Segregation of calcium on the surface of aluminum-based powders and its effect on oxidation kinetics

Segregation in the surface layers of an aluminum alloy powder containing 1.3 wt % calcium is studied. With the use of X-ray photoelectron spectroscopy, it is found that the surface calcium content is increased to 34 wt % compared to the bulk. Oxidation of the powder in air studied with the use of thermogravimetry and differential scanning calorimetry showed that the high surface concentration and high chemical activity of calcium result in a doubling of the reaction yield at a temperature of 1750 K.     

Dynamics of the Oxygen Adsorption Process on the Surface of Aluminum–Cerium Alloy in Polycrystalline and Amorphous States

Protection of Metals and Physical Chemistry of Surfaces - Based on the concept of collective vibrations of ions in the bulk of metal systems, the frequency of vibrations of an oxygen molecule on...     

Oxidation of Powdered Aluminum after Surface Modification with Mn,Fe, Co,and Ni Formates

Protection of Metals and Physical Chemistry of Surfaces - The effect of small additives of manganese, iron, cobalt, and nickel oxides on the oxidation of aluminum powder of ASD-4 grade while...     

High-Temperature Compatibility of Al–Rare Earth Alloys with Titanium Carbide

The wetting of titanium carbide by molten Al–rare earth alloys was studied. The physicochemical properties of the alloys were correlated with the contact angle and the carbon and oxygen affinities of the substrate and alloy. The properties of the alloys were investigated as a function of composition. The phase relations in the Al-rich corners of the Al–Y and Al–Nd phase diagrams were refined using viscosity data. The x-ray microanalysis and Auger electron spectroscopy data were used to assess the melt structure, adsorption behavior of the melt components at the liquid–gas and liquid–solid interfaces, interfacial area, and composition of the transition layer. The introduction of rare-earth additions into Al was found to reduce the temperature at which good adhesion to TiC can be achieved by 100–200 K.     

Energetic characteristics of the adsorption of oxygen on surfaces of polycrystalline and amorphous aluminum-cerium alloy

Based on modeling the optical-conductivity spectrum estimated from the data of optical experiments, the electronic structure of nonoxidized and oxidized surfaces of liquid, amorphous, and polycrystalline Al-8 at % Ce alloy is studied. The conduction band of the alloy in the liquid and amorphous states is found to be split. In the polycrystalline state, there is no splitting. The heat of adsorption of oxygen on the alloy surface is calculated for amorphous and polycrystalline alloy states.     

Thermodynamics of initial stage of oxygen adsorption on surface of amorphous aluminum-cerium alloy

An equation is proposed to connect the characteristics of the energy and the surface level population on pure and oxidized metal surface with the value of heat of the physical absorption of oxygen. The electron structure is studied of pure and oxidized surface of the amorphous Al-8 at. % Ce alloy by analyzing the results of modeling the optical conductivity obtained from the optical experiment data. The conductivity band of the alloy is shown to be split. The heat value is calculated from the oxygen absorption on the amorphous alloy surface.     

Surface activity of barium and its effect on the reactivity of aluminum-based powder

Segregation in the surface layers of a powder of aluminum alloy containing 0.26 at % barium is studied. XPS data revealed an increase in the surface barium content to 13 at % compared to the bulk concentration. Investigations of the oxidation of the powder in air with the use of thermogravimetry and differential scanning calorimetry showed that the high surface and chemical activity of barium results in an increase in the thermal kinetic and energetic characteristics of the interaction.     

The effect of Ca,Ba, and V<Subscript>2</Subscript>O<Subscript>5</Subscript> on oxide-film stability and the mechanism of oxidation of disperse aluminum

The results of a reactivity study of aluminum powders modified with surfactants of different natures allowing one to decrease the protective properties of an oxide film on a particle surface during heating in the oxidizing medium are given. Ca, Ba, and V₂O₅ used as modifiers were shown to allow considerably increasing the completeness and rate of oxidation of ASD-4-type aluminum powders used as fuels in composite propellant compositions. The mechanism of action of modifiers on the oxidation and combustion of disperse aluminum was established.