Pulsed laser photoacoustic detection of SO_2 near 2257 nm

2001 ◽  
Vol 40 (12) ◽  
pp. 2010 ◽  
Author(s):  
Mohammed A. Gondal ◽  
Joseph Mastromarino
Keyword(s):  
Pulsed Laser ◽  
Photoacoustic Detection

scholarly journals Ultrahigh Resolution Pulsed Laser-Induced Photoacoustic Detection of Multi-Scale Damage in CFRP Composites

2020 ◽  
Vol 10 (6) ◽  
pp. 2106 ◽  
Author(s):  
Siqi Wang ◽  
Jesse Echeverry ◽  
Luis Trevisi ◽  
Kiana Prather ◽  
Liangzhong Xiang ◽  
...  
Keyword(s):  
Pulsed Laser ◽  
Projection Algorithm ◽  
Two Dimensional ◽  
High Frequency Ultrasound ◽  
Photoacoustic Detection ◽  
Ultrahigh Resolution ◽  
Multi Scale ◽  
Cfrp Composites ◽  
Macro Scale ◽  
Non Destructive

This paper presents a photoacoustic non-destructive evaluation (pNDE) system with an ultrahigh resolution for the detection of multi-scale damage in carbon fiber-reinforced plastic (CFRP) composites. The pNDE system consists of three main components: a picosecond pulsed laser-based ultrasonic actuator, an ultrasound receiver, and a data acquisition/computing subsystem. During the operation, high-frequency ultrasound is generated by pulsed laser and recorded by an ultrasound receiver. By implementing a two-dimensional back projection algorithm, pNDE images can be reconstructed from the recorded ultrasound signals to represent the embedded damage. Both potential macroscopic and microscopic damages, such as surface notches and delamination in CFRP, can be identified by examining the reconstructed pNDE images. Three ultrasonic presentation modes including A-scan, B-scan, and C-scan are employed to analyze the recorded signals for the representation of the detected micro-scale damage in two-dimensional and three-dimensional images with a high spatial resolution of up to 60 µm. Macro-scale delamination and transverse ply cracks are clearly visualized, identifying the edges of the damaged area. The results of the study demonstrate that the developed pNDE system provides a non-destructive and robust approach for multi-scale damage detection in composite materials.

Photoacoustic Detection of Formaldehyde as a Minority Component in Gas Mixtures

1988 ◽  
Vol 42 (8) ◽  
pp. 1520-1524 ◽  
Author(s):  
M. Boutonnat ◽  
D. A. Gilmore ◽  
K. A. Keilbach ◽  
N. Oliphant ◽  
G. H. Atkinson
Keyword(s):  
Photoacoustic Spectroscopy ◽  
Pulsed Laser ◽  
Gas Permeation ◽  
Selective Detection ◽  
Experimental Protocol ◽  
Photoacoustic Detection ◽  
Gaseous Mixtures ◽  
Spectral Signatures ◽  
Order Of Magnitude ◽  
Co Concentrations

Concentrations of H2CO in the part-per-billion by volume (ppbv) range are determined in gaseous mixtures containing large excesses of NO2 CH3CHO, and N2 by the use of photoacoustic spectroscopy (PAS). Mixtures containing H2CO as a minority component are prepared by gas permeation methods and examined by pulsed laser PAS in the ultraviolet and visible spectral regions. The relative concentrations of the major components of each mixture are an order of magnitude or more larger than the H2CO component under study. PA spectra with 0.5-cm−1 resolution in the 302.5–303.8 nm region are presented in Fig. 3 and are used to identify spectral signatures needed for selective detection. The dependence of PA signals on concentration is determined separately for each of the three polyatomic components in samples with N2. An experimental protocol for quantitatively measuring H2CO concentrations near 50 ppbv in NO2, CH3CHO, and N2 mixtures is described.

Observations on the growth of YBa2Cu3O7-δ thin films on MgO by pulsed-laser ablation

1991 ◽  
Vol 49 ◽  
pp. 1068-1069
Author(s):  
M. Grant Norton ◽  
C. Barry Carter
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Laser Ablation ◽  
Substrate Surface ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Laser Ablation Process ◽  
Deposition Parameters

Pulsed-laser ablation has been widely used to produce high-quality thin films of YBa2Cu3O7-δ on a range of substrate materials. The nonequilibrium nature of the process allows congruent deposition of oxides with complex stoichiometrics. In the high power density regime produced by the UV excimer lasers the ablated species includes a mixture of neutral atoms, molecules and ions. All these species play an important role in thin-film deposition. However, changes in the deposition parameters have been shown to affect the microstructure of thin YBa2Cu3O7-δ films. The formation of metastable configurations is possible because at the low substrate temperatures used, only shortrange rearrangement on the substrate surface can occur. The parameters associated directly with the laser ablation process, those determining the nature of the process, e g. thermal or nonthermal volatilization, have been classified as ‘primary parameters'. Other parameters may also affect the microstructure of the thin film. In this paper, the effects of these ‘secondary parameters' on the microstructure of YBa2Cu3O7-δ films will be discussed. Examples of 'secondary parameters' include the substrate temperature and the oxygen partial pressure during deposition.

Microanalysis of silicate glass films grown on α-Al2O3 by pulsed-laser deposition

1993 ◽  
Vol 51 ◽  
pp. 438-439
Author(s):  
Michael P. Mallamaci ◽  
James Bentley ◽  
C. Barry Carter
Keyword(s):  
Liquid Phase ◽  
Single Crystal ◽  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Ceramic Materials ◽  
Laser Deposition ◽  
Triple Junctions ◽  
Ion Milling ◽  
Multicomponent Oxides ◽  
Glass Films

Glass-oxide interfaces play important roles in developing the properties of liquid-phase sintered ceramics and glass-ceramic materials. Deposition of glasses in thin-film form on oxide substrates is a potential way to determine the properties of such interfaces directly. Pulsed-laser deposition (PLD) has been successful in growing stoichiometric thin films of multicomponent oxides. Since traditional glasses are multicomponent oxides, there is the potential for PLD to provide a unique method for growing amorphous coatings on ceramics with precise control of the glass composition. Deposition of an anorthite-based (CaAl2Si2O8) glass on single-crystal α-Al2O3 was chosen as a model system to explore the feasibility of PLD for growing glass layers, since anorthite-based glass films are commonly found in the grain boundaries and triple junctions of liquid-phase sintered α-Al2O3 ceramics.Single-crystal (0001) α-Al2O3 substrates in pre-thinned form were used for film depositions. Prethinned substrates were prepared by polishing the side intended for deposition, then dimpling and polishing the opposite side, and finally ion-milling to perforation.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

Long-Pulsed Laser Speeds Ecchymosis Healing

2009 ◽  
Vol 40 (6) ◽  
pp. 32
Author(s):  
MIRIAM E. TUCKER
Keyword(s):  
Pulsed Laser
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