the samples to 300 C at 1.0 or 0.5 C/min could not prevent crack formation. This indicated that heating rate was not the critical parameter causing cracking of the samples. Sectioning of green bodies revealed the inhomogeneous nature of the binder/lubricant distribution in the samples. Increased homogeneity would reduce the amount of binder/lubricant required, which should in turn, reduce the degree of cracking observed during heating to the binder burnout temperature. A

SINTERING EFFECTS ON THE DENSIFICATION OF NANOCRYSTALLINE HYDROXYAPATITE

Directory of Open Access Journals (Sweden)

M. Amiriyan

2011-06-01

Full Text Available The effects of sintering profiles on the densification behaviour of synthesized nanocrystalline hydroxyapatite (HA powder were investigated in terms of phase stability and mechanical properties. A wet chemical precipitation method was successfully employed to synthesize a high purity and single phase HA powder. Green HA compacts were prepared and subjected to sintering in air atmosphere over a temperature range of 700° C to 1300° C. In this study two different holding times were compared, i.e. 1 minute versus the standard 120 minutes. The results revealed that the 1 minute holding time sintering profile was indeed effective in producing a HA body with high density of 98% theoretical when sintered at 1200° C. High mechanical properties such as fracture toughness of 1.41 MPa.m1/2 and hardness of 9.5 GPa were also measured for HA samples sintered under this profile. Additionally, XRD analysis indicated that decomposition of the HA phase during sintering at high temperatures was suppressed.

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

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-01

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

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.

Study of effect of dynamic mill treatment on the compaction and sintering of UO2-5wt%CeO2

International Nuclear Information System (INIS)

Na, S. H.; Kim, S. H.; Kim, Y. K.; Lee, Y. W.; Yoo, M. J.

2002-01-01

Some properties (apparent density, green density, sintered density and grain size) of the simulated mixed oxide(UO 2 -5wt%CeO 2 ) prepared by using the dynamic mill newly developed were investigated. As the dynamic milling time increases, these properties increase. However, the increases of sintered density and grain size were saturated above 2 hrs and 4 hrs of dynamic milling treatment, respectively. It appeared that the dynamic mill has a similar capability to that of other milling methods, and hence can manufacture the pellets having desired properties by controlling milling time

A study of pressureless microwave sintering, microwave-assisted hot press sintering and conventional hot pressing on properties of aluminium/alumina nanocomposite

Energy Technology Data Exchange (ETDEWEB)

Abedinzadeh, Reza; Safavi, Seyed Mohsen; Karimzadeh, Fathallah [Isfahan University, Isfahan (Iran, Islamic Republic of)

2016-05-15

Bulk Al/4wt-%Al{sub 2}O{sub 3} nanocomposites were prepared by consolidating nanocomposite powders using pressureless microwave sintering, microwave-assisted hot press sintering and conventional hot pressing techniques. Microstructural observations revealed that the microwave-assisted hot press sintering at different sintering temperatures of 400.deg.C and 500.deg.C resulted in more densification and smaller grain size for Al/Al{sub 2}O{sub 3} nanocomposite as compared with the conventional hot pressing. Moreover, the application of pressure in microwave sintering process led to more densification and grain growth. Mechanical properties resulting from microhardness and nanoindentation tests were also compared between three-method processed samples. It was found that the microwave-assisted hot-pressed sample exhibited higher hardness and elastic modulus in comparison with microwave-sintered and conventional hot-pressed samples. The improvement in the mechanical properties can be ascribed to lower porosity of microwave-assisted hot-pressed sample.

Heterogeneous burnable poisons. Sinterability study in oxidizing atmosphere of alumina-gadolinia and alumina-boron carbide compounds

International Nuclear Information System (INIS)

Agueda, H.C.; Leiva, S.F.; Russo, D.O.

1990-01-01

Solid burnable poisons are used in reactors cooled by pressure light water (PLWR) with the purpose of controlling initial reactivity in the first reactor's core. The burnable poisons may be uniformly mixed with the fuel -known as 'homogeneous' poisons-; or constituting separate elements -known as heterogeneous poisons-. The purpose of this work is to present the results of two sinterability studies, performed on Al 2 O 3 -Gd 2 O 3 and Al 2 O 3 -B 4 C, where alumina acts as inert matrix, storing the absorbing elements as Gd 2 O 3 or B 4 C. The elements were sintered at an air atmosphere and additives permitting the obtention of a greater density alumina were tested at lower temperatures than the characteristic for this material, in order to determine its compatibility with the materials dealt with herein. (Author) [es

Effect Of Compaction Pressure And Sintering Temperature On The Liquid Phase Sintering Behavior Of Al-Cu-Zn Alloy

Directory of Open Access Journals (Sweden)

Lee S.H.

2015-06-01

Full Text Available The liquid phase sintering characteristics of Al-Cu-Zn alloy were investigated with respect to various powder metallurgy processing conditions. Powders of each alloying elements were blended to form Al-6Cu-5Zn composition and compacted with pressures of 200, 400, and 600 MPa. The sintering process was performed at various temperatures of 410, 560, and 615°C in N2 gas atmosphere. Density and micro-Vickers hardness measurements were conducted at different processing stages, and transverse rupture strength of sintered materials was examined for each condition, respectively. The microstructure was characterized using optical microscope and scanning electron microscopy. The effect of Zn addition on the liquid phase sintering behavior during P/M process of the Al-Cu-Zn alloy was also discussed in detail.

High Temperature Oxidation of Spark Plasma Sintered and Thermally Sprayed FeAl-Based Iron Aluminides

Czech Academy of Sciences Publication Activity Database

Haušild, P.; Karlík, M.; Skiba, T.; Sajdl, P.; Dubský, Jiří; Palm, M.

2012-01-01

Roč. 122, č. 3 (2012), s. 465-468 ISSN 0587-4246. [International Symposium on Physics of Materials (ISPMA)/12./. Prague, 04.09.2011-08.09.2011] Institutional support: RVO:61389021 Keywords : thermal spraying * plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.531, year: 2012

Comparative sinterability of combustion synthesized and commercial titanium carbides

International Nuclear Information System (INIS)

Manley, B.W.

1984-11-01

The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 0 C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables

Contribution to the densification study of silicon and zirconium carbides by an innovating process: the Spark Plasma Sintering; Contribution a l'etude de la densification des carbures de silicium et de zirconium par un procede innovant: le spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Allemand, A. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DMN/SRMA/LTMEx), 91 - Gif-sur-Yvette (France); Guillard, F.; Galy, J. [Centre d' Elaboration de Materiaux et d' Etudes Structurales (CEMES-CNRS), 31 - Toulouse (France)

2007-07-01

In the framework of the CPR ISMIR, the works presented here take up the results of the thesis of F. Guillard defended on december 2006. This thesis has dealt with the Spark Plasma Sintering (SPS) technique and more particularly have been studied: 1)the {beta}SiC and ZrC sintering 2)the modelling of ZrC sintering by the SPS technique and 3)the studies of the carbides/oxides interfaces carried out by SPS. Concerning the {beta}SiC and ZrC sintering: the two carbides have been sintered between 1450 and 1950 C with times periods of 10 minutes and pressures between 50 and 150 MPa. These experiments have shown that the way to apply the pressure is of major importance. Moreover, 92% of densification can be reached after 5 minutes in 1850 C for SiC. For ZrC, 95% of densification is reached as soon as 5 minutes in 1750 C. Different correlations between grains size, density and the way to apply pressure are presented. For the SPS modelling of ZrC, two existing models, taking into account the diffusion laws, are used to try to model the SPS. The results are presented and discussed. At last, the SPS allows to make interfaces starting from powders or materials previously sintered. The SiC/ZrC and ZrO{sub 2}/SiC interfaces have been studied. A microstructural study is presented as well as a technique which allows the assembling with no cracks of SiC and ZrC. (O.M.)

