Hongqi Wan

Influence of Polyfluo-Wax on the Friction and Wear Behavior of Polyimide/Epoxy Resin–Molybdenum Disulfide Bonded Solid Lubricant Coating

ABSTRACT Polyimide/Epoxy resin–molybdenum disulfide bonded solid lubricant coatings (denoted as PI/EP-MoS2) were prepared. The influence of polyfluo-wax (denoted as PFW) on the microhardness and friction and wear behavior of as-prepared PI/EP-MoS2 lubricant coating was measured using a microhardness tester and a reciprocating ball-on-disc tribometer, respectively. The worn surfaces of the lubricant coatings were observed with a scanning electron microscope, and their wear rate was determined with a Micro XAM surface mapping microscope. Moreover, the transfer films formed on the counterpart steel ball surfaces were analyzed by X-ray photoelectron spectroscopy. Results indicate that the incorporation of a proper content of PFW filler is effective at improving the antifriction performance of the PI/EP-MoS2 lubricant coating while maintaining better wear resistance. Moreover, the friction coefficient of the lubricant coating decreases with increasing content of PFW from 2 to 10%, and the one with a filler content over 6% PFW has a steady friction coefficient of 0.07. The improvement in the antifriction performance of the lubricant coating with the incorporation of the PFW filler is attributed to the excellent lubricity of homogeneously distributed PFW.

Synthesis and Fluorescence Property of the Gold Nanoparticles Modified with 9-Methyl -9-(8-thiooctyl) -fluorene

Gold nanoparticles protected by the self-assembled monolayers of 9-methyl-9-(8-thiooctyl)-fluorene (FMC8SH) have been prepared via a phase-transfer method, which are characterized by UV-vis spectrum, TEM, and IR spectra. The fluorescence properties of these surface-modified nanoparticles are investigated in detail. Compared to the neat FMC8SH, the fluorescence intensities of the gold nanoparticles modified by FMC8SH are weak. This could indicate that the fluorescence of FMC8SH is quenched by the gold nanoparticles.

Surface-Modified Sb2S3 Nanoparticles and Their Tribological Behaviors in Liquid Paraffin

Sb2S3 nanoparticles surface-modified with S-tetradecyl N, N-dihydroxyethyl dithiocarbamate (C14DTC-Sb2S3) have been synthesized via extraction of Sb2S3 colloidal particles from ethylene glycol into toluene in the presence of C14DTC. The obtained products were characterized by high-resolution transmission electron microscope (HRTEM) and Fourier transformation infrared (FTIR), and their tribological behaviors as an additive in liquid paraffin were investigated using a four-ball tribometer. The results show that C14DTC-Sb2S3 nanoparticles can significantly improve the friction reduction, anti-wear, and load-carrying properties of base oils. The preliminary lubrication mechanism was discussed based on the SEM and XPS investigation of the rubbed surfaces.

Study on the Tribological Behaviors of N,N-dioctyldithiocarbamate Monolayer-Stabilized Copper Nanoparticles in Liquid Paraffin

Copper nanoparticles surface-modified with self-assembled monolayers of N,N-dioctyldithiocarbamate (S2CNR2, R = n-octyl) have been prepared in the presence of cetyltrimethylammonium bromide (CTAB). The trobological behaviors of the S2CNR2-coated copper nanoparticles as an additive in liquid paraffin are investigated using a block-on-ring tribometer. The results indicate that copper nanoparticles as additive in liquid paraffin are capable to greatly reduce the friction coefficient and wear rate of the steels counterparts even at an extremely low concentration. The tribochemically reacted films with Cu, FeS, Fe2O3, and SO4 2− formed during the friction process are contributed to the good tribological properties of the S2CNR2-coated copper nanoparticles as additive in liquid paraffin.

