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Louis Schlapbach - One of the best experts on this subject based on the ideXlab platform.

Laurent-dominique Piveteau - One of the best experts on this subject based on the ideXlab platform.

Somrerk Chandra-ambhorn - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Process Parameters on Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Low Carbon Steels
    Oxidation of Metals, 2013
    Co-Authors: Somrerk Chandra-ambhorn, Komsan Ngamkham, Noppon Jiratthanakul
    Abstract:

    The present work investigated the effects of process parameters in a hot-rolling line, finishing and coiling temperatures, on Mechanical Adhesion of scale on low carbon steel substrate using a tensile test. Modification of our previous model to quantify Mechanical Adhesion energy was proposed for a system consisting of a cracked scale on a metallic substrate by introducing a distribution function of stress in scale. When a linear distribution was assumed, the quantified Mechanical Adhesion energy lay in the range of 40–890 J m^−2. Higher finishing temperature had a prominent role on increasing final scale thickness and weakening scale Adhesion. For scale with similar thickness, the Mechanical Adhesion energy was lowered for the sample subjected to higher temperature gradient between finishing and coiling temperatures. This was considered to be from the increased water vapour in atmosphere due to the higher amount of water used to cool down the steel strip. The Mechanical Adhesion test was further conducted to attest this assumption. It was found that humidified atmosphere during oxidation weakened the scale Adhesion to low carbon steel substrate measured at room temperature.

  • Adhesion of Thermal Oxide Scales on Hot-Rolled Conventional and Recycled Steels
    Oxidation of Metals, 2013
    Co-Authors: Thanasak Nilsonthi, Somrerk Chandra-ambhorn, Yves Wouters, A. Galerie
    Abstract:

    International audienceThe Mechanical Adhesion of thermally-formed oxide scales formed on industrial hot-rolled low carbon steel strips produced through the blast-furnace route (conventional steel) or the electric-arc-furnace route (recycled steel) was studied. A new macro-tensile test was compared to a micro-tensile test previously used. It was observed that spallation of scales during straining increased with increasing the tensile strain rate. A higher strain rate resulted in a lower strain inducing the first spallation. As a result, the Mechanical Adhesion energy of scales actually formed on the recycled steel was in the range 300-700 J m(-2). Comparison at the same strain rate of the conventional and recycled steels showed higher scale Adhesion for the recycled steel due to the presence of high amounts of interfacial silica

  • Adhesion of Thermal Oxide Scales on Hot-Rolled Conventional and Recycled Steels
    Oxidation of Metals, 2013
    Co-Authors: Thanasak Nilsonthi, Somrerk Chandra-ambhorn, Y. Wouters, A. Galerie
    Abstract:

    The Mechanical Adhesion of thermally-formed oxide scales formed on industrial hot-rolled low carbon steel strips produced through the blast-furnace route (conventional steel) or the electric-arc-furnace route (recycled steel) was studied. A new macro-tensile test was compared to a micro-tensile test previously used. It was observed that spallation of scales during straining increased with increasing the tensile strain rate. A higher strain rate resulted in a lower strain inducing the first spallation. As a result, the Mechanical Adhesion energy of scales actually formed on the recycled steel was in the range 300-700 J m(-2). Comparison at the same strain rate of the conventional and recycled steels showed higher scale Adhesion for the recycled steel due to the presence of high amounts of interfacial silica.

  • Development of Tensile Test to Investigate Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Steel Strips Produced Using Different Finishing Temperatures
    Key Engineering Materials, 2011
    Co-Authors: Komsan Ngamkham, Satian Niltawach, Somrerk Chandra-ambhorn
    Abstract:

    The objective of this work was to carry out tensile tests to investigate the effect of finishing temperature on Mechanical Adhesion of thermal oxide scale on hot-rolled low carbon steel strips. Two hot-rolled low carbon steel strips were produced in an industrial hot rolling line by fixing a coiling temperature at 620 °C and varying finishing temperatures at 820 and 910 °C. Two testing methods were conducted. First, each of a number of samples was subjected to a given imposed strain with ex-situ imaging of scale surface after straining. Second, only one sample was strained in a test with ex-situ imaging of scale surface at every 2 mm elongation of the sample. A spallation ratio, an area where scale was spalled out and normalised by the total area observed by microscope, was plotted as a function of the imposed strain. These two methods gave the same tendency of results as follows. At a given strain, the spallation ratio of scale on steel produced using higher finishing temperature was larger. The gradient of spallation ratio with respect to the imposed strain of that scale was also steeper. This reflects the higher susceptibility of scale to spall out with increasing imposed strain. This behaviour might be related to the larger thickness of scale on steel produced using higher finishing temperature. For the second testing method, lowering the magnification of microscope to observe scale spallation from 50x to 20x increased R2 of the curve of spallation ratio versus the imposed strain, as well as improved the reproducibility of the test.

