단일 롤 방법으로 제작한 3원계 Al-Cr-Si 급냉리본의 구조 및 열 특성

한창석,김기웅,김우석 한국재료학회 2021 한국재료학회지 Vol.31 No.5

Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al74Cr20Si6 composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a twophase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al74Cr20Si6, Al77Cr13Si10 and Al90Cr6Si4 compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al90Cr6Si4 composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al90Cr6Si4, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al90Cr6Si4 composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

Al-Si 도금된 보론강과 Zn 도금된 DP강 TWB 레이저 용접부내의 Al-편석부 미세조직에 미치는 핫스탬핑 열처리의 영향

정병훈 ( Byung Hun Jung ),공종판 ( Jong Pan Kong ),강정윤 ( Chung Yun Kang ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.6

Al-Si coated boron steel and Zn coated DP steel plates were laser-welded to manufacture a Tailor Welded Blank (TWB) for a car body frame. Hot-stamping heat treatment (900℃, 5 min) was applied to the TWB weld, and the microstructural change and transformation mechanism were investigated in the Al-rich area near the bond line of the Al-Si coated steel side. There was Al-rich area with a single phase, Fe3(Al,Si), which was transformed to α-Fe (Ferrite) after the heat treatment. It could be explained that the Fe3(Al,Si) phase was transformed to α-Fe during heat treatment at 900℃ for 5 min and the resultant α-Fe phase was not transformed by rapid cooling. Before the heat treatment, the microstructures around the Fe3(Al,Si) phase consisted of martensite, bainite and α-Fe while they were transformed to martensite and δ-Fe after the heat treatment. Due to the heat treatment, Al was diffused to the Fe3(Al,Si) and this resulted in an increase of Al content to 0.7 wt% around the Al-rich area. If the weld was held at 900℃ for 5 min it was transformed to a mixture of austenite (γ) and δ-Fe, and only γ was transformed to the martensite by water cooling while the δ-Fe was remained unchanged.

Synthesis of high-energy-density fuel over mesoporous aluminosilicate catalysts

Kim, Jongjin,Shim, Beomseok,Lee, Gayoung,Han, Jeongsik,Kim, Ji Man,Jeon, Jong-Ki Elsevier 2018 CATALYSIS TODAY - Vol.303 No.-

<P><B>Abstract</B></P> <P>This study focused on the effect of the incorporation of aluminum on the catalytic performance of KIT-6 in the norbornadiene cyclodimerization reaction. An Al-KIT-6 material synthesized through Al grafting over siliceous KIT-6 was shown to have a well-ordered mesoporous structure and a large pore size. The grafting of Al onto siliceous KIT-6 generated weak acid sites consisting of Lewis acid sites and Brönsted acid sites. Cyclodimerization of norbornadiene was carried over Al-KIT-6 catalysts in a batch reactor in order to compare their activity with that of the Al-MCM-41 catalyst. The activity of norbornadiene cyclodimerization over the Al-KIT-6 catalyst was higher than that over the Al-MCM-41 catalyst, which could be attributed to the larger pore diameters of the Al-KIT-6 catalyst. The acidity and the catalytic activity of the Al-KIT-6 catalyst as used here could easily be recovered through filtering and calcination in an air atmosphere at 550°C.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Al-KIT-6 material was synthesized through Al grafting over siliceous KIT-6. </LI> <LI> The grafting of Al onto siliceous KIT-6 generated weak acid sites. </LI> <LI> Al-KIT-6 catalyst was applied to cyclodimerization of norbornadiene. </LI> <LI> The activity over the Al-KIT-6 catalyst was higher than that over the Al-MCM-41 catalyst. </LI> <LI> The deactivated Al-KIT-6 catalyst could easily be regenerated through calcination. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

