• 한국정밀공학회지
• /
• 제18권1호
• /
• pp.129-138
• /
• 2001

This study examined the effects of the annealing heat treatments on the mechanical properties of the Invar(Fe-36%Ni Alloy) materials. Invar materials were annealed at various temperatures range 900~120$0^{\circ}C$ in vacuum(10-4Torr) and hydrogen atmospheres. And annealing conditions were changed by cooling rate and holding time at 110$0^{\circ}C$. The grain size of rolled Invar materials was very fine but those of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere increased with increasing annealing temperature. The micro-vickers hardness values of annealed Invar materials were decreased about 15% that of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions. The tensile strength and yield strength of annealed Invar materials at 900~120$0^{\circ}C$ in vacuum and hydrogen atmosphere were decreased 10.0~14.4% and 34.6~39.1% those of the rolled Invar materials, respectively. The strength ratio(tensile strength/ yield strength) of annealed Invar materials was improved to 1.7~1.8 from the value of 1.2~1.3 of rolled Invar materials. The degree of spring back of annealed Invar materials was about 50% of the rolled Invar materials, regardless of the various of annealing temperatures, atmosphere(vacuum, hydrogen) and annealing conditions.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
• /
• pp.194-194
• /
• 2003

As a result of the recent miniaturization an enhancement in the performance of thin film inductors and thin film transformers, there are increased demands for the thin films with high magnetic permeability in the high frequency range, high saturation magnetization, in high electrical resistivity, and low coercive force. In order to improve high frequency properties, we will investigate anisotropy field by shape and size of pattern. The Fe-Al-O thin films of 16mm and 1 $\mu\textrm{m}$ thickness were deposited on Si wafer, using RF magnetron reactive sputtering technique with the mixture of argon and oxygen gases. The fabricating conditions are obtained in the working partial pressure of 2mTorr, O$_2$ partial pressure of 5%, input power of 400W, and Al pellets on an Fe disk with purity of 99,9%. Magnetic properties of the continuous films as followed: the 4$\pi$M$\_$s/ of 19.4kG, H$\_$c/ of 0.6Oe, H$\_$k/ of 6.0Oe and effective permeability of 2500 up to 100㎒ were obtained. In this work, we expect to enhance effect of magnetic anisotropy on patterned of Fe-Al-O thin films.

• 한국결정성장학회지
• /
• 제22권4호
• /
• pp.200-206
• /
• 2012

무기계 폐자원인 화력발전소 바닥재(이하 바닥재로 칭함)와 폐촉매 슬래그를 7 : 3(무게비)으로 혼합, 성형하고 직화소성법으로 인공골재를 제조한 뒤, 원료들의 입도 및 소성온도가 골재의 발포특성에 미치는 영향을 고찰하였다. 대부분의 인공골재는 원료 입도에 관계없이 $1150^{\circ}C$ 이상의 소성온도에서 발포거동을 나타내었으며, 그 결과 비중이 급격히 낮아져 $1250^{\circ}C$에서 약 1.4로 수렴하였다. 그러나 폐촉매 슬래그의 입도를 변화시킨 골재 중 가장 작은 입도($90{\mu}m$)를 사용한 시편만은 두드러진 발포특성을 보이지 않았다. $1050{\sim}1150^{\circ}C$의 저온구간에서 소성된 인공골재의 경우, 원료로 사용된 바닥재와 폐촉매 슬래그 입도가 클수록 비중이 증가하였다. 또한 모든 골재들은 소성온도와 함께 흡수율이 낮아지는 경향을 보였다. 이 실험에서 제조된 인공골재의 비중은 1.4~1.7, 그리고 흡수율은 8~19 %를 나타내어 경량골재의 기준을 만족함으로써 다양한 분야에 적용이 가능할 것으로 판단된다.

