Nickel- and copper-containing oxide films on titanium

We have studied the composition and structure of films 20–30 μm thick prepared by plasmaassisted electrochemical oxidation (PEO) and additionally modified by impregnation in aqueous solutions of nickel and copper nitrates and then annealed. The investigative tools used were powder X-ray diffraction, electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy. Unmodified film/titanium composites have a certain catalytic activity in CO oxidation to CO₂ at temperatures above 300°C; for modified layers, these temperatures are noticeably higher. Modification influences the surface structure, relief, and elemental composition. Relations between the composition and catalytic properties of the oxide layers are discussed.     

Preparation,properties, and catalytic activity of platinum-modified plasma electrolytic oxide structures on aluminum

Catalytically active Pt-containing oxide composites on aluminum have been prepared by plasma electrolytic oxidation (PEO) and by additional modification of the resulting coating by impregnation with an aqueous solution of chloroplatinic acid followed by calcination. The oxide film/metal composites have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy. The modified films contain the γ-Al₂O₃ and Pt crystalline phases. Platinum in the surface and subsurface layers is in the Pt⁰ state. There are platinum-rich areas on the surface of the PEO films. A higher catalytic activity in CO oxidation into CO₂ is shown by the samples whose oxide film contains nickel and copper along with platinum.     

Deposition,composition, and activity in CO oxidation of anodic layers with platinum on aluminum and titanium

Pt + TiO₂/Ti(Al) and Pt + CeO₂ + ZrO₂ + TiO₂/Ti composites were formed by plasma electrolytic oxidation and their surface composition and catalytic activity in CO oxidation to CO₂ were studied.     

Silicate coatings on titanium, modified with transition metal oxides and their activity in CO oxidation

CuO+M _x O _y /TiO₂+SiO₂/Ti composites (M = Mn, Fe, Co, Ni) were produced by plasma-electrolytic oxidation and impregnation, followed by annealing. The elemental and phase composition of these composites were examined and their activity series in CO oxidation was determined.     

Plasma-electrochemical formation of oxide layers on titanium in aqueous electrolytes with trilonate complexes of manganese

Layered oxide coatings catalyzing oxidation of CO to CO₂ by plasma-electrolytic oxidation in aqueous electrolytes with trilonate complexes of manganese were studied. Data on the elemental composition of their surface and deep layers, phase composition, and specific features of growth were obtained.     

金红石相TiO2-石墨烯复合材料的制备及其光催化性能

以鳞片石墨为原料, 用改进的Hummers法制备氧化石墨烯(GO), 以异丙醇钛为钛源经一步水热法制备得到金红石相TiO₂-石墨烯复合材料(rGO-TiO₂), 考察了氧化石墨烯用量对复合材料光催化性能的影响. 采用X射线衍射(XRD), 比表面积(BET), 透射电镜(TEM), 扫描电镜(SEM), 拉曼光谱, 紫外-可见(UV-Vis)吸收光谱和荧光光谱(PL)等测试手段对复合材料进行表征. 结果表明: 复合材料中TiO₂为针簇状结构的金红石相, 与石墨烯能够均匀复合; 与纯金红石相TiO₂相比, 复合材料具有较大的比表面积. 研究了该复合材料在紫外光下对罗丹明B 以及可见光下对甲基橙光降解效果. 当氧化石墨烯浓度为0.5 mg·mL^-1时, 制备得到的复合材料rGO-TiO₂具有较好的光催化效果.     

Composition,structure, and catalytic activity of Ni- and Cu-containing plasma-electrolytic coatings on titanium

Unmodified and modified nickel- and copper-containing oxide layers were formed on a titanium support and their composition, structure, and catalytic activity in a model reaction of CO oxidation were studied.     

