Aluminum oxide resistivity

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific apphcations (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumna) Carbon, activated carbon Ion exchange Molecular sieves and Silicon compounds, synthetic inorganic silicates). 

Galvalume has been shown to have two to six times the life of an equivalent thickness of 2inc, including marine atmospheres. Eor high temperature oxidation resistance up to 700°C, Galvalume is equivalent to pure aluminum. 

There is also a two-step process of chromizing foUowed by aluminizing. Above 900°C the chromizing begins to rediffuse and the protective oxide changes to Al O from Cr202. Aluminum oxide is less volatile than chromium oxide and better for high temperature oxidation resistance above 1000°C. 

Other alloys have been developed for use in particular corrosive environments at high temperatures. Several of these are age-hardenable alloys which contain additions of aluminum and titanium. Eor example, INCONEL alloys 718 and X-750 [11145-80-5] (UNS N07750) have higher strength and better creep and stress mpture properties than alloy 600 and maintain the same good corrosion and oxidation resistance. AHoy 718 exhibits excellent stress mpture properties up to 705°C as well as good oxidation resistance up to 980°C and is widely used in gas turbines and other aerospace appHcations, and for pumps, nuclear reactor parts, and tooling. 

Next to Cr C2, TiC is the principal component for heat and oxidation-resistant cemented carbides. TiC-based boats, containing aluminum nitride, AIN, boron nitride, BN, and titanium boride, TiB2, have been found satisfactory for the evaporation of metals (see Boron compounds, refractory boron compounds Nitrides). 

Extremely high softening resistance is available in alloy C15720 through dispersion strengthening by aluminum oxide. This alloy has been used successhiUy as a welding rod material and in other specific appHcations that can bear its cost. 

Rigid Porous Media These are available in sheets or plates and tubes. Materials used include sintered stainless steel and other metals, graphite, aluminum oxide, silica, porcelain, and some plastics—a gamut that allows a wide range of chemical and temperature resistance. Most applications are for clarification. 

Aluminum coatings on steel will perform in a manner similar to zinc coatings. Aluminum has good resistance to many atmospheres in addition, being anodic to steel, it will galvanically protect exposed areas. Aluminum-coated steel products are quite serviceable under high-temperature conditions, for which gooa oxidation resistance is required. 

Zinc diffusion is used for protection against atmospheric corrosion. Aluminum diffusion is used to improve the oxidation resistance of low-carbon steels. 

Aluminum has a low density it is a strong metal and an excellent electrical conductor. Although it is strongly reducing and therefore easily oxidized, aluminum is resistant to corrosion because its surface is passivated in air by a stable oxide film. The thickness of the oxide layer can be increased by making aluminum the anode of an electrolytic cell the result is called anodized aluminum. Dyes may be added to the dilute sulfuric acid electrolyte used in the anodizing process to produce surface layers with different colors. 

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