Application of X-rays to characterization of ultramicro samples and micro areas

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1. Crystalline orientation and distribution in plates of heat-resistant porcelain and glass ceramics containing some kinds of crystals with marked thermal anisotropy were studied by use of an X-ray microdiffractometer with a curved position sensitive proportional counter and a three-dimensional goniometer. The surface of the porcelain plate contained mainly crystallites of 3-quartz solid solution. As being far from the surface, the quantity of 3-quartz solid solution reduced rapidly, and the crystallites of indialite and enstatite increased. Crystallites of indialite and enstatite were distributed uniformly in the interior more than 200 um from the surface. It suggests a possibility of improvement in the capability against thermal shock by reducing the crystalline size and by homogenizing the crystallite distribution in the vicinity of the surface. In the case of two kinds of glass ceramics, almost the same X-ray microdiffraction (XRMD) patterns were obtained from any position of the plate. This indicates that random orientation and uniform distribution of their crystalline constituents, which explain their superior resistance against thermal shock.2. A brass sample holder with an exchangeable copper wire was made for XRMD analysis of small samples. An individual particle in airborne particulates, which was sorted under a microscope, was stuck with adhesive onto the wire tip of the holder, and analyzed by use of an X-ray microdiffractometer. It allowed to identify clearly a greater number of minor components in airborne particulate samples, and even a particle as small as about 0.03 ug. For example, ultramicro amounts of phlogopite and mullite were detected in Dukou's dust fall. It also indicated that Dukou dust fall contained magnetite of several different forms, i.e., as a major constituent in black grains and fragments, and as a minor constituent in reddish black aggregates and black spheres; So were hematite, calcite, and mullite.