Thermal Diffusivity of Zinc Aluminum – Layered Double Hydroxide Using Photoflash Technique

Thermal diffusivity of zinc aluminum layered double hydroxide (Zn-Al-LDH) was measured by using photoflash technique. It used a simple camera flash and polyvinlidene diflouride (PVDF) film as signal generating source and detector respectively. Three series of sample were prepared at pH 7, 8 and 10 and with molar ratios of Zn to Al in a range from 2 to 6 (Zn/Al = 2, 3, 4, 5 and 6). The ZnO peaks appeared in x-ray diffraction pattern for all samples except for samples prepared at pH 7 with ratio 2 and 3 (Zn/Al = 2 and 3) and sample prepared at pH 8 with ratio 4. The ZnO peaks observed were between 2 = 30° to 2 = 37°. Thermal diffusivity for all three series samples (pHs 7, 8 and 10) was measured at room temperature. The thermal diffusivity for all three series of samples was found to increase for the case of molar ratio 2 to 6. The thermal diffusivity for Zn-Al-LDH at different ratios of Zn-Al-LDH increased with increasing ratio of Zn to Al. The increasing of thermal diffusivity is due to increasing of ZnO. Thermal diffusivity at pH 7, increased from 0.15 10−6m2 / s × to 0.22 10−6m2 / s × . Thermal diffusivity of sample prepared at pH 8 increased from 0.16 10−6m2 / s × to 0.20 10−6m2 / s × while at pH 10, if increased from 0.20 10−6m2 / s × to 0.25 10−6m2 / s × . Thermal diffusivity at pH 7 has the lowest value and at pH 10 has the highest value. The sample prepared at pH 7 with ratio 4 (Zn/Al = 4) was heat-treated at different temperature from 200°C to 600°C, prior to thermal diffusivity measurement at room temperature. In the case of heat treated samples, the thermal diffusivity increased from 0.25 10−6m2 / s × to 0.40 10−6m2 / s × with increasing treatment temperature

Effect of heat treatment on thermal diffusivity of Zn/Al layered double hydroxide synthesized using photoflash technique

Thermal diffusivity of zinc-aluminum layered double hydroxides was synthesized at different molar ratio of zinc and aluminum salts in the pH=7 and measured by using polyvinlidene diflouride (PVDF) by photoflash technique. The samples were prepared using Zn(NO3)2 and Al(NO3)3 solutions by drop wise addition of NaOH solution with vigorous stirring under nitrogen atmosphere. The samples then heat treated by control an electrical furnace from 200 to 600 °C for 5 hours. Thermal diffusivity was increased for all samples after sintering. The samples were studied by powder x-ray diffraction method, Fourier transform infrared (FTIR), scanning electron microscope (SEM) and thermal diffusivity. Our results indicate the very different role of sintering in the structure and thermal diffusivity of samples

Thermal diffusivity of zinc-aluminum layered double hydroxide using PVDF photoflash technique

Thermal diffusivity of zinc-aluminum layered double hydroxides synthesized at different molar ratios of Zn to Al, at pH 7 and 8 were measured using polyvinlidene diflouride (PVDF) photoflash technique. The samples were prepared using Zn(NO3)2 and Al(NO3)2 solutions by dropwise addition of NaOH solution with vigorous stirring under nitrogen atmosphere. The different ratios of Zn to Al were obtained by changing the molar ratio of Zn(NO3)2 to Al(NO3)2 solutions. The slurry formed was kept at 70 ˚C in an oil bath shaker for 18 h and then filtered, washed and dried in an oven for another 48 h at 70 ˚C. A simple photoflash and PVDF transducer were used as light source and thermal wave detector, respectively. All the measurements of thermal diffusivity of Zn-Al layered double hydroxide were carried out at room temperature. For Zn/Al > 3, the thermal diffusivity of all series of sample prepared at pH = 7 and 8 increase with the increasing of Zn composition. Thermal diffusivity values of zinc-aluminum layered doubled hydroxide synthesized at pH 8 are higher than the values obtained for samples prepared at pH = 7 except for Zn/Al higher than 5