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Chromium nitride (CrN) coatings with different steps of intermediate argon plasma treatments were deposited with primary (200) orientation by multi-arc ion plating technique. By virtue of scanning electron microscopy, X-ray diffraction and high-resolution transmission electron microscopy, the influence of intermediate argon plasma treatments on the coating microstructures, mechanical properties and corrosion properties as well as tribological behaviors in artificial seawater solutions were systematically investigated. It was assumed that the mechanical properties, adhesion strength, corrosion and tribological performances of coatings depended on argon plasma treatment steps. High-performance coatings could be obtained by proper plasma treatment steps. The superior anti-corrosion ability of coating with appropriate treatment steps may be ascribed to the increased charge transfer resistance due to alternative interface and CrN layer and the compact microstructure. On the other hand, the excellent tribological performances in seawater conditions may be attributed to the enhanced mechanical properties. Otherwise, further increase in treatment steps was assumed to distinctly increase defects and deteriorate the coating integrity thus weakening coating properties and behaviors. Copyright © 2016 John Wiley & Sons, Ltd.

Graphene (G) and graphene oxide (GO) were added into epoxy resin (EP) respectively via chemical modification and physical ultrasound technology to improve the tribological behaviour of EP coating. The topographies of G and GO were detected by scanning probe microscopy. The chemical structures of the fillers before and after modification were identified by Fourier transform infrared spectrometer. The across-section topographies of the coatings were detected by scanning electron microscopy. The tribological behaviour of the coatings was evaluated by UMT-3 tribology tester, surface profiler and scanning electron microscopy. The results revealed that the coefficient of friction of the coatings decreased, and the wear resistance of the coatings improved with the addition of the G and GO. GO could improve the tribological performance of EP further compared to G. When containing 0.5 wt% G and 0.75 wt% GO, the coatings had the lowest coefficient of friction and best wear resistance. When the contents of G reached 0.75 wt%, and GO reached 1 wt%, the tribological performance of the composite coatings decreased as a result of the agglomeration of the fillers. Finally, the anti-friction and anti-wear mechanisms of G-EP and GO-EP composite coatings were discussed in detail based on the results obtained in the preceding texts. Copyright © 2016 John Wiley & Sons, Ltd.

Transformers are imaginary hard robots that could deform into various shapes according to external circumstances, and the development of intelligent soft Transformers is of great interest. Herein, novel remotely controlled soft Transformers based on a shape memory hydrogel system is proposed. The hydrogel is obtained by embedding Fe3O4 magnetic nanoparticles into a poly(N‐(2‐hydroxyethyl) acrylamide)‐gelatin double network structure. The reversible coil‐triple‐helix transformation of gelatin renders the hydrogel with shape memory and self‐healing behaviors. The introduction of Fe3O4 nanoparticles provides both photothermal heating and magnetic manipulation functions. The hydrogel can deform on navigation in a magnetic field, and the deformed shape can be fixed and shape recovery can also be accomplished with the assistance of light irradiation. Taking advantage of the magnetically driven actuation and light‐assisted shape memory, remotely controlled shape memory process can be accomplished. Moreover, a series of soft robots, including hydrogel athlete which can do sit‐ups, hydrogel Transformers that can deform and navigate through a maze, hydrogel space station and hydrogel spacecraft that can be docked in the air, are fabricated. This work will inspire the design and fabrication of novel smart polymer systems with synergistic functions.

Novel 3D hierarchically porous and nitrogen-doped graphene-like microspheres (3D NPGSs) are prepared by precursor-assisted chemical vapor deposition. 3D NPGSs obtained by using Ni microspheres as a structural template exhibit a 3D conductive framework, and have a well-defined porous structure, large surface area and appropriate heteroatom doping, making them suitable for high-performance storage of lithium ions. Consequently, a good rate capability and excellent cycle performance are achieved using the 3D NPGSs as anodes for lithium storage, and a high reversible capacity of 840 mA h g−1 is obtained after 200 cycles. For a further capacitance boost, a thin layer of iron oxide nanoparticles is deposited onto the 3D NPGSs. The resulting 3D FeOx–NPGS electrode exhibits a stable reversible capacity up to 1343 mA h g−1 after 100 cycles.

Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric microsupercapacitor is prepared using a simple electro-deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as-made GQDs micro-supercapacitor has superior rate capability up to 1000 V s − 1 , excellent power response with very short relaxation time constant ( τ 0 = 103.6 μ s in aqueous electrolyte and τ 0 = 53.8 μ s in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO 2 asymmetric supercapacitor is also built using MnO 2 nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specifi c capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro-supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.

Nanofibrous biocomposite scaffolds of poly(vinyl alcohol) (PVA) and graphene oxide (GO) were prepared by using electrospinning method. The microstructure, crystallinity, and morphology of the scaffolds were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The mechanical properties were investigated by tensile testing. Moreover, Mouse Osteoblastic Cells (MC3T3-E1) attachment and proliferation on the nanofibrous scaffolds were investigated by MTT [3-(4,5-dimeth-ylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, SEM observation and fluorescence staining. XRD and FTIR results verify the presence of GO in the scaffolds. SEM images show the three-dimensional porous fibrous morphology, and the average diameter of the composite fibers decreases with increasing the content of GO. The mechanical properties of the scaffolds are altered by changing the content of GO as well. The tensile strength and elasticity modulus increase when the content of GO is lower than 1 wt %, but decrease when GO is up to 3 and 5 wt %. MC3T3-E1 cells attach and grow on the surfaces of the scaffolds, and the adding of GO do not affect the cells' viability. Also, MC3T3-E1 cells are likely to spread on the PVA/GO composite scaffolds. Above all, these unique features of the PVA/GO nanofibrous scaffolds prepared by electrospinning would open up a wide variety of future applications in bone tissue engineering and drug delivery systems.

