Aluminum oxidation

Using the data of Table X-2, estimate the contact angle for benzene on aluminum oxide and the corresponding adhesion tension. 

The monolayer amount adsorbed on an aluminum oxide sample was determined using a small molecule adsorbate and then molecular-weight polystyrenes (much as shown in Ref. 169). The results are shown in the table. Calculate the fractal dimension of the oxide. 

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. 

METHOD 1 [112l-5g phenol in dH20 is stirred 5 hours at 20 C with some ferric sulfate (Fe2(S04)3, an additional 7mLs dH20, 13mLs 6% H2O2 and a pinch of aluminum oxide (AI2O3). Yield of catechol is 2.5g (50%). 

Ethylene oxide Acids and bases, alcohols, air, 1,3-nitroaniline, aluminum chloride, aluminum oxide, ammonia, copper, iron chlorides and oxides, magnesium perchlorate, mercaptans, potassium, tin chlorides, alkane thiols... 

Microstructurc. Crystal size, porosity, and impurity phases play a major role in fixing the fracture characteristics and toughness of an abrasive grain. As an example, rapidly cooled fused aluminum oxide has a microcrystalline stmcture promoting toughness for heavy-duty grinding appHcations, whereas the same composition cooled slowly has a macrocrystalline stmcture more suitable for medium-duty grinding. 

Corundum. Comndum [1302-75-5] (see Aluminum compounds) is a naturally occurring massive crystalline mineral composed of aluminum oxide. It is an impure form of the gems mby and sapphke. Prior to 1900 comndum was an important abrasive for the production of grinding wheels. Today it is mainly employed as a loose abrasive for grinding and polishing optical lenses. Almost all the world s supply of comndum now comes from Africa, primarily from Zimbabwe. 

Sol—Gel Sintered Aluminum Oxide. A new and much more versatile sintered alumina abrasive is now produced from aluminum monohydrate, with or without small additions of modifiers such as magnesia, by the sol—gel process (see Sol-gel technology). The first modified sol—gel abrasive on the market, Cubitron, was patented (27) and produced by the 3M Corporation for products such as coated belts and disks. The success of this material promoted intensive research into sol—gel abrasives. 

Except for siUca and natural abrasives containing free siUca, the abrasive materials used today are classified by NIOSH as nuisance dust materials and have relatively high permissable dust levels (55). The OSHA TWA allowable total dust level for aluminum oxide, siUcon carbide, boron carbide, ceria, and other nuisance dusts is 10 mg/m. SiUca, in contrast, is quite toxic as a respkable dust for cristobaUte [14464-46-1] and tridymite [15468-32-3] the allowable TWA level drops to 0.05 mg/m and the TWA for quartz [14808-60-7] is set at 0.1 mg/m. Any abrasive that contains free siUca in excess of 1% should be treated as a potential health hazard if it is in the form of respkable dust. Dust masks are requked for those exposed to such materials (see Industrial hygene). 

See Adsorption, LIQUID separation Aluminum compounds, aluminum oxide (alumina) Carbon, activated carbon Ion exchange Molecular sieves Silicon... 

Physical Properties. Physical properties of importance include particle size, density, volume fraction of intraparticle and extraparticle voids when packed into adsorbent beds, strength, attrition resistance, and dustiness. These properties can be varied intentionally to tailor adsorbents to specific apphcations (See Adsorption liquid separation Aluminum compounds, aluminum oxide (alumna) Carbon, activated carbon Ion exchange Molecular sieves and Silicon compounds, synthetic inorganic silicates). 

Traditional adsorbents such as sihca [7631 -86-9] Si02 activated alumina [1318-23-6] AI2O2 and activated carbon [7440-44-0], C, exhibit large surface areas and micropore volumes. The surface chemical properties of these adsorbents make them potentially useful for separations by molecular class. However, the micropore size distribution is fairly broad for these materials (45). This characteristic makes them unsuitable for use in separations in which steric hindrance can potentially be exploited (see Aluminum compounds, aluminum oxide (ALUMINA) Silicon compounds, synthetic inorganic silicates). 

