Ca-Doped ZnO:Al Thin Films: Synthesis and Characterization

We unveiled the effect of doping on the morpho-structural and opto/electrical properties of Ca-doped ZnO:Al thin films obtained by RF magnetron sputtering. Scanning electron microscopy (SEM) was performed to reveal the surface morphology, while the composition and crystal structure were investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The correlation between the microstructure and the electrical conductivity identifies an increase in electrical conductivity up to 145 × 10−3 Ω−1·m−1 at 5 wt.% Ca doping level with the decrease in the grain size. Furthermore, the presence of Ca dopant triggers the occurrence of the emission peak at 430 nm and an increase of the green emission peak in PL spectra. Corroborating the electrical measurements with X-ray diffraction and optical measurements, one can infer that the electrical conductivity is dominated by intrinsic defects developed during deposition and by the existence of dopants.

Effect of Calcium Doping Using Aqueous Phase Reforming of Glycerol over Sonochemically Synthesized Nickel-Based Supported ZrO2 Catalyst

The aqueous phase reforming (APR) of glycerol was studied using sonochemically synthesized 10%Ni-x%Ca/ZrO2 catalysts (where x = 0, 0.5, 3, and 5) for the production of value-added liquid products. The APR reaction was performed in a batch reactor under the following conditions: 20 bar, 230 °C 450 rpm, and 1 h of reaction time. The synthesized catalysts were characterized using XRD, FESEM, BET, and H2-TPR to observe the effect of Ca doping on the physio-chemical properties of the catalysts. The results revealed that, at higher Ca loading, the catalysts experienced serious particles’ agglomeration, which resulted in a larger particles’ size, smaller surface area, and smaller pore volume owing to uneven distribution of the particles. The characterization results of the catalysts confirmed that the Us catalysts have a slightly higher surface area, pore volume, and pore size, as well as highly reducible and fine crystalline structure, compared with WI catalysts. The catalytic performance of the catalysts shows that 1,3-propanediol (1,3-PDO) and 1,2-propanediol (1,2-PDO) were the two main liquid products produced from this reaction. The highest selectivity of 1,3-PDO (23.84%) was obtained over the 10%Ni/ZrO2 catalyst, while the highest selectivity of 1,2-PDO (25.87%) was obtained over the 10%Ni-5%Ca/ZrO2 catalyst.