Molecular dynamics simulations are performed on the atomic origin of the growth process of graphite-like carbon film on silicon substrate. The microstructure, mass density, and internal stress of as-deposited films are investigated systematically. A strong energy dependence of microstructure and stress is revealed by varying the impact energy of the incident atoms (in the range 1–120 eV). As the impact energy is increased, the film internal stress converts from tensile stress to compressive stress, which is in agreement with the experimental results, and the bonding of C-Si in the film is also increased for more substrate atoms are sputtered into the grown film. At the incident energy 40 eV, a densification of the deposited material is observed and the properties such as density, sp 3 fraction, and compressive stress all reach their maximums. In addition, the effect of impact energy on the surface roughness is also studied. The surface morphology of the film exhibits different characteristics with different incident energy. When the energy is low (

Four kinds of molecularly thin films of room temperature ionic liquids (RTILs) with different functional cations were prepared on silicon substrates by dip-coating method. Thermal stability of the RTILs was evaluated using Mettler thermal gravity analysis (TGA) in a nitrogen atmosphere. Chemical compositions of the RTIL nanofilms were examined by means of multifunctional XPS. Nanoscaled adhesion and friction forces between the films and AFM tip were measured by FFM whereas the morphologies of the films were also investigated. Microscaled friction and wear behaviors between the films and Si3N4 ball were further measured by the microtribometer. The micro/nanotribological behaviors of different RTIL films were comparatively investigated and discussed in terms of functional cations of the RTILs molecules. Results in this paper revealed that the functional cations of the RTIL films significantly affected their tribological behaviors both in micro- and nanoscales. The corresponding micro/nanotribological mechanism of the tested ultrathin RTIL films under the test conditions was consequently proposed based on the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.

TiC/a-C:H and a-C:H nanocomposite coatings were prepared on AISI 440C steel substrates using magnetron sputtering process. A comparative study was made on their composition and microstructure by Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). The tribological properties of two types of carbon-based coatings were investigated by pin-on-disc tribometer under the sand-dust conditions concerning the influence of applied load, amount of sand and sand particle sizes. The results show that these carbon-based coatings exhibited high tribological performance with low friction coefficient and wear rate under the sand-dust environments. However, the TiC/a-C: H coatings exhibit relatively higher fluctuant friction coefficient as well as higher wear rate in comparison with the a-C: H coatings under sand-dust environments. The formation of nanocrystalline hard TiC phase distributed in amorphous carbon matrix decreased the residual stress but significantly increased the hardness and Young's modulus of TiC/a-C: H coatings, and consequently caused a relatively higher abrasive and fatigue wear loss under the sand-dust conditions.

Several single-component and two-component imidazolium ionic liquids (ILs) ultrathin films were formed on Si substrates by a dip-coating and heat treatment process. The formation and surface properties of the films were analyzed by means of ellipsometric thickness measurement, X-ray photoelectron spectra and atomic force microscope. The adhesive and nanotribological behaviors of the films were evaluated by a homemade colloidal probe. A ball-on-plate tribometer was used to test the microtribological performances of these films. As a result, the two-component ILs ultrathin film containing 80% solid-like ILs phase shows more homogenous surface morphologies and optimal micro/nano-tribological properties as compared to single-component ILs films, which is ascribed to a synergic effect between the steady solid-like ILs phase as the backbone and the proper amount of flowable liquid-like ILs phase. By studying the influence of various solid/liquid ILs ratios on tribological properties of the two-component ILs films, we might find the way to design ILs films with excellent comprehensive tribological properties. Copyright © 2010 John Wiley & Sons, Ltd.

Hydrogenated nanocomposite aluminum/carbon thin films (Al/a-C:H) were fabricated on stainless steel and silicon wafer substrates via unbalanced reactive magnetron sputtering from an Al target in CH4/Ar plasma. The composition and structure of Al/a-C:H films were investigated by high-resolution transmission electron microscope (HRTEM), XPS and micro-Raman spectroscopy. Nanoindenter, interferometer and ball-on-disc tribometer were carried out to evaluate the hardness, internal stress and tribological properties of Al/a-C:H films. HRTEM observations confirmed that the metallic Al nanocrystallites were uniformly dispersed in the amorphous carbon matrix. XPS and Raman analyses indicated that the sp2 content increased with the increase of Al content in the films. Nanoindenter and interferometer tests exhibited that the uniform incorporation of Al nanocrystallites can diminish drastically the magnitude of internal stress with maintaining the higher hardness of as-deposited films. Especially, the ball-on-disc tribometer measurements revealed that the nanocomposite film with 2.3 at.% Al content exhibited relatively better wear resistance and self-lubrication performance with a friction coefficient of 0.06 and wear rate of 3.1 × 10−16 m3/ N·m under ambient air, which can be attributed to the relatively higher hardness, the formation of continuous graphitized transfer film on counterface and the reduced reaction of oxygen with carbon. Copyright © 2010 John Wiley & Sons, Ltd.

A G 4.0 dendrimer-like poly(amido amine) (PAMAM) based on silica nanoparticles was fabricated via a divergent approach. It was built from γ-aminopropyl silica nanoparticles (APSN) core via repetitive addition of acrylate (MA) and hexylenediamine (HDA). FT-IR and EA were used to monitor the progress of dendrimer during each step. The amino group content of the resulting product increased from 0.49 to 3.72 mmol/g after the 4th generation. In addition, the percentage of grafting increased with increasing generation and reached to 65.9% after 4th generation. It was found that the resulting silica nanoparticles could be dispersed in methanol with a mean hydrodynamic particle diameter of 152.7 nm although the silica nanoparticles had agglomerated during the storage period.

