Block Copolymer Elastomer with Graphite Filler: Effect of Processing Conditions and Silane Coupling Agent on the Composite Properties

The control of morphology and interface in poly(styrene-ethylene/butylene-styrene) (SEBS) composites with graphitic fillers is extremely important for the design of piezoresistive sensors for body motion or flexible temperature sensors. The effects of a high amount of graphite (G) and silane coupling agent on the morphology and properties of SEBS composites with anisotropic mechanical properties are reported. The physical and chemical bonding of silane to both G and SEBS surface was proved by EDX and TGA results; this improved interface influenced both the thermal and mechanical properties of the composite. The vinyltriethoxysilane (VS) promoted the formation of char residue and, being tightly bound to both SEBS and G, did not show separate decomposition peak in the TGA curve of composites. The mechanical properties were measured on two perpendicular directions and were improved by both the addition of VS and the increased amount of G; however, the increase of storage modulus due to orientation (from 5 to 15 times depending on the composition and direction of the test) was more important than that provided by the increase of G concentration, which was a maximum of four times that obtained for 15 wt % graphite. A mechanism to explain the influence of G content and treatment on the variation of storage modulus and tan δ depending on the direction of the test was also proposed

Caracterisation of ionized magnetron sputtering plasma for thin film deposition

Les exigences de plus en plus élevés concernant la qualité et propriétés de couches minces ont soutenu le développement de nouveaux procédés de pulvérisation. Ainsi, la décharge magnétron conventionnelle en courant continu, une des sources d’atomes la plus utilisée pour le dépôt de couches minces, a été améliorée par le couplage avec une décharge additionnelle de radio fréquence pour obtenir le nouveau procédé RF-IPVD (Radio Frequency-Ionized Physical Vapour Deposition). Ce procédé permet de générer un degré d’ionisation supérieur à celui dans la décharge magnétron classique, nécessaire pour contrôler les propriétés des couches minces. Un procédé alternatif pour augmenter d’avantage l’ionisation consiste à appliquer des impulsions haute puissance sur la cathode HPPMS (High Power Pulsed Magnetron Sputtering), pour des durés courtes de l’ordre de ųs ou dizaines de ųs. L’étude menée porte sur les phénomènes de pulvérisation et de transport des espèces du métal dans ces trois versions de la décharge magnétron par les moyens de spectroscopie laser à l’aide des diodes laser accordables. Le développement récent de ces diodes nous a permis de sonder les niveaux fondamentaux du Titane et de l’Aluminium, et de caractériser la dépendance spatiale de la densité et température ainsi que la fonction de distribution en vitesse de ces atomes. L’effet des paramètres clés, comme l’intensité du courant et la pression du gaz, est étudie et décrit pour la décharge magnétron conventionnelle. La distribution spatiale et angulaire de la fonction de distribution en vitesses a été mesurée dans la région devant la cible magnétron, afin de caractériser les flux du métal et leur comportement dans le volume de la décharge. L’étude sur les atomes du métal dans le procédé RF-IPVD est concentrée sur l’effet de la décharge additionnelle sur le dépeuplement du niveau fondamental. Une efficacité plus grande des processus d’ionisation est trouvée à plus haute pression et plus haute puissance RF injecté. On a montré aussi que les atomes affectés par les processus d’ionisation sont ceux thermalisées, tandis que la distribution de atomes rapides n’est quasiment pas affectés par la décharge additionnelle.Le diagnostic de la décharge pulsée a nécessité le développement d’une nouvelle procédure expérimentale, capable de suivre l’évolution de la densité et de la température des espèces neutres avec une résolution de l’ordre de la ųs. Cette procédure nous a servi pour décrire l’évolution spatio-temporel des atomes du métal (Ti et Al) et les atomes métastables d’Ar. Ces études offrent une vue globale sur le transport de atomes pulvérisés pendant la post décharge, ainsi qu’une description du fonctionnement de la décharge pulsé via la création des métastables d’Argon.The higher requirements on the thin films quality have supported the development of new sputtering techniques. Thus, the conventional DC magnetron discharge, one of the most widely used source of atoms for thin film deposition, has been improved by the addition of an auxiliary radio frequency discharge - new technique called RF-IPVD (Radio Frequency -Ionized Physical Vapor Deposition). This technique highly increases the ionization degree compared to conventional magnetron discharge, which is necessary for a better control of the thin films properties. An alternative method to increase the ionization is based on the use of high power pulses on the cathode, HPPMS (High Power Pulsed Magnetron Sputtering), for short periods of time ranging from ųs to tens of ųs.The present study focuses on the sputtering phenomena and the transport of metal sputtered species in these three versions of the magnetron discharge, by means of laser spectroscopy using tunable laser diodes. The recent developments of these diodes have allowed to probe the fundamental levels of titanium and aluminum, and to characterize the spatial dependency of the density and temperature as well as the velocity distribution functions of these atoms. The effect of key discharge parameters, such as current intensity and gas pressure, is studied and described for the conventional magnetron discharge. The spatial and angular velocity distribution functions were measured in front of the magnetron target, in order to characterize the metal fluxes and their behavior in the discharge volume.The study on the metal atoms in the RF-IPVD process is focused on the effect of the additional discharge on the depopulation of the ground state level. Higher ionization efficiency is found at relatively high pressure and it increases with the injected RF power. It was also showed that the thermalized atoms are the ones involved in the ionization process, while the distribution of fast atoms is almost unaffected by the additional discharge.The diagnostics of the HPPMS discharge required the development of a novel experimental procedure, able to monitor the density and temperature of neutral species with a time resolution of ųs. This procedure was used to describe the spatiotemporal evolution of metal atoms (Ti and Al) and Ar metastable atoms. These studies provide an overview on the transport of sputtered atoms during the afterglow, and a description of the pulsed discharge operation, via the creation of metastable argon atoms

