Mechanical Engineering Seminar


Thermally Insulating Yet Optically Clear Mesoporous Silica Monoliths for Energy Efficient Windows


Prof. Laurent Pilon


University of California, Los Angeles; Mechanical and Aerospace Engineering Dept.


Monday, February 27, 2023 at 10:00:00 AM   


GTMI Building, Room Auditorium


Peter Loutzenhiser


Building operations account for about 40% of the total U.S. primary energy consumption. Approximately 30-40% of this energy is consumed for heating, ventilation, and air conditioning. In addition, emissions from buildings accounts for 12% of the U.S. total greenhouse gas (GHG) emissions, mostly due to combustion of fossil fuels for heating in the winter months. One way to reduce building energy consumption and the associated GHG emissions is to reduce heat losses through the building envelope. Windows are arguably the weakest constituent of that envelope. However, while double pane windows have excellent thermal, optical, and acoustic performance, their adoption has been relatively slow. In fact, between 30 and 40% of single pane windows remain in use in the Northeastern/Midwestern and Southern regions of the US, respectively. This talk presents new synthesis methods and characterization of new thermally insulating and optically transparent mesoporous silica monoliths. The thermal conductivity of transparent materials (e.g., glass) can be reduced by introducing porosity. However, it is typically accompanied by the presence of large pores (> 30 nm) which tend to scatter visible light and render the material opaque or translucent instead of transparent. In addition, thick mesoporous slabs provide superior thermal insulation. However, they are prone to cracking during synthesis. Here, thick mesoporous silica monoliths synthesized at room temperature and atmospheric pressure are presented. They feature porosity ranging from 50% to 90% with narrow pore size distribution with all pores less than 20 nm resulting in excellent optical clarity and very low thermal conductivity. Interestingly, not only porosity but also pore size and mass fractal dimension were found to affect the thermal conductivity of the mesoporous silica. In addition, the superior transparency of the monoliths was shown to be due to dependent scattering among the silica nanoparticles. Finally, the materials were integrated into window solutions and their thermal, optical, and acoustic performance will be discussed.


Laurent Pilon received his BS and MS in Physics from the Grenoble Institute of Technology, France and his PhD in Mechanical Engineering from Purdue University in 2002. He then joined the Mechanical and Aerospace Engineering Department at the University of California, Los Angeles (UCLA) where he is now Professor. His research group is engaged in a wide range of interdisciplinary research projects at the intersection of interfacial and transport phenomena, and material science for the development of sustainable energy conversion, storage, and efficiency technologies. He has authors more than 190 archival journal publications. He is also the recipient of several prestigious awards including the CAREER Award from the National Science Foundation (2005), the Bergles-Rohsenow Young Investigator Award in Heat Transfer (2008), and the Heat Transfer Memorial Award (2021) from the American Society of Mechanical Engineers (ASME). He is a Fellow of ASME.


Refreshments will be served.