• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2010년도 추계학술대회 논문집
• /
• pp.77-78
• /
• 2010

• The Journal of Advanced Prosthodontics
• /
• 제9권2호
• /
• pp.130-137
• /
• 2017

PURPOSE. The purpose of this study was to evaluate the effect of nano-structured alumina surface coating on shear bond strength between Y-TZP ceramic and various dual-cured resin cements. MATERIALS AND METHODS. A total of 90 disk-shaped zirconia specimens (HASS CO., Gangneung, Korea) were divided into three groups by surface treatment method: (1) airborne particle abrasion, (2) tribochemicalsilica coating, and (3) nano-structured alumina coating. Each group was categorized into three subgroups of ten specimens and bonded with three different types of dual-cured resin cements. After thermocycling, shear bond strength was measured and failure modes were observed through FE-SEM. Two-way ANOVA and the Tukey's HSD test were performed to determine the effects of surface treatment method and type of cement on bond strength (P<.05). To confirm the correlation of surface treatment and failure mode, the Chi-square test was used. RESULTS. Groups treated with the nano-structured alumina coating showed significantly higher shear bond strength compared to other groups treated with airborne particle abrasion or tribochemical silica coating. Clearfil SA Luting showed a significantly higher shear bond strength compared to RelyX ARC and RelyX Unicem. The cohesive failure mode was observed to be dominant in the groups treated with nano-structured alumina coating, while the adhesive failure mode was prevalent in the groups treated with either airborne particle abrasion or tribochemical silica coating. CONCLUSION. Nano-structured alumina coating is an effective zirconia surface treatment method for enhancing the bond strength between Y-TZP ceramic and various dual-cured resin cements.

• 대한기계학회논문집B
• /
• 제39권7호
• /
• pp.599-607
• /
• 2015

본 연구에서는 나노유체의 유동학 특성을 반영한 히트파이프 열적특성을 연구하였다. $Al_2O_3$와 CuO 나노입자를 적용한 나노유체를 작동유체로 하여 나노입자 부피비와 응집도에 대한 히트파이프 성능을 확인하였다. 나노입자의 부피비와 응집도가 증가할수록 점성과 열전도도는 증가하는 것으로 나타났으며 두 인자는 히트파이프 성능에 영향을 주었다. 나노입자응집이 없는 경우에는 나노입자의 부피비 증가가 모세관압력한계 성능을 향상시켰지만 응집도가 증가하면 입자부피비가 증가해도 모세관압력한계가 감소했다. 그리고 나노입자의 열전도도, 부피비, 응집도에 대한 히트파이프 열저항을 분석하였다. 히트파이프의 투과율이 높을수록 최대열수송량은 입자부피비에 미치는 영향이 컸으며 3차원 그래프를 통해 윅 특성에 대한 최적화된 나노입자부피비를 확인하였다.

• 공업화학
• /
• 제24권3호
• /
• pp.260-265
• /
• 2013

본 연구에서는 비타민나무 잎 추출물의 에틸아세테이트 분획 0.01, 0.03, 0.05, 0.10% 함유한 나노에멀젼을 제조하였고, 5주 동안 이들 나노에멀젼의 입자 크기, 입도분포 및 피부 투과능을 평가하였다. 나노에멀젼은 균질기(homogenizer) 처리 후 고압유화기(micro-fluidizer)를 이용하여 제조하였다. 비타민나무 잎 추출물의 에틸아세테이트 분획을 함유한 나노에멀젼은 단분산 형태를 나타내었다. 5주 동안 실험에서, 0.03% 에틸아세테이트 분획을 함유한 나노에멀젼이 가장 안정하였다. 0.03% 에틸아세테이트 분획 함유 나노에멀젼의 in vitro 피부 투과 실험을 Franz diffusion cell을 이용하여 수행하였다. Oil-in-water (O/W) 에멀젼과 비교할 때 나노에멀젼이 피부 흡수가 더 잘되는 것으로 나타났다. 이러한 결과들은 비타민나무 잎 추출물을 함유한 나노에멀젼이 O/W 에멀젼보다 안정성과 피부 투과능이 우수함을 나타낸다.

• 대한의용생체공학회:의공학회지
• /
• 제28권1호
• /
• pp.148-152
• /
• 2007

In this paper, we have synthesized $Gd_2O_3:Eu^{3+}$ nano phosphor particle using a low temperature solution-combustion method. We have investigated the structure and the luminescent characteristic as the sintering temperature and europium concentration. From XRD(X-ray diffraction) and SEM(scanning electron microscope) results, we have verified that the phosphor particle was fabricated a spherical shape with $30{\sim}40nm$ particle size. From the photoluminescence results, the strong peak exhibits at 611 um and the luminescent intensity depends on europium concentration. $Gd_2O_3:Eu$ fine phosphor particle has shown excellent luminescent efficiency at 5 wt% of europium concentration. The phosphors calcinated at $500^{\circ}C$ have possessed the x-ray peaks corresponding to the cubic phase of $Gd_2O_3$. As calcinations temperature increased to $700^{\circ}C$, the new monoclinic phase has identified except cubic patterns. From the luminescent decay time measurements, mean lifetimes were $2.3{\sim}2.6ms$ relatively higher than conventional bulk phosphors. These results indicate that $Gd_2O_3:Eu$ nano phosphor is possible for the operation at the low x-ray dose, therefore, the application as medical imaging detector.

