Gd/TiO2气相光催化降解乙烯的动力学研究

采用溶胶-凝胶法和浸渍法制备了Gd3 掺杂TiO2光催化剂Gd/TiO2,以乙烯作为模拟污染物进行气相光催化降解实验,研究乙烯的流速、催化剂的粒径、热效应、反应温度等动力学因素对光催化降解反应的影响.结果表明,乙烯的流速≥20mL·min-1时,光催化活性趋于稳定;粒径大小对光催化活性基本上没有影响.乙烯在纯TiO2和Gd/TiO2样品上的光催化氧化是一级反应,光催化活性随着反应温度的升高而增强,其中,Gd/TiO2样品的光催化性能随反应温度的变化更显著.纯TiO2和Gd/TiO2样品的表观活化能分别为21.5 kJ·mol-1和16.3 kJ·mol-1,反应活化能降低,反应速率加快可能是纯TiO2掺杂Gd3 后光催化活性提高的动力学方面的原因.     

掺Mo~(6+)附Ag纳米TiO_2在可见光下降解酸性大红3R

通过溶胶-凝胶法结合光催化还原法制备掺Mo6+附Ag的TiO2纳米颗粒,并在可见光下对酸性大红3R进行降解实验,研究其在可见光下的催化活性,并与纯TiO2、仅掺Mo6+或仅附Ag的TiO2进行对比。进一步讨论在可见光照射下掺杂量、焙烧温度等因素对掺Mo6+附Ag纳米TiO2降解性能的影响。结果表明:可见光下Ag/Mo6+/TiO2比纯TiO2、仅掺Mo6+或仅附Ag的TiO2显示出更高的活性,这是因为金属Mo6+的掺杂和贵金属银的沉积使二氧化钛的吸收带边发生红移,拓宽了可见光的响应范围;Ag/Mo6+/TiO2催化剂的催化活性最高时的Mo6+掺杂量为4.5%,银的附着量为2%。焙烧温度为500℃,这种掺Mo6+附Ag纳米TiO2对酸性大红3R的降解率可达87.6%.     

La掺杂对TiO2光催化剂的影响

采用溶胶-凝胶法制备了La掺杂的TiO2.通过X射线衍射分析、扫描电镜、紫外-可见光漫反射测试等手段对TiO2进行了结构和光吸收性能研究.结果表明La3+阻碍了锐钛矿向金红石转变,提高了晶形转变温度,La3+掺杂之后的TiO2粒径变小,La3+掺杂TiO2光吸收与煅烧温度有关.     

Fe3+掺杂对TiO2材料光催化活性的影响

采用溶胶-凝胶法制备了TiO2粉末,讨论了不同Fe3+掺杂浓度对TiO2光催化活性的影响,并采用XRD、UV-VIS检测技术对其进行了表征.结果表明,Fe3+掺杂能够显著的提高TiO2薄膜的光催化活性,最佳掺杂浓度为6.04×1016个·cm-3,且随着TiO2光催化活性的提高,薄膜的吸收带边发生了明显的红移,提高了可见光的利用率.XRD分析表明,Fe3+的掺杂使锐钛矿相TiO2的粒径明显减小,锐钛矿相含量明显增加.     

铈掺杂TiO2光催化降解甲基橙的研究

采用溶胶-凝胶法制备纯的及掺杂不同量Ce的TiO2纳米粒子,利用UV-Vis漫反射光谱及XRD等对所制备样品进行表征和解释,以高压汞灯为光源,甲基橙水溶液的脱色为模型反应,研究了CeO2/TiO2的光催化降解反应活性.实验发现掺杂Ce的TiO2纳米粒子反射光谱特性向可见光方向红移到了500 nm;掺杂Ce的TiO2纳米粒子比纯的TiO2纳米粒子对光的吸收率高、吸收能力强;掺杂的Ce4+仅有少量进入TiO2晶格中,而大部分的Ce4+没有进入TiO2晶格中,而是以小团簇的CeO2形态均匀地分散在TiO2纳米粒子中或者是覆盖在其表面上,说明掺杂Ce能提高TiO2光催化反应活性,且掺杂Ce量有最佳值.实验结果表明在TiO2中掺杂Ce的摩尔百分含量为2%,甲基橙起始浓度为20 mg·L-1,CeO2/TiO2用量为0.400 g,双氧水用量为5.88 mmol·L-1,pH值为6.4时,光照8 h,甲基橙的脱色率可达96.8%.     

