Amorphous rapid cooling

Electron diffraction studies indicate that phosphoms pentoxide vapor consists of P O q molecules. The vapor usually condenses to the hexagonal crystalline modification but under rapid cooling can be condensed to an amorphous soHd (P-form). The Hquid obtained by melting the stable orthorhombic modification cools to form a glass which is the P-form. The Hquid obtained from the H modification also can be supercooled to a glass. 

Supercooling The rapid cooling of a normally crystalline plastic through its crystallization temperature, so it does not get a chance to crystallize and it remains in the amorphous state. 

The crystallinity in PET soft drink bottles is about 25%. Because a more crystalline state is normal for PET, the amorphous content is increased intentionally by copolymerization and rapid cooling for the molten PET from the melt to a temperature below the glass transition temperature. Companies which perform high-speed blow molding of PET prefer PET resins made with small amounts of glycol and diacid comonomers. 

Because of the conversion of orthorhombic sulfur to monoclinic form, the above values of melting points are difficult to observe, as the resulting allotropic mixture melts at only 115 C. Amorphous or plastic sulfur can be produced through the rapid cooling of molten sulfur. X-ray crystallographic studies show that the amorphous form may have a helical structure with eight atoms per turn. This form is metastable at room temperature and gradually reverts back to crystalline within hours to days but this conversion can be rapidly catalyzed. 

Amorphous polymers with irregular bulky groups are seldom crystallizable, and unless special techniques are used even ordered polymers are seldom 100% crystalline. The combination of amorphous and crystalline structures varies with the structure of the polymer and the precise conditions that have been imposed on the material. For instance, rapid cooling often decreases the amount of crystallinity because there is not sufficient time to allow the long chains to organize themselves into more ordered structures. The reason linear ordered polymers fail to be almost totally crystalline is largely kinetic, resulting from an inability of... 

Silicon forms two oxides, silica or the dioxide, Si02, and a divalent monoxide, SiO. The latter is obtained by heating silica with elementary silicon at 1,450°C in vacuum. Silicon sublimes as its monoxide, which on rapid cooling forms light brown amorphous SiO ... 

PBTP crystallises considerably more rapidly than PETP. In an injection moulding process, where short cycle times are required, and thus rapid crystallisation during the rapid cooling in the mould, PBTP may, therefore, be preferred. PETP would stay amorphous, and, therefore, not usable above its Tg (69 °C). 

Cooling solutions to below their freezing point results in the formation of ice. If solutions of sugars are cooled rapidly, non-equilibrium ice formation occurs. This is the most common form of ice in frozen dairy products (e.g. ice-cream). Rapid freezing of ice-cream mixes results in the freeze concentration of lactose and other sugars, resulting in supersaturated solutions if the temperature is too low to permit crystallization. The rapid cooling of lactose results in the formation of a supersaturated, freeze-concentrated amorphous matrix. 

Entrapment in amorphous (glassy) matrices achieved by rapid cooling or by drying. 

By rapidly cooling the fluid mixture it is possible to minimise the readjustment of the equilibrium and to attain a solid condition in which tire original proportions of the mixture are approximately retained in the solid state tire allotropic change is so very slow as to allow careful and fairly prolonged examination of the mixture. It is then found that, the normal mobile liquid constituent (S ) has given rise to crystalline sulphur, soluble in carbon disulphide, whereas the dark-coloured viscous constituent (S ) has produced an amorphous solid, insoluble in this solvent4 (see also p. 10). A rough analysis of molten sulphur in... 

New approaches to the synthesis of SVO cathode material have been reported. In 1995, Takeuchi and Thiebolt patented a new preparation for SVO cathodes prepared via addition of elemental silver to vanadium compounds present in an anhydrous mixture. Oxygen-deficient SVO compounds were found, as well as compounds designed to provide a desired shape in the electrical discharge curve of the cell [59], Following this work in 1996, Takeuchi and Thiebolt patented several methods for the preparation of amorphous SVO prepared by chemical addition reaction at temperatures high enough to melt the mixture, coupled with rapid cooling... 

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