Facile Synthesis of Mesoporous Carbon Spheres Using 3D Cubic Fe-KIT-6 by CVD Technique for the Application of Active Electrode Materials in Supercapacitors.

Mesoporous carbon spheres (MCS-750, MCS-800, MCS-850, MCS-900, and MCS-950) have been synthesized by a facile strategy with low temperature and rapid chemical vapor deposition technique. The synthesized MCS possess relatively large surface area (570-670 m2 g-1), good graphitization, remarkable porosity, and redox functionalities on the surface of the synthesized MCS. Combination of these structural and surface properties of the synthesized MCS as an electrode material (MCS-850) showed an excellent charge-storage capacity with a specific capacitance of 338 F/g at 1 mV/s, 217 F/g at 0.5 A/g. MCS-850 shows long-term cycling stability with capacitive retention of more than 96% after 2000 cycles in 6 M KOH electrolyte. In addition, a fabricated two-electrode symmetric cell obtained 86% retention after 2000 cycles. The two-electrode symmetric device exhibited a specific capacitance of 63 F/g at 5 mV/s with an energy density of 7.1 Wh/kg.

Effects of Nanofillers on the Thermo-Mechanical Properties and Chemical Resistivity of Epoxy Nanocomposites.

MWCNTs was synthesized using Ni-Cr/MgO by CVD method and were purified. The purified MWCNT was used as a filler material for the fabrication of epoxy nanocomposites. The epoxy nanocomposites with different amount (wt% = 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0) of nanofillers (CB, SiO2 and MWCNTs) were prepared by casting method. The effects of nanofillers on the properties of neat epoxy matrix were well studied. The thermal properties of nanocomposites were studied using DSC, TGA and flame retardant, and also the mechanical properties such as tensile strength, flexural strength, compressive strength, impact strength, determination of hardness and chemical resistance were studied extensively. Based on the experiment's results, 2 wt% MWCNTs loading in epoxy resin showed the highest improvement in tensile strength, as compared to neat epoxy and to other epoxy systems (CB/epoxy, SiO2/epoxy). Improvements in tensile strength, glass transition temperature and decomposition temperature were observed by the addition of MWCNTs. The mechanical properties of the epoxy nanocomposites were improved due to the interfacial bonding between the MWCNTs and epoxy resin. Strain hardening behavior was higher for MWCNT/epoxy nanocomposites compared with CB/epoxy and SiO2/epoxy nanocomposites. The investigation of thermal and mechanical properties reveals that the incorporation of MWCNTs into the epoxy nanocomposites increases its thermal stability to a great extent. Discrete increase of glass transition temperature of nanocomposites is linearly dependent on MWCNTs content. Due to strong interfacial bonding between MWCNTs and epoxy resin, the chemical resistivity of MWCNT/epoxy nanocomposites is superior to neat epoxy and other epoxy systems.

Facile synthesis of high quality multi-walled carbon nanotubes on novel 3D KIT-6: application in high performance dye-sensitized solar cells.

A novel hard templating strategy for the synthesis of high quality multi-walled carbon nanotubes (MWCNTs) with a uniform diameter was developed. MWCNTs were successfully synthesized through chemical vapour deposition (CVD) using acetylene by employing 3D bicontinuous mesoporous silica (KIT-6) as a hard template and used as the counter electrode in dye-sensitized solar cells (DSSCs). Here, we report that Ni-Cr-KIT-6 and Co-Cr-KIT-6 systems are the most suitable catalysts for the growth of MWCNTs. Raman spectroscopy and TEM analysis revealed that the synthesized MWCNTs were of high quality and well graphitized. Impressively, DSSCs with a MWCNT counter electrode demonstrated high power conversion efficiencies (PCEs) of up to 10.53%, which was significantly higher than that of 9.87% obtained for a DSSC with a conventional Pt counter electrode. Moreover, MWCNTs had a charge transfer resistance (Rct) of only 0.74 Ω cm(2) towards the I3(-)/I(-) electrolyte commonly applied in DSSCs, which is several orders of magnitude lower than that of a typical Pt electrode (2.78 Ω cm(2)). These results indicate that the synthesized MWCNT counter electrodes are versatile candidates that can increase the power conversion efficiency (PCE) of DSSCs.

Extended vapor-liquid-solid growth of silicon carbide nanowires.

