1,720,992 research outputs found
Ceramic Composites Derived From Polysiloxane/al/nb By Afcop Process
No full textIn this work, ceramic matrix composites (CMC) were prepared by AFCOP process, using a polysiloxane network filled with metallic niobium and aluminum powders as active fillers. The liquid polysiloxane precursor was loaded with a suitable polymer/filler ratio in relation to stoichiometric Nb: C and Al: O molar ratios. Changing Al for α-Al2O3, which acted as an inert filler, non-stoichiometric conditions were obtained. The mixtures were blended, uniaxially warm pressed, and pyrolysed in flowing argon at 800, 1000 and 1200°C Thermogravimetry was used to follow the weight changes during the pyrolysis process. X-ray diffraction was used to identify the formation of new crystalline phases, such as Al2O3, NbC, Nb2C and Al3Nb in the composites. Sintered specimens were also characterized by SEM and EDS. The results indicated good potential for this system to obtain multiphasic composite material in the Al-Nb system at lower temperatures.498-499375380Greil, P., (2000) Adv. Eng. Mater, 2, p. 339Wei, Q., Pippel, E., Woltersdorf, J., Scheffler, M., Greil, P., (2002) Mater. Chem. and Phys, 73, p. 281Greil, P., (1995) J. Am. Ceram. Soc, 78, p. 835Schiavon, M.A., Radovanovic, E., Yoshida, I.V.P., (2002) Powder Technol, 123, p. 232Dernovsek, O., Bressiani, J.C., Bressiani, A.H.A., Aechar, W., Greil, P., (2000) J. Mater. Sci, 35, p. 2201Schiavon, M.A., Pardini, L.C., Yoshida, I.V.P., (2001) Key Eng. Mater, 189, p. 48Schiavon, M.A., Redondo, S.A.U., Pina, S.R.O., Yoshida, I.V.P., (2002) J. Non-Cryst. Solids, 304, p. 92. , 10Powder Diffraction File Search Manual, Joint Committee on Powder Diffraction Standarts, Swarthmore, (1973)Michalet, T., Parlier, M., Beclin, F., Duelos, R., Crampon, J., (2002) J. Eur. Ceram. Soc, 22, p. 14
Investigation On Kinetics Of Thermal Decomposition In Polysiloxane Networks Used As Precursors Of Silicon Oxycarbide Glasses
No full textIn this study, polysiloxane networks prepared by hydrosilylation or hydrolysis/condensation reactions were considered to be potential precursors for Si-C-O systems. Different precursors had different pyrolytic properties, which was essentially due to their molecular architecture. The kinetics parameters, such as the activation energy, E (kJ/mol) involved in the polymer-to-ceramic conversion, were investigated by thermogravimetry using a multiple heating rate kinetic method. The relationships between the molecular architecture and the precursor composition were compared to that of a linear poly(dimethylsiloxane) precursor. Solid-state 29Si nuclear magnetic resonance, infrared spectroscopies, density measurements, and X-ray diffraction measurements were made on the final samples. These products were typically amorphous, with a molecular structure formed by a random distribution of different silicon sites and variable amounts of free carbon residue. © 2002 Elsevier Science B.V. All rights reserved.3041-392100Riedel, R., (1996) Materials Science and Technology. A Comprehensive Treatment, 17, p. 1. , R.W. Cahn, P. Haasen, E.J. Kramer (Eds.), VCH, WeinheimBill, J., Aldinger, F., (1999) Precursor-Derived Ceramics: Synthesis, Structures, and High Temperature