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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%.
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.
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.
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.
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.
TiB2/TiAl 계 금속간화합물기 복합재료의 in-situ 합성에 관한 연구
박원구,황선근,이태원,이지환 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.7
This study was focused to examine fabrication process of TiB₂ particle reinforced TiAl based intermetallic composites by reactive synthesis. The mixed powders were canned, hot-pressed under vacuum and then hot-extruded at 420℃ under extrusion ratio of 15:1. Subsequently. reactive synthesis was carried out at 700℃ under vacuum Thermal analysis has been perfomed to investigate the ignition temperature and combustion temperature for Ti-Al system and Ti-Al-B system. The combustion temperature of Ti-Al-B powder mixture was found to be higher than that of Ti-Al powder mixture. The Ti-Al-B powder mixture was reacted exothermically to form the material consisting of TiAl and TiB₂. The tensile strength of the TiB₂/TiAl composites was proved to be higher than that of the matrix. Swelling phenomenon, resulting from formation of a large amount of pores was observed at all reactive synthesis conditions.
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.