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포세린 소성시 냉각속도에 따른 PFM용 금합금의 경도와 미세구조의 변화
설효정(Hyo-Joung Seol),심재성(Jae-Seong Sim),조미향(Mi-Hyang Cho),박미경(Mi-Gyoung Park),권용훈(Yong Hoon Kwon),김형일(Hyung-Il Kim) 대한치과재료학회 2011 대한치과재료학회지 Vol.38 No.1
The hardness and microstructural changes by cooling rate in a Pd-free Au-Pt-Zn alloy containing minor ingredients during firing cycles were elucidated by characterizing the age-hardening behavior and age-hardenability, phase transformation and microstructural changes during aging process, changes in hardness after simulated firing with various cooling rates, changes in hardness and microstructure after simulated complete firing with controlled cooling rate. The age-hardening and softening mechanisms of a Pd-free Au-Pt-Zn alloy were homogeneous grain-interior precipitation of the Pt-rich phase and the subsequent lamellar-forming grain boundary reaction, respectively. The lamellar structure was composed of the Pt-depleted Au-rich α1’ matrix layer and the Pt-rich α3 precipitate layer, and the growth of lamellar structure was directly connected with the decrease in hardness. The maximum hardness value was obtained at stage 1 after simulated firing with various cooling rates (ice quenching, quick cooling, stage 0, stage 1, stage 2, stage 3). After simulated complete firing with controlled cooling rate (stage 1), the hardness value of t he solution-treated specimen increased apparently from 89.3 (Hv) t o 170 (Hv) without apparent lamellar-forming grain boundary reaction. It is advisable to control the cooling rate in the final firing stage of the complete firing cycles.
모의소성과정이 Au-Cu-Zn-Cr 합금의 구강내온도에서의 시효경화능에 미치는 영향
설효정(Hyo-Joung Seol),조수연(Su-Yoen Cho),이광영(Gwang-Young Lee),정지인(Ji-In Jeong),전병욱(Byung-Wook Jeon),권용훈(Yong Hoon Kwon),김형일(Hyung-Il Kim) 대한치과재료학회 2013 대한치과재료학회지 Vol.40 No.1
In the present study, the effect of simulated firing cycle on age-hardenability of Au-Cu-Zn alloy containing Cr at intraoral temperature was evaluated by means of hardness test, X-ray diffraction (XRD) study, scanning electron microscopic (SEM) observation, electron probe micro analysis (EPMA) and differential thermal analysis (DTA) after solution-treatment and then aging at intraoral temperature after simulated firing cycle. The Au-Cu-Zn alloy containing 10-15 at.% Cr was softened during simulated firing, and was hardened during cooling process after simulated firing. The hardening effect during cooling process of the Au-Cu-Zn alloy containing 10-15 at.% Cr after simulated firing cycle decreased apparently by the repetitive firing. The Cr addition up to 15 at.% instead of Cu in AuCu-20Zn (at.%) alloy did not result in appreciable change of the order-disorder transition temperature and solidus temperature. The age-hardenability at intraoral temperature of Au-Cu-Zn alloy containing 10-15 at.% Cr decreased apparently after solution-treatment and then simulated firing and aging at intraoral temperature.
Au-Cu-Zn계 합금의 구강내 온도에서의 시효경화효과에 미치는 첨가원소의 영향
설효정(Hyo-Joung Seol),조수연(Su-Yoen Cho),이광영(Gwang-Young Lee),정지인(Ji-In Jeong),표애리(Ae-Ri Pyo),권용훈(Yong Hoon Kwon),김형일(Hyung-Il Kim) 대한치과재료학회 2013 대한치과재료학회지 Vol.40 No.1
In the present study, the age-hardenability at intra-oral temperature of various Au-Cu-Zn alloys containing Ga, Ti, Sn, Cr was evaluated by means of hardness test and X-ray diffraction (XRD) study after solution-treatment at various temperatures and then aging at intra-oral temperature. By the addition of Ti and Sn, the age-hardenability at intra-oral temperature of Au-Cu-Zn alloys decreased apparently. And by the addition of Ga and Cr, the apparent age-hardenability at intra-oral temperature of Au-Cu-Zn alloys was preserved. In Cr-added Au-Cu-Zn alloys, the reduction of Cu content rather than Zn content was much more effective for preserving the age-hardenability at intra-oral temperature. The apparent age-hardenability at intra-oral temperature of Ga- or Cr-added Au-Cu-Zn alloys attributed to the formation of the AuCu Ⅱ ordered phase. In the Au-Cu-Zn alloys containing Cr, the increased Cr content did not prevent the formation of AuCu Ⅱ ordered phase at intra-oral temperature, but possibly reduced the driving force for the formation of AuCu Ⅱ ordered phase at intra-oral temperature. If Ga- or Cr-added Au-Cu-Zn alloy having apparent age-hardenability at intra-oral temperature is used as a dental alloy, it will become harder in the oral cavity without additional heat-treatment.
