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Thermal-mechanical coupled effect on fracture mechanism and plastic characteristics of sandstone

Science China(Technological Sciences) 2007年第6期50卷 833-843页

作者： ZUO JianPing1,2, XIE HePing2,3, ZHOU HongWei1,2 PENG SuPing1 1 State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, China 2 Institute of Rock Mechanics and Fractals, China University of Mining and Technology, Beijing 100083, China 3 Sichuan University, Chengdu 610065, China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology Beijing China Institute of Rock Mechanics and Fractals China University of Mining and Technology Beijing China Sichuan University Chengdu China

Scanning electronic microscopy (sem) was employed to investigate fractographs of sandstone in mine roof strata under thermal-mechanical coupled effect. Based on the evolution of sandstone surface morphology in the failure process and frac- tography, the fracture mechanism was studied and classified under meso and mi- cro scales, respectively. The differences between fractographs under different tem- peratures were examined in detail. Under high temperature, fatigue fracture and plastic deformation occurred in the fracture surface. Therefore, the temperature was manifested by these phenomena to influence strongly on micro failure mechanism of sandstone. In addition, the failure mechanism would transit from brittle failure mechanism at low temperature to coupled brittle-ductile failure mechanism at high temperature. The variation of sandstone strength under differ- ent temperature can be attributed to the occurrence of plastic deformation, fatigue fracture, and microcracking. The fatigue striations in the fracture surfaces under high temperature may be interpreted as micro fold. And the coupled effect of tem- perature and tensile stress may be another formation mechanism of micro fold in geology.

关键词： sandstone, thermal-mechanical coupled effects, fractograph, plastic deformation, sem, micro fold

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Synthesis and structural characterization of Zn_3N_2 powder

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 201-210页

作者： ZONG Fujian1, MA Honglei1, XUE Chengshan2, ZHUANG Huizhao2, ZHANG Xijian1, MA Jin1, JI Feng1 & XIAO Hongdi1 1. School of Physics and Microelectronics, Shandong University, Jinan 250100, China 2. Institute of semiconductor, Shandong Normal University, Jinan 250014, China School of Physics and Microelectronics Shandong University Jinan 250100 China Institute of semiconductor Shandong Normal University Jinan 250014 China

Zinc nitride (Zn3N2) powder has been synthesized through the nitridation reaction of Zn powder with NH3 gas (at the flow rate of 500 ml/min) at the nitridation temperature of 600℃ for 120 min. X-ray diffraction (XRD) indicates that Zn3N2 is cubic in structure with the lattice constant being a = 0.9788 nm. Scanning electron microscopy (sem) and transmission electron microscopy (TEM) show that Zn3N2 powder has surface morphology of various types. X-ray photoelectron spectroscopy (XPS) shows the differences in chemical bonding states between Zn3N2 and ZnO, and confirms the formation of N–Zn bonds. Observation through high resolution transmission electron microscopy (HRTEM) also indicates that the computer simulation of the structure of Zn3N2 is consistent with the structural model put forward by Partin.

关键词： nitridation, Zn3N2 powder, structure, XRD, sem, TEM, HRTEM, XPS.

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Simulation of calcium oxalate stone in vitro

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Science China Chemistry 2003年第3期46卷 234-242页

作者：欧阳健明姚秀琼苏泽轩崔福斋 Institute of Biomineralization and Lithiasis Research Jinan University Department of Materials Science & Engineering Tsinghua University

