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Functional materials for sustainable energy and new electronicsnanogenerators,piezotronics and piezo-phototronics

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Functional materials for sustainable energy and new electron...

Towards property nanom easurements by in- situTEM- presentand prospects

第七届中国功能材料及其应用学术会议

作者： WANG Zhong-lin (school of materials science and engineering,Georgia Institute of Technology,Atlanta USA)

Developing wireless nanodevices and nanosystems is of critical importance for sensing,medical science, environmental/infrastructure monitoring,defense technology and even personal electronics.It is highly desirable for wireless devices to be self-powered without using battery.This is a new initiative in today’s energy research for mico/nano-systems in searching for sustainable self-sufficient power sources.It is essential to explore innovative nanotechnologies for converting mechanical energy,vibration energy,and hydraulic energy into electric energy that will be used to power nanodevices.We have invented an innovative approach for converting nano-scale mechanical energy into electric energy by piezoelectric zinc oxide nanowire arrays.The operation mechanism of the nanogenerator relies on the piezoelectric potential created by an external strain;a dynamic straining of the nanowire results in a transient flow of the electrons in the external load due to the driving force of the piezopotential.We have developed the nanogenerator from fundamental science,to engineering integration and to technological scale-up.As today,a gentle straining can output 1.2 V from an integrated nanogenerator ,using which a self-powered nanosensor has been demonstrated.A commercial LED has been lid up.This is a key step for developing a totally nanowire-based nanosystem.Alternatively,by substituting the gate voltage in a field effect transistor(FET) with the piezopotential creating by an external strain,we have fabricated a series of devices that rely on a coupling between semiconductor and piezoelectric properties and are controlled/tuned by externally applied force/pressure,such as diode,strain sensor and strain-gated logic unites, which are a new field called piezotronics.A three way coupling among piezoelectricity,semiconductor and photonic excitation has demonstrated the piezo-phototronic effect.

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电子显微学报 2000年第1期 4-16页

作者： WANG Zhong\|lin (school of materials science and engineering Georgia Institute of Technology Atlanta GA 30332\|0245 USA)

纳米材料的研究无论是在基础科学还是在应用技术上都面临着许多新的挑战。纳米材料的性能极大地取决于它们的尺寸和形状。测量大面积或大量的纳米材料所得的性能是整个样品的平均值,因此,单个纳米颗粒或单根纳米管的不寻常的特性就被掩... 详细信息

纳米材料的研究无论是在基础科学还是在应用技术上都面临着许多新的挑战。纳米材料的性能极大地取决于它们的尺寸和形状。测量大面积或大量的纳米材料所得的性能是整个样品的平均值,因此,单个纳米颗粒或单根纳米管的不寻常的特性就被掩盖了。测量由原子结构所决定的单一纳米结构的性能是纳米科学的一个基本方向。对现有的测试技术和试验方法来说,表征单一纳米颗粒纳米管纳米纤维的性能是一难题。首先,因为它的尺寸(直径和长度)相当小,现有的实验手段不适用,像纤维类材料的弹性和蠕变实验,要求样品的尺寸足够大,能够固定在试样台的夹具上,这种简单易行的方法对于纳米结构的纤维则不适用。其次,纳米结构的小尺寸使得手工操作相当困难,需要有一种针对单一纳米结构设计的专门测试技术来进行操作。因此,为了准确测量单一纳米结构的性能,开发新的方法和手段是十分必要的。我们的工作目的就在于此。本文综述了我们在开拓和发展原位透射电子显微学在表征纳米材料的力学,电学和热力学性能方面的现状和展望。该研究的焦点集中在如何定量测试一微结构已知的单一纳米结构的物理性能,从而实现了表征结构—性能关联中的一对一关系,开拓了原位透射电子显微镜在纳米材料科学研究中的新方向和新天地。

关键词：纳米结构纳米材料科学 presentand prospects situTEM 纳米颗粒透射电子显微学纳米管

Nanomechanics of Fiber-like Nanomaterials

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Journal of materials science & technology 2001年第3期17卷 303-305页

作者： Z.L. Wang school of materials science and engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA E-mail: zhong.wang@mse.gatech.edu school of materials science and engineering Georgia Institute of Technology

Property characterization of nanomaterials is challenged by the small size of the structure be-cause of the difficulties in manipulation Here we demonstrate a novel approach that allows a direct measurement of the mechanical properties of individual nanotube-like structures by in-situ transmission electron microscopy (TEM). The technique is powerful in a way that it can directly correlate the atomic-scale microstructure of the carbon nanotube with its physical properties, providing a one-to-one correspondence in structure-property characterization Applications of the technique will be demonstrated on mechanical properties, the electron field emission and the ballistic quantum conductance in individual nanotubes.

关键词： Nanomechanics of Fiber-like Nanomaterials

Piezoelectric Nanogenerators Based on Aligned Nanowires/Nanobelts

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Piezoelectric Nanogenerators Based on Aligned Nanowires/Nano...

