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Showing 1 - 64 of 64 Journals sorted alphabetically
ACS Central Science     Open Access   (Followers: 9)
ACS Physical Chemistry Au     Open Access   (Followers: 7)
ACS Sensors     Hybrid Journal   (Followers: 7)
Acta Physico-Chimica Sinica     Free  
Advances in Image and Video Processing     Open Access   (Followers: 20)
Advances in Physical Chemistry     Open Access   (Followers: 13)
Annual Review of Physical Chemistry     Full-text available via subscription   (Followers: 14)
Applied Materials Today     Hybrid Journal   (Followers: 1)
Biophysical Chemistry     Hybrid Journal   (Followers: 8)
Catalysis, Structure & Reactivity     Open Access   (Followers: 2)
Chemical Physics     Hybrid Journal   (Followers: 18)
Chemical Physics Letters     Hybrid Journal   (Followers: 17)
Chemistry and Physics of Lipids     Hybrid Journal   (Followers: 2)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Colloids and Surfaces A: Physicochemical and Engineering Aspects     Hybrid Journal   (Followers: 6)
Current Physical Chemistry     Hybrid Journal   (Followers: 1)
Doklady Physical Chemistry     Hybrid Journal  
EPJ B - Condensed Matter and Complex Systems     Hybrid Journal   (Followers: 1)
EPJ E - Soft Matter and Biological Physics     Hybrid Journal   (Followers: 3)
Friction     Open Access   (Followers: 4)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 35)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 1)
Handbook on the Physics and Chemistry of Rare Earths     Full-text available via subscription   (Followers: 2)
Indian Journal of Biochemistry and Biophysics (IJBB)     Open Access   (Followers: 3)
Indian Journal of Chemistry - Section A     Open Access   (Followers: 9)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 6)
International Journal of Quantum Chemistry     Hybrid Journal   (Followers: 5)
International Reviews in Physical Chemistry     Hybrid Journal   (Followers: 3)
Journal of Biophysical Chemistry     Open Access   (Followers: 3)
Journal of Chemical Physics     Hybrid Journal   (Followers: 36)
Journal of Chromatographic Science     Hybrid Journal   (Followers: 15)
Journal of Macromolecular Science, Part B: Physics     Hybrid Journal   (Followers: 2)
Journal of Physical and Chemical Reference Data     Hybrid Journal   (Followers: 4)
Journal of Physical Chemistry A     Hybrid Journal   (Followers: 28)
Journal of Physical Chemistry B     Hybrid Journal   (Followers: 48)
Journal of Physical Chemistry C     Hybrid Journal   (Followers: 36)
Journal of Physical Chemistry Letters     Hybrid Journal   (Followers: 26)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 3)
Journal of Quantum Chemistry     Open Access   (Followers: 1)
Journal of Radiation Research     Open Access   (Followers: 3)
Macromolecular Chemistry and Physics     Hybrid Journal   (Followers: 2)
Molecular Physics: An International Journal in the Field of Chemical Physics     Hybrid Journal   (Followers: 24)
Nature Communications     Open Access   (Followers: 323)
Open Journal of Physical Chemistry     Open Access  
Physical Chemistry     Open Access   (Followers: 2)
Physical Chemistry Chemical Physics     Hybrid Journal   (Followers: 29)
Physical Chemistry Research     Open Access   (Followers: 1)
Physical Review A     Full-text available via subscription   (Followers: 23)
Physical Review Accelerators and Beams     Open Access   (Followers: 3)
Physical Review B     Full-text available via subscription   (Followers: 33)
Physical Review D     Full-text available via subscription   (Followers: 11)
Physical Review E     Full-text available via subscription   (Followers: 41)
Physical Review Letters     Full-text available via subscription   (Followers: 133)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription  
Physics and Chemistry of Liquids: An International Journal     Hybrid Journal  
Physics and Chemistry of the Earth, Parts A/B/C     Hybrid Journal   (Followers: 10)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 2)
Protection of Metals and Physical Chemistry of Surfaces     Hybrid Journal   (Followers: 15)
Revista Fuentes     Open Access  
Russian Journal of Physical Chemistry A, Focus on Chemistry     Hybrid Journal  
Russian Journal of Physical Chemistry B, Focus on Physics     Hybrid Journal  
Solid State Ionics     Hybrid Journal   (Followers: 5)
The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics     Hybrid Journal   (Followers: 29)
The European Physical Journal Special Topics     Hybrid Journal   (Followers: 1)
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Journal Cover
Friction
Journal Prestige (SJR): 0.684
Citation Impact (citeScore): 2
Number of Followers: 4  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2223-7690 - ISSN (Online) 2223-7704
Published by SpringerOpen Homepage  [228 journals]
  • Role of capillary adhesion in the friction peak during the tacky
           transition

