‘Friends call me racist’: Experiences of repercussions from writing comments on newspaper websites

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Plasma state in pulsed arc, laser and electron deposition

Thin coatings can be produced with good hardness and wear protection under the low-pressure processes of plasma enhanced deposition. The aim of these coatings is to reduce mechanical wear, abrasion on tools and to protect the surface of different components against corrosion to guarantee their optical and decorative properties. With arc current, laser beam and a pulsed electron beam of channel spark discharge, it is possible to produce a power density over 10(exp 8) W cm(-2) on a target surface. The advantage of these techniques over other PVD processes like EB evaporation or magnetron sputtering is the characteristic of the plasmas with high energetic excitation and the high kinetic energy of the particles. In particular, these plasma conditions have an influence on the structure of the coatings. In this work, the plasma parameters of the laser deposition, arc deposition and channel spark discharge are compared. These plasma sources are able to produce full ionized plasmas on aluminum and carbon surfaces. The amount of double ionized ions in the plasmas can be over 75 per cent. Experimentally determined electron temperatures in the centers of the different plasmas reach values between 1 and 2 eV. In addition, the average kinetic energy of expanding motion of the ions is in the range 30-250 eV. The process of hydrodynamic expansion of the plasmas will be discussed

DLC and metallic nanometer multilayers deposited by laser-arc

The method of laser-induced vacuum arc (laser-arc) combines the good controllability of pulsed laser deposition with the high efficiency of a vacuum arc technique. One advantage of this technique is the essential reduction of droplets allowing the deposition of high-quality amorphous carbon films. These hydrogen-free films with very high hardness up to the superhard range exhibit excellent wear resistance and low friction. In the present paper, another advantage of the laser-arc is demonstrated, i.e. the possibility of depositing multilayer coatings down to the nanometer level of each individual layer thickness with high efficiency and high accuracy. These possibilities open new ways to overcome the principal problem of hard PVD coatings, i.e. the high internal stress which restricts the film thickness. Multilayer systems of Al-C and Ti-C with systematic variations of single layer thickness and thickness relationship were analysed by electron microscopy and Auger electron spectroscopy. The Young's moduli were measured by the non-destructive ultrasonic surface wave method (US-SAW). The alternating hard and ductile layers allowed a remarkable relaxation of the internal stresses. Furthermore, the growth of the particle induced defects (droplets) could be strongly reduced

Verschleissbestaendiger, mechanisch hochbelastbarer und reibungsarmer Randschichtaufbau fuer Titan oder seine Legierungen sowie Verfahren zu seiner Herstellung

NOVELTY - Surface layer structure for titanium and its alloys consists of a 200-400 nm thick hard amorphous carbon layer (4), a 5-50 nm thick intermediate layer (3) and a 0.3-2.0 nm thick laser gas alloyed layer (2) having a hardness of 600-1400 HV0.1. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included comprising melting the component surfaces to be protected with a high performance laser. The laser density p of the laser beam is 1 x 104 to 2 x 105 W/cm2. Melting is carried out at an oxygen partial pressure of less than 5 ppm. The reactive atmosphere consists of N2 and Ar, in which a relative nitrogen content of 40-80% is chosen. A degree of overlapping is expressed as: U = (a-c)/a (where a and c are track widths). The component is polished to a surface roughness of not more than 0.2 microns and purified in a high vacuum apparatus. The intermediate layer is applied by a vacuum arc process and the hard amorphous carbon layer also deposited by a vacuum arc process. USE - To pro tect oscillating human implants and for use in air and space travel. ADVANTAGE - The structure is highly wear resistant

Studies of the tribological and mechanical properties of laminated CrC-SiC coatings produced by r.f. and d.c. sputtering

Multilayer CrC-SiC coatings were produced by both direct current and radio frequency sputtering of Cr and Si targets in an Ar-C2H2 atmosphere. Coatings of constant thickness of about 4mu m, but with the number of layers varying between two and 200, were prepared and studied. Investigations of coating morphology were performed by scanning elecron microscopy (SEM), and coating composition was investigated using Glow Discharge Optical Spectroscopy (GDOS) and Auger Electron Spectroscopy (AES). Microhardness measurements, scratch adhesion, pin on disc, ASTM rubber wheel and impact wear tests were performed and the results were related to the individual layer thicknesses. It is shown that the improvement observed in hardness tests does not necessarily result in the improvement of other mechanical properties, e.g. adhesion and toughness. When two comparatively hard materials are combined in a multilayer coating, the result can be an increase in brittleness due to an absence of plastic release mechanisms for dislocation accumulation at layer boundaries. Thus, it is necessary to seek a compromise in the hardness of multilayer films in order to achieve optimal behaviour across a range of different surface contact conditions

Couches minces pour les contacts lubrifiés en slip-rolling (glissement-roulement) sous haute pression hertzienne initiale

Le secteur automobile doit faire face actuellement à de nouveaux challenges au niveau de la construction allégée, des économies de carburant et des coûts. Ces exigences motivent la mise au point de tribosystèmes pouvant résister à des pressions de contact de plus en plus élevées avec de faibles coefficients de frottement. L’optimisation de systèmes existants par l’application de revêtements de surface performants représente une alternative intéressante. Ce texte présente les performances de couches minces dans des conditions d’essais de slip-rolling (roulement à composante de glissement) en présence de lubrifiants liquides. Après une première sélection à température ambiante, les revêtements les plus performants ont été testés à 120 °C. Il s’agit de revêtements DLC en carbone hydrogéné (a-C:H) et en carbone tétraédrique (ta-C) de dernières générations ainsi qu’un nouveau système « revêtement/substrat ». Certains des revêtements DLC développés récemment sont résistants en slip-rolling au moins jusqu’à 10 millions de cycles à 120 °C dans l’huile moteur sous des pressions hertziennes de contact de P0max = 2600 / 2940 MPa. De plus, le nouveau système revêtement Zr(C,N)x/substrat peut résister au moins à 1 million de cycles sous des pressions hertziennes initiales de contact allant jusqu’à P0max = 3500 MPa et à des températures de lubrifiant d’au moins 120 °C