Effects of coating parameters on the morphology of SiO2-coated TiO2 and the pigmentary properties

SiO₂-coated TiO₂ powders were prepared by the chemical deposition method starting from rutile TiO₂ and Na₂SiO₃. The SiO₂-coated TiO₂ powders were characterized by X-ray photoelectron spectroscopy, Zeta-potential analysis, Fourier transform infrared spectroscopy, and transmission electron microscopy. The evolution of island-like and uniform coating layers was found to depend upon the ratio of Na₂SiO₃ to TiO₂, reaction temperature, and pH. The whiteness and brightness of the SiO₂-coated TiO₂ powders increased in response to an increase in the SiO₂ loading, but there was a maximum value among the light scattering indexes. The SiO₂-coated TiO₂ powders possessed more negative Zeta potentials than the naked TiO₂. The dispersibility of the SiO₂-coated TiO₂ powders with the continuous and uniform SiO₂ coating layers was higher than that of the naked TiO₂ and the SiO₂-coated TiO₂ powders with the island-like SiO₂ coating layers.     

Physical and electrical properties of band-engineered SiO2/(TiO2) x (SiO2)1−x stacks for nonvolatile memory applications

In our study, the physical properties of (TiO₂) _x (SiO₂)_1?x , including band-gap, band-offset, and thermal stability and the electrical properties of band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x tunnel barrier stacks, including the tunneling current and charge-trapping characteristics for applications to nonvolatile memory devices were investigated. It was observed that the band-gap and band-offset of (TiO₂) _x (SiO₂)_1?x can be controlled by adjustment in the composition of the (TiO₂) _x (SiO₂)_1?x films. Ti-silicate film with TiO₂:SiO₂ cycle ratio of 1:5 was maintained in an amorphous phase, even after annealing at 950 °C. The tunneling current of the band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier was larger than that of a single SiO₂ barrier under a higher external bias, while the tunneling current of a SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier under a lower external bias was smaller. Charge-trapping tests showed that the voltage shift for SiO₂/(TiO₂) _x (SiO₂)_1?x is slightly larger than that for single SiO₂.     

Crystal structure and spin state of Fe0.5Co0.5(NCS)2(bpa)2

Fe(NCS)₂(bpa)₂, Co(NCS)₂(bpa)₂, and Fe_0.5Co_0.5(NCS)₂(bpa)₂ were synthesized. X-ray structural analysis revealed that the structure was the same among the three complexes. Although the metal-ligand distance in the mixed crystals was shorter than the distance in Fe(NCS)₂(bpa)₂ and was similar to that in Co(NCS)₂(bpa)₂, the spin state remained temperature-independent Fe^II high-spin state in ⁵⁷Fe M?ssbauer spectra.     

Structure of Artificial Grain Boundaries in Sapphire Bicrystals with Intermediate Layers

The structure of the artificial grain boundaries in Al₂O₃ bicrystals withY₃Al₅O₁₂ and Y-stabilizedZrO₂ (Y-ZrO₂) intermediate layers was studiedwith high resolution electron microscopy, electron diffraction and energydispersive X-ray analysis. TheY₃Al₅O₁₂ intermediate layer wasfound to be polycrystalline with three different orientation relationshipsbetween the ₂O₃ and theY₃Al₅O₁₂. The structure of theY₃Al₅O₁₂/₂O₃ interfaces is described.Also₂O₃ bicrystals with an Y-ZrO₂/₂O₃/Y-ZrO₂/₂O₃/Y-ZrO₂intermediate layer, prepared at two different temperatures, werestudied.Recry stallization of the intermediate layers occurred during thesolid phase intergrowth of the ₂O₃ bicrystalsparts and only an Y-ZrO₂ layer was found as intermediatelayer. The misorientation between the consecutive Y-ZrO₂grains was less than 1.5°. Misfit dislocations and atomic height stepsdecorate the Y-ZrO₂/₂O₃interface.     