    • Abstract: Abstract The friction peak that occurs in tire-road sliding when the contact changes from wet to dry was previously attributed to capillary cohesion, van der Waals attraction, and surface roughness, but the detailed mechanisms have yet to be revealed. In this study, friction and static contact experiments were conducted using a custom-built in situ optical microtribometer, which allowed us to investigate the evolution of the friction, normal load, and contact area between a polydimethylsiloxane (PDMS) film and a silicon nitride ball during water volatilization. The friction coefficient increased by 100%, and the normal force dropped by 30% relative to those in the dry condition during the wet-to-dry transition. In static contact experiments, the probe indentation depth increased, and the normal load decreased by ∼60% as the water evaporated. Combining the friction and static contact results, we propose that the large friction peak that appeared in this study can be attributed to the combined effects of increased adhesive capillary force and increased plowing during the wet-to-dry transition.
      PubDate: 2022-08-01
       
  • Preparation and wear properties of high-vanadium alloy composite layer

    • Abstract: Abstract A high-vanadium alloy composite layer was prepared on the surface of a carbon steel using cast composite technology, and the wear properties of the composite layer were investigated. The results showed that the microstructure of the composite layer was composed of primary vanadium carbides (VC), flake martensite, residual austenite, and fine VC. The hardness of the cast alloy layer was 63 HRC. The abrasive wear resistance and impact wear resistance were increased by 60% and 26%, respectively, compared with those of high-chromium cast iron. The excellent wear resistance of the cast alloy layer is attributed to the high-hardness primary vanadium carbide and the large number of fine secondary vanadium carbides precipitated out of the cast alloy layer.
      PubDate: 2022-08-01
       
  • Robust scalable reversible strong adhesion by gecko-inspired composite
           design

    • Abstract: Abstract Bio-inspired reversible adhesion has significant potential in many fields requiring flexible grasping and manipulation, such as precision manufacturing, flexible electronics, and intelligent robotics. Despite extensive efforts for adhesive synthesis with a high adhesion strength at the interface, an effective strategy to actively tune the adhesion capacity between a strong attachment and an easy detachment spanning a wide range of scales has been lagged. Herein, we report a novel soft-hard-soft sandwiched composite design to achieve a stable, repeatable, and reversible strong adhesion with an easily scalable performance for a large area ranging from ∼1.5 to 150 cm2 and a high load ranging from ∼20 to 700 N. Theoretical studies indicate that this design can enhance the uniform loading for attachment by restraining the lateral shrinkage in the natural state, while facilitate a flexible peeling for detachment by causing stress concentration in the bending state, yielding an adhesion switching ratio of ∼54 and a switching time of less than ∼0.2 s. This design is further integrated into versatile grippers, climbing robots, and human climbing grippers, demonstrating its robust scalability for a reversible strong adhesion. This biomimetic design bridges microscopic interfacial interactions with macroscopic controllable applications, providing a universal and feasible paradigm for adhesion design and control.
      PubDate: 2022-08-01
       
  • Load dependent microstructural evolution in an as-cast 26% Cr high
           chromium cast iron during unlubricated sliding

    • Abstract: Abstract In the current study, an as-cast 26% Cr high chromium cast iron (HCCI) alloy was subjected to dry-sliding linear wear tests, under different loads. The loads were selected based on analytically computing the critical load (PC) i.e., the load necessary to induce plastic deformation. The PC was calculated to be 15 N and accordingly, a sub-critical load (5 N) and an over-critical load (20 N) were chosen. The influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding carbides. The morphological aspects of the wear tracks, and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM), respectively. No evidence of plastic deformation of the matrix was observed below PC. On the contrary, at loads equal to and higher than PC, the austenitic matrix plastically deformed as evidenced by the presence of slip bands. Electron backscattered diffraction (EBSD) measurements in terms of grain reference orientation deviation, and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40 µm at the maximum applied load of 20 N. The active wear mechanisms during sliding were a combination of both adhesive and abrasive wear, although increasing the load shifted the dominant mechanism towards abrasion. This was primarily attributable to the increased propensity for carbide cracking and fracturing, combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide fragments. Moreover, the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently, the wear rate.
      PubDate: 2022-08-01
       
