Thermal cycling 과 시효처리가 Glass-Ionomer수복재의 인장강도에 미치는 영향

이승익,백병주,김재곤,이승영,김문현 大韓小兒齒科學會 1999 大韓小兒齒科學會誌 Vol.26 No.4

본 연구에서는 구강환경과 유사한 액상의 조건하에서의 온도변화가 광중합형 글래스아이오노머계 수복재의 인장강도에 미치는 영향을 평가하기 위해 대조군으로 2종의 재래형 glass ionomer를 선택하고 실험군으로 2종의 광중합형의 resin-modified glass ionomer와 2종의 polyacid-modified resin composite을 선택한 다음 수중에서의 thermal cycling과 시효처리를 행하였으며, 다음과 같은 결론을 얻었다. 1. 글래스아이오노머 수복재의 인장강도를 측정한 결과, polyacid-modified resin composite, resin-modified glass ionomer 그리고 재래형 glass ionomer의 순으로 나타났다. 2. 인장강도는 30일간의 시효처리로 증가되는 경향을 보였다. 3. 재래형 glass ionomer 수복재의 인장강도는 thermal cycling 처리로 증가되는 경향을 보였으며, 37℃의 증류수 중에 1시간 침적한 군과 10,000회의 thermal cycling을 비교한 결과 유의한 차이로서 강도의 증가를 나타냈다(P<0.01). 4. thermal cycling 군의 인장강도는 DR군이 45.4MPa로 최대치를, FL군이 13.4MPa로 최소치를 나타냈으며, 각 군간의 통계적 유의성을 검증한 결과 polyacid-modified resin composite의 인장강도가 나머지 군과 유의한 차이를 보였다(p<0.05). 5. 특성강도는 DR군이 48.6MPa로 가장 높은 강도치를 보였으나, Weibull 계수는 CG군이 8.9로 가장 높은 값을 보여 시험재료 중에서 가장 작은 강도의 분산을 나타냈다. This study was performed to evaluate the effect of aging and thermal cycling on the tensile strength of six commercially available glass-ionomer materials: two chemically set glass-ionomer materials(Fuji Ⅱ, fuji Ⅸ), two resin-modified glass-ionomer materials(Fuji Ⅱ LC, Vitremer), and two polyacid-modified composite resins(Compoglass, Dyract). Rectangular tension test specimens were fabricated in a teflon mold giving 5mm in gauge length and 2mm in thickness. All samples were divided into 3 groups. Group 1 was immersed in a 37℃ distilled water for 1 hour. Group 2 was immersed in a 37℃ distilled water for 30 days. Group 3 was subjected to 10,000 thermal cycles between 5℃ and 55℃, and the immersion time in each bath was 15 seconds per cycle. Tensile testing was carried out at a cross-head speed of 0.5mm/min and fracture surfaces were examined with scanning electron microscope. The results obtained were summarized as follows; 1. The polyacid-modified composite resins were stronger than the resin-modified glass-ionomer materials, which were much stronger than the conventional glass-ionomer materials. 2. Tensile strengths were slightly increased after aging treatments for 30days. 3. Tensile strengths of conventional glass ionomers were significantly increased after thermal cycling treatment(p<0.01). 4. The highest tensile strength value of 45.4MPa was observed in the Dyract group and the lowest value of 13.3MPa was observed in the Fuji Ⅱ LC group after the thermal cycling test, and the strengths of polyacid-modified composite groups were significantly higher than those of other groups. 5. The highest characteristic strength value of 48.6MPa was obtained in the Dyract group, however the highest Weibull modulus value of 8.9MPa was obtained in the Compoglass group after thermal cycling test.

