scholarly journals Thermal Conductivity of Cubic and Hexagonal Mesoporous Silica Thin Films

2009 ◽  
Author(s):  
Thomas Coquil ◽  
Neal Hutchinson ◽  
Laurent Pilon ◽  
Erik Richman ◽  
Sarah Tolbert
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Mesoporous Silica ◽  
Film Thickness ◽  
Wall Thickness ◽  
Room Temperature ◽  
Strong Dependence ◽  
Fused Silica ◽  
Silica Thin Films ◽  
The Cross

This paper reports the cross-plane thermal conductivity of highly ordered cubic and hexagonal templated mesoporous amorphous silica thin films synthesized by evaporation-induced self-assembly process. Cubic and hexagonal films featured spherical and cylindrical pores and average porosity of 25% and 45%, respectively. The pore diameter ranged from 3 to 18 nm and film thickness from 80 to 540 nm while the average wall thickness varied from 3 to 12 nm. The thermal conductivity was measured at room temperature using the 3ω method. The experimental setup and the associated analysis were validated by comparing the thermal conductivity measurements with data reported in the literature for the silicon substrate and for high quality thermal oxide thin films with thickness ranging from 100 to 500 nm. The cross-plane thermal conductivity of the synthesized mesoporous silica thin films does not show strong dependence on pore size, wall thickness, or film thickness. This is due to the fact that heat is mainly carried by very localized non propagating vibrational modes. The average thermal conductivity for the cubic mesoporous silica films was 0.30 ± 0.02 W/mK, while it was 0.20 ± 0.01 W/mK for the hexagonal films. This corresponds to a reduction of 79% and 86% from bulk fused silica at room temperature.

Thermal Conductivity of Cubic Mesoporous Silica Thin Films

2007 ◽  
Author(s):  
Soojung C. Hur ◽  
Laurent Pilon ◽  
Adam Christensen ◽  
Samuel Graham
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Mesoporous Silica ◽  
Self Assembly ◽  
Room Temperature ◽  
Mean Free Path ◽  
Fused Silica ◽  
Silica Thin Films ◽  
The Cross ◽  
Cubic Mesoporous

This paper reports, for the first time, the cross-plane thermal conductivity of highly ordered cubic mesoporous silica thin films with porosity of 31% and thickness ranging between 200 and 500 nm. The mesoporous thin films are synthesized based on evaporation induced self-assembly process. The pores are spherical with average inter-pore spacing and pore diameter equal to 5.95 nm and 5 nm, respectively. The thermal conductivity is measured at room temperature using the 3ω method. The experimental setup and the associated analysis are validated by comparing the thermal conductivity measurements for the silicon substrate and for high quality thermal oxide thin films with data reported in the literature. The cross-plane thermal conductivity of the synthesized mesoporous silica thin films does not strongly depend on film thickness due to the reduction in phonon mean free path caused by the presence of nanopores. The average thermal conductivity is 0.61 ± 0.011 W/mK, which is 56% lower than that of bulk fused silica at room temperature.

Thermal Conductivity of Highly Ordered Amorphous and Crystalline Mesoporous Titania Thin Films

2010 ◽  
Author(s):  
Thomas Coquil ◽  
Laurent Pilon ◽  
Christian Reitz ◽  
Torsten Brezesinski ◽  
Joseph E. Nemanick ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Film Thickness ◽  
Pore Size ◽  
Wall Thickness ◽  
Sol Gel ◽  
Atomic Scale ◽  
Mesoporous Titania ◽  
Titania Films ◽  
The Cross

This paper reports the cross-plane thermal conductivity of amorphous and crystalline templated mesoporous titania thin films synthesized by evaporation-induced self-assembly. Both sol-gel and nanocrystal-based films were considered, with respective average porosities of 30% and 35%. The pore diameter ranged from 7 to 25 nm and film thickness from 60 to 370 nm while the average wall thickness varied from 3 to 25 nm. Nanocrystals in crystalline mesoporous films featured diameters between 9 and 13 nm. The thermal conductivity was measured at room temperature using the 3ω method. The experimental setup and the associated analysis were validated by comparing the thermal conductivity measurements with data reported in the literature for dense titania films with thickness ranging from 95 to 1000 nm. The cross-plane thermal conductivity of the amorphous mesoporous titania thin films did not show strong dependence on pore size, wall thickness, or film thickness. This can be attributed to the high atomic scale disorder of amorphous materials. Heat is thus mainly carried by localized non-propagating vibrational modes. The average thermal conductivity of the amorphous mesoporous titania films was identical to that of the nanocrystal-based films and equal to 0.37 W/m.K. Thermal conductivity of sol-gel crystalline mesoporous titania thin films was significantly larger than that of their amorphous counterparts. It also depended on the organic template used to make the films. The results indicated that the pore size was not an important factor. Instead thermal conductivity depended only on porosity, crystallinity, nanocrystal size and connectivity.