  • An advanced efficient model for adhesive wear in elastic—plastic
           spherical contact

    • Abstract: Abstract A finite element (FE) model combining submodel technique is presented for the adhesive wear in elastic—plastic spherical contact. It consists of a global model, showing the potential location of fracture under combined normal and tangential loading, and a refined mesh submodel covering only the region near the potential fracture. This allows to describe the morphology of wear particle more accurately than that in a previously developed model by the authors. A range of normal loading is studied to show its effect on the shape and volume of wear particles. Two main regimes of mild and severe wear (along with a relatively narrow transition region between them) are found, which show almost linear and power-law dependency of wear rate on normal loading, respectively. Such behavior agrees with published experimental observations. However, the transition region is theoretically predicted here for the first time.
      PubDate: 2022-08-01
       
  • Bio-inspired smart surface to achieve controllable locomotion through
           adjustable anisotropic friction

    • Abstract: Abstract Anisotropic friction generated by microstructured surfaces is crucial for performing functions such as directional locomotion and adhesion in biological systems. Hence, an epoxy-based shape memory polymer (SMP) incorporating Fe3O4 nanoparticles is used in this study to create a smart surface with oriented structures to mimic anisotropic friction and exploit human-developed controllable locomotion systems. Applying the specific properties of the epoxy-based SMP, fast switching friction can be achieved by adjusting the topography and stiffness of the microstructures on the surface. In addition, the photothermogenesis effect of Fe3O4 nanoparticles induces changes in the asymmetric topography and stiffness on the SMP surface under the irradiation of near-infrared (NIR) light, thereby inducing a rapid switching of the friction force. Furthermore, a microbot is created to demonstrate remotely controlled locomotion, such as unidirectional and round-trip movements, and braking by switching the friction force under NIR light. These results are promising for the design of new intelligent surfaces and interfaces; additionally, they may facilitate the investigation of biological structures and processes.
      PubDate: 2022-08-01
       
  • Laser pattern-induced unidirectional lubricant flow for lubrication track
           replenishment

    • Abstract: Abstract Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation. Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades. This paper proposes the use of surface effect, wettability gradient, to achieve the goal. This method is simple and can be nicely implemented using femtosecond laser ablation. A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied. Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution, thereby escalating oil replenishment to the lubrication track. The effect is due to the unbalanced interfacial force created by the surface pattern. The influence of the shape and the pitch of teeth, which are the two governing factors, on oil transport is also reported. The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply. These results are promising, demonstrating the reduction in bearing friction and the increase in lubricating film thickness.
      PubDate: 2022-08-01
       
  • Tribological performance and scuffing behaviors of several automobile
           piston rings mating with chrome-plated cylinder liner

    • Abstract: Abstract The friction and wear properties, as well as the scuffing resistance, of different piston-ring coatings mating with a chrome-plated cylinder liner were investigated. Interrupted wear tests under the lubricant starvation condition were conducted to examine the wear behavior of Cr-diamond coating (GDC) and diamond-like coating (DLC). The results indicated that the DLC coating had outstanding tribological properties (small coefficient of friction and wear loss) at 150 °C, while the GDC coating exhibited better performance at an elevated temperature (240 °C). The DLC coating had a better scuffing resistance; no material adhesion occurred for 70 min under the unlubricated condition. The interrupted wear behaviors revealed that the scuffing process of the GDC coating involved the consumption of lubricant oil with relatively stable wear, a reduction in the friction force, and the occurrence of scuffing, in sequence. In contrast, although the friction force also increased after a short period of weak friction, no scuffing was observed. This is attributed to the formation of a mixed oxide and graphitic C tribolayer.
      PubDate: 2022-08-01
       
  • Unlocking the secrets behind liquid superlubricity: A state-of-the-art
           review on phenomena and mechanisms

