Aluminum nitride (AlN) features an extremely interesting combination of very high thermal conductivity and excellent electrical insulation; therefore, it has been widely used in the high power electronic devices. The hydrolytic reaction of aluminum nitride powder decays the shelf-life and lowers the high power operating performance of the electronic devices. A protecting film of the polymer derived silicon oxycarbonitride ceramic is coated and fully wrapped on the surface of aluminum nitride powder against facilitating hydrolysis. Poly (organosilazane) precursor is incorporated with the commercial aluminum nitride powder pyrolyzed at 700 °C under argon environment for few hours to form a core-shell structure with a film thickness, 10–20 nm of silicon oxycarbonitride (SiCNO) ceramic shell and the aluminum nitride core. Measuring the pH value of SiCNO/AlN core-shell powder in deionized water at room temperature is to observe the hydrolytic behavior that its pH value is stable to maintain about 10 at ambient environment over ten days, whereas for the characterization of the reaction products, XRD, SEM and TEM analyses are employed. The hydrolytic behavior measured at 90 °C also shows that the SiCNO/AlN core-shell powder is still able to keep the protection from high temperature hydrolysis. XRD spectra proves that the characteristic crystalline peaks of SiCNO/AlN core-shell powder after hydrolysis over ten days are still the same as those of the commercial aluminum nitride powder before hydrolysis. These results directly indicate that the polymer derived silicon oxycarbonitride ceramic film fully protects the aluminum nitride powder from hydrolysis. When the content of silicon oxycarbonitride shell reduces to reach certain value, the hydrolytic protection gradually vanishes for long time.

Present investigation deal with the facile synthesis of Co9Se8 nanoparticles (NPs) and their application as the potential anode for lithium-ion battery (LIB). The primary size of the Co9Se8 NPs can be achieved between 10 ~ 25 nm while the secondary cluster size ranging from 150 ~ 200 nm as observed by transmission electron microscope (TEM). The specific capacity of Co9Se8 NPs LIB anode can reach around ~610 mAhg−1 during charging (lithium ion released from Co9Se8 nanoparticles), and ~730 mAhg−1 during discharging (lithium ion intercalated) at an applied current density of ~100 mAg−1. These values are significantly higher than that of the commercial graphite anode (theoretical capacity ~372 mAhg−1). The irreversibility of Co9Se8 anode (~15%) is also significantly lower than that of most metal oxides and silicon-based anodes (irreversibility ranging between 30 ~ 50% or higher for Si). The reason for superior specific capacity and low irreversibility compared to metal oxides and silicon-based materials could be owing to the stable nano-cluster size which help to reduce the diffusion path and internal resistance to lithium ion

A novel multilayer carbon nanostructure catalyst (MCNC), composed of carbon fiber (CF), carbon nanotube (CNT), precious metal dispersions (Pt/Pd/Ru) and silicon carbonitride (SiCN) layer derived from a liquid based polymeric precursor, has been developed in this work with the aim to be used as the electrode for decomposing water into hydrogen. The ternary Pt/Pd/Ru catalysts are deposited on the thin film coating of SiCN functionalized carbon nanotube (SiCN/CNT) electrophoretically deposited (EPD) on carbon fiber. The silicon carbonitride layer makes the silicon-transition metal bond form a sub-nanometric layer of metal catalyst to increase the surface-to-volume ratio and catalytic efficiency. Sodium borohydride, NaBH4, solution spontaneously reacts with MCNC to generate hydrogen in a very fast rate, depending on its concentrations. The ternary catalyst shows a higher generation rate compared to the binary and single catalytic systems already prepared with the same synthetic procedure. The reaction mechanism and the catalytic efficiency have been described in terms of the reaction pattern that involves an electric charge transfer, due to the negative charge on the BH4− ion transferred with one hydrogen atom via SiCN/CNT structure, ensuring the generation rate increase. As an electrical potential is applied between two MCNC electrodes in sodium borohydride electrolyte, the generation rate of hydrogen can be tuned by the applied potential. When the concentration of NaBH4 is much diluted, this electrolytic and hydrolytic reaction obeys the Faraday's law. Due to diluted solution, the reaction of hydrogen generation is dominated by electrolytic reaction that can be decomposed at a very low potential ∼0.5 V. This result indicates that the band gap of the semiconductive MCNC electrode can be lowered by the applied potential. The figure-of-merit, FOM can reach 1150 L min−1 [NaBH4]−1gmet−1, as one volt applied. When a constant voltage applied, FOM gradually decreases with [NaBH4] increase till to reach the steady state that the zero order reaction is achieved. The MCNC electrode is robust and re-useable by alcohol rinsing and dry after reaction.

