锐钛矿TiO_2-Ag纳米纤维的可控制备及光催化性能研究

制备TiO2高效光催化试剂近年来备受关注.利用静电纺丝技术成功获得了尺寸均一的TiO2纳米纤维,在此基础上,以硝酸银(AgNO3)为掺杂剂,合成了TiO2-Ag复合纳米纤维.采用扫描电子显微镜(SEM)及X射线衍射(XRD)对该复合材料进行了表征.结果显示,产物为锐钛矿TiO2-Ag复合纳米纤维,且纤维分散性好、长径比大.随后以亚甲基蓝为降解对象,研究了该复合材料的光催化活性,探讨了Ag掺杂量对TiO2光催化效果的影响.结果表明:TiO2-Ag复合纳米纤维具有良好的光催化活性,且掺杂0.8wt%Ag的TiO2-Ag复合纳米纤维对亚甲基蓝的降解效率最高.     

碳量子点/硅酸铋纳米片复合光催化剂的构建及其光催化性能增强

通过一步法控制合成了碳量子点(CQDs)修饰的硅酸铋(Bi_2SiO_5)纳米片光催化剂。将平均直径6~8nm的CQDs分散在Bi_2SiO_5纳米片的表面。片状结构可加速载流子在Bi_2SiO_5纳米片内部之间的转移,通过CQDs表面修饰可以促进表面电荷分离。将CQDs引入Bi_2SiO_5纳米片后,在模拟太阳光照射下,可提高催化剂对罗丹明B的降解速率。这是由于CQDs的引入可以促进羟基自由基和超氧自由基的产生,从而提高了光催化性能。当CQDs的复合量为2%时,CQDs/Bi_2SiO_5纳米片的光催化活性最高,在模拟太阳光下照射90min后对RhB的降解率达到96%。     

碳纤维绳材试验研究与分析

FRP筋由于已完成固化,不易改变形状;FRP筋的弯折损伤又会造成强度折减,因此FRP筋不利于布置为体内曲线预应力筋.纯纤维绳没有经过树脂固化工序,具有模量高、强度高、抗折能力强等特点,可用于结构中为混凝土施加预应力.本文基于平行布置碳纤维绳展开,分析了其强度性质和试验表现,通过纤维绳试件拉伸强度试验总结得到:两端固化中间自由的纤维绳,其破坏均在固化界面;试样纤维强度利用率较低,但细试件要高于粗试件.纤维绳拉伸试验中,受固化界面的影响,绳子破坏强度低于其计算值.欲提高纤维强度利用效率,需改进绳的生产工艺和张拉锚固技术.     

SiO_2/Ag复合微球的制备及光催化性能研究

采用水热法在SiO_2纳米微球表面修饰Ag纳米颗粒,制备二元SiO_2/Ag复合微球(SiO_2/Ag CMs)。通过改变AgNO_3用量,调控Ag纳米颗粒的尺寸及分布,并利用透射电子显微镜、X射线衍射等技术探究产物的表面形貌、微观结构及组成。相比于单分散性的SiO_2微球和Ag纳米颗粒,SiO_2/Ag CMs的光吸收峰发生明显红移,且具有较宽的SPR光吸收范围。以亚甲基蓝(MB)为有机染料模型,研究SiO_2/Ag CMs对MB的光催化降解性能,结果表明:SiO_2/Ag CMs光催化剂催化性能优于SiO_2纳米微球及Ag纳米颗粒;当AgNO_3用量为0.10g时所制备的SiO_2/Ag CMs表现出较为优异的光催化活性,且在可见光照射80min时其催化效率达到97.7%。     

SiO_2-BiVO_4负载涤纶织物光催化性能的影响因素

通过浓碱对涤纶织物进行碱减量处理,再用低温浸渍法将SiO_2-Bi VO4粉体复合光催化剂负载在碱减量后的涤纶布表面,制备出涤纶负载SiO_2-Bi VO4光催化功能织物。考察染料初始浓度、盐浓度、p H值、表面活性剂浓度和H2O2浓度对涤纶负载SiO_2-Bi VO4光催化功能织物光催化效果影响,同时进行了粉体和涤纶负载布光催化性能的对比。     

