Showing papers on "Ceramic matrix composite published in 2002"

C/C-SiC Composites for Advanced Friction Systems

Abstract: Ceramic Matrix Composites (CMC), based on reinforcements of carbon fibres and matrices of silicon carbide, show superior tribological properties in comparison to grey cast iron or carbon/carbon. In combination with their low density, high thermal shock resistance and good abrasive resistance, these Si-infiltrated carbon/carbon materials, called C/SiC or C/C-SiC composites, are promising candidates for advanced friction systems. Generally, the carbon fibres lead to an improved damage tolerance in comparison to monolithic SiC, whereas the silicon carbide matrix improves the wear resistance compared to carbon/carbon. In combination with new design approaches cost-efficient manufacturing processes have been developed and have lead to successfully tested prototypes of brake pads and disks, especially for passenger cars and emergency brake systems.

Ceramic matrix composite structure having integral cooling passages and method of manufacture

Abstract: A multi-layer ceramic matrix composite structure (40) having a plurality of fiber-reinforced cooling passages (42) formed therein. The cooling passages are formed by the removal of a fugitive material. The fugitive material is part of a wrapped fugitive material structure containing a layer of reinforcing ceramic fibers (26) that is used to lay-up the multi-layer structure. An intermediate layer of ceramic fabric may be placed alternately over and under the wrapped fugitive material structure to separate the cooling passages into alternating upper and lower cooling passages. The transversely oriented fibers surrounding the cooling passages serve to increase the interlaminar strength of the structure when compared to prior art designs. An airfoil member incorporating such reinforced integral cooling passages is provided.

The morphology of silicon carbide in C/C-SiC composites

Abstract: In the present investigations C/C–SiC has been studied by means of SEM, X-ray diffraction (XRD) and TEM to reveal the morphology of the silicon carbide areas. It was found that there exist two different areas of SiC, a fine grained β-SiC layer with a high amount of stacking faults at the C–SiC interface, and a zone of coarser β-SiC at the SiC–Si interface. From these observations, reaction mechanisms governing the siliconization of porous C/C preforms are proposed. After an initial reaction of carbon with silicon vapour, liquid silicon has to diffuse through the already formed SiC. A violent reaction far away from equilibrium conditions and a high number of nucleation sites leads to the observed formation of a fine grained SiC with a high density of stacking faults. Thermodynamically this is an instable configuration so that the coarser grained zone emerges by solution and precipitation.

Hybrid monolithic ceramic and ceramic matrix composite airfoil and method for making the same

Abstract: The present invention is a low density hybrid airfoil comprising a temperature resistant exterior layer and a tough, high impact resistant interior layer. Specifically, the airfoil comprises a monolithic ceramic exterior layer and a fiber reinforced ceramic matrix composite interior layer. Both the monolithic ceramic and fiber reinforced ceramic matrix composite are low density materials. Additionally, the monolithic ceramic is a high temperature resistant material, and the fiber reinforced ceramic matrix composite is a relatively high impact resistant structure. Encapsulating the airfoil with a temperature resistant exterior layer protects the airfoil in a high temperature environment, and supporting the airfoil with a high impact resistant, fiber reinforced ceramic matrix composite improves the overall impact resistance of the airfoil thereby resulting in a tough, high temperature resistant, low density airfoil.

Method for repairing articles of ceramic composites

Abstract: A method for repairing an article made of a fiber-reinforced ceramic matrix composite comprises attaching sections of a fiber-reinforced tape to the damaged area and then infiltrating the sections with the ceramic matrix or ceramic matrix precursor material. The material around the damaged area may be removed first to form a depression that is then filled with sections of the fiber-reinforced tape and further infiltrated with the ceramic matrix or ceramic matrix precursor material. The repaired article shows stress-strain curve similar to a defect-free article.

