二氧化钛微晶结构和光催化性能关联性研究

研究了不同煅烧温度、煅烧时间的系列二氧化钛样品悬浮体系光催化降解X-3B活性艳红的催化活性。分析了晶粒尺寸、晶相、晶格畸变应力和光催化体系等诸多因素对二氧化钛光催化活性的影响。发现晶格畸变应力对空穴电子对复合速率的影响在诸因素中占主导地位,并在一定程度上决定了二氧化钛悬浮体系的光催化效能。     

Preparation and properties of silicon- and titanium-containing hybrid nanocomposite films based on ethyl cellulose

Nanocomposite hybrid films containing silicon and titanium compounds in the polymer matrix are prepared through the sol-gel method via the hydrolytic polycondensation of Si and Ti alkoxides (tetraethoxysilane and titanium tetrabutoxide) in the THF solution of a hydrophobic polymer, ethyl cellulose. Their structure and properties are studied with the use of a complex of physicochemical methods. During the hydrolysis of tetraethoxysilane and the subsequent polycondensation of the reaction products, silicon atoms are incorporated into the polymer and form -O-Si-O-bonds involving hydroxyl groups of ethyl cellulose. In the sol-gel method, titanium alkoxide yields nanosized particles of titanium dioxide that play the role of fillers in the polymer matrix. Titanium-containing films show solubility in THF and, after prolonged contact with the solvent, precipitate titanium dioxide from the solution. Hybrid films containing silicon are insoluble owing to the formation of a chemical network between polymer molecules and Si-OH groups of the products of hydrolysis of silicon alkoxide, as confirmed by the IR data. It is shown that the amounts and types of alkoxides and the diameters of the structures formed in the polymer matrix via the sol-gel procedure affect the hydrophilicity levels of ethyl cellulose hybrid films and their abilities to swell in water and aqueous solutions of organic dyes (brilliant blue and methylene blue). Ethyl cellulose hybrid films are hydrophilic, and they facilitate the removal of dye molecules from aqueous solutions. The best properties are featured by the films containing nanosized particles of titanium dioxide in the polymer matrix.     

Effect of pH on the viscosity of titanium dioxide aqueous dispersions with carboxylic acids

Dispersions of titanium dioxide nanoparticles with terephthalic acid, isophthalic acid, salicylic acid, benzoic acid, and pyridine-2,5-dicarboxylic acid were prepared by aqueous grinding. The pH of the dispersions was adjusted by adding either HCl or NaOH, and the viscosity of the dispersions was measured. It was found that the viscosity of the system depends strongly on pH. The qualitative interpretation of the results based on the DLVO theory is presented. The evidence of the effect of bridging interactions on the viscosity of titanium dioxide-dicarboxylic acid dispersions is discussed.     

Sorption rate of uranyl ions by Hyphan cellulose exchangers and by hydrated titanium dioxide

Summary Sorption of uranyl ions by the cellulose exchanger Hyphan proceeds rather fast. Two steps are observed with half-times of the order of 10 s and 2 min. The majority of the uranyl ions is bound in 1 min. Sorption of uranyl ions by titanium dioxide is a very slow process. For particle sizes between 0,1 and 0.5 mm the half-time is about 3 h and equilibrium is attained in about 1 day. The effect of stirring suspensions of inorganic sorbents like titanium dioxide in solution is investigated in detail. Sorption of uranyl ions by titanium dioxide and change in pH in solution are measured simultaneously as a function of time.Alexander von Humboldt fellow     

Electrorheological behavior of the hybrid material prepared by cohydrolysis of titanium(IV) isopropoxide with minor additions of a liquid crystal

A new organic-inorganic hybrid material based on Ti(IV) dioxide and a liquid crystal of alkyloxybenzoic acid with variable-length alkyl chain was prepared by the sol-gel procedure. Physicochemical analysis of the resulting material was carried out, and the electrorheological activity and dielectric properties of the dispersions of the synthesized powders in polydimethylsiloxane (PMS-20) were examined in relation to the length of the alkyl chain of the liquid crystal.     

