Glasses chemical properties

The glass-ceramic phase assemblage, ie, the types of crystals and the proportion of crystals to glass, is responsible for many of the physical and chemical properties, such as thermal and electrical characteristics, chemical durabiUty, elastic modulus, and hardness. In many cases these properties are additive for example, a phase assemblage comprising high and low expansion crystals has a bulk thermal expansion proportional to the amounts of each of these crystals. 

Chemical Properties. Stoichiometric vitreous sihca contains two atoms of oxygen for every one of sihcon, but it is extremely doubtful if such a material really exists. In general, small amounts of impurities derived from the starting materials are present and various stmctural defects can be introduced, depending on the forming conditions. Water is incorporated into the glass stmcture as hydroxyls. 

The physical and chemical properties of silicate glasses depend on the composition of the material, ion size, and cation coordination number (9). A melt or glass having a Si02/Na20 ratio of 1, ie, sodium metasiUcate [1344-09-8] is expected to possess a high proportion of (SiO ) chains. At a ratio of 2, sheets might predominate. However, litde direct evidence has been shown for a clear predominance of any of these stmctures. The potential stmctures of sihcate melts of different ratios are discussed in detail elsewhere (10—12). 

Because of their unique combination of physical and chemical properties, manufactured carbons and graphites are widely used in several forms in high temperature processing of metals, ceramics, glass, and fused quartz. A variety of commercial grades is available with properties tailored to best meet the needs of particular appHcations (45). Industrial carbons and graphites are available in a broad range of shapes and sizes. 

The things that we have been talking about so far - metal crystals, amorphous metals, solid solutions, and solid compounds - are all phases. A phase is a region of material that has uniform physical and chemical properties. Water is a phase - any one drop of water is the same as the next. Ice is another phase - one splinter of ice is the same as any other. But the mixture of ice and water in your glass at dinner is not a single phase because its properties vary as you move from water to ice. Ice + water is a two-phase mixture. 

Physical and Chemical Properties - Physical State at 15 XI and 1 atm. Liquid Molecular Weight 192.26 Boiling Point at 1 atm. Not pertinent (decomposes) 523, 273, 546 Freezing Point (sets to glass) -49, -45, 228 Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.022 at 20 °C(liquid) Vapor (Gas) Density Notpertinent Ratio cf eciflc Heats of Vapor (Gas) Not pertinent Latent Heat of Vaporization Data not available Heat of Combustion (est.) -13,700, -7,6610, -318 Heat of Decomposition Not pertinent. 

Silicon shows a rich variety of chemical properties and it lies at the heart of much modern technology/ Indeed, it ranges from such bulk commodities as concrete, clays and ceramics, through more chemically modified systems such as soluble silicates, glasses and glazes to the recent industries based on silicone polymers and solid-state electronics devices. The refined technology of ultrapure silicon itself is perhaps the most elegant example of the close relation between chemistry and solid-state physics and has led to numerous developments such as the transistor, printed circuits and microelectronics (p. 332). 

One of the most commonly used measures of durability, i.e. the loss of sodium from the glass, is important to the pharmaceutical and chemical industries, but other changes such as loss of surface quality, are of equal importance for optical and window glasses. The properties of a wide range of technical glasses are well catalogued but the data are often inadequate when considering a particular application and where possible nonstandard whole article tests are advisable. 

The highest mechanical strengths are usually obtained when the fibre is used in fine fabric form but for many purposes the fibres may be used in mat form, particularly glass fibre. The chemical properties of the laminates are largely determined by the nature of the polymer but capillary attraction along the fibre-resin interface can occur when some of these interfaces are exposed at a laminate surface. In such circumstances the resistance of both reinforcement and matrix must be considered when assessing the suitability of a laminate for use in chemical plant. Glass fibres are most commonly used for chemical plant, in conjunction with phenolic resins, and the latter with furane, epoxide and, sometimes, polyester resins. 

This difference in spatial characteristics has a profound effect upon the polymer s physical and chemical properties. In thermoplastic polymers, application of heat causes a change from a solid or glassy (amorphous) state to a flowable liquid. In thermosetting polymers, the change of state occurs from a rigid solid to a soft, rubbery composition. The glass transition temperature, Tg, ... 

PHYSICAL AND CHEMICAL PROPERTIES OF GLASS Thermal Capacity... 

Graeral Chemical Properties of Glass Metbtance to Chemical Actions... 

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