g-C3N4/Bi12O17Cl2复合物的制备及其光催化性能

以硝酸铋、氯化钠和氢氧化钠为原料用液相沉淀法制备g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂,并用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis DRS)等手段表征其组成、微观形貌和性能,以罗丹明B为模拟污染物研究了在可见光照射下g-C₃N₄对g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂活性的影响及其光催化机理。结果表明,2% (质量分数) g-C₃N₄/Bi₁₂O₁₇Cl₂复合光催化剂的光催化性能最好,见光90 min后对罗丹明B的降解率达到98%。     

Bi2O3/BiOCl异质复合材料的制备及其光催化性能

本文以五水硝酸铋和氯化钾为原料,利用水热法一步制备了Bi2O3/BiOCl异质复合光催化材料,采用X射线粉末衍射(XRD)、扫描电镜(SEM)和紫外可见漫反射光谱(UV-Vis)对样品进行了表征。以罗丹明B为目标降解物,研究n(Bi)/n(Cl)摩尔比对合成Bi2O3/BiOCl异质复合光催化剂的形貌和光催化性能的影响。结果表明:随着n(Bi)/n(Cl)摩尔比的增加,Bi2O3/BiOCl的光催化活性显著增强,在n(Bi)/n(Cl)=1.75时,制备的Bi2O3/BiOCl异质复合光催化材料具有最高的光催化活性。     

Ag/Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si结构铁电薄膜制备及其铁电性能的研究

利用溶胶-凝胶(sol-gel)方法,在硅基底上制备了Bi3.25La0.75Ti3O12/Bi4Ti3O12/Si铁电薄膜,其中Bi4Ti3O12作为缓冲层.用XRD方法分析了该结构铁电薄膜的物相结构;用扫描电镜对薄膜样品进行表面形貌观察;并且对该结构的铁电性能进行了研究.     

网状结构Bi2O3光催化剂的合成及其光催化性能

以Bi(NO3)3·5H2O为原料,天然棉花为模板结合热处理工艺,成功合成了具有网状结构的三斜晶相Bi2O3光催化材料,利用XRD、SEM、TG-DTA和UV-Vis漫反射等技术对样品的晶型结构、形貌及吸光性能等进行了表征。以亚甲基蓝染料分子模拟环境污染物,考察了样品的光催化性能。结果表明,棉花纤维在网状Bi2O3的制备中起到了充分的诱导作用,这种网状结构是由一些直径不一的Bi2O3扁平状网线交错排列、稀疏盘结而形成。TGA分析结果表明,适当的热处理在去除棉花模板的同时可以实现Bi 3+→Bi2O3的转化。在可见光照射下,网状Bi2O3的光催化活性及重复使用性能均优于粉体Bi2O3,反应100min后,对MB的脱色率可达到93%左右,并且重复使用4次后仍可使MB的脱色率保持在85%以上。此外,对网状Bi2O3的形成机理进行了探讨。     

Bi2O2CO3/TiO2复合粉体的制备及其光催化性能研究

采用水热法制备了Bi2O2CO3,并将其与TiO2进行了复合。XRD数据表明此复合光催化剂中Bi2O2CO3结晶性良好,紫外-可见漫反射光谱说明Bi2O2CO3的加入使其吸收带边有一定的红移。研究了紫外-可见光照射下Bi2O2CO3/TiO2复合光催化剂对亚甲基蓝溶液的降解性能,结果表明当Bi2O2CO3与TiO2的质量比为0.032时,得到性能最优的复合光催化剂,其光催化活性优于TiO2。     

BiOCl/Bi2O3异质结复合光催化剂的制备和光催化性能研究

以五水硝酸铋、硝酸、氢氧化钠、盐酸为原料,用盐酸浸渍法制备了盐酸与氧化铋物质的量比分别为0.3∶1、0.5∶1、0.7∶1、1∶1的BiOCl/Bi2O3异质结新型复合光催化剂。用X射线衍射(XRD)、热重-差热分析(TG-DSC)和扫描电子显微镜(SEM)等手段对材料进行了表征。250 W高压汞灯照射下,用光催化降解罗丹明B反应来测试催化剂的光催化活性,结果表明BiOCl/Bi2O3复合光催化剂的性能明显优于单体Bi2O3。当盐酸与氧化铋物质的量比为0.7∶1时,BiOCl/Bi2O3催化剂的光催化活性最佳。最后研究了抑制剂对BiOCl/Bi2O3复合光催化剂降解罗丹明B的影响,发现三乙醇胺和碘化钾都有一定的抑制作用。     

