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Featured researches published by Hongsheng Zhao.


Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 2002

Micromechanism of residual stress reduction by low frequency alternating magnetic field treatment

S. Wu; A.L Lu; Hongsheng Zhao; Hong-Sheng Fang; F. Tang

Low frequency alternating magnetic field is used to process welded samples having internal residual stress. Magnetic treatment parameters and the magnitude of stress relaxation are investigated quantitatively. The microstructural change of the material during magnetic treatment is observed by TEM and discussed from the point of view of the dislocation behavior in the processed material. A physical model of residual stress relaxation produced by magnetic treatment is presented based on the experimental results and microstructural observation.


Key Engineering Materials | 2017

ZrSi2-SiC/SiC Anti-Oxidant Coatings Prepared on Graphite Spheres by Two-Step Pack Cementation Process

Zu Jie Zheng; Ping Zhou; Hongsheng Zhao; Zi Qiang Li; Xiao Xue Liu; Kai Hong Zhang; Bing Liu

A ZrSi2-SiC/SiC double layer was fabricated on the surface of graphite spheres by two-step pack cementation with zirconium, silicon, and graphite powders as mainly raw materials. The microstructure, phase, oxidation behavior, and thermal shock resistance of the ZrSi2-SiC/SiC composite coatings were studied. The results show that the outer coating is composed of ZrSi2 and SiC and the inner coating is composed of SiC, of which the thickness is 450 μm. Isothermal oxidation test was conducted in air at 1773 K for 20 h and a weight increase of 1.69% were recorded. After 10 times of thermal shock tests between 1473 K and room temperature, the weight of the coated specimens decreased by only 1.14%. The excellent oxidation resistance is due to the production of SiO2 and ZrSiO4 in the process of the oxidation of SiC and ZrSi2, forming a glass phase that can effectively prevent further oxidation.


Key Engineering Materials | 2014

Synthesis and Characteristics of Porous Silicon Carbide Ceramic Reinforced by Silicon Carbide Whiskers

Xiao Xue Liu; Hongsheng Zhao; Hui Yang; Kai Hong Zhang; Zi Qiang Li

Silicon powder and phenolic resin were used as raw materials to produce porous silicon carbide (SiC) ceramics, with SiC whiskers (SiCw) as reinforcement additionally. Starting with the preparation of core-shell structure precursor powder through coat-mix method, and then by carrying out molding, carbonization and sintering processes, SiCw/SiC ceramic examples were produced. The phase composite, fracture surface morphology, pore size and porosity, bending strength and thermal expansion coefficient of the final product were measured. Results show that the addition of SiCw apparently improved the intensive property of the products and the changing pattern were quantitatively analyzed; while little influence was observed on some other properties such as phase composition and thermal expansion coefficient. It means that SiCw can strengthen porous silicon carbide ceramics without weakening their thermal properties, which is particularly important because of its application in the field of high temperature fluid filtration. Incorporated SiCw is supposed to work in accordance with some toughening mechanism such as load transferring and matrix prestressing. Microstructure, pore evaluation and weight loss rate during carbonation and sintering were also noted to describe the procedure better.


Materials Science Forum | 2016

SiC/SiO2 Coating on Matrix Graphite Spheres of HTR Fuel Element Produced by a Two-Step Pack Cementation/High-Temperature Oxidation Process

Ping Zhou; Zi Qiang Li; Hongsheng Zhao; Kai Hong Zhang; Xiao Xue Liu; Bing Liu

Graphite is one of the most important material for the reactor core and fuel elements of high temperature gas-cooled reactor (HTR). Improving the oxidation resistance of graphite is very essential for the research of new fuel elements and the development of HTR. In this study, a gradient SiC layer of 500~700 μm was prepared on matrix graphite spheres by a two-step pack cementation, and the outer SiO2 layer prepared by the high-temperature oxidation process. The phases, microstructure, bonding strength and oxidation resistance of SiC/SiO2 coated matrix graphite spheres were investigated. The SiC/SiO2 coated matrix graphite spheres were carried on rapid thermal shocking tests from 1773 K to room temperature for 50 times without any cracks. The SiC/SiO2 coated matrix graphite spheres exhibits excellent anti-oxidation properties. No obvious weight loss was found after isothermal oxidation in air at 1273 K for 50 h and the weight gain was less than 1% at 1773 K in air for 50 h due to the oxidation of SiC layer.


