Sr4Al14O25∶Eu2+,Dy3+/TiO2-xNx复合材料制备及光催化性能

采用溶胶-凝胶法在长余辉发光材料(Sr4Al14O25∶Eu2+,Dy3+)的表面包覆TiO2-xNx.利用X-射线衍射(XRD)、扫描电子显微镜(SEM)对复合材料的结构,形貌进行了表征;并研究了Sr4Al14O25∶Eu2+,Dy3+/TiO2-xNx复合材料对甲基橙的光催化降解性能.     

Sr4Al14O25:Eu2+,Dy3+/TiO2-xNx复合材料制备及光催化性能

采用溶胶-凝胶法在长余辉发光材料(Sr4Al14O25:Eu2+,Dy3+)的表面包覆TiO2-xNx。利用X-射线衍射(XRD)、扫描电子显微镜(SEM)对复合材料的结构,形貌进行了表征;并研究了Sr4Al14O25:Eu2+,Dy3+/TiO2-xNx复合材料对甲基橙的光催化降解性能。     

正交设计法优化磷光体SrAl2O4：Eu^2＋，Dy^3＋的制备工艺

为了探讨SrAl2O4：Eu^2＋,Dy^3＋磷光体的最佳制备工艺,利用正交设计法对合成条件进行了优化,以初始亮度和余辉时间为指标,考察煅烧温度、尿素与硝酸盐的质量比、硼酸的物质的量分数、镝与铕物质的量比对制备工艺的影响。结果表明：最佳制备工艺是煅烧温度600℃,尿素质量等于硝酸盐质量的2倍,硼酸的物质的量分数为0．08,镝与铕的物质的量比为1．0。     

Al2O3/TiO2复合膜的结构及光催化性能

利用电沉积方法在铝硫酸阳极氧化膜表面制备了具有光催化活性的T iO2薄膜。分析了A l2O3/T iO2复合膜的结构,观察了薄膜表面形貌及断面构造,并分析了薄膜表面的化学成分,通过紫外光照射下甲基橙溶液的光催化降解反应初步研究了该复合膜的光催化活性。结果表明,未经热处理的A l2O3/T iO2复合膜处于非晶态,550℃热处理3 h后,T iO2转变为锐钛矿结构;沉积在铝氧化膜表面的T iO2薄膜厚度约5μm,呈均匀不连续状态,表面存在大量裂纹,电沉积T iO2过程中基体氧化铝存在着部分溶解;薄膜表面主要由T i、O两种元素构成,同时存在较少量的A l、S、K等元素。该A l2O3/T iO2复合膜可光催化降解甲基橙溶液,具有光催化活性。     

Y2O3：Eu^3＋薄膜的制备及发光性能的研究

以稀土氧化物为原料，用溶胶-凝胶法制备前驱液，加入适量的聚乙烯醇做成膜物质，用浸渍拉提法在石英玻璃表面上得到均匀的薄膜，然后经过适当的干燥和热处理得到Y2O3：Eu^3＋发光薄膜．讨论了Eu^3＋的掺杂浓度和热处理温度对薄膜发光性能的影响．试验表明：Eu^3＋的最佳掺杂浓度为8％（摩尔分数），薄膜的发光性能随热处理温度提高而增强，当热处理温度达到700℃后，薄膜的发光性能基本上稳定．同时用原子力显微镜和X射线衍射分析了薄膜的表面形貌和结构．     

YVO4：Eu^3＋，Bi^3＋荧光粉的制备及荧光性能研究

用溶胶凝胶法在较低温度下制备了YVO4：Eu^3＋，Bi^3＋荧光粉，采用X射线衍射仪（XRD），扫描电子显微镜（SEM）及荧光分光光度计测试，研究了合成产物的结构、表面形貌，分析了在Eu3’含量一定的情况下掺杂Bi^3＋的浓度的变化对发光性能的影响。结果表明，溶胶凝胶法合成的YVO4：Eu^3＋，Bi^3＋荧光粉为单相结构、粒径在1um左右、无团聚现象；Bi^3＋对Eu^3＋离子有敏化作用，在一定浓度下使荧光粉的发射强度增加。     

