Lithium intercalation in TiS2

We report the intercalation of lithium in Li_XTiS₂ corresponding to 0 ≤ x ≤ 3. Intercalation to x = 3 results in a new phase whose charge-discharge behavior displays hysteresis. This is in contrast to the behavior of Li_xTiS₂ for 0 ≤ x ≤ 2.     

Structure refinement of stoichiometric TiS2

The structure parameters of TiS₂ have been refined using the least squares method. The structure belongs to the space group P3?ml (164) with nearly ideal octahedral coordination of the sulfur atoms about the titanium. The hexagonal, laminar structure has $\text{c}\text{= 5.6953}\text{A}\text{?}$ and $\text{a}\text{= 3.4073}\text{A}\text{?}$ with the interlayer sulfur-sulfur distance of 3.462(5) Å.     

Structure refinement of nonstoichiometric TiS2

The structure of non-stoichiometric titanium disulfide (Ti_1.023S₂) was refined from single crystal X-ray data. It was shown that the additional cations are inserted in the $\text{z}\text{=}\text{1}\text{2}$ plane. The two TiS₆ octahedra are only slightly distorded. The thermal movement of the Ti is higher than that of S.     

Preparation of In2O3 octahedrons by heating InCl3 aqueous solution on the Si substrate

In₂O₃ octahedrons have been synthesized by heating InCl₃ aqueous solution on the Si substrate at 400-900 °C for 2 h. The average size of In₂O₃ octahedrons is decreased by increasing the heating temperature. The In₂O₃ octahedrons are single-crystalline with the body-centered cubic structure and have controllable sizes in the range of 0.7-1.0 μm. A possible mechanism was also proposed to account for the formation of In₂O₃ octahedrons. A strong photoluminescence with a peak at 458 nm was observed from the In₂O₃ octahedrons at room temperature. This emission can be attributed to oxygen vacancies and indium-oxygen vacancy centers.     

Photoelectrochemical properties of donor doped BaTiO3 electrodes

The photoelectrochemical behaviour of donor-doped BaTiO₃ ceramic anodes has been investigated in comparison with that of H₂-reduced BaTiO₃ and SrTiO₃. Donor-doped BaTiO₃ has response to visible light without mechanical polishing and is unaffected by chemical etching or etching followed by polishing. H₂BaTiO₃ also has photoresponse in the visible; it is, however, modulated by mechanical polishing. Whereas, H₂SrTiO₃ has response in visible light, only on mechanical polishing. The visible photoresponse of BaTiO₃ is due to the mid-band gap states arising from lattice defects such as Ti³⁺V_O and Ba-vacancies. The differences between BaTiO₃ and SrTiO₃ is explained in terms of the changed characteristics of V_Ba(Sr)-energy states.     

Preparation of TiS2 under high pressure

Preparation of stoichiometric TiS₂ was attempted at 1000°C under high pressures. TiS₂ was firstly formed accompanying nonstoichiometric TiS₂ from the starting stoichiometric mixture of Ti and S. The further reaction to stoichiometric TiS₂ takes much longer time than the reaction of equimolar mixtures of Ti and TiS₃. The reaction of Ti and TiS₃ gave an almost stoichiometric TiS₂ at 1000°C after the duration of 2hrs.     

The verification of the existence of TiS2

The intrinsic electronic properties of TiS₂ are currently under some debate. It has not been conclusively demonstrated if TiS₂ is a semimetal or a degenerate semiconductor. We have thoroughly studied this problem by first characterizing the material composition and then determining the electronic properties. Precision x-ray diffraction, mass density, and chemical analysis have been used to characterize TiS₂. Trends in the Ti_xS₂ series of nonstoichiometric compounds have been monitored by intercalation, scanning electron microscope, magnetic susceptibility and electron transport measurements. We conclude from the total body of data collected that TiS₂ exists as a stoichiometric compound and that its semimetallic properties are intrinsic.     

Solid solution of RF3 in CaF2

Solid solution, CaF₂ · rRF₃, where 0 < r < 0.7, and R = Tb, Dy, Ho, Y and Er, can be characterized by a constant partial molar volume of 27.21 cm³ for RF₃.     

