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Sample records for carbide ceramic components

  1. Ceramic Fabric Coated With Silicon Carbide

    Science.gov (United States)

    Riccitiello, S. R.; Smith, M.; Goldstein, H.; Zimmerman, N.

    1988-01-01

    Material used as high-temperature shell. Ceramic fabric coated with silicon carbide (SiC) serves as tough, heat-resistant covering for other refractory materials. Developed to protect reusable insulating tiles on advanced space transportation systems. New covering makes protective glaze unnecessary. Used on furnace bricks or on insulation for engines.

  2. Novel fabrication of silicon carbide based ceramics for nuclear applications

    Science.gov (United States)

    Singh, Abhishek Kumar

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These materials include refractory alloys based on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as SiC--SiCf; carbon--carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor components is necessary for improved efficiency. Improving thermal conductivity of the fuel can lower the center-line temperature and, thereby, enhance power production capabilities and reduce the risk of premature fuel pellet failure. Crystalline silicon carbide has superior characteristics as a structural material from the viewpoint of its thermal and mechanical properties, thermal shock resistance, chemical stability, and low radioactivation. Therefore, there have been many efforts to develop SiC based composites in various forms for use in advanced energy systems. In recent years, with the development of high yield preceramic precursors, the polymer infiltration and pyrolysis (PIP) method has aroused interest for the fabrication of ceramic based materials, for various applications ranging from disc brakes to nuclear reactor fuels. The pyrolysis of preceramic polymers allow new types of ceramic materials to be processed at relatively low temperatures. The raw materials are element-organic polymers whose composition and architecture can be tailored and varied. The primary focus of this study is to use a pyrolysis based process to fabricate a host of novel silicon carbide-metal carbide or oxide composites, and to synthesize new materials based on mixed-metal silicocarbides that cannot be processed using conventional techniques. Allylhydridopolycarbosilane (AHPCS), which is an organometal polymer, was used as the precursor for silicon carbide. Inert gas pyrolysis of AHPCS produces near-stoichiometric amorphous

  3. Bonding and Integration Technologies for Silicon Carbide Based Injector Components

    Science.gov (United States)

    Halbig, Michael C.; Singh, Mrityunjay

    2008-01-01

    Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding, titanium interlayers (PVD and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness (10, 20, and 50 microns), processing time and temperature, and cooling rates were investigated. Microprobe analysis was used to identify the phases in the bonded region. For bonds that were not fully reacted an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner titanium interlayers and/or longer processing times resulted in stable and compatible phases that did not contribute to microcracking and resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Non-destructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

  4. Dynamic strength of reaction-sintered boron carbide ceramic

    Science.gov (United States)

    Savinykh, A. S.; Garkushin, G. V.; Razorenov, S. V.; Rumyantsev, V. I.

    2015-06-01

    The shock compression wave profiles in three modifications of boron carbide ceramic are studied in the compressive stress range 3-19 GPa. The Hugoniot elastic limit and the spall strength of the materials are determined. It is confirmed that the spall strength of high-hardness ceramic changes nonmonotonically with the compressive stress in a shock wave.

  5. Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

    Science.gov (United States)

    Singh, M.; Levine, S. R.

    1995-01-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  6. Characterization of silicon-silicon carbide ceramic derived from carbon-carbon silicon carbide composites

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vijay K. [Indian Institute of Technology, Varanasi (India). Dept. of Mechanical Engineering; Krenkel, Walter [Univ. of Bayreuth (Germany). Dept. of Ceramic Materials Engineering

    2013-04-15

    The main objective of the present work is to process porous silicon - silicon carbide (Si - SiC) ceramic by the oxidation of carboncarbon silicon carbide (C/C - SiC) composites. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si- SiC ceramics in order to study the material's microstructure. The effects of various parameters such as fiber alignment (twill weave and short/chopped fiber) and phenolic resin type (resol and novolak) are characterized.

  7. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    Energy Technology Data Exchange (ETDEWEB)

    DR. DENNIS NAGLE; DR. DAJIE ZHANG

    2009-03-26

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm{sup -3} (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si

  8. SILICON CARBIDE CERAMICS FOR COMPACT HEAT EXCHANGERS

    International Nuclear Information System (INIS)

    Silicon carbide (SiC) materials are prime candidates for high temperature heat exchangers for next generation nuclear reactors due to their refractory nature and high thermal conductivity at elevated temperatures. This research has focused on demonstrating the potential of liquid silicon infiltration (LSI) for making SiC to achieve this goal. The major advantage of this method over other ceramic processing techniques is the enhanced capability of making high dense, high purity SiC materials in complex net shapes. For successful formation of net shape SiC using LSI techniques, the carbon preform reactivity and pore structure must be controlled to allow the complete infiltration of the porous carbon structure which allows complete conversion of the carbon to SiC. We have established a procedure for achieving desirable carbon properties by using carbon precursors consisting of two readily available high purity organic materials, crystalline cellulose and phenolic resin. Phenolic resin yields a glassy carbon with low chemical reactivity and porosity while the cellulose carbon is highly reactive and porous. By adjusting the ratio of these two materials in the precursor mixtures, the properties of the carbons produced can be controlled. We have identified the most favorable carbon precursor composition to be a cellulose resin mass ratio of 6:4 for LSI formation of SiC. The optimum reaction conditions are a temperature of 1800 C, a pressure of 0.5 Torr of argon, and a time of 120 minutes. The fully dense net shape SiC material produced has a density of 2.96 g cm-3 (about 92% of pure SiC) and a SiC volume fraction of over 0.82. Kinetics of the LSI SiC formation process was studied by optical microscopy and quantitative digital image analysis. This study identified six reaction stages and provided important understanding of the process. Although the thermal conductivity of pure SiC at elevated temperatures is very high, thermal conductivities of most commercial Si

  9. Ceramic components for MHD electrode

    Science.gov (United States)

    Marchant, D.D.

    A ceramic component which exhibits electrical conductivity down to near room temperatures has the formula: Hf/sub x/In/sub y/A/sub z/O/sub 2/ where x = 0.1 to 0.4, y = 0.3 to 0.6, z = 0.1 to 0.4 and A is a lanthanide rare earth or yttrium. The component is suitable for use in the fabrication of MHD electrodes or as the current leadout portion of a composite electrode with other ceramic components.

  10. Refractory ceramics to silicon carbide. 5. tot. rev. ed

    Energy Technology Data Exchange (ETDEWEB)

    Elvers, B. (ed.); Hawkins, S. (ed.); Russey, W. (ed.); Schulz, G. (ed.)

    1993-01-01

    This volume contains 28 contributions to the following topics: Refractory Ceramics, Reinforced Plastics; Release Agents; Resins, Natural; Resins, Synthetic; Resorcinol; Resources of Oil and Gas; Rhenium and Rhenium Compounds; Rodenticides; Rubber (1. Survey, 2. Natural, 3. Synthetic, 4. Chemicals, 5. Technology, 6. Testing); Rubidium and Rubidium Compounds; Salicylic Acid; Saponins; Sealing Materials; Seasonings; Sedatives; Selenium and Selenium Compounds; Semiconductors; Shoe Polishes; Silica; Silicates; Silicon; Silicon Carbide. (orig.)

  11. Abrasion, erosion and scuffing resistance of carbide and oxide ceramic thermal sprayed coatings for different applications

    Science.gov (United States)

    Barbezat, G.; Nicoll, A. R.; Sickinger, A.

    1993-04-01

    In the area of antiwear coatings, carbide-containing coatings and oxide ceramic coatings are applied using different thermal spray processes in the form of individual layers. In many industries these coatings have become technically significant on components where wear and friction can cause critical damage in the form of abrasion, erosion and scuffing together with corrosion. Carbide-containing and ceramic coatings have been produced with different thermal spray processes for the determination of abrasive, adhesive and erosive wear resistance. Two types of abrasion test, namely an adhesion wear test and an erosion test in water at a high velocity, were used for the characterization of wear resistance under different conditions. The coatings were also characterized with regard to microstructure, composition and fracture toughness. The influence of the thermal spraying process parameters on the microstructure is presented together with the influence of the microstructure on the behavior of the coatings under simulated service conditions.

  12. Indentation fatigue in silicon nitride, alumina and silicon carbide ceramics

    Indian Academy of Sciences (India)

    A K Mukhopadhyay

    2001-04-01

    Repeated indentation fatigue (RIF) experiments conducted on the same spot of different structural ceramics viz. a hot pressed silicon nitride (HPSN), sintered alumina of two different grain sizes viz. 1 m and 25 m, and a sintered silicon carbide (SSiC) are reported. The RIF experiments were conducted using a Vicker’s microhardness tester at various loads in the range 1–20 N. Subsequently, the gradual evolution of the damage was characterized using an optical microscope in conjunction with the image analysing technique. The materials were classified in the order of the decreasing resistance against repeated indentation fatigue at the highest applied load of 20 N. It was further shown that there was a strong influence of grain size on the development of resistance against repeated indentation fatigue on the same spot. Finally, the poor performance of the sintered silicon carbide was found out to be linked to its previous thermal history.

  13. Cytocompatibility of bio-inspired silicon carbide ceramics.

    Science.gov (United States)

    López-Alvarez, M; de Carlos, A; González, P; Serra, J; León, B

    2010-10-01

    Due to its good mechanical and biochemical properties and, also, because of its unique interconnected porosity, bio-inspired silicon carbide (bioSiC) can be considered as a promising material for biomedical applications, including controlled drug delivery devices and tissue engineering scaffolds. This innovative material is produced by molten-Si infiltration of carbon templates, obtained by controlled pyrolysis of vegetable precursors. The final SiC ceramic presents a porous-interconnected microstructure that mimics the natural hierarchical structure of bone tissue and allows the internal growth of tissue, as well as favors angiogenesis. In the present work, the in vitro cytocompatibility of the bio-inspired SiC ceramics obtained, in this case, from the tree sapelli (Entandrophragma cylindricum) was evaluated. The attachment, spreading, cytoskeleton organization, proliferation, and mineralization of the preosteoblastic cell line MC3T3-E1 were analyzed for up to 28 days of incubation by scanning electron microscopy, interferometric profilometry, confocal laser scanning microscopy, MTT assay, as well as red alizarin staining and quantification. Cells seeded onto these ceramics were able to attach, spread, and proliferate properly with the maintenance of the typical preosteoblastic morphology throughout the time of culture. A certain level of mineralization on the surface of the sapelli-based SiC ceramics is observed. These results demonstrated the cytocompatibility of this porous and hierarchical material. PMID:20737554

  14. Raman spectroscopic characterization of the core-rim structure in reaction bonded boron carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jannotti, Phillip; Subhash, Ghatu, E-mail: subhash@ufl.edu [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611 (United States); Zheng, James Q.; Halls, Virginia [Program Executive Office—Soldier Protection and Individual Equipment, US Army, Fort Belvoir, Virginia 22060 (United States); Karandikar, Prashant G.; Salamone, S.; Aghajanian, Michael K. [M-Cubed Technologies, Inc., Newark, Delaware 19711 (United States)

    2015-01-26

    Raman spectroscopy was used to characterize the microstructure of reaction bonded boron carbide ceramics. Compositional and structural gradation in the silicon-doped boron carbide phase (rim), which develops around the parent boron carbide region (core) due to the reaction between silicon and boron carbide, was evaluated using changes in Raman peak position and intensity. Peak shifting and intensity variation from the core to the rim region was attributed to changes in the boron carbide crystal structure based on experimental Raman observations and ab initio calculations reported in literature. The results were consistent with compositional analysis determined by energy dispersive spectroscopy. The Raman analysis revealed the substitution of silicon atoms first into the linear 3-atom chain, and then into icosahedral units of the boron carbide structure. Thus, micro-Raman spectroscopy provided a non-destructive means of identifying the preferential positions of Si atoms in the boron carbide lattice.

  15. Advanced Gas Turbine (AGT) Technology Development Project, ceramic component developments

    Science.gov (United States)

    Teneyck, M. O.; Macbeth, J. W.; Sweeting, T. B.

    1987-01-01

    The ceramic component technology development activity conducted by Standard Oil Engineered Materials Company while performing as a principal subcontractor to the Garrett Auxiliary Power Division for the Advanced Gas Turbine (AGT) Technology Development Project (NASA Contract DEN3-167) is summarized. The report covers the period October 1979 through July 1987, and includes information concerning ceramic technology work categorized as common and unique. The former pertains to ceramic development applicable to two parallel AGT projects established by NASA contracts DEN3-168 (AGT100) and DEN3-167 (AGT101), whereas the unique work solely pertains to Garrett directed activity under the latter contract. The AGT101 Technology Development Project is sponsored by DOE and administered by NASA-Lewis. Standard Oil directed its efforts toward the development of ceramic materials in the silicon-carbide family. Various shape forming and fabrication methods, and nondestructive evaluation techniques were explored to produce the static structural components for the ceramic engine. This permitted engine testing to proceed without program slippage.

  16. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    Energy Technology Data Exchange (ETDEWEB)

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  17. AGT 101: Ceramic component development: Advanced Gas Turbine Program: Topical report, October 1979-July 1987

    Energy Technology Data Exchange (ETDEWEB)

    Ten Eyck, M.O.; MacBeth, J.W.; Sweeting, T.B.

    1987-11-01

    This topical report summarizes the ceramic component technology development activity conducted by Standard Oil Engineered Materials Company. Standard Oil, acting as a principal subcontractor and supplier of ceramic components, directed its efforts toward the development of ceramic materials in the silicon-carbide family. Various shape forming and fabrication methods, and non-destructive evaluation techniques were explored to produce the static structural components for the ceramic engine. This enabled engine testing to proceed without program slippage, and developed the approaches for producing low-cost, production quantity processes. Standard Oil contributed to the acceptance of ceramics as a viable approach for automotive gas turbine engines and to the advancement of this vital ceramic technology. 174 figs., 33 tabs.

  18. PVD and CVD gradient coatings on sintered carbides and sialon tool ceramics

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2010-12-01

    Full Text Available Purpose: The main objective of the work is to investigate the structure and properties of multilayer gradient coatings produced in PVD and CVD processes on sintered carbides and on sialon ceramics, and to define the influence of the properties of the coatings such as microhardness, adhesion, thickness and size of grains on the applicable properties of cutting edges covered by such coatings.Design/methodology/approach: The investigation studies pertaining to the following have been carried out: the structures of the substrates and coatings with the application of transmission electron microscopy; the structure and topography of coating surfaces with the use of electron scanning microscopy; chemical composition of the coatings using the GDOES and EDS methods; phase composition of the coatings using X-ray diffraction and grazing incident X-ray diffraction technique (GIXRD; grain size of the investigated coatings using Scherrer’s method; properties of the coatings including thickness, microhardness, adhesion and roughness; properties of the operating coatings in cutting trials. The models of artificial neural networks have been worked out which involve the dependencies between the durability of the cutting edge and properties of the coatings.Findings: Good adhesion of the coatings to the substrate from sintered carbides is connected with the diffusive mixing of the components of the coating and substrate. In the case of PVD coatings obtained on sialon ceramics, the highest adhesion to the substrate (Lc=53-112 N has been demonstrated by the coatings containing the AlN phase of the hexagonal lattice having the same type of atomic (covalence bond in the coating as in the ceramic substrate. The damage mechanism of the investigated coatings depends to a high degree on their adhesion to the substrate. The durability of cutting edges covered by the investigated coatings depends principally on the adhesion of the coatings to the substrate, and to a lesser

  19. Thermal-shock Resistance of a Ceramic Comprising 60 Percent Boron Carbide and 40 Percent Titanium Diboride

    Science.gov (United States)

    Yeomans, C M; Hoffman, C A

    1953-01-01

    Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride was investigated. The material has thermal shock resistance comparable to that of NBS body 4811C and that of zirconia, but is inferior to beryllia, alumina, and titanium-carbide ceramals. It is not considered suitable for turbine blades.

  20. Dilatometric studies of (SiO2-RE2O3-Al2O3 silicon carbide ceramics

    Directory of Open Access Journals (Sweden)

    Juliana Marchi

    2005-06-01

    Full Text Available Silicon carbide is an important structural ceramic and finds applications as abrasives, as a refractory and in automotive engine components. This material can attain high densities during liquid phase sintering if suitable additives are used. Silicon carbides containing silica, alumina and rare earth oxides have suitable characteristics to promote liquid phase sintering. In this paper, the sintering behavior of silicon carbide ceramics with additives based on the (SiO2-RE2O3-Al2O3 system (RE = Y, Dy has been studied. Samples with different compositions and containing 90 vol.% SiC were sintered in a dilatometer at 1950 °C/1h and in a graphite resistance furnace from 1500 °C/1h up to 1950 °C/1h. The shrinkage behavior as a function of rare earth oxide used and additive composition was also studied. The sintered materials were characterized by density and weight loss measurements. The crystalline phases were identified by X-ray diffraction analysis. The sintering kinetics of these materials can be related to the formation of secondary crystalline phases.

  1. Development and Characterization of the Bonding and Integration Technologies Needed for Fabricating Silicon Carbide Based Injector Components

    Science.gov (United States)

    Halbig,Michael C.; Singh, Mrityunjay

    2008-01-01

    Advanced ceramic bonding and integration technologies play a critical role in the fabrication and application of silicon carbide based components for a number of aerospace and ground based applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. Ceramic to ceramic diffusion bonding and ceramic to metal brazing technologies are being developed for this injector application. For the diffusion bonding technology, titanium interlayers (coatings and foils) were used to aid in the joining of silicon carbide (SiC) substrates. The influence of such variables as surface finish, interlayer thickness, and processing time were investigated. Electron microprobe analysis was used to identify the reaction formed phases. In the diffusion bonds, an intermediate phase, Ti5Si3Cx, formed that is thermally incompatible in its thermal expansion and caused thermal stresses and cracking during the processing cool-down. Thinner interlayers of pure titanium and/or longer processing times resulted in an optimized microstructure. Tensile tests on the joined materials resulted in strengths of 13-28 MPa depending on the SiC substrate material. Nondestructive evaluation using ultrasonic immersion showed well formed bonds. For the joining technology of brazing Kovar fuel tubes to silicon carbide, preliminary development of the joining approach has begun. Various technical issues and requirements for the injector application are addressed.

  2. Enabling Technologies for Ceramic Hot Section Components

    Energy Technology Data Exchange (ETDEWEB)

    Venkat Vedula; Tania Bhatia

    2009-04-30

    Silicon-based ceramics are attractive materials for use in gas turbine engine hot sections due to their high temperature mechanical and physical properties as well as lower density than metals. The advantages of utilizing ceramic hot section components include weight reduction, and improved efficiency as well as enhanced power output and lower emissions as a result of reducing or eliminating cooling. Potential gas turbine ceramic components for industrial, commercial and/or military high temperature turbine applications include combustor liners, vanes, rotors, and shrouds. These components require materials that can withstand high temperatures and pressures for long duration under steam-rich environments. For Navy applications, ceramic hot section components have the potential to increase the operation range. The amount of weight reduced by utilizing a lighter gas turbine can be used to increase fuel storage capacity while a more efficient gas turbine consumes less fuel. Both improvements enable a longer operation range for Navy ships and aircraft. Ceramic hot section components will also be beneficial to the Navy's Growth Joint Strike Fighter (JSF) and VAATE (Versatile Affordable Advanced Turbine Engines) initiatives in terms of reduced weight, cooling air savings, and capability/cost index (CCI). For DOE applications, ceramic hot section components provide an avenue to achieve low emissions while improving efficiency. Combustors made of ceramic material can withstand higher wall temperatures and require less cooling air. Ability of the ceramics to withstand high temperatures enables novel combustor designs that have reduced NO{sub x}, smoke and CO levels. In the turbine section, ceramic vanes and blades do not require sophisticated cooling schemes currently used for metal components. The saved cooling air could be used to further improve efficiency and power output. The objectives of this contract were to develop technologies critical for ceramic hot section

  3. Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

    Science.gov (United States)

    Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

    1999-01-01

    A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

  4. Densification studies of silicon carbide-based ceramics with yttria, silica and alumina as sintering additives

    Directory of Open Access Journals (Sweden)

    J. Marchi

    2001-10-01

    Full Text Available Silicon carbide has been extensively used in structural applications, especially at high temperatures. In this work, Y2O3, Al2O3 and SiO2 were added to beta-SiC in order to obtain highly dense ceramics. Sintering was conducted in a dilatometer and in a graphite resistance furnace and the densification behaviour was studied. Sintered samples were characterised by density measurements, the crystalline phases were identified by X-ray diffraction. Microstructural observation of polished and polished/etched samples was carried out with help of scanning electron microscopy. Silicon carbide ceramics with more than 90% of the theoretical density were obtained by pressureless sintering if a suitable proportion of the additives is used.

  5. 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

    2015-10-01

    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•m0.5. Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  6. 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.

  7. Microstructural Characterization of Reaction-Formed Silicon Carbide Ceramics. Materials Characterization

    Science.gov (United States)

    Singh, M.; Leonhardt, T. A.

    1995-01-01

    Microstructural characterization of two reaction-formed silicon carbide ceramics has been carried out by interference layering, plasma etching, and microscopy. These specimens contained free silicon and niobium disilicide as minor phases with silicon carbide as the major phase. In conventionally prepared samples, the niobium disilicide cannot be distinguished from silicon in optical micrographs. After interference layering, all phases are clearly distinguishable. Back scattered electron (BSE) imaging and energy dispersive spectrometry (EDS) confirmed the results obtained by interference layering. Plasma etching with CF4 plus 4% O2 selectively attacks silicon in these specimens. It is demonstrated that interference layering and plasma etching are very useful techniques in the phase identification and microstructural characterization of multiphase ceramic materials.

  8. Surface modification of sialon ceramics and cemented carbides by PVD coating deposition

    OpenAIRE

    L.A. Dobrzański; M. Staszuk

    2011-01-01

    Purpose: The paper includes investigation results of structures and mechanical properties of coatings deposited by the physical vapor deposition (PVD) techniques onto both sialon tool ceramics and sintered carbides. The paper includes two kinds of coating materials, isomorphic containg phases with TiN and AlN.Design/methodology/approach: In the paper were presented some observations of coating structures, before carried out in the scanning electron microscope. Phases composition analysis was ...

  9. PVD and CVD gradient coatings on sintered carbides and sialon tool ceramics

    OpenAIRE

    L.A. Dobrzański; M. Staszuk

    2010-01-01

    Purpose: The main objective of the work is to investigate the structure and properties of multilayer gradient coatings produced in PVD and CVD processes on sintered carbides and on sialon ceramics, and to define the influence of the properties of the coatings such as microhardness, adhesion, thickness and size of grains on the applicable properties of cutting edges covered by such coatings.Design/methodology/approach: The investigation studies pertaining to the following have been carried ou...

  10. Advancement of Cellular Ceramics Made of Silicon Carbide for Burner Applications

    International Nuclear Information System (INIS)

    Lower emissions of CO and NOx as well as a higher power density were observed in combustion processes performed in porous media like ceramic foams. Only a few materials are applicable for porous burners. Open-celled ceramic foams made of silicon carbide are of particular interest because of their outstanding properties. Two different SiC materials have been investigated, silicon-infiltrated silicon carbide (SiSiC) and pressureless sintered silicon carbide (SSiC). The oxidation behaviour of both has been characterized by furnace oxidation and burner tests up to 500 h operating time. Up to a temperature of 1200 deg. C SiSiC exhibited a good oxidation resistance in combustion gases by forming a protective layer of silica. High inner porosity up to 30% in the ceramic struts was found in the SSiC material. Caused by inner oxidation processes the pure material SSiC allows only short time applications with a temperature limit of 1550 deg. C in combustion gases. An increase of the lifetime of the SSiC foams was obtained by development of a new SSiC with an inner porosity of less than 12%. The result was a considerable reduction of the inner oxidation processes in the SSiC struts.

  11. Synthesis of nanoporous silicon carbide ceramics by thermal evaporation process

    Science.gov (United States)

    Wei, Jian

    2010-09-01

    New nanoporous β-SiC ceramics were synthesized by a simple thermal evaporation method with commercial silicon powder and activated carbon fragments. The results of scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and X-ray diffraction indicated that the microstructure of the β-SiC nanoporous ceramics was uniform and consistent with the pore size of 50-100 nm. The β-SiC nanocrystal grains of 50-200 nm were accumulated together to form a nanopore network. The formation mechanism was attributed to a template synthesis process, in which activated carbon fragments were employed as the template and they reacted with vaporized silicon through a vapor-solid way.

  12. Synthesis of nanoporous silicon carbide ceramics by thermal evaporation process

    International Nuclear Information System (INIS)

    New nanoporous β-SiC ceramics were synthesized by a simple thermal evaporation method with commercial silicon powder and activated carbon fragments. The results of scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy and X-ray diffraction indicated that the microstructure of the β-SiC nanoporous ceramics was uniform and consistent with the pore size of 50-100 nm. The β-SiC nanocrystal grains of 50-200 nm were accumulated together to form a nanopore network. The formation mechanism was attributed to a template synthesis process, in which activated carbon fragments were employed as the template and they reacted with vaporized silicon through a vapor-solid way.

  13. Fabrication of silicon nitride-silicon carbide nanocomposite ceramics

    International Nuclear Information System (INIS)

    Silicon nitride-silicon carbide nanocomposites have so far been fabricated by hot-pressing fine amorphous Si-C-N powder produced by CVD. This composite exhibited excellent strength and fracture toughness and maintained high strength to temperatures above 1200 C. The current work deals with the fabrication of nanocomposites produced using mixtures of Si3N4 and nanosize SiC powders. Conventional processing techniques were used to optimise the dispersion of the SiC particles. Densification was achieved by pressureless sintering, gas pressure sintering and sinter/HIPping. Mechanical properties such as hardness, fracture toughness and strength at room temperature were assessed. The nanocomposites produced were compared with composites produced using alternative starting materials. (orig.)

  14. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

    Science.gov (United States)

    Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application. PMID:27524006

  15. Porous biomorphic silicon carbide ceramics coated with hydroxyapatite as prospective materials for bone implants.

    Science.gov (United States)

    Gryshkov, Oleksandr; Klyui, Nickolai I; Temchenko, Volodymyr P; Kyselov, Vitalii S; Chatterjee, Anamika; Belyaev, Alexander E; Lauterboeck, Lothar; Iarmolenko, Dmytro; Glasmacher, Birgit

    2016-11-01

    Porous and cytocompatible silicon carbide (SiC) ceramics derived from wood precursors and coated with bioactive hydroxyapatite (HA) and HA-zirconium dioxide (HA/ZrO2) composite are materials with promising application in engineering of bone implants due to their excellent mechanical and structural properties. Biomorphic SiC ceramics have been synthesized from wood (Hornbeam, Sapele, Tilia and Pear) using a forced impregnation method. The SiC ceramics have been coated with bioactive HA and HA/ZrO2 using effective gas detonation deposition approach (GDD). The surface morphology and cytotoxicity of SiC ceramics as well as phase composition and crystallinity of deposited coatings were analyzed. It has been shown that the porosity and pore size of SiC ceramics depend on initial wood source. The XRD and FTIR studies revealed the preservation of crystal structure and phase composition of in the HA coating, while addition of ZrO2 to the initial HA powder resulted in significant decomposition of the final HA/ZrO2 coating and formation of other calcium phosphate phases. In turn, NIH 3T3 cells cultured in medium exposed to coated and uncoated SiC ceramics showed high re-cultivation efficiency as well as metabolic activity. The recultivation efficiency of cells was the highest for HA-coated ceramics, whereas HA/ZrO2 coating improved the recultivation efficiency of cells as compared to uncoated SiC ceramics. The GDD method allowed generating homogeneous HA coatings with no change in calcium to phosphorus ratio. In summary, porous and cytocompatible bio-SiC ceramics with bioactive coatings show a great promise in construction of light, robust, inexpensive and patient-specific bone implants for clinical application.

  16. Preparation of β-silicon carbide sintered ceramics

    International Nuclear Information System (INIS)

    Current status of research and problems involving β-SiC ceramics in Japan is summarized, focusing on microstructural changes during sintering. SiC has been studied extensively for the past three decades for technical purposes, but generalized research such as on the detailed mechanism of the sintering process has not yet been fully discussed. This paper describes research on SiC for structural materials, and in addition, the issues related to activating SiC industries are discussed based on experimental results. (orig.)

  17. Tribological properties of hot-pressed boron carbide ceramic

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Sliding friction experiments were conducted on hot-pressed B4C ceramic under the condition of sliding contact with themselves in air. The tests were run at average sliding velocity of 1.41  m/s and normal forces ranging from 11.8  N to 37.6  N. The friction coefficients decrease with the increase of sliding distance and the increase of normal load. The lowest friction coefficient is as low as 0.09, compared to 0.35~0.40 as the initial friction coefficient. X-ray diffraction was used to analyze the sliding surface before and after friction tests. The results show that the tribochemical reaction between B4C and O2 produces B2O3, and B2O3 undergoes a secondary chemical reaction with moisture in the air to form H3BO3, which is responsible for the lower friction coefficients. The low-friction mechanism of boric acid is associated with its layered-triclinic-crystal structure. The atoms on each layer are closely packed and strongly bonded to each other, but the layers are widely separated and are held together by van der Waals force. Regarding the wear rate of B4C ceramics used in friction experiments, there is not any wear could be measured by using a surface profilometer.

  18. Calculation and experimental investigation of multi-component ceramic systems

    International Nuclear Information System (INIS)

    This work shows a way to combine thermodynamic calculations and experiments in order to get useful information on the constitution of metal/non-metal systems. Many data from literature are critically evaluated and used as a basis for experiments and calculations. The following multi-component systems are treated: 1. Multi-component systems of 'ceramic' materials with partially metallic bonding (carbides, nitrides, oxides, borides, carbonitrides, borocarbides, oxinitrides of the 4-8th transition group metals) 2. multi-component systems of non-metallic materials with dominant covalent bonding (SiC, Si3N4, SiB6, BN, Al4C3, Be2C) 3. multi-component systems of non-metallic materials with dominant heteropolar bonding (Al2O3, TiO2, BeO, SiO2, ZrO2). The interactions between 1. and 2., 2. and 3., 1. and 3. are also considered. The latest commercially available programmes for the calculation of thermodynamical equilibria and phase diagrams are evaluated and compared considering their facilities and limits. New phase diagrams are presented for many presently unknown multi-component systems; partly known systems are completed on the basis of selected thermodynamic data. The calculations are verified by experimental investigations (metallurgical and powder technology methods). Altogether 690 systems are evaluated, 126 are calculated for the first time and 52 systems are experimentally verified. New data for 60 ternary phases are elaborated by estimating the data limits for the Gibbs energy values. A synthesis of critical evaluation of literature, calculations and experiments leads to new important information about equilibria and reaction behaviour in multi-component systems. This information is necessary to develop new stable and metastable materials. (orig./MM)

  19. FILTER COMPONENT ASSESSMENT--CERAMIC CANDLES--

    Energy Technology Data Exchange (ETDEWEB)

    M.A. Alvin

    2004-04-23

    Efforts at Siemens Westinghouse Power Corporation (SWPC) have been focused on development of hot gas filter systems as an enabling technology for advanced coal and biomass-based gas turbine power generation applications. SWPC has been actively involved in the development of advanced filter materials and component configuration, has participated in numerous surveillance programs characterizing the material properties and microstructure of field tested filter elements, and has undertaken extended, accelerated filter life testing programs. This report summarizes the results of SWPC's filter component assessment efforts, identifying the performance and stability of porous monolithic, fiber reinforced, and filament wound ceramic hot gas candle filters, potentially for {ge}3 years of viable pressurized fluidized-bed combustion (PFBC) service operating life.

  20. Stability of Chromium Carbide/Chromium Oxide Based Porous Ceramics in Supercritical Water

    Science.gov (United States)

    Dong, Ziqiang

    This research was aimed at developing porous ceramics as well as ceramic-metal composites that can be potentially used in Gen-IV supercritical water reactors (SCWR). The research mainly includes two parts: 1) fabricating and engineering the porous ceramics and porous ceramic-metal composite; 2) Evaluating the stability of the porous ceramics in SCW environments. Reactive sintering in carbonaceous environments was used to fabricate porous Cr3C2/Cr2O3-based ceramic. A new process consisting of freeze casting and reactive sintering has also been successfully developed to fabricate highly porous Cr3C 2 ceramics with multiple interconnected pores. Various amounts of cobalt powders were mixed with ceramic oxides in order to modify the porous structure and property of the porous carbide obtained by reactive sintering. The hardness of the M(Cr,Co)7C3-Co composite has been evaluated and rationalized based on the solid solution of cobalt in the ceramic phase, the composite effect of soft Co metal and the porous structure of the ceramic materials. Efforts have also been made in fabricating and evaluating interpenetrating Cr3C2-Cu composites formed by infiltrating liquid copper into porous Cr3C2. The corrosion evaluation mainly focused on assessing the stability of porous Cr3C2 and Cr2O3 under various SCW conditions. The corrosion tests showed that the porous Cr3C 2 is stable in SCW at temperatures below 425°C. However, cracking and disintegrating of the porous Cr3C2 occurred when the SCW temperature increased above 425°C. Mechanisms of the corrosion attack were also investigated. The porous Cr2O3 obtained by oxidizing the porous Cr3C2 was exposed to various SCW environments. It was found that the stability of Cr 2O 3 was dependent on its morphology and the SCW testing conditions. Increasing SCW temperature increased the dissociation rate of the Cr2O 3. Adding proper amount of Y2O3 can increase the stability of the porous Cr2O3 in SCW. It was also concluded that decreasing

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

    Science.gov (United States)

    Guo, Xing-zhong; Yang, Hui

    2005-01-01

    Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

  2. Ceramic material suitable for repair of a space vehicle component in a microgravity and vacuum environment, method of making same, and method of repairing a space vehicle component

    Science.gov (United States)

    Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

    2009-01-01

    A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium diboride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

  3. Sintered silicon carbide: a new ceramic vessel material for microwave chemistry in single-mode reactors.

    Science.gov (United States)

    Gutmann, Bernhard; Obermayer, David; Reichart, Benedikt; Prekodravac, Bojana; Irfan, Muhammad; Kremsner, Jennifer M; Kappe, C Oliver

    2010-10-25

    Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors.

  4. On the use of Raman spectroscopy and instrumented indentation for characterizing damage in machined carbide ceramics

    Science.gov (United States)

    Groth, Benjamin Peter

    Machining is a necessary post-processing step in the manufacturing of many ceramic materials. Parts are machined to meet specific dimensions, with tight tolerances, not attainable from forming alone, as well as to achieve a desired surface finish. However, the machining process is very harsh, often employing the use of high temperatures and pressures to achieve the wanted result. In the case of silicon carbide, a material with extremely high hardness and stiffness, machining is very difficult and requires machining conditions that are highly aggressive. This can leave behind residual stresses in the surface of the material, cause unwanted phase transformations, and produce sub-surface deformation that can lead to failure. This thesis seeks to determine the effect of various machining conditions on the Raman spectra and elastic properties of sintered silicon carbide materials. Sample sets examined included hot-pressed silicon carbide tiles with four different surface finishes, as well as "ideal" single crystal silicon carbide wafers. The surface finishes studied were as follows: an as-pressed finish; a grit blast finish; a harsh rotary ground finish; and a mirror polish. Each finish imparts a different amount, as well as type, of deformation to the sample and are each utilized for a specific application. The sample surfaces were evaluated using a combination of Raman spectroscopy, for phase identification and stress analysis, and nanoindentation, for obtaining elastic properties and imparting uniform controlled deformation to the samples. Raman spectroscopy was performed over each sample surface using 514- and 633-nm wavelength excitation, along with confocal and non-confocal settings to study depth variation. Surfaces stresses were determined using peak shift information extracted from Raman spectra maps, while other spectral variations were used to compare levels of machining damage. Elastic modulus, hardness, and plastic work of indentation maps were generated

  5. Compressive deformation of liquid phase-sintered porous silicon carbide ceramics

    Directory of Open Access Journals (Sweden)

    Taro Shimonosono

    2014-12-01

    Full Text Available Porous silicon carbide ceramics were fabricated by liquid phase sintering with 1 wt% Al2O3–1 wt% Y2O3 additives during hot-pressing at 1400–1900 °C. The longitudinal strain at compressive fracture increased at a higher porosity and was larger than the lateral strain. The compressive Young's modulus and the strain at fracture depended on the measured direction, and increased with the decreased specific surface area due to the formation of grain boundary. However, the compressive strength and the fracture energy were not sensitive to the measured direction. The compressive strength of a porous SiC compact increased with increasing grain boundary area. According to the theoretical modeling of the strength–grain boundary area relation, it is interpreted that the grain boundary of a porous SiC compact is fractured by shear deformation rather than by compressive deformation.

  6. Joining Silicon Carbide Components for Space Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I program will identify the joining materials and demonstrate the processes that are suited for construction of advanced ceramic matrix composite...

  7. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai, E-mail: katohy@ornl.gov [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Koyanagi, Takaaki; Hinoki, Tatsuya [Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011 (Japan); Henager, Charles H. [Pacific Northwest National Laboratory, 902 Battelle Blvd., Richland, WA 99352 (United States); Ferraris, Monica [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino (Italy)

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 °C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to ∼3 dpa at 500 °C, thus indicating the first results obtained on irradiation-stable SiC joints. Under the more aggressive irradiation conditions (800 °C, ∼5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  8. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, Yutai; Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel; Koyanagi, Takaaki; Hinoki, Tatsuya; Henager, Charles H.; Ferraris, Monica

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 °C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to ~3 dpa at 500 °C, thus indicating the first results obtained on irradiation-stable SiC joints. Finally, under the more aggressive irradiation conditions (800 °C, ~5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  9. Investigation of properties and performance of ceramic composite components

    Energy Technology Data Exchange (ETDEWEB)

    Stinchcomb, W.W.; Reifsnider, K.L.; Dunyak, T.J. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Engineering Science and Mechanics)

    1992-06-15

    The objective of the work reported herein is to develop an understanding of the mechanical behavior of advanced ceramic composites subjected to elevated temperature and dynamic (cyclic) loading, to develop a test system and test methods to obtain the properties and performance information required to design engineering components made from ceramic composite materials, and to provide critical and comprehensive evaluations of such materials to material synthesizers and developers to support and enhance progress in ceramic composite material development. The accomplishments of the investigation include the design, development, and demonstration of a high temperature, biaxial mechanical test facility for ceramic composite tubes and the development and validation of a performance simulation model (MRLife) for ceramic composites.

  10. Advances in resonance based NDT for ceramic components

    Science.gov (United States)

    Hunter, L. J.; Jauriqui, L. M.; Gatewood, G. D.; Sisneros, R.

    2012-05-01

    The application of resonance based non-destructive testing methods has been providing benefit to manufacturers of metal components in the automotive and aerospace industries for many years. Recent developments in resonance based technologies are now allowing the application of resonance NDT to ceramic components including turbine engine components, armor, and hybrid bearing rolling elements. Application of higher frequencies and advanced signal interpretation are now allowing Process Compensated Resonance Testing to detect both internal material defects and surface breaking cracks in a variety of ceramic components. Resonance techniques can also be applied to determine material properties of coupons and to evaluate process capability for new manufacturing methods.

  11. Development of a hard nano-structured multi-component ceramic coating by laser cladding

    International Nuclear Information System (INIS)

    The present paper reports laser-assisted synthesis of a multi-component ceramic composite coating consisting of aluminum oxide, titanium di-boride and titanium carbide (Al2O3-TiB2-TiC). A pre-placed powder mixture of aluminum (Al), titanium oxide (TiO2) and boron carbide (B4C) was made to undergo self-propagating high-temperature synthesis (SHS) by laser triggering. Laser subsequently effected cladding of the products of SHS on the substrate. The effect of laser scanning speed on the hardness, microstructure and phase composition of the composite coating was investigated. The coating exhibited an increase in hardness and a decrease in grain size with increase in laser scanning speed. A maximum micro-hardness of 2500 HV0.025 was obtained. X-ray diffraction (XRD) of the top surface of the coating revealed the presence of aluminum oxide (Al2O3), titanium di-boride (TiB2) and titanium carbide (TiC) along with some non-stoichiometric products of the Ti-Al-B-C-O system. Field emission gun scanning electron microscopy (FESEM) and high-resolution transmission electron microscopic (HRTEM) analysis revealed some nano-structured TiB2 and Al2O3, which are discussed in detail.

  12. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Yuri, E-mail: yufi55@mail.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 2/3 Akademicheskiy Ave. Tomsk, 634055 (Russian Federation); National Research Tomsk State University, 36 Lenina Str., Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenina Str., Tomsk, 634050 (Russian Federation); Tolkachev, Oleg, E-mail: ole.ts@mail.ru; Petyukevich, Maria, E-mail: petukevich@tpu.ru; Polisadova, Valentina, E-mail: polis@tpu.ru [National Research Tomsk Polytechnic University, 30 Lenina Str., Tomsk, 634050 (Russian Federation); Teresov, Anton, E-mail: tad514@sibmail.com [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 2/3 Akademicheskiy Ave. Tomsk, 634055 (Russian Federation); National Research Tomsk State University, 36 Lenina Str., Tomsk, 634050 (Russian Federation); Ivanova, Olga, E-mail: ivaov@mail.ru; Ikonnikova, Irina, E-mail: irina-ikonnikova@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq., Tomsk, 634003 (Russian Federation)

    2016-01-15

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm{sup 2}, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  13. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    Science.gov (United States)

    Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

    2016-01-01

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  14. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    International Nuclear Information System (INIS)

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance

  15. Feature extraction for ultrasonic sensor based defect detection in ceramic components

    Science.gov (United States)

    Kesharaju, Manasa; Nagarajah, Romesh

    2014-02-01

    High density silicon carbide materials are commonly used as the ceramic element of hard armour inserts used in traditional body armour systems to reduce their weight, while providing improved hardness, strength and elastic response to stress. Currently, armour ceramic tiles are inspected visually offline using an X-ray technique that is time consuming and very expensive. In addition, from X-rays multiple defects are also misinterpreted as single defects. Therefore, to address these problems the ultrasonic non-destructive approach is being investigated. Ultrasound based inspection would be far more cost effective and reliable as the methodology is applicable for on-line quality control including implementation of accept/reject criteria. This paper describes a recently developed methodology to detect, locate and classify various manufacturing defects in ceramic tiles using sub band coding of ultrasonic test signals. The wavelet transform is applied to the ultrasonic signal and wavelet coefficients in the different frequency bands are extracted and used as input features to an artificial neural network (ANN) for purposes of signal classification. Two different classifiers, using artificial neural networks (supervised) and clustering (un-supervised) are supplied with features selected using Principal Component Analysis(PCA) and their classification performance compared. This investigation establishes experimentally that Principal Component Analysis(PCA) can be effectively used as a feature selection method that provides superior results for classifying various defects in the context of ultrasonic inspection in comparison with the X-ray technique.

  16. Needs assessment for manufacturing ceramic gas turbine components

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.; McSpadden, S.B.; Morris, T.O.; Pasto, A.E.

    1995-11-01

    An assessment of needs for the manufacturing of ceramic gas turbine components was undertaken to provide a technical basis for planning R&D activities to support DOE`s gas turbine programs. The manufacturing processes for ceramic turbine engine components were examined from design through final inspection and testing. The following technology needs were identified: Concurrent engineering early in the design phase to develop ceramic components that are more readily manufacturable. Additional effort in determining the boundaries of acceptable design dimensions and tolerances through experimental and/or analytical means. Provision, by the designer, of a CAD based model of the component early in the design cycle. Standardization in the way turbine components are dimensioned and toleranced, and in the way component datum features are defined. Rapid means of fabricating hard tooling, including intelligent systems for design of tooling and rapid prototyping of tooling. Determination of process capabilities by manufacturing significant numbers of parts. Development of more robust ceramic manufacturing processes which are tolerant of process variations. Development of intelligent processing as a means of controlling yield and quality of components. Development of computer models of key manufacturing steps, such as green forming to reduce the number of iterations required to manufacture intolerance components. Development of creep feed or other low-damage precision grinding for finish machining of components. Improved means of fixturing components for finish machining. Fewer and lower-cost final inspection requirements. Standard procedures, including consistent terminology and analytical software for dimensional inspection of components. Uniform data requirements from the US turbine engine companies. An agreed-upon system of naming ceramic materials and updating the name when changes have been made.

  17. Continuous fiber ceramic matrix composites for heat engine components

    Science.gov (United States)

    Tripp, David E.

    1988-01-01

    High strength at elevated temperatures, low density, resistance to wear, and abundance of nonstrategic raw materials make structural ceramics attractive for advanced heat engine applications. Unfortunately, ceramics have a low fracture toughness and fail catastrophically because of overload, impact, and contact stresses. Ceramic matrix composites provide the means to achieve improved fracture toughness while retaining desirable characteristics, such as high strength and low density. Materials scientists and engineers are trying to develop the ideal fibers and matrices to achieve the optimum ceramic matrix composite properties. A need exists for the development of failure models for the design of ceramic matrix composite heat engine components. Phenomenological failure models are currently the most frequently used in industry, but they are deterministic and do not adequately describe ceramic matrix composite behavior. Semi-empirical models were proposed, which relate the failure of notched composite laminates to the stress a characteristic distance away from the notch. Shear lag models describe composite failure modes at the micromechanics level. The enhanced matrix cracking stress occurs at the same applied stress level predicted by the two models of steady state cracking. Finally, statistical models take into consideration the distribution in composite failure strength. The intent is to develop these models into computer algorithms for the failure analysis of ceramic matrix composites under monotonically increasing loads. The algorithms will be included in a postprocessor to general purpose finite element programs.

  18. Processing and mechanical properties of silicon nitride/silicon carbide ceramic nanocomposites derived from polymer precursors

    Science.gov (United States)

    Gasch, Matthew Jeremy

    Creep deformation of silicon nitride and silicon carbide ceramics is dominated by a solution-precipitation process through the glassy interface phase at grain boundary regions, which is formed by the reaction of oxide additives with the silicon oxide surface layer of the ceramic powder particles during liquid phase sintering. The ultimate approach to increase the creep resistance of these materials is to decrease the oxide content at the grain boundaries, rendering the solution-precipitation process non-effective. This research presents a new method of enhancing the creep properties of silicon nitride/silicon carbide composites by forming micro-nano and nano-nano microstructures during sintering. Starting from amorphous Si-C-N powders of micrometric size particles, powders were consolidated in three ways: (1) Consolidation of pyrolyzed powders without additives, (2) Electric Field Assisted Sintering (EFAS) of pyrolyzed powders with and without additives and (3) High pressure sintering. In all three cases, nanocomposites with varied grain size were achieved. High temperature mechanical creep testing was performed on the samples sintered by EFAS. Creep rates ranged from 1 x 10-8/s to 1 x 10-11/s depending on method in which powders were prepared and total oxide additive amount. For samples with high oxide contents the stress exponent was found to be n ˜ 2 with an activation energy of Q ˜ 600kJ/mol*K, indicating the typical solution precipitation process of deformation. But for the nano-nano composites sintered with little to none oxide additive, the stress exponent was found to be n ˜ 1 with and activation energy of Q ˜ 200kJ/mol*K, hinting at a diffusion controlled mechanism of creep deformation. For the nano-nano composites sintered without oxide additives, oxygen was found in the microstructure. However, oxygen contamination was found to distribute at grain boundary regions especially triple junctions. It is suggested that this highly dispersed distribution of

  19. Ceramic coatings on diesel engine components. Period covered: January 1979-August 1979

    Energy Technology Data Exchange (ETDEWEB)

    Kvernes, I; Lillerud, K P

    1979-10-01

    Diesel engines with imporved thermal efficiency and fuel economy or flexibility will be required to meet automotive energy conservation goals. These goals can be met by minimizing engine heat loss to the coolant, i.e., by the use of a thermal insulating barrier on the interior surfaces of the combustion space. The development and testing of ceramic coatings for diesel engine components are discussed. These coatings include oxides of Al, Cr, Zr, Mg, Si, Ti, and Ca, and Mo and Ch carbides. Data on their application and thermodynamic and wear characteristics are presented. It was concluded that, although the spraying processes used have not been optimized, plasma-spray technology has made it possible to coat diesel engine parts with ceramic materials. Preliminary results show that, relative to valves and piston crowns: stabilized ZrO/sub 2/ coating under certain conditions increases the working life of various components; higher combustion temperature may improve the thermal efficiency by increased turbocharger air delivery; reduction in the component temperatures decreases the thermal stresses; the ZrO/sub 2/.MgO shows improved corrosion resistance in combustion gases compared to ZrO/sub 2/.Y/sub 2/O/sub 3/ and ZrO/sub 2/.CaO; the limitations of the coatings have to be defined in more detail; and the adherence of thicker coatings has to be improved. Optimization of the spraying process with respect to particle fusion is necessary. Also, Mo and Ch carbide coatings were found to increase the service life of piston rings. (LCL)

  20. Impact design methods for ceramic components in gas turbine engines

    Science.gov (United States)

    Song, J.; Cuccio, J.; Kington, H.

    1991-01-01

    Methods currently under development to design ceramic turbine components with improved impact resistance are presented. Two different modes of impact damage are identified and characterized, i.e., structural damage and local damage. The entire computation is incorporated into the EPIC computer code. Model capability is demonstrated by simulating instrumented plate impact and particle impact tests.

  1. Effect of Density and Surface Roughness on Optical Properties of Silicon Carbide Optical Components

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-Ling; HUANG Zheng-Ren; LIU Xue-Jian; JIANG Dong-Liang

    2008-01-01

    @@ The effect of density and surface roughness on the optical properties of silicon carbide optical components is investigated.The density is the major factor of the total reflectance while the surface roughness is the major factor of the diffuse reflectance.The specular reflectance of silicon carbide optical components can be improved by increasing the density and decreasing the surface roughness,in the form of reducing bulk absorption and surface-related scattering,respectively.The contribution of the surface roughness to the specular reflectance is much greater than that of the density.When the rms surface roughness decreases to 2.228nm,the specular reflectance decreases to less than 0.7% accordingly.