Mechanical Properties, p. 33. , J. Bill, F. Wakai, F. Aldinger (Eds.), Wiley-VCH, WeinheimGreil, P., (1995) J. Am. Ceram. Soc., 78, p. 835Renlund, G.M., Prochaska, S., Doremus, R.H., (1991) J. Mater. Res., 6, p. 2723Rouxel, T., Massouras, G., Sorarù, G.D., (1999) J. Sol-Gel Sci. Tech., 14, p. 87Kalfat, R., Babonneau, F., Gharbi, N., Zarouk, H., (1996) J. Mater. Chem., 6, p. 1673Liu, Q., Shi, W., Babonneau, F., Interrante, L.V., (1997) Chem. Mater., 9, p. 2434Radovanovic, E., Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Non-Cryst. Solids, 248, p. 37Pantano, C.G., Singh, A.K., Zhang, H., (1999) J. Sol-Gel Sci. Tech., 14, p. 7Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Mater. Sci., 34, p. 155Gozzi, M.F., Yoshida, I.V.P., (1997) Eur. Polym. J., 33, p. 1301Schiavon, M.A., Pardini, L.C., Yoshida, I.V.P., (2001) Key Eng. Mater., 189, p. 48Redondo, S.U.A., Radovanovic, E., Torriani, I.L., Yoshida, I.V.P., (2001) Polymer, 42, p. 1319Ozawa, T., (1965) Bull. Chem. Soc. Jpn., 38, p. 1881Thomas, T.H., Kendrick, T.C., (1969) J. Polym. Sci.: Part A-2, 7, p. 537Campostrini, R., D'Andrea, G., Carturan, G., Ceccato, R., Sorarù, G.D., (1996) J. Mater. Chem., 6, p. 585Çolak, N., Akgün, A., (1999) Polym. Plast. Technol. Eng., 38, p. 647Tutas, M., Saglam, M., Yüksel, M., Güler, Ç., (1987) Termochim. Acta, 111, p. 121Li, D., Hwang, S.-T., (1992) J. Appl. Polym. Sci., 44, p. 1979Michalczyk, M.J., Farneth, W.E., Vega, A.J., (1993) Chem. Mater., 5, p. 1687(1973) Powder Diffraction File Search Manual, , Joint Committee on Powder Diffraction Standarts, SwarthmoreHurwits, F.I., Meador, M.A.B., (1999) J. Sol-Gel Sci. Tech., 14, p. 75Camino, G., Lomakin, S.M., Lazzari, M., (2001) Polymer, 42, p. 2395Ikeda, M., Nakamura, T., Nagase, Y., Ikeda, K., Sekine, Y., (1981) J. Polym. Sci.: Polym. Chem. Ed., 19, p. 259
Glasses In The Si{single Bond}o{single Bond}c{single Bond}n System Produced By Pyrolysis Of Polycyclic Silazane/siloxane Networks
No full textIn this work, polycyclic silazane/siloxane networks bearing Si{single bond}O and Si{single bond}N bonds were synthesized, via hydrosilylation reaction, from cyclotrisilazane, [CH2{double bond, long}CH(CH3)SiNH]3, and cyclotetrasiloxane, [CH3(H)SiO]4, with different Si{single bond}H:Si{single bond}vinyl molar ratios. The resulting polymers were pyrolyzed up to 1000 °C, in N2 atmosphere, producing SiOCN glasses. The polymer-to-ceramic transformation was studied by thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), and chemical analysis. The 1000-1500 °C, high temperature structural evolution was also studied using X-ray diffraction (XRD) and FTIR. The hydrosilylation reaction produced ethylenic bridge crosslinked polymeric precursors with good thermal stability. The SiOCN glasses obtained with ceramic yields higher than 80 wt% showed spectra absorptions of Si{single bond}N, Si{single bond}O, and Si{single bond}C bonds in FTIR. The XRD patterns of the products obtained at 1500 °C displayed diffraction peaks characteristic of β-SiC and a broad halo centered at 22° (2θ), due to the amorphous silica phase. β-SiC diffraction peaks in the XRD patterns were more intense for the precursor richer in polysiloxane units, although absorptions of Si{single bond}N, Si{single