Papers by Keyword: Nanoindentation

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Authors: Xuan Zhang, Yan Li Zhong, Xiao Wen Zhang, Lei Li, Yue Yan
Abstract: The assessment of aging properties of organic coatings on plastics is critical to the using safety and service life evaluation. This paper was dedicated to evaluate the aging properties, including humidity-heat and temperature shock tests, of various anti-scratch silicon coatings deposited on polycarbonate (PC) by adhesion and nanoindentation measurements. Adhesion behaviors through conventional cross-cut and tap peel tests reveal that there are no obvious changes of these coatings after aging experiments, all ranked as 5B. However, the changes of nanomechanical properties (elastic modulus and hardness) of coatings on PC after aging tests are obvious different for these coatings. Base on these results, it is proved that nanoindetation technique could be an available method to assess aging behaviors of thin coatings.
378
Authors: Yun Hee Lee, Kazuki Takashima, Yakichi Higo, Dong Il Kwon
Abstract: A direct measurement of the crack-driving stress has been attempted by applying a nanoindentation-combined, stress-probing technique to the expected crack routes ahead of a Vickers impression. The nanoindentation curves close to the remnant indent were compared to those of an unstressed bare sample and were interpreted into quantitative stress values. In detail, from the difference of two stress distributions measured from uncracked and cracked indentation corners, the driving stress for the radial cracking was estimated; a rapid decaying response with a distance to the Vickers indent center with the peak value 406.7MPa. The fracture toughness of soda-lime glass, estimated by taking into account the results measured in this study was 0.74 ± 0.15 2 / 1 m MPa × and was comparable with that of the literature.
286
Authors: Sukky Jun, Young Min Lee, Sung Youb Kim, Se Young Im
Abstract: Molecular dynamics simulation of nanoindentation on Al(111) surface is presented. The simulation is performed using the Ercolessi-Adams glue potential and the Berendsen thermostat. Boundary conditions of 'pseudo' thin film are imposed in order to focus on the dislocation motion in ultra-thin film. Nucleation and development of defects underneath the indenter tip are visualized, and the gliding patterns of dislocation loops are investigated with particular emphasis on the effect of film thickness. Simulation results show that the early emission of dislocation loop is highly dependent on the film thickness.
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Authors: Chung Ming Tan, Yeau Ren Jeng, Yung Chuan Chiou
Abstract: This paper employs static atomistic simulations to investigate the effect of a void on the nanoindentation of Cu(111). The simulations minimize the potential energy of the complete system via finite element formulation to identify the equilibrium configuration of any deformed state. The size and depth of the void are treated as two variable parameters. The numerical results reveal that the void disappears when the indentation depth is sufficiently large. A stress concentration is observed at the internal surface of the void in all simulations cases. The results indicate that the presence of a void has a significant influence on the nanohardness extracted from the nanoindentation tests.
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Authors: Hong You Wang, Kang Ning Sun, Ting Shan, Xiu Qing Yang, Yan Zhao, Yan Jie Liang
Abstract: In the present study, a simple method of regenerating microstructure of human tooth under near-physiological conditions (pH 7.0, 37 °C, 1 atm) was developed. Commercial gelatin was used as matrix materials in this method, which nucleated the formation of fluorapatite (FA) nanocrystals and regulated the growth of nanocrystals. As a result, the resulting thin FA coatings had been prepared on human tooth slices and sintered hydroxyapatite disks, which were in tight contact with the substrates. Besides, the morphologies of FA nanocrystals changed from acicular to hexagonal with the exchange cycle of gel increased. Electron dispersive spectrometer analysis indicated that some sodium and carbonate ions were incorporated into the FA crystal lattices and the calcium to phosphorus ratio was approximate 1.58. The mechanical properties of the resulting FA coating were investigated through nanoindentation system, which showed the similar hardness with dentin. In conclusion, this method demonstrated a potential application to repair tooth damage in dental clinics.
