α-Fe₂O₃/AI₂O₃(0001) 박막 결정화의 방사광 X-선 산란 연구

조태식 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.8

The crystallization of amorphous $\alpha$-Fe$_2$O$_3$/$\alpha$-AI$_2$O$_3$(0001) thin films during thermal annealing in air has been studied using real-time synchrotron x-ray scattering. The well aligned (0.02$^{\circ}$/ FWHM) $\alpha$-Fe$_2$O$_3$and Fe$_3$O$_4$interfacial crystallites (50- -thick) coexist on the $\alpha$-AI$_2$O$_3$(0001) in the sputter-grown amorphous films at room temperature. The amorphous precursor is crystallized to the epitaxial $\alpha$-Fe$_2$O$_3$grains in three steps with annealing temperature; i ) the growth of the well aligned $\alpha$-Fe$_2$O$_3$interfacial crystallites, together with the transformation of the Fe$_3$O$_4$crystallites to the $\alpha$-Fe$_2$O$_3$ crystallites, ii ) the growth of the less aligned (3.08$^{\circ}$ FWHM)$\alpha$-Fe$_2$O$_3$grains on the well aligned grains (>40$0^{\circ}C$), and iii) the nucleation of the other less aligned (1.39$^{\circ}$ FWHM) $\alpha$-Fe$_2$O$_3$grains directly on the $\alpha$-AI$_2$O$_3$substrate (>$600^{\circ}C$). The effective thickness thinner than 230 may be very useful for enhancing the epitaxial quality of $\alpha$-Fe$_2$O$_3$/AI$_2$O$_3$(0001) thin films.

밀 스케일을 사용한 Sr-페라이트의 특성에 미치는 산화제의 영향

조태식,최승덕,Cho, Tae-Sik,Choi, Seung-Duek 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.2

We have been studied the effects of oxidant on the properties of Sr-ferrite magnets using mill scale for motor. The small-added (0.5 wt%) $NaNO_3$ oxidant improved significantly the degree of oxidation and the grindability of mill scale, and then highly enhanced the magnetic properties of anisotropic Sr-ferrite sintered magnets; such as the remanent flux density from 3.55 to 3.80 kG, the intrinsic coercivity from 2.75 to 3.22 kOe, and the maximum energy product from 2.90 to 3.45 MGOe.

Phase Transformation of Sn-Pb-Bi Solder for Photovoltaic Ribbon: A Real-time Synchrotron X-ray Scattering Study

조태식 한국전기전자재료학회 2014 Transactions on Electrical and Electronic Material Vol.15 No.3

The phase transformation of Sn-Pb-Bi solder for photovoltaic ribbon during soldering was studied using real-timesynchrotron x-ray scattering. At room temperature, Sn and Pb crystal phases in the solder existed separately. Byheating to 92℃, a new PbBi alloy crystal phase was formed, which grew further up to 160℃. The Sn crystal phase firststarted to melt at 160℃, and was mostly melted at 165℃. In contrast, the Pb and PbBi crystal phases started to meltat 165℃, and were mostly melted at 170℃. The useful result was obtained, that the solder's melting temperaturedecreased from 183℃ to 170℃ by addition of a small amount of Bi atoms to the eutectic Sn62-Pb38 (wt%) solder. Our study first revealed the detailed in-situ phase transformation of Sn-Pb-Bi solder during heating to the eutectictemperature. Considering the results of peel strength and hardness, adding 1 wt% of Bi atoms to the Sn62-Pb38 (wt%)solder produced an appropriate composition.

