MoS2/Mayenite Electride Hybrid as a Cathode Host for Suppressing Polysulfide Shuttling and Promoting Kinetics in Lithium-Sulfur Batteries.

The commercial viability of emerging lithium-sulfur batteries (LSBs) remains greatly hindered by short lifespans caused by electrically insulating sulfur, lithium polysulfides (Li2Sn; 1 ≤ n ≤ 8) shuttling, and sluggish sulfur reduction reactions (SRRs). This work proposes the utilization of a hybrid composed of sulfiphilic MoS2 and mayenite electride (C12A7:e-) as a cathode host to address these challenges. Specifically, abundant cement-based C12A7:e- is the most stable inorganic electride, possessing the ultimate electrical conductivity and low work function. Through density functional theory simulations, the key aspects of the MoS2/C12A7:e- hybrid including electronic properties, interfacial binding with Li2Sn, Li+ diffusion, and SRR have been unraveled. Our findings reveal the rational rules for MoS2 as an efficient cathode host by enhancing its mutual electrical conductivity and surface polarity via MoS2/C12A7:e-. The improved electrical conductivity of MoS2 is attributed to the electron donation from C12A7:e- to MoS2, yielding a semiconductor-to-metal transition. The resultant band positions of MoS2/C12A7:e- are well matched with those of conventional current-collecting materials (i.e., Cu and Ni), electrochemically enhancing the electronic transport. The accepted charge also intensifies MoS2 surface polarity for attracting polar Li2Sn by forming stronger bonds with Li2Sn via ionic Li-S bonds than electrolytes with Li2Sn, thereby preventing polysulfide shuttling. Importantly, MoS2/C12A7:e- not only promotes rapid reaction kinetics by reducing ionic diffusion barriers but also lowers the Gibbs free energies of the SRR for effective S8-to-Li2S conversion. Beyond the reported applications of C12A7:e-, this work highlights its functionality as an electrode material to boost the efficiency of LSBs.

Development of Personal Protective Clothing for Reducing Exposure to Insecticides in Pesticide Applicators.

Wearing appropriate personal protective equipment during the application of pesticides is one method of reducing dermal exposure to pesticides. Thus, the aim of this research is to develop personal protective clothing (PPC) coated with gum rosin and investigate the efficiency of its level of protection against chlorpyrifos and cypermethrin. Comparison of the protection efficiency of each PPC with Tychem® C coveralls was also investigated. Five commercially available cotton fabrics were chosen for tailoring the PPC, and then, the PPC was coated with a gum rosin finish to provide water repellence. The efficiency of the level of protection of the gum rosin-coated PPC against insecticides was tested in a laboratory (closed chamber). The remarkable findings were that the % protection efficiencies for all the PPC, with the exception of one, were not significantly different to those for Tychem® C coveralls. The protection efficiencies ranged from 99.85% to 99.97% against chlorpyrifos and 99.11% to 99.89% against cypermethrin. Therefore, our results suggest that gum rosin-coated clothing provided satisfactory levels of protection against insecticides and could be considered as suitable protective clothing for pesticide applicators. Choice of an appropriate fabric for coating with gum rosin also needs to be considered. A further study in field conditions is warranted to confirm the protection efficiency in a working environment.

Characterization of Phase Evolution, Microstructure and Electrical Properties of Sol-Gel Auto-Combustion Derived BCZT Ceramics.

This work aims to study the effect of sintering temperature on properties of barium calcium zirconate titanate (BCZT) ceramics. The BCZT is a Pb-free material that shows excellent piezoelectric properties. In this study, BCZT ceramics were prepared from BCZT powders synthesized from barium nitrate, calcium nitrate, zirconium (IV) oxynitrate hydrate, titanium (IV) butoxide and citric acid precursors by the sol-gel auto-combustion method. The BCZT powder was calcined at the temperature ranging from 700 to 1000 °C. Green bodies were sintered at various temperatures (1200-1450 °C). The X-ray diffraction patterns showed only non-crystalline phase of as-burnt powder. For the calcined powders, XRD patterns showed that the amount of crystalline, perovskite phase increased with increasing calcination temperature. The crystalline particles have a spherical shape and the size in the range of 25-35 nm. For the BCZT ceramics sintered at 1200-1300 °C, the density tended to increase with increasing sintering temperature. Very high bulk densities of 5.62-5.63 g/cm3 (which were higher than those of the ceramics synthesized by the wet-chemical method) were achieved at the sintering temperature of 1400-1450 °C. Ceramics produced at these temperatures possessed fully-developed microstructures, very good dielectric properties as well as high response of polarization and strain to applied electric field.

