X‐Ray Powder Diffraction Assembly for Studies at Elevated Temperatures and High Gas Pressures

1957 ◽  
Vol 28 (5) ◽  
pp. 342-344 ◽  
Author(s):  
Edward J. Goon ◽  
John T. Mason ◽  
Thomas R. P. Gibb
Keyword(s):  
Powder Diffraction ◽  
Elevated Temperatures ◽  
X Ray ◽  
Gas Pressures

scholarly journals Amorphous Mg–Fe silicates from microwave-dried sol–gels

2019 ◽  
Vol 624 ◽  
pp. A136
Author(s):  
S. P. Thompson ◽  
A. Herlihy ◽  
C. A. Murray ◽  
A. R. Baker ◽  
S. J. Day ◽  
...  
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Microwave Drying ◽  
Drying Methods ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Context. Laboratory analogues can provide physical constraints to the interpretation of astronomical observations of cosmic dust but clearly do not experience the same formation conditions. To distinguish between properties intrinsic to the material and properties imprinted by their means of formation requires extensive characterisation. Aims. Sol–gel methods can produce amorphous silicates with potentially high reproducibility, but often require long drying times (24+ h) at elevated temperatures in air, controlled atmosphere, or vacuum. We investigate the possibility that microwave drying can be used to form amorphous silicate on a timescale of ∼10 min and characterise their structural and spectroscopic properties relative to silicates produced by other drying methods. Methods. Microwave-dried amorphous MgSiO3, Fe0.1Mg0.9SiO3 and Mg2SiO4 are characterised using X-ray powder diffraction, total X-ray scattering, small angle X-ray scattering and mid-IR FTIR spectroscopy, and compared to samples produced from the same gels but dried in-air and under vacuum. The development of crystalline structure in the microwave-dried silicates via thermal annealing up to 999°C is also investigated using in situ X-ray powder diffraction. Results. At the inter-atomic level the silicate structures are largely independent of drying method, however larger-scale structured domains, ranging from a ∼few × 10 Å to ∼100’s Å in size, are observed. These are ordered as mass fractals with discernible variation caused by the drying processes. The mid-IR 10 μm band profile is also found to be influenced by the drying process, likely due to the way removal of water and bonded OH influences the distribution of tetrahedral species. However, microwave drying also allows Fe to be easily incorporated into the silicate structure. In situ annealing shows that for amorphous MgSiO3 crystalline forsterite, enstatite and cristobalite are high temperature phases, while for Mg2SiO4 forsterite crystallises at lower temperatures followed by cristobalite at high temperature. For Fe0.1Mg0.9SiO3 the crystallisation temperature is significantly increased and only forsterite is observed. Crystalline SiO2 may be diagnostic of Mg-rich, Fe-poor grain mineralogies. The results are discussed in relation to the different thermal conditions required for dust to crystallise within protoplanetary disk lifetimes. Conclusions. Sol–gel microwave drying provides a fast and easy method of producing amorphous Mg- and Fe,Mg-silicates of both pyroxene and olivine compositions. Their structure and spectroscopic characteristics although similar to silicates produced using other drying methods, exhibit subtle variations which are particularly manifest spectroscopically in the mid-IR, and structurally over medium- and long-range length scales.

scholarly journals Characterisation of oxygen defects and nitrogen impurities in TiO2 photocatalysts using variable-temperature X-ray powder diffraction

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Christopher Foo ◽  
Yiyang Li ◽  
Konstantin Lebedev ◽  
Tianyi Chen ◽  
Sarah Day ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Visible Light ◽  
Powder Diffraction ◽  
Nitrogen Doping ◽  
Elevated Temperatures ◽  
Variable Temperature ◽  
Anatase Phase ◽  
Structural Defects ◽  
Powder Materials ◽  
X Ray

AbstractTiO2-based powder materials have been widely studied as efficient photocatalysts for water splitting due to their low cost, photo-responsivity, earthly abundance, chemical and thermal stability, etc. In particular, the recent breakthrough of nitrogen-doped TiO2, which enhances the presence of structural defects and dopant impurities at elevated temperatures, exhibits an impressive visible-light absorption for photocatalytic activity. Although their electronic and optical properties have been extensively studied, the structure-activity relationship and photocatalytic mechanism remain ambiguous. Herein, we report an in-depth structural study of rutile, anatase and mixed phases (commercial P25) with and without nitrogen-doping by variable-temperature synchrotron X-ray powder diffraction. We report that an unusual anisotropic thermal expansion of the anatase phase can reveal the intimate relationship between sub-surface oxygen vacancies, nitrogen-doping level and photocatalytic activity. For highly doped anatase, a new cubic titanium oxynitride phase is also identified which provides important information on the fundamental shift in absorption wavelength, leading to excellent photocatalysis using visible light.

