钼钨（复合）氧化物微纳米结构的形貌可控合成及其在光致发光和锂离子电池中的应用

发布时间：2018-05-31 04:05

本文选题：La_2(WO_4)_3 + NaLa(WO_4)_2　；参考：《南京大学》2014年博士论文

【摘要】：本论文通过水热合成法制备了La2(WO4)3纳米晶、NaLa(WO4)2微纳米晶、MoO2微米空心球以及MoO2纳米空心球等几种钼钨(复合)氧化物的微纳米结构,并成功实现了对NaLa(WO4)2形貌和尺寸以及对Mo02微米空心球内部空间大小的调控。利用粉末X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)等手段对所得材料的晶相、结构、尺寸和形貌等进行了详细的表征,并基于这些表征提出了在不同反应条件下所得不同结构的形成机理。最后,通过荧光光谱(PL)、电化学工作站和锂离子电池性能测试系统等考察了所得材料的光致发光性能或锂离子电池阳极材料性能,并揭示微纳米材料的性能与其结构之间的内在联系。主要内容概括如下：1.纯相La2(WO4)3:Eu3+纳米晶和纺锤状NaLa(WO4)2:Yb3+/Er3+微纳米晶：选择性合成、形貌以及光致发光性能基于同一反应体系选择性合成了纯相La2(WO4)3纳米晶和均一的纺锤状且尺寸可调的NaLa(WO4)2微纳米晶。研究显示Na+对选择性合成起着至关重要的影响；后续的水热处理对La2(WO4)3的形貌有很大影响；水热温度,水热时间以及甘油添加量对NaLa(WO4)2的形貌和尺寸都有很重要的影响。基于时间依赖实验,提出了纺锤状NaLa(WO4)2的形成机理为奥斯特瓦尔德熟化。所制备的La2(WO4)3:Eu3+纳米晶在467 nm激光激发下能发射出纯度很高的明亮的红光,更为重要的是其能很好地分散在蒸馏水中。在980 nm红外激光激发下,NaLa(WO4)2:Yb3+/Er3+的上转换发射强度随其中Yb3+含量的增加而快速增加,表明了从Yb3+到Er3+的高效能量传递。另外,随着其中Yb3+含量的增加,发光色能从黄绿色变为绿色。La2(WO4)3和NaLa(WO4)2的这些独特性质与它们独特的晶体晶格紧密相关。2.形貌可控合成NaLa(WO4)2:形貌依赖的光致发光性能以及单相白光荧光粉NaLa(WO4)2:Tm3+/Tb3+/Eu3通过添加极少量的EDTA-2Na,在水热条件下制备了均一的NaLa(WO4)2单晶微米纺锤。同时,通过简单的调节添加剂用量以及反应溶剂的比例可使产物的形貌调变为微米平板、纳米晶、亚微米哑铃以及互相连接的孪微米球。通过对比NaLa(WO4)2:Eu3+微米纺锤和微米平板的光致发光性能,发现NaLa(WO4)2:Eu3+微米纺锤有更强烈的荧光发射强度,并进一步探讨了其中的可能原因。更重要的是,由于Tm3+, Tb3+向Eu3+的有效能量传递,通过调节优化Tm3+、Tb3+和Eu3+在NaLa(WO4)2微米纺锤基质中的摩尔比例,成功制备了新型的近紫外激发的单相白光荧光粉NaLa(WO4)2:Tm3+/Tb3+/Eu3+。3.MoO2@C微米空心球的合成及其显著提高的锂离子电池阳极材料性能以Mo03微米带取代体相Mo03作为起始原料,通过简单的水热过程制备了内部空间大小可调的Mo02微米空心球。实验结果表明反应物的形貌对产物的形貌有很重要的影响,且可通过改变NaOH水溶液的添加量来调节微米空心球的内部空间大小,接着我们进一步提出了Mo02微米空心球可能的形成机理。结合水热法及煅烧步骤,在MoO2微米空心球表面包覆了一层无定形碳。所制备的Mo02@C微米空心球作为锂离子电池的阳极材料显示了高的比容量及库仑效率、优异的循环稳定性及倍率性能。MoO2@C微米空心球显著提高的锂离子电池阳极材料性能可归因于其合理的结构设计,如纳米尺度的基本构建单元、导电碳包覆和中空结构等,尤其是碳包覆与中空结构之间的协同效应。4.均一Mo02@C纳米空心球的简易制备及其优异的储锂性能通过简单的软模板水热方法结合后续的煅烧处理合成了尺寸200 nm左右的MoO2@C纳米空心球,并阐述了MoO2@C纳米空心球可能的形成机理。这一方法有效的将材料制备与碳层包覆整合为一个步骤,有利于材料的工业化制备。由于MoO2@C纳米空心球独特的结构,如极小的构建单元,中空结构,碳包覆,因而展现了优异的储锂性能,如高的可逆容量(909.8 mAh·g-1),良好的循环稳定性以及优异的倍率性能。
[Abstract]:In this paper, the microstructures of La2 (WO4) 3 nanocrystals, NaLa (WO4) 2 micronanocrystals, MoO2 micron hollow spheres and MoO2 nano hollow spheres were prepared by hydrothermal synthesis method. The morphology and size of NaLa (WO4) 2 and the internal space size of Mo02 micrometer hollow spheres were successfully realized. Powder X rays were used. Diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) are used to characterize the crystalline phase, structure, size and morphology of the obtained materials. Based on these characterization, the formation mechanism of different structures under different reaction conditions is proposed. Finally, the fluorescent light is used. Spectrum (PL), electrochemical workstation and lithium ion battery performance testing system have been used to investigate the photoluminescence properties of the materials or the properties of lithium ion battery anode materials, and reveal the internal relations between the properties of the micro and nanomaterials and their structures. The main contents are as follows: 1. pure phase La2 (WO4) 3:Eu3+ nanocrystals and spindle NaLa (WO4) 2:Yb3+/Er 3+ micro nanocrystals: selective synthesis, morphology and photoluminescence properties are selective synthesis of pure phase La2 (WO4) 3 nanocrystals and homogeneous spindle like and adjustable NaLa (WO4) 2 micro nanocrystals based on the same reaction system. Studies show that Na+ plays a vital role in selective synthesis; followed by hydrothermal treatment on the morphology of La2 (WO4) 3. The effect of hydrothermal temperature, hydrothermal time and glycerol addition on the morphology and size of NaLa (WO4) 2 is very important. Based on the time dependence experiment, the formation mechanism of the spindle like NaLa (WO4) 2 is developed in Ostwald. The prepared La2 (WO4) 3:Eu3+ nanocrystals can emit a high