• Title/Summary/Keyword: Reaction layer

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Epitaxial Growth of Polyurea Film by Molecular Layer Deposition

  • Choe, Seong-Eun;Gang, Eun-Ji;Lee, Jin-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.264.2-264.2
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    • 2013
  • Molecular layer deposition (MLD) is sequential, self-limiting surface reaction to form conformal and ultrathin polymer film. This technique generally uses bifunctional precursors for stepwise sequential surface reaction and entirely organic polymer films. Also, in comparison with solution-based technique, because MLD is vapor-phase deposition based on ALD, it allows epitaxial growth of molecular layer on substrate and is especially good for surface reaction or coating of nanostructure such as nanopore, nanochannel, nanwire array and so on. In this study, polyurea film that consisted of phenylenediisocyanate and phenylenediamine was formed by MLD technique. In situ Fourier Transform Infrared (FTIR) measurement on high surface area SiO2 substrate was used to monitor the growth of polyurethane and polyurea film. Also, to investigate orientation of chemical bonding formed polymer film, plan-polarized grazing angle FTIR spectroscopy was used and it showed epitaxial growth and uniform orientation of chemical bones of polyurea films.

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Fabrication of Porous Reaction Bonded Silicon Carbide with Multi-Layered Pore Structures (다층 기공구조를 갖는 다공성 반응소결 탄화규소 다공체 제조)

  • Cho, Gyoung-Sun;Kim, Gyu-Mi;Park, Sang-Whan
    • Journal of the Korean Ceramic Society
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    • v.46 no.5
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    • pp.534-539
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    • 2009
  • Reaction Bonded Silicon Carbide(RBSC) has been used for engineering ceramics due to low-temperature fabrication and near-net shape products with excellent structural properties such as thermal shock resistance, corrosion resistance and mechanical strength. Recently, attempts have been made to develop hot gas filter with gradient pore structure by RBSC to overcome weakness of commercial clay-bonded SiC filter such as low fracture toughness and low reliability. In this study a fabrication process of porous RBSC with multi-layer pore structure with gradient pore size was developed. The support layer of the RBSC with multi-layer pore structure was fabricated by conventional Si infiltration process. The intermediate and filter layers consisted of phenolic resin and fine SiC powder were prepared by dip-coating of the support RBSC in slurry of SiC and phenol resin. The temperature of $1550^{\circ}C$ to make Si left in RBSC support layer infiltrate into dip-coated layer to produce SiC by reacting with pyro-carbon from phenol resin.

A Study on Bonding Strength and Interfacial Structure of Copper-Stainless Steel Brazed Joint(ll) (동-스테인리스 강 브레이징 접합부의 계면조직과 접합강도에 관한 연구(ll))

  • Lee, U-Cheon;Gang, Chun-Sik;Jeong, Jae-Pil;Lee, Bo-Yeong
    • Korean Journal of Materials Research
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    • v.3 no.6
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    • pp.668-677
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    • 1993
  • The microstructural and shear tests of STS304/, STS430/ and low-C steel/Cu joints brazed using Cu-P, Cu-P-Sn(four type) and Cu-P-Sn-Ag(three type) filler metals at 1003 and 1033K for 1.2ks in Ar atomsphere were performed. Interfacial microstructures were divided into three type ; first, reaction layer contained cracks second, dispersed layer without cracks third, dispersed layer and reaction layer contained cracks. The joints composed only of dispersed layer without cracks have the high shear strength of above 40-60 MPa and result in failure in copper base metal. Low shear strength and joint failure result from the formation of reaction layer which induced cracks. The reaction layer is a Fe-P compound. This tendency of microstructure and shear strength depends on the existence and/or nonexistence of Sn in filler metals as well as Ni (and Cr) in base metals.

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Effect of Heat Treatment on the Deformation and Fracture Behaviors of 3-ply Cu/Al/Cu Clad Metal (3층 Cu/Al/Cu 클래드재의 열처리온도에 따른 변형 및 파단거동)

