Jiwu Shang

Fabrication and enhanced dielectric properties of graphene–polyvinylidene fluoride functional hybrid films with a polyaniline interlayer

Graphene–polyvinylidene fluoride hybrid films (GPNs–PVDF) with a polyaniline (PANI) interlayer are fabricated by a facile and effective process. The morphology of the graphene–polyaniline nanoflakes (GPNs) is examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the interaction between graphene and PANI is investigated by Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The GPNs have a layered structure resembling a cake with the graphene sheets sandwiched between the PANI layers. The GPNs have a uniform morphology which can be controlled by adjusting the ratio of PANI to graphene. The PANI inter-layer plays an active role in the dielectric properties of the GPNs–PVDF composites which have low dielectric loss, high breakdown field, and large energy density. The enhanced dielectric performance originates from the insulating PANI layer which not only ensures good dispersion of graphene sheets in the PVDF but also acts as an inter-particle barrier to prevent direct contact with the graphene sheets.

Structure and magnetic properties of soft organic ZnAl-LDH/polyimide electromagnetic shielding composites

The imidization mechanism, structure, and magnetic properties of organic modified Zinc-aluminum layered double hydroxides/polyimide composites are investigated. During imidization, organic modified Zinc-aluminum layered double hydroxides lose the hydroxyl group and sodium dodecyl sulfate modifier decomposes partly resulting in a loose contact between PI and oxidized Zinc-aluminum layered double hydroxides. The thermal properties of composites are slightly decreased with increasing organic modified Zinc-aluminum layered double hydroxides but the wettability varies oppositely. Comparing to organic modified Zinc-aluminum layered double hydroxides, the saturated magnetization of heated organic modified Zinc-aluminum layered double hydroxides is enhanced slightly due to structural improvement in Fe3O4 crystalline domain. Therefore, the magnetic properties are not affected by imidization procedure. The soft magnetic composites have large potential in electromagnetic shielding.

Green dielectric materials composed of natural graphite minerals and biodegradable polymer

Polymeric nanocomposites are a promising dielectric due to their low cost, easy processability and flexibility but most polymers are difficult to treat and recycle leading to “white pollution”. Here, we report an eco-friendly “green” dielectric material made from natural graphite minerals and biodegradable poly(butylene succinate) synthesized by solution casting and hot pressing. Dielectric constant of resulting composite films agreed quite well with percolation theory and a low percolation threshold fc = 5.98% was obtained due to a high aspect ratio of natural graphite minerals. Composite films possessed a high dielectric constant of 113, around 28 times higher than that of pristine PBS (103) when volume fraction reached 5.5%. Furthermore, dynamic mechanical properties of composite films can be improved at the same time. Dielectric constant of composite films can be greatly improved by incorporating natural graphite minerals while mechanical flexibility can be maintained to be as good as that of pure polymer matrix.

Cu2O immobilized on reduced graphene oxide for the photocatalytic treatment of red water produced from the manufacture of TNT

In this paper, we report on the synthesis of nanocomposite catalysts composed of cuprous oxide (Cu2O) and reduced graphene oxide (rGO) formed at room temperature. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopic analysis, ultraviolet-visible diffuse reflection absorptive spectroscopy, etc. The results show that the cuprous oxide particles can be immobilized on the surface of rGO and that the rGO improves the optical properties of Cu2O thereby enhancing the utilization of visible light. Compared with Cu2O under similar synthesis condition, the Cu2O/rGO composites demonstrate improved photodegradative activity of red water. This study verifies the viability of the use of Cu2O/rGO composites in the treatment of red water.

Utilization of recycled chemical residues from sodium hydrosulfite production in solid lubricant for drilling fluids

AbstractThe chemical residues from sodium hydrosulfite production contain complex chemical composition and give out a bad odor posing a grave threat to the environment and public health. The organic residues containing thiodiglycol, 2,2′-dithiodiethanol, and 1,4-thioxane are suitable for high pressure lubrication applications. In this paper, the chemical residues were recycled and used to prepare the solid lubricant for drilling fluids. The lubricity of solid lubricant was illustrated and the experimental results indicated that the solid lubricant could improve lubricity of drilling fluids, which had met the requirement of industrial applications. Experimental studies were also performed on its salt resistance, temperature resistance, and compatibility. The solid lubricant had passed pilot experiments and been used in the Changqing and Dagang oil fields in China. This study not only enables recycling of industrial products but also makes the clean production come true, which contributed to environment pro...

A Promising Material by Using Residue Waste from Bisphenol A Manufacturing to Prepare Fluid-Loss-Control Additive in Oil Well Drilling Fluid

The residues mixture from Bisphenol A manufacturing process was analyzed. Fourier transform infrared (FTIR) spectroscopy, gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) were used to characterize the residues. The results indicated that the residues were complex mixture of several molecules. 3-(2-Hydroxyphenyl)-1,1,3-trimethyl-2,3-dihydro-1H-inden-5-ol and phenol were the main components of the residues. The technical feasibility of using it as phenol replacement in fluid-loss-control additive production was also investigated. The fluid-loss-control capacity of the novel additive was systematically investigated. It was discovered that the well fluid-loss performance of the prepared additive can be achieved, especially at high temperature.

Dielectric property of all-organic composite film composed of cobalt phthalocyanine and poly(vinylidene fluoride)

Due to the mechanical flexibility, tunable properties and easy processing, polymer based composites, especially the electroactive polymer composites based on the poly(vinylidene fluoride), which can be applied in the sensors, transistors and the capacitors, have been widely investigated. In this paper, all-organic composite films composed of cobalt phthalocyanine and poly(vinylidene fluoride) with high dielectric permittivity are simply synthesized by solution casting on the glass. The dielectric property over the broad frequency from 1Hz to 107Hz is investigated. The high dielectric permittivity 86.4(102Hz), about 9 times of the pure poly(vinylidene fluoride), is achieved when the fraction of the cobalt phthalocyanine is 20wt% that is similar to other semiconductors reinforced polymer composites. The significant increase of the dielectric constant and the dielectric loss tangent can be explained by the threshold theory. The origin of dramatically enhancement of dielectric permittivity and dielectric loss tangent over the low frequency is the Maxwell-Wagner-Sillars polarization. The results show that the dielectric property is very sensitive to the fraction of cobalt phthalocyanine. Additionally, when the fraction of the cobalt phthalocyanine was 10wt%, the dielectric permittivity and the conductivity of composite films are 17.1 and 1.1×10-6s/cm respectively which indicated that it is potentially applied in the capacitors.