Structure of mono- and bimetallic heterogeneous catalysts based on noble metals obtained by means of fluid technology and metal-vapor synthesis

Monometallic nanocomposites are obtained with the use of supercritical carbon dioxide (fluid technique) and metal-vapor synthesis (MVS), while bimetallic nanocomposites of Pt and Au noble metals and ??-Al₂O₃ oxide matrix are synthesized by a combination of these two methods. The structures, concentrations, and chemical states of metal atoms in composites are studied by means of small-angle X-ray scattering (SAXS), transparent electron microscopy (TEM), X-ray fluorescent analysis (XFA), and X-ray photoelectron spectroscopy (XPS). The neutral state of metal atoms in clusters is shown by XPS and their size distribution is found according to SAXS; as is shown, it is determined by the pore sizes of the oxide matrices and lies in the range of 1 to 50 nm. The obtained composites manifest themselves as effective catalysts in the oxidation of CO to CO₂.     

Oxidation and carbidation of laser-ablated amorphized Ti particles in carbon monoxide

IR laser ablation of hexagonal titanium in vacuum leads to amorphization of ablated Ti particles and when carried out in gaseous carbon monoxide it proceeds as reactive ablation involving particles amorphization, oxidation and carbidation. The films deposited in vacuum and in the presence of CO were examined by Fourier transform infrared, Raman and X-ray photoelectron spectroscopy, X-ray and electron diffraction and electron microscopy. The Ti films become oxidized upon contact with air and the Ti/C/O films are composed of Ti–O, Ti–C and C–O bonds-containing structures with Ti in Ti²⁺–Ti⁴⁺ state and incorporating crystalline rutile and elemental carbon. The ablation in vacuum represents a new approach to amorphous titanium and it is judged that hot ablated Ti particles are modified by reactions with CO decomposition products into amorphous Ti oxycarbides which undergo rapid post-pulse amorphization.     

XPS chemical state analysis of sputter depth profiling measurements for annealed TiAl-SiO2 and TiAl-W layer stacks

For the application of surface acoustic wave sensors at high temperatures, both a high-temperature stable piezoelectric substrate and a suitable metallization for the electrodes are needed. Our current attempt is to use TiAl thin films as metallization because this material is also known to be high temperature stable. In this study, Ti/Al multilayers and Ti-Al alloy layers were prepared in combination with an SiO₂ cover layer or a W barrier layer at the interface to the substrate (thermally oxidized Si or Ca₃TaGa₃Si₂O₁₄) as an oxidation protection. To form the high-temperature stable γ-TiAl phase and to test the thermal stability of the layer systems, thermal treatments were done in vacuum at several temperatures. We used X-ray photoelectron spectroscopy (XPS) sputter depth-profiling to investigate the film composition and oxidation behavior. In this paper, we demonstrate how the semiautomatic peak fitting can help to extract beside the elemental information also the chemical information from the measured depth profiles.     

Improvement of the oxidation behavior of Ti1-xAlxN hard coatings by optimization of the Ti/Al ratio

The oxidation behavior of cubic Ti_1-xAl_xN films was improved by decreasing the Ti/Al ratio from 50/50 in the direction of the phase transition between cubic and hexagonal structure. Metastable, polycrystalline, single-phase Ti_1-xAl_xN films were deposited on high speed steel (HSS) substrates by reactive magnetron sputtering ion plating (MSIP). The composition of the bulk was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). A Ti_1-xAl_xN film with a Ti/Al atomic ratio of 38/62 was deposited in cubic NaCl structure, whereas a further decrease of the Ti/Al ratio down to 27/73 led to a two-phase film with both cubic and hexagonal constituents. The Ti_0.38Al_0.62N film was oxidized in synthetic air for 1 h at 800?°C. The oxidic overlayer was analyzed by X-ray photoelectron spectroscopy (XPS) sputter depth profiling, EPMA crater edge linescan analysis, and secondary neutrals mass spectroscopy (SNMS). Scanning electron microscopy (SEM) micrographs of the cross sectional fracture were taken for morphological examination. With higher Ti content, the Ti_1-xAl_xN formed a TiO_2-x rich sublayer beneath an Al₂O₃ rich toplayer, whereas the oxide layer on the Ti_0.38Al_0.62N film consisted of pure Al₂O₃. The thickness of the oxide layer was determined to 60–80 nm, about a quarter of the oxide layer thickness detected on Ti_0.5Al_0.5N films. The absence of a TiO_2-x sublayer was also confirmed by XRD. The results show a distinct improvement of the oxidation resistance of cubic Ti_1-xAl_xN films by increasing the Al content from x = 0.5 to 0.62, whereas a further increase leads to the hexagonal structure, which is less suitable for tribological applications due to its tendency to form cracks during oxidation.     

