Showing papers on "Ceramic matrix composite published in 1999"
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TL;DR: In this paper, the potential application of ceramic matrix composites to aero-engine components is discussed, including combustors, nozzle flaps, bladed disks, and others.
Abstract: The present paper describes the potential application of ceramic matrix composites to aero-engine components by reviewing the related published papers and our experience in this field. It contains the material requirements for aero-engines, trends in aero-engine materials use, Japanese projects related to ceramic matrix composites (CMCs) and potential application of CMCs to aero-engines, such as combustors, nozzle flaps, bladed disks and others. From the point of application to aero-engines, the remaining research and development issues are discussed to some extent. Material developments, particularly of the interface and fibers for high temperature, are still required and stressed.
340 citations
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TL;DR: In this paper, a Si-B-C ceramic matrix has been developed to improve the oxidation resistance and the lifetime in an oxygen environment of carbon-fiber-reinforced ceramic-matrix composites.
210 citations
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TL;DR: A Japanese 100 kW automotive ceramic gas turbine (CGT) project was started in 1990 and was concluded successfully in 1997 as mentioned in this paper, which achieved higher thermal efficiency over 40% at a turbine inlet temperature of 1350°C, lower exhaust emissions to meet Japanese regulations, and multi-fuel capabilities.
116 citations
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TL;DR: In this article, a high spark-resistive tool, ZrB2-Cu, was used for electrical discharge machining (EDM), where steel was used as the cathode workpiece and the MMC was employed as the anode tool.
Abstract: Frequent replacement of electrodes, due to their high wear rate, is an undesired feature of most thermal plasma processes. Hence, the discovery of a high spark-resistive tool, ZrB2-Cu, is of interest. Performance evaluation of this metal matrix ceramic (MMC) employed electrical discharge machining (EDM), where steel is used as the cathode workpiece and the MMC is used as the anode tool. Compared with the performance of copper and graphite tools, ZrB2-Cu yields the highest workpiece removal rate,; and the lowest tool wear rate at high plasma heat flux conditions, resulting in an extremely low wear ratio. Energy dispersive spectroscopy shows deposition of workpiece materials (Fe, Cr, Ni and S) on the ZrB2-Cu surface after EDM. This is due to the difference between the surface temperature of the tool and the workpiece. Scanning electron microscopy and elemental mapping analysis reveal that the composite electrode erodes by a combination of dominant evaporation and melting of the metal phase, negligible melting and thermal spalling in the ceramic phase, quick refreezing of the metal phase back to the surface, and deposition of the workpiece (steel) on the tool surface. Most of the heat is conducted through the Cu phase, reducing thermal stress in the ceramic phase. This causes lower surface temperatures for the molten ZrB2 matrix; hence, the Cu tends to refreeze quickly near the surrounding ceramic matrix.
112 citations
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TL;DR: In this article, a curved layer laminated object manufacturing (LOM) was designed for efficient fabrication of curved layer structures made from ceramics and fiber reinforced composites, and a new LOM machine was created, referred to as curved layer LOM.
Abstract: A novel rapid prototyping technology incorporating a curved layer building style was developed. The new process, based on laminated object manufacturing (LOM), was designed for efficient fabrication of curved layer structures made from ceramics and fiber reinforced composites. A new LOM machine was created, referred to as curved layer LOM. This new machine uses ceramic tapes and fiber prepregs as feedstocks and fabricates curved structures on a curved‐layer by curved‐layer basis. The output of the process is a three‐dimensional “green” ceramic that is capable of being processed to a seamless, fully dense ceramic using traditional techniques. A detailed description is made of the necessary software and hardware for this new process. Also reviewed is the development of ceramic preforms and accompanying process technology for net shape ceramic fabrication. Monolithic ceramic (SiC) and ceramic matrix composite (SiC/SiC) articles were fabricated using both the flat layer and curved layer LOM processes. For making curved layer objects, the curved process afforded the advantages of eliminated stair step effect, increased build speed, reduced waste, reduced need for decubing, and maintenance of continuous fibers in the direction of curvature.