• 한국전기전자재료학회논문지
• /
• 제26권4호
• /
• pp.271-274
• /
• 2013

Power Metal Oxide Semiconductor Field Effect Transistor's (MOSFETs) are well known for superior switching speed, and they require very little gate drive power because of the insulated gate. In these respects, power MOSFETs approach the characteristics of an "ideal switch". The main drawback is on-resistance RDS(on) and its strong positive temperature coefficient. While this process has been driven by market place competition with operating parameters determined by products, manufacturing technology innovations that have not necessarily followed such a consistent path have enabled it. This treatise briefly examines metal oxide semiconductor (MOS) device characteristics and elucidates important future issues which semiconductor technologists face as they attempt to continue the rate of progress to the identified terminus of the technology shrink path in about 2020. We could find at the electrical property as variation p base dose. Ultimately, its ON state voltage drop was enhanced also shrink chip size. To obtain an optimized parameter and design, we have simulated over 500 V Field ring using 8 Field rings. Field ring width was $3{\mu}m$ and P base dose was $1e15cm^2$. Also the numerical multiple $2.52cm^2$ was obtained which indicates the doping limit of the original device. We have simulated diffusion condition was split from $1,150^{\circ}C$ to $1,200^{\circ}C$. And then $1,150^{\circ}C$ diffusion time was best condition for break down voltage.

• 수산해양교육연구
• /
• 제28권6호
• /
• pp.1662-1672
• /
• 2016

To address physicochemical factors of yellow clay for removing Cochlodinium polykrikoides blooms, the correlation of removal efficiency with mineralogical characteristics of yellow clay collected from various areas was surveyed. Yellow clay from different localities showed the wide range of chemical compositions $SiO_2$ : 43~71%, $Al_2O_3$ : 13~26%, $Fe_2O_3$ : 5~14%, MgO : 0.4~1.8%, $K_2O$ : 0.6~3.3%, L.O.I.(Loss of Ignition) : 4.5~15%. The mineral compositions of yellow clay were mainly consisted of quartz and feldspar including small amounts of kaolinite, chlorite, and Fe-oxides. The result of size analysis showed that $6{\Phi}(31{\sim}16{\mu}m)$ and $7{\Phi}(16{\sim}8{\mu}m)$ were dominated sizes. The zeta-potential were in the range of -4.1~-20.7mV(average -13.7). As increasing removal efficiency of C. polykrikoides, contents of $Al_2O_3$, $Fe_2O_3$ and L.O.I. in yellow clay increased, whereas $SiO_2$ content decreased. Furthermore, the amounts of silt mineral and small particle were high when the removal efficiency was high. According to factor analysis using principle component analysis, two components of factor 1 and factor 2 showed 79% of the total variance, which is related to cohesion and adsorption. Inducing cell lysis of C. polykrikoides by cohension and adsorption between C. polykrikoides and yellow clay.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
• /
• pp.64-64
• /
• 2000

Since its discovery in 1991, the carbon nanotube has attracted much attention all over the world; and several method have been developed to synthesize carbon nanotubes. According to theoretical calculations, carbon nanotubes have many unique properties, such as high mechanical strength, capillary properties, and remarkable electronical conductivity, all of which suggest a wide range of potential applications in the future. Here we report the synthesis in the catalytic decomposition of acetylene at ~65 $0^{\circ}C$ over Ni deposited on SiO2, For the catalyst preparation, Ni was deposited to the thickness of 100-300A using effusion cell. Different approaches using porous materials and HF or NH3 treated samples have been tried for synthesis of carbon nanotubes. It is decisive step for synthesis of carbon nanotubes to form a round Ni particles. We show that the formation of round Ni particles by heat treatment without any pre-treatment such as chemical etching and observe the similar size of Ni particles and carbon nanotubes. Carbon nanotubes were synthesized by chemial vapour deposition ushin C2H2 gas for source material on Ni coated Si substrate. Ni film gaving 20~90nm thickness was changed into Ni particles with 30~90nm diameter. Heat treatment of Ni fim is a crucial role for the growth of carbon nanotube, High-resolution transmission electron microscopy images show that they are multi-walled nanotube. Raman spectrum shows its peak at 1349cm-1(D band) is much weaker than that at 1573cm-1(G band). We believe that carbon nanotubes contains much less defects. Long carbon nanotubes with length more than several $\mu$m and the carbon particles with round shape were obtained by CVD at ~$650^{\circ}C$ on the Ni droplets. SEM micrograph nanotubes was identified by SEM. Finally, we performed TEM anaylsis on the caron nanotubes to determine whether or not these film structures are truly caron nanotubes, as opposed to carbon fiber-like structures.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.222-222
• /
• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 1992년도 춘계학술발표회
• /
• pp.26-27
• /
• 1992