Preparation and study of bi-supported Ziegler-Natta catalyst with nano graphene oxide and magnesium ethoxide supports for polymerization of polyethylene

In this study, we have reported the preparation of bi-supported Ziegler-Natta catalysts using magnesium ethoxide and graphene oxide as support. The polymerization process was carried out in slurry phase using triisobutylaluminum as a co-catalyst.The XRD analysis of TiCl₄/graphene oxide/Mg(OEt)₂ catalyst demonstrated that the space between the layers of graphene oxide had increased to 0.2 nm.The catalyst was characterized by XPS, BET, BJH, SEM, and TGA. The catalyst activity was studied for various Al/Ti molar ratios, and the catalyst activity was optimum at Al/Ti molar ratio of 315.     

Microwave and UV Assisted Methods for Obtaining Novel Composites Based on Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> with Embedded Gold Nanoparticles

Metallic nanoparticles embedded into the structure of metal oxides may play a role of catalytic substances. Such composites are mostly applied in oxidation reactions. The paper presents two one-step-methods for obtaining nanocomposites of gold embedded in the structure of iron oxide matrices (nanoAu/Fe₂O₃). Gold nanoparticles were formed in situ in the process of iron hydroxide dehydration. Thanks to the use of tannic acid it was possible to effectively reduce gold ions and stabilize the forming metal nanoparticles. The composites were prepared in the fields of microwave, ultraviolet radiation. The physicochemical properties of products were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray analysis and high-resolution transmission electron microscopy technique with EDS and elemental mapping mode. Also, the catalytic activity of the nanocomposites obtained was evaluated based on the process of methyl orange degradation. It was observed that products obtained according to the microwave radiation method are characterized by improved applying properties.     

Catalytic properties of aluminum/nickel-, copper-containing oxide film compositions

The possibility of the single-step formation of nickel- and copper-containing thin-film oxide systems on aluminum by plasma electrolytic oxidation was demonstrated. The resulting structures were found to be active in the reaction of CO oxidation to CO₂ in the temperature region 300–500°C. However, the resulting structures exhibited stable catalytic activity only in the simultaneous presence of nickel and copper compounds. The films were studied using X-ray diffraction, X-ray spectroscopic analysis, X-ray photoelectron spectroscopy, and electron microscopy. The resulting films exhibited an essentially inhomogeneous composition through the thickness. Electrolyte elements such as nickel, copper, sodium, and phosphorus were concentrated at the surface. Nickel occurred as Ni²⁺, and copper occurred as Cu⁺ and Cu²⁺. The surface contained carbon in detectable amounts.     

An effect of heat processing on catalytic activity of a system MnO x ,SiO2/TiO2/Ti

An effect of annealing in air at temperatures 250, 350, 500, and 700°C on composition, surface structure, and catalytic activity in CO oxidation of a system MnO _x ,SiO₂/TiO₂/Ti formed by combining methods of plasma electrolytic oxidation and impregnation was examined.     

Sol–gel preparation and structural characterization of Ba2TiSi2O8 powder

Fresnoite (Ba₂TiSi₂O₈, BTS) nano-particles were successfully synthesized at a low temperature of 900?°C by a modified Pechini sol?Cgel process with starting materials of Ba(NO₃)₂, Si(OC₂H₅)₄ and Ti(OC₃H₇)₄. The structural characterization of the precursors and derived synthesized oxide powders is done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TG-DTG) and electron microscopy (SEM, EDX and TEM) studies. The effect of heat-treating temperature on the crystallinity of the fresnoite was investigated. Combined the XRD data and the strong FTIR peaks assigned to Ti?CO and Si?CO vibration, indicate the formation of fresnoite phase at a temperature of 900?°C. Also the nano-crystals size distribution was studied and the main diameter of nanoparticles was about 47?nm.     