Bi2O3纳米晶玻璃三阶非线性光吸收性质的研究

利用溶胶凝胶法结合气氛控制方式合成了含Bi2O3纳米晶钠硼硅玻璃.利用X射线粉末衍射仪(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、X射线能量色散谱(EDX)、扫描模式透射电子显微镜(STEM)、高分辨透射电子显微镜(HRTEM)以及选区电子衍射(SAED)对掺杂在钠硼硅玻璃中Bi2O3纳米晶的形貌和微结构进行了表征,同时,利用飞秒开孔Z-scan技术详细地研究了Bi2O3纳米晶玻璃在800 nm处不同激发光强度下的三阶非线性光吸收性质.结果表明,在钠硼硅玻璃中形成了尺寸小于10 nm的Bi2O3单斜晶系纳米晶.随着激发光强度的增强,该玻璃的三阶非线性光吸收性质产生由饱和吸收向反饱和吸收的转变.进一步,计算得到的该玻璃三阶非线性极化率χ(3)的数量级范围在10-19~10-18m2/V2之间.这一结果说明该玻璃具有良好的非线性光学性能,并且在光限幅器等非线性光学领域具有潜在的应用价值.     

S型异质结Bi4O5Br2/CeO2的制备及其光催化CO2还原性能

光催化CO₂还原技术的关键是开发高效光催化剂,而构建具有紧密界面结构的异质结是增强界面电荷转移,实现高效光催化活性的有效途径。本研究采用静电纺丝技术结合水热法,将Bi₄O₅Br₂纳米片镶嵌在CeO₂纳米纤维表面,制得Bi₄O₅Br₂/CeO₂纤维光催化材料(B@C-x,x对应反应物的加入量)。利用不同方法表征其微观结构、形貌和光电性能。结果表明,适当Bi₄O₅Br₂含量的Bi₄O₅Br₂/CeO₂异质结可以显著提高CeO₂纳米纤维的光催化性能。与纯Bi₄O₅Br₂和CeO₂相比,B@C-2在模拟太阳光下表现出最佳光催化活性,不使用任...     

水热法制备CoFe2O4纳米颗粒及其穆斯堡尔谱与磁性能研究

用水热法在不同温度下制备结晶性较好、颗粒均一的CoFe2O4纳米颗粒,无需进一步煅烧。利用X射线衍射仪(XRD)、场发射扫描电镜(SEM)、穆斯堡尔谱仪和综合物性测量系统(PPMS)对不同温度下合成的样品进行表征。结果表明,随着合成温度的升高,CoFe2O4纳米颗粒的结晶性增强,粒径逐渐增大,样品的饱和磁化强度逐渐增强。当合成温度为500℃时,CoFe2O4纳米颗粒的饱和磁化强度达到64.1A.m2/kg,与块体的CoFe2O4(72A.m2/kg)接近。穆斯堡尔谱分析表明,当晶粒粒径超过了超顺磁性的临界尺寸,样品的超顺磁性消失,随着合成温度的升高,B位上Fe3+离子的比例增高,磁性能增强。     

