• 한국분말재료학회지
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• 제24권5호
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• pp.389-394
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• 2017

Ni wires with a diameter and length of 0.4 and 100 mm, respectively, and a purity of 99.9% are electrically exploded at 25 cycles per minute. The Ni nanopowders are successfully synthesized by a pulsed wire evaporation (PWE) method, in which Ar gas is used as the ambient gas. The characterization of the nanopowders is carried out using X-ray diffraction (XRD) and a high-resolution transmission electronmicroscope (HRTEM). The Ni nanopowders are classified for a multilayer ceramic condenser (MLCC) application using a type two Air-Centrifugal classifier (model: CNI, MP-250). The characterization of the classified Ni nanopowders are carried out using a scanning electron microscope (SEM) and particle size analysis (PSA) to observe the distribution and minimum classification point (minimum cutting point) of the nanopowders.

• Tribology and Lubricants
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• 제39권6호
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• pp.244-249
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• 2023

This paper presents a comprehensive analysis of the impact of surface roughness on the friction and wear properties of SUS 321, an austenitic stainless steel variant produced using the laser powder bed fusion (LPBF) technique, which is a prevalent additive manufacturing method. After the LPBF fabrication, the specimens go a heat treatment process aimed at alleviating residual stress. Subsequently, they are polished extensively to achieve a refined and smooth surface. To deliberately introduce controlled variations in surface roughness, an etching process is employed. This multi-step method encompassed primary etching in a 3M hydrochloric acid solution, followed by secondary etching in a 35 wt% ferric chloride solution, with varying durations applied to different specimens. A comprehensive evaluation of the surface characteristics ensued, employing precise techniques such as surface roughness measurements and meticulous assessments of water droplet contact angles. Following the surface treatment procedures, a series of friction tests are performed to explore the tribological behavior of the etched specimens. This in-depth investigation reached its peak by revealing valuable insights. It clarified a strong correlation between intentionally altered surface roughness, achieved through etching processes, and the resulting tribological performance of LPBF-fabricated SUS 321 stainless steel. This significantly advances our grasp of material behavior in tribological applications.

• 보존과학회지
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• 제36권2호
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• pp.82-92
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• 2020

현대 미술작품은 재료와 제작기법, 종류가 매우 다양하게 사용되고 있으며 특히 조각작품 중 많은 비율을 차지하는 금속의 경우 형태가 다양하고 여러 재질과 혼합된 작품이 다수 존재한다. 이러한 구조적, 재료적 특성은 보존처리 시 기존의 처리 방법을 적용하기 어려운 경우가 많아 보다 다양한 처리 재료 및 방법이 요구된다. 본 연구에서는 금속 작품의 효과적인 보존처리를 위해 방청제(Rust inhibitor, 防錆劑)를 작품에 직접적으로 도포하는 방법이 아닌 기화성 방청제를 적용하였으며, 기화성 방청제 및 이를 함유한 방청필름의 방청효과를 평가하였다. 금속 시편을 대상으로 기화성 방청제를 적용한 방청처리 결과, 시편의 색도 변화는 미미하였으며, 부식 속도는 방청 미처리 시편과 비교하였을 때 절반 정도 감소하는 것을 확인하였다. 방청필름 적용 실험 결과, 방청필름 사용 시 미처리 및 폴리에틸렌 필름을 사용한 시편보다 부식화합물의 발생이 감소하였다. 접촉각 및 표면에너지, 표면전기저항 측정을 통해 표면의 물성을 측정하였으며 방청피막이 형성됨을 확인하였다. 또한 기화성 방청제 및 방청필름을 실제 조각작품에 적용하여 방청효과를 확인하였다.

• 한국재료학회지
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• 제24권9호
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• pp.495-501
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• 2014

Despite having many attractive properties, $ZrO_2$ ceramic has a low fracture toughness which limits its wide application. One of the most obvious tactics to improve its mechanical properties has been to add a reinforcing agent to formulate a nanostructured composite material. Nanopowders of $ZrO_2$ and Cr were synthesized from $CrO_3$ and Zr powder by high energy ball milling for 10 h. Dense nanocrystalline $2/3Cr-ZrO_2$ composite was consolidated by a high-frequency induction heated sintering method within 5 min at $600^{\circ}C$ from mechanically synthesized powder. The method was found to enable not only rapid densification but also the inhibition of grain growth, preserving the nano-scale microstructure. Highly dense $2/3Cr-ZrO_2$ composite with relative density of up to 99.5% was produced under simultaneous application of a 1 GPa pressure and the induced current. The hardness and fracture toughness of the composite were 534 kg/mm2 and $7MPa{\cdot}m1/2$, respectively. The composite was determined to have good biocompatibility.