Conversion of nitrogen oxides in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures subjected to a dc corona discharge

This paper concerns the influence of a direct current (dc) corona discharge on production and reduction of NO, NO₂ and N₂O in N₂:O₂:CO₂ and N₂:O₂:CO₂:NO₂ mixtures. The corona discharge was generated in a needle-to-plate reactor. The positively polarized electrode consisted of 7 needles. The grounded electrode was a stainless steel plate. The gas flow rate through the reactor was varied from 28 to 110 cm³/s. The time-averaged discharge current ranged from 0 to 6 mA. It was found that in the N₂:O₂:CO₂ mixture the corona discharge produced NO, NO₂ and N₂O. In the N₂:O₂:CO₂:NO₂ mixture the reduction of NO₂ was between 6–56%, depending on the concentration of O₂, gas flow rate and corona discharge current. The NO₂ reduction was accompanied by production of NO and N₂O. The results show that efficient reduction of nitrogen oxides by a corona discharge cannot be expected in the mixtures containing N₂ and O₂ if reducing additives are not employed.     

A novel blue-emitting phosphor: BaAl2B2O7: Pb

Pb²⁺ doped BaAl₂B₂O₇ materials were prepared by a solution combustion synthesis. The phase of the synthesized materials was determined using the powder X-ray diffraction. The photoluminescent properties of Pb²⁺ doped BaAl₂B₂O₇ materials were investigated using spectrofluorometer at room temperature. The emission and excitation bands of BaAl₂B₂O₇: Pb²⁺ were observed at 423 and 266 nm, respectively. The dependence of the emission intensity on the Pb²⁺ concentration for BaAl₂B₂O₇: Pb²⁺ was investigated. The Stokes shifts of BaAl₂B₂O₇: Pb²⁺ was calculated to be 13 953 cm⁻¹.     

Photocatalytic performance of TiO2/V2O5 nanocomposite powder prepared by DC arc plasma

TiO₂/V₂O₅ nanocomposite powder was synthesized by the DC arc plasma, and its photocatalytic activity was examined by decompositions of Rhodamine B solution and toluene gas. In the synthesis of TiO₂/V₂O₅ nanocomposite powder, TiCl₄ and VOCl₃ precursors were introduced into thermal plasma flame with argon carrier gases through separated two gas bubblers. They were decomposed by Ar–N₂ thermal plasma generating Ti and V vapors, followed by the formation of oxides with the injection of additional oxygen into a plasma reactor. Nanocomposite composed of relatively small size V₂O₅ nanoparticles on a spherical TiO₂ nanoparticle which was about 250 nm in diameter was identified by X-ray diffractometry, electronic microscopy, and energy dispersive spectroscopy when the ratio of carrier gas flow rates for TiCl₄ to VOCl₃ was 1:4 or 1:5. In ultraviolet–visible absorption spectroscopy, the absorbed wavelength of light for synthesized TiO₂/V₂O₅ nanocomposite powder was wider than that for commercially available TiO₂ nanopowder. Therefore, Rhodamine B solution exposed to visible light was decomposed by TiO₂/V₂O₅ nanocomposite, whereas it was not decomposed by TiO₂ nanopowder. In addition, toluene decomposition in a dielectric barrier discharge reactor was carried out with nano-sized photocatalysts of TiO₂ nanopowder and TiO₂/V₂O₅ nanocomposite. Relatively higher removal rate of toluene was found in the case of TiO₂/V₂O₅ nanocomposite in virtue of improved photocatalytic performance.     

Raman characterizations and structural properties of the binary TeO2?WO3, TeO2?CdF2 and ternary TeO2?CdF2?WO3 glasses

The Raman spectroscopy technique was used to characterize the microstructure and the crystallization properties of the as‐cast and heat‐treated binary TeO₂ WO₃, TeO₂ CdF₂ and ternary TeO₂ CdF₂ WO₃ glasses and glass ceramics. The results were compared with those obtained by using the X‐ray diffraction technique. The effect of the WO₃ and CdF₂ contents on the TeO₂ glass network and the intensity ratios of the deconvoluted Raman peaks were determined. The shifts in the Raman band wavenumbers and the intensity values for each band were investigated. The Raman results indicated that the glasses were mainly formed by the [TeO₄] and [TeO₃] units. The [TeO₄] units convert to [TeO₃] units with the addition of WO₃ and CdF₂ into tellurite glasses. All the crystalline phases such as α‐TeO₂, δ‐TeO₂ and γ‐TeO₂ existing in the TeO₂ WO₃, TeO₂ CdF₂ and TeO₂‐ WO₃ CdF₂ glasses were determined. The transformation of the metastable γ‐TeO₂ phase into stable α‐TeO₂ was observed for the (1 − x)TeO₂ xWO₃ (where x = 0.15, 0.20, 0.25), 0.90Te₂ 0.10CdF₂, the 0.85TeO₂ 0.10CdF₂ 0.05WO₃ and 0.80TeO₂ 0.10CdF₂ 0.10WO₃ glasses, and the transformation of the metastable δ‐TeO₂ phase into the stable α‐TeO₂ was also observed for the TeO₂ CdF₂ WO₃ glass system. In addition, an unidentified phase formation, labeled ε, was determined. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of TiO2 addition on the crystallization of quenched glasses in the SiO2–Al2O3–ZrO2 system