에어로졸 증착 공정을 통해 제작한 Al2O3 코팅층의 Al2O3 입자 크기에 따른 성막 메커니즘 연구

김익수,조명연,구상모,이동원,오종민 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.3

Al2O3 powders with particle sizes of 0.35 μm, 0.5 μm, 1.5 μm, and 2.5 μm are deposited onto glass and Cu substrates using the aerosol deposition (AD) process. The deposition characteristics of Al2O3 films using those four types of Al2O3 powders are investigated to determine the influence of the particle size on the films. To observe detailed micro-structures of the films, the cross-section and surface morphology are observed. Then, the crystalline size and internal strain are calculated from X-ray diffraction peaks in order to confirm the hammering effect as well as the micro-strain during the AD deposition. From the above results, deposition mechanisms related to the particle size are studied. The results of this study indicate the optimal particle size and formation mechanisms for dense Al2O3 film with a smooth surface roughness as well as for a porous Al2O3 film with a rough surface roughness. 0.35 μm, 0.5 μm, 1.5 μm 및 2.5 μm의 입자 크기가 다른 Al2O3 분말이 에어로졸 증착 공정을 통해 유리 기판과 구리 기판에 증착되었다. 입자 크기가 코팅층 성막에 미치는 영향을 알아보기 위해 네 종류의 Al2O3 분말을 사용하여 코팅된 Al2O3 필름의 성막 특성을 조사하였다. Al2O3 필름의 미세구조를 자세히 분석하기 위해, 단면과 표면 형상을 관찰하였다. 또한, 증착이 일어나는 동안 미세 변형과 망치 효과를 확인하기 위해 X-ray 회절 피크로부터 결정 크기 및 내부 변형을 계산하였다. 상기의 분석 결과로부터, 입자 형상과 관련지어 증착 메커니즘을 연구하였다. 본 연구에서는 거친 표면 거칠기를 갖는 다공성 Al2O3 필름뿐만 아니라 부드러운 표면 거칠기를 갖는 치밀한 Al2O3 필름 제작을 위한 최적의 입자 크기를 각각 제안하고자 한다.

TiAl 합금의 내산화성 개선을 위한 Al-21Ti-23Cr 플라즈마 용사코팅

李在敬,吳明勳,李炯根,韋當文 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.10

To improve the oxidation resistance of γ-based TiAl alloy, Al-Ti-Cr coatings of approximately 150 ㎛ thickness were deposited on Ti-48Al alloy using an air plasma spraying(APS) process. We used Al-Ti-Cr powders with the composition of Al-2lTi-23Cr(at.%). Isothermal and cyclic oxidation tests at 1000℃ in air were utilized to investigate the oxidation resistance of both Al-Ti-Cr coatings and of TiAl alloys with Al-Ti-Cr coatings. Phase identification of Al-Ti-Cr coatings was performed by XRD. After exposure at 1000℃ in air, rutile TiO_2, which resulted from the oxidation of Ti during spraying, was always found in addition to protective α-Al_2O_3 in the oxide scale. However, isothermal and cyclic oxidation tests of a Ti-48Al alloy coated with an Al-Ti-Cr coating showed that this coating improved the oxidation resistance of TiAl alloy at 1000℃ despite partial spalling in the Al-Ti-Cr coating layer. Moreover, cyclic oxidation tests of Al-Ti-Cr coatings showed stable oxidation behavior at 1000℃ up to 100h because of good adhesion between the coating layer and the oxide scale although the growth rate of oxide was relatively high. Therefore, it could be suggested that the Al-Ti-Cr coating was effective in enhancing the oxidation resistance of the TiAl alloy at 1000℃, although the improvement of adhesion between the coating layer and the TiAl substrate was required.

