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1.
在高温固相法制备K4Nb6O17的基础上,采用油水自组装合成复合光催化剂Ag@Ag Cl/K4Nb6O17,利用XRD、SEM、TEM、EDX、UV-Vis、PL、BET等多种手段对复合光催化剂的微观结构、形貌和性能进行了表征,并研究了可见光下降解亚甲基蓝(MB)的催化性能。研究表明,Ag@Ag Cl的粒径约为20 nm,均匀分散在二维层状结构K4Nb6O17的表面上;贵金属Ag纳米粒子的表面等离子体效应显著,对可见光的吸收范围从400 nm拓展到800 nm;Ag@Ag Cl(25%(质量分数))/K4Nb6O17在可见光照射60 min对亚甲基蓝的降解率为88.2%,远远高于单体Ag@Ag Cl和K4Nb6O17的活性。循环实验证明催化剂具有较好的稳定性,同时对苯酚和罗丹明B(Rh B)也具有一定的催化降解活性。淬灭实验表明自由基和空穴均为活性物种,并在此基础上提出降解机理。  相似文献   

2.
采用固相法合成层状半导体K4Nb6O17,通过层间离子交换反应、胺插入反应以及硫化反应制备了纳米PbS插层的K4Nb6O17复合光催化剂(记作K4Nb6O17/PbS).利用X射线衍射(XRD),场发射扫描电镜(SEM),X射线荧光光谱仪(XRF),紫外可见漫反射(UV-Vis)和分子荧光光谱(PL)等技术对其进行表征.考察了催化剂在Na2SO3和Na2S为牺牲剂的光催化制氢活性.结果表明,PbS的插层拓展了K4Nb6O17对可见光的响应,催化制氢活性也有明显提高.在紫外光和可见光下3 h产氢量分别达到123.94和0.66 mmol/(g cat).最后讨论了插层复合催化剂光生电荷转移的机理.  相似文献   

3.
半导体光解水研究进展   总被引:1,自引:0,他引:1  
概述了半导体光解水的原理、光催化剂及光催化体系等方面的研究进展,主要介绍了TiO2、层状结构的铌酸盐K4Nb6O17、InTaO4和碱性金属钽酸盐ATaO3(A=Li、Na、K)等光催化剂,并展望了该领域未来的研究.  相似文献   

4.
K4Nb6O17光催化分解水产氢活性的研究   总被引:1,自引:0,他引:1  
通过高温固相反应法合成了层状K4Nb6O17,采用X射线衍射、比表面积测定、扫描电镜等对K4Nb6O17进行了结构和形貌表征.在I-为电子给体、RuO2为助催化剂的情况下研究了RuO2的负载量、I-离子浓度和溶液pH值对K4Nb6O17光催化分解水产氢活性的影响.研究结果表明,表面负载RuO2可以显著提高K4Nb6O17光催化产氢速度.当I-浓度为15mmol/L,pH=9,RuO2负载量为0.7%时,约400nm紫外光辐射下K4Nb6O17光催化产氢的活性最佳,氢气生成的速度为798.9μmol/L·h.  相似文献   

5.
Ni、Co、Mn、Cu掺杂对K4 Nb6 O17光催化活性的影响   总被引:1,自引:0,他引:1  
杨亚辉  陈启元  尹周澜  李洁 《材料导报》2005,19(5):117-119,124
通过高温固相反应合成了铌酸盐K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 (5.0%mol)掺杂的K4Nb6O17并采用X射线衍射、紫外可见漫反射光谱、扫描电镜、比表面积分析等对其进行了结构和形貌表征.在甲醇为电子给体、Pt为助催化剂的情况下,研究了K4Nb6O17及Ni2 、Co3 、Mn4 、Cu2 掺杂的K4Nb6O17作为催化剂在约400nm紫外辐射下分解水产氢的光催化活性,并讨论了引起催化剂活性差异的原因.  相似文献   

6.
以可溶性的草酸铌为前体,通过聚合络合法合成了可见光响应光催化剂K4Ce2Nb10O30.XRD、SEM、BET以及UV-Vis等表征结果表明:通过该法制备的光催化剂相对于传统高温固相反应法制备的样品具有更小(20~50nm)且分布均匀的纳米颗粒和较高的比表面积.在可见光下(λ>400 nm)分解水的活性测试中,聚合络合法获得K4Ce2Nb10O30比高温固相样品具有更高的光催化分解水活性,并且在紫外光段下(λ>300 nm)具备了完全分解纯水的光催化活性.  相似文献   

7.
苏未安  边小兵刘鹏 《功能材料》2004,35(Z1):1240-1242
Mg4Nb2O9具有与α-Al2O3相同的刚玉型晶体结构,可望成为取代氧化铝陶瓷的新一代高Q值基板陶瓷.在900~1400℃温度范围内,合成了Mg4Nb2O9化合物,采用X射线粉末衍射法进行了相结构分析.结果表明,生成物中含有Mg4Nb2O9、Mg4Nb2O6和MgO三种物相,主晶相是Mg4Nb2O9;在900~1300℃温度范围内,随着温度的升高,MgNb2O6和MgO反应生成Mg4Nb2O9相,主晶相含量线性增加,但在1300℃以上,主晶相含量随温度的升高而减小;Mg4Nb2O9相的最佳合成温度为1300℃.这些结果对研究开发Mg4Nb2O9微波基板材料有着重要的意义.  相似文献   

