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Fractionation of Polyolefin Elastomer by a Modified SSA Technique

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Chinese Journal of Polymer Science 2022年第10期40卷 1252-1258,I0010页

作者： Xin-Tong Zhao Yong-Feng Men State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Schoolof Applied Chemistry and Engineering University of Science and Technology of ChinaHefei 230026China

As an important part of semicrystalline polymer materials,polyolefin elastomers are widely used,and the in-depth analysis of their molecular chain structure information is of great significance to promote their rapid development.We show in this work an effort in characterizing a commercial polyolefin elastomer of ethylene/1-octene copolymer by a modified successive self-nucleation and annealing(SSA)technique.A small amount of linear polyethylene was blended with the ethylene/1-octene copolymer serving as nucleation agent during SSA.It turned out that a tiny fraction of linear polyethylene can significantly promote the crystallization of the copolymer during cooling from different annealing temperatures and increase the melting temperature of the fractions so that providing apparent methylene sequence length much closer to the real value than obtained by traditional SSA technique.

关键词： Polyolefin elastomer Ethylene-co-octene Thermal fractionation SSA micro structure

RESEARCH OF micro ELECTRO DISCHARGE MACHINING EQUIPMENT AND PROCESS TECHNIQUES

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Chinese Journal of Mechanical Engineering 2002年第2期15卷 177-181页

作者： Li Yong Guo Min Li Fang Zhou Zhaoying Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, China Department of Precision Instruments and Mechanology Tsinghua University 北京 100084

micro electro discharge machining (micro EDM) is a feasible way tomanufacture micro structures and has potential application in advanced industrial fields. For therealization of micro EDM, it is necessary to pay careful attention to its equipment design and thedevelopment of process techniques. The present status of research and development of micro EDMequipment and process techniques is overviewed. A micro electro discharge machine incorporated withan inchworm type of micro feed mechanism is introduced, and a micro electro discharge machine fordrilling micro holes suitable to industrial use is also introduced. Some of the machiningexperiments carried out on the micro EDM prototypes are shown and the feasibility of the micro EDMtechnology to practical use is discussed.

关键词： micro electro discharge machining Inchworm mechanism Friction drivemechanism micro electrode micro hole micro structure

Effect of freeze-thaw cycles on soil engineering properties of reservoir bank slopes at the northern foot of Tianshan Mountain

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Journal of Mountain Science 2021年第2期18卷 541-557页

作者： QIN Zi-peng LAI Yuan-ming TIAN Yan ZHANG Ming-yi State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China College of Civil Engineering and Mechanics Lanzhou UniversityLanzhou 730000China

The instability of soil bank slopes induced by freeze-thaw cycles at the northern foot of Tianshan Mountain is very common.The failure not only caused a large amount of soil erosion,but also led to serious reservoir sedimentation and water quality degradation,which exerted a lot of adverse effects on agricultural production in the local irrigation areas.Based on field investigations on dozens of irrigation reservoirs there,laboratory tests were carried out to quantitatively analyze the freeze-thaw effect on the soil engineering characteristics to reveal the facilitation on the bank slope instability.The results show that the softening characteristics of the stressstrain curves gradually weaken,the effective cohesions decline exponentially,the seepage coefficients enlarge,and the thermal conductivities decrease after 7 freeze-thaw cycles.The freeze-thaw effect on the specimens with low confining pressures,low dry densities and high water contents is more significant.The water migration and the phase transition between water and ice result in the variations of the soil internal microstructures,which is the main factor affecting the soil engineering characteristics.Sufficient water supply and the alternation of positive and negative temperatures at the reservoir bank slopes in cold regions make the water migration and phase transition in the soil very intensely.It is easy to form a large number of pores and micro cracks in the soil freezing and thawing areas.The volume changes of the soil and the water migration are difficult to reach a dynamic balance in the open system.Long-term freeze-thaw cycles will bring out the fragmentation of the soil particles,resulting in that the micro cracks on the soil surfaces are developing continuously.The soil of the bank slopes will fall or collapse when these cracks penetrate,which often happens in winter there.

关键词： Mechanical properties Seepage coefficient Thermal conductivity micro structure Freeze-thaw cycles Reservoir bank slope

REHEATING TEMPERATURE CONTRAST AND microstructureS OF 7075 Al ALLOY CAST BY LIQUIDUS SEMI-CONTINUOUS CASTING

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Acta Metallurgica Sinica(English Letters) 2002年第6期15卷 551-555页

作者： J. Dong, G.M. Lu and J.Z. CuiThe Key Lab. of Electromagnetic Processing of Material, Ministry of Education, Northeastern University, Shenvane 110004, China Ministry of Education Northeastern Univ. Shenyang 110004 China

In this study, reheating of liquidus semi-continuous cast billets of 7075 Al alloy was carried out in a resistance furnace, and the temperature contrast of the outer and the center of the reheated billets was investigated, then the reheating microstructures were investigated. Results show that: the difference of temperature between the outer and center is small and the difference of their microstructures are also small. During reheating at 576℃ the spheroidization of grains is significant after 5min and no rosettes are visible after 20min by optical microscopy. Similar observations were madeon materials reheated at 596℃, but the ripening process is faster. The grains growup to 30-60μm, fine enough for thixoforming.

