Chunying Min

Improved hydrophilicity, permeability, antifouling and mechanical performance of PVDF composite ultrafiltration membranes tailored by oxidized low-dimensional carbon nanomaterials

Polyvinylidene fluoride (PVDF)–oxidized carbon nanotubes (OMWCNTs), PVDF–graphene oxide (GO) and PVDF–OMWCNTs–GO composite ultrafiltration membranes were prepared by solution-blending the ternary mixture of PVDF–oxidized low-dimensional carbon nanomaterials–dimethylacetamide in combination with the phase inversion method. The microscope images of the PVDF matrix microstructure showed that the composite membranes exhibited a bigger mean pore size and higher roughness parameters than pristine membranes. The contact angle of the membranes decreased from 78.5° (PVDF) to 66.8° (PVDF–OMWCNTs), 66.4° (PVDF–GO) and 48.5° (PVDF–OMWCNTs–GO). For the PVDF–OMWCNTs, PVDF–GO and PVDF–OMWCNTs–GO composite membranes, there was a 99.33%, 173.03% and 240.03% increase in permeation flux and a 21.71%, 17.23% and 14.29% increase in bovine serum albumin (BSA) rejection, respectively, compared with those of the pristine membranes. The newly developed composite ultrafiltration membranes demonstrate an impressive prospect for the anti-irreversible fouling performance in multi-cycle operations from BSA treatment. Additionally, the addition of OMWCNTs and GO increased the tensile strength of composite membranes from 1.866 MPa to 2.106 MPa and 2.686 MPa, respectively. Conspicuously, the PVDF composite ultrafiltration membranes endowed with oxidized low-dimensional carbon nanomaterials demonstrated fascinating hydrophilicity, permeability, antifouling and mechanical performance and promising application prospects owing to the rich oxygen-containing functional groups, high specific surface and synergistic effect of inorganic additive.

Flexible morphology-controlled synthesis of monodisperse α-Fe2O3 hierarchical hollow microspheres and their gas-sensing properties

Microspheres constructed with α-FeOOH nanorods were fabricated by a sodium dodecylbenzenesulfonate (SDBS) assisted hydrolysis process in an ethanol/H2O co-solvent system, and could be transformed into hollow microspheres constructed with α-Fe2O3 nanorods by calcining in air at 600 °C for 2 h. α-Fe2O3 hierarchical hollow microspheres with size about 320 nm in diameter were constructed by the radically oriented single-crystalline nanorods with length and diameter of about 20–40 nm and 15–20 nm, respectively. The investigation on the evolution formation revealed that SDBS was critical for controlling the assembly of the freshly formed nanocrystallites, and hollowing formation was proven to be the Ostwald ripening process by tracking the structure of the products at different growth stages. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure of the synthesized products. An investigation of the gas-sensing properties showed that α-Fe2O3 hierarchical hollow spheres exhibited high gas response to ethanol at the optimum working temperature of 300 °C.

Synthesis of multi-walled carbon nanotubes/β-FeOOH nanocomposites with high adsorption capacity

A hybrid nanostructure of multi-walled carbon nanotubes (CNTs) and β-ferric oxyhydroxide (β-FeOOH) nanoparticles is synthesized by ultrasonic-assisted in situ hydrolysis of the precursor ferric chloride and CNTs. Characterization by X-ray diffraction, scanning electron microscopy , and transmission electron microscopy establishes the nanohybrid structure of the synthesized sample. The results revealed that the surface of CNTs was uniformly assembled by numerous β-FeOOH nanoparticles and had an average diameter of 3xa0nm. The formation route of anchoring β-FeOOH nanoparticles onto CNTs was proposed as the intercalation and adsorption of iron ions onto the wall of CNTs, followed by the nucleation and growth of β-FeOOH nanoparticles. The values of remanent magnetization (Mr) and coercivity (Hc) of the as-synthesized CNTs/β-FeOOH nanocomposites were 0.1131xa0emu g, and 490.824xa0Oe, respectively. Furthermore, CNTs/β-FeOOH nanocomposites showed a very high adsorption capacity of Congo red and thus these nanocomposites can be used as good adsorbents and can be used for the removal of the dye of Congo red from the waste water system.

Preparation and tribological behaviors of poly (ether ether ketone) nanocomposite films containing graphene oxide nanosheets

The composite films of poly (ether ether ketone) (PEEK) filled with different proportions of graphene oxide (GO) nanosheets were prepared by the cast method. The tribological behaviors of the composite films under boundary lubrication (water and liquid paraffin oil lubrication) were investigated and compared with that under dry sliding on an UMT-2 friction and wear machine, by running a steel sphere against the composite films. The results were as follows: GO nanosheets as the filler greatly improve the wear resistance of PEEK under boundary lubrication, though the composites show a different dependence of wear resistance on the filler content. Scanning electron microscopy and optical microscopy performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of GO could be attributed to their small size and extremely thin laminated structure, which allow the GO to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

Preparation and Tribological Properties of Polyimide/Carboxyl-Functionalized Multi-walled Carbon Nanotube Nanocomposite Films Under Seawater Lubrication

