Glass, borosilicate, properties

Glass is composed mainly of silica, Si02, with various oxides added to change the properties. The property differences are substantial, and different amounts of added oxide compounds produce glasses with very different applications derived from these properties. Often the added material is B203 and the products are called borosilicate glasses. From standard... 

Properties Borosilicate glass PNL 76-68 Russian Na-aluminophosphale glass Synroc-C... 

This material also has a porous structure by virtue of its being made by etching a phase-separated borosilicate glass. PS chains have also been introduced into the pores of this type of glass [146], but the only results to date involve mechanical property measurements, and scattering investigations. 

Chemical Properties. The chemical durability is a function of the durability of the crystals and the residual glass. Generally, highly siliceous glass-ceramics with low alkali residual glasses, such as glass-ceramics based on quartz and (3-spodumene, have excellent chemical durability and corrosion resistance similar to that obtained in borosilicate glasses. 

Porcelain enamels are basically alkali borosilicate glasses. These enamels are complex, however, because of the large number and types nf oxides which are needed to develop proper adherence and functional properties. Network-forming ingredients and modifiers arc used as in normal glass... 

One of the most satisfactory metal-to-glass seals involves an Fe-Ni-Co alloy called Kovar. The coefficient of expansion of this alloy is close to that of Pyrex, to which it can be directly bonded however, an even better match in expansion coefficients is obtained with a special borosilicate glass (Corning 7052, Kimble EN-1 or K-650). A variety of tubes is available commercially involving a Kovar tube sealed to a Pyrex tube through one or more intermediate glasses. Die properties of Kovar are discussed in Appendix IV under iron (Section IV.I.E). 

Certain alloys of iron, nickel, and cobalt (Kovar, Fernico, etc.) have thermal expansion curves which nearly match those of borosilicate glasses, and a good bond may be formed between the two. Kovar is similar to carbon steel in its chemical properties. For example, it oxidizes when heated in air and is not wet by mercury. It may be machined, welded, copper brazed, and soft soldered. Silver solders should not be used with Kovar since they may cause embrittlement. At low temperatures Kovar undergoes a phase transformation, and the change in expansion coefficient below this temperature may be sufficient to cause failure of a glass-to-Kovar seal. The transformation temperature usually is below... 

Sodium and borosilicate glasses are generally used, but some low-cost Sirasu brand microspheres have started to be manufactured in Japan using volcanic glass and ashes16 17). The properties of some glass microspheres manufactured in USA are given in Table 1 18). 

Physical properties Fused silica Borosilicate glass Photoetchable special glasses... 

Risen and Wang developed a method and compositions for producing microlenses and optical filters. According to their method, carboxylated silicone or polysilicone precursor composition is applied to the surface of a substrate to form a precursor droplet, which is thermally oxidized to form a microlens. The substrates utilized were silica, silicates, borosilicate glasses, and silicones. The precursors, which are present in concentrated solutions, are viscous fluids which are used to form microdroplet precursors. A solvent such as ethanol or acetone is added to the precursors to modify and control their flow and surface tension properties, to facihtate the formation of spherical shape of the precursor on substrates. The precursor droplet volume is 4-600 picoliters and forms a droplet of 20 to 1000 micrometers in diameter. 

The coefficient of expansion is 0.8 x 10 per °C, which is considerably less than that of borosilicate glasses and very little more than pure silica, so the annealing properties are good. 

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