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Effects of Sr on the microstructure,tensile and creep properties of AZ61-0.7Si magnesium alloy

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International Journal of Minerals,Metallurgy and Materials 2009年第1期16卷 89-95页

作者： ming-bo yang Jia Shen Liang Bai Fu-sheng Pan Materials Science and Engineering College Chongqing Institute of Technology Chongqing 400050 China Materials Science and Engineering College Chongqing University Chongqing 400030 China

The modification and refinement of Mg2Si phase is thought to be one of the key aspects to improve the mechanical properties of Si-containing magnesium alloys. In this article, the effects of Sr on the microstructure, tensile and creep properties of AZ61-0.7Si magnesium alloy were investigated. The results indicate that adding small amounts of Sr to AZ61-0.7Si alloy can modify and refine Chinese script shaped Mg2Si phases in the alloy. After adding 0.03wt%-0.09wt% Sr to AZ61-0.7Si alloy, the Mg2Si phases in the alloy change from the coarse Chinese script shape to fine granule and/or irregular polygonal shapes. The modification and refinement mechanisms of Mg2Si phases in Sr-containing AZ61-0.7Si alloys are possibly related to the reduction of growth rate and the enhancement of nucleation ratio for Mg2Si particles during the solidification process. Owing to the modification and refinement of Mg2Si phases, the tensile and creep properties of Sr-containing AZ61-0.7Si alloys are greatly improved.

关键词： magnesium alloy Mg2Si phase Sr addition mechanical properties microstructure

Effects of aging treatment processes on microstructures and mechanical properties of AZ63 casting magnesium alloy

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China Foundry 2023年第4期20卷 307-314页

作者： Chun-yu Li Hao-bo Wei Shi-hui Ruan Jie-yi Chen Zong-gang Wu ming-bo yang Materials Science&Engineering College Chongqing University of TechnologyChongqing 400050China

The effects of three different aging treatment processes,namely single-stage,double-stage,and reverse double-stage aging treatment processes,on the microstructures and mechanical properties of the AZ63(Mg-6Al-3Zn-0.25Mn)casting magnesium alloy were investigated and *** results indicate that the microstructures of all the aged alloys under the three treatment processes are mainly composed ofα-Mg,Mg17Al12),and Al4Mn phases,indicating that the double-stage and reverse double-stage aging treatments have no obvious effect on the type of alloy ***,as compared with the single-stage and double-stage processes,the reverse double-stage process has a great effect on the quantity of the *** the reverse double-stage aging treatment,which results in a stronger drive for decomposition of the supersaturated solid solution,the number of Mg17Al12phases precipitated in the grains significantly *** addition,as compared with the single-stage aged alloy,the tensile properties at room temperature for both the double-stage and reverse double-stage aged alloys are significantly *** them,the reverse double-stage aged alloy achieves the highest tensile strength,yield strength,and elongation of 295 MPa,167 MPa,and 8.6%,respectively.

关键词： magnesium alloys Mg-Al based alloys AZ63 alloy heat treatment aging treatment

Directed Self-assembly of Vertical PS-b-PMMA Nanodomains Grown on Multilayered Polyelectrolyte Films

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Chinese Journal of Polymer Science 2020年第1期38卷 92-99,I0008页

作者： Kai Liu Chun-ming yang bo-ming yang Lan Zhang Wen-Chao Huang Xiao-Ping Ouyang Fu-Gang Qi Nie Zhao Feng-Gang Bian College of Materials Science and Engineering Xiangtan UniversityXiangtan 411105China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai201204China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai201204China

Layer-by-layer polyelectrolyte self-assembly, a common method for preparing high-quality ultra-thin films, was employed to direct the self-assembly behavior of polystyrene-block-poly(methyl methacrylate)(PS-b-PMMA) block copolymer for the first time. Differing from the previous neutral polymer brushes anchored to silicon substrates via chemical modification, polyelectrolyte multilayers(PEMs) were anchored by electrostatic interaction and provided a stable, smooth, and neutral interface. In the present study, PS-b-PMMA was deposited on poly(acrylamide hydrochloride)/poly(acrylic acid)(PAH/PAA) PEMs prepared by layer-by-layer self-assembly to successfully yield vertical nanodomains after thermal annealing. Seven layered PEMs revealed an excellent, smooth surface, with a low roughness of 0.6 nm. The periodic structure with interlamellar spacing of 47 nm was determined by grazing-incidence small-angle X-ray scattering(GISAXS). The morphology of the PS-b-PMMA nanodomains depended on the polyanion-to-polycation concentration ratio, which is related to the interaction between the block copolymer and the substrate. Our results demonstrate that layer-by-layer self-assembly is a helpful method for the phase separation of block polymers and the fabrication of vertical, ordered nanodomains.