Gd3+,Eu3+在介孔Y2O3中的能量传递

通过模板法与溶胶-凝胶法相结合,在温和的条件下制备了介孔Y2O3.再采用水热反应法制得Eu3+、Gd3+单掺杂及Eu3+,Gd3+双掺杂的三种介孔Y2O3组装体(介孔Y2O3∶Eu3+,介孔Y2O3∶Gd3+,介孔Y2O3∶Eu3+,Gd3+).利用广角和小角X射线衍射(XRD)、透射电子显微镜(TEM)对介孔Y2O3进行了表征,结果表明,所制备的介孔Y2O3为立方相,具有六方孔道结构,孔径约10nm.对介孔Y2O3和组装体系进行了荧光光谱(PL)分析,发现在550℃热扩散处理后,介孔Y2O3∶Eu3+的发光存在基质对Eu3+的能量传递,Y2O3∶Eu3+,Gd3+体系中Gd3+对Eu3+也有能量传递作用.     

钆掺杂TiO_2纳米管的制备及光致发光性能研究

采用溶胶-凝胶法及500℃煅烧工艺制备了纯的和不同Gd掺杂量的TiO_2纳米粉,并以其为前驱物,通过微波水热合成法制备了相应的TiO_2纳米管,利用场发射扫描电镜(FESEM),场发射透射电镜(FETEM),X射线衍射(XRD)和荧光光谱(FS)仪等对样品进行表征,考察不同Gd的掺杂量对TiO_2纳米粉及纳米管形貌、结晶度和光致发光性能的影响。结果表明,纯的TiO_2纳米粉为15 nm左右,随着Gd掺杂量的提高,煅烧后TiO_2纳米粉粒径降低;当Gd含量为2%时,TiO_2纳米粉粒径减小到10 nm左右。纯的和掺杂Gd的TiO_2纳米管形貌均为两端开口,内中空,管的直径为8 nm左右,长度为100~500 nm,说明Gd掺杂含量对TiO_2纳米管的形貌影响不大。XRD分析表明,TiO_2纳米管的结晶度普遍低于纳米粉的结晶度,而适当Gd元素掺杂使TiO_2纳米管能保持一定的结晶度。另外,Gd掺杂量也影响TiO_2纳米粉以及纳米管的FS信号强度。随着Gd掺杂量的增加,TiO_2纳米管的FS信号强度有先增加后降低的变化趋势,当Gd掺杂量为0.5%和0.2%时,TiO_2纳米管的FS信号强度达到最大值。     

掺杂镧纳米TiO2的制备和结构表征

本文以钛酸四丁酯、无水乙醇、冰醋酸、硝酸镧和水为原料,通过控制原料配比、反应温度、陈化温度、焙烧温度和焙烧时间,采用溶胶-凝胶法制备了纯的纳米TiO2和四种不同镧掺杂量的TiO2纳米粉体。确定的工艺参数为:原料按照体积比为V水∶V钛酸丁酯∶V无水乙醇∶V冰醋酸=17∶17∶80∶15,凝胶干燥温度选择80℃,粉体焙烧温度为500℃。对所得产物分别采用FT-IR和粉末XRD法进行了表征,FT-IR分析结果表明,掺杂La3+后TiO2的红外吸收峰的位置基本没有发生变化,但部分吸收峰明显宽化,表明掺杂镧引起基团间作用力的改变,使基团的存在环境和键的强弱发生变化,从而导致了红外吸收峰宽化。XRD测试得出所制备的纯TiO2和四种不同镧掺杂量的TiO2粉体的结构均为锐钛矿型TiO2,且随着La掺杂量的增加,TiO2的粒径越来越小,从未掺杂时的26 nm减小到掺杂1%镧时的8 nm,说明镧的掺杂有细化晶粒的作用。     

