Papers by Keyword: Polymeric Precursor

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Authors: Wei You Yang, Zhi Peng Xie, Hua Tao Wang, Guo Quan Liu, He Zhuo Miao, Li Nan An
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Authors: Ana Lúcia Exner Godoy, José Carlos Bressiani, Ana Helena A. Bressiani
Abstract: The influence of polymer precursor additions on liquid phase sintering of SiC:Al2O3:Y2O3 has been evaluated. Two polymer precursors were used: polymethylhydrogensiloxane and D4Vi (1,3,5,7-tetramethyl-1,3,5,7-tetraviniylcyclotetrasiloxane). The ceramic phase had the following composition in wt%: 91.6 SiC, 4.2 Al2O3 and 4.2 Y2O3. The composites were prepared using the following ceramic phase to polymer ratios in wt%: 82.7: 17.3; 74.0: 26.0 and 71.5: 28.5. Density measurements were carried out using a helium picnometry and the Archimedes method. The crystalline phases were identified by X-ray diffraction analysis and the microstructures were observed by optical and scanning electron microscopy.
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Authors: A.H.M. González, A.Z. Simões, José Arana Varela, M.A. Zaghete, Elson Longo
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Authors: Kyoung Hoon Park, In Kyung Sung, Dong Pyo Kim
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Authors: Norazlianie Sazali, W.N.W. Salleh, Zawati Harun, Ahmad Fauzi Ismail
Abstract: Membrane gas separation is a forthcoming technology that advertised a great commercial potential in diverse industrial applications. Consequently, membrane-based natural gas processing has been among the fastest growing segments of the economic growth. The turbostratic structure of carbon membranes has been affirmed to accommodate with good separation selectivity for permanent gases. With that, the most auspicious technique acquired is by controlling the carbonization temperature during the carbon membrane fabrication. In this study, polymer-based carbon tubular membranes have been fabricated and characterized in terms of its structural morphology and gas permeation properties. Polyimide (Matrimid 5218) was used as a precursor for carbon tubular membrane preparation to produce high quality of carbon membrane via carbonization process. The polymer solution was coated on TiO2 –ZrO2 tubular tubes (Tami) by using dip-coating method. The polymer tubular membrane was then carbonized under Nitrogen atmosphere at 600, 750, and 850 ◦C. The structural morphology of the resultant carbon membranes was analyzed by means of scanning electron microscope (SEM). Pure gas permeation tests were performed using CO2 and N2 gases at 8 bars and room temperature. Based on the results, the highest CO2/ N2 selectivity of 79.53 was obtained for carbon membrane prepared at 850 oC.
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Authors: Shu Yong Wang, Xiao Xing Zhang, Ya Qiong Wang, Wen Lin Xu
Abstract: Ti-based PbO2 electrodes with Sb-SnO2 interlayers were prepared by thermal decomposition. The effects of calcination temperature and Sb content of the Sb-SnO2 interlayer on the service life and microstructural characteristics of the Ti/Sb-SnO2/PbO2 anodes were investigated. The results show that the Ti-based PbO2 electrodes without the Sb-SnO2 interlayer, Ti/PbO2 electrodes, are rapidly deactivated at the experiment conditions, while the service life of the Ti/Sb-SnO2/PbO2 electrodes increases remarkably. Calcination temperature and Sb content for preparing the Sb-SnO2 interlayer exhibit remarkable effects on the service life of the Ti/Sb-SnO2/PbO2 anodes.
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Authors: Douglas Washington da Silva, Daniela Cristina Manfroi, Guilhermina Ferreira Teixeira, Leining Antônio Perazolli, Maria Aparecida Zaghete, Alberto Adriano Cavalheiro
Abstract: Semiconductor-mediated photocatalytic oxidation is an interesting method for water decontamination and a specially modified TiO2 is said to be a promising material. This study verified that the synthesis of 1wt%Ag modified-Sc0.01Ti0.99O1.995 powder samples prepared by Polymeric Precursor Method is capable of forming a mixture of anatase-rutile phase with high photocatalytic performance. This kind of material is found to have a lower bandgap compared to the TiO2-anatase commercial powders, which can be associated to an innovative hybrid modification. The simultaneous insertion of scandium in order to generate a p-type semiconductor and a metallic silver nanophase acting as an electron trapper demonstrated being capable of enhancing the degradation of rhodamine B compared to the commercial TiO2. In spite of the different thermal treatments or phase amounts, the hybrid modified powder samples showed higher photocatalytic activity than the commercial ones.
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Authors: V. Andal, G. Buvaneswari
Abstract: CuO nanoparticles showing different morphologies were prepared by polymeric precursor method using three different copper sources: basic copper carbonate, copper nitrate and copper hydroxide. The decomposition temperature of the precursors varies from 200 C to 400 C. The effect of the concentration of the polymeric additive was studied. The CuO nanopowder was reduced to metallic copper at low temperature using hydrazine hydrate as a reducing agent. The oxide was treated with the reducing agent in two forms: (1) as dispersion in 0.1% PVA (dispersion method) (2) as slurry with 0.1% PVA applied on a glass plate (plate method). The maroon copper metal nanofluid achieved in dispersion method was stable for six months and the copper nanopowder obtained from the plate method showed stability for more than six months. The precursor, CuO and Cu nanomaterials were characterized by powder XRD, FT-IR, TGA, SEM and TEM techniques.
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Authors: S. Mondal, A.K. Banthia
Abstract: Nitrides remain a relatively unexplored class of materials primarily due to the difficulties associated with their synthesis and characterization. Several synthetic routes, including high temperature reactions, microwave assisted synthesis, and the use of plasmas, to prepare binary and ternary nitrides have been explored. Transition metal nitrides form a class of materials with unique physical properties, which give them varied applications, as high temperature ceramics, magnetic materials, superconductors or catalysts. They are commonly prepared by high temperature conventional processes, but alternative synthetic approaches have also been explored, more recently, which utilize moderate temperature condition. Transition metal nitrides particularly, molybdenum nitride, niobium nitride, and tungsten nitride have important applications as catalyst in hydrodenitridation reactions. These nitrides have been traditionally synthesized using high temperature nitridation treatments of the oxides. The nitridation temperatures are very high (> 800- 1000 oC). The aim of our work is to synthesize molybdenum nitride by a simple, low-temperature route. The method involves pyrolysis of a polymeric precursor, which was prepared from the condensation reaction between triethanolamine and molybdic acid. The melting point of the product is 180oC. The polymeric precursor and its pyrolyzed products are characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). X-ray diffraction shows that molybdenum nitride (MoN) obtained from this method has hexagonal crystal structure. MoN is obtained by this method at very low temperature (~ 400 oC).
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