Removal of fluoride from aqueous solution by polypyrrole/Fe3O4 magnetic nanocomposite

Polypyrrole (PPy)/Fe₃O₄ magnetic nanocomposite as a novel adsorbent was prepared via in-situ polymerization of pyrrole (Py) monomer using FeCl₃ oxidant in aqueous medium in which Fe₃O₄ nanoparticles were suspended. The adsorbent was characterized by Attenuated Total Reflectance Fourier transform infrared spectroscope (ATR-FTIR), Brunauer–Emmet–Teller (BET) method, field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HR-TEM), X-ray photoelectron spectroscope (XPS) and X-ray diffraction (XRD). Magnetic property of the adsorbent was measured by electron spin resonance (ESR). Subsequently, the ability of the adsorbent to remove fluoride ions from aqueous solution was demonstrated in a batch sorption mode. Results reveal that the adsorption is rapid and that the adsorbent has high affinity for fluoride, which depends on temperature, solution pH and adsorbent dose. From equilibrium modelling, the equilibrium data is well described by Freundlich and Langmuir–Freundlich isotherms while the adsorption kinetics is described by the pseudo-second-order model. Thermodynamic parameters confirm the spontaneity and endothermic nature of the fluoride adsorption. Meanwhile, the fluoride adsorption proceeds by an ion exchange mechanism.     

锂离子电池负极材料TiS3 纳米片的制备和性能

先用直流(DC)电弧法制备TiH_1.924纳米粉作为前驱体,再用固-气相反应制备了片状结构的TiS₃纳米粉体。使用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、原子力显微镜(AFM)、拉曼光谱分析和性能测试等手段对其表征,研究了TiS₃纳米片的结构和将其用作负极的锂离子电池的性能。结果表明：TiS₃纳米片具有特殊的片状结构,其厚度约为35 nm。将TiS₃纳米片用作负极的锂离子电池具有良好的电化学性能,在500 mA/g电流密度下循环300圈后其容量仍保持在430 mAh/g。以5 A/g的大电流密度放电其比容量为240 mAh/g,电流密度恢复到100 mA/g其放电比容量稳定在500 mAh/g。TiS₃良好的倍率性能,源于其特殊的纳米片状结构。这种单层片状结构,能较好地适应电极材料在大电流密度多次放电/充电过程中产生的应变引起的体积变化,使其免于粉碎。     

Changes of symmetry in the structure of SrCeO3 -BaZrO3 solid solution

The structural behaviour of SrCeO₃ -BaZrO₃ solid solution was determined and the crystal constants were calculated from X-ray diffraction data. Several displacive changes of symmetry were detected, related to distortion introduced by Sr and Ce atoms in the perovskite framework of the solid solution. Deviation from Vegard's law was observed and related to structure changes.     

Photoelectrochemical property of ZnFe2O4/TiO2 double-layered films

ZnFe₂O₄/TiO₂ double-layered films on indium-tin oxide (ITO) substrate were prepared by a dip-coating method, and the optical absorption and photocurrent of the as-prepared films were measured. In the double-layered films, the onset of fundamental absorption edge shifts to a longer wavelength, and even shifts to a longer wavelength than that of ZnFe₂O₄-only film as the ZnFe₂O₄ layer thickness increases. Application of the coupled photoanodes double-layered films composed of ZnFe₂O₄ and TiO₂ can obviously increase the photocurrent. It was found that the photocurrent density of ZnFe₂O₄/TiO₂ double-layered films first increased and then decreased with increasing the ZnFe₂O₄ layer thickness. A five-fold increase in the photocurrent density was obtained compared with TiO₂-only films under optimum condition.     

Solid state and solution synthesis of Ba(Mg1/3Ta2/3)O3: A comparative study

Ba(Mg_1/3Ta_2/3)O₃ [BMT] dielectric ceramics are prepared by solid state (one step, two step and molten salt synthesis) and wet chemical methods (precipitation, citrate gel and sol-gel). The formation mechanism of BMT in each synthesis technique is discussed. The formation temperature and particle size of the formed BMT were found to be much lesser (in nanometer range) for solution synthesized powders. It is found that synthesis by sol-gel method resulted in the formation of ultra pure nanopowders of BMT at about 600 °C with average crystallite size of about 18 nm where as in solid state synthesis the formation of BMT was formed at about 1100 °C with average crystallite size of 220 nm. On sintering these powders, densification and grain growth of the chemically derived powders were found to be lower than that of solid state synthesized BMT powder. This has resulted in a slight decrease in density and microwave dielectric properties of the solution synthesized BMT samples. It is found that the microwave dielectric properties improved with increase in the average grain diameter of the sintered BMT ceramics.     

