Illustrated in this talk will be the use of premixed and diffusion flames as reaction environments for carbon nanotube synthesis. We have tested both systems using catalysts as aerosols and supported upon substrates. Highlights will be shown demonstrating success and further challenges. For illustration, this abstract illustrates two key parameter spaces, namely gas composition and catalyst size and composition in premixed and diffusion flames, respectively.

A sectional method for determining particle size distributions has been implemented within the particle tracking module included with CHEMKIN-PRO. The module is available for use with many types of reactor models, ranging from 0-D batch reactors to laminar flame simulations. Coupled with the Burner-stabilized Stagnation Flame (BSSF) Model, the sectional model offers a high-fidelity, robust, and efficient computational framework for simulating flame synthesis of particles in a laminar, premixed stagnation flame environment. The CHEMKIN-PRO coupling allows inclusion of detailed gas-phase chemistry that determines key particle-formation precursors, along with physical processes such as nucleation and coagulation of particles. These capabilities are demonstrated for two flame-particle systems of practical importance, viz. nanocrystalline titania synthesis and soot formation. The results are compared with experimental data obtained at the University of Southern California (USC) flame facility. Computed particle size distributions show good agreement with experimental data. Simulations have led to exploration of the parameter space for particle production and particle-size influences.

The purpose of this work is the development and control of a high temperature reactor for the production of engineered nanoparticles, taking advantage from our previous studies on combustion-generated fine carbonaceous particles. The reactor consists of a laminar premixed flame, homogenously doped with monodisperse droplets of metal precursors dissolved or dispersed in volatile solvents. The droplets are generated by a vibrating orifice aerosol generator, and injected directly into the burner. Fuel-lean and stoichiometric flames allow producing pure metal oxide particles of nanometric sizes.

Particles are collected by thermophoresis inserting a cold substrate in the flame by means of a pneumatic actuator. Morphological and dimensional analysis are performed on the collected particles by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SEM and AFM allow inferring both qualitative and quantitative information on many physical properties including size, morphology, surface texture and roughness.

Experimental results have been obtained from a premixed stoichiometric flame of ethylene and air, doped with 75 microns droplets of magnesium nitrate hexahydrate dissolved in ethanol. Roughly monodisperse magnesium oxide particles, having a desired size ranging from 50 nm down to 7 nm, have been produced by altering the precursor concentration in the solution and the residence time of the synthesis process.

Topology of the surface micro- and nano- structures induced by the synthesis of NiTi intermetallic phases under Selective Laser Sintering is studied by Scanning Electron Microscopy. According previously developed us method, those data were analysed by image processing software for identification and discussion of common features and peculiarities of the phase and structural transformations. It was shown, that fine substructures have self- ordering nature. Geometric similarity of synthesizing structures expects their fractal nature. The dependence between the fractal dimension -D of low-dimensional nanostructures and laser energy input -A was found. The change of the fractal dimension of low dimensional structures clearly correlates with the change of roughness, while the increase of the laser energy input influences the fractal dimension - D in different ways. Shown that particularities of phase structural transformations at the intermetallic synthesis in the Ni-Ti system have been defined an appearance of nano sized and self-ordering substructures of cellular, dendrite or mosaic types. A sharp variation of the D orientation indicates about of change of the phase-formation mechanism.

Hybrid magnetic/plasmonic nanoparticles possess properties originating from each individual material. Such properties are beneficial for biological applications including bio-imaging, targeted drug delivery, in vivo diagnosis and therapy. Limitations regarding their stability and toxicity, however, challenge their safe use. Here, the one-step flame synthesis of composite SiO2-coated Ag/Fe2O3 nanoparticles is demonstrated. The hermetic SiO2 coating does not influence the morphology, the superparamagnetic properties of the iron oxide particles and the plasmonic optical properties of the silver particles. Therefore, the hybrid SiO2-coated Ag/Fe2O3 nanoparticles exhibit desired properties for their employment in bio-applications.

Nanophosphors are a promising new class of inorganic labels for bio-imaging applications, possessing a narrow emission bandwidth, good photostability and low toxicity. The effect of crystallinity of the host matrix on the phosphorescence of Tb-doped (1-5 at% Tb) Y2O3 nanophosphors is explored. Nanophosphors with different crystal phase (cubic and monoclinic) and morphology (uncoated and SiO2-coated) but with similar sizes were prepared by flame spray synthesis. That allowed the direct comparison of their phosphorescence performance excluding any observed size effect. The as prepared nanophosphors were characterized by X-ray diffraction, high resolution electron microscopy and photoluminescence spectroscopy. The meta-stable monoclinic crystal structure of Y2O3:Tb3+ nanophosphors favors their green phosphorescence.

Nanostructured Al3+ doped Ni0.75Zn0.25Fe2-xAlxO4 (x = 0.0,0.2,0.4,0.6,0.8, and 1.0) ferrites were synthesized via wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 °C .With the doping of Al3+, the particle size of Ni0.75Zn0.25Fe2-xAlxO4 first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. Saturation magnetization decreased linearly with Al3+ due to magnetic dilution. The coercive field showed an inverse dependence on the particle size of ferrites.