低量Gd^3＋／Fe^3＋共掺杂TiO2制备及催化活性

利用溶胶-凝胶法在煅烧温度540℃制备了纯的和不同Gd^3＋／^3＋共掺杂的TiO2纳米粉体,并用XRD技术对样品进行了表征。研究了Gd^3＋／Fe^3＋共杂量对样品相结构、晶粒尺寸和光催化降解亚甲基蓝的活性的影响,利用相结构与纳米TiO2光催化活性关系探讨了Gd^2＋／Fe^3＋共掺杂对纳米TiO2的光催化活性。结果表明,与纯TiO2相比,适量共掺杂Gd^3＋／Fe^3＋可以显著提高其光催化活性。当Gd^3＋／Fe^3＋共掺杂量为0．04％／0．04％,Ti02纳米粉体的光催化活性最佳,降解率为89．96％,其金红石相含量为32％,平均晶粒粒径为30nm,Gd^3＋／Fe^3＋共掺杂强烈地抑制TiO2由锐钛矿相向金红石相的转变,减小晶粒尺寸这两方面均有利于提高光催化活性。     

Fe^3＋／Ce^3＋掺杂纳米TiO2的制备及光催化性能研究

采用溶胶-凝胶法制备了不同粒径的纯纳米TiO2和掺杂Fe^3＋和Ce^3＋的纳米TiO2。样品的X射线衍射（XRD）和透射电镜（TEM）表征说明：在相同的制备条件下，掺杂可以减小粒子粒径，掺Fe^3＋和Ce^3＋可以抑制晶相转变。光催化降解NO2的结果表明，在相同的制备方法和掺杂量的条件下合成的光催化剂对亚硝酸盐的降解率由高到低的顺序为：掺铁TiO2〉掺铈TiO2〉TiO2。     

Influence of annealing temperature on luminescent properties of Eu~(3+)/V~(5+) co-doped nanocrystalline Gd_2Ti_2O_7 powders

Nanosized Gd2(1-x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...     

Study on analysis of crystal structure in CeO₂ doped with Er₂O₃ or Gd₂O₃

To simulate the effects of burnable poison doping in nuclear fuel UO2,Er2O3(or Gd2O3)-doped CeO2 pellets were prepared. Changes in lattice constant and atomic disordering for CeO2 due to the Er2O3 and Gd2O3 doping were measured by means of XRD and XAFS. By the Er2O3 doping,the lattice constant decreased,and a disordering of lattice structure was induced in the samples. The doping with Er2O3 also induced the disordering of atomic arrangement around Er atoms,which was observed through the change in XAFS spectra. In contrast,the effect of Gd2O3 doping was smaller than that of Er2O3 doping. The result was discussed in terms of ionic size of dopants in CeO2 crystal.     

Preparation,characterization of Y~(3+)-doped TiO_2 nanoparticles and their photocatalytic activities for methyl orange degradation

A series of pure and Y3+-doped TiO2 nanoparticles with high photocatalytic activities were prepared by a sol-gel method using tetra-n-butyl titanate as precursor.The as-prepared catalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and diffuse reflectance spectroscopy(DRS).The results indicated that yttrium doping could effectively reduce the crystalline size,inhibit the anatase-to-rutile phase transformation and surppress the recombination of the photogenerated electron-h...     

Sm2O3掺杂BSTN陶瓷的制备与介电性能

采用溶胶凝胶法制备了Sm3+掺杂(Ba,Sr)TiO3/(Ba,Sr)Nb2O6复相陶瓷,XRD衍射表明,样品由钙钛矿相和钨青铜相组成,无其他杂相生成。随着Sm3+掺杂量的增加,样品衍射峰向小角度方向移动,表明掺杂的Sm3+取代了体系中Nb5+及Ti4+。检测了样品的介电-温度性能,结果表明,随着Sm3+掺杂量的增加,样品的介电常数及介电损耗都有所降低,当Sm3+掺杂量达到0.004时,样品介电损耗最低,再增加Sm3+的掺杂量,样品的介电损耗又出现增加的趋势。可以得出,适量Sm3+的掺杂可以有效降低样品的介电损耗。     

Electrical characteristics of MOS capacitor using amorphous Gd2O3-doped HfO2 insulator

This work described the electrical characteristics of a kind of amorphous Gd2O3-doped HfO2 insulator for high-k metal-oxide-semiconductor(MOS) capacitors.Compared with pure HfO2,the doped HfO2 with an optimum concentration of Gd2O3 as MOS gate dielectric exhibited a lower leakage current,thinner effective oxide thickness and less fixed oxide charges density.The result indicated that Gd2O3 doping power of 60 W exhibited the best electrical characteristics,maximum capacitance,lowest leakage current of 9.35079...     