Comparative study of conventional and hybrid blocking layers for solid-state dye-sensitized solar cells

In hybrid solar cells a blocking layer between the transparent electrode and the mesoporous titanium dioxide is used to prevent short-circuits between the hole-conductor and the front electrode. The conventional approach is to use a compact film of titanium dioxide. This layer has to be of optimum thickness: it has to cover the rough surface of the anode material completely while keeping it as thin as possible since the layer acts as an ohmic resistance itself. A competitive alternative arises when using an amphiphilic diblock copolymer as a functional template to produce thin, hybrid films containing a conducting titanium dioxide network embedded in an insulating ceramic material. These hybrid films can be produced much thinner compared to the conventional approach and, hence, they possess a 32% higher conductivity. The conventional and the hybrid blocking layer are characterized by conductive scanning probe microscopy and macroscopic conductance measurements. Additionally, the functionality of both blocking layers in solid-state dye-sensitized solar cells, as tested with current-voltage measurements, is verified.     

Symmetry and stability of nanotubes based on titanium dioxide

The process of rolling a monolayer of bulk crystal with biperiodical planar lattice to the nanotube was analyzed. It was shown by an example of the carbon nanotubes how the tube symmetry can be revealed through the analysis of symmetry of graphene layers (the layer group with a hexagonal planar lattice) and its changes at the rolling to form the tube. The developed approach can be used to analyze the symmetry of any nanotube. A computer program we developed is discussed that allows to determine the nanotube symmetry using the data on the symmetry and coordinates of the atoms in the nanolayer and get the coordinates of the atoms in the unit cell of the nanotube which can be used for the further quantum-chemical calculations. The method and results of ab initio calculations of the titanium dioxide monolayer stability in the LCAO basis optimized for the bulk crystal, using the hybrid exchange-correlation potential PBE0 are presented. Symmetry properties of nanotubes obtained by rolling the three- and six-plane monolayers (101) and (001) of anatase are discussed. Atomic and electronic structure of TiO₂ nanotubes found by geometry optimization is analyzed. It is shown that titanium dioxide nanotubes based on the three-plane monolayers with hexagonal and square lattice are approximately of the same stability. The data on the stability of nanotubes are essential for the synthesis of new nanomaterials based on titanium dioxide.     

Synthesis of rutile titanium dioxide from Russian raw materials

The conditions of the structure formation of rutile titanium dioxide from titanium dioxide (anatase) and titanium hydroxide isolated by thermolysis from the titanium compound (NH₄)₂TiO(SO₄)₂ · H₂O and by thermal hydrolysis of a titanium sulfate(IV) solution, respectively, were studied. It was shown that the mechanical activation of the studied powders causes, in addition to a decrease in the initial grain size, deep destructuring with the formation of the transition phase, which, in the process of the subsequent high-temperature treatment, functions as a matrix for the formation of rutile. The research results will be used for the development of a new variant of the technology for the synthesis of titanium dioxide, which is an important component of compositions for polymeric materials—in particular, the K-300-61 and K-153 adhesives.     

Concentration factor and rheology of aqueous titanium dioxide dispersions

The rheological properties of aqueous titanium dioxide dispersions have been studied by rotational viscometry. It has been established that the studied disperse systems are highly structured, and their degree of structuring dramatically increases with the volume fraction φ of the solid phase. At solid phase contents φ ≥ 0.164, the breakage of the disperse structure is accompanied by the appearance of local discontinuities and an abnormal dependence of viscosity on shear stress. The results obtained have been analyzed in terms of the Uriev theory of aggregated systems. The radii of aggregates and maximum solid phase content φ_m that corresponds to the formation of a continuous disperse structure under the conditions of dynamic impact have been calculated.     

Green synthesis of titanium dioxide nanoparticles via bacterial cellulose (BC) produced from agricultural wastes

Cellulose - Bacterial cellulose (BC) produced from Achrmobacter sp. M15, was used to reduce titanium tetra isopropoxide into titanium dioxide nanoparticles (TiO2NPs) via green process. Addition of...     

