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Sample records for sintering ceramic composition

  1. Reaction sintering of ceramic-metal composites

    International Nuclear Information System (INIS)

    Botta Filho, W.J.; Rodrigues, J.A.; Tomasi, R.; Pandolfelli, V.C.; Passos, J.F.S.S.; Folgueras, M.V.

    1990-01-01

    Reaction sintering experiments have been carried out in the system Al 2 O 3 -ZrAl 2 -Nb 2 O 5 with the objective of producing ceramic-metal composites of improved toughness. The sintering treatments have been done in the temperature range of 700 0 C to 1400 0 C under different conditions of vacuum and in air and argon atmospheres. The treated samples have been analysed by X-ray diffraction and analytical electron microscopy. The results are discussed in function of the degree of reaction, the development of microstructure and the densification. These results have shown that although an exchange reaction can occur to produce a composite, the control of the reaction to obtain a dense microstructure has not been possible yet. (author) [pt

  2. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    Science.gov (United States)

    Gephart, Sean

    The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques. This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering. The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4 x 4 x 0.315 inches3 (101.6 x 101.6 x 8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered

  3. The influence of sintering on the dispersion of carbon nanotubes in ceramic matrix composites

    Science.gov (United States)

    Tapasztó, Orsolya; Lemmel, Hartmut; Markó, Márton; Balázsi, Katalin; Balázsi, Csaba; Tapasztó, Levente

    2014-10-01

    Optimizing the dispersion of carbon nanostructures in ceramic matrix composites is a fundamental technological challenge. So far most efforts have been focused on improving the dispersion of nanostructures during the powder phase processing, due to the limited information and control on their possible redistribution during the sintering. Here, we address this issue by comparing multi-walled carbon nanotubes reinforced Si3N4 composites prepared from the same starting powder dispersion but sintered using two different techniques. We employ ultra-small angle neutron scattering measurements to gain reliable information on the dispersion of nanostructures allowing a direct comparison of their redistribution during the sintering.

  4. Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

    International Nuclear Information System (INIS)

    Aloisi, Mirko; Karamanov, Alexander; Taglieri, Giuliana; Ferrante, Fabiola; Pelino, Mario

    2006-01-01

    A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 deg. C/min, increased by about 20% and 30%, respectively

  5. Effect of sintering temperatures on titanium matrix composites reinforced by ceramic particles

    Energy Technology Data Exchange (ETDEWEB)

    Romero, F.; Amigo, V.; Busquets, D.; Klyatskina, E. [Mechanical and Materials Engineering Department. Polytechnical University of Valencia, Valencia (Spain)

    2005-07-01

    Titanium and titanium composites have a potential use in aerospace and biotechnology industries, and nowadays in others like sports and fashion ones. In this work composite materials, based on titanium matrix reinforced with ceramic particles, have been developed. PM route is used to obtain compact and sintered samples. TiN and TiAl powders, are milled with Ti powder in different volumetric percentages in a ball mill. These mixtures are pressed in a uniaxial press and sintered in a vacuum furnace at different temperatures between 1180 to 1220 deg. C. Porosity of samples is analysed, before and after the sintering process, by Archimedes technique and by image analysis. Mechanical properties and the reinforcement particles influence in the titanium matrix are studied by flexion test in green and sintered states, and by hardness and microhardness tests. Complimentarily, a microstructural analysis is carried out by optical and electron microscopy, and the reactivity between the reinforce particles and titanium matrix are studied. (authors)

  6. Boric oxide or boric acid sintering aid for sintering ceramics

    International Nuclear Information System (INIS)

    Lawler, H.A.

    1979-01-01

    The invention described relates to the use of liquid sintering aid in processes involving sintering of ceramic materials to produce dense, hard articles having industrial uses. Although the invention is specifically discussed in regard to compositions containing silicon carbide as the ceramic material, other sinterable carbides, for example, titanium carbide, may be utilized as the ceramic material. A liquid sintering aid for densifying ceramic material is selected from solutions of H 3 BO 3 , B 2 O 3 and mixtures of these solutions. In sintering ceramic articles, e.g. silicon carbide, a shaped green body is formed from a particulate ceramic material and a resin binder, and the green body is baked at a temperature of 500 to 1000 0 C to form a porous body. The liquid sintering aid of B 2 O 3 and/or H 3 BO 3 is then dispersed through the porous body and the treated body is sintered at a temperature of 1900 to 2200 0 C to produce the sintered ceramic article. (U.K.)

  7. 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.

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

    CERN Document Server

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

    1998-01-01

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

  9. Mechanical Properties and Plasma Erosion Resistance of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} Ceramic Composites under Different Sintering Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yu; Duan Xiaoming; Jia Dechang; Yang Zhihua; Meng Qingchang; Yu Yang [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin, 150001 (China); Yu Daren; Ding Yongjie, E-mail: dxmhit@126.com [School of Energy Science and Technology, Harbin Institute of Technology, Harbin, 150001 (China)

    2011-10-29

    ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites were hot pressed under different sintering temperature. The ceramic composites were composed by BN, m-ZrO{sub 2}, t-ZrO{sub 2} and SiO{sub 2}. The relative density, bending strength, elastic modulus and fracture toughness increase with the sintering temperature increasing, the maximum value of which at the sintering temperature of 1800 deg. C are 97.5%, 229.9MPa, 60.8GPa and 3.55MPam{sup 1/2}, respectively. The erosion resistance ability of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites rise gradually with the sintering temperature increasing, and the erosion rate of the ceramic composite sintered at 1800 deg. C is 8.03x10{sup -3}mm/h.

  10. Spark plasma sintering of ceramic matrix composite based on alumina, reinforced by carbon nanotubes

    Science.gov (United States)

    Leonov, A. A.; Khasanov, A. O.; Danchenko, V. A.; Khasanov, O. L.

    2017-12-01

    Alumina composites reinforced with 3 vol.% multi-walled carbon nanotubes (MWCNTs) were prepared by spark plasma sintering (SPS). The influence of sintering temperature (1400-1600 °C) on the composites microstructure and mechanical properties was investigated. Microstructure observations of the composite shows that some CNTs site along alumina grains boundary, while others embed into the alumina grains and shows that CNTs bonded strongly with the alumina matrix contributing to fracture toughness and microhardness increase. MWCNTs reinforcing mechanisms including CNT pull-out and crack deflection were directly observed by scanning electron microscope (SEM). For Al2O3/CNT composite sintered at 1600 °C, fracture toughness and microhardness are 4.93 MPa·m1/2 and 23.26 GPa respectively.

  11. Microwave sintering of ceramic materials

    Science.gov (United States)

    Karayannis, V. G.

    2016-11-01

    In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

  12. Bonding of TRIP-Steel/Al2O3-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus

    OpenAIRE

    Miriyev, Aslan; Gr?tzner, Steffen; Kr?ger, Lutz; Kalabukhov, Sergey; Frage, Nachum

    2016-01-01

    A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully appl...

  13. Phase Composition and Microstructure of Hot-Pressing Sintered Ti2AlN Metal-Ceramic Bulk Material

    Directory of Open Access Journals (Sweden)

    LIANG Suying

    2017-06-01

    Full Text Available Ti2AlN metal-ceramic bulk material was fabricated by hot-pressing sintering (HPS using TiN, Ti and Al powder in a stoichiometric ratio of 1:1:1.03 after mechanical mixing. XRD, SEM and TEM were employed to investigate the phase composition and microstructures of the products. The results show that the high purity Ti2AlN can be obtained by HPS at 1300 ℃ for 2.5 h. The sintered Ti2AlN presented a hexagonal system layered structure with an anisotropy. Twins are found in the Ti2AlN. There were a few nano-scale TiN particles in the products.

  14. Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite

    International Nuclear Information System (INIS)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin

    2015-01-01

    Highlights: • Glass ceramic composite is prepared from oil shale fly ash and MSWI bottom ash. • A novel method for the production of glass ceramic composite is presented. • It provides simple route and lower energy consumption in terms of recycling waste. • The vitrified slag can promote the sintering densification process of glass ceramic. • The performances of products decrease with the increase of oil shale fly ash content. - Abstract: Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2 h) showed the properties of density of 1.92 ± 0.05 g/cm 3 , weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced

  15. Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite.

    Science.gov (United States)

    Zhang, Zhikun; Zhang, Lei; Li, Aimin

    2015-04-01

    Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2h) showed the properties of density of 1.92 ± 0.05 g/cm(3), weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics

    Directory of Open Access Journals (Sweden)

    Mendes A.M.

    2017-02-01

    Full Text Available In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ commercial ceramics has been studied using the central composite design (CCD method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr atoms coordinated to seven oxygen (O atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics.

  17. The sintering of nitrogen ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hampshire, S.

    1986-01-01

    The mechanism of densification with oxide additives and the role of the ..cap alpha..-BETA phase transformation is investigated in a detailed kinetic study. Selected compositions in the Si-Al-O-N system are detailed, with and without additives. Although the work is mainly concerned with the identification of the mechanisms of sintering, some property measurements on a sintered BETA-sialon are reported and the feasibility of preparing pure ..cap alpha..-sialon phases is explored.

  18. Sintering behavior of LZSA glass-ceramics

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2009-06-01

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

  19. Bonding of TRIP-Steel/Al2O3-(3Y-TZP Composites and (3Y-TZP Ceramic by a Spark Plasma Sintering (SPS Apparatus

    Directory of Open Access Journals (Sweden)

    Aslan Miriyev

    2016-07-01

    Full Text Available A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening.

  20. 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

  1. Sintering techniques for microstructure control in ceramics

    Science.gov (United States)

    Rosenberger, Andrew T.

    Sintering techniques can be manipulated to enhance densification in difficult to sinter materials and to produce property enhancing microstructures. However, the interplay between materials, sintering techniques, and end properties is not fully understood in many material systems, and some fundamental aspects of sintering such as the nature of the effects of electric fields remains unknown. The processing property relationships were examined in two classes of materials; zirconium diboride ultra high temperature ceramic composites, and all solid lithium-ion battery phosphate materials. Investigation of zirconium diboride ceramics focused on the effects of zirconium carbide as a secondary or tertiary phase in ZrB2 and ZrB2 -- SiC. Addition of zirconium carbide was observed to increase flexural strength of composites up to 590MPa at 50wt% ZrC, significantly higher than the flexural strength of 380MPa observed in similarly prepared ZrB2 -- SiC. This difference was attributed to the absence of CTE mismatch induced residual stresses in the ZrB2 -- ZrC composites. A high temperature reaction between ZrB2 and TiC producing Zr1-xTixB2 -- ZrC composites was discovered and found to enhance densification while reducing the average grain size to as small as 1.4mum, lower than the starting powder size of 1.8mum. While a high flexural strength of 670MPa was observed, a strength dependence on the ZrC grain size indicative of CTE mismatch residual stresses was also seen. Finally, the oxidation and ablation resistance of ZrB2 -- ZrC -- SiC composites as a function of ZrC fraction and ZrC:SiC ratio was investigated. Above 5vol% ZrC, the oxidation and ablation resistance of the composites was significantly reduced due to ZrC oxidation, regardless of SiC content. While ZrC can significantly enhance the mechanical properties of the composite, the volume fraction must be kept low to avoid an undesirable reduction in the oxidation resistance. The influence of applied electrical fields

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

    Directory of Open Access Journals (Sweden)

    Roberto Orrù

    2013-04-01

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

  3. 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.

  4. 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

  5. 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

  6. 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)

  7. Study of ceramics sintering under high pressures

    International Nuclear Information System (INIS)

    Kunrath Neto, A.O.

    1990-01-01

    A systematic study was made on high pressure sintering of ceramics in order to obtain materials with controlled microstructure, which are not accessible by conventional methods. Some aspects with particular interest were: to achieve very low porosity, with fine grains; to produce dispersed metastable and denser phases which can act as toughening agents; the study of new possibilities for toughening enhancement. (author)

  8. Phase and Microstructural Correlation of Spark Plasma Sintered HfB2-ZrB2 Based Ultra-High Temperature Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Ambreen Nisar

    2017-07-01

    Full Text Available The refractory diborides (HfB2 and ZrB2 are considered as promising ultra-high temperature ceramic (UHTCs where low damage tolerance limits their application for the thermal protection system in re-entry vehicles. In this regard, SiC and CNT have been synergistically added as the sintering aids and toughening agents in the spark plasma sintered (SPS HfB2-ZrB2 system. Herein, a novel equimolar composition of HfB2 and ZrB2 has shown to form a solid-solution which then allows compositional tailoring of mechanical properties (such as hardness, elastic modulus, and fracture toughness. The hardness of the processed composite is higher than the individual phase hardness up to 1.5 times, insinuating the synergy of SiC and CNT reinforcement in HfB2-ZrB2 composites. The enhanced fracture toughness of CNT reinforced composite (up to a 196% increment surpassing that of the parent materials (ZrB2/HfB2-SiC is attributed to the synergy of solid solution formation and enhanced densification (~99.5%. In addition, the reduction in the analytically quantified interfacial residual tensile stress with SiC and CNT reinforcements contribute to the enhancement in the fracture toughness of HfB2-ZrB2-SiC-CNT composites, mandatory for aerospace applications.

  9. Co-Sintering behaviour of zirconia-ferritic steel composites

    Directory of Open Access Journals (Sweden)

    Alexander Michaelis

    2016-08-01

    Full Text Available The combination of metallic and ceramic materials allows the combination of positive properties of both and can be applied in various industrial fields. At the moment, the deployment of these composites faces difficult and complex manufacturing. One attempt, which offers a short process route and a high degree of flexibility regarding design is a combined shaping (co-shaping with a combined sintering (co-sintering. The article will show co-sintering results of different metal-ceramic symmetric and asymmetric multi-layered tapes, consisting of yttria stabilized zirconia combined with a ferritic iron chromium steel. Focus is on the densification and co-sintering behaviour of ceramic layers depending on the sintering behaviour of metallic layers. Co-sintered composites were characterized by field emission scanning electron microscopy, x-ray diffraction measurements and in terms of adhesive tensile strength.

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

    Directory of Open Access Journals (Sweden)

    Shujing Li

    2005-01-01

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

  11. Sintering additives for zirconia ceramics

    International Nuclear Information System (INIS)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification

  12. Sintering additives for zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification.

  13. Sintering and deformation of nanocrystalline ceramics

    International Nuclear Information System (INIS)

    Hahn, H.; Averback, R.S.; Hofler, H.J.; Logas, J.

    1991-01-01

    Nanocrystalline ceramics have been produced by the method of inert gas condensation of ultra-small particles and in situ consolidation. Sintering characteristics and microstructural parameter such as grain size, porosity and pore size distributions have been investigated by a variety of techniques, including: X-ray diffraction, gravimetry, nitrogen adsorption, scanning electron microscopy and small angle neutron scattering. In pure TiO 2 , the sintering temperatures are drastically lowered compared to conventional ceramics, however, extensive grain growth occurs before full densification is achieved. High density, nanocrystalline ceramics can be prepared by pressure assisted sintering, doping and additions of second phases. High temperature microhardness and creep deformation in compression were measured and it was found that creep processes occur at lower temperatures than in ceramics with larger grain sizes. Nanocrystalline TiO 2 with densities >99% can be deformed plastically without fracture at temperatures below half the melting point. The total strains exceed 0.6 at strain rates as high as 10 -3 s -l . The stress exponent of the strain rate, n, is approximately 3 and the grain size dependence is G -q with q in the range of 1-1.5. In this paper it is concluded that the creep deformation occurs by an interface reaction controlled mechanism

  14. Protocol for Ultralow-Temperature Ceramic Sintering: An Integration of Nanotechnology and the Cold Sintering Process.

    Science.gov (United States)

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

    2016-11-22

    The sintering process is an essential step in taking particulate materials into dense ceramic materials. Although a number of sintering techniques have emerged over the past few years, the sintering process is still performed at high temperatures. Here we establish a protocol to achieve dense ceramic solids at extremely low temperatures (sustainable manufacturing practices.

  15. Densification and mechanical properties of sintered Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} ceramic composite

    Energy Technology Data Exchange (ETDEWEB)

    Paneto, Flavio Jose; Pereira, Joaquim Lopes; Oliveira, Jean de Lima; Jesus Filho, Edson de; Silva, Leandro Anselmo da; Cabral, Ricardo de Freitas; Santos, Claudinei dos [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Lima, Eduardo de Sousa [Institutlo Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil)

    2014-06-15

    In this work, Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} ceramic composites were developed with different proportions of Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12}, which were mixed and compacted at different pressures of 40MPa to 100MPa, being consequently sintered at 1600 deg C-2h. The sintered samples were characterized by X-ray diffraction presenting α-Al{sub 2}O{sub 3} and Y{sub 3}Al{sub 5}O{sub 12} as crystalline phases. Samples with relative densities ranging from 78 to 80% and 87 to 91% were obtained depending on the composition and the compaction pressure used. The hardness values obtained were of 1010 to 1080HV and 370- 470HV, for mixes Al{sub 2}O{sub 3}-Y{sub 3}Al{sub 5}O{sub 12} having the composition with levels of 20 and 36.5wt.%, respectively. (author)

  16. Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

    Science.gov (United States)

    Singh, M.

    2011-01-01

    During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

  17. Synergistic Sintering of Lignite Fly Ash and Steelmaking Residues towards Sustainable Compacted Ceramics

    Directory of Open Access Journals (Sweden)

    V. G. Karayannis

    2017-01-01

    Full Text Available The development of value-added ceramic materials deriving only from industrial by-products is particularly interesting from technological, economic, and environmental point of views. In this work, the synergistic sintering of ternary and binary mixtures of fly ash, steelmaking electric arc furnace dust, and ladle furnace slag for the synthesis of compacted ceramics is reported. The sintered specimens’ microstructure and mineralogical composition were characterized by SEM-EDS and XRD, respectively. Moreover, the shrinkage, apparent density, water absorption, and Vickers microhardness (HV were investigated at different sintering temperatures and raw material compositions. The characterization of the sintered compacts revealed the successful consolidation of the ceramic microstructures. According to the experimental findings, the ceramics obtained from fly ash/steel dust mixtures exhibited enhanced properties compared to the other mixtures tested. Moreover, the processing temperature affected the final properties of the produced ceramics. Specifically, a 407% HV increase for EAFD and a 2221% increase for the FA-EAFD mixture were recorded, by increasing the sintering temperature from 1050 to 1150°C. Likewise, a 972% shrinkage increase for EAFD and a 577% shrinkage increase for the FA-EAFD mixture were recorded, by increasing the sintering temperature from 1050 to 1150°C. The research results aim at shedding more light on the development of sustainable sintered ceramics from secondary industrial resources towards circular economy.

  18. Influence of B2O3 content on sintering behaviour and dielectric properties of La2O3-B2O3-CaO/Al2O3 glass-ceramic composites for LTCC applications

    Science.gov (United States)

    Wang, F. L.; Zhang, Y. W.; Chen, X. Y.; Mao, H. J.; Zhang, W. J.

    2018-01-01

    La2O3-B2O3-CaO glasses with different B2O3 content were synthesized by melting method to produce glass/ceramic composites in this work. XRD and DSC results revealed that the diminution of B2O3 content was beneficial to increase the crystallization tendency of glass and improve the quality of crystalline phase, while decreasing the effect of glass during sintering process as sintering aids. The choice of glass/ceramic mass ratio was also influenced by the B2O3 content of glass. Dense samples sintered at 875 ºC showed good dielectric properties which meet the requirement of LTCC applications: moderate dielectric constant (7.8-9.4) and low dielectric loss (2.0×10-3).

  19. Yttrium oxide transparent ceramics by low-temperature microwave sintering

    International Nuclear Information System (INIS)

    Luo, Junming; Zhong, Zhenchen; Xu, Jilin

    2012-01-01

    Graphical abstract: The figure shows the SEM photos of the surfaces of the Y 2 O 3 transparent ceramic samples obtained by microwave sintering and vacuum sintering. It is clearly demonstrated that the grain distribution of the vacuum sintering sample is not uniform with the smallest and the largest particle size at about 2 μm and 15 μm respectively, while the grain distribution of microwave sintering sample is uniform with the average diameter at about 2–4 μm (the smallest reported so far) and with no abnormal growth-up or coarsening phenomenon. We have further found out that the smaller the grain size, the higher the mechanical and optical properties. Display Omitted Highlights: ► The microwave sintering temperature of the sample is lower compared with vacuum. ► The microwave sintering time of the sample is shorter compared with vacuum. ► The mechanical properties of the microwave sintering sample is improved greatly. ► The Y 2 O 3 grain of microwave sintering sample is the smallest reported so far. -- Abstract: Yttrium oxide (Y 2 O 3 ) transparent ceramics samples have been successfully fabricated by microwave sintering processing at relatively low temperatures. In comparison with the vacuum sintering processing, Y 2 O 3 transparent ceramics can be obtained by microwave sintering at lower sintering temperature and shorter sintering time, and they possess higher transmittances and mechanical properties. The technologies of low-temperature microwave sintering and the relationships of the microstructures and properties of the specified samples have been investigated in detail. We have found out that the low-temperature microwave sintering technique has its obvious advantages over the conventional methods in manufacturing yttrium oxide transparent ceramics.

  20. Low-Temperature Sintering of Ba0.5Sr0.5TiO3-SrMoO4 Dielectric Tunable Composite Ceramics for LTCC Applications

    Science.gov (United States)

    Tang, Linjiang; Wang, Jinwen; Zhai, Jiwei

    2013-08-01

    A sintering-aid system using melting of B-Li glass for barium strontium titanate (BST)-based compositions to be used in low-temperature cofired ceramic (LTCC) layers is introduced. The effects of the sintering aid on the microstructure, dielectric properties, and application in LTCC were investigated. The composition Ba0.5Sr0.5TiO3-SrMoO4 with 3 wt.% B-Li glass sintered at 950°C exhibits optimized dielectric properties, including low dielectric constant (368), low dielectric loss (0.007), and moderate tunability (13%, 60 kV/cm) at 10 kHz. At 1.44 GHz, it possesses a dielectric constant of 218 and Q value of 230. LTCC multilayer ceramic capacitors fabricated by the tape-casting process have steady relative tunability of 12% at 300 V, suggesting that BST50-SrMoO4-B-Li glass composite ceramic is a promising candidate for electrically tunable LTCC microwave device applications.

  1. The effects of sintering behavior on piezoelectric properties of porous PZT ceramics for hydrophone application

    International Nuclear Information System (INIS)

    Zeng Tao; Dong Xianlin; Chen Heng; Wang Yonglin

    2006-01-01

    Porous lead zirconate titanate (PZT) ceramics were fabricated by adding polymethyl methacrylate (PMMA) and the effects of sintering behavior on their microstructure and piezoelectric properties were investigated. The porosity of PZT ceramics decreased with an increase in the sintering temperature at a fixed PMMA addition. The dielectric constant (ε), longitudinal piezoelectric coefficient (d 33 ) and hydrostatic figures of merit (d h g h ) of 34% porous PZT ceramics increased with an increase in sintering temperature from 1050 to 1300 deg. C. When sintered at 1300 deg. C, longitudinal piezoelectric coefficient of 34% porous PZT ceramic was very close to that of 95% dense PZT ceramics, while the hydrostatic figures of merit of 34% porous PZT ceramics is about fifteen times more than that of 95% dense PZT ceramics. Compared with PZT-polymer composites, the dielectric constant of 34% porous PZT sintered at 1300 deg. C is much higher, which can be more efficient to resist the interference in receiving sensitivities caused by loading effect of the cable

  2. Compositional Design of Dielectric, Ferroelectric and Piezoelectric Properties of (K, Na)NbO3 and (Ba, Na)(Ti, Nb)O3 Based Ceramics Prepared by Different Sintering Routes

    Science.gov (United States)

    Eiras, José A.; Gerbasi, Rosimeire B. Z.; Rosso, Jaciele M.; Silva, Daniel M.; Cótica, Luiz F.; Santos, Ivair A.; Souza, Camila A.; Lente, Manuel H.

    2016-01-01

    Lead free piezoelectric materials are being intensively investigated in order to substitute lead based ones, commonly used in many different applications. Among the most promising lead-free materials are those with modified NaNbO3, such as (K, Na)NbO3 (KNN) and (Ba, Na)(Ti, Nb)O3 (BTNN) families. From a ceramic processing point of view, high density single phase KNN and BTNN ceramics are very difficult to sinter due to the volatility of the alkaline elements, the narrow sintering temperature range and the anomalous grain growth. In this work, Spark Plasma Sintering (SPS) and high-energy ball milling (HEBM), following heat treatments (calcining and sintering), in oxidative (O2) atmosphere have been used to prepare single phase highly densified KNN (“pure” and Cu2+ or Li1+ doped), with theoretical densities ρth > 97% and BTNN ceramics (ρth ~ 90%), respectively. Using BTTN ceramics with a P4mm perovskite-like structure, we showed that by increasing the NaNbO3 content, the ferroelectric properties change from having a relaxor effect to an almost “normal” ferroelectric character, while the tetragonality and grain size increase and the shear piezoelectric coefficients (k15, g15 and d15) improve. For KNN ceramics, the results reveal that the values for remanent polarization as well as for most of the coercive field are quite similar among all compositions. These facts evidenced that Cu2+ may be incorporated into the A and/or B sites of the perovskite structure, having both hardening and softening effects. PMID:28773304

  3. Method and apparatus for radio frequency ceramic sintering

    Science.gov (United States)

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  4. Spark Plasma Sintered AlN-BN Composites and Its Thermal Conductivity

    NARCIS (Netherlands)

    Zhao Haiyang, [No Value; Wang Weimin, [No Value; Wang Hao, [No Value; Fu Zhengyi, [No Value

    2008-01-01

    A series of samples of hexagonal boron nitride-aluminum nitride ceramic composites with different amounts of CaF(2) as sintering aid were prepared by spark plasma sintered at 1700-1850 degrees C for 5 min. The addition of CaF(2) effectively lowered the sintering temperature and promoted the

  5. 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

  6. Reaction sintering of a zirconia-containing barium feldspar ceramic

    International Nuclear Information System (INIS)

    Nordmann, A.; Cheng, Y-B.; Muddle, B. C.

    1996-01-01

    Zircon (ZrSiO 4 ) is a natural mineral resource known to react with certain oxides to produce a dispersion of zirconia particles within ceramic or glass-ceramic matrices. Barium aluminosilicates, particularly the celsian polymorphs of BaO- Al 2 O 3 2SiO 2 display oxidation resistance and refractory characteristics commensurate with the properties required of high temperature materials. Such properties, coupled with the high melting point of ZrO 2 (2680 deg C), suggest that barium aluminosilicates and zirconia are an ideal combination from which to fabricate high temperature materials. A recent study has indicated that a barium aluminosilicate containing up to 40mol% ZrO 2 can be prepared via a sol-gel process. However, the desire to utilise a natural resource in the form of zircon in the present work has led to the choice of reaction sintering as an alternative processing route. The current work was undertaken to investigate the possibility of forming a zirconia-containing barium feldspar composite material using the reaction sintering of zircon and assuming the following stoichiometric reaction: 2ZrSiO 4 + BaCO 3 + Al 2 O 3 → 2ZrO 2 + BaO-Al 2 O 3 -2SiO 2 + CO 2 ↑. The reaction sintering of zircon with alumina and barium carbonate produces a composite material comprising distributed ZrO 2 in a continous barium feldspar matrix. Yttria added during processing allows a significant fraction of the ZrO 2 to be retained as tetragonal phase to room temperature and thus the potential for a measure of transformation toughening

  7. 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.

  8. Microstructure evolution during pressureless sintering of bulk oxide ceramics

    Directory of Open Access Journals (Sweden)

    Karel Maca

    2009-06-01

    Full Text Available The author’s experience concerning the infl uence of the choice of different pressureless heating schedules on the fi nal microstructure of oxide ceramic materials is summarized in the paper. Alumina, ceria, strontium titanate, as well as tetragonal (3 mol% Y2O3 and cubic (8 mol% Y2O3 zirconia were cold isostatically pressed or injection moulded and pressureless sintered with different heating schedules – namely with Constant-Rate of Heating with different dwell temperatures (CRH, with Rate-Controlled Sintering (RCS and with Two-Step Sintering (TSS. It was examined whether some of these three sintering schedules, with the same fi nal density achieved, can lead to a decrease of the grain size of sintered ceramics. The results showed that only TSS (and only for selected materials brought significant decrease of the grain size.

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

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

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

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

    Science.gov (United States)

    Malič, Barbara; Koruza, Jurij; Hreščak, Jitka; Bernard, Janez; Wang, Ke; Fisher, John G.; Benčan, Andreja

    2015-01-01

    The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). PMID:28793702

  11. Sintering of silicon nitride ceramics with magnesium silicon nitride and yttrium oxide as sintering aids

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J; Xu, J Y [Shanghai Institute of Technology, Shanghai 200235 (China); Peng, G H [Guangxi Normal University, Guilin 541004, Guangxi (China); Zhuang, H R; Li, W L; Xu, S Y [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Mao, Y J, E-mail: guojianjiang@sit.edu.cn [Shanghai University, Shanghai 200444 (China)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramics had been produced through pressureless sintering and hot-pressing sintering with MgSiN{sub 2}-Y{sub 2}O{sub 3} or only MgSiN{sub 2} as sintering aids. The influences of the amount of MgSiN{sub 2} and Y{sub 2}O{sub 3} and sintering methods on the properties of Si{sub 3}N{sub 4} ceramics were investigated. The results show that the bend strength of Si{sub 3}N{sub 4} ceramic fabricated through pressureless sintering at 1820 deg. C for 4 h with 5.6 wt.% MgSiN{sub 2}-15.8 wt.% Y{sub 2}O{sub 3} as sintering additive could achieve 839 MPa. However, the bend strength of Si{sub 3}N{sub 4} ceramic produced by hot-pressing sintering at 1750 deg. C for 1 h under uniaxial pressure of 20 MPa with 4.76 wt.% MgSiN{sub 2} was 1149 MPa. The thermal conductivity of the Si{sub 3}N{sub 4} ceramic 2 3 4 could reach to 129 W{center_dot}m{sup -1{center_dot}}K{sup 1}. The present work demonstrated that MgSiN{sub 2} aids and hot-pressing sintering were effective to improve the thermal conductivity of Si{sub 3}N{sub 4} ceramic.

  12. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    Fareed, Ali [Honeywell Advanced Composites Inc. (HACI), Newark, DE (United States); Craig, Phillip A. [Honeywell Advanced Composites Inc. (HACI), Newark, DE (United States)

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  13. [Characterization of alumina adobe and sintered body of GI-infiltrated ceramic].

    Science.gov (United States)

    Wang, H; Chao, Y; Liao, Y; Liang, X; Zhu, Z; Gao, W

    2001-06-01

    This study was conducted to elucidate the mechanism of formation of porous structure by investigating the porosity of the alumina adobe and sintered body of GI-II Infiltrate Ceramic, and its role in strengthening and toughening this kind of ceramic composite. The alumina powder size-mass distribution was obtained by BI-XDC powder size analysis device; the open pore parameters of alumina adobe and sintered body were analyzed using the mercury pressure method. Their fracture surfaces were observed under scanning electronic microscope. Fine powder had two main size groups of 0.09-0.1 micron and 0.2-0.5 micron, respectively, and coarse powder, with size between 1.5 to 4.5 microns, occupied the majority of powder mass. Alumina adobe's pores became larger after sintering. The median pore radii of adobe and sintered body were 0.2531 micron and 0.3081 micron, respectively; the average pore radii changed from 0.0956 micron to 0.1102 micron. Under scanning electronic microscope, fine alumina powders were fused partially together and their surfaces were blunted, but coarse powders did not show such phenomena. The alumina size distribution contributes to the formation of porous structure of alumina sintered body. This porous structure is not only the shape skeleton but also the mechanical skeleton of GI-II Infiltrated Ceramic. It plays an important role in raising the mechanical properties of this kind of ceramic composite.

  14. Process for making a ceramic composition for immobilization of actinides

    Science.gov (United States)

    Ebbinghaus, Bartley B.; Van Konynenburg, Richard A.; Vance, Eric R.; Stewart, Martin W.; Walls, Philip A.; Brummond, William Allen; Armantrout, Guy A.; Herman, Connie Cicero; Hobson, Beverly F.; Herman, David Thomas; Curtis, Paul G.; Farmer, Joseph

    2001-01-01

    Disclosed is a process for making a ceramic composition for the immobilization of actinides, particularly uranium and plutonium. The ceramic is a titanate material comprising pyrochlore, brannerite and rutile. The process comprises oxidizing the actinides, milling the oxides to a powder, blending them with ceramic precursors, cold pressing the blend and sintering the pressed material.

  15. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  16. Microwave sintering of nanophase ceramics without concomitant grain growth

    Science.gov (United States)

    Eastman, Jeffrey A.; Sickafus, Kurt E.; Katz, Joel D.

    1993-01-01

    A method of sintering nanocrystalline material is disclosed wherein the nanocrystalline material is microwaved to heat the material to a temperature less than about 70% of the melting point of the nanocrystalline material expressed in degrees K. This method produces sintered nanocrystalline material having a density greater than about 95% of theoretical and an average grain size not more than about 3 times the average grain size of the nanocrystalline material before sintering. Rutile TiO.sub.2 as well as various other ceramics have been prepared. Grain growth of as little as 1.67 times has resulted with densities of about 90% of theoretical.

  17. Kiln furniture for sintering electronic ceramics. Ceramics shosei jigu (doguzai) ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Fushimi, T.; Shibata, S. (Toshiba Ceramics Co. Ltd., Tokyo (Japan))

    1994-05-01

    This paper summarizes refractory jigs used in manufacturing electronic ceramics. Jigs used vary with types of sintering kilns. Sintering kilns include pusher kiln, trolley kiln, roller hearth kiln, batch kiln, and HIP. The paper describes jigs by electronic ceramics materials. Ferrites are sintered in a pusher kiln, where such jigs are used as a base plate, stanchions, shelf plates, saggers, and a setter. Jigs that contact with ferrite are demanded not to give such adverse effects to materials to be sintered as crystal growth. Soft ferrites of Mn/Zn and Ni/Zn systems use jigs of pure alumina and zirconia nature, while large-size soft ferrites use setters with rough surface. A barium titanate system as a ceramic dielectric uses a zirconia jig, and materials containing Pb and Bi such as for varistors use magnesia and spinel jigs. Alumina porcelain substrates use mullite or high-alumina pusher kilns and alumina jigs. 4 refs., 1 fig., 4 tabs.

  18. Novel sintered ceramic materials incorporated with EAF carbon steel slag

    Science.gov (United States)

    Karayannis, V.; Ntampegliotis, K.; Lamprakopoulos, S.; Papapolymerou, G.; Spiliotis, X.

    2017-01-01

    In the present research, novel sintered clay-based ceramic materials containing electric arc furnace carbon steel slag (EAFC) as a useful admixture were developed and characterized. The environmentally safe management of steel industry waste by-products and their valorization as secondary resources into value-added materials towards circular economy have attracted much attention in the last years. EAF Carbon steel slag in particular, is generated during the manufacture of carbon steel. It is a solid residue mainly composed of rich-in- Fe, Ca and Si compounds. The experimental results show that the beneficial incorporation of lower percentages of EAFC up to 6%wt. into ceramics sintered at 950 °C is attained without significant variations in sintering behavior and physico-mechanical properties. Further heating up to 1100 °C strongly enhances the densification of the ceramic microstructures, thus reducing the porosity and strengthening their mechanical performance. On the other side, in terms of thermal insulation behavior as well as energy consumption savings and production cost alleviation, the optimum sintering temperature appears to be 950 °C.

  19. Manipulating microstructure and mechanical properties of CuO doped 3Y-TZP nano-ceramics using spark-plasma sintering

    NARCIS (Netherlands)

    Ran, S.; Vleugels, Jozef; Huang, Shuigen; Vanmeensel, Kim; Blank, David H.A.; Winnubst, Aloysius J.A.

    2010-01-01

    Nano-powder composites of 3Y-TZP doped with 8 mol% CuO were processed by spark-plasma sintering (SPS). A 96% dense composite ceramic with an average grain size of 70 nm was obtained by applying the SPS process at 1100 °C and 100 MPa for 1 min. In contrast to normal, pressureless, sintering during

  20. 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.

  1. Flame-sintered ceramic exoelectron dosimeter samples

    International Nuclear Information System (INIS)

    Petel, M.; Holzapfel, G.

    1979-01-01

    New techniques for the preparation of integrating solid state dosimeters, particularly exoelectron dosimeters, have been initiated. The procedure consists in melting the powdered dosimeter materials in a hot, fast gas stream and depositing the ceramic layer. The gas stream is generated either through a chemical flame or by an electrical arc plasma. Results will be reported on the system Al 2 O 3 /stainless steel as a first step to a usable exoelectron dosimeter

  2. Influence of Bi2O3 on sintering and crystallization of cordierite ceramics

    Directory of Open Access Journals (Sweden)

    Đorđević N.

    2005-01-01

    Full Text Available The influence of Bi2O3 on the process of cordierite ceramics preparation, 2MgO-2Al2O3-5SiO2 (MAS was investigated. The following binary systems were used for the presented research: MgO/Bi2O3 (sintered at 820ºC and 1100ºC, Al2O3/Bi2O3 and SiO2/Bi2O3 (sintered at 1100ºC. The composition of these systems consisted of 80% of oxide and 20% Bi2O3. The effects of sintering, composition and morphology were investigated by X-ray diffraction, scanning electron microscopy and EDS analysis. It has been found that Bi2O3, besides a liquid phase, forms intermediary unstable compounds with MgO and Al2O3. MAS ceramics were sintered with 10% Bi2O3 at 1000ºC, 1100ºC and 1200ºC. .

  3. Effects of Sintering on the Thermal and Optical Properties of Zinc Oxide Ceramic

    Science.gov (United States)

    Tabasco-Novelo, C.; May-Crespo, J.; Ramírez-Rincón, J. A.; Forero-Sandoval, I. Y.; Rodríguez-Gattorno, G.; Quintana, P.; Alvarado-Gil, J. J.

    2018-02-01

    Microstructure and composition are factors determining heat transfer in ZnO ceramic materials, which define the performance of the material after Joule heating, generated by electron transport. In this study, photothermal radiometry was applied to investigate the influence of the sintering temperature, ranging from 800 {°}C to 1300 {°}C, by measuring the thermal diffusivity and thermal conductivity at room temperature, of commercial and sol-gel ZnO pellets. Our results show that the values of these thermal properties for both types of ZnO increase when the sintering temperature increases, displaying maximum energy dissipation at 1200 {°}C. Additionally, the role of the sintering temperature on the optical properties was also analyzed using diffuse reflectance spectroscopy, and from these data the optical band-gap was obtained.

  4. Mechanical Characterization of Zirconia Ceramic Composite

    Directory of Open Access Journals (Sweden)

    Jin Kelvin Chew Wai

    2018-01-01

    Full Text Available In this day and age, zirconia ceramics are used widely in the medical field as biomaterials for the replacement of damaged body parts. This is because zirconia is one of the closest replacements for bone tissue. However, there were a few cases regarding the failure of zirconia ceramic hip transplants. To overcome this issue, composite materials are being studied as they are able to combine different properties which are not present in a material. This study of Y-TZP/stainless steel 316 composite is carried out with the idea of providing a solution for failure of zirconia implants and also an improvement in biomaterials which will benefit the biomedical world. The study aims to determine the effects on how the increasing of stainless-steel content in the composite will affect the relative density, Vickers hardness, fracture toughness and ageing resistance of the Y-TZP/stainless steel 316 composite. To carry out the research, the composite samples were prepared by mixing the powder of each samples according to their determined content with ethanol. After the powders were mixed, the powders were then pressed, followed by undergoing a Cold Isostatic Press process (CIP and then it underwent sintering at its determined temperature. After sintering, the samples underwent grinding and polishing before being ready for testing. The outcomes of the research showed that as the sintering temperature and the content of stainless-steel increase in the composite, the fracture toughness and ageing resistance improved while the Vickers hardness and relative density decreased.

  5. Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

    Directory of Open Access Journals (Sweden)

    Feng Wang

    2017-06-01

    Full Text Available Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering. Poly (vinyl alcohol (PVA was added as binder and pore morphology controller in this work. The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries. Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics. The solid content of slurries and PVA content varied from 60 to 67.5 wt% and 2–6 wt%, respectively. Besides, the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 °C. Porous SiC ceramics with an average porosity of 42.72%, flexural strength of 59.28 MPa were obtained at 2150 °C from 67.5 wt% slurries with 2 wt% PVA.

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

    Science.gov (United States)

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

    2017-09-01

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

  7. Effect of mechanical cycling on the flexural strength of densely sintered ceramics

    NARCIS (Netherlands)

    Itinoche, Koiti Marco; Ozcan, Mudu; Bottino, Marco Antonio; Oyafuso, Denise

    2006-01-01

    Objectives. The aim of this study was to evaluate the effect of mechanical cycling on the biaxial flexural strength of two densely sintered ceramic materials. Methods. Disc shaped zirconia (In-Ceram Zirconia) and high alumina (Procera AllCeram) ceramic specimens (diameter: 15 min and thickness: 1.2

  8. Fabrication and properties of YBa2Cu3O7- x ceramics at different sintering temperatures

    Science.gov (United States)

    Prayoonphokkharat, Poom; Jiansirisomboon, Sukanda; Watcharapasorn, Anucha

    2013-07-01

    The influence of sintering temperatures on the fabrication of YBCO ceramics under normal air atmosphere was investigated in this study. YBCO ceramics were prepared by mixing starting compounds of Y2O3, BaCO3 and CuO powders, which were calcined at 850°C for 12 h. The powder was pelletized and sintered at different temperatures, from 930°C-1050°C, for 12 h. Phase identification was carried out by x-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study microstructure and chemical composition. In addition, density, Vickers hardness properties, the change of resistance and dielectric properties with temperature above T c were investigated. It was found that, at 950°C-1000°C, high-purity YBCO ceramic could be obtained. Outside this temperature range, either impurity phases were present or melting occurred. SEM images showed that grain size, which ranged from 1.5-2.5 µm, and hardness were related to density and liquid phase present in the sample. Furthermore, the sintering temperature affected oxygen content which, in turn, determined the conductive or semi-conductive behavior observed by electrical property measurement.

  9. Effects of Laser Treatment on the Bond Strength of Differently Sintered Zirconia Ceramics.

    Science.gov (United States)

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

    2016-07-01

    The purpose of this study was to investigate the effects of carbon dioxide (CO2) and Erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiations on the shear bond strength (SBS) of differently sintered zirconia ceramics to resin cement. Eighty zirconia specimens were prepared, sintered in two different periods (short = Ss, long = Ls), and divided into four treatment groups (n = 10 each). These groups were (a) untreated (control), (b) Er:YAG laser irradiated with 6 W power for 5 sec, (c) CO2 laser with 2 W power for 10 sec, (d) CO2 laser with 4 W power for 10 sec. Scanning electron microscope (SEM) images were recorded for each of the eight groups. Eighty composite resin discs (3 × 3 mm) were fabricated and cemented with an adhesive resin cement to ceramic specimens. The SBS test was performed after specimens were stored in water for 24 h by an universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed with two way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test (α = 0.05). According to the ANOVA, the sintering time, surface treatments and their interaction were statistically significant (p  0.05). Variation in sintering time from 2.5 to 5.0 h may have influenced the SBS of Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Although CO2 and Er:YAG laser irradiation techniques may increase the SBS values of both tested zirconia ceramics, they are recommended for clinicians as an alternative pretreatment method.

  10. Compaction of lithium-silicate ceramics using spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Kubatík, Tomáš František; Lukáč, František; Mušálek, Radek; Brožek, Vlastimil; Stehlíková, K.; Chráska, Tomáš

    2017-01-01

    Roč. 61, č. 1 (2017), s. 40-44 ISSN 0862-5468 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Li2Si2O5 * Li2SiO3 * Spark plasma sintering (SPS) * Quantitative Rietveld refinement * X-ray diffraction (XRD) Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 0.439, year: 2016 http://www.ceramics-silikaty.cz/index.php?page=cs_detail_doi&id=789

  11. Preparation and characterization of porous alumina-zirconia composite ceramics

    Czech Academy of Sciences Publication Activity Database

    Pabst, W.; Gregorová, E.; Sedlářová, I.; Černý, Martin

    2011-01-01

    Roč. 31, č. 14 (2011), s. 2721-2731 ISSN 0955-2219. [International Conference on Ceramic Processing Science /11./. Zürich, 29.08.2010-01.09.2010] Institutional research plan: CEZ:AV0Z30460519 Keywords : sintering * slip casting * composites Subject RIV: JI - Composite Materials Impact factor: 2.353, year: 2011

  12. Glass reactive sintering as an alternative route for the synthesis of NZP glass-ceramics

    International Nuclear Information System (INIS)

    Chenu, Sebastien; Lebullenger, Ronan; Benard-Rocherulle, Patricia; Calvez, Guillaume; Guillou, Olivier; Rocherulle, Jean; Kidari, Abdessamad; Pomeroy, Mickael J.; Hampshire, Stuart

    2012-01-01

    The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal expansion properties or interesting ionic conductivity. However, NZP is difficult to fabricate into monoliths because it requires both high temperatures and long sintering times. An alternative low temperature route to obtain a tungsten (IV) and tin (IV) containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass. Using a microwave oven, a glass with the appropriate composition in the NaPO 3 -Sn(II)O-W(VI)O 3 ternary diagram is prepared by a conventional melting and casting technique. After crushing, the glass powder is pressed at room temperature. The green pellet is cured during various times at temperatures where glass reactive sintering takes place. From XRD and DTA experiments, we have shown that different parameters influence the achievement of NZP phase. Consequently, specific conditions, such as (i) initial glass composition, (ii) equimolar quantities of SnO and WO 3 , (iii) glass particle size lower than 100 μ m, and (iv) curing conducted under air, are required to obtain a glass-ceramic with a single crystalline phase with the NZP-type crystal structure. (authors)

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

    Directory of Open Access Journals (Sweden)

    Mondiu Olayinka DUROWOJU

    2017-06-01

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

  14. Effect of sintering atmosphere on the electrical and optical properties of (ZnO)1-x(MnO2)x NTCR ceramics

    International Nuclear Information System (INIS)

    Yan Xiaoxing; Xu Guoyue

    2009-01-01

    Nominal composition of (ZnO) 1-x (MnO 2 ) x (0.005≤x≤0.2) ceramics have been prepared by the standard solid-state reaction method in three different sintering atmospheres: Ar, air, and reductive atmosphere. The effect of sintering atmosphere on the electron spin resonance (ESR), negative temperature coefficient of resistivity (NTCR), and photoluminescence (PL) properties of (ZnO) 1-x (MnO 2 ) x ceramics has been investigated in detail. The results demonstrate that the sintering atmosphere has significant effects on the ESR signals of (ZnO) 1-x (MnO 2 ) x ; the NTCR of the samples sintered in air is larger than those sintering in Ar and reductive atmosphere; the deep-level PL related to oxygen vacancy increases when sintered in the reductive atmosphere.

  15. Ceramic composites: Enabling aerospace materials

    Science.gov (United States)

    Levine, S. R.

    1992-01-01

    Ceramics and ceramic matrix composites (CMC) have the potential for significant impact on the performance of aerospace propulsion and power systems. In this paper, the potential benefits are discussed in broad qualitative terms and are illustrated by some specific application case studies. The key issues in need of resolution for the potential of ceramics to be realized are discussed.

  16. Effects of varied porosity on the physic-mechanical properties of sintered ceramic from Ifon clay

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE

    2017-12-01

    Full Text Available The effects of saw dust admixture on the physic-mechanical properties of sintered clay bonded carbonized palm kernel shell ceramic was investigated. Composite mixtures of powdered carbonized palm kernel shell and clay from Ifon deposit were produced using equal amount of clay and carbonized palm kernel shell. These were then mixed with varied amount of saw dust (0%, 5% and 10% in a ball mill for 6 hours. From this standard sample specimens were produced using uniaxial compression after mixing each mixture with 10% moisture of clay contents. The compressed samples were sintered at 9500C and soaked for one hour. The sintered samples were characterized for various physic-mechanical properties using state of the art equipment’s. The fired samples were also characterized using ultra-high-resolution field emission scanning electron microscope (UHR-FEGSEM equipped with energy dispersive spectroscopy (EDX. It was observed that the apparent porosity and water absorption of the clay bonded carbonized palm kernel shell ceramic increased with increased amount of saw dust admixture, cold crushing strength, Young’ modulus of elasticity and absorbed energy of the sample reduced with increased amount of saw dust admixture. It was concluded that the sample with 0% saw dust admixture is judged to possess optimum physic-mechanical properties.

  17. [Influence on microstructure of dental zirconia ceramics prepared by two-step sintering].

    Science.gov (United States)

    Jian, Chao; Li, Ning; Wu, Zhikai; Teng, Jing; Yan, Jiazhen

    2013-10-01

    To investigate the microstructure of dental zirconia ceramics prepared by two-step sintering. Nanostructured zirconia powder was dry compacted, cold isostatic pressed, and pre-sintered. The pre-sintered discs were cut processed into samples. Conventional sintering, single-step sintering, and two-step sintering were carried out, and density and grain size of the samples were measured. Afterward, T1 and/or T2 of two-step sintering ranges were measured. Effects on microstructure of different routes, which consisted of two-step sintering and conventional sintering were discussed. The influence of T1 and/or T2 on density and grain size were analyzed as well. The range of T1 was between 1450 degrees C and 1550 degrees C, and the range of T2 was between 1250 degrees C and 1350 degrees C. Compared with conventional sintering, finer microstructure of higher density and smaller grain could be obtained by two-step sintering. Grain growth was dependent on T1, whereas density was not much related with T1. However, density was dependent on T2, and grain size was minimally influenced. Two-step sintering could ensure a sintering body with high density and small grain, which is good for optimizing the microstructure of dental zirconia ceramics.

  18. Colloidal forming of metal/ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Herencia, A.J.; Gutierrez, C.A.; Millan, A.J.; Nieto, M.I.; Moreno, R. [Inst. de Ceramica y Vidrio, Madrid (Spain)

    2002-07-01

    Metal/Ceramic composites have very attractive properties as either structural or electronic materials. For certain applications, complex microstructures and shapes are required. Colloidal processing of ceramics has proved to provide better properties and allows to obtain near net complex shaped parts. However colloidal processing has not received a similar attention in powder metallurgy. This work deals with the colloidal approach to the forming of metallic and metal/ceramic composites in an aqueous medium. Rheological behavior of concentrated pure nickel, nickel/alumina and nickel/zirconia suspensions is studied and optimized for obtaining flat surfaces or near net shaped parts by tape casting and gel casting respectively. In each case the influence of the processing additives (acrylic binders for tape casting and carrageenans for gel casting) on the rheological behavior of the slurries is determined. Pure nickel and nickel/ceramic composites with different compositions have been prepared. Static and dynamic sintering studies were performed at different conditions in order to control the porosity and microstructure of the final bodies, which were characterized by optical microscopy. (orig.)

  19. Density determination of sintered ceramic nuclear fuel materials

    International Nuclear Information System (INIS)

    Landspersky, H.; Medek, J.

    1980-01-01

    The feasibility was tested of using solids for pycnometric determination of the density of uranium dioxide-based sintered ceramic fuel materials manufactured by the sol-gel method in the shape of spherical particles of 0.7 to 1.0 mm in size and of particles smaller than 200 μm. For fine particles, this is the only usable method of determining their density which is a very important parameter of the fine fraction when it is employed for the manufacture of fuel elements by vibration compacting. The method consists in compacting a mixture of pycnometric material and dispersed particles of uranium dioxide, determining the size and weight of the compact, and in calculating the density of the material measured from the weight of the oxide sample in the mixture. (author)

  20. Formation of porous wollastonite-based ceramics after sintering with yeast as the pore-forming agent

    Directory of Open Access Journals (Sweden)

    Obradović Nina

    2017-01-01

    Full Text Available In this paper, synthesis of porous wollastonite-based ceramics was reported. Ceramic precursor, methylhydrocyclosiloxane, together with micro-sized CaCO3, was used as starting material. After 20 min of ultrasound treatment, and calcination at 250 oC for 30 min, yeast as a pore-forming agent was added to the as-obtained powders. Sintering regime was set up based on the results obtained by differential thermal analysis. Prepared mixture was pressed into pallets and sintered at 900 oC for 1 h. After the sintering regime, porous wollastonite-based ceramics was obtained. The phase composition of the sintered samples as well as microstructures was analyzed by X-ray diffraction method and SEM. In a batch test, the influence of pH, contact time and initial ion concentration on adsorption efficiency of As+5, Cr+6, and phosphate ions on synthesized wollastonite-based ceramics were studied. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber-Morris model that predicted intra-particle diffusion as a rate-controlling step of overall process. High adsorption capacities 39.97, 21.87, and 15.29 mgg-1 were obtained for As+5, Cr+6, and phosphate ions, respectively.

