R. A. Muñoz Hernández

Method for measurement of the thermal diffusivity in solids: Application to metals, semiconductors, and thin materials

We present a method for determining the thermal diffusivity in opaque solids by means of an analysis of the photoacoustic phase signal at low modulation frequencies using the open -cell photoacoustic technique. We show for f ⩽ (π/2)2fc, where fc is the modulation frequency at which the thermal diffusion length matches the sample thickness, the photoacoustic phase signal can be written in linear form with the modulation frequency f. Then, obtaining the proportionality coefficient by fitting the experimental data, the thermal diffusivity of the sample can be determined. The advantage of this method is that it is realized in a range of modulation requencies below those normally used, hence, the photoacoustic signal should be alone attributed to the mechanism of thermal diffusion. Moreover, the signal-to-noise ratio will be more reliable. This method was tested in some samples and it is also shown to be important in solids with high diffusivity values and thin materials.

Thermal Diffusivity in Bone and Hydroxyapatite

We report thermal diffusivity measurements in bull bone and commercial hydroxyapatite (HA), both in powder form, in order to determinate the thermal compatibility between these materials. Besides this, we report a comparison between these measured values and those of metallic samples frequently used in implants, as high purity titanium and stainless steel. Our results show a good thermal compatibility (74%) between HA and bone, both in powder form. Finally, it was obtained a one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and HA being this difference greater in titanium than in stainless steel, which is important to consider in some biomedical and dental applications.

Microstructure and Thermal Characterization of Dense Bone and Metals for Biomedical Use

We present a microstructural study and thermal diffusivity measurements at room temperature in two different sections of bull dense bone, bull bone and commercial hydroxyapatite, the last two in powder form. A comparison was realised between these measured values and those obtained from metallic samples frequently used in implants, as high purity titanium and 316L stainless steel. Our results show that the porosity and its orientation in the bone are two important factors for the heat flux through the bone. On the other hand, we obtained that the hydroxyapatite, in compact powder form, presents a thermal diffusivity value close to those obtained for the samples of bone which gives a good thermal agreement between these materials. Finally, it was obtained at one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and hydroxyapatite being this difference greater in titanium than in stainless steel.

Heat diffusion in the two layer system GaAs/GaSb joined by the fusion technique

Heat difusion is study in the two layer GaAs/GaSb system. Analysis of the thermal diffusivity of these systems demostrates the rol that the union plays in heat transport in these systems as a function of the temperature used in the joining process. The termal diffusivity measurementswere carried out by mean of the photoacoustic technique in a heat transmission configuration.