purity under the 467 nm laser excitation. Bright red light and more important is that it can be well dispersed in distilled water. Under 980 nm infrared laser excitation, the upconversion intensity of NaLa (WO4) 2:Yb3+/Er3+ increases rapidly with the increase of Yb3+ content, indicating the efficient energy transfer from Yb3+ to Er3+. In addition, with the increase of Yb3+ content, the luminescent color can be from yellowish green. These unique properties changed into green.La2 (WO4) 3 and NaLa (WO4) 2 with their unique crystal lattice closely related to.2. morphology to synthesize the photoluminescence properties of NaLa (WO4) 2: morphologies and the single-phase white light phosphor NaLa (WO4) 2:Tm3+/Tb3+/Eu3 by adding a very small amount of EDTA-2Na, and preparing a homogeneous 2 single crystal under the hydrothermal condition. At the same time, the morphologies of the products can be modulated into micron plates, nanocrystals, submicron dumbbell and interconnected twin microspheres by simply adjusting the amount of additives and the proportion of the reactive solvents. The NaLa (WO4) 2:Eu3+ micron spindle has been found by comparing the photoluminescence properties of the NaLa (WO4) 2:Eu3+ micron spindle and the micron plate. The stronger fluorescence intensity and possible reasons are further discussed. More importantly, the new type of single-phase white phosphor NaLa (WO4) 2:Tm3+/T of a new type of near ultraviolet excitation is successfully prepared by adjusting the effective energy transfer of Tm3+, Tb3+ to Eu3+, and by adjusting the molar ratio of Tm3+, Tb3+ and Eu3+ in the 2 micron spindle matrix of NaLa (WO4). The synthesis of b3+/Eu3+.3.MoO2@C micron hollow sphere and its remarkable improvement in the performance of lithium ion battery anode material with Mo03 micron band instead of the body phase Mo03 as starting materials, the inner space and adjustable Mo02 micrometer hollow spheres are prepared by a simple hydrothermal process. The experimental results show that the morphology of the reactants is very important to the morphology of the products. The internal space of the microspheres can be adjusted by changing the amount of the NaOH aqueous solution. Then we further put forward the possible formation mechanism of the Mo02 microsphere hollow sphere. In combination with the hydrothermal method and the calcination step, a layer of amorphous carbon is coated on the surface of the hollow sphere of the MoO2 micron. The prepared Mo02@C microsphere hollow sphere is used as the lithium separation. The anode material of the subbattery shows a high specific capacity and coulomb efficiency. The excellent performance of the anode material of the.MoO2@C micron hollow sphere is due to its reasonable structural design, such as the basic construction unit of nanoscale, the conductive carbon coating and the hollow structure, especially the carbon coating. The synergistic effect between the hollow structure and the.4. homogeneous Mo02@C nano hollow sphere is easy to be prepared and its excellent lithium storage properties have been synthesized by a simple soft template water heat method combined with subsequent calcination, and the possible formation mechanism of MoO2@C nano hollow spheres is described. This method is effective. The combination of material preparation and carbon coating is beneficial to the industrialization of materials. Due to the unique structure of MoO2@C nanospheres, such as small construction unit, hollow structure, carbon coating, it shows excellent lithium storage properties, such as high reversible capacity (909.8 mAh. G-1), good cyclic stability and excellent multiplier. Performance.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM912;TB383.1

【相似文献】