via Pete Ramon: NANOTECHNOLOGY SAMPLING AND CONDITIONING Nanoparticle Formation & Processing Nanomaterials have novel electrical, catalytic, magnetic, mechanical, thermal, and optical properties. The types of processing techniques used to create them are as varied as the types of nanoparticles that are created. Nanoparticle synthesis can be divided into two general categories: gas synthesis and wet synthesis. The choice of gas vs. wet is often based on the type of nanoparticle being created. In many cases however, both options are viable for the nanoparticle of interest (i.e., carbon nanotubes, TiO2, FeO). Gas Synthesis In gas phase synthesis, the nanoparticle formation reaction takes place in a gas. Typically precursors are gaseous, but they can also be solid (furnace reactors) or aerosol (particles suspended in a gas). Some of the most popular synthesis schemes and some researchers who did influential early work on these techniques is listed below. Gas Synthesis Technique Early Research Contributors Evaporation & Condensation - Gleiter 1989, Siegel 1991, 1994 Combustion Flame - Zachariah 1994, Calcoste & Keil 1997, Axelbaum 1997, Pratsinis 1997 Plasma - Rao et al. 1997 Laser Ablation- Becker et al. 1997 Chemical Vapor condensation - Kear et al. 1997 Spray pyrolisis - Messing et al. 1994 Electrospray - de la Mora et al. 1994 Plasma Spray - Berndt et al. 1997 Micro Plasma - Sankaran 2007 Wet Synthesis In wet synthesis nanoparticle processing, the nanoparticle formation reaction takes place in a liquid. A precipitation agent is added to a liquid precursor. The primary process control parameters for this type of process are the chemistry of the solution and the temperature and pressure treatment of the mixture. Wet Synthesis Advantages Wet processing is frequently used because it is a mature technology. The precursors and process setpoints are well known and the processes have a high degree of repeatability. There are also a large number of liquid based characterization tools available. On-line aerosol techniques can also be used for many wet synthesis applications if the nanoparticle product can be aerosolized. Aerosolization of Wet Synthesis Product If the nanoparticle product is in an aqueous solution, or if it can be transferred to an aqueous solution, the Electrospray Aerosol Generator (EAG – Model 3480) can be used to aerosol the product. Böttger et al9 from Lund University in Sweden successfully electrosprayed colloidal gold particles and measured them with the SMPS™ Spectrometer. SiO2, TiO2 and other nanomaterials have also been successfully aerosolized and subsequently characterized with on-line aerosol measurement techniques. However, electrospray was invented in the 1960s. Between 1964 and 1969 Sir Geoffrey Ingram Taylor produced the theoretical underpinning of electrospraying. https://google/webhp…
Posted on: Sun, 11 Jan 2015 07:57:52 +0000
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