High-purity disperse α-Al2O3 nanoparticles synthesized by high-energy ball milling

The use of direct current arc atomic emission spectrometry (DC-arc-AES) with a CCD spectrometer for the direct determination of the trace impurities Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr in three well characterized boron carbide powders is described. The detection limits obtained by the procedure were found to be between 0.2 (Mg) and 25 (Na) μg g−1 for the above elements. Three boron carbide powder samples with trace element concentrations between 0.9 (Cu) and 934 (Si) μg g−1 for Al, Ca, Cr, Cu, Fe, Mg, Mn, Na, Ni, Si, Ti, and Zr — including the standard reference material ERM®-ED102 — were analyzed by DC-arc-AES. The relative standard deviations for 9 measurements when using 5.0 ± 0.3 mg of the respective samples were found to vary from 6.2 to 27% for Al and Cu, respectively. The trace elements Al, Ca, Cr, Cu, Fe, Mn, Ni, Si, Ti and Zr could be determined in the standard reference material and their concentrations determined by DC-arc AES were found to be between 89 and 116% of the accepted values. Fe and Ti were determined by DC-arc AES in the three boron carbide samples as well as in Al2O3, BN, SiC, coal fly ash, graphite and obsidian rock. The correlation coefficients of the plots of the net intensities versus the accepted values over the concentration ranges from 18 to 1750 and from 6 to 8000 μg g−1 are 0.999 and 0.990 for Fe and Ti, respectively.

Direct multielement determination of trace elements in boron carbide powders by direct current arc atomic emission spectrometry using a CCD spectrometer

The effect of volatiles present in the kiln atmosphere on the sinterability and microstructure of alumina ceramics was studied. The experiments were so designed that the volatile impurities generated from the respective salts of Na, Cu, Zn, Ni, Cr and Fe were allowed to act on pure alumina ceramics.

The properties studied included porosity, density, fired shrinkage, microhardness, power factor, loss factor, volume resistivity and dielectric strength. Scanning Electron Microscopy was used for the characterization of the resulting microstructures. The results when compared with the corresponding properties of alumina ceramics fired under a pure environment have been presented.

S. K. Guha

Papers

Effect of environmental impurities on the microstructure and sinterability of alumina ceramics