Aluminum oxide atmosphere

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. 

The most important reactions of trichloroethylene are atmospheric oxidation and degradation by aluminum chloride. Atmospheric oxidation is cataly2ed by free radicals and accelerated with heat and with light, especially ultraviolet. The addition of oxygen leads to intermediates (1) and (2). 

A yield of approximately 98% can be obtained at 200°C and 1000 atmospheres of pressure. The process makes use of a catalyst which is usually finely divided, mixed iron oxides containing small amounts of potassium oxide, K20, and aluminum oxide, Al203. 

The decomposition of aluminum alkyls, such as (CH3)3A1 or ( 2115)3Al, in an oxidizing atmosphere, such as O2 orN20, produces alumina deposits in a temperature range of 250-500°C.l l... 

All reactions and manipulations were carried out under an inert atmosphere (N2 or Ar gas) using the Schlenk technique. Solvents were freshly distilled under an Ar atmosphere using the standard procedures (Na/BC/benzophenone or CaH2). Chromatography was performed on alumina (aluminum oxide, activity Il-IV(Merck art 1097). The H- and C-NMR spectra were recorded on a Bruker AC-200 spectrometer ( H, 200 MHz) and Nippon... 

Another way to protect a metal uses an impervious metal oxide layer. This process is known as passivation, hi some cases, passivation is a natural process. Aluminum oxidizes readily in air, but the result of oxidation is a thin protective layer of AI2 O3 through which O2 cannot readily penetrate. Aluminum oxide adheres to the surface of unoxidized aluminum, protecting the metal from further reaction with O2. Passivation is not effective for iron, because iron oxide is porous and does not adhere well to the metal. Rust continually flakes off the surface of the metal, exposing fresh iron to the atmosphere. Alloying iron with nickel or chromium, whose oxides adhere well to metal surfaces, can be used to prevent corrosion. For example, stainless steel contains as much as 17% chromium and 10% nickel, whose oxides adhere to the metal surface and prevent corrosion. 

A particularly simple example would be the energy of a sample of aluminum metal in air. The surface of the metal is covered with a continuous layer of aluminum oxide which may be less than 20 angstroms in thickness in a dry atmosphere but will be much thicker in moist air or after contact with hot water. Consequently, the... 

Aluminum reacts with acids and strong alkali solutions. Once aluminum is cut, the fresh surface begins to oxidize and form a thin outer coating of aluminum oxide that protects the metal from further corrosion. This is one reason aluminum cans should not be discarded in the environment. Aluminum cans last for many centuries (though not forever) because atmospheric gases and soil acids and alkalis react slowly with it. This is also the reason aluminum is not found as a metal in its natural state. 

The heat of combustion amounts to 4272 cal/g of aluminum fuel and the adiabatic flame temperature calculated by the chemical equilibrium program is 3036 K. Thus, the heat released when aluminum is burned with steam is about 57% of the amount released when aluminum is burned with O2. Many experimental investigations have been carried out on the combustion of aluminum in atmospheres where the primary oxidizer was O2 [7-16], and also in atmospheres where the primary oxidizer was H2O and/or CO2 [16-19]. There is general... 

When aluminized AP composite propellant burns, a high mole fraction of aluminum oxide is produced as a combustion product, which generates visible smoke. If smoke has to be avoided, e. g. for miUtary purposes or a fireworks display, aluminum particles cannot be added as a component of an AP composite propellant In addition, a large amount of white smoke is produced even when non-aluminized AP composite propellants bum. This is because the combustion product HCl acts as a nucleus for moisture in the atmosphere and relatively large-sized water drops are formed as a fog or mist This physical process only occurs when the relative humidity in the atmosphere is above about 60%. If, however, the atmospheric temperature is below 260 K, white smoke is again formed because of the condensation of water vapor with HCl produced as combustion products. If the HCl smoke generated by AP combustion cannot be tolerated, the propellant should be replaced with a double-base propellant or the AP particles should be replaced with another... 

When fine aluminum particles are incorporated into AP pyrolants, aluminum oxide (AI2O3) particles are formed when they bum. Dispersal of these aluminum oxide particles in the atmosphere generates white smoke even when the atmosphere is dry. The mass fraction of aluminum particles added is approximately 0.2 for the complete combustion of AP pyrolants. Though an excess of aluminum... 

Aprotic solvents such as xylene, chlorobenzene, and toluene can be used instead of benzene. If the boiling point of the product is close to that of the solvent, the mixture of aluminum oxide and the allene may be heated to distil at ca. 150°C under an atmosphere of nitrogen. 

Toon, O. B., J. B. Pollack, and B. N. Khare, 1976. The optical constants of several atmospheric aerosol species ammonium sulfate, aluminum oxide and sodium chloride, J. Geophys. Res.. 81, 5733-5748. 

There is clear evidence that live 26A1 was incorporated into presolar silicon carbide and aluminum oxide grains (see Chapter 5). These grains acquired their 26 Al in the atmospheres of the dying stars in which they formed. It had almost certainly decayed away long before the grains reached the solar system. In presolar grains,26 Al serves as a probe of nucleosynthesis in the parent stars. 

AH was prepared in the usual manner from a suspension of 2.0 g LAH in 75 mL anhydrous THF, cooled to 0 °C and well stirred in an inert atmosphere of He, and treated with 1.33 mL of 100% H2S04 added dropwise. There was added, drop-wise and over the course of 10 min, a solution of 3.1 g 3-ethylthio-4,5-dimethoxy-B-nitrostyrene in 15 mL anhydrous THF. At the end of the addition, the reaction mixture was returned to room temperature, and finally heated on the steam bath for 10 min. After cooling again, there was added enough IPA to decompose the excess hydride and sufficient 10% NaOH to convert the aluminum oxide to a white, easily filterable mass. This was removed by filtration, the filter cake washed with additional IPA, and the filtrate and washes combined and the solvent removed under... 

No reliable studies were located regarding cancer effects in animals following acute- or intermediate-duration inhalation exposure to aluminum or its compounds. An increase in cancer was not observed in male and female Wistar rats exposed via whole-body inhalation to atmospheres containing 2.18-2.45 mg Al/m3 as alumina fibers ( 96% aluminum oxide) for 86 weeks (Pigott et al. 1981). 

The impedance hygrometer measures the water content of a sample by means of a probe whose electrical impedance is a function of the vapor pressure of moisture in the fluid. The probe consists of an aluminum strip that is anodized to form a porous layer of aluminum oxide. A thin coat of gold is applied over the aluminum oxide. Water vapor penetrates the gold layer and equilibrates on the aluminum oxide. Leads from the gold and aluminum electrodes of the probes connect the sensing element to the measuring circuitry. The moisture content of solids can also be measured indirectly by detecting the moisture in the atmosphere above or near the process solids because the atmosphere near the solids is in equilibrium with the moisture content of the process materials. 

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