Water in Glasses and Melts

Virtually all oxide glasses contain chemically bonded water in the form of various types of hydroxyl (Si-OH, Ge-OH, etc.), while other protonic species, including silanes (Si-H, Ge-H, etc.), or molecular hydrogen, may or may not be present. Since the effect of water on the optical and physical behavior of glasses is so important, discussion of these species merits a separate chapter. A detailed discussion of the formation of bound hydrogen species, their effect on the optical spectra and physical properties of glasses, and the diffusion and solubility of water in glasses and melts is found in Chapter 11. 

Kumar et al used spectroscopic techniques such as NMR to study the properties and structures of mixed glass systems. Rosenhahn et al. obtained insight into the structure and dynamics of the binary As-Se glass system from high temperature Se NMR studies of molten salts. Ab initio molecular orbital calculations have been carried out for sihcate, aluminosilicate and aluminate clusters to study the NMR characteristics of various types of hydroxyl that are possibly present in hydrous silicate glasses and melts. Xue and Kanzaki in particular studied the specification and dynamics of dissolved water in the silicate glasses. 

Water absorption of the resultant cured materials was measured after immersion for 24 hrs at room temperature and reported as % weight gain. The modulus was measured according to ASTM D 2240, and the dielectric constant and dissipation factor were measured using a method similar to ASTM D 150. Glass and melting transitions were measured by differential scanning calorimetry (DSC). The thermal stability was determined in a forced air oven... 

Boron occurs in nature as part of oxygenated compounds, or borates, that have been known since ancient times for their use in glass and metal production. In 1808 Joseph-Lotiis Gay-Lussac and Louis Jacques Thenard of France and Humphry Davy of England discovered the element boron almost concurrently. Another century passed before boron was successfully isolated in pure form. Elemental boron in its amorphous form is a dark brown powder it is a yellowish-brown, hard, brittle solid in its monoclinic crystalline form. It melts at 2,300°C (4,172°E). Boron is unreactive to oxygen, water, acids, and alkalis. Boron compotmds burn yellow-green during the flame test. 

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