Sintering of B{sub 4}C powder obtained by a modified carbo-thermal reaction

Energy Technology Data Exchange (ETDEWEB)

Rocha, R.M.; Kazumi, M.H.; Goncalves, D.P.; Melo, F.C.L. [Centro Tecnico Aeroespacial (CTA) - Instituto de Aeronautica e Espaco, Praca Marechal Eduardo Gomes, 50 Campus do CTA - Vila das Acacias, 12228-904 Sao Jose dos Campos-SP (Brazil)

2005-07-01

Boron carbide is one of the hardest materials and a highly refractory material that is of great interest for structural, electronic and nuclear applications. B{sub 4}C is commercially manufactured by the carbo-thermal reduction of a mixture of boron oxide (B{sub 2}O{sub 3}) in an batch electric arc furnace process. However the carbo-thermal reaction on the stoichiometric starting composition results an excess carbon residue because of the boron loss in the form of B{sub 2}O{sub 2}. Thus, a modified carbo-thermal reaction is applied with an excess B{sub 2}O{sub 3} to compensate the loss and to obtain stoichiometric powders. The aim of this work is to study the sinterability of this powder with the lower carbon residue acting as sintering additive. Pressureless sintering in the temperatures of 1900 deg. C/30 min and 2100 deg. C/30 min in argon atmosphere were applied. The synthesized powders were analysed by XRD and SEM. Density of 94% of theoretical density was achieved for sample prepared with the powder obtained with 50% B{sub 2}O{sub 3} excess synthesized at 1700 deg. C/15 min. (authors)

The sintering behavior of close-packed spheres

DEFF Research Database (Denmark)

Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

2012-01-01

The sintering behavior of close-packed spheres is investigated using a numerical model. The investigated systems are the body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed spheres (hcp). The sintering behavior is found to be ideal, with no grain growth until full dens...... density is reached for all systems. During sintering, the grains change shape from spherical to tetrakaidecahedron, similar to the geometry analyzed by Coble [R.L. Coble, J. Appl. Phys. 32 (1961) 787]....

Final report on initial samples supplied by LLNL for task 3.3 binder burnout and sintering schedule optimisation

Energy Technology Data Exchange (ETDEWEB)

Walls, P

1999-01-04

Sixteen of the twenty-one samples have been investigated using the scanning laser dilatometer. This includes all three types of samples with different preparation routes and organic content. Cracks were observed in all samples, even those only heated to 300 C. It was concluded that the cracking was occurring in the early part of the heat treatment before the samples reached 300 C. Increase in the rate of dilation of the samples occurred above 170 C which coincided with the decomposition of the binder/wax additives as determined by differential thermal analysis. A comparison was made with SYNROC C material (Powder Run 143), samples of which had been CIPed and green machined to a similar diameter and thickness as the 089 mm SRTC pucks. These samples contained neither binder nor other organic processing aids and had been kept in the same desiccator as the SRTC samples. The CIPed Synroc C samples sintered to high density with zero cracks. As the cracks made up only a small contribution to the change in diameter of the sample compared to the sintering shrinkage, useful information could still be gained from the runs. The sintering curves showed that there was much greater shrinkage of the Type III samples containing only the 5% PEG binder compared to the Type I which contained polyolefin wax as processing aid. Slight changes in gradient of the sintering curve were observed, however, due to the masking effect of the cracking, full analysis of the sintering kinetics cannot be conducted. Even heating the samples to 300 C at 1.0 or 0.5 C/min could not prevent crack formation. This indicated that heating rate was not the critical parameter causing cracking of the samples. Sectioning of green bodies revealed the inhomogeneous nature of the binder/lubricant distribution in the samples. Increased homogeneity would reduce the amount of binder/lubricant required, which should in turn, reduce the degree of cracking observed during heating to the binder burnout temperature. A

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

Science.gov (United States)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-25

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Mechanism of UO2 selfdisintegration by oxidation

International Nuclear Information System (INIS)

Ohai, D.; Furtuna, I.; Dumitrescu, I.

2008-01-01

Full text: The paper present the results of the study of UO 2 sintered pellets oxidation, part of FIPRED (Fission Product Release from Debris Bed) Project. The FIPRED Project is dedicated to the study the fission products release from irradiated pellets existing in debris bed. The product release is produced by oxidative self disintegration of sintered pellets at air ingress and it depends on temperature. The experimental program covered experiments of 300-1000 deg. C in air diluted with nitrogen at different oxygen concentrations. The experiments were performed using the SETARAM thermo gravimetric equipment and the FIPRED EQ equipment designed and manufactured especially for this type of experiment. The powders (fragments), resulted from UO 2 pellets self disintegration, were characterized by sieving and SEM. The self disintegration mechanism was demonstrated using the experimental results obtained and thermodynamical data of uranium oxides. (authors)

Effects of sintering temperature on the density and porosity

African Journals Online (AJOL)

2013-03-01

bonding) between the salt beads at all the temperatures in which sintering was performed. .... and the sintering of some covalent solids and low- stability ceramics. The entire sintering process is gen- erally considered to occur in ...

Sintering characteristics of nano-ceramic coatings

NARCIS (Netherlands)

de Hosson, J.T.M.; 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

Sintering of Pt nanoparticles via volatile PtO_2: Simulation and comparison with experiments

International Nuclear Information System (INIS)

Plessow, Philipp N.; Abild-Pedersen, Frank

2016-01-01

It is a longstanding question whether sintering of platinum under oxidizing conditions is mediated by surface migration of Pt species or through the gas phase, by PtO_2(g). Clearly, a rational approach to avoid sintering requires understanding the underlying mechanism. A basic theory for the simulation of ripening through the vapor phase has been derived by Wynblatt and Gjostein. Recent modeling efforts, however, have focused entirely on surface-mediated ripening. In this work, we explicitly model ripening through PtO_2(g) and study how oxygen pressure, temperature, and shape of the particle size distribution affect sintering. On the basis of the available data on α-quartz, adsorption of monomeric Pt species on the support is extremely weak and has therefore not been explicitly simulated, while this may be important for more strongly interacting supports. Our simulations clearly show that ripening through the gas phase is predicted to be relevant. Assuming clean Pt particles, sintering is generally overestimated. This can be remedied by explicitly including oxygen coverage effects that lower both surface free energies and the sticking coefficient of PtO_2(g). Additionally, mass-transport limitations in the gas phase may play a role. Using a parameterization that accounts for these effects, we can quantitatively reproduce a number of experiments from the literature, including pressure and temperature dependence. Lastly, this substantiates the hypothesis of ripening via PtO_2(g) as an alternative to surface-mediated ripening.

Studies on the synthesis of nanocrystalline Y{sub 2}O{sub 3} and ThO{sub 2} through volume combustion and their sintering

Energy Technology Data Exchange (ETDEWEB)

Sanjay Kumar, D. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Ananthasivan, K., E-mail: asivan@igcar.gov.in [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Venkata Krishnan, R. [Fuel Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Amirthapandian, S. [Material Physics Division, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India); Dasgupta, Arup [Microscopy and Thermo-Physical Property Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, Tamil Nadu (India)

2016-10-15

Volume combustion was observed in the auto-ignition of the citrate gels containing the nitrates of yttrium/thorium for the first time in mixture with a fuel (citric acid) to oxidant (Y{sup 3+} or Th{sup 4+} nitrate) ratio close to that demanded by the stoichiometry. These nanocrystalline powders were characterized for their bulk density, specific surface area, particle size distribution, carbon residue and X-ray crystallite size and were sintered by both the conventional and the two-step method. The maximum relative sintered density of Y{sub 2}O{sub 3} was 98.9% TD. The sintered density of thoria (97.8% TD) is the highest among the values reported so far, for nanocrystalline ThO{sub 2}. Characterization of the pellets and powders by using scanning electron microscopy and transmission electron microscopy reaffirmed nanocrystallinity and that the sintered pellets comprised faceted sintered grains. The two-step sintering was found to restrict “runaway” sintering. - Highlights: • Scaled-up synthesis of nanocrystalline Y{sub 2}O{sub 3} and ThO{sub 2} using citrate gel-combustion method. • VCR was observed at a fuel to nitrate ratio (R) of 0.125 and 0.17 in mixtures containing Th(NO{sub 3}){sub 4} and Y(NO{sub 3}){sub 3} respectively. • The calcined powders were compacted and sintered by using a novel two-step sintering method. • Sintered densities as high as 97.8% T.D. (ThO{sub 2}, T{sub H} = 0.48) and 98.9% T.D. (Y{sub 2}O{sub 3}, T{sub H} = 0.61) were obtained.

Removable partial denture alloys processed by laser-sintering technique.

Science.gov (United States)

Alageel, Omar; Abdallah, Mohamed-Nur; Alsheghri, Ammar; Song, Jun; Caron, Eric; Tamimi, Faleh

2018-04-01

Removable partial dentures (RPDs) are traditionally made using a casting technique. New additive manufacturing processes based on laser sintering has been developed for quick fabrication of RPDs metal frameworks at low cost. The objective of this study was to characterize the mechanical, physical, and biocompatibility properties of RPD cobalt-chromium (Co-Cr) alloys produced by two laser-sintering systems and compare them to those prepared using traditional casting methods. The laser-sintered Co-Cr alloys were processed by the selective laser-sintering method (SLS) and the direct metal laser-sintering (DMLS) method using the Phenix system (L-1) and EOS system (L-2), respectively. L-1 and L-2 techniques were 8 and 3.5 times more precise than the casting (CC) technique (p laser-sintered and cast alloys were biocompatible. In conclusion, laser-sintered alloys are more precise and present better mechanical and fatigue properties than cast alloys for RPDs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1174-1185, 2018. © 2017 Wiley Periodicals, Inc.

