Annealing constant rate

Brysen Coating Laboratories. Some of the gold-mirror substrates were purchased with a 10-nm layer of SiOj on them. The SiOj-coated mirrors were cleaned and annealed to produce model hydrophilic surfaces. Half of these slides were then reacted with dichloro-dimethylsilane to produce model hydrophobic surfaces. Using a clean gold mirror for a reference, IR reflection-absorption spectra of these model surfaces were collected both before and after each step in the preparation of the model surfaces. Finally, the model surfaces were soaked in BFN solutions stabilized with Tris buffer. For comparison, a clean gold substrate was soaked in a O.IJI lysozyme in 0.15 N NaCl solution (pH 7.2). After pulling the substrate out of this solution at a slow, constant rate of speed with a motor, spectra were collected both before and after rinsing with deionized water. All spectra were collected after the surfaces had dried. 

Alternatively, it may be possible to demonstrate for the pure metals that the catalytic activity is independent of film weight in a certain weight range. For example, rates of ethylene oxidation were constant over pure palladium films, deposited and annealed at 400°C and weighing between 4 and 40 mg (73). Then, if electron micrographs show that the crystallite size is relatively independent of composition, a satisfactory comparison of catalytic activity can be made at the various alloy compositions. Finally, surface area measurements are less urgently needed when activity varies by orders of magnitude, or where the main interest lies outside the determination of absolute reaction rates. 

Figure 7.5 shows the relative endotherms of PVDF/PMMA blends as a function of PVDF content. A relative endotherm is defined here as the ratio of a melt endotherm at a certain PVDF blend composition to the endotherm of the pure annealed PVDF in DSC measurements. The DSC measurements are at a constant heating rate of lOC/min. For annealed and solution-cast blends, the relative endotherms are in general greater than those of quenched blends of the same composition. Endotherms can be detected at all compositions when the blends are annealed. The quenched PVDF shows only 75% endotherm relative to the annealed PVDF. No endotherm can be detected when the PVDF content is lower than 50 wt % in quenched PVDF/PMMA blends. Obviously the thermal history of the blends has a tremendous effect on the final performance of the material. 

A diffusion measurement at the temperature To is made by annealing a diffusion couple comprised of two semi-infinite bars. However, there is a complication after the completion of the isothermal anneal, carried out at To for the time to, the specimen must be cooled to room temperature at a finite rate. During this cooling period, a small amount of additional nonisothermal diffusion occurs. If an expression can be found for the amount of time, At, required to produce this same additional increment of diffusion at the constant temperature To, the specimen could be analyzed very simply at the end of the experiment by assuming that it was annealed at To for the time to + At. Assume that D = D0 exp —E/(kT)] and that the temperature during the cooling period is... 

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