Papers by Keyword: Transition Metal

Abstract: Electron paramagnetic resonance (EPR) spectrometer was widely applied to physics, chemistry and biomedicine. This research provided possible electron and valence information of environmental samples interaction through high sensitivity. The EPR signals of transition metals and organic radicals were distinguished well. Three kinds of carbon nanotubes (CNTs) (MW50, MW30 and MWG) had strong EPR signals. Addition of transition metals may be a suitable way to decrease environmentally persistent free radicals (EPFRs). The potential risks of EPFRs in BC and the reactive free electron in transition metals must be addressed to ensure their safe and scientific absorption application.

Abstract: Composites H₃PW₁₂O₄₀/TiO₂-M (M=Fe, Co, Ni, Zn) were synthesized by combining sol-gel technology with impregnation method. The structures and properties were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and UV-Vis diffuser reflectance spectrum (UV-Vis DRS). The XRD and FT-IR results showed that the TiO₂ particles had the anatase phase, and the Keggin structure of H₃PW₁₂O₄₀ remained intact. The UV-Vis DRS results indicated that compared with pure TiO₂, an obvious red shift occurred after introducing H₃PW₁₂O₄₀. The composites were used as heterogeneous photocatalyst to the degradation of methyl orange, and the influences of catalyst dosage, H₃PW₁₂O₄₀ loading and metal ion species were studied. Results show that, under the optimum parameters pH value 2.00, 0.4 g·L^-1 catalyst dosage and 30% H₃PW₁₂O₄₀ loading, 96.6% methyl orange was degraded after 30 min irradiation (365 nm) using composite H₃PW₁₂O₄₀/TiO₂-Zn. The photodegradation process fitted Langmuir-Hinshelwood first order kinetics.

Abstract: Two isostructural transition metal complexes based on the 4,4'-{[2,2'-(ethane-1,2-bicarboxymethyl)] amino-bis (acetyl)} dibenzoic acid (H₄L) were synthesized under hydrothermal conditions, namely, [M(H₂L)(H₂O)]·3H₂O (M=Ni, 1 ; Co, 2). The two compounds were structurally characterized by infrared spectra, thermogravimetric analysis and single crystal X-ray diffractions. Compounds 1-2 are mononuclear units and further extended to generate the two dimensional structures by hydrogen-bonds and π-π interactions. Compounds 1 exhibit the high thermal stability.

Abstract: Thin films of MXN (M stands for early transition metal and X = Si, Ge, Sn) are studied as protective coatings. To extend the knowledge about the formation of nanocomposite films, various MXN systems have been compared. TiSiN, TiGeN, TiSnN, NbSiN, ZrSiN and CrSiN thin films were deposited by reactive magnetron sputtering, from confocal targets in a mixed Ar/N2 atmosphere. The chemical reactivity of germanium and tin with nitrogen is significantly lower than that of Si and Ti. Therefore, the TiGeN and TiSnN systems are different from TiSiN. Important changes in the morphology and structure of MXNfilms are induced by X addition. Nanocrystalline composite films are formed in all these investigated ternary systems.

Abstract: The structures and optical performances of TiO₂ doped with 4^th periodic transition metal ions were investigated in this paper. The characterization results of X-ray photoelectron spectroscopy and X-ray diffraction showed that the transition metal ions existed in oxidative states, and composites formed because of the reaction between doped metal ions and TiO₂. The absorption spectroscopy of TiO₂ doped with zinc was mainly in ultraviolet region, close to that of the pure TiO₂. While for TiO₂ doped with other transition metal ions including V, Cr, Mn, Fe, Co, Ni and Cu ions, the absorption spectroscopies covered ultraviolet region and visible light region, much broader than that of the pure TiO₂.

