Slurry Infiltrated Fiber Reinforced

A special type of this material is called SIFCA slurry infiltrated fiber-reinforced castable. This is a composite material of ceramic matrix with calcium aluminate cement and with aggregate made of aluminum oxide, mullite, zircon and calcined fireclay. The matrix is reinforced with stainless-steel fibres. SIFCA is used to made pre-cast elements for refractory structures, where temperature can rise up to 1100°C. Heat curing is often used during the pre-casting. Another kind of similar material is called SIMCON slurry infiltrated mat concrete in which arrays of single fibres are replaced by a system of steel mats for better and easier distribution of reinforcement (Murakami and Zeng 1998). 

The teehnique used for slurry infiltration is the same as that used for glass (Section 15.3.2.2) and to improve the densification, it is normal to adopt a multiple slurry impregnation process. The technique is most effective for glass ceramics, although recent attention has concentrated on SiC reinforcement. A limitation when coating continuous fiber is that the impregnated and dried tow has an excess of matrix particles, which persists after densification. 

Three dimensional carbon fiber reinforced SiC and SisN4 composites were fabricated using repeated infiltration of organosilicon slurry under vacuum and pressure by Nakano et al [192]. The open porosity of the infiltrated body was reduced from 40% after the first infiltration to approximately 8% after the seventh cycle. Further porosity reduction to less than 3% was achieved by hot press densification. The maximum values of flexural strength and fracture toughness were 260 MPa and 7.3 MPam for C-Si3N4 composites, and 185 MPa and 6 MPam for C-SiC composite. 

In the fabrication process of three dimensional carbon fiber reinforced SiC matrix composite, Suzuki and Nakano [207] applied PCVI as the final densification process for the specimen, which was made by the joint process of slurry infiltration and organosilicon polymer pyrolysis. The open porosity and bulk density of the specimen changed from 5.3% and 2.63 g-cm (relative density of 94%) to 3.5% and 2.67 g cm (relative density of 95%) by the apphcation of PCVI (1173 1223K, total 90,000 pulses). The flexural strength of the specimen increased over 20% (mean value =153 MPa, maximum value = 174 MPa). 

Carbon fiber reinforced Si.Al.O.N composite materials were prepared by Dodds et al [219] using slurry infiltration of continuous carbon fiber tows, winding, filter pressing and uniaxial hot pressing using a graphite die in air. 

Ceramic fibers can be coated with ceramic slurries and hot-pressed to make dense fiber reinforced ceramic- or glass-matrix composites, Alternatively, continuous ceramic fibers can be combined with other fibers, whiskers, or powders and formed into porous shapes used for insulation (e.g., space-shuttle tiles) or subsequently infiltrated by CVD techniques to form fiber reinforced ceramic matrix composites without hot-pressing. For example, Nextel-SiC composites made by infiltration are being considered for applications such as heat exchangers and radiant gas burner tubes [210]. 

The PIP method includes the slurry infiltration of fiber preforms by means of resin transfer molding (RTM) with suitable precursors such as polycarbosUane (PCS) or pol-yvinylsilane (PVS) followed by subsequent crosslinking to thermosets (resulting in fiber-reinforced polymers). The polymer composite is then pyrolyzed at temperatures below 1400°C in inert atmospheres to yield a CMC (Fig. 12.9(c)). 

The material system that was examined was Hi-Nicalon fiber-reinforced, slurry cast, melt infiltrated SiC/BN/SiC in a balanced 5 harness satin 0°/90° architectine. Coupons were provided by Rolls-Royce Corporation. A mean thickness of 3.39 mm (0.06 std. deviation) led to a mean 0.14 fiber volume ratio in the longitudinal direction. 

J. MagnanL R. Pailler, Y. Le Petitcorps, L. Mailld, A. Guette, J. Marthe, and E. Philippe, Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering, J. Eurt. Ceram. Soc., 33, 181-190... 

The strength and tensile behavior, at room and high temperatures, as well as the structure of three dimensional earbon fiber/SiC composites, fabricated by the slurry pulse/CVI combined process, were eharacterized by Suzuki et al [207-209]. Carbon fiber preforms, constructed with 4-step braid, 4-step/axial braid, 2-step braid and orthogonal weave, were used as reinforcements of the composites. The composites were fabrieated by a process consisting of slurry and dissolved organosilicon polymer infiltrations, followed by the application of pulse CVI. 

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