The glass formation in the SiO₂-rich region of the ternary oxide system Al₂O₃–ZrO₂–SiO₂ with MgO, CaO, and TiO₂ as melting aids was analyzed. The crystallization of glasses with different content of TiO₂ and phase evolution with the temperature was studied by X-ray diffraction, infrared, laser Raman spectroscopy and transmission electron microscopy. The use of TiO₂ favored formation and crystallization of the glasses due to the decrease of the viscosity of melts and acting as a nucleating agent. The crystalline phase of t-ZrO₂ was developed at temperatures as low as 880°C whereas in as prepared specimens without TiO₂ its presence was not detected. For the specimens with TiO₂, t-ZrO₂ and mullite were the principal phases at 1000°C. TiO₂ addition did not change the crystallization sequence but decreased the formation temperature of the crystalline phases. Most of Ti⁴⁺ ions entered into t-ZrO₂ and only a small portion in mullite, but the surplus was detected in ZrTiO₄.     

XPS investigation of diffusion of two-layer ZrO2/SiO2 and SiO2/ZrO2 sol–gel films

Two-layer ZrO₂/SiO₂ and SiO₂/ZrO₂ films were deposited on K9 glass substrates by sol–gel dip coating method. X-ray photoelectron spectroscopy (XPS) technique was used to investigate the diffusion of ZrO₂/SiO₂ and SiO₂/ZrO₂ films. To explain the difference of diffusion between ZrO₂/SiO₂ and SiO₂/ZrO₂ films, porous ratio and surface morphology of monolayer SiO₂ and ZrO₂ films were analyzed by using ellipsometry and atomic force microscopy (AFM). We found that for the ZrO₂/SiO₂ films there was a diffusion layer with a certain thickness and the atomic concentrations of Si and Zr changed rapidly; for the SiO₂/ZrO₂ films, the atomic concentrations of Si and Zr changed relatively slowly, and the ZrO₂ layer had diffused through the entire SiO₂ layer. The difference of diffusion between ZrO₂/SiO₂ and SiO₂/ZrO₂ films was influenced by the microstructure of SiO₂ and ZrO₂.     

Preparation of aminofunctionalized TiO2 surfaces by binding of organophosphates

Titanium dioxide (TiO₂) powder was chemically modified with 2-aminoethyl dihydrogen phosphate (AEPH₂) and with 2-aminoethyl hydrogen ammonium phosphate (AEPHNH₄) in order to achieve an aminofunctionalized high-surface-area TiO₂ carrier suitable for more complex functionalizing. AEPH₂ was found to form the monoammonium salt AEPHNH₄ with ammonium ion rather than the diammonium salt AEP(NH₄)₂. The AEPHNH₄ was thoroughly characterized by various techniques and compared with AEPH₂. Bonding of AEPH₂ and AEPHNH₄ with TiO₂ powder was studied. According to the ³¹P NMR and elemental analysis results, AEPH₂ and AEPHNH₄ form covalent chelate bidentate bonds between the phosphate group and the TiO₂, while the amino groups remain accessible, creating uniform aminofunctionalized TiO₂ surface fully occupied by AEP groups. Amount of AEP groups on TiO₂ was limited to 1.5 wt-%.     