Transparent Silver Coatings with Copper Addition for Improved Conductivity by Combined DCMS and HiPIMS Process

The demand for transparent conductive coatings has increased over recent years, leading to the development of various technical solutions. One of the approaches is to use metallic coatings very close to their coalescence thickness, so that a good compromise between transparency and conductivity is obtained. In this contribution, a combination of two elements with high potential in this field is used, namely silver and copper. The continuity of silver films on a dielectric transparent substrate is significantly improved by the addition of a copper seed layer that promotes the formation of a continuous layer at smaller effective thicknesses. Two distinct deposition processes are used for the deposition of the two materials, namely HiPIMS (High Power Impulse magnetron sputtering) for copper and DC sputtering for silver. The use of HiPIMS enables a better control of the structure and quantity of deposited material, allowing us to deposit a very small amount of material. The mono-element coatings are characterized from the optical and electrical point of view, and then mixed to form a structure with better transparency, up to 80% in the visible spectrum, good electrical properties, resistivity of ~2 × 10−5 (Ω × cm), and significantly lower surface roughness, down to 0.2 nm

Caractérisation du procédé plasma de pulvérisation cathodique magnétron à ionisation additionnelle pour la synthèse de couches minces

Les exigences de plus en plus élevés concernant la qualité et propriétés de couches minces ont soutenu le développement de nouveaux procédés de pulvérisation. Ainsi, la décharge magnétron conventionnelle en courant continu, une des sources d atomes la plus utilisée pour le dépôt de couches minces, a été améliorée par le couplage avec une décharge additionnelle de radio fréquence pour obtenir le nouveau procédé RF-IPVD (Radio Frequency-Ionized Physical Vapour Deposition). Ce procédé permet de générer un degré d ionisation supérieur à celui dans la décharge magnétron classique, nécessaire pour contrôler les propriétés des couches minces. Un procédé alternatif pour augmenter d avantage l ionisation consiste à appliquer des impulsions haute puissance sur la cathode HPPMS (High Power Pulsed Magnetron Sputtering), pour des durés courtes de l ordre de ųs ou dizaines de ųs. L étude menée porte sur les phénomènes de pulvérisation et de transport des espèces du métal dans ces trois versions de la décharge magnétron par les moyens de spectroscopie laser à l aide des diodes laser accordables. Le développement récent de ces diodes nous a permis de sonder les niveaux fondamentaux du Titane et de l Aluminium, et de caractériser la dépendance spatiale de la densité et température ainsi que la fonction de distribution en vitesse de ces atomes. L effet des paramètres clés, comme l intensité du courant et la pression du gaz, est étudie et décrit pour la décharge magnétron conventionnelle. La distribution spatiale et angulaire de la fonction de distribution en vitesses a été mesurée dans la région devant la cible magnétron, afin de caractériser les flux du métal et leur comportement dans le volume de la décharge. L étude sur les atomes du métal dans le procédé RF-IPVD est concentrée sur l effet de la décharge additionnelle sur le dépeuplement du niveau fondamental. Une efficacité plus grande des processus d ionisation est trouvée à plus haute pression et plus haute puissance RF injecté. On a montré aussi que les atomes affectés par les processus d ionisation sont ceux thermalisées, tandis que la distribution de atomes rapides n est quasiment pas affectés par la décharge additionnelle.Le diagnostic de la décharge pulsée a nécessité le développement d une nouvelle procédure expérimentale, capable de suivre l évolution de la densité et de la température des espèces neutres avec une résolution