Amorphous ordinary

Insoluble Sulfur. In natural mbber compounds, insoluble sulfur is used for adhesion to brass-coated wire, a necessary component in steel-belted radial tires. The adhesion of mbber to the brass-plated steel cord during vulcanization improves with high sulfur levels ( 3.5%). Ordinary rhombic sulfur blooms at this dose level. Crystals of sulfur on the surface to be bonded destroy building tack and lead to premature failure of the tire. Rubber mixtures containing insoluble sulfur must be kept cool (<100°C) or the amorphous polymeric form converts to rhombic crystals. 

The solution in equihbrium with amorphous sihca at ordinary temperatures contains monomeric monosilicic acid, Si(OH)4. The acid is dibasic, dissociating in two steps (36) ... 

Elemental arsenic normally exists in the a-crystaUine metallic form which is steel-gray in appearance and britde in nature, and in the P-form, a dark-gray amorphous soHd. Other aHotropic forms, ie, yellow, pale reddish-brown to dark brown, have been reported (1), but the evidence supporting some of these aHotropes is meager. MetaUic arsenic, heated under ordinary conditions, does not exhibit a discrete melting point but sublimes. Molten arsenic can be obtained by heating under pressure. 

The extension of an amorphous material under a tensile force can be resolved into three parts first, an immediate elastic extension. Which is immediately recoverable on removing the tensile force Mcondly, a delayed elastic extension which is recoverable slowly and thirdly, a plastic extension, viscous flow, or creep, which cannot be glteovered. With glass at ordinary temperatures, this plastic exten- ion is practically absent. A very slow delayed elastic extension OOCUrs. This effect can be troublesome in work with torsion fibres. The delayed elastic effect in vitreous silica fibres is 100 times less than in other glass fibres, and viscous flow of silica is negligible below OO C (N. J. Tighe, 1956). For exact work vitreous sihea torsion flbres are therefore used. 

In ordinary solids such as crystalline or amorphous glassy materials, an externally applied force changes the distance between neighboring atoms, resulting in interatomic or intermolecular forces. In these materials, the distance between two atoms should only be altered by no more than a fraction of an angstrom if the deformation is to be recoverable. At higher deformations, the atoms slide past each other, and either flow takes place or the material fractures. The response of rubbers on the other hand is almost entirely intramolecular [4,5]. 

From this point of view a one-stage process of simultaneous GIC exfoliation, impregnation of EG by amorphous carbon precursor and its subsequent carbonization would be very attractive. But up to now this simple one-stage process could not be realized because of high exfoliation temperature of the ordinary GICs needed (900 - 1200°C), which leads to almost complete burnout of AC precursor at the atmospheric air conditions. 

Polymerisation.—The simple aldehydes polymerise very easily. Anhydrous formaldehyde, indeed, cannot be kept for long, but changes very rapidly into an amorphous solid of high molecular weight (CH20)n, paraformaldehyde. At ordinary temperature this substance breaks down again slowly to the simple molecule, a change which takes place... 

At a given (low) temperature and pressure a crystalline phase of some substance is thermodynamically stable vis a vis the corresponding amorphous solid. Furthermore, because of its inherent metastability, the properties of the amorphous solid depend, to some extent, on the method by which it is prepared. Just as in the cases of other substances, H20(as) is prepared by deposition of vapor on a cold substrate. In general, the temperature of the substrate must be far below the ordinary freezing point and below any possible amorphous crystal transition point. In addition, conditions for deposition must be such that the heat of condensation is removed rapidly enough that local crystallization of the deposited material is prevented. Under practical conditions this means that, since the thermal conductivity of an amorphous solid is small at low temperature, the rate of deposition must be small. 

The oxide exhibits two crystalline modifications, the reddish or orange-red alpha form, known as litharge, and the yellow beta form, massicot. The alpha form constitutes tetragonal crystals while the beta modification is a yellow amorphous powder of orthorhombic crystal structure. The alpha form is stable at ordinary temperatures, converting to the beta form when heated at 489°C density 9.35 g/cm (beta form) Moh s hardness 2 (alpha form) the oxide melts at 888°C vaporizes at 1,472°C with decomposition vapor pressure 1 torr at 943° C and 5 torr at 1,039°C practically insoluble in water (the solubdity of alpha form is 17 mg/L at 20°C and that of beta form 23 mg/L at 22°C) insoluble in ethanol soluble in dilute nitric acid and aUtahes. 

Black sulfide is a black amorphous powder or crystalline substance (beta form) cubic structure metastable at ordinary temperatures converts to red sulfide by sublimation at ordinary pressure density 7.73 g/cm melts at 583.5°C insoluble in water, alcohol and nitric acid soluble in aqua regia, alkalies, and solutions of alkali metal sulfides. 

At ordinary temperatures, the metal surface is coated with a very fine thin amorphous film of its dioxide, about 2 to 3 nm thick. Silicon combines with oxygen forming innumerable silicates. A few silicates have been mentioned above. 

Because of the kinetic energy present in the molecule, amorphous flexible polymer chains are usually in constant motion at ordinary temperatures. The extent of this wiggling-like segmental motion decreases as the temperature is lowered in this reversible process. The temperature at which this segmental or micro-Brownian motion of amorphous polymers becomes significant as the temperature is increased is called the glass transition temperature, Te The term free volume is used to describe the total vplume occupied by the holes. 

Tetrammino-uranyl Nitrate, [UO2(NH3)4](NO3)a. (C2H10O), may be obtained from the diammino-uranyl ether compound by the action of liquid ammonia. It is a deep orange-red amorphous powder, which is stable below 5° C., but decomposes rapidly at ordinary temperature, yielding the triammino-derivative.2... 

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