• 한국공작기계학회논문집
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• 제15권1호
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• pp.119-126
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• 2006

The finishing process of die requires the processing technique of a height efficiency and precision. Because the precision of die gives the quality of goods the influence directly. The hydro-static polishing device employs the hydro-static axis and is able to polish the structure of complex picture under the constant pressure and is got constant surface roughness at all polished plane. Therefore, In order to polish precision sculptured surface, it was used the hydro-static polishing device. Polishing device's polishing characteristic is estimated by polishing conditions which are size of abrasive, material of tools. And, because the surface quality of workpiece depends on polishing pattern which relates to motion of abrasive grain. The polishing characteristic according to polishing pattern was evaluated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.59-60
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• 2006

The slurry stability and removal rate during recycling of slurry in silicon wafer polishing was studied. Average abrasive size of slurry was not changed with recycling time, however, large particles appeared as recycling time increased. Large particles were related foreign substances from pad or abraded silicon flakes during polishing. The removal rate as well as pH of slurry was decreased as recycling time increased. It suggests that the consumption of OH ions during recycling is the main cause of decrease of removal rate. Therefore, it is important to control pH of slurry to obtain optimum removal rate during polishing.

• 대한금속재료학회지
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• 제49권7호
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• pp.522-529
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• 2011

Carbon fiber reinforced plastics (CFRP), which have been developed for their high mechanical properties, are insufficient to secure machinery. This paper investigates the use of magnetic abrasive finishing methods and the characteristics of surface roughness for mirror machining of CFRP. The cylindrical surface of CFRP was ground using a diamond paste with sizes of 0.1, 0.5, 1 and 6${\mu}m$. Consequently, an effective surface roughness of 0.03${\mu}m(R_a)$ could be obtained via a paste size of 0.5${\mu}m$. The surface roughness was not improved due to epoxy abrasion between the carbon fiber and the epoxy.

• Nano
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• 제13권12호
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• pp.1850144.1-1850144.13
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• 2018

A nano-$MoS_2$/montmorillonite K-10 (K10) composite was prepared and characterized. The composite contains two types of 2H-$MoS_2$ nanoparticles. One is the hollow spherical $MoS_2$ with a size range of 75 nm, and the other is the spherical nano cluster of $MoS_2$ with a size range of 30 nm. The two kinds of nano-$MoS_2$ were formed via assembly of numerous $MoS_2$ nano-platelets with a size of ~10 nm. A tribological comparison was then made among nano-$MoS_2$/K10, K10, nano-$MoS_2$ and a mechanical mixture of K10 and nano-$MoS_2$. K10 reduced the wear but slightly increased the friction. Nano-$MoS_2$ remarkably reduced both friction and wear. The mechanical mixture demonstrated better wear resistance than nano-$MoS_2$, indicating a synergistic anti-wear effect of nano-$MoS_2$ and K10. The synergistic effect was reinforced using nano-$MoS_2$/K10 instead of the mechanical mixture. A part of the $MoS_2$ in the contact region always lubricated the friction pair, and the rest formed a tribofilm. K10 segregated the friction pair to alleviate the ablation wear but magnified the abrasive wear. S-$MoS_2$ protects K10 and they together function as both a lubricant and an isolating agent to reduce the ablation and abrasive wear.

• Journal of Astronomy and Space Sciences
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• 제21권2호
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• pp.141-152
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• 2004

우주망원경용 비구면 반사경 가공 공정은 고정입자 연삭, 자유입자 래핑, 연마의 순서를 따른다. 숙련공에 의한 경험적 공정조절에 의해 목표 비구면을 가공하는 전통적 연삭 공정에서는 수 ${mu}m$ 높이의 표면 밑 손상을 남기며 뒤이은 자유입자 래핑 및 연마 공정에서 이를 제거하며 가공한다. 본 연구는 컴퓨터 수치 제어 연삭 공정진화 모델을 개발하여, 연삭가공을 통해 반사경 표면조도 최소 40nm이하, 가공 예측정확도 20nm급을 이루었다. 구체적인 방법론으로 초정밀가공기의 연삭모듈을 이용하여 연삭 휠 입자의 크기, 이송속도, 공작물 회전선속도 등 연삭 변수를 변화시키며 직경 20, 100mm Zerodur 소재를 초기 연삭하였다. 초기 연삭 변수와 측정된 표면조도와의 관계를 경험적 해석과 다 변수 회귀분석 해석 방법을 통하여 공정조절용 수치 연삭 모델을 구성하였다. 정량적 공정제어는 입력된 연삭변수들로부터 가공 후 표면조도를 예측하고, 측정된 표면조도를 이용하여 수치연삭 모델을 개량한 후 다음 가공에서 측정될 표면조도를 예측하는 순으로 만복 진행되었다. 본 연구에서는 CNC 연삭공정조절로부터 최소 평균 표면조도 36nm, 예측정확도 ${pm}20nm$를 얻었다. 이 연구결과는 정량적 연삭공정제어 모델을 사용하여 자유입자 래핑 공정을 수행할 필요 없이 연삭에서 직접 연마 공정으로 진행할 수 있는 획기적인 공정 효율 향상을 의미한다.