  2. Investigation of properties and performance of ceramic composite components. Final report on Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Curtin, W.A.; Reifsnider, K.L.; Oleksuk, L.L.S.; Stinchcomb, W.W. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)

    1994-10-31

    The purpose of Phase 2 of the Investigation of Properties and Performance of Ceramic Composite Components has been to build on and extend the work completed during Phase 1 to further advance the transition from properties of ceramic composite materials to performance of ceramic composite components used in fossil energy environments. The specific tasks of Phase 2 were: (1) develop and validate reliable and accurate high temperature, biaxial mechanical tests methods for structural ceramic composite components; (2) test and evaluate ceramic composite components, specifically tubes; (3) characterize long-term, mechanical performance of ceramic composite tubes at high temperatures; (4) develop a fundamental understanding of the mechanical degradation and performance limitations of ceramic composite components under service conditions; (5) develop predictive models for damage tolerance and reliability; and (6) relate component performance to microstructure and, thereby, provide feedback to the associated process-development effort, to improve performance. Accomplishments for each task are given.

  3. Characterization of Ceramic Matrix Composite Combustor Components: Pre and Post Exposure

    Science.gov (United States)

    Ojard, G.; Linsey, G.; Brennan, J.; Naik, R.; Cairo, R.; Stephan, R.; Hornick, J.; Brewer, D.

    2001-01-01

    The pursuit of lower emissions and higher performance from gas turbine engines requires the development of innovative concepts and the use of advanced materials for key engine components. One key engine component is the combustor, where innovative design and material improvements have the potential to lower emissions. Efforts to develop a High Speed Civil Transport with low emissions were focused on the evaluation of combustor concepts with liners fabricated from a ceramic matrix composite of silicon carbide fibers in a silicon carbide matrix (SiC/SiC). The evaluation of SiC/SiC composites progressed from simple coupons (to establish a first-order database and identify operant failure mechanisms and damage accumulation processes), to feature-based subelements (to assess fabricability and in situ material response), to actual components (to assess structural integrity, dimensional, and compositional fidelity) tested under simulated engine conditions. As in the case of all evolutionary material and process work, a key element to resolving fabrication issues is the evaluation of witness areas taken from fabricated components before testing the actual component. The witness material from these components allowed microstructural and mechanical testing to be performed and compared to the ideal, flat panel, conditions and data that are typical of basic characterization. This also allowed samples of similar design to be taken from components after 115 hours of combustion exposure. Testing consisted of tensile, double notch shear, ring burst, and thermal conductivity that sampled various regions of the components. The evaluation of the witness material allowed an understanding of the fabrication process, highlighting critical issues, in an early phase of the learning curve development of these configuration and material unique parts. Residual property testing, after exposure, showed if degradation of the material under actual service conditions was occurring. This paper

  4. Development of high-temperature resistant noncorrodible silicon-carbide components for gas turbine application. Follow-up-report. Entwicklung von hochwarmfesten, korrosionsbestaendigen Siliciumcarbid-Formkoerpern fuer die Verwendung im Gasturbinenbau. Fortschrittsbericht

    Energy Technology Data Exchange (ETDEWEB)

    Blecha, M.; Pohlmann, H.J.

    1985-03-01

    The report under review describes the work of phase 3 (1980 - 1983) of the project 'Ceramic Materials for Automobile Gas Turbines', which has been sponsored by the Ministry for Research and Technology of the Federal Republic of Germany since 1974. Special effort has been put on the improvement of different silicon carbide materials and suitable production techniques for the production of static gas turbine components and a heat exchanger prototype. Tight connection of production techniques, construction and testing in simulated application conditions made it possible to transfer improved material data from test specimens to structural components. Prototypes of combustion chambers, heat exchangers were produced and tested. The positive results of this R+D-project lead to the series production of silicon carbide components for engineering.

  5. Nanoscale multilayered and porous carbide interphases prepared by pressure-pulsed reactive chemical vapor deposition for ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, S., E-mail: jacques@lcts.u-bordeaux1.fr [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France); Jouanny, I.; Ledain, O.; Maillé, L.; Weisbecker, P. [LCTS, University of Bordeaux 1, CNRS, Herakles-Safran, CEA, 3 allee de la Boetie, F-33600 Pessac (France)

    2013-06-15

    In Ceramic Matrix Composites (CMCs) reinforced by continuous fibers, a good toughness is achieved by adding a thin film called “interphase” between the fiber and the brittle matrix, which acts as a mechanical fuse by deflecting the matrix cracks. Pyrocarbon (PyC), with or without carbide sub-layers, is typically the material of choice to fulfill this role. The aim of this work was to study PyC-free nanoscale multilayered carbide coatings as interphases for CMCs. Nanoscale multilayered (SiC–TiC){sub n} interphases were deposited by pressure-Pulsed Chemical Vapor Deposition (P-CVD) on single filament Hi-Nicalon fibers and embedded in a SiC matrix sheath. The thicknesses of the carbide interphase sub-layers could be made as low as a few nanometers as evidenced by scanning and transmission electron microscopy. By using the P-ReactiveCVD method (P-RCVD), in which the TiC growth involves consumption of SiC, it was not only possible to obtain multilayered (SiC–TiC){sub n} films but also TiC films with a porous multilayered microstructure as a result of the Kirkendall effect. The porosity in the TiC sequences was found to be enhanced when some PyC was added to SiC prior to total RCVD consumption. Because the porosity volume fraction was still not high enough, the role of mechanical fuse of the interphases could not be evidenced from the tensile curves, which remained fully linear even when chemical attack of the fiber surface was avoided.

  6. Recent trends and theoretical background in sintering of silicon carbide ceramics

    Science.gov (United States)

    Suzuki, H.

    1983-01-01

    This article gives an outline of sintering techniques of silicon carbide and refers to recent developments. These techniques are also applicable to other oxides with a high melting point and particularly high sinterability, namely MgO and BeO.

  7. Joining of Silicon Carbide-Based Ceramics for MEMS-LDI Fuel Injector Applications

    Science.gov (United States)

    Halbig, Michael C.; Singh, Mrityunjay

    2012-01-01

    Deliver the benefits of ceramics in turbine engine applications- increased efficiency, performance, horsepower, range, operating temperature, and payload and reduced cooling and operation and support costs for future engines.

  8. IMPROVING ENERGY EFFICIENCY OF SILICON CARBIDE CERAMICS PRODUCTION BY BATCH REGULATION

    Directory of Open Access Journals (Sweden)

    Dmitriy Zhukov

    2015-09-01

    Full Text Available The article discusses an energy-efficient method for producing SiC-based composites via doping with oxide eutectic compositions and batch granulometry regulation. The influence of batch granulometry on physico-mechanical properties of ceramics is studied, and fractions ratio is determined allowing us to obtain a dense material with improved strength and fracture toughness. Such ceramics shows excellent mechanical behavior and holds much promise as a structural and armor material.

  9. Joining of SiC-ceramics by means of boron carbide, silicon and carbon for high temperature applications

    International Nuclear Information System (INIS)

    The present work is a contribution to joining of SiC-Ceramics for high temperature applications. The aim was to develop a joining technique for Silicon Carbide ceramics by means of boron, carbon and silicon. The joint is created by the formation of a welding zone, which consists of SiC as it is the material to be joined. For this purpose are used the follow means: (a) sputtering layers of B4C, Si and C, (b) vacuum coatings of Si or Si foils and C, (c) powder mixtures of B4C, Si and C. The joints were examined at ceramographic cross sections of the bonding zone, by means of XRD, REM/EDAX, TEM and EPMA. The bond strength was determined in the 4-point bend test at room temperature and at 1370 C. It was found that a useable result can be obtained, if the temperature of the joining process exceeds the melting point of Si (1410 C). A high bending strength with a high Weibull modulus was achieved by using sputter layers. The powder mixtures provided a satisfactory bending strength with a low Weibull modulus. (orig.)

  10. Thermal expansion of laminated, woven, continuous ceramic fiber/chemical-vapor-infiltrated silicon carbide matrix composites

    Science.gov (United States)

    Eckel, Andrew J.; Bradt, Richard C.

    1990-01-01

    Thermal expansions of three two-dimensional laminate, continuous fiber/chemical-vapor-infiltrated silicon carbide matrix composites reinforced with either FP-Alumina (alumina), Nextel (mullite), or Nicalon (Si-C-O-N) fibers are reported. Experimental thermal expansion coefficients parallel to a primary fiber orientation were comparable to values calculated by the conventional rule-of-mixtures formula, except for the alumina fiber composite. Hysteresis effects were also observed during repeated thermal cycling of that composite. Those features were attributed to reoccurring fiber/matrix separation related to the micromechanical stresses generated during temperature changes and caused by the large thermal expansion mismatch between the alumina fibers and the silicon carbide matrix.

  11. Impurities in silicon carbide ceramics and their role during high temperature creep

    Science.gov (United States)

    Backhaus-Ricoult, M.; Mozdzierz, N.; Eveno, P.

    1993-12-01

    The high-temperature compressive creep behaviour of hot-pressed silicon carbide ceramics with different additive packages (boron and carbon or no additive) is investigated as a function of several parameters: the microstructure, the nature of the additives and that of the impurities. Additional carbon is present in all the materials investigated, as graphite precipitates of various size and amount. In materials densified with addition of boron, large precipitates of B{25}C and small amorphous silica pockets are identified. In the case of materials containing impurities, small precipitates of FeSi, Fe or Ti5Si3 are detected. Creep experiments are conducted on materials with no additives and on others containing boron and carbon additives, at temperatures ranging from 1 773 K to 1 973 K and under stresses from 100 to 1 100 MPa. A comparison of the creep behaviour of the various materials points out to the destructive effect of carbon precipitates on the creep rate: the stationary creep rate of the material containing carbon (and boron) additives is by a factor 2.5-5 faster, eventhough its grain size is much larger! The creep of both investigated materials is described by a power law with a stress exponent of 1.5 in a low stress range and 3.5-4 in a high stress range. The corresponding activation energies are 364 kJ/mole and 453 kJ/mole in the low stress range and about 629 kJ/mole in the high stress range. At low stresses the materials deform by grain boundary sliding compensated mainly by diffusion along the grain boundaries and to a lesser extent by limited cavitation, as a result of the barrier role played by grain boundaries for dislocations. At high stresses the grain boundaries are no longer an obstacle to dislocation motion, which becomes the dominant deformation mechanism. La microstructure de deux céramiques, SiC sans ajouts et SiC avec bore et carbone, est étudiée par microscopie électronique à transmission dans le but d'évaluer l'influence des

  12. Development of impact design methods for ceramic gas turbine components

    Science.gov (United States)

    Song, J.; Cuccio, J.; Kington, H.

    1990-01-01

    Impact damage prediction methods are being developed to aid in the design of ceramic gas turbine engine components with improved impact resistance. Two impact damage modes were characterized: local, near the impact site, and structural, usually fast fracture away from the impact site. Local damage to Si3N4 impacted by Si3N4 spherical projectiles consists of ring and/or radial cracks around the impact point. In a mechanistic model being developed, impact damage is characterized as microcrack nucleation and propagation. The extent of damage is measured as volume fraction of microcracks. Model capability is demonstrated by simulating late impact tests. Structural failure is caused by tensile stress during impact exceeding material strength. The EPIC3 code was successfully used to predict blade structural failures in different size particle impacts on radial and axial blades.

  13. Transient liquid phase sintering of tantalum carbide ceramics by using silicon as the sintering aid and its effects on microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Lianbing [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Liu, Limeng, E-mail: liulimeng@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Worsch, Christian; Gonzalez, Jesus; Springer, André [Otto Schott Institute of Materials Research, Friedrich-Schiller-University Jena, Lobdergraben 32, D-07743 Jena (Germany); Ye, Feng [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-01-15

    Tantalum carbide composites with 0.76–8.85 wt.% elemental silicon as a sintering aid were fabricated by spark plasma sintering (SPS) at 1700 °C and 30 MPa for 5 min. The transient-liquid-phase sintering behavior, the microstructures and the mechanical properties of the tantalum carbide composites were investigated. Oxide impurities present on the surfaces of the tantalum carbide particles were eliminated by reactions with the elemental silicon in a temperature range from 1271 °C to 1503 °C to benefit densification. Then the silicon melted at its melting point temperature of 1413 °C to facilitate rearrangement of the tantalum carbide particles. By the end of the densification, the elemental silicon transformed into more refractory TaSi{sub 2} and SiC in the consolidated ceramics by reactions with the tantalum carbide at temperatures lower than 1773 °C. Both TaSi{sub 2} and SiC particles improved densification by physically pinning growth of the tantalum carbide grains. Further densification was resulted from creep flow of the silicides after brittle-to-ductile transformation of the silicides at temperatures <1650 °C. Due to the good effects of using elemental silicon as the sintering aid, all the compositions reached densities >96.7% theoretical. The average grain sizes in the consolidated materials decreased with the silicon addition from about 19 μm in the 0.76 wt.% Si composition to about 9 μm in the 8.85 wt.% Si composition. A good flexural strength up to ∼709 MPa was reached in the 8.85 wt.% Si material due to full density and fine microstructure. - Highlights: • Tantalum carbide ceramics were densified by using 0.76–8.85 wt.% silicon as the sintering aids. • The transient liquid phase sintering behavior of the material system was discussed. • The elemental silicon improved densification and subsequently replaced by TaSi{sub 2} and SiC. • The tantalum carbide ceramic with 8.85 wt.% silicon addition showed a good flexural

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-04-01

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

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

    International Nuclear Information System (INIS)

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

  16. Method for improving the toughness of silicon carbide-based ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Tein, Tseng-Ying (Ann Arbor, MI); Hilmas, Gregory E. (Dexter, MI)

    1996-01-01

    Method of improving the toughness of SiC-based ceramics. SiC, , AlN, Al.sub.2 O.sub.3 and optionally .alpha.-Si.sub.3 N.sub.4 are hot pressed to form a material which includes AlN polytypoids within its structure.

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

    International Nuclear Information System (INIS)

    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

  18. Silicon carbide thin films as nuclear ceramics grown by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Filipescu, M., E-mail: morarm@nipne.ro [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania); Velisa, G. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Ion, V.; Andrei, A. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania); Scintee, N.; Ionescu, P. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Stanciu, S.G. [Center for Microscopy- Microanalysis and Information Processing, University ' POLITEHNICA' of Bucharest, Bucharest (Romania); Pantelica, D. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O.BOX MG-6, Bucharest - Magurele (Romania); Dinescu, M. [National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125, Magurele - Bucharest (Romania)

    2011-09-01

    Silicon carbide has been identified as a potential inert matrix candidate for advanced fuel. In this work, the growth of SiC thin films by pulsed laser deposition is reported. The stoicheometry and thickness of deposited films was investigated by non-Rutherford backscattering spectrometry. The influence of the deposition parameters, i.e. substrate temperature and laser fluence on the structure, morphology and optical properties of the deposited thin layers was studied. It was found that polycrystalline SiC thin films with uniform surface morphology were obtained at 873 K.

  19. Development of high toughness, high strength aluminide-bonded carbide ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Becher, P.F.; Plucknett, K.P.; Tiegs, T.N. [Oak Ridge National Lab., TN (United States)] [and others

    1997-04-01

    Cemented carbides are widely used in applications where resistance to abrasion and wear are important, particularly in combination with high strength and stiffness. In the present case, ductile aluminides have been used as a binder phase to fabricate dense carbide cermets by either sintering of mixed powders or a melt-infiltration sintering process. The choice of an aluminide binder was based on the exceptional high temperature strength and chemical stability exhibited by these alloys. For example, TiC-based composites with a Ni{sub 3}Al binder phase exhibit improved oxidation resistance, Young`s moduli > 375 GPa, high fracture strengths (> 1 GPa) that are retained to {ge} 900{degrees}C, and fracture toughness values of 10 to 15 MPa{radical}m, identical to that measured in commercial cobalt-bonded WC with the same test method. The thermal diffusivity values at 200{degrees}C for these composites are {approximately} 0.070 to 0.075 cm{sup 2}/s while the thermal expansion coefficients rise with Ni3Al content from {approximately} 8 to {approximately}11 x 10{sup {minus}6}/{degrees}C over the range of 8 to 40 vol. % Ni{sub 3}Al. The oxidation and acidic corrosion resistances are quite promising as well. Finally, these materials also exhibit good electrical conductivity allowing them to be sectioned and shaped by electrical discharge machining (EDM) processes.

  20. Processing, characterization and mechanical behavior of novel aluminum/silicon carbide metal-ceramic nanolaminates

    Science.gov (United States)

    Singh, Danny Rao Pratap

    Nanoscale laminated composites are a novel class of materials with excellent mechanical properties like strength, flexibility, and toughness. Properties in these materials can be tailored by varying layer thicknesses, microstructure, and controlling internal stresses. Most of research to-date has focused on metal-metal and ceramic-ceramic laminates. The field of metal-ceramic laminates has remained relatively unexplored. From a mechanical structure point of view, metal-ceramic systems present a good combination of strength and hardness. Hence, there is a need for understanding and evaluating these composites in nanolaminate form. In this work, the deformation behavior of Al-SiC nanolaminates as a model system has been studied. The work has been categorized into 3 major areas of research. The first involves processing and microstructural characterization of these novel materials. Nanoscale Al/SiC layered composites were fabricated using magnetron sputtering. Samples with varying volume fractions of Al and SiC were synthesized. The second area involves quantifying the residual stresses in these materials. These are quantified by x-ray synchrotron and beam-curvature techniques. The third area focuses on understanding the fundamental mechanisms for deformation damage, and fracture under indentation and micro-compression loading. Fracture/Damage analysis is carried out using focused ion beam (FIB) and scanning electron microscopy (SEM). The systematic study has revealed the enhanced mechanical properties of metal-ceramic nanolaminates and the fundamental mechanisms governing the strength and failure of these materials. It has been found that Al/SiC metal-ceramic systems can exhibit high strength together with high toughness and flexibility. High compressive residual stresses are generated during the sputter deposition of these nanolaminates which are associated with the large number of interfaces present in the nanolaminate architecture. The mechanical properties

  1. Effect of Starting Powder Polytype on Thermal Conductivity of Liquid-Phase Sintered Silicon Carbide Ceramics

    International Nuclear Information System (INIS)

    Thermal conductivity of PBAT fuel is one of very important factors for plant safety and energy efficiency of nuclear reactors. PBAT fuels encapsulated with SiC enable a nuclear reactor to reduce the stored energy in the core and produce more thermal energy. For this reason, improvement in the thermal conductivity of SiC matrix is an important research issue for PBAT fuel. According to the previous reports, the thermal conductivity of high-purity SiC single crystal was 490 W/m*K and maximum experimental value of hotpressed polycrystalline SiC ceramics was 270 W/m*K. The SiC ceramic was obtained by hot-pressing SiC powders with BeO additive. However, the application of the material has been limited because of the toxicity of Be. Therefore, developments of new additive compositions for polycrystalline SiC is essential for developing PBAT fuels encapsulated with SiC with high thermal conductivity. Recently, a fully dense SiC ceramic with a high thermal conductivity (234 W/m*K) was reported by hot-pressing β-SiC powders with 1 vol% Y2O3-Sc2O3 as a sintering additive. In the present study, the effect of initial α-SiC content on the microstructure and thermal properties of the hotpressed SiC ceramics have been investigated. The effect of crystalline phase (α-phase content) in starting powders on microstructure and thermal properties of SiC ceramics has been investigated by using submicron-sized α- and/or β-SiC starting powders. The addition of small amount (1 vol%) of Y2O3-Sc2O3 additives resulted in 99.9% densification of submicron SiC powder mixtures by hot-pressing at 2050 .deg. C for 6 h. The thermal conductivity decreased with increasing α-SiC content in the starting composition. Such results suggest that both the presence of α/β phase boundaries and the occurrence of β→α phase transformation of SiC are detrimental for improving the thermal conductivity of polycrystalline SiC ceramics. A maximal thermal conductivity of 159 W/m*K was obtained when 10%

  2. Effect of Starting Powder Polytype on Thermal Conductivity of Liquid-Phase Sintered Silicon Carbide Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Kwang-Young; Lee, Seung-Jae [KEPCO Nuclear Fuel, Daejeon (Korea, Republic of); Kim, Young-Wook [Univ. of Seoul, Seoul (Korea, Republic of)

    2014-10-15

    Thermal conductivity of PBAT fuel is one of very important factors for plant safety and energy efficiency of nuclear reactors. PBAT fuels encapsulated with SiC enable a nuclear reactor to reduce the stored energy in the core and produce more thermal energy. For this reason, improvement in the thermal conductivity of SiC matrix is an important research issue for PBAT fuel. According to the previous reports, the thermal conductivity of high-purity SiC single crystal was 490 W/m*K and maximum experimental value of hotpressed polycrystalline SiC ceramics was 270 W/m*K. The SiC ceramic was obtained by hot-pressing SiC powders with BeO additive. However, the application of the material has been limited because of the toxicity of Be. Therefore, developments of new additive compositions for polycrystalline SiC is essential for developing PBAT fuels encapsulated with SiC with high thermal conductivity. Recently, a fully dense SiC ceramic with a high thermal conductivity (234 W/m*K) was reported by hot-pressing β-SiC powders with 1 vol% Y{sub 2}O{sub 3}-Sc{sub 2}O{sub 3} as a sintering additive. In the present study, the effect of initial α-SiC content on the microstructure and thermal properties of the hotpressed SiC ceramics have been investigated. The effect of crystalline phase (α-phase content) in starting powders on microstructure and thermal properties of SiC ceramics has been investigated by using submicron-sized α- and/or β-SiC starting powders. The addition of small amount (1 vol%) of Y{sub 2}O{sub 3}-Sc{sub 2}O{sub 3} additives resulted in 99.9% densification of submicron SiC powder mixtures by hot-pressing at 2050 .deg. C for 6 h. The thermal conductivity decreased with increasing α-SiC content in the starting composition. Such results suggest that both the presence of α/β phase boundaries and the occurrence of β→α phase transformation of SiC are detrimental for improving the thermal conductivity of polycrystalline SiC ceramics. A maximal thermal

  3. Effect of SiO2 on the Preparation and Properties of Pure Carbon Reaction Bonded Silicon Carbide Ceramics

    Institute of Scientific and Technical Information of China (English)

    WU Qi-de; GUO Bing-jian; YAN Yong-gao; ZHAO Xiu-jian; HONG Xiao-lin

    2004-01-01

    Effect of SiO2 content and sintering process on the composition and properties of Pure CarbonReaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C - SiO2 green body by infiltrating siliconwas presented. The infiltrating mechanism of C - SiO2 preform was also explored. The experimental results indicatethat the shaping pressure increases with the addition of SiO2 to the preform, and the pore size of the body turnedfiner and distributed in a narrower range, which is beneficial to decreasing the residual silicon content in the sin-tered materials and to avoiding shock off, thus increasing the conversion rate of SiC. SiO2 was deoxidized by car-bon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body atan elevated temperature. If the green body is deposited at 1800℃ in vacuum before infiltration crack will not beproduced in the preform and fully dense RBSC can be obtained. The ultimate material has the following properties:a density of3.05-3.12g/cm3 ,a strength of 580±32MPa and a hardness of (HRA)91-92.3.

  4. Specific Nature of Application of Various Carbon Components for Mechanochemical Synthesis of Titanium Carbide

    Science.gov (United States)

    Reva, V. P.; Yagofarov, V. U.; Gulevskii, D. A.; Filatenkov, A. E.; Mansurov, Yu N.

    2016-08-01

    It has been established that structure of carbon modifications, obtained via pyrolysis of vegetable feed, and ash content of natural graphite are crucial factors during mechanochemical synthesis of titanium carbide under vibratory conditions. The possibility of synthesis of titanium carbide with minimal sulfur content has been shown.

  5. Method for removing volatile components from a ceramic article, and related processes

    Science.gov (United States)

    Klug, Frederic Joseph; DeCarr, Sylvia Marie

    2002-01-01

    A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

  6. Method For Removing Volatile Components From A Gel-Cast Ceramic Article

    Science.gov (United States)

    Klug, Frederic Joseph; DeCarr, Sylvia Marie

    2004-09-07

    A method of removing substantially all of the volatile component in a green, volatile-containing ceramic article is disclosed. The method comprises freezing the ceramic article; and then subjecting the frozen article to a vacuum for a sufficient time to freeze-dry the article. Frequently, the article is heated while being freeze-dried. Use of this method efficiently reduces the propensity for any warpage of the article. The article is often formed from a ceramic slurry in a gel-casting process. A method for fabricating a ceramic core used in investment casting is also described.

  7. Effects of superfine refractory carbide additives on microstructure and mechanical properties of TiB2–TiC+Al2O3 composite ceramic cutting tool materials

    International Nuclear Information System (INIS)

    Highlights: • The superfine carbides determined the mechanical properties of composites. • Superfine HfC or TaC caused some oxide impurities in composites. • Superfine VC or NbC refined and homogenized the microstructure. • Failure of composites containing HfC or TaC was produced by larger grains. • Composite containing VC exhibited more bridging and transcrystalline failure. -- Abstract: A study to increase the mechanical properties of TiB2–TiC+Al2O3 composite ceramic cutting tool material by using superfine refractory carbide additives is presented. Four superfine refractory carbides are considered to investigate their effects on the phase composition, element distribution, grain size, fracture surface, crack propagation of the metal ceramic. The physicochemical properties of superfine carbides, such as chemical activities and atom radius, were found to have the significant effects on the microstructure and mechanical properties of the metal ceramic. Hafnium carbide (HfC) and Tantalum carbide (TaC) reduced the mechanical properties of the metal ceramic because of their poor solubility with the Ni binder phase and the formation of oxides. The mechanical properties of the metal ceramic were increased by the addition of superfine niobium carbide (NbC) and vanadium carbide (VC), and their optimum values were a flexural strength of 1100 ± 62 MPa, fracture toughness of 8.5 ± 0.8 MPa.m1/2 and hardness of 21.53 ± 0.36 GPa, respectively, when 3.2 wt% superfine VC was used

  8. Effects of superfine refractory carbide additives on microstructure and mechanical properties of TiB{sub 2}–TiC+Al{sub 2}O{sub 3} composite ceramic cutting tool materials

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Bin, E-mail: zou20011110@163.com [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China); Ji, Wenbin; Huang, Chuanzhen; Wang, Jun [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China); Li, Shasha [Shandong Special Equipment Inspection Institute, Jinan 250013 (China); Xu, Kaitao [Centre for Advanced Jet Engineering Technologies (CaJET), School of Mechanical Engineering, Shandong University, Jinan 250061 (China); Key Laboratory of High Efficiency and Clean Mechanical Manufacture, Shandong University, Ministry of Education (China)

    2014-02-05

    Highlights: • The superfine carbides determined the mechanical properties of composites. • Superfine HfC or TaC caused some oxide impurities in composites. • Superfine VC or NbC refined and homogenized the microstructure. • Failure of composites containing HfC or TaC was produced by larger grains. • Composite containing VC exhibited more bridging and transcrystalline failure. -- Abstract: A study to increase the mechanical properties of TiB{sub 2}–TiC+Al{sub 2}O{sub 3} composite ceramic cutting tool material by using superfine refractory carbide additives is presented. Four superfine refractory carbides are considered to investigate their effects on the phase composition, element distribution, grain size, fracture surface, crack propagation of the metal ceramic. The physicochemical properties of superfine carbides, such as chemical activities and atom radius, were found to have the significant effects on the microstructure and mechanical properties of the metal ceramic. Hafnium carbide (HfC) and Tantalum carbide (TaC) reduced the mechanical properties of the metal ceramic because of their poor solubility with the Ni binder phase and the formation of oxides. The mechanical properties of the metal ceramic were increased by the addition of superfine niobium carbide (NbC) and vanadium carbide (VC), and their optimum values were a flexural strength of 1100 ± 62 MPa, fracture toughness of 8.5 ± 0.8 MPa.m1/2 and hardness of 21.53 ± 0.36 GPa, respectively, when 3.2 wt% superfine VC was used.

  9. New Progress in the Preparation of Sintering and Application of Boron Carbide Ceramics%碳化硼陶瓷的烧结与应用新进展

    Institute of Scientific and Technical Information of China (English)

    杨亮亮; 谢志鹏; 刘维良; 魏红康; 赵琳; 宋明

    2015-01-01

    碳化硼陶瓷具有高硬度、高弹性模量、耐磨损、耐腐蚀等优点,是一种综合性能优异的结构材料。碳化硼陶瓷可通过有效添加剂、适当的温度与压力等条件实现致密化烧结,从而提高其综合性能,因此碳化硼的致密化烧结是其关键技术。本文论述了碳化硼陶瓷致密化烧结工艺的基本原理及烧结方法,在此基础上总结了碳化硼陶瓷在陶瓷装甲、核能和耐磨技术等重要领域的应用。%Boron carbide ceramics are typical structural materials with excellent comprehensive properties, due to their high hardness, high elastic modulus, excellent resistance to wear and corrosion, as well as other advantages. The densiifcation of boron carbide ceramics can be realized by effective additives, appropriate temperature and pressure to improve their mechanical behaviors. Thus, the sintering and densiifcation are the key steps in the entire preparing process. Here, the basic principle and routes of the sintering of boron carbide ceramics are summarized, and their applications in the ifeld of armor, nuclear power, and abrasives are presented.

  10. Modeling injection molding of net-shape active ceramic components.

    Energy Technology Data Exchange (ETDEWEB)

    Baer, Tomas (Gram Inc.); Cote, Raymond O.; Grillet, Anne Mary; Yang, Pin; Hopkins, Matthew Morgan; Noble, David R.; Notz, Patrick K.; Rao, Rekha Ranjana; Halbleib, Laura L.; Castaneda, Jaime N.; Burns, George Robert; Mondy, Lisa Ann; Brooks, Carlton, F.

    2006-11-01

    To reduce costs and hazardous wastes associated with the production of lead-based active ceramic components, an injection molding process is being investigated to replace the current machining process. Here, lead zirconate titanate (PZT) ceramic particles are suspended in a thermoplastic resin and are injected into a mold and allowed to cool. The part is then bisque fired and sintered to complete the densification process. To help design this new process we use a finite element model to describe the injection molding of the ceramic paste. Flow solutions are obtained using a coupled, finite-element based, Newton-Raphson numerical method based on the GOMA/ARIA suite of Sandia flow solvers. The evolution of the free surface is solved with an advanced level set algorithm. This approach incorporates novel methods for representing surface tension and wetting forces that affect the evolution of the free surface. Thermal, rheological, and wetting properties of the PZT paste are measured for use as input to the model. The viscosity of the PZT is highly dependent both on temperature and shear rate. One challenge in modeling the injection process is coming up with appropriate constitutive equations that capture relevant phenomenology without being too computationally complex. For this reason we model the material as a Carreau fluid and a WLF temperature dependence. Two-dimensional (2D) modeling is performed to explore the effects of the shear in isothermal conditions. Results indicate that very low viscosity regions exist near walls and that these results look similar in terms of meniscus shape and fill times to a simple Newtonian constitutive equation at the shear-thinned viscosity for the paste. These results allow us to pick a representative viscosity to use in fully three-dimensional (3D) simulation, which because of numerical complexities are restricted to using a Newtonian constitutive equation. Further 2D modeling at nonisothermal conditions shows that the choice of

  11. The status of ceramic turbine component fabrication and quality assurance relevant to automotive turbine needs

    Energy Technology Data Exchange (ETDEWEB)

    Richerson, D.W.

    2000-02-01

    This report documents a study funded by the U.S. Department of Energy (DOE) Office of Transportation Technologies (OTT) with guidance from the Ceramics Division of the United States Automotive Materials Partnership (USAMP). DOE and the automotive companies have funded extensive development of ceramic materials for automotive gas turbine components, the most recent effort being under the Partnership for a New Generation of Vehicles (PNGV) program.

  12. The development and testing of ceramic components in piston engines. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McEntire, B.J. [Norton Co., Northboro, MA (United States). Advanced Ceramics Div.; Willis, R.W.; Southam, R.E. [TRW, Inc., Cleveland, OH (United States)

    1994-10-01

    Within the past 10--15 years, ceramic hardware has been fabricated and tested in a number of piston engine applications including valves, piston pins, roller followers, tappet shims, and other wear components. It has been shown that, with proper design and installation, ceramics improve performance, fuel economy, and wear and corrosion resistance. These results have been obtained using rig and road tests on both stock and race engines. Selected summaries of these tests are presented in this review paper.

  13. Ceramic versus cobalt-chrome femoral components; wear of polyethylene insert in total knee prosthesis.

    Science.gov (United States)

    Oonishi, Hironobu; Ueno, Masaru; Kim, Sok Chol; Oonishi, Hiroyuki; Iwamoto, Mikio; Kyomoto, Masayuki

    2009-04-01

    The present study aimed to determine the effect of femoral component materials and sterilization methods on wear properties of total knee prostheses by using a knee simulator test and retrieval analysis. The simulator test revealed that ultrahigh molecular weight polyethylene (UHMWPE) inserts had remarkably lower wear against the ceramic femoral component than against the Co-Cr femoral component. However, the retrieval study revealed no significant difference in the linear wear between the former and the latter. The alumina ceramic/UHMWPE insert combination showed a mild wear. However, whether cross-linking by gamma-ray sterilization reduces wear remained unconfirmed. In contrast, oxidative degradation and/or delamination was confirmed. Thus, we conclude that alumina ceramic/ethylene oxide gas-sterilized UHMWPE insert in a total knee prosthesis might exhibit a good wear resistance. PMID:18524533

  14. Standardization Efforts for Mechanical Testing and Design of Advanced Ceramic Materials and Components

    Science.gov (United States)

    Salem, Jonathan A.; Jenkins, Michael G.

    2003-01-01

    Advanced aerospace systems occasionally require the use of very brittle materials such as sapphire and ultra-high temperature ceramics. Although great progress has been made in the development of methods and standards for machining, testing and design of component from these materials, additional development and dissemination of standard practices is needed. ASTM Committee C28 on Advanced Ceramics and ISO TC 206 have taken a lead role in the standardization of testing for ceramics, and recent efforts and needs in standards development by Committee C28 on Advanced Ceramics will be summarized. In some cases, the engineers, etc. involved are unaware of the latest developments, and traditional approaches applicable to other material systems are applied. Two examples of flight hardware failures that might have been prevented via education and standardization will be presented.

  15. Adverse sequelae following revision of a total hip replacement for a fractured ceramic component: case report

    Directory of Open Access Journals (Sweden)

    Lee Ling Hong

    2015-01-01

    Full Text Available Revision total hip replacement following a fractured ceramic bearing component presents a challenge in the choice of the new bearing implant. A femoral head made of equal or harder material should be implanted to prevent catastrophic wear. Despite this, patients and surgeons must be wary of potential complications.

  16. Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

    Institute of Scientific and Technical Information of China (English)

    J.A.da Silva; B.M.Moreschi; G.C.R.Garcia; S.Ribeiro

    2013-01-01

    Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics.This work involved a study of the wetting of SiC ceramics by two oxide systems,Al2O3/Dy2O3 and Al2O3/Yb2O3,which have so far not been studied for application in the sintering of SiC ceramics.Five mixtures of each system were prepared,with different compositions close to their respective eutectic ones.Samples of the mixtures were pressed into cylindrical specimens,which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace.The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle,the parameter that measures the degree of wettability.The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading.All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere.The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX).The DRX analysis showed that Al2O3 and RE2O3 reacted and formed the Dy3Al5O12 (DyAg) and Yb3Al5O12 (YbAg) phases.The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.

  17. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    Science.gov (United States)

    Werheit, Helmut

    2016-10-01

    The complex, highly distorted structure of boron carbide is composed of B12 and B11C icosahedra and CBC, CBB and B□B linear elements, whose concentration depends on the chemical composition each. These concentrations are shown to be consistent with lattice parameters, fine structure data and chemical composition. The respective impacts on lattice parameters are estimated and discussed. Considering the contributions of the different structural components to the energy of the overall structure makes the structure and its variation within the homogeneity range reasonable; in particular that of B4.3C representing the carbon-rich limit of the homogeneity range. Replacing in B4.3C virtually the B□B components by CBC yields the hypothetical moderately distorted B4.0C (structure formula (B11C)CBC). The reduction of lattice parameters related is compatible with recently reported uncommonly prepared single crystals, whose compositions deviate from B4.3C.

  18. Current status and future aspects of R and D activities on electro- ceramic components in Japanese industry

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Hiroshi, E-mail: takagihr@murata.co.jp [Material Development Group, Technology and Business Development Unit, Murata Mfg. Co., Ltd., Yasu-shi, Shiga 520-2393 (Japan)

    2011-05-15

    The oldest pottery in Japan was made 16,500 years ago in Jomon period. On the background of a long history of Japanese ceramics, Murata and other Japanese manufacturers have been developing electro-ceramic materials and manufacturing many kinds of electronic components using them. In 1937, TDK manufactured ferrite cores first in the world. Then, Japanese electro-ceramic industry has led the world on electro-ceramic materials and components until now, especially in the fields of BaTiO{sub 3}, PZT, PTC thermistor, ZnO varistor and insulating ceramics. From the analysis of the papers reported lately, R and D activities of Japanese manufacturers are understood to cover not only improving properties of electro-ceramics, but also appropriate technologies and basic technologies.

  19. Synthesis and Analysis of Alpha Silicon Carbide Components for Encapsulation of Fuel Rods and Pellets

    Energy Technology Data Exchange (ETDEWEB)

    Kevin M. McHugh; John E. Garnier; George W. Griffith

    2011-09-01

    The chemical, mechanical and thermal properties of silicon carbide (SiC) along with its low neutron activation and stability in a radiation field make it an attractive material for encapsulating fuel rods and fuel pellets. The alpha phase (6H) is particularly stable. Unfortunately, it requires very high temperature processing and is not readily available in fibers or near-net shapes. This paper describes an investigation to fabricate a-SiC as thin films, fibers and near-net-shape products by direct conversion of carbon using silicon monoxide vapor at temperatures less than 1700 C. In addition, experiments to nucleate the alpha phase during pyrolysis of polysilazane, are also described. Structure and composition were characterized using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Preliminary tensile property analysis of fibers was also performed.

  20. Slow Crack Growth and Fatigue Life Prediction of Ceramic Components Subjected to Variable Load History

    Science.gov (United States)

    Jadaan, Osama

    2001-01-01

    Present capabilities of the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code, which has also been modified to have the ability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.

  1. A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding

    Directory of Open Access Journals (Sweden)

    Enrico Mick

    2015-07-01

    Full Text Available Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (Ø10 mm × 56 mm made of alumina toughened zirconia (ATZ, as well as titanium grade 5, were bonded by glass solder on their end faces. As a control, a two-component adhesive glue was utilized. The samples were investigated without further treatment, after 30 and 90 days of storage in distilled water at room temperature, and after aging. All samples were subjected to quasi-static four-point-bending tests. We found that the glass solder bonding provided significantly higher bending strength than adhesive glue bonding. In contrast to the glued samples, the bending strength of the soldered samples remained unaltered by the storage and aging treatments. Scanning electron microscopy (SEM and energy-dispersive X-ray (EDX analyses confirmed the presence of a stable solder-ceramic interface. Therefore, the glass solder technique represents a promising method for optimizing dental and orthopedic implant bondings.

  2. Composition Comprising Silicon Carbide

    Science.gov (United States)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  3. Variations in the constant component of the phase voltage in ore-smelting furnaces for the production of phosphorus and calcium carbide

    Science.gov (United States)

    Pedro, A. A.; Arlievskii, M. P.

    2009-12-01

    Phosphorus and carbide furnaces are considered as an example to study the character of changes in and the nature of constant component U cc in the phase voltage of an ore-smelting furnace with a closed furnace top. The value and polarity of U cc depend on the relation between the chemical interaction of an electrode with the reaction-zone components and the degree of development and the conditions of an electric arc.

  4. Phase Field Theory and Analysis of Pressure-Shear Induced Amorphization and Failure in Boron Carbide Ceramic

    Directory of Open Access Journals (Sweden)

    John D. Clayton

    2014-07-01

    Full Text Available A nonlinear continuum phase field theory is developed to describe amorphization of crystalline elastic solids under shear and/or pressure loading. An order parameter describes the local degree of crystallinity. Elastic coefficients can depend on the order parameter, inelastic volume change may accompany the transition from crystal to amorphous phase, and transitional regions parallel to bands of amorphous material are penalized by interfacial surface energy. Analytical and simple numerical solutions are obtained for an idealized isotropic version of the general theory, for an element of material subjected to compressive and/or shear loading. Solutions compare favorably with experimental evidence and atomic simulations of amorphization in boron carbide, demonstrating the tendency for structural collapse and strength loss with increasing shear deformation and superposed pressure.

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

    Science.gov (United States)

    Balaraman Yadhukulakrishnan, Govindaraajan

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

  6. Oxidation of zirconium diboride-silicon carbide ceramics under an oxygen partial pressure of 200 Pa: Formation of zircon

    International Nuclear Information System (INIS)

    The formation and evolution of zircon during oxidation of ZrB2-20 vol.% SiC ceramics under a low oxygen partial pressure of 200 Pa is studied. The formation mechanism of zircon is proposed according to experimental results and thermodynamic consideration. And the main reason to the formation of zircon can be attributed to the active oxidation of SiC. Two steps can be divided for the formation and evolution of zircon: (1) nucleation from silica glass; and (2) crystal growth into prism like particles. Furthermore, the emergence of zircon significantly improves the oxidation resistance performance.

  7. Federal Aviation Administration (FAA airworthiness certification for ceramic matrix composite components in civil aircraft systems

    Directory of Open Access Journals (Sweden)

    Gonczy Stephen T.

    2015-01-01

    Full Text Available Ceramic matrix composites (CMCs are being designed and developed for engine and exhaust components in commercial aviation, because they offer higher temperature capabilities, weight savings, and improved durability compared to metals. The United States Federal Aviation Administration (FAA issues and enforces regulations and minimum standards covering the safe manufacture, operation, and maintenance of civil aircraft. As new materials, these ceramic composite components will have to meet the certification regulations of the FAA for “airworthiness”. The FAA certification process is defined in the Federal Aviation Regulations (Title 14 of the Code of Federal Regulations, FAA policy statements, orders, advisory circulars, technical standard orders, and FAA airworthiness directives. These regulations and documents provide the fundamental requirements and guidelines for design, testing, manufacture, quality assurance, registration, operation, inspection, maintenance, and repair of aircraft systems and parts. For metallic parts in aircraft, the FAA certification and compliance process is well-established for type and airworthiness certification, using ASTM and SAE standards, the MMPDS data handbook, and FAA advisory circulars. In a similar manner for polymer matrix composites (PMC, the PMC industry and the FAA have jointly developed and are refining parallel guidelines for polymer matrix composites (PMCs, using guidance in FAA circulars and the CMH-17 PMC handbook. These documents discuss design methods and codes, material testing, property data development, life/durability assessment, production processes, QA procedures, inspection methods, operational limits, and repairs for PMCs. For ceramic composites, the FAA and the CMC and aerospace community are working together (primarily through the CMH-17 CMC handbook to define and codify key design, production, and regulatory issues that have to be addressed in the certification of CMC components in

  8. Life prediction methodology for ceramic components of advanced vehicular heat engines: Volume 1. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Khandelwal, P.K.; Provenzano, N.J.; Schneider, W.E. [Allison Engine Co., Indianapolis, IN (United States)

    1996-02-01

    One of the major challenges involved in the use of ceramic materials is ensuring adequate strength and durability. This activity has developed methodology which can be used during the design phase to predict the structural behavior of ceramic components. The effort involved the characterization of injection molded and hot isostatic pressed (HIPed) PY-6 silicon nitride, the development of nondestructive evaluation (NDE) technology, and the development of analytical life prediction methodology. Four failure modes are addressed: fast fracture, slow crack growth, creep, and oxidation. The techniques deal with failures initiating at the surface as well as internal to the component. The life prediction methodology for fast fracture and slow crack growth have been verified using a variety of confirmatory tests. The verification tests were conducted at room and elevated temperatures up to a maximum of 1371 {degrees}C. The tests involved (1) flat circular disks subjected to bending stresses and (2) high speed rotating spin disks. Reasonable correlation was achieved for a variety of test conditions and failure mechanisms. The predictions associated with surface failures proved to be optimistic, requiring re-evaluation of the components` initial fast fracture strengths. Correlation was achieved for the spin disks which failed in fast fracture from internal flaws. Time dependent elevated temperature slow crack growth spin disk failures were also successfully predicted.

  9. Temperature Fluctuation Synthesis/Simultaneous Densification and Microstructure Control of Titanium Silicon Carbide (Ti3SiC2) Ceramics

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@A novel temperature fluctuation synthesis/simultaneous densification process was developed for the preparation of Ti3SiC2 bulk ceramics. In this process, Si is used as an in-situ liquid forming phase and it is favorable for both the solid-liquid synthesis and the densification of Ti3SiC2 ceramics. The present work demonstrated that the temperature fluctuation synthesis/simultaneous densification process is one of the most effective and simple methods for the preparation of Ti3SiC2 bulk materials providing relatively low synthesis temperature, short reaction time, and simultaneous synthesis and densification. This work also showed the capability to control the microstructure, e.g., the preferred orientation, of the bulk Ti3SiC2 materials simply by applying the hot pressing pressure at different stages of the temperature fluctuation process. And textured Ti3SiC2 bulk materials with {002} faces of laminated Ti3SiC2 grains normal to the hot pressing axis were prepared.

  10. Method Developed for the High-Temperature Nondestructive Evaluation of Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites

    Science.gov (United States)

    Goldsby, Jon C.

    1998-01-01

    Ceramic matrix composites have emerged as candidate materials to allow higher operating temperatures (1000 to 1400 C) in gas turbine engines. A need, therefore, exists to develop nondestructive methods to evaluate material integrity at the material operating temperature by monitoring thermal and mechanical fatigue. These methods would also have potential as quality inspection tools. The goal of this investigation at the NASA Lewis Research Center is to survey and correlate the temperature-dependent damping and stiffness of advanced ceramic composite materials with imposed thermal and stress histories that simulate in-service turbine engine conditions. A typical sample size of 100 by 4 by 2 cubic millimeters, along with the specified stiffness and density, placed the fundamental vibration frequencies between 100 and 2000 Hz. A modified Forster apparatus seemed most applicable to simultaneously measure both damping and stiffness. Testing in vacuum reduced the effects of air on the measurements. In this method, a single composite sample is vibrated at its fundamental tone; then suddenly, the mechanical excitation is removed so that the sample's motion freely decays with time. Typical results are illlustrated in this paper.

  11. High-temperature tensile behavior of a boron nitride-coated silicon carbide-fiber glass-ceramic composite

    International Nuclear Information System (INIS)

    Tensile properties of a cross-ply glass-ceramic composite were investigated by conducting fracture, creep, and fatigue experiments at both room temperature and high temperatures in air. The composite consisted of a barium magnesium aluminosilicate (BMAS) glass-ceramic matrix reinforced with SiC fibers with a SiC/BN coating. The material exhibited retention of most tensile properties up to 1,200 C. Monotonic tensile fracture tests produced ultimate strengths of 230--300 MPa with failure strains of ∼1%, and no degradation in ultimate strength was observed at 1,100 and 1,200 C. In creep experiments at 1,100 C, nominal steady-state creep rates in the 10-9 s-1 range were established after a period of transient creep. Tensile stress rupture experiments at 1,100 and 1,200 C lasted longer than one year at stress levels above the corresponding proportional limit stresses for those temperatures. Tensile fatigue experiments were conducted in which the maximum applied stress was slightly greater than the proportional limit stress of the matrix, and, in these experiments, the composite survived 105 cycles without fracture at temperatures up to 1,200 C. Microscopic damage mechanisms were investigated by TEM, and microstructural observations of tested samples were correlated with the mechanical response. The SiC/BN fiber coatings effectively inhibited diffusion and reaction at the interface during high-temperature testing. The BN layer also provided a weak interfacial bond that resulted in damage-tolerant fracture behavior

  12. Ferroelectromagnetic solid solutions on the base piezoelectric ceramic materials for components of micromechatronics

    Science.gov (United States)

    Bochenek, Dariusz; Zachariasz, Radosław; Niemiec, Przemysław; Ilczuk, Jan; Bartkowska, Joanna; Brzezińska, Dagmara

    2016-10-01

    In the presented work, a ferroelectromagnetic solid solutions based on PZT and ferrite powders have been obtained. The main aim of combination of ferroelectric and magnetic powders was to obtain material showing both electric and magnetic properties. Ferroelectric ceramic powder (in amount of 90%) was based on the doped PZT type solid solution while magnetic component was nickel-zinc ferrite Ni1-xZnxFe2O4 (in amount of 10%). The synthesis of components of ferroelectromagnetic solid solutions was performed using the solid phase sintering. Final densification of synthesized powder has been done using free sintering. The aim of the work was to obtain and examine in the first multicomponent PZT type ceramics admixed with chromium with the following chemical composition Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3 and next ferroelectromagnetic solid solution based on a PZT type ferroelectric powder (Pb0.94Sr0.06(Zr0.46Ti0.54)O3+0.25 at% Cr2O3) and nickel-zinc ferrite (Ni0.64Zn0.36Fe2O4), from the point of view of their mechanical and electric properties, such as: electric permittivity, ε; dielectric loss, tanδ; mechanical losses, Q-1; and Young modulus, E.

  13. A new high temperature resistant glass–ceramic coating for gas turbine engine components

    Indian Academy of Sciences (India)

    Someswar Datta; Sumana Das

    2005-12-01

    A new high temperature and abrasion resistant glass–ceramic coating system (based on MgO–Al2O3–TiO2 and ZnO–Al2O3–SiO2 based glass systems) for gas turbine engine components has been developed. Thermal shock resistance, adherence at 90°-bend test and static oxidation resistance at the required working temperature (1000°C) for continuous service and abrasion resistance are evaluated using suitable standard methods. The coating materials and the resultant coatings are characterized using differential thermal analysis, differential thermogravimetric analysis, X-ray diffraction analysis, optical microscopy and scanning electron microscopy. The properties evaluated clearly showed the suitability of these coatings for protection of different hot zone components in different types of engines. XRD analysis of the coating materials and the resultant coatings showed presence of a number of microcrystalline phases. SEM micrographs indicate strong chemical bonding at the metal–ceramic interface. Optical micrographs showed smooth glossy impervious defect free surface finish.

