Distribution of molten layer and anode erosion pattern caused by constricted vacuum arcs

This study addresses the effect of process parameters viz., loading ratio (mass of explosive/mass of flyer plate) and preset angle on dynamic bend angle, collision velocity and flyer plate velocity in dissimilar explosive cladding. In addition, the variation in interfacial microstructure and mechanical strength of aluminium 5052-stainless steel 304 explosive clads is reported. The interface exhibits a characteristic undulating interface with a continuous molten layer formation. The interfacial amplitude increases with the loading ratio and preset angle. Maximum hardness is observed at regions closer to the interface

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Pulsed Microwave Processing of High-TC Superconducting Films

MRS Proceedings ◽

10.1557/proc-269-187 ◽

1992 ◽

Vol 269 ◽

Author(s):

R. B. James ◽

R. A. Alvarez ◽

A. K. Stamper ◽

X. J. Bao ◽

T. E. Schlesinger ◽

...

Keyword(s):

Phase Transition ◽

Barium Copper Oxide ◽

Precursor Film ◽

Silicon Substrates ◽

Molten Layer ◽

Time Resolved ◽

Barium Copper ◽

In Situ Experiments ◽

Yttrium Barium

ABSTRACTWe have used 2.0-μsec microwave pulses at a frequency of 2.856 GHz to rapidly heat thin amorphous yttrium-barium-copper-oxide (YBCO) films deposited onto silicon substrates. The samples were irradiated inside a WR-284 waveguide by single-pass TE10 pulses in a traveling wave geometry. X-ray diffractometry studies show that an amorphous-to-crystalline phase transition occurs for incident pulse powers exceeding about 6 MW, in which case the amorphous YBCO layer is converted to Y2BaCuO5. Microscopy of the irradiated film reveals that the phase transition is brought about by melting of the YBCO precursor film and crystallization of the molten layer upon solidification. Time-resolved in situ experiments of the microwave reflectivity (R) and transmissivity (T) show that there is an abrupt change in R for microwave pulse powers exceeding the melt threshold, so that measurements of R and T can be used to monitor the onset of surface melting.

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Transient Conductance Measurements During Pulsed Laser Annealing

MRS Proceedings ◽

10.1557/proc-4-209 ◽

1981 ◽

Vol 4 ◽

Cited By ~ 2

Author(s):

M. O. Thompson ◽

G. J. Galvin ◽

J. W. Mayer ◽

R. B. Hammond ◽

N. Paulter ◽

...

Keyword(s):

Single Crystal ◽

Laser Annealing ◽

Pulsed Laser ◽

Interface Velocity ◽

Laser Pulses ◽

Molten Layer ◽

Pulsed Laser Annealing ◽

Complete Melting ◽

Solid Liquid Interface ◽

Solid Liquid

ABSTRACTMeasurements were made of the conductance of single crystal Au-doped Si and silicon-on-sapphire (SOS) during irradiation with 30 nsec ruby laser pulses. After the decay of the photoconductive response, the sample conductance is determined primarily by the thickness and conductivity of the molten layer. For the single crystal Au-doped Si, the solid-liquid interface velocity during recrystallization was determined from the current transient to be 2.5 m/sec for energy densities between 1.9 and 2.6 J/cm2, in close agreement with numerical simulations based on a thermal model of heat flow. SOS samples showed a strongly reduced photoconductive response, allowing the melt front to be observed also. For complete melting of a 0.4 μm Si layer, the regrowth velocity was 2.4 m/sec.

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Temperature Field Simulation of Anode Erosion in Electric Discharge Machining

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.455.345 ◽

2010 ◽

Vol 455 ◽

pp. 345-349

Author(s):

B.C. Xie ◽

Zhen Long Wang ◽

Yu Kui Wang ◽

Jing Zhi Cui

Keyword(s):

Temperature Field ◽

Electric Discharge ◽

Material Removal ◽

Machining Process ◽

Model Parameters ◽

Temperature Dependent ◽

Electric Discharge Machining ◽

Field Simulation ◽

Simulation And Experiment ◽

Anode Erosion

In this paper, a thermo-physical model of the electric discharge machining process using finite element method is presented. In this model, parameters such as convection, the latent heat and the thermal properties based on temperature dependent etc. are studied to predict the temperature distribution in the workpiece. The temperature field simulation and experiment were carried out by adopting parameters through optimum pulse curve, and amending the effects of recast layer, the simulation results amended shows a better agreement with experimental results, indicating a theoretical foundation for mechanism of material removal in EDM machining.

