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Academic Calendar

Event Scheduled for Aug 21, 2017

 

Event: Ph.D Proposal Defense - Mingwan Zhang

Location: IMS-159

Time: 01:00 pm

Details of Event:
PhD Proposal Defense

Presenter: Mingwan Zhang

Major Advisor: Dr. Puxian Gao

Associate Advisors: Dr. Mei Wei, Dr. George A. Rossetti, Jr., Dr. Steven L. Suib, and Dr. Yang Cao

Date: Monday, August 21, 2017

Time: 1:00 pm

Room: IMS-159

Title: Scalable Microwave-Assisted Continuous Flow Synthesis of ZnO Nanowire Arrays on Three-Dimensional Substrates for Environmental Remediation and Monitoring

Abstract: This dissertation work intends to design, control and understand the synthesis and manufacturing process of ZnO nanowire arrays (nano-arrays) with well-controlled morphology and uniformity on various three-dimensional (3-D) substrates through a scalable continuous flow synthesis (CFS) technique as assisted by microwave heating. Aligned ZnO nanowire arrays were synthesized on both honeycomb monoliths and cylindrical optical fiber substrates using continuous flow hydrothermal synthesis under conventional resistive heating and microwave heating, and their combinative heating methods. Experimental results suggest the microwave irradiation boosts more on nanostructure nucleation than on growth, providing preferential benefits in homogenous chemical reactions than in heterogeneous ones. As a result, ZnO nanowire arrays growth under microwave irradiation showed a narrower size distribution on both 2-D planar silicon wafers and 3-D channeled cordierite honeycombs. Supplying fresh precursors during regular intervals in a CFS process was found to help maintain hydrothermal reaction and deposition at high rate, enabling the high yield and high efficiency. The microwave-heating during a continuous-flow-synthesis process makes a highly efficient and scalable integration process of ZnO nanowire arrays onto channeled honeycombs. The aspect ratio and uniformity of ZnO nanowire arrays are improved by using microwave-assisted CFS method, in comparison with microwave-assisted batch synthesis or conventional CFS method. A detailed statistical analysis and mechanism for effects of microwave irradiation over nanowire crystal growth are proposed as a guide for future research and studies. The 3-D cordierite honeycombs integrated with metal oxide nanowire array have been demonstrated in the past few years in our group, with enhanced catalytic and functional performance toward various reactions for energy production, efficient energy utilization, and environment protection. This work also demonstrates superior desulfurization performance of ZnO nano-array integrated monoliths to that of power-form catalysts for environmental remediation. Meanwhile, ZnO nanowire arrays have been integrated with etched cylindrical optical fiber substrates. After decoration of Pt nanoparticles, these ZnO nanowire array integrated optical fibers have displayed as effective transmission-based optical sensors for detection of various gases such as CO and H2 at high temperature. Further studies are proposed to help understand the accelerated nucleation and growth process of ZnO nanowire arrays under microwave irradiation through a systematic structure characterization and comparative synthetic investigation, as well as their optical sensing characteristics and mechanism.

Target Audience: Not Available

Sponsored By: Materials Science and Engineering Program

Pamphlet/Flyer: No Pamphlet/Flyer Available


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