Multi-metallic anodes for solid oxide fuel cell applications; Anodos multi-metalicos para aplicacoes em celulas a combustivel de oxido solido

Energy Technology Data Exchange (ETDEWEB)

Restivo, T.A. Guisard; Mello-Castanho, S.R.H. [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia dos Materiais; Leite, D. Will [Instituto de Pesquisas e Estudos Industriais (IPEI/FEI), Sao Bernardo do Campo, SP (Brazil). Fac. de Engenharia Industrial

2009-07-01

A new method for direct preparation of materials for solid oxide fuel cell anode - Ni- YSZ cermets - based on mechanical alloying (MA) of the original powders is developed, allowing to admix homogeneously any component. Additive metals are selected from thermodynamic criteria, leading to compacts consolidation through sintering by activated surface (SAS). The combined process MA-SSA can reduce the sintering temperature by 300 deg C, yielding porous anodes. Densification mechanisms are discussed from quasi-isothermal sintering kinetics results. Doping with Ag, W, Cu, Mo, Nb, Ta, in descending order, promotes the densification of pellets through liquid phase sintering and evaporation of metals and oxides, which allow reducing the sintering temperature. Powders and pellets characterization by electronic microscopy and X-ray diffraction completes the result analyses. (author)

Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

International Nuclear Information System (INIS)

Freitas, C.T. de.

1980-06-01

The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO 2 gels and UO 2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO 2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author) [pt

Borides and vitreous compounds sintered as high-energy fuels

International Nuclear Information System (INIS)

Mota, J.M.; Abenojar, J.; Martinez, M.A.; Velasco, F.; Criado, A.J.

2004-01-01

Boron was chosen as fuel in view of its excellent thermodynamic values for combustion, as compared to traditional fuels. The problem of the boron in combustion is the formation of a surface layer of oxide, which delays the ignition process, reducing the performance of the rocket engine. This paper presents a high-energy fuel for rocket engines. It is composed of sintered boron (borides and carbides and vitreous compounds) with a reducing chemical agent. Borides and boron carbide were prepared since the combustion heat of the latter is similar to that of the amorphous boron (in: K.K. Kuo (Ed.), Boron-Based Solid Propellant and Solid Fuel, Vol. 427, CRC Press, Boca Raton, FL, 1993). Several chemical reducing elements were used, such as aluminum, magnesium, and coke. As the raw material for boron, different compounds were used: amorphous boron, boric acid and boron oxide

Sintering equation: determination of its coefficients by experiments - using multiple regression

International Nuclear Information System (INIS)

Windelberg, D.

1999-01-01

Sintering is a method for volume-compression (or volume-contraction) of powdered or grained material applying high temperature (less than the melting point of the material). Maekipirtti tried to find an equation which describes the process of sintering by its main parameters sintering time, sintering temperature and volume contracting. Such equation is called a sintering equation. It also contains some coefficients which characterise the behaviour of the material during the process of sintering. These coefficients have to be determined by experiments. Here we show that some linear regressions will produce wrong coefficients, but multiple regression results in an useful sintering equation. (orig.)

Immobilization of Uranium Silicides in Sintered Glass

International Nuclear Information System (INIS)

Mateos, P.; Russo, D.O.; Heredia, A.D.; Sanfilippo, M.

2003-01-01

High activity nuclear spent fuels vitrification by fusion is a well known technology which has industrial scale in France, England, Japan, EEUU. Borosilicates glasses are used in this process.Sintered glasses are an alternative to the immobilization task in which there is also a wide experience around the world.The available technics are: cold pressing and sintering , hot-pressing and hot isostatic pressing.This work compares Borosilicates and Iron silicates sintered glasses behaviour when different ammounts of nuclear simulated waste is added

Granulation of coke breeze fine for using in the sintering process

Directory of Open Access Journals (Sweden)

Mohamed F.M.

2010-01-01

Full Text Available Coke breeze is the main fuel used in the sintering process. The value of -3+1 mm. represents the most favorable particle size for coke breeze in the sintering process. About 20% of total coke fines (-0.5 mm are produced during different steps of preparation. Introducing these fines during the sintering process proves to be very harmful for different operating parameters. Thus ,this study aims at investigating the production of granules resulting from these fines using molasses as organic binder and its application in sintering of an iron ore. The results showed that the granules having the highest mechanical properties were obtained with 14.5 wt % molasses addition. The sintering experiments were performed by using coke breeze in different shapes (-3+1 mm in size, coke breeze without sieving and coke breeze granules -3+1 mm. The reduction experiments, microscopic structure and X-ray analysis for the produced sinter were carried out. The results revealed that, all sinter properties (such as shatter test, productivity of sinter machine and blast furnace, reduction time and chemical composition for produced sinter by using coke breeze with size -3+1 mm and coke breeze granules were almost the same. The iron ore sinter which was produced by using coke breeze without sieving yielded low productivity for both sinter machine and blast furnace. Furthermore, using coke breeze without sieving in sintering of an iron ore decreases the vertical velocity of sinter machine and increases the reduction time.

Initial sintering stage kinetics of CeO2 studied by stepwise isothermal dilatometry

International Nuclear Information System (INIS)

El Sayed Ali, M.; Toft Soerensen, O.

1985-02-01

The kinetics of the initial sintering stage of CeO 2 is studied by a new dilatometric technique in which the heating of the sample is controlled by its shrinkage rate. By this technique the shrinkage characteristically takes place in 'isothermal steps' which allows both the mechanism and its activation energy to be determined in a single experiment. The basic equations necessary to evaluate the shrinkage data are described, and using these equations on the curves recorded for CeO 2 it it shown that the controlling mechanism for the initial sintering stage for this oxides is grain-boundary diffusion of Ce 4+ -ions with an activation energy of 119.4 kcal/mole (5.2 eV). The corresponding diffusion coefficient is estimated to vary between 8.5 x 10 -17 - 3.1 x 10 -15 cm 2 /sec (1005 - 1099sup(o)C). (author)

Dry recovery test of plutonium-uranium mixed oxide fuel pellets

International Nuclear Information System (INIS)

Kinugasa, Manabu; Kawamata, Kazuhiko; Kashima, Sadamitsu

1981-01-01

The oxidation conditions for pulverizing directly Pu-U mixed oxide pellets without mechanical crushing were examined to simplify the process and to reduce radiation exposure during the dry recovery of highly enriched Pu pellets. The specimens used were the Pusub(0.3) Usub(0.7) Osub(2-x) pellets with different density, which were sintered at 1650 deg C for 2 hours under an atmosphere of 5 % H 2 - N 2 . The oxidation experiment was carried out under several conditions. The oxidation products were examined by weight gain, X-ray diffraction, appearance pictures, SEM photographs and so on. From these studies, it can be concluded that the oxidation in NO 2 diluted with air was very powerful, but if only the coarse spalling of Pusub(0.3) Usub(0.7) O 2 sintered pellets is required, it is sufficient to oxidize them in air for 1 hr in a temperature range from 400 to 600 deg C. (Asami, T.)

Compressive creep of silicon nitride

International Nuclear Information System (INIS)

Silva, C.R.M. da; Melo, F.C.L. de; Cairo, C.A.; Piorino Neto, F.

1990-01-01

Silicon nitride samples were formed by pressureless sintering process, using neodymium oxide and a mixture of neodymium oxide and yttrio oxide as sintering aids. The short term compressive creep behaviour was evaluated over a stress range of 50-300 MPa and temperature range 1200 - 1350 0 C. Post-sintering heat treatments in nitrogen with a stepwise decremental variation of temperature were performed in some samples and microstructural analysis by X-ray diffraction and transmission electron microscopy showed that the secondary crystalline phase which form from the remnant glass are dependent upon composition and percentage of aditives. Stress exponent values near to unity were obtained for materials with low glass content suggesting grain boundary diffusion accommodation processes. Cavitation will thereby become prevalent with increase in stress, temperature and decrease in the degree of crystallization of the grain boundary phase. (author) [pt

Sintering diagrams of UO2

International Nuclear Information System (INIS)

Mohan, A.; Soni, N.C.; Moorthy, V.K.

1979-01-01

Ashby's method (see Acta Met., vol. 22, p. 275, 1974) of constructing sintering diagrams has been modified to obtain contribution diagrams directly from the computer. The interplay of sintering variables and mechanisms are studied and the factors that affect the participation of mechanisms in UO 2 are determined. By studying the physical properties, it emerges that the order of inaccuracies is small in most cases and do not affect the diagrams. On the other hand, even a 10% error in activation energies, which is quite plausible, would make a significant difference to the diagram. The main criticism of Ashby's approach is that the numerous properties and equations used, communicate their inaccuracies to the diagrams and make them unreliable. The present study has considerably reduced the number of factors that need to be refined to make the sintering diagrams more meaningful. (Auth.)

