三种方法制备CaGdAlO4:Eu3+荧光粉及其发光性质研究

分别采用柠檬酸溶胶-凝胶法、半干半湿法和高温固相法制备了CaGdAlO4：Eu^3＋荧光粉，并用X线衍射（XRD）分析、场发射扫描电镜（FE—SEM）观察和荧光光谱分析研究了不同制备方法和制备条件对CaGdAlO4：Eu^3＋形貌、粒径和发光性质的影响。XRD结果表明，柠檬酸溶胶-胶法、半干半湿法和固相法制备CaGdAlO4：Eu^3＋生成纯相的温度分别为900，1200和1400℃。FE—SEM照片显示CCaGdAlO4：Eu^3＋颗粒粒径随温度的升高而增大，在同一烧结温度下，粒径大小为柠檬酸溶胶-凝胶法最小，半干半湿法居中，高温固相法最大而且团聚现象严重。以280nm近紫外光激发，CaGdAlO4：Eu^3＋发出明亮的橙红色荧光，以Eu^3＋的^5D0→^7F2跃迁为主，发光强度随烧结温度的升高而增加，在1400℃烧结温度下，以半干半湿法得到的样品发光最强。室温和低温发射谱中Eu^3＋的^5D0→^7Fj，发射峰的数目都表明：Eu^3＋在CaGdAlO4中只占据偏离反演中心的一种格位。     

高效长余辉发光薄膜及粉体的溶胶—凝胶工艺研究

研究了溶胶－凝胶工艺制备SrAl2O4:Eu^2 ,Dy^3 高效长余辉发光薄膜及粉体的工艺条件,以无机盐为原料,成功制备了均一、稳定、透明的SrAl2O4溶胶,并在较低温度下制备了均匀、无裂纹的发光薄膜和颗粒均匀的针状纳米发光粉体。通过热失重和X射线衍射结果分析了样品的结晶过程和晶相组成,并通过扫描电镜、透射电镜和荧光光谱的分析对薄膜和粉体的微结构、表面形态及发光性能进行了表征。结果表明,在本文的工艺条件下,制备的薄膜和粉体的发光特性与传统的高温固相烧结法相似,但烧结温度可降低300℃左右。     

杂质的添加对SrAl2O：Eu^2＋,Dy^3＋余辉发光特性的改善

采用溶胶－凝胶法制备SrAl2O4:Eu^2 ,Dy^3 磷光体,并在合成过程中添加硼或硅以探讨光致发光及长余辉发光性质。发现硼、硅添加物不仅是助熔剂,且能改良SrAl2O4:Eu^2 ,Dy^3 之长余辉的持续时间及余辉发光强度。基于不同磷光体样品的实验结果比较,综合材料表面微结构观察、X射线衍射图谱、热释发光光谱与余辉衰减曲线的测量等实验结果分析,推断在SrAl2O4:Eu^2 ,Dy^3 中添加硼、硅可导致磷光体缺陷增加并稳定活化剂Eu^2 的价态。     

红色长余辉发光材料Ca2Zn4Ti15O36：Pr^3＋的合成和发光性质

分别采用高温固相法和溶胶-凝胶法合成了新型红色长余辉发光材料Ca2Zn4Ti15O36:Pr。高温固相法合成Ca2Zn4Ti15O36需要在1200℃灼96h才能形成纯物相。热重分析曲线和X射线衍射分析结果表明：溶胶-凝胶法制得的前驱体在700℃灼烧12h开始形成Ca2Zn4Ti15O36物相；在1000℃灼烧24h得到Ca2ZnTi15O36纯物相；最佳反应温度为1000℃，激活剂Pr^3 的最佳浓度为0．6mol％，发光强度比高温固相法增强了510％。     

