국산 APT 로부터 금속텅그스텐분말의 환원에 관한 고찰 (2) : 입도분포에 관하여 On the Particle size distribution of the reduced tungsten powder

박원구 대한금속재료학회(대한금속학회) 1973 대한금속·재료학회지 Vol.11 No.3

APT와 WO₃의 환원조건이 생성된 금속텅그스텐 분말의 입도에 미치는 영향을 밝히고저 환원온도, 수소유량, 수소중의 수분함량 및 장입량의 변화에 따른 입도변화를 조사하였다. 입도분포는 침강법에 의해 측정하였고, 분말의 형태와 입도는 전자현미경으로 관찰하였다. WO₃는 환원온도, 장입량 및 수소중의 수분함량이 증가할수록 W와 WO₃가 수소중의 수분의 영향으로 증발-응고 작용을 반복하여 입자를 성장시킴으로 생성된 분말의 입도를 크게 하였다. 그러나 APT를 600℃에서 수소로 예비환원하여 WO₃의 성장과정을 거치지 않고 WO₂로 환원한 후 이를 금속텅그스텐으로 환원했을 때는 증발-응고현상이 800℃ 내지 900℃에서는 억제되기 때문에 2μ이하의 분말이 78%나 되는 미세한 금속텅그스텐분말을 쉽게 얻을 수 있음이 밝혀졌다. Effects of reduction temperature, hydrogen flow rate, water content of hydrogen, and amount of the charge on the particle size of the reduced tungsten powder from APT or WO₃ were investigated. The size distribution of the reduced powder was measured with sedimentation balance and the shape and particle size of the powder was observed with electron microscope. It is considered that the growth of the reduced metallic tungsten particle was occurred the evaporation and condensation reaction of WO₃ in wet hydrogen atmosphere and the reaction was accelerated with the increase of reducing temperature, amount of charge, and water vapor content of hydrogen. The evaporation and condensation reaction, however, was retarded by two step reduction of APT with hydrogen since preliminary reduction at 600℃ transforms APT to fine WO₂ which has the highest sublimation point among the tungsten oxides. And the subsequent final reduction of WO₂ at 800℃ provided the fine metallic tungsten powder. The portion of the fine metallic tungsten powder under 2μ obtained by the two step reduction process was amounted to 78%.

Mischmetal 이 18 Ni 300 급 Maraging Steel 의 석출경화에 미치는 영향

박원구 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.2

18 Ni 300級 maraging鋼에 mischmetal을 0.02%∼0.08% 添加했을 때, 이것이 maraging鋼의 特性에 미치는 影響을 調査하고 그 原因을 究明하였다. 燒鈍된 maraging鋼을 一定한 速度로 加熱하면서, 그 때 생기는 示差熱分析 및 電氣抵抗曲線上의 異狀點으로부터 强化反應이 進行되는 溫度를 求하였다. 求해진 各溫度에서 時效處理하여 溫度一時間에 對한 機械的 特性의 變化를 調査하고 電子顯微鏡으로 析出物을 觀察하였다. maraging鋼에 mischmetal을 添加하면 482℃ 以下의 溫度에서는 長時間 時效 處理하여도 過時效에 依한 機械的 特性의 低下가 적었다. 이는 (001)α//(001)pp, [100]α//[100]pp, [01￣1]α//[010]pp와 드물게는 {112}α//{001}pp의 方位關係를 가진 orthorhombic의 Ni₃Mo가 板狀으로 析出되어 表地와의 整合을 繼續 維持하는 엷은 板狀으로 存在하기 때문이라고 判斷되었다. 이러한 析出物의 成長이 抑制되고 素地에 對한 整合性이 좋은 理由는 mischmetal이 添加됨으로써 Ni과 Mo의 擴散이 抑制되기 때문이라고 본다. The effects of mischmetal addition from 0.02% to 0.08% on the mechanical properties of 18 Ni 300 grade maraging steel were investigated. DTA and electrical resistivity measurements at a constant heating rate showed singular points and aging treatments were performed at these singular temperatures. Mechanical properties of the maraging steels were examined according to the aging treatment. Also the precipitates were investigated by the thin film electron microscope technique. It was found that 18 Ni 300 grade managing steel maintains its strength by an addition of mischmetal even after a prolonged aging treatment at temperatures below 482℃. Over-aging is not particularly detrimental to its mechanical properties. The coherency of the thin plate-like precipitates is maintained during the aging treatment for 160 hr at 482℃. Their orientations with respect to matrix are (011)α//(001)pp, [100]α//[100]pp, [01￣1]α//[010]pp or occasionally {112}α//{001}pp. The reason for such an unsual behavior is believed due to the fact that mischmetal inhibits the coarsening of precipitates by decreasing the diffusion rate of Ni and Mo forming orthorhombic Ni₃Mo.

1992년도 추계 학술강연 및 발표대회 개요 - 분말야금 ( 발표 211 ) : SiC 피복 탄화텅스텐의 제조와 소결에 관한 연구

박원구,양준모 대한금속재료학회 ( 구 대한금속학회 ) 1992 대한금속재료학회 학술대회 개요집 Vol.1992 No.1

저상버스 탑승객의 온열 쾌적성에 관한 수치연구

박원구,김만회 한국수소및신에너지학회 2015 한국수소 및 신에너지학회논문집 Vol.26 No.6

Numerical study on human thermal comfort in a low floor bus has been conducted. Human thermal comfort in a bus depends mainly on air temperature, air velocity, mean radiant temperature, humidity, and direct solar flux, as well as the level of activity and thermal properties of clothing. The paper presents the velocity and temperature distribution, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices for the driver and passengers.

