铁掺杂二氧化钛负载空微球光催化剂制备及应用

采用溶胶凝胶法将TiO_2用Fe(Ⅲ)改性并负载玻璃微珠制得复合光催化剂,探讨煅烧时间、Fe-Ti原子比、煅烧温度等因素对催化性能的影响,确定最佳制备条件,并对其进行表征。结果表明,最佳制备条件:V钛酸丁酯∶V乙醇∶V硝酸∶V去离子水=5∶20∶0.4∶1,Fe-Ti原子比为4%,煅烧温度500℃,煅烧时间2 h。在自然光条件下反应0.5 d,TOC降解率复合催化剂比P25高8.61%。     

(Ni0.75Fe0.25-xMgO)/YSZ anode for direct methane solid-oxide fuel cells

(Ni_0.75Fe_0.25-xMgO)/YSZ samples—with a varying weight percentage x (0, 5%, 10%) of MgO with respect to Ni_0.75Fe_0.25—were prepared and studied as anodes for intermediate temperature solid oxide fuel cells (SOFCs) operated on humidified methane (3% H₂O). Among the cells with different anode compositions, it was found that the cell with the (Ni_0.75Fe_0.25-5%MgO)/YSZ anode showed the highest power density, giving 648 mW cm⁻² at 800 °C. The cells with MgO-doped anodes were able to operate stably for 20 h under a current density of 0.53 A cm⁻² at 700 °C without observed degradation, while the cells without MgO degraded rapidly. The mechanisms responsible for the superior performance and duration of the (Ni_0.75Fe_0.25-5%MgO)/YSZ anode were analyzed.     

Role of iron in the ferromagnetic-antiferromagnetic boundary of La0.5Ca0.5Mn1-xFexO3+δ (0≤x≤0.5) manganites

Samples of La_0.5Ca_0.5Mn_1−xFe_xO_3+δ (0≤x≤0.5) were synthesized using a solid-state reaction method involving a milling process and thermal treatment up to 1200 °C in an air atmosphere. Samples were characterized structurally with X-ray diffraction analysis and Rietveld refinement with morphology characterization using scanning electron microscopy. Magnetic properties were investigated using a physical property measurement system to obtain zero field cooling and the associated curves to plot hysteresis loops. Our results revealed the interplay between the structural and magnetic properties as Fe ions attached to the crystalline structure. A mechanism based on the substitution of Mn³⁺ and Mn⁴⁺ by low-spin Fe³⁺ and Fe⁴⁺ ions, respectively, was hypothesized to interpret the experimental data. More specifically, the temperature at which the transition from ferromagnetic to paramagnetic occurred increased with increasing Fe content as a result of a greater density of oxygen-mediated ferromagnetic bonds. Conversely, the magnetization weakened because the t_2g electrons were distributed in the respective d orbitals by adopting a low-spin configuration. Such a configuration is preferred as a result of the unit cell distortion in the milling process where the greater ionic radius of the Fe⁴⁺ ions leads to an elongated c-axis tetragonal symmetry and a greater unit cell volume. Finally, low-temperature magnetic behavior revealed the occurrence of a reentrant spin-glass type state within the ferromagnetic matrix favored by a milling-driven structural disorder and the existence of competitive superexchange interactions.     

Fe掺杂CuO纳米粉末铁磁性研究

利用固态反应法制备了Fe掺杂CuO纳米粉末并实现了铁磁性。研究了Fe掺杂CuO纳米粉末的结构和磁学特性,X射线粉末衍射谱显示该样品为CuO单斜结构,不存在杂质相,证明Fe离子融入了CuO晶格,铁磁性起源于Fe离子与CuO晶格的相互作用。     

铁掺杂PbO2/Ti电极电催化氧化苯酚的实验研究

以苯酚为目标化合物,研究了新型铁掺杂PbO2/Ti阳极电催化氧化有机污染物的特性,结果表明,该电极对苯酚的降解显示了良好的电催化活性,有较好的环保应用前景。同时,初步探讨了反应的动力学和氧化机理。     

Influence of gamma irradiation on the refractive index of Fe-doped barium titanate thin films

Polycrystalline Fe-doped barium titanate (Fe-doped BaTiO₃) thin films were grown by thermal decomposition of the precursors deposited from a sol-gel system onto quartz substrates. The changes in the transmittance spectra induced by gamma irradiation on the Fe-doped BaTiO₃ thin films were quantified. The values for the optical energy band gap were in the range of 3.42-3.95 eV depending on the annealing time. The refractive index of the film, as measured in the 350-750 nm wavelength range was in the 2.17-1.88 range for the as prepared film, and this increased to 2.34-1.95 after gamma irradiation at 15 kGy. The extinction coefficient of the film was in the order of 10⁻² and increased after gamma irradiation. We obtained tuneable complex refractive index of the films by exposure to various gamma rays doses.     

Fe掺杂片状ZnO晶体的制备及光学性能研究

采用均匀沉淀法在常温开放体系下制备了片状ZnO晶体前驱物,经600℃煅烧得到纯ZnO晶体;在此基础上,采用原位掺杂的方法制备了片状掺Fe的ZnO晶体。通过体视显微镜、XRD、UV-Vis吸收和PL研究了Fe掺杂对片状ZnO晶体结构和光学性能的影响。结果显示掺Fe后ZnO晶体仍具有正六边形形貌和纤锌矿结构,其在398nm处的紫外发射峰和458nm处的蓝光发射峰位置保持不变,但晶片直径减小,禁带宽度增大,发光峰强度降低。     

Fe掺杂GaN中Fe相关缺陷发光特性研究

利用氢化物气相外延方法制备了 Fe掺杂GaN单晶.材料发光特性随掺杂浓度、温度和激发功率的变化规律表明,位于蓝光波段的发光与掺杂的Fe离子有关.随着Fe掺杂浓度的增加,红外波段发光强度将被抑制,而蓝光波段发光强度显著增加.在较高位错密度样品中,相比于蓝光,红外发光强度显著增加.掺杂样品的光致激发光谱进一步说明了 Fe离子相关的红外和蓝光发光能级跃迁特征及过程.结果表明GaN中的本征缺陷结构以及位错对Fe相关能级跃迁具有重要影响.     

Novel method for doping nano TiO2 photocatalysts by chemical vapour deposition

Highly active photocatalytic Fe-doped nano TiO₂ was successfully synthesised by chemical vapour deposition (CVD) method using FeCl₃ as Fe source. CVD was carried out by evaporating FeCl₃ at 350°C in nitrogen flow during 30–90?min. The amount of Fe incorporated into TiO₂ framework is adjusted by the amount of FeCl₃ used and the evaporation time. The obtained sample was characterised by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), energy dispersive X-ray spectroscopy (EDS), UV-Vis, Fourier transform-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activities of the samples were tested in photocatalytic decomposition of 2-propanol in liquid phase using visible light instead of UV light irradiation. Non-doped TiO₂ and high Fe loading TiO₂ samples showed very low photocatalytic activity, whereas the low Fe loading TiO₂ sample exhibited high photocatalytic activity under visible light. The high photocatalytic activity of this sample was rationalised by the existence of defects (Ti–OH groups) as the active sites.