Sapphire oxide

Diamond behaves somewhat differently in that n is low in air, about 0.1. It is dependent, however, on which crystal face is involved, and rises severalfold in vacuum (after heating) [1,2,25]. The behavior of sapphire is similar [24]. Diamond surfaces, incidentally, can have an oxide layer. Naturally occurring ones may be hydrophilic or hydrophobic, depending on whether they are found in formations exposed to air and water. The relation between surface wettability and friction seems not to have been studied. 

Aluminium oxide occurs naturally as emery (an impure form) and as corundum. Corundum is a crystalline form which may be coloured by traces of impurity, for example as ruby (red) and sapphire (blue). Small synthetic rubies and sapphires have been made by heating alumina with the colouring oxide in an oxy-hydrogen flame. 

The compounds of greatest importance are aluminum oxide, the sulfate, and the soluble sulfate with potassium (alum). The oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glassmaking and refractories. Synthetic ruby and sapphire are used in lasers for producing coherent light. 

AI2O3 (aluminium oxide) in ruby laser, 346 in titanium-sapphire laser, 348 3142 (cyclic) interstellar, 120 3142 (linear) interstellar, 120... 

Thermal—Oxidative-Resistance Coatings. The thermal stabihty of coatings produced by either covalendy or noncovalendy incorporating 2,4-dinitroaniline into an inorganic siUcate network and coating it onto a sapphire substrate has been examined (67). Although some increase in the thermal... 

Aluminum compounds, particularly the hydroxides and oxides are very versatile. Properties range from a hardness iadicative of sapphire and comndum to a softness similar to that of talc [14807-96-6] and from iuertness to marked reactivity. Aluminas that flow and filter like sand may be used for chromatography (qv) others are viscous, thick, unfilterable, and even thixotropic (1). 

Aluminum oxide. Al3+ ions are present in corundum Heft), ruby (top right), and sapphire (bottom right). The anion in each case is 02-. 

As a contradistinction to the relatively simple case of AI2O3 Cr(III) where the color is due to a metal-centred electronic transition, we mention now on one hand the fact that the Cr(III) ion colors many transition-metal oxides brown (e.g. rutile Ti02 or the perovskite SrTi03 [15]), and on the other hand the fact that the color of blue sapphire (AI2O3 Fe, Ti [16]) is not simply due to a metal-centred transition. By way of illustration Fig. 1 shows the diffuse reflection spectrum of SrTiOj and SrTi03 Cr(III) [17], and Fig. 2 the absorption spectrum of Al203 Ti(III) and Al203 Ti(III), Fe(III) [18]. It has been shown that these colors are due to MMCT transitions and cannot simply be described by metal-centred transitions [19],... 

In order to develop more informative and direct method of studying the spillover effect of active particles, the authors of [37] suggested to use the sensor method of detecting migrating particles based on separation of sensor and emitter (donor) of active particles. The latter consists of small metal globules, or clusters (with a diameter of about 20-30 A) of Pt, Pd, Ni, etc. (activator) deposited on quartz or sapphire (AI2O3) plate in the form of a strip less than 1 cm wide. The sensor for detection of hydrogen atoms consisted of a zinc oxide strip (with a width of about 0.1 cm and thickness wlOO nm) deposited on the same plate at a distance of 0.03 or 0.6 cm (two versions) from the inner boundaries of activator strips [38]. 

A colorless mineral known as corundum (composed of aluminum oxide) is colorless. A red variety of corundum known as ruby, a precious stone, owes its color to impurities of chromium within the crystal structure of corundum. Blue and violet varieties of corundum are classified as sapphires, the blue being the result of iron and titanium impurities, and the violet of vanadium impurities within the corundum crystal structure. Another colorless mineral is beryl (composed of beryllium aluminum silicate) but blue aquamarine, green emerald, and pink morganite, are precious varieties of beryl including different impurities aquamarine includes iron, emerald chromium and vanadium, and morganite manganese. 

Ruby and Sapphire. Ruby and sapphire are "sister stones" both are gemstone forms of the mineral corundum (composed of aluminum oxide). Pure corundum is colorless, but a variety of trace elements cause corundum to exhibit different colors. Ruby is red corundum, while sapphire is corundum in all colors except red. The red in rubies is caused by trace amounts of chromium the more intense the red color of a ruby, the more chromium it contains. The blue in sapphires is caused by titanium and/or iron impurities (Garland 2002 Hughes 1997). 

Sapphires are naturally occurring gem stones, and are transparent to translucent. We know from ancient records that they have always been highly prized. Natural sapphires are found in many igneous rocks, especially syenites and pegmatites. Alternatively, synthetic sapphires may be made by doping aluminium oxide AI2O3 with a chro-mophore. 

Aluminum oxide is used to make synthetic rubies and sapphires for lasers beams. It has many pharmaceutical uses, including ointments, toothpaste, deodorants, and shaving creams. 

Chlorine trifluoride dioxide resembles chlorine fluorides and oxy-fluorides in its corrosive and oxjidizing properties. It must be handled in systems consisting of corrosion-resistant metals, Teflon, or sapphire. It appears to be marginally stabli in a well-passivated system at ambient temperature, It is a strong oxidative fluorinator as evidenced by its... 

---