Some electrons arrive at the surface of melted
silica glass, and they attach to oxygen atoms on the surface because oxygen atoms have a high electron affinity [74].
Ultrasonic vibration of the
silica glass sample, which is actually reciprocation harmonic motion with high frequency and low amplitude, is created by a piezoelectric actuator with the input of sine voltage signal derived from an ultrasonic generator.
Still, the majority of all E' centers result from trapping of holes ([h.sup.+]) at a neutral oxygen vacancies in pure-silica-glass networks otherwise comprising Si[[empty set].sub.4] tetrahedra linked at the corners; (the notation "[empty set]" indicates that in a hypothetically defect-free
silica glass each oxygen, O, forms a bridge between, and is thus shared by, the central Si and one of its four nearest-neighbor silicons).
In the semiconductor industry, this machining technique is frequently used to work silicon, silicon carbide,
silica glass, and glass-ceramic composites such as Zerodur, holding dimensions with surface finish to 0.2[micro]m--0.000008"--or better.
This technology enables room temperature entrapment of organic and bioactive molecules in
silica glass beads.
The team created it by mixing an organosilica precursor (
silica glass, containing organic groups) with a surfactant--essentially, a soap that mixes oil and water--that causes the organosilica to self-assemble into a nanostructure.
Hirose and his colleagues took a mixture of quartz crystals and
silica glass and compressed it between two small diamonds to pressures approaching 3 million times the pressure exerted by the atmosphere at sea level.
As its trace element content is extremely low, use of Aerosil EG50 yields
silica glass that meets the purity requirements of applications in the optics, semiconductor, and information technology industries.
It is necessary to use refractories with a low amount of free Si[O.sub.2] or
silica glass (preferably with a phosphate based bond), which effectively closes the pores to prevent penetration of molten aluminum into the refractory pores.
The "time capsule" is shaped liked a DVD but made out of
silica glass to withstand extreme temperatures and durable enough to last five centuries.
"These aqueous glasses have properties similar to the
silica glass in windows - except that they form at temperatures hundreds of degrees lower.
Figure 1 shows the transmission characteristics of
silica glass, where several windows or spectral regions of lower attenuation are in the vicinity of 810, 1310 and 1550 nm.