H. Ziegele

Bio: H. Ziegele is an academic researcher from University of Hull. The author has contributed to research in topics: Thin film & Amorphous carbon. The author has an hindex of 7, co-authored 9 publications receiving 469 citations. Previous affiliations of H. Ziegele include Fraunhofer Society.

Structure, mechanical and tribological properties of nitrogen-containing chromium coatings prepared by reactive magnetron sputtering

Abstract: Cr1−xNx coatings were deposited by magnetron sputtering at a substrate temperature of 200°C onto AISI 316 stainless-steel substrates immersed in an Ar/N2 plasma. The goal of this investigation was to study the influence of nitrogen content on the structural, mechanical and tribological properties of the Cr1−xNx coatings (with x being in the range of 0–0.4). The coating composition and microstructure were evaluated utilizing glow discharge optical emission spectroscopy and glancing angle X-ray diffraction, whereas the morphology was evaluated by scanning electron microscopy. Knoop microhardness, scratch adhesion, pin-on-disc sliding, ball-on-plate impact and abrasive wheel wear tests were performed to evaluate the mechanical and tribological properties. The presence of Cr, Cr2N, CrN (and mixtures of these phases) has been identified and related to the film composition. For Cr1−xNx coatings with x≤0.16, only the α-Cr phase could be detected. A progression towards a denser microstructure was found with increasing nitrogen content up to x=0.29, associated with an increase in hardness from 700 up to 2400 HK0.025. Cr1−xNx coatings with x=0.10–0.16 showed good adhesion and the best abrasive and pin-on-disk sliding wear resistance, together with less crack development around the indentation area (and thus improved toughness) in impact tests after 50 000 impacts, against both steel and cemented tungsten carbide balls. The hardest coating (Cr0.71N0.29) performed best in terms of reducing the resulting impact indentation volume.

Deposition of superhard amorphous carbon films by pulsed vacuum arc deposition

Abstract: The deposition of superhard amorphous carbon films demands high energies of all impinging particles for film formation by subplantation instead of condensation. Such conditions may be realized by vacuum arc discharge. By using pulsed arc currents and laser controlled ignition (Laser-Arc) the usual problems in arc ablation of carbon targets have been overcome. In this way, smooth and very hard films with hardness in the superhard range between 40 and 80 GPa have been prepared with high deposition rates comparable to conventional industrial arc deposition. Due to the high ion energies, low deposition temperatures are possible without reducing the adherence. They are even necessary for the formation of the diamond bonds by avoiding relaxation towards a graphitic structure. Hence, materials besides metals such as steels or aluminum, temperature-sensitive materials such as polymers have been successfully coated with these hard layers.

Structure, mechanical and tribological properties of Ti–B–N and Ti–Al–B–N multiphase thin films produced by electron-beam evaporation

Abstract: Titanium-based multiphase ceramic coatings were deposited by electron-beam plasma-assisted physical vapor deposition, evaporating mixtures of Ti, TiB2, and (Ti0.6Al0.4)B2.19N1.47 material in Ar or Ar/N2 plasmas. All exhibited dense microstructures, however varying amounts of droplets or spits incorporated in the coatings produced could be observed for the different evaporation materials depending on their fabrication route. Results on the chemical composition of the coatings, obtained from glow discharge optical emission spectroscopy and Auger electron spectroscopy, showed no preferential evaporation of any element from the different evaporation source materials used, resulting in very similar compositions between evaporant and coating. Hardness values of up to 40 GPa were found for Ti–B–N based coatings containing both TiB2 and c-BN phases. Lower hardness values of around 30 GPa were observed for coatings deposited within the quaternary Ti–Al–B–N system, due to the presence of h-BN. Two micron thick Ti–Al–B–N coatings showed only minimal wear in pin-on-disk sliding wear tests against cemented tungsten carbide balls and, with increasing h-BN content, a slight decrease in “stick–slip” oscillation and friction coefficient. In contrast to Ti–Al–B–N coatings (whose impact adhesion was relatively poor) Ti–B–N coatings approximately 1.5 μm thick showed no coating spallation in impact tests against cemented tungsten carbide balls and consequently superior impact wear resistance.

Deposition of superhard amorphous carbon films by pulsed arc sources

Abstract: Hydrogen-free amorphous carbon films with hardness comparable to crystalline superhard materials have been deposited by special pulsed arc techniques. With the combination of very high hardness, high smoothness, and low adhesion activity to other materials which are in contact with them, these films show superior behavior in wear and slide applications. The influence of plasma and deposition conditions on these film properties and the choice of optimum conditions are discussed.

