Sol–gel synthesis and hydrothermal processing of anatase nanocrystals from titanium n-butoxide

The alkoxide sol–gel synthesis of nanostructured TiO₂ has been studied systematically to examine the processing parameters that control crystallite size and phase. A hydrothermal method has been proposed to prepare uniform and unaggregated nanocrystals of pure anatase in nitric acidic medium. Hydrolysis and polycondensation of titanium n-butoxide (Ti(OC₄H₉)₄) have been performed in the presence of polyethylene glycol (PEG). The use of polyethylene glycol (PEG) and the effect of its concentrations on the formation of anatase phase have been described in detail using X-ray diffraction and transmission electron microscopy. It was found that nanocrystalline anatase particle (< 10 nm) was derived by hydrothermal processing at 160 °C for 5 h.     

Vanadium oxide loaded tin–titanium phosphates: Surface structures and performance for the oxidative dehydrogenation of ethane

Mixed crystalline tin–titanium phosphates with nominal Ti:Sn ratios of 0.5 and 3.0 have been prepared by precipitation of Sn(IV) and Ti(IV) soluble salts with H₃PO₄. Vanadium was then incorporated by chemical grafting with a VOCl₃ precursor up to levels of 2% vanadium. Both the tin–titanium phosphates (TS) and their V-loaded counterparts (V/TS3 and V/TS0.5) were characterized by X-ray diffraction, Raman spectroscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy, and their reactivity was tested for the C₂H₆ oxydehydrogenation reaction. It was shown that a part of vanadium segregates as V₂O₅ in the V/TS3 sample, while Sn segregation occurs in V/TS0.5 and this system shown no formation of V₂O₅ crystallites. Both the TS and V/TS systems were found to be active for this reaction, although significant differences were observed depending on the crystallinity and surface enrichment of tin. The V/TS0.5 system displayed the best performance. Selectivity for dehydrogenation decreased only slightly with increasing ethane conversion, whereas the selectivity to CO₂ increased to the detriment of the selectivity to C₂H₄ because CO selectivity remained close to zero. The high selectivity to C₂H₄ along the C₂H₆ interval explored appears to be related to highly dispersed vanadium species on the catalyst surface.     

Modifications in the molecular structure of hydroxyapatite induced by titanium ions

The purpose of this study was to contribute to the understanding of the effect of titanium ions released from a metallic substrate on the molecular structure of hydroxyapatite. The effects of pH, time of incubation and concentration of titanium ions were investigated. The solids were analysed by X-ray diffraction, Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, energy dispersive X-ray analysis and thermogravimetric analysis. The results clearly indicate the presence of a titanium phosphate, Ti(HPO₄)₂·nH₂O (n=1–3), which probably has a double layered structure. The formation of this compound is dependent on the titanium concentration and its crystallinity increases with the time of incubation.     

New route to prepare nanocrystalline TiO2 and its reaction mechanism

Titanium oxide nanoparticles are prepared by electrochemical dissolution of pure titanium in a mixed acetylacetone and ethanol solution followed by direct sol-gel process of the electrolyte. Infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and TEM have been used to investigate the structure of precursor and nanocrystalline TiO₂. Characterization of the electrochemical product reveals that Ti(OEt)_m(acac)_n was formed by anodic dissolution of titanium in a mixed acetylacetone and ethanol solution. Infrared experiments show that hydrolysis of Ti(OEt)_m(acac)_n precursor removes first OEt groups, the chelating acac groups are still observed in the gel and can only be removed upon heating to 473 K. This study also shows that nanocrystalline TiO₂ prepared by this route has a textural and thermal stability with size distribution of 5-20 nm.     

Transformation of microporous titanium glycolate nanorods into mesoporous anatase titania nanorods by hot water treatment

High surface area titanium glycolate microporous multi-faceted nanorods were synthesized from the reaction of titanium alkoxides (Ti(OEt)₄, Ti(O ⁱ Pr)₄, or Ti(O ⁿ Bu)₄) with ethylene glycol, using a sol–gel reflux method. The specific surface area of the as-synthesized titanium glycolate nanorods obtained from Ti(OEt)₄ is ~480 m²/g. A hot water treatment at 90 °C for 1 h transformed the titanium glycolate microporous nanorods into mesoporous anatase TiO₂ nanorods. The shape of the nanorods was conserved after hot water treatment and the microporous to mesoporous transformation took place without significant change in the surface area (477 m²/g). Micro Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, solid state NMR, and nitrogen adsorption/desorption were used to characterize the samples. As a demonstration of potential applications, the thus formed mesoporous anatase TiO₂ nanorods were tested for their photocatalytic efficiency in the degradation of crystal violet, and a photodegradation mechanism is proposed.     