bond}C, and Si{single bond}O bonds were also observed in the FTIR spectra. Thus, the final materials were characterized as SiC/SiOCN composites in nano/amorphous phases. © 2007 Elsevier B.V. All rights reserved.35322-2322802288Yajima, S., Omori, M., Hayashi, J., Okamura, K., Matsuzawa, T., Liaw, C.F., (1976) Chem. Lett., p. 551Yajima, S., Shishido, T., Kayano, H., (1976) Nature, 264, p. 237Schiavon, M.A., Yoshida, I.V.P., (2004) J. Mater. Sci., 39, p. 4507Bréquel, H., Parmentier, J., Walter, S., Badheka, R., Trimmel, G., Masse, S., Latournerie, J., Babonneau, F., (2004) Chem. Mater., 16 (13), p. 2585Schmidt, H., Borchardt, G., Muller, A., Bill, J., (2004) J. Non-Cryst. Solids, 341, p. 133Pantano, C.G., Singh, A.K., Zhang, H., (1999) J. Sol-Gel Sci. Technol., 14, p. 7Schiavon, M.A., Radovanovic, E., Yoshida, I.V.P., (2002) Powder Technol., 123, p. 232Kroke, E., Li, Y.-L., Konetschny, C., Lecomte, E., Fasel, C., Riedel, A., (2000) Mater. Sci. Res., R (26), p. 97Schiavon, M.A., Sorarù, G.D., Yoshida, I.V.P., (2002) J. Non-Cryst. Solids, 304, p. 76Breuming, T., (1999) J. Anal. Appl. Pyrol., 49, p. 43Chollon, G., (2000) J. Eur. Ceram. Soc., 20, p. 1959Bao, X., Edirisnghe, M.J., (1999) Compos.: Part A, 30, p. 601Pan, X., Mayer, J., Ruhle, M., Niihara, K., (1996) J. Am. Ceram. Soc., 79, p. 585Rendtel, A., Hubner, H., Hermann, M., Schubert, C., (1998) J. Am. Ceram. Soc., 81, p. 1109Lee, S.Y., (1998) J. Am. Ceram. Soc., 81, p. 1262Iwamoto, Y., Volger, W., Kroke, E., Riedel, R., Saiton, T., Matsunaga, K., (2001) J. Am. Ceram. Soc., 84, p. 2170Hemida, A.T., Birot, M., Pillot, J.P., Dunogues, J., Pailler, R., (1997) J. Mater. Sci., 32, p. 3475Borda, P.P., Legzdins, P., (1980) Anal. Chem., 52, p. 1777Schiavon, M.A., Sorarù, G.D., Yoshida, I.V.P., (2004) J. Non-Cryst. Solids, 348, p. 156Parashar, V.K., Raman, V., Bahl, O.P., (1997) J. Mater. Sci. Lett., 16, p. 1260Lavedrine, A., Bahloul, D., Goursat, P., Coong Kwet Yive, N., Corriu, R., Leclerq, D., Mutin, H., Vioux, A., (1991) J. Eur. Ceram. Soc., 8, p. 221Bahloul, D., Pereira, M., Goursat, P., Choong Kwet Yive, N.S., Corriu, R.J.P., (1993) J. Am. Ceram. Soc., 76, p. 1156Sorarù, G.D., D'Andrea, G., Campostrini, R., Babonneau, F., (1995) J. Mater. Chem., 5 (9), p. 1363Bahloul, D., Pereira, M., Gérardin, C., (1997) J. Mater. Chem., 7, p. 109Gérardin, C., Taulelle, F., Bahloul, D., (1997) J. Mater. Chem., 7, p. 117Schmidt, W.R., Narsavage-Heald, D.M., Jones, D.M., Marchetti, P.S., Raker, D., Maciel, G.E., (1999) Chem. Mater., 11, p. 1455Soraru, G.D., Modena, S., Belotti, P., Das, G., Marrioto, G., Pavesi, L., (2003) Appl. Phys. Lett., 83, p. 749Sorarú, G.D., Suttor, D., (1999) J. Sol-Gel Sci. Technol., 14, p. 69Radovanovic, E., Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Non-Cryst. Solids, 248, p. 37Duan, R.G., Roebben, G., Vleugels, J., Van der Biest, O., (2005) Acta Mater., 53, p. 2547Wang, C.M., Emoto, H., Mitomo, M., (1998) J. Am. Ceram. Soc., 81, p. 1125Scheffler, M., Pippel, E., Woltersdorf, J., Greil, P., (2003) Mater. Chem. Phys., 80, p. 56
Ceramics Derived From Hybrid Polymer And Multiwall Carbon Nanotubes
