Prestrain‐Free Dielectric Elastomers Based on Acrylic Thermoplastic Elastomer Gels: A Morphological and (Electro)Mechanical Property Study

Recent efforts have established that thermoplastic elastomer gels (TPEGs) composed of styrenic triblock copolymers swollen with a midblock‐selective solvent exhibit remarkable electromechanical properties as high‐performance dielectric elastomers. This class of electroactive polymers typically requires high electric fields for actuation, and a shortcoming that continues to thwart the widespread commercialization of such materials in general is the need to apply mechanical prestrain prior to electroactuation to decrease film thickness and, thus, the electric potential required to promote actuation. To alleviate this requirement, TPEGs consisting of acrylic triblock copolymers differing in molecular weight and composition, and swollen with a high dielectric, midblock‐selective solvent are investigated. Synchrotron small‐angle x‐ray scattering is used to probe the nanoscale morphologies of the resultant materials, and analysis of quasi‐static and cyclic tensile properties provides additional insight into both blend morphologies and electroactuation efficacy. Actuation strains measured in the absence of mechanical prestrain exceed 100% on an area basis, and electric fields capable of inducing actuation are as low as ～20 kV/mm. Failure occurs by either electromechanical instability or dielectric breakdown, depending on the copolymer and TPEG composition employed. The electromechanical properties of these acrylic‐based TPEGs match or exceed those of skeletal muscle, in which case they constitute an attractive and unexplored alternative to existing dielectric elastomers.     

Controlling interferometric properties of nanoporous anodic aluminium oxide

A study of reflective interference spectroscopy [RIfS] properties of nanoporous anodic aluminium oxide [AAO] with the aim to develop a reliable substrate for label-free optical biosensing is presented. The influence of structural parameters of AAO including pore diameters, inter-pore distance, pore length, and surface modification by deposition of Au, Ag, Cr, Pt, Ni, and TiO₂ on the RIfS signal (Fabry-Perot fringe) was explored. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at different voltages (30 to 70 V) and anodization times (10 to 60 min). Results show the strong influence of pore structures and surface modifications on the interference signal and indicate the importance of optimisation of AAO pore structures for RIfS sensing. The pore length/pore diameter aspect ratio of AAO was identified as a suitable parameter to tune interferometric properties of AAO. Finally, the application of AAO with optimised pore structures for sensing of a surface binding reaction of alkanethiols (mercaptoundecanoic acid) on gold surface is demonstrated.     

Removal of anionic dye Congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent: equilibrium, thermodynamic, kinetics, mechanism and process design

Pine cone a natural, low-cost agricultural by-product in Australia has been studied for its potential application as an adsorbent in its raw and hydrochloric acid modified form. Surface study of pine cone and treated pine cone was investigated using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The modification process leads to increases in the specific surface area and decreases mean particle sizes of acid-treated pine cone when compared to raw pine cone biomass. Batch adsorption experiments were performed to remove anionic dye Congo red from aqueous solution. It was found that the extent of Congo red adsorption by both raw pine cone biomass and acid-treated biomass increased with initial dye concentration, contact time, temperature but decreased with increasing solution pH and amount of adsorbent of the system. Overall, kinetic studies showed that the dye adsorption process followed pseudo-second-order kinetics based on pseudo-first-order and intra-particle diffusion models. The different kinetic parameters including rate constant, half-adsorption time, and diffusion coefficient were determined at different physico-chemical conditions. Equilibrium data were best represented by Freundlich isotherm model among Langmuir and Freundlich adsorption isotherm models. It was observed that the adsorption was pH dependent and the maximum adsorption of 32.65 mg/g occurred at pH of 3.55 for an initial dye concentration of 20 ppm by raw pine cone, whereas for acid-treated pine cone the maximum adsorption of 40.19 mg/g for the same experimental conditions. Freundlich constant 'n' also indicated favourable adsorption. Thermodynamic parameters such as ?G(0), ?H(0), and ?S(0) were calculated. A single-stage batch absorber design for the Congo red adsorption onto pine cone biomass also presented based on the Freundlich isotherm model equation.     

The performance enhancements of upflow anaerobic sludge blanket (UASB) reactors for domestic sludge treatment--a state-of-the-art review

Nowadays, carbon emission and therefore carbon footprint of water utilities is an important issue. In this respect, we should consider the opportunities to reduce carbon footprint for small and large wastewater treatment plants. The use of anaerobic rather than aerobic treatment processes would achieve this aim because no aeration is required and the generation of methane can be used within the plant. High-rate anaerobic digesters receive great interests due to their high loading capacity and low sludge production. Among them, the upflow anaerobic sludge blanket (UASB) reactors have been most widely used. However, there are still unresolved issues inhibiting the widespread of this technology in developing countries or countries with climate temperature fluctuations (such as subtropical regions). A large number of studies have been carried out in order to enhance the performance of UASB reactors but there is a lack of updated documentation. In face of the existing limitations and the increasing importance of this technology, the authors present an up-to-date review on the performance enhancements of UASB reactors over the last decade. The important aspects of this article are: (i) enhancing the start-up and granulation in UASB reactors, (ii) coupling with post-treatment unit to overcome the temperature constraint, and (iii) improving the removal efficiencies of the organic matter, nutrients and pathogens in the final effluent. Finally the authors have highlighted future research direction based on their critical analysis.     

