【作者】 余丽丽；

【导师】 崔得良；

【作者基本信息】 山东大学 ， 材料物理与化学， 2009， 博士

【摘要】 我们以傅立叶变换红外（FTIR）光谱为主要研究手段,以BBr₃和N（CH₃）₃为原料,对苯热条件下由络合物Br₃B·N（CH₃）₃分解生成BN的反应过程进行了系统研究,初步弄清了该体系中cBN和tBN的生成反应机理。并以此为基础,对反应设备和方法进行了改进和完善,实现了纯相氮化硼的可控合成。主要结果如下:为了弄清络合物Br₃B·N（CH₃）₃分解生成BN的反应机理,我们首先针对该络合物的热稳定性质进行了研究,并提出了初步的反应模型。进一步地,为了验证提出的模型,我们利用FTIR光谱,对配合物Br₃B·N（CH₃）₃分解生成BN的中间反应过程进行了原位跟踪监测,确认了中间态物质BrB=NCH₃的存在及其结构随温度、反应时间的变化规律,给出了的BN反应机理模型。同时,我们结合相应的验证实验结果对给出的模型进行检验和修正,基本弄清了在苯热条件下cBN和tBN的生成机理。通过反应机理的研究,我们认识到:中间过渡态物种及其结构对最终得到的氮化硼的结构具有决定作用。因此,对中间态物种的调控将是实现氮化硼选相合成的关键。根据反应机理模型（见下面给出的Scheme）,我们一方面对现有反应设备和合成方法进行了改进和完善,通过对中间态物质的调控,实现了tBN在粒度、纯度以及结晶质量方面的可控制备,以及纯相cBN纳米晶的可控合成。另一方面,我们提出了新的选相原位合成方法,并利用它首次在溶剂热下合成了具有较高结晶质量的新物相c₁BN。对反应机理的把握是实现材料可控制备的前提。但是,溶剂热反应体系复杂多变,长期以来人们只能通过大量的实验摸索对其规律进行归纳和总结,而极端反应条件下的溶剂热反应过程（反应机理）正是一个前人没有涉足的课题。本文正是在这种背景下,对溶剂热合成氮化硼的反应机理进行了开创性的探索。尽管现有的结果还有很多不完善之处,但我们相信这项工作不仅具有很强的创新性,而且具有重要的基础和应用价值。另外,通过系统的文献调研,我们发现合成氮化硼常用的原料是BX₃（X:H、O、F、Br等）和NR₃（R:H、Li、CH₃（简称Me））,可见本文给出的反应机理应该具有较强的普适性;另外,以反应机理研究为基础提出的新方法和新设备,不仅适用于BN的制备,同样也适用于其它亚稳态结构材料的制备。更多还原

【Abstract】 Using Fourier transformation infrared （FTIR） spectrometer as the main tool and BBr₃ and N（CH₃）₃ as starting materials, the reaction process of Br₃BN（CH₃）₃ forming boron nitride （BN） was systematically investigated, and the formation mechanisms of both cubic boron nitride （cBN） and turbostractic boron nitride （tBN） were understood. Then according to the obtained mechanism, through improving both equipments and methods, controllable synthesis of pure phase of BN was realized. The main results are as follows:In order to well know the formation mechanism of BN from complex compound Br₃B·N（CH₃）₃, first the thermal stability of Br₃B·N（CH₃）₃ was studied and primary reaction model was proposed. Then, FTIR spectrometer was used to in-situ monitor and collect the spectra of Br₃B·N（CH₃）₃ forming BN, verifying the intermediate BrB=NCH₃ existence, and its transmutation rules with temperature and reaction time was understood. According to the monitor results, formation mechanism model of BN was presented. Furthermore, based on the verification experiments results, the proposed mechanism was modified and the reaction mechanisms of cBN and tBN in benzene-thermal condition were understood.Through the above investigation, it is known that the final product structure is directly related to the intermediate compound. Therefore, how to control the intermediate compound is the key to realize BN selective synthesis. According to the reaction mechanism model （see the Scheme 3）, on one hand, the equipments in possession and synthetic methods were improved and perfected, realizing the controllable synthesis of tBN with high yield and cBN with rather high quality. On the other hand, a new selective-phase synthetic method was proposed, using which a pure and new phase of cubic boron nitride （named c₁BN） nano-crystal with rather high quality in benzene-thermal route was successfully prepared for the first time.Understanding the reaction mechanism is the base to realize the controllable synthesis of materials. However, because of the complexity and mutability of the solvothermal system, for a long time, people had to do many experiments to conclude and summarize the rules. And the solvothermal reaction mechanism in extreme conditions is a completely new subject. No one has ever studied it before. Considering these, it is the first time for us to explore the formation mechanism of BN in benzene-thermal condition. Although the results are still imperfect, it is confirmed that they are not only of strong innovation but also of great value for both basic and application studies. In addition, through systematically literature study, it is found that the raw materials for BN synthesis can be presented as BX₃ （X: H, 0, F, Br and etc） and NR₃ （R: H, Li, CH3 and so on）. Thus, the mechanism proposed in this paper is rather universal. Moreover, the developed new equipments and methods are not only fit for BN preparation, but also suit to form other metastable materials.更多还原