No full textCeramic samples (labelled NT and CS) were obtained from a hybrid polymeric precursor derived from poly(methylsiloxane) and divinylbenzene with and without carbon nanotubes (MWCNT), respectively, as an additional C-source. The precursor was pyrolysed under Ar atmosphere at 1500 °C for different pyrolysis times. XRD patterns of CS ceramics showed broad diffractions of β-SiC, C-graphitic and opaline-SiO2 phases. For NT ceramics, besides the diffractions observed for CS ceramics, an intense diffraction peak of cristobalite was observed. The introduction of MWCNT changed the morphology of the resulting ceramics and decreased the solubility of SiO2 in the matrix, promoting the formation of relatively large cristobalite crystals.Schiavon, M.A., Redondo, S.U.A., Pina, S.R.O., Yoshida, I.V.P., Investigation on kinetics of thermal decomposition in polysiloxane networks used as precursors of silicon oxycarbide glasses (2002) Journal of Non-Crystalline Solids, 304, pp. 92-100Kleebe, H.-J., Gregori, G., Babonneau, F., Blum, Y.D., MacQueen, D.B., Masse, S., Evolution of c-rich sioc ceramics. Part I. Characterization by integral spectroscopic techniques: Solid-state nmr and raman spectroscopy (2006) International Journal of Materials Research, 97, pp. 699-709Pinho, R.O., Radovanovic, E., Torriani, I.L., Yoshida, I.V.P., V, P.I., Hybrid materials derived from divinylbenzene and cyclic siloxane (2004) European Polymer Journal, 40, pp. 615-622Tuinstra, F., Koenig, J.L., Raman spectrum of graphite (1970) Journal of Chemical Physics, 53, pp. 1126-1130Li, F., Wen, G., Song, L., Growth of nanowires from annealing sibonc nanopowders (2006) Journal of Crystal Growth, 290, pp. 466-472Graetsch, H., Gies, H., Topalovié, I., Nmr, xrd and ir study on microcrystalline opals (1994) Physics and Chemistry of Minerals, 21, pp. 166-175Bois, L., Maquet, J.J., Babonneau, F., Structural characterization of sol-gel derived oxycarbide glasses 2. study of the thermal stability of the silicon oxycarbide phase (1995) Chemistry of Materials, 7, pp. 975-98
The Protective Role Of Poly(borosiloxanes)-derived Ceramics In Carbon Fiber Composites
No full textThis 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
N-propylpyridinium Chloride-modified Poly(dimethylsiloxane) Elastomeric Networks: Preparation, Characterization, And Study Of Metal Chloride Adsorption From Ethanol Solutions
No full textAn n-propylpyridinium chloride-modified PDMS elastomeric network, PDMS/Py+Cl-, was prepared from linear PDMS chains containing Si(CH3)2{single bond}OH end-groups cross-linked by 3-chloropropyltrimethoxysilane and posterior reaction with pyridine. PDMS/Py+Cl- material was structurally characterized by infrared spectroscopy (IR) and solid state 13C and 29Si NMR. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 450 K. The ion-exchange capacity of the PDMS/Py+Cl- was 0.65 mmol g-1. Metal halides, MClz [M = Fe3+, Cu2+, and Co2+], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes MClz + n n -. The nature of the anionic complex structure was proposed by UV-vis diffuse reflectance spectra. The species adsorbed were FeCl- 4, CuCl2- 4, and CoCl2- 4. The specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. The trend in affinities of PDMS/Py+Cl- for the metal halides were found to be FeCl3 > CuCl2 ∼ CoCl2. © 2007 Elsevier Inc. All rights