热处理温度对TiO2-x/Al2O3复合材料的光催化性能影响研究

以钛酸铝(Al2TiO5)为原料,在碳粉埋烧条件下,利用原位固相热分解法制备了TiO2-x/Al2O3异质结构复合光催化剂.研究了不同热处理温度对TiO2-x/Al2O3样品的物相结构、微观形貌和紫外可见光吸收性能的影响规律.并通过对亚甲基蓝(MB)染料的降解率来表征样品的光催化性能.实验结果表明,热处理温度为1100...     

不同添加剂对Sr4Al14O25: Eu, Dy长余辉光致发光性能的影响

研究了-H3BO3,NH4H2PO4,CaF2几种添加剂对Sr4Al14O25Eu,Dy发光性能的影响.结果发现这些添加剂的加入,有利于Sr4Al14O25相的生成.发射光谱显示,随着H3BO3,NH4H2PO4,CaF2的加入,Sr4Al14O25Eu,Dy磷光材料的发射光谱主峰出现蓝移现象.而且,添加剂的加入,不同程度上改善了Sr4Al14O25Eu,Dy磷光材料长余辉发光性能.尤其是H3BO3的加入,使Sr4Al14O25Eu,Dy材料的初始亮度大大提高,并使发光持续时间延长.初始亮度从1756mcd@m-2增加到5327mcd@m-2.     

草酸沉淀法制备Y2O3：Eu^3＋粉体粒度控制

利用草酸沉淀法制备Y2O3：Eu^3 粉体。通过研究草酸沉淀过程中温度、酸度、浓度及前驱体煅烧温度等条件对粒度的影响，获得控制最终产物粒度的各种手段，进而得到分散性能良好、不结团、高光效、流明特性稳定的微米级Y2O3：Eu^3 荧光粉，以满足荧光粉生产的需要。     

制备方法对Al2TiO5-Si3N4复合材料性能的影响

采用“直接法”、“反应复合法一”、“反应复合法二”3种方法制备了Al2TiO5—Si3N4复合材料。研究了3种制备方法对材料的显气孔率、吸水率、体积密度、抗折强度、烧成线收缩率、抗热震次数、显微结构等性能的影响。研究结果表明,采用“反应复合法－”制备的Al2TiO5-Si3N4复合材料的综合性能最佳,其显气孔率为16．61％、吸水率为6．01％、体积密度为2．77g/cm^2、抗折强度为45．34MPa、抗热震次数达到11次、结构最致密。     

红色荧光粉CaWO4:Eu3+,Gd3+的合成及其发光性能的研究

利用高温固相法合成了CaWO4:Eu3+,Gd3+红色荧光粉,通过X射线衍射、X射线光电子能谱和荧光光谱等对该荧光粉进行了表征。结果表明,CaWO4:Eu3+,Gd3+的荧光强度明显高于CaWO4:Eu3+,钆离子的最佳掺杂量为0.04。同时说明了钆离子引入到CaWO4:Eu3+中对其发光性能影响的机理以及不同浓度的钆对发光强度的影响。     

Unusual concentration induced antithermal quenching of the Eu2+ emission at 490 nm in Sr4Al14O25:Eu2+ for near ultraviolet excited white LEDs

