• 한국분말재료학회지
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• 제3권1호
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• pp.49-56
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• 1996

The effect of$H_{2}/N_{2}$gas sintering atmosphere on the carbon content and mechanical properties during the metal injection molding process of carbonyl iron-nickel powder was studied. The carbon content of the specimen after debinding in the pure$N_{2}$atmosphere appeared 0.78 wt%. After showing the maximum value of 1.48 wt.% in the debinding atmosphere of 10%$H_{2}/N_{2}$gas mixture, the carbon content of the debinded specimen decreased gradually with increasing the$H_2$content in the$H_{2}/N_{2}$gas mixture. The carbon contents of the sintered specimen were 0.46~0.63wt% in Na gas atmosphere, while they appeared extremely low above 40%$H_{2}/N_{2}$gas atmosphere. The relative sintered density increased abruptly from 88~90% to 93~96% with the addition of Ni, while the density nearly unchanged above 2% Ni addition. The sintered density increased with increasing the fraction of$H_{2} in H_{2}/N_{2}$gas mixture. Tensile strength and hardness increased, and elongation decreased with increasing carbon and Ni content. In spite of high carbon content of 0.63 wt%, the superior elongation value of 10% was shown.

• Nuclear Engineering and Technology
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• 제34권4호
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• pp.323-330
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• 2002

Various types of compounds were tested with the aspects of decomposition and formation of residue in a $CO_2$ or 7H$_2$+93$N_2$ atmosphere. The evaporation temperature range of each compound was determined from thermogravimetric curve. Decomposition of dicarbon amide, stearic acid, acrowax and zinc stearate was studied by thermogravimetry in $CO_2$ or in 7H$_2$+93$N_2$ atmosphere. All compounds were decomposed in $CO_2$ atmosphere at lower than 40$0^{\circ}C$, but the residue, ZnO remained for zinc stearate. ZnO did not decompose in $CO_2$ atmosphere up to 130$0^{\circ}C$, but reduced into Zn metal and disappeared in the temperature range of $600^{\circ}C$ to 120$0^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. The effect of residue, which trapped in closed pores of sintered pellet, on the thermal stability was studied using the resintering test at 1$700^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. In the case of oxidative sintered pellet with admixing zinc stearate, the cavity formation accompanied with a density drop after resintering is due to the pressure of the Zn gases trapped in the isolated pores.

• 한국세라믹학회지
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• 제37권1호
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• pp.1-5
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• 2000

Cathodoluminescence(CL) properties of ZnO:Zn green phosphor were investigated. ZnO:Zn phosphor was synthesized by varying reducing agents and firing temperatures. ZnS, charcoal and 5% H2 gas mixed with 95% N2 gas(5H2-95N2) were used as the reducing agent and atmosphere. The highest CL intensity of ZnO:Zn phosphor was observed under the condition of 5H2-95N2 atmosphere and firing temperature of 90$0^{\circ}C$ for 1h. Charocal and ZnO as reducing agents in the syntehsis of ZnO:Zn phosphor exhibited about 60% and 40%, respectively, of the CL intensity obtained with 5H2-95N2 atmosphere.

• Nuclear Engineering and Technology
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• 제26권4호
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• pp.484-492
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• 1994

Nb$_2$O$_{5}$가 첨가된 $UO_2$ 소결체의 미세조직을 수소와 이산화탄소 분위기에서 연구하였다. Pellet을 1$700^{\circ}C$ 수소분위기 그리고 130$0^{\circ}C$ 이산화탄소 분위기에서 1-41 시간 동안 소결하였다. Nb$_2$O$_{5}$를 첨가하면 큰 기공들이 형성되고, 이 기공들은 수소분위기에서는 어느정도 수축하지만 이산화탄소 분위기에서는 거의 소멸하지 않는다. 작은 기공들은 수소분위기에서는 거의 전부 소멸되며 이산화탄소 분위기에서는 거의 소멸하지 않는다. 그리고 결정립의 크기도 수소분위기에서 훨씬 증대한다. 따라서 Nb$_2$O$_{5}$ 첨가에 의한 우라늄 확산은 수소분위기에서 훨씬 증가하는 것으로 생각된다. 수소 분위기에서 소결한 Nb$_2$O$_{5}$ 첨가 $UO_2$ pellet의 미세조직을 노내성능의 관점에서 평가하였다. 우라늄 확산의 증가를 설명하기 위해서 Nb$_2$O$_{5}$ 첨가에 의해서 형성 가능한 결함들을 고찰하였다.함들을 고찰하였다.

• 한국세라믹학회지
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• 제27권6호
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• pp.755-762
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• 1990

The tungsten paste was printed on the surface of 92% alumina sheet which was made by type casting process. The printed tungsten was bonded on the Al2O3 by co-firing in reducing atmosphere. During the co-firing, the binder burn-out was easier in wet H2 atmosphere than in dry H2, which affected sintered density. In practically, the use of wet H2 above 100$0^{\circ}C$ was beneficial for density of alumina and bond strength. This phenomena occured more distinctly when atmosphere varied from dry H2 to wet H2 than varied dew point in wet H2. In wet H2, the improvement in bonding strength can be attributed to good glass migration into the metal layer due to inhibition of the tungsten particle growth, with increase of alumina density, at the temperatrue higher than 100$0^{\circ}C$.

