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방열 모듈 적용을 위한 Cu/Sn-3.0Ag-0.5Cu/Al 접합부의 계면반응 및 접합강도에 미치는 후속 열처리 영향 분석
정동익,김가희,김도헌,오민철,김건홍,박영배 대한금속·재료학회 2024 대한금속·재료학회지 Vol.62 No.4
The effects of post-annealing times at 150°C on the bonding strength and interfacial characteristicsof Cu/Sn-3.0Ag-0.5Cu (SAC305)/Al were systematically evaluated. In the as-bonded sample, Cu6Sn5intermetallic compound (IMC) was formed at the upper Cu/SAC305 interface, while Ag3Al IMC was formedat the lower SAC305/Al interface, and a black layer of Al2Cu IMC was formed at a distance of about 20 μmfrom the Al interface. The Al atoms from the Al pad diffused towards the SAC305 solder during the bondingprocess and reacted with Cu to form the Al2Cu IMC. After post-annealing for 500 h at 150°C, the growth ofCu-Sn and Al2Cu IMCs followed a linear relationship with the square root of the annealing time, which couldbe understood by a diffusion-dominant mechanism. To measure the bonding strength, the lap shear test wasevaluated on the Cu/SAC305/Al structure with time during post-annealing at 150°C. Initial bonding strengthof around 118.80 MPa decreased to 92.4MPa after post-annealing for 200h, and then remained constant until500 h. And the fracture locus was the mixed mode of SAC305/Al2Cu interface and cohesive inside SAC305solder. Also, when the post-annealing time was increased from 150 h to 200 h, the fracture toughnessdecreased sharply from 438 J/m3 to 100 J/m3. This decrease seems to be closely related to an increase in theSAC305/Al2Cu interface fracture mode. This is believed to be due to the increase in the SAC305/Al2Cuinterface fracture mode due to the growth of the Al2Cu layer thickness.
초기분말의 결정상이 $Al_2O_3$를 소결 조제로한 고온가압 SiC 세라믹스의 기계적 특성에 미치는 영향
정동익,강을손,최원봉,백용기 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.3
Densification behavior, microstructural evolution, and mechanical properties of hot-pressed specimens using $\beta$-SiC and $\alpha$-SiC powder with Al2O3 additive were studied. Beta-SiC powder was fully densified as 205$0^{\circ}C$, but $\alpha$-SiC powder was at 210$0^{\circ}C$. The maximum flexural strength and the fracture toughness of the specimen hot-pressed using $\beta$-SiC powder were 681 MPa and 6.7 MPa{{{{ SQRT {m } }}, and thosevalues of specimen hot-pressed using $\alpha$-SiC powder were 452 MPa and 4.7 MPa{{{{ SQRT {m } }}, respectively. The strength superiority of specimen hot-pressed using $\beta$-SiC powder was due to the finer grain size, and higher density. The higher toughness of specimen hot-pressed using $\beta$-SiC powder than $\alpha$-SiC powder than $\alpha$-SiC powder was due to the crack deflection mechanism arised from the difference of thermal expansion coefficient between $\alpha$ and $\beta$-SiC phases which were co-existed in the sintered body.
백용기,강을손,정동익,최원봉 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.4
Two kinds of alumina specimens with different grain size (1 and 51 $\mu\textrm{m}$) but same density were prepared by hot-pressing. Fracture strength and fracture toughness of these specimens at low strain rate, sonic velocity, and elastic property were evaluated. Ballistic performance against Cal. 50 AP projectile was characterized by thick-backing method by using A16061-T6 reference block. Mechanical properties measured at low strain rate showed that the specimen with samll grain (SG) were better than specimen with large grain (LG). Fracture strength and fracture toughness of LG specimen were 131 MPa and 3.01 MPa{{{{ SQRT { m} }}, but those of SG specimen were 349 and 4.23, respectively. Sonic velocity and elastic properties of these specimen were similar, but bulk velocity and bulk modulus were different at amount of 4 and 9%. The tendency of ballistic performance was not consistent with the mechnaical properties at low strain rate. The ballistic performance based on quantitative efficiency revealed that the LG specimen (5.13) was ballistically better than the SG specimen (4.00) in spite of their lower mechanical properties.