Acrylonitrial butadiene rubber (NBR)/Polyvinyl chloride (PVC) composites with different PVC content were prepared. The effect of PVC content on the mechanical strength and tribological properties of the NBR/PVC composites was investigated. The morphologies of the worn traces and debris of NBR/PVC composites and worn traces of mating ball were observed using a scanning electron microscope (SEM). It was found that the friction and wear of NBR/PVC was lower than that of NBR without PVC. The NBR/PVC composite with 30% PVC content showed the best synthetic mechanical and tribological properties. The inferior elastic properties and the lesser deformation under the applied load of composites with PVC resulted in hysteric force and adhesion force decrease, which leading to a lower friction and wear of NBR/PVC composites. The frictional failure unit of NBR70/PVC30 composite being smaller should be an important reason of the wear of the composite being lowest. The lubricating effect of PVC played an important role in decreasing the friction coefficient and wear of NBR/PVC composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Micrometer- and nanometer-Al2O3-particle-filled poly(phthalazine ether sulfone ketone) (PPESK) composites with filler volume fractions ranging from 1 to 12.5 vol % were prepared by hot compression molding. We evaluated the tribological behaviors of the PPESK composites with the block-on-ring test rig by sliding PPESK-based composite blocks against a mild carbon steel ring under dry-friction conditions. The effects of different temperatures on the wear rate of the PPESK composites were also investigated with a ball-on-disc test rig. The wear debris and the worn surfaces of the PPESK composites were investigated with scanning electron microscopy, and the structures of the PPESK composites were analyzed with IR spectra. The lowest wear rate, 7.31 × 10−6 mm3 N−1 m−1, was obtained for the composite filled with 1 vol %-nanometer Al2O3 particles. The composite with nanometer particles exhibited a higher friction coefficient (0.58–0.64) than unfilled PPESK (0.55). The wear rate of 1 vol %-nanometer-Al2O3-particle-filled PPESK was stable and was lower than that of unfilled PPESK from the ambient temperature to 270°C. We anticipate that 1 vol %-nanometer-Al2O3-particle-filled PPESK can be used as a good frictional material. We also found that micrometer-Al2O3-particle-filled PPESK had a lower friction coefficient at a filler volume fraction below 5%. The filling of micrometer Al2O3 particles greatly increased the wear resistance of PPESK under filler volume fractions from 1 to 12.5%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 993–1001, 2005

The communication provides a novel and alternative route to generate chemically techered binary polymerbursh pattern through two-step surface-initiated atomictransfer radical polymerization (SI-ATRP). Polymer brushwas prepared by S1-ATRP, passivated by a reaction with NaN 3 and etched with CV irradiation through a transmission electron microscopy grid to create exposed sites for the subsequently attached initiator on which polymer brush-2 was grown.

Langmuir—Blodgett (LB) films of 22-tricosenoic acid and of 22-tricosenoic acid polymerised in the presence of an electron beam, and in situ composite LB films of 22-tricosenoic acid/CdS were prepared. The friction and wear behaviour of the LB films were investigated with a ball-on-block one-way reciprocating friction tester. The structures and morphologies of the LB films were analysed and observed using atomic force microscopy. The wear resistance of the LB films was increased after polymerisation of the acid, and the composite LB film of 22-tricosenoic acid/CdS showed better wear resistance because the inorganic nanocores of CdS acted to resist wear and to carry load. The LB film of the acid experienced structural changes during the friction process.

Diethyldithiocarbamyl-modified silica nanoparticles were prepared and used as macroinitiator for the surface-initiated atom transfer radical polymerization (SI-ATRP) of styrene under UV irradiation. Well-defined polymer chains were grown from the nanoparticle surfaces to yield particles composed of a silica core and a well-defined, densely grafted outer PS layer with a mass ratio of styrene to silica, or percentage grafting, of 276.3% after an UV irradiation time of 5 h. Copyright © 2004 Society of Chemical Industry

A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of sophoridine and matrine in rat plasma. Sophoridine and matrine in the resulting supernatant of the plasma deproteinized with acetonitrile containing an internal standard (acetanilide) were directly determined by reversed-phase HPLC and ultraviolet detection. The result of limits of quantitation for matrine and sophoridine were 200 and 350 ng/mL in plasma, respectively, and recovery of both analytes was greater than 98%. The assay was linear from 250 to 4000 ng/mL for matrine and from 500 to 8000 ng/mL for sophoridine. Variation over the range of the standard curve was less than 15%. The method was used to determine the concentration-time profiles of matrine and sophoridine in the plasma following oral administration of Kexieling tablets, which is one of the preparations of Kudouzi at a dose equivalent to 30 and 60 mg/kg of matrine and sophoridine, respectively.

Micrometer and nanometer TiO2 particle-filled poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions from 0.5 to 7.5 vol % were prepared by heating compression molding. The friction and wear behaviors of the PPESK composites were evaluated using the block-on-ring test rig by sliding PPESK-based composite blocks against a mild carbon steel ring under dry friction conditions. The wear debris and the worn surfaces of the PPESK composites filled with micrometer and nanometer TiO2 particles were investigated by using a scanning electron microscope (SEM), while the structures of PPESK composites and wear debris were analyzed with IR spectra. Experimental results show that antiwear properties of the PPESK composites can be improved greatly by filling nanometer TiO2 particles, and the friction coefficient decreases when the filler volume fraction is below 2.5%, but when the filler volume fraction is above 2.5% the friction coefficient increases gradually with increasing filler volume fraction. In the case of micrometer TiO2 filler, wear rates increase with increasing filler volume fractions under identical test conditions, and the friction coefficients are less sensitive to the filler volume fraction. It was also found that the wear mechanism of micrometer TiO2 particle-filled PPESK is mainly severe adhesion and abrasive wear, while that of nanometer TiO2 particle-filled PPESK is mainly slight abrasive wear. In the former case, there are no transfer film formed on the surface of the counterpart steel, and wear debris are in the form of long and large ribbon. While in the latter case, the wear debris was granule and their size was about 10 μm. In case of 1 vol % nanometer TiO2 particle-filled PPESK composites, the transfer film was fairly thinner and smoother, and the transfer film provided better coverage on the surface of steel ring, while that of 7.5 vol % was thicker and discrete. These account for the different friction and wear behavior of micrometer and nanometer TiO2 particle-filled PPESK composite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 906–914, 2004

An N-modified nano / micrometre borate (MNMB) as an oil additive was synthesised by an ultrasonic dispersion and emulsion reaction in the microemulsion phase. The particles of the MNMB additive were between 20 and 500 nm in diameter. The tribological properties of the MNMB as an oil additive were investigated using a four-ball tester. The results reveal that the MNMB possesses good tribological properties. When the boron concentration is 0. 05 wt. %, the wear-scar diameter is smallest and the seizure load is highest. The antiwear and extreme-pressure properties of the MNMB were best at a viscosity of 65. 3 mms2. Small-area X-ray photoelectron spectroscopy (XPS) and electron probe microanalysis (EPMA) indicate that the MNMB additive can form a tribological mixed reaction film containing C, O, B, N, and Na on a rubbing surface. The elemental boron exists in four different chemical states, but is mainly present in the form of BN on the rubbing surface.