Flower-like self-assembly of vanadium pentoxide (V2O5) has been synthesized via a facile, eco-friendly and bottom-up approach using hydrothermal process at low temperature with high-yield for the first time. This hierarchical flower-like structure is found to be accumulated with numerous plate-like subunits, and each unit seems to be a complete structure of randomly grown hexagonal nano/micro plates. A possible reaction mechanism for the formation of hierarchical flower-like structures of V2O5 has also been proposed. The reduction process (from V5+ to V4+ or some mix oxidation states) is carried out through sulphur-reduction by using an advanced homemade CVD system with argon as the carrier gas at different temperatures. The sulphur reduced V2O5 structure formed shows excellent lithium storage and rate capability. After sulphur-reduction, the specific capacity of the flower-like V2O5 as the cathode material can achieve 400 mAh g(-1), 300 mAh g(-1), 250 inAh g(-1) and 100 mAh ri at different rates of 0.07C, 1C, 2.3C and 29 C, respectively between 1.75 V and 4 V. (C) 2015 Elsevier B.V. All rights reserved.

The shuttling process involving lithium polysulfides is one of the major factors responsible for the degradation in capacity of lithium–sulfur batteries (LSBs). Herein, we demonstrate a novel and simple strategy—using a bifunctional separator, prepared by spraying poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on a pristine separator—to obtain long-cycle LSBs. The negatively charged SO3− groups present in PSS act as an electrostatic shield for soluble lithium polysulfides through mutual coulombic repulsion, whereas PEDOT provides chemical interactions with insoluble polysulfides (Li2S, Li2S2). The dual shielding effect can provide an efficient protection from the shuttling phenomenon by confining lithium polysulfides to the cathode side of the battery. Moreover, coating with PEDOT:PSS transforms the surface of the separator from hydrophobic to hydrophilic, thereby improving the electrochemical performance. We observed an ultralow decay of 0.0364% per cycle when we ran the battery for 1000 cycles at 0.25C—far superior to that of the pristine separator and one of the lowest recorded values reported at a low current density. We examined the versatility of our separator by preparing a flexible battery that functioned well under various stress conditions; it displayed flawless performance. Accordingly, this economical and simple strategy appears to be an ideal platform for commercialization of LSBs.

Different morphologies of vanadium pentoxide (V2O5) have been synthesized via a facile, eco-friendly, bottom-up and self-assembly approach using hydrothermal process at low temperature for the first time. The as-prepared V2O5 plate-like structure shows excellent lithium storage and rate capability compared to tube-like structure and commercial V2O5 powder. The specific capacity of V2O5 plate can reach 470 mA h g(-1) at the first cycle with a current density, 17 mA g(-1) (about 0.05 C) and 110-120 mA h g(-1) at high current density, 1360 mA g(-1) (about 13 C). The gravimetric energy densities of the plate-like V2O5 structure can achieve 1073Wh kg(-1) and 722Wh kg(-1) with the current densities of 51 mA g(-1) and 680 mA g(-1), respectively.

A low-cost sensing mechanism of hydrogen gas is developed using polymer-derived ceramic, a liquid organic precursor, polysilazane with the addition of 5wt% of photoinitiator, 2,2 Dimethoxy-2-phenyl acephenone. UV photopolymerization is utilized to partially cross-link the H-shaped free standing specimen, and then pyrolyzed at 1400 degrees C in hot isostatic press under nitrogen gas to convert the partially cross-linked polymer into conducting and amorphous ceramic, silicon carbonitride. This work presents the preparation of free standing silicon carbonitride specimens as the sensor body for sensing hydrogen gas, depending on the semiconductive behavior of polymer-derived ceramics in high-temperature environments. The band gap of silicon carbonitride would be varied from adsorbing hydrogen molecules on the surface of the H-shaped free standing specimen with two different thicknesses. An amenable specimen-geometry for the four-point test of measuring resistance is developed in a furnace filled with pure hydrogen and vacuumed environments.

