Oxide coatings are formed on die-cast AZ91D Mg alloy through an environmentally friendly plasma electrolytic oxidation(PEO) process using an electrolytic solution of NaAlO2, KOH, and KF. The effects of PEO condition with different duty cycles (10 %, 20 %, and 40 %) and frequencies(500 Hz, 1,000 Hz, and 2,000 Hz) on the crystal phase, composition, microstructure, and micro-hardness properties of the oxide coatings are investigated. The oxide coatings on die-cast AZ91D Mg alloy mainly consist of MgO and MgAl2O4 phases. The proportion of each crystalline phase depends on various electrical parameters, such as duty cycle and frequency. The surfaces of oxide coatings exhibit as craters of pancake-shaped oxide melting and solidification particles. The pore size and surface roughness of the oxide coating increase considerably with increase in the number of duty cycles, while the densification and thickness of oxide coatings increase progressively. Differences in the growth mechanism may be attributed to differences in oxide growth during PEO treatment that occur because the applied operating voltage is insufficient to reach breakdown voltage at higher frequencies. PEO treatment also results in the oxide coating having strong adhesion properties on the Mg alloy. The micro-hardness at the cross-section of oxide coatings is much higher not only compared to that on the surface but also compared to that of the conventional anodizing oxide coatings. The oxide coatings are found to improve the micro-hardness with the increase in the number of duty cycles, which suggests that various electrical parameters, such as duty cycle and frequency, are among the key factors controlling the structural and physical properties of the oxide coating.

삼불화알루미늄(AlF3)이 포함된 염화물-불화물 혼합 용융염에서 ZIRLO 튜브를 이용한 지르코늄 전해정련공정을 실증하였다. 순환 전압전류실험 결과, AlF3의 농도가 증가함에 따라 금속환원의 개시 전위가 일정하게 증가하고 지르코늄-알루미늄 합금형성과 관련된 추가적인 peak의 크기가 점차 증가하는 것으로 나타났다. 전류조절 전착법과 달리, −1.2 V의 일정전위 에서 수행한 지르코늄 전해정련에서 방사형 판 구조의 지르코늄 성장이 염의 상단 표면에서 확연하게 나타났으며, 전착물 지름의 크기는 AlF3의 농도에 따라 점차 증가하는 것으로 나타났다. 주사전자현미경(SEM)과 에너지 분산 X선 분광기(EDX) 와 X선 광전자 분광기(XPS)를 이용하여 판 구조의 지르코늄 전착물을 분석한 결과, 극미량의 알루미늄이 지르코늄-알루미늄 합금 형태로 존재하며, 전착물의 상단과 하단 간에 서로 다른 화학성분구조를 갖는 것으로 나타났다. AlF3의 첨가는 전착물 내 잔류염 양을 줄이고, 지르코늄 회수를 위한 전류효율을 향상시키는 데 효과적인 것으로 나타났다.

Embedding of active devices in a printed circuit board has increasingly been adopted as a future electronic technology due to its promotion of high density, high speed and high performance. One responsible technology is to embedded active device into a dielectric substrate with a build-up process, for example a chipin-substrate (CiS) structure. In this study, desmear treatment was performed before Cu metallization on an FR-4 surface in order to improve interfacial adhesion between electroless-plated Cu and FR-4 substrate in Cu via structures in CiS systems. Surface analyses using atomic force microscopy and x-ray photoemission spectroscopy were systematically performed to understand the fundamental adhesion mechanism; results were correlated with peel strength measured by a 90o peel test. Interfacial bonding mechanism between electrolessplated Cu and FR-4 substrate seems to be dominated by a chemical bonding effect resulting from the selective activation of chemical bonding between carbon and oxygen through a rearrangement of C-C bonding rather than from a mechanical interlocking effect. In fact, desmear wet treatment could result in extensive degradation of FR-4 cohesive strength when compared to dry surface-treated Cu/FR-4 structures.

