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Diederik Depla - One of the best experts on this subject based on the ideXlab platform.
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perspective is there a Hysteresis during reactive high power impulse magnetron sputtering r hipims
Journal of Applied Physics, 2017Co-Authors: Koen Strijckmans, Filip Moens, Diederik DeplaAbstract:This paper discusses a few mechanisms that can assist to answer the title question. The initial approach is to use an established model for DC magnetron sputter deposition, i.e., RSD2013. Based on this model, the impact on the Hysteresis Behaviour of some typical HiPIMS conditions is investigated. From this first study, it becomes clear that the probability to observe Hysteresis is much lower as compared to DC magnetron sputtering. The high current pulses cannot explain the Hysteresis reduction. Total pressure and material choice make the abrupt changes less pronounced, but the implantation of ionized metal atoms that return to the target seems to be the major cause. To further substantiate these results, the analytical reactive sputtering model is coupled with a published global plasma model. The effect of metal ion implantation is confirmed. Another suggested mechanism, i.e., gas rarefaction, can be ruled out to explain the Hysteresis reduction. But perhaps the major conclusion is that at present, there...
Jerry Westerweel - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of torque Hysteresis Behaviour of taylor couette flow
Journal of Fluid Mechanics, 2018Co-Authors: M Gul, G E Elsinga, Jerry WesterweelAbstract:This paper describes the Hysteresis in the torque for Taylor–Couette flow in the turbulent flow regime for different shear Reynolds numbers, aspect ratios and boundary conditions. The Hysteresis increases with decreasing shear Reynolds number and becomes more pronounced as the aspect ratio is increased from 22 to 88. Measurements conducted in two different Taylor–Couette set-ups depict the effect of the flow conditions at the ends of the cylinders on the flow Hysteresis by showing reversed Hysteresis Behaviour. In addition, the flow structure in the different branches of the Hysteresis loop was investigated by means of stereoscopic particle image velocimetry. The results show that the dominant flow structures differ in shape and magnitude depending on the branch of the Hysteresis loop. Hence, it can be concluded that the geometry could have an effect on the Hysteresis Behaviour of turbulent Taylor–Couette flow, but its occurrence is related to a genuine change in the flow dynamics.
Nikos Hadjichristidis - One of the best experts on this subject based on the ideXlab platform.
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interpretation of Hysteresis Behaviour of pi ps multigraft copolymers by adapting to the dynamic flocculation model
European Polymer Journal, 2008Co-Authors: Ulrike Staudinger, Ralf Schlegel, Roland Weidisch, Juliane Fritzsche, Manfred Kluppel, Gert Heinrich, Jimmy W Mays, David Uhrig, Nikos HadjichristidisAbstract:Hysteresis Behaviour of highly elastic multigraft copolymers with a polyisoprene (PI) backbone and branched polystyrene (PS) arms has been interpreted by applying the extended non-affine tube model of filler reinforced rubber elasticity (dynamic flocculation model), which takes into account that conformational fluctuations in bulk networks are strongly suppressed by packing effects. Originally, this model was developed to describe hyperelasticity of unfilled networks, and later, stress softening and Hysteresis of filler reinforced elastomer materials like carbon black and silica filled rubbers. The evaluation of stress softening is obtained via pre-strain dependent hydrodynamic amplification of the rubber matrix by a fraction of rigid filler clusters with virgin filler filler bonds. The filler-induced Hysteresis is described by a cyclic breakdown and re-aggregation of the residual fraction of more soft filler clusters with already broken filler filler bonds. We show, for the first time that the developed concept is in fair agreement with experimental stress strain data of superelastic PI PS multigraft copolymers. Depending on the PS-content and their functionality multigraft copolymers form microphase separated structures according to the constituting block copolymer concept, where the PS arms act as multi-domains in a PI matrix. The adaptation of the model is based on the assumptionmore » that the PS-domains are acting similar to filler clusters. The obtained microscopic material parameters appear reasonable for the description of the structure and mechanical properties of multigraft copolymers.« less
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mechanical properties and Hysteresis Behaviour of multigraft copolymers
Macromolecular Symposia, 2006Co-Authors: Ulrike Staudinger, Roland Weidisch, Jimmy W Mays, David Uhrig, Yuqing Zhu, Samuel P Gido, Hermis Iatrou, Nikos HadjichristidisAbstract:PS-PI multigraft copolymers with tri- tetra- and hexafunctional polystyrene branch points have been studied to investigate the influence of molecular architecture on morphological and tensile properties and to find novel material concepts. It was found that the morphological Behaviour of these grafted copolymers can be predicted using theoretical approaches. The number of branch points, however, greatly influences the long-range order of microphase separation. Additionally, two new parameters for adjusting mechanical properties of multigraft copolymers are found in our investigations: 1) functionality of the graft copolymer: tri-, tetra- or hexafunctional and 2) number of branch points per molecule. Tetrafunctional multigraft copolymers show surprising high strain at break values up to 1550 %. With increasing number of branch points strain at break and tensile strength increase, where a linear dependence of mechanical properties on the number of branch points is obvious. Excellent elasticity of tetra and hexafunctional multigraft copolymers at high deformation was proved in Hysteresis experiments.
Ulf Helmersson - One of the best experts on this subject based on the ideXlab platform.
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Studies of Hysteresis effect in reactive HiPIMS deposition of oxides
Surface & Coatings Technology, 2011Co-Authors: Tomas Kubart, Montri Aiempanakit, Joakim Andersson, Tomas Nyberg, Sören Berg, Ulf HelmerssonAbstract:High power impulse magnetron sputtering (HiPIMS) has proven to be capable of substantial improvement of the quality of deposited coatings. Lately, there have been a number of reports indicating that the Hysteresis effect may be reduced in HiPIMS mode resulting in an increase of the deposition rate of stoichiometric compound as compared to a direct current magnetron sputtering process in oxide mode. In this contribution, we have studied the Hysteresis Behaviour of Ti metal targets sputtered in Ar + O(2) mixtures. For fixed pulse on time and a constant average power, there is an optimum frequency minimizing the Hysteresis. The effect of gas dynamics was analyzed by measurements of the gas refill time and rarefaction. Results indicate that the gas rarefaction may be responsible for the observed Hysteresis Behaviour. The results are in agreement with a previous study of Al oxide reactive process.
Koen Strijckmans - One of the best experts on this subject based on the ideXlab platform.
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perspective is there a Hysteresis during reactive high power impulse magnetron sputtering r hipims
Journal of Applied Physics, 2017Co-Authors: Koen Strijckmans, Filip Moens, Diederik DeplaAbstract:This paper discusses a few mechanisms that can assist to answer the title question. The initial approach is to use an established model for DC magnetron sputter deposition, i.e., RSD2013. Based on this model, the impact on the Hysteresis Behaviour of some typical HiPIMS conditions is investigated. From this first study, it becomes clear that the probability to observe Hysteresis is much lower as compared to DC magnetron sputtering. The high current pulses cannot explain the Hysteresis reduction. Total pressure and material choice make the abrupt changes less pronounced, but the implantation of ionized metal atoms that return to the target seems to be the major cause. To further substantiate these results, the analytical reactive sputtering model is coupled with a published global plasma model. The effect of metal ion implantation is confirmed. Another suggested mechanism, i.e., gas rarefaction, can be ruled out to explain the Hysteresis reduction. But perhaps the major conclusion is that at present, there...