Materials Research at University of Nevada, Las Vegas

2016 ◽  
Vol 879 ◽  
pp. 386-389
Author(s):  
Ravhi S. Kumar ◽  
Weldu Gabrimicael ◽  
Andrew L. Cornelius
Keyword(s):  
High Pressure ◽  
Interdisciplinary Research ◽  
High Pressures ◽  
Las Vegas ◽  
Science And Engineering ◽  
High Pressure Studies ◽  
Materials Research ◽  
Potential Applications ◽  
Indirect Band Gap ◽  
The Relationship

High-pressure studies on thermoelectric materials allow the study of the relationship between structural, elastic, and electronic properties. The High Pressure Science and Engineering Center (HiPSEC) at UNLV performs interdisciplinary research on a wide variety of materials at high pressures. One such system, CrSi2 is an indirect band gap semiconductor that has potential applications in solar cells.

HIGH METALLIC RESISTIVITIES AND RESISTIVITY SATURATION: HIGH-PRESSURE AND THERMAL EXPANSION EFFECTS

1993 ◽  
Vol 07 (08) ◽  
pp. 491-499 ◽  
Author(s):  
BERTIL SUNDQVIST
Keyword(s):  
High Pressure ◽  
Thermal Expansion ◽  
High Pressures ◽  
Measured Temperature ◽  
Metallic Materials ◽  
High Pressure Studies ◽  
Graphite Intercalation ◽  
Recent Developments ◽  
High Transition ◽  
Source Of Information

Some recent developments in the field of resistivity saturation in metallic materials are discussed, concentrating on effects of thermal expansion and high pressures. It is shown that thermal expansion effects can significantly modify the measured temperature dependence of the resistivity, and that high pressure studies are an important, but little used, source of information. Examples are shown for transition metals and alloys, high transition temperature superconductors, and graphite intercalation compounds.

ULTRASONIC PROPAGATION IN SOLENHOFEN LIMESTONE AT HIGH PRESSURES

Geophysics ◽  
1978 ◽  
Vol 43 (5) ◽  
pp. 1014-1017
Author(s):  
I. J. Fritz
Keyword(s):  
High Pressure ◽  
Wave Propagation ◽  
Phase Transitions ◽  
Seismic Waves ◽  
High Pressures ◽  
Sound Propagation ◽  
Wave Measurements ◽  
Ultrasonic Propagation ◽  
Propagation Properties ◽  
The Relationship

The measurement of ultrasonic velocities at high pressure in minerals and rocks provides information pertinent to a variety of geophysical and engineering problems such as those of determining the state of matter in the earth's interior, understanding the propagation of seismic waves, and characterizing mechanical behavior of materials that are important in mining technology. In recent years there have been a number of reported high pressure sound velocity measurements in various kinds of limestone. (A concise review of this work can be found in a recent paper by Singh and Kennedy, 1974.) Such measurements continue to be of interest because of the relationship to shock‐wave propagation properties (Grady et al, 1977). From the previous measurements it has been found that the phase transitions in calcite, which is the main constituent of limestone, strongly influence the sound velocities. The phase transitions in pure calcite occur at 14.5 kbar (calcite I–II) and 17.4 kbar (calcite II–III) (Singh and Kennedy, 1974); however, because the transitions may be shifted in pressure and spread out over a range of pressures in a rock, it is necessary to make measurements to pressures in excess of 20 kbar in order to characterize the effects of the transitions. To date there has been only one experimental study of the effect of the II–III transition on sound propagation, namely the longitudinal wave measurements in Oak Hall limestone made by Wang and Meltzer (1973). In order to further characterize the effect of the II–III transition on sound propagation in limestone, we have made measurements to 25 kbar on Solenhofen limestone. We were able to measure both longitudinal and transverse velocities over the full pressure range; thus, our measurements represent the first study of the effect of the II–III transition on shear wave propagation under conditions of hydro static pressure.

scholarly journals High-pressure diffraction studies of molecular organic solids. A personal view

2007 ◽  
Vol 64 (1) ◽  
pp. 218-231 ◽  
Author(s):  
Elena V. Boldyreva
Keyword(s):  
High Pressure ◽  
Solid State ◽  
High Pressures ◽  
Experimental Studies ◽  
Personal View ◽  
Organic Solids ◽  
High Pressure Studies

This paper discusses the trends in the experimental studies of molecular organic solids at high pressures by diffraction techniques. Crystallization of liquids, crystallization from solutions and solid-state transformations are considered. Special attention is paid to the high-pressure studies of pharmaceuticals and of biomimetics.

scholarly journals X-Ray Diffraction and Electron Microscopy Studies of the Size Effects on Pressure-Induced Phase Transitions in CdS Nanocrystals

MRS Advances ◽  
2020 ◽  
pp. 1-9
Author(s):  
Lingyao Meng ◽  
Hongyou Fan ◽  
J. Matthew Lane ◽  
Luke Baca ◽  
Jackie Tafoya ◽  
...  
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
High Pressure ◽  
Phase Transitions ◽  
Size Effects ◽  
High Pressures ◽  
Bulk Material ◽  
Cds Nanoparticles ◽  
X Ray ◽  
Potential Applications

Abstract In recent years, investigations of the phase transition behavior of semiconducting nanoparticles under high pressure has attracted increasing attention due to their potential applications in sensors, electronics, and optics. However, current understanding of how the size of nanoparticles influences this pressure-dependent property is somewhat lacking. In particular, phase behaviors of semiconducting CdS nanoparticles under high pressure have not been extensively reported. Therefore, in this work, CdS nanoparticles of different sizes are used as a model system to investigate particle size effects on high-pressure-induced phase transition behaviors. In particular, 7.5, 10.6, and 39.7 nm spherical CdS nanoparticles are synthesized and subjected to controlled high pressures up to 15 GPa in a diamond anvil cell. Analysis of all three nanoparticles using in-situ synchrotron wide-angle X-ray scattering (WAXS) data shows that phase transitions from wurtzite to rocksalt occur at higher pressures than for bulk material. Bulk modulus calculations not only show that the wurtzite CdS nanomaterial is more compressible than rocksalt, but also that the compressibility of CdS nanoparticles depends on their particle size. Furthermore, sintering of spherical nanoparticles into nanorods was observed for the 7.5 nm CdS nanoparticles. Our results provide new insights into the fundamental properties of nanoparticles under high pressure that will inform designs of new nanomaterial structures for emerging applications.