  1. 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 (presin cement and differently sintered zirconium-oxide ceramics. Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  2. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... C showing resistor behaviour even at low carbon content (1 wt%). In this work, ceramic carbon composites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology of the sintered samples was characterized by field emission gun (FEG) electron ...

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

    Science.gov (United States)

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

    2016-02-01

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

  4. Effect of sintering process parameters on the properties of 3Y-PSZ ceramics

    International Nuclear Information System (INIS)

    Chu, H L; Chen, R S; Wang, C L; Hwang, W S; Lee, H E; Sie, Y Y; Wang, M C

    2013-01-01

    The effect of sintering process parameters on the properties of 3 mol% yttria partially stability zirconia (3Y-PSZ) ceramics has been investigated. The relative density of the sintered pellet rapidly increases from 70.5 to 93.6% with rose temperature from 1473 to 1573 K. In addition, the relative density only slightly increases from 94.9 to 96.6 %, when rose sintered temperature from 1573 to 1773 K. This result shows that no significant influence on the densification behavior when sintering at 1573 to 1773 K for 2 h. The Vickers hardness and toughness also increase with the sintered temperature

  5. 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.

  6. Properties of Carbide Ceramics from Gelcasting and Pressure-less Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Dongliang; Zhang Jingxian, E-mail: dljiang@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Shanghai 200050 (China)

    2011-10-29

    In this paper, the properties of carbide ceramics (SiC, and B{sub 4}C) from aqueous gelcasting and pressure-less sintering were studied systematically. The optimized sintering process was achieved via a series of experiments with effective control of grain size and microstructure for developing high performance ceramics. SiC samples can be pressure-less sintered to 98% TD with B{sub 4}C and C as the sintering additives. The samples showed excellent mechanical properties, homogeneous microstructure and improved reliability. B{sub 4}C samples can also be pressure-less sintered with the relative density around 96%. Results showed that gelcasting is a reliable process for the manufacturing of carbide ceramics with satisfied properties.

  7. Physics and Technology of Transparent Ceramic Armor: Sintered Al2O3 vs Cubic Materials

    National Research Council Canada - National Science Library

    Krell, Andreas; Hutzler, Thomas; Klimke, Jens

    2006-01-01

    Sintered sub-micrometer alumina (alpha-Al2O3) is the hardest transparent armor. However, its trigonal structure gives rise to a strong thickness effect that makes thicker components translucent. Cubic ceramics (no birefringence...

  8. An investigation in texturing high Tc superconducting ceramics by creep sintering

    International Nuclear Information System (INIS)

    Regnier, P.; Deschanels, X.; Maurice, F.; Schmirgeld, L.; Aguillon, C.; Senoussi, S.; Mac Carthy, M.; Tatlock, G.J.

    1991-01-01

    We study in detail the possibility of high-T c superconducting ceramics texturing by high pressing them during sintering. We show texture variations as a function of the applied load, of the deformation, of the temperature, and of the sintering stage length, of the rate of variation of temperature, of the material nature in contact with ceramic and of the original powder quality. We present results obtained by optical microscopy, electronic microscopy, X-rays, and local chemical analysis

  9. 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.

  10. Self-Growth of Centimeter-Scale Single Crystals by Normal Sintering Process in Modified Potassium Sodium Niobate Ceramics

    Science.gov (United States)

    Ahn, Cheol-Woo; Lee, Ho-Yong; Han, Guifang; Zhang, Shujun; Choi, Si-Young; Choi, Jong-Jin; Kim, Jong-Woo; Yoon, Woon-Ha; Choi, Joon-Hwan; Park, Dong-Soo; Hahn, Byung-Dong; Ryu, Jungho

    2015-01-01

    In this manuscript, an interesting phenomenon is reported. That is the self-growth of single crystals in Pb-free piezoelectric ceramics. These crystals are several centimeters in size. They are grown without any seed addition through a normal sintering process in modified potassium sodium niobate ceramics. It has been achieved by the composition designed to compensate the Na+ loss which occurs during the liquid phase sintering. The composition of the crystals is (K0.4925Na0.4925−xBa0.015+x/2)Nb0.995+xO3 [x is determined by the Na+ loss, due to Na2O volatilization]. These crystals have high piezoelectric voltage coefficients (g33, 131 10−3Vm/N), indicating that they are good candidates for piezoelectric sensors and energy harvesting devices. We hope that this report can offer the opportunity for many researchers to have an interest in these crystals. PMID:26631973

  11. Comparative studies on mechanical properties of WC-Co composites sintered by SPS and conventional techniques

    Directory of Open Access Journals (Sweden)

    Pristinskiy Yuri

    2017-01-01

    Full Text Available Spark plasma sintering (SPS is an extremely fast solidification technique for compounds that are difficult to sinter within the material group metals, ceramics, or composites thereof, SPS uses a uniaxial pressure and a very rapid heating cycle to consolidate these materials. With SPS the main benefit is the ability to control the WC grain size due to the short sintering times at high temperature. Additionally, its allows to avoid negative reactions between WC and cobalt and to minimize the formation of undesirable phases in sintered composites. The WC-6wt.% Co cermet prepared by SPS processing achieves the enhanced mechanical properties with the hardness of 18.3 GPa and the fracture toughness of 15.5 MPa·m1/2 in comparison to standard reference tungsten carbide/cobalt material.

  12. Sinter recrystalization and properties evaluation of glass-ceramic from waste glass bottle and magnesite for extended application

    Directory of Open Access Journals (Sweden)

    As'mau Ibrahim Gebi

    2016-12-01

    Full Text Available In a bid to address environmental challenges associated with the management of waste Coca cola glass bottle, this study set out to develop glass ceramic materials using waste coca cola glass bottles and magnesite from Sakatsimta in Adamawa state. A reagent grade chrome (coloring agent were used to modify the composition of the coca cola glass bottle;  X-ray fluorescence(XRF, X-ray diffraction (XRD and Thermo gravimetric analysis (TGA were used to characterize raw materials, four batches GC-1= Coca cola glass frit +1%Cr2O3, GC-2=97% Coca cola glass frit+ 2% magnesite+1%Cr2O3, GC-3=95% Coca cola glass frit+ 4%magnesite+1%Cr2O3, GC-4=93%Coca cola glass frit+ 6%magnesite+ 1%Cr2O3 were formulated and prepared. Thermal Gradient Analysis (TGA results were used as a guide in selection of three temperatures (7000C, 7500C and 8000C used for the study, three particle sizes -106+75, -75+53, -53µm and 2 hr sintering time were also used, the sinter crystallization route of glass ceramic production was adopted. The samples were characterized by X-ray diffraction (XRD and Scanning Electron Microscope (SEM, the density, porosity, hardness and flexural strength of the resulting glass ceramics were also measured. The resulting glass ceramic materials composed mainly of wollastonite, diopside and anorthite phases depending on composition as indicated by XRD and SEM, the density of the samples increased with increasing sintering temperature and decreasing particle size. The porosity is minimal and it decreases with increasing sintering temperature and decreasing particle size. The obtained glass ceramic materials possess appreciable hardness and flexural strength with GC-3 and GC-4 having the best combination of both properties.

  13. Microwave-assisted sintering of non-stoichiometric strontium bismuth niobate ceramic: Structural and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Rajveer [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India); Department of Physics, Atmaram Sanatan Dharma College, University of Delhi, Dhaula Kuan, New Delhi 110021 (India); Luthra, Vandna [Department of Physics, Gargi College, University of Delhi, Siri Fort Road, New Delhi 110049 (India); Tandon, R.P., E-mail: ram_tandon@hotmail.com [Department of Physics and Astrophysics, University of Delhi, New Delhi 110007 (India)

    2016-11-01

    In recent years the microwave sintering has been utilized for the synthesis of materials in enhancement of the properties. In this paper strontium bismuth niobate (Sr{sub 0.8}Bi{sub 2.2}Nb{sub 2}O{sub 9}:SBN) bulk ceramic has been synthesized by microwave reactive sintering and conventional heating techniques. A relative density of 99.6% has been achieved for microwave sintered SBN, which is higher than that of (98.81%) conventionally sintered SBN. The phase formation of SBN synthesized by both processes has been confirmed by X-ray diffraction (XRD). The surface morphology of SBN was observed by scanning electron microscopy (SEM). The microstructure was found to be more uniform in case of SBN sintered by microwave sintering. The dielectric properties of SBN were studied as a function of frequency in the temperature range of 30–500 °C. Both the samples synthesized by two different processes were found to follow Curie–Weiss law above the transition temperature. The Curie temperature was found to be higher for microwave sintered SBN. The dielectric constant and the transition temperature were observed to be higher for SBN ceramic synthesized by microwave sintering technique. The ac and dc activation energy values were also found to be higher for microwave sintered SBN as compared to conventional sintering technique.

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

    Directory of Open Access Journals (Sweden)

    Hashmi M. U.

    2013-12-01

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

  15. Reactive sintering of ceramic lithium ion electrolyte membranes

    Science.gov (United States)

    Badding, Michael Edward; Dutta, Indrajit; Iyer, Sriram Rangarajan; Kent, Brian Alan; Lonnroth, Nadja Teresia

    2017-06-06

    Disclosed herein are methods for making a solid lithium ion electrolyte membrane, the methods comprising combining a first reactant chosen from amorphous, glassy, or low melting temperature solid reactants with a second reactant chosen from refractory oxides to form a mixture; heating the mixture to a first temperature to form a homogenized composite, wherein the first temperature is between a glass transition temperature of the first reactant and a crystallization onset temperature of the mixture; milling the homogenized composite to form homogenized particles; casting the homogenized particles to form a green body; and sintering the green body at a second temperature to form a solid membrane. Solid lithium ion electrolyte membranes manufactured according to these methods are also disclosed herein.

  16. Thermal conductivity analysis of SiC ceramics and fully ceramic microencapsulated fuel composites

    International Nuclear Information System (INIS)

    Lee, Hyeon-Geun; Kim, Daejong; Lee, Seung Jae; Park, Ji Yeon; Kim, Weon-Ju

    2017-01-01

    Highlights: • Thermal conductivity of SiC ceramics and FCM pellets was measured and discussed. • Thermal conductivity of FCM pellets was analyzed by the Maxwell-Eucken equation. • Effective thermal conductivity of TRISO particles applied in this study was assumed. - Abstract: The thermal conductivity of SiC ceramics and FCM fuel composites, consisting of a SiC matrix and TRISO coated particles, was measured and analyzed. SiC ceramics and FCM pellets were fabricated by hot press sintering with Al 2 O 3 and Y 2 O 3 sintering additives. Several factors that influence thermal conductivity, specifically the content of sintering additives for SiC ceramics and the volume fraction of TRISO particles and the matrix thermal conductivity of FCM pellets, were investigated. The thermal conductivity values of samples were analyzed on the basis of their microstructure and the arrangement of TRISO particles. The thermal conductivity of the FCM pellets was compared to that predicted by the Maxwell-Eucken equation and the thermal conductivity of TRISO coated particles was calculated. The thermal conductivity of FCM pellets in various sintering conditions was in close agreement to that predicted by the Maxwell-Eucken equation with the fitted thermal conductivity value of TRISO particles.

  17. A review on the advances in 3D printing and additive manufacturing of ceramics and ceramic matrix composites for optical applications

    Science.gov (United States)

    Goodman, William A.

    2017-09-01

    This paper provides a review of advances in 3D printing and additive manufacturing of ceramic and ceramic matrix composites for optical applications. Dr. Goodman has been pioneering additive manufacturing of ceramic matrix composites since 2008. He is the inventor of HoneySiC material, a zero-CTE additively manufactured carbon fiber reinforced silicon carbide ceramic matrix composite, briefly mentioned here. More recently Dr. Goodman has turned his attention to the direct printing of ceramics for optical applications via various techniques including slurry and laser sintering of silicon carbide and other ceramic materials.

  18. Study on the performance of ceramic composite projectile penetrating into ceramic composite target

    Directory of Open Access Journals (Sweden)

    Rong-cheng Yi

    2017-08-01

    Full Text Available In order to study the performance of ceramic composite projectile penetrating into ceramic composite target, the contrast test and numerical simulations of the penetration of standard projectile and the ceramic composite projectile into a ceramic composite target were conducted. The results show that the penetration performance of ceramic composite projectile is obvious superior to that of standard projectile for ceramic composite target. The ceramic nose of ceramic composite projectile fully destroys the ceramic panels anterior to its following armor-piercing projectile body, thus maintaining the penetration ability of the following armor-piercing projectile body.

  19. Broadband dielectric response of AlN ceramic composites

    Directory of Open Access Journals (Sweden)

    Iryna V. Brodnikovska

    2014-03-01

    Full Text Available Aluminium nitride (AlN is considered as a substrate material for microelectronic applications. AlN ceramic composites with different amount of TiO2 (up to 4 vol.% were obtained using hot pressing at different sintering temperature from 1700 to 1900 °C. It was shown that milling of the raw AlN powder has strongly influence on sintering and improves densification. Broadband dielectric spectroscopy was used as a nondestructive method for monitoring of the ceramic microstructures. TiO2 additive affects the key properties of AlN ceramics. Thus, porosity of 0.1 %, dielectric permeability of σ = 9.7 and dielectric loss tangent of tanδ = 1.3·10-3 can be achieved if up to 2 vol.% TiO2 is added.

  20. Evaluation of clayey masses compositions starting from the residue incorporation of the red ceramic industry to obtain tubular ceramic membranes

    International Nuclear Information System (INIS)

    Silva, Adriano Lima da; Chaves, Alexsandra Cristina; Luna, Carlos Bruno Barreto; Neves, Gelmires de Araujo; Lira, Helio de Lucena

    2017-01-01

    The inappropriate residue disposal of red ceramic industry is very high. Nowadays, one of the major challenges is the investigation of processes to obtain alternative materials, enabling the use of these residues to manufacture new materials. This work's objective is to study clayey masses' compositions starting from the residue incorporation of the red ceramic industry to be used in tubular ceramic membranes. Two compositions of ceramic masses were established, composition A (50% of residue) and composition B (70% of residue). Granulometric analysis of the ceramic masses presented an average size of particles, what indicates membranes in the microfiltration scale. Another observed factor is related to the increase of residue amount, what favored a decrease in the ceramic mass' plasticity. A rise in the apparent porosity was also observed, probably because of a possible growing in the bigger pores numbers, due to the sintering high temperature and the elevation of residue quantity itself. (author)

  1. Microstructural, compositional and mechanical properties of the archaeological indigenous ceramics of Caninhas, Sao Paulo,Brazil

    International Nuclear Information System (INIS)

    Nakano, F.P.; Taguchi, S.P.; Ribeiro, R.B.; Rosa, S.J.L.; Bornal, W.G.; Queiroz, C.M.

    2009-01-01

    Archaeological ceramics contain infinity of data about social and cultural indigenous site Caninhas/SP. The ceramics present a gradient of color (ochre to dark gray), when from the surface to the center of the piece, indicating compositional variability caused by inefficient sintering carried out by indigenous peoples. It was analyzed the composition phases by X-rays diffraction (XRD) and mapping by EDS, identifying the illite, quartz and lutecite phases (ochre region) and illite, quartz, hydrated alumina and lutecite phases (dark gray region). The results of EDS confirmed the stages identified by X-rays diffraction and suggesting the presence of roots and scrap of ceramics sintered in the composition of indigenous ceramics, when compared by optical microscope and scanning electron microscope. Vickers hardness identified as fragile and heterogeneous are archaeological ceramics, reaching approximately 203 HV in the grains of silica and 16 HV in the ceramic matrix. (author)

  2. Compositionally Graded Multilayer Ceramic Capacitors.

    Science.gov (United States)

    Song, Hyun-Cheol; Zhou, Jie E; Maurya, Deepam; Yan, Yongke; Wang, Yu U; Priya, Shashank

    2017-09-27

    Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. Here, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (design of miniature filters and power converters.

  3. Experimental and finite element modeling study of co-sintering of multilayer, multifunctional ceramics

    Science.gov (United States)

    Wu, Kuan

    2007-12-01

    The co-sintering behavior of low temperature co-fired ceramics (LTCC) is investigated by combining experiment and simulation methods. The numerical method offers a way to provide quantitative information regarding the final sintered shape of multilayer ceramics, which can be used to optimize the design of multilayer, multifunctional components and help reduce tedious and expensive empirical design iterations. To predict the sintering behavior of LTCC, parameters in the viscoplastic constitutive equations for single materials (such as shear viscosity G, bulk viscosity K, and sintering stress sigma s, etc.) need to be known. An apparatus was constructed for in situ measurements of the longitudinal and radial shrinkage during free sintering and sinter forging experiments. Cylindrical samples of individual LTCC materials (DuPont 951AX, Heraeus CT-800, Ferro A6-S) were made. Free sintering and sinter-forging experiments have been performed at various heating rates and under different intermittently applied axial loads. Various methods for analyzing the data were used to extract those parameters and their dependence on temperature and relative density. The constitutive parameters obtained from experiments were then implemented in the user subroutine UMAT of the general-purpose finite element program ABAQUS to simulate the free sintering behavior of bi-layer structures (DU951/CT800) with different thickness ratios. The simulation results were then compared with the actual experimental results, which were obtained by free co-sintering bi-layer planar samples with different thickness ratios. Simulation results showed the finite element analysis was successful in predicting the shape changes and the stresses at different positions during sintering of bi-layer structures. This finite element model was also used to examine the sensitivity to various parameters of the sintering results, such as elastic Poisson's ratio v, Young's modulus E, sintering stress sigmas, shear and

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-07-19

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

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

    Directory of Open Access Journals (Sweden)

    Bin Qian

    2014-06-01

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

  6. Cyclic mechanical fatigue in ceramic-ceramic composites: an update

    International Nuclear Information System (INIS)

    Lewis, D. III

    1983-01-01

    Attention is given to cyclic mechanical fatigue effects in a number of ceramics and ceramic composites, including several monolithic ceramics in which significant residual stresses should be present as a result of thermal expansion mismatches and anisotropy. Fatigue is also noted in several BN-containing ceramic matrix-particulate composites and in SiC fiber-ceramic matrix composites. These results suggest that fatigue testing is imperative for ceramics and ceramic composites that are to be used in applications subject to cyclic loading. Fatigue process models are proposed which provide a rationale for fatigue effect observations, but do not as yet provide quantitative results. Fiber composite fatigue damage models indicate that design stresses in these materials may have to be maintained below the level at which fiber pullout occurs

  7. Radiation resistant ceramic matrix composites

    International Nuclear Information System (INIS)

    Jones, R.H.; Steiner, D.; Heinisch, H.L.; Newsome, G.A.; Kerch, H.M.

    1997-01-01

    Ceramic matrix composites are of interest for nuclear applications because of their high-temperature properties, corrosion resistance, fracture toughness relative to monolithic ceramics, and low neutron activation and after heat. Evaluations of the radiation resistance of commercially available SiC/SiC composites have revealed their promise for this application, but also the need for further development to achieve the desired performance. This paper summarizes the results of a workshop cosponsored by the Offices of Fusion Energy and Basic Energy Sciences of the US Department of Energy and Lockheed-Martin Corporation with forty attendees from national laboratories, universities and industry. A number of promising routes for optimizing the radiation stability of ceramic matrix composites were identified at this workshop. These routes included the newer, more stoichiometric fibers and alternate fiber/matrix interfaces and matrix processing routes. (orig.)

  8. 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

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

    Directory of Open Access Journals (Sweden)

    Karthiselva N. S.

    2016-09-01

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

  10. [The effect of sintering temperature on the physical and mechanical properties of dental zirconia toughened ceramic].

    Science.gov (United States)

    Zhang, Bin; Chen, Ji-hua; Sun, Lian-jun

    2003-07-01

    To investigate the effects of sintering temperature on the physical and mechanical properties of dental zirconia toughened ceramic (ZTC). 3 mol% yttria-stabilized zirconia compacts were prepared by dry press method and then sintered at 1,490 degrees C, 1,530 degrees C, 1,570 degrees C and 1,610 degrees C respectively. The physical properties and bending strength were then measured. The result of the study indicated along with the rise of sintering temperature density and shrinkage of ZTC increased, but the pore structure decreased. It also showed the peak of bending strength was in 1,570 degrees C. In terms of sintering temperature and bending strength among the selected temperature, the best sintering temperature of 3 mol% yttria-stabilized zirconia should be about 1,570 degrees C.

  11. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    NiZnCu hexagonal ferrite (abbreviated as ZT/NZC) composite samples were prepared successfully by using restricted shrinkage sintering process (RSS) (Liu et al 2009a, b). But the electromagnetic performance degra- dation of co-sintered layer ...

  12. Nd:YAG transparent ceramics fabricated by direct cold isostatic pressing and vacuum sintering

    Science.gov (United States)

    Ge, Lin; Li, Jiang; Zhou, Zhiwei; Liu, Binglong; Xie, Tengfei; Liu, Jing; Kou, Huamin; Shi, Yun; Pan, Yubai; Guo, Jingkun

    2015-12-01

    The sintering behavior of neodymium doped yttrium aluminum garnet (Nd:YAG) ceramics was investigated on the basis of densification trajectory, microstructure evolution and transmittance. Nd:YAG ceramics with in-line transmittance of 83.9% at 1064 nm and 82.5% at 400 nm were obtained by direct cold isostatic pressing (CIP) at 250 MPa and solid-state reactive sintering at 1790 °C for 30 h under vacuum. Compared with the porosity and the average pore diameter of the sample from uniaxial dry-pressing followed by CIP, those from direct CIP are much smaller. The samples pressed at 250 MPa were sintered from 1500 °C to 1750 °C for 0.5-20 h to study their sintering behavior. At the temperature higher than 1500 °C, pure YAG phase is formed, followed by the densification and grain growth process. The relative density and the grain size increase with the increase of sintering time and temperature, and the sintering behavior is more sensitive to temperature than holding time. The mechanism controlling densification and grain growth at sintering temperature of 1550 °C is grain boundary diffusion.

  13. EFFECT OF SINTERING PROFILES ON THE PROPERTIES AND AGEING RESISTANCE OF Y-TZP CERAMIC

    Directory of Open Access Journals (Sweden)

    C.Y. Tan

    2011-12-01

    Full Text Available A commercially available Y-TZP ceramic powder was fabricated under four different sintering profiles in order to investigate the effects of conventional single-stage sintering (SSS with dwell times of 1 min and 2 h, respectively, compared with two-stage sintering (TSS, on the physical and mechanical properties of Y-TZP. Sintering was performed up to 1400oC at a ramp rate of 10oC/min. It was revealed that samples sintered via TSS yielded better properties than the SSS samples sintered at 1400oC using a dwell time of 2 h. In the hydrothermal ageing test, TSS samples did not undergo low-temperature degradation via the tetragonal to monoclinic phase transformation. Nevertheless, it was found by XRD analysis that Y-TZP ceramics sintered by the SSS method using a short dwell time of 1 min were effective in maintaining tetragonal phase stability after 50 h of exposure to superheated steam conditions.

  14. 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)

  15. Directly susceptible, noncarbon metal ceramic composite crucible

    Science.gov (United States)

    Holcombe, Jr., Cressie E.; Kiggans, Jr., James O.; Morrow, S. Marvin; Rexford, Donald

    1999-01-01

    A sintered metal ceramic crucible suitable for high temperature induction melting of reactive metals without appreciable carbon or silicon contamination of the melt. The crucible comprises a cast matrix of a thermally conductive ceramic material; a perforated metal sleeve, which serves as a susceptor for induction heating of the crucible, embedded within the ceramic cast matrix; and a thermal-shock-absorber barrier interposed between the metal sleeve and the ceramic cast matrix to allow for differential thermal expansions between the matrix and the metal sleeve and to act as a thermal-shock-absorber which moderates the effects of rapid changes of sleeve temperature on the matrix.

  16. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; de Florio, D. Z.

    2017-01-01

    Gadolinium, yttrium and samarium-doped barium cerate pressed pellets were submitted to flash sintering experiments isothermally in the temperature range 800-1300oC under 200 V cm-1 electric field. The pellets were positioned inside a dilatometer furnace with Pt-Ir electrodes connected either...... to a power supply or to an impedance analyzer to evaluate the bulk and the grain boundary contributions to the electrical resistivity. Near full density was achieved in the sintered samples. The combined results of dilatometry and impedance measurements in conventionally and flash sintered specimens show...... substantial improvement of the electrical conductivity. Joule heating is assumed to be the primary effect for sintering. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively, as the reasons for the decrease...

  17. Pressureless sintering behavior of injection molded alumina ceramics

    Directory of Open Access Journals (Sweden)

    Liu W.

    2014-01-01

    Full Text Available The pressureless sintering behaviors of two widely used submicron alumina (MgOdoped and undoped with different solid loadings produced by injection molding have been studied systematically. Regardless of the sinterability of different powders depending on their inherent properties, solid loading plays a critical role on the sintering behavior of injection molded alumina, which greatly determines the densification and grain size, and leads to its full densification at low temperatures. As compared to the MgO-doped alumina powder, the undoped specimens exhibit a higher sinterability for its smaller particle size and larger surface area. While full densification could be achieved for MgO-doped powders with only a lower solid loading, due to the fact that MgO addition can reduce the detrimental effect of the large pore space on the pore-boundary separation.

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ka-Young; Seo, Yongho; Kim, Ki Buem [HMC & Green Energy Research Institute, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of); Song, Sun-Ju [Department of Materials Science and Engineering, Chonnam National University, Gwangju 550-749 (Korea, Republic of); Park, Byoungnam [Department of Materials Science and Engineering, Hongik University, Seoul 121-791 (Korea, Republic of); Park, Jun-Young, E-mail: jyoung@sejong.ac.kr [HMC & Green Energy Research Institute, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of)

    2015-08-05

    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{sub 0.85}Y{sub 0.15}O{sub 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{sub 2}O{sub 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{sup −2} S cm{sup −1} (by the polymer gelation method) vs. 0.53 × 10{sup −2} S cm{sup −1} by the solid-state method at 600 °C in wet 5% H{sub 2} in Ar.

  19. 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

  20. Properties and rapid sintering of a nanostructured tetragonal zirconia composites

    Science.gov (United States)

    Shon, In-Jin; Yoon, Jin-Kook; Hong, Kyung-Tae

    2017-09-01

    4YSZ is generally used as oxygen sensors, fuel cells, thermal barrier and hip and knee joint replacements as a result of these excellent properties with its high biocompatibility, low density, good resistance against corrosion, high ionic conductivity, hard phase and melting point. However, 4YTZ with coarse grain has low resistance to wear and abrasion because of low hardness and low fracture toughness at room temperature. The fracture toughness and hardness of a 4YTZ can be improved by forming nanostructured composites and addition of a second hard phase. In this study, nanostuctured 4YTZ-graphene composites with nearly full density were achieved using high-frequency induction heated sintering for one min at a pressure of 80 MPa. The rapid consolidation and addition of graphene to 4YTZ retained the nano-scale structure of the ceramic by inhibiting grain growth. The grain size of 4YTZ was reduced remarkably by the addition of graphene and the addition of graphene to 4YTZ greatly improved the fracture toughness without decrease of hardness.

  1. Strengthening of porous matrix materials with evaporation/condensation sintering for composite materials applications

    Science.gov (United States)

    Haslam, Jeffery John

    1998-12-01

    The need for improved fuel economy and reduced environmental emissions from power turbines has prompted the development of high temperature fiber composite materials. One use of these materials is for liners of the hot combustion regions of jet engines and land based power turbines. Stability of the composite materials against oxidative damage during long term use at high temperatures has motivated recent research into fiber composite materials composed entirely of oxide ceramics. All-oxide fiber reinforced composites containing porous, strongly bonded matrices have become of interest. The porosity provides for crack deflection along the fibers to prevent catastrophic failure of the fiber reinforcements. A new application of a processing method that produces evaporation/condensation sintering was employed to prevent shrinkage of the matrix. This processing method and the properties of the matrix, fibers, and composite were evaluated in this work. Producing a matrix without shrinkage is important to prevent undesirable crack-like voids from forming in the matrix. These voids are caused by constraint against shrinkage by the fiber reinforcements. Dry hydrogen chloride gas produced a reactive gas atmosphere that was used to sinter the zirconia particles with minimal shrinkage because the gas promotes evaporation/condensation sintering with zirconia. Sintering of samples that did not contain fiber reinforcements was studied to evaluate the properties of the matrix material. The sintering of monoclinic, tetragonal, and cubic zirconias in the reactive gas atmosphere was compared. Additions of mullite (which did not sinter significantly at processing temperatures) further reduced the shrinkage. The effects of the processing conditions on the sintering shrinkage, microstructure development, and mechanical properties were studied. Cubic and monoclinic zirconia coarsened significantly in the HCl gas sintering atmosphere. The coarsening of the particles during the sintering

  2. Effect of CASP glass doping on sintering and dielectric properties of SBN ceramics

    International Nuclear Information System (INIS)

    Chen Guohua; Qi Bing

    2009-01-01

    16CaO-29Al 2 O 3 -34SiO 2 -13PbO-4B 2 O 3 -2ZnO-2P 2 O 5 (CASP) glass doped-Sr 0.5 Ba 0.5 Nb 2 O 6 (SBN50) ceramics have been synthesized by solid-state ceramic route. The effects of CASP glass on the firing, microstructure and dielectric characterization of SBN50 ceramics are investigated. The densities of the ceramic samples firstly increase and then slightly decrease with increasing CASP glass content. The appropriate amount of doping glass is 2%. The SBN50 ceramics doped with CASP glass can be sintered at a relatively low temperature, 1200 deg. C. X-ray diffraction analysis shows the single phase (tetragonal tungsten bronze type structure) is preserved for all the samples. The diffuse character of the ceramic system increases and the dielectric constant at phase transition temperature (T c ) markedly decreases as CASP glass content increases. Interestingly, the CASP glass addition drastically alters the microstructure of the sintered ceramics. The isotropic grains in the pure SBN50 ceramics transform to rod like grains after the addition of CASP glass. The grain size of SBN phase is found to obviously increase with increase in CASP glass doping level

  3. Laser sintering of ceramics of Y2O3 pure e doped

    International Nuclear Information System (INIS)

    Oliveira, T.C. de; Goncalves, R.S.; Silva, R.S. da

    2012-01-01

    The Yttria (Y 2 O 3 ) is one of the most promising materials for refractory and optical applications due mainly to its high corrosion resistance, wide range of optical transmission and high melting point. However, due to its high melting point, ceramic bodies to obtain high density Y 2 O 3 high temperatures and require special sintering. Recently it has been proposed in the literature a new method of sintering in which a CO 2 laser, in continuous mode, is employed as the primary source of heat during sintering. Irradiation with laser light produces heating surface at elevated temperatures in a time interval of a few seconds, allowing to obtain dense ceramic bodies at elevated temperatures and with different properties from those sintered by conventional methods. In this paper, Y 2 O 3 powders of pure and doped with Mn, Ca and Zn were synthesized by the polymeric precursors and after calcination at 600 ° C/4h showed single phase. For the production and characterization of the samples used techniques DTA / TG, XRD Dilatometry, SEM and Radioluminescence. The sintered ceramics had a high relative density and strong dependence on the dopant used, which accelerate the densification process. Measures Radioluminescence showed characteristic peaks of Y 2 O 3 and dependence on the dopant used. (author)

  4. Sintered gahnite–cordierite glass-ceramic based on raw materials ...

    Indian Academy of Sciences (India)

    Sci., Vol. 38, No. 7, December 2015, pp. 1731–1736. c Indian Academy of Sciences. Sintered gahnite–cordierite glass-ceramic based on raw materials with different fluorine sources. ESMAT M A HAMZAWY1,∗ and MOHAMMED A BIN HUSSAIN2. 1National Research Centre, Glass Department, Dokki, Cairo 12622, Egypt.

  5. 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

  6. High doping Nd:YAG transparent ceramics fabricated by solid-state reactive sintering

    International Nuclear Information System (INIS)

    Liu, Jing; Liu, Qiang; Cheng, Xiaonong; Li, Jiang; Ba, Xuewei; Liu, Wenbin; Kou, Huamin; Jiang, Benxue; Pan, Yubai; Guo, Jingkun

    2013-01-01

    Nd:YAG transparent ceramics with different doping concentrations were fabricated by a solid-state reaction method and vacuum sintering. Powder mixture of α-Al 2 O 3 , Y 2 O 3 , and Nd 2 O 3 doped with tetraethoxysilane (TEOS) and MgO were sintered between 1500 o C and 1750 o C to examine the densification behavior in Nd:YAG ceramics. For the high doping 5 at%Nd:YAG transparent ceramics, the sintering kinetics and microstructure evolution were mainly discussed. It is found that the optimal sintering temperature for 5.0 at%Nd:YAG ceramics was at ∝1700 o C, and the in-line transmittance increased with the increase of holding time. The best specimen with the holding time of 30h achieved 82.2% in transmittance at 1064nm, whose average grain size was ∝15μm. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. 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

  8. Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

    International Nuclear Information System (INIS)

    Wang, Y.P.; Zhou, L.; Zhang, M.F.; Chen, X.Y.; Liu, J.-M.; Liu, Z.G.

    2004-01-01

    Single-phased ferroelectromagnet BiFeO 3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 deg. C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm 2 , 4.0 μC/cm 2 , and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe 2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials

  9. Near-Net-Shape Processing of Sintered Fibrous Ceramics Achieved

    Science.gov (United States)

    Angel, Paul W.

    2000-01-01

    A variety of sintered fibrous ceramic (SFC) materials have been developed over the last 50 years as thermal barrier materials for reentry applications. SFC materials typically exhibit very low thermal conductivities combined with low densities and good thermal stability up to 2500 F. These materials have flown successfully on the space shuttle orbiters since the 1960's. More recently, the McDonnell Douglas Corporation successfully used SFC tiles as a heat shield on the underside of its DC X test vehicle. For both of these applications, tiles are machined from blocks of a specific type of SFC called an alumina-enhanced thermal barrier (AETB). The sizes of these blocks have been limited by the manufacturing process. In addition, as much as 80 to 90 percent of the material can be lost during the machining of tiles with significant amounts of curvature. To address these problems, the NASA Glenn Research Center at Lewis Field entered a cooperative contract with the Boeing Company to develop a vacuum-assisted forming process that can produce large (approximately 4 square feet), severely contoured panels of AETB while saving costs in comparison to the conventional cast-and-machine billet process. For shuttle use, AETB is slurry cast, drained, and fired to form square billets conforming to the shape of the filtration box. The billets are then cut into tiles of the appropriate size for thermally protecting the space shuttle. Processing techniques have limited the maximum size of AETB billets to 21.5 square inches by 6.5-in. thick, but the space shuttles use discrete heat shield tiles no more than 8 to 12 square inches. However, in other applications, large, complex shapes are needed, and the tiling approach is undesirable. For such applications, vacuum-assisted forming can produce large parts with complex shapes while reducing machining waste and eliminating cemented joints between bonded billets. Because it allows contoured shapes to be formed, material utilization is

  10. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; Zanetti De Florio, Daniel

    2017-01-01

    -5 A the electric current pulse amplitude. The sintering experiments were carried out in ambient atmosphere with the pellets positioned inside a vertical dilatometer furnace with Pt-Ir electrodes connected either to a power supply for applying the electric field or to an impedance analyzer for collecting [-Z''(ω) x......Gadolinium, yttrium and samarium-doped barium cerate (BCGd, BCY and BCSm, respectively) polycrystalline green pellets were submitted to electric field-assisted pressureless sintering experiments isothermally in the temperature range 800-1200oC under 100-200 V cm-1 electric fields, limiting to 1...... of the electrical conductivity of flash sintered specimens. Joule heating is assumed to be the primary effect of the electric current pulse through the specimens. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively...

  11. Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique

    Directory of Open Access Journals (Sweden)

    Chmielewski Marcin

    2017-01-01

    Full Text Available The presented paper investigates the relationship between the microstructure and thermal properties of copper-silicon carbide composites obtained through hot pressing (HP and spark plasma sintering (SPS techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal-ceramic boundary. It is the product of silicon dissolving process in copper occurring at an elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

  12. Magnetic Glass Ceramics by Sintering of Borosilicate Glass and Inorganic Waste

    Directory of Open Access Journals (Sweden)

    Inès M. M. M. Ponsot

    2014-07-01

    Full Text Available Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based on two iron-rich slags, coming from non-ferrous metallurgy and recycled borosilicate glass. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1000 °C, whereas glass/slag interactions resulted in the formation of magnetite crystals, providing ferrimagnetism. Such behavior could be exploited for applying the obtained glass ceramics as induction heating plates, according to preliminary tests (showing the rapid heating of selected samples, even above 200 °C. The chemical durability and safety of the obtained glass ceramics were assessed by both leaching tests and cytotoxicity tests.

  13. Ceramic matrix composite article and process of fabricating a ceramic matrix composite article

    Science.gov (United States)

    Cairo, Ronald Robert; DiMascio, Paul Stephen; Parolini, Jason Robert

    2016-01-12

    A ceramic matrix composite article and a process of fabricating a ceramic matrix composite are disclosed. The ceramic matrix composite article includes a matrix distribution pattern formed by a manifold and ceramic matrix composite plies laid up on the matrix distribution pattern, includes the manifold, or a combination thereof. The manifold includes one or more matrix distribution channels operably connected to a delivery interface, the delivery interface configured for providing matrix material to one or more of the ceramic matrix composite plies. The process includes providing the manifold, forming the matrix distribution pattern by transporting the matrix material through the manifold, and contacting the ceramic matrix composite plies with the matrix material.

  14. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    Administrator

    Department of Ceramic Technology, Govt. College of Engineering & Ceramic Technology, Kolkata 700 010, India. †. School of Material Science & Technology,. ††. Ex-emeritus Professor (AICTE), ... According to the latest diagram, MgO has considerable solubility in MgAl2O4, and hence magnesia-enriched spinel formed at ...

  15. 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)

  16. Non-Oxide Structural Ceramics - Alloy Design for Improved Sinterability and Mechanical Performance

    National Research Council Canada - National Science Library

    Chen, I

    1998-01-01

    Research on non-oxide structure ceramics including silicon nitride, silicon carbide and titanium diboride has been conducted Multiphase silicon nitride composites with melilite and other high nitrogen...

  17. Liquid Film Capillary Mechanism for Densification of Ceramic Powders during Flash Sintering

    Directory of Open Access Journals (Sweden)

    Rachman Chaim

    2016-04-01

    Full Text Available Recently, local melting of the particle surfaces confirmed the formation of spark and plasma during spark plasma sintering, which explains the rapid densification mechanism via liquid. A model for rapid densification of flash sintered ceramics by liquid film capillary was presented, where liquid film forms by local melting at the particle contacts, due to Joule heating followed by thermal runaway. Local densification is by particle rearrangement led by spreading of the liquid, due to local attractive capillary forces. Electrowetting may assist this process. The asymmetric nature of the powder compact represents an invasive percolating system.

  18. A Gas Pressure Sintering Furnace for Structural Ceramics

    National Research Council Canada - National Science Library

    Chen, I-Wei

    2001-01-01

    .... Since funds were used from University sources to advance the payment of the gas pressure sintering, we have used the residue funds to purchase characterization equipment for a' -SiAlON research. The new equipment has been delivered and has allowed characterization of a'-SiAlON, especially the mechanical properties (R-curve, creep, and high temperature strength) to be carried out in our laboratory.

  19. [Influence of compaction pressure and pre-sintering temperature on the machinability of zirconia ceramic].

    Science.gov (United States)

    Huang, Huil; Li, Jing; Zhang, Fuqiang; Sun, Jing; Gao, Lian

    2011-10-01

    In order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic. 3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. Pre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality. The best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.

  20. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    Abstract. Zinc–magnesium titanate dielectrics/nickel–zinc–copper ferrite layer composites were prepared by tape- casting technique combined with a uniaxial pressure shaping technique. The sintering and camber development of the composites were investigated. The results show that the difference of shrinkage in the ...

  1. Effect of Nb doping on sintering and dielectric properties of PZT ceramics

    Directory of Open Access Journals (Sweden)

    Ali Mirzaei

    2016-09-01

    Full Text Available The extensive use of piezoelectric ceramics such as lead zirconate titanate (PZT in different applications became possible with the development of donor or acceptor dopants. Therefore, studies on the effect of dopants on the properties of PZT ceramics are highly demanded. In this study undoped and 2.4 mol% Nb-doped PZT (PZTN powders were successfully obtained by a solid-state reaction and calcination at 850 °C for 2 h. Crystallinity and phase formation of the prepared powders were studied using X-ray diffraction (XRD. In order to study morphology of powders, scanning electron microscopy (SEM was performed. The crystalline PZT and Nb-doped PZT powders were pelleted into discs and sintered at 1100, 1150 and 1200 °C, with a heating rate of 10 °C/min, and holding time of 1–6 h to find the optimum combination of temperature and time to produce high density ceramics. Microstructural characterization was conducted on the fractured ceramic surfaces using SEM. Density measurements showed that maximal density of 95% of the theoretical density was achieved after sintering of PZT and PZTN ceramics at 1200 °C for 2 h and 4 h, respectively. However, the results of dielectric measurements showed that PZTN ceramics have higher relative permittivity (εr ∼17960 with lower Curie temperature (∼358 °C relative to PZT (εr = 16000 at ∼363 °C as a result of fine PZTN structure as well as presence of vacancies. In addition, dielectric loss (at 1 kHz of PZT and PZTN ceramics with 95% theoretical density was 0.0087 and 0.02, respectively. The higher dielectric loss in PZTN was due to easier domain wall motions in PZTN ceramics.

  2. Bioactive Glass-Ceramic Scaffolds from Novel ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Science.gov (United States)

    Elsayed, Hamada; Rincón Romero, Acacio; Ferroni, Letizia; Gardin, Chiara; Zavan, Barbara; Bernardo, Enrico

    2017-01-01

    Highly porous wollastonite-diopside glass-ceramics have been successfully obtained by a new gel-casting technique. The gelation of an aqueous slurry of glass powders was not achieved according to the polymerization of an organic monomer, but as the result of alkali activation. The alkali activation of a Ca-Mg silicate glass (with a composition close to 50 mol % wollastonite—50 mol % diopside, with minor amounts of Na2O and P2O5) allowed for the obtainment of well-dispersed concentrated suspensions, undergoing progressive hardening by curing at low temperature (40 °C), owing to the formation of a C–S–H (calcium silicate hydrate) gel. An extensive direct foaming was achieved by vigorous mechanical stirring of partially gelified suspensions, comprising also a surfactant. The open-celled structure resulting from mechanical foaming could be ‘frozen’ by the subsequent sintering treatment, at 900–1000 °C, causing substantial crystallization. A total porosity exceeding 80%, comprising both well-interconnected macro-pores and micro-pores on cell walls, was accompanied by an excellent compressive strength, even above 5 MPa. PMID:28772531

  3. Barium titanate nanometric polycrystalline ceramics fired by spark plasma sintering.

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Ryukhtin, Vasyl; Cinert, Jakub; Lukáč, František

    2016-01-01

    Roč. 42, č. 14 (2016), s. 15989-15993 ISSN 0272-8842 R&D Projects: GA ČR GB14-36566G; GA MŠk LM2015056 Institutional support: RVO:61389021 ; RVO:61389005 Keywords : BaTiO3 * Spark plasma sintering * Electrical properties Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; JH - Ceramics, Fire-Resistant Materials and Glass (UJF-V) Impact factor: 2.986, year: 2016 http://www.sciencedirect.com/science/article/pii/S0272884216311695

  4. 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)

  5. The effect of spark plasma sintering on lithium disilicate glass-ceramics.

    Science.gov (United States)

    Al Mansour, Fatima; Karpukhina, Natalia; Grasso, Salvatore; Wilson, Rory M; Reece, Mike J; Cattell, Michael J

    2015-10-01

    To evaluate the effects of spark plasma sintering (SPS) on the microstructure of lithium disilicate glass-ceramics. IPS e.max CAD glass-ceramic samples were processed using spark plasma sintering (SPS) and conventionally sintered (CS) as a comparison. Specimens were sintered at varying temperatures (T1: 840°C, T2: 820°C, T3: 800°C), heating rates (HR1: 150°C/min, HR2: 300°C/min, HR3: 500°C/min) and pressures (P1: 15MPa, P2: 50MPa, P3: 70MPa). IPS e.max Press glass powder samples were densified at 750 and 800°C (50 or 200MPa pressure). Samples were characterized using XRD, HTXRD, and SEM and quantitative image analysis. There was a significant increase in median crystal size (MCS) between the CS and the SPS T1 groups. A statistical difference (p>0.05) in MCS between SPS T1 and SPS T2 groups was observed. The SPS HR3 sample produced a smaller MCS than the CS, SPS HR1 and HR2 groups (pglass samples resulted in fine fibrils or graduated lithium disilicate crystals. The effects of SPS were used to refine the microstructure of IPS e.max CAD lithium disilicate glass-ceramics. Densification by SPS of IPS e.max Press glass resulted in textured and fine nano-crystalline microstructures. SPS generated glass-ceramic microstructures may have unique properties and could be useful in the production of CAD/CAM materials for dentistry. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  6. 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)

  7. Effect of specific absorbed power on microwave sintering of 3YSZ ceramics

    Science.gov (United States)

    Bykov, Yu V.; Egorov, S. V.; Eremeev, A. G.; Plotnikov, I. V.; Rybakov, K. I.; Sorokin, A. A.; Kholoptsev, V. V.

    2017-07-01

    Samples of 3 % yttria-stabilized zirconia (3YSZ) ceramics have been sintered to near full density with no appreciable grain growth using an ultra-rapid microwave sintering process. The sintering experiments were carried out on a 24 GHz / 6 kW gyrotron system for microwave processing of materials with automatic process control. By varying the properties of the thermal insulation surrounding the samples it was possible to vary the microwave power required for heating. The final relative density of 3YSZ ceramic samples microwave heated at a rate of 50 °C/min to a temperature of 1400 °C without isothermal hold varied from 91.6 % when the specific absorbed microwave power was 4 W/cm3 to 99.4 % when the specific absorbed microwave power was 90 W/cm3. The specific absorbed power is therefore demonstrated to be the key parameter determining the achievable density in ultra-rapid field-assisted sintering processes.

  8. ADVANCED CERAMIC MATERIALS FOR DENTAL APPLICATIONS SINTERED BY MICROWAVE HEATING

    OpenAIRE

    Presenda Barrera, Álvaro

    2016-01-01

    [EN] Zirconia has become a widely utilized structural ceramic material with important applications in dentistry due to its superb mechanical properties, biocompatibility, aesthetic characteristics and durability. Zirconia needs to be stabilized in the t-phase to obtain improved mechanical properties such as hardness and fracture toughness. Fully dense yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) materials are normally consolidated through the energy-intensive processing of po...

  9. [Study on friction and wear properties of dental zirconia ceramics processed by microwave and conventional sintering methods].

    Science.gov (United States)

    Guoxin, Hu; Ying, Yang; Yuemei, Jiang; Wenjing, Xia

    2017-04-01

    This study evaluated the wear of an antagonist and friction and wear properties of dental zirconia ceramic that was subjected to microwave and conventional sintering methods. Ten specimens were fabricated from Lava brand zirconia and randomly assigned to microwave and conventional sintering groups. A profile tester for surface roughness was used to measure roughness of the specimens. Wear test was performed, and steatite ceramic was used as antagonist. Friction coefficient curves were recorded, and wear volume were calculated. Finally, optical microscope was used to observe the surface morphology of zirconia and steatite ceramics. Field emission scanning electron microscopy was used to observe the microstructure of zirconia. Wear volumes of microwave and conventionally sintered zirconia were (6.940±1.382)×10⁻², (7.952±1.815) ×10⁻² mm³, respectively. Moreover, wear volumes of antagonist after sintering by the considered methods were (14.189±4.745)×10⁻², (15.813±3.481)×10⁻² mm³, correspondingly. Statistically significant difference was not observed in the wear resistance of zirconia and wear volume of steatite ceramic upon exposure to two kinds of sintering methods. Optical microscopy showed that ploughed surfaces were apparent in zirconia. The wear surface of steatite ceramic against had craze, accompanied by plough. Scanning electron microscopy showed that zirconia was sintered compactly when subjected to both conventional sintering and microwave methods, whereas grains of zirconia sintered by microwave alone were smaller and more uniform. Two kinds of sintering methods are successfully used to produce dental zirconia ceramics with similar friction and wear properties.
.

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

    Directory of Open Access Journals (Sweden)

    Karima Amer Almasri

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

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

    Science.gov (United States)

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

    2010-01-15

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

  12. Indentation Behavior and Mechanical Properties of Tungsten/Chromium co-Doped Bismuth Titanate Ceramics Sintered at Different Temperatures.

    Science.gov (United States)

    Xie, Shaoxiong; Xu, Jiageng; Chen, Yu; Tan, Zhi; Nie, Rui; Wang, Qingyuan; Zhu, Jianguo

    2018-03-27

    A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi₄Ti 2.95 W 0.05 O 12.05 + 0.2 wt % Cr₂O₃, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi₂Ti₂O₇ grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall-Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase.

  13. Sintering and crystallization behavior of CaMgSi2O6-NaFeSi2O6 based glass-ceramics

    International Nuclear Information System (INIS)

    Goel, Ashutosh; Kansal, Ishu; Ferrari, Anna Maria; Pascual, Maria J.; Barbieri, Luisa; Bondioli, Federica; Lancellotti, Isabella; Ribeiro, Manuel J.; Ferreira, Jose M. F.

    2009-01-01

    We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi 2 O 6 -10 mol % NaFeSi 2 O 6 . The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850-950 deg. C in both air and N 2 atmosphere. X-ray diffraction studies adjoined with the Rietveld-reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with diopside as the primary crystalline phase were obtained where the amount of diopside varied with the heating conditions.

  14. Corrosion behaviors of ceramics against liquid sodium. Sodium corrosion characteristics of sintering additives

    International Nuclear Information System (INIS)

    Tachi, Yoshiaki; Kano, Shigeki; Hirakawa, Yasushi; Yoshida, Eiichi

    1998-01-01

    It has been progressed as the Frontier Materials Research to research and develop ceramics to apply for several components of fast breeder reactor using liquid sodium as coolant instead of metallic materials. Grain boundary of ceramics has peculiar properties compared with matrix because most of ceramics are produced by hardening and firing their raw powders. Some previous researchers indicated that ceramics were mainly corroded at grain boundaries by liquid sodium, and ceramics could not be used under corrosive environment. Thus, it is the most important for the usage of ceramics in liquid sodium to improve corrosion resistance of grain boundaries. In order to develop the advanced ceramics having good sodium corrosion resistance among fine ceramics, which have recently been progressed in quality and characteristics remarkably, sodium corrosion behaviors of typical sintering additives such as MgO, Y 2 O 3 and AlN etc. have been examined and evaluated. As a result, the followings have been clarified and some useful knowledge about developing advanced ceramics having good corrosion resistance against liquid sodium has been obtained. (1) Sodium corrosion behavior of MgO depended on Si content. Samples containing large amount of Si were corroded severely by liquid sodium, whereas others with low Si contents showed good corrosion resistance. (2) Both Y 2 O 3 and AlN, which contained little Si, showed good sodium corrosion resistance. (3) MgO, Y 2 O 3 and AlN are thought to be corroded by liquid sodium, if they contain some SiO 2 . Therefore, in order to improve sodium corrosion resistance, it is very important for these ceramics to prevent the contamination of matrix with SiO 2 through purity control of their raw powders. (author)

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

    Czech Academy of Sciences Publication Activity Database

    Ctibor, P.; Kubatík, Tomáš František; Sedláček, J.; Kotlan, Jiří

    2016-01-01

    Roč. 22, č. 3 (2016), s. 435-439 ISSN 1392-1320 Institutional support: RVO:61389021 Keywords : titanates * dielectric ceramics * spark plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.393, year: 2016 http://www.matsc.ktu.lt/index.php/MatSc/article/view/8767

  16. Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics.

    Science.gov (United States)

    Osorio, Raquel; Castillo-de Oyagüe, Raquel; Monticelli, Francesca; Osorio, Estrella; Toledano, Manuel

    2012-07-01

    To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al₂O₃-particles); and Group 3: Silica-coating (50 µm silica-modified Al₂O₃-particles). Composite samples were randomly bonded to the pretreated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm² sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups.

