Lead-free glasses with a low melting point and good chemical durability are desirable for the sealing process in the ceramic and electronic fields. In this study, V2O5, ZnO, and TeO2 were used to prepare lead-free sealing glasses with a low melting temperature. The glass forming region, thermal stability, and surface morphology observation were investigated. Glass transition temperature, softening temperature, and thermal expansion coefficients were measured in detail in the ternary systems (V2O5-ZnO-TeO2). The dependencies of these properties on composition were quantitatively characterized. The ternary system glass (33.5 mol% V2O5-18.7 mol% ZnO-47.8 mol% TeO2) exhibited a low melting property, expedient thermal expansion coefficient, an amorphous structure, and good sealing properties. The lead-free glass had especially low glass transition temperature (=216°C), high thermal stability (ΔT= 145°C) and low sealing temperature (=350°C). In a sealing examination with a plane fluorescent lamp incorporated in a digital camera, we succeeded in achieving excellent sealing. The prepared lead-free glass exhibited a high performance as a substitute for the commercially available lead glass.
For the purpose of waste gypsum board recycling and selective generation of CaS, reductive decomposition behavior of CaSO4.2H2O under CO-CO2-N2 atmosphere was investigated by using a thermogravimetric analyzer. As a result, it was found that the reductive decomposition of CaSO4·2H2O to CaS in the presence of CO started at temperatures above 1023 K. However, at a temperature above 1173 K, CaS oxidation to CaO was observed and the oxidation was considered to proceed either by reaction of CaSO4 with CaS yielding CaO or by reaction of CaS with CO2 yielding CaO. Hence, to avoid the CaS oxidation, it was considered that the decomposition temperature should be kept below 1173 K. Furthermore, it was found that CaS generation increased with an increase in CO gas concentrations and the conversion of CaSO4.2H2O to CaS greater than 90% was obtained at a temperature of 1073 K, under CO : 10% and N2 : 90% atmosphere.
This study examined the strength characteristics of the reproduction concrete by using the waste concrete pole as reproduction aggregate to attempt the application growth of concrete waste. As a result of the study, the relation between the replacement ratio and the strength characteristics (compressive strength, Young's modulus, and tensile strength) of the reproduction aggregate that used the waste concrete pole was clarified.