Application of Novel Materials and Radio Frequency Field Assisted Heating to Enable Out-of-oven Ceramic Processing and Chemical Manufacturing.
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Date
2020-11-18
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Abstract
This work addresses the hypothesis that Radio Frequency (RF) assisted heating of carbon nanotubes and silicon carbides can enable low-infrastructure direct and out-of-oven heating, based on only electrical power. This thesis is part of a larger manufacturing industry-wide thrust toward the use of electricity to generate heat for manufacturing and investigates this hypothesis in ceramic and chemical manufacturing setting.
For enabling out-of-oven ceramic manufacturing, we have studied two RF susceptors: (a) Multiwalled carbon nanotubes and (b) Silicon carbide (SiC) fibers. (a) The addition of multiwalled carbon nanotubes allows for rapid molecular RF curing of preceramic polymers; it also prevents the viscosity drop at melting point. This technique was engineered for rapid 3D printing of silicon carbides and fiber manufacturing. (b) RF heating response of commercial silicon carbide fibers like Hi-Nicalon and Sylramic fibers used as a reinforcing material for ceramic matrix composites was studied under low power RF fields. The presence of turbostratic carbon on surface of Hi-Nicalon fibers results in the significant heating of these fibers under RF fields. RF heating response of Hi-Nicalon SiC fibers is used to make SiC/SiC ceramic matrix composites via polymer route.
In order to facilitate out-of-oven chemical manufacturing, a novel integration of RF responsive nanomaterials with conventional catalytic materials is used to realize a new class of heterogeneous catalysts that undergo uniform volumetric and localized heating to drive chemical transformations at the modular scale. Approximately 80% of chemical manufacturing involves heterogeneous catalytic reactions, which currently require heating via steam utilities or fired furnaces, and thus contribute to global greenhouse gas emissions while also limiting distributed chemicals production. A proof of concept was demonstrated by carrying out methanol steam reforming over a platinum catalyst using carbon nanotubes and SiC fibers as susceptors. This technology has direct application for on-site and on-demand portable chemical production.
The out-of-oven RF heating approach was also studied for stabilization of polyacrylonitrile (PAN) in order to reduce the cost and improve energy efficiency of the process. PAN is a precursor to carbon fibers, a commonly used reinforcing material in the aerospace and automotive industries. The volumetric heating of PAN using Radio Frequency fields in 1 -200 MHz range is demonstrated for two forms: i) film and ii) nanofiber mat. Surprisingly, PAN films show rapid RF heating behavior and PAN nanofibers do not heat at all.
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Keywords
RF heating, out-of-oven manufacturing