Dynamics of Laser Ablation and Vaporization of PbZr0.54Ti0.66O3: Laser Fluence and Ambient Gas Effects

1991 ◽  
Vol 243 ◽  
Author(s):  
R.E. Leuchtner ◽  
J.S. Horwitz ◽  
D.B. Chrisey
Keyword(s):  
Laser Fluence ◽  
Direct Evidence ◽  
Gas Pressure ◽  
Laser Vaporization ◽  
Reaction Cell ◽  
First Order ◽  
Scattering Rate ◽  
Ambient Gas ◽  
Reactive Gases ◽  
Background Gas

AbstractA systematic study of the gas phase products observed from the pulsed laser vaporization of a PbZro.54Ti0.46O3 target was performed as a function of laser fluence and ambient gas pressure. At low fluences, ≤0.3 J/cm2, only Pb and PbO were observed, while at higher fluences, between 0.3 - 1.3 J/cm2, neutral atomic species Pb, Zr, and Ti were detected. Small oxide molecules and atomicions were also observed. These regimes are associated with two ejection mechanisms: thermal evaporation and ablation, respectively. No direct evidence of chemical reactions was found over the gas pressure range explored (0-5 mTorr). Within the 25 cm reaction cell distance however, the addition of both inert and reactive gases greatly changed the velocity distributions of the ejected species. The decrease in velocity (energy) as a function of gas pressure was due to physical scattering and could be modeled as a pseudo-first order bimolecular collision process. The scattering rate increased linearly with the physical cross-section of the background gas and was independent of the kinetic energy of the ablated species.

Deposition of particulate-free thin films by two synchronised laser sources: effects of ambient gas pressure and laser fluence

2004 ◽  
Vol 446 (2) ◽  
pp. 178-183 ◽  
Author(s):  
E. György ◽  
I.N. Mihailescu ◽  
M. Kompitsas ◽  
A. Giannoudakos
Keyword(s):  
Thin Films ◽  
Laser Fluence ◽  
Gas Pressure ◽  
Laser Sources ◽  
Ambient Gas

Effect of laser fluence and ambient gas pressure on surface morphology and chemical composition of hydroxyapatite thin films deposited using pulsed laser deposition

2018 ◽  
Vol 427 ◽  
pp. 458-463 ◽  
Author(s):  
Hiroaki Nishikawa ◽  
Tsukasa Hasegawa ◽  
Akiko Miyake ◽  
Yuichiro Tashiro ◽  
Satoshi Komasa ◽  
...  
Keyword(s):  
Thin Films ◽  
Chemical Composition ◽  
Surface Morphology ◽  
Pulsed Laser Deposition ◽  
Laser Fluence ◽  
Pulsed Laser ◽  
Gas Pressure ◽  
Laser Deposition ◽  
Ambient Gas

Internal Crack Symmetry Phenomena during Gas-Induced Rupture of Elastomers

1992 ◽  
Vol 65 (2) ◽  
pp. 350-373 ◽  
Author(s):  
B. J. Briscoe ◽  
D. Liatsis
Keyword(s):  
Analytical Investigation ◽  
Gas Pressure ◽  
Internal Crack ◽  
Desorption Process ◽  
Hydrostatic Tension ◽  
First Order ◽  
Gas Desorption ◽  
Gas Transport Properties ◽  
Sophisticated Model ◽  
Ambient Gas

Abstract This paper describes an experimental and analytical investigation of the consequences of removing a high ambient gas pressure environment from a number of elastomers after they had been allowed to equilibrate under high gas pressure. The elastomers are irreversibly damaged, and the phenomenology of this damage is described. One particular type of damage, the formation of internal symmetrical cracks whose geometry is the same as that of the sample, is examined in detail. The experimental data are interpreted using two models. The first provides a first order, but somewhat artificial, description of the phenomenon observed. A more sophisticated model invokes two separate processes as the origin of the rupture phenomenon. It is argued that ruptures arise as a result of the combined effects of an overall hydrostatic tension and a localized tensile field which is created by the effusion of gas from the polymer. The severity of the latter is shown to be a function of the gas transport properties of the elastomer under the conditions which prevail during the gas desorption process.

scholarly journals Residual Stress and Raman Spectra of Laser Deposited Highly Tetrahedral-Coordinated Amorphous Carbon Films

