UV-Induced Fractal Surfaces

Fractals ◽  
1997 ◽  
Vol 05 (02) ◽  
pp. 275-280 ◽  
Author(s):  
Cs. Beleznai ◽  
R. Vajtai ◽  
L. Nánai
Keyword(s):  
Surface Morphology ◽  
Structural Parameters ◽  
Strong Dependence ◽  
Pulsed Laser ◽  
Fractal Dimensions ◽  
Laser Source ◽  
Physical Parameters ◽  
Fractal Surfaces

Poly (tetrafluorethylene) and polyimide samples were irradiated by a pulsed laser source at 308 nm and the resulting surface morphology was investigated. The photoablated surfaces show a strong dependence on the optical and structural parameters of the polymers. The roughness of the fractal surfaces has been characterized by means of calculating their fractal dimensions and the results are interpreted as a function of the polymer physical parameters.

Effect of Annealing Temperature on Two-Step Method of GaN Films

2012 ◽  
Vol 629 ◽  
pp. 9-13
Author(s):  
Mei Liu ◽  
Xue You Xu ◽  
Bao Yuan Man ◽  
De Min Kong
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Annealing Temperature ◽  
Laser Energy ◽  
Pulsed Laser ◽  
Nitrogen Atmosphere ◽  
Laser Source ◽  
Step Method ◽  
Experimental Conditions ◽  
Force Microscopy

GaN thin films have been deposited on Si (111) substrates by pulsed laser deposition (PLD) of a GaN target in nitrogen atmosphere. An Nd: YAG pulsed laser with a wavelength of 1064 nm was used as a laser source. The results indicate that the GaN thin films deposited only by PLD are amorphous. By annealing in an NH3 atmosphere, the quality of the GaN thin films is improved, and the crystallzinity GaN thin films were obtained. The influence of annealing temperature on the crystallinity, structure, surface morphology and optical properties of GaN films have been examined by X-ray diffraction (XRD), atomic force microscopy (AFM) and infrared spectrum. In our experimental conditions, the GaN thin films deposited by PLD with a laser energy of 250 mJ, growth temperature of 800 °C and annealed at 1000 °C have the best surface morphology and crystalline quality.

scholarly journals Smoothing additive manufactured parts using ns-pulsed laser radiation

2021 ◽  
Author(s):  
Florian Kuisat ◽  
Fernando Lasagni ◽  
Andrés Fabián Lasagni
Keyword(s):  
Surface Roughness ◽  
Mechanical Performance ◽  
State Of The Art ◽  
Pulsed Laser ◽  
Industrial Applications ◽  
Laser Source ◽  
Pulsed Laser Radiation ◽  
Current State ◽  
The Impact

AbstractIt is well known that the surface topography of a part can affect its mechanical performance, which is typical in additive manufacturing. In this context, we report about the surface modification of additive manufactured components made of Titanium 64 (Ti64) and Scalmalloy®, using a pulsed laser, with the aim of reducing their surface roughness. In our experiments, a nanosecond-pulsed infrared laser source with variable pulse durations between 8 and 200 ns was applied. The impact of varying a large number of parameters on the surface quality of the smoothed areas was investigated. The results demonstrated a reduction of surface roughness Sa by more than 80% for Titanium 64 and by 65% for Scalmalloy® samples. This allows to extend the applicability of additive manufactured components beyond the current state of the art and break new ground for the application in various industrial applications such as in aerospace.

Influence of Momentary Annealing on the Nanoscale Surface Morphology of Room Temperature Pulsed Laser Deposited NiO(111) Epitaxial Thin Films on Atomically Stepped Sapphire (0001) Substrates

2013 ◽  
Vol 1507 ◽  
Author(s):  
Ryosuke Yamauchi ◽  
Geng Tan ◽  
Daishi Shiojiri ◽  
Nobuo Tsuchimine ◽  
Koji Koyama ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Room Temperature ◽  
Pulsed Laser ◽  
Film Surface ◽  
Transient State ◽  
Epitaxial Thin Films ◽  
Flat Surfaces ◽  
Surface Nanostructure ◽  
Atomically Flat

ABSTRACTWe examined the influence of momentary annealing on the nanoscale surface morphology of NiO(111) epitaxial thin films deposited on atomically stepped sapphire (0001) substrates at room temperature in O2 at 1.3 × 10−3 and 1.3 × 10−6 Pa using a pulsed laser deposition (PLD) technique. The NiO films have atomically flat surfaces (RMS roughness: approximately 0.1–0.2 nm) reflecting the step-and-terrace structures of the substrates, regardless of the O2 deposition pressure. After rapid thermal annealing (RTA) of the NiO(111) epitaxial film deposited at 1.3 × 10−3 Pa O2, a periodic straight nanogroove array related to the atomic steps of the substrate was formed on the film surface for 60 s. In contrast, the fabrication of a transient state in the nanogroove array formation was achieved with RTA of less than 1 s. However, when the O2 atmosphere during PLD was 1.3 × 10−6 Pa, random crystal growth was observed and resulted in a disordered rough surface nanostructure after RTA.

