Vol 27, No 1 (2018)

The paper addresses to the practical development of a novel process technology for large-tonnage SHS-production of alloying agents and master alloys–metallurgical SHS process technology. The suggested and tested technique is based on use of various metallurgically produced allows, including dusty wastes of ferroalloy plants. The replacement of high-purity starting powders by less expensive and accessible ferroalloys afforded for transition from existing laboratory-scale fabrication of SHS materials to large-tonnage SHS manufacture.

The work aimed at preparation of the MgB₂ doped with alloying metals (Al, Cu, Ag, Zn) by SHS in a mode of thermal explosion. The measured combustion temperatures fell within the range 940–1030°С. Detailed XRD analysis has shown that, among other selected metals, it is solely Al that can enter the MgB₂ lattice. According to time-resolved XRD results, the formation of final product (Mg, Al)B₂ in the Mg–Al–B system involved no intermediate phases. But in the Mg–Cu–B system, the volume reaction additionally yielded MgB₄, Cu₂Mg, and CuMg₂ due to the presence of the liquid phase. In final products, the agglomerates of MgB₂ grains had a size of 500–1000 nm, while the size of Cu₂Mg and CuMg₂ inclusions was within 0.5–2 μm.

Solid solution (AlN)_x(SiC)_1–x (x = 0.7) was prepared from Al–SiC mixtures by SHS under high pressure of nitrogen gas (50, 70 MPa) and characterized by XRD and SEM. Combustion product was found to have a wurtzite 2H structure with lattice parameters a = 3.10889 ± 0.00022 Å and c = 5.00741 ± 0.00080 Å.

We suggest a new approach to synthesis of nano nickel ferrites via combustion synthesis in electric and microwave ovens. The oxidation of organic compounds, decomposition of salts, and their degradation were explored by TGA–DTA. As-prepared nanopowders were characterized by X-ray powder diffraction. Structures of both ferrites were slightly different. Detailed material parameters such as crystallite size (D), lattice constant (a), micro strain (ε), X-ray density (Δ_X), dislocation density (ρ_X), hopping lengths (L_A and L_B), bond lengths (A–O and B–O), ionic radii (r_A and r_B), texture coefficient [TC(hkl)], and mechanical properties were measured and comparatively analyzed.

Fine Ti powders were prepared through magnesiothermic reduction in TiO₂–Mg–Ca mixtures under 4 MPa of Ar followed by acid leaching (with HCl or HNO₃) and characterized by XRD, SEM/EDS, and chemical analysis. Thus prepared Ti powders exhibited the specific surface ranging between 7.0 and 30.0 m²/g. The produced Ti powders can find their application in pyrotechnics, powder metallurgy, and as raw material for SHS of inorganic compounds.