Corrosion silicon nitrides

As noted, the oxidation resistance of silicon nitride ceramics depends on the type and concentration of the sintering aids. In materials designed for high temperature appHcations the specific weight gain resulting from oxidation upon a 500-h air exposure at 1200°C and 1350°C is about 1—2 g/m and 2—4 g/m, respectively. The kinetics of the oxidation process have been iavestigated (63,64) as has the corrosion resistance (65). Corrosion resistance is also dependent on material formulation and density. 

As a future alternative to glassed steel there is ceramics-coated steel which is resistant to abrasion, corrosion and high temperatures. The base metal is coated with silicon nitride formed in situ. Silicon nitride has resistance to both acid and alkali and it is durable at temperatures up to 1 000°C, suggesting a promising future coating in aggressive operating environments. 

Silicon nitride (Si3N4) is an excellent electrical insulator, which is increasingly replacing Si02 because it is a more effective diffusion barrier, especially for sodium and water which are maj or sources of corrosion and instability in microelectronic devices. As a result, it can perform... 

Other useful refractory nitrides for corrosion protection are silicon nitride (Si3N4) and boron nitride (BN). Silicon nitride has good corrosion resistance and is not attacked by most molten metals as shown in Table 17.6 (see Ch. 10). 

Materials made of silicon nitride, silicon oxynitride, or sialon-bonded silicon carbide have high thermal shock and corrosion resistance and may be used for pump parts, acid spray nozzles, and in aluminum reduction cells (156—159). A very porous silicon carbide foam has been considered for surface combustion burner plates and filter media. It can also be used as a substrate carrying materials such as boron nitride as planar diffusion source for... 

Silicon-based materials (silicon carbide, silicon nitride) usually form a superficial film of silicon dioxide that protects the material against corrosion in acidic or neutral media. At pH equal to or higher than eleven it suffers corrosion heavily because the silicon dioxide is dissolved [25],... 

NISTCERAM National Institute of Standards and Techology Gas Research Institute, Ceramics Division mechanical, physical, electrical, thermal, corrosive, and oxidation properties for alumina nitride, beryllia, boron nitride, silicon carbide, silicon nitride, and zirconia... 

Ricoult-Barkhausen M, Gogotsi YG (1996) Identification of Oxidation Mechanisms in Silicon Nitride Ceramics by TEM. In Fordham PJ, Baxter DJ, Graziani T (eds) Corrosion of Advanced Ceramics. Key Eng Mat 113. Trans Tech Publications, Switzerland, p 81... 

Ogbuji LUJT (1994) The Oxidation Process in Silicon Nitride. In Nickel KG (ed) Corrosion of Advanced Ceramics - Measurement and Modelling. Kluwer Academic Publishers, Dordrecht, p 117... 

Komeya K, Meguro T, Atago S, Lin CH, Abe Y, Komatsu M (1999) Corrosion Resistance of Silicon Nitride Ceramics. In Niihara K, Sekino T, Yasuda E, Sasa T (eds) The Science of Engineering Ceramics II. Key Eng Mat 161-163, Trans Tech Publications, Switzerland, p 235... 

Kanbara K, Uchida N, Uematsu K, Kurita T, Yoshimoto K, Suzuki Y (1993) Corrosion of Silicon Nitride Ceramics by Nitric Acid. In Chen IW, Becher PF, Mitomo M, Petzow G, Yen TS (eds) Silicon Nitride Ceramics, Mat Res Soc Symp Proc 287. Mat Res Soc, Pittsburgh, p 533... 

Figure 14. Corrosion behavior of reduction reactor materials samples ( 7), Inconel 625 (O), silicon (Q), silicon nitride (%), alonized Inconel 62 (M silicon carbide and ( f), Inconel 657. Furnace temperature, 482°C S03, 25 see/min steam, 58 see/min argon, 78 see/min.

Hot gas corrosion behavior of various silicon-based non-oxide ceramic materials (e.g., silicon carbide, silicon nitride, etc.) can vary widely depending on the stoichiometry, structure and sintering aids. Silicon carbide materials exhibit excellent corrosion resistance towards sulfur-containing atmospheres even at a high temperature around 1,400X [Fdrthmann and Naoumidis, 1990]. 

Mixed oxide, Al203-Si02, bond phases are generally the next most corrosion resistant to acids including low quantities of HF. Silicon nitride and silicon oxynitride bonded silicon carbides perform similarly to mixed oxide bonds. Table 19-2 shows typical weight loss and retained strength values for these products in contact with common acidic solutions for the times and temperatures shown. ... 

Silicon carbide, widely employed as an abrasive (carborundum), is finding increasing use as a refractory. It has a better thermal conductivity at high temperatures than any other ceramic and is very resistant to abrasion and corrosion especially when bonded with silicon nitride. Hot-pressed, self-bonded SiC may be suitable as a container for the fuel elements in high-temperature gas-cooled reactors and also for the structural parts of the reactors. Boron carbide, which is even harder than silicon carbide, is now readily available commercially because of its value as a radiation shield, and is being increasingly used as an abrasive. 

Silicon nitride (Si3N4) has received considerable research and development interest because it has high mechanical properties, electronic properties, low density and corrosive resistance at high temperatures. It can be widely used in structural and functional applications. The CVD process is an effective technique to manufacture silicon nitride materials with ultra-high-purity and unique properties. 

Silicon nitride (see Nitrides) is a key material for structural ceramic applications in environments of high mechanical and thermal stress such as in vehicular propulsion engines. Properties which make this material uniquely suitable are high mechanical strength at room and elevated temperatures, good oxidation and creep resistance at high temperatures, high thermal shock resistance, excellent abrasion and corrosion resistance, low density, and, consequendy, alow moment of inertia. Additionally, silicon nitride is made from abundant raw materials. 

Ion-Selective Field Effect Transistors. Ion-selective field effect transistors (ISFETs) are semiconductor devices related to the solid-state detectors used in spectroscopy (discussed in Chapter 5). In this case, the surface of the transistor is covered with silicon nitride, which adsorbs H ions from the sample solution. The degree of adsorption is a function of the pH of the sample solution and the adsorption of H" " ions results in a change in the conductivity of the ISEET channel. The cell requires an external reference electrode. ISEET pH sensors can be made extremely small (about 2 mm ) and are extremely rugged, unlike the fragile glass bulb pH electrode. They have rapid response times and can operate in corrosive samples, slurries, and even wet solids such as food products. The sensor can be scrubbed clean with a toothbrush, stored in a dry condition, and does not require hydrating... 

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