Preparation and characterization of nitrogen-doped titanium dioxides

A type of high visible-light active titanium oxinitride(TiO2-xNx) powder was prepared by a simple proc-ess:the calcination of the hydrated titanium dioxide at the atmosphere of ammonia-argon using a tu-bular electric furnace at high temperatures. The hydrated titanium dioxide was synthesized as the precursor of TiO2-xNx using titanic acid as raw material,which came from sulfate technique of produc-ing titanium white. The effects of temperature and reaction time on the nitrogen content,grain size and crystal structure were studied. The visible-light activity and photocatalysis capability of the powder were also investigated.     

Characterization of the chemical interaction between single-walled carbon nanotubes and titanium dioxide nanoparticles by thermogravimetric analyses and resonance Raman spectroscopy

Raman spectroscopy is a powerful technique that is used to characterize or observe alterations in the structure or properties of carbon nanotubes and its composites. This method can provide information about electronic changes or quantify them. We used Raman spectroscopy to study the chemical and electronic changes in a composite formed by titanium dioxide nanoparticles and single-walled carbon nanotubes. This composite was characterized by scanning electron microscopy to investigate the morphology and by thermogravimetric analyses to assess the thermal stability of the isolated carbon nanotubes as compared with the nanotubes by titanium dioxide nanoparticles. The Raman results showed that the modification of the nanotubes with the TiO₂ nanoparticles generates a new material with different structure of the nanotubes, resulting in a decrease in defects. The charge transfer from the TiO₂ nanoparticles to the nanotubes alters the electronic properties of both moieties in the hybrid material. The interaction between the nanotubes and nanoparticles decreases the CC bound order of the nanotubes and decreases their thermal stability.     

Determination of titanium dioxide in foods using inductively coupled plasma optical emission spectrometry

Titanium dioxide is a common food additive of increasing interest in dietary intake studies and dietary exclusion studies. Food labelling for titanium dioxide is imprecise so a method was developed for its rapid determination in foods using acid digestion and inductively coupled plasma optical emission spectrometry (ICPOES). Twenty-five foods thought to contain titanium dioxide were obtained. Based on preliminary digestion studies, samples (500 mg) were digested in 18 mol l-1 H2SO4 at 250 degrees C for 1 h and then diluted to 5.9 mol l-1 H2SO4 before determination of titanium by ICPOES at 336.121 nm. Emission intensity was suppressed by H2SO4 so standards were matched for acid concentration. Titanium dioxide embedded in gelatine was used to assess accuracy. A standard reference material of known titanium concentration and six foods of known titanium dioxide content were used as external reference materials. Limits of detection were 2-7.5 ppb, depending on spectral integration times, and the signal was linear up to 5 ppm. Results for all control samples were in good agreement with the expected values. Twelve of the foods contained detectable titanium, ranging from 0.001 to 0.782% by weight, but only eight indicated this on their labels, four being exempt under food labelling regulations. Based on food portion sizes, an individual's daily intake of titanium dioxide could exceed 200 mg from just one of these products. This method may facilitate future studies on titanium dioxide intake, given the present limitations of food labelling.     

Matrix isolation spectroscopic and theoretical study of carbon dioxide activation by titanium oxide molecules

The reactions of titanium monoxide and dioxide molecules with carbon dioxide were investigated by matrix isolation infrared spectroscopy. It was found that the titanium monoxide molecule is able to activate carbon dioxide to form the titanium dioxide-carbon monoxide complex upon visible light excitation via a weakly bound TiO(η(1)-OCO) intermediate in solid neon. In contrast, the titanium dioxide molecule reacted with carbon dioxide to form the titanium monoxide-carbonate complex spontaneously on annealing. Theoretical calculations predicted that both activation processes are thermodynamically exothermic and kinetically facile.     

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye. The PHF molecules adsorbed to the surface of titanium dioxide due to electrostatic forces, with adsorption density being higher at lower pH values. The surface coverage of titanium dioxide nanoparticles by PHF molecules determined the extent of enhancement, with an optimum dosed weight ratio of PHF to titanium dioxide at 0.001. Hydroxylation and concomitant solubilization of fullerenes allow their unique electronic properties to be harnessed for photocatalysis.     

