Ceramic matrix composite

About: Ceramic matrix composite is a research topic. Over the lifetime, 7807 publications have been published within this topic receiving 117020 citations.

Low‐Temperature Processing of Ceramic Woven Fabric/Ceramic Matrix Composites

Abstract: Two-dimensional Al{sub 2}O{sub 3} and SiC woven laminate composites, and oxide and nonoxide monolithic ceramics with 5 to 10 wt% of polycarbosilane binder, were consolidated up to 75% of TD (theoretical density) at 1150 C by the multiple impregnations of a polycarbosilane solution. The processing conditions were optimized without causing fiber damage. The near-net-shape composite fabricated by this process showed high reproducibility in terms of relative density and flexural strength. The mechanical properties were characterized by flexural testing with strain gauges. All of the woven laminate composites exhibited good composite-type fracture behavior, e.g., load-carrying capacity following maximum load. The room-temperature flexural strength and first-matrix cracking stress of SiC fabric/SiC composite with 73% TD were about 300 77 MPa, respectively.

Chemical reactivities of hafnium and its derived boride, carbide and nitride compounds at relatively mild temperature

Abstract: MB 2 /SiC composites are materials of choice for ultra-high-temperature structural applications, primarily in the aerospace arena. These composites are processed in a hot-press operation at a temperature range of 1900 to 2200°C. This article assesses potential mild-temperature (below 1500°C) chemical reactions that may lead to structures and coatings made of HfB 2 /SiC under pressureless or mild-pressure conditions. The reactions are anticipated to be involved in reactive and shape-forming processes, where ceramic precursors and/or reactive powders are incorporated. This article pays special attention to exothermic reactions as well as to formers of a liquid phase; both can aid the desired phase formation, microstructure development, and sintering of the composite under milder conditions than currently practiced. Reactions between loosely mixed powders with melting points significantly above 1500°C were detected by X-ray diffraction (XRD) analyses. Significant solid-phase reactions of the loose powder mixtures were observed at this mild temperature in powder form. Preliminary microstructural studies using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray Spectroscopy (EDX) techniques have confirmed the presence of unique reaction mechanisms between the loosely connected particles. Good examples are the reactions between Hf powder and powders of BN or B 4 C, all having melting points above 2200°C, which form at 1500°C, or below HfB 2 /HfN and HfB 2 /HfC crystalline domains, respectively. These reactions are less intuitive than the reaction with B 2 O 3 , which forms HfB 2 /HfO 2 , potentially via molten or gaseous phases of boron oxide.

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...