비정질상인 Ti₅Si₃ MA분말의 가압소결 동안 소결체의 치밀화 촉진현상 요인에 대한 조사

한창석,진성윤,권혁구,Han, Chang-Suk,Jin, Sung-Yooun,Kwon, Hyuk-Ku 한국재료학회 2020 한국재료학회지 Vol.30 No.6

In this study, factors considered to be causes of promotion of densification of sintered pellets identified during phase change are reviewed. As a result, conclusions shown below are obtained for each factor. In order for MA powder to soften, a temperature of 1,000 K or higher is required. In order to confirm the temporary increase in density throughout the sintered pellet, the temperature rise due to heat during phase change was found not to have a significant effect. While examining the thermal expansion using the compressed powder, which stopped densification at a temperature below the MA powder itself, and the phase change temperature, no shrinkage phenomenon contributing to the promotion of densification is observed. The two types of powder made of Ti-silicide through heat treatment are densified only in the high temperature region of 1,000 K or more; it can be estimated that this is the effect of fine grain superplasticity. In the densification of the amorphous powder, the dependence of sintering pressure and the rate of temperature increase are shown. It is thought that the specific densification behavior identified during the phase change of the Ti-37.5 mol.%Si composition MA powder reviewed in this study is the result of the acceleration of the powder deformation by the phase change from non-equilibrium phase to equilibrium phase.

김정한 소설어 연구 -민중성의 구현을 중심으로-

한창석 ( Chang Suk Han ) 한민족문화학회 2011 한민족문화연구 Vol.36 No.-

본고는 다음에 대략 네 가지 문제의식을 상정하고 이에 대한 답을 도출하고자 하였다. 첫째, 김정한의 소설어는 왜 창조가 아닌 복원인가? 김정한이 천착한 민중의 삶은 과거에서 현재까지 지속적인 것이었다. 허구나 전망이기 보다 증언이므로 신어나 조어가 아니라 삶의 모습을 복원하고 재현할 기존의 어휘를 소설어로 살려쓰기 위한 노력을 기울인다. 둘째, 김정한의 소설어는 왜 민중어인가? 민중의 삶을 증언하는 것은 민중의 언어로 이루어져야 한다. 아울러, 민중의 삶을 생동감 있게 증언하기 위해서는 추상어가 아닌 감각어, 생활어, 고유어로 이루어져야 한다. 셋째, 김정한의 소설어는 어떤 방식으로 작가의식의 구현에 기여하는가? ① 민중의 조락상(凋落相)의 증언; 빈궁어의 전경화 ② 민중어의 갈래; 속담과 관용어/한자성어/고유어/감각어/종교어 ③ 민중과 반(反)민중의 이분법; 구체성과 연대성 넷째, 민중과 반(反)민중의 대립구도는 어떻게 규정되는가? 민중을 수탈하고 질곡으로 몰아넣는 계급(일제, 친일파, 지주, 부패승려, 권력층)은 반민중성을 지닌다. 그런데 김정한 소설에는 반(反)민중의 역할을 수행하는 인물군의 경우에도 계급적으로는 민중의 일원인 경우가 나타난다. 따라서 반민중적 인물은 지위나 신분이 아닌 역할에 따라 판별해야 할 것이다. This manuscript is about to come up the following four kinds of the consciousness of question and obtain the answer for that. 1. What Kim chung han`s novel language is called not creation but restoration for? The populace life that Kim chung han has scrutinized is continuous up to the present time from the past. As it is a testimony to a fabrication or a prospect. The existing language reappearing and restoring their original looks rather than the need for new vocabulary to be selected as the novel language. 2. Why is Kim chung han`s novel language called as the populace language? Testifying the populace language. In addition, to testify the populace life actively. It has to be established not as an abstract language but a sensual language, a living language and their own language. 3.What`s split for language inquire into Kim chung han`s writer`s consciousness? This manuscript describe it separately as follows ① The testimony of a populace`s withering situation: The aspect of poor language. ② The restoration of a populace`s language: a proverb and idiom/idiom/chinese proverb/a existing language/a sensual language/religion language. ③ The bisect method between the populace and anti- the populace: the confrontation expression on a person and the situation. 4. Can the composition of confrontation between the populace and anti-the populace be shown effectively or pertinently? the concept language of the anti-the populace should be careful to adapt generally in the range and the standard of using, because in case of the persons performing the role of the anti-populace in work, the birth might be belonged to the members of the populace. accordingly, It is reasonable to get through the composition of confrontation with the bisect method of the populace under the key point of the role of an exploiter and a person deprived.