  17. Fabrication of functionally gradient materials with internal channels in ceramics and ceramic composites

    Science.gov (United States)

    Shin, Hyea-Weon

    Functionally Gradient Materials (FGMs) are inhomogeneous materials whose compositions vary from one phase to another. By tailoring the inhomogeneous properties, FGMs can be used to reduce the stresses that are caused by severe thermal gradients. Thermal gradient loading can further be compensated by heat transfer into a cooling fluid circulating in a network of channels and manifolds. In an envisioned application, heat from a localized source is transferred to the cooling fluid, easing sharp thermal loads while minimizing the unwanted spread of heat energy to the ambient surroundings. This study reports on the fabrication of functionally gradient ceramics and the embedding of simple internal channels within these ceramics. Functional gradiency (variation of composition) is built in via the layering of different components across the thickness of a plate sample. Traditional powder processing techniques are applied to fabricate the test pieces, and recently developed methods of joining are used to build assemblies from individually sintered plate layers. For a well-formed FGM to be made, materials parameters need to be selected based on mechanical, thermal and chemical properties. As a class, ceramics are hard, wear-resistant, refractory, electrically and thermally insulative, nonmagnetic, chemically stable, and oxidation-resistant. However, because of their brittleness, ceramics with minute channels are difficult to machine. Instead, for this study, a graphite fugitive phase is used as a spacer to support channel volumes within a ceramic powder compact; during pre-sintering, the graphite burns out to expose a network of channels. Full sintering fixes the final shape. At the operating temperatures of the ovens used in our fabrication study, sintering of alumina, partially stabilized zirconia, fully stabilized zirconia and hydroxyapatite have been successful, and these ceramic powders form the basis of the present fabrication studies. Inhomogeneities inherent in the

  18. Bioactive Glass-Ceramic Foam Scaffolds from ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Directory of Open Access Journals (Sweden)

    Hamada Elsayed

    2018-02-01

    Full Text Available Highly porous bioactive glass-ceramic scaffolds were effectively fabricated by an inorganic gel casting technique, based on alkali activation and gelification, followed by viscous flow sintering. Glass powders, already known to yield a bioactive sintered glass-ceramic (CEL2 were dispersed in an alkaline solution, with partial dissolution of glass powders. The obtained glass suspensions underwent progressive hardening, by curing at low temperature (40 °C, owing to the formation of a C–S–H (calcium silicate hydrate gel. As successful direct foaming was achieved by vigorous mechanical stirring of gelified suspensions, comprising also a surfactant. The developed cellular structures were later heat-treated at 900–1000 °C, to form CEL2 glass-ceramic foams, featuring an abundant total porosity (from 60% to 80% and well-interconnected macro- and micro-sized cells. The developed foams possessed a compressive strength from 2.5 to 5 MPa, which is in the range of human trabecular bone strength. Therefore, CEL2 glass-ceramics can be proposed for bone substitutions.

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

    Science.gov (United States)

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

    2017-05-01

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

  20. Cellular ceramics made from porcelain tile polishing wastes: influence of sintering time

    International Nuclear Information System (INIS)

    Guimaraes, A.F.; Zanelatto, C.C.; Uggioni, E.; Bernardin, A.M.

    2009-01-01

    This paper deals with the physical, microstructural and mechanical characterization of cellular ceramics made from porcelain polishing wastes, which were expanded by the bubble formation technique during the sintering process. The microstructure, linear expansion, bulk density (mercury immersion) and mechanical behavior (compressive strength) were determined to characterize the glass foam obtained. Moreover, the porcellaneous residue was characterized by chemical and phase analyses, particle size (laser diffraction) and thermal behavior. As a result, the higher the soaking time during heat treatment at 1200 deg C the lower the density obtained for the cellular ceramic due to CO 2 expansion, and lower the mechanical strength of the samples. The microstructure shows spherical cells and completely closed pores, resulting in a cheap way to obtain low density material with adequate mechanical strength, avoiding the disposal of wastes from the ceramic industry. (author)

  1. Dynamic crack arrest in ceramics and ceramic composites

    Science.gov (United States)

    Kobayashi, A. S.; Yang, K. H.

    1989-01-01

    The results of past dynamic crack arrest experiments involving structural ceramics and ceramic composites are reviewed and analyzed. The lack of dynamic crack arrest in very brittle materials is discussed and contrasted with dynamic crack arrest in somewhat brittle metallic and polymeric materials. Numerical analyses show that the lack of crack arrest is due to reduced dynamic fracture resistance of the material and is not due to the kinetic energy.

  2. Method of forming a ceramic matrix composite and a ceramic matrix component

    Science.gov (United States)

    de Diego, Peter; Zhang, James

    2017-05-30

    A method of forming a ceramic matrix composite component includes providing a formed ceramic member having a cavity, filling at least a portion of the cavity with a ceramic foam. The ceramic foam is deposited on a barrier layer covering at least one internal passage of the cavity. The method includes processing the formed ceramic member and ceramic foam to obtain a ceramic matrix composite component. Also provided is a method of forming a ceramic matrix composite blade and a ceramic matrix composite component.

  3. Production of mullite-zirconia ceramics composites by 'In situ' reaction

    International Nuclear Information System (INIS)

    Melo, F.C.L. de; Cairo, C.A.A.; Piorino Neto, F.; Devezas, T.C.

    1987-01-01

    Mullita-zirconia ceramic composites were produced by 'In situ' reaction of alumina and brazilian zircon. The ideal curve of thermal treatment (reaction + sinterization) was determined for the obtention of composites of maximum mechanical resistence. The retained fraction of tetragonal fase was evaluated by X-ray difraction and correlated with the values of mechanical resistence obtained by different treatment curves. The performance of the developed composites under corrosion and thermal shock was evaluated by glass casting. (Author) [pt

  4. Elaboration of new ceramic composites containing glass fibre production wastes

    International Nuclear Information System (INIS)

    Rozenstrauha, I.; Sosins, G.; Krage, L.; Sedmale, G.; Vaiciukyniene, D.

    2013-01-01

    Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50 % of organic matter as well as waste glass from aluminium borosilicate glass fibre with relatively high softening temperature (> 600 degree centigrade). In order to elaborate different new ceramic products (porous or dense composites) the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia) with illite content in clay fraction up to 80-90 % was used as a matrix. The raw materials were investigated by differential-thermal (DTA) and XRD analysis. Ternary compositions were prepared from mixtures of 15 - 35 wt % of sludge, 20 wt % of waste glass and 45 - 65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 degree centigrade in different treatment conditions. Materials produced in temperature range 1090 - 1100 degree centigrade with the most optimal properties - porosity 38 - 52 %, water absorption 39 -47 % and bulk density 1.35 - 1.67 g/cm 3 were selected for production of porous ceramics and materials showing porosity 0.35 - 1.1 %, water absorption 0.7 - 2.6 % and bulk density 2.1 - 2.3 g/cm 3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM). By X-ray diffraction analysis (XRD) the quartz, diopside and anorthite crystalline phases were detected. (Author)

  5. Influence of feldspar containing lithium in the sintering of triaxial ceramics

    International Nuclear Information System (INIS)

    Oliveira, Camila Felippe de; Strecker, Kurt

    2011-01-01

    In this work, the properties of a ceramic material based on a triaxial mass composed of clay, quartz and 15 to 30% feldspar, albite or spodumene, has been investigated. Specimen were prepared by uniaxial pressing under 28.5MPa and sintering at temperatures of 1000, 1100 and 1200 deg C, for 1h. The samples were characterized by their linear shrinkage, apparent porosity, apparent density and flexural strength, as well as analysis of the microstructure. The best results were obtained for samples prepared with 30% spodumene and sintered at 1200 deg C, with a shrinkage of 6.4%, density of 2.01g/cm 3 , porosity of 14.3% and flexural strength of 13.4MPa, while samples prepared with albite exhibited shrinkage of 5.8%, density of 1.9g/cm 3 , porosity of 18.9% and strength of 9.8MPa. Therefore, by the substitution of albite by spodumene in the ceramic triaxial mass, lower sintering temperatures may be employed, thus reducing production costs by the lesser energy consumption. (author)(

  6. Production and characterization of sintered ceramics from paper mill sludge and glass cullet.

    Science.gov (United States)

    Asquini, L; Furlani, E; Bruckner, S; Maschio, S

    2008-03-01

    Three different types of paper mill sludge were first incinerated and then attrition milled separately or mixed with glass cullet in varying proportions to obtain powders of different compositions. These powders were then dried, sieved, uniaxially pressed into samples and air sintered. Fired samples were characterized by density, water absorption, shrinkage on firing, strength, hardness and fracture toughness measurements; SEM and X-ray diffractions were also carried out to investigate microstructure and phase composition. Some sintered samples displayed fairly good physical and mechanical properties as a consequence of their low residual porosity and fine microstructure.

  7. Effect of ZrO2 on the sintering behavior, strength and high-frequency dielectric properties of electrical ceramic porcelain insulator

    Science.gov (United States)

    Singh Mehta, Niraj; Sahu, Praveen Kumar; Ershad, Md; Saxena, Vipul; Pyare, Ram; Ranjan Majhi, Manas

    2018-01-01

    In the present study, the effect of ZrO2 on the sintering, strength and dielectric behavior of electrical ceramic porcelain insulator with substituting alumina content by zirconia (in weight percentage from 0% to 30%) is investigated. The different composition of samples containing different zirconia (ZrO2) contents of 0, 10, 20, and 30 wt% are prepared using the uniaxial pressure technique applying 160 MPa pressure. Further, the prepared samples are also analyzed for sintering temperatures (1350 °C), and effects are observed on mechanical and electric properties of porcelain insulator. Different characterizations such as Dilatometer, x-ray diffraction, scanning electron microscopy and differential thermal analysis/thermo gravimetric analysis were used to evaluate the thermal, phase detection, micro structural and weight loss changes by increasing concentration of ZrO2 on base porcelain composition. At 1350 °C, for the composition having 20 wt% ZrO2 with 10 wt% alumina, the maximum density was observed 2.81 g cm-3 with a porosity of 2.23%. The highest tensile strength of 41 ± 3 MPa is observed for the same sample composition. The minimum value of thermal expansion coefficient is found to be in the range of 10-6 for the sample with 30 wt% ZrO2 content sintered at 1350 °C compared to other prepared samples. Similarly, the highest dielectric value (5.1-4.4) having dielectric loss (0.08-0.12) is achieved for the sample with 30 wt% ZrO2 content sintered at 1350 °C in the frequency range of 4-20 GHz at room temperature. According to the mechanical properties, the composition having 20 wt% ZrO2 on base ceramic porcelain composition has enormous potential to serve as a high strength refractory material. For dielectric properties, the composition having 30 wt% ZrO2 is more suitable for the electrical application.

  8. Microwave sintering of cordierite ceramic precursors obtained by starch direct consolidation

    International Nuclear Information System (INIS)

    Sandoval, M.L.; Talou, M.H.; Camerucci, M.A.; Universidad Nacional de Mar Del Plata; Souto, P.M. de; Kiminami, R.H.G.A.

    2009-01-01

    Microwave sintering of cordierite disk precursors (mixture of kaolin, talc and alumina) with potato starch was studied. Green disks were obtained by thermal consolidation of stable aqueous suspensions of the ceramic powders (29.6 % vol.) with potato starch (11.5 % vol.) at 75 and 85 deg C, 4h; drying (50 deg C,12h) and calcination (650 deg C, 2h). The reaction-sintering by microwave heating (power: 2.45 GHz; heating rate: 50 deg C/min) at different temperatures (1250-1330 deg C) and dwell times (10-20 min) was carried out. For comparative purposes, the reaction-sintering by conventional heating was analyzed (1330 deg C, 4h a 3 deg C/min). The evolution of the phases as a function of temperature and time was studied by XRD analysis. The developed microstructures (dense or porous) were characterized by density and porosity measurements, and SEM. The obtained results were analyzed in relation to the characteristics of starch behavior in aqueous suspension at temperature and the employed consolidation and sintering conditions. (author)

  9. Colloidal processing of Fe-based metal ceramic composites with high content of ceramic reinforcement

    Energy Technology Data Exchange (ETDEWEB)

    Escribano, J. A.; Ferrari, B.; Alvaredo, P.; Gordo, E.; Sanchez-Herencia, A. J.

    2013-07-01

    Major difficulties of processing metal-matrix composites by means of conventional powder metallurgy techniques are the lack of dispersion of the phases within the final microstructure. In this work, processing through colloidal techniques of the Fe-based metal-matrix composites, with a high content of a ceramic reinforcement (Ti(C,N) ), is presented for the first time in the literature. The colloidal approach allows a higher control of the powders packing and a better homogenization of phases since powders are mixed in a liquid medium. The chemical stability of Fe in aqueous medium determines the dispersion conditions of the mixture. The Fe slurries were formulated by optimising their zeta potential and their rheology, in order to shape bulk pieces by slip-casting. Preliminary results demonstrate the viability of this procedure, also opening new paths to the microstructural design of fully sintered Fe-based hard metal, with 50 vol. % of Ti(C,N) in its composition. (Author)

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

    Science.gov (United States)

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

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

  11. 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.

  12. Fabrication of unglazed ceramic tile using dense structured sago waste and clay composite

    International Nuclear Information System (INIS)

    Aripin; S Tani; S Mitsudo; T Saito; T Idehara

    2010-01-01

    In Indonesia, the sago processing industry generates every year huge amount of sago waste, and converting this waste into a useful material is possible. In the present study, physical properties of dense structured sago waste and clay composite were investigated in order to study the feasibility of reuse this sample as raw material in the producing of ceramics. Firstly, the chemical composition of ash (obtained from the sago waste) and clay was characterized. The prepared sample was sintered at the temperature range from 800 to 1,200 °C using electric furnace. The density, linear shrinkage and water absorption of the sintered sample were determined by using the Archimedes' method. The experimental result indicated that the density of the sintered sample increased with increasing sintering temperature up to 1100°C and then slightly decreased afterward. The water absorption of the products decreased with an increase in sintering temperature. In the sintered sample at 1,100 °C, the water absorption decreased rapidly and water adsorption of less than 1 % was achieved. This water absorption was less than 5 % which was needed for unglazed floor tile. The result of water adsorption suggest that it is possible to use this sample as a raw material for producing the ceramic floor tile. (author)

  13. The influence of electrocorundum granulation on the properties of sintered Cu/electrocorundum composites

    Directory of Open Access Journals (Sweden)

    Strojny-Nędza A.

    2015-01-01

    Full Text Available Copper/alumina composites are extensively used in automotive and aerospace industry for products that are subjected to severe thermal and mechanical loadings, such as rocket thrusters and components of aircraft engines. These materials are well-known for their good frictional wear resistance, good resistance to thermal fatigue, high thermal conductivity and high specific heat. In this paper, the sintering process of copper/electrocorundum composites reinforced by electrocorundum particles with diameters of 3 or 180 μm and 1, 3, 5 vol.% content is presented. The effects of different particle sizes of the ceramic reinforcement on the microstructure, physical, mechanical, tribological and thermal properties of the fabricated composites are discussed.

  14. Residual stress in ceramics and ceramic composites

    International Nuclear Information System (INIS)

    Oden, M.

    1992-01-01

    Residual stresses in Si 3 N 4 and SiC have been measured with X-ray diffraction after grinding and thermal shock. The produced surface stresses are compressive after both treatments. The stresses show a strong dependence on the quenching temperature up to a certain temperature when cracks relax the stresses. The influence of the amount of reinforcing phase on the residual stress state in a Al 2 O 3 /SiC whisker composite was investigated and correlated to a modified Eshelby model. The agreement is excellent. The composite was quenched in liquid He (4K) and the stress state measured after show no relaxation of stresses, indicating elastic behaviour. An in situ strain measurement as a function of temperature conducted on a Al 2 O 3 /SiC whisker composite and a SiC/TiB 2 particle composite show very good agreement with the Eshelby model for the Al 2 O 3 /SiC system but not agreement for the SiC/TiB 2 system. The reason is believed to be stress relaxation during sample preparation. (au) (53 refs., 24 figs., 14 tabs.)

  15. Celsian Glass-Ceramic Matrix Composites

    Science.gov (United States)

    Bansal, Narottam P.; Dicarlo, James A.

    1996-01-01

    Glass-ceramic matrix reinforced fiber composite materials developed for use in low dielectric applications, such as radomes. Materials strong and tough, exhibit low dielectric properties, and endure high temperatures.

  16. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism.

    Science.gov (United States)

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-10-27

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675-1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m(0.5). Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  17. AC conductivity of BiFeO3 ceramics obtained by spark plasma sintering of nanopowder

    Science.gov (United States)

    Sadykov, S. A.; Palchaev, D. K.; Murlieva, Zh. Kh.; Alikhanov, N. M.-R.; Rabadanov, M. Kh.; Gadzhimagomedov, S. Kh.; Kallaev, S. N.

    2017-09-01

    The structure and electrical properties of BiFeO3 ceramics obtained by spark plasma sintering of a nanopowder are investigated. The nanopowder was synthesized by burning of an organic nitrate precursor. The ac conductivity was measured in a frequency range of 1 kHz-10 MHz in a temperature interval of 25-500°C. It is established that the temperature conductivity coefficients above and below 350°C significantly differ with both alternating and direct currents. The frequency dependence of the conductivity obeys the Jonscher power law σ ω s , where s < 1. The interpretation of this behavior is given in the framework of the model of correlated hops of charge carriers over potential barriers. It is assumed that the hopping mechanism is realized between Fe2+ and Fe3+ ions in ceramic grains. The role of oxygen vacancies in the conduction is also discussed.

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

    Science.gov (United States)

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

    2015-04-01

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

  19. Investigation into the Properties of Sintered Ceramics from Dysna Clay and Non-Plastics Additives

    Directory of Open Access Journals (Sweden)

    Jolanta Pranckevičienė

    2011-04-01

    Full Text Available Recycling mineral wool spinning waste represents a rather serious problem. The results of the present research show that the suggested sintering ceramics out of low melting illite clay and mineral wool spinning waste is a promising way for solving the problem of mineral wool waste utilization. The conducted research into the properties of this compound has shown that by introducing 20% of waste into low melting clay allows producing ceramic materials possessing the following parameters: value of absorption is equal to 2,2%, density – 2169 kg/m3.The data of dilatometric investigation have demonstrated that adding 20 % of MVCF component leads to reducing length from 2,8% to 1,4% at the temperature of 1070 ºC. Article in Lithuanian

  20. An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system

    DEFF Research Database (Denmark)

    Pallesen, U.; Dijken van, J.W.V.

    2000-01-01

    sensitivity was reported by one patient for 8 months. Of the 32 inlays evaluated during the 8 yr, 3 failed due to fracture of the material. No secondary caries was found adjacent to the inlays. No significant differences in the clinical performance were found between inlays made of the two ceramics. It can......The purpose of this study was to evaluate Cerec CAD/CAM inlays processed of two industrially made machinable ceramics during an 8-yr follow-up period. Each of 16 patients received two similar ceramic inlays. Half the number of the inlays were made of a feldspathic (Vita Mark II) and the other...... of a glass ceramic (Dicor MGC) block. The inlays were luted with a dual resin composite and evaluated clinically using modified USPHS criteria at baseline, 8 months, 2, 3, 5, 6 and 8 yr, and indirectly using models. At baseline, 84% of the inlays were estimated as optimal and 16% as acceptable. Postoperative...

  1. An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system

    DEFF Research Database (Denmark)

    Pallesen, U.; Dijken van, J.W.V.

    2000-01-01

    of a glass ceramic (Dicor MGC) block. The inlays were luted with a dual resin composite and evaluated clinically using modified USPHS criteria at baseline, 8 months, 2, 3, 5, 6 and 8 yr, and indirectly using models. At baseline, 84% of the inlays were estimated as optimal and 16% as acceptable. Postoperative......The purpose of this study was to evaluate Cerec CAD/CAM inlays processed of two industrially made machinable ceramics during an 8-yr follow-up period. Each of 16 patients received two similar ceramic inlays. Half the number of the inlays were made of a feldspathic (Vita Mark II) and the other...... sensitivity was reported by one patient for 8 months. Of the 32 inlays evaluated during the 8 yr, 3 failed due to fracture of the material. No secondary caries was found adjacent to the inlays. No significant differences in the clinical performance were found between inlays made of the two ceramics. It can...

  2. Influence of the amount containing spodumene or albite on the sintering of a triaxial ceramic

    International Nuclear Information System (INIS)

    Oliveira, Camila Felippe de; Strecker, Kurt

    2012-01-01

    In this study, we investigated the properties of porcelain stoneware, made with albite or spodumene. The amount of the feldspar in the compositions ranged from 15 to 30% by weight. Specimens were pressed and sintered at 1000, 1100, 1200 and 1280 °C with an isotherm of 1 hour at the maximum temperature. The samples were characterized by analysis of the fracture surface using scanning electron microscopy and the vitrification curves, showing both the linear shrinkage and porosity in relation to the sintering temperature. The best results were obtained for samples containing 30% spodumene sintered at 1280 °C, with a linear shrinkage of 9.97% and porosity of 13.28%, while the corresponding results of samples containing 30% albite were 10.13% and 12.17%, respectively. It is concluded that the use of spodumene in the production of porcelain stoneware is viable, resulting in comparable properties. (author)

  3. Progress in Dual (Piezoelectric-Magnetostrictive Phase Magnetoelectric Sintered Composites

    Directory of Open Access Journals (Sweden)

    Rashed Adnan Islam

    2012-01-01

    Full Text Available The primary aims of this review article are (a to develop the fundamental understanding of ME behavior in perovskite piezoelectric-spinel magnetostrictive composite systems, (b to identify the role of composition, microstructural variables, phase transformations, composite geometry, and postsintering heat treatment on ME coefficient, and (c to synthesize, characterize, and utilize the high ME coefficient composite. The desired range of ME coefficient in the sintered composite is 0.5–1 V/cm⋅Oe. The studies showed that the soft piezoelectric phase quantified by smaller elastic modulus, large grain size of piezoelectric phase (~1 μm, and layered structures yields higher magnitude of ME coefficient. It is also found that postsintering thermal treatment such as annealing and aging alters the magnitude of magnetization providing an increase in the magnitude of ME coefficient. A trilayer composite was synthesized using pressure-assisted sintering with soft phase [0.9 PZT–0.1 PZN] having grain size larger than 1 μm and soft ferromagnetic phase of composition Ni0.8Cu0.2Zn0.2Fe2O4 [NCZF]. The composite showed a high ME coefficient of 412 and 494 mV/cm⋅Oe after sintering and annealing, respectively. Optimized ferrite to PZT thickness ratio was found to be 5.33, providing ME coefficient of 525 mV/cm⋅Oe. The ME coefficient exhibited orientation dependence with respect to applied magnetic field. Multilayering the PZT layer increased the magnitude of ME coefficient to 782 mV/cm⋅Oe. Piezoelectric grain texturing and nanoparticulate assembly techniques were incorporated with the layered geometry. It was found that with moderate texturing, d33 and ME coefficient reached up to 325 pC/N and 878 mV/cm⋅Oe, respectively. Nanoparticulate core shell assembly shows the promise for achieving large ME coefficient in the sintered composites. A systematic relationship between composition, microstructure, geometry, and properties is

  4. High temperature synthesis of ceramic composition by directed reaction of molten titanium or zirconium with boron carbide

    International Nuclear Information System (INIS)

    Johnson, W.B.

    1990-01-01

    Alternative methods of producing ceramics and ceramic composites include sintering, hot pressing and more recently hot isostatic pressing (HIP) and self-propagating high temperature synthesis (SHS). Though each of these techniques has its advantages, each suffers from several restrictions as well. Sintering may require long times at high temperatures and for most materials requires sintering aids to get full density. These additives can, and generally do, change (often degrade) the properties of the ceramic. Hot pressing and hot isostatic pressing are convenient methods to quickly prepare samples of some materials to full density, but generally are expensive and may damage some types of reinforcements during densification. This paper focuses on the preparation and processing of composites prepared by the directed reaction of molten titanium or zirconium with boron carbide. Advantages and disadvantages of this approach when compared to traditional methods are discussed, with reference to specific examples. Examples of microstructure are properties of these materials are reported

  5. Ceramic fiber reinforced glass-ceramic matrix composite

    Science.gov (United States)

    Bansal, Narottam P. (Inventor)

    1993-01-01

    A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

  6. Characterization of fabricated three dimensional scaffolds of bio ceramic-polymer composite via microstereolithography technique

    International Nuclear Information System (INIS)

    Marina Talib; Covington, J.A.; Bolarinwa, A.

    2013-01-01

    Full-text: Microstereolithography is a method used for rapid proto typing of polymeric and ceramic components. This technique converts a computer-aided design (CAD) to a three dimensional (3D) model, and enables layer per layer fabrication curing a liquid resin with UV-light or laser source. The aim of this project was to formulate photo curable polymer reinforced with synthesized calcium pyrophosphate (CPP), and to fabricate a 3D scaffolds with optimum mechanical properties for specific tissue engineering applications. The photo curable ceramic suspension was prepared with acrylate polyester, multifunctional acrylate monomer with the addition of 50-70 wt % of CPP, photo initiators and photo inhibitors. The 3D structure of disc (5 mm height x 4 mm diameter) was successfully fabricated using Envisiontec Perfactory3. They were then sintered at high temperature for polymer removal, to obtain a ceramic of the desired porosity. The density increased to more than 35 % and the dimensional shrinkage after sintering were 33 %. The discs were then subjected compressive measurement, biodegradation and bioactivity test. Morphology and CPP content of the sintered polymer was investigated with SEM and XRD, respectively. The addition of CPP coupled with high temperature sintering, had a significant effect on the compressive strength exhibited by the bio ceramic. The values are in the range of cancellous bone (2-4 MPa). In biodegradation and bioactivity test, the synthesized CPP induced the formation of apatite layer and its nucleation onto the composite surface. (author)

  7. Fibrous-Ceramic/Aerogel Composite Insulating Tiles

    Science.gov (United States)

    White, Susan M.; Rasky, Daniel J.

    2004-01-01

    Fibrous-ceramic/aerogel composite tiles have been invented to afford combinations of thermal-insulation and mechanical properties superior to those attainable by making tiles of fibrous ceramics alone or aerogels alone. These lightweight tiles can be tailored to a variety of applications that range from insulating cryogenic tanks to protecting spacecraft against re-entry heating. The advantages and disadvantages of fibrous ceramics and aerogels can be summarized as follows: Tiles made of ceramic fibers are known for mechanical strength, toughness, and machinability. Fibrous ceramic tiles are highly effective as thermal insulators in a vacuum. However, undesirably, the porosity of these materials makes them permeable by gases, so that in the presence of air or other gases, convection and gas-phase conduction contribute to the effective thermal conductivity of the tiles. Other disadvantages of the porosity and permeability of fibrous ceramic tiles arise because gases (e.g., water vapor or cryogenic gases) can condense in pores. This condensation contributes to weight, and in the case of cryogenic systems, the heat of condensation undesirably adds to the heat flowing to the objects that one seeks to keep cold. Moreover, there is a risk of explosion associated with vaporization of previously condensed gas upon reheating. Aerogels offer low permeability, low density, and low thermal conductivity, but are mechanically fragile. The basic idea of the present invention is to exploit the best features of fibrous ceramic tiles and aerogels. In a composite tile according to the invention, the fibrous ceramic serves as a matrix that mechanically supports the aerogel, while the aerogel serves as a low-conductivity, low-permeability filling that closes what would otherwise be the open pores of the fibrous ceramic. Because the aerogel eliminates or at least suppresses permeation by gas, gas-phase conduction, and convection, the thermal conductivity of such a composite even at

  8. Pressureless sintering and gas flux properties of porous ceramic membranes for gas applications

    Science.gov (United States)

    Obada, David O.; Dodoo-Arhin, David; Dauda, Muhammad; Anafi, Fatai O.; Ahmed, Abdulkarim S.; Ajayi, Olusegun A.

    The preparation and characterization of kaolin based ceramic membranes using styrofoam (STY) and sawdust (SD) as pore formers have been prepared by mechano-chemical synthesis using pressureless sintering technique with porogen content between (0-20) wt% by die pressing. Pellets were fired at 1150 °C and soaking time of 4 h. The membranes cast as circular disks were subjected to characterization studies to evaluate the effect of the sintering temperature and pore former content on porosity, density, water absorption and mechanical strength. Obtained membranes show effective porosity with maximum at about 43 and 47% respectively for membranes formulated with styrofoam and sawdust porogens but with a slightly low mechanical strength that does not exceed 19 MPa. The resultant ceramic bodies show a fine porous structure which is mainly caused by the volatilization of the porogens. The fabricated membrane exhibited high N2 gas flux, hence, these membranes can be considered as efficient for potential application for gas separation by reason of the results shown in the gas flux tests.

  9. Pressureless sintering and gas flux properties of porous ceramic membranes for gas applications

    Directory of Open Access Journals (Sweden)

    David O. Obada

    Full Text Available The preparation and characterization of kaolin based ceramic membranes using styrofoam (STY and sawdust (SD as pore formers have been prepared by mechano-chemical synthesis using pressureless sintering technique with porogen content between (0–20 wt% by die pressing. Pellets were fired at 1150 °C and soaking time of 4 h. The membranes cast as circular disks were subjected to characterization studies to evaluate the effect of the sintering temperature and pore former content on porosity, density, water absorption and mechanical strength. Obtained membranes show effective porosity with maximum at about 43 and 47% respectively for membranes formulated with styrofoam and sawdust porogens but with a slightly low mechanical strength that does not exceed 19 MPa. The resultant ceramic bodies show a fine porous structure which is mainly caused by the volatilization of the porogens. The fabricated membrane exhibited high N2 gas flux, hence, these membranes can be considered as efficient for potential application for gas separation by reason of the results shown in the gas flux tests. Keywords: Porosity, Pore formers, Kaolin, Physico-mechanical properties, Gas separation, Gas flux

  10. The effect of sintering temperature on reliability of extruded ceramic Raschig ring

    Directory of Open Access Journals (Sweden)

    Salem, A.

    2009-02-01

    Full Text Available The feasibility of illitic-kaolinitic clay in ceramic packing manufacturing was assessed. Industrial illitic-kaolinitic clay was formed by extrusion method in the shape of Raschig ring and was sintered at temperatures between 1100 and 1300 oC. The samples were characterized after sintering and open, total and closed porosity were determined by standard methods. For better understanding the role of firing temperature on compressive strength and reliability of Raschig rings, the diametric compressive strength tests were performed and the results were analyzed by Weibull statistical theory. The obtained experimental results showed that the Weibull modulus was significantly affected by sintering temperature and decreases as function of total porosity. Furthermore, the microstructures of samples sintered at different temperatures were observed by scanning electron microscopy, SEM, to confirm the statistical results. In conclusion, though the compressive strength of ceramic Raschig rings improves as the total porosity decreases but, the reliability of them strongly depends on sintering temperature.

    La viabilidad de las arcillas ilítico-caoliníticas en la fabricación de cerámica se evaluó. Las arcilas ilítico-caoliníticas se conformaron por el método de extrusión en forma de anillo Raschig y se sinterizaron a temperaturas entre 1100 y 1300 ºC. Las muestras se caracterizaron después de sinterización y la porosidad abierta, cerrada y total se determinó por métodos estándar. Para entender mejor la influencia de la temperatura de cocción sobre las propiedades de resistencia a la compresión, la fiabilidad de los anillos Raschig y la resistencia a la compresión diamétrica se realizaron los correspondientes ensayos que fueron analizados por la teoría estadística de Weibull. Los resultados experimentales obtenidos mostraron que el módulo de Weibull se vio considerablemente afectado por la temperatura de sinterización y disminuye a

  11. Characterization of Al2O3-Co ceramic composite obtained by high energy mill

    International Nuclear Information System (INIS)

    Souza, J.L.; Assis, R.B. de; Carlos, E.M.; Oliveira, T.P.; Costa, F.A. da

    2014-01-01

    This work aims to characterize the ceramic composite Al 2 O3-Co obtained by high energy grinding. The composites were obtained by milling Al 2 O 3 and Co in a high energy mill at a speed of 400 rpm, in proportions of 5 to 20% Cobalt (Co). Ceramic composites with 5 and 20% cobalt were sintered at 1200 and 1300 ° C, with a 60-minute plateau and a heating rate of 10 ° C / min. The samples were characterized by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG / DSC) and scanning electron microscopy (SEM). The results show the significant effect of cobalt percentage and high energy grinding on the final properties of the Al 2 O 3 - Co ceramic composite, presenting satisfactory values for the composite with a 20% cobalt percentage, showing to be a promising material for application in cutting tools

  12. Rugometric and microtopographic non-invasive inspection in dental-resin composites and zirconia ceramics

    Science.gov (United States)

    Fernández-Oliveras, Alicia; Costa, Manuel F. M.; Pecho, Oscar E.; Rubiño, Manuel; Pérez, María. M.

    2013-11-01

    Surface properties are essential for a complete characterization of biomaterials. In restorative dentistry, the study of the surface properties of materials meant to replace dental tissues in an irreversibly diseased tooth is important to avoid harmful changes in future treatments. We have experimentally analyzed the surface characterization parameters of two different types of dental-resin composites and pre-sintered and sintered zirconia ceramics. We studied two shades of both composite types and two sintered zirconia ceramics: colored and uncolored. Moreover, a surface treatment was applied to one specimen of each dental-resin. All the samples were submitted to rugometric and microtopographic non-invasive inspection with the MICROTOP.06.MFC laser microtopographer in order to gather meaningful statistical parameters such as the average roughness (Ra), the root-mean-square deviation (Rq), the skewness (Rsk), and the kurtosis of the surface height distribution (Rku). For a comparison of the different biomaterials, the uncertainties associated to the surface parameters were also determined. With respect to Ra and Rq, significant differences between the composite shades were found. Among the dental resins, the nanocomposite presented the highest values and, for the zirconia ceramics, the pre-sintered sample registered the lowest ones. The composite performance may have been due to cluster-formation variations. Except for the composites with the surface treatment, the sample surfaces had approximately a normal distribution of heights. The surface treatment applied to the composites increased the average roughness and moved the height distribution farther away from the normal distribution. The zirconia-sintering process resulted in higher average roughness without affecting the height distribution.

  13. Composite Laser Ceramics by Advanced Bonding Technology.

    Science.gov (United States)

    Ikesue, Akio; Aung, Yan Lin; Kamimura, Tomosumi; Honda, Sawao; Iwamoto, Yuji

    2018-02-09

    Composites obtained by bonding materials with the same crystal structure and different chemical compositions can create new functions that do not exist in conventional concepts. We have succeeded in bonding polycrystalline YAG and Nd:YAG ceramics without any interstices at the bonding interface, and the bonding state of this composite was at the atomic level, similar to the grain boundary structure in ceramics. The mechanical strength of the bonded composite reached 278 MPa, which was not less than the strength of each host material (269 and 255 MPa). Thermal conductivity of the composite was 12.3 W/mK (theoretical value) which is intermediate between the thermal conductivities of YAG and Nd:YAG (14.1 and 10.2 W/mK, respectively). Light scattering cannot be detected at the bonding interface of the ceramic composite by laser tomography. Since the scattering coefficients of the monolithic material and the composite material formed by bonding up to 15 layers of the same materials were both 0.10%/cm, there was no occurrence of light scattering due to the bonding. In addition, it was not detected that the optical distortion and non-uniformity of the refractive index variation were caused by the bonding. An excitation light source (LD = 808 nm) was collimated to 200 μm and irradiated into a commercial 1% Nd:YAG single crystal, but fracture damage occurred at a low damage threshold of 80 kW/cm². On the other hand, the same test was conducted on the bonded interface of 1% Nd:YAG-YAG composite ceramics fabricated in this study, but it was not damaged until the excitation density reached 127 kW/cm². 0.6% Nd:YAG-YAG composite ceramics showed high damage resistance (up to 223 kW/cm²). It was concluded that composites formed by bonding polycrystalline ceramics are ideal in terms of thermo-mechanical and optical properties.

  14. 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.

  15. Hybrid Ceramic Matrix Fibrous Composites: an Overview

    Science.gov (United States)

    Naslain, R.

    2011-10-01

    Ceramic-Matrix Composites (CMCs) consist of a ceramic fiber architecture in a ceramic matrix, bonded together through a thin interphase. The present contribution is limited to non-oxide CMCs. Their constituents being oxidation-prone, they are protected by external coatings. We state here that CMCs display a hybrid feature, when at least one of their components is not homogeneous from a chemical or microstructural standpoint. Hybrid fiber architectures are used to tailor the mechanical or thermal CMC-properties whereas hybrid interphases, matrices and coatings to improve CMC resistance to aggressive environments.

  16. Hybrid Ceramic Matrix Fibrous Composites: an Overview

    Energy Technology Data Exchange (ETDEWEB)

    Naslain, R, E-mail: naslain@lcts.u-bordeaux1.fr [University of Bordeaux 3, Allee de La Boetie, 33600 Pessac (France)

    2011-10-29

    Ceramic-Matrix Composites (CMCs) consist of a ceramic fiber architecture in a ceramic matrix, bonded together through a thin interphase. The present contribution is limited to non-oxide CMCs. Their constituents being oxidation-prone, they are protected by external coatings. We state here that CMCs display a hybrid feature, when at least one of their components is not homogeneous from a chemical or microstructural standpoint. Hybrid fiber architectures are used to tailor the mechanical or thermal CMC-properties whereas hybrid interphases, matrices and coatings to improve CMC resistance to aggressive environments.

  17. Hybrid Ceramic Matrix Fibrous Composites: an Overview

    International Nuclear Information System (INIS)

    Naslain, R

    2011-01-01

    Ceramic-Matrix Composites (CMCs) consist of a ceramic fiber architecture in a ceramic matrix, bonded together through a thin interphase. The present contribution is limited to non-oxide CMCs. Their constituents being oxidation-prone, they are protected by external coatings. We state here that CMCs display a hybrid feature, when at least one of their components is not homogeneous from a chemical or microstructural standpoint. Hybrid fiber architectures are used to tailor the mechanical or thermal CMC-properties whereas hybrid interphases, matrices and coatings to improve CMC resistance to aggressive environments.

  18. Structural defects and non-ferroelectric piezoelectricity in an unpoled SrTiO3–Bi12TiO20 (ST–BT) composite ceramics

    International Nuclear Information System (INIS)

    Zhang, L.J.; Wang, T.; Wang, L.H.; Liu, J.D.; Zhao, M.L.; Ye, B.J.

    2012-01-01

    Anomalous piezoelectricity SrTiO 3 –Bi 12 TiO 20 (ST–BT) composite ceramics fabricated by traditional sintering technology were first studied by positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy. A large number of crystal defects were observed in ST–BT composite ceramics with the sintering temperature below 980 °C. The piezoelectric effect appeared concurrently with a high concentration of single-vacancy defects in the ceramics, suggesting that it may be closely related to the microstructure. This further proves that the flexoelectric effect is the origin of non-ferroelectric piezoelectricity.

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

    Directory of Open Access Journals (Sweden)

    Román-Manso, B.

    2014-04-01

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

  20. Ceramic matrix composites by microwave assisted CVI

    International Nuclear Information System (INIS)

    Currier, R.P.; Devlin, D.J.

    1993-01-01

    Chemical vapor infiltration (CVI) processes for producing continuously reinforced ceramic composites are reviewed. Potential advantages of microwave assisted CVI are noted and numerical studies of microwave assisted CVI are reviewed. The models predict inverted thermal gradients in fibrous ceramic preforms subjected to microwave radiation and suggest processing strategies for achieving uniformly dense composites. Comparisons are made to experimental results on silicon-based composite systems. The role played by the relative ability of fiber and matrix to dissipate microwave energy is noted. Results suggest that microwave induced inverted gradients can be exploited to promote inside-out densification. 10 refs., 2 figs

  1. 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

  2. Combining Esthetic Layering and Lithium Disilicate Sintering Technique on Zirconia Frameworks: A Veneering Option to Prevent Ceramic Chipping.

    Science.gov (United States)

    Saeidi Pour, Reza; Edelhoff, Daniel; Rafael, Caroline Freitas; Prandtner, Otto; Frei, Stefan; Maziero Volpato, Claudia Angela; Liebermann, Anja

    Major and minor chipping of veneering porcelain are two of the most frequent complications in all-ceramic restorations with zirconia frameworks. In cases of major chipping, replacement of the affected restoration may be necessary. High-strength lithium disilicate ceramic offers new options to serve as veneering material in a sintering technique or as repair material for chipping in combination with the adhesive technique. The purpose of three case presentations here was to describe the use of lithium disilicate ceramic on zirconia frameworks for reliable and esthetic veneering in the posterior region and to repair extended chipping in conventional veneering materials.

  3. Glass-ceramic coating material for the CO2 laser based sintering of thin films as caries and erosion protection.

    Science.gov (United States)

    Bilandžić, Marin Dean; Wollgarten, Susanne; Stollenwerk, Jochen; Poprawe, Reinhart; Esteves-Oliveira, Marcella; Fischer, Horst

    2017-09-01

    The established method of fissure-sealing using polymeric coating materials exhibits limitations on the long-term. Here, we present a novel technique with the potential to protect susceptible teeth against caries and erosion. We hypothesized that a tailored glass-ceramic material could be sprayed onto enamel-like substrates to create superior adhesion properties after sintering by a CO 2 laser beam. A powdered dental glass-ceramic material from the system SiO 2 -Na 2 O-K 2 O-CaO-Al 2 O 3 -MgO was adjusted with individual properties suitable for a spray coating process. The material was characterized using X-ray fluorescence analysis (XRF), heating microscopy, dilatometry, scanning electron microscopy (SEM), grain size analysis, biaxial flexural strength measurements, fourier transform infrared spectroscopy (FTIR), and gas pycnometry. Three different groups of samples (each n=10) where prepared: Group A, powder pressed glass-ceramic coating material; Group B, sintered hydroxyapatite specimens; and Group C, enamel specimens (prepared from bovine teeth). Group B and C where spray coated with glass-ceramic powder. All specimens were heat treated using a CO 2 laser beam process. Cross-sections of the laser-sintered specimens were analyzed using laser scanning microscopy (LSM), energy dispersive X-ray analysis (EDX), and SEM. The developed glass-ceramic material (grain size d50=13.1mm, coefficient of thermal expansion (CTE)=13.310 -6 /K) could be spray coated on all tested substrates (mean thickness=160μm). FTIR analysis confirmed an absorption of the laser energy up to 95%. The powdered glass-ceramic material was successfully densely sintered in all sample groups. The coating interface investigation by SEM and EDX proved atomic diffusion and adhesion of the glass-ceramic material to hydroxyapatite and to dental enamel. A glass-ceramic material with suitable absorption properties was successfully sprayed and laser-sintered in thin films on hydroxyapatite as well as on

  4. Effects of silicon carbide on the phase developments in mullite-carbon ceramic composite

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE

    2017-12-01

    Full Text Available The effects of the addition of silicon carbide and sintering temperatures on the phases developed, in sintered ceramic composite produced from kaolin and graphite was investigated. The kaolin and graphite of known mineralogical composition were thoroughly blended with 4 and 8 vol % silicon carbide. From the homogeneous mixture of kaolin, graphite and silicon carbide, standard samples were prepared via uniaxial compaction. The test samples produced were subjected to firing (sintering at 1300°C, 1400°C and 1500°C. The sintered samples were characterized for the developed phases using x‐ray diffractometry analysis, microstructural morphology using ultra‐high resolution field emission scanning electron microscope (UHRFEGSEM. It was observed that microstructural morphology of the samples revealed the evolution of mullite, cristobalite and microcline. The kaolinite content of the raw kaolin undergoes transformation into mullite and excess silica, the mullite and the silica phases contents increased with increased sintering temperature. It is also generally observed that the graphite content progressively reduced linearly with increased sintering temperature. It is concluded that silicon carbide acts as anti-oxidant for the graphite, this anti-oxidant effect was more effective at 4 vol % silicon carbide.

  5. Ceramic composites by chemical vapor infiltration

    International Nuclear Information System (INIS)

    Stinton, D.P.

    1987-01-01

    Composites consisting of silicon carbide matrices reinforced with continuous ceramic fibers are being developed for high-temperature structural applications. Chemical vapor deposition (CVD) techniques are very effective in fabricating composites with high strengths and exceptional fracture toughness. Mechanical properties of infiltrated composites are controlled by the strength of the interfacial bond between the fibers and matrix. This paper describes two CVD techniques and reviews the models being developed to better understand and control the infiltration process

  6. Solid state reaction in alumina nanoparticles/LZSA glass-ceramic composites

    International Nuclear Information System (INIS)

    Montedo, O.K.; Oliveira, A.N. de; Raupp-Pereira, F.

    2016-01-01

    Full text: The aim of this work is to present results related to solid state reactions on LZSA glass-ceramic composites containing alumina reinforcement nano-particles. A LZSA (Li2O-ZrO2-SiO2-Al2O3) glass-ceramic has been prepared by sintering of powders and characterized. Composites containing 0 to 77 vol.% of alumina nanoparticles (27-43 nm APS, 35 m2.g-1 SSA) and a 16.9Li2O•5.0ZrO2•65.1SiO2•8.6Al2O3 glass-ceramic matrix have been prepared. X-ray diffractometry studies have been performed in order of investigating the solid state reactions occurring in LZSA-based composites. Results of the XRD patterns have been related to the coefficient of thermal expansion (CTE), Young modulus, and dielectric constant, showing that, in comparison with the glass-ceramic composition, the composites showed a decrease of CTE with the alumina concentration increasing, due to the increasing of beta-spodumeness formation (solid solution of beta-spodumene, Li2O.Al2O3.4-10SiO2). The performance of the glass-ceramic was improved with the alumina nano-particles addition, showing potential of using in the preparation of Low Thermal Co-fired Ceramics (LTCC). (author)

  7. Development of hierarchical magnesium composites using hybrid microwave sintering.

    Science.gov (United States)

    Habibi, Meisam Kouhi; Joshi, Shailendra P; Gupta, Manoj

    2011-01-01

    In this work, hierarchical magnesium based composites with a micro-architecture comprising reinforcing constituent that is a composite in itself were fabricated using powder metallurgy route including microwave assisted rapid sintering technique and hot extrusion. Different level-I composite particles comprises sub-micron pure aluminum (Al) matrix containing Al2O3 particles of different length scale (from micrometer to nanometer size). Microstructural characterization of the hierarchical composites revealed reasonably uniform distribution of level-I composite particles and significant grain refinement compared to monolithic Mg. Hierarchical composite configurations exhibited different mechanical performance as a function of Al2O3 length scale. Among the different hierarchical formulations synthesized, the hierarchical configuration with level-I composition comprising Al and nano-Al2O3 (0.05 microm) exhibited the highest improvement in tensile yield strength (0.2% YS), ultimate tensile strength (UTS), tensile failure strain (FS), compressive yield strength (0.2% CYS) and ultimate compressive strength (UCS) (+96%, +80%, +42%, +80%, and +83%) as compared to monolithic Mg. An attempt has been made in the present study to correlate the effect of different length scales of Al2O3 particulates on the microstructural and mechanical response of magnesium.

  8. Combinatorial bulk ceramic magnetoelectric composite libraries of strontium hexaferrite and barium titanate.

    Science.gov (United States)

    Pullar, Robert C

    2012-07-09

    Bulk ceramic combinatorial libraries were produced via a novel, high-throughput (HT) process, in the form of polycrystalline strips with a gradient composition along the length of the library. Step gradient ceramic composite libraries with 10 mol % steps of SrFe12O19-BaTiO3 (SrM-BT) were made and characterized using HT methods, as a proof of principle of the combinatorial bulk ceramic process, and sintered via HT thermal processing. It was found that the SrM-BT libraries sintered at 1175 °C had the optimum morphology and density. The compositional, electrical and magnetic properties of this library were analyzed, and it was found that the SrM and BT phases did not react and remained discrete. The combinatorial synthesis method produced a relatively linear variation in composition. The magnetization of the library followed the measured compositions very well, as did the low frequency permittivity values of most compositions in the library. However, with high SrM content of ≥80 mol %, the samples became increasingly conductive, and no reliable dielectric measurements could be made. Such conductivity would also greatly inhibit any ferroelectricity and magnetoelectric coupling with these composites with high levels of the SrM hexagonal ferrite.

  9. Advanced ceramic matrix composites for high energy x-ray generation

    International Nuclear Information System (INIS)

    Khan, Amir Azam; Labbe, Jean Claude

    2011-01-01

    High energy x-ray targets are the anodes used in high performance tubes, designed to work for long operating times and at high power. Such tubes are used in computed tomography (CT) scan machines. Usually the tubes used in CT scanners have to continuously work at high temperatures and for longer scan durations in order to get maximum information during a single scan. These anodes are composed of a refractory substrate which supports a refractory metallic coating. The present work is a review of the development of a ceramic metal composite based on aluminium nitride (AlN) and molybdenum for potential application as the substrate. This composite is surface engineered by coating with tungsten, the most popular material for high energy x-ray targets. To spray metallic coatings on the surface of ceramic matrix composites dc blown arc plasma is employed. The objective is to increase the performance and the life of an x-ray tube. Aluminium nitride-molybdenum ceramic matrix composites were produced by uniaxial hotpressing mixtures of AlN and Mo powders. These composites were characterized for their mechanical, thermal, electrical and micro-structural properties. An optimized composition was selected which contained 25 vol.% of metallic phase dispersed in the AlN matrix. These composites were produced in the actual size of an anode and coated with tungsten through dc blown arc plasma spraying. The results have shown that sintering of large size anodes is possible through uniaxial pressing, using a modified sintering cycle

  10. Glasses, ceramics, and composites from lunar materials

    Science.gov (United States)

    Beall, George H.

    1992-02-01

    A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

  11. Measurement and model on thermal properties of sintered diamond composites

    International Nuclear Information System (INIS)

    Moussa, Tala; Garnier, Bertrand; Peerhossaini, Hassan

    2013-01-01

    Highlights: ► Thermal properties of sintered diamond used for grinding is studied. ► Flash method with infrared temperature measurement is used to investigate. ► Thermal conductivity increases with the amount of diamond. ► It is very sensitive to binder conductivity. ► Results agree with models assuming imperfect contact between matrix and particles. - Abstract: A prelude to the thermal management of grinding processes is measurement of the thermal properties of working materials. Indeed, tool materials must be chosen not only for their mechanical properties (abrasion performance, lifetime…) but also for thermal concerns (thermal conductivity) for efficient cooling that avoids excessive temperatures in the tool and workpiece. Sintered diamond is currently used for grinding tools since it yields higher performances and longer lifetimes than conventional materials (mineral or silicon carbide abrasives), but its thermal properties are not yet well known. Here the thermal conductivity, heat capacity and density of sintered diamond are measured as functions of the diamond content in composites and for two types of metallic binders: hard tungsten-based and soft cobalt-based binders. The measurement technique for thermal conductivity is derived from the flash method. After pulse heating, the temperature of the rear of the sample is measured with a noncontact method (infrared camera). A parameter estimation method associated with a three-layer nonstationary thermal model is used to obtain sample thermal conductivity, heat transfer coefficient and absorbed energy. With the hard metallic binder, the thermal conductivity of sintered diamond increased by up to 64% for a diamond content increasing from 0 to 25%. The increase is much less for the soft binder: 35% for diamond volumes up to 25%. In addition, experimental data were found that were far below the value predicted by conventional analytical models for effective thermal conductivity. A possible explanation

  12. Ti-Nb-Sn-hydroxyapatite composites synthesized by mechanical alloying and high frequency induction heated sintering.

    Science.gov (United States)

    Wang, Xiaopeng; Chen, Yuyong; Xu, LiJuan; Xiao, Shulong; Kong, Fantao; Woo, Kee Do

    2011-11-01

    A β-type Ti-based composite, Ti-35Nb-2.5Sn-15-hydroxyapatite (HA), has been synthesized by mechanical alloying and powder metallurgy. The effects of milling time on microstructure, mechanical properties and biocompatibility of the sintered composites were investigated by scanning electronic microscopy (SEM), X-ray diffraction (XRD), microhardness tests, compression tests and cells culture. The results revealed when milling time increased, the homogeneity and relative density of the sintered composite increased, but the finished sintering temperature decreased. The compression Young's modulus of sintered composite from 12 h milled powders was about 22 GPa and its compression strength was 877 MPa. The cell culture results indicated cell viability for these sintered composites was very good. These results revealed the Ti-35Nb-2.5Sn-15HA composite could be useful for medical implants. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. Ceramic nanostructure materials, membranes and composite layers

    NARCIS (Netherlands)

    Burggraaf, A.J.; Keizer, Klaas; van Hassel, B.A.

    1989-01-01

    Synthesis methods to obtain nanoscale materials will be briefly discussed with a focus on sol-gel methods. Three types of nanoscale composites (powders, membranes and ion implanted layers) will be discussed and exemplified with recent original research results. Ceramic membranes with a thickness of

  14. Microstructures and mechanical properties of Fe-28Al-5Cr/TiC composites produced by hot-pressing sintering

    International Nuclear Information System (INIS)

    Zhang Xinghua; Yang Jun; Ma Jiqiang; Bi Qinling; Cheng Jun; Liang Yongmin; Liu Weimin

    2011-01-01

    Highlights: → The near fully dense Fe-28Al-5Cr/TiC composites are produced by hot-pressing sintering. → All the materials exhibit high compressive and bending strength. → Compressive strength increases but bending strength and ductility diminish with rising TiC amount in the composites. → Wear resistance significantly increases with rising TiC amount. - Abstract: The mechanical properties and microstructures of Fe-28Al-5Cr based composites reinforced with 15, 25, 35, 50 wt.% TiC ceramic particle, produced by hot-pressing sintering method, were investigated. The relative density of all the composites was up to 99%. The distribution of TiC was uniform in the composites. Results of XRD analysis showed that the composites were composed of TiC and disorder Fe 3 Al phases. All the materials exhibited very high strength of 1200-2000 MPa. The hardness and compressive strength of the composites increased obviously but compressive strain decreased gradually except 50% composite with increasing TiC content. The bending strength and deflection of the composites decreased significantly with increasing TiC content. The bending fracture surfaces of all the materials were examined using scanning electron microscopy (SEM). The fracture mode transformed gradually from tough dimple fracture mode to brittle cleavage facets crack mode with the increase of TiC content. Wear resistance of the Fe-28Al-5Cr alloy was also significantly improved by addition of TiC.

