Experimental Investigations on the Crystallization of Zinc by Direct Irradiation of Zinc Oxide in a Solar Furnace

Abstract

Concentrated solar irradiation was used to thermally dissociate ZnO and to study the zinc vapor condensation process in the presence of oxygen under several dilution, temperature, pressure, and irradiation conditions. Product samples were taken from targets on the condenser surface and were analyzed with X-ray diffractometry and scanning electron microscopy. The zinc oxide formation by reoxidation of zinc was found to be of a heterogeneous nature, with homogeneously condensed zinc serving as the main nucleation sites. High zinc yields were obtained under conditions which favor supersaturation of zinc vapor and high deposition rates of zinc, whereby separation of condensing zinc and oxygen is desired.

Review of the Two-Step H2O/CO2-Splitting Solar Thermochemical Cycle Based on Zn/ZnO Redox Reactions

“…Exploratory experimentation to thermally dissociate ZnO was carried out at the solar furnaces and high-flux solar simulators of PSI/ETH (Switzerland) and CNRS-Odeillo/Nancy (France). Initially, small-scale solar reactors containing ZnO pellets or powders within transparent enclosures were directly subjected to high-flux solar radiation while product Zn(g) was condensed on cold surfaces or collected downstream in a filter [ 34 , 35 , 36 , 37 ]. Scalable solar reactor concepts have been realized with packed-bed reactors—such as rotary cavity-receivers—and aerosol flow reactors.…”

Kinetics of the thermal dissociation of ZnO exposed to concentrated solar irradiation using a solar‐driven thermogravimeter in the 1800–2100 K range

“…Nonstoichiometry and lattice defects were found to affect the kinetics under vacuum at 1013 and 1053 K 13. Exploratory tests were carried out in solar furnaces with batch reactors 20–23. Recently, a 10 kW solar chemical reactor prototype featuring a rotating cavity‐receiver lined with ZnO particles has been experimentally demonstrated in a solar furnace 24.…”

Evolution of zinc oxide nanostructures through kinetics control

“…The oxidation of the Zn core under ZnO shell is typically controlled by the diffusion of Zn or O 2 through the ZnO surface layer – the Wagner oxidation theory. 42, 43 …”

“…The oxidation of the Zn core under ZnO shell is typically controlled by the diffusion of Zn or O 2 through the ZnO surface layer-the Wagner oxidation theory. 42,43 Below $500 K is the region V, where the deposition appeared black and was identified as metallic Zn as shown in Fig. 3 and Fig.…”