Bi2O3助熔剂对CaO-B2O3-SiO2/Al2O3玻璃陶瓷复合材料性能的影响

以CaO-B₂O₃-SiO₂(CBS)玻璃粉体和Al₂O₃陶瓷粉体为原料,通过在CBS与Al₂O₃的质量比固定为50:50的玻璃-陶瓷复合材料中添加适量的Bi₂O₃作为烧结助熔剂,探讨了Bi₂O₃助熔剂对CBS/Al₂O₃复合材料的烧结性能、介电性能、抗弯强度和热膨胀系数的影响规律.研究表明:Bi₂O₃助熔剂能通过降低CBS玻璃的转变温度和黏度促进CBS/Al₂O₃复合材料的致密化进程,于880 ℃下烧结即能获得结构较致密、气孔较少的CBS/Al₂O₃复合材料.然而,过量添加Bi₂O₃将使玻璃的黏度过低,从而恶化CBS/Al₂O₃复合材料的烧结性能、介电性能及抗弯强度.当Bi₂O₃的添加量为CBS/Al₂O₃复合材料的1.5wt%时,于880 ℃下烧结即能获得最为致密的CBS/Al₂O₃复合材料,密度为2.82 g·cm^-3,这一材料具有良好的介电性能(介电常数为7.21,介电损耗为1.06×10^-3),抗弯强度为190.34 MPa,0~300 ℃的热膨胀系数为3.52×10^-6 K^-1.     

热处理对Bi2O3-B2O3-SiO2凝胶玻璃粉体结构与性能的影响

采用溶胶-凝胶法制备了一种Bi₂O₃-B₂O₃-SiO₂系玻璃粉体,在200 ℃、400 ℃、600 ℃和800 ℃温度下分别对凝胶玻璃粉体进行热处理,借助SEM、TEM、XRD、FT-IR、Raman、XPS、DSC、热膨胀仪及“纽扣”烧结实验分别测定了经不同温度热处理后玻璃粉体的结构与性能,分析了其结构变化对玻璃粉体转变温度T_g和烧结特性的影响。结果显示,在实验温度范围内,随热处理温度升高,Bi³⁺逐渐进入玻璃网络中,[BiO₆]八面体和[BiO₃]三角体、[BO₄]四面体和[BO₃]三角体分别与[SiO₄]四面体以顶角相连的方式构建玻璃网络结构。O1s和Bi4f的电子结合能逐渐增大,B1s的电子结合能减小,玻璃网络结构稳定性增强,导致玻璃转变温度T_g及玻璃膨胀软化点温度T_d升高、 润湿性降低且热膨胀系数略有降低。经600 ℃热处理后,玻璃粉体具有较优的烧结性能,T_g、T_d分别约为485 ℃及542 ℃,热膨胀系数α约为7.067×10-6/℃。     

Spectroscopic properties of red Bi4Ge3O12 by vertical Bridgman method

Red Bi₄Ge₃O₁₂ (BGO) single crystals had been grown by vertical Bridgman (VB) method. The structure of this crystal was determined by XRD. The absorption and emission spectra of the red BGO in visible and near infrared region (NIR) were measured at room temperature. The emission intensity of the red BGO is weaker than that of ordinary BGO at about 500 nm. Interestingly, the red BGO shows a significant emission band centered at about 1495 nm. The red BGO faded and its properties recovered after ultraviolet (UV) irradiation or annealing.     

Anisotropic grain growth of Bi4Ti3O12 in molten salt fluxes

Bismuth titanate (Bi₄Ti₃O₁₂) platelets were obtained by the molten salt synthesis method in NaCl-KCl and Na₂SO₄-K₂SO₄ fluxes, using an amorphous Bi₄Ti₃O₁₂ precursor and a mechanically mixed Bi₂O₃-TiO₂ mixture as the starting materials. It was found that the synthesizing temperature, salt species and starting materials could significantly affect the crystallization habit and morphology of Bi₄Ti₃O₁₂ platelets. Under the same processing conditions (i.e. in Na₂SO₄-K₂SO₄ flux at 1000 °C), the Bi₄Ti₃O₁₂ platelets synthesized from the Bi₂O₃-TiO₂ mixture generally showed a smaller particle size than those synthesized using the amorphous Bi₄Ti₃O₁₂ precursor. The Bi₄Ti₃O₁₂ platelets prepared in the chloride flux were faceted along either (0 0 1) or (1 1 2) planes, while those prepared in the sulfate flux were solely (0 0 1) faceted. The former system also had smaller particle size than the latter. Furthermore, the salt content and the addition of plate-like Bi₄Ti₃O₁₂ seeds in the amorphous Bi₄Ti₃O₁₂ precursor showed a strong influence on the particle size of the synthesized Bi₄Ti₃O₁₂ platelets. The particle size of Bi₄Ti₃O₁₂ platelets prepared in the sulfate flux decreased as the mole ratio of the sulfate salts to Bi₄Ti₃O₁₂ was increased from 7.9 to 23.7. And the addition of 10 wt.% plate-like Bi₄Ti₃O₁₂ seeds into the amorphous Bi₄Ti₃O₁₂ precursor led to a significant increase in the particle size of the resulting Bi₄Ti₃O₁₂ platelets.     

