T ransition peaks occurring at t 2 8 8 2 2 k w ere

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Unformatted text preview: e was no measureable hysteresis in the temperature of the transition between heating and cooling s c a n s , indicating that there is no isothermal heat absorption. This lack of hystereisis is c onsjstent w ith previously proposed ( 2 2 , 2 3 , 6 5) s econd order nature of the disorder transition of the silver intercalate. T h e change in the baseline slope before and after the transition (indicating a change in the specific heat of the sample) in both heating and cooling scans also supports the supposition of a second order transition. 5 -3 ( b) SAMPLE A ( quenched from 800 C ) . C alorimetric data o f t he Ag T iS - L OW T EMPERATURE D SC s amples (A) obtained i n x 2 t he temperature region from 180 K t o 2 6 0 K r evealed another transition for samples with x > 0 . 2 0 . T h e program used for T he the lower temperature scans is outlined in Appendix 1 1 . scans for x 0 .35 s howed a reproducible transition at T 2 0 8 2 2 K u pon heating ( F i g . 2 1b). = C ooling curves were not obtainable due to the lack of cooling efficiency and sensitivity of the equipment. The peak height of the transition was found to increase with increasing mole fraction of silver intercalate indicating that the transition is associated with the silver intercalate. Page - 5 2 - 5-4 ( a) S AMPLE B ( q u e n c h e d from C ). 1000 DSC - T here were again no distinguishable transition peaks in t h e temperature r a n g e from 1 8 0 K t o 4 0 0 K f or silver mole fractions x < = 0 . 1 s u p p o r t i n g the supposition of a dilute g as p hase for these c o n c e n t r a t i o n s . T h e calorimetric data for samples where 0 . 1 < x < 0 . 2 5 c learly s h o w transitions occuring at T x = 0.2 = 26822 K f or x = 0.1 a nd T = 272 f 2 K f or w ith the peak height of the transition increasing with increasing mole f r a c t i o n of silver ( x). t emperature " T = 2882 2 K T h e transition w as again found to be independent o f the intercalate concentration for silver mole fraction...
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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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