【作者】 娄骁；

【导师】 翁文剑；

【作者基本信息】 浙江大学 ， 材料学， 2010， 博士

【摘要】 材料合成与制备的发展趋势是实现从源物质到目标材料的全过程控制,以调控材料的组成、结构和性能。本文选择水基湿化学合成方法,分别以沉淀和溶液燃烧方式合成了以硒化镉和钛酸钡盐为代表的非氧化物和氧化物材料,并针对合成条件控制、产物组分控制、过程中间相形成及其对目标材料合成的影响等问题,开展了深入的研究。主要研究内容如下:（1）为了克服传统非水体系合成CdSe纳米晶需采用复杂的有机先驱体、高反应温度和复杂的反应装置等缺陷,本文采用水溶性先驱体,在水溶液中合成了不含氧化物杂质的CdSe和CdSeS纳米晶。CdSe的形成过程中温度、酸碱度和反应时间起到了重要作用:在pH=12,T=80℃,t=5h时,最有利于高纯的CdSe的形成;其中OH^-控制了含Se前驱体向溶液中释放Se^2-,在CdSe形成中起到了决定性的作用。（2）为了改善CdSe纳米晶的可分散性并增强其发光性能,本文采用有机聚合物（PVA）和双官能团巯基酸类化合物分别在水基体系中直接对CdSe纳米晶进行表面修饰改性,以改善纳米晶粒分散性,提高其荧光性能。经巯基丙酸表面修饰改性后,CdSe纳米晶可通过巯基丙酸的羧基端与牛血清白蛋白V（BSA）的氨基端发生脱水缩合形成肽键,从而与BSA结合,并显示出对蛋白质分子良好的荧光标识性能。（3）为了采用水基湿化学方式合成纯相Ba₂Ti₉O₂₀,本文研究了溶液干燥方式对所得干胶的均匀性及相组成等的影响,发现平板快速干燥有利于获得高度均一的干胶,进而有利于合成纯相Ba₂Ti₉O₂₀。在此基础上采用溶液直接均匀加热、燃烧的方式获得了高度均一的前驱体粉末。并通过调节初始溶液中硝酸根/柠檬酸（n/c）比的变化,对其燃烧产物、中间相产物以及最终陶瓷相的影响分别进行了研究:结果表明在n/c=6.33的条件下,中间产物中存在较高含量的BaTi₅O₁₁相,进而有利于Ba₂Ti₉O₂₀相的形成。（4）为了研究水基溶液燃烧法合成Ba₂Ti₉O₂₀相时制备条件对中间相、最终产物及其性能的影响,本文首先通过调节初始溶液助燃剂硝酸铵（AN）的不同加入量,研究了燃烧程度对Ba₂Ti₉O₂₀相形成的影响:不完全燃烧形成的残余有机物将引起产物中非晶态Ti氧化物量增加,不利于中间相BaTi₅O₁₁的形成,最终影响了Ba₂Ti₉O₂₀相的纯度;此外,本文通过燃烧产物预烧温度、时间等条件的调节研究了Ba₂Ti₉O₂₀陶瓷热处理制度与其性能的关系:结果表明燃烧产物经过900℃热处理4小时得到的陶瓷先驱体粉末再经1200℃烧结4小时后能得到性能较好的Ba₂Ti₉O₂₀陶瓷材料,其相对致密度达到了96%（4.26g/cm³）,介电常数也达到了42左右。（5）为了进一步研究以水基溶液燃烧法制备复杂氧化物陶瓷,本文在制备Ba₂Ti₉O₂₀的基础上,开展了制备组分、结构更为复杂的钨青铜结构多元氧化物介电陶瓷的研究:以水基溶液燃烧法成功制备出Ba_6-3xSm_8+2xTi₁₈O₅₄钨青铜结构陶瓷材料,并可通过先驱体溶液中的Sm含量控制最终陶瓷中的Sm含量（x=0.5,0.67,0.75）的;同时,研究发现先驱体溶液中柠檬酸/金属离子（CA/M）摩尔比变化对其燃烧产物,中间相产物以及最终陶瓷相的形成有着显著的影响:当CA/M=1.2的条件下,所制得的Ba_6-3xSm_8+2xTi₁₈O₅₄（x=0.67）陶瓷材料具有较好的陶瓷性能及介电性能:其中密度和相对致密对分别都达到了较大值（5.73g/cm³,97.7%）,而介电常数也达到了相对较大值（82.1）。更多还原

