• Journal of the Korean Ceramic Society
• /
• v.55 no.6
• /
• pp.625-634
• /
• 2018

In this work, we describe a novel and simple technique to produce non-hydrate surfactant complexes for the formation of highly crystalline fatty acid modified SPIONs by thermolysis of iron oleate (FeOl) complexes in a non-coordinating solvent. FeOl complexes were prepared by direct coordination of iron ions and carboxylic acid; thus, we could control the stoichiometric composition of the precursor by changing the molar ratio of fatty acid and metal ions. The discrete thermal behaviors and chemical coordination of the intermediate non-hydrated FeOl were studied by thermo-analytic techniques including differential scanning calorimetry, thermal gravimetric analysis, and Fourier transform infrared spectroscopy.

• Applied Microscopy
• /
• v.43 no.1
• /
• pp.9-13
• /
• 2013

The helium ion microscope (HIM) has recently emerged as a novel tool for imaging and analysis. Based on a bright ion source and small probe, the HIM offers advantages over the conventional field emission scanning electron microscope. The key features of the HIM include (1) high resolution (ca. 0.25 nm), (2) great surface sensitivity, (3) great contrast, (4) large depth-of-field, (5) efficient charge control, (6) reduced specimen damage, and (7) nanomachining capability. Due to the charge neutralization by flood electron beam, there is no need for conductive metal coating for the observation of insulating biological specimens by HIM. There is growing evidence that the HIM has substantial potential for high-resolution imaging of uncoated insulating biological specimens at the nanoscale.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.560-563
• /
• 2008

A modified polyol process is developed to enhance Pt loading during the preparation of Pt/C catalysts. With the help of the zeta potential, the effect of pH on the electrostatic forces between the support and the Pt colloid is investigated. It is shown experimentally that the surface charge on the carbon support becomes more electropositive when the solution pH is changed from alkaline to acidic. However, this change does not affect the electronegative surface charge of Pt colloids already attained and stabilized by glycolate anions. This new behavior caused by the change in the solution pH accounts for the enhanced yield of the process and does not affect the Pt particle size. All our experimental results reveal that this simple modification is a cost effective method for the synthesis of highly Pt loaded Pt/C catalysts for fuel cells.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.119-123
• /
• 2006

The ionic-polymer-metal-composite actuators have the best merit for bio-mimetic locomotion because of their large bending performance. Especially, they have the advantage for mimicking a fish-like motion because IPMCs are useful to be actuated in water. So we have developed IPMC actuators with multiple electrodes for realization of biomimetic motion. Generally, the IPMC actuator has been fabricated in electroless plating technique, while it needs very long fabrication time and shows poor repeatability in the actuation performance owing to the variables in chemical fabrication process. Therefore, the novel fabrication methods were investigated by combining electroless plating and electroplating techniques capable of patterning precisely. On the whole, two different methods were compared and analyzed with similar thickness level of Platinum electrodes. Present results show that mixing chemical reduction and electroplating can be a promising candidate for electrode patterning.

• 한국가스학회:학술대회논문집
• /
• 2006.11a
• /
• pp.123-128
• /
• 2006

This paper describes NDIR $CO_2$ gas sensor that shows the characteristics of temperature compensation. It consists of novel optical cavity that has two elliptical mirrors and a thermopile detector that includes ASIC chip in the same metal package for the amplification of detector output voltage and temperature sensor. The newly developed sensor modules shows high accuracy (less than +/-40 ppm) throughout the measuring concentration of $CO_2$ gas from 0 ppm to 2,000 ppm. After implementing the calculation methods of gas concentration, which is based upon the experimental results, the sensor module shows high accuracy less than +/- 5 ppm error throughout the measuring temperature range $(15^{\circ}C\;to\; 35^{\circ}C)$ and gas concentrations.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.160-160
• /
• 2003

This paper describes some of the key issues associated with the patterning of metal electrodes of sub-micron (especially at the critical dimension (CD) of 0.15 $\mu\textrm{m}$) dynamic random access memory (DRAM) devices. Due to reactive ion etching (RIE) lag, the Pt etch rate decreased drastically below the CD of 0.20 $\mu\textrm{m}$ and thus the storage node electrode with the CD of 0.15 $\mu\textrm{m}$ could not be fabricated using the Pt electrodes. Accordingly, we have proposed novel techniques to surmount the above difficulties. The Ru electrode for the stack-type structure is introduced and alternative schemes based on the introduction of the concave-type structure using Pt or Ru as an electrode material are outlined.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.130-130
• /
• 2003

