Adventitious carbon general

Adventitious Carbon in General. Having briefly described the ESCA characteristics of graphitic materials and hydrocarbon polymers, we must now see if we can use these features to provide a careful (and hopefully useful) chemical description of AC. 

EA, NM, ET, WK, and IL), all but ET are relatively high either in carbon (>1%) or iron (>10%), or both. Whether this pattern of results is chemically significant or merely adventitious cannot be stated definitely at this time. In contrast, those ashes on which all PAHs exhibit photoreactivity (TX and AR) are low both in carbon and iron. ET is the only ash which deviates from this general trend. 

Acid-catalysed addition of primary, secondary, and tertiary alcohols to 3,4-dihy-dro-2//-pyran in dichloromethane at room temperature is the only general method currently in use for preparing THP ethers and the variations cited below concern the choice of acid. The reaction proceeds by protonation of the enol ether carbon to generate a highly electrophilic oxonium ion which is then attacked by the alcohol. Yields are generally good. Favoured acid catalysts include p-toluenesulfonic acid or camphorsulfonic acid. To protect tertiary allylic alcohols and sensitive functional groups such as epoxides, the milder acid pyridinium p-toluenesulfonate has been employed (Scheme 4.316]. A variety of other acid catalysts have been used such as phosphorus oxychloride, iodotrimethylsilane- and bis(trimethylsilyl)sulfate. but one cannot help but suspect that in all of these cases, the real catalyst is a proton derived from reaction of the putative catalysts with adventitious water. Scheme 4.317 illustrates the use of bis(trimethylsilyl)sulfate in circumstances where other traditional methods failed. - For the protection of tertiary benzylic alcohols, a transition metal catalyst, [Ru(MeCN)2(triphos)](OTf)2 (0.05 mol%) in dichloromethane at room temperature is effective. ... 

In contrast, carbon fibres are inert under normal service temperatures they are usually considered insensitive to moisture and only little affected by alkaline environments. Therefore, apparent degradations of carbon fibre-reinforced composite are in general exclusively due to the interaction between the matrix and the environment. Besides, it is of note that galvanic corrosion may occur if CFRP composites are adventitiously placed in contact with metal elements, which usually contributes to accelerated corrosion of the metal components (Tavakkolizadeh and Saadatmanesh, 2001). 

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