• 전기학회논문지
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• 제58권8호
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• pp.1559-1565
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• 2009

Resistivity changes and intermetallic growth after thermal aging of Matter tin-plated copper sheet for current collector in fuel cell were investigated to survey the diffusion of Cu into Sn in interface and surface. The results show that the intermetallic growth and resistivity depended on thermal aging temperature and dwell time. In Sn plate on a Cu substrate, Cu6Sn5(${\mu}$) and Cu3Sn(${\varepsilon}$) intermetallics layer were formed at plate/substrate interface. Cu6Sn5(${\mu}$) intermetallics layer gradually changed Cu3Sn(${\varepsilon}$). Moreover Cu get through Sn layer and it was diffused in the surface at $200^{\circ}C$. On the other hand, only Cu3Sn(${\varepsilon}$) intermetallics layer were formed at plate/substrate interface at $300^{\circ}C$. Consequently, the intermetallics formation, thermal condition and oxidation of surface, causes increase in the resistivity of Tin-plated copper sheet.

• 한국표면공학회지
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• 제55권6호
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• pp.408-416
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• 2022

In this study, the effect of Au-Sn alloy coating on reliability of electrical contacts was investigated via comparison with Au-Co alloy coating. The results show that Au-Sn alloy exhibited lower contact resistance and higher solder spreadability than those of Au-Co alloy after thermal aging. In the case of Au-Co alloy plating, the underlying Ni element diffused into Au-Co layer to form Ni oxides on surface during thermal aging, leading to increased contact resistance and decreased solder spreadability. Meanwhile, for Au-Sn alloy plating, Au-Ni-Sn metallic compound was formed at the interface between Au-Sn layer and underlying Ni layer. This compound acted as a diffusion barrier, thereby inhibiting the diffusion of Ni to Au-Sn layer during thermal aging. Consequently, Au-Sn alloy layer showed better contact reliability than that of Au-Co alloy layer.

• The Journal of Advanced Prosthodontics
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• 제16권1호
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• pp.25-37
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• 2024

PURPOSE. To investigate the effect of sintering programs and surface treatments on surface properties, phase transformation and flexural strength of monolithic zirconia. MATERIALS AND METHODS. Zirconia specimens were sintered using three distinct sintering programs [classic (C), speed (S), and superspeed (SS)] (n = 56, each). One sample from each group underwent scanning electron microscopy (SEM) and grain size analysis following sintering. Remaining samples were divided into five subgroups (n = 11) based on the surface treatments: control (CL), polish (P), glaze (G), grind + polish (GP), and grind + glaze (GG). One sample from each subgroup underwent SEM analysis. Remaining samples were thermally aged. Monoclinic phase volume, surface roughness, and three-point flexural strength were measured. Monoclinic phase volume and surface roughness were analyzed by Kruskal-Wallis and Dunn tests. Flexural strength was analyzed by two-way ANOVA and Weibull analysis. The relationships among the groups were analyzed using Spearman's correlation analysis. RESULTS. Sintering program, surface treatment, and sintering × surface treatment (P ≤ .010) affected the monoclinic phase volume, whereas the type of surface treatment and sintering × surface treatment affected the surface roughness (P < .001). Type of sintering program or surface treatment did not affect the flexural strength. Weibull analysis revealed no significant differences between the m and σ_o values. Monoclinic phase volume was positively correlated with surface roughness in the SGG and SSP groups. CONCLUSION. After sintering monolithic zirconia in each of the three sintering programs, each of the surface treatments can be used. However, for surface quality and aging resistance, G or GG can be recommended as a surface finishing method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.930-933
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• 2001

Titanium Alloys used in this experiment has an good corrosion resistance and specific strength, and is the new material developed for medical supplies living goods. In this study the rolled titanium alloy is done by annealing, solution heat-treatment and aging and then is worked by wire EDM. With changing the process conditions, the process properties of surface hardness, surface roughness, shape of process surface and the analysis of ingredients are measured through experiment repeating main cut and finish cut. It is confirmed to gain good measure values as increasing the number of processing of wire EDM. In this experiment the phenomena of processing is studied and the appropriate process condition is proposed.