광중합형 수복용 복합레진의 기계적 성질에 미치는 수중침적과 Thermal Cycling의 영향

배태성,김태조,김효성,Bae, Tae-Sung,Kim, Tae-Jo,Kim, Hyo-Sung 대한의용생체공학회 1996 의공학회지 Vol.17 No.3

This study was performed to investigate the effec% of immersion in water and thermal cycling on the mechanical peoperties of light cured restorative composite resins. Five commerically available light-cured composite resins(Photo Clearfil A : CA, Lite-Fil A . LF, Clearril Photo Posterior CP, Prisms AP.H.. PA, 2100 : ZH) were unto The specimens of 12 m in diameter and 0.7 m in thickness were made, and an immersion in $37^{\circ}C$ water for 7 days and a thermal cycling of 1000 cycles at 15 second dwell time each in $5^{\circ}C$ and $55^{\circ}C$ baths were performed. Biaxial flexure test was conducted using the ball-on-three-ball method at the crosshead speed of 0.5mm/min. In order to investigate the deterioration of composite resins during the thermal cycling test, Weibull analysis for the biaxial flexure strengths was done. Fracture surfaces and the surfaces before and after the thermal cycling test were examined by SEM. The highest Weibull modulus value of 10.09 after thermal cycling tests which means the lowest strength variation, was observed in the CP group, and the lowest value of 4.47 was obsered in the LF Group. Biaxial flexure strengths and Knoop hardness numbers significantly decreased due to the thermal cycling ($\textit{p}$< 0.01), however, they recovered when specimens were drie4 The highest biaxial flexure strength of 125.65MPa was observed in the ZH group after the thermal cycling test, and the lowest value of 64.86MPa was observed in the CA group. Biaxial flexure strengths of ZH and CP groups were higher than those of PA, CF, and CA groups after thermal cycling test($\textit{p}$< 0.05). Knoop hardness numbers of CP group after the thermal cycling test was the highest(95.47 $\pm$ 7.35kg/$mm^2$) among the samples, while that of CA group was the lowest(30.73 $\pm$ 2.58kg/$mm^2$). Knoop hardness numbers showed the significant differences between the CP group and others after the thermal cycling test(($\textit{p}$< 0.05). Fracture surfaces showed that the composite resin failure developed along the matrix resin and the filler/resin interface region, and the cracks propagated in the conical shape from the maximum tensile stress zone.

Effect of thermal cycling frequency on the durability of Yb-Gd-Y-based thermal barrier coatings

Lyu, Guanlin,Choi, Baig-Gyu,Lu, Zhe,Park, Hyeon-Myeong,Jung, Yeon-Gil,Zhang, Jing Elsevier 2019 Surface & coatings technology Vol.364 No.-

<P><B>Abstract</B></P> <P>The effects of thermal cycling frequency and buffer layer on the crack generation and thermal fatigue behaviors of Yb–Gd–Y-stabilized zirconia (YGYZ)-based thermal barrier coatings (TBCs) were investigated through thermally graded mechanical fatigue (TGMF) test. TGMF tests with low- (period of 10 min) and high-frequency (period of 2 min) cycling were performed at 1100 °C with a 60 MPa tensile load. Different cycling frequencies in TGMF test generate two kinds of crack propagation modes. The sample with low-frequency cycling condition shows penetration cracks in the YGYZ top coat, and multiple narrow vertical cracks are generated in high-frequency cycling. To enhance the thermomechanical properties, different buffer layers were introduced into the TBC systems, which were deposited with the regular (RP) or high-purity 8 wt% yttria stabilized zirconia (HP-YSZ) feedstock. The purity of the feedstock powder used for preparing the buffer layer affected the fracture behavior, showing a better thermal durability for the TBCs with the HP-YSZ in both frequency test conditions. A finite element model is developed, which takes creep effect into account due to thermal cycling. The model shows the high stresses at the interfaces between different layers due to differential thermal expansion. The failure mechanisms of YGYZ-based TBCs in TGMF test are also proposed. The vertical cracks are preferentially created, and then the vertical and horizontal cracks will be propagated when the vertical cracks are impeded by pores and micro-cracks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Yb-Gd-Y-stabilized zirconia (YGYZ) based TBCs with buffer layer was well prepared. </LI> <LI> Thermal cycling frequency caused different crack growth behavior in TGMF test. </LI> <LI> HP-YSZ buffer layer showed a better thermal durability in low-frequency TGMF test. </LI> <LI> A finite element model showed the high stresses at the interfaces between different layers. </LI> <LI> The failure mechanisms of YGYZ-based TBCs in TGMF test were proposed. </LI> </UL> </P>