  14. Physics-Based Design Tools for Lightweight Ceramic Composite Turbine Components with Durable Microstructures

    Science.gov (United States)

    DiCarlo, James A.

    2011-01-01

    Under the Supersonics Project of the NASA Fundamental Aeronautics Program, modeling and experimental efforts are underway to develop generic physics-based tools to better implement lightweight ceramic matrix composites into supersonic engine components and to assure sufficient durability for these components in the engine environment. These activities, which have a crosscutting aspect for other areas of the Fundamental Aero program, are focusing primarily on improving the multi-directional design strength and rupture strength of high-performance SiC/SiC composites by advanced fiber architecture design. This presentation discusses progress in tool development with particular focus on the use of 2.5D-woven architectures and state-of-the-art constituents for a generic un-cooled SiC/SiC low-pressure turbine blade.

  15. Synthesis and processing of beta silicon carbide powder by silicon - carbon reaction

    International Nuclear Information System (INIS)

    SiC is an important structural ceramic and finds applications in nuclear industry. Processing of SiC ceramic components for such applications require sinter-active beta silicon carbide powders. Various novel methods have been reported for the synthesis of beta SiC powder based on silica - carbon and silicon - carbon reactions. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. In this research, beta-silicon carbide (β-SiC) was synthesized from the reaction of Si and C. Stoichiometric amount of silicon and petroleum coke having agglomerate size ∼ 5-8μ were planetarily wet mixed, dried, granulated and compacted to reaction specimens

  16. History of ``NANO''-Scale VERY EARLY Solid-State (and Liquid-State) Physics/Chemistry/Metallurgy/ Ceramics; Interstitial-Alloys Carbides/Nitrides/Borides/...Powders and Cermets, Rock Shocks, ...

    Science.gov (United States)

    Maiden, Colin; Siegel, Edward

    History of ``NANO'': Siegel-Matsubara-Vest-Gregson[Mtls. Sci. and Eng. 8, 6, 323(`71); Physica Status Solidi (a)11,45(`72)] VERY EARLY carbides/nitrides/borides powders/cermets solid-state physics/chemistry/metallurgy/ ceramics FIRST-EVER EXPERIMENTAL NANO-physics/chemistry[1968 ->Physica Status Solidi (a)11,45(`72); and EARLY NANO-``physics''/NANO-``chemistry'' THEORY(after: Kubo(`62)-Matsubara(`60s-`70s)-Fulde (`65) [ref.: Sugano[Microcluster-Physics, Springer('82 `98)

  17. Surface engineering glass-metal coatings designed for induction heating of ceramic components

    Science.gov (United States)

    Khan, Amir Azam; Labbe, Jean Claude

    2014-06-01

    The term Surface Engineering is of relatively recent origin and use, however, the use of coatings and treatments to render surfaces of materials more suitable for certain application or environment is not new. With the advent of Vacuum Technology, Surface Engineering has gained a whole new impetus, whereby expensive materials with adequate mechanical, chemical and thermal properties are being coated or treated on their surfaces in order to achieve what is called as Surface Engineered materials. The present paper presents an overview of recent achievements in Surface Engineering and gives a detailed view of a specific application where glass-metal composite coatings were deposited on ceramic components in order to render them sensitive to induction heating. Sintered glaze coatings containing silver particles in appropriate concentration can be used for the induction heating of porcelain. Mixtures of glass ceramic powders with silver are used to prepare self-transfer patterns, which are deposited over porcelain. Several configurations of these coatings, which are aesthetic to start with, are employed and heating patterns are recorded. The microstructure of these coatings is discussed in relation to the heating ability by a classical household induction system. The results show that this technique is practical and commercially viable.

  18. Surface engineering glass-metal coatings designed for induction heating of ceramic components

    International Nuclear Information System (INIS)

    The term Surface Engineering is of relatively recent origin and use, however, the use of coatings and treatments to render surfaces of materials more suitable for certain application or environment is not new. With the advent of Vacuum Technology, Surface Engineering has gained a whole new impetus, whereby expensive materials with adequate mechanical, chemical and thermal properties are being coated or treated on their surfaces in order to achieve what is called as Surface Engineered materials. The present paper presents an overview of recent achievements in Surface Engineering and gives a detailed view of a specific application where glass-metal composite coatings were deposited on ceramic components in order to render them sensitive to induction heating. Sintered glaze coatings containing silver particles in appropriate concentration can be used for the induction heating of porcelain. Mixtures of glass ceramic powders with silver are used to prepare self-transfer patterns, which are deposited over porcelain. Several configurations of these coatings, which are aesthetic to start with, are employed and heating patterns are recorded. The microstructure of these coatings is discussed in relation to the heating ability by a classical household induction system. The results show that this technique is practical and commercially viable

  19. Investigation of properties and performance of ceramic composite components: Final report on Phases 3 and 4

    Energy Technology Data Exchange (ETDEWEB)

    Curtin, W.A.; Halverson, H.; Carter, R.H.; Miraj, N.; Reifsnider, K.L. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)

    1998-01-15

    The objective of the Fossil Energy Advanced Research and Technology Development (AR and TD) Materials Program is to conduct research and development on materials for longer-term fossil energy applications as well as for generic needs of various fossil fuel technologies. The research program of the Materials Response Group at Virginia Tech addresses the need for reliable and durable structural ceramic composites to perform in high temperature environments. The research effort provides an experimental and analytical basis for the transition from properties of materials to performance of actual component structures. Phases 1 and 2 of the present program focused on the development of test capabilities, initial studies of component mechanical response under various conditions and the development of a life prediction methodology. These efforts have been described in previous reports. This report summarizes the major tasks completed under Phases 3 and 4 of the project. Overall, the authors have made significant progress in a broad spectrum of tasks in this program. Their efforts have encompassed component evaluation, assessment of new SiC-based composites with improved high-temperature potential, development of oxide coating materials for SiC, and the extension and development of new models for predicting the durability of composite components under specific operating conditions for various CMC applications. Each of these areas of work is an important area for achieving the ultimate goal of usable SiC-based composites in high-temperature corrosive environments typical of fossil energy applications.

  20. New Technology for Increasing Through-Life Reliability of Ceramics Components Using Self-Crack-Healing Ability

    Directory of Open Access Journals (Sweden)

    Kotoji Ando

    2013-01-01

    Full Text Available Structural ceramics are superior to metallic materials in terms of their high-temperature strengths and critical heat proof temperatures. However, compared to metallic materials, ceramics exhibit lower fracture toughness, so they are more sensitive to flaws such as pores and cracks. The shortness considerably decreases the component reliability. To overcome the shortness, in this study, special attention is paid to structural ceramics with self-crack-healing ability. There are several advantages for using a material with self-crack-healing ability. (1 After an efficient machine operation, the materials are able to self-heal the cracks introduced by the machining. (2 The materials are able to self-heal the cracks introduced during service and recover the strength completely at healing temperature. However, ways of organizing the available knowledge to increase the through-life reliability of ceramics components have not been extensively studied. The authors propose a new concept and the corresponding flowchart. This new concept is a promising technique for increasing the through-life reliability of ceramics components with excellent self-crack-healing ability.

  1. Adhesive strength of total knee endoprostheses to bone cement - analysis of metallic and ceramic femoral components under worst-case conditions.

    Science.gov (United States)

    Bergschmidt, Philipp; Dammer, Rebecca; Zietz, Carmen; Finze, Susanne; Mittelmeier, Wolfram; Bader, Rainer

    2016-06-01

    Evaluation of the adhesive strength of femoral components to the bone cement is a relevant parameter for predicting implant safety. In the present experimental study, three types of cemented femoral components (metallic, ceramic and silica/silane-layered ceramic) of the bicondylar Multigen Plus knee system, implanted on composite femora were analysed. A pull-off test with the femoral components was performed after different load and several cementing conditions (four groups and n=3 components of each metallic, ceramic and silica/silane-layered ceramic in each group). Pull-off forces were comparable for the metallic and the silica/silane-layered ceramic femoral components (mean 4769 N and 4298 N) under standard test condition, whereas uncoated ceramic femoral components showed reduced pull-off forces (mean 2322 N). Loading under worst-case conditions led to decreased adhesive strength by loosening of the interface implant and bone cement using uncoated metallic and ceramic femoral components, respectively. Silica/silane-coated ceramic components were stably fixed even under worst-case conditions. Loading under high flexion angles can induce interfacial tensile stress, which could promote early implant loosening. In conclusion, a silica/silane-coating layer on the femoral component increased their adhesive strength to bone cement. Thicker cement mantles (>2 mm) reduce adhesive strength of the femoral component and can increase the risk of cement break-off. PMID:25781660

  2. [Finite element analysis of a cemented ceramic femoral component for the assembly situation in total knee arthroplasty].

    Science.gov (United States)

    Schultze, Christine; Klüss, Daniel; Martin, Heiner; Hingst, Volker; Mittelmeier, Wolfram; Schmitz, Klaus-Peter; Bader, Rainer

    2007-08-01

    The femoral components of the total knee replacements are generally made of metal. In contrast, ceramic femoral components promise improved tribological and allergological properties. However, ceramic components present a risk of failure as a result of stress peaks. Stress peaks can be minimised through adequate implant design, proper material composition and optimum force transmission between bone and implant. Thus, the quality of the implant fixation is a crucial factor. The objective of the present study was to analyse the influence of the cement layer thickness on stress states in the ceramic femoral component and in the femur. Two- and three- dimensional finite element analyses of an artificial knee joint with cement layers of different thickness and with an unbalanced cement layer thickness between the ceramic femoral component and the femur were performed. Higher stress regions occurred in the area of force transmission and in the median plane. The maximum calculated stresses were below the accepted tensile strength. Stresses were found to be lower for cement layer thickness of <2.0 mm. PMID:17691864

  3. High temperature interaction behavior at liquid metal-ceramic interfaces

    Science.gov (United States)

    McDeavitt, S. M.; Billings, G. W.; Indacochea, J. E.

    2002-08-01

    Liquid metal/ceramic interaction experiments were undertaken at elevated temperatures with the purpose of developing reusable crucibles for melting reactive metals. The metals used in this work included zirconium (Zr), Zr-8 wt.% stainless steel, and stainless steel containing 15 wt.% Zr. The ceramic substrates include yttria, Zr carbide, and hafnium (Hf) carbide. The metal-ceramic samples were placed on top of a tungsten (W) dish. These experiments were conducted with the temperature increasing at a controlled rate until reaching set points above 2000 °C; the systems were held at the peak temperature for about five min and then cooled. The atmosphere in the furnace was argon (Ar). An outside video recording system was used to monitor the changes on heating up and cooling down. All samples underwent a post-test metallurgical examination. Pure Zr was found to react with yttria, resulting in oxygen (O) evolution at the liquid metal-ceramic interface. In addition, dissolved O was observed in the as-cooled Zr metal. Yttrium (Y) was also present in the Zr metal, but it had segregated to the grain boundaries on cooling. Despite the normal expectations for reactive wetting, no transition interface was developed, but the Zr metal was tightly bound to yttria ceramic. Similar reactions occurred between the yttria and the Zr-stainless steel alloys. Two other ceramic samples were Zr carbide and Hf carbide; both carbide substrates were wetted readily by the molten Zr, which flowed easily to the sides of the substrates. The molten Zr caused a very limited dissolution of the Zr carbide, and it reacted more strongly with the Hf carbide. These reactive wetting results are relevant to the design of interfaces and the development of reactive filler metals for the fabrication of high temperature components through metal-ceramic joining. Parameters that have a marked impact on this interface reaction include the thermodynamic stability of the substrate, the properties of the modified

  4. A Novel Technique for the Connection of Ceramic and Titanium Implant Components Using Glass Solder Bonding

    OpenAIRE

    Enrico Mick; Joachim Tinschert; Aurica Mitrovic; Rainer Bader

    2015-01-01

    Both titanium and ceramic materials provide specific advantages in dental implant technology. However, some problems, like hypersensitivity reactions, corrosion and mechanical failure, have been reported. Therefore, the combining of both materials to take advantage of their pros, while eliminating their respective cons, would be desirable. Hence, we introduced a new technique to bond titanium and ceramic materials by means of a silica-based glass ceramic solder. Cylindrical compound samples (...

  5. Processing development of 4 tantalum carbide-hafnium carbide and related carbides and borides for extreme environments

    Science.gov (United States)

    Gaballa, Osama Gaballa Bahig

    Carbides, nitrides, and borides ceramics are of interest for many applications because of their high melting temperatures and good mechanical properties. Wear-resistant coatings are among the most important applications for these materials. Materials with high wear resistance and high melting temperatures have the potential to produce coatings that resist degradation when subjected to high temperatures and high contact stresses. Among the carbides, Al4SiC4 is a low density (3.03 g/cm3), high melting temperature (>2000°C) compound, characterized by superior oxidation resistance, and high compressive strength. These desirable properties motivated this investigation to (1) obtain high-density Al4SiC4 at lower sintering temperatures by hot pressing, and (2) to enhance its mechanical properties by adding WC and TiC to the Al4SiC4. Also among the carbides, tantalum carbide and hafnium carbide have outstanding hardness; high melting points (3880°C and 3890°C respectively); good resistance to chemical attack, thermal shock, and oxidation; and excellent electronic conductivity. Tantalum hafnium carbide (Ta4HfC 5) is a 4-to-1 ratio of TaC to HfC with an extremely high melting point of 4215 K (3942°C), which is the highest melting point of all currently known compounds. Due to the properties of these carbides, they are considered candidates for extremely high-temperature applications such as rocket nozzles and scramjet components, where the operating temperatures can exceed 3000°C. Sintering bulk components comprised of these carbides is difficult, since sintering typically occurs above 50% of the melting point. Thus, Ta4 HfC5 is difficult to sinter in conventional furnaces or hot presses; furnaces designed for very high temperatures are expensive to purchase and operate. Our research attempted to sinter Ta4HfC5 in a hot press at relatively low temperature by reducing powder particle size and optimizing the powder-handling atmosphere, milling conditions, sintering

  6. Life prediction methodology for ceramic components of advanced heat engines. Phase 1: Volume 1, Final report

    Energy Technology Data Exchange (ETDEWEB)

    Cuccio, J.C.; Brehm, P.; Fang, H.T. [Allied-Signal Aerospace Co., Phoenix, AZ (United States). Garrett Engine Div.] [and others

    1995-03-01

    Emphasis of this program is to develop and demonstrate ceramics life prediction methods, including fast fracture, stress rupture, creep, oxidation, and nondestructive evaluation. Significant advancements were made in these methods and their predictive capabilities successfully demonstrated.

  7. Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

    Institute of Scientific and Technical Information of China (English)

    A. El-Shershaby; A. Sroor; F. Ahmed; A.S. Abdel-Haleem; Z. Abdel

    2004-01-01

    The concentrations of 20 trace elements in several ceramics tiles and ceramic composites used in Egypt were elementally analyzed by neutron activation analysis(NAA) technique. The samples and standard were irradiated with reactor for 4 h( in the Second The gamma-ray spectra obtained were measured for several times by means of the hyper pure germanium detection system( HPGe).Also a solid state nuclear track detector(SSNTD) CR-39, was used to measure the emanation rate of radon for these samples. The radium concentrations were found to vary from 0.39-3.59 ppm and the emanation rates were found to vary from (0.728-5.688) x 10-4The elemental analysis of the ceramic tiles and ceramic composites have a great importance in assigning the physical properties and in turn the quality of the material.

  8. Life prediction methodology for ceramic components of advanced heat engines. Phase 1: Volume 2, Appendices

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-03-01

    This volume presents the following appendices: ceramic test specimen drawings and schematics, mixed-mode and biaxial stress fracture of structural ceramics for advanced vehicular heat engines (U. Utah), mode I/mode II fracture toughness and tension/torsion fracture strength of NT154 Si nitride (Brown U.), summary of strength test results and fractography, fractography photographs, derivations of statistical models, Weibull strength plots for fast fracture test specimens, and size functions.

  9. Densification of silicon and zirconium carbides by a new process: spark plasma sintering

    International Nuclear Information System (INIS)

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

  10. High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

    Science.gov (United States)

    Halbig, Michael C.; Singh, Mrityunjay

    2015-01-01

    Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.

  11. Effect of SUS316L stainless steel surface conditions on the wetting of molten multi-component oxides ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jin, E-mail: wangjinustb@gmail.com [Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka, 808-0196 (Japan); Matsuda, Nozomu [Bar and Wire Product Unit, Nippon steel and Sumitomo Metal Corporation, Fukuoka, 802-8686 (Japan); Shinozaki, Nobuya [Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Fukuoka, 808-0196 (Japan); Miyoshi, Noriko [The Center for Instrumental Analysis, Kyushu Institute of Technology, Fukuoka, 804-8550 (Japan); Shiraishi, Takanobu [Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, 852-8588 (Japan)

    2015-02-01

    Highlights: • Multi-component oxides had a good wetting on stainless substrates with pretreatments. • Various substrates surface roughness caused the difference of final contact angles. • The wetting rate was slow on polished substrate due to the slow surface oxidation. - Abstract: A study on the effect of SUS316L stainless steel surface conditions on the wetting behavior of molten multi-component oxides ceramic was performed and aimed to contribute to the further understanding of the application of oxides ceramic in penetration treatment of stainless steel coatings and the deposition of stainless steel cermet coatings. The results show that at 1273 K, different surface pre-treatments (polishing and heating) had an important effect on the wetting behavior. The molten multi-component oxides showed good wettability on both stainless steel substrates, however, the wetting process on the polished substrate was significantly slower than that on the heated substrates. The mechanism of the interfacial reactions was discussed based on the microscopic and thermodynamic analysis, the substrates reacted with oxygen generated from the decomposition of the molten multi-component oxides and oxygen contained in the argon atmosphere, and the oxide film caused the molten multi-component oxides ceramic to spread on the substrates surfaces. For the polished substrate, more time was required for the surface oxidation to reach the surface composition of Heated-S, which resulted in relatively slow spreading and wetting rates. Moreover, the variance of the surface roughness drove the final contact angles to slightly different values following the sequence Polished-S > Heated-S.

  12. Hydrothermal degradation of tetragonal ZrO2 ceramic components used in dental applications

    International Nuclear Information System (INIS)

    With the evolution of the dental restoration techniques, a considerable growth in the demand of ceramic products occurred. These materials present good strength associated to reliability. In this work, micrometric and nanometric scale tetragonal ZrO2 blocks were sintered at 1500 deg C-2h and 1350 deg C-2h, respectively, ground and polished. Ceramics with relative density higher than 98% were obtained. The specimens were immersed in hot water (150 deg C), for times ranging from 10h to 30h. The mass variation of the samples was measured and the crystalline phases present before and after the degradation tests were identified by X-ray diffractometry, in order to evaluate the capacity of these ceramics in resisting to aqueous medium exposure. Materials with nanometric structure present higher resistance to degradation than those with micrometric scale, and this interferes in structural stability after the test, and reduces the martensitic transformation. (author)

  13. 粉末表面涂层陶瓷的硬质合金刀具材料%Advanced Cutting Tool Material by Hot-Pressing Ceramic Coated Carbide Powders

    Institute of Scientific and Technical Information of China (English)

    陈元春; 黄传真; 艾兴; 王宝友

    2000-01-01

    Carbide powders were coated with very thin alumina films by the sol-gel process. The coated powders were then hot-pressed as a novel cutting tool material. This material possessed relatively high hardness, which led to similar wear resistant ability with ceramics. At the same time, its bending strength and toughness were higher than that of the ceramic cutting tool materials with similar composition. As a result, these tools show good performance in cutting high-hardness materials. SEM and TEM photographs of coated powders and fracture surface were presented as an aid to illustrate the strengthen mechanism.%使用溶胶-凝胶法在硬质合金粉末表面涂覆了一层氧化铝陶瓷,涂层粉末经热压烧结后, 制得一种新型的涂层刀具材料. 这种刀具材料的耐磨性与陶瓷材料接近,并且具有较高的强度和韧性,在切削高硬度材料时表现出良好性能,具有广阔的应用前景.

  14. 碳化硅陶瓷膜处理采油污水的中试试验%Pilot tests on the treatment of oil extraction wastewater with silicon carbide ceramic membranes

    Institute of Scientific and Technical Information of China (English)

    吴玉祥; 陈勇; 徐燕

    2012-01-01

    用0.02 μm的多通道非对称性碳化硅陶瓷膜对采油污水进行了现场中试.在各种运行条件下,陶瓷膜出水SS< 1.0 mg/L,油<10 mg/L,粒径中值<1.0μm.还考察了不同运行条件下陶瓷膜膜通量和跨膜压差的变化,以及强化混凝过滤对膜通量的影响.根据试验结果对陶瓷膜在采油污水处理中的进一步研究提出了建议,并对其工程应用前景进行了展望.%The multipath and asymmetrical silicon carbide membranes whose pore side is 0.02 μm have been used for carrying on the pilot tests of oil extraction wastewater. Under various operating conditions, the suspended solids of ceramic membrane effluent are less than 1.0 mg/L,oil content of effluent is <10 mg/L,and particle diameter median< 1.0 μm. Under different operating conditions, the changes of the membrane pressure difference of the membrane flux of ceramic membranes,the transmembrane pressure difference,and the effect of reinforced coagulation-filtration on membrane flux are investigated. According to the test results, suggestions on further research of applying ceramic membranes to the treatment of oil extraction wastewater are brought forward.

  15. Review of corrosion behavior of ceramic heat exchanger materals: Corrosion characteristics of silicon carbide and silicon nitride. Final report, September 11, 1992--March 11, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Munro, R.G.; Dapkunas, S.J.

    1993-09-01

    The present work is a review of the substantial effort that has been made to measure and understand the effects of corrosion with respect to the properties, performance, and durability of various forms of silicon carbide and silicon nitride. The review encompasses corrosion in diverse environments, usually at temperatures of 1000C or higher. The environments include dry and moist oxygen, mixtures of hot gaseous vapors, molten salts, molten metals, and complex environments pertaining to coal ashes and slags.

  16. Defect production in ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J. [Oak Ridge National Lab., TN (United States); Kinoshita, C. [Kyushu Univ. (Japan)

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  17. Development of Cost-Effective Low-Permeability Ceramic and Refractory Components for Aluminum Melting and Casting

    Energy Technology Data Exchange (ETDEWEB)

    Kadolkar, Puja [ORNL; Ott, Ronald D [ORNL

    2006-02-01

    A recent review by the U.S. Advanced Ceramics Association, the Aluminum Association, and the U.S. Department of Energy's Office of Industrial Technologies (DOE/OIT) described the status of advanced ceramics for aluminum processing, including monolithics, composites, and coatings. The report observed that monolithic ceramics (particularly oxides) have attractive properties such as resistance to heat, corrosion, thermal shock, abrasion, and erosion [1]. However, even after the developments of the past 25 years, there are two key barriers to commercialization: reliability and cost-effectiveness. Industry research is therefore focused on eliminating these barriers. Ceramic coatings have likewise undergone significant development and a variety of processes have been demonstrated for applying coatings to substrates. Some processes, such as thermal barrier coatings for gas turbine engines, exhibit sufficient reliability and service life for routine commercial use. Worldwide, aluminum melting and molten metal handling consumes about 506,000 tons of refractory materials annually. Refractory compositions for handling molten aluminum are generally based on dense fused cast silica or mullite. The microstructural texture is extremely important because an interlocking mass of coarser grains must be bonded together by smaller grains in order to achieve adequate strength. At the same time, well-distributed microscopic pores and cracks are needed to deflect cracks and prevent spalling and thermal shock damage [2]. The focus of this project was to develop and validate new classes of cost-effective, low-permeability ceramic and refractory components for handling molten aluminum in both smelting and casting environments. The primary goal was to develop improved coatings and functionally graded materials that will possess superior combinations of properties, including resistance to thermal shock, erosion, corrosion, and wetting. When these materials are successfully deployed in

  18. Thermally Sprayed Silicon Carbide Coating

    OpenAIRE

    Mubarok, Fahmi

    2014-01-01

    Thermal spraying of silicon carbide (SiC) material is a challenging task since SiC tends to decompose during elevated temperature atmospheric spraying process. The addition of metal or ceramic binders as a matrix phase is necessary to facilitate the bonding of SiC particles, allowing SiC coatings to be deposited. In the conventional procedure, the matrix phase is added through mechanical mixing or mechanical alloying of the powder constituents, making it difficult to achieve homogeneous distr...

  19. Development of nondestructive-evaluation techniques for high-temperature ceramic heat-exchanger components

    Science.gov (United States)

    Kupperman, D. S.; Yuhas, D.; Michaels, T. E.; Michaels, J. E.

    1982-01-01

    An assessment was made of ultrasonic techniques developed to date for nondestructive evaluation of SiC heat exchanger tubes. The results suggest that ultrasonic inspection is a useful and valuable technique for inspecting these tubes, including ceramic butt joints. However, this method alone is currently not sufficiently effective to detect all critical flaws because of (1) the difficulties in following the surface of an out of round tube; (2) the high velocity and thus the large angle of refraction of sound in SiC, which for small diameter tubes leads to significant beam distortion; and (3) insuffient resolution, relative to the small critical flaw size in ceramics, at conventional ultrasonic testing frequencies. The experiments show that higher frequencies (up to 35 MHz) are required for effective wall thickness measurements and detection of laminar type flaws.

  20. 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.

  1. Next generation grinding spindle for cost-effective manufacture of advanced ceramic components

    Energy Technology Data Exchange (ETDEWEB)

    Kovach, J.A.; Laurich, M.A.

    2000-01-01

    Finish grinding of advanced structural ceramics has generally been considered an extremely slow and costly process. Recently, however, results from the High-Speed, Low-Damage (HSLD) program have clearly demonstrated that numerous finish-process performance benefits can be realized by grinding silicon nitride at high wheel speeds. A new, single-step, roughing-process capable of producing high-quality silicon nitride parts at high material removal rates while dramatically reducing finishing costs has been developed.

  2. Microstructural and Mechanical characterization of WC-Co cemented carbides

    OpenAIRE

    Zakia, Rizki

    2013-01-01

    WC-Co cemented carbides are ceramic-metal composite materials made of carbides embedded in a metal phase that acts as a binder. They exhibit an exceptional combination of strength, toughness and wear resistance as a result of the extremely different properties of their two constitutive phases. Consequently, cemented carbides have been positioned as suitable options when selecting materials for tribomechanical applications, and their implementation continues to gain a place in t...

  3. Development of ceramic coatings for metallic components in supercritical water-cooled reactors

    International Nuclear Information System (INIS)

    A series of ceramic coatings have been prepared by spray pyrolysis processes on P91 substrates. Primary results show that coatings obtaining with different coating compositions and procedures can reduce the weight gain of P91 samples by factors of two to ten for exposure times up to 500 hours in deaerated supercritical water at 500oC and 25 MPa. Results also show that the weigh gain of a P91 sample with Al2O3 coating is about nine times less that that of uncoated P91 after exposures for 400 hours in thermally deaerated supercritical water at 650 oC and 25 MPa. These results indicate that the Al2O3 coating shows promise for preventing oxidation of P91 alloy under supercritical water conditions. Ceramic coatings on Zircaloy substrates have also been prepared using a plasma electrolytic oxidation process. After 400 hours of testing in SCW at 500 oC, the samples with ceramic coatings show improved corrosion resistance compared to the bare Zircaloy substrates. (author)

  4. The influence of high-energy impacts on the microstructure of synthesized metal ceramics

    Science.gov (United States)

    Ovcharenko, V. E.; Solonenko, O. P.; Chesnokov, A. E.; Fomin, V. M.

    2012-11-01

    On the example of the metal-ceramic alloy of titanium carbide (TiC) with nickel-chromium (Ni-Cr) binder, the comparative analysis of the influence of different high-energy impacts on the dispersion of the internal structure and phase composition of the synthesized metal ceramics 70 vol % TiC + 30 vol % (Ni-Cr) has been performed for the first time (self-spreading high-temperature synthesis (SSHTS) under pressure, preliminary mechanical activation (MA) of metal components of the initial powder mixture titanium-carbon-nickel-chromium binder, subsequent MA of the whole powder mixture, and intense plastic deformation of the synthesis product). It has been demonstrated that, under intense plastic deformation with extrusion of the high-temperature synthesis product, there a metal-ceramic structure forms containing particles of the nanosized carbide phase of the stoichiometric composition.

  5. Lightweight high performance ceramic material

    Science.gov (United States)

    Nunn, Stephen D [Knoxville, TN

    2008-09-02

    A sintered ceramic composition includes at least 50 wt. % boron carbide and at least 0.01 wt. % of at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb, and Lu, the sintered ceramic composition being characterized by a density of at least 90% of theoretical density.

  6. 多孔碳化硅陶瓷的原位氧化反应制备及其性能%FABRICATION AND PROPERTIES OF POROUS SILICON CARBIDE CERAMICS BY AN IN-SITU OXIDIZING REACTION

    Institute of Scientific and Technical Information of China (English)

    刘施峰; 曾宇平; 江东亮

    2008-01-01

    以SiC为陶瓷骨料,Al2O3作为添加剂,通过原位氧化反应制备了Sic多孔陶瓷,并对其氧化反应特性及性能进行了研究.结果表明:在1 300~1 500℃,随烧结温度的升高,SiC的氧化程度增加,SiC多孔陶瓷的强度逐渐增加,但开口孔隙率有所降低.莫来石相在1 500℃开始生成·当烧结温度升高到1 550℃时,莫来石大量生成,得到了孔结构相互贯通且颈部发育良好的莫来石结合SiC多孔陶瓷;由于在SiC颗粒表面上覆盖了致密的莫来石层,SiC的氧化受到抑制,开口孔隙率因而升高,SiC多孔陶瓷的强度因莫来石的大量生成而增加.由平均粒径为5.0um的SiC,并添加20%(质量分数)Al2O3,经1 550℃烧结2h制备的SiC多孔陶瓷具有良好的性能,其抗弯强度为158.7MPa、开口孔隙率为27.7%.%Porous silicon carbide (SIC) ceramics were prepared in air from SiC by an in-situ oxidizing reaction technique using Al2O3as additive. The oxidizing reaction characteristics and properties of the porous silicon carbide ceramics were studied. With the in-crease in sintering temperature from 1 300℃ to 1 500℃, the oxidation degree of SiC increases and the strength of the porous SiCceramics increases gradually, while the open porosity decreases. MuUite phase appears at 1 500℃. A large amount of mullite isformed and mullite-bonded open porous SiC ceramics with well-developed necks are obtained at 1 550℃. The oxidation of SiC issuppressed at 1 550℃ because the surface of SiC particles is covered by a dense mullite layer, and the open porosity of the ceramicsincreases, while the strength increases sharply. Porous SiC ceramics with good properties can be prepared by using 80% (mass frac-tion, the same below) SiC powder with an average particle size of 5.0um and 20% Al2O3 as raw materials. These porous SiC ceramicsexhibit a flexural strength of 158.7 MPa and an open porosity of 27.7% when sintered at 1 550℃ for 2 h.

  7. Proceedings of the national symposium on materials and processing: functional glass/glass-ceramics, advanced ceramics and high temperature materials

    International Nuclear Information System (INIS)

    With the development of materials science it is becoming increasingly important to process some novel materials in the area of glass, advanced ceramics and high temperature metals/alloys, which play an important role in the realization of many new technologies. Such applications demand materials with tailored specifications. Glasses and glass-ceramics find exotic applications in areas like radioactive waste storage, optical communication, zero thermal expansion coefficient telescopic mirrors, human safety gadgets (radiation resistance windows, bullet proof apparels, heat resistance components etc), biomedical (implants, hyperthermia treatment, bone cement, bone grafting etc). Advanced ceramic materials have been beneficial in biomedical applications due to their strength, biocompatibility and wear resistance. Non-oxide ceramics such as carbides, borides, silicides, their composites, refractory metals and alloys are useful as structural and control rod components in high temperature fission/ fusion reactors. Over the years a number of novel processing techniques like selective laser melting, microwave heating, nano-ceramic processing etc have emerged. A detailed understanding of the various aspects of synthesis, processing and characterization of these materials provides the base for development of novel technologies for different applications. Keeping this in mind and realizing the need for taking stock of such developments a National Symposium on Materials and Processing -2012 (MAP-2012) was planned. The topics covered in the symposium are ceramics, glass/glass-ceramics and metals and materials. Papers relevant to INIS are indexed separately

  8. Development of Cost-Effective Low-Permeability Ceramic and Refractory Components for Aluminum Melting and Casting

    Energy Technology Data Exchange (ETDEWEB)

    Dale E. Brown (Pyrotek); Puja B. Kadolkar (ORNL)

    2005-12-15

    The primary goal of this project was to develop and validate new classes of cost-effective low-permeability ceramic and refractory components for handling molten aluminum in both melting and casting environments. Three approaches were employed with partial to full success to achieve this goal: (1) Develop materials and methods for sealing surface porosity in thermal-shock-resistant ceramic refractories; (2) Develop new ceramic coatings for extreme service in molten aluminum operations, with particular emphasis on coatings based on highly stable oxide phases; and (3) Develop new monolithic refractories designed for lower-permeability applications using controlled porosity gradients and particle size distributions. The results of the research work and the field tests performed utilizing these three approaches are listed below: (1) It was demonstrated that high-density IR heating could be a tool for altering and sealing the surface porosity of fused silica. However, the process was not very cost-effective. (2) A low-cost glaze composition having a coefficient of thermal expansion (CTE) similar to that of a DFS tube was identified and was successfully tested for its integrity and adherence to DFS. Although the glaze acted as a barrier between the molten aluminum and the DFS, persistent porosity and crazing within the glaze affected its performance during the reactivity tests, thus acting as an obstacle in scaling up production of this glaze. (3) Pyrotek's XL glaze showed great success in improving the life of the DFS tubes. Pyrotek has reported an increasing market demand for the XL-coated DFS tubes, which exhibit useful lifetimes three times better than those of uncoated tubes. (4) A computer model to optimize particle size distribution for reduced permeability was developed and successfully applied to casting formulations. Silica riser tubes produced using these new formulations have been tested in a commercial aluminum casting facility and have been reported to

  9. Dental ceramics: An update

    OpenAIRE

    Shenoy Arvind; Shenoy Nina

    2010-01-01

    In the last few decades, there have been tremendous advances in the mechanical properties and methods of fabrication of ceramic materials. While porcelain-based materials are still a major component of the market, there have been moves to replace metal ceramics systems with all ceramic systems. Advances in bonding techniques have increased the range and scope for use of ceramics in dentistry. In this brief review, we will discuss advances in ceramic materials and fabrication techniques. Examp...

  10. Hugoniot equation of state and dynamic strength of boron carbide

    Science.gov (United States)

    Grady, Dennis E.

    2015-04-01

    Boron carbide ceramics have been particularly problematic in attempts to develop adequate constitutive model descriptions for purposes of analysis of dynamic response in the shock and impact environment. Dynamic strength properties of boron carbide ceramic differ uniquely from comparable ceramics. Furthermore, boron carbide is suspected, but not definitely shown, to undergoing polymorphic phase transformation under shock compression. In the present paper, shock-wave compression measurements conducted over the past 40 years are assessed for the purpose of achieving improved understanding of the dynamic equation of state and strength of boron carbide. In particular, attention is focused on the often ignored Los Alamos National Laboratory (LANL) Hugoniot measurements performed on porous sintered boron carbide ceramic. The LANL data are shown to exhibit two compression anomalies on the shock Hugoniot within the range of 20-60 GPa that may relate to crystallographic structure transitions. More recent molecular dynamics simulations on the compressibility of the boron carbide crystal lattice reveal compression transitions that bear similarities to the LANL Hugoniot results. The same Hugoniot data are complemented with dynamic isentropic compression data for boron carbide extracted from Hugoniot measurements on boron carbide and copper granular mixtures. Other Hugoniot measurements, however, performed on near-full-density boron carbide ceramic differ markedly from the LANL Hugoniot data. These later data exhibit markedly less compressibility and tend not to show comparable anomalies in compressibility. Alternative Hugoniot anomalies, however, are exhibited by the near-full-density data. Experimental uncertainty, Hugoniot strength, and phase transformation physics are all possible explanations for the observed discrepancies. It is reasoned that experimental uncertainty and Hugoniot strength are not likely explanations for the observed differences. The notable mechanistic

  11. Hugoniot equation of state and dynamic strength of boron carbide

    Energy Technology Data Exchange (ETDEWEB)

    Grady, Dennis E. [Applied Research Associates, Southwest Division, 4300 San Mateo Blvd NE, A-220, Albuquerque, New Mexico 87110-129 (United States)

    2015-04-28

    Boron carbide ceramics have been particularly problematic in attempts to develop adequate constitutive model descriptions for purposes of analysis of dynamic response in the shock and impact environment. Dynamic strength properties of boron carbide ceramic differ uniquely from comparable ceramics. Furthermore, boron carbide is suspected, but not definitely shown, to undergoing polymorphic phase transformation under shock compression. In the present paper, shock-wave compression measurements conducted over the past 40 years are assessed for the purpose of achieving improved understanding of the dynamic equation of state and strength of boron carbide. In particular, attention is focused on the often ignored Los Alamos National Laboratory (LANL) Hugoniot measurements performed on porous sintered boron carbide ceramic. The LANL data are shown to exhibit two compression anomalies on the shock Hugoniot within the range of 20–60 GPa that may relate to crystallographic structure transitions. More recent molecular dynamics simulations on the compressibility of the boron carbide crystal lattice reveal compression transitions that bear similarities to the LANL Hugoniot results. The same Hugoniot data are complemented with dynamic isentropic compression data for boron carbide extracted from Hugoniot measurements on boron carbide and copper granular mixtures. Other Hugoniot measurements, however, performed on near-full-density boron carbide ceramic differ markedly from the LANL Hugoniot data. These later data exhibit markedly less compressibility and tend not to show comparable anomalies in compressibility. Alternative Hugoniot anomalies, however, are exhibited by the near-full-density data. Experimental uncertainty, Hugoniot strength, and phase transformation physics are all possible explanations for the observed discrepancies. It is reasoned that experimental uncertainty and Hugoniot strength are not likely explanations for the observed differences. The notable

  12. Stabilization of boron carbide via silicon doping.

    Science.gov (United States)

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  13. Development of wear-resistant ceramic coatings for diesel engine components

    Energy Technology Data Exchange (ETDEWEB)

    Naylor, M.G.S. (Cummins Engine Co., Inc., Columbus, IN (United States))

    1992-06-01

    The tribological properties of a variety of advanced coating materials have been evaluated under conditions which simulate the piston ring -- cylinder liner environment near top ring reversal in a heavy duty diesel engine. Coated ring'' samples were tested against a conventional pearlitic grey cast iron liner material using a high temperature reciprocating wear test rig. Tests were run with a fresh CE/SF 15W40lubricant at 200 and 350{degrees}C, with a high-soot, engine-tested oil at 200{degrees}C and with no lubrication at 200{degrees}C. For lowest wear under boundary lubricated conditions, the most promising candidates to emerge from this study were high velocity oxy-fuel (HVOF) Cr{sub 3} C{sub 2} - 20% NiCr and WC - 12% Co cermets, low temperature arc vapor deposited (LTAVD) CrN and plasma sprayed chromium oxides. Also,plasma sprayed Cr{sub 2}O{sub 3} and A1{sub 2}O{sub 3}-ZrO{sub 2} materials were found to give excellent wear resistance in unlubricated tests and at extremely high temperatures (450{degrees}C) with a syntheticoil. All of these materials would offer substantial wear reductions compared to the conventional electroplated hard chromium ring facing and thermally sprayed metallic coatings, especially at high temperatures and with high-soot oils subjected to degradation in diesel environments. The LTAVD CrN coating provided the lowest lubricated wear rates of all the materials evaluated, but may be too thin (4 {mu}m) for use as a top ring facing. Most of the coatings evaluated showed higher wear rates with high-soot, engine-tested oil than with fresh oil, with increases of more than a factor of ten in some cases. Generally, metallic materials were found to be much more sensitive to soot/oil degradation than ceramic and cermet coatings. Thus, decreased soot sensitivity'' is a significant driving force for utilizing ceramic or cermet coatings in diesel engine wear applications.

  14. Testing Boron Carbide and Silicon Carbide under Triaxial Compression

    Science.gov (United States)

    Anderson, Charles; Chocron, Sidney; Nicholls, Arthur

    2011-06-01

    Boron Carbide (B4C) and silicon carbide (SiC-N) are extensively used as armor materials. The strength of these ceramics depends mainly on surface defects, hydrostatic pressure and strain rate. This article focuses on the pressure dependence and summarizes the characterization work conducted on intact and predamaged specimens by using compression under confinement in a pressure vessel and in a thick steel sleeve. The techniques used for the characterization will be described briefly. The failure curves obtained for the two materials will be presented, although the data are limited for SiC. The data will also be compared to experimental data from Wilkins (1969), and Meyer and Faber (1997). Additionally, the results will be compared with plate-impact data.

  15. Methods of Si based ceramic components volatilization control in a gas turbine engine

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Crespo, Andres Jose; Delvaux, John; Dion Ouellet, Noemie

    2016-09-06

    A method of controlling volatilization of silicon based components in a gas turbine engine includes measuring, estimating and/or predicting a variable related to operation of the gas turbine engine; correlating the variable to determine an amount of silicon to control volatilization of the silicon based components in the gas turbine engine; and injecting silicon into the gas turbine engine to control volatilization of the silicon based components. A gas turbine with a compressor, combustion system, turbine section and silicon injection system may be controlled by a controller that implements the control method.

  16. PPTC(Ceramic Positive Temperature Coefficent)-components protect electric motors, control systems and transformers; PPTC-Bausteine schuetzen Elektromotoren und Steuerungen sowie Transformatoren

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Faraz [Tyco Electronics, Menlo Park, CA (United States). Raychem Circuit Protection Products

    2009-03-09

    PPTC(Ceramic Positive Temperature Coefficent)-components offer protection for power supply systems, transformers, industrial control systems and electric motors against overpower and over temperature. They protect electronics against inductive conditioned voltage peaks, short term over volatges as not correctly connected or dipoled power supply systems. (orig./GL)

  17. Phase Diagram Calculation and Fabrication of Multi-component Zirconia-Based Ceramics%多元氧化锆基陶瓷材料的相图计算和制备

    Institute of Scientific and Technical Information of China (English)

    黄水根; 李麟

    2005-01-01

    @@ Ceria-yttria co-doped zirconia-based multi-components ceramics, with superfine alumina dispersed in the matrix, possess excellent fracture toughness,strength and thermal stability. However, the mechanical properties and microstructure are strongly dependent on the composition and the fabrication procedure, especially the composition of zirconia containing multi-component ceramics.

  18. Thin Film Heat Flux Sensor Development for Ceramic Matrix Composite (CMC) Systems

    Science.gov (United States)

    Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.; Zhu, Dongming; Laster, Kimala L.; Gonzalez, Jose M.; Gregory, Otto J.

    2010-01-01

    The NASA Glenn Research Center (GRC) has an on-going effort for developing high temperature thin film sensors for advanced turbine engine components. Stable, high temperature thin film ceramic thermocouples have been demonstrated in the lab, and novel methods of fabricating sensors have been developed. To fabricate thin film heat flux sensors for Ceramic Matrix Composite (CMC) systems, the rough and porous nature of the CMC system posed a significant challenge for patterning the fine features required. The status of the effort to develop thin film heat flux sensors specifically for use on silicon carbide (SiC) CMC systems with these new technologies is described.

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

    International Nuclear Information System (INIS)

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

  20. Dynamic properties of ceramic materials

    International Nuclear Information System (INIS)

    The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis of shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process

  1. Biomimetic component coating on 3D scaffolds using high bioactivity of mesoporous bioactive ceramics

    Directory of Open Access Journals (Sweden)

    Yun HS

    2011-10-01

    Full Text Available Hui-suk Yun1, Sang-Hyun Kim2, Dongwoo Khang3, Jungil Choi4, Hui-hoon Kim2, Minji Kang31Functional Materials Division, Korea Institute of Materials Science, Gyeongnam, Korea; 2Department of Pharmacology, School of Medicine, Kyungpook National University, Jung-Gu, Daegu, Korea; 3School of Nano and Advanced Materials Science and Engineering and Center for NMBE, Gyeongsang National University, Jinju, Korea; 4Department of Anatomy, Institute of Health Science and School of Medicine, Gyeongsang National University, Jinju, Gyeongnam, KoreaBackground: Mesoporous bioactive glasses (MBGs are very attractive materials for use in bone tissue regeneration because of their extraordinarily high bone-forming bioactivity in vitro. That is, MBGs may induce the rapid formation of hydroxy apatite (HA in simulated body fluid (SBF, which is a major inorganic component of bone extracellular matrix (ECM and comes with both good osteoconductivity and high affinity to adsorb proteins. Meanwhile, the high bioactivity of MBGs may lead to an abrupt initial local pH variation during the initial Ca ion-leaching from MBGs at the initial transplant stage, which may induce unexpected negative effects on using them in in vivo application. In this study we suggest a new way of using MBGs in bone tissue regeneration that can improve the strength and make up for the weakness of MBGs. We applied the outstanding bone-forming bioactivity of MBG to coat the main ECM components HA and collagen on the MBG-polycarplolactone (PCL composite scaffolds for improving their function as bone scaffolds in tissue regeneration. This precoating process can also expect to reduce initial local pH variation of MBGs.Methods and materials: The MBG-PCL scaffolds were immersed in the mixed solution of the collagen and SBF at 37°C for 24 hours. The coating of ECM components on the MBG-PCL scaffolds and the effect of ECM coating on in vitro cell behaviors were confirmed.Results: The ECM components were fully

  2. Preparation of Silicon Carbide with High Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to prepare silicon carbide with high properties, three kinds of SiC powders A, B, and C with different composition and two kinds of additives, which were Y2O3-Al2O3 system and Y2O3-La2O3 system, were used in this experiment. The properties of hot-pressed SiC ceramics were measured. With the same additives, different SiC powder resulted in different properties. On the other hand, with the same SiC powder, increasing the amount of the additive Y2O3-Al2O3 improved properties of SiC ceramics at room temperature, and increasing the amount of the additive Y2O3-La2O3 improved property SiC ceramics at elevated temperature. In addition, the microstructure of SiC ceramics was studied by scanning electron microscopy.

  3. Analytical Micromechanics Modeling Technique Developed for Ceramic Matrix Composites Analysis

    Science.gov (United States)

    Min, James B.

    2005-01-01

    Ceramic matrix composites (CMCs) promise many advantages for next-generation aerospace propulsion systems. Specifically, carbon-reinforced silicon carbide (C/SiC) CMCs enable higher operational temperatures and provide potential component weight savings by virtue of their high specific strength. These attributes may provide systemwide benefits. Higher operating temperatures lessen or eliminate the need for cooling, thereby reducing both fuel consumption and the complex hardware and plumbing required for heat management. This, in turn, lowers system weight, size, and complexity, while improving efficiency, reliability, and service life, resulting in overall lower operating costs.

  4. Cost effective machining and inspection of structural ceramic components for advanced high temperature application. Final CRADA report for CRADA number Y-1292-0151

    Energy Technology Data Exchange (ETDEWEB)

    Abbatiello, L.A. [Lockheed Martin Energy Systems, Inc., Oak Ridge, TN (United States); Haselkorn, M. [Caterpillar, Inc., Peoria, IL (United States)

    1996-11-29

    This Cooperative Research and Development Agreement (CRADA) was a mutual research and development (R and D) effort among the participants to investigate a range of advanced manufacturing technologies for two silicon nitride (Si{sub 3}N{sub 4}) ceramic materials. The general objective was to identify the most cost-effective part manufacturing processes for the ceramic materials of interest. The focus was determining the relationship between material removal rates, surface quality, and the structural characteristics of each ceramic resulting from three innovative processes. These innovated machining processes were studied using silicon nitride advanced materials. The particular (Si{sub 3}N{sub 4}) materials of interest were sintered GS-44 from the Norton Company, and reaction-bonded Ceraloy 147-3. The processes studied included the following activities: (1) direct laser machining; (2) rotary ultrasonic machining; and (3) diamond abrasive grinding, including both resinoid and vitreous-bonded grinding wheels. Both friable and non-friable diamond types were included within the abrasive grinding study. The task also conducted a comprehensive survey of European experience in use of ceramic materials, principally aluminum oxide. Originally, the effort of this task was to extend through a prototype manufacturing demonstration of selected engine components. During the execution of this program, however changes were made to the scope of the project, altering the goals. The Program goal became only the development of assessment of their impacts on product strength and surface condition.

  5. The Affordable Pre-Finishing of Silicon Carbide for Optical Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Creare proposes to develop a novel, laser-assisted, pre-finishing process for chemical vapor deposition (CVD) coated silicon-carbide ceramics. Our innovation will...

  6. Oxidation Behavior of Carbon Nanoparticles/Silicon Carbide Composite Ceramics%纳米碳颗粒/碳化硅陶瓷基复合材料的氧化行为

    Institute of Scientific and Technical Information of China (English)

    陆有军; 王燕民; 吴澜尔; 黄振坤

    2013-01-01

    以微米硅(Si)和纳米碳黑(Cp)粉体为主要原料,采用经机械化学法合成的碳化硅(SiC)和15%和25%的纳米碳颗粒与碳化硅(Cp-SiC)的复合粉体,并经无压烧结得到了Cp/SiC陶瓷基复合材料,分析了在不同温度条件下Cp/SiC烧结体的氧化行为。结果表明:当温度小于700℃时,Cp/SiC复合陶瓷在空气中的氧化受C-O2反应控制,致使其为均匀氧化;700℃时,氧化后的复合材料显气孔率最大,弯曲强度达极小值;大于700℃,氧化过程受O2的气相扩散控制,呈非均匀氧化;700~900℃之间,O2通过微裂纹的扩散控制着Cp/SiC的氧化过程;900~1100℃之间,O2通过SiC缺陷的扩散控制着Cp/SiC的氧化过程,并在1000℃时的最初的2 h内,复合材料弯曲强度增大,且达到了极大值。同时表明,纳米碳含量是影响复合材料强度及氧化行为的关键因素,添加纳米碳质量分数为15%的Cp/SiC复合陶瓷可以作为一种抗氧化性能优良的玻璃夹具材料。%The oxidation behavior of three pressureless-sintered silicon carbide (SiC), 15%Cp/SiC and 25%Cp/SiC composites,which were prepared with carbon nanoparticles (Cp) and silicon micron-sized particles by a mechanochemical method, at various tempera-tures was investigated. The results show that the oxidation of Cp/SiC ceramics in air is controlled via C+O2 reaction at<700℃, the bending strength of samples decreases to a minimum value at 700℃; the oxidation is controlled by O2 diffusion through mi-cro-cracks unequally in the range of 700-900℃;the oxidation of Cp/SiC is controlled by O2 diffusion through the structural defects of matrix in the range of 900-1 100℃. The bending strength of composites reaches to a maximum value during initial 2 h at 1 000℃due to the formation of SiO2 layer and the healing defects of matrix. It is also indicated that the addition of Cp in the composite has an effect on the bending strength and the

  7. Electron-Spin Resonance in Boron Carbide

    Science.gov (United States)

    Wood, Charles; Venturini, Eugene L.; Azevedo, Larry J.; Emin, David

    1987-01-01

    Samples exhibit Curie-law behavior in temperature range of 2 to 100 K. Technical paper presents studies of electron-spin resonance of samples of hot pressed B9 C, B15 C2, B13 C2, and B4 C. Boron carbide ceramics are refractory solids with high melting temperatures, low thermal conductives, and extreme hardnesses. They show promise as semiconductors at high temperatures and have unusually large figures of merit for use in thermoelectric generators.

