Annealing history

Czamanske, G.K., Desborough, G.A. and Geoff, F.E. (1973) Annealing history limits for inhomogeneous native gold grains as determined from Au-Ag diffusion rates. Econ. Geol, 68, 1275-1288. 

In contrast to the well-defined equilibrium crystals, there exist a multitude of glasses of the same chemical stmcture, differing only in the cooling or annealing history. Also, an analogous extrapolation of the liquid and solid free enthalpies beyond the transition temperature, as possible for crystals is not permitted as implied by the parentheses in Fig. 2.118. 

Semiconducting Ceramics. Most oxide semiconductors are either doped to create extrinsic defects or annealed under conditions in which they become non stoichiometric. Although the resulting defects have been carefully studied in many oxides, the precise nature of the conduction is not well understood. Mobihty values associated with the various charge transport mechanisms are often low and difficult to measure. In consequence, reported conductivities are often at variance because the effects of variable impurities and past thermal history may overwhelm the dopant effects. 

Among these three polybibenzoates, PTEB has a smectic mesophase stable during several days at any temperature below its isotropization point, although the transformation into a three-dimensional crystal can be attained by annealing at the appropriate temperatures, thus making it possible to analyze the effect of the thermal history on the dynamic mechanical relaxations of PTEB [27]. 

In conclusion, the different thermal histories imposed to PTEB have a minor effect on the /3 and y relaxations, while the a. transition is greatly dependent on the annealing of the samples, being considerably more intense and narrower for the specimen freshly quenched from the melt, which exhibits only a liquid crystalline order. The increase of the storage modulus produced by the aging process confirms the dynamic mechanical results obtained for PDEB [24], a polyester of the same series, as well as the micro-hardness increase [22] (a direct consequence of the modulus rise) with the aging time. 

Experience shows that the density of Ob-vacs can be varied by changing the anneal temperature or the anneal time [66], Wendt et al. [18] assessed this systematically by demonstrating a linear dependence of the Ob-vac density (measured by STM) on the sample history, the latter being defined as the anneal temperature x anneal time. 

A comparison of the dynamic mechanical properties of our HB at 35 Hz has been made to that of LDPE in Figures 14 A and B. The thermal and sample preparative history affects the mechanical properties of HB films to such an extent that in order to make a meaningful comparison one has to describe the exact history of the samples. Such a thermal history dependence has been examined for LDPE(54,57) and recently for HB.(12) Shown in Figures A and B are the mechanical spectra for HB-PQ, HB-Tol, and LDPE-PQ films. The compression molded films were prepared 1 to 2 days prior to the test. The solution cast film (from toluene), HB-Tol, was annealed at 80°C for 2-3 days and stored at room temperature for 1 week... 

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