• Journal of Power System Engineering
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• v.14 no.4
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• pp.50-55
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• 2010

In order to investigate tribological effects of nano copper particles impregnated(CuN) on surface polytetrafluoroethylene(PTFE) on sealing wear and an experimental study was carried out to determine the wear behavior of copper nano-particles impregnation two kind thickness in super critical $CO_2$ liquid. Experimental results showed that the friction coefficients of CuN PTFE at the low sliding speed(0.44m/s) and the oil temperature ($60^{\circ}C$) were higher than that of virgin PTFE. And a thin nano copper particles impreganated thickness was formed on the surface in the PTFE and the specimen with this treatment has much better friction properties than the original one. Fortunately, at the high load(80 N) and the oil temperature, the friction coefficient of CuN PTFE was lower than that of virgin PTFE. This evidenced the load carrying capacity of CuN PTFE was much better than that of virgin PTFE under the high load condition(80 N) specially. Therefore, it can be concluded that the friction coefficient variation of CuN PTFE is very small but its wear rate decreases greatly with increase in sliding speed.

• KSTLE International Journal
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• v.1 no.1
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• pp.12-20
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• 2000

Nano-wear and friction of carbon overcoated laser-textured and mechanically-textured computer hard disk were characterised after contact start/stop (CSS) wear test. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties and friction characteristics of the coating arising from the contact start/stop wear test These techniques include: the atomic force microscopy (AFM), the continuous nano-indentation test, the nano-scratch test, the time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and the auger electron spectroscopy (AES). It was shown that the surface roughness of the laser-textured (LT) bump and mechanically textured (MT) Bone was reduced approximately am and 7nm, respectively, after the CSS wear test. The elastic modulus and hardness values increased after the CSS test, indicating straining hardening of the top coating layer, A critical load was also identified fer adhesion failure between the magnetic layer and the Ni-P layer, The TOF-SIMS analysis also revealed some reduction in the intensity of C and $C_2$$F_59$, confirming the wear of lubricant elements on the coating surface.

• Coupled systems mechanics
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• v.11 no.3
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• pp.267-284
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• 2022

Due to the high usage of ABS in industries, such as aerospace, auto, recreational devices, boat, submarines, etc., the purpose of this project was to find a way to weld this material, which gives advantages, such as affordable, high speed, and good connection quality. In this experimental project, the friction welding method was applied with parameters such as numerical control (NC) machine with two different speeds and three cross-sections, including a flat surface, cone, and step. After the end of the welding process, samples were then applied for both tensile and bending tests of materials, and the results showed that, with increasing the machining velocity Considering of samples, the friction of the surface increased and then caused to increase in the surface temperature. Considering mentioned contents, the melting temperature of composite materials increased. This can give a chance to have a better combination of Nanomaterial to base melted materials. Thus, the result showed that, with increasing the weight percentage (wt %) of Nanomaterials contents, and machining velocity, the mechanical behavior of welded area for all three types of samples were just increased. This enhancement is due to the better melting process on the welded area of different Nano contents; also, the results showed that the shape of the welding area could play a significant role, and by changing the shape, the results also changed drastically.A better shape for the welding process was dedicated to the step surface.

• Transactions of Materials Processing
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• v.18 no.6
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• pp.465-470
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• 2009

The frictional behaviors of Cermets/Cr-Ceramics and Cu-Al coatings of piston ring were investigated. Friction tests were carried out by pin-on-disk test and materials properties of coating layer were analyzed by nano indentation tester. The effect of surface roughness of cylinder liner on the friction coefficient was analyzed. This study provided tribological data of hard and soft piston ring coatings against cylinder liner. The surface roughness does exert an influence on the average friction coefficient, with smoother surfaces generally yielding lower friction coefficients. In case of hard-coating, the scratch depth, width and pile-up height had close relationship with hardness. So the scratch width, depth and pile-up height increases with decreasing friction coefficient. But in case of soft-coating, the friction coefficients are strongly dependent on the morphological characteristics such as, scratch depth, width, pile-up height and elastic modulus.

