The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Spyros Kamnis - One of the best experts on this subject based on the ideXlab platform.
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experimental study of high velocity oxy fuel sprayed wc 17co coatings applied on complex geometries part b influence of kinematic spray parameters on microstructure phase composition and decarburization of the coatings
Surface & Coatings Technology, 2017Co-Authors: Vasileios Katranidis, Bryan Allcock, Tomas Ramirez Reina, E Alpay, Spyros KamnisAbstract:The aim of this study is to evaluate comprehensively the effect of spray angle, spray distance and gun traverse speed on the microstructure and phase composition of HVOF sprayed WC-17 coatings. An experimental setup that enables the isolation of each one of the kinematic parameters and the systemic study of their interplay is employed. A mechanism of particle partition and WC-cluster rebounding at short distances and oblique spray angles is proposed. It is revealed that small angle inclinations benefit notably the WC distribution in the coatings sprayed at long stand-off distances. Gun traverse speed, affects the oxygen content in the coating via cumulative superficial oxide scales formed on the as-sprayed coating surface during deposition. Metallic W continuous rims are seen to engulf small splats, suggesting crystallization that occurred in-flight.
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experimental study of high velocity oxy fuel sprayed wc 17co coatings applied on complex geometries part a influence of kinematic spray parameters on thickness porosity residual stresses and microhardness
Surface & Coatings Technology, 2017Co-Authors: Vasileios Katranidis, Bryan Allcock, Spyros KamnisAbstract:Abstract When a complex geometry is rotated in front of the thermal spray gun, the following kinematic parameters vary in a coupled fashion dictated by the geometry: Stand-off distance, spray angle and gun traverse speed. These fluctuations affect the conditions of particle impact with major implications on the coating's properties. This work aims to probe into the interplay and isolated effect of these parameters on vital coating characteristics in applications requiring variable stand-off distance and spray angles. WC-17Co powders are sprayed via HVOF on steel substrates in a set of experiments that simulates the spray process of a non-circular cross section, while it allows for individual control of the kinematic parameters. Comprehensive investigation of their influence is made on deposition rate, residual stresses, porosity and microhardness of the final coating. It was determined that oblique spray angles and long stand-off distances compromise the coating properties but in some cases, the interplay of the kinematic parameters produced non-linear behaviours. Microhardness is related negatively with oblique spray angles at short distances while a positive correlation emerges as the stand-off distance is increased. Porosity and residual stresses are sensitive to the spray angle only in relatively short stand-off distances.
J J Laserna - One of the best experts on this subject based on the ideXlab platform.
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the development of fieldable laser induced breakdown spectrometer no limits on the horizon
Spectrochimica Acta Part B: Atomic Spectroscopy, 2010Co-Authors: F J Fortes, J J LasernaAbstract:In this review, new trends in the development of fieldable instrumentation based on laser-induced breakdown spectroscopy (LIBS) and its recent applications is presented. Depending on the LIBS configuration we will distinguish between portable, remote and stand-off instruments. Moreover, the development of portable systems gives greater flexibility and also increases the range of LIBS applications. In general, portable instruments are employed in close-contact applications like immovable artworks, contaminated soils and environmental diagnostic, while remote and stand-off instruments are normally used in analytical applications at distances where access to the sample is difficult or hazardous. Although remote and stand-off instruments are both used for chemical analysis at distances, the instrumental configurations are completely different. In remote analysis, an optical fiber is employed to deliver the laser energy a certain distance. This approach has been usually restricted to industrial applications, bulk analysis in water, geological measurements and chemical analysis on nuclear stations. In the case of stand-off applications, the laser beam and the returning plasma light are transmitted in an open-path configuration. In this article we also discuss the instrumental requirements in the design of remote and stand-off instruments.
