Advanced Powder Technology 

Abstract: Control of particle size and morphology has increasingly captured the attention of researchers for decades. The exploration of unique sizes and shapes as they relate to various properties has become a great quest for large field applications. To meet these demands, this review covers recent developments in particle processing. An aerosol-assisted self-assembly technique, with a spray-drying method as a representative of it, to create particles is thoroughly reviewed. Its popularity and its broad use in industry for producing particles are the main reason of this review; thus, elucidation of this method is important for the improvement of particle technology. A practical spray-drying method is described from the step-by-step process to the selection of apparatus types (merits and demerits). Elaboration of particle processing of several morphologies (sphere, doughnut, encapsulated, porous, hollow, and hairy) is discussed in terms of the selection of material types, the addition of supporting materials, and the change of process conditions. Controllable size is also discussed in terms of the adjustment of the droplet size, initial precursor concentration, and the addition of specific techniques. A comparison between a theoretical mechanism and current experimental results (over a 15-year period) are shown to clarify how particles with various sizes and morphologies are designed. This method must be considered an art rather than a science because of its advantages in creating wonderful and unique particle shapes. The performance of various particle morphologies is also demonstrated, which is essential for an understanding of the importance that shape can exert on practical use. Because the method outlined here can be broadly applied to the production of various types of functional materials, we believe that this report contributes new information to the field of chemical, material, environmental, and medical engineering.

Abstract: A review of synthesis and performance of flame-made catalytic materials is presented. Emphasis is placed on flame technology for its dominance in aerosol manufacturing of materials of high purity with minimal liquid byproducts. Flame aerosol processes are characterized in terms of the precursor state supplied to the flame. During the last decade, a better understanding of aerosol and combustion synthesis of materials contributed to the development of one-step, dry synthesis of catalysts that are prepared conventionally by multi-step wet-phase processes. This includes TiO 2 -based photocatalysts, mixed oxides (e.g. V 2 O 5 /TiO 2 , TiO 2 /SiO 2 , perovskites, etc.) as well as supported metals (e.g. Pt/TiO 2 , Pd/Al 2 O 3 , Pt/CeO 2 /ZrO 2 , Pt/Ba/Al 2 O 3 , Ag/ZnO, Cu/ZnO/Al 2 O 3 bimetallic Pd/Pt/Al 2 O 3 and Au/TiO 2 ) made by single- or multi-nozzle flames. In general, highly crystalline and non-porous nanoparticles are formed during flame synthesis, resulting in materials with high thermal stability. Unique particle structures, only available through aerosol processes, lead to improved performance in various catalytic applications.

Abstract: The Fe3O4-chitosan nanoparticles with core-shell structure have been prepared by crosslinking method. Oleic acid modified Fe3O4 nanoparticles were firstly prepared by co-precipitation then chitosan was added to coat on the surface of the Fe3O4 nanoparticles by physical absorption. The Fe3O4-chitosan nanoparticles were obtained by crosslinking the amino groups on the chitosan using glutaraldehyde. Transmission electron microscopy showed that the Fe3O4-chitosan nanoparticles were quasi-spherical with a mean diameter of 10.5 nm. X-ray diffraction pattern and X-ray photoelectron spectra indicated that the magnetic nanoparticles were pure Fe3O4 with a cubic inverse spinel structure. The modification using chitosan did not result in a phase change. The binding of chitosan to the Fe3O4 nanoparticles was also demonstrated by the measurement of fourier transform infrared spectra and thermogravimetric analysis. Magnetic measurement revealed that the saturation magnetization of the composite nanoparticles was 30.7 emu/g and the nanoparticles were superparamagnetic at room temperature. Furthermore, the inductive heating property of the composite nanoparticles in an alternating current magnetic field was investigated and the results indicated that the heating effect was significant. The Fe3O4-chitosan nanoparticles prepared have great potential in hyperthermia. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Abstract: In this paper, the effect of a magnetic field on natural convection in a half-annulus enclosure with one wall under constant heat flux using control volume based finite element method. The fluid in the enclosure is a water-based nanofluid containing Cu nanoparticles. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell–Garnetts (MG) and Brinkman models, respectively. Numerical simulations were performed for different governing parameters namely the Hartmann number, Rayleigh number and inclination angle of enclosure. The results indicate that Hartmann number and the inclination angle of the enclosure can be control parameters at different Rayleigh number. In presence of magnetic field velocity field retarded and hence convection and Nusselt number decreases.

Abstract: Bio-mediated synthesis of metal oxide nanoparticles using plant extract is a promising alternative of traditional chemical synthesis. The present study reports the synthesis of ZnO nanoparticles by biological method. Highly stable and hexagonal phase ZnO nanoparticles were synthesized using Pongamia pinnata leaves extract and were characterized by XRD, UV–vis, DLS, SEM, TEM and FT-IR spectroscopy. The synthesized ZnO nanoparticles were confirmed by XRD and FTIR spectra. Morphology studies indicates spherical nature of the ZnO NPs and EDX shows the highly pure ZnO nanoparticles. The antibacterial activity of ZnO nanoparticles and ZnO nanoparticles coated cotton fabric were tested against Staphylococcus aureus (gram positive) and Escherichia coli (gram negative) organisms by agar diffusion method. Finally, the current study has clearly demonstrated that the ZnO NPs are responsible for significant higher antibacterial activities. Therefore, the study reveals an efficient, ecofriendly and simple method for the green synthesis of multifunctional ZnO NPs using green synthetic approach.