An in situ study of the phase transitions among CaCO3 high-pressure polymorphs

2018 ◽  
Vol 83 (02) ◽  
pp. 191-197 ◽  
Author(s):  
Xueyin Yuan ◽  
Chao Gao ◽  
Jing Gao
Keyword(s):  
Phase Transitions ◽  
Intermediate Phase ◽  
The Other ◽  
Three Samples ◽  
Short Period ◽  
Two Samples ◽  
Wide Pressure Range ◽  
Diamond Anvil ◽  
Wide Pressure

AbstractThe phase transitions involving calcite (CaCO3-I), CaCO3-II, CaCO3-III and CaCO3-IIIb were investigated using a diamond anvil cell and micro-Raman spectroscopy. Based on the results obtained from in situ observations and Raman measurements made with six natural calcite crystals, the phase transition from calcite to CaCO3-II took place between 1.56 and 1.67 GPa under ambient temperature. Under a precise pressure of 1.97 ± 0.03 GPa, three CaCO3 samples were observed to transform from CaCO3-II directly to CaCO3-III, while in the other three samples both CaCO3-III and CaCO3-IIIb crystal structures were detected. Transformation from CaCO3-IIIb to CaCO3-III was completed in a short period in one sample, whereas in the other two samples coexistence of CaCO3-III and CaCO3-IIIb was observed over a wide pressure range from 1.97 to 3.38 GPa, with sluggish transformation from CaCO3-IIIb to CaCO3-III being observed after the samples were preserved under 3.38 GPa for 72 h. Hence, it can be concluded that CaCO3-IIIb is a metastable intermediate phase occurring during the reconstructive transformation from CaCO3-II to CaCO3-III. Splitting of the C–O in-plane bending (ν4) and symmetric stretching (ν1) vibrations and appearance of new lattice vibrations in the Raman spectra of CaCO3-III and CaCO3-IIIb suggest a lowering in crystal symmetry during the transformation from CaCO3-II through CaCO3-IIIb to CaCO3-III, which is in good agreement with the observed sequence of phase symmetries.

PHASE TRANSITION IN LAYERED PEROVSKITE LIKE MANGANATE Ca3Mn2O7 UNDER HIGH PRESSURE

2001 ◽  
Vol 15 (18) ◽  
pp. 2491-2497 ◽  
Author(s):  
J. L. ZHU ◽  
L. C. CHEN ◽  
R. C. YU ◽  
F. Y. LI ◽  
J. LIU ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Diamond Anvil Cell ◽  
The Other ◽  
Layered Perovskite ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Diamond Anvil

In situ high pressure energy dispersive X-ray diffraction measurements on layered perovskite-like manganate Ca 3 Mn 2 O 7 under pressures up to 35 GPa have been performed by using diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca 3 Mn 2 O 7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca 3 Mn 2 O 7 underwent two phase transitions under pressures in the range of 0~35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.

scholarly journals A Study of the Micropore Structure of Carbonized Rayon Yarn by Nitrogen Adsorption and Nonane Pre-Adsorption

1985 ◽  
Vol 2 (2) ◽  
pp. 89-95 ◽  
Author(s):  
J. N. Bohra ◽  
K. S. W. Sing
Keyword(s):  
External Surface ◽  
Nitrogen Adsorption ◽  
The Other ◽  
Adsorption Method ◽  
Micropore Structure ◽  
Surface Areas ◽  
Three Samples ◽  
Two Samples ◽  
Before And After ◽  
Gain Access

Adsorption isotherms of nitrogen have been determined at 77 K on three samples of carbonized rayon yarn, both before and after the pre-adsorption of n-nonane. In their original state the three samples were all highly microporous. Application of the αs-method of isotherm analysis reveals that their micropore volumes were 0·17–0·19 cm3g−1 and their external surface areas 20–27 m2g−1 (the corresponding BET areas being 427–483 m2g−1). Nonane pre-adsorption resulted in blockage of the entire micropore structure only in the case of one sample: micropore volumes ∼0·1 cm3g−1 were still available for nitrogen adsorption in the other two samples. It appears that nitrogen molecules were able to gain access to some parts of these micropore structures through wider pore entrances which were not completely blocked by the pre-adsorbed nonane. The work has shown that the nonane pre-adsorption method requires further investigation before it can be used with confidence for the assessment of microporosity.