Change of phase transformation and bond strength of Y-TZP with various hydrofluoric acid etching

Yu Mi-Kyung,Oh Eun-Jin,Lim Myung-Jin,Lee Kwang-Won 대한치과보존학회 2021 Restorative Dentistry & Endodontics Vol.46 No.4

Objectives The purpose of this study was to quantify phase transformation after hydrofluoric acid (HF) etching at various concentrations on the surface of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), and to evaluate changes in bonding strength before and after thermal cycling. Materials and Methods A group whose Y-TZP surface was treated with tribochemical silica abrasion (TS) was used as the control. Y-TZP specimens from each experimental group were etched with 5%, 10%, 20%, and 40% HF solutions at room temperature for 10 minutes. First, to quantify the phase transformation, Y-TZP specimens (n = 5) treated with TS, 5%, 10%, 20% and 40% HF solutions were subjected to X-ray diffraction. Second, to evaluate the change in bond strength before and after thermal cycling, zirconia primer and MDP-containing resin cement were sequentially applied to the Y-TZP specimen. After 5,000 thermal cycles for half of the Y-TZP specimens, shear bond strength was measured for all experimental groups (n = 10). Results The monoclinic phase content in the 40% HF-treated group was higher than that of the 5%, 10%, and 20% HF-treated groups, but lower than that of TS-treated group (p < 0.05). The 40% HF-treated group showed significantly higher bonding strength than the TS, 5%, and 10% HF-treated groups, even after thermal cycling (p < 0.05). Conclusions Through this experiment, the group treated with SiO2 containing air-borne abrasion on the Y-TZP surface showed higher phase transformation and higher reduction in bonding strength after thermal cycling compared to the group treated with high concentration HF. Objectives The purpose of this study was to quantify phase transformation after hydrofluoric acid (HF) etching at various concentrations on the surface of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), and to evaluate changes in bonding strength before and after thermal cycling. Materials and Methods A group whose Y-TZP surface was treated with tribochemical silica abrasion (TS) was used as the control. Y-TZP specimens from each experimental group were etched with 5%, 10%, 20%, and 40% HF solutions at room temperature for 10 minutes. First, to quantify the phase transformation, Y-TZP specimens (n = 5) treated with TS, 5%, 10%, 20% and 40% HF solutions were subjected to X-ray diffraction. Second, to evaluate the change in bond strength before and after thermal cycling, zirconia primer and MDP-containing resin cement were sequentially applied to the Y-TZP specimen. After 5,000 thermal cycles for half of the Y-TZP specimens, shear bond strength was measured for all experimental groups (n = 10). Results The monoclinic phase content in the 40% HF-treated group was higher than that of the 5%, 10%, and 20% HF-treated groups, but lower than that of TS-treated group (p < 0.05). The 40% HF-treated group showed significantly higher bonding strength than the TS, 5%, and 10% HF-treated groups, even after thermal cycling (p < 0.05). Conclusions Through this experiment, the group treated with SiO2 containing air-borne abrasion on the Y-TZP surface showed higher phase transformation and higher reduction in bonding strength after thermal cycling compared to the group treated with high concentration HF.

Thermal cycling characteristics of a 3D-printed serpentine microchannel for DNA amplification by polymerase chain reaction

Park, Jaehyun,Park, Heesung Elsevier 2017 Sensors and actuators. A Physical Vol.268 No.-

