X-ray diffraction high-temperature

Keywords solid-state ion exchange, high-temperature X-ray diffraction, zeolite Cd-Y. 

The effect of the partial pressure of oxygen and of CO2 is also very important for the decomposition behaviour of siderite and rhodochrosite. The formation of the iron oxides was followed by TG and by high temperature X-ray diffraction. Below 10-6 mm Hg oxygen pressure only Fe304 was formed. 

With respect to the higher temperature transition at 445 °C, there are two conflicting views of this transition, namely that the phase above 445 °C is a smectic C and the other that it is nematic. Based on high temperature X-ray diffraction studies, Yoon et al. have concluded that it is a smectic C (see Fig. 4) [28], Thus, in Fig. 4, the disappearance of the 211 peak indicates that the nematic E structure is converting to a nematic C. In our work, using polarizing optical microscopy, we have observed a nematic texture for high molar mass specimens heated rapidly to 480 °C, sheared, and then quenched. In the case of a... 

High temperature x-ray diffraction was done with selected samples using a Tem-Pres model SX diffractometer furnace on a Picker model 3488E diffractometer using filtered Cu radiation. High temperature runs were conducted with samples in a continuously replenished air atmosphere of 7.9 and 740 torr PH2 o. 

An alumina supported bismuth molybdate catalyst with a bismuth to molybdenum atomic ratio equal to one was examined by high-temperature X-ray diffraction techniques during propylene oxidation (86). Ac-... 

The structural information had been reported by Turcotte et al. (1973), using high temperature X-ray diffraction. The electron diffraction pattern of the PrOtsis phase is completely different from those of CeOi.sis and TbOi.sis phases (see Figure 33) (Tuenge and Eyring, 1982). 

In many cases, high-temperature modifications of sulfidic compounds cannot be quenched for room temperature examination. Inversion twinnings, crystal morphology, or other crystallographic features may indicate the appearance of polymorphism. Under these circumstances differential thermal analysis (DTA) can be suitable for the determination of the exact phase transition temperatures. DTA determinations are practically valuable if used in conjunction with high-temperature X-ray diffraction methods. DTA apparatus can operate up to 1100 °C and can be specially designed for sulfides2-4) individual experimental techniques are included in these references. 

Potassium carbonate is a well-known catalyst for the steam gasification of carbonaceous materials. We discuss the use of in situ high temperature X-ray diffraction to demonstrate that intercalation compound-like structures are not involved as stable intermediates. 

The x-ray studies were made with a high-temperature x-ray diffraction camera of Hume-Rothery design. This camera had a 9-cm. diameter and employed the Straumanis film setting. A fine Chromel-Alumel thermocouple within the furnace cavity and adjacent to the sample served to measure and control temperature. The sample temperature was calibrated against the thermocouple e.m.f. through a series of lattice-constant measurements on pure silver. 

The absorption-isotherm method provides a very useful approach to the study of a gas-solid system. Inflection points in the isotherms locate phase boundaries, and a plot of log P vs. 1/T (Arrhenius plot) permits calculation of heats of solution and estimation of the eutectoid temperature. The shape of the isotherms depends only on those phases which affect the hydrogen absorption, rather than all phases present. The actual phases present were identified by high-temperature x-ray diffraction. The designation of the phases follows terminology commonly used in U. S. Atomic Energy Commission studies ... 

In order to confirm that there is the phase transition in this compound we measured the high temperature X-ray diffraction and the experiment patterns are shown in Figure 3 and Figure 4. 

Table 1. High temperature X-ray diffraction results for BaTb2Mn207-...

The thermal expansion of the group 4 carbonitrides was measured by high-temperature X-ray diffraction and can be expressed as a function of the [C]/([C] + [N]) ratio ... 

Existence of five polymorphic forms was shown by high-temperature X-ray diffraction (1, 6, 7) and differential thermal analysis (6, 7). Both o- and 0-forms persisted at room temperature, but the a-form appeared only on quenching of high-temperature forms (1,). The o-form transformed to 0 near 490 K (J, 6), but the reverse transformation was not observed. Single-crystal X-ray diffraction showed the o-form to be orthorhombic (8). 

Cowley RA (1964) The theory of Raman scattering from crystals. Proc Phys Soc 84 281-296 Ghose S, Ito Y, Hatch DM (1991) Paraelectric-antrferroelectric phase transition in titanite, CaTiSiOs. I. A high temperature X-ray diffraction study of the order parameter and transition mechansim. Phys Chem Miner 17 591-603... 

H. J. Goldschmidt. High Temperature X-Ray Diffraction Techniques. Bibliography 1, 1964. (International Union of Crystallography.) Available in the U.S.A. from Polyciystal Book Service (see [5.1]). 

The high temperature oxidation of (J-NiAl, undoped and doped with Ce, Y and Hf was studied in situ by thermogravimetry in He with p(02) = 5 10 6bar at 1000°C and by high temperature X-ray diffraction at 950 and 1000°C in air. After the in situ experiments the samples were analysed metallographically by optical microscopy and by scanning electron microscopy (SEM) with energy dispersive analysis (EDX). 

The NbiSn phase was first determined to be superconducting at 18.0 K in 1954 by Matthias et al. [39]. NbiSn adopts the cubic [Cr.iSij structure (Fig. 2-5) with an -axis spacing of about 5.29 A. NbjSn is a nonductile material with a CTE of 9.8 ppm/K as determined using high temperature X-ray diffraction from 25 to 700 °C (Table 2-4). The CVD synthesis of Nb Sn was first realized in 1964 by G. W. Cullen et al. [40]. This was a landmark contribution as it was the first LTS superconducting material to be synthesized by CVD. Two reviews by researchers at RCA provide additional details and specialized information on Nb Sn CVD [40, 41]. 

Combining a high-temperature X-ray camera with a thermobalance is difficult due to geometrical and focus problems. However, Wiedemann and Bayer (61) have described such a technique in which high-temperature X-ray diffraction patterns and information about its mass-loss can be obtained on a single sample. This new technique, which they called thermomolecular beam analysis (TMBA), is illustrated schematically in Figure 3.35. The... 

The crystal structure measurements were carried out using high temperature X-ray diffraction. Reference measurements were also obtained at 25°C, from which the lattice parameters, a = (3.233 0.001) x 10 m and c = (5.1475 0.0015) x 10 m, axial ratio, ate = (0.6281 0.0004), unit eell volume, (46.595 + 0.037) x 10 m and density, (6.501 0.005) g-cm were determined. High temperature measurements were taken from 950 to 1164 K for a-zirconium, however, there was a reasonable amount of scatter in the data obtained at these temperatures. Crystal structure measurements were also taken for p-zirconium. For this phase, reference measurements were taken at 1252 K leading to a lattice parameter of a = (3.6162 + 0.0020) x 10 m, a unit cell volume of (47.285 0.080) x 10 m" and a density of (6.406 0.011) g-cm ... 

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