• Journal of Korean Ophthalmic Optics Society
• /
• v.9 no.1
• /
• pp.35-41
• /
• 2004

This study investigated the crystal growth, crystalline structure and the basic optical properties of $PbSnSe/BaF_2$ epilayers. The PbSnSe epilayer was grown on $BaF_2$(111) insulating substrates using a hot wall epitaxy (HWE) technique. It was found from the analysis of X-ray diffraction patterns that $PbSnSe/BaF_2$ epilayer was grown single crystal with a rock-salt structure oriented along [111] the growth direction. Using Rutherford back scattering, the atomic ratios of the PbSnSe was found to be proper stoichiometric. The best values for the full width at half maximum (FWHM) of the DCXRD was 162 arcsec for PbSnSe epilayer. The epilayer-thickness dependence of the FWHM of the DCXRD shows that the quality of the $PbSnSe/BaF_2$ is as expected. The dielectric function ${\varepsilon}(E)$ of a semiconductor is closely related to its electronic energy band structure and such relation can be drawn from features around the critical points(CPs) in the optical spectra. The real and imaginary parts(${\varepsilon}1$ and ${\varepsilon}2$) of the dielectric function ${\varepsilon}$ of PbSe were measured, and the observed spectra reveal distinct structures at energies of the E1, E2 and E3 CPs. These data are analyzed using a theoretical model known as the model dielectric function (MDF). The optical constants related to dielectric function such as the complex refractive index ($n^*=n+ik$), absorption coefficient (${\alpha}$) and normal-incidence reflectivity (R) are also presented for $PbSnSe/BaF_2$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.23 no.1
• /
• pp.51-57
• /
• 2013

We have applied mechanical alloying (MA) to produce Heusler $Fe_2VAl$ thermoelectric alloy using a mixture of elemental $Fe_{50}V_{25}Al_{25}$ powders. An optimal milling and heat treatment conditions to obtain the single phase of Fe2VAl compound with fine microstructure were investigated by X-ray diffraction and differential scanning calorimetry (DSC) measurement. The $Fe_{50}V_{25}Al_{25}$ MA sample ball-milled for 60 hours exhibits a bcc ${\alpha}$-(Fe,V,Al) solid solution. Single phase of Heusler $Fe_2VAl$ compound can be obtained by MA of $Fe_{50}V_{25}Al_{25}$ mixture for 60 hours and subsequently heated up to $700^{\circ}C$. Sintering of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies at $900{\sim}1000^{\circ}C$ under 60 MPa. The Vickers hardness of bulk sample sintered at $1000^{\circ}C$ was high value of Hv 870. All compact bodies have a high relative density above 90 % with metallic glare on the surface.

• Korean Journal of Crystallography
• /
• v.16 no.1
• /
• pp.38-42
• /
• 2005

The crystal structure of Bis(ethylenediamine) cuprate(II)$\cdot$dichromate, $Cu(C_2H_8N_2)_2{\cdot}Cr_2O_7$, has been determined by X-ray crystallography. Crystal data: a=5.682(2), b=8.567(3), c=14.839(3) ${\AA},\;{\alpha}=97.50(2),\;{\beta}=101.06(1),\;{\gamma}=109.38(2)^{\circ}$ Triclinic, P-1 (SG No=2), Z=2, V=653.9(2) ${\AA}^3,\;D_c=2.030gcm^{-3},\;{\mu}=3.273mm^{-1}$. The structure was solved by Patterson method and refined by full matrix least-square methods uslng unit weights. The final R and S values were $R_1=0.0256,\;R_w=0.0708,\;R_{all}=0.0316,\;S=1.151$ for the observed 2291 reflections. The two cupper complex ion has the usual distorted octahedral structure with mean four Cu-N distances of 2.010(3) $\AA$ and the longer mean Cu-O distance of 2.525(2) $\AA$. The Cu-complex and dichromate ions are linked to form infinite chain arranged alternatively along the [111]-direction. The neighboring chains in the (0-11) plane are connected with N1-O5 and N3-O1 hydrogen bonds.

• Applied Chemistry for Engineering
• /
• v.26 no.6
• /
• pp.730-736
• /
• 2015

Cyclotrimethylene trinitramine (RDX) is a high explosive commonly used for military applications. Submicronization of RDX particles has been a critical issue in order to alleviate the unintended and accidental stimuli toward safer and more powerful performances. The purpose of this study is to optimize experimental variables for drowning-out crystallization applied to produce submicron RDX particles. Effects of RDX concentration, anti-solvent temperature and anti-solvent mass were analyzed by the central composite rotatable design. The adjusted determination coefficient of regression model was calculated to be 0.9984 having the p-value less than 0.01. Response surface plots based on the central composite rotatable design determined the optimum conditions such as RDX concentration of 3 wt%, anti-solvent temperature of $0.2^{\circ}C$ and anti-solvent mass of 266 g. The optimum and experimental diameters of RDX particles were measured to be $0.53{\mu}m$ and $0.53{\mu}m$, respectively. The regression model satisfactorily predicts the average diameter of RDX particles prepared by drowning-out crystallization. Structure of RDX crystals was found to be ${\alpha}$-form by X-ray diffraction analysis and FT-IR spectroscopy.