교합면 열구 법랑질의 미세구조 및 산부식 형태

조태식,이상호,윤정훈,김수관 大韓小兒齒科學會 2005 大韓小兒齒科學會誌 Vol.32 No.2

치면열구전색제의 접착력에 영향을 줄 수 있는 교합면 열구 법랑질의 미세구조 및 산부식 형태, 그리고 산부식 형태에 영향을 줄 수 있는 prismless enamel의 존재 여부 및 법랑질의 화학적 조성을 규명하고자 소구치를 대상으로 협설면과 근원심으로 각각 절단하여 열구내의 법랑질 표면과 산부식 형태를 주사전자현미경으로 관찰하고 EDX를 사용하여 법랑질의 화학적 조성을 분석한 결과 다음과 같은 결과를 얻었다. 1. 열구내 법랑질은 대부분이 prismless enamel이 존재하였다. 2. 미성숙 영구치와 성숙된 영구치 간의 열구내 법랑질 표면 구조 및 산부식 형태는 차이가 없었다. 3. 열구 법랑질은 부위 에 관계없이 60초 산부식 이 15초, 30초, 45초에 비해 산부식 효과가 가장 켰으며 15초, 30초, 45초의 산부식 시간에서는 적절한 유지력을 얻을 수 있는 산부식 상이 관찰되지 않았다. 4. 열구 법랑질의 표면을 기계적으로 제거한 경우는 30초의 산부식 시간에서도 60초 산부식 시간에 못지않은 전형적 인 산부식 상이 관찰되었다. 5. 산부식 형태는 주로 rod 주위가 소실된 제 2형의 산부식 상이 관찰되었다. 6. 열구 내 법랑질의 부위별 화학적 조성의 차이는 없었으나 미성숙 영구치와 성숙된 영구치 사이의 칼슘/인 비는 유의한 차이를 보였다. 이상의 연구결과를 종합하면 교합면 열구내 법랑질은 대부분 산에 저항성이 큰 prismless enamel로 덮여 있어 기존에 제안된 15-30초의 산부식 시간으로는 적절한 유지력을 얻을 수 있는 산부식 상을 형성할 수 없다는 사실을 알 수 있다. 따라서 기존의 제안된 산부식 시간에 대한 재고가 필요하며 이와 함께 적절한 산부식 상을 얻기 위한 방안으로 산부식 전bur를 사용하여 열구내 법랑질 표면을 제거해 주는 보조적인 술식에 대한 검토가 필요하리 라 사료된다. The purpose of this study was to compare the effectiveness of mechanical and acid treatment on enamel surfaces for the retention of pit and fissure sealants and evaluate the presence of a prismless layer. The etch pattern produced on enamel from immature and mature premolar teeth extracted with varying period of acid etching using 37% phosphoric acid was examined using a scanning electron microscope(SEM). The composition of each groups was evaluated using an energy dispersive x-ray(EDX) spectroscopy. The result of present study can be summarized as follows: 1. Prismless layer was commonly observed on the fissure enamel in young and mature premolar. 2. There were no differences in micro-structure and etching pattern on fissure enamel between the young and the mature premolar. 3. The most effective etching pattern for retention of pit and fissure sealant was observed in 60 seconds of etching time and no apparent difference of etching pattern was found among 15, 30, and 45 seconds of etching time which showed non-retentive etching patterns. 4. The etching pattern obtained by grinding enamel surface with bur followed by 60 seconds of etching was similar to that of 60 seconds of etching without any pretreatment of fissure surface. 5. Type 2 etching pattern was commonly found on fissure enamel in both young and mature premolar. 6. The calcium content and P/Ca ratio in fissure enamel between the young and the mature premolar were significantly different(PK0.05). But content of calcium, phosphate and P/Ca ratio on various regions of fissure enamel in both young and mature premolar did not showed any difference. Based on these results, prismless layer may negatively influence the retention of pit and fissure sealants. 'Therefore, the mechanical removal of the prismless layer by grinding prior to etching or by prolonged etching time of enamel within the fissure system should result in an improved bonding of a pit and fissure sealant.

Enhancement of the Surface Smoothness of Cu Ribbon for Solar Cell Modules

조태식,조철식 한국전기전자재료학회 2015 Transactions on Electrical and Electronic Material Vol.16 No.1

We studied the relationship between the surface smoothness of the internal Cu ribbon and the morphology of theSn-Pb plating layer for solar cell modules. A bumpy surface was observed on the surface of the solar ribbon, whichcaused irregular reflection of light. Large, Pb-rich, primary α-phases were found below the convex surface of the solarribbon, passing from the surface of the internal Cu ribbon to the surface of the plating layer. The primary α-phasesheterogeneously nucleated on the convex surface of the Cu ribbon, and then largely grew to the convex surface of theplating layer. The restriction of the primary α-phase's formation was enabled by enhancing the smoothness of the Curibbon's surface; it was also possible to increase the adhesive strength and decrease contact resistance. We confirmedthat the solar ribbon's surface smoothness depends on the internal Cu ribbon's surface smoothness.

