超重力场与CuxTi熔体溶蚀固体C反应耦合制备超细TiC

On account of the problems of high reaction temperature, long production period, difficulty on producing ultrafine powders and quality control, the technical route “TiC synthesis via solid carbon dissolution in CuxTi melt and separation with supergravity” is proposed in this project. Firstly we will illuminate the peeling mechanism between CuxTi melt and solid C, and clarify the precipitation and dispersion behavior of TiC phase via the rapid cooling-offline test and in situ online observation method; By investigating the location of reaction interface and the kinetic restriction step we will clarify the formation of TiC grain boundary and its desorption mechanism, then the solid-liquid reaction mechanism and the law of kinetic can be revealed; The segregation behavior of impurities will be tracked, and the influence rules of carbon amount and impurity content etc. on the stoichiometric of TiC powders will be investigated by the evaluation of TiC lattice constant; The quantitative relations among the surface tension of melt, the gravity coefficient and the wetting angle between CuxTi melt and TiC particle can be simulated by mathematical modeling. And then the intensified filtration separation mechanism by supergravity field can be uncovered. All in all, the fundamental research in this project is carried out in terms of the precipitation of TiC, the migration of impurities and the coupled intensifying of reaction and separation by supergravity, which can provide significant scientific basis for the implement of this technical route.

针对传统TiC粉末制备方法反应温度高、生产时间长、超细粉末制备难度大、质量难控制等问题，提出“超重力场与CuxTi熔体溶蚀固体C反应耦合制备超细TiC”这一技术路线。通过瞬态急冷-离线检测与原位在线观察手段，阐明CuxTi熔体中固体C的剥离机制与TiC相析出、分散行为；探究反应界面层位置与动力学限制性环节，明确TiC晶界的产生以及从产物层脱附的机制，揭示固体C与CuxTi熔体之间的固-液反应机理与动力学规律；研究TiC析出过程中杂质元素的偏析行为，通过计算TiC粉体的点阵常数，考察配C量、杂质含量等因素对TiC粉体化学计量的影响规律；建立超重力场相际分离模型，拟合出熔体表面张力、固液相间润湿角以及超重力系数三者之间的定量关系，进而掌握超重力场强化分离机制。本项目围绕TiC相析出、杂质成分迁移、超重力场耦合强化这三个方面展开基础研究，为该技术路线的实施提供重要科学依据。

通过项目所提出的铜钛熔体溶蚀固体碳-超重力分离制备碳化钛这一方法，将传统方法中的钛粉、铜粉原料由海绵钛和电解铜块替代，从而将其原料成本降低3-4倍，同时大幅度降低反应温度。通过电解铜粒与海绵钛块制备的铜钛熔体，能够与石墨颗粒反应制备出化学计量数为0.8左右，平均粒径为3 μm的TiCx颗粒。分析了铜钛熔体侵蚀碳颗粒时碳化钛的析出机理，发现在反应过程中碳颗粒表面所产生的碳化钛层将不断重复“产生-增厚-剥离-产生”这一周期性过程，明晰了该体系下碳钛反应的动力学限制性环节为碳原子在碳化钛层晶格空位中的传质过程。构建了碳颗粒溶蚀反应的动力学模型，分别推导出了球形、圆柱形、平板碳源颗粒在CuxTi熔体中发生溶蚀反应的动力学模型。作为拓展方向，成功采用铜钛熔体溶蚀固体碳法制备出了铜基碳化钛复合材料，在相同的碳化钛体积分数情况下相比传统方法制备的复合材料具有近似的导电、硬度等性能，并且表现出更优的机械强度。在碳化钛与铜基体结合界面处发现了由铜原子渗入碳化钛晶格形成的厚度约为100 nm的过渡层，找到了该方法所制备铜基碳化钛复合材料基体与增强相之间具有高强结合力的原因。虽然目前在进一步提高碳化钛化学计量和消除残碳方面存在问题，但是本课题的研究成果为该方法在碳化钛制备和金属基复合材料制备方面提供了坚实的理论基础，为这一研究方向形成了良好开端，相关的研究方法有望在今后拓展到更多原位反应体系的研究中去。