Feature: Ceramics Processing through Energy Consumption Reduction (Green Processing): Full papers
Synthesis and characterization of CaO@SiO2 nanoparticle for chemical thermal storage
2016 年 124 巻 1 号 p. 55-59
詳細
2016 年 124 巻 1 号 p. 55-59
Preparation of CaO core-SiO2 shell nanoparticles as a chemical thermal storage through hydration/de-hydration of CaO/Ca(OH)2 was proposed. Firstly, SiO2 was coated on CaCO3 template surface using sol–gel route and then the core–shell particles were heated at 700°C to form CaO@SiO2 nanoparticle by de-carbonization. A thermal storage performance of the CaO@SiO2 was confirmed by a thermogravimetry (TG) analysis and the result was compared with that of as-received CaCO3. The heating program was performed as following steps as (i) at 700°C for 30 min for de-carbonization under nitrogen (N2) atmosphere, (ii) at room temperature for 60 min for hydration under water vapor, and (iii) at 500°C for de-hydration under N2. By repeating of (ii) hydration/(iii) de-hydration cycle, effect of the number of cycles on thermal storage ability was investigated. An efficiency of thermal storage was defined as difference in weight change between hydration/de-hydration reactions. For the as-received CaCO3 nanoparticles, with increase in the number of cycles, the thermal storage performance gradually decreased. The microscopic results showed that the heating cycles induces coalescence of CaCO3 nanoparticles and that decreases specific surface area. On the other hands, efficiency of thermal storage of CaO@SiO2 didn’t reach theoretical value because CaCO3 didn’t completely transform into CaO owing to SiO2’s thermal insulation ability. By decreasing SiO2 coating thickness, the thermal storage performance of CaO@SiO2 was improved. The microscopic results showed that the SiO2 coating prevented from coalescence of CaCO3 nanoparticles.
