In this work, we measure the thermal conductivity of mesoporous silica and aerogel thin-films using a non-destructive optical technique: time domain thermoreflectance (TDTR). Due to the rough surfaces of the optically transparent silica-based films, we evaporate an Al film on a glass cover slide and fabricate the silica structures directly on the Al film, providing a “probe-through-the-glass” configuration for TDTR measurements. This allows the thermal conductivity of mesoporous silica and aerogel thin films to be measured with traditional TDTR analyses. As the thermoreflectance response is highly dependent on the thermal effusivity of the porous structures, we estimate the density of the films by varying the heat capacity in our analysis. This density determination assumes that the solid matrix in the silica structure has the thermal conductivity as bulk SiO 2 , which is valid if all the lattice vibrations are localized, consistent with the minimum thermal conductivity concept. We independently determine the density of the porous silica films with nitrogen sorption measurements of thin films using a surface acoustic wave (SAW) technique. The difference between the determined from the SAW technique and that estimated by the TDTR effusivity analysis lends insight into the relative contributions of localized and propagating modes to thermal transport.

We conducted an experiment to demonstrate the thermoelectric nano-gap, which is recently expected to own high performance, in principle, because it does not have conductive heat flow between the high and low temperature region. In this study, the thermoelectric nano-gap is realized with a pair of probe and substrate where they are finely positioned. A temperature difference of ca. 10 K is imposed to the nano-gap under vacuum circumstances. A representative thermoelectric voltage, tunneling-current and gap were 250 μV, 0.3 nA and 50 nm. The obtained voltage and current, with assuming an effective probe-diameter of 10 nm, roughly agreed to a theoretical study (G. Despesse and T. Jager, J. Appl. Phys., Vol.96, p.5026-, 2004). However, the obtained gap was 25 times larger than that from the theoretical study.

In this study, a method to directly form an electrically conductive layer on the surface of polymeric material by using infrared laser irradiation was investigated. Polyacrylonitrile, which was shaped into a small disk 20 mm in diameter and 5 mm thick, was used as a test specimen. The conditions for pyrolysis were obtained by referencing the conditions for commercial carbon fiber. First, the specimen was processed in air at a relatively low temperature (around 250°C) for the stabilization treatment (i.e., fireproofing), then its surface was heated at a higher temperature (above 1000°C) for the carbonization treatment (i.e., graphitizing). Both an infrared furnace and a carbon dioxide laser were used as heating devices to find optimal conditions. Property changes in the material due to the thermal treatment were measured using Fourier transform infrared spectroscopy, and the electrical conductivity of the carbonized surface was measured using a four-probe method. The results showed that an electrical conductivity of 11.4 S/cm (siemens per centimeter) was achieved with a laser intensity of 8.6 W/cm 2 for 5 min for the stabilization, and a laser intensity of 34 W/cm 2 for 10 s for the carbonization.

The purpose of this study is to measure the fluorescence properties of Indocyaninegreen (ICG) which is a fluorescence dye to be used as a fluorescence probe for the use of fluorescence imaging in biomedical applications. The fluorescence molecular imaging is expected to solve the issues in preclinical studies which require a lot of time, labors and sacrificed animals. Information of living body can be obtained by measuring the fluorescent properties of the probe in biological media. The absorption and emission spectra and the lifetime of ICG in non-scattering and scattering media were measured in this study. ICG was dissolved in water, in plasma, in Intralipid, and in a mixture of plasma and Intralipid to simulate the environment in living tissues. The absorption and emission spectra were measured using a fluorescence spectrophotometer. The fluorescence lifetimes were measured using a time-resolved measurement method. Results suggest that the fluorescent properties are affected by the reaction between ICG and biological tissues.

During atmospheric (re-)entries, planetary probes encounter huge heat fluxes due to their significant speed (up to 13 km/s for an Earth re-entry). The total heat flux received by the probe can be divided into two main components: a convective one (coming from the conduction and diffusion phenomena occuring in the shock layer) and a radiative one (due to the radiation of certain species). Numerical simulations have been performed for both Titan (Huygens mission) and Earth (Fire II mission) entries. The main parameters influencing the results are the atmosphere composition, the chemical reaction scheme, the transport model and the radiative model. The results obtained gave us information on the flowfield (temperature, pressure, species densities...) and values for the heat fluxes on the wall that are useful for experimental or flight data comparison.

This article investigates thermophysical property measurement of femtogram-level polymeric samples by using the 3ω method on a heated microcantilever probe. A localized thermal scooping method was employed to acquire 449 fg of polyethylene terephthalate (PET) sample, measured gravimetrically, directly onto the heater of the cantilever. It is shown that the sample case has a 3ω signal that is smaller in magnitude than the bare case, suggesting that sample properties could be determined using the processes discussed here. A finite element analysis (FEA) model was also developed to compute the steady periodic behavior of the cantilever in the frequency domain. In order to drastically reduce the computational cost and consider the transient effect of the surrounding air, the FEA model implements the complex thermal conductance of the air as the boundary condition rather than modeling the air as a separate domain. The comparison of the modified model with the model that includes the air in the system reveals that the running time has improved by one order of magnitude while showing excellent agreement. The obtained results will expand the characterization and functionality of microcantilevers leading to advancements in localized thermal analysis.

Liquid hold-up and phase split have been measured to study flow pattern dynamics around a vertical dividing junction with 0.005 m internal diameter pipes. Liquid phase viscosities were varied systematically between 1 mPa s and 36 mPa s. Test matrix implemented varied between 0–32 m/s for gas superficial velocity and 0.003–1.3 m/s for liquid superficial velocity respectively. Dynamic signals were acquired during the passage of gas–liquid two-phase flow employing electrical resistance between pairs of flush-mounted ring conductance probes located around the junction. The time varying void and phase split data have been examined at a number of levels. First, information about distribution of phases and flow pattern classification along each segment of the pipe is presented using probability Density Function (PDF) generated from time varying void fraction. PDF characteristic signature exhibits lower peaks and a marked shift towards decreasing void fraction as liquid viscosity increases. For a viscous liquid phase, bubbly flow approaching the junction changes to slug flow pattern after splitting at the junction in the vertical direction. Flow pattern in the horizontal side arm remains inevitably stratified irrespective of increase in liquid viscosity. At another level, liquid hold-up and phase split were examined. This analysis reveals additional flow assurance details. Liquid hold-up was seen to increase with increase in both liquid viscosity and gas take-off at the horizontal segment of the junction. However, effect of liquid viscosity only become significant when gas take-off exceeds a threshold of 0.40. Plot of the liquid hold-up against mixture velocity at various take-offs and different liquid viscosities fingerprints churn-annular transition boundary around gas superficial velocity of 15 m/s.