An amine salt of an alkoxylphosphate (a P- and N-containing organic compound, PN) was synthesised. Its extreme-pressure, antiwear, and friction-reducing properties were evaluated as an additive in liquid paraffin and a mineral oil. Tests were performed on a four-ball friction and wear tester with an AISI 52100 steel ball self-mated pair and the results were compared with those of sulphurised olefin (SO), zinc di-n-butyldithio-phosphate (ZDDP), and dibutylphosphite (DBP). The morphologies of the worn steel surfaces were observed using a scanning electron microscope, while the binding energies of some typical elements on the worn surfaces were determined using X-ray photoelectron spectroscopy. The additives were found to increase the load-carrying capacity and to reduce wear and friction coefficient considerably. PN as an additive exhibits better load-carrying, antiwear, and friction-reducing properties than SO, ZDDP, and DBP under the same test conditions.

SiO2 nanoparticle filled–poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions were made by heating compression molding. The tribological behavior of the PPESK composites was investigated using a block-on-ring test rig by sliding PPESK-based composite blocks against a mild carbon steel ring. The morphologies of the worn composite surfaces, wear debris, and the transferred films formed on the counterpart steel surface were examined with a scanning electron microscope, whereas the chemical state of the Fe element in the transfer film was analyzed with X-ray photoelectron spectroscopy. In addition, IR spectra were taken to characterize the structure of wear debris and PPESK composites. It was found that SiO2 nanoparticle filled–PPESK composites exhibit good wear resistance and friction-reduction behavior. The friction and wear behavior of the composites was improved at a volume fraction between 4.2 and 14.5 vol % of the filler SiO2. The results based on combined SEM, XPS, and IR techniques indicate that SiO2 nanoparticle filled–PPESK composite is characterized by slight scuffing in dry sliding against steel and polishing action between composite surface and that of the countpart ring, whereas unfilled PPESK is characterized by severe plastic deformation and adhesion wear. In the former case a thin, but not complete, transfer film was formed on the surface of the counterpart steel, whereas in the latter case, a thick and lumpy transfer film was formed on the counterpart steel surface. This accounts for the different friction and wear behavior of unfilled PPESK and SiO2 nanoparticle filled–PPESK composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2136–2144, 2002

The tribological behavior of poly(tetrafluoroethylene) composites filled with various metallic particles was investigated under the extreme friction conditions of a heavy load and reciprocation with a small amplitude. Two obviously distinct friction stages corresponding to the contact conditions were found. The phenomena of the accumulation of fillers on the contact surface and extrusion wear of the poly(tetrafluoroethylene) matrix were also observed. Based on the experimental results, the actions of metallic fillers on the transfer film formation were analyzed. It was noted that the transfer and accumulation of fillers could actually be considered to be an assimilating process of the friction pairs. Accordingly, the physical model of the transfer film formation process was described and some suggestions on the mechanism of load-supporting actions of hard fillers were also proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1832–1840, 2002

Oil–water emulsions stabilized by surfactants are fine dispersions of oil in water or of water in oil and difficult to separate which will lead to serious water pollution. A more recent development is the ability to fabricate oleophobic–hydrophilic surfaces in air, which are not easy to construct due to the difference surface tension between water and oil. Herein, a cellulose sponge with multipore structure is fabricated to increase the removal efficiency. Amphiphilic molecular brushes of polyethylene glycol with short perfluorinated end caps (F-PEG) are grafted on cellulose sponges to solve the contradictory relation of hydrophilicity and oleophobicity and improve oil/water selective wettability and fouling resistance. Besides, stable superhydrophilicity and superoleophobicity under water, corrosive liquids, and high oleophobicity in air conditions are exhibited in the F-PEG grafted porous cellulose sponges with textured surfaces (F-g-CS). And the separation efficiency and rate of F-g-CS with surface of nanopores are 99.92% and 180 L m−2 h−1, while that of micropores are 99.83% and 297 L m−2 h−1 only under gravity. It is demonstrated that the grafting F-PEG molecules imparted F-g-CS of micropores surface with high flux and separation efficiency simultaneously. Furthermore, antifouling property and collection of water in oil–water mixture without fouling are possessed in F-g-CS.

The load-carrying capacity, antiwear, and friction reduction properties of a novel S—P—N additive (BMDDP) added to a synthetic lubricant, polyalphaolefin (PAO), were evaluated using a four-ball test machine. The results were compared with those of a commercial S—P—N additive (T307), and show that BMDDP is an excellent extreme pressure and antiwear additive in polyalphaolefin, similar to T307. The rubbed surfaces were investigated using X-ray photoelectron spectroscopy, and the antiwear mechanism is discussed.