• Journal of the Korean Chemical Society
• /
• v.21 no.5
• /
• pp.307-319
• /
• 1977

The crystal structure of $N-({\alpha}-dimethyl\;{\beta}-hydroxy)ethyl\;N'-cyclohexyl\;thiourea,\;C_{ll}H_{22}N_2OS)$, has been determined by X-ray diffraction method. The compound crystallizes in the orthorhombic space group Pbca with a = 10.33(3), b = 11.82(3), c = 22.57(4)${\AA}$ and Z = 8. A total of 1414 observed reflections collected by the Weissenberg photographs and was solved by heavy atom method and refined by block diagonal least-squares methods to the R value of 0.13. The cyclohexane ring has a normal chair conformation and the thiourea unit is planar. The primary alcoholic group O-H bonded to C(l) makes an intramolecular hydrogen bond with N(2), which leads to stablize the molecule. There are two independent hydrogen bonds in the structure. One of them is of the type N-H${\cdot}{\cdot}{\cdot}$O intramolecular hydrogen bond with the length 2.71${\AA}$, another is of the type O-H${\cdot}{\cdot}{\cdot}$S intermolecular hydrogen bond with the length 3.21${\AA}$ parallel to the b axis. Apart from the hydrogen bonding system the molecules are held together by van der Waals forces in the crystal.

• Journal of the Korean Chemical Society
• /
• v.38 no.5
• /
• pp.359-365
• /
• 1994

The crystal stucture of hexapotassium undecahydrogen tetratungsto hexaantimonate(V) tetrahydrate has been determined from single crystal X-ray diffraction data. Crystal data are as follows: $K_6H_{12}[Sb_6W_4O_{36}]{\cdot}4H_2O$, Fw = 2360.62, tetragonal, I$4_1$/a, a = 10.799(1) ${\AA}$, c = 35.244(5) ${\AA}$, V = 4110.1(7) ${\AA}^3$, Z = 4, $D_x$ = 3.82 g$cm^{-3}$, $\mu(MoK\alpha)$ = 160.15 $cm^{-1}$, T = 293 K, final R = 0.0356 for 2400($F_0 > 3\sigma(F_0))$ independent reflections. The $[H_{12}Sb_6W_4O_{36}]^{-6}$ polyanion independently consists of one tungsten, two antimony, and nine oxygen atoms and belongs to the $\bar4(S_4)$ point group. This polyanion is formed by two open octahedra five membered ring of Sb(3)$O_6-W(1)O_6-Sb(2)O_6-W(1)O_6-Sb(3)O_6$ which is connected at right angle. The Sb-W, Sb-O, and W-O bond distances range from 3.2304(9) to 3.2403(5) $\AA$, 1.745(8) to 2.334(6) $\AA$, and 1.914(7) to 2.039(7) $\AA$, respectively.

• Journal of the Korean Magnetics Society
• /
• v.3 no.2
• /
• pp.130-134
• /
• 1993

The magnetic properties of the amorphous $Fe_{73.5-X}Co_{X}Cu_{1}Nb_{3}Si_{13.5}B_{9}(x=2,\;4)$ alloys, fabricated by a single roll rapid quenching technique and annealed at $400~650^{\circ}C$, have been investigated. The optimum annealing temperature is $550^{\circ}C$ for the amorphous $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy. The properties of the nanocrystalline $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy show the relative permeability of $1.1{\times}10^{4}$ and the coercive force of 0.22 Oe at 1 kHz. When annealed at $600^{\circ}C$, the nanocrystalline $Fe_{69.5}Co_{4}Cu_{1}Nb_{3}Si_{13.5)B_{9}$ alloy shows the relative permeability of $1.0{\times}10^{4}$ and the coercive force of 0.19 Oe at 1 kHz. From the X-ray measurement, it is found that the remarkably improved soft magnetic properties are the effect of the formation of $\alpha$-Fe(Si) grain. By the results of FMR exper-imeIlt, the optimum annealing condition is just below temperature which the peak-to-peak line width of FMR spectrum increase rapidly.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1998.02a
• /
• pp.77-77
• /
• 1998