reserved.31413845Mark, J.E., (2004) Acc. Chem. Res., 37, p. 946Patwardhan, S.V., Taori, V.P., Hassan, M., Agashe, N.R., Franklin, J.E., Beaucage, G., Mark, J.E., Clarson, S.J., (2006) Eur. Polym. J., 42, p. 167Jose, N.M., Prado, L.A.S.A., Schiavon, M.A., Redondo, S.U., Yoshida, I.V.P., (2007) J. Polym. Sci. Part B Polym. Phys., 45, p. 299Silva, V.P., Gonçalves, M.C., Yoshida, I.V.P., (2006) J. Appl. Polym. Sci., 101, p. 290Gotardo, M.C.A.F., Guedes, A.A., Schiavon, M.A., José, N.M., Yoshida, I.V.P., Assis, M.D., (2004) J. Mol. Catal. A Chem., 229, p. 137Guedes, A.A., Mac Leod, T.C.O., Gotardo, M.C.A.F., Schiavon, M.A., Yoshida, I.V.P., Ciuffi, K.J., Assis, M.D., (2005) Appl. Catal. 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Photocatalytic Activity Of Tio2-containing Ceramic Matrix Composite
No full textTiO2 powder was incorporated into a polysiloxane matrix and this green body (GB) was pyrolysed at 1500°C, giving rise to a TiO 2-containing ceramic matrix composite (CMC). GB and CMC were analyzed by X-ray diffraction, density, total pore volume and average pore size determinations, scanning electron microscopy and UV-vis spectroscopy. The photocatalytic activity of GB and CMC was evaluated with respect to the photodegradation of salicylic acid (SA) in water, under UV radiation, by total organic carbon measurements. CMC promoted the photodegradation of 33 % of SA and it can be proposed as a promising alternative ceramic material for decontamination of water by heterogeneous photocatalysis.Gao, Y., Liu, H., Preparation and catalytic property study of a novel kind of suspended photocatalyst of TiO2-activated carbon immobilized on silicone rubber film (2005) Materials Chemistry and Physics, 92, pp. 604-608Paschoalino, M.P., Kiwi, J., Jardim, W.F., Gas-phase photocatalytic decontamination using polymer supported TiO 2 (2006) Applied Catalysis B-Environmental, 68, pp. 68-73Schiavon, M.A., Radovanovic, E., Yoshida, I.V.P., Microstructural characterisation of monolithic ceramic matrix composites from polysiloxane and SiC powder (2002) Powder Technology, 123, pp. 232-241Bernardo, E., Colombo, P., Manias, E., SiOC glass modified by montmorillonite clay (2006) Ceramics International, 32, pp. 679-686Schiavon, M.A., Yoshida, I.V.P., Ceramic matrix composites derived from CrSi2-filled silicone polycyclic network (2004) Journal of Materials Science, 39, pp. 4507-4514Lowell, S., Shields, J.E., Thomas, M.A., Thommes, M., Characterization of porous solids and powders: Surface area (2006) Pore Size and Density, , Springer, Dordrecht, The Netherlands, chap. 2Kim, Y., Kim, S., Kim, H., Park, C.B., Processing of closed-cell silicon oxycarbide foams from a preceramic polymer (2004) Journal of Materials Science, 39, pp. 5647-5652(1997) JCPDS-International Centre for Diffraction Data, 130. , PDF card 211272, PCPDFWIN(1997) JCPDS-International Centre for Diffraction Data, 130. , PDF card 211276, PCPDFWIN(1997) JCPDS-International Centre for Diffraction Data, 130. , PDF card 391425, PCPDFWINBurns, G.T., Taylor, R.B., Xu, Y., Zangvil, A., Zank, G.A., High temperature chemistry of the conversion of siloxanes to silicon carbide (1992) Chemistry of Materials, 4, pp. 1313-132
Ceramic Composites Derived From Nb/al2o3-filled Polysilsesquioxane
