Aluminum signal Integration

For all the oxides calcined at Tc<973 K, octahedral (Al, 2-10 ppm), pentahedral (Al, 23-35 ppm) and tetrahedral (Al, 54-65 ppm) aluminum were detected, the latter being most abundant (Fig. 1 to 4, Tables 2 and 3). All the signals were not well resolved and relatively wide due to quadrupole broadening. Thus, a exact quantification of the different aluminum species by deconvolution-integration was rather difficult. Nevertheless, the method could provide a good estimate of the amounts of Al in different coordinations [6]. No effect of the synthesis additive was found on the A1 speciation in alumina... 

D. E. O Reilly [23], in early Al experiments, considered the observability of surface aluminum atoms in aluminas. As summarized in Fig. 4, O Reilly obtained room-temperature data on a series of aluminas with varying surface areas and found that for an equal number of aluminum nuclei, each of the other aluminas had a weaker Al NMR signal than that observed for a-alumina. Specifically, for an equal number of spins the integrated signal was inversely proportional to the surface area of the particular alumina. O Reilly reasoned that the reduction in observed signal occurred because surface aluminum atoms... 

Figure 12-12 illustrates one form ofa lithium-drifted detector, which is fashioned from a wafer of crystalline silicon, There are three layers in the crystal a p-type semiconducting layer that faces the X-ray source, a central intrintic zone, and an -type layer. T he outer surface of the p-iype layer is coaled with a thin layer of gold for electrical contact often, it is also covered with a thin beryllium window that is transparent to X-rays. The signal output is taken from an aluminum layer that coats the n-type silicon this output is fed into a preampliftcr vc ith a gain of about 10. The preamplifier is frequently a field-effect transistor that is fabricated as an integral part of the detector. 

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