改性PAN基纳米纤维膜的防水透气性能研究

用超声分散法对二氧化硅(SiO_2)纳米颗粒进行分散处理,加入聚丙烯腈(PAN)进行PAN的溶解,经气流纺丝工艺制备SiO_2/PAN杂化纳米纤维膜,并在空气中低温煅烧进行预氧化处理,用该方法制得的纤维膜具有良好的透气性。使用扫描电子显微镜对纤维膜表面进行观察,研究了不同SiO_2掺杂量的纤维膜表面形貌与防水透气性能的变化。结果显示,SiO_2的加入和预氧化大大提高了材料表面的粗糙度,减少了纤维膜内的微孔孔径,提高了PAN纳米纤维膜的拉伸强度,从而使预氧化SiO_2/PAN杂化纳米纤维膜具有良好的防水透气性。     

ZrO_2-ZrSiO_4复合陶瓷制备与表征

为了提高矿物固化体的长期安全稳定性,采用复合陶瓷作为高放废物的固化基材是有效手段之一。研究以ZrO_2和SiO_2为原料,通过合理配方设计,采用高温固相法成功合成了xZrO_2-ZrSiO_4(0.05≤x≤0.25)系列复合陶瓷,采用XRD、SEM对获得的复合陶瓷进行了表征,研究了ZrO_2含量对复合陶瓷的物相、结构及致密性的影响。初步推测了ZrO_2对复合陶瓷致密性的增强机制。     

水热法制备碳纳米纤维与二氧化钛复合材料及其光催化性质的研究

通过静电纺丝技术和水热方法的结合,制备碳纳米纤维(CNFs)与二氧化钛(TiO2)复合材料.通过扫描电镜检测,TiO2纳米粒子成功生长在碳纳米纤维的表面.制备的CNFs/TiO2复合材料在紫外光照射下降解罗丹明B,其降解效率高于用同样水热方法制备的单纯的TiO2纳米粒子的光催化效果.复合材料光催化活性被增强主要归因于碳纳米纤维好的导电性,将光生电子及时转移,延长了TiO2电子——空穴对的分离时间.复合材料可以通过沉降被简单的回收再利用,且其光催化活性没有明显降低.     

CuFeMnO4@SiO2@TiO2磁负载光催化材料的制备及磁回收性能

以三元硝酸盐水溶液为原料,采用微乳液烧结法制备了CuFeMnO4纳米材料.通过层层沉积法合成了核-壳-壳结构的CuFeMnO4@SiO2@TiO2磁负载光催化材料.采用XRD,SEM,TEM,FT-IR,EDS和UV-Vis对制备的磁负载光催化材料进行了表征.结果表明,磁负载光催化材料为光滑球形纳米粒子,具有较好的紫外-可见吸收能力.通过光催化降解罗丹明B溶液评价其光催化活性,光照6 h,降解率达到88.9％,经5次磁回收循环降解实验,仍具有较高的光催化活性.     

SiO_2/TiO_2复合材料的制备及其光催化性能

首先以P123(EO_(20)PO_(70)EO_(20))和PEG(聚乙二醇)为复合模板,制备了短棒状介孔SiO_2,然后采用电子转移催化剂再生-原子转移自由基聚合(ARGET ATRP)方法对其进行改性。以改性后的SiO_2为模板,以钛酸四丁酯(TBT)为钛源,制备了带有TiO_2壳的短棒状介孔SiO_2/TiO_2光催化剂复合材料。采用热重分析(TGA)、透射电子显微镜(TEM)、X射线衍射分析(XRD)、比表面和空隙分析仪对其进行了表征,通过甲基橙光降解反应研究了其光催化性能。结果表明:亲水性聚合物成功改性介孔SiO_2;锐钛矿相的TiO_2纳米粒子均匀分散在SiO_2表面;制得的SiO_2/TiO_2复合材料具有双峰孔结构;在可见光照射下,4.5 h后对甲基橙的降解率最高可达到99.5%,具有较高的光催化效率。     