微乳液法制备MAl2O4：Eu^2＋，Dy^3＋（M=Ca，Sr，Ba）发光材料及其发光性能

采用微乳液法合成了MAl2O4：Eu^2＋，Dy^3＋（M=Ca，Sr，Ba）长余辉发光材料，并对其晶体结构和发光性能进行了比较与讨论。XRD分析表明，所合成的Ca2O4：Eu^2＋，Dy^3＋，SrAl2O4：Eu^2＋，Dy^3＋粉体为单斜晶系结构，BaAl2O4：Eu^2＋，Dy^3＋粉体为六方晶体结构。MAl2O4：Eu^2＋，Dy^3＋（M=Ca，Sr，Ba）发光材料的激发光谱都为一宽带连续谱，表明从紫外至可见光均可有效的激发该材料。发射光谱的发射波长峰值分别为440nm（M=Ca），520nm（M=Sr）和496nm（M=Ba）。对应的发光颜色分别为蓝色、黄绿色和蓝紫色。余辉衰减曲线分为快衰减、中间过渡衰减和随后极长的慢衰减过程，符合双曲线方程I=At^-n，余辉亮度与时间顺序为Sr〉Ca〉Ba。     

沸石中组装SrAl2O4:Eu2+,Dy3+的可调发光现象

首先用溶胶-凝胶法制备符合SrAl2O4：Eu^2 ，Dy^3 化学组成的溶胶，然后通过机械研磨、水热反应和微波加热反应三种不同的组装方法和微波还原扩散法使其进入主体ZSM-5沸石的孔道中。主客体材料的荧光光谱出现显著蓝移，余辉光谱出现400nm和517nm两个发射峰，两个余辉峰的相对发射强度随组装方法和组装浓度的改变而具有可调性，呈现有规律的变化。分析其原因是由于发光材料进入沸石的纳米级孔洞引起的。     

红色长余辉发光材料Ca2Zn4Ti15O36∶Pr3+的合成和发光性质

分别采用高温固相法和溶胶-凝胶法合成了新型红色长余辉发光材料Ca2Zn4Ti15O36∶Pr. 高温固相法合成Ca2Zn4Ti15O36需要在1200 ℃灼烧96 h才能形成纯物相. 热重分析曲线和X射线衍射分析结果表明 溶胶-凝胶法制得的前驱体在700 ℃灼烧12 h开始形成Ca2Zn4Ti15O36物相; 在1000 ℃灼烧24 h得到Ca2Zn4Ti15O36纯物相; 最佳反应温度为1000 ℃, 激活剂Pr3+的最佳浓度为0.6mol%, 发光强度比高温固相法增强了510%.     

SrAl_2O_4∶Eu~(2 ),Dy~(3 )纳米长余辉发光材料的制备与表征

采用溶胶鄄凝胶法制备了SrAl2O4∶Eu2 ,Dy3 纳米长余辉发光材料,研究了pH值、反应温度和络合剂等对溶胶鄄凝胶形成的影响,研究了灼烧温度对SrAl2O4∶Eu2 ,Dy3 晶相、颗粒尺度和发光性能的影响。利用XRD,SEM,光谱分析等手段对产物进行了结构和性能分析。实验结果表明,在800℃时SrAl2O4晶相开始形成但没有发光,而在1100℃烧结的样品则具有很好的发光性能。样品平均晶粒尺寸随灼烧温度升高而增加,平均晶粒尺寸为20~40nm。样品的激发光谱是峰值在240,330,378和425nm的连续宽带谱,发光光谱是峰值在523nm的宽带谱,与SrAl2O4∶Eu2 ,Dy3 粗晶材料相比,发光光谱发生了“红移”现象。样品的热释光峰值位于157℃,与SrAl2O4∶Eu2 ,Dy3 粗晶材料相比,峰值向低温移动了13℃。     