Mechanisms of Enhancement of Photocatalytic Properties and Activity of Nd^3＋ -Doped TiO2 for Methyl Orange Degradation

Nd^3 -doped TiO2 powders were prepared by the sol-gel method. Their crystal pattern and parameter, the specific surface area, the surface chemical state of Ti and the ratio of O/Ti were characterized. The results show that Nd impurity hinders the crystal transformation, and decreases the relative intensity of (101) peak. The crystallite sizes of Nd^3 -doped TiO2 powders decrease while their specific surface area increase owing to the Nd^3 doping. The XPS measurement shows that the content of Ti (Ⅲ) and ratio of O/Ti on their surfaces increase significantly with the increase of Nd^3 dosage. The adsorption and photodegradation experiments show that the optimum molar content of Nd^3 is 1.2%.     

Effect of Li+ ions doping on structure and luminescence of (Y,Gd)BO3:Tb3+

The (Y,Gd)BO3:Tb3+ and Li+-doped (Y,Gd)BO3:Tb3+ phosphors were prepared by high temperature solid-state method. The inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the excitation and emission spectra were used to characterize the samples. The results of ICP-AES and XRD indicated that Li+ ions could enter the (Y,Gd)BO3:Tb3+ lattice and induce the lattice expansion. It could be seen from SEM that the particles were spherical a...     

Improvement of Luminescent Properties of PbWO4 by Doping with Gd3＋ Ions

The luminescent properties of PbW04: Gd3 were studied. The luminescence of Gd3 in PbWO4: Gd3 was quenched. It is possible that the excitation states of Gd3 locate in the conduction band of PbW04 crystal. The luminescent intensity of the green and the blue band of PbW04 emission increases by doping with about 0.005% and 0.01% (molar fraction) Gd3 respectively. Mechanism of this enhancement of PbWO4:Gd3 luminescence is probably due to energy transfer from Gd3 to PbW04 host in the crystal. The PbW04 doped with low concentration of Gd (about 0.005% -0.01% ) is a good scintillating material.     

Influences of Nd~（3＋） doping on structure and electrochemical performance of layered Li_（1.05）V_3O_8

Nd3+-doped Li1.05V3O8 was synthesized by liquid-state reactions combined calcination.The influences of Nd3+ doping on physical and electrochemical performances of Li1.05V3O8 were investigated using X-ray diffraction (XRD),cyclic voltammograms,a.c.impedance and galvanostatic charge-discharge tests,etc.Results indicated that Nd3+-doped products had well developed crystal structure of layered LiV3O8 and uniform particle size distribution.Nd3+ doping with a proper amount improved the initial discharge capacity,discharge voltage and ion conductivity of the cathode material to some extent.Nd3+ did not participate in the electrochemical reactions and was beneficial to stability of the crystal structure during cycling.     

Photoluminescence Characteristics of Gd2Mo3O9 ： Eu Phosphor Particles by Solid State Reaction Method

Eu^3＋-doped Gd2Mo3O9 was prepared by solid-state reaction method using Na2CO3 as flux and characterized by powder X-ray diffractometry. According to X-ray diffraction, this material belonged to a tetragonal system with space group I41/α. The effects of flux content and sintering temperature on the luminescent properties were investigated with the emission and excitation spectra. The results showed that flux content and sintering temperature had effects on the luminescent properties, the optimized flux content and the best temperature was 3 % and 800 ℃ respectively. The excitation and emission spectra also showed that this phosphor could be effectively excited by C-T band （280 nm）, ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 and 465 nm were nicely fitting in with the widely applied output wavelengths of ultraviolet or blue LED chips. Integrated emission intensity of Gd2Mo3O9 ： Eu was twice higher than that of Y2O2S ： Eu^3 ＋ under 395 nm excitation. The Eu^3＋ doped Gd2Mo309 phosphor may be a better candidate in solid-state lighting applications.