  15. Thermoelectric properties of SiC/C composites from wood charcoal by pulse current sintering

    NARCIS (Netherlands)

    Fujisawa, M; Hata, T; Bronsveld, P; Castro, [No Value; Tanaka, F; Kikuchi, H; Imamura, Y

    2005-01-01

    SiC/C composites were investigated by sintering a mix of wood charcoal and SiO2 powder (32-45 mu m) at 1400, 1600 and 1800 degrees C under N-2 atmosphere with a pulse current sintering method. Thermoelectric properties of SiC/C composites were investigated by measuring the Seebeck coefficient and

  16. Comparison of thermal analysis, micro structural and compositional of archaeological indigenous ceramic (Caninhas site of Canas - SP) with actual clay/ceramic of region

    International Nuclear Information System (INIS)

    Nakano, F.P.; Taguchi, S.P.; Matos, C.C.; Ribeiro, R.B.

    2009-01-01

    The ceramic material found at the archaeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archaeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archaeological ceramics were identified by the illite, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archaeological application. (author)

  17. Comparison of thermal analysis, micro structural and compositional of archaeological indigenous ceramic (Caninhas site of Canas - SP) with actual clay/ceramic of region

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, F.P.; Taguchi, S.P.; Matos, C.C.; Ribeiro, R.B., E-mail: japaum@alunos.eel.usp.br, E-mail: simone@demar.eel.usp.br, E-mail: cristhian@alunos.eel.usp.br, E-mail: baptistan@demar.eel.usp.br [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia. Departamento de Materiais; Rosa, S.J.L., E-mail: sarinhaleone@gmail.com [Centro Universitario de Volta Redonda, Volta Redonda, RJ (Brazil)

    2009-07-01

    The ceramic material found at the archaeological site in Caninhas, shows funerary structures of combustion and various objects of Tupi-Guarani indigenous use. These pieces and fragments were saved and cataloged, in approximately 4000 units. The ceramics present a gradient of color, from ochre to dark gray, when from the surface to the center of the piece, indicating compositional variation caused by inefficient sintering carried out by indigenous people. The goal of this study was to observe the phase transition temperature, decomposition, mass variation and reactions that occur in the archaeological and nowadays ceramics (by DSC/TG), together with micro structural analysis (by SEM), phase analysis (by XRD) and chemical composition (by EDS). Ceramics nowadays are sintered with air, in a temperature ranging between 400-800 °C for one hour, and presents heterogeneous microstructure. The archaeological ceramics were identified by the illite, hydrated alumina, lutecite and quartz phase, and the caulinite, lutecite and quartz phase in clay produced today from that region differs in all characteristics and aspects according to time. The interaction between different areas of expertise is fundamental to aggregate knowledge: the use of ceramic material engineering to archaeological application. (author)

  18. Emerging Ceramic-based Materials for Dentistry

    Science.gov (United States)

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  19. Composite treatment of ceramic tile armor

    Science.gov (United States)

    Hansen, James G. R. [Oak Ridge, TN; Frame, Barbara J [Oak Ridge, TN

    2010-12-14

    An improved ceramic tile armor has a core of boron nitride and a polymer matrix composite (PMC) facing of carbon fibers fused directly to the impact face of the tile. A polyethylene fiber composite backing and spall cover are preferred. The carbon fiber layers are cured directly onto the tile, not adhered using a separate adhesive so that they are integral with the tile, not a separate layer.

  20. LOWERING THE SINTERING TEMPERATURE OF BARIUM STRONTIUM TITANATE BULK CERAMICS BY BARIUM STRONTIUM TITANATE-GEL AND BaCu(B₂O₅

    Directory of Open Access Journals (Sweden)

    Uwe Gleissner

    2016-03-01

    Full Text Available In this paper the influence of barium strontium titanate (BST xerogel as a sinter additive and BaCu(B₂O₅(BCB as a liquid phase sintering aid on the sintering behavior of BST bulk ceramics is investigated. BST as well as BCB powders were synthesized via a mixed oxide route and BST gel via a sol-gel process. Compared to pure BST bulk ceramics, BST gel reduces the sintering start (onset temperature by up to 174°C and increases the density for a sintering temperature of 1200°C. By adding BCB to the BST powder the sintering was completed much faster and the onset temperatures were reduced by 281°C and 312°C for 1 mol% and 2.5 mol%, respectively. With 2.5 mol% BCB, the highest density of 96 % (5.41 g/cm³ was achieved at 950°C.

  1. Development of ceramics based fuel, Phase I, Kinetics of UO2 sintering by vibration compacting of UO2 powder (Introductory report)

    International Nuclear Information System (INIS)

    Ristic, M.M.

    1962-10-01

    After completing the Phase I of the task related to development of ceramics nuclear fuel the following reports are presented: Kinetics of UO 2 sintering; Vibrational compacting and sintering of UO 2 ; Characterisation of of UO 2 powder by DDK and TGA methods; Separation of UO 2 powder

  2. CMH-17 Volume 5 Ceramic Matrix Composites

    Science.gov (United States)

    Andrulonis, Rachael; Kiser, J. Douglas; David, Kaia E.; Davies, Curtis; Ashforth, Cindy

    2017-01-01

    A wide range of issues must be addressed during the process of certifying CMC (ceramic matrix composite) components for use in commercial aircraft. The Composite Materials Handbook-17, Volume 5, Revision A on ceramic matrix composites has just been revised to help support FAA certification of CMCs for elevated temperature applications. The handbook supports the development and use of CMCs through publishing and maintaining proven, reliable engineering information and standards that have been thoroughly reviewed. Volume 5 contains detailed sections describing CMC materials processing, design analysis guidelines, testing procedures, and data analysis and acceptance. A review of the content of this latest revision will be presented along with a description of how CMH-17, Volume 5 could be used by the FAA (Federal Aviation Administration) and others in the future.

  3. 3D Printing Bioinspired Ceramic Composites.

    Science.gov (United States)

    Feilden, Ezra; Ferraro, Claudio; Zhang, Qinghua; García-Tuñón, Esther; D'Elia, Eleonora; Giuliani, Finn; Vandeperre, Luc; Saiz, Eduardo

    2017-10-23

    Natural structural materials like bone and shell have complex, hierarchical architectures designed to control crack propagation and fracture. In modern composites there is a critical trade-off between strength and toughness. Natural structures provide blueprints to overcome this, however this approach introduces another trade-off between fine structural manipulation and manufacturing complex shapes in practical sizes and times. Here we show that robocasting can be used to build ceramic-based composite parts with a range of geometries, possessing microstructures unattainable by other production technologies. This is achieved by manipulating the rheology of ceramic pastes and the shear forces they experience during printing. To demonstrate the versatility of the approach we have fabricated highly mineralized composites with microscopic Bouligand structures that guide crack propagation and twisting in three dimensions, which we have followed using an original in-situ crack opening technique. In this way we can retain strength while enhancing toughness by using strategies taken from crustacean shells.

  4. A new method to fabricate Fe-TiC composite using conventional sintering and steam hammer

    OpenAIRE

    LAHOUEL, Ali; BOUDEBANE, Saïd; IOST, Alain; MONTAGNE, Alex

    2017-01-01

    International audience; The aim of this research paper is to fabricate a Fe-TiC composite by a novel and simple manufacturing method. The latter is based on two cumulative processes; a conventional sintering (transient liquid phase sintering) and a hot forging with steam hammer respectively. The blinder phase of the studied simples is varied from carbon steel to high alloy steel using alloying additive powders. The obtained outcomes showed that after the sintering process, the relative densit...

  5. Preparation and piezoelectric properties of (K0.5Na0.5)NbO3 lead-free piezoelectric ceramics with pressure-less sintering

    International Nuclear Information System (INIS)

    Du Hongliang; Li Zhimin; Tang Fusheng; Qu Shaobo; Pei Zhibin; Zhou Wancheng

    2006-01-01

    Lead-free piezoelectric ceramics (K 0.5 Na 0.5 )NbO 3 (abbreviated as KNN) with the relative density of 97.6% have been synthesized by press-less sintering owing to the careful control of processing conditions. The phase structure of KNN ceramics with different sintering temperature and heating rate was analyzed. Results show that the pure perovskite phase with orthorhombic symmetry is in all ceramics specimens. The effect of heating rate and sintering temperature on microstructure and piezoelectric properties of KNN ceramics was investigated. The densification behavior and piezoelectric properties of KNN ceramics were enhanced by improving heating rate and sintering temperature. Pure KNN ceramics sintered at 1120 deg. C with heating rate of 5 deg. C/min showed optimized densification and piezoelectric properties (ρ = 4.4 g/cm 3 , d 33 = 120 pC/N -1 , k p = 0.40 and T c = 400 deg. C). The results show that KNN is a promising candidate for lead-free piezoelectric ceramics

  6. Elaboration of silicon carbides nano particles (SiC): from the powder synthesis to the sintered ceramic; Elaboration de ceramiques nanostructurees en carbure de silicium (SiC): de la synthese de poudre a la ceramique frittee

    Energy Technology Data Exchange (ETDEWEB)

    Reau, A. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMA), 91 - Gif-sur-Yvette (France)

    2008-07-01

    Materials for the reactor cores of the fourth generation will need materials supporting high temperatures with fast neutrons flux. SiC{sub f}/SiC ceramics are proposed. One of the possible elaboration process is to fill SiC fiber piece with nano particles SiC powder and to strengthen by sintering. The aim of this thesis is to obtain a nano structured SiC ceramic as a reference for the SiC{sub f}/SiC composite development and to study the influence of the fabrication parameters. (A.L.B.)

  7. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-10-15

    Oct 15, 2017 ... In this work, ceramic carboncomposites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology ofthe sintered samples was characterized by field emission gun (FEG) electron microscopy. Phase analysis was done by X-raydiffraction (XRD). Electrical ...

  8. Potential use of only Yb2O3 in producing dense Si3N4 ceramics with high thermal conductivity by gas pressure sintering

    OpenAIRE

    Zhu, Xinwen; Zhou, You; Hirao, Kiyoshi; Ishigaki, Takamasa; Sakka, Yoshio

    2010-01-01

    Yb2O3 is an efficient sintering additive for enhancing not only thermal conductivity but also the high-temperature mechanical properties of Si3N4 ceramics. Here we report the fabrication of dense Si3N4 ceramics with high thermal conductivity by the gas pressure sintering of α-Si3N4 powder compacts, using only Yb2O3 as an additive, at 1900 °C under a nitrogen pressure of 1 MPa. The effects of Yb2O3 content, sample packing condition and sintering time on the densification, microstructure and th...

  9. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  10. Synthesis of (Zn, Mg)TiO{sub 3}-TiO{sub 2} composite ceramics for multilayer ceramic capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C. [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Wu, S.P., E-mail: chwsp@scut.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Tu, W.P.; Jiao, L.; Zeng, Z.O. [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China)

    2010-11-01

    (Zn{sub 0.8}Mg{sub 0.2})TiO{sub 3}-xTiO{sub 2} composite ceramics has been prepared via the solid-phase synthesis method. TiO{sub 2} was employed to tone temperature coefficient of resonant frequency ({tau}{sub f}) and stabilize hexagonal (Zn, Mg)TiO{sub 3} phase. 3ZnO-B{sub 2}O{sub 3} was effective to promote sintering. The movement of grain boundary was obvious because of the liquid phase sintering. The scanning electron microscope (SEM) photographs and energy dispersive spectrometer (EDS) patterns showed that segregation and precipitation of dissociative (Zn, Mg)TiO{sub 3} grains occurred at grain boundary during sintering. SnO{sub 2} was used as inhibitor to prevent the grain boundary from moving. The dielectric behaviors of specimen strongly depended on structural transition and microstructure. We found that 1.0 wt.% 3ZnO-B{sub 2}O{sub 3} doped (Zn, Mg)TiO{sub 3}-0.25TiO{sub 2} ceramics with 0.1 wt.% SnO{sub 2} additive displayed excellent dielectric properties (at 1000 deg. C): {epsilon}{sub r} = 27.7, Q x f = 65,490 GHz (at 6.07 GHz) and {tau}{sub f} = -8.88 ppm deg. C{sup -1}. The above-mentioned material was applied successfully to make multilayer ceramic capacitors (MLCCs), which exhibited an excellent electrical property. The self-resonance frequency (SRF) and equivalent series resistance (ESR) of capacitor decreased with capacitance increasing, and the quality factor (Q) of capacitor reduced as frequency or capacity increased.

  11. Ceramic matrix and resin matrix composites - A comparison

    Science.gov (United States)

    Hurwitz, Frances I.

    1987-01-01

    The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

  12. Ceramic matrix and resin matrix composites: A comparison

    Science.gov (United States)

    Hurwitz, Frances I.

    1987-01-01

    The underlying theory of continuous fiber reinforcement of ceramic matrix and resin matrix composites, their fabrication, microstructure, physical and mechanical properties are contrasted. The growing use of organometallic polymers as precursors to ceramic matrices is discussed as a means of providing low temperature processing capability without the fiber degradation encountered with more conventional ceramic processing techniques. Examples of ceramic matrix composites derived from particulate-filled, high char yield polymers and silsesquioxane precursors are provided.

  13. Mechanical properties of polymer-infiltrated-ceramic (sodium aluminum silicate) composites for dental restoration.

    Science.gov (United States)

    Cui, Bencang; Li, Jing; Wang, Huining; Lin, Yuanhua; Shen, Yang; Li, Ming; Deng, Xuliang; Nan, Cewen

    2017-07-01

    To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine. The Vickers hardness and elastic modulus were calculated from the results of nano-indentation. The microstructures were investigated using secondary electron detector. The density of the porous ceramic blocks was obtained through TG-DTA. The conversion degrees were calculated from the results of mid-infrared spectroscopy. The obtained polymer infiltrated composites have a maximum flexural strength value of 214±6.5MPa, Vickers hardness of 1.76-2.30GPa, elastic modulus of 22.63-27.31GPa, fracture toughness of 1.76-2.35MPam 1/2 and brittleness index of 0.75-1.32μm -1/2 . These results were compared with those of commercial CAD/CAM blocks. Our results suggest that these materials with good mechanical properties are comparable to two commercial CAD/CAM blocks. The sintering temperature could dramatically influence the mechanical properties. Restorative composites with superior mechanical properties were produced. These materials mimic the properties of natural dentin and could be a promising candidate for CAD/CAM applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Mechanical energy dissipation in natural ceramic composites.

    Science.gov (United States)

    Mayer, George

    2017-12-01

    Ceramics and glasses, in their monolithic forms, typically exhibit low fracture toughness values, but rigid natural marine ceramic and glass composites have shown remarkable resistance to mechanical failure. This has been observed in load-extension behavior by recognizing that the total area under the curve, notably the part beyond the yield point, often conveys substantial capacity to carry mechanical load. The mechanisms underlying the latter observations are proposed as defining factors for toughness that provide resistance to failure, or capability to dissipate energy, rather than fracture toughness. Such behavior is exhibited in the spicules of glass sponges and in mollusk shells. There are a number of similarities in the manner in which energy dissipation takes place in both sponges and mollusks. It was observed that crack diversion, a new form of crack bridging, creation of new surface area, and other important energy-dissipating mechanisms occur and aid in "toughening". Crack tolerance, key to energy dissipation in these natural composite materials, is assisted by promoting energy distribution over large volumes of loaded specimens by minor components of organic constituents that also serve important roles as adhesives. Viscoelastic deformation was a notable characteristic of the organic component. Some of these energy-dissipating modes and characteristics were found to be quite different from the toughening mechanisms that are utilized for more conventional structural composites. Complementary to those mechanisms found in rigid natural ceramic/organic composites, layered architectures and very thin organic layers played major roles in energy dissipation in these structures. It has been demonstrated in rigid natural marine composites that not only architecture, but also the mechanical behavior of the individual constituents, the nature of the interfaces, and interfacial bonding play important roles in energy dissipation. Additionally, the controlling

  15. A special percolation problem in ceramic composites

    International Nuclear Information System (INIS)

    Ang Chen; Xi Dai; Yu Zhi; Yahua Bao

    1993-11-01

    The interface effect is taken into consideration, and a special percolation model is proposed for a two-phases metal/ceramic composite in the present paper. The computer simulation shows that the percolation threshold of this interface-controlled percolation behaviour is 4.5% in the three dimensional f.c.c. lattices, which is in good agreement with the experimental data. (author). 9 refs, 3 figs

  16. 3D Printing Bioinspired Ceramic Composites

    OpenAIRE

    Feilden, Ezra; Ferraro, Claudio; Zhang, Qinghua; García-Tuñón, Esther; D’Elia, Eleonora; Giuliani, Finn; Vandeperre, Luc; Saiz, Eduardo

    2017-01-01

    Natural structural materials like bone and shell have complex, hierarchical architectures designed to control crack propagation and fracture. In modern composites there is a critical trade-off between strength and toughness. Natural structures provide blueprints to overcome this, however this approach introduces another trade-off between fine structural manipulation and manufacturing complex shapes in practical sizes and times. Here we show that robocasting can be used to build ceramic-based ...

  17. Synthesis and characterization of copper–alumina metal matrix composite by conventional and spark plasma sintering

    International Nuclear Information System (INIS)

    Dash, K.; Ray, B.C.; Chaira, D.

    2012-01-01

    Graphical abstract: The evolution of microstructure, density and hardness of Cu–Al 2 O 3 metal matrix composites with different techniques of sintering has been demonstrated here. The effect of sintering atmosphere has also been discussed. Synthesis of microcomposites was carried out by reinforcing 5, 10 and 15 vol.% of alumina powder particle (average size ∼5.71 μm) in copper matrix via conventional sintering using H 2 and N 2 atmospheres. Nanocomposites of 1, 5, 7 vol.% alumina (average size 2 O 3 metal matrix microcomposites and nanocomposites via conventional route and spark plasma sintering routes are studied and compared. Maximum Vickers hardness of 60 and 80 are obtained when the Cu–15 vol.% Al 2 O 3 is conventionally sintered in N 2 and H 2 atmosphere respectively. However, maximum hardness value of 125 is achieved for the Cu–5 vol.% Al 2 O 3 nanocomposite prepared by spark plasma sintering. It has been observed that Cu–Al 2 O 3 metal matrix composite (MMC) shows poor mechanical properties when it is conventionally sintered in N 2 atmosphere than H 2 atmosphere. Highlights: ► Better matrix–reinforcement interfacial bonding and compatibility in hydrogen atmosphere than nitrogen atmosphere. ► An improvement in density and hardness under hydrogen atmosphere than in nitrogen atmosphere is manifested. ► Spark plasma sintering method results in higher density and hardness values than conventional sintering. - Abstract: The evolution of microstructure, density and hardness of Cu–Al 2 O 3 metal matrix composites with different techniques of sintering have been demonstrated here. The effect of sintering atmosphere on the interfacial compatibility of matrix and reinforcement has also been discussed. Synthesis of microcomposites was carried out by reinforcing 5, 10 and 15 vol.% of alumina powder particles (average size ∼5.71 μm) in copper matrix via conventional sintering using N 2, H 2 and Ar atmospheres. Nanocomposites of 1, 5, 7 vol

  18. Sinterable powders

    International Nuclear Information System (INIS)

    Zanghi, J.S.; Kasprzyk, M.R.

    1979-01-01

    A description is given of sinterable powders and methods of producing sintered products using such powders. The powders consist of (a) a particulate ceramic material, e.g. SiC, having specified particle size and surface area; (b) a carbon source material, e.g. sugar or a phenol-formaldehyde resin; and (c) a residue from a solution of H 3 BO 3 , B 2 O 3 , or mixtures of these as sintering aid. (U.K.)

  19. Simulation of the d.c. critical current in superconducting sintered ceramics

    International Nuclear Information System (INIS)

    Riedinger, R.; Habig, P.; Hlil, E.K.; Arnaud, M.; Boulesteix, C.

    1990-01-01

    The new superconducting high-T c sintered ceramics can be described in some case as a lattice of interconnected rods, in other cases as a more or less random packing of parallelepiped crystallites; their size is about a few microns. The d.c. critical current at zero voltage of such a material is not related to the critical current of the bulk material, but to its granular structure. Indeed, the critical current between two adjacent cells is governed by the critical current of the weak link between them; this link behaves within some limits as a Josephson junction, the critical current of which is known. For our present problem, the system can be modeled as a lattice of Josephson junctions. We present here results for the d.c. critical current at zero voltage of lattices of identical Josephson junctions in two dimensions. The influence of the finiteness of size of the sample is examined. The relationship with normal conductivity simulations and percolation is discussed

  20. 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.

  1. Production and study of the behavior of ceramic sintering SR2ALWO5,5 to application on the oil industry

    International Nuclear Information System (INIS)

    Lima, M.M.; Ferreira, R.A. Sanguinetti; Yadava, Y.P.

    2011-01-01

    The complex perovskita ceramics based on tungsten are highly inert corrosive environments. For this reason, this type of ceramic is used in the manufacture of parts and components for the oil industry where the hostile environment is constant problem. We are working in manufacturing temperature sensors encased in ceramic to petroleum industry. Produce ceramic Sr 2 AlWO 5,5 thermo-mechanical process using a ball mill and subsequently heat treatment temperature of 1200°C for 24 hours. Studied the sintering behavior in the temperature range from 1200 to 1350 °C. In this process, the ceramic powder had a high homogeneity in terms of size and distribution of particles, which facilitates sintering at low temperature and shorter time. Structure and microstructure of calcined ceramic was analyzed by X-ray diffraction and scanning electron microscopy and presented at the congress. (author)

  2. Preparation of new composite ceramics based on gadolinium-doped ceria and magnesia nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jingying; Schelter, Matthias; Zosel, Jens; Oelssner, Wolfram [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Mertig, Michael [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Physikalische Chemie, Mess- und Sensortechnik, Technische Universitaet Dresden (Germany)

    2017-09-15

    To achieve solid electrolyte materials for electrochemical energy storage devices with very high oxygen ion conductivity, composites of gadolinium-doped ceria (GDC) and magnesia (MgO) are developed in this study. Three different preparation methods are used to prepare nanoparticles from these two components. According to the characterization results, the self-propagating high-temperature synthesis is best suited for the preparation of both nanometer-sized GDC powder as solid electrolyte and MgO powder as insulator. The structures of the prepared nanometer-sized powders have been characterized by X-ray diffraction and transmission electron microscopy. They show narrow size distributions in the lower nanometer range. Then, dense composite ceramics are prepared from a MgO-GDC mixture by sintering. The size of the crystallite domains in the sintered ceramic is in the upper nanometer range. TEM and TEM-EDX images of a new composite ceramic based on gadolinium-doped ceria and magnesia nanoparticles. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

    Science.gov (United States)

    Levine, Stanley R. (Editor)

    1992-01-01

    The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

  4. Fabrication of laminated ZrC-SiC composite by vacuum hot-pressing sintering

    Directory of Open Access Journals (Sweden)

    Yuanyuan Li

    2015-03-01

    Full Text Available Laminated ZrC-SiC ceramic was prepared through tape casting and hot pressing. The green tapes of ZrC and SiC were prepared at room temperature. In order to improve the density of composite, the binder of green tapes were removed at 550 °C for 1 h. The laminated structure and the cracks propagation path, which is not a straight line, are observed by optical metalloscope. The compact laminated ZrC-SiC composite sintered by vacuum hot-pressing at 1650 °C for 90 min under pressure of 20 MPa was researched by X-ray diffraction and scanning electron microscopy (SEM equipped with energy dispersive X-ray analysis. The results showed that interlayer bonding is tight, and no disordered phase has formed in the interlayers of ZrC or SiC, and the combination mode is physical mechanism.

  5. A new temperature stable microwave dielectric ceramics: ZnTiNb{sub 2}O{sub 8} sintered at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Guo Mei [Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Gong Shuping, E-mail: spgong@mail.hust.edu.cn [Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China); Dou Gang; Zhou Dongxiang [Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2011-05-19

    Highlights: > The sintering temperature of ZnTiNb{sub 2}O{sub 8}-xTiO{sub 2} ceramics with BCB was reduced to 950 deg. C. > The {tau}{sub f} was modified to 0 ppm/deg. C with reasonably good Q x f and {epsilon}{sub r}. > The {epsilon}{sub r} = 38.89, Q x f = 14,500 GHz and {tau}{sub f} = 0 ppm/deg. C were achieved. > It represented very promising candidates as LTCC dielectric materials. - Abstract: The phases, microstructure and microwave dielectric properties of ZnTiNb{sub 2}O{sub 8}-xTiO{sub 2} composite ceramics with different weight percentages of BaCu(B{sub 2}O{sub 5}) additive prepared by solid-state reaction method have been investigated using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results showed that the microwave dielectric properties were strongly dependent on densification, grain sizes and crystalline phases. The sintering temperature of ZnTiNb{sub 2}O{sub 8} ceramics was reduced from 1250 deg. C to 950 deg. C by doping BaCu(B{sub 2}O{sub 5}) additive and the temperature coefficient of resonant frequency ({tau}{sub f}) was adjusted from negative value of -52 ppm/deg. C to 0 ppm/deg. C by incorporating TiO{sub 2}. Addition of 2 wt% BaCu(B{sub 2}O{sub 5}) in ZnTiNb{sub 2}O{sub 8}-xTiO{sub 2} (x = 0.8) ceramics sintered at 950 deg. C showed excellent dielectric properties of {epsilon}{sub r} = 38.89, Q x f = 14,500 GHz (f = 4.715 GHz) and {tau}{sub f} = 0 ppm/deg. C, which represented very promising candidates as LTCC dielectrics for LTCC applications.

  6. Synthesis and characterization of Al2O3NbC composite and the effect of Y2O3 addition on its sintering

    International Nuclear Information System (INIS)

    Pasotti, Rosa Maria da Rocha

    1999-01-01

    Alumina composites containing ceramic particles have been intensively studied because they show improved mechanical properties and some advantages over fibres and whiskers based composites mainly for processing. The embedment of NbC particles in an Al 2 O 3 matrix has been investigated in this work. Composite materials were obtained by the conventional ceramic processing with compositions Al 2 O 3 -x NbC where x=10, 20, and 40 weight %. Materials were sintered in argon at 1650 deg C/30 min, and at 1750 deg C/15min using a graphite resistance furnace. Three sets of samples were processed: containing NbC powder as received; containing NbC powder milled for 30 h; and containing 3 weight % of Y 2 O 3 added to the Al 2 O 3 matrix. After sintering samples were analysed to evaluate the densification grade. Phases were determined by X-ray diffraction, and samples were analysed by optical microscopy, scanning electron microscopy and transmission electron microscopy to observe the microstructure features. Hardness and fracture toughness at room temperature were also determined by the indentation method, and the sintering kinetic was evaluated by dilatometry. The present work shows that Al 2 O 3 -NbC composite can be produced by using pressureless sintering, leading to materials with densities higher than 95% of the theoretical density for all composites containing NbC and sintered at 1750 deg C. The same result can be obtained for composites containing 10 and 20 weight % of NbC, and sintered at temperatures as low as 1650 deg C. Higher concentration of NbC in the Al 2 O 3 matrix promotes an improvement of fracture toughness. Samples with 40-wt % of NbC show K IC equals to 4.5 MPa.m 1/2 . This value is compared to the ones previously determined for Al 2 O 3 - TiC composites, available commercially and used in ceramic cutting-tools. (author)

  7. Microstructural, compositional and mechanical properties of the archaeological indigenous ceramics of Caninhas, Sao Paulo,Brazil; Analise microestrutural, composicional e propriedades mecanicas das ceramicas indigenas do sitio arqueologico Caninhas, Sao Paulo, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, F.P.; Taguchi, S.P., E-mail: japaum@alunos.eel.usp.b [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia de Lorena. Dept. de Engenharia de Materiais; Ribeiro, R.B.; Rosa, S.J.L. [Faculdades Integradas Teresa D' Avila (FATEA), Lorena, SP (Brazil). Rede Salesianas. Dept. de Desenho Industrial; Bornal, W.G.; Queiroz, C.M. [Fundacao Cultural de Jacarehy, Jacarei, SP (Brazil). Nucleo de Arqueologia do Vale do Paraiba

    2009-07-01

    Archaeological ceramics contain infinity of data about social and cultural indigenous site Caninhas/SP. The ceramics present a gradient of color (ochre to dark gray), when from the surface to the center of the piece, indicating compositional variability caused by inefficient sintering carried out by indigenous peoples. It was analyzed the composition phases by X-rays diffraction (XRD) and mapping by EDS, identifying the illite, quartz and lutecite phases (ochre region) and illite, quartz, hydrated alumina and lutecite phases (dark gray region). The results of EDS confirmed the stages identified by X-rays diffraction and suggesting the presence of roots and scrap of ceramics sintered in the composition of indigenous ceramics, when compared by optical microscope and scanning electron microscope. Vickers hardness identified as fragile and heterogeneous are archaeological ceramics, reaching approximately 203 HV in the grains of silica and 16 HV in the ceramic matrix. (author)

  8. Processing and characterization of ceramic superconductor/polymer composites

    International Nuclear Information System (INIS)

    Kander, R.G.; Namboodri, S.L.

    1993-01-01

    One way to more easily process a brittle high-temperature ceramic superconductor into a useful structure is to combine it with a polymer to form a composite material. Processing of polymer-based composites into complex shapes is well established and relatively easy when compared with traditional ceramic processing unit operations. In addition, incorporating a ceramic superconductor into a polymer matrix can improve mechanical performance as compared with a monolithic ceramic. Finally, because ceramic superconductors are susceptible to attack by moisture, a polymer-based composite structure can also provide protection from deleterious environmental effects. This paper focuses on the processing and subsequent characterization of ceramic superconductor/polymer composites designed primarily for electromagnetic shielding and diamagnetic applications. YBa 2 Cu 3 O 7-x [YBCO] ceramic superconductor is combined with poly(methyl methacrylate) [PMMA] to form novel composite structures. Composite structures have been molded with both a discontinuous superconducting phase (i.e., ceramic particulate reinforced polymers) and with a continuous superconducting phase (i.e., polymer infiltrated porous ceramics). Characterization of these composite structures includes the determination of diamagnetic strength, electromagnetic shielding effectiveness, mechanical performance, and environmental resistance. The goal of this program is to produce a composite structure with increased mechanical integrity and environmental resistance at liquid nitrogen temperatures without compromising the electromagnetic shielding and diamagnetic properties of the superconducting phase. Composites structures of this type are potentially useful in numerous magnetic applications including electromagnetic shielding, magnetic sensors, energy storage, magnetic levitation, and motor windings

  9. 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)

  10. Composite reinforced alumina ceramics with titan and lantana for use in coating storage tanks and transport of crude oil

    International Nuclear Information System (INIS)

    Mendes, C.E.; Rego, S.A.B.C.; Oliveira, J.C.S.; Ferreira, R.A. Sanguinetti; Yadava, Y.P.

    2011-01-01

    The objective of this work is to use ceramics to improve the performance of the tanks that store and transport crude oil and which use metallic materials for their manufacture. These tanks in contact with crude oil undergo a process of degradation on their surfaces, since crude oil is a highly corrosive substance. And in turn ceramic materials have good stability in hostile environments. However, they are inherently fragile for display little plastic deformation. Therefore, the choice of a ceramic composite alumina-titania-lantana has high mechanical strength and high toughness which were produced by thermo-mechanical processing. These composites were sintered at 1350 ° C for 36 hours, and it was held Vickers hardness testing and microstructural characterization to assess their surfaces before and after the attack by crude to use such material as ceramic coating. These results will be presented at the congress. (author)

  11. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics.

    Science.gov (United States)

    Kapoor, Saurabh; Goel, Ashutosh; Correia, Ana Filipa; Pascual, Maria J; Lee, Hye-Young; Kim, Hae-Won; Ferreira, José M F

    2015-08-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO-(19.24-x) MgO-x ZnO-5.61 P2O5-38.49 SiO2-0.59 CaF2 (x=2-10) have been synthesised by melt-quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content >4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. A Li-Garnet composite ceramic electrolyte and its solid-state Li-S battery

    Science.gov (United States)

    Huang, Xiao; Liu, Cai; Lu, Yang; Xiu, Tongping; Jin, Jun; Badding, Michael E.; Wen, Zhaoyin

    2018-04-01

    A high strength Li-Garnet solid electrolyte composite ceramic is successfully prepared via conventional solid state method with Li6.4La3Zr1.4Ta0.6O12 and nano MgO powders. Well sintered ceramic pellets and bars are obtained with 0-9 wt.% MgO. Fracture strength is approximately 135 MPa for composite ceramics with 5-9 wt.% MgO, which is ∼50% higher than that of pure Li6.4La3Zr1.4Ta0.6O12 (90 MPa). Lithium-ion conductivity of the composite is above 5 × 10-4 S cm-1 at room temperature; comparable to the pure Li6.4La3Zr1.4Ta0.6O12 material. SEM cross-sections of the composite ceramic shows a much more uniform microstructure comparing with pure ones, owing to the grain growth inhibition effect of the MgO second phase. A battery cell consisting of Li/composite ceramics/Sulfur-Carbon at 25 °C exhibits a capacity of 685 mAh g-1 at 0.2 C at the 200th cycle, while maintaining a coulombic efficiency of 100%. These results indicate that the composite ceramic Li6.4La3Zr1.4Ta0.6O12-MgO is promising for the production of electrolyte membrane and fabrication of Li-Sulfur batteries.

  13. Microstructural and electrochemical characterization of Ni/Ti/sub 2/N composite coating for sintered NdFeB permanent magnets

    International Nuclear Information System (INIS)

    Ali, A.; Ahmad, A.; Deen, K.M.; Ahmad, R.

    2009-01-01

    Sintered NdFeB magnets have complex microstructure that makes them susceptible to corrosion in humid or moist environments. The paper presents the anticorrosion characteristics of a novel Ni/Ti/sub 2/N composite coating applied through electrodeposition and cathodic arc physical vapour deposition (CAPVD) to sintered NdFeB permanent magnets. The performance of composite coating was evaluated in simulated marine environment with the help of dc polarization techniques. The rate of coating degradation was also determined by employing ac electrochemical impedance spectroscopy (EIS). The coating morphology and surface chemistry were studied with scanning electron microscope (SEM). X-ray diffraction (XRD) was used for identification of component phases in the coating-substrate system. The results showed that the composite coating provided an adequately improved corrosion protection to the sintered NdFeB magnets in the simulated marine environment compared to the earlier reported ceramic and metallic coatings. The composite coating did not damage the magnetic properties of coating-substrate system that remained at par with the ceramic and nickel coating having copper interlayer. (author)

  14. Phase evolution and dielectric properties of MgTi2O5 ceramic sintered with lithium borosilicate glass

    International Nuclear Information System (INIS)

    Shin, Hyunho; Shin, Hee-Kyun; Jung, Hyun Suk; Cho, Seo-Yong; Hong, Kug Sun

    2005-01-01

    Phase evolution, densification, and dielectric properties of MgTi 2 O 5 dielectric ceramic, sintered with lithium borosilicate (LBS) glass, were studied. Reaction between LBS glass and MgTi 2 O 5 was significant in forming secondary phases such as TiO 2 and (Mg,Ti) 2 (BO 3 )O. The glass addition was not necessarily deleterious to the dielectric properties due to the formation of TiO 2 : permittivity increased and temperature coefficient of resonance frequency could be tuned to zero with the addition of LBS glass, although the inevitable glass-induced decrease of quality factor was not retarded by the formation of TiO 2 . The sintered specimen with 10 wt% LBS fired at 950 deg. C for 2 h showed permittivity of 19.3, quality factor of 6800 GHz, and τ f of -16 ppm/ deg. C

  15. Effect of LiF as Sintering Agent on the Densification and Phase Formation in Al2O3-4 Wt Pct Nb2O5 Ceramic Compound

    Science.gov (United States)

    Santos, J. L.; Marçal, R. L. S. B.; Jesus, P. R. R.; Gomes, A. V.; Lima, E. P.; Monteiro, S. N.; de Campos, J. B.; Louro, L. H. L.

    2017-10-01

    Different amounts of LiF were added to an Al2O3-4 pct Nb2O5 basic ceramic, as sintering agent. Improved new ceramics were obtained with LiF concentrations varying from 0.25 to 1.50 wt pct and three sintering temperatures of 1573 K, 1623 K, and 1673 K (1300 °C, 1350 °C, and 1400 °C). The addition of 0.5 wt pct LiF yielded the highest densification, 94 pct of the theoretical density, in association with a sintering temperature of 1673 K (1400 °C). Based on X-ray diffraction (XRD), this improvement was due not only to the presence of transformed phases, more precisely Nb3O7F, but also to the absence of LiAl5O8. The preferential interaction of LiF with Nb2O5, instead of Al2O3, contributed to increase the alumina sintering ability by liquid phase formation. Scanning electron microscopy (SEM) results revealed well-connected grains and isolated pores, whereas the chemical composition analysis by energy dispersive energy (EDX) indicated a preferential interaction of fluorine with niobium, in agreement with the results of XRD. It was also observed from thermal analysis that the polyethylene glycol binder burnout temperature increased for all LiF concentrations. This may be related to the formation of hydrogen bridge bonds.

  16. Conductive ceramic composition and method of preparation

    Science.gov (United States)

    Smith, J.L.; Kucera, E.H.

    1991-04-16

    A ceramic anode composition is formed of a multivalent metal oxide or oxygenate such as an alkali metal, transition metal oxygenate. The anode is prepared as a non-stoichiometric crystalline structure by reaction and conditioning in a hydrogen gas cover containing minor proportions of carbon dioxide and water vapor. The structure exhibits a single phase and substantially enhanced electrical conductivity over that of the corresponding stoichiometric structure. Unexpectedly, such oxides and oxygenates are found to be stable in the reducing anode fuel gas of a molten carbonate fuel cell. 4 figures.

  17. Ceramic Matrix Composite (CMC) Materials Characterization

    Science.gov (United States)

    Calomino, Anthony

    2001-01-01

    Under the former NASA EPM Program, much initial progress was made in identifying constituent materials and processes for SiC/SiC ceramic composite hot-section components. This presentation discusses the performance benefits of these approaches and elaborates on further constituent and property improvements made under NASA UEET. These include specific treatments at NASA that significantly improve the creep and environmental resistance of the Sylramic(TM) SiC fiber as well as the thermal conductivity and creep resistance of the CVI Sic matrix. Also discussed are recent findings concerning the beneficial effects of certain 2D-fabric architectures and carbon between the BN interphase coating and Sic matrix.

  18. Ceramic Matrix Composite (CMC) Materials Development

    Science.gov (United States)

    DiCarlo, James

    2001-01-01

    Under the former NASA EPM Program, much initial progress was made in identifying constituent materials and processes for SiC/SiC ceramic composite hot-section components. This presentation discusses the performance benefits of these approaches and elaborates on further constituent and property improvements made under NASA UEET. These include specific treatments at NASA that significantly improve the creep and environmental resistance of the Sylramic(TM) Sic fiber as well as the thermal conductivity and creep resistance of the CVI Sic matrix. Also discussed are recent findings concerning the beneficial effects of certain 2D-fabric architectures and carbon between the BN interphase coating and Sic matrix.

  19. Preparation and Photocatalytic Property of TiO2/Diatomite-Based Porous Ceramics Composite Materials

    Directory of Open Access Journals (Sweden)

    Shuilin Zheng

    2012-01-01

    Full Text Available The diatomite-based porous ceramics was made by low-temperature sintering. Then the nano-TiO2/diatomite-based porous ceramics composite materials were prepared by hydrolysis deposition method with titanium tetrachloride as the precursor of TiO2 and diatomite-based porous as the supporting body of the nano-TiO2. The structure and microscopic appearance of nano-TiO2/diatomite-based porous ceramics composite materials was characterized by XRD and SEM. The photocatalytic property of the composite was investigated by the degradation of malachite green. Results showed that, after calcination at 550°C, TiO2 thin film loaded on the diatomite-based porous ceramics is anatase TiO2 and average grain size of TiO2 is about 10 nm. The degradation ratio of the composite for 5 mg/L malachite green solution reached 86.2% after irradiation for 6 h under ultraviolet.

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

    Directory of Open Access Journals (Sweden)

    Denghao Li

    2014-06-01

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

  1. Influence of ZnO/MgO substitution on sintering, crystallisation, and bio-activity of alkali-free glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Saurabh [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Goel, Ashutosh [Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08854-8065 (United States); Correia, Ana Filipa [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal); Pascual, Maria J. [Instituto de Cerámica y Vidrio (CSIC), Kelsen 5, Campus de Cantoblanco, 28049 Madrid (Spain); Lee, Hye-Young; Kim, Hae-Won [Institute of Tissue Regeneration Engineering (ITREN) & College of Dentistry, Dankook University, Cheonan 330714 (Korea, Republic of); Department of Nanobiomedical Science & BK21 PLUS NBM Global Research Centre for Regenerative Medicine, Dankook University, Cheonan 330714 (Korea, Republic of); Ferreira, José M.F., E-mail: jmf@ua.pt [Department of Materials and Ceramics Engineering, University of Aveiro, CICECO, 3810-193 Aveiro (Portugal)

    2015-08-01

    The present study reports on the influence of partial replacement of MgO by ZnO on the structure, crystallisation behaviour and bioactivity of alkali-free bioactive glass-ceramics (GCs). A series of glass compositions (mol%): 36.07 CaO–(19.24 − x) MgO–x ZnO–5.61 P{sub 2}O{sub 5}–38.49 SiO{sub 2}–0.59 CaF{sub 2} (x = 2–10) have been synthesised by melt–quench technique. The structural changes were investigated by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray diffraction and differential thermal analysis. The sintering and crystallisation behaviours of glass powders were studied by hot-stage microscopy and differential thermal analysis, respectively. All the glass compositions exhibited good densification ability resulting in well sintered and mechanically strong GCs. The crystallisation and mechanical behaviour were studied under non-isothermal heating conditions at 850 °C for 1 h. Diopside was the primary crystalline phase in all the GCs followed by fluorapatite and rankinite as secondary phases. Another phase named petedunnite was identified in GCs with ZnO content > 4 mol. The proliferation of mesenchymal stem cells (MSCs) and their alkaline phosphatase activity (ALP) on GCs was revealed to be Zn-dose dependent with the highest performance being observed for 4 mol% ZnO. - Highlights: • The addition of zinc to glasses decreased T{sub g} and promoted crystallisation. • Zinc enhanced the sintering ability and increased mechanical strength by 36%. • The apatite formation ability decreased with increasing Zn contents. • Zinc stimulated mesenchymal stem cell proliferation in a dose dependent manner.

  2. PREPARATION OF ZrWMoO8-CONTAINING COMPOSITES WITH ZERO THERMAL EXPANSION PROPERTY USING Al(NO33.9H2O AS A SINTERING AID

    Directory of Open Access Journals (Sweden)

    Qinqin Liu

    2015-12-01

    Full Text Available Mixed oxide β-ZrWMoO8-containing composites with monoclinic zirconia (m-ZrO2 were prepared in search for zero thermal expansion ceramics over a wide temperature range. Thermomechanical analyzer (TMA results indicate that the thermal expansion coefficients of the β-ZrWMoO8-containing composites decrease with increasing amount of β-ZrWMoO8 and that the composite with 50 wt. % β-ZrWMoO8 and 50 wt. % m-ZrO2 exhibits near-zero thermal expansion from 30 to about 600oC. However, its relative density is low. The addition of a small amount of Al(NO33.9H2O as a sintering aid increases the density (possibly because the Al3+ ion promotes sintering and densification while affecting the structure and thermal expansion only insignificantly.

  3. Development of high-density ceramic composites for ballistic applications

    International Nuclear Information System (INIS)

    Rupert, N.L.; Burkins, M.S.; Gooch, W.A.; Walz, M.J.; Levoy, N.F.; Washchilla, E.P.

    1993-01-01

    The application of ceramic composites for ballistic application has been generally developed with ceramics of low density, between 2.5 and 4.5 g/cm 2 . These materials have offered good performance in defeating small-caliber penetrators, but can suffer time-dependent degradation effects when thicker ceramic tiles are needed to defeat modem, longer, heavy metal penetrators that erode rather than break up. This paper addresses the ongoing development, fabrication procedures, analysis, and ballistic evaluation of thinner, denser ceramics for use in armor applications. Nuclear Metals Incorporated (NMI) developed a process for the manufacture of depleted uranium (DU) ceramics. Samples of the ceramics have been supplied to the US Army Research Laboratory (ARL) as part of an unfunded cooperative study agreement. The fabrication processes used, characterization of the ceramic, and a ballistic comparison between the DU-based ceramic with baseline Al 2 O 3 will be presented

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

    Science.gov (United States)

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

    2009-02-01

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

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

    Directory of Open Access Journals (Sweden)

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

    2009-01-01

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

  6. Al2O3-TiC Composite Prepared by Spark Plasma Sintering Process: Evaluation of Mechanical and Tribological Properties

    Science.gov (United States)

    Kumar, Rohit; Chaubey, A. K.; Bathula, Sivaiah; Prashanth, K. G.; Dhar, Ajay

    2018-03-01

    Al2O3-10TiC composites were synthesized by spark plasma sintering (SPS) process. Microstructural and mechanical properties of the composite reveal homogeneous distribution of the fine TiC particles in the matrix. The samples were produced with different sintering temperature, and it shows that the hardness and density gradually increases with increasing sintering temperature. Abrasion wear test result reveals that the composite sintered at 1500 °C shows high abrasion resistance (wt. loss 0.016 g) and the lowest abrasion resistance was observed for the composite sample sintered at 1100 °C (wt. loss 1.459 g). The profilometry surface roughness study shows that sample sintered at 1100 °C shows maximum roughness ( R a = 6.53 µm) compared to the sample sintered at 1500 °C ( R a = 0.66 µm) corroborating the abrasion wear test results.

  7. Al2O3-TiC Composite Prepared by Spark Plasma Sintering Process: Evaluation of Mechanical and Tribological Properties

    Science.gov (United States)

    Kumar, Rohit; Chaubey, A. K.; Bathula, Sivaiah; Prashanth, K. G.; Dhar, Ajay

    2018-01-01

    Al2O3-10TiC composites were synthesized by spark plasma sintering (SPS) process. Microstructural and mechanical properties of the composite reveal homogeneous distribution of the fine TiC particles in the matrix. The samples were produced with different sintering temperature, and it shows that the hardness and density gradually increases with increasing sintering temperature. Abrasion wear test result reveals that the composite sintered at 1500 °C shows high abrasion resistance (wt. loss 0.016 g) and the lowest abrasion resistance was observed for the composite sample sintered at 1100 °C (wt. loss 1.459 g). The profilometry surface roughness study shows that sample sintered at 1100 °C shows maximum roughness (R a = 6.53 µm) compared to the sample sintered at 1500 °C (R a = 0.66 µm) corroborating the abrasion wear test results.

  8. ANL-1(A) - Development of nondestructive evaluation methods for structural ceramics

    International Nuclear Information System (INIS)

    Ellingson, W.A.; Roberts, R.A.; Gopalsami, N.; Dieckman, S.; Hentea, T.; Vaitekunas, J.J.

    1989-01-01

    This section includes the following papers: Development of Nondestructive Evaluation Methods for Structural Ceramics; Effects of Flaws on the Fracture Behavior of Structural Ceramics; Design, Fabrication, and Interface Characterization of Ceramic Fiber-Ceramic Matrix Composites; Development of Advanced Fiber-Reinforced Ceramics; Modeling of Fibrous Preforms for CVD Infiltration; NDT of Advanced Ceramic Composite Materials; Joining of Silicon Carbide Reinforced Ceramics; Superconducting Film Fabrication Research; Short Fiber Reinforced Structural Ceramics; Structural Reliability and Damage Tolerance of Ceramic Composites for High-Temperature Applications; Fabrication of Ceramic Fiber-Ceramic Matrix Composites by Chemical Vapor Infiltration; Characterization of Fiber-CVD Matrix interfacial Bonds; Microwave Sintering of Superconducting Ceramics; Improved Ceramic Composites Through Controlled Fiber-Matrix Interactions; Evaluation of Candidate Materials for Solid Oxide Fuel Cells; Ceramic Catalyst Materials: Hydrous Metal Oxide Ion-Exchange Supports for Coal Liquefaction; and Investigation of Properties and Performance of Ceramic Composite Components

  9. Microstructure-electrical properties relation of zirconia based ceramic composites

    International Nuclear Information System (INIS)

    Fonseca, Fabio Coral

    2001-01-01

    The electrical properties of zirconia based ceramic composites were studied by impedance spectroscopy. Three materials were prepared with different relative compositions of the conducting and insulating phases: (ZrO 2 :8 mol% Y 2 ) 3 ) + MgO, (ZrO 2 :8 mol% Y 2 O 3 ) + Y 2 O 3 and ZrO 2 + 8 mol% Y 2 O 3 . All specimens were analyzed by X-ray diffraction and scanning electron microscopy for microstructural characterization and for correlation of microstructural aspects with electrical properties. For (ZrO 2 :8 mol% Y 2 O 3 ) + MgO the main results show that the dependence of the different (microstructural constituents) contributions to the electrical resistivity on the magnesia content follows two stages: one below and another above the solubility limit of magnesia in Yttria-stabilized zirconia. The same dependence is found for the lattice parameter determined by X-ray diffraction measurements. The impedance diagrams of the composites have been resolved allowing the identification of contributions due to the presence of each microstructural constituent in both stages. Magnesia as a second phase is found to inhibit grain growth in Yttria-stabilized zirconia and the solubility limit for magnesia in the zirconia matrix is around 10 mol%. For (ZrO 2 :8 mol% Y 2 O 3 ) + Y 2 O 3 the main results show that: Yttria is present as a second phase for 1350 deg C /0.1 h sintering; the addition of 2 mol% of Yttria does not modify significantly the electrical properties; the solubility limit for Yttria is around 2 mol% according to electrical measurements. Similarly to magnesia, Yttria inhibits grain growth on Yttria-stabilized zirconia. The general effective medium theory was used to analyze the percolation of the insulating phase; the percolation threshold is different if one considers separately the total, bulk and grain boundary contributions to the electrical conductivity: 32.0, 38.5 and 27.8 vol% for total, intra and intergranular contributions, respectively. The increase of

  10. 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

  11. Compositional homogeneity in a medical-grade stainless steel sintered with a Mn–Si additive

    International Nuclear Information System (INIS)

    Salahinejad, E.; Hadianfard, M.J.; Ghaffari, M.; Mashhadi, Sh. Bagheri; Okyay, A.K.

    2012-01-01

    In this paper, chemical composition uniformity in amorphous/nanocrystallization medical-grade stainless steel (ASTM ID: F2581) sintered with a Mn–Si additive was studied via scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The results show that as a result of sintering at 1000 °C, no dissociation of Mn–Si additive particles embedded in the stainless steel matrix occurs. In contrast, sintering at 1050 °C develops a relatively homogeneous microstructure from the chemical composition viewpoint. The aforementioned phenomena are explained by liquation of the Mn–Si eutectic additive, thereby wetting of the main powder particles, penetrating into the particle contacts and pore zones via capillary forces, and providing a path of high diffusivity. - Highlights: ► Local chemical composition in a sintered stainless steel was studied. ► Due to sintering at 1000 °C, no dissociation of additive particles occurs. ► Sintering at 1050 °C provides a uniform chemical composition.

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

    Science.gov (United States)

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

    1992-01-01

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

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

    Science.gov (United States)

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

    1992-01-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  15. Phase composition of yttrium-doped zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hennig, Christoph; Scheinost, Andreas C. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Molecular Structures; Weiss, Stephan [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Ikeda-Ohno, Atsushi [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Gumeniuk, R. [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Experimentelle Physik

    2017-06-01

    Ceramic material might be an alternative to borosilicate glass for the immobilization of nuclear waste. The crystallinity of ceramic material increases the corrosion resistance over several magnitudes in relation to amorphous glasses. The stability of such ceramics depend on several parameters, among them the crystal phase composition. A reliable quantitative phase analysis is necessary to correlate the macroscopic material properties with structure parameters. We performed a feasibility study based on yttrium-doped zirconia ceramics as analogue for trivalent actinides to ascertain that the nanosized crystal phases in zirconia ceramics can be reliably determined.

  16. 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.

  17. 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.)

