• 박물관보존과학
• /
• 제2권
• /
• pp.1-8
• /
• 2000

국립중앙박물관에서는 국내외에서 구입한 유물들을 전시하기 위하여 보존처리를 실시하였다. 처리유물은 금속제 유물을 비롯하여 목제, 회화, 목·칠기 등 다양한데, 이중 금속유물 42점의 보존처리 내용을 재질별로 소개하였다. 유물의 현재 상태를 파악하기 위해 현미경 조사 및 X-선 촬영을 실시하였으며 재질에 따라 이물질 제거 방법, 안정화 처리 방법 등의 처리 방향을 설정하였다. 또한 역사적 자료를 보존하고 일반인들에게 전시할 수 있는 조치를 취하였다.

• 대한화학회지
• /
• 제4권1호
• /
• pp.7-9
• /
• 1957

On sparking carbon-arc in water we found that a inflammable gas was generated. The object of this experiment is to prepare sols of metals by applying the gas mentioned to a solution of metallic salts. As the result of this experiment we found that : 1) By this method we can prepare easily some kinds of Ag-sol from $AgNO_3$ solution in about 30 sec. by adjusting the temperature, the quantity of stabilizer and the concentration of metallic salt. 2) The appropriate concentration of $AgNO_3$ is about 0.01% by volume, that of the stabilizer, 0.9104 N-NaOH is 0.03-2 cc/100 cc of 0.01% $AgNO_3$ solution. And the lower the temperature, the more concentrated the Ag-sol. But to check the possibility of applying this method to metals other than Au and Ag, measurement of the particle size and properties of a sol prepared by this method, should be studied. Especially, we must study what kinds of gases are generated by sparking the carbon-arc in water.

• Corrosion Science and Technology
• /
• 제7권3호
• /
• pp.145-151
• /
• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 하계학술대회 논문집 C
• /
• pp.1574-1576
• /
• 1994

$SF_6$ gas has become an important insulation medium in modern electric power apparatus, because of its high insulation withstand levels and good arc quenching capability. For the application of $SF_6$ gas in GIS the estimation of insulation properties is a fundamental point. Moreover the reduction of withstand levels in case of inhomogeneous fields caused by particles or fixed protrusions is of special interest. It is known that the presence of free conducting particles in GIS can significantly lower the insulating level of $SF_6$ gas at elevated pressure and also it has been recently shown that dielectric strength is greatly reduced by fast transients such as disconnector surges where metallic particles are involved. In this paper, we have disigned the particle test chamber rated 362kV for the purpose of investigating the discharge characteristics in SF6 gas where inhomogenius fields are caused by metallic particles.

• 한국결정성장학회지
• /
• 제9권5호
• /
• pp.480-485
• /
• 1999

FED용의 적색 형광체로 Al과 Pr이 첨가된 $SrTiO_3$의 제조와 형광특성에 대하여 연구하였다. 이 형광체는 metallic nitrates, ethylene glycol, citric acid를 출발물질로 하여 polymeric complex를 형성하는 Pechini 법으로 합성하였다. 본 실험에서 합성된 분말의 성장기구는 $900^{\circ}C$를 경계로 서로 다른 경향을 보이고 있으며, $600^{\circ}C$의 저온에서도 $SrTiO_3$상이 형성됨을 확인하였다. 또한 빛 발광특성의 경우는 Pr 이온에 의한 359 nm에서의 여기 스펙트럼과 저전압 음극선 발광의 경우 617 nm에서 최대 피크를 갖고 575 nm와 650 nm 사이에서 적색의 발광 스펙트럼이 관찰되었다. Pechini 법으로 합성된 $SrTiO_3$:Al, Pr 형광체의 경우 FED의 적색 형광체에 적용될 수 있을 것이다.

• 대한금속재료학회지
• /
• 제46권7호
• /
• pp.464-470
• /
• 2008

Metallic nanostructures have great potential for bio-chemical sensor applications due to the excitation of localized surface plasmon and its sensitive response to environmental change. Unlike the commonly explored absorption-based sensing, the optical scattering provides single particle detection scheme. For the localized surface plasmon resonance spectroscopy, the metallic nanostructures with controlled shape and size have been usually fabricated on adhesion-layer pre-coated transparent glass substrates. In this study, we calculated the optical scattering properties of plasmonic Au nanodisc using a discrete dipole approximation method and analyzed the effect of adhesion layer on them. Our result also indicates that there is a trade-off between the surface plasmon damping and the capability of supporting nanostructures in determining the optimal thickness of adhesion layer. Marginal thickness of Ti adhesion layer for supporting Au nanostructures fabricated on a silica glass substrate was experimentally analyzed by an adhesion strength test using a nano-indentation technique.