Silicon Oxycarbonitride (SiOCN) functionalization is proposed for stable, reproducible, reliable, and enhanced gas-sensing properties in carbon nanotube (CNT) gas sensors. The process is very simple: liquid precursor completely coats the surfaces of the CNTs without requiring any surface modification and a thin layer of semiconductor ceramic SiOCN is created on the CNTs after heat treatment. This new kind of conductometric gas sensors can detect 10ppm NH3 and 2ppm NO2 at temperatures up to 350 degrees C. The stability of the functionalized CNT sensor is verified up to 520 degrees C, while the CNT sensor without the SiOCN coating lost conductance after 250 degrees C due to the structural modification. SiOCN functionalization of CNT changes the recovery from irreversible to reversible and the recovery time decreases from 60min at 100 degrees C to 19min at 350 degrees C.

Elementary sulphur (S) has been shown to be an excellent cathode material in energy storage devices such as Li-S batteries owing to its very high capacity. The major challenges associated with the sulphur cathodes are structural degradation, poor cycling performance and instability of the solid-electrolyte interphase caused by the dissolution of polysulfides during cycling. Tremendous efforts made by others have demonstrated that encapsulation of S materials improves their cycling performance. To make this approach practical for large scale applications, the use of low-cost technology and materials has become a crucial and new focus of S-based Li-ion batteries. Herein, we propose to use a low temperature spraying process to fabricate graphene/S electrode material, where the ink is composed of graphene flakes and the micron-sized S particles prepared by grinding of low-cost S powders. The S particles are found to be well hosted by highly conductive graphene flakes and consequently superior cyclability (similar to 70% capacity retention after 250 cycles), good coulombic efficiency (similar to 98%) and high capacity (similar to 1500 mA h g(-1)) are obtained. The proposed approach does not require high temperature annealing or baking; hence, another great advantage is to make flexible Li-ion batteries. We have also demonstrated two types of flexible batteries using sprayed graphene/S electrodes.

This research discovers the burning reaction of the Pt/C catalyst on ink preparation and the effect of the untreated and burned Pt/C catalysts for the proton exchange membrane fuel cells (PEMFCs). The platinum nanoparticles on the carbon support aggregate to form bigger cluster sizes due to the burning reaction of the untreated Pt/C catalyst reacting with the Nafion solution or isopropyl alcohol. After several times of "purposely" burning reaction, the specific surface area of the fully burned Pt/C reduces from 150.9 to 46.6 m(2) g(-1) which is 3 times smaller than the untreated Pt/C catalyst. The crystallite size of platinum catalyst changes from 8.4 to 46.2 nm via the calculation of Debye-Scherrer equation from X-ray diffraction (XRD) and the electrochemical surface area (ECSA) obviously decreases from 85.6 to 14.8 m(2) g(-1). The variation of the ratio of Pt/C to Nafion influences the consequent electrochemical performances. Three catalyst coated membranes (CCMs) coated with untreated, fully burned, and partial burned Pt/C catalysts are analyzed and compared in this study. The CCM coated with the untreated Pt/C catalyst shows the best polarization curve which presents the peak power density, 897 mW cm(-2). Moreover, it presents the slowest degradation rate (0.1 mA min(-1)) at a constant voltage of 0.4V for 4000 min, even though the result of Nyquist plots is slightly worse than others The work confirms that the burning reaction of Pt/C catalyst influences the electrochemical performance and structural balance of the catalyst layer.

The specific capacity of commercially available cathode carbon-coated lithium iron phosphate is typically 120-160 mAh g(-1), which is lower than the theoretical value 170 mAhg(-1). Here we report that the carbon-coated lithium iron phosphate, surface-modified with 2 wt% of the electrochemically exfoliated graphene layers, is able to reach 208 m Ah g(-1) in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes, where the graphene flakes exhibit a capacity higher than 2,000 m Ah g(-1). The highly conductive graphene flakes wrapping around carbon-coated lithium iron phosphate also assist the electron migration during the charge/discharge processes, diminishing the irreversible capacity at the first cycle and leading to similar to 100% coulombic efficiency without fading at various C-rates. Such a simple and scalable approach may also be applied to other cathode systems, boosting up the capacity for various Li batteries.

