Formation Of Aluminum Hydroxide Research Articles

The formation of aluminium hydroxide in the sliding wear of alumina

The wear of ceramics is often affected by tribochemical reactions with the surrounding environment. This paper examines the development of aluminium hydroxide interfacial layers in the wear of alumina at intermediate wear rates and the effect of these layers on wear and friction. Since the humidity of the surrounding atmosphere promotes the formation of these layers, a dramatic effect of humidity on the wear rate is brought about by the changes in layer formation. In supporting experiments, it was found that alpha-alumina reacts directly to form boehmite (Al(OH)) under moderate pressures and high temperatures.

Mechanistic Aspects of the Deposition of thin Alumina Films Deposited by Mocvd

AbstractThe object of this study is the decomposition mechanism of Aluminium-Tri- Isopropoxide and its influence on the deposition of A12O3 by MOCVD. DSC experiments reveal that the decomposition occurs in two steps: formation of aluminum hydroxide, followed by dehydration.Deposition of A12O3 takes place by diffusion of AI(OH)3 to the substrate surface, followed by dehydration to Al2O3. This is supported by the insignificant amount of carbon found in the coating analyzed by XPS. A Langmuir type adsorption of the reactive components explains the change in reaction order of ATI from one at atmospheric pressure to two at 3 torr.

Effect of aluminium on the polymerization silicic acid in aqueous solution and the deposition of silica of silica

The effect of aluminium on the polymerization of silicic acid was studied at pH 7, 8 and 9 in the aluminium concentration range of 0–26 ppm (Al) by spectrophotometry, gel chromatography and 27Al NMR. Retarding and accelerating effects of aluminium on the growth of polysilicic acid particles and on the reaction between monosilicic acid and polysilicic acid were observed by changing the pH. It is suggested that the accelerating effect on the reaction between polysilicic acid particles is due to the formation of aluminium hydroxide on the surface of polysilicic acid. The rate of decrease in the monosilicic acid concentration in the presence of aluminium was faster than that in the absence of aluminium at pH 9, because monosilicic acid could be adsorbed rapidly on the aluminium hydroxide. From the results it was presumed that the formation of aluminium hydroxide on the solid surface may accelerate the deposition of silicic acid from geothermal water.

ChemInform Abstract: Aluminium Speciation Studies in Biological Fluids. A New Investigation of Aluminium Hydroxide Equilibria Under Physiological Conditions

Abstract(37 °C, 0.15 M aqueous NaCl).

Aluminum Corrosion in Slightly Alkaline Sodium Sulfate Solutions at Different Hydrostatic Pressures

Abstract The effect of variable SO4− − concentrations (10− 2 to 10− 1 M) in slightly alkaline solutions (pH 8.2) on aluminum corrosion has been studied at different hydrostatic pressures (1, 100, and 300 atm). The solution temperature was 20 C, and it contained ∼8 ppm of dissolved oxygen. It was observed that SO4− − ions have an inhibiting effect on aluminum corrosion for the entire pressure interval. At 10− 2 M Na2SO4 concentration, the aluminum corrosion rate increases as the hydrostatic pressure increases. This increase is attributed to the preferential formation of aluminum hydroxide in the oxidized film, which is more soluble at 300 atm than at atmospheric pressure and is therefore less protective. At higher SO4− − concentrations, the aluminum corrosion rate does not seem to be markedly affected by an increase in hydrostatic pressure.

Aluminium speciation studies in biological fluids. A new investigation of aluminium hydroxide equilibria under physiological conditions

Aluminium is prone to hydrolyse within a large range of physiological pH. Although this phenomenon has drawn much attention in the recent past, no reliable hydroxide formation constants have been produced so far that can be applied to physiological conditions of ionic strength and temperature. Prior to future aluminium–ligand equilibrium studies, aluminium hydroxide formation at 37 °C in aqueous NaCl (0.15 mol dm–3) has been investigated. The following species have been characterized: [Al(OH)]2+, Al(OH)3, [Al(OH)4]–, [Al3(OH)11]2–, [Al6(OH)15]3+, and [Al8(OH)22]2+.