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Thermodynamic and Kinetic Studies of Pulsed-Laser Annealing from Transient Conductivity Measurements

MRS Proceedings ◽

10.1557/proc-35-53 ◽

1984 ◽

Vol 35 ◽

Cited By ~ 13

Author(s):

P.S. Peercy ◽

Michael O. Thompson

Keyword(s):

Melting Temperature ◽

Silicon Germanium ◽

Laser Annealing ◽

Pulsed Laser ◽

Kinetic Studies ◽

Alloy System ◽

Velocity Versus ◽

Solidification Velocity ◽

Molten Layer ◽

Amorphous Si

ABSTRACTSimultaneous measurements of the transient conductance and time-dependent surface reflectance of the melt and solidification dynamics produced by pulsed laser irradiation of Si are reviewed. These measurements demonstrate that the melting temperature of amorphous Si is reduced 200 ± 50 K from that of crystalline Si and that explosive crystallization in amorphous Si is mediated by a thin (≤ 20 nm) molten layer that propagates at ~ 15 m/sec. Studies with 3.5 nsec pulses permit an estimate of the dependence of the solidification velocity on undercooling. Measurements of the effect of As impurities on the solidification velocity demonstrate that high As concentrations decrease the melting temperature of Si (~ 150 K for 7 at.%), which can result in surface nucleation to produce buried melts. Finally, the silicon-germanium alloy system is shown to be an ideal model system for the study of superheating and undercooling. The Si50Ge50 alloy closely models amorphous Si, and measurements of layered Si-Ge alloy structures indicate superheating up to 120 K without nucleation of internal melts. The change in melt velocity with superheating yields a velocity versus superheating of 17 ± 3 k/m/sec.

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Explosive Anode Erosion in High Current Sparks

Applied Optics ◽

10.1364/ao.9.001695 ◽

1970 ◽

Vol 9 (7) ◽

pp. 1695 ◽

Cited By ~ 4

Author(s):

K. Schönbach ◽

H. Fischer

Keyword(s):

High Current ◽

Anode Erosion

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Excimer Laser Amorphous Silicon Film Crystallization: A Study of Time Resolved Reflectivity Measurements

MRS Proceedings ◽

10.1557/proc-297-539 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 3

Author(s):

C. Summonte ◽

M. Bianconi ◽

D. Govoni

Keyword(s):

Heat Flow ◽

Amorphous Silicon ◽

Silicon Film ◽

Optical Simulation ◽

Molten Layer ◽

Time Resolved ◽

Flow Calculation ◽

Explosive Crystallization ◽

Bulk Nucleation ◽

Calculation Results

Time Resolved Reflectivity during XeCl pulsed laser irradiation of amorphous silicon films deposited on glass was measured. Simulation of the process by a Heat Flow Calculation in which explosive crystallization was not forced to occur, predicts the coexistence of partial bulk nucleation and a traveling molten layer. Optical simulation of Time Resolved Reflectivity was used to critically examine the Heat Flow Calculation results, substantially confirming the existence of a mixture of thermodynamical phases.

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CFD Study on the Role of Gas Friction on the Molten Layer Shape and Melt Removal Mechanism in Laser Cutting Process of Steel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.856.220 ◽

2013 ◽

Vol 856 ◽

pp. 220-225 ◽

Cited By ~ 1

Author(s):

Karim Kheloufi ◽

El Hachemi Amara

Keyword(s):

Friction Force ◽

Laser Cutting ◽

Cutting Process ◽

Gradient Force ◽

Pressure Gradient Force ◽

Central Plane ◽

Removal Mechanism ◽

Molten Layer ◽

Wavy Structure

A numerical analysis of the role of the gas friction force on the shape of the melt surface in laser cutting process is carried out. The liquid film shape is analyzed in the central plane of cutting for both cases with the pressure gradient force only and for the case of gas friction force contribution. It is shown that, the gas friction force has a significant role in the formation of humps in the central kerf zone and the transition from the smooth melt ejection regime to a wavy structure characterized by humps formation.

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Physico-Chemical Changes in the KCl-MgCl2/La-FAU Composite Catalyst Induced by Oxidative Dehydrogenation of Ethane

Catalysts ◽

10.3390/catal11030392 ◽

2021 ◽

Vol 11 (3) ◽

pp. 392

Author(s):

Mehran Sajad ◽

Roman Bulánek ◽

Stanislav Šlang

Keyword(s):

Oxidative Dehydrogenation ◽

Catalyst Deactivation ◽

Eutectic Mixture ◽

Textural Properties ◽

Composite Catalyst ◽

Molten Layer ◽

Characterization Methods ◽

Binary Eutectic ◽

Spent Catalysts ◽

Alkali Chlorides

In this research, a binary eutectic composition of KCl and MgCl2 supported over lanthanum exchanged FAU (faujasite) zeolite has been investigated for the oxidative dehydrogenation (ODH) of ethane. The catalyst was prepared by the thermal treatment of La-FAU with a mechanical mixture of alkali chlorides under a flow of helium at 500 °C. The eutectic mixture of alkali chlorides formed at this temperature and a molten layer were spread over the support. Synthesized fresh and spent catalysts were characterized to obtain information about changes in crystallinity, textural properties, phase content, chemical composition, and morphology of the catalyst over the reaction time. The initial conversion of ethane was 80% with ethene as the main product (65% yield). The catalyst deactivation has been demonstrated over time on the stream (TOS). The characterization methods confirmed that the chlorine was being removed from the catalyst. The side products detected by mass spectroscopy, including chlorinated hydrocarbons, have been found as a key pathway of chlorine removal from the catalyst. The exchange of chlorine for oxygen in the catalyst led to a significant decrease in the activity and production of higher hydrocarbons and their oxygenates as side products of the ODH reaction.

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