A Green High-k Dielectric from Modified Carboxymethyl Cellulose-Based with Dextrin.

Many crucial components inside electronic devices are made from non-renewable, non-biodegradable, and potentially toxic materials, leading to environmental damage. Finding alternative green dielectric materials is mandatory to align with global sustainable goals. Carboxymethyl cellulose (CMC) is a bio-polymer derived from cellulose and has outstanding properties. Herein, citric acid, dextrin, and CMC based hydrogels are prepared, which are biocompatible and biodegradable and exhibit rubber-like mechanical properties, with Young modulus values of 0.89 MPa. Hence, thin film CMC-based hydrogel is explored as a suitable green high-k dielectric candidate for operation at low voltages, demonstrating a high dielectric constant of up to 78. These fabricated transistors reveal stable high capacitance (2090 nF cm-2) for ≈±3 V operation. Using a polyelectrolyte-type approach and poly-(2-vinyl anthracene) (PVAn) surface modification, this study demonstrates a thin dielectric layer (d ≈30 nm) with a small voltage threshold (Vth ≈-0.8 V), moderate transconductance (gm ≈65 nS), and high ON-OFF ratio (≈105). Furthermore, the dielectric layer exhibits stable performance under bias stress of ± 3.5 V and 100 cycles of switching tests. The modified CMC-based hydrogel demonstrates desirable performance as a green dielectric for low-voltage operation, further highlighting its biocompatibility.

Surface Electroactive Sites of Tungstated Zirconia Catalysts for Vanadium Redox Flow Batteries.

Surface electroactive sites for tungstate zirconia (WZ) were created by utilizing tungstate-immobilized UiO-66 as precursors via a double-solvent impregnation method under a mild calcination temperature. The WZ-22-650 catalyst, containing a moderate W content (22%), demonstrated a high density of surface electroactive sites. Proper heat treatment facilitated the binding of oligomeric tungsten clusters to stabilized tetragonal ZrO2, resulting in improved catalytic performance toward the VO2+/VO2+ redox couples compared to other tested samples. The substantial surface area, mesoporous structure, and establishment of new W-O-Zr bonds affirm the firm anchoring of WOx to ZrO2. This robust attachment enhances surface electroactive sites, elevating the electrochemical performance of vanadium redox flow batteries (VRFBs). Charge-discharge tests further demonstrate that the superior voltage efficiency (VE) and energy efficiency (EE) for VRFBs using the WZ-22-650 catalyst are 87.76 and 83.94% at 80 mA cm-2, which are 13.42% VE and 10.88% EE better than heat-treated graphite felt, respectively. Even at a higher current density of 160 mA cm-2, VRFBs utilizing the WZ-22-650 catalyst maintained considerable efficiency, recording VE and EE values of 76.76 and 74.86%, respectively. This facile synthesis method resulted in WZ catalysts displaying superior catalytic activity and excellent cyclability, offering a promising avenue for the development of metal-oxide-based catalysts.

Improvement of the mechanical property and thermal stability of polypropylene/recycled rubber composite by chemical modification and physical blending.

The binary blend materials containing the modified recycled rubber powder with maleic a hydride modified polypropylene thermoplastic elastomer were prepared by dynamic vulcanization and blended with a variety of additives such as activated agent, accelerator, solubilizer, and the crosslinking agent. The thermal properties and mechanical properties including tensile strengths and impact strengths of pristine rubber, polypropylene and their corresponding binary blends were investigated. Besides, the effects of the amount of rubber powder, polypropylene, crosslinking agent, accelerator, activator, and solvent were studied and the microstructures of the pristine rubber, pristine polypropylene, and their corresponding binary blends were observed by scanning electron microscopy. It was found that the compatibilizer could effectively disperse the size of 120 mesh of recycled rubber powder into the polypropylene in the same manner and the homogeneous tear section of the rubber/polypropylene thermoplastic elastomer was obtained. The results on the effects of additives on mechanical and morphological properties of recycled rubber/polypropylene binary blends guide the rational design of novel polymeric composites from recycled polymeric materials.

Microwave-assisted pyrolysis of Pachira aquatica leaves as a catalyst for the oxygen reduction reaction.

In this study, biomimetic Mg-N x -C y from Pachira aquatica leaves were mixed with carbon black (L/C catalyst), in which the mixture was treated by a conventional microwave oven at 700 W and 2 min, exhibiting high catalytic activity for the oxygen reduction reaction (ORR). By using a microwave-assisted process, it not only offers a cheaper and faster way to synthesize the catalyst compared to the conventional furnace process but also avoids the decomposition of the N4-structure. Using the optimized conditions, the L/C catalyst exhibits an electron transfer number of 3.90 and an HO2 - yield of only 5% at 0.25 V vs. RHE, which is close to the perfect four electron-transfer pathway. Besides, the L/C catalyst offers superior performance and long-term stability up to 20 000 s. The L/C catalyst contains a high proportion of quaternary-type nitrogen, Mg-N x -C y , and -C-S-C- which can be the active sites for the ORR.