Structure, morphology and fibroblasts adhesion of surface-porous titanium via anodic oxidation

Surface-porous titanium samples were prepared by anodic oxidation in H₂SO₄, H₃PO₄ and CH₃COOH electrolytes under various electrochemical conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were employed to characterize the structure, morphology and chemical composition of the surface layer, respectively. Closer analysis on the effect of the electrochemical conditions on pore configuration was involved. It can be indicated that porous titania was formed on the surface layer, and the pore configuration was influenced by electrolyte composition and crystal structure of the titania. The fibroblast cells experiment showed that anodic oxidation of titanium surface could promote fibroblast adhesion on Ti substrate. The results suggested that anodic oxidation of Ti in CH₃COOH was suitable to obtain surface-porous titanium oxides layers, which might be beneficial for better soft tissue ingrowths.     

Raman,FT-IR and dielectric studies of PZT 40/60 films deposited by MOD technology

Ferroelectric Pb(Zr_0.4Ti_0.6) O₃ (PZT 40/60) thin films with uniform composition have been fabricated using the metallo-organic precursor compounds lead di-ethylhexanoate Pb(C₇H₁₅COO)₂, titanium di-methoxy-di-neodecanoate Ti(OCH₃)₂(C₉H₁₉COO)₂ and zirconium octoate Zr(C₇H₁₅COO)₄. These metallo-organic precursors were stored for more than four years and are very stable in ambient conditions, compared to sol-gel solutions. The structural development of these films under different annealing temperatures was systematically studied using X-ray diffraction, FT-IR spectroscopy and Raman scattering. The results show that the overlapping of (h 0 0) and (0 0 I) peaks of the PZT 40/60 films in X-ray diffraction patterns, mainly due to the small grain sizes in films, makes it very difficult to distinguish individual diffraction peaks and to identify the phases. In FT-IR measurements, the intensity of Zr/TiO₆ metal-oxygen octahedral vibrational modes becomes stronger with increasing annealing temperatures, while the FT-IR spectral peaks of vibrations of the residual carbon ligands (COO^–) finally disappear at high temperatures, showing that FT-IR spectroscopy is a good way to monitor the growth of the perovskite phase in PZT 40/60 films. Raman measurements undoubtedly reveal the Raman spectra of these PZT 40/60 films in the tetragonal phase field, demonstrating that Raman spectroscopy is an effective tool to identify structures, especially in the case of thin films having small grains. The values of high dielectric constant and the total remanent polarization obtained by ferroelectric pulse measurements show that the PZT film is a suitable material for non-volatile random access memory and dynamic random access memory applications.     

Hydrothermal synthesis of surface-modified iron oxide nanoparticles

We synthesized surface-modified iron oxide nanoparticles in aqueous phase by heating an aqueous solution of iron sulfate (FeSO₄) at 473 K with a small amount of either n-decanoic acid (C₉H₁₉COOH) or n-decylamine (C₁₀H₂₁NH₂), which is not miscible with water at room temperature. Transmission electron microscopy showed that the addition of n-decanoic acid or decylamine changed the shape of the obtained nanoparticles. X-ray diffraction spectra revealed that the synthesized nanoparticles were in α-Fe₂O₃ or Fe₃O₄ phase while Fourier transform infrared spectroscopy and thermogravimetry indicated the existence of an organic layer on the surface of the nanoparticles. In the synthetic condition, decreased dielectric constant of water at higher temperature increased the solubility of n-decanoic acid or n-decylamine in water to promote the reaction between the surface of iron oxide nanoparticles and the organic reagents. After the synthesis, the used organic modifiers separated from the aqueous phase at room temperature, which may help the environmentally benign synthesis of surface-modified metal oxide nanoparticles.     

Influence of Coating Parameter and Sintering Atmosphere on the Corrosion Resistance Behavior of Electrophoretically Deposited Composite Coatings

The purpose of this study is to synthesize and characterize nanosized titania (TiO₂), zinc oxide (ZnO), and its composite coating on Ti–6Al–4V to enhance its corrosion protection behavior in Ringer's solution. Nanosized powders of TiO₂ and ZnO was characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and scanning electron microscopy - energy dispersive atomic spectroscopy (SEM-EDAX) analysis. As a result of antibacterial activity, both ZnO and TiO₂/ZnO have produce remarkable inhibition zone on Escherichia coli. The antibacterial activity of composites are due to the combined effect of ZnO on TiO₂. The adherence and surface uniformity of TiO₂/ZnO composite film on titanium implant was examined by optical microscopy and Vickers microhardness test. Corrosion resistant behavior of the coating on titanium implant was investigated by tafel polarization and impedance analysis. The composite coatings on Ti–6Al–4V have produced improved corrosion resistance with a pronounced shift in the anodic corrosion potential (E_corr) with a corresponding less corrosion current density (I_corr) compared to monophase coating. Similar results have been obtained for impedance analysis which indicated a reduction in double layer capacitance (C_dl) and with enhancement in charge transfer resistance (R_ct). These observations suggest improved corrosion resistance property of TiO₂/ZnO composite coating on Ti–6Al–4V.     