  • Kim, In-Kyu;Ha, Jongsu;Hong, Sun Ig
    • Korean Journal of Metals and Materials
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    • v.50 no.12
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    • pp.939-948
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    • 2012
  • A 3-ply clad metal consisting of aluminum and copper was fabricated by roll bonding process and the microstructures and mechanical properties of the roll-bonded and post-roll-bonding heat treated Cu/Al/Cu clad metal were investigated. A brittle interfacial reaction layer formed at the Cu/Al interfaces at and above $400^{\circ}C$. The thickness of the reaction layer increased from $12{\mu}m$ at $400^{\circ}C$ to $28{\mu}m$ at $500^{\circ}C$. The stress-strain curves demonstrated that the strength decreased and the ductility increased with heat treatment up to $400^{\circ}C$. The clad metal heat treated at $300^{\circ}C$ with no indication of a reaction layer exhibited an excellent combination of the strength and ductility and no delamination of layers up to final fracture in the tensile testing. Above $400^{\circ}C$, the ductility decreased rasxpidly with little change of strength, reflecting the brittle nature of the intermetallic interlayers. In Cu/Al/Cu clad heat treated above $400^{\circ}C$, periodic parallel cracks perpendicular to the stress axis were observed at the interfacial reaction layer. In-situ optical microscopic observation revealed that cracks were formed in the Cu layer due to the strain concentration in the vicinity of horizontal cracks in the intermetallic layer, promoting the premature fracture of Cu layer. Vertical cracks parallel to the stress axis were also formed at 15% strain at $500^{\circ}C$, leading to the delamination of the Cu and Al layers.

Preparation of Hexagonal Boron Nitride from Boron Oxide and Sodium Amide (산화붕소의 소듐아미드로부터 육방정 질화붕소의 합성)

  • 손영국;장윤식;오기동
    • Journal of the Korean Ceramic Society
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    • v.27 no.7
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    • pp.869-876
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    • 1990
  • Hexagonal boron nitride was synthesized from boron oxide and sodium amide in ammonia gas stream. The reaction mechanisms and characteristics of as synthesized boron nitride was investigated by means of TG, DTA, IR, XRD, SEM and PSA. The results are ; 1) hexagonal boron nitride was synthesized from reactions at temperatures above 40$0^{\circ}C$ 2) Sodium metaborate was present as by-product after reaction so that the reaction mechanism is reduced as follows : 2B2O3+3NaNH2longrightarrowBN+3NaBO2+2NH3. 3) boron nitride obtained at the reaction temperature below 40$0^{\circ}C$ is found to have random layer strudcture but the structure transits to ordered layer structure rapidly with increasing reaction temperature, showing separation of (101) differaction line from (10)band in XRD pattern of the reaction product at 50$0^{\circ}C$.

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Effect of Reaction Temperature on Properties of CdS Thin Films Prepared by Chemical Bath Deposition (화학적으로 증착된 CdS 박막의 반응온도에 따른 물성)

  • Song, Woo-Chang
    • Journal of the Korean institute of surface engineering
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    • v.38 no.3
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    • pp.112-117
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    • 2005
  • In this paper, CdS thin films, which were widely used as a window layer of the CdS/CdTe and the $CdS/CuInSe_2$heterojunction solar cell, were grown by chemical bath deposition, and the structural, optical and electrical properties of the films on reaction temperatures were investigated. Cadmium acetate and thiourea were used as cadmium and sulfur source, respectively. And Ammonium acetate was used as the buffer solution. As the reaction temperatures were increased, the deposition rate of CdS fllms prepared by CBD was increased and the grain size was large due to increasing reaction rate in solution, also optical transmittance of the films in visible lights was increased on rising reaction temperatures.

The Pullout Behavior of a Large-diameter Batter ]Reaction Piles During Static Pile Load Test for a Large Diameter Socketed Pipe Pile (대구경 말뚝의 정재하시험시 대구경 경사반력말뚝의 인발거동)

  • 김상옥;성인출;박성철;정창규;최용규
    • Journal of the Korean Geotechnical Society
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    • v.18 no.1
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    • pp.5-16
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    • 2002
  • The pullout behavior of large-diameter steel pipe piles(diameter = 2,500mm, length = 38~40m), which were designed as compression piles but used as reaction piles during a static compression load test on a pile(diameter = 1,000m, length = 40m), was investigated. The steel pipe piles were driven by 20m into a marine deposit and weathered soil layer and then socketed by 10m into underlying weathered and soft rock layers. The sockets and pipe were filled with reinforced concrete. The steel pipe and concrete in the steel pipe zone and concrete and rebars in the socketed zone were fully instrumented to measure strains in each zone. The pullout deformations of the reaction pile heads were measured by LVDTs. Over the course of the study, a maximum uplift deformation of 7mm was measured in the heads of reaction piles when loaded to 10MN, and 1mm of residual uplift deflection was measured. In the reaction piles, about 83% and about 12% of the applied pullout loads were transferred in the weathered rock layer and in the soft rock layer, respectively. Also, at an uplift force of 10MN, shear stresses due to the uplift in the weathered rock layer md soft rock layer were developed as much as 125.3kPa and 61.8kPa, respectively. Thus, the weathered rock layer should be utilized as resisting layer in which frictional farce could be mobilized greatly.

