논문현황

INSTITUTE FOR ADVANCED ENGINEERING

융합소재연구센터 Recycling process for recovery of gallium from GaN an e-waste of LED industry through ball milling, annealing and leaching

· 저자

Basudev Swain, Chinmayee Mishra, 강이승, 박경수, 이찬기, 홍현선


Waste dust generated during manufacturing of LED contains significant amounts of gallium and indium, needs suitable treatment and can be an important resource for recovery. The LED industry waste dust contains primarily gallium as GaN. Leaching followed by purification technology is the green and clean technology. To develop treatment and recycling technology of these GaN bearing e-waste, leaching is the primary stage. In our current investigation possible process for treatment and quantitative leaching of gallium and indium from the GaN bearing e-waste or waste of LED industry dust has been developed. To recycle the waste and quantitative leaching of gallium, two different process flow sheets have been proposed. In one, process first the GaN of the waste the LED industry dust was leached at the optimum condition. Subsequently, the leach residue was mixed with Na2CO3, ball milled followed by annealing, again leached to recover gallium. In the second process, the waste LED industry dust was mixed with Na2CO3, after ball milling and annealing, followed acidic leaching. Without pretreatment, the gallium leaching was only 4.91 w/w % using 4 M HCl, 100 °C and pulp density of 20 g/L. After mechano-chemical processing, both these processes achieved 73.68 w/w % of gallium leaching at their optimum condition. The developed process can treat and recycle any e-waste containing GaN through ball milling, annealing and leaching.


융합소재연구센터 Recycling of metal-organic chemical vapor deposition waste of GaN based power device and LED industry by acidic leaching: Process optimization and kinetics study

· 저자

Basudev Swain, Chinmayee Mishra, 강이승, 박경수, 이찬기, 홍현선, 박정진


Recovery of metal values from GaN, a metal-organic chemical vapor deposition (MOCVD) waste of GaN based power device and LED industry is investigated by acidic leaching. Leaching kinetics of gallium rich MOCVD waste is studied and the process is optimized. The gallium rich waste MOCVD dust is characterized by XRD and ICP-AES analysis followed by aqua regia digestion. Different mineral acids are used to find out the best lixiviant for selective leaching of the gallium and indium. Concentrated HCl is relatively better lixiviant having reasonably faster kinetic and better leaching efficiency. Various leaching process parameters like effect of acidity, pulp density, temperature and concentration of catalyst on the leaching efficiency of gallium and indium are investigated. Reasonably, 4 M HCl, a pulp density of 50 g/L, 100 °C and stirring rate of 400 rpm are the effective optimum condition for quantitative leaching of gallium and indium.


융합소재연구센터 Synthesis of Cu3(MoO4)2(OH)2 nanostructures by simple aqueous precipitation: understanding the fundamental chemistry and growth mechanism

· 저자

Basudev Swain, 이덕희, 박재량, 이찬기, 이근재, 김동완, 박경수


Lindgrenite (Cu3(MoO4)2(OH)2) nanoflowers were synthesized through the simplest possible route by an aqueous chemical precipitation technique at room temperature without using any surfactants, template, expensive chemicals, complex instrumentation or tedious multistage synthesis process. Their morphology, structure, thermal properties, surface area, synthesis chemistry, and structural and growth mechanisms involved in the synthesis process were analyzed. Using XRD, FE-SEM, HR-TEM and FT-IR spectroscopy, their structure and morphology were analyzed. The thermal stability, surface area and porosity of the Cu3(MoO4)2(OH)2 nanoflowers were analyzed by TGA and BET. XRD analysis showed that the Cu3(MoO4)2(OH)2 nanoflowers have a pure monoclinic structure. The morphological analysis showed that the Cu3(MoO4)2(OH)2 nanoflowers are ∼10 μm in size, which are formed from self-assembly of thin nanosheets with a thickness of ∼20 nm. TGA indicated that the Cu3(MoO4)2(OH)2 nanoflowers are stable materials up to 328 °C and the isotherm from BET analysis indicated that the Cu3(MoO4)2(OH)2 nanoflowers are non-porous materials. The BET surface area of the synthesized Cu3(MoO4)2(OH)2 nanoflowers was found to be 21.357 m2 g−1. Moreover, the effects of the pH value and reaction time on the morphology of the Cu3(MoO4)2(OH)2 nanoflowers were studied and their optimization was performed. The results of the optimization study indicated that the reaction time and pH are two important parameters influencing the nucleation, growth, morphology, and synthesis mechanism. These flower-shaped Cu3(MoO4)2(OH)2 nanostructures are promising precursors for preparing molybdenum oxide materials which have various applications and can be synthesized in a very simple one-pot reaction system using commonly available chemicals without using a complex route.


