Peculiarities of Granulation of the PAP-2 Aluminum Powder in the Technology of the Al–Al2O3 Powder Composite with a Layered Structure

An analysis of modern scientific-and-technical information evidences great prospects for using composite materials (CMs) based on the Al–Al2O3 system. It is shown in works of the Materials Science Department of the Moscow Aviation Institute that one promising method of fabricating aluminum-based CMs is the reaction sintering in air of blanks made of highly dispersed powders of the PAP-2 brand. However, to implement the proposed method in practice, it is necessary to solve a series of problems, in particular, associated with their low manufacturing properties, such as a lack of fluidity and extremely low apparent density. To granulate the PAP-2 aluminum powder, various process approaches are applied. They are based on process operations such as powder heating in air with subsequent isothermal holding at 350°C, introducing water-diluted sodium silicate glass into its composition, mechanical processing of the powder in a high-energy planetary mill, its heat treatment in vacuum at 650°C, and initiating the stearin saponification reaction on the surface of the PAP-2 flaked particles with the formation of the organic plasticizer component. It is found that the proposed granulation methods of the industrial PAP-2 powder make it possible to improve and vary the process characteristics of the initial powder, as well as modifying its composition and structure. The highest apparent density (up to 1.25 g/cm3) is attained when using the mechanical treatment of the initial powder in a high-energy planetary mill with the formation of rounded granules 50–150 μm in size. The most producible and cost-effective method is based on the initiation of the chemical reaction of stearin saponification on the surface of powder particles (the apparent density is ~0.4 g/cm3).