scholarly journals Thermal conductivity of cubic and hexagonal mesoporous silica thin films

2009 ◽  
Vol 106 (3) ◽  
pp. 034910 ◽  
Author(s):  
Thomas Coquil ◽  
Erik K. Richman ◽  
Neal J. Hutchinson ◽  
Sarah H. Tolbert ◽  
Laurent Pilon
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Mesoporous Silica ◽  
Hexagonal Mesoporous Silica ◽  
Silica Thin Films

scholarly journals Investigation on the Power Factor of Skutterudite Smy(FexNi1-x)4Sb12 Thin Films: Effects of Deposition and Annealing Temperature

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5773
Author(s):  
Giovanna Latronico ◽  
Paolo Mele ◽  
Cristina Artini ◽  
Pietro Manfrinetti ◽  
Sian Wei Pan ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Power Factor ◽  
Room Temperature ◽  
Fused Silica ◽  
Annealing Process ◽  
Seebeck Coefficients ◽  
Heating And Cooling ◽  
Scattering Centers ◽  
Filled Skutterudites

Filled skutterudites are currently studied as promising thermoelectric materials due to their high power factor and low thermal conductivity. The latter property, in particular, can be enhanced by adding scattering centers, such as the ones deriving from low dimensionality and the presence of interfaces. This work reports on the synthesis and characterization of thin films belonging to the Smy(FexNi1-x)4Sb12-filled skutterudite system. Films were deposited under vacuum conditions by the pulsed laser deposition (PLD) method on fused silica substrates, and the deposition temperature was varied. The effect of the annealing process was studied by subjecting a set of films to a thermal treatment for 1 h at 423 K. Electrical conductivity σ and Seebeck coefficient S were acquired by the four-probe method using a ZEM-3 apparatus performing cycles in the 348–523 K temperature range, recording both heating and cooling processes. Films deposited at room temperature required three cycles up to 523 K before being stabilized, thus revealing the importance of a proper annealing process in order to obtain reliable physical data. XRD analyses confirm the previous result, as only annealed films present a highly crystalline skutterudite not accompanied by extra phases. The power factor of annealed films is shown to be lower than in the corresponding bulk samples due to the lower Seebeck coefficients occurring in films. Room temperature thermal conductivity, on the contrary, shows values comparable to the ones of doubly doped bulk samples, thus highlighting the positive effect of interfaces on the introduction of scattering centers, and therefore on the reduction of thermal conductivity.

Thermal Conductivity of Ordered Mesoporous Silicon Thin Films Made From Magnesium Reduction of Polymer Templated Silica

2011 ◽  
Author(s):  
Jin Fang ◽  
Laurent Pilon ◽  
Chris B. Kang ◽  
Sarah H. Tolbert
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Film Thickness ◽  
Crystalline Silicon ◽  
Average Crystallite Size ◽  
Face Centered Cubic ◽  
Mesoporous Silicon ◽  
X Ray ◽  
Silicon Thin Films ◽  
The Cross

This paper reports the cross-plane thermal conductivity of ordered polycrystalline mesoporous silicon thin films between 30 and 320 K. The films were produced by a combination of evaporation induced self-assembly (EISA) of mesoporous silica followed by magnesium reduction. The periodic ordering of pores in mesoporous silicon was characterized by a combination of 1D X-ray diffraction, 2D small angle X-ray scattering, and direct SEM imaging. The average crystallite size, porosity, and film thickness were about 13–18 nm, 25–35%, and 140–260 nm, respectively. The pores were arranged in a face-centered cubic lattice. Finally, the cross-plane thermal conductivity of the meso-porous silicon thin films was measured using the 3ω method. The measured thermal conductivity was about 3 to 5 orders of magnitude smaller than that of the bulk dense crystalline silicon for the temperature range considered. The effects of temperature and film thickness on the thermal conductivity were investigated.