96 citations
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TL;DR: In this paper, sintered alumina-30% zirconia ceramic composites were joined by hybrid heating using microwave radiation (2.45 GHz, 700 W), along with sodium silicate glass powder as an interlayer.
96 citations
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TL;DR: In this paper, the microstructure and damage tolerance mechanism of Ti3SiC2 was investigated, and the result demonstrated that the Ti3 SiC2 ceramics prepared by the in-situ hot pressing/solid-liquid reaction process had a dual micro-structure, i.e., large laminated grains were distributed within small equiaxial grains.
Abstract: Titanium silicon carbide (Ti3SiC2) is a damage tolerance material that is expected to be used in a number of high temperature applications. In this work, the microstructure and damage tolerance mechanism of Ti3SiC2 was investigated. The result demonstrated that the Ti3SiC2 ceramics prepared by the in-situ hot pressing/solid-liquid reaction process had a dual microstructure, i.e., large laminated grains were distributed within small equiaxial grains. This microstructure is analogous to that of platelets reinforced ceramic matrix composites. The bending test using single-edge-notched-beam specimens revealed that Ti3SiC2 was a damage tolerance material. The damage tolerance mechanisms for Ti3SiC2 are basal plane slip, grain buckling, crack deflection, crack branching, pull-out and delamination of the laminated grains.
94 citations
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TL;DR: The long term durability of CMCs is limited by two factors: (1) creep and rupture of the fibers, and (2) environmental degradation of the constituents, primarily in the nonoxide composites as discussed by the authors.
Abstract: The long term durability of CMCs is limited by two factors: (1) creep and rupture of the fibers, and (2) environmental degradation of the constituents, primarily in the nonoxide composites. Oxide CMCs are limited by the creep resistance of the fiber at this stage of development and by interphase concepts that are not yet mature. Nonoxide fibers have been developed with excellent creep resistance relative to oxide fibers, but oxidation of the interphase and the interface, particularly at intermediate temperatures, causes embrittlement of these composites. This effect is particularly severe when matrix cracks are present and under cyclic loading conditions.
93 citations
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TL;DR: In this article, a model is presented to estimate the reliability and time-to-failure of an unidirectional continuous fiber-reinforced ceramic composite when subjected to stresses beyond the matrix cracking stress.
Abstract: A model is presented to estimate the reliability and time-to-failure of an unidirectional continuous fiber-reinforced ceramic composite when subjected to stresses beyond the matrix cracking stress. The particular case of oxidation-assisted stress-rupture at intermediate temperatures is considered. The effects of stress and temperature on the reliability of the model composite are examined. Model predictions are presented for the specific case of CG-Nicalon™/SiC CFCCs with carbonaceous fiber coatings.
90 citations
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TL;DR: In this article, a raw material system and the fabrication process used to prepare two-dimensional cloth reinforced composites are presented, and the typical tensile, shear and compressive properties of CMCs prepared with the two types of reinforcements are presented.
Abstract: Preceramic polymers offer a unique method to fabricate ceramic matrix composites (CMC). Relatively large and complex shapes were fabricated using a polysilazane polymer and silicon carbide based reinforcements of CG Nicalon™ and HI-nicalon™ fibers. This paper summarizes a raw material system and the fabrication process used to prepare two-dimensional cloth reinforced composites. Typical tensile, shear and compressive properties of CMCs prepared with the two types of reinforcements are presented. Although CG Nicalon reinforced composites exhibit good mechanical stability at moderate stress levels at 1100°C, HI-Nicalon reinforced composites show improved creep behavior at 1200°C.
72 citations
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TL;DR: In this article, near fully dense in-situ particulate reinforced ceramic matrix composites (CMCs) were fabricated from fine Ti-B4C, Ti-BN, Ti−BN, Al-TiO2 powder blends with or without the addition of Ni.
