可见光下钙钛矿LaCoO3光催化杀菌性能的应用研究

采用柠檬酸配合法制备纳米钙钛矿型LaCoO3及Sr掺杂的La0.9Sr0.1CoO3。在可见光下考察了催化剂浓度、菌液浓度对LaCoO3杀菌性能的影响。结果表明,在以30W日光灯为光源,距光源20cm处,辐照30min时,当菌液浓度为10^2～10^4cfu／mL,对大肠杆菌的杀菌率达90％以上,金黄色葡萄球菌46％。Sr掺杂后La0.9Sr0.1CoO3杀菌率分别可达98％,52％。通过XRD、SEM、DRS表征分析表明,催化剂粒径为60—80nm,在大于400nm的可见光区均有较好的吸收,Sr掺杂有助于提高杀菌效果。通过溶胶提拉法在瓷砖上附着钙钛矿膜,膜表面的杀菌率仍可保持在80％,40％以上。     

LaNixFe1-xO3钙钛矿光催化降解碱性品红

通过溶胶-凝胶法控制合成一系列掺杂型LaNixFe1-xO3(x=0.1,0.3,0.5,0.7,0.9)钙钛矿材料,研究其在氙灯条件下对碱性品红降解的效果并解析其降解机理.结合X射线衍射(XRD)、扫描电镜(SEM)、光电子能谱(XPS)等分析测试与光催化降解评价结果,探究复合氧化物的结构性能与催化效能.研究发现,该LaNixFe1-xO3材料在降解碱性品红溶液时均具有良好效果,其中LaNio.9Feo1O3催化效果最好,当Ni的掺杂量较高时具有更大的比表面积,暴露更多的活性位点,催化剂表面含有更多吸附氧O-/O2-物种,有利于降解碱性品红分子,降解率可达到97％,且有稳定高效的重复利用率.     

钙钛矿型金属氧化物粉体的制备与光催化性能

综述了ABO3钙钛矿型金属氧化物光催化性能的研究进展。主要介绍了化学共沉淀法、超声波共沉淀法、溶胶-凝胶法、水热法、固相研磨法、凝胶浇注法、甘氨酸燃烧法等制备方法及其优缺点。讨论了光催化降解有机污染物、光催化还原CO2制备有机物和光催化分解H2O的反应机理。分析了电荷转移能、B-O的结合能、B原子电负性、A、B原子价态、电子构型、掺杂等因素对催化剂光催化效率的影响。     

金属卤化物钙钛矿量子点的制备及其光催化应用研究进展

利用太阳能光催化技术生产清洁燃料、降解污染物及转化高附加值产品,是解决当前能源短缺和环境污染问题的有效途径。随着对金属卤化物钙钛矿的深入研究,成功开发出一系列能够制备出成分和形貌控制精确、产物均匀性好、结晶度高的钙钛矿量子点的合成方法,使钙钛矿量子点应用到光催化领域中。综述了热注入法、配体辅助再沉淀法、溶剂热法、微波辅助法等金属卤化物钙钛矿量子点的合成方法及金属卤化物钙钛矿量子点在光催化析氢、光催化还原二氧化碳、光催化合成有机物以及光催化降解有机物等方面的研究进展,最后对金属卤化物钙钛矿光催化剂的发展前景进行了展望。     

钙钛矿SrNiO3光催化降解染料的研究

用柠檬酸络合法制备钙钛矿型复合氧化物SrNiO3,并以其为光催化剂对水溶性染料进行光催化降解实验.讨论了光催化反应时间、催化剂投加量、光照强度、pH值、以及外加氧化剂(H2O2)等因素对光催化活性的影响.实验结果表明:在催化剂投加量0.4 g,降解时间180min,pH值为2,光照强度200 W,H2O2的投加量5 mL时,大红染料的降解率可达99.47%.     

钙钛矿型氧化物LaFeO3光催化活性的研究

本文用柠檬酸络合法制备了ＬａＦｅＯ２及Ｌａ１－ｘＣａｘＦｅＯ３、ＬａＦｅ１－ｘＣｕｘＯ３等钙钛矿型复合氧化物。以这些氧化物作催化剂在荧光高压汞灯照射下进行水溶性染料光催化降解试验,探讨了掺杂对ＬａＦｅＯ３光催化活性的影响。     

钙钛矿氧化物LaNiO_3对结晶紫的光催化降解研究

采用了溶胶-凝胶法和流变相法合成出钙钛矿复合氧化物LaBO3(B=Co、Ni),用X衍射线和透射电镜TEM对其结构进行表征,重点研究了合成的催化剂对染料结晶紫的光催化降解条件。结果表明LaNiO3对结晶紫的降解有较高的活性,当结晶紫的浓度为10 mg/L时,紫外光照射,光照时间为8 h,pH=9,催化剂的投加量为2.5 g/L的条件对结晶紫光有较好的降解效果,降解率达到99.30%。     

