The properties of a mixed metallic and semiconducting carbon nanotube (CNT) sample dispersed in nonconjugated poly(methyl methacrylate) (PMMA) and conjugated poly(bisdodecylquaterthiophene) (PQT12) were compared, with and without p-doping by NOBF4. The CNTs were distributed much more evenly, and percolated at much lower concentrations (ca. 2%), in the PMMA as compared to PQT12, as judged by optical microscopy and electronic conductivity measurements. Seebeck coefficients (S) obtained on the PMMA samples indicated dominance by the metallic fraction, with values <10 µV/K. Composites made with PQT12 alone showed slightly higher values of S, but with the addition of 3 wt % dopant, S increased markedly to about 100 µV/K at 5-10% CNT fractions, while conductivity was unexpectedly low. As the CNT fraction in the doped sample was increased to 25-30%, conductivity approached that of the comparable concentration of CNTs in PMMA, while S, ca. 15 µV/K, was still higher than that measured in PMMA. The observations inform interpretations of CNT-polymer composite thermoelectric data, pointing out the roles of conjugated main chains and added dopants in modulating contributions of CNTs to thermoelectric composite performance.

Up-converting thermographic phosphors are of significant interest due to specific advantages for temperature measurement applications over traditional contact-based methods. Typically, infrared excitation stimulates visible fluorescence only from the target phosphor and not the surrounding medium. This is in contrast to ultraviolet excitation which may also produce interfering luminescence from cells and other biological tissue in the vicinity, for instance. When traversing a material, usually infrared losses due to scattering and absorption are less than for ultraviolet wavelengths. An example is human skin. This investigation follows logically from earlier efforts incorporating thermographic phosphors into elastomers and aerogels and their function as a reusable temperature sensor has been previously demonstrated by the authors. Layered phosphor/PDMS/aerogel composites are also currently under investigation by the authors for heat flux sensing. For maximum utility and understanding; physical, optical and thermal properties are characterized over a wide range of temperatures. Y2O2S:Yb,Er and La2O2S:Yb,Er up-converting phosphor composites with a fixed doping concentration were synthesized for this study and fully characterized as a function of temperature. The excitation/ emission characteristics of the powder alone and the prepared composites were investigated between -50 °C and +200 °C in an environmental chamber and the decay behavior of each sample type was measured. Here, the authors report on decay behavior and emission intensity of the PDMS composites as a function of temperature. Results were compared with powder –only parameters and are reported here.

Vanadium Pentoxide (V2O5) has been identified as a potential cathode material owning to its high specific capacity, theoretically, 441 mAh g-1 for 3Li+ ions insertion/extraction. However, the intrinsic drawbacks of V2O5, i.e. structural instability and poor electronic and ionic conductivity, greatly inhibit its application as a cathode. Here, we report a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal reaction to synthesize V2O5 nanoclusters. Unique aggregated fiber structure was obtained after annealing. To achieve a porous structure and increase the conductivity, nitrogen-doped Graphene (NG) suspended in ethylene glycol was added to the reaction mixture. The obtained spherical V2O5 nanoparticles and NG sheets were randomly dispersed in the matrix of the V2O5 spheres. As a cathode material for lithium-ion batteries, the V2O5/NG hybrids demonstrate better rate performance compared to the bundle-like V2O5 fibers, delivering higher specific capacity of ∼ 300 and 150 mAh g-1 at a rate of C/10 and 5C, respectively. The enhanced performance in lithium storage are attributed to the synergistic effect of the nanostructured V2O5/NG composites.

Lithium sulfide (Li2S) is one of the most attractive cathode materials for high energy density lithium batteries as it has a high theoretical capacity of 1166 mA h g-1. However, Li2S suffers from poor rate performance and short cycle life due to its insulating nature and polysulfide shuttle during cycling. In this work, we report a facile and viable approach to address these issues. We propose a method to synthesize a Li2S based nanocomposite cathode material by dissolving Li2S as the active material, polyvinylpyrrolidone (PVP) as the carbon precursor, and graphene oxide (GO) as a matrix to enhance the conductivity, followed by a co-precipitation and high-temperature carbonization process. The Li2S/rGO cathode yields an exceptionally high initial capacity of 817 mAh g-1 based on Li2S mass at C/20 rate and also shows a good cycling performance. The carbon-coated Li2S/rGO cathode demonstrates the capability of robust core-shell nanostructures for different rates and improved capacity retention, revealing carbon coated Li2S/rGO composites as an outstanding system for high-performance lithium-sulfur batteries.