Ag의 함량에 따른 Ag-Pd-In계 합금의 광학적 특성 및 미세구조의 변화
설효정(Hyo-Joung Seol),조수연(Su-Yoen Cho),조미향(Mi-Hyang Cho) 대한치과재료학회 2018 대한치과재료학회지 Vol.45 No.3
In this study, change of optical properties and microstructure of an Ag-Pd-In alloy according to Ag content was investigated. For this purpose, specimen alloys were prepared by adding 0-100 wt.% of Ag to the 50Pd-50In (wt.%) alloy. When the content of Ag was more than 40 wt.%, the color difference with pure gold specimen was increased(p<0.001). L* value increased as the Ag content of the specimen increased, but a* and b* value increased until the addition of 20 wt.% Ag, and then decreased with increasing Ag content(p<0.001). Ag-free specimen was single phase in the as-cast state, but when the content of Ag was more than 20 wt.%, the phase separation occurred and two phases of matrix and dendrite or granular structure were confirmed. The dendrite or granular structure was composed of the InPd phase, and the matrix was composed of the Ag-rich phase. From these results, it can be concluded that the specimens with Ag content of 20-70 wt.% have the Ag-rich matrix which has a high L* value and low a* and b* value, and have the dendrite structure which has a low L* value and high a* and b* value. As the content of Ag increased, the color changed from light yellow to silver white due to the increase in the ratio of the matrix to the dendrite or granular structure.
Temperature changes and compressive properties of bulk-fill composites by light curing
Dong-ho Yi(이동호),Hyo-Joung Seol(설효정),Yong Hoon Kwon(권용훈) 대한치과재료학회 2020 대한치과재료학회지 Vol.47 No.4
The purpose of the present study was to assess the temperature change and compressive property of bulk-fill composites (BFCs) by the light curing. Seven resin-based composites (RBCs), including five BFCs, were chosen to evaluate their maximum temperature rise and exothermic heat during and after light curing and compressive strength (CS) and modulus (CM) for 4-mm thick state. Light attenuation coefficients (ACs) showed reasonably high correlation with filler content (vol% and wt%). Except one resin product, AC values of BFCs were lower than those of RBCs tested. All the tested specimens showed temperature rise (9.8-23.6℃) and exothermic heat (4.2-18.3℃) for 4-mm thick case. CS and CM values of the tested specimens ranged approximately 69 to 116 MPa and 1.3 to 2.8 GPa, respectively. The difference of temperature changes and compressive properties (CS and CM) between BFCs and RBCs was not consistent and had no statistically consistent significance.
Effects of light wavelength on the microhardenss and polymerization shrinkage of composite resins
Seung-Seo Kim(김승서),Seol-Hyo Joung(설효정),Yong-Hoon Kwon(권용훈) 대한치과재료학회 2017 대한치과재료학회지 Vol.44 No.4
As an activator of photoinitiator, the selection of a light source (wavelength) can affect the result of polymerization. This study examined how the wavelength of a light source affects the curing of composite resins. Four light-curing units (LCUs) (405, 457, and 473 nm lasers with 530 mW/cm2 and one light-emitting diode (LED) with 900 mW/cm2) and three composite resins (one only camphorquinone-containing and two camphorquinone+coinitiator-containing as an initiator) were used. To determine the degree of polymerization, the microhardness and polymerization shrinkage were assessed. On the top surface, two camphorquinone+coinitiator-containing specimens cured using the 473 nm laser showed slightly lower microhardness than those cured using the 405 and 457 nm lasers. However, specimen that contains only camphorquinone showed the lowest microhardness when cured using the 405 nm laser. On the bottom surface, the microhardness increased gradually as laser wavelength changed from 405 to 473 nm. The specimens cured using the LED LCU showed the highest polymerization shrinkage compared to that by the lasers. This study highlights the potential of blue lasers on the curing of various composite resins to the level that the LED LCU can achieve.