Xenon thermal behavior in sintered titanium nitride, foreseen inert matrix for GFR

International Nuclear Information System (INIS)

Bes, R.

2010-11-01

This work concerns the generation IV future nuclear reactors such as gas-cooled fast reactor (GFR) for which refractory materials as titanium nitride (TiN) are needed to surround fuel and act as a fission product diffusion barrier. This study is about Xe thermal behavior in sintered titanium nitride. Microstructure effects on Xe behavior have been studied. In this purpose, several syntheses have been performed using different sintering temperatures and initial powder compositions. Xenon species have been introduced into samples by ionic implantation. Then, samples were annealed in temperature range from 1300 C to 1600 C, these temperatures being the accidental awaited temperature. A transport of xenon towards sample surface has been observed. Transport rate seems to be slow down when increasing sintering temperature. The composition of initial powder and the crystallographic orientation of each considered grain also influence xenon thermal behavior. Xenon release has been correlated with material oxidation during annealing. Xenon bubbles were observed. Their size is proportional with xenon concentration and increases with annealing temperature. Several mechanisms which could explain Xe intragranular mobility in TiN are proposed. In addition with experiments, very low Xe solubility in TiN has been confirmed by ab initio calculations. So, bi-vacancies were found to be the most favoured Xe incorporation sites in this material. (author)

Influence of sintering necks on the spectral behaviour of ITO clusters using the Discrete Dipole Approximation

International Nuclear Information System (INIS)

Skorupski, Krzysztof; Hellmers, Jens; Feng, Wen; Mroczka, Janusz; Wriedt, Thomas; Mädler, Lutz

2015-01-01

In this paper we study the spectral behaviour of indium tin oxide (ITO) nanoparticle clusters using different sinter neck models for the connections between the primary particles. The investigations include light scattering calculations based on the Discrete Dipole Approximation (DDA). The corresponding clusters are generated using the Cluster–Cluster algorithm proposed by Filippov et al. Different sintering neck models led to significantly different spectral features. A spectral neck factor that reveals the thickness of the necks connecting the primary particles with a simple measurement method is introduced. - Highlights: • We investigate the necking phenomenon in ITO fractal-like aggregates. • Extinction diagrams are sensitive to changes of the neck size. • We propose a simple procedure for measuring the neck size in ITO aggregates

Low Temperature Synthesis and Properties of Gadolinium-Doped Cerium Oxide Nanoparticles

DEFF Research Database (Denmark)

Machado, Marina F. S.; P. R. Moraes, Leticia; Monteiro, Natalia K.

2017-01-01

Gadolinium-doped cerium oxide (GDC) is an attractive ceramic material for solid oxide fuel cells (SOFCs) both as the electrolyte or in composite electrodes. The Ni/GDC cermet can be tuned as a catalytic layer, added to the conventional Ni/yttria-stabilized zirconia (YSZ), for the internal steam...... sintering temperature needed to obtain a fully dense ceramic body, which can result in undesired reactions with YSZ. In this study, a green chemistry route for the synthesis of 10 mol% GDC nanoparticles is proposed. Such a low temperature synthesis provides control over particle size and sinterability...

Effects of Sintering and Extrusion on the Microstructures and Mechanical Properties of a SiC/Al-Cu Composite

Science.gov (United States)

Sun, Chao; Shen, Rujuan; Song, Min

2012-03-01

This article studied the effects of sintering and extrusion on the microstructures and mechanical properties of SiC particle reinforced Al-Cu alloy composite produced by powder metallurgy method. It has been shown that both extrusion and increasing sintering temperature can significantly improve the strength and plasticity of the composite. The extrusion and increase of the sintering temperature can break up the oxide coating on the matrix powder surfaces, decrease the number of pores, accelerate the elements' diffusion and increase the density and particle interfacial bonding strength, thus significantly improve the mechanical properties of the composite. The strength and hardness of the composite increase and the elongation decreases with increasing the aging time at under-aged stage, while the strength and hardness start to decrease and the elongation starts to increase with increasing the aging time at over-aged stage due to the formation and growth of the secondary strengthening precipitates in the Al-Cu matrix.

Powder metallurgy: Solid and liquid phase sintering of copper

Science.gov (United States)

Sheldon, Rex; Weiser, Martin W.

1993-01-01

Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

Ash chemistry and sintering, verification of the mechanisms

Energy Technology Data Exchange (ETDEWEB)

Hupa, M; Skrifvars, B J; Backman, R; Lauren, T; Uusikartano, T; Malm, H; Stenstroem, P; Vesterkvist, M [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

1997-10-01

In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). During 1996 the work has focused on identifying bed agglomeration mechanisms and analysing bed agglomerates in both full scale and lab scale FB reactors, as well as comparing how well the compression strength based sintering test can predict bed agglomeration in an FB furnace. (orig.)

Rapid laser sintering of metal nano-particles inks.

Science.gov (United States)

Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

2016-09-23

Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

Constrained sintering of an air-plasma-sprayed thermal barrier coating

International Nuclear Information System (INIS)

Cocks, A.C.F.; Fleck, N.A.

2010-01-01

A micromechanical model is presented for the constrained sintering of an air-plasma-sprayed, thermal barrier coating upon a thick superalloy substrate. The coating comprises random splats with intervening penny-shaped cracks. The crack faces make contact at asperities, which progressively sinter in-service by interfacial diffusion, accommodated by bulk creep. Diffusion is driven by the reduction in interfacial energy at the developing contacts and by the local asperity contact stress. At elevated operating temperature, both sintering and creep strains accumulate within the plane of the coating. The sensitivities of sintering rate and microstructure evolution rate to the kinetic parameters and thermodynamic driving forces are explored. It is demonstrated that the sintering response is governed by three independent timescales, as dictated by the material and geometric properties of the coating. Finally, the role of substrate constraint is assessed by comparing the rate of constrained sintering with that for free sintering.

The pressureless sintering and mechanical properties of AlON ceramic

Energy Technology Data Exchange (ETDEWEB)

Zhang, N., E-mail: zhangning5832@163.com [Key Lab. of Advanced Materials and Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China); Liang, B.; Wang, X.Y.; Kan, H.M.; Zhu, K.W. [Key Lab. of Advanced Materials and Manufacturing Technology of Liaoning Province, Shenyang University, Shenyang, Liaoning 110044 (China); Zhao, X.J. [Department of Materials Science and Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004 (China)

2011-07-25

Highlights: {yields} A one-step pressureless sintering process was proposed, which is simple and viable. {yields} Cheap and easily available {alpha}-Al{sub 2}O{sub 3} and aluminum powders were chosen as raw materials substituting for expensive AlN ultrafine powders. {yields} The sintering temperature of AlON ceramic was reduced by 50 deg. C and the flexural strength was enhanced by 29.4%. - Abstract: Aluminum oxynitride (AlON) ceramic was synthesized by one-step pressureless sintering technology using low cost and easily available {alpha}-Al{sub 2}O{sub 3} and aluminum powders as raw materials. The sintering temperature was reduced because aluminum powders were nitridized into high activity AlN under the flowing nitrogen atmosphere. The curves of thermal analysis, microstructure and atomic distribution were investigated. The influence of sintering temperatures on phase composition, sintering densification and flexural strength was also explored. The experimental results showed that {alpha}-Al{sub 2}O{sub 3} and aluminum powders were acceptable substitutes for more expensive AlN ultrafine powders. Under the optimum sintering process at 1750 deg. C for 2 h, the sintered density and flexural strength of AlON ceramic were higher, 3.62 g/cm{sup 3} and 321 MPa, respectively. The sintering temperature was decreased by 50 deg. C because newly formed high activity AlN in situ reacted with Al{sub 2}O{sub 3} into Al{sub 23}O{sub 27}N{sub 5}, enhancing flexural strength by 29.4%. However, the sintering temperature could not be too high because grain growth and displacement of oxygen atoms from AlON ceramics by nitrogen atoms caused a decline in sintering densification and flexural strength.

Coarsening-densification transition temperature in sintering of uranium dioxide

International Nuclear Information System (INIS)

Balakrishna, Palanki; Narasimha Murty, B.; Chakraborthy, K.P.; Jayaraj, R.N.; Ganguly, C.

