Oxide crystals

Oxides. Although not widespread commercially, glass-ceramics consisting of various oxide crystals in a matrix of siUceous residual glass offer properties not available with mote common siUcate crystals. In particular, glass-ceramics based on spinels and perovskites can be quite refractory and can yield useful optical and electrical properties. 

Calcium carbonate has normal pH and inverse temperature solubilities. Hence, such deposits readily form as pH and water temperature rise. Copper carbonate can form beneath deposit accumulations, producing a friable bluish-white corrosion product (Fig. 4.17). Beneath the carbonate, sparkling, ruby-red cuprous oxide crystals will often be found on copper alloys (Fig. 4.18). The cuprous oxide is friable, as these crystals are small and do not readily cling to one another or other surfaces (Fig. 4.19). If chloride concentrations are high, a white copper chloride corrosion product may be present beneath the cuprous oxide layer. However, experience shows that copper chloride accumulation is usually slight relative to other corrosion product masses in most natural waters. 

Figure 4.18 As in Fig. 4.17 but with carbonate mound removed to reveal sparkling lavender cuprous oxide crystals. 

Figure 4.19 Scanning electron microscope picture of cuprous oxide crystals as shown in Fig. 4.18. Note the partial octahedral symmetry.

Figure 4.25 As in Figs. 4.23 and 4.24. Corrosion product mound broken open to reveal sparkling cuprous oxide crystals.

Internal surfaces of all tubes were severely attacked (Fig. 4.29). A brown deposit layer consisting of magnetite, iron oxide hydroxide, and silica covered all surfaces. Deposition was thicker and more tenacious along the bottom of tubes. These deposits had a distinct greenish-blue cast caused by copper corrosion products beneath the deposit. Underlying corrosion products were ruby-red cuprous oxide crystals (Fig. 4.29). Areas not covered with deposits suffered only superficial attack, but below deposits wastage was severe. 

To a stirred suspension of 10 grams (35 mmol) of 7-chloro-5-phenyl-3H-1,4-benzodiazepin-2(1H) one 4-oxide in approximately 150 ml of methanol was added in portions an excess of a solution of diazomethane in ether. After about one hour, almost complete solution had occurred and the reaction mixture was filtered. The filtrate was concentrated in vacuo to a small volume and diluted with ether and petroleum ether. The reaction product, 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2(1 H)-one 4-oxide, crystallized in colorless prisms. The product was filtered off and recrystallized from acetone, MP 188°-189°C. 

The Fe—O distances in hematite are 1.99 and 2.06 A. The (Mn,Fe)—O distances in bixbyite are expected to be the same in case that (Mn, Fe) has the coordination number 6, and slightly smaller, perhaps 1.90 A, for coordination number 4. The radius of 0= is 1.40 A, and the average O—O distance in oxide crystals has about twice this value. When coordinated polyhedra share edges the O—O distance is decreased to a minimum value of 2.50 A, shown by shared edges in rutile, anatase, brookite, corundum, hydrargillite, mica, chlorite, and other crystals. Our experience with complex ionic crystals leads us to believe that we may... 

Tsai RY, Wang CN, Chan HL (1995) Aluminum oxide crystal microdermabrasion. A new technique for treating facial scarring. Dermatol Surg 21 539-542... 

Zinc hydroxy double salts are layered materials similar to layered double hydroxides which show intercrystalline reactivity and incorporate organic compounds between layers.337 Hydroxy double salts of high crystallinity can be obtained by reacting ZnO with organic metal salts in water. Zinc oxide crystals could then be prepared by thermal treatment of hydroxy zinc acetate.338... 

M. P. Shaw, Dislocations Produced in Magnesium Oxide Crystals Due to Contact Pressures Developed by Softer Cones , Jour. Mater. Sci., 14,2727 (1989). 

Oxidative damage, role of ascorbic acid in preventing, 25 769 Oxidative degradation, 70 682 of gasoline, 72 399-400 Oxidative dehydrogenation, 23 342-343 Oxidative pyrolysis, 27 466 Oxidative stability, of olefin fibers, 77 229 Oxidative stability test, 72 400 Oxide crystal glass-ceramics, 72 641 Oxide-dispersion-strengthened alloys, 77 103-104... 

The Boina emission products show a more or less continuous differentiation trend from transitional basalt to pantellerite. In the nonperalkaline field, the transition from basalt to ferro-basalt is dominated first by olivine F > 0.65) and then by plagioclase F > 0.45), with minor clinopyroxene. A second differentiation step with the appearance of Fe-Ti oxide crystals begins at F = 0.45 Fe and Ti decrease abruptly. Less marked discontinuities are also observed at F = 0.3 (silica-oversaturated trachytes) and F = 0.15 (peralkalinity field). 

Magnesium oxide crystals about 500 A. in diameter were prepared in vacuo by Nicolson 26). Lattice determinations by X-rays showed that the parameter of these small crystals was smaller than that of large crystals. The surface tension obtained from these experiments (- -3,020 dynes/cm.) was 46% of the theoretical value. Similar experiments were carried out with sodium chloride crystals made in vacuo (size about 2000 A), and the agreement between experiment and theory was better, the observed surface tension (- -390 dynes/cm.) being 70% of that calculated. 

The ballistic properties of ADN, HNF, and HNIW as monopropellants and as oxidizers in composite propellants have been extensively studied.P2-351 Since ADN, HNF, and HNIW particles produce excess oxygen among their combustion products, these particles are used as oxidizer crystals in composite propellants. The pressure exponents of crystalline ADN and HNIW particles are both approximately about the same value as those for HMX and RDX when they are burned as pressed pellets. However, the pressure exponent of HNF is 0.85-0.95,135] higher than those of the other energetic crystalline oxidizers. 

Interplanar spacings for the iron oxide crystal systems. 

These sections are mainly concerned with synthetic iron oxides. The morphologies of Fe oxide crystals in rocks, soils and biota are described in Chapters 15, 16 and 17. Table 4.2 provides an overview of the common crystal habits of the various Fe " oxides. 

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