Mechanisms for Film Formation During Room Temperature Micro Cold Spray of Ceramics

这笔赠款促进了人们对最近发现的直写、添加剂制造工艺的理解，该工艺用于生产薄膜。直接写入的添加制造是从数字计算机模型生产图案化薄膜的过程，而不需要掩模或其他特定于零件的工具。这项技术具有革命性的制造方式的潜力，因为它可以显著降低为低产量部件制造图案化薄膜的成本，甚至允许为每个部件定制几何形状。有许多现有的直写制造工艺可以生产图案化的薄膜。然而，它们通常需要较高的温度，这可能会损害薄膜所在的衬底，这对陶瓷薄膜来说尤其有问题，因为加工温度通常非常高。该奖项支持基础研究，为开发用于沉积陶瓷的常温直写添加剂制造工艺提供所需的知识。这一过程将使在室温下沉积高质量的陶瓷薄膜成为可能。与可以使用相同工艺沉积的金属薄膜相结合，这些陶瓷薄膜可以用于需要多种材料的混合设备，如传感器、执行器和充电电池。因此，这项研究的结果将有利于美国的经济和社会。这项研究需要实验和计算材料科学方面的专业知识。多学科方法将对学生进行培训，这些领域可以立即对工业和外联活动作出贡献，从而扩大女性工程学学生参与研究的范围，并对工程学教育产生积极影响。与现有的沉积金属和陶瓷厚膜的制造工艺相比，微冷喷涂工艺具有独特的优势：1)沉积在室温或接近室温时发生，允许使用对温度敏感的薄膜材料和衬底；2)无需非常专业和昂贵的设备，就可以沉积氧气敏感和熔化温度极高的金属；3)非平衡混合材料可以沉积到各种衬底材料上，表面处理最少。然而，实验表明，微冷喷涂只能在很窄的工艺参数范围内获得高质量的陶瓷薄膜。之所以需要现有的经验方法，是因为对粒子键合的机制(S)仍然知之甚少。对薄膜形成物理的基本理解将允许建立一个先验的工艺窗口，这将大大减少使用微冷喷涂生产高质量图案化厚陶瓷薄膜所需的实验次数。为了了解影响微冷喷涂沉积薄膜的因素，需要研究新的基础科学来推进制造工艺，因为极高的应变率、大应变、主要是压应力状态和微冷喷涂颗粒碰撞过程中出现的局部高温的组合在陶瓷加工中是独一无二的，以前从未被探索过。这项奖励使用实验和分子动力学模拟相结合的方法来建立推进这一制造过程的科学基础，并提供了对导致薄膜形成的颗粒和团聚变形机制的基本了解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This grant advances the understanding of a recently discovered direct-write, additive manufacturing process for producing films. Additive manufacturing by direct writing is the process of producing a patterned film from a digital computer model without the need for a mask or other part-specific tooling. The technique has the potential to revolutionize the way things are made because it can dramatically lower the cost for making patterned films for low production volume parts or even allow custom geometries for each part. There are many existing direct-write manufacturing processes that can produce patterned films. However, they generally require high temperature which can damage the substrate that the films are deposited on and this is particularly problematic for ceramic films since the processing temperatures are usually very high. This award supports fundamental research to provide needed knowledge for the development of a room temperature direct-write additive manufacturing process for depositing ceramics. This process will enable the deposition of high-quality ceramic films at room temperature. Combined with metal films that can be deposited using the same process, these ceramic films can be use in hybrid devices that require multiple materials such as sensors, actuators, and rechargeable batteries. Therefore, results from this research will benefit the U.S. economy and society. This research requires expertise in both experimental and computational materials science. The multi-disciplinary approach will train students in an areas that can contribute immediately to industry and outreach activities that will broaden participation of female engineering students in research and positively impact engineering education. The micro cold spray process offers unique advantages compared to existing manufacturing processes for depositing thick films of metals and ceramics: 1) Deposition occurs at or near room temperature allowing for the use of film materials and substrates that are temperature sensitive; 2) It is possible to deposit oxygen-sensitive and very high melting temperature metals without highly specialized and expensive equipment; 3) Non-equilibrium mixtures of materials can be deposited onto a wide range of substrate materials with minimal surface preparation. However, experiments have shown that micro cold spray produces high quality ceramic films only over a narrow window of processing parameters. The existing empirical approach was required because the mechanism(s) for particle bonding remain poorly understood. A fundamental understanding of the physics of film formation would allow the establishment of a processing window a priori that would dramatically reduce the number of experiments required to produce high quality patterned thick ceramic films using micro cold spray. An understanding of the factors that affect film deposition by micro cold spray requires the study of new fundamental science to advance the manufacturing process because the combination of extremely high strain rates, large strains, primarily compressive stress states, and locally high temperatures that arise during particle impact for micro cold spray are unique in ceramics processing and have not been previously explored. This grant uses a combined experimental and molecular dynamics simulation-based approach to establish the scientific underpinnings advancing this manufacturing process and provides a fundamental understanding of the particle and agglomerate deformation mechanisms that lead to film formation.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.