Chemical-oxidation-resistant elemental

The high heterogeneity with respect to the chemical nature and origin of the BC constituents means that various terms are nonspecifically applied for different fractions. For example, the term BC is used not only for the whole continuum (Masiello, 2004) but also more specifically for the more resistant fractions (Kuhlbusch, 1995 Alexis et al., 2006) the expression charcoal or char can be a synonym for the total burnt materials (Knicker et al., 2006) but can also describe more specifically the burnt material identified by visual assessment (Preston and Schmidt, 2006). The expression elemental carbon (EC) is used in association with the oxidation-resistant fraction in analysis of atmospheric aerosols and soot. The fraction remaining after chemical oxidation has been described as chemical-oxidation-resistant elemental carbon (COREC) (Bird and Grocke, 1997 Rumpel et al., 2006 Knicker et al.,... 

Chemical erosion can be suppressed by doping with substitutional elements such as boron. This is demonstrated in Fig. 14 [47] which shows data for undoped pyrolitic graphite and several grades of boron doped graphite. The mechanism responsible for this suppression may include the reduced chemical activity of the boronized material, as demonstrated by the increased oxidation resistance of B doped carbons [48] or the suppressed diffusion caused by the interstitial trapping at boron sites. 

Shiny silvery metal that is relatively soft in its pure form. Forms a highly resistant oxide coat. Used mainly in alloys, for example, in construction steel. Tiny amounts, in combination with other elements such as chromium, makes steel rustproof and improves its mechanical properties. Highly suited for tools and all types of machine parts. Also applied in airplane turbines. Chemically speaking, the element is of interest for catalysis (for example, removal of nitric oxides from waste gases). Vanadium forms countless beautiful, colored compounds (see Name). Essential for some organisms. Thus, natural oil, which was formed from marine life forms, contains substantial unwanted traces of vanadium that need to be removed. 

Most lubricating oils for engine use contain additives designed to improve such properties as lubricity, detergency, oxidation resistance, and viscosity. The additives contain elements that could be potentially harmful to catalysts. Table I lists these elements and their typical concentration in lubrication oils of 1973. The first three elements are combined usually in one compound, zinc dialkyldithiophosphate. Thus, before combustion, sulfur and phosphorus in oil are in a different chemical state than the same elements are in fuel. Little is known whether combustion nullifies these differences partially or fully. Some data, to be discussed subsequently, are available on the separate poisoning effects of these elements as derived either from the fuel or from the oil. 

The Dynasafe static kiln is a near-spherical, armored, dual-walled high-alloy stainless steel detonation chamber (heated retort) inside a containment structure (Ohlson et al., 2004).18 The total thickness, including a safety layer, is 15 cm. The detonation chamber can operate in a pyrolytic or oxidizing environment. Intact munitions are indirectly heated by electrical resistance elements between the inner and outer walls of the detonation chamber. The munitions are heated to a temperature of 400°C-600°C, resulting in deflagration, detonation, or burning of the munition s explosive till. The chemical agent in the munition is destroyed as a result of the... 

CERAMICS. Tliese are brittle and corrosion resistant compounds made out of metallic and nornnetaUic elements. Some examples of ceramics are A/2O3 (alumina), SiC (silicon carbide), MgO (magnesia), Fe O (magnetite), and ZrO (zirconia). Other ceramics are made of basic ceramics and are known as bricks, clay, concrete, porcelain and the like. On the other hand, refractories are ceramics that withstand very high temperatures prior to melting, such as NhC (niobium carbide) 3615°C and MgO 2852°C In addition, ceramics are immune to corrosion by almost all environments. Those which are not dissolve by chemical oxidation. 

The reason for their extreme resistance can be explained as follows. Ceramics are compounds between metallic and non-metallic elements. Corrosion products are also ceramics. Hence, ceramic may be thought of as having already been corroded [2]. Contrary to the corrosion of metals, corrosion of ceramics, if at all they corrode, involves chemical dissolution. Metals corrode by electrochemical processes. Another form of corrosion is oxidation. Oxidation takes place in an oxidizing environment. In this respect, the oxidation resistance of materials is to be considered. When we consider ceramics for application in an oxidizing environment, the nonoxide ceramics may not be that resistant. Members of the ceramic spectrum of borides, carbides, nitrides, silicides, and so on tend to get oxidized when exposed to an oxidizing atmosphere. Herein, oxide ceramics are the most stable. In general, ceramics are more stable than metals in terms of their oxidation. 

In special cases where the surface hardness must be increased or chemical corrosion resistance is necessary (e.g. plasma etching with chlorine), anodized aluminum surfaces can be useful. Alloying elements, impurities, and heat treatment can influence the nature and quality of the anodized coating - typically, the more pure the aluminum alloy, the better the anodized layer. To build up a thick anodized layer on aluminum, it is necessary for the electrolyte to continuously corrode the oxide, producing a porous oxide layer. ASTM Specification B-580-73 designates seven thicknesses (up to 50 microns) for anodization. 

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