Thermal quenching of phosphor is an important challenge for its practical application in phosphor-converted white light-emitting diodes (pc-WLEDs) and it usually becomes aggravated with the increase of activator concentration. Conversely, this work finds the thermal quenching of Eu²⁺ emission at 490 nm in Sr₄Al₁₄O₂₅:Eu²⁺ does not follow this in the temperature range of 300 to 480 K, and the rate of it is even slowed down as the concentration of Eu²⁺ increases. However, at the same time, the experiment on three heating-cooling cycles of Sr₄Al₁₄O₂₅:Eu²⁺ reveals that the thermal degradation of Eu²⁺ emission becomes improved. Once Eu²⁺ ions are doped into Sr₄Al₁₄O₂₅, they will prefer substituting for the 10- and 7-coordinated strontium sites Sr1 and Sr2, respectively. The emission centers Eu1 and Eu2, therefore, appear. The abnormal phenomenon is perhaps partly due to the enhanced energy transfer from the emission center Eu1 at 407 nm to the one Eu2 at 490 nm. It is also found interesting that the introduction of AlN can enhance the emission of Sr₄Al₁₄O₂₅:Eu²⁺ without leading to the deterioration of thermal degradation. In the end, a prototype of pc-WLED was fabricated with Sr₄Al₁₄O₂₅:Eu²⁺ to demonstrate the application of white lighting. This work is not only beneficial to the understanding of the relationship between concentration and thermal quenching, but also conducive to the design of the heavily doped phosphor for WLEDs with better resistance to thermal quenching.     

溶剂热法合成片状SrAl2O4:Eu2+,Dy3+长余辉荧光粉的研究

利用溶剂热法制备了由片组装的花状前驱体,1300℃烧结2h后获得了SrAl2O4:Eu2+,Dy3+片状荧光材料.利用XRD和SEM技术表征了在不同比例的乙醇和水的混合溶液中反应制得的荧光材料的物相组成和形貌,用荧光分光光度计测定了荧光材料的发光性质.结果发现,当乙醇和水的比例为3∶1时,所制备的荧光材料具有较高的结晶性,较好的形貌和较强的发光强度.     

Luminescent properties of long‐lasting BaAlxOy:Eu2+,Dy3+ nanocomposites

BaAl_xO_y:Eu²⁺,Dy³⁺ blue‐green phosphor samples were synthesized by a combustion method at the low temperature of 500°C. Phosphor nanocrystallites with high brightness were obtained without significantly changing the crystalline structure of the host. The crystallite sizes determined from the Scherrer equation ranged between 34 and 41 nm. Different volume fractions of the BaAl_xO_y:Eu²⁺,Dy³⁺ powder were then introduced in LDPE polymer. The resulting composites were similarly analyzed and also thermally characterized by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). PL results indicate that the LDPE‐phosphor interface, which is considered to have an influence on the composite behavior, did not significantly change the spectral positions of the phosphor materials, whose major emission peaks occurred at about 505 nm. The improved afterglow results for the composites may have been caused by morphological changes due to increased surface area and defects. Thermal results indicate that the BaAl_xO_y:Eu²⁺,Dy³⁺ particles acted as nucleating centers and enhanced the overall crystallinity in the LDPE nanocomposite while preventing lamellar growth, hence reducing the crystallite sizes in LDPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photocatalytic activity of Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions

Cu₂O/TiO₂, Bi₂O₃/TiO₂ and ZnMn₂O₄/TiO₂ heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV–vis spectroscopy analysis showed that the junctions-based Cu₂O, Bi₂O₃ and ZnMn₂O₄ are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000 nm). This fact was confirmed in the case of Cu₂O/TiO₂ and Bi₂O₃/TiO₂ by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV–vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena that were observed in each case are discussed.     

柠檬酸凝胶燃烧法制备Nd3+,Yb3+:Y2O3多晶原料及其相组成和荧光特性的研究

本文采用柠檬酸凝胶燃烧法合成了性能优良的Nd3+,Yb3+:Y2O3多晶原料。XRD、IR和SEM测试结果表明样品在900℃煅烧可获得纯相的Nd3+,Yb3+:Y2O3,平均粒径约为40 nm;TG-DTA测试结果表明样品在30～600℃之间失重约为49.28%;从荧光光谱上可以看出两个主要发射峰位于970～1100 nm之间,最强发射峰位于1030nm,对应Yb3+的2F5/2→2F7/2能级跃迁。     

