Investigation of the Internal Structure of a Modern Seafloor Hydrothermal Chimney With a Combination of EBSD, EPMA, and XRD.

Samples from the sphalerite-dominated zone of a seafloor massive sulfide chimney, the Satanic Mills Chimney of the PACMANUS hydrothermal field, have been investigated to determine the internal macrostructure and microstructure of this zone, the phases present, and the distribution of metals. A combination of electron probe microanalysis, electron backscattered diffraction, and x-ray diffraction has been used. At the macroscale, this zone of the chimney wall is heavily porous and is comprised primarily of sphalerite, enclosing minor chalcopyrite, pyrite, and wurtzite. A Pb­As sulfosalt layer of possible microbial origins is present at the outer edge of the sphalerite matrix, next to a pore. The sphalerite has grown in globules on the order of 300 µm in diameter. At the microscale, the sphalerite features a colloform texture and a duplex-type grain structure consisting of either fine-grain regions in the center surrounded by coarse-grained regions or radiating coarse grains only. Pb- and As-rich bands have been detected in the colloform sphalerite, and growth twins have been observed in both the sphalerite and chalcopyrite crystals. A qualitative description of the growth of a typical globule is given, including nucleation, crystal growth, and solute redistribution.

Incorporation of γ-butyrolactone (GBL) dramatically lowers the phase transition temperature of formamidinium-based metal halide perovskites.

We demonstrate that the δ to α phase transition temperature of formamidinium-based perovskites is reduced by ∼50 °C through the incorporation of ∼2 wt% γ-butyrolactone (GBL) into the crystal lattice. The intercalation of GBL is found to expand the unit cell of the δ-phase, reducing the energy barrier for thermal conversion.

A flow cell for the study of gas-solid reactions via in situ powder X-ray diffraction.

This paper describes the development and testing of a novel capillary flow cell for use in in situ powder X-ray diffraction experiments. It is designed such that it achieves 200° of rotation of the capillary whilst still allowing the flow of gas through the sample and the monitoring of off gas via mass spectrometry, gas chromatography, or other such analytical techniques. This high degree of rotation provides more uniform heating of the sample than can be achieved in static cells or those with lower rotational ranges and consequently also improves particle statistics. The increased uniformity of heating provides more accurate temperature calibration of the experimental setup as well. The cell is designed to be held in a standard goniometer head and is therefore suitable for use in many laboratory and synchrotron instruments.

Vacancy Generation and Oxygen Uptake in Cu-Doped Pr-CeO2 Materials using Neutron and in Situ X-ray Diffraction.

The oxygen uptake ability of Pr-CeO2-based oxygen carriers, catalysts, and solid oxide fuel cells can be attributed to 3+ cation generation and the presence of vacant oxygen sites. Oxygen occupancies of CeO2, Pr-CeO2, and 5% Cu-doped Pr-CeO2 were investigated using neutron diffraction and related to the oxygen uptake as determined using thermogravimetric analysis (TGA). The presence of vacant tetrahedral oxygen sites at room temperature did not correspond to low-temperature oxygen uptake. The materials did not uptake oxygen at 420 °C, but oxygen uptake was observed at 600 °C, which indicated that a minimum temperature needs to be met to generate sufficient vacancies/3+ cations. Variations in the lattice parameter as a function of temperature were revealed using in situ X-ray diffraction (XRD). With increasing temperature the lattice parameter increased linearly due to thermal expansion and was followed by an exponential increase at ∼300-400 °C as cations were reduced. Despite segregation of Cu into CuO at high dopant concentration, at 600 °C a higher O2 uptake was obtained for Ce0.65Pr0.20Cu0.15O2-δ (120 µmol g-1), in comparison to Ce0.75Pr0.2Cu0.05O2-δ (92 µmol g-1), and was higher than that for Ce0.8Pr0.2O2-δ (55 µmol g-1). Both Pr and Cu introduce vacancies and promote the O2 uptake of CeO2.

In situ synchrotron X-ray diffraction investigation of the evolution of a PbO2/PbSO4 surface layer on a copper electrowinning Pb anode in a novel electrochemical flow cell. Corrigendum.

Figures 7 and 8 of the article by Clancy et al. [(2015), J. Synchrotron Rad. 22, 366-375] are corrected.

In situ synchrotron X-ray diffraction investigation of the evolution of a PbO2/PbSO4 surface layer on a copper electrowinning Pb anode in a novel electrochemical flow cell.

This paper describes the quantitative measurement, by in situ synchrotron X-ray diffraction (S-XRD) and subsequent Rietveld-based quantitative phase analysis and thickness calculations, of the evolution of the PbO2 and PbSO4 surface layers formed on a pure lead anode under simulated copper electrowinning conditions in a 1.6 M H2SO4 electrolyte at 318 K. This is the first report of a truly in situ S-XRD study of the surface layer evolution on a Pb substrate under cycles of galvanostatic and power interruption conditions, of key interest to the mining, solvent extraction and lead acid battery communities. The design of a novel reflection geometry electrochemical flow cell is also described. The in situ S-XRD results show that ß-PbO2 forms immediately on the anode under galvanostatic conditions, and undergoes continued growth until power interruption where it transforms to PbSO4. The kinetics of the ß-PbO2 to PbSO4 conversion decrease as the number of cycles increases, whilst the amount of residual PbO2 increases with the number of cycles due to incomplete conversion to PbSO4. Conversely, complete transformation of PbSO4 to ß-PbO2 was observed in each cycle. The results of layer thickness calculations demonstrate a significant volume change upon PbSO4 to ß-PbO2 transformation.

A flow cell for in situ synchrotron x-ray diffraction studies of scale formation under Bayer processing conditions.

The design, construction, and commissioning of a stainless steel flow cell for in situ synchrotron x-ray diffraction studies of scale formation under Bayer processing conditions is described. The use of the cell is demonstrated by a study of Al(OH)(3) scale formation on a mild steel substrate from synthetic Bayer liquor at 70 degrees C. The cell design allows for interchangeable parts and substrates and would be suitable for the study of scale formation in other industrial processes.