This paper deals with the effects of the surfactant and preplate process (sensitization and activation) on electroless copper plating on carbon nano-fiber (CNF). Ultrasonic irradiation was applied both during dispersion of CNF and during electroless plating containing preplate process. The dispersion of CNF and flatness of the plated copper film were discussed based on the changes in surfactant concentration and preplate process time. It was clearly shown that high concentration of surfactant and long time of preplate process could promote the agglomeration of CNF and uneven copper plating on CNF.

본 연구에서는 포도의 저장성을 향상시킬 수 있는 방법을 모색하기 위하여 'Sheridan'과 'Muscat Bailey A' 품종을 전해산성수 가습처리와 오존수 살균처리 및 전해산성수 살균처리하여 0±1℃에서 90±2%의 상대습도에서 60일간 저장하면서 포도의 품질 특성을 조사하였다. 모든 처리구에서 대조구에 비하여 저장성이 향상된 것을 알 수 있었으며, 중량감모율, 비정상과 발생률, 탈립율, 당도 및 진균수 억제 효과는 처리구별로 무처리구에 비하여 전해산성수 가습처리하여 포도를 저장하였을 때 중량감모율이 가장 적게 변화하여 좋은 효율을 나타내었고, 오존수 살균처리 및 전해산성수 살균처리 방법에서 비정상과 발생률, 탈립율, 당도 및 진균수에 대한 억제 효율을 나타내었는데, 오존수 살균방법보다 전해산성수 살균방법에서 높은 효과를 나타났다. 유리당과 총산 함량은 저장기간의 증가에 따라 약간의 감소를 보였으며, 과피의 anthocyanin 함량도 약간 증가하였다. 본 실험결과 전해산성수 가습방법과 살균방법이 우수한 효과를 나타냄을 확인할 수 있었다.

Pure Mg and Mg-6wt.%Al alloy were coated by the plasma electrolytic oxidation with various coating times and the microstructural and mechanical characteristics of the coatings were investigated. The coatings on pure Mg and Mg-6wt.%Al alloy consisted of MgO and Mg2SiO4. The surface roughness and thickness of the coatings became larger as the coating time increased. The coatings on the Mg-6wt.%Al alloy were more uniform and thicker than those on pure Mg. The microhardness and friction coefficient of the coatings increased progressively as the coating time increased. In addition, the coatings on the Mg-6wt.%Al alloy compared to pure Mg showed improved microhardness and a better friction coefficient.

Plasma electrolytic oxidation (PEO) treatment was performed on cast Mg-6 wt%Al alloy solution-treated at 693K for 16h and aged at 498K. The surface roughness, thickness, micro-hardness, wear and corrosion properties of coatings on solution-treated and aged Mg-6 wt%Al alloy were investigated. The coatings on aged Mg-6 wt%Al alloy had thinner layer and lower micro-hardness and wear resistance than the solution-treated Mg-6 wt%Al alloy. As the aging time increased, the thickness of coatings decreased while the surface roughness was almost no changed. In addition, the micro-hardness and wear property of coatings decreased with increasing the aging time unlike the uncoated Mg-6 wt%Al alloy showing the peak micro-hardness and the best wear property after aging for 16 h. However, the coatings on Mg-6 wt%Al alloy peak-aged for 16h revealed the best corrosion resistance in 3.5% NaCl solution, which was explained based on the microstructural characteristics.

HI몰랄리티가 9.5 mol/kg-H2O인 HI의 전해-전기투석을 시판의 양이온교환막(CMB)을 이용하여 요오드의 존재하에 실험을 진행하였다. 수소이온 투과의 선택성을 증가시키기 위해, 막은 전자선 가속기를 이용하여 방사선 처리하였다. 방사선 처리한 막의 막특성(막 저항, 이온교환용량, 함수율)을 측정하였다. 각각의 방사선량에서 처리한 막의 2 mol/dm3의 KCl 용액에서 막저항, 이온교환용량과 함수율은 처리하지 않은 막과 거의 동등의 값을 가졌다. HI몰랄리티가 9.5 mol/kg-H2O인 HI의 전해-전투기투석을 75℃, 9.6 A/dm2에서 진행하였다. 전자선 가속기에 의해 방사선 처리한 양이온교환막은 처리하지 않은 막과 비교하여 고분자의 가교구조와 함께 수소이온투과의 높은 선택성을 가졌다.