Protective overlayer for ceramics

Abstract: A xenotime phosphate protective overlayer ( 22 ) for protecting a ceramic material ( 24 ) from a high temperature, moisture-containing environment. Yttrium phosphate may be used as a protective overlayer to protect an underlying mullite layer to temperatures in excess of 1,500° C. The coating may have porosity of greater than 15% for improved thermal shock protection. To prevent the ingress of oxygen to an underlying ceramic non-oxide material, such as silicon carbide or silicon nitride, an oxygen barrier layer ( 34 ) is disposed between the xenotime phosphate coating and the non-oxide material. Such a protective overlayer may be used for an article having a ceramic matrix composite substrate.

Porous ceramic composite bone grafts

Abstract: The invention relates to porous ceramic composites incorporating biodegradable polymers for use as a bone substitute in the fields of orthopaedics and dentistry or as a scaffold for tissue engineering applications. The porous ceramic composite implant for connective tissue replacement comprises a porous ceramic matrix having a biodegradable polymer provided on internal and external surfaces of the ceramic matrix. The biodegradable polymer allows for the passage and/or delivery of a variety of agents throughout the porous ceramic matrix and improves mechanical properties of the implant in vivo.

Method of manufacturing a ceramic matrix composite

Abstract: A method of manufacturing a ceramic matrix composite comprises forming a slurry comprising a ceramic sol, filler particles and a solvent and forming laminates of fibers (12). The laminates of fibers (12) are impregnated with the slurry and are stacked (14) on a mold (10). The stack (14) of laminates of fibers (12) is covered by a porous membrane (16), a breather fabric (18) and a vacuum bag (20). The vacuum bag (20) is evacuated and is heated to a temperature of 60° C. for 10 hours to produce a ceramic matrix composite. The ceramic matrix composite is then heated to a temperature of 1200° C. at atmospheric pressure to sinter the ceramic matrix composite.

The creep mechanism of ceramic matrix composites at low temperature and stress, by a material science approach

Abstract: This paper deals with the creep mechanism for ceramic matrix composites reinforced by long ceramic fibers in a ceramic or glass-ceramic matrix, tested at low stresses (

Fiber-reinforced ceramic composite material comprising a matrix with a nanolayered microstructure

Abstract: A fiber-reinforced ceramic matrix composite material exhibiting increased matrix cracking strength and fracture toughness is produced by sequentially depositing a plurality of 5-500 nanometer-thick layers of a primary ceramic matrix material phase periodically separated by 1-100 nanometer-thick intermediate layers of a secondary matrix material phase onto the reinforcing fibers upon their consolidation. The resultant nanolayered matrix enhances the resistance to the onset of matrix cracking, thus increasing the useful design strength of the ceramic matrix composite material. The nanolayered microstructure of the matrix constituent also provides a unique resistance to matrix crack propagation. Through extensive inter-layer matrix fracture, debonding and slip, internal matrix microcracks are effectively diverted and/or blunted prior to their approach towards the reinforcing fiber, thus increasing the apparent toughness of the matrix constituent. This unique toughening mechanism serves to dampen energetic co-planar macrocrack propagation typically observed in conventionally manufactured ceramic matrix composites wherein matrix cracks are usually deflected at the fiber/matrix interphase region.

Method for producing melt-infiltrated ceramic compositions using formed supports

Abstract: A method for producing shaped articles of ceramic composites provides a high degree of dimensional tolerance to these articles. A fiber preform is disposed on a surface of a stable formed support, a surface of which is formed with a plurality of indentations, such as grooves, slots, or channels. Precursors of ceramic matrix materials are provided to the fiber preform to infiltrate from both sides of the fiber preform. The infiltration is conducted under vacuum at a temperature not much greater than a melting point of the precursors. The melt-infiltrated composite article substantially retains its dimension and shape throughout the fabrication process.

