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Aluminum atoms, heat treatment

Key words high-strength aluminum alloys, heat treatment, mechanical properties, structure, casting, water atomization. [Pg.163]

Aluminum oxide is a widely used catalyst, mainly as a support. The surface of AI2O3 possesses both acidic and basic sites after heat treatment above 670 K. The acid sites are mainly Lewis acid sites strong Bronsted sites are absent. The Lewis acid site is visualized as a coordinatively unsaturated A1 atom formed by dehydroxylation, and the weak Broonsted sites act as acidic surface hydroxyls, while the basic sites are considered to be basic hydroxyls and oxide ions. Three OH groups are... [Pg.3400]

Here A i(nAl) is the peak area of each deconvoluted curve of Si-MASNMR spectra. When the dealumination occurred after heat treatment of NH -Y or La-Y, the aluminum atoms of Si(3A1) and Si(2A1) are preferentially removed from the framework, which may decrease the acidity. And the increased values of (Si/A1)nmr from (Si/Al)ca indicate the dealumination. Especially for H-Y(4.8) calcined in air, serious dealumination from the framework has been... [Pg.584]

The commercially available HPLC-grade aluminas consist latgdy of y-alumina, a form prepared by heat treatment between S(X) and 8(XPC. TIm structure of y-alumina is spinel, where the unit cell contains 32 oxygen atoms arranged in 64 tetrahedrons and 32 octahedrons (19). The aluminum atoms are heterogeneously distributed over the tetrahedrons and octahedrons of the unit cell. This leads to a formation of Lewis base sites for the vacant positions and Lewis acid sites for the occupied positions. Like the surface of silka, the surface of alumina is covered by hydroxy groups. However, the number of hydroxy groups and their coordination is different (11) ... [Pg.96]

Integrated circuit interconnects are normally made of aluminum—instead of metals such as copper, silver, and gold that have higher electrical conductivities—on the basis of diffusion considerations. During high-temperature heat treatments, interconnect metal atoms diffuse into the silicon appreciable concentrations wiU compromise the chip s functionahty. [Pg.159]

D5 One integrated circuit design calls for the diffusion of aluminum into sihcon wafers the background concentration of A1 in Si is 1.75 X 10 atoms/m. The predeposition heat treatment is to be conducted at 715°C for 1.25 h, with a constant surface concentration of 4 X 10 A1 atoms/m. At a drive-in treatment temperature of 1050°C, determine the diffusion time required for a jrmction depth of 1.75 pm. For this system, values of Qaand Dq are 3.41 eV/atom and 1.38 x lO m /s, respectively. [Pg.167]

A mixture of 500 g. (3.25 moles) of biphenyl and 208 g. (6.5 gram atoms) of sulfur is heated to 115-120°, and 25 g. (0.19 mole) of anhydrous aluminum chloride is added over a period of 75 minutes. The temperature is held at 115-120° for another 2 hours, followed by a gradual increase to 240° over a period of 5 hours. The cool residue is extracted with three 500-ml. portions of hot water and then with eight 1-1. portions of ethanol. Evaporation and cooling of the ethanolic solution after a charcoal treatment gives a 65-70% yield of dibenzo-thiophene melting at 98°. Material melting at 99° is obtained by distillation, b.p. 152-154°/3 mm., and recrystallization from ethanol. [Pg.109]

Current explanations of tribochemical reactions state that the more obvious consequence of mechanical treatments, the increase of the surface area of a solid, is a minor factor, which contributes only to 10% of the reactivity increase. The more important effect is due to the accumulation of energy in lattice defects which can relax either physically by the emission of heat, or chemically by the ejection of atoms or electrons, formation of excited states on the surface, bond breakages, and other chemical transformations. Mechanical stress can be applied as single or periodic shocks, rapid loads, etc. An example is that of the mechanochemical decomposition of aluminum hydride, which increases with the frequency of the applied stress (Fig. 2).i ... [Pg.111]

The forward scheme is shown here. Benzene is first converted into toluene upon treatment with methyl chloride and aluminum trichloride (via a Friedel-Crafts alkylation). Upon treatment with NBS and heat, a bromine atom is installed at the benzylic position, giving benzyl bromide. An azide synthesis then converts benzyl bromide into benzyl amine. A reductive amination then installs a methyl group, followed by acetylation with acetyl chloride to give the product ... [Pg.946]


See other pages where Aluminum atoms, heat treatment is mentioned: [Pg.449]    [Pg.80]    [Pg.105]    [Pg.113]    [Pg.238]    [Pg.149]    [Pg.113]    [Pg.316]    [Pg.318]    [Pg.189]    [Pg.200]    [Pg.9]    [Pg.105]    [Pg.113]    [Pg.228]    [Pg.64]    [Pg.113]    [Pg.789]    [Pg.455]    [Pg.163]    [Pg.215]    [Pg.176]    [Pg.198]    [Pg.6]    [Pg.201]    [Pg.241]    [Pg.490]    [Pg.186]    [Pg.885]    [Pg.47]    [Pg.246]   
See also in sourсe #XX -- [ Pg.200 ]




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Aluminum atomization

Aluminum treatment

Atomic heat

Atomization, heat

Heat treatment

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