Papers by Author: Jia Lin Sun

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Authors: Xi Gao Peng, Jia Lin Sun, Gan Shi, Shao Ping Huang
Abstract: Based on an extensive comparison of test methods for abrasion resistance from home and abroad, a new technique for abrasion resistance at elevated temperature has been developed with some improvements. Two connected airtight chambers are designed to prevent compressed air from entering the sample chamber, so that heat loss of the sample chamber can be reduced and the chamber temperature is less disturbed. The sample surface temperature can reach stable within 5 min and the temperature fluctuation on sample surface can be less than 20°C in the course of inleting the compressed air at working temperatures up to1400°C. The repeatability was tested using float-glass plate as reference sample at ambient temperature and using high alumina bricks for elevated temperature. A variation coefficient under 7% at ambient temperature has been achieved. Comparison of abrasion resistance at elevated temperature was tested respectively on a high alumina brick and on a silicon nitride bonded silicon carbide brick and the results could be significantly distinguished. Nitrogen can be blown into sample chamber during heating the furnace to prevent nonoxide bearing samples from being oxidized.
Authors: Y.H. Chen, X.J. Li, X.F. Zhou, Jia Lin Sun, W.H. Huang, J. Hu
Abstract: Mechanical properties of DNA, for example the elastic modulus, are of vital importance for its biological function. Previously, the modulus is mainly obtained by bending, stretching and twisting DNA using various techniques and tools. By applying vibrating mode scanning polarization force microscopy (VPSFM), deformations of DNA under ultra-small indentation forces can be measured and so the radial modulus can be computed. In this paper, modeling of the VPSFM measuring system is presented. The system is modeled as a spring-mass-damper oscillator under various force fields, such as van der Waals force, attractive electrical force and repulsive interactions between the tip and sample. The electrical polarization force is described by using uniformly charged line model and the DNA is considered to be a simple elastic rod. By numerically integrating the equation of tip motion, the contact force and the radial modulus of DNA under different deformation can be calculated. We found that in measuring radial modulus of DNA, the existence of substrate cannot be neglected, especially when the relative large deformation is reached.
Authors: Hua Zhi Gu, Hou Zhi Wang, Yan Ruo Hong, Jia Lin Sun, Wen Jie Zhang
Abstract: Hydration resistance of three commercially available high-purity MgO-CaO clinkers were investigated and compared in the present paper. The results show that, as well as CaO content, microstructural morphology of MgO–CaO clinker affects its hydration resistance. The microstructure in which CaO is present at the grain boundaries of MgO leads to poorer hydration resistance, whereas the one in which CaO and MgO are distributed alternately confers much improved hydration resistance on the clinker, especially when MgO level is high enough to cover most of the CaO crystals.
Authors: Mu Yun Lei, Cun Xin Huang, Jia Lin Sun
Abstract: In this paper, transparent polycrystalline magnesium aluminate spinel was fabricated by hot pressing ultra fine high purity spinel powder using LiF as the sintering aid in vacuum, then hot isostatic pressing (HIPing) the sintered body to improve the optical properties of the sample. The transmittance and the strength of the samples before and after HIPing were measured; morphologies of the fracture surface of the samples before and after HIPing were observed. Following hot pressing, the grain size of the sample is small; the transmission values are low and may varied at different sites in the same sample. After HIPing, the strength of the sample decreased, the grain size increased obviously, and the transmittance and the uniformity of transmittance increased significantly. The panel of transparent spinel up to 200 mm in diameter and 8 mm thick was fabricated by this method; the average transmittance of the spinel is above 80% in the range between 2 μm and 5 μm .
Authors: Xiao Hui Wei, Yan Jun Wang, Hong Xia Li, Jia Lin Sun
Abstract: The influence of silicon addition on the microstructure and properties of corundum-mullite refractory was studied. Results show that Si addition as raw material of the matrix can accelerate mullite crystal formation. The oxidation of Si leads to nucleation of mullite via liquid phase and gas phase. The network microstructure is formed by tiny mullite crystals with few glass phase. So it enhances obviously the high temperature strength of sintered corundum-mullite refractory.
Authors: Rong Lin Wang, Jing Long Bu, Zhi Fa Wang, Jia Lin Sun
Abstract: Zr-Al-O-N composites were prepared in N2 atmosphere at 1600oC with Ca-PSZ and Al powders as raw materials. Phase composition of the composites and formation reaction mechanism were investigated by XRD and SEM analyses. With Al content increaseing from 1% to 50%, phase composition of the composites were changed step by step. The results showed that phase compositions of the composites are related to Al content.
Authors: Shao Feng Wang, Chang An Wang, Jia Lin Sun, Li Zhong Zhou, Yong Huang
Abstract: Porous SiC ceramics with high porosity and high strength were fabricated by gelcasting, with tert-butyl alcohol (TBA) as solvent, acrylamide (AM) as monomer, and in-situ reaction bonding with a-Al2O3 as sintering additive. SiC suspension with 10 vol% solid loading was successfully solidified by gel-casting to form high strength green body. The results showed that the compressive strength of the porous SiC ceramics increased with sintering temperature from 1300 to 1450°C, but porosity had little change, due to formation of more volume of cristobalite and mullite phases on the surface of SiC grains, accompanied by a large volume expansion effect. Very narrow single-peak distributions with about 2 mm median pore diameter could be found for the porous SiC ceramics. The porosity and compressive strength of the porous SiC ceramics sintered at 1450°C were 71.21 % and 12.14 MPa, respectively.
Authors: Hua Zhi Gu, Hou Zhi Wang, Jia Lin Sun, Wen Jie Zhang, Dong Zhi Hou, Cheng Ji Deng, Yan Ruo Hong
Authors: Feng Cao, Shi Gang Long, Jia Lin Sun, Yan Ruo Hong
Authors: Jian Xin Deng, Tong Kun Cao, Jia Lin Sun
Abstract: Al2O3/TiC ceramic tool materials with the addition of solid lubricants such as BN and CaF2 were produced by hot pressing. Effect of the solid lubricants on the microstructure and mechanical properties has been studied. Results showed that AlN phase resulted from the reaction of Al2O3 with BN was formed in Al2O3/TiC/BN composite after sintering. Significant micro-cracks resulted from the residual stress owing to the difference in the thermal expansion coefficient were found on the polished surface, and caused large mechanical properties degradation. While Al2O3/TiC/CaF2 composite showed higher flexural strength, fracture toughness, and hardness compared with that of Al2O3/TiC/BN composite owing its porosity absent and finer microstructure.
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