Abstract

For direct heat capacity measurement continuous and step-by step scanning methods are widely used. The disadvantage of these methods is that it is necessary to reproduce accurately the same rate of change and temperature values at all stages and effectively protect the calorimetric cell measuring from external influences disturbing. In addition, these methods have a fairly low performance. The main purpose of the article is to develop the method of measuring the heat capacity by simultaneously investigation of several samples in step-by-step scanning and comparing them with a reference sample, as well as creating an appropriate measuring instrument. The measuring system for determining the heat capacity of materials is a multi-cell differential scanning calorimeter. The essence of the modification is that, under the influence of a stepwise varying temperature, the samples and the referent are simultaneously exposed in a single working chamber. In the working chamber there are working measuring calorimetric cells into which the analyzed materials samples are placed, a reference cell with the reference material sample and a reference cell that is left empty. By applying stepwise heating to all cells from the lower boundary of the temperature range to the upper one, the heat fluxes, brought to the cells, are measured, and the total heat spent on heating each sample at each step is determined by integrating the heat flux into time. The value of the temperature scanning step is not included in the measurement equation. As a result, the direct influence of the inaccuracy of the temperature setting on the measurement error is excluded. The description of the calorimetric measuring system and its main technical characteristics are given: the specific heat capacity measuring range is from 300 J/(kg·K) to 3000 J/(kg·K); range of operating temperature is from 300 K to 450 K; the number of samples examined simultaneously is 5 pieces; the error in measuring the specific heat is not more than ± 2%. The proposed method of measuring heat capacity with step-by-step temperature scanning and simultaneous comparison with a reference sample made it possible to create a calorimetric system in which the effect of external disturbances and the instability of the reproduction of the temperature scan plot are compensated, and it is also possible to study several samples simultaneously.

Authors and Affiliations