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One of the properties of coal, used to evaluate the qualitative features of this mineral, is the microhardness of its particular components (macerals). Unfortunately, that parameter is relatively seldom used in analyses of this substance. Microhardness measurements are mostly used in research into metals, ceramics or composites; they are also sometimes used to analyse minerals and rocks. The objective of the paper presented here was to conduct coal's microhardness tests and to determine the relationship between strength parameters obtained in the course of these tests and other coal parameters commonly used in analyses of that substance. As part of the study, 22 coal samples from the mines of the Upper Silesian Coal Basin were analysed. In order to achieve the research objectives, the results of technical, gas and petrographic analyses were used, as well as the results of Vickers microhardness tests. As a result, the authors obtained 20 parameters which were subsequently correlated with one another. The conducted research shows that the strength parameters and the coalification degree correlate quite visibly with the gas parameters of coal, in particular with the sorption capacity (correlation on the level of 0.73). Slightly poorer results were obtained in the course of multiple correlations, determined between strength parameters and other analysed parameters. The preliminary research discussed in the paper shows that correlation between microhardness parameters and the results of petrographic, technical and gas analyses might constitute a significant complement to standard analyses of hard coal. However, the authors are of the opinion that further, more detailed studies into the issue are required. [ABSTRACT FROM AUTHOR]

High speed high pressure torsion (HS HPT) is proposed as a novel method to produce metal matrix multilayer composites. The HS HPT technique derivate from traditional High pressure torsion (HPT), which is the most widely used in exertion of severe plastic deformation on bulk metallic samples. HS HPT involves combination of high pressure with torsional straining but differs from the classical method through implementation of an elevated rotation speed of superior anvil and slippage between sample and anvils. The process is kindred to steer friction. Therefore, HS HPT is not only able to produce ultrafine grained and nanostructured disks, cones or rings but also may produce the bonding, too. In experiments was used a typical bimetal system Al/Cu. The composites have 2, 3, 5, 7, 9 and respectively 11 layers. The manufacturing process of Al/Cu multilayers and its effects on microstructure and mechanical properties of Al/Cu composites was studied. Vickers microhardness were conducted to investigate the Al and Cu layers and joint effectiveness, according to the increasing number of layers. The experimental results confirm the method HS HPT as having real potential in gaining multilayer metallic nanocomposites. [ABSTRACT FROM AUTHOR]

The mixed alkali effect on zinc borate glasses have been reported. The glass systems of nominal composition 10Zn + xLi2O + y Na2O + 80B2O3 ( x = y = 0, 5, 10, 15 mol% ) were prepared using standard melt quenching method. The structural, physical and mechanical properties of the samples have been studied using X-ray diffraction(XRD), density measurement and Vickers hardness measurement, respectively. A consistent increase in the density was observed, which explains the role of the modifiers (Li2O and Na2O) in the network modification of borate structure. The molar volume is decreasing linearly with the alkali concentration, which is attributed to the conversion of tetrahedral boron (BO4/2)- into (BO3/2)-. The microhardness studies reveals the anisotropy nature of the material. It further confirms that the samples belong to hard glass category. [ABSTRACT FROM AUTHOR]