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박막을 형성한 원통형 덩어리 모델의 다공성 기체확산 전극 유효성인자
노제승,홍성안,서성섭 ( Je Seung Roh,Seong Ahn Hong,Sung Sup Suh ) 한국화학공학회 1996 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.34 No.5
The porous gas diffusion electrode was described by cylindrical agglomerate model with electrolyte thin film to investigate the effectiveness factor. System variables such as reaction rate constant, diffusion coefficients, conductivity, agglomerate size, electrode thickness and temperature were combined into four dimensionless parameters. The effectiveness factor was slightly larger than that for slab agglomerate model. However, the effects of the system variables on the effectiveness factor were similar. The effect of electrolyte thin film was very small where the ratio of the thin film thickness to the agglomerate size was less than 0.01. The electrode thickness for the optimum electrode performance was independent of the agglomerate shape.
도재용착용 Ni-Cr계 합금의 이트륨 첨가물이 도재전단결합강도에 미치는 영향
우제승,노세라,노형록,임청하,이정환 대한치과기공학회 2019 대한치과기공학회지 Vol.41 No.2
Purpose: In this study, to evaluate the effect of oxide changes on the shear bond strength according to the composition of Ni-Cr alloys for porcelain fused matal crown, T-4 alloys, Zeroy alloys and Zeroy-X alloys were selected. Methods: 20 specimens were fabricated using selected Ni-Cr alloys and porcelain powders. A Ni-Cr alloy having a diameter of 5 ㎜ and a height of 25 ㎜ was produced and the metal surface was polished. Porcelain powder was fired on the polished metal surface to a diameter of 5 mm and a height of 3 mm. The experiment group consisted of three groups, T-4(TNA), Zeroy(ZNA) and Zeroy-X(ZXA). The fabricated specimens were mounted on a jig of a universal testing machine(UTM) and fracture strength was measured by applying a shear force at a UTM crosshead speed of 0.5 ㎜/min. The fracture strength was calculated as the bond strength between the porcelain and the alloy. The surface of the fractured alloy was analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM), and the components of the oxide were measured by energy dispersive X-ray spectroscopy(EDX) line profile method. Results: In SEM, XRD and EDX analysis, yttrium tended to increase the mechanical and chemical bonding forces. The shear bond strength of ZXA group containing yttrium showed the highest value at 27.53 MPa. Conclusion: Based on the results of this study, it is considered that the yttrium-added Ni-Cr alloy is clinically acceptable in porcelain shear bond strength.
오인환,홍성안,서성섭,남석우,임태훈,주재백,노제승 한국화학공학회 1994 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.32 No.5
덩어리 모델(agglomerate model)로써 표현될 수 있는 다공성 기체 확산 전극의 유효성인자에 대해서 조사하였다. 유효성인자는 확산 저항이 있는 전극에서 실제로 생성되는 전류와 확산 저항이 없는 경우에 생성되는 전류의 비로 정의하였다. 반응 속도, 확산 계수와 덩어리 크기 등 시스템의 여러 가지 변수들을 세 개의 무차원 파라미터로 나타내었고 이들이 유효성 인자에 미치는 영향을 살펴보았으며 전극의 두께가 늘어나도 유효성인자가 더 이상 커지지 않는 지점이 존재함을 볼 수 있었다. Effectiveness factor which was defined as the ratio of the current produced by the electrode under diffusional resistance to that produced by the electrode without diffusional resistance was investigated for porous gas diffusion electrode described by agglomerate model. System variables including reaction rate, diffusion coefficient, and agglomerate size were combined into three dimensionless parameters, and their effects on effectiveness factor were studied. Effectiveness factor reaches a maximum value with a critical electrode thickness.