Abstract
In this work, micrometer-thick organic-inorganic hybrid films are fabricated. A photothermal experiment is designed and conducted to characterize the thermophysical properties of hybrid films, as well as the thermal contact resistance between the film and substrate. The molecular cagelike or nanopores, which can strongly enhance the phonon scattering, are considered to be formed inside the films during fabrication. The first order estimation of the volume fraction of cavities and its effect on thermophysical properties are obtained. The effect of zirconium(IV) propoxide (ZPO) concentration on the thermophysical properties of hybrid films is also studied. The effective (measured) thermal conductivity and thermal effusivity of hybrid films are close to those of polymethyl methacrylate (PMMA) films, and are not significantly affected by the added ZPO, which is used to adjust the optic properties of films. The extracted bulk thermal conductivity of the hybrid films is close or smaller than that of bulk PMMA, and shows certain thermal conductivity reduction by the ZPO addition. The thermal effusivity study indicates that the response of the surface temperature change to an abrupt heat flux across the surface of hybrid films will be similar to that of PMMA films.
| Original language | English |
|---|---|
| Article number | 013528 |
| Journal | Journal of Applied Physics |
| Volume | 104 |
| Issue number | 1 |
| DOIs | |
| State | Published - 2008 |
| Externally published | Yes |
Bibliographical note
Funding Information:This work was supported by National Science Foundation (CMS: 0457471), Nebraska Research Initiative, Air Force Office for Scientific Research, and MURI from ONR. The authors especially appreciate the strong support from the China Scholarship Council for the State Scholarship Fund to pursue the research. Table I. Measured and effective physical properties of hybrid films and PMMA film. Molar concentration ZPO / ( MAPTMS + ZPO ) 0% 5% 10% 20% 25% PMMA Thickness ( μ m ) 8.3 6.6 6.3 4.1 4.4 2.15 k eff ( W / m K ) a 0.138 0.158 0.144 0.131 0.148 0.149 k eff ( W / m K ) b ⋯ 0.162 0.155 0.139 0.147 0.143 k eff ( W / m K ) c ⋯ 0.143 0.143 0.138 0.139 0.133 ρ ⋅ c p ( 10 6 J / m 3 K ) a 1.030 1.115 1.087 1.119 1.169 1.086 ρ ⋅ c p ( 10 6 J / m 3 K ) b ⋯ 1.179 1.140 1.120 1.178 0.946 ρ · c p ( 10 6 J / m 3 K ) c ⋯ 1.119 1.143 1.190 1.084 1.014 φ ( % ) d 35.3 29.0 32.1 31.2 28.6 32.7 k bulk ( W / m K ) d 0.251 0.255 0.246 0.220 0.237 0.258 a Measurement results for the first time. b Measurement results for the second time. c Measurement results of unheated samples. d Calculated using the measurement result of the first time. Table II. Measurement results at four different spots of sample with 25% ZPO. Measurement point 1 2 3 4 Thickness ( μ m ) 4.4 4.4 4.4 4.4 k eff ( W / m K ) 0.139 0.130 0.128 0.137 ρ ⋅ c p ( 10 6 J / m 3 K ) 1.063 1.098 1.030 1.084 Table III. Volume fraction of components and the resulted volumetric specific heat in Eq. (7) . Molar concentration ZPO / ( MAPTMS + ZPO ) 0% 5% 10% 20% 25% PMMA PMMA ( vol % ) 86.65 66.01 79.00 78.86 78.77 100.00 SiO 2 ( vol % ) 13.35 32.63 19.30 17.65 16.80 0.00 ZrO 2 ( vol % ) 0.00 1.36 1.70 3.49 4.43 0.00 ( ρ ⋅ c p ) bulk ( 10 6 J / m 3 K ) 1589.9 1571.1 1599.9 1625.1 1638.3 1614.1 FIG. 1. Schematic of the experimental principle. FIG. 2. Schematic of the experimental setup. FIG. 3. Schematic of a N-layer sample (Ref. 18 ). FIG. 4. Measured phase shift of the reflected laser beam and absolute time delay induced by the instrument. FIG. 5. Data fitting of phase shift for the thermal radiation from the PMMA sample surface. FIG. 6. Data fitting of phase shift for the thermal radiation from the hybrid sample surfaces. FIG. 7. SEM pictures of the hybrid film with 10% ZPO ( 6.3 μ m thick). FIG. 8. Optical microscope picture of the hybrid film with 10% ZPO ( 6.3 μ m thick). FIG. 9. Effective thermal effusivity and predicted thermal effusivity of bulk PMMA and hybrid films.
ASJC Scopus subject areas
- General Physics and Astronomy