Sintering and dielectric properties of fine-grained BaTiO3 ceramics

A new sintering method, spark plasma sintering (SPS), is described for the sintering of fine-grained BaTiO₃ ceramics. Dense ceramics with fine grain size of near 170 run are obtained using SPS at low temperature of 900°C without holding time. The dielectric measurements of various grain size specimens show that the dielectric constants decrease with the reduce of grain size, and diffuse phase transition showed in the dielectric-temperature spectra. The variation in dielectric properties with grain size is explained.     

CO2捕集技术的研究进展

化石燃料燃烧排放的CO_2是当今温室气体中CO_2污染的主要来源。介绍了CO_2捕集技术中吸附法、吸收法和膜分离法的研究进展,并分析了各种方法的特点,归纳总结了目前新型吸附/吸收剂中金属有机骨架、相变吸收剂、离子液体吸收剂和纳米流体吸收剂的研究成果。降低能耗和成本是今后研究工作的重点。开发新型吸附/吸收剂、优化反应过程和联合使用不同方法是未来CO_2捕集技术的发展方向。     

Preparation and structure characteristics of nano-Bi2O3 powders with mixed crystal structure

The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi(NO3)3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi(NO3)3 reacts at 90℃ for 2 h, the Bi203 powders with 60 nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi^3 to O^2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.     

Sol—Gel Synthesis of Normal Spinel LiMn2O4 and Its Characteristics

Normal spinel LiMn2O4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials.LiMn2O4 was characterized by XRD,TG-DTA,IR,SEMand AAS,The optimum conditions for the synthesis were explored.Citric and ethylene glycol were mixed with molar ratio of 0.25,and the mixtrue was esterified at 140℃ for 4 hours.Then lithium nitrate and manganese nitrate were added with molar ratio of 0.6,In the system,the total molar of cations was equal to that of citric acid.At last,reflux the system at 105℃ for 2 hours,Dried gel was fired at 600℃ for 8 hours.Particle diameters of raw product were about 100nm mainly.Further research shows that lithium ion of LiMn2O4 is easy to be extracted,and normal spinel λ-MnO2 can be obtained after lithium ion extraction.     

沸石负载Mn,N共掺杂TiO2及光催化性能

为提高传统TiO₂光催化剂的可见光催化活性,本文采用溶胶-凝胶法合成了Mn,N共掺杂TiO₂光催化剂,改善了传统TiO₂光生载流子易复合的问题;进一步采用沸石作为载体对改性后的TiO₂样品进行负载,解决了传统光催化剂存在的难分离回收问题,以达到光催化剂可重复使用的目的.借助X-射线衍射仪、扫描电子显微镜、紫外分光光度计、傅立叶变换红外光谱仪等测试手段对Mn,N共掺杂TiO₂光催化剂的结构、元素组成、微观形貌和光催化降解性能进行系统分析与研究.研究结果表明,沸石负载Mn,N共掺杂TiO₂的样品较未改性的TiO₂样品具有更高的光催化降解活性,在可见光照射下,在最优掺杂条件下获得的TiO₂光催化剂在60 min内对孔雀石绿的降解率可达到97%,这主要归因于锰离子掺杂能够对TiO₂光生载流子的复合产生抑制作用,促进光生电荷分离,与此同时氮元素掺杂可有效拓宽TiO₂半导体光催化剂光响应范围.此外,经过5次循环使用后,对孔雀石绿的降解率没有较大程度的减弱,依然能够维持在88%以上,表明沸石负载Mn,N共掺杂TiO₂的样品具有较好的光催化循环稳定性.     

Solvothermal preparation and thermoelectric properties of quasi-binary Sn(Pb) Te-Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> compounds

Bulk samples of quasi-binary compounds in the Sn(Pb)Te-Bi₂Te₃ system were prepared by solvothermal method followed by a sintering procedure of compacted pellets. The formation mechanism of the precursor powders, microstructure and thermoelectric properties of the final bulk samples were studied.     