2001-01-01

The concept of coarsening-densification transition temperature (CDTT) has been proposed to explain the experimental observations of the study of sintering undoped uranium dioxide and niobia-doped uranium dioxide powder compacts in argon atmosphere in a laboratory tubular furnace. The general method for deducing CDTT for a given material under the prevailing conditions of sintering and the likely variables that influence the CDTT are described. Though the present work is specific in nature for uranium dioxide sintering in argon atmosphere, the concept of CDTT is fairly general and must be applicable to sintering of any material and has immense potential to offer advantages in designing and/or optimizing the profile of a sintering furnace, in the diagnosis of the fault in the process conditions of sintering, and so on. The problems of viewing the effect of heating rate only in terms of densification are brought out in the light of observing the undesirable phenomena of coring and bloating and causes were identified and remedial measures suggested

Evaluation of sintering effects on SiC-incorporated UO2 kernels under Ar and Ar–4%H2 environments

International Nuclear Information System (INIS)

Silva, Chinthaka M.; Lindemer, Terrence B.; Hunt, Rodney D.; Collins, Jack L.; Terrani, Kurt A.; Snead, Lance L.

2013-01-01

Silicon carbide (SiC) is suggested as an oxygen getter in UO 2 kernels used for tristructural isotropic (TRISO) particle fuels and to prevent kernel migration during irradiation. Scanning electron microscopy and X-ray diffractometry analyses performed on sintered kernels verified that an internal gelation process can be used to incorporate SiC in UO 2 fuel kernels. Even though the presence of UC in either argon (Ar) or Ar–4%H 2 sintered samples suggested a lowering of the SiC up to 3.5–1.4 mol%, respectively, the presence of other silicon-related chemical phases indicates the preservation of silicon in the kernels during sintering process. UC formation was presumed to occur by two reactions. The first was by the reaction of SiC with its protective SiO 2 oxide layer on SiC grains to produce volatile SiO and free carbon that subsequently reacted with UO 2 to form UC. The second process was direct UO 2 reaction with SiC grains to form SiO, CO, and UC. A slightly higher density and UC content were observed in the sample sintered in Ar–4%H 2 , but both atmospheres produced kernels with ∼95% of theoretical density. It is suggested that incorporating CO in the sintering gas could prevent UC formation and preserve the initial SiC content

Recrystallization and embrittlement of sintered tungsten

International Nuclear Information System (INIS)

Bega, N.D.; Babak, A.V.; Uskov, E.I.

1982-01-01

The recrystallization of sintered tungsten with a cellular structure of deformation is studied as related to its embrittlement. It is stated that in case of preliminary recrystallization the sintered tungsten crack resistance does not depend on the testing temperature. The tungsten crack resistance is shown to lower with an increase of the structure tendency to primary recrystallization [ru

Low sintering temperature and high piezoelectric properties of Li-doped (Ba,Ca)(Ti,Zr)O{sub 3} lead-free ceramics

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiaoming [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Ruan, Xuezheng; Zhao, Kunyun [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); He, Xueqing [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China); Zeng, Jiangtao, E-mail: zjt@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Li, Yongsheng [School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zheng, Liaoying [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Park, Chul Hong [Department of Physics Education, Pusan National University, Pusan 609735 (Korea, Republic of); Li, Guorong [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

2015-05-25

Highlights: • Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoceramics were prepared by the two-step synthesis and solid-state reaction method. • Their sintering temperature decreases from about 1540 °C down to about 1400 °C. • With the proper addition of Li, the densities and grain sizes of ceramics increase. • The ceramics not only have the characteristics of hard piezoceramics but also possesses the features of soft piezoceramics at low sintering temperature. - Abstract: Li-doped Ba{sub 0.85}Ca{sub 0.15}Ti{sub 0.9}Zr{sub 0.1}O{sub 3} (BCZT) lead-free piezoelectric ceramics were prepared by the two-step synthesis and the solid-state reaction method. The density and grain size of ceramics sufficiently increases by Li-doped sintering aid, and their sintering temperature decreases from about 1540 °C down to about 1400 °C. X-ray diffraction reveals that the phase structure of Li-doped BCTZ ceramics is changed with the sintering temperature, which is consistent with their phase transition observed by the temperature-dependent dielectric curves. The well-poled Li-doped BCZT ceramics show a high piezoelectric constant d{sub 33} (512 pC/N) and a planar electromechanical coupling factor k{sub p} (0.49), which have the characteristics of soft Pb(Zr,Ti)O{sub 3} (PZT) piezoceramic, on the other hand, the mechanical quality factor Q{sub m} is about 190, which possesses the features of hard PZT piezoceramics. The enhanced properties of the Li-doped BCZT are explained by the combination of Li-doped effect and sintering effect on the microstructure and the phase transition around room temperature.

LOW-TEMPERATURE SINTERED (ZnMg2SiO4 MICROWAVE CERAMICS WITH TiO2 ADDITION AND CALCIUM BOROSILICATE GLASS

Directory of Open Access Journals (Sweden)

BO LI

2011-03-01

Full Text Available The low-temperature sintered (ZnMg2SiO–TiO2 microwave ceramic using CaO–B2O3–SiO2 (CBS as a sintering aid has been developed. Microwave properties of (Zn1-xMgx2SiO4 base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO2 additives on the crystal phases, microstructures and microwave characteristics of (ZnMg2SiO4 (ZMS ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMS–TiO2 ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO2. Proper amount of TiO2 could tune the large negative temperature coefficient of resonant frequency (tf of ZMS system to a near zero value. (Zn0.8Mg0.22SiO4 codoped with 10 wt.% TiO2 and 3 wt.% CBS sintered at 950°C exhibits the dense microstructure and excellent microwave properties: εr = 9.5, Q·f = 16 600 GHz and tf = −9.6 ppm/°C.

Preparation of Ti3Al intermetallic compound by spark plasma sintering

Science.gov (United States)

Ito, Tsutomu; Fukui, Takahiro

2018-04-01

Sintered compacts of single phase Ti3Al intermetallic compound, which have excellent potential as refractory materials, were prepared by spark plasma sintering (SPS). A raw powder of Ti3Al intermetallic compound with an average powder diameter of 176 ± 56 μm was used in this study; this large powder diameter is disadvantageous for sintering because of the small surface area. The samples were prepared at sintering temperatures (Ts) of 1088, 1203, and 1323 K, sintering stresses (σs) of 16, 32, and 48 MPa, and a sintering time (ts) of 10 min. The calculated relative densities based on the apparent density of Ti3Al provided by the supplier were approximately 100% under all sintering conditions. From the experimental results, it was evident that SPS is an effective technique for dense sintering of Ti3Al intermetallic compounds in a short time interval. In this report, the sintering characteristics of Ti3Al intermetallic compacts are briefly discussed and compared with those of pure titanium compacts.

Real-time operation guide system for sintering process with artificial intelligence

Institute of Scientific and Technical Information of China (English)

FAN Xiao-hui; CHEN Xu-ling; JIANG Tao; LI Tao

2005-01-01

In order to optimize the sintering process, a real-time operation guide system with artificial intelligence was developed, mainly including the data acquisition online subsystem, the sinter chemical composition controller, the sintering process state controller, and the abnormal conditions diagnosis subsystem. Knowledge base of the sintering process controlling was constructed, and inference engine of the system was established. Sinter chemical compositions were controlled by the strategies of self-adaptive prediction, internal optimization and center on basicity. And the state of sintering was stabilized centering on permeability. In order to meet the needs of process change and make the system clear, the system has learning ability and explanation function. The software of the system was developed in Visual C++ programming language. The application of the system shows that the hitting accuracy of sinter compositions and burning through point prediction are more than 85%; the first-grade rate of sinter chemical composition, stability rate of burning through point and stability rate of sintering process are increased by 3%, 9% and 4%, respectively.

Study on the effect of UO2 composition on dissolution of sintered (Th-U)O2 MOX by microwave heating

International Nuclear Information System (INIS)

Singh, G.; Malav, R.K.; Fulzele, A.K.; Prakash, A.; Afzal, Md.; Panakkal, J.P.