关键词： reheating 7075 Al alloy liquidus casting micro structure

microstructural Characteristic of Montmorillonite and Its Thermal Treatment Products

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Journal of Wuhan University of Technology(Materials Science) 2005年第1期20卷 83-88页

作者：吴平霄 Department of Environmental Science and Engineering South China Universithy of TechnologyGuangzhou 510640China

The montmorillonite was studied by differen t methods, such as chemical analysis, DAT, TG, X RD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octa hedra sheets begins dehydrating when the thermal treatment temperature reaches 659℃, but th e layer structure remains the same,and the corresponding Al(Ⅵ) is turned into Al(Ⅳ) in octahedra sheets. When the temperature reaches 900℃, the layer struct ure of montmorillontite is destroyed, and the new mineral phase μ-cordierite i s found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase.Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅵ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.

关键词： montmorillonite thermal treatment product micro structure μ-cordierite

Hydration Kinetics of Phosphorus Slag-cement Paste

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Journal of Wuhan University of Technology(Materials Science) 2011年第1期26卷 142-146页

作者：陈霞 School of Civil Engineering Wuhan University Department of Mateials and structure Changjiang River Scientific Research lnstitute

Hydration characteristics of Portland cement paste with phosphorus slag powder incorporated and hydration kinetics was investigated with SEM, X-ray diffraction, DTA-TG and calorimeter Ⅱ80. Results showed that phosphorus slag powder could reduce total amount of hydration products yet had little influence on the type of hydration products. The total amount of heat of hydration was decreased by 49.11% and the final setting was postponed by 2.28 h when phosphorus slag powder substituted 35% Portland cement by mass. The accelerating stage of this composite paste was controlled by catalysis, decreasing stage controlled by both catalysis and diffusion while stabilizing stage by diffusion alone. Hydration resistance and activation energy were reduced and hydration speed was accelerated.

关键词： phosphorus slag hydration kinetics cement micro structure mechanism.

microstructureS AND THE structure STABILITY OF INCONEL 725, A NEW AGE-HARDENABLE CORROSION RESISTANT SUPERALLOY

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Acta Metallurgica Sinica(English Letters) 2003年第2期16卷 145-150页

作者： J.X.Dong M.C.Zhang S.K.Mannan School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083ChinaSchool of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083ChinaSpecial Metals CorporationHuntingtonWV25705USA

INCONEL725 is a highly corrosion resistant nickel based alloy capable of being age-hardened to high strength levels. The micro structure observations and the phase identification after a standard heat treatment were investigated. The results show that the precipitation phases include the strengthening phasesγ', γ', and 8 phase, primary carbide phase TiC, as well as M6 C carbide and a little extent MC (mainly TiC) precipitates which nucleate mainly at grain boundaries. An isothermal aging study was carried out on this alloy for up to 10 000 hours at 593℃. This additional aging did not affect the tensile strength. However, micro structures show that the thermal exposure has a little additional effect. With increasing the exposure time, the size of γ' phase slightly increases, almost no change for γ' phase, while M6C carbides precipitated at grain boundaries have an increased and complex tendency on a few grain boundaries. The experimental results illustrate the excellent structure stability of the age-hardenable IN725 at 593℃.

关键词： superalloy INCONEL725 micro structure long-term exposure

THE INTERFACE OF TERNARY-BORIDE-BASED HARD CLADDING MATERIAL

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 47-50页

作者： Y.G.Wang Z.Q.Li D.Zhang State Key Laboratory of Metal Matrix Composites Shanghai Jiaotong UniversityShanghai 200030 ChinaMechanical Engineering DepartmentShandong University Jinan 250061 ChinaState Key Laboratory of Metal Matrix CompositesShanghai Jiaotong UniversityShanghai 200030China

The interfacial microstructure of ternary-boride-based hard cladding material (YF-2) has been studied using scanning electron microanalyser (SEM), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). Results show that there are chemical reactions and elements diffusion in the interfacial zone, which make the interface bonding well and bonding strength ideal at the interface. The results gotten by studying of crack produced by Vickers indentation technique in the interfacial zone show that it is difficult to produce crack in the interface, the crack length in the cladding layer is longer than that to the interface, the crack which propagate to the interface stops at the interface rather than propagates along the interface. This suggests negligible residual stresses have developed because of thermal expansion mismatch. The bonding strength of the interface is 550MPa, which has been gotten by cutting test. The result gotten by analyzing the fracture surface shows that the fracture occurs at the side of cladding layer, which confirms that the bonding strength at the interface is higher than that in the cladding layer.

关键词： ternary boride cladding material interface micro structure

Rietveld refinement of powder X-ray diffraction,microstructural and mechanical studies of magnesium matrix composites processed by high energy ball milling

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Journal of Magnesium and Alloys 2018年第4期6卷 390-398页

作者： T.Ramkumar M.Selvakumar R.Vasanthsankar A.S.Sathishkumar P.Narayanasamy G.Girija Department of Mechanical Engineering Dr.Mahalingam College of Engineering and TechnologyPollachi 642003India Department of Automobile Engineering Dr.Mahalingam College of Engineering and TechnologyPollachi 642003India Department of Mechanical Engineering Sree Sowdambika College of EngineeringAruppukottai 626134India Department of Mechanical Engineering Kamaraj College of Engineering and TechnologyVirudhunagar 626001India

This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.microstructural examination is carried out using Scanning Electron microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.

关键词： Rietveld refinement X-ray diffraction Crystal structure micro structure Wear and corrosion