Synthesis and Fluorescence Properties of Gold Nanoparticles Modified with Dithiocarbamate Functionalized Carbazole

Gold nanoparticles protected by the self-assembled monolayers of 9-[6-(N,N-dibutyl-amino-dithiocarbamate)-hexyl]-carbazole, CHBDTC in short, were prepared via a phase-transfer method. These surface-modified nanoparticles were characterized with UV-vis, photoluminescence spectroscopy and TEM. It was found that the CHBDTC-capped gold nanoparticles were stable under ambient conditions, which is attributed to the protection of the CHBDTC densely packed on the gold nanoparticle surface. The fluorescence emission spectra indicated that the fluorescence of CHBDTC was quenched to some extent by gold nanoparticles. And the CHBDTC-capped Au nanoparticles could be promisingly applied as biomolecular labels and in fabrication of novel photo-based nanodevices as well, owing to the photoactive sensitivity of CHBDTC.

Synthesis and Tribological Behavior of Surface Coated Cu Nanoparticles in Liquid Paraffin

The Cu nanoparticle surface coated with S-hexyl N,N-dihydroxyethyl dithiocarbamate (SHNDD) was synthesized by the controlled reduction of aqueous copper salts using the modified Brust synthesis. The morphology, structure and thermal properties of the modified Cu nanoparticles (SHNDD-nano Cu) was investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrum, and thermogravimetric analysis. As the results of TEM and IR spectrum shown, the size of as-prepared nanoparticles is about 6 nm and existence of the organic carbon chain on the surface of nanoparticles is observed. The tribological behaviors of Cu nanoparticles in liquid paraffin were evaluated on a four-ball testing machine. The results show that Cu nanoparticles as oil additives can improve the load-carrying capacity and antiwear property of the base oil. The rubbed surfaces were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It can be inferred that a tribological reaction film was formed, which contributed to the good tribological properties of surface modified Cu nanoparticles.

Synthesis and Characterization of a Novel Water-Soluble Poly(p-phenylene) with Ionic Liquid Side Chain

A novel water-soluble poly(p-phenylene) derivative with ionic liquid side chain, poly{2,5-bis[3-(4-methyl-1-imidazolium)-1-oxabutyl]-1,4-phenylene-alt-1,4 phenylene} dibromide (PPP-IL), has been successfully synthesized via a Suzuki coupling polymerization reaction in the presence of a Pd (0)-catalyst. FTIR, 1H-NMR, element analysis, TGA, UV-Vis and fluorescent spectra are employed to investigate the structure and performance of the titled polymer. It is found that the PPP-IL shows excellent thermal stability, solubility, and efficient blue fluorescent properties.

Marvelous abilities for polyhedral oligomeric silsesquioxane to improve tribological properties of polyamide-imide/polytetrafluoroethylene coatings

POSS-doped organic–inorganic nanocomposites (POSS referring to polyhedral oligomeric silsesquioxane) as a new generation of high-performance materials are of special significance, since they simultaneously possess the high rigidity and stability of inorganic species as well as the desired flexibility, ductility and processability of polymer species. Thus, octa(3-amino propyl) POSS (amino-functionalized POSS, denoted as NH2-POSS) was incorporated into polyamide-imide (denoted as PAI) to obtain a series of NH2-POSS/PAI hybrid composites. The molecular structures of NH2-POSS and NH2-POSS/PAI hybrid composites were analyzed by Fourier transform infrared spectrometry and X-ray diffraction. The impact of NH2-POSS on the thermal stability and mechanical properties of PAI as well as the tribological properties of PAI/PTFE-based (PTFE referring to polytetrafluoroethylene) bonded solid lubricant coatings was investigated. Findings indicate that the introduction of a proper amount of NH2-POSS leads to an increase in the glass transition temperature (Tg) as well as hydrophobicity and microhardness of PAI. Besides, NH2-POSS contributes to reducing the friction coefficient and wear rate of PAI/PTFE-bonded solid lubricant coatings. Particularly, the introduction of 7% (mass fraction) of NH2-POSS leads to a decrease in the wear rate of PAI/PTFE-bonded solid lubricant coating by about 50%. This could be attributed to the increase in the load-bearing capacity and decrease in the surface energy of the polymer matrix coatings upon the addition of NH2-POSS.