1994 ◽  
Vol 349 ◽  
Author(s):  
T. A. Friedmann ◽  
M. P. Siegal ◽  
D. R. Tallant ◽  
R. L. Simpson ◽  
F. Dominguez
Keyword(s):  
Compressive Stress ◽  
Raman Spectra ◽  
Amorphous Carbon ◽  
Growth Parameters ◽  
Pyrolytic Graphite ◽  
Carbon Films ◽  
Gas Pressure ◽  
Residual Compressive Stress ◽  
Reactive Gases ◽  
Background Gas

ABSTRACTWe are studying carbon thin films by using a pulsed excimer laser to ablate pyrolytic graphite targets to form highly tetrahedral coordinated amorphous carbon (at-C) films. These films have been grown on room temperature p-type Si (100) substrates without the intentional incorporation of hydrogen. In order to understand and optimize the growth of at-C films, parametric studies of the growth parameters have been performed. We have also introduced various background gases (H2, N2 and Ar) and varied the background gas pressure during deposition. The residual compressive stress levels in the films have been measured and correlated to changes in the Raman spectra of the at-C band near 1565 cm−1. The residual compressive stress falls with gas pressure, indicating a decreasing atomic sp3-bonded carbon fraction. We find that reactive gases such as hydrogen and nitrogen significantly alter the Raman spectra at higher pressures. These effects are due to a combination of chemical incorporation of nitrogen and hydrogen into the film as well as collisional cooling of the ablation plume. In contrast, films grown in non-reactive Ar background gases show much less dramatic changes in the Raman spectra at similar pressures.

Effect of Non-equilibrium Pulsed Ejection of Si Species into Background Gas on the Formation of Si Nanocrystallite and Nanocrystal-film

2011 ◽  
Vol 1305 ◽  
Author(s):  
Ikurou Umezu ◽  
Shunto Okubo ◽  
Akira Sugimura
Keyword(s):  
Laser Ablation ◽  
Film Growth ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Hydrogen Gas ◽  
Gas Pressure ◽  
Spatial Confinement ◽  
The Individual ◽  
Background Gas ◽  
Non Equilibrium

ABSTRACTThe Si nanocrystal-films are prepared by pulsed laser ablation of Si target in a mixture of helium and hydrogen gas. The total gas pressure and hydrogen partial gas pressure were varied to control structure of nanocrystal-film. The surface of Si nanocrystallite was hydrogenated and degree of hydrogenation increased with increasing hydrogen partial gas pressure. The aggregate structure of nanocrystal-film depended on both the total gas pressure and the hydrogen partial gas pressure. The former and the latter alter spatial confinement of Si species during deposition and the surface hydrogenation of individual nanocrystal, respectively. Spatial confinement increases probability of collision between nanocrystals in the plume. While, surface hydrogenation prevents coalescence of nanocrystals. The individual or aggregated nanocrystals formed in the plume reach the substrate and the nanocrystal-film is deposited on the substrate. The non-equilibrium growth processes during pulsed laser ablation are essential for the formation of the surface structure and the subsequent nanocrystal-film growth. Our results indicate that the structure of nanocrystal-film depends on the probabilities of collision and coalescence between nanocrystals in the plume. These probabilities can be varied by controlling the total gas pressure and the hydrogen partial gas pressure.

Experimental and theoretical study of the characteristics of LSPR peaks for metal NPs produced by controlling Ar ambient gas pressure to enhance the efficiency of solar cells

2021 ◽  
pp. 1-6
Author(s):  
Serap Yiğit Gezgin ◽  
Abdullah Kepceoğlu ◽  
Hamdi Şükür Kiliç
Keyword(s):  
Metal Nanoparticles ◽  
Ag Nanoparticles ◽  
Solar Spectrum ◽  
Wavelength Region ◽  
Gas Pressure ◽  
Metal Nanoparticle ◽  
Ag Nanoparticle ◽  
Extinction Cross Section ◽  
Ambient Gas ◽  
Ar Gas

In this study, silver (Ag) nanoparticle thin films were deposited on microscope slide glass and Si wafer substrates using the pulsed-laser deposition (PLD) technique in Ar ambient gas pressures of 1 × 10−3 and 7.5 × 10−1 mbar. AFM analysis has shown that the number of Ag nanoparticles reaching the substrate decreased with increasing Ar gas pressure. As a result of Ar ambient gas being allowed into the vacuum chamber, it was observed that the size and height of Ag nanoparticles decreased and the interparticle distances decreased. According to the absorption spectra taken by a UV–vis spectrometer, the wavelength where the localised surface plasmon resonance (LSPR) peak appeared was shifted towards the longer wavelength region in the solar spectrum as Ar background gas pressure was decreased. This experiment shows that LSPR wavelength can be tuned by adjusting the size of metal nanoparticles, which can be controlled by changing Ar gas pressure. The obtained extinction cross section spectra for Ag nanoparticle thin film was theoretically analysed and determined by using the metal nanoparticle–boundary element method (MNPBEM) toolbox simulation program. In this study, experimental spectrum and simulation data for metal nanoparticles were acquired, compared, and determined to be in agreement.

