Supplementary Material: Thermal properties of methyltrimethoxysilane aerogel thin films Leandro N. Acquaroli, 1, a) Pascal Newby, 2 Clara Santato, 1 1, b) and Yves-Alain Peter 1) Department of Engineering Physics, Polytechnique Montreal, P.O. Box 6079, Station Centre-Ville, Montreal, QC H3C 3A7, Canada. 2) Department of Mechanical Engineering, Université de Sherbrooke, 3000 Bv. Université, Sherbrooke, QC J1K 0A5, Canada. (Dated: 23 September 2016) a) Electronic mail: leandro-nicolas.acquaroli@polymtl.ca b) Electronic mail: yves-alain.peter@polymtl.ca 1
FIG. S1. Molecular structure of methyltrimethoxysilane (MTMS). Reference: CSID:13803, www.chemspider.com/chemical-structure.13803.html (accessed 14:55, Aug 3, 2016) 2
FIG. S2. (a) Solid alcogel obtained after gel and aging step in the sol-gel synthesis. (b) Solution after homogenization with ultrasonic device. (c-d) Aerogel thin films deposited by spin coating at 2000 rpm for 40 s. 3
FIG. S3. Example of the metal 4-pads configuration used for the thermal characterization of the aerogel films. The four probes are also observed. The ratio between the lengths ( 1 mm) and the widths ( 10 µm) of the meteal lines adopted were chosen to be 100. The metal chosen was Au given its high c tr value. 4
Thickness [nm] 1800 1300 800, profilometry, profilometry (a) Thickness [nm] 1800 1300 800, profilometry, profilometry 300 0.0 2.5 5.0 7.5 10.0 TMOS v/v% 300 (b) TEOS v/v% FIG. S4. Comparison of thicknesses between ellipsometry and profilometry for MTMS aerogels mixed with different v/v% of TMOS (a) and TEOS (b). Lines are visual guides. 1800 100 120 Thickness [nm] 1300 800 Porosity [%] 80 60 Roughness [nm] 80 40 300 (a) TEOS [%] 40 (b) TEOS [%] 0 (c) TEOS [%] FIG. S5. Porosity, thickness, and RMS roughness of as-deposited and thermally treated aerogel films fabricated with MTMS with different TEOS v/v%. Inset of (a): refractive index (at λ = 550 nm) vs. TEOS v/v%,. Lines are visual guides. 5
Absorbance [arb. u.] 790 cm 1 Si-O vibrations 1275 cm 1 30% TEOS 20% TEOS 10% TEOS 0% TEOS 700 900 1100 1300 1500 Wavenumber [cm 1 ] FIG. S6. Absorbance FTIR spectra of the MTMS aerogel films synthesized with different TEOS v/v%. The broad band around 1090 cm 1 shows typical Si O contributions in silica aerogels, while bands at 790 cm 1 and 1275 cm 1 are associated to the Si CH 3 related modes. 6
Temperature rise Th,2ω [arb. u.] 0% TMOS 1% TMOS 2.5% TMOS 10% TEOS 20% TEOS 10 0 10 1 10 2 10 3 10 4 Frequency [Hz] (a) Temperature rise Th,2ω [K] 2.5 2.0 1.5 1.0 0.5 0.0 Model Experiment 0.5 10 0 10 1 10 2 10 3 Frequency [Hz] (b) FIG. S7. (a) Experimental (dots) and theoretical fit (full lines) spectra of the complex temperature rise for aerogel samples fabricated with different proportions of TMOS and TEOS co-precursors. The dashed line in the center indicates the zero-temperature separating the real part of the temperature rise (positive) from the imaginary one (negative). Temperature scale was normalized to make spectra more visible in the figure. (b) Fitting of the in phase and out of phase spectra of a soda lime glass substrate. The 3-omega setup was validated through the characterization of a well-known material substrate such as soda lime glass. The thermal conductivity obtained was 1.065 W m 1 K 1 which is in the range of accepted values between 0.9 and 1.3 W m 1 K 1 [1]. The thermal diffusivity of the soda lime yielded was 3.9 10 7 m 2 s 1, in good agreement with other authors [2]. Example of resistance-temperature measurements to determine the thermal coefficient of resistance (c tr ) can be seen in Fig. S8. In order to complete the validity of the 3-omega experimental setup [3,4], the linearity of the 3-omega signal for different driving currents was tested. In all cases the proportionality is fulfilled as can be checked in Fig. S9. An analysis of the thermal boundary resistance between the heater and the sample shows an average insignificant value around 10 10 m 2 K W 1, reason why it was disregarded. References [1] L. P. B. M. Janssen and M. M. C. G. Warmoeskerken, Transport phenomena data companion (Delft: VVSD, (2006). [2] M. Baesso, J. Shen, and R. Snook, Time-resolved thermal lens measurement of thermal diffusivity of soda-lime glass, Chem. Phys. Let. 197, 255 (1992). 7
Resistance [Ω] 40 35 30 25 0% 1% TMOS 2.5% TMOS 10% TEOS Thermal SiO 2 Sput. SiO 2 Glass 20 15 20 30 40 50 Temperature [ C] FIG. S8. Resistance-temperature plots for different aerogel samples. The temperature coefficient of resistance were calculated using c tr = (1/R 0 (T 0 ))(dr/dt), where T is the x-axis and R the y-axis of the plot. Measurements were performed at T 0 = 23 C, and the resistances R 0 were taken at this temperature. 16 Glass 3ω signal, v3ω [mv] 12 8 4 0% 1% TMOS 2.5% TMOS 10% TEOS Sputtered SiO 2 Thermal SiO 2 0 0e+00 3e+04 6e+04 9e+04 1e+05 Cubed current, I 3 1ω [ma3 ] FIG. S9. 3-omega voltage as a function of the cubed driven current for several samples with different synthesis conditions. The frequency used for the different measurements was 500 Hz, and it was proven not to affect the results. Lines are visual guides. [3] C. Dames and G. Chen, 1ω, 2ω, and 3ω methods for measurements of thermal properties, Rev. Sci. Instrum. 76, 124902 (2005). [4] C. Dames, Measuring the thermal conductivity of thin films: 3-omega and related electrothermal methods, in Annual Review of Heat Transfer, Vol. 16 (Begell House Digital Library, 2013) Chap. 2. 8
Thermal conductivity [Wm 1 K 1 ] 0.20 0.15 0.10 0.05 0.00 (a) TEOS v/v% Thermal diffusivity [m 2 s 1 ] 5e-08 3e-08 1e-08 (b) TEOS v/v% FIG. S10. Thermal conductivity (a) and diffusivity (b) of as-deposited and thermally treated MTMS aerogel films fabricated with different TEOS v/v%. Thermal conductivity [Wm 1 K 1 ] 0.20 0.15 0.10 0.05 Model, Eq. (2) 0.00 0 200 400 600 800 Aerogel density [kgm 3 ] FIG. S11. Thermal conductivity of the aerogel films fabricated with MTMS/TEOS plotted as a function of the density. The full line depicts the model through equations (2). Values of as-deposited and thermally treated aerogels were included. 9
10 0 Thermal conductivity [Wm 1 K 1 ] 10 1 10 2 10 3 10 4 Total (effective) Solid Gaseous Radiative TEOS v/v% FIG. S12. Contributions of the solid, gas and radiative phases to the total thermal conductivity of MTMS/TEOS synthesized aerogels. The full lines correspond to the as-deposited samples and the dashed lines to the thermally dried samples. 10