융합소재연구센터 Synthesis of cosmetic grade TiO2-SiO2 core-shell powder from mechanically milled TiO2 nanopowder for commercial mass production

· 저자

Basudev Swain, 박재량, 박경수, 이찬기


TiO2 nanoparticles as an active sunscreen ingredient generate reactive oxygen species (ROS) upon UVA irradiation which is cytotoxic, genotoxic and potential to damage the DNA. The health concern and potential risks from TiO2 can be mitigated by shielding the particles through the suitable coating. Considering the advantages of SiO2, SiO2 coated TiO2 nanoparticles can be a potential material which can replace TiO2 for thickening, whitening, lubricating, and sunscreen ingredient in cosmetics. This article reports the synthesis of cosmetic grade TiO2-SiO2 core-shell nanopowder from mechanically milled TiO2 nanopowder for commercial mass production. From commercial TiO2 nanopowder was fabricated through size reduction by nanoset milling. Followed by the fabricated TiO2 nanopowder coated with SiO2 through sol-gel technique. A suitable optimum condition was explored for cosmetic grade TiO2-SiO2 core-shell nanopowder. Various physical properties and optical properties were analyzed. Synthesized of cosmetic grade TiO2-SiO2 core-shell nanopowder found to be at 100 nm size, with a homogeneous SiO2 coating having UVA protection factor 39 and sun protection factor (SPF) is 42. From the size, safety, and SPF perspective it can be an excellent cosmetic grade powder and from process simplicity perspective it can be commercially viable.


융합소재연구센터 One-pot wet chemical synthesis of fluorine-containing TiO2 nanoparticles with enhanced photocatalytic activity

· 저자

이덕희, Basudev Swain, 신동윤, 안낙균, 박재량, 박경수


Two types of TiO2 nanoparticles: i) fluorine-containing TiO2 (F-TiO2) and ii) fluorine-free TiO2 (H-TiO2) nanoparticles, were prepared through a simple, scalable wet-chemical synthesis process, and a comparative study of their photocatalytic properties was conducted. This facile process begins with a one-pot precipitation process at 90 °C, followed by heat treatment at 600 °C for 1 h in air, resulting in hierarchical, sphere-like, mesoporous structures composed of primary nanoparticles. The microstructural features and crystallographic structures of both types of nanoparticles were systematically investigated by X-ray diffraction, thermogravimetric/differential thermal analysis, X-ray photoelectron spectroscopy, N2 physical adsorption-desorption, field emission scanning electron microscopy, and transmission electron microscopy analyses. The photocatalytic activities were also evaluated by measuring the degradation of MB. The F-TiO2 nanoparticles showed enhanced photocatalytic activity compared to H-TiO2, which can be attributed to adsorbed fluorine on the surface which leads to various positive effects on the photocatalytic degradation reactions.