• 한국세라믹학회지
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• 제42권1호
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• pp.37-42
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• 2005

유리연마슬러지와 graphite를 발포제로 사용하여 경량골재를 제조하였으며, 경량골재 내부기공과 물성과의 상관성을 도출하였다. 이때 graphite 함량을 각각 달리하여 성구를 제조하였으며, $700^{circ}C$ 및 $800^{circ}C$에서 20분 동안 소성하였다. 소성 전후 골제의 부피 변화를 검토한 결과, 발포제의 첨가량보다는 소성 온도가 즘 더 큰 영향을 미침을 확인하였다 기공의 크기 및 면적은 발포제 첨가량과 소성 온도 상승에 따라 증가하는 특징을 나타내었으나, 발포제 첨가량 $1\%$ 이상에서는 큰 폭의 증가를 동반하지 않았다. 흡수율/열전도율과 기공과의 상관성은 매우 높아, 각각의 상관관계계수는 $0.8\pm$ 이상을 나타내었다.

• Tribology and Lubricants
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• 제39권2호
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• pp.72-75
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• 2023

Silicon carbide (SiC) is used as a substrate material for power semiconductors; however, SiC chemical mechanical polishing (CMP) requires considerable time owing to its chemical stability and high hardness. Therefore, researchers are attempting to increase the material removal rate (MRR) of SiC CMP using various methods. Mixed-abrasive CMP (MAS CMP) is one method of increasing the material removal efficiency of CMP by mixing two or more particles. The aim of this research is to study the mathematical modeling of the MRR of MAS CMP of SiC with SiO₂ and TiO₂ particles. With a total particle concentration of 32 wt, using 80-nm SiO₂ particles and 25-nm TiO₂ particles maximizes the MRR at 8 wt of the TiO₂ particle concentration. In the case of 5 nm TiO₂ particles, the MRR tends to increase with an increase in TiO₂ concentration. In the case of particle size 10-25 nm TiO₂, as the particle concentration increases, the MRR increases to a certain level and then decreases again. TiO₂ particles of 25 nm or more continuously decreased MRR as the particle concentration increased. In the model proposed in this study, the MRR of MAS CMP of SiC increases linearly with changes in pressure and relative speed, which shows the same result as the Preston's equation. These results can contribute to the future design of MAS; however, the model needs to be verified and improved in future experiments.

• Tribology and Lubricants
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• 제18권3호
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• pp.204-210
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• 2002

Automotive brake pads with four different sizes of zircon particles (average sizes of 1㎛, 6㎛, 75㎛, and 140㎛, respectively) were investigated to evaluate the size effect of abrasive particles on friction performance. Results showed that the brake pads with the larger size of zircon particles tend to show better frictional stability and low pad wear. However, the rotor surface was severely abraded in the case of using larger zircon particles. On the other hand, the small zircon particles in the pads showed the fast increase of the coefficient of friction with friction force oscillation and the tendency was pronounced at low sliding speeds. The brake pads with small particle sizes also exhibited strong fade phenomena at elevated temperatures.

• 한국세라믹학회지
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• 제46권3호
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• pp.249-252
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• 2009

Nanocrystalline ceria particles were prepared by using the ultrasonic spray pyrolysis method. The prepared ceria particles were found to be spherical and non-agglomerated by the SEM and TEM analyses. It was found that carrier gas influences the size and morphology. It was found that the air stream of carrier gas results in porous agglomerated structure of ceria abrasives, whereas solid nano-sphere can be obtained in a more oxidizing atmosphere.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.201-202
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• 2002

The abrasive wear behaviour of $Al_2O_3$ particle-reinforced aluminium composite was investigated. The wear rate of the composite and the matrix alloy has been expressed in terms of the applied load, sliding distance and particle size using linear factorial design approach.