有序多孔氧化锆材料的合成及其改性研究

2019-02-22 18:12:48

多孔 porous 氧化锆 有序 oxide









中文题名有序多孔氧化锆材料的合成及其改性研究

 





副题名 





外文题名 





论文作者陈航榕   





导师严东生院士  施剑林研究员   





学科专业材料科学与工程   





研究领域\研究方向 





学位级别博士 





学位授予单位中国科学院上海硅酸盐研究所   





学位授予日期2001   





论文页码总数126页   





关键词氧化锆  纳米材料  有序多孔氧化锆   





馆藏号BSLW

/2001

/TB383

/66 





【中文摘要】

    本文以十六烷基三甲基溴化胺为模板剂,按照表面活性剂辅助模板途径,采用水热合成工艺进行有序多孔氧化锆材料的合成。研究表明,高质量有序多孔氧化锆材料的合成与反应体系中表面活性剂与锆源的合适摩尔比以及适当的水热处理温度有关;同时将前驱体粉料经过一定浓度的磷酸进行后处理,可有效提高多孔氧化锆材料的热稳定性。
   利用荧光分光光度仪,我们首次在室温下观测到了有序多孔氧化锆材料的荧光发射谱。借助紫外—可见吸收光谱(UV-vis)、顺磁共振图谱(EPR)等分析手段对其特殊的荧光发射现象进行了分析探讨。研究表明,有序多孔氧化锆材料其特殊的荧光发射现象是材料本身结构所特有的,并与磷酸后处理工艺有关。这对进一步开发研究这种材料在光电领域的应用具有潜在的应用前景。
   在成功合成高质量有序多孔氧化锆的基础上,借助XRD、N〓吸附脱附分析、HRTEM、EDS、Raman、XPS以及UV-vis等分析手段,我们还进行了过渡金属离子的掺杂改性、稀土氧化铈负载型催化材料的合成以及氧化物纳米团簇在孔道中的组装等方面的研究。
   利用直接水热合成法,我们首次报道了高含量过渡金属Ti在有序多孔氧化锆骨架中的掺杂。研究表明,钛取代锆位进入氧化锆墙体中的最大掺量可达20mol%,并且适量钛的掺入能使基体材料的比表面积和热稳定性得到明显的改善,同时钛的掺杂可使多孔氧化锆基体材料的吸收峰强度明显增强,并且随着钛掺量的增加,掺杂试样发生有规律的吸收边红移现象,这对于进一步在光电器件等方面的应用研究有潜在的意义。
   利用液相移植工艺,我们合成了氧化铈负载型的有序多孔氧化锆催化材料,并对其表面氧性质进行表征。研究表明,利用液相移植工艺可将稀土元素铈成功负载入有序多孔ZrO〓基体材料中,但能够进入氧化锆骨架中的铈含量较低(<4mol%),多余的铈将以氧化铈纳米晶形式分散在孔道中或孔道表面。该复合体系呈现出优异的氧化—还原性能,并且其稀土元素铈的用量较传统方法大大降低。进一步担载上贵金属Pt后,可进一步降低铈锆催化体系的还原温度,促进氧的迁移性,这在催化反应方面具有实际应用价值。
   利用醇溶液浸溃法及后续的热处理工艺成功实现了氧化锰团簇粒子在有序多孔氧化锆孔道中的组装。研究表明,氧化锰团簇粒子能较均匀地分散于规则的孔道中,团簇粒子的存在使有序多孔氧化锆材料的比表面积及孔容量显著降低,但孔道的有序结构仍然较好保存。并且观测到,随着热处理温度的提高,团簇粒子的生长受到孔道大小的限制。借助EPR分析手段,研究同时发现,存在于孔道中的氧化锰团簇粒子显示出与较大尺寸氧化锰粒子完全不同的强顺磁信号。此外,对锰负载试样的O〓-TPD分析表明,组装于氧化锆孔道中的氧化锰团簇粒子还具有优异的表面氧吸附特性,其催化活性中心不仅包括氧化锰本身的晶格氧,还包括Mn/ZrO〓体系的表面吸附氧。这对于开发新型顺磁材料以及氧化还原催化材料等具有潜在的应用价值。