  18. Low-temperature sintering and compatibility with silver electrode of Ba4MgTi11O27 microwave dielectric ceramic

    International Nuclear Information System (INIS)

    Chen, Xiuli; Zhou, Huanfu; Fang, Liang; Liu, Laijun; Li, Changda; Guo, Ruli; Wang, Hong

    2010-01-01

    Ba 4 MgTi 11 O 27 microwave dielectric ceramic was investigated using X-ray diffraction, scanning electron microscopy and dielectric measurement. The pure Ba 4 MgTi 11 O 27 ceramic shows a high sintering temperature (∼1275 o C) and good microwave dielectric properties as Q x f of 19,630 GHz, ε r of 36.1, τ f of 14.6 ppm/ o C. It was found that the addition of BaCu(B 2 O 5 ) (BCB) can effectively lower the sintering temperature from 1275 to 925 o C, and does not induce much degradation of the microwave dielectric properties. The BCB-doped Ba 4 MgTi 11 O 27 ceramics can be compatible with Ag electrode, which makes it a promising ceramic for LTCC technology application.

  19. Improvement of thermal conductivity of ceramic matrix composites for 4. generation nuclear reactors

    International Nuclear Information System (INIS)

    Cabrero, J.

    2009-11-01

    This study deals with thermal conductivity improvement of SiCf/SiC ceramic matrix composites materials to be used as cladding material in 4. generation nuclear reactor. The purpose of the study is to develop a composite for which both the temperature and irradiation effect is less pronounced on thermal conductivity of material than for SiC. This material will be used as matrix in CMC with SiC fibers. Some TiC-SiC composites with different SiC volume contents were prepared by spark plasma sintering (SPS). The sintering process enables to fabricate specimens very fast, with a very fine microstructure and without any sintering aids. Neutron irradiation has been simulated using heavy ions, at room temperature and at 500 C. Evolution of the thermal properties of irradiated materials is measured using modulated photothermal IR radiometry experiment and was related to structural evolution as function of dose and temperature. It appears that such approach is reliable to evaluate TiC potentiality as matrix in CMC. Finally, CMC with TiC matrix and SiC fibers were fabricated and both mechanical and thermal properties were measured and compare to SiCf/SiC CMC. (author)

  20. Furnace for the continuous sintering of pellets of ceramic nuclear fuel material

    International Nuclear Information System (INIS)

    Heyraud, J.

    1977-01-01

    The furnace comprises a hearth for the longitudinal displacement of pellet containers, means for injecting gas at both ends of the furnace, for sucking gas between preheating and sintering zones and for condensing the binder, means for displacing the containers from an introduction lock-chamber to an extraction lock-chamber, a conveyor belt which passes through a glove box and provides a leak-tight connection between the lock-chambers. A station for loading containers with pellet sub-containers prior to sintering and a station for unloading the pellet sub-containers after sintering are juxtaposed within the glove box. 3 claims, 1 drawing figure

  1. EMF measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions

    Science.gov (United States)

    Shishkovskiy, I.; Sherbakov, V.; Morozov, Yu.

    2007-06-01

    Rapid prototyping (RP) and manufacturing (M) is a novel layer-by-layer fabrication technique which has become increasingly popular due to its inherent flexibility for the manufacture of simple and complex 3D parts. Early we had been shown opportunity of selective laser sintering (SLS) of different type powder systems (intermetallics, ceramics, ferrites, high-temperature superconductors), traditional use for self-propagated high-temperature synthesis (SHS). The non-thermal heating affect of an external electromagnetic field during SHS is related to the specific system under study due to differences in movement of defects and ions at the 'plasma-like' molten combustion wave front. We have developed and refined the testing scheme for electro-thermal phenomena studies which can directly influence on the SHS combustion wave front. This work studies electromotive force (EMF) measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions (Ni-Ti, Ni-Al). Analysis using an analog-digital-analog computer converter allowed some control of the laser movement and hence some control of the exothermal reaction - in so doing it provided near optimum conditions for forming layered 3D articles. Comparative results of structural-phase transformation during laser control SHS in reaction-capable compositions are presented.

  2. Synthesis and characterization of interpenetrating phase ceramic metal composites

    International Nuclear Information System (INIS)

    Kanwal, T.

    2011-01-01

    Alumina powder was sintered in MW furnace under vacuum, without vacuum and conventional sintering furnace at different temperatures followed by characterization to observe the effect of sintering mode. Zirconia-Nickel and Alumina-Nickel systems were selected to study the effect of metallic phase interconnectivity on the electrical and thermal behavior in interpenetrating phase composites (IPCs). In order to obtain the homogenous mixture of Alumina and Nick powders, a detailed investigation was performed on the de-agglomeration and prop mixing of powders. Sintering parameters were optimized for the homogenization o Alumina with Nickel in planetary ball mill without sticking of powders with jar.- Homogenization of Zirconia-Nickel and Alumina-Nickel powders was perform using planetary ball mill as well as pestle mortar. Compaction of composites was performed uniaxially and sintering was carried in microwave furnace, tubular furnace with Argon environment and in vacuum sintering furnace. Electrical and thermal behavior of microwave as well as conventionally sintered ZrO/sub 2/-Ni and Al/sub 2/O/sub 3/-Ni IPCs was also observed. Electrical behavior of Composites was characterized b determining the impedance of the composites. To find the percolation limit for both Alumina-Nickel and Zirconia-Nickel composite systems the real part of impedance was used. On the basis of electrical characterization, samples were selected for SEM, BET surface area and CTE analysis. SEM of selected samples was performed t observe the connectivity of Nickel in composites. Finally, the effect of percolation limit on thermal behavior of IPCs was investigated with the help of CTE. (author)

  3. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 1. Sintering ... To eliminate or decrease the camber, a new method semi-fixed uniaxial pressure technique (SUP) was proposed. ... Department of Materials Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, P. R. China ...

  4. Sintering characteristic and microwave dielectric properties of 0.45Ca0.6Nd0.267TiO3-0.55Li0.5Nd0.5TiO3 ceramics with La2O3-B2O3-ZnO additive

    Science.gov (United States)

    Chen, Yawei; Zhang, Shuren; Li, Enzhu; Niu, Na; Yang, Hongcheng

    2018-02-01

    The La2O3-B2O3-ZnO (LBZ) glass was proved to be an effective sintering aid of the 0.45Ca0.6Nd0.26TiO3-0.55Li0.5Nd0.5TiO3 (CNT-LNT) ceramics. The influence of LBZ glass on the phase composition, low temperature sintering process, microstructure, activation energy, and dielectric properties of CNT-LNT ceramics was investigated in detail. The LBZ glass induced an obvious decrease of the CNT-LNT ceramics sintering temperature from 1350 to 1000 °C due to the liquid phase formation, which reduced the activation energy ( E a) of the CNT-LNT ceramics. In addition, the near zero temperature coefficient of resonant frequency (τƒ) value was obtained by adding moderate quantity of LBZ glass. CNT-LNT + 5 wt% LBZ (CNT-LNT + 5L) ceramics sintered at 1000°C/4 h displayed good microwave dielectric properties of: ɛ r = 101.7, Q × f = 1560 GHz ( f = 3.25 GHz) and τ ƒ = 2.3 ppm °C-1.

  5. [Effect of hydrofluoric acid concentration on the surface morphology and bonding effectiveness of lithium disilicate glass ceramics to resin composites].

    Science.gov (United States)

    Hailan, Qian; Lingyan, Ren; Rongrong, Nie; Xiangfeng, Meng

    2017-12-01

    This study aimed at determining the influence of hydrofluoric acid (HF) in varied concentrations on the surface morphology of lithium disilicate glass ceramics and bond durability between resin composites and post-treated lithium disilicate glass ceramics. After being sintered, ground, and washed, 72 as-prepared specimens of lithium disilicate glass ceramics with dimensions of 11 mm×13 mm×2 mm were randomly divided into three groups. Each group was treated with acid solution [32% phosphoric acid (PA) or 4% or 9.5% HF] for 20 s. Then, four acidified specimens from each group were randomly selected. One of the specimens was used to observe the surface morphology using scanning electron microscopy, and the others were used to observe the surface roughness using a surface roughness meter (including Ra, Rz, and Rmax). After treatment with different acid solutions in each group, 20 samples were further treated with silane coupling agent/resin adhesive/resin cement (Monobond S/Multilink Primer A&B/Multilink N), followed by bonding to a composite resin column (Filtek™ Z350) with a diameter of 3 mm. A total of 20 specimens in each group were randomly divided into two subgroups, which were used for measuring the microshear bond strength, with one of them subjected to cool-thermal cycle for 20 000 times. The surface roughness (Ra, Rz, and Rmax) of lithium disilicate glass ceramics treated with 4% or 9.5% HF was significantly higher than that of the ceramic treated with PA (Pglass ceramics treated with 9.5% HF also demonstrated better surface roughness (Rz and Rmax) than that of the ceramics treated with 4% HF. Cool-thermal cycle treatment reduced the bond strength of lithium disilicate glass ceramics in all groups (Pglass ceramics treated with HF had higher bond strength than that of the ceramics treated with PA. The lithium disilicate glass ceramics treated with 4% HF had higher bond strength than that of the ceramics treated with 9.5% HF (Pglass ceramics treated with 4

  6. Glass-ceramic composition for hermetic seals

    International Nuclear Information System (INIS)

    Ballard, C.P. Jr.

    1979-01-01

    The invention relates to a glass-ceramic composition having a high fracture strength adaptable for hermetically sealing to chromium bearing iron or nickel base alloys at temperatures of between about 950 0 C to about 1100 0 C to form a hermetically sealed insulator body, comprising from about 55 to about 65 weight percent SiO 2 , from about 0 to about 5 weight percent Al 2 O 3 , from about 6 to about 11 weight % Li 2 O, from about 25 to about 32 weight percent BaO, from about 0.5 to about 1.0 weight percent CoO and from about 1.5 to about 3.5 weight percent P 2 O 5

  7. Glass-ceramic composition for hermetic seals

    Science.gov (United States)

    Ballard, Jr., Clifford P.

    1979-01-01

    The invention relates to a glass-ceramic composition having a high fracture strength adaptable for hermetically sealing to chromium bearing iron or nickel base alloys at temperatures of between about 950.degree. C to about 1100.degree. C to form a hermetically sealed insulator body, comprising from about 55 to about 65 weight percent SiO.sub.2, from about 0 to about 5 weight percent Al.sub.2 O.sub.3, from about 6 to about 11 weight % Li.sub.2 O, from about 25 to about 32 weight percent BaO, from about 0.5 to about 1.0 weight percent CoO and from about 1.5 to about 3.5 weight percent P.sub.2 O.sub.5.

  8. Thermal Performance of Ablative/ Ceramic Composite

    Directory of Open Access Journals (Sweden)

    Adriana STEFAN

    2014-12-01

    Full Text Available A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM and Ceramic Matrix Composite (CMC material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C, at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar conditions. The average weigh loss was calculated for all the samples from one set, without differentiating the adhesive used as the weight loss is due to the ablative material consumption that is the same in all the samples and is up to 2%. The thermal shock test proves that, thermally, all joints behaved similarly, the two parts withstanding the test successfully and the assembly maintaining its integrity.

  9. 4TH International Conference on High-Temperature Ceramic Matrix Composites

    National Research Council Canada - National Science Library

    2001-01-01

    .... Topic to be covered include fibers, interfaces, interphases, non-oxide ceramic matrix composites, oxide/oxide ceramic matrix composites, coatings, and applications of high-temperature ceramic matrix...

  10. Preparation and Characterization of Pu0.5Am0.5O2-x-MgO Ceramic/Ceramic Composites

    International Nuclear Information System (INIS)

    Jankowiak, A.; Jorion, F.; Donnet, L.; Maillard, C.

    2008-01-01

    This study describes the preparation and characterization of Pu 0.5 Am 0.5 O 2-x -MgO ceramic/ceramic (cercer) composites with 20 and 30 vol% of Pu 0.5 Am 0.5 O 2-x . The sintered materials demonstrated very different reduction behavior when exposed to a reducing sintering cycle. The composites were studied by combined X-ray diffraction (XRD) and oxygen-to-metal ratio measurements and exhibited various amounts of body-centered-cubic (bcc) and face-centered-cubic (fcc) phases corresponding to different reduction states of the mixed actinide oxide. The fcc phases correspond to a near stoichiometry phase while the bcc phases are attributed to most reduced phases, which demonstrate a greater similarity with the Am 2 O 3 bcc phase. The XRD results suggest a reduction of Am prior to Pu, which explains this greater similarity. In addition, the 30 vol% composite contains 65 wt% of the bcc phase while the 20 vol% composite exhibits only 29 wt%. This result can be explained by the percolation theory when applied to the oxygen diffusivity and indicates that a threshold value for Pu 0.5 Am 0.5 O 2-x content in the cercer composite exists where the reduction of the mixed oxide significantly increases. (authors)

  11. Ceramic fiber-reinforced monoclinic celsian phase glass-ceramic matrix composite material

    Science.gov (United States)

    Bansal, Narottam P. (Inventor); Dicarlo, James A. (Inventor)

    1994-01-01

    A hyridopolysilazane-derived ceramic fiber reinforced monoclinic celsian phase barium aluminum silicate glass-ceramic matrix composite material is prepared by ball-milling an aqueous slurry of BAS glass powder and fine monoclinic celsian seeds. The fibers improve the mechanical strength and fracture toughness and with the matrix provide superior dielectric properties.

  12. Mechanics and Durability of Fiber Reinforced Porous Ceramic Composites

    OpenAIRE

    Huang, Xinyu

    2001-01-01

    Porous ceramics and porous ceramic composites are emerging functional materials that have found numerous industrial applications, especially in energy conversion processes. They are characterized by random microstructure and high porosity. Examples are ceramic candle filters used in coal-fired power plants, gas-fired infrared burners, anode and cathode materials of solid oxide fuel cells, etc. In this research, both experimental and theoretical work have been conducted t...

  13. A Basis for Modelling Ceramic Composite Armour Defeat

    Science.gov (United States)

    1989-06-01

    MRL-RR-3-89 ABSTRACT This work takes some of the major features of ceramic composite armour failure, viz. fracture conoid formation, dishing failure...fractured in the form of a conoid followed by tensile failure in the ceramic initiating at the ceramic/backing plate interface, opposite the impact location...damage simulated by Wilkins 131 is similar to observed fracture conoids and at similar angles to cone cracks seen in quasi-static indentation of glass

  14. Sintering behavior of Y2O3 doped Bi2O3 ceramics

    Directory of Open Access Journals (Sweden)

    Alizadeh M.

    2007-01-01

    Full Text Available Influence of sintering temperature and soaking time on densification of Bi2O3 samples doped with 25%mol Y2O3 was investigated by shrinkage and relative density measurements. Samples were sintered in air at different temperatures in the range of 800 to 1000°C for 24 hr. The results showed that samples sintered at 950°C have the maximum relative density. Several samples were sintered at 950°C for duration of 0 to 36 hr in order to evaluate the effect of soaking time on densification of samples. It was found that the samples were sintered at 950°C for 36hr had higher relative density than others did for smaller time duration X-ray diffraction (XRD analyses detected δ -Bi2O3 as the sole stable phase in all samples. Scanning Electron Microscopy (SEM investigation of fractured surface of the samples showed that porosities decrease by increasing of sintering temperature and grow by further increasing of temperature.

  15. Acoustic emission as a screening tool for ceramic matrix composites

    Science.gov (United States)

    Ojard, Greg; Goberman, Dan; Holowczak, John

    2017-02-01

    Ceramic matrix composites are composite materials with ceramic fibers in a high temperature matrix of ceramic or glass-ceramic. This emerging class of materials is viewed as enabling for efficiency improvements in many energy conversion systems. The key controlling property of ceramic matrix composites is a relatively weak interface between the matrix and the fiber that aids crack deflection and fiber pullout resulting in greatly increased toughness over monolithic ceramics. United Technologies Research Center has been investigating glass-ceramic composite systems as a tool to understand processing effects on material performance related to the performance of the weak interface. Changes in the interface have been shown to affect the mechanical performance observed in flexural testing and subsequent microstructural investigations have confirmed the performance (or lack thereof) of the interface coating. Recently, the addition of acoustic emission testing during flexural testing has aided the understanding of the characteristics of the interface and its performance. The acoustic emission onset stress changes with strength and toughness and this could be a quality tool in screening the material before further development and use. The results of testing and analysis will be shown and additional material from other ceramic matrix composite systems may be included to show trends.

  16. Robocast Pb(Zr0.95Ti0.05)O3 Ceramic Monoliths and Composites

    International Nuclear Information System (INIS)

    Tuttle, Bruce A.; Smay, James E.; Cesarano, Joseph III; Voigt, James A.; Scofield, Timothy W.; Olson, Walter R.; Lewis, J.A.

    2000-01-01

    Robocasting, a computer controlled slurry deposition technique, was used to fabricate ceramic monoliths and composites of chemically prepared Pb(Zr 0.95 Ti 0.05 )O 3 (PZT 95/5) ceramics. Densities and electrical properties of the robocast samples were equivalent to those obtained for cold isostatically pressed (CIP) parts formed at 200 MPa. Robocast composites consisting of alternate layers of the following sintered densities: (93.9%--96.1%--93.9%), were fabricated using different levels of organic pore former additions. Modification from a single to a multiple material deposition robocaster was essential to the fabrication of composites that could withstand repeated cycles of saturated polarization switching under 30 kV/cm fields. Further, these composites withstood 500 MPa hydrostatic pressure induced poled ferroelectric (FE) to antiferroelectric (AFE) phase transformation during which strain differences on the order of 0.8% occurred between composite elements

  17. Improving Turbine Performance with Ceramic Matrix Composites

    Science.gov (United States)

    DiCarlo, James A.

    2007-01-01

    Under the new NASA Fundamental Aeronautics Program, efforts are on-going within the Supersonics Project aimed at the implementation of advanced SiC/SiC ceramic composites into hot section components of future gas turbine engines. Due to recent NASA advancements in SiC-based fibers and matrices, these composites are lighter and capable of much higher service temperatures than current metallic superalloys, which in turn will allow the engines to operate at higher efficiencies and reduced emissions. This presentation briefly reviews studies within Task 6.3.3 that are primarily aimed at developing physics-based concepts, tools, and process/property models for micro- and macro-structural design, fabrication, and lifing of SiC/SiC turbine components in general and airfoils in particular. Particular emphasis is currently being placed on understanding and modeling (1) creep effects on residual stress development within the component, (2) fiber architecture effects on key composite properties such as design strength, and (3) preform formation processes so that the optimum architectures can be implemented into complex-shaped components, such as turbine vanes and blades.

  18. Support Services for Ceramic Fiber-Ceramic Matrix Composites

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, J.P.

    2000-06-06

    Structural and functional materials used in solid- and liquid-fueled energy systems are subject to gas- and condensed-phase corrosion and erosion by entrained particles. For a given material, its temperature and the composition of the corrodents determine the corrosion rates, while gas flow conditions and particle aerodynamic diameters determine erosion rates. Because there are several mechanisms by which corrodents deposit on a surface, the corrodent composition depends not only on the composition of the fuel, but also on the temperature of the material and the size range of the particles being deposited. In general, it is difficult to simulate under controlled laboratory conditions all of the possible corrosion and erosion mechanisms to which a material may be exposed in an energy system. Therefore, with funding from the Advanced Research Materials Program, the University of North Dakota Energy & Environmental Research Center (EERC) is coordinating with NCC Engineering and the National Energy Technology Laboratory (NETL) to provide researchers with no-cost opportunities to expose materials in pilot-scale systems to conditions of corrosion and erosion similar to those occurring in commercial power systems. The EERC has two pilot-scale solid-fuel systems available for exposure of materials coupons. The slagging furnace system (SFS) was built under the DOE Combustion 2000 Program as a testing facility for advanced heat exchanger subsystems. It is a 2.5-MMBtu/hr (2.6 x 10{sup 6} kJ/hr) solid-fuel combustion system with exit temperatures of 2700 to 2900 F to ensure that the ash in the main combustor is molten and flowing. Sample coupons may be exposed in the system either within the slagging zone or near the convective air heater at 1800 F (980 C). In addition, a pilot-scale entrained-bed gasifier system known as the transport reactor development unit (TRDU) is available. Also operating at approximately 2.5 MMBtu/hr (2.6 x 10{sup 6} kJ/hr), it is a pressurized unit

  19. Pressureless sintering and mechanical properties of hydroxyapatite/functionalized multi-walled carbon nanotube composite.

    Science.gov (United States)

    Abden, M J; Afroze, J D; Alam, M S; Bahadur, N M

    2016-10-01

    This work aims to study the optimum sintering conditions of hydroxyapatite/functionalized multi-walled carbon nanotube (HA/f-MWCNT) composite with improved mechanical properties for bone implant applications using a pressureless sintering technique. The carboxyl functional group (COOH) introduced by the acid treatment on the MWCNT surface by which HA molecules are grafted onto the surface of functionalized MWCNT with strong interfacial bonding. The composite exhibits a lower hemolytic rate of 1.27%. The flexible nature of f-MWCNT makes them bend and attached to the HA grains, indicates that f-MWCNT bear significant stress by sharing a portion of the load and it leads to improve their mechanical properties. The maximum Vickers hardness of 3.6GPa is obtained for the HA/f-MWCNT composite sintered at 1100°C, whereas the highest compressive strength of 481.7MPa and fracture toughness of 2.38MPa.m(1/2) achieved after sintering at 1150°C. This study demonstrated that HA/f-MWCNT composite create suitable structures by vacuum pressureless sintering technique to satisfy the mechanical requirements for bone tissues. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Synthesis and characterization of aluminium–alumina micro- and nano-composites by spark plasma sintering

    International Nuclear Information System (INIS)

    Dash, K.; Chaira, D.; Ray, B.C.

    2013-01-01

    Graphical abstract: The evolution of microstructure by varying the particle size of reinforcement in the matrix employing spark plasma sintering has been demonstrated here in Al–Al 2 O 3 system. An emphasis has been laid on varying the reinforcement particle size and evaluating the microstructural morphologies and their implications on mechanical performance of the composites. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size 2 O 3 micro- and nano-composites fabricated by spark plasma sintering. • Better matrix-reinforcement integrity in nanocomposites than microcomposites. • Spark plasma sintering method results in higher density and hardness values. • High density and hardness values of nanocomposites than microcomposites. • High dislocation density in spark plasma sintered Al–Al 2 O 3 composites. - Abstract: In the present study, an emphasis has been laid on evaluation of the microstructural morphologies and their implications on mechanical performance of the composites by varying the reinforcement particle size. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size 2 O 3 nancomposites respectively. Spark plasma sintering imparts enhanced densification and matrix-reinforcement proximity which have been corroborated with the experimental results

  1. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  2. CaZn1/3Nb2/3O3-based dielectric ceramics for silver co-sintering applications

    Directory of Open Access Journals (Sweden)

    Chaouchi A.

    2012-01-01

    Full Text Available The Ca(Zn1/3Nb2/3O3 (CZN complex perovskite oxide has been studied for its attractive dielectric properties (εr=34, Qxf=15 890GHz, τf=-48 ppm.°C-1 for applications such as multilayer ceramics capacitors or hyperfrequency resonators. Nevertheless, high temperatures (>1250°C are required to obtain well dense CZN ceramic, prohibiting any silver co-sintering (Tf (Ag = 961°C. For that reason, the sintering temperature lowering of CZN by glass phase’s additions has been investigated. This material is finally sinterable at low temperature with combined glass phase -lithium salt additions, and exhibits, at 1MHz, very low dielectric losses, a relatively high dielectric constant with a good stability versus temperature. The 2%weight of ZnO-SiO2-B2O3 glass phase and 1%wt of LiF added CZN sample sintered at 920°C exhibits a relative density higher than 95% and attractive dielectric properties: a dielectric constant εr of 22, low dielectrics losses (tan (δ< 10-3, a temperature coefficient of the permittivity τε<100 ppm.°C-1, and an insulating resistivity higher than 1013Ω.cm. Its interesting properties and its co-sinterability with silver electrodes make this ceramic suitable for L.T.C.C applications.

  3. Two-Step Sintering Behavior of Sol-Gel Derived Dense and Submicron-Grained YIG Ceramics

    Science.gov (United States)

    Chen, Ruoyuan; Zhou, Jijun; Zheng, Liang; Zheng, Hui; Zheng, Peng; Ying, Zhihua; Deng, Jiangxia

    2018-04-01

    In this work, dense and submicron-grain yttrium iron garnet (YIG, Y3Fe5O12) ceramics were fabricated by a two-step sintering (TSS) method using nano-size YIG powder prepared by a citrate sol-gel method. The densification, microstructure, magnetic properties and ferromagnetic resonance (FMR) linewidth of the ceramics were investigated. The sample prepared at 1300°C in T 1, 1225°C in T 2 and 18 h holding time has a density higher than 98% of the theoretical value and exhibits a homogeneous microstructure with fine grain size (0.975 μm). In addition, the saturation magnetization ( M S) of this sample reaches 27.18 emu/g. High density and small grain size can also achieve small FMR linewidth. Consequently, these results show that the sol-gel process combined with the TSS process can effectively suppress grain-boundary migration while maintaining active grain-boundary diffusion to obtain dense and fine-grained YIG ceramics with appropriate magnetic properties.

  4. Composite glass ceramics - a promising material for aviation

    Directory of Open Access Journals (Sweden)

    М. В. Дмитрієв

    2000-12-01

    Full Text Available The analysis of the technical and technological characteristics of the composite ceramic as a material for electrical and structural parts in aircraft. The economic and technological advantages compared to ceramic pottery and proposed options for development of production in Ukraine

  5. 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.

  6. Structural comparison of sintering products made of "TiC + Ti" composite powders and "Ti + C" powder mixtures

    Science.gov (United States)

    Krinitcyn, Maksim G.; Pribytkov, Gennadii A.; Korosteleva, Elena N.; Firsina, Irina A.; Baranovskii, Anton V.

    2017-12-01

    In this study, powder composite materials comprised of TiC and Ti with different ratios are processed by sintering of Ti and C powder mixtures and self-propagating high-temperature synthesis (SHS) in "Ti+C" system followed by sintering. The microstructure and porosity of obtained composites are investigated and discussed. The dependence of porosity on sintering time is explained theoretically. Optimal regimes that enable to obtain the most homogeneous structure with the least porosity are described.

  7. 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.

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

    Science.gov (United States)

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

    2017-11-01

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

  9. Nano-sized ceramic particles of hydroxyapatite calcined with an anti-sintering agent.

    Science.gov (United States)

    Okada, Masahiro; Furuzono, Tsutomu

    2007-03-01

    Nano-sized crystals of calcined hydroxyapatite (HAp) having spherical morphologies were fabricated by calcination at 800 degrees C for 1 h with an anti-sintering agent surrounding the original HAp particles and the agent was subsequently removed by washing after calcination. The original HAp particles were prepared by a modified emulsion system, and surrounded with poly(acrylic acid, calcium salt) (PAA-Ca) by utilizing a precipitation reaction between calcium hydroxide and poly(acrylic acid) adsorbed on the HAp particle surfaces in an aqueous medium. In the case of calcination without PAA-Ca, micron-sized particles consisting of sintered polycrystals were mainly observed by scanning electron microscopy, indicating the calcination-induced sintering among the crystals. On the other hand, most of the crystals calcined with the anti-sintering agent were observed as isolated particles, and the mean size of the HAp crystals was around 80 nm. This result indicates that PAA-Ca and its thermally decomposed product, CaO, surrounding the HAp crystals could protect them against calcination-induced sintering during calcination at 800 degrees C. The HAp crystals calcined with PAA-Ca showed high crystallinity, and no other calcium phosphate phases could be detected.

  10. Influence of the raw-material characteristics on mullite-zirconia composites obtained by reactions sintering

    International Nuclear Information System (INIS)

    Emiliano, J.V.; Segadaes, A.M.B.C.

    1989-01-01

    A number of authors have shown that there are some difficulties in preparing mullite-zirconia composites with good thermomechanical properties through reaction-sintering of Al 2 O 3 and ZrSiO 4 powders. The present work was aimed at investigating the effect of the characteristics of the alumina powders on the reaction-sintering behaviour, microstructural development and final properties of the composites prepared by conventional processes. The results obtained showed that the use of high purity reactive powders, supposed to yield enhanced properties can be overshadowed when conventional techniques of powder processing are used, as these give rise to microstructural inhomogeneities [pt

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

    Czech Academy of Sciences Publication Activity Database

    Chráska, Tomáš; Pala, Zdeněk; Mušálek, Radek; Medřický, Jan; Vilémová, Monika

    2015-01-01

    Roč. 24, č. 4 (2015), s. 637-643 ISSN 1059-9630 R&D Projects: GA ČR GAP107/12/1922 Institutional support: RVO:61389021 Keywords : ceramic s * heat treatment * nanostructured materials Subject RIV: JH - Ceramic s, Fire-Resistant Materials and Glass Impact factor: 1.568, year: 2015

  12. Modeling the Mechanical Behavior of Ceramic Matrix Composite Materials

    Science.gov (United States)

    Jordan, William

    1998-01-01

    Ceramic matrix composites are ceramic materials, such as SiC, that have been reinforced by high strength fibers, such as carbon. Designers are interested in using ceramic matrix composites because they have the capability of withstanding significant loads while at relatively high temperatures (in excess of 1,000 C). Ceramic matrix composites retain the ceramic materials ability to withstand high temperatures, but also possess a much greater ductility and toughness. Their high strength and medium toughness is what makes them of so much interest to the aerospace community. This work concentrated on two different tasks. The first task was to do an extensive literature search into the mechanical behavior of ceramic matrix composite materials. This report contains the results of this task. The second task was to use this understanding to help interpret the ceramic matrix composite mechanical test results that had already been obtained by NASA. Since the specific details of these test results are subject to the International Traffic in Arms Regulations (ITAR), they are reported in a separate document (Jordan, 1997).

  13. Ceramic Matrix Composite Environmental Barrier Coating Durability Model, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — As the power density of advanced engines increases, the need for new materials that are capable of higher operating temperatures, such as ceramic matrix composites...

  14. Metallic Joining to Advanced Ceramic Composites, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Orion Launch Abort System (LAS) utilizes attitude control motors (ACM) with advanced ceramic composite components that function as a valve control system to...

  15. Metallic Joining to Advanced Ceramic Composites, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Currently, advanced ceramic composites are state-of-the-art for hypersonic airbreathing and space propulsion applications. The Launch Abort System (LAS) of the Orion...

  16. Ceramic Matrix Composite Environmental Barrier Coating Durability Model, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — As the power density of advanced engines increases, the need for new materials that are capable of higher operating temperatures, such as ceramic matrix composites...

  17. Modern Nondestructive Test Methods for Army Ceramic Matrix Composites

    National Research Council Canada - National Science Library

    Strand, Douglas J

    2008-01-01

    .... Ceramic matrix composites (CMC) are potentially good high-temperature structural materials because of their low density, high elastic moduli, high strength, and for those with weak interfaces, surprisingly good damage tolerance...

  18. Effect of BaCu(B2O5) additive on the sintering temperature and microwave dielectric properties of BaTi4O9 ceramics

    International Nuclear Information System (INIS)

    Lim, Jong-Bong; Kim, Min-Han; Kim, Jae-Chul; Nahm, Sahn; Paik, Jong-Hoo; Kim, Jong-Hee

    2006-01-01

    BaCu(B 2 O 5 ) (BCB) additive was used to decrease the sintering temperature of the BaTi 4 O 9 ceramics. The amount of Ba 4 Ti 13 O 30 second phase increased with the addition of BCB, whereas that of the BaTi 4 O 9 phase decreased. The bulk density and dielectric constant (ε γ ) considerably increased with the addition of BCB. An increase in the Q-value was also observed for the BaTi 4 O 9 ceramics with a small amount of BCB. Good microwave dielectric properties with values of ε γ =32, Q x f 10800 GHz and τ f =32 ppm/degC were obtained in the BaTi 4 O 9 ceramics with 12.0 mol% of BCB sintered at 875degC for 2h. (author)

  19. Evaluation of clayey masses compositions starting from the residue incorporation of the red ceramic industry to obtain tubular ceramic membranes; Avaliacao das composicoes de massas argilosas a partir da incorporacao de residuo da industria de ceramica vermelha na obtencao de membranas ceramicas tubulares

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Adriano Lima da; Chaves, Alexsandra Cristina; Luna, Carlos Bruno Barreto; Neves, Gelmires de Araujo; Lira, Helio de Lucena, E-mail: adrianolimadasilva@hotmail.com, E-mail: alexsandra.chaves@ifap.edu.br, E-mail: brunobarretodemaufcg@hotmail.com, E-mail: gelmires@ufcg.edu.br, E-mail: helio@ufcg.edu.br [Universidade Federal de Campina Grande (UAEMa/CCT/UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais

    2017-01-15

    The inappropriate residue disposal of red ceramic industry is very high. Nowadays, one of the major challenges is the investigation of processes to obtain alternative materials, enabling the use of these residues to manufacture new materials. This work's objective is to study clayey masses' compositions starting from the residue incorporation of the red ceramic industry to be used in tubular ceramic membranes. Two compositions of ceramic masses were established, composition A (50% of residue) and composition B (70% of residue). Granulometric analysis of the ceramic masses presented an average size of particles, what indicates membranes in the microfiltration scale. Another observed factor is related to the increase of residue amount, what favored a decrease in the ceramic mass' plasticity. A rise in the apparent porosity was also observed, probably because of a possible growing in the bigger pores numbers, due to the sintering high temperature and the elevation of residue quantity itself. (author)

  20. Sintering of fly ash based composites with zeolite and bentonite addition for application in construction materials

    Directory of Open Access Journals (Sweden)

    Terzić Anja

    2017-01-01

    Full Text Available Due to pozzolanic characteristics, fly ash is commonly used as a cement replacement in construction composites. Addition of natural clays with sorption ability (i.e. zeolite and bentonite in to the fly ash based construction materials is of both scientific and industrial interest. Namely, due to the application of sorptive clay minerals, it is possible to immobilize toxic heavy metals from the composite structure. The thermal compatibility of fly ash and zeolite, as well as fly ash and bentonite, within the composite was observed during sintering procedure. The starting components were used in 1:1 ratio and they were applied without additional mechanical treatment. The used compaction pressure for the tablets was 2 t•cm-2. The sintering process was conducted at 1000ºC and 1200ºC for two hours in the air atmosphere. The mineralogical phase composition of the non-treated and sintered samples was analyzed using X-ray diffraction method. Scanning electron microscopy was applied in the analysis of the microstructure of starting and sintered samples. The thermal behavior was observed via DTA method. The influence of temperature on the properties of fly ash-zeolite and fly ash-bentonite composites was investigated. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45008 and OI 172057

  1. Bone formation: The rules for fabricating a composite ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, A.I. (Case Western Reserve Univ., Cleveland, OH (USA))

    1990-01-01

    Bone, teeth and shells are complex composite ceramics which are fabricated at low temperature by living organisms. The detailed understanding of this fabrication process is required if we are to attempt to mimic this low temperature assembly process. The guiding principles and major components are outlined with the intent of establishing non-vital fabrication schemes to form a complex composite ceramic consisting of an organix matrix inorganic crystalline phase. 19 refs.

  2. Metallic-fibre-reinforced ceramic-matrix composite

    International Nuclear Information System (INIS)

    Prevost, F.; Schnedecker, G.; Boncoeur, M.

    1994-01-01

    A refractory metal wire cloth is embedded in an oxide ceramic matrix, using a plasma spraying technology, in order to elaborate composite plates. When mechanically tested, the composite fails with a pseudo-ductile fracture mode whereas the ceramic alone is originally brittle. It exhibits a higher fracture strength, and remains in the form of a single piece even when straining is important. No further heat treatment is needed after the original processing to reach these characteristics. (authors). 2 figs., 2 refs

  3. Ceramic Laser Materials

    Science.gov (United States)

    Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

    2012-01-01

    Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

  4. Thermal Conductivity and Microstructure of Copper Coated Graphite Composite by Spark Plasma Sintering Process

    Directory of Open Access Journals (Sweden)

    Park S.H.

    2017-06-01

    Full Text Available This study focuses on the fabrication of thermal management material for power electronics applications using graphite flake reinforced copper composites. The manufacturing route involved electroless plating of copper in the graphite flake and sintering process are optimized. The microstructures, interface, thermal properties, and relative density of graphite/Cu composites are investigated. The relative density of the composites shows 99.5% after sintering. Thermal conductivities and coefficients of thermal expansion of this composites were 400-480 Wm−1K−1 and 8 to 5 ppm k−1, respectively. Obtained graphite nanoplatelets-reinforced composites exhibit excellent thermo-physical properties to meet the heat dispersion and matching requirements of power electronic devices to the packaging materials.

  5. 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.

  6. Giant room-temperature magnetodielectric coupling in spark plasma sintered brownmillerite ceramics

    International Nuclear Information System (INIS)

    Wu, J. W.; Wang, J.; Liu, G.; Wu, Y. J.; Liu, X. Q.; Chen, X. M.

    2014-01-01

    The dielectric, magnetic, and magnetodielectric properties of Ca 2 FeAO 5+δ (A = Al, Ga) ceramics were investigated together with their crystal structures. Rietveld refinement of the X-ray diffraction data indicated that the space group of the Ca 2 FeAlO 5+δ ceramic was Ibm2, whereas that of the Ca 2 FeGaO 5+δ ceramic was Pcmn. Dielectric relaxation above room temperature, originating from the Maxwell–Wagner effect and polaronic hole hopping between Fe 3+ and Fe 4+ ions, was observed in both ceramics. Weak ferrimagnetic behavior was identified from the magnetic-field-dependent magnetization in these ceramics, which was attributed to the non-cancelled spins of the antiferromagnetic-ordered Fe 3+ and Fe 4+ ions. An intrinsic, giant, room-temperature magnetodielectric coefficient of up to −23.3% was achieved in the Ca 2 FeAlO 5+δ ceramic at 50 MHz, which was attributed to the suppression of charge fluctuations of Fe 3+ and Fe 4+ ions in the magnetic field

  7. Crack Driving Forces in a Multilayered Coating System for Ceramic Matrix Composite Substrates

    Science.gov (United States)

    Ghosn, Louis J.; Zhu, Dongming; Miller, Robert A.

    2005-01-01

    The effects of the top coating thickness, modulus and shrinkage strains on the crack driving forces for a baseline multilayer Yttria-Stabilized-Zirconia/Mullite/Si thermal and environment barrier coating (TEBC) system for SiC/SiC ceramic matrix composite substrates are determined for gas turbine applications. The crack driving forces increase with increasing modulus, and a low modulus thermal barrier coating material (below 10 GPa) will have no cracking issues under the thermal gradient condition analyzed. Since top coating sintering increases the crack driving forces with time, highly sintering resistant coatings are desirable to maintain a low tensile modulus and maintain a low crack driving force with time. Finite element results demonstrated that an advanced TEBC system, such as ZrO2/HfO2, which possesses improved sintering resistance and high temperature stability, exhibited excellent durability. A multi-vertical cracked structure with fine columnar spacing is an ideal strain tolerant coating capable of reducing the crack driving forces to an acceptable level even with a high modulus of 50 GPa.

  8. Sintering and electrical properties of PZT/Pt dual-phase composites

    NARCIS (Netherlands)

    Duan, N.; ten Elshof, Johan E.; Verweij, H.

    2001-01-01

    Lead zirconate titanate–platinum dual phase composites, which have been shown to exhibit a very interesting electric field dependence of the dielectric constant, were prepared. The sintering properties and microstructure were analyzed. No chemical reaction between PZT and Pt was found in the

  9. CAD/CAM machining Vs pre-sintering in-lab fabrication techniques of Y-TZP ceramic specimens: Effects on their mechanical fatigue behavior.

    Science.gov (United States)

    Zucuni, C P; Guilardi, L F; Fraga, S; May, L G; Pereira, G K R; Valandro, L F

    2017-07-01

    This study evaluated the effects of different pre-sintering fabrication processing techniques of Y-TZP ceramic (CAD/CAM Vs. in-lab), considering surface characteristics and mechanical performance outcomes. Pre-sintered discs of Y-TZP ceramic (IPS e.max ZirCAD, Ivoclar Vivadent) were produced using different pre-sintering fabrication processing techniques: Machined- milling with a CAD/CAM system; Polished- fabrication using a cutting device followed by polishing (600 and 1200 SiC papers); Xfine- fabrication using a cutting machine followed by grinding with extra-fine diamond bur (grit size 30 μm); Fine- fabrication using a cutting machine followed by grinding with fine diamond bur (grit size 46 μm); SiC- fabrication using a cutting machine followed by grinding with 220 SiC paper. Afterwards, the discs were sintered and submitted to roughness (n=35), surface topography (n=2), phase transformation (n=2), biaxial flexural strength (n=20), and biaxial flexural fatigue strength (fatigue limit) (n=15) analyses. No monoclinic-phase content was observed in all processing techniques. It can be observed that obtaining a surface with similar characteristics to CAD/CAM milling is essential for the observation of similar mechanical performance. On this sense, grinding with fine diamond bur before sintering (Fine group) was the best mimic protocol in comparison to the CAD/CAM milling. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Electrochemical corrosion and bioactivity of Ti-Nb-Sn-hydroxyapatite composites fabricated by pulse current activated sintering.

    Science.gov (United States)

    Xiaopeng, Wang; Fantao, Kong; Biqing, Han; Yuyong, Chen

    2017-11-01

    Ti-Nb-Sn-hydroxyapatite (HA) composites were prepared by mechanical alloying for different times (unmilled, 4, 8 and 12h), followed by pulse current activated sintering. The effects of the milling time on the electrochemical corrosion resistance and bioactivity of the sintered Ti-35Nb-2.5Sn-15HA composites were investigated. Potentiodynamic polarization test results indicated that the sintered Ti-35Nb-2.5Sn-15HA composites exhibited higher corrosion resistance with increasing milling time. The corrosion potential and current of the Ti-35Nb-2.5Sn-15HA composite sintered by 12h milled powders were - 0.261V and 0.18μA/cm 2 , respectively, and this sintered composite showed a stable and wide passivation region. The hemolysis rate of the sintered Ti-35Nb-2.5Sn-15HA composites reduced with increasing milling time and the lowest hemolytic rate of the composites was 0.87%. In addition, the in vitro cell culture results indicated that the composite sintered by 12h milled powders had good biocompatibility. These results indicate the significant potential of Ti-35Nb-2.5Sn/xHA composites for biomedical implant applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Translucence in dental prosthesis based on zirconia ceramics: effect of the sintering parameters; Translucidez em proteses dentarias a base de zirconia estabilizada com itria: efeito dos parametros de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Santos, C., E-mail: claudinei@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Costa, L.; Habibe, R.H.; Souza, J.V.C.; Habibe, C.H. [Centro Universitario de Volta Redonda (MeMAT/UNIFOA), RJ (Brazil). Pro-Reitoria de Pesquisa e Extensao; Silva, O.M.M. [Centro Tecnico Aeroespacial (CTA/IAE/AMR), Sao Jose dos Campos, SP (Brazil)

    2011-07-01

    In this work the translucence of Zirconia dental ceramics was evaluated as function of sintering conditions (temperature and isothermal holding time). Samples with 15x15x1mm, were sintered at 1450 to 1600 deg C, with holding of 2h or 4h. Sintered samples were characterized by relative density, crystalline phases and microstructural aspects. Full density was obtained in samples sintered at 1530 and 1600 deg C, which presented higher grain sizes. Na increasing of translucence was observed in samples sintered at 1530 and 1600, correlating these properties with increasing of density and grain size of the samples. (author)

  12. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Directory of Open Access Journals (Sweden)

    Zorica Branković

    2016-12-01

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

  13. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  14. Elaboration of new ceramic composites containing glass fibre production wastes

    Directory of Open Access Journals (Sweden)

    Rozenstrauha, I.

    2013-04-01

    Full Text Available Two main by-products or waste from the production of glass fibre are following: sewage sludge containing montmorillonite clay as sorbent material and ca 50% of organic matter as well as waste glass from aluminiumborosilicate glass fibre with relatively high softening temperature (> 600 ºC. In order to elaborate different new ceramic products (porous or dense composites the mentioned by-products and illitic clay from two different layers of Apriki deposit (Latvia with illite content in clay fraction up to 80-90% was used as a matrix. The raw materials were investigated by differential-thermal (DTA and XRD analysis. Ternary compositions were prepared from mixtures of 15–35 wt % of sludge, 20 wt % of waste glass and 45–65 wt % of clay and the pressed green bodies were thermally treated in sintering temperature range from 1080 to 1120 ºC in different treatment conditions. Materials produced in temperature range 1090–1100 ºC with the most optimal properties - porosity 38-52%, water absorption 39–47% and bulk density 1.35–1.67 g/cm3 were selected for production of porous ceramics and materials showing porosity 0.35–1.1%, water absorption 0.7–2.6 % and bulk density 2.1–2.3 g/cm3 - for dense ceramic composites. Obtained results indicated that incorporation up to 25 wt % of sewage sludge is beneficial for production of both ceramic products and glass-ceramic composites according to the technological properties. Structural analysis of elaborated composite materials was performed by scanning electron microscopy(SEM. By X-ray diffraction analysis (XRD the quartz, diopside and anorthite crystalline phases were detected.Durante la obtención de ciertas fibras de vidrio se generan dos subproductos o residuos principalmente: Lodo de arcilla montmorillonítica capaz de adsorber el 50 % de materia orgánica y un vidrio silicato alumínico con temperatura de reblandecimiento relativamente alta (> 600 ºC. Con el fin de elaborar nuevos

  15. Low temperature sintering and microwave dielectric properties of ZnTiNb2O8 ceramics with BaCu(B2O5) additions

    International Nuclear Information System (INIS)

    Zhou Dongxiang; Dou Gang; Guo Mei; Gong Shuping

    2011-01-01

    Highlights: → The sintering temperature of ZnTiNb 2 O 8 ceramics with BCB was reduced to 950 deg. C. → The properties were dependent on densification, grain sizes and crystalline phases. → The ε r 32.56, Q x f = 20,100 GHz (f = 5.128 GHz) and τ f = -64.87 ppm/deg. C were achieved. → It represented very promising candidates as LTCC dielectric materials. - Abstract: The phases, microstructure and microwave dielectric properties of ZnTiNb 2 O 8 ceramics with BaCu(B 2 O 5 ) additions prepared by solid-state reaction method have been investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The pure ZnTiNb 2 O 8 ceramic shows a high sintering temperature of about 1250 deg. C. However, it was found that the addition of BaCu(B 2 O 5 ) lowered the sintering temperature of ZnTiNb 2 O 8 ceramics from above 1250 deg. C to 950 deg. C due to the BCB liquid-phase. The results showed that the microwave dielectric properties were strongly dependent on densification, crystalline phases and grain size. Addition of 3 wt% BCB in ZnTiNb 2 O 8 ceramics sintered at 950 deg. C afforded excellent dielectric properties of ε r = 32.56, Q x f = 20,100 GHz (f = 5.128 GHz) and τ f = -64.87 ppm/deg. C. These represent very promising candidates for LTCC dielectric materials.

  16. Development of optical ceramic materials for infrared applications by optimizing sintering conditions

    Science.gov (United States)

    Isogai, Masafumi; Sano, Masahiko

    2017-05-01

    The authors developed production process of polycrystalline Zinc Sulfide (ZnS) materials which have been widely applied to windows and domes for infrared sensor systems. Commercially available ZnS powders of ca. 5 um particle sizes were used as a starting material and Spark Plasma Sintering method (SPS) was applied to the powders for firing process. It was found that the densification of the sintered materials was inhibited by outgassing from ZnS powders during the sintering process (ca. 400 Celsius). Thermal desorption spectroscopy analyses revealed the components of outgassing, such as hydrogen sulfide, sulfur oxide and organic molecules. Based on these analyses, the optimum conditions on heating rate and starting temperature of uniaxial pressurization were investigated to remove the outgassing. The polycrystalline ZnS materials fired under the optimized SPS conditions have such characteristics as better transmittance than 65 % and good uniformity in both 3 - 5 um and 8 - 12 um wavelength regions. These results show the importance of removing outgassing from starting materials.

  17. An Experimental Study of Sintered (Ni-Cr-xAl2O3 Composites

    Directory of Open Access Journals (Sweden)

    Alaa Abdulhasan Atiyah

    2016-09-01

    Full Text Available This paper deals with the (Ni-Cr- xAl2O3 metallic composites (MCCs. Restraining of of thermal expansion at adequate mechanical and corrosion properties is the main objective of this work. Composites are fabricated with four weight percentages of (x = 1, 2, 5 and 10% Al2O3. Compacting and sintering has accomplished at (636 MPa and 1250oC for 7 hrs. All sintered compacts were examined for phases and microstructure featuring. Results have indicated, the incorporation of Al2O3 with the matrix is due to the efficient sintering conditions, that diminishing the grain growth and increasing the softening temperature from 850°C to become 1350°C. Volume expansion appeared in the base sintered composites (NiCr-xAl2O3 due to pores evolution according to SEM observation. As, the Al2O3 has increased, the microhardness and corrosion resistance have improved. DSC results show a clear one exothermic and one endothermic reaction were occurred during the heating cycle. Corrosion behavior of fabricated composites was estimated by polarization curves using Potentiostat at scan rate 3 mV.sec-1. Potential-time measurements showed the formation of protective layer on surface composites compared with Ni-Cr base composite through an obtaining of the nobler open circuit potentials for composites. Corrosion parameters were estimated by the Tafel extrapolation method, these parameters indicated that the corrosion potential shifted toward a positive direction in addition to get lower corrosion current density especially for Ni-Cr/5%Alumina composite.

  18. Sol-gel coatings of ceramic fibres for composites with ceramic matrix

    International Nuclear Information System (INIS)

    Maier, B.; Grathwohl, G.; Spallek, M.; Pannhorst, W.

    1992-01-01

    The aim of this work was to show the feasibility in principle of sol-gel coating of ceramic reinforcement components for composites from technical aspects as well. The complexity of the coating task rises with the transition from individual fibres to bundles of fibres of different thickness to weaves, and finally to composites. (orig.) [de

  19. Composite metal foil and ceramic fabric materials

    Science.gov (United States)

    Webb, Brent J.; Antoniak, Zen I.; Prater, John T.; DeSteese, John G.

    1992-01-01

    The invention comprises new materials useful in a wide variety of terrestrial and space applications. In one aspect, the invention comprises a flexible cloth-like material comprising a layer of flexible woven ceramic fabric bonded with a layer of metallic foil. In another aspect, the invention includes a flexible fluid impermeable barrier comprising a flexible woven ceramic fabric layer having metal wire woven therein. A metallic foil layer is incontinuously welded to the woven metal wire. In yet another aspect, the invention includes a material comprising a layer of flexible woven ceramic fabric bonded with a layer of an organic polymer. In still another aspect, the invention includes a rigid fabric structure comprising a flexible woven ceramic fabric and a resinous support material which has been hardened as the direct result of exposure to ultraviolet light. Inventive methods for producing such material are also disclosed.

  20. The Effect of adding pore formers on the microstructure of NiO-YSZ ceramic composite

    International Nuclear Information System (INIS)

    Silva, F.S.; Santos, F.S.; Medeiros, L.M.; Yoshito, W.K.; Lazar, D.R.R.; Ussui, V.

    2011-01-01

    The ceramic composite of nickel oxide (NiO) with zirconium stabilized with 8 mol% yttria (8-YSZ) is the most employed material for use as anode for solid oxide fuel cells (SOFC). The nickel oxide in the composite is reduced to metallic nickel and this result in a 15% of porosity although the porosity needed to a proper function of an anode is about 30%, demanding the use of a pore former. In this work, NiO-YSZ composite powders were synthesized by a combustion process with urea as fuel, and the effect of the addition of carbon black and corn and rice starch as pore former were investigated. Powders were pressed as cylindrical pellets, sintered at 1350 °C for 60 minutes and density were measured by an immersion method and microstructure were observed by scanning electron microscopy. Results showed that ceramic composite has homogeneous microstructure and pores have different morphology and size depending on the kind of the pore former employed. (author)

  1. Reactive sintering of TiAl–Ti5Si3 in situ composites

    Energy Technology Data Exchange (ETDEWEB)

    Alman, David E.

    2005-06-01

    TiAl with between 0 and 20 vol%Ti5Si3 was produced by reactive sintering (700 °C for 15 min in vacuum) of cold pressed compacts of elemental Ti, Al and Si powder. The results show that adding Si to Ti and Al reduces the swelling associated with reactive sintering of TiAl, as composites containing more than 5 vol%Ti5Si3 densified during reactive sintering. However, composites containing more than 10 vol%Ti5Si3 did not retain their shape and the TiAl+20 vol%Ti5Si3 composite completely melted during the sintering process. A thermodynamic analysis indicated that the simultaneous formation of TiAl and Ti5Si3 increases the adiabatic flame temperature during the reaction between the powders. In fact, the analysis predicted that the maximum temperature of the reaction associated with the formation TiAl+20 vol%Ti5Si3 should exceed the melting point of TiAl, and this was observed experimentally. Differential thermal analysis (DTA) revealed that an Al–Si eutectic reaction occurred in mixtures of Ti, Al and Si powders prior to the formation of the TiAl and Ti5Si3 phases. There was no such pre-reaction formation of a eutectic liquid in Ti and Al powder mixtures. The formation of the pre-reaction liquid and the increase in adiabatic flame temperature resulted in the melting that occurred and the enhanced densification (minimization of swelling) during reactive sintering of the in situ composites.