Magnetic properties of UT2Si2 and UT2Ge2 (T = Co,Ni, Cu) intermetallic systems

Neutron diffraction and magnetization measurements indicate that, at low temperatures, long-range magnetic order is present in UCO₂Si₂, UNi₂Si₂, UCu₂Si₂, UNi₂Ge₂, and UCo₂Ge₂. UCo₂Si₂ and UNi₂Ge₂ are simple collinear antiferromagnets of +-+- type, UCu₂Si₂ a simple collinear ferromagnet. In UNi₂Si₂, a magnetic phase transition from a LSW type structure to collinear antiferromagnetism of +-+- type was found, while in UCu₂Ge₂, the antiferromagnetic structure of ++-- transforms into collinear ferromagnetism. Crystal structure and magnetic parameters are given. No magnetic moment on transition metal ions was found within the accuracy of a powder neutron diffraction experiment. The stability of particular magnetic ordering schemes is discussed in terms of an isotropic RKKY mechanism.     

γ-Fe2O3中的氢含量

利用热中子透射法测定γ-Fe₂O₃的氢含量。利用差热分析、磁分析以及穆斯堡尔效应研究γ-Fe₂O₃的相变,实验结果表明在γ-Fe₂O₃结构中确实含有一定量的氢,当γ-Fe₂O₃结构中的阳离子空位被H¹⁺,Co²⁺,Si⁴⁺,P⁵⁺等离子占据时,将 关键词：     

V<Subscript>2</Subscript>O<Subscript>5</Subscript>-SiO<Subscript>2</Subscript> hybrid as anode material for aqueous rechargeable lithium batteries

V₂O₅-SiO₂ hybrid material was fabricated by heat-treating a mixture of H₂SiO₃ and V₂O₅. SEM, TEM, XRD, and N₂ isotherm analyses were performed to characterize the morphology and structure details of the as-prepared V₂O₅-SiO₂. The possibility of using the as-prepared V₂O₅-SiO₂ as anode material for aqueous lithium-ion batteries was investigated. Potentiostatic and galvanostatic results indicated that the intercalation/de-intercalation of Li⁺ in this material in aqueous electrolyte was quasi-reversible. It was also found that a discharge capacity of up to 199.1 mAh g^?1 was obtained at a current density of 50 mA g^?1 in aqueous solution of 1 M Li₂SO₄, a value which is much higher than the available reported capacities of vanadium (+5) oxides in aqueous electrolytes.     

Improvement of a novel anode material TeO2 by chlorine doping

A simple and versatile method for the preparation of chlorine-doped TeO₂ was developed via thermal decomposition of Te₆O₁₁Cl₂ in situ. Te₆O₁₁Cl₂ was prepared with TeCl₄ and ethanol as reagents, while TeO₂ was fabricated with water as a solvent. The morphology, surface, and electrochemical performances of the obtained materials were systematically studied. It was found that chlorine-doped TeO₂ demonstrated the highest cycling efficiency and stability than Te₆O₁₁Cl₂ and TeO₂. The presence of Te–Cl bond is expected to contribute to the reversible capacity and Li inserting process.     

Surface modification of Mg2B2O5 whisker and its effect on the mechanical properties and thermostability of polycarbonate/Mg2B2O5w composites

The Mg₂B₂O₅ whiskers (Mg₂B₂O₅w) were modified by boric acid ester (BE) coupling agent and used to prepare polycarbonate (PC) composites. Surface wettability test and evaluation of dispersibility of BE-modified Mg₂B₂O₅w (BE-Mg₂B₂O₅w) in n-heptane were carried out by water contact angle measurement and polarizing microscopy, respectively. The surface chemical characteristics of BE-Mg₂B₂O₅w and estimation of the amount of tightly bonded organic modifier were examined by Fourier transform infrared spectrometry (FT-IR) and thermogravimetric analysis (TGA), respectively. The influence of BE-Mg₂B₂O₅w on the mechanical property, morphology and thermostability of PC composites was investigated by using universal testing machine, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and TGA, respectively. It was found that BE was successfully grafted to the surface of Mg₂B₂O₅w, and the hydrophobic BE-Mg₂B₂O₅w leads to high ratio of adhesion work to interfacial tension between PC and BE-Mg₂B₂O₅w, and its better dispersibility in n-heptane. Furthermore, the incorporation of BE-Mg₂B₂O₅w into PC matrix resulted in higher tensile properties of PC/BE-Mg₂B₂O₅w than that of PC/Mg₂B₂O₅w composites and lower maximum weight loss rate than that of PC. The storage modulus of the PC/Mg₂B₂O₅w composites increased obviously as a function of whisker content, especially for the composites with BE-Mg₂B₂O₅w, but the T_g value changed little.     

