Silicon carbide metal matrix composites

An., Continuous Silicon Carbide Metal Matrix Composites, Technical Brochure, Textron Specialty Materials, Lowell, MA... 

Cerium oxide Conversion coatings, cerium oxide coatings on aluminium alloys and aluminium/silicon carbide metal matrix composites [13,14]... 

M. Eslamian, J. Rak, and N. Ashgriz. Preparation of aluminum/silicon carbide metal matrix composites using centrifugal atomization. Powder Technology, 184(l) ll-20, 2008. 

Nunez-Lopez, C. A., Habazaki, H., Skeldon, P., Thompson, G. E., Karimzadeh, H., Lyon, P., and Wilks, T. E., An Investigation of Microgalvanic Corrosion Using a Model Magne-siiun-Silicon Carbide Metal Matrix Composite, Corrosion Science, Vol. 38, No. 10, 1996, pp. 1721-1729. 

Developments in metal-matrix composites technology has resulted in aluminum matrix materials filled with siUcon carbide [409-21 -2] SiC, (see Carbides, silicon carbide) particles (15 to 60 vol %) that provide the possibihty of weight reduction for brakes (20). These composite materials are being tested and evaluated. 

Meial Mairix Composites. Silicon carbide particles are contributing to easy-to-cast metal-matrix composites (MMCs). When compared with their non-reinforced counterparts, the SiCp/Al components are more wear resistant, stiffer, and stronger, accompanied by improved thermal stability. Additional advantages include lower density and lower cost. Nearly all prior aluminum MMCs required labor-intensive methods, such as powder metallurgy, diffusion bonding, squeeze casting, or thermal spraying. 

Metals and ceramics (claylike materials) are also used as matrices in advanced composites. In most cases, metal matrix composites consist of aluminum, magnesium, copper, or titanium alloys of these metals or intermetallic compounds, such as TiAl and NiAl. The reinforcement is usually a ceramic material such as boron carbide (B4C), silicon carbide (SiC), aluminum oxide (A1203), aluminum nitride (AlN), or boron nitride (BN). Metals have also been used as reinforcements in metal matrices. For example, the physical characteristics of some types of steel have been improved by the addition of aluminum fibers. The reinforcement is usually added in the form of particles, whiskers, plates, or fibers. 

In electrochemical composite plating inert particles are deliberately added to the plating bath to obtain metal matrix composite coatings. Figure 1 shows an example of metal matrix composite coating of electroless nickel-phosphorous in which silicon carbide particles are incorporated. The particle materials used should be inert to the bath in the... 

The bulk analysis of /3-SiC whiskers shows the least variation in chemistry. In some whiskers, the residual metals content can vary, most likely, as a result of additives that used as catalysts during synthesis. These include iron, cobalt, and chromium. Studies by Karasek et al. [56] have shown that the physical properties of silicon carbide whisker-reinforced composites do not correlate to the bulk properties of the whiskers significantly. This lack of significant correlation is mainly due to the fact that the important phase chemistry of the whisker-matrix interface is controlled by the matrix chemistry and the surface chemistry of the whiskers. There seems to be little impact of the diffusion of materials into or out of the bulk whisker material. 

Recent advances further enhance their commercial potential in metal matrix composites such as aluminum, nickel, and copper ceramic matrix composites, such as alumina, zirconia and silicon nitride and glass ceramic matrix composites such as lithium aluminosilicate. Silicon carbide whiskers increase strength, reduce crack propagation, and add structural reliability in ceramic matrix composites. Structural applications include cutting tool inserts, wear parts, and heat engine parts. They increase strength and stiffness of a metal, and support the design of metal matrix composites with thinner cross sections than those of the metal parts they replace, but with equal properties in applications such as turbine blades, boilers and reactors. 

Continuous sapphire fibers (Chapter 4) and continuous sheath/core bicomponent silicon carbide/carbon fibers (Chapter 3) offer impressive performance as reinforcing fibers and in ceramic and metal matrix composites. Here are some noteworthy commonalties and differences. 