  8. SHS/PHIP of ceramic composites using ilmenite concentrate

    Energy Technology Data Exchange (ETDEWEB)

    Kholghy, M. [Yerevan State University and Isfahan University of Technology, Dept. of Materials Eng (Iran, Islamic Republic of); Kharatyan, S. [Yerevan State University, Yerevan, A. Manukyan str. 1, AM-0025 (Armenia); Edris, H., E-mail: h-edris@cc.iut.ac.i [Isfahan University of Technology, Dept. of Materials Eng. Isfahan, 8415683111 (Iran, Islamic Republic of)

    2010-07-23

    Self-propagating high-temperature synthesis (SHS) process in the mixture of ilmenite, boron carbide and aluminum combined with a pseudo hot isostatic pressing (PHIP) is used in this research to produce a compact multi-ceramic composite Al{sub 2}O{sub 3}/TiB{sub 2}/TiC with Fe as a binder. Several tests were performed to identify the optimum partial weight percent of the ilmenite, boron carbide and aluminum to produce a suitable amount of each components of the product. On the other hand, a number of tests were performed to measure the delay time, optimum compaction time and optimum compaction force to produce a compact high toughness samples. The results of phase analysis using XRD tests and microstructure using SEM and EDS show that the product is a multi-ceramic composite of the Al{sub 2}O{sub 3}/TiB{sub 2}/TiC with Fe as a binder. It was shown that there are no primary reactants in the product. In this work, the combustion characteristics (combustion wave propagation velocity and temperature) of the process, as well as density and hardness of the combustion product were measured. The fracture toughness of the product was measured using Vickers indenter and Brazilian test. This shows that the samples have a high toughness in comparison to conventional ceramics.

  9. Assessment of strength limiting flaws in ceramic heat exchanger components: Phase 1, Final report, September 28, 1984-June 30, 1986

    Energy Technology Data Exchange (ETDEWEB)

    Powers, T.; Snyder, J.

    1986-10-01

    Assurance of energy efficient design lifetimes of high temperature structural ceramics requires the ability to specify acceptance criteria and to test to those criteria. These criteria will be established through nondestructive testing, to determine which defects are detectable, together with fracture mechanics, to calculate effects of indetectable flaws. The first phase of this program is to examine heat exchanger material with four test methods which have shown promise for use in ceramics; ultrasonic scanning, microfocus x-ray, Scanning Laser Acoustic Microscope, and Acoustic Holography. The capabilities, limits, and potential for improvement of these are presented in this report. Destructive testing, material sectioning, and fractography are included. 24 refs., 68 figs., 6 tabs.

  10. Influence of sputtering power on components and mechanical properties of boron carbide films%溅射功率对碳化硼薄膜组分与力学性能的影响

    Institute of Scientific and Technical Information of China (English)

    张玲; 何智兵; 李俊; 许华; 谌家军

    2013-01-01

    Boron carbide films were fabricated by radio frequency magnetron sputtering at different sputtering powers.The structure and components of the boron carbide films were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.Using MTS Nano Indenter XP with CSM method,the hardness and modulus of the boron carbide films were analyzed.The results show that B prefers to combining with C to form B-C bond as the RF power increases.When the sputtering power reaches 250 W,the number of B-C bonds is the most,and the atomic concentration ratio between B and C reaches to the maximum of 5.66.Both the hardness and modulus of the boron carbide films increase firstly and then decrease with the sputtering powers increasing.Both of them reach to the maximum of 28.22 GPa and 314.62 GPa,respectively.%采用射频磁控溅射技术,在不同溅射功率条件下制备了碳化硼薄膜,并用X射线光电子能谱(XPS)和傅里叶变换红外吸收光谱(FT-IR)对碳化硼薄膜的组分进行了定量表征,分析了功率变化对碳化硼组分的影响.利用纳米压入仪通过连续刚度法(CSM)对碳化硼薄膜的硬度和模量等力学性能进行了分析.研究表明:随着功率的增大,硼与碳更易结合形成B-C键,在功率增大到250 W时,B-C键明显增多;在250 W时,硼与碳的原子分数比出现了最大值5.66;碳化硼薄膜的硬度与模量都随功率的增大呈现出先增大后减小的趋势,且在250 W时均出现了最大值,分别为28.22 GPa和314.62 GPa.

  11. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    Science.gov (United States)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  12. Development of wear-resistant ceramic coatings for diesel engine components. Volume 1, Coating development and tribological testing: Final report: DOE/ORNL Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    Naylor, M.G.S. [Cummins Engine Co., Inc., Columbus, IN (United States)

    1992-06-01

    The tribological properties of a variety of advanced coating materials have been evaluated under conditions which simulate the piston ring -- cylinder liner environment near top ring reversal in a heavy duty diesel engine. Coated ``ring`` samples were tested against a conventional pearlitic grey cast iron liner material using a high temperature reciprocating wear test rig. Tests were run with a fresh CE/SF 15W40lubricant at 200 and 350{degrees}C, with a high-soot, engine-tested oil at 200{degrees}C and with no lubrication at 200{degrees}C. For lowest wear under boundary lubricated conditions, the most promising candidates to emerge from this study were high velocity oxy-fuel (HVOF) Cr{sub 3} C{sub 2} - 20% NiCr and WC - 12% Co cermets, low temperature arc vapor deposited (LTAVD) CrN and plasma sprayed chromium oxides. Also,plasma sprayed Cr{sub 2}O{sub 3} and A1{sub 2}O{sub 3}-ZrO{sub 2} materials were found to give excellent wear resistance in unlubricated tests and at extremely high temperatures (450{degrees}C) with a syntheticoil. All of these materials would offer substantial wear reductions compared to the conventional electroplated hard chromium ring facing and thermally sprayed metallic coatings, especially at high temperatures and with high-soot oils subjected to degradation in diesel environments. The LTAVD CrN coating provided the lowest lubricated wear rates of all the materials evaluated, but may be too thin (4 {mu}m) for use as a top ring facing. Most of the coatings evaluated showed higher wear rates with high-soot, engine-tested oil than with fresh oil, with increases of more than a factor of ten in some cases. Generally, metallic materials were found to be much more sensitive to soot/oil degradation than ceramic and cermet coatings. Thus, decreased ``soot sensitivity`` is a significant driving force for utilizing ceramic or cermet coatings in diesel engine wear applications.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guillard, F

    2006-12-15

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

  14. In-situ EBCs for High Performance Composite Propulsion Components Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Silicon Carbide based ceramic matrix composites (CMCs) offer the potential to fundamentally change the design and manufacture of aeronautical and space propulsion...

  15. Carbon nanotube-ceramic nanocomposites: Synthesis and characterization

    Science.gov (United States)

    Clark, Michael David

    Ceramic materials are widely used in modern society for a variety of applications including fuel cell electrolytes, bio-medical implants, and jet turbines. However, ceramics are inherently brittle making them excellent candidates for mechanical reinforcement. In this work, the feasibility of dispersing multi-walled carbon nanotubes into a silicon carbide matrix for mechanical property enhancement is explored. Prior to dispersing, nanotubes were purified using an optimized, three step methodology that incorporates oxidative treatment, acid sonication, and thermal annealing rendering near-superhydrophobic behavior in synthesized thin films. Alkyl functionalized nanotube dispersability was characterized in various solvents. Dispersability was contingent on fostering polar interactions between the functionalized nanotubes and solvent despite the purely dispersive nature of the aliphatic chains. Interpretation of these results yielded values of 45.6 +/- 1.2, 0.78 +/- 0.04, and 2 4 +/- 0.9 mJ/m2 for the Lifshitz-van der Waals, electron acceptor and electron donor surface energy components respectively. Aqueous nanotube dispersions were prepared using a number of surfactants to examine surfactant concentration and pH effects on nanotube dispersability. Increasing surfactant concentrations resulted in a solubility plateau, which was independent of the surfactant's critical micelle concentration. Deviations from neutral pH demonstrated negligible influence on non-ionic surfactant adsorption while, ionic surfactants showed substantial pH dependent behavior. These results were explained in the context of nanotube surface ionization and Debye length variation. Successful MWNT dispersion into a silicon carbide based matrix is reported by in-situ ceramic formation using two routes; sol-gel chemistry and pre-ceramic polymeric precursor workup. For the former, nanotube dispersion was assisted by PluronicRTM surfactants. Pyrolytic treatment and consolidation of formed powders

  16. Bioactivation of biomorphous silicon carbide bone implants.

    Science.gov (United States)

    Will, Julia; Hoppe, Alexander; Müller, Frank A; Raya, Carmen T; Fernández, Julián M; Greil, Peter

    2010-12-01

    Wood-derived silicon carbide (SiC) offers a specific biomorphous microstructure similar to the cellular pore microstructure of bone. Compared with bioactive ceramics such as calcium phosphate, however, silicon carbide is considered not to induce spontaneous interface bonding to living bone. Bioactivation by chemical treatment of biomorphous silicon carbide was investigated in order to accelerate osseointegration and improve bone bonding ability. Biomorphous SiC was processed from sipo (Entrandrophragma utile) wood by heating in an inert atmosphere and infiltrating the resulting carbon replica with liquid silicon melt at 1450°C. After removing excess silicon by leaching in HF/HNO₃ the biomorphous preform consisted of β-SiC with a small amount (approximately 6wt.%) of unreacted carbon. The preform was again leached in HCl/HNO₃ and finally exposed to CaCl₂ solution. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared analyses proved that oxidation of the residual carbon at the surface induced formation of carboxyl [COO⁻] groups, which triggered adsorption of Ca(2+), as confirmed by XPS and inductively coupled plasma optical emission spectroscopy measurements. A local increase in Ca(2+) concentration stimulated in vitro precipitation of Ca₅(PO₄)₃OH (HAP) on the silicon carbide preform surface during exposure to simulated body fluid, which indicates a significantly increased bone bonding activity compared with SiC.

  17. Silicon carbide microsystems for harsh environments

    CERN Document Server

    Wijesundara, Muthu B J

    2011-01-01

    Silicon Carbide Microsystems for Harsh Environments reviews state-of-the-art Silicon Carbide (SiC) technologies that, when combined, create microsystems capable of surviving in harsh environments, technological readiness of the system components, key issues when integrating these components into systems, and other hurdles in harsh environment operation. The authors use the SiC technology platform suite the model platform for developing harsh environment microsystems and then detail the current status of the specific individual technologies (electronics, MEMS, packaging). Additionally, methods

  18. A study on the production of titanium carbide nano-powder in the nanostate and its properties

    Science.gov (United States)

    Shiryaeva, L. S.; Rudneva, S. V.; Galevsky, G. V.; Garbuzova, A. K.

    2016-09-01

    The plasma synthesis of titanium carbide nano-powder in the conditions close to industrial was studied. Titanium carbide TiC is a wear- and corrosion-resistant, hard, chemically inert material, demanded in various fields for the production of hard alloys, metal- ceramic tools, heat-resistant products, protective metal coatings. New perspectives for application titanium carbide in the nanostate can be found in the field of alloys modification with different composition and destination.

  19. Optical and optomechanical ultralightweight C/SiC components

    Science.gov (United States)

    Papenburg, Ulrich; Pfrang, Wilhelm; Kutter, G. S.; Mueller, Claus E.; Kunkel, Bernd P.; Deyerler, Michael; Bauereisen, Stefan

    1999-11-01

    Optical and optomechanical structures based on silicon carbide (SiC) ceramics are becoming increasingly important for ultra- lightweight optical systems that must work in adverse environments. At IABG and Dornier Satellite Systems (DSS) in Munich, a special form of SiC ceramics carbon fiber reinforced silicon carbide (C/SiCR) has been developed partly under ESA and NASA contracts. C/SiCR is a light-weight, high- strength engineering material that features tunable mechanical and thermal properties. It offers exceptional design freedom due to its reduced brittleness and negligible volume shrinkage during processing in comparison to traditional, powder-based ceramics. Furthermore, its rapid fabrication process produces near-net-shape components using conventional NC machining/milling equipment and, thus, provides substantial schedule, cost, and risk savings. These characteristics allow C/SiCR to overcome many of the problems associated with more traditional optical materials. To date, C/SiCR has been used to produce ultra-lightweight mirrors and reflectors, antennas, optical benches, and monolithic and integrated reference structures for a variety of space and terrestrial applications. This paper describes the material properties, optical system and structural design aspects, the forming and manufacturing process including high-temperature joining technology, precision grinding and cladding techniques, and the performance results of a number of C/SiCR optical components we have built.

  20. Diffusion in ceramics

    CERN Document Server

    Pelleg, Joshua

    2016-01-01

    This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. Solutions of Fick’s second law for constant D, diffusion in grain boundaries and dislocations are presented along with a look at the atomistic approach for the random motion of atoms. In the second part, the author discusses diffusion in several technologically important ceramics. The ceramics selected are monolithic single phase ones, including: A12O3, SiC, MgO, ZrO2 and Si3N4. Of these, three refer to oxide ceramics (alumina, magnesia and zirconia). Carbide based ceramics are represented by the technologically very important Si-ca...

  1. Advanced microstructure of boron carbide.

    Science.gov (United States)

    Werheit, Helmut; Shalamberidze, Sulkhan

    2012-09-26

    The rhombohedral elementary cell of the complex boron carbide structure is composed of B(12) or B(11)C icosahedra and CBC, CBB or B□B (□, vacancy) linear arrangements, whose shares vary depending on the actual chemical compound. The evaluation of the IR phonon spectra of isotopically pure boron carbide yields the quantitative concentrations of these components within the homogeneity range. The structure formula of B(4.3)C at the carbon-rich limit of the homogeneity range is (B(11)C) (CBC)(0.91) (B□B)(0.09) (□, vacancy); and the actual structure formula of B(13)C(2) is (B(12))(0.5)(B(11)C)(0.5)(CBC)(0.65)(CBB)(0.16) (B□B)(0.19), and deviates fundamentally from (B(12))CBC, predicted by theory to be the energetically most favourable structure of boron carbide. In reality, it is the most distorted structure in the homogeneity range. The spectra of (nat)B(x)C make it evident that boron isotopes are not randomly distributed in the structure. However, doping with 2% silicon brings about a random distribution.

  2. Portfolio: Ceramics.

    Science.gov (United States)

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  3. Experimental investigation on flank wear and tool life, cost analysis and mathematical model in turning hardened steel using coated carbide inserts

    Directory of Open Access Journals (Sweden)

    Ashok Kumar Sahoo

    2013-10-01

    Full Text Available Turning hardened component with PCBN and ceramic inserts have been extensively used recently and replaces traditional grinding operation. The use of inexpensive multilayer coated carbide insert in hard turning is lacking and hence there is a need to investigate the potential and applicability of such tools in turning hardened steels. An attempt has been made in this paper to have a study on turning hardened AISI 4340 steel (47 ± 1 HRC using coated carbide inserts (TiN/TiCN/Al2O3/ZrCN under dry environment. The aim is to assess the tool life of inserts and evolution of flank wear with successive machining time. From experimental investigations, the gradual growth of flank wear for multilayer coated insert indicates steady machining without any premature tool failure by chipping or fracturing. Abrasion is found to be the dominant wear mechanisms in hard turning. Tool life of multilayer coated carbide inserts has been found to be 31 minute and machining cost per part is Rs.3.64 only under parametric conditions chosen i.e. v = 90 m/min, f = 0.05 mm/rev and d = 0.5 mm. The mathematical model shows high determination coefficient, R2 (99% and fits the actual data well. The predicted flank wear has been found to lie very close to the experimental value at 95% confidence level. This shows the potential and effectiveness of multilayer coated carbide insert used in hard turning applications.

  4. 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.)

  5. High-temperature carbidization of carboniferous rocks

    Science.gov (United States)

    Goldin, B. A.; Grass, V. E.; Nadutkin, A. V.; Nazarova, L. Yu.

    2009-08-01

    Processes of thermal metamorphism of carboniferous rocks have been studied experimentally. The conditions of high-temperature interaction of shungite carbon with components of the contained rocks, leading to formation of carbide compounds, have been determined. The results of this investigation contribute to the works on searching for new raw material for prospective material production.

  6. High-performance ceramic filters for energy engineering. Final report; Filter aus Hochleistungskeramik fuer die Energietechnik. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Westerheide, R. [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany); Adler, J. [Fraunhofer-Institut fuer Keramische Technologien und Sinterwerkstoffe (IKTS), Dresden (Germany); Buhl, H. [ESK-SIC GmbH, Frechen-Grefrath (Germany); Fister, D. [H.C. Starck GmbH, Laufenburg (Germany); Krein, J. [LLB Lurgi Lentjes Energietechnik GmbH, Frankfurt (Germany); Voelker, W. [Annawerk GmbH, Roedental (Germany); Walch, A. [eds.] [USF Schumacher Umwelt- und Trenntechnik GmbH, Crailsheim (Germany)

    1999-09-30

    The hot gas particulate removal of many advanced coal fired power generation technologies works at temperatures above 800 C. The filter elements for these applications are often based on ceramic materials, e.g. silicon carbide. However, the mostly clay bonded silicon carbide is subject to creep and oxidation due to probable changes of the binder phase. In this work the development of new ceramic filter materials based on silicon carbide and alumina is described. The goal of the development was to increase the potential application temperature. To obtain the goal, the work was performed together with ceramic powder manufacturers, developers of ceramic materials and components as well as with companies who operate test facilities. Different routes were chosen to increase the high temperature resistance in consideration of corrosion resistance, fracture strength and pressure loss of the filter materials. One of these routes was the optimization of the binder phase of the silicon carbide materials. Other routes were concentrated on the base material and the investigation of other possibilities for the silicon carbide bonding, i.e. a recrystallization process of SiC (RSiC) or a self bonding of granulated small grained silicon carbide powder. Additionally filter materials based on alumina were developed. The report covers these material development oriented topics as well as the additional work in materials reliability, coating development and modeling of microstructure. (orig.) [German] In der Kombikraftwerkstechnik wird insbesondere bei Kohlefeuerung die Heissgasreinigung oft bei Temperaturen ueber 800 C eingesetzt. Die Filterelemente fuer diese Anwendungen bestehen oft aus keramischen Materialien. Das haeufig eingesetzte tongebundene Siliciumcarbid unterliegt jedoch besonders aufgrund der Beschaffenheit der Bindephase Kriech- und Oxidationsschaedigungen. In diesem Bericht wird die Entwicklung von neuen keramischen Filtermaterialien, die auf Siliciumcarbid oder

  7. Selective-area laser deposition (SALD) Joining of silicon carbide with silicon carbide filler

    Science.gov (United States)

    Harrison, Shay Llewellyn

    Selective Area Laser Deposition (SALD) is a gas-phase, solid freeform fabrication (SFF) process that utilizes a laser-driven, pyrolytic gas reaction to form a desired solid product. This solid product only forms in the heated zone of the laser beam and thus can be selectively deposited by control of the laser position. SALD Joining employs the SALD method to accomplish 'welding' of ceramic structures together. The solid reaction product serves as a filler material to bond the two parts. The challenges involved with ceramic joining center around the lack of a liquid phase, little plastic deformation and diffusivity and poor surface wetting for many ceramic materials. Due to these properties, traditional metal welding procedures cannot be applied to ceramics. Most alternative ceramic welding techniques use some form of a metal addition to overcome these material limitations. However, the metal possesses a lower ultimate use temperature than the ceramic substrate and therefore it decreases the temperature range over which the joined part can be safely used. SALD Joining enjoys several advantages over these ceramic welding procedures. The solid filler material chemistry can be tailored to match the type of ceramic substrate and therefore fabricate monolithic joints. The SALD filler material bonds directly to the substrate and the joined structure is made in a one step process, without any post-processing. The research documented in this dissertation focused on SALD Joining of silicon carbide structures with silicon carbide filler material. A historical progression of gas-phase SFF research and a literature review of the most prominent ceramic joining techniques are provided. A variety of SiC substrates were examined, as were various conditions of gas precursor pressures and mixtures, laser beam scan speed and joint configuration. The SALD material was characterized for composition and structure by x-ray diffraction, transmission electron microscopy and nuclear magnetic

  8. Study on solder joint reliability of ceramic ball grid array component based on design of experiment method

    Institute of Scientific and Technical Information of China (English)

    Wu Zhaohua; Huang Chunyue; Zhou Dejian

    2006-01-01

    Four process parameters, pad diameter, stencil thickness, ball diameter and stand-off were chosen as four control factors.By using an L25 ( 56 ) orthogonal array the ceramic ball grid array ( CBGA ) solder joints which have 25 different combinations of process parameters were designed.The numerical models of all the 25 CBGA solder joints were developed using the Surface Evolver.Utilizing the surface coordinate exported from the 25 CBGA solder joints numerical models, the finite element analysis models were set up and the nonlinear finite element analysis of the CBGA solder joints under thermal cycles were performed by ANSYS.The thermal fatigne life of CBGA solder joint was calculated using Coffin-Manson equation.Based on the calculated thermal fatigue life results, the range analysis and the variance analysis were performed.The results show that the fatigue life of CBGA solder joint is affected by the pad diameter, the stencil thickness, the ball diameter and the standoff in a descending order, the best combination of process parameters results in the longest fatigue life is 0.07 mm stand-off,0.125 mm stencil thickness of, 0.85 mm ball diameter and 0.89 mm pad diameter.With 95% confidence the pad diameter has a significant effect on the reliability of CBGA solder joints whereas the stand-off, the stencil thickness and the ball diameter have little effect on the reliability of CBGA solder joints.

  9. Ceramic Technology Project

    Energy Technology Data Exchange (ETDEWEB)

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  10. Making Ceramic Reference Specimens Containing Seeded Voids

    Science.gov (United States)

    Baaklini, George Y.; Klima, Stanley J.; Roth, Don J.

    1994-01-01

    Internal and surface voids of known sizes incorporated into silicon carbide and silicon nitride ceramic reference specimens at prescribed locations. Specimens used to demonstrate sensitivity and resolution in nondestructive examination techniques like scanning laser acoustic microscopy and x-radiography, and to assist in establishing proper examination procedures.

  11. a Study on the Role of Sintering Additives for Fabrication of sic Ceramic

    Science.gov (United States)

    Yoon, Han Ki; Lee, Young Ju; Cho, Ho Jun; Kim, Tae Gyu

    Silicon carbide (SiC) materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. The SiC ceramics have been fabricated by a NITE (Nano Infiltration Transient Eutectic Phase) Process, using Nano-SiC powder. The sintering additives used for forming liquid phase under sintering process, used the sintering additives ratios were an Al2O3-Y2O3 system or add SiO2 contents. A major R&D focus for the SiC ceramics is the production to obtain high purity SiC ceramics. In this study, we investigated roles of the sintering additives(Al2O3:Y2O3) to fabrication of the SiC ceramics. The effects of SiO2 contents and density properties of the SiC ceramics were also investigated. To investigate the effects of SiO2, Al2O3/Y2O3 composition were fixed and then SiO2 ratios were changed as several kinds, and to confirm the effects of sintering additives ratios (Al2O3:Y2O3) they were changed between 4:6 and 6:4 in x wt.%.

  12. Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor

    Science.gov (United States)

    Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

    2001-01-01

    A process for producing polycrystalline silicon carbide by heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

  13. High pressure ceramic joint

    Science.gov (United States)

    Ward, Michael E.; Harkins, Bruce D.

    1993-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  14. Ceramic/polymer functionally graded material (FGM) lightweight armor system

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.; McClellan, K.J.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Functionally graded material is an enabling technology for lightweight body armor improvements. The objective was to demonstrate the ability to produce functionally graded ceramic-polymer and ceramic-metal lightweight armor materials. This objective involved two aspects. The first and key aspect was the development of graded-porosity boron-carbide ceramic microstructures. The second aspect was the development of techniques for liquid infiltration of lightweight metals and polymers into the graded-porosity ceramic. The authors were successful in synthesizing boron-carbide ceramic microstructures with graded porosity. These graded-porosity boron-carbide hot-pressed pieces were then successfully liquid-infiltrated in vacuum with molten aluminum at 1,300 C, and with liquid polymers at room temperature. Thus, they were able to demonstrate the feasibility of producing boron carbide-aluminum and boron carbide-polymer functionally graded materials.

  15. On the critical thickness of ceramic to shatter WC-Co bullet cores

    OpenAIRE

    Hazell, P.J.; Roberson, C. J.

    2011-01-01

    In this paper, the 7.62 mm x 51 mm FFV round consisting of a tungsten carbide core (1550 HV) and copper gilding jacket was fired at silicon nitride, titanium diboride, tungsten carbide and silicon carbide ceramics. Of particular interest is the thickness of the ceramic required to change the penetration mechanism from that of an intact body to broken body, and finally, to becoming completely fragmented during penetration. There appears to be a correlation between the acousti...

  16. Influence of Material Properties on the Ballistic Performance of Ceramics for Personal Body Armour

    Directory of Open Access Journals (Sweden)

    Christian Kaufmann

    2003-01-01

    Full Text Available In support of improved personal armour development, depth of penetration tests have been conducted on four different ceramic materials including alumina, modified alumina, silicon carbide and boron carbide. These experiments consisted of impacting ceramic tiles bonded to aluminum cylinders with 0.50 caliber armour piercing projectiles. The results are presented in terms of ballistic efficiency, and the validity of using ballistic efficiency as a measure of ceramic performance was examined. In addition, the correlation between ballistic performance and ceramic material properties, such as elastic modulus, hardness, spall strength and Hugoniot Elastic Limit, has been considered.

  17. Silicon carbide thyristor

    Science.gov (United States)

    Edmond, John A. (Inventor); Palmour, John W. (Inventor)

    1996-01-01

    The SiC thyristor has a substrate, an anode, a drift region, a gate, and a cathode. The substrate, the anode, the drift region, the gate, and the cathode are each preferably formed of silicon carbide. The substrate is formed of silicon carbide having one conductivity type and the anode or the cathode, depending on the embodiment, is formed adjacent the substrate and has the same conductivity type as the substrate. A drift region of silicon carbide is formed adjacent the anode or cathode and has an opposite conductivity type as the anode or cathode. A gate is formed adjacent the drift region or the cathode, also depending on the embodiment, and has an opposite conductivity type as the drift region or the cathode. An anode or cathode, again depending on the embodiment, is formed adjacent the gate or drift region and has an opposite conductivity type than the gate.

  18. The APS ceramic chambers

    Energy Technology Data Exchange (ETDEWEB)

    Milton, S.; Warner, D.

    1994-07-01

    Ceramics chambers are used in the Advanced Photon Source (APS) machines at the locations of the pulsed kicker and bumper magnets. The ceramic will be coated internally with a resistive paste. The resistance is chosen to allow the low frequency pulsed magnet field to penetrate but not the high frequency components of the circulating beam. Another design goal was to keep the power density experienced by the resistive coating to a minimum. These ceramics, their associated hardware, the coating process, and our recent experiences with them are described.

  19. Nondestructive evaluation of structural ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Klima, S.J.; Baaklini, G.Y.; Abel, P.B.

    1987-01-01

    A review is presented on research and development of techniques for nondestructive evaluation and characterization of advanced ceramics for heat engine applications. Highlighted in this review are Lewis Research Center efforts in microfocus radiography, scanning laser acoustic microscopy (SLAM), scanning acoustic microscopy (SAM), scanning electron acoustic microscopy (SEAM), and photoacoustic microscopy (PAM). The techniques were evaluated by applying them to research samples of green and sintered silicon nitride and silicon carbide in the form of modulus-of-rupture bars containing seeded voids. Probabilities of detection of voids were determined for diameters as small as 20 microns for microfucus radiography, SLAM, and SAM. Strengths and limitations of the techniques for ceramic applications are identified. Application of ultrasonics for characterizing ceramic microstructures is also discussed.

  20. Organometallic precursors of titanium and vanadium nitride and carbide. Doctoral thesis. Precurseurs organometalliques de nitrure et de carbure de titane et de vanadium

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, F.

    1992-06-29

    The author reports on research to produce titanium nitride, titanium carbide, vanadium nitride, and vanadium carbide from organometallic compounds using chemical vapor deposition. He also describes exploratory work to synthesize heterobimetallic complexes of titanium and vanadium, with a view to producing a single precursor of V-Ti-C-N ceramic.

  1. Ceramics in gas turbines - Powder and process characterization

    Science.gov (United States)

    Dutta, S.

    1977-01-01

    The role of powder and process characterization in producing high quality silicon nitride and silicon carbide components, for gas turbine applications, is described. Some of the intrinsic properties of various forms of Si3N4 and SiC are listed and limitations of such materials' availability have been pointed out. The essential features/parameters to characterize a batch of powder have been discussed including the standard techniques for such characterization. In process characterization, parameters in sintering, reaction sintering, and hot pressing processes are discussed including the factors responsible for strength limitations in ceramic bodies. It is inevitable that significant improvements in material properties can be achieved by reducing or eliminating the strength limiting factors with consistent powder and process characterization along with process control.

  2. The valve effect of the carbide interlayer of an electric resistance plug

    International Nuclear Information System (INIS)

    The welded electric resistance plug (ERP) usually contains a carbide interlayer at the plug-carbon material interface. The interlayer forms during welding the contact metallic alloy with the carbon material when the oxide films of the alloy are reduced on the interface surface by carbon to the formation of carbides and the surface layer of the plug material dissolves carbon to saturation. Subsequently, during solidification of the plug material it forms carbides with the alloy components. The structural composition of the carbide interlayer is determined by the chemical composition of the contact alloy. In alloys developed by the author and his colleagues the carbide forming elements are represented in most cases by silicon and titanium and, less frequently, by chromium and manganese. Therefore, the carbide interlayers in the ERP consisted mainly of silicon and titanium carbides

  3. Ceramic Stereolithography: Additive Manufacturing for Ceramics by Photopolymerization

    Science.gov (United States)

    Halloran, John W.

    2016-07-01

    Ceramic stereolithography and related additive manufacturing methods involving photopolymerization of ceramic powder suspensions are reviewed in terms of the capabilities of current devices. The practical fundamentals of the cure depth, cure width, and cure profile are related to the optical properties of the monomer, ceramic, and photo-active components. Postpolymerization steps, including harvesting and cleaning the objects, binder burnout, and sintering, are discussed and compared with conventional methods. The prospects for practical manufacturing are discussed.

  4. On Ceramics.

    Science.gov (United States)

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  5. Ceramic Technology Project semiannual progress report, October 1992--March 1993

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.

    1993-09-01

    This project was developed to meet the ceramic technology requirements of the OTS`s automotive technology programs. Although progress has been made in developing reliable structural ceramics, further work is needed to reduce cost. The work described in this report is organized according to the following work breakdown structure project elements: Materials and processing (monolithics [Si nitride, carbide], ceramic composites, thermal and wear coatings, joining, cost effective ceramic machining), materials design methodology (contact interfaces, new concepts), data base and life prediction (structural qualification, time-dependent behavior, environmental effects, fracture mechanics, nondestructive evaluation development), and technology transfer.

  6. Advanced Ceramics

    International Nuclear Information System (INIS)

    The First Florida-Brazil Seminar on Materials and the Second State Meeting about new materials in Rio de Janeiro State show the specific technical contribution in advanced ceramic sector. The others main topics discussed for the development of the country are the advanced ceramic programs the market, the national technic-scientific capacitation, the advanced ceramic patents, etc. (C.G.C.)

  7. Thermal properties of wood-derived silicon carbide and copper-silicon carbide composites

    Science.gov (United States)

    Pappecena, Kristen E.

    Wood-derived ceramics and composites have been of interest in recent years due to their unique microstructures, which lead to tailorable properties. The porosity and pore size distribution of each wood type is different, which yields variations in properties in the resultant materials. The thermal properties of silicon carbide ceramics and copper-silicon carbide composites derived from wood were studied as a function of their pore structures. Wood was pyrolyzed at temperatures ranging from 300-2400°C to yield porous carbon. The progression toward long-range order was studied as a function of pyrolyzation temperature. Biomorphic silicon carbide (bioSiC) is a porous ceramic material resulting from silicon melt infiltration of these porous carbon materials. BioSiC has potential applicability in many high temperature environments, particularly those in which rapid temperature changes occur. To understand the behavior of bioSiC at elevated temperatures, the thermal and thermo-mechanical properties were studied. The thermal conductivity of bioSiC from five precursors was determined using flash diffusivity at temperatures up to 1100°C. Thermal conductivity results varied with porosity, temperature and orientation, and decreased from 42-13 W/mK for porosities of 43-69%, respectively, at room temperature. The results were compared with to object-oriented finite-element analysis (OOF). OOF was also used to model and understand the heat-flow paths through the complex bioSiC microstructures. The thermal shock resistance of bioSiC was also studied, and no bioSiC sample was found to fail catastrophically after up to five thermal shock cycles from 1400°C to room temperature oil. Copper-silicon carbide composites have potential uses in thermal management applications due to the high thermal conductivity of each phase. Cu-bioSiC composites were created by electrodeposition of copper into bioSiC pores. The detrimental Cu-SiC reaction was avoided by using this room temperature

  8. Role of nickel ion coordination on spectroscopic properties of multi-component CaF2-Bi2O3-P2O5-B2O3 glass-ceramics

    Science.gov (United States)

    Suresh, S.; Narendrudu, T.; Kumar, A. Suneel; Rao, M. V. Sambasiva; Ram, G. Chinna; Rao, D. Krishna

    2016-10-01

    Multi-component CaF2-Bi2O3-P2O5-B2O3 glasses doped with different concentrations of NiO were crystallized through heat treatment. The prepared glass ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) as well as conventional spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR) and Raman. The XRD and SEM studies have indicated that the samples contain well defined and randomly distributed grains of different crystalline phases. The optical absorption studies together with FTIR and Raman measurements indicated the gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 1.5 mol%. All these investigations have indicated that the growing degree of disorder in the glass ceramic network at higher concentrations of NiO. Glass ceramics doped with NiO beyond 1.5 mol% appear to be suitable for getting laser emission due to 3T2(F) → 3A2(F) transition in NIR region. These glass-ceramics can be expected as an amplification medium for tunable lasers and broadband optical amplifiers for wavelength division multiplexing transmission system.

  9. Nanosized Borides and Carbides for Electroplating. Metal-Matrix Coatings: Specifications, Performance Evaluation

    Science.gov (United States)

    Galevskiy, G. V.; Rudneva, V. V.; Galevskiy, S. G.; Il’yashchenko, D. P.; Kartsev, D. S.

    2016-04-01

    This paper summarizes experience of application of nano-sized carbides and borides of titanium and chromium, silicon carbide as components of electro-depositable coating compositions based on nickel, zinc, and chromium. Basic physical and mechanical properties of the coatings are determined. Technological and economic evaluation is completed; practicability of high-cost nano-diamonds substitution for nano-sized borides and carbides is justified.

  10. Silicon Carbide Nanotube Oxidation at High Temperatures

    Science.gov (United States)

    Ahlborg, Nadia; Zhu, Dongming

    2012-01-01

    Silicon Carbide Nanotubes (SiCNTs) have high mechanical strength and also have many potential functional applications. In this study, SiCNTs were investigated for use in strengthening high temperature silicate and oxide materials for high performance ceramic nanocomposites and environmental barrier coating bond coats. The high · temperature oxidation behavior of the nanotubes was of particular interest. The SiCNTs were synthesized by a direct reactive conversion process of multiwall carbon nanotubes and silicon at high temperature. Thermogravimetric analysis (TGA) was used to study the oxidation kinetics of SiCNTs at temperatures ranging from 800degC to1300degC. The specific oxidation mechanisms were also investigated.

  11. Intermetallic bonded ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Plucknett, K.P.; Tiegs, T.N.; Alexander, K.B.; Becher, P.F.; Schneibel, J.H.; Waters, S.B.; Menchhofer, P.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1995-07-01

    A range of carbide and oxide-based cermets have been developed utilizing ductile nickel aluminide (Ni{sub 3}Al) alloy binder phases. Some of these, notably materials based upon tungsten and titanium carbides (WC and TiC respectively), offer potential as alternatives to the cermets which use cobalt binders (i.e. WC/Co). Samples have been prepared by blending commercially available Ni{sub 3}Al alloy powders with the desired ceramic phases, followed by hot-pressing. Alumina (Al{sub 2}O{sub 3}) matrix materials have also been prepared by pressurized molten alloy infiltration. The microstructure, flexure strength and fracture toughness of selected materials are discussed.

  12. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    Science.gov (United States)

    Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

    2013-01-22

    Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.

  13. Sintered silicon carbide

    International Nuclear Information System (INIS)

    A sintered silicon carbide body having a predominantly equiaxed microstructure consists of 91 to 99.85% by weight of silicon carbide at least 95% of which is the alpha phase, up to 5.0% by weight carbonized organic material, 0.15 to 3.0% of boron, and up to 1.0% by weight additional carbon. A mixture of 91 to 99.85 parts by weight silicon carbide having a surface area of 1 to 100 m2/g, 0.67 to 20 parts of a carbonizable organic binder with a carbon content of at least 33% by weight, 0.15 to 5 parts of a boron source containing 0.15 to 3.0 parts by weight boron and up to 15 parts by weight of a temporary binder is mixed with a solvent, the mixture is then dried, shaped to give a body with a density of at least 1.60 g/cc and fired at 1900 to 22500C to obtain an equiaxed microstructure. (author)

  14. Chemical Analysis Methods for Silicon Carbide

    Institute of Scientific and Technical Information of China (English)

    Shen Keyin

    2006-01-01

    @@ 1 General and Scope This Standard specifies the determination method of silicon dioxide, free silicon, free carbon, total carbon, silicon carbide, ferric sesquioxide in silicon carbide abrasive material.

  15. Ceramic joining

    Energy Technology Data Exchange (ETDEWEB)

    Loehman, R.E. [Sandia National Lab., Albuquerque, NM (United States)

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  16. Ceramic Processing

    Energy Technology Data Exchange (ETDEWEB)

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

  17. Modification of optical surfaces employing CVD boron carbide coatings

    International Nuclear Information System (INIS)

    Non-reflective or high emissivity optical surfaces require materials with given roughness or surface characteristics wherein interaction with incident radiation results in the absorption and dissipation of a specific spectrum of radiation. Coatings have been used to alter optical properties, however, extreme service environments, such as experienced by satellite systems and other spacecraft, necessitate the use of materials with unique combinations of physical, chemical, and mechanical properties. Thus, ceramics such as boron carbide are leading candidates for these applications. Boron carbide was examined as a coating for optical baffle surfaces. Boron carbide coatings were deposited on graphite substrates from BCl3, CH4, and H2 gases employing chemical vapor deposition (CVD) techniques. Parameters including temperature, reactant gas compositions and flows, and pressure were explored. The structures of the coatings were characterized using electron microscopy and compositions were determined using x-ray diffraction. The optical properties of the boron carbide coatings were measured, and relationships between processing conditions, deposit morphology, and optical properties were determined

  18. Investigation on the preparation of Si/mullite/Yb_2Si_2O_7 environmental barrier coatings onto silicon carbide

    Institute of Scientific and Technical Information of China (English)

    许越; 闫钊通

    2010-01-01

    With the development of aero-engine,gas import temperatures of hot section structural materials are increasingly higher.Metal alloy materials due to the rapidly decreased mechanical properties at relative high temperature are gradually replaced with silicon-based non-oxide silicon carbide ceramics.However,silicon carbide ceramic materials tend to spall and deform in engine combustion environment,need environmental barrier coatings for the protection of the matrix.The preparation of Si/mullite/Yb2Si2O7 envir...

  19. Novel Processing of Unique Ceramic-Based Nuclear Materials and Fuels

    International Nuclear Information System (INIS)

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These include refractory alloys base on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as those based on silicon carbide (SiCf-SiC); carbon-carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor components is necessary for improved efficiency. Improving thermal conductivity of the materials used in nuclear fuels and other temperature critical components can lower the center-line fuel temperature and thereby enhance durability and reduce the risk of premature failure.

  20. Electrospinning of ceramic nanofibers

    Science.gov (United States)

    Eick, Benjamin M.

    Silicon Carbide (SiC) nanofibers of diameters as low as 20 nm are fabricated. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene (PS) and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fibers flowing during pyrolysis. Electrospun SiC fibers were characterized by FTIR, TGA-DTA, SEM, TEM, XRD, and SAED. Fibers were shown to be polycrystalline and nanograined with alpha-SiC 15R polytype being dominant, where commercial fiber production methods form beta-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced alpha-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core-shell structure of an oxide scale that was variable by pyrolysis conditions. Metal oxide powders (chromium oxide, cobalt oxide, iron oxide, silicon oxide, tantalum oxide, titanium oxide, tungsten oxide, vanadium oxide, and zirconium oxide), were converted to metal carbide powders and metal nitride powders by the process of carbothermal reduction (CTR). Synthetic pitch was explored as an alternative to graphite which is a common carbon source for CTR. It was shown via characterization with XRD that pitch performs as well and in some cases better than graphite and is therefore a viable alternative in CTR. Conversion of metal oxide powders with pitch led to conversion of sol-gel based metal oxide nanofibers produced by electrospinning. Pitch was soluble in the solutions xv that were electrospun allowing for intimate contact between the sol-gel and the carbon source for CTR. This method became a two step processing method to produce metal carbide and nitride nanofibers: first electrospin sol-gel based metal oxide nanofibers and subsequently pyrolize them in the manner of CTR to transform them. Results indicate

  1. ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

    Directory of Open Access Journals (Sweden)

    Zhang Changrui

    2016-07-01

    Full Text Available An entirely aqueous solution-gel route has been developed for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide powders. Zirconium oxychloride (ZrOCl₂.8H₂O, malic acid (MA and ethylene glycol (EG were dissolved in water to form the aqueous zirconium carbide precursor. Afterwards, this aqueous precursor was gelled and transformed into zirconium carbide at a relatively low temperature (1200 °C for achieving an intimate mixing of the intermediate products. Hafnium and the ternary carbide powders were also synthesized via the same aqueous route. All the zirconium, hafnium and ternary carbide powders exhibited a particle size of ∼100 nm.

  2. High pressure ceramic heat exchanger

    Science.gov (United States)

    Harkins, Bruce D.; Ward, Michael E.

    1998-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  3. Methods of producing continuous boron carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  4. Effect of Constituents of Silicon Carbide Composites on Oxidation Behaviour

    International Nuclear Information System (INIS)

    Silicon carbide (SiC) composites consist with SiC fibers, SiC matrix and fiber/matrix interphase. SiC composites and monolithic SiC ceramics which are the reference materials for the SiC composite matrices were exposed in air or steam environment up to 1400°C. Significant degradation was observed for the composites with C interphase after exposure in air or steam. Oxidation behaviour was also affected by impurities in SiC. (author)

  5. High Carbon Alloy Steels with Multiple Types of Ultra-fine Carbides and Their Characteristics

    Institute of Scientific and Technical Information of China (English)

    MA Yong-qing; GAO Hong-tao; QI Yu-hong; ZHANG Zhan-ping; DAI Yu-mei; LIU Yan-xia

    2004-01-01

    Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7C3, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength,flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.

  6. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  7. Preparation of porous silicon carbide by combustion synthesis

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-min; ZHANG Jian-han; HAN Jie-cai

    2005-01-01

    Porous silicon carbide ceramics were prepared by combustion synthesis technique. SiC/TiC composite was gained by combustion reaction of Si, C and Ti. Thermodynamics analysis of Si-C-Ti system indicates that the content of TiC in products should be larger than 30%. The experimental results show that the content of Ti+C should be larger than 25% to achieve a complete combustion reaction. The X-ray diffractometry results show that the final products with a relative density of 45%-64% are composed of α-SiC, β-SiC, TiC and a small quantity of Si. The images of scanning electron microscopy show that the structures of grain in SiC based porous ceramics consist of particles with a few microns in size.

  8. Recent advances and issues in development of silicon carbide composites for fusion applications

    Science.gov (United States)

    Nozawa, T.; Hinoki, T.; Hasegawa, A.; Kohyama, A.; Katoh, Y.; Snead, L. L.; Henager, C. H., Jr.; Hegeman, J. B. J.

    2009-04-01

    Radiation-resistant advanced silicon carbide (SiC/SiC) composites have been developed as a promising candidate of the high-temperature operating advanced fusion reactor. With the completion of the 'proof-of-principle' phase in development of 'nuclear-grade' SiC/SiC composites, the R&D on SiC/SiC composites is shifting toward the more pragmatic phase, i.e., industrialization of component manufactures and data-basing. In this paper, recent advances and issues in (1) development of component fabrication technology including joining and functional coating, e.g., a tungsten overcoat as a plasma facing barrier, (2) recent updates in characterization of non-irradiated properties, e.g., strength anisotropy and chemical compatibility with solid lithium-based ceramics and lead-lithium liquid metal breeders, and (3) irradiation effects are specifically reviewed. Importantly high-temperature neutron irradiation effects on microstructural evolution, thermal and electrical conductivities and mechanical properties including the fiber/matrix interfacial strength are specified under various irradiation conditions, indicating seemingly very minor influence on the composite performance in the design temperature range.

  9. Microstructural Study of Titanium Carbide Coating on Cemented Carbide

    DEFF Research Database (Denmark)

    Vuorinen, S.; Horsewell, Andy

    1982-01-01

    Titanium carbide coating layers on cemented carbide substrates have been investigated by transmission electron microscopy. Microstructural variations within the typically 5µm thick chemical vapour deposited TiC coatings were found to vary with deposit thickness such that a layer structure could...... be delineated. Close to the interface further microstructural inhomogeneities were obsered, there being a clear dependence of TiC deposition mechanism on the chemical and crystallographic nature of the upper layers of the multiphase substrate....

  10. Rotational accuracy of all-ceramic restorations on ceraone components = Liberdade rotacional de restaurações totalmente cerâmicas sobre componentes ceraone

    Directory of Open Access Journals (Sweden)

    Webster, Jacqueline

    2005-01-01

    Full Text Available Objetivo: Este estudo avaliou a desadaptação interna de sistemas cerâmicos em prótese sobre implantes em relação à liberdade rotacional das restaurações após várias cocções da porcelana. Materiais e métodos: Foram analisados três sistemas cerâmicos: Procera AllCeram, In-Ceram e CeraOne sobre análogo e intermediário CeraOne. A liberdade rotacional foi medida com um dispositivo acoplado a um relógio comparador em quatro tempos: fase de coifa, após aplicação do corpo da porcelana e glaze, e após duas queimas adicionais. Os dados foram analisados por testes de Friedman, de Kruskal-Wallis e de Wilcoxon, α = 0,01. Resultados: As médias de liberdade rotacional em graus foram: 0,08 para In-Ceram/Análogo; 1,64 para Procera/ Intermediário; 1,72 para CeraOne/Intermediário; 1,88 para CeraOne/Análogo e 1,97 para Procera/Análogo. O sistema In-Ceram sobre o análogo apresentou níveis de liberdade rotacional dez a vinte vezes menores que CeraOne e Procera. Não houve diferença entre as fases de confecção da restauração para In-Ceram. O comportamento de CeraOne e Procera foi similar, com aumento da liberdade rotacional sobre intermediário e análogo com a progressão da confecção da restauração. A liberdade rotacional sobre intermediário foi menor que sobre análogo. Conclusão: A liberdade rotacional variou em função da etapa do processo de fabricação dependendo do sistema totalmente cerâmico

  11. Porosity of detonation coatings on the base of chromium carbide

    International Nuclear Information System (INIS)

    Porosity of detonation coatings on the base of chromium carbide is estimated by the hydrostatic weighing. The open porosity value dependence on the distance of spraying, depth of the charge, ratio and volume of the detonator barrie filing with gas components is established. Pore distribution in the cross section of a specimen tested for porosity is studied by the methods of metallographic analysis

  12. Sintering of ceramics using low frequency rf power

    International Nuclear Information System (INIS)

    Sintering with low frequency rf power (∼50 MHz) is a new technique with unique capabilities that has been used to sinter a variety of ceramic materials, including zirconia-toughened alumina, alumina, silicon carbide, and boron carbide. Processing with low frequencies offers many advantages compared to processing with conventional microwave frequencies (915 MHz and 2.45 GHz). Because of the longer wavelength, the rf electric field penetrates materials more than microwaves. This effect allows the processing of a wider variety of materials and allows for an increase in the physical size of the material being processed. In addition, the material is heated in a single mode cavity with a uniform electric field, which reduces the occurrence of hot-spot generation and thermal runaway effects. This technique has been used to sinter large crack-free alumina samples (3 inch square) to > 97% density. The sintering and/or annealing of a number of carbide materials has been demonstrated as well, including silicon carbide, boron carbide, tungsten carbide, and titanium carbide

  13. Engineering ceramics

    CERN Document Server

    Bengisu, Murat

    2001-01-01

    This is a comprehensive book applying especially to junior and senior engineering students pursuing Materials Science/ Engineering, Ceramic Engineering and Mechanical Engineering degrees. It is also a reference book for other disciplines such as Chemical Engineering, Biomedical Engineering, Nuclear Engineering and Environmental Engineering. Important properties of most engineering ceramics are given in detailed tables. Many current and possible applications of engineering ceramics are described, which can be used as a guide for materials selection and for potential future research. While covering all relevant information regarding raw materials, processing properties, characterization and applications of engineering ceramics, the book also summarizes most recent innovations and developments in this field as a result of extensive literature search.

