scholarly journals Laser-induced plasma in water at high pressures up to 40 MPa: A time-resolved study

2020 ◽  
Vol 28 (12) ◽  
pp. 18122 ◽  
Author(s):  
Ye Tian ◽  
Ying Li ◽  
Lintao Wang ◽  
Fuzhen Huang ◽  
Yuan Lu ◽  
...  
Keyword(s):  
High Pressures ◽  
Time Resolved ◽  
Laser Induced Plasma

Numerical Study of Temperature and Incandescence Intensity of Nanosecond Pulsed-Laser Heated Soot Particles at High Pressures

2005 ◽  
Author(s):  
Fengshan Liu ◽  
David R. Snelling ◽  
Gregory J. Smallwood
Keyword(s):  
Soot Particle ◽  
High Pressures ◽  
Particle Diameter ◽  
Aggregate Size ◽  
Primary Particle Diameter ◽  
Time Resolved ◽  
Soot Particles ◽  
Nanosecond Pulsed Laser ◽  
Primary Particles ◽  
Laser Heated

Histories of temperature and incandescence intensity of nanosecond pulsed-laser heated soot particles of polydispersed primary particles and aggregate sizes were calculated using an aggregate-based heat transfer model at pressures from 1 atm up to 50 atm. The local gas temperature, distributions of soot primary particle diameter and aggregate size assumed in the calculations were similar to those found in an atmospheric laminar diffusion flame. Relatively low laser fluences were considered to keep the peak particle temperatures below about 3400 K to ensure negligible soot particle sublimation. The shielding effect on the heat conduction between aggregated soot particles and the surrounding gas was accounted for based on results of direct simulation Monte Carlo calculations. After the laser pulse, the temperature of soot particles with larger primary particles or larger aggregates cools down slower than those with smaller primary particles or smaller aggregates due to smaller surface area-to-volume ratios. The effective temperature of soot particles in the laser probe volume was calculated based on the ratio of thermal radiation intensities of the soot particle ensemble at 400 and 780 nm. Due to the reduced mean free path of molecules with increasing pressure, the heat conduction between soot particles and the surrounding gas shifts from the free-molecular to the transition regime. Consequently, the rate of conduction heat loss from the soot particles increases significantly with pressure. The lifetime of laser-induced incandescence (LII) signal is significantly reduced as the pressure increases. At high pressures, the time resolved soot particle temperature is very sensitive to both the primary particle diameter and the aggregate size distributions, implying the time-resolved LII particle sizing techniques developed at atmospheric pressure lose their effectiveness at high pressures.

Effect of Different Atmospheres on the Excitation Process of TEA-CO2 Laser-Induced Shock Wave Plasma

1992 ◽  
Vol 46 (4) ◽  
pp. 581-586 ◽  
Author(s):  
H. Kurniawan ◽  
T. Kobayashi ◽  
K. Kagawa
Keyword(s):  
Pulse Width ◽  
Noble Gases ◽  
Tea Co2 Laser ◽  
Total Emission ◽  
Excitation Process ◽  
Time Resolved ◽  
Laser Induced Plasma ◽  
Plasma Characteristics ◽  
Excitation Processes ◽  
Reduced Pressures

The plasma characteristics and excitation process of laser-induced plasma with the use of a TEA CO2 laser of 750 mJ pulse energy and 100 ns pulse width are studied in different surrounding gases at reduced pressures. From the time-resolved spatial distribution, it is clear that in helium and argon atmospheres, two different excitation processes take place in forming the plasma. The first excitation process is due to the blast wave, while the second process is due to the metastable state of the noble gases. It is believed that this second process transfers metastable energy to the vaporized atoms of the target for emission, even long after the laser bombardment ends, thus giving total emission intensity that is higher in the noble gases than in air. The displacement of the front of the emission line under different atmospheres is also presented.

scholarly journals Nanostructured Metal Hydrides for Hydrogen Storage Studied by In Situ Synchrotron and Neutron Diffraction

2010 ◽  
Vol 1262 ◽  
Author(s):  
Volodymyr Yartys ◽  
Roman Denys ◽  
Jan Petter Maehlen ◽  
Colin J Webb ◽  
Evan MacA Gray ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Hydrogen Exchange ◽  
High Pressures ◽  
Storage Systems ◽  
Time Resolved ◽  
Fast Kinetics ◽  
Al Content ◽  
Unit Cells ◽  
Complementary Techniques