    • Abstract: Abstract Superlubricity, the state of ultralow friction between two sliding surfaces, has become a frontier subject in tribology. Here, a state-of-the-art review of the phenomena and mechanisms of liquid superlubricity are presented based on our ten-year research, to unlock the secrets behind liquid superlubricity, a major approach to achieve superlubricity. An overview of the discovery of liquid superlubricity materials is presented from five different categories, including water and acid-based solutions, hydrated materials, ionic liquids (ILs), two-dimensional (2D) materials as lubricant additives, and oil-based lubricants, to show the hydrodynamic and hydration contributions to liquid superlubricity. The review also discusses four methods to further expand superlubricity by solving the challenge of lubricants that have a high load-carrying capacity with a low shear resistance, including enhancing the hydration contribution by strengthening the hydration strength of lubricants, designing friction surfaces with higher negative surface charge densities, simultaneously combining hydration and hydrodynamic contribution, and using 2D materials (e.g., graphene and black phosphorus) to separate the contact of asperities. Furthermore, uniform mechanisms of liquid superlubricity have been summarized for different liquid lubricants at the boundary, mixed, and hydrodynamic lubrication regimes. To the best of our knowledge, almost all the immense progresses of the exciting topic, superlubricity, since the first theoretical prediction in the early 1990s, focus on uniform superlubricity mechanisms. This review aims to guide the research direction of liquid superlubricity in the future and to further expand liquid superlubricity, whether in a theoretical research or engineering applications, ultimately enabling a sustainable state of ultra-low friction and ultra-low wear as well as transformative improvements in the efficiency of mechanical systems and human bodies.
      PubDate: 2022-08-01
       
  • Optimization of several surface treatment processes for alleviating
           fretting damage of a locking pin

    • Abstract: Abstract The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism. The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage. Based on the two basic principles of surface strengthening and friction reduction, a substrate (AISI 4135 steel) surface was treated by laser quenching (LQ), plasma nitriding (PN), and bonded MoS2 coating. Systematic fretting wear tests were conducted, and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated. The results indicate that the wear resistances of the LQ- and PN-treated surfaces were significantly improved, and their main wear mechanisms were abrasive wear, delamination, and oxidation wear. The MoS2 coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property, but it incurs the highest wear rate and failure in the form of plastic deformation. Furthermore, the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface, consequently resulting in a significant reduction in wear. An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation, which provides a reference for the anti-fretting protection of related mechanical components.
      PubDate: 2022-08-01
       
  • RETRACTED ARTICLE: Thermal, mechanical, and tribological properties of
           sodium-montmorillonite-nanoparticle-reinforced polyethersulfone and
           polytetrafluoroethylene ternary composites

    • Abstract: The Editor-in-Chief has retracted this article [1] because a large number of figures as well significant parts of the text overlap with the 2017 Ph.D. thesis by Zhen Zuo [2]. All authors agree to this retraction.
      PubDate: 2022-07-01
       
  • RETRACTED ARTICLE: Structural and contact analysis of a three-dimensional
           disc-pad model with and without thermal effects

    • Abstract: This article has been retracted at the request of the Editor-in-chief, since substantial parts of this article were previously published in Tribology in Industry: A. Belhocine , N.M. Ghazali, O.I. Abdullah. Structural and Contact Analysis of a 3-Dimensional Disc-Pad Model with and without Thermal Effects. 2014. Tribology in Industry 36(4): 406—418 (2014).
      PubDate: 2022-07-01
       
  • Erratum to: Study on contact fatigue of a wind turbine gear pair
           considering surface roughness

    • Abstract: The article “Study on contact fatigue of a wind turbine gear pair considering surface roughness”, written by Heli LIU, Huaiju LIU, Caichao ZHU, Zhangdong SUN, Houyi BAI, was erroneously originally published online without open access. After online first publication this was corrected and the article is now an open access publication. The article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The original article has been corrected.
      PubDate: 2022-07-01
       
  • Flammable gases produced by TiO2 nanoparticles under magnetic stirring in
           water

