Pulse-heated copper sample

The specific heat at constant pressure, Cpf of the HIP-treated sample with nominal composition LaVg 25 0,7504 was measured over the temperature range 4-400 K by the heat pulse method in a calorimeter that incorporates a feedback system to regulate the temperature of concentric radiation shields surrounding the sample (9). The Cp values are accurate to within 1%, as determined by calibration runs using a polycrystalline copper sample and a sapphire single crystal sample. 

The dynamics of heating in the initiation region was studied with the help of a copper-constantan thermocouple mounted on the heater surface (not shown in Fig. 2). The results of the measurements are presented in Fig. 3 (the arrow indicates the instant of switching on the pulse heater). Whatever the pulse energy, no reaction burst is observed in nonirradiated samples after switching on the heater (Fig. 3, solid curve). In the preirradiated CB + Cl2 system,... 

Surface areas were measured by the BEIT one point method using N2 gas. For the estimation of the dispersion of copper, the amounts of CO adsoiption were measured by the pulse method. The ground catalyst samples were heated in a helium stream at 773K for 4 hours to desorb oxygen. Most copper exposed to the gas phase was then reduced to Cu which can adsorb CO. Afterwards, the catalyst was cooled down in a helium atmosphere to room temperature and a CO pulse was introduced to the helium stream to measure the amount of CO adsorption, which is considered to be roughly proportional to the dispersion of Cu. 

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