• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.222-222
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• 2003

나노크기 금속입자가 분산된 세라믹 나노복합재료는 향상된 기계적 특성과 함께 독특한 전기적, 자기적 특성을 보여주어 새로운 기능성 재료로의 응용가능성을 갖고 있다. 그러나 소결 중의 반응이나 입자성장 등으로 형성된 반응상 또는 조대한 입자상이 세라믹 기지의 입계 등에 존재한다면, 나노크기 금속상 분산에 의한 기계적 특성의 향상과 독특한 기능성 부여라는 장점들이 없어지게 된다. 따라서 요구되는 특성을 구현할 수 있는 금속분산 나노복합재료의 제조를 위해서는 미세조직 제어를 위한 최적의 제조공정 확립과 미세조직과 특성 등의 관계에 대한 연구가 요구된다. 본 연구에서는 기지상으로 A1$_2$O$_3$를, 분산상으로는 저융점 금속이며 일반적인 A1$_2$O$_3$의 가압소결시에 (약 140$0^{\circ}C$) 액상으로 존재하는 금속 Cu를 선택하여 조성이 5 vol% Cu가 되도록 복합재료를 제조하였다. $Al_2$O$_3$와 CuO 원료분말들은 습식 및 건식 볼 밀링을 통하여 균일한 분말혼합체로 제조되었다. 혼합분말은 열간가압소결기 내에 장입한 후 35$0^{\circ}C$에서 30분 동안 H$_2$가스를 흘려주며 CuO를 Cu로 환원 처리하였다. 계속해서 H$_2$분위기를 유지하며 승온한 후, 각각 1000-145$0^{\circ}C$에서 분위기를 Ar 으로 치환하였다. 소결은 145$0^{\circ}C$에서 30 ㎫의 압력으로 1시간동안 행하였다 소결한 시편들은 직사각형 형태로 가공하였으며 표면은 0.5$\mu\textrm{m}$의 다이아몬드 입자로 연마하였다. XRD, SEM 및 TEM을 이용하여 상분석 및 미세조직관찰을 행하였다. 파괴강도는 3중점 굽힘 법으로 (3-point bending test) 측정하였다. 이때 시편 하부의 지지 점간의 거리는 30mm, cross-head 속도는 0.5 mm/min으로 하였고 5개의 시편을 측정하여 평균값을 구하였다.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.8-12
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• 2010

TEM is a powerful tool for semiconductor material analyses in structure or biological sample in micro structure. TEM observation need to make to coincide specimens for special purpose. in this paper, we have experimented for minimum surface damage on bulk wafer and patterned specimen by various conditions such as accelerating energy, depth of ion beam, ion milling types, and etc. in various specimen preparation methods by FIB (Focus Ion Beam). The optimal qualified specimens are contain low mounts of surface damage(about 5 nm) on patterned specimen.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.1-7
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• 2011

Micromachining is gaining popularity due to recent advancements in MEMS(Micro Electro Mechanical Systems). Using conventional micromachining, it is relatively difficult to produce moving components in the order of microns. Photolithography for silicon material has high accuracy machining, but it has low aspect ratio. X-ray lithography has ultra high accuracy machining, but it has expensive cost. Micro-EDM(electro discharge machining) has been gaining popularity as a new alternative method to fabricate micro-structures. In this study, Micro-EDM machine is developed available for fabricate micro-structures and two processes such as side cut EDM and milling EDM is proposed. Several sets of experiment results have been performed to study the characteristics of the machining process.

• Journal of the Korean Vacuum Society
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• v.2 no.3
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• pp.304-313
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• 1993

집속 이온빔 기술은 고해상도의 이온빔 리토그라피, 마스크가 필요없는 이온주입, 그리고 Ion beam induced deposition 등 반도체 소자의 미세가공에 널리 이용되어 왔다. 좋은 안정도와 높은 전류밀도, 적은 에너지 퍼짐 그리고 낮은 에미턴스와 높은 선명도를 갖는 집속 이온빔 장비를 위한 액체 갈륨 이온원이 한국에서 개발 시업되었다. 이온빔의 전압이 15kV, 렌즈전압이 7kV 그리고 렌즈상단에 위치한 aperture의 직경이 0.2mm일 때, 0.1$mu extrm{m}$의 빔 직경으로 집속되는 정전 einzel렌즈가 설계 조립되었고, FIB 진공 chamber는 렌즈부와의 차 등 진공시스템으로 구성되어 설계제작되었다. FIB 장비가 조만간 한국에서 이온빔 밀링, ion beam induced deposition 그리고 잘못된 부분의 수정 등 반도체 제작공정에서의 응용에 큰 기여를 할 것이라 기대된다.