Solidification behavior of SiC_w/Al-18Si composites

中国化学会第二十五届学术年会

作者： Zhong lin (ZL) Wang school of materials science and engineering, Georgia Institute of Technology, Atlanta USA Department of Advanced materials and Nanotechnology, College of engineering, Peking University National Center of Nanoscience and technology, Beijing

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Rare Metals 2007年第S1期26卷 237-241页

作者： wei Hongmei,GENG lin,and ZHANG Xuexi school of materials science and engineering,Harbin institute of technology,Harbin 150001,China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China

SiCw/Al-18Si composites were prepared by squeeze casting technique.Solidification behavior of SiCw/Al-18Si composites was studied by differential scanning calorimeter(DSC) and scanning electron microscopy(SEM).The re-melting temperature has little effect on the solidification behavior and microstructure of composites.With the increase of SiC whisker content,onset and peak temperatures of primary Si decrease and the average size of primary silicon becomes smaller and smaller.Sr addition lowers onset and peak temperatures of primary Si,however,onset and peak temperatures of eutectic were barely affected by Sr addition.The average sizes of primary Si and Al-Si eutectic both decrease by Sr addition.

关键词： SiC_w/Al-18Si composites DSC solidification microstructure

Synthesis and characterization of ZnO nanostructures prepared by a thermal evaporation process

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Rare Metals 2007年第S1期26卷 153-156页

作者： CAI wei,and LIU Wencheng school of materials science and engineering,Harbin institute of technology,Harbin 150001,China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China

A series of ZnO nanostructures such as nanowires,nanobelts,nanocombs and mesoporous nanoballs were fabricated by a simple carbon reduction method without catalyst.The morphologies and microstructures of all samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and energy dispersive X-ray spectroscopy.The results indicate that different deposition temperatures have great impact on different shapes of ZnO nanostructures.The growth mechanisms of these ZnO nanostructrues suggest that,by controlling the experiment parameters,different morphological configurations nanostructures can be fabricated.

关键词： ZnO nanostructures thermal evaporation nanowires vapor deposition

Enhancement of interfacial bond strength of Al_2O_(3f)/Al-15Si composite by solidification process

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Rare Metals 2007年第S1期26卷 286-290页

作者： ZHANG Xuexi,wei Hongmei,WANG Dezun,and GENG lin school of materials science and engineering,Harbin institute of technology,Harbin 150001,China Harbin Inst Technol Sch Mat Sci & Engn Harbin 150001 Peoples R China

To build the relationship between solidification conditions and the interfacial bond strength,Al2O3f/Al-15Si composite solidified at different cooling rates were investigated by microstructure observation and mechanical testing.The results show that the interfacial bond strength of the as-cast composite is significantly enhanced after furnace-or air-cooling processes owning to the preferential nucleation and growth of the eutectic silicon on the fiber surface.The discontinuously distributed eutectic silicon on the fiber surface makes the fiber become coarse,resulting in the enhanced mechanical bond strength between fiber and matrix.However,the interfacial bond strength of the oil-cooled composite is not improved,showing that the silicon on the fiber surface is important for the improvement of the interfacial bond strength.The air-and furnace-cooled composites also have a higher tensile strength.

关键词： metal matrix composites solidification mechanical property interface

Evaluation of the acoustic nonlinearity parameter of materials with Rayleigh waves excited directly

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Chinese Journal of Acoustics 2010年第2期29卷 107-119页

作者： SHUI Guoshuang WANG Yuesheng Jianmin Qu Jin-Yeon Kim Laurence J. Jacobs institute of engineering Mechanics Beijing Jiaotong University Beijing 100044 school of Mechanical engineering Georgia Institute of Technology Atlanta Georgia 30332-0405 USA

An experimental technique for the determination of the relative acoustic nonnnearity parameter of materials with Rayleigh waves excited directly is presented. Rayleigh surface waves were directly generated in materials by the specific piezoelectric transducer fixed at the specimen＇s edge, and were measured with a laser interferometer system. After the Rayleigh wave signals were processed with FFT method, the relative acoustic nonlinearity parameter of materials was then determined from the absolute magnitudes of the fundamental and second harmonics of Rayleigh surface waves. This procedure was used to determine the acoustic non- linearity parameters of aluminum alloys 2024 and 6061. It is shown that the results comply well with those available in the literature; this method can thus be used to evaluate the acous- tic nonlinearity parameter of materials effectively. This technique can provide a practical way in the nondestructive characterization of degradation of materials and structures in the early fatigue life.

关键词： line Evaluation of the acoustic nonlinearity parameter of materials with Rayleigh waves excited directly

Preparation of multi-walled carbon nanotube-reinforced TiNi matrix composites from elemental powders by spark plasma sintering

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Rare Metals 2012年第1期31卷 48-50页

作者： CAI wei,FENG Xue,and SUI Jiehe National Key Laboratory Precision Hot Processing of Metals,school of materials science and engineering,Harbin institute of technology,Harbin 150001,China National Key Laboratory Precision Hot Processing of Metals School of Materials Science and Engineering Harbin Institute of Technology Harbin China

Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders.The phase structure,morphology and transformation behaviors were studied.It was found that thermoelastic martensitic transformation be-haviors could be observed from the samples sintered above 800 ℃ even with a short sintering time (5min),and the transformation tempera-tures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation.Although decreasing the sin-tering temperature and time to 700 ℃ and 5min could not protect defective MWCNTs from reacting with Ti,still-perfect MWCNTs re-mained in the specimens sintered at 900 ℃.This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.

关键词： metallic composites shape memory materials carbon nanotubes spark plasma sintering