반도체 기억소자 contact hole의 선택적 충진의 최적 조건을 연구하기 위하여 무전해Ni도금방법을 채택하여 실리콘의 활성화와 선택적 도금의 공정조건이 Contact Hole 도금피막의 제반 특성에 미치는 영향을 조사하였다. p형 실리콘 100 소지 표면의 활성화 처리는 RCA처리에 의해 먼저 표면을 세척한 다음 온도, PdCl$_2$농도, 시간. 교반의 영향을 조사하였다 전처리의 최적조건은 7$0^{\circ}C$, 0.5M HF, ImM PdCl$_2$, 2mM EDTA, 90second이었다. 무전해도금은 NiS0$_4$.6$H_2O$를 DMAB를 환원제로 하여 온도, DMAB 농도, pH, 도금시간의 영향을 조사하였다. 무전해 도금 피막은 비교적 우수한 접촉저 항을 나타냈다. 1$\mu$m의 도금막을 얻는 데 본 실험조건에서 DMAB의 농도가 8mM일 때 30 분이 소요되었다. 도금막의 표면은 온도가 낮을수록 pH가 높을수록 평활하였고,특히 온도 6$0^{\circ}C$와 pH6.8에서 가장 우수하였다. 미세경도는 600Hv 정도였으며, 결정립의 크기 가 증가할수록 저항과 미세경도가 감소하였다.

• 공업화학
• /
• 제8권6호
• /
• pp.994-999
• /
• 1997

참치 뼈로부터 추출한 hydroxyapatite [$Ca_{10}(PO_4)_6(OH)_2$] 와 여기에 소결성 증진을 위해 wollastonite($CaSiO_3$)를 첨가하여 고상반응시킨 세라믹 소결체의 결정상, 미세구조와 꺽임강도(bending strength) 등의 특성을 고찰하였다. 참치 뼈에서 추출한 hydroxyapatite자체의 소결성은 매우 취약하였는데, 이는 건식법의 입자분쇄 한계 때문으로 보인다. Hydroxyapatite에 wollastonite가 첨가된 경우 소결온도가 $1250^{\circ}C$이하에서는 hydroxyapatite와 pseudowollastonite(${\alpha}-CaSiO_3$)가 혼재된 결정상을 보였으나, 온도가 증가할수록 hydroxyapatite의 분해에 따른 whitlockite [$Ca_3(PO_4)_2$] 상이 관찰되었다. 소결온도가 $1250^{\circ}C$이하에서는 미세한 입자들과 많은 기공들이 분포하였으며, 소결온도가 증가할수록 입자의 크기는 증가하여 소결이 상당히 진행된 미세구조를 나타내었다. Wollastonite가 첨가된 소결시편의 평균 꺽임강도는 18MPa로서 해면골(cancellous bone)의 최대 꺽임강도인 20MPs에 근접한 것으로 나타났다.

• 한국재료학회지
• /
• 제3권5호
• /
• pp.497-504
• /
• 1993

기본조성 52.5mol% $Fe_2O_3$, 25.5mol% MnO, 22mol% ZnO로 구성된 Mn-Zn페라이트에 $Bi_2O_3$ 및 $CaCO_3$을 각각 0.02, 0.05wt%첨가한 시편에 대해서 $Ta_2O_5,ZrO_2$및 $SiO_2$의 미량 첨가한 따른 미세구조와 자기적 특성변화를 조사하였다. $Ta_2O_5,ZrO_2$첨가에 따라 결정립 크기가 감소되었고, 전기시 균일한 입자로 형성된 미세구조를 가진 재료를 얻었다. $SiO_2$첨가에 따라 결정립의 이상성장이 관찰되었고 소결밀도, 전기저항, 초투자율은 감소하고 고주파 영역에서 상대손실이 증가되었다. 본 연구결과 초투자자율은 균일한 결정립에서 최대의 값을 가지며 0.02wt%$Bi_2O_3$, 0.05wt%$CaCO_3$, 0.1wt%$Ta_2O_5$ 첨가시편의 경우 10kHz, $25^{\circ}C$에서 초투자율($\mu_i$)은 6260이고 상대손실 계수(tan$\delta /\mu_i$)는 $4.2 \times 10^{-6}$ 인 높은 투자율과 낮은 손실 특성을 가진 자성재료를 얻었다.