Heating or cooling the sample at slower rates reduces

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Unformatted text preview: ing/cooling r ate m = s ample mass Y = y -axis range setting dY= (measured difference between heating and cooling c urves)/2 T h e sapphire ( A1 O ) d isk supplied with the equipment 23 w as used to determine the cell calibration coefficient (E). Multiple scans were taken with the sapphire calibration sample placed in an aluminum sample pan and an identical empty sample pan used a s t he reference. T h e cell calibration P age - 45c oefficient was determined over the temperature range of 1 80 K to 3 60 K by comparing the measured specific heat of A1 0 32 w ith the accepted values ( 66-DSC m anual). Heating and cooling rates of 1 0 K /min w ere used for all scans with a l ow temperature l i m i t o f 1 50 K a nd high temperature limit of 4 00 K . T he high temperature endpoint of the scan was limited to 4 00 K to avoid overtaxing the capabilities of the heating unit. outlined in Appendix 1 1 1 . The D SC p rogram used is T he difference between the heating and cooling curves were measured at increments of 2 0 K o ver the temperature range 2 00 - 3 60 K . Measurements between 1 50 t o 1 80 K i n the heating mode and between 4 0 0 t o 3 70 K i n the cooling mode were not taken because of the time lag for the equipment to equilibriate o n starting to heat or cool respectively. The difference between consecutive heating and cooling curves was measured in order to reduce the n ons ymmetric behavior of the equipment between heating and cooling scans. The cell calibration coefficient was then calculated using the equation 4 - 1 1 . T hree consecutive heating-cooling scans were taken and the results averaged at each temperature in order to'eliminate any spurious results and reduce the time dependent characteristics of the equipment when running multiple repetitive scans (such as the build up of frost o n the cooling apparatus). The cell calibration coefficient was found to be constant over the latter temperature range ( 2 0 0 - 3 00 K ) h aving a value of Page - 4 6 - 4 -7 ( b ) Cell C o e f f i c i e n t C h e c k T h e heat of fusion of m e r c u r y and indium was used to c h e c k t h e cell c a...
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This note was uploaded on 10/08/2009 for the course CME MAT E 630 taught by Professor Dr. during the Fall '09 term at University of Alberta.

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