• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.314-322
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• 2017

This study investigates changes in the mechanical behavior, such as changes in indentation load-displacement curve, wear resistance and contact fatigue resistance of thermal barrier coatings (TBCs) by thermal cycling test and thermal shock test. Relatively dense and porous TBCs on nickel-based bondcoat/superalloy are prepared; the highest temperature applied during thermal durability test is $1350^{\circ}C$. The results indicate that the porous TBCs have relatively longer lifetime during thermal cycling and thermal shock tests, while denser TBCs have relatively higher wear and contact fatigue resistance. The mechanical behavior is influenced by sintering of the TBCs by exposure to high temperature during tests.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.5
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• pp.443-449
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• 2007

The structural and thermal stability of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ electrode during cycling process was studied. The sample was prepared by simple combustion method. Although there were irreversible changes on the initial cycle, O3 stacking for $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ structure was retained during the first and subsequent cycling process. Impedance of the test cell was decreased after the first charge-discharge process, which would be of benefit to intercalation and deintercalation of lithium ion on subsequent cycling. As expected, cycling test for 75 times increased impedance of the cell a little, instead, thermal stability of $Li[Co_{0.1}Ni_{0.15}Li_{0.2}Mn_{0.55}]O_2$ was improved. Moreover, based on DSC analysis, the initial exothermic peak was shifted to high temperature range and the amount of heat was also decreased after cycling test, which displayed that thermal stability was not deteriorated during cycling.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.27-32
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• 2002

In this paper, global full 3D finite element analysis fatigue models are constructed for flip-chip BGA on board to predict the creep fatigue life of solder joints during the thermal cycling test. The fatigue model applied is based on Darveaux's empirical equation approach with non-linear viscoplastic analysis of solder joints. It was estimated by the creep life as the variations of the four kinds of thermal cycling test conditions, pad structure, composition and size of solder ball. The shortest fatigue life of results was obtained at the thermal cycling testing condition of -65℃ ∼ 150℃. It was increased about 3.5 times in comparison with that of 0℃ ∼ 100℃. As the change of pad structure at the same other conditions, the fatigue life of SMD structure increased about 5.7% as compared with NSMD structure. Consequently, it was confirmed that the fatigue life became short as the creep strain energy density increased in solder joint.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.288-292
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• 2009

This article shows various factors that influence the thermal-cycling reliability of semiconductor devices utilizing the lead-on-chip (LOC) die attach technique. This work details how the modification of LOC package design as well as the back-grinding and dicing process of semiconductor wafers affect passivation reliability. This work shows that the design of an adhesion tape rather than a plastic package body can play a more important role in determining the passivation reliability. This is due to the fact that the thermal-expansion coefficient of the tape is larger than that of the plastic package body. Present tests also indicate that the ceramic fillers embedded in the plastic package body for mechanical strengthening are not helpful for the improvement of the passivation reliability. Even though the fillers can reduce the thermal-expansion of the plastic package body, microscopic examinations show that they can cause direct damage to the passivation layer. Furthermore, experimental results also illustrate that sawing-induced chipping resulting from the separation of a semiconductor wafer into individual devices might develop into passivation cracks during thermal-cycling. Thus, the proper design of the adhesion tape and the prevention of the sawing-induced chipping should be considered to enhance the passivation reliability in the semiconductor devices using the LOC die attach technique.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.297-304
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• 2019

