Swelling Effects on the Conductivity of Graphene/PSS/PAH Composites

Graphene/poly-(sodium-4-styrene sulfonate)(PSS)/poly-(allylamine hydrochloride) (PAH) composite is a frequently adopted system for fabricating polyelectrolyte multilayer films. Swelling is the bottleneck limiting its applications, and its effects on the conductivity is still controversial. Herein, we report successful swelling of a graphene/PSS/PAH composite in a vapor atmosphere, and the relation with the mass fraction of water is uncovered. The composite was prepared via a layer-by-layer assembly technique and systematically characterized. The results indicated that the average thickness for each bilayer was about 0.95 nm. The hardness and modulus were 2.5 ± 0.2 and 68 ± 5 GPa, respectively, and both were independent of thickness. The sheet resistance decreased slightly with the prolongation of immersion time, but was distinct from that of the water mass fraction. It reduced from 2.44 × 105 to 2.34 × 105 ohm/sq, and the change accelerated as the water mass fraction rose, especially when it was larger than 5%. This could be attributing to the lubrication effect of the water molecules, which sped up the migration of charged groups in the polyelectrolytes. Moreover, molecular dynamics simulations confirmed that a microphase separation occurred when the fraction reached an extreme value owing to the dominated interaction between PSS and PAH. These results provide support for the structural stability of this composite material and its applications in devices.

Wear Behaviors of Stainless Steel and Lubrication Effect on Transitions in Lubrication Regimes in Sliding Contact

The wear behavior of AISI304 stainless steel was investigated under dry, water-, and oil-lubricated conditions. A block-on-disk wear test was conducted in this work, since the test conditions could be controlled easily. For oil-lubricated contact, a significant amount of thin and elongated cutting chip-like debris was observed. This is attributed to the high lubricating effect of oil. Strain-induced martensitic (SIM) transformation was observed for all AISI304 blocks after the wear test, while AISI304 consisted of a single γ-austenite phase prior to the wear test. The Stribeck curve and the corresponding lubrication regimes were also considered to explain the wear behaviors and lubrication effect of AISI304. In comparison to the dry or water-lubricated conditions, which fall in the boundary lubrication regime at a low rotation speed, it is considered that the high viscosity of the oil-based lubricant causes the lubrication condition to enter the mixed lubrication regime early at a lower speed, thus reducing the specific wear rate over the 100–300 rpm range.

Research on Active Pressurized Forced Lubrication Deep Drawing Process and Evaluation of Lubrication Effect

Friction and lubrication are important parameters that affect the quality of sheet metal forming, excellent lubrication condition and less harmful friction can reduce local thinning of sheet metal, delay fracture and improve surface quality. Aiming at the poor friction conditions and difficult lubrication in the flange area during deep drawing, an active pressurized forced lubrication deep drawing(FLDD) process was proposed in this paper. A hydraulic system was employed to flush high pressure lubricating oil into the contact gap between die and sheet in the flange area. The high pressure hydrostatic oil film in the contact gap can reduce the real contact area and improve the lubrication condition effectively. The equipment is simple, the cost is low, and lubricating oil pressure can be measured and controlled. Under the conditions of 20kN, 35kN and 50kN blank holder force(BHF), FLDD test of box parts was carried out with 5MPa and 9MPa pressure water-based lubricating oil. The horizontal comparison experiment was conducted with common lubricating media such as polyethylene film(PE film), high-purity molybdenum disulfide particles, vegetable oil and water-based lubricating oil under the same process conditions. Lubrication effect was evaluated by obtaining test data. Test results illustrated that the lubrication effect of high-purity molybdenum disulfide particles was the best and that of vegetable oil was the worst. The lubrication effect of water-based mineral lubricant was significantly improved after pressurization. The maximum forming height was increased by 17.97%, the maximum forming force was reduced by 8.9%, the maximum wall thickness thinning rate was reduced by 7%, and the lubrication effect of 9MPa pressure was superior to that of 5MPa. Although there is still a certain shortfall with special lubricating media such as high-purity molybdenum disulfide, FLDD process has definite application value in improving production environment, pollution control and automatic production.

Lubrication Effect of the Nozzle Layout for Arc Tooth Cylindrical Gears

In order to study the influence of fuel injection nozzle arrangement on the lubrication effect of arc tooth cylindrical gear, a model of fuel injection lubrication was established, and computational fluid dynamics (CFD) software was used for simulation calculation. The focus on the influence of gear parameters, oil jet conditions and nozzle layout on gear lubrication performance is studied. The results show that reducing the oil jet distance not only improves the lubrication performance of the gear but also reduces the offset of the oil jet streamline. The reasonable of nozzle layout is the premise of ensuring better lubrication conditions, and the best nozzle layout scheme is obtained through data comparison analysis. The lubrication effect decreases when the nozzle angle is offset. The lubrication effect does not change when the nozzle is horizontally offset by a distance of 0.5 module in the direction of the pinion, and the lubrication performance is degraded when the distance exceeds 0.5 module. Finally, the influence of nozzle diameter on lubrication is analyzed, the lubrication effect is directly proportional to the nozzle diameter.

