Papers by Keyword: Hot-Pressing

Abstract: In this study, bulk lithium-ion conducting solid electrolyte of Ga-doped Li₇La₃Zr₂O₁₂ (Li_7-3XGa_xLa₃Zr₂O₁₂) where x = 0.1 (Ga-LLZO) was prepared via hot pressing at 500 °C. Precursor powder for hot-pressing was prepared using conventional solid state reaction method. Planetary ball milling was employed to investigate the particle size effect on the structure and densification of hot-pressed samples. XRD patterns of the bulk hot-pressed sample revealed a crystalline phase of which the major peaks observed can be indexed to a cubic LLZO structure; however, a major impurity phase of La₂Zr₂O₇ was observed for the ball-milled sample. Thermogravimetric and differential thermal analysis showed about 12% weight loss below 900 °C which may have affected the observed hot-pressing structure. Although lower density measurement and an impurity phase of La₂Zr₂O₇ were observed for the ball-milled sample, ball-milling also resulted to a more homogeneous and finer particle size as shown by SEM images results.

Abstract: C_f/SiO₂ composites were prepared by slurry impregnation-hot pressing process, and their mechanical properties, microstructure and surface morphologies were then investigated. The results indicated that the composites showed the best mechanical properties, and the tensile strength, bending curvature, compression strength were 58MPa, 170MPa, 256MPa respectively. XRD spectrums showed that fused quartz appeared no crystallization during the process. Also from the TEM analysis, we can see that the C_f/SiO₂ composites exhibited the best compactness. All the tests were carried out on the composites autoclaved at 1400°C for 60min, according to which the best hot pressing process was concluded.

Abstract: The transparent β-Si₃N₄ ceramic with a whisker-like microstructure was prepared by hot-pressing at 2000 °C for 26 h, with MgSiN₂ as an additive. The resultant material achieves the maximum transmittance of 70 % at the wavelength of about 2.5 μm and the transmittance value keeps higher than 60 % in the range of 700-4500 nm wavelength, which is attributed to the very small amount of the intergranular amorphous phase along with high density. The present transparent β-Si₃N₄ ceramic exhibits an indentation fracture toughness of 7.2±0.3 MPa m^1/2.

Abstract: There is a continuous demand for next-generation industrial materials because they offer advantages such as high performance, reliable life cycle, reasonable cost, and ease of mass production. Carbon nanotubes (CNTs), which possess unique properties such as beneficial mechanical, electrical, and thermal properties, as well as chemical stability, have received considerable attention as candidates for reinforcing ultra-high-performance nanocomposites. CNT-reinforced Al alloy matrix nanocomposites were fabricated by mechanical ball-milling and hot-pressing processes. The effects of different CNTs on the mechanical properties of the composites were investigated. The mechanical properties were found to change significantly depending on the type of CNT blended with the matrices. The mechanical performance of the nanocomposites can thus be controlled by using different types of CNT reinforcements.

Abstract: Two kinds of 2:17R Sm-Co alloys, Sm₂(Fe,Cu,Zr,Co)₁₇ and pure binary Sm₂Co₁₇ were prepared, and the amorphous powder was prepared by high-energy ball milling Sm-Co alloys. The bulk nanocrystalline SmCo₇ was prepared by hot-pressing the amorphous powder, and the magnetic properties and phase composition were studied. Initial Sm₂(Fe,Cu,Zr,Co)₁₇ showed a large value of coercivity while the pure Sm₂Co₁₇ almost showed no coercivity. However, after ball milling the grain size of alloys decreased dramatically until completely amorphous. Two kinds of alloys showed the different phase composition and magnetic properties after hot-pressing. It was found that the pure Sm₂Co₁₇ bulk magnet showed a high coercivity H_c and had the 1:7H phase. On the other hand, the Sm₂(Fe,Cu,Zr,Co)₁₇ showed high saturation magnetization M_s and very low H_c since the Fe-Co and Sm₂Co₃ phase were precipitated from the alloy.

Abstract: A novel method called hot-pressing method of preparing porous membrane was firstly reported in this paper. Compared with other method such as none-solvent induced phase separation method, melt-spinning and cold-stretching method, the hot-pressing method was simple, easy to operate, environment-friendly. First, a silica needle arrays (SNA) template with a hexagonal close-packed structure was prepared by TAFE method. Then the SNA template was used to press into the plastic wrap in order to form the uniform pores. After that, a uniform porous membrane was prepared. The diameter of the porous membrane was affected by the pressure of hot-pressing as well as the hot-pressing temperature.

Abstract: Copper-carbon composites are very promising functional materials used as electrical contact devices due to their high electrical conductivity, thermal conductivity and excellent wear resistance. In the present study the influence of carbon forms (including carbon nanotubes, graphite nanopowder and graphene) on the properties of copper matrix composites was examined. The composites were fabricated using the powder metallurgy method. The optimal parameters of the hot-pressing process in vacuum were fixed as follows: the temperature of 525°C, the pressure of 600 MPa and the time of 10 min. The wear tests were performed in dry conditions using an SRV (Schwingungs Reibung und Verschleiss) friction and wear tester in a reciprocating motion. The friction and wear behaviour of copper with 3 vol.% of carbon were investigated. Scanning electron microscopy (SEM) was used to analyse the worn surfaces and debris, and finally the wear mechanism was discussed.

Abstract: In order to explore the enhancing method of rice straw based composites, glass fiber (GF) was introduced into the preparation of composites of poly (vinyl alcohol) (PVA) and rice straw slice (RSS). The tensile performances and hardness of composites were characterized. Results showed that GF had obvious enhancing role on PVA/RSS composites. The tensile strength of the composites first increased and then decreased with increasing GF amount. When the mass ratio of RSS, PVA and GF was 20:15:7, the composite reached its maximum strength of 23.45 MPa, which increased by 1.49 times compared to the composites without GF. The strength at tensile break of composites increased with the increase of GF amount. The maximum of strength at tensile break was 23.12 MPa when GF amount was 9 g. The stretch of composites first increased and then decreased with increasing GF amount. The addition of GF had no effect on the hardness of composites.

Abstract: Composites with the chopped segments of lower part of rice straw (LRSS) as main constituent, poly (vinyl alcohol) (PVA) as adhesive constituent and waste paper (WP) as enhancing constituent were prepared by hot-pressing method. WP showed good enhancing role and certain toughening effect. WP made tensile strength increase by 86% and strength at tensile break by 69%; when composites were prepared at 40% PVA content, 140°C for 10 min. The tensile stretch and stretch at maximum tensile force of WP enhanced composite were respectively 16.5% and 14.3%, while those were respectively 12.3% and 11.9% without WP. The tensile strength of the composites increased with increasing PVA content. From 20% PVA content to 50% PVA content, tensile strength increased by 42.8%. When PVA content was 50%, the composite reached its maximum strength of 8.71 MPa. The hardness of composites lay between 91 and 97.

Abstract: By using α-and/or β-SiC powders, the effects of initial α-phase content on the microstructure and thermal properties of the SiC ceramics sintered with Y₂O₃ and Sc₂O₃ were investigated. When α-SiC powder was used, the microstructure consisted of large equiaxed grains and small equiaxed grains. The average grain size decreased with increasing α-SiC content in the starting composition. The thermal conductivity decreased with increasing α-SiC content in the starting composition. Such results suggest that the grain growth of SiC ceramics is beneficial in increasing the thermal conductivity of liquid-phase sintered SiC ceramics. The thermal conductivity of SiC ceramics processed from a 90% β-SiC-10% α-SiC powder mixture was 159 W/m∙K at room temperature.