플랜트공정개발센터 알카라인 연료전지 가스확산층 내구성 향상을 위한 초발수 코팅 최적화 연구

· 저자

엄성현,김숭연 서민혜


본 연구에서는 알카라인 연료전지 환원극 가스확산층에 내열화학성이 우수한 초발수 성능을 부여하기 위하여 PDMS 코팅 공정을 최적화하였다. 성격이 상이한 두 개의 상용 가스확산층을 선택하였으며, 소재의 열적 안정성을 검토하여 코팅 온도를 최적화하고, PDMS 점도를 제어하여 코팅 균일성을 확보하고자 하였다. PDMS 전구체의 점도와 관계없이 200 ℃ 부근에서 코팅하게 되면 모든 확산층 표면에서 높은 초발수 성능을 나타내었다. 가혹실험 조건에서 초발수 성능 변화를 측정한 결과 1000 CS PDMS를 이용하여 28BC 가스확산층에 코팅한 경우가 가장 높은 내구성을 나타내었다.


플랜트공정개발센터 온도조절 화학기상증착법을 활용한 대용량 허니컴 구조촉매 제조 연구

· 저자

엄성현,서민혜,김숭연,김영독


본 연구에서는 대용량 구조 촉매의 제조 및 활용 가능성을 확인하고자 셀 밀도가 높은 세라믹 허니컴 구조체와 온도조절 화학기상증착법을 활용하여 촉매를 제조하고 건식 개질 반응에 대한 촉매 활성을 평가하였다. 셀 밀도 600 cpsi 코디어라이트 허니컴(CDR)을 대상으로 니켈을 코팅한 NiO/CDR 촉매는 코팅 조건과 시간을 조절함으로써 허니컴 구 조체 셀 내부까지 충분한 균일 증착이 가능하였다, 800 ℃, 공간속도 10,000 h-1과 CH4와 CO2를 1 : 1로 주입한 조건에서 CH4는 약 83%, CO2는 약 90% 이상의 우수한 전환율을 보여 건식 개질 반응에 효과적으로 적용이 가능하다는 것을 확인하였다. 이 결과를 토대로 대면적, 대용량 촉매 제조 시 온도조절 화학기상증착법이 매우 유용하게 활용될 수 있음을 확인하였다.


플랜트공정개발센터 산화철 허니컴 구조 촉매를 활용한 일산화탄소 저온 산화반응 연구

· 저자

엄성현,이동헌


코디어라이트 허니컴 표면에 알루미나 워시코트 지지체를 형성시키고 비교적 단순한 건식 코팅 공정으로 산화철 촉 매를 코팅함으로써 실제 환경에 효과적으로 적용이 가능한 모노리스 구조 촉매를 제조하였다. 허니컴 통로 벽 구석으로 형성된 워시코트 알루미나 미세 기공으로 균일하게 코팅된 산화철 촉매를 확인하였으며, 일산화탄소 산화 반응에 적용하기 위하여 산화철 촉매의 열처리 효과를 검증하였다. 350 ℃ 부근에서 처리한 산화철 촉매가 가장 우수한 촉매 성능을 발휘하였고, 200 ℃ 이상의 온도 영역에서 100% 전환율을 나타내었다.


플랜트공정개발센터 Highly stable barium zirconate supported nickel oxide catalyst for dry reforming of methane: From powders toward shaped catalysts

· 저자

엄성현,서민혜,김숭연


We report the barium zirconate supported NiOx catalysts (NiOx/BZO) for dry reforming of methane and feasibility test for their industrial application by using temperature-regulated chemical vapor deposition together with extrusion. Nickel oxide nanoparticles are well deposited and dispersed on BZO powders as well as structures in a gear form, showing high catalytic activity and extraordinary stability even at relatively lower temperature and higher space velocity. The NiOx/BZO catalyst are highly coke resistant for 50 h operation with almost negligible agglomeration of NiOx nanoparticles. Judging from XPS and high ion conducting properties of BZO supports, the eOH or eO species are expected to play an important role in promoting the self-decoking of surface carbon species to form CO and CO2.