A2La8(SiO4)6O2(A=Ca,Sr,Ba)的合成及其导电性能

以溶胶-凝胶法和固相反应方法分别合成了硅酸盐氧基磷灰石A2La8(SiO4)6O2(A=Ca,Sr,Ba),经XRD表征,证明所得产品为磷灰石相.和固相反应方法相比,溶胶-凝胶法合成磷灰石反应温度低,高温焙烧时问短.电化学阻抗谱研究表明:随着A(A=Ca,Sr,Ba)半径的增大,电导率也逐步加大,活化能却逐步减小.700℃时溶胶·凝胶法合成的Ba2La8(SiO4)6O2的电导率(4.42×10-6S·cm-1)要比固相反应法合成的电导率大一个数量级.离子迁移数和氧分压对电导率的研究表明,主要的电荷载体是O2-离子.     

无铅或少铅钙钛矿CH3NH3M1-xPbxX3(M=Sn,Sr;X=Cl,Br,I)太阳能电池的研究进展

本文综述了Sn2+或Sr2+取代的无铅或少铅钙钛矿CH3NH3PbX3 (X=Cl,Br,I)的结构及其主要的制备方法,评述了各种方法的优缺点.简要介绍了无铅或少铅钙钛矿材料的能隙以及材料的稳定性对太阳能电池的影响,并对其发展前景进行了展望.     

纳米LaMO3(M＝Cr,Mn,Fe,Co)化合物的光催化氧化活性分析

采用柠檬酸络合法制备了纳米钙钛矿型LaMO3(M =Cr,Mn ,Fe ,Co)化合物 ,并对其进行XRD和TEM分析 ,发现所制样品具有单一晶相结构 ,粒径在 1～ 10 0nm之间。在纳米LaMO3(M =Cr,Mn ,Fe ,Co)悬浮体系中进行了水溶性染料酸性红 3B光催化降解实验 ,其光催化氧化活性变化趋势为LaCrO3相似文献   

复合钙钛矿型Ba（Mg1／3Ta2／3）O3中B位有序结构的研究

本文讨论了复合钙钛矿型Ｂａ（Ｍｇ１／３Ｔａ２／３）Ｏ３中Ｂ位离子的有序程序同材料的介电损耗之间的关系。用Ｘ射线谱和Ｒａｍａｎ光谱研究了陶瓷烧结温度对Ｂａ（Ｍｇ１／３Ｔａ２／３）Ｏ３中Ｂ位离子的有序程度的影响，当适当提高烧结温度可增大有序程度。     

Photochemical synthesis of AZrO3−X thin films (A=Ba,Ca and Sr) and their characterization

(Ba, Ca, Sr)ZrO_3−X thin films were prepared by a photochemical method using thin films of β-diketonate complexes as precursors. The photolysis of these films induces the fragmentation of the 2,2,6,6-tetramethyl-3,5-heptanedionate ligand and the partial reduction of metal ion together with volatile organic compounds as sub-products. When the metallic complexes are irradiated in air, the final product of the reaction are ternary metal oxides. The photoreactivity of these films was monitored by FT-IR spectroscopy by a period of 72 h, followed by post-annealing at 950 °C. X-ray photoelectron spectroscopy and X-ray diffraction techniques were used to analyze the chemical composition and the crystalline structure of the films obtained. The results indicate that Ba, Ca, Sr, Zr and O are present in the form of perovskita, preferably adopting an amorphous structure. The surface morphology examined by atomic force microscopy revealed a rough and irregular surface. The UV–vis measurements suggest a slight increase in the optical band gap values, which promote a reduction of the intermediary energy levels or defects.     

Bi掺杂(Ba,Sr,Ca)TiO3陶瓷的结构及介电和铁电性能

采用固相反应技术制备了铋掺杂(Ba1-xCax)0.925Bi0.05TiO3(x=0.10,Bi-BCT)和(Ba1-xSrx/2Cax/2)0.925Bi0.05TiO3(Bi-BCST)(x=0.10,Bi-BSCT)铁电陶瓷,研究了样品的结构、介电和铁电性能。结果表明:在Bi-BCT陶瓷中存在一种弥散的老化效应,点缺陷引起的可逆畴翻转机制能够合理地解释Bi-BCT陶瓷中异常的双电滞回线,这种机制有望进一步解释Bi-BSCT陶瓷中异常的介电行为。     

Expanding gaudefroyite family to Sr2MBi(REEO)3(BO3)4 (M = Ca,Sr, Ba; REE = Y,Eu) borates with large second harmonic generation responses