The Investigations of Dielectric Properties of BaTiO3 Thin Films on Polycrystalline Pt Substrates by Rf Magnetron Sputtering

1996 ◽  
Vol 433 ◽  
Author(s):  
Jin Wook Jang ◽  
Woon Jo Cho ◽  
Taek Sang Hahn ◽  
Sang Sam Choi ◽  
Su Jin Chung
Keyword(s):  
Thin Films ◽  
Dielectric Properties ◽  
Magnetron Sputtering ◽  
Film Thickness ◽  
Room Temperature ◽  
Strong Dependence ◽  
Hysteresis Loops ◽  
Rf Magnetron Sputtering ◽  
Thickness Dependence ◽  
Grain Sizes

AbstractThickness dependence of ferroelectric and structural properties of BaTiO3 thin films were investigated. Stoichiometric BaTiO3 thin films were prepared by off-axis rf magnetron sputtering on polycrystalline Pt substrates at 700°C. Film thickness range was 2,100–20,000Å. Room temperature permittivity, frequency dependence of permittivity, and D-E hysteresis loops were measured and lattice parameters were determined as a function of the film thickness. It has been found that these properties had the strong dependence on film thickness, which was mainly due to grain sizes of BaTiO3 thin films. The main cause of thickness dependence of dielectric properties was thought to be crystallinity and stresses of thin films which is resulted from changes in grain sizes.

MeV Ion-Beam Bombardment Effects on The Thermoelectric Figures of Merit of Zn4Sb3 and ZrNiSn-Based half-heusler compounds

2007 ◽  
Vol 1020 ◽  
Author(s):  
S. Budak ◽  
S. Guner ◽  
C. Muntele ◽  
C. C. Smith ◽  
B. Zheng ◽  
...  
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Measurement System ◽  
Ion Beam ◽  
Electrical Energy ◽  
Figures Of Merit ◽  
Material Systems ◽  
The Cross ◽  
Conductivity Of Thin Films

AbstractSemiconducting â-Zn4Sb3and ZrNiSn-based half-heusler compound thin films were prepared by co-evaporation for the application of thermoelectric (TE) materials. High-purity solid zinc and antimony were evaporated by electron beam to grow the â-Zn4Sb3thin film while high-purity zirconium powder and nickel tin powders were evaporated by electron beam to grow the ZrNiSn-based half-heusler compound thin film. Rutherford backscattering spectrometry (RBS) was used to analyze the composition of the thin films. The grown thin films were subjected to 5 MeV Si ions bombardments for generation of nanostructures in the films. We measured the thermal conductivity, Seebeck coefficient, and electrical conductivity of these two systems before and after 5 MeV Si ions beam bombardments. The two material systems have been identified as promising TE materials for the application of thermal-to-electrical energy conversion, but the efficiency still limits their applications. The electronic energy deposited due to ionization in the track of MeV ion beam can cause localized crystallization. The nanostructures produced by MeV ion beam can cause significant change in both the electrical and the thermal conductivity of thin films, thereby improving the efficiency. We used the 3ù-method measurement system to measure the cross-plane thermal conductivity ,the Van der Pauw measurement system to measure the cross-plane electrical conductivity, and the Seebeck-coefficient measurement system to measure the cross-plane Seebeck coefficient. The thermoelectric figures of merit of the two material systems were then derived by calculations using the measurement results. The MeV ion-beam bombardment was found to decrease the thermal conductivity of thin films and increase the efficiency of thermal-to-electrical energy conversion.

Photo-orientation of Mesoporous Silica Thin Films on Photocrosslinkable Polymer Films

2005 ◽  
Vol 17 (8) ◽  
pp. 1035-1039 ◽  
Author(s):  
H. Fukumoto ◽  
S. Nagano ◽  
N. Kawatsuki ◽  
T. Seki
Keyword(s):  
Thin Films ◽  
Mesoporous Silica ◽  
Polymer Films ◽  
Silica Thin Films
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