지능기계시스템센터 Acoustic emission characteristics of stress corrosion cracks in a type 304 stainless steel tube

· 저자

Woonggi Hwang, Seunggi Bae, Jaeseong Kim, Sungsik Kang, Nogwon Kwag, Boyoung Lee


Acoustic emission (AE) is one of the promising methods for detecting the formation of stress corrosion cracks (SCCs) in laboratory tests. This method has the advantage of online inspection. Some studies have been conducted to investigate the characteristics of AE parameters during SCC propagation. However, it is difficult to classify the distinct features of SCC behavior. Because the previous studies were performed on slow strain rate test or compact tension specimens, it is difficult to make certain correlations between AE signals and actual SCC behavior in real tube-type specimens. In this study, the specimen was a AISI 304 stainless steel tube widely applied in the nuclear industry, and an accelerated test was conducted at high temperature and pressure with a corrosive environmental condition. The study result indicated that intense AE signals were mainly detected in the elastic deformation region, and a good correlation was observed between AE activity and crack growth. By contrast, the behavior of accumulated counts was divided into four regions. According to the waveform analysis, a specific waveform pattern was observed during SCC development. It is suggested that AE can be used to detect and monitor SCC initiation and propagation in actual tubes.


지능기계시스템센터 The Effect of Welding Residual Stress for Making Artificial Stress Corrosion Crack in the STS 304 Pipe

· 저자

Jae-Seong Kim, Bo-Young Lee, Woong-Gi Hwang and Sung-Sik Kang


The stress corrosion crack is one of the fracture phenomena for the major structure components in nuclear power plant. During the operation of a power plant, stress corrosion cracks are initiated and grown especially in dissimilar weldment of primary loop components. In particular, stress corrosion crack usually occurs when the following three factors exist at the same time: susceptible material, corrosive environment, and tensile stress (residual stress included). Thus, residual stress becomes a critical factor for stress corrosion crack when it is difficult to improve the material corrosivity of the components and their environment under operating conditions. In this study, stress corrosion cracks were artificially produced on STS 304 pipe itself by control of welding residual stress. We used the instrumented indentation technique and 3D FEM analysis (using ANSYS 12) to evaluate the residual stress values in the GTAW area. We used the custom-made device for fabricating the stress corrosion crack in the inner STS 304 pipe wall. As the result of both FEM analysis and experiment, the stress corrosion crack was quickly generated and could be reproduced, and it could be controlled by welding residual stress


지능기계시스템센터 Characteristics of GMAW Narrow Gap Welding on the Armor Steel of Combat Vehicles

· 저자

Jae-Seong Kim and Hui-Jun Yi*


The primary purpose of this investigation was to study the characteristics of the armor steel weldment of combat vehicles by using GMAW narrow gap welding (NGW). The results showed that the mechanical properties and residual stress distribution of NGW weldment were improved, compared with conventional X-groove weldment. Additionally, ballistic tests according to MIL-HDBK-1941 were carried out to verify the ballistic ability of NGW weldment and the result showed that the NGW process was qualified for welding the armor steel of combat vehicle.


지능기계시스템센터 The study for direct SCC fabrication in STS 304 pipe

· 저자

Sung-Sik Kang, Jae-Seong Kim & Bo-Young Lee


Stress corrosion cracking is one of the aging phenomena for the major structure components in nuclear power plant. During the operation of a power plant, stress corrosion cracks are initiated and grown especially in dissimilar weldment of primary loop components. Among the three factors (susceptible material, residual stress, and corrosive environment) which make the SCC, the residual stress becomes a critical factor for stress corrosion crack when it is difficult to improve the material of the components and their environment under operating conditions. In this study, stress corrosion cracks were artificially produced on STS (stainless steel) 304 pipe itself by control of welding residual stress. The instrumented indentation technique and 3D finite element method (FEM) analysis (using ANSYS 12) were used to evaluate the residual stress values in the GTAW area. As the result of both FEM analysis and experiment, the stress corrosion crack was quickly generated and could be reproduced, and controlled by welding residual stress. Also non-destructive evaluation signals by Acoustic Emission will be discussed for the initiation and growth of SCC.