2010-01-01

Full text: Complete dissolution of sample is a prerequisite for any chemical analysis in liquid form. Dissolution of ThO 2 based mixed oxide sample like (Th-U)O 2 , (Th-Pu)O 2 is a challenging job due to single oxidation state of thorium (IV). The present paper describes a study carried out on effect of UO 2 composition on dissolution of sintered (Th-U)O 2 mixed oxide pellets, in 0.05M HF prepared in 16 M HNO 3 . The experiments were performed in PTFE pressure vessels which could stand up to ∼ 250 deg C and safely operated up to 120 psi in an indigenous 700 watts microwave digestion system. ThO 2 , ThO 2 -3.75%UO 2 and ThO 2 -5%UO 2 pellets (∼ 6 g each) were dissolved in 60 mL of 16M HNO 3 /HF mixtures (0.05M HF in 16 M HNO 3 ) in PTFE (teflon) made pressure vessels (each experiment triplicate) at a pressure of ∼ 120 psi. Samples (two at an instant) were withdrawn after each hour and Th in the solution was determined by EDTA complexometric titration where end point was detected visually. Table 1 shows the results of percent dissolution of Th (mean of three experiments) for the sintered pellet after each interval of time until 100% dissolution. The plot for percent dissolution of Th (mean Th %) against time taken for sintered pellets is shown. Application of microwave heating has been applied for the dissolution of uncrushed sintered ThO 2 and (Th-U)O 2 pellets. It is quite evident from Th% dissolved versus time curves that the dissolution is faster as percentage of UO 2 in (Th-U)O 2 MOX solid solution increases. This is attributed to UO 2 as it can easily absorb microwave energy, leading to high temperature

U3O8 microspheres sintering kinetics

International Nuclear Information System (INIS)

Godoy, A.L.E.

1986-01-01

U 3 O 8 microspheres sintering kinetics was determined using a hot-stage optical microscopy apparatus, able to reach temperature up to 1350 0 C in controlled atmospheres. The sintered material had its microstructure analysed by optical and electron microscopy. The microspheres were characterized initialy utilizing X-ray diffractometry and thermogravimetry. The equation which describes the microspheres shrinkage in function of the time was obtained using finite difference analysis X-ray diffractometry indicated hexagonal structure for the microspheres main starting material, ammonium diuranate thermogravimetric analysis showed reduction of this material to U 3 O 8 at 600 0 C. Ceramography results showed 5 hours sintered microspheres grain sizes G vary with the temperature. Sintered U 3 O 8 micrographs compared with published results for UO 2 , indicate similar homogeneity microstructural characteristics and suggest the processed micorspheres to be potentially useful as nuclear fuels. (Author) [pt

Thermally stable sintered porous metal articles

International Nuclear Information System (INIS)

Gombach, A.L.; Thellmann, E.L.

1980-01-01

A sintered porous metal article is provided which is essentially thermally stable at elevated temperatures. In addition, a method for producing such an article is also provided which method comprises preparing a blend of base metal particles and active dispersoid particles, forming the mixture into an article of the desired shape, and heating the so-formed article at sintering temperatures

Effect of fabrication conditions on the properties of indium tin oxide powders

International Nuclear Information System (INIS)

Xie Wei

2008-01-01

This paper reports that indium tin oxide (ITO) crystalline powders are prepared by coprecipitation method. Fabrication conditions mainly as sintering temperature and Sn doping content are correlated with the phase, microstructure, infrared emissivity in and powder resistivity of indium tin oxides by means of x-ray diffraction, Fourier transform infrared, and transmission electron microscope. The optimum sintering temperature of 1350°C and Sn doping content 6∼8wt% are determined. The application of ITO in the military camouflage field is proposed. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Stable and easily sintered BaCe0.5Zr0.3Y0.2O3−δ electrolytes using ZnO and Na2CO3 additives for protonic oxide fuel cells

International Nuclear Information System (INIS)

Li, Yong; Guo, Ruisong; Wang, Chao; Liu, Yu; Shao, Zongping; An, Jing; Liu, Chongwei

2013-01-01

Highlights: ► Sintering temperature of BCZY-Z pellets was reduced by adding ZnO and Na 2 CO 3 . ► Chemical stability of BCZY-Z towards CO 2 was improved with Na 2 CO 3 addition. ► Good chemical stability against boiling water was observed for BCZY-Z-C2 sample. ► The electrical conductivity is 7.68 × 10 −3 S cm −1 for BCZY-Z-C2 sample at 700 °C. ► An anode-supported POFC delivered a peak output 302 mW cm 2 at 700 °C. -- Abstract: BaCe 0.5 Zr 0.3 Y 0.2 O 3−δ (BCZY) based composite electrolyte materials were fabricated with ZnO sintering aid (BCZY-Z). The effects of Na 2 CO 3 modification on sintering behavior, chemical stability and electrochemical performance were systematically investigated. The X-ray diffraction patterns indicate that the specimens with Na 2 CO 3 addition possessed a single perovskite structure after sintering at 1320 °C for 2 h. The linear shrinkage of 0.5 mol% Na 2 CO 3 -modified BCZY-Z sample (BCZY-Z-C2) was about 17.5%, higher than that without Na 2 CO 3 addition (14.9%). Energy dispersive spectrometer shows that Na and C elements still existed and mainly distributed along the grain boundaries. Reactivities with carbon dioxide and boiling water of BCZY-Z and Na 2 CO 3 -modified BCZY-Z samples were also evaluated and good chemical stability was observed for Na 2 CO 3 -modified BCZY-Z samples. A conductivity of 7.68 × 10 −3 S cm −1 for BCZY-Z-C2 was obtained at 700 °C in 3% wet hydrogen atmosphere. An anode-supported fuel cell with thin-film BCZY-Z-C2 as electrolyte was fabricated. The fuel cell delivered a peak power density of 302 mW cm 2 and interface resistance value of 0.08 Ω cm 2 at 700 °C

Preliminary investigation of liquid phase sintering in ferrous systems

International Nuclear Information System (INIS)

Klein, J.

1975-04-01

Liquid phase sintering was utilized to achieve, by a simple compaction and sintering procedure involving short times and moderate temperatures, a virtually full dense high carbon Fe:C alloy and high boron Fe:B alloy. Parameters such as powder characteristics and mixing, compacting pressure, heating program and the liquid phase fraction were found to influence the sintered density. The response of the Fe:C alloy to a heat treatment is reported along with preliminary experiments in the iron base ternary system Fe:W:C. Residual porosities observed in microstructures of certain liquid phase sintered compacts were accounted for by a proposed capillary flow of the liquid phase and a local densification competing against an overall densification. Some general recommendations are made for liquid phase sintering of powder aggregates. 15 fig., 7 tables

Zone refining of sintered, microwave-derived YBCO superconductors

International Nuclear Information System (INIS)

Warrier, K.G.K.; Varma, H.K.; Mani, T.V.; Damodaran, A.D.; Balachandran, U.

1993-07-01

Post-sintering treatments such as zone melting under thermal gradient has been conducted on sintered YBCO tape cast films. YBCO precursor powder was derived through decomposition of a mixture of nitrates of cations in a microwave oven for ∼4 min. The resulting powder was characterized and made into thin sheets by tape casting and then sintered at 945 C for 5 h. The sintered tapes were subjected to repeated zone refining operations at relatively high speeds of ∼30 mm/h. A microstructure having uniformly oriented grains in the a-b plane throughout the bulk of the sample was obtained by three repeated zone refining operations. Details of precursor preparation, microwave processing and its advantages, zone refining conditions, and microstructural features are presented in this paper

The behaviour of doped elements in tungsten sintering

International Nuclear Information System (INIS)

Scheiner, L.

1975-01-01

The lecture deals with the occurrence of bubbles in the sintering of doped tungsten. The doping of tungsten normally takes place by the addition of K, Al and Si compounds. A part of the doping substances disappears with sintering which can easily be proved by chemical analyses. In the process described here, the evaporation is non-destructively observed during sintering with an absorption spectrometer. Temperature, absorption slope and sintering resistance are recorded. The evaluation of the absorption curves gives a diffusion equation. The discussion of the curves resulted so far in that a doped substance compound sets free the single elements of the compound at high temperature. Aluminium and silicon diffuse out. In the case of aluminium, the activation energy can be determined. (GSC/LH) [de

Liquid Phase Sintering of (Ti,Zr)C with WC-Co.

Science.gov (United States)

Ma, Taoran; Borrajo-Pelaez, Rafael; Hedström, Peter; Blomqvist, Andreas; Borgh, Ida; Norgren, Susanne; Odqvist, Joakim

2017-01-11

(Ti,Zr)C powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,Zr)C, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,Zr)C phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ₁) or Zr (γ₂). The γ₂ phase grains have a core-shell structure with a (Ti,Zr)C core following the full sintering cycle. The major differences observed in (Ti,Zr)C with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ₁, and γ₂) is about 10% smaller in WC-(Ti,Zr)C-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

Liquid Phase Sintering of (Ti,ZrC with WC-Co

Directory of Open Access Journals (Sweden)

Taoran Ma

2017-01-01

Full Text Available (Ti,ZrC powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,ZrC, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,ZrC phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ1 or Zr (γ2. The γ2 phase grains have a core-shell structure with a (Ti,ZrC core following the full sintering cycle. The major differences observed in (Ti,ZrC with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ1, and γ2 is about 10% smaller in WC-(Ti,ZrC-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

The physical chemistry and materials science behind sinter-resistant catalysts.

