scholarly journals On the crystallisation temperature of very high-density amorphous ice

2018 ◽  
Vol 20 (18) ◽  
pp. 12589-12598 ◽  
Author(s):  
Josef N. Stern ◽  
Thomas Loerting
Keyword(s):  
Low Temperature ◽  
High Pressures ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Amorphous Ice ◽  
Elevated Pressures ◽  
Temperature Boundary ◽  
Crystallisation Temperature ◽  
High Pressures And Temperatures ◽  
Very High

VHDA prepared at high pressures and temperatures appears to be mainly free of (nano)crystallinity. It is the thermally most stable amorphous solid phase of water at elevated pressures reported so far. Water's no man's land's low temperature boundary is thus shifted to higher temperatures by up to 4 K.

Oxidative coupling of methane at elevated pressures: reactor concept and its validation

2018 ◽  
Vol 3 (2) ◽  
pp. 151-154 ◽  
Author(s):  
M. Albrecht ◽  
U. Rodemerck ◽  
D. Linke ◽  
E. V. Kondratenko
Keyword(s):  
Oxidative Coupling ◽  
High Pressures ◽  
Oxidative Coupling Of Methane ◽  
Elevated Pressures ◽  
High Pressures And Temperatures

A novel quartz reactor has been developed for heterogeneously catalysed reactions at high pressures and temperatures.

The Pressure-temperature Phase and Reaction Diagram for Carbon

1995 ◽  
Vol 383 ◽  
Author(s):  
Francis P. Bundy
Keyword(s):  
Melting Temperature ◽  
Triple Point ◽  
High Pressures ◽  
Solid Phase ◽  
Theoretical Calculations ◽  
Closed Surface ◽  
Temperature Phase ◽  
Stable Form ◽  
Metallic State ◽  
Very High

ABSTRACTCarbon atoms form very strong bonds to each other, yielding materials like: (i) crystalline graphite, diamond and their many “amorphous” hybrids; (ii) crystalline forms of giant closed–surface molecules such as the fullerenes; and (iii) liquid and gas phases which have molecular contents which are complicated and not yet defined or understood. Because of the high bonding energy the melting and vaporization temperatures of the solid forms are very high, and the activation energies required to transform one solid form to another are large. One consequence is that at lower temperatures the different solid phases may continue to exist metastably far into a P, T region in which another solid phase is the thermodynamically stable one.In the thermodynamic sense the vapor pressure line of graphite, the graphite/liquid/vapor triple point, the graphite melting line, the graphite/diamond equilibrium line, and the graphite/diamond/liquid triple point are quite well established. Data for the melting temperature of diamond vs. pressure are sparse and rough, but they indicate that the melting temperature increases with pressure,-in agreement with some theories. Although carbon should transform to a solid metallic state at very high pressures, experimental evidence shows diamond to be stable to over 400GPa, and theoretical calculations indicate that it could be the stable form up to pressures of 1200 to 2300GPa. Attention is given to the solid state transformations which can take place when graphite is compressed and heated along different P, T paths under different conditions.

A compact high-performance low-field NMR apparatus for measurements on fluids at very high pressures and temperatures

2014 ◽  
Vol 85 (2) ◽  
pp. 025102 ◽  
Author(s):  
R. Freedman ◽  
V. Anand ◽  
B. Grant ◽  
K. Ganesan ◽  
P. Tabrizi ◽  
...  
Keyword(s):  
High Performance ◽  
High Pressures ◽  
Low Field ◽  
Low Field Nmr ◽  
High Pressures And Temperatures ◽  
Very High

The Possible Importance of Pressure in Metastable Precipitate Formation in Ion Implanted Metals

1988 ◽  
Vol 100 ◽  
Author(s):  
John H. Evans
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Solid Phase ◽  
Inert Gas ◽  
Fine Scale ◽  
Host Matrix ◽  
Driven Cavity ◽  
Precipitate Formation ◽  
Very High ◽  
Metastable Precipitate

ABSTRACTPrompted by the recent discovery that the heavier inert gas atoms implanted into metals precipitate in the solid phase, indicative of very high pressures (,>,1 GPa), the present paper discusses the conditions under which such pressures might be expected. The metal/inert gas results are briefly described and then used as a model to show that the two essential features apart from low or moderate metal temperatures, are the insolubility of the implanted species in the host matrix and its precipitation on a very fine scale. This combination suppresses the bias-driven cavity swelling that would otherwise control vacancy acquisition in an irradiation environment.The extrapolation to other combinations of implanted ion and metal will be discussed. Where the implanted ion is insoluble and precipitates on a scale similar to the inert gas atoms, exact analogy suggests that the precipitates will again be under high pressure. The formation of high pressure phases might not be unexpected and could be a factor in explaining the presence of phases previously thought to be metastable.

Discovery of bridgmanite, the most abundant mineral in Earth, in a shocked meteorite

Science ◽  
2014 ◽  
Vol 346 (6213) ◽  
pp. 1100-1102 ◽  
Author(s):  
Oliver Tschauner ◽  
Chi Ma ◽  
John R. Beckett ◽  
Clemens Prescher ◽  
Vitali B. Prakapenka ◽  
...  
Keyword(s):  
Perovskite Structure ◽  
High Pressures ◽  
Solid Phase ◽  
Phase Assemblage ◽  
Half Century ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Earth’S Mantle ◽  
High Pressures And Temperatures ◽  
Peak Shock

Meteorites exposed to high pressures and temperatures during impact-induced shock often contain minerals whose occurrence and stability normally confine them to the deeper portions of Earth’s mantle. One exception has been MgSiO3 in the perovskite structure, which is the most abundant solid phase in Earth. Here we report the discovery of this important phase as a mineral in the Tenham L6 chondrite and approved by the International Mineralogical Association (specimen IMA 2014-017). MgSiO3-perovskite is now called bridgmanite. The associated phase assemblage constrains peak shock conditions to ~ 24 gigapascals and 2300 kelvin. The discovery concludes a half century of efforts to find, identify, and characterize a natural specimen of this important mineral.

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