Aluminum-containing propellants deflver less than the calculated impulse because of two-phase flow losses in the nozzle caused by aluminum oxide particles. Combustion of the aluminum must occur in the residence time in the chamber to meet impulse expectations. As the residence time increases, the unbumed metal decreases, and the specific impulse increases. The soHd reaction products also show a velocity lag during nozzle expansion, and may fail to attain thermal equiUbrium with the gas exhaust. An overall efficiency loss of 5 to 8% from theoretical may result from these phenomena. However, these losses are more than offset by the increase in energy produced by metal oxidation (85—87). 

There are several processes available for the manufacture of cryoHte. The choice is mainly dictated by the cost and quaUty of the available sources of soda, alumina, and fluoriae. Starting materials iaclude sodium aluminate from Bayer s alumina process hydrogen fluoride from kiln gases or aqueous hydrofluoric acid sodium fluoride ammonium bifluoride, fluorosiUcic acid, fluoroboric acid, sodium fluosiUcate, and aluminum fluorosiUcate aluminum oxide, aluminum sulfate, aluminum chloride, alumina hydrate and sodium hydroxide, sodium carbonate, sodium chloride, and sodium aluminate. 

Formamide decomposes thermally either to ammonia and carbon monoxide or to hydrocyanic acid and water. Temperatures around 100°C are critical for formamide, in order to maintain the quaUty requited. The lowest temperature range at which appreciable decomposition occurs is 180—190°C. Boiling formamide decomposes at atmospheric pressure at a rate of about 0.5%/min. In the absence of catalysts the reaction forming NH and CO predominates, whereas hydrocyanic acid formation is favored in the presence of suitable catalysts, eg, aluminum oxides, with yields in excess of 90% at temperatures between 400 and 600°C. 

Mag nesia. ndAlumina. Suspension. A mixture of salts, available as Maalox, Mylanta, Gelusil, and Aludrox, contains magnesium hydroxide [1309-42-8] Mg(OH)2, and variable amounts of aluminum oxide in the form of aluminum hydroxide and hydrated aluminum oxide, ie, 2.9—4.2% magnesium hydroxide and 2.0—2.4% aluminum oxide, Al O, for a mixture of 4.9—6.6% combined magnesium hydroxide and aluminum oxide. This mixture may contain a flavoring and antimicrobial agents in a total amount not to exceed 0.5% (see Aluminum compounds, aluminum oxide). 

The amount of herbicide sorbed by a given soil is influenced by properties of both the soil and the herbicide. Important properties related to the soil s retention abiHty include clay mineralogy, organic matter content, soil pH, and iron and aluminum oxide content. These properties, in turn, affect the... 

Hollow Fiber with Sorbent Walls. A cellulose sorbent and dialy2ing membrane hoUow fiber was reported in 1977 by Enka Glan2stoff AG (41). This hoUow fiber, with an inside diameter of about 300 p.m, has a double-layer waU. The inner waU consists of Cuprophan ceUulose and is very thin, approximately 8 p.m. The outer waU, which is ca 40-p.m thick, consists mainly of sorbent substance bonded by ceUulose. The advantage of such a fiber is that it combines the principles of hemodialysis with those of hemoperfusion. Two such fibers have been made one with activated carbon in the fiber waU, and one with aluminum oxide, which is a phosphate binder (also see Dialysis). 

A commercial process which uses hydrothermal leaching on a large scale is the Bayer process for production of aluminum oxide (see Aluminum compounds). This process is used to extract and precipitate high grade alurninum hydroxide (gibbsite [14762-49-3]) from bauxite [1318-16-7] ore. The hydrothermal process step is the extraction step in which concentrated sodium hydroxide is used to form a soluble sodium aluminate complex ... 

---