• 한국표면공학회지
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• 제48권1호
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• pp.27-32
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• 2015

Advanced high strength steels undergo recrystallization annealing in reducing gas atmosphere before galvanizing to improve mechanical properties. The selective oxidations of elements such as Mn, Si, Cr and Al during annealing decrease wettability of liquid zinc, resulting in bare spots and other defects. In this work, Fe-3wt%Mn steel sheet was annealed at $780^{\circ}C$ for 1200 sec. in 5% $H_2-N_2$ atmosphere and then dipped into zinc bath held at $460^{\circ}C$, which contained 0.2wt% dissolved Al. MnO crystallines in the average size of 200 nm were formed on the surface after annealing. It is estimated that MnO has been detached into bath with the formation and growth of inhibition layer with longer immersion time during galvanizing. No evidence of aluminothermic reduction of MnO has been found in this study.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.157-161
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• 2000

Blue phosphor of Ba-Mg-Al-O:Eu$^{2+}$ phase was fabricated by conventional firing techniques under reducing atmosphere and its photoluminescence properties are studied with varying Eu concentration and phost-annealing temperature under air atmosphere. This phosphors were well crystallized with particle size in the range of 3~5um and emitted a blue light at a dominent wavelength 450nm for 254nm UV irradiation. The concentration quenching wit Eu$^{2+}$ was that with increasing Eu concentration the energy transfer between the activator ions steadily improves, so that the excitation energy is transported over larger distances through the lattice before luminescence can occur. Thermal quenching also occurred in this phosphor means that in a host lattice with the $\beta$-alumina structure the bond of an Eu$^{2+}$ ion with the nearest-neighbour oxygen ion is much stronger than in a lattice with the magnetoplumbite structure.cture.

• 한국세라믹학회지
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• 제31권8호
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• pp.893-901
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• 1994

In this study, AlN powder of fine particle size and of high purity was synthesized by the carbothermal reduction-nitridation of monodisperse, spherical Al(OH)3 which had been prepared by sol-gel method using Al(O-sec-C4H9)3 as the starting material. Depending on the mixing order and kinds of reducing agents, the optimum condition for the preparation of AlN was determined as follows. AlN single-phase was produced by the carbothermal reduction-nitridation of (1) Benzene-washed Al(OH)3 and the reducing agent, carbon, which was mixed in a ball mill: for 5 hours at 140$0^{\circ}C$ under NH3 atmosphere; (2) The mixture prepared by hydrolysis of alkoxide solution into which carbon had been dispersed beforehand: for 5 hours at 135$0^{\circ}C$ ; (3) Al(OH)3 Poly(furfuryl alcohol) composite powder: for 2.5 hours at 135$0^{\circ}C$; (4) The mixture of Al(OH)3 and polyacrylonitrile: for 5 hours at 140$0^{\circ}C$. Addition of CaF2 increased the nitridation rate when carbon or polyacrylonitrile was used as the reducing agent; but it had no effect on the nitridation rate when furfuryl alcohol was used as the reducing agent.

• Nuclear Engineering and Technology
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• 제28권5호
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• pp.458-466
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• 1996

The effects of dopants on the modification of microstructure of UO$_2$ and UO$_2$-4wt%CeO$_2$ sintered pellets have been studied in hydrogen and $CO_2$/CO mixture atmospheres by using $Ta_2O_5$, TiO$_2$ and $Nb_2O_5$ as sintering additives. The dopant were added as oxide powders and homogenized by attrition milling. The mixed powders were pressed, and then sintered in hydrogen at 1$700^{\circ}C$ , or in oxidizing atmosphere using Controlled $CO_2$/CO mixtures at 125$0^{\circ}C$. Both density and microstructure of UO$_2$ are modified by the addition of dopants in reducing atmosphere. The sintered density is increased with $Ta_2O_5$ addition up to 0.33wt% and subsequently decreased with higher content of the additive. The effect on the densification and the gain growth are apparent with the addition of 0.24wt% $Nb_2O_5$. With 0.lwt% titania and 0.6wt% $Ta_2O_5$, the sintered density is decreased, but the grain size is increased. In oxidizing atmosphere, the grain sizes for UO$_2$ doped with the above additives are smaller than that for pure UO$_2$. The grain size of Ta or Nb-doped UO$_2$ is decreased with increasing $CO_2$/CO ratio, but that of pure UO$_2$or T-doped UO$_2$ is increased. A large portion of second phases is observed in UO$_2$ doped with 0.lwt% TiO$_2$ sintered in hydrogen atmosphere, while, in $CO_2$/CO atmospheres, the second phases or dopant agglomerates are not observed. For UO$_2$-4wt%CeO$_2$ mixed oxide, the effect of additives on the gain growth is not so much as that for the pure UO$_2$. This is attributed to the formation of clusters by dopant cations and Ce ions, so that the additives contribute to a lesser exent to the grain growth for the mixed oxide.

