【作者】 田广茹；

【导师】 孙思修；

【作者基本信息】 山东大学 ， 无机化学， 2009， 博士

【摘要】 作为材料科学发展的先导,纳米材料的设计合成,是材料得到进一步研究并推广应用的基础。如何探索发展纳米材料设计与合成的新途径、新方法,始终是纳米材料研究领域中的一个重要课题。目前合成纳米材料的方法虽然很多,但获得尺寸可控、粒度均匀的纳米材料仍然存在一定的困难,因此探索一种设计简单、操作方便、成本低、产率高的方法,来实现对纳米材料的尺寸大小、粒径分布以及晶体结构和形貌的控制仍然是化学家和材料学家关心的课题之一。本论文以含铬族元素的氧化物、含氧酸盐为研究对象,探索前驱体煅烧法、双表面活性剂微乳/反胶束法、软模板法、微乳液法等方法在制备材料、控制材料的结构、形貌和尺寸方面的作用,期望得到形貌可控、性能优良的微/纳米材料。论文的主要工作总结如下:1、采用前躯体煅烧法制备无机纳米材料的合成技术,利用有机碱的缓慢水解,用不同的铬源,在水和乙醇或者其他混合溶剂中进行水热反应,首先制得前躯体Cr（OH）₃,然后通过煅烧得到Cr₂O₃纳米粒子。使用不同的铬源得到的前躯体大部分是球形形貌。改变溶剂成分,对前躯体的形貌没有明显的影响。影响前躯体和最终产物尺寸大小的主要因素是所使用的有机碱（沉淀剂）的种类。2、选择性地合成了两种铬酸盐。（a）通过调节双表面活性剂反胶束溶液的pH值,并以水热法辅助制得了Pb₂CrO₅纳米棒。该反胶束溶液由阳离子表面活性剂十六烷基三甲基溴化铵CTAB和阴离子表面活性剂十二烷基磺酸钠SDS组成。发现表面活性剂的种类、混合胶束中阳离子和阴离子表面活性剂的摩尔比、反应时间和温度,在单晶Pb₂CrO₅的形成和生长过程中起到重要作用。这种双表面活性剂形成的反胶束体系可以作为一种很有前途的溶液中合成一维无机纳米结构的介质。（b）尝试了一种便捷有效的新的胶束体系,这种PVP/H₂O/环己醇的新胶束体系在低温下合成正交相的BaCrO₄微纳材料非常实用。与传统的以烷烃作为油相的微乳液相比,这种新的胶束体系表现出一定的特殊性。环己醇形成油相,提供了一种高度均一的环境,得到的产品大小均一,分布均匀,并且不需要极端的温度和压力,不需要其他的特殊仪器设备,易于操作。3、通过两种不同的方法合成了BaMoO₄微/纳米材料。（a）通过调节双表面活性剂组成的反胶束的pH值并辅助以水热法制得了具有三维双锥构型的单晶BaMoO₄微晶,该反胶束由阳离子表面活性剂十六烷基三甲基溴化铵CTAB和阴离子表面活性剂十二烷基磺酸钠SDS组成。实验中发现,外部条件,例如两种表面活性剂的摩尔比、反应时间和温度对产物的结晶和形貌演变进程没有什么重要影响。晶体的内部的性质才是决定这种特殊形貌的真正决定因素。双表面活性剂的共存以及定向聚集和奥斯特瓦尔德熟化的协同作用对晶体的形成起着重要的作用。混合的阳离子-阴离子双表面活性剂对溶液中BaMoO₄微晶的生长施加了一种微妙的控制,比在相同条件下单独添加一种表面活性剂表现出强大的优势。这种合成策略为在溶液中制备多级的三维的纳米或微米结构提供了一种新途径。（b）在温和条件下,使用柠檬酸盐作为一种简单添加剂,成功制得了高质量的由纳米颗粒、纳米纤维自组装形成的哑铃状、纺锤状和麦穗状单晶BaMoO₄。随着一些实验参数的调节,产品的形貌发生了一系列的变化。这种合成策略或许能够为在溶液中温和条件下合成多级组装纳米或微米结构提供一种新的途径。此外,BaMoO₄产品的光学性质也通过光致发光波谱进行了表征。这些简便易得的方法可以推广至其他的无机体系。4、丰富了添加剂辅助的化学液相合成技术。分别采用柠檬酸钠和十六烷基三甲基溴化铵作为模板,合成了SrWO₄微/纳米材料。（a）当反应体系中加入柠檬酸钠,SrWO₄纳米晶随着反应时间和反应条件的变化,所表现出的一个新奇的从零维微球到一维棒状或者带状,再到零维梭状颗粒的形貌变化。与传统的从零维到一维再到三维的生长过程相比,在这种情况下,零维的微球易得,但是这种形貌与最终的产品形貌不同。详细的实验结果表明,柠檬酸盐的添加和水热反应的条件和反应时间控制着SrWO₄纳米晶的形貌演变过程。（b）我们用十六烷基三甲基溴化铵CTAB作为模板合成了SrWO₄微球,并通过对比实验推测了其生长过程。此外,SrWO₄产品的光学性质也已经通过光致发光光谱进行了表征。上述实验方法可以推广至制备其他的材料,有目的地合成特殊的零维或一维结构。更多还原

