Session: 11-05-02: Thermophysical Properties: Characterization and Modeling Across Scales

Paper Number: 150289

150289 - Measuring Multi-Scale Thermal Properties of a Novel Carbon Capture Adsorbent 

Climate change is among the most critical challenges facing humanity today. Society’s infrastructure, agriculture, and health are threatened by global warming, which leads to floods, unprecedented weather patterns, and damaging natural disasters. To mitigate irreparable damage to the Earth, it is predicted that global warming must increase no more than 1.5°C. To achieve this, a net zero of carbon emissions must be reached by 2050. Even with great advancements in renewable energy sources, societal acceptance, and implementation, to truly reach a net-zero carbon emission goal (and undo the damage already done), CO₂ must also be actively removed from the atmosphere. Direct air capture (DAC) of CO₂ systems are a recent technology to address this need. But there remain significant unknowns regarding DAC CO₂ adsorbent materials and system design that still limit this technology. One approach is using solid DAC adsorbents, such as Metal-Organic Frameworks (MOFs), which require an increase in temperature to allow the adsorbent to release the CO₂ and regenerate the material. Most of the energy required during the use of these materials in devices comes from the associated thermal energy required for the release of CO₂. Understanding the thermal transport properties of complex nanoporous MOFs is critical and requires studying both the nano- and macroscales. On the nanoscale, phonons, quantized modes of lattice vibrations with wavelengths near 10^-10 m, are the primary carriers of heat and determine intrinsic thermal conductivity (k). However, phonons can be scattered, and it is expected that k will decrease as they do. In this talk I will present our frequency domain thermoreflectance (FDTR) technique for nano- and microscale investigations, combined with thermal wave sensors (TWS) and a transient plane source (Hot Disk TPS) for the micro- and macroscale thermal property measurements of MOFs to better understand these thermal mechanisms. FDTR is a non-contact ultrafast optical pump-probe technique that locally heats a surface and can sense the thermal response of the anisotropic material based on the temperature-dependent reflectance of a deposited metallic optical transducer layer. For transport on the nanoscale, FDTR measurements are favorable due to their spot sizes (~ 1 micron) and small thermal penetration depths (as small as 10 nm). On the macroscale, a larger penetration depth is necessary and can be achieved with the TWS or Hot Disk TPS methods. TWS is a frequency-domain technique that utilizes joule heating of a metal line to measure a material’s thermal transfer function and determine its thermal properties. The Hot Disk TPS method is a time-domain thermal conductivity measurement method complementary to TWS and with the largest thermal penetration depths. It requires more mathematical corrections than either FDTR or TWS due to temperature drift that may occur around the sensor and interfacial thermal resistance between the sample and the sensor, but is still valuable in providing quick, bulk measurements with little fabrication requirements. At the larger scale, the shift from intrinsic properties to effective bulk properties, or how the properties change when features beyond a perfect single crystal are present, is critical to understand as they are nearly entirely unknown in this class of MOFs currently. I will present our  ongoing efforts to gather data in both the nano- and macroscales to determine which mechanisms dominate thermal transport for each regime in these complex MOF systems.

Presenting Author: Savannah Schisler Boston University

Presenting Author Biography: Savannah Schisler is a PhD candidate at Boston University. She earned a Bachelor of Science in Mechanical Engineering and a Bachelor of Arts in Physics & Astronomy from the University of Rochester in 2022. Her current research focuses on multi-scale thermal properties of Direct Air Capture (DAC) adsorbent materials, notably Metal-Organic Frameworks (MOFs). The thermal properties of these materials change as carbon dioxide and humidity levels change and differ at the intrinsic versus the bulk scales. Her focus is primarily understanding how these differences manifest in MOFs for DAC of carbon dioxide.

Authors:

Savannah Schisler Boston University
Sean Lubner Boston University