• Transactions of Materials Processing
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• v.21 no.1
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• pp.13-18
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• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• KSTLE International Journal
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• v.8 no.2
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• pp.26-28
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• 2007

Si(100) surfaces were topographically modified i.e. the surfaces were patterned at micro-scale using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and microchannels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating a thin DLC film. The surfaces were then evaluated for their friction behavior at micro-scale in comparison with those of bare Si(100) flat, DLC coated Si(100) flat and uncoated patterned surfaces. Experimental results showed that the chemically treated (DLC coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the surfaces. This indicates that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro-Electro-Mechanical-Systems (MEMS).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.37 no.3
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• pp.33-40
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• 2005

In this study, a nano-colloidal silica sol was applied to control the anti-slip property by spraying on kraft paper. Two kinds of nano-colloidal silica sol which have cationic and anionic charge were applied in kraft paper, and the friction and physical strength properties of kraft paper were investigated. The application of colloidal silica sol on wet web in wet-end process by spraying method was tried to improve the friction property and to avoid the general problems of machine contaminations caused by the scattering of sprayed silica particles in dryer part. The physical properties of sheet were also improved by the application of wet web spraying method, and the optimum conditions of wet web spraying operation were closely related with the conditions of pH and electrical charge of wet web and silica sol.

• Tribology and Lubricants
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• v.17 no.4
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• pp.276-282
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• 2001

Nano adhesion between SPM (scanning probe microscope) tips and 075 (octadecyltrichlorosilane) SAM (self-assembled monolayer) was experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes in various conditions of relative humidity. OTS SAM was formed on Si-wafer (100) surfaces, and Si$_3$N$_4$ tips of different radius of curvature were used. When the surface was hydrophobic, the adhesion and friction forces were found lower than those of bare Si-wafer. Results also showed that micro-adhesion force increased as the relative humidity and the tip radius of curvature increased. The main parameter for affecting the micro-adhesion was found absorbed humidity on the contact surface. These results were discussed with the JKR model and a capillary force caused by absorbed water.

• Tribology and Lubricants
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• v.24 no.5
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• pp.264-268
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• 2008

A large number of additives have been used with the efforts of improving the performance of lubricants used along with the development of internal combustion engine. In this study, nano-sized graphite was used as liquid-lubricant additive. In order to disperse graphite into oil, we esterified the nano-carbon manufactured by our company with various types of alcohol. After measuring the anti-wear in accordance with the types of alcohol and added concentration, it has been found that its anti-wear/friction decrease has been improved in case of adding 0.1% of the sample composed with C12/14 mixed alcohol & hexadecanol.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.159-159
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• 2013

Atomically thin graphene is the ideal model system for studying nanoscale friction due to its intrinsic two-dimensional anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro and nano-mechanical devices. Here, we report that the tribological properties can be easily altered via simple chemical modifications of the graphene surface. Friction force microscopy measurements show that hydrogenated, fluorinated, and oxidized graphenes exhibit, 2-, 6-, and 7-fold enhanced nanoscale friction on their surfaces, respectively, compared to pristine graphene. The measured nanoscale friction should be associated with the adhesive and elastic properties of the chemically modified graphenes. Density functional theory calculations suggest that, while the adhesive properties of chemically modified graphenes are marginally reduced down to ~30%, the out-of-plane elastic properties are drastically increased up to 800%. Based on these findings, we propose that nanoscale friction on graphene surfaces is characteristically different from that on conventional solid surfaces; stiffer graphene exhibits higher friction, whereas a stiffer three-dimensional solid generally exhibits lower friction. The unusual friction mechanics of graphene is attributed to the intrinsic mechanical anisotropy of graphene, which is inherently stiff in plane, but remarkably flexible out of plane. The out-of-plane flexibility can be modulated up to an order of magnitude by chemical treatmentof the graphene surface. The correlation between the measured nanoscale friction and the calculated out-of-plane flexibility suggests that the frictional energy in graphene is mainly dissipated through the out-of-plane vibrations, or the flexural phonons of graphene.