• 한국재료학회지
• /
• 제26권1호
• /
• pp.54-60
• /
• 2016

We have investigated the crystallization mechanism of the lithium disilicate ($Li_2O-2SiO_2$, LSO) glass particles with different sizes by isothermal and non-isothermal processes. The LSO glass was fabricated by rapid quenching of melt. X-ray diffraction and differential scanning calorimetry measurements were performed. Different crystallization models of Johnson-Mehl-Avrami, modified Ozawa and Arrhenius were adopted to analyze the thermal measurements. The activation energy E and the Avrami exponent n, which describe a crystallization mechanism, were obtained for three different glass particle sizes. Values of E and n for the glass particle with size under $45{\mu}m$, $75{\sim}106{\mu}m$, and $125{\sim}150{\mu}m$, were 2.28 eV, 2.21 eV, 2.19 eV, and ~1.5 for the isothermal process, respectively. Those values for the non-isothermal process were 2.4 eV, 2.3 eV, 2.2 eV, and ~1.3, for the isothermal process, respectively. The obtained values of the crystallization parameters indicate that the crystallization occurs through the decreasing nucleation rate with a diffusion controlled growth, irrespective to the particle sizes. It is also concluded that the smaller glass particles require the higher heat absorption to be crystallized.

• 자원리싸이클링
• /
• 제15권4호
• /
• pp.19-26
• /
• 2006

함은 폐재의 리싸이클링을 위한 연구의 일환으로써 Hydrazine Hydrate을 환원제로 사용하여 질산은 수용액으로부터 Ag 나노분말을 제조하기 위한 실험을 수행하였다. 이를 위해 질산은을 소정 농도로 증류수에 용해시킨 수용액에 Ag 미립자의 응집방지를 위한 분산제로써 Tamol NN8906 혹은 Tween 20을 미리 혼합한 다음 환원제인 Hydrazine Hydrate 용액을 첨가하는 방법으로 환원반응을 실시하였다. 환원반응을 통하여 제조한 Ag 미립자는 입도분석기 및 TEM 측정을 통하여 형상과 평균입도를 측정하였다. Hydrazine Hydrate에 의한 은의 환원을 위해서는 이론치의 약 2배를 첨가해 주어야 하는 것으로 나타났으며, Tamol NN8906을 분산제로 사용하여 제조한 Ag 나노분발은 매우 좁은 입도범위의 분포특성을 보여 주었다. Tween 20을 분산제로 사용한 경우의 입도 분포는 bimodal 혹은 multimodal distribution을 보였으며, 입자 모양에 있어서는 Tamol NN8906과 Tween 20이 모두 비슷하게 표면이 매끄러운 불규칙한 모양의 입자들로 구성되어 있었다.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.437-442
• /
• 2023

This research aims to enhance the efficiency of Pt/C catalysts due to the limited availability and high cost of platinum in contemporary fuel cell catalysts. Nano-sized platinum particles were distributed onto a carbon-based support via the polyol process, utilizing the metal precursor H₂PtCl₆·6H₂O. Key parameters such as pH, temperature, and RPM were carefully regulated. The findings revealed variations in the particle size, distribution, and dispersion of nano-sized Pt particles, influenced by temperature and pH. Following sodium hydroxide treatment, heat treatment procedures were systematically executed at diverse temperatures, specifically 120, 140, and 160 ℃. Notably, the thermal treatment at 140 ℃ facilitated the production of Pt/C catalysts characterized by the smallest platinum particle size, measuring at 1.49 nm. Comparative evaluations between the commercially available Pt/C catalysts and those synthesized in this study were meticulously conducted through cyclic voltammetry, X-ray diffraction (XRD), and field-emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM EDS) methodologies. The catalyst synthesized at 160 ℃ demonstrated superior electrochemical performance; however, it is imperative to underscore the necessity for further optimization studies to refine its efficacy.

• 한국염색가공학회지
• /
• 제22권4호
• /
• pp.356-361
• /
• 2010

This study was aimed to investigate the antibacterial efficiency of silver nano-particles and the dyeing properties of a brushed warp-knitted fabric. The properties of the brushed warp-knitted fabric containing silver nano-particle by field production processes were evaluated by analyzing its silver contents, antibacterial activity, color difference, exhaustion curve, fastness and tearing strength. Bacterial reduction ratio amounts to 91.4 and 99.9 for Staphylococcus aureus and Klebsiella pneumoniae respectively. As the brushed pile length of its fabrics is longer, the exhaution rate of disperse dye becomes higher. The brushing process of its fabrics reduces the tearing strength. The results indicate that the brushed warp knitted fabric containing silver nano-particle can be a practically promising product.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.233.2-233.2
• /
• 2006