현재, 메탈의 내부식성 코팅막 제조에 사용되고 있는 크로메이트 기반 코팅제는 유독성 물질에 대한 환경 규제에 따라 조만간 사용이 금지 될 예정이다. 본 연구에서는 이러한 유독성 금속 내부식성 코팅제를 대체할 새로운 환경 친화적인 코팅 재료로서 A1OOH 나노졸이 분산된 ZrOCl$_2$ㆍ8$H_2O$-GPS(3-Glycidoxypropyltrimethoxysilane)하이브리드 졸을 제조하고 이의 내 부식성 특성에 대하여 조사하였다. AlOOH 졸이 첨가된 유/무기 하이브리드 졸은 염화 알루미늄을 염기로 침전 시킨 수산화 알루미늄 침전물에ZrOCl$_2$ㆍ8$H_2O$를 10 ~ 20 wt% 첨가하고 열처리한 후 여기에 GPS를 AlOOH에 대하여 4 ~ 6몰 배 첨가하여 제조하였다. 제조된 하이브리드 형 졸은 가시관 투광성이 우수하며 시간에 따른 범도 변화가 거의 없었다. 이 코팅 졸을 아연 도금 강판에 딥 코팅법으로 코팅한 후, 상온~20$0^{\circ}C$에서 열처리하여 염수 시험법으로 하이브리드 졸의 조성 및 열처리 조건에 따른 코팅막의 내부식성 특성을 조사하였다. 또한, 코팅막의 두께를 전자 현미경으로 관찰하였고, 코팅막 경도는 연필 경도계로 조사하였다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.123-123
• /
• 2003

나노튜브는 반도체 재료로서 뿐만 아니라 다른 분야로까지 다양한 응용범위를 가진 물질로서 기존에는 주의 탄소를 사용하여 제작, 사용되어지고 있으나 게이트옥사이드(Gate Oxide) 물질인 지르코니아(ZrO$_2$), 타이타니아(TiO2$_2$) 등을 이용한 나노튜브는 많이 제작되어지고 있지 못하다. 따라서 보다 나은 성질을 갖는 물질로서 나노튜브를 제작할 시 반도체 재료에서의 고집적화를 통해 좋은 성질을 갖게 할 수 있으며 여러 분야로까지 확대가 가능한 재료를 사용하여 광학 및 환경분야 등 응용범위를 넓힐 수 있다. 본 실험은 나노튜브 제작에 있어서 템플레이트의 구멍 내부를 ALD 기술을 이용하여 균일한 두께를 갖는 금속 산화물층을 성장시킨 후 템플레이트 재료의 식각을 통해 금속산화물 나노튜브가 남아있게 하여 제작하는 방법이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2007.12a
• /
• pp.200-201
• /
• 2007

The present study was conducted in three fields at Namhae to examine the removal efficiency of organic free, heavy metal immobilized sediment on Cochlodinium polykrikoidesand and on sea water quality. The present study results concluded that removal efficiency was depends on the initial number of red tide cells. There was no drastic change in the sea water quality after sediment spray. For the comparison of effectiveness of betonite, zeolite and lime were mixed with sediment did not show any marked difference in removal. Finally, the present study evaluated 50g/$m^{2}$ sediment is sufficient to remove 100% cells density, even though various environmental factors are interfering the mechanism.

• Structural Monitoring and Maintenance
• /
• v.7 no.1
• /
• pp.27-42
• /
• 2020

Dynamic stability of graded nonlocal nano-dimension plates on elastic substrate due to in-plane periodic loads has been researched via a novel 3- unknown plate theory based on exact position of neutral surface. Proposed theory confirms the shear deformation effects and contains lower field components in comparison to first order and refined 4- unknown plate theories. A modified power-law function has been utilized in order to express the porosity-dependent material coefficients. The equations of nanoplate have been represented in the context of Mathieu-Hill equations and Chebyshev-Ritz-Bolotin's approach has been performed to derive the stability boundaries. Detailed impacts of static/dynamic loading parameters, nonlocal constant, foundation parameters, material index and porosities on instability boundaries of graded nanoscale plates are researched.