• Korean Chemical Engineering Research
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• 제46권3호
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• pp.545-549
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• 2008

${\gamma}-AlO$(OH) 졸 입자 뿐만 아니라 소성처리된 ${\gamma}-Al_2O_3$ 입자의 표면특성을 ${\gamma}-AlO$(OH) 졸 제조시 숙성단계에 의하여 조절하였다. 연구결과, ${\gamma}-AlO$(OH) 졸 입자의 등전점은 숙성 증가에 따라 pH 9.25에서 pH 8.70까지 감소하였으며 ${\gamma}-Al_2O_3$ 입자의 경우는 pH 9.90에서 pH 8.86까지 감소하였다. 숙성에 따른 ${\gamma}-Al_2O_3$ 입자의 산, 염기 특성을 고찰한 결과, ${\gamma}-Al_2O_3$ 입자의 산량은 숙성시간의 증가에 따라 0.1367 mmol/g에서 0.0783 mmol/g까지 감소하였으며, Hammett 산성도함수 $H_o$는 4.8 이상의 산세기를 보였다. 한편 ${\gamma}-Al_2O_3$ 입자의 염기량은 숙성시간의 증가에 따라 0.4399 mmol/g에서 0.3074 mmol/g 까지 감소하였다. 따라서 졸-겔법에 의한 ${\gamma}-Al_2O_3$ 제조시 숙성공정이 산, 염기점의 양을 포함한 표면특성을 조절할 수 있는 중요 공정변수임을 제시하였다.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.86-94
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• 1997

Quick aging of catalysts has done with IAE(Institute for advanced engineering) AGING MODE suggested by IAE. To estimate the effects of number of aging cycle, temperature and $H_2O$, characteristics of surfaces, mechanical properties and weibull modulus were estimated. Also, the conversion efficiency of aged catalysts was evaluated with model gas bench test. The area of surface and pore volume were decreased according to the number of aging cycle. The precious metal which is well dispersed in fresh state was sintered and agglomerated with aging. The mechanical of deactivation and sintering of catalysts are discussed on the basis of mechanical tests. The conversion efficiency was decreased with the repeats of aging. Especially, the existence of $H_2O$ in supply gas had a main role in catalyst deactivation withy high temperature.

• 한국식품영양학회지
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• 제6권3호
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• pp.219-230
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• 1993

This research aims to study the changes In gastrointestinal function attributed to aging In human. The thresholds for recognition and detection of flavors became elevated and salivary gland acinar cells decreased in the old age. But most esophageal function remained relatively Intact. Although gastric emptying time has been slowed with aging, the total intestinal transit time did not differ. Atropic gastritis due to H. pylori in old man decreased secretion of acid and Intrinsic factor and absorbability of calcium and iron. Pancreatic secretion is droned in older persons. Prevalence of gallstones rised with age. Liver size and portal blood flow decreased significantly with age. Mucosal surface area has been reported to be slightly diminished in the aging man. Glucose transporters decreased and Insulin tolerance Increased. Absorption of aromatic amino acid is diminished with age. Dietary protein In that aging human increased fecal nitrogen excretion. Vitamin A tolerance increased. Vitamin D receptor concentration decreased and resistance to 1,25-(OH)2D3 action increased. Permeability of aging small Intestine Increased. Zinc balance dirt not differ Copper absorption appeared not to be significantly affected by age. Neurotensin secretion decreased thus slowed colonic peristaltic movements and Intestinal mucosal growth.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.10-14
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• 2001