• 한국결정성장학회지
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• 제29권6호
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• pp.372-378
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• 2019

산화구리를 함유하는 전통 세라믹 유약은 황색포도상구균과 대장균에 대해 항균활성을 나타낸다. 환원 분위기에 소결한 모든 시편들은 황색포도상구균과 대장균에 대해 항균활성을 나타내나 산화분위기에서 소결한 일부 시편들만 황색포도상구균과 대장균에 대해 항균활성을 나타내었다. 산화구리를 함유하는 전통 세라믹 유약의 항균기작을 설명하기 위해 유약의 결정상, 미세구조, 이온용출, 표면 제타전위 분석을 실시하였다. 환원 분위기에서 소결한 시편들은 유약층에 Cu 입자들이 형성되는 것을 확인할 수 있다. Cu 용출량은 전체적으로 0.05 ppm 이하이며 가장 많이 용출되는 이온은 Ca 이었다. 산화구리를 3 wt.% 이상 첨가한 모든 시편들은 높은 음극의 표면 제타전위를 나타내었다. 세라믹 유약의 항균활성은 일반적으로 용출되는 양이온들과 연관되어 보이나 산화분위기에서 소결한 시편들의 대장균에 대한 항균활성은 직접적인 연관성이 나타나지 않는다. 세라믹 유약 시편의 표면 제타전위가 이온용출과 더불어 대장균에 대한 항균활성에 보조적 기여를 하는 것으로 보인다.

• 한국가스학회지
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• 제9권1호
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• pp.9-15
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• 2005

수소는 온실효과 가스배출을 저감하기 위한 다양한 연소장치에 이용되는 에너지 전달체로 가장 중요한 물질로 인식되고 있다. 그러나 에너지 전달체로 이용되기 위해서는 수소를 이용하는 장치와 관련된 안전의 문제점이 충분히 조사하고 이해되어야 한다. 따라서 누출된 수소가스와 공기의 혼합 가스운의 확산거동과 점화 가능성에 대한 연구가 필요하다. 본 연구에서는 대기 조건에 따라 대기 중에서 수소가스의 확산거동을 부력을 고려하여 살펴보았다. 풍하방향으로 위험범위는 대기안정도 및 풍속이 증가할수록 증가하게 되고, 지면에서 가스농도는 수소가스의 부력 때문에 거의 제로이다. 그러므로 누출된 수소가스 운의 점화 가능성은 낮고, 화재$\cdot$폭발 위험성은 타 연료가스 즉 부탄 및 프로판에 비하여 낮은 것으로 사료된다.

• 한국세라믹학회지
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• 제49권2호
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• pp.191-196
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• 2012

In this study, tin phosphate glass system($SnO_2-(1-x)P_2O_5-xB_2O_3$) that occur during the melting of the metal oxide inhibition of the oxidation reaction, and to reduce oxides of high melting temperature in the following three methods were melting. The first is the general way in the atmosphere, and the second by injecting $N_2$ gas under a neutral atmosphere, and finally in the air were melted by the addition of a reducing agent Melt in the atmosphere when the oxidation of the metal oxide is inhibited by low temperatures were melting. In addition, the deposition of crystals within glassy or inhibit devitrification phenomenon is also improved over 80% transmittance. This phenomenon, when the melting of glass, many of $Sn^{4+}$ ions are reduced to the $Sn^{2+}$ was forming oxides SnO, because it acts as a modifier oxide.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1995년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.25-25
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• 1995

Liquid phase sintering of 90W-6Ni-4Mn alloy has been investigated as functions of sintering atmosphere, heating rate, and reduction temperature. The present work accounts for the thermodynamic oxidatiodreduction reactions of constituent powders of W, Ni and Mn. By discounting these reactions, the previous investigations would obtain only the alloy with large pores and the lowered relative sintered density, by the liquid phase sintering under a dry hydrogen atmosphere. the sintering cycle consisted of a rapid heating to reduction temperatures under high purity nitrogen atmosphere, and holding for 4 hours and sintering at $1260^{\circ}C$ for 1 hour under a dry hydrogen gas. The relative density of the sintered alloy increased with increasing heating rate. As the reduction temperature increased, the relative density increased to the lm theotical density at the duction temture above $1150^{\circ}C$. The mimsturcatre of sintered alloys has been analysed by a scanning election microscope. The sintered density was compared with those obtained from the other investigators. It was found that the reduction $1150^{\circ}C$ results in the lowered densification of 90W-6Ni-4Mn alloy. This is caused by the fact that reducing reactions of W and Ni oxides contained in W an Ni powders concomitantly leads to oxidizing reaction of Mn powder the oxidized Mn is hardly reduced at sintering temperature and thereby remains large pores in the alloy. It is concluded that the W-Ni-Mn alloy with full density can be obtained by the precise control of atmosphere, heating rate, and sintering temperature.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.101-101
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• 2007

• 전기의세계
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• 제22권3호
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• pp.7-12
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• 1973

Single crystals of BaTiO$_{3}$ which were grown by Remeika's method were on reducing them is hydrogen atmosphere at about 400-1000.deg. C for about 30hrs. They became light brown and seems to have an effect on their properties by oxygen deffects especially at a Curie temperature of 122.deg. C exhibitted abnormal reducting resistivity. These semiconducting tendency were studied experimentally by observing through several electrical properties and were discussed on the basis of exchange semiconductor mechanism.