• Journal of Conservation Science
• /
• v.30 no.2
• /
• pp.111-122
• /
• 2014

In Bongseon-ri site, the central type and the local type of the Baekje tombs co-exist together. Many swords with ring pommel which to regional leaders in Seocheon the Beekje government granted are excavated from these tombs. These represent that the regional leaders were controlled by the Baekje government gradually. Four swords with ring pommel and one simple sword are investigated metallurgically and we seek what swords have a function of weapon or what sword produce for grave goods. The simple sword is made by solid carburizing technology and quenching of heat treatment so it's possibly used as a weapon. In contrast, four swords with ring pommel has little chance of weapon because the blade of swords consists of microstructure that have low hardness and the back of swords don't have microstructure can absorb the shock. The most identical characteristic of the simple sword and swords with ring pommel is that they are possible to classify clearly into practical/non-practical tools. Additionally, according to non-metallic inclusion analysis result of these swords, w$\ddot{u}$stite and glass phase are found together. Thus, it is able to say that reduction method in low temperature is applied during smelting process.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.6
• /
• pp.497-503
• /
• 2016

Flue gas desulfurization gypsum is produced from emission process of fossil fuel power plant to remove sulfur dioxide ($SO_2$) from exhaust gas. Production of flue gas desulfurization gypsum in Republic of Korea has been increasing due to the enforced regulations by government agency. Since flue gas desulfurization gypsum has characteristic that is similar to that of natural gypsum, there is a strong possibility for flue gas desulfurization gypsum to replace the role of natural gypsum. However, consumption of such material is still limited, only used for agricultural purposes or to make gypsum boards, it is necessary to expand the use of this material more aggressively. In this research, the chemical and mineralogical properties of flue gas desulfurization gypsum were investigated, and flue gas desulfurization gypsum with heat treatment was used to make cement paste. According to the results, it was found that flue gas desulfurization gypsum used in this experiment was a very high purity gypsum, and shown to have similar property to that of natural gypsum. Heat treating flue gas desulfurization gypsum above $100^{\circ}C$ was shown to bring beneficial effect on both compressive strength and drying shrinkage

• Clean Technology
• /
• v.28 no.4
• /
• pp.269-277
• /
• 2022

With the recent development of the biological enzymatic reaction industry, lactic acid (LA) can be mass-produced from biomass sources. In particular, a catalytic process that converts LA into acrylic acid (AA) is receiving much attention because AA is used widely in the petrochemical industry as a monomer for superabsorbent polymers (SAP) and as an adhesive for displays. In the LA conversion process, NaY zeolites have been previously shown to be a high-activity catalyst, which improves AA selectivity and long-term stability. However, NaY zeolites suffer from fast deactivation due to severe coking. Therefore, the aim of this study is to modify the acid-base properties of the NaY zeolite to address this shortcoming. First, base promoters, Ca ions, were introduced to the NaY zeolites to tune their acidity and basicity via ion exchange (IE) and incipient wetness impregnation (IWI). The IWI method showed superior catalyst selectivity and stability compared to the IE method, maintaining a high AA yield of approximately 40% during the 16 h reaction. Based on the NH₃- and CO₂-TPD results, the calcium salts that impregnated into the NaY zeolites were proposed to exit as an oxide form mainly at the exterior surface of NaY and act as additional base sites to promote the dehydration of LA to AA. The NaY zeolites were further treated with KOH before calcium impregnation to reduce the total acidity and improve the dispersion of calcium through the mesopores formed by KOH-induced desilication. However, this KOH treatment did not lead to enhanced AA selectivity. Finally, calcium loading was increased from 1wt% to 5wt% to maximize the amount of base sites. The increased basicity improved the AA selectivity substantially to 65% at 100% conversion while maintaining high activity during a 24 h reaction. Our results suggest that controlling the basicity of the catalyst is key to obtaining high AA selectivity and high catalyst stability.