Abstract: Near fully dense in-situ particulate reinforced ceramic matrix composites (CMCs) were fabricated from fine Ti–B4C, Ti–BN, Ti–Al–BN, Ti–SiC, Ti–B6Si and Al–TiO2 powder blends with or without the addition of Ni. Two reactive synthesis techniques were employed: thermal explosion/TE (SHS) under pressure, where the compacted reagent blend was placed and rapidly heated in a pressure die preheated slightly above the ignition temperature, and reactive hot pressing/RHP. In both approaches, the processing or preheating temperature (≤1250°C) was considerably lower than those typical of the current methods used for the processing of ceramic matrix composites. Partial to full conversion of reagents into products was achieved during TE, and a moderate external pressure of ≤150 MPa was sufficient to ensure full density of the final products. Rapid cooling from the combustion temperature due to the ‘heat sink’ action of the pressure die resulted in the fine/micronsize microstructures of the in-situ composites synthesized. RHP processing yielded dense materials with even finer microstructures, however full conversion of reagents into products has not been achieved.
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TL;DR: In this article, carbon and SiC fiber-reinforced ceramic matrix composites were prepared via infiltration of fiber preforms using the polymer infiltration technique and polymer pyrolysis.
Abstract: Carbon and SiC fiber-reinforced ceramic matrix composites were prepared via infiltration of fiber preforms using the polymer infiltration technique and polymer pyrolysis. Suitable silazane (SiCN) precursors with appropriate thermosetting behavior, viscosity and ceramic yield were synthesized, starting from functionalized chlorosilanes. Microstructural development and fracture behavior was studied after various infiltration and pyrolysis cycles. Residual stresses induced during processing were evaluated. Mechanical and thermo-physical properties of the composites with polymer-derived matrix, i.e. 3-pt bending strength and thermal expansion coefficients (CTE), were measured dependent on reinfiltration cycles and fiber orientation. The oxidation resistance was investigated. Specific pyrolyzed samples were infiltrated via silicon melts in order to enhance corrosion and wear resistance.
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TL;DR: In this paper, the material design of ceramic matrix composites (CMCs) is discussed in terms of fiber nature and architecture, interphases (pyrocarbon, BN, multilayers), matrices and seal-coating, taking into account lifetime considerations.
Abstract: The material design of ceramic matrix composites (CMCs) is discussed in terms of fiber nature and architecture, interphases (pyrocarbon, BN, multilayers), matrices and seal-coating, taking into account lifetime considerations. CMCs are processed by liquid or gas phase routes. Besides the well established processing routes, such as polymer impregnation and pyrolysis (PIP), slurry impregnation/hot pressing (SIHP) and isothermal/isobaric chemical vapor infiltration (I-CVI) techniques, emerging processes allowing densification times of the order of a day, are discussed.
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TL;DR: In this article, a continuous, aligned, 5·5μm diameter polycrystalline yttrium aluminium garnet (YAG) fibre was manufactured from an aqueous sol-gel precursor which contained chlorine, and compared to a similar nitrate containing YAG precursor fibre, the precursor sol was found to be stable at a higher concentration than the nitrate-containing sol, and this resulted in denser gel fibres which demonstrated better sintering at equivalent temperatures, giving a 98·5% sintered YAG fibre at 1550°C with a grain
Abstract: Continuous ceramic fibres are finding applications as reinforcements in ceramic matrix composites, and yttrium aluminium garnet (YAG) is a particularly attractive candidate material on account of its creep resistance at high temperatures. A continuous, aligned, 5·5 μm diameter polycrystalline YAG fibre was manufactured from an aqueous sol–gel precursor which contained chlorine, and compared to a similar nitrate containing YAG precursor fibre we have reported previously. The precursor sol was found to be stable at a higher concentration than the nitrate containing sol, and this resulted in denser gel fibres which demonstrated better sintering at equivalent temperatures, giving a 98·5% sintered YAG fibre at 1550°C with a grain size of only 1 μm. However, on firing in air, the fibres formed fully crystalline YAG between 800 and 900°C, a temperature 100°C higher than the fibres containing nitrate, and they were weakened by the presence of many hemispherical faults. It was shown that both of these features were due to the retention of chlorine until the onset of formation of the crystalline YAG phase, and a series of steaming experiments were devised to remove the halide before this process could occur. It was found that steaming the precursor fibre from 200 to 500°C over 3 h, followed by firing to the required temperature in air, removed the chlorine and the problems it caused in the formation of the YAG phase without any change in the sintering characteristics or grain size. The steamed fibres were of a strength and quality comparable to fibres drawn from organometallic precursors. Empirical friability measurements showed the strength was maintained after firing to 1550°C, although there was a deterioration in apparent strain to break of the aligned blanket product above 1200°C. Conversely, the creep resistance, measured using the BSR test, improved with increase in temperature. The fibres fired to 1550°C were fully relaxed at temperatures 100–150°C below that of coarser, larger YAG fibres previously reported with a 3 μm grain size and 120 μm diameter. However, when allowance was made for grain size, the difference in creep rates was within the range obtained by extrapolating previous data using lattice diffusion and grain boundary effect models. Fibres fired to 1400°C were much finer grained but only slightly inferior to the 1550°C fibre in terms of creep. The alumina sol used in this work contained a significant level of sodium, and this suggests that the creep rates are effected by grain boundary impurities, especially sodium. A sodium free sol has been procured and further work is recommended to clarify the effect of impurities and improve fibre properties.