  2. Investigation of the sinterability of ZrO{sub 2} (Y{sub 2}O3{sub )}-bioglass dental ceramics by dilatometry; Estudo da sinterabilidade de ceramicas dentarias de ZrO{sub 2} (Y{sub 2}O3{sub )}-biovidro usando dilatometria

    Energy Technology Data Exchange (ETDEWEB)

    Bicalho, Luiz de Araujo; Barboza, Miguel Ribeiro Justino [Universidade de Sao Paulo (USP), Lorena, SP (Brazil). Escola de Engenharia; Strecker, Kurt [Universidade Federal de Sao Joao del Rei (UFSJ), MG (Brazil); Santos, Claudinei dos; Habibe, Alexandre Fernandes; Magnago, Roberto de Oliveira [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil)

    2013-06-15

    The objective of this work is to study by dilatometry, the liquid phase sintering of ZrO{sub 2} ceramics using bioglass as sintering additive. Y{sub 2} O{sub 3} - stabilized ZrO{sub 2} powders were mixed with 3, 5 and 10 wt% of bioglass with the composition based on 3CaOP{sub 2} O{sub 5} -MgO-SiO{sub 2} system. Specimens were prepared by cold uniaxial pressing under 80MPa and the green relative density was determined. The sintering behavior was studied by measuring the linear shrinkage of samples in a dilatometer in relation to the temperature. The heating and cooling rates used in this study were 10 deg C/min and the maximum sintering temperatures was 1300 deg C with a 120 min isothermal holding time. The results of the shrinkage and shrinkage rates in regard of the sintering temperature and time were related to the amount of bioglass added. The sintered samples were characterized by X-ray diffraction analysis and their relative density. SEM micrographs indicates similar microstructure, and an increase of bioglass content leads to increasing of monoclinic ZrO{sub 2} phase content. The dilatometry results indicate a reduction of the temperature where a maximum shrinkage rate occurs, as function of bioglass increasing. Furthermore, the use of liquid phase reduces the maximum sintering temperature of 1447 deg C to 1250-1280 deg C. (author)

  3. Porous ceramic - metal composites obtained by infiltration methods

    Directory of Open Access Journals (Sweden)

    A. Boczkowska

    2013-07-01

    Full Text Available A pressure-vacuum infiltration (T = 720 ºC, p = 15 MPa, t = 15 min and gas-pressure infiltration (GPI in an autoclave (T = 700ºC, p=4 MPa, t=5 min were applied for infiltration of porous Al2O3 ceramics by cast aluminum alloy. Effect of the method of the infiltration on the microstructure and mechanical properties of ceramic-metal composites, was studied. Ceramic preforms were formed by method of copying the cellular structure of the polymer matrix. The results of the X-ray tomography proved very good infiltration of the pores by the metal for each method.

  4. Emerging ceramic-based materials for dentistry.

    Science.gov (United States)

    Denry, I; Kelly, J R

    2014-12-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. © International & American Associations for Dental Research.

  5. Tribology of ceramics and composites materials science perspective

    CERN Document Server

    Basu, Bikramjit

    2011-01-01

    This book helps students and practicing scientists alike understand that a comprehensive knowledge about the friction and wear properties of advanced materials is essential to further design and development of new materials. With important introductory chapters on the fundamentals, processing, and applications of tribology, the book then examines in detail the nature and properties of materials, the friction and wear of structural ceramics, bioceramics, biocomposites, and nanoceramics, as well as lightweight composites and the friction and wear of ceramics in a cryogenic environment.

  6. Werkstoffwoche 98. Vol. 7. Symposium 9: Ceramics. Symposium 14: Simulation of ceramics

    International Nuclear Information System (INIS)

    Heinrich, J.; Ziegler, G.; Hermel, W.; Riedel, H.

    1999-01-01

    The leading subject of this proceedings volume is ceramic materials, with papers on the following subject clusters: Processing (infiltration, sintering, forming) - Physics and chemistry of ceramics (functional ceramics, SiC, ceramic precursors, microstructural properties) - Novel concepts (composites, damage induced by oxidation and mechanical stress, performance until damage under mechanical and thermal stress, layers, nanocomposites). 28 of the conference papers have been prepared for individual retrieval from the ENERGY database. (orig./CB) [de

  7. Ceramic scaffolds produced by computer-assisted 3D printing and sintering: characterization and biocompatibility investigations.

    NARCIS (Netherlands)

    Warnke, P.H.; Seitz, H.; Warnke, F.; Becker, S.T.; Sivananthan, S.; Sherry, E.; Liu, Q.; Wiltfang, J.; Douglas, T.E.L.

    2010-01-01

    Hydroxyapatite (HAP) and tricalcium phosphate (TCP) are two very common ceramic materials for bone replacement. However, in general HAP and TCP scaffolds are not tailored to the exact dimensions of the defect site and are mainly used as granules or beads. Some scaffolds are available as ordinary

  8. Continuous Fiber Ceramic Composite (CFCC) Program: Gaseous Nitridation

    Energy Technology Data Exchange (ETDEWEB)

    R. Suplinskas G. DiBona; W. Grant

    2001-10-29

    Textron has developed a mature process for the fabrication of continuous fiber ceramic composite (CFCC) tubes for application in the aluminum processing and casting industry. The major milestones in this project are System Composition; Matrix Formulation; Preform Fabrication; Nitridation; Material Characterization; Component Evaluation

  9. Glass/Ceramic Composites for Sealing Solid Oxide Fuel Cells

    Science.gov (United States)

    Bansal, Narottam P.; Choi, Sung R.

    2007-01-01

    A family of glass/ceramic composite materials has been investigated for use as sealants in planar solid oxide fuel cells. These materials are modified versions of a barium calcium aluminosilicate glass developed previously for the same purpose. The composition of the glass in mole percentages is 35BaO + 15CaO + 5Al2O3 + 10B2O3 + 35SiO2. The glass seal was found to be susceptible to cracking during thermal cycling of the fuel cells. The goal in formulating the glass/ ceramic composite materials was to (1) retain the physical and chemical advantages that led to the prior selection of the barium calcium aluminosilicate glass as the sealant while (2) increasing strength and fracture toughness so as to reduce the tendency toward cracking. Each of the composite formulations consists of the glass plus either of two ceramic reinforcements in a proportion between 0 and 30 mole percent. One of the ceramic reinforcements consists of alumina platelets; the other one consists of particles of yttria-stabilized zirconia wherein the yttria content is 3 mole percent (3YSZ). In preparation for experiments, panels of the glass/ceramic composites were hot-pressed and machined into test bars.

  10. Efeito da adição de polímero precursor cerâmico na sinterização de alumina Effect of the addition of ceramic polymeric precursor on alumina sintering

    Directory of Open Access Journals (Sweden)

    A. L. E Godoy

    2010-03-01

    Full Text Available Foram estudados os efeitos da adição de polímero precursor na sinterização, microestrutura e dureza da alumina. O polímero inorgânico polifenilmetilvinilhidrogenosilsesquioxano (PPS foi utilizado como aditivo em cerâmicas de alumina sinterizadas a 1650 ºC. Os materiais sinterizados foram caracterizados por dilatometria, determinando-se a densidade aparente por picnometria de hélio, pela análise de carbono total, por difração de raios X, por microscopia eletrônica de varredura, espectrometria de energia dispersiva de raios X e por análise de indentação Vickers para determinação de dureza e tenacidade a fratura. Foram obtidas fases heterogêneas de Si2Al4O4N4 nas amostras com PPS. Dentre as amostras analisadas, a que contém 5% de PPS apresentou dureza e tenacidade à fratura superiores à da alumina pura. A preparação de compósitos cerâmicos com pequenas quantidades de polímero precursor mostrou-se um processo adequado para cerâmicas à base de alumina, sendo uma rota simples de conformação com grande potencial para a obtenção de peças com geometria complexa.The effects of the addition of precursor polymer on sintering, microstructure and hardness of alumina ceramics were studied. The linear shrinkage of cold-pressed specimens was studied by dilatometry. Polyphenylmethylvinylhidrogensilsesquioxane (PPS polymer sintering aid was used for alumina based ceramics sintered at 1650 ºC. The sintered materials were characterized by determination of apparent density by helium picnometry, by evaluation of total carbon content, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, and by Vickers indentation analysis for determining hardness and fracture toughness. Heterogeneous Si2Al4O4 phases were obtained in specimens with PPS. The specimens with 5% of PPS presented hardness and toughness greater than the obtained for pure alumina. The preparation of ceramic composites using small amounts of

  11. Solid state synthesis and sintering of monazite-type ceramics: application to minor actinides conditioning

    International Nuclear Information System (INIS)

    Bregiroux, D.

    2005-11-01

    In the framework of the French law of 1991 concerning the nuclear waste management, several studies are undertaken to develop specific crystalline conditioning matrices. Monazite, a rare earth (TR 3+ ) orthophosphate with a general formula TR 3+ PO 4 , is a natural mineral containing significant amount of thorium and uranium. Monazite has been proposed as a host matrix for the minor actinides (Np, Am and Cm) specific conditioning, thanks to its high resistance to self irradiation and its low solubility. Its is now of prime importance to check the conservation of these properties on synthesized materials, which implies to master all the stages of the elaboration process, from the powder synthesis to the sintering of controlled microstructure pellets. This work can be divided into two main parts: The first part deals with the synthesis by high temperature solid state route of TR 3+ PO 4 powders (with TR 3+ = La 3+ to Gd 3+ , Pu 3+ and Am 3+ ). The chemical reactions occurring during the firing of starting reagents are described in the case of monazite with only one or several cations. From these results, a protocol of synthesis is described. The incorporation of tetravalent cations (Ce 4+ , U 4+ , Pu 4+ ) in the monazite structure was also studied. The second part of the present work deals with the elaboration of controlled density and microstructure monazite pellets and their related mechanical and thermal properties. The study of crushing and sintering is presented. For the first time, experimental results are confronted with theoretical models in order to deduce the densification and grain growth mechanisms. By the comprehension of the various physicochemical phenomena occurring during the various stages of the monazite pellets elaboration process (powder synthesis, crushing, sintering...), this work allowed the development of a protocol of elaboration of controlled microstructure monazite TR 3+ PO 4 pellets. The determination of some mechanical and thermal

  12. Sintering behavior and property of bioglass modified HA-Al2O3 composite

    Directory of Open Access Journals (Sweden)

    Wang Li-li

    2012-01-01

    Full Text Available The bioglass modified HA-Al2O3 composites were successfully fabricated by mixing HA, synthesized by wet chemical method between precursor materials H3PO4 and Ca(OH2, with 25wt% Al2O3 and different content of bioglass (5%, 25%, 45%, 65wt% respectively, with a mole fraction of 53.9%SiO2, 22.6%Na2O, 21.8%CaO, and 1.7wt%P2O5, sintered in air at various temperatures (750-950°C for 2h. when the content of bioglass is below 45wt% in the composite, HA decomposes completely and transforms to β-TCP. The main phase in this case are β-TCP, Al2O3 and Ca3(AlO32.When the content of bioglass is above 45wt% in the composite, the decomposition of HA to β-TCP is suppressed and the main phases in this case are Al2O3 and HA, DCP□CaHPO4□ and β-TCP, which almost have the same chemical composition, forming ternary-glass phase, and have better bioactive than pure HA. It can also be found that at the certain addition of bioglass, the higher sintered temperature, the bigger volume density and flexural strength of the composite are, but when the sintered temperature reaches 950°C, they decrease. This modified HA-Al2O3 composites by calcium silicate glass have a much lower sintering temperature and decrease the production cost much.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-15

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

  14. Titanium diboride-chromium diboride-yttrium titanium oxide ceramic composition and a process for making the same

    International Nuclear Information System (INIS)

    Holcombe, C.E.; Dykes, N.L.

    1991-01-01

    This patent describes a ceramic composition. The ceramic composition consists essentially of from about 84 to 96 w/o titanium diboride, from about 1 to 9 w/o chromium diboride, and from about 3 to about 15 w/o yttrium-titanium-oxide. A method of making the ceramic composition is also described. The method of making the ceramic composition comprises the following steps: Step 1 - A consolidated body containing stoichiometric quantities of titanium diboride and chromium diboride is provided. Step 2 - The consolidated body is enclosed in and in contact with a thermally insulated package of yttria granules having a thickness of at least 0.5 inches. Step 3 - The consolidated body enclosed in the thermally insulated package of yttria granules is heated in a microwave oven with microwave energy to a temperature equal to or greater than 1,900 degrees centigrade to sinter and uniformly disperse yttria particles having a size range from about 1 to about 12 microns throughout the consolidated body forming a densified body consisting essentially of titanium diboride, chromium diboride, and yttrium-titanium-oxide. The resulting densified body has enhanced fracture toughness and hardness

  15. Surface treatments for repair of feldspathic, leucite - and lithium disilicate-reinforced glass ceramics using composite resin.

    Science.gov (United States)

    Neis, Christian Alencar; Albuquerque, Nadine Luísa Guimarães; Albuquerque, Ivo de Souza; Gomes, Erica Alves; Souza-Filho, Celso Bernardo de; Feitosa, Victor Pinheiro; Spazzin, Aloisio Oro; Bacchi, Atais

    2015-01-01

    The aim of this study was to evaluate the efficacy of different surface conditioning methods on the microtensile bond strength of a restorative composite repair in three types of dental ceramics: lithium disilicate-reinforced, leucite-reinforced and feldspathic. Twelve blocks were sintered for each type of ceramic (n=3) and stored for 3 months in distilled water at 37 °C. The bonding surface of ceramics was abraded with 600-grit SiC paper. Surface treatments for each ceramic were: GC (control) - none; GDB - diamond bur #30 µm; GHF - hydrofluoric acid (10%); GT- tribochemical silica coating (45-μm size particles). Treatments were followed by cleaning with phosphoric acid 37% for 20 s + silane + adhesive. The composite resin was used as restorative material. After repair, samples were subjected to thermocycled ageing (10,000 cycles between 5 °C and 55 °C for 30 s). Thereafter, the samples were sectioned into 1.0 mm2 sticks and tested for microtensile bond strength with 0.5 mm/min crosshead speed. Data were compared by two-way ANOVA and Tukey's test (α=0.05). The superficial wear with diamond bur proved to be suitable for feldspathic porcelain and for leucite-reinforced glass ceramic while hydrofluoric acid-etching is indicated for repairs in lithium disilicate-reinforced ceramic; tribochemical silica coating is applicable to leucite-reinforced ceramic. Predominance of adhesive failures was observed (>85% in all groups). In conclusion, the success of surface treatments depends on the type of ceramic to be repaired.

  16. Aspects regarding the tribological evaluation of sintered composites obtained from mixture of copper with carbon fibers

    Science.gov (United States)

    Caliman, R.

    2015-11-01

    This paper presents a study of the tribological properties of sintered composite materials made from combination of copper with short carbon fibers. Sintered composite materials are more effective if refer to specific properties per unit volume compared to conventional isotropic materials. Potential advantages of copper - carbon composite materials are: high resistance to breakage and high value ratios strength/density; resistance to high temperatures; low density and high resistance to wear; low or high friction coefficient. The sintered composite materials used in this research work are obtained combining different percentages of copper with short carbon fibres with iron and lead in order to investigate the variation of the friction behaviour. Varying the percentage of copper from 92,2% to 97,6% and the percentage of short carbon fibres from 7,8% to 2,4%, five different composite materials are obtained and tested. Friction tests are carried out, at room temperature, in dry conditions, on a pin-on-disc machine. The friction coefficient was measured using abrasive discs made from steel 4340 having the average hardness of 40 HRC, and sliding velocity of 0,6 m/sec. The main objective of this research work it was to identify a combination of materials with improved friction behaviour. The experimental results revealed that the force applied on the specimen during the tests, is playing a very important role regarding friction coefficient and also the wearing speed. Graphite particles are conveyed consistently inside the net, enhancing scraped spot safety and voltage drop over normal composite material. The static tests demonstrated that this new kind of sintered composite material has preferable electrical execution over previous brush material in the same conditions, and the element tests demonstrated that the temperature climb is not enormous when the brush with this new composite material is exchanged on with huge current and the surface scraped spot is littler amid

  17. Ceramic matrix composites -- Advanced high-temperature structural materials

    International Nuclear Information System (INIS)

    Lowden, R.A.; Ferber, M.K.; DiPietro, S.G.

    1995-01-01

    This symposium on Ceramic Matrix Composites: Advanced High-Temperature Structural Materials was held at the 1994 MRS Fall Meeting in Boston, Massachusetts on November 28--December 2. The symposium was sponsored by the Department of Energy's Office of Industrial Technology's Continuous Fiber Ceramic Composites Program, the Air Force Office of Scientific Research, and NASA Lewis Research Center. Among the competing materials for advanced, high-temperature applications, ceramic matrix composites are leading candidates. The symposium was organized such that papers concerning constituents--fibers and matrices--were presented first, followed by composite processing, modeling of mechanical behavior, and thermomechanical testing. More stable reinforcements are necessary to enhance the performance and life of fiber-reinforced ceramic composites, and to ensure final acceptance of these materials for high-temperature applications. Encouraging results in the areas of polymer-derived SiC fibers and single crystal oxide filaments were given, suggesting composites with improved thermomechanical properties and stability will be realized in the near future. The significance of the fiber-matrix interface in the design and performance of these materials is evident. Numerous mechanical models to relate interface properties to composite behavior, and interpret test methods and data, were enthusiastically discussed. One issue of great concern for any advanced material for use in extreme environments is stability. This theme arose frequently throughout the symposium and was the topic of focus on the final day. Fifty nine papers have been processed separately for inclusion on the data base

  18. Ceramic powders of CaZrO3. Preparation and sintering

    International Nuclear Information System (INIS)

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

    2003-01-01

    Calcium zirconate (CaZrO 3 ) is a compound belonging to the perovskite family of the A 2+ B 4+ O 3 6- type with orthorhombic crystalline structure (distorted perovskite).CaZrO 3 is used in the manufacture of sensors of oxygen, humidity, hydrogen and hydrocarbides.Additionally, it is also being studied for the manufacture of thermistors.The calcium zirconate preparation by solid state reaction from stoichiometric mixtures of CaCO 3 and ZrO 2 is studied.The formation reaction was followed by thermal analysis techniques (DTA-TG-DTG) and X-ray diffraction (XRD).The different behaviour of the mixtures was studied according to the milling type employed.It could be observed a shift of some peaks, mainly of TG (gravimetry) with a tendency to a temperature decrease.These changes are mainly influenced by the amorphization effects on the carbonate and by the mixing caused by the milling type used.The powder (CaZrO 3 ) was isostatically pressed obtaining then green densities of 50% of the theoretical one.Sintering was made in air between 1300 and 1600degC at times between 0 and 240.Densities reached were between 90 and 95% increasing with the temperature and the sintering time

  19. "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.

  20. Influences of spark plasma sintering temperature on the microstructures and thermoelectric properties of (Sr0.95Gd0.05)TiO3 ceramics

    Science.gov (United States)

    Li, Liang-Liang; Qin, Xiao-Ying; Liu, Yong-Fei; Liu, Quan-Zhen

    2015-06-01

    (Sr0.95Gd0.05)TiO3 (SGTO) ceramics are successfully prepared via spark plasma sintering (SPS) respectively at 1548, 1648, and 1748 K by using submicron-sized SGTO powders synthesized from a sol-gel method. The densities, microstructures, and thermoelectric properties of the SGTO ceramics are studied. Though the Seebeck coefficient shows no obvious difference in the case that SPS temperatures range from 1548 K to 1648 K, the electrical conductivity and the thermal conductivity increase remarkably due to the increase in grain size and density. The sample has a density higher than 98% theoretical density as the sintering temperature increases up to 1648 K and shows average grain sizes increasing from ˜ 0.7 μm to 7 μm until 1748 K. As a result, the maximum of the dimensionless figure of merit of ˜ 0.24 is achieved at ˜ 1000 K for the samples sintered at 1648 K and 1748 K, which was ˜ 71% larger than that (0.14 at ˜ 1000 K) for the sample sintered at 1548 K due to the enhancement of the power factor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174292, 51101150, and 11374306).

  1. Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 ceramics with BaCu(B2O5) additions

    International Nuclear Information System (INIS)

    Zhou Huanfu; Wang Hong; Chen Yuehua; Li Kecheng; Yao Xi

    2009-01-01

    The effects of BaCu(B 2 O 5 ) (BCB) additions on the sintering temperature and microwave dielectric properties of Ba 3 Ti 5 Nb 6 O 28 ceramic have been investigated using dilatometer, X-ray diffraction, scanning electron microscopy and dielectric measurement. The pure Ba 3 Ti 5 Nb 6 O 28 ceramic shows a high sintering temperature (∼1250 deg. C) and good microwave dielectric properties as Q x f of 11,400 GHz, ε r of 37.0, τ f of -8 ppm deg. C -1 . It was found that the addition of BCB to Ba 3 Ti 5 Nb 6 O 28 could lower the sintering temperature from 1250 to 925 deg. C. The reduced sintering temperature was attributed to the BCB liquid phase. The addition of BCB also enhanced the microwave dielectric properties to Q x f of 19,191 GHz, ε r of 38.2, τ f of 12 ppm deg. C -1

  2. The studies of a new ceramic composite — (Zr0.92Y0.08)O1.96 dispersed lanthanum titanium aluminium oxide

    International Nuclear Information System (INIS)

    Zhang, Peng; Choy, Kwang-leong

    2016-01-01

    A new ceramic composite (Zr 0.92 Y 0.08 )O 1.96 dispersed in LaTi 2 Al 9 O 19 as a thermal barrier material was synthesized by the hybrid sol–gel method. The composite ceramic has good thermochemical stability up to 1500 °C. The thermal conductivity of composite ceramic is circa. 1.0 W/m·K at ambient temperature and the coefficients of thermal expansion are very stable and comparable to (Zr 0.92 Y 0.08 )O 1.96 about 10.7 × 10 −6 K −1 at 1223 K. The sintering resistance and mechanical properties become better after being dispersed. Therefore, the new ceramic composite synthesized by hybrid sol–gel method can be a promising candidate as a thermal barrier material on Ni-based superalloy. - Highlights: • New composite 4 mol% yttria stabilized zirconia (4YSZ) dispersed LaTi 2 Al 9 O 19 (LTA) is synthesized by a hybrid sol-gel method. • The new ceramic composite shows good thermochemical stability up to 1500 o C. • The thermal conductivity of the new ceramic composite is lower than each component at ambient temperature. • The coefficient of thermal expansion of 4YSZ dispersed in LTA (LTA-4YSZ) is comparable to 4YSZ. • Compared with LTA and 4YSZ, LTA-4YSZ has the best sintering resistance. • The Young’s Modulus of LTA-4YSZ composite becomes lower while the hardness becomes higher.

  3. Method of making a continuous ceramic fiber composite hot gas filter

    Science.gov (United States)

    Hill, Charles A.; Wagner, Richard A.; Komoroski, Ronald G.; Gunter, Greg A.; Barringer, Eric A.; Goettler, Richard W.

    1999-01-01

    A ceramic fiber composite structure particularly suitable for use as a hot gas cleanup ceramic fiber composite filter and method of making same from ceramic composite material has a structure which provides for increased strength and toughness in high temperature environments. The ceramic fiber composite structure or filter is made by a process in which a continuous ceramic fiber is intimately surrounded by discontinuous chopped ceramic fibers during manufacture to produce a ceramic fiber composite preform which is then bonded using various ceramic binders. The ceramic fiber composite preform is then fired to create a bond phase at the fiber contact points. Parameters such as fiber tension, spacing, and the relative proportions of the continuous ceramic fiber and chopped ceramic fibers can be varied as the continuous ceramic fiber and chopped ceramic fiber are simultaneously formed on the porous vacuum mandrel to obtain a desired distribution of the continuous ceramic fiber and the chopped ceramic fiber in the ceramic fiber composite structure or filter.

  4. Improved Internal Reference Oxygen Sensors with Composite Ceramic Electrodes

    DEFF Research Database (Denmark)

    Hu, Qiang; Jacobsen, Torben; Hansen, Karin Vels

    2012-01-01

    Potentiometric oxygen sensors with an internal reference electrode, which uses the equilibrium pO2 of the binary mixture of Ni/NiO as the reference, are demonstrated. The cells employ Pt or composite ceramics as the sensing electrode. The cells are fabricated by a flexible and potentially low cos...... and performance are highly reproducible. The composite ceramics, based on strontium doped manganite and yttria doped zirconia, are proven superior over Pt to serve as the electrode material.......Potentiometric oxygen sensors with an internal reference electrode, which uses the equilibrium pO2 of the binary mixture of Ni/NiO as the reference, are demonstrated. The cells employ Pt or composite ceramics as the sensing electrode. The cells are fabricated by a flexible and potentially low cost...

  5. Structure and Magnetic Properties of Bi5Ti3FeO15 Ceramics Prepared by Sintering, Mechanical Activation and Edamm Process. A Comparative Study

    Directory of Open Access Journals (Sweden)

    Jartych E.

    2016-06-01

    Full Text Available Three different methods were used to obtain Bi5Ti3FeO15 ceramics, i.e. solid-state sintering, mechanical activation (MA with subsequent thermal treatment, and electrical discharge assisted mechanical milling (EDAMM. The structure and magnetic properties of produced Bi5Ti3FeO15 samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi5Ti3FeO15 ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi5Ti3FeO15 compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi5Ti3FeO15 ceramics produced by various methods is in paramagnetic state.

  6. Modeling the Stress Strain Behavior of Woven Ceramic Matrix Composites

    Science.gov (United States)

    Morscher, Gregory N.

    2006-01-01

    Woven SiC fiber reinforced SiC matrix composites represent one of the most mature composite systems to date. Future components fabricated out of these woven ceramic matrix composites are expected to vary in shape, curvature, architecture, and thickness. The design of future components using woven ceramic matrix composites necessitates a modeling approach that can account for these variations which are physically controlled by local constituent contents and architecture. Research over the years supported primarily by NASA Glenn Research Center has led to the development of simple mechanistic-based models that can describe the entire stress-strain curve for composite systems fabricated with chemical vapor infiltrated matrices and melt-infiltrated matrices for a wide range of constituent content and architecture. Several examples will be presented that demonstrate the approach to modeling which incorporates a thorough understanding of the stress-dependent matrix cracking properties of the composite system.

  7. Calcium phosphate/microgel composites for 3D powderbed printing of ceramic materials.

    Science.gov (United States)

    Birkholz, Mandy-Nicole; Agrawal, Garima; Bergmann, Christian; Schröder, Ricarda; Lechner, Sebastian J; Pich, Andrij; Fischer, Horst

    2016-06-01

    Composites of microgels and calcium phosphates are promising as drug delivery systems and basic components for bone substitute implants. In this study, we synthesized novel composite materials consisting of pure β-tricalcium phosphate and stimuli-responsive poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate-co-vinylimidazole) microgels. The chemical composition, thermal properties and morphology for obtained composites were extensively characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, IGAsorp moisture sorption analyzer, thermogravimetric analysis, granulometric analysis, ESEM, energy dispersive X-ray spectroscopy and TEM. Mechanical properties of the composites were evaluated by ball-on-three-balls test to determine the biaxial strength. Furthermore, initial 3D powderbed-based printing tests were conducted with spray-dried composites and diluted 2-propanol as a binder to evaluate a new binding concept for β-tricalcium phosphate-based granulates. The printed ceramic bodies were characterized before and after a sintering step by ESEM. The hypothesis that the microgels act as polymer adhesive agents by efficient chemical interactions with the β-tricalcium phosphate particles was confirmed. The obtained composites can be used for the development of new scaffolds.

  8. Support Services for Ceramic Fiber-Ceramic Matrix Composites

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, JP

    2001-08-16

    products of coal combustion found on the coupons exposed during those tests are reported. Finally, a relative comparison of ceramic and alloy material performance based on the SEM results is presented.

  9. Fabrication and properties of yttria, ceria doped zirconia-aluminia ceramic composites

    International Nuclear Information System (INIS)

    Lyubushkin, R.A.; Ivanov, O.N.; Chuev, V.P.; Buzov, A.A.

    2011-01-01

    At present, zirconia-based ceramics are gaining popularity in dentistry, particularly in fixed prosthodontics. clinically, it is important that ceramic restorations reproduce the translucency and color of natural teeth. Zirconia based ceramics is a high performance material with excellent biocompatibility and mechanical properties, which suggest its suitability for posterior fixed partial dentures. Y 2 O 3 -stabilized tetragonal zirconia polycrystalline (YTZ/Al 2 O 3 ) and CeO 2 -stabilized tetragonal zirconia polycrystalline (CZA) ceramics with high-performance were prepared for dental application by use the wet chemical route, consolidated by cold isostatic pressing, and two-step sintering method. Physical and mechanical properties test results show that the bending strength, fracture toughness, and the density of full sintered ceramics suggest that the material is relatively suitable for dental restoration.

  10. Spark plasma sintering of Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x} monolithic ceramics obtained by mechanically induced self-sustaining reaction

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, Amparo, E-mail: aborrell@upvnet.upv.es [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Salvador, Maria Dolores [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garcia-Rocha, Victoria [ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Fernandez, Adolfo [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Chicardi, Ernesto; Gotor, Francisco J. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Calle Americo Vespucio 49, 41092 Sevilla (Spain)

    2012-05-01

    Nanometer-sized titanium-niobium carbonitride powders (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with different Ti/Nb atomic ratios were obtained by a mechanically induced self-sustaining reaction, and sintered by spark plasma sintering technique at 1500 Degree-Sign C for 1 min in a vacuum atmosphere. Mechanical properties such as hardness and Young's modulus were determined by nanoindentation technique and friction and wear coefficients assessed by ball-on-disk testing using alumina ball in dry sliding conditions. The fracture surface and wear tracks of samples were examined by scanning electron microscopy. Results showed that it is possible to obtain dense monolithic ceramics from the solid solution (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti{sub 0.3}Nb{sub 0.7}C{sub 0.5}N{sub 0.5} ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa.

  11. Mechanical Properties of Composites with Titanium Diboride Fabricated by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Sulima I.

    2017-09-01

    Full Text Available Microstructure and mechanical properties of the 316L steel composite reinforced with TiB2 phase were examined. The test materials were obtained by SPS technique from powders. From testing of the mechanical properties it follows that the optimum temperature for the fabrication of 316Lsteel-TiB2 composites by SPS is 1100°C. Studies have also proved that the critical content of TiB2 phase in steel matrix should not exceed 6vol%. Above this level, the plastic properties of the composite become unstable and strongly dependent on the time of sintering.

  12. Preliminary study of chemical compositional data from Amazon ceramics

    International Nuclear Information System (INIS)

    Toyota, Rosimeiri G.; Munita, Casimiro S.; Luz, Fabio A.; Neves, Eduardo G.; Oliveira, Paulo M.S.

    2005-01-01

    Eighty seven ceramic samples from Acutuba, Lago Grande and Osvaldo archaeological sites located in the confluence of the rivers Negro and Solimoes were submitted to chemical analysis using instrumental neutron activation analysis to determine As, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Rb, Na, Nd, Sb, Sc, Sm, Ta, Tb, Th, Yb, Zn, and U. The database were studied using the Mahalanobis distance, and discriminant analysis. The results showed that the ceramics of each site differ from each other in chemical composition and that they form three different groups. Chemical classification of the ceramics suggests that vessels were made locally, as only ceramics from the same area show homogeneity of data. (author)

  13. Oxidation Characterization of Hafnium-Based Ceramics Fabricated by Hot Pressing and Electric Field-Assisted Sintering

    Science.gov (United States)

    Gasch, Matt; Johnson, Sylvia; Marschall, Jochen

    2010-01-01

    Ceramic borides, such as hafnium diboride (HfB2) and zirconium diboride (ZrB2), are members of a family of materials with extremely high melting temperatures referred to as Ultra High Temperature Ceramics (UHTCs). UHTCs constitute a class of promising materials for use in high temperature applications, such as sharp leading edges on future-generation hypersonic flight vehicles, because of their high melting points. The controlled development of microstructure has become important to the processing of UHTCs, with the prospect of improving their mechanical and thermal properties. The improved oxidation resistance of HfB2 has also become important if this material is to be successfully used at temperatures above 2000 C. Furthermore, the use of UHTCs on the leading edges of vehicles traveling at hypersonic speeds will mean exposure to a mixed oxidation environment comprised of both molecular and atomic oxygen. The current study has investigated the high-temperature oxidation behavior of HfB2-based materials in a pure O2 environment, as well as in environments containing different levels of dissociated oxygen (O/O2). Materials were processed by two techniques: conventional hot pressing (HP) and electric field-assisted sintering (FAS). Their oxidation behavior was evaluated in both a tube furnace at 1250 C for 3 hours and in a simulated re-entry environment in the Advanced Heating Facility (AHF) arcjet at NASA Ames Research Center, during a 10-minute exposure to a cold wall heat flux of 250W/sq cm and stagnation pressure of 0.1-0.2 atm. The microstructure of the different materials was characterized before and after oxidation using scanning electron microscopy (SEM).

  14. Study of Thermal Properties of Cast Metal- Ceramic Composite Foams

    OpenAIRE

    Gawdzińska K.; Chybowski L.; Przetakiewicz W.

    2017-01-01

    Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC). A certificate of non-combustibil...

  15. Fatigue and frictional heating in ceramic matrix composites

    DEFF Research Database (Denmark)

    Jacobsen, T.K.; Sørensen, B.F.; Brøndsted, P.

    1997-01-01

    This paper describes an experimental technique for monitoring the damage evolution in ceramic matrix composites during cyclic testing. The damage is related to heat dissipation, which may be measured as radiated heat from the surface of the test specimen. In the present experimental set...... with a high spatial and temperature resolution and changes in the heat dissipation can be measured almost instantaneously. The technique has been tested on uni-directional ceramic matrix composites. Experimental results are shown and the possibilities and the limitations of the technique are discussed....

  16. Synthesis and ceramic processing of zirconia alumina composites for application as solid oxide fuel cell electrolytes

    International Nuclear Information System (INIS)

    Garcia, Rafael Henrique Lazzari

    2007-01-01

    The global warmness and the necessity to obtain clean energy from alternative methods than petroleum raises the importance of developing cleaner and more efficient systems of energy generation, among then, the solid oxide fuel cell (SOFC). Cubic stabilized zirconia (CSZ) has been the most studied material as electrolyte in SOFC, due to its ionic conductivity and great stability at operation conditions. However, its low fracture toughness difficulties its application as a thin layer, what could lead to an improvement of cell efficiency. In this sense, the alumina addition in CSZ forms a composite, which can shift its mechanical properties, without compromising its electrical properties. In this work, coprecipitation synthesis route and ceramic processing of zirconia-alumina composites were studied, in order to establish optimum conditions to attain high density, homogeneous microstructure, and better mechanical properties than CSZ, without compromising ionic conductivity. For this purpose, composites containing up to 40 wt % of alumina, in a 9 mol % yttria-stabilized zirconia (9Y-CSZ) matrix were evaluated. In order to optimize the synthesis of the composites, a preliminary study of powder obtaining and processing were carried out, at compositions containing 20 wt % of alumina, in 9Y-CSZ. The ceramic powders were characterized by helium picnometry, X-ray diffraction, scanning electronic microscopy, transmission electronic microscopy, thermogravimetry, differential scanning calorimetry, granulometry by laser diffraction and gas adsorption (BET). The characterization of sinterized compacts were performed by X-ray diffraction, scanning electron microscopy, optical microscopy, density measurements, Vickers indentation and impedance spectroscopy. The obtained results show that the alumina addition, in the 9Y-CSZ matrix powders, raises the specific surface area, promotes deagglomeration of powders and elevates the oxides crystallization temperature, requiring higher

  17. Mechanical and magnetic properties of semi-Heusler/light-metal composites consolidated by spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Koller, M.; Chráska, Tomáš; Cinert, Jakub; Heczko, Oleg; Kopeček, Jaromír; Landa, Michal; Mušálek, Radek; Rameš, Michal; Seiner, Hanuš; Stráský, J.; Janeček, M.

    2017-01-01

    Roč. 126, July (2017), s. 351-357 ISSN 0264-1275 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 ; RVO:68378271 ; RVO:61388998 Keywords : Metal–metal composites * Spark plasma sintering * Light metals * Ferromagnetic alloys * Mechanical properties Subject RIV: JI - Composite Materials; JI - Composite Materials (FZU-D); JI - Composite Materials (UT-L) OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics; Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics (FZU-D); Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics (UT-L) Impact factor: 4.364, year: 2016 https://www.sciencedirect.com/science/article/pii/S0264127517303842?via%3Dih

  18. Microstructure and mechanical properties of pressureless sintered B4C- C composite using phenolic resin

    Science.gov (United States)

    Nikravan, A.; Baharvandi, H. R.; Jebelli, F. B.; Abdizadeh, H.; Ehsani, N.

    2007-10-01

    Boron carbide is an extremely promising material for a variety of applications that require high hardness and good wear resistance. However, due to the very high sintering temperatures which are required for B4C densification, wide spread use of that is limited. Various solutions have been studied to modifying densification behavior of B4C. Pressureless sintering in the presence of different additives has been tried by researchers. The effect of additives such as TiB2, SiC, Al, B, ZrO2, talc and Si have been evaluated. It was shown that the densification and mechanical properties may be improved with sintering aids. The Effects of phenolic resin additive on the microstructure and mechanical properties of B4C were explained in this study. Experimental composition was batched corresponding from 0 to 10 wt% of the additive. All samples were sintered for 60 minutes at 2150°C. The heating and cooling rates were 10°C/min for all samples. It was found that below 7.5 wt% of phenolic resin additive, the density increased with additive increasing and above that, decreased by phenolic resin addition. Mechanical properties such as fracture toughness, strength and hardness increased as a result of densification enhancement.

  19. Synthesis and characterization of aluminium–alumina micro- and nano-composites by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dash, K., E-mail: khushbudash@gmail.com; Chaira, D.; Ray, B.C.

    2013-07-15

    Graphical abstract: The evolution of microstructure by varying the particle size of reinforcement in the matrix employing spark plasma sintering has been demonstrated here in Al–Al{sub 2}O{sub 3} system. An emphasis has been laid on varying the reinforcement particle size and evaluating the microstructural morphologies and their implications on mechanical performance of the composites. Nanocomposites of 0.5, 1, 3, 5, 7 volume % alumina (average size < 50 nm) reinforced in aluminium matrix were fabricated by powder metallurgy route using spark plasma sintering technique technique at a temperature of 773 K and pressure of 50 MPa. Another set of specimens having composition 1, 5, 20 vol.% of alumina (average size ∼ 10 μm) had been fabricated to compare the physical as well as mechanical attributes of the microcomposite as well as the nanocomposites. These micro- and nano-composites have been characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy followed by density, microhardness and nanoindentation measurements. The alumina nanoparticles revealed an interface showing appreciable physical intimacy with the aluminium matrix compared to that of the alumina microparticles. The interfacial integrity in case of nanocomposites is better than in the microcomposite which has been studied using microscopic techniques. Spark plasma sintering imparts enhanced densification as well as matrix-reinforcement proximity which has been corroborated with the experimental results. - Highlights: • The Al–Al{sub 2}O{sub 3} micro- and nano-composites fabricated by spark plasma sintering. • Better matrix-reinforcement integrity in nanocomposites than microcomposites. • Spark plasma sintering method results in higher density and hardness values. • High density and hardness values of nanocomposites than microcomposites. • High dislocation density in spark plasma sintered Al–Al{sub 2}O{sub 3} composites. - Abstract: In the

  20. Sintering kinetics and mass transport in ceramic engobes; Cinetica de sinterizacion y transporte de masa en engobes ceramicos por el metodo Pechini

    Energy Technology Data Exchange (ETDEWEB)

    Dal Bo, M.; Boschi, A. O.; Hotza, D.

    2013-10-01

    This work is concerned to study the sintering rate and mass transport mechanism in ceramic engobes. Specimens of engobes were prepared from a determined formulation by slip casting. Sintering was carried in two steps: (i) at constant heating rate of 7.5 degree centigrade/min and (ii) with an isothermal treatment, during 120 min. According to the dilatometric curves obtained with the engobe sintering during isothermal treatment, the dominant sintering mechanism and the rate of reactions, between the 775 and 975 degree centigrade, were determined. The results showed that between 775 and 800 degree centigrade, the sintering rate can be described by ln[d({Delta}L/L{sub 0})/dt] = -5.64 + 1.77.E10{sup -}3T. At higher temperatures, from 850 to 975 degree centigrade, this rate can be expressed by ln[d({Delta}L/L{sub 0})/ dt] = -30.73 + 3.E10{sup -}2T. The dominant transport mass mechanisms were the grain rearrangement, solution-precipitation and grain boundaries reaction. (Author)

  1. Synthesis, Mechanical Behavior, and Multi-Scale Tribological Performance of Carbon Nanoparticle Reinforced Ceramic Composites

    Science.gov (United States)

    Nieto, Andy

    This dissertation investigates the effects of carbon nanoparticles on the synthesis, mechanical behavior, and tribological performance of ceramic based composites. Specifically graphene Nanoplatelet (GNP) reinforced Al 2O3 and nanodiamond (ND) reinforced WC-Co systems are investigated. Carbon based nanoparticles such as GNPs and NDs are ideal reinforcements for ceramic based composites because of their unique functional and mechanical properties. GNPs have exceptional mechanical properties such as yield strength and elastic modulus, along with superb functional properties such as thermal conductivity and electrical conductivity. NDs possess the highest hardness of any materials, very high elastic modulus, and have a very high thermal conductivity. GNPs are demonstrated to affect the sintering of Al2O 3 matrix composites by wrapping around grains, inhibiting diffusion, and thereby suppressing grain growth. High applied pressures (90 MPa) during sintering are observed to exacerbate grain growth suppression, while promoting attainment of fully dense ceramic composites. Higher applied pressures facilitate the wrapping of GNPs around grains, which promotes the onset of GNP induced grain growth suppression. Grain growth suppression compensates for the decreased hardness induced by low strength of the GNPs phase along the c-axis direction. GNPs enhanced the toughness and wear resistance of the nanocomposites by 21% and 39%, respectively, due to the intrinsic energy dissipating mechanisms such as GNP sheet kinking and sliding and GNP induced phenomena such as micro-cracking and crack bridging. The addition of ND affects the deposition of thermally sprayed coatings. Porosity increased in samples deposited by high velocity oxyacetylene flame spray (HVOF) and decreased in samples deposited by air plasma spray (APS). NDs are believed to inhibit solid state diffusion during splat impact, in the low thermal energy and high kinetic energy HVOF process. The high thermal

  2. 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.

  3. Low-temperature sintered ZnNb2O6–CaTiO3 ceramics with near-zero τf

    International Nuclear Information System (INIS)

    Guo, Mei; Li, Yuxia; Dou, Gang; Gong, Shuping

    2014-01-01

    The phases, microstructure and microwave dielectric properties of ZnNb 2 O 6 –xCaTiO 3 ceramics with BaCu(B 2 O 5 ) glass additions prepared by solid state reaction method were charactered by using X-ray diffraction, Scanning electron microscopy and Advantest network analyzer. The τ f of ZnNb 2 O 6 was modified to near 0 ppm °C −1 by incorporating CaTiO 3 with opposite τ f values on the basis of Lichtenecker empirical rule. The microwave dielectric properties of ZnNb 2 O 6 –xCaTiO 3 (x = 8.0 wt.%) samples with BaCu(B 2 O 5 ) glass additives sintered in 900–1000 °C were investigated, and the results indicated that the behaviors of the ε r and Q × f were associated with the sintering temperature and the amount of BaCu(B 2 O 5 ) glass. The sintering temperature of the ceramics was reduced to 950 °C from 1175 °C. Addition of 5.0 wt.% BaCu(B 2 O 5 ) glass in ZnNb 2 O 6 –xCaTiO 3 (x = 8.0 wt.%) ceramics sintered at 950 °C showed excellent dielectric properties of ε r  = 20.2, Q × f = 14,100 GHz (f = 7.3 GHz) and τ f  = 0 ppm °C −1 . Moreover, the material had a chemical compatibility with silver, which represented a promising candidate materials for low-temperature-co-fired ceramics applications. - Highlights: • The τ f of ZnNb 2 O 6 was modified to near 0 ppm °C −1 by incorporating CaTiO 3 . • The sintering temperature of ZnNb 2 O 6 –xCaTiO 3 ceramics with BCB was reduced to 950 °C. • The good dielectric properties of ε r  = 20.2, Q × f = 14,100 GHz, τ f  = 0 ppm °C −1 were achieved. • It represented a promising candidate materials for LTCC applications

  4. Tribological behaviour and statistical experimental design of sintered iron-copper based composites

    Science.gov (United States)

    Popescu, Ileana Nicoleta; Ghiţă, Constantin; Bratu, Vasile; Palacios Navarro, Guillermo

    2013-11-01

    The sintered iron-copper based composites for automotive brake pads have a complex composite composition and should have good physical, mechanical and tribological characteristics. In this paper, we obtained frictional composites by Powder Metallurgy (P/M) technique and we have characterized them by microstructural and tribological point of view. The morphology of raw powders was determined by SEM and the surfaces of obtained sintered friction materials were analyzed by ESEM, EDS elemental and compo-images analyses. One lot of samples were tested on a "pin-on-disc" type wear machine under dry sliding conditions, at applied load between 3.5 and 11.5 × 10-1 MPa and 12.5 and 16.9 m/s relative speed in braking point at constant temperature. The other lot of samples were tested on an inertial test stand according to a methodology simulating the real conditions of dry friction, at a contact pressure of 2.5-3 MPa, at 300-1200 rpm. The most important characteristics required for sintered friction materials are high and stable friction coefficient during breaking and also, for high durability in service, must have: low wear, high corrosion resistance, high thermal conductivity, mechanical resistance and thermal stability at elevated temperature. Because of the tribological characteristics importance (wear rate and friction coefficient) of sintered iron-copper based composites, we predicted the tribological behaviour through statistical analysis. For the first lot of samples, the response variables Yi (represented by the wear rate and friction coefficient) have been correlated with x1 and x2 (the code value of applied load and relative speed in braking points, respectively) using a linear factorial design approach. We obtained brake friction materials with improved wear resistance characteristics and high and stable friction coefficients. It has been shown, through experimental data and obtained linear regression equations, that the sintered composites wear rate increases

  5. DC-magnetron sputtering of ZnO:Al films on (00.1)Al2O3 substrates from slip-casting sintered ceramic targets

    International Nuclear Information System (INIS)

    Miccoli, I.; Spampinato, R.; Marzo, F.; Prete, P.; Lovergine, N.

    2014-01-01

    Highlights: • ZnO:Al was DC-sputtered on sapphire >350 °C by slip-casting sintered AZO target. • Films are highly (00.1)-oriented, smooth and transparent in the NIR–visible range. • Films growth rate decreases with temperature, while their grain size increases. • A high temperature reduction for sticking coefficients of impinging species is proved. • We prove that Thornton model does not apply to high-temperature DC-sputtered ZnO. - Abstract: High (>350 °C) temperature DC-sputtering deposition of ZnO:Al thin films onto single-crystal (00.1) oriented Al 2 O 3 (sapphire) substrates is reported, using a ultrahigh-density, low-resistivity and low-cost composite ceramic target produced by slip-casting (pressureless) sintering of ZnO–Al 2 O 3 (AZO) powders. The original combination of high-angle θ–2θ (Bragg–Brentano geometry) X-ray diffraction with low angle θ–2θ X-ray reflectivity (XRR) techniques allows us to define the AZO target composition and investigate the structural properties and surface/interface roughness of as-sputtered ZnO:Al films; besides, the growth dynamics of ZnO:Al is unambiguously determined. The target turned out composed of the sole wurtzite ZnO and spinel ZnAl 2 O 4 phases. X-ray diffraction analyses revealed highly (00.1)-oriented (epitaxial) ZnO:Al films, the material mean crystallite size being in the 13–20 nm range and increasing with temperature between 350 °C and 450 °C, while the film growth rate (determined via XRR measurements) decreases appreciably. XRR spectra also allowed to determine rms surface roughness <1 nm for present films and showed ZnO:Al density changes by only a few percent between 350 °C and 450 °C. The latter result disproves the often-adopted Thornton model for the description of the sputter-grown ZnO films and instead points out toward a reduction of the sticking coefficients of impinging species, as the main origin of film growth rate and grain size dependence with temperature. Zn

  6. Development of a dielectric ceramic based on diatomite-titania. Part one: powder preparation and sintering study

    Directory of Open Access Journals (Sweden)

    Tavares Elcio Correia de Souza

    1997-01-01

    Full Text Available This work presents powder preparation and sintering experiments of a mixture diatomite-titania. X-ray diffraction, DTA, TGA as well as chemical and microstructural analyses were made. The sintering process was investigated as a function of sintering temperature and time, mass variation, linear shrinkage and activation energy. The results show that sintering of diatomite-titania could be described by a viscous flow mechanism.