No full textCeramic matrix composites (CMC) were prepared by the active-filler- controlled polymer pyrolysis process (AFCOP) using a polysilsesquioxane resin filled with metallic niobium and alumina powders. Samples containing 60 wt% of polysilsesquioxane and 40 wt% of metallic niobium and alumina powders mixtures were homogenized, uniaxially pressed and pyrolysed in an alumina tube furnace up to 1400°C, under argon flow. The ceramic products were characterized by X-ray diffraction (XRD), thermogravimetry (TGA), differential thermal analysis (DTA), Fourier transform infrared (FTIR) and energy-dispersive (EDS) spectroscopies. XRD analysis of the products showed the presence of crystalline phases such as NbC, Nb3Si, Nb5Si3, SiC, crystoballite and mullite. Thermogravimetry data of the composites presented low weight losses at 1000°C. DTA curves showed an endothermic peak at 1350°C, which was associated to the beginning of carbothermic reduction and/or the formation of silicon oxide and carbide. In addition, an exothermic peak at 1400°C was associated to the formation of the mullite phase.498-499369374Greil, P., (1998) J. Eur. Ceram. Soc, 18, p. 1905Greil, P., (1995) J. Am. Ceram. Soc, 78, p. 835Chantrell, P.G., Popper, P., (1965) Special ceramics, p. 67. , Popper academic pressYajima, S., Hayashi, J., Omori, M., Okamura, K., (1976) Nature, 261, p. 683Bois, L., Marquet, J., Babonneau, F., Mutin, H., Bahlou, D., (1994) Chem. Mater, 6, p. 796Schiavon, M.A., Radovanovic, E., Yoshida, I.V.P., (2002) Powder Technol, 123, p. 232Walter, S., Suttor, D., Erny, T., Hahn, B., Greil, P., (1996) J. Eur. Ceram. Soc, 16, p. 387Radovanovic, E., Gozzi, M.F., Gonçalves, M.C., Yoshida, I.V.P., (1999) J. Non-Cryst. Solids, 248, p. 37Sorarù, G.D., Kleebe, H.J., Ceccato, R., Pederiva, L., (2000) J. Eur. Ceram. Soc, 20, p. 2509Suttor, D., Kleebe, H.J., Ziegler, G., (1997) J. Am. Ceram. Soc, 80, p. 2541Walter, S., Sorarù, G.D., Bréquel, H., Enzo, S., (2002) J. Eur. Ceram. Soc, 22, p. 2389Wei, Q., Pippel, E., Woltersdorf, J., Scheffler, M., Greil, P., (2002) Mater. Chem. Phys, 73, p. 281Kaindl, A., Lehner, W., Greil, P., Kim, D.J., (1999) Mater. Sci. Eng. A-Struct, 260, p. 101Martin, H.P., Müller, E., (1999) J. Mater. Sci, 34, p. 2671Martin, H.P., Müller, E., Dachselt, U., (1999) J. Mater. Sci, 34, p. 2665Acchar, W., Wolff, D.M.B., (2001) Int. J. Refrac. Metals Hard Mater, 19, p. 40
Poly(dimethylsiloxane) Networks Modified With Poly(phenylsilsesquioxane)s: Synthesis, Structural Characterisation And Evaluation Of The Thermal Stability And Gas Permeability
No full textSelf-supported translucent films constituted of semi-inorganic polymeric materials were prepared by sol-gel process from poly(phenylsilsesquioxane) (PPSQ) and poly(dimethylsiloxane) (PDMS), modified by diphenylsilanediol (DPS), phenyltriethoxysilane (PTES) and/or tetraethoxysilane (TEOS). These materials were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Permeability to N2, O2, CH4 and CO2 and selectivity for a specific gas pair were investigated using the time-lag method. In the gas separation process high permeability and selectivity coefficients were observed, particularly for the membrane containing DPS and PTES as additives, which presented potential applications in the separation of CO2/CH4 and CO2/N2. The materials also showed good thermal stability, which could be correlated to the relative amounts between di-functional (D), tri-functional (T) and tetra-functional (Q) silicon units. © 2008 Elsevier Ltd. 