스텐레스강 평직망에 담지된 Pt/Al_2O_3촉매 제조 및 그의 에틸렌 산화활성

김기중,안호근 한국환경기술학회 2011 한국환경기술학회지 Vol.12 No.3

Pt/Al_2O_3 catalysts supported on stainless steel wire cloth(SSWC) were prepared using aluminum nitrate(Al(NO_3)_3) and chloroplatinic acid(H_2PtCl_6) as precursors. SSWC was thermally or acid treated to increase the adhesive strength of Al_2O_3 by improving superficial roughness. SSWC was coated with Al_2O_3 by an impregnation method using either an Al(NO_3)_3 solution or a mixed solution containing Al(NO_3)_3 and a binding agent. After Al_2O_3 coating, Pt particles as a catalytic component were deposited on the Al_2O_3/SSWC. These catalysts were characterized by N_2 gas adsorption, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and adhesive ability of Al_2O_3 on SSWC. The catalytic activity for ethylene oxidation was investigated using a flow reactor under atmospheric pressure. The apparent roughness of SSWC was markedly increased by thermal oxidation, and adhesive ability of the Al_2O_3 was enhanced compared to bare SSWC. The optimum Al_2O_3 adhesion was obtained by thermal oxidation at 800℃ for 12hr(SSWC800). Surface roughness of SSWC was increased with increasing treatment temperature and time. It was also known that the amount of Pt particles deposited on Al_2O_3/SSWC800 depended strongly on adhesive ability of Al_2O_3(or adhesive amount), and optimum concentration of H_2PtCl_6 solution for Pt loading was about 10wt% on Al_2O_3^(2nd)/SSWC800. Catalytic activity for C_2H_4 was decreased with increasing gas hourly space velocity(GHSV). It was also shown that the GHSV had a great affect on the C_2H_4 conversion at lower reaction temperature. 본 연구에서는 질산 알루미늄(Al(NO_3)_3)과 염화 백금산(H_2PtCl_6)을 전구체로 이용하여 스텐레스강 평직망(SSWC)에 담지된 Pt/Al_2O_3촉매를 제조하였다. SSWC에 대한 Al_2O_3의 부착력을 향상시키기 위하여 바인더를 첨가하거나 표면 산화법(산 또는 고온)을 이용하였으며, 활성금속으로서 백금을 Al_2O_3/SSWC에 담지 하였다. 질소가스 흡착, X-선 회절분석기, 주사전자 현미경, 투과전자 현미경, 그리고 Al_2O_3의 부착력을 통하여 물리적 특성을 분석하고, 상압 유통식 고정층 반응기를 이용하여 에틸렌에 대한 산화 활성을 조사하였다. 결과적으로, 습식 및 고온 산화법을 이용하여 SSWC를 전처리하면 표면의 거칠기가 증가하여 SSWC보다 Al_2O_3 부착력이 향상되었다. 고온 산화법을 이용하여 SSWC를 열처리할 때 온도가 증가할수록, 열처리 시간이 길수록 표면의 거칠어지는 정도는 증가하였으며, 최적의 Al_2O_3부착력은 800℃에서 12시간 동안 열처리할 때로 나타났다. Al_2O_3/SSWC800에서 백금의 담지특성은 Al_2O_3의 부착량(또는 부착력)에 크게 의존하였다. Al_2O_3/SSWC-800에 백금을 담지할 때 백금 전구체의 농도가 증가할수록 에틸렌의 완전산화가 저온에서 일어났으며, 최적의 담지량은 코팅된 Al_2O_3에 대하여 약 10wt%이었다. 공간속도가 증가함에 따라 에틸렌 전화율은 감소하였으며, 반응온도가 낮을수록 공간속도의 영향이 커짐을 알 수 있었다.

Aluminum Solubility of Andisols in Jeju Island, Korea

이규호,송윤구,문지원,문희수,Lee, Gyoo-Ho,Song, Yun-Goo,Moon, Ji-Won,Moon, Hi-Soo The Korean Society of Economic and Environmental G 2012 자원환경지질 Vol.45 No.2

