Silica, Vitreous

Abstract

Vitreous silica is a single‐component glass commercially available in a wide range of purities. It is used in a wide variety of applications, from “low tech” tubing and container applications to “high tech” applications, such as lens elements in microlithography steppers and optical waveguides. It has superior chemical resistance, low thermal expansion, and excellent optical transmission from the vacuum ultraviolet (uv) to the near‐infrared (ir). Thermal history and trace contamination can have significant effects on a number of properties, ranging from electrical conductivity to absorption characteristics. Vitreous silica is the material of choice for a variety of commercial and scientific applications, including tubing and containers for chemical processing, uv‐optical elements, envelope material of mercury vapor lamps, and windows for space vehicles. Vitreous silica’s high viscosity, even at its melting point, precludes the use of traditional glass‐forming techniques. Manufacture usually involves specialized methods, such as flame hydrolysis or high temperature sintering in helium or vacuum.

Polylactic Acid and Polylactic Acid-Based Nanocomposite Photooxidation

“…The haze is reduced when particles are small and refractive indices are similar. Indeed, despite the presence of similar micrometric aggregates, this effect is not observed with SiO 2 , owing to the refractive index (≈1.46) very similar to that of PLA (≈1.45), whereas refractive index of sepiolite is higher (≈1.50)…”

“…In PLACl20A these two bands are more evident and at the same time it is possible to recognize the ν as CH 2 and ν s CH 2 of the organic modifier, respectively, at 2922 and 2853 cm −1 . In the case of PLASEP, the main difference is a structured band of the inorganic part with a maximum at 983 and 469 cm −1 , respectively, to Si−O−Si stretching and bending. , Finally, PLASiO 2 present a large band at about 472 cm −1 Si−O−Si bending …”