High-Pressure Gear Pumps

1946 ◽  
Vol 155 (1) ◽  
pp. 417-452 ◽  
Author(s):  
T. E. Beacham
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Journal Bearings ◽  
Volumetric Efficiency ◽  
Solid Matter ◽  
Excessive Pressure ◽  
Low Viscosity ◽  
Large Numbers ◽  
Gear Pumps ◽  
The Relationship

Gear pumps have been used in very large numbers for the various hydraulic services of war aircraft. For the higher pressures the main problems have been in connexion with the load on the journal bearings, with wear, and with the reduction in volumetric efficiency caused by internal leakage. The journal loads are affected by the number of teeth and by the ratio of width to diameter of the gears. With high pressures it is difficult to accommodate standard ball or roller races on account of their diameter: designs are illustrated using a combination of standard races and special needle roller bearings. Small amounts of wear cause comparatively large reductions in volumetric efficiency. Major causes of wear are rubbing on the gear end faces and solid matter in suspension in the liquid and methods of dealing with these are discussed. The percentage slip due to internal leakage varies inversely as the factor (r.p.m. × viscosity). At low speeds and with low-viscosity liquids, internal leakage often limits the pressure at which the pump can be used. Multistage pumps reduce the leakage and have been used extensively for undercarriage operation. Internal leakage becomes relatively less as the size of the pump is increased and the paper gives a graph, showing the relationship between the limit of pressure at which 80 per cent volumetric efficiency is possible, the capacity and rotational speed of the pump, and the viscosity of the liquid. Aircraft pumps generally use gears with involute teeth: ports in the end covers of the casing are used to prevent excessive pressure in the liquid trapped between the teeth. Low- and high-leakage conditions call for difficult arrangements of ports, and this involves differing displacements and variations in flow velocity.

High Pressure Materials Physics Research at UNLV

2014 ◽  
Vol 783-786 ◽  
pp. 1836-1838
Author(s):  
Andrew L. Cornelius ◽  
Brant Abeln ◽  
Daniel Antonio ◽  
Jason Baker ◽  
Patricia E. Kalita ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Ambient Pressure ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
High Pressure Studies ◽  
Heat Capacity Measurements

High-pressure studies on strongly correlated-electron systems allow the study of the relationship between structural, elastic, electronic, and magnetic properties of d-and f-band systems. The High Pressure Science and Engineering Center (HiPSEC) at UNLV performs interdisciplinary research on a wide variety of materials at high pressures. One such system, YbB2 displays antiferromagnet order at ambient pressure. We present heat capacity measurements at high magnetic fields to 9 T and structural measurement at pressures up to 5 GPa on YbB2.

Charge density wave, superconductivity, and non-metallic behaviour under high pressure in ZrTe3

2002 ◽  
Vol 12 (9) ◽  
pp. 97-98
Author(s):  
K. Igarashi ◽  
S. Yasuzuka ◽  
K. Inagaki ◽  
S. Tanda ◽  
Y. Okajima ◽  
...  
Keyword(s):  
High Pressure ◽  
Fermi Surface ◽  
Charge Density ◽  
Charge Density Wave ◽  
High Pressures ◽  
Density Wave ◽  
Metallic State ◽  
Resistivity Measurements ◽  
Low Dimensional ◽  
The Relationship

The charge-density-wave (CDW) order of low-dimensional inorganic conductor ZrTe3 is found to increase with increasing pressure, while the superconductivity with filamentary nature is significantly suppressed. It was evidenced in resistivity measurements under pressure up to 0.8 Cpa. The present results suggest that competition between the superconductivity and the CDW is not simply explained by a nesting effect of the Fermi surface, but other origin is needed. Non-metallic behaviour is also found below 4 K under high pressures above 0.6 Gpa. The relationship between the non-metallic state and the pressure-enhanced CDW is expected, although yet inexplicable.

scholarly journals Jovian seismology

1994 ◽  
Vol 147 ◽  
pp. 481-511
Author(s):  
Benoît Mosser
Keyword(s):  
High Pressure ◽  
Internal Structure ◽  
Low Temperatures ◽  
High Pressures ◽  
Giant Planets ◽  
The Other ◽  
Interior Structure ◽  
Theoretical Approaches ◽  
Thermodynamical Laws ◽  
The Relationship

AbstractThis paper reviews a new astrophysical subject: seismology of the giant planets. Seismology is dedicated to the sounding of the interior structure of any object; on the other hand, the interiors of the Jovian planets need to be constrained, in order to improve our knowledge of their structure and of their evolution, as well as the thermodynamical laws involved at high pressures and low temperatures. The relationship between Jovian seismology and, first, Jovian internal structure, and second, high pressure physics, is examined, in order to determine the task of “dioseismology”† in the next years. We present then the seismological theoretical approaches developped since the pionnering work of Vorontsov et al. (1976), who calculated the frequencies of the Jovian eigenmodes. We report the first observational attempts for the detection of the oscillations of Jupiter. We discuss the observational results and examine what can be done in the future.

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