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.

플라즈마 스프레이방법을 이용하여 Ti 언더코트를 제작한 SUS316L강의 부식피로 특성

한창석,김우석,Han, Chang-Suk,Kim, Woo-Suk 한국재료학회 2021 한국재료학회지 Vol.31 No.3

In this study, using the plasma spray method, tensile and compression fatigue tests are performed in saline solution to examine the effect of Ti undercoat on corrosion fatigue behavior of alumina-coated specimens. The alumina-coated material using Ti in the undercoat shows better corrosion fatigue strength than the base material in the entire stress amplitude range. Fatigue cracking of UT specimens occurs in the recess formed by grit-blasting treatment and progresses toward the base metal. Subsequently, the undercoat is destroyed at a stage where the deformation of the undercoat cannot follow the crack opening displacement. The residual stress of the UT specimen has a tensile residual stress up to about 100 ㎛ below the surface of the base material; however, when the depth exceeds 100 ㎛, the residual stress becomes a compressive residual stress. In addition, the inside of the spray coating film is compressive residual stress, which contributes to improving the fatigue strength characteristics. A hardened layer due to grit-blasting treatment is formed near the surface of the UT specimen, contributing to the improvement of the fatigue strength characteristics. Since the natural potential of Ti spray coating film is slightly higher than that of the base material, it exhibits excellent corrosion resistance; however, when physiological saline intrudes, a galvanic battery is formed and the base material corrodes preferentially.

성형벨트를 부착시킨 장비를 이용하여 용융드래그방법으로 제작한 마그네슘 합금의 제작조건 확립

한창석,권용준,Han, Chang-Suk,Kwon, Yong-Jun 한국재료학회 2021 한국재료학회지 Vol.31 No.10

To improve the shortcomings and expand the advantages of the single-roll melt drag method, which is a type of continuous strip casting method, the melt drag method with a molding belt is applied to AZ31 magnesium alloy. By attaching the forming belt to the melt drag method, the cooling condition of the thin plate is improved, making it possible to manufacture thin plates even at high roll speed of 100 m/min or more. In addition, it is very effective for continuous production of thin plates to suppress oxidation of the molten metal on the roll contact surface by selecting the protective gas. As a result of investigating the relationship between the contact time between the molten metal and the roll and the thickness of the sheet, it is possible to estimate the thickness of the sheet from the experimental conditions. The relationship between the thin plate thickness and the grain size is one in which the thinner the thin plate is, the faster the cooling rate of the thin plate is, resulting in finer grain size. The contact state between the molten metal and the roll greatly affects the grain size, and the minimum average grain size is 72 ㎛. The thin plate produced using this experimental equipment can be rolled, and the rolled sample has no large cracks. The tensile test results show a tensile strength of 303 MPa.

용융드래그방법을 이용한 마그네슘 합금 박판의 제조조건 확립

한창석,권용준,Han, Chang-Suk,Kwon, Yong-Jun 한국재료학회 2021 한국재료학회지 Vol.31 No.9

An investigation is performed to clarify the manufacturing conditions of pure magnesium and AZ31 magnesium alloy thin plate using the melt drag method. By the melt drag method, suitable for magnesium molten metal, pure magnesium can be produced as a continuous thin plate with a thickness of 1.4 mm to 2.4 mm in the range of 5 m/min to 20 m/min of roll speed, and the width of the thin plate to the nozzle outlet width. AZ31 magnesium alloy is able to produce a continuous sheet of thickness in the range of 5 m/min to 30 m/min in roll circumferential speed, with a thickness of 0.6 mm to 1.6 mm and a width of the sheet matching the nozzle outlet width. In the magnesium melt drag method, the faster the circumferential speed of the roll, the shorter the contact time between the molten metal and the roll, and it is found that the thickness of the produced thin plate becomes thinner. The effect of the circumferential roll speed on the thickness of the thin plate is evident in the low roll circumferential region, where the circumferential speed is 30 m/min or less. The AZ31 thin plate manufactured by the melt drag method has a finer grain size as the thickness of the thin plate decreases, but it is currently judged that this is not the effect of cooling by the roll.

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.

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.