Science.gov (United States)

Dai, Yunqian; Lu, Ping; Cao, Zhenming; Campbell, Charles T; Xia, Younan

2018-06-18

Catalyst sintering, a main cause of the loss of catalytic activity and/or selectivity at high reaction temperatures, is a major concern and grand challenge in the general area of heterogeneous catalysis. Although all heterogeneous catalysts are inevitably subjected to sintering during their operation, the immediate and drastic consequences can be mitigated by carefully engineering the catalytic particles and their interactions with the supports. In this tutorial review, we highlight recent progress in understanding the physical chemistry and materials science involved in sintering, including the discussion of advanced techniques, such as in situ microscopy and spectroscopy, for investigating the sintering process and its rate. We also discuss strategies for the design and rational fabrication of sinter-resistant catalysts. Finally, we showcase recent success in improving the thermal stability and thus sinter resistance of supported catalytic systems.

c-Plane oriented Bi-oxide superconductor

International Nuclear Information System (INIS)

Kugimiya, K.; Kawashima, S.; Inoue, O.; Adachi, S.

1988-01-01

A newly found Bi-Sr-Ca-Cu-O superconductor with T c =80 K was synthesized in an almost pure phase. It is a laminar oxide with an Aurivillius phase and easily breaks into thin flakes. By slip-casting the flakes under pressure or by hot-pressing sintered bodies of isostatically formed green compacts, c-planes of the phase were highly oriented by more than 95%, mostly 98.5%. Sintered compacts generally contained materials with T c of 80 and 110 K as proved by the Meissner effect. 11 refs.; 6 figs

Sintering of ultra high molecular weight polyethylene

Indian Academy of Sciences (India)

Abstract. Ultra high molecular weight polyethylene (UHMWPE) is a high performance polymer having low coefficient of friction, good abrasion resistance, good chemical ... In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering ...

Synthesis and characterization of nickel oxide doped barium strontium titanate ceramics

Energy Technology Data Exchange (ETDEWEB)

Banerjee, M. [Dept. of Electrical Engineering, Bengal Institute of Technology Kolkata (India); Mukherjee, S. [Dept. of Metallurgical Engineering, Jadavpur University, Kolkata (India); Maitra, S. [Govt. College of Engg. and Ceramic Technology, Kolkata (India)

2012-01-15

Barium strontium titanate (BST) ceramics (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} were synthesized by solid state sintering using barium carbonate, strontium carbonate and rutile as the precursor materials. The samples were doped with nickel oxide in different proportions. Different phases present in the sintered samples were determined from X-ray diffraction investigation and the distribution of different phases in the microstructure was assessed from scanning electron microscopy study. It was observed that the dielectric properties of BST were modified significantly with nickel oxide doping. These ceramics held promise for applications in tuned circuits. (author)

Foam glass obtained through high-pressure sintering

DEFF Research Database (Denmark)

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

2018-01-01

Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (106.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use...... a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N2) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies...... are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic...

Porous 45S5 Bioglass®-based scaffolds using stereolithography: Effect of partial pre-sintering on structural and mechanical properties of scaffolds.

Science.gov (United States)

Thavornyutikarn, Boonlom; Tesavibul, Passakorn; Sitthiseripratip, Kriskrai; Chatarapanich, Nattapon; Feltis, Bryce; Wright, Paul F A; Turney, Terence W

2017-06-01

Scaffolds made from 45S5 Bioglass® ceramic (BG) show clinical potential in bone regeneration due to their excellent bioactivity and ability to bond to natural bone tissue. However, porous BG scaffolds are limited by their mechanical integrity and by the substantial volume contractions occurring upon sintering. This study examines stereolithographic (SLA) methods to fabricate mechanically robust and porous Bioglass®-based ceramic scaffolds, with regular and interconnected pore networks and using various computer-aided design architectures. It was found that a diamond-like (DM) architecture gave scaffolds the most controllable results without any observable closed porosity in the fired scaffolds. When the pore dimensions of the DM scaffolds of the same porosity (~60vol%) were decreased from 700 to 400μm, the compressive strength values increased from 3.5 to 6.7MPa. In addition, smaller dimensional shrinkage could be obtained by employing partially pre-sintered bioglass, compared to standard 45S5 Bioglass®. Scaffolds derived from pre-sintered bioglass also showed marginally improved compressive strength. Copyright © 2017 Elsevier B.V. All rights reserved.

Phosphorus containing sintered alloys (review)

International Nuclear Information System (INIS)

Muchnik, S.V.

1984-01-01

Phosphorus additives are considered for their effect on the properties of sintered alloys of different applications: structural, antifriction, friction, magnetic, hard, superhard, heavy etc. Data are presented on compositions and properties of phosphorus-containing materials produced by the powder metallurgy method. Phosphorus is shown to be an effective activator of sintering in some cases. When its concentration in the material is optimal it imparts the material such properties as strength, viscosity, hardness, wear resistance. Problems concerning powder metallurgy of amorphous phosphorus-containing alloys are reported

Microwave sintering of zirconia toughened alumina at 28GHz

International Nuclear Information System (INIS)

Samandi, M.; Ji, H.; Miyake, S.

1998-01-01

Microwave radiation from a 10 kW, CW gyrotron operating at 28 GHz was employed to sinter 10% zirconia toughened alumina (ZTA) ceramic samples. It has been established that the use of millimetre wave radiation circumvents the difficulties encountered during the sintering of ceramics, i e. formation of hot spot, by radiation at industrially permissible frequency of 2.45GHz. Further, careful density measurement and microstructural characterisation of mm- wave and conventionally sintered samples by XRD, SEM and TEM has unequivocally demonstrated the effectiveness of mm-wave radiation for obtaining high density ceramics at lower sintering temperatures. Copyright (1998) Australasian Ceramic Society

Kinetics of UO{sub 2} sintering; Kinetika sinterovanja UO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Ristic, M M [Institute of Nuclear Sciences Vinca, Laboratorija za reaktorske materijale, Beograd (Serbia and Montenegro)

1962-10-15

Detailed conclusions related to the UO{sub 2} sintering can be drawn from investigating the kinetics of the sintering process. This report gives an thorough analysis of the the data concerned with sintering available in the literature taking into account the Jander and Arrhenius laws. This analysis completes the study of influence of the O/U ratio and the atmosphere on the sintering. Results presented are fundamentals of future theoretical and experimental work related to characterisation of the UO{sub 2} sintering process.

The effect of surface treatments on the microroughness of laser-sintered and vacuum-cast base metal alloys for dental prosthetic frameworks.

Science.gov (United States)

Castillo-Oyagüe, Raquel; Osorio, Raquel; Osorio, Estrella; Sánchez-Aguilera, Fátima; Toledano, Manuel

2012-09-01

This study aimed to evaluate the effect of four chemomechanical surface treatments on the surface average microroughness and profile of laser-sintered and vacuum-cast dental prosthetic structures. Square-shaped blocks (10 mm × 10 mm × 1.5 mm) were prepared as follows: (1) laser-sintered CoCr (L) (ST2724G); (2) cast Co-Cr (C) (Gemium-cn); and (3) cast Ni-Cr-Ti (T) (Tilite). Specimens of each alloy group were randomly divided into five subgroups (n = 10 each), depending on the conditioning method used: (1) no treatment (control); (2) sandblasting (125 μm Al₂O₃-particles); (3) silica coating (50 μm silica-modified Al₂O₃-particles); (4) oxidation; and (5) oxidation plus opacification. Subgroups 2 and 3 represent "inner" pretreatments proposed for ceramometal restorations to improve the metal surface area available for luting cements. Subgroups 4 and 5 are the "outer" pretreatments required for bonding the aesthetic veneering ceramics to the underlying metal frameworks. Average surface roughness (Ra/μm) was determined using a surface profilometer. Data were analyzed by two-way ANOVA and Student-Newman-Keuls tests (α = 0.05). Metal surface topography was SEM-analyzed. Despite the inner pretreatment applied, L samples resulted in the highest microroughness (P < 0.001), whereas sandblasting produced a surface-smoothing effect in cast specimens. After oxidation, a significant increase in surface roughness occurred in all groups compared with controls, L specimens being the roughest (P < 0.001). Opacification caused a flattening effect of all oxidized structures; all opacified groups resulting in similar microroughness. Laser sintering of Co-Cr enhances the roughness of metal structures, which may improve the frameworks' microretention of the cements, and of the opaquer before the copings are veneered with the aesthetic ceramics. Copyright © 2012 Wiley Periodicals, Inc.

Sintering and microstructure evolution in columnar thermal barrier coatings

International Nuclear Information System (INIS)

Krishnamurthy, Ramanathan; Srolovitz, David J.

