Silicon carbide particles

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. 

A wide range of applications for hard, wear-resistant coatings of electroless nickel containing silicon carbide particles have been discussed by Weissenberger . The solution is basically for nickel-phosphorus coatings, but contains an addition of 5-15 g/1 silicon carbide. Hiibner and Ostermann have published a comparison between electroless nickel-silicon carbide, electrodeposited nickel-silicon carbide, and hard chromium engineering coatings. 

In the silicon carbide manufacturing process the major bioactive dusts identified are quartz particles and silicon carbide fibers generated in the process. In contrast to the silicon carbide fibers, silicon carbide particles were... 

Figure 12.15 Measured infrared extinction by silicon carbide particles (dashed curve) compared with calculations for spheres and a continuous distribution of ellipsoids (CDE).

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. 

Figure 8. Weight % unreacted silica in silicon carbide particles as a function of silicon carbide volume.

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... 

Figure 1. Cross-section of an electroless nickel-phosphorous coating on aluminium 6063-T6 with incorporated silicon carbide particles.

An experiment with a dilute ceramic suspension was made as follows A very small quantity of silicon carbide particles (d 6 /xm) was dissolved in silicon oil ( 350mPas). The suspension was pumped at high pressure through a glass capillary (d = 0.6 mm). The experimental setup is shown in Fig. 3. The velocities of the silicon carbide particles in the capillary are detected by an optical sensor. From these data, the statistics of the particles velocities is calculated. Due to the optical properties of the sensor, the particles are only detected in a wedge-like sector of the cross-section of the capillary. The measured velocity distribution of the particles (Fig. 4) depends on the shape of this sector and, additionally, on the measuring tolerances of the sensor. 

In the case of the alloyed carbon, microcrystalline silicon carbide particles are randomly interspersed in the carbon matrix. The presence of this SiC phase greatly contributes to the hardness and wear resistance of these alloys compared to pure pyrolytic carbon. 

Phosphoric acid fuel cell (PAFC) was the first fuel cell to be commercialized. PAFC uses liquid phosphoric acid as an electrolyte, which is soaked in silicon carbide particle matrix using capillary action. PAFC is tolerant to CO2 feed stream because the electrolyte is an acid. However, carbon monoxide poisons the Pt electrodes so that its concentration should be below 3-5 volume % in the feed stocks. 

Medout-Marere, V., Partyka, S., Dutartre, R., et al. (2003). Surface heterogeneity of passively oxidized silicon carbide particles vapor adsorption isotherms. J. Colloid Interface Sci., 262, 309-20. 

A trickle-bed reactor 2.5 cm in diameter and 60 cm long was used by Baker to study sulfur and nitrogen removal from a heavy oil [37]. The catalyst in the form of 1.5-mm x 4.5-mm extrudates was diluted with an equal volume of 1.0-mm silicon carbide particles. Characteristics of the oil are given in Table 8.1. Test results are given in Table 8.2. 

Twaron SRM uses silicone carbide particles as a protective coating deposited onto a special matrix composition that coats the Twaron aramid fabric substrate (Fig. 7.16). The major function of the carbide particles is to dull the blades and make the blade... 

Examples of stab resistant body armour are often quite different in constractional character. For example, some comprise a matrix of overlapping metal or composite plates located between fabric layers (based on para-aramid or UHMW polyethylene), others are based on more flexible aramid woven textiles which have been coated with silicon carbide particles to blunt the knife point and others incorporate fine tungsten wire within a knitted fabric matrix. Copying the ancient chain mail concept, similar fine mail constructed from stainless steel or titanium wire may be included as a layer. Obviously the overall weight and thickness of the resulting armour is of crucial importance for the comfort of the wearer but this will be determined largely by the magnitude of the threat. 

Other abrasive materials include silicon carbide particles, diamond particles, and ceramic particles. 

Fig. 9.34 Transmission electron micrographs of microstructures of the nanocomposite tested at 1300 °C and 50 MPa in tension, showing examples of rotating and plunging of intergranular silicon carbide particles and associated cavity formation. The stress direction is indicated by arrows [23], With kind permission of John Wiley and Sons...

Silicon carbide particles in SiC/Al MMCs have Uttle effect on passive currents. In a chloride-free, sodium tetraborate-boric acid solution of pH 8.4, the passive current of a SiCV6061 Al MMC was only slightly greater tluin that of monoUthic 6061 aluminum [55]. In deaerated 0.1 N NaCl, the passive current densities (at potentials less than Epu) of 20 % S1CV2024 Al and 20 % SiCw/6061 Al MMCs were actually shghdy less than that of their monolithic matrix alloys. The passive current densities were on the order of 10 A/cm [50]. 

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]... 

When the flame bums the sample with silicone carbone the tight fire resistant chark appears, it protects the sample from burning itself. The plastic form of silicone carbide particles generates the barrier layer that also protects sample from the flame. 

L. Carroll, M. Sternitzke, and B. Derby, Silicon Carbide Particle Size Effects in Alumina Based Nanocomposites, Acta mater., 44, 4543 4552 (1996). 

Song et al. (2002) suggested using a mixture of fine and coarse silicon carbide particles to improve electrolyte and gas management in the matrix. Similar results can be obtained with a combination of silicon carbide and zirconium silicate particles (Neergat and Shukla, 2001). 

A second generation of EN plating has been developed by codepositing micrometer-sized particles of silicon carbide with the nickel, thereby creating an extremely wear- and corrosion-resistant coating. In this composite coating, the nickel alloy matrix provides corrosion resistance while the silicon carbide particles add wear resistance. 

Many composites, such as PMCs reinforced with carbon and aramid fibers, and silicon carbide particle-reinforced aluminum, have low CTEs, which are advantageous in applications requiring dimensional stability. Examples include spacecraft structures, instrument structures, and optical benches. By appropriate selection of reinforcements and matrix materials, it is possible to produce composites with near-zero CTEs. 

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