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1.
蓝紫色ZnO-Al2O3-SiO2长余辉陶瓷   总被引:5,自引:1,他引:4  
通过高温固相法首次合成并报道了兰紫色ZnO-Al2O3-SiO2长余辉陶瓷,系统地研究了其发光和缺陷性质,在强度0.6mW.cm^-2,主峰254nm的UVP紫外灯下激发15min,然后关闭激发源,样品发射兰紫色长余辉,撤去激发源以后5s,余辉初始强度为230mcd.m^-1,色坐标为(0.1292,0.0984),暗视场中,8h以后余辉仍然肉眼可辨,样品的紫外可见发射和不同时间的余辉发射光谱显示,荧光发射位于390nm,来源于基质的自致发光,而余辉有两个发射峰,主峰位于390nm,肩峰位于520nm,这表明样品中存在两种余辉发射中心,由余辉衰减曲线可以看出,这两种余辉发光都由一个快过程和一个慢过程组成,其中,慢过程决定了材料的长余辉时间,从时间依赖的余辉强度倒数曲线可以看出,余辉强度与时间成反比,这表明余辉发光的机理为电子空穴复合过程,热释光谱显示,样品分别在92和250℃附近出现两个宽的热释峰,说明材料中至少存在两种具有不同陷阱深度的电子或空穴缺陷中心。  相似文献   

2.
La2O3:Sm发光粉的合成与发光性质的研究   总被引:6,自引:2,他引:4  
以La2O3和Sm2O3为原料,用碳酸盐沉淀法制备了La2O3:Sm^3 发光粉,并分别用XRD,SEM和发光光谱及寿命进行了表征,La2O3晶相的形成温度为800℃,其发光强度随温度升高而增强,La2O3基质中Sm^3 的最佳掺杂浓度为1.5%(摩尔分数)。  相似文献   

3.
采用溶胶-凝胶法合成了以Sr2MgSi2O7为基质,掺杂Eu^2 ,Dy^3 的长余辉发光材料,并表征其结构,激发-发射光谱和余辉衰减曲线。XRD分析表明,所合成的样品为Sr2MgSi2O7晶体结构。发光粉体的激发波长范围较宽,表明从紫外至可见光均可激发该发光材料。发射光谱主峰位于466nm。样品在自然光照射后持续发出明亮的蓝光,余辉时间持续8h以上。  相似文献   

4.
通过沉淀、回流和浸渍法制备了镓掺杂的纳米级固体超强酸SO4^2-/Ga2O3/ZrO2,并用X射线衍射、透射电镜、热重、吡啶吸附红外光谱、低温N2-BET及化学分析等技术对SO4^2-/Ga2O3/ZrO2的结构、表面性质及其对正丁烷异构化反应的催化活性进行了研究.结果表明,掺杂Ga2O3可以抑制制备过程中ZrO2晶粒长大,有利于抑制高温下催化剂由四方相转变为单斜相.与未掺杂的催化剂相比,Ga2O3的掺杂提高了催化剂表面SO4^2-的分解温度,有利于催化剂表面形成更多的酸中心.SO4^2-/Ga2O3/ZrO2对正丁烷异构化反应显示出优异的催化性能.其中,含3%Ga2O3的样品的活性最高,220℃下其初活性为59.1%;反应1h后,其活性基本保持稳定,稳态转化率大于51%,接近该反应条件下正丁烷的平衡转化率.  相似文献   

5.
用TEOS-Zr-HAD-H2O-Etheanol体系合成了Zr-HAD的中孔分子筛,脱除模板剂后用0.5mol/L硫酸处理和550℃高温焙烧3h,制得一种中孔SO4^2-/Zr-HAD超强酸催化剂,采用XRD对其结构进行表征,用指示剂法,TG和NH3-TPD对其酸性进行了表征。结果表明,经过一系列处理后制得的SO4^2-/Zr-HAD催化剂具备HMS中孔分子筛的结构特征,其酸强度可达H0=-13.75,在锆及SO4^2-含量远远低于SO4^2-/ZrO2的条件下,SO4^2-/Zr-HAD催化剂对于苯酐和正丁醇酯化反应的活性仍高于SO4^2-/ZrO2催化剂。  相似文献   

6.
激活CaO-MgO-SiO_2长余辉玻璃发光性质   总被引:1,自引:1,他引:0  
报道了一种新型的Eu~(2+)离子激活硅酸盐玻璃,该玻璃组成为2CaO-MgO-3SiO_2-0.015Eu_2O_3(CMSE)。通过透射光谱、稳态荧光光谱、余辉光谱和热释光等技术手段对CMSE的发光性质进行了深入研究。研究发现CMSE可以被紫光和近紫外光激发,获得黄色长余辉发光。热释光曲线的分析表明,CMSE的长余辉性质主要来自于玻璃基质中陷阱深度为0.83 e V左右的定域能级。研究认为对CMSE发光性质的研究有利于开发新型稀土离子激活近紫外激发LED用硅酸盐玻璃发光材料。  相似文献   

7.
固体超强酸SO4^2-/SnO2-Al2O3的红外光谱研究   总被引:3,自引:0,他引:3  
以四氯化锡、硫酸铝为原料,氨水为沉淀剂,采用共沉淀法制得新型固体超强酸SO4^2-/SnO2-Al2O3。采用FT-IR技术考察了金属元素摩尔比、焙烧温度、浸渍液以及掺杂稀土氧化物对该固体超强酸结构和性能的影响。兀:lR结果表明在该固体超强酸中,锡和硫酸根是以螯合和桥式两种方式配位结合,其中起催化活化作用的主要是和硫酸根以螯合双齿结合的锡;和SO4^2-/SnO2型超强酸相比,SO4^2-/SnO2-Al2O3超强酸的硫酸根FT-IR特征吸收峰发生蓝移,显示出更强的酸性。锡铝摩尔比为9:1、焙烧温度为773K、焙烧时间为3h时。制得的SO4^2-/SnO2-Al2O3样品对酯化反应的催化性能最好。  相似文献   