掺铕Y2O3发光薄膜的制备及发光性能

溶胶-凝胶法;荧光;掺铕Y2O3发光薄膜的制备及发光性能     

BaCe0.5Zr0.4Y0.1O3-δ粉体的溶胶-凝胶法和高温固相法制备及性能表征

分别通过溶胶-凝胶法和高温固相反应法制备了BaCe0.5Zr0.4Y0.1O3-δ粉体.采用热重-差热分析(TG-DTA),粉末X射线衍射(XRD),扫描电子显微镜(SEM),傅立叶红外衍射(FT-IR),N2吸附-脱附等方法对所制备的粉体进行了表征.结果表明:用溶胶-凝胶法在1200 ℃×10 h可以合成纯的BaCe0.5Zr0.4Y0.1O3-δ粉体,合成温度比传统的高温固相反应法降低400 ℃左右;溶胶-凝胶法合成粉体具有多孔结构特征,与固相法合成粉体相比具有较高的比表面积.但致密化试验表明:溶胶-凝胶法合成粉体与固相法合成粉体相比具有较低的烧结活性.溶胶-凝胶法合成粉体颗粒表面残余的有机基团和颗粒内部的大量微孔将在致密化过程中产生空间位阻,从而影响高温下原子的迁移,阻碍材料的致密化过程.     

二氧化碳加氢合成二甲醚的研究ZrO2含量对Cu-ZnO-SiO2-ZrO2催化剂的影响

考察了CO2加氢合成CH3OCH3反应中ZrO2含量对Cu-ZnO-SiO2-ZrO2催化剂的影响. 采用TPR, XRD, BET和TEM等技术对催化剂的结构形态、表面性质和ZrO2的作用进行了研究. 结果表明,催化剂中加入ZrO2能提高催化剂的比表面积及CO2转化率和CH3OCH3产率,降低最佳反应温度; ZrO2含量以2%～3%为佳. 催化剂中的CuO以三种形式存在: 小晶粒CuO, 聚集的无定形CuO及均匀分散的无定形CuO. ZrO2的作用是将均匀分散的无定形CuO转变成聚集的无定形CuO, 增加活性中心数目,还可使小晶粒CuO的晶粒变得更小.     

TiO2光催化消除H2S的研究

在TiO₂上进行了气相H₂S光催化氧化消除的研究.氧对H₂S的光催化氧化消除过程是不可缺少的,对含量为560mg/m³的H₂S,当加入的氧气与原料气中H₂S的分子比为42:1,空速为28000h^-1时,去除率达到97%.在H₂S光催化氧化消除过程中,单质硫的产生可使TiO₂失活,经光照再生单质硫转化为SO₄^2-后,TiO₂活性恢复,而且SO₄^2-的生成对催化剂的中毒有抑制作用.     

Syntheses on the basis of 2H-chromen-2-one and 2H-chromene-2-thione

4-Hydroxy-2H-chromen-2-one and 4-hydroxy-2H-chromene-2-thione reacted with allyl bromide, 1,1,3-trichloroprop-1-ene, and 1,3-dichlorobut-2-ene to give the corresponding ethers, which were oxidized to (2-oxo-2H-chromen-4-yloxy)acetic acid with potassium permanganate, and various derivatives of that acid were obtained. 3-(3,3-Dichloroprop-2-enyl)-7-hydroxy-4-methyl-2H-chromen-2-one and 3-(3,3-dichloroprop-2-enyl)-7-hydroxy-4-methyl-2H-chromene-2-thione were synthesized, and some their transformations were studied.     

Impact of greenhouse gas CO2 on the heterogeneous reaction of SO2 on alpha-Al2O3

The heterogeneous reaction of SO₂ on mineral dust surfaces is generally considered as an important chemical pathway for secondary sulfate formation in the troposphere. To this day, there are no reported studies that assess the impact of atmospheric CO₂ in sulfate production on mineral dust surfaces. In this work, we investigate the impact of CO₂ on SO₂ uptake on dust proxy aluminum oxide particles using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). CO₂ is demonstrated to suppress the heterogeneous oxidation of SO₂ on alpha-Al₂O₃. Compared to that measured in the CO₂-free case, the uptake coefficient is decreased by nearly 57% when Al₂O₃ particles are exposed to the gas flow with atmospheric CO₂ at a relative humidity (RH) of 25%. It is also found that there is a balance between the yield of active moiety −OH provided by Al(OH)₃(CO)(OH)₂ clusters and the loss of basic hydroxyl group on aluminum oxide surfaces blocked by CO₂-derived (bi)carbonate species. This work, for the first time, reveals a negative effect of atmospheric CO₂ on the sulfate formation, which potentially decreases solar-radiation scattering and further exacerbates global warming.     

