Control of nanoparticle size in RF thermal plasma synthesis of ...

Table 5. Results of tests with liquid precursorTest Filteryield (g/h)SSA(m 2 /g)Meandiameter(nm)T1 3.8 90 29T2 1.44 70 37T3 3.89 60 43Figure 4. SEM image of nanosilica powders from filterTable 6. Composition (w%) of samples collected in the filterTest C O Si AuT2 5.35 50.96 35.32 8.36T3 3.74 48.95 37.78 9.52In Figure 4, a SEM picture shows that all particlescollected are nanometric and that they show a tendencyto form agglomerates. It can be noticed from EDS thata higher purity of product can be obtained from TEOSwith respect to that of powders obtained from solidprecursors (see Table 6). Comparison of results of testT1 and test T3 (see Table 5) show that increasing thefeed rate the filter yield slightly changes and samplednanoparticles are characterized by slightly lower SSA.6. ConclusionResults show that the ratio between the filter yield andthe precursor feed rate is higher for solid than for liquidprecursors. However, non-vaporized precursor powdershave been collected in the filter in case of solidprecursor, whereas with liquid precursor only nanosizedparticles have been obtained. Furthersimulative/experimental studies will be conducted todetermine operating conditions for the silica synthesisprocess that guarantee optimal evaporation rate of solidprecursors as dependent from their dimension and massflow rate, also taking into account loading effects.Moreover, it has been shown that the use of curtaingases generally gives the possibility to collect a higheramount of powders in the filter and at the same timeleads to a reduction of their mean diameters.To better understand the effects of the curtain gasescomposition on the chemical-physical process ofnanosilica synthesis further studies on the use of aquenching gas need to be conducted.References[1] S. Y. Fu, X. Q. Feng, B. Lauke, Y. W. Mai, Effectsof particle size, particle/matrix interface adhesion andparticle loading on mechanical properties ofparticulate–polymer composites, Composites: Part B39 (2008) 933-961.[2] J. A. Smyder, T. D. Krauss, Coming attractions forsemiconductor quantum dots, Materials Today 14(2011) 382-396.[3] T. K. Barik, B. Sahu, V. Swain, Nanosilica frommedicine to pest control, Parasitology Research 103(2008) 253-258.[4] B. W. Jo, C. H. Kim, G. H. Tae, J. B. Park,Characteristics of cement mortar with nano-SiO2particles, Construction and Building Materials 21(2007) 1351-1355.[5] C. Borgonovo, D. Apelian, Manufacture ofAluminum Nanocomposites: A Critical Review,Advances in Metal Matrix Composites - MaterialsScience Forum 678 (2011) 1-22.[6] D. Kim, M. A. Scibioh, S. Kwak, I. H. Oh, H. Y.Ha, Nano-silica layered composite membranesprepared by PECVD for direct methanol fuel cells,Electrochemistry Communications 6 (2004) 1069-1074.[7] D. Vollath, Plasma synthesis of nanopowders,Journal of Nanoparticle Research 10 (2008) 39-57.[8] S. Brunauer, P. H. Emmett, E. Teller, Adsorptionof Gases in Multimolecular Layers, Journal of theAmerican Chemical Society 60 (1938) 309-319.[9] D. Harbec, F. Gitzhofer, A. Tagnit-Hamou,Induction plasma synthesis of nanometric spheroidizedglass powder for use in cementitious materials, PowderTechnology 214 (2011) 356-364.