DLC and metallic nanometer multilayers deposited by laser-arc

Abstract: 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.

Low dielectric constant materials.

Abstract: Modern computer microprocessor chips are marvels of engineering complexity. For the current 45 nm technology node, there may be nearly a billion transistors on a chip barely 1 cm2 and more than 10 000 m of wiring connecting and powering these devices distributed over 9-10 wiring levels. This represents quite an advance from the first INTEL 4004B microprocessor chip introduced in 1971 with 10 μm minimum dimensions and 2 300 transistors on the chip! It has been disclosed that advanced microprocessor chips at the 32 nm node will have more than 2 billion transistors.1 For instance, Figure 1 shows a sectional 3D image of a 90 nm IBM microprocessor, containing several hundred million integrated devices and 10 levels of interconnect wiring, designated as the back-end-of-the-line (BEOL). Since the invention of microprocessors, the number of active devices on a chip has been exponentially increasing, approximately doubling every two years. This trend was first described in 1965 by Gordon Moore,2 although the original discussion suggested doubling the number of devices every year, and the phenomenon became popularly known as Moore’s Law. This progress has proven remarkably resilient and has persisted for more than 50 years. The enabler that has permitted these advances is known as scaling, that is, the reduction of minimum device dimensions by lithographic advances (photoresists, tooling, and process integration optimization) by ∼30% for each device generation.3 It allowed more active devices to be incorporated in a given area and improved the operating characteristics of the individual transistors. It should be emphasized that the earlier improvements in chip performance were achieved with very few changes in the materials used in the construction of the chips themselves. The increase of performance with scaling * Corresponding author. E-mail: gdubois@us.ibm.com. † IBM Almaden Research Center. ‡ Stanford University. Willi Volksen received his B.S. in Chemistry (magna cum laude) from New Mexico Institute of Mining and Technology in 1972 and his Ph.D. in Chemistry/Polymer Science from the University of Massachusetts, Lowell, in 1975. He then joined the research group of Prof. Harry Gray/Dr. Alan Rembaum at the California Institute of Technology as a postdoctoral fellow and upon completion of the one-year appointment joined Dr. Rembaum at the Jet Propulsion Laboratory as a Senior Chemist in 1976. In 1977 Dr. Volksen joined the IBM Research Division at the IBM Almaden Research Center in San Jose, CA, where he is an active research staff member in the Advanced Materials Group of the Science and Technology function.

Solid lubricants: a review

Abstract: The fundamental mechanisms of solid lubrication are reviewed with examples from well-known solid lubricants like the transition metal dichalcogenides and diamond-like carbon families of coatings. Solid lubricants are applied either as surface coatings or as fillers in self-lubricating composites. Tribological (friction and wear) contacts with solid lubricant coatings typically result in transfer of a thin layer of material from the surface of the coating to the counterface, commonly known as a transfer film or tribofilm. The wear surfaces can exhibit different chemistry, microstructure, and crystallographic texture from those of the bulk coating due to surface chemical reactions with the surrounding environment. As a result, solid lubricant coatings that give extremely low friction and long wear life in one environment can fail to do so in a different environment. Most solid lubricants exhibit non-Amontonian friction behavior with friction coefficients decreasing with increasing contact stress. The main mechanism responsible for low friction is typically governed by interfacial sliding between the worn coating and the transfer film. Strategies are discussed for the design of novel coating architectures to adapt to varying environments.

Historical developments and new trends in tribological and solid lubricant coatings.

Abstract: In recent years, several new solid lubricant and modern lubrication concepts have been developed to achieve better lubricity and longer wear life in demanding tribological applications. Most of the traditional solid lubricants were prepared in the form of metal, ceramic and polymer-matrix composites. They have been used successfully in various engineering applications. Recent progress in thin-film deposition technologies has led to the synthesis of new generations of adaptative, self-lubricating coatings with composite or multilayered architectures, by using duplex/multiplex surface treatments. These modern self-lubricating coatings progressively make their way into the commercial marketplace and meet the ever-increasing performance demands of more severe applications. The present paper reviews our recent understanding of the lubrication mechanisms of both traditional and new solid lubricants, with particular emphasis on solid lubricant methods and practices.