Anatase TiO2 films crystallized on SnO2:F substrates in an aqueous solution

Anatase TiO₂ films were fabricated on SnO₂:F substrates in an aqueous solution. The films were constructed of assemblies of nano-TiO₂. Surface of the films showed large roughness due to nano/micro-asperity of the assemblies. The thickness was increased to 260 nm, 360 nm, 600 nm and 760 nm with the deposition time of 2 h, 5 h, 25 h and 48 h, respectively. The films showed strong intensity of 004 X-ray diffraction possibly because the needles, i.e., nano-TiO₂, elongated along the c-axis. Low-temperature synthesis of crystalline anatase TiO₂ films has a great deal of potential in the development of electronic devices, optical devices, dye-sensitized solar cells, photocatalytic devices and biomolecule sensors.     

Preparation of LiMn2O4 thin films by aqueous solution deposition

Cathode material LiMn₂O₄ thin films were prepared by aqueous solution deposition using lithium acetate and manganese acetate as starting materials. The structures, morphologies, and the first discharge specific capacity of the thin films were investigated as a function of annealing temperature and time. The cycling properties of the thin films were also examined. The results show that LiMn₂O₄ thin films prepared by this method are homogenous and crack-free. The thin film annealed at 750°C for 30 min has good rechargeability. The capacity loss per cycle is about 0.05% after being cycled 100 times.     

Photoelectrochemical properties of thin Bi2WO6 films

Thin Bi₂WO₆ film prepared from an amorphous heteronuclear complex via dip-coating method is investigated as a visible light-driven photoelectrode material. Photoelectrochemical properties of the resultant film are investigated on the basis of linear sweep voltammetry and current-time curves, and conduction and valence band edges of the film electrode are determined from the photocurrent voltage response. Anodic photocurrent associated with the oxidation of water is obtained under visible light irradiation. Furthermore, the film as a photoanode can degrade rhodamine B (RhB) and methylene blue (MB) in aqueous solution under visible light irradiation slowly. The application of bias potential further improves the photodegradation efficiency of RhB and MB. Based on the analytic result of current-time curve, the stability of the film electrode is confirmed.     

Impedance spectroscopy study of LaMnO3 modified BaTiO3 ceramics

Ba_0.97Ti_0.97La_0.02Mn_0.04O₃ nanocrystalline powder was prepared by chemical route with the help of soluble tartarate complex of Ti⁴⁺ ion. Preliminary X-ray diffraction analysis of crystal structure showed that a single-phase compound was formed exhibiting tetragonal system. Average crystallite size and particle size were observed to be between 27 and 33 nm, which were analyzed through XRD and transmission electron microscope respectively. Wide range impedance spectroscopy study from 200 to 600 °C showed the presence of both bulk and grain boundary effects up to 500 °C. The bulk conductivity indicated an Arrhenius-type thermally activated process and oxygen vacancies are the possible ionic charge carriers at higher temperatures. The variation of ac conductivity as a function of frequency indicated the possibility of hopping mechanism for electrical process in the system with a non-exponential type of conductivity relaxation.     

Chemical synthesis of α-iron in aqueous FeCl3

Iron-aluminium composite and α-iron powder have been prepared by chemical reduction of aqueous FeCl₃ with aluminium at different conditions. Experiments showed that the concentration of FeCl₃ and aluminium particle size are the main factors to influence the reaction. XRD, SEM and potentiometric titration were employed to characterize the products. SEM showed that as iron particles grow they tend to form spherical seed on the surface of aluminium. XRD revealed that the α-iron was single phase after deposit treatment by NaOH solution. The purity of as-prepared α-iron was 99.5%, as determined from the X-ray fluorescence spectroscopy. The possible formation mechanism is a two-stage red-ox-process: Fe³⁺→Fe²⁺→α-Fe.     

Photoelectrochemical properties of MgTiO3 and other titanates with the ilmenite structure

The photoelectrochemical properties and the diffuse reflection spectrum of MgTiO₃ are reported. MgTiO₃ shows an optical absorption edge' near 3.7 eV. This makes the material unsuitable for solar energy applications. The diffuse reflection spectra of CoTiO₃ and MnTiO₃ are presented. The optical absorption edge shifts to lower energy due to the occurrence of Me²⁺ → Ti⁴⁺ charge-transfer transitions. For various reasons discussed no photocurrents were observed for CoTiO₃ and MnTiO₃.     

Synthesis and shape evolution of novel cuniform-like MnO2 in aqueous solution

In this paper, the cuniform-like MnO₂ particles were first successfully synthesized with dodecylbenzenesulfonic acid (DBSA) as surfactant in aqueous solution. The samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopy (IR). The possible mechanisms of the shape evolution for the formation of MnO₂ samples were discussed.