AbstractnThe polyimide (PI)/carboxyl-functionalized multi-walled carbon nanotube (MWCNTs-COOH) nanocomposite films were synthesized by situ polymerization method. The results showed that the incorporation of MWCNTs-COOH greatly enhanced thermal stability and mechanical property of PI. PI/MWCNTs-COOH nanocomposites exhibited better tribological properties under seawater lubrication than other conditions because of excellent lubricating effect of seawater. Besides, the wear resistance of PI under seawater lubrication had been greatly improved by filling MWCNTs-COOH, because strong interfacial adhesion between PI matrix and MWCNTs-COOH nanofillers could transfer load effectively between contact surfaces. In particular, when the content of MWCNTs-COOH was 0.7xa0wt%, the corresponding PI/MWCNTs-COOH nanocomposites had the best tribological properties under seawater lubrication.Graphical AbstractThe polyimide (PI)/carboxyl-functionalized multi-walled carbon nanotube (MWCNTs-COOH) nanocomposite films were synthesized by in situ polymerization using 4,4′-oxydianiline (ODA), carboxyl-functionalized multi-walled carbon nanotube (MWCNTs-COOH) and pyromellitic dianhydride (PMDA). The tribological properties of PI/MWCNTs-COOH nanocomposite films were measured under dry sliding condition, pure water condition and seawater lubrication condition. This study can provide some guidance to develop polymer materials with excellent wear resistance suitable for ocean environment.

A new one-step synthesis method for coating multi-walled carbon nanotubes with iron oxide nanorods

A facile solution-chemical method has been developed to be capable of covering a multiwalled carbon nanotube (MWNTs) with iron oxide nanorods without using any bridging species. MWNTs in this composite were decorated randomly by α-Fe2O3 nanorods with diameters in the range of 3–5xa0nm and lengths of 15–30xa0nm. The formation route to anchor α-Fe2O3 nanorods onto MWNTs was proposed as the intercalation and adsorption of iron ions onto the wall of MWNTs, followed by the nucleation and growth of α-Fe2O3 nanorods. α-Fe2O3/MWNTs nanocomposites show specific high Brunauer–Emmett–Teller surface areas. The photocatalytic activity experiment indicated that the prepared α-Fe2O3/MWNTs nanocomposites exhibited a higher photocatalytic activity for the photocatalytic decolorization of rhodamine B aqueous solution under the visible-light illumination than the single phase α-Fe2O3 samples. This methodology made the synthesis of MWNTs-nanorods composites possible and may be further extended to prepare more complicated nanocomposites based on MWNTs for technological applications.

Effect of MWCNTs-COOH Reinforcement on Tribological Behaviors of PI/MWCNTs-COOH Nanocomposites Under Seawater Lubrication

Abstract The carboxyl-functionalized multiwalled carbon nanotube (MWCNT-COOH) was achieved by grafting carboxyl (COOH) groups onto surfaces of MWCNTs. Then polyimide (PI)-based nanocomposites reinforced with MWCNTs-COOH and MWCNTs were prepared by in situ polymerization and the tribological behaviors of PI/MWCNTs-COOH and PI/MWCNT nanocomposites were studied under dry friction and seawater lubrication. The results showed that the incorporation of MWCNTs-COOH and MWCNTs could greatly improve the wear resistance of PI because of the lubricating effect of MWCNTs-COOH and MWCNTs. In additon, the PI/MWCNTs-COOH exhibited better tribological performance than the PI/MWCNTs under dry friction due to functionalization of MWCNTs. In addition, PI/MWCNTs-COOH nanocomposites presented better tribological properties under seawater lubrication than other conditions because of the excellent lubricating effect of seawater, especially when the content of MWCNTs-COOH was 0.7 wt%. Furthermore, the effects of applied load and sliding speed on the tribological behaviors of PI/MWCNTs-COOH nanocomposites were studied under seawater lubrication. It was found that 0.7 wt% PI/MWCNTs-COOH nanocomposites had the best friction reduction and antiwear properties when the applied load and sliding speed were 3 N and 0.26 m/s, respectively, under seawater lubrication.

Influence of graphene oxide as filler on tribological behaviors of polyimide/graphene oxide nanocomposites under seawater lubrication

Polymer-based composites reinforced by lubricated fillers have aroused wide concern in the field of tribology. In this manuscript, the effect of graphene oxide (GO) as lubricated filler on the tribological behaviors of polyimide (PI)/graphene oxide (GO) nanocomposites prepared by hot press molding method was investigated under seawater to provide a practical guidance for the use of the polymer-based composites in ocean environment. It was found that the incorporation of GO could greatly improve the wear resistance of pure PI under seawater lubrication, especially when the content of GO was about 0.5xa0wt%. This was due to the lubricated effect of GO. In addition, PI/GO nanocomposites exhibited better friction and wear properties under seawater-lubricated condition than that under dry friction condition because of excellent lubricating effect of seawater. Optical photographs of the worn surface morphology had revealed that the main wear mechanism of the PI/GO nanocomposites was slight abrasive wear.Graphical abstract

Graphene oxide/carboxyl-functionalized multi-walled carbon nanotube hybrids: powerful additives for water-based lubrication

The development of water-based lubricants with well dispersed ultrafine particles is in high demand. In this article, graphene oxide (GO) nanosheets/carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs–COOH) hybrids have been synthesized via vacuum filtration of a solution hybrid dispersion, as additives for water-based lubricants. The tribological performance of GO/MWCNTs–COOH hybrids in water was systematically investigated. The lubrication properties of water-based lubricant can be significantly improved by adding GO/MWCNTs–COOH hybrids in comparison with adding only GO nanosheets or MWCNTs–COOH as lubricant additives. Notably, the water with as little as 0.7 wt% of GO/MWCNTs–COOH hybrids exhibits the best lubrication performance in terms of friction and wear reduction. This unique tribological performance of GO/MWCNTs–COOH hybrids in water suggests the existence of a synergistic effect of GO and MWCNTs–COOH on reducing friction and wear.