Polytetrafluoroethylene (PTFE)-based composites filled with various inorganic fillers in a volume fraction of 30% were prepared. The tribological behavior of the PTFE composites sliding against AISI52100 steel under dry and liquid paraffin-lubricated conditions was investigated on an MHK-500 model ring-on-block test rig. The morphologies of worn surfaces and wear debris were observed with a scanning electron microscope (SEM) and an optical microscope. As the results, different fillers show different effects on the tribological behavior of the PTFE composites, while the composite shows much different tribological behavior under lubricated conditions as compared with dry sliding. The tribological behavior of the PTFE composites under dry sliding is greatly related to the uniformity and thickness of the transfer films. Only the PTFE composites with a transfer film of good uniformity and proper thickness may have excellent tribological behavior. The PTFE composites show much better tribological behavior under lubrication of liquid paraffin than under dry sliding, namely, the friction coefficients are decreased by 1 order of magnitude and the wear rate by 1–3 orders of magnitude. Observation of the worn composite surfaces with SEM indicates that fatigue cracks were generated under lubrication of liquid paraffin, owing to the absorption and osmosis of liquid paraffin into the microdefects of the PTFE composites. The creation and development of the fatigue cracks led to fatigue wear of the PTFE composites. This would reduce the mechanical strength and load-supporting capacity of the PTFE composites. Therefore, the tribological behavior of the PTFE composites under lubrication of liquid paraffin is greatly dependent on the compatibility between the PTFE matrix and the inorganic fillers. In other words, the better is the compatibility between PTFE and fillers the better is the tribological behavior of the composites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1891–1897, 2001

Composites of polyphenylene sulfide (PPS) filled with solid lubricant particles of graphite (C), molybdenum disulfide (MoS 2 ), and polytetrafluoroethylene (PTFE) were prepared by compression molding. The size of the solid lubricant particles was 3-5 μm. The friction and wear behaviors of the composites were examined with a pinon-disk test rig. The worn composite pin surfaces and the transfer films formed on the counterface were analyzed with scanning electron microscopy. An X-ray photoelectron spectroscope (XPS) was used to characterize the chemical states of the elements in the transfer film. It has been found that graphite and PTFE as the fillers increase the wear resistance of PPS considerably, while MoS 2 as the filler decreases the wear resistance of PPS greatly. The fillers promote the decomposition of PPS and generate compounds, which accounts for the changes in the wear resistance of the composites.

The effects of lubricating-oil additive zinc dialkyldithiophosphate (ZDDP) on the friction and wear properties of polymers and their composites sliding against GCr15 bearing steel were studied by using an MHK-500 ring-on-block wear tester (Timken wear tester). Then the frictional surfaces of the friction pairs were examined by using electron probe microanalysis (EPMA). Experimental results show that the ZDDP contained in liquid paraffin has little effect on the friction coefficients of the polyimide (PI) or polyamide 66 (PA66) against GCr15 bearing steel friction pairs compared with that under the lubrication of liquid paraffin, but it slightly reduces the friction coefficients of polytetrafluoroethylene (PTFE) or its composites against GCr15 bearing steel friction pairs. Under lubrication of liquid paraffin containing 2 wt % ZDDP, the ZDDP film absorbed on the frictional surfaces of the PTFE composites–GCr15 bearing steel friction pairs exhibits obvious antiwear properties; it greatly reduces the wear of pure PTFE and the PTFE composites filled with Pb, PbO, and MoS2; and the wear of the PTFE composites can be reduced by one order of magnitude compared with that under lubrication of pure liquid paraffin. Meanwhile, the inorganic fillers Pb, PbO, and MoS2 contained in PTFE have little effect on the absorption of ZDDP to the frictional surfaces, so they have little effect on the friction coefficients of the PTFE composites–GCr15 bearing steel friction pairs under the lubrication of liquid paraffin containing 2 wt % ZDDP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1240–1247, 2000

The composites of poly(ether ether ketone) (PEEK) filled with micrometer-sized Cu and Fe particles were prepared by compression molding. The friction and wear behaviors of the composites were examined on a pin-on-disc friction-and-wear tester by sliding PEEK-based composites against tool steel at a sliding speed of 1.0 m s−1 and a normal load of 19.6N. Optical microscopic analysis of the transfer film and of the worn pin surfaces and wear debris was performed to investigate the wear mechanisms of the composites. It was found that Cu and Fe used as filler considerably decreased the wear rate of PEEK. A thin, uniform, and tenacious transfer film was formed when Cu was used as the filler, and a nonuniform and thick transfer film was formed when Fe was used as the filler. The transfer film played a key role in increasing the wear resistance of the PEEK composites. Plastic deformation was dominant for wear of PEEK–Cu, while abrasion and adhesion were dominant for wear of PEEK–Fe. Because of the strong affinity between Fe as filler and its identical counterpart in the counterface tool steel surface, the adhesion between the PEEK–Fe composite surface and the counterface tool steel surface was thus severe. This contributed to the generation of a thicker transfer film for PEEK–Fe. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 179–184, 2000

Micrometer and nanometer copper particle-filled polyoxymethylene composites (coded as POM-micro Cu and POM-nano Cu, respectively) were prepared by compression molding. The compression strength and tensile strength of the composites were evaluated with a DY35 universal materials tester. An RFT-III reciprocating friction and wear tester was used to examine the tribological properties of the composites. The elemental compositions in the transfer films and the chemical states of the elements in the composite-worn surfaces were analyzed with electron probe microanalysis and X-ray photoelectron spectroscopy, while the surface morphologies were observed with scanning electron microscopy. It was found that Cu(CH2O)n was produced in sliding of a POM-nano Cu pin against an AISI 1045 steel block and Cu2O was produced in sliding of a POM-micro Cu pin against the same counterface. POM-micro Cu exhibited higher copper concentration in the transfer film compared with POM-nano Cu, and the transfer film of the former was thick and patchy compared with that of the latter. It was also found that micrometer and nanometer copper particles as fillers in POM exhibit a distinctive size effect in modifying the wear mechanisms of the composites. In other words, the wear mechanism of POM-micro Cu is mainly scuffing and adhesion, while that of POM-nano Cu is mainly plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2404–2410, 2000

The composites of polyetheretherketone (PEEK) filled with nanometer SiC of different proportions were prepared by compression molding. The tribological behaviors of the composites under lubrication of distilled water were investigated and compared with that under dry sliding, on an M-200 friction and wear test rig, by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The worn surfaces of nanometer SiC filled-PEEK and the transfer film were observed by means of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). As the results, nanometer SiC as the filler greatly improves the wear resistance of PEEK under dry sliding and distilled water lubrication, though the composites show different dependence of wear resistance on the filler content. Nanometer SiC-filled PEEK showed signs of slight scuffing under distilled water lubrication, while a thin, uniform, and tenacious transfer film was formed on the surface of the counterpart steel ring. On the contrary, unfilled PEEK under lubrication of water showed signs of severe plowing and erosion, while the worn surface of the counterpart ring was very rough, and a discontinuous PEEK transfer film was formed. Thus, the different friction and wear behaviors of unfilled PEEK and nanometer SiC-filled PEEK can be attributed to the different characteristics of the corresponding transfer films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 609–614, 2000

