Processing Of Monolithic Ceramic Bodies From Polysiloxane Precursor

A low temperature process for the manufacture of ceramic-body composite, with preceramic polymer as binder, has been shown to be a promising technique for the preparation of monolithic ceramic blocks in a process that excluded powder-sintering phenomena. This work reports the direct transformation of a silicone polycyclic network into silicon oxycarbide in the presence of ceramic powders, such as SiC or Si3N4, which act as inert fillers. They prevent the shrinkage usually observed during polymer pyrolysis. The preparation of ceramic bodies using a ceramic powder/polysiloxane system was achieved by hydrosilylation reaction between functional siloxane cyclic oligomers, using a transition metal catalyst (PtII) in the presence of the powder filler, at different volume fractions. In order to develop green bodies, the ceramic powder/polysiloxane mixtures were pressed and cured at 70°C for 3 hours. Afterwards, they were then pyrolysed in argon atmosphere at 1000°C, producing ceramic matrix composites SiC/SiCxO4-x and Si3N4/SiCxO4-x having no cracks. Microstructural characterization was performed by 29Si MAS NMR, suggesting a random distribution of SiC4, SiC3O, SiC2O2 and SiO4 sites in the SiCxO4-x phase. Scanning Electron Microscopy showed evidence of a homogeneous distribution of the polymer in the green bodies and in the SiCxO4-x phase after pyrolysis. Impact resistance and flexural strength performed mechanical characterization of the ceramic composites. The results highlighted the potential benefits of this strategy to produce resistant ceramic composite bodies.189-1914853Riedel, R., Passing, G., Schönfelder, M., Brook, R.J., (1992) Nature, 355, p. 714Gonon, M.F., Fantozzi, G., Murat, M., Disson, J.P., (1995) J. Eur. Ceram. Soc., 15, p. 591Kin, Y., Kin, W., (1997) J. Mater. Sci. Let., 16, p. 1384Greil, P., Seibold, M., (1992) J. Mater. Sci., 27, p. 1053Greil, P., (1995) J. Am. Ceram. Soc., 78 (4), p. 835Greil, P., (1998) Ceram. Forum. Intern., 75, p. 15Schwartz, K.B., Rowcliffe, D.J., Blum, Y.D., (1988) Adv. Ceram. Mater., 3 (4), p. 320Seyferth, D., Czubarow, P., (1994) Chem. Mater., 6, p. 10Lewis, J.A., Cima, M.J., Rhine, W.E., (1994) J. Am. Ceram. Soc., 77 (7), p. 1839Radovanovic, E., Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Non-Cryst. Solids, 248, p. 37Michalczyk, M.J., Farneth, W.E., Vega, A.J., (1993) Chem. Mater., 5, p. 1687Niihara, K., (1990) Ceram. Soc. Japan, 99, p. 974Mano, E.B., (1991) Polímeros Como Materiais de Engenharia, pp. 9-17. , Ed. Blücher, SPKalfat, R., Babonneau, F., Gharbi, N., Zarrouk, H., (1996) J. Mater. Chem., 6, p. 1773Renlund, G.M., Prochaska, S., Doremus, R.H., (1991) J. Mater. Res., 6, p. 272

The Protective Role Of Poly(borosiloxanes)-derived Ceramics In Carbon Fiber Composites

This work reports the synthesis and thermal characterization of poly(borosiloxanes) (PBS) derived from methyltrietoxysilane (MTES) and vinyltriethoxysilane (VTES), aiming to use these polymers as precursors of ceramic matrices for the protection of carbon fibers in ceramic matrix composites (CMCs). The resulting materials exhibited better thermal stability than the carbon fiber, especially the Cfiber/SiBCO composite derived of the methyltriethoxysilane (MTES) system prepared with a B/Si ratio of 0.5. This study showed that poly(borosiloxanes) are promising materials for the oxidation protection of carbon fibers, and consequently for thermal protection systems.587-588182186Schiavon, M.A., Yoshida, I.V.P., (2004) Journal of Material Science, 39, p. 4507Schiavon, M.A., Gervais, C., Babonneau, F., Sorarù, G.D., (2004) Journal of the American Ceramic Society, 82, p. 203Riedel, R., Mera, G., Hauser, R., Klonczynski, A., (2006) Journal of the Ceramic Society of Japan, 114, p. 425Wang, Z.-C., Aldinger, F., Riedel, R., (2001) Journal of the American Ceramic Society, 84, p. 2179Labruquère, S., Blanchard, H., Pailler, R., Naslain, R., (2002) Journal of the European Ceramic Society, 22, p. 1001Lee, Y.-J., Joo, H.-J., Radovic, L.R., (2003) Carbon, 41, p. 2591Ehrburger, P., Lahaye, J., (1986) Carbon, 4, p. 495Sorarù, G.D., Babonneau, F., Gervais, C., Dallabona, N., (2000) Journal of Sol-Gel Science and Technology, 18, p. 11Sorarù, G.D., Dallabona, N., Gervais, C., Babonneau, F., (1999) Chemistry of Materials, 11, p. 910Siqueira, R.L., Yoshida, I.V.P., Pardini, L.C., Schiavon, M.A., (2007) Materials Research, 10, p. 147Ozawa, T., (1965) Bulletin of the Chemical Society of Japan, 38, p. 1881Howe, J.Y., Jones, L.E., (2004) Carbon, 42, p. 461J. Latournerie, P. Dempsey, D.H.-Bahloul, J.P. Bonnet, Journal of the American Ceramic Society 89 (2006), p. 148