8.
Sr0.4Ba0.6Nb2O6物相形成过程的XRD分析   总被引:3,自引:1,他引:2  
采用X射线衍射技术(Guinier-Hagg相机)分析了Sr0.4Ba0.6Nb2O6(SBN40)原始混合粉料经不同温度煅烧后的相组成,并利用PIRUM程序对不同反应温度下形成铌酸锶钡相的晶胞尺寸进行了计算.结果表明:在Sr0.4Ba0.6Nb2O6的形成过程中将出现中间相Na5Nb4O15、Sr5Nb4O15、SrNb2O6与BaNb2O6,而SrNb2O6与BaNb2O6最终反应生成铌酸锶钡.反应生成的铌酸锶钡的晶胞参数随反应温度的升高而变小.依据这些实验结果,文中提出了Sr0.4Ba0 6Nb2O6相的形成机制.  相似文献   

9.
SrNb2O6/Nb2O5复合物光催化降解甲基橙的研究   总被引:1,自引:0,他引:1  
光催化剂SrNb2O6采用传统固相反应分别在合成温度为950℃(低温)和1400℃(高温)进行制备.通过XRD粉末衍射和UV-Vis吸收光谱分析,表征了样品的物相和光谱吸收特性.通过对高低温样品的测试和分析表明,高温样品具有单一的物相,而低温样品反应并不完全,是一个混合物.在SrNb2O6光催化活性研究中,常用的甲基橙被选作染料光降解模型,对比试验表明低温样品的光催化活性远高于纯相样品SrNb2O6或Nb2O5.经过讨论和分析,推断出低温产物中存在的异质结(SrNb2O6/Nb2O6)是提高光催化性能的根本原因.  相似文献   

10.
Sr0.4Ba0.6Nb2O6物相形成过程的XRD分析   总被引:3,自引:0,他引:3  
采用X射线衍射技术(Guinier-Hagg相机)分析了Sr0.4Ba0.6Nb2O6(SBN40)原始混合粉料经不同温度煅烧后的相组成,并利用PIRUM程序对不同反应温度下形成铌酸锶钡相的晶胞尺寸进行了计算。结果表明:在Sr0.4Ba0.6Nb2O6的形成过程中将出现中间相Na5Nb4O15、Sr5Nb4O15、SrNb2O6与BaNb2O6,而SrNb2O6与BaNb2O6最终反应生成铌酸锶钡。反应生成的铌酸锶钡的晶胞参数随反应温度的升高而变小。依据这些实验结果,文中提出了Sr0.4Ba0.6Nb2O6相的形成机制。  相似文献   

11.
Carbon nanotubes (CNTs) are promising catalyst supports for fuel cell applications. Metal oxide/CNT nanocomposites are also being studied for dye-sensitized solar-cell, photocatalyst, and sensor applications. The fabrication of nanocomposites consisting of highly crystalline NbOx nanotubes and cup-stacked carbon nanotubes (CSCNTs) is reported herein. The CSCNTs were selected for the carbon materials because of their distinctive structure. The CSCNTs were photochemically treated with vacuum ultraviolet light, which increased the amount of oxygen-containing functional groups therein. NbOx nanotubes with no defects were successfully prepared with the chemical treatment of highly crystalline, layered, flux-grown K4Nb6O17 crystals. First, K4Nb6O17 crystals were grown from a KCl flux at a holding temperature of 800 degrees C. Next, NbOx nanosheets were prepared from the layered K4Nb6O17 crystals via a two-step exfoliation process, which consists of proton exchange in an acid solution and intercalation of the tetrabutylammonium ions. The NbOx nanosheets were rolled up into nanotubes with diameters of about 20 nm and lengths of 100-500 nm on the surfaces of the CSCNTs; thus, unique and complex NbOx/CSCNT nanocomposites were successfully fabricated.  相似文献   

12.
Hydrothermal synthesis of K4Nb6O17   总被引:5,自引:0,他引:5  
A new approach for the synthesis of K4Nb6O17.3H2O by hydrothermal method was examined using different alkaline solutions such as Nb2O5-KOH-NaOH-H2O, Nb2O5-KOH-NH4OH-H2O and Nb2O5-KOH-H2O. K4Nb6O17.3H2O was formed as single phase in Nb2O5-KOH-H2O system in the region of KOH concentration 1.0-1.5 m and temperature 220-285°C. KNbO3 was also formed as single phase in 3.0 m KOH solutions above 250°C. Addition of methanol was useful to decrease the particle size and increase the specific surface area of K4Nb6O17.3H2O.  相似文献   

