【作者】 马杰；

【导师】 吴庆生；

【作者基本信息】 同济大学 ， 无机化学， 2008， 博士

【摘要】 稀土含氧酸盐作为一类重要的功能性材料被广泛的研究和开发。随着纳米科技的发展,如何构筑此类物质的纳米结构材料也已成为一个研究热点。本论文首先探索和建立了一种简单的、温和的、绿色的、经济的构筑方法——固相水热法（Solid phase hydrothermal route,S-HT）或称为氧化物水热法（Oxides-Hydrothermal Method,O-HT）。它与经典的水热法的最主要的区别在于:O-HT路线选择的反应前驱体均为常温下不溶于水的氧化物,后者一般选用的反应前驱体是溶于水的稀土盐类。和后者相比其优点表现在:成本低、简化了工艺、无副产物、减少了环境污染,晶体的缺陷和杂质离子的污染少。利用稀土氧化物和五氧化二钒为前驱体经O-HT路线成功地构建了多种稀土正钒酸盐纳米结构材料。首次实现利用常态下不溶于水相的物质以水为介质的水热合成反应,证实了O-HT路线的可操作性。研究了体系的温度、时间、添加剂、酸度对产品的晶型、生长状况及形貌的影响;在O-HT反应体系下,实现LnVO₄纳米材料晶相和形貌的控制;实验发现利用红外光谱可以辅助判定LaVO₄的晶相类型;提出了稀土钒氧化合物在氧化物水热合成体系中的自磨-水解-结晶生长机制（Self-Milling Hydrolysis Crystallized Mechanism,SMHCM）及添加剂控制下的溶解-结晶机制;研究了YVO₄和Eu³⁺掺杂的LaVO₄的荧光性能。在上述研究的基础上,在无任何助剂的条件下,又以稀土氧化物和三氧化二硼为原料经O-HT路线构筑了系列的稀土正硼酸盐棒、束或片状纳米材料,探讨了其合成条件。首次构建出多层自组装的纳米片状稀土正硼酸盐纳米材料（厚度大约50 nm,直径可达10-13μm）,并证实硼酸钕具有不同于通常报道的六方相晶体结构;详细地考察了影响六方相硼酸钕纳米片状晶体生长和形貌的包括温度、时间、填充度和酸碱度等多种因素,热不可逆相变化特征,以及其形成因素;考察了六方相稀土硼酸盐纳米材料的构建的难易程度与稀土离子半径的递变规律;得到经O-HT路线合成硼酸铒和硼酸钇纳米材料的条件;通过稀土掺杂过程可以实现加速或减缓晶体生长的速率;探讨了Sm³⁺和Dy³⁺掺杂的LaBO₃纳米棒的荧光性能;揭示了合成稀土正硼酸在O-HT体系中的两步骤反应机制。对O-HT路线进行了有益的拓展,利用稀土氧化物与五氧化二磷或磷酸为前驱体、不控制溶液的酸碱度、无任何助剂的条件下合成了系列稀土正磷酸盐纳米棒（直径约为20-30 nm,长径比达400-500）和纳米粒子,探讨了温度、时间、P/La摩尔比、添加剂或溶剂对产品的晶相、尺寸及形貌的影响。在所考察的温度范围内,首次展示密闭的含水体系P/La摩尔比（≥1）对产品晶相没有影响,但是对产品的形貌有重要影响:首次展示了溶剂的变化对产品的形貌有重要影响;合成系列Sm³⁺和Dy³⁺掺杂的LaPO₄纳米棒;揭示了O-HT路线下,稀土磷酸盐REPO₄（RE=La—Dy）由六方相含水晶相向单斜无水相转变的生长过程。三类稀土无机化合物纳米材料经O-HT路线的成功获得,可以预见O-HT法不仅具有重要的研究价值和广泛的适用性,也具有广阔的应用前景。更多还原

