UCLA

This dissertation investigates the synthesis, characterization, and application of electrically conducting carbon nanotube (CNT) porous structures for electromagnetic interference (EMI) shielding and chemical production. The study addresses two critical challenges: enhancing the electrical conductivity and mechanical strength of CNT films for effective EMI shielding, and developing energy-efficient methods for caustic (NaOH) production.

First, we present a facile one-step method for fabricating pure and metal-decorated densified CNT films. These films exhibit high electrical conductivity (~106 S m-1) and exceptional EMI shielding effectiveness (EMI SE) of 99.999992% (71 dB) at frequencies between 8.2 GHz and 12.4 GHz with a thickness of 14.3µm. The densification process reduces contact resistance between neighboring CNTs, significantly enhancing the overall conductivity and mechanical strength of the films. Furthermore, decorating the CNT films with a thin layer of gold increases the EMI SE from 56.67 dB to 66.12 dB, demonstrating the potential of these materials for protecting modern lightweight and compact electronic devices from electromagnetic interference.

Second, we explore the electrochemical production of caustic using a flow-through membrane/cathode electrolysis process. Traditional chlor-alkali processes for caustic production are energy-intensive and require high-purity feedstocks, high concentrations of NaCl, and elevated operating temperatures. Our innovative process produces caustic solutions (pH 10.22-12.26) at a specific energy consumption (SEC) of 1.71 kWhe/kg NaOH using a 3.5% NaCl solution at room temperature, while also generating pure hydrogen. The high flow rates through the cathode enhance mass transport and facilitate hydrogen gas stripping, reducing energy consumption and operational complexity. This method is particularly suitable for on-site caustic production in carbon capture and sequestration (CCS) applications, where increasing the alkalinity of water can enhance CO2 capture and storage efficiency.

Overall, this dissertation demonstrates the development of multifunctional CNT-based materials with significant potential for applications in EMI shielding and sustainable chemical production, addressing key challenges in both fields and contributing to the advancement of modern electronic and industrial technologies.