13.
K(Ta,Nb)O3薄膜中钙钛矿相的形成机理研究   总被引:1,自引:0,他引:1  
研究了工艺参数和衬底材料对K(Ta,Nb)O3薄膜生长的影响,研究表明钙钛矿相由焦绿石中间相转变而成,热处理时低速升温同样可以获得纯钙钛矿相的K(Ta,Nb)O3薄膜,分析了(100)SrTiO3,(100)MgO单晶衬底上钙钛矿相的形成机理,并解释了在硅单晶和石英玻璃衬底上纯钙钛矿结构的K(Ta,Nb)O3薄膜不易形成的原因。  相似文献   

14.
In this work,high-entropy ceramics(Hf0.25 Zr0.25Ta0.25Nb0.25)C(HZTNC) and HZTNC doped with 20 vol%SiC(HZTNC-SiC) were fabricated by spark plasma sintering.Their oxidation behavior was investigated over the temperature range of 1300-1500℃ for up to 60 min.Both HZTNC and HZTNC-SiC exhibited good oxidation resistance,and their weight change as a function of oxidation time obeyed a parabolic law.Through XRD,microstructure observation,and elemental mapping analysis of the oxide layers,it was found that the formation of Nb2 Zr6 O17,Hf6 Ta2 O17,and(Ta,Nb)2 O5 mixed-oxide layers effectively protected the matrix from further oxidation.Microcracks began to appear on the oxide layer of HZTNC at high temperatures after 60 min of oxidation.However,the addition of SiC in HZTNC suppressed these microcracks at high temperatures due to the active oxidation of SiC.Compared with the oxides formed on HZTNC,the additional formation of Hf(Zr)SiO4 on HZTNC-SiC could further improve its oxidation resistance over HZTNC ceramics.  相似文献   

15.
Transparent glass samples in (100-3x) (Li2O-2B2O3)-x(SrO-Bi2O3-0.7Nb2O5-0.3V2O5) (10 < or = x < or = 60, in molar ratio) system have been fabricated via conventional melt-quenching technique. The as-quenched samples, of all the compositions under study have been confirmed to be amorphous, by X-ray powder diffraction (XRD) studies. Differential thermal analysis (DTA) was employed to confirm the glassy nature of the as-quenched glasses. Glass composites comprising vanadium doped strontium bismuth niobate nanocrystallites were obtained by controlled heat-treatment of the as-quenched glasses at 783 K for 6 h. Perovskite SrBi2(Nb0.7VO3)2O9-delta phase formation was found to be preceded by an intermediate fluorite phase which was established via XRD and transmission electron microscopy (TEM). The dielectric constants (epsilonr) of the as-quenched glasses as well as the glass nanocrystal composites decreased with increase in frequency (100 Hz-10 kHz) at 300 K. Interestingly, the dielectric constant of the glass nanocrystal composite (heat-treated at 783 K/6 h) undergoes a maximum in the vicinity of the crystallization temperature of the host glass (Li2B4O7) reaching an anomalously high value (approximately 10(6)) at 800 K. Different dielectric mixture formulae were employed to rationalize the dielectric properties of the glass nanocrystal composite. The optical transmission properties of these glass nanocrystal composites were found to have strong compositional dependence.  相似文献   

16.
Lead-free (K0.5Na0.5)(Nb0.7Ta0.3)O3 piezoelectric material was successfully synthesized via a sol-gel process. Crystalline (K0.5Na0.5)(Nb0.7Ta0.3)O3 nanopowders were obtained after heat treatment at 700 degrees C. The particle size was estimated to be 87nm +/- 23 nm. The transmission electron microscopy images showed that individual nanoparticles were single crystalline and had a pseudo-cubic structure with a lattice parameter of -3.96 angstroms. Both X-ray diffraction and scanning electron microscopy studies consistently showed that the crystallization of the (K0.5Na0.5)(Nb0.7Ta0.3)O3 occurred slightly above 500 degrees C. The samples have an appropriate stoichiometry as found via energy dispersive X-ray spectroscopy. The demonstration of the synthesis of (K0.5Na0.5)(Nb0.7Ta0.3)O3 via a sol-gel process as presented in this paper can provide an important foundation for the development of a synthetic route towards (K0.5Na0.5)(Nb0.7Ta0.3)O3 doped with various other elements for high performance piezoelectric devices.  相似文献   

17.
赵景畅  鲍慈光 《功能材料》1999,30(4):397-398,401
利用H2/H2O体系获得不同的氧分压,上电极法 掺杂SrLi1/4Nb3/4O3的SrTiO3瓷体在800-1200℃,Po2=10^17-10^5Pa的电导率。通过logPo2-logσ图,计算出半导化活化焓约为287.7kJ/mol,讨论了SrLi1/4Nb3/4O3掺杂的SrTiO3在不同氧分压区域的主n型半导体化向p型半导化转变的特点。  相似文献   

18.
Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed.  相似文献   

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