scholarly journals Effect of Thickness on Tribological Behavior of Hydrogen Free Diamond-like Carbon Coating

Coatings ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 243 ◽  
Author(s):  
Biao Huang ◽  
Qiong Zhou ◽  
Er-geng Zhang
Keyword(s):  
Steady State ◽  
Friction Coefficient ◽  
Internal Stress ◽  
Carbon Coating ◽  
Tribological Behavior ◽  
High Energy ◽  
Diamond Like Carbon ◽  
Lubrication Film ◽  
High Energy Particles

The effects of film thickness on the tribological behavior have been investigated for hydrogen-free diamond-like carbon coating in this paper. The film was deposited on cemented carbide substrate (YG10C) by applying a high power impulse magnetron sputtering (HiPIMS) technique. The reciprocating ball on the disc test was conducted on the film with different thicknesses from 0.66~1.26 μm against the ZrO2 ball. The friction coefficient and wear resistance of the coating with different thickness showed a unimodal change. Numerous defects were observed on the surface of the film with a thickness of 0.66 μm and the wear mechanism was mainly plow-grinding. Therefore, the steady-state friction coefficient reached the maximum value of 0.22. The coating with a thickness of 1.01 μm had a higher sp3 content and a smoother, dense surface. A graphite transfer layer with low shear strength was detected on the ZrO2 ball against the film with a thickness of 1.01 μm, which led to the reduction in friction, thus the steady-state friction coefficient reached the minimum value of 0.10. However, the internal stress of the film increased with increasing thickness due to the distortion of the bond angle of internal structure when the film was bombarded by high-energy particles. The peeling coating was observed under reciprocating sliding, which both played the role of plowing and boundary lubrication film. The steady-state friction coefficient was 0.14 with a coating thickness of 1.26 μm. As a result, the hydrogen-free diamond-like carbon coating with optimized thickness shows a smooth and compact surface, low internal stress, high sp3 content, and better tribological properties.

The Effect of CNT Content on the Tribological Properties of CNTs Doped Diamond-Like Carbon Films

2015 ◽  
Vol 642 ◽  
pp. 231-235
Author(s):  
Che Hung Wei ◽  
Jui Feng Yang ◽  
Chao I Wang
Keyword(s):  
Friction Coefficient ◽  
Critical Load ◽  
Internal Stress ◽  
Tribological Properties ◽  
Chemical Vapor ◽  
Carbon Films ◽  
Diamond Like Carbon ◽  
Element Analysis ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Diamond-like carbon (DLC) films is useful in many applications. To improve the tribological properties in DLC, we spin coat the multi-walled carbon nanotubes (CNTs) with different solution on (100) silicon. DLC was deposited by plasma enhanced chemical vapor deposition (PECVD) with C2H2and H2. The results show that the ID/IGratio is increasing with higher CNTs content while the friction coefficient and critical load are decreasing with larger CNTs contents. The decreasing friction coefficient results from graphitation on the surface due to higher sp2content. The decreasing critical load is attributed to higher internal stress. The effect of friction coefficient and CNT concentration on stress distribution is studied by a nanoscratch finite element analysis. The results indicate that low friction coefficient and high CNT concentration will reduce the stress magnitude in the film. Therefore, the decreasing friction coefficient in CNT doped DLC film with increasing CNT concentration should reduce stress in the film and is good for adhesion. The discrepancy between friction coefficient and critical load is explained in terms of high internal stress during deposition. A surface treatment on CNT before deposition to reduce internal stress is currently under investigation.

A Mechanism of Sliding on the Nanometer-Thick Ag Layers

2005 ◽  
Author(s):  
F. Honda ◽  
M. Goto
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
High Vacuum ◽  
High Energy ◽  
Thin Layers ◽  
Ultra High Vacuum ◽  
Wear And Friction ◽  
Thickness Measurements

Tribological performance of sub-nano to nanometer-thick Ag layers deposited on Si(111) have been examined to understand the role of surface thin layers to the wear and friction characteristics. The slider was made of diamond sphere of 3 mm in radius. Sliding tests were carried out in an ultra-high vacuum environment (lower than 4 × 10−8 Pa) and analyzed in-situ by Auger electron spectroscopy (AES) for the quantitative thickness-measurements, by reflection high-energy electron diffraction (RHEED) to clarify the substrate cleanliness and crystallography of the Ag films, and by scanning probe microscopy (SPM) for the morphology of the deposited/slid film surfaces. As the results, a minimum of the friction coefficient 0.007 was observed from the film thickness range of 1.5–10 nm, and exactly no worn particles were found after 100 cycles of reciprocal sliding. Results have directly indicated that solid Ag(111) sliding planes allowed to reduce the friction coefficient very low without any detectable wear particles, and Ag nanocrystallites in Ag polycrystalline layers increase the size to 20–40 nm order, during sliding. The friction coefficient was slightly dependent to the normal load. Results were discussed on the role of the surface atoms to the friction, and a mechanism of sliding on Ag thin layers.