The Importance Of Quimica Nova And Journal Of The Brazilian Chemical Society For The Development Of Chemistry In Brazil [a Importância Das Revistas Química Nova E Journal Of The Brazilian Chemical Society No Crescimento Da área De Química No Brasil]

Quimica Nova and the Journal of the Brazilian Chemical Society are two examples of successful initiatives taken by the Brazilian Chemical Society (SBQ - Sociedade Brasileira de Química), and may serve as models for the scientific societies of developing countries. Pillars of the SBQ, these two periodicals are undeniable demonstrations that idealism, utopia and dignity are the essential ingredients for transforming dreams into reality. Few believed that the Brazilian chemical community would one day have, as it does today, two scientific research periodicals indexed in the principal international data banks.30614911497Galembeck, F., (1997) Edição Comemorativa dos 10 Anos da SBQ, p. 18. , julhoRoth, D.L., (2005) Curr. Sci, 89, p. 1531Marques, F., (2006) Pesquisa FAPESP, (126), p. 24Benchimol, J.L., Cerqueira, R.C., Martins, R.B., Mendonça, A., (2007) História, Ciências, Saúde - Manguinhos, 14, p. 1Maciel, M.A.M., Pinto, A.C., Veiga Jr., V.F., (2002) Quim. Nova, 25, p. 429Veiga Jr., V.F., Pinto, A.C., Maciel, M.A.M., (2005) Quim. Nova, 28, p. 519Pinto, A.C., Silva, D.H.S., Bolzani, V.S., Lopes, N.P., Epifanio, R.A., (2002) Quim. Nova, 25, p. 45Vidotti, E.C., Rollemberg, M.C.E., (2004) Quim. Nova, 27, p. 139Castro, H.F., Mendes, A.A., Santos, J.C., (2004) Quim. Nova, 27, p. 146Costa Neto, P.R., Rossi, L.F.S., Zagonel, G.F., Ramos, L.P., (2000) Quim. Nova, 23, p. 531Ferrari, R.A., Oliveira, V.S., Scabio, A., (2005) Quim. Nova, 28, p. 19Eichler, M., Del Pino, J.C., (2000) Quim. Nova, 23, p. 835Santos, A.R., Vidotti, E.C., Silva, E.L., Maionchi, F., Hioka, N., (2002) Quim. Nova, 25, p. 844Terci, D.B.L., Rossi, A.V., (2002) Quim. Nova, 25, p. 684Ferreira, M.M.C., Antunes, A.M., Melgo, M.S., Volpe, P.L.O., (1999) Quim. Nova, 22, p. 724Mattoso, L.H.C., (1996) Quim. Nova, 19, p. 388Moreira, J.C., Barek, K., (1995) Quim. Nova, 18, p. 362Guaratini, C.C.I., Zanoni, M.V.B., (2000) Quim. Nova, 23, p. 71Lopes, W.A., de Andrade, J.B., (1996) Quim. Nova, 19, p. 497Arakaki, L.N.H., Airoldi, C., (1999) Quim. Nova, 22, p. 246Coelho, F., Almeida, W.P., (2000) Quim. Nova, 23, p. 98Crepaldi, E.L., Valim, J.B., (1998) Quim. Nova, 21, p. 300Aleixo, P.C., Nóbrega, J.A., Santos Jr., D., Muller, R.C.S., (2000) Quim. Nova, 23, p. 310Maia, D.J., De Paoli, M.