GOALI: Flame-based Synthesis of Metal Nanoparticles at Millisecond Residence Times
Mark Swihart Principal Investigator
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PI: Swihart, Mark <br/>Institution: SUNY at Buffalo <br/>Proposal Number: 1066945<br/>Title: GOALI: Flame-based Synthesis of Metal Nanoparticles at Millisecond Residence Times<br/><br/>The PIs plan to apply the combined expertise of their University at Buffalo (SUNY) and Praxair teams to develop a new flame-based process for producing metal nanoparticles. <br/><br/>Printed electronics, antimicrobial plastics and other applications of metal nanoparticles are rapidly growing. Currently, these particles are prepared using large quantities of solvents, high-value surfactants and polymers. A gas-phase flame-based process will provide a lower-cost, more environmentally friendly route to these nanomaterials if it can provide sufficient control of size, size distribution, and degree of agglomeration. Most large-scale production of metal oxide nanomaterials (TiO2, ZrO2, etc.) and carbon black is done in flame processes for these reasons. However, this is not the case for most metals, because they oxidize in the flame. The approach pursued here, based on a thermal nozzle technology developed at Praxair, provides the high temperature, short residence time, rapid mixing, and reducing conditions needed for metal nanoparticle production. The nozzle and downstream reactor provide a highly uniform environment for particle growth, improving control of particle size, size distribution, and morphology compared to other gas-phase processes. Most importantly, this approach decouples the precursor chemistry from the flame chemistry, allowing use of precursors such as low-cost aqueous salts that cannot be used in other flame-based methods, and allowing the residence time for particle formation to be controlled independently of the flame dynamics. Specific aims of the proposed research are to:<br/>1. Systematically study the effects of key operating parameters on single-component nanoparticle size distribution and morphology, to optimize yield and control particle size distribution.<br/>2. Explore production and structure control of multicomponent (alloy and core-shell) nanoparticles, coated metallic nanoparticles, and additional novel nanomaterials including dendritic carbon.<br/>3. Develop, validate and apply computational reactor models to understand the physico-chemical basis of the experimental results and enable predictive, rational process improvement.<br/>4. Complete a cost analysis and market analysis to identify pathways to commercialization.<br/><br/>Intellectual Merit: The intellectual merit of this work derives from the novel adaptation of an existing technology for a promising and very different new purpose. The thermal nozzle reactor is elegant in its simplicity; it merely separates combustion from particle formation by passing the hot combustion products through a converging-diverging nozzle. The resulting hot gas jet provides effective atomization of liquid precursors and extraordinarily fast mixing. Rapid initiation and termination of particle formation (by heating and quenching) are the keys to the production of nanoparticles in the gas phase at high throughput, and this is exactly what this system provides. Moreover, the PIs will investigate the formation of alloy and core-shell particles and novel carbon nanomaterials in this system, potentially generating structures that cannot be obtained by other methods. State-of-the-art aerosol dynamics modeling will be performed in parallel with experiments, providing fundamental insight into the particle formation process. The combined expertise of the UB and Praxair teams is essential to the success of the project.<br/><br/>Broader Impacts: The work will lead to development of a new high-throughput low-cost process for the production of metallic nanoparticles. This will have technological impact by lowering costs and expanding the range of application of these materials. Through this work, a Ph.D. student, MS students, and undergraduates will be trained in aerosol synthesis of nanomaterials and develop cross-disciplinary chemistry, materials science, and chemical engineering skills. All participants will benefit from the academic-industrial collaboration. Undergraduates will participate through the NSF REU program, and additional targeted programs such as the McNair Scholars and Louis Stokes Alliance for Minority Participation (LS-AMP) programs. This project will allow the PIs to build on their growing success in recruiting minority participants, and expand it with outreach to high-school students and teachers.<br/><br/>Transformative Nature of this Project: This project has potential to transform the way nanoparticles of metals and other non-oxide materials are produced. This is a novel millisecond residence-time reactor for nanomaterials. The impact of this process on nanomaterials processing and aerosol reaction engineering could very well match the impact of other millisecond contact-time reactors (e.g. those developed by Lanny Schmidt et al.) on reaction engineering for reforming and partial oxidation, affecting directions of both scientific research and industrial practice.