de l ordre de la ųs. Cette procédure nous a servi pour décrire l évolution spatio-temporel des atomes du métal (Ti et Al) et les atomes métastables d Ar. Ces études offrent une vue globale sur le transport de atomes pulvérisés pendant la post décharge, ainsi qu une description du fonctionnement de la décharge pulsé via la création des métastables d Argon.The higher requirements on the thin films quality have supported the development of new sputtering techniques. Thus, the conventional DC magnetron discharge, one of the most widely used source of atoms for thin film deposition, has been improved by the addition of an auxiliary radio frequency discharge - new technique called RF-IPVD (Radio Frequency -Ionized Physical Vapor Deposition). This technique highly increases the ionization degree compared to conventional magnetron discharge, which is necessary for a better control of the thin films properties. An alternative method to increase the ionization is based on the use of high power pulses on the cathode, HPPMS (High Power Pulsed Magnetron Sputtering), for short periods of time ranging from ųs to tens of ųs.The present study focuses on the sputtering phenomena and the transport of metal sputtered species in these three versions of the magnetron discharge, by means of laser spectroscopy using tunable laser diodes. The recent developments of these diodes have allowed to probe the fundamental levels of titanium and aluminum, and to characterize the spatial dependency of the density and temperature as well as the velocity distribution functions of these atoms. The effect of key discharge parameters, such as current intensity and gas pressure, is studied and described for the conventional magnetron discharge. The spatial and angular velocity distribution functions were measured in front of the magnetron target, in order to characterize the metal fluxes and their behavior in the discharge volume.The study on the metal atoms in the RF-IPVD process is focused on the effect of the additional discharge on the depopulation of the ground state level. Higher ionization efficiency is found at relatively high pressure and it increases with the injected RF power. It was also showed that the thermalized atoms are the ones involved in the ionization process, while the distribution of fast atoms is almost unaffected by the additional discharge.The diagnostics of the HPPMS discharge required the development of a novel experimental procedure, able to monitor the density and temperature of neutral species with a time resolution of ųs. This procedure was used to describe the spatiotemporal evolution of metal atoms (Ti and Al) and Ar metastable atoms. These studies provide an overview on the transport of sputtered atoms during the afterglow, and a description of the pulsed discharge operation, via the creation of metastable argon atoms.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Ti-Ar scattering cross sections by direct comparison of Monte Carlo simulations and laser-induced fluorescence spectroscopy in magnetron discharges

International audienceA 3D Monte Carlo code (OMEGA) was developed to simulate the transport of sputtered atoms in a magnetron discharge operating in direct current mode. Collisions between the sputtered Ti atoms and the neutral process gas atoms (Ar) were modelled. Spatially resolved simulated velocity distributions of the sputtered particles parallel as well as perpendicular to the cathode surface for different operating pressures were recorded and benchmarked against experimentally obtained profiles using laser-induced fluorescence. New differential (angular and energy-dependent) cross sections for Ti-Ar elastic collisions were thereby obtained, which resulted in good agreement between modelled and experimental results. The differences with respect to commonly used extrapolated Ar-Ar cross sections to describe the Ti-Ar interaction are highlighted and discussed