PURPOSE. This in vitro study investigated the repair bond strength of the zirconia ceramic after different aging conditions. MATERIALS AND METHODS. In order to imitate the failure modes of veneered zirconia restorations, veneer ceramic, zirconia, and veneer ceramic-zirconia specimens were prepared and were divided into 4 subgroups as: control ($37^{\circ}C$ distilled water for 24 hours ) and 3000, 6000, 12000 thermal cycling groups (n=15). Then, specimens were bonded to composite resin using a porcelain repair kit according to the manufacturer recommendation. The repair bond strength (RBS) test was performed using a universal testing machine (0.5 mm/min). Failure types were analyzed under a stereomicroscope. Two-way ANOVA and Bonferroni test were used for statistical analysis. RESULTS. The RBS values of zirconia specimens were statistically significant and higher than veneer ceramic and veneer ceramic-zirconia specimens in control, 3000 and 6000 thermal cycling groups (P<.05). When 12000 thermal cycles were applied, the highest value was found in zirconia specimens but there was no statistically significant difference between veneer ceramic and veneer ceramic-zirconia specimens (P>.05). Veneer ceramic specimens exhibited cohesive failure types, zirconia specimens exhibited adhesive failure types, and veneer ceramic-zirconia specimens exhibited predominately mixed failure types. CONCLUSION. Thermal cycling can adversely affect RBS of composite resin binded to level of fractured zirconia ceramics.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.415-419
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• 2004

Thermal barrier systems are susceptible to instability of the thermally grown oxide(TGO) at the interface between the bond coat(BC) and the thermal barrier coating(TBC). The instabilities have been linked to thermal cycling and initial geometrical imperfections, as well as to misfit strains due to oxide growth and expansion misfit. In this work, deformation of TGO near a surface groove due to thermal cycling has been observed at high temperatures, $1100^{circ}C$, $1150^{circ}C$, $1200^{circ}C$. The effect of peak temperature and the thickness of substrate are presented.

• Journal of the Korean Society of Safety
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• v.20 no.2 s.70
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• pp.1-5
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• 2005

An experimental study was conducted to develop an understanding of failure of ceramic coating when subjected to a thermal cycling. Number of cycles to failure were decreased as the coating thickness and the oxide of bond coat were increased. Using the finite element method, an analysis of stress distribution in ceramic coatings was performed. Radial compressive stress was increased in the top/bond coat interface with increasing coating thickness and oxide of bond coat.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.156-156
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• 2011

VPH (Volume Phase Hologram) grating is one of the transmission gratings and is known as its remarkable efficiency (>90%). It has two different densities of gelatins causing interference patterns. The VPH grating is favored in many astronomical instruments these days and also IGRINS, which is up coming near infrared high-resolution spectroscope expected to see the first light next year, uses the VPH grating as its cross-disperser. The infrared astronomical instruments operate at cryogenic temperature (~100K) in order to cut down thermal noise and the optical components of IGIRNS will be operated at 130K. The VPH grating is sandwiched in between fused silica or glass and glued together using optical adhesive. IGRINS is expected to go through 50 times of thermal cycling in 10 years including the performance test and this research is to check whether the physical characteristic such as the adhesion or dichromatic gelatin does not break and change from the several cryogenic thermal cycling. The two identical test gratings provided from Kaiser Optical System, Inc. are used in this test. One VPH grating is cooled down to 100K for 2 hours with maximum dT/dt = 5 and warmed up to the room temperature and another grating is kept stored in the room temperature and used as a control sample. In order to check the change, we inspected the grating with eyes and checked its efficiency and transmission at the room temperature every 10 cycling. From the 40 times of cryogenic temperature cool down cycling, the VPH grating showed no signs of change within the error compared to the control sample. We concluded the VPH grating is durable through several cryogenic thermal cycling.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.677-687
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• 1999

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 $37^{\circ}C$ distilled water for 1 hour. Group 2 was immersed in a $37^{\circ}C$ distilled water for 30 days. Group 3 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. 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.

• Journal of Korea Foundry Society
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• v.10 no.5
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• pp.399-407
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• 1990

The effect of thermal cycling and isothermal exposure on the high temperature microstructural stability of unidirectionally solidified $Al-CuAl_2$ eutectic composite has been studied. A coarsening procedures of lamellar eutectic structures were initiated at growth fault region because of diffusion through low angle boundary at this region. It was considered that thermally induced residual stresses produced by thermal cycling were high enough to increase the dislocation density in Al-rich matrix phase. However, it was also considered that dislocations generated by these high thermal stresses were annihilated at high temperature by stress relaxation. Consequently, the thermal cycling up to 1440 cycles between 20 and $520^{\circ}C$ did not affect the microstructural stability.