Micro XRD

KEYWORDS sulfide alteration, Acid Mine Drainage, micro-XRD, micro-XRF, micro-XANES. 

Micro-XRD and micro-XANES analyses showed that the earliest stage of sulfide alteration is marked by the progressive oxidation of sulfide-S to sulfate-S that is then rapidly leached out from the system. Sulfide oxidation starts from particle rims or from intra-grain microfractures and is accompanied by a progressive loss of sulfur sulfides are then pseudomorphically replaced by goethite and minor bemalite. In addition to sulfides, many gangue silicates are efficiently altered and only quartz is preserved within the altered layers. 

Micro-XRD confirms that secondary phases are generally aggregates of micro-or nano-scale crystallites, or in some cases amorphous or short-range ordered. Arsenic-mineral associations within... 

Walker, S.R., Jamieson, H.E., Lanzirotti, A., Andrade, C.F., Hall, G.E.M. 2005. The speciation of arsenic in iron oxides in mine wastes from the Giant gold mine, N.W.T. Application of synchrotron micro-XRD and micro-XANES at the grain scale. Canadian Mineralogist, 43, 1205-1224. 

Although a number of secondary minerals have been predicted to form in weathered CCB materials, few have been positively identified by physical characterization methods. Secondary phases in CCB materials may be difficult or impossible to characterize due to their low abundance and small particle size. Conventional mineral identification methods such as X-ray diffraction (XRD) analysis fail to identify secondary phases that are less than 1-5% by weight of the CCB or are X-ray amorphous. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), coupled with energy dispersive spectroscopy (EDS), can often identify phases not seen by XRD. Additional analytical methods used to characterize trace secondary phases include infrared (IR) spectroscopy, electron microprobe (EMP) analysis, differential thermal analysis (DTA), and various synchrotron radiation techniques (e.g., micro-XRD, X-ray absorption near-eidge spectroscopy [XANES], X-ray absorption fine-structure [XAFSJ). 

SR-based micro-XRD (MacDowell et al. 2001) is also becoming useful for identification of pm scale particles in complex environmental samples (e g., Tamura et al. 2002 Manceau et al., this volume). Single crystal diffraction studies of the structure of very small crystals (50-160 pm3 in volume) are also possible using SR sources (e g., Pluth et al. 1997 Broach et al. 1999 Neder et al. 1999 Bums et al. 2000). Diffraction studies of such small crystals using conventional sealed or rotating anode X-ray tubes are not possible because of their very small diffracting volumes. 

Fig. 6 Illustration of the common characteristics of powder diffraction patterns collected with micro-XRD. Notice that the individual spots are from larger, micron-sized crystallites while the spotted rings are indicative of micro-crystalline particles (a). The spottiness of the rings is an indication of insufficient number of grains in the dif aetion volume of the sample. The continuous rings indicate that all lattice planes hkl are simultaneously present in all orientations relative to the incident X-ray beam. In micro-diffraction with spot sizes on the micron-scale this usually occurs only with nanocrystalline particles (b)...

Canadian urban single family dwelling. This sample is characterized by a potentially hazardous concentration of total Pb (1,670 mg kg ), of which 95% is bioaccessible. Health Canada required information about the solid sample Pb speciation to provide information about potential sourcefs) for the elevated Pb, and the reason for the high metal bioaccessibility. This was achieved using a combination of bulk XAFS, micro-XRF and micro-XRD analyses. 

XRD may be applied to a wide variety of ceramic problems such as simple phase identifications, crystallite size measurements, and determination of crystal lattice parameters. The mineral assemblages produced during firing or in different service environments can be readily studied. Techniques are now available for micro XRD, in which an intense X-ray beam is collimated or focused onto a specific feature in the sample in order to characterize the crystal structure. 

In addition, the punctual measurement of X-ray diffraction pattern over a complex sample provides information on the variation of its crystallographic structure XRD) over a heterogeneous object. Micro-XRD is becoming common on many X-ray microprobes. Micro-XRD maps can be obtained together with the maps of elemental information and can assist in characterizing heterogeneous samples. 

In Fig. 4 a scheme of a micro-XRD set up using a 2D CCD detector is depicted as used by Reinsberg et al. [23]. A single bounce capillary is used to produce a low-divergence beam focus. The reflections can be radially integrated to give ID powder diffraction patterns. 

Specific surface areas of the catalysts used were determined by nitrogen adsorption (77.4 K) employing BET method via Sorptomatic 1900 (Carlo-Erba). X-ray difiraction (XRD) patterns of powdered catalysts were carried out on a Siemens D500 (0 / 20) dififactometer with Cu K monochromatic radiation. For the temperature-programmed desorption (TPD) experiments the catalyst (0.3 g) was pre-treated at diflferent temperatures (100-700 °C) under helium flow (5-20 Nml min ) in a micro-catalytic tubular reactor for 3 hours. The treated sample was exposed to methanol vapor (0.01-0.10 kPa) for 2 hours at 260 °C. The system was cooled at room temperature under helium for 30 minutes and then heated at the rate of 4 °C min . Effluents were continuously analyzed using a quadruple mass spectrometer (type QMG420, Balzers AG). 

