نتایج جستجو برای: b4c bn
تعداد نتایج: 8878 فیلتر نتایج به سال:
Abstract Directionally solidified B4C–NbB2-SiC ternary composites were prepared by a floating zone method based on crucible-free melting of compacted powders. The eutectic composition B4C–15NbB2–35SiC (mol.%) was characterized boron carbide matrix, directionally reinforced lamella-type NbB2 and SiC phases. inclusions about 1−2 μm in thickness uniformly dispersed B4C matrix B4C–NbB2–SiC composit...
Boron carbide (B4C) is very hard, but its applications are hindered by stress-induced amorphous band formation. To explain this behavior, we used density function theory (Perdew-Burke-Ernzerhof flavor) to examine the response to shear along 11 plausible slip systems. We found that the (0111)/<1101> slip system has the lowest shear strength (consistent with previous experimental studies) and tha...
Aluminium metal matrix composites reinforced with SiC and B4C particles are a unique class of advanced engineered materials that have been developed to use in high strength , high wear resistant and tribological applications. The conventional techniques of producing these composites have some drawbacks. In this study, the aluminium hybrid composite is fabricated using stir casting method. 10 % ...
The distinction between mild pathogenic mtDNA mutations and population polymorphisms can be ambiguous because both are homoplasmic, alter conserved functions, and correlate with disease. One possible explanation for this ambiguity is that the same variant may have different consequences in different contexts. The NADH dehydrogenase subunit 1 (ND1) nucleotide 3394 T > C (Y30H) variant is such a ...
This paper describes the synthesis of B4C/carbon nanotube (CNT) composite by hot-pressing and shows details for effectiveness CNT addition, additive amount its orientation on thermal shock resistance. CNTs tend to array perpendicular direction, which caused anisotropic mechanical properties B4C/CNT composite. We investigated residual bending strength thermally shocked composites determined crit...
This thesis is a theoretical study of configurationally disordered icosahedral boronrich solids, in particular boron carbides, using density functional theory and alloy theory. The goal is to resolve discrepancies, regarding the properties of boron carbides, between experiments and previous theoretical calculations which have been a controversial issue in the field of icosahedral boron-rich sol...
Aluminum (Al) matrix composites with boron carbide (B4C) reinforcements were fabricated by solid state powder metallurgy using the hot-pressing process. Composite materials at different volume fractions of B4C particles, ranging from 2% to 12%, evaluate impact on thermal and mechanical properties composite materials. Thermal properties, such as conductivity (TC) coefficient expansion (CTE), mea...
The assessed binary phase diagram of boron-carbon exhibits a single intrinsically disordered alloy phase designated “B4C” with rhombohedral symmetry occupying a broad composition range that falls just short of the nominal carbon content of 20%. As this composition range is nearly temperature independent, the phase diagram suggests a violation of the third law of thermodynamics, which typically ...
The aim of this work is to apply the Gamma Ray Transmission (GRT), a non destructive technique, for structural characterization of ceramic samples. With this technique, the porosity of Alumina (Al2O3) and Boron Carbide (B4C) ceramic samples, in tablet format, was determined. The equipment employed is constituted by a 241 Am gamma ray source (59.6 keV and 100mCi), a 2”x2” diameter NaI (Tl) scint...
The densification behavior and mechanical properties of B4C hot-pressed at 2000°C for 1 h with additions of Al2O3 up to 10 vol% were investigated. Sinterability was greatly improved by the addition of a small amount of Al2O3. The improvement was attributed to the enhanced mobility of elements through the Al2O3 near the melting temperature or a reaction product formed at the grain boundaries. As...
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