Cryocooled detector

From Fig. 3.12, we see that at fixed (low) temperature, the specific heat of various solids range over many orders of magnitude. Low specific heat materials (high Debye temperature) are for example very important in the realization of detectors (see Chapter 15). High specific heat materials are essential as regenerators in cryocoolers (see Chapter 5 and Fig. 3.13). 

TPR has been carried out in a Micromeritics Autochem 2910 instrument equipped with the CryoCooler system for reaching subambient temperature by means of liquid nitrogen. A molecular sieve trap has been put between the sample holder and the detector in order to absorb water that is formed dining the rednction process. 100 mg of wet sample has been introduced in the sample holder, dried in situ by a nitrogen flow at 393 K for two h. Then the sample was cooled down to 153 K under Ar flow (50 cm min" ) after which, the flow was switched to 5% H2 in Ar (50 cm min ) and maintained throughout the analysis. After a baseline had been established, the temperature was started at a rate of 5 K min up to 623 K. A TPR experiment on sample Pduns reference was carried out on 10 mg of sample following the same procedure described above for the catalysts. 

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