본 연구에서는 제주도 토양 중 화산쇄설암과 현무암을 모재로 발달하는 두 Andisol 토양의 Al 용해도 특성을 규명하고자 하였다. 토양 A층은 높은 유기물함량과 $Al_{pyrophosphate}/Al_{oxalate}$ 비를 나타내는 반면, 토양 Bo층은 낮은 유기물함량과 $Al_{pyrophosphate}/Al_{oxalate}$ 비를 나타낸다. 이는 반응성 Al이 A층에서는 대부분이 유기물과 결합한 형태로 존재하고 있는 반면, 토양 Bo층에서는 무기질의 광물과 결합하고 있음을 지시한다. Acid-oxalate 용해처리, 그리고 150 및 $350^{\circ}C$ 열처리 전후의 FT-IR 스펙트럼 비교, 투과전자현미경(TEM)을 이용한 관찰결과, 토양 Bo층에 상당량의 이모골라이트(Imogolite)가 존재함을 확인하였다. 이들 시료에 대한 Al-용해도 특성규명을 위한 Batch 평형실험결과, 토양 Bo층에서의 Al-용해도는 ITM(Imogolite-type material)과 Al hydroxy-interlayered aluminosilicate에 의한 Simultaneous equilibrium보다는 ITM의 Congruent dissolution model을 따르는 것으로 나타났다. 투석과 Aging과정 후의 용해도 특성 변화는 PI(Proto imogolite) sol의 생성이 되고, 이들의 이모골라이트로의 상전이가 Al-용해도에 영향을 주었음을 지시한다. 이러한 결과는, 실내실험 결과를 보완해주는 것으로, 제주도 Andisol토양에서의 Al-용해도 특성이 ITM에 의한 Congruent dissolution에 의해 조절되고 있음을 지시한다. The solubility of aluminum for two Andisol profiles formed on pyroclastic materials and basaltic rocks from Jeju Island, Korea was investigated. It is found that high organic carbon content and $Al_{pyrophosphate}/Al_{oxalate}$ ratios in the A horizons, suggesting the substantial amounts of reactive Al are associated with organic matter, whereas the low organic carbon content and the $Al_{pyrophosphate}/Al_{oxalate}$ ratios in the Bo horizons indicate that a major part of the reactive Al should be bound inorganically. The differential FT-IR spectra following acid-oxalate dissolution and heating up to 150 and $350^{\circ}C$, and transmission electron microscope (TEM) observation confirm that imogolite is in the Bo horizon. Our results of equilibration experiments demonstrate that the Al solubility in the Bo horizon for Andisols can be clarified by the congruent dissolution model for imogolite-type material (ITM), rather than by the simultaneous equilibrium with both ITM and Al hydroxy-interlayered aluminosilicate. With results from dialysis and aging procedures, it is noted that the formation of a proto imogolite sol showing its transformation to imogolite, which supports the congruent dissolution of ITM primarily controlling the Al solubility of Andisols in Jeju Island, Korea.

고압 금형 주조용 Al-4 wt%Mg-0.9 wt%Si계 합금의 인장특성에 미치는 Fe, Mn함량의 영향

김헌주 ( Heon Joo Kim ) 한국주조공학회 2013 한국주조공학회지 Vol.33 No.3

Effect of Fe and Mn contents on the tensile properties of Al-4 wt%Mg-0.9 wt%Si alloy system has been studied. Common phases of Al-4 wt%Mg-0.9 wt%Si alloy system were α-Al, Mg2Si, α-Al12(Fe,Mn)3Si and β-Al5FeSi. As Fe content of Al-4 wt%Mg-0.9 wt%Si alloy system increased from 0.15 wt% to above 0.3 wt%, β-Al5FeSi compound appeared. When Mn content of the alloy increased from 0.3 wt% to 0.5 wt%, morphology of plate shaped β-Al5FeSi compound changed to chinese script α-Al12(Fe,Mn)3Si. As Fe content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Mn alloy increased from 0.15 wt% to 0.4 wt%, tensile strength of the as-cast alloy decreased from 191 MPa to 183 MPa and, elongation of the alloy also decreased from 8.0% to 6.2%. Decrease of these properties can be explained as the formation of plate shape, β-Al5FeSi phase with low Mn/Fe ratio of the alloy. However, when Mn content of Al-4 wt%Mg-0.9 wt%Si-0.3 wt%Fe alloy increased from 0.3 wt% to 0.5 wt%, tensile strength of as-cast alloy increased from 181 MPa to 194 MPa and, elongation of the alloy increased from 6.8% to 7.0%. These improvements attribute to the morphology change from β-Al5FeSi phase to chinese script, α-Al15(Mn,Fe)3Si2 phase shape-modified from with high Mn/Fe ratio of the alloy.