We developed an alloy catalytic method to explain extended vapor-liquid-solid (VLS) growth of silicon carbide nanowires (SiC NWs) by a simple thermal evaporation of silicon and activated carbon mixture using lanthanum nickel (LaNi5) alloy as catalyst in a chemical vapor deposition process. The LaNi5 alloy binary phase diagram and the phase relationships in the La-Ni-Si ternary system were play a key role to determine the growth parameters in this VLS mechanism. Different reaction temperatures (1300, 1350 and 1400 degrees C) were applied to prove the established growth process by experimentally. Scanning electron microscopy and transmission electron microscopy studies show that the crystalline quality of the SiC NWs increases with the temperature at which they have been synthesized. La-Ni alloyed catalyst particles observed on the top of the SiC NWs confirms that the growth process follows this extended VLS mechanism. The X-ray diffraction and confocal Raman spectroscopy analyses demonstrate that the crystalline structure of the SiC NWs was zinc blende 3C-SiC. Optical property of the SiC NWs was investigated by photoluminescence technique at room temperature. Such a new alloy catalytic method may be extended to synthesis other one-dimensional nanostructures.

Low temperature growth of double walled carbon nanotubes using FeMoMgO catalyst.

The chemical vapour deposition technique was utilised to grow the double walled carbon nanotubes (DWCNTs) over FeMoMgO catalyst at low temperature (550 degrees C) under the mixture of argon, hydrogen and acetylene gas. Thermogravimetric analysis revealed that synthesised nanotubes have thermal stability and high purity. The high-resolution transmission electron microscopy image showed the formation of DWCNTs with tube diameter of 2.5-3.5 nm. We observed radial breathing mode (RBM) in Raman spectrum, which is related to the diameter of DWCNTs. This synthesis process is simple and economically viable ascribed to low synthesis temperature, simplicity and well graphitization with high yield.

Effect of MoO3 on the synthesis of boron nitride nanotubes over Fe and Ni catalysts.

Synthesis of boron nitride nanotubes at reduced temperature is important for industrial manufactures. In this study boron nitride nanotubes were synthesized by thermal evaporation method using B/Fe2O3/MoO3 and B/Ni2O3/MoO3 mixtures separately with ammonia as the nitrogen source. The growth of boron nitride nanotubes occurred at 1100 degrees C, which was relatively lower than other metal oxides assisted growth processes requiring higher than 1200 degrees C. MoO3 promoted formation of B2O2 and aided boron nitride nanotubes growth at a reduced temperature. The boron nitride nanotubes with bamboo shaped, nested cone structured and straight tubes like forms were evident from the high resolution transmission electron microscopy. Metallic Fe and Ni, formed during the process, were the catalysts for the growth of boron nitride nanotubes. Their formation was established by X-ray diffraction. FT Raman showed a peak due to B-N vibration of BNNTs close to 1370 cm(-1). Hence MoO3 assisted growth of boron nitride nanotubes is advantageous, as it significantly reduced the synthesis temperature.

Synthesis and characterization of Mn-MCM-41--its catalytic activity for the synthesis of carbon nanotubes.

Mn-MCM-41 was synthesized in various (Si/Mn = 25, 50, 75 and 100) ratios, using manganese acetate as source for manganese by hydrothermal method and was calcined at 550 degrees C for 6 hrs. The physico-chemical characterizations of Mn-MCM-41 showed the formation of hexagonally arranged mesopores with high surface area. The calcined Mn-MCM-41 was used as catalytic templates for the growth of large amount of carbon nanotubes. Acetylene was used as carbon source and nitrogen as carrier gas for the formation of carbon nanotubes by chemical vapor deposition method. The effect of temperature was carried out 750, 800, 850 and 900 degrees C, at a flow rate of 40 ml/min of acetylene precursor. The SEM, TEM and XRD confirmed the formation of large amount of carbon nanotubes.

Effective uptake of decontaminating agent (citric acid) from aqueous solution by mesoporous and microporous materials: an adsorption process.

The presence of citric acid in decontamination waste can cause complexation of the radioactive cations resulting in interferences in their removal by various treatment processes such as chemical precipitation, ion-exchange, etc., which are employed for the removal of radioactivity and may cause potential danger to the environment. Mesoporous Al-MCM-41 (Si/Al=30, 51, 72 and 97) and Si-MCM-41 molecular sieves were synthesized hydrothermally and characterized by XRD, BET (surface area) and FT-IR to evaluate the removal of citric acid through an adsorption process. Adsorption of citric acid over Al-MCM-41 shows the applicability of Freundlich and Langmuir isotherm and follows first order kinetics. The effects of contact time, concentration of citric acid, adsorbents (various Si/Al ratios of Al-MCM-41, Si-MCM-41, Hbeta zeolite and commercial carbon) and pH have been investigated. It has been found that the amount of citric acid adsorbed per unit gram of catalyst followed the order Al-MCM-41 (Si/Al=30)>Al-MCM-41 (Si/Al=51)>activated charcoal>Al-MCM-41 (Si/Al=72)>Al-MCM-41 (Si/Al=97)>Si-MCM-41>Hbeta zeolite.