Search

Powders of garnet-type complex oxide Y2.5Nd0.5Al5O12 (YAG:Nd) – x vol% W, Mo (x = 0, 10, 20) were obtained using wet chemistry techniques and precipitation of the metal phase from salt solutions. After synthesis, nanoparticles of YAG:Nd garnet cluster into submicron agglomerates. Spark Plasma Sintering (SPS) was used to obtain fine-grain ceramic-metal composites YAG:Nd – (W, Mo) with a relative density of ∼99%. The effect that metal concentration (tungsten, molybdenum) has on density, microstructure properties, and mechanical properties (microhardness, fracture toughness) of ceramics was studied. SPS activation energies were determined and it was demonstrated that the intensity of shrinkage of the fine-grained YAG:Nd – (W,Mo) ceramic-metal composites close to the activation energy of creep in tungsten (molybdenum). It has been demonstrated that the intensity of creep during SPS of fine-grained composites at medium temperatures is determined by the intensity of volume oxygen diffusion in the lattice of garnet nanoparticles, whereas at high temperatures it is determined by grain-boundary diffusion.

Powders based on the complex garnet-type oxide Y2.5Nd0.5Al5O12 - x wt. % Ni (x = 0, 10, 20) were prepared using wet chemistry methods. Ceramics based on these compounds were obtained by Spark Plasma Sintering (SPS) with a relative densities: 99%. 4% (TD = 4.77 g/cm3 (0%)), 97.6% (TD = 4.88 g/cm3 (10%)), 94.4% (TD = 5.06 g/cm3 (20%)). The influence of nickel concentration on the mechanical (fracture toughness, microhardness) and thermophysical (thermal conductivity) properties of the composites was studied.

Complex oxide Y 2.5 Nd 0.5 Al 5 O 12 with garnet structure and phosphates NdPO 4 and GdPO 4 with monazite structure were obtained by using precipitation methods. Ceramics Y 2.5 Nd 0.5 Al 5 O 12 and NdPO 4 were processed by Spark Plasma Sintering (SPS). Relative density more 98%, sintering time did not exceed 8 min, sintering temperature 1330–1390 °C. Leaching rates of elements from ceramics were 10 −6 –10 −7 g/(cm 2 d). The process of ceramics sintering has two-stage character: the first step of sintering-compaction process is related to the plastic flow of the material, the second step–to the process of grain boundary diffusion and grain growth.

The possibility to fabricate highly dense (95.3–95.8% of theoretical density) composite ceramics CeO2 – x α-SiC (x = 10, 20 vol %) as a promising mineral-like material for the inert fuel matrices (IFM) by Spark Plasma Sintering (SPS) has been explored. The kinetics of SPS of the CeO2 – SiC composites in the heating-up conditions was found to have a multi-stage character. The introduction of the α-SiC particles resulted in a shift of the characteristic sintering temperatures towards higher values, allows forming the highly dense fine-grained structure, and leads to increasing of the thermal conductivity of the cerium dioxide – based ceramics.

The powder of phosphate Ca1/4Sr1/4Zr2(PO4)3 was synthesized by sol–gel processes in the presence of citric acid and ethylene glycol. Ceramic samples were prepared from this powder by Spark Plasma Sintering (SPS), their relative densities were found to be 99.5 ± 0.3% after the isothermal treatment at 860 °С for 3 min. Sintered disc-shaped ceramic samples (d = 10 mm, h = 4 mm) were bombarded at 300 K by 167 MeV Xe26+ ions with fluences ranging from 6 ⋅ 1010 to 1 ⋅ 1013 ions/cm2. It was found that exposure to the highest fluence (1013 ion/cm2) led to a complete amorphization of the irradiated layer. The observed phase transition is ascribed to the formation of amorphous latent tracks via dense electronic excitations. Postradiation heat treatment revealed that the transformation from metamict to crystalline form took place after annealing at T = 200, 300, 400, 500, 600 and 800 °С and t = 3, 13, 11, 5, 17 and 15 h, respectively.