Papers by Keyword: Microwave Sintering

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Authors: Hua Wei He, Bo Li, Guang Da Li, Zhi Xiu He, Zhi Qing Chen
Abstract: This study sought to compare the biocompatibility of four dental ceramics so as to provide indications useful for the further development of dental materials. Osteoblasts were obtained by culturing the cranial explant of SD rat and cultured in vitro when they were seeded onto four different materials: hydroxyapatite, bioactive glass ceramics, tricalciumphosphate-hydroxyapatite and nano-hydroxyapatite (nHA). The phase contrast microscope and scanning electron microscope were used to evaluate the cell morphology and attachment. The content of alkaline phosphatase was calculated by molecular biological methods. MTT method was performed to find the alteration of proliferation. Then by use of wash way method, the adhesion ability was tested. The results showed that all of the four bioceramics had good cytocompatibility. There were significant differences among them on the levels of cell growth, differation and adhesion in vitro. The biocompatibility of nHA is the best and of conventional HA is the worst.
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Authors: S. Chockalingam, J.P. Kelly, V.R.W. Amarakoon, James R. Varner
Abstract: Microwave sintered Si3N4-MgO system that contains 2, 4 and 10 wt% of ZrO2 as secondary particulates were investigated with respect to phase transformation and microstructure development. The experimental results of microwave sintered samples were compared with conventional methods. Complete α to β phase transformation was observed in the case of microwave sintered samples due to the volumetric nature of microwave heating. High temperature X-ray diffraction (HTXRD) analysis was performed to study in-situ the oxidation behavior of Si3N4 specimens. Si3N4 specimens with 10 wt % ZrO2 were exposed to air at temperature between 25°C and 900°C for up to 24 hours. Microwave sintered sample were structurally stable in air 25°C and 900°C for up to 24 hours of testing.
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Authors: Kazuki Tajima, Hae Jin Hwang, Mutsuo Sando, Koichi Niihara
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Authors: Kazuki Tajima, Hae Jin Hwang, Mutsuo Sando, Koichi Niihara
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Authors: Li Xiang Chen, Chu Lei, Ning Zhang, Chang Shun Jin, Yan Sheng Yin
Abstract: In this paper, we use electromagnetic simulation software HFSS to investigate the distribution of electromagnetic field of microwave sintering cavity, and establish a simulation model for the TE103 single mode cavity. We then obtain the optimal condition for the distribution of electromagnetic field by capturing the contour of distribution of electrical field of cavity through simulation. Our research shows that electromagnetic simulation software HFSS can use color to effectively demonstrate the intensity distribution of electromagnetic field of internal space and various cross-sections within the microwave sintering cavity, which provides a novel method for improving and applying new ways to compute and predict the key features of field distribution. The simulation results by HFSS can guide the practical microwave sintering techniques as well as the design and improvement of the sintering cavity.
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Authors: Tehreem Kanwal, Rub Nawaz Shahid, Naeem Ul Haq Tariq, Fahad Ali, M. A. Rafiq, Muhammad Iqbal, J.I. Akhter, Bin Awais Hasan
Abstract: The ceramic-metal composites that have all phases continuous throughout the structure are known as Interpenetrating Phase Composites (IPCs) and they have many applications in various fields. In this investigation ZrO2-Ni IPCs of varied compositions were synthesized using tubular furnace and microwave furnace routs. Samples were Characterized using BET surface area, Pycnometer density, dilatometry and scanning electron microscopy. The Electrical parameters of the composites were measured using impedance spectrometer. Results indicate that threshold percolation reached at 40 volume percent of Ni in both cases. Moreover, no significant difference was observed in BET surface area and CTE of composites prepared by conventional and microwave sintering processes.
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Authors: A. Arellano, J. Lemus-Ruiz, D. Bouvard, L. Olmos
Abstract: The effect of the transformation of phase in nanopowders of transition alumina has showed to be detrimental for the final characteristics of the consolidated materials. It was found that the complete transformation from gamma (γ-Al2O3) to alpha (α-Al2O3) alumina generated larger grain sizes and lower relative densities. This work studies the effect of slip casting preformed on the transformation phase of alumina during microwave sintering of α-alumina nanopowders. The sintering of the samples was carried out in a typical unimodal microwave furnace with a 2.5 GHz frequency. Sintering was carried out under air atmosphere at temperatures vary between 1100 and 1500 °C with heating rate of 100 and 200 °C/min and with a sintering plateau of 5 minutes. Sample characterization was performed by XRD, SEM, and TEM. The phase quantification was calculated using the Rietveld software from the XRD patterns. To have a good heating control in the microwave system it is possible by using slip casting to preform compact. It was observed that the heating rate has a strong effect on the phase transformations. Secondary phases like θ, θ’(x, y) appeared in samples sintered with a heating rate of 200 °C/min no matter the sintering temperature. Meanwhile the complete alumina transformation was found when sample were heating at 100 °C/min.
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Authors: Mao Yan Fan, Li Fang Zhang
Abstract: As a typical composite with perovskite structure, (Ba1-xSrx)TiO3 (briefly named BST) shows many merits, This paper provides a new sol-gel method to prepare BST gel, and carry out a research and analysis on the thermal evolution of gel. The BST nanopowder is prepared by the heat treatment through the traditional sintering method and microwave sintering technique, respectively. The synthesis temperature of perovskite phase by sol-gel method decreases from 1380°C to 900°C, comparing with that by traditional solid-state reaction method. The XRD and SEM results show that microwave sintering technique can control effectively the grain growth size of BST ceramic, and the powder has the uniform chemical components and grain size of around 60nm. Furthermore, the grain size is reduced, the dielectric constant increased dramatically and the dispersivity reduced.
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Authors: Jie Zhao, Jiang Fu, Yong Fu, Yu Na Zhao, Yong Chang Ma
Abstract: Sr, Ca and Fe doped cathode materials Ln0.7Sr0.2Ca0.1Co0.7Fe0.3O2.85 (LnSCCF, Ln=La, Pr and Nd; abbreviated as L-72173, P-72173 and N-72173) were synthesized by microwave sintering (MWS) techniques. The formation process, phase structure and composition were characterized using TG/DTA, XRD and EDS. The thermal expansion behavior of the samples was analyzed in the range of 20-950 °C by thermal dilatometer. The electrical conductivity of the samples was measured with DC four-terminal method from 25 to 900 °C. The X-ray diffraction shows that the samples exhibit a single phase with rhombohedral or cubic perovskite structure after sintered at 1200 °C for 20 min. The electrical conductivity of the samples increases with temperature up to a maximum, and then decreases gradually at higher temperature owing to the creation of oxygen vacancies. The small polaron hopping is regarded as the conducting mechanism (T 550 °C). L-72173 has higher mixed conductivity ( >300 S·cm-1) in 550-800 °C. The average TECs of L-72173, P-72173 and N-72173 are 1.389× 10-5 K-1, 1.417 × 10-5 K-1 and 1.416 × 10-5 K-1 in the range of 25-800 °C, respectively. They are thermally matched to the GDC better than the YSZ and SDC.
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