We investigate the insertion energetics of Ca at low concentrations in four promising vanadium oxide phases (α and δ vanadium pentoxide (V2O5) polymorphs as well as rutile- (R) and bronze-type (B) vanadium dioxide (VO2)) using density functional theory (DFT). We find α-V2O5 to be the most suitable material for an application as cathode, driven by a stable coordinative environment, while VO2(R) does not exhibit a stable low-concentration CaxVO2 phase due to severe distortions of the host lattice due to the large calcium ion. The results provide insight into the possibility of employing these phases as active cathode materials of Ca-ion batteries.

Increasing the operation voltage of LiCoO2 (LCO) is a direct way to enhance the energy density of the Li-ion batteries. However, at high voltages, the cycling stability degrades very fast due to the irreversible changes in the electrode structure, and formation of an unstable solid electrolyte interface layer. In this work, Ag thin film was prepared on commercial LCO cathode by using magnetron sputtering technique. Ag coated electrode enabled an improved electrochemical performance with a better cycling capability. After 100 cycles, Ag coated LCO delivers a discharge capacity of 106.3 mAh g-1 within 3 - 4.5 V at C/5, which is increased by 45 % compared to that of the uncoated LCO. Coating the electrode surface with Ag thin film also delivered an improved Coulombic efficiency, which is believed to be an indication of suppressed parasitic reactions at the electrode interface. This work may lead to new methods on surface modifications of LCO and other cathode materials to achieve high-capacity Li-ion batteries for high-voltage operations.

This study reports a high-performance tin (Sn)-coated vertically aligned carbon nanofiber array anode for lithium-ion batteries. The array electrodes have been prepared by coaxial sputter-coating of tin (Sn) shells on vertically aligned carbon nanofiber (VACNF) cores. The robust brush-like highly conductive VACNFs effectively connect high-capacity Sn shells for lithium-ion storage. A high specific capacity of 815 mAh g-1 of Sn was obtained at C/20 rate, reaching toward the maximum value of Sn. However, the electrode shows poor cycling performance with conventional LiPF6 based organic electrolyte. The addition of fluoroethylene carbonate (FEC) improve the performance significantly and the Sn-coated VACNFs anode shows stable cycling performance. The Sn-coated VACNF array anodes exhibit outstanding capacity retention in the half-cell tests with electrolyte containing 10 wt.% FEC and could deliver a reversible capacity of 480 mAh g-1 after 50 cycles at C/3 rate.

The crystallization of (9-X) K2O-1Li2O-12MgO-10B2O3-40SiO2-16Al2O3-12MgF2-X PbO/BaO/ZnO (X =0/5) composition (wt.%) were studied by means of dilatometry, DSC, XRD, SEM and microhardness analysis. Density of base K-Li-Mg-B-Si-Al-F glass (2.59 g.cm–3) is found to be increased on addition of the network modifier oxides PbO, BaO and ZnO content. Addition of Pb2+, Ba2+ and Zn2+ furthermore increased the glass transition temperature (Tg.). A characteristic exothermic hump is found to be appeared in DSC thermograph at the temperature range 800-950°C; and that is ascribed to the formation of crystalline phase fluorophlogopite mica, KMg3(AlSi3O10)F2. Opaque glass-ceramics were prepared from K-Li-Mg-B-Si-Al-F glasses (with and without containing PbO, BaO and ZnO content) by controlled heat-treatment at 1000°C. Interlocked type microstructure combined of flake like fluorophlogopite mica crystals is obtained in ZnO-containing K-Li-Mg-B-Si-Al-F glass-ceramic; and such microstructural pattern is ascribed to cause large thermal-expansion (>11.5×10-6/K, 50-800°C).Vickers Microhardness of base glass-ceramic (5.12 GPa) is increased when contains ZnO (5.26 GPa). ZnO-containing boroaluminosilicate glass-ceramic is, hence, considered with potential interest as they can exhibit the microcrack resistivity in high temperature recycling operation (like SOFC).