Nano-structured metal-containing polymer precursors for high temperature non-oxide ceramics and ceramic fibers—syntheses, pyrolyses and properties

Abstract: Nano-structured metal-containing ceramic polymer precursors have a potential for progress in the field of polymer-derived ceramics. In this paper the synthesis and characterization of nano-metallopolycarbosilanes (nMPCS) and their transformation into ceramic materials are reported. The formation of metal nano-particles via fast thermolysis of metal- containing compounds in polymer solution or melt previously developed by the authors was applied to preceramic polymers. Tetrabenzyltitanium, tetrabenzylzirconium, bis(cyclopentadienil)dichloride-titanium and zirconium as well as tetrachlorides of these metals and tetrakis(diethylamino)zirconium were used for the introduction of metal nano-particles. The products were characterized by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), differential-thermal analysis (DTA), gel-penetration (GP)-chromatography, X-ray diffraction (XRD), scanning electron microscopy (SEM) and other special analyses. The results of these studies may be useful for the fabrication of non-oxide ceramic fibers, interphase coatings and high temperature ceramic matrix composite (HT-CMC) matrices. Cp2ZrCl2 and Zr[N(C2H5)2]4 provided nano-particles with diameters of 2–4 nm and turned out to be the most suitable compounds for the preparation of ceramic matrices. Besides, they open a new way of oxygen-free curing. Coreless fibers were obtained from nZrPCS with up to 3 mass% of metal. Future investigations will be focused on optimization of the oligocarbosilanes used as starting materials and the development of less reactive polycarbosilane (PCS)–metal-containing compound (MCC) systems.

Longitudinal and transverse piezoelectric coefficients of lead zirconate titanate/vinylidene fluoride-trifluoroethylene composites with different polarization states

Abstract: Composite films comprising lead zirconate titanate (PZT) ceramic particles dispersed in a vinylidene fluoride-trifluoroethylene copolymer matrix have been prepared by compression molding. The ceramic and copolymer phases of the composite films are polarized separately, resulting in samples with three different polarization states: only the ceramic phase polarized, both phases polarized in the same direction, and two phases polarized in opposite directions. The effect of polarization state on the longitudinal and transverse piezoelectric coefficients (d33 and d31) of the composite film has been investigated as functions of ceramic volume fraction φc. When the ceramic and copolymer phases of a composite film are polarized in the same direction, their piezoelectric activities partially cancel each other, thereby giving almost zero piezoelectric activity at φc∼0.4. On the other hand, when the phases of a composite film are polarized in opposite directions, their piezoelectric activities reinforce. However, de...

Ceramic hollow fibers made from nanoscale powder particles

Abstract: The invention relates to a method for producing ceramic hollow fibers from nanoscale particles and to hollow fibers produced in such a manner. The inventive method is characterized in that the ceramic material has a solids content of > 25 % by volume, preferably > 30 % by volume and is processed by means of extrusion and spinning. The hollow fiber is sintered according to conventional sintering methods. A hollow fiber produced in this manner is used for metal, polymer and ceramic matrix reinforcements, for artificial organs, for microsystems technology components, for fiber optical waveguides, for ceramic membranes, for solid electrolyte in fuel cells (SOFC), for tissue engineering and for producing extremely light ceramic parts, such as heat shields or brake systems, that are subjected to temperature stresses. The inventive ceramic batch can also be processed by means of silk screening whereby resulting in the production of filigree structures over the ceramic silk screening.

Flexible insulation blanket having a ceramic matrix composite outer layer

Abstract: A flexible insulation blanket having a ceramic matrix composite (CMC) outer layer, and a method of producing a flexible insulation blanket having a smooth, aerodynamically suitable, outer surface by infiltrating ceramic material within the outer ceramic fabric layer of the flexible insulation blanket and curing the ceramic material to form a CMC layer. The CMC layer is cured while the blanket is under compression such that the resulting CMC layer has a smooth surface.

Method of joining ceramic matrix composites and metals

Abstract: A method of joining a ceramic matrix composite rocket nozzle to a metal manifold is provided, wherein a silicon nitride insert is disposed inside the ceramic matrix composite rocket nozzle and the metal manifold to provide a joint therebetween. The silicon nitride insert is preferably co-processed with the ceramic matrix composite rocket nozzle such that the ceramic matrix provides a bond between the rocket nozzle and the insert. The metal manifold is then secured to the silicon nitride insert, preferably using brazing, to form a joint assembly.

