Baoming Zhou

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.

Facile and low-cost approach towards a PVDF ultrafiltration membrane with enhanced hydrophilicity and antifouling performance via graphene oxide/water-bath coagulation

Addressed herein is a facile and low-cost approach to endow hydrophobic polyvinylidene fluoride (PVDF) membranes with reliable hydrophilicity and antifouling properties. Porous asymmetric hydrophilic membranes with tunable morphology were facilely fabricated via phase inversion using an aqueous solution of graphene oxide (GO) as the coagulation bath. An increment in pore size and surface roughness was observed for membranes treated by a GO/water-coagulation bath (GB). The bovine serum albumin rejection of GB-treated membranes increased by 38.99% when the concentration of GO in the coagulation bath was 0.5 g L−1. The contact angle of membranes decreased from 75.9° to 58.8° and the water flux increased by 140% when the dosage of GO was 2 g L−1. Furthermore, fouling resistances of membranes revealed that GB-treated membranes had a higher flux recovery ratio (85.7%) than pristine PVDF (43.3%). Meanwhile, the protein adsorption of GB-treated membranes was decreased by 69.3% compared with that of pristine PVDF membranes. The cost of the membranes can be lowered by using a GB approach compared with GO-mixed matrix membranes because of the reusability of GO in a coagulation bath. This research presents an effective method to tailor membrane performance via GB rather than embedding GO in the membrane matrix.

Nano-structure and property transformations of carbon systems under γ-ray irradiation: a review

Carbon-based materials have been used quite successfully for decades within industry sectors. Especially, the application of them in the field of aerospace has been paid lots of attention. The severe environment such as γ-rays in space, which may give rise to the formation of atomic defects, may deteriorate the performance of carbon-based devices significantly. However, in addition to the well-known cases of destroying the properties of carbon systems, recent experiments show that γ-ray irradiation can also be employed as an attractive tool for the fabrication, modification and manipulation of carbon materials. In this article, we briefly review the recent progress in our understanding of γ-ray irradiation-induced phenomena in some carbon systems with experimental results and theoretical analysis. Particular emphasis is put on the discussion of the effects of γ-rays on nanostructure and morphology of carbon fibers, graphite, carbon nanotubes, graphene and diamond, as well as the methods for tailoring their mechanical, chemical and electronic properties. Finally, we attempt to identify the future directions in which the irradiation-induced modification field is likely to develop.

Modifying graphite oxide nanostructures in various media by high-energy irradiation

The alterations of GO nanostructures after γ-ray irradiation in water, air and styrene with an absorbed dose of 200 kGy are systematically investigated. The interlayer structures of the ultimate products are confirmed to be remarkably different from each other due to the distinct changes of functional groups on single-sheets in various media. After irradiation in water, oxygen groups in graphite oxide are shown to be obviously decreased owing to the generation of reductive radicals by the decomposition of water molecules, which is reflected in the decrease of graphite oxide interlayer spacing. The interlayer distance of graphite oxide irradiated in air is found to be significantly increased, which may be attributed to the increase of the hydroxyl groups and the topological defects. However, the graphite oxide seems to be mainly exfoliated and functionalized by the intercalation of the monomers and the grafting of polystyrene chains when irradiated in styrene. It is expected that γ-ray irradiation in different media should be a promising strategy for manipulating nanostructures and properties of graphite oxide for improving its applicability in fields of composites, catalysts and sensors.

Improving dielectric properties of poly(vinylidene fluoride) composites: effects of surface functionalization of exfoliated graphene

To investigate the effects of surface functionalization of exfoliated graphene (EG) on the crystalline form of β-phase and dielectric properties of poly(vinylidene fluoride) (PVDF), we prepared PVDF-based composites reinforced by different functionalized EG. The X-ray photoelectron spectroscopy results indicated that a wide variety of chemical functional groups such as C–OH, C–O–C, C=O, COOH and C–F could be introduced on the surface of modified EG. As confirmed by results of Fourier transform infrared spectrum and X-ray diffraction, the β-phase PVDF can be produced in the composites with the incorporation of functionalized EG. In the frequency ranging from 102 to 107 Hz, the dielectric permittivity of PVDF composites shows an obvious increase owing to a variation of the carbonyl group (C=O) content. Among all the composites, the EG grafted with polymethyl methacrylate/PVDF composite has the highest dielectric permittivity and dielectric loss.