Mineralogy and formation of evaporite deposits from the Lewis Cliff ice tongue, Antarctica

2014 ◽  
Vol 27 (1) ◽  
pp. 73-84 ◽  
Author(s):  
Tingting Liu ◽  
David L. Bish ◽  
Richard A. Socki ◽  
Ralph P. Harvey ◽  
Eric Tonui
Keyword(s):  
Room Temperature ◽  
Precipitation Process ◽  
Secondary Mineral ◽  
X Ray Diffraction ◽  
Sulfate Ions ◽  
X Ray ◽  
Bodies Of Water ◽  
Evaporite Minerals ◽  
Glacial Tills ◽  
First Time

AbstractThe mineralogy of evaporites from the Lewis Cliff ice tongue (LCIT), Antarctica, and their mineral stabilities and transformation behaviours under different temperature and relative humidity (RH) conditions have been evaluated to elucidate formation mechanism(s). A variety of sodium (Na)-rich evaporite minerals were documented using RH-controlled powder X-ray diffraction (XRD) methods including Na-sulfates (mirabilite and thenardite), Na-carbonate/bicarbonates (nahcolite, occasional trona and natron) and Na-borates (qilianshanite and borax). Mirabilite begins to dehydrate to thenardite, and natron to trona and natrite when exposed to room temperature, even when maintained at RH values similar to those measured at the LCIT (50–70%). The boron-mineral qilianshanite was discovered for the first time in Antarctica within the evaporite mounds. The mirabilite-rich mounds are deduced to have formed via a freezing/sublimation process that occurred in glacial or subglacial bodies of water supplied by glacial tills containing microbially oxidized sulfate ions. The needle-like nahcolite crystals growing on the exteriors of the mounds suggest a dissolution/precipitation process involving atmospheric CO2 and water. The co-existence of nahcolite and boron-bearing minerals indicates the presence of a Na+-, HCO3-- and boron-bearing alkaline brine, which produces qilianshanite as a secondary mineral by reaction of nahcolite and borax in atmospheric CO2 and H2O.

scholarly journals Physical Stability and Viscoelastic Properties of Co-Amorphous Ezetimibe/Simvastatin System

2019 ◽  
Vol 12 (1) ◽  
pp. 40 ◽  
Author(s):  
Justyna Knapik-Kowalczuk ◽  
Krzysztof Chmiel ◽  
Karolina Jurkiewicz ◽  
Natália Correia ◽  
Wiesław Sawicki ◽  
...  
Keyword(s):  
Elevated Temperature ◽  
Viscoelastic Properties ◽  
Room Temperature ◽  
Physical Stability ◽  
Ternary Systems ◽  
Storage Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Conditions ◽  
First Time

The purpose of this paper is to examine the physical stability as well as viscoelastic properties of the binary amorphous ezetimibe–simvastatin system. According to our knowledge, this is the first time that such an amorphous composition is prepared and investigated. The tendency toward re-crystallization of the amorphous ezetimibe–simvastatin system, at both standard storage and elevated temperature conditions, have been studied by means of X-ray diffraction (XRD). Our investigations have revealed that simvastatin remarkably improves the physical stability of ezetimibe, despite the fact that it works as a plasticizer. Pure amorphous ezetimibe, when stored at room temperature, begins to re-crystallize after 14 days after amorphization. On the other hand, the ezetimibe-simvastatin binary mixture (at the same storage conditions) is physically stable for at least 1 year. However, the devitrification of the binary amorphous composition was observed at elevated temperature conditions (T = 373 K). Therefore, we used a third compound to hinder the re-crystallization. Finally, both the physical stability as well as viscoelastic properties of the ternary systems containing different concentrations of the latter component have been thoroughly investigated.

Temperature dependence of the AV3O7 (A = Ca, Sr) structure

2007 ◽  
Vol 63 (6) ◽  
pp. 836-842 ◽  
Author(s):  
Sebastian Prinz ◽  
Karine M. Sparta ◽  
Georg Roth
Keyword(s):  
Single Crystal ◽  
Temperature Dependence ◽  
Crystal Structures ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups ◽  
Temperature Ranges ◽  
First Time

The V4+ (spin ½) oxovanadates AV3O7 (A = Ca, Sr) were synthesized and studied by means of single-crystal X-ray diffraction. The room-temperature structures of both compounds are orthorhombic and their respective space groups are Pnma and Pmmn. The previously assumed structure of SrV3O7 has been revised and the temperature dependence of both crystal structures in the temperature ranges 297–100 K and 315–100 K, respectively, is discussed for the first time.

