• Title/Summary/Keyword: 2D-hexagonal

Search Result 138, Processing Time 0.024 seconds

Magnetite Nanoparticles Containing Nanoporous Carbon for the Adsorption of Ibuprofen (마그네타이트 나노입자를 포함한 탄소나노세공체 합성과 아이부프로펜 흡착거동)

  • Park, Sung Soo;Ha, Chang-Sik
    • Journal of Adhesion and Interface
    • /
    • v.14 no.2
    • /
    • pp.82-87
    • /
    • 2013
  • Preliminary studies on the synthesis of magnetic nanoparticles including nanoporous carbon materials have been done via a direct carbonization process from resol, ferric nitrate and triblock copolymer F127. The results show that the nanoporous magnetite/carbon ($Fe_3O_4$/carbon) with a low $Fe_3O_4$ content (1 wt%) possesses an ordered 2-D hexagonal (p6mm) structure, uniform nanopores (3.6 nm), high surface areas (up to 635 $m^2/g$) and pore volumes (up to 0.48 $cm^3/g$). Magnetite nanoparticles with a small particle size (10.2 nm) were confined in the matrix of amorphous carbon frameworks with superparamagnetic property (7.7 emu/g). The nanoporous magnetite/carbon showed maximum adsorption amount (995 mg/g) of ibuprofen after 24 h at room temperature. The nanoporous magnetite/carbon was separated from solution easily by using a magnet. The nanoporous magnetite/carbon material is a good adsorbent for hydrophobic organic drug molecules, i.e. ibuprofen.

Synthesis and Photoluminescence Properties of Red Phosphors Gd1-xAl3(BO3)4:Eux3+ (적색 형광체 Gd1-xAl3(BO3)4:Eux3+의 합성과 발광 특성)

  • Cho, Shin-Ho;Cho, Seon-Woog
    • Korean Journal of Materials Research
    • /
    • v.22 no.3
    • /
    • pp.145-149
    • /
    • 2012
  • Red phosphors of $Gd_{1-x}Al_3(BO_3)_4:{Eu_x}^{3+}$ were synthesized by using the solid-state reaction method. The phase structure and morphology of the phosphors were measured using X-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM), respectively. The optical properties of $GdAl_3(BO_3)_4:Eu^{3+}$ phosphors with concentrations of $Eu^{3+}$ ions of 0, 0.05, 0.10, 0.15, and 0.20 mol were investigated at room temperature. The crystals were hexagonal with a rhombohedral lattice. The excitation spectra of all the phosphors, irrespective of the $Eu^{3+}$ concentrations, were composed of a broad band centered at 265 nm and a narrow band having peak at 274 nm. As for the emission spectra, the peak wavelength was 613 nm under a 274 nm ultraviolet excitation. The intensity ratio of the red emission transition ($^5D_0{\rightarrow}^7F_2$) to orange ($^5D_0{\rightarrow}^7F_1$) shows that the $Eu^{3+}$ ions occupy sites of no inversion symmetry in the host. In conclusion, the optimum doping concentration of $Eu^{3+}$ ions for preparing $GdAl_3(BO_3)_4:Eu^{3+}$ phosphors was found to be 0.15 mol.

Photoelectrochemical Cell Study on Closely Arranged Vertical Nanorod Bundles of CdSe and Zn doped CdSe Films