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test of a stand off laser induced breakdown spectroscopy sensor for the detection of explosive residues on solid surfaces
Journal of Analytical Atomic Spectrometry, 2006Co-Authors: Cristina Lopezmoreno, J J Laserna, S Palanco, Frank C Delucia, Andrzej W Miziolek, Jeremy Rose, Roy A Walters, Andrew I WhitehouseAbstract:The detection and characterization of energetic materials at distances up to 45 m using stand-off laser induced breakdown spectroscopy (LIBS) has been demonstrated. A field-portable open-path LIB spectrometer working under a coaxial configuration was used. A preliminary study allowed choosing a single-pulse laser source over a double-pulse system as the most suitable source for the stand-off analysis of organic samples. The C2 Swan system, as well as the hydrogen, oxygen and nitrogen emission intensity ratios were the necessary parameters to identify the analyte as an organic explosive, organic non-explosive and non-organic samples. O/N intensity ratios of 2.9 and 2.16 with relative standard deviations of 4.03% and 8.36% were obtained for 2,4-dinitrotoluene and aluminium samples, respectively. A field test with known samples and a blind test were carried out at a distance of 30 m from the sample. Identification of energetic compounds in such conditions resulted in 19 correct results out of 21 samples.
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design construction and assessment of a field deployable laser induced breakdown spectrometer for remote elemental sensing
Spectrochimica Acta Part B: Atomic Spectroscopy, 2006Co-Authors: S Palanco, Cristina Lopezmoreno, J J LasernaAbstract:A field-deployable laser-induced breakdown spectrometer for measurements in the hundreds of meters range has been presented. The system is capable of elemental analysis with no previous preparation and in near real time, with the only requirement of a free line-of-sight between the instrument and the sample. Main factors influencing LIBS performance at stand-off distances are outlined. LIBS signal is shown to depend on range of analysis, peak power, beam quality, laser wavelength and optics dimensions. A careful control of focusing conditions has been shown to be of importance to avoid interferences from air breakdown by the stand-off focused beam.
Vasileios Katranidis - One of the best experts on this subject based on the ideXlab platform.
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experimental study of high velocity oxy fuel sprayed wc 17co coatings applied on complex geometries part b influence of kinematic spray parameters on microstructure phase composition and decarburization of the coatings
Surface & Coatings Technology, 2017Co-Authors: Vasileios Katranidis, Bryan Allcock, Tomas Ramirez Reina, E Alpay, Spyros KamnisAbstract:The aim of this study is to evaluate comprehensively the effect of spray angle, spray distance and gun traverse speed on the microstructure and phase composition of HVOF sprayed WC-17 coatings. An experimental setup that enables the isolation of each one of the kinematic parameters and the systemic study of their interplay is employed. A mechanism of particle partition and WC-cluster rebounding at short distances and oblique spray angles is proposed. It is revealed that small angle inclinations benefit notably the WC distribution in the coatings sprayed at long stand-off distances. Gun traverse speed, affects the oxygen content in the coating via cumulative superficial oxide scales formed on the as-sprayed coating surface during deposition. Metallic W continuous rims are seen to engulf small splats, suggesting crystallization that occurred in-flight.
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experimental study of high velocity oxy fuel sprayed wc 17co coatings applied on complex geometries part a influence of kinematic spray parameters on thickness porosity residual stresses and microhardness
Surface & Coatings Technology, 2017Co-Authors: Vasileios Katranidis, Bryan Allcock, Spyros KamnisAbstract:Abstract When a complex geometry is rotated in front of the thermal spray gun, the following kinematic parameters vary in a coupled fashion dictated by the geometry: Stand-off distance, spray angle and gun traverse speed. These fluctuations affect the conditions of particle impact with major implications on the coating's properties. This work aims to probe into the interplay and isolated effect of these parameters on vital coating characteristics in applications requiring variable stand-off distance and spray angles. WC-17Co powders are sprayed via HVOF on steel substrates in a set of experiments that simulates the spray process of a non-circular cross section, while it allows for individual control of the kinematic parameters. Comprehensive investigation of their influence is made on deposition rate, residual stresses, porosity and microhardness of the final coating. It was determined that oblique spray angles and long stand-off distances compromise the coating properties but in some cases, the interplay of the kinematic parameters produced non-linear behaviours. Microhardness is related negatively with oblique spray angles at short distances while a positive correlation emerges as the stand-off distance is increased. Porosity and residual stresses are sensitive to the spray angle only in relatively short stand-off distances.