TiAl 계 금속간화합물의 반응합성온도에 미치는 압출과 승온속도의 영향

박원구,황선근,김석준,이태원,이지환 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.10

This paper was focused to investigate the effect of extrusion and heating rate on the reactive synthesis and the microstructure of products formed by reactive synthesis. The mixing of elemental powders was carried out by V-blender. The mixed powders were canned, sealed under vacuum, and were hot extruded at 450℃ under extrusion ratio 20 : 1. For powder extruded and cold compacted specimens, thermal analysis have been performed. In the effect of extrusion, the ignition temperature(T₁) of extruded specimens was found to be lower than that of cold compacted specimens. This may be due to breakdown of aluminium oxide films and elongation of mixed powders by hot plastic-deformation. In the effect of heating rate, both ignition temperature(T₁) and combustion temperature(T_c) was found to be increased with increasing heating rate. In particular, the ignition temperature of extruded specimens was below the melting temperature of aluminium under the heating rate of 40℃/min. Also, phase of reaction products depended upon combustion temperature. Microstructure of reaction products consists of unreacted titanium, TiAl and Ti₃Al. However, unreacted titanium was not observed after heat treatment.

저품위 동광석의 세균침출에 관한 연구 4

박원구,이강순 한국미생물학회 1973 미생물학회지 Vol.11 No.4

With the gradual expansion of copper demands, the utilization of enormous tonnages of waste copper mineral containig up to 0.5% copper becomes available. In order to investigate the possibilities on the application of bacterial leaching method to waste dumps or abandoned mines, the authors had carried out microbial leaching of copper minerals by F.ferrooxidans isolated from the Dalsung copper mine water. The results obtained were as follows : 1. The copper extraction rate from the Dalsung chalcopyrite has been a little accerelated by using flasks in place of percolators. 2. The percentage of copper extracted from the Dalsung chalcopyrite sample was 100% in 30 days in the presence of iron-oxidizing bacteria F.ferrooxidans while 9.27% in the absence of bacteria. 3. F.ferroxidans was capable of producing sufficient quantities of ferric sulfate and sulfuric acid from ferrous iron to bring about the dissolution of 100% of copper from the Dalsung chalcopyrite.

骨間結紮의 生體力學的 性質에 미치는 結紮形狀의 影響

朴元坵,卞鐘秀,李相韓 慶北大學校 齒科大學 1987 慶北齒大論文集 Vol.4 No.1

In order to determine the effect of ligature shape on biomechanical properties of interosseous wires,the author studied the tensile and bending forces of interosseous wires with 0.23, 0.40, 0.50mm diameter using to metal die and dog's bone. The results were summarized as follows: In case of metal die, maximum tensile and bending forces were 236.1±3.2kg.f, 225.3±4.6kg·f in shape of double ligature with 0.5mm diameter and minimum tensile and bending forces were 120.9±7.1kg.f, 120.7±2.5kg·f in shape of simple ligature with 0.23mm diameter. In case of dog's bone,maximum tensile and bending forces were 146.1±8.7kg.f, 139.5±kg.f in shape of double ligature with 0.5mm diameter and minimum tensile and bending forces were 103.9±9.8kg.f, 101.4±9.2kg.f in shape of simple ligature with 0.23mm diameter. Depending on the ligature shapes, maximum forces were expressed by double ligature, combined simple and figure-of-eight ligature, firgure-of-eight ligature, simple ligature.

산화소결된 UO2 Pellet 의 열적 고밀화에 관한 연구

박원구,한장규 대한금속재료학회 1984 대한금속재료학회 학술대회 개요집 Vol.1984 No.0

베릴륨 박막 용가재에 의한 Zircaloy 튜브 brazing 효과

박원구,정성훈 대한금속재료학회(대한금속학회) 1981 대한금속·재료학회지 Vol.19 No.12

In joining spacers and pads on the cladding tube of the Candu type nuclear fuel pin, brazing is employed with a filler metal of Be. It is well known that the mechanical properties of the joint depends significantly on the thickness of the filler metal as well as on the brazing time and temperature. In the present study, it was attempted to find the optimum thickness of the filler metal which could give a good joint between thin Zr-4 tube and the spacer. Furthermore, the corrosion rate of the brazed area was examined in conjunction with the microstructures of the brazed zone. Brazing was carried out by induction heating for 20 seconds at 1000℃-1040℃ which is just above the eutectic point of α-Zr-ZrBe₂, the best result was obtained with the thickness of the filler metal in the range of 8-10 ㎛, where the joint strength was 20㎏/㎟. The basket weave structure was observed in the heat affected zone in brazing. The corrosion rate of this area was lower than that of the annealed structure.

WC-Ni 계 초경합금 소결에 관한 연구

박원구,이홍열 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.2

The effect of coating SiC on WC powder surface was investigated in an effort to replace Co with Ni as the binder metal for cemented carbides based on WC-Co system. The density, microstructure and pore distribution of materials conventionally sintered at 1450℃ were examined as a function of the amount of SiC. The SiC-coating retarded coarsening of WC grains compared to conventional WC-Ni so that it resulted in a relatively uniform distribution of the grain size. Other improved characteristics of SiC-coated material include suppression of formation of the pores and θ phase (W₃Ni₃C), which are trouble some in WC-Ni system because of their deleterious effect on transverse rupture strength, and enhancement of hardness as compared to similar materials based on WC-Co and WC-Ni.