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509Metal powders are widely used in modern technol ogies-in particular, as fillers for the production of various composites. In recent years, metal powders have sometimes been subject to mechanical activation prior to use [1,2]. Mechanical activation improves the compatibility of the powdered filler with a matrix, but it can also modify physicochemical properties of the metal powder, thus changing the properties of the final composite. However, the influence of mechanical activation on the physicochemical (in particular, ther mal) properties of powdered metals has been insuffi ciently studied.This Letter presents the results of an investigation of the effect of mechanical activation on the heat capacity of a powdered metal. This treatment is usu ally accompanied by an additional oxidation of metal particles. In order to minimize the role of this factor, we have chosen tungsten as the object for investiga tion, since this metal is characterized by high resis tance to oxidation.The experiments were performed on a commercial tungsten powder (PVN grade) with particle dimen sions within 2-3 µm. The metal powder was mechan ically activated by treatment in a centrifugal planetary grinder of AGO 2U type [3]. The process was carried out in air, and the mill drums were cooled by water jackets. The working charge included 10 g of initial material and 100 steel balls with a diameter of 8 mm.The specific heat capacity C p of the sample metal powder was determined using the method of differen tial scanning calorimetry (DSC). The measurements were performed in air on a DSC Q100 instrument (Intertech Co., United States) at a sample heating rate of 5°C/min in a temperature interval from 20 to 300°C.The results of DSC measurements of the heat capacity of the sample metal powder before and after mechanical activation showed that this treatment led to an increase in the C p value as measured in the tem perature interval of 20-120°C. As can be seen from the data presented in the table, the magnitude of this effect depends on the treatment duration: C p varies in a nonmonotonic manner with increasing activation time. From this it may be concluded that the observed effect is not related to oxidation of the metal, since otherwise an increase in the treatment duration would lead to a monotonic variation of the parameter mea sured.It can be suggested that a certain role in the observed increase in C p is played by an additional com minution of metal particles, which unavoidably accompanies treatment in the mill. As is known [4], a decrease in the average particle size leads to an increase in the heat capacity of a metal powder. Irre spective of the size of particles, the powder heat capacity at temperatures above 30 K obeys the law C ~ T 3 [4].Abstract-We have studied the heat capacity (C p ) of a mechanically activated tungsten powder. It is estab lished that the mechanical processing leads to an increase in C p of the metal powder at low temperatures and modifies the character of the temperature dependence of this parameter. The depende...

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