Preparation and characterization of mesoporous lithium borosilicate material via the sol–gel process

The lithium borosilicate gels were prepared from the cohydrolysis of the tetraehtylorthosilicate (Si(C₂H₅O)₄) and triethylborate (B(C₂H₅O)₃) by using an ethanolic solution of tetradecyltrimethylammonium bromide (TTAB) as surfactant. The Li⁺ ions were introduced from an acidic solution of lithium carbonate (Li₂CO₃). Depending on the B/Si, Li/Si and TTAB/Si molar ratios at pH equal to 1 and at room temperature, monolithic and transparent colourless gels were obtained. The structure of the gel was investigated by infrared spectroscopy (IR), ²⁹Si, ¹¹B and ⁷Li solid-state magnetic resonance (MAS NMR) and by thermal analysis (DTA–TG). The results show the possibility of obtaining a borosilicate network via B–O–Si bonds in which Li⁺ ions were dispersed. The adsorption–desorption isotherms of the xerogel were characteristic of mesoporous materials. These materials may provide a greater free volume through which conducting ions can move.     

Nb-doped TiO2 thin films for photovoltaic applications

Polycrystalline titania and Nb:TiO₂ thin films were deposited by RF magnetron sputtering. The influence of post-deposition annealing in vacuum and hydrogen atmosphere on the structure, morphology, oxidation states and optical properties was studied by X-ray diffraction, atomic force microscopy, XPS and UV–VIS spectroscopy. The heat treatment of titanium dioxide thin films in vacuum and H₂ atmosphere induces structural and morphological changes. The band gap narrowing was observed for the transparent as-deposited Nb:TiO₂ films, while annealing at 420 °C in H₂ atmosphere resulted in an enhancement of the electrical conductivity. Further on, TiO₂/p-CdTe photovoltaic devices with efficiency of 1.8% were fabricated and their characteristic ‘enhancement’ is discussed.     

Structural, optical, and magnetic characterization of Co and N co-doped ZnO nanopowders

Co and N co-doped ZnO nanopowders with Co and N concentration 4, 6, and 8 mol% were synthesized by sol–gel method. Powder X-ray diffraction reveals that Co and N co-doped ZnO crystallize in wurtzite structure having space group C _6v . Photo-luminescence studies show the reduction in band gap with increase in concentration of dopants. Micro Raman studies show the red shift for 1LO phonon peak with increase in doping, generally credited to the stress caused by lattice mismatch due to N doping in ZnO. X-ray absorption spectroscopy reveals that Co replaces the Zn atoms and N replace the O atoms in the host ZnO lattice. Magnetic studies show that Co and N co-doped ZnO nanopowders exhibit ferromagnetic character at room temperature.     

Supercapacitive performance of hydrous ruthenium oxide (RuO2 · nH2O) thin films synthesized by chemical route at low temperature

In the present investigation, we report the synthesis of ruthenium oxide (RuO₂ · nH₂O) thin films by simple chemical bath deposition (CBD) method at low temperature on the stainless steel substrate. The prepared thin films are characterized for their structural and morphological properties by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). The structural study revealed that the ruthenium oxide thin films are amorphous. Scanning electron microscopy study shows compact morphology with small overgrown particles on the surface of the substrate. FT–IR study confirms the formation of RuO₂ · nH₂O material. The supercapacitor behaviour of RuO₂ · nH₂O thin film was studied using cyclic voltammetry (CV) technique in 0 · 5 M H₂SO₄electrolyte. RuO₂ · nH₂O film showed maximum specific capacitance of 192 F · g^{? 1}at a scan rate of 20 mV · s^{? 1}. The charge–discharge studies of RuO₂ · nH₂O carried out at 300 μA · cm^{? 2}current density revealed the specific power of 1 · 5 kW.kg^{? 1}and specific energy of 41 · 6 Wh.kg^{? 1}with 95% coulombic efficiency.     