• 한국세라믹학회지
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• 제41권8호
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• pp.567-572
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• 2004

The variation of the sintered density and grain size of UO$_2$ as a function of the Li$_2$O amount and sintering atmosphere was observed. Li$_2$O enhanced the grain growth of the UO$_2$ pellet in H$_2$, but rather hindered it in $CO_2$ atmosphere. Grain size of the UO$_2$ and UO$_2$-0.1 wt%Li$_2$O pellets was, respectively, 8 $\mu$m and 100 $\mu$m at 168$0^{\circ}C$ in the H$_2$ atmosphere, and that of each pellet was, respectively, 24 $\mu$m and 17 $\mu$m at the same temperature in the $CO_2$ atmosphere. As-received Li$_2$O powder, which had been composed of Li$_2$O and LiOH, was converted to the Li$_2$CO$_3$ phase after heating to 80$0^{\circ}C$ in $CO_2$. On the other hand, the Li$_2$O and LiOH phases remained unchanged in H$_2$ atmosphere. In the H$_2$, the as-received Li$_2$O powder began to evaporate at about 105$0^{\circ}C$ and then about 20 wt% residue was left at 150$0^{\circ}C$. But, most of the Li elements evaporated at 150$0^{\circ}C$ in the $CO_2$ atmosphere.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.162-165
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• 2006

AZO (ZnO:Al) were fabricated by RF magnetron sputtering In $H_2/Ar(5%\;H_2)$ atmosphere, and structural, electrical and optical properties were investigated. The substrate temperatures were varied at RT, $100^{\circ}C,\;150^{\circ}C$ and$200^{\circ}C$. The resistivity of the films grown in $H_2/Ar(5%\;H_2)$ were reduced from $7.67{\times}10^{-4}{\Omega}\;cm$ to $5.95{\times}10^{-4}{\Omega}\;cm$ comparing that Ar (100%) and the transmittance of the ZnO:Al films in the visible range was 85%.

• 한국세라믹학회지
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• 제48권6호
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• pp.641-647
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• 2011

The present study aims to identify the effect of sintering atmosphere [$O_2$, 75$N_2$-25 $H_2$ (mol%) and $H_2$] on microstructural evolution at the relatively low sintering temperature of 1040$^{\circ}C$. Samples sintered in $O_2$ showed a bimodal microstructure consisting of fine matrix grains and large abnormal grains. Sintering in 75 $N_2$ - 25 $H_2$ (mol %) and $H_2$ caused the extent of abnormal grain growth to increase. These changes in grain growth behaviour are explained by the effect of the change in step free energy with sintering atmosphere on the critical driving force necessary for rapid grain growth. The results show the possibility of fabricating $(K_{0.5}Na_{0.5})NbO_3$ at low temperature with various microstructures via proper control of sintering atmosphere.

• 한국분말재료학회지
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• 제24권1호
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• pp.41-45
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• 2017

The effects of the heat treatment temperature and of the atmosphere on the dehydrogenation and hydrogen reduction of ball-milled $TiH_2-WO_3$ powder mixtures are investigated for the synthesis of Ti-W powders with controlled microstructure. Homogeneously mixed powders with refined $TiH_2$ particles are successfully prepared by ball milling for 24h. X-ray diffraction (XRD) analyses show that the powder mixture heat-treated in Ar atmosphere is composed of Ti, $Ti_2O$, and W phases, regardless of the heat treatment temperature. However, XRD results for the powder mixture, heat-treated at $600^{\circ}C$ in a hydrogen atmosphere, show $TiH_2$ and TiH peaks as well as reaction phase peaks of Ti oxides and W, while the powder mixture heat-treated at $900^{\circ}C$ exhibits only XRD peaks attributed to Ti oxides and W. The formation behavior of the reaction phases that are dependent on the heat treatment temperature and on the atmosphere is explained by thermodynamic considerations for the dehydrogenation reaction of $TiH_2$, the hydrogen reduction of $WO_3$ and the partial oxidation of dehydrogenated Ti.

• 한국분말재료학회지
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• 제23권4호
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• pp.303-306
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• 2016

An optimum route to synthesize Ti-Mo system powders is investigated by analyzing the effect of the heat treatment atmosphere on the formation of the reaction phase by dehydrogenation and hydrogen reduction of ball-milled $TiH_2-MoO_3$ powder mixtures. Homogeneous powder mixtures with refined particles are prepared by ball milling for 24 h. XRD analysis of the heat-treated powder in a hydrogen atmosphere shows $TiH_2$ and $MoO_3$ peaks in the initial powders as well as the peaks corresponding to the reaction phase species, such as $TiH_{0.7}$, TiO, $MoO_2$, Mo. In contrast, powder mixtures heated in an argon atmosphere are composed of Ti, TiO, Mo and $MoO_3$ phases. The formation of reaction phases dependent on the atmosphere is explained by the partial pressure of $H_2$ and the reaction temperature, based on thermodynamic considerations for the dehydrogenation reaction of $TiH_2$ and the reduction behavior of $MoO_3$.