Effect of Bi content in precursor solutions on microstructure and ferroelectric properties of bismuth cerium titanate thin films

Sol-gel derived bismuth cerium titanate (BCT) thin films with different Bi contents in precursor solutions were deposited on the Pt/Ti/SiO₂/Si substrates. The effect of Bi content in the precursor solutions on the microstructure and ferroelectric properties of the films was investigated. It is found that with Bi content increasing from 90% to 110% of the nominal value in the precursor solutions, the dissipation factor and leakage current density of the BCT films obtained decrease, while the grain sizes, dielectric constant and remanent polarizations (2Pr) increase, and concurrently, a Bi-deficient phase of Bi₂Ti₂O₇ gradually disappears. The film prepared from solution with 110% of the nominal Bi content exhibits pure Bi-layered Aurivillius polycrystalline phase, and the 2Pr value and coercive field value are 67.1 μC/cm² and 299.7 kV/cm, respectively. Their dielectric constant and the dissipation factor are about 172 and 0.033 at 1 kHz, respectively. Moreover, this film shows no polarization fatigue after 4.46×10⁹ switching cycles. Supported by the Hubei Province Natural Science Foundation (Grant No. 2007ABA309)     

Structure and electrochemical properties of LiCoO2 synthesized by microwave heating

Microwave synthesis method was applied to the fast preparation of LiCoO₂. The structure of the synthesized oxides was analyzed by using X-ray diffraction. Only single-phase LiCoO₂ was obtained. Electrochemical behaviors of LiCoO₂ were investigated by charge-discharge cycling properties in the voltage range of 3.00 – 4.35 V (vs Li). The results show that the prepared LiCoO₂ powders calcinated at 900 °C for 120 min exhibit an initial charge and discharge capacity of 168 and 162 mA · h · g⁻¹ at 0.1C current rate, respectively, as compared to 159 and 154 mA · h · g⁻¹ of LiCoO₂ synthesized by conventional means. In addition, more than 95% of the capacity is retained even after 10 cycles. But with the increase of calcinating time, its electrochemical properties deteriorate. Compared with the conventional method, the microwave heating method is simple, fast, and with high energy efficiency.     

Cu2O/Cu2S 复合材料制备及可见光催化降解甲基橙的研究

通过水热法制备Cu₂O/Cu₂S 复合材料对甲基橙(MO) 进行光催化降解实验。在Cu₂O 中引入S 元素, 通过 改变Cu/S 投加摩尔比, 从而得到不同Cu/S 的复合材料。利用XRD、SEM、UV-vis、EIS 等手段对材料进行表征, 并 对MO 进行光催化降解实验。XRD 结果表明, 随着S 含量的增多, Cu₂S 的衍射强度逐渐上升, Cu₂O 的f111g 晶面 衍射强度逐渐降低。SEM 结果表明Cu₂S 能较好地包覆在Cu₂O 八面体的表面。通过UV-vis 和EIS 结果计算得知, 复合材料带隙为1.49 eV, 电荷转移电阻大幅降低。降解实验结果表明复合材料最佳Cu/S 投加摩尔比为15 : 1, 其在 100 min 时对MO (100 mL, 10 mg/L) 降解率达到91.4%, 明显高于纯Cu₂O 对于MO 的降解率(60.3%)。猝灭实验表 明了?OH 和 ?O₂ ^-在光催化过程中起到主要作用。     

Preparation of Nanometer-structured TiO2 Thin Films by-Sol-Gel Method

The transparent anatse TiO2 nanometer thin films were prepared by the sol-gel method on soda-line glass,X-ray diffraction,thermal analysis and UV-visible spectrophotometer were used to analyze the formation of the phases,Only increasing the heat-treatment time,the average graing size has no obvious change,The mechanism of grain growth in TiO2 thin film is probably as follows:the grain of coating will become grain core later;TiO2 sol constantly deposited on the surface of TiO2 grain and formed membrance with increasing of coating cylce time ;TiO2 grain in the film grow steadily.