Non-equilibrium Technology of Obtaining Nanoamorphous Metals
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Non-equilibrium Technology of Obtaining Nanoamorphous Metals Malkhasyan R.T. Scientific Production Enterprise “ATOM” Tevosyan 3/1. Yerevan 375076 Republic of Armenia, e-mail: [email protected] ABSTRACT A new non-equilibrium technology of obtaining structureless amorphous nanosize metals (not alloys) is presented in the given paper. The new content of definition of amorphous metals is discussed with an example of synthesized nanosize amorphous metals: W* and Mo*, with the grain size of less than 5 nm. A comparison of some properties of these metals with those of nanosize but crystalline ones (Wcr and Mocr ) are presented. It is shown that they are much more reactive than the crystalline metals of analogous size. INTRODUCTION The existing definition of amorphous substance (including amorphous alloys) is based on their comparison with liquid state, from which they are obtained, more often, for instance, by the means of rapid quenching their melts [1-2]. At the same time it is necessary to emphasize that it is impossible to obtain amorphous metals (not alloys) in free state by such a method. It is considered that it is necessary to raise the rate of rapid quenching from the widely used values of no more than 106 grad/sec [2-3], to 1010-1013 grad/sec (which is not practically feasible), in order to obtain such amorphous free metals as Fe, Mo and W. According to that an amorphous substance is defined as a substance which has a short range order (as all the liquids) and no a long range order. If a short range order for liquids is determined by coordination number 4.1 and by dimension of approximately 1.0 nm, in the case of quenched metallic alloys it reaches 1.4 – 1.8 nm [4], and its coordination number is allowable up to the magnitude of 5.5 – 6.0. Therefore, at present, a nanoparticle of any substance with such a radius and a grain size of 3.2±0.4nm may be considered formally as an amorphous one. If such grain size is attained by means of ball milling, the considerable destruction and shear deformation of the grain shell draws together the existing concepts of amorphous state and nanosize materials, in additional way [5]. However one cannot consider the abovementioned nominal amorphous materials as true amorphous ones, because there are true amorphous substances (including nanosize amorphous metals in free state) which are as if they were analogues of condensed “frozen- gas”, but not a liquid in a frozen state. In the given paper I will present a quantum-chemical technology of obtaining such a substance on the example of condensed or “frozen” atoms of true amorphous molybdenum and tungsten [610] that is worked out by the staff of SPE “ATOM”. Our quantum-chemical technology differs from the known plasma-chemical technology by the fact that we use only non-equilibrium inner energy of the reagents at the practically complete absence of their heat energy.
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It should be noted that such long-living vibrationally excited molecules are very reactive and the reaction rate constant in endothermic reactions ri
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