Alumina coatings

2 Ludox CL from Dupont (Commercial Alumina-Coated Silica) Properties Alumina silica mass ratio 4 26 [1799]. The potential (0.001 M KCl, 20°C, Malvem Zetasizer II c) was positive at pH 3-8 and negative outside that range. [1799]. 

3 From EKA Nobel Al-modihed silicas with 1-16% surface silicon atoms substituted by aluminum. Washed by ultrafiltration using salt solutions. 

1 Alumina on Ludox Silica Acidified AKNO,), solution and an equivalent amount of NaOH solution were added to a dispersion of Ludox silica. The procedure was repeated several times. 

Properties BET specific surface area 103 in /g (less than original Ludox) [1192]. 

PZC/IEP of Alumina-Coated Ludox Silica Electrolyte T Method Instrument pH Reference 

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ALUMDIUMCOMPOUNDS - ALUMINIUMOXIDE(ALUMINA) - HYDRATED] (Vol 2) Alumina-coated silica sols... 

Other coatings, such as TiAlN (96), TiCN, Zr02, and ZrN (97), and CrN (98) were developed for special appHcations. The last was developed for higher speed machining of titanium alloys. Sometimes a coating is developed not for its wear-resistance but for its heat insulation. The case in point is alumina coating of cBN to reduce the heat conductivity at the surface so that the cBN performance can be enhanced (99). 

The seemingly simple question of the relation the characteristics of a mechanically prepared metal surface and adhesion to that surface has sporadically occupied attention for many decades without any very general conclusion being reached [69]. In some recent work, Amada et al. [70,71] grit-blasted a steel substrate, varying the angle between the gun and the specimen surface, and measured the adhesion of a plasma-sprayed alumina coating. They examined profiles of the... 

CASE STUDY INORGANIC ZIRCONIA y-ALUMINA-COATED MEMBRANE ON CERAMIC SUPPORT... 

Fig. 16.25. Mixture of zirconia and alumina coated on the ceramic membrane.

Figure 16.23 presents the alumina-coated ceramic membrane. There were opportunities to fabricate a crack-free ceramic membrane coated with y-alumina. The supported zirconia-alumina membrane on the ceramic support shows an irregular surface. The non-uniform surface of ceramic support causes the irregular surface on the top layer of the membrane. Some of the membrane sol was trapped in the porous ceramic support during coating, and caused the irregularity of the membrane surface. 

Olefination Reactions Involving Phosphonate Anions. An important complement to the Wittig reaction involves the reaction of phosphonate carbanions with carbonyl compounds 253 The alkylphosphonic acid esters are made by the reaction of an alkyl halide, preferably primary, with a phosphite ester. Phosphonate carbanions are generated by treating alkylphosphonate esters with a base such as sodium hydride, n-butyllithium, or sodium ethoxide. Alumina coated with KF or KOH has also found use as the base.254... 

Tridehydro[18]annulene here and in the sequel refers to the symmetrical isomer shown in the formula, admixed with smaller quantities of an unsymmetrical isomer and tetradehydro[18]annulene.6 These can be separated by chromatography on alumina coated with 20% silver nitrate, but this is unnecessary for the synthesis of [18]annulene sinceallthree substances give this annulene on catalytic hydrogenation.8... 

In fact, it is extremely important to eliminate as completely as possible the solvent imbedded into the thin layer of coated adsorbent. It is achieved conveniently first by air-drying the TLC plates for a duration of 30 minutes and then in a hot-air oven maintained at 110 °C for another 30 minutes and subsequently cooling them in a dessicator. This drying process helps a great extent in rendering the adsorbent layer active. In order to achieve very active layers, silica gel and alumina coated plates may be heated upto 150 °C for a duration of 4 hours and colling them in a dessicator. 

Thin-layer chromatography (TLC) is often used as a faster alternative to paper chromatography. Instead of paper, a thin layer of silica gel or alumina coated onto glass, metal or plastic is used. The water held on the silica gel or alumina is the stationary phase. The mobile phase is a suitable solvent or a mixture of solvents. The solvent flows through the stationary phase and carries the components of the mixture with it. Different components in the mixture travel across the stationary phase at different rates. 

Recently, this method has been modified by application of a milder base (KF/AI2O3, alumina, coated with potassium fluoride) (04SC1425). N,N-Diethylpropin-l-amine 79 can be substituted for nitriles 27, so N,N-disubstituted pyrans 131 can be obtained (73JHC165) (Scheme 46). 

Vapor Phase Hydrogenation of Acetic Anhydride Acetic anhydride was pumped into an evaporator where it was mixed with hydrogen. The temperature of anhydride-hydrogen mixture was raised to the reaction temperature in a preheater zone, made of a 2 feet bed packed with 2 mm glass beads. The reaction took place in a 2 feet catalyst bed packed with 1 m.m. alpha-alumina coated with 0.5% Pd. The effluent was condensed and analyzed by G.C. 

Fig. I. Methods for forming metal vapors, (a) Evaporation from a resistance-heated, alumina-coated Mo or W spiral. This is a method suitable for Cr, Mn, Fe, Co, Ni, Cu, Pd, Ag, Au and other metals that do not attack alumina, (b) Evaporation from a resistance-heated Ta or W boat. This method is useful for V, Cr, and some lanthanides, (c) Sublimation from a resistance-heated free-hanging loop of wire, e.g., Ti, Mo, or W. (d) Evaporation from a cooled hearth using laser or electron bombardment heating. This method may be used with all metals.

For a method to be used to follow the course of a chemical research, the method given in Ref 33 might be used to advantage. In this method RDX is detd in HMX in concns of 0.05 to 5% by Thin-Layer Chromatography on alumina coated plates. The RDX is recovered from the subscrate by extraction with acetonitrile and is measured by spectrophotometry at 228 millimicrons. See also Analytical Procedures under RDX in this Volume Note This Section was written in collaboration with E.F. Reese of PicnArsn)... 

Sun, S., and Jaffe, P.R. (1996). Sorption of phenanthrene from water onto alumina coated with dianionic surfactants. Environ. Sci. Technol., 30, 2906-2913. 

The highest surface area enhancement factors were determined for the alumina coatings prepared with AISB, followed by alumina from aluminum triisopropylate, silica and titania. Alumina coatings were deposited in a ready-mounted micro structured reactor. The coatings had a thickness of 2-3 pm. They were impregnated with palladium and successfully applied to hydrogen oxidation [67] (see Section 2.5.1). 

About 1.5 g of nickel was vaporized at 1823 K over 30 min from a resistively heated alumina-coated molybdenum wire spiral inside an evacuated 200-mm diameter glass vessel which was partly immersed in liquid nitrogen. About 20 g of the allyl halide was simultaneously vaporized into the vessel and condensed with the nickel vapor on the cold walls. During this cocondensation, the pressure in the vessel was below 2 x 10 4Torr so that few gas-phase intermolecular collisions occurred. 

Au-iron oxide Alumina-coated metal monohth, Pt group... 

M.R. Hendrick, The Effects of Combustion CVD-Applied Alumina Coatings on the High Temperature Oxidation of a Ni-Cr Alloy, Thesis, Georgia Institute of Technology, Atlanta, 1996. 

M.R. Hendrick, J.M. Hampikian, and W.B. Carter, Combustion CVD-Applied Alumina Coatings and Their Effects on the Oxidation of a Ni-Based Chromia Former, Journal of Electrochemical Society, Vol.145, No.ll, 1998, pp.3986-3994. 

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