The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Jianghong Gong - One of the best experts on this subject based on the ideXlab platform.
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effect of porosity on the Microhardness Testing of brittle ceramics a case study on the system of nio zro2
Ceramics International, 2013Co-Authors: Qi Tang, Jianghong GongAbstract:Microhardness tests were conducted on a series of NiO–ZrO2 ceramics with different porosities ranging from 2% to 18%. For each sample, the measured hardness decreases with increasing indentation load, showing a significant indentation size effect. The indentation data were analyzed according to the modified proportional specimen resistance (PSR) model and it was found that the resultant load-independent hardness decreases with increasing porosity. The porosity-dependence of the load-independent hardness was analyzed and a concept of true hardness was proposed to characterize the actual material resistance to indentation-induced plastic deformation. Furthermore, the applicability of the modified PSR model in describing the indentation size effect observed on porous materials is discussed. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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effect of metallic binder content on the Microhardness of ticn based cermets
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: Jianghong Gong, Hezhuo Miao, Zhe ZhaoAbstract:Microhardness Testing was conducted on a series of TiCN-based cermets with different contents of metallic binders in the applied load range from 0.49 to 9.8 N. Significant indentation size effect (ISE) in the measured Microhardness was observed for each test sample. The traditional Meyer's law and the modified proportional specimen resistance (MPSR) model were employed to analyze the load-dependence of the measured hardness. It was found that the Meyer's exponent n increases with the metallic binder content, implying that increasing the metallic binder content would restrain the ISE. The load-independent hardness was found to decrease with the increasing metallic binder content. This can be attributed to the fact that the hardness of metallic binder is lower than that of the TiCN matrix.
G V Kalinnikov - One of the best experts on this subject based on the ideXlab platform.
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microstructural response of mono and multilayer hard coatings during indentation Microhardness Testing
Surface & Coatings Technology, 1997Co-Authors: A Bloyce, Rostislav A Andrievski, G V KalinnikovAbstract:Abstract An investigation of indentation crack patterns and the nature of fracture mechanisms of hard coatings can provide useful information to aid in the understanding of failure mechanisms occurring as a result of scratch and wear tests. Examples of several different types of single and multilayer coating systems are presented in this study. The effect of substrate and microstructure on the brittle-ductile transition behaviour is discussed. The concept of energy dissipation is introduced to interpret deformation and fracture behaviour during indentation tests. If a hard coating undergoes some densification or plastic flow to dissipate a proportion of the energy, then the premature adhesive failure due to the non-compliance of the strain at hard coating/substrate interface can be avoided. The compaction or plastic flow of the hard coating also effectively disperses concentrated stress and delays the formation tensile cracks around indentations.
N. E. Anashkina - One of the best experts on this subject based on the ideXlab platform.
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Change in the Functional Chemical Composition of the Surface and Technological Properties of Natural Quartz under the Influence of High-Voltage Nanosecond Pulses
Bulletin of the Russian Academy of Sciences: Physics, 2019Co-Authors: I. Zh. Bunin, V. A. Chanturiya, M. V. Ryazantseva, N. E. AnashkinaAbstract:FTIR, Hammett indicator adsorption, Microhardness Testing, and other physicochemical means of analysis (electrokinetic potential, contact angle of wetting, floatability) are used to study the mechanism of structural–chemical transformations of the surface, the change in physicochemial, mechanical, and technological properties of natural quartz under the influence of high-voltage nanosecond pulses. The impact of pulse energy causes softening, an increase in electron donor ability, and a reduction in the acceptor ability of the quartz surface. This lowers the sorption activity of the mineral with respect to oxyhydryl (carboxylic) flotation collecting agents (sodium oleate).
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Modifying the physicochemical and electrical properties of tantalite and columbite surfaces under conditions of electrochemical treatment and high-voltage nanosecond pulses
Bulletin of the Russian Academy of Sciences: Physics, 2017Co-Authors: V. A. Chanturiya, I. Zh. Bunin, M. V. Ryazantseva, E. L. Chanturiya, E. V. Koporulina, N. E. AnashkinaAbstract:Structural and chemical modifications of tantalite and columbite surfaces, induced by treating the minerals with anolyte—a product derived via the electrolysis of aqueous solutions—and high-voltage electromagnetic pulses, are studied by means of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscopy, and electrophoretic light scattering. The mechanical properties of the surfaces are characterized via Vickers Microhardness Testing. Treating the minerals with anolyte removes iron-containing surface films and leads to considerable conversion of surface-confined Fe(II) species into Fe(III), increasing the differences between the physicochemical and electrical properties of these rare earth minerals. The nonthermal impact of high-voltage pulses results in effective surface softening, a reduction in Microhardness, and the disintegration of mineral particles, yielding surface micro- and nanosized phases enriched with iron and oxygen.
J V Fernandes - One of the best experts on this subject based on the ideXlab platform.
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ultra Microhardness Testing procedure with vickers indenter
Surface & Coatings Technology, 2002Co-Authors: J M Antunes, A Cavaleiro, L F Menezes, M I Simoes, J V FernandesAbstract:Abstract Depth-sensing indentation equipment is widely used for evaluation of the hardness and Young's modulus of materials. The depth resolution of this technique allows the use of ultra-low loads. However, aspects related to the determination of the contact area under indentation should be cautiously considered when using this equipment. These are related to the geometrical imperfections of the tip, the diamond pyramidal punch and the formation of pileup or the presence of sink-in, which alter the shape and size of the indent. These and other aspects, such as the thermal drift of the equipment and the scattering at the zero indentation depth position related to surface finishing, are discussed in this work. A study concerning the hardness and the Young's modulus results determined by Vickers indentation on different materials was performed. Samples of fused silica, BK7 glass, aluminium, copper and mild steel (for which the values of Young's modulus were previously known) were tested using indentation loads in the range 10–1000 mN. Moreover, two methods are proposed for performing the indentation geometrical calibration of the contact area; these are compared with a former method proposed by Oliver and Pharr (OP). The present methods are based on: (i) analysis of the punch profile using atomic force microscopy (AFM); and (ii) a linear penetration-depth function correction (LM), based on knowledge of the values of the Young's modulus of several materials. By applying these methods to the indentation load/indentation depth results, it was possible to draw some conclusions about the benefit of the AFM and LM methods now under proposal.
A Bloyce - One of the best experts on this subject based on the ideXlab platform.
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microstructural response of mono and multilayer hard coatings during indentation Microhardness Testing
Surface & Coatings Technology, 1997Co-Authors: A Bloyce, Rostislav A Andrievski, G V KalinnikovAbstract:Abstract An investigation of indentation crack patterns and the nature of fracture mechanisms of hard coatings can provide useful information to aid in the understanding of failure mechanisms occurring as a result of scratch and wear tests. Examples of several different types of single and multilayer coating systems are presented in this study. The effect of substrate and microstructure on the brittle-ductile transition behaviour is discussed. The concept of energy dissipation is introduced to interpret deformation and fracture behaviour during indentation tests. If a hard coating undergoes some densification or plastic flow to dissipate a proportion of the energy, then the premature adhesive failure due to the non-compliance of the strain at hard coating/substrate interface can be avoided. The compaction or plastic flow of the hard coating also effectively disperses concentrated stress and delays the formation tensile cracks around indentations.