Search

This paper reports on the preparation of xenotime-structured ceramics using the Spark Plasma Sintering (SPS) method. Y0.95Gd0.05PO4 (YPO4:Gd) phosphates were obtained using the sol-gel method. The synthesized powders were nanodispersed and were agglomerated (the agglomerates sizes were 10–50 µm). The ceramics had a fine-grained microstructure and a high relative density (98.67 ± 0.18%). The total time of the SPS process was approximately 18 min. The sintered high-density YPO4:Gd ceramics with a xenotime structure were irradiated with 132Xe+26 ions with 167 MeV of energy and fluences in the range of 1 × 1012–3 × 1013 cm−2. Complete amorphization was not achieved even at the maximum fluence. The calculated value of the critical fluence was (9.2 ± 0.1) × 1014 cm−2. According to the results of grazing incidence X-ray diffraction (GIXRD), the volume fraction of the amorphous structure increased from 20 to 70% with increasing fluence from 1 × 1012 up to 3 × 1013 cm−2. The intensity of the 200 YPO4:Gd XRD peak reached ~80% of the initial intensity after recovery annealing (700 °C, 18 h).

The present work was aimed at the investigation of the effect of high-energy ball milling (HEBM) time on the sintering kinetics, structure, and properties of the heavy tungsten alloy (HTA) W-7%Ni-3%Fe. The HTA samples were obtained from nanopowders (20–80 nm) using conventional liquid-phase sintering (LPS) in hydrogen and using spark plasma sintering (SPS) in vacuum. The HTA density was shown to depend non-monotonously on the HEBM time that originates from the formation of nonequilibrium solid solutions in the W-Ni-Fe systems during HEBM. The SPS kinetics of the HTA nanopowders was shown to have a two-stage character, the intensity of which depends on the Coble diffusion creep rate and on the intensity of diffusion of the tungsten atoms in the crystal lattice of the γ-phase. The kinetics of sintering of the initial submicron powders has a single-stage character originating from the intensity of the grain boundary diffusion in the γ-phase. The dependencies of the hardness and of the yield strength on the grain sizes were found to obey the Hall–Petch relation. The hardness, strength, and dynamic strength in the compression tests of the fine-grained tungsten alloys obtained using SPS and LPS were studied.