With the combined methods of 29Si NMR spectroscopy, X-ray diffraction, HRTEM and SAED we were able to characterize the Ti-Beta particle growth. 29Si NMR spectroscopy gave us an opportunity to see the formation of nanoparticles even before they were detectable with other techniques such as XRD. The above mentioned techniques enabled us to obtain sufficient knowledge to prepare Ti-Beta nanoparticles which were than successfully incorporated in novel micro/mesoporous materials [1],... 

Micro-scale characterization (p-XRF, p-XANES, p-XRD, petrography, and EPMA) was able to confirm As forms identified by bulk XRD and in all cases identify additional As forms. Grain-scale mineralogical analysis unambiguously identified a minimum of two and typically four or more As-bearing phases in each tailings sample (Fig. 2, Table 2). 

The elastic properties of PS depend on its microstructure and porosity. The Young s modulus for meso PS, as measured by X-ray diffraction (XRD) [Ba8], acoustic wave propagation [Da5], nanoindentation [Bel3] and Brillouin spectroscopy [An2], shows a roughly (1-p)2 dependence. For the same values of porosity (70%), micro PS shows a significantly lower Young s modulus (2.4 GPa) than meso PS (12 GPa). The Poisson ratio for meso PS (0.09 for p=54%) is found to be much smaller than the value for bulk silicon (0.26) [Ba8]. 

Fig. 7.4 XRD signal for powder samples prepared from bulk Si (top) and micro PS films produced on p-type electrodes using different anodization current densities, as indicated in...

XRD was used to identify crystalline mineral phases in the samples. A Rigaku-Geigerflex goniometer was used (copper X-ray source, 45 kV, 35 mA, 1575 W). Samples were run in triplicate and a fourth run was conducted after tungsten was added to one of the replicates as an external standard. The data were evaluated for possible crystalline phases using the PC-based search and match program MICRO-ID (Materials Data Corp., Livermore, CA). 

A ,Ga)As buffer layer is grown before epitaxy of (Ga,Mn)As. To control strain in the film, strain-relaxed thick (In,Ga)As ( 1 /zm) with the lattice constant a0 greater than the subsequent (Ga,Mn)As layer can be employed. The Mn composition x in the Gai - Mn As films can be determined from measurements of a0 by x-ray diffraction (XRD), once the dependence a0(x)is calibrated by other means, such as electron probe micro-analysis (EPMA) or secondary ion mass spectroscopy (SIMS). 

Fig. 2. XRD patterns of as-synthesized micro-mesoporous composite materials prepared with increasing the time of microwave irradiation (a) sample 1, (b) sample II, (b ) calcined (b), (c) sample III, (c1) calcined (c), and (d) sample IV. See Table 1 for the notations of I, II, III and IV.

A liquid-handling robot was customized for both sol-gel [46] and evaporative wafer-based syntheses [44]. The appropriate precursors are mixed from stock solutions into micro-titer plates and then volumetrically transferred to the support wafers. Key variables in these syntheses are the drying environment and drying temperature and post treatments. The liquid or gel is dried under controlled conditions and then thermally processed in a tube furnace exposed to desired process gases. After synthesis is complete, the wafers are analyzed by XRD, SEM, and XRF to monitor structural phases, morphologies, and compositions respectively. 

Chin et al. [31] studied Pd/ZnO catalysts for methanol steam reforming, heading for a 10-50 W micro structured fuel processor. The catalysts under investigation contained 4.8, 9.0 and 16.7 wt.% Pd deposited on ZnO powder by impregnation. The catalysts were thoroughly characterized by thermogravimetry (TG), TPR, XRD and TEM. 

Metallic monoliths made of both rhodium ([HCR 1]) and FeCrAlloy (72.6% Fe, 22% Cr and 4.8% Al ([HCR 3]) carrying micro channels of 120 pm x 130 pm cross-section at various length (5 and 20 mm) were applied. The monoliths were prepared of micro structured foils by electron beam welding. After bonding, the FeCrAlloy was oxidized in air at 1 000 °C for 4 h to form an a-alumina layer, which was verified by XRD. Its thickness was determined as < 10 pm by SEM/EDX. The alumina layer was impregnated with rhodium chloride and alternatively with a nickel salt solution. The catalyst loading with nickel (30 mg) was much higher than that with rhodium (1 mg) (see Table 2.4). The amount of rhodium on the catalyst surface was determined as 3% by XPS. 

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