Amorphous Carbon definition

The major results described could be partially anticipated from those previously reported for linear polyethylene (17) as well as those for cis polyisoprene. (] ) For the latter polymer, by taking advantage of its crystallization kinetic characteristics, it was possible to compare the relaxation parameters of the completely amorphous and partially crystalline polymer (31% crystallinity) at the same temperature, 0°C. This is a unique situation and allows for some unequivocal comparisons. It was definitively observed that for all the carbons of cis polyisoprene the T] s did not change with crystallization. 

When prepared by chemical methods, y-sulphur is frequently accompanied by an apparently amorphous powder which is readily soluble in carbon disulphide. This has been regarded, by some investigators, as a definite form of sulphur and given the name soluble amorphous sulphur 2 in reality, however, it consists of minute spheroidal crystals of rhombic sulphur possibly together with nacreous sulphur.3 Another so-called modification of amorphous sulphur, described 4 as soluble in carbon disulphide but becoming insoluble on evaporation of the solvent, is probably no distinct form, but only a mixture of y-sulphur with finely divided crystalline sulphur. 

Other forms of amorphous sulphur, which have been described at various tunes in chemical literature, are the so-called blue sulphur and black sulphur our present state of knowledge of these is far from satisfactory, and their existence as definite modifications of pure sulphur is questionable, especially in the case of the latter variety, the colour of which appears to be due to small quantities of carbon or of metallic sulphides.1... 

Layer or layers of minerals (especially calcium carbonate) deposited, by the throwing down, or precipitation, onto a heat-transfer surface, reducing its U value. Scales are often hard and dense and difficult to remove. The scale can be crystalline in nature (a solid body having a characteristic internal structure, with symmetrically arranged plane surfaces and definite angles), or amorphous (lacking any characteristic crystalline shape). 

In the first case, within the conglomerates of martensite and carbon at a temperature below 1000°, there may be formed a definite compound, which separates from the mass amorphous, it forms a cement between the crystals of martensite or of graphite this compoimd, whose formula is FeaC, is cemeniite. 

Phenylgermanic acid anhydride, (CgHsGeOjaO.—Equimolecular proportions of mercury diphenyl and germanium tetrachloride in dry xylene are heated in a sealed Pyrex bulb for two days, then diluted with dry ether and filtered. The solid residue is pure phenylmercuric chloride, and the filtrate is treated with benzene, and finally with water containing a few drops of ammonium hydroxide. The granular precipitate which separates at the liquid interface is removed and dried at 115° C. The anhydride is a white, fluffy, amorphous solid, with no definite melting-point, soluble in excess of alkali, and reprecipitated by carbon dioxide, insoluble in water and organic solvents. 

Our English word silica has a very broad connotation it includes silicon dioxide in all its crystalline, amorphous, soluble, or chemically combined forms in which the silicon atom is surrounded by four or six oxygen atoms. This definitely excludes all the organosilicon compounds made by man in which carbon atoms have been linked directly to silicon atoms—commonly referred to as silicones , which do not occur in nature. Silica is soluble enough in water to play important roles in many forms of life. It forms the skeletons of diatoms, the earliest form of life that absorbed sunlight and began to release oxygen into the atmosphere. Many plants use silica to stiffen stems and form needles on the surface for protection. 

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