  • Mechanical Adhesion and Pickling Behaviour of Thermal Oxide Scales on Hot-Rolled Low Carbon Steel Strips Produced by Different Finishing Temperatures
    Materials Science Forum, 2011
    Co-Authors: Komsan Ngamkham, Satian Niltawach, Somrerk Chandra-ambhorn
    Abstract:

    Hot-rolled low carbon steel strips were produced using two different finishing temperatures at 910 and 820 °C in an industrial hot-rolling line. Mechanical Adhesion of scale on the steel substrate at 40 mm from the edge was investigated by tensile test. It was found that the strain initiating the first spallation of scale produced at higher finishing temperature was lower. Spallation ratio which is a spalled area of scale divided by the total area of scale examined under an optical microscope was steeper when the scale was produced at higher finishing temperature. The lower values of strain initiating the first spallation and the higher values of spallation ratio of scale formed both at higher finishing temperature were due to higher thickness of that scale. Pickling behaviour of the hot-rolled steels was investigated by immersing the studied steels in a 10%v/v HCl solution at 80 °C. X-ray diffraction (XRD) peak of hematite relative to that of iron decreased with pickling time and approached zero during pickling periods from 3 to 10 s, while magnetite-and-iron ratio gradually decreased and tended to be zero at longer pickling time. This might indicate the existence of hematite as the outermost layer of scale and subscale containing magnetite as the inner part.

Beat Gasser - One of the best experts on this subject based on the ideXlab platform.

Joël Alexis - One of the best experts on this subject based on the ideXlab platform.

  • Mechanical Adhesion of SiO2 thin films onto polymeric substrates
    Surface Engineering, 2019
    Co-Authors: Joël Alexis, Anita Dehoux, Sébastien Châtel, Olivier Dalverny, Yannick Balcaen, Bruce Faure
    Abstract:

    Quantification of Adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick polymeric coating was performed by analysing the SiO2 buckle morphologies generated under compressive stress. Impacts of Mechanical properties of SiO2 layers, as well as a surface pretreatment on Adhesion, are shown. Interfacial toughness of both configurations are assessed using the Hutchinson and Suo model, which involves buckle dimensions determined in situ by an optical profilometer, and elastic modulus Ef, of the SiO2 thin films, characterised by nanoindentation. The surface pretreatment led to initiation of buckling at a higher strain. The same trend is observed for a layer with a lower stiffness and residual stress.

  • Assessment of candidate metallization systems deposited on diamond using nano-indentation and nano-scratching tests
    Thin Solid Films, 2016
    Co-Authors: Sabeur Msolli, Joël Alexis, Olivier Dalverny, Moussa Karama
    Abstract:

    Mechanical suitability of ohmic contacts among the select metallization systems, deposited on a p-type heavily boron-doped homoepitaxial diamond layer, was evaluated via Mechanical tests on the nanoscale. Two candidate metallization systems were considered: Si/Al and Ti/Pt/Au. Metallizations were performed using two different techniques: plasma-enhanced chemical vapour deposition and “lift-off”. Effectiveness of the techniques was assessed via Mechanical tests on the microscale and the nanoscale. Nano-indentation experiments were performed to determine the Mechanical properties of the layers. Nano-scratching experiments were used to evaluate the Mechanical Adhesion on the diamond substrate. Scanning electron microscopy was applied for observation of the morphology of the surface and the indent and for detecting defects.

  • Mechanical Adhesion of SIO2 thin film on a polymeric substrate under compressive stress
    2016
    Co-Authors: Caroline Ho, Anita Dehoux, Loïc Lacroix, Sébastien Châtel, Joël Alexis, Olivier Dalverny, Bruce Faure
    Abstract:

    To ensure good Adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of Adhesion at this interface is needed. To reach this purpose, quantification of Adhesion is performed by analyzing SiO2 buckle morphologies generated under compressive stress. This Adhesion test was chosen for its representativeness of defects observed in real life. Interfacial toughness can be determined by applying Hutchinson & Suo model. This analytical model involves accurate value of elastic modulus Ef of SiO2 thin film. Small dimensions at stake make characterization of elastic modulus challenging. First part of the study focuses on using both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus. Results showed significant influence of substrate for both techniques. Impact on Mechanical properties between SiO2 thin films with different intrinsic stresses was also investigated and suggests that higher density of SiO2 thin film leads to higher elastic modulus. Compression tests resulted in formation of straight-sided buckles that evolve into telephone cords upon unloading. Numerical simulation and Digital Image Correlation were implemented to ensure homogeneous strain of substrate and favor regular distribution of buckles. Values of energy release rates of SiO2 / Hardcoat range from 2.7 J/m² to 8.9 J/m², depending on moduli values found on wafer or lens substrate.

  • An assessment of contact metallization for high power and high temperature diamond Schottky devices
    Diamond and Related Materials, 2012
    Co-Authors: Sodjan Koné, Sabeur Msolli, Henri Schneider, Karine Isoird, Fabien Thion, Jocelyn Achard, Riadh Issaoui, Joël Alexis
    Abstract:

    Different metals W, Al, Ni and Cr were evaluated as Schottky contacts on the same p-type lightly boron doped homoepitaxial diamond layer. The current-voltage (I-V) characteristics, the series resistance and the thermal stability are discussed in the range of RT to 625 K for all Schottky devices. High current densities close to 3.2 kA/cm2 are displayed and as the series resistance decreases with increasing temperature, proving the potential of diamond for high power and high temperature devices. The thermal stability of metal/diamond interface investigated with regards to the Schottky barrier height (SBH) and ideality factor n fluctuations indicated that Ni and W are thermally stable in the range of RT to 625 K. Current-voltage measurements at reverse bias indicated a maximum breakdown voltage of 70 V corresponding to an electric field of 3.75 MV/cm. Finally, these electrical measurements have been completed with Mechanical Adhesion tests of contact metallizations on diamond by nano-scratching technique. These studies clearly reveal Ni as a promising contact metallization for high power, high temperature and good Mechanical strength diamond Schottky barrier diode applications.