【Abstract】 Rare earth oxysalts have been widely investigated and applied as one series important functional materials. It has been a hot topic field how to product their nanostructure materials.The dissertation is devoted to quest for and establish a facile, eco-friend, low-cost mild approach to metal oxysalt nano-material, which is named as solid phase hydrothermal （S-HT） or oxides-hydrothermal method （O-HT）. This method the most essentially differ from the classical hydrothermal method as follow: the former directly utilizes insoluble/slight-soluble oxides as precursors, and the latter uses soluble rare earth salt as reagent. Compared with the latter, the 0-HT method exhibits many advantages, such as no side-products, facile operation, low cost, special crystal structure and morphology, and the prefect crystallization.The series of REVO₄ （RE= La, Nd, Sm, Y） and rare earth ion doped REVO₄ nanomaterials are facilely fabricated by the O-HT route directly used insoluble V₂O₅ and RE₂O₃ as precursors under appropriate conditions. It is original to accomplish the hydrothermal synthesis reaction among common insoluble reagents in water system and substantiates the feasibility of the O-HT route. The influences of many factors included temperature, time, additives, pH value of the system on products are investigated. The pure rodlike monoclinic （m-） and tetragonal phase （t-） LaVO₄ nanocrystals also are controllably constructed via the oxides-hydrothermal approach. It is found that FTIR spectra can be used as a simple means to detect crystal phase of LaVO₄. The self-mill hydrolysis crystallized mechanism （SMHCM） and dissolution-precipitation mechanism controlled by additives are hypothesized to interpret the rare earth orthovanadate nanomaterials obtained and controlling phase transition in 0-HT system. The fluorescence properties of YVO₄ and Eu³⁺ doped LaVO₄ nanomaterials are investigated.Based on above result, By O-HT approach, the REBO₃ （RE= La, Nd, Sm, Dy, Gd, Er, Y） and some ion doped REBO₃ nanomaterials are firstly obtained by mixing stoichiometric rare earth oxide Ln₂O₃ and boric oxide B₂O₃ into proper deionized water in a surfactant-free system, and the formation conditions of the nanomaterials are investigated. Pseudo-vaterite NdBO₃ and its self-assembled layer-by-layer （SALBL） nanopancakes （the thickness ca.50nm with the size ca. 10-13μm） are originally obtained via the O-HT route. The influences of treatment time, temperature, filling ratio, and pH value of solution on the hexagonal NdBO₃ nanopancakes, the thermal stability and irreversible phase transition properties, and the formation factors of pseudo-vaterite NdBO₃ crystal in O-HT system are investigated. The relationship between ionic radium and crystal growth of hexagonal REBO₃ nanomaterials are discussed. The preparing condition of pure ErBO₃ and YBO₃ nanomaterials are ascertained in the O-HT routes. It is firstly found that the crystal growth rate can be modified by different ions doped processes. The fluorescence properties of Sm³⁺ and Dy³⁺ doped LaBO₃ nanorods are investigated. And the two-step reaction mechanism is found and confirmed.The O-HT route is extended to prepare rare earth phosphates. Many REPO₄ （RE= La, Nd, Sm, Tb, Gd, Dy, Er, Y,） nanorods （the diameter ca. 20-30 nm with the aspect ca. 400-500） or nanoparticles are initially synthesized by mixing RE₂O₃ and P₂O₅ or H₃PO₄ via pH-free and additive-free oxides-hydrothermal process. The effects of time, temperature, P/La molar ratio on the products additive and solvent for LaPO₄ nanorods, and some factor for other lanthanum orthophosphate are investigated thoroughly. It is firstly demonstrated that the P/ La ratio （>1） can not influent the composition but the sizes and morphologies of products in the inspected O-HT system. It firstly confirmed that additives and solvent significantly influent the size and shapes of the LaPO₄ nanomaterials. It is firstly exhibited the phase transition growth mechanism of the REPO₄ （RE=La—Dy） nanomaterials in O-HT system.In summary, the O-HT route exhibits important applicable value in nanosciences and nanotechnologies, and great industizal prespect in future.更多还原