  • Soundararajan, D.;Yoon, J.K.;Kwon, J.S.;Kim, Y.I.;Kim, S.H.;Park, J.H.;Kim, Y.J.;Park, D.Y.;Kim, B.C.;Wallac, G.G.;Ko, J.M.
    • Bulletin of the Korean Chemical Society
    • /
    • v.31 no.8
    • /
    • pp.2185-2189
    • /
    • 2010
  • Closely arranged CdSe and Zn doped CdSe vertical nanorod bundles were grown directly on FTO coated glass by using electrodeposition method. Structural analysis by XRD showed the hexagonal phase without any precipitates related to Zn. FE-SEM image showed end capped vertically aligned nanorods arranged closely. From the UV-vis transmittance spectra, band gap energy was found to vary between 1.94 and 1.98 eV due to the incorporation of Zn. Solar cell parameters were obtained by assembling photoelectrochemical cells using CdSe and CdSe:Zn photoanodes, Pt cathode and polysulfide (1M $Na_2S$ + 1M S + 1M NaOH) electrolyte. The efficiency was found to increase from 0.16 to 0.22 upon Zn doping. Electrochemical impedance spectra (EIS) indicate that the charge-transfer resistance on the FTO/CdSe/polysulfide interface was greater than on FTO/CdSe:Zn/polysulfide. Cyclic voltammetry results also indicate that the FTO/CdSe:Zn/polysulfide showed higher activity towards polysulfide redox reaction than that of FTO/CdSe/polysulfide.

Midinfrared Pulse Compression in a Dispersion-decreasing and Nonlinearity-increasing Tapered As2S3 Photonic Crystal Fiber

  • Shen, Jianping;Zhang, Siwei;Wang, Wei;Li, Shuguang;Zhang, Song;Wang, Yujun
    • Current Optics and Photonics
    • /
    • v.5 no.3
    • /
    • pp.250-260
    • /
    • 2021
  • A tapered As2S3 photonic crystal fiber (PCF) with four layers of air holes in a hexagonal array around the core is designed in this paper. Numerical simulation shows that the dispersion D decreases and the nonlinearity coefficient γ increases from the thick to the thin end along the tapered PCF. We simulate the midinfrared pulse compression in the tapered As2S3 PCF using the adaptive split-step Fourier method. Initial Gaussian pulses of 4.4 ps and a central wavelength of 2.5 ㎛ propagating in the tapered PCF are located in the anomalous dispersion region. With an average power of assumed input pulses at 3 mW and a repetition frequency of 81.0 MHz, we theoretically obtain a pulse duration of 56 fs and a compression factor of 78 when the pulse propagates from the thick end to the thin end of the tapered PCF. When confinement loss in the tapered PCF is included in the simulation, the minimum pulse duration reaches 72 fs; correspondingly, the maximum compression factor reaches 61. The results show that in the anomalous-dispersion region, midinfrared pulses can be efficiently compressed in a dispersion-decreasing and nonlinearity-increasing tapered As2S3 PCF. Due to confinement loss in the tapered fiber, the efficiency of pulse compression is suppressed.

Two-dimensional isotropic patterns for core materials in applications to sandwich structures (샌드위치 구조물 내에서의 응용과 관련된 2차원 단위 셀 형상을 지닌 심재에 대한 연구)

  • Kim, Beom-Keun
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.32 no.8
    • /
    • pp.82-90
    • /
    • 2004
  • The mechanical characteristics of three types of core with two-dimensional isotropic patterns-triangular, hexagonal and starcell-were studied in applications to sandwich structures. The Young's modulus and shear modulus were calculated for the three core types in the direction normal to the faces. The compressive buckling strength and shear buckling strength were calculated by modeling each cell wall of the core as a plate under compressive or shear load. To verify this model, tests were conducted on scaled specimens to measure the compressive buckling strength of each core. The bending flexibilites of the three cores were also studied. Compliances for the three cores were measured using biaxial flexural tests. The three isotropic core patterns exhibited distinct characteristics. In the direction normal to the faces, all three cores had the same stiffness. However, the starcell core exhibited high flexibility compared to the other cores, indicating potential for application to curved sandwich structures.