• 한국환경과학회지
• /
• 제26권6호
• /
• pp.767-778
• /
• 2017

This research investigates the characteristics of metallic and ionic elements in $PM_{10}$ and $PM_{2.5}$ on haze day and non-haze day in Busan. $PM_{10}$ concentration on haze day and non-haze day were 85.75 and $33.52{\mu}g/m^3$, respectively, and $PM_{2.5}$ on haze day and non-haze day were 68.24 and $23.86{\mu}g/m^3$, respectively. Contribution rate of total inorganic water-soluble ion to $PM_{10}$ mass on haze day and non haze day were 58.2% and 61.5%, respectively, and contribution rate of total water-soluble ion to $PM_{2.5}$ mass on haze day and non haze day were 58.7% and 64.7%, respectively. Also, contribution rate of secondary ion to $PM_{10}$ mass on haze day and non haze day were 52.1% and 47.5%, respectively, and contribution rate of secondary ion to $PM_{2.5}$ mass on haze day and non haze day were 54.4% and 53.6%, respectively. AC (anion equivalents)/CE (cation equivalents) ratio of $PM_{10}$ mass on haze day and non haze day were 1.09 and 1.0, respectively, and AC/CE ratios of $PM_{2.5}$ mass on haze day and non haze day were 1.12 and 1.04, respectively. Also, SOR (Sulfur Oxidation Ratio) of $PM_{10}$ mass on haze day and non haze day were 0.32 and 0.17, respectively, and SOR of $PM_{2.5}$ on haze day and non haze day were 0.30 and 0.15, respectively. Lastly, NOR (Nitrogen Oxidation Ratio) of $PM_{10}$ on haze day and non haze day were 0.17 and 0.08, respectively, and NOR of $PM_{2.5}$ on haze day and non haze day were 0.13 and 0.06, respectively.

• 한국분말재료학회지
• /
• 제18권2호
• /
• pp.105-111
• /
• 2011

This study investigated the effect of wire diameter and applied voltage on the fabrication of Ni-free Fe-based alloy nano powders by employing the PWE (pulsed wire evaporation) in liquid, for high temperature oxidation-resistant metallic porous body for high temperature particulate matter (or soot) filter system. Three different diameter (0.1, 0.2, and 0.3 mm) of alloy wire and various applied voltages from 0.5 to 3.0 kV were main variables in PWE process, while X-ray diffraction (XRD), field emission scanning microscope (FE-SEM), and transmission electron microscope (TEM) were used to investigate the characteristics of the Fe-Cr-Al nano powders. It was controlled the number of explosion events, since evaporated and condensed nano-particles were coalesced to micron-sized secondary particles, when exceeded to the specific number of explosion events, which were not suitable for metallic porous body preparation. As the diameter of alloy wire increased, the voltage for electrical explosion increased and the size of primary particle decreased.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권10호
• /
• pp.894-898
• /
• 2016

Solution plasma is a unique method which provides a direct discharge in solutions. It is one of the promising techniques for various applications including the synthesis of metallic/non-metallic nanomaterials, decomposition of organic compounds, and the removal of microorganism. In the context of nanomaterial syntheses, solution plasma has been utilized to produce carbon nanoparticles and metallic-carbon nanoparticle systems. The main purpose of this study was to synthesize nickel nanoparticles embedded in a matrix of carbon particles by solution plasma in one-step using waste vegetable oil as the carbon source. The experimental setup was done by simply connecting a bipolar pulsed power generator to nickel electrodes, which were submerged in the waste vegetable oil. Black powders of the nickel nanoparticles-embedded carbon (NiNPs/Carbon) particles were successfully obtained after discharging for 90 min. The morphology of the synthesized NiNPs/Carbon was investigated by a scanning electron microscope, which revealed a good dispersion of NiNPs in the carbon-particle matrix. The X-ray diffraction of NiNPs/Carbon clearly showed the co-existence of crystalline Ni nanostructures and amorphous carbon. The crystallite size of NiNPs (through the Ni (111) diffraction plane), as calculated by the Scherrer equation was found to be 64 nm. In addition, the catalytic activity of NiNPs/Carbon was evaluated by cyclic voltammetry in an acid solution. It was found that NiNPs/Carbon did not show a significant catalytic activity in the acid solution. Although this work might not be helpful in enhancing the activity of the fuel cell catalysts, it is expected to find application in other processes such as the CO conversion (by oxidation) and cyclization of organic compounds.

• 한국재료학회지
• /
• 제33권2호
• /
• pp.63-70
• /
• 2023

In this study, crystallization was effectively suppressed in Al-based metallic glasses (Al-MGs) during pulverization by cryo-milling by applying an extremely low processing temperature and using a surfactant. Before Al-MGs can be used as an additive in Ag paste for solar cells, the particle sizes of the Al-MGs must be reduced by milling. However, during the ball milling process crystallization of the Al-MG is a problem. Once the Al-MG is crystallized, they no longer exhibit glass-like behavior, such as thermoplastic deformation, which is critical to decrease the electrical resistance of the Ag electrode. The main reason for crystallization during the ball milling process is the heat generated by collisions between the particles and the balls, or between the particles. Once the heat reaches the crystallization temperature of the Al-MGs, they start crystallization. Another reason for the crystallization is agglomeration of the particles. If the initially fed particles become severely agglomerated, they coalesce instead of being pulverized during the milling. The coalesced particles experience more collisions and finally crystallize. In this study, the heat generated during milling was suppressed by using cryo-milling with liquid-nitrogen, which was regularly fed into the milling jar. Also, the MG powders were dispersed using a surfactant before milling, so that the problem of agglomeration was resolved. Cryo-milling with the surfactant led to D50 = 10 um after 6 h milling, and we finally achieved a specific contact resistance of 0.22 mΩcm² and electrical resistivity of 2.81 μΩcm using the milled MG particles.