NIRT: Multi-Scale Simulation of Nanoparticle Aggregation for Scale Up of High-Rate Synthesis Methods

摘要CTS-0403864R。福克斯，爱荷华州立大学NIRT：纳米粒子聚集的多尺度模拟用于放大高速合成方法纳米粒子是许多新材料的基本构件。在几乎所有的纳米颗粒的高速合成方法中，化学前体通过湍流混合聚集在一起，形成颗粒核，由于表面的添加和聚集，颗粒核迅速长大。当合成方法扩大时，下一代纳米颗粒的应用将需要对产品质量进行精确控制。从颗粒表面化学和湍流中随时间变化的剪切速率出发，预测纳米颗粒的聚集是实现高速合成方法规模化的关键步骤。在这个项目中，一个由科学家和工程师组成的国际跨学科团队将开发和验证基于基本化学和物理模型的多尺度计算工具，这些工具可以预先预测高速合成方法放大后产生的纳米颗粒团簇的性质。计算方法从颗粒表面化学的量子计算(原子到分子尺度)，到有和没有剪切(纳米到微米尺度)的纳米颗粒聚集的布朗动态模拟，到湍流(从微米到宏观尺度)中颗粒尺寸分布的直接数值和大涡模拟。实验验证的方法从原子力显微镜直接测量粒子间势，到用光散射测量静态体系中的团簇尺寸分布，再到原位测量Taylor-Couette流中的团簇尺寸和分维。所研究的模型体系是单分散胶体功能化的乳胶纳米颗粒。这些纳米粒子将在我们的实验室进行合成，以期仔细调节和了解该体系中的聚集机制。将研究三种功能化纳米粒子：(1)未改性胶乳、(2)磺化胶乳和(3)羧化胶乳，并通过改变表面覆盖度来探讨表面化学对纳米粒子聚集机制的影响。这些官能团的加入改变了乳胶粒子的疏水表面，并使研究未修饰和修饰纳米颗粒混合物中的聚集机制成为可能。模型系统的选择还取决于我们对表面修饰的胶乳纳米粒子之间的表面-表面、表面-分子和分子-分子相互作用进行详细的从头计算的能力。利用纳米粒子表面化学的这种详细的原子描述，我们将开发用于布朗动力学模拟的粗粒粒间势模型，以预测剪切流动中的团簇尺寸分布和团簇形态。根据这些信息，Smoluchowski方程所需的聚集核将被提取并在湍流中颗粒聚集的一般动力学方程中实现。在模型开发的每一步，都将进行适当的实验验证测试，以确保多尺度模拟工具符合实际。拟议活动的智力优点：合理设计和放大纳米级合成和处理方法是实现纳米颗粒在广泛技术应用中的商业可行性的关键一步。通过开发和验证多尺度、多现象的模拟工具，该项目将首次展示从基本的化学和物理理论模型出发，在扩大规模后预测由高速合成方法产生的纳米颗粒的性能的能力。为解决这一问题而组建的跨学科团队是唯一有资格在成功完成这项任务所需的巨大长度和时间范围以及相应的数值和实验挑战之间架起桥梁的团队。拟议活动的广泛影响：该项目将导致参与的大学开发纳米级科学和技术的新课程。本科生教育将通过爱荷华州立大学的REU计算化学、物理和数学项目以及明尼苏达大学的推广项目(COS、APEX、MCSRO)得到加强。研究生教育将通过与工业和国际合作伙伴的实习计划以及明尼苏达州纳米粒子科学和工程的IGERT得到加强。将通过参加爱荷华州的Lead、Science Bound和PWSE项目以及明尼苏达州的类似项目，积极开展K-12项目对少数族裔和女性的招募。该项目的成果将通过工业和国际伙伴关系、专业会议的专门会议、一年一度的纳米科学和工程讲习班以及档案出版物广泛传播。本提案涉及的研究和教育主题：(按重要性排序)1.纳米尺度的制造工艺2.纳米尺度下的多尺度、多现象理论、建模与仿真环境中的纳米级过程

AbstractCTS-0403864R. Fox, Iowa State UniversityNIRT: Multi-Scale Simulation of Nanoparticle Aggregation for Scale Up of High-Rate Synthesis MethodsNanoparticles are the basic building blocks for many novel materials. In nearly all high-rate synthesis methods for nanoparticles, chemical precursors are brought together by turbulent mixing to form particle nuclei that grow rapidly due to surface addition and aggregation. Next-generation applications of nanoparticles will require precise control of product quality when synthesis methods are scaled up. Predicting nanoparticle aggregation starting with detailed knowledge of particle surface chemistry and the time-dependent shear rate in a turbulent flow is the key step for scale up of high-rate synthesis methods. In this project, an international, interdisciplinary team of scientists and engineers will develop and validate multi-scale computational tools based on fundamental chemical and physical models that can predict a priori the properties of nanoparticle clusters produced after scale up of high-rate synthesis methods.The computational approaches range from quantum calculations of particle surface chemistry (atomic to molecular scale), to Brownian dynamic simulations of nanoparticle aggregation with and without shear (nano to micron scale), to direct-numerical and large-eddy simulations of the particle size distribution in turbulent flow (micron to macro scale). The experimental validation approaches range from direct measurements of the interparticle potentials using atomic force microscopy, to measurements of the cluster size distribution in quiescent systems using light scattering, to in situ measurements of cluster size and fractal dimension in Taylor-Couette flow.The model system to be investigated is monodisperse colloidal functionalized latex nanoparticles. The nanoparticles will be synthesized in our lab with a view to