scholarly journals Analysis of Picosecond Pulsed Laser Melted Graphite

1986 ◽  
Vol 74 ◽  
Author(s):  
J. Steinbeck ◽  
G. Braunstein ◽  
J. Speck ◽  
M. S. Dresselhaus ◽  
C. Y. Huang ◽  
...  
Keyword(s):  
Pulsed Laser ◽  
Laser Melting ◽  
Pulse Laser Radiation ◽  
Liquid Carbon ◽  
Additional Information ◽  
Nanosecond Pulsed Laser ◽  
Graphite Crystallite ◽  
Raman Microprobe ◽  
Melting Experiments

AbstractA Raman microprobe and TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582cm−1 and the disorder-induced mode at 1360cm−1 , the average graphite crystallite size in the resolidified region is determined as a function of incident pulse energy density. By comparing with Rutherford backscattering spectra and Raman spectra from nanosecond pulsed laser melting experiments, additional information about the disorder depth in picosecond pulsed laser melted graphite is obtained. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence. The similarities in the resolidified regions under both irradiation schemes discourages a determination of the properties of liquid carbon after the liquid has resolidified.

An Equation for Melting and Freezing Transition Rates

1986 ◽  
Vol 74 ◽  
Author(s):  
Philip H. Bucksbaum ◽  
Michael O. Thompson
Keyword(s):  
Large Deviations ◽  
Intermediate State ◽  
Reaction Rate ◽  
Pulsed Laser ◽  
Sharp Interface ◽  
Rate Theory ◽  
Transition Rates ◽  
Laser Melting ◽  
Kinetic Rate ◽  
Melting Experiments

AbstractStatistical thermodynamics is used to derive the reaction rate for melting and freezing by considering an atomically sharp interface with or without an activated intermediate state. The resulting predictions differ substantially from those of the classical kinetic rate theory at large deviations from equilibrium. The model may be appropriate for the analysis of pulsed laser melting experiments where large deviations are expected.

Time-Resolved Measurements of Solidification and Undercooling in Metals and Alloys

1989 ◽  
Vol 157 ◽  
Author(s):  
Harry A. Atwater ◽  
Jeffrey A. West ◽  
Patrick M. Smith ◽  
M.J. Aziz ◽  
J.Y. Tsao ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Heat Flow ◽  
Rapid Solidification ◽  
Pulsed Laser ◽  
Metal Films ◽  
Laser Melting ◽  
Time Resolved ◽  
Resistivity Measurements ◽  
Planar Crystal

ABSTRACTWe have performed nanosecond-resolution measurements of the lateral electrical resistivity of thin metal films on insulating substrates. Comparison of transient resistivity measurements with optical reflectivity measurements and heat-flow calculations permits the determination of the position and velocity of a planar crystal/melt interface, and an estimate of undercooling during pulsed laser melting of metals. We report detailed results for rapid solidification of Ni, including the observation of hypercooling of .liquid Ni.

scholarly journals High level activen+doping of strained germanium through co-implantation and nanosecond pulsed laser melting

2018 ◽  
Vol 123 (16) ◽  
pp. 165101 ◽  
Author(s):  
David Pastor ◽  
Hemi H. Gandhi ◽  
Corentin P. Monmeyran ◽  
Austin J. Akey ◽  
Ruggero Milazzo ◽  
...  
Keyword(s):  
Pulsed Laser ◽  
Laser Melting ◽  
Nanosecond Pulsed Laser ◽  
High Level

Pulsed Laser Melting of Graphite

1985 ◽  
Vol 51 ◽  
Author(s):  
G. Braunstein ◽  
J. Steinbeck ◽  
M. S. Dresselhaus ◽  
G. Dresselhaus ◽  
B. S. Elman ◽  
...  
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Crystalline Structure ◽  
Pulse Energy ◽  
Laser Pulse Energy ◽  
Pulsed Laser ◽  
Laser Melting ◽  
Liquid Carbon ◽  
Pulse Energy Density ◽  
Ion Implanted

ABSTRACTExperimental evidence for laser melting of graphite, by irradiation with 30ns pulses from a ruby laser, is presented. RBS-channeling analysis, Raman scattering and TEM measurements reveal that the surface of graphite melts at a threshold energy density of about 0.6 J/cm2. For laser pulse energy densities above 0.6 J/cm2, the melt front penetration depth increases nearly linearly with increasing energy density. An intense emission of carbon particles during and after irradiation is observed. The thickness of the carbon layer removed in this process also increases nearly linearly with increasing pulse fluence. A dramatic redistribution of ion implanted impurities is also observed. Furthermore, the crystalline structure of the resolidified material is shown to depend on the energy density of the laser pulse. In order to explain these phenomena, a model for laser melting of graphite at high temperatures to form liquid carbon has been developed in which a free electron gas approximation is used to describe the properties of liquid carbon. The model is solved numerically to give the time and depth dependences of the temperature as a function of the laser pulse energy density. Very good agreement is found between the observed melt depth dependence on laser pulse energy density, as determined by RBS-channeling, and the model calculations. The redistribution of ion implanted impurities and the modification of the crystalline structure, caused by the pulsed laser irradiation, are also consistent with the model and permit the determination, for the first time, of interfacial segregation coefficients for impurities in liquid carbon. The model also predicts that liquid carbon at low pressure (p < 1 kbar) has metallic properties.

Inside process of glass with nanosecond pulsed laser

2008 ◽  
Author(s):  
Takeji Arai ◽  
Noritaka Asano ◽  
Akihiko Minami ◽  
Hideaki Kusano
Keyword(s):  
Pulsed Laser ◽  
Nanosecond Pulsed Laser

Basic set of experiments for determination of mechanical properties of sand

2014 ◽  
Vol 62 (1) ◽  
pp. 129-137
Author(s):  
A. Sawicki ◽  
J. Mierczyński
Keyword(s):  
Mechanical Properties ◽  
Soil Mechanics ◽  
Physical And Mechanical Properties ◽  
Local Strain ◽  
Initial State ◽  
Laboratory Equipment ◽  
Additional Information ◽  
Basic Set ◽  
Initial Anisotropy

Abstract A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.

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