• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.114-114
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• 2009

ZnO has received considerable attention due to its potential applicability to optoelectronic devices such as ultraviolet-light emitting diodes (UVLEDs) and laser diodes (LDs). As well known, however, polar ZnO with the growth direction along the c-axis has spontaneous and piezoelectric polarizations that will result in decreased quantum efficiency. Recently, nonpolar ZnO has been studied to avoid such a polarization effect. In order to realize applications of nonpoar ZnO-based films to LEDs, growth of high quality alloys for quantum well structures is one of the important tasks that should be solved. $Mg_xZn_{1-x}O$ and $Cd_xZn_{1-x}O$ is ones of most promising alloys for this application because the alloys of ZnO with MgO and CdO provide a wide range of band-gap engineering spanning from 2.4 to 7.8 eV. In this study, we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios. The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). With the relatively low Mg/Zn flux ratios, a typical striated anisotropic surface morphology which was generally observed from the nonpolar (11-20) ZnO film on r-plane sapphire substrates. By increasing the Mg/Zn flux ratio, however, additional islands were appeared on the surface and finally the surface morphology was entirely changed, which was generally observed for the (0001) polar ZnO films by losing the striated morphology. Investigations by X-ray $\Theta-2{\Theta}$ diffraction revealed that (0002) and (10-11) ZnO planes are appeared in $Mg_xZn_{1-x}O$ films by increasing the Mg/Zn flux ratio. Further detailed investigation by transmission electron microscopy (TEM) and photoluminescence (PL) will be discussed.

• 한국재료학회지
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• 제2권1호
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• pp.3-11
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• 1992

점토 광물로부터 황산 처리법을 이용하여 수화 황산 알루미늄을 제조하였다. 하동 카올린 을 황산 처리하였을 때 수화 황산 알루미늄 형성에 미치는 카올린의 하소 온도와 하소 시간, 산처리 반응 온도와 반응 시간 및 황산의 농도의 영향을 조사하였다. 또한, 황산 처리된 용액으로부터 수화 황산 알루미늄이 석출되는 최적 조건을 구하였으며, 생성된 수화 황산 알루미늄을 상온에서 $1200^{\circ}C$ 까지 각각의 온도 구간에서 열처리한 분말에 대해서 XRD, TG-DTA, FT-IR, SEM, 입도 분석 및 불순물 분석을 하였다. 최적 조건 하에서, 카올린 중의 알루미나가 수화 황산 알루미늄으로 생성되는 전화율은 약 60%였고, XRD, TG-DTA, FT-IR 등의 분석 결과로 부터 생성된 수화 황산 알루미늄의 열분해 반응은 $Al_2(SO_4)_3{\cdot}18H_2O{\rightarrow}Al_2(SO_4)_3{\cdot}6H_2O{\rightarrow}Al_2(SO_4){\rightarrow}\;amorphous\;alumina{\rightarrow}{\gamma}-alumina{\rightarrow}{\delta}-alumina{\rightarrow}{\theta}-alumina{\rightarrow}{\alpha}-alumina$이었다. 또한 생성된 수화 황산 알루미늄을 $1200^{\circ}C$에서 하소 하여 얻은 알루미나 분말의 순도는 99.99%였다.

• Progress in Superconductivity
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• 제6권1호
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• pp.74-78
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• 2004

YBCO coated conductor is one of the most promising materials as a new generations wire especially for practical power applications. In this work, $YBa_2$$Cu_3$$O_{7}$ -$\delta$/(YBCO) coated conductors (CC) were deposited by pulsed laser deposition (PLD) from buffer layers to superconducting layer on hi-axially textured metal tape. The oxide multilayer buffered substrate of architectures of $CeO_2$/$YSZ/Y_2$$O_3$ was fabricated by PLD at steady status. Then YBCO layer was deposited on RABiTS substrate by stationary and reel-to-reel (R2R) continuous process and we compared with deposition conditions of both processes. The degree of texture of each layer was investigated using X-ray diffraction including $\theta$-2$\theta$ scans, $\omega$-scans and $\Phi$-scans analysis. Their surface morphology was observed by scanning electron microscopy (SEM). The FWHM of the X-ray $\Phi$-scans and $\Phi$-scans indicated that YBCO and buffer layers closely replicate the in-plane and out-of-plane texture of metal tape. Critical current (Ic) at 77 K, self-field of 75.8 A/cm-width, critical temperature (Tc) of 85 K, and critical current density (Ic) of 3.7 MA/$\textrm{cm}^2$ were measured from coated conductor deposited by stationary process. And coated conductor deposited by R2R continuous process had Ic of 57.5 A/cm-width, Tc of 86.5 K and Jc of 2.0 MA/$\textrm{cm}^2$. The film also exhibits a homogeneous and dense surface morphology.