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15 Mar 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times and the composite exhibited excellent strength and toughness improvement up to 1400 C.
Abstract: Intermetallic compound MoSi2 has long been known as a high temperature material that has excellent oxidation resistance and electrical/thermal conductivity. Also its low cost, high melting point (2023 C), relatively low density (6.2 g/cu cm versus 9 g/cu cm for current engine materials), and ease of machining, make it an attractive structural material. However, the use of MoSi2 has been hindered due to its poor toughness at low temperatures, poor creep resistance at high temperatures, and accelerated oxidation (also known as 'pest' oxidation) at temperatures between approximately 450 and 550 C. Continuous fiber reinforcing is very effective means of improving both toughness and strength. Unfortunately, MoSi2 has a relatively high coefficient of thermal expansion (CTE) compared to potential reinforcing fibers such as SiC. The large CTE mismatch between the fiber and the matrix resulted in severe matrix cracking during thermal cycling. Addition of about 30 to 50 vol % of Si3N4 particulate to MoSi2 improved resistance to low temperature accelerated oxidation by forming a Si2ON2 protective scale and thereby eliminating catastrophic 'pest failure'. The Si3N4 addition also improved the high temperature creep strength by nearly five orders of magnitude, doubled the room temperature toughness and significantly lowered the CTE of the MoSi2 and eliminated matrix cracking in SCS-6 reinforced composites even after thermal cycling. The SCS-6 fiber reinforcement improved the room temperature fracture toughness by seven times and impact resistance by five times. The composite exhibited excellent strength and toughness improvement up to 1400 C. More recently, tape casting was adopted as the preferred processing of MoSi2-base composites for improved fiber spacing, ability to use small diameter fibers, and for lower cost. Good strength and toughness values were also obtained with fine diameter Hi-Nicalon tow fibers. This hybrid composite remains competitive with ceramic matrix composites as a replacement for Ni-base superalloys in aircraft engine applications.
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TL;DR: In this article, the effects of temperature on microstructural stability and the creep behavior of directionally solidified alumina/YAG eutectic monofilaments were studied.
Abstract: Fiber strength retention and creep currently limit the use of polycrystalline oxide fibers in ceramic matrix composites making it necessary to develop single crystal fibers. Two-phase alumina/YAG single crystal structures in the form of monofilaments show that the room temperature tensile strength increases according to the inverse square root of the microstructure size. Therefore, microstructure stability will play a significant role in determining the ‘use temperature’ of these fibers along with its creep resistance. In this work, the effects of temperature on microstructural stability and the creep behavior of directionally solidified alumina/YAG eutectic monofilaments were studied. Microstructural stability experiments were conducted in air from 1200 to 1500°C and creep tests at temperatures of 1400 to 1700°C. Inherent microstructure stability was found to be very good, however, extraneous impurity-induced heterogeneous coarsening was significant above 1400°C. The creep strength of monofilaments with aligned microstructures were superior to ones with low aspect ratio morphologies. Mechanisms for microstructural coarsening and creep behavior are discussed.
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TL;DR: In this paper, the tribological properties of zirconia (Y-TZP), alumina (ZTA), and their composites, alumina dispersed in zirconsia (ADZ), were investigated.