AbstractThis work was focused on studies of the metal hydride materials having a potential in building hydrogen storage systems with high gravimetric and volumetric efficiencies of H storage and formed / decomposed with high rates of hydrogen exchange. In situ diffraction studies of the metal-hydrogen systems were explored as a valuable tool in probing both the mechanism of the phase-structural transformations and their kinetics. Two complementary techniques, namely Neutron Powder Diffraction (NPD) and Synchrotron X-ray diffraction (SR XRD) were utilised. High pressure in situ NPD studies were performed at D2 pressures reaching 1000 bar at the D1B diffractometer accommodated at Institute Laue Langevin, Grenoble. The data of the time resolved in situ SR XRD were collected at the Swiss Norwegian Beam Lines, ESRF, Grenoble in the pressure range up to 50 bar H2 at temperatures 20-400°C.The systems studied by NPD at high pressures included deuterated Al-modified Laves-type C15 ZrFe2-xAlx intermetallics with x = 0.02; 0.04 and 0.20 and the CeNi5-D2 system. D content, hysteresis of H uptake and release, unit cell expansion and stability of the hydrides systematically change with Al content.Deuteration exhibited a very fast kinetics; it resulted in increase of the unit cells volumes reaching 23.5 % for ZrFe1.98Al0.02D2.9(1) and associated with exclusive occupancy of the Zr2(Fe,Al)2 tetrahedra.For CeNi5 deuteration yielded a hexahydride CeNi5D6.2 (20°C, 776 bar D2) and was accompanied by a nearly isotropic volume expansion reaching 30.1% (∆a/a=10.0%; ∆c/c=7.5%). Deuterium atoms fill three different interstitial sites including Ce2Ni2, Ce2Ni3 and Ni4. Significant hysteresis was observed on the first absorption-desorption cycle. This hysteresis decreased on the absorption-desorption cycling.A different approach to the development of H storage systems is based on the hydrides of light elements, first of all the Mg-based ones. These systems were studied by SR XRD. Reactive ball milling in hydrogen (HRBM) allowed synthesis of the nanostructured Mg-based hydrides.The experimental parameters (PH2, T, energy of milling, ball / sample ratio and balls size), significantly influence rate of hydrogenation. The studies confirmed (a) a completeness of hydrogenation of Mg into MgH2; (b) indicated a partial transformation of the originally formed -MgH2 into a metastable -MgH2 (a ratio / was 3/1); (c) yielded the crystallite size for the main hydrogenation product, -MgH2, as close to 10 nm. Influence of the additives to Mg on the structure and hydrogen absorption/desorption properties and cycle behaviour of the composites was established and will be discussed in the paper.

scholarly journals Time-resolved spectroscopic diagnostic of laser-induced plasma on germanium targets

2011 ◽  
Vol 109 (10) ◽  
pp. 103304 ◽  
Author(s):  
J. J. Camacho ◽  
L. Diaz ◽  
J. M. L. Poyato
Keyword(s):  
Time Resolved ◽  
Laser Induced Plasma

Metal deformation and phase transitions at extremely high strain rates

MRS Bulletin ◽  
2010 ◽  
Vol 35 (12) ◽  
pp. 999-1006 ◽  
Author(s):  
R. E. Rudd ◽  
T. C. Germann ◽  
B. A. Remington ◽  
J. S. Wark
Keyword(s):  
Phase Transitions ◽  
High Pressures ◽  
Materials Science ◽  
Strain Rates ◽  
Ambient Conditions ◽  
Time Resolved ◽  
Study Materials ◽  
Recent Developments ◽  
Metal Deformation ◽  
Kinetic Effects

The powerful lasers being constructed for inertially confined fusion generate enormous pressures extremely rapidly. These extraordinary machines both motivate the need and provide the means to study materials under extreme pressures and loading rates. In this frontier of materials science, an experiment may last for just 10s of nanoseconds. Processes familiar at ambient conditions, such as phase transformations and plastic flow, operate far from equilibrium and show significant kinetic effects. Here we describe recent developments in the science of metal deformation and phase transitions at extreme pressures and strain rates. Ramp loading techniques enable the study of solids at high pressures (100s of GPa) at moderate temperatures. Advanced diagnostics, such as in situ x-ray scattering, allow time-resolved material characterization in the short-lived high-pressure state, including crystal structure (phase), elastic compression, the size of microstructural features, and defect densities. Computer simulation, especially molecular dynamics, provides insight into the mechanisms of deformation and phase change.

Early stage expansion and time-resolved spectral emission of laser-induced plasma from polymer

2009 ◽  
Vol 255 (24) ◽  
pp. 9566-9571 ◽  
Author(s):  
Myriam Boueri ◽  
Matthieu Baudelet ◽  
Jin Yu ◽  
Xianglei Mao ◽  
Samuel S. Mao ◽  
...  
Keyword(s):  
Early Stage ◽  
Spectral Emission ◽  
Time Resolved ◽  
Laser Induced Plasma
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