检索结果-南通市图书馆

Structure and Magnetic Properties of Ni-doped ZnO Powder

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2010年第5期25卷 770-773页

作者：高放赵俊 Department of Electronic science and technology Huazhong University of Science and Technology

Ni-doped ZnO nanopowder （Zn0.98Ni0.2.） was synthesized by improved coprecipitation method. The average particle size of the powder was estimated to be 50 nm. The powder was then processed by thermal treatment. Samples were annealed at 1 073, 1 2.3, and 1 473 K, respectively. The solubility of NiO in ZnO and the lattice parameters of ZnO both increased with the temperature. The magnetic property of the doped samples was examined, and hysteresis loops were got. The results showed all the samples were ferromagnetic, while powder processed at 1 2.3 K for 4 h got a highest saturation magnetization （Ms） of 0.0457 emu/g. Also, magnetic properties were related to the grain size of the powder.

关键词： ferromagnetism diluted magnetic semiconductor Ni-doped ZnO coprecipitation solid state reaction

Indeterminate direction relation model based on fuzzy description framework

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2008年第S1期51卷 72-80页

作者： LIU YaoLin1,HE JianHua1,YU Yan2.& TANG XinMing3 1 school of Resource and Environment science,{2. university,{2. 430079,china 2.school of Resource and Environment Engineer,{2. university of technology,{2. 43.070,china 3 Chinese Academy of Surveying and Mapping,Beijing 10083,china school of Resource and Environment science Wuhan University Wuhan China school of Resource and Environment Engineer Wuhan University of Technology Wuhan China Chinese Academy of Surveying and Mapping Beijing China

The indetermination of direction relation is a hot topic for fuzzy GIS researchers. The existing models only study the effects of indetermination of spatial objects,but ignore the uncertainty of direction reference framework. In this paper,first a for-malized representation model of indeterminate spatial objects is designed based on quadruple (x,y,A,μ),then a fuzzy direction reference framework is constructed by revising the cone method,in which the partitions of direction tiles are smooth and continuous,and two neighboring sections are overlapped in the transitional zones with fuzzy method. Grounded on these,a fuzzy description model for indeterminate direction relation is proposed in which the uncertainty of all three parts (source object,reference object and reference frame) is taken into account simultaneously. In the end,case studies are implemented to test the rationality and validity of the model.

关键词： direction relation fuzzy description framework fuzzy representation model uncertainty

Relationship between the Corrosion and Cr-Ni Content of Stainless Steel in Borax Bath

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2011年第6期26卷 1137-1139页

作者：王俊元 school of Mechanical Engineering and automation North University of China

The corrosion of stainless steel was experimentally investigated and analyzed to improve the service-life of the crucible and fixture clamps. Through the experiment, stainless steel was found to satisfy the crucible and fixture clamps materials. As the chromium element mass percentage of the stainless steel increased, the corrosion decreased rapidly at first and then slowly increased. With the corrosion time prolonging, the corrosion growth rate is generally a downward trend. With Chromium 2.%, the corrosive were the least. With Nickel element mass percentage increased, the corrosion increased rapidly at first and then decreased rapidly, flatten at the last. It was special that the corrosion had little relationship with the Chromium and Nickel mass percentage when the Nickel percentage is more than 35%. The most remarkable corrosion is corresponding with the Nickel element 12., the least corrosion with Nickel element 80%. So Nickel element 35% is the most optional.

关键词： corrosion chromium nickel stainless steel borax bath

Effect of Tin on the Reaction Synthesis of Ternary Carbide Ti_3AlC_2

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2009年第2期24卷 283-286页

作者：周卫兵 school of Materials science and Engineering Wuhan University of Technology

The effect of tin on synthesis of Ti3AlC2.by spark plasma sintering （SPS） from TiC/Ti/Al powders was investigated. X-ray diffraction （XRD） and scanning electron microscopy （SEM） were used for phase identification and microstructure evaluation. The experimental results show that addition of tin can considerably accelerate the synthesis reaction of Ti3AlC2.and fully dense, essentially single-phase polycrystalline Ti3AlC2.could be successfully obtained by sintering 2.iC/1Ti/1Al/0.2.n powders at 12.0-12.0 ℃ under a pressure of 30 MPa. SEM images show that Ti3AlC2.samples in about 2.5 μm thick and 10-2.μm long platelets can be obtained. The fracture toughness and flexural strength of Ti3AlC2.were 6.5±0.2.MPa·m^1/2.and 560±10 MPa, respectively.