Key Engineering Materials | 2016

Sintering of SiC Coating Layer on Graphite Spheres Prepared by Pack Cementation

Ping Zhou; Zi Qiang Li; Hongsheng Zhao; Kai Hong Zhang; Xiao Xue Liu; Bing Liu

Pack cementation is an effective method in the manufacture of SiC coating on carbon material substrate surface, which is a controllable and simple process. Meanwhile, due to the reactive infiltration process of powder mixture into the substrate, a gradient transition structure layer is formed between the substrate and outer layer. In this paper, SiC was coated on the spherical substrates taken from the matrix graphite pebbles of high temperature gas-cooled reactor (HTR) fuel element. Relations between the Si/C content ratio of the pack mixture and the thickness of SiC layer were studied. Analysis found that Si/C content ratio, powder size and sintering time are factors influenced the thickness of the coating layers. When the Si/C content ratio was higher than 3:1, a uniform thickness coating bonded well with the substrate was obtained. The composition phases and thickness of coating layer etc. also had obvious changes along with the change of the Si/C content ratio in this research.Results also show that sintering atmosphere and particle size of powders are important factors affecting coating microstructure, while a vacuum atmosphere can smaller powder size can help to get a dense structure.


Key Engineering Materials | 2012

Effect of Aging pH Value on the Properties of Porous SiC Ceramics Produced through Coat-Mix Process

Hui Yang; Hongsheng Zhao; Zhong Guo Liu; Zi Qiang Li; Kai Hong Zhang

The core-shell structure precursor powder was synthesized through coat-mix process, and a small amount of Al2O3, SiO2 and Y2O3 composite additives were added. Porous silicon carbide ceramics were produced after molding, carbonization and sintering, and the crystalline phase, weight loss, porosity, bending strength, and thermal expansion coefficient were measured. The effect of aging pH value of coat-mix process on the characterization of porous SiC ceramics had been analyzed. The results indicate that the crosslink degree and curing rate of the phenolic resin is adjusted by changing the aging pH value, and the coating effect in the coat-mix process is improved. Thereby, the flexural strength, thermal expansion coefficient, porosity and pore distribution of the porous SiC ceramics could be adjusted according to the application requirements. When the pH value ranges from 3 to 5 or higher than 7, the phenolic resin shows a lower crosslink degree and char yield, while the ceramics show a higher porosity and a lower thermal expansion coefficient; and the flexural strength decreases as the aging environmental pH value increases.


International Journal of Minerals Metallurgy and Materials | 2009

Purity of SiC powders fabricated by coat-mix

Limin Shi; Hongsheng Zhao; Chunhe Tang

Abstract Silicon carbide powders were synthesized by the coat-mix process, with phenolic resin and silicon powders as starting materials. The effects of synthetic conditions, including sintering temperature and the molar ratio of resin-derived carbon to silicon on the composition and the purity of the resultant powders were investigated. The results show that a higher sintering temperature and an appropriate molar ratio of resin-derived carbon to silicon are favorable for producing high purity silicon carbide powders. It is found that the silicon carbide content increases slightly with increasing the sintering temperature during the solid-solid reaction. The temperature gradient plays an important role on this trend. When the sintering temperature is raised up to 1500°C, the formation of silicon carbide is based on the liquid-solid reaction, and high purity (99.8wt%) silicon carbide powders can easily be obtained. It can also be found that the optimum molar ratio of resin-derived carbon to silicon is 1:1.


Energy | 2014

Automatic X-ray inspection for escaped coated particles in spherical fuel elements of high temperature gas-cooled reactor

Min Yang; Qi Liu; Hongsheng Zhao; Ziqiang Li; Bing Liu; Xingdong Li; Fanyong Meng


Archive | 2012

System and method for detecting diameter of spherical workpiece

Ziqiang Li; Hongsheng Zhao; Kaihong Zhang; Wei Wang; Kang Wang; Xiaoxue Liu; Chunhe Tang


Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 2003

Influence of cerium on the performance of LaMO3+λ (M = Mn or Mn–Cu) perovskite-type catalyst

Duan Weng; Hongsheng Zhao; Xiaodong Wu; Luhua Xu; Meiqing Shen

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