聚碳硼烷的合成及先驱体/乳液法制备碳化硼靶丸研究

Ignition by laser driven inertial confinement fusion is one of the most effective way to achieve nuclear fusion. Design and preparation technology of the target have always been the core technology in the study of laser driven inertial confinement fusion. The simulation results show that using pure B4C hollow microspheres as the target is very conducive to the ignition experiment. But the suitable preparation process of B4C microspheres is lacked now. In this project, B4C hollow microspheres are prepared combined with the advantage of the precursor transformation method and the emulsion method. First, polycarborane is synthesized on the basis of design of B4C ceramics precursor. Then the hollow polycarborane microsphere is prepared with emulsion method because of the good fabrication properties of the preceramic polymer. And then the B4C hollow microspheres were prepared after the cross-linking and pyrolysis processes of the polycarborane microsphere. The composition and structure of the B4C hollow microspheres could be regulated through the design and improvement of precursor synthesis technology. The diameter, wall thickness and internal and external surface finish of the hollow microsphere could be controlled by the optimization of hollow microspheres preparation technology. The basic scientific problems, such as molecular design and synthesis of polycarborane and the preparation technology-structure-performance correlation of the B4C hollow microspheres, would be studied in detail in this work. Completion of this project has the important theory and practical significance for the solution of the B4C hollow microspheres preparation technology and their application in nuclear fusion targets.

激光驱动惯性约束点火是实现核聚变的最有效途径之一，靶丸的设计与制备技术是核聚变研究中的核心技术。模拟计算表明，以纯碳化硼空心微球为靶丸十分有利于点火实验，但目前还缺乏合适的碳化硼空心微球制备成型工艺。本项目拟结合先驱体转化法和乳液法的优势，制备碳化硼空心微球。首先在先驱体分子设计的基础上，合成高陶瓷产率高硼含量的聚碳硼烷；利用聚碳硼烷先驱体聚合物工艺性好的特点，采用乳液法制备出聚碳硼烷空心微球；然后再经过高温烧成，实现无机化制备出碳化硼陶瓷空心微球。通过设计和改善先驱体合成工艺，调节碳化硼空心微球的组成和结构；优化乳液成球和无机化工艺参数，控制碳化硼空心微球孔径、壁厚及内外表面光洁度。重点研究聚碳硼烷的分子设计与合成、碳化硼空心微球的制备工艺-组成结构-性能的相关性等基本科学问题。本项目的完成，对于解决碳化硼空心微球的制备及其作为核聚变靶丸应用的关键基础问题，具有重要理论和现实意义。

本项目针对激光惯性约束核聚变对碳化硼陶瓷空心微球靶丸的迫切需求，开展碳化硼空心微球的制备研究，完成了高陶瓷产率高硼含量聚碳硼烷的设计与合成、聚碳硼烷的组成、结构、性能与反应机理、聚碳硼烷的交联和无机化、聚碳硼烷空心微球的制备、碳化硼空心微球的制备等研究内容。首先，采用过渡金属催化剂以及离子液体催化剂对十硼烷与烯烃之间的反应进行催化，制备出了烷基化十硼烷衍生物作为单体。通过选用不同的催化剂，同时调节原料投料比、反应温度、反应溶剂等实验条件，提高了单体的合成产率，并减少了副反应的发生。利用烯烃与硼烷的硼氢化反应，制备了十硼烷分别在主链和侧链上的碳化硼先驱体均聚物。对两类先驱体组成与结构进行了表征，结果表明主链型己烯基十硼烷先驱体具有更高的软化点（90℃）及陶瓷产率（1000℃下68%）。采用所制备的主链型碳化硼陶瓷先驱体，通过乳液蒸发技术制备了外径在1mm到1.5mm、壁厚在15μm到30μm之间、表面光洁、球形度较好的碳化硼空心陶瓷微球。其次，采用Grubbs催化剂催化烯烃开环复分解聚合反应，制备碳化硼先驱体嵌段共聚物（PND-b-PCD），通过调控聚合时两种单体与催化剂的投料比，调节了共聚产物的分子量大小，改善了先驱体的溶解性以及陶瓷产物的结晶性，并研究了先驱体共聚物的陶瓷化机理。最后，设计合成了聚双苯基间碳硼烷PCB系列先驱体，并以此为原料、由浆料涂模制备得到了B4C/C空心微球。以间碳硼烷为起始物，经正丁基锂拔氢和亚铜盐催化制备得到三种双氯苯基间碳硼烷单体。两种单体在镍(0)催化下进行Ullmann偶联聚合，得到先驱体P4CB和P3CB。而双（2-氯苯基）间碳硼烷因空间位阻效应而无法聚合为P2CB。其中P4CB先驱体化学性质稳定，900℃陶瓷产率高达90.2%。由P4CB/PAN浆料经浆料涂模和多步热处理烧成制备得到了一种直径约1.3mm、壁厚20-40μm、球形度达到98.95%的B4C/C空心微球。本项目的完成为碳化硼空心微球的制备及其作为核聚变靶丸应用奠定了坚实的技术基础。