Formation,structure, composition,and catalytic properties of Ni-, Cu-, Mn-, Fe-, and co-containing films on aluminum

Layers containing oxygen compounds of copper and nickel and(or) of one of transition metals (manganese, cobalt, iron) were formed on an aluminum alloy by the plasma-electrolytic oxidation method. The layers were characterized by means of X-ray phase analysis, X-ray fluorescence microanalysis, and scanning electron microscopy and tested in the reaction of CO oxidation to CO₂.     

Basicity of carbonyl complexes of transition metals : X . Interaction of (π-C5H5)Mn(CO)(Ph2PCH2CH2PPh2) with aprotic acids in solution

The interaction of CpMn(CO)(Ph₂PCH₂CH₂PPh₂) with some aprotic acids in solution has been studied by infrared, electronic and ESR spectroscopy and electroconductivity. It is shown, that reactions with π-acids and some π-complexes such as CpTiX₃, CP₂MCl₂ (M  Ti, Zr, Hf, V) take place with oxidation of the manganese atom electron transfer to the acceptor molecule and the formation of the cation-radical of the donor molecule. It is also shown that an increase in the oxidation state of the Mn atom occurs in the reactions with halides of Al, Ti, Sn and Hg and the structure of the products is discussed. Less basic complexes CpMn(CO)₃, Et₅C₅Mn(CO)₃ and Et₅C₅Mn(CO)₂PPh₃ are not oxidised in the presence of tetracyanoethylene but form charge-transfer complexes.     

X-ray photoelectron spectroscopy and magnetic studies on the effect of pore size, wall thickness, and wall composition on superparamagnetic cobaltocene mesoporous Nb, Ta, and Ti composites

Recent results in our group demonstrated that mixed oxidation state mesoporous niobium oxide cobaltocene composites display superparamagnetism at certain composition ratios. This was the first report of superparamagnetism in nanoscale molecular ensembles. A series of mesoporous niobium oxide materials were synthesized in order to understand the role of pore size and thickness of the walls in the mesostructure on the magnetic properties. Mesoporous Ti oxide and Ta oxide composites were also synthesized in order to investigate the effect of changing the wall composition on the magnetic properties of this new series of materials. All samples were characterized by X-ray diffraction, nitrogen adsorption, ultraviolet spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and superconducting quantum interference device magnetometry. The results of this study showed that variation of wall thickness or pore size in the Nb system had little effect on the properties and that superparamagnetism most likely arises from mixed oxidation state cobaltocene grains residing in the individual pores and not from the free electrons in the mesostructure or much larger domains. The Langevin function was applied to the isothermal magnetic data from the Nb composites and gave mean superparamagnetic particle sizes of ca. 14 nm in each system. The Co(II) to Co(III) ratios in these materials were approximately 1:1. The Ti and Ta materials showed no sign of superparamagnetism and only very low levels of neutral cobaltocene in the pores. This suggests that a critical amount of cobaltocene is required to bring about superparamagnetic behavior.     

CeO2-TiO2复合氧化物的制备、表征及其对CO氧化的催化性能

采用溶胶-凝胶法制备了一系列不同n(Ce)/n(Ti)的CeO2-TiO2复合氧化物,对复合氧化物的物相结构、形貌特征、比表面积和氧化还原性质进行了表征,并考察了复合氧化物对CO氧化反应的催化性能.结果表明,n(Ce)/n(Ti)>0.10时,复合氧化物为无定形结构;n(Ce)/n(Ti)=0.10~0.30时,复合氧化物失去CeO2和TiO2各自的特征,形成CeO2-TiO2固溶体,具有较大的比表面积.CeO2-TiO2复合氧化物本身对CO氧化反应的催化活性不如TiO2或CeO2的高,但Pd/CeO2-TiO2比Pd/TiO2或Pd/CeO2具有更高的催化活性.