Jost O.l. Wendt - One of the best experts on this subject based on the ideXlab platform.
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ignition in 40 kw co axial turbulent diffusion oxy coal jet flames
Proceedings of the Combustion Institute, 2011Co-Authors: Jingwei Zhang, Eric G. Eddings, Kerry Kelly, Jost O.l. WendtAbstract:This paper is directed towards understanding how composition of the coal transport medium (primary CO2 and O2) affects the observed ignition stand-off distance in 40 kW co-axial turbulent diffusion, oxy-coal flames, supported in a specially designed combustion test rig, rated at 100 kW. First, a methodology to define and quantify the observed ignition stand-off distance in laboratory combustor scale turbulent pulverized coal jets was developed and is described in detail. Results are presented in the form of probability density profiles of the measured stand-off distance, as obtained from replicate runs each consisting of six thousand photoimages. Several probability density functions showed multi-modal behavior representing semi-stable attached flames. Special tests in which the transport fluid only was interchanged between N2 and CO2, led to additional qualitative insight into ignition of coal in practical, turbulent diffusion flames. Results show that flame stability is affected by primary PO2 , secondary preheat temperature, secondary PO2 , and transport medium. Increasing secondary PO2 can stabilize the flame with zero PO2 in transport stream. The results presented in this paper can also provide a basis for validation of future detailed simulations of this process.
R C Wiens - One of the best experts on this subject based on the ideXlab platform.
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laser induced breakdown spectroscopy for space exploration applications influence of the ambient pressure on the calibration curves prepared from soil and clay samples
Spectrochimica Acta Part B: Atomic Spectroscopy, 2005Co-Authors: B Salle, S Maurice, David A Cremers, R C WiensAbstract:Abstract Recently, there has been an increasing interest in the laser-induced breakdown spectroscopy (LIBS) technique for stand-off detection of geological samples for use on landers and rovers to Mars, and for other space applications. For space missions, LIBS analysis capabilities must be investigated and instrumental development is required to take into account constraints such as size, weight, power and the effect of environmental atmosphere (pressure and ambient gas) on flight instrument performance. In this paper, we study the in-situ LIBS method at reduced pressure (7 Torr CO2 to simulate the Martian atmosphere) and near vacuum (50 mTorr in air to begin to simulate the Moon or asteroids' pressure) as well as at atmospheric pressure in air (for Earth conditions and comparison). Here in-situ corresponds to distances on the order of 150 mm in contrast to stand-off analysis at distance of many meters. We show the influence of the ambient pressure on the calibration curves prepared from certified soil and clay pellets. In order to detect simultaneously all the elements commonly observed in terrestrial soils, we used an Echelle spectrograph. The results are discussed in terms of calibration curves, measurement precision, plasma light collection system efficiency and matrix effects.
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laser induced breakdown spectroscopy for mars surface analysis capabilities at stand off distances and detection of chlorine and sulfur elements
Spectrochimica Acta Part B: Atomic Spectroscopy, 2004Co-Authors: Beatrice Salle, Jeanluc Lacour, Evelyne Vors, Pascal Fichet, S Maurice, David A Cremers, R C WiensAbstract:Abstract An international consortium is studying the feasibility of performing in situ geochemical analysis of Mars soils and rocks at stand-off distances up to several meters using the Laser-Induced Breakdown Spectroscopy (LIBS) technique. Stand-off analysis for Martian exploration imposes particular requirements on instrumentation, and it is necessary to first test the performance of such a system in the laboratory. In this paper, we test the capabilities of two different experimental setups. The first one is dedicated to the qualitative analysis of metals and rocks at distances between 3 and 12 m. With the second one, we have obtained quantitative results for aluminum alloys and developed a spectral database under Martian conditions for sulfur and chlorine, two elements that are geologically interesting but generally difficult to detect by LIBS under standard conditions (atmospheric pressure, close distance). These studies were carried out to determine an optimal instrumental design for in situ Mars analysis. The quality of analytical results affected by the optical elements and spectrometer has been particularly highlighted.