-A., Alves, O.L., Zarbin, A.J.G., das Neves, S., (2000) Quim. Nova, 23, p. 204Pinto, A.C., de Andrade, J.B., (1999) Quim. Nova, 22, p. 448Ferraz, H. M. C.Pardini, V. L.Quim. Nova 1997, 20 (Especial), 75de Castro, L. A. B.Prescott, E.Quim. Nova 1997, 20 (Especial), 15Paniago, E. B.Quim. Nova 1997, 20 (Especial), 23Pinto, A. C.Peixoto, E. A. M.Galembeck, F.de Andrade, J. B.de Paoli, M. A.Avaca, L. A.Alves, O. L.Quim. Nova 1997, 20 (Especial), 81Loh, W., Vargas, M.D., (2005) J. Braz. Chem. Soc, 16, p. 3Loh, W., Dias, L.C., (2006) J. Braz. Chem. Soc, 17, p. 3Loh, W., Dias, L.C., (2007) J. Braz. Chem. Soc, 18, p. 3Schuchardt, U., Sercheli, R., Vargas, R.M., (1998) J. Braz. Chem. Soc, 9, p. 199Pinto, A.C., Guarieiro, L.L.N., Rezende, M.J.C., Ribeiro, N.M., Torres, E.A., Lopes, W.A., Pereira, P.A.P., de Andrade, J.B., (2005) J. Braz. Chem. Soc, 16, p. 1313Dias, L.C., (1997) J. Braz. Chem. Soc, 8, p. 289Dupont, J., Consorti, C.S., Spencer, J., (2000) J. Braz. Chem. Soc, 11, p. 337Dupont, J., (2004) J. Braz. Chem. Soc, 15, p. 341Longhinotti, E., Pozza, F., Furlan, L., (1998) Sanchez, M. N. M.Klug, M.Laranjeira, M. C. M.Fávere, V. T.J. Braz. Chem. Soc, 9, p. 435da Silva, J.F.M., Garden, S.J., Pinto, A.C., (2001) J. Braz. Chem. Soc, 12, p. 273Foschiera, J.L., Pizzolato, T.M., Benvenutti, E.V., (2001) J. Braz. Chem. Soc, 12, p. 159Gomes, L.A.D., Padilha, P.D., Moreira, J.C., Newton, L., Dias Filho, N.L., Gushikem, Y., (1998) J. Braz. Chem. Soc, 9, p. 494Dupont, J., Suarez, P.A.Z., Umpierre, A.P., de Souza, R. F. (2000) J. Braz. Chem. Soc, 11, p. 293Gunther, H., (1999) J. Braz. Chem. Soc, 10, p. 241de Andrade, J.B., Andrade, M.V., Pinheiro, H.L.C., (1998) J. Braz. Chem. Soc, 9, p. 219Toma, H.E., Alexiou, A.D.P., (1995) J. Braz. Chem. Soc, 6, p. 267Pasquini, C., (2003) J. Braz. Chem. Soc, 14, p. 198De Moura, K.C.G., Emery, F.S., Neves-Pinto, C., (2001) Pinto, M. C. F. R.Dantas, A. P.Salomão, K.de Castro, S. L.Pinto, A. V.J. Braz. Chem. Soc, 12, p. 325Gushikem, Y., Rosatto, S.S., (2001) J. Braz. Chem. Soc, 12, p. 695Gushikem, Y., Campos, E.A., (1998) J. Braz. Chem. Soc, 9, p. 273Cestari, A.R., Airoldi, C., (1995) J. Braz. Chem. Soc, 6, p. 291Freire, R.S., Pessoa, C.A., Mello, L.D., Kubota, L.T., (2003) J. Braz. Chem. Soc, 14, p. 230Varela, H., Torresi, R.M., Buttry, D.A., (2000) J. Braz. Chem. Soc, 11, p. 32Martelli, P.B., Reis, B.F., Korn, M., (1997) Rufini, I. A.J. Braz. Chem. Soc, 8, p. 479Cardoso, S.L., Nicodem, D.E., Moore, T.A., (1996) Moore, A. L.Gust, D.J. Braz. Chem. Soc, 7, p. 19Delgado, G., Torresi, R.M., (2005) J. Braz. Chem. Soc, 16, p. 289de Castro, L.D., (2006) J. Braz. Chem. Soc, 17, p. 1053Toma, H.E., (2006) J. Braz. Chem. Soc, 17, p. 145