自由基抑制剂对不同晶型TiO2光催化反应的影响

以荧光光谱法研究了不同晶型 TiO₂ 的光催化反应体系中羟基自由基(·OH)的产生情况,表明在H₂O₂存在条件下,金红石型 TiO₂ 经可见光激发可持续稳定产生·OH,而以锐钛矿型 TiO₂ 作光催化剂时,则检测不到·OH的生成。光催化结果表明,在H₂O₂存在条件下,苯酚可被 TiO₂ 可见光催化降解;往反应体系加入自由基抑制剂(叔丁醇或甲醇)时,明显降低了金红石型 TiO₂ 的降解效率,但对锐钛矿型 TiO₂ 的影响较弱。以金红石型 TiO₂ 作光催化剂时,苯酚的降解反应主要发生在溶液中;而以锐钛矿型 TiO₂ 作光催化剂时,则苯酚的降解反应主要发生在催化剂的表面。     

Chenguodaite （Ag9FeTe2S4）： a new tellurosulfide mineral from the gold district of East Shandong Peninsula,China

Chenguodaite, approved by IMA-CNMMN （2004-042a）, was discovered in the Bunan quartz vein-type gold deposit in the gold district of East Shandong Peninsula. The mineral occurs in high grade Au-Ag-Cu ores, coexisting with galena, chalcopyrite, hessite, electrum, unnamed Ag6TeS2 and AglsFeBiTe3Se, enclosed and replaced by native silver and acanthite. In the reflected light microscope, the mineral has light gray color, indistinguishable anistropism and hardness around 2-3. The color indices of chenguodaite relative to ICE C illuminator are： x=0.3027, y=0.3076, Y=25.78%,λd=474 nm, Pe=3.68%, similar to those of canfieldite. The average chemical composition from 16 microprobe analyses is Ag8.97Fe1.00Te1.99S4.04, idealized to AggFeTe2S4. The polycrystalline X-ray diffraction of chenguodaite by Gandolfi camera and synchrotron oscillation photography results in 67 reflections with the 12 strongest being （relative intensity in bracket）： 6.742（69）, 6.416（39）, 5.951（33）, 3.265（100）, 2.981（24）, 2.649（22）, 2.25（24）, 2.188（71）, 2.142（22）, 2.123（31）, 2.044（23）, 1.949（33）, which are indexed to a primitive orthorhombic cell with a=12.769 （2） A, b= 14.814（2） A, c= 16.233 （1） A, V= 3070.6 A^3, Z= 9, Dcal.=6.85 g/cm^3. The name is for the late Prof. Chen Guoda, a famous Chinese geologist and the founder of Diwa-Geodepression theory of tectonics.     

Xieite, a new mineral of high-pressure FeCr2O4 polymorph

Xieite, a new mineral, occurs in the shock vein of the Suizhou meteorite. The mineral has an orthorhombic structure and its space group is Bbmm. The cell parameters are a = 9.462（6） A, b = 9.562（9） A, c = 2.916（1）A. The crystal-chemical formula is （Fe0.87Mg0.13Mn0.01）1.01（Cr1.62AI0.25Ti0.08V0.02）1.97O4, or simply formula FeCr2O4. Stronger X-ray diffraction lines are [d （A）, I/Io]： （2.675, 100）, （2.389, 20）, （2.089, 10）, （1.953, 90）, （1.566, 60）, （1.439, 15）, （1.425, 15）, （1.337, 40）. Xieite is a high pressure polymorph of FeCr2O4 and formed by solid-state transformation of chromite under shock-induced high pressure and temperature, in association with other high-pressure minerals including ringwoodite, majorite, lingunite and tuite. The P-Tcondition for the formation of xieite is estimated to be 18--23 GPa and 1800--1950℃, respectively. Xieite has recently been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association （IMA 2007-056）. The mineral name, xieite, is named after Xiande Xie.     

Crystal structure determining of 7-ADCA based on X-ray powder diffraction

Traditionally, crystal structure data can be collected and determined from single-crystal X-ray diffraction. However, in the fields of organic and macromolecular crystallography, it is often difficult or impractical to grow single crystals with suitable sizes and purity. Therefore, it will be benefited from the newly growing analytical tool that combining X-ray powder diffraction based on polycrystalline samples and ab initio calcula- tion[1]. 7-ADCA is one of the most important intermediate…     

Photocatalytic effect of nature and modified V-bearing rutile

A natural rutile TiO2, which displays photocatalysis on degrading halohydrocarbon pollutants, was reported. The rutile contains up to 1.22% V2O5 (weight percent). Substitutions of Ti by V, as well as Fe, Cu and Zn, result in lattice distortions and defects. Grinding, heating and quenching modify the surface characteristics of ruffle, and consequently increase its photoactivity. It is found that the heating and quenching treatments enhance visible-light absorption of ruffle, especially at 1000 and 1100℃. Ground rutile is effective to degrade tetrachloroethylene and trichloroethylene. While, heating at 1000℃, and quenching at 1000 and 1100℃ distinctly improve degradation rate of samples. The special properties of the natural rutile have particular capabilities in photocatalytic oxidation, especially in degradation of halohydrocarbons.     