Crystallization of calcium oxalate is studied mainly in the diluted healthy urine using scanning electron microscopy (sem), and is compared with the crystallization in the diluted patho-logical urine. It suggests that the average sizes of calcium oxalate crystals are not in direct propor-tion to the concentrations of Ca2+ and Ox2- ions. Only in the concentration range of 0.60—0.90 mmol/L can larger size of CaOx crystals appear. When the concentrations of Ca2+ and Ox2- ions are 1.20, 0.80, 0.60, 0.30 and 0.15 mmol/L in the healthy urine, the average sizes of calcium ox-alate crystallites are 9.5 × 6.5, 20.0 × 13.5 and 15.0 mm × 10.0 mm, respectively, for the former three samples after 6 d crystallization. No crystal appears even after 30 d crystallization for the samples of concentrations of 0.30 and 0.15 mmol/L due to their low supersaturations. The results theoretically explain why the probability of stone forming is clinically not in direct proportion to the concentrations of Ca 2+ and Ox2- ions. Laser scattering technology also confirms this point. The reason why healthy human has no risk of urinary stone but stone-formers have is that there are more urinary macromolecules in healthy human urines than that in stone-forming urines. These macromolecules may control the transformation in CaOx crystal structure from monohydrate cal-cium oxalate (COM) to dihydrate calcium oxalate (COD). COD has a weaker affinity for renal tu-bule cell membranes than COM. No remarkable effect of the crystallization time is observed on the crystal morphology of CaOx. All the crystals are obtuse hexagon. However, the sizes and the number of CaOx crystals can be affected by the crystallization time. In the early stage of crystalli-zation (1—6 d), the sizes of CaOx crystals increase and the number of crystal particles changes little as increasing the crystallization time due to growth control. In the middle and late stages (6—30 d), the number of crystals increases markedly while the growth rate changes little due to the nucleation cont

关键词： urinary stone, calcium oxalate, sem, biomineralization, laser scattering spectra.

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B10铜镍合金海水加速腐蚀行为

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材料工程 2017年第5期45卷 31-37页

作者：刘天娇陈惠鹏张卫方娄伟涛北京航空航天大学可靠性与环境工程技术国防科技重点实验室北京100191

B10铜镍合金具有优良的耐海水腐蚀性能,为研究其在海水中的腐蚀行为,取厦门天然海水,加入双氧水作为腐蚀加速剂,在室内模拟海水全浸腐蚀实验,采用失重法、电化学阻抗谱(EIS)技术分析B10合金在海水腐蚀中的腐蚀速率随腐蚀时间的变化规律...

B10铜镍合金具有优良的耐海水腐蚀性能,为研究其在海水中的腐蚀行为,取厦门天然海水,加入双氧水作为腐蚀加速剂,在室内模拟海水全浸腐蚀实验,采用失重法、电化学阻抗谱(EIS)技术分析B10合金在海水腐蚀中的腐蚀速率随腐蚀时间的变化规律,用不同腐蚀周期的电化学阻抗谱特征来表征工作面积为1cm^2的合金表面氧化膜的生长破坏情况。结合扫描电子显微镜(sem)、能谱分析(EDX)、XPS和拉曼光谱技术分析B10合金表面腐蚀产物膜的成分以及B10合金在海水腐蚀中的腐蚀类型。结果表明,氧化膜的生成与破坏使得合金在海水中的瞬态腐蚀速率呈先减小后增大的趋势,腐蚀产物包含碱式氯化铜Cu_2(OH)_3Cl和氧化亚铜Cu_2O,腐蚀由点蚀开始,逐渐经历了晶间腐蚀-剥蚀。

关键词： B10铜镍合金, 海水腐蚀, EIS, sem, 腐蚀产物

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Observation of the effect of cleaning the smear layer and tubule plugs with sem

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Chinese Journal of Biomedical Engineering(English Edition) 2001年第1期10卷 44-46页

作者： YU Dan-ni1,DONG Ya-li2 1 Department of stomatology of the 2nd Hospital of Tianjin Medical University,Tianjin 300211,China 2 The Electron Microscope Center of Tianjin Medical University, Tianjin 300070,China Department of stomatology of the 2nd Hospital of Tianjin Medical University Tianjin 300211China The Electron Microscope Center of Tianjin Medical University Tianjin 300070China

To clean out the smear layer on teeth surface, and protect the teeth medulla, the experiment applied the study observing the cleanup of six groups of surface smear layer of dental caries and the tubule plugs reserving effect after using of different cavity cleansers with the help of sem. The result implied that both the acidic preparations and chelator could clean out the smear layer on teeth surface in some way, but the later one could also reserve partial tubule plugs, which reduce the stimulation to the teeth medulla. So the chelator is better cleansers in clinical use.

关键词： sem, smear layer, tubule plugs, cavity cleansers

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