Evolution of Alcogel Physical Properties During the Aging Process.
effects of aging alcogel on the thermophysical properties of the resulting aerogel are
well understood. However, little has been done to characterize alcogel physical
properties during the aging process. Previous work has shown that the porous structure
undergoes physical changes as a result of aging, suggesting physical property change. A
better understanding of the overall agi... read moreng process can be developed by measuring the
changes of the physical properties in the alcogel as a function of aging time and
temperature. This work focuses on volume shrinkage and mechanical strength at different
aging conditions. Volume shrinkage is determined by measuring sample dimensions before
and after aging. Tests run at aging temperatures of 50 °C, 60 °C, 65 °C,
and 70 °C have shown a maximum volume percent change occurring at different times.
The maximum amount of shrinkage was found to be 2.5% at aging temperatures greater than
60 °C with aging time to fully cure becoming shorter at higher temperatures. The
Avrami function was used to fit the data and showed an activation energy of 238.6 kJ/mol
at high aging temperatures. In a parallel effort, tensile testing showed that the
Young's modulus reaches an early peak over the same temperature interval and then levels
out at a constant value of about 15 MPa as aging progressed. Both shrinkage and modulus
leveled out at the same aging time, which was determined to be a function of the aging
Thesis (M.S.)--Tufts University, 2011.
Submitted to the Dept. of Mechanical Engineering.
Advisor: Douglas Matson.
Committee: Luisa Chiesa, and Mez Polad.
Keywords: Mechanical Engineering, and Materials Science.read less