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Microstructure and Mechanical Properties of TiB_2/(Ni+Mo) Composites Fabricated by Hot Pressing

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Journal of Materials Science & Technology 2000年第6期16卷 634-636页

作者： Zhang, J.y. fu, Z.y. Wang, W.M. Wang, H. Wuhan Univ. of Technol. Wuhan 430070 China

The fabrication of TiB2 ceramics with high performance at a relatively low temperature requires a second phase to assist the densification and control the microstructure. Moreover the interface characteristics of composites must also be considered. Nickel was chosen as a good metallic-bearing additive in this study. In order to optimize the interface, Mo was added. The results show that Mo can affect the interaction between TiB2 and Ni, and metallic liquid plays an important role in limiting the TiB2 grain growth in sintering.

关键词： NiMo Composites Fabricated by Hot Pressing Microstructure and Mechanical Properties of TiB2 Ni+Mo TiB

STUDy ON NANOMETER ZINC PARTICLES FABRICATED By GAS EVAPORATION METHOD

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Acta Metallurgica Sinica(English Letters) 2003年第3期16卷 161-168页

作者： A.A.A.Saleh X.J.Zhai y.C.Zhai y.fu A.L.Zhang School of Materials and Metallurgy Northeastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004ChinaSchool of Materials and MetallurgyNortheastern UniversityShenyang110004China

Nanometer Zn particles with mean diameters 12-100nm made by evaporating its powders in argon gas were studied mainly by X-ray diffraction and electron microscopy. They are collected at various distances and those factors influencing the mean particle size were studied. The optimal synthetic conditions were obtained, i.e., evaporation temperature is 1200℃; argon flow rate is 0.4m3/h; amount of powder charged is 3g; distance from evaporation source is 10cm. It was found that the size of particles was governed by argon flow rate, evaporation temperature, amount of metal charged and distance from the source. The size increases remarkably with distance in the space where no metal vapor exists. This implies that the crystallites grow by coalescence. Electron micrographs and diffraction patterns are reproduced to show the size, shape and state of oxidations. Nanoparticles with definite crystal habits were sometimes observed among those with irregular ones.

关键词： gas evaporation method nanometer Zn XRD TEM

An AlGaN/GaN HEMT with a reduced surface electric field and an improved breakdown voltage

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Chinese Physics B 2012年第8期21卷 360-364页

作者：谢刚 Edward Xu Niloufar Hashemi 张波 Fred y.fu Wai Tung Ng The Edward S.Rogers Sr.Electrical and Computer Engineering Department University of Toronto State key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of China Crosslight Software Inc.Burnaby BCCanada

A reduced surface electric field in an AlGaN/GaN high electron mobility transistor （HEMT） is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas （2-DEG） channel as an electric field shaping layer. The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions. Compared with the HEMTs with conventional sourceconnected field plates and double field plates, the HEMT with a Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge. By optimizing both the length of Mg-doped layer, Lm, and the doping concentration, a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure, respectively. In a device with VGS = -5 V, Lm 1.5 m, a peak Mg doping concentration of 8×10^17 cm-3 and a drift region length of 10 m, the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty.

关键词： AlGaN/GaN HEMT reduced surface electric field Mg-doped layer breakdown voltage

Optimal operation of water distribution networks under local pipe failures

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Journal of Central South University of Technology 2007年第3期14卷 436-441页

作者：田一梅 G.y.fu 迟海燕刘烨 School of Environmental Science and Engineering Tianjin University Department of Civil Engineering Faculty of Applied Science University of British Columbia Vancouver BC V6T 1Z4 Canada

The optimal operation of water distribution networks under local pipe failures, such as water main breaks, was proposed. Based on a hydraulic analysis and a simulation of water distribution networks, a macroscopic model for a network under a local pipe failure was established by the statistical regression. After the operation objectives under a local pipe failure were determined, the optimal operation model was developed and solved by the genetic algorithm. The program was developed and examined by a city distribution network. The optimal operation alternative shows that the electricity cost is saved approximately 11%, the income of the water corporation is increased approximately 5%, and the pressure in the water distribution network is distributed evenly to ensure the network safe operation. Therefore, the proposed method for optimal operation under local pipe failure is feasible and cost-effective.

