Effects of log storage conditions and steaming process on the formaldehyde emissions of particleboard manufactured from eucalyptus (E. camaldulensis) wood

The aim of this study was to determine the changes in formaldehyde emissions of eucalyptus particleboards produced from logs stored under different conditions (indoor, outdoor, and under water) or steamed. The pH and Stiasny values of particles changed significantly according to the storage condition and log steaming process. The pH values of particles obtained from steamed logs and stored outdoors for 4 months were found to be lower than those of the particles obtained from logs stored in the other aforementioned two conditions. The peaks of acetyl groups in the IR-spectra of the four group particles were similar. There was a strong relationship among the formaldehyde emission values of the panels pressed at 150 °C and the Stiasny values of the particles from which the panels were produced. The formaldehyde emission values of the panels pressed at 190 °C were lower than those of the panels pressed at 150 °C.     

Processing and electrical properties of (1 − x)[(1 − y)(Pb(Mg1/3Nb2/3)O3)–y(Pb(Yb1/2Nb1/2)O3)]–xPbTiO3 ceramics

Ferroelectric ceramics in the vicinity of morphotropic phase boundary (MPB) with compositions represented as (1 ? x)[(1 ? y)(Pb(Mg_1/3Nb_2/3)O₃)–y(Pb(Yb_1/2Nb_1/2)O₃)]–xPbTiO₃ were prepared by solid state reaction. The addition of PYbN to PMN–PT decreased the sintering temperature from 1200 °C (y = 0.25) to 1000 °C (y = 0.75). The PT content, where the MPB was observed, increased with the PYbN addition. A remanent polarization value of 28.5 µC/cm² and a coercive field value of 11 kV/cm were measured from 0.62[0.25PMN–0.75PYbN]–0.38PT ceramics, which were close to the ones measured from PMN–0.32PT ceramics. In addition, the Curie temperature was found to increase with PYbN additions.     

Engineered catalyst layer design with graphene-carbon black hybrid supports for enhanced platinum utilization in PEM fuel cell

In this study, a new approach was applied to prepare platinum/reduced graphene oxide/carbon black (Pt/rGO/CB) hybrid electrocatalysts. Unlike literature firstly GO and CB in varying ratios are homogeneously mixed with a high shear mixer and then Pt was impregnated onto the hybrid support structure according to the polyol method. According to our approach CB was used as a spacer and intercalating agent in both Pt impregnation and electrode preparation to avoid restacking and increase the Pt utilization. Thus rGO/CB based hybrid support can ease the diffusion while it is promoting to the use of high electrical connectivity and surface area of graphene. The maximum power density of 645 mW cm^?2 with Pt utilization efficiency of 2.58 kW/gPt was achieved with the hybrid containing the smallest amount of CB. It seems that this small amount of CB effectively modifies the electrode structure. The enhanced fuel cell performance can be attributed to synergistic effects from graphene and CB providing better mass transport and Pt utilization in the catalyst layer.     

Synthesis and performance evaluation of thin film PPy-PVDF multilayer electroactive polymer actuators

Bending-type microactuators less than 1 mm in length and comprising of two polypyrrole (PPy) layers separated by polyvinylidene fluoride (PVDF) membrane have previously been fabricated and was shown to operate both in air and aqueous media. The main limiting factor to increase the bending angle and to further miniaturise these actuators was the thickness of the commercially-available PVDF membrane used (～110 μm). In this study, we have synthesised a porous PVDF thin film with a thickness of 32 μm using a spin coating technique, and electrochemically deposited PPy layers on both sides of this thin film to make ultra thin film polymer actuators. The electromechanical and electrochemical properties are investigated and compared with those of the thicker actuator system using the commercially-available PVDF and under identical conditions. The thin film shows very promising performance compared to its thicker counterpart.     

Enhancement of actuation ability of ionic-type conducting polymer actuators using metal ion implantation

In this study, we present the results and implications of an experimental study into the effect of gold-ion implantation on the actuation performance of ionic-type conducting polymer actuators, represented here by cantilevered tri-layer polypyrrole (PPy) actuators. We implant gold ions beneath the outer surfaces of PPy-based conducting polymer layers of the actuators in order to increase the conductivity of these layers, and therefore improve the overall conductivity of the actuators. A Filtered Vacuum Cathode Arc (FVCA) ion source was used to implant gold particles into the conducting polymer layers. Electrode resistance and capacitance, surface resistance, current response, mechanical work output of the actuator samples were measured and/or calculated for the actuator samples with and without gold implantation in order to demonstrate the effect of the gold-implantation. The current passing through the conducting polymer electrodes during their ‘electrochemomechanical’ actuation was measured to determine the charging time constant of the actuators. The mechanical displacement output of the actuators was recorded. The results demonstrate that the conductivity of the actuators increases noticeably, which has a flow on effect on the current response (i.e., charge injected into the polymer layers) and the mechanical work output. While the gold implanted actuators had a higher mechanical stiffness therefore a smaller displacement output, their time constant is smaller, indicating a higher response speed. The gold-implanted actuators generated a 15% higher mechanical work output despite the adverse effects on the polymer of the vacuum processing needed for the ion implantation.     

