• 공업화학
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• 제23권6호
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• pp.567-571
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• 2012

전통회화의 변색은 온도, 습도, 빛, 그리고 대기 오염에 의한 각종 화학 물질들과 사용된 무기 안료와의 화학반응에 의해 일어나기도 한다. 본 연구에서는 조선종이라고 불리는 한지에 석록, 석청 무기 안료를 사용해 전통방법으로 시험편을 제작하고, 인위적인 노화시험을 통해 안료와 환경 요인의 상호 작용에 의한 노화과정을 조사하였다. 석청은 XRD 및 TGA 결과로부터 내후성 시험의 습기와 내염수 시험의 염무에 의해 영향을 받는 것을 알 수 있었다. 하지만 석록은 내후성 시험이나 내자외선 시험 중 주로 자외선에 의해 화학적 변화가 일어나는 것을 색차 및 TGA 결과로부터 볼 수 있었다.

• 한국방재학회 논문집
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• 제9권1호
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• pp.99-105
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• 2009

본 연구에서는 2006년 집중호우로 인해 발생한 토석류 관련 수해 및 그에 대한 복구현황에 대한 분석을 실시하였다. 이를 위해 문헌조사 및 현장답사를 통해서 2006년에 발생한 토석류의 특성, 이로 인한 수해 및 복구현황 등을 분석하였다. 2006년 강우기간 동안 최대시우량 113.5 mm, 1일 최대 강우량 355 mm의 호우가 발생하였는데 이는 80-500년의 강우빈도에 해당된다. 분석 결과에 의하면 수해의 대부분은 사면유실로부터 기인한 토석류에 의해서 발생하였다. 수해기간 동안의 강수량 자료에 대한 분석결과 강우강도와 수해 발생시점은 직접적인 관계가 있는 것으로 나타났다. 현재 수해와 관련되어 계곡부에 사방댐 및 자연 사면에 대해 사면보호공이 실시되어 있다. 본 연구에서 분석된 결과를 통하여 현행 사면수해 복구 및 관리와 관련된 문제점에 대해 대안을 제시하고자 한다.

• 한국표면공학회지
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• 제45권3호
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• pp.111-116
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• 2012

Oblique angle deposition (OAD) is a physical vapor deposition method which utilizes non-normal angles between the substrate and the vaporizing source. It has been known that tilting the substrate changes the properties of the film deposited on it, which was thought to be a result of morphological change of the film. In this study, OAD has been applied to prepare single and multilayer Al films by magnetron sputtering. The magnetron sputtering source of 4 inch diameter was used to deposit the films. Al films have been deposited on Si wafers and cold-rolled steel sheets. The multilayer films were prepared by changing the tilting angle upside down at each layer interval, which means that when the first layer was deposited at an angle of $+45^{\circ}$, the second layer was deposited at an angle of $-45^{\circ}$, and vice versa. The microstructure, surface roughness and reflectance of the films were investigated using a scanning electron microscope, a surface profiler and a spectrophotometer, respectively. The corrosion resistance was measured and compared using the salt spray test. The single layer film prepared at an oblique angle of $60^{\circ}$ prepared at other angles. However, for the multilayer films, the film prepared at an oblique angle of $45^{\circ}$ showed the most compact and featureless structure. The multilayer films were found to exhibit higher corrosion resistance than the single layer films.

• 대한금속재료학회지
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• 제48권6호
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• pp.506-513
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• 2010

The composite coatings of $(ZrO_2-8Y_2O_3)$/(Ni-22Cr-10Al-1Y) were prepared by the air plasma spraying method. They consisted of (Ni,Cr)-rich regions,$(ZrO_2-Y_2O_3)$-rich regions, and $Al_2O_3$-rich regions that were formed by oxidation of Al from (Ni-22Cr-10Al-1Y) during spraying. The coatings corroded at 800 and $900^{\circ}C$ in NaCl-$Na_2SO_4$ molten salts up to 50 hr. Ni, Cr and Al oxidized to NiO, $Cr_2O_3$ and ${\alpha}-Al_2O_3$, respectively. These oxides and $(ZrO_2-Y_2O_3)$ were dissolved off into the molten salts during hot corrosion, which resulted in the ever-lasting corrosion of the composite coatings. Chromium diffused out from the (Ni,Cr)-rich regions and oxidized to $Cr_2O_3$, which was most frequently found as surface scales. Aluminum retained in the (Ni,Cr)-rich regions were similarly diffused out.

• 방사선산업학회지
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• 제3권1호
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• pp.7-11
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• 2009

Hard magnet was usually used by coating $SiO_2$ ceramic thick films followed by the thermal annealing process. In this work, the alternative annealing process for NdFeB magnets using e-beam sources (1~2 MeV, 50~400 kGy) was investigated. NdFeB magnets was coated with ceramic thick films using the spray method. The optimal annealing parameter for e-beam source reveals to be 1 MeV and 300 kGy. The sample prepared at 1 MeV and 300 kGy was characterized by the analysis of the surface morphology, film hardness, adhesion and chemical stability. The mechanical property of thick film, especially film hardness, is better than that of thermal annealed samples at $180^{\circ}C$. As a result, e-beam annealing process will be one of candidate and attractive heat treatment process. In future, manufacturing process will be carried out in cooperation with the magnet company.

