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CONTENTS
Volume 2, Number 2, June 2014
 

Abstract
Solvothermal treatment of late transition metal acetylacetonates in a novel medium composed either of pure acetophenone or acetophenone mixtures with amino alcohols offers a general approach to uniform hydrophilic metal nanoparticles with high crystallinity and low degree of aggregation. Both pure metal and mixed-metal particles can be accesses by this approach. The produced materials have been characterized by SEM-EDS, TEM, FTIR in the solid state and by Nanoparticle Tracking Analysis in solutions. The chemical mechanisms of the reactions producing nanoparticles has been followed by NMR. Carrying out the process in pure acetophenone produces palladium metal, copper metal with minor impurity of Cu2O, and NiO. The synthesis starting from the mixtures of Pd and Ni acetylacetonates with up to 20 mol% of Pd, renders in minor yield the palladium-based metal alloy along with nickel oxide as the major phase. Even the synthesis starting from a mixed solution of Cu(acac)2 and Ni(acac)2 produces oxides as major products. The situation is improved when aminoalcohols such as 2-aminoethanol or 2-dimethylamino propanol are added to the synthesis medium. The particles in this case contain metallic elements and pairs of individual metals (not metal alloys) when produced from mixed precursor solutions in this case.

Key Words
metal nanoparticle; solvothermal synthesis; solvent effect; beta-hydrogen transfer; solution stability

Address
Marion Collart Dutilleul: Ecole National Supériore de Chimie de Clermont Ferrand, 24 Avenue des Landais, 63170 Aubière, France
Gulaim A. Seisenbaeva and Vadim G. Kessler: Department of Chemistry, Biocenter, Swedish University of Agricultural Sciences, Box 7015, SE-75007 Uppsala, Sweden

Abstract
A novel and simple method for the synthesis of nano-magnetite particles is disclosed. In the novel procedure, Fe2+ is the only source of metal cation. Carboxymethylcellulose (CMC) is used as the structure directing agent. The phase analysis of the nano-particles was performed using XRD and electron diffraction techniques. Size and morphology analysis was performed using light scattering and TEM techniques. The effect of NH4OH solution (32 wt. %) at different CMC concentrations on the size distribution of the final magnetite powders is studied. An optimal base concentration exists for each CMC concentration leading to minimal agglomeration. There exists a minimum CMC concentration (0.0016 wt. %), lower than that no magnetite forms. It is shown that using the new method, it is possible to immobilize a lipase enzyme (Candida Rugosa) with immobilization efficiency larger than 98 % with a loading more than 3 times the reported value in the literature. The latter phenomenon is explained based on the agglomerate state of the nano-particles in the liquid phase.

Key Words
chemical synthesis; precipitation; light scattering

Address
Maryam Ghodrati Syahmazgi: Biochemistry Department, Islamic Azad University, P.O. Box 19585-466, Tehran, Iran
Cavus Falamaki: Chemical Engineering Department, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran, Iran
Abbas Sahebghadam Lotfi: Biochemistry Department, Tarbiat Modarres University, P.O. Box 14115-115, Tehran, Iran

Abstract
Experiments are performed to investigate the single-phase flow heat transfer augmentation of MWCNT/HT-B Oil in both smooth and micro-fin helical tubes with constant wall temperature. The tests in laminar regime were carried out in helical tubes with three curvature ratios of 2R/d=22.1, 26.3 and 30.4. Flow Reynolds number varied from 170 to 1800 resulting in laminar flow regime. The effect of some parameters such as the nanoparticles concentration, the dimensionless curvature radius (2R/d) and the Reynolds number on heat transfer was investigated for the laminar flow regime. The weight fraction of nanoparticles in base fluid was less than 0.4%. Within the applied range of Reynolds number, results indicated that for smooth helical tube the addition of nanoparticles to the base fluid enhanced heat transfer remarkably. However, compared to the smooth helical tube, the average heat transfer augmentation ratio for finned tube was small and about 17%. Also, by increasing the weight fraction of nanoparticles in micro-fin helical tubes, no substantial changes were observed in the rate of heat transfer enhancement.

Key Words
convective heat transfer; nanofluid; helical tube; micro-fin tube; enhancement

Address
M.H. Kazemi, M.A. Akhavan-Behabadiand M. Nasr: School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

Abstract
The chemical synthesis of anisotropic defective polyaniline/Ag composite (PANI/Ag) is explored using silver nitrate (AgNO3) as the precursor material. This study provides a simple method for the formation of PANI/Ag nanocomposites at two different aniline concentrations 5ul (PANC5) and 10ul (PANC10). The composite PANC5 exhibits UV-Visible absorption peaks at 436 nm and 670 nm whereas, PANC10 exhibits absorption peaks at 446 nm and 697 nm. This shift is caused by the strong interaction between polyaniline and silver. The characterized FTIR peaks observed at around 3410 cm-1 (PANC5) and 3420 cm−1 (PANC10) was due to the N-H stretching vibrations. The appearance of a broad band instead of a sharp peak can be attributed due to the presence of a high concentration of N–H groups in the nanocomposite. The TEM images show that the sample contains defective spherical, truncated triangular and rod shaped particles. The results showed that the PANI/Ag nanocomposites are composed of nano-sized particles of 43-53 nm that contain Ag domains of 33-37 nm with polymer thickness 5.7-11.2 nm at two different aniline concentrations.

Key Words
silver nanoparticles; polyaniline; polyaniline-silver nanocomposites; trisodium citrate; polymer

Address
Vaishali Kamble, Gunjan Kodwani, Ramdoss Sridharkrishna
and Balaprasad Ankamwar: Bio-Inspired Materials Science Laboratory, Department of Chemistry, University of Pune, Ganeshkhind, Pune-411007, India


Abstract
Polymer nanocomposites are advanced nanomaterials which exhibit dramatic improvements in various mechanical, thermal and barrier properties as compared with the neat polymer. Polystyrene/ alumina nanocomposites were prepared by an ultrasound-assisted solution casting method at filler loadings ranging from 0.2 to 2% and also at different ultrasonic frequencies, viz. 58 kHz, 192/58 kHz, 430 kHz, 470 kHz and 1 MHz. The composites were subjected to mechanical property tests (tensile and impact tests) and cavitation erosion tests to study the enhancement in functional properties. Filler dispersion in the polymer matrix was observed by SEM analysis. The effect of frequency on filler dispersion in the matrix was studied by SEM analysis and functional property enhancement of the composite material. The composites prepared at dual (high/ low) frequency (192/58 kHz) were found to show better property enhancement at low filler loadings as compared with neat polymer and also with composites prepared without ultrasound, thus reinforcing the finding that ultrasound-assisted synthesis is a promising method for the synthesis of nanocomposites.

Key Words
ultrasound; nanocomposites; dispersion; mechanical properties; cavitation erosion

Address
Mercy A. Philip, Upendra Natarajan and Ramamurthy Nagarajan: Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai-600036, India


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