关键词： water distribution network local pipe failure macroscopic model optimal operation

MODIFICATION OF ABSORPTION SPECTRUM OF GaAs/AlGaAs QUANTUM WELL INFRARED PHOTODETECTOR By POSTGROWTH ADJUSTMENT

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红外与毫米波学报 2006年第1期25卷 1-5页

作者： y fu yANG Chang-Li Theoretical Chemistry Department of Biotechnology Royal Institute of Technology AlbaNova S-106 91 Stockholm Sweden East China Normal University North Zhongshen Rd. 3663 200062 Shanghai China

Quantum well intermixing techniques modify the geometric shape of quantum wells to allow postgrowth *** tuning effect on the optical response property of a GaAs/AlGaAs quantum well infrared photodetector(QWIP) induced by the interdifussion of Al atoms was studied *** assuming an improvement of the heterointerface quality and an enhanced Al interdiffusion caused by postgrowth intermixings,the photoluminescence spectrum shows a blue-shifted,narrower and enhanced photoluminescence *** infrared optical absorption spectrum also shows the expected redshift of the response ***,the variation in the absorption peak intensity depends on the boundary conditions of the photo generated *** high-quality QWIP samples,the mean free path of photocarriers is long so that the photocarriers are largely coherent when they transport across quantum *** this case,the enhanced Al interdiffusion can significantly degrade the infrared absorption property of the *** effects are therefore needed to maintain and/or improve the optical properties of the QWIP device during postgrowth treatments.

关键词：吸收光谱量子阱红外光电探测器修正

Formation Mechanism of Impure Phases and Crystallinity Investigation of yAG Powders Synthesized via the Co-precipitation Method

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Journal of Wuhan University of Technology(Materials Science) 2021年第4期36卷 517-525页

作者： MA Benyuan PU Chunying HE Junbao ZHOU Dawei fu yü WEI Nian LU Tiecheng College of Physics and Electronic Engineering Nanyang Normal UniversityNanyang 473061China Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education Sichuan UniversityChengdu 610064China

We investigated the impure phase problem and summarized its two formation mechanisms of yAG powders synthesized via the co-precipitation *** ions loss problem caused by high concentration reaction solution in the titration process was emphatically studied,and the corresponding thermodynamic explanation was carried *** addition,influence of powder crystallinity and its new qualitative and quantitative standards were *** reason of impure phase is the local nonuniform mixture of y and Al elements in precursor,which easily causes intermediate phases during calcination and difficulty of high pure powders at low *** other reason is the precipitation dissolution during titration and then the y^(3+)/Al^(3+) loss,caused by high concentration of reaction *** powder crystallinity can be promoted by increasing calcination temperature or holding time of *** the routine XRD method,the TEM-EDX method should be also introduced to directly determine the quality of crystallinity.

关键词： transparent ceramics phase transition crystallinity co-precipitation activity coefficient

Formation,characteristics and control of sludge in Al-containing magnesium alloys:An overview

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Journal of Magnesium and Alloys 2022年第3期10卷 643-658页

作者： y.fu G.G.Wang A.Hu y.Li K.B.Thacker J.P.Weiler H.Hu Department of Mechanical Automotive and Materials EngineeringUniversity of Windsor401 Sunset AveWindsorON N9B 3P4Canada Global Technology Centre Meridian Lightweight Technologies25 MacNab AveStrathroyON N7G 4H6Canada