• Journal of Powder Materials
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• v.9 no.5
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• pp.329-335
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• 2002

Recently, the fabrication process of the W-Cu nanocomposite powders has been studied to improve the sinterability through the mechanical alloying and reduction of W and Cu oxide mixtures. In this study. the W-Cu composites were produced by mechanochemical process (MCP) using $WO_3-CuO$ mixtures with two different milling types of low and high energy, respectively. These ball-milled mixtures were reduced in $H_2$ atmosphere. The ball-milled and reduced powders were analyzed through XRD, SEM and TEM. The fine W-Cu powder could be obtained by the high energy ball-milling (HM) compared with the large Cu-cored structure powder by the low energy ball-milling (LM). After the HM for 20h, the W grain size of the reduced W-Cu powder was about 20-30 nm.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.334-339
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• 2004

Ultraprecision machining and MEMS technology have been taken more and more important position in machining of microparts. Micro endmilling is one of the prominent technology that has wide spectrum of application field ranging from macro parts to micro products. Also, the method of micro-grooving using micro endmilling is used widely owing to many merit, but has problems of precision and quality of products due to tool wear and tool fracture. This investigation deals with state monitoring using acoustic emission(AE) signal in the micro-grooving. Characteristic evaluation of AE raw signal, AE hit and frequency analysis for state monitoring is also presented in the paper.

• Journal of Powder Materials
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• v.5 no.3
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• pp.210-219
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• 1998

The W-Cu composite powders were synthesized from W and Cu elemental powders by ball-milling process, and their microstructural changes and sintering behaviors were evaluated. The ball milling process was carried out in a 3-dimensional mixer (Turbula mixer) using zirconic ($ZrO_2$) ball and alumina ($Al_2O_3$) vial up to 300 hrs. The ball-milled W-Cu powders revealed nearly spherical shape. Microstructure of the composite powders showed onion-like structure which consists of W and Cu shells due to the moving characteristic of Turbula mixer. The W and Cu elements in the composite powders milled for 300 hrs were homogeneously distributed, and W grain size in the ball-milled powder was smaller than 0.5 $\mu\textrm{m}$. Fe impurity introduced during ball milling process was very low as of 0.001 wt%. The relative sintered density of ball-milled W-Cu specimens reached about 94% after sintering at $1100^{\circ}C$.

• Tribology and Lubricants
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• v.27 no.1
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• pp.1-6
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• 2011

The possibility of Cu-Al-Ni intermetallic coating on the mild steel through the combustion synthesis has been investigated. In particular, the effect of the ball milling energy on the microstructure of the coating layer was examined to obtain the best coating condition. Experimental results show that Cu-Al-Ni powder compact was explosively synthesized and successfully coated with the steel matrix. It was revealed that the formation of $Cu_9Al_4$ intermetallic decreased with increase in the ball milling energy. This result supports that the high energy ball milling would be effective for obtaining the most suitable microstructure for Cu-Al-Ni coating layer. However, the excessive ball milling energy seems to decrease the bonding strength between the coating layer and the matrix.

• Journal of Powder Materials
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• v.6 no.2
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• pp.139-144
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• 1999

The pure Ti, Ni and carbon powders were reaction milled to synthesize the TiC-Ni based cermet powders with ultrafine microstructures. After milling, the ultrafine TiC or amorphous Ti-Ni phase was obtained, respectively, according to the milling condition. The effects of milling variables on the synthesizing behavior of the powders were investigated in detail. The sintered TiC-Ni based cermet of the reaction milled powders consisted of very fine TiC of 0.2~1.5$\mu$m, as compared with that of a commercial cermet of 3~5$\mu$m. This demonstrates the potenial of reaction milling as an effective processing route for the preparation of cermet materials.