Mohd Shahril Husin

Laser-fabricated castor oil-capped silver nanoparticles

Silver nanoparticles were fabricated by ablation of a pure silver plate immersed in castor oil. A Nd:YAG-pulsed Q-switch laser with 1064-nm wavelength and 10-Hz frequency was used to ablate the plate for 10 minutes. The sample was characterized by ultraviolet-visible, atomic absorption, Fourier transform-infrared spectroscopies, and transmission electron microscopy. The results of the fabricated sample showed that the nanoparticles in castor oil were about 5-nm in diameter, well dispersed, and showed stability for a long period of time.

Thermal diffusivity measurement of silver nanofluid by thermal lens technique

The thermal lens technique was utilized in silver nanofluid containing silver nanoparticles in polyvinylpyrrolidone solution to study the effect of nanoparticle size on thermal diffusivity. The different sizes of silver nanoparticles were prepared by irradiating the solution of silver nitrate in polyvinylpyrrolidone with respective dose of γ-radiation. The average sizes of particle in the prepared samples were measured using nanophox machine. The thermal lens measurement was carried out by using a diode laser of wavelength 514 nm and a He–Ne laser for the excitation source and the probe beam, respectively. The obtained result showed a decrease in the thermal diffusivity of nanofluid with the decrease in particle size.

Formation of silver microbelt structures by laser irradiation of silver nanoparticles in ethanol

In the present work, we prepared silver nanoparticles by laser ablation of pure silver plate in ethanol and then irradiated the silver nanoparticles using a 532 nm Q-switched Nd:YAG pulsed laser. Transmission electron microscopic images of the sample after irradiation clearly showed formation of big structures, such as microrods and microbelts in ethanol. The obtained microbelts had a width of about 0.166 μm and a length of 1.472 μm. The reason for the formation of such a big structure is the tendency of the nanoparticles to aggregate in ethanol before irradiation, which causes fusion of the nanoparticles.

Camera flash heating of a three-layer solid composite: An approximate solution

Camera flash heating and the subsequent thermal wave propagation in a solid composite material is studied using the Laplace transform technique. Full-field rear surface temperature for a single-layer, two-layer and three-layer solid composites are obtained directly from the Laplace transform conversion tables as opposed to the tedious inversion process by integral transform method. This is achieved by first expressing the hyperbolic-transcendental equation in terms of negative exponentials of square root of sα and expanded same in a series by the binomial theorem. Electrophoretic deposition (EPD) and dip coating processes were used to prepare three-layer solid composites consisting ZnO/Cu/ZnO and starch/Al/starch respectively. About 0.5ml of deionized water enclosed within an air-tight aluminium container serves as the third three layer sample (AL/water/AL). Thermal diffusivity experiments were carried out on all the three samples prepared. Using Scaled Levenberg-Marquardt algorithm, the approximate tempe...

Photoflash thermal diffusivity measurement of carbon nanotube-filled PVDF composite at low temperature

The suitability of a simple photoflash technique was further examined in the measurement of thermal diffusivity of nanotube-filled polyvinylidene difluoride (PVDF) film composites at low temperature. The effect of temperature and carbon nanotube (CNT) composition in PVDF composite on its thermal diffusivity is presented as equivalent to the effect of changing thermal phonon mean free path. It is done by assuming no other thermal carrier effects other than from phonons detected during measurement by using photoflash technique. The results show that thermal diffusivity of CNT-filled PVDF film composites was found to have consistently increased with increasing the CNT concentration or decreasing temperature, as in the case of insulators with dominant phonon thermal carriers. At any particular temperature, a dramatic increase in thermal diffusivity was noticed at the beginning as the CNT concentration was systematically increased up to a 1% turning point, from which the thermal diffusivity increased further at a much smaller rate with the CNT addition up to 10%. The thermal diffusivity of the samples was in the range of about (10–35) × 10− 8 m2/s depending on the temperature and the CNT concentration of the composites.

Effect of Electron Thermal Carriers on Thermal Diffusivity of Metals

A photoflash method of thermal diffusivity measurement was used to determine the value of thermal diffusivity of a sandwiched aluminum layer in a three-layer sample when the sample is simultaneously subjected to both thermal and electric field gradients. The value of the thermal diffusivity of the sample initially measured before electric field was applied agreed well with other reported results. The thermal diffusivity was also found to decrease or increase under the influence of the electric field strength or direction.