Correlation between Substrate Ion Fluxes and the Properties of Diamond-Like Carbon Films Deposited by Deep Oscillation Magnetron Sputtering in Ar and Ar plus Ne Plasmas

Recently, the use of Ne as a processing gas has been shown to increase the ionization degree of carbon in High Power Impulse Magnetron Sputtering (HiPIMS) plasmas. In this work, time-resolved measurements of the substrate's current density were carried out in order to study the time evolution of the ionic species arriving at the growing film. The addition of Ne to the plasma resulted in a steep increase of the sp(3)/sp(2) ratio in the films once the Ne contents in the processing atmosphere exceeded 26%. Increasing the Ne content is shown to increase both the total number of C ions generated in the plasmas and the ratio of C/gaseous ions. The time-resolved substrate ion current density was used to evaluate the possibility of substrate biasing synchronizing with the discharge pulses in the HiPIMS process. It is shown that in pure Ar plasmas, substrate biasing should be confined to the time interval between 25 and 40 mu s after the pulse starts, in order to maximize the C+/Ar+ ratio bombarding the substrate and minimize the formation of film stresses. However, Ne addition to the processing gas shortens the traveling time of the carbon species towards the substrate, reducing the separation between the gaseous and carbon ion arrival times

Optical Properties and Stability of Copper Thin Films for Transparent Thermal Heat Reflectors

The use of thin metallic layers at the thickness limit where transparency or spectral selectivity are achieved is gaining increased interest. The use of cheap and abundant materials is desirable in the attempt to avoid environment or economical costs. The use of Cu as a replacement for Ag as a heat reflector is one of the solutions that can be employed. The stability over time is a known issue, copper being prone to atmospheric oxidation and degradation. In this contribution, the stability of Cu obtained by magnetron sputtering is investigated, using both DC and HiPIMS processes for obtaining the Cu thin films. The bias voltage is used to obtain thin films with different properties, their time stability being investigated through the variation of spectrophotometric curves. The best performing thin films are evaluated in theoretical heat reflector structures, using SiNx of different qualities as dielectric layers to form the dielectric/metal/dielectric structure

Improvement of CoCr Alloy Characteristics by Ti-Based Carbonitride Coatings Used in Orthopedic Applications

The response of the human body to implanted biomaterials involves several complex reactions. The potential success of implantation depends on the knowledge of the interaction between the biomaterials and the corrosive environment prior to the implantation. Thus, in the present study, the in vitro corrosion behavior of biocompatible carbonitride-based coatings are discussed, based on microstructure, mechanical properties, roughness and morphology. TiCN and TiSiCN coatings were prepared by the cathodic arc deposition method and were analyzed as a possible solution for load bearing implants. It was found that both coatings have an almost stoichiometric structure, being solid solutions, which consist of a mixture of TiC and TiN, with a face-centered cubic (FCC) structure. The crystallite size decreased with the addition of Si into the TiCN matrix: the crystallite size of TiCN was 16.4 nm, while TiSiCN was 14.6 nm. The addition of Si into TiCN resulted in smaller Ra roughness values, indicating a beneficial effect of Si. All investigated surfaces have positive skewness, being adequate for the load bearing implants, which work in a corrosive environment. The hardness of the TiCN coating was 36.6 ± 2.9 GPa and was significantly increased to 47.4 ± 1 GPa when small amounts of Si were added into the TiCN layer structure. A sharp increase in resistance to plastic deformation (H3/E2 ratio) from 0.63 to 1.1 was found after the addition of Si into the TiCN matrix. The most electropositive value of corrosion potential was found for the TiSiCN coating (−14 mV), as well as the smallest value of corrosion current density (49.6 nA cm2), indicating good corrosion resistance in 90% DMEM + 10% FBS, at 37 ± 0.5 °C