• 한국산학기술학회논문지
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• 제10권8호
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• pp.1783-1788
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• 2009

스컬 공정으로 제조된 큐빅지르코니아에서 보석용으로 사용되는 부분 외에 일반적으로 버려지는 에지부 폐지르코니아를 분쇄하여 1550$^{circ}C$-2hr의 저온 소결 공정으로 소결한 소결체의 물성을 분석하여 재활용 가능성을 확인해보았다. 비교를 위한 새 지르코니아와 30 mol%-$Y_2O_3$ 혼합분말 (모두 1㎛ 길이의 셀룰러형)로 만든 소결체는 직경 $\sim$10㎛의 조밀 소결체가 결합된 형태를 보였으나, 1$\sim$30㎛의 크기 및 형태가 일정하지 않은 분말로 제조된 폐지르코니아 소결체는 $\sim$30㎛ 이상의 결정립을 가진 미세구조를 보였다. 새 지르코니아 혼합 분말로 만든 소결체는 cubic상인 $Y_2O_3$, $Z_{r0.8}O_{1.9}$와 monoclinic상인 $Z_rO_2$의 혼합상을 보였으나, 폐지르코니아 분말 소결체의 경우 tetragonal 단일상을 보임을 확인하였다. 폐지르코니아 소결체도 70 이상의 비커스 경도와 4.11 g/cc의 소결밀도를 보여서 구조재로 사용이 가능하였다.

• 한국염색가공학회지
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• 제25권2호
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• pp.118-125
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• 2013

Poly(vinyl alcohol) (PVA)/titanium dioxide ($TiO_2$) composite nanofibers were produced at different $TiO_2$ concentrations (0.5, 1 and 1.5 wt.%) using the electrospinning method. The parameters of electrospinning including polymer contents, voltage and tip-to-collector distance (TCD) were optimized for fabrication process. The study showed that 7.5 wt.% PVA, 15 kV applied voltage and 15 cm TCD are the best condition to obtain uniform PVA/$TiO_2$ nanofibers. $TiO_2$ nanoparticles give significant effect in fiber morphology. $TiO_2$ content increases the diameter of the fibers and roughen the fiber surfaces. The PVA/$TiO_2$ nanofibers were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD).

• Bulletin of the Korean Chemical Society
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• 제33권4호
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• pp.1242-1246
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• 2012

The Co oxide microfibers were synthesized using the electrospinning process and formed $Co_3O_4$ microfibers after being calcined at high temperatures. The calcination temperature influenced the diameters, morphology, crystalline phase, and chemical environment of the fibers. The surface morphology of the obtained fibers was examined by using the scanning electron microscope (SEM). As the calcination temperatures increased from room temperature to 873 and 1173 K, the diameters of the cobalt oxide fibers decreased from 1.79 to 0.82 and 0.32 mm, respectively. The structure of the fibers was investigated with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The calcined $Co_3O_4$ fibers had crystalline face-centered cubic (fcc) structure. The X-ray photoelectron spectroscopy (XPS) results revealed that increasing the calcination temperature promoted the formation of $Co^{2+}$ and $Co^{3+}$ species.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.385-385
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• 2010

Copper oxide thin films were deposited on the p-type Si(100) by r.f. magnetron sputtering as a function of different oxygen concentration. The deposited copper oxide thin films were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The SEM and SE data show that the thickness of the copper oxide films was in the range of 100-400 nm. AFM images show that the surface morphology was depended on the oxygen ratio. The crystal structure of copper oxide films was changed from metallic copper to copper oxide with increasing oxygen concentration. The oxidation states of Cu 2p and O 1s resulted from XPS were consistent with XRD results.

• 자원환경지질
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• 제36권1호
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• pp.1-8
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• 2003

본 연구는 X-선분말회절(XRD)을 이용하여 감포와 연일에서 산출되는 벤토나이트에 대한 팽창성과 부합성산란영역크기(CSDs)를 측정하고, 이를 세계표준 벤토나이트(SAz-1, STx-1, SWy-2사 비교해 보고자 하였다. 에틸렌글리콜(EG)포화 시료에서 측정한 001 피크의 저각도 쪽 굴곡과 001 피크의 강도비(saddle/001 강도비)를 이용하여 감포와 연일 벤토나이트의 팽창성을 측정한 결과, 77-100% S$_{XRD}$를 보였으며, GP-56을 제외한 대부분은 무질서형 일라이트-스멕타이트 혼합층광물(RO I-S)로 구성되어 있었다. BWA(Bertaut-Warren-Averbach) 방법으로 CSDs를 측정한 결과, EG-포화시료의 001 피크는 혼합층에 의한 피크의 변형(Mering의 제 1 원칙)이 관찰되었으며, CSDs측정에 부적절하였다. 반면에, 300^{\circ}C$ 열-처리 시료의 001 피크는 혼합층에 의한 변형이 발생하지 않았으며 CSDs측정에 적합하였다. 열-처리 시료로부터 측정한 감포와 연일 벤토나이트의 평균 CSDs는 3.8-5.4층간으로 측정되었으며, 세계표준 벤토나이트와 비교하였을 때, CSDs 분포는 곤잘레스(STx-1)와 와이오밍(SWy-2) 벤토나이트와 유사하였다

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.575-578
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• 2000

In this work, all solid-state thin film supercapacitor(TFSC) was fabricated using tungsten trioxide (WO$_3$) with a structure WO$_3$/LiPON/WO$_3$/Pt/TiO$_2$/Si (substrate). After TiO$_2$ was deposited on Si(100) wafer by d.c. reactive sputtering, the Pt current collector films were grown on TiO$_2$glue layer without breaking vacuum by d.c. sputtering. Fabrication conditions of WO$_3$ thin film were such that substrate temperature, working pressure, gas ratio of $O_2$/Ar and r.f. power were room temperature, 5 mTorr, 20% (O$_2$(8sccm)/Ar(32sccm)) and 200W, respectively. LiPON electrolyte film were grown on the WO$_3$ film using r.f. magnetron sputtering at room temperature. The XRD pattern of the as-deposited WO$_3$ thin film were shown no crystalline peak (amorphous). The SEM image of as-deposited WO$_3$ thin film showed that the surface is smooth and uniform. The capacitiy of as-fabricated TFSC was 0$\times$10$^{-2}$ F/$\textrm{cm}^2$-${\mu}{\textrm}{m}$.