Facile synthesis of nanosized sodium magnesium hydride, NaMgH3

The ternary magnesium hydride NaMgH 3 has been synthesised via reactive milling techniques.The method employed neither a reactive H2 atmosphere nor high pressure sintering or other post-treatment processes.The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio.High purity NaMgH 3 powder(orthorhombic space group Pnma,a 5.437(2),b 7.705(5),c 5.477(2) ;Z 4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction(PXD),Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDX).The products formed sub-micron scale(typically 200-400 nm in size) crystallites that were approximately isotropic in shape.The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption(TPD).The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K.     

Preparation and film-growing mechanism of hydrous zirconia coated on TiO2

To overcome the photochemical activity of rutile used as a pigment and improve its durability in application, hydrous zirconia-coated TiO₂ was prepared by the precipitation method. High-resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and surface structure of hydrous zirconia-coated TiO₂. The ζ-potential and ultraviolet (UV) absorption of both coated and uncoated rutile were examined. The results show that hydrous zirconia can not only improve the durability but also raise the lightness. A suitable ZrO₂ content of hydrous zirconia-coated TiO₂ is about 1.0wt%, and a dense film on the surface of rutile can be formed with better pigmentary properties. Based on the thermodynamic analysis, the zirconia-coating process and the film growth mechanism were discussed.     

Fabrication and character ization of electrospun TiO2/CuS micro–nano-scaled composite fibers

A process to fabricate a kind of novel micro–nano scaled TiO2/CuS composite fibers by electrospinning technique and chemical precipitation method was developed in the present study. The microstructures and photoelectronic properties of the fibers were characterize d using SEM, FT-IR, UV–vis and fluorescence spectroscopy. The results revealed that the TiO2 portion in the composite fibers was a mixture rutile and anatase phases while TiO2 and CuS had been fully composite. The fibers had smooth surface with a diameter of 50–300 nm. Comparing with pure TiO2 fiber, the TiO2/CuS micro–nano-scaled composite fibers exhibited a strong absorption in the visible light region and the efficiency of photo-induced charge separation were enhanced. This composite system is of widely potential applications in the areas such as solar cells, supercapacity, photocatalysis, etc.     

Environmentally-friendly harvesting TiO2 nanospheres and V2O5 microrods from spent selective catalytic reduction catalysts

Spent selective catalytic reduction (SCR) catalysts are defined as hazardous wastes because of the toxicity of V₂O₅ to the ecological environment. Recycling of V₂O₅ and TiO₂ from the spent SCR catalysts has strikingly social and environmental benefits as well as economic values. In this work, a “NaOH ​+ ​Na₂CO₃” system was employed to recycle 99.2% of anatase/rutile TiO₂ nanospheres with a nanospherical morphology from the spent SCR catalysts by a simple sintering-leaching process. The observed photocatalytic performance of anatase/rutile TiO₂ nanospheres was higher than that of the other TiO₂ recovered from the spent SCR catalysts, commercial TiO₂, and chemosynthetic TiO₂, which can be ascribed to the enhanced separation of photo-excited electron/hole in a direct Z-scheme of anatase/rutile TiO₂ homostructures. Additionally, high-purity V₂O₅ microrods with high H₂S removal performance were efficiently prepared by a hydrothermal method in the leaching solution, which is superior to the traditional method including NH₄VO₃ precipitation and solvent extraction as the present method can recycle vanadate from low-grade filtrate with a 99.6% of recovery rate. This study develops an alternative method for controlling pollution of vanadate to soil and water and recycling of valuable metals.     

Xiuyan crater,China: Impact origin confirmed

The well-preserved 1.8-km-diameter Xiuyan crater is located in the low mountain-hill region of the northern part of Liaodong Peninsula of northern China. Recently, a 307-m-deep borehole at the centre of crater became available. After penetrating 107 m lacustrine sediments, a breccia lens about 188 m in thickness was encountered. The crater-fill breccia is deposits of rock clasts and fragments more or less shock-metamorphosed. The features of geological structure and stratigraphic configuration within the crater, shock-melted rocks, and PDFs in quartz found in the basement rocks close to the crater rim and in the crater-fill breccia provide clear evidence for an impact origin of the Xiuyan crater.     

