Combustion synthesis method

A recent comparative investigation of the NO + CO reaction shows a significant rate enhancement in the formation of N2 on Ce0.98Pda02O2 8 prepared via a combustion synthesis method in comparison with conventional Pd-based catalysts supported on alumina... 

Pure metal nanoparticles have shown exceptional catalytic properties which have motivated modem researchers to come up with innovative ideas to synthesize nanoparticles in a cost effective manner. Apart from catalysis, potential applications of metal nanoparticles ate well known in other fields such as pigments, electronic and magnetic materials, dmg deUvery etc. Here we report solution combustion synthesis method to synthesize transition metals (Ni, Cu and Co) in a single step process. Metal nitrates and glycine are used as synthesis precursors and dissolved in water to make a homogeneous aqueous solution which is combusted to produce metal nanoparticles with desired composition. 

The idea of the combustion synthesis method is based on the assumption that nanoparticles can be formed by a very rapid heat pulse (the combustion or explosion). A typical reaction mixture consists of metal nitrates and a propellant. On combustion, the mixmre yields the desired products and volatile by-products. The reaction scheme for such a reaction might be ... 

Feynman s vision of miniaturization and the Drexler-versus-Smalley debate on feasibility of mechanosynthetic reactions using molecular assemblers were discussed. Fullerenes are the third allotropic form of carbon. Soccer-ball-structured Cgo with a surface filled with hexagons and pentagons satisfies Euler s law. Howard patented the first generation combustion synthesis method for fullerene production. The projected price of the fullerenes has decreased from 165,000 per kg to 200 per kg in the second-generation process. Fullerenes can also be synthesized using chemical methods, a supercritical extraction method, and the electric arc process. Applications of fullerenes include high temperature superconductors, bucky onion catalysts, advanced composites and electromechanical systems, synthetic diamonds. 

The solution combustion synthesis method has proven to be a great technique to obtain various types of oxides at the nanometer scale and is used for a variety of technological applications, as can be seen in Table 2.1. This wide range of oxides is prepared with an eye on their magnetic, mechanical, dielectric, catalytic, optical and luminescent properties. 

Ringuede, A., Labrincha, J.A., Trade, J.R. A combustion synthesis method to obtain alternative cermet materials for SOFC anodes. Solid State Ionics 141, 549-557 (2001)... 

Lanthanum chromite perovskite is another catalyst deposited on silicon carbide and cordierite honeycombs with the aim to investigate the oxidation of soot [56]. The perovskite was synthesized using a combustion synthesis method and showed promising activity. 

As a useful modification method, carbon coating has been proven to be an effective method for improving the electrochemical performance of Li2FeP207 [75]. In addition, Barpanda et al. [76] developed an eco-efiicient splash combustion synthesis method for Li2FeP207/C nanocomposite. This method is also applicable to the preparation of the family of Li2(Fei jcMnjc)P207 and Li(Fei jcMn ,)P04 (x = 0-1) nanocomposites. 

The combustion synthesis method has several advantages over the other two methods. It is a relatively cheap, easy and rapid way of obtaining the precursors. Normally, the p>recursor obtained is pure, of very fine particles and they are more homogeneous in terms of size and shape. The p>article size is often sub-micron but this depends on the calcination temperatures and the time duration of the heating process. The synthesis method also involves the... 

Nanocrystalline yttria (Y2O3) powders with most suitable characteristics for the fabrication of yttria crucibles were synthesized by the sol-gel method [85]. The combustion synthesis method was used starting with high-purity (99.9%) yttrium nitrate hexahydrate and citric acid. Different fuel to oxidant (citric acid/nitrate) ratios (0.25, 0.5, 0.75, 1.0, and 1.1) were tested. These mixtures were heated at 373 K until a viscous gel was formed, and its decomposition into powder formation was realized by thermal treatment at 473 K for 3 h. In all mixtures, yttria powders were obtained by thermal treatment at 1073 K. Scanning electron microscopy (SEM) showed that these powders were porous, whereas high-resolution transmission electron microscopy (HRTEM) revealed that they consist of randomly oriented cuboidal nanocrystallites with an average crystallite size of about 17-30 nm. In order to obtain dense ceramics, the powders were compacted as pellets at 120 MPa and were sintered at 1673 K. Pellets with a sintered density as high as 98-99% of the theoretical density could be obtained from powders prepared with fuel to oxidant ratios (/ ) of 0.75 and 1.0. 

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