Nanometer Si3N4 filled poly(ether ether ketone) (PEEK) composite blocks with different filler proportions were prepared by compression molding. Their friction and wear properties under distilled water lubrication, as well as under ambient dry conditions, were investigated on a block on ring machine by running a plain carbon steel (AISI 1045 steel) ring against the PEEK composite block. The worn surfaces of nanometer Si3N4 filled PEEK and the transfer film were observed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The results showed that distilled water could reduce the friction coefficient of nanometer Si3N4 filled PEEK but with the sacrifice of a large reduction in wear resistance. The SEM and EPMA pictures of the worn surfaces indicated that the wear mechanisms of nanometer Si3N4 filled PEEK under distilled water lubrication and ambient dry rubbing conditions were different. Under water lubrication, the dominant wear mechanism of the filled PEEK was severe abrasive wear with surface fracture. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1394–1400, 2001

The composite of poly(ether ether ketone) (PEEK) filled with micron silicon carbide (SiC) with different filler proportions was prepared by compression molding. The friction and wear properties of the composite were investigated at ambient conditions on a block on ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The morphologies of the worn composite surfaces and the transfer film on the counterpart steel ring were examined with scanning electron microscopy and electron probe microanalysis. The results showed that the friction and wear of PEEK was slightly reduced at a filler proportion of micron SiC of 2.5-5.0 wt %. Abrasive wear was dominant for the PEEK composite; this was especially so at higher filler proportion. Meanwhile, abrasion and transfer to the composite surface of the counterpart steel ring were also observed.

Polytetrafluoroethylene (PTFE)-based composites, filled with CeO 2 , CeF 3 , and La 2 O 3 in volume contents of 5, 10, 15, 20, and 30%, were prepared. Then, the friction and wear behavior of these PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin-lubricated conditions was evaluated using an MHK-500 ring-on-block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites were investigated using a scanning electron microscope (SEM) and an optical microscope. Experimental results showed that filling CeO 2 , CeF 3 , and La 2 O 3 into PTFE can reduce the wear of the PTFE composites by 1-2 orders of magnitude. When the content of CeO 2 in PTFE is 15%, the friction and wear properties of the CeO 2 -filled PTFE composite are the best. Meanwhile, when the content of La 2 O 3 in PTFE is between 15 and 20%, the PTFE composite filled with La 2 O 3 exhibits excellent friction and wear-reducing properties. However, the friction coefficient of the CeF 3 -filled PTFE composite increases but its wear decreases with increase in the content of CeF 3 from 5 to 30%. The friction and wear-reducing properties of CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites can be greatly improved by lubrication with liquid paraffin, but the limit loads of the PTFE composites decrease with increase in the content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE (from 5 to 30%) under the same conditions. Investigations of worn surfaces show that the interaction between liquid paraffin and the CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites, especially the absorption of liquid paraffin into the microdefects of the PTFE composites, creates some cracks on the worn surfaces of the PTFE composites and that the creation and development of the cracks reduces the mechanical strength and the load-supporting capacity of the PTFE composites. However, with increase of the content of CeO 2 , CeF 3 , and La 2 O 3 in the PTFE, the microdefects in the PTFE composites also increase, which would lead to increase in the number of the cracks on the worn surfaces of the PTFE composites under load and, so, in turn, lead to the reduction of the limit loads of the CeO 2 -, CeF 3 -, and La 2 O 3 -filled PTFE composites under lubrication with liquid paraffin.

Five kinds of polytetrafluoroethylene (PTFE)-based composites were prepared: PTFE, PTFE + 30 vol % SiC, PTFE + 30 vol % Si3N4, PTFE + 30 vol % BN, and PTFE + 30 vol % B2O3. The friction and wear properties of these ceramic particle filled PTFE composites sliding against GCr15 bearing steel under both dry and liquid paraffin lubricated conditions were studied by using an MHK-500 ring-block wear tester. The worn surfaces and the transfer films formed on the surface of the GCr15 bearing steel of these PTFE composites were investigated by using a scanning electron microscope (SEM)and an optical microscope, respectively. The experimental results show that the ceramic particles of SiC, Si3N4, BN, and B2O3 can greatly reduce the wear of the PTFE composites; the wear-reducing action of Si3N4 is the most effective, that of SiC is the next most effective, then the BN, and that of B2O3 is the worst. We found that B2O3 reduces the friction coefficient of the PTFE composite but SiC, Si3N4, and BN increase the friction coefficients of the PTFE composites. However, the friction and wear properties of the ceramic particle filled PTFE composites can be greatly improved by lubrication with liquid paraffin, and the friction coefficients of the PTFE composites can be decreased by 1 order of magnitude. Under lubrication of liquid paraffin the friction coefficients of these ceramic particle filled PTFE composites decrease with an increase of load, but the wear of the PTFE composites increases with a load increase. The variations of the friction coefficients with load for these ceramic particle filled PTFE composites under lubrication of liquid paraffin can be properly described by the relationship between the friction coefficient (μ) and the simplified Sommerfeld variable N/P as given here. The investigations of the frictional surfaces show that the ceramic particles SiC, Si3N4, BN, and B2O3 enhance the adhesion of the transfer films of the PTFE composites to the surface of GCr15 bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of the GCr15 bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. Meanwhile, the interactions between the liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, create some cracks on the worn surfaces of the ceramic particle filled PTFE composites; the creation and development of these cracks reduces the load-supporting capacity of the PTFE composites. This leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2611–2619, 1999