THE ENHANCED SUPERCONDUCTIVITY OF Cu-1234 UNDER HIGH PRESSURE

2005 ◽  
Vol 19 (01n03) ◽  
pp. 335-337 ◽  
Author(s):  
C. Q. JIN ◽  
X. M. QIN ◽  
K. SHIMIZU ◽  
M. NISHIYAMA ◽  
T. NAMIKI ◽  
...  
Keyword(s):  
Pressure Range ◽  
Diamond Anvil Cell ◽  
Pressure Effect ◽  
Positive Pressure ◽  
Superconducting Transition ◽  
Wide Pressure Range ◽  
Diamond Anvil ◽  
The One ◽  
Enhanced Superconductivity ◽  
Wide Pressure

The evolution of superconducting transition of CuBa 2 Ca 3 Cu 4 O 10+δ (i.e. Cu -1234) superconductor has been studied by using diamond anvil cell technique. The Tc of Cu -1234 can be enhanced continuously from ambient reaching to 123 K at 15 GPa. This seems the one more system besides Hg -12( n -1) n which demonstrate the positive pressure effect on Tc over a wide pressure range above 10 GPa.

SWELLING BEHAVIOUR OF MIXED-LAYER CLAYS IN HYDROCARBON RESERVOIRS

1994 ◽  
Vol 34 (1) ◽  
pp. 366
Author(s):  
Julian C. Baker ◽  
Philippa J.R. Uwins ◽  
Ian D.R. Mackinnon
Keyword(s):  
Morphological Change ◽  
Mixed Layer ◽  
Hydrocarbon Reservoirs ◽  
Environmental Scanning ◽  
Three Samples ◽  
Two Samples ◽  
Before And After ◽  
Porosity And Permeability ◽  
Freshwater Sensitivity

The freshwater sensitivity of a variety of mixed-layer illite/smectite and chlorite/smectite clays has been studied with an Environmental Scanning Electron Microscope (ESEM) in order to determine whether all hydrocarbon reservoirs hosting these clays should be regarded as freshwater sensitive. Experimental procedures involved closely comparing in situ mixed-layer clay within selected areas at high magnification before and after prolonged freshwater treatments.The response of smectite-rich illite/smectite (two samples; 10–20 per cent illite interlayers) to freshwater immersion varied greatly. One sample rapidly swelled to many times its original volume to form a pervasive gel that greatly reduced porosity and permeability, whereas the other sample underwent only a subtle morphological change that had little or no adverse effect on reservoir quality. Illite-rich illite/smectite (three samples; 65—>85 per cent illite interlayers) and chlorite-rich chlorite/smectite (two samples; 50 per cent and >70 per cent chlorite interlayers) underwent no morphological change when immersed in freshwater for up to three months, indicating that these clays in sandstones are unlikely to cause formation damage due to swelling if exposed to freshwater-based fluids.

Diversity of entomopathogenic nematodes (Nematoda: Steinernematidae, Heterorhabditidae) from Arasbaran forests and rangelands in north-west Iran

Nematology ◽  
2010 ◽  
Vol 12 (5) ◽  
pp. 767-773 ◽  
Author(s):  
Mostafa Nikdel ◽  
Gholamreza Niknam ◽  
Christine T. Griffin ◽  
Naser Eivazian Kary
Keyword(s):  
Entomopathogenic Nematodes ◽  
Common Species ◽  
Soil Samples ◽  
The Other ◽  
Undescribed Species ◽  
North West ◽  
Three Samples ◽  
Two Samples ◽  
Molecular Studies ◽  
Species Being

Abstract A survey for entomopathogenic nematodes (EPN) was carried out in the Arasbaran forests and rangelands, East Azarbaijan province, north-west Iran, during 2006 to 2008. A total of 691 soil samples were collected from 62 localities across the region of which 21 samples (3%) were positive for EPN, including nine samples (1.3%) with heterorhabditids and 12 (1.7%) with steinernematids. Seven isolates (four Steinernema and three Heterorhabditis) were recovered from rangelands and 14 (eight Steinernema and six Heterorhabditis) from forest soil samples. Based on morphology and molecular studies, the Heterorhabditis isolates were identified as H. bacteriophora and the Steinernema isolates as S. carpocapsae, S. bicornutum, S. feltiae, S. glaseri, S. kraussei and three undescribed species referred to here as Steinernema sp. IRAZ7, Steinernema sp. IRAZ13 and Steinernema sp. IRAZ21. Heterorhabditis bacteriophora, the most common species, was present in nine soil samples collected across the forests and rangelands, and of the Steinernema species, S. bicornutum was obtained from three samples, the other species being found from only one or two samples.