This study presents an advanced ozone production process using the solid polymer electrolyte (SPE) technique, similar to the fabrication of proton exchange membrane fuel cell (PEMFC) membrane electrode assembly (MEA). Tungsten carbide and platinum on carbon black are coated on anode and cathode sides of a polymer membrane (Du Pont), respectively, to produce high concentration of ozone water. The water electrolysis of ozone generation requires a higher voltage than that of hydrogen production. On one hand, tungsten carbide, which is a platinum-like behavior electrocatalyst, plays a key role in preventing the MEA from corroding or oxidizing under high voltage. On the other hand, the carbon paper is replaced by a titanium porous disc to bear higher voltage. Moreover, an outstanding electronic control system can produce 1.37 ppm ozone water at atmosphere by adjusting the voltage range (6–10 V) with a current set to the maximum of 3 A for a household demand of ozone water generation.

This study uses the reverse electrochemical reaction of Proton Exchange Membrane (PEM) fuel cells, called PEM water electrolysis to produce high concentration hydrogen and oxygen (both 99.99%). The proposed technique can decrease carbon dioxide (CO2.) emissions. However, the oxidation and corrosion of the catalysts and gas diffusion layer (GDL) of the anode side remain challenging problems. The carbon fiber is used as the gas diffusion layer for PEM water electrolysis owing to its low density and porosity as well as its good conductivity even under low compression. Noble metal catalysts are coated with a micro-protective layer (MPL) on one side of the gas diffusion layer to extend the lifetime of PEM water electrolysis. The lifetime can reach over 2000 h at high current density (1400 mA cm(-2)) that is ten times longer than that of a sample coated only with carbon black (XC-72) as the microporous layer. The proposed micro-protective layer can transform active oxygen species to harmless oxygen gas and increase the catalyst's resistance to corrosion and oxidation during water electrolysis.

We report further increase in the figure-of-merit (EOM) for hydrogen generation from NaBH4 than reported in an earlier paper [1], where a sub-nanometer layer of metal catalysts are deposited on carbon nanotube paper (CNT paper) that has been functionalized with polymer-derived silicon carbonitride (SiCN) ceramic film. Ternary, Ru-Pd-Pt, instead of the binary Pd-Pt catalyst used earlier, together with a thinner CNT paper is shown to increase the figure-of-merit by up to a factor of six, putting is above any other known catalyst for hydrogen generation from NaBH4. The catalysts are prepared by first impregnating the functionalized CNT-paper with solutions of the metal salts, followed by reduction in a sodium borohydride solution. The reaction mechanism and the catalyst efficiency are described in terms of an electric charge transfer, whereby the negative charge on the BH4- ion is exchanged with hydrogen via the electronically conducting SiCN/CNT substrate [1]. (c) 2010 Elsevier B.V. All rights reserved.

A multilayer catalyst consisting of a electrophoretically deposited thin film of carbon nanotubes (CNTs) on a substrate of carbon fibers, followed by a coating of polymer-derived silicon carbonitride (SiCN), which is then decorated with a monolayer of transition metals is shown to perform at the upperbound of the phenomemological prediction from an earlier work [1]. A figure-of-merit for first order kinetics is equal to 4600 L min(-1) [NaBH4](-1) g(met)(-1), which is nearly 30 times the value reported in literature, is achieved. This high FOM is attributed to the CNT-thin film, as opposed to the thick CNT-paper used in previous work, thus needing merely 0.15 wt% quantities of precious metals for effective catalysis. This new architecture corroborates the concepts that: (i) the catalytic activity derives mainly from the surface of the CNT substrate, and (ii) the silicon carbonitride interlayer is instrumental in dispersing the transition metals into a monolayer. The hydrogen generation rate (HGR) for zero order kinetics, which is obtained when [NaBH4] > 0.03 M. is measured to be 75 L min(-1) g(met)(-1), which is among the higher values reported in the literature. The present multilayer catalysts are able to perform without fading for many cycles, presumably because the bondings in the substrate are predominantly covalent. This feature adds further uniqueness to this multilayer catalyst.

The graphene paper fabricated through an electrochemical exfoliation and filtration process provides high quality and massive graphene sheets in an ink form synthesised using artificial graphite as starting material. The product is mainly composed of bilayer and few layer graphene. Their lateral size can be up to >10 μm, and the quality determined by Raman spectroscopy is better than reduced graphene oxide. The cross-plane and in-plane thermal conductivity of the graphene paper can reach 5·5 and 3300 W m−1 K−1 measured by the direct method and the thermoelectric method respectively.