• Proceedings of the Korean Nuclear Society Conference
• /
• 1995.05b
• /
• pp.739-744
• /
• 1995

연소도 33 MWD/kgU에 해당하는 simulate $UO_2$ 소결체를 제조하여, 산화 (대기중 40$0^{\circ}C$), 고온산화 (대기중 110$0^{\circ}C$), 환원 (수소분위기 $600^{\circ}C$)을 차례로 실시하였다. 이 분말을 다시 산화/환원 처리를 반복하면서 분말의 크기, 비표면적, morphology를 조사하였다. 분말의 비표면적은 고온산화에 의해서 크게 감소했다가 산화/환원 cycle이 반복될수록 증가하는 경향을 보인다. attrition 분쇄에 의해서 분말의 비표면적은 매우 커지며, 그 증가폭은 산화/환원 cycle이 많아질수록 커진다. 고온산화 후 산화/환원 cycle을 2회 반복했을 때 소결밀도가 가장 높았다.

• Resources Recycling
• /
• v.21 no.6
• /
• pp.32-38
• /
• 2012

In this study, direct reduction of $ZrO_2$ using liquid calcium was investigated. The influence of molar ratio of Ca and $ZrO_2$, reaction time and temperature on the reduction behavior of $ZrO_2$ was studied. Experiments were conducted in a closed stainless steel chamber under Ar atmosphere during 5 to 60 minutes. Most of the $ZrO_2$ was reduced to Zr in 5 minutes at 1223 K and 3 Ca/$ZrO_2$ molar ratio. The minimum oxygen content in reduced metal Zr was obtained about 0.66 wt% at 1373 K after 30 minutes and 4 Ca/$ZrO_2$ molar ratio. The morphology of zirconium powder obtained was highly affected by the reaction temperature and reaction time.

• Cement
• /
• s.206
• /
• pp.44-49
• /
• 2015

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2003.04a
• /
• pp.28-28
• /
• 2003

• Proceedings of the KWS Conference
• /
• 1993.10a
• /
• pp.122-124
• /
• 1993

• Resources Recycling
• /
• v.32 no.2
• /
• pp.19-32
• /
• 2023

A novel method for the synthesis of titanium hydride powder from titanium tetrachloride via the magnesiothermic reduction in an hydrogen gas atmosphere was investigated. To examine the influence of temperature on the formation of titanium hydride, the reduction was conducted at 1023~1123 K under 1 atm of hydrogen gas atmosphere for approximately 30 min. Subsequently, the titanium hydride powder was sintered by maintaining the temperature for 0~120 min, and the decrease in the oxygen concentration of the powder was investigated. The experimental results showed that TiH_1.924 was produced at 1023 K, whereas mixtures of TiH_1.924 and TiH_1.5 were produced at 1073 K and 1123 K. In addition, the hydrogen concentration in the powder decreased with increasing temperature. The concentration of oxygen in the powder decreased with increasing temperature and sintering time owing to the decrease in the specific surface area of the powder. The minimum concentration of oxygen was 0.246 mass% when the mixture of TiH_1.924 and TiH_1.5 was obtained at 1073 K and a sintering time of 120 min.

• Resources Recycling
• /
• v.22 no.6
• /
• pp.41-47
• /
• 2013

In this study, deoxidation of Ti scrap using liquid calcium was investigated. Experiments were conducted in a closed stainless steel chamber under Ar atmosphere during 30 to 90 minutes. Oxygen content of Ti scrap was reduced from 0.54 to 0.19 wt% by calciothermic reduction in 30 minutes at $1000^{\circ}C$ and 2.5 Ti/Ca mass ratio. By the calciothermic reduction of Ti scrap for 30 minutes under the reaction temperature of $1100^{\circ}C$ and 2.5 Ti/Ca mass, a minimum oxygen content of about 0.126 wt% in Ti scrap was obtained.

• Clean Technology
• /
• v.8 no.3
• /
• pp.111-117
• /
• 2002

Catalytic decomposition and reduction of NO have been carried out on copper loaded mordenites in a packed bed flow reactor. For the decomposition of NO, $Cu^{\circ}/HM$ exhibited higher activities than CuO/HM at high copper content, which may be related to the difference in the amount of $Cu^{2+}$ ions and the reducibility of CuO between $Cu^{\circ}/HM$ and Cuo/HM. However, $Cu^{\circ}/HM$ showed higher reduction activities than CuO/HM at low copper content. This result may be dependent on the difference in the amount of high-reducibility CuO between $Cu^{\circ}/HM$ and CuO/HM.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.3
• /
• pp.279-285
• /
• 2017

In this study, the development of concrete preventing initial frost damage and durability about that were evaluated by using anti-aging agent and admixture(reduced slag). As a result of experiment, initial hydration heat was increased by $C_{12}A_7$ of reduced slag components but it was not effective to development of strength. Also fluidity decreased with increasing replacement of reduced slag. This suggested that fluidity was low by rapid setting due to absent of gypsum in reduced slag components. In case of CR2G specimen that added 4% gypsum, the flow ability was higher than plain. It is considered that concrete developed using reduced slag should use $SO_3$. Result of durability experiments, the durability decreased with increasing replacement amount of reduced slag.

• Resources Recycling
• /
• v.21 no.3
• /
• pp.74-83
• /
• 2012

Rare earth metals have been made from rare earth compounds which were prepared from rare earth ore concentrates through successive processes such as leaching(i.e. extraction of rare earth elements to liquid media), separation, purification, precipitation. Here, process for treating monazite and bastnasite ore concentrates were briefly reviewed, and metallothermic reduction and fused salt electrolysis methods were introduced as the extraction technologies for rare earth metals.