An investigation into the temperature phase transitions of synthesized materials with Al- and Mg-doped lithium manganese oxide spinels by in situ powder X-ray diffraction

2016 ◽  
Vol 32 (1) ◽  
pp. 23-30
Author(s):  
C. D. Snyders ◽  
E. E. Ferg ◽  
D. Billing
Keyword(s):  
Phase Transitions ◽  
Intermediate Phase ◽  
Phase Changes ◽  
Synthesis Process ◽  
Temperature Phase ◽  
Gravimetric Analysis ◽  
Spinel Oxide ◽  
X Ray Diffraction ◽  
X Ray

Three spinel materials were prepared and characterized by in situ powder X-ray diffraction (PXRD) techniques to track their phase changes that occurred in the typical batch synthesis process from a sol–gel mixture to the final crystalline spinel oxide. The materials were also characterized by thermal gravimetric analysis, whereby the materials decomposition mechanisms that were observed as the precursor, was gradually heated to the final oxide. The results showed that all the materials achieved their total weight loss at about 400 °C. The in situ PXRD analysis showed the progression of the phase transitions where certain of the materials changed from a crystalline precursor to an amorphous intermediate phase and finally to the spinel cathode oxide (Li1.03Mg0.2Mn1.77O4). For other materials, the precursor would start as an amorphous phase and upon heating, convert into an impure intermediate phase (Mn2O3) before forming the final spinel oxide (Li1.03Mn1.97O4). On the other hand, the LiAl0.4Mn1.6O4 would start with an amorphous precursor, with no intermediate phases and immediately formed the final spinel oxide phase. The in situ PXRD study also showed the increases in the materials respective lattice parameters of the crystalline unit cells upon heating and the significant increases in their crystallite sizes when heated above 600 °C.

Use of Sodium Substitutes in Cottage Cheese and Buttermilk

1986 ◽  
Vol 49 (2) ◽  
pp. 117-120 ◽  
Author(s):  
B. J. DEMOTT ◽  
J. P. HITCHCOCK ◽  
P. M. DAVIDSON
Keyword(s):  
Sodium Concentration ◽  
The Other ◽  
Cottage Cheese ◽  
Psychrotrophic Bacteria ◽  
Three Samples ◽  
Two Samples ◽  
Salt Substitute ◽  
Standard Plate ◽  
Plate Counts ◽  
Yeasts And Molds

Twenty-four market samples of cottage cheese had an average sodium concentration of 4.91 ± 1.20 mg/g. Two samples of cottage cheese formulated to contain 1.1% “Lite” and Zyest, and having sodium concentrations of 3.23 and 2.54 mg/g had significantly lower flavor scores than a sample containing 1.4% NaCl and having 6.25 mg of Na/g. The Standard Plate Counts and the yeast and mold counts on the cottage cheese after storing 10 d at 4°C were not different between samples containing salt, salt substitute or salt substitute plus a dry yeast preparation. Psychrotrophic bacteria were more numerous in the samples containing the yeast preparation. Four samples of buttermilk containing .015% “Zyest 45-F” and .25% NaCl, .25% “Lite” and .015% “Zyest 45-F”, .25% NaCl, or .25% “Lite” had comparable flavor scores. The sodium concentrations of the four samples were 1.096, .793, 1.125 and .771 mg/g, respectively. The growth of yeasts and molds in samples containing “Zyest 45-F” and “Lite” was slightly but not significantly greater than the other three samples. Psychrotrophic counts on buttermilk after 7 d of storage at 4°C were much lower than the original counts, but were not influenced by the additives used.

Resistivity Measurement of P+-Implanted 4H-SiC Samples Prepared at Different Implantation and Annealing Temperatures Using Terahertz Time-Domain Spectroscopic Ellipsometry

2020 ◽  
Vol 1004 ◽  
pp. 272-277
Author(s):  
Kotaro Ishiji ◽  
Seiji Kawado ◽  
Yasuharu Hirai ◽  
Shinji Nagamachi
Keyword(s):  
Raman Spectra ◽  
Spectroscopic Ellipsometry ◽  
Time Domain ◽  
Resistivity Measurement ◽  
The Other ◽  
Lattice Disorder ◽  
Annealing Temperatures ◽  
Three Samples ◽  
Two Samples ◽  
Peak Widths

The resistivities of P+-implanted 4H-SiC samples, each prepared at different implantation and annealing temperatures, were measured using terahertz time-domain spectroscopic ellipsometry and compared with the results of the previously reported Raman spectra. The 4H-SiC samples of one group were implanted with P+ at 30 °C, 150 °C, 300 °C, and 500 °C, respectively, and annealed at 1600 °C. The resistivity was found to be approximately 8 mΩ·cm for the samples implanted at 30 and 150 °C and approximately 2 mΩ·cm for the remaining two samples. The 4H-SiC samples of the other group were implanted at 500 °C followed by annealing at 1200 °C, 1400 °C, 1600 °C, and 1800 °C, respectively. The resistivity was measured as 10 mΩ·cm for the sample annealed at 1200 °C and 3.0−1.8 mΩ·cm for the remaining three samples. These resistivity values are correlated with the Raman peak widths that reflect the lattice disorder.

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