8.
Eu^2+激活的CaS:Eu^[1],Eu^3+和Sm^3+激活的硫氧化物^[2],Pr^3+激活的Ca0.8Zn0.2Ti03^[3]以及Eu^2+和Mn^2+掺杂的SrY2S4^[4]都是重要的红色发光材料。然而,这些红色荧光粉的发射峰波长都短于650nm,对于农用日光转换材料^[5],红色发射峰波长达到660nm才能与叶绿素的红区吸收相吻合。  相似文献   

9.
用共沉淀法制备了固体超强酸S2O8^2-/ZrO2-CeO2催化剂,通过XRD,FTIR,BET,TEM,DSC/TG等分析手段对其结构进行了表征,并考察了其对乳酸丁酯合成反应的催化活性。结果表明.Ce的引入可以有效地抑制ZrO2晶粒由四方相向单斜晶相转变和催化剂表面含硫物种的流失;当焙烧温度高于500℃时,体系内部有四方相Ce0.16Zr0.84O2固溶体形成,最佳焙烧温度为600℃。在n(乳酸):n(正丁醇)=1.0:3.0,。(S2O8^2-/ZrO2-CeO2)=12.0%,反应温度145℃,反应时间2.0h的条件下,S2O8^2-/ZrO2-CeO2催化剂对乳酸的酯化率达96.6%。  相似文献   

10.
SO3/γ-Al2O3固体酸催化剂的制备、结构与酸性表征   总被引:3,自引:0,他引:3  
用酸中和法制备了活性γ-Al2O3,并在其表面负载SO3得到固体酸催化剂SO3/γ-Al2O3,用XRD,TG-DTA,FT-IR,NMR,NH3-TPD等对其进行了结构和酸性研究.结果表明:在SO3/γ-Al2O3的制备过程中形成少量的Al2(SO4)3,同时SO3与γ-Al2O3表面上的羟基反应,形成强的Br(oe)nsted酸位,根据^1H/^27Al双共振(TRAPDOR)MAS NMR与FT-IR实验结果提出了Br(oe)nsted酸结构模型.SO3/γ-Al2O3表面存在两种不同强度的酸中心,其酸强度大于分子筛HZSM-5,但弱于传统的固体超强酸SO4^2-/γ-AL2O3.  相似文献   

11.
Scandium magnesium gallide, Sc2MgGa2, and yttrium magnesium gallide, Y2MgGa2, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo2FeB2‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc2MgGa2 was determined from single‐crystal diffraction intensities and the isostructural Y2MgGa2 was identified from powder diffraction data.  相似文献   

12.
13.
On Dialkali Metal Dichalcogenides β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 and Rb2Te2 The first presentation of pure samples of α- and β-Rb2S2, α- and β-K2Te2, and Rb2Te2 is described. Using single crystals of K2S2 and K2Se2, received by ammonothermal synthesis, the structure of the Na2O2 type and by using single crystals of β-Na2S2 and β-K2Te2 the Li2O2 type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na2O2 type to the Li2O2 type will be explained by means of the examples α-/β-Na2S2 and α-/β-K2Te2. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb2S2 is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.  相似文献   

14.
15.
[(n‐Bu)2Sn(O2PPh2)2] ( 1 ), and [Ph2Sn(O2PPh2)2] ( 2 ) have been synthesized by the reactions of R2SnCl2 (R=n‐Bu, Ph) with HO2PPh2 in Methanol. From the reaction of Ph2SnCl2 with diphenylphosphinic acid a third product [PhClSn(O2PPh2)OMe]2 ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P21/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)2 linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.  相似文献   

16.
17.
The structures of the hypophosphites KH2PO2 (potassium hypophosphite), RbH2PO2 (rubidium hypophosphite) and CsH2PO2 (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.  相似文献   

18.
Summary The ability of [MoS4]2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe2+. The present study has been restricted to linear complexes such as (NEt4)2 [Cl2FeS2MoS2] and (NEt4)2[Cl2FeS2MoS2FeCl2]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS2, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl2]2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl4Fe2MoS4]2–[Cl2FeMoS4]2–+FeCl2. The equilibrium constant, KD, was evaluated by differential pulse polarography. KD is tightly related to the donor number of the solvent.  相似文献   

19.
TG and DTA studies on Me3SnO2PCl2, Me2Sn(O2PCl2)2 and Ph3SnO2PCl2 were carried out under dynamic argon atmosphere. The results show that the decomposition proceeds in different stages leading to the formation of Sn3(PO4)2 as a stable product. This compound was characterized by IR spectroscopy. Decomposition schemes involving reductive elimination reactions were proposed.  相似文献   

20.
Wu YT  Linden A  Siegel JS 《Organic letters》2005,7(20):4353-4355
[reaction: see text] Fluoranthene 2 and heptacycle 3 are easily accessible from the reaction of diyne 1 and norbornadiene (NBD) in the presence of the rhodium catalyst. The unusual [(2+2)+(2+2)] adduct 3 was confirmed by the X-ray crystal structure analysis.  相似文献   

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