Photocatalytic degradation of microcystin-LR using TiO2 nanotubes under irradiation with UV and natural sunlight

In order to investigate the catalytic performance of anodic TiO2 nanotubes and their practical application in the treatment of refractory microcystins(MCs) in natural-water samples,TiO2 nanotubes of diameter of 50-80 nm were fabricated by anodization in C2H2O4·2H2O containing NH4F.Under irradiation with natural sunlight,MC-LR was totally degraded after 1 d using the anodic TiO2 nanotubes.In contrast,the removal efficiency without TiO2 nanotubes was as low as 47.7% within 20 d.In addition,a mixture of anatase and rutile TiO2 gave higher photocatalytic activity than the single phase did.The pH also influenced the adsorption capacity of the TiO2 nanotubes.The order of MC-LR degradation efficiencies at different pH values was 3.5 > 8.0 > 10.0.After five repeated experiments on the degradation of MC-LR for 7 h,the degradation efficiency was still stable.     

Low energy H+ effects on the photovoltaic and optical properties of polycrystalline silicon solar cells

Low energy hydrogen ion was used to passivate the electrically active defects existing in grains and grain boundaries of polycrystalline silicon solar cells. Short-circuit current of H⁺ implanted cells remarkably increased before and after preparing TiO₂AR (antireflective) coating. The measurements (at λ=6328 Å) of the optical properties of H⁺ implanted silicon samples show that: the value of absorption coefficient reached the level of a-Si; refractive indexn and ref?ectivityR significantly decreased; the optical band gap increased from 1.1 eV to 1.3 eV. The results indicate that Si-H bonds have been formed after H⁺ implantation. The calculation shows that the optical thickness cycle of TiO₂ AR coating will reduce correspondingly in order to obtain the optimum optical match between AR coating and implanted silicon since refractive index decreases after H⁺ implantation.     

Effect of hydrolysis conditions on hydrous TiO2 polymorphs precipitated from a titanyl sulfate and sulfuric acid solution

The relationship between hydrolysis conditions and hydrous titania polymorphs obtained in a titanyl sulfate and sulfuric acid solution was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The results revealed that the feeding rate of the titanyl sulfate stock solution, the concentration of sulfuric acid, and the seed dosage of rutile crystal could significantly affect the hydrolysis rate, thus influencing the titania crystal phase. Hydrous TiO₂ in the form of rutile, anatase, or the mixture of both could be obtained in solutions of low titanium concentrations and 2.5wt% to 15wt% sulfuric acid at 100°C. When the hydrolysis rate of titanium expressed by TiO₂ was more than or equal to 0.04 g/(L·min), the hydrolysate was almost phase-pure anatase, while the main phase state was rutile when the hydrolysis rate was less than or equal to 0.01 g/(L·min). With the hydrolysis rate between 0.02 and 0.03 g/(L·min), the hydrolysate contained almost equal magnitude of rutile and anatase. It seems that although rutile phase is thermodynamically stable in very acidic solutions, anatase is a kinetically stable phase.     

Synthesis and characterization of a three-ring bent-core compound

To investigate the vacuum-deposited films of the banana-shaped mesogens, we prepared a three-ring bent-core （that is, banana-shaped） compound m-bis（4-p-octoxysryrenyl）benzene （m-OSB） and used it as a prototype for studying the related film physics. Herein the synthesis and the structural characterization of m-OSB are reported.^13C and ^1H NMR spectra and ^1R spectrum confirm that m-OSB has a symmetric and all-trans conformation. The results of differential scanning calorimetry, polarizing optical microscopy and X-ray diffractometry indicate that no liquid crystalline phase but two crystalline phases are present in this material： phase Ⅰ （T〈66℃） and phase Ⅱ （66~C〈T〈157℃）; an isotropic state is observed at above 157℃. Combining the X-ray diffraction and the electronic diffraction, we assign the room-temperature crystalline phase I to orthorhombie system and P212121 space group with cell parameters of a = 7.43A°. b=6.34A°, c=72.07A°, and α=β=γ=90°. Molecular modeling reveals that the molecules in the unit cell adopt a layered structure with an antiferro-eleetrie alignment. The structure of phase Ⅱ is very similar to that of phase Ⅰ. Nonlinear optical measurement shows that m-OSB is active for the second harmonic generation （SHG）. Such characterization of the bulk material is necessary for the understanding of the growth and microstructures in the films.     