Ceramic matrix composite turbine components

Abstract: A method for producing apertures in hot section components of gas turbine engines made from ceramic matrix composites that have at least one oxidizable component. The method involves forming the apertures using a laser beam controlled by parameters that ablate the ceramic matrix composite in the path of the beam, while simultaneously heating the matrix material, SiC or SiN, to a sufficient temperature to oxidize it to form a silica. Sufficient heat is supplied by the beam to melt the silica to cause it to flow. The melted silica is quickly solidified as recast silica along the walls of the newly created aperture before it has an opportunity to flow and form undesirable geometries. The wall of the aperture is formed of recast silica that is a smooth surface and that forms an oxidation barrier to inhibit any further oxidation of the underlying composite as it is exposed to the high temperatures and oxidative, corrosive atmosphere of an operating gas turbine.

Fabrication of silicon carbide whiskers and whisker-containing composite coatings without using a metallic catalyst

Abstract: Silicon carbide has been focused on by many researchers because of its outstanding mechanical and chemical properties. Silicon carbide whiskers are important for the reinforcement of ceramic matrix composites. However, metallic catalysts, which are necessary for the growth of whiskers, can cause degradation of their properties. Thus, we have made silicon carbide whiskers without using the metallic catalyst. Whiskers were obtained with an input gas ratio of above 20, and their diameter decreased as the input gas ratio increased. As the input gas ratio [H2(+N2)/MTS] increases, a transition from whisker growth to film growth occurred at a higher pressure. We also deposited whisker-containing coatings based on the above conditions by alternating the whisker growth and the matrix filling process. The coatings showed pebble-like structures, and their morphologies differed according to the growth condition of the whiskers in the coating layer.

Method for forming a rare earth silicate coating on a silicon based ceramic component by controlled oxidation for improved corrosion resistance

Abstract: A low cost process for self-forming a uniformly adherent protective rare earth silicate coating on a silicon-based ceramic component for protecting the component against corrosive/erosive environments. The coating is self-formed by an oxidation process of a silicon-based ceramic associated with a reaction between a silica (SiO2) film layer on the surface of silicon-based ceramic and the rare earth oxide existing inside of silicon-based ceramic component.

Method for fabricating ceramic matrix composite

Abstract: A method for fabricating a CMC (Ceramic Matrix Composite) article, comprising: performing a CVI (Chemical Vapor Infiltration) treatment for forming a SiC matrix layer on the surface of a woven fabric; performing a machining process, after the CVI treatment, for machining the woven fabric; and performing a PIP (Polymer Impregnation and Pyrolysis) treatment, after the machining process, for impregnating an organic silicon polymer as a base material into voids in the matrix layer and pyrolyzing the organic silicon polymer. By this method, the throughput of CMC articles can be preferably increased. The throughput may be further increased by performing a slurry impregnation treatment before or after the PIP treatment, in which slurried SiC is impregnated into the voids in the matrix layer.

Effect of Matrix Cracks on Damping in Unidirectional and Cross-Ply Ceramic Matrix Composites

Abstract: The paper elucidatesthe methodsof es timating damping in ceramic matrix composites (CMC) with matrix cracks. Unidirectional composites with bridging matrix cracks and cross-ply laminates with tunneling cracks in transverse layers and bridging cracks in longitudinal layers are considered. It is shown that bridging matrix cracksdramatically increase damping in unidirectional CMC due to a dissipation of energy along damaged sections of the fiber-matrix interface (interfacial friction). Such friction is absent in the case of tunneling cracks in transverse layers of cross-ply laminates where the changes in damping due to a degradation of the stiffness remain small. However, damping in cross-ply laminates abruptly increases, if bridging cracks appear in the longitudinal layers.