Analysis of Mixtures of Gamma Lithium Aluminate, Lithium Aluminum Carbonate Hydroxide Hydrate, and Lithium Carbonate
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XRD spectra were recorded from 50 to 700 20 with a step size of 0.02' and a count time of 1 s. Primary and secondary Sollar slits, 0.50 aperture, 0.50 scattered radiation and 0.30 detector diaphragms, a monochromator and a copper tube running at 40 kV and 50 mA were used. For the single peak analysis, the 20 ranges used were: 10.8 to 12.50 for LACHH; 21.6 to 22.90 for gamma LiAIO 2; 31 to 32.30 for Li 2CO 3; and 51.7 to 53.40 for corundum. Conversions were calculated using the integrated areas for the samples, or the integrated area ratio relative to corundum. The Reference Intensity Ratio (RIR) was calculated for each phase by preparing 1:1 mixtures of corundum with LACHH, Li 2CO 3, and LiA10 2 and recording the XRD spectra. The spectra were processed with the computer program Jade+ ver. 3.1 (MDI). The spectra were smoothed, background corrected, and theta calibrated to the internal standard corundum before calculation of the RIR. The (pattern simulation) quantitative analysis function of Jade+ was used to analyze both the standards described earlier in this section and the samples. Patterns were also analyzed with Peakfitm ver. 4.0 (SPSS) and the Pearson VII amplitude function. Data were smoothed, background corrected and converted to ASCII with Siemens Diffrac AT ver 3.3, and normalized to the total corundum area for import into PeakfitTM Patterns for the phases were then simulated with Lotus 1-2-3 rel. 5. Total integrated area for each simulated phase was then calculated. Plotting and least squares were performed with Axum® 4.0 for Windows (Trimetrix). RESULTS The conversion of gamma LiA10 2 to LACHH is given in eq. (1). The progress of this reaction can be followed by weight gain, increase in carbonate content, or quantitative XRD analysis. 4LiAIO 2 + 9H 2 0 +2CO 2 -" Li 2A14 (CO 3)(OH)l 2 3H20 + Li2 CO 3
(1)
Figure 1 shows the three spectra that were used to calculate the RIR and the XRD sprectum of the sample that was exposed to 70% RH for 86 days. Table I and Figure 2 summarize the RIR analysis. Accuracy is good. However, for the two samples exposed to 70% RH, recovery of the corundum was higher than the expected value of 50%. The significant broadening for the 100% peak for the LACHH formed in situ compared to the synthesized LACHH should be noted. Calibration curves for the single peak internal standard analysis and the whole pattern simulations are given in Figure 3. Figure 4 shows the simulated patterns of LACHH extracted from the sample that had been exposed to 70% RH for 86 days compared to the pattern extracted from the 26% standard. Note the significant broadening of the 100% peak for LACHH formed in situ. Quantitative results obtained by all analytical methods are given in Table II.
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