    • Abstract: Abstract The friction between nanomaterials and Teflon magnetic stirring rods has recently drawn much attention for its role in dye degradation by magnetic stirring in dark. Presently the friction between TiO2 nanoparticles and magnetic stirring rods in water has been deliberately enhanced and explored. As much as 1.00 g TiO2 nanoparticles were dispersed in 50 mL water in 100 mL quartz glass reactor, which got gas-closed with about 50 mL air and a Teflon magnetic stirring rod in it. The suspension in the reactor was magnetically stirred in dark. Flammable gases of 22.00 ppm CO, 2.45 ppm CH4, and 0.75 ppm H2 were surprisingly observed after 50 h of magnetic stirring. For reference, only 1.78 ppm CO, 2.17 ppm CH4, and 0.33 ppm H2 were obtained after the same time of magnetic stirring without TiO2 nanoparticles. Four magnetic stirring rods were simultaneously employed to further enhance the stirring, and as much as 30.04 ppm CO, 2.61 ppm CH4, and 8.98 ppm H2 were produced after 50 h of magnetic stirring. A mechanism for the catalytic role of TiO2 nanoparticles in producing the flammable gases is established, in which mechanical energy is absorbed through friction by TiO2 nanoparticles and converted into chemical energy for the reduction of CO2 and H2O. This finding clearly demonstrates a great potential for nanostructured semiconductors to utilize mechanical energy through friction for the production of flammable gases.
      PubDate: 2022-07-01
       
  • Photorheological fluids of azobenzene polymers for lubrication regulation

    • Abstract: Abstract Fluid viscosity is ubiquitous property and is of practical importance in intelligent fluids, industrial lubrication, and pipeline fluid transportation. Recently, there has been a surging interest in viscosity regulation. Here, we have developed a group of photorheological fluids by utilizing azobenzene polymers with a light-induced microstructure transformation. In this work, a photosensitive polymer with 4,4′-bis-hydroxyazobenzene as the main chain was designed and synthesized as a pivotal functional material. The sufficiently large structural difference under ultraviolet and near-infrared light makes it possible to regulate the viscosity of a polyethylene glycol solution. The viscosity of the photosensitive rheological fluids under ultraviolet light radiation is found to be up to 45.1% higher than that under near-infrared light radiation. To explore this intelligent lubricating technology, the friction regulation of ceramic sliding bearings was investigated utilizing photosensitive rheological fluids. Reversible friction regulation with a ratio of up to 3.77 has been achieved by the alternative irradiation of near-infrared and ultraviolet light, which can be attributed to the differences in mechanical properties and molecular structures under ultraviolet and near-infrared light according to both simulations and experiments. Such photorheological fluids will have promising applications in controllable lubrication, intelligent rheological fluids, and photosensitive dampers.
      PubDate: 2022-07-01
       
  • Influence of the cage on the migration and distribution of lubricating oil
           inside a ball bearing

    • Abstract: Abstract The migration and distribution of lubricant oil in a rolling bearing strongly affect the elastohydrodynamic lubrication performance between the balls and rings. However, oil re-lubrication is highly dependent on the bearing design, which is different from the ball-on-disc model. This study directly observed the distribution of the lubricant film in a custom-made model-bearing rig, with an outer ring replaced by a glass ring to allow full optical access. The influence of the cage type and surface properties were presented. The physical origin of the re-lubrication mechanism, including capillary flow and mechanical redistribution, was discussed.
      PubDate: 2022-07-01
       
  • Effects of groove-textured surfaces filled with Sn-Ag-Cu and MXene-Ti3C2
           composite lubricants on tribological properties of CSS-42L bearing steel

    • Abstract: Abstract To improve the tribological performance of CSS-42L bearing steel, smooth surfaces (SSs), groove-textured surfaces (GSs), GSs with Sn-Ag-Cu (GSs-SAC), and GSs with Sn-Ag-Cu-Ti3C2 (GSs-SACT) were prepared on CSS-42L. In addition, experimental studies were conducted on tribological properties. The obtained results indicated that GSs-SACT exhibited the best anti-friction and noise reduction performances. These remarkable tribological performances were attributed to the synergistic effects of grooves, Sn-Ag-Cu, and MXene-Ti3C2. The inconsistent rules of frictional forces were improved by the grooves and SACT, which inhibit the friction-induced noise. The micro-nano size-effects of MXene-Ti3C2 enhanced the repairing effect and anti-friction property of composite lubricants, which improved the profile characteristics of GSs-SACT.
      PubDate: 2022-07-01
       