  14. Tailored ceramics

    International Nuclear Information System (INIS)

    In polyphase tailored ceramic forms two distinct modes of radionuclide immobilization occur. At high waste loadings the radionuclides are distributed through most of the ceramic phases in dilute solid solution, as indicated schematically in this paper. However, in the case of low waste loadings, or a high loading of a waste with low radionuclide content, the ceramic can be designed with only selected phases containing the radionuclides. The remaining material forms nonradioactive phases which provide a degree of physical microstructural isolation. The research and development work with polyphase ceramic nuclear waste forms over the past ten years is discussed. It has demonstrated the critical attributes which suggest them as a waste form for future HLW disposal. From a safety standpoint, the crystalline phases in the ceramic waste forms offer the potential for demonstrable chemical durability in immobilizing the long-lived radionuclides in a geologic environment. With continued experimental research on pure phases, analysis of mineral analogue behavior in geochemical environments, and the study of radiation effects, realistic predictive models for waste form behavior over geologic time scales are feasible. The ceramic forms extend the degree of freedom for the economic optimization of the waste disposal system

  15. Novel Processing of Unique Ceramic-Based Nuclear Materials and Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Hui Zhang; Raman P. Singh

    2008-11-30

    Advances in nuclear reactor technology and the use of gas-cooled fast reactors require the development of new materials that can operate at the higher temperatures expected in these systems. These include refractory alloys base on Nb, Zr, Ta, Mo, W, and Re; ceramics and composites such as those based on silicon carbide (SiCf-SiC); carbon-carbon composites; and advanced coatings. Besides the ability to handle higher expected temperatures, effective heat transfer between reactor componets is necessary for improved efficiency. Improving thermal conductivity of the materials used in nuclear fuels and other temperature critical components can lower the center-line fuel temperature and thereby enhance durability and reduce the risk of premature failure.

  16. Structure-Property Relationships in Polymer Derived Amorphous/Nano-Crystalline Silicon Carbide for Nuclear Applications

    International Nuclear Information System (INIS)

    Silicon carbide (SiC) is a promising candidate for several applications in nuclear reactors owing to its high thermal conductivity, high melting temperature, good chemical stability, and resistance to swelling under heavy ion bombardment. However, fabricating SiC by traditional powder processing route generally requires very high temperatures for pressureless sintering. Polymer derived ceramic materials offer unique advantages such as ability to fabricate net shaped components, incorporate reinforcements and relatively low processing temperatures. Furthermore, for SiC based ceramics fabricated using polymer infiltration process (PIP), the microstructure can be tailored by controlling the processing parameters, to get an amorphous, nanocrystalline or crystalline SiC. In this work, fabrication of polymer derived amorphous and nano-grained SiC is presented and its application as an in-core material is explored. Monolithic SiC samples are fabricated by controlled pyrolysis of allyl-hydrido-poly-carbo-silane (AHPCS) under inert atmosphere. Chemical changes, phase transformations and microstructural changes occurring during the pyrolysis process are studied as a function of the processing temperature. Polymer cross-linking and polymer to ceramic conversion is studied using infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are performed to monitor the mass loss and phase change as a function of temperature. X-ray diffraction studies are done to study the intermediate phases and microstructural changes. Variation in density is carefully monitored as a function of processing temperature. Owing to shrinkage and gas evolution during pyrolysis, precursor derived ceramics are inherently porous and composite fabrication typically involves repeated cycles of polymer re-infiltration and pyrolysis. However, there is a limit to the densification that can be achieved by this method and porosity in the final materials presents

  17. Modelling of Tape Casting for Ceramic Applications

    DEFF Research Database (Denmark)

    Jabbari, Masoud

    of functional ceramics research. Advances in ceramic forming have enabled low cost shaping techniques such as tape casting and extrusion to be used in some of the most challenging technologies. These advances allow the design of complex components adapted to desired specific properties and applications. However......Functional ceramics find use in many different applications of great interest, e.g. thermal barrier coatings, piezoactuators, capacitors, solid oxide fuel cells and electrolysis cells, membranes, and filters. It is often the case that the performance of a ceramic component can be increased markedly......, there is still only very limited insight into the processes determining the final properties of such components. Hence, the aim of the present PhD project is to obtain the required knowledge basis for the optimized processing of multi-material functional ceramics components. Recent efforts in the domain...

  18. Structural Ceramics Database

    Science.gov (United States)

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  19. Sealing of ceramic SOFC-components with glass seals; Fuegen von keramischen Komponenten der Hochtemperatur-Brennstoffzellen mittels Glas- und Glaskeramikloten

    Energy Technology Data Exchange (ETDEWEB)

    Schillig, Cora

    2012-07-10

    The solid oxide fuel cell (SOFC) converts chemical energy of a fuel directly into electrical energy. However, for the implementation of SOFC-technology in competition to conventional power plants costs have to be reduced. The use of an alternative tubular cell design without closed end would allow reducing costs during cell manufacturing. However, this change in design makes a gastight sealing inside the generator near the gas inlet necessary. Different ceramic materials with varying coefficients of thermal expansion have to be sealed gastight and electrical insulating at temperatures between 850 C and 1000 C to prevent the gases from mixing and an electrical shortcut between the cells. This work comprises analysis of commercially available glass and glass-ceramic systems manufactured by Schott Electronic Packaging, Areva T and D and Ferro Corporation. Additionally new developed sealing glass and glass-ceramic systems were investigated and all systems were characterized fundamentally for the use as sealing material in SOFC generators. Therefore different test assemblies and series were conducted. Essential characteristics of a suitable sealing system are a thermal expansion coefficient between 9,5 and 12 . 10{sup -6}K{sup -1}, a viscosity in the range between 10{sup 4} to 10{sup 6} dPa{sup *}s and a wetting angle smaller than 90 during the sealing process. Also unwanted chemical side reactions between the sealing partners must be prevented, because a change in the phase composition or the creation of new phases in the sealing material could endanger the stability of the seal. Heat cycles, particularly those during generator operation, cause deterioration of the sealing material and subsequent reduction in its ability to prevent mixing of the gases. Sealant leaks can drastically impact efficiency of the generator. In order to ensure optimum operation low leak rates around 2,3 . 10{sup -4} mbar l/sec/cm{sup 2} must be maintained. Especially glass and glass-ceramics

  20. Studies of silicon carbide and silicon carbide nitride thin films

    Science.gov (United States)

    Alizadeh, Zhila

    Silicon carbide semiconductor technology is continuing to advance rapidly. The excellent physical and electronic properties of silicon carbide recently take itself to be the main focused power device material for high temperature, high power, and high frequency electronic devices because of its large band gap, high thermal conductivity, and high electron saturation drift velocity. SiC is more stable than Si because of its high melting point and mechanical strength. Also the understanding of the structure and properties of semiconducting thin film alloys is one of the fundamental steps toward their successful application in technologies requiring materials with tunable energy gaps, such as solar cells, flat panel displays, optical memories and anti-reflecting coatings. Silicon carbide and silicon nitrides are promising materials for novel semiconductor applications because of their band gaps. In addition, they are "hard" materials in the sense of having high elastic constants and large cohesive energies and are generally resistant to harsh environment, including radiation. In this research, thin films of silicon carbide and silicon carbide nitride were deposited in a r.f magnetron sputtering system using a SiC target. A detailed analysis of the surface chemistry of the deposited films was performed using x-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy whereas structure and morphology was studied atomic force microscopy (AFM), and nonoindentation.

  1. Influence of binder composition on the properties of feedstock for cemented carbides

    Directory of Open Access Journals (Sweden)

    K. Gołombek

    2011-10-01

    Full Text Available Purpose: The plastic mixtures shaping of polymer-powder slurries with use of injection moulding and extrusion techniques for development and optimization of metal matrix tool materials reinforced with hard carbide phases.Design/methodology/approach: Mixtures preparation and preliminary tests, injection moulding and extrusion moulding processes optimization, the grain size measurement with use of laser diffraction method, torque measurement, rheological characterization, differential scanning calorimetry.Findings: All of investigated polymer-powder mixtures are proper for injection moulding and extrusion processes. Increasing the maximal possible fraction of carbides powder in the mixture is possible due to SA acid addition in the composition of binder. Advantages of SA acid as a component of binder are connected with significant decreasing the viscosity of polymer-powder mixtures as a result of SA acid presence. Binder fraction in injection moulded and extruded materials should be as small as possible, but enough for slurry moulding process. Too large fraction of binder causes the problems during degradation process because of higher shrinkage value and can be a reason of the distortion effect during sintering process. The results of bending strength measurements of injection moulded and extruded samples depends mainly on the moulding conditions, which should be optimized, to obtain the homogeneous structure of material with no discontinuities.Practical implications: Using investigated PM methods makes it possible to take advantage of injection moulding benefits obtained in area of polymer materials to fabrication of metallic materials, cermets and ceramics. There are wide possibilities of PIM (Powder Injection Moulding method application for “near-net-shape” production of small size units with complicated shape and extended surface so the range of practical use of this method is wide and covers many aspects of life. The elimination the

  2. Palladium interaction with silicon carbide

    International Nuclear Information System (INIS)

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC–5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation

  3. Palladium interaction with silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Gentile, M., E-mail: Marialuisa.Gentile@manchester.ac.uk [Centre for Nuclear Energy Technology (C-NET), School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom); Xiao, P. [Materials Science Centre, School of Materials, The University of Manchester, Manchester M13 9PL (United Kingdom); Abram, T. [Centre for Nuclear Energy Technology (C-NET), School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-07-15

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC–5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd{sub 3}Si and SiO{sub 2} phases, while the second peak and the third peak are correlated with the formation of Pd{sub 2}Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO{sub 2} phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiC{sub x}O{sub y} phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  4. Palladium interaction with silicon carbide

    Science.gov (United States)

    Gentile, M.; Xiao, P.; Abram, T.

    2015-07-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC-5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  5. Rheology of Superplastic Ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Constitutive equation of rheglogy describing a phenomenological level of superplastic deformation as functional correlation between tensor components of stress and strain rate has been analyzed for the case of superplastic ceramic flow. Rheological properties of material are taken into account by means of scalar rheological coefficients of shear and volume viscosity, which are functions of temperature, effective stress (or strain rate) and density of material.

  6. Effects of SiC and MgO on aluminabased ceramic foams filters

    Directory of Open Access Journals (Sweden)

    CAO Da-li

    2007-11-01

    Full Text Available Alumina-based foam ceramic filters were fabricated by using alumina, SiC, magnesia powder as major materials. It has been found that this ceramic filter has a uniform macrostructure for filtering molten metals. The influences of SiC and magnesia content, the sintering temperatures on ceramic properties were discussed. Aluminabased foam ceramic filters containing 2.2 mass% magnesia and 7.6 mass% SiC has a compressive strength of 1.36 MPa and a thermal shock resistance of 5 times. Its main phases after 1 hour sintering at 1 500 consist of alumina, silicon carbide, spinel and mullite.

  7. Ceramic stationary gas turbine

    Energy Technology Data Exchange (ETDEWEB)

    Roode, M. van [Solar Turbines Inc., San Diego, CA (United States)

    1995-10-01

    The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.

  8. Knoop Hardness - Apparent Yield Stress Relationship in Ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Swab, Jeffrey J [ORNL; LaSalvia, Jerry [U.S. Army research Laboratory, Adelphi, MD; Wereszczak, Andrew A [ORNL; Strong, Kevin T [ORNL; Danna, Dominic [U.S. Army research Laboratory, Adelphi, MD; Ragan, Meredith E [ORNL; Ritt, Patrick J [ORNL

    2012-01-01

    In Tabor's classical studies of the deformation of metals, the yield stress (Y) and hardness (H) were shown to be related according to H/Y {approx} 3 for complete or fully plastic deformation. Since then it has been anecdotally shown for ceramics that this ratio is <3. Interest exists to explore this further so Hertzian indentation was used to measure the apparent yield stress of numerous ceramics and metals and their results were compared with each material's load-dependent Knoop hardness. The evaluated ceramics included standard reference materials for hardness (silicon nitride and tungsten carbide), silicon carbide, alumina, and glass. Several steel compositions were also tested for comparison. Knoop hardness measurements at 19.6 N (i.e., toward 'complete or fully plastic deformation'), showed that 2 < H/Y < 3 for the metals and 0.8 < H/Y < 1.8 for the glasses and ceramics. Being that H/Y {ne} 3 for the ceramics indicates that Tabor's analysis is either not applicable to ceramics or that full plastic deformation is not achieved with a Knoop indentation or both.

  9. Metallic nut for use with ceramic threads

    Science.gov (United States)

    Norton, Paul F.; Shaffer, James E.

    1996-01-01

    A nozzle guide vane assembly has ceramic components therein having a conventional thread thereon including a preestablished pitch and having a preestablished rate of thermal expansion. The nozzle guide vane assembly has a metallic components therein having a preestablished rate of thermal expansion being greater that the rate of thermal expansion of the ceramic components is positioned in a gas turbine engine. The metallic component, a nut, has a thread therein including a plurality of crests being spaced on a pitch equal to that of the ceramic component and has a pair of contacting surfaces extending from the plurality of crests. A notch spirally extends intermediate adjacent ones of the plurality of crests and has a preestablished depth which is at least twice the size of the conventional pitch. Furthermore, the pair of contacting surfaces are in contact with only a portion of the threaded surface of the ceramic components.

  10. Investigation of the Deposition and Densification Parameters on the Mechanical Properties of Pressurized Spray Deposited (PSD) 3-D Printed Ceramic Components

    Energy Technology Data Exchange (ETDEWEB)

    Menchhofer, Paul A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Becker, Benjamin [HotEnd Works, LLC, Oberlin, OH (United States)

    2016-07-28

    Oak Ridge National Laboratory (ORNL) and HotEnd Works teamed to investigate the use of pressurized spray deposition (PSD) technology for the production of ceramic parts via additive manufacturing. Scanning electron microscopy of sintered parts provided by HotEnd Works revealed voids large enough to compromise the mechanical properties of PSD manufactured parts. Scanning electron microscopy and particle size analysis of the alumina oxide powder feedstocks indicated that the powders contained some large particles and some agglomerations in the powder. Further classification of the powder feedstocks and removal of the agglomerates by sonication in the liquid used for the PSD process are recommended. Analysis of sintered parts indicated that the sonic modulus for the alumina part is consistent with other known values for alumina. The density for this part was determined by standard Archimedes immersion density methods and was found to be > 99.7 % of the theoretical density for pure alumina.

  11. Laser melting of uranium carbides

    Science.gov (United States)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  12. Silver diffusion through silicon carbide in microencapsulated nuclear fuels TRISO; Difusion de plata a traves de carburo de silicio en combustibles nucleares microencapsulados TRISO

    Energy Technology Data Exchange (ETDEWEB)

    Cancino T, F.; Lopez H, E., E-mail: Felix.cancino@cinvestav.edu.mx [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Saltillo, Av. Industria Metalurgica No. 1062, Col. Ramos Arizpe, 25900 Saltillo, Coahuila (Mexico)

    2013-10-15

    The silver diffusion through silicon carbide is a challenge that has persisted in the development of microencapsulated fuels TRISO (Tri structural Isotropic) for more than four decades. The silver is known as a strong emitter of gamma radiation, for what is able to diffuse through the ceramic coatings of pyrolytic coal and silicon carbide and to be deposited in the heat exchangers. In this work we carry out a recount about the art state in the topic of the diffusion of Ag through silicon carbide in microencapsulated fuels and we propose the role that the complexities in the grain limit can have this problem. (Author)

  13. Template-synthesized porous silicon carbide as an effective host for zeolite catalysts.

    Science.gov (United States)

    Gu, Lijun; Ma, Ding; Yao, Songdong; Liu, Xiumei; Han, Xiuwen; Shen, Wenjie; Bao, Xinhe

    2009-12-14

    A facile method has been developed for the fabrication of porous silicon carbide (SiC) by means of sintering a mixture of SiC powder and carbon pellets at a relatively lower temperature, that is, 1450 degrees C, in air. The pore density and the total pore volume of the resulting porous SiC could be tuned by changing the initial SiC/C weight ratio. The structure evolution and the associated property changes during the preparation were examined through X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, (29)Si magic-angle spinning (MAS) NMR spectroscopy, and mercury-intrusion porosimetry analyses. Silica and SiO(x)C(y) ceramics formed in situ during the calcination process acted as binders of the porous SiC grains. The porous SiC can be used as a host for the growth of ZSM-5 zeolite crystals to form the ZSM-5/porous-SiC composite material. After loading another catalytic active component of molybdenum, a novel catalytic material, Mo-ZSM-5/porous-SiC, was obtained, which exhibited improved catalytic activity in the methane dehydroaromatization reaction.

  14. Laser ablative cutting of ceramics for electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Warner, B. E., LLNL

    1996-03-01

    Pulsed, high-beam quality lasers offer unique materials processing characteristics. In processing metals, copper vapor and pulsed Nd:YAG lasers have produced micron-scale cuts and holes with submicron heat-affected zones. Since the cost of laser photons is high and average material removal rates can be slow with ablation, high value-added applications are necessary to justify processing costs. Ceramics present a special challenge for manufacturing because of their high hardness, relatively low thermal conductivity, and brittle nature. Surface damage typically limits the strength of a ceramic part to a small fraction of its bulk strength. This work investigates the use of copper vapor and pulsed diode-pumped Nd:YAG lasers to cut precision features in ceramic substrates. Variations in laser wavelength and power, processing speed, ceramic type, and assist gas were investigated with the goal of producing <100-{mu}m wide by 600-{mu}m deep cuts through silicon-carbide and alumina/titanium-carbide substrates for potential use in electronics. Silicon-carbide bars 250-{mu}m wide by 600-{mu}m high by 2.5-cm long were laser cut from substrates without fracture.

  15. Gas emission from ultradispersed carbide powders

    International Nuclear Information System (INIS)

    The process of gas emission from the ultra-dispersed carbides (B4C, SiC, TiC) powders formed by pulsed plasma synthesis technology (condensator discharge) in the environment of corresponding chlorides and methan with the additions of H2 and Ar was investigated. The emitted gases consisted of CH4, H2O, Co(N2), CO2. Calculated heats of gas emission processes (less than 200 kJ/mol) for different components show their adsorption nature up to 700 deg C. The emission of components having mass numbers 28 and 44 raises at higher temperatures that can be considered as a consequence of high temperature reactions between oxygen and carbon containing phases in synthesized powders

  16. Ceramic microfabrication by rapid prototyping process chains

    Indian Academy of Sciences (India)

    R Knitter; W Bauer

    2003-02-01

    Fabrication of micropatterned ceramics or ceramic microparts make high demands on the precision and resolution of the moulding process. As finishing of miniaturised or micropatterned ceramic components is nearly impossible, shaping has to be done by a replication step in the green, unfired state. To avoid high tooling costs in product development, a rapid prototyping process chain has been established that enables rapid manufacturing of ceramic microcomponents from functional models to small lot series within a short time. This process chain combines the fast and inexpensive supply of master models by rapid prototyping with accurate and flexible ceramic manufacturing by low-pressure injection moulding. Besides proper feedstock preparation and sufficient small grain size, the quality of the final components is mainly influenced by the quality of the master model. Hence, the rapid prototyping method must be carefully selected to meet the requirements of the component to be fabricated.

  17. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

    Institute of Scientific and Technical Information of China (English)

    马淳安; 张文魁; 成旦红; 周邦新

    2002-01-01

    The tungsten carbide(WC) electrocatalysts with definite phase components and high specific surface area were prepared by gas-solid reduction method. The crystal structure, phase components and electrochemical properties of the as-prepared materials were characterized by XRD, BET(Brunauer Emmett and Teller Procedure) and electrochemical test techniques. It is shown that the tungsten carbide catalysts with definite phase components can be obtained by controlling the carburizing conditions including temperature, gas flowing rate and duration time. The electrocatalysts with the major phase of W2C show higher electrocatalytic activity for the hydrogen evolution reaction. The electrocatalysts with the major phase of WC are suitable to be used as the anodic electrocatalyst for hydrogen anodic oxidation, which exhibit higher hydrogen anodic oxidation electrocatalytic properties in HCl solutions.

  18. Silicon carbide as platform for energy applications

    DEFF Research Database (Denmark)

    Syväjärvi, Mikael; Jokubavicius, Valdas; Sun, Jianwu;

    Silicon carbide is emerging as a novel material for a range of energy and environmental technologies. Previously, silicon carbide was considered as a material mainly for transistor applications. We have initiated the use of silicon carbide material towards optoelectronics in general lighting...

  19. Thermal conductivity of boron carbides

    Science.gov (United States)

    Wood, C.; Emin, D.; Gray, P. E.

    1985-01-01

    Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

  20. Palladium interaction with silicon carbide

    OpenAIRE

    M. Gentile, P. Xiao, T. Abram

    2015-01-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide...

  1. Effects of space exposure on ion-beam-deposited silicon-carbide and boron-carbide coatings.

    Science.gov (United States)

    Keski-Kuha, R A; Blumenstock, G M; Fleetwood, C M; Schmitt, D R

    1998-12-01

    Two recently developed optical coatings, ion-beam-deposited silicon carbide and ion-beam-deposited boron carbide, are very attractive as coatings on optical components for instruments for space astronomy and earth sciences operating in the extreme-UV spectral region because of their high reflectivity, significantly higher than any conventional coating below 105 nm. To take full advantage of these coatings in space applications, it is important to establish their ability to withstand exposure to the residual atomic oxygen and other environmental effects at low-earth-orbit altitudes. The first two flights of the Surface Effects Sample Monitor experiments flown on the ORFEUS-SPAS and the CRISTA-SPAS Shuttle missions provided the opportunity to study the effects of space exposure on these materials. The results indicate a need to protect ion-beam-deposited silicon-carbide-coated optical components from environmental effects in a low-earth orbit. The boron-carbide thin-film coating is a more robust coating able to withstand short-term exposure to atomic oxygen in a low-earth-orbit environment.

  2. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  3. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed. PMID:27609195

  4. Ceramic technology for Advanced Heat Engines Project

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.

    1991-07-01

    Significant accomplishments in fabricating ceramic components for advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and database and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. An assessment of needs was completed, and a five year project plan was developed with extensive input from private industry. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities. This project is managed by ORNL for the Office of Transportation Technologies, Office of Transportation Materials, and is closely coordinated with complementary ceramics tasks funded by other DOE offices, NASA, DOD, and industry.

  5. Flash sintering of ceramic materials

    Science.gov (United States)

    Dancer, C. E. J.

    2016-10-01

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

  6. Ceramic heat exchangers. (Latest citations from the NTIS bibliographic database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-08-01

    The bibliography contains citations concerning the development, fabrication, and performance of ceramic heat exchangers. References discuss applications in coal-fired gas turbine power plants. Topics cover high temperature corrosion resistance, fracture properties, nondestructive evaluations, thermal shock and fatigue, silicon carbide-based ceramics, and composite joining. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  7. Liquid phase sintering of SiC ceramics with rare earth sesquioxides

    OpenAIRE

    Biswas, Koushik

    2002-01-01

    The objective of this work is to develop SiC ceramics using high refractory sintering additives which posses good high temperature as well as room temperature properties. Silicon carbide ceramics were produced by pressureless sintering of a mixture of alpha- and beta-SiC powders along with different combinations of rare earth sesquioxides and aluminium nitride as sintering additives. In order to understand the densification behaviour, the green bodies were sintered in Ar or N2 atmosphere in t...

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

    Science.gov (United States)

    Kalluri, Ajith Kumar

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

  9. Ceramic Cerami Turbine Nozzle

    Science.gov (United States)

    Boyd, Gary L.

    1997-04-01

    A turbine nozzle vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes an outer shroud and an inner shroud having a plurality of horizontally segmented vanes therebetween being positioned by a connecting member positioning segmented vanes in functional relationship one to another. The turbine nozzle vane assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the other component.

  10. Ceramic turbine nozzle

    Science.gov (United States)

    Shaffer, James E.; Norton, Paul F.

    1996-01-01

    A turbine nozzle and shroud assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes a plurality of segmented vane defining a first vane segment and a second vane segment. Each of the first and second vane segments having a vertical portion. Each of the first vane segments and the second vane segments being positioned in functional relationship one to another within a recess formed within an outer shroud and an inner shroud. The turbine nozzle and shroud assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being less than the preestablished rate of thermal expansion of the other component.

  11. Method of joining ceramics

    Science.gov (United States)

    Henager, Jr., Charles H.; Brimhall, John L.

    2000-01-01

    According to the method of the present invention, joining a first bi-element carbide to a second bi-element carbide, has the steps of: (a) forming a bond agent containing a metal carbide and silicon; (b) placing the bond agent between the first and second bi-element carbides to form a pre-assembly; and (c) pressing and heating the pre-assembly in a non-oxidizing atmosphere to a temperature effective to induce a displacement reaction creating a metal silicon phase bonding the first and second bi-element carbides.

  12. Continuous method of producing silicon carbide fibers

    Science.gov (United States)

    Barnard, Thomas Duncan (Inventor); Nguyen, Kimmai Thi (Inventor); Rabe, James Alan (Inventor)

    1999-01-01

    This invention pertains to a method for production of polycrystalline ceramic fibers from silicon oxycarbide (SiCO) ceramic fibers wherein the method comprises heating an amorphous ceramic fiber containing silicon and carbon in an inert environment comprising a boron oxide and carbon monoxide at a temperature sufficient to convert the amorphous ceramic fiber to a polycrystalline ceramic fiber. By having carbon monoxide present during the heating of the ceramic fiber, it is possible to achieve higher production rates on a continuous process.

  13. Friction and wear behavior of chromium carbide coatings

    International Nuclear Information System (INIS)

    Chromium carbides, tungsten carbide, and chromium oxide have been tested and evaluated as coatings to protect high-temperature gas-cooled reactor (HTGR) steam generator and other HTGR components from adhesion, galling associated with sliding wear or from fretting. Tests were performed in commercially-pure helium and in helium doped with various gaseous impurities (H2, H2O, CH4, CO) to simulate the primary coolant of an HTGR. Several types of chromium carbide coatings including Cr3C2, Cr7C3, and Cr23C6, were tested for wear resistance and resistance to long-term spalling. Tungsten carbide and chromium oxide coatings were tested in sliding wear tests. Cr23C6-NiCr coatings showed the best performance (from 400 to 8160C) whether they were applied by detonation gun or plasma gun spraying methods. The presence of the Cr23C6-NiCr coatings did not affect the creep rupture properties of Alloy 800H substrates at temperatures up to 7600C. Low-cycle fatigue life of similar specimens at 5930C was reduced to 10 to 20% when tested in the 1 to 0.6% strain range

  14. Evaluation of the role of reactive oxygen species in the interactive toxicity of carbide-cobalt mixtures on macrophages in culture.

    Science.gov (United States)

    Lison, D; Lauwerys, R

    1993-01-01

    The lung toxicity of a carbide-cobalt mixture is more important than that of each individual component; the mechanism of this interaction is not understood. The capacity of cobalt metal particles alone and mixed with different carbides to generate hydroxyl radicals was examined with the deoxyribose assay. In a chemical system, cobalt ions and cobalt metal particles (Co) were found to catalyse the degradation of deoxyribose in the presence of hydrogen peroxide. Carbides were able to directly oxidize deoxyribose, but their respective activities did not support such a mechanism to explain the carbide-cobalt interactive toxicity, since there was no direct relationship between deoxyribose degradation ability and cytotoxicity toward macrophages. Tungsten, niobium, titanium and chromium carbides (interactive carbides) were only weak oxidants and conversely molybdenum, vanadium and silicon carbides (non-interactive carbides) were the most potent ones. The ability of cobalt metal to produce hydroxyl radicals in the presence of hydrogen peroxide was not increased by tungsten carbide. The role of reactive radical formation in the toxicity of these particles was further assessed in a macrophage culture model. Catalase (4000 U/ml), superoxide dismutase (300 U/ml), sodium azide (1 mM), sodium benzoate, mannitol, taurine and methionine (all 20 mM) were all unable to protect against the cytotoxic effects of cobalt ions and cobalt metal alone or mixed with tungsten carbide. In conclusion, no evidence was found that production of reactive oxygen species contributes to the elective toxicity of carbide-cobalt mixtures. PMID:8396391

  15. Combustion Synthesis of h-BN-SiC Ceramic Composites

    Institute of Scientific and Technical Information of China (English)

    LI Hong-bo; ZHENG Yong-ting; ZHOU Li-juan; HAN Jie-cai

    2006-01-01

    The feasibility was demonstrated to fabricate h-BN-SiC ceramics through combustion synthesis of the mixture of boron carbide and silicon powders under 100 MPa nitrogen pressure. The mass fraction of BN and SiC in the combustion products were found to be 72 % and 28 % respectively. The thermodynamics of the synthesis reaction and the adiabatic combustion temperature were calculated on the theoretical ground. The bending strengths of the ceramics were measured to be 65.2 MPa at room temperature and 55 MPa at 1350 ℃. The phase composition and microstructure of the combustion products were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

  16. Laser cladding in-situ carbide particle reinforced Fe-based composite coatings with rare earth oxide addition

    Institute of Scientific and Technical Information of China (English)

    吴朝锋; 马明星; 刘文今; 钟敏霖; 张红军; 张伟明

    2009-01-01

    Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...

  17. Stored energy in irradiated silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Snead, L.L.; Burchell, T.D. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    This report presents a short review of the phenomenon of Wigner stored energy release from irradiated graphite and discusses it in relation to neutron irradiation of silicon carbide. A single published work in the area of stored energy release in SiC is reviewed and the results are discussed. It appears from this previous work that because the combination of the comparatively high specific heat of SiC and distribution in activation energies for recombining defects, the stored energy release of SiC should only be a problem at temperatures lower than those considered for fusion devices. The conclusion of this preliminary review is that the stored energy release in SiC will not be sufficient to cause catastrophic heating in fusion reactor components, though further study would be desirable.

  18. a Plutonium Ceramic Target for Masha

    Science.gov (United States)

    Wilk, P. A.; Shaughnessy, D. A.; Moody, K. J.; Kenneally, J. M.; Wild, J. F.; Stoyer, M. A.; Patin, J. B.; Lougheed, R. W.; Ebbinghaus, B. B.; Landingham, R. L.; Oganessian, Yu. Ts.; Yeremin, A. V.; Dmitriev, S. N.

    2005-09-01

    We are currently developing a plutonium ceramic target for the MASHA mass separator. The MASHA separator will use a thick plutonium ceramic target capable of tolerating temperatures up to 2000 °C. Promising candidates for the target include oxides and carbides, although more research into their thermodynamic properties will be required. Reaction products will diffuse out of the target into an ion source, where they will then be transported through the separator to a position-sensitive focal-plane detector array. Experiments on MASHA will allow us to make measurements that will cement our identification of element 114 and provide for future experiments where the chemical properties of the heaviest elements are studied.

  19. Enhanced mechanical properties of nanocrystalline boron carbide by nanoporosity and interface phases.

    Science.gov (United States)

    Madhav Reddy, K; Guo, J J; Shinoda, Y; Fujita, T; Hirata, A; Singh, J P; McCauley, J W; Chen, M W

    2012-01-01

    Ceramics typically have very high hardness, but low toughness and plasticity. Besides intrinsic brittleness associated with rigid covalent or ionic bonds, porosity and interface phases are the foremost characteristics that lead to their failure at low stress levels in a brittle manner. Here we show that, in contrast to the conventional wisdom that these features are adverse factors in mechanical properties of ceramics, the compression strength, plasticity and toughness of nanocrystalline boron carbide can be noticeably improved by introducing nanoporosity and weak amorphous carbon at grain boundaries. Transmission electron microscopy reveals that the unusual nanosize effect arises from the deformation-induced elimination of nanoporosity mediated by grain boundary sliding with the assistance of the soft grain boundary phases. This study has important implications in developing high-performance ceramics with ultrahigh strength and enhanced plasticity and toughness.

  20. Economical Fabrication of Thick-Section Ceramic Matrix Composites

    Science.gov (United States)

    Babcock, Jason; Ramachandran, Gautham; Williams, Brian; Benander, Robert

    2010-01-01

    A method was developed for producing thick-section [>2 in. (approx.5 cm)], continuous fiber-reinforced ceramic matrix composites (CMCs). Ultramet-modified fiber interface coating and melt infiltration processing, developed previously for thin-section components, were used for the fabrication of CMCs that were an order of magnitude greater in thickness [up to 2.5 in. (approx.6.4 cm)]. Melt processing first involves infiltration of a fiber preform with the desired interface coating, and then with carbon to partially densify the preform. A molten refractory metal is then infiltrated and reacts with the excess carbon to form the carbide matrix without damaging the fiber reinforcement. Infiltration occurs from the inside out as the molten metal fills virtually all the available void space. Densification to thick-section components required modification of the conventional process conditions, and the means by which the large amount of molten metal is introduced into the fiber preform. Modification of the low-temperature, ultraviolet-enhanced chemical vapor deposition process used to apply interface coatings to the fiber preform was also required to accommodate the high preform thickness. The thick-section CMC processing developed in this work proved to be invaluable for component development, fabrication, and testing in two complementary efforts. In a project for the Army, involving SiC/SiC blisk development, nominally 0.8 in. thick x 8 in. diameter (approx. 2 cm thick x 20 cm diameter) components were successfully infiltrated. Blisk hubs were machined using diamond-embedded cutting tools and successfully spin-tested. Good ply uniformity and extremely low residual porosity (41 ksi (approx. 283 MPa) flexural strength.

  1. High Strength Silicon Carbide Foams and Their Deformation Behavior

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Silicon carbide (SiC) foams with a continuously connected open-cell structure were prepared and characterized for their mechanical performance. The apparent densities of SiC foams were controlled between about 0.4 and 1.3 g/cm3, with corresponding compressive strengths ranging from about 13 to 60 MPa and flexural strengths from about 8 to 30 MPa. Compressive testing of the SiC foams yielded stress-strain curves with only one linear-elastic region, which is different from those reported on ceramic foams in literature. This can possibly be attributed to the existence of filaments with fine, dense and high strength microstructures. The SiC and the filaments respond homogeneously to applied loading.

  2. Chemical, Electrical and Thermal Characterization of Nanoceramic Silicon Carbide

    Science.gov (United States)

    Martin, Hervie; Abunaemeh, Malek; Smith, Cydale; Muntele, Claudiu; Budak, Satilmish; Ila, Daryush

    2009-03-01

    Silicon carbide (SiC) is a lightweight high bandgap semiconductor material that can maintain dimensional and chemical stability in adverse environments and very high temperatures. These properties make it suitable for high temperature thermoelectric converters. At the Center for Irradiaton of Materials (CIM) we design, manufacture and fabricate nanoceramic SiC, and perform electrical, thermal and chemical characterization of the material using particle induced X-ray emission (PIXE), Rutherford backscattering spectroscopy (RBS), Seebeck coefficient, electrical conductivity, and thermal conductivity measurements to calculate its efficiency as a thermoelectric generator. We are looking to compare the electrical and thermal properties of SiC ceramics with some other materials used for the same purposes.

  3. New method for synthesis of metal carbides, nitrides and carbonitrides

    Energy Technology Data Exchange (ETDEWEB)

    Koc, R.; Folmer, J.S.; Kodambaka, S.K. [Southern Illinois Univ., Carbondale, IL (United States)] [and others

    1997-04-01

    The purpose of this work is to develop a novel synthesis method using a carbothermic reduction reaction of carbon coated precursors for producing high purity, submicron, non-agglomerated powders of metal carbide, metal nitride and metal boride systems. The authors also want to demonstrate the advantages of the process and provide information on the applicability of the process for synthesizing related advanced ceramic powders (e.g. SiC, WC, TiN, TiB{sub 2}, Si{sub 3}N{sub 4}). During the FY96 of the project, steps are taken to investigate the reaction mechanisms and phase evolution during the formation of TiC from carbon coated titania precursors and to produce submicron TiC powders with desired stoichiometries. Depending on the carbon content in the coated titania precursor, TiC powder was produced with different stoichiometries (different amount of oxygen and free carbon).

  4. Ceramic Technology Project semiannual progress report, April 1992--September 1992

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, D.R.

    1993-07-01

    This project was developed to meet the ceramic technology requirements of the DOE Office of Transportation Systems` automotive technology programs. Significant progress in fabricating ceramic components for DOE, NASA, and DOE advanced heat engine programs show that operation of ceramic parts in high-temperature engines is feasible; however, addition research is needed in materials and processing, design, and data base and life prediction before industry will have a sufficient technology base for producing reliable cost-effective ceramic engine components commercially. A 5-yr project plan was developed, with focus on structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines.

  5. Imaging subtle microstructural variations in ceramics with precision ultrasonic velocity and attenuation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Generazio, E.R.; Roth, D.J.; Baaklini, G.Y.

    1987-11-01

    Acoustic images of a silicon carbide ceramic disk were obtained using a precision scanning contact pulse echo technique. Phase and cross-correlation velocity, and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with x-ray radiography.

  6. Imaging subtle microstructural variations in ceramics with precision ultrasonic velocity and attenuation measurements

    Science.gov (United States)

    Generazio, Edward R.; Roth, Don J.; Baaklini, George Y.

    1987-01-01

    Acoustic images of a silicon carbide ceramic disk were obtained using a precision scanning contact pulse echo technique. Phase and cross-correlation velocity, and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with X-ray radiography.

  7. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  8. Conduction mechanism in boron carbide

    Science.gov (United States)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  9. Method to manufacture tungsten carbide

    International Nuclear Information System (INIS)

    The patent deals with an improved method of manufacturing tungsten carbide. An oxide is preferably used as initial product whose particle size and effective surface approximately corresponds to that of the endproduct. The known methods for preparing the oxide are briefly given. Carbon monoxide is passed over the thus obtained oxide particles whereby the reaction mixture is heated to a temperature at which tungsten oxide and carbon monoxide react and tungsten carbide is formed, however, below that temperature at which the tungsten-containing materials are caked or sintered together. According to the method the reaction temperature is about below 9000C. The tungsten carbide produced has a particle size of under approximately 100 A and an active surface of about 20 m2/g. It has sofar not been possible with the usual methods to obtain such finely divided material with such a large surface. These particles may be converted back to the oxide by heating in air at low temperature without changing particle size and effective surface. One thus obtains a tungsten oxide with smaller particle size and larger effective surface than the initial product. (IHOE)

  10. Electron microscopy study of radiation effects in boron carbide

    International Nuclear Information System (INIS)

    Boron carbide is a disordered non-stoechiometric material with a strongly microtwinned polycristallyne microstructure. This ceramic is among the candidate materials for the first wall coating in fusion reactor and is used as a neutron absorber in the control rods of fast breeder reactors. The present work deals with the nature of radiation damage in this solid. Because of helium internal production, neutron irradiated boron carbide is affected by swelling and by a strong microcracking which can break up a pellet in fine powder. These processes are rather intensitive to the irradiation parameters (temperature, flux and even neutron spectrum). Transmission electron microscopy of samples irradiated by the fast neutrons of a reactor, the electrons of a high voltage electron microscope and of samples implanted with helium ions was used to understand the respective roles of helium and point defects in the processes of swelling and microcracking. The design of an irradiation chamber for helium implantation at controlled temperature from 600 to 17000C was an important technical part of this work

  11. Study of Gamma Ray Exposure Buildup Factor for Some Ceramics with Photon Energy, Penetration Depth and Chemical Composition

    Directory of Open Access Journals (Sweden)

    Tejbir Singh

    2013-01-01

    Full Text Available Gamma ray exposure buildup factor for some ceramics such as boron nitride (BN, magnesium diboride (MgB2, silicon carbide (SiC, titanium carbide (TiC and ferrite (Fe3O4 has been computed using five parametric geometric progression (G.P. fitting method in the energy range of 0.015 to 15.0 MeV, up to the penetration of 40 mean free path (mfp. The variation of exposure buildup factors for all the selected ceramics with incident photon energy, penetration depth, and chemical composition has been studied.

  12. In-situ Formation of Reinforcement Phases in Ultra High Temperature Ceramic Composites

    Science.gov (United States)

    Stackpoole, Margaret M (Inventor); Gasch, Matthew J (Inventor); Olson, Michael W (Inventor); Hamby, Ian W. (Inventor); Johnson, Sylvia M (Inventor)

    2013-01-01

    A tough ultra-high temperature ceramic (UHTC) composite comprises grains of UHTC matrix material, such as HfB.sub.2, ZrB.sub.2 or other metal boride, carbide, nitride, etc., surrounded by a uniform distribution of acicular high aspect ratio reinforcement ceramic rods or whiskers, such as of SiC, is formed from uniformly mixing a powder of the UHTC material and a pre-ceramic polymer selected to form the desired reinforcement species, then thermally consolidating the mixture by hot pressing. The acicular reinforcement rods may make up from 5 to 30 vol % of the resulting microstructure.

  13. Structural prediction for scandium carbide monolayer sheet

    Science.gov (United States)

    Ma, Hong-Man; Wang, Jing; Zhao, Hui-Yan; Zhang, Dong-Bo; Liu, Ying

    2016-09-01

    A two-dimensional tetragonal scandium carbide monolayer sheet has been constructed and studied using density functional theory. The results show that the scandium carbide sheet is stable and exhibits a novel tetracoordinated quasiplanar structure, as favored by the hybridization between Sc-3d orbitals and C-2p orbitals. Calculations of the phonon dispersion as well as molecular dynamics simulations also demonstrate the structural stability of this scandium carbide monolayer sheet. Electronic properties show that the scandium carbide monolayer sheet is metallic and non-magnetic.

  14. Methods for producing silicon carbide fibers

    Science.gov (United States)

    Garnier, John E.; Griffith, George W.

    2016-03-01

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  15. Silicon carbide fibers and articles including same

    Science.gov (United States)

    Garnier, John E; Griffith, George W

    2015-01-27

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  16. Polytype distribution in circumstellar silicon carbide.

    Science.gov (United States)

    Daulton, T L; Bernatowicz, T J; Lewis, R S; Messenger, S; Stadermann, F J; Amari, S

    2002-06-01

    The inferred crystallographic class of circumstellar silicon carbide based on astronomical infrared spectra is controversial. We have directly determined the polytype distribution of circumstellar SiC from transmission electron microscopy of presolar silicon carbide from the Murchison carbonaceous meteorite. Only two polytypes (of a possible several hundred) were observed: cubic 3C and hexagonal 2H silicon carbide and their intergrowths. We conclude that this structural simplicity is a direct consequence of the low pressures in circumstellar outflows and the corresponding low silicon carbide condensation temperatures. PMID:12052956

  17. Investigation of the Corrosion Behaviors of HVOF-Sprayed Carbide Cernet Coatings in Molten Al-Zn-Si Alloy Bath

    Institute of Scientific and Technical Information of China (English)

    JIANG Zhen-hua; TAN Xing-hai; ZHANG Yue-gang; SUN Jia-shu

    2004-01-01

    In continuous hot-dip galvanization process the corrosion and chemical stability of the sink roll in the galvanizing bath are important problem which effects on the quality and productivity. In order to protect the sink roll the carbide cermet and/or ceramic coatings were deposited on the surface of the sink roll. The WC-, Cr3 C2-cermet coatings were deposited by high velocity oxygen fuel (HVOF) spray, respectively. The coating samples were immersed in molten Zn-alloy containing 50 wt % aluminum at 833 K for 24 hr and 144 hr, respectively. The inter-diffusion and inter-reaction of Zn, Al and elements in coating and corrosion behaviors of these coatings were investigated by XRD, SEM and EPMA etc. The corrosion mechanisms of the carbide cermet coatings and ceramic coatings in molten High Al-Zn-alloy were approached.

  18. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.

  19. Valence electronic structure of tantalum carbide and nitride

    Institute of Scientific and Technical Information of China (English)

    FAN; ChangZeng

    2007-01-01

    The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent, metallic and ionic characters. For a quantitative analysis of the relative strength of these components, their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN, which coincides to that deduced from the first-principles method.……

  20. Ceramic Technology for Advanced Heat Engines Project

    Energy Technology Data Exchange (ETDEWEB)

    1990-08-01

    The Ceramic Technology For Advanced Heat Engines Project was developed by the Department of Energy's Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Advanced Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the Department of Energy (DOE), National Aeronautics and Space Administration (NASA), and Department of Defense (DOD) advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. However, these programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. An assessment of needs was completed, and a five year project plan was developed with extensive input from private industry. The objective of the project is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on structural ceramics for advanced gas turbine and diesel engines, ceramic hearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines.

  1. Challenges and Opportunities in Reactive Processing and Applications of Advanced Ceramic Materials

    Science.gov (United States)

    Singh, Mrityunjay

    2003-01-01

    Recently, there has been a great deal of interest in the research, development, and commercialization of innovative synthesis and processing technologies for advanced ceramics and composite materials. Reactive processing approaches have been actively considered due to their robustness, flexibility, and affordability. A wide variety of silicon carbide-based advanced ceramics and composites are currently being fabricated using the processing approaches involving reactive infiltration of liquid and gaseous species into engineered fibrous or microporous carbon performs. The microporous carbon performs have been fabricated using the temperature induced phase separation and pyrolysis of two phase organic (resin-pore former) mixtures and fiber reinforcement of carbon and ceramic particulate bodies. In addition, pyrolyzed native plant cellulose tissues also provide unique carbon templates for manufacturing of non-oxide and oxide ceramics. In spite of great interest in this technology due to their affordability and robustness, there is a lack of scientific basis for process understanding and many technical challenges still remain. The influence of perform properties and other parameters on the resulting microstructure and properties of final material is not well understood. In this presentation, mechanism of silicon-carbon reaction in various systems and the effect of perform microstructure on the mechanical properties of advanced silicon carbide based materials will be discussed. Various examples of applications of reactively processed advanced silicon carbide ceramics and composite materials will be presented.

  2. Development of Advanced Ceramic Manufacturing Technology

    Energy Technology Data Exchange (ETDEWEB)

    Pujari, V.K.

    2001-04-05

    Advanced structural ceramics are enabling materials for new transportation engine systems that have the potential for significantly reducing energy consumption and pollution in automobiles and heavy vehicles. Ceramic component reliability and performance have been demonstrated in previous U.S. DOE initiatives, but high manufacturing cost was recognized as a major barrier to commercialization. Norton Advanced Ceramics (NAC), a division of Saint-Gobain Industrial Ceramics, Inc. (SGIC), was selected to perform a major Advanced Ceramics Manufacturing Technology (ACMT) Program. The overall objectives of NAC's program were to design, develop, and demonstrate advanced manufacturing technology for the production of ceramic exhaust valves for diesel engines. The specific objectives were (1) to reduce the manufacturing cost by an order of magnitude, (2) to develop and demonstrate process capability and reproducibility, and (3) to validate ceramic valve performance, durability, and reliability. The program was divided into four major tasks: Component Design and Specification, Component Manufacturing Technology Development, Inspection and Testing, and Process Demonstration. A high-power diesel engine valve for the DDC Series 149 engine was chosen as the demonstration part for this program. This was determined to be an ideal component type to demonstrate cost-effective process enhancements, the beneficial impact of advanced ceramics on transportation systems, and near-term commercialization potential. The baseline valve material was NAC's NT451 SiAION. It was replaced, later in the program, by an alternate silicon nitride composition (NT551), which utilized a lower cost raw material and a simplified powder-processing approach. The material specifications were defined based on DDC's engine requirements, and the initial and final component design tasks were completed.

  3. Formation and corrosion of a 410 SS/ceramic composite

    Science.gov (United States)

    Chen, X.; Ebert, W. L.; Indacochea, J. E.

    2016-11-01

    This study addressed the possible use of alloy/ceramic composite waste forms to immobilize metallic and oxide waste streams generated during the electrochemical reprocessing of spent reactor fuel using a single waste form. A representative composite material was made to evaluate the microstructure and corrosion behavior at alloy/ceramic interfaces by reacting 410 stainless steel with Zr, Mo, and a mixture of lanthanide oxides. Essentially all of the available Zr reacted with lanthanide oxides to generate lanthanide zirconates, which combined with the unreacted lanthanide oxides to form a porous ceramic network that filled with alloy to produce a composite puck. Alloy present in excess of the pore volume of the ceramic generated a metal bead on top of the puck. The alloys in the composite and forming the bead were both mixtures of martensite grains and ferrite grains bearing carbide precipitates; FeCrMo intermetallic phases also precipitated at ferrite grain boundaries within the composite puck. Micrometer-thick regions of ferrite surrounding the carbides were sensitized and corroded preferentially in electrochemical tests. The lanthanide oxides dissolved chemically, but the lanthanide zirconates did not dissolve and are suitable host phases. The presence of oxide phases did not affect corrosion of the neighboring alloy phases.

  4. Technology Research of Ultrafine Grinding Boron Carbide%碳化硼超细粉碎工艺研究

    Institute of Scientific and Technical Information of China (English)

    王圈库; 焦永峰

    2013-01-01

    碳化硼(B4C)是重要的超硬材料,B4C陶瓷是高性能的工程陶瓷材料,采用亚微米级超细粉体原料是制备碳化硼陶瓷良好性能的关键.本文采用砂磨工艺制备亚微米B4C超细粉体,对砂磨工艺的球料比、料水比和分散剂用量等工艺参数进行了考察,成功制备得到中位粒径D50小于0.6μm的碳化硼超细粉体,并用以制备得到了高致密度无压烧结碳化硼陶瓷.%Boron carbide (B4C) is an important super hard materials,and B4C ceramics is one kind of high performance engineering ceramics.Sub-micron B4C powder is the key to ensure good performance for ceramic materials.In this paper,sub-micron boron carbide powder was fabricated by attrition milling process,and the ball-feed ratio,feed-water ratio and the amount of dispersant were investigated.The boron carbide powder which grain size D50 is less than 0.6 μ m was prepared successful,and then high density pressure less sintering boron carbide ceramic was prepared.