Environmental problems of finely dispersed titanium dioxide production

Finely dispersed titanium dioxide is widely used in modern technologies. Proved reserves of titanium ores in Russia are expected to meet industrial needs. However, the available facilities for the manufacture of titanium dioxide from ores are clearly insufficient, which naturally requires new plants to be put into operation. The technologies used for the production of titanium dioxide were developed as early as 1940s, when ecological aspects of the production process were almost not taken into account. The present survey analyzes environmental problems related to the titanium dioxide production according to the sulfate and chloride technologies in comparison with the fluoride process proposed for industrial implementation. The fluoride process has been examined as applied to ilmenite from the Turan deposit in Tomsk oblast, and some actions directed toward improvement of ecological parameters of this process have been proposed.     

Investigation of thermal power of reaction of titanium slag with sulphuric acid

Enriched titanium raw materials with high titanium content called titanium slags are received by the electrothermal reduction of ilmenite. Titanium slags are most frequently used in the titanium dioxide industry. The reaction of titanium slags with sulphuric acid is strongly exothermic and creates danger of thermal explosion. Kinetics of this reaction depends on the parameters such as temperature of initiation, sulphuric acid concentration and dimension of particles of titanium slag. The reaction of titanium slag with sulphuric acid was investigated at non-isothermal conditions in a special construction calorimeter. The observed thermal power changes in the calorimeter (“calorimeter run”), are the basis for estimation of reaction kinetics. A proposed model describing the thermal power changes and taking into account the moment of initiation of reaction is presented. The calorimetric investigations showed, that reaction rate of titanium slags with sulphuric acid depends on initial temperature of reaction, size of particles of titanium raw material and sulphuric acid concentration.     

聚苯胺复合二氧化钛的制备及其降解硝基苯研究

以苯胺和二氧化钛为原料,采用化学氧化法,合成光降解复合材料聚苯胺(PANI)/二氧化钛(TiO₂),并对其进行表征。采用该复合材料对50mg·L^-1的硝基苯模拟废水进行自然光催化降解研究,实验结果显示,当二氧化钛和苯胺用量摩尔数之比为10∶1,在自然光条件下获得最佳的催化效果,同时讨论了不同pH值和投加量对降解效果的影响,发现当pH=7,投加量为0.5g·L^-1时,2h自然光降解效率达到95.2%,反应速率常数增长了3.25倍。     

Bulk titanium for structural and biomedical applications obtaining by spark plasma sintering (SPS) from titanium hydride powder

Titanium is a low density element with excellent mechanical properties, and is an attractive material for structural and biomedical applications. In recent years, a new process technology is emerging by which titanium and titanium alloys can be obtained by using titanium hydride (TiH₂) as a precursor for Ti and its mixture with alloying elements. The feasibility of this manufacturing approach has been fully demonstrated from powder to sintering and from microstructure to mechanical properties. In this paper, a study concerning powder metallurgy processing of Ti by spark plasma sintering (SPS) route is presented. The influence of the technological parameters on the hardness and microstructures change during SPS has been studied. The experimental results are related to microscopic, thermal, and mechanical analysis.     

Photocatalytic and magnetic titanium dioxide/polystyrene/magnetite composite hybrid polymer particles

Novel multifunctional titanium dioxide (TiO₂)/polystyrene/magnetite composite hybrid polymer particle dispersions with TiO₂ nanoparticles in the surface and magnetite nanoparticles encapsulated inside the polymer matrix were produced by Pickering miniemulsion polymerization in one single step. Whereas TiO₂ nanoparticles were used to impart photocatalytic functionality and colloidal stability, magnetite nanoparticles were incorporated to allow an easy extraction for recovery and reuse of the composite multifunctional particles. The morphology of the composite particles was assessed by scanning transition electron microscopy (STEM) and energy‐dispersive X‐ray spectroscopy (EDX). The paramagnetism of the particles was analyzed using a SQUID magnetometer and their photocatalytic activity was assessed by degrading methylene blue (MB) solutions under UV light and by recovering and reusing of the particles in five consecutive cycles. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3350–3356