SU1068740A1 - Differential scanning microcalorimeter - Google Patents

Abstract

DIFFEREVDIAL SCANNING MICO-CALORIMETER, containing a calorimetric unit, in the cavity of which working and reference chambers with temperature-sensitive and heating elements placed on them are installed, characterized in that it is equipped with a gas system to improve the accuracy of measurement under conditions of temperature and overpressure, it is equipped with a gas system. in the calorimetric block under the chambers dp of blowing the latter and the screen mounted above it in the form of a disk with openings made coaxially geometric with m cameras.

Description

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O The invention relates to calorimetry, in particular to devices implementing a differential thermal analysis method (DT) A calorimeter for DTA containing a hollow calorimetric unit is known, in which a barrel and a reference chamber, shaped like crucibles, are welded to the bottom plate holder. thermocouples 1. The disadvantage of such a calorimeter is the impossibility of conducting experiments at high temperatures and with an excessive gas pressure, which is closest to the one proposed by the technical essence and reached The intended result is a differential scanning microcalorimeter. (DSM) containing a calorimetric unit, in the cavity of which, the working and reference chambers with temperature-sensitive and heating elements 2 are placed on it. A disadvantage of the known calorimeter is the low accuracy of measurement when conducting research in conditions due to the intense and uneven convective heat exchange of its chambers with the environment. The aim of the invention is to increase the schusti measurements in conditions of elevated temperature, touring and overpressure. This goal is achieved by the fact that a duffering scanning microcalorimeter containing a calorimetric unit, in the cavity of which working and reference chambers with heat-sensitive and heating elements are placed, is equipped with a gas supply system placed in the calorimetric unit under the chambers for blowing the latter and installed above the chrome a disk-shaped screen with holes made coaxially with the geometrical axis of the chambers. In the proposed calorimeter, the suppression of free convection heat exchange between working and reference chambers with structural elements is ensured by means of controlled extrusion convection - by stabilizing blowing of the chambers with a gas flow created by the presence of a screen with holes. FIG. 1 shows the proposed device, a general view; in fig. 2 - camera construction. The calorimeter contains a working 1 and reference 2 chambers made of highly thermally conductive material (for example, platinum) installed by forging 4 by means of holders 3 and equipped with temperature-sensitive elements (resistance thermometers) 5 and heaters 6, respectively, intended to measure power and heat chambers to the required temperature The working 1 and reference 2 chambers are placed in the cavity of the high pressure vessel formed by base 4, the lid 7, which is thermostatically controlled with running water supplied through fittings 8 and 9. The tightness of the high pressure vessel is provided by lock 10 and gasket 11. Gas supply to the vessel is carried out through shtutsera 12 and 13, respectively, in the base 4 and the lid 7, and directly below the working and reference chambers, via a pipe 14, made in the form of a plug. Above it is a screen 15, made in the form of a disk with holes arranged symmetrically to the axis of each of the chambers. Chambers 1 and 2 are integrated into a single unit by a design of a calorimetric unit 16. Easily connected to the holder 3 of the calorimetric unit 16. A sealed lead-in 17 with a set of gaskets 18 is provided for removing the electrical wires from the vessel. The chamber design (working or reference) includes a housing 19 with heat-sensitive element 5 and heater 6, insulating gaskets 20, made of a material with high temperature resistance (fluoroflog), a holder 21, by means of which the camera is fixed in block 16, and an insulating gasket. 22 holders, also made of fluoroflogopite. The operation of the calorimeter to measure the thermal properties of substances at elevated temperatures up to 1000 C and an overpressure of gas up to 10 MPa is as follows. With the cover 7 and disk screen 15 previously removed, a container with the test substance is placed in the working chamber 1, and the same container, Ner, but empty in the reference chamber 2. Then, the chambers are closed with a screen 15, mounted on the base 4 with a gasket 11 to the Kryjia 7 and sealed by tightening the lock clamp 10. The working pressure and gas flow required in the experiment are set by feeding it through the Ipuser 12. The gas is drained into the atmosphere through fitting 13. By applying electrical voltage to the heaters 6 of the chambers 1 and 2, the desired temperature of the test substance is reached. The control and implementation of the experiment program is carried out with the help of conventionally not shown on

FIG. 1 and 2 power supply units, electronic control and registration of heat output. As the sensor use thermosensitive elements 5, located at the base of the camera body 1 and 2.

The principle of the DSM is based on the compensation of the thermal effect that occurs in the working chamber and the recording of the electrical power supplied for compensation. During the heat gap or the heat absorption in the test substance, between the calorimetric chambers, a temperature difference of l T occurs, causing an imbalance in the highly sensitive bridge circuit of the control unit.

 eight

11 4

in which the temperature-sensitive elements 5 are included. According to the bridge mismatch signal, the calorimetric chambers 1 and 2 are heated or cooled with the help of heaters 6 until compensation reaches L. T.

The compensation current of the first microprocessor is proportional to the power of the measured thermal effect.

The invention provides high accuracy in recording thermal processes when conducting calorimetric studies under conditions of elevated temperatures and excessive gas pressure.

18

17

fi & .1

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13

FIG. 2

Claims (1)

A DIFFERENTIAL SCANNING MICROCALORIMETER containing a calorimetric unit, in the cavity of which a working and reference chamber with heat-sensitive and heating elements placed on them is installed, characterized in that, in order to increase the measurement accuracy at elevated temperatures and overpressure, it is equipped with a gas pipeline system located in a calorimetric block under the chambers for blowing the latter and a screen mounted above it in the form of a disk with holes made coaxially with the geometric axes of the spacecraft measures.