About the Hot Disk instrument
The
Hot Disk Thermal Constants Analyzer is a system designed to conveniently measure the thermal transport properties of a sample, i.e. thermal conductivity and thermal diffusivity. From these two parameters the specific heat capacity can be derived. The system is based on a patented Transient Plane Source (TPS) technique, which can be used to study materials with thermal conductivities from 0.005 to 1800 W/mK and covering a temperature range from 30 to 1000 K. The following modes of operation are available with the Hot Disk instrument:
Introduction Thermal conductivity measurements on powders of varying composition are readily carried out with the Hot Disk TPS 2500 system. Commercial powder has been tested for thermal conductivity. Since the properties of the sample in powder form will differ from the bulk properties of the individual grains, the tests were carried out with varying pressure. This procedure indicates that the Hot Disk TPS 2500 system could be used for character rising pressed tablets or loose powder in situ. The routine described in this application note is applicable to most powder types. Measurements The tests were carried out with a Hot Disk TPS 2500 system and a powder sample holder for powder samples, see fig. 1 below. A sensor with radius approximately 6.4 mm was used together with measurement time 40 seconds and power 40 mW. Three tests were carried out with 0 pressure applied and also when 5471 g of weight was applied. All other measurements were only carried out one time.
| Weight (g) |
0 |
176 |
471 |
1741 |
5471 |
10471 |
| Thermal Conductivity(W/mK) |
0.1141 |
0.1234 |
0.1267 |
0.1324 |
0.1494 |
0.1545 |
Comments The thermal conductivity increases monotonically with increasing pressure. This can be explained by the fact that as the powder particles get closer and closer to each other the air content in the sample is reduced. The measurements show that it is possible, within one experimental set-up, to analysis compressed powders, such as tablets or pellets. For these measurements the largest weight available was a loose 10 kg weight plus additional small weights (471 g). The measurement points which were repeated (0 g and 5471 g applied) repeated themselves within 0.5 %. Measurements on powders are easily carried out with the Hot Disk TPS 2500 system with standard Method.
