• Title/Summary/Keyword: Thermal Crack

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Development of SiC Composite Solder with Low CTE as Filling Material for Molten Metal TSV Filling (용융 금속 TSV 충전을 위한 저열팽창계수 SiC 복합 충전 솔더의 개발)

  • Ko, Young-Ki;Ko, Yong-Ho;Bang, Jung-Hwan;Lee, Chang-Woo
    • Journal of Welding and Joining
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    • v.32 no.3
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    • pp.68-73
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    • 2014
  • Among through silicon via (TSV) technologies, for replacing Cu filling method, the method of molten solder filling has been proposed to reduce filling cost and filling time. However, because Sn alloy which has a high coefficient of thermal expansion (CTE) than Cu, CTE mismatch between Si and molten solder induced higher thermal stress than Cu filling method. This thermal stress can deteriorate reliability of TSV by forming defects like void, crack and so on. Therefore, we fabricated SiC composite filling material which had a low CTE for reducing thermal stress in TSV. To add SiC nano particles to molten solder, ball-typed SiC clusters, which were formed with Sn powders and SiC nano particles by ball mill process, put into molten Sn and then, nano particle-dispersed SiC composite filling material was produced. In the case of 1 wt.% of SiC particle, the CTE showed a lowest value which was a $14.8ppm/^{\circ}C$ and this value was lower than CTE of Cu. Up to 1 wt.% of SiC particle, Young's modulus increased as wt.% of SiC particle increased. And also, we observed cross-sectioned TSV which was filled with 1 wt.% of SiC particle and we confirmed a possibility of SiC composite material as a TSV filling material.

Preparation and characterization of nanoporous monolith with high thermal insulation performance (나노 기공성 단열 실리카 모노리스 제조 및 특성 연구)

  • Choi, Hyun-Muk;Kim, Seong-Woo
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.1
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    • pp.83-91
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    • 2014
  • In this study, we synthesized two different silica monoliths by using sol-gel, solvent exchange, surface modification, ambient pressure drying processes, and surfactant-based templating technique followed by calcination process. All of the prepared two silica monoliths showed crack-free appearance with fairly good transparency, and furthermore were confirmed to have extremely high porosity, specific surface area, and mean pore size below 30 nm. The silica aerogel sample exhibited finer and more homogeneous nano-sized pore structure due to spring back effect caused by surface modification, which resulted in better thermal insulation performance. Based on measured thermal conductivities and theoretical relationship, multi-layered glass window system in which silica monolith prepared in this study was inserted as a middle layer was revealed to have superior thermal insulation performance compared to conventional air-inserted glass window system.

Effect of Heat Treatment on Interface Behavior in Ni-P/Cr Double Layer (열처리 시간에 따른 Ni-P/Cr 이중 도금 층의 계면 거동에 관한 연구)

  • Choi, Myung-Hee;Park, Young-Bae;Rhee, Byong-ho;Byon, Eungsun;Lee, Kyu Hwan
    • Journal of the Korean institute of surface engineering
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    • v.48 no.6
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    • pp.260-268
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    • 2015
  • The thermal barrier coating (TBC) for inner wall of liquid-fuel rocket combustor consists of NiCrAlY as bonding layer and $ZrO_2$ as a top layer. In most case, the plasma spray coating is used for TBC process and this process has inherent possibility of cracking due to large difference in thermal expansion coefficients among bonding layer, top layer and metal substrate. In this paper, we suggest crack-free TBC process by using a precise electrodeposition technique. Electrodeposited Ni-P/Cr double layer has similar thermal expansion coefficient to the Cu alloy substrate resulting in superior thermal barrier performance and high temperature oxidation resistance. We studied the effects of phosphorous concentrations (2.12 wt%, 6.97 wt%, and 10.53 wt%) on the annealing behavior ($750^{\circ}C$) of Ni-P samples and Cr double layered electrodeposits. Annealing temperature was simulated by combustion test condition. Also, we conducted SEM/EDS and XRD analysis for Ni-P/Cr samples. The results showed that the band layers between Ni-P and Cr are Ni and Cr, and has no formed with heat treatment. These band layers were solid solution of Cr and Ni which is formed by interdiffusion of both alloy elements. In addition, the P was not found in it. The thickness of band layer was increased with increasing annealing time. We expected that the band layer can improve the adhesion between Cr and Ni-P.