Brazing of Aluminium Nitride(AlN) to Copper with Ag-based Active Filler Metals (은(Ag)계 활성금속을 사용한 질화 알미늄(AlN)과 Cu의 브레이징)

  • Huh, D.;Kim, D.H.;Chun, B.S.
    • Journal of Welding and Joining
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    • v.13 no.3
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    • pp.134-146
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    • 1995
  • Aluminium nitride(AlN) is currently under investigation as potential candidate for replacing alumium oxide(Al$_{2}$ $O_{3}$) as a substrate material for for electronic circuit packaging. Brazing of aluminium nitride(AlN) to Cu with Ag base active alloy containing Ti has been investigated in vacuum. Binary Ag$_{98}$ $Ti_{2}$(AT) and ternary At-1wt.%Al(ATA), AT-1wt.%Ni(ATN), AT-1wt.% Mn(ATM) alloys showed good wettability to AlN and led to the development of strong bond between brate alloy and AlN ceramic. The reaction between AlN and the melted brazing alloys resulted in the formation of continuous TiN layers at the AlN side iterface. This reaction layer was found to increase by increase by increasing brazing time and temperature for all filler metals. The bond strength, measured by 4-point bend test, was increased with bonding temperature and showed maximum value and then decreased with temperature. It might be concluded that optimum thickness of the reaction layer was existed for maximum bond strength. The joint brazed at 900.deg.C for 1800sec using binary AT alloy fractured at the maximum load of 35kgf which is the highest value measured in this work. The failure of this joint was initiated at the interface between AlN and TiN layer and then proceeded alternately through the interior of the reaction layer and AlN ceramic itself.

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Estimation of Tribological Properties on Surface Modified SiC by Chlorine Gas Reaction at Various Temperatures (다양한 온도에서 염소가스 반응에 의해 표면 개질된 SiC의 트라이볼로지 특성평가)

  • Bae, Heung-Taek;Jeong, Ji-Hoon;Choi, Hyun-Ju;Lim, Dae-Soon
    • Journal of the Korean Ceramic Society
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    • v.46 no.5
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    • pp.515-519
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    • 2009
  • Carbon layers were fabricated on silicon carbide by chlorination reaction at temperatures between $1000^{\circ}C$ and $1500^{\circ}C$ with $Cl_2/H_2$ gas mixtures. The effect of reaction temperature on the micro-structures and tribological behavior of SiC derived carbon layer was investigated. Tribological tests were carried out ball-on-disk type wear tester. Carbon layers were characterized by X-ray diffractometer, Raman spectroscopy and surface profilometer. Both friction coefficients and wear rates were maintained low values at reaction temperature up to $1300^{\circ}C$ but increased suddenly above this temperature. Variation of surface roughness as a function of reaction temperature was dominant factor affecting tribological transition behavior of carbon layer derived from silicon carbide at high temperature.

Interfacial Structure of Inconel/$Si_3N_4$ Joint Using Ag-Cu-Ti Brazing Metal (Ag-Cu-Ti Brazing 금속을 이용한 Inconel/$Si_3N_4$ 접합의 계면구조)

  • 정창주;장복기;문종하;강경인
    • Journal of the Korean Ceramic Society
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    • v.33 no.12
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    • pp.1421-1425
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    • 1996
  • Sintered Si3N4 and Inconel composed of Ni(58-63%) Cr(21-25%) Al(1-17%) Mn(<1%) fe(balance) were pressurelessly joined by using Ag-Cu-Ti brazing filler metal at 950℃ and 1200℃ under N2 gas atmosphere of 1atm and their interfacial structures were investigated. In case that the reaction temperature was low as 950℃ its interfacial structure was "Inconel metal/Ti-rich phase layer/brazing filler metal layer/Si3N4 " Ti used as reactive metal existed in between inconel steel and brazing metal and moved to the interface of between brazing filler metal nd Si3N4 according as reaction temperature increased up to 1200℃. The interfacial structure of inconel steel-Si3N4 reacted at 1200℃ was ' inconel metal/Ni-rich phase layer containing of Fe. Cr and Si/Cu-rich phase layer containing of Mn and Si/Si3N4 " Cr Mn, Ni and Fe diffused to the interface of between brazing filler metal and Si3N4 and reacted with Si3N4 The most reactive components of ingredients of inconel metal were Cr and Mn. On the other hand Ti added as reactive components to Ag-Cu eutectic segregated into Ni-rich phase layer,.

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