• Computers and Concrete
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• 제29권4호
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• pp.263-278
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• 2022

Limestone calcined clay cement (LC³) is a low carbon alternative to conventional cement. Literature shows that using limestone and calcined clay in LC³ increases the thermal degradation of LC³ pastes and can increase the magnitude of fire risk in LC³ concrete structures. Higher thermal degradation of LC³ paste prompts this study toward understanding the fire performance of LC³ concrete and the associated magnitude of fire risk. For fire performance, concrete prepared using ordinary Portland cement (OPC), pozzolanic Portland cement (PPC) and LC³ were exposed to 16 scenarios of different elevated temperatures (400℃, 600℃, 800℃, and 1000℃) for different durations (0.5 h, 1 h, 2 h, and 4 h). After exposure to elevated temperatures, mass loss, residual ultrasonic pulse velocity (rUPV) and residual compressive strength (rCS) were measured as the residual properties of concrete. XRD (X-ray diffraction), TGA (thermogravimetric analysis) and three-factor ANOVA (analysis of variance) are also used to compare the fire performance of LC³ with OPC and PPC. Monte Carlo simulation has been used to assess the magnitude of fire risk in LC³ structures and devise recommendations for the robust application of LC³. Results show that LC³ concrete has weaker fire performance, with average rCS being 11.06% and 1.73% lower than OPC and PPC concrete. Analysis of 106 fire scenarios, in Indian context, shows lower rCS and higher failure probability for LC³ (95.05%, 2.22%) than OPC (98.16%, 0.22%) and PPC (96.48%, 1.14%). For robust application, either LC³ can be restricted to residential and educational structures (failure probability <0.5%), or LC³ can have reserve strength (factor of safety >1.08).

• 한국전기전자재료학회논문지
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• 제17권8호
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• pp.840-845
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• 2004

The microstructure and microwave dielectric properties of $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics were investigated. The specimens were prepared by the conventional mixed oxide method with sintering temperature of 140$0^{\circ}C$∼150$0^{\circ}C$. To improve the quality factor and the temperature coefficient of resonant frequency,$ Ti{O}_2(\varepsilon\Gamma=100, Q\times f_\Gamma=40,000 GHz,\ta_f= +450 ppm\diagup^{\circ}C $ was added in ${Mg}_4{Ta}_2{O}_9$ceramics. The dielectric and structural properties were investigated. According to the XRD patterns, $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics had the ${Mg}_4{Ta}_2{O}_9$ phase(hexagonal) and ${MgTi}_2{O}_5$phase(orthorhombic). The dielectric constant($\varepsilon_r$). quality($Qtimes{f}_r$${\tau}_f$) of the $(1-x){Mg}_4{Ta}_2{O}_9-xTi{O}_2(x=0\sim0.9)$ ceramics were 8.12∼18.59, 18,750∼186,410 GHz and －36.02∼＋3.46 ppm/$^{\circ}C$, respectively.

• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.83-89
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• 1995

In this paper, the specimens-($Ba_{0.997}$ L $a_{0.003}$)Ti $O_{3}$ + xTi $O_{2}$, x=0.005, 0.01, 0.02, 0.03[mol]- were fabricated by a solid-state reaction method which is easy in microstructure control and good in mass production. Their crystalline structures and microstructures were analysed, and electrical properties were investigated. The perovskite-crystalline structure is confirmed by XRD, and it is exhibited by SEM that the grain grows with an addition of Ti $O_{2}$. Resistivity decreases with increasing sinteiing temperature, and the specimen of ($Ba_{0.997}$ L $a_{0.003}$)Ti $O_{3}$ + 0.02Ti $O_{2}$ sintered at 1350.deg. C shows the best PTC effects. The complex impedance plots exhibit the serial equivalent circuit of ( $R_{gb}$ / $C_{gb}$ ) and $R_{g}$ it is realized that PTC effect is attributed to the resistivity of grain boundary.ary.y.

• 폴리머
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• 제29권1호
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• pp.87-90
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• 2005

본 연구에서는 폴리스티렌/점토 나노복합재료를 스티렌 단량체를 이용한 in-situ 중합법으로 제조하면서, 여러가지 유기화제로 처리한 점토들의 박리거동을 실시간 XRD 분석을 통해 확인하였다. 실시간 XRD 실험은 포항 가속기 연구소의 4CI 빔라인에서 수행되었다. 사용된 점토의 양이온 교환능과 유기화제의 구조에 의해서 서로 다른 박리거동을 보여주었다. 양이온교환능이 높은 10A-MMT와 15A-MMT의 경우, 스티렌 단량체의 중합과정중 점토의 특성피크 위치는 변화가 없었다. 하지만, 양이온교환능이 상대적으로 낮고 벤질그룹 혹은 비닐그룹을 포함하고 있는 점토들(25A-MMT와 VDAC-MMT)의 경우, 중합초기 점토의 특성피크가 중합시간이 증가함에 따라 점진적으로 저각도쪽으로 움직이며 점토층간 박리현상이 진행되는 것을 확인하였다.