Measurement of thermal diffusivity and specific heat capacity of polymers by laser flash method

Measurement of the thermal coefficients of rewritable phase-change optical recording media

We describe a method to estimate the heat capacity of the substrate, the dielectric layer, and the phase-change layer of phase-change optical recording media as well as the thermal conductivity of the phase-change layer in its crystalline state. Measurements were carried out on spinning disks with the beam of light focused and locked onto the groove track. The method relies on the identification of the solid-to-liquid phase transition that occurs in the phase-change layer and takes advantage of the dependence of thermal diffusion on track velocity and irradiation time.

Estimation of thermal conductivity of magneto-optic media

We describe a method to estimate the thermal conductivity of the substrate, the dielectric layer, and the magneto-optic (MO) layer of MO recording media. The method relies on the disappearance of the polar Kerr rotation above the Curie temperature of the MO layer. We obtain the thermal conductivities by taking into account the differences in the heat diffusion behavior under different sized focused spots. The results are reliable to better than 5% accuracy.

Measurement of the thermal conductivity of erasable phase-change optical recording media

We describe a method to estimate the thermal conductivity of the substrate, the dielectric layer, the phase-change (PC) layer, and the reflective layer of PC optical recording media. The method relies on the amorphous-to-crystalline phase transition that occurs in the PC layer and takes advantage of the difference in the thermal diffusion behavior under different-sized focused spots. All the results obtained here are reliable with better than ?5% accuracy, which is within the margin of our experimental error.

Dynamic heat capacity changes of laser-irradiated type I collagen films

BACKGROUND AND OBJECTIVE

A common assumption made in the thermal response of biological materials due to laser irradiation is the constancy of the specific heat capacity at constant pressure, CP. In this investigation, CP of pure hydrated Type I collagen films is measured in time during laser irradiation.

STUDY DESIGN/MATERIALS AND METHODS

A Nd:YAG laser scanning calorimeter is developed and used to test the constant heat capacity assumption by monitoring transient, laser-induced thermal transitions in the collagen films.

RESULTS

Results of preliminary studies on the irreversible, laser induced thermal denaturation of collagen with heating rates of up to 110 K/sec show a broad CP transition that can attain large values (20 J/g K).

CONCLUSION

The magnitude of the CP change that occurs in response to laser irradiation shows that the assumption of a constant CP when modeling heat transport in tissues is not always valid.