Al掺杂TiO_2的制备及酸化处理对其光催化活性的影响

锐钛矿相TiO2的光催化活性高于金红石相。采用化学溶液分解法制备了Al掺杂锐钛矿TiO2,并用硝酸对其进行酸化处理。利用TG-DTA、XRD、FTIR、BET和UV-vis等手段对样品进行了表征,通过对甲基橙的降解分析了酸化处理对Al掺杂TiO2光催化活性的影响。结果表明:掺杂Al能有效抑制TiO2由锐钛矿向金红石转变。酸化处理因能增大Al掺杂TiO2的比表面积而使其光催化活性提高。Al/Ti掺杂比为1∶4的样品在酸化处理后具有的光催化活性最高,60min后对甲基橙的降解达到100%。     

Improved and excellent CO sensing properties of Cu-doped TiO<Subscript>2</Subscript> nanofibers

Cu-doped TiO2 nanofibers with an average diameter of about 80 nm are synthesized through an electrospinning method. Both anatase and rutile crystallographic structures are found in the fibers based on XRD results. Compared with pure TiO2 nanofibers, the Cu-doped TiO2 nanofibers exhibit improved CO sensing properties at 300°C. The sensitivity of Cu-doped TiO2 nanofibers is up to 3 when the sensor is exposed to 5 ppm CO, and the response and recovery times are about 4 and 8 s, respectively. Good selectivity i...     

用部分中和法制备超细二氧化钛粉体

采用部分中和法制备超细TiO2粉体,通过TEM、XRD和TG-DTA对产品进行了表征,指出水合TiO2在煅烧过程中逐步失去游离水和化合水,再形成TiO2结晶,且随着煅烧温度的上升,颗粒的粒度迅速增大.在600℃以下煅烧时所形成的TiO2颗粒为锐钛型,在800*!℃时完全转化为金红石型.     

Effect of B2O3 on the aqueous tape casting and microwave properties of Li2O–Nb2O5–TiO2 ceramics

The effect of B2O3 addition on the aqueous tape casting, sintering, microstructure and microwave dielectric properties of Li2O-Nb2O5-TiO2 ceramics has been investigated. The tape casting slurries exhibit a typical shear-thinning behavior without thixotropy, but the addition of B2O3 increases the viscosity of the slurries significantly. It was found that doping of B2O3 can decrease the tensile strength, strain to failure and density of the green tapes. The sintering temperature could be lowed down to 900℃ with the addition of 2 wt% B2O3 due to the liquid phase effect. No secondary phase is observed. The addition of B2O3 does not induce much degradation on the microwave dielectric properties. Optimum microwave dielectric properties of εr 67, Q×f 6560 GHz are obtained for Li2O-Nb2O5-TiO2 ceramics containing 2 wt% B2O3 sintered at 900 1C. It represents that the ceramics could be promising for multilayer low-temperature co-fired ceramics (LTCC) application.     

Isothermal oxidation behavior and mechanism of a nickel-based superalloy at 1000℃

The oxidation behavior of a nickel-based superalloy at 1000℃ in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales (Cr₂O₃, (TiO₂ + MnCr₂O₄)) and internal oxides (Al₂O₃,TiN), were formed on the surface or sub-surface of the substrate at 1000℃ in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr₂O₃ scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO₂ rutile and MnCr₂O₄ spinel, and the growth of TiO₂ particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ' (Ni₃(Al,Ti)) and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000℃ for 80 h.     

Synthesis of Cu–TiO2/CuS p-n heterojunction via in situ sulfidation for highly efficient photocatalytic NO removal

Cu doped TiO₂/CuS (Cu–TiO₂/CuS) p-n heterojunction was synthesized via in situ sulfidation method for efficient photocatalytic removal of NO at ppb-level. The results show that optimized Cu–TiO₂/CuS heterojunction possessed a maximum efficiency of 85% for the removal of NO under visible light irradiation, which was approximately 8.5, 4.3 and 1.2 times that of CuS, TiO₂ and Cu–TiO₂, respectively. The improved photocatalytic performance is attributed to the enhancement of visible light absorption and charge carrier separation induced by the construction of p-n heterojunction. Meanwhile, the p-n heterojunction charge transfer mechanism of Cu–TiO₂/CuS was verified by systematic investigations. The appropriate band structures of the two components and the internal electric field formed at the interface of the heterojunction were two factors for this charge transfer mechanism. Furthermore, the role of active species in NO removal was explored, and the corresponding mechanism for NO removal of the heterojunction was proposed. This work provides a promising approach for the synthesis of heterojunction photocatalysts and facilitates the application of photocatalysts in sustainable and efficient pollutant removal.