Sajan, D George; Vallabhan, C P G; Heck, M; Radhakrishnan, P; Nampoori, V P N(Taylor & Francis, 2002)
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Abstract:
An open cell photoacoustic (PA) configuration has been employed to evaluate the thermal diffusivity of intrinsic InP as well as InP doped with tin and iron. Thermal diffusivity data have been evaluated from variation of phase of PA signal as a function of modulation frequency. In doped samples, we observe a reduced value for thermal diffusivity in comparison with intrinsic InP. We also observed that, while the phase of the PA signal varies linearly with the square root of chopping frequency for doped samples, the intrinsic material does not exhibit such behaviour in the experimental frequency range. These results have been interpreted in terms of the heat generation and phonon assisted heat diffusion mechanisms in semiconductors.
Nampoori, V P N; Radhakrishnan, P; Girijavallabhan, C P; George, N A; Paul, T; Sebastian,M T(Journal of Materials Science Letters,Kluwer Academic Publishers, 2000)
Radhakrishnan, P; Nampoori, V P N; Girijavallabhan, C P; Sajan, D George; George, A K(Smart Materials and Structures, July 5, 2007)
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Abstract:
Complete thermal characterization of liquid crystal mixtures in the smectic
phase consisting of various relative volume fractions of cholesterol and
1-hexadecanol have been carried out using the photoacoustic technique.
Thermal diffusivity values of these liquid crystal mixtures are evaluated using
the open cell photoacoustic technique whereas the thermal effusivity value is
measured using the conventional photoacoustic technique. From the
measured values of these transient thermophysical parameters, the thermal
conductivity and heat capacity of the sample under investigation are
calculated. Analyses of the results show that all the thermophysical
parameters depend strongly on the volume fraction of the constituents.
Results are interpreted in terms of enhanced hydrogen bonding and the
consequent enhancement in cohesive thermal energy transport with
increasing volume fraction of 1-hexadecanol
Nampoori, V P N; Radhakrishnan, P; Girijavallabhan, C P; Sajan, D George; George, A K(Smart Materials and Structures, July 5, 2007)
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Abstract:
Complete thermal characterization of liquid crystal mixtures in the smectic
phase consisting of various relative volume fractions of cholesterol and
1-hexadecanol have been carried out using the photoacoustic technique.
Thermal diffusivity values of these liquid crystal mixtures are evaluated using
the open cell photoacoustic technique whereas the thermal effusivity value is
measured using the conventional photoacoustic technique. From the
measured values of these transient thermophysical parameters, the thermal
conductivity and heat capacity of the sample under investigation are
calculated. Analyses of the results show that all the thermophysical
parameters depend strongly on the volume fraction of the constituents.
Results are interpreted in terms of enhanced hydrogen bonding and the
consequent enhancement in cohesive thermal energy transport with
increasing volume fraction of 1-hexadecanol
V P N Nampoori; Santhi Ani, Joseph; Misha, Hari; Mathew, S; Gaurav, Sharma; Soumya; Hadiya, V M; Radhakrishnan, P(Elsevier, Journal of Optics Communications, October 6, 2009)
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Abstract:
Dual beam mode-matched thermal lens method has been employed to measure the heat diffusion in
nanofluid of silver with various volumes of rhodamine 6G, both dispersed in water. The important observation
is an indication of temperature dependent diffusivity and that the overall heat diffusion is slower
in the chemically prepared Ag sol compared to that of water. The experimental results can be explained
assuming that Brownian motion is the main mechanism of heat transfer under the present experimental
conditions. Light induced aggregation of the nanoparticles can also result in an anomalous diffusion
behavior.