Ceramic matrix composite growth

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

Both TiN and TiC are widely used in ceramic matrix composites for improving electrical conductivity and mechanical properties [178,184,185]. The formation of a rutile scale was observed on the surfaces. The growth of such a scale should be related to the diffusion of titanium to the surface of the composite and its oxidation according to the reaction ... 

Transportation equipment wiU also post healthy gains, with growth resulting from an acceleration in the production of both aerospace and motor vehicle equipment, as well as through the increased use of ceramics in catalytic converter substrates, engine bearings, ceramic armor for military vehicles, diesel engine particulate filters, and ceramic matrix composite brakes. 

The fastest growth area for ceramic matrix composites wiU also be in engine parts, while cutting tool and wear part applications wiU lag in their overall growth. In... 

Market research conducted by the Freedonia group (Freedonia Custom Research, 2006) indicates a US advanced ceramics demand of more than US 12 bilhon in 2010, of which 87% will be for monoUthic ceramics, 9% for ceramic coatings, and 4% for ceramic matrix composites (CMCs). The Freedonia group study estimated the worldwide demand for automotive electronics to be US 117 biUion in 2009, showing a growth rate of 7% annually-much more rapid than that for vehicle production itself. The greatest success, however, was proposed to relate to ceramic armor, with the structural ceramics market being expected to double in size, from US 650 million in 2004 to US 1.3 billion in 2009, as the demand for ceramic armor continued. 

Fatigue can also occur in ceramic matrix composites. If a crack propagates under tensile loading, it will be bridged by the fibres and partially unloaded (see section 9.3.3). This can cause stable crack growth under static loading, with the crack not propagating further unless the load is raised (see... 

Ceramic-matrix fiber composites, 26 775 Ceramics mechanical properties, 5 613-638 cyclic fatigue, 5 633-634 elastic behavior, 5 613-615 fracture analysis, 5 634-635 fracture toughness, 5 619-623 hardness, 5 626-628 impact and erosion, 5 630 plasticity, 5 623-626 strength, 5 615-619 subcritical crack growth, 5 628—630 thermal stress and thermal shock, 5 632-633... 

Since the significant majority of the published literature on high temperature crack growth under static and cyclic loads is predicated upon experiments conducted on alumina and alumina matrix composites, the examples cited in the present review have centered around oxide ceramics and their composites. However, the implications of the results to other classes of ceramics, intermetallics, and brittle matrix composites are also described, wherever feasible, along with any available information in an attempt to illustrate the generality of the concepts developed here. 

Chemical vapor infiltration (CVI) is a CVD variant capable of internally coating porous objects, e.g., an object made out of carbon fibers, with a ceramic material. Silicon carbide (SiC) or boron carbide (B4C) are examples of ceramic matrix materials that are used in combination with carbon fibers. Strong, light, durable, wear-resistant, and biocompatible joint prostheses made of ceramic-ceramic composites are manufactured by means of CVI. Figure 6.18 shows how the degree of penetration is affected by temperature and pressure. Clearly, to get deposit deep in the interior of the porous object low temperatures are necessary for reaction limitation and low pressures for helping the diffusion. Under these conditions growth rates are low. 

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