Ti/Al/STS 클래드재의 접합특성에 미치는 예비 열처리의 영향

배동현 ( Dong Hyun Bae ),정수정 ( Su Jung Jung ),조영래 ( Young Rae Cho ),정원섭 ( Won Sup Jung ),정호신 ( Ho Shin Jung ),강창룡 ( Chang Yong Kang ),배동수 ( Dong Su Bae ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9

Titanium/aluminum/stainless steel(Ti/Al/STS) clad materials have received much attention due to their high specific strength and corrosion-resisting properties. However, it is difficult to fabricate these materials, because titanium oxide is easily formed on the titanium surface during heat treatment. The aim of the present study is to derive optimized cladding conditions and thereupon obtain the stable quality of Ti/Al/STS clad materials. Ti sheets were prepared with and without pre-heat treatment and Ti/Al/STS clad materials were then fabricated by cold rolling and a post-heat treatment process. Microstructure of the Ti/ Al and STS/Al interfaces was observed using a Scanning Electron Microscope(SEM) and an Energy Dispersed X-ray Analyser(EDX) in order to investigate the effects of Ti pre-heat treatment on the bond properties of Ti/ Al/STS clad materials. Diffusion bonding was observed at both the Ti/Al and STS/Al interfaces. The bonding force of the clad material with non-heat treated Ti was higher than that with pre-heat treated Ti before the cladding process. The bonding force decreased rapidly beyond 400℃, because the formed Ti oxide inhibited the joining process between Ti and Al. Bonding forces of STS/Al were lower than those of Ti/Al, because brittle Fe3Al, Al3Fe intermetallic compounds were formed at the interface of STS/Al during the cladding process. In addition, delamination of the clad material with pre-heat treated Ti was observed at the Ti/Al interface after a cupping test.

TiB₂코팅이 함침법으로 제조되는 B₄C/Al 복합체의 기계적 특성에 미치는 영향

김선혜,임경란,심광보,김창삼 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.8

B$_4$C/Al 복합체의 기계적 물성은 제조 과정에서 B$_4$C와 Al의 반응에 의한 반응생성물의 종류와 양에 의해서 결정되므로, 강하고 경량 소재로서의 특성이 요구되는 복합체를 만들려면 반응생성물을 조절할 필요가 있다. TiB$_2$는 알루미늄과 반응성이 거의 없고 B$_4$C보다 낮은 접촉각(100$0^{\circ}C$에서 85$^{\circ}$)을 가지고 있다. 그러므로 B$_4$C를 TiB$_2$로 코팅하면 B$_4$C/Al복합체를 함침법으로 제조하는 경우 알루미늄의 함침 온도를 낮출 수 있다. 본 연구에서는 TiB$_2$가 B$_4$C/Al 복합체의 미세구조와 기계적 특성에 미치는 영향을 조사하였다. TiB$_2$를 코팅한 B$_4$C 분말을 졸겔법을 이용하여 준비하였다. B$_4$C 입자에 코팅된 TiB$_2$ 입자 크기는 20-50 nm이었다. TiB$_2$를 코팅하고 제작한 B$_4$C/Al 복합체에는 l7wt%의 미반응 알루미늄이 남아있었고, 코팅하지 않고 제작한 것에는 l4 wt%가 남았다. 결과적으로 코팅하고 제작한 복합체는 코팅하지 않고 제작한 것보다 파괴인성은 높고 경도는 낮았으며, 이러한 결과에서 TiB$_2$가 알루미늄의 함침 온도를 낮추고 B$_4$C와 Al이 반응하는 것을 억제하고 있다는 것을 알 수 있었다. The mechanical properties of B$_4$C/Al composites normally depend on the species and quantity of reaction products between B$_4$C and Al and then the control of reaction products is necessary to make desirable composites for lightweight advanced or armor materials. TiB$_2$ is chemically inert with aluminum and has a lower contact angle (85$^{\circ}$ at 100$0^{\circ}C$) to liquid aluminum than B$_4$C. Thus, TiB$_2$ coating on B$_4$C may lower infiltration temperature of aluminum when the B$_4$C/Al composites is fabricated by infiltration process. In this study, the effects of TiB$_2$ on the microstructure and mechanical properties of the B$_4$C/Al composites have been investigated. TiB$_2$ coated B$_4$C powder was prepared using the sol-gel technique. It was found that the B$_4$C surface is homogeneously covered with TiB$_2$ having a particles size of 20-50 nm. While the B$_4$C/Al composites prepared by infiltration after TiB$_2$ coating had 17 wt% of unreacted Al, on the other hand, the B$_4$C/Al composites without coating included 14 wt% of Al. As a result, the composites infiltrated after the coating showed higher fracture toughness and lower hardness. This strongly suggests that TiB$_2$ not only lowers the infiltration temperature, but also inhibits the reaction between B$_4$C and Al.