Effects of Bi0.5Na0.5TiO3 Dopant on Microstructure and Thermoelectric Properties of Na(x)CoO2 Ceramics.

Bi0.5Na0.5TiO3-doped Na(x)CoO2 ceramics with varied doping concentration of 0, 0.01, 0.03, 0.05 and 0.07 mol fraction were prepared by conventional solid state reaction method. The firing condition used was 950 degrees C for 8 h. X-ray diffraction pattern results showed that all produced ceramics were single phase with a hexagonal structure. Due to the substitution of BNT inside Na(x)CoO2 lattice, there was a slight shift of X-ray diffraction pattern to the left which indicated the lattice expansion. The scanning electron micrographs of ceramics indicated that small amount of BNT addition could eliminate pore and improved densification. A small amount of undissolved BNT was also present in Na(x)CoO2 matrix and dispersed at grain boundaries causing a decrease in grain size of the ceramic. The electrical conductivity and Seebeck coefficient of ceramics showed that all samples possessed metallic conduction behavior. However, BNT addition caused a reduction of electrical conductivity, Seebeck coefficient and power factor of Na(x)CoO2 ceramics.

Crystal structure and electrical properties of bismuth sodium titanate zirconate ceramics.

Lead-free bismuth sodium titanate zirconate (Bi0.5Na0.5Ti1-xZrxO3 where x = 0.20, 0.35, 0.40, 0.45, 0.60, and 0.80 mole fraction) [BNTZ] ceramics were successfully prepared using the conventional mixed-oxide method. The samples were sintered for 2 h at temperatures lower than 1,000°C. The density of the BNTZ samples was at least 95% of the theoretical values. The scanning electron microscopy micrographs showed that small grains were embedded between large grains, causing a relatively wide grain size distribution. The density and grain size increased with increasing Zr concentration. A peak shift in X-ray diffraction patterns as well as the disappearance of several hkl reflections indicated some significant crystal-structure changes in these materials. Preliminary crystal-structure analysis indicated the existence of phase transition from a rhombohedral to an orthorhombic structure. The dielectric and ferroelectric properties were also found to correlate well with the observed phase transition.

Structure-property relations of co-doped bismuth layer-structured Bi3.25La0.75(Ti1-xMox)3O12 ceramics.

In this work, the fabrication and investigation of substituting higher-valence Mo6+ for Ti4+ ion on the B-site of La3+-doped Bi4Ti3O12 [BLT] structure to form Bi3.25La0.75(Ti1-xMox)3O12 [BLTM] (when x = 0, 0.01, 0.03, 0.05 0.07, 0.09, and 0.10) ceramics were carried out. X-ray diffraction patterns of BLTM ceramics indicated an orthorhombic structure with lattice distortion, especially with a higher concentration of a MoO3 dopant. Microstructural investigation showed that all ceramics composed mainly of plate-like grains. An increase in MoO3 doping content increased the length and thickness of the grain but reduced the density of the ceramics. Electrical conductivity was found to decrease, while the dielectric constant increased with Mo6+ doping concentration. Ferroelectric properties were found to be improved with increasing MoO3 content and were optimized at x = 0.1.

Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic.

Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba0.7Sr0.3)TiO3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

Influences of phase transition and microstructure on dielectric properties of Bi0.5Na0.5Zr1-xTixO3 ceramics.

Bismuth sodium zirconate titanate ceramics with the formula Bi0.5Na0.5Zr1-xTixO3 [BNZT], where x = 0.3, 0.4, 0.5, and 0.6, were prepared by a conventional solid-state sintering method. Phase identification was investigated using an X-ray diffraction technique. All compositions exhibited complete solubility of Ti4+ at the Zr4+ site. Both a decrease of unit cell size and phase transition from an orthorhombic Zr-rich composition to a rhombohedral crystal structure in a Ti-rich composition were observed as a result of Ti4+ substitution. These changes caused dielectric properties of BNZT ceramics to enhance. Microstructural observation carried out employing SEM showed that average grain size decreased when addition of Ti increased. Grain size difference of BNZT above 0.4 mole fraction of Ti4+ displayed a significant increase of dielectric constant at room temperature.

Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics.

This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/xZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/xZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics.