• 한국정밀공학회지
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• 제22권4호
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• pp.167-172
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• 2005

In this paper. micro electrochemical machining (ECM) for micro structure fabrications is presented. By applying ultra short pulses. the chemical reaction can be restricted only to the region very close to the electrode. Micro ECM is applied to machining micro structures through electrochemical milling process becasuse it doesn't suffer from tool wear. Using this method. 3D micro structures were machined on stainless steel. It was found that micro machining is possible with good surface quality in the low concentration electrolyte,0.1 M H₂SO₄. In ECM, as the machining depth increases, better flushing of electrolyte is required for sufficient ion supply. Layer-by-layer milling is advantageous in flushing. However, layer-by-layer milling causes taper of structures. To reduce the taper, application of a disk-type electrode was introduced. By electrochemical milling, various 3D micro structures including a hemisphere with 60 ㎛ diameter were fabricated.

• Journal of the Korean Wood Science and Technology
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• 제42권6호
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• pp.700-707
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• 2014

본 연구에서는 고온증기 및 오존처리 전처리 후, 습식 고전단 해섬하여 국내산 잣나무로부터 리그노셀룰로오스 나노섬유를 제조하였다. 고온증기 및 오존 전처리에 의해 헤미셀룰로오스 및 리그닌 성분은 각각 약 40%, 42%의 감소효과를 보였으며, 무처리 목분에 비교하여 습식 고전단 해섬처리 시간이 증가함에 따라 섬유의 직경이 더욱 크게 감소하였으며, 좁은 치수분포를 나타냈다. 두 전처리 후 얻어진 리그노셀룰로오스 나노섬유는 평균직경이 각각 19 nm 및 12 nm로 매우 가느다란 것으로 관찰되었다. 얻어진 리그노셀룰로오스 나노섬유를 폴리우레탄 폴리머의 강화필러로 첨가한 결과, 첨가량 및 해섬처리 시간이 증가함에 따라 복합재료의 인장강도와 탄성율이 증가하였다. 특히, 두 전처리 후 얻어진 리그노셀룰로오스 나노섬유의 경우가 전처리하지 않은 경우에 비해 복합재료의 인장강도 특성을 더 향상시키는 것을 알 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제43권1호
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• pp.17-24
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• 2015

본 연구에서는 잣나무 목분의 탈리그닌 정도가 습식디스크밀을 이용한 해섬처리의 효율에 미치는 영향과 얻어진 해섬물의 성질을 조사하였다. 또한, 탈리그닌 정도가 종이의 인장강도 특성에 미치는 영향도 조사하였다. 탈리그닌의 정도는 아염소산나트륨과 초산을 사용하는 Wise법의 처리횟수를 달리함으로서 조절하였다. 탈리그닌 정도가 증가함에 따라 해섬효율은 향상되었으며, 디스크밀 처리횟수가 증가함으로서 섬유직경은 감소, 여수시간은 증가하였다. 또한 종이의 인장강도 및 탄성률도 탈리그닌 정도 및 디스크밀 처리횟수가 증가할수록 증가하였다.

• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.737-745
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• 2017

This study was carried out to investigate the changes in micro- and nanoscopic morphology of cellulose nanofibrils (CNFs) from various bioresources by investigating various mechanical milling systems. Mechanical milling in herbaceous bioresources was more effective than in woody bioresources, demonstrating lower energy consumption and finer morphology. The milling time to reach nanoscopic size was longer in woody bioresources than in herbaceous bioresources. Furthermore, at the same level of wet disk milling time, CNFs from herbaceous bioresources showed more slender morphology than those from woody bioresources. Tensile properties of nanopaper prepared from CNFs of herbaceous bioresources were higher than those of woody bioresources. The highest tensile strength was found to be 77.4 MPa in the nanopaper from Evening prim rose.

• Applied Microscopy
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• 제29권4호
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• pp.493-498
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• 1999

기억저장매체로서 광디스크의 개발이 활발히 진행되고 있으며 최근의 레이저 기술의 발전, 제조기술의 발전에 따른 기억밀도의 증가로서 기존의 자기기록매체와 경쟁을 하고 있다. 기록밀도의 증대와 신뢰성의 향상을 위하여 다층박막 구조를 가지는 광디스크의 미세구조는 더욱 복잡하며 소형화되고 있다. 이종의 물질로 구성된 다층박막형 광디스크의 미세구조 관찰 및 분석을 위해서는 투과전자현미경과 같은 미소영역 분석법이 필수적이며 비교적 간단하고 신뢰성 높은 시편준비법의 확립이 선행되어야 한다. 본 연구에서는 투과전자현미경 분석을 위한 광디스크의 평면 및 단면시료 제작법을 제시하고 제조된 시편으로부터 얻어진 광디스크의 미세구조 분석결과를 보고한다.

• 자원리싸이클링
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• 제13권1호
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• pp.54-58
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• 2004

Wollastonite-type glass ceramics were prepared by milling and firing at various temperatures using an automobile waste glass and waste shell as starting materials. Powder mixture ground by disk-type ball mill for 3 hours was pressed into a disk. The pressed specimen was fired at $850^{\circ}C$,$950^{\circ}C$ and $1050^{\circ}C$ for 1 hour in air. From FE-SEM observation, with an increase of the firing temperature from $850^{\circ}C$ to $1050^{\circ}C$, whisker-type phase was grown to about 10 $\mu\textrm{m}$ in length. Specimen fired at $1050^{\circ}C$ showed the formation of well-crystallized whisker-type wollastonite grains and the highest compressive strength.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.407-412
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• 2005

For micro electrochemical machining (ECM), tool electrodes with various sizes and shapes are necessary. In this paper, tool electrodes were fabricated by micro electrical discharge machining (EDM). Electrode material is tungsten carbide which has high rigidity and good conductivity for micro electrochemical machining. Disk-type and sphere-type electrodes were fabricated to prevent taper shape of side walls or to produce spherical features. Various 3D micro structures were fabricated by electrochemical milling with developed electrodes.

• 한국정밀공학회지
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• 제14권11호
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• pp.147-153
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• 1997

Fault diagnosis technique in machining system which is one of engineering techniques absolutely necessary to automation of manufacturing system has been proposed. As a whole, diagnosis process is explained by two steps: sensor data acquisition and reasoning current state of system with the given sensor data. Flexible disk grinding process implemented in milling machine was employed in order to obtain empirical manufacturing process information. Resistance force data during machining were acquired using tool dynamometer known as sensor which is comparably accurate and reliable in operation. Tool status during the process was analyzed using influnece diagram assigning probability from the statistical analysis procedure.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.31.1-31.1
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• 2009

In an approach to acclimate ourselves torecent ecological consciousness trend, a lead-free piezoelectric material, bismuth sodium titanate (abbreviated as BNT) based bismuth sodium barium titanate (abbreviated as BNT-BT), was considered as an environment-friendly alternative for a lead based piezoelectric system. Ceramic specimens of0.94[(BixNa0.5)TiO3]-0.06[BaTiO3] (x = 0.500~0.515) compositions were prepared by a modified mixed oxide method. To increase the chemical homogeneity andre action activity, high energy mechanical milling machine and pre-milled nanosized powder has been used. In this method (BixNa0.5)TiO3 (x=0.500~0.515) andBaTiO3 were prepared separately from pre-milled constituent materials at low calcination temperature and then separately prepared BNTX (X=1, 2, 3 and 4) and BT were mixed by high energy mechanical milling machine. Without further calcination step the mixed powders were pressed into disk shape and sintered at $1110^{\circ}C$. Microstructures, phase structures and electrical properties of the ceramic specimens were systematically investigated. Highly dense ceramic specimens with homogenous grains were prepared in spite of relatively low sintering temperature. Phase structures were not significantly influenced by the excess amount Bi. Large variation on the piezoelectric and dielectric properties was detected at relative high excess Bi amounts. When $x{\leq}0.505$, the specimens exhibit insignificant variation in piezoelectric and dielectric constant though depolarization temperature is found to be decreased. Considerable amount of decrease in piezoelectric and dielectric properties are observed with higher excess of Bi amounts ($x{\geq}0.505$). This research indicates the advantages of high energy mechanical milling and importance of proper maintenance of Bi stoichiometry.

• The Journal of Advanced Prosthodontics
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• 제12권5호
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• pp.259-264
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• 2020

PURPOSE. The aim of this study was to investigate and compare the color stability of provisional restorative materials fabricated by 3D printing, dental milling, and conventional materials. MATERIALS AND METHODS. For the experimental groups, two commercially available 3D-printing provisional resins (E-Dent 100; EnvisionTEC GmbH, Germany & VeroGlaze™; Stratasys^®, USA), two dental milling blocks (PMMA Disk; Yamahachi Dental Co., Japan & Telio^®CAD; Ivoclar Vivadent AG, Liechtenstein), and two conventional materials (Alike™; GC Co., Japan & Luxatemp automix plus; DMG, Germany) were used. The water sorption and solubility test were (n=10, respectively) carried out according to ISO4049:2000 (International Standards Organization, Geneva, Switzerland). For the color stability test (n=10), coffee and black tea were used as staining solutions, and the specimens were stored for 12 weeks. Data were analyzed by one-way ANOVA and Tukey's HSD using SPSS version 22.0 (SPSS Inc. Chicago, IL, USA) (P<.05). RESULTS. Alike and Veroglaze showed the highest values and Luxatemp showed the lowest water sorption. In the color stability test, the ΔE of conventional materials varied depending on the staining solution. PMMA milling blocks showed a relatively low ΔE up to 4 weeks, and then significantly increased after 8 weeks (P<.05). 3D-printed materials exhibited a high ΔE or a significant increase over time (P<.05). CONCLUSION. The degree of discoloration increased with time, and a visually perceptible color difference value (ΔE) was shown regardless of the materials and solutions. PMMA milled and 3D-printed materials showed more rapid change in discoloration after 8 weeks.