carefully modulate and understand aggregation mechanisms in this system. Three types of functionalized nanoparticles will be investigated: (1) unmodified latex, (2) sulfonated latex, and (3) carboxylated latex; and the extent of surface coverage will be varied to probe the effect of surface chemistry on nanoparticle aggregation mechanisms. The addition of these functionalities modifies the hydrophobic surface of the latex particles, and enables interrogation of aggregation mechanisms in mixtures of unmodified and modified nanoparticles. The choice for the model system is also driven by our ability to perform detailed ab initio quantum calculations of surface-surface, surface-molecular, and molecular-molecular interactions between surface-modified latex nanoparticles.Using this detailed atomistic description of nanoparticle surface chemistry, we will develop coarse-grainedinterparticle potential models for use in Brownian dynamics simulations to predict cluster size distribution and cluster morphology in shear flow. From this information, aggregation kernels needed for the Smoluchowski equation will be extracted and implemented in the general dynamic equation for particle aggregation in turbulent flow. At each step of model development, appropriate experimental validation tests will be carried out to ensure that the multi-scale simulation tools agree with reality.Intellectual merit of the proposed activity: The rational design and scale up of nanoscale synthesis and processing methods is a crucial step towards the commercial viability of nanoparticles for widespread technological applications. By developing and validating multi-scale, multi-phenomena simulation tools, this project will demonstrate for the first time the capability to predict the properties of nanoparticles produced by high-rate synthesis methods after scale up starting from the fundamental chemical and physical theoretical models. The interdisciplinary team assembled to attack this problem is uniquely qualified to bridge the enormous range of length and time scales, and the corresponding numerical and experimental challenges, that are required to accomplish successfully this task.Broader impacts of the proposed activity: This project will lead to the development of new courses in Nanoscale science and technology at the participating universities. Undergraduate education will be enhanced through an REU program in computational chemistry, physics and mathematics at Iowa State; and outreach programs (CoS, APEXES, MCSRO) at the University of Minnesota. Graduate education will be enhanced by internship programs with industrial and international partners, and the IGERT for nanoparticle science and engineering at Minnesota. K-12 outreach and recruitment of minorities and women will be actively pursued through participation in the LEAD, Science Bound, and PWSE programs at Iowa State, and similar programs at Minnesota. Results from the project will be disseminated broadly through the industrial and international partnerships, dedicated sessions at professional meetings, annualnanoscale science and engineering workshops, and archival publications. Research and education themes addressed in this proposal: (in order of significance)1. Manufacturing Processes at the Nanoscale2. Multi-scale, Multi-phenomena Theory, Modeling and Simulation at the Nanoscale3. Nanoscale Processes in the Environment