关键词： Block copolymer Polyelectrolyte Self-assembly GISAXS

Synthesis of Inorganic Silica Grafted Three-arm PLLA and Their Behaviors for PLA Matrix

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Chinese Journal of Polymer Science 2019年第3期37卷 216-226页

作者： Da-Wei Shi Xiang-Ling Lai Yuan-Ping Jiang Cong Yan Zheng-Ying Liu Wei yang ming-bo yang State Key Laboratory of Polymer Materials Engineering College of Polymer Science and Engineering Sichuan University

The low melt strength and poor crystallization behavior severely limit the processing and application of poly(lactic acid)(PLA) as biodegradable film materials. In this work, three-arm poly(L-lactic acid)(3A-PLLA) grafted silica nanoparticles with two kinds of topology structures were introduced into PLA matrix to improve the biodegradation performance. Different methods were used to characterize the structure of the grafted 3A-PLLA chains, the grafting density, and the thermal decomposition behavior of the nanoparticles. By varying the mass ratios of raw materials and altering the order of dropping solution in the reaction, high grafting densitytangled 3A-PLLA grafted SiO_2 was synthesized as "3A-PLLA grafting to SiO_2"(GTS), while low grafting density-stretched 3A-PLLA grafted SiO_2 was obtained as "SiO_2 grafting to 3A-PLLA"(GTA). Topology of nanoparticles as well as the filler-matrix interaction is critically important to structure bio-nanocomposites with desirable properties. Thus, the GTS and GTA nanoparticles were introduced into PLA matrix to assess the effect. The SEM images showed the uniform dispersion of the modified nanoparticles, while the shear rheology results revealed that GTA nanoparticles made a more significant contribution on the melt-strengthening and relaxation time-extension of PLA. Moreover, it is suggested that GTA nanoparticles were more effective to act as a nucleating agent for PLA, which was proved by differential scanning calorimetry(DSC) and polarized optical microscopy(POM) researches. All of the improvements mentioned above of GTA nanocomposites can be ascribed to stronger entanglements between 3A-PLLA stretched by nano-SiO_2 and PLA matrix.

关键词： Poly(lactic acid) Nanocomposites Surface grafting Topology Crystallization

Sustainable conversion regenerated cellulose into cellulose oleate by sonochemistry

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Frontiers of Chemical Science and Engineering 2023年第8期17卷 1096-1108页

作者： De-Fa Hou Pan-Pan Yuan Zi-Wei Feng Meng An Pei-Yao Li Can Liu ming-bo yang National Joint Engineering Research Center for Highly-Efficient Utilization Technology of Forestry Resource Southwest Forestry UniversityKunming 650224China College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China

Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and ***,due to the low reactivity of natural cellulose,it remains challenging to rapidly prepare cellulose derivatives with high degrees of ***“cavitation effect”of ultrasound can reduce the particle size and crystalline index of cellulose,which provides a possible method for preparing cellulose ***,a feasible method was proposed for efficiently converting regenerated cellulose to cellulose oleate with the assistance of ultrasonic *** adjusting the reaction conditions including ultrasonic intensity,feeding ratios of oleic acid,reaction time,and reaction solvent,a series of cellulose oleates with degrees of substitution ranging from 0.37 to 1.71 were ***,the effects of different reaction conditions on the chemical structures,crystalline structures,and thermal behaviors were investigated *** oleates with degrees of substitution exceeding 1.23 exhibited amorphous structures and thermoplasticity with glass transition temperatures at 159.8 to 172.6℃.This study presented a sustainable and practicable method for effectively derivatizing cellulose.

关键词： regenerated cellulose cellulose oleate sonochemistry degree of substitution thermoplasticity

Self-assembled core-shell polydopamine@MXene with synergistic solar absorption capability for highly efficient solar-to-vapor generation

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Nano Research 2020年第1期13卷 255-264页

作者： Xing Zhao Xiang-Jun Zha Li-Sheng Tang Jun-Hong Pu Kai Ke Rui-Ying Bao Zheng-ying Liu ming-bo yang Wei yang College of Polymer Science and Engineering Sichuan UniversityState Key Laboratory of Polymer Materials EngineeringChengdu610065China

As a renewable and environment-friendly technology for seawater desalination and wastewater purification,solar energy triggered steam generation is attractive to address the long-standing global water scarcity ***,practical utilization of solar energy for steam generation is severely restricted by the complex synthesis,low energy conversion efficiency,insufficient solar spectrum absorption and water extraction capability of state-of-the-art ***,for the first time,we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine(PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability(≈96%in a wide solar spectrum range of 250–1,500 nm wavelength).Moreover,such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA,as well as the interspacing between core-shell *** solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2%and 93.6%,***,the PDA@MXene photothermal layer renders the system durable mechanical properties,allowing producing clean water from seawater with the salt rejection rate beyond 99%.Furthermore,stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of ***,this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.