Thermal Shock Behavior of $Al_2O_3$-$ZrO_2$ Ceramics Prepared by a Precipitation Method (침전법으로 제조한 $Al_2O_3$-$ZrO_2$계 세라믹스의 열충격 거동)

  • 홍기곤;이홍림
    • Journal of the Korean Ceramic Society
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    • v.28 no.1
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    • pp.11-18
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    • 1991
  • A precipitation method, one of the most effective liquid phase reaction methods, was adopted in order to prepare high-tech Al2O3/ZrO2 composite ceramics, and the effects of stress-induced phase transformation of ZrO2 on thermal shock behavior of Al2O3-ZrO2 ceramics were investigated. Al2(SO4)3.18H2O, ZrOCl2.8H2O and YCl3.6H2O were used as starting materials and NH4OH as a precipitation agent. Metal hydroxides were obtained by single precipitation(process A) and co-precipitation(process B) method at the condition of pH=7, and the composition of Al2O3-ZrO2 composites was fixed as Al2O3-15v/o ZrO2(+3m/o Y2O3). Critical temperature difference showing rapid strength degradation by thermal shock showed higher value in Al2O3/ZrO2 composites(process A : 20$0^{\circ}C$, process B : 215$^{\circ}C$) than in Al2O3(175$^{\circ}C$). The improvement of thermal shock property for Al2O3/ZrO2 composites was mainly due to the increase of strength at room temperature by adding ZrO2. The strength degradation was more severe for the sample with higher strength at room temperature. Crack initiation energies by thermal shock showed higher values in Al2O3/ZrO2 composites than in Al2O3 ceramics due to increase of fracture toughness by ZrO2.

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Evaluation of Defects of Thermal Barrier Coatings by Thermal Shock Test Using Eddy Current Testing (열차폐 코팅층의 고온 열충격 시험후 ECT를 이용한 결함 평가)

  • Heo, Tae-Hoon;Cho, Youn-Ho;Lee, Joon-Hyun;Oh, Jeong-Seok;Lee, Koo-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.5
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    • pp.450-457
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    • 2009
  • Periodical thermal shock can introduce defects in thermal barrier coating made by layers of CoNiCrAlY bond coating(BC) and $ZrO_2-8wt%Y_2O_3$ ceramic top coating(TC) on Inconel-738 substrate using plasma spraying. Thermal shock test is performed by severe condition that is to heat until $1000^{\circ}C$ and cool until $20^{\circ}C$. As the number of cycle is increased, the fatigue by thermal shock is also increased. After test, the micro-structures and mechanical characteristics of thermal barrier coating were investigated by SEM, XRD. The TGO layer of $Al_2O_3$ is formed between BC and TC by periodical thermal shock test, and its change in thickness is inspected by eddy current test(ECT). By ECT test, it is shown that TGO and micro-crack can be detected and it is possible to predict the life of thermal barrier coating.

Failure Study for Tribological Characteristics Including with Pad, Lining and Hub disk in Vehicle Brake System (자동차 제동시스템의 패드, 라이닝, 허브디스크에 관련된 트라이볼로지적인 특성에 관한 고장사례연구)

  • Lee, Il-Kwon;Kim, Chung-Kyun;Cho, Seung-Hyun
    • Tribology and Lubricants
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    • v.27 no.5
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    • pp.269-274
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    • 2011
  • The purpose of this paper is to study and analyze the improvement method for the failure examples including the vehicle brake system in actual field. It was verified that the indicator plate of pad wear scratched the brake disk because of wearing after displacement of non- identification parts pad. The caliper of other vehicle was installed with brake system verified the phenomenon produced groove in center point because of one side wear when the pad was not fully contacted with the rub disk by other action surface pressure and pad action condition. It verified that the crack phenomenon fatigue was produced by brake thermal deformation because of decreasing the thickness by grinding to modify the non-uniformed wear of brake disk. It verified that the friction sound was produced by the friction phenomenon because of non-uniformed contact of lining and an alien substance with inner of the drum and lining braking by crack phenomenon with brake drum surface.