2009-01-01

Sintering of thermal barrier coatings changes their key properties, such as thermal conductivity and thermal shock resistance, thus adversely impacting their reliability. We present a novel modeling approach to study the evolution of coating structure during sintering. We model the sintering of individual columns using a thermodynamic principle, and incorporate the center-to-center approach rates for the columns calculated using this principle in a larger scale discrete dynamics model for the evolution of a large number of columns. Surface energies, grain boundary energies and strain energies associated with the deformation of the columns are all included in this framework, while sintering is assumed to occur by the concerted action of surface and grain boundary diffusion. Two sets of initial conditions corresponding to different extents of pre-sintering among neighboring columns are considered. When the extent of pre-sintering is small, we observe that small clusters containing 5-20 columns are formed. In contrast, where a larger amount of pre-sintering exists, we observe, especially at large column densities, that clusters containing 50-100 columns separated by large inter-cluster pores/channels that appear to organize themselves into a network are formed. These observations are in good agreement with recently published experimental observations. We also explain how these results can explain the development of a 'mud-crack'-like pattern

[Study on preparation and physicochemical properties of surface modified sintered bone].

Science.gov (United States)

Li, Jingfeng; Zheng, Qixin; Guo, Xiaodong

2012-06-01

The aim of this study is to investigate a new method for preparing a biomimetic bone material-surface modified sintered bovine cancellous bone, and to improve its bioactivity as a tissue engineering bone. The prepared sintered bovine cancellous bones with the same size were randomly divided into two groups, immersing in 1 and 1. 5 times simulated body fluid (SBF), respectively. The three time periods of soak time were 7, 14, and 21 days. After sintered bone was dried, the surface morphology of sintered bone and surface mineralization composition were observed under scanning electron microscopy (SEM). By comparing the effect of surface modification of sintered bone materials, we chose the most ideal material and studied its pore size, the rate of the porosity, the compress and bend intensity. And then the material and the sintered bone material without surface modification were compared. The study indicated that sintered bone material immersed in SBF (1.5 times) for 14 days showed the best effect of surface modification, retaining the original physico-chemical properties of sintered bone.

Size-Selective Oxidation of Aldehydes with Zeolite Encapsulated Gold Nanoparticles

DEFF Research Database (Denmark)

Højholt, Karen Thrane; Laursen, Anders Bo; Kegnæs, Søren

2011-01-01

Here, we report a synthesis and catalytic study of hybrid materials comprised of 1–3 nm sinter-stable Au nanoparticles in MFI-type zeolites. An optional post-treatment in aqua regia effectively remove Au from the external surfaces. The size-selective aerobic aldehyde oxidation verifies that the a......Here, we report a synthesis and catalytic study of hybrid materials comprised of 1–3 nm sinter-stable Au nanoparticles in MFI-type zeolites. An optional post-treatment in aqua regia effectively remove Au from the external surfaces. The size-selective aerobic aldehyde oxidation verifies...... that the active Au is accessible only through the zeolite micropores....

In situ Transmission Electron Microscopy of catalyst sintering

DEFF Research Database (Denmark)

DeLaRiva, Andrew T.; Hansen, Thomas Willum; Challa, Sivakumar R.

2013-01-01

Recent advancements in the field of electron microscopy, such as aberration correctors, have now been integrated into Environmental Transmission Electron Microscopes (TEMs), making it possible to study the behavior of supported metal catalysts under operating conditions at atomic resolution. Here......, we focus on in situ electron microscopy studies of catalysts that shed light on the mechanistic aspects of catalyst sintering. Catalyst sintering is an important mechanism for activity loss, especially for catalysts that operate at elevated temperatures. Literature from the past decade is reviewed...... along with our recent in situ TEM studies on the sintering of Ni/MgAl2O4 catalysts. These results suggest that the rapid loss of catalyst activity in the earliest stages of catalyst sintering could result from Ostwald ripening rather than through particle migration and coalescence. The smallest...

XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite-Bioglass (registered) 45S5 co-sintered bioceramics

Energy Technology Data Exchange (ETDEWEB)

Demirkiran, Hande [Graduate Student, Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States); Hu Yongfeng; Zuin, Lucia [Beamline Scientist, Canadian Light Source, Saskatoon, SK (Canada); Appathurai, Narayana [Beamline Scientist, Synchrotron Radiation Center, Madison, WI (United States); Aswath, Pranesh B., E-mail: aswath@uta.edu [Materials Science and Engineering Department, University of Texas at Arlington, Arlington, TX (United States)

2011-03-12

Bioglass (registered) 45S5 was co-sintered with hydroxyapatite at 1200 deg. C. When small amounts (< 5 wt.%) of Bioglass (registered) 45S5 was added it behaved as a sintering aid and also enhanced the decomposition of hydroxyapatite to {beta}-tricalcium phosphate. However when 10 wt.% and 25 wt.% Bioglass (registered) 45S5 was used it resulted in the formation of Ca{sub 5}(PO{sub 4}){sub 2}SiO{sub 4} and Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite-Bioglass (registered) 45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L{sub 2,3}-edge and calcium (Ca) K-edge XANES. Si L{sub 2,3}-edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination. Using P L{sub 2,3}-edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and {beta}-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na{sub 3}Ca{sub 6}(PO{sub 4}){sub 5} in a silicate matrix indicating that it is more soluble compared to the other compositions.

Peculiarities of formation and sintering of fine dispersed molybdenum powders

International Nuclear Information System (INIS)

Kalamazov, R.U.; Pak, V.I.; Tsvetkov, Yu.V.; Lem, I.N.

1989-01-01

Pressing of fine dispersed Mo powders sintering of compacts in H 2 and vacuum is studied. It is shown that powder preannealing at 600 deg C in H 2 for 2 hours is necessary for formation of dense sintered compacts. Qualitatively choice of pressing conditions is possible when using electron-positron annihilation method. Peculiarities of compacting and sintering of fine- and coarse-dispersed powder mixtures are considered. The obtained results are discussed from the view point of sintering recrystallization mechanism

Low modulus and bioactive Ti/α-TCP/Ti-mesh composite prepared by spark plasma sintering.

Science.gov (United States)

Guo, Yu; Tan, Yanni; Liu, Yong; Liu, Shifeng; Zhou, Rui; Tang, Hanchun

2017-11-01

A titanium mesh scaffold composite filled with Ti/α-TCP particles was prepared by spark plasma sintering (SPS). The microstructures and interfacial reactions of the composites were investigated by scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The compressive strength and elastic modulus were also measured. In vitro bioactivity and biocompatibility was evaluated by using simulated body fluid and cells culture, respectively. After high temperature sintering, Ti oxides, Ti x P y and CaTiO 3 were formed. The formation of Ti oxides and Ti x P y were resulted from the diffusion of O and P elements from α-TCP to Ti. CaTiO 3 was the reaction product of Ti and α-TCP. The composite of 70Ti/α-TCP incorporated with Ti mesh showed a high compressive strength of 589MPa and a low compressive modulus of 30GPa. The bioactivity test showed the formation of a thick apatite layer on the composite and well-spread cells attachment. A good combination of mechanical properties and bioactivity indicated a high potential application of Ti/α-TCP/Ti-mesh composite for orthopedic implants. Copyright © 2017. Published by Elsevier B.V.

SnO{sub 2}{sup *}CoO ceramic obtained by microwave sintering; Ceramicas de SnO{sub 2} {sup *}CoO obtidas por sinterizacao microondas

Energy Technology Data Exchange (ETDEWEB)

Bordignon, M.A.N; Moura, F.; Zaghete, M.A.; Varela, J.A.; Perazolli, L. [Universidade Estadual Paulista (UNESP), Araraquara, SP (Brazil). Chemistry Institute. Dept. de Biochemistry and Technological Chemistryl

2009-07-01

This work consists in the sintering study of CoO doped SnO{sub 2} using microwave sintering oven and silicon carbide as a susceptor. The powders were obtained by dry oxides mixture and conformed in cylindrical shapes with 6mmx8mm and green density to 60%. Then the compacts were sintering up to 1.050 deg C, using heating rate of 50 deg C/min and isotherm up to 30min. The densities obtained were above 95% for both techniques. It was observed that occurred a temperature reducing of 400 deg C and time reducing of 210min to obtain the same densities, when was used the microwave oven without the phenomena of thermal runaway. So the sintered compacts were accomplished using DRX and SEM. It was made the electrical characterization (current x voltage) and it was found to have great potential in the production of dense ceramic-based SnO{sub 2} with low resistivity to obtain electro-ceramic devices. (author)

One step sintering of homogenized bauxite raw material and kinetic study