MBE-Grown GaNAsBi Matched to GaAs with 1.3-μm Emission Wavelength

2004 ◽  
Vol 829 ◽  
Author(s):  
Masahiro Yoshimoto ◽  
Wei Huang ◽  
Kunishige Oe
Keyword(s):  
Room Temperature ◽  
Molecular Beam ◽  
Laser Diodes ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Matching ◽  
Peak Energy ◽  
First Time ◽  
Lattice Matched

ABSTRACTGaNyAs1-x-yBix alloy lattice-matched to GaAs has been grown by molecular beam epitaxy (MBE). The lattice-matching of GaNyAs1-x-yBix to GaAs was investigated by X-ray diffraction measurements on a series of GaNyAs1-x-yBix with various GaN molar fractions. GaNyAs1-x-yBix lattice-matched to GaAs was obtained, which was confirmed by its diffraction peak overlapped with the peak of GaAs. Photoluminescence (PL) of 1.3 μm was observed from GaNyAs1-x-yBix epilayer matched to GaAs at room temperature. The temperature coefficient of the PL peak energy in a temperature range 150–300K for GaNyAs1-x-yBix was 1/3 of InGaAsP with a bandgap corresponding to 1.3-μm emission. Both lattice-matching to GaAs and bandgap adjustment to 1.3-μm waveband were achieved for GaNyAs1-x-yBix for the first time. This alloy will lead to the fabrication of laser diodes with an emission of temperature insensitive wavelength.

Effects on the amorphous Ga2O3 film surfaces by sub-IB-metal-nano-layers

MRS Advances ◽  
2019 ◽  
Vol 4 (5-6) ◽  
pp. 285-292
Author(s):  
L. I. Juárez-Amador ◽  
M. Galván-Arellano ◽  
Y. M. Hernández-Rodríguez ◽  
J. A. Andraca-Adame ◽  
G. Romero-Paredes ◽  
...  
Keyword(s):  
Room Temperature ◽  
Rf Sputtering ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
Amorphous Films ◽  
X Ray ◽  
Plasmon Frequency ◽  
First Time ◽  
Amorphous Character

AbstractThis work reports by the first time a method to control the geometry of Ga2O3 films nanocrystallites at 350 °C. The formation of controlled shaped nano-crystallites of γ-Ga2O3 from amorphous Ga2O3 films grown by RF-Sputtering at room temperature driven by nano-layers of group IB metals (Cu, Ag or Au) is studied. The reported results can be explained by the role of subsurface metal nano-layers and the non-equilibrium nature of the sputtering processes. To study the effects on the surface structure and their optical properties arrays of amorphous-Ga2O3/IB-metal/amorphous-Ga2O3 were annealed in dry N2 atmosphere at 350 °C by 50, 100 and 150 min. The experimental results can be explained by the evolution of the amorphous character of the films amorphous films towards the nanocrystalline γ-Ga2O3 phase driven by the metal nano-layer seed nature. As the annealing time was increased the transition from amorphous-Ga2O3 to the nanocrystalline γ-Ga2O3 phase was detected by X-ray diffraction analysis. The transition to the nanocrystalline γ-Ga2O3 is demonstrated by the formation of octahedral, triangle and ball shape nanocrystallites with sizes of ∼5 to 50 nm according to FE-SEM analysis. The influence of the metal nano-layer is clearly seen by the shift of the plasmon frequency resonance produced by the Ga2O3/IB-metal/Ga2O3 arrays in the region from 400 to 600 nm caused by the modification of the interface Ga2O3/IB-metal produced by the applied annealing stages.

RF-Magnetron Sputtered Strontium Titanate: Structure, Processing and Property Relationships

1999 ◽  
Vol 603 ◽  
Author(s):  
B.J. Gibbons ◽  
Y. Fan ◽  
A.T. Findikoglu ◽  
D.W. Reagor ◽  
Q.X. Jia
Keyword(s):  
Room Temperature ◽  
Low Frequency ◽  
Ozone Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Treated Sample ◽  
Diffraction Peaks ◽  
Compositional Variations ◽  
First Time

AbstractThe low frequency dielectric properties of epitaxial SrTiO3 thin films deposited on LaAlO3 are presented. The films were deposited using radio-frequency magnetron sputtering from stoichiometric targets in an Ar/O2 atmosphere. For the first time, the effects of in situ ozone annealing during the early stages of deposition were explored. X-ray diffraction results indicated that the ozone treatment resulted in more symmetric and sharper diffraction peaks (2 Θ- FWHM decreased from 0.17° to 0.10°). In addition, the peaks for the ozone treated samples were shifted in 2 Θ towards values approaching the bulk value. Rutherford backscattering measurements showed Sr/Ti ratios of 1:1 for these samples, indicating these peak shifts are not due to compositional variations. The dielectric constant of the ozone treated samples increased from 275 at room temperature to 1175 at 22 K (measured at 100 kHz). The effective loss tangent of the device remained between 1 × 10−4 and 1 × 10−3 down to 100 K, where it began to increase. The tunability was also measured. The ozone treated sample showed tunability of 46%, 43% and 38% at 22 K, 40 K and 60 K, respectively. Finally, similar measurements were completed at 1 MHz, indicating a minimal dependence of these properties on frequencies in this range.

