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- Broitman, E., et al.
(author)
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Mechanical and tribological properties of CNx films deposited by reactive magnetron sputtering
- 2001
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In: Wear. - 0043-1648 .- 1873-2577. ; 248:1-2, s. 55-64
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Journal article (peer-reviewed)abstract
- The hardness, elasticity, wear rate and friction coefficient of carbon nitride (CNx) films of defined microstructure and composition are presented. CNx films were deposited by dc reactive magnetron sputtering from a C target in N2/Ar plasma. Films were grown on Si (001), Ni, and HSS substrates to thickness of ~0.5 µm at a total pressure of 3 mTorr with the N2 fraction varied from 0 to 1, and the substrate temperature Ts, varied from ambient to 350°C. The mechanical and tribological properties of the coatings were evaluated by nanoindentation and dry ball-on-disk test. For CNx (0 = x = 0.35) films deposited below 200°C (amorphous structure), the elastic recovery and hardness do not change significantly with increasing N concentration, however, the friction coefficient increases from 0.19 to 0.45, while the coating wear rate is low. For CNx (0 = x = 0.15) films grown at Ts = 350°C, where a transition from a graphite-like to a "fullerene-like" phase occurs, a dramatic increase in hardness and elasticity is observed. Furthermore, the rms surface roughness decreases from 15.0 to 0.4 nm. For 0.15 = x = 0.20, CNx films deposited at Ts = 350°C (fullerene-like phase) exhibit a smooth surface, high hardness and elasticity (~90% recovery), and a coefficient of friction against hard steel of ~0.25. For all substrates, film friction coefficient tends to increase as the nitrogen content in the film is increased. Results also indicate the formation of a transfer layer which improves the tribological properties of the films. © 2001 Elsevier Science B.V. All rights reserved.
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- Hellgren, Jonas, 1974, et al.
(author)
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A Systematic Way of Choosing Driveline Confriguration and Sizing Components in Hybrid Vehicles
- 2000
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In: 2000 Future Transportation Technology Conference, August 21-23, 2000, in Costa Mesa, California, USA, 2000.
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Conference paper (other academic/artistic)abstract
- Energy saving in general and less polluting vehicles in specific, become more and more urgent topics. One reason is that, in a world where the demand for fast transportation is increasing, the risk of global warming is a fact. Hybrid Vehicles (HV:s) are proposed as a more environmentally friendly candidate than conventional vehicles. Nowadays, there are numerous different types of HV:s and the components can, in theory, be sized in infinite ways. There is no simple answer to how to choose driveline configuration and size components in a HV. This paper describes one method, Driveline Synthesis (DS), that systematically presents a suitable driveline, on the basis of demands and conditions. Examples of demands are driving cycle and emission free zones. Some conditions are fuel price, tax on pollution and discount rate. The most suitable driveline is defined as the most cost effective. Total cost is defined as the sum of: cost of components, fuel cost, cost of external energy and cost of pollution. Genetic algorithms are used as an optimization method.Two major types of drivelines are compared in a case study, a conventional bus with a diesel engine and automatic transmission versus a series hybrid bus with different types of primary power units (diesel engine or fuel cell) and storage devices (super capacitor or NiMH battery). DS gives reasonable answers but needs further validation and development. One conclusion from the work is that the most suitable driveline configuration depends very much on demands, conditions and present technology, i.e. HV:s are only preferable to conventional vehicles under special circumstances.
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- Hultman, Lars, et al.
(author)
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Fullerene-like carbon nitride : A resilient coating material
- 2003
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In: MRS bulletin. - 0883-7694 .- 1938-1425. ; 28:3, s. 194-202
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Journal article (peer-reviewed)abstract
- Carbon nitride is an emerging material for wear-resistant coatings. The fullerene-like CNx compounds generally exhibit extreme elasticity in combination with a low work of indentation hardness. Yet CNx shows a low-to-moderate resistance to penetration, depending on deposition conditions. Since the deformation energy is predominantly stored elastically, the material possesses an extremely resilient character. This new class of materials consists of sp(2)-coordinated basal planes that are buckled from the incorporation of-pentagons and cross-linked at sp(3)-hybridized C sites, both of which are caused by structural incorporation of nitrogen. Carbon nitride thus deforms elastically due to bending of the structural units. The orientation, radius of curvature of the basal planes, and the degree of cross-linking between them defines the structure and properties of the material. Due to the unique deformation behavior, the hardness requires special care to assess, but can be very high for films with a large degree of cross-linking. This article is a review of the research on CNx films deposited by reactive magnetron sputtering, with examples from our recent work. The findings are significant for the design of fracture-tough materials.
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