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Formation and vanishment of the intragranular microstructure in Si_2._2./Si_3N_4 nanocomposites

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science china(Technological sciences) 2010年第1期53卷 284-286页

作者： LUO JunTing,LIU RiPing & QI Li state key {2. of metastable materials science and technology,College of Mechanical Engineering,yanshan university,qinhuangdao 066004,china 1. state key {2. of metastable materials science and technology College of Mechanical Engineering Yanshan University Qinhuangdao 066004 China

Si2.2./Si3N4 nanocomposites were fabricated by liquid phase sintering of amorphous nano-sized silicon nitride *** intragranular microstructure was observed and *** microstructure's β-Si3N4 was formed in Si2.2. matrix at the sintering temperature higher than 1650°*** was discovered that intragranular microstructure could also disappear by transformation during high temperature *** possible mechanisms of the disappearance of intragranular microstructure were *** effect of intragranular microstructure on main mechanical properties was also investigated.

关键词： Si2.2./Si3N4 nanocomposite intragranular microstructure transformation vanishment

In situ X-ray diffraction study of structural evaluation in Fe_(73)Cu_(1.5)Nd_3Si_(13.5)B_9 amorphous alloy at high temperature

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science china(Physics,Mechanics & Astronomy) 2008年第4期51卷 445-450页

作者： LI Gong,XU Tao,GAO YunPeng & LIU RiPing key laboratory of {2. materials science and technology,yanshan university,qinhuangdao 066004,china key laboratory of {2. materials science technology Yanshan University Qinhuangdao 066004 China

The thermodynamics structural relaxation of Fe73Cu1.5Nd3Si13.5B9 amorphous alloy from room temperature to 400℃ has been investigated by measuring the structure factor with in situ X-ray diffraction. The structural information of the atomic con-figuration such as radial distribution function (RDF) and neighbor atomic distance was gained by Fourier transformation. The research result shows that the amor-phous structure remains stable in the temperature range of 30 to 400℃ but exhibits distinct changes in local atomic configuration with the increase of temperature. The quantitative determination of the neighbor atomic distance suggests that the de-gree of short-range order changes by the temperature altering the second nearest neighbor local atomic configuration of the amorphous when structural relaxation occurs.

关键词： Fe-based amorphous alloys in situ X-ray diffraction short-range order structure

Effects of Plastic Warm Deformation on Cementite Spheroidization of a Eutectoid Steel

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Journal of Iron and Steel Research International 2012年第8期19卷 60-66页

作者： WU Tao, WANG Ming-zhi, GAO Yu-wei, LI Xiao-pu, ZHAO Yu-cheng, ZOU Qin (state key {2. of metastable materials science and technology, yanshan university, qinhuangdao 066004, hebei, china) state key {2. of metastable materials science and technology Yanshan University Qinhuangdao 066004 Hebei China

The warm compression tests were performed on the eutectoid steel to investigate the evolution of cementite morphology. Several processing parameters, such as temperature, strain rate and reduction, were changed to analyze the effect of each parameter on spheroidization of cementite. The results showed that the warm compression promoted the fragmentize and the spheroidization of lamellar cementites. When the specimen was compressed with reduction of 50% at 700 ℃ and in the strain rate of 0.01 s-1, the excellent spheroidized cementite was obtained. The mechanism of fragmentation and spheroidization of lamellar cementites during compression was discussed by using transmission electron microscope. The formation of spheroidized cementite was related to the time of compression process. The fragmentize of lamellar cementites was due to the extension of sub-grain boundary in the cementite. The spheroidization of cementite depended on the diffusion of carbon atoms at the tip of bended and breakup cementite.

关键词： eutectoid steel warm compression lamellar cementite fragmentize cementite spheroidization

Thermodynamic properties of under-cooled silver melts

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science china(Physics,Mechanics & Astronomy) 2010年第1期53卷 76-80页

作者： ZHU YuYing 1 , LI Qiang 1,2.3, WANG Ge 1 , JING Qin 2., WANG Xu 1 , GAO Ying 3 & GAO JingNa 3 1 Department of Mechanical Engineering, yanshan university, qinhuangdao 066004,{2. 2.key laboratory of metastable materials science & technology, yanshan university, qinhuangdao 066004,{2. 3 Department of materials science & Engineering, hebei university of science and technology, Shijiazhuang 050018,{2. 1. Department of Mechanical Engineering Yanshan University Qinhuangdao 066004 China2. Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao 066004 China3. Department of Materials Science & Engineering Hebei University of Science and Technology Shijiazhuang 050018 China

Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specific heat of the under-cooled melt showed a linear dependence on the temperature in the range of the obtained under-cooling from 0 to 198 K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the under-cooled melt and the solid phase, were derived from the measured specific heat. The relations between the temperature and the thermal diffusion or the thermal conductivity of the under-cooled melt were analyzed respectively.