Mechanical properties of Al2O3/ZrO2 composites

In the present study, both t-phase zirconia and m-phase zirconia particles are incorporated into an alumina matrix. Dense Al₂O₃/(t-ZrO₂+m-ZrO₂) composites were prepared by sintering pressurelessly at 1600 °C. The microstructure of the composites are characterized, the elastic modulus, strength and toughness determined. Because the ZrO₂ inclusions are close to each other in the Al₂O₃ matrix, the yttrium ion originally in t-ZrO₂ particles can diffuse to nearby m-ZrO₂ particles during sintering, and the m-phase zirconia is thus stabilized after sintering. The strength of the Al₂O₃/(t-ZrO₂+m-ZrO₂) composites after surface grinding can reach values as high as 940 MPa, which is roughly three times that of Al₂O₃ alone. The strengthening effect is contributed by microstructural refinement together with the surface compressive stresses induced by grinding. The toughness of alumina is also enhanced by adding both t-phase and m-phase zirconia, which can reach values as high as two times that of Al₂O₃ alone. The toughening effect is attributed mainly to the zirconia t–m phase transformation.     

Enhancing photoluminescence properties of Mn4+-activated Sr4−xBaxAl14O25 red phosphors for plant cultivation LEDs

Non–rare earth Mn⁴⁺-activated strontium aluminate phosphor is considered to be a promising material for plant cultivation field owing to their advantage of inexpensively, environment friendly, nontoxic, and appropriate spectral range. In this paper, a Sr_4−xBa_xAl_13.99O₂₅:0.01Mn⁴⁺,1.4H₃BO₃ strontium aluminate phosphor is synthesized by a convenient high-temperature solid-state reaction. The photoluminescence spectra located at red region with a peak at 655 nm in the range of 600 to 750 nm that can be excited under the excitation of ultraviolet (~346 nm) or blue light (~450 nm). The shape emission band at 655 nm is attributed to the transition of ²E_g-⁴A_2g. Furthermore, the emission intensity of Sr_4−xBa_xAl_13.99O₂₅: 0.01Mn⁴⁺,1.4H₃BO₃ phosphor is conducted in detail with the variety of Ba²⁺ doping concentration and the intensity can be enhanced to 140.9% than the Sr₄Al_13.99O₂₅:0.01Mn⁴⁺,1.4H₃BO₃ when the value of Ba²⁺ concentration equal to 0.1 mol. In addition, the X-ray diffraction spectra, element mapping, composition modifying, optical properties, FT-IR spectra, diffuse reflectance spectra, thermal stability, and fluorescence lifetime are systematically investigated. According to the electro-luminescent spectra of as-packaged LED, indicating that the Sr_3.9Ba_0.1Al_13.99O₂₅:0.01Mn⁴⁺,1.4H₃BO₃ phosphor will become a great candidate for plant cultivation LEDs due to the emission spectra match well the plant pigment spectrum.     

薄膜化固体超强酸SO4^2-／TiO2-WO3光催化降解甲基橙

采用硫酸溶液漫渍处理TiO2—WO3制得SO4^2-／TiO2-WO3薄膜光催化剂,考察了光催化荆对甲基橙溶液的光催化降解行为。结果表明,在硫酸浓度为0．2mol·L-1、焙烧温度为550℃、WO3掺杂量为2％的最佳条件下制备的光催化剂活性最高,甲基橙降解90min的降解率达到72％。     

Formation of Y3Al5O12–Al2O3 eutectic microstructure with off-eutectic composition

Homogeneous-eutectic microstructure of Y₃Al₅O₁₂–Al₂O₃ system without coarse primary crystals was formed at an off-eutectic composition. This method utilizes a low migration rate in an amorphous phase. A mixture of Y₂O₃ and Al₂O₃ having the off-eutectic composition was melted and quenched rapidly to form an amorphous phase. A heat-treatment of the amorphous phase at 1000 °C and 1300 °C for 30 min formed Y₃Al₅O₁₂ and Al₂O₃ phases. SEM observation of this material, which was formed from the amorphous phase at 1300 °C for 30 min, showed homogeneous eutectic-like microstructure. The formation of the primary crystals (coarse Al₂O₃), which are always observed in the off-eutectic compositions by ordinary method, was completely suppressed.