Lubrication Effect of Polyvinyl Alcohol/Polyethylene Glycol Gel for Artificial Joints

One of the most common problems encountered by patients using artificial joints is the high wear rate. In this study, a polyvinyl alcohol/polyethylene glycol (PVA/PEG) gel was prepared through the cross-linking reaction between polyvinyl alcohol (PVA) and polyethylene glycol (PEG) solutions. This gel can lubricate artificial joints, thereby lowering their coefficient of friction (COF) and increasing their service life. Various techniques, such as Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, X-ray photon spectroscopy, and thermogravimetric analyses, were used to analyze the structure of this synthetic gel. The tribological results indicated that the synthetic gel’s lubrication effect was the most optimum when it contained PVA (10 wt%) and PEG (15 wt%). An average COF of 0.05 was obtained under a load of 10 N and at a speed of 1.0 cm/s. In addition, the wear rate was reduced in comparison to distilled water. Furthermore, the biological tests proved that the PVA/PEG gel was highly biocompatible. Thus, this study introduces a novel technique to prepare PVA/PEG gels that improve the tribological performance of artificial joints.

Synergistic lubrication effect of antioxidant and low content ZDDP on PFPE grease

Purpose The purpose of this study is to reduce the use of Zinc dialkyl dithiophosphates (ZDDP) and improve the frictional properties and thermal oxidation stability of Perfluoropolyether (PFPE) grease by adding antioxidant additives. The addition of antioxidants can reduce the consumption of ZDDP as an antioxidant, thus improving the anti-wear efficiency of ZDDP and reducing the excess phosphorus element in the grease. Design/methodology/approach In this study, an antioxidant with good comprehensive performance was selected from several antioxidants by tribological tests and high-temperature tests. Then, the effect of its combination additive with ZDDP on PFPE grease was investigated. The anti-wear property, anti-friction property, thermal oxidation stability and extreme pressure property of greases containing different proportions of ZDDP and antioxidant were tested by four-ball tester and synchronous thermal analyzer (STA). The effects of additives on properties of grease were analyzed by SEM, EDS, LSCM, XPS and FT-IR. Findings The research shows that 2,6-Di-tert-butyl-4-methylphenol (BHT) can be used as an antioxidant in combined additives to reduce the antioxidant reactions of ZDDP, thus improving the anti-wear efficiency of ZDDP and further enhancing the anti-wear performance of the grease. Moreover, BHT and ZDDP have a synergistic effect on the high temperature performance of the PFPE grease due to their different antioxidant mechanisms. Social implications In this paper, the problems related to PFPE grease are studied, which has a certain guiding effect on the industrial application of fluorine grease and the related formulation design. Originality/value In this paper, the properties of PFPE grease under different lubricating condition were studied. The synergistic lubrication effect of antioxidant and ZDDP are discussed. It provides experimental and theoretical support for reducing the content of ZDDP and improving the performance of additives.

Comparison of mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation

To compare the merits of Ni and Cu, the mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation were studied. The results demonstrated that the CrBN-Cu coatings presented a lower friction coefficient than CrBN and CrBN-Ni coatings owing to the improved lubrication effect of the CuO layer originating from the tribochemical reaction. However, the hardness decline due to Cu incorporation was much greater than that of Ni incorporation. Thus, the CrBN-Cu coatings exhibited a higher wear rate than the CrBN coating. In contrast, the plastic deformation enhancement induced by Ni incorporation exceeded the hardness decline. Therefore, the wear of CrBN-Ni coatings partially turned to plastic deformation to present a lower wear rate than that of the CrBN coating.

Lubrication Performances of Carbon-Doped MoSe2 Nanoparticles and Their Biocompatibility Characterization In Vitro

Health and environmental protection issues have become major focus areas in many research and development projects. In this context, recent MTT cytotoxicity assessments performed on carbon-doped MoSe2 nanoparticles have indicated that they exhibit excellent biocompatibility. Therefore, these nanoparticles have attracted considerable interest from researchers worldwide. Herein, we report the successful synthesis of carbon-doped MoSe2 nanoparticles using an ultrasonic method to enhance their lubrication effect for use as oil additives. Carbon-doped MoSe2 nanoparticles are smaller than untreated MoSe2 nanoparticles and can easily access the contact area to form a tribofilm, reducing the friction coefficient and generating less wear. Moreover, carbon-doped MoSe2 nanoparticles and waste water prepared with the nanoparticles display excellent biocompatibility. Hence, they can be used in practical applications such as oil additives.