High-resolution thermogravimetry of polyethersulfone chips in four atmospheres

H2O- and ethanol concentration-responsive polymer/gel inverse opal photonic crystal

Responsive photonic crystals have attracted much attention due to their strong capability to manipulate the propagation of light in the visible region, but it is still a big challenge to invisibility and mechanical stability. Here, the novel Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals, which have high mechanical stability and can release visible patterns after wetting with water, are discussed. The Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals are also responsive to the concentration of ethanol, and the structural color response times increase with increasing ethanol concentration. This design uses the selective infiltration, hydrogen bonding and capillary action of solvent to realize the spectral diversity of reflectance. Owing to the high polarity and hydrogen bonding ability of carboxyl groups, water molecules are adsorbed easily by the poly(acrylic acid) gel. Subsequently, the encrypted information is decrypted due to the redshift of the structural color. Because of its lower polarity and hydrogen bonding ability relative to water, ethanol can impede the absorption of solvent by gel. Therefore, the ethanol concentration can be identified based on the structural color response time. Furthermore, reliable information decryption methods make Poly(ether sulfone)/Poly(acrylic acid) inverse opal photonic crystals potentially uesful as trusted encryption devices.

High electromagnetic interference shielding of poly(ether-sulfone)/multi-walled carbon nanotube nanocomposites fabricated by an eco-friendly route

High-performance polymer matrix nanocomposites based on poly(ether-sulfone) (PES) matrix reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated using planetary ball mill followed by hot pressing. Their electrical properties and the electromagnetic interference shielding effectiveness (EMI-SE) were investigated and discussed. A percolation threshold of about 0.65 vol% MWCNT was obtained. The electrical conductivity was increased by more than ten orders of magnitude at the percolation threshold and to approximately 0.01 S cm^-1 at 6.67 vol% (or 10 wt%) MWCNT. This is a significant improvement. The highest EMI-SE of about 29-30 dB (both in the X-band and K_u-band) was obtained for the 6.67 vol% MWCNT filled nanocomposites with a thickness of 0.9 mm. The specific EMI-SE of these nanocomposites were found to be higher than the literature values. The thermal stability and the char yield (measured at 900 °C) of the nanocomposites were found to be more than 470 °C and 40.6%, respectively.

Preparation of Ti, Ti/TiC or Ti/TiN based hollow fibres with extremely low electrical resistivity

Porous Ti based hollow fibres with extremely low electrical resistivity (4.1–9.6 μΩ m), orders of magnitude smaller than reported for Ti-fibres in the literature, were produced by dry-wet spinning of a mixture of Ti-particles, polyethersulfone (PES), and N-methylpyrrolidone (NMP). Utilizing a two-step thermal decomposition of PES, consisting of treatment in air at 475 °C, followed by treatment in argon at 800 °C, hollow fibres of entirely metallic Ti are obtained, as confirmed by XRD, SEM-EDS, and TGA-MS analyses. Only a thin oxide layer is formed due to ambient surface oxidation, as identified by XPS analysis. Carbonization of the polymer under an inert atmosphere can be used to produce a Ti/TiC-composite. To obtain a Ti/TiN composite, the porous Ti-tubes can be treated in nitrogen atmosphere at 800 °C. The porosity, pore size distribution, and bending-strength of the fibres were determined for a low (800 °C) and high (1100 °C) degree of sintering, and it was found that these are largely independent of the chemical surface composition. The presence of TiC or TiN, likely in an outer, but crystalline shell (based on XRD and XPS data), results in lower resistivity than of the pure Ti fibres, which can be attributed to the insulating layer of TiC or TiN preventing capacitive effects at the Ti/air interface. The developed preparation methodology results in porous metallic and composite Ti based fibres, which are very suitable for electrochemical applications.

Preparative conditions are provided to obtain hollow fibers composed of Ti, Ti/TiC or Ti/TiN with extremely low electrical resistivity.

Hydrophilic SiC hollow fiber membranes for low fouling separation of oil-in-water emulsions with high flux

The dry-wetting spinning technique involving immersion-induced phase inversion and dry-sintering was applied to prepare two types of SiC and Al₂O₃ hollow fiber membranes.