In the present study, the thermal behavior of pure Al6061 and fly ash reinforced Al6061 with varying particulate sizes were investigated for the first time. Metal matrix syntactic foams of ceramic fly ash (4 – 16 wt. %) embedded in aluminum (Al6061) matrix have been fabricated by using stir casting technique with different fly ash particulate sizes of size below 50µm and 53µm-100µm, respectively. The microstructural characteristics were studied by using scanning electron microscopy (SEM). It has been observed that there is a uniform distribution of lower particulate size fly ash as compared to higher particulate size in the aluminium matrix respectively. For all the cases, the accumulation of fly ash in Al6061 decreases the thermal conductivity and increases the specific heat carrying capacity of a hybrid composite. Increase in weight percentage of fly ash in Al6061 decreases thermal conductivity and thermal diffusivity respectively.

Fly Ash Cenospheres (FACs) are obtained from the coal power plants in the form of hollow spherical particles by burning the coal. FAC was started to use in early 1980-1985 as lightweight filler material in producing composites of cementitious and at present many researchers are focusing on use of FAC as filler in polymer and metals. In this paper, the systematic review on research activities and application of FAC in manufacturing light weight products are done. The FAC influence on the mechanical and physical properties of incorporated polymer and alloy based composites were summarized. Prospects of future for its use were also suggested and summarized in this paper.

Metal oxide nanoparticles are popular candidates for chemiresistive sensors application. Cerium oxide (CeO2) based semiconducting gas sensors have gained rapid interest in recent years. In this study, an environment-friendly green synthesis approach was employed for the synthesis of macroporous CeO2 nanoparticles using Mimosa pudica leaf extract. Later the performance of CeO2 nanoparticles for humidity sensor is demonstrated. X-ray diffraction studies revealed the cubic fluorite crystal structure with no impurities, scanning electron microscopy analysis revealed the macroporous morphology of CeO2 hierarchical nanoparticles. Humidity sensing properties were studied using interdigitated electrode coated with CeO2 nanoparticles. The results showed the sensing response of 0.5 times for 10% RH (relative humidity) and seven times for 90% RH. The response and recovery times were found to be as low as 12 s and 15 s, respectively. The experimental results provided an environment-friendly approach for the synthesis of CeO2 particles and revealed promising results in humidity sensing application.