关键词： titanium aluminum carbide spark sintering technique synthesis

Refinement Role of Electromagnetic Stirring and Calcium in AZ91 Magnesium Alloy

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science Edition) 2008年第2期23卷 194-197页

作者： HAN Hui LIU Shengfa KANG Liugen LIU Linyan (school of Materials science and Engineering,{2. university of technology,{2. 43.070,china) school of Materials science and Engineering Wuhan University of Technology Wuhan China

Effects of calcium addition and electromagnetic stirring on the microstructure of AZ91 magnesium alloy and refinement mechanism were *** results show that calcium addition ranging from 0.1wt% to 0.3 wt% does not lead to formation of any new phases but cause the refinement of as- cast ***,combined calcium alloying and electromagnetic stirring significantly decrease the grain size,change the morphologies of theβ-Mg17Al12.hases,and reduce their volume *** minimum grain size of AZ91 alloy is obtained in the case of the addition of 0.2.wt%Ca with exciting voltage of 100 *** microstructural refinement is attributed to the increase of the degree of undercooling and nucleation temperature of primaryα-Mg phases on the basis of DTA analysis results.

关键词： AZ91 magnesium alloy electromagnetic stirring calcium microstructural refinement

A quasi-human algorithm for solving the three-dimensional rectangular packing problem

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Information sciences) 2010年第12期53卷 2389-2398页

作者： HE Kun & HUANG WenQi school of Computer science and {2., Huazhong university of science and {2., wuhan 430074, china school of Computer science and {2. Huazhong University of Science and Technology Wuhan China

Based on the concept of maximal rectangular space that can be filled at current time and the siege warfare tactics, we make several critical improvements on the quasi-human caving-degree approach to get a stronger algorithm ICDA for a classical NP hard problem: the three-dimensional rectangular packing problem. Within similar computing time, the new algorithm gained an average volume utilization of 90.92. on the natural and difficult 100 benchmarks, called BR15, where items to be packed are almost different in size. Compared with current best record just reported in the literature in 2.10, our result makes an improvement by 0.54%.

关键词： NP hard three-dimensional packing quasi-human action space caving degree

Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2009年第4期24卷 515-519页

作者：张津 school of Materials science & Engineering University of Science and Technology Beijing College of Materials science & Engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

Fabrication of Ti_2.lC by Spark Plasma Sintering from Elemental Powders and Thermodynamics Analysis of Ti-Al-C System

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2007年第2期22卷 325-328页

作者：王苹 State Key Laboratory of Advanced technology for Materials Synthesis and Processing Wuhan University of Technology

A ternary-layered carbide Ti2.lC material could be synthesized by spark plasma sintering（SPS） technology using elemental powder mixture of Ti, Al and active carbon. By means of XRD and SEM, phases were identified and microscopically evaluated. The experimental results show that the main phase in the product was fully crystallized Ti2.lC with small particle size when sintered at 12.0℃. The synthesis temperature of SPS was 2.0-400℃ lower than that of hot pressing （HP） or hot isostatic pressing （HIP）. Through thermodynamics calculations, the mechanism of Ti2.lC was studied by calculating changes of Gibbs free energy of reactions.

关键词： Ti2.lC spark plasma sintering elemental powder thermodynamics analysis

Electronic Structures and Bonding Properties of Ti_2.lC and Ti_3AlC_2

在线全文

学校读者我要写书评

暂无评论

Journal of wuhan university of {2.(Materials science) 2007年第1期22卷 27-30页

作者：闵新民 Department of Applied Chemistry School of Science Wuhan University of Technology State Key Laboratory of Advanced technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China

The relation among electronic structure, chemical bond and property of Ti2.lC, Ti3AlC2.and doping Si into Ti2.lC was studied by density function and the discrete variation （DFT-DVM） method. After adding Si into Ti2.lC, the interaction between Si and Ti is weaker than that between Al and Ti, and the strengths of ionic and covalent bonds decrease both. The ionic and covalent bonds in Ti3AlC2. especially in Ti-Al, are stronger than those in Ti2.lC. Therefore, in synthesis of Ti2.lC, the addition of Si enhances the Ti3AlC2.content instead of Ti2.lC. The density of state （DOS） shows that there is mixed conductor characteristic in Ti2.lC and Ti3AlC2. The DOS of Ti3AlC2.is much like that of Ti2.lC. Ti2.iAl1-xC has more obvious tendency to form a semiconductor than Ti2.lC, which is seen from the obvious difference of partial DOS between Si and Al 3/7.

关键词： Ti2.lC Ti3SiC2 doping electronic structure chemical bond