The effect of stress on the dielectric constants of Bi4Ti3O12 films

Both experiment and theory have shown that the stress has a notable impact on the polarization of Nd-doped Bi₄Ti₃O₁₂ films. In this paper, thermodynamic theory is used to study the effect of stress on the dielectric constants of Bi₄Ti₃O₁₂ films at room temperature with a two-dimensional model. Results indicate that the change of the dielectric constant for a-phase induced by the lattice distortion is far greater than that for c-phase. Considering the domain reorientation, the external tensile stress may lead to an obvious decrease in the effective dielectric constant of Bi₄Ti₃O₁₂ films.     

二硫化钼花状微球的水热合成及其微观结构表征

以钼酸铵作为钼源,硫脲作为硫源和还原剂,采用简便的水热法合成二硫化钼花状微球。采用X射线衍射仪、拉曼光谱仪、扫描电子显微镜和透射电子显微镜对二硫化钼样品的形貌和结构进行表征。考察了钼硫比、反应时间、反应温度对二硫化钼花状微球形貌和结构的影响。结果表明,当钼硫物质的量比为1∶2.25,反应温度为220℃,反应时间为18h时合成了结晶性好的纳米片(厚度为10nm)组装而成的二硫化钼花状微球,其具有较大的比表面积,是一种性能优异的锂离子电池电极材料。     

HREM surface profile images of Bi2Sr2CaCu2O8

Surface profile images of Bi₂Sr₂CaCu₂O₈ have been obtained using high-resolution electron microscopy. The cleaved (001) surface of the crystals terminates with a single Bi-O atomic layer. The modulated structure developed in this surface atomic layer was observed directly. The (hk0) surfaces were found to decompose in air into an amorphous coating layer. This coating layer was unlikely recrystallized into the original structure under electron beam irradiation. The amorphous layer on the (hk0) surface formed in pure Ar atmosphere was relatively thin and could be recrystallized into some secondary phases in which a Bi loss was observed. The original (001) surface might also be covered by an amorphous-like layer. This disordered layer could be recrystallized under electron beam irradiation into BiSr₂Ca₂Cu₃O₉, BiSr₂CuO₅, etc. which intergrow with the parent crystal perfectly on the (001) planes.The author thanks the EPSRC for financial support.     

Hydrothermal synthesis of single-crystalline Bi2Te3 nanoplates

Novel Bi₂Te₃ nanoplates with about 0.2-1 μm in diagonal and 100 nm in thickness have been facilely synthesized via hydrothermal routes in the presence of polyvinylpyrrolidone (PVP). Various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectrometry (FT-IR) have been used to characterize the obtained products. The results show that the existence of PVP is vital to the formation of the plate-like morphology. Other factors, such as the reaction temperature and the different surfactants also have influence on the morphology of the final products to some extent.     

Topochemical synthesis of plate-like Na0.5Bi0.5TiO3 templates from Bi4Ti3O12

Plate-like templates for the development of grain oriented microstructures are required for lead-free piezoelectric ceramics with directionality of properties. Plate-like Na_0.5Bi_0.5TiO₃ templates with perovskite structure were synthesized by the Topochemical Microcrystal Conversion (TMC) method from bismuth layer-structured ferroelectric compound Bi₄Ti₃O₁₂. The TMC-derived NBT templates, with diameters of 5-15 µm and an average thickness of 0.7 µm, maintained the morphology of Bi₄Ti₃O₁₂ precursors, showing a high degree of preferred pseudocubic < 001> orientation. The Na_0.5Bi_0.5TiO₃ particles prepared could serve as good templates for the preparation of grain oriented lead-free NBT-based piezoelectric ceramics.