Silicon Oxide Quartz

Furthermore, if the quartz is dry - that is, if it contains little or no dissolved H2O or other water-related spedes (H, OH , etc.) - then any deformation is difficult even under hydrostatic-confining pressures. For example, under a confining pressure of 1.5 GPa, Griggs and Black 83,84] found the CRSS for basal slip of dry quartz to be 2.2 GPa at 300 °C and 1.6 GPa at 700 °C, which is about 5% of the shear modulus of 40 G Pa. This intrinsic resistance to plastic deformation of quartz remains high to at least 1300 °C ( 0.8 T ), where the CRSS is still in excess of 0.5 GPa [12,85). Where deformation has been induced under hydrostatic onfining pressures, various slip planes - (0001), 1010, 1120, lOll, Oil - and dislocations with various Burgers vectors-1/3 (1120), [0001], and 1/3 (1123)-have often been found. These Burgers vectors correspond to the three shortest lattice translations in quartz, namely 0.491, 0.541, and 0.730 nm, respectively. 

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Silicon oxide, cristobalite, high (SIO2) Silicon oxide, cristobalite, low (Si02) Silicon oxide, quartz (Si02)... 

Occurrence. Silicon is the second most abundant element in the earth s crust, after oxygen (about 28% by weight). It occurs mainly in oxides (quartz, agate, opal, etc.) and a great variety of silicate minerals (feldspar, clay, mica, olivine, etc.). 

Silica Silicon oxide (Si02(s)), which can occur in crystalline form, e.g., quartz, or noncrystaUine form, e.g., opal. 

The value of this standard potential is slightly modified depending on the solid oxide structure and reaches —0.857 V for the quartz structure. In most acidic or neutral solutions, this silicon oxide forms a protecting layer. However, when the solution pH is increased, the oxide will give rise to various sparingly soluble compounds due to the following dissociahon reactions ... 

Production. Silicon is typically produced in a three-electrode, a-c submerged electric arc furnace by the carbothermic reduction of silicon dioxide (quartz) with carbonaceous reducing agents. The reductants consist of a mixture of coal (qv), charcoal, petroleum coke, and wood chips. Petroleum coke, if used, accounts for less than 10% of the total carbon requirements. Low ash bituminous coal, having a fixed carbon content of 55—70% and ash content of <4%, provides a majority of the required carbon. Typical carbon contribution is 65%. Charcoal, as a reductant, is highly reactive and varies in fixed carbon from 70—92%. Wood chips are added to the reductant mix to increase the raw material mix porosity, which improves the SiO (g) to solid carbon reaction. Silica is added to the furnace in the form of quartz, quartzite, or gravel. The key quartz requirements are friability and thermal stability. Depending on the desired silicon quality, the total oxide impurities in quartz may vary from 0.5—1%. 

Fig. 1 Quartz minerals consisting of covalently linked silicon-oxide tetrahedra that are corner-connected and twisted in a helical fashion around three- and six-fold screw axes, rendering individual quartz crystals chiral...

Figure 12.4 Fluorescence emission from biomolecules on ZnO NRs versus various control substrates after performing the identical biotreatment processes. (A) No fluorescence signal is detected on control substrates including glass, quartz, silicon oxide, silicon nanorods (SiNRs), and polymeric surfaces. On the other hand, strong fluorescence signal is observed from individual and striped ZnO NR platforms regardless of the spectroscopic properties fluorophores. (B) Normalized fluorescence intensity observed from biomolecules on various substrates. (C) Fluorescence...

S. Yamazaki and K. Tsutsumi, Synthesis of an A-type zeolite membrane on silicon oxide film-silicon, quartz plate and quartz fiber filter, Microporous Materials 4 205 (1995). 

Most igneous and metamorphic rocks are composed predominantiy of aluminosilicate minerals, including feldspar such as albite (NaAlSi Og) or anorthite (CaAl2Si20g) and crystaUine forms of silica such as quartz (Si02). Various mixed metal-plus-silicon oxides such as oHvine [(Mg,Fe)2(SiO ] and... 

Dissolution of silicon oxides is geographically important since silica is one of the most abundant minerals in the Earth s crust. At least nine different Si02 phases are found in natural and engineered earth systems in the form of quartz, cristobalite,... 

The nature of the silica-water interface is determined by adsorption/desorption of the species in the water. When a silicon oxide, e.g., quartz, is fractured, the initial surface is composed of dangling silicon and oxygen bonds (Fig. 4.30a) which are not stable and hydroxylate easily with available waterThe hydroxylated surface is dominated by SiOH groups (Fig. 4.30b). The initial adsorbed water adjacent to the surface is oriented and has properties different from the bulk water. As this adsorbed water layer increases to more than three monolayers, its properties become more like bulk water. The surface potential changes as a result of the adsorption of the ionic species in the water. °... 

The many etch rate equations described above are empirical in nature even though mechanistic arguments are made in each specific case. One important omission in these quantitative formulations on the etching kinetics is the lack of consideration of the effect of the structure of silicon oxides. As shown in Fig. 4.40, etch rate can vary over more than three orders of magnitude for different types of oxides. It increases with increasing disorder of the oxide structure with the most ordered oxide, that is, quartz, having the lowest etch rate. The structural disorder of the silicon oxide can be due to impurities, partial oxidation of the silicon atoms, and degree of crystallinity. 

Layered aluminosilicates include the micas and clay minerals they share the characteristic of having alternating layers of a gibbsite-like aluminol sheet and a silicon oxide (silanol) sheet, but differ in the stacking of these sheets, the presence of additional cations in various structural locations, and the amount of structural water and hydroxyl groups. By virtue of analogy with amorphous silica and quartz, the silanol sheets are not... 

Figure 4.23. The results of a qualitative analysis of a multiple phase sample. Three crystalline phases are clearly identifiable lithium silicate - Li2Si03, silicon oxide - SiOj (quartz), and a different pol)imorph of silicon oxide - tridymite. A low quality diffraction pattern collected during a fast experiment was employed in this example. The data shown on top were smoothed, the background was subtracted, and the Ktt2 components were stripped before the digitized pattern (shown below the smoothed profile) was obtained using an automatic peak search. Note, that many weak Bragg reflections were missed in the peak search,...

By far the most widespread of these oxygen compounds is silicon oxide, or silica (SiOa), which we know in such various forms as sand, sandstone, quartz, flint, agate, and opal. 

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