Weiwei Cui

In situ anchor of magnetic Fe3O4 nanoparticles onto natural maifanite as efficient heterogeneous Fenton-like catalyst

In situ anchor of magnetic Fe3O4 nanoparticles (NPs) onto the surface of natural maifanite was realized by chemical oxidation coprecipitation in hot alkaline solution. The Fe3O4/maifanite composites were characterized by XRD, FTIR, SEM, and TEM. These results indicated that polycrystalline Fe3O4 NPs with inverse spinel structure were formed and tightly dispersed on maifanite surface. Based on the measurement of surface Zeta potential of maifanite at different medium pHs, the possible combination mechanism between natural maifanite and Fe3O4 NPs was proposed. Then, the asobtained composites were developed as highly efficient heterogeneous Fenton-like catalyst for the discoloration of an azo dye, Methyl Orange (MO). The comparative tests on MO discoloration in different systems revealed that Fe3O4/maifanite composite exhibited much higher Fenton-like catalytic activity than Fe3O4 NPs and the heterogeneous Fentonlike reaction governed the discoloration of MO. Kinetic results clearly showed that MO discoloration process followed the second-order kinetic model. Fe3O4/maifanite composites exhibited the typical ferromagnetic property detected by VSM and could be easily separated from solution by an external magnetic field.

Preparation of a low contact angle water-based coating using ultrasonic irradiation

Purpose The key purpose of this study was to investigate the effects of different ultrasonic irradiation times on the wettability and other properties of the resulting water-based coating. The subject water-based coating was prepared using water-soluble polyester and amino resins by ultrasonic oscillation. Design/methodology/approach The coating was prepared by polymerising polyester and amino resins in water using ultrasonic oscillation. The coating was baked for 40 seconds at 350°C to coalesce and solidify the film. The contact angle, thermal stability and mechanical properties of the film, as well as the molecular weight (MW) and structure of the polyester resin, were determined. Findings The contact angle of the coating was found to decrease with ultrasonic irradiation; the mechanical properties and thermal stability were not altered when the irradiation time was longer than 5 hours. The MW of the polyester initially decreased then increased and stabilized with ultrasonic irradiation. The structure of polyester molecule and aggregated state of the solidified coating were not changed by ultrasonic irradiation. Research limitations/implications In the study reported here, the effects of different ultrasonic irradiation times were investigated. Results of this research could benefit in-depth understanding of the influence of ultrasonic treatment on polyester resins and polyester coatings and could further promote the development of water-based coatings. Originality/value The contact angle of the water-based coating decreased by mechanical means. The effects of ultrasound on microstructure and properties of the coating and resin were discussed in detail.

Fabrication and characterization of polyimide/Al2O3 composite films via surface modification and ion exchange technique

Purpose – The aim of this study was to fabricate polyimide (PI)/Al2O3 composite films via surface modification and ion exchange techniques, and examine their properties. Design/methodology/approach – The method involves hydrolyzing the PI film double surface layers in an aqueous potassium hydroxide (KOH) solution and incorporating aluminium ions (Al3+) into the hydrolyzed layers of the PI film via subsequent ion exchange, followed by a treatment of the Al3+-loaded PI films with an aqueous ammonia solution, which leads to the formation of Al(OH)3 in the surface-modified layers. After a final thermal annealing treatment in ambient air, the Al(OH)3 decomposes to Al2O3, and forms composite layers on both surfaces of the re-imidized PI film. Findings – The PI/Al2O3 composite film obtained with a 6 hours of KOH treatment exhibited excellent thermal stability, good mechanical properties and better electric breakdown strength and corona-resistance properties than the pristine PI film. Practical implications – The...

Performance study of flame-retardant semi-rigid polyurethane foam with modified expandable graphite

Purpose In this paper, boric acid was loaded on the surface of expandable graphite (EG), polyvinyl alcohol (PVA) and silane coupling agent (KH550) served as a bridge. The purpose of this study was to improve the flame retardant properties of semi-rigid polyurethane, meanwhile, the mechanical properties of the foam got ameliorated. Design/methodology/approach PVA was dissolved in hot water. EG was added to this solution. After stirring for 0.5 h at 85°C in ultrasonic agitation, the system was put at room temperature to cool. The silane coupling agent KH550 was added dropwise into the solution system, stirring to fully hydrolyze. Boric acid was added into the system, placing it in an oven at 90°C to dry after filtration. Changing of flame retardant properties and mechanical properties of semi-rigid polyurethane adding modified EG were characterized. Findings The flame retardant performance of the foam with EG has been improved, whereas the tensile strength decreased with an increase in the content of EG. After adding modified EG, compared to semi-rigid polyurethane with EG, flame retardant performance and tensile strength of the foam improved. Research limitations/implications In the study reported here, the surface of EG was modified by boric acid. The modified EG was added into semi-rigid polyurethane foam. The flame retardant performance and tensile strength of the foam after adding modified EG were discussed. Results of this research could benefit in-depth study of the influence of adding modified EG to semi-rigid polyurethane. The study could promote the application of flame-retardant polyurethane foam. Originality/value The flame retardant performance and tensile strength of the semi-rigid polyurethane were improved by adding modified EG. The effects of modified EG on the flame retardant performance and tensile strength of semi-rigid polyurethane were discussed in detail.

Bending behaviors of electroresponsive PVA/PAA SIPN hydrogels under electric field

Semi-Interpenetrating networks (SIPN) hydrogel composed of poly (acrylic acid) (PAA) and poly (vinyl alcohol) (PVA) was prepared by using Ammonium persulfate (APS) and sodium bisulfite as initiator and glutaraldehyde as crosslinking agent. The structure and microscopic morphology were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), respectively. The results showed that PVA and PAA formed the interpenetrating network and there are lots of pores were evenly dispersed in hydrogel matrix. The electric stimuli responsive measurement results indicated the hydrogel bent toward the anode initially when it was placed in a high concentration NaCl aqueous solution. When the NaCl solution concentration is low, the hydrogel bent toward the cathode and kept invariant. The effects of different applied voltage and different AA contents on bending behaviors of hydrogel were also investigated.

Investigation on the morphology and dielectric properties of PI/BaTiO 3 composite films

Polyimides (PI) are widely used in microelectronic industries because of their outstanding characteristics such as good mechanical, thermal and dielectric properties. In this paper, a series of polyimide/barium titanate (PI/BaTiO3) composite films with different BT volumn contents were prepared. Modifier 3-amino-propyl-triethoxysilane was added during composite preparation to disperse the BaTiO3 particles in polyimide matrix. The effects of BaTiO3 addition on the microstructure and properties, especially the dielectric property of composite films were investigated. It was found that thermal stability of the composites could be improved with the incorporation of BaTiO3 particles. The dielectric constant (ε) and the dielectric loss (tan δ) of these composites increased with the increase of the volume fraction of BT particles, which was 45 and 0.013 respectively at 50 Hz as the composite contains 40vol% BaTiO3. The results of this work demonstrate the potential use of BaTiO3 powder for obtaining enhanced dielectric properties in a PI/BaTiO3 composite for application in an embedded capacitor.