Five kinds of polytetrafluoroethylene (PTFE)-based composites, pure PTFE, PTFE + 30(v)% MoS2, PTFE + 30(v)% PbS, PTFE + 30(v)% CuS, and PTFE + 30(v)% graphite (GR) composites, were first prepared. Then the friction and wear properties of these PTFE composites, sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions, were studied by using an MHK-500 ring-on-block wear tester. Finally, the worn surfaces and the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that filling with MoS2, PbS, CuS, or graphite to PTFE can reduce the wear of the PTFE composites by two orders of magnitude compared to that of pure PTFE under dry friction conditions. However, the friction and wear-reducing properties of these PTFE composites can be greatly improved by lubrication with liquid paraffin. Investigations of transfer films show that MoS2, PbS, CuS, and graphite promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel under dry friction conditions, but the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin. SEM examinations of worn surfaces show that with lubrication of liquid paraffin, the creation and development of the cracks occurred on the worn surfaces of the PTFE composites under load, which reduces the load-supporting capacity of the PTFE composites. This would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads (>600N). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 751–761, 1999

The friction and wear behaviors of polytetrafluoroethylene (PTFE)-based composites filled with rare earth compounds CeO 2 , CeF 3 , and La 2 O 3 in volume content from 5 to 30% sliding against GCr15 bearing steel under dry friction conditions were evaluated by using an MHK-500 ring-block wear tester. The wear debris and the worn surfaces of the PTFE composites were investigated by using a scanning electron microscope (SEM), whereas the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were examined by using an optical microscope. Experimental results show that the antiwear properties of the PTFE composites can be improved greatly by filling PTFE with different contents of CeO 2 , CeF 3 , and La 2 O 3 , and that the wear of the PTFE composites can be decreased by one to two orders of magnitude compared with that of pure PTFE. The wear of the CeF 3 -filled PTFE composite decreases with the increase of the content of CeF 3 from 5 to 30 vol %, but its friction coefficient increases with the increase of the content of CeF 3 in PTFE. When the content of CeO 2 in PTFE is 15 vol %, the friction and wear properties of CeO 2 -filled PTFE composite are the best. But when the content of La 2 O 3 in PTFE is between 15 and 20 vol %, the PTFE composite filled with La 2 O 3 exhibits excellent friction and wear-reducing properties. Microscope investigations show that rare earth compounds CeO 2 , CeF 3 , and La 2 O 3 in PTFE not only inhibit the large-scale destruction of the banded structure of PTFE but also enhance the adhesion of the transfer films of the PTFE composites to the surface of GCr15 bearing steel, so they greatly reduce the wear of the PTFE composites. With the increase of the content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE, the actions with which the rare earth compounds inhibit the large-scale destruction of the banded structure of PTFE are enhanced; so the wear of the PTFE composites decreases. Meanwhile, because CeO 2 - and La 2 O 3 -filled PTFE composites can easily form uniform transfer films on the surface of GCr15 bearing steel, the friction and wear-reducing properties of CeO 2 - and La 2 O 3 -filled PTFE composites are better than those of CeF 3 -filled PTFE composites under dry friction conditions.

Four kinds of polytetrafluoroethylene (PTFE)-based composites, such as pure PTFE, PTFE + 30(v)%Cu, PTFE + 30(v)%Cu2O, and PTFE + 30(v)%CuS composite, were prepared. Then the friction and wear properties of the PTFE composites filled with Cu, Cu2O, or CuS sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions were studied by using an MHK-500 ring-block wear tester. Finally, the worn surfaces and the transfer films of these PTFE composites formed on the surface of GCr15-bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that the antiwear properties of these PTFE composites can be greatly improved by filling Cu, Cu2O, or CuS to PTFE, and the wear of these PTFE composites can be decreased by two orders of magnitude compared to that of pure PTFE under dry friction conditions. Meanwhile, CuS increases the friction coefficient of the PTFE composite, but Cu and Cu2O reduce the friction coefficients of the PTFE composites. However, the friction and wear properties of Cu, Cu2O, or CuS-filled PTFE composites can be greatly improved by lubrication with liquid paraffin. The friction coefficients of these PTFE composites can be decreased by one order of magnitude compared to those under dry friction conditions, while the wear of these PTFE composites can be decreased by one to two orders of magnitude. The PTFE + 30(v)%Cu composite exhibits excellent friction and wear-reducing properties under higher loads in liquid paraffin-lubricated conditions, so the PTFE + 30(v)%Cu composite is much more suitable for application under oil-lubricated conditions in practice. Optical microscope investigation of transfer films shows that Cu, Cu2O, and CuS enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, so they greatly reduce the wear of the PTFE composites. However, the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. SEM examination of worn surfaces shows that the interaction between liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, creates some cracks on the worn surfaces of Cu2O or CuS-filled PTFE composites, the creation and development of the cracks reduces the load-carrying capacity of the PTFE composites; this leads to the deterioration of the friction and wear properties of the PTFE composites under higher loads in liquid paraffin lubrication. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1455–1464, 1998

SiC whisker-reinforced polyetheretherketone (PEEK) composites with different filler proportions were made into block specimens by compression molding. The friction and wear properties of the composites were investigated on a block-on-ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block under ambient conditions. The morphologies of the wear traces and wear debris were observed by scanning electron microscopy (SEM). It was found that SiC whisker-reinforced PEEK exhibited considerably lower friction coefficient compared with pure PEEK, while SiC whisker as a filler at a content of 1.25 to 2.5 wt % was very effective in reducing the wear rate of PEEK. Especially, the lowest wear rate was obtained with the composite containing 1.25 wt % SiC whisker. The SEM pictures of the wear traces indicated that PEEK composites undertook abrasive wear that was enhanced with increasing SiC whisker content, while for the frictional couple of carbon steel ring/ composite block (reinforced with 1.25 wt % filler), a thin, uniform, and tenacious transfer film was formed on the ring surface. It was also supposed that the differences in the content of SiC whisker as filler could cause the differences in the wear mechanisms of SiC whisker-reinforced PEEK composites.

