Papers by Keyword: Nanoindentation

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Authors: Han Qing Gu, Xiao Jing Yang
Abstract: The finite element method and nanoindentation experiment are used in this paper, to analysis mechanical properties of monocrystalline germanium on micro/nanoscale. The cloud charts of stress and strain distribution are obtained by finite element method. It is shown that the depth increment of the contact makes the value of stress and strain in the surface layer greater and the area of action larger in the process of nanoindentation of monocrystalline germanium. In the nanoindentation experiment, load and displacement curve is different with different crystal orientations. With the increase of load, contact depth has been increased. The residual deformation depth of three crystal orientations is also different. The results of FEM is is closed to the crystal orientation of [100].
Authors: Xing Na Peng, Yun Peng, Jin Shan Wei, Zhi Ling Tian
Abstract: Nanoindentation technique was employed to examine the nanohardness and elastic modulus of weld joints of 1000MPa Class high strength low alloy (HSLA) steel. The distribution of micro scales mechanical behavior was analyzed combined with microstructure observation by OM, SEM and TEM. It was shown that weld metal and base metal were mainly of bainite and their nanohardness is about 4.0GPa. In the heat affected zone, fine grained heat affected zone and coarse grained heat affected zone with lath martensite structure had the maximum hardness (above 4.75GPa). From inter critical region, the hardness of HAZ decreased to 2.5 GPa. However, the elastic modulus of metallic material is not much sensitive to the microstructure.
Authors: Liang Yun Lan, Chun Lin Qiu, De Wen Zhao
Abstract: Nanoindentation technique was employed to study the hardness and elastic modulus for different regions in the welded joint of high strength steel. And the variation in mechanical behavior at micro scales was analyzed combined with microstructure observation. Experimental results showed that both maximum hardness (4.11GPa) and maximum elastic modulus (210.3GPa) were obtained in the coarse grained HAZ and the corresponding microstructure was granular bainite. While the weld metal and fine grained HAZ had similar values of hardness and elastic modulus, and corresponding microstructures were acicular ferrite and polygonal ferrite respectively.
Authors: Z.H. Cao, X.K. Meng
Abstract: The strain rate sensitivity of rolled nanocrystalline (NC) Ni was studied by nanoindentation. The grain continuously grows from 20 nm to 92 nm after rolling deformation. The stress driven grain boundary migration accompanied by dislocation emission leads to the grain growth. The strain sensitivity first increase and then decrease with the increased rolling strain, which has a similar variation of dislocation density in rolled NC Ni. The remarkable shift of rate sensitivity is attributed to the dislocation supported grain boundary mediated process.
Authors: Roselita Fragoudakis, Michael A. Zimmerman, Anil Saigal
Abstract: Lateral Diffused Metal Oxide Semiconductors (LDMOS) normally have a Cu-W flange, whose CTE is matched to Si. Low cost Cu substrate material provides 2X high thermal conductivity, and along with a AuSi eutectic solder is recommended for optimal thermal performance. However, the CTE mismatch between Cu and Si can lead to failure of the semiconductor as a result of die fracture, due to thermal stresses developed during the soldering step of the manufacturing process. Introducing a Ag ductile layer is very important in minimizing such thermal stresses and preventing catastrophic failure of the semiconductor. Ag is a ductile material electroplated on the Cu substrate to absorb stresses developed during manufacturing due to the CTE mismatch between Si and Cu. The Ag layer thickness affects the magnitude of the resulting thermal stresses. This study attempts to measure the yield strength of the Ag layer, and examines the optimal layer thickness to minimize die stresses and prevent failure. The yield stress of the ductile layer deposited on a Cu flange was measured by nanoindentation. The Oliver and Pharr method was applied to obtain modulus of elasticity and yield depth of Ag. A finite element analysis of the package was performed in order to map die stress distribution for various ductile layer thicknesses. The analysis showed that increasing the ductile layer thickness up to 0.01 - 0.02 mm, decreases the Si die stresses.
Authors: F. Rubio, Sofia Pérez-Villar, Miguel Angel Garrido, Juan Rubio, J.L. Oteo
Abstract: In this work it has been carried out the diffusion of silver ions in medieval glasses by a heat treatment process. Silver ions are transformed into both silver nanoparticles and nanoclusters after redox reactions with reducing glass ions. Changes in glass colour due to the formation of these silver nanoparticles have been analysed by means of visible spectroscopy. At the same time, changes in glass structure have been analysed by means of Raman scattering. By using confocal Raman spectroscopy the in deep glass structural changes occurring after silver ion diffusion and silver nanoparticle formation have been studied. These changes have been corroborated by means of gradient Raman spectroscopy where the silver ion and silver nanoparticle diffusion have been analysed on a fractured glass surface. In all cases have been observed that silver nanoparticles produce a depolymerisation of the glass structure and that such depolymerisation increases with the amount of silver nanoparticles. By using Microprobe Analysis it has been found that the higher silver nanoparticle concentration is on the glass surface and it decreases with the distance to the surface according to a diffusion process. By using nanoindentation measurements on original and gradient glass surfaces it has been found an increase of the Young modulus from 60 to 85 GPa, being the first value that corresponding to the glass surface with high silver nanoparticle concentration, and the second one for the glass without silver. This result is in accordance with Raman and Microprobe analysis.