关键词： under-cooled silver melts specific heat thermodynamic properties

Magnetron sputtering synthesis of large area well-ordered boron nanowire arrays

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science china(Physics,Mechanics & Astronomy) 2004年第4期47卷 403-415页

作者： CAO Limin1,2. ZHANG Ze2.& WANG Wenkui1,2.1. key laboratory of {2. materials science and technology and College of materials science and Engineering, yanshan university, qinhuangdao 066004, china 2. Institute of Physics, Chinese Academy of sciences, Beijing 100080, china 1. key laboratory of {2. materials science and technology and College of materials science and Engineering Yanshan University 066004 Qinhuangdao China 2. Institute of Physics Chinese Academy of Sciences 100080 Beijing China

One-dimensionally nanostructured materials, such as nanowires and nanotubes, are the smallest dimensional structures for efficient transport of electrons and excitons, and are therefore critical building blocks for nanoscale electronic and mechanical devices. In this paper, boron nanowires with uniform diameters from 2. to 80 nm were synthesized by radio-frequency magnetron sputtering of pure boron powder and B2.3 powder mixtures in argon atmosphere. The boron nanowires produced stand vertically on the substrate surface to form well-ordered arrays over large areas with self- organized arrangements without involvement of any template and patterned catalyst. The high-density boron nanowires are parallel to each other and well distributed, forming highly ordered and uniform arrays. A more interesting and unique feature of the boron nanowires is that most of their tips are flat rather than hemispherical in morphologies. Detailed studies on its structure and composition indicate that boron nanowires are amorphous. Boron nanowire appears as a new member in the family of one-dimensional nanostructures. Considering the unique properties of boron-rich solids and other nanostructures, it is reasonable to expect that the boron nanowires will display some exceptional and interesting properties. A vapor-cluster-solid (VCS) mechanism was proposed to explain the growth of boron nanowires based on our experimental observations.

关键词： boron nanowires, magnetron sputtering, arrays, self-assembly.

Manufacture of biomorphic Al2.3 ceramics using filter paper as template

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Progress in Natural science:materials International 2011年第6期21卷 455-459页

作者： Chun-yan ZUO,Qing-shan LI,Gui-rong PENG,Guang-zhong XING state key {2. for metastable materials and technology,yanshan university,qinhuangdao 066004,china state key {2. for metastable materials and technology Yanshan University Qinhuangdao 066004 China

Biomorphic Al2.3ceramics were prepared through the surface sol-gel process with filter papers as *** filter papers were infiltrated withγ-AlOOH sol and subsequently sintered in air at high temperatures to produce the biomorphic *** results show that the final materials have a hierarchical structure originated from the morphology of cellulose paper. The sintering temperatures exhibit a strong effect on the surface pore-size distribution of obtained *** scanning calorimeter,scanning electron microscopy,X-ray diffraction and BET analysis were employed to characterize the microstructure,morphology and phase compositions of the final products.

关键词： sol-gel process biomorphic filter paper ceramics

Structure evolution of cubic boron nitride under spark plasma sintering

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金刚石与磨料磨具工程 2008年第S1期28卷 165-167页

作者： Zhao Yucheng Wang Mingzhi (state key {2. of metastable materials science and technology, yanshan university,qinhuangdao 066004,china)

Cubic boron nitride(CBN) micro powders and mixture of CBN micro powders with Al or Ti powders were fast heated at 1 300,1 400,1 450,1 500℃,and then kept for 5 min under spark plasma sintering (SPS).The obtained powders were analyzed with *** results show that,simple CBN kept cubic structure after heated at 1 300℃;when the temperature rose to 1 400℃,some CBN was transformed into hexagonal structured boron nitride(hBN).As for CBN micro powders mixed with aluminum or titanium micro powders,the onset transforming temperature of CBN to hBN get *** results indicated that the structural transformation of boron nitride begun from the surface of CBN crystal particle,different coexist elements affect the surface situation of CBN *** the stabilities of CBN crystal particle surface improved,the onset structural transform temperature of CBN was also increased.

关键词： cubic boron nitride structure evolution transformation spark plasma sintering(SPS)

Large-scale boron nanowire nanojunctions and their highly-oriented arrays

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science china(Physics,Mechanics & Astronomy) 2004年第5期47卷 621-632页

作者： CAO Limin1,2. ZHANG Ze2.& WANG Wenkui1,2.1. key laboratory of {2. materials science and technology, yanshan university, qinhuangdao 066004, china 2. Institute of Physics, Chinese Academy of sciences, Beijing 100080, china 1. key laboratory of {2. materials science and technology Yanshan University 066004 Qinhuangdao China 2. Institute of Physics Chinese Academy of Sciences 100080 Beijing China

Highly oriented multiple boron nanowire nanojunctions with unilateral feather- like morphology were first successfully prepared using a radio-frequency magnetron sputtering method. The branched boron nano-feathers always nucleate and grow on the same sidewall of the stems, and align in parallel to form multiple T- and/or Y-type nanojunctions. The diameters of the branches and the stems are in the range of 2.—40 and 60—80 nm, respectively. The thinner branches and thicker stems of the boron nanowires self-assembled into large-scale, highly ordered arrays on various substrates. During the formation and self-assembly of the arrays, no template or catalyst was needed. We believe that the approach presented here can be used to fabricate heterostructures with bottom-up assembly of a wide variety of one-dimensional nanostructures via the rational design of targets and the proper control of the experimental conditions.

关键词： boron nanowires, nanojunctions, self-assembly, magnetron sputtering.

Effect of Additives on the Sintering of Amorphous Nano-sized Silicon Nitride Powders

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Journal of Wuhan university of technology({2. science) 2009年第4期24卷 537-539页

作者：骆俊廷 state key {2. of metastable materials science and technology College of Mechanical EngineeringYanshan University

Amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering. The influences of the additives of Y2.3 and Al2.3 prepared by two different ways, the polyacrylamide gel method and the precipitation method, were investigated. The grain sizes of the additives prepared by the first method were finer than those of prepared by the latter method. When sintered at the same temperature, 1700 ℃, the average grain size of the silicon nitride is 0.3 um for the sample with the former additives, which is much finer than the one with the latter additives. The density of additives prepared by precipitation method is clearly lower than those of prepared by polyacrylamide gel method.

关键词： amorphous silicon nitride liquid phase sintering additives