CAREER: A Research and Education Program for Studying Particulate-based Tribosystems in Nanotechnology

围绕纳米技术的出现的许多兴奋是由于在地形尺度和以下的相对运动表面的行为的阐明。从宏观尺度到纳米尺度理解摩擦表面的摩擦、润滑和磨损的摩擦学研究具有重要的科学和工业意义。此外，当负载下的真实的表面摩擦在一起时，磨损碎片或外来颗粒经常存在于流体中（即，空气或液体）填充的界面。这个问题被称为“颗粒增强混合润滑”（PAML）是非常动态的，因此很难预测;然而，当颗粒是纳米尺寸或亚微米时，它对纳米技术的进步具有重要的技术意义。随着计算能力的爆炸式增长，复杂的基于颗粒的摩擦系统很快就可以通过模拟在不同长度和时间尺度上演变的动态过程，而不简化问题的范围，如润滑近似和全局应用的磨损率关系，用多物理方法完全建模。因此，这项工作提出建立一个研究和教育计划，使用多物理场建模方法研究基于PAML的摩擦系统，并进行实验验证，以研究为基础的教育和推广。多的物理数值粒子增强混合润滑模型将与一个教育计划，使学生在应用基础知识的经验，摩擦学概念到纳米技术的前沿问题。由于PAML摩擦系统的现有模型通常基于单一甚至双重数学物理描述，因此它们无法捕获在几个长度和时间尺度上发生的相关PAML现象。例如，化学机械抛光（CMP）是一种基于PAML的工艺，其中沉积有薄膜的旋转晶片在被压向旋转垫时被抛光;垫充满了含有纳米颗粒的化学反应浆料。这种复杂的基于PAML的问题是制造纳米器件的最关键步骤之一。与大多数PAML过程一样，预测其行为的尝试是不够的，因为他们无法捕捉到在几个空间尺度上发生的所有相关物理现象。因此，所提出的研究提供了一个突破性的建模方法PAML系统，将通过使用化学机械抛光作为实验测试台进行验证。拟议的研究方法包括三个相互重叠和相关的阶段：（一）建模，（二）验证实验和表征，（三）以研究为基础的教育和推广。在第一阶段，将开发一个数值多物理场粒子增强混合润滑模型。在第二阶段，将进行纳米表征和CMP实验，以验证颗粒增强混合润滑模型。在第三阶段，一个particleassociated tribology仿真工具，采用PAML建模方法，将培养学生理解建模的复杂tribological systems.The更广泛的影响，拟议的工作是，PAML建模框架将产生根本性的突破，在理解磨损相关的基于粒子的摩擦学。这将使各种技术的进步，如（i）集成电路（IC）和数据存储纳米技术，（ii）全关节置换，（iii）纳米颗粒/流体润滑，（iv）煤流能源系统，（v）牙科摩擦学，以及（vi）在流体环境中遇到颗粒的其他技术。拟议的研究为基础的教育计划也将广泛影响摩擦学社区，通过教学生使用基本摩擦学模型作为组件，以更大的更复杂的多物理场摩擦学问题。学生将有机会参加一个增强的摩擦学课程与战略协调的任务，旨在教（1）基本的摩擦学解决问题的技能，相关的（2）教育多物理摩擦学仿真工具，其中模型可以（3）通过实验室实验验证。最后，CAREER的研究成果将被用作大学预科讲习班的材料，旨在增加少数民族学生在科学，技术，工程和数学领域的职业生涯。

Much of the excitement surrounding the advent of nanotechnology is due to the elucidation of the behavior of surfaces in relative motion at the topography-scale and below. Understanding the tribology study of friction, lubrication, and wear of the rubbing surfaces from the macro-scale to the nanoscale is of great scientific and industrial relevance. Additionally, when real surfaces under load rub together, wear debris or foreign particles often exist in the fluid (i.e., air or liquid) filled interface. This problem known as "particle-Augmented Mixed Lubrication" (PAML) is very dynamic and hence difficult to predict; yet, it is of great technical importance to the advancement of nanotechnology when the particles are nano-sized or sub-micron. With the explosive growth in computational power, complex particulate-based tribosystems can soon be completely modeled with multi-physics approaches by simulating dynamic processes that evolve over varying length and time scales without simplifying the scope of the problem such as lubrication approximations and globally applied wear rate relations. Consequently, this effort proposes to build a research and education program to study PAML-based tribosystems using a multiphysics modeling approach, with experimental validation, research-based education, and outreach.The intellectual merit of this research program is that a generalized, multi-physics numerical particle augmented mixed lubrication model will be developed in conjunction with a educational program that gives students experience in applying fundamental tribology concepts to a cutting-edge problems in nanotechnology. Because existing models of PAML tribosystems are typically based on single or even dual mathematical physics descriptions, they are unable to capture the relevant PAML phenomena that occur over several length and time scales. For example, chemical mechanical polishing (CMP) is a PAML-based process where a rotating wafer, deposited with thin films, is polished as it is pressed against a rotating pad; the pad is flooded with a chemically reactive slurry with nanoparticles in it. This complex PAML-based problem is one of the most critical steps in the fabrication of nano-enabled devices. As with most PAML processes, attempts to predict its behavior have been inadequate in that they were unable to capture all the relevant physics phenomena occurring over several space scales. Therefore, the proposed research offers a breakthrough modeling approach for PAML systems that will be validated by using chemical mechanical polishing as the experimental test-bed. The proposed research approach consists of three overlapping and related phases: (i) modeling, (ii) validation experiments and characterization, and (iii) research-based education and outreach. In phase I, a numerical multi-physics particle augmented mixed lubrication model will be developed. In phase II, nano-characterization and CMP experiments will be conducted to validate the particle augmented mixed lubrication model. In phase III, a particleassociated tribology simulation tool that employs the PAML modeling approach, will be developed to train students to understand modeling of complex tribological systems.The broader impacts of the proposed work are that the PAML modeling framework will yield fundamental breakthroughs in understanding wear associated particle-based tribology. This will enable advancements in a wide range of technologies such as (i) integrated circuit (IC) and data storage nanotechnology, (ii) total joint replacement, (iii) nanoparticulate/fluid lubrication, (iv) coal flow energy systems, (v) dental tribology, and (vi) other technologies that encounters particles in fluidic environments. The proposed research-based education plan will also broadly impact the tribology community by teaching students to use fundamental tribology models as components to a larger more complex multiphysics tribology problem. Students will have the opportunity to participate in an enhanced tribology course with strategically coordinated assignments designed to teach (1) fundamental tribology problemsolving skills, related to (2) an educational multi-physics tribology simulation tool, where models can be (3) validated by laboratory experiments. Finally, the CAREER research results will be used as materials in pre-college workshops which aim to increase the number of minority students pursuing careers in science, technology, engineering, and mathematics.