Polybenzimidazole as proton conducting filler in polydimethylsiloxane: Enhanced oxidative stability and membrane properties

In this work, pyridine-based low-molecular-weight polybenzimidazole (LMP) was synthesized (inherent viscosity: 0.52 dL g⁻¹) by controlling the reaction time. The synthesized LMP was incorporated into polydimethylsiloxane (PDMS) matrix to impart proton conductivity. The composite membrane containing 30 wt % of LMP exhibited proton conductivity of 16 mS cm⁻¹ at 100–120 °C. The LMP chains were bundled and formed clusters (aggregates) in the PDMS matrix as observed in field emission scanning electron microscopy. This is attributed to nonpolar (siloxane)–polar (polybenzimidazole) repulsion. An impressive weight loss of 8.6% was observed after 120 h Fenton's test that indicates the high oxidative stability of composite membranes. However, elongation of composite membranes was decreased compared to that of pristine PDMS, which is attributed to the incorporation of rigid LMP chains. The resultant composite membranes exhibited moderate proton conductivity, low moisture absorption, and good thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48151.     

A multi-attribute decision making approach of mix design based on experimental soil characterization

The clay mineral composition is one of the major factors that governs the physical properties of silty sand subgrade. Therefore, a thorough knowledge of mineral composition is essential to predict the optimum engineering properties of the soil, which is generally characterized by different indices like maximum dry density (MDD), California bearing ratio (CBR), unconfined compressive strength (UCS) and free swelling index (FSI). In this article, a novel multiattribute decision making (MADM) based approach of mix design has been proposed for silty sand–artificial clay mix to improve the characteristic strength of a soil subgrade. Experimental investigation has been carried out in this study to illustrate the proposed approach of selecting appropriate proportion for the soil mix to optimize all the above mentioned engineering properties simultaneously. The results show that a mix proportion containing approximately 90% silty sand plus 10% bentonite soil is the optimal combination in context to the present study. The proposed methodology for optimal decision making to choose appropriate combination of bentonite and silty sand is general in nature and therefore, it can be extended to other problems of selecting mineral compositions.     

Electrical impedance spectroscopic study of mandarin orange during ripening

Electrical impedance spectroscopy (EIS) as non-destructive investigation has been conducted to study the electrical impedance variations during ripening of mandarin orange. The objective of the work is to study the electrical impedance variations and variations in weight of the orange fruit with different ripening state. Electrical equivalent circuit has been modeled relative to the Nyquist plot obtained during the ripening of orange by non-linear curve fitting technique. EIS studies on orange fruit have been conducted by applying a small amount of alternating current through an array of Ag/AgCl electrodes attached to the orange fruit. The impedance and phase angles of orange fruit are measured at frequency sweep from 50 Hz to 1 MHz for 100 frequency points. The results revealed that the impedance, real part and imaginary part of the impedance all are increased and the weight of orange are decreased with the increase in ripening state. It is observed that the electrical equivalent circuit of orange fruit contains a constant phase element.     

In situ monitoring of NiO–Al2O3 nanoparticles synthesis by thermo-Raman spectroscopy

Simultaneous thermogravimetric analysis and thermo-Raman spectroscopy (TRS) measurements for in situ monitoring of wet chemical reaction of Ni(OH)₂·4H₂O and Al(OH)₃ forming NiO–Al₂O₃ nanoparticles is studied and compared with the solid-state reaction. Herein, a different approach of synthesis and monitoring of NiO–Al₂O₃ by TRS is presented, in which, in situ thermo-Raman spectra are recorded at every degree interval from 25 to 800 °C to understand the structural and compositional changes in NiO–Al₂O₃ as a function of temperature. Slow controlled heating of the sample as in TRS, enables better control over morphology and particle size distribution (～10–20 nm diameter). The X-ray diffraction (XRD) shows that smaller particle size is obtained using wet chemical reaction than the solid-state reaction (～25 nm diameter). TRS studies also reveal that, the bulk NiAl₂O₄ forms at temperatures above 800 °C, although, the onset of formation is around 600 °C. Condensation of Al(OH)₃ forming Al₂O₃ is also monitored, wherein, presence of hydrocarbon is found to contribute to the observed fluorescence background. Based on the TRS and complementary characterizations using XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis, the formation of supported NiO–Al₂O₃ is discussed.