Papers by Keyword: Liquid Phase Sintering (LPS)

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Authors: R.A. Terpstra, J.P.G.M. van Eijk, J.C.T. van der Heijde
Authors: Sang Ll Lee, Yun Seok Shin, Jin Kyung Lee, Joon Hyun Lee, Jun Young Park
Abstract: This paper dealt with the fabricating process of liquid phase sintered (LPS) SiC ceramics containing the oxide additives of Al2O3 and Y2O3, in conjunction with the evaluation of their mechanical properties. LPS-SiC ceramics was sintered at the temperature of 1820 oC under an applied pressure of 20 MPa and a pressure holding time of 2 hour. A commercial SiC powder with an average size of about 0.3 μm was used as a starting powder. LPS-SiC ceramics with additive composition ratios of 1.5 and 2.3 (Al2O3/Y2O3) represented an excellent density of about 3.2 Mg/m3. LPS-SiC ceramics had a flexural strength of about 800 MPa and a fracture toughness of about 8.0 MPa⋅m0.5 at an additive composition ratio (Al2O3/Y2O3) of 1.5.
Authors: Ibrahim Hafed, Aziz Azizan, Rahmat Azmi, Mohammed S. Kahtan
Abstract: In this article, studies were conducted to evaluate the densification of W-Cu sintered compacts produced using two methods; liquid phase sintering (LPS) and combination of liquid phase sintering and liquid infiltration technique (LPS+LI) named Cu-melt infiltration (Cu-MI). Low concentration of nickel (1wt.%) was used to activate the sintering process in both methods. Isothermal sintering was carried out in alumina tube furnace at temperatures of 1150°C for 2 hr. under H2/Ar. as protective gas. The infiltration (Cu-MI) method proved to be effective in the densification, microstructure and hardness enhancement of the 80W-Cu compact as opposed to the other conventionally liquid phase sintered compacts. The relative densities of 80W-Cu-1Ni composites prepared by using insert method (Cu-melt infiltration) achieved 96.22% of theoretical density.
Authors: Z.S. Nikolić
Abstract: The microstructure during liquid phase sintering may change either by larger particles growing during the Ostwald ripening process or by shape accommodation. In this study, simulation of liquid phase sintering based on sub-models for solution-precipitation and grain coarsening will be considered. This paper describes a two-dimensional computer-based simulation method for determination of a qualitative and a quantitative effect of the moving grain boundary on the solid/liquid interface during liquid phase sintering of porous structure.
Authors: Zoran S. Nikolic
Abstract: This paper summarizes and reviews a number of important theoretical and experimental results connected to study of gravitational effects on liquid phase sintering. However, we will also investigate numerically gravity induced skeletal structure evolution during liquid phase sintering. Applying domain methodology, solid skeleton evolution will be introduced by definition of skeleton units determined by equilibrium dihedral angle and formation of large solid skeleton arranged in long chain of connected solid-phase domains. The settling procedure will be simulated by two submodels: free settling model in which solid-phase domains fall under gravity over already settled domains, and extended model in which settled domains continue their motion till they reach a position of their local equilibrium. Three more submodels will be also defined: rearrangement densification model, settling densification model, and Brownian motion model. It will be assumed that under gravity condition Stokes’s law settling usually dominates microstructure formation, where the settling procedure as well as settling time will be used for computation of average migration distance during defined time interval. Thus gravity induced solid-phase domain structure evolution will be simulated by simultaneous computation of displacement of the center of mass. The new methodology will be applied for simulation of microstructural evolution of a regular multi-domain model under gravity and gravity conditions.
Authors: Zoran S. Nikolic, Masahiro Yoshimura
Abstract: In this paper, we investigated numerically gravity induced skeletal settling during liquid phase sintering. The microstructural evolution will be simulated by simultaneous computation of displacement of the center of mass and mass transport due to dissolution and precipitation at the interfaces between solid-phase and liquid matrix. Common to this study based on domain methodology for definition of regular multi-domain model will be the need to relate some diffusional phenomena to essential geometric and topological attributes of the W-Ni porous microstructure influenced by skeletal settling combined with extrication of some solid-phase domains during liquid phase sintering.
Authors: Ibrahim Hafed, Azizan Aziz, Rahmat Azmi
Abstract: In this work, one stage and two stages compaction technique were used to fabricate the tungsten-copper composite powder. Liquid infiltration technique was used to consolidate the W-Cu green compact and a low concentration iron powder was added as activation material to enhance the sintering behavior. In addition, two-steps compaction process was developed for improving mechanical properties of W-Cu composite as well as segregation of Fe around W grain. The green compact was directly infiltrated at 1250 °C for about 2 hours under vacuum conditions. The microstructure, inter-boundary layer and the contamination levels of the infiltrated compacts were characterized using the scanning electron microscope (SEM) and the energy dispersive X-ray analysis (EDX). Relative sintering density varied in the range of 97.1 to 99.3 % of theoretical density, and it was highly depended on Fe concentration and method of compaction. In contrast to one stage compaction, the experimental results showed that the composites fabricated by the two stages of compact ion had better homogeneous structure, high densification and a clear segregation of inter-boundary layer of Fe-W around W grains.
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