등방성 Sr-페라이트 과립을 이용한 새로운 자성도자기 소지

조태식,정지욱 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.8

The new magnetic porcelain materials have been studied by mixing magnetic St-ferrite powders with traditional porcelain materials before forming process. For the maintenance of magnetic characteristics after glaze firing process, the Sr-ferrite grains with the size of 1∼2 ${\mu}{\textrm}{m}$ were agglomerated as the isotropic granules with the size of 0.5∼2 mm. The high characteristics of magnetic porcelain materials were achieved at the following conditions; isotropic Sr-ferrite granules of 30 wt%, granule size of 1.4∼2 mm, and glaze firing temperature of $1250^{\circ}C$ in air The magnetic porcelain materials indicated the high magnetic properties, such as the remanent flux density of 240 G, the intrinsic coercivity of 3910 Oe, and the surface flux density of 178 G. The extraction properties of the magnetic tea cups were high compared to that of the traditional tea cups.

방사광 x-선 기법에 의한 다층형 Fe/Cr 자성박막의 계면확산 연구

조태식 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.2

We have studied the interfacial diffusion of Fe/Cr multilayers using synchrotron x-ray techniques, such as x-ray reflectivity, extended x-ray absorption fine structures (EXAFS), and high-resolution x-ray scattering. The results of x-ray reflectivity indicated that the interfacial roughness of Fe/Cr multilayers increased with the Cr-layer thickness. The Fourier transform (FT) of EXAFS data clearly showed that the Fe atoms dominantly diffused into the stable Cr layers at the Fe/Cr interface. The results of high-resolution x-ray scattering supported the interfacial diffusion of Fe atoms. Out study revealed that the dominantly interfacial diffusion of Fe atoms into the Cr layers effects the interfacial roughness of the Fe/Cr multilayers.

산화철의 분체특성이 Sr-ferrite의 자기특성에 미치는 영향

조태식,김효준,최승덕,남효덕,염충진 한국자원리싸이클링학회 1998 資源 리싸이클링 Vol.7 No.4

다양한 hard ferrite용 국산 산화철(${\alpha}Fe_2O_3$)의 분체특성이 Sr-ferrite의 자기특성에 미치는 영향을 조사하였다. 산화철의 평균입도와 입도분호는 철강 냉연공장의 염산폐액 정제방법에 따라 서로 구분되었으며, Sr-ferrite의 자기특성과 미세조직에 큰 영향을 주었다. Ruthner 산화철의 응집현상은 Sr-ferrite의 포화자화를 감소시켰으며, Chemirite(CY) 산화철의 $0.80{\mu}\textrm{m}$이상의 조대한 입자는 Sr-ferrite의 고유보자력을 감소시켰다. 평균입도가 $0.14\mu\textrm{m}$로 가장 작은 Chemirite 포항2냉연(EP) 산화철을 사용하여, 5.8mol, $1150^{\circ}C$/1시간의 하소조건에서 제조된 Sr-ferrite는 포화자화가 68.2emu/g, 고유보자력이 4300Oe인 최적의 자기특성을 나타내었다. We investigated the effects of the powder characteristics of various domestic iron oxides (${\alpha}Fe_2O_3$) on the magnetic properties of Sr-ferrites The particle size and the distribution of iron oxides were classified hy three different rerinning methods, and greatly a affected on the magn$\xi$tic prope$\pi$ies and the mmphology of Sr-ferntes. The agglomeration of Ruthner iron oxides and the large particles of Chemirite (CY) above $0.80{\mu}\textrm{m}$ were degraded the prope며es of Sr-fcrrites. The optimal magnetic prope$\pi$ies of Srt territes, showing 68.2 emu/g of saturation magnetization and 4300 Oe of intrinsic coerClvity, were achieved at the following c conditions; Chemirite (P2EP) iron oxides of $0.14{\mu}\textrm{m}$ molar ratio of 5.8. and calcination of $1150^{\circ}C$/1 hr.

文化院 經營對策과 經營者의 課題

趙泰植 경기대학교경영대학원 1993 最高經營者課程 經營硏究 Vol.7 No.-

3D 초음파 영상에서 방광 내 잔뇨량 추정을 위한 새로운 알고리즘

조태식,이수열,조민형,Cho, Tae Sik,Lee, Soo Yeol,Cho, Min Hyoung 대한의용생체공학회 2016 의공학회지 Vol.37 No.1

For the patients with bladder dysfunction, measurement of urine volume inside the bladder is very critical to avoid bladder failure. In measuring urine volume inside a bladder, low-resolution 3D ultrasound images are widely used. However, urine volume estimation from 3D ultrasound images is prone to big errors and inconsistency because of low spatial resolution and low signal-to-noise ratio of ultrasound images. We developed a new robust volume estimation algorithm which is not computationally expensive. We tested the algorithm on a lab-built ultrasound bladder phantom and volunteers. The average error rate of the human bladder volume estimation was 5.9% which was better than the commercial machine.