  5. Dispersion of boron carbide in a tungsten carbide/cobalt matrix

    International Nuclear Information System (INIS)

    Particles of boron carbide (105-125 microns) were coated with a layer (10-12 microns) of titanium carbide in a fluidized bed. These coated particles have been successfully incorporated in a tungsten carbide--cobalt matrix by hot pressing at 1 tonf/in2, (15.44 MN/m2) at 13500C. Attempts to produce a similar material by a cold pressing and sintering technique were unsuccessful because of penetration of the titanium carbide layer by liquid cobalt. Hot-pressed material containing boron carbide had a static strength in bend of approximately 175,000 lbf/in2, (1206MN/m2) which compares favorably with the strength of conventionally produced tungsten carbide/cobalt. The impact strength of the material containing boron carbide was however considerably lower than tungsten carbide/cobalt. In rock drilling tests on Darley Dale sandstone at low speeds and low loads, the material containing boron carbide drilled almost ten times as far without seizure as tungsten carbide/cobalt. In higher speed and higher load rotary drilling tests conducted by the National Coal Board, the material containing boron carbide chipped badly compared with normal NCB hardgrade material

  6. Boron carbide whiskers produced by vapor deposition

    Science.gov (United States)

    1965-01-01

    Boron carbide whiskers have an excellent combination of properties for use as a reinforcement material. They are produced by vaporizing boron carbide powder and condensing the vapors on a substrate. Certain catalysts promote the growth rate and size of the whiskers.

  7. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This techn

  8. Production and characterization of ceramics for armor application

    International Nuclear Information System (INIS)

    The fabrication of devices for ballistic protection as bullet proof vests and helmets and armored vehicles has been evolving over the past years along with the materials and models used for this specific application. The requirements for high efficient light-weight ballistic protection systems which not interfere in the user comfort and mobility has driven the research in this area. In this work we will present the results of characterization of two ceramics based on alumina and silicon carbide. The ceramics were produced in lab scale and the specific mass, scanning electron microscopy (SEM) microstructure, Vickers hardness, flexural resistance at room temperature and X-ray diffraction were evaluated. Ballistic tests performed in the selected materials showed that the ceramics present armor efficiency. (author)

  9. Structural changes induced by heavy ion irradiation in titanium silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nappe, J.C., E-mail: jc.nappe@yahoo.fr [Ecole Nationale Superieure des Mines, SPIN/PMMC, LPMG UMR CNRS 5148, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France); Monnet, I. [CIMAP, CEA-CNRS-ENSICAEN-Universite de Caen Basse Normandie, Bd Henri Becquerel, BP 5133, F-14070 Caen cedex 5 (France); Grosseau, Ph. [Ecole Nationale Superieure des Mines, SPIN/PMMC, LPMG UMR CNRS 5148, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France); Audubert, F. [CEA, DEN, DEC/SPUA/LTEC, Cadarache, 13108 St. Paul lez Durance (France); Guilhot, B. [Ecole Nationale Superieure des Mines, CIS/B2M, 158 cours Fauriel, 42023 Saint-Etienne cedex 2 (France); Beauvy, M. [CIMAP, CEA-CNRS-ENSICAEN-Universite de Caen Basse Normandie, Bd Henri Becquerel, BP 5133, F-14070 Caen cedex 5 (France); Benabdesselam, M. [Universite de Nice - Sophia Antipolis, LPMC UMR CNRS 6622, Parc Valrose, 06108 Nice cedex 2 (France); Thome, L. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS-IN2P3-Universite Paris Sud, UMR 8609, Bat. 108, 91405 Orsay (France)

    2011-02-01

    Carbide-type ceramics, which have remarkable thermomechanical properties, are sensed to manufacture the fuel cladding of Generation IV reactors that should work at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished from other materials by their ability to have some plasticity, even at room temperature. For this study, polycrystalline Ti{sub 3}SiC{sub 2} was irradiated with ions of different energies, which allow to discriminate the effect of both electronic and nuclear interactions. After characterization by low-incidence X-ray diffraction and cross-sectional transmission electron microscopy, it appears that Ti{sub 3}SiC{sub 2} is not sensitive to electronic excitations while nuclear shocks damage its structure. The results show the creation of many defects and disorder in the structure, an expansion of the hexagonal close-packed lattice along the c axis, and an increase in the microstrain yield.

  10. Structural changes induced by heavy ion irradiation in titanium silicon carbide

    Science.gov (United States)

    Nappé, J. C.; Monnet, I.; Grosseau, Ph.; Audubert, F.; Guilhot, B.; Beauvy, M.; Benabdesselam, M.; Thomé, L.

    2011-02-01

    Carbide-type ceramics, which have remarkable thermomechanical properties, are sensed to manufacture the fuel cladding of Generation IV reactors that should work at high temperature. The MAX phases, and more particularly titanium silicon carbide, are distinguished from other materials by their ability to have some plasticity, even at room temperature. For this study, polycrystalline Ti 3SiC 2 was irradiated with ions of different energies, which allow to discriminate the effect of both electronic and nuclear interactions. After characterization by low-incidence X-ray diffraction and cross-sectional transmission electron microscopy, it appears that Ti 3SiC 2 is not sensitive to electronic excitations while nuclear shocks damage its structure. The results show the creation of many defects and disorder in the structure, an expansion of the hexagonal close-packed lattice along the c axis, and an increase in the microstrain yield.

  11. Thermal analysis study of polymer-to-ceramic conversion of organosilicon precursors

    Directory of Open Access Journals (Sweden)

    Galusek D.

    2008-01-01

    Full Text Available The organosilicon precursors attract significant attention as substances, which upon heating in inert or reactive atmosphere convert directly to oxide or non-oxide ceramics, like nitrides, carbides, carbonitrides, boroncarbonitrides, oxycarbides, alons, etc. In characterisation, and in study of conversion of these polymers to ceramics thermal analysis plays an important role. The degree of cross-linking of the polymer vital for achievement of high ceramic yield is estimated with the use of thermal mechanical analysis (TMA. Decomposition of polymers and their conversion to ceramics is studied by the combination of differential thermal analysis (DTA, differential scanning calorimetry (DSC thermogravimetry(TG, and mass spectrometry (MS. The use of these methods in study of the polymer-to-ceramic conversion is illustrated by case studies of a commercially available poly(allylcarbosilane as the precursor of SiC, and a poly(hydridomethylsilazane as the precursor of SiCN.

  12. Preparation and Easy-Cleaning Property of Rare Earth Composite Ceramic

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Rare earth and far-infrared mineral composite materials were added to ceramic glazes to prepare easy-cleaning ceramic. The morphology of easy-cleaning ceramic was observed by SEM. The influence of easy-cleaning ceramic on water surface tension and contact angles of water were investigated. Through calculation of ceramic surface free energy and observation of oil drop on ceramic surface in water, the easy-cleaning mechanism of rare earth composite ceramic was studied. It is found that the rare earth composite ceramic can make water surface tension decrease. The surface free energy and the polar component of rare earth composite ceramic are increased. The rare earth composite ceramics have the easy-cleaning property.

  13. Electro Conductive Alumina Nanocomposites From Different Alumina-Carbides Mixtures

    Directory of Open Access Journals (Sweden)

    Díaz Luis A.

    2016-01-01

    SiC whiskers reinforced electrically conductive ceramic compositions provide a fully dense material with optimal mechanical properties. The capability of electro-discharge machining obtains good surface quality, chip-free edges, dimensional accuracy and complex shapes. The fracture toughness is improved two to three fold over individual ceramic components. Strength and hardness is also increased. Some composites were tested as a cutting tool to machine IN-718 nickel-base superalloy industrial laminating cylinders. The composites were formed and electro-discharge machined to a standard size cutting insert.

  14. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.;

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first...... example of a cationic terminal carbide complex, [RuC(Cl)(CH3CN)(PCy3)2]+, is described and characterized by NMR, MS, X-ray crystallography, and computational studies. The experimentally observed irregular variation of the carbide 13C chemical shift is shown to be accurately reproduced by DFT, which also...... demonstrates that details of the coordination geometry affect the carbide chemical shift equally as much as variations in the nature of the auxiliary ligands. Furthermore, the kinetics of formation of the sqaure pyramidal dicyano complex, trans-[RuC(CN)2(PCy3)2], from RuC has been examined and the reaction...

  15. Lightweight Ceramic Composition of Carbon Silicon Oxygen and Boron

    Science.gov (United States)

    Leiser, Daniel B. (Inventor); Hsu, Ming-Ta (Inventor); Chen, Timothy S. (Inventor)

    1997-01-01

    Lightweight, monolithic ceramics resistant to oxidation in air at high temperatures are made by impregnating a porous carbon preform with a sol which contains a mixture of tetraethoxysilane, dimethyldiethoxysilane and trimethyl borate. The sol is gelled and dried on the carbon preform to form a ceramic precursor. The precursor is pyrolyzed in an inert atmosphere to form the ceramic which is made of carbon, silicon, oxygen and boron. The carbon of the preform reacts with the dried gel during the pyrolysis to form a component of the resulting ceramic. The ceramic is of the same size, shape and form as the carbon precursor. Thus, using a porous, fibrous carbon precursor, such as a carbon felt, results in a porous, fibrous ceramic. Ceramics of the invention are useful as lightweight tiles for a reentry spacecraft.

  16. Chemical characterization of marajoara ceramics

    International Nuclear Information System (INIS)

    In this study the elemental concentration of Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn were determined by instrumental neutron activation analysis (INAA) in 204 fragments of Marajoara archaeological ceramics, of which 156 were provided by the Archaeology and Ethnology Museum of Sao Paulo University (MAE) and 48 were provided by Dr. Denise Pahl Schaan, Marajo Museum curator. Also, 9 contemporary ceramics produced and marketed at Marajo Island were analyzed. Electron paramagnetic resonance (EPR) analyses were performed in 8 archaeological samples and 1 contemporary sample in order to identify the burning temperature of the samples. X-ray diffraction (XRD) analyses were performed in 13 archaeological samples and 2 contemporary samples for the investigation of their mineralogical composition. Mahalanobis distance was used for the study of outlier while modified filter was used for the study of the temper added to the ceramic paste. Result interpretation was performed using cluster analysis, principal components analysis and discriminant analysis. Procrustes analysis was used for variable selection and it showed that the Ce, Fe, Eu, Hf, K and Th variables are adequate for the characterization of the analyzed samples. The comparative study among the archaeological and contemporary ceramics showed the arrangement of two well-defined and close groups for the archaeological samples and a third, distant group for the contemporary ones. This result indicates that the archaeological and contemporary ceramics differ in their composition. EPR and XRD analysis were inconclusive for the differentiation of archaeological and contemporary ceramics. (author)

  17. Study of influence content of TiB2 by reaction in situ B4C and TiC in mechanical properties on B4C ceramics

    International Nuclear Information System (INIS)

    The low density of ceramic materials promoted a change in research lines in the defense field. Research efforts and development directed to obtaining products of high density sintered of Al2O3, SiC and B4C, using different routes, both traditional as innovative, led to promising initial results, which justify the convergence of skills for the consolidation of research lines and the nationalization that sintered components of B4C with characteristics and properties compatible with the technical requirements established for the ballistic application. The low density of boron carbide (2.52 g/cm3) gives in the final product a weight approximately 30% lower than armor made of alumina (3.96 g/cm3). (author)

  18. Development of technology for high-level radwaste treatment to ceramic matrix by method of self-propagating high-temperature synthesis

    International Nuclear Information System (INIS)

    For the purpose of reduction of the risk of spread of transuranic actinides, carbon-14 and other radionuclides contained in the NPP HLW, the Rosenergoatom concern decided to develop a technology of self-propagating high-temperature synthesis (SHS) to obtain a ceramic matrix suitable for long-term and ecologically safe deep geological disposal of the high-level radwaste of the nuclear industry. The proposed graphite HLW treatment method to immobilise the radionuclides into the thermally, chemically and radiation stable carbide-corundum matrix is based on a SHS-process according to the chemical reaction in the system C+Al+TiO2, where the component C is irradiated graphite of the RBMK reactor core moderators. This paper reports the results of the R and D activities for optimising the SHS technology on a pilot plant using non-irradiated graphite and fuel spill simulators (HLW). (author)

  19. Reliability and Creep/Fatigue Analysis of a CMC Component

    Science.gov (United States)

    Murthy, Pappu L. N.; Mital, Subodh K.; Gyekenyesi, John Z.; Gyekenyesi, John P.

    2007-01-01

    High temperature ceramic matrix composites (CMC) are being explored as viable candidate materials for hot section gas turbine components. These advanced composites can potentially lead to reduced weight and enable higher operating temperatures requiring less cooling; thus leading to increased engine efficiencies. There is a need for convenient design tools that can accommodate various loading conditions and material data with their associated uncertainties to estimate the minimum predicted life as well as the failure probabilities of a structural component. This paper presents a review of the life prediction and probabilistic analyses performed for a CMC turbine stator vane. A computer code, NASALife, is used to predict the life of a 2-D woven silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine stator vane due to a mission cycle which induces low cycle fatigue and creep. The output from this program includes damage from creep loading, damage due to cyclic loading and the combined damage due to the given loading cycle. Results indicate that the trends predicted by NASALife are as expected for the loading conditions used for this study. In addition, a combination of woven composite micromechanics, finite element structural analysis and Fast Probability Integration (FPI) techniques has been used to evaluate the maximum stress and its probabilistic distribution in a CMC turbine stator vane. Input variables causing scatter are identified and ranked based upon their sensitivity magnitude. Results indicate that reducing the scatter in proportional limit strength of the vane material has the greatest effect in improving the overall reliability of the CMC vane.

  20. 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.

  1. An investigation on gamma attenuation behaviour of titanium diboride reinforced boron carbide-silicon carbide composites

    Science.gov (United States)

    Buyuk, Bulent; Beril Tugrul, A.

    2014-04-01

    In this study, titanium diboride (TiB2) reinforced boron carbide-silicon carbide composites were investigated against Cs-137 and Co-60 gamma radioisotope sources. The composite materials include 70% boron carbide (B4C) and 30% silicon carbide (SiC) by volume. Titanium diboride was reinforced to boron carbide-silicon carbide composites as additive 2% and 4% by volume. Average particle sizes were 3.851 µm and 170 nm for titanium diboride which were reinforced to the boron carbide silicon carbide composites. In the experiments the gamma transmission technique was used to investigate the gamma attenuation properties of the composite materials. Linear and mass attenuation coefficients of the samples were determined. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental results and theoretical results were compared and evaluated with each other. It could be said that increasing the titanium diboride ratio causes higher linear attenuation values against Cs-137 and Co-60 gamma radioisotope sources. In addition decreasing the titanium diboride particle size also increases the linear and mass attenuation properties of the titanium diboride reinforced boron carbide-silicon carbide composites.

  2. In Situ Synthesis of Uranium Carbide and its High Temperature Cubic Phase

    Energy Technology Data Exchange (ETDEWEB)

    Reiche, Helmut Matthias [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-03-25

    New in situ data for the U-C system are presented, with the goal of improving knowledge of the phase diagram to enable production of new ceramic fuels. The none quenchable, cubic, δ-phase, which in turn is fundamental to computational methods, was identified. Rich datasets of the formation synthesis of uranium carbide yield kinetics data which allow the benchmarking of modeling, thermodynamic parameters etc. The order-disorder transition (carbon sublattice melting) was observed due to equal sensitivity of neutrons to both elements. This dynamic has not been accurately described in some recent simulation-based publications.

  3. Effect of Biofield Treatment on Structural and Morphological Properties of Silicon Carbide

    OpenAIRE

    Trivedi, Mahendra; Nayak, Gopal

    2015-01-01

    Silicon carbide (SiC) is a well-known ceramic due to its excellent spectral absorbance and thermo-mechanical properties. The wide band gap, high melting point and thermal conductivity of SiC is used in high temperature applications. The present study was undertaken to investigate the effect of biofield treatment on physical, atomic, and structural characteristics of SiC powder. The control and biofield treated SiC powder was analysed using X-ray diffraction (XRD), particle size analyzer, surf...

  4. Ceramic Replaces Metal In High Performance Optomechanical Structures

    Science.gov (United States)

    Vasquez, Peter; Fox, Robert L.; Sandford, Stephen P.

    1995-01-01

    Recently developed ceramic materials and fabrication techniques integrated by Langley Research Center workers to produce superior optomechanical structures for spacecraft and aircraft instrumentation. Basic features of these novel supports, such as dimensional stability, low cost, and ease of fabrication, also make them ideal for many commerical optical systems as well. Ceramic supports for optical components and benches offer important advantages over usual metal parts. Ceramic materials expand and contract only slightly with changes in temperature. Moreover, they are relatively inexpensive and lightweight.

  5. Did we push dental ceramics too far? A brief history of ceramic dental implants.

    Science.gov (United States)

    Haubenreich, James E; Robinson, Fonda G; West, Karen P; Frazer, Robert Q

    2005-01-01

    Humankind has developed and used ceramics throughout history. It currently has widespread industrial applications. Dental ceramics are used for fabricating highly esthetic prosthetic denture teeth, crowns, and inlays. However, ceramic's biocompatibility and compressive strength are offset by its hardness and brittleness. Nonetheless, a single crystal sapphire aluminum oxide endosseous implant was developed in 1972 as an alternative to metal. It was more esthetic than its metallic counterparts and was eventually produced in a variety of shapes and sizes. Clinical studies demonstrated its excellent soft and hard tissue biocompatibility, yet the range of problems included fractures during surgery, fractures after loading, mobility, infection, pain, bone loss, and lack of osseointegration. Ultimately, single crystal sapphire implants fell into irredeemable disfavor because of its poor impact strength, and dentists and surgeons eventually turned to other implant materials. However, bioactive ceramic coatings on metal implants have kept ceramics as a key component in dental implantology.

  6. GRAIN BOUNDARIES IN POLYPHASE CERAMICS

    OpenAIRE

    Clarke, D

    1985-01-01

    The majority of polyphase ceramics contain a residual glass phase at their grain boundaries. The stability of these phases, particularly at the two-grain boundaries, is of significance since they affect the properties of the material as a whole. Drawing analogies with soap films, the stability of a continuous intergranular phase is considered in terms of the balance between the capillarity and disjoining pressures. The individual components to the disjoining pressures are discussed. It is arg...

  7. Ceramic Laser Materials

    Directory of Open Access Journals (Sweden)

    Guillermo Villalobos

    2012-02-01

    Full Text Available 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.

  8. Fatigue of dental ceramics

    OpenAIRE

    Zhang, Yu; Sailer, Irena; lawn, brian

    2013-01-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics

  9. Hydrothermal synthesis of xonotlite from carbide slag

    Institute of Scientific and Technical Information of China (English)

    Jianxin Cao; Fei Liu; Qian Lin; Yu Zhang

    2008-01-01

    Carbide slag was used as the calcareous materials for the first time to prepare xonotlite via dynamic hydrothermal synthesis.The effects of influential factors including different calcination temperatures,pretreatment methods of the carbide slag and process param-eters of hydrothermal synthesis on the microstructure and morphology of xonotlite were explored using XRD and SEM techniques.The results indicate that the carbide slag after proper calcination could be used to prepare pure xonotlite;and different calcination tern-peratures have little effect on the crystallinity of synthesized xonotlitc,but have great impact on the morphology of secondary particles.The different pretreatment methods of the carbide slag pose great impact on the crystallinity and morphology of secondary particles of xonotlite.Xonotlite was also synthesized from pure CaO under the salne experimental conditions as that prepared from calcined carbide slag for comparison.Little amount of impurities in carbide slag has no effect on the mechanism of hydrothermal synthesizing xonotlite from carbide slag.

  10. Precipitating Mechanism of Carbide in Cold-Welding Surfacing Metals

    Institute of Scientific and Technical Information of China (English)

    Yuanbin ZHANG; Dengyi REN

    2004-01-01

    Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metal and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitable amount of Nb, Ti and V coexisted in weld metal, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxide which dispersed in liquid weld metal, and then grew into multi-layer complex carbide particles by epitaxial growth. At different sites, carbide particles may present as different morphologies.

  11. Ceramic art in sculpture

    OpenAIRE

    Rokavec, Eva

    2014-01-01

    Diploma seminar speaks of ceramics as a field of artistic expression and not just as pottery craft. I presented short overview of developing ceramic sculpture and its changing role. Clay inspires design and touch more than other sculpture media. It starts as early as in prehistory. Although it sometimes seems that was sculptural ceramics neglected in art history overview, it was not so in actual praxis. There is a rich tradition of ceramics in the East and also in Europe during the renaissanc...

  12. Ceramic Laser Materials

    OpenAIRE

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

    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,...

  13. Dimensional analysis and extended hydrodynamic theory applied to long-rod penetration of ceramics

    Directory of Open Access Journals (Sweden)

    J.D. Clayton

    2016-08-01

    Full Text Available Principles of dimensional analysis are applied in a new interpretation of penetration of ceramic targets subjected to hypervelocity impact. The analysis results in a power series representation – in terms of inverse velocity – of normalized depth of penetration that reduces to the hydrodynamic solution at high impact velocities. Specifically considered are test data from four literature sources involving penetration of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test data can be accurately represented by the linear form of the power series, whereby the same value of a single fitting parameter applies remarkably well for all four ceramics. Comparison of the present model with others in the literature (e.g., Tate's theory demonstrates a target resistance stress that depends on impact velocity, linearly in the limiting case. Comparison of the present analysis with recent research involving penetration of thin ceramic tiles at lower typical impact velocities confirms the importance of target properties related to fracture and shear strength at the Hugoniot Elastic Limit (HEL only in the latter. In contrast, in the former (i.e., hypervelocity and thick target experiments, the current analysis demonstrates dominant dependence of penetration depth only by target mass density. Such comparisons suggest transitions from microstructure-controlled to density-controlled penetration resistance with increasing impact velocity and ceramic target thickness.

  14. Radiation Effects in Nuclear Ceramics

    Directory of Open Access Journals (Sweden)

    L. Thomé

    2012-01-01

    Full Text Available Due to outstanding physicochemical properties, ceramics are key engineering materials in many industrial domains. The evaluation of the damage created in ceramics employed in radiative media is a challenging problem for electronic, space, and nuclear industries. In this latter field, ceramics can be used as immobilization forms for radioactive wastes, inert fuel matrices for actinide transmutation, cladding materials for gas-cooled fission reactors, and structural components for fusion reactors. Information on the radiation stability of nuclear materials may be obtained by simulating the different types of interactions involved during the slowing down of energetic particles with ion beams delivered by various types of accelerators. This paper presents a review of the radiation effects occurring in nuclear ceramics, with an emphasis on recent results concerning the damage accumulation processes. Energetic ions in the KeV-GeV range are used to explore the nuclear collision (at low energy and electronic excitation (at high energy regimes. The recovery by electronic excitation of the damage created by ballistic collisions (SHIBIEC process is also addressed.

  15. Properties and Performance of Ceramic Composite Components

    Energy Technology Data Exchange (ETDEWEB)

    Case, S.W.; Halverson, H.G.; Carter, R.H.; Wone, M.; Reifsnider, K.L.

    1999-08-09

    The objective of the Fossil Energy Advanced Research and Technology Development (AR and TD) Materials program is to conduct research and development on materials for longer-term fossil energy applications as well as for generic needs of various fossil fuel technologies. These needs have prompted research aimed toward a better understanding of material behavior in fossil energy environments and the development of new materials capable of substantial enhancement of plant operations, reliability, and efficiency.

  16. Casimir force measurements from silicon carbide surfaces

    Science.gov (United States)

    Sedighi, M.; Svetovoy, V. B.; Palasantzas, G.

    2016-02-01

    Using an atomic force microscope we performed measurements of the Casimir force between a gold- coated (Au) microsphere and doped silicon carbide (SiC) samples. The last of these is a promising material for devices operating under severe environments. The roughness of the interacting surfaces was measured to obtain information for the minimum separation distance upon contact. Ellipsometry data for both systems were used to extract optical properties needed for the calculation of the Casimir force via the Lifshitz theory and for comparison to the experiment. Special attention is devoted to the separation of the electrostatic contribution to the measured total force. Our measurements demonstrate large contact potential V0(≈0.67 V ) , and a relatively small density of charges trapped in SiC. Knowledge of both Casimir and electrostatic forces between interacting materials is not only important from the fundamental point of view, but also for device applications involving actuating components at separations of less than 200 nm where surface forces play dominant role.

  17. Ceramics for fusion devices

    International Nuclear Information System (INIS)

    Ceramics are required for a number of applications in fusion devices, among the most critical of which are magnetic coil insulators, windows for RF heating systems, and structural uses. Radiation effects dominate consideration of candidate materials, although good pre-irradiation properties are a requisite. Materials and components can be optimized by careful control of chemical and microstructural content, and application of brittle material design and testing techniques. Future directions for research and development should include further extension of the data base in the areas of electrical, structural, and thermal properties; establishment of a fission neutron/fusion neutron correlation including transmutation gas effects; and development of new materials tailored to meet the specific needs of fusion reactors

  18. Thermal Expansion of Hafnium Carbide

    Science.gov (United States)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  19. Penetration of tungsten-alloy rods into composite ceramic targets: Experiments and 2-D simulations

    International Nuclear Information System (INIS)

    A series of terminal ballistics experiments, with scaled tungsten-alloy penetrators, was performed on composite targets consisting of ceramic tiles glued to thick steel backing plates. Tiles of silicon-carbide, aluminum nitride, titanium-dibroide and boron-carbide were 20-80 mm thick, and impact velocity was 1.7 km/s. 2-D numerical simulations, using the PISCES code, were performed in order to simulate these shots. It is shown that a simplified version of the Johnson-Holmquist failure model can account for the penetration depths of the rods but is not enough to capture the effect of lateral release waves on these penetrations

  20. New high boron content polyborane precursors to advanced ceramic materials: New syntheses, new applications

    Science.gov (United States)

    Guron, Marta

    There is a need for new synthetic routes to high boron content materials for applications as polymeric precursors to ceramics, as well as in neutron shielding and potential medical applications. To this end, new ruthenium-catalyzed olefin metathesis routes have been devised to form new complex polyboranes and polymeric species. Metathesis of di-alkenyl substituted o-carboranes allowed the synthesis of ring-closed products fused to the carborane cage, many of which are new compounds and one that offers a superior synthetic method to one previously published. Acyclic diene metathesis of di-alkenyl substituted m-carboranes resulted in the formation of new main-chain carborane-containing polymers of modest molecular weights. Due to their extremely low char yields, and in order to explore other metathesis routes, ring opening metathesis polymerization (ROMP) was used to generate the first examples of poly(norbornenyl- o-carboranes). Monomer synthesis was achieved via a two-step process, incorporating Ti-catalyzed hydroboration to make 6-(5-norbornenyl)-decaborane, followed by alkyne insertion in ionic liquid media to achieve 1,2-R2 -3-norbornenyl o-carborane species. The monomers were then polymerized using ROMP to afford several examples of poly(norbornenyl- o-carboranes) with relatively high molecular weights. One such polymer, [1-Ph, 3-(=CH2-C5H7-CH2=)-1,2-C 2B10H10]n, had a char yield very close to the theoretical char yield of 44%. Upon random copolymerization with poly(6-(5-norbornenyl) decaborane), char yields significantly increased to 80%, but this number was well above the theoretical value implicating the formation of a boron-carbide/carbon ceramic. Finally, applications of polyboranes were explored via polymer blends toward the synthesis of ceramic composites and the use of polymer precursors as reagents for potential ultra high temperature ceramic applications. Upon pyrolysis, polymer blends of poly(6-(5-norbornenyl)-decaborane) and poly

  1. Development of advanced pump impeller fabrication technology using direct nano- ceramic dispersion casting for long time erosion durability

    Energy Technology Data Exchange (ETDEWEB)

    Rhee, Chang Kyu; Lee, Min Ku; Park, Jin Ju [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)] (and others)

    2008-09-15

    Many components of pump impeller of nuclear power plants is generally made of stainless steel and Al-bronze with superior corrosion resistance to sea water. However, they should be replaced by one- to five-year period because of material damage by a very big cavitation impact load, even though their designed durability is twenty years. Especially, in case of Young-Gwang nuclear power plant located at the west sea, damage of components of pump impeller is so critical due to the additional damage by solid particle erosion and hence their replacement period is very short as several months compared to other nuclear power plants. In addition, it is very difficult to maintain and repair the components of pump impeller since there is no database on the exact durability and damage mechanism. Therefore, in this study, fabrication technology of new advanced materials modified by dispersion of nano-carbide and -oxide ceramics into the matrix is developed first. Secondly, technology to estimate the dynamic damage by solid particle erosion is established and hence applied to the prediction of the service life of the components of pump impeller.

  2. Structural diversity in lithium carbides

    Science.gov (United States)

    Lin, Yangzheng; Strobel, Timothy A.; Cohen, R. E.

    2015-12-01

    The lithium-carbon binary system possesses a broad range of chemical compounds, which exhibit fascinating chemical bonding characteristics, which give rise to diverse and technologically important properties. While lithium carbides with various compositions have been studied or suggested previously, the crystal structures of these compounds are far from well understood. In this work, we present the first comprehensive survey of all ground state (GS) structures of lithium carbides over a broad range of thermodynamic conditions, using ab initio density functional theory (DFT) crystal structure searching methods. Thorough searches were performed for 29 stoichiometries ranging from Li12C to LiC12 at 0 and 40 GPa. Based on formation enthalpies from optimized van der Waals density functional calculations, three thermodynamically stable phases (Li4C3 , Li2C2 , and LiC12) were identified at 0 GPa, and seven thermodynamically stable phases (Li8C , Li6C , Li4C , Li8C3 , Li2C , Li3C4 , and Li2C3 ) were predicted at 40 GPa. A rich diversity of carbon bonding, including monomers, dimers, trimers, nanoribbons, sheets, and frameworks, was found within these structures, and the dimensionality of carbon connectivity existing within each phase increases with increasing carbon concentration. We find that the well-known composition LiC6 is actually a metastable one. We also find a unique coexistence of carbon monomers and dimers within the predicted thermodynamically stable phase Li8C3 , and different widths of carbon nanoribbons coexist in a metastable phase of Li2C2 (Imm2). Interesting mixed sp2-sp3 carbon frameworks are predicted in metastable phases with composition LiC6.

  3. Additive manufacturing of polymer-derived ceramics.

    Science.gov (United States)

    Eckel, Zak C; Zhou, Chaoyin; Martin, John H; Jacobsen, Alan J; Carter, William B; Schaedler, Tobias A

    2016-01-01

    The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging. PMID:26721993

  4. Additive manufacturing of polymer-derived ceramics

    Science.gov (United States)

    Eckel, Zak C.; Zhou, Chaoyin; Martin, John H.; Jacobsen, Alan J.; Carter, William B.; Schaedler, Tobias A.

    2016-01-01

    The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging.

  5. Synthesis of Silicon Nitride and Silicon Carbide Nanocomposites through High Energy Milling of Waste Silica Fume for Structural Applications

    Science.gov (United States)

    Suri, Jyothi

    Nanocomposites have been widely used in a multitude of applications in electronics and structural components because of their improved mechanical, electrical, and magnetic properties. Silicon nitride/Silicon carbide (Si 3N4/SiC) nanocomposites have been studied intensively for low and high temperature structural applications, such as turbine and automobile engine components, ball bearings, turbochargers, as well as energy applications due to their superior wear resistance, high temperature strength, high oxidation resistance and good creep resistance. Silica fume is the waste material produced during the manufacture of silicon and ferro-silicon alloys, and contains 94 to 97 wt.% SiO2. In the present dissertation, the feasibility of using waste silica fume as the raw material was investigated to synthesize (I) advanced nanocomposites of Si3N4/SiC, and (2) porous silicon carbide (SiC) for membrane applications. The processing approach used to convert the waste material to advanced ceramic materials was based on a novel process called, integrated mechanical and thermal activation process (IMTA) process. In the first part of the dissertation, the effect of parameters such as carbothermic nitridation and reduction temperature and the graphite concentration in the starting silica fume plus graphite mixture, were explored to synthesize nanocomposite powders with tailored amounts of Si3N4 and SiC phases. An effective way to synthesize carbon-free Si3N 4/SiC composite powders was studied to provide a clear pathway and fundamental understanding of the reaction mechanisms. Si3N4/SiC nanocomposite powders were then sintered using two different approaches, based on liquid phase sintering and spark plasma sintering processes, with Al 2O3 and Y2O3 as the sintering aids. The nanocomposites were investigated for their densification behavior, microstructure, and mechanical properties. Si3N4/SiC nanocomposites thus obtained were found to possess superior mechanical properties at much

  6. Fracture toughness of advanced alumina ceramics and alumina matrix composites used for cutting tool edges

    Directory of Open Access Journals (Sweden)

    M. Szutkowska

    2012-10-01

    Full Text Available Purpose: Specific characteristics in fracture toughness measurements of advanced alumina ceramics and alumina matrix composites with particular reference to α-Al2O3, Al2O3-ZrO2, Al2O3-ZrO2-TiC and Al2O3-Ti(C,N has been presented.Design/methodology/approach: The present study reports fracture toughness obtained by means of the conventional method and direct measurements of the Vickers crack length (DCM method of selected tool ceramics based on alumina: pure alumina, alumina-zirconia composite with unstabilized and stabilized zirconia, alumina–zirconia composite with addition of TiC and alumina–nitride-carbide titanium composite with 2wt% of zirconia. Specimens were prepared from submicro-scale trade powders. Vicker’s hardness (HV1, fracture toughness (KIC at room temperature, the indentation fracture toughness, Young’s modulus and apparent density were also evaluated. The microstructure was observed by means of scanning electron microscopy (SEM.Findings: The lowest value of KIC is revealed by pure alumina ceramics. The addition of (10 wt% unstabilized zirconia to alumina or a small amount (5 wt% of TiC to alumina–zirconia composite improve fracture toughness of these ceramics in comparison to alumina ceramics. Alumina ceramics and alumina-zirconia ceramics reveal the pronounced character of R-curve because of an increasing dependence on crack growth resistance with crack extension as opposed to the titanium carbide-nitride reinforced composite based on alumina. R-curve has not been observed for this composite.Practical implications: The results show the method of fracture toughness improvement of alumina tool ceramics.Originality/value: Taking into account the values of fracture toughness a rational use of existing ceramic tools should be expected.

  7. Thin film ceramic thermocouples

    Science.gov (United States)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  8. Hydrothermal degradation of tetragonal ZrO{sub 2} ceramic components used in dental applications; Efeito da degradacao em meio aquoso de componentes ceramicos a base de ZrO{sub 2} tetragonal para uso odontologico

    Energy Technology Data Exchange (ETDEWEB)

    Mukaeda, L.E.; Robin, A.; Taguchi, S.P. [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia de Lorena. Dept. de Engenharia de Materiais; Santos, C. [ProtMat Materiais Avancados, Guaratingueta, SP (Brazil)

    2009-07-01

    With the evolution of the dental restoration techniques, a considerable growth in the demand of ceramic products occurred. These materials present good strength associated to reliability. In this work, micrometric and nanometric scale tetragonal ZrO{sub 2} blocks were sintered at 1500 deg C-2h and 1350 deg C-2h, respectively, ground and polished. Ceramics with relative density higher than 98% were obtained. The specimens were immersed in hot water (150 deg C), for times ranging from 10h to 30h. The mass variation of the samples was measured and the crystalline phases present before and after the degradation tests were identified by X-ray diffractometry, in order to evaluate the capacity of these ceramics in resisting to aqueous medium exposure. Materials with nanometric structure present higher resistance to degradation than those with micrometric scale, and this interferes in structural stability after the test, and reduces the martensitic transformation. (author)

  9. Electroextraction of boron from boron carbide scrap

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Ashish [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Anthonysamy, S., E-mail: sas@igcar.gov.in [Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ghosh, C. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Ravindran, T.R. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); Divakar, R.; Mohandas, E. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India)

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ∼ 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  10. Vanadium carbide coatings: deposition process and properties

    International Nuclear Information System (INIS)

    Vanadium carbide coatings on carbon and alloyed steels were produced by the method of diffusion saturation from the borax melt. Thickness of the vanadium carbide layer was 5-15 μm, depending upon the steel grade and diffusion saturation parameters. Microhardness was 20000-28000 MPa and wear resistance of the coatings under conditions of end face friction without lubrication against a mating body of WC-2Co was 15-20 times as high as that of boride coatings. Vanadium carbide coatings can operate in air at a temperature of up to 400 oC. They improve fatigue strength of carbon steels and decrease the rate of corrosion in sea and fresh water and in acid solutions. The use of vanadium carbide coatings for hardening of various types of tools, including cutting tools, allows their service life to be extended by a factor of 3 to 30. (author)

  11. High temperature thermoelectric properties of boron carbide

    International Nuclear Information System (INIS)

    Boron carbides are refractory solids with potential for application as very high temperature p-type thermoelectrics in power conversion applications. The thermoelectric properties of boron carbides are unconventional. In particular, the electrical conductivity is consistent with the thermally activated hopping of a high density (∼1021/cm3) of bipolarons; the Seebeck coefficient is anomalously large and increases with increasing temperature; and the thermal conductivity is surprisingly low. In this paper, these unusual properties and their relationship to the unusual structure and bonding present in boron carbides are reviewed. Finally, the potential for utilization of boron carbides at very high temperatures (up to 2200 degrees C) and for preparing n-type materials is discussed

  12. Calcium carbide poisoning via food in childhood.

    Science.gov (United States)

    Per, Hüseyin; Kurtoğlu, Selim; Yağmur, Fatih; Gümüş, Hakan; Kumandaş, Sefer; Poyrazoğlu, M Hakan

    2007-02-01

    The fast ripening of fruits means they may contain various harmful properties. A commonly used agent in the ripening process is calcium carbide, a material most commonly used for welding purposes. Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous. Once dissolved in water, the carbide produces acetylene gas. Acetylene gas may affect the neurological system by inducing prolonged hypoxia. The findings are headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema and seizures. We report the case of a previously healthy 5 year-old girl with no chronic disease history who was transferred to our Emergency Department with an 8-h history of coma and delirium. A careful history from her father revealed that the patient ate unripe dates treated with calcium carbide.

  13. Nano powders, components and coatings by plasma technique

    Science.gov (United States)

    McKechnie, Timothy N. (Inventor); Antony, Leo V. M. (Inventor); O'Dell, Scott (Inventor); Power, Chris (Inventor); Tabor, Terry (Inventor)

    2009-01-01

    Ultra fine and nanometer powders and a method of producing same are provided, preferably refractory metal and ceramic nanopowders. When certain precursors are injected into the plasma flame in a reactor chamber, the materials are heated, melted and vaporized and the chemical reaction is induced in the vapor phase. The vapor phase is quenched rapidly to solid phase to yield the ultra pure, ultra fine and nano product. With this technique, powders have been made 20 nanometers in size in a system capable of a bulk production rate of more than 10 lbs/hr. The process is particularly applicable to tungsten, molybdenum, rhenium, tungsten carbide, molybdenum carbide and other related materials.

  14. NASA/CARES dual-use ceramic technology spinoff applications

    Science.gov (United States)

    Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.; Nemeth, Noel N.

    1994-01-01

    NASA has developed software that enables American industry to establish the reliability and life of ceramic structures in a wide variety of 21st Century applications. Designing ceramic components to survive at higher temperatures than the capability of most metals and in severe loading environments involves the disciplines of statistics and fracture mechanics. Successful application of advanced ceramics material properties and the use of a probabilistic brittle material design methodology. The NASA program, known as CARES (Ceramics Analysis and Reliability Evaluation of Structures), is a comprehensive general purpose design tool that predicts the probability of failure of a ceramic component as a function of its time in service. The latest version of this software, CARESALIFE, is coupled to several commercially available finite element analysis programs (ANSYS, MSC/NASTRAN, ABAQUS, COSMOS/N4, MARC), resulting in an advanced integrated design tool which is adapted to the computing environment of the user. The NASA-developed CARES software has been successfully used by industrial, government, and academic organizations to design and optimize ceramic components for many demanding applications. Industrial sectors impacted by this program include aerospace, automotive, electronic, medical, and energy applications. Dual-use applications include engine components, graphite and ceramic high temperature valves, TV picture tubes, ceramic bearings, electronic chips, glass building panels, infrared windows, radiant heater tubes, heat exchangers, and artificial hips, knee caps, and teeth.

  15. Effect of surface free energy of ceramic glaze on oil droplet shape and its behavior in water

    Institute of Scientific and Technical Information of China (English)

    LIANG Jin-sheng; MENG Jun-ping; LIANG Guang-chuan; WANG Li-juan; ZHANG Jin; LI Ji-yuan

    2006-01-01

    A super-hydrophilic functional ceramic was prepared by adjusting the chemical components of ceramic glaze. Effect of surface free energy of ceramic glaze on oil droplet shape and its behavior in water were studied. The results show that water can spread on ceramic surface with high surface free energy,and oil droplet can aggregate rapidly and separate from the ceramic surface in water. For the ceramic with lower surface free energy,the polar shares are dependant on its easy-cleaning property. The higher the polar shares,the better the easy-cleaning property,and the easier the droplet separates from the ceramic surface in water.

  16. Facile synthesis of silicon carbide-titanium dioxide semiconducting nanocomposite using pulsed laser ablation technique and its performance in photovoltaic dye sensitized solar cell and photocatalytic water purification

    Science.gov (United States)

    Gondal, M. A.; Ilyas, A. M.; Baig, Umair

    2016-08-01

    Separation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO2) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet-visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.

  17. Ultrarapid microwave synthesis of superconducting refractory carbides

    International Nuclear Information System (INIS)

    Nb1-xTaxC Carbides can be synthesized by high power MW methods in less than 30 s. In situ and ex situ techniques probing changes in temperature and dielectric properties with time demonstrate that the reactions self-terminate as the loss tangent of the materials decreases. The resulting carbides are carbon deficient and superconducting; Tc correlates linearly to unit cell volume, reaching a maximum at NbC. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  18. Selective etching of silicon carbide films

    Science.gov (United States)

    Gao, Di; Howe, Roger T.; Maboudian, Roya

    2006-12-19

    A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

  19. Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

    Science.gov (United States)

    Williams, Brian E.; Bernander, Robert E.

    2007-01-01

    Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 F (approx.1,600 C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 F (approx.2,400 C) in a highly oxidizing thrust chamber environment. Moreover, because the melt- infiltration-based process takes much less time, the finished products are expected to cost much less. Fabrication begins with the preparation of a carbon fiber preform that, typically, is of the size and shape of a part to be fabricated. By use of low-temperature ultraviolet-enhanced chemical vapor deposition, the carbon fibers in the preform are coated with one or more interfacial material(s), which could include oxides. The interfacial material helps to protect the fibers against chemical attack during the remainder of the fabrication process and against oxidation during subsequent use; it also enables slippage between the fibers and the matrix material, thereby helping to deflect cracks and distribute loads. Once the fibers have been coated with the interfacial material, the fiber preform is further infiltrated with a controlled amount of additional carbon, which serves as a reactant for the formation of the carbide matrix material. The next step is melt infiltration. The preform is exposed to molten zirconium, which wicks into the preform, drawn by capillary action. The molten metal fills most of the interstices of the preform and reacts with the added carbon to form the zirconium carbide matrix material. The zirconium does not react with the underlying fibers because they

  20. Influence Of Ultrasonic Waves On The Formation Of High Pores Silicon Carbide

    Science.gov (United States)

    Toana, Musfirah C. F.; Soegijono, B.; Hikam, M.

    2009-09-01

    The Challenge to produce a quality Silicon Carbide that combination high surface area is promising and this material can be used in many application such as Hydrogen storage materials. Synthesis of high surface area carbon materials by selective etching of Silicon Carbide with choric acid while exposing ultrasonic wave have been made. Powder Of Sic (surface area 17.8 m2/g) was treated in the chloric acetic as well as their mixture of various compositions and various time exposure of ultrasonic waves. Surface area and pore size can be controlled by temperature and concentration composition of Chloric and time exposure of ultrasonic wave. The resultant carbon and carbon-silicon carbide composite powders were characterized X-ray diffraction and Electron microscope. To determine a conversion degree of silicon carbide due to influence of the ultrasonic wave, the samples were annealed in open air at 1000° C. There by carbon component of the carbon/silicon carbide composite was completely oxidized. The analysis of the samples shows the strong influence of time exposure of ultrasonic waves on the formation of pores.

  1. Influence Of Ultrasonic Waves On The Formation Of High Pores Silicon Carbide

    International Nuclear Information System (INIS)

    The Challenge to produce a quality Silicon Carbide that combination high surface area is promising and this material can be used in many application such as Hydrogen storage materials. Synthesis of high surface area carbon materials by selective etching of Silicon Carbide with choric acid while exposing ultrasonic wave have been made.Powder Of Sic (surface area 17.8 m2/g) was treated in the chloric acetic as well as their mixture of various compositions and various time exposure of ultrasonic waves. Surface area and pore size can be controlled by temperature and concentration composition of Chloric and time exposure of ultrasonic wave.The resultant carbon and carbon-silicon carbide composite powders were characterized X-ray diffraction and Electron microscope. To determine a conversion degree of silicon carbide due to influence of the ultrasonic wave, the samples were annealed in open air at 1000 deg. C. There by carbon component of the carbon/silicon carbide composite was completely oxidized. The analysis of the samples shows the strong influence of time exposure of ultrasonic waves on the formation of pores.

  2. Assessment of damage in ceramics and ceramic matrix composites using ultrasonic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Rokhlin, S.I.; Chu, Y.C. [Ohio State Univ., Columbus, OH (United States). Dept. of Welding Engineering; Baaklini, G.Y. [NASA Lewis Research Center, Cleveland, OH (United States)

    1995-07-01

    This paper addresses the application of ultrasonic methods to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock and oxidation at elevated temperatures. The damage-induced changes in elastic constant and elastic anisotropy are determined by measuring the velocities of ultrasonic waves in different propagation directions within the sample. Thermal shock damage measurement is performed in ceramic samples of reaction bonded silicon nitride (RBSN) and aluminum oxide. Thermal shock treatment from different temperatures up to 1,000 C is applied to produce the microcracks. Both surface and bulk ultrasonic wave methods are used to correlate the change of elastic constants to microstructural degradation and to determine the change in elastic anisotropy induced by microcrack damage. Oxidation damage is studied in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1,400 C, for 100 hours. Significant changes of ultrasonic velocities were observed for composites before and after oxidation. The elastic constants of the composites were determined from the measured velocity data. The Young`s modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600 C but retains its original value at temperatures above 1,200 C. This agrees well with the results of destructive tests by other authors. The transverse longitudinal and shear moduli obtained from ultrasonic measurements decrease continually until 1,200 C. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

  3. Assessment of damage in ceramics and ceramic matrix composites using ultrasonic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Y.C.; Baaklini, G.Y.; Rokhlin, S.I.

    1993-05-01

    This paper addresses the application of ultrasonic sensing to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock or oxidation at elevated temperatures, which often results in elastic anisotropy. This damaged-induced anisotropy is determined by measuring the velocities of ultrasonic waves in different propagation directions. Thermal shock damage is assessed in ceramic samples of reaction bonded silicon nitride (RBSN). Thermal shock treatment from different temperatures up to 1000 C is applied to produce the microcracks. Results indicate that most microcracks produced by thermal shock are located near sample surfaces. Ultrasonic measurements using the surface wave method are found to correlate well with measurements of degradation of mechanical properties obtained independently by other authors using destructive methods. Oxidation damage is assessed in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400 C, for 100 hr. The Youngs' modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600 C but retains its original value at temperatures above 1200 C. This agrees well with the results of destructive tests by other authors. On the other hand, the transverse moduli obtained from ultrasonic measurements decrease continually until 1200 C. Measurements on the shear stiffnesses show behavior similar to the transverse moduli. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

  4. Assessment of damage in ceramics and ceramic matrix composites using ultrasonic techniques

    Science.gov (United States)

    Chu, Y. C.; Baaklini, G. Y.; Rokhlin, S.I.

    1993-01-01

    This paper addresses the application of ultrasonic sensing to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock or oxidation at elevated temperatures, which often results in elastic anisotropy. This damaged-induced anisotropy is determined by measuring the velocities of ultrasonic waves in different propagation directions. Thermal shock damage is assessed in ceramic samples of reaction bonded silicon nitride (RBSN). Thermal shock treatment from different temperatures up to 1000 C is applied to produce the microcracks. Results indicate that most microcracks produced by thermal shock are located near sample surfaces. Ultrasonic measurements using the surface wave method are found to correlate well with measurements of degradation of mechanical properties obtained independently by other authors using destructive methods. Oxidation damage is assessed in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400 C, for 100 hr. The Youngs' modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600 C but retains its original value at temperatures above 1200 C. This agrees well with the results of destructive tests by other authors. On the other hand, the transverse moduli obtained from ultrasonic measurements decrease continually until 1200 C. Measurements on the shear stiffnesses show behavior similar to the transverse moduli. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.

  5. Challenges of Engineering Grain Boundaries in Boron-Based Armor Ceramics

    Science.gov (United States)

    Coleman, Shawn P.; Hernandez-Rivera, Efrain; Behler, Kristopher D.; Synowczynski-Dunn, Jennifer; Tschopp, Mark A.

    2016-06-01

    Boron-based ceramics are appealing for lightweight applications in both vehicle and personnel protection, stemming from their combination of high hardness, high elastic modulus, and low density as compared to other ceramics and metal alloys. However, the performance of these ceramics and ceramic composites is lacking because of their inherent low fracture toughness and reduced strength under high-velocity threats. The objective of the present article is to briefly discuss both the challenges and the state of the art in experimental and computational approaches for engineering grain boundaries in boron-based armor ceramics, focusing mainly on boron carbide (B4C) and boron suboxide (B6O). The experimental challenges involve processing these ceramics at full density while trying to promote microstructure features such as intergranular films to improve toughness during shock. Many of the computational challenges for boron-based ceramics stem from their complex crystal structure which has hitherto complicated the exploration of grain boundaries and interfaces. However, bridging the gaps between experimental and computational studies at multiple scales to engineer grain boundaries in these boron-based ceramics may hold the key to maturing these material systems for lightweight defense applications.

