Search

NASICON-like Na3Zr2(SiO4)2PO4 (NZSP) ceramic solid electrolyte with high ionic conductivity, safety, and durability becomes the main focus and attention as an alternative for traditional liquid electrolytes. NZSP containing NH4H2PO4 and Na3PO4⋅12H2O as the phosphate source has been extensively studied as a solid electrolyte, but a deep understanding of the relationship between crystal growth and ionic conductivity is still lacking. Herein, we synthesized NZSP via a solid-state reaction using NaH2PO4 as the phosphate source. The impact of different sintering holding times on the crystal phase, microstructure, ionic conductivity, and relaxation time of NZSP solid electrolytes was investigated. Microstructure studies revealed that the faceted NZSP sintered at 1100 °C for 24 h has the lowest formation of ZrO2 and highest densification with the least pores. In addition, the sample achieved the highest room temperature ionic conductivity (4.11 ⨯ 10−4 S cm−1) and the shortest relaxation time (0.4 μs), which are also crucial factors for the development of rechargeable all-solid-state batteries (ASSBs). [ABSTRACT FROM AUTHOR]

The effects of the sintering holding time and cooling rate on the microstructure and mechanical properties of nanocrystalline Fe-Cr-C alloy were investigated. Nanocrystalline Fe-1.5Cr-1C (wt.%) alloy was fabricated by mechanical alloying and spark plasma sintering. Different process conditions were applied to fabricate the sintered samples. The phase fraction and grain size were measured using X-ray powder diffraction and confirmed by electron backscatter diffraction. The stability and volume fraction of the austenite phase, which could affect the mechanical properties of the Fe-based alloy, were calculated using an empirical equation. The sample names consist of a number and a letter, which correspond to the holding time and cooling method, respectively. For the 0A, 0W, 10A, and 10W samples, the volume fraction was measured at 5.56, 44.95, 6.15, and 61.44 vol.%. To evaluate the mechanical properties, the hardness of 0A, 0W, 10A, and 10W samples were measured as 44.6, 63.1, 42.5, and 53.8 HRC. These results show that there is a difference in carbon diffusion and solubility depending on the sintering holding time and cooling rate.

Cold pressing and conventional sintering was used to prepare an Al-Cu-Mg alloy and the effects of isothermal sintering time at 620℃ on evolution of the microstructure were studied. The results showed that at an isothermal sintering time of 30 min, the eutectic liquid of Al-Mg, Al-Cu-Mg and Al-Cu filled the particle gaps, resulting in a reduction of pores and rapid densification of the alloy; at isothermal sintering times of 30−120 min, the grains began to grow continuously which increased the density of the alloy a little; at 180 min, a large number of micropores appeared in the alloy which caused the density to decrease. Examination of the alloy micro-area elements showed that Cu diffused from the grain core to the grain boundary during sintering, which promoted the hard and brittle θ phase at the grain boundary. This increased the grain boundary strength and hence the tensile strength and hardness of the alloy. At an isothermal sintering time of 180 min, the strength of the alloy decreased. Optimum mechanical properties of the alloy were obtained at an isothermal sintering time of 120 min, the tensile strength and elongation were 237.9 MPa and 12.67% respectively, and the hardness was 87.7 HBW. A spinel phase, observed at the grain boundary of the aluminum alloy, provided evidence for the role of Mg in destroying the oxide film to promote sintering of the liquid phase.

Abstract: The effect of employing a short sintering holding time of 12min as compared to that of the commonly employed holding time of 120min (2h) on the properties of undoped and 1wt% manganese oxide (MnO2)-doped Y-TZP ceramics were studied. Sintering studies was conducted over the temperature range of 1150–1600°C. Bulk density, Young''s modulus, Vickers hardness and fracture toughness tests were carried out on the sintered samples. The results revealed that the 12min sintering holding time was effective in promoting densification of the 1wt% MnO2-doped Y-TZP without sacrificing tetragonal phase stability or mechanical properties and incurring grain growth. Microstructure investigation by using the scanning electron microscope (SEM) of the fracture MnO2-doped Y-TZP samples which was subjected to rapid quenching in liquid nitrogen revealed distinct microstructural features believed to be associated with the presences of a transient liquid phase during sintering. A sintering mechanism was subsequently proposed to explain the densification behaviour of MnO2-doped Y-TZP ceramics. [Copyright &y& Elsevier]