Failure distribution based crack propagation in solid propellant container: Comparison with experiment (고체추진기기의 고장분포 기반의 균열전파 모델: 실험과의 비교)

  • Yoh Jai-ick
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • v.y2005m4
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    • pp.47-52
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    • 2005
  • We present a simple idea to simulate dynamic fracture and fragmentation of a propulsion system exposed to an extreme condition, such as a fire. The system consists of energetic materials confined in a steel cylinder. The strain failure model of the confinement is a modified Johnson-Cook model with a statistical failure distribution. By using the size distribution data of the fragments from the thermal explosion tests, the failure strain distribution can be empirically obtained and then entered into the model. The simulated fracture and fragment sizes are compared with the experimental records.

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Effects of the Czochralski growth parameters on the growth of $LiNbO_3$ crystals ($LiNbO_3$단결정에 미치는 CZ 성장조건의 영향)

  • Lee, Sang-Hak;Yun, Ui-Park
    • Korean Journal of Materials Research
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    • v.2 no.1
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    • pp.52-57
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    • 1992
  • The macro defects of $LiNbO_3$ crystals grown by the Czochralski method were strongly influenced by the single crystal growth parameters such as growth rate, thermal gradient and crystal rotation rate. The optimum growth conditions of a $LiNbO_3$ single crystal with 1" in diameter were $70~100^{circ}C/cm$ temperature gradient, 5~10 mm/hr growth rate and 40 rpm crystal rotation rate. In these conditions, we could grow crystals which had no cellular structure with easy diameter control, and any crack was not formed after the crystal was cooled.oled.

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Effect of Sintering Temperature on Microstructure and Mechanical Properties of Cu Particles Dispersed Al2O3 Nanocomposites (Cu 입자분산 Al2O3 나노복합재료의 미세조직과 기계적 특성에 미치는 소결온도의 영향)

  • Jeong, Young-Keun;Oh, Sung-Tag;Choa, Yong-Ho
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.366-370
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    • 2006
  • The microstructure and mechanical properties of hot-pressed $Al_2O_3/Cu$ composites with a different sintering temperature have been studied. The size of matrix grain and Cu dispersion in composites increased with increase in sintering temperature. Fracture toughness of the composite sintered at high temperature exhibited an enhanced value. The toughness increase was explained by the thermal residual stress, crack bridging and crack branching by the formation of microcrack. The nanocomposite, hot-pressed at $1450^{\circ}C$, showed the maximum fracture strength of 707 MPa. The strengthening was mainly attributed to the refinement of matrix grains and the increased toughness.

Microcapsules Containing Self-Healing Agent with Red Dye (빨간 색소를 함유한 자가치료제 마이크로캡슐)

  • Guang, Yang;Lee, Jong Keun
    • Polymer(Korea)
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    • v.37 no.3
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    • pp.356-361
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    • 2013
  • Microcapsules of two different self-healing agents, 5-ethylidene-2-norbornene (ENB) and ENB with a crosslinker, surrounded by a melamine-urea-formaldehyde shell were manufactured. In this work, a red dye was incorporated into the self-healing agents as a tracer for better visual observations. It revealed that the incorporation of a red dye into self-healing agents did not disturb the formation of microcapsules from the examination of thermal resistance, particle size/size distribution and morphology of the resulting microcapsules. Releasing of self-healing liquid into the induced crack from ruptured microcapsules and filling between crack planes were observed using an optical microscope. Also observed was the reaction of filled healing agent with embedded Grubbs' catalyst in an epoxy coating layer.