  • One-step method to enhance biotribological properties and biocompatibility
           of DLC coating by ion beam irradiation

    • Abstract: Abstract A one-step method was developed to create a highly biocompatible micropatterned surface on a diamond-like carbon (DLC) through irradiation with a nitrogen ion beam and thus enhance the biocompatibility of osseointegrated surfaces and biotribological performance of articular surfaces. The biocompatibility and biotribological mechanisms were analyzed in terms of the structure and morphology of DLC. It was demonstrated that a layer enriched in sp3 C−N bonds was formed on the surface of the DLC after nitrogen ion beam irradiation. Moreover, with an increase in the radiation dose, the content of sp3 C−N on the DLC surface increased significantly, and the biocompatibility was positively correlated with it. The adhesion of the MC3T3 osteoblasts increased significantly from 32% to 86% under an irradiation dose of 8 × 1015 ions/cm2. In contrast, the micropattern had a significant negative effect on the adhesion of the osteoblasts as it physically hindered cell expansion and extension. The micropattern with a depth of 37 nm exhibited good friction properties, and the coefficient of friction was reduced by 21% at relatively high speeds.
      PubDate: 2022-07-01
       
  • Constructing a biomimetic robust bi-layered hydrophilic lubrication
           coating on surface of silicone elastomer

    • Abstract: Abstract Silicone elastomers-based materials have been extensively involved in the field of biomedical devices, while their use is extremely restricted due to the poor surface lubricity and inherent hydrophobicity. This paper describes a novel strategy for generating a robust layered soft matter lubrication coating on the surface of the polydimethylsiloxane (PDMS) silicone elastomer, by entangling thick polyzwitterionic polyelectrolyte brush of poly (sulfobetaine methacrylate) (PSBMA) into the sub-surface of the initiator-embedded stiff hydrogel coating layer of P(AAm-co-AA-co-HEMA-Br)/Fe, to achieve a unified low friction and high load-bearing properties. Meanwhile, the stiff hydrogel layer with controllable thickness is covalently anchored on the surface of PDMS by adding iron powder to provide catalytic sites through surface catalytically initiated radical polymerization (SCIRP) method and provides high load-bearing capacity, while the topmost brush/hydrogel composite layer is highly effective for aqueous lubrication. Their synergy effects are capable of attaining low friction coefficient (COFs) under wide range of loaded condition in water environment with steel ball as sliding pair. Furthermore, the influence of mechanical modulus of the stiff hydrogel layer on the lubrication performance of layered coating is investigated, for which the COF is the lowest only when the modulus of the stiff hydrogel layer well matches the PDMS substrate. Surprisingly, the COF of the modified PDMS could remain low friction (COF < 0.05) stably after encountering 50,000 sliding cycles under 10 N load. Finally, the surface wear characterizations prove the robustness of the layered lubricating coating. This work provides a new route for engineering lubricious silicon elastomer with low friction, high load-bearing capacity, and considerable durability.
      PubDate: 2022-07-01
       
  • Mechanochemical reactions of GaN-Al2O3 interface at the nanoasperity
           contact: Roles of crystallographic polarity and ambient humidity

    • Abstract: Abstract Mechanochemical reactions of the GaN-Al2O3 interface offer a novel principle for scientific and technological merits in the micro-/nano-scale ultra-precision surface machining. In this work, the mechanochemical reactions on Ga- and N-faced GaN surfaces rubbed by the Al2O3 nanoasperity as a function of the environmental humidity were investigated. Experimental results indicate that the N-face exhibits much stronger mechanochemical removal over the relative humidity range of 20%–80% than the Ga-face. Increasing water molecules in environmental conditions significantly promotes the interfacial mechanochemical reactions and hence accelerates the atomic attrition on N-face. The hypothesized mechanism of the selective water-involved mechanochemical removal is associated with the dangling bond configuration, which affects the mechanically-stimulated chemical reactions via altering the activation energy barrier to form the bonding bridge across the sliding interface. These findings can enrich the understanding of the underlying mechanism of mechanochemical reactions at GaN-Al2O3 interface and a broad cognition for regulating the mechanochemical reactions widely existing in scientific and engineering applications.
      PubDate: 2022-07-01
       
 
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