Influence of Inorganic and Organic Ligands on the Formation of Aluminum Hydroxides and Oxyhydroxides

AbstractHydroxide and oxyhydroxide products of aluminum were formed at room temperature at an initial Al concentration of 2 × 10-3 M, pH 8.2, and at varying concentrations of organic and inorganic ligands commonly found in nature. The effectiveness of the ligands in promoting the formation of noncrystalline products over crystalline Al(OH)3 polymorphs was found to be in the following order: phthalate ≅ succinate < glutamate < aspartate < oxalate < silicate ≅ fluoride < phosphate < salicylate ≅ malate < tannate < citrate < tartrate. The lowest ligand/Al molar ratio at which the production of Al hydroxides or oxyhydroxides was inhibited ranged from 0.02 to 15. Above critical ligand/Al ratios, crystalline products were inhibited and ligands coprecipitated with noncrystalline products which remained unchanged for at least 5 months. Polydentate and large ligands generally were more inhibitive than those with fewer functional groups or of smaller size.The perturbing ligands promoted and stabilized the formation of pseudoboehmite over crystalline Al(OH)3 polymorphs in the following sequence: chloride < sulfate < phthalate ≅ succinate < glutamate < silicate < aspartate < phosphate < salicylate ≅ malate < tannate < citrate < tartrate. The optimal range of the ligand/Al molar ratios for the formation of pseudoboehmite varied, for example, from 0.005–0.015 for tartrate to 600–1000 for chloride. Pseudoboehmite was not formed in the presence of fluoride.

The formation of aluminium hydroxide doped with Fe(III) and Cr(III)

The formation of aluminium hydroxide doped with Fe(III) and Cr(III)

Hydrogen generation by means of the aluminum/water reaction

An aluminum amalgam will react with water at ordinary temperatures with the formation of aluminum hydroxide and the liberation of free hydrogen. In the case of a block or sheet of the metal having an amalgamated surface, this reaction will continue until all the aluminum has been consumed. The reaction rate is observed to be temperature dependent, and this affords a simple means of regulating the output of hydrogen. If the supply of water and disposal of waste is discounted the reaction is shown to be superior, on a volumetric basis, to all other common means of producing hydrogen, and furthermore is competitive on a weight and cost basis with other chemical production methods. The inherent simplicity of such a scheme for hydrogen generation offers attractive advantages in terms of reliability.

Electrochemical Behavior of High Purity Aluminum in Chloride Containing Solutions

Abstract The electrochemical behavior of high purity aluminum has been studied to clarify the corrosion behavior of the metal when exposed to oxygen free and oxygen saturated saline solutions of varying pH. The mixed or corrosion potential, EM, of the electropolished high purity aluminum decreases as the pH is increased except in the intermediate pH range (4 to 8) where EM increases. A local maximum in the corrosion potential curve as a function of pH is thus observed. The potentiostatic polarization data and controlled potential weight loss data obtained at pH 4.0 suggest that the rate of dissolution of high purity aluminum is independent of electrode potential over a fairly wide range, relatively insensitive to the presence of dissolved oxygen in the electrolyte, and highly sensitive to changes in pH. Based on the potentiostatic data, a corrosion diagram believed to be approximately valid from pH 0 to pH 14 has been constructed. The corrosion diagram is consistent with the observed relation between EM and pH, and also yields estimates of the rate of dissolution of aluminum as a function of pH. The rate of dissolution of high purity aluminum increases slightly between pH 0 and 4, decreases between pH 4 and 8, and increases from pH 8 to 14. The minimum at pH 8 may be the point at which the rate of formation of aluminum hydroxide on the electrode surface equals the rate of formation of the aluminate ion.