PHYSICAL AND CHEMICAL PROPERTIES OF GLASS

PHYSICAL AND CHEMICAL PROPERTIES OF GLASS Thermal Capacity... 

Shelby, J. E. Introduction to Glass Science and Technology. Cambridge, England Royal Society of Chemistry, 2005. A college-level textbook with detailed information on the physical and chemical properties of glass. 

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). 

It seems that sometime during the third millennium b.c.e., somewhere in the Middle East, it was discovered that when a mixture of silica sand and soda is heated to relatively high temperatures, the mixture fuses to form glass. Few other human-made materials are derived, as is glass, from such common and abundant raw materials. Its remarkable physical and chemical properties made glass, already in antiquity, one of the most useful and ubiquitous materials in many areas of the world. 

The physical and chemical properties of MgO films prepared by the sol-gel technique were the area interest of the examinations presented by Shukla75. The aim of mentioned work was to produce films with nano size particles so as to employ them for the sensor applications, as adsorption in such films increases many folds due to the increase of surface area. Infra-red spectroscopic studies indicated the presence of solvent in the precursor, which helped in decomposition to nano-particles during nucleation of the film. The MgO sol-gel films were deposited on the glass rod bend in U-shape for humidity sensor. 

The dye NKX-2311, shown in Fig. 1, was kindly given by Hayashibara Biochemical Laboratories. The physical and chemical properties of the dye have already been reported [9], The ZnO and Ti02 films were prepared on a glass or sapphire substrate by a similar procedure reported elsewhere [10], The dye was loaded by just immersing the bare ZnO and T1O2 films into dye solution to make dye-sensitized films, abbreviated as NKX-2311/ZnO and NKX-2311/Ti02, respectively. 

The name fine ceramics is based on the grain size distribution of the hard components in the ceramic mass. This rather differs from the distribution as it is seen in the ceramic branch of industry which produces for instance bricks, the coarse ceramic industry. Another difference is that all fine ceramic products are provided with a protective and in some cases also decorative coating, a so-called glaze. In this section much attention will be paid to glazes because this technique is rather unique for fine ceramics and because it offers the possibility to explore the subject glass and some important physical and chemical properties of materials. 

The rubbery character and particular physical and chemical properties of polyisobutene stem from its paraffinic origins. Its outstanding properties are its low glass transition temperature, very low water vapor permeability and resistance to many chemicals. At room temperature polyisobutene is resistant to dilute and concentrated mineral acids and bases, as well as hydrogen peroxide. 

The physical and chemical properties of both the solidified adhesive and the plastic substrate affect the quality of the bonded joint. Major elements of concern are the thermal expansion coefficient, modulus, and glass transition temperature of the substrate relative to the adhesive. Special consideration is also required of polymeric surfaces that can change during normal aging or on exposure to operating environments. 

One of the most important bulk property variables of polymers is the glass transition temperature 7g, which must be well below the use temperature to allow the interdiffusion and entanglement of polymer chains when the particles get in contact, once the aqueous phase has been evaporated. Thus, the monomer(s) used have to be selected such that the desired is obtained. Useful tables showing Tg and other physical and chemical properties of homopolymers are available in the literature [66-68]. The well-known Fox equation [69] can be used to estimate the Tg of a copolymer as a function of monomer composition and TgS of the component monomers. It is important to take into account that polar polymers tend to hydroplasticize, reducing the in the film formation process [70]. Several commercial latexes are terpolymers that contain two of the monomers present in major amounts to grossly obtain the basic desired properties, with the third monomer present in a minor amount for fine tuning of a special property [71-73]. 

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