• Applied Biological Chemistry
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• 제26권2호
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• pp.137-142
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• 1983

한국산 고구마의 두 품종, 수원 147 호와 천미의 전분을 분리하여 전분입자의 성상과 이화학적 특성을 조사 검토하였다. 광학현미경과 scanning electron microscopy로 관찰한 고구마 전분은 둥근형과 다각형이었으며, 그 크기는 수원 147 호가 $14{\sim}30{\mu}m$, 천미가 $16{\sim}34{\mu}m$이었다. X-선회절도는 $2{\theta}$가 14.8, 17.2, 22.5에서 약한 결정성을 보이므로 실험한 고구마 전분은 Ca결정형으로 생각된다. Blue value는 수원 147호가 0.342, 천미가 0.279, 아밀로즈 함량은 27.6%, 23.6%, 물결합 능력은 178.7%, 185.5%이었다. 전분의 팽화력은 $50^{\circ}C$까지는 변화가없다가 그후 급격히 증가하였으며 수원 147호가 천미보다 완만한 증가를 보였다. 전분 현탁액(0.2%)의 광투과도는 두 전분 모두 $65^{\circ}C$부터 급격히 증가하였고 $65{\sim}80^{\circ}C$까지 single stage의 호화 양상을 보였다. 아밀로 그라프에 의한 4% 전분 용액의 호화는 모두 최고 점도가 나타나지 않았으며 $92.5^{\circ}C$에서 수원 147호의 점도는 증가하였으나 천미 전분의 점도는 감소하였다.

• 한국분말재료학회지
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• 제16권5호
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• pp.363-369
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• 2009

The amorphization process and the thermal properties of amorphous Ti$_{40}$Cu$_{40}$Ni$_{10}$Al$_{10}$ powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2$\theta$ = 42.4$^{\circ}$) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t$_m$ $\leq$ 3 h), disintegration (3 h < t$_m$ $\leq$ 20 h), and homogenization (20 h < t$_m$ $\leq$ 40 h) (t$_m$: milling time). In the DSC experiment, the peak temperature T$_p$ and crystallization temperature T$_x$ were 466.9$^{\circ}C$ and 444.3$^{\circ}C$, respectively, and the values of T$_p$, and T$_x$ increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T$_p$.

• 한국염색가공학회지
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• 제8권2호
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• pp.1-7
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• 1996

Thermotropic liquid-crystalline polyurethanes were synthesized by the polyaddition reaction of such para-substiuted diisocyanate monomer as 1,4-phenylene diisocyanate(1,4-PDI) and 2,5-tolylene diisocyanate(2,5-TDI), with 4,4'-bis($\omega$-hydroxyalkoxy)biphenyls(BPm: $HOC_{m}OC_{6}H_{4}C_{6}H_{4}OC_{m}H_{2m}OH$; m is the carbon number of the hydroxyalkoxy group). These polyurethanes have mesogenic biphenyl units in the main chain. Properties of polymers were studied by differential scanning calorimetry, wide-angle X-ray scattering, thermogravimetic analysis, polarizing microscopy, and infraed spectroscopy. DSC thermograms for these polymers exhibited two endothermic peaks corresponding to phase transitions of melting and isotropization. Mesomorphic behavior of the polyurethanes were also observed under the polarizing microscope. For example, polyurethane 2,5-YDI/BP5 with [$\theta$]=0.44 prepared from 2,5-TDI and BP5 exhibited a liquid crystalline phase from 194 to 205$^{\circ}C$. Infrared spectrum study indicated that the hydrogen bonding between urethane linkages affected the mesomorphism. The thermostabilities of polyurethanes 2,5-TDI/BP5 and 1,4-PDI/BP5 were measured at a heating rate of 1$0^{\circ}C$/min in air. The temperatures of 5% weight loss for 2,5-TDI/BP5 and 1,4-PDI/BP5 were 297 and 334$^{\circ}C$, respectively.

• 한국전기전자재료학회논문지
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• 제30권7호
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• pp.427-431
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• 2017

In this paper, we discuss ${\beta}-Ga_2O_3$ thin films that have been grown on freestanding GaN (FS-GaN) using furnace oxidation. A GaN template was grown by horizontalhydride vapor phase epitaxy (HVPE), and FS-GaN was fabricated using the laser lift off (LLO) system. To obtain ${\beta}-Ga_2O_3$ thin film, FS-GaN was oxidized at $900{\sim}1,100^{\circ}C$. Surface and cross-section of prepared ${\beta}-Ga_2O_3$ thin films were observed by field emission scanning electron microscopy (FE-SEM). The single crystal FS-GaNs were changed to poly-crystal ${\beta}-Ga_2O_3$. The oxidized ${\beta}-Ga_2O_3$ thin film at $1,100^{\circ}C$ was peel off from FS-GaN. Next, oxidation of FS-GaNwas investigated for 0.5~12 hours with variation of the oxidation time. The thicknesses of ${\beta}-Ga_2O_3$ thin films were measured from 100 nm to 1,200 nm. Moreover, the 2-theta XRD result indicated that (-201), (-402), and (-603) peaks were confirmed. The intensity of peaks was increased with increased oxidation time. The ${\beta}-Ga_2O_3$ thin film was generated to oxidize FS-GaN.

