Magnesium diffraction pattern

Clays are composed of extremely fine particles of clay minerals which are layer-type aluminum siUcates containing stmctural hydroxyl groups. In some clays, iron or magnesium substitutes for aluminum in the lattice, and alkahes and alkaline earths may be essential constituents in others. Clays may also contain varying amounts of nonclay minerals such as quart2 [14808-60-7] calcite [13397-26-7] feldspar [68476-25-5] and pyrite [1309-36-0]. Clay particles generally give well-defined x-ray diffraction patterns from which the mineral composition can readily be deterrnined. 

All of the hydrotaleite-derived magnesia supports were prepared by first coprecipitating magnesium aluminum hydroxycarbonate in the presence of Mg and Al nitrates, KOH, and K2C03 according to procedures already described (8,9). Hydrotaleites were then decomposed by calcination at 873 K for 12-15 h to yield the binary oxide to be used for a catalyst support. The specific surface area of the hydrotaleites determined by nitrogen adsorption was typically about 220 m2g 1 after calcination. X-ray powder diffraction patterns of the materials were recorded on a Scintag X-ray diffractometer. 

X-ray diffraction patterns of three obtained samples are plotted in Fig. 2. Their phase analysis showed follows. The pattern of pure catalyst sample (Fig. 2a) contains the structural peaks of magnesium oxide MgO, and also the weak, strongly widened peaks which correspond to MgFe204 Calculated MgO particles... 

The unique moment of discovery came in April 1982 when Dan Shechtman was doing some electron diffraction experiments on alloys, produced by very rapid cooling of molten metals. In the experiments with molten aluminum with added magnesium, cooled rapidly, he observed an electron diffraction pattern with tenfold symmetry (see, the pattern in the Introduction). It was as great a surprise as it could have been imagined for any well-trained crystallographer. Shechtman s surprise was recorded with three question marks in his lab notebook, 10-fold [140],... 

Figure 9.4 shows the X-ray diffraction output of a magnesium-potassium phosphate ceramic in which boric acid was added as a retardant. The amount of boric acid was 1 wt% of MgO in the powder blend. The X-ray diffraction pattern indicated that the polymeric coating on the MgO particles was a low-solubility magnesium-boron-phosphate compound, called liinebergite ... 

Fig. 7.1 shows X-ray diffraction patterns of a mixture of anhydrous magnesium, aluminium and silicon oxides and a mixture of correspondent hydroxides after mechanical activation in a planetary mill followed by annealing at 1260°C for 2 h. In the former case, the reflections of spinel MgAlA (0.245, 0.207,... 

The X-ray powder diffraction (XRPD) pattern (XD 490, Shimadzu, Japan) of magnesium silicate is shown in Fig. 7.12. Magnesium silicate clearly shows amorphous characteristics with broad peaks throughout the diffraction pattern range. Only three minor peaks are evident at 25-30°, 35-39°, and 58-61° 26. 

Hectorite is an aluminum-free mineral of the smectite type. Isomorphous substitution could occur at tetrahedral silicon sites as well as at the octahedral sites originally occupied by lithium and magnesium. Monitoring the x-ray powder diffraction patterns as a frmction of crystallization time, it was found that the hydrothermal crystallization was complete after 12h at 200°C, independent of the alumina content of the reaction mixture. However, NMR spectroscopy proves that some structural change still occurs after this time period. 

Palladium black was prepared from palladium nitrate and formaldehyde solution by dropwise addition of potassium hydroxide solution (50 wt. %) at about 10°. The solution and precipitate were warmed at about 60° and the precipitate washed several times by decantation. It was then placed in a Soxhlet extractor and washed for 48 hr. (about 100 times). The precipitate was then dryed at 110°. The palladium-silver system is known to be one of complete miscibility (3). Alloys of silver-palladium were prepared following a procedure discussed elsewhere 4). Their preparation involved a low-temperature coprecipitation of both metals from a solution containing proper amounts of their nitrates. Alloy formation was checked by means of x-ray diffraction patterns which were obtained with Cu-Ka radiation. The computed lattice constants are shown in Fig. 1 to be a linear function of the alloy composition. Hydrogen, used for pretreatment of all samples, was obtained from a commercial tank and purified by passage through a Deoxo unit, magnesium perchlorate, and a charcoal trap immersed in liquid nitrogen. 

All samples showed diffraction pattern similar to that ofhydrotalcite without any discrete crystalline impurity phases. In situ PXRD studies revealed varying phase evolution processes depending on the concentration of magnesium, complemented by in situ DRIFT measurements. The thermal stability of the materials improved with an increase in magnesium concentration, as evidenced from TG-DTA measurements. Details of physicochemical properties of these samples arc disclosed elsewhere (94]. 

In response to Fundal (1982), Lee (1983) pointed out the bimodality of alite birefringence determined by Maki and Kato (1982), who demonstrated relationships with magnesium oxide content in the crystal. Lee restated the conclusion by Maki and Kato that the M, (monoclinic) phase appears pseudotrigonal in an X-ray powder-diffraction pattern. Lee believed that Fundal s comparison of alite compositional and optical data with a tectosilicate solid-solution series, such as plagio... 

The second model of the structure is based on the works of Allman and Tailor who identified structures of the minerals (hydrotalcite and manasseite) [28,29] and showed that magnesium and aluminium ions are located in octahedral voids of hydroxide layer. Anions X and water molecules form another layer. Using this approach, Serna assumed on the basis of electron microdiffraction data and X-ray diffraction patterns of powders that the structure of LADH-CO3 obtained by the hydrolysis of aluminium-tri-(sec-butoxide) in hthium carbonate is based on closely packing two-dimensional layer (30 ]. Two thirds of the octahedral voids in this layer are occupied by aluminium cations located in a manner similar to that of gibbsite. The remaining one third of voids is occupied by lithium cations. On... 

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