• 한국식품영양과학회지
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• 제32권5호
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• pp.673-678
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• 2003

양념 창란젓갈 제조시 감마선의 산업적 적용을 위하여 시판품 제조 방법과 동일하게 제조된 양념 창란젓갈을 0, 2.5, 5.0 및 10 kGy로 감마선 조사하고 미생물학적 및 관능적 품질을 관찰하였다. 또한 고춧가루를 10 kGy의 감마선 조사로 살균한 후 시판품 제조방법으로 제조된 양념 창란젓갈의 품질특성도 비교하였다. 시판 고춧가루는 이미 3.9$\times$$10^{6}$ CFU/$m\ell$의 호기성 미생물수를 나타내었으며 10kGy의 감마선 조사로 약 4 log cycle의 감균효과를 볼 수 있었다. 양념 창란젓갈 제조 후 2.5, 5.0, 10 kGy 감마선 조사는 12주동안 1$0^{\circ}C$에서 저장 후 각각 약 3,6,7 log cycle의 감균효과를 가져왔으며, 고춧가루를 10 kGy로 조사하여 제조된 양념 창란젓갈도 약 2 log cycle의 감균효과를 가져왔다. 관능검사 결과 2.5 및 5kGy 조사구는 종합적 기호도에서 비조사구와 유의적인 차이가 없는 것으로 나타났다. 따라서 제조된 양념젓갈에 2.5kGy의 감마선 조사는 양념 창란젓갈의 유통안전성을 개선시키는데 효과적이며 또한 고춧가루에 감마선 조사도 위생성 향상 측면에서 상당한 효과를 가져오는 것으로 나타났다.

• 한국분말재료학회지
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• 제17권6호
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• pp.456-463
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• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

• 신재생에너지
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• 제4권1호
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• pp.11-18
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• 2008

In-situ lithiated NiO has been manufactured as a conventional cathode material of molten carbonate fuel cell (MCFC), however this material has a weakness for commercialization of MCFC because NiO is spontaneously dissolved into the electrolyte under MCFC operating conditions, resulting in short circuit between cathode and anode. In this research, therefore, $Co(OH)_2$-coated Ni powder was prepared by precipitation method with controlling pH at low temperature and atmospheric pressure. Modified cathode was fabricated by a conventional tape casting method and sintered at 700$^{\circ}C$ in a $H_2/N_2$ atmosphere, Based on characterization result, Pore size distribution and porosity was suitable for the cathode of MCFC. According to the result of dissolution, Ni solubility of modified cathode was 33% lower than that of conventional cathode. In addition, modified electrode showed a good performance from the single cell operation.

• Transactions on Electrical and Electronic Materials
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• 제12권1호
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• pp.11-15
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• 2011

In this study, $ZnGa_2O_4$ phosphors in its application to field emission displays and electroluminescence were synthesized through the precipitation method and $Mn^{2+}$ ions. A green luminescence activator, $Cr^{3+}$ ions, and a red luminescence activator were separately doped into $ZnGa_2O_4$, which was then screen printed to an indium tin oxide substrate. The thick films of the $ZnGa_2O_4$ were deposited with the various thicknesses using nano-sized powder. The best luminescence characteristics were shown at a thickness of 60 ${\mu}m$. Additionally, green-emission $ZnGa_2O_4:Mn^{2+}$ and red-emission $ZnGa_2O_4:Cr^{3+}$ phosphor thick films, which have superior characteristics, were manufactured through the screen-printing method. These results indicate that $ZnGa_2O_4$ phosphors prepared through the precipitation method have wide application as phosphor of the full color emission.

• 한국세라믹학회지
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• 제43권1호
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• pp.1-3
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• 2006

Well-shaped NaA zeolite cubic crystals of a large size of $5-7{\mu}m$ were synthesized by a hydrothermal method in a mother solution having a $3.55Na_2O:Al_2O_3:1.6SiO_2:593\~2000H_2O$ composition. Thermal treatment of NaA zeolite crystals resulted in the formation of a crystalline phase of $NaAlSiO_4-Camegeite$ between 800 and $900^{\circ}C$. Even at $1000^{\circ}C,\;NaAlSiO_4$ phase was found as a major product. Environmental Scanning Electron Microscopy (ESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray powder Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, and DTA/TGA and BET analyses were used to characterize the initial materials and the obtained products after various heat treatments.

• 대한치과보철학회지
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• 제29권3호
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• pp.87-99
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• 1991

The effect of oven firing on the color stability and surface texture of extrinsic stains used characterization and color modification of metal cermic restoration were studied by comparing different temperatures and techniques. They were autoglaze technique, applied glaze technique, two step low-fusing glaze technique and one step low-fusing glaze technique. Autoglaze technique and applied glaze technique were air-fired to manufacturer's recommended temperature. Two step low-fusing glaze technique is separated staining and overglazing. Thin slurry of stain powder were air-fired to $1500^{\circ}F$, Overglaze powder powder was then mixed with seam medium and air-fired to $170^{\circ}F$. One step low-fusing glaze technique is combined staining and overglazing. Thin slurry of stain and glaze powder were air-fired to $170^{\circ}F$. The obtained results were as fellows. 1. Slightly significant color differences by colorimeter were found between different stain application and fusion techniques(P<0.05). 2. Two step low-fusing glaze method showed the most rough surface, especially ceramco orage stain(P<0.05). 3. Surface roughness increased gradually in order of autoglaze, applied glaze, one step low-fusing glaze but they were not significantly different(P<0.05). 4. When two step low-fusing glaze was applied, both color measurement and surface texture were sinificantly different from other groups(P<0.05).