• 한국환경과학회지
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• 제27권2호
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• pp.83-90
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• 2018

In this study, zeolite (Z-C2) was synthesized using a fusion/hydrothermal method on coal fly ash (FA) discharged from a thermal power plant in the Ulsan area and then analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The Z-C2 was characterized in terms of mineralogical composition and morphological analysis. The XRD results showed that its peaks had the characteristics of Na-A zeolite in the range of $2{\theta}$ of 7.18~34.18. The SEM images confirmed that the Na-A zeolite crystals had a chamfered-edge crystal structure almost identical to that of the commercial zeolite. The adsorption kinetics of Cu, Co, Mn and Zn ions by Z-C2 were described better by the pseudo-second-order kinetic model more than by the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model did. The maximum adsorption capacities of Cu, Co, Mn and Zn ions obtained from the Langmuir model were in the following order : Cu (94.7 mg/g) > Co (77.7 mg/g) > Mn (57.6 mg/g) > Zn (51.1 mg/g). These adsorption capacities are regarded as excellent compared to those of commercial zeolite.

• ALGAE
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• 제28권4호
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• pp.331-341
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• 2013

Rhinomonas reticulata var. atrorosea G. Novarino is a photosynthetic marine flagellate that is known to have typical characteristics of cryptomonads. We examined the flagellar apparatus of R. reticulata var. atrorosea by transmission electron microscopy. The major components of the flagellar apparatus of R. reticulata var. atrorosea consisted of four types of microtubular roots (1r, 2r, 3r, and mr), a non-keeled rhizostyle (Rhs), mitochondrion-associated lamella (ML), two connections between basal bodies, a striated fibrous root (SR) and a striated fiber-associated microtubular root (SRm). Four types of microtubular roots originated near the ventral basal body and extended toward the left side of the basal bodies. The non-keeled Rhs originated at the Rhs-associated striated fiber, which was located between two basal bodies and extended into the middle of the cell. The ML was a plate-like fibrous structure associated with mitochondria and originating from a Rhs-associated fiber. It split into two parts and extended toward the dorsal-posterior of the cell to a mitochondrion. The SR and SRm extended parallel to the anterior lobe of the cell. The overall configuration of the flagellar apparatus in R. reticulata var. atrorosea was similar to the previously reported descriptions of those of Cryptomonas paramecium, C. pyrenoidifera, C. ovata, Hanusia phi, Guillardia theta, and Proteomonas sulcata. However, the flagellar apparatus system of R. reticulata var. atrorosea was more complex than those of other cryptomonad species due to the presence of an additional microtubular root and other distinctive features, such as a rhizostyle-associated striated fiber and large ML.

• Advances in nano research
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• 제7권4호
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• pp.233-240
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• 2019

The present research work reports in-vitro anti-cancer activity of biologically synthesized ZnO nanoparticles (ZnO NPs) against human carcinoma cells viz SCC-40, SK-MEL-2 and SCC-29B using Sulforhodamine-B (SRB) Assay. ZnO NPs were synthesized by a unique and novel biological route using Temperature-gradient phenomenon where the extract of combination of Catharanthus roseus (L.) G. Don (C. roseus), Azadirachta indica (A. indica), Ficus religiosa (F. religiosa) and NaOH solution were used as synthesis medium. The morphology of the ZnO NPs was characterized by Transmission Electron Microscopy (TEM). TEM images reveal that particle size of the samples reduces from 76 nm to 53 nm with the increase in reaction temperature and 68 nm to 38 nm with the increase in molar concentration of NaOH respectively. XRD study confirms the presence of elements and reduction in crystallite size with increase in reaction temperature and NaOH concentration. The diffraction peaks show broadening and a slight shift towards lower Bragg angle ($2{\theta}$) which represents the reduction in crystallite size as well as presence of uniform strain. The FTIR spectra of the extract show transmittance peak fingerprint of Zn-O bond and presence of bioactive molecules These NPs exhibit inhibition greater than 50% for SCC-40, SK-MEL-2 and SCC-29B cell lines and more than 50% cell kill for SCC-29B cells at concentrations < $80{\mu}g/ml$. Nanoparticles with smallest size have shown better anti-cancer activity and peculiar cell-selectivity. The combination of extracts of these plants with ZnO NPs can be used in targeted drug delivery as an effective anti-cancer agent, a potential application in cancer treatment.