  7. Cellular ceramics made from porcelain tile polishing wastes: influence of sintering time; Ceramicas cellulares obtidas a partir de residuo de polimento de porcelanato: influencia do tempo de sinterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, A.F.; Zanelatto, C.C.; Uggioni, E. [Universidade do Extremo Sul Catarinense (UNESC), Criciuma, SC (Brazil). Dept. de Engenharia de Materiais; Bernardin, A.M., E-mail: amb@unesc.ne [Servico Nacional de Aprendizagem Industrial, Tijucas, SC (Brazil). Tecnologia em Ceramica

    2009-07-01

    This paper deals with the physical, microstructural and mechanical characterization of cellular ceramics made from porcelain polishing wastes, which were expanded by the bubble formation technique during the sintering process. The microstructure, linear expansion, bulk density (mercury immersion) and mechanical behavior (compressive strength) were determined to characterize the glass foam obtained. Moreover, the porcellaneous residue was characterized by chemical and phase analyses, particle size (laser diffraction) and thermal behavior. As a result, the higher the soaking time during heat treatment at 1200 deg C the lower the density obtained for the cellular ceramic due to CO{sub 2} expansion, and lower the mechanical strength of the samples. The microstructure shows spherical cells and completely closed pores, resulting in a cheap way to obtain low density material with adequate mechanical strength, avoiding the disposal of wastes from the ceramic industry. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-01

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

  9. Sinterização de cerâmicas em microondas. Parte III: Sinterização de zircônia, mulita e alumina Microwave sintering of ceramics. Part III: Sintering of zirconia, mullite and alumina

    Directory of Open Access Journals (Sweden)

    R. R. Menezes

    2007-09-01

    Full Text Available O aquecimento utilizando microondas possui muitas vantagens com relação aos métodos convencionais de aquecimento, como redução no tempo de processamento, economia de energia e melhora na uniformidade microestrutural dos corpos cerâmicos. Assim esse trabalho tem por objetivo a utilização da sinterização híbrida com microondas na queima rápida de materiais cerâmicos. Foram utilizados materiais que requerem altas temperaturas para densificação. Foram sinterizados materiais que apresentam bruscas e acentuadas mudanças nas suas propriedades dielétricas com a elevação da temperatura, zircônia, e materiais com baixas perdas dielétricas na temperatura ambiente, que apresentam dificuldades de aquecimento com microondas em baixas temperaturas, alumina e mulita. Foi utilizando material susceptor como agente auxiliar de aquecimento. Com base nos resultados obtidos pode-se concluir que o sistema de sinterização híbrida desenvolvido pode ser utilizado com sucesso na sinterização rápida e uniforme dos materiais estudados, sendo possível a sinterização de zircônia em ciclos de 20 min, mulita em ciclos de 16 min e alumina em ciclos de 40 min.Thermal processing by microwaves offers several advantages over conventional heating methods, such as shorter processing times, energy savings and improved microstructural homogeneity of ceramic bodies. Thus, this work focused on the fast hybrid microwave sintering of ceramic materials that require high sintering temperatures for densification. The materials studied here were zirconia, which displays abrupt and severe increases in dielectric loss with rising temperature, and alumina and mullite, which show low dielectric losses at ambient temperature and are difficult to microwave at low temperatures. A susceptor was used as an auxiliary heating agent. The results indicate that the sintering system developed here can be used efficiently for the rapid, homogeneous sintering of all the ceramics

  10. Inducing bioactivity of dental ceramic/bioactive glass composites by Nd:YAG laser.

    Science.gov (United States)

    Beketova, Anastasia; Poulakis, Nikolaos; Bakopoulou, Athina; Zorba, Triantafillia; Papadopoulou, Lambrini; Christofilos, Dimitrios; Kantiranis, Nikolaos; Zachariadis, George A; Kontonasaki, Eleana; Kourouklis, Gerasimos A; Paraskevopoulos, Konstantinos M; Koidis, Petros

    2016-11-01

    Aims of this study were to investigate the optimal conditions of laser irradiation of a novel Bioactive Glass/Dental Ceramic-BP67 composite for acceleration of hydroxyapatite-HA formation and to assess cellular responses on the precipitated HA region. BP67 (Bioactive Glass: 33.3%, Dental Ceramic: 66.7%) was fabricated by the sol-gel method. A laser assisted biomimetic-LAB process was applied to BP67 sintered specimens immersed in 1.5-times concentrated simulated body fluid-1.5×-SBF. The effect of various energy densities of pulsed nanosecond Nd-YAG (1064nm) laser and irradiation exposure times (30min, 1 and 3h) were evaluated for HA precipitation. The HA film was characterized by FTIR, XRD, SEM and micro Raman techniques. ICP-AES was used for revealing changes in chemical composition of the 1.5×-SBF during irradiation. Cell viability and morphological characteristics of periodontal ligament fibroblasts-PDLFs, human gingival fibroblasts-HGFs and SAOS-2 osteoblasts on the HA surface were evaluated by MTT assays and SEM. At optimal energy fluence of 1.52J/cm 2 and irradiation time for 3h followed by immersion in 1.5×-SBF at 60°C, a dense HA layer was formed on laser-irradiated BP67 within 7 days. The resulting HA film was tightly bonded to the underlying substrate and had mineral composition similar to cementum. MTT assay showed a consistent reduction of cell proliferation on the HA layer in comparison to conventional control ceramic and BP67 for all 3 cell lines studied. These findings suggest LAB is an effective method for acceleration of HA formation on materials with low bioactivity, while cellular responses need further investigation. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Effect of ZrO2 Addition on Microstructure, Morphology and Pressure Sensing Behaviour of Pb(ZrxTi1-x)O3 Ceramics Sintered in Al2O3 Environment

    International Nuclear Information System (INIS)

    Norhashimah Ramli; Muhamad Mat Salleh; Muhammad Yahaya; Mohammad Hafizuddin Jumali

    2009-01-01

    The effect of ZrO 2 addition on the microstructure, morphology and pressure sensing behaviour of Pb(Zr x Ti 1-x )O 3 ceramics was studied in five different compositions of ZrO 2 , namely x = 0.48, 0.50, 0.52, 0.54 and 0.56. The samples were prepared through the solid-state reaction method using high purity metal oxides powders. In order to control the PbO losses due to high temperature sintering, a novel approach were explored whereby the samples were sintered in Al 2 O 3 environment. Structural investigation using X-ray diffraction (XRD) method revealed that all samples exhibited a tetragonal crystal structure. However the c/a lattice parameters ratios exhibited a decreasing trend as the ZrO 2 content was increased, indicating that PZT crystals gradually evolved towards pseudo cubic structure. SEM micrographs showed different morphology of each composition with the grain size varies in the range of 1.5 μm to 3.15 μm. The performance of pressure sensing behaviour showed that sample with composition x = 0.52 exhibited the best piezoelectric properties with high sensitivity. However, all samples failed to show good stability and repeatability due to slow recovery after severe lattice strain. (author)

  12. An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

    Science.gov (United States)

    Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

    2013-05-01

    The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

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

    Directory of Open Access Journals (Sweden)

    Halyna Klym

    2015-03-01

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

  14. Toughening effect of multi-walled boron nitride nanotubes and their influence on the sintering behaviour of 3Y-TZP zirconia ceramics

    Czech Academy of Sciences Publication Activity Database

    Tatarko, Peter; Grasso, S.; Chlup, Zdeněk; Porwal, H.; Kasiarova, M.; Dlouhý, Ivo; Reece, M.J.

    2014-01-01

    Roč. 34, č. 7 (2014), s. 1829-1843 ISSN 0955-2219 EU Projects: European Commission(XE) 264526 - GLACERCO Institutional support: RVO:68081723 Keywords : Zirconia * Boron nitride nanotubes * Composite * Spark plasma sintering * Toughening mechanism Subject RIV: JI - Composite Materials Impact factor: 2.947, year: 2014

  15. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... the produced carbon is responsible for low electrical specific resistance of the ceramic carbon composites. References. [1] Takahashi M, Adachi K, Menchavez R L and Fuji M 2006 J. Mater. Sci. 41 1965. [2] ShuKMandTuGC2003Int. J. Machine Tools Manufacture43. 845. [3] Mikeska K R 1997 United States ...

  16. Silicone Resin Applications for Ceramic Precursors and Composites

    Directory of Open Access Journals (Sweden)

    Masaki Narisawa

    2010-06-01

    Full Text Available This article reviews the applications of silicone resins as ceramic precursors. The historical background of silicone synthesis chemistry is introduced to explain the production costs and supply availability of various silicones. Thermal degradation processes of silicones are classified in terms of the main chain structure and cyclic oligomer expulsion process, which determine the resulting ceramic yield and the chemical composition. The high temperature decomposition of Si-O-C beyond 1,400 °C in an inert atmosphere and formation of a protective silica layer on material surfaces beyond 1,200 °C in an oxidative atmosphere are discussed from the viewpoints of the wide chemical composition of the Si-O-C materials. Applications of the resins for binding agents, as starting materials for porous ceramics, matrix sources with impregnation, fiber spinning and ceramic adhesions are introduced. The recent development of the process of filler or cross-linking agent additions to resin compounds is also introduced. Such resin compounds are useful for obtaining thick coatings, MEMS parts and bulk ceramics, which are difficult to obtain by pyrolysis of simple organometallic precursors without additives.

  17. Fracture characteristics of refractory composites containing metakaolin and ceramic fibers

    Directory of Open Access Journals (Sweden)

    Ondřej Holčapek

    2015-03-01

    Full Text Available The aim of present article is to describe influence of composition of refractory composites on its response to gradual thermal loading. Attention was focused on the impact of ceramic fibers and application of metakaolin as an aluminous cement supplementary material. Studied aluminate binder system in combination with natural basalt fine aggregates ensures sufficient resistance to high-temperature exposure. Influence of composition changes was evaluated by the results of physical and mechanical testing—compressive and flexural strength, bulk density, and fracture energy were determined on the different levels of temperature loading. Application of ceramic fibers brought expected linear increase of ductility in studied composites. Metakaolin replacement showed the optimal dose to be just about 20% of aluminous cement weight.

  18. The mechanism of hard metal TiC-TiNi composite liquid-phase sintering

    International Nuclear Information System (INIS)

    Akimov, V.V.

    2006-01-01

    The sintering conditions are investigated for hard alloys on their production from powders of titanium nickelide with particle size of 10-25 μ and titanium carbide with particles of 5-10 μ at temperatures of 1280-1350 deg C under pressure of 0.1 MPa with holding at heat for 180-900 s. The analysis of experimental data shows that optimum sintering conditions are determined by the quantity of a binding phase TiNi. In the systems with a binding phase content no more than 40 % a heterogeneous structure with nonuniform aggregates of TiC and TiNi phases is observed. With increasing a binding phase amount up to 50-70 % and a temperature up to 1350 deg C, titanium nickelide melts and spreads uniformly among carbide grains. This results in a low porosity of the composite material and in an increase of thermodynamic stability of the system [ru

  19. Study on the Ingredient Proportions and After-Treatment of Laser Sintering Walnut Shell Composites

    Directory of Open Access Journals (Sweden)

    Yueqiang Yu

    2017-12-01

    Full Text Available To alleviate resource shortage, reduce the cost of materials consumption and the pollution of agricultural and forestry waste, walnut shell composites (WSPC consisting of walnut shell as additive and copolyester hot melt adhesive (Co-PES as binder was developed as the feedstock of selective laser sintering (SLS. WSPC parts with different ingredient proportions were fabricated by SLS and processed through after-treatment technology. The density, mechanical properties and surface quality of WSPC parts before and after post processing were analyzed via formula method, mechanical test and scanning electron microscopy (SEM, respectively. Results show that, when the volume fraction of the walnut shell powder in the WSPC reaches the maximum (40%, sintered WSPC parts have the smallest warping deformation and the highest dimension precision, although the surface quality, density, and mechanical properties are low. However, performing permeating resin as the after-treatment technology could considerably increase the tensile, bending and impact strength by 496%, 464%, and 516%, respectively.

  20. Study on the Ingredient Proportions and After-Treatment of Laser Sintering Walnut Shell Composites.

    Science.gov (United States)

    Yu, Yueqiang; Guo, Yanling; Jiang, Ting; Li, Jian; Jiang, Kaiyi; Zhang, Hui

    2017-12-02

    To alleviate resource shortage, reduce the cost of materials consumption and the pollution of agricultural and forestry waste, walnut shell composites (WSPC) consisting of walnut shell as additive and copolyester hot melt adhesive (Co-PES) as binder was developed as the feedstock of selective laser sintering (SLS). WSPC parts with different ingredient proportions were fabricated by SLS and processed through after-treatment technology. The density, mechanical properties and surface quality of WSPC parts before and after post processing were analyzed via formula method, mechanical test and scanning electron microscopy (SEM), respectively. Results show that, when the volume fraction of the walnut shell powder in the WSPC reaches the maximum (40%), sintered WSPC parts have the smallest warping deformation and the highest dimension precision, although the surface quality, density, and mechanical properties are low. However, performing permeating resin as the after-treatment technology could considerably increase the tensile, bending and impact strength by 496%, 464%, and 516%, respectively.

  1. W/Cu composites produced by low temperature Pulse Plasma Sintering

    International Nuclear Information System (INIS)

    Rosinski, M.S.; Fortuna, E.; Michalski, A.J.; Kurzydlowski, K.J.

    2006-01-01

    The plasma facing components (PFCs) must withstand the thermal, mechanical and neutron loads under cyclic mode of operation and vacuum. Despite that PFCs of ITER and demonstration reactors must assure reliability and long in service lifetime. For that reason PFCs are designed to be made of beryllium, tungsten or carbon fibre composites armours and copper based heat sink material. Such design concepts can only be used if joining methods of these dissimilar materials are resolved. Several techniques have been developed for joining W and Cu e. g. casting of pure Cu onto W, high temperature brazing, direct diffusion bonding or CVDs of W onto Cu. The main problem in the development of such joints is the large difference in the coefficients of thermal expansion, CTE (alpha Cu > 4 alpha W) and elastic modula (ECu > 0.2 EW). These differences result in large stresses at the W/Cu interfaces during manufacturing and/or during operation, which may lead to cracking or delamination reducing lifetime of the components. Possible solution to this problem is the use of W-Cu composites (FGM). W-Cu composites are widely used for spark erosion electrodes, in heavy duty circuit breakers and as heat sinks of microelectronic devices. They are commonly produced by infiltration of a porous sintered tungsten by liquid copper. Other technological route is powder metallurgy. Coatings can be produced by low pressure plasma spraying. All these methods, however, are known to have some disadvantages. For infiltration there is a 30 wt.% limit of Cu content while for powder metallurgy and plasma spraying techniques porosity is of concern. In our work the W-Cu composites of different composition were produced by pulse plasma sintering (PPS). This new method utilizes pulsed high electric discharges to heat the powders under uniaxial load. The arc discharges clean surface of powder particles and intensify diffusion. The total sintering time is reduced to several minutes. In our investigations various

  2. Processing and Material Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics.

    Science.gov (United States)

    Cox, Sarah B.

    2014-01-01

    The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.

  3. 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.

  4. Current Issues with Environmental Barrier Coatings for Ceramics and Ceramic Composites

    Science.gov (United States)

    Lee, Kang N.

    2004-01-01

    The environmental barrier coating (EBC) for SiC/SiC ceramic matrix composites and Si3N4 ceramics is an emerging field as the application of silicon-based ceramics in the gas turbine engine hot section is on the horizon, both for aero and industrial gas turbines. EBC is an enabling technology for silicon-based ceramics because these materials without an EBC cannot be used in combustion environments due to rapid surface recession. Significant progress in EBC development has been made during the last decade through various government-sponsored programs. Current EBCs are based on silicon, mullite (3Al2O3-2SiO2) and BSAS (barium strontium aluminum silicate with celsian structure). Volatility of BSAS, BSAS-silica chemical reaction, and low melting point of silicon limit temperature capability of current EBCs to about 1350 C for long-term applications. There is a need for higher temperature EBCs as the temperature capability of silicon-based ceramics continue to increase. Therefore, research is underway to develop EBCs with improved temperature capability compared to current EBCs. The current status and issues with the advanced EBC development efforts will be discussed.

  5. Laminated alumina/zirconia ceramic composites prepared by electrophoretic

    Czech Academy of Sciences Publication Activity Database

    Hadraba, Hynek; Drdlík, D.; Chlup, Zdeněk; Maca, K.; Dlouhý, Ivo; Cihlář, J.

    2012-01-01

    Roč. 32, č. 9 (2012), s. 2053-2056 ISSN 0955-2219. [Engineering Ceramics 2011 - from Materials to Components. Smolenice, 09.05.2011-12.05.2011] R&D Projects: GA ČR(CZ) GAP108/11/1644 Institutional research plan: CEZ:AV0Z20410507 Institutional support: RVO:68081723 Keywords : electrophoretic deposition * composites * hardness * Al2O3 * ZrO2 Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.360, year: 2012

  6. Phase composition of murataite ceramics for excess weapons plutonium immobilization

    Science.gov (United States)

    Sobolev, I. A.; Stefanovsky, S. V.; Myasoedov, B. F.; Kullako, Y. M.; Yudintsev, S. V.

    2000-07-01

    Among the host phases for actinides immobilization, murataite (cubic, space group Fm3m) with the general formula A4B2C7O22-x (A=Ca, Mn, Na, Ln, An; B=Mn, Ti, Zr, AnIV; C=Ti, Al, Fe; 0ceramics in detail has shown occurrence of several murataite varieties with three-, five-, and eight-fold fluorite unit cells. [1-3] The goal of the present step of work is to study an effect of waste elements on phase composition of murataite ceramic and isomorphic capacity of waste elements.

  7. Potential use of only Yb2O3in producing dense Si3N4ceramics with high thermal conductivity by gas pressure sintering.

    Science.gov (United States)

    Zhu, Xinwen; Zhou, You; Hirao, Kiyoshi; Ishigaki, Takamasa; Sakka, Yoshio

    2010-12-01

    Yb 2 O 3 is an efficient sintering additive for enhancing not only thermal conductivity but also the high-temperature mechanical properties of Si 3 N 4 ceramics. Here we report the fabrication of dense Si 3 N 4 ceramics with high thermal conductivity by the gas pressure sintering of α-Si 3 N 4 powder compacts, using only Yb 2 O 3 as an additive, at 1900 °C under a nitrogen pressure of 1 MPa. The effects of Yb 2 O 3 content, sample packing condition and sintering time on the densification, microstructure and thermal conductivity were investigated. Curves of the density plotted against the Yb 2 O 3 content exhibited a characteristic ' N ' shape with a local minimum at 3 mol% Yb 2 O 3 and nearly complete densification below and above this concentration. The effects of the sample packing condition on the densification, microstructure and thermal conductivity strongly depended on the Yb 2 O 3 content. The embedded condition led to more complete densification but also to a decrease in thermal conductivity from 119 to 94 W m -1 K -1 upon 1 mol% Yb 2 O 3 addition. The sample packing condition had little effect on the density and thermal conductivity (102-106 W m -1 K -1 ) at 7 mol% Yb 2 O 3 . The thermal conductivity value was strongly related to the microstructure.

  8. Potential use of only Yb2O3 in producing dense Si3N4 ceramics with high thermal conductivity by gas pressure sintering

    Directory of Open Access Journals (Sweden)

    Xinwen Zhu, You Zhou, Kiyoshi Hirao, Takamasa Ishigaki and Yoshio Sakka

    2010-01-01

    Full Text Available Yb2O3 is an efficient sintering additive for enhancing not only thermal conductivity but also the high-temperature mechanical properties of Si3N4 ceramics. Here we report the fabrication of dense Si3N4 ceramics with high thermal conductivity by the gas pressure sintering of α-Si3N4 powder compacts, using only Yb2O3 as an additive, at 1900 °C under a nitrogen pressure of 1 MPa. The effects of Yb2O3 content, sample packing condition and sintering time on the densification, microstructure and thermal conductivity were investigated. Curves of the density plotted against the Yb2O3 content exhibited a characteristic 'N' shape with a local minimum at 3 mol% Yb2O3 and nearly complete densification below and above this concentration. The effects of the sample packing condition on the densification, microstructure and thermal conductivity strongly depended on the Yb2O3 content. The embedded condition led to more complete densification but also to a decrease in thermal conductivity from 119 to 94 W m-1 K−1 upon 1 mol% Yb2O3 addition. The sample packing condition had little effect on the density and thermal conductivity (102–106 W m−1 K−1 at 7 mol% Yb2O3. The thermal conductivity value was strongly related to the microstructure.

  9. Effect of sintering temperature on the electromechanical properties of 0.945Bi0.5Na0.5TiO3-0.055BaZrO3 ceramics

    Science.gov (United States)

    Rahman, Jamil Ur; Hussain, Ali; Maqbool, Adnan; Malik, Rizwan Ahmed; Kim, Min Su; Kim, Myong Ho

    2015-04-01

    In this work, lead-free 0.945B0.5N0.5TiO3-0.055BaZrO3 (BNT-BZ) ceramics were synthesized by using conventional solid-state reaction method and the effect of different sintering temperatures (1145-1200 °C) on its structure and electromechanical properties were investigated. XRD patterns revealed single a phase-perovskite structure for all samples sintered at different temperatures. An optimum sintering temperature enhanced densification, promoted grain growth, and improve the dielectric and piezoelectric properties. However, at low (1145 °C) and high (1200 °C) sintering temperatures, the BNT-BZ ceramics showed inferior electromechanical properties. BNT-BZ ceramics sintered at an optimum temperature (1175 °C) showed an enhanced strain (0.39%) response at an applied electric field of 7 kV/mm with a high dynamic piezoelectric coefficient ( d 33* = 557 pm/V). These results can be attributed to the high density of the BNT-BZ ceramics sintered at 1175 °C.

  10. Disposition of excess plutonium using ''off-spec'' MOX pellets as a sintered ceramic waste form

    International Nuclear Information System (INIS)

    Armantrout, G.A.; Jardine, L.J.

    1996-02-01

    The authors describe a potential strategy for the disposition of excess weapons plutonium in a way that minimizes (1) technological risks, (2) implementation costs and completion schedules, and (3) requirements for constructing and operating new or duplicative Pu disposition facilities. This is accomplished by an optimized combination of (1) using existing nuclear power reactors to ''burn'' relatively pure excess Pu inventories as mixed oxide (MOX) fuel and (2) using the same MOX fuel fabrication facilities to fabricate contaminated or impure excess Pu inventories into an ''off-spec'' MOX solid ceramic waste form for geologic disposition. Diversion protection for the SCWF to meet the ''spent fuel standard'' introduced by the National Academy of Sciences can be achieved in at least three ways. (1) One can utilize the radiation field from defense high-level nuclear waste by first packaging the SCWF pellets in 2- to 4-L cans that are subsequently encapsulated in radioactive glass in the Defense Waste Processing Facility (DWPF) glass canisters (a ''can-in-canister'' approach). (2) One can add 137 Cs (recovered from defense wastes at Hanford and currently stored as CsCl in capsules) to an encapsulating matrix such as cement for the SCWF pellets in a small hot-cell facility and thus fabricate large monolithic forms. (3) The SCWF can be fabricated into reactor fuel-like pellets and placed in tubes similar to fuel assemblies, which can then be mixed in sealed repository containers with irradiated spent nuclear fuel for geologic disposition

  11. A high temperature testing system for ceramic composites

    Science.gov (United States)

    Hemann, John

    1994-01-01

    Ceramic composites are presently being developed for high temperature use in heat engine and space power system applications. The operating temperature range is expected to be 1090 to 1650 C (2000 F to 3000 F). Very little material data is available at these temperatures and, therefore, it is desirable to thoroughly characterize the basic unidirectional fiber reinforced ceramic composite. This includes testing mainly for mechanical material properties at high temperatures. The proper conduct of such characterization tests requires the development of a tensile testing system includes unique gripping, heating, and strain measuring devices which require special considerations. The system also requires an optimized specimen shape. The purpose of this paper is to review various techniques for measuring displacements or strains, preferably at elevated temperatures. Due to current equipment limitations it is assumed that the specimen is to be tested at a temperature of 1430 C (2600F) in an oxidizing atmosphere. For the most part, previous high temperature material characterization tests, such as flexure and tensile tests, have been performed in inert atmospheres. Due to the harsh environment in which the ceramic specimen is to be tested, many conventional strain measuring techniques can not be applied. Initially a brief description of the more commonly used mechanical strain measuring techniques is given. Major advantages and disadvantages with their application to high temperature tensile testing of ceramic composites are discussed. Next, a general overview is given for various optical techniques. Advantages and disadvantages which are common to these techniques are noted. The optical methods for measuring strain or displacement are categorized into two sections. These include real-time techniques. Finally, an optical technique which offers optimum performance with the high temperature tensile testing of ceramic composites is recommended.

  12. Synthesis and Characterization of Low Loss Dielectric Ceramics Prepared from Composite of Titanate Nanosheets with Barium Ions

    Directory of Open Access Journals (Sweden)

    Aleksandra Wypych-Puszkarz

    2017-01-01

    Full Text Available We report a strategy for preparing barium titanate precursor, being the composite of titanate nanosheets (TN with barium ions (Ba-TN, which subjected to step sintering allows obtaining TiO2 rich barium titanate ceramics of stoichiometry BaTi4O9 or Ba2Ti9O20. These compounds are important in modern electronics due to their required dielectric properties and grains’ size that can be preserved in nanometric range. The morphology studies, structural characterization, and dielectric investigations were performed simultaneously in each step of Ba-TN calcinations in order to properly characterize type of obtained ceramic, its grains’ morphology, and dielectric properties. The Ba-TN precursor can be sintered at given temperatures, so that its dielectric permittivity can be tuned between 25 and 42 with controlled temperature coefficients that change from negative 32 ppm/°C for Ba-TN sintered at 900°C up to positive 37 ppm/°C after calcination at 1300°C. XRD analysis and Raman investigations performed for the Ba-TN in the temperature range of 900÷1250°C showed that below 1100°C we obtained as a main phase BaTi4O9, whereas the higher calcinations temperature transformed Ba-TN into Ba2Ti9O20. Taking into account trend of device miniaturization and nanoscopic size requirements, temperatures of 900°C and 1100°C seem to be an optimal condition for Ba-TN precursor calcinations that guarantee the satisfactory value of dielectric permittivity (ε=26 and 32 and ceramic grains with a mean size of ~180 nm and ~550 nm, respectively.

  13. Sintering behavior and dielectric properties of BaTiO{sub 3} ceramics with glass addition for internal capacitor of LTCC

    Energy Technology Data Exchange (ETDEWEB)

    Hsiang, H.-I [Particulate Materials Research Center, Department of Resources Engineering, National Cheng Kung University, Tainan, Taiwan (China)], E-mail: hsingi@mail.ncku.edu.tw; Hsi, C.-S. [Department of Materials Science and Engineering, National United University, Miaoli, Taiwan (China); Huang, C.-C.; Fu, S.-L. [Department of Materials Science and Engineering, I-Shou University, Kaoshiung, Taiwan (China)

    2008-07-14

    The addition effects of ZnO-B{sub 2}O{sub 3}-SiO{sub 2} (ZBS) glass on both the sintering behavior and dielectric properties of BaTiO{sub 3} were investigated in developing low-temperature-fired BaTiO{sub 3}-based ceramics for LTCC devices. X-ray diffractometer (XRD), scanning electron microscopy (SEM), and a dilatometer were used to examine the effect of ZBS glass on BaTiO{sub 3} densification and the chemical reaction between the glass and BaTiO{sub 3}. The results indicate that ZBS glass can be used as a sintering aid to reduce the sintering temperature of BaTiO{sub 3} from 1300 to 900 deg. C without secondary phase formation. The dielectric properties of BaTiO{sub 3} with ZBS glass sintered at 900 deg. C show a relative density of 95%, a high dielectric constant of 994, and a dielectric loss of 1.6%.

  14. Microwave sintering of cordierite ceramic precursors obtained by starch direct consolidation; Sinterizacion por microondas de precursores ceramicos de cordierita obtenidos por consolidacion directa con almidon

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval, M.L.; Talou, M.H.; Camerucci, M.A., E-mail: andcamer@fi.mdp.edu.a [Consejo Nacional de Investigaciones Cientificas e Tecnicas (INTEMA-CONICET-UNMdP), Mar del Plata (Argentina). Inst. de Investigaciones en Ciencia y Tecnologia de Materiales. Lab. de Materiales Estructurales; Universidad Nacional de Mar Del Plata (UNMdP) (Argentina). Fac. de Ingenieria; Souto, P.M. de; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (DEMa/UFScar), SP (Brazil). Dept. de Engenharia de Materiais

    2009-07-01

    Microwave sintering of cordierite disk precursors (mixture of kaolin, talc and alumina) with potato starch was studied. Green disks were obtained by thermal consolidation of stable aqueous suspensions of the ceramic powders (29.6 % vol.) with potato starch (11.5 % vol.) at 75 and 85 deg C, 4h; drying (50 deg C,12h) and calcination (650 deg C, 2h). The reaction-sintering by microwave heating (power: 2.45 GHz; heating rate: 50 deg C/min) at different temperatures (1250-1330 deg C) and dwell times (10-20 min) was carried out. For comparative purposes, the reaction-sintering by conventional heating was analyzed (1330 deg C, 4h a 3 deg C/min). The evolution of the phases as a function of temperature and time was studied by XRD analysis. The developed microstructures (dense or porous) were characterized by density and porosity measurements, and SEM. The obtained results were analyzed in relation to the characteristics of starch behavior in aqueous suspension at temperature and the employed consolidation and sintering conditions. (author)

  15. Update on CMH-17 Volume 5 Ceramic Matrix Composites

    Science.gov (United States)

    Andrulonis, Rachael; Kiser, J. Douglas; David, Kaia E.; Davies, Curtis R.; Ashforth, Cindy

    2017-01-01

    A wide range of issues must be addressed during the process of certifying CMC (ceramic matrix composite) components for use in commercial aircraft. The Composite Materials Handbook-17, Volume 5, Revision A on ceramic matrix composites has just been revised to help support FAA certification of CMCs for elevated temperature applications. The handbook supports the development and use of CMCs through publishing and maintaining proven, reliable engineering information and standards that have been thoroughly reviewed. Volume 5 contains detailed sections describing CMC materialsprocessing design, analysisguidelines, testing procedures, and data analysis and acceptance. A review of the content of this latest revision will be presented along with a description of how CMH-17, Volume 5 could be used by the FAA (Federal Aviation Administration) and others in the future.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-11-15

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

  17. Bonding of glass ceramic and indirect composite to non-aged and aged resin composite.

    Science.gov (United States)

    Gresnigt, Marco; Özcan, Mutlu; Muis, Maarten; Kalk, Warner

    2012-02-01

    Since adhesion of the restorative materials to pre-polymerized or aged resin composites presents a challenge to the clinicians, existing restorations are often removed and remade prior to cementation of fixed dental prostheses (FDPs). This study evaluated bond strength of non-aged and aged resin composite to an indirect resin composite and pressed glass ceramic using two resin cements. Disk-shaped specimens (diameter: 3.5, thickness: 3 mm) (N = 160) produced from a microhybrid resin composite (Quadrant Anterior Shine) were randomly divided into eight groups. While half of the specimens were kept dry at 37°C for 24 h, the other half was aged by means of thermocycling (6000 times, 5°C to 55°C). The non-aged and aged resin composites were bonded to a highly filled indirect composite (Estenia) and a pressed glass ceramic (IPS Empress II) using either a photopolymerizing (Variolink Veneer) or a dual-polymerizing (Panavia F2.0) resin cement. While cementation surfaces of both the direct and indirect composite materials were silica coated (30 µm SiO2, CoJet-Sand) and silanized (ESPE-Sil), ceramic surfaces were conditioned with hydrofluoric acid (20 s), neutralized, and silanized prior to cementation. All specimens were cemented under a load of 750 g. Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). Failure types of the specimens were identified after debonding. Significant effects of aging (p ceramic in combination with both cements showed no significant difference (p > 0.05). Both indirect composite (24.3 ± 5.1 MPa) and glass ceramic in combination with Variolink (22 ± 9 MPa) showed the highest results on non-aged composites, but were not significantly different from one another (p > 0.05). On the aged composites, indirect composite and glass ceramic showed no significant difference in bond strength within each material group (p > 0.05), with both Panavia (17.2 ± 6 and 15 ± 5.5 MPa, respectively) and Variolink (19 ± 8

  18. Elaboration of thorium uranium phosphate-diphosphate({beta}-TUPD) and {beta}-TUPD/monazite composite materials from crystallized precursors: sintering and study of the long term behavior of the ceramics; Elaboration de phosphate-diphosphate de thorium et d'uranium ({beta}-PDTU) et de materiaux composites {beta}-PDTU/Monazite a partir de precurseurs cristallises. Etudes du frittage et de la durabilite chimique

    Energy Technology Data Exchange (ETDEWEB)

    Clavier, N

    2004-11-01

    Thorium Phosphate-Diphosphate ({beta}-TPD) is actually considered as potential host matrix for the immobilization of radionuclides, and especially actinides, in the field of an underground repository. The studies reported in this work are based on the precipitation of the Thorium Phosphate Hydrogen-Phosphate Hydrate (TPHPH) as a precursor of {beta}-TPD. The crystal structure of TPHPH was solved then the reactions involved during its transformation into {beta}-TPD were established. It allows us to put in evidence a new monoclinic variety of TPD, called {alpha}-TPD, acting as intermediate of reaction. Moreover, the existence of a complete solid solution between TPHPH and UPHPH was demonstrated.The experimental conditions of sintering leading to an optimal densification of the pellets were determined. The relative density of the samples was always between 95 and 100% of the calculated value while a significant improvement of the homogeneity of the samples was noted. By this way, the process based on the precipitation of low-temperature crystallized precursors followed by their heat treatment at high temperature was applied to the preparation of {beta}-TUPD/Monazite based composites in the aim to incorporate simultaneously tri- and tetravalent actinides. The chemical durability of {beta}-TUPD sintered samples was evaluated. The normalized leaching rates determined in several experimental conditions revealed the good resistance of the solids to aqueous alteration. Moreover, the normalized dissolution rates exhibited a low dependence to temperature, pH as well as to several ions present in the leachate. For all the samples, thorium was quickly precipitated as a neo-formed phosphate phase identified to TPHPH. (author)

  19. Mechanical properties of molybdenum alloyed liquid phase-sintered tungsten-based composites

    International Nuclear Information System (INIS)

    Kemp, P.B.; German, R.M.

    1995-01-01

    Tungsten-based composites are fabricated from mixed elemental powders using liquid phase sintering, usually with a nickel-iron matrix. During sintering, the tungsten undergoes grain growth, leading to microstructure coarsening that lowers strength but increases ductility. Often the desire is to increase strength at the sacrifice of ductility, and historically, this has been performed by postsintering deformation. There has been considerable research on alloying to adjust the as-sintered mechanical properties to match those of swaged alloys. Prior reports cover many additions, seemingly including much of the periodic table. Unfortunately, many of the modified alloys proved disappointing, largely due to degraded strength at the tungsten-matrix interface. Of these modified alloys, the molybdenum-containing systems exhibit a promising combination of properties, cost, and processing ease. For example, the 82W-8Mo-7Ni-3Fe alloy gives a yield strength that is 34% higher than the equivalent 90W-7Ni-3Fe alloy (from 535 to 715 MPa) but with a 33% decrease in fracture elongation (from 30 to 20% elongation). This article reports on experiments geared to promoting improved properties in the W-Mo-Ni-Fe alloys. However, unlike the prior research which maintained a constant Ni + Fe content and varied the W:Mo ratio, this study considers the Mo:(Ni + Fe) ratio effect for 82, 90, and 93 wt pct W

  20. Bifunctional behavior of Er3+ ions as the sintering additive and the fluorescent agent in Er3+ single doped γ-AlON transparent ceramics

    International Nuclear Information System (INIS)

    Wang, Ying; Xie, Xiumin; Qi, Jianqi; Wang, Shanshan; Wei, Nian; Lu, Zhongwen; Chen, Xingtao; Lu, Tiecheng

    2016-01-01

    We report on the sintering promoting and fluorescent activator roles of Er 3+ in AlON:Er 3+ transparent ceramics prepared by pressureless sintering with Er 2 O 3 and AlON powder. There shows that the transparency of samples varied with the content of Er 2 O 3 additive. The AlON:Er 3+ ceramics showed upconversion luminescence peaking at 546 nm, 662 nm and 840 nm under the 980 nm excitation due to transition of 4 S 3/2 / 2 H 11/2 → 4 I 15/2 , 4 F 9/2 → 4 I 15/2 and 4 S 3/2 / 2 H 11/2 → 4 I 13/2 of Er 3+ ions, respectively. The infrared spectra exhibited strong emission at 1534 nm corresponds to 4 I 13/2 → 4 I 15/2 transition. The mechanism of the IR and visible emission bands in AlON:Er 3+ ceramics are discussed, which suggest it should be attractive for lighting and display devices applications.

  1. Ceramic/Metal Composites with Positive Temperature Dependence of Thermal Conductivity

    International Nuclear Information System (INIS)

    Li Jianhui; Yu Qi; Sun Wei; Zhang Rui; Wang Ke; Li Jingfeng; Ichigozaki, Daisuke

    2013-01-01

    Most materials show decreasing thermal conductivity with increasing temperature, but an opposite temperature dependence of thermal conductivity is required for some industrial applications. The present work was conducted with a motivation to develop composite materials with a positive temperature dependence of thermal conductivity. ZrO 2 / stainless steel powders (304L) composite, with 3% stearic acid, was prepared by normal sintering under the protecting of Ar after mixing by mechanical ball milling technique. With the 304L content increasing from 10% to 20%, the thermal conductivity values increased. For all samples, the thermal conductivity in the temperature range of room temperature to 700 °C decreased with temperature below 300 °C, and then began to increase. The increasing thermal conductivity of the composites (within the high temperature range was attributed to the difference of the thermal conductivity and thermal expansion coefficient between ZrO 2 ceramic and 304L stainless steel powders. Two simple models were also used to estimate the thermal conductivity of the composites, which were in good agreement with the experiment results.

  2. Mathematical and numerical modeling of melting in metal-ceramic composite beds

    Science.gov (United States)

    Mughal, Mohammad Pervez

    2006-05-01

    Many of the ceramics used in the manufacture of the metal-ceramic composites are available as powders, which has encouraged investigators to develop tool less manufacturing techniques. Innovative processes like combustion synthesis and laser sintering processes offer great potential for specific material combinations. These processes involve heat and mass transfer in porous matrix with melting, solidification and may be chemical reaction. Since the resulting transport is relatively complex, there are few mathematical models available. In the present study, melting and transport of metal is demonstrated for a one-dimensional bed with uniform heat generation and convectively cooled boundaries. The effects of different Bond, Biot and Prandtl numbers are discussed using constant and temperature varying material properties. At low bond number the transport is controlled by capillary forces and temperature and saturation distribution is symmetric about the center of the bed. For Biot number larger than ten the process is internally controlled. Effect of Prandtl number is opposite of that of the Bond number. Use of constant properties overpredicts the process rate by 13%.

  3. Property-porosity relationships for polymer-impregnated superconducting ceramic composite

    International Nuclear Information System (INIS)

    Salib, S.; Vipulanandan, C.

    1990-01-01

    A thermoplastic polymer, poly(methyl methacrylate) (PMMA), was used to improve the flexural properties of the high-temperature superconducting ceramic (YBa 2 Cu 3 O 7-δ ). Ceramic specimens with different porosities were prepared by dry compacting 12.5-mm-diameter disk specimens at various uniaxial pressures. Density-pressure relationships have been developed for before- and after-sintering conditions. The PMMA polymer was impregnated into the porous ceramic at room temperature. The mechanical properties were evaluated by concentrically loading simply supported disk specimens. The load-displacement responses were analyzed using the finite-element method. Impregnation of PMMA polymer at room temperature increased the flexural strength and modulus of the superconducting ceramic without affecting its electrical properties. The flexural properties depended on the porosity of the ceramics, and, hence, linear and nonlinear property-porosity relationships have been used to characterize the behavior of superconducting ceramic with an without the polymer

  4. Method for producing ceramic composition having low friction coefficient at high operating temperatures

    Science.gov (United States)

    Lankford, Jr., James

    1988-01-01

    A method for producing a stable ceramic composition having a surface with a low friction coefficient and high wear resistance at high operating temperatures. A first deposition of a thin film of a metal ion is made upon the surface of the ceramic composition and then a first ion implantation of at least a portion of the metal ion is made into the near surface region of the composition. The implantation mixes the metal ion and the ceramic composition to form a near surface composite. The near surface composite is then oxidized sufficiently at high oxidizing temperatures to form an oxide gradient layer in the surface of the ceramic composition.

  5. Effect of calcium fluoride on sintering behaviour of SiO2-CaO-Na2O-MgO glass-ceramic system

    Directory of Open Access Journals (Sweden)

    Bahman Mirhadi

    2012-09-01

    Full Text Available The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM system containing calcium fluoride (CaF2 have been investigated by differential thermal analysis (DTA, X-ray diffraction (XRD and scanning electron microscopy (SEM. The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 °C.

  6. Improved lifetime of new fibrous carbon/ceramic composites

    Science.gov (United States)

    Gumula, Teresa

    2018-03-01

    New carbon/ceramic composites have been synthesized from low-cost phenol-formaldehyde resin and polysiloxane preceram. A reference carbon composite reinforced with carbon fibre (CC composite) is obtained in first place from a carbon fibre roving impregnated with a solution of phenol-formaldehyde resin in isopropyl alcohol. To obtain fibrous carbon/ceramic composites the CC perform is impregnated with polymethylphenylsiloxane polymer and then a thermal treatment in an inert atmosphere is applied. Depending on the temperature of this process, the resulting ceramics can be silicon carbide (SiC) or silicon oxycarbide (SiCO). Three representative samples, named CC/SiCO( a) (obtained at 1000 °C), CC/SiCO( b) (1500 °C) and CC/SiC (1700 °C), have been tested for fatigue behaviour and oxidation resistance. The value of the Young's modulus remains constant in fatigue tests done in flexion mode for the three new composites during a high number of cycles until sudden degradation begins. This is an unusual and advantageous characteristic for this type of materials and results in the absence of delamination during the measurements. In contrast, the CC reference composite shows a progressive degradation of the Young's modulus accompanied by delamination. SEM micrographs revealed that the formation of filaments of submicrometer diameter during the heat treatment can be responsible for the improved behaviour of these composites. The CC/SiC composite shows the best oxidation resistance among the three types of composites, with a 44% mass loss after 100 h of oxidation.

  7. 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)

  8. Mullite (3Al2O3·2SiO2 ceramics obtained by reaction sintering of rice husk ash and alumina, phase evolution, sintering and microstructure

    Directory of Open Access Journals (Sweden)

    M.F. Serra

    2016-03-01

    Partial densification was achieved (30% and highly converted materials were obtained. The developed microstructure consisted in a dense ceramic matrix with homogenous interconnected porosity, with a narrow pore size distribution below 20 μm. The developed material gives enough information for designing mullite ceramics materials with either porous or dense microstructures with structural, insulating or filtering applications employing RHA as silica source and calcined alumina as the only other raw material.

  9. Quartz crystal reinforced quartz glass by spark plasma sintering

    International Nuclear Information System (INIS)

    Torikai, D.; Barazani, B.; Ono, E.; Santos, M.F.M.; Suzuki, C.K.

    2011-01-01

    The Spark Plasma Sintering presents fast processing time when compared to conventional sintering techniques. This allows to control the grain growth during sintering as well as the diffusion rate of a multi-material compounds, and make possible obtainment of functionally graded materials and nanostructured compounds. Powders of high purity silica glass and crystalline silica were sintered in a SPS equipment at temperatures around 1350° C, i.e., above the softening temperature of silica glass and below the melting temperature of quartz crystal. As a result, glass ceramics with pure silica glass matrix reinforced with crystalline alpha-quartz grains were fabricated at almost any desired range of composition, as well as controlled size of the crystalline reinforcement. X-ray diffraction and density measurements showed the possibility to manufacture a well controlled density and crystallinity glass-ceramic materials. (author)

  10. Effects of BaCu(B2O5) addition on sintering temperature and microwave dielectric properties of Ba5Nb4O15–BaWO4 ceramics

    International Nuclear Information System (INIS)

    Jia Rui-Long; Su Hua; Tang Xiao-Li; Jing Yu-Lan

    2014-01-01

    The effects of BaCu(B 2 O 5 ) (BCB) addition on the microstructure, phase formation, and microwave dielectric properties of Ba 5 Nb 4 O 15 −BaWO 4 ceramic are investigated. As a sintering aid, BaCu(B 2 O 5 ) ceramic could effectively lower the sintering temperature of Ba 5 Nb 4 O 15 −BaWO 4 ceramic from 1100 °C to 950 °C due to the liquid-phase effect. Meanwhile, BaCu(B 2 O 5 ) addition effectively improves the densification of Ba 5 Nb 4 O 15 −BaWO 4 ceramic and significantly influences the microwave dielectric properties. X-ray diffraction analysis reveals that Ba 5 Nb 4 O 15 and BaWO 4 coexist with no crystal phase of BaCu(B 2 O 5 ) in the sintered ceramics. The Ba 5 Nb 4 O 15 −BaWO 4 ceramics with 1.0 wt% BaCu(B 2 O 5 ) sintered at 950 °C for 2 h presents good microwave dielectric properties of ε r = 19.0, high Q×f of 33802 GHz and low τ f of 2.5 ppm/°C. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  11. Wear Resistance of Sintered Composite Hardfacings under Different Abrasive Wear Conditions

    OpenAIRE

    SIMSON, Taavi; KULU, Priit; SURŽENKOV, Andrei; TARBE, Riho; GOLJANDIN, Dmitri; TARRASTE, Marek; VILJUS, Mart; TRAKSMAA, Rainer

    2017-01-01

    The article focuses on vacuum liquid phase sintered (PM) composite hardfacings and their behaviour under different abrasive wear conditions. Hardfacings studied contained 30 – 50 vol % fine, coarse or multimodal (fine and coarse) hardmetal reinforcement. For wear resistance studies, we used the Abrasive Rubber Wheel Wear (ARWW) test as a three-body abrasive wear test, the Abrasive Wheel Wear (AWW) test as a two-body abrasive wear test and the Abrasive-Impact Erosion wear (AIEW) test as an abr...

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

    Directory of Open Access Journals (Sweden)

    Xiulin Ji

    2016-09-01

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

  13. Development of ceramic composites from mixture of alumina and ceramic precursor polymer poly (silsesquioxane))

    International Nuclear Information System (INIS)

    Machado, Glauson Aparecido Ferreira

    2009-01-01

    Processing of ceramics materials, by polymer precursors pyrolysis, has been intensively researched over the past decades, due to advantages that this path provides, such as: lower temperature process compared to conventional techniques; structure control at molecular level; synthesis possibility of a wide range of ceramic compounds; obtaining parts with dimensions of the final product etc. The active filler controlled polymer pyrolysis (AFCOP) process, enables the synthesis of ceramic composites, by reaction between added filler (oxides, metals, intermetallic etc.) and solid and gaseous products, from polymer decomposition. In this study, based on this process, samples of alumina, with addition of 10 and 20 mass% of poly silsesquioxane polymer precursor, were manufactured. These samples were pyrolyzed at 900 degree C and thermal treated at temperatures of 1100, 1300 and 1500 degree C. The samples were characterized for bulk density, porosity and hardness, after each stage of thermal treatment. Structural transformations were analyzed by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Samples treated until 1300 degree C resulted in composites of alumina and silicon oxycarbide, while those treated at 1500 degree C, formed composites of mullite and alumina. The samples with 20% of polymer added started to density around 800 degree C and high retraction rate was observed at 1400 degree C. (author)

  14. Sintering, microstructure and properties of WC-AISI304 powder composites

    Energy Technology Data Exchange (ETDEWEB)

    Marques, B.J. [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal); Fernandes, C.M., E-mail: cmfernandes@ua.pt [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal); ISEC, Mechanical Department, Engineering Institute of Coimbra, Rua Pedro Nunes, 3030-199 Coimbra (Portugal); Senos, A.M.R. [Department of Materials and Ceramic Engineering, CICECO University of Aveiro, 3810-193 Aveiro (Portugal)

    2013-06-15

    Highlights: ► Total replacement of Co binder by stainless steel AISI 304 in WC based composites. ► Processing conditions for WC–stainless steel composites. ► Mechanical behavior and oxidation resistance of WC–stainless steel composites. -- Abstract: Tungsten carbide–stainless steel (AISI 304) based composites were successfully prepared by powder metallurgy routes using vacuum sintering at a maximum temperature of 1500 °C. The effects of the binder amount (between 6 and 15 wt.%) on the phase composition, microstructure and mechanical properties, namely hardness and fracture toughness, were investigated. Appreciable amount of (M,W){sub 6}C up to 12 wt.% was detected, especially for the higher SS contents. However, a good compromise between toughness and hardness was observed. Besides that, improved oxidation resistance was noticed in WC–SS based composites compared with WC–Co composites. The results are discussed having in mind the correlation between chemical composition, phase composition, microstructure and mechanical behavior.

  15. NANOSTRUCTURED CERAMICS AND COMPOSITES FOR REFRACTORY APPLICATIONS IN COAL GASIFICATION

    Energy Technology Data Exchange (ETDEWEB)

    Paul Brown

    2005-01-31

    A class of ceramics, capable of exhibiting low coefficients of thermal expansion and catalytic properties was investigated. Investigations were directed towards nanoengineering of NZP ceramics and NZP-based composites by chemical means by controlling their compositions and processing variables. NaZr{sub 2}(PO{sub 4}){sub 3} (NZP) was synthesized by combining water-soluble precursors leading to the precipitation of a gel that was dried, calcined, pressed into pellets, then fired at 850 C. Without chemical additives, the resulting ceramic comprised pores ranging in size from approximately 25 to 50 nm and a surface area of about 30m{sup 2}/g. Hydroxyapatite, which has a needle-like morphology, was mechanically mixed with the calcined gel to template NZP crystallization. What resulted was a coarsening of the pore structure and a decrease in surface area. When copper nitrate was added to the solution during synthesis, the resulting ceramic underwent shrinkage upon firing as well as an increase in strength. HAp and copper additions combined resulted in 40% volume shrinkage and a doubling of the tensile strength to 16MPa. A very different type of porosity was achieved when silica was partly substituted for phosphorous in the NZP structure. Na{sub 3}Zr{sub 2}(Si{sub 2}P)O{sub 12} (NASCION) was synthesized in the same manner as NZP, but the fired ceramic possessed a reticulated pore structure comprising large cavities ranging in size from 5 to 50 {micro}m. The NASCION ceramic either shrank or expanded upon firing depending on when the silica was added during synthesis. When the silica precursor (amorphous, precipitated silica) was added before the calcining step, the pressed pellets expanded during firing, whereas they shrank when the silica was added after the gel was calcined. The observed dilation increased with increasing calcining temperature and particle size, up to 26%. The contraction of the ceramic when fired increased with increasing calcining temperature and a

  16. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    Science.gov (United States)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  17. Sintered gahnite–cordierite glass-ceramic based on raw materials ...

    Indian Academy of Sciences (India)

    1732. Esmat M A Hamzawy and Mohammed A Bin Hussain. Table 1. Chemical composition of the base glass in wt% and the additives. Oxides from raw materials in wt%. Commercial additions. Oxides. SiO2. Al2O3. Fe2O3. CaO MgO Na2O K2O TiO2. ZnO. AlF3 a. MgF2 a. CaF2 a. SCb. 51.36. 34.86. —. —. 13.78. —. —. —.

  18. XRD investigation of the Effect of MgO Additives on ZTA-TiO2 Ceramic Composites

    Science.gov (United States)

    Azhar, Ahmad Zahirani Ahmad; Manshor, Hanisah; Ali, Afifah Mohd

    2018-01-01

    Alumina (Al2O3) based ceramics possess good mechanical properties and suitable for the application of cutting inserts. However, this monolithic ceramics suffer from lack of toughness. Hence, there are some modification were made such as the addition of yttria stabilized zirconia (YSZ) to the Al2O3 helps in increasing the toughness of the Al2O3 ceramics. Some additives such as MgO and TiO2 were used to further improve the mechanical properties of ZTA. In this study, high purity raw materials which consist of ZTA-TiO2 were mixed with different amount of MgO (0.0 – 1.0 wt %). The mixture of materials was going through wet mixing, compaction and pressureless sintering at 1600°C for one hour. The samples were characterized for phase analysis, microstructure, shrinkage rate, bulk density, Vickers hardness and fracture toughness. Based on the XRD analysis results, the secondary phase (MgAl2O4) was detected in the sample with 0.5 wt% of MgO onwards which leads to grains refinement, thus improve the density and hardness of ZTA-TiO2-MgO ceramics composites.

  19. Caracterização de cerâmicas sinterizadas por fluxo viscoso Phase formation of viscous flow sintered ceramics

    Directory of Open Access Journals (Sweden)

    C. Gibertoni

    2005-12-01

    Full Text Available Este trabalho visou o estudo de cerâmicas sinterizadas por fluxo viscoso com ênfase na formação de fases e desenvolvimento microestrutural. Foram estudadas composições de grês porcelanato, preparadas a partir de mistura de argila plástica, caulim, feldspato, quartzo e talco: i uma composição baseada em formulação encontrada em literatura, e ii composições preparadas com a finalidade de se observar o efeito da adição de um formador de fase vítrea obtido em laboratório, em substituição ao feldspato. A formação de uma grande quantidade de fase líquida viscosa, durante o processo de queima do grês porcelanato a elevadas temperaturas, favoreceu a eliminação da maioria dos poros e, como conseqüência, a densificação do corpo. A adição da fase vítrea resultou em amostras com boas propriedades físicas e necessidade de menores temperaturas de queima. Portanto, é possível substituir a matéria-prima de maior custo - o feldspato - por uma fase vítrea inerte, sem comprometimento do processamento, propriedades físicas e estéticas do produto final.This work describes an investigation carried out for ceramics sintered by viscous flow with emphasis on phase formation and microstructural development. In this work, compositions prepared by mixing ball clay, kaolin, feldspar, quartz and talc were studied They consisted of a composition based on the formulation of stoneware tileand reported in the literature and compositions intentionally prepared to observe the effect of the addition of a vitreous phase former, replacing feldspar on the phase formation and final characteristics. The formation of a great amount of liquid viscous phase during the firing process of the stoneware tiles at high temperatures provided the elimination of the majority of the pores and, consequently, the densification of the body. The addition of vitreous phase former resulted in samples with good physical properties fired at relatively low temperatures

  20. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Compared with SBTi ceramics and other lanthanide-substituted compositions, the incorporation of La3+ results in clear improvement in properties for SBLT ( ∼ 0.75) with respect to the values of hardness and Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for ...

  1. Ceramics composites for next generation nuclear reactors

    International Nuclear Information System (INIS)

    Pouchon, Manuel A.; Rebac, Tomislav; Chen, Jiachao; Dai, Yong; Hoffelner, Wolfgang

    2011-01-01

    Silicon carbide and carbon based composite materials are promising candidates for structural components of future nuclear systems. From non nuclear applications, both, the silicon carbide and the carbon matrix are well known for their excellent high temperature behavior and in case of the carbide, for the chemical inertness. The usage of these materials in their composite variant is inevitable, as the additionally introduced ductility is absolutely necessary in safety relevant components. Possible applications are structural components in high temperature reactors and claddings of advanced reactor systems, such as gas cooled fast reactors, including subcritical ones. The basic mechanical behavior of many of these composite materials is well known, however, little data is available about the degradation in mechanical performance after irradiation. The present paper investigates the mechanical behavior of four different composite materials before and after proton and neutron irradiation. The testing method is a three point bend experiment on non-notched sample bars. Four kinds of materials were tested. Two chemically vapor infiltrated CVI composites with silicon carbide matrices, one with a 2D silicon carbide fiber structure, and the other one with carbon fibers woven in a 2D structure. The two others were liquid silicon infiltrated LSI, both with carbon fibers, but one with a random and the other one with a 2D woven structure. The CVI samples with carbon fibers showed the highest mechanical strength after irradiation. The CVI material with silicon carbide fibers degraded most, but starting from a very high strength before irradiation. Both LSI materials showed a quite constant performance, before and after irradiation. (author)

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

    Science.gov (United States)

    Almansoori, Alaa; Majewski, Candice; Rodenburg, Cornelia

    2017-11-01

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

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

    Directory of Open Access Journals (Sweden)

    Dmytro Demirskyi

    2015-12-01

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

  4. Computer Modeling of Ceramic Boride Composites

    Science.gov (United States)

    2014-11-01

    hardness of the films are given in Fig. 101. Fig. 101. Correlation between the fractal dimensionality and the hardness of the chromium films...with the dissipative microstructural alloy dynamics described by the parabolic equations for phase variables determining the local phase (liquid or... microstructure of the composite — diboride fibers uniformly distributed in the matrix of lanthanum hexaboride. Computer simulation of the formation of

  5. Ceramic compositional analysis in archaeological perspective

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, R.L.; Rands, R.L.; Holley, G.R.

