Synthesis of ZnTiO3/tourmaline/Ni foam catalyst and enhanced photocatalytic performance

ZnTiO₃/tourmaline loaded on the nickel foam (ZnTiO₃/tourmaline/Ni-foam) is prepared by a facile coating method. Morphology and structure of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electrons microscopy (SEM), raman spectroscopy, UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic properties of the materials were tested by using the Rhodamine B (RhB) solution as the target pollutant. The results indicates that the ZnTiO₃/tourmaline/Ni foam exhibited higher photocatalytic activity than that of ZnTiO₃ and ZnTiO₃/Ni foam under ultraviolet (UV) light irradiation, and its degradation rate was up to 99.2%. Moreover, the degradation rate remained at 91.3% after eight consecutive photocatalytic reaction cycles. The outstanding photocatalytic performances of ZnTiO₃/tourmaline/Ni foam was mainly attributed to the existence of tourmaline, which can help to inhibit the recombination of electron-hole paris, and the proper pore structure of the carrier. Meanwhile, the trapping experiments indicated that ·O₂^– was the main active species in the photocatalytic degradation of RhB.     

The effect of tourmaline additives in TiO2 photoanode for high-efficiency dye sensitized solar cells

Tourmaline is a kind of borosilicatemineral and has spontaneous polarization property. Due to this property, it can generate a feeble current around 0.06 mA[1 O'Regan, B., &; Grätzel, M. (1991). Nature 353, 737.[Crossref], [Web of Science ®] , [Google Scholar]]. We fabricated the TiO₂ photoanode with different wt.% ratio of tourmaline and investigated the effect of tourmaline additive on dye sensitized solar cells (DSSCs). We carried out electrochemical impedance spectroscopy (EIS) and current density-voltage (J-V) measurement. The results showed that the electron lifetime and the power conversion efficiency of the DSSCs with TiO₂ photoanode containing 3wt% tourmaline were enhanced by about 42% and 20%, respectively, as compared to the DSSCs using pristine TiO₂ photoanode.     

石墨烯/电气石/二氧化钛复合材料的制备及其光催化降解异丙醇性能

光催化是一种理想的应对全球能源短缺和环境污染问题的绿色化学技术,可以实现有机物降解、水分解和二氧化碳光还原等.光催化反应效率受诸多因素影响,其中光生载流子(电子和空穴)的分离和传输具有至关重要的作用.以往研究表明,构筑多元复合光催化材料体系有利于光生电子和空穴有效分离和传递,促进催化剂表面的还原和氧化反应,从而提高其光催化效率.基于以上考虑,我们提出了一种新型的石墨烯/电气石/TiO2三元复合光催化材料体系,其中TiO2因其价格低廉、无毒和抗光腐蚀等优点而被广泛用作光催化材料;石墨烯(G)拥有独特的二维结构、高的电子迁移率、大的比表面积,是一种优异的催化剂载体;电气石(T)的一个重要性质是表面存在自发极化的静电场,该静电场将会影响光激发载流子的分离、传递和光催化反应过程.利用水热法合成了不同成分的石墨烯/电气石/TiO2三元复合材料体系.为了对比研究石墨烯表面电荷性质的影响,其中一组的石墨烯(氧化石墨)为直接采用改良的Hummers法所制备,其表面带负电;另一组的石墨烯经聚二烯丙基二甲基氯化铵(PDDA)修饰,使其表面带正电.X射线衍射结果显示,三元复合材料中TiO2为锐钛矿相,其结晶性没有因为与石墨烯和电气石的复合而受到影响.扫描和透射电子显微分析表明,TiO2的平均颗粒大小为15 nm左右,并且与石墨烯和电气石均匀复合.傅里叶变换红外光谱和zeta电位表征分析证实,PDDA可以有效地对石墨烯进行功能化改性,使其表面带正电.紫外-可见分光光谱显示,石墨烯/电气石/TiO2三元复合材料与TiO2的吸收带边一致,复合材料中石墨烯和电气石并没有改变TiO2的光吸收特征.光催化降解异丙醇实验表明,石墨烯/电气石/TiO2三元复合材料优于单纯的TiO2、石墨烯/TiO2以及电气石/TiO2二元复合材料,当石墨烯和电气石的质量百分比分别为0.5%和5%时,三元复合材料降解异丙醇产生丙酮的速率达到最高(223μmol/h).特别值得指出的是,由表面带负电的石墨烯组成的复合材料比由带正电荷的PDDA-石墨烯组成的复合材料具有更高的光催化性能,原因如下:在水溶液中显示正zeta电位值的TiO2与带负电的石墨烯/电气石复合物静电吸引而均匀紧密复合,有利于TiO2中光生电子和空穴的快速分离和传递,从而使得石墨烯/电气石/TiO2三元复合材料具有较高的光催化性能;而带正电的PDDA-石墨烯/电气石复合物和TiO2颗粒相互排斥而不宜复合,导致PDDA-石墨烯基复合材料的光催化活性降低.机理研究揭示,在三元复合材料光催化降解异丙醇的反应中起主要作用的是光生电子和空穴.基于以上研究结果,我们提出了三元复合材料光催化降解异丙醇的反应机理.     

Boron determination in tourmaline by neutron induced radiography

The technique of neutron induced radiography has been applied to determine the boron concentration and its spatial distribution in mineral tourmaline collected from Swat Tourmaline Granite, Northern Pakistan. The technique involves the simultaneous irradiation of sample and a standard fixed on a track detector with thermal neutrons and the counting of alpha and ⁷Li tracks produced in the detector from the nuclear reaction ¹⁰B(n,)⁷Li. Boron concentration is determined by comparing the ⁷Li and alpha particle tracks density with that of a standard of known boron concentration. Boron concentration in tourmaline has been found to be (3.40±0.01)% in this study which is on the upper side within the normal range (2.5–3.8)% reported in the world. The presence of somewhat higher concentration of boron in tourmaline indicates that the Swat Tourmaline Granite was generated as a late stage hydrothermal activity during the Himalayan Orogeny.     

Zero-field elastic constants of uvite

The theories of Kyame [1] and Koga et al. [2] on stress wave propagation in piezoelectric media are critically studied and compared with each other. Solutions of the modified Christoffel's equations predicted by each theory for piezoelectric crystals in class 3m are derived. The velocities of ultrasonic waves propagated through a gem quality uvite specimen in particular directions were measured at 293 K using the pulse-echo overlap method. All of the independent zero-field elastic moduli were calculated from the measured wave velocities and compared with the available data in the literature. The values of the elastic constants in 10¹²$\text{dyn}\text{cm}{}^2$ were found to be C₁₁ = 3.016 ± 0.2% C₆₆ = 1.028 ± 0.3% C₃₃ = 1.698 ± 0.2% C₁₃ = 0.47 ± 3% C₄₄ = 0.655 ± 0.3% c₁₄ = ?0.089 ± 6%. The calculated bulk modulus, shear modulus and Poisson's ratio, using the Voigt-Reuss-Hill (VRH) approximation, are K_H = 1.226 × 10¹²$\text{dyn}\text{cm}{}^2$, G_H = 0.826 × 10¹²$\text{dyn}\text{cm}{}^2$ and σ_H = 0.224. The Debye temperature is 764 K.