지능기계시스템센터 A Study on the Cooling Performance of Newly Developed Slice Die in the Hot Press Forming Process

· 저자

Seung Hwan Lee, Jaewoong Park, Kiyoung Park, Dong Keun Kweon, Hyunwoo Lee, Daeho Yang, Hongrae Park and Jaeseung Kim*


The cooling performance of a slice die is studied numerically and experimentally. The slice die is designed to improve the cooling performance compared to that of a conventional die that is generally used in the Hot Press Forming (HPF) process by modifying the cooling channel layout and arrangement. In order to understand the physical phenomenon of the slice die cooling performance, the cooling performance of the conventional die is also simulated and their results are compared with the slice die results. From the results of the maximum temperature of the blank and die and the temperature distribution of the blank, the slice die has considerably improved cooling performance. To validate the simulation results, the slice die is prototyped and a blank is produced by the HPF process. Blank temperatures are measured by a thermal imaging camera at several holding times. The simulation and experimental results of the blank temperatures are compared and agree with the error rate of 3%. In order to verify the quality of the produced blank, ultimate tensile stress, yield stress, and elongation tests are conducted for specimens that are extracted from the blank and are compared with existing literature results.


지능기계시스템센터 Development of two-dimensional piezoelectric laser scanner with large steering angle and fast response characteristics

· 저자

Ho-Sang Kim, Dae-Hee Lee, Deok Jae Hur and Dong-Chan Lee


We describe a two-dimensional piezoelectric laser scanner designed and tested to ob-tain the large steering angle of 1 degree and fast response characteristics with 200 Hz. To overcome the relatively small expansion capability of piezoelectric actuator, the displacement amplification mechanisms with two levers in series are employed to magnify the end tip of the lever which is connected to the 0.5-inch glass mirror. For fast response characteristics, the natural frequencies of the hinge mechanisms were calculated by using finite element analysis technique. In order to evaluate the perfor-mance of the proposed scanner, the hinge mechanism has been manufactured of titani-um alloy and by exciting the actuator, the natural frequencies have been estimated. Al-so, the actual machining test in the burning paper has been done by using high power laser and it is shown that the proposed laser scanner is capable of steering the laser beam in 1 degree and with frequency of 200 Hz successfully.


지능기계시스템센터 Random Vibration Analysis of the Tip-tilt System in the GMT Fast Steering Secondary Mirror

· 저자

Kyoung-Don Lee, Young-Soo Kim, Ho-Sang Kim, Chan-Hee Lee, and Won Gi Lee


A random vibration analysis was accomplished on the tip-tilt system of the fast steering secondary mirror (FSM) for the Giant Magellan Telescope (GMT). As the FSM was to be mounted on the top end of the secondary truss and disturbed by the winds, dynamic effects of the FSM disturbances on the tip-tilt correction performance was studied. The coupled dynamic responses of the FSM segments were evaluated with a suggested tip-tilt correction modeling. Dynamic equations for the tip-tilt system were derived from the force and moment equilibrium on the segment mirror and the geometric compatibility conditions with four design parameters. Statically stationary responses for the tip-tilt actuations to correct the wind-induced disturbances were studied with two design parameters based on the spectral density function of the star image errors in the frequency domain. Frequency response functions and root mean square values of the dynamic responses and the residual star image errors were numerically calculated for the off-axis and on-axis segments of the FSM. A prototype of on-axis segment of the FSM was developed for tip-tilt actuation tests to confirm the ratio of tip-tilt force to tip-tilt angle calculated from the suggested dynamic equations of the tip-tilt system. Tip-tilt actuation tests were executed at 4, 8 and 12 Hz by measuring displacements of piezoelectric actuators and reaction forces acting on the axial supports. The derived ratios of rms tip-tilt force to rms tip-tilt angle from tests showed a good correlation with the numerical results. The suggested process of random vibration analysis on the tip-tilt system to correct the wind-induced disturbances of the FSM segments would be useful to advance the FSM design and upgrade the capability to achieve the least residual star image errors by understanding the details of dynamics.