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05 May 1999
TL;DR: In this paper, the ability to produce iron-based phosphate ceramic systems is enabled by the addition of an oxidizing or reducing step during the acid-base reactions that form the phosphate ceramic products.
Abstract: Known phosphate ceramic formulations are improved and the ability to produce iron-based phosphate ceramic systems is enabled by the addition of an oxidizing or reducing step during the acid-base reactions that form the phosphate ceramic products. The additives allow control of the rate of the acid-base reactions and concomitant heat generation. In an alternate embodiment, waste containing metal anions are stabilized in phosphate ceramic products by the addition of a reducing agent to the phosphate ceramic mixture. The reduced metal ions are more stable and/or reactive with the phosphate ions, resulting in the formation of insoluble metal species within the phosphate ceramic matrix, such that the resulting chemically bonded phosphate ceramic product has greater leach resistance.
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TL;DR: In this article, the thermal shock behavior of a ceramic matrix composite consisting of an alumina matrix containing 20 vol% of discrete iron particles was investigated, and the composite material has been produced by both hot pressing and conventional sintering techniques.
Abstract: Over recent years, it has been established that the incorporation of metallic particles into a ceramic matrix can lead to enhanced fracture properties. Relatively few attempts, however, have been made to establish whether or not the improved fracture toughness typically observed in such composite systems can offer improved performance in demanding environments. The current study is concerned with the thermal shock behaviour of a ceramic matrix composite consisting of an alumina matrix containing 20 vol% of discrete iron particles. The composite material has been produced by both hot pressing and conventional sintering techniques. The hot pressed composite shows a greater resistance to thermal shock than the monolithic matrix, both in terms of the critical temperature differential and retained strength, whereas the sintered material has been found to behave as a typical low strength refractory ceramic. The calculation of thermal shock resistance parameters for the composites and the monolith has indicated possible explanations for the differences in thermal shock behaviour.
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TL;DR: In this article, the authors conducted ball-on-flat tests on prepared sections cut from cast iron, silicon nitride, and silicon-nitride/12.5 vol% graphite composite valve guides over a range of temperatures, normal loads, speeds, and lubrication conditions.
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TL;DR: In this paper, the effects of whisker orientation on toughening mechanisms were discussed based on microscopic fractographic observation and micromechanics analyses, and the results indicated that the whisker orientations are a decisive factor for the essential toughness of whiskers, and only in the case of small θ and weak interface can whisker pullout occur, and whisker has maximum toughness.
Abstract: Si 3 N 4 ceramic matrix composites reinforced by nearly unidirectionally aligned SiC whiskers have been prepared by extrusion and hot pressing. Unlike the case in traditional Si 3 N 4 ceramic matrix composites reinforced by random SiC whiskers, the mechanical properties of the composites exhibit a significant dependence on whisker orientation. In the direction of whisker alignment for SiC(w)/Si 3 N 4 composites, increments in bending strength and fracture toughness of 200 MPa and 3 MPa·m 1/2 are obtained respectively, compared to the values in the direction perpendicular to whisker alignment. Based on microscopic fractographic observation and micromechanics analyses, the effects of whisker orientation on toughening mechanisms are discussed. The results indicate that the whisker orientation, θ , is a decisive factor for the essential toughening mechanisms of whiskers. Only in the case of small θ and weak interface can whisker pullout occur, and whisker has maximum toughening effect. The results show that effects of whisker strengthening and toughening can be improved simultaneously through whisker oriented alignment. ©
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TL;DR: In situ fiber fracture characteristics have been investigated for Si-Ti-C-O fibres after tensile testing up to 1380°C in vacuum and in air as mentioned in this paper, and the results indicated that fibres tested in air at elevated temperature have significantly lower strengths and average Weibull parameter, m, compared to the room-temperature, 1200 and 1300°C/vacuum cases, and this is attributed to oxygen damage of the fibre together with oxidation of the fiber/matrix interface.
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TL;DR: In this paper, an excimer laser-based system for mapping the surface temperature of turbine engine parts coated with thermographic phosphors has been developed, and the intensity measured for Y2O3:Eu over the temperature range ∼500-750°C is presented.