Metal matrix composites (MMCs) are metals that are reinforced with fibers or particles that usually are stiff, strong, and lightweight. The fibers and particles can be metal (e.g., tungsten), nonmetal (e.g., carbon or boron), or ceramic (e.g., silicon carbide (SiC) or (alumina) AljOj). The purpose for reinforcing metals with fibers or particles is to create composites that have properties more useful than that of the individual constituents. For example, fibers and particles are used in MMCs to increase stiffness [/], strength [f ], and thermal conductivity [2], and to reduce weight [f], thermal expansion [3], fiiction [4], and wear [5]. 

Nunes, P. C. R. and Ramanathan, L. V., Corrosion Behavior of Alumina-Aluminum and Silicon Carbide-Aluminum Metal-Matrix Composites, Corrosion, Vol. 51, No. 8,1995, pp. 610-617. 

Buarzaiga, M. M. and Thorpe, S. J., Corrosion Behavior of As-Cast, Silicon Carbide Particulate-Aluminum Alloy Metal-Matrix Composites, Corrosion, Vol. 50, No. 3, 1994, pp. 176-185. 

Kiourtsidis, G. E. and Skolianos, S. M., "Stress Corrosion [724] Behavior of Aluminum Alloy 2024/Silicon Carbide Particles (SiCp) Metal Matrix Composites, Corrosion, Vol. 56, No. 6, [725]... 

Short-fibre reinforced metal matrix composites are significantly less expensive than long-fibre reinforced materials and can thus be used in automotive engineering or in sports equipment. For example, short-fibre reinforced aluminium-silicon carbide composites can be used as pistons in diesel engines at elevated temperatures [49]. Golf clubs and bicycle components can also be manufactured from aluminium matrix composites. Frequently, whiskers (see section 6.2.8) are used as short fibres because of their high strength and favourable aspect ratio. 

Monticelli, C. Zucchi, F. Brunoro, G. Trabanelli, G. (1997). Stress corrosion cracking behaviour of some aluminium-based metal matrix composites. Corrosion Science, Vol. 39, No. 10-11, pp. 1949-1963, ISSN 0010938X Muhamed Ashraf, P. Shibli, S. M. A. (2007). Reinforcing aluminium with cerium oxide A new and effective technique to prevent corrosion in marine environments. Electrochemistry Communications, Vol. 9, No. 3, pp. 443-448, ISSN 13882481 Niino, M. Maeda, S. (1990). Recent Development Status of Fxmctionally Gradient Materials. ISIJ International, Vol. 30, No. 9, pp. 699-703, ISSN 09151559 Nunes, P. C. R. Ramanathan, L. V. (1995). Corrosion behavior of alumina-aluminium and silicon carbide-aluminium metal-matiix composites. Corrosion, Vol. 51, No. 8, pp. 610-617, ISSN 00109312... 

Ceramic fibers. The other fibers shown in Table 4.6 have varying uses, and several are still in development. Silicon carbide continuous fiber is produced in a chemical vapor deposition (CVD) process similar to that for boron, and it has many mechanical properties identical to those of boron. The other fibers show promise in metal matrix composites, as high-temperature polymeric ablative reinforcements, in ceramic-ceramic composites, and in microwave transparent structures (radomes or microwave printed wiring boards). 

Composites are usually classified by the type of material used for the matrix. The four primary categories of composites are polymer matrix composites (PMCs), metal matrix composites (MMCs), ceramic matrix composites (CMCs), and carbon matrix composites (CAMCs). The last category, CAMCs, includes carbon/carbon composites (CCCs), which consist of carbon matrices reinforced with carbon fibers. For decades, CCCs were the only significant type of CAMC. However, there are now other types of composites utilizing a carbon matrix. Notable among these is silicon carbide fiber-reinforced carbon, which is being used in military aircraft gas turbine engine components. 

As noted above, the range of fibers employed does not precisely overlap with those employed for organic composites. Because the formation of the MMCs generally requires melting of the metal-matrix, the fibers need to have some stability to relatively high temperatures. Such fibers include graphite, silicon carbide, boron, alumina-silica, and alumina fibers. Most of these are available as continuous and discontinuous fibers. It also includes a number of thin metal wires made from tungsten, titanium, molybdenum, and beryllium. 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

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