전열응고해석법을 이용한 마그네슘합금의 열전달계수 및 롤의 온도변화 측정

한창석,이찬우,Han, Chang-Suk,Lee, Chan-Woo 한국재료학회 2022 한국재료학회지 Vol.32 No.9

Research is being actively conducted on the continuous thin plate casting method, which is used to manufacture magnesium alloy plate for plastic processing. This study applied a heat transfer solidification analysis method to the melt drag process. The heat transfer coefficient between the molten magnesium alloy metal and the roll in the thin plate manufacturing process using the melt drag method has not been clearly established until now, and the results were used to determine the temperature change. The estimated heat transfer coefficient for a roll speed of 30 m/min was 1.33 × 10⁵ W/m²·K, which was very large compared to the heat transfer coefficient used in the solidification analysis of general aluminum castings. The heat transfer coefficient between the molten metal and the roll estimated in the range of the roll speed of 5 to 90 m/min was 1.42 × 10⁵ to 8.95 × 10⁴ W/m²·K. The cooling rate was calculated using a method based on the results of deriving the temperature change of the molten metal and the roll, using the estimated heat transfer coefficient. The DAS was estimated from the relationship between the cooling rate and DAS, and compared with the experimental value. When the magnesium alloy is manufactured by the melt drag method, the cooling rate of the thin plate is in the range of about 1.4 × 10³ to 1.0 × 10⁴ K/s.

무전해 코발트계 석출막에 미치는 기판의 영향

한창석,천창환,한승오,Han, Chang-Suk,Chun, Chang-Hwan,Han, Seung-Oh 한국재료학회 2009 한국재료학회지 Vol.19 No.6

The deposition behavior and structural and magnetic properties of electroless Co-B and Co-Fe-B deposits, as well as the amorphous ribbon substrates, were investigated. These Co-based alloy deposits exhibited characteristic polycrystalline structures and surface morphology and magnetic properties that were dependent on the type of amorphous substrates. The catalytic activity sequence of the amorphous ribbon electrodes for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath that did not contain the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of the substrates. The deposition rate linearly varied against the deposition time. The initial deposition potential may have also determined the structural and magnetic properties of the deposit based on the thickness of ${\mu}m$ order. Furthermore, a basic study of the electroless deposition processes on an amorphous ribbon substrate has been carried out in connection with the structural and magnetic properties of the deposits.

전착법을 이용한 Co계 합금박막의 표면형태와 자기특성과의 관계

한창석,김상욱,Han, Chang-Suk,Kim, Sang-Wook 한국재료학회 2017 한국재료학회지 Vol.27 No.11

In this study, we investigated the overpotential of precipitation related to the catalytic activity of electrodes on the initial process of electrodeposition of Co and Co-Ni alloys on polycrystalline Cu substrates. In the case of Co electrodeposition, the surface morphology and the magnetic property change depending on the film thickness, and the relationship with the electrode potential fluctuation was shown. Initially, the deposition potential(-170 mV) of the Cu electrode as a substrate was shown, the electrode potential($E_{dep}$) at the $T_{on}$ of electrodeposition and the deposition potential(-600 mV) of the surface of the electrodeposited Co film after $T_{off}$ and when the pulse current was completed were shown. No significant change in the electrode potential value was observed when the pulse current was energized. However, in a range of number of pulses up to 5, there was a small fluctuation in the values of $E_{dep}$ and $E_{imm}$. In addition, in the Co-Ni alloy electrodeposition, the deposition potential(-280 mV) of the Cu electrode as the substrate exhibited the deposition potential(-615 mV) of the electrodeposited Co-Ni alloy after pulsed current application, the $E_{dep}$ of electrodeposition at the $T_{on}$ of each pulse and the $E_{imm}$ at the $T_{off}$ varied greatly each time the pulse current was applied. From 20 % to less than 90 % of the Co content of the thin film was continuously changed, and the value was constant at a pulse number of 100 or more. In any case, it was found that the shape of the substrate had a great influence.