Anin situpowder diffraction cell for high-pressure hydrogenation experiments using laboratory X-ray diffractometers

2015 ◽  
Vol 48 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Romain Moury ◽  
Klaus Hauschild ◽  
Wolfgang Kersten ◽  
Jan Ternieden ◽  
Michael Felderhoff ◽  
...  
Keyword(s):  
High Pressure ◽  
Powder Diffraction ◽  
Experimental Setup ◽  
X Ray Diffraction ◽  
X Ray ◽  
Elevated Pressures ◽  
Temperature Suitability ◽  
Proof Of Principle ◽  
Gas Pressures

Anin situdiffraction cell is presented which has been designed and constructed for in-house powder diffraction experiments under high gas pressures up to 30 MPa. For a proof of principle, thein situcell has been tested for several hydrogenation experiments under elevated pressures and temperatures. LaNi5was chosen as an example for hydrogenation, applying simultaneously 5.5 MPa H2pressure at a temperature of 423 K. For testing the high-pressure–temperature suitability of thein situcell, pressure–temperature experiments up to 14 MPa at 373 K were performed, studying the rehydrogenation of NaH and Al to NaAlH4. The experimental setup enables recording ofin situX-ray diffraction data on laboratory instruments with short data acquisition times at elevated hydrogen pressures and temperatures.

A fixture for X-ray crystallographic studies of biomolecules under high gas pressure

1988 ◽  
Vol 21 (1) ◽  
pp. 4-10 ◽  
Author(s):  
R. F. Tilton
Keyword(s):  
Data Collection ◽  
Powder Diffraction ◽  
Slight Modification ◽  
Sperm Whale ◽  
Gas Pressure ◽  
X Ray Diffraction ◽  
Data Set ◽  
X Ray ◽  
Nominal Resolution ◽  
Gas Pressures

A fixture is described for collecting X-ray diffraction data from biomolecule crystals under gas pressures up to 300 atm (30 MPa). The fixture is completely portable and can be used on conventional diffractometers. Normal procedures for crystal mounting, alignment and data collection require only slight modification. A test data set of the protein sperm whale metmyoglobin under a gas pressure of 145 atm of N2 gas has been collected to a nominal resolution of 2.0 Å using Cu Kα radiation and refined to an R-factor of 16.2%. Data collection beyond 2.0 Å resolution is hampered by the presence of strong powder diffraction from the beryllium shroud.

Powder diffraction data of novel complexes CdX2-2(NH2-PhY), part I

2010 ◽  
Vol 25 (4) ◽  
pp. 359-367 ◽  
Author(s):  
Anna Dobija ◽  
Alicja Rafalska-Łasocha ◽  
Wiesław Łasocha
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Elevated Temperatures ◽  
Point Of View ◽  
Phenyl Radical ◽  
Powder Diffraction Data ◽  
Monoclinic System ◽  
X Ray ◽  
Triclinic System ◽  
New Compounds

Four new compounds with general formula CdI2-2(NH2-PhX) (Ph represents phenyl radical; X represents Cl or H atoms) were obtained and characterized. Two of them, bisaniline diiodidecadmium(II) — CdI2⋅2[NH2–C6H5] {1} and bis(2-chloroaniline) diiodidecadmium(II) — CdI2⋅2[NH2–C6H4Cl] {2}, crystallize in monoclinic system, whereas another two, bis(3-chloroaniline) diiodidecadmium(II) — CdI2⋅2[NH2–C6H4Cl]{3} and bis(4-chloroaniline) diiodidecadmium(II) hemi(4-chloroanilate) — CdI2⋅2[NH2–C6H4Cl]½[NH2–C6H4Cl] {4}, crystallize in triclinic system. The investigated compounds, from chemical point of view, are similar to the so-called cisplatin—a compound used as a chemotherapy drug to treat many types of cancers. Their syntheses and results of X-ray powder diffraction studies at room and elevated temperatures are described in this paper.

Reaction of α-Fe2O3 (hematite) with potassium carbonate at elevated temperatures

1986 ◽  
Vol 51 (4) ◽  
pp. 809-818 ◽  
Author(s):  
Jaroslav Vinš ◽  
Markéta Urbanová ◽  
Jan Šubrt ◽  
Vladimír Zapletal ◽  
Aleksander A. Zakharov ◽  
...  
Keyword(s):  
Phase Composition ◽  
Powder Diffraction ◽  
Potassium Carbonate ◽  
Elevated Temperatures ◽  
X Ray ◽  
Rate Law ◽  
Molar Ratios ◽  
Cubic Structure ◽  
Diffraction Patterns ◽  
Kinetics Of

The kinetics of the reaction between α-Fe2O3 and K2CO3 have been investigated over the temperature range 600 to 800 °C, and the phase composition of the products has been determined. The reaction follows the rate law α = 1 - exp (-kτn). At molar ratios K : Fe 1, KFeO2 is the only product. At K : Fe 1, initially formed KFeO2 reacts with hematite to yield K2Fe4O7. The latter phase has been assigned a cubic structure with a = 1.681 ± 0.003 nm. based on X-ray powder diffraction patterns and Mossbauer spectra, the structure of K2Fe4O7 is proposed to be a cubic close-packed array of oxygen atoms, part of these being replaced by potassium atoms, with Fe atoms occupying the octahedral interstices.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

New horizons for the structural characterization of stainless steel slags by X-ray powder diffraction

2007 ◽  
Vol 2007 (suppl_26) ◽  
pp. 61-66 ◽  
Author(s):  
B. Peplinski ◽  
B. Adamczyk ◽  
G. Kley ◽  
K. Adam ◽  
F. Emmerling ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Powder Diffraction ◽  
Structural Characterization ◽  
X Ray ◽  
New Horizons
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