Feedback control of tri-layer polymer actuators to improve their positioning ability and speed of response

Improving positioning ability of electroactive polymer actuators typified by polypyrrole (PPy) through feedback control of their position has been considered. The actuators operate in air, as opposed to their predecessors. One of the problems associated with the actuators is the forward relaxation/creep or drift, which occurs after the full reduction and oxidation processes are completed. A high-resolution laser displacement sensor was used to detect the position of the cantilever-type polymer actuators and the classical, yet effective, Proportional, Integral and Derivative (PID) control method has been employed to generate the appropriate control input in order to make sure that no drift occurs in the user-specified position of the actuators. A set of experimental results with and without feedbacking the position data are presented to demonstrate the efficacy of the control method for improving the positioning ability and the speed of response. The rise time is reduced by more than 500 times and the position tracking error is less than 10% for a time-varying user-specified position command.     

Platinum nanoparticles decorated carbon nanofiber hybrids as highly active electrocatalysts for polymer electrolyte membrane fuel cells

Increasing the efficiency of electrocatalyst is the key demand for the polymer electrolyte membrane fuel cells (PEMFC). To address the activity and performance challenges of commercial electrocatalyst, Pt/C, we introduce a new hybrid catalyst support for Pt nanoparticles. In this regard, combining or mixing specific type of carbon-based supports is a feasible strategy to increase catalyst utilization and performance. In the current study, Pt nanoparticles (NPs) were decorated on a new hybrid network, comprising of carbon nanofiber (CNF) and carbon black (CB), by means of a facile and efficient microwave (MW) assisted reduction method. All synthesized electrocatalysts were characterized to elucidate chemical and morphological structures. Then, the hybrid electrocatalysts were utilized as hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) electrocatalysts and their electrocatalytic activities were investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), respectively. We found that the hybridization of CNF with CB substantially improved not only the electrocatalytic activity but also the fuel cell performance, which can be attributed to a consecutive conductive network, in which CB acts as a spacer, and synergistic effects between the CNF and CB. The hybrid electrocatalyst (Pt/CNF-CB with 50:50 wt%) showed a superior activity toward HOR and ORR while also offering exceptional fuel cell performance. That hybrid possessed the highest electrochemically active surface area (ECSA) compared with Pt/CNF and Pt/CB. In addition, the mass activity (at 0.80 V vs RHE) of the Pt/CNF-CB (50:50 wt%) is about 3.3 and 3.5 times higher than that of Pt/CNF and Pt/CB, respectively. Furthermore, that hybrid electrocatalyst exhibited enhanced fuel cell performance with 907 mW.cm⁻¹ maximum power density. This work demonstrated that the CNF-CB supported Pt nanoparticles as electrocatalysts are extremely promising for fuel cell reactions.     

Polyethylene glycol‐sugar composites as shape stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG)‐sugar composites have been investigated as cost effective shape‐stabilized phase change materials for thermal energy storage. PEGs form internal hydrogen bonds stabilizing their chains at solid state. However low molecular weight PEGs are liquid due to short chains as high molecular weight PEGs have too little concentration of hydroxyl groups. Therefore, glucose, fructose, and lactose are used as hydrogen bond source in this study. Consequently it is found that sugars stabilized PEGs up to 90% PEG constitution in solid state except for 90%PEG10,000/10% fructose blend. Fourier transform‐infrared (FT‐IR) analysis revealed considerable interactions between PEGs. The maximum changes in the spectra were observed in the OH stretching region as band broadening due to increasing hydrogen bonding interactions. Differential scanning calorimetry (DSC) analysis are used to determine phase change temperatures and enthalpy of the shape‐stabilized composites that are slightly lower than those of PEG precursors due to the interference effect of sugar in crystallization process. The enthalpies of the blends are 89%, 95%, and 94% of expected from 90%PEG/10% glucose blends, 93%, 94%, and 93% of expected from 90% PEG/10% fructose blends, and 99%, 96%, and 96% of expected from 90% PEG/10% lactose blends respectively when PEGs with 1,000; 6,000; and 10,000 g/mol average molecular weights are used respectively. The diameter of the spherulitic crystals of PEGs decreases with the addition of any of sugar derivatives and spherulites of the composites turns to semi‐amorphous solid structures at temperatures above melting point of PEG precursor. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers