Now showing 1 - 4 of 4
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    Ordered nanoporous carbons (NCCR-56): Synthesis, characterization and applications
    (01-12-2010) ;
    Murthy, Palle Ramana
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    Krishna, Nunna Vamsi
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    Viswanathan, Balasubramanian
    Ordered nanoporous carbons having very high surface area are of great technological interest for the development of catalytic, electrocatalytic and hydrogen-storage systems. These carbons with various structures, e.g. CMK-1, CMK-3, NCCR-41, etc., have been synthesized by carbonization of sucrose, furfuryl alcohol and other suitable carbon containing precursors within the pores of nanoporous silicate molecular sieves. The inorganic templates were then removed by etching with HF, followed by filtration, washing and heat treatment to obtain the nanoporous carbons and nitrogen containing carbons. In the present study, ordered nanoporous carbon, designated as NCCR-56, was prepared using IITM-56 silica as the hard template and sucrose as the carbon source. This carbon was then used as a support for the preparation of mono dispersed gold nanoparticles (Au/NCCR-56), which shows promise for glycerol oxidation of reaction.
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    Synthesis of γ-Alumina nanoparticles by wire-explosion process: Characterisation and formation mechanism
    (18-12-2017)
    Ranjan, Prem
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    Selvam, Esun
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    Suematsu, H.
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    Single-step synthesis of γ-Alumina (γ-Al2O3), by wire-explosion process (WEP), is described in this work. Molecular oxygen is used as ambient gas with different levels of pressure to obtain the corresponding oxide nanoparticles (NPs). The energy (E) deposited to the capacitor, used for the explosion is in multiples of the sublimation energy. XRD and TEM techniques are used to characterise the synthesized nanoparticles. The content of γ-Al2O3 increases with increase in E and/or oxygen pressure (P). The average particle size of the nanoparticles reduces with the increase in E and/or decrease in P. The Born-Haber cycle is used to calculate the lattice energy (LE) of the bulk Al2O3. The dependence of LE and the formation enthalpy of alumina nanoparticles with size are evaluated. A classical homogenous nucleation theory is used to see the effect of saturation ratio and temperature on the activation energy and the nucleation rate of the NPs correlating it with size dependence on E and P used in the WEP.
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    A guideline for designing more durable catalysts based on the cohesive characteristics of 3d, 4d and 5d metals
    (01-01-2013)
    Suzuki, Ai
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    Williams, Mark C.
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    Miura, Ryuji
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    Hatakeyama, Nozomu
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    Miyamoto, Akira
    Analogical trends were found in the intra metallic bond energy of the 3d, 4d and 5d metals. The intra metallic bond energies increase from Ca, Sr, and Ba to near the center of the series and then decrease toward Zn, Cd, and Hg. The shape was like a volcano at the maximum at the half-filled d-electrons, and at the minimum at the no or full-filled d-electrons.
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    Publication
    Ordered nanoporous silicates (IITM-56): Synthesis, characterization and applications
    (01-12-2010) ;
    Krishna, Nunna Vamsi
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    Viswanathan, Balasubramanian
    Mesoporous molecular sieves are special class of materials with ordered arrays of uniform pores, high surface areas and large pore volumes. These periodic silica/silica-based materials are promising for variety applications including catalysis, adsorption and separation processes. Two most common types involve MCM-41 and SBA-15 has ordered structures consisting of two dimensional hexagonal arrays of uniform mesoporous. SBA-15 has larger pores, thicker walls and higher thermal stability as compared to other mesoporous silicas including MCM-41. However, it is of interest to make materials with a combination of moderate pore size and thicker wall structure. Therefore, in this investigation, an attempt has been made to prepare materials with desired characteristics using oligomeric alkyl poly ethylene oxide (Brij-56) surfactant template. We report here, for the first time, a novel mesoporous silicate material, designated as IITM-56, with a (moderate) pore size of 38.4 Å and a wall thickness of 21 Å. XRD pattern of IITM-56 depicts structure which is typical characteristics of MCM-41/SBA-15. TG studies of IITM-56 show a 49% weight loss in conjunction with exothermic transition (DTA) suggestive of mesoporous nature of the material. This further confirmed by N2 sorption measurements, which indicate type IV isotherm with capillary condensation at 0.3-0.4 (P/Po).