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TL;DR: In this paper, a model of failure for two-component brittle layered composites (in particular, ceramic-matrix composites) is presented. But the model is applied for the description of the mechanical behavior of two component ceramic-metrix layered composite.
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TL;DR: In this article, a linear softening bridging law is used to describe the metal particle bridging behavior and an integral equation of the thermal crack problem incorporating the bridging effect is derived and the thermal stress intensity factor at the bridged crack tip is calculated numerically.
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TL;DR: In this article, the microstructure and mechanical properties of the ceramic matrix composites were investigated using X-ray diffraction, optical microscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), and microhardness.
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TL;DR: In this paper, an analytical model for the matrix crack evolution was proposed using the energy balance calculation based on Kuo and Chou, with the modification of including the effects of damage mode interaction as well as Poisson contraction in the debonded regions.
Abstract: Matrix crack evolution was studied for SiC fiber-reinforced glass-matrix cross-ply laminates. A novel in situ SEM (scanning electron microscope) observation was conducted to measure the fiber/matrix debonding and sliding in 0° plies using specimens with parallel micro-lines printed on the surfaces. Interfacial debondings were found to grow intermittently as the applied stress increased. The debonding length distribution depends on the number of 90° plies as well as the type of damage modes. An analytical model for the matrix crack evolution was proposed using the energy balance calculation based on Kuo and Chou (Kuo WS, Chou TW. Multiple cracking of unidirectinal and cross-ply ceramic matrix composites. J Am Ceram Soc 1995;78(3):745–755), with the modification of including the effects of damage mode interaction as well as Poisson contraction in the debonded regions. The predicted evolution agrees well with the experimental one.
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TL;DR: In this paper, a commercial polysilazane is used as a silicon carbonitride matrix precursor for the manufacture of ceramic matrix composites using bi-directional SiC Nicalon fabrics as reinforcing material.
Abstract: A commercial polysilazane is used as a silicon carbonitride matrix precursor for the manufacture of ceramic matrix composites using bi-directional SiC Nicalon fabrics as reinforcing material. The objective is to develop a simple and fast process leading to materials able to compete with SiC/C/SiC composites obtained by the Chemical Vapour Infiltration (CVI) route. Two processes are investigated: (1) a ‘conventional’ process using the densification of a SiC fibre preform by several cycles of impregnation of the preform with the polymer followed by pyrolysis and (2) a ‘modified’ process consisting in a powder filling of the fibre preform prior to the precursor impregnation and pyrolysis. This paper describes the different steps of both processes. The materials obtained are characterised in terms of their porosity, microstructure and mechanical properties. ©
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TL;DR: In this paper, a dense silicon carbide matrix composite reinforced by Hi-Nicalon fibers with boron nitride coating was fabricated by slurry impregnation and subsequent reaction sintering process.
Abstract: A dense silicon carbide matrix composite reinforced by Hi-Nicalon fibers with boron nitride coating was fabricated by slurry impregnation and subsequent reaction sintering process. Hi-Nicalon fibers were not stable in contact with molten silicon. Accordingly the effect of the fiber coating structure and the infiltrating metal composition on the mechanical properties of the composite was investigated. Selecting a boron nitride and silicon carbide dual coating structure and a boron-doped silicon as the infiltrating metal, a ceramic matrix composite with excellent fracture energy could be newly developed. The microstructure and the bending strength at room and high temperatures were also evaluated. Optimized composite showed cumulative failure mode both at room temperature and at 1573K. The failure behavior kept this cumulative fracture mode even after oxidation at 1573K for 360ks. Good oxidation resistance was thought to be caused by the presence of the dense SiC matrix.
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07 Dec 1999
TL;DR: A multiphase material comprises a ceramic matrix material having one or more of Sn, Sb, Bi, Pb, Ag, In, Si and Ge nanodispersed in the matrix.
Abstract: A multiphase material comprises a ceramic matrix material having one or more of Sn, Sb, Bi, Pb, Ag, In, Si and Ge nanodispersed in the matrix. The ceramic matrix is preferably based upon carbides, nitrides and oxides of group IV-VI transition metals taken singly or in combination.