반응성 스프레이방법으로 제작한 티타늄 알루미나이드/탄화물 복합박막의 미세조직과 경도

한창석,진성윤,Han, Chang-Suk,Jin, Sung-Yooun 한국재료학회 2020 한국재료학회지 Vol.30 No.7

A variety of composite powders having different aluminum and carbon contents are prepared using various organic solvents having different amounts of carbon atoms in unit volume as ball milling agents for titanium and aluminum ball milling. The effects of substrate temperature and post-heat treatment on the texture and hardness of the coating are investigated by spraying with this reduced pressure plasma spray. The aluminum part of the composite powder evaporates during spraying, so that the film aluminum content is 30.9 mass%~37.4 mass% and the carbon content is 0.64 mass%~1.69 mass%. The main constituent phase of the coating formed on the water-cooled substrate is a non-planar α₂ phase, obtained by supersaturated carbon regardless of the alloy composition. When these films are heat-treated at 1123 K, the main constituent phase becomes γ phase, and fine Ti₂AlC precipitates to increase the film hardness. However, when heat treatment is performed at a higher temperature, the hardness is lowered. The main constitutional phase of the coating formed on the preheated substrate is an equilibrium gamma phase, and fine Ti₂AlC precipitates. The hardness of this coating is much higher than the hardness of the coating in the sprayed state formed on the water-cooled substrate. When hot pressing is applied to the coating, the porosity decreases but hardness also decreases because Ti₂AlC grows. The amount of Ti₂AlC in the hot-pressed film is 4.9 vol% to 15.3 vol%, depending on the carbon content of the film.

Fe 입자를 미세 분산 시킨 AlN 박막의 물리적 성질

한창석,김장우,Han, Chang-Suk,Kim, Jang-Woo 한국재료학회 2011 한국재료학회지 Vol.21 No.1

This paper describes the fabrication of AlN thin films containing iron and iron nitride particles, and the magnetic and electrical properties of such films. Fe-N-Al alloy films were deposited in Ar and $N_2$ mixtures at ambient temperature using Fe/Al composite targets in a two-facing-target DC sputtering system. X-ray diffraction results showed that the Fe-N-Al films were amorphous, and after annealing for 5 h both AlN and bcc-Fe/bct-$FeN_x$ phases appeared. Structure changes in the $FeN_x$ phases were explained in terms of occupied nitrogen atoms. Electron diffraction and transmission electron microscopy observations revealed that iron and iron nitride particles were randomly dispersed in annealed AlN films. The grain size of magnetic particles ranged from 5 to 20 nm in diameter depending on annealing conditions. The saturation magnetization as a function of the annealing time for the $Fe_{55}N_{20}Al_{25}$ films when annealed at 573, 773 and 873 K. At these temperatures, the amount of iron/iron nitride particles increased with increasing annealing time. An increase in the saturation magnetization is explained qualitatively in terms of the amount of such magnetic particles in the film. The resistivity increased monotonously with decreasing Fe content, being consistent with randomly dispersed iron/iron nitride particles in the AlN film. The coercive force was evaluated to be larger than $6.4{\times}10^3Am^{-1}$ (80 Oe). This large value is ascribed to a residual stress restrained in the ferromagnetic particles, which is considered to be related to the present preparation process.

