Papers by Keyword: TG-DTA

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Authors: António Santos Silva, M. Paiva, J. Ricardo, Manuela M. Salta, A.M. Monteiro, António Estevao Candeias
Abstract: Roman mortars from the industrial archaeological site of Tróia (Portugal) have been studied by means of chemical, mineralogical and microstructural analysis. The mortars are calcitic aerial lime mortars differing in the type and proportion of aggregates used, including crushed carbonaceous rocks (limestone and dolomite), siliceous sand and crushed ceramics. The results show that although these mortars have been subjected to a very aggressive environment they are still in a very good state of conservation.
1643
Authors: Arvyvie Abie Jamil, I. Rubia, Jahimin A. Asik, Brian Brandon Bernard, Bryan Gindana, Florinna Tan
Abstract: Cu nanoparticles on Al2O3 catalyst were prepared via impregnation method and two different activation conditions were examined. The morphology of the catalyst has been characterized by using scanning electron microscopy (SEM); while, the crystallography was determined by using powder X-ray diffraction (XRD). The thermal stability of the catalyst was analysed by using thermogravimetry and differential thermal analysis (TG-DTA). Overall, from the XRD pattern, it was revealed that the nanoparticles Cu catalyst produced in air and nitrogen conditions is CuO and Cu active phase. At 400°C under air condition, the crystal size of CuO produced are in between 23.57 and 23.61 nm, while in nitrogen condition the crystal size was 30.24 to 30.31 nm. These results indicate that the size of the Cu nanoparticles catalyst produced under nitrogen flow was slightly bigger compared to air conditions. The results were further confirmed using SEM image in which catalyst activation under nitrogen flow has produced abundance microcrystal structure than under air condition. Meanwhile, the thermal stability of the nano-Cu catalyst shows that the both activation procedure was a single stage of thermal degradation at 260°C.
96
Authors: Kiyotaka Tanaka, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: The development of lead-free piezoelectric materials has been required from the viewpoint of environmental preservation. We focused the lead-free KNbO3-based systems, and used a chemical solution deposition (CSD) process to obtain their precursor. (Na1-xKx)NbO3 precursor solutions were prepared from metal alkoxides and solvents such as absolute ethanol and 2-methoxyethanol. Crystallization behavior of the precursor gels obtained from the above solutions was investigated by the thermogravimetry differential thermal analysis (TG-DTA) measurement.
85
Authors: Xanthippi Chatzistavrou, Nikolaos Kantiranis, Lambrini Papadopoulou, Eleana Kontonasaki, Aldo Roberto Boccaccini, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: In this study new ternary bioactive mixtures were investigated, which are appropriate for applications as coatings on the surface of dental ceramics. The fabrication of mixtures based on the combination of dental ceramic, hydroxyapatite and bioactive glass was demonstrated. The mixtures were characterized by FTIR, XRD and SEM and their bioactive behavior was investigated by immersion in Simulated Body Fluid (SBF). The ternary mixture consisted of a high fusing leucite-feldspathic dental ceramic which exhibited the highest bioactive behavior assigned to the characteristic crystal phases occurring under the specific heat treatment investigated.
111
Authors: Agnese Brangule, Kārlis Gross, Laura Komarovska, Arturs Viksna
Abstract: nclusion of zinc in apatites is not completely understood due to complexes in solution preventing the incorporation or the inclusion of defects. Some work has shown zinc addition by alternative synthesis routes, but the level of incorporation has not been reassessed. This work uses a newly developed approach whereby zinc is included in an amorphous phase and subsequently crystallized. Different phosphate reactants (ammonium, sodium or potassium phosphates) were mixed together with calcium salts (calcium nitrate or calcium acetate) and the pH level adjusted (with ammonia or KOH) to investigate the ease of forming an amorphous phase and the inclusion of zinc. X-ray diffraction revealed that all reactants showed a tendency to form an amorphous phase, supporting the requirement of a high pH to prevent crystallization. X-ray fluorescence showed higher inclusion in the absence of ammonia. Potassium phosphate led to the highest zinc incorporation, accompanied by simultaneous inclusion of potassium. Crystallization at 700 °C indicated that zinc levels close to 20% replacement of calcium were the highest possible before the onset of tricalcium phosphate formation. FTIR-DRIFT showed a change in bonding conditions at higher zinc concentrations. This work shows the importance of reactants for including zinc, the larger zinc inclusion accompanied by potassium and zinc levels that can maintain the apatite structure.
171
Authors: So Jin Kim, Won Kyu Han, Sung Goon Kang, Min Su Han, Young Hun Cheong
Abstract: Lanthanum hydroxide and oxide were prepared by the precipitation method in an aqueous medium at room temperature. The precipitate was examined using thermal analysis, X-ray diffraction and Scanning Electron Microscopy to investigate the phase evaluation and the thermal transformation by decomposition. The as-precipitated powder from the precipitation method was hexagonal La(OH)3. The lanthanum hydroxide was decomposed to oxide in two-steps as La(OH)3 → LaOOH + H2O and 2LaOOH → La2O3 + H2O.
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Authors: Xanthippi Chatzistavrou, E. Hatzistavrou, Nikolaos Kantiranis, Lambrini Papadopoulou, Eleana Kontonasaki, K. Chrissafis, Petros Koidis, Konstantinos M. Paraskevopoulos, Aldo Roberto Boccaccini
Abstract: The aim of this study was the fabrication using a sol-gel technique of a new glass-ceramic with potential use in dental applications. The characterization of the composition and microstructural properties of the produced material confirmed the similarity between the new sol-gel derived glass-ceramic and a commercial leucite based fluorapatite dental glass-ceramic. The produced material has potential application in dental restorations and it is expected to exhibit better control of composition, microstructure and properties due to the intrinsic advantages of the sol-gel preparation method.
153
Authors: Dun Jia Wang, Yan Fang Kang, Ben Po Xu
Abstract: The polyoxometalate complexes of ciprofloxacin with HnXW12O40 (X=B, Si, P) were prepared from ciprofloxacin hydrochloride and HnXW12O40·nH2O (X=B, Si, P) in aqueous solution, and characterized by elemental analysis, IR spectra and TG-DTA. The IR spectrum confirmed the presence of Keggin-type anion of heteropoly acids and the characteristic functional group of ciprofloxacin after the polyoxometalate complexes are formed. The TG/DTA curves showed that their thermal decomposition was a more-steps process consisting of simultaneous processes involving also Keggin anion. The residue of decomposition is a mixture of WO3 and B2O3, SiO2 or P2O5, confirmed by X-ray diffraction and IR spectroscopy. And the possible thermal decomposition mechanisms of the complexes are proposed.
1075
Authors: Fan Ming Zeng, Chun Li, Hai Lin, Xiao Dong Yang, Dan Wang, Jing He Liu
Abstract: Nd:YAG nanopowder was prepared by urea co-precipitation method. XRD, TG-DTA, SEM and spectra analysis were utilized to study the properties of the powder. Results indicated that fine Nd:YAG nanopowder can be acquired at 1000°C for 10h. The fluorescence spectra shown that the strongest peak was located at 1061nm, corresponding to the 4F3/24I11/2 energy level transition of Nd3+ ion.
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Authors: Hajime Okumura, Shigeharu Kamado, T. Tabata, A. Matsui, Yo Kojima
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