    1980-01-01

    The primary significance of compositional analysis in archaeology lies on the spatial dimension, in distinguishing products made by locally or regionally-based groups. If compositional analysis is to be carried beyond the descriptive recording of similarities and differences, the resource procurement zone (and its geographical relationship to inferred places of manufacture) is a basic operational concept (Rands and Bishop 1980). A zonal concept is clearly indicated in the case of pottery, which frequently is derived from raw materials, clay and temper, that do not necessarily coincide in their place of procurement. Moreover, depending on geomorphological and geochemical variables, these materials may show considerable homogeneity over a fairly extended area. On the other hand, unless there is strong, selective patterning in the exploitation of resources, great heterogeneity within a restricted region may result in fragmented procurement zones that are difficult to equate with the products of specific manufacturing centers. Under favorable circumstances, however, it appears that methods of compositional analysis are approaching the point at which microzones of limited geographical extent can be recognized and assigned heuristically useful boundaries.

  6. Production of Composite Ceramic Material for Thermal Spraying

    OpenAIRE

    Оковитый, В. А.; Пантелеенко, Ф. И.; Оковитый, В. В.; Асташинский, В. М.

    2017-01-01

    A composite ceramic material has been developed for thermal spraying that permits to increase wear resistance due to introduction of high-chromium steel and molybdenum in its structure, to obtain optimum porosity in the starting charge material while synthesizing  FeCrMo – MoS2/CaF2/С – TiC compositions,  to improve technological parameters of powders and thereby increase coefficient of powder usage in spraying, to reduce cost of wear-resistant coating technology. The paper presents character...

  7. Magnetic Resonance Imaging of Gel-cast Ceramic Composites

    Science.gov (United States)

    Dieckman, S. L.; Balss, K. M.; Waterfield, L. G.; Jendrzejczyk, J. A.; Raptis, A. C.

    1997-01-16

    Magnetic resonance imaging (MRI) techniques are being employed to aid in the development of advanced near-net-shape gel-cast ceramic composites. MRI is a unique nondestructive evaluation tool that provides information on both the chemical and physical properties of materials. In this effort, MRI imaging was performed to monitor the drying of porous green-state alumina - methacrylamide-N.N`-methylene bisacrylamide (MAM-MBAM) polymerized composite specimens. Studies were performed on several specimens as a function of humidity and time. The mass and shrinkage of the specimens were also monitored and correlated with the water content.

  8. Effect of sintering aid on microwave dielectric behaviors of Ni{sub 0.5}Ti{sub 0.5}NbO{sub 4} ceramics for LTCC applications

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, Ching-Fang, E-mail: cftseng@nuu.edu.tw; Chen, Chao-Chen; Lin, Chen-Wei

    2014-10-15

    The effects of ZnO glass addition on the microwave dielectric properties of Ni{sub 0.5}Ti{sub 0.5}NbO{sub 4} (NTN) ceramics prepared by solid-state reaction method have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The pure NTN ceramics have ε{sub r} of 60.6, Q × f value of 70,100 GHz, and τ{sub f} value of 76.6 ppm {sup °}C{sup −1} sintered at 1140 °C for 6 h. The results indicate that the addition of ZnO can effectively benefit the densification and further improve the dielectric constant. Moreover, the lower sintering temperature of NTN ceramics from 1140 to 930 °C is obtained by the addition of ZnO glass. However, an excess of ZnO suppresses the grain growth and decreases the Q × f value of NTN ceramics. The NTN ceramics with 2 wt% ZnO sintered at 930 °C for 6 h possess promising microwave dielectric properties: ε{sub r} of 56.3, Q × f value of 67,000 GHz, and τ{sub f} value of 78.6 ppm °C{sup −1}, which shows that the materials are suitable for low-temperature co-fired ceramics applications. - Highlights: • Microwave dielectric properties of NTN ceramics with sintering aid for LTCC applications were investigated. • ZnO-doped NTN ceramics decreased the sintering temperature to 930 °C for LTCC applications. • The ε{sub r} of 56.7, Q × f of 67,000, and τ{sub f} of +78.6 were obtained for 2 wt% ZnO-doped NTN ceramics sintered at 930 °C for 6 h. • A significant maintenance of dielectric properties was achieved by ZnO-doped NTN system sintered at 930 °C.

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

    Directory of Open Access Journals (Sweden)

    Lis M.

    2015-06-01

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

  10. Study of Thermal Properties of Cast Metal- Ceramic Composite Foams

    Directory of Open Access Journals (Sweden)

    Gawdzińska K.

    2017-12-01

    Full Text Available Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC. A certificate of non-combustibility test of cast aluminum-ceramic foam for marine applications was included inside the paper. The composite foam was prepared by the gas injection method, consisting in direct injection of gas into liquid metal. Foams with closed and open cells were examined. The foams were foaming with foaming gas consisting of nitrogen or air. This work is one of elements of researches connected with description of properties of composite foams. In author's other works acoustic properties of these materials will be presented.

  11. THE POLARIZING EFFECTS IN SINTERED KAOLIN

    African Journals Online (AJOL)

    compacted and sintered density of the ceramic have been studied, and a density — pressure relationship for before- and after-sintering conditions obtained. INTRODUCTION. Ceramics have been known to mankind for thousands of years, and have been used in construction materials. In many applications, ceramics have.

  12. Dynamic fracture toughness of ceramic composites

    Science.gov (United States)

    Yang, K. H.; Kobayashi, A. S.; Emery, A. F.

    1988-01-01

    The dynamic fracture toughness vs crack velocity relationships of TiB2 particulate-reinforced SiC-matrix and SiC whisker-reinforced Al2O3-matrix composites were determined at both room temperature and 1200 C with impacted, single-edge notched three-point bend specimens. Rapid crack initiation and propagation were monitored by a laser interferometric-displacement gage system. A FEM model that transmitted the measured outside-impact load to the specimen within the furnace was used to characterize the entire loading system-specimen unit. Small differences were measured between the room temperature and 1200 C dynamic responses.

  13. Mechanical characteristics of hybrid multilayer Green Tape[sup TM] ceramics sintered in a 2. 45 GHz single mode microwave cavity. [A commercial alumina-based product

    Energy Technology Data Exchange (ETDEWEB)

    Bansky, J.; Engemann, J. (Univ. of Wuppertal (Germany)); Bartley, D.; Asmussen, J.; Case, E.; Connery, S. (Michigan State Univ., East Lansing (United States))

    1993-04-01

    Research indicates that microwave energy offers many advantages over conventional heating methods. These advantages generally can be divided into two categories. One of them is the reduction in processing time and temperature, and the second one is the fabrication of materials with unique and/or superior properties. Microwave energy appears to be especially advantageous for the processing of many types of ceramics requiring high thermal process temperatures. This is connected with the increased coupling efficiency of ceramics at high temperatures with the microwave energy, the more uniform volumetric heating, and increased densification rates at lower processing temperatures. This paper describes microwave sintering of a commercial alumina-based product, Green Tape[sup TM] Dielectric 851AT (DuPont), that is designed for use as a material for hybrid integrated multilayer structures in the production of hybrid integrated circuits, as well as for some unconventional applications (ion optics, sensors, etc) (4,5). This study compares mechanical properties of conventionally and microwave sintered Green Tape[sup TM] 851AT hybrid multilayer structures.

  14. Composites of amorphous and nanocrystalline Zr–Cu–Al–Nb bulk materials synthesized by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Drescher, P., E-mail: philipp.drescher@uni-rostock.de [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Witte, K. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Yang, B. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Steuer, R.; Kessler, O. [Chair of Materials Science, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany); Burkel, E. [Physics of New Materials, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Schick, C. [Polymer Physics, Institute of Physics, University of Rostock, 18051 Rostock (Germany); Seitz, H. [Fluidic Technology and Microfluidics, Faculty of Mechanical Engineering and Marine Technology, University of Rostock, 18059 Rostock (Germany)

    2016-05-15

    The fabrication of Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} bulk metallic glass composite samples by spark plasma sintering (SPS) process has been successfully realized. The unique characteristics of bulk metallic glasses could lead to the possibility of future applications as new structural and functional materials. The densification of an amorphous Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} powder was realized in a systematic study changing the sintering temperature in the SPS process leading to stable composites characteristic of amorphous and nanocrystalline structures. X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis, transmission electron microscopy (TEM) as well as hardness tests were applied to determine the structural and mechanical properties of the sintered materials. A stable amorphous bulk metallic glass based on Zr{sub 70}Cu{sub 24}Al{sub 4}Nb{sub 2} with a low fraction of crystallites could be fabricated applying a nominal sintering temperature of 400 °C. Higher sintering temperatures lead to composites with high fractions of nanocrystalline material with porosities below 0.5%.

  15. Sinterização de cerâmicas em microondas. Parte I: aspectos fundamentais Microwave sintering of ceramics. Part I: fundamental aspects

    Directory of Open Access Journals (Sweden)

    R. R. Menezes

    2007-03-01

    Full Text Available O processamento de materiais baseado no aquecimento por meio de energia de microondas vem ganhado a cada dia mais destaque e importância em várias aplicações industriais, em virtude de uma série de vantagens em potenciais frente aos métodos convencionais de aquecimento. Na sinterização de materiais cerâmicos o uso de microondas permite redução no tempo de processamento, economia de energia e melhora na uniformidade microestrutural dos corpos cerâmicos. Como conseqüência das vantagens frente às técnicas de aquecimentos convencionais, a sinterização usando microondas vem sendo estudada por vários grupos de pesquisa em todo o mundo. Entretanto, os benefícios do uso das microondas só são obtidos quando a sinterização é realizada com o controle e entendimento científico de uma série de parâmetros e aspectos envolvidos no processo. Assim, esse trabalho tem por objetivo abordar aspectos científicos fundamentais do processo de sinterização de cerâmicas usando microondas, enfocando particularmente a interação matéria/microondas, aspectos peculiares do processo e a técnica de sinterização híbrida.Processing of materials based on heating by microwave energy has gained increasing importance in many industrial applications due to its potential advantages over conventional heating methods. In the sintering of ceramic materials, the use of microwave energy decreases the processing time, saves energy and improves the microstructural homogeneity of ceramic bodies. These advantages have motivated various research groups around the world to study microwave sintering. However, the benefits deriving from the use of microwaves depend on the control and scientific understanding of the parameters and aspects of the process. This paper offers a review of the fundamental scientific aspects of microwave sintering of ceramics, focusing on the interaction between materials and microwaves and highlighting particular points of the hybrid

  16. Microstructure, Hardness, and Corrosion Behavior of TiC-Duplex Stainless Steel Composites Fabricated by Spark Plasma Sintering

    Science.gov (United States)

    Han, Ying; Zhang, Wei; Sun, Shicheng; Chen, Hua; Ran, Xu

    2017-08-01

    Duplex stainless steel composites with various weight fractions of TiC particles are prepared by spark plasma sintering. Ferritic 434L and austenitic 316L stainless steel powders are premixed in a 50:50 weight ratio and added with 3-9 wt.% TiC. The compacts are sintered in the solid state under vacuum conditions at 1223 K for 5 min. The effects of TiC content on the microstructure, hardness, and corrosion resistance of duplex stainless steel composites fabricated by powder metallurgy are evaluated. The results indicate that the TiC particulates as reinforcements can be distributed homogeneously in the steel matrix. Densification of sintered composites decreases with increasing TiC content. M23C6 carbide precipitates along grain boundary, and its neighboring Cr-Mo-depleted region is formed in the sintered microstructure, which can be eliminated subsequently with appropriate heat treatment. With the addition of TiC, the hardness of duplex stainless steel fabricated by powder metallurgy can be markedly enhanced despite increased porosity in the composites. However, TiC particles increase the corrosion rate and degrade the passivation capability, particularly for the composite with TiC content higher than 6 wt.%. Weakened metallurgical bonding in the composite with high TiC content provides the preferred sites for pitting nucleation and/or dissolution.

  17. Sintering study of NiO-YSZ composite obtained by coprecipitation route; Estudo de sinterabilidade do composito de NiO-YSZ obtido pela rota de coprecipitacao

    Energy Technology Data Exchange (ETDEWEB)

    Yoshito, W.K.; Resitivo, T.A.G.; Ussui, V.; Lazar, D.R.R.; Paschoal, J.O.A., E-mail: wyoshito@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

    2009-07-01

    NiO-YSZ composite is a widely used anode material for solid oxide fuel cell. The main purpose of the present work was the evaluation of the appropriate conditions of ceramic processing, by sintering behavior study of NiO-YSZ pressed powders, synthesized by hydroxide coprecipitation route. Using the empirical rate equation developed by Makipirtti-Meng, it was analyzed shrinkage rate in the temperature ranges of 900-1400 deg C as function of time. The powders were characterized by X-ray diffraction, scanning electron microscopy, gas adsorption, laser diffraction and helium picnometry. The microstructural characterization of the samples was evaluated by X-ray diffraction, scanning electron microscopy and relative density by the Archimedes method. It was found that activation energy value is 48,3 kJ.mol{sup -1} in the temperature range of 900-950 deg C and 604,83 kJ.mol{sup -1} for 1000-1200 deg C. These values correspond to the change that occurs in the microstructure during the heat treatment process. The sintering process was evaluated by the dilatometry date treatment. (author)

  18. Neural network applied to elemental archaeological Marajoara ceramic compositions

    International Nuclear Information System (INIS)

    Toyota, Rosimeiri G.; Munita, Casimiro S.; Boscarioli, Clodis

    2009-01-01

    In the last decades several analytical techniques have been used in archaeological ceramics studies. However, instrumental neutron activation analysis, INAA, employing gamma-ray spectrometry seems to be the most suitable technique because it is a simple analytical method in its purely instrumental form. The purpose of this work was to determine the concentration of Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb, and Zn in 160 original marajoara ceramic fragments by INAA. Marajoara ceramics culture was sophisticated and well developed. This culture reached its peak during the V and XIV centuries in Marajo Island located on the Amazon River delta area in Brazil. The purpose of the quantitative data was to identify compositionally homogeneous groups within the database. Having this in mind, the data set was first converted to base-10 logarithms to compensate for the differences in magnitude between major elements and trace elements, and also to yield a closer to normal distribution for several trace elements. After that, the data were analyzed using the Mahalanobis distance and using the lambda Wilks as critical value to identify the outliers. The similarities among the samples were studied by means of cluster analysis, principal components analysis and discriminant analysis. Additional confirmation of these groups was made by using elemental concentration bivariate plots. The results showed that there were two very well defined groups in the data set. In addition, the database was studied using artificial neural network with unsupervised learning strategy known as self-organizing maps to classify the marajoara ceramics. The experiments carried out showed that self-organizing maps artificial neural network is capable of discriminating ceramic fragments like multivariate statistical methods, and, again the results showed that the database was formed by two groups. (author)

  19. Neural network applied to elemental archaeological Marajoara ceramic compositions

    Energy Technology Data Exchange (ETDEWEB)

    Toyota, Rosimeiri G.; Munita, Casimiro S., E-mail: rosimeiritoy@yahoo.com.b, E-mail: camunita@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Boscarioli, Clodis, E-mail: boscarioli@gmail.co [Universidade Estadual do Oeste do Parana, Cascavel, PR (Brazil). Centro de Ciencias Exatas e Tecnologicas. Colegiado de Informatica; Hernandez, Emilio D.M., E-mail: boscarioli@gmail.co [Universidade de Sao Paulo (USP), SP (Brazil). Escola Politecnica; Neves, Eduardo G.; Demartini, Celia C., E-mail: eduardo@pq.cnpq.b [Museu de Arqueologia e Etnologia (MAE/USP), Sao Paulo, SP (Brazil)

    2009-07-01

    In the last decades several analytical techniques have been used in archaeological ceramics studies. However, instrumental neutron activation analysis, INAA, employing gamma-ray spectrometry seems to be the most suitable technique because it is a simple analytical method in its purely instrumental form. The purpose of this work was to determine the concentration of Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb, and Zn in 160 original marajoara ceramic fragments by INAA. Marajoara ceramics culture was sophisticated and well developed. This culture reached its peak during the V and XIV centuries in Marajo Island located on the Amazon River delta area in Brazil. The purpose of the quantitative data was to identify compositionally homogeneous groups within the database. Having this in mind, the data set was first converted to base-10 logarithms to compensate for the differences in magnitude between major elements and trace elements, and also to yield a closer to normal distribution for several trace elements. After that, the data were analyzed using the Mahalanobis distance and using the lambda Wilks as critical value to identify the outliers. The similarities among the samples were studied by means of cluster analysis, principal components analysis and discriminant analysis. Additional confirmation of these groups was made by using elemental concentration bivariate plots. The results showed that there were two very well defined groups in the data set. In addition, the database was studied using artificial neural network with unsupervised learning strategy known as self-organizing maps to classify the marajoara ceramics. The experiments carried out showed that self-organizing maps artificial neural network is capable of discriminating ceramic fragments like multivariate statistical methods, and, again the results showed that the database was formed by two groups. (author)

  20. Polymer derived ceramic composites as environmental barrier coatings on steel

    Science.gov (United States)

    Torrey, Jessica D.

    Polymer derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as fibers and coatings. They offer advantages over traditional ceramic processing routes including lower pyrolysis temperatures and the ability to employ polymeric processing techniques. The main drawback to preceramic polymers is that they undergo a shrinkage during pyrolysis that can be greater than 50-volume%. One way to overcome this shrinkage is to add filler particles, usually elemental or binary metals, which will expand upon reaction with the pyrolysis atmosphere, thereby compensating for the shrinkage of the polymer. The aim of this study is to develop a polymer derived ceramic composite coating on steel as a barrier to oxidation and carburization, while concurrently gaining insight as to the fundamental mechanisms for compositional and microstructural evolution within the system. A systematic approach to selecting the preceramic polymer and expansion agents was taken. Six commercially available poly(silsesquioxane) polymers and a polysiloxane were studied. Several metals and an intermetallic were considered as potential expansion agents. The most desirable polymer/expansion agent combination was achieved with poly(hydridomethylsiloxane) as the matrix and titanium disilicide as the filler. Processing parameters have been optimized and a relationship derived to predict final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals an amorphous composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating-steel interface, indicating good bonding. The optimized coatings are ˜18mum thick, have some residual porosity and a density of 2.57g/cm3. A systematic study of the phase transformations and microstructural changes in the coating and its components during pyrolysis in air is also presented. The system evolves from a polymer filled with a binary metal at

  1. Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

    Science.gov (United States)

    Jarmon, David C.; Ojard, Greg; Brewer, David N.

    2013-01-01

    As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-10-29

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

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

    Directory of Open Access Journals (Sweden)

    Sara Rengifo

    2017-01-01

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

  4. Retention strength between veneering resin composites and laser-sintered cobalt-chromium alloy.

    Science.gov (United States)

    Kamada, Kohji; Taira, Yohsuke; Sumi, Tadateru; Sawase, Takashi

    2017-01-01

    The purpose of the present study was to evaluate the retention strength between a resin composite veneering material and three types of cobalt-chromium (Co-Cr) alloy substrates. Co-Cr alloy specimens with 81 retention devices (LSR), with 144 retention devices (LDR), and without retention device (LN) were fabricated using a laser-sintering system. The specimens were air-abraded with alumina, conditioned with a primer [Alloy primer (AP) or M.L. primer (ML)], and veneered with a light-polymerized resin composite (Gradia). Three control groups (LSR-N, LDR-N, and LN-N) without primer were also prepared. After 20,000 thermocycles in 4 and 60 °C water, tensile retention strengths were determined using a universal testing machine. Data were analyzed by analysis of variance and a post hoc Tukey-Kramer HSD test (α = 0.05, n = 8). The highest retention strengths were obtained in LSR-AP (28.3 MPa), LSR-ML (23.3 MPa), LDR-AP (26.9 MPa), and LDR-ML (27.8 MPa), and these values were not significantly different. In the absence of a retention device, the retention strengths were significantly different in the following order: LN-N (0.1 MPa) LDR-N (17.1 MPa). No significant difference was found between the numbers of retention devices, which were 81 and 144. In conclusion, the combined use of the primers and the retention devices is recommended when the laser-sintered Co-Cr alloy is veneered with the resin composite materials to maximize the retention strength.

  5. Thermoelectric generator based on composites obtained by sintering of detonation nanodiamonds

    Science.gov (United States)

    Eidelman, E. D.; Meilakhs, A. P.; Semak, B. V.; Shakhov, F. M.

    2017-11-01

    A model of a thermoelectric generator is proposed, in which composite materials obtained by sintering diamond nanoparticles are used as the main component. To increase the useful conversion of heat into electric current, it is proposed to use the effect of electron drag by ballistic phonons. To reduce the ineffective heat spread, it is proposed to use the effect of thermal resistance of the boundaries between the graphite-like and diamond-like phases of the composite. An experimental confirmation of the existence of an optimal volume ratio between graphite-like and diamond-like phases of the composite is predicted and obtained. The highest achieved value of thermoelectric coefficient in the actual structure is 80 µV K-1 (which means 20 times increase compared to that of composites not of the optimal structure), with a thermal conductivity of 50 W m-1 K-1. These results were obtained with constant electrical conductivity. The combined influence of these two effects in case of the ideal composite structure should result in an increase of the thermoelectric efficiency parameter by three orders of magnitude.

  6. Rapid prototyping of functional ceramic composites

    International Nuclear Information System (INIS)

    Griffin, E.A.; Mumm, D.R.; Marshall, D.B.

    1996-01-01

    Laminated object manufacturing (LOM reg-sign) is one of several manufacturing systems developed recently to produce a solid part directly from a 3D CAD drawing, without the use of hard tooling or dies. These systems begin with a conventional 3-D CAD file--solid model or wire-form model--that is converted to a de facto standard format for flexible manufacturing (.STL file) and sliced into thin cross sections by a separate computer program. These slices are then used to control the equipment that produces the component slice-by-slice. This paper describes an application of the CerLOM approach to produce multilayered composites of ZrO 2 and Al 2 O 3 . The choice of materials is based on previous studies that showed that a beneficial increase in toughness can be achieved with multilayered microstructures in this system. The toughness increase is due to martensitic transformation in the ZrO 2 phase. Because the CerLOM process produces the component directly from a CAD file without tooling, dies or molds, the production is rapid and cost effective. Components of complex shape can be fabricated readily, and design changes can be made easily

  7. Durable, High Thermal Conductivity Melt Infiltrated Ceramic Composites for Turbine Engine Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Durable, creep-resistant ceramic composites are necessary to meet the increased operating temperatures targeted for advanced turbine engines. Higher operating...

  8. Oxygen exchange and transport in dual phase ceramic composite electrodes.

    Science.gov (United States)

    Druce, John; Téllez, Helena; Ishihara, Tatsumi; Kilner, John A

    2015-01-01

    Composites consisting of a perovskite-based electronic or mixed conductor with a fluorite-structured ionic conductor are often used as electrodes in solid oxide electrochemical energy conversion devices. After sintering the materials, there is often evidence for inter-reaction between the two phases, or inter-diffusion of cations or impurities between the two phases. We studied the (18)O exchange properties of a composite consisting of CGO and LSCF in a 50 : 50 ratio. High resolution ToF-SIMS mapping reveals that the (18)O fraction at the very outer surface of grains of the CGO phase is much higher than expected from D* and k* values for the single-phase parent material. Surface compositional analysis by ToF-SIMS and low energy ion scattering (LEIS) spectroscopy suggests that the surfaces of the CGO grains in the composite do not show the impurities which typically segregate to the surface in single-phase CGO. Thus, the "cleaning" of impurities from the CGO surface by dissolution into the perovskite phase may be one explanation for the apparent enhanced surface exchange for CGO in these composites.

  9. Experimental study on the penetration effect of ceramics composite projectile on ceramic / A3 steel compound targets

    Directory of Open Access Journals (Sweden)

    Di-qi Hu

    2017-08-01

    Full Text Available In order to improve the penetration of projectiles into ceramic composite armors, the nose of 30 mm standard projectile was replaced by a toughened ceramic nose, and the performance of ceramic-nose projectiles penetrating into ceramic/A3 steel composite targets has been experimentally researched. According to impact dynamics theory,, the performances of 30 mm ceramic-nose projectile and 30 mm standard projectile penetrating into the ceramic/A3 steel composite targets were analyzed and compared using DOP method, especially focusing on the effects made by different nose structures and materials. The aperture and depth of perforation of projectile into the armor plates as well as the residual mass of bullet core under the same conditions were comparatively analyzed. A numerical simulation was built and computed by ANSYS/LS-DYNA. Based on the simulated results, the penetration performance was further analyzed in terms of the residual mass of bullet core. The results show that the ceramic nose has a great effect on the protection of bullet core.

  10. Effect of sintering temperature on electrical and microstructure properties of hot pressed Cu-TiC composites

    Directory of Open Access Journals (Sweden)

    Islak S.

    2014-01-01

    Full Text Available In this study, Cu-TiC composites were successfully produced using hot pressing method. Cu-TiC powder mixtures were hot-pressed for 4 min at 600, 700 and 800°C under an applied pressure of 50 MPa. Phase composition and microstructure of the composites hot pressed at different temperatures were characterized by X-ray diffraction, scanning electron microscope, and optic microscope techniques. Microstructure studies revealed that TiC particles were distributed uniformly in the Cu matrix. With the increasing sintering temperature, hardness of composites changed between 64.5 HV0.1 and 85.2 HV0.1. The highest electrical conductivity for Cu-10 wt.% TiC composites was obtained for the sintering temperature of 800°C, with approximately 68.1% IACS.

  11. Integration Science and Technology of Silicon-Based Ceramics and Composites:Technical Challenges and Opportunities

    Science.gov (United States)

    Singh, M.

    2013-01-01

    Ceramic integration technologies enable hierarchical design and manufacturing of intricate ceramic and composite parts starting with geometrically simpler units that are subsequently joined to themselves and/or to metals to create components with progressively higher levels of complexity and functionality. However, for the development of robust and reliable integrated systems with optimum performance for high temperature applications, detailed understanding of various thermochemical and thermomechanical factors is critical. Different technical approaches are required for the integration of ceramic to ceramic and ceramic to metal systems. Active metal brazing, in particular, is a simple and cost-effective method to integrate ceramic to metallic components. Active braze alloys usually contain a reactive filler metal (e.g., Ti, Cr, V, Hf etc) that promotes wettability and spreading by inducing chemical reactions with the ceramics and composites. In this presentation, various examples of brazing of silicon nitride to themselves and to metallic systems are presented. Other examples of joining of ceramic composites (C/SiC and SiC/SiC) using ceramic interlayers and the resulting microstructures are also presented. Thermomechanical characterization of joints is presented for both types of systems. In addition, various challenges and opportunities in design, fabrication, and testing of integrated similar (ceramic-ceramic) and dissimilar (ceramic-metal) material systems will be discussed. Potential opportunities and need for the development of innovative design philosophies, approaches, and integrated system testing under simulated application conditions will also be presented.

  12. New High-Performance SiC Fiber Developed for Ceramic Composites

    Science.gov (United States)

    DiCarlo, James A.; Yun, Hee Mann

    2002-01-01

    Sylramic-iBN fiber is a new type of small-diameter (10-mm) SiC fiber that was developed at the NASA Glenn Research Center and was recently given an R&D 100 Award for 2001. It is produced by subjecting commercially available Sylramic (Dow Corning, Midland, MI) SiC fibers, fabrics, or preforms to a specially designed high-temperature treatment in a controlled nitrogen environment for a specific time. It can be used in a variety of applications, but it currently has the greatest advantage as a reinforcement for SiC/SiC ceramic composites that are targeted for long-term structural applications at temperatures higher than the capability of metallic superalloys. The commercial Sylramic SiC fiber, which is the precursor for the Sylramic-iBN fiber, is produced by Dow Corning, Midland, Michigan. It is derived from polymers at low temperatures and then pyrolyzed and sintered at high temperatures using boron-containing sintering aids (ref. 1). The sintering process results in very strong fibers (>3 GPa) that are dense, oxygen-free, and nearly stoichiometric. They also display an optimum grain size that is beneficial for high tensile strength, good creep resistance, and good thermal conductivity (ref. 2). The NASA-developed treatment allows the excess boron in the bulk to diffuse to the fiber surface where it reacts with nitrogen to form an in situ boron nitride (BN) coating on the fiber surface (thus the product name of Sylramic-iBN fiber). The removal of boron from the fiber bulk allows the retention of high tensile strength while significantly improving creep resistance and electrical conductivity, and probably thermal conductivity since the grains are slightly larger and the grain boundaries cleaner (ref. 2). Also, as shown in the graph, these improvements allow the fiber to display the best rupture strength at high temperatures in air for any available SiC fiber. In addition, for CMC applications under oxidizing conditions, the formation of an in situ BN surface layer

  13. Reaction sintering process of tyranno SA/SiC composites and their characterization

    International Nuclear Information System (INIS)

    Lee, S.P.; Yoon, H.K.; Park, J.S.; Katoh, Y.; Kohyama, A.; Kim, D.H.; Lee, J.K.

    2002-01-01

    This paper deals with the efficiency of fiber preform preparation route for the fabrication of reaction sintering (RS) SiC f /SiC composites and their characterization, including density, microstructure and mechanical property. The applicability of carbon interfacial layer has been investigated in the RS process. The fiber preform was prepared by the consecutive slurry infiltration process, which associated with the combination of constant gas impregnation pressure and different magnitudes of cold pressure. The consecutive slurry infiltration process used for the preparation of fiber preform can be regarded as a promising technique for high density RS-SiC f /SiC composites, even if their mechanical properties depend on the magnitudes of cold pressure used. RS-SiC f /SiC composites entirely showed the morphology of near stoichiometric SiC phase in the intra-fiber bundle matrix, compared to that in the inter-fiber bundle matrix. The carbon interfacial layer was insufficient for the pseudo-ductile failure of RS-SiC f /SiC composites, even if some amount of fiber pull-out and interfacial delamination was observed in the tensile surface of bending test sample

  14. Melt Infiltrated Ceramic Composites (Hipercomp) for Gas Turbine Engine Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gregory Corman; Krishan Luthra

    2005-09-30

    This report covers work performed under the Continuous Fiber Ceramic Composites (CFCC) program by GE Global Research and its partners from 1994 through 2005. The processing of prepreg-derived, melt infiltrated (MI) composite systems based on monofilament and multifilament tow SiC fibers is described. Extensive mechanical and environmental exposure characterizations were performed on these systems, as well as on competing Ceramic Matrix Composite (CMC) systems. Although current monofilament SiC fibers have inherent oxidative stability limitations due to their carbon surface coatings, the MI CMC system based on multifilament tow (Hi-Nicalon ) proved to have excellent mechanical, thermal and time-dependent properties. The materials database generated from the material testing was used to design turbine hot gas path components, namely the shroud and combustor liner, utilizing the CMC materials. The feasibility of using such MI CMC materials in gas turbine engines was demonstrated via combustion rig testing of turbine shrouds and combustor liners, and through field engine tests of shrouds in a 2MW engine for >1000 hours. A unique combustion test facility was also developed that allowed coupons of the CMC materials to be exposed to high-pressure, high-velocity combustion gas environments for times up to {approx}4000 hours.

  15. Phase-Pure of BiFeO3 Ceramic Based on Citric Acid - Assisted Gel by Sintering Time Variation

    Science.gov (United States)

    Suastiyanti, Dwita; Ismojo

    2017-07-01

    Bismuth ferrite powder (BiFeO3/BFO) with high purity was synthesized by sol-gel process. It was used Bi5O(OH)9(NO3)4 and Fe(NO3)3.9H2O as main compound sources. Citric acid (C6H8O7) was used as fuell. As multiferroic material, BFO promises important technological applications in several devices like data strorage, spinotronics, sensor, actuator devices etc. This research would know the optimum process condition of sol-gel process to produce BFO powder by varying of sintering time. The novelty of this research is how to produce BFO in single phase by simple method. It was used calcination condition at 160°C for 4 hours and sintering condition at 600°C with varying of sintering time of 4, 6 and 8 hours. Thermogravimetric Analysis/Differential Thermal Analysis (TGA/DTA), X Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were used to characterize the powder. Loss of mass and heat flow were seen at TGA/DTA test at 160°C approximately (used as reference of calcination temperature). BFO powder sintered at for 8 hours has no secondary phase, meanwhile for another sintering time (4 and 6 hours) it has Bi2O3 as secondary phase. It is also show at SEM observation result that powder with sintering time of 8 hours has finer grain than of 4 and 6 hours sintering at the same temperature. The grains of BFO powder has heterogenous in size, shape and still agglomerated.

  16. Analysis of Damage in a Ceramic Matrix Composite

    DEFF Research Database (Denmark)

    Sørensen, Bent F.; Talreja, Ramesh

    1993-01-01

    Mechanisms of damage and the associated mechanical response are stud ied for a unidirectionally fiber-reinforced ceramic matrix composite subjected to uniaxial tensile loading parallel to fibers. A multi-stage development of damage is identified, and for each stage the governing mechanisms...... are discussed. For distributed matrix micro cracking a continuum damage model is used as the basis for describing the associated stress-strain behavior. A simplified analysis of frictional sliding at the fiber/matrix inter face is made to elucidate its effect on the stress-strain response....

  17. Ceramic Matrix Composite Turbine Disk for Rocket Engines

    Science.gov (United States)

    Effinger, Mike; Genge, Gary; Kiser, Doug

    2000-01-01

    NASA has recently completed testing of a ceramic matrix composite (CMC), integrally bladed disk (blisk) for rocket engine turbopumps. The turbopump's main function is to bring propellants from the tank to the combustion chamber at optimal pressures, temperatures, and flow rates. Advantages realized by using CMC blisks are increases in safety by increasing temperature margins and decreasing costs by increasing turbopump performance. A multidisciplinary team, involving materials, design, structural analysis, nondestructive inspection government, academia, and industry experts, was formed to accomplish the 4.5 year effort. This article will review some of the background and accomplishments of the CMC Blisk Program relative to the benefits of this technology.

  18. Ultrasonic and radiographic evaluation of advanced aerospace materials: Ceramic composites

    Science.gov (United States)

    Generazio, Edward R.

    1990-01-01

    Two conventional nondestructive evaluation techniques were used to evaluate advanced ceramic composite materials. It was shown that neither ultrasonic C-scan nor radiographic imaging can individually provide sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic imaging are required for preliminary evaluation of these complex systems. The material variations that were identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment, fiber registration, fiber parallelism, and processing density flaws. The degree of bonding between fiber and matrix cannot be determined by either of these methods. An alternative ultrasonic technique, angular power spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-26

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

  20. Influence of green compaction on the sintering behaviour of SiC-TiC-TiB{sub 2} composites

    Energy Technology Data Exchange (ETDEWEB)

    Waesche, R.; Yarim, R.; Nicolaides, D. [Federal Inst. for Materials Research and Testing (BAM), Berlin (Germany)

    2004-07-01

    The influence of different processing parameters like powder milling time and die pressure during manufacturing of SiC-TiC-TiB{sub 2} particulate composites has been investigated. The results show that at least a pressure of 90 MPa is necessary for obtaining fully dense samples. The degree of densification is dependent on the compaction process. At low green densities only the powder agglomerates are able to sinter. With increasing compaction pressure the contact area between the agglomerates increases also leading to increasing sintering densities up to fully dense samples. (orig.)

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

    CERN Document Server

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

    2000-01-01

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

  2. The mechanical properties and microstructure of the bionic alloy-ceramic laminated composite

    International Nuclear Information System (INIS)

    Shi, Guodong; Wu, Zhanjun; Wang, Zhi; Liang, Jun

    2012-01-01

    Highlights: → The bionic alloy-ceramic laminated composite was fabricated by EB-PVD. → Mechanical properties and microstructure of laminated composite were investigated. → Laminated composite was heat treated in order to improve the tensile strength. -- Abstract: In the present work, the bionic alloy-ceramic laminated composite was fabricated by electron beam-physical vapor deposition method. The ingots of Ni-20Co-12Cr-4Al (wt.%) and ZrO 2 -8 mol%Y 2 O 3 were used as the sources of the alloy layer and ceramic layer, respectively. The laminated composite was generally destroyed within the ceramic layer when the interlaminar strength was determined, which revealed that the excellent interface bonding between the ceramic layer and the alloy layer. The obvious diffusion interfaces between the ceramic and alloy layers were readily detected, which was favorable to the mechanical properties of the laminated composite. In the heat treatment process, the diffusion of the flaws within the ceramic layer and/or alloy layer to the interface between the ceramic layer and alloy layer was easier compared with the occurrence of interlaminar diffusion. It was confirmed by the X-ray diffractometer that the reaction of the ceramic layer with alloy layer was simple physical diffusion. The tensile strength of the laminated composite increased first and then decreased as the heat treatment time increased, which was attributed to the mutual reaction of the increase in the relative density with the formation of the flaws located at the interface.

  3. Measurement of J-integral in CAD/CAM dental ceramics and composite resin by digital image correlation.

    Science.gov (United States)

    Jiang, Yanxia; Akkus, Anna; Roperto, Renato; Akkus, Ozan; Li, Bo; Lang, Lisa; Teich, Sorin

    2016-09-01

    Ceramic and composite resin blocks for CAD/CAM machining of dental restorations are becoming more common. The sample sizes affordable by these blocks are smaller than ideal for stress intensity factor (SIF) based tests. The J-integral measurement calls for full field strain measurement, making it challenging to conduct. Accordingly, the J-integral values of dental restoration materials used in CAD/CAM restorations have not been reported to date. Digital image correlation (DIC) provides full field strain maps, making it possible to calculate the J-integral value. The aim of this study was to measure the J-integral value for CAD/CAM restorative materials. Four types of materials (sintered IPS E-MAX CAD, non-sintered IPS E-MAX CAD, Vita Mark II and Paradigm MZ100) were used to prepare beam samples for three-point bending tests. J-integrals were calculated for different integral path size and locations with respect to the crack tip. J-integral at path 1 for each material was 1.26±0.31×10(-4)MPam for MZ 100, 0.59±0.28×10(-4)MPam for sintered E-MAX, 0.19±0.07×10(-4)MPam for VM II, and 0.21±0.05×10(-4)MPam for non-sintered E-MAX. There were no significant differences between different integral path size, except for the non-sintered E-MAX group. J-integral paths of non-sintered E-MAX located within 42% of the height of the sample provided consistent values whereas outside this range resulted in lower J-integral values. Moreover, no significant difference was found among different integral path locations. The critical SIF was calculated from J-integral (KJ) along with geometry derived SIF values (KI). KI values were comparable with KJ and geometry based SIF values obtained from literature. Therefore, DIC derived J-integral is a reliable way to assess the fracture toughness of small sized specimens for dental CAD/CAM restorative materials; however, with caution applied to the selection of J-integral path. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Abstracts of the 7. workshop solid state chemistry and ceramics

    International Nuclear Information System (INIS)

    1988-11-01

    79 contributions have been presented as titles with abstracts. They deal with preparation, investigation, and properties of ceramic powders, sintered materials, metal oxides, oxide minerals, nitrides, solid electrolytes, glass ceramics, composite materials, and ceramic superconductors of the type Y-Ba-Cu-O. Phase studies of mixed oxide systems and different chemical processes of the solid state are included. 11 of them are in INIS scope and are processed individually

  5. Investigation on microstructural and mechanical properties of B4C–aluminum matrix composites prepared by microwave sintering

    Directory of Open Access Journals (Sweden)

    Ehsan Ghasali

    2015-10-01

    Full Text Available B4C reinforced aluminum composites were fabricated by microwave heating of the mixture of B4C (10, 15 and 20 wt% and aluminum powders at 650, 750, 850 and 950 °C. The effect of different amounts of B4C on the microstructure and mechanical properties of aluminum matrix was examined. The maximum bending (238 ± 10 MPa and compressive strength (330 ± 10 MPa values were measured for composites sintered at 950 and 750 °C, respectively. The maximum hardness (112 Vickers was measured for Al–20 wt% B4C composite sintered at 850 °C. XRD investigations showed the decomposition of boron carbide and also the formation of Al3BC by heating the composites at 850 °C. SEM micrographs showed uniform distribution of reinforcement particles in Al matrix.

  6. Role of sintering time, crystalline phases and symmetry in the piezoelectric properties of lead-free KNN-modified ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Marcos, F., E-mail: frmarcos@icv.csic.es [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Marchet, P.; Merle-Mejean, T. [SPCTS, UMR 6638 CNRS, Universite de Limoges, 123, Av. A. Thomas, 87060 Limoges (France); Fernandez, J.F. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain)

    2010-09-01

    Lead-free KNN-modified piezoceramics of the system (Li,Na,K)(Nb,Ta,Sb)O{sub 3} were prepared by conventional solid-state sintering. The X-ray diffraction patterns revealed a perovskite phase, together with some minor secondary phase, which was assigned to K{sub 3}LiNb{sub 6}O{sub 17}, tetragonal tungsten-bronze (TTB). A structural evolution toward a pure tetragonal structure with the increasing sintering time was observed, associated with the decrease of TTB phase. A correlation between higher tetragonality and higher piezoelectric response was clearly evidenced. Contrary to the case of the LiTaO{sub 3} modified KNN, very large abnormal grains with TTB structure were not detected. As a consequence, the simultaneous modification by tantalum and antimony seems to induce during sintering a different behaviour from the one of LiTaO{sub 3} modified KNN.

  7. Influence of sintering temperature on the phases and photoelectric characteristics of BiOCl/ZnO composite powders

    Science.gov (United States)

    Chen, Song; Zhu, De-gui

    2017-12-01

    Zinc oxide is a typical functional oxide that has been widely researched for various industry applications due to its peculiar physical characteristics. However, to achieve its potential in promising applications, much work has been diligently performed to improve the physical properties of ZnO. In this work, an aqueous suspension route was used to prepare BiOCl/ZnO composite powders, and sintering processes were applied to investigate the influence of sintering temperature on the phase evolutions, microstructures, and photoelectric characteristics of BiOCl/ZnO composite powders. The results indicated that the photoelectric properties mainly depend on the relevant content of BiOCl in the composite powders and the sintering temperature. The photoelectric measurements in K2SO4 solutions show that the photoelectric properties of the samples with the appropriate BiOCl content (0.3mol% and 2.0mol%) are better than those of ZnO and commercial TiO2 (P25) powders, but the photoelectric measurements in NaOH solutions indicate that the photoelectric characteristics of the as-sintered samples are only better than those of P25.

  8. Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

    Directory of Open Access Journals (Sweden)

    Manoj Gupta

    2013-05-01

    Full Text Available In this study, magnesium composites with nano-size boron nitride (BN particulates of varying contents were synthesized using the powder metallurgy (PM technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture.

  9. Influence of composition and rate heating on formation of black core in bodies obtained with red ceramic

    International Nuclear Information System (INIS)

    Santana, L.N.L.; Goncalves, W.P.; Silva, B.J. da; Macedo, R.S.; Santos, R.C.; Lisboa, D.

    2011-01-01

    In the heating of pieces of red pottery can the defect known as black core, this may deteriorate the technical and aesthetic characteristics of the final product. This study evaluated the influence of chemical composition and heating rate on the formation of black core in bodies red ceramic. The masses were treated and samples were extruded, dried, sintered at 900 °C, with heating rates of 5, 10, 15, 20 and 30 °C / min. and determined the following properties: water absorption, linear shrinkage and flexural strength. The pieces made with the mass containing lower content of iron oxide showed better resistance to bending when subjected to rapid heating. The presence of the black core was identified through visual analysis of the pieces after the break, being more apparent in parts subject to rates above 5 °C / min. (author)

  10. Comparison of the TL intensity of the sintered composites of CaSO4+Tm

    International Nuclear Information System (INIS)

    Junot, O.D.; Sousa, F.L. de; Chagas, M.A.P.; Souza, D.N.

    2009-01-01

    The objective of this work is to compare the thermoluminescent intensity (TL) of CaSO 4 +Tm, CaSO 4 +Tm+glass and glass+Tm composites for use as thermoluminescent dosimeter (TLD). The route used to prepare the CaSO 4 +Tm and the CaSO 4 +Tm+glass was by mixing 1 g of CaSO 4 with 0.02 g of thulium oxide (99,9% purity) and 0.3 g of commercial and colorless glass. To mixing the composites were taken to a magnetic stirrer for 30 min with 10 mL of distilled water for better homogenization. The powder mixtures were dried in a stove at 100 deg C for 24 h. After drying, it was added polyvinyl alcohol (PVA) to improve the binding material. The pellets were compacted by application of an uniaxial pressing and sintered at 700 deg C/ 6 h. The route used in the preparation of glass+Tm pellets was similar to one previously mentioned, except by the use of 1 g of glass and 0.02 of Tm. After the sintering, the pellets dimensions were 1 mm thick and 6 mm in diameter. All samples were irradiated by a beta source ( 90 Sr + 90 Y) and received doses from 1.00 Gy to 20 Gy. Each composite presented a characteristic emission curve. The dosimeter of CaSO 4 +Tm+glass presented two peaks, the first at 115 deg C, and the second, very intense, ate 150 deg C. The CaSO 4 +Tm dosimeter showed a less intense peak at 140 deg C and another, more intense, at 235 deg C. In the composites of glass+Tm, the most intense peak has a thermoluminescent signal 94,04% lower than the most intense peak of CaSO 4 +Tm+glass and 81.57% lower than the most intense peak of CaSO 4 +Tm. After the analysis of TL emission curves, we observed that the CaSO 4 +Tm+glass have the highest TL intensity and a TL response proportional to the dose absorbed. (author)

  11. Laser Machining of Melt Infiltrated Ceramic Matrix Composite

    Science.gov (United States)

    Jarmon, D. C.; Ojard, G.; Brewer, D.

    2012-01-01

    As interest grows in considering the use of ceramic matrix composites for critical components, the effects of different machining techniques, and the resulting machined surfaces, on strength need to be understood. This work presents the characterization of a Melt Infiltrated SiC/SiC composite material system machined by different methods. While a range of machining approaches were initially considered, only diamond grinding and laser machining were investigated on a series of tensile coupons. The coupons were tested for residual tensile strength, after a stressed steam exposure cycle. The data clearly differentiated the laser machined coupons as having better capability for the samples tested. These results, along with micro-structural characterization, will be presented.

  12. Update on CMH-17 Volume 5: Ceramic Matrix Composites

    Science.gov (United States)

    David, Kaia; Pierce, Jennifer; Kiser, James; Keith, William P.; Wilson, Gregory S.

    2015-01-01

    CMC components are projected to enter service in commercial aircraft in 2016. A wide range of issues must be addressed prior to certification of this hardware. The Composite Materials Handbook-17, Volume 5 on ceramic matrix composites is being revised to support FAA certification of CMCs for hot structure and other elevated temperature applications. The handbook supports the development and use of CMCs through publishing and maintaining proven, reliable engineering information and standards that have been thoroughly reviewed. Volume 5 will contain detailed sections describing CMC materials processing, design analysis guidelines, testing procedures, and data analysis and acceptance. A review of the status of and plans for two of these areas, which are being addressed by the M and P Working Group and the Testing Working Group, will be presented along with a timeline for the preparation of CMH-17, Volume 5.

  13. Bonded carbon or ceramic fiber composite filter vent for radioactive waste

    Science.gov (United States)

    Brassell, Gilbert W.; Brugger, Ronald P.

    1985-02-19

    Carbon bonded carbon fiber composites as well as ceramic or carbon bonded ceramic fiber composites are very useful as filters which can separate particulate matter from gas streams entraining the same. These filters have particular application to the filtering of radioactive particles, e.g., they can act as vents for containers of radioactive waste material.

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

    Directory of Open Access Journals (Sweden)

    Nurul Akidah Baharuddin

    2016-05-01

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

  15. Ceramic Composite Mechanical Fastener System for High-Temperature Structural Assemblies, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Under Phase I, the feasibility of a novel thermal stress-free ceramic composite mechanical fastener system suitable for assembly of high-temperature composite...

  16. Modeling Macroscopic Shape Distortions during Sintering of Multi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye

    Ceramic multi-layered composites are being used as components in various technologies ranging from electronics to energy conversion devices. Thus, different architectures of multi-layers involving ceramic materials are often required to be produced by powder processing, followed by sintering...... the camber development during co-firing. The effect of extrinsic factors (e.g. gravity, thickness ratio and friction) on the shape evolution of bi-layers during co-firing has been studied using the developed model and experiments. Furthermore, a new analytical model describing stresses during sintering...... of tubular bi-layer structures has been developed by using the direct correspondence between elasticity and linear viscous problems. The finite element model developed in this study and sintering experiments of tubular bi-layer sample have been used to verify and validate the developed analytical model...

  17. Sintering and Characterization of (Li, Sb, Ta-Modified (Na, KNbO3 Lead-Free Ceramics

    Directory of Open Access Journals (Sweden)

    Peng Qi

    2011-01-01

    scanning electron microscopy (SEM and optical microscopy. The KNLNT-S8 sample sintered at 1100°C possessed highest piezoelectric constant 33 and high-field piezoelectric strain coefficient ∗33 of 332 pC/N and 530 pm/V, respectively, with electromechanical coupling factors of 0.52 and of 0.48.

  18. Basic study of Eu.sup.2+./sup.-doped garnet ceramic scintillator produced by spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Sugiyama, K.; Yanagida, T.; Fujimoto, Y.; Yokota, Y.; Ito, A.; Nikl, Martin; Goto, T.; Yoshikawa, A.

    2012-01-01

    Roč. 35, č. 2 (2012), s. 222-226 ISSN 0925-3467 R&D Projects: GA MŠk LH12150 Institutional research plan: CEZ:AV0Z10100521 Keywords : Eu 2+ 5d–4f transition * scintillator * spark plasma sintering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.918, year: 2012

  19. High-strength CAD/CAM-fabricated veneering material sintered to zirconia copings--a new fabrication mode for all-ceramic restorations.

    Science.gov (United States)

    Beuer, Florian; Schweiger, Josef; Eichberger, Marlis; Kappert, Heinrich F; Gernet, Wolfgang; Edelhoff, Daniel

    2009-01-01

    With this in vitro study the fracture strength of zirconia-based crown copings being veneered with a CAD/CAM generated high-strength ceramic cap by sintering is compared with anatomically identical zirconia-based crowns, which were either overpressed or veneered by the layering technique for completion. A 1.2mm, 360 degrees chamfer preparation was performed on a second maxillary molar and was dublicated 15 times in a cobalt-chromium-alloy. A sample of 45 zirconia copings was produced and divided into three groups. In the first group (VT) zirconia copings received conventional veneering in layering technique, in the second group the veneering porcelain was pressed over the zirconia coping (PT), and for the third group (ST) a CAD/CAM-fabricated high-strength anatomically shaped veneering cap was sintered onto the zirconia coping. All crowns were cemented conventionally onto their dies and tested in the universal testing machine until clinical failure. The fracture load data were compared by a one-way analysis of variance and a multiple comparison posthoc test (alphacrowns and fixed partial dentures with a potential lower risk of chippings.

  20. Effect of air annealing on the color center in Yb:Y3Al5O12 transparent ceramics with MgO as sintering additive

    Science.gov (United States)

    Lu, Zhongwen; Lu, Tiecheng; Wei, Nian; Zhang, Wei; Ma, Benyuan; Qi, Jianqi; Guan, Yongbing; Chen, Xingtao; Wu, Huajun; Zhao, Yu

    2015-09-01

    High quality Yb:Y3Al5O12 (YAG) transparent ceramics were fabricated by vacuum sintering with MgO as sintering aids. The Yb:YAG samples were annealed at 1250-1450 °C for 20 h in air. The experimental results showed that the transparency of Yb:YAG samples declined markedly with the annealing temperatures of 1250-1450 °C. The samples became increasingly orange-yellow in color with the increase of annealing temperature. The potential reasons of discoloration were discussed for the first time. It was attributed to the complex color center [Mg2+F+] formed during the annealing, which was evidenced by optical absorption in the range of 300-500 nm wavelength and the presence of an electron spin resonance (ESR) line at g = 1.9806. The formation mechanism of the complex color center was explained in detail. The complex color center can be eliminated after post-HIP (hot isostatic pressing). And by air annealing and post-HIP, the transmittance of the samples increased from 80.3% to 83.4%.