N₂와 NH₃ 반응성가스를 사용하여 마그네트론 스퍼터링법으로 제작한 AlN박막의 특성

한창석,Han, Chang-Suk 한국재료학회 2015 한국재료학회지 Vol.25 No.3

Aluminum nitride, a compound semiconductor, has a Wurtzite structure; good material properties such as high thermal conductivity, great electric conductivity, high dielectric breakdown strength, a wide energy band gap (6.2eV), a fast elastic wave speed; and excellent in thermal and chemical stability. Furthermore, the thermal expansion coefficient of the aluminum nitride is similar to those of Si and GaAs. Due to these characteristics, aluminum nitride can be applied to electric packaging components, dielectric materials, SAW (surface acoustic wave) devices, and photoelectric devices. In this study, we surveyed the crystallization and preferred orientation of AlN thin films with an X-ray diffractometer. To fabricate the AlN thin film, we used the magnetron sputtering method with $N_2$, NH3 and Ar. According to an increase in the partial pressures of $N_2$ and $NH_3$, Al was nitrified and deposited onto a substrate in a molecular form. When AlN was fabricated with $N_2$, it showed a c-axis orientation and tended toward a high orientation with an increase in the temperature. On the other hand, when AlN was fabricated with $NH_3$, it showed a-axis orientation. This result is coincident with the proposed mechanism. We fabricated AlN thin films with an a-axis orientation by controlling the sputtering electric power, $NH_3$ pressure, deposition speed, and substrate temperature. According to the proposed mechanism, we also fabricated AlN thin films which demonstrated high a-axis and c-axis orientations.

분말야금법으로 제작한 NiAl합금의 기계적성질 및 형상기억특성

한창석,진성윤,권혁구,Han, Chang-Suk,Jin, Sung-Yooun,Kwon, Hyuk-Ku 한국재료학회 2020 한국재료학회지 Vol.30 No.5

The composition of martensite transformation in NiAl alloy is determined using pure nickel and aluminum powder by vacuum hot press powder metallurgy, which is a composition of martensitic transformation, and the characteristics of martensitic transformation and microstructure of sintered NiAl alloys are investigated. The produced sintered alloys are presintered and hot pressed in vacuum; after homogenizing heat treatment at 1,273 K for 86.4 ks, they are water-cooled to produce NiAl sintered alloys having relative density of 99 % or more. As a result of observations of the microstructure of the sintered NiAl alloy specimens quenched in ice water after homogenization treatment at 1,273 K, it is found that specimens of all compositions consisted of two phases and voids. In addition, it is found that martensite transformation did not occur because surface fluctuation shapes did not appear inside the crystal grains with quenching at 1,273 K. As a result of examining the relationship between the density and composition after martensitic transformation of the sintered alloys, the density after transformation is found to have increased by about 1 % compared to before the transformation. As a result of examining the relationship between the hardness (Hv) at room temperature and the composition of the matrix phase and the martensite phase, the hardness of the martensite phase is found to be smaller than that of the matrix phase. As a result of examining the relationship between the temperature at which the shape recovery is completed by heating and the composition, the shape recovery temperature is found to decrease almost linearly as the Al concentration increases, and the gradient is about -160 K/at% Al. After quenching the sintered NiAl alloys of the 37 at%Al into martensite, specimens fractured by three-point bending at room temperature are observed by SEM and, as a result, some grain boundary fractures are observed on the fracture surface, and mainly intergranular cleavage fractures.

B2형 금속간화합물 NiTi 중에 L2₁형 Ni₂AlTi상의 석출

한창석,Han, Chang-Suk 한국재료학회 2007 한국재료학회지 Vol.17 No.8

Precipitation behavior has been studied in NiTi-based ordered alloy using transmission electron microscopy. The hardness after solution treatment is high in NiTi alloy suggesting the large contribution of solid solution strengthening in this alloy system. However, the amount of age hardening is not large as compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1-type$ $Ni_2AlTi$ precipitates keep a lattice coherency with the NiTi matrix. By longer periods of aging $Ni_2AlTi$ precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. Misfit dislocations, which are observed on {100} planes of H-precipitates have the Burgers vector of a <100> with a pure edge type. The lattice misfits of $NiTi-Ni_2AlTi$ system is estimated from the spacings of misfit dislocations to be 1.3% at 1273 K. The lattice misfits decrease with increasing aging temperature in this system.