Four kinds of polytetrafluoroethylene (PTFE)-based composites, such as pure PTFE, PTFE + 30(vol.)% carbon fiber, PTFE + 30(vol.)% glass fiber, and PTFE + 30(vol.)% K2Ti6O13 whisker composite, were prepared. The friction and wear properties of these fiber- and whisker-reinforced PTFE composites sliding against GCr15-bearing steel (SAE52100 steel) under both dry and liquid paraffin lubricated conditions were studied by using an MHK-500 ring-block wear tester (Timken wear tester). Then the worn surfaces of these PTFE composites and the transfer films formed on the surface of GCr15-bearing steel were investigated by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of the PTFE composites reinforced with carbon fiber, glass fiber, and a K2Ti6O13 whisker can be greatly improved by lubrication with liquid paraffin, and the friction coefficients of these PTFE composites can be decreased by one order of magnitude compared to those under dry friction conditions. Meanwhile, the wear of the fiber- and whisker-reinforced PTFE composites in liquid paraffin lubrication increases with the increase of load, but the friction coefficients of these PTFE composites first decrease with the increase of load, and then increase with the increase of load. The variations of friction coefficients with load for these PTFE composites in liquid paraffin lubrication can be described properly by the Stribeck's curve as given in this article. However, when the load increases to the load limits of the PTFE composites, their friction and wear increase sharply. SEM and optical microscope investigations show that the interactions between liquid paraffin and the PTFE composites, especially the absorption of liquid paraffin into the surface layers of the PTFE composites, create some obvious cracks on the worn surfaces of the PTFE composites. The creation and the development of the cracks reduce the load-carrying capacity of the PTFE composites, and therefore lead to the increase of the friction and wear of the PTFE composites under higher loads. Meanwhile, the transfer of the fiber- and whisker-reinforced PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin, but the transfer still takes place. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1393–1402, 1998

Nanometer ZrO2 filled polyetheretherketone (PEEK) composite blocks with different filler proportions were prepared by compression molding. Their friction and wear properties were investigated on a block-on-ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The morphologies of the wear traces were observed by scanning electron microscopy (SEM). Results indicated that nanometer ZrO2-filled PEEK exhibited lower friction coefficient and wear rate in comparison with pure PEEK. The lowest wear rate was obtained with the composite containing 7.5 wt % ZrO2 . The SEM pictures of the wear traces indicated that the plucked and ploughed marks appeared on the wear scar of pure PEEK, while the scuffing on the wear scar of 7.5 wt % nanometer ZrO2-filled PEEK was obviously abated. Thus, it was inferred that the improvement in the tribological behavior of nanometer ZrO2- filled PEEK composite was closely related to the improved characteristics of the worn surfaces.

The fretting wear behaviors of perfluorinated ethylene-propylene copolymer ( FEP) were studied on an SRV fretting wear tester with the plane contact of FEP against a bearing steel at room temperature of about 15°C. In our tests, the product of load (L) and total sliding distance (S) was preset to be a constant as the wear coefficient K w , can be expressed as K w = W. P m /(L.S), where W is the volume of material loss, P m is the flow pressure of the softer material (FEP), L and S are the load and the total sliding distance, respectively. Under our test conditions, no wear of the bearing steel was observed when fretted against FEP. The sudden change of wear rate of FEP or its wear weight was governed by the critical PV value, an important parameter for polymers and polymer composites under sliding friction, which was the product of normal stress and average sliding speed. The critical PV value of FEP under study was 3 x 10 4 Pa m/s. It was also found that the topography of wear trace formed on FEP were fairly well corresponding with that of their transferred films on steel surface. Both on worn surface of FEP and on metal surface, three sharply defined regions, wear debris formation region, high-stress region, and slightly sliding wear region, can be distinguished. It indicated that the higher the normal stress, the more difficult the formation of thick transfer film.

Four kinds of polytetrafluoroethylene(PTFE)-based composites, such as pure PTFE, PTFE + 30%(v) PbO, PTFE + 30%(v) Pb 3 O 4 , and PTFE + 30%(v) Cu 2 O composite, were prepared. The friction and wear properties of these metal oxides filled PTFE composites sliding against GCr15 bearing steel in both dry and lubricated conditions were studied by using an MHK-500 ring-block wear tester. Then the worn surfaces of these PTFE composites and the transfer films of these PTFE composites formed on the surface of GCr15 bearing steel were examined by using a Scanning Electron Microscope (SEM) and an Optical Microscope, respectively. Experimental results show that the friction and wear properties of these metal oxide-filled PTFE composites can be greatly improved by liquid paraffin lubrication, and the friction coefficients can be decreased by one order of magnitude. Meanwhile, the interactions between liquid paraffin and metal oxide-filled PTFE composites, especially the absorption of liquid paraffin into the surface layers of these PTFE composites, reduce the mechanical strength and the load-carrying capacity of these metal oxide-filled PTFE composites. This leads to the deterioration of the friction and wear properties of these PTFE composites. Investigations of the frictional surfaces show that Pb 3 O 4 , Cu 2 O, and PbO enhance the adhesion of the transfer films to the surface of GCr15-bearing steel, and thus promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel. Therefore, they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by lubrication with liquid paraffin.

Porous chitosan (CS)/graphene oxide (GO) composite xerogels were prepared through a simple and “green” freeze-drying method. Scanning electron microscopy, Fourier transform infrared spectrometry, powder X-ray diffraction, and compressive strength measurements were performed to characterize the microstructures and mechanical properties of as-prepared composite xerogels. The results show that the incorporation of GO resulted in an observable change in the porous structure and an obvious increase in the compressive strength. The abilities of the composite xerogels to absorb and slowly release an anticancer drug, doxorubicin hydrochloride (DOX), in particular, the influence of different GO contents, were investigated systematically. The porous CS/GO composite xerogels exhibited efficient DOX-delivery ability, and both the adsorption and slow-release abilities increased obviously with increasing GO content. Additionally, the best adsorption concentration of DOX was 0.2 mg/mL, and the cumulative release percentage of DOX from the xerogels at pH4 much higher than that at pH 7.4. Therefore, such porous CS/GO composite xerogels could be promising materials as postoperation implanting stents for the design of new anticancer drug-release carriers.