Papers by Keyword: Spark Plasma Sintering (SPS)

Abstract: WC-8wt%Co nanopowder was consolidated by spark plasma sintering at process temperatures (T_SPS) from 1100 to 1400 °C. The nanoindentation hardness and Young’s modulus of the consolidated specimens were measured under different peak load levels (P_max). The hardnesses and modulus of WC-8wt% Co shows a clear dependence on the microstructures and peak load levels. At 1200 and 1300 °C, the hardness and modulus were higher than those at 1100 and 1400 °C due to the higher relative density and fine grain size. The relationship of stiffness (S) and contact depth (h_c) of nanoindentation was discussed.

Abstract: Titanium carbide (TiC) was consolidated with 20 mol% zirconium carbide (ZrC) by spark plasma sintering in the temperature range of 1773–2473 K, and the phase formation, microstructure, relative density and mechanical properties were investigated. The composite consisted of Ti-rich (Ti, Zr)C and Zr-rich (Zr, Ti)C solid solutions at 1773–2373 K, and was single-phase (Ti, Zr)C at 2473 K. The relative density of the composite was over 98% above 2073 K. The composite prepared at 2273 K exhibited the maximum H_V of 29.7 GPa with the K_IC of 3.76 MPa m^1/2.

Abstract: MgB₂-based superconducting composites with magnetic nanoparticles were fabricated by spark plasma sintering technique. Two methods have been used to create nanoparticles within MgB₂ matrix: i) direct insertion of passivated magnetic nanoparticles; ii) growth of magnetic nanoparticles by thermolysis of polymers or metallo-organic precursors. These composites display an enhanced critical current density due to the additional magnetic pinning generated by the magnetic interaction with the flux lines.

Abstract: Multiwalled carbon nanotube (MWCNT) reinforced Al-Si (11 wt%) alloy based nanocomposites were synthesized by spark plasma sintering using high energy ball milled nanocrystalline Al-Si powders mixed with physically functionalized MWCNTs. Improvement in MWCNT dispersion and associated improvement in densification of the nanocomposites were confirmed. The microhardness and elastic modulus of the nanocomposites measured by nanoindentation exhibited appreciable improvement. Grain size measurement by X ray diffraction and transmission electron microscopy confirmed achievement of nanocrystalline grains in Al-Si powder after ball milling, as well as in the consolidated nanocomposites. TEM analysis was performed to reveal the dislocation activity, effect of presence of primary Si and distribution of MWCNTs in the nanocomposites.

Abstract: To enhance the mechanical properties of Mg alloys, 0-30vol% Al₂O₃/Mg powders were formed by ball milling powder mixtures of pure Mg and Al₂O₃ particles, and then Spark plasma sintering (SPS) compacts (Al₂O₃/Mg discs) were made by the Al₂O₃/Mg powders. The effect of the cooling conditions in the SPS process on the mechanical properties of the Al₂O₃/Mg discs was investigated. From the results of SEM, XRD and TEM-EDS, the microstructures of the Al₂O₃/Mg discs were identified to consist of α-Mg solid solution, Al₂O₃ particles, refined MgO particles and refined needle-like Mg₁₇Al₁₂ ( more than 20vol% Al₂O₃ content). The mechanical properties of the discs were able to control by the regulation of the cooling conditions (cooling rate (v_c) and applied pressure in the cooling (p_c)) in SPS process, and as a result, the SPS discs possessing the mechanical properties beyond HP compacts were obtained under the cooling conditions of “v_c = 0.83K/s and p_c = 20MPa”. Main factor that the cooling conditions in SPS process effect on the mechanical properties of the Al₂O₃/Mg discs are considered to be the compresive residual stress generated in the α - Mg solid solution by the thermal stress associated with deference of the coefficients of thermal expansion between the α - Mg and ceramics particles (Al₂O₃ and MgO) in the discs.

Abstract: Good crystalline of ATO thin films is necessary to improve the electrical and optical properties. In this paper, ATO thin films were fabricated using PLD method at high temperature of 550 °C, and the effect of laser energy density on the microstructure, electrical property and optical property of the ATO films is discussed. The results suggest that ATO films show good crystalline when deposited at high temperature of 550 °C. Both the electrical and optical properties have been enhanced with the increasing of laser energy density. When the laser energy density is 5.4 J/cm², the lowest resistivity of ATO thin film is obtained with the value of 6.52×10^-4 Ω·cm and the average optical transmittances is 82.0 %.

Abstract: Using the mixed powders containing gas-atomized powders of metallic glassy alloys (Cu₅₀Zr₄₅Al₅, Fe₇₃Si₇B₁₇Nb₃, Ni_52.5Nb₁₀Zr₁₅Ti₁₅Pt_7.5) blended with high-conductive Cu particulates, we produced bulk metallic glassy alloy composites with high strength and high electrical conductivity, as well as with enhanced plasticity and satisfying large size requirements by a spark plasma sintering process. In this paper we present and review our research results on the fabrication and properties of the bulk glassy alloy composites by the spark plasma sintering process.

Abstract: By using the Mg₆₅Zn₃₀Ca₅ amorphous powder prepared by ball-milling of the master alloy or its mixture powders, we produced Mg₆₅Zn₃₀Ca₅ bulk amorphous alloy and its composites by a spark plasma sintering process. The microstructure and corrosion properties of the prepared Mg₆₅Zn₃₀Ca₅ bulk amorphous alloy and its composites were investigated. The bulk amorphous alloy and its composites exhibited a high relative density and high corrosion resistance than commercial Mg alloys.

Abstract: There is a need to enhance or develop high temperature capabilities of structural materials for advanced coal‐fired power plants. These materials require a combination of high temperature strength, creep resistance and corrosion resistance in the oxygen‐rich and hydrogen‐rich high pressure environments. In this study, atomized Ni‐20Cr (wt.%) powder was mechanically milled with Y₂O₃ nanopowder (30‐40 nm powder size) to produce an alloy with a chemical composition of Ni‐20Cr‐1.2Y₂O₃ (wt.%) alloy using high energy ball milling. To minimize agglomeration during milling, 1 wt.% stearic acid was added to the powder mixture prior to milling. Microstructural characteristics of the powder were primarily characterized by the X‐ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size and lattice strain were measured by XRD whereas powder morphology (powder size, shape) was studied by SEM. A milling time of 2 h was found to be optimal for the purpose that yttria particles are not dissolved yet uniformly distributed. Subsequently, the milled powder was consolidated into bulk specimens (12.5 mm in diameter) via spark plasma sintering (SPS) at 1100 °C for 30 minutes. Following SPS, the density and hardness of the specimens were measured. Microstructural characterization of the SPSed specimens was performed using SEM and TEM. The microstructural characteristics were correlated with the measured mechanical properties.

Abstract: Cubic Yttria-stabilized zirconia (c-YSZ) is a candidate material for high temperature applications due to its chemical inertness, high thermal stability and low thermal conductivity. In addition, due to c-YSZ’s high radiation stability, there is a new interest in this ceramic for thermal insulating cladding material in Supercrticial Water Nuclear Reactors (SCWR). However, due to the aggressive environment of supercritical water, the degradation behaviour of the ceramic must be well understood prior to its industrial application. In this research, moderately dense 8 mol% Yttria stabilized zirconia (YSZ) as well as YSZ composites containing 5, 10 and 15 mol% CeO₂ were fabricated via Spark Plasma Sintering (SPS) and subjected to static corrosion testing in supercritical water (SCW) at 400°C and 31MPa. Weight loss and crystal lattice changes associated with SCW exposure were studied.