Hologram indexing in LiNbO_3 with a tunable pulsed laser source

1979 ◽  
Vol 18 (15) ◽  
pp. 2555 ◽  
Author(s):  
D. A. Woodbury ◽  
T. A. Rabson ◽  
F. K. Tittel
Keyword(s):  
Pulsed Laser ◽  
Laser Source

Pulsed Laser Deposition (PLD) Technique to Prepare Biocompatible Thin Films

2006 ◽  
Vol 49 ◽  
pp. 56-61 ◽  
Author(s):  
Joseph J. Beltrano ◽  
Lorenzo Torrisi ◽  
Anna Maria Visco ◽  
Nino Campo ◽  
E. Rapisarda
Keyword(s):  
Thin Films ◽  
Pulsed Laser ◽  
Target Material ◽  
Xrd Analysis ◽  
Spot Size ◽  
Laser Deposition ◽  
Laser Source ◽  
Medical Field ◽  
Hot Plasma ◽  
532 Nm

A Nd:YAG laser is employed to ablate different materials useful in the bio-medical field. The laser source operates in the IR (1064 nm), VIS (532 nm) and UV (355 nm) regions with a pulse duration of 3-9 ns, a pulse energy of 3-300 mJ, a spot size of 1 mm2 and a repetition rate of 1- 30 Hz. Target material of interest are Titanium, Carbon, Hydroxyapatite (HA) and Polyethylene (PE). Laser irradiation occurs in vacuum, where hot plasma is generated, and thin films are deposited on near substrates. Generally, substrates of silicon, titanium, titanium-alloys and polymers were employed. Biocompatible thin films are investigated with different surface techniques, such as IR spectroscopy, Raman spectroscopy, XRD analysis and SEM investigations. Depending of the kind of possible application, films require special properties concerning the grain size, porosity, uniformity, wetting, hardness, adhesion, crystallinity and composition. The obtained results will be presented and discussed with particular regard to HA..

Application of an Anode Model to Investigate Physical Parameters in an Internal Reforming Solid-Oxide Fuel Cell

2005 ◽  
Vol 2 (2) ◽  
pp. 136-140 ◽  
Author(s):  
Eric S. Greene ◽  
Maria G. Medeiros ◽  
Wilson K. S. Chiu
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Structural Parameters ◽  
Porous Electrode ◽  
Cell Voltage ◽  
Solid Oxide ◽  
Physical Parameters ◽  
Oxide Fuel ◽  
Internal Reforming ◽  
Porous Anode

A one-dimensional model of chemical and mass transport phenomena in the porous anode of a solid-oxide fuel cell, in which there is internal reforming of methane, is presented. Macroscopically averaged porous electrode theory is used to model the mass transfer that occurs in the anode. Linear kinetics at a constant temperature are used to model the reforming and shift reactions. Correlations based on the Damkohler number are created to relate anode structural parameters and thickness to a nondimensional electrochemical conversion rate and cell voltage. It is shown how these can be applied in order to assist the design of an anode.

scholarly journals Structure and Strength of Artificial Soils Containing Monomineral Clay Fractions

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4688
Author(s):  
Grzegorz Jozefaciuk ◽  
Kamil Skic ◽  
Agnieszka Adamczuk ◽  
Patrycja Boguta ◽  
Krzysztof Lamorski
Keyword(s):  
Fine Particles ◽  
Structural Parameters ◽  
Fractal Dimensions ◽  
Soil Strength ◽  
Uniaxial Compression Test ◽  
Mineral Particle ◽  
Type Curve ◽  
Surface Fractal ◽  
First Time

Structure and strength are responsible for soil physical properties. This paper determines in a uniaxial compression test the strength of artificial soils containing different proportions of various clay-size minerals (cementing agents) and silt-size feldspar/quartz (skeletal particles). A novel empirical model relating the maximum stress and the Young’s modulus to the mineral content basing on the Langmuir-type curve was proposed. By using mercury intrusion porosimetry (MIP), bulk density (BD), and scanning electron microscopy (SEM), structural parameters influencing the strength of the soils were estimated and related to mechanical parameters. Size and shape of particles are considered as primary factors responsible for soil strength. In our experiments, the soil strength depended primarily on the location of fine particles in respect to silt grains and then, on a mineral particle size. The surface fractal dimension of mineral particles played a role of a shape parameter governing soil strength. Soils containing minerals of higher surface fractal dimensions (rougher surfaces) were more mechanically resistant. The two latter findings appear to be recognized herein for the first time.

Surface morphology of AlN films synthesized by pulsed laser deposition

Vacuum ◽  
2009 ◽  
Vol 84 (1) ◽  
pp. 155-157 ◽  
Author(s):  
S. Bakalova ◽  
A. Szekeres ◽  
G. Huhn ◽  
K. Havancsak ◽  
S. Grigorescu ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Laser Deposition
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