Sludge consisting of heavy element phases and oxides is often generated during the casting operation of aluminum(Al)and magnesium(Mg)*** the help of the well-established Sludge Factor(SF)formula,it is relatively easy to control the sludge generation in aluminum *** formation mechanisms and characteristics of sludge in die casting magnesium alloys are still *** ensure the production of high quality die cast components at a low cost,a full understanding of sludge in die casting Mg alloys and its proper control measures need to be developed,since excessive sludge formation affects deleteriously material and operation cost,and casting *** the present report,the formation,characteristics and control of Mg die-casting sludge,based on the established knowledge of sludge formation and sludge factor in Al die casting alloys,are *** work on characterization and assessment of sludge in die cast Mg alloys are *** principles for control of sludge in ingot production in association with die casting of Mg alloys are *** assessment of Mg oxide and intermetallics relevant to sludge formation in Mg alloys are highlighted.

关键词： Sludge Magnesium alloys Die casting Al-Mn(-Fe)intermetallics Magnesium oxide Microstructure characterization

Uniformity of TiN Films Fabricated by Hollow Cathode Discharge

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Plasma Science and Technology 2010年第2期12卷 212-217页

作者：姜海富巩春志田修波杨士勤 R.K.y.fu P.K.CHU State Key Lab.of Advanced Welding Production & Technology School of Material Science and Engineering Harbin Institute of Technology Department of Physics and Materials Science City University of Hong Kong

Titanium nitride （TIN） films were deposited on AISI 304 stainless steel substrates using hollow cathode plasma physical vapor deposition （HC-PVD）. Titanium was introduced by eroding the Ti cathode nozzle and TiN was formed in the presence of a nitrogen plasma excited by radio frequency （RF）. The substrate bias voltage was varied from 0 to -300 V and the uniformity in film thickness, surface roughness, crystal size, microhardness and wear resistance for the film with a diameter of 20 mm was evaluated. Although the central zone of the plasma had the highest ion density, the film thickness did not vary appreciably across the sample. The results from atomic force microscopy （AFM） revealed a low surface roughness dominated by an island-like morphology with a similar crystal size on the entire surface. Higher microhardness was measured at the central zone of the sample. The sample treated at -200 V had excellent tribological properties and uniformity.

关键词： hollow cathode TiN film uniformity

Spatial Potential Distribution around Trench Target during Plasma Immersion Ion Implantation

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Journal of Materials Science & Technology 2003年第Z1期19卷 94-96页

作者： Xiubo Tian Chunbei Wei Shiqin yang Paul K. Chu Ricky K.y. fu State Key Lab. of Welding Production Technology School of Mater. Sci. & Eng. Harbin Institute of Technology Harbin 15001 China Department of Physics & Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong State Key Lab. of Welding Production Technology School of Mater. Sci. & Eng. Harbin Institute of Technology Harbin 15001 China Department of Physics & Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong State Key Lab. of Welding Production Technology School of Mater. Sci. & Eng. Harbin Institute of Technology Harbin 15001 China Department of Physics & Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong State Key Lab. of Welding Production Technology School of Mater. Sci. & Eng. Harbin Institute of Technology Harbin 15001 China Department of Physics & Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong State Key Lab. of Welding Production Technology School of Mater. Sci. & Eng. Harbin Institute of Technology Harbin 15001 China Department of Physics & Materials Science City University of Hong Kong Tat Chee Avenue Kowloon Hong Kong

Plasma ion implantation, an alternative to conventional beam-line ion implantation, is a sheath-acceleration ionbombardment technique and the initial sheath is crucial to the process efficacy and surface properties. The initialspatial potential distribution in the plasma sheath around a trench-shaped target is simulated using a two-dimensionalmodel in this work. The results demonstrate that the sheath structure depends very much on the trench width. Thepotential drop in the trench may be quite small and the sheath expands outward if the width is small. This leadsto a smaller incident ion dose into the sidewalls of the trench. In contrast, the initial potential distribution in thecentral region is quite similar to that without a trench if the trench width is larger than twice the ion-matrix sheaththickness for an infinite plane. Consequently, a higher ion dose into the sidewalls is possible.

关键词： Plasma ion implantation, Trench target, Potential distribution