In-situ neutron diffraction

In this paper we present in-situ neutron diffraction work in order to elucidate the reaction pathway of the system under both self generated deuterium pressure and under a dynamic vacuum on heating to 730°C. 

The defect structure of Fei O with the NaCl-type structure had been estimated to be a random distribution of iron vacancies. In 1960, Roth confirmed, by powder X-ray diffraction, that the defect structure of wiistite quenched from high temperatures consists of iron vacancies (Vp ) and interstitial iron (Fcj) (there are about half as many FCj as Vpe). This was a remarkable discovery in the sense that it showed that different types of crystal defects with comparable concentrations are able to exist simultaneously in a substance, Roth also proposed a structure model, named a Roth cluster, shown in Fig. 1.84. Later this model (defect complex = vacancy -F interstitial) was verified by X-ray diffraction on a single crystal and also by in-situ neutron diffraction experiments. Moreover, it has been shown that the defect complex arranges regularly and results in a kind of super-structure, the model structure of which (called a Koch-Cohen model) is shown in Fig. 1.85 together with the basic structures (a) and (b). 

In situ neutron diffraction studies have provided insight into the mechanism of surface conversion of ice particles to carbon dioxide hydrate particles (Henning et al., 2000). The experiments were performed at 230-276 K and around 6.2 MPa. It was proposed from these measurements that after the initial period of fast... 

When pressurizing LDA and by monitoring the structural state using in situ neutron diffraction, double-peaked diffraction patterns and a progressing... 

Redfern, S.A.T., Dove, M.T., Wood, D.R.R. (1997b) Static lattice simulation of feldspar solid solutions ferroelastic instabilities and order/disorder. Phase Trans 61 173-194 Redfern, S.A.T., Knight, K.S., Henderson, C.M.B., Wood, B.J. (1998) Fe-Mn cation ordering in fayalite-tephroite (FexMni U2Si04 olivines a neutron diffraction study. Mineral Mag 62 607-615 Redfern, S.A.T., Harrison, R.J., O Neill, H.St.C., Wood, D.R.R. (1999) Thermodynamics and kinetics of cation ordering in MgAl204 spinel up to 1600°C from in situ neutron diffraction. Am Mineral 84 299-310... 

Harrison RJ, Redfem SAT, O Neill HSC (1998) The temperature dependence of the cation distribution in synthetic hercynite (FeAl204) from in situ neutron diffraction. Am Mineral 83 1092-1099 Harrison RJ, Redfem SAT, Smith R1 (2000a) In situ study of the i 3 to i 3c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron powder diffraction. Am Mineral 85 194-205... 

Fig. 1 In Situ Neutron Diffraction Cell Functional items described in text. Gas, electrical power, and thermocouple feedthrus reside in KF flanges atop the ASAl 1 flange and are not shown for visual clarity.

Price TEC, Grant D M, Telepeni I, Yu X B and Walker G S (2008), The decomposition pathways for LiBD4-MgD2 multicomponent systems investigated by in-situ neutron diffraction, J. Alloys. Compounds, doi 10.1016/j.jallcom.2008.05.030. 

Mazzucato E, Artioli G, Gualtieri A (1999) High temperature dehydroxylation of muscovite-2Mi a kinetic study by in situ XRPD. Phys Chem Minerals 26 375-381 Mookheqee M, Redfem SAT, Hewat A (2000) Structural response of phengite IM to temperature an in situ neutron diffraction study. EMPG VIII, Bergamo, April 16-19, Abstracts, p 75 Moriarty JA (1995) First-principles equations of state for AI, Cu, Mo and Pb to ultrahigh pressures. High Press Res 13 343-365... 

S. McIntosh JF, Vente WG, Haije DHA, Blank, Bouwmeester HJM. Oxygen stoichiometry and chemical expansion of Ba0.5Sr0.5Co0.8Fe0.203-d measured by in-situ neutron diffraction. Chem Mater. 2006 18 2187. 

Oxygen Anion Transport in Soiid Oxides, Fig. 9 Oxygen stoichiometry of (a) Bao.5Sro.5Coo.gFeo.203 g at p02 =10 atm determined by in-situ neutron diffraction (open symbols) and thermogravrmetry (closed symbols) [33]... 

Cox-Galhotra R, Huq A, Hodges JP, Kim J, Yu C, Wang X, Jacobson AJ, McIntosh S (2013) Visualizing oxygen anion transport pathways in NdBaCo205+e by in situ neutron diffraction. J Mater Chem A 1(9) 3091-3100... 

Wilding M, Guthrie M, Bull CL, Tucker MG, McMillan PF (2008) Feasibility of in situ neutron diffraction studies of non-crystalline silicates up to pressures of 25 GPa. J Phys Condens Matter 20(24) 244122... 

We studied the nuclear density distributions of Ceo.5Zro.5O2 at 1832 K and of Ce02 at 1826 K by in situ neutron diffraction and MEM (Fig. 1.31). The nuclear density distribution of oxide ions in Ceo.5Zro.5O2 (Fig. 1.31(a)) indicates the large positional disorder of oxide ions, spreading over a wide area and a shift to the <111> directions. Possible diffusion paths of the oxide ions can be seen along the... 

In-situ neutron diffraction was used to monitor the structural evolution of the phase decomposition of MAX phases at high-temperature in real time. Diffraction patterns were collected using WOMB AX at OPAL or the Polaris at ISIS, both are high-intensity medium-resolution powder diffractometers. Samples were mounted in a high-temperature niobium furnace which was fitted with a thin tantalum foil element and tantalum and vanadium heat shields that allows it to reach 2000°C, and operates under a high dynamic, i.e., it is continuously evacuated with a vacuum of 10 - 10 torr. A precision electronic scale was used to weigh the sample before it was loaded into the furnace. 

Xhe phase transitions in several MAX phases and their relative phase abundances at various temperatures as revealed by in-situ neutron diffraction is shown in Figure 1. A weight loss of - 4% was observed for decomposed Xi3SiC2 which may be attributed to the release of gaseous Si by sublimation during the decomposition process. For Xi3AlC2, its decomposition into XiC and Xi2AlC... 

In-situ neutron diffraction was used to monitor the structural evolution of the phase decomposition of MAX phases at high-temperature in real time. Diffraction patterns were collected using Wombat at OPAL or the Polaris at ISIS, both are... 

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