Photocatalytic activity under visible light illumination of organic dyes over g-C3N4/MgAl2O4 nanocomposite

Using a grinding method, nanocomposites of graphitic carbon nitride (g-C₃N₄) and magnesium aluminate (MgAl₂O₄) spinel were successfully synthesized for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Variously formulated g-C₃N₄/MgAl₂O₄ nanocomposites were characterized by thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and surface area and micropore analysis (BET surface area). The g-C₃N₄ powder exhibited a nanosheet structure whereas the MgAl₂O₄ spinel comprised agglomerated nanoparticles. The optical properties of the g-C₃N₄/MgAl₂O₄ nanocomposites were investigated by diffuse reflectance spectroscopy (DRS). As the g-C₃N₄ loading content increased from 0 to 30%, the optical band gap energy of the nanocomposite decreased from 3.84 to 2.86 eV, the specific surface area decreased from 153.78 to 114.45 m²/g, and the porosity decreased from 0.447 to 0.347 cm³/g. A 20%g-C₃N₄/MgAl₂O₄ nanocomposite proved to be the most effective photocatalyst and degraded MB faster and more completely than MO. The degradation rates of both MO (0.0107 min^?1) and MB (0.0386 min^?1) in a mixed MO-MB system were greater than the degradation rates in their single systems. The key factor that improved the photocatalytic degradation of MO was the synergistic effect whereas the synergistic effect and photosensitization were the key factors that enhanced the photocatalytic degradation of MB. The g-C₃N₄/MgAl₂O₄ nanocomposite is suitable for the photocatalytic degradation of mixed dyes because its point of zero charge is neutral and it is stable and recyclable.     

MgCO3分子的解离产物合成MgAl2O4分子

本研究碳酸镁MgCO₃分子的解离过程及其解离产物与三氧化二铝Al₂O₃合成MgAl₂O₄的微观过程．利用Gaussian 09软件采用CCSD(T) 6-311++G(d,p)和M06-2x/6-311++G(d,p)方法分别计算反应物碳酸镁MgCO₃分子单点能和频率,并计算反应物受热分解的过程,寻找解离的过渡态.并通过高温烧结法,在实验室用MgCO₃和Al₂O₃粉末为原料,1450℃合成铝酸镁MgAl₂O₄,通过X-ray diffraction即XRD测试表征实验产物与理论计算是一致的.     

氢化物发生-原子荧光光谱法测定高纯铝酸钙粉中砷的研究

采用氢化物发生-原子荧光光谱法对高纯铝酸钙粉中砷的测定进行了研究。样品以盐酸(1+1)、硝酸(1+1)溶解,研究了酸介质及酸浓度、硫脲-抗坏血酸用量对砷测定的影响。在优化的实验条件下,得到砷标准曲线的线性相关系数大于0.999 5。对样品进行了精密度和加标回收实验,得到测定砷相对标准偏差为1.8%～2.6%,加标回收率在98.5%～108%。方法能满足高纯铝酸钙粉中砷的测定。     

水蒸气对PtSn/ZnAl2O4催化剂结构的影响

利用X-射线衍射研究了经氢还原及还原后又经高温水蒸气处理的PtSn／ZnAl2O4催化剂,结果表明,催化剂的相结构是Sn载量的函数．还原态的Pt／ZnAl2O4催化剂中Pt以金属态存在,Pt／Sn原子比为1：1、1：3及1：10的PtSn／ZnAl2O4催化剂还原后分别生成PtZn、PtSn、尽Sn及Pt物相;高温水蒸气处理对Pt／ZnAl2O4样品的相结构及Pt晶粒尺寸无明显影响,但却使Ptsn／ZnAl2O4催化剂的相结构发生显著变化;对于1：l及1：3的Ptsn／ZnAl2O4,水蒸气使各自还原态中的PtZn、PtSn合金重构为Pt3Sn合金,同时使1：10PtSn／ZnAl2O4的民β-Sn及Pt物相消失,而生成了新的PtSn合金相．     

