反应-扩散对材料结构调控作用和机制研究

It is a dream of human being to design and synthesize materials rationally. The difficulty to realize this dream is the complexity and diversity of material structures and the uncertainty on the controlling mechanism of these structures, which challenges the progress and development of material science and engineering. It is believed that the structures of materials are controlled by the interplay of thermodynamics and kinetics. When the kinetics dominates the development of material structure, complex hierarchical structures are prone to be formed. In this proposal, we aim to discover the mechanism controlling the structures of materials from a point of view of chemical engineering. The material is built up by the diffusion of building blocks (including ions, atoms, clusters) followed by their collision and reaction. Therefore, the diffusion and reaction are two general processes involved in the formation of materials. At the same time, the diffusion and reaction are the core issue of chemical engineering. In our previous studies, we have recognized the role of diffusion and reaction in shaping materials via qualitatively regulating the diffusion and reaction of chemicals in the formation of materials. In this proposal, first, we want to regulate the diffusion and reaction rates quantitatively to figure out the rule of diffusion and reaction in shaping materials. Then we want to extend the diffusion and reaction method to other material systems to examine the generality of this method. A molecular level investigation will be followed to discover the change of microenvironment on the crystal surface to reveal the mechanism of diffusion and reaction in shaping materials. The proposed mechanism will be evaluated by the experiments and simulation. After these detailed studies, a model to correlate the diffusion and reaction with the development of material structures will be set up, which is expected to be helpful in advancing the design and controllable synthesis of materials.

材料的理性设计与定向合成是人们的梦想，也是材料科学的一个挑战性问题，其难点在于材料结构的多样性和复杂性以及人们对材料结构控制机制的不清楚。材料结构受热力学和动力学共同影响，当动力学控制材料结构演化时，易于生成复杂有序的结构。本申请拟从化工的角度出发，以材料组成单元（离子/原子/团簇等）的扩散速率和反应速率为调控手段，探讨他们对材料结构的调控作用。在前期工作中，通过定性地调节反应和扩散速率，初步证实了反应-扩散对材料结构的调控作用；在本申请中，拟以反应-扩散定量调节为主，明确反应-扩散对材料结构的调控规律；将反应-扩散方法拓展到不同材料体系中，检验反应-扩散对材料结构调控作用的普适性；探讨反应-扩散对材料生长微环境的影响，提出反应-扩散对材料结构的调控机制；通过实验和计算机模拟，验证所提出的调控机制，构建基于反应-扩散的材料结构调控模型，为材料结构的理性设计和定向合成提供理论指导。

材料结构可控制备是纳米材料产业化急需解决的关键问题，申请人从化学工程的基本原理出发，提出了通过反应速率和传质速率调控材料结构的演化过程，建立了基于反应-传质调控的材料结构可控合成新方法。在银颗粒制备过程中，申请人首先通过不同方法调控反应速率和传质速率，验证了反应-传质对银颗粒形貌的调控规律。接下来，将反应-传质研究拓展到铜和金等贵金属体系及碳酸钙氧化物中，获得了相似的调控规律，验证了反应-传质对颗粒形貌的普适性调控作用；并通过反应-传质调控首次合成了雪花形片状碳酸钙。采用达姆科勒准数量化了反应和传质这一耦合过程，发现了达姆科勒准数与颗粒形貌的对应关系。提出了反应-传质对颗粒形貌的调控机制，即反应-传质通过改变生长界面前段反应物浓度分布影响颗粒形貌的演化；采用激光干涉法测量了生长界面的浓度梯度，证明了浓度梯度对材料结构的调控作用，建立了基于界面浓度场的颗粒形貌演化模型。界面浓度场将宏观的反应和传质与微观的颗粒生长过程关联起来，对材料设计和定向合成具有重要的理论指导价值。基于界面浓度场调控，可控制备了不同形貌的银纳米催化剂，并通过外场强化实现了快速充电条件下锂电池枝晶的抑制，目前正在与中石化等企业开展合作研究。项目执行期间，反应-传质研究发表SCI论文10篇，此外还有4篇论文审稿中，培养研究生8人，获得了中国颗粒学会自然科学一等奖1项。