Lowest amorphous materials

The zeolite products with the highest XRD intensities and with the lowest amorphous material impurities were used as the quantitative standards for both Na-ZSM-5 and mordenite. The degree of crystallization was estimated by comparing the sum of the respective XRD peak areas (around 20 = 20-30°) with those of the standard. 

Amplitudes of the structure factors are sampled by D(u)sinx(u) when they are transferred to the image. The most significant effect of the lens to the amplitudes is caused by the sinx(u) part, which oscillates with u. Reflections in the resolution regions where sinx(u) 1 are maximally transferred by the lens, while those at resolutions where sinx(u) 0 are not transferred at all. This can be seen in the Fourier transform of HREM images from amorphous materials (Fig. 6), where the highest amplitudes (brightest areas) correspond to sinx(u) 1, while the lowest amplitudes (darkest areas) correspond to sinx(u) 0. If there is no astigmatism in the objective lens, a... 

Effect of 6- Caprolactone and Adipic Acid Molar Ratio for Copolyester III on the Hydrolysis by R. delemar Lipase. The hydrolysis of various copolymers by R. delemar lipase was exam ed to see whether there was an optimum chemical structure or not. Mn of those copolyesters was selected from 17 0 to 2220, to diminish the effect of molecular weight. Optimum molar ratio of e- caprolactone and adipic acid was about from 90 10 to 70 30 (Figure 5). The Tm at the optimum molar ratio was the lowest of all. So it seemed that the existence of optimum molar ratio came from the lowest Tm, which would show the most amorphous material, rather than the optimum chemical structure. 

The glass transition temperature, T, is the temperature at which an amorphous material changes from a brittle glassy state to a rubbery state. Poly(methyl methacrylate) has the highest glass transition temperature (105°C) and poly(2-ethylhexyl-acrylate) the lowest (-55°C). Other predominantly acrylic polymers and copolymers lie between the two (Edward, 1968). 

Amorphous materials are always in a higher energy state than their crystalline counterparts. Excess free energy and entropy are accrued in the solids as they are converted into the amorphous phase, since solidification occurs rapidly without permitting the basic structural units to attain their lowest energy state. The thermodynamic instability inherent in such a system results in a higher solubility and faster dissolution rate. 

When comparing the influence of the polymers, the most apparent result is the incomplete consumption of clinker phases in the c/PVAc samples, whereas in the c/PVA samples, the clinker phases are consumed in less then four days. It should be noted that the consumption of the clinker phases is the lowest for c/PVAc in pure water. The reason for this is the above mentioned hydrophobic nature of PVAc, which requires alkaline pH values for saponification before the polymer can be dissolved. Thus, the XRD measurements are consistent with the NMR measurements. Additionally, approx. 10% more amorphous material is formed in the case of c/PVAc. This is again a result of the hydrophobic nature of PVAc. As discussed in the NMR section, c/PVAc swells at a lower rate than c/PVA. This limits the access of water to the clinker phases, which hampers the formation of larger crystallite sizes. 

The effect of the pH upon the formation of o.33[Cu-Cr-Cl]3R is similar. The best crystallized phase is obtained at the lowest pH value of 5.5. Below this pH, an additional unidentified phase appears. It must be noticed that, in some cases, the pH does not have a direct observable effect on the diffraction pattern. The typical example comes from the q 33[Ni-Cr-Cl] phase. ITiis phase displays the same powder X-ray diffraction patterns characteristic of a quasi-amorphous material, whatever the pH of precipitation from 5.5 to 11.5. However, under hydrothermal treatment, the only phase that crystallizes is the LDH prepared at pH = 11.5. 

---