Manipulation of Grain Boundary Structures by Electric Fields

非技术描述：在用于制造应用的陶瓷加工期间施加电偏压具有显著改善加工时间、降低所需温度和减小所需机械压力的潜力。这些陶瓷工艺改进的机制尚不清楚;这项研究揭示了根本原因。在这项研究中的实验工作是由理论建模的补充。这项研究的预期结果是告知如何利用电场来改善现有材料的加工条件，以及定制新的功能陶瓷材料。研究生和本科生正在接受材料科学和工程领域的培训，以便在学术界或高科技制造领域从事后续职业。参与的大学生正在指导传统上代表性不足的社区的高中生，以提高科学素养和大学入学率。技术优势：电场辅助烧结已经证明了加速粉末压坯致密化、降低加工温度和抑制晶粒生长的可行性。然而，在没有电流的情况下电场的作用仍然是未知的。一个主要的挑战是在纳米晶陶瓷由于随机取向的一般晶界的压倒性数量的新兴缺陷结构的系统调查。在一个定制的设置双晶体的扩散连接是用来系统地调查原子和电子晶界结构作为一个功能的应用领域的强度，方向和晶界几何形状。这种实验方法允许比较特定选择的晶界几何形状作为所施加的电场的函数，并阐明外部施加的电场是否影响晶界的热力学稳定性。实验的补充，是基于晶界核心内的原子密度的变化的新的建模例程。扩散结合，原子分辨率表征，和理论建模的界面热力学状态的组合是用来获得定量的机械理解电场对晶界形成的影响。晶界网络的场辅助改性有望成为一种突破性的技术，用于定制具有前所未有的宏观物理性能的新微观结构。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: The application of an electrical bias during ceramic processing for manufacturing applications has the potential to dramatically improve processing times, lower required temperatures, and decrease required mechanical pressures. The mechanisms for these process improvements of these ceramics is unclear; this research is revealing the underlying reasons. The experimental work in this study is complemented by theoretical modeling. The anticipated results of this study are informing how electric fields can be utilized for enhancing processing conditions for existing materials, and tailoring of new functional ceramic materials. Graduate and undergraduate students are being trained in areas of materials science and engineering for subsequent careers in academia or fields of high-tech manufacturing. Participating university students are mentoring high school students from traditionally underrepresented communities to improve science literacy and college-going rates.TECHNICAL DETAILS: Electric field assisted sintering has demonstrated the feasibility to accelerate densification of powder compacts, lower processing temperatures, and suppress grain growth. The role of electric fields in the absence of current flow remains, however, mostly unknown. A major challenge is the systematic investigation of emerging defect structures in nanocrystalline ceramics due to the overwhelming number of randomly oriented general grain boundaries. Diffusion bonding of bicrystals in a custom-built setup is used to systematically investigate atomic and electronic grain boundary structures as a function of applied field strength, direction, and grain boundary geometry. This experimental approach allows the comparison of specifically selected grain boundary geometries as a function of the applied electric field, and elucidates whether externally applied electric fields impact on the thermodynamic stability of grain boundaries. Experiments are complemented by novel modelling routines that are based on variations of atomic density within the grain boundary cores. The combination of diffusion bonding, atomic resolution characterization, and theoretical modelling of the interfacial thermodynamic state is used to gain a quantitative mechanistic understanding of electric field effects on grain boundary formation. Field-assisted modifications of grain boundary networks are expected to become a disruptive technology for tailoring of new microstructures with unprecedented macroscopic physical properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.