Mo첨가가 $Al_2O_3$ 세라믹스의 미세구조 및 기계적 성질에 미치는 영향
박정현,문성환,백승수,정동익 한국세라믹학회 1988 한국세라믹학회지 Vol.25 No.3
Mo 입자의 첨가가 Al_2O_3$ 세라믹스의 미세구조와 기계적 성질에 미치는 영향을 알아보기 위하여 평균입경이 2-micron인 Mo와 6-micron인 Mo를 Al_2O_3$에 각 분산시켜 1$600^{\circ}C$, $H_2$ 분위기에서 5시간 소결하였다. Mo는 Al_2O_3$의 입자성장을 억제시켰으며 Mo의 입자가 작을 때 그 효과는 크게 나타났다. 2-micron Mo를 분산한 경우 꺽임강도와 파괴인성은 크게 증가하여하였으며, 6-micron Mo를 분산한 경우 강도는 증가하지 않았으나 파괴인성은 다소 증가하였다. Al_2O_3$-Mo계의 인성증진기구는 균열편향에 의한 파단면의 증가와 미세균열에 의한 균열전파에너지의 분산에 의한 것으로 보인다. To investigate the effects of Mo addition on the microstructures and mechanical properties of Al_2O_3$ ceramics, two kinds of Mo particles with average sizes of 2-${\mu}{\textrm}{m}$ and 6-${\mu}{\textrm}{m}$ were used as additives. It was shown that Mo particles inhibited the grain growth of Al_2O_3$, and the smaller Mo particles were more effective. In case of 2-${\mu}{\textrm}{m}$ Mo dispersion, the bending strength and the fracture toughness were increased. Dispersion of 6-${\mu}{\textrm}{m}$ MO did not increase the strength but improved the fracture toughness a little. The toughening mechanisms of Al_2O_3$-Mo composites are thought to be the crack deflection and microcracking mechanisms.
김희주,박의석,임병건,이동규,정동익 대한마취통증의학회 2016 Korean Journal of Anesthesiology Vol.69 No.4
Pneumocephalus is common after brain surgeries, but usually is not substantial enough to cause serious complications. We recently encountered a case of post-operative tachypnea after an endoscopic 3rd ventriculostomy. At first, we thought that the hyperventilation was the result of residual paralysis after emergence from anesthesia, but during further evaluation we found a massive pneumocephalus. In such unusual post-operative situations, physicians should consider surgeryrelated complications as the possible cause as well, along with the anesthetic factors.
Preparation and Thermoelectric Properties of Bi2Te2.7Se0.3 Nanocomposites
김일호,최순목,서원선,정동익 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.9
Cu- or Ag-dispersed Bi<SUB>2</SUB>Te<SUB>2.7</SUB>Se<SUB>0.3</SUB> nanocomposites were prepared by metal acetate decomposition and hot pressing. Cu or Ag nanoparticles were well-dispersed in the Bi<SUB>2</SUB>Te<SUB>2.7</SUB>Se<SUB>0.3</SUB> matrix, and thereby the power factor was greatly increased due to increase in the effective mass of a carrier. However, Cu or Ag dispersion did not affect the carrier concentration and could not reduce the lattice thermal conductivity because Cu or Ag nanoparticles did not act as phonon scattering centers effectively. Thermoelectric figure of merit was enhanced remarkably over wide temperature range of 323-523 K due to high power factor. Cu dispersion was much more effective to enhance the thermoelectric performance compared to Ag dispersion.
Synthesis and thermoelectric properties of Cu-dispersed Bi2Te2.7Se0.3
김일호,최순목,서원선,정동익,강형 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2
Cu-dispersed Bi2Te2.7Se0.3 nanocomposites were prepared by Cu(OAc)2 acetate decomposition and their thermoelectric properties were evaluated. The electrical conductivity did not change significantly by the Cu nanoparticle dispersion because the doping effect by Cu nanoparticles did not occur effectively to increase the carrier concentration and Cu nanoparticles were too small to introduce charge carrier scattering. All specimens had a negative Seebeck coefficient, which confirmed that the electrical charge was transported mainly by electrons. The absolute Seebeck coefficient was remarkably increased by the Cu dispersion and slightly reduced with an increase in the temperature. The power factor values for Cu-dispersed Bi2Te2.7Se0.3were maintained higher in the whole temperature range, and the maximum power factor at 323 K reached around two times higher than that of Bi2Te2.7Se0.3. The thermal conductivity of Cu-dispersed Bi2Te2.7Se0.3 was slightly increased with an increase in the temperature because of the electronic contribution, and the Cu dispersion could not reduce it. The thermoelectric figure of merit was enhanced remarkably over a wide temperature range of 323~523 K due to the high power factor and the maintenance of a low thermal conductivity.
전기선폭발법으로 제조한 나노 W(텅스텐) 분말의 환원처리 및 방전플라즈마소결에 의한 조밀화
김지순,김철희,박은주,권영순,김진천,이성호,정동익,Kim Ji-Soon,Kim Cheol-Hee,Park Eun-Ju,Kwon Young-Soon,Kim Jin-Chun,Lee Sung-Ho,Jung Dong-Ik 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.4
[ ${\beta}-W(W_3O)$ ] oxide layer on the surface of each W(tungsten) nanopowder produced by the electric explosion of wire(EEW) process were formed during the 1vol.% air passivation process. The oxide layer hindered sintering densification of compacts during SPS process. The oxide phase was reduced to the pure W phase during SPS. The W nanopowder's compacts treated by the hydrogen reduction showed high sintered density of 94.5%. after SPS process at $1900^{\circ}C$.