关键词： self-assembly polydopamine(PDA)@MXene microsphere synergistic light absorption solar-to-vapor generation light absorption stability

Influence of Extrusion Speed on the Microstructure Evolution, Interface bonding and Mechanical Response of Mg MB26/Al 7075 Composite Rod

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Acta Metallurgica Sinica(English Letters) 2019年第2期32卷 253-262页

作者： Yu Chen Rui Zhang Tao Zhou Li Hu Jian Tu Lai-Xin Shi Yan Zhi Li-Wei Lu Qiang Chen Ben-Hong Liao Lei Liu Wen-Jun Ge Jing Xiao ming-bo yang College of Material Science and Engineering Chongqing University of Technology Institute of Light Metal Structural Materials Hunan University of Science and Technology Southwest Technology and Engineering Research Institute Precision Forming Integrated Manufacturing Technology of Collaborative Innovation Center

The Mg MB26/Al 7075 composite rod,in which Mg MB26 serves as the sleeve and Al 7075 serves as the core,is fabricated via the process of *** influence of extrusion speed on the microstructure evolution,interface bonding and mechanical response of the Mg MB26/Al 7075 composite rod is *** results show that the typical extrusion texture of Mg sleeve does not change during co-extrusion;however,the average grain size in the Mg sleeve slightly changes from 1.57 lm in the case of extrusion speed of 0.3 mm/s to 2.78 lm in the case of extrusion speed of2.1 mm/*** thickness of interface transition layer increases significantly from 5.5 to 50 lm,and therefore,the interface bonding becomes deteriorative with increasing extrusion speed;in particular,many cavities emerge in the case of 1.2 and2.1 mm/s.

关键词： MB26/7075 composite rod Extrusion speed Microstructure evolution Interface bonding Mechanical response

Correction to:Influence of Extrusion Speed on the Microstructure Evolution,Interface bonding and Mechanical Response of Mg MB26/Al 7075 Composite Rod

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Acta Metallurgica Sinica(English Letters) 2024年第11期37卷 1993-1994页

作者： Yu Chen Rui Zhang Tao Zhou Li Hu Jian Tu Lai-Xin Shi Yan Zhi Li-Wei Lu Qiang Chen Ben-Hong Liao Lei Liu Wen-Jun Ge Jing Xiao ming-bo yang College of Material Science and Engineering Chongqing University of TechnologyChongqing400054China Institute of Light Metal Structural Materials Hunan University of Science and TechnologyXiangtan411201China Southwest Technology and Engineering Research Institute Chongqing400039China Precision Forming Integrated Manufacturing Technology of Collaborative Innovation Center Chongqing400039China

Correction to:Acta Metallurgica Sinica(English Letters)(2019)32:253-262 https://***/10.1007/s40195-018-0838-x Errorin Table In the original publication[1],there was an error in the contents of Mn element and Cr elemen... 详细信息

关键词： Microstructure element corrected

论公共性民生教育问题及其解决:公共政策的视角

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教育发展研究 2016年第19期36卷 8-14页

作者：杨明赵凌杨飞华杨波浙江大学教育学院杭州310028 浙江同济科技职业学院杭州311231 浙江省宁波市江东区教育局宁波315040

保障基本民生是目前我国社会建设的中心任务。民生教育问题是民众获取教育产品、分享教育权益过程中的基本民生问题。民生教育问题的实质是个人教育困扰向群体性教育困扰的转变。公共性民生教育问题主要包括教育中法律道德规定的教育问... 详细信息

保障基本民生是目前我国社会建设的中心任务。民生教育问题是民众获取教育产品、分享教育权益过程中的基本民生问题。民生教育问题的实质是个人教育困扰向群体性教育困扰的转变。公共性民生教育问题主要包括教育中法律道德规定的教育问题、许多人共同面临且个人无法解决的教育问题、具有极大的外部性的教育问题。为解决公共性民生教育问题,政府需着力制定实施公共政策。在政策问题认定、政策备选方案规划、政策确定和政策评价四个环节,决策者需要充分考虑民意诉求和保障民众教育利益。

关键词：民生教育困扰社会问题公共性民生教育问题公共政策决策机制