Neutron and X-ray single-crystal diffraction from protein microcrystalsviamagnetically oriented microcrystal arrays in gels

2016 ◽  
Vol 72 (7) ◽  
pp. 823-829 ◽  
Author(s):  
Shu Tsukui ◽  
Fumiko Kimura ◽  
Katsuhiro Kusaka ◽  
Seiki Baba ◽  
Nobuhiro Mizuno ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Structure Determination ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Diffraction Structure ◽  
First Time ◽  
Magnetically Aligned

Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.

Photoluminescence and Structure of Chemically Etched Si

1991 ◽  
Vol 256 ◽  
Author(s):  
S. Shih ◽  
K. H. Jung ◽  
T. Y. Hsieh ◽  
J. Sarathy ◽  
C. Tsai ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Morphology ◽  
Chemical Etching ◽  
Room Temperature ◽  
Porous Si ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Time ◽  
Scanning Electron

ABSTRACTWe demonstrate for the first time that chemical etching of Si in HF-HNO3-based solution without applying bias can produce a room temperature photoluminescent porous Si layer. Scanning electron microscope studies reveal a surface morphology similar to that of the conventionally anodized porous Si. The formation mechanism of the chemically etched (CE) film can be explained by a local anodization concept. X-ray diffraction studies on the luminescent CE porous Si show a broad amorphous peak.

Magnetic Anisotropy in Single Crystal Terfenol-D Thin Films

1997 ◽  
Vol 475 ◽  
Author(s):  
V. Oderno ◽  
C. Dufour ◽  
K. Dumesnil ◽  
A. Mougin ◽  
Ph. Bauer ◽  
...  
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Growth Direction ◽  
X Ray Diffraction ◽  
Bulk Alloy ◽  
Easy Magnetization ◽  
Magnetization Direction ◽  
Kerr Rotation ◽  
X Ray ◽  
First Time

ABSTRACTTb03.Dy0.7Fe2 (known as Terfenol-D) thin films have been epitaxially grown for the first time with [110] as the growth direction. X-Ray diffraction measurements evidence that the films are strained compared to the bulk alloy. Mössbauer spectroscopy and Kerr rotation measurements show that the easy magnetization direction varies from <116> at 4.2 K to around <133> at 300 K. This variation is different from the bulk case (for which the magnetization is along <100> at 4.2 K and along <111> at room temperature). This effect can be qualitatively understood if we consider the influence of the strains induced by epitaxy on the various energy terms which govern the direction of magnetization.

Room Temperature Epitaxy of Al (100) on Si (111)

1993 ◽  
Vol 317 ◽  
Author(s):  
Marek Sosnowski ◽  
Samuel Ramac ◽  
Walter L. Brown ◽  
Young O. Kim
Keyword(s):  
Epitaxial Growth ◽  
Room Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Effusion Cell ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
First Time ◽  
Post Deposition

ABSTRACTThere are a number of published reports on the epitaxial growth of Al(111) on Si(111) surfaces usually following a high temperature treatment of the Si surface in UHV. In contrast to these results, we have for the first time observed dominant epitaxial growth of Al(100) films on Si(111) surfaces that have been carefully cleaned and hydrogen terminated and not heated prior to effusion cell deposition of Al at room temperature in UHV. X-ray diffraction shows sharp and intense Al (200) diffraction, enhanced by post deposition annealing. Crystal quality and the dominance of Al(100) structure depend strongly on the substrate treatment and the off-cut angle, both of which control the steps on the Si(111) surface. The steps were found responsible for the epitaxial alignment of the film and the substrate lattices. Details of this alignment were observed in TEM cross-sectional images of the interface.

Ce0.8Gd0.2O1.9 Powders Synthesized by Co-Precipitation and Amorphous Citrate Processes

2005 ◽  
Vol 498-499 ◽  
pp. 624-629 ◽  
Author(s):  
Márcia Caldeira Brant ◽  
Felipe da Silva Possa ◽  
Fernando Soares Lameiras
Keyword(s):  
Room Temperature ◽  
Simple Technique ◽  
Fluorite Structure ◽  
Theoretical Density ◽  
Precipitation Process ◽  
Doped Ceria ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Techniques ◽  
Co Precipitation

Powders of Ce0.8Gd0.2O1.9 were synthesized by co-precipitation and amorphous citrate routes and their compositions and structures were compared. Co-precipitation process was carried out at room temperature, while amorphous citrate synthesis was performed at 60-70 °C. The powders obtained were calcined at 700 °C for 1 h. X-ray diffraction analyses showed that a single fluorite structure was formed by both synthesis techniques. Pellets from these powders were prepared by compaction at 30 kN/cm2 and sintered at 1593 °C in air. WDS analysis confirmed the homogeneity of the pellets. The sintered pellets obtained by amorphous citrate and by coprecipitation routes showed relative densities over 97 % of the theoretical density. These results indicated that the citrate amorphous route is an interesting and simple technique to prepare gadolinium-doped ceria powders with high sinterability.

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