Nb-doped rutile titanium dioxide nanorods for lithium-ion batteries

Rutile titanium dioxide is a promising negative electrode material for lithium-ion batteries due to low volume change on lithium-ion insertion, fast ion diffusion, and large surface area. However, the low theoretical capacity and conductivity of titanium dioxide has limited its application. In this work, rutile TiO₂ was synthesized using a batch hydrothermal method, and doped with Nb⁵⁺ (3.5 at%). <Potentiodynamic/galvanostatic > cycling in the range 1.0–3.0 V vs Li/Li⁺ was used to determine the Li-ion capacity of the doped and pristine TiO₂ material, and electrochemical cycling was used to measure the extent of conversion from the lithiated to de-lithiated state. The nanoscale structures of the pristine and doped materials were determined by powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller surface area measurements. Cycling in the range 1.0–3.0 V vs Li/Li⁺ showed that Nb⁵⁺ doping into the structure resulted in higher charge capacities. After 100 cycles at 100 mA g⁻¹, the Nb-doped rutile TiO₂ maintained a capacity of ca. 390 mAh g⁻¹, 64% higher than undoped TiO₂. For electrochemical cycling in the range 0.05–3.0 V vs Li/Li⁺, the introduction of Nb⁵⁺ resulted in a higher conversion of rutile TiO₂ from the lithiated to de-lithiated state. The higher capacity of the doped TiO₂ is shown to be mainly due to the smaller particle size, optimized surface area, and orientation of the nanorods.     

Synthesis of nanosized titanium dioxide from tetrabutoxytitanium

Mesoporous TiO₂ has been obtained by template synthesis. The introduction of a surfactant in the hydrolysis of tetrabutoxytitanium in aqueous ethanol allows the structure of the resulting material to be controlled. The amorphous TiO₂ resulting from hydrolysis turns into anatase on being calcined at 300°C. As determined by X-ray diffraction, the anatase crystallite size is 70 nm in the presence of the highest surfactant concentration examined and 210 nm in the absence of a surfactant. Amorphous materials have been characterized by electron microscopy and differential thermal analysis. The ultimate benzene adsorption value has been determined for calcined mesoporous TiO₂.     

机械力化学反应法制备纳米金红石型二氧化钛的研究

以Ti (C4H9O)4 和 C2H2O4·2H2O 为原料在室温下利用机械力化学反应法制备前驱体,利用热重-微商热重法(TG-DTG)决定前驱体的分解温度,通过在特定温度下对前驱体进行热分解得到TiO2.利用XRD,SEM,ZETA 电位粒度分析仪以及紫外光谱仪对所得样品物相,形貌,粒度和光学性能进行分析和表征.结果显示所得粉体微观形貌为球形,其直径(＞ 95%)小于60nm,粒径较小的粉体对紫外线UVA波段的吸收效果较好.     

Interaction mechanisms between uranium(VI) and rutile titanium dioxide: from single crystal to powder

This paper is devoted to the study of the mechanisms of interaction between uranyl ion and rutile TiO2. Among the radionuclides of interest, U(VI) can be considered as a model of the radionuclides oxo-cations. The substrate under study here is the rutile titanium dioxide (TiO2) which is an interesting candidate as a methodological solid since it can be easily found as powder and as manufactured single crystals. This material presents also a wide domain of stability as a function of pH. Then, it allows the study of the retention processes on well-defined crystallographic planes, which can lead to a better understanding of the surface reaction mechanisms. Moreover, it is well-established that the (110) crystallographic orientation is dominating the surface chemistry of the rutile powder. Therefore, the spectroscopic results obtained for the U(VI)/rutile (110) system and other relevant crystallographic orientations were used to have some insight on the nature of the uranium surface complexes formed on rutile powder. This goal was achieved by using time-resolved laser-induced fluorescence spectroscopy (TRLFS) which allows the investigation, at a molecular scale, of the nature of the reactive surface sites as well as the surface species. For rutile surfaces, oxygen atoms can be 3-fold, 2-fold (bridging oxygens), or single-fold (top oxygens) coordinated to titanium atoms. However, among these three types of surface oxygen atoms, the 3-fold coordinated ones are not reactive toward water molecules or aqueous metallic cations. This study led to conclude on the presence of two uranium(VI) surface complexes: the first one corresponds to the sorption of aquo UO22+ ion sorbed on two bridging oxygen atoms, while the second one, which is favored at higher surface coverages, corresponds to the retention of UO22+ by one bridging and one top oxygen atom. Thus, the approach presented in this paper allows the establishment of experimental constraints that have to be taken into account in the modeling of the sorption mechanisms.     