Abstract: On simulated organic wastewater treatment by catalytic wet oxidation (CWAO) experiments, the transition metal compound Cu-Fe-La/FSC catalysts were characterized by SEM, TEM and FT-IR, and its application in CWAO reaction process conditions were optimized. Catalyst characterization experiments show that the active components on the surface of the Cu-Fe-La/FSC uniformly distribute, and the particle size is 10 to 50 nm; the chemical composition of-OH-and-Al-O-key are remarkable. To optimize the operation process with the orthogonal experiments of catalytic wet air oxidation (CWAO), the results show that in the five factors of influencing COD_Cr removal rates of wastewater, they are arranged according to the influences on water treatment from high to low: catalyst dose, system total pressure, influent concentration, reaction temperature, reaction time. The optimized operating conditions: catalyst dose of 8 g/L, total system pressure of 2.0 MPa, influent concentration of 3000 mg/L, reaction temperature of 180 °C¡æ, reaction time of 60 min. Under the optimized operating conditions, the COD_Cr removal rate of simulated wastewater reached 77.9%.

Abstract: Cu-Mn/Al₂O₃, Cu-Mn/TiO₂ and Cu-Mn/SBA-15 were prepared by incipient wetness impregnation. The activity of those catalysts for selective catalytic oxidation (SCO) of ammonia to nitrogen at low temperature (100°C~250°C) is not so satisfying. 5%Cu-5%Zr/TiO₂ has the highest NH₃ conversion and highest NO, NO₂ yield. 5%Cu-5%Mn/Al₂O₃ is a promising NH₃ selective catalytic oxidation catalyst, but still needs further study. SBA-15 is a bad support for Cu-Mn. Al₂O₃-based catalysts and TiO₂-based catalysts were also prepared by incipient wetness impregnation to sure the synergistic effect between transition metal. The results find the activity on Cu-Mn/Al₂O₃ is better than Cu-Mn/TiO₂, but NH₃ conversion on Cu-Zr/TiO₂ is rather well with high yield of NO. The role of supports and transition metals play in catalyst are discussed by a series of experiments. Key ward: SCO, NH₃, transition metal, γ-Al₂O₃, TiO₂, SBA-15

Abstract: An influence of the degree of account of the non-diagonal couplings between d electrons sited on different atoms in a transition metal on the main characteristics of the first minimums of the Wills-Harrison (WH) effective pair potentials in liquid Fe, Co and Ni are investigated. It is found that at full aforementioned account the WH potential is transformed to the simple-metal-pseudopotential-theory effective pair potential and that first-minimum positions of WH potentials abruptly shift to right side at predominance of the non-diagonal d-d-couplings in a metal.

Abstract: Ce, Nd and Gd doped strontium titanate nanomaterial was prepared by a sol-gel method. Effects of transition metals doping on photocatalytic activities of the prepared materials were studied. The pure strontium titanate had photocatalytic degradation activity of 31.0%. The maximum degradation rate happened at Ce content of 20% and nearly 32.5% of the initial methyl orange was degraded on the material after 30 min of irradiation. Although there was a slight variation of photocatalytic degradation rate with the increasing Nd doping content, the materials doped with Nd had lower photocatalytic activity compared with pure strontium titanate. Nearly all the samples doped with Gd in the range up to 30% had much lower activity that the pure strontium titanate.

Abstract: Porous nanocomposites of M/Ce-K-O (M=Co, Ni, Cu) were prepared by the citrate-gel thermal decomposition and selective reduction process, and the effect of transition metal nanoparticles on their microstructure, catalytic performance were studied by XRD, SEM, BET, XPS and TG analysis. The nanocomposites consist of the fluorite-type matrix of CeO2 nanoparticles about 13-20 nm and metallic nanoparticles ~26 nm. These nanocomposites have a nanoporous structure with high specific surface area and their pore sizes, pore structures, surface morphologies are largely affected by the dispersed nano metal species. For M/Ce-K-O (M=Co, Ni, Cu) nanocomposites, all the catalysts show a high catalytic activity for soot combustion, and among them, the Cu/Ce-K-O nanocomposite has a lowest T50 of 315 °C mainly due to a higher lattice oxygen content and a weaker Cu-O interaction intensity.