【Abstract】 The synthesis and design for the nanomaterials, as forerunner of the material science, are the base of the application and the future development of nanoscience and nanotechnology. Up to now, it is still important task in the field of materials that how to develop a new method for preparing nanomaterials. Although there are many methods reported for preparing nanomaterials, it is still difficult to obtain materials with controllable morphologies and sizes. Therefore, it is attracting a great deal of attention of the chemists and materials researchers to explore a new method for obtaining low-cost mild reaction.In this dissertation, we focused on the synthesis and characterization of micro/nanomaterials of oxide and oxysalt of chromium, molybdenum and tungsten. We used precursor-calcined technique, catanionic reverse micelles method, soft-model technique and microemulsion method to get structure, morphology and size-controlled materials. Main points are summarized as follows:1. Precursor-calcined technique was developed to synthesize inorganic nanoscale materials. Organic alkali hydrolyzed slowly in H₂O and C₂H₅OH or the other mixed solvent. We got the precursor Cr（OH）₃ from the reaction of chromium salt and organic alkali in the above system. Then the precursor was calcined in the muffle at 600℃for 3 hours, and the final products Cr₂O₃ was obtained. Using different chromium salt, we got sphere-like precursor. The morphology of the precursor was almost the same in different solvent system. The kinds of organic alkali had the most important influence on the morphology and size of the precursor and product.2. We selectively synthesized two kinds of chromate. （a） Single-crystalline Pb₂CrO₅ with nanorod-shape has been synthesized by adjusting the pH value of the catanionic reverse micelles formed by a cationic surfactant CTAB and an anionic surfactant SDS, followed by a hydrothermal process. Discussion and analysis indicate that the kinds of the surfactants, the molar ratio （r） between the mixed cationic and anionic surfactants, reaction time and temperature play important roles in the crystallization and morphologies of Pb₂CrO₅ nanocrystals. Such catanionic reverse micelles systems may present promising media for the solution synthesis of one-dimensional inorganic nanostructures. （b） On the basis of relative references, we tried a facile, effective and new micelle system to synthesize micro/nanomaterials. In the new micelle system of PVP/H₂O/ cyclohexanol, BaCrO₄ micro/nanomaterials were synthesized practically in the low temperature. In comparison with the traditional microemulsion in which alkyl hydrocarbon was the oil phase, the new micelle system exhibited some particularity. Cyclohexanol as the oil phase can afford a stable and homogeneous reaction environments. And we could get products with uniform size and well-proportioned distribution. There was no need of extreme temperature and press in the system, and the equipment was simple and easy-controlled.3. We synthesized BaMoO₄ micro/nanomaterials through two kinds of different method, （a） Single-crystalline BaMoO₄ microcrystals with 3D bipyramidal-like architectures were synthesised by adjusting the pH value of the catanionic reverse micelles formed by a cationic surfactant CTAB （hexadecyltrimethylammonium bromide） and an anionic surfactant SDS （sodium dodecyl sulfonate）, followed by a hydrothermal process. It was found that the external conditions such as the molar ratio of the two kinds of surfactants, reaction time, and temperature had no crucial influence on the crystallisation and the shape evolution of the products. The internal properties of the crystals were the real reason for the typical morphology. The coexistence of the dual surfactants and the cooperation of oriented attachment and Ostwald ripening played important roles in the formation of the crystals. （b） Large-scale high-quality BaMoO₄ nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have dumbbell-like, spindle-like and wheatear-like morphologies assembled from nanoparticles, nanofibers. The results showed experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. In addition, the optical properties of the BaMoO₄ products had been examined by PL spectrum. Furthermore, the feasibility and ease of this synthesis route are worth exploring for other inorganic systems.4. An additive-assisted solution-phase approach was developed to prepare SrWO₄ micro/nanomaterials. （a） We report a novel shape evolution of SrWO₄ crystals from 0-D microspheres to 1-D rods or belts and to 0-D shuttle-like particles with prolonged reactiontime and special reaction conditions. In contrast to the traditional crystal growth from 0-D to 1-D to 3-D, in this case, 0-D microparticles were easily obtained within a short reaction time, but it was different with the final products. Detailed experimental results revealed that the addition of the citrate and the hydrothermal reaction conditions and reaction time controlled the shape evolution of the SrWO₄ crystals. （b） We used CTAB as a model to synthesize SrWO₄ microspheres in the solution. In addition, the optical properties of the SrWO₄ products have been examined by PL spectrum. This method can be extended to other materials to purposefully prepare 0-D and 1-D structures.更多还原