Synthesis and characterization of TiO2–SiO2 nanoparticles as catalyst for dehydrogenation of 1,4-dihydropyridines

Nanoparticles of binary TiO₂–SiO₂ mixed oxides was prepared via sol–gel method using tetraethylorthosilicate (TEOS) and titanium isopropoxide (TIPP) in different reaction conditions (solvent and pH) using ammonium hyhdroxide, acetic acid, sodium hydroxide, ethyleneglycol and polyethylene glycol followed by calcination at 850–970 °C. The morphologies, structures and chemical compositions were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transmission infrared spectroscopy (FTIR) techniques. The catalytic activity of the obtained nanomaterials was explored for the dehydrogenation of 1,4-dihydropyridines (1,4-DHPs). Observation of 86–100% conversion and 100% selectivity towards the formation of desired products with prepared nanoparticles will be discussed here.     

Preparation of hydroxyapatite-containing titania coating on titanium substrate by micro-arc oxidation

Hydroxyapatite-containing titania coatings on titanium substrates were formed by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH₃COO)₂Ca·H₂O) and sodium phosphate monobasic dihydrate (NaH₂PO₄·2H₂O) using a pulse power supply. Scanning electron microscopy (SEM) with Energy dispersive X-ray spectrometer (EDX) and X-ray diffraction (XRD) were employed to characterize the microstructure, elemental composition and phase components of the coatings. The coatings were rough and porous, without apparent interface to the titanium substrates. All the oxidized coatings contained Ca and P as well as Ti and O, and the porous coatings were made up of anatase, rutile and hydroxyapatite. Such MAO films are expected to have significant applications as artificial bone joints and dental implants.     

Tartaric acid-assisted preparation and photocatalytic performance of titania nanoparticles with controllable phases of anatase and brookite

Titanium dioxide with different ratios of anatase to brookite has been prepared by a facile hydrothermal method in the presence of tartaric acid. The resulting samples were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectra, and Brunauer–Emmett–Teller analysis. The contents of anatase and brookite in the TiO₂ particles have been successfully controlled by simply adjusting molar ratio of tartaric acid to Ti in reaction system. The degradation of Rhodamine B in aqueous solutions reveals that the catalyst containing 78.7?% anatase and 21.3?% brookite has the highest photocatalytic activity. A proposed mechanism is discussed to interpret the evolution of the phases based on the effect of different C₄H₆O₆/Ti molar ratios.     

Formation and transformation of ZnTiO3 prepared by sol–gel process

ZnTiO₃ powders with pure hexagonal phase were prepared by the sol–gel process with Zn(NO₃)₂·6H₂O and Ti(OC₄H₉)₄ materials. The thermal behavior and phase transformation of the gels were investigated by the differential scanning calorimetry–thermogravimetry (DSC–TG) analysis, X-ray diffraction (XRD) patterns, Fourier-transforming infrared (FT-IR) spectroscopy, and Raman scattering spectroscopy. The results revealed that pure hexagonal phase of ZnTiO₃ could be obtained at low temperature of 800 °C. However, in further increased temperature above 900 °C, hexagonal ZnTiO₃ would decompose into cubic Zn₂TiO₄ and rutile TiO₂.     

Characterization and thermal behaviour of gel grown mixed rare-earth (Didymium) tartrate crystals

Sherulites, crystal aggregates and platelets of Di₂ (C₄H₄O₆)₃ · 5H₂O mixed crystals were grown in gel using the single tube diffusion method. The material was characterized by using different techniques such as chemical analysis, EDAX, X-ray and electron diffraction, infrared and mass spectroscopy. The thermal behaviour of the material was studied using differential thermal analysis, DTG, thermogravimetric analysis and differential scanning calorimetry. The material is thermally unstable and starts decomposing at 50‡ C. Thermal analysis results indicate the application of the contracting cylindrical kinetic model for the solid state reactions involved in the decomposition process. The values of kinetic parameters, e.g. order of reaction, activation energy and frequency factor are worked out. The implications are discussed.     

Fabrication of nanocomposites based on carbon nanotubes containing Pt nanoparticles and TiO<Subscript>2</Subscript>

Using conical multiwalled carbon nanotubes (CNTs), we have prepared Pt/CNT and Pt/TiO₂/CNT nanocomposites with an average platinum particle size of 3–5 nm, Pt/Ti molar ratio on the surface in the range 3.5–4, and C/Pt = 21–22. Titania was deposited onto the CNTs through titanium tetrachloride (TiCl₄) hydrolysis. Platinum particles were produced by reducing chloroplatinic acid (H₂PtCl₆) with sodium borohydride (NaBH₄) in the presence of CNTs. The composition and structure of the composites have been studied using X-ray photoelectron spectroscopy, electron microscopy, X-ray diffraction, and thermogravimetry. The materials have been tested as catalysts for hydrogen oxidation and oxygen reduction. The results demonstrate that the modification of Pt/CNT with titania enhances the catalytic activity of the material.