【Abstract】 In synthesis or preparation of advanced materials,the whole process from the very original resources to the final products should be well controlled,thus the compositions,structures and even performances of the final materials can be well tailored.In this thesis,cadmium selenide（CdSe） and barium titanates,which were selected as typical materials for non-oxide and multicomponent oxide,were prepared through different aqueous wet chemical synthesis,i.e.,aqueous coprecipitation and aqueous solution combustion.The influences of aqueous wet chemical synthesis on the formation of these materials were investigated.The research results are summarized as:（1）Aqueous coprecipitation was adopted to synthesize CdSe and CdSeS nanocrystals in order to overcome the shortcomings of conventional organic-based methods,such as complex precursors,high reaction temperature,sophisticated equipment and etc.It was found the optimized conditions for CdSe formation were 12 for pH value,80℃for reaction temperature and 5 hours for reaction time.The suitable alkalinity could restrain the fast release of Se^2- and subsequently facilitate CdSe nanocrystal nanocrystal.（2）Organic polymer（PVA） and mercapto compound with two functional groups were used to modify the surface of CdSe nanocrystals respectively.The results showed that the dispersibility and the stability of both modified nanocrystals in aqueous solution were improved,and their photoluminescence was also enhanced.It was found that the amide of the BSA could conjugate to CdSe nanocrystals through carboxyl in mercaptopropionic acid,and the corresponding conjugates exhibited good photoluminescence performance,thus good potential for protein labelling.（3）In synthesizing pure Ba₂Ti₉O₂₀ phase through aqueous wet chemical route,the influences of drying methods on the homogeneity and phase composition of dry product were first investigated.It was found fast plate drying favored the formation of homogeneous dry gel powders,and eventually pure Ba₂Ti₉O（20）.Hence,a solution direct combustion method was developed to prepare homogeneous barium titanate precursor powders.It was found that the nitrate/citrate（n/c） ratio in starting solution, greatly affected the phase formation in as-combusted precursor powder,re-calcined powder and the final product.In all the ratios tested,n/c ratio of 6.33 was optimal. More intermediate BaTi₅O₁₁ phase,which is beneficial for final Ba₂Ti₉O₂₀ formation, was found in the re-calcined powder.Then the citrate solution combustion process was also analyzed and discussed.Since Ba₂Ti₉O₂₀ phase was obtained after 900℃calcination and 1200℃re-calcination,the relations between intermediate BaTi₅O₁₁ and the purity of Ba₂Ti₉O₂₀ were investigated.The results showed that the purity of Ba₂Ti₉O₂₀ phase in re-calcined product was affected by the n/c ratio due to different amount of intermediate BaTi₅O₁₁ phase in the calcined products.（4）The influences of processing parameters on intermediate phase content,final Ba₂Ti₉O₂₀ phase formation as well as dielectric performance were studied.Different precursor solutions were designed and prepared to control the combustion.The results showed that the complete combustion facilitated Ba₂Ti₉O₂₀ formation through increasing the content of intermediate BaTi₅O₁₁ in re-calcined product,while incomplete combustion showed opposite effect through segregation of Ti-rich amorphous phase.Also,re-calcination temperature affected the final dielectric performance through a sintering activity manner although the phases were exactly the same.900℃re-calcination favored the densification of final bulk ceramic.As a result, Ba₂Ti₉O₂₀ ceramics from the precursor powders calicined at 900℃for 4 hours had a relative density of 96%（4.26g/cm³） and dielectric constant of 42.（5）Aqueous solution solution combustion method was also adopted to prepare Ba_6.3xSm_8+2xTi₁₈O₅₄ tungsten bronze type dielectric materials.Ba_6.3xSm_8+2xTi₁₈O₅₄ materials with tailorable x value（x=0.5,0.67,0.75） were prepared.It was also found citrate/metal ion（CA/M） molar ratio of the precursor solution is one of the key factor in Ba_6-3xSm_8+2xTi₁₈O₅₄ phase formation.When CA/M value was 1.2,the corresponding Ba_6-3xSm_8+2xTi₁₈O₅₄（x=0.67） ceramics showed a relative density of 97.7%（5.73g/cm³） and a dielectric constant of 82.1.更多还原