Testing.1 – Thermal Conductivity Measurements on Aluminum Oxide (Al2O3) Powder of Different Particle Sizes
Thermal conductivity and thermal diffusivity measurements were made on various particle size aluminum oxide powders by the Hot Disk Transient Plane Source (TPS) 1500 Instrument. Thermal conductivity and thermal diffusivity were measured directly, with automatic calculation of volumetric heat capacity. The Hot Disk TPS technique has the ability to measure thermal conductivity, thermal diffusivity and heat capacity of solids, liquids, pastes and powders, with conductivity values ranging from 0.001 W/m•K to 1800 W/m•K. The Hot Disk TPS 1500 is specifically designed to measure thermophysical properties of insulating materials and has a measureable thermal conductivity range of 0.001 W/m•K to 20 W/m•K.
Aluminum oxide finds many uses in industry, such as in the Hall-Heroult process which is the major industrial process for smelting aluminum. It is also used as a catalyst (for conversion of hydrogen sulfide to elemental sulfur) and catalyst support (for hydrodesulfurization and Ziegler-Natta polymerizations).
The powder sample cell was used for this testing, which consists of a two piece hollow metal cylinder with a horizontal opening to accommodate the TPS sensor. The bottom half of the sample cell is filled with powder so the level of powder just reaches the sensor opening. The sensor is then slid into the sample cell and additional powder is added on top of the sensor until the sample cell is full. If limited amounts of powder are available for testing, then a single-sided sensor may be used.
Five measurements were recorded for each sample using the TPS auto-schedule and the average of the five measurements was taken. The samples of aluminum oxide investigated were millipowder and micropowder containing particles sizes in their respective ranges. All measurement were made at ambient density and room temperature (24 °C).
Table 1. Experimental results for thermal conductivity, thermal diffusivity and volumetric heat capacity for Al2O3 milli and micropowders.
|Powder Particle Size||Thermal Conductivity (W/m•K)||Thermal Diffusivity (mm2/s)||Volumetric Heat Capacity (MJ/m3K)|
|Millipowder||0.2732 RSD:0.14%||0.1502 RSD: 0.17%||1.818 RSD: 0.17%|
|Micropowder||0.1410 RSD:0.79%||0.1399 RSD: 2.2%||1.009 RSD: 1.4%|
Experimental Parameters Used:
Millipowder: 40 second test time, 60 mW power, sensor 5501 (6.4 mm radius)
Micropowder: 40 second test time, 40 mW power, sensor 5501 (6.4 mm radius)