Rh／SiO_2上H_2的化学吸附

Ｒｈ／ＳｉＯ_２上Ｈ_２的化学吸附陈耀强，龚茂初，明虹，周建略，杜宗英，祝小红，陈豫（四川大学化学系，成都，６１００６４）关键词Ｒｈ／ＳｉＯ_２催化剂，Ｈ_２化学吸附，ＩＲＨ２在Ｒｈ上的化学吸附被认为是解离化学吸附［１］．而Ｒｈ－Ｈ的红外振动谱带是Ｈ２在...     

Heterogeneous reaction of SO2 on TiO2 particles

The heterogeneous reaction of SO₂ on TiO₂ particles was studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The influences of the oxygen concentration, relative humidity (RH), and ultraviolet (UV) light illumination (λ ≈ 365 nm) intensity on the reaction were investigated. The main product of the heterogeneous reaction of SO₂ on TiO₂ particles was sulfate with UV illumination and sulfite without it. The production of sulfate was promoted significantly with UV illumination or water, and there was a synergistic effect when both were present. In the dry system without UV, the heterogeneous reaction of SO₂ on TiO₂ particles was found to be second-order for SO₂ and the initial uptake coefficient, γ_BET, was determined to be 1.94 × 10^?6. With UV and RH = 40%, the reaction order was first-order and the initial uptake coefficient was 1.35 × 10^?5.     

Oriented adsorption of NO2 on WSe2 monolayer

An oriented adsorption behavior of NO₂ is disclosed on the WSe₂ monolayer in this work regardless the monolayer is perfect or defective based on density functional theory study by large-scale sampling. The presence of typical defects, including selenium vacancy, tungsten vacancy, and antisite defect of selenium on tungsten site, does not modify the anisotropic adsorption behavior of NO₂ molecule at all. The adsorbed NO₂ exhibits similar behavior on the four kinds of monolayers with its extending orientation all main lines along the two directions of the Se–W bond and the Se–W–Se trough, in spite of the symmetry is decreased somewhat from trigonal of the perfect monolayer to bilateral of the defective monolayers. Molecular dynamic simulations well reproduce these trends. The anisotropic adsorption behavior can be attributed to the polar properties of both heteroatomic bond of the WSe₂ monolayer and NO₂ molecule itself. Out of plane polarization is believed to play key role in the vertical and then the oriented adsorption behavior formation. The sensitivity is estimated to be very good based on moderate adsorption energy (0.35, 0.42, 0. 95 and 0.78 eV on pure, selenium vacancy, tungsten vacancy, and selenium on tungsten site monolayers) and considerable charge transfer number (0.205, 0.208, 0.164, and 0.160 e, respectively), with different degrees of change by defect. These fantastic findings may provide substantial foundation for wide applications beyond thought.     

TiO2光催化还原CO2

光催化还原CO₂技术在CO₂的治理与利用方面有着潜在的应用价值和良好的开发前景。该文简要综述了近年来用于光催化还原CO₂反应的TiO₂光催化剂材料,包括纯TiO₂催化剂、负载型TiO₂催化剂、金属改性TiO₂催化剂、半导体复合TiO₂催化剂和有机光敏化TiO₂催化剂等,并介绍了各类催化剂光催化还原CO₂的反应性能。     

Photocatalytic characteristics of TiO2 supported on SiO2

The photocatalytic decomposition of acetaldehyde was carried out on TiO₂/SiO₂. The presence of a support (SiO₂) in TiO₂/SiO₂ helped to promote the efficiency of the photocatalyst. The silica support enhanced the effective surface area of TiO₂ and adsorption of acetaldehyde on TiO₂/SiO₂. TiO₂/SiO₂ synthesized from Ti(SO₄)₂ showed promoting effect on acetaldehyde decomposition. The XPS results revealed that TiO₂/SiO₂ prepared with Ti(SO₄)₂ generated SO ₄ ^2? sites on the TiO₂ surface. The increased acidity could promote the adsorption of acetaldehyde and photocatalytic degradation of acetaldehyde. The sulfate ion seemed to generate the bifunctional sites (acid sites and photoactive sites) and promoted the acetaldehyde decomposition on TiO₂/SiO₂.