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Authors: Muhammad Nubli Zulkifli, Azman Jalar, Shahrum Abdullah, Norinsan Kamil Othman
Abstract: The evaluation of the strength and bondability of gold, Au ball bond requires a new approach to provide a more detail data. Nanoindentation test was used as a new approach to evaluate the strength distribution and bondability of Au ball. Au ball bonds that experienced different value of wire bonding parameter namely bonding force, bonding time, bonding power, and stage temperature were used as samples for the present analysis. The distribution of strength based on hardness and reduced modulus values located at the bonding area of Au ball bonds were found to be related with the values of the wire bonding parameter. Nanoindentation test was found to be a suitable approach to analyze and evaluate the bondability of Au ball bond in a localized and detailed manner. In addition, the responsible mechanism for the thermosonic Au wire bonding can be identified and analyzed by using the results obtained from the nanoindentation test.
132
Authors: Ji Sheng Sheng, Dong Hui Wen, Shi Ming Ji
Abstract: Ceramic materials are widely used in the fields of aviation, chemical industry, military, machinery, electronics, so there are so many researches on ceramic materials. This article is mainly about ceramic sample preparation by polishing process for nano-indentation, taking Alumina ceramic and Zirconia ceramic for example. As we know, nano-indentation test is an effective mean to study materials. It is concluded that after polishing, the ceramic surface roughness can reach Ra<10nm and maximum scratches<1nm, flatness<1μm, we can get good quality surface, that well meets the surface requirements in nano-indentation.
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Authors: C.L. Chen, G.D. West, Rachel C. Thomson
Abstract: Multicomponent Al-Si based casting alloys are used for a variety of engineering applications. The presence of additional elements in the Al-Si alloy system allows many complex intermetallic phases to form, which make characterisation non-trivial due to the fact that some of the phases have either similar crystal structures or only subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) have therefore been used for discrimination between the various phases. It is shown that this is a powerful technique for microstructure characterisation and provides detailed information which can be related to microstructure evolution during initial casting and subsequent heat treatment. The mechanical properties of different intermetallic phases have been investigated as a function of temperature using the nanoindentation technique. In particular, the hardness and modulus of a number of phases have been established for a range of alloy compositions. Physical properties of some of the intermetallic phases are also discussed. Phase identity, composition, physical and mechanical properties are set in context to inform alloy design strategies.
359
Authors: Ágnes Csanády, László Ipacs, Gyula Kakuk, Erika Kálmán, Péter M. Nagy, Katalin Papp, István E. Sajó, András Szalay
Abstract: The aim of the present work is to produce new types of solid nanomaterials for different purposes (coatings, fillers, foams, bulk pieces, etc.). Technologies such as RS Al flake production, high energy mechanical milling and high energy rate forming technology (HERF) for compacting are used. The products are analyzed mainly by XRD, SEM and TEM methods. It was shown that the new-type of RS Al “flake” material is suitable not only for pigments but also for powder metallurgical purposes, i.e. Al based nanocomposites. By choosing suitable parameters for mechanical alloying with the Fritsch Planetary mill 4, very fine, alloyed and composited nanostructures can be produced (Al-4.5w%Cu- 10w%Al2O3, Al-15w%Pb) Dynamic compaction (HERF) using explosive techniques seems to offer a good way for the compaction of Al (metal) matrix nanostructured composites.
321
Authors: Y.L. Chiu, W. George Ferguson
Abstract: Nanoindentation technique has been widely used for measuring mechanical properties from a very small volume of material. The hardness measured using the depth sensing nanoindentation technique often decreases with increasing indentation size, the so called indentation size effect (ISE)[1, 2]. It has been generally acknowledged that the ISE in crystalline materials originates from the density change of geometrically necessary dislocations (GND) needed to accommodate a permanent indentation imprint. Conventionally, to characterize an ISE often requires a series measurement of hardness values at different indentation size. Based on the celebrated Oliver-Pharr scheme[3]. We propose a method to derive the ISE from the loading curve of one single indentation test. The application and limitation of the proposed method will be discussed.
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