二氧化钛介孔分子筛的合成和表征

以高嵌段共聚物为模板剂在中性条件下制备二氧化钛介孔分子筛,并以TG-DTA,XRD,TEM和N~2吸附方法对脱除模板剂后的样品进行了表征。实验结果表明,该介孔分子筛具有较高的比表面,以及六方堆积的均匀孔道,焙烧过程中孔壁可部分晶化成锐钛矿型TiO~2的小晶粒。在分子筛孔壁中引入稀土元素可提高介孔结构稳定性。     

Hazard in reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw material with sulphuric acid was investigated in ‘hazard’ type calorimetric system. The investigations show the essential influence of initial temperature, particle size distribution and concentration of sulphuric acid on rate and heat power of reaction and determine the limits of safety of the process and also its efficiency.     

Study of kinetics of reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw materials with sulphuric acid has been studied in a non-isothermal-non-adiabatic type calorimeter. The influence of different starting conditions, temperature and ilmenite particle-size distribution on the thermo-kinetics of the reaction was investigated. A kinetic model is presented for this heterogeneous system for a specified ilmenite particle-size distribution and starting temperature. On the basis of this model and experimentally determined parameters it it possible to analyse by simulation the autothermic reaction of digestion of different titanium ores with sulphuric acid.     

Low temperature deposition of nanocrystalline titanium dioxide from titanium tetraisopropoxide

Effect of ozone and water vapor on the chemical deposition of TiO₂ from the gas phase in the system of titanium tetraisopropylate-oxygen was examined. Introduction of ozone in the reaction medium was shown to result in the precipitation of smooth TiO₂ layers at 240°C, and the addition of water vapor leads to the formation with higher rate of unconsolidated layers. Adding ozone to the reaction medium with low moisture content (up to 0.65 Pa) allows obtaining at temperatures 250–350°C with high rate of growth the TiO₂ layers with the anatase nanocrystals of high photocatalytic activity.     

Synthesis and physicochemical study of ZSM-5 high-silica zeolite from natural raw materials

ZSM-5 high-silica zeolite was obtained from metakaolinite, Dzhenranchel’sk volcanic ash, and silica gel at T = 150–220°C, pH 9–13, and τ = 48–240 h with the use of an organic structure-forming additive, butanediol-1,4, in an alkaline solution. Optimum conditions for the synthesis of ZSM-5 zeolite were found (T = 200°C, pH 10, τ = 144 h). The catalytic properties of its H-form in vapor-phase esterification of acetic acid (I) with ethanol (II) were studied at 140–180°C and a I: II molar ratio from 1 to 2. Synthesized HZSM-5 showed high activity and selectivity in this reaction.     

Nano-hydroxyapatite preparation from biogenic raw materials

Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous and pure Hap.      

Synthesis of nanoscale titanium dioxide by precipitation using supercritical anti-solvent

The method of synthesis of nanoscale titanium dioxide from organic precursor using supercritical fluid technology was suggested. It was demonstrated that the obtained product consists of amorphous particles with a narrow size distribution. It possesses a high porosity and a large value of specific surface area. The effect of temperature, pressure, and concentration of the titanium(IV) isopropoxide precursor on the average size of TiO₂ nanoparticles has been studied. The method allows preparation of titanium dioxide free from precursor compounds. Complex physico-chemical study of the obtained product has been performed.     

Synthesis and antibacterial activity of novel titanium dioxide doped with silver

Pure and silver doped nanoparticles of titanium dioxide (TiO₂) was prepared using novel, modified sol–gel method. The samples were characterized by transmission electron microscopy, X-ray diffraction, N₂ adsorption measurement, atomic absorption spectroscopy (AAS), UV–vis spectroscopy (UV–vis). The antibacterial activity of the prepared samples was indicated by minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) values according to the reference methods of Clinical and Laboratory Standards Institute for the determination of MIC of aerobic bacteria by broth microdilution. The results showed very good antibacterial activity of silver nanoforms to bacteria strains: Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Klebsiella pneumoniae. The sensitivity of the tested bacteria to silver nanoforms depends on the crystalline form of the carrier—TiO₂, its surface area, porosity, the content of silver, its particle size and oxidation state. The originality of this work is the synthesis of novel type of nanocomposites TiO₂ doped with silver and determination its excellent antibacterial activity.     