In order to assess the long-tenn reliability of polymer insulators for distribution power systems, we have developed the accelerated aging test method which can simulate the operation conditions. In this study, 3000 hours aging test for 4 kinds of polymer insulators has been completed by the developed accelerated aging test. After 3000 hours aging test, visual inspection and electrical tests were carried for identifying a change of characteristics. Some specimens showed the surface erosion and the manufacturing defect. In the electrical tests, the wet flashover voltage was significant1y decreased by the accelerated aging test. In comparison with the field-aged polymer insulators, it can be concluded that the developed test method can evaluate the long-tenn reliability within short time and screen the manufacturing defect.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3723-3729
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• 2010

We investigated the high-excitation voltage cathodoluminescence (CL) performance of blue light-emitting (ZnS:Ag,Al,Cl) and green light-emitting (ZnS:Cu,Al) phosphors coated with metal oxides ($SiO_2$, $Al_2O_3$, and MgO). Hydrolysis of the metal oxide precursors tetraethoxysilane, aluminum isopropoxide, and magnesium nitrate, with subsequent heat annealing at $400^{\circ}C$, produced $SiO_2$ nanoparticles, an $Al_2O_3$ thin film, and MgO scale-type film, respectively, on the surface of the phosphors. Effects of the phosphor surface coatings on CL intensities and aging behavior of the phosphors were assessed using an accelerating voltage of 12 kV. The MgO thick film coverage exhibited less reduction in initial CL intensity and was most effective in improving aging degradation. Phosphors treated with a low concentration of magnesium nitrate maintained their initial CL intensities without aging degradation for 2000 s. In contrast, the $SiO_2$ and the $Al_2O_3$ coverages were ineffective in improving aging degradation.

• 대한소아치과학회지
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• 제34권3호
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• pp.359-369
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• 2007

본 연구는 다양한 순환 및 시효 조건 하에서 제V급 복합레진 수복물의 표면전색이 미세변연누출에 미치는 효과에 대해 알아보고자 하였다. 100개의 건전한 소구치의 협면에 제V급 와동을 형성하고 제조사의 지시대로 광중합형 복합레진으로 수복하였다. 무작위로 나누어 표면전색을 시행하지 않는 I군과 표면을 산부식 후 표면전색을 시행한 II군으로 설정한 후 열순환(thermocycling)을 하였다. 각 군에서 하위군(A군= 열순환 외 다른 시효조건이 없는 군, B군=칫솔질군, C군=부하순환군, D군=칫솔질과 부하순환을 모두 시행한 군, E군=6개월간 증류수에 보관한 군)으로 나누어 각각에 맞는 시효조건을 시행하였다. 2% methylene blue 용액에 침윤시켜 변연의 미세누출정도를 평가하여 다음과 같은 결과를 얻었다. 1. 표면전색을 시행하지 않은 군의 교합변연과 치은변연에서 시효조건에 따른 미세누출의 유의한 차이는 보이지 않았다(p>0.05). 2. 표면전색을 시행한 군의 교합변연에서는 시효조건에 따른 미세누출의 유의한 차이가 없었다(p>0.05). 3. 표면전색을 시행한 군의 치은변연에서는 부하순환이나 6개월간 증류수에서 보관하는 시효과정을 거친 군에서 미세누출이 유의하게 크게 나타났다(p<0.05). 4. 시효조건이 없는 군과 칫솔질군의 경우, 표면전색을 시행한 군이 표면전색을 시행하지 않은 군에 비해 유의하게 적은 미세누출결과를 보였다(p<0.05). 5. 부하순환을 시행한 군과 6개월간 증류수에서 보관한 경우에는 표면전색을 시행한 군과 표면전색을 시행하지 않은 군 사이에 미세누출의 차이가 있었지만 유의차가 없었다(p>0.05). 따라서 이 연구의 결과는 변연부분의 미세간격으로 침투한 표면전색제가 처음에는 미세누출을 감소하는데 효과를 보여주었으나, 교합시 교두가 휘어져서 생기는 응력과 장기간의 수분흡수로 인한 변화를 견디기에 불충분함을 보여주었다.