<P><B>Abstract</B></P> <P>A polymerase chain reaction (PCR) device with integrated heaters for DNA amplification is proposed by using 3D-printing technology, which has the advantages of fast prototyping, design flexibility, and low cost. The thermal characteristics of the 3D-printed device for PCR are reported for the first time. The overall dimensions of the PCR device are 30mm×40mm where a serpentine microchannel is created to implement 27 thermal cycles. The serpentine microchannel of 260μm in depth, 450μm in width and 1470mm in length has been designed to inspect shape conformity and temperature variations. Thermal cycling experiments has showed that three temperature zones for denaturation (90–95°C), annealing (55–65°C) and extension (70–77°C) were successfully produced for DNA amplification. The thermal cycling efficiency ranges 67.4% to 47.8% when the flow rate is changed from 5μL/min to 10μL/min. The study demonstrates the feasibility of a low-cost 3D-printed PCR device that enables DNA amplification by thermal cycling. This paper concludes that 3D-printing technology can be applied for bio-microfluidic devices that require precise temperature control.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 3D-printed thermal cycling device is experimentally studied. </LI> <LI> The dimensions of the device are 3×4cm with 27 thermal cycles. </LI> <LI> Thermal cycling efficiency is evaluated by the produced temperature zones. </LI> <LI> 3D-printing technology is feasible to microscale thermal cycler. </LI> </UL> </P>

Thermal Cycling에 따른 자가중합 레진의 결합강도에 관한 연구

조혜원,하점임,Cho, Hye-Won,Ha, Jum-In 대한치과보철학회 1997 대한치과보철학회지 Vol.35 No.4

The purpose of this study was to evaluate the effects of two metal adhesive primers on the shear bond strengths of self-curing resin to Ni-Cr a]toy and the effects of 1000 thermal cycling on the durability of the bond. The two selected metal adhesive primers were Metal Primer II(G-C corp., Japan) and MR Bond(Tokuyama corp., Japan) and no treatment groups were used as control. All specimens were divided into two groups according to thermal cycling. In the group without thermal cycling, the specimens were stored in water for 24 hours. In the group with thermal cycling, the specimens were thermocycled 1000 times at temperature of $5^{\circ}C\;and\;55^{\circ}C$. Shear bond strengths were measured using the Universal testing machine(Zwick 145641, Germany) with a crosshead speed of 0.5 mm/min. The results were as follows: 1. MR Bond significantly improved the shear bond strength of resin to Ni-Cr alloy before and after thermal cycling. 2. There were no difference in the shear bond strength of resin to Ni-Cr alloy between Metal Primer II treated group and no treatment group. 3. Regardless of the type and the use of adhesive primers, there were tendency of decrease in shear bond strength with 1000 thermal cycling.

시효처리와 thermal cycling이 치관전장용 복합레진의 2축굽힘강도에 미치는 영향

정관호,하일수,송광엽,Jeong, Gwan-Ho,Ha, Il-Soo,Song, Kwang-Yeob 대한치과보철학회 1999 대한치과보철학회지 Vol.37 No.5

This study was performed to evaluate the effect of aging and thermal cycling on the biaxial flexure strength of low commercially available veneering resin composites for crown(Dentacolor : DC, Artglass : AG, Esternia : ET and Targis : TG). Disc specimens were fabricated in a teflon mold giving 12mm in diameter and 1mm in thickness. All samples were divided into 4 groups. Group 1 was dried in a dessicator at $25^{\circ}C$ for 30 days. Group 2 was immersed in distilled water at $37^{\circ}C$ for 30 days. Group 3 was immersed in distilled water at $65^{\circ}C$ for 30 days. Group 4 was subjected to 10,000 thermal cycles between $5^{\circ}C\;and\;55^{\circ}C$, and the immersion time in each bath was 15 seconds per cycle. Biaxial flexure test was conducted using the ball-on-three-ball method at the cross head speed of 0.5mm/min and fracture surfaces were observed with scanning electoron microscope. The results obtained were summarized as follows; 1. Weibull modulus values, except for the AG group, decreased after thermal cycling treatment. 2. Biaxial flexure strength values of aging group at $37^{\circ}C$ were the lowest in all sample groups. Except for the DC group, strength values were significantly decreased for the drying group. 3. After thermal cycling test, the highest value of biaxial flexure strength of 188.8 MPa was observed in the ET group and the lowest value of 73.2 MPa was observed in the DC group. The strength values showed the significant differences in each group (p<0.05). 4. Observation of surfaces after thermal cycling test revealed the ditching in the part of surrounding large fillers.