scholarly journals Long-lasting injection of solar energetic electrons into the heliosphere

2018 ◽  
Vol 613 ◽  
pp. A21 ◽  
Author(s):  
N. Dresing ◽  
R. Gómez-Herrero ◽  
B. Heber ◽  
A. Klassen ◽  
M. Temmer ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Solar Energetic Particle ◽  
High Energy ◽  
Interaction Region ◽  
Energetic Electrons ◽  
Coronal Activity ◽  
High Energy Particles ◽  
Electron Event

Context. The main sources of solar energetic particle (SEP) events are solar flares and shocks driven by coronal mass ejections (CMEs). While it is generally accepted that energetic protons can be accelerated by shocks, whether or not these shocks can also efficiently accelerate solar energetic electrons is still debated. In this study we present observations of the extremely widespread SEP event of 26 Dec 2013 To the knowledge of the authors, this is the widest longitudinal SEP distribution ever observed together with unusually long-lasting energetic electron anisotropies at all observer positions. Further striking features of the event are long-lasting SEP intensity increases, two distinct SEP components with the second component mainly consisting of high-energy particles, a complex associated coronal activity including a pronounced signature of a shock in radio type-II observations, and the interaction of two CMEs early in the event. Aims. The observations require a prolonged injection scenario not only for protons but also for electrons. We therefore analyze the data comprehensively to characterize the possible role of the shock for the electron event. Methods. Remote-sensing observations of the complex solar activity are combined with in situ measurements of the particle event. We also apply a graduated cylindrical shell (GCS) model to the coronagraph observations of the two associated CMEs to analyze their interaction. Results. We find that the shock alone is likely not responsible for this extremely wide SEP event. Therefore we propose a scenario of trapped energetic particles inside the CME–CME interaction region which undergo further acceleration due to the shock propagating through this region, stochastic acceleration, or ongoing reconnection processes inside the interaction region. The origin of the second component of the SEP event is likely caused by a sudden opening of the particle trap.

scholarly journals Selective Effects in Cosmic Rays Induced by Coulombian Interactions with Finite Temperature Plasmas

1981 ◽  
Vol 94 ◽  
pp. 365-366
Author(s):  
J. Pérez-Peraza ◽  
S. S. Trivedi
Keyword(s):  
Cosmic Rays ◽  
Energy Levels ◽  
Cosmic Ray ◽  
High Energy ◽  
Energy Losses ◽  
Deceleration Rate ◽  
Acceleration Rate ◽  
Charge States ◽  
High Energy Particles

The role of Coulombian energy losses in cosmic ray physics is generally over simplified by using the Bethe-Block formulation which does not depend explicitly on the temperature of the medium. The role of low energy particles is usually neglected, as a result of the over estimation of losses when the temperature of the medium is ignored. A deep analysis of Coulombian losses may raise the importance of these particles in the dynamics of the Galaxy. In fact, the deceleration of these particles is determined by charge interchange processes with the target ions and electrons, which energy dependence is roughly the inverse of ionisation losses. Even high energy particles may be subject to this kind of deceleration if the temperature is very high. The consideration of Coulombian losses through all energy ranges with explicit dependence on the temperature has been discussed by Perez and Lara (1979): a fully ionized medium of hydrogen has been assumed to prevail in most of cosmic ray sources. One kind of the implications is the determination of particle composition. It is claimed that a given kind of ion is preferentially accelerated or depleted depending on whether the acceleration is higher or lower than the deceleration rate at the beginning of the acceleration of thermal material. Species which undergo depletion are accelerated only if their energy is higher than that for which both rates are equated (Ec,E′c and E′c′) in such a way that only those of the hot tails of their thermal distributions are effectively accelerated. These will appear depleted relative to other species which are free accelerated because their deceleration rates at low energies are lower than the acceleration rate. It can be noted in the next figures, that if both rates would not intersect at the beginning of the acceleration, they would not join at higher energies because the acceleration rate grows faster with energy than the deceleration rate. Three arbitrary acceleration rates are used for illustration: Fermi-2nd order (αβW), Betatron or adiabatic heating (αβ2W) and shock wave acceleration (αW), where α, β and W are the efficiency, the particles velocity and the total energy per nucleon respectively. In Fig. 1 it can be seen that this selective acceleration relative to Coulombian losses is defined at different energy levels depending on the kind of acceleration involved. Since the main effect of the temperature on the losses at the beginning of the acceleration is through the local charge states of the ions, the sequence of energy losses among different species is highly assorted. This is translated in a great amount of possibilities of particle enhancements and depletions according to the temperature of the source and the kind of acceleration operating therein. If particles under go acceleration in a fully stripped state, the sequence of losses at all energy levels is such that the heavy elements are depleted in relation with the lighter ones; same is the situation, what-ever the initial charge state, for high energy particles in the range of ionisation. It may be concluded, on basis to the observational enhancement of heavy cosmic rays, that hot regions are not likely sources, and that acceleration initiates from thermal energies. On Fig. 2 it is illustrated the enhancement of Fe over 0 in solar flare conditions, on basis to the charge states as given by Jordan (1969). If α < 2.71 s−1 both elements would be depleted, whereas if α>3.45 s−1 both would be preferentially accelerated.

