Journal ArticleDOI
Hardness-grain-size relations in ceramics
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TLDR
In this paper, the Vickers and Knoop hardness (H) was measured at two or more loads in the range of 100-2000 g (most commonly 100 and 500 g) for a variety of dense oxide and non-oxide materials, covering a range of grain sizes (G), including single crystals where possible, were shown to generally be consistent with (often more limited) literature data.Abstract:
Both Vickers and Knoop hardness (H), measured at two or more loads in the range of 100–2000 g (most commonly 100 and 500 g) for a variety of dense oxide and non-oxide materials, covering a range of grain sizes (G), including single crystals where possible, were shown to generally be consistent with (often more limited) literature data. Apparently, conflicting trends of H (1) showing either no G dependence, (2) decreasing from single-crystal or large G values with decreasing G, or (3) having the generally accepted increase with decreasing G are shown to be due to the combination of the limited extent of data and H generally heing determined by two basic trends. These two trends are (a) the normal inverse G (i.e., H–G−1/2) dependence at finer G, (b) a variable G minimum at intermediate G, and (c) H increasing with increasing G at larger G (to. single-crystal values). The H minimum is due to local cracking around the indent (mostly along grain boundaries), generally reaching a maximum effect, e.g., minimum in H, when the indent and grain sizes are similar, and tends to be greater for Vickers vs Knoop indents, higher loads and probably greater grain boundary Impurity, additive contents, and stresses.read more
Citations
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Synthesis and Design of Superhard Materials
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Nanocrystalline hydroxyapatite with simultaneous enhancements in hardness and toughness.
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References
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TL;DR: In this paper, the authors presented a convenient method to describe the degree of elastic anisotropy in a given cubic crystal, and then discussed its practical values, including the folowing properties of practical importance.
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TL;DR: In this article, a model based on energy and stress considerations is applied to the phenomenon of spontaneous fracture of materials due to phase transformations and thermal expansion anisotropy, and results are shown to be in reasonable agreement with observations of the grain-size dependence of such cracking and the effects of internal stresses on strength.
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Koichi Niihara,Toshio Hirai +1 more
TL;DR: In this article, the microhardness of amorphous and crystalline chemical vapour-deposited silicon nitride (Pyrolytic-Si3N4) prepared under various deposition conditions using SiCl4, NH3 and H2 has been measured at room temperature.
Journal ArticleDOI
Thermal expansion and thermal expansion anisotropy of SiC polytypes
Zhuang Li,Richard C. Bradt +1 more
TL;DR: In this paper, the principal axial thermal expansion coefficients for the (3C, (4H), (5H), and (6H) polytypes of SiC are investigated to identify the structural role of the stacking layer sequence as it affects the thermal expansion.
Journal ArticleDOI
Mechanical Properties of Fine‐Grained Substoichiomebic Titanium Carbide
Daniel B. Miracle,H. A. Lipsitt +1 more
TL;DR: In this article, an attempt was made to lower the ductile-to-brittle transition temperature (DBTT) of polycrystalline TiC and to prevent the premature intergranular fracture noted in stoichiometric Tic at high temperatures by producing four substoichiometric compositions chosen from the single-phase TiC phase field.
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