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Mechanical Properties and Thermal Shock Resistance of SrAl_(2)Si_(2)O_(8) Reinforced BN Ceramic Composites
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作者 WANG Bo CAI Delong +7 位作者 ZHU Qishuai LI Daxin YANG Zhihua DUAN Xiaoming LI Yanan WANG Xuan JIA Dechang ZHOU Yu 《无机材料学报》 SCIE EI CAS CSCD 北大核心 2024年第10期1182-1188,共7页
Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their ... Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather unsatisfactory.In this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and toughness.Then,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were investigated.The thermal shock resistance of BN-SAS ceramic composites was evaluated.Results show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight decline.At a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),respectively.Composites sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxidation on the ceramic surface and cracks due to thermal stress are also increased gradually. 展开更多
关键词 BN MATRIX composite hot-press SINTERING mechanical PROPERTY thermal shock resistance service reliability
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Effect of compression ratio on microstructure evolution of Mg−10%Al−1%Zn−1%Si alloy prepared by SIMA process 被引量:3
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作者 Li-jie CAO Guo-rui MA +2 位作者 Chun-xia WANG Zheng-jian CHEN Jia-heng ZHANG 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第9期2597-2605,共9页
A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experime... A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated.The results indicate that the average size ofα-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%.In addition,the eutectic Mg2Si phase in the Mg−10%Al−1%Zn−1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process.With the increasing of compression ratio,the morphology and average size of Mg2Si phases do not change obviously.The morphology modification mechanism of Mg2Si phase in Mg−10%Al−1%Zn−1%Si alloy by SIMA process was also studied. 展开更多
关键词 Mg−Al−Zn−Si alloy compression ratio microstructure evolution eutectic Mg2Si phase strain induced melt activation(SIMA)process
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无铅四方相钙钛矿短周期超晶格压电效应机理研究
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作者 朱振业 《物理学报》 SCIE EI CAS CSCD 北大核心 2018年第7期242-251,共10页
超晶格压电行为与内部正离子之间的内在联系尚缺乏相关的研究.本文基于密度泛函理论的第一性原理方法,研究了三种无铅四方相钙钛矿铁电超晶格(BaTiO_3/SrTiO_3,KNbO_3/KTaO_3和BaTiO_3/KNbO_3)中A,B位正离子对整体的极化和压电贡献.通... 超晶格压电行为与内部正离子之间的内在联系尚缺乏相关的研究.本文基于密度泛函理论的第一性原理方法,研究了三种无铅四方相钙钛矿铁电超晶格(BaTiO_3/SrTiO_3,KNbO_3/KTaO_3和BaTiO_3/KNbO_3)中A,B位正离子对整体的极化和压电贡献.通过计算超晶格不同轴向应变条件下原子结构和Born有效电荷,获得了超晶格和各个正离子的极化值和压电系数.结果表明,在轴向压缩应变条件下(-0.15—0 A),无铅超晶格中的正离子位移D(A)和D(B)受到抑制,在拉应变时位移才显著增大,因此极化和压电行为不明显.在轴向拉伸应变作用下(0—0.15 A),无铅超晶格中各原子的极化贡献显著增大,特别是B位原子Ti,Nb和Ta的极化贡献使得总的极化强度也显著提高,并当拉应变达到一定值,超晶格才会出现明显的压电行为.无铅超晶格的极化和压电行为主要由B位正离子贡献. 展开更多
关键词 无铅钙钛矿铁电超晶格 极化 压电系数 第一性原理计算
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Phase equilibria in Co−Al−Re ternary system at 1100 and 1300℃
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作者 Ling-ling LI Jin-bin ZHANG +3 位作者 Yue-chao CHEN Shui-yuan YANG Cui-ping WANG Xing-jun LIU 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2021年第6期1740-1747,共8页
Isothermal sections of the Co−Al−Re ternary system at 1100 and 1300℃ were determined experimentally by electron probe microanalysis and X-ray diffraction.The results show that there are seven three-phase regions in t... Isothermal sections of the Co−Al−Re ternary system at 1100 and 1300℃ were determined experimentally by electron probe microanalysis and X-ray diffraction.The results show that there are seven three-phase regions in the 1100℃ isothermal section and five three-phase regions in the 1300℃ isothermal section.The solid solubilities ofαCo,εRe and CoAl increase a little with temperature increasing from 1100 to 1300℃.The solubility of Co in compounds AlRe2,Al11Re4 and Al4Re is negligible,<1.5 at.%.And no ternary compounds are found. 展开更多
关键词 Co−Al−Re phase equilibria isothermal section
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