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(Eds), Elsevier Science, Amsterdam chapter 13Stern, S.A., Polymers for gas separation - the next decade (1994) J Membr Sci, 94, pp. 1-65Roberson, M., Burgoyne, W.F., Langsan, M., Savavoca, A.C., Tien, C.F., High performance polymers for membrane separation (1994) Polymer, 35, pp. 4970-4978Wu, P., Field, R.W., Brisdon, B.J., England, R., Barkley, S., Optimisation of organofunction PDMS membranes for the pervaporative recovery of phenolic compounds from aqueous streams (2001) J Sep Purif Technol, 22, pp. 339-345Senthilkumar, U., Reddy, B.S.R., Structure-gas separation property relationships of non-ionic and cationic amino-hydroxy functionalized poly(dimethylsiloxane) membranes (2004) J Membr Sci, 232, pp. 73-83Pinnau, I., He, Z., Pure- and mixed-gas permeation properties of polydimethylsiloxane for hydrocarbon/methane and hydrocarbon/hydrogen separation (2004) J Membr Sci, 244, pp. 227-233Jose, N.M., Prado, L.A.S.A., Yoshida, I.V.P., Synthesis, characterization, and permeability evaluation of hybrid organic-inorganic films (2004) J Polym Sci B: Polym Phys, 42, pp. 4281-4292Senthilkumar, U., Rajini, R., Reddy, B.S.R., Gas permeation and sorption properties of non-ionic and cationic amino-hydroxy functionalized poly(dimethylsiloxane) membranes (2005) J Membr Sci, 254, pp. 169-177Shi, Y., Burns, C.M., Feng, X., Poly(dimethylsiloxane) thin film composite membranes for propylene separation from nitrogen (2006) J Membr Sci, 282, pp. 115-123Wu, F., Li, L., Xu, Z., Tan, S., Zhang, Z., Transport study of pure and mixed gases through PDMS membrane (2006) Chem Eng J, 117, pp. 51-59Senthilkumar, U., Reddy, B.S.R., Polysiloxanes with pendent bulky groups having amino-hydroxy functionality: structure-permeability correlation (2007) J Membr Sci, 292, pp. 72-79Jose, N.M., Prado, L.A.S.A., Schiavon, M.A., Redondo, S.U.A., Yoshida, I.V.P., Partially pyrolyzed poly(dimethylsiloxane)-based networks: thermal characterization and evaluation of the gas permeability (2007) J Polym Sci B: Polym Phys, 45, pp. 299-309Stern, S.A., Mi, Y., Gas permeability of a new silicone ring polymer: isotactic poly(phenylsilsesquioxane) (1991) J Polym Sci B Polym Phys, 29, pp. 389-393Baney, R.H., Itoh, M., Sakakibara, A., Suzuki, T., Silsesquioxanes (1995) Chem Rev, 95, pp. 1409-1430Hench, L.L., West, J.K., The sol-gel process (1990) Chem Rev, 90, pp. 33-72Prado, L.A.S.A., Radovanovic, E., Pastore, H.O., Yoshida, I.V.P., Torriani, I.L., Poly(phenylsilsesquioxane)s: structural and morphological characterization (2000) J Polym Sci A: Polym Chem, 38, pp. 1580-1589Bellamy, L.J., (1957) The infrared spectra of complex molecules, , Wiley, New York(1975) Polymer handbook, , Polymer Handbook. 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Processing Of Monolithic Ceramic Bodies From Polysiloxane Precursor
No full textA 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
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