Friction and wear behavior of hydrogenated diamond-like carbon coating against titanium alloys under large normal load and variable velocity

2017 ◽  
Vol 69 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Jun Liu ◽  
Zhinan Zhang ◽  
Zhe Ji ◽  
Youbai Xie
Keyword(s):  
Friction Coefficient ◽  
Service Life ◽  
Carbon Coating ◽  
Friction And Wear ◽  
Wear Behavior ◽  
Normal Load ◽  
Diamond Like Carbon ◽  
Content Type ◽  
Friction And Wear Behavior ◽  
Dlc Coating

Purpose This paper aims to investigate the effects of reciprocating frequency, large normal load on friction and wear behavior of hydrogenated diamond-like carbon (H-DLC) coating against Ti-6Al-4V ball under dry and lubricated conditions. Design/methodology/approach The friction and wear mechanisms are analyzed by scanning electron microscope, energy dispersive spectroscopy and Raman spectroscopy. Findings The results show that as reciprocating frequency increases under lubricated conditions, the friction coefficient decreases first and then increases. When the reciprocating frequency is 2.54 Hz, the value of friction coefficient reaches the minimum. The friction reduction is because of the transformation from sp3 to sp2, the formation of transfer layer on Ti-6Al-4V ball and the reduction in viscous friction, whereas the increase of friction coefficient is related to wear. In dry conditions, the friction coefficient is between 0.06 and 0.1. And, the service life of H-DLC coating decreases with the increase in reciprocating frequency and normal load. Research limitations/implications It is confirmed that adding the lubricant could prolong the service life of H-DLC coating and reduce friction and wear efficiently. And, the wear mechanisms under dry and lubricated conditions encompass abrasive wear and adhesive wear. Originality/value The results are helpful for application of diamond-like carbon coating.

FEATURES OF PHOTOCONDUCTIVITY OF Ge AND Si WITH DISORDERED REGIONS

2010 ◽  
Vol 24 (31) ◽  
pp. 2985-2996 ◽  
Author(s):  
V. YEVSEYEV
Keyword(s):  
Large Scale ◽  
High Energy ◽  
Fast Neutrons ◽  
Potential Relief ◽  
Photoelectrical Properties ◽  
Recombination Centers ◽  
First Time ◽  
High Energy Particles ◽  
Disordered Regions

Influence of large radiation defects — disordered regions on photoconductivity of semiconductors Ge and Si , compensated as a result of an irradiation with fast neutrons and 1 GeV protons, is investigated. For the first time, the combined role of disordered regions and a large-scale potential relief in photoelectrical properties of Ge and Si , irradiated by high energy particles is defined. The model of photoconductivity that takes into consideration disordered regions as specific sensitizing recombination centers and allows formation of the spatial potential relief is developed.

scholarly journals Uv Galaxies

1983 ◽  
Vol 6 ◽  
pp. 459-466 ◽  
Author(s):  
E. Ye Khachikian
Keyword(s):  
Absolute Magnitude ◽  
High Energy ◽  
List Type ◽  
Type Number ◽  
Nuclear Region ◽  
Continuous Emission ◽  
Radio Halo ◽  
High Energy Particles ◽  
Relativistic Particles

The systematical statement of the concept of the activity of the nuclei of galaxies was first made public by Ambartsumian about 25 years ago (Ambartsumian 1958, 1962, 1965). Since 1965 he has been advancing and developing the idea of the basic role of the nuclei of galaxies in their life and evolution.According to Ambartsumian the “activity” of the nuclei of galaxies manifests itself mainly in the following forms: 1.Outflow of ordinary gas matter (in form of jets or clouds) from the nuclear region at the velocity of up to hundreds of kilometres per second.2.Continuous emission of the flux of relativistic particles or other agents, producing high energy particles, as a result of which a radio halo may form around the nucleus.3.Eruptive ejections of gas matter (M82 type).4.Eruptive ejections of concentrations of relativistic plasma (NGC 4486, 5128, etc.)I should like to emphasize on the form of activity which says: 5.Ejection of compact blue condensations with an absolute magnitude of the order of luminosity of dward galaxies (NGC 3561, IC 1182). Here the division of the nucleus into two or more comparable componentsis also presumed; initiating the formation of multiple galaxies.

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