지능기계시스템센터 Diamond turning of large off-axis aspheric mirrors using a fast tool servo with on-machine measurement

· 저자

Ho-Sang Kim, Eui-Jung Kim and Byung-Suk Song


We describe a systematic approach of diamond turning which has been devised to fabricate large aspheric off-axis mirrors demanded for the construction of three-mirror-anastigmatic telescopes. To obtain sub-micrometer form accuracy, the machine axes errors are compensated for real time using a fast tool servo driven by a piezoelectric actuator along with an on-machine measurement scheme. Besides, a special chucking device is used to mount the mirror substrate on the spindle with a required large offset to the axis of rotation, which has been specially designed to minimize elastic deformation caused by centrifugal inertia and clamping force. Actual machining data are discussed in detail to prove that the proposed approach is capable of fabricating aluminum mirrors of 620 mm diameter to a form accuracy of 0.7 m in peak-to-valley error value. Key words: Diamond turning, large off-axis aspheric mirrors, real-time error compensation, fast tool servo, on-machine measurement, three-mirror-anastigmatic telescopes.


지능기계시스템센터 Feed-forward control of fast tool servo for real-time correction of spindle error in diamond turning of flat surfaces

· 저자

Ho-Sang Kim and Eui-Jung Kim


We describe a fast tool servo designed and tested to obtain sub-micrometer form accuracy in diamond turning of flat surfaces. The thermal growth spindle error is compensated for real time using a fast tool servo driven by a piezoelectric actuator along with a capacitive displacement sensor. To overcome the inherent non-linearity of the piezoelectric actuator, Proportional Integral (PI) feedback control with a notch filter is implemented. Besides, feed-forward control based on a simple feed-forward predictor is added to achieve better tracking performance. Actual machining data are discussed in detail to prove that the proposed fast tool servo is capable of fabricating flat aluminum specimens of 100 mm in diameter to a form accuracy of 0.10 m in peak-to-valley error value. Key words: Fast tool servo, diamond turning, real-time error compensation, feed-forward control, piezoelectric actuator.


지능기계시스템센터 Fabrication of free-form surfaces using a long-stroke fast tool servo and corrective figuring with on-machine measurement

· 저자

Ho-Sang Kim, Kwang-Il Lee, Kyoung-Min Lee, Young-Bong Bang


Fabrication of free-form surfaces that are frequently demanded for the construction of optical imaging systems is described. To obtain a tool motion with large amplitude and high bandwidth, a novel long-stroke fast tool servo is proposed and installed on the Z-axis of a diamond turning machine as an additional synchronized axis. In addition, a special on-machine measurement device is used to measure the optical parameters of the machined surface and to compensate for the residual form errors that are commonly produced in the diamond turning process. Actual machining test results show that the proposed procedures are capable of generating the copper free-form mirrors of 50 mm diameter to a form accuracy of 0.15 m in peak-to-valley value error. Key words: Long-stroke fast tool servo, diamond turning, free-form surface, on-machine measurement, corrective figuring.


지능기계시스템센터 Effects of Hospital Ward Curtains on Ventilation in a Four-bed Hospital Ward

· 저자

Jung-Hun Noh, Jungsuk Lee, Kwang-Chul Noh, Young-Won Kim, Se-Jin Yook


Various highly infective pathogens that are present in hospital wards can spread through the air and infect patients. To remove pathogens effectively in order to reduce infections, the efficient ventilation of hospital wards is critical. This study used age of air data to analyze the ventilation efficiency within hospital wards. The validity of the numerical analysis method was verified by comparison with the age of air data obtained from an experimental test on a four-bed hospital ward. The verified numerical analysis method was used to establish the airflow within a hospital ward in relation to the use of ventilation systems, air cleaners, and individual patient curtains. The efficiency of ventilation according to each factor was compared using age of air data. Considerable differences in the age of the air were identified, depending on the location of the patient with respect to both the air cleaner and the inlet/outlet duct of the ventilation system. Furthermore, individual curtains were found to interfere with air circulation, reducing ventilation efficiency and increasing the age of the air at the location of each patient.