Effect of electron irradiation on the heat capacity of [NH2(CH3)2]2 · CuCl4 in the phase transition region

The specific heat of crystalline [NH₂(CH₃)₂]₂ · CuCl₄ in the ferroelectric phase, both nonirradiated and irradiated by electrons, was measured calorimetrically. The temperature region of existence of the ferroelectric phase was shown to broaden under electron irradiation. The existence of an incommensurate phase above the Curie point T _c1 in the crystal was confirmed. The phase-transition sequence observed in [NH₂(CH₃)₂]₂ · CuCl₄ is shown to be described by a phenomenological model for A ₂ BX ₄-type ferroelectrics with an organic cation.     

锂硼钒酸盐玻璃的11B核磁共振研究

用¹¹B连续波核磁共振谱研究了锂硼钒酸盐玻璃的结构,测量了BO₄,BO_3s和BO_3A各结构单元的比例。实验表明,锂硼钒酸盐玻璃中N₄的最大值近似为一常数,与V₂O₅的含量无关。Li₂O被V₂O₅和B₂O₃分享。并推测V₂O< 关键词：     

Preparation of SiO2 overlayers on oxide substrates by chemical vapor deposition of Si(OC2H5)4

The deposition of SiO₂ onto ZrO₂, TiO₂, MgO, SiO₂ and Al₂O₃ by chemical vapor deposition (CVD) of Si(OC₂H₅)₄ was studied by temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). TPD showed that Si(OC₂H₅)₄, adsorbed at 300 K, decomposed on ZrO₂, TiO₂, MgO and Al₂O₃ to give ethene and H₂O during the TPD. SiO₂ did not adsorb Si(OC₂H₅)₄ at 300 K. The decomposition of Si(OC₂H₅)₄ on ZrO₂ decreased as the amount of SiO₂ grew. The Zr AES signals attenuated strongly while that of Si increased. We conclude that a SiO₂ thin film about 10 Å thick forms on ZrO₂. This thin film was stable in vacuum up to 723 K but, at 823 K, either rearranged into small clusters or formed a solid solution with the surface of ZrO₂. The decomposition activity of TiO₂ for Si(OC₂H₅)₄ did not decrease strongly as SiO₂ deposition proceeded. This is accounted for if SiO₂ clusters are produced leaving TiO₂ sites exposed. Over both ZrO₂ and TiO₂ adsorption of CO₂ was suppressed by the deposition of SiO₂. There is no significant carbon buildup during deposition on ZrO₂ but on all the other oxides its accumulation is important.     

Formation pathways of HO2 and OH changing as a function of temperature in photolytically initiated oxidation of dimethyl ether

The time resolved product formation in oxidation of dimethyl ether (DME) has been studied between 298-625 K and 20-90 torr total pressure. Near-infrared frequency modulation spectroscopy (FMS) with Herriott type multi pass optics and UV absorption spectroscopy (UV) were conducted in the same cell. The reaction was initiated by pulsed photolysis in a mixture of Cl₂, O₂, and DME via CH₃OCH₂ radical formation. The reaction process was investigated through FMS measurement of HO₂ and OH, and UV measurement of CH₃OCH₂O₂. The yields of HO₂ and OH are obtained by comparison with reference mixtures, Cl₂, O₂, and CH₃OH for HO₂, and Cl₂, O₂, CH₃OH, and NO for OH, which convert 100% of initial Cl to HO₂ and OH. The CH₃OCH₂O₂ yield is also obtained. It was found that the HO₂ yield increases sharply over 500 K mainly with a longer time constant than that of R + O₂ reaction, while a prompt component exists throughout the temperature range at a few percent yield. OH was found to be produced promptly at a yield considerably larger than that known for the simplest alkanes. The CH₃OCH₂O₂ profile has a prompt rise followed by a gradual decay whose rate is consistent with the slow HO₂ formation. The species profiles were successfully predicted with a model constructed by modifying the existing one to suit the reduced pressure condition. After modification, it was inferred that the HO₂ formation over 500 K is secondary from HCHO + OH and HCO + O₂ and a part of HCO is formed directly from the O₂ adduct, whereas the HO₂ formation below 500 K is governed by CH₃OCH₂O₂ chemistry. The HCO forming pathway via isomerization-decomposition of the O₂ adduct, which was not included in the former models, was supported by our quantum-chemical calculations.