W-type hexaferrite-epoxy composites for wide-band radar absorption (광대역 레이다 흡수용 W-type 육방정 페라이트-에폭시 복합 소재)

  • Su-Mi Lee;Tae-Woo Lee;Young-Min Kang;Hyemin Kim
    • Journal of Aerospace System Engineering
    • /
    • v.17 no.1
    • /
    • pp.42-50
    • /
    • 2023
  • In this study, hexagonal ferrite powder with chemical formula SrZn2-xCoxFe16O27 was synthesized by a solid-state reaction method and its electromagnetic (EM) wave absorption characteristics were evaluated in the frequency range of 0.1-18 GHz with absorber thickness range of 0 - 10 mm. Reflection loss (RL) affecting electromagnetic wave absorption performance was calculated based on the transmission line theory using measured complex permeabilities and permittivities. RL spectra were also directly measured for some samples. They were well matched with calculated results. High-frequency complex permeability characteristics were changed gradually according to the amount of Co substitution (x). The EM wave absorption frequency band could be tuned accordingly. Hexaferrite samples with x = 1.0, 1.25, and 1.5 exhibited remarkable maximum electromagnetic wave absorption performances with minimum RL (RLmin) lowered than -50 dB. They also showed a very broad frequency band (Δf > 10 GHz) in which more than 90% of the EM wave energy absorption occurred (RL ≤ -10 dB).

Thermal Development from Hybrid Gels of Compounds for Use in Fibre-Reinforced Oxide Ceramics

  • MacKenzie, Kenneth J.D.;Kemmitt, Tim;Meinhold, Richard H.;Schmucker, Martin;Mayer, Lutz
    • The Korean Journal of Ceramics
    • /
    • v.4 no.4
    • /
    • pp.323-330
    • /
    • 1998
  • Mixed oxide compounds of potential usefulness for fibre coatings (hexagonal celsian, $BaAl_2Si_2O_8$ and lanthanum hexaluminate, $LaAl_{11}O_{18}$) or for matrix materials (yttrium aluminium garnet, $Y_3Al_5O_{12}$) were prepared by hybrid sol-gel synthesis and their thermal crystallisation was monitored by thermal analysis, X-ray diffraction and multinuclear solid state MAS NMR. All the gels convert to the crystalline phase below about $12200^{\circ}C$, via amorphous intermediates in which the Al shows and NMR resonance at 36-38 ppm sometimes ascribed to Al in 5-fold coordination. Additional information about the structural changes during thermal treatment was provided by $^{29}Si$, $^{137}Ba$ and $^{89}Y$ MAS NMR spectroscopy, showing that the feldspar framework of celsian begins to be established by about $500^{\circ}C$ but the Ba is still moving into its polyhedral lattice sites about $400^{\circ}C$ after the sluggish onset of crystallization. Lanthanum hexaluminate and YAG crystallise sharply at 1230 and $930^{\circ}C$ respectively, the former via $\gamma-Al_2O_3$, the latter via $YAlO_3$. Yttrium moves into the garnet lattice sites less than $100^{\circ}C$ after crystallisation.