  6. Influence of Rare Earth on Carbide in Weld Metal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yuan-Bin; REN Deng-Yi

    2003-01-01

    The influence of rare earths (RE) on carbides in high carbon steel weld metal was studied by transmission electron microscope (TEM) and energy dispersive X-ray microanalysis (EDX). It is found that rare earth markedly affects the quantity, morphology and distribution of carbides. The precipitating mechanism of carbides was proposed in which rare earth compounds with high surface energy serve as the nucleation sites for carbides in superheated liquid metal and the induced carbides are precipitated extensively and distributed evenly. The preferential precipitation of carbides decreases the carbon content in matrix, which is transformed into low carbon lath martensite after welds are chilled to room temperature.

  7. Glass-ceramic joining and coating of SiC/SiC for fusion applications

    International Nuclear Information System (INIS)

    The aim of this work is the joining and the coating of SiC/SiC composites by a simple, pressureless, low cost technique. A calcia-alumina glass-ceramic was chosen as joining and coating material, because its thermal and thermomechanical properties can be tailored by changing the composition, it does not contain boron oxide (incompatible with fusion applications) and it has high characteristic temperatures (softening point at about 1400 C). Furthermore, the absence of silica makes this glass-ceramic compatible with ceramic breeder materials (i.e. lithium-silicates, -alluminates or -zirconates). Coatings and joints were successfully obtained with Hi-Nicalon fiber-reinforced CVI silicon carbide matrix composite. Mechanical shear strength tests were performed on joined samples and the compatibility with a ceramic breeder material was examined. (orig.)

  8. Boron carbide neutron screen for GRR-1 neutron spectrum tailoring

    International Nuclear Information System (INIS)

    The presence of fast neutron spectra in new reactor concepts (such as Gas Cooled Fast Reactor, new generation Sodium Cooled Fast Reactor, Lead Fast Reactor, Accelerator Driven System and nuclear Fusion Reactors) is expected to induce a strong impact on the contained materials, including structural materials (e.g. steels), nuclear fuels, neutron reflecting materials (e.g. beryllium) and tritium breeding materials (for fusion reactors). Therefore, effective operation of these reactors will require extensive testing of their components, which must be performed under neutronic conditions representative of those expected to prevail inside the reactor cores when in operation. Depending on the material, the requirements of a test irradiation can vary. In this work preliminary studies were performed to observe the behavior of the neutron spectrum within a boron carbide neutron screen inserted in a hypothetical reflector test hole of the Greek Research Reactor. Four different screen configurations were simulated with Monte Carlo code TRIPOLI-4. The obtained data showed that the insertion of boron carbide caused not only elimination of the thermal (E < 1 eV) component of the neutron energy spectrum but also absorption of a considerable proportion of the intermediate energy neutrons (1x10-6 MeV < E < 1 MeV). (author)

  9. Bonding of a mica-based castable ceramic material with a tri-n-butylborane-initiated adhesive resin.

    Science.gov (United States)

    Morikawa, T; Matsumura, H; Atsuta, M

    1996-07-01

    Adhesive bonding of a mica-based castable ceramic material (Olympus Castable Ceramics, OCC) was evaluated in vitro with the use of a silane primer in conjunction with an adhesive luting material. The primer contained a silane coupler and 4-methacryloxyethyl trimellitate anhydride (4-META), while the methyl methacrylate (MMA)-based luting agent was initiated with a tri-n-butylborane derivative (TBB) and contained 4-META (4-META/MMA-TBB resin). Ceramic specimens were sanded with No. 600 silicon carbide paper followed by blasting with alumina and/or etching with ammonium bifluoride. The specimens were bonded with various combinations and shear bond strengths were determined. Both priming and alumina blasting enhanced the bond between 4-META resin and OCC. Although etching with ammonium bifluoride roughened the ceramic surface, this procedure did not improve the bond strength. Electron probe microanalysis of the ceramic surface revealed a decrease in silicon and aluminium elements after etching with ammonium bifluoride.

  10. Ceramics in Restorative and Prosthetic DENTISTRY1

    Science.gov (United States)

    Kelly, J. Robert

    1997-08-01

    This review is intended to provide the ceramic engineer with information about the history and current use of ceramics in dentistry, contemporary research topics, and potential research agenda. Background material includes intra-oral design considerations, descriptions of ceramic dental components, and the origin, composition, and microstructure of current dental ceramics. Attention is paid to efforts involving net-shape processing, machining as a forming method, and the analysis of clinical failure. A rationale is presented for the further development of all-ceramic restorative systems. Current research topics receiving attention include microstructure/processing/property relationships, clinical failure mechanisms and in vitro testing, wear damage and wear testing, surface treatments, and microstructural modifications. The status of the field is critically reviewed with an eye toward future work. Significant improvements seem possible in the clinical use of ceramics based on engineering solutions derived from the study of clinically failed restorations, on the incorporation of higher levels of "biomimicry" in new systems, and on the synergistic developments in dental cements and adhesive dentin bonding.

  11. Ultrasonic NDE of structural ceramics for power and propulsion systems

    Energy Technology Data Exchange (ETDEWEB)

    Vary, A.; Generazio, E.R.; Roth, D.J.; Baaklini, G.Y.

    1987-01-01

    A review of research investigations of several ultrasonic evaluation techniques applicable to structural ceramics for advanced heat engines is presented. This review highlights recent work conducted under the sponsorship of and at the Lewis Research Center. Results obtained with scanning acoustic microscopy, scanning laser acoustic microscopy, photo acoustic microscopy, and scanning electron acoustic microscopy are compared. In addition to these flaw imaging techniques, microstructure characterization by analytical ultrasonics is described. The techniques were evaluated by application to research samples of monolithic silicon nitride and silicon carbide in the form of discs and bars containing naturally occurring and deliberately-introduced flaws and microstructural anomalies. Strengths and limitations of the techniques are discussed.

  12. GEN IV: Carbide Fuel Elaboration for the 'Futurix Concepts' experiment

    Energy Technology Data Exchange (ETDEWEB)

    Vaudez, Stephane; Riglet-Martial, Chantal; Paret, Laurent; Abonneau, Eric [Commissariat a l' Energie Atomique (C.E.A.), Direction de l' Energie Nucleaire, Centre d' Etudes de Cadarache, 13108 Saint Paul lez Durance Cedex (France)

    2008-07-01

    In order to collect information on the behaviour of the future GFR (Gas Fast Reactor) fuel under fast neutron irradiation, an experimental irradiation program, called 'Futurix-concepts' has been launched at the CEA. The considered concept is a composite material made of a fissile fuel embedded in an inert ceramic matrix. Fissile fuel pellets are made of UPuN or UPuC while ceramics are SiC for the carbide fuel and TiN for the nitride fuel. This paper focuses on the description of the carbide composite fabrication. The UPuC pellets are manufactured using a metallurgical powder process. Fabrication and handling of the fuels are carried out in glove boxes under a nitrogen atmosphere. Carbide fuel is synthesized by carbo-thermic reduction under vacuum of a mixture of actinide oxide and graphitic carbon up to 1550 deg. C. After ball milling, the UPuC powder is pressed to create hexagonal or spherical compacts. They are then sintered up to 1750 deg. C in order to obtain a density of 85 % of the theoretical one. The sintered pellets are inserted into an inert and tight capsule of SiC. In order to control the gap between the fuel and the matrix precisely, the pellets are abraded. The inert matrix is then filled with the pellets and the whole system is sealed by a BRASiC{sup R} process at high temperature under a helium atmosphere. Fabrication of the sample to be irradiated was done in 2006 and the irradiation began in May 2007 in the Phenix reactor. This presentation will detail and discuss the results obtained during this fabrication phase. (authors)

  13. Ceramic tamper-revealing seals

    Science.gov (United States)

    Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

    1992-01-01

    A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

  14. Analyses of fine paste ceramics

    International Nuclear Information System (INIS)

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics

  15. Analyses of fine paste ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sabloff, J A [ed.

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  16. Nanostructured component fabrication by electron beam-physical vapor deposition

    Science.gov (United States)

    Singh, Jogender; Wolfe, Douglas E.

    2005-08-01

    Fabrication of cost-effective, nano-grained net-shaped components has brought considerable interest to Department of Defense, National Aeronautics and Space Administration, and Department of Energy. The objective of this paper is to demonstrate the versatility of electron beam-physical vapor deposition (EB-PVD) technology in engineering new nanostructured materials with controlled microstructure and microchemistry in the form of coatings and net-shaped components for many applications including the space, turbine, optical, biomedical, and auto industries. Coatings are often applied on components to extent their performance and life under severe environmental conditions including thermal, corrosion, wear, and oxidation. Performance and properties of the coatings depend upon their composition, microstructure, and deposition condition. Simultaneous co-evaporation of multiple ingots of different compositions in the high energy EB-PVD chamber has brought considerable interest in the architecture of functional graded coatings, nano-laminated coatings, and design of new structural materials that could not be produced economically by conventional methods. In addition, high evaporation and condensate rates allowed fabricating precision net-shaped components with nanograined microstructure for various applications. Using EB-PVD, nano-grained rhenium (Re) coatings and net-shaped components with tailored microstructure and properties were fabricated in the form of tubes, plates, and Re-coated spherical graphite cores. This paper will also present the results of various metallic and ceramic coatings including chromium, titanium carbide (TiC), titanium diboride (TiB2), hafnium nitride (HfN), titanium-boron-carbonitride (TiBCN), and partially yttria stabilized zirconia (YSZ) TBC coatings deposited by EB-PVD for various applications.

  17. Continuous Fiber Ceramic Composites

    Energy Technology Data Exchange (ETDEWEB)

    None

    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.

  18. Measuring Fracture Times Of Ceramics

    Science.gov (United States)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

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

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-09-01

    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.

  20. Tribological behavior of hot-pressed boron carbide with oxidation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The oxidation behavior at 973-1 273 K and the effect of oxidation on the room-temperature tribological properties of hot-pressed boron carbide ceramic were investigated. Oxidized samples were studied by X-ray diffractometer and scanning electron microscopy. It is demonstrated that the oxidation results in the formation of a thin transparent B2O3 film, and the oxide film is severely cracked during cooling due to the thermal expansion mismatch between the oxide film and B4C substrate. B2O3 reacts with moisture in air to form boric acid, which is a kind of solid lubricant. The sliding friction factors of oxidized B4C pair are about 0.05-0.08, compared to 0.25-0.35 of the as-received B4C pair. When the oxidation temperature is up to 1 273 K, severe unstability and increase of friction factor are observed. Visual inspection of the wear track reveals that the lubricant film is broken and some debris particles occur on and around the rubbing surfaces, because the friction interface is rough by the severe etching of grain boundaries.

  1. In situ processing of silicon carbide layer structures

    International Nuclear Information System (INIS)

    A novel route to low-cost processing of silicon carbide (SiC) layer structures is described. The processing involves pressureless liquid-phase cosintering of compacted powder layers of SiC, containing alumina (Al2O3) and yttria (Y2O3) sintering additives to yield a yttrium aluminum garnet (YAG) second phase. By adjusting the β:α SiC phase ratios in the individual starting powders, alternate layers with distinctly different microstructures are produced: (i) homogeneous microstructures, with fine equiaxed SiC grains, designed for high strength; and (ii) heterogeneous microstructures with coarse and elongate SiC grains, designed for high toughness. By virtue of the common SiC and YAG phases, the interlayer interfaces are chemically compatible and strongly bonded. Exploratory Hertzian indentation tests across a bilayer interface confirm the capacity of the tough heterogeneous layer to inhibit potentially dangerous cracks propagating through the homogeneous layer. The potential for application of this novel processing approach to other layer architectures and other ceramic systems is considered

  2. Nondestructive evaluation of a ceramic matrix composite material

    Science.gov (United States)

    Grosskopf, Paul P.; Duke, John C., Jr.

    1992-01-01

    Monolithic ceramic materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited because of their sensitivity to small imperfections. To overcome this extreme sensitivity to small imperfections, ceramic matrix composite materials have been developed that have the ability to withstand some distributed damage. A borosilicate glass reinforced with several layers of silicon-carbide fiber mat has been studied. Four-point flexure and tension tests were performed not only to determine some of the material properties, but also to initiate a controlled amount of damage within each specimen. Acousto-ultrasonic (AU) measurements were performed periodically during mechanical testing. This paper will compare the AU results to the mechanical test results and data from other nondestructive methods including acoustic emission monitoring and X-ray radiography. It was found that the AU measurements were sensitive to the damage that had developed within the material.

  3. Combustor and Vane Features and Components Tested in a Gas Turbine Environment

    Science.gov (United States)

    Roinson, R. Craig; Verrilli, Michael J.

    2003-01-01

    The use of ceramic matrix composites (CMCs) as combustor liners and turbine vanes provides the potential of improving next-generation turbine engine performance, through lower emissions and higher cycle efficiency, relative to today s use of superalloy hot-section components. For example, the introduction of film-cooling air in metal combustor liners has led to higher levels of nitrogen oxide (NOx) emissions from the combustion process. An environmental barrier coated (EBC) siliconcarbide- fiber-reinforced silicon carbide matrix (SiC/SiC) composite is a new material system that can operate at higher temperatures, significantly reducing the film-cooling requirements and enabling lower NOx production. Evaluating components and subcomponents fabricated from these advanced CMCs under gas turbine conditions is paramount to demonstrating that the material system can perform as required in the complex thermal stress and environmentally aggressive engine environment. To date, only limited testing has been conducted on CMC combustor and turbine concepts and subelements of this type throughout the industry. As part of the Ultra-Efficient Engine Technology (UEET) Program, the High Pressure Burner Rig (HPBR) at the NASA Glenn Research Center was selected to demonstrate coupon, subcomponent feature, and component testing because it can economically provide the temperatures, pressures, velocities, and combustion gas compositions that closely simulate the engine environments. The results have proven the HPBR to be a highly versatile test rig amenable to multiple test specimen configurations essential to coupon and component testing.

  4. Tensile Strength Measurements of Ceramic Materials at High Rates of Strain

    OpenAIRE

    Gálvez, F.; Rodríguez, J.; V. Sánchez

    1997-01-01

    Ceramic materials are usually assumed linear elastic up to failure and the failure criterion is accustomed to be a limit condition related to the tensile strength. Due to the difficulties associated with the uniaxial tensile test, some different alternatives have been posed such as Brazilian tests and spalling test of long bars. In this work, a comparative study of these methods has been broached. Specimens of alumina and silicon carbide have been tested at different strain rates, showing the...

  5. Development of UHTC- Ultra-high-temperature ceramics for aerospace and industrial applications

    OpenAIRE

    Bellosi, Alida

    2009-01-01

    Zirconium and Hafnium diborides and carbides belong to the class of Ultra-High-Temperature Ceramics (UHTC) for their high melting point (2700-3900?C). The interest on these materials is due to the unique combination of properties 8High hardness, high electrical and thermal conductivity, chemical inertness). They constitute a clss of promising materials for HT applications in industrial secors like foundry, refractory or nuclear plants. Applications are also found in aerospace industry: leadin...

  6. Hot-Pressed BN-AlN Ceramic Composites of High Thermal Conductivity

    Science.gov (United States)

    Kanai, Takao; Tanemoto, Kei; Kubo, Hiroshi

    1990-04-01

    Hexagonal boron nitride-aluminum nitride (75-25 wt%) ceramic composites are synthesized by uniaxial hot pressing. High thermal conductivity, 247 W/(m\\cdotK), is attained for the perpendicular direction of the hot-pressing axis of the sintered body, by optimizing the amount of added sintering aid, calcium carbide. The composites have remarkable anisotropy with respect to structure and thermal conductivity. The revelation mechanism of high thermal conductivity is discussed.

  7. Using the Voice to Design Ceramics

    DEFF Research Database (Denmark)

    Hansen, Flemming Tvede; Jensen, Kristoffer

    2011-01-01

    SoundShaping, a system to create ceramics from the human voice. Based on a generic audio feature extraction system, and the principal component analysis to ensure that the pertinent information in the voice is used, a 3D shape is created using simple geometric rules. This shape is output to a 3D printer...

  8. Silicon Carbide Solar Cells Investigated

    Science.gov (United States)

    Bailey, Sheila G.; Raffaelle, Ryne P.

    2001-01-01

    The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.

  9. CALPHAD study of cubic carbide systems with Cr

    OpenAIRE

    He, Zhangting

    2015-01-01

    Cubic carbides (titanium, tantalum, niobium, and zirconium carbides) can constitute a significant proportion of so-called cubic and cermet grades, where it is added to substitute a portion of tungsten carbide. It is thus critical to understand and be able to thermodynamically model the cubic carbide systems. In order to do this, the thermodynamic descriptions of lower order systems, such as the Ti-Cr-C system, need to be well studied. To approach this goal, an extensive literature survey of t...

  10. Silicon carbide, an emerging high temperature semiconductor

    Science.gov (United States)

    Matus, Lawrence G.; Powell, J. Anthony

    1991-01-01

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  11. Silicon carbide, an emerging high temperature semiconductor

    Science.gov (United States)

    Matus, Lawrence G.; Powell, J. Anthony

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  12. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  13. Ceramic Technology Project. Semiannual progress report, April 1991--September 1991

    Energy Technology Data Exchange (ETDEWEB)

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS`s Materials Development Program, was developed to meet the ceramic technology requirements of the OTS`s automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  14. Synergistic methods for the production of high-strength and low-cost boron carbide

    Science.gov (United States)

    Wiley, Charles Schenck

    2011-12-01

    Boron carbide (B4C) is a non-oxide ceramic in the same class of nonmetallic hard materials as silicon carbide and diamond. The high hardness, high elastic modulus and low density of B4C make it a nearly ideal material for personnel and vehicular armor. B4C plates formed via hot-pressing are currently issued to U.S. soldiers and have exhibited excellent performance; however, hot-pressed articles contain inherent processing defects and are limited to simple geometries such as low-curvature plates. Recent advances in the pressureless sintering of B4C have produced theoretically-dense and complex-shape articles that also exhibit superior ballistic performance. However, the cost of this material is currently high due to the powder shape, size, and size distribution that are required, which limits the economic feasibility of producing such a product. Additionally, the low fracture toughness of pure boron carbide may have resulted in historically lower transition velocities (the projectile velocity range at which armor begins to fail) than competing silicon carbide ceramics in high-velocity long-rod tungsten penetrator tests. Lower fracture toughness also limits multi-hit protection capability. Consequently, these requirements motivated research into methods for improving the densification and fracture toughness of inexpensive boron carbide composites that could result in the development of a superior armor material that would also be cost-competitive with other high-performance ceramics. The primary objective of this research was to study the effect of titanium and carbon additives on the sintering and mechanical properties of inexpensive B4C powders. The boron carbide powder examined in this study was a sub-micron (0.6 mum median particle size) boron carbide powder produced by H.C. Starck GmbH via a jet milling process. A carbon source in the form of phenolic resin, and titanium additives in the form of 32 nm and 0.9 mum TiO2 powders were selected. Parametric studies of

  15. 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.

  16. Properties of ceramic candle filters

    Energy Technology Data Exchange (ETDEWEB)

    Pontius, D.H.

    1995-06-01

    The mechanical integrity of ceramic filter elements is a key issue for hot gas cleanup systems. To meet the demands of the advanced power systems, the filter components must sustain the thermal stresses of normal operations (pulse cleaning), of start-up and shut-down conditions, and of unanticipated process upsets such as excessive ash accumulation without catastrophic failure. They must also survive the various mechanical loads associated with handling and assembly, normal operation, and process upsets. For near-term filter systems, these elements must survive at operating temperatures of 1650{degrees}F for three years.

  17. Ultrarapid microwave synthesis of superconducting refractory carbides

    Energy Technology Data Exchange (ETDEWEB)

    Vallance, Simon R. [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); School of Chemistry, University Nottingham (United Kingdom); Round, David M. [School of Chemistry, University Nottingham (United Kingdom); Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Cussen, Edmund J. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow (United Kingdom); Kingman, Sam [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); Gregory, Duncan H. [WestCHEM, Department of Chemistry, University of Glasgow (United Kingdom)

    2009-11-26

    Nb{sub 1-x}Ta{sub x}C Carbides can be synthesized by high power MW methods in less than 30 s. In situ and ex situ techniques probing changes in temperature and dielectric properties with time demonstrate that the reactions self-terminate as the loss tangent of the materials decreases. The resulting carbides are carbon deficient and superconducting; T{sub c} correlates linearly to unit cell volume, reaching a maximum at NbC. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  18. Fading corrections to electronic component substrates in retrospective accident dosimetry

    International Nuclear Information System (INIS)

    Accurate and rapid assessments of accidentally accrued radiation doses are imperative so that medical authorities may correctly identify exposed individuals and then counsel and triage them appropriately for treatment. Previous investigations have demonstrated very high dose response efficiencies in a wide range of manufactured insulators, including a variety of alumina ceramics, silicon carbides, aluminum nitrides, and others. Many of these serve as circuit and resistor substrates or encapsulants in modern electronic devices and are generally housed in light-tight enclosures; thus, they could in principle serve as accurate and sensitive dosimeters for the general population, should a need for such dosimetry ever arise. The radiation-induced luminescence signal in alumina porcelain resistor substrates has previously been observed to exhibit anomalous fading when a low-temperature preheat is applied. In this study, measurements were carried out using several preheat temperatures in order to determine whether the unstable component of the OSL signal could be eliminated. It was determined that increasing the preheat temperature has a minimal effect on the signal fading rate but results in significantly decreased sensitivity; therefore, a low-temperature preheat (160 oC) may be more appropriate when maximum sensitivity is required.

  19. Verification of ceramic structures

    NARCIS (Netherlands)

    Behar-Lafenetre, S.; Cornillon, L.; Rancurel, M.; Graaf, D. de; Hartmann, P.; Coe, G.; Laine, B.

    2012-01-01

    In the framework of the "Mechanical Design and Verification Methodologies for Ceramic Structures" contract [1] awarded by ESA, Thales Alenia Space has investigated literature and practices in affiliated industries to propose a methodological guideline for verification of ceramic spacecraft and instr

  20. Frequency mixing in boron carbide laser ablation plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; Nalda, R. de, E-mail: r.nalda@iqfr.csic.es; Castillejo, M.

    2015-05-01

    Graphical abstract: - Highlights: • Two-color frequency mixing has been studied in a laser ablation boron carbide plasma. • A space- and time-resolved study mapped the nonlinear optical species in the plasma. • The nonlinear process maximizes when charge recombination is expected to be completed. • Neutral atoms and small molecules are the main nonlinear species in this medium. • Evidence points to six-wave mixing as the most likely process. - Abstract: Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B{sub 4}C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

  1. Aluminium surface treatment with ceramic phases using diode laser

    Science.gov (United States)

    Labisz, K.; Tański, T.; Brytan, Z.; Pakieła, W.; Wiśniowski, M.

    2016-07-01

    Ceramic particles powder feeding into surface layer of engineering metal alloy is a well-known and widely used technique. New approach into the topic is to obtain finely distributed nano-sized particles involved in the aluminium matrix using the traditional laser technology. In this paper are presented results of microstructure investigation of cast aluminium-silicon-copper alloys surface layer after heat treatment and alloying with ceramic carbides of WC and ZrO2 using high-power diode laser. The surface layer was specially prepared for the reason of reducing the reflectivity, which is the main problem in the up-to-date metal matrix composites production. With scanning electron microscopy, it was possible to determine the deformation process and distribution of WC and ZrO2 ceramic powder phase. Structure of the surface after laser treatment changes, revealing three zones—remelting zone, heat-affected zone and transition zone placed over the Al substrate. The structural changes of ceramic powder, its distribution and morphology as well as microstructure of the matrix material influence on functional properties, especially wear resistance and hardness of the achieved layer, were investigated.

  2. Ultra-rapid processing of refractory carbides; 20 s synthesis of molybdenum carbide, Mo2C.

    Science.gov (United States)

    Vallance, Simon R; Kingman, Sam; Gregory, Duncan H

    2007-02-21

    The microwave synthesis of molybdenum carbide, Mo(2)C, from carbon and either molybdenum metal or the trioxide has been achieved on unprecedented timescales; Ex- and in-situ characterisation reveals key information as to how the reaction proceeds.

  3. Ceramic HEPA Filter Program

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, M A; Bergman, W; Haslam, J; Brown, E P; Sawyer, S; Beaulieu, R; Althouse, P; Meike, A

    2012-04-30

    Potential benefits of ceramic filters in nuclear facilities: (1) Short term benefit for DOE, NRC, and industry - (a) CalPoly HTTU provides unique testing capability to answer questions for DOE - High temperature testing of materials, components, filter, (b) Several DNFSB correspondences and presentations by DNFSB members have highlighted the need for HEPA filter R and D - DNFSB Recommendation 2009-2 highlighted a nuclear facility response to an evaluation basis earthquake followed by a fire (aka shake-n-bake) and CalPoly has capability for a shake-n-bake test; (2) Intermediate term benefit for DOE and industry - (a) Filtration for specialty applications, e.g., explosive applications at Nevada, (b) Spin-off technologies applicable to other commercial industries; and (3) Long term benefit for DOE, NRC, and industry - (a) Across industry, strong desire for better performance filter, (b) Engineering solution to safety problem will improve facility safety and decrease dependence on associated support systems, (c) Large potential life-cycle cost savings, and (d) Facilitates development and deployment of LLNL process innovations to allow continuous ventilation system operation during a fire.

  4. Synthesis and properties of low-carbon boron carbides

    International Nuclear Information System (INIS)

    This paper reports on the production of boron carbides of low carbon content (3 and CCl4 at 1273-1673 K in a chemical vapor deposition (CVD) reactor. Transmission electron microscopy (TEM) revealed that phase separation had occurred, and tetragonal boron carbide was formed along with β-boron or α-boron carbide under carbon-depleted gas-phase conditions. At temperatures greater than 1390 degrees C, graphite substrates served as a carbon source, affecting the phases present. A microstructure typical of CVD-produced α-boron carbide was observed. Plan view TEM of tetragonal boron carbide revealed a blocklike structure

  5. Development in laser peening of advanced ceramics

    Science.gov (United States)

    Shukla, Pratik; Smith, Graham C.; Waugh, David G.; Lawrence, Jonathan

    2015-07-01

    Laser peening is a well-known process applicable to surface treat metals and alloys in various industrial sectors. Research in the area of laser peening of ceramics is still scarce and a complete laser-ceramic interaction is still unreported. This paper focuses on laser peening of SiC ceramics employed for cutting tools, armor plating, dental and biomedical implants, with a view to elucidate the unreported work. A detailed investigation was conducted with 1064nm Nd:YAG ns pulse laser to first understand the surface effects, namely: the topography, hardness, KIc and the microstructure of SiC advanced ceramics. The results showed changes in surface roughness and microstructural modification after laser peening. An increase in surface hardness was found by almost 2 folds, as the diamond footprints and its flaws sizes were considerably reduced, thus, enhancing the resistance of SiC to better withstand mechanical impact. This inherently led to an enhancement in the KIc by about 42%. This is attributed to an induction of compressive residual stress and phase transformation. This work is a first-step towards the development of a 3-dimensional laser peening technique to surface treat many advanced ceramic components. This work has shown that upon tailoring the laser peening parameters may directly control ceramic topography, microstructure, hardness and the KIc. This is useful for increasing the performance of ceramics used for demanding applications particularly where it matters such as in military. Upon successful peening of bullet proof vests could result to higher ballistic strength and resistance against higher sonic velocity, which would not only prevent serious injuries, but could also help to save lives of soldiers on the battle fields.

  6. Ceramics As Materials Of Construction

    OpenAIRE

    Zaki, A.; Eteiba, M. B.; Abdelmonem, N.M.

    1988-01-01

    This paper attempts to review the limitations for using the important ceramics in contact with corrosive media. Different types of ceramics are included. Corrosion properties of ceramics and their electrical properties are mentioned. Recommendations are suggested for using ceramics in different media.

  7. Fabrication and characterization of reaction bonded silicon carbide/carbon nanotube composites

    International Nuclear Information System (INIS)

    Carbon nanotubes have generated considerable excitement in the scientific and engineering communities because of their exceptional mechanical and physical properties observed at the nanoscale. Carbon nanotubes possess exceptionally high stiffness and strength combined with high electrical and thermal conductivities. These novel material properties have stimulated considerable research in the development of nanotube-reinforced composites (Thostenson et al 2001 Compos. Sci. Technol. 61 1899, Thostenson et al 2005 Compos. Sci. Technol. 65 491). In this research, novel reaction bonded silicon carbide nanocomposites were fabricated using melt infiltration of silicon. A series of multi-walled carbon nanotube-reinforced ceramic matrix composites (NT-CMCs) were fabricated and the structure and properties were characterized. Here we show that carbon nanotubes are present in the as-fabricated NT-CMCs after reaction bonding at temperatures above 1400 deg. C. Characterization results reveal that a very small volume content of carbon nanotubes, as low as 0.3 volume %, results in a 75% reduction in electrical resistivity of the ceramic composites. A 96% decrease in electrical resistivity was observed for the ceramics with the highest nanotube volume fraction of 2.1%

  8. Using the Voice to Design Ceramics

    DEFF Research Database (Denmark)

    Tvede Hansen, Flemming; Jensen, Kristoffer

    2011-01-01

    Digital technology makes new possibilities in ceramic craft. This project is about how experiential knowledge that the craftsmen gains in a direct physical and tactile interaction with a responding material can be transformed and utilized in the use of digital technologies. The project presents...... SoundShaping, a system to create ceramics from the human voice. Based on a generic audio feature extraction system, and the principal component analysis to ensure that the pertinent information in the voice is used, a 3D shape is created using simple geometric rules. This shape is output to a 3D printer...... to make ceramic results. The system demonstrates the close connection between digital technology and craft practice....

  9. Ceramic application for regenerative burner system

    Energy Technology Data Exchange (ETDEWEB)

    Han, D.B.; Park, B.H.; Kim, Y.W.; Bae, W.S. [RIST, Pohang (Korea)

    1999-05-01

    Recently, regenerative burner system was developed and begins to be gradually used for better energy savings. Compared to conventional burner system, the regenerative one has the several merits such as higher fuel efficiency, light weight of apparatus, low harmful toxic gas and homogeneous heating zone, etc. The regenerative material, a very important component of the new regenerative burner system should possess the properties of low specific density, higher surface area and high specific heat capacity. Ceramics is the best regenerative material because of stable mechanical properties even at high temperature and better thermal properties and excellent chemical stability. In this study, alumina ball, alumina tube, 3-D ceramic foam and honeycomb as regenerative materials were tested and evaluated. The computer simulation was conducted and compared to the result of field test. This paper is aimed to introduce a new application of ceramics at high temperature. 7 refs., 5 figs., 3 tabs.

  10. Boron carbide morphology changing under purification

    Science.gov (United States)

    Rahmatullin, I. A.; Sivkov, A. A.

    2015-10-01

    Boron carbide synthesized by using coaxial magnetoplasma accelerator with graphite electrodes was purified by two different ways. XRD-investigations showed content changing and respectively powder purification. Moreover TEM-investigations demonstrated morphology changing of product under purification that was discussed in the work.

  11. Direct plasmadynamic synthesis of ultradisperse silicon carbide

    Science.gov (United States)

    Sivkov, A. A.; Nikitin, D. S.; Pak, A. Ya.; Rakhmatullin, I. A.

    2013-01-01

    Ultradisperse cubic silicon carbide (β-SiC) has been obtained by direct plasmadynamic synthesis in pulsed supersonic carbon-silicon plasma jet incident on a copper obstacle in argon atmosphere. The powdered product has a high content of β-SiC in the form of single crystals with average size of about 100 nm and nearly perfect crystallographic habit.

  12. Casimir forces from conductive silicon carbide surfaces

    NARCIS (Netherlands)

    Sedighi Ghozotkhar, Mehdi; Svetovoy, V. B.; Broer, W. H.; Palasantzas, G.

    2014-01-01

    Samples of conductive silicon carbide (SiC), which is a promising material due to its excellent properties for devices operating in severe environments, were characterized with the atomic force microscope for roughness, and the optical properties were measured with ellipsometry in a wide range of fr

  13. Casimir force measurements from silicon carbide surfaces

    NARCIS (Netherlands)

    Sedighi, M.; Svetovoy, V. B.; Palasantzas, G.

    2016-01-01

    Using an atomic force microscope we performed measurements of the Casimir force between a gold-coated (Au) microsphere and doped silicon carbide (SiC) samples. The last of these is a promising material for devices operating under severe environments. The roughness of the interacting surfaces was mea

  14. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Ming; Kossoy, Anna; Jarvinen, G. D.; Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Brinkman, Kyle; Fox, Kevin M.; Amoroso, Jake; Marra, James C.

    2014-02-03

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (~1–5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  15. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    Science.gov (United States)

    Tang, Ming; Kossoy, Anna; Jarvinen, Gordon; Crum, Jarrod; Turo, Laura; Riley, Brian; Brinkman, Kyle; Fox, Kevin; Amoroso, Jake; Marra, James

    2014-05-01

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (∼1-5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  16. Experimental evaluation of chromium-carbide-based solid lubricant coatings for use to 760 C

    Science.gov (United States)

    Dellacorte, Christopher

    1987-01-01

    A research program is described which further developed and investigated chromium carbide based self-lubricating coatings for use to 760 C. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The three coating components were blended in powder form, applied to stainless steel substrates by plasma spraying and then diamond ground to the desired coating thickness. A variety of coating compositions was tested to determine the coating composition which gave optimum tribological results. Coatings were tested in air, helium, and hydrogen at temperatures from 25 to 760 C. Several counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications, such as piston ring/cylinder liner couples for Stirling engines. In general, silver and fluoride additions to chromium carbide reduced the friction coefficient and increased the wear resistance relative to the unmodified coating. The lubricant additives acted synergistically in reducing friction and wear.

  17. Prior Surface Integrity Assessment of Coated and Uncoated Carbide Inserts Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Abdulla Almazrouee

    2011-04-01

    Full Text Available Coated carbide inserts are considered vital components in machining processes and advanced functional surface integrity of inserts and their coating are decisive factors for tool life. Atomic Force Microscopy (AFM implementation has gained acceptance over a wide spectrum of research and science applications. When used in a proper systematic manner, the AFM features can be a valuable tool for assessment of tool surface integrity. The aim of this paper is to assess the integrity of coated and uncoated carbide inserts using AFM analytical parameters. Surface morphology of as-received coated and uncoated carbide inserts is examined, analyzed, and characterized through the determination of the appropriate scanning setting, the suitable data type imaging techniques and the most representative data analysis parameters using the MultiMode AFM microscope in contact mode. The results indicate that it is preferable to start with a wider scan size in order to get more accurate interpretation of surface topography. Results are found credible to support the idea that AFM can be used efficiently in detecting flaws and defects of coated and uncoated carbide inserts using specific features such as “Roughness” and “Section” parameters. A recommended strategy is provided for surface examination procedures of cutting inserts using various AFM controlling parameters.

  18. Qualification of Indigenously Developed Special Coatings for Aero-Engine Components

    Directory of Open Access Journals (Sweden)

    V. Sambasiva Rao

    1999-10-01

    Full Text Available The demand for higher performance and reliability of aero-engiaes necessitates its components to worksatisfactorily under severe operating conditions. The durability of various components in these environmentis often enhanced by applying suitable coatings. The development of new materials/processing methods andalso various coatings to protect the components have been driven by the ever-increasing severity of theaero-engine internal environment. While the selection of a coating is dictated by the operating conditionsand the nature of the environment and also on the substrate, the durability of the coating depends uponthe mode of degradation of the coating and substrate in service.Though certification of an aero-engine after developmt obviously includes: validation of the componentsand its coatings, indigenous substitution of an already-qualified component system requires a re-orientationof the qualification methodology. This paper describes an approach for qualification of indigenously developedspecial coatings processes for application on aero-engine components. This approach has been adoptedsuccesshlly in validating several indigenous coatingslpmcesses, viz, aluminium-silicon diffusion coating appliedby pack cementation for oxidationhot comsion resistance, cobalt-chromium carbide coating by electrodepositionfor wear resistance, chromium carbide-nickel chromium coating applied by detonation gun and yttria-stabilisedzirconia thermal barrier coating applied by plasma spray.The approaih consists of a series of validation tests configured to assess the coating-substrate system.The rationale in evolving the qualification tests based on the type of coating, coating process, operating conditionsfor the components, probable failure modes and coating-base metal interaction, are described. In addition,comparison of the test results obtained on the test specimens coated with indigenously developed coatingsand imported coatings is also enumerated to show

  19. Microelectrical Discharge Machining: A Suitable Process for Machining Ceramics

    Directory of Open Access Journals (Sweden)

    Andreas Schubert

    2015-01-01

    Full Text Available Today ceramics are used in many industrial applications, for example, in the biomedical field, for high-temperature components or for cutting tools. This is attributed to their excellent mechanical and physical properties, as low density, high strength, and hardness or chemical resistance. However, these specific mechanical properties lead to problems regarding the postprocessing of ceramics. In particular, cutting processes require expensive tools which cause high manufacturing costs to machine ceramics. Consequently, there is a demand for alternative machining processes. Microelectrical discharge machining (micro-EDM is a thermal abrasion process which is based on electrical discharges between a tool and a workpiece. The advantages of micro-EDM are more and more in focus for ceramic machining. These advantages include the process of being a noncontact technology, an independency of material brittleness and hardness, a low impact on the material, and the achievable microstructures. This paper presents the current state of investigations regarding micro-EDM of ceramics. Beside the process principle of EDM, the used procedures for machining ceramics and insulating ceramics are described. Furthermore several machining examples are presented to demonstrate the possibilities of the micro-EDM process with regard to the machining of ceramics.

  20. Silicon nitride ceramic material having an in-situ continuous gradient function, process for manufacture, properties and applications thereof

    OpenAIRE

    Belmonte, Manuel; González Julián, Jesús; Miranzo López, Pilar; Osendi, María Isabel

    2008-01-01

    [EN] The present invention relates to a silicon mitride ceramic material having a continuous gradient in the microstructural characteristics thereof and in the properties thereof, from one extremity to the other of the ceramic component. Furthermore a method is described for the manufacture in situ of said ceramic materials having a gradient function from a single homogenous composition of ceramic powders and employing a sintering process through electric discharge modifying the temperatu...

  1. Frequency mixing in boron carbide laser ablation plasmas

    Science.gov (United States)

    Oujja, M.; Benítez-Cañete, A.; Sanz, M.; Lopez-Quintas, I.; Martín, M.; de Nalda, R.; Castillejo, M.

    2015-05-01

    Nonlinear frequency mixing induced by a bichromatic field (1064 nm + 532 nm obtained from a Q-switched Nd:YAG laser) in a boron carbide (B4C) plasma generated through laser ablation under vacuum is explored. A UV beam at the frequency of the fourth harmonic of the fundamental frequency (266 nm) was generated. The dependence of the efficiency of the process as function of the intensities of the driving lasers differs from the expected behavior for four-wave mixing, and point toward a six-wave mixing process. The frequency mixing process was strongly favored for parallel polarizations of the two driving beams. Through spatiotemporal mapping, the conditions for maximum efficiency were found for a significant delay from the ablation event (200 ns), when the medium is expected to be a low-ionized plasma. No late components of the harmonic signal were detected, indicating a largely atomized medium.

  2. In-process EDM truing to generate complex contours on metal-bond, superabrasive grinding wheels for precision grinding structural ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Piscotty, M.A.; Davis, P.J.; Saito, T.T.; Blaedel, K.L.; Griffith, L.

    1997-08-01

    The demand and use of precision grinding of structural ceramics continue to increase as the worldwide advanced ceramic industry surpasses $20 billion is sales. Included in this industry are engineering structural ceramics, electronic ceramics, bioceramics and others. These materials are used in applications such as engine components, casting and extrusion dies, bearings, medical implants, nozzles, thermal insulators, and more. Along with the variety of ceramic applications comes a broad range of precision requirements, which in turn leads to various required processes to accommodate a spectrum of specifications. A process for grinding ceramic components to micrometer tolerances was employed and further developed at Lawrence Livermore National Laboratory for two separate grinding projects.

  3. Interfacial adhesion of dental ceramic-resin systems

    Science.gov (United States)

    Della Bona, Alvaro

    The clinical success of resin bonding procedures for indirect ceramic restorations and ceramic repairs depends on the quality and durability of the bond between the ceramic and the resin. The quality of this bond will depend upon the bonding mechanisms that are controlled in part by the surface treatment that promotes micromechanical and/or chemical bonding to the substrate. The objective of this study is to correlate interfacial toughness (K A) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment. The analytical procedures focused on characterizing the microstructure and fracture properties of EmpressRTM ceramics (a leucite-based core ceramic, two lithia disilicate-based core ceramics, and a glass veneer) and determining the ceramic-resin adhesion zone bond strength characteristics. Microstructure and composition are controlling factors in the development of micromechanical retention produced by etching. Silane treated ceramics negated the effect of surface roughening produced by etching, inducing lower surface energy of the ceramic and, reduced bonding effectiveness. There was a positive correlation between WA, tensile bond strength (a), and KA, i.e., higher mean WA value, and higher mean sigma and KA values. This study suggests that (1) the sigma and KA values for ceramic bonded to resin are affected by the ceramic microstructure and the ceramic surface treatments; (2) the definition of the adhesion zone is essential to classify the modes of failure, which should be an integral component of all failure analyses; (3) the microtensile test may be preferable to conventional shear or flexural tests as an indicator of composite-ceramic bond quality; and (4) careful microscopic analysis of fracture surfaces and an x-ray dot map can produce a more consistent and complete description of the fracture process and interpretation of the modes of failure. The mode of failure and fractographic analyses

  4. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties

    OpenAIRE

    Hongfang Sun; Zishanshan Li; Jing Bai; Shazim Ali Memon; Biqin Dong; Yuan Fang; Weiting Xu; Feng Xing

    2015-01-01

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (...

  5. The impact of carbon on single crystal nickel-base superalloys: Carbide behavior and alloy performance

    Science.gov (United States)

    Wasson, Andrew Jay

    Advanced single crystal nickel-base superalloys are prone to the formation of casting grain defects, which hinders their practical implementation in large gas turbine components. Additions of carbon (C) have recently been identified as a means of reducing grain defects, but the full impact of C on single crystal superalloy behavior is not entirely understood. A study was conducted to determine the effects of C and other minor elemental additions on the behavior of CMSX-4, a commercially relevant 2nd generation single crystal superalloy. Baseline CMSX-4 and three alloy modifications (CMSX-4 + 0.05 wt. % C, CMSX-4 + 0.05 wt. % C and 68 ppm boron (B), and CMSX-4 + 0.05 wt. % C and 23 ppm nitrogen (N)) were heat treated before being tested in high temperature creep and high cycle fatigue (HCF). Select samples were subjected to long term thermal exposure (1000 °C/1000 hrs) to assess microstructural stability. The C modifications resulted in significant differences in microstructure and alloy performance as compared to the baseline. These variations were generally attributed to the behavior of carbide phases in the alloy modifications. The C modification and the C+B modification, which both exhibited script carbide networks, were 25% more effective than the C+N modification (small blocky carbides) and 10% more effective than the baseline at preventing grain defects in cast bars. All C-modified alloys exhibited reduced as-cast gamma/gamma' eutectic and increased casting porosity as compared to baseline CMSX-4. The higher levels of porosity (volume fractions 0.002 - 0.005 greater than the baseline) were attributed to carbides blocking molten fluid flow during the final stages of solidification. Although the minor additions resulted in reduced solidus temperature by up to 16 °C, all alloys were successfully heat treated without incipient melting by modifying commercial heat treatment schedules. In the B-containing alloy, heat treatment resulted in the transformation of

  6. A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing of Ceramic Composites. Part III; Additive Manufacturing and Characterization of Ceramic Composites

    Science.gov (United States)

    Halbig, Michael C.; Grady, Joseph E.; Singh, Mrityunjay; Ramsey, Jack; Patterson, Clark; Santelle, Tom

    2015-01-01

    This publication is the third part of a three part report of the project entitled "A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing" funded by NASA Aeronautics Research Institute (NARI). The objective of this project was to conduct additive manufacturing to produce ceramic matrix composite materials and aircraft engine components by the binder jet process. Different SiC powders with median sizes ranging from 9.3 to 53.0 microns were investigated solely and in powder blends in order to maximize powder packing. Various infiltration approaches were investigated to include polycarbosilane (SMP-10), phenolic, and liquid silicon. Single infiltrations of SMP-10 and phenolic only slightly filled in the interior. When the SMP-10 was loaded with sub-micron sized SiC powders, the infiltrant gave a much better result of filling in the interior. Silicon carbide fibers were added to the powder bed to make ceramic matrix composite materials. Microscopy showed that the fibers were well distributed with no preferred orientation on the horizontal plane and fibers in the vertical plane were at angles as much as 45deg. Secondary infiltration steps were necessary to further densify the material. Two to three extra infiltration steps of SMP-10 increased the density by 0.20 to 0.55 g/cc. However, the highest densities achieved were 2.10 to 2.15 g/cc. Mechanical tests consisting of 4 point bend tests were conducted. Samples from the two CMC panels had higher strengths and strains to failure than the samples from the two nonfiber reinforced panels. The highest strengths were from Set N with 65 vol% fiber loading which had an average strength of 66 MPa. Analysis of the fracture surfaces did not reveal pullout of the reinforcing fibers. Blunt fiber failure suggested that there was not composite behavior. The binder jet additive manufacturing method was used to also demonstrate the fabrication of turbine engine vane components of two different designs and sizes. The

  7. The exposure history of the Apollo 16 sites. An assessment based on methane and carbide measurements. [in lunar soils

    Science.gov (United States)

    Pillinger, C. T.; Eglinton, C.; Gowar, A. P.; Jull, A. J. T.; Maxwell, J. R.

    1974-01-01

    Soils from eight stations at the Apollo 16 landing site have been analyzed for methane and carbide. These results, in conjunction with published data from photogeology, bulk chemistry, rare gases, primordial and radionuclides, and agglutinate abundances have been interpreted in terms of differing contributions from three components, North and South Ray crater ejecta and Cayley Plains material.

  8. Ceramic Solar Receiver

    Science.gov (United States)

    Robertson, C., Jr.

    1984-01-01

    Solar receiver uses ceramic honeycomb matrix to absorb heat from Sun and transfer it to working fluid at temperatures of 1,095 degrees and 1,650 degrees C. Drives gas turbine engine or provides heat for industrial processes.

  9. Ceramic fiber filter technology

    Energy Technology Data Exchange (ETDEWEB)

    Holmes, B.L.; Janney, M.A.

    1996-06-01

    Fibrous filters have been used for centuries to protect individuals from dust, disease, smoke, and other gases or particulates. In the 1970s and 1980s ceramic filters were developed for filtration of hot exhaust gases from diesel engines. Tubular, or candle, filters have been made to remove particles from gases in pressurized fluidized-bed combustion and gasification-combined-cycle power plants. Very efficient filtration is necessary in power plants to protect the turbine blades. The limited lifespan of ceramic candle filters has been a major obstacle in their development. The present work is focused on forming fibrous ceramic filters using a papermaking technique. These filters are highly porous and therefore very lightweight. The papermaking process consists of filtering a slurry of ceramic fibers through a steel screen to form paper. Papermaking and the selection of materials will be discussed, as well as preliminary results describing the geometry of papers and relative strengths.

  10. Advanced Ceramics Property Measurements

    Science.gov (United States)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2013-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the "what, how, how not, and why" for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of standards in one volume.

  11. Making Ceramic Cameras

    Science.gov (United States)

    Squibb, Matt

    2009-01-01

    This article describes how to make a clay camera. This idea of creating functional cameras from clay allows students to experience ceramics, photography, and painting all in one unit. (Contains 1 resource and 3 online resources.)

  12. Interface coatings for Carbon and Silicon Carbide Fibers in Silicon Carbide Matrixes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Interface coatings for fiber-reinforced composites are an enabling technology for high temperature ceramic matrix composites. Because of their availability and...

  13. Experimental investigation on shrinkage and surface replication of injection moulded ceramic parts

    DEFF Research Database (Denmark)

    Islam, Aminul; Giannekas, Nikolaos; Marhöfer, David Maximilian;

    2014-01-01

    Ceramic moulded parts are increasingly being used in advanced components and devices due to their unprecedented material and performance attributes. The surface finish, replication quality and material shrinkage are of immense importance for moulded ceramic parts intended for precision applications....... The current paper presents a thorough investigation on the process of ceramic moulding where it systematically characterizes the surface replication and shrinkage behaviours of precision moulded ceramic components. The test parts are moulded from Catamold TZP-A which is Y2O3-stabilised ZrO2 having...

  14. Production and characterization of ceramics for armor application; Producao e caracterizacao de ceramicas para blindagem balistica

    Energy Technology Data Exchange (ETDEWEB)

    Alves, J.T.; Lopes, C.M.A. [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil). Div. de Engenharia Mecanica-Aeronautica; Assis, J.M.K.; Melo, F.C.L., E-mail: cmoniz@iae.cta.b [Instituto de Aeronautica e Espaco (IAE), Sao Jose dos Campos, SP (Brazil). Div. de Materiais

    2010-07-01

    The fabrication of devices for ballistic protection as bullet proof vests and helmets and armored vehicles has been evolving over the past years along with the materials and models used for this specific application. The requirements for high efficient light-weight ballistic protection systems which not interfere in the user comfort and mobility has driven the research in this area. In this work we will present the results of characterization of two ceramics based on alumina and silicon carbide. The ceramics were produced in lab scale and the specific mass, scanning electron microscopy (SEM) microstructure, Vickers hardness, flexural resistance at room temperature and X-ray diffraction were evaluated. Ballistic tests performed in the selected materials showed that the ceramics present armor efficiency. (author)

  15. Selecting Ceramics - Introduction

    OpenAIRE

    Cassidy, M.

    2002-01-01

    AIM OF PRESENTATION: To compare a number of materials for extracoronal restoration of teeth with particular reference to CAD-CAM ceramics. CASE DESCRIPTION AND TREATMENT CARRIED OUT: This paper will be illustrated using clinical examples of patients treated using different ceramic restorations to present the advantages and disadvantages and each technique. The different requirements of tooth preparation, impression taking and technical procedures of each system will be presented and compar...