Numerical Investigation on the Effect of Advanced Breakup Model on Spray Simulation of a Multi-Hole Injector

2018 ◽  
Author(s):  
Srinibas Tripathy ◽  
Sridhar Sahoo ◽  
Dhananjay Kumar Srivastava
Keyword(s):  
Mass Fraction ◽  
Gas Pressure ◽  
Gas Jet ◽  
Computational Time ◽  
Fuel Vapor ◽  
Computational Domain ◽  
Penetration Length ◽  
Spray Penetration ◽  
Ambient Gas ◽  
Vapor Mass

Computational fluid dynamics (CFD) plays a tremendous role in evaluating and visualizing the spray breakup, atomization and vaporization process. In this study, ANSYS Forte CFD tool was used to simulate the spray penetration length and spray morphology in a constant volume chamber at different grid size of a multi-hole injector. An unsteady gas jet model was coupled with Kelvin-Helmholtz (KH) and Rayleigh-Taylor (RT) model for multi-hole spray simulation. The effect of CFD cell size and ambient gas pressure on spray penetration length and spray morphology of fuel vapor mass fraction were investigated for both KH-RT and KH-RT with the unsteady gas jet model. It is found that KH-RT with the unsteady gas jet model shows mesh independent spray penetration length and spray morphology of fuel vapor mass fraction as compared to KH-RT model. This can be explained by the Lagrangian-Eulerian coupling of axial droplet-gas relative velocity is modeled on the principle of unsteady gas jet theory instead of discretizing very fine grid to the computational domain. This reduces the requirement of fine mesh near the nozzle and allows larger time step during spray injection. It is also observed that at higher ambient gas pressure, an aerodynamic force between the droplet and gas intensifies which reduces the overall spray penetration length and fuel vapor mass. The distorted spray morphology of fuel vapor mass fraction was accurately predicted at high ambient gas pressure using the KH-RT with an unsteady gas jet model which results in mesh independent drag predictions. The use of advanced spray model results in the mesh size dependency reduction and accurate drag prediction with less computational time and faster accurate solutions over all conventional spray breakup models.

The concentration and pressure dependent diffusion of carbon dioxide in nitrile rubbers

1992 ◽  
Vol 339 (1655) ◽  
pp. 497-519 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Diffusion Coefficient ◽  
High Pressures ◽  
Ambient Pressure ◽  
Weight Fraction ◽  
Gas Pressure ◽  
Time Dependent ◽  
Initial Increase ◽  
Parametric Function ◽  
Ambient Gas

The paper reports the results of an experimental and associated analytical study of the time dependent adsorption of carbon dioxide gas into two nitrile elastomers. The mass gas sorption has been measured using a device based on a vibrating reed to a weight fraction accuracy of ca . 0.05 % at 47 °C in the ambient gas pressure range 0.1-34 MPa. The experimental method is described and data are provided. These data are used to compute the most effective description of the diffusion process by invoking a number of different diffusion coefficient, D(θ), characteristics, where θ denotes lapsed time, ambient pressure and local ambient gas concentration within the elastomers. The numerical procedures adopted to perform the fitting of the experimental data with various D(θ) characteristics are described and the quality of the fit is assessed. The D(θ) characteristics chosen have no particular physical basis but follow established empirical precedents. The characteristics of the parameters associated with the various D(θ) functions generally indicate that as the gas is embibed with progressively increasing ambient pressures the diffusion coefficient increases. At high pressures the diffusion is arrested and the coefficient decreases. We have associated the initial increase with gas induced plasticization and the eventual decreases with the effect of the hydrostatic component of the ambient gas pressure. The parameter fitting also indicates that the diffusion is arrested with lapsed time which is tentatively associated with time dependent volumetric relaxations. These interpretations apart, the data and analyses clearly indicate that the transport is not simply fickian and a relatively complex parametric function to describe the sensitivity of the diffusion coefficient to time, concentration and pressure is necessary for these systems.

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