Low-cost synthesis of titanium dioxide anatase nanoclusters as advanced materials for hydrogen photoproduction

Research on Chemical Intermediates - Sub-nm titanium dioxide (TiO2) clusters are synthesized via the hydrolysis of TiCl4 in order to produce clean and surfactant-free oxide surfaces. By controlling...     

Structure and photocatalytic properties of materials based on titanium dioxide and silver nanoparticles

Phase composition and structure of mesostructured materials, titanium dioxide and titanium dioxide modified with silver nanoparticles, have been studied by X-ray diffraction analysis. Introduction of Ag(I) ions into the initial composition and variation of the annealing temperature over the 500–950°C range allows controlling the anatase to rutile crystal phase ratio in the samples. The photocatalytic activity of TiO₂ and TiO₂/Ag samples has been demonstrated using the methyl orange degradation reaction. The catalytic properties of the materials have been found to depend on the anatase to rutile phase ratio and on the presence of silver nanoparticles.     

超临界合成Pt修饰的TiO2用于光催化CO2还原制备太阳能燃料

考察了超临界条件下合成TiO2基光催化剂的性质,尤其是在超临界CO2下得到的分散在TiO2上Pt的特性,并与商品化TiO2性能进行了比较.另外,所得催化剂的光催化活性用CO2光还原制太阳能燃料进行了评价.结果表明,该催化剂可得到具有比商用TiO2更好或类似的性能(高比表面积、结晶度、表面羟基浓度,大的孔容、增强的可见光吸收、高的甲烷生成速率)而用于CO2还原制备燃料的反应中.这可归因于该催化剂超临界介质合成过程.     

Effects of material properties on sedimentation and aggregation of titanium dioxide nanoparticles of anatase and rutile in the aqueous phase

This study investigated the sedimentation and aggregation kinetics of titanium dioxide (TiO(2)) nanoparticles with varying material properties (i.e., crystallinity, morphology, and chemical composition). Used in the study were various types of commercially available TiO(2) nanoparticles: three spherical anatase (nominal diameters of 5, 10, and 50 nm) and two rutile nanoparticles (10×40 and 30×40 nm). The 50 nm anatase and 10×40 nm rutile showed higher stability in deionized water and 5 mM NaCl solutions at pH 7 than the 5, and 10 nm anatase nanoparticles in sedimentation experiments. In aggregation experiments, critical coagulation concentration values for the 50 nm anatase were the highest, followed by the 10×40 nm rutile and the 5 nm anatase nanoparticles in NaCl and CaCl(2) solutions. The aggregation kinetics was fitted reasonably well with the Derjaguin-Landau-Verwey-Overbeek (DLVO) equations for the TiO(2) nanoparticles tested. Results showed that crystallinity and morphology are not influential factors in determining the stability of TiO(2) nanoparticle suspensions; however, the differences in their chemical compositions, notably, the varying concentrations of impurities (i.e., silicon and phosphorus) in the pristine materials, determined the surface charge and therefore the sedimentation and aggregation of TiO(2) nanoparticles in the aqueous phase.     

Sodium-reduced tantalum powders produced from plumbomicrolite raw materials

Effect of various extractive systems (triisoamyl phosphate/HF+H₂SO₄, n-octanol/HF+H₂SO₄, n-octanol/HF+HNO₃) used to obtain potassium heptafluorotantalate from plumbomicrolite-based raw materials on the purity and characteristics of sodium-reduced tantalum powders was studied. Application of the extractive systems provides production of high-purity potassium heptafluorotantalate from raw materials based on products formed in processing of the plumbomicrolite concentrate.     

Recovery of metals from raw materials of industrial origin

Interaction of d elements and their compounds (oxides, sulfides, carbonates, and other compounds poorly soluble in water) with organic ligands in aprotic solvents was studied. Methods for recovery of metals from nonaqueous solutions of the resulting complex compounds are suggested.