  16. R and D of joining technology for SiC components with channel

    International Nuclear Information System (INIS)

    Full text of publication follows: Silicon carbide fiber reinforced silicon carbide matrix composites (SiC/SiC) are attractive structural material for high-temperature components as advanced energy system because of their excellent thermo-mechanical and low activation properties. Nevertheless, there are some critical issues connected to the size and complex shapes of the component for practical use because of machining difficulties. The solution to this problem is to use joining to build up large or complex shapes from a series of smaller and simply shaped components. Joining of SiC/SiC has been demonstrated using various techniques including diffusion bonding, brazing bonding and hot pressing with sinterable SiC powder. Development of reliable and simple joining method for SiC/SiC composites that satisfies the requirements of mechanical integrity, thermal properties and safety during operation and maintenance or accident is strongly required. In this study, joining methods with SiC powder as the joining adhesives were studied in order to avoid the residual stresses coming from CTE (Coefficient of Thermal Expansion) mismatch between substrate and joining layer. The mechanical strength and microstructure of joining material between SiC substrates are investigated. It has been also examined to produce SiC component with channel by using joining technique like powder sintering and diffusion bonding. The commercial Hexoloy-SA (Saint-Gobain Ceramics, USA) used in this work as substrate material. The fine β-SiC nano-powder which the average particle size is below 30 nm, Al2O3, Y2O3, and SiO2 were used as joining adhesives. The specimens were joined with 20 MPa and 1400-1900 deg. C by hot pressing in argon atmosphere. The tensile and shear tests were performed to investigate the bonding strength. The cross-section of the joint was characterized by using an optical microscope and scanning electron microscopy (SEM). The joining conditions for SiC component with channel were

  17. Silicon carbide TRIPLEX materials for CANDU fuel cladding and pressure tubes

    International Nuclear Information System (INIS)

    Ceramic Tubular Products has developed a superior silicon carbide (SiC) material TRIPLEX, which can be used for both fuel cladding and other zirconium alloy materials in light water reactor (LWR) and heavy water reactor (CANDU) systems. The fuel cladding can replace Zircaloy cladding and other zirconium based alloy materials in the reactor systems. It has the potential to provide higher fuel performance levels in currently operating natural UO2 (NEU) fuel design and in advanced fuel designs (UO2(SEU), MOX thoria) at higher burnups and power levels. In all the cases for fuel designs TRIPLEX has increased resistance to severe accident conditions. The interaction of SiC with steam and water does not produce an exothermic reaction to produce hydrogen as occurs with zirconium based alloys. In addition the absence of creep down eliminates clad ballooning during high temperature accidents which occurs with Zircaloy blocking water channels required to cool the fuel. (author)

  18. Microstructural study of oxidation of carbon-rich amorphous boron carbide coating

    Institute of Scientific and Technical Information of China (English)

    Bin ZENG; Zu-de FENG; Si-wei LI; Yong-sheng LIU

    2008-01-01

    Carbon-rich amorphous boron carbide (BxC) coatings were annealed at 400℃, 700℃, 1000℃ and 1200℃ for 2 h in air atmosphere. The microstructure and composition of the as-deposited and annealed coat-ings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectro-scopy and energy dispersive X-ray spectroscopy (EDS). All of the post-anneal characterizations demonstrated the ability of carbon-rich BxC coatings to protect the graphite substrate against oxidation. Different oxidation modes of the coatings were found at low temperature (400℃), moderate temperature (700℃) and high temper-ature (1000℃ and 1200℃). Finally, the feasibility of the application of carbon-rich BxC instead of pyrolytic car-bon (PyC) as a fiber/matrix interlayer in ceramics-matrix composites (CMCs) is discussed here.

  19. Use of Silicon Carbide as Beam Intercepting Device Material: Tests, Issues and Numerical Simulations

    CERN Document Server

    Delonca, M; Gil Costa, M; Vacca, A

    2014-01-01

    Silicon Carbide (SiC) stands as one of the most promising ceramic material with respect to its thermal shock resistance and mechanical strengths. It has hence been considered as candidate material for the development of higher performance beam intercepting devices at CERN. Its brazing with a metal counterpart has been tested and characterized by means of microstructural and ultrasound techniques. Despite the positive results, its use has to be evaluated with care, due to the strong evidence in literature of large and permanent volumetric expansion, called swelling, under the effect of neutron and ion irradiation. This may cause premature and sudden failure, and can be mitigated to some extent by operating at high temperature. For this reason limited information is available for irradiation below 100°C, which is the typical temperature of interest for beam intercepting devices like dumps or collimators. This paper describes the brazing campaign carried out at CERN, the results, and the theoretical and numeric...

  20. An evaluation of the impact of surface coatings on the heat transfer in high temperature ceramic recuperators

    International Nuclear Information System (INIS)

    Engineering ceramics, particularly silicon carbide (SiC), are increasingly being used as materials in high temperature recuperators for preheating combustion air from furnace exhaust gases. As typical flue gases from these furnaces may contain sodium, potassium, halides, etc. that may attack SiC, protective coatings, such as alumina, zirconia, and others, have been investigated as a means of increasing the life and reliability of these SiC recuperators. This paper presents a study to determine the effect of coating properties, such as emissivity and thermal conductivity, on the heat transfer performance of these high temperature ceramic recuperators

  1. Clinical application of bio ceramics

    Science.gov (United States)

    Anu, Sharma; Gayatri, Sharma

    2016-05-01

    Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

  2. Ceramic electrolyte coating and methods

    Science.gov (United States)

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2007-08-28

    Aqueous coating slurries useful in depositing a dense coating of a ceramic electrolyte material (e.g., yttrium-stabilized zirconia) onto a porous substrate of a ceramic electrode material (e.g., lanthanum strontium manganite or nickel/zirconia) and processes for preparing an aqueous suspension of a ceramic electrolyte material and an aqueous spray coating slurry including a ceramic electrolyte material. The invention also includes processes for depositing an aqueous spray coating slurry including a ceramic electrolyte material onto pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  3. Probing Field Emission from Boron Carbide Nanowires

    Institute of Scientific and Technical Information of China (English)

    TIAN Ji-Fa; GAO Hong-Jun; BAO Li-Hong; WANG Xing-Jun; HUI Chao; LIU Fei; LI Chen; SHEN Cheng-Min; WANG Zong-Li; GU Chang-Zhi

    2008-01-01

    High density boron carbide nanowires are grown by an improved carbon thermal reduction technique. Transmission electron microscopy and electron energy lose spectroscopy of the sample show that the synthesized nanowires are B4 C with good crystallization. The field emission measurement for an individual boron nanowire is performed by using a Pt tip installed in the focused ion beam system. A field emission current with enhancement factor of 106 is observed and the evolution process during emission is also carefully studied. Furthermore, a two-step field emission with stable emission current density is found from the high-density nanowire film. Our results together suggest that boron carbide nanowires are promising candidates for electron emission nanodevices.

  4. Behavior of disordered boron carbide under stress.

    Science.gov (United States)

    Fanchini, Giovanni; McCauley, James W; Chhowalla, Manish

    2006-07-21

    Gibbs free-energy calculations based on density functional theory have been used to determine the possible source of failure of boron carbide just above the Hugoniot elastic limit (HEL). A range of B4C polytypes is found to be stable at room pressure. The energetic barrier for shock amorphization of boron carbide is by far the lowest for the B12(CCC) polytype, requiring only 6 GPa approximately = P(HEL) for collapse under hydrostatic conditions. The results clearly demonstrate that the collapse of the B12(CCC) phase leads to segregation of B12 and amorphous carbon in the form of 2-3 nm bands along the (113) lattice direction, in excellent agreement with recent transmission electron microscopy results.

  5. Hadfield steels with Nb and Ti carbides

    International Nuclear Information System (INIS)

    The Hadfield Steels and the mechanisms responsible for its high strain hardening rate were reviewed. Addition of carbide forming alloying elements to the base compostion was discussed, using the matrix sttel concept. Three experimental crusher jaws were cast, with Nb and Nb + Ti added to the usual Hadfiedl compostion, with enough excess carbon to allow the formation of MC carbides. Samples for metallographic analysis were prepared from both as cast and worn out castings. The carbic morphology was described. Partition of alloying elements was qualitatively studied, using Energy Dispersive Espectroscopy in SEM. The structure of the deformed layer near the worn surface was studied by optical metalography and microhardness measurements. The results showed that fatigue cracking is one of the wear mechanisms is operation in association with the ciclic work hardening of the surface of worn crusher jaws. (Author)

  6. An improved method of preparing silicon carbide

    International Nuclear Information System (INIS)

    A method of preparing silicon carbide is described which comprises forming a desired shape from a polysilane of the average formula:[(CH3)2Si][CH3Si]. The polysilane contains from 0 to 60 mole percent (CH3)2Si units and from 40 to 100 mole percent CH3Si units. The remaining bonds on the silicon are attached to another silicon atom or to a halogen atom in such manner that the average ratio of halogen to silicon in the polysilane is from 0.3:1 to 1:1. The polysilane has a melt viscosity at 1500C of from 0.005 to 500 Pa.s and an intrinsic viscosity in toluene of from 0.0001 to 0.1. The shaped polysilane is heated in an inert atmosphere or in a vacuum to an elevated temperature until the polysilane is converted to silicon carbide. (author)

  7. Reliable Breakdown Obtained in Silicon Carbide Rectifiers

    Science.gov (United States)

    Neudeck, Philip G.

    1997-01-01

    The High Temperature Integrated Electronics and Sensor (HTIES) Program at the NASA Lewis Research Center is currently developing silicon carbide (SiC) for use in harsh conditions where silicon, the semiconductor used in nearly all of today's electronics, cannot function. Silicon carbide's demonstrated ability to function under extreme high-temperature, high-power, and/or high-radiation conditions will enable significant improvements to a far-ranging variety of applications and systems. These range from improved high-voltage switching for energy savings in public electric power distribution and electric vehicles, to more powerful microwave electronics for radar and cellular communications, to sensor and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines.

  8. On the addition of conducting ceramic nanoparticles in solvent-free ionic liquid electrolyte for dye-sensitized solar cells

    KAUST Repository

    Lee, Chuan-Pei

    2009-08-01

    Titanium carbide (TiC) is an extremely hard conducting ceramic material often used as a coating for titanium alloys as well as steel and aluminum components to improve their surface properties. In this study, conducting ceramic nanoparticles (CCNPs) have been used, for the first time, in dye-sensitized solar cells (DSSCs), and the incorporation of TiC nanoparticles in a binary ionic liquid electrolyte on the cell performance has been investigated. Cell conversion efficiency with 0.6 wt% TiC reached 1.68%, which was higher than that without adding TiC (1.18%); however, cell efficiency decreased when the TiC content reached 1.0 wt%. The electrochemical impedance spectroscopy (EIS) technique was employed to analyze the interfacial resistance in DSSCs, and it was found that the resistance of the charge-transfer process at the Pt counter electrode (Rct1) decreased when up to 1.0 wt% TiC was added. Presumably, this was due to the formation of the extended electron transfer surface (EETS) which facilitates electron transfer to the bulk electrolyte, resulting in a decrease of the dark current, whereby the open-circuit potential (VOC) could be improved. Furthermore, a significant increase in the fill factor (FF) for all TiC additions was related to the decrease in the series resistance (RS) of the DSSCs. However, at 1.0 wt% TiC, the largest charge-transfer resistance at the TiO2/dye/electrolyte interface was observed and resulted from the poor penetration of the electrolyte into the porous TiO2. The long-term stability of DSSCs with a binary ionic liquid electrolyte, which is superior to that of an organic solvent-based electrolyte, was also studied. © 2009 Elsevier B.V. All rights reserved.

  9. Coarsening behaviour of M23C6 carbides in creep-resistant steel exposed to high temperatures

    Science.gov (United States)

    Godec, M.; Skobir Balantič, D. A.

    2016-07-01

    High operating temperatures can have very deleterious effects on the long-term performance of high-Cr, creep-resistant steels used, for example, in the structural components of power plants. For the popular creep-resistant steel X20CrMoV12.1 we analysed the processes of carbide growth using a variety of analytical techniques: transmission electron microscopy (TEM) and diffraction (TED), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The evolution of the microstructure after different aging times was the basis for a much better understanding of the boundary-migration processes and the growth of the carbides. We present an explanation as to why some locations are preferential for this growth, and using EBSD we were able to define the proper orientational relationship between the carbides and the matrix.

  10. The development of carbides in the phase boundary between delta ferrite and martensite in 9-14% chromium steels

    International Nuclear Information System (INIS)

    Materials with a sufficient toughness have to be used for safety-relevant components. In martensitic 12% chromium steels delta ferrite may occur, at higher contents (>0,5%) the fracture toughness of the material may be reduced considerably. This means that the DBTT (ductile to brittle transition temperature) is shifted towards higher temperatures during impact tests. In two-phase steels consisting of delta-ferrite and martensite, this behavior of brittle fracture is found to be caused by the massive dendritic carbide surrounding the delta-ferrite. The generation of this carbide is described by means of CCT diagrams (continuous cooling transformation diagrams). Carbide formation depends on both the chromium content and the cooling velocity. (orig.)

  11. Formation of Al2O3-HfO2 Eutectic EBC Film on Silicon Carbide Substrate

    Directory of Open Access Journals (Sweden)

    Kyosuke Seya

    2015-01-01

    Full Text Available The formation mechanism of Al2O3-HfO2 eutectic structure, the preparation method, and the formation mechanism of the eutectic EBC layer on the silicon carbide substrate are summarized. Al2O3-HfO2 eutectic EBC film is prepared by optical zone melting method on the silicon carbide substrate. At high temperature, a small amount of silicon carbide decomposed into silicon and carbon. The components of Al2O3 and HfO2 in molten phase also react with the free carbon. The Al2O3 phase reacts with free carbon and vapor species of AlO phase is formed. The composition of the molten phase becomes HfO2 rich from the eutectic composition. HfO2 phase also reacts with the free carbon and HfC phase is formed on the silicon carbide substrate; then a high density intermediate layer is formed. The adhesion between the intermediate layer and the substrate is excellent by an anchor effect. When the solidification process finished before all of HfO2 phase is reduced to HfC phase, HfC-HfO2 functionally graded layer is formed on the silicon carbide substrate and the Al2O3-HfO2 eutectic structure grows from the top of the intermediate layer.

  12. Magnetism of hydrogen-irradiated silicon carbide

    International Nuclear Information System (INIS)

    Spin-polarized density functional theory is used to study two-hydrogen defect complexes in silicon carbide. We find that the magnetism depends on the distances of the two hydrogen atoms. Magnetism appears when the two hydrogen defects are distant from each other, and magnetism cancels out if they are close to each other. The critical distance between the two hydrogen defects is determined.

  13. Interaction of energetic tritium with silicon carbide

    International Nuclear Information System (INIS)

    In order to investigate the physical and chemical interactions of energetic hydrogen isotope species with silicon carbide, recoil tritium from the 3He(n,p)T reaction has been allowed to react with K-T silicon carbide and silicon carbide powder. The results show that if the silicon carbide has been degassed and annealed at 14000C prior to tritium bombardment, a considerable fraction of the tritium (ca. 40%) is released as HTO from the SiC upon heating to 13500C under vacuum conditions. Most of the remaining tritium is retained in SiC, e.g., the retention of the tritium in the K-T SiC was found to be 62 and 22% upon heating to 600 and 13500C, respectively. This is in direct contrast to graphite samples in which the tritium is not released to any significant extent even when heated to 13500C. Samples which were exposed to H2O and H2 prior to tritium bombardment were heated to 6000C after the irradiation. The results obtained indicate that a total of 38.7 and 2.49% of the tritium is released in the form of HT and CH3T in the case of H2 or H2O exposure, respectively. Treatment of degassed samples after tritium bombardment with H2O and H2 at temperatures up to 10000C leads to the release of up to 44.9% of the tritium as HT and CH3T. 42 references, 2 figures, 2 tables

  14. Diamond-silicon carbide composite and method

    Science.gov (United States)

    Zhao, Yusheng

    2011-06-14

    Uniformly dense, diamond-silicon carbide composites having high hardness, high fracture toughness, and high thermal stability are prepared by consolidating a powder mixture of diamond and amorphous silicon. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPam.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness.

  15. Cutting Performance and Mechanism of RE Carbide Tools

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The research of rare earth elements (RE), added into cemented carbide tools, is one of the recent developments of new types of tool materials in China. Systematic experiments about RE carbides YG8R (K30), YT14R (P20) and YW1R (M10) were made to study on the cutting performance in comparison with non-RE carbides YG8, YT14 and YW1. The cutting experiments were as follows: tool life, cutting force, tool-chip friction coefficient and interrupted machining. The action of RE on the carbide materials and the cutting mechanism of the RE carbide tools in the cutting process were verified with the aid of SEM and energy spectrum analysis. Experimental results show that the RE carbide tools have a good overall performance.

  16. Nonlinear optical imaging of defects in cubic silicon carbide epilayers.

    Science.gov (United States)

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Matei, Alecs; Stanciu, George A

    2014-06-11

    Silicon carbide is one of the most promising materials for power electronic devices capable of operating at extreme conditions. The widespread application of silicon carbide power devices is however limited by the presence of structural defects in silicon carbide epilayers. Our experiment demonstrates that optical second harmonic generation imaging represents a viable solution for characterizing structural defects such as stacking faults, dislocations and double positioning boundaries in cubic silicon carbide layers. X-ray diffraction and optical second harmonic rotational anisotropy were used to confirm the growth of the cubic polytype, atomic force microscopy was used to support the identification of silicon carbide defects based on their distinct shape, while second harmonic generation microscopy revealed the detailed structure of the defects. Our results show that this fast and noninvasive investigation method can identify defects which appear during the crystal growth and can be used to certify areas within the silicon carbide epilayer that have optimal quality.

  17. 碳化硼的研究进展%Progress of Research on Boron Carbide

    Institute of Scientific and Technical Information of China (English)

    刘珅楠; 孙帆; 谭章娜; 袁青; 周凯静; 马剑华

    2015-01-01

    碳化硼是高性能陶瓷材料中的一种重要原料,包含诸多的优良性能,除了高硬度、低密度等性能外,它还具备高化学稳定性和中子吸收截面及热电性能等特性,在国防军事设备、功能陶瓷、热电元件等诸多领域具有十分广泛的应用。本文重点介绍了碳化硼的相关性质、研究进展和应用现状。详细地介绍了碳化硼的制备方法,如电弧炉碳热还原法、自蔓延高温法、化学气相沉积法、溶胶-凝胶法等方法,并分析了它们的优缺点。%Boron carbide is a kind of important raw materials of high performanceceramic material, including many excellent performance. In addition to highhardness and low density properties, it also has high chemical stability andneutron absorption cross section and thermoelectric properties, which are widely used in national defense and military equipment, functional ceramics and thermoelectric element fields. The current research progress and application of relevant properties, boron carbide were introduced. The preparation methods of boron carbide, such as carbon arc furnace reduction method, self-propagating high temperature method, chemical vapor deposition, sol-gel method, were mainly introduced, and their advantages and disadvantages were analyzed.

  18. Method for improving the performance of oxidizable ceramic materials in oxidizing environments

    Science.gov (United States)

    Nagaraj, Bangalore A. (Inventor)

    2002-01-01

    Improved adhesion of thermal barrier coatings to nonmetallic substrates using a dense layer of ceramic on an underlying nonmetallic substrate that includes at least one oxidizable component. The improved adhesion occurs because the application of the dense ceramic layer forms a diffusion barrier for oxygen. This diffusion barrier prevents the oxidizable component of the substrate from decomposing. The present invention applies ceramic by a process that deposits a relatively thick and dense ceramic layer on the underlying substrate. The formation of the dense layer of ceramic avoids the problem of void formation associated with ceramic formation by most prior art thermal decomposition processes. The formation of voids has been associated with premature spalling of thermal barrier layers and other protective layers applied to substrates.

  19. Extended defects in insulating MgAl2O4 ceramic materials studied by PALS methods

    International Nuclear Information System (INIS)

    Extended positron-trapping defects in technological modified insulating nanoporous MgAl2O4 ceramics are characterized by positron annihilation lifetime spectroscopy. The results are achieved using three-component fitting procedure with arbitrary lifetimes applied to treatment of measured spectra. Within this approach, the first component in the lifetime spectra reflects microstructure specificity of the spinel structure, the second component responsible to extended defects near intergranual boundaries and the third component correspond to ortho-positronium 'pick-off' decaying in nanopores of ceramics. It is shown that in ceramics of different technological modifications the same type of positron traps prevails.

  20. Doping of silicon carbide by ion implantation

    International Nuclear Information System (INIS)

    It appeared that in some fields, as the hostile environments (high temperature or irradiation), the silicon compounds showed limitations resulting from the electrical and mechanical properties. Doping of 4H and 6H silicon carbide by ion implantation is studied from a physicochemical and electrical point of view. It is necessary to obtain n-type and p-type material to realize high power and/or high frequency devices, such as MESFETs and Schottky diodes. First, physical and electrical properties of silicon carbide are presented and the interest of developing a process technology on this material is emphasised. Then, physical characteristics of ion implantation and particularly classical dopant implantation, such as nitrogen, for n-type doping, and aluminium and boron, for p-type doping are described. Results with these dopants are presented and analysed. Optimal conditions are extracted from these experiences so as to obtain a good crystal quality and a surface state allowing device fabrication. Electrical conduction is then described in the 4H and 6H-SiC polytypes. Freezing of free carriers and scattering processes are described. Electrical measurements are carried out using Hall effect on Van der Panw test patterns, and 4 point probe method are used to draw the type of the material, free carrier concentrations, resistivity and mobility of the implanted doped layers. These results are commented and compared to the theoretical analysis. The influence of the technological process on electrical conduction is studied in view of fabricating implanted silicon carbide devices. (author)

  1. Methyldichloroborane evidenced as an intermediate in the chemical vapour deposition synthesis of boron carbide.

    Science.gov (United States)

    Reinisch, G; Patel, S; Chollon, G; Leyssale, J-M; Alotta, D; Bertrand, N; Vignoles, G L

    2011-09-01

    The most recent ceramic-matrix composites (CMC) considered for long-life applications as thermostructural parts in aerospace propulsion contain, among others, boron-rich phases like boron carbide. This compound is prepared by thermal Chemical Vapour Infiltration (CVI), starting from precursors like boron halides and hydrocarbons. We present a study aiming at a precise knowledge of the gas-phase composition in a hot-zone LPCVD reactor fed with BCl3, CH4 and H2, which combines experimental and theoretical approaches. This work has brought strong evidences of the presence of Methydichloroborane (MDB, BCl2CH3) in the process. It is demonstrated that this intermediate, the presence of which had never been formally proved before, appears for processing temperatures slightly lower than the deposition temperature of boron carbide. The study features quantum chemical computations, which provide several pieces of information like thermochemical and kinetic data, as well as vibration and rotation frequencies, reaction kinetics computations, and experimental gas-phase characterization of several species by FTIR, for several processing parameter sets. The main results are presented, and the place of MDB in the reaction scheme is discussed.

  2. Development of a feedstock formulation based on PP for MIM of carbides reinforced M2

    Directory of Open Access Journals (Sweden)

    A. Várez

    2008-04-01

    Full Text Available Purpose: Influence of binder composition on some selected properties of feedstock contained powder of M2 with 10% of carbides powders are demonstrated in the paper.Design/methodology/approach: Torque-load test, rheological tests.Findings: Examination of the effect of the binder type and portion on structure and properties of the experimental tool materials with the cermets structure revealed that using the stearic acid reduces viscosity, thus improving technological properties of the feedstock. Employment of polyethylene instead of the high density polypropylene reduces viscosity and torque-load of the investigated feedstocks. Therefore, there is a possibility to increase the portion of the metallic or ceramic powder.Practical implications: It is expected that further investigations of these materials will make possible their injection moulding, as well as their heat treatment increasing hardness and strength of matrix and thereby of the whole tool material. The extrusion process or PIM (Powder Injection Moulding gives the possibility to manufacturing tools materials on the basis of high speed-steel which characterised very good properties with their final or near net shape.Originality/value: In the paper the using extruding of the polymer-powder mix gives the possibility to fabricate cermets which, with their structure and mechanical properties, fill the gap in tool materials between the high-speed steels and cemented carbides.

  3. Analytical and experimental evaluation of joining silicon carbide to silicon carbide and silicon nitride to silicon nitride for advanced heat engine applications Phase 2. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Sundberg, G.J.; Vartabedian, A.M.; Wade, J.A.; White, C.S. [Norton Co., Northboro, MA (United States). Advanced Ceramics Div.

    1994-10-01

    The purpose of joining, Phase 2 was to develop joining technologies for HIP`ed Si{sub 3}N{sub 4} with 4wt% Y{sub 2}O{sub 3} (NCX-5101) and for a siliconized SiC (NT230) for various geometries including: butt joins, curved joins and shaft to disk joins. In addition, more extensive mechanical characterization of silicon nitride joins to enhance the predictive capabilities of the analytical/numerical models for structural components in advanced heat engines was provided. Mechanical evaluation were performed by: flexure strength at 22 C and 1,370 C, stress rupture at 1,370 C, high temperature creep, 22 C tensile testing and spin tests. While the silicon nitride joins were produced with sufficient integrity for many applications, the lower join strength would limit its use in the more severe structural applications. Thus, the silicon carbide join quality was deemed unsatisfactory to advance to more complex, curved geometries. The silicon carbide joining methods covered within this contract, although not entirely successful, have emphasized the need to focus future efforts upon ways to obtain a homogeneous, well sintered parent/join interface prior to siliconization. In conclusion, the improved definition of the silicon carbide joining problem obtained by efforts during this contract have provided avenues for future work that could successfully obtain heat engine quality joins.

  4. Stereology of carbide phase in modified hypereutectic chromium cast iron

    Directory of Open Access Journals (Sweden)

    J. Suchoń

    2010-04-01

    Full Text Available In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C, ferroniobium (FeNb and mixture of ferroniobium and rare-earth (RE. The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  5. Characterization of boron carbide with an electron microprobe

    Science.gov (United States)

    Matteudi, G.; Ruste, J.

    1983-01-01

    Within the framework of a study of heterogeneous materials (Matteudi et al., 1971: Matteudi and Verchery, 1972) thin deposits of boron carbide were characterized. Experiments using an electronic probe microanalyzer to analyze solid boron carbide or boron carbide in the form of thick deposits are described. Quantitative results on boron and carbon are very close to those obtained when applying the Monte Carlo-type correction calculations.

  6. Stereology of carbide phase in modified hypereutectic chromium cast iron

    OpenAIRE

    J. Suchoń; A. Studnicki; M. Przybył

    2010-01-01

    In paper are presented results of studies of carbide phase stereology modified hypereutectic wear resistance chromium cast iron which contains carbon about 3,5% and chromium about 25%. Three substances were applied to the modification: boron carbide (B4C), ferroniobium (FeNb) and mixture of ferroniobium and rare-earth (RE). The measurements of geometrical features of carbides were conducted on microsection taken from castings wich were cooled with various velocities.

  7. Delivering carbide ligands to sulfide-rich clusters.

    Science.gov (United States)

    Reinholdt, Anders; Herbst, Konrad; Bendix, Jesper

    2016-02-01

    The propensity of the terminal ruthenium carbide Ru(C)Cl2(PCy3)2 (RuC) to form carbide bridges to electron-rich transition metals enables synthetic routes to metal clusters with coexisting carbide and sulfide ligands. Electrochemical experiments show the Ru≡C ligand to exert a relatively large electron-withdrawing effect compared with PPh3, effectively shifting redox potentials.

  8. Sintering of nano crystalline silicon carbide by doping with boron carbide

    Indian Academy of Sciences (India)

    M S Datta; A K Bandyopadhyay; B Chaudhuri

    2002-06-01

    Sinterable nano silicon carbide powders of mean particle size (37 nm) were prepared by attrition milling and chemical processing of an acheson type alpha silicon carbide having mean particle size of 0.39 m (390 nm). Pressureless sintering of these powders was achieved by addition of boron carbide of 0.5 wt% together with carbon of 1 wt% at 2050°C at vacuum (3 mbar) for 15 min. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by scanning electron microscopy and transmission electron microscopy. This study shows that the mechanism is a solid-state sintering process. Polytype transformation from 6H to 4H was observed.

  9. Tungsten carbide platelet-containing cemented carbide with yttrium containing dispersed phase

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li; CHEN Shu; WANG Yuan-jie; YU Xian-wang; XIONG Xiang-jun

    2008-01-01

    A fine and platelet tungsten carbide patterned structure with fine yttrium containing dispersed phase was observed in liquid phase sintered WC-20%Co-1%Y2O3 cemented carbide with ultrafine tungsten carbide and nano yttrium oxide as starting materials. By comparing the microstructures of the alloy prepared by hot-press at the temperature below the eutectic melting temperature and by conventional liquid phase sintering, it is shown that hexagonal and truncated trigonal plate-like WC grains are formed through the mechanism of dissolution-precipitation (recrystallization) at the stage of liquid phase sintering. Yttrium in the addition form of oxide exhibits good ability in inhibiting the discontinuous or inhomogeneous WC grain growth in the alloy at the stage of solid phase sintering.

  10. Silicon carbide sintered body manufactured from silicon carbide powder containing boron, silicon and carbonaceous additive

    Science.gov (United States)

    Tanaka, Hidehiko

    1987-01-01

    A silicon carbide powder of a 5-micron grain size is mixed with 0.15 to 0.60 wt% mixture of a boron compound, i.e., boric acid, boron carbide (B4C), silicon boride (SiB4 or SiB6), aluminum boride, etc., and an aluminum compound, i.e., aluminum, aluminum oxide, aluminum hydroxide, aluminum carbide, etc., or aluminum boride (AlB2) alone, in such a proportion that the boron/aluminum atomic ratio in the sintered body becomes 0.05 to 0.25 wt% and 0.05 to 0.40 wt%, respectively, together with a carbonaceous additive to supply enough carbon to convert oxygen accompanying raw materials and additives into carbon monoxide.

  11. Carbides in Nodular Cast Iron with Cr and Mo

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2007-07-01

    Full Text Available In these paper results of elements microsegregation in carbidic nodular cast iron have been presented. A cooling rate in the centre of the cross-section and on the surface of casting and change of moulding sand temperature during casting crystallization and its self-cooling have been investigated. TDA curves have been registered. The linear distribution of elements concentration in an eutectic grain, primary and secondary carbides have been made. It was found, that there are two kinds of carbides: Cr and Mo enriched. A probable composition of primary and secondary carbides have been presented.

  12. Thermodynamic and kinetic study of uranium carbide pyrophoricity

    International Nuclear Information System (INIS)

    This research thesis concerns the development of nuclear reactors of fourth generation, and more particularly the use of carbide fuels instead of oxide fuels. An experimental part allows the investigation of mechanisms resulting in the pyrophoric reaction of a powder of uranium carbide, and addresses the determination of kinetic parameters intrinsic to the oxidation of powdered uranium carbide. Experimental results are then used to develop models of oxidation of powders of carbide uranium which are applied to a simplified mono-dispersed powder, and then introduced in a computation code. Simulation results are compared with experimental results

  13. Silicon Carbide Corrugated Mirrors for Space Telescopes Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Trex Enterprises Corporation (Trex) proposes technology development to manufacture monolithic, lightweight silicon carbide corrugated mirrors (SCCM) suitable for...

  14. Oxygen ion-conducting dense ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Balachandran, Uthamalingam (Hinsdale, IL); Kleefisch, Mark S. (Plainfield, IL); Kobylinski, Thaddeus P. (Prospect, PA); Morissette, Sherry L. (Las Cruces, NM); Pei, Shiyou (Naperville, IL)

    1998-01-01

    Preparation, structure, and properties of mixed metal oxide compositions and their uses are described. Mixed metal oxide compositions of the invention have stratified crystalline structure identifiable by means of powder X-ray diffraction patterns. In the form of dense ceramic membranes, the present compositions demonstrate an ability to separate oxygen selectively from a gaseous mixture containing oxygen and one or more other volatile components by means of ionic conductivities.

  15. Piezoelectric Ceramics and Their Applications

    Science.gov (United States)

    Flinn, I.

    1975-01-01

    Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

  16. Cooled Ceramic Turbine Vane Project

    Data.gov (United States)

    National Aeronautics and Space Administration — N&R Engineering will investigate the feasibility of cooled ceramics, such as ceramic matrix composite (CMC) turbine blade concepts that can decrease specific...

  17. Mechanical properties of ceramics

    CERN Document Server

    Pelleg, Joshua

    2014-01-01

    This book discusses the mechanical properties of ceramics and aims to provide both a solid background for undergraduate students, as well as serving as a text to bring practicing engineers up to date with the latest developments in this topic so they can use and apply these to their actual engineering work.  Generally, ceramics are made by moistening a mixture of clays, casting it into desired shapes and then firing it to a high temperature, a process known as 'vitrification'. The relatively late development of metallurgy was contingent on the availability of ceramics and the know-how to mold them into the appropriate forms. Because of the characteristics of ceramics, they offer great advantages over metals in specific applications in which hardness, wear resistance and chemical stability at high temperatures are essential. Clearly, modern ceramics manufacturing has come a long way from the early clay-processing fabrication method, and the last two decades have seen the development of sophisticated technique...

  18. OXYGEN TRANSPORT CERAMIC MEMBRANES

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  19. Non-catalytic facile synthesis of superhard phase of boron carbide (B13C2) nanoflakes and nanoparticles.

    Science.gov (United States)

    Xie, Sky Shumao; Su, Liap Tat; Guo, Jun; Vasylkiv, Oleg; Borodianska, Hanna; Xi, Zhu; Krishnan, Gireesh M; Su, Haibin; Tokl, Alfred I Y

    2012-01-01

    Boron Carbide is one the hardest and lightest material that is also relatively easier to synthesis as compared to other superhard ceramics like cubic boron nitride and diamond. However, the brittle nature of monolithic advanced ceramics material hinders its use in various engineering applications. Thus, strategies that can toughen the material are of fundamental and technological importance. One approach is to use nanostructure materials as building blocks, and organize them into a complex hierarchical structure, which could potentially enhance its mechanical properties to exceed that of the monolithic form. In this paper, we demonstrated a simple approach to synthesize one- and two-dimension nanostructure boron carbide by simply changing the mixing ratio of the initial compound to influence the saturation condition of the process at a relatively low temperature of 1500 degrees C with no catalyst involved in the growing process. Characterization of the resulting nano-structures shows B13C2, which is a superhard phase of boron carbide as its hardness is almost twice as hard as the commonly known B4C. Using ab-initio density functional theory study on the elastic properties of both B12C3 and B13C2, the high hardness of B13C2 is consistent to our calculation results, where bulk modulus of B13C2 is higher than that of B4C. High resolution transmission electron microscopy of the nanoflakes also reveals high density of twinning defects which could potentially inhibit the crack propagation, leading to toughening of the materials.

  20. Ceramic package fabrication for YMP nuclear waste disposal

    Energy Technology Data Exchange (ETDEWEB)

    Wilfinger, K.

    1994-08-01

    The purpose of this work is to develop alternate materials/design concepts to metal barriers for the Nevada Nuclear Waste Storage Investigations Project. There is some potential that site conditions may prove to be too aggressive for successful employment of the metal alloys under current consideration or that performance assessment models will predict metal container degradation rates that are inconsistent with the goal of substantially complete containment included in the NRC regulations. In the event that the anticipated lifetimes of metal containers are considered inadequate, alternate materials (i.e. ceramics or ceramic/metal composites) will be chosen due to superior corrosion resistance. This document was prepared using information taken from the open literature, conversations and correspondence with vendors, news releases and data presented at conferences to determine what form such a package might take. This discussion presents some ceramic material selection criteria, alternatives for the materials which might be used and alternatives for potential fabrication routes. This includes {open_quotes}stand alone{close_quotes} ceramic components and ceramic coatings/linings for metallic structures. A list of companies providing verbal or written information concerning the production of ceramic or ceramic lined waste containers appears at the end of this discussion.

  1. 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.

  2. Metal-Matrix/Hollow-Ceramic-Sphere Composites

    Science.gov (United States)

    Baker, Dean M.

    2011-01-01

    A family of metal/ceramic composite materials has been developed that are relatively inexpensive, lightweight alternatives to structural materials that are typified by beryllium, aluminum, and graphite/epoxy composites. These metal/ceramic composites were originally intended to replace beryllium (which is toxic and expensive) as a structural material for lightweight mirrors for aerospace applications. These materials also have potential utility in automotive and many other terrestrial applications in which there are requirements for lightweight materials that have high strengths and other tailorable properties as described below. The ceramic component of a material in this family consists of hollow ceramic spheres that have been formulated to be lightweight (0.5 g/cm3) and have high crush strength [40.80 ksi (.276.552 MPa)]. The hollow spheres are coated with a metal to enhance a specific performance . such as shielding against radiation (cosmic rays or x rays) or against electromagnetic interference at radio and lower frequencies, or a material to reduce the coefficient of thermal expansion (CTE) of the final composite material, and/or materials to mitigate any mismatch between the spheres and the matrix metal. Because of the high crush strength of the spheres, the initial composite workpiece can be forged or extruded into a high-strength part. The total time taken in processing from the raw ingredients to a finished part is typically 10 to 14 days depending on machining required.

  3. Theoretical investigation of nano zirconium carbide sheet: A study of NMR, NBO, EPR and Polar

    Directory of Open Access Journals (Sweden)

    Roya Rouhani

    2015-09-01

    Full Text Available In this work, we have focused on the zirconium carbide (ZrC sheet. The result exhibited that ZrC exhibits various outstanding physical and chemical properties, such as high hardness (25 Gpa, high melting point (3420°C, high corrosion and wear resistance, solid-state phase stability as well as chemical stability. Hence, ZrC has been considered a good potential material for ultra-high temperature applications. Applications range from cutting tools, grinding wheels and abrasives for mechanical as well as structural components in chemical and electronic industries. Abinitio calculation was carried out for Zirconium carbide sheet (ZrC using Gaussian 09 program for the first time (Fig 1. We choose B3LYP for calculating natural bond orbital (NBO, Nuclear magnetic resonance (NMR, Electron paramagnetic resonance (EPR and polar.

  4. Assessment of ceramic membrane filters

    Energy Technology Data Exchange (ETDEWEB)

    Ahluwalia, R.K.; Geyer, H.K.; Im, K.H. [and others

    1995-08-01

    The objectives of this project include the development of analytical models for evaluating the fluid mechanics of membrane coated, dead-end ceramic filters, and to determine the effects of thermal and thermo-chemical aging on the material properties of emerging ceramic hot gas filters. A honeycomb cordierite monolith with a thin ceramic coating and a rigid candle filter were evaluated.

  5. Ceramic vane drive joint

    Science.gov (United States)

    Smale, Charles H. (Inventor)

    1981-01-01

    A variable geometry gas turbine has an array of ceramic composition vanes positioned by an actuating ring coupled through a plurality of circumferentially spaced turbine vane levers to the outer end of a metallic vane drive shaft at each of the ceramic vanes. Each of the ceramic vanes has an end slot of bow tie configuration including flared end segments and a center slot therebetween. Each of the vane drive shafts has a cross head with ends thereof spaced with respect to the sides of the end slot to define clearance for free expansion of the cross head with respect to the vane and the cross head being configured to uniformly distribute drive loads across bearing surfaces of the vane slot.

  6. Analysis of the influence of process conditions on the surface finish of ceramic materials manufactured by EDM; Analisis de la influencia de las condiciones de proceso sobre el acabado superficial de materiales ceramicos fabricados por electroerosion

    Energy Technology Data Exchange (ETDEWEB)

    Puertas-Arbizu, I.; Luis-Perez, C. J.

    2004-07-01

    Electrical discharge machining (EDM) is an emerging alternative versus some other manufacturing processes of conductive ceramic materials, such as: laser machining, electrochemical machining, abrasive water jet, ultrasonic machining and diamond wheel grinding. Due to its interest in the industrial field, in this work a study of the influence of process conditions on the surface aspect of three conductive ceramic materials: hot-pressed boron carbide (B{sub 4}C), reaction-bonded silicon carbide (SiSiC) and cobalt-bonded tungsten carbide (WC-Co) is carried out. These materials are to be electrical discharge machined under different machining conditions and in the particular case of finish stages (Ra{<=} 1 {mu}m). (Author)

  7. Materials Development Program: Ceramic Technology Project bibliography, 1984--1992

    Energy Technology Data Exchange (ETDEWEB)

    1994-03-01

    The Ceramic Technology [for Advanced Heat Engines] Project was begun in 1983 to meet the ceramic materials needs of the companion DOE automotive engine program, the Advanced Gas Turbine (AGT) project, and the Heavy Duty Transport (low-heat-rejection, heavy-duty diesel) project. Goal is to develop an industry technology base for reliable and cost effective ceramics for applications in advanced automotive gas turbine and diesel engines. Research areas were identified following extensive input from industry and academia. Majority of research is done by industry (60%); work is also done at colleges and universities, in-house, and at other national laboratories and government agencies. In the beginning, reliability of ceramic components was the key issue. The reliability issues have largely been met and, at the present time, cost is the driving issue, especially in light of the highly cost-sensitive automotive market. Emphasis of the program has now been shifted toward developing cost-effective ceramic components for high-performance engines in the near-term. This bibliography is a compilation of publications done in conjunction with the Ceramic Technology Project since its beginning. Citations were obtained from reports done by participants in the project. We have tried to limit citations to those published and easily located. The end date of 1992 was selected.

  8. Thin Film Ceramic Strain Sensor Development for High Temperature Environments

    Science.gov (United States)

    Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M.; Laster, Kimala L.

    2008-01-01

    The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed. The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in harsh environments. The effort at the NASA Glenn Research Center (GRC) to develop high temperature thin film ceramic static strain gauges for application in turbine engines is described, first in the fan and compressor modules, and then in the hot section. The near-term goal of this research effort was to identify candidate thin film ceramic sensor materials and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. A thorough literature search was conducted for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible with the NASA GRCs microfabrication procedures and substrate materials. Test results are given for tantalum, titanium and zirconium-based nitride and oxynitride ceramic films.

  9. Catastrophic failure of ceramic-polyethylene bearing total hip arthroplasty.

    Science.gov (United States)

    Needham, Justin; Burns, Travis; Gerlinger, Tad

    2008-06-01

    Complications of ceramic-polyethylene bearing total hip arthroplasty (THA) include osteolysis, loosening, dislocation, and component failure. Catastrophic acetabular component failure involves severe damage to both the polyethylene liner and metal shell. This case study presents the first reported complete wear-through of the acetabular portion of a ceramic-polyethylene arthroplasty presenting as a dislocation and a review of the literature. In this study, a patient's alumina ceramic femoral head penetrated the polyethylene liner and titanium shell and presented as a dislocated THA. The contributing factors for this catastrophic failure include young patient age, high activity level, thin polyethylene liner, backside wear, component positioning, polyethylene sterilization with gamma irradiation in air, and lack of appropriate follow-up. Revision THA was performed without complications. PMID:18514888

  10. Supported microporous ceramic membranes

    Science.gov (United States)

    Webster, E.; Anderson, M.

    1993-12-14

    A method for the formation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms. 4 figures.

  11. Research and development status of ceramic breeder materials

    International Nuclear Information System (INIS)

    The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was also recognized by the International Thermonuclear Experimental Reactor (ITER) design team in its selection of ceramics as the first option breeder material. Blanket design studies have indicated areas in the properties data base that need further investigation. Current studies are focusing on issues such as tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests are underway, some as part of an international collaboration for development of ceramic breeder materials. 36 refs

  12. Fabrication of hexagonal boron nitride based ceramics by combustion synthesis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Pure h-BN (hexagonal boron nitride) and h-BN based ceramic parts were fabricated by combustion synthesis technique, i.e. self-propagating high-temperature synthesis (SHS). Components were manufactured by the combustion reaction of 80  MPa nitrogen and the compact made by cool isostatic pressing. In h-BN based ceramic parts, h-BN powder was used as diluent and SiO2 powder as reinforcing phase. The density of pure h-BN and h-BN-based ceramic parts were 58% and 78% of theoretical density, respectively. With XRD and SEM, phases and microstructures of ceramic parts were analyzed. Mechanical properties were also tested.

  13. Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

    Science.gov (United States)

    Sullivan, Roy M.

    2016-01-01

    The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

  14. Columnar-to-Equiaxed Transition in Metal-Matrix Composites Reinforced with Silicon Carbide Particles

    Directory of Open Access Journals (Sweden)

    Alicia E. Ares

    2013-01-01

    Full Text Available The present work is focused on the study of the effect of directional heat extraction on the silicon-carbide (SiC distribution in zinc-aluminum matrix composites (MMCs and on the columnar-to-equiaxed (CET position in directionally solidified samples. To this end, a ZA-27 alloy matrix was reinforced with ceramic particles of SiC and vertically directionally solidified. The cooling rates, temperature gradients, and interphase velocities were then measured, and their influence on the solidification microstructure of the MMCs was analyzed. The recalescence detected and measured during the equiaxed transition was of the order of 3.5°C to 1.1°C. The values of the temperature gradients reached a minimum during the CET and were even negative in most cases (between −3.89 K and 0.06 K. The interphase velocities varied between 0.07 mm/s and 0.44 mm/s at the transition. Also, the presence of ceramic particles in ZA-27 alloys affected the thermodynamic local conditions and the kinetics of nucleation, producing a finer microstructure.

  15. Integral ceramic superstructure evaluation using time domain optical coherence tomography

    Science.gov (United States)

    Sinescu, Cosmin; Bradu, Adrian; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

    2014-02-01

    Optical Coherence Tomography (OCT) is a non-invasive low coherence interferometry technique that includes several technologies (and the corresponding devices and components), such as illumination and detection, interferometry, scanning, adaptive optics, microscopy and endoscopy. From its large area of applications, we consider in this paper a critical aspect in dentistry - to be investigated with a Time Domain (TD) OCT system. The clinical situation of an edentulous mandible is considered; it can be solved by inserting 2 to 6 implants. On these implants a mesostructure will be manufactured and on it a superstructure is needed. This superstructure can be integral ceramic; in this case materials defects could be trapped inside the ceramic layers and those defects could lead to fractures of the entire superstructure. In this paper we demonstrate that a TD-OCT imaging system has the potential to properly evaluate the presence of the defects inside the ceramic layers and those defects can be fixed before inserting the prosthesis inside the oral cavity. Three integral ceramic superstructures were developed by using a CAD/CAM technology. After the milling, the ceramic layers were applied on the core. All the three samples were evaluated by a TD-OCT system working at 1300 nm. For two of the superstructures evaluated, no defects were found in the most stressed areas. The third superstructure presented four ceramic defects in the mentioned areas. Because of those defects the superstructure may fracture. The integral ceramic prosthesis was send back to the dental laboratory to fix the problems related to the material defects found. Thus, TD-OCT proved to be a valuable method for diagnosing the ceramic defects inside the integral ceramic superstructures in order to prevent fractures at this level.

  16. Development and characterization of solid solution tri-carbides

    Science.gov (United States)

    Knight, Travis; Anghaie, Samim

    2001-02-01

    Solid-solution, binary uranium/refractory metal carbide fuels have been shown to be capable of performing at high temperatures for nuclear thermal propulsion applications. More recently, tri-carbide fuels such as (U, Zr, Nb)C1+x with less than 10% metal mole fraction uranium have been studied for their application in ultra-high temperature, high performance space nuclear power systems. These tri-carbide fuels require high processing temperatures greater than 2600 K owing to their high melting points in excess of 3600 K. This paper presents the results of recent studies involving hypostoichiometric, single-phase tri-carbide fuels. Processing techniques of cold uniaxial pressing and sintering were investigated to optimize the processing parameters necessary to produce high density (low porosity), single phase, solid solution mixed carbide nuclear fuels for testing. Scanning electron microscopy and xray diffraction were used to analyze samples. Liquid phase sintering with UC1+x at temperatures near 2700 K was shown to be instrumental in achieving good densification in hyper- and near-stoichiometric mixed carbides. Hypostoichiometric carbides require even higher processing temperatures greater than 2800 K in order to achieve liquid phase sintering with a UC liquid phase and good densification of the final solid solution, tri-carbide fuel. .

  17. Critically coupled surface phonon-polariton excitation in silicon carbide.

    Science.gov (United States)

    Neuner, Burton; Korobkin, Dmitriy; Fietz, Chris; Carole, Davy; Ferro, Gabriel; Shvets, Gennady

    2009-09-01

    We observe critical coupling to surface phonon-polaritons in silicon carbide by attenuated total reflection of mid-IR radiation. Reflectance measurements demonstrate critical coupling by a double scan of wavelength and incidence angle. Critical coupling occurs when prism coupling loss is equal to losses in silicon carbide and the substrate, resulting in maximal electric field enhancement. PMID:19724526

  18. Preparation and Electrocatalytic Activity of Tungsten Carbide Nanorod Arrays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    High density tungsten carbide nanorod arrays have been prepared by magnetron sputtering (MS) using the aluminum lattice membrane (ALM) as template. Electrocatalytic properties of nitromethane electroreduction on the tungsten carbide nanorod arrays electrode were investigated by electrochemical method, and their electrocatalytic activity is approached to that of the Pt foil electrode.

  19. Silicon Carbide Tiles for Sidewall Lining in Aluminium Electrolysis Cells

    Institute of Scientific and Technical Information of China (English)

    RUANBo; ZHAOJunguo; 等

    1999-01-01

    The paper introduces the nitride bonded silicon carbide used for sidewall lining in aluminium eletrolysis cells ,including technical process,main properties and application results.Comparison tests on various physical properties of silicon carbide products made by LIRR and other producers worldwide have also been conducted in an independent laboratory.

  20. Effect of zirconia type on its bond strength with different veneer ceramics

    NARCIS (Netherlands)

    M.N. Aboushelib; C.J. Kleverlaan; A.J. Feilzer

    2008-01-01

    Purpose: The bond strength between veneer ceramic and the zirconia framework is the weakest component in the layered structure. This bond was proven to be sensitive to the surface finish of the framework material and to the type of the veneer ceramic and its method of application. New colored zircon