Catalytic Activity Studies of Modified Alumina in the Esterification of Benzyl Alcohol with Different Aliphatic Acids

244-252<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">A varied percentage of Fe, Co and Fe-Co mixtures were deposited on alumina support by dry impregnation method. The prepared materials were analyzed for their crystallinity, surface functional groups, morphology and elemental composition by P-XRD, FT-IR, and SEM-EDS techniques. Specific surface area of the catalytic materials was determined by BET technique using nitrogen as adsorbent. Further, surface acidity was estimated by TPD-NH3 and n- butylamine back titration method. The catalytic performances of these materials were checked in the esterification of benzyl alcohol with various aliphatic acids. The catalytic activity of Fe-Co/Al2O3 with 15% metal loading was found to be superior to other catalysts. The higher catalytic performance of the catalyst may be attributed to the higher surface acidity as well as synergetic effect of the metals. Further, the catalyst Fe-Co/Al2O3 (15%) was recyclable up to 5 times with negligible loss of its catalytic activity. A close relationship was noticed between surface acidity and catalytic performance of the materials.</span

Synthesis of carbon nanotubes over transition metal ions supported on Al(OH)₃

663-668Production of carbon nanotubes on bi-metallic (Fe/Co, Co/Ni, Fe/Ni, Fe/Mo, Co/Mo, Ni/Mo) and trimetallic (Fe/Co/Mo, Co/Ni/Mo, Fe/Ni/Mo) catalysts supported on Al(OH)₃ by catalytic chemical vapor deposition is reported. The support-catalyst systems have been prepared by incipient dry impregnation method and characterized by BET, powder XRD, SEM, and TG/DSC techniques. The carbon nanotubes have been synthesized by allowing C₂H₂ and N₂ to pass over a catalyst bed at 700°C placed on a quartz plate in a tubular furnace. The carbon deposit is examined using TEM. All the catalysts have been found to be active to different extents for the production of multiwall carbon nanotubes of varying thickness (10-15 nm). In the case of catalysts containing Fe/Co or Fe/Ni, a carbon deposit to an extent of 210 to 220% of the initial weight of the catalyst is obtained. This deposit also contains good quantities of carbon nanotubes. The tubes produced on nickel catalysts have been found to be thin and long. The effect of molybdenum on the nature of the carbon nanotubes produced is dependant on whether it is associated with one or two of the other transition metal ions supported over Al(OH)₃. To synthesize good quantities of carbon nanotubes, a binary mixture of Fe, Co and Ni without Mo is the best

A Comparative Study on Electrochemical Behaviour of Co3O4 and Co3O4-MWCNTs for Supercapacitors

Co3O4 and Co3O4/MWCNTs were prepared by hydrothermal process under autogenous pressure in Teflon lined autoclave and calcined at 250 degrees C. Both samples were characterized by PXRD, FT-IR, SEM-EDS, TEM & FT-Raman to evaluate their surface and bulk properties. The PXRD pattern of the materials indicated the formation of cubic phase of Co3O4. FT-IR results showed the presence of metal oxygen bond in the samples. The SEM and TEM images of the Co3O4 / MWCNTs indicated spherical and cubic aggregates of metal oxide particles (10-30 nm) decorated both on the surface and inside the tubes of carbon nanotubes. The characteristic Ig and Id (graphitic and defects) Raman bands indicated the retention of tubular structure of MWCNTs even after the deposition of Co3O4. The calcined Co3O4-MWCNTs composites and Co3O4 exhibited specific capacitance of 284 & 205 F/g at a sweep rate of 2mVs(-1) in 6M KOH by cyclic voltammetry. The psuedocapacitance performances of calcined Co3O4-MWCNTs were found to be better than Co3O4. Chronopotentiometric studies made for the materials at a current density of 500mA/g indicated 100% columbic efficiency at 2000th cycle for Co3O4/ MWCNTs which is a better electrode material than Co3O4

<span style="font-size:15.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">A Comparative Study on Electrochemical Behaviour of Co₃O₄and Co₃O₄-MWCNTs for Supercapacitors</span>

202-208Co3O4 and Co3O4/MWCNTs were prepared by hydrothermal process under autogenous pressure in Teflon lined autoclave and calcined at 2500C. Both samples were characterized by PXRD, FT-IR, SEM-EDS, TEM & FT-Raman to evaluate their surface and bulk properties. The PXRD pattern of the materials indicated the formation of cubic phase of Co3O4. FT-IR results showed the presence of metal oxygen bond in the samples. The SEM and TEM images of the Co3O4 / MWCNTs indicated spherical and cubic aggregates of metal oxide particles (10-30 nm) decorated both on the surface and inside the tubes of carbon nanotubes. The characteristic Ig and Id (graphitic and defects) Raman bands indicated the retention of tubular structure of MWCNTs even after the deposition of Co3O4. The calcined Co3O4-MWCNTs composites and Co3O4 exhibited specific capacitance of 284 & 205 F/g at a sweep rate of 2mVs-1 in 6M KOH by cyclic voltammetry. The psuedocapacitance performances of calcined Co3O4-MWCNTs were found to be better than Co3O4. Chronopotentiometric studies made for the materials at a current density of 500mA/g indicated 100% columbic efficiency at 2000th cycle for Co3O4 / MWCNTs which is a better electrode material than Co3O4.</sub

Experimental investigation on HSFP using MWCNT based nanofluids for high power light emitting diodes

LEDs, of late, have received attention as the next generation lighting system for enhanced luminous efficiency and higher lifespan. However, the thermal management of the LEDs is the crucial parameter to be countered for global acceptance as a revolutionary illumination source. This paper reports the experimental investigation of natural convective heat transfer of high power LED COBs using MWCNT and MWCNT-CuO nanofluids mixed with de-ionized water. The study uses MWCNT based nanofluids as a route to enhance the heat transfer of high power LEDs by the passive cooling technique. This study presents an innovative cooling device integrated with numerous fluid pockets, called the HSFP, to achieve the enhanced thermal performance of heat sinks for applications in high intensity LED lights. Nanofluids of various concentrations were formulated and their heat transfer performance evaluated using a series of experiments and compared with liquid cooling and a conventional heat sink. The experimental finding reveals 20– 30% lowered thermal resistance using the new HSFP (nanofluids). Thus, the HSFP found to effectively dissipates the heat in high-power LED COBs using nanofluids as the cooling medium compared to the conventional heat sink