Authors: Vit Šmilauer, František Škvára, Jiří Němeček, Lubomír Kopecký, Petr Hlaváček
Abstract: Research of alkali-activated materials has been a traditional domain of chemists. This paper exploits contribution of micromechanics to the subject. A new model for volumetric evolution of chemical phases is formulated. The first homogenization level identifies elasticity on the scale of N-A-S-H gel. Nanoindentation sensing technique yielded the intrinsic Young's modulus of N-A-S-H gel as ~18 GPa, which was further downscaled to the solid gel particles. Percolation theory had to be introduced to match an early-age elasticity. The second homogenization level takes into account an unreacted fly ash. Homogenization models match well the experimental elasticity and demonstrate stiffening of N-A-S-H gel, induced by increasing packing density of the solid gel particles. The percolation model explains a long setting time of alkali-activated materials.
Authors: Hong Mei Wang, Pei Jing Shi, He Long Yu, Wei Zhang, Bin Shi Xu
Abstract: As new engineering coatings get ever thinner and more technologically advanced, there is an increasing demand for accurate assessment of the mechanical properties of thin films. The rapidly expanding field of depth-sensing evaluation and techniques related provides a quantitative method for mapping the micro/nano mechanical properties. A new type of nano test system was introduced, the technology principle and the data analysis method were described. It was used to test the performance of brush-plated nanocomposite coatings, supersonic plasma-sprayed coatings and self-repairing microcapsule for corrosion-proof coatings, including the distribution of mechanical properties across the surface and the section and nanoindentation creep. The results show that nanoindentation techniques play an incomparable role in charactering the performance of surface coatings.
Authors: Avi Shalav, Sherman Wong, Simon Ruffell, Robert G. Elliman
Abstract: This study demonstrates a novel technique for the fabrication of ordered arrays of Au rich nanoparticles on a Si substrate. Si substrates, with their native oxides intact, are pre-patterned using nanoindentation to create regions on the surface that readily alloy at higher temperatures with a thin thermally evaporated Au layer. Larger Au rich particles are observed to form at the indentation sites after high temperature annealing in an inert atmosphere. After mechanical wiping, the Au rich particles lying within the indentation sites remain while almost all the particles on the native oxide surface are readily removed. Using PECVD techniques, multi-prong Si nanowires are shown to grow from the remaining arrays of Au rich particles.
Authors: Mei Ling Lau, Kin Tak Lau, Harry Ku, Debes Bhattacharyya, Joong Hee Lee
Abstract: Among different sterilization methods, heat-treatment of bone is recognized as one of the simple and practical methods to lower the human immunodeficiency virus (HIV) infection and overcome the risks of rejection and disease transfer from allograft and xenograft during bone transplantation. In order to best characterize the micro-structural mechanical property of bone after heat treatment, the nanoindentation technique was applied in this study to measure the localized elastic modulus and hardness for interstitial lamellae and osteons lamellae of bovine cortical bones at temperature 23°C (room temperature-pristine specimen), 37°C, 90°C, 120°C and 160°C, respectively. The elastic modulus (E) and hardness (H) of interstitial lamellae obtained higher values as compared with osteons lamellae which show that interstitial lamellae are more stiff and mineralized than osteons. Moreover, as a specimen pre-heat treated at 90°C, the E and H values of interstitial lamellae and osteons were closed to a pristine specimen. For a specimen pre-heat treated at 120°C, both interstitial lamellae and osteons obtained an increase in E and H values. As a specimen pre-heat treated at 160°C, the interstitial lamellae and osteons obtained a slight decrease in E and H values. These findings are correlated to results reported by other researchers [1, 2] that calcified collagen molecules starts to degenerate at about 120°C and complete at 160°C. Interestingly, when a specimen was pre-heat treated at 37°C, both interstitial lamellae and osteons obtained significant decreases in E values of 57% and 40%, respectively as compared to the pristine specimen; while in H values, there was a decrease of 27.4% and 15%, respectively. Thus, this paper will investigate the mechanical properties of bovine cortical bones under various temperature ranges by nanoindentation technique.
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