Thermo-mechanical Degradation of NiCr Thin Film Subjected to Thermal Cycling

( Eui Jong Lee ),( Tai Min Noh ),( Min Seok Jeon ),( Hyun Gyoo Shin ),( Hee Soo Lee ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.2

The thermo-mechanical degradation of NiCr films during thermal cycling was investigated in terms of microstructural and chemical changes to the surface. Thermal cycling was performed between room temperature and 200℃ in thermally evaporated NiCr films on an Mn-Ni-Co-O substrate. Isothermal exposures were also performed as a control experiment. The sheet resistance of the NiCr films increased linearly (from 35 to 52 Ω/sq.) with a temperature difference of the thermal cycling, whereas the films subjected to isothermal aging increased only slightly, from 35 to 38 Ω/sq. After 300 thermal cycles at ΔT=175℃, cracks formed and proliferated on the coating surface, and local delamination occurred at the interfaces. XPS results showed that the intensity of a metallic peak at 574.0 eV decreased and that of the Cr oxide peak at ~577 eV increased with an increase of the thermal cycles. Consequently, the degradation of the NiCr films by accelerated thermal cycling stress was attributed to a proliferation of lateral surface cracks from thermally induced tensile stress compounded by surface oxidation, causing an increase in sheet resistance.

316 스테인레스강의 열충격 특성

이상필(Sang-Pill Lee),김영만(Young-Man Kim),민병현(Byung-Hyun Min),김창호(Chang-Ho Kim),손인수(In-Soo Son),이진경(Jin-Kyung Lee) 한국해양공학회 2013 韓國海洋工學會誌 Vol.27 No.5

The present work dealt with the high temperature thermal shock properties of 316 stainless steels, in conjunction with a detailed analysis of their microstructures. In particular, the effects of the thermal shock temperature difference and thermal shock cycle number on the properties of 316 stainless steels were investigated. A thermal shock test for 316 stainless steel was carried out at thermal shock temperature differences from 300℃ to 1000℃. The cyclic thermal shock test for the 316 stainless steel was performed at a thermal shock temperature difference of 700℃ up to 100 cycles. The characterization of 316 stainless steels was evaluated using an optical microscope and a three point bending test. Both the microstructure and flexural strength of 316 stainless steels were affected by the high-temperature thermal shock. The flexural strength of 316 stainless steels gradually increased with an increase in the thermal shock temperature difference, accompanied by a growth in the grain size of the microstructure. However, a thermal shock temperature difference of 800℃ produced a decrease in the flexural strength of the 316 stainless steel because of damage to the material surface. The properties of 316 stainless steels greatly depended on the thermal shock cycle number. In other words, the flexural strength of 316 stainless steels decreased with an increase in the thermal shock cycle number, accompanied by a linear growth in the grain size of the microstructure. In particular, the 316 stainless steel had a flexural strength of about 500 MPa at 100 thermal-shock cycles, which corresponded to about 80% of the strength of the as-received materials.

Residual stress distributions and their influence on post-manufacturing deformation of injection-molded plastic parts

Kim, B.,Min, J. Elsevier 2017 Journal of materials processing technology Vol.245 No.-

<P>Post-manufacturing thermal exposure of injection-molded parts may result in unexpected permanent deformation. In this study, the mechanism of the post-manufacturing thermal deformation of injection-molded parts is investigated. A simple stress lattice part was used, and injection-molding experiments were carried out to characterize the deformation that occurred in post-manufacturing thermal cycling. The stress lattice part was chosen so that the thermal stress could be investigated with different cooling rates in the same part. The stress lattice parts were thermally cycled using a thermal chamber. A series of computer-aided engineering (CAE) analyses, including injection-molding analysis and finite element analysis (FEA), were performed to describe the deformation following the thermal cycle. The results of these analyses were in good agreement with the experimental results, and revealed that the residual stress formed during the injection molding process was the primary cause of the permanent deformation following the post-manufacturing thermal cycling. (C) 2017 Elsevier B.V. All rights reserved.</P>