• Tribology and Lubricants
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• 제34권6호
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• pp.217-225
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• 2018

In this study, we spray a Ni-Cr composite powder onto AISI 4340 steel using the high velocity oxygen fuel method. We subsequently subject the Ni-Cr coating (as-sprayed) to ultrasonic nanocrystal surface modification (UNSM) process to improve the tribological performance. This study aims at increasing the wear resistance and durability of the Ni-Cr coating by altering the surface integrity and microstructure via the UNSM process. The UNSM process reduces the surface roughness of the as-sprayed coating by about 64%, which is explained by observing the elimination of high peaks and valleys and filling up micro-pores. Furthermore, a change in the microstructure of the coating due to continuous high-frequency strikes to the surface by a tip can lead to an increase in hardness from about 48 to 60 HRC. Furthermore, we investigate the characterization of the friction and wear behavior of Ni-Cr coating by a ball-on-disc tribometer in the dry conditions. We determine that after the UNSM process, there is a significant reduction in the friction coefficient of the as-sprayed coating from approximately 1.1 to 0.75. This is owing to the increased hardness and smoothed surface roughness. In addition, we investigate the surface morphology and wear track of the coatings before and after the UNSM process using a scanning electron microscope, energy dispersive spectrometer, and three-dimensional laser scanning microscope. We observe that the wear track of the Ni-Cr coating after the UNSM process is lower than that of the as-sprayed one. Thus, we confirm that the UNSM process has a significant influence on the improvement of the tribological performance of the Ni-Cr composite coating.

• 한국기계가공학회지
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• 제20권10호
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• pp.19-26
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• 2021

In fine-particle injection processing, hard fine particles, such as silicon carbide or aluminum oxide, are injected - using high-pressure air, and a small amount of material is removed by applying an impact to the workpiece by spraying at high speeds. In this study, a two-axis stage device capable of sequence control was developed to spray various shapes, such as circles and squares, on the surface during the micro-particle jetting process to understand the surface-shape micro-particle-processing characteristics. In the experimental device, two stepper motors were used for the linear movement of the two degree-of-freedom mechanism. The signal output from the microcontroller is - converted into a signal with a current sufficient to drive the stepper motor. The stepper motor rotates precisely in synchronization with the pulse-signal input from the outside, eliminating the need for a separate rotation-angle sensor. The major factors of the processing conditions are fine particles (silicon carbide, aluminum oxide), injection pressure, nozzle diameter, feed rate, and number of injection cycles. They were identified using the ANOVA technique on the design of the experimental method. Based on this, the surface roughness of the spraying surface, surface depth of the spraying surface, and radius of the corner of the spraying surface were measured, and depending on the characteristics, the required spraying conditions were studied.

• 유기물자원화
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• 제27권1호
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• pp.33-38
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• 2019

본 연구는 전국적으로 운영되고 있는 음식물류 폐기물 공공자원화 시설 중에서 초기에 제시된 운전조건과 맞지 않게 비정상적으로 운전되고 있는 DDM환경자원센터의 탈취시설을 대상으로 하여 실시하였다. DDM환경자원 센터의 비정상적인 탈취시설에 대한 쟁점사항은 퇴비화시설내부의 탈취와 실내공기질 문제 및 시설 전반적인 탈취문제이며 특히 축열식 연소장치(RTO)의 운전 중 정지되는 현상과 세정탑 내 살수 불량현상 등으로 나타났다. 이러한 비정상적인 운전시설을 정상적 운전시설로 전환하기 위한 개선방안 및 대안으로는 발효조 상부의 전면필터 제거와 분진제거용 스크레버, 기수분리기, 롤필터 등의 설치를 제안하고자 한다.

• 한국분무공학회지
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• 제23권4호
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• pp.227-233
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• 2018

An automobile is composed of a combination of a lot of parts, and it is difficult to maintain the same performance from a new car until it's scrapped. Greenhouse gases included in automobile emissions are typically carbon dioxide and methane. It is expected that this greenhouse gas will change depending on the aging (cumulative mileage) of the automobile However, the greenhouse gas characteristics by cumulative mileage lack of actual data due to time and economic difficulties. Therefore, in this paper, we selected automobile with high sales by displacement in korea and carbon dioxide and methane were measured by using method of the related law. The cumulative mileage is as follows; within 160 km (Statutory mileage by 2010), 6500 km (current statutory mileage), 15000 km (approximately 1-year average mileage of Non-business passenger vehicle). As a result of the test, the emission of carbon dioxide and methane was the smallest at 6,500 km, and increased in order of 15000 km, within 160 km. Also, it was confirmed that the $CO_2$ emission change of a large displacement automobile is more smaller at each mileage. Although the greenhouse gas tends to increase as the mileage of the vehicle, it is thought that additional confirmation is required of since 15,000 km as well, because it can occur deviations due to taming process or mechanical friction of the automobile.

• 한국수소및신에너지학회논문집
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• 제29권6호
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• pp.635-641
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• 2018

To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.