【外文摘要】

 Abstract
   This paper focuses on the synthesis of thermally stable mesostructure zirconium oxide with a surfactant templating technique. It was shown that the suitable molar ratio of the surfactant to zirconium as well as the suitable temperature of the hydrothermal treatment are of great importance in the synthesis of high quality porous zirconium oxide material. Besides, under the suitable concentration treatment, the phosphoric acid can greatly enhance the thermal stability of the porous material.
   Photoluminescence (PL) measurements show that two strong PL bands were emitted at room temperature in the ordered porous zirconium oxide material. The UVVis spectroscopy and Electron Paramagnetic Resonance (EPR) spectroscopy were adopted for the investigation on the PL effects. It was concluded that the two PL bands are related to the structure of the porous oxide. In addition, the suitable treatment concentration of phosphoric acid is believed to be an important parameter to generate the PL responses. The significant optical properties of this new material may be very interesting for its potential application in the photoelectric fields.
   On the basis of the successful synthesis of high quality zirconium oxide with ordered pore structure, various techniques have been developed to modify the ordered porous ZrO〓, as to explore more interesting chemical and physical properties for possible applications. X-ray powder diffraction, N〓 adsorption analysis, HRTEM, Raman, XPS, UV-Vis spectroscopy, and EPR spectroscopy were adopted for the characterization of the synthesized materials.
   The ordered porous zirconium oxide incorporated with high amounts of titanium was reported in the paper for the first time, via a direct-hydrothermal synthesis procedure. The experimental results show that titanium ions are homogeneously dispersed into the framework of ZrO〓, when the amount of titanium doping is not higher than 20mol%. And a suitable amount of titanium incorporation is favorable to the thermal stability of the porous zirconium oxide. Furthermore, the increased intensity of absorption peaks and the magnitude of red-shift of the adsorption bands correspond well to the amount of the Ti incorporation. These new Ti-ZrO〓 materials may be potentially useful as novel catalytic or photoelectric materials.
   Cerium incorporated ordered porous zirconia materials have been prepared by a solution grafting method. EPR analysis was adopted for the characterization of the surface oxygen properties of the synthesized materials. It was shown that small amount of cerium had been successfully incorporated into the framework of ZrO〓 at a cerium loading not higher than 4mol%. The excess cerium was separated out as CeO〓 nano-crystallites on the surface or in the pore channels. The synthesized ceria/zirconia porous material shows excellent oxidation and reduction properties. Also, the amount of cerium used can be much reduced than that in the traditional method. After further loading with the noble metal Pt, the temperatures for catalysis reduction of the ceria/zirconia porous material can be greatly decreased, which could be expected to have important applications in practical catalysis.
   Manganese oxide nanoclusters were synthesized within ordered porous ZrO〓 by using wet impregnation technique. The results indicate that the nanoclusters of manganese oxide could be successfully confined and uniformly distributed into the pores of ZrO〓. XRD and TEM investigations showed that the ordered porous host structure was still maintained after loading with MnO〓. The UV-absorption edge is found to have a significant red-shift at the elevated heat treatment temperature, and the grow of the nanoclusters have shown to be restrained by the dimension of the pore channels. EPR measurement shows that there is a significant change in their magnetic property of the nano-sized clusters which were confined in the pore channels as compared to ordinary MnO〓 particles. In addition, the excellent oxygen adsorption properties of the manganese oxide clusters confined in the pore channels have been found by a O〓-TPD analysis. It is believed that the active catalysis centers include both the lattice oxygen of MnO〓 as well as the surface adsorbed oxygen on the Mn/ZrO〓 material surface. It could be expected to have potential applications in catalysis or be used as a novel paramagnetic material.