The synthesis, crystal structure, and characterization of a few new noncentrosymmetric rare-earth borates of gaudefroyite family Sr₂MBi(REEO)₃(BO₃)₄ (M = Ca, Sr, Ba; REE = Y, Eu) are represented. Samples of Sr₂MBi(YO)₃(BO₃)₄ (M = Ca, Sr, Ba) borates were synthesized by multi-step solid state reactions. The crystal structures of Sr₃Bi(YO)₃(BO₃)₄, Sr₂CaBi(YO)₃(BO₃)₄ and Sr₂BaBi(YO)₃(BO₃)₄ were refined in P6₃ space group to R₁ 0.059, 0.058 and 0.018, respectively. Second-harmonic generation measured with Kurtz-Perry powder technique shows an increase in the nonlinear optical activity of materials by almost two times upon partial substitutions of Sr for Ca and Ba in the Sr₃Bi(REEO)₃(BO₃)₄ and its decrease if Y atoms are replaced by Eu. Thermal expansion coefficients for Sr₂MBi(YO)₃(BO₃)₄ (M = Ca, Sr, Ba) borates and Ca₄(MnO)₃(BO₃)₃(CO₃) gaudefroyite are calculated for the first time. Thermal expansion of these compounds is almost isotropic due to the arrangement of BO₃ units which are located in the ab and ac planes.     

Crystal structure,phonon modes and dielectric properties of B site ordered ABiLiTeO6 (A = Ba,Sr) double perovskites

ABiLiTeO₆ (A = Ba, Sr) double perovskite oxides were synthesised through conventional solid - state ceramic route. X-Ray diffraction patterns indicated pseudocubic symmetry for both compounds. Deconvoluted Raman spectra using Lorentzian function gave 7 first order Raman modes for both BaBiLiTeO₆ and SrBiLiTeO₆ whereas Infrared spectroscopy gave 8 modes for BaBiLiTeO₆ and 9 modes for SrBiLiTeO₆. Observed phonon modes were in good agreement with the corresponding group theoretical predictions for space group I4/m for both compounds. Rietveld refinement of the XRD patterns also confirmed I4/m space group for ABiLiTeO₆ (A = Ba, Sr) with 1:1 B site ordering of Te⁶⁺ and Li⁺ cations. The random occupancy of Ba²⁺ and Bi³⁺ at the A site in BaBiLiTeO₆ whereas Sr²⁺ and Bi³⁺ in SrBiLiTeO₆ were revealed from Rietveld refinement. Microstructure of both the compounds gave average grain size of less than 3?µm. At 1?MHz, BaBiLiTeO₆ and SrBiLiTeO₆ possess porosity corrected dielectric constants of 49.5 and 34.4 and dielectric losses of 0.029 and 0.028 respectively.     

Effect of crystal structures on nucleation mechanism in hydrothermal synthesis of MZrO3 (M=Ba,Sr, Ca)

Hydrothermal method is widely used in the synthesis of perovskite-type oxides, whereas few studies are reported for the nucleation mechanism, so that the relationship between the crystal structures and reactive activities of reactants and products is still unknown. Herein, the reaction processes are analyzed on the basis of XRD, SEM and Raman characterizations, and the nucleation mechanism is investigated for the hydrothermal synthesis of MZrO₃ (M = Ba, Sr, Ca). We propose that the negative charged cyclic tetramer complexes [Zr₄(OH)₈(OH)₁₆]^8- form in the hydrothermal reaction, which play major roles in the nucleation process. The tetramer complexes continually dehydrate and condensate to form substructural units composed of alkali-earth ions and 6-fold Zr tetramers; substructural units further dehydrate and distort to form perovskite structures. The reactive activation energy increases with the decreasing of M²⁺ (M = Ba, Sr, Ca) ionic radius because the incorporation of smaller A site ions in the perovskite structure is accompanied by greater rotation and distortion of the ZrO₆ octahedra, leading to the decrease of reactive activity accordingly. In a word, the proposed nucleation mechanism in this paper is of great significance for the study of perovskite.     

Methane-water redox reaction on A2SnO4 (A=Mg, Ca, Sr, Ba) oxide to produce C2 hydrocarbons

A₂BO₄ type oxides consisting of an alkali earth metal and tin showed high selectivity (>99%) and activity for the oxidative coupling of methane at 1023 K in a methane-water redox system where active oxygen species were regenerated by water. The products were C₂ hydrocarbons and hydrogen. Repeated reaction-oxidation cycles showed that the oxide is stable under both oxidative and reductive atmosphere. Doping of Bi to the oxide was found to enhance the activity for the oxidative coupling of methane. This revised version was published online in July 2006 with corrections to the Cover Date.