Miniaturization of mechanical milling for powder X-ray diffraction

Abstract

To enable mechanical milling of small (0.1–1.0 g) samples, a cylindrical grinding vessel machined from polypropylene and furnished with tungsten carbide rods has been designed and produced for use inside the conventional jar of a McCrone Micronizing Mill. The vessel is about one-seventh the volume of the conventional jar supplied by the manufacturer. The conditions of milling for both the conventional and the miniaturized-grinding assemblies were tested using quartz sand as a limiting case. The median grain sizes of the resultant powders were measured by an X-ray gravitational-sedimentation method, with contamination from the grinding media measured by Rietveld refinement and by instrumental neutron activation analysis. The use of tungsten carbide grinding elements permits rapid wet milling of a small sample to the same median grain size in about one-third of the time required by a regular sample ground in corundum. The relative contamination (by tungsten carbide on a weight basis) using the miniaturized-grinding assembly is about 6(1)% of the proportion of corundum contamination yielded by the conventional grinding assembly.

Effect of the magnetic field produced by a Halbach array magnetizer on water UV absorption, removal of scale and change in calcium carbonate polymorphs

“…In this research, the XRD technique was applied to calculate the wt% of aragonite phase using the diffraction peak heights. 10,32,46 The calibration curve of the standard peak heights was obtained by measuring each pure polymorphic powder (calcite and aragonite) using XRD. For aragonite phase identification, diffraction peaks of (111) and (021) planes at 2 θ angles of 26.25° and 27.23° were used, whereas the (104) plane positioned at a 2 θ angle of 29.43° was used for calcite.…”

“…The percentage of aragonite in each sample was calculated by the standard curve technique, as described in ref. 10 and 32.…”

Trace Elemental Partitioning on Clays Derived From Hydrothermal Muds of the El Tatio Geyser Field, Chile

“…Because opal was tentatively identified in several samples using scanning electron microscopy (SEM) (see results), 10% (w/w) of synthetic CaF 2 was added to each sample as an internal standard for quantification of this amorphous phase. Following the addition of CaF 2 , each sample was ground for a further 40 s under anhydrous ethanol using stainless steel elements in a miniaturized McCrone milling assembly (using the design of Locock et al., 2012). Following McCrone milling, each powdered sample was mounted in a back‐loaded cavity mount against a piece of frosted glass to minimize the preferred orientation of crystallites.…”

Production Technologies of Ancient Bricks from Padua, Italy: Changing Colors and Resistance over Time

“…The mineralogical composition was determined by Powder X-Ray Diffraction (PXRD) with a PANalytical X'Pert PRO diffractometer in Bragg-Brentano geometry equipped with a cobalt X-ray tube and a X'Celerator detector (Malvern Panalytical Ltd., Malvern, UK). Powder samples were micronized following the indications proposed by Locock et al [34]. The working conditions were CoKα radiation, 40 kV voltage, 30 mÅ current, 3-70 • 2θ range, step size 0.02 • and 1 s counts per step.…”