BaMgAl10O17∶Eu(BAM)蓝粉热劣化机理研究

提出了BAM的热劣化模型 ,该模型能较好地说明热处理气氛中含氧量同BAM热劣化程度的关系。BAM的热劣化程度ΔZ与气氛中氧分压的 1/ 6次方 (PO2 )成正比 ,符合关系式ΔZ =α(PO2 ) 1/ 6+ β。α是与温度有关的参数 ,随温度升高 ,α增大 ;β在数值上等于氧分压为零时的ΔZ值。按照上述关系式 ,作者对热劣化实验数据作了拟合 ,两者能较好地吻合     

Thermoluminescence and synchrotron radiation studies on the persistent luminescence of BaAl2O4:Eu,Dy

The persistent luminescence materials, barium aluminates doped with Eu²⁺ and Dy³⁺ (BaAl₂O₄:Eu²⁺,Dy³⁺), were prepared with the combustion synthesis at temperatures between 400 and 600 °C as well as with the solid state reaction at 1500 °C. The concentrations of Eu²⁺/Dy³⁺ (in mol% of the Ba amount) ranged from 0.1/0.1 to 1.0/3.0. The electronic and defect energy level structures were studied with thermoluminescence (TL) and synchrotron radiation (SR) spectroscopies: UV-VUV excitation and emission, as well as with X-ray absorption near-edge structure (XANES) methods. Theoretical calculations using the density functional theory (DFT) were carried out in order to compare with the experimental data.     

钇掺杂量对LuxY1-xAlO3:Ce晶体结构和发光性能的影响

研究了Y掺杂量对LuxY1-xAlO3：Ce晶体结构和发光性能的影响，结果表明：固溶体晶体LuxY1-xAlO3：Ce（x=0～0．3）仍为正交晶系赝钙钛矿型结构。随着Y掺杂量的减少，晶胞体积减小、晶体密度增大、本征吸收降低、光输出增大，衰减时间由YAlO3：Ce的29．7ns降低至Lu0.3Y0.7Al03：Ce的24．2ns。随着Y掺杂量的减少，发射谱的峰位由YAlO3：Ce的390nm逐步紫移至Lu0.3Y0.7AlO3：Ce的384nm，这表明尽管LuxY1-xAlO3：Ce晶体的光激发一发射机制并未发生明显的变化，但掺杂还是引起了稀土格位晶体场的变化，激活离子Ce^3＋的激发态与基态能级之间的能级差随Y掺杂量的减少逐步加大。Y掺杂含量的降低在改善晶体闪烁性能的同时也降低了晶体的热稳定性，增强了晶体的放射性本底。     

用OP作增感剂原子吸收光谱法测定微量钙

研究以表面活性剂OP作增感剂。火焰原子吸收光谱法测定微量钙的方法。试验发展OP的加入可使吸光度增加70％,分析灵敏度得到提高。同时,以0．5mg.ml^-1钾、6．0mg.ml^-1镧盐及2．0mg.ml^-18－羟基喹啉作消电离剂、释放剂和保护剂消除基体物质的干扰。据此建立了标准加入法直接测定铝酸钠溶液中微量钙的分析方法。其线性范围为0－7．5mg.L^-1。灵敏度为0．05mg.L^-1/1%。方法灵敏度高,操作简便,结果准确度和精密度满足分析要求。     

掺杂B3+在SrAl2O4∶Eu,Dy中的作用及其机制研究

研究了H3BO3在碱土铝酸盐长余辉发光材料中的作用, 发现H3BO3不但影响固相反应速度, 还对粉体晶相组成、粒径以及长余辉发光性能产生很大的影响. TG-DTA, XRD和SEM分析表明, H3BO3参与了固相反应, 降低了成核温度与界面反应能垒, 使晶粒生长反应速度加快, 粉体粒径增大. 激发与发射光谱、发射峰强度衰减以及热释光谱分析表明, H3BO3的掺入使发光中心离子浓度增加、陷阱深度和密度加大, 从而使发光亮度增加, 余辉寿命延长.     

Comprehensive Model of Synthetic Bayer Liquors. Part 3. Sodium Aluminate Solutions and the Solubility of Gibbsite and Boehmite

Summary. A Pitzer model representing the thermodynamics of alkaline sodium aluminate solutions is presented. It constitutes a key part of our 10-component synthetic Bayer liquor model communicated in this series of papers. The present model calculates thermodynamic properties, such as heat capacities, osmotic coefficients, and densities, of these solutions as well as the solubilities of gibbsite and boehmite over temperature and concentration ranges of industrial interest.