  • PDF

Strain induced/enhanced ferromagnetism in $Mn_3Ge_2$thinfilms

  • Dung, Dang Duc;Feng, Wuwei;Thiet, Duong Van;Sin, Yu-Ri-Mi;Jo, Seong-Rae
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • 2010.02a
    • /
    • pp.135-135
    • /
    • 2010
  • In Mn-Ge equilibrium phase diagram, many Mn-Ge intermetallic phases can be formed with difference structures and magnetic properties. The MnGe has the cubic structure and antiferromagnetic(AFM) with Neel temperature of 197 K. The calculation predicted that the $MnGe_2$ with $Al_2Cu$-type is hard to separate between the paramagnetic(PM) states and the AFM states because this compound displays PM and AFM configuration swith similar energy. Mn-doped Ge showed the FM with Currie temperature of 285 K for bulk samples and 116 K for thin films. In addition, the $Mn_5Ge_3$ compound has hexagonal structure and FM with Curie temperature around 296K. The $Mn_{11}Ge_8$ compound has the orthorhombic structure and Tc is low at 274 K and spin flopping transition is near to 140 K. While the bulk $Mn_3Ge_2$ exhibited tetragonal structure ($a=5.745{\AA}$;$c=13.89{\AA}$) with the FM near to 300K and AFM below 150K. However, amorphous $Mn_3Ge_2$ ($a-Mn_3Ge_2$) was reported to show spin glass behavior with spin-glass transition temperature (Tg) of 53 K. In addition, the transition of crystalline $Mn_3Ge_2$ shifts under high pressure. At the atmospheric pressure, $Mn_3Ge_2$ undergoes the magnetic phase transition from AFM to FM at 158 K. The pressure dependence of the phase transition in $Mn_3Ge_2$ has been determined up to 1 GPa. The transition was found to occur at 1 GPa and 155 K with dT/dP=-0.3K/0.1 GPa. Here report that Ferromagnetic $Mn_3Ge_2$ thin films were successfully grown on GaAs(001) and GaSb(001) substrates using molecular beam epitaxy. Our result revealed that the substrate facilitates to modify magnetic and electrical properties due to tensile/compressive strain effect. The spin-flopping transition around 145 K remained for samples grown on GaSb(001) while it completely disappeared for samples grown on GaAs(001). The antiferromagnetism below 145K changed to ferromagnetism and remained upto 327K. The saturation magnetization was found to be 1.32 and $0.23\;{\mu}B/Mn$ at 5 K for samples grown on GaAs(001) and GaSb(001), respectively.

  • PDF

Magnetic and Microwave Absorbing Properties of M-type Ba-ferrite($BaFe_{12-2X}Ti_XCo_XO_{19}$)with Planar Magnetic Anisortropy (면내 자기이방성을 갖는 M-type Ba-ferrite($BaFe_{12-2X}Ti_XCo_XO_{19}$)의 자기적특성 및 전파흡수특성)

  • 조한신;김성수
    • Resources Recycling
    • /
    • v.7 no.4
    • /
    • pp.22-26
    • /
    • 1998
  • The purpose of this experimenL is to investigate the magnetic anisotropy and microwave absorbing properties in M-type Bat territe (${BaFe}_{12-2X}{A}_{X}{Me}_{X}{O}_{19}$), where $Fe_{3+}$ is substituted by $Ti_{4+}$ in A site and $Co_{2+}$ in Me site. The saturation magnetization (Ms) is linearly decreased with the substitution rate(x) and the coerciviLy (He) is rapidly decreased in accordance with the reduction in t the magnetocrystalline anisotropy For the specimen with x=0.8 and thickness of 2 mm, the reflection loss calculated from the n material constants is less than -10 dB (90% absorption) in the frequency range of 10~16 GHz. The absorption loss is pre이.ctcd t to be more than 20 dElern in the frequency range of 12-16 GHz. The results demonstrate that the Ti-Co substituted M-type Ba-ferrite can be effectively used as a microwave absorber at high frequency range.

  • PDF

Effect of Vacuum Annealing on the Properties of ITO Thin Films (진공 열처리에 따른 ITO 박막의 특성 변화)

  • Heo, Sung-Bo;Kim, So-Young;Kim, Seung-Hong;Kim, Sun-Kyung;Kim, Yu-Sung;Kim, Daeil
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.26 no.2
    • /
    • pp.55-58
    • /
    • 2013
  • ITO thin films deposited on glass substrate with RF magnetron sputtering were vacuum annealed at 100, 200 and $300^{\circ}C$ for 30 minutes and then effect of annealing temperature on the structural, electrical and optical properties of ITO films were investigated. The structural properties are strongly related to annealing temperature. The annealed films above $100^{\circ}C$ are grown as a hexagonal wurtzite phase and the largest grain size is observed in the films annealed at $300^{\circ}C$. The electrical resistivity also decreases as low as $4.65{\times}10^{-4}{\Omega}cm$ with a increase in annealing temperature and ITO film annealed at $300^{\circ}C$ shows the lowest sheet resistance of $43.6{\Omega}/{\Box}$. The optical transmittance in a visible wavelength region also depends on the annealing temperature. The films annealed at $300^{\circ}C$ show higher transmittance of 80.6% than those of the films prepared in this study.