Present silicon dioxide (SiOz) 떠m as intennetal dielectridIMD) layers will result in high parasitic c capacitance and crosstalk interference in 비gh density devices. Low dielectric materials such as f f1uorina뼈 silicon oxide(SiOF) and f1uoropolymer IMD layers have been tried to s이ve this problem. I In the SiOF ftlm, as fluorine concentration increases the dielectric constant of t뼈 film decreases but i it becomes unstable and wa않r absorptivity increases. The dielectric constant above 3.0 is obtain어 i in these ftlms. Fluoropolymers such as polyte$\sigma$따luoroethylene(PTFE) are known as low dielectric c constant (>2.0) materials. However, their $\alpha$)Or thermal stability and low adhesive fa$\pi$e have h hindered 야1리ru뚱 as IMD ma따"ials. 1 The concept of a plasma processing a찌Jaratus with 비gh density plasma at low pressure has r received much attention for deposition because films made in these plasma reactors have many a advantages such as go여 film quality and gap filling profile. High ion flux with low ion energy in m the high density plasma make the low contamination and go어 $\sigma$'Oss피lked ftlm. Especially the h helicon plasma reactor have attractive features for ftlm deposition 야~au똥 of i앙 high density plasma p production compared with other conventional type plasma soun:es. I In this pa야Jr, we present the results on the low dielectric constant fluorocarbonated-SiOF film d밑JOsited on p-Si(loo) 5 inch silicon substrates with 00% of 0dFTES gas mixture and 20% of Ar g gas in a helicon plasma reactor. High density 띠asma is generated in the conventional helicon p plasma soun:e with Nagoya type ill antenna, 5-15 MHz and 1 kW RF power, 700 Gauss of m magnetic field, and 1.5 mTorr of pressure. The electron density and temperature of the 0dFTES d discharge are measUI벼 by Langmuir probe. The relative density of radicals are measured by optic허 e emission spe따'Oscopy(OES). Chemical bonding structure 3I피 atomic concentration 따'C characterized u using fourier transform infrared(FTIR) s야3띠"Oscopy and X -ray photonelectron spl:’따'Oscopy (XPS). D Dielectric constant is measured using a metal insulator semiconductor (MIS;AVO.4 $\mu$ m thick f fIlmlp-SD s$\sigma$ucture. A chemical stoichiome$\sigma$y of 야Ie fluorocarbina$textsc{k}$영-SiOF film 따~si야영 at room temperature, which t the flow rate of Oz and FTES gas is Isccm and 6sccm, res야~tvely, is form려 야Ie SiouFo.36Co.14. A d dielec$\sigma$ic constant of this fIlm is 2.8, but the s$\alpha$'!Cimen at annealed 5OOt: is obtain려 3.24, and the s stepcoverage in the 0.4 $\mu$ m and 0.5 $\mu$ m pattern 킹'C above 92% and 91% without void, res야~tively. res야~tively.

• Journal of the Mineralogical Society of Korea
• /
• v.5 no.1
• /
• pp.14-21
• /
• 1992

Allanite crystals rich in rare-earth elements(REE) occur in soil developed on top of anorthositic rocks in the Jungsu-ri area of Okjong-myun, Hadong-run, where large Ti orebodies are embedded in the bed rock. In this study allanite is investigated mainly by transmitted light microscopy, electron microprobe analysis, atomic absoption spectrophotometry, X-ray diffraction, infrared spectrocopy. In addition, its specific gravity and micro=indentation hardness value are measured. Allanite occurs with max. dimension of $3cm{\times}6cm$ and coexists with quartz, epidote, zircon, biotite and muscovite. It shows nearly nonmetamict crystallinity, although ${\alpha}$-particles bombardment from the disintegration of the radioactive element Th is detected by an autoradiography. The allanite is particularly enriched in REE(19.88-23.99 wt.%), but is deficient in CaO(8.35-10.29wt.%). Genesis of the allanite in this area is not understood yet. It is, however, assumed to have been formed from magmatic fluid rich in REE and Ti, based on the facts that it ocexists with zircon and that it has high $TiO_2$(0.89-1.13 wt.%) whose concentration is significant in the country rocks.

• Applied Chemistry for Engineering
• /
• v.8 no.6
• /
• pp.994-999
• /
• 1997

The sintering properties of hydroxyapatite isolated from tuna bone and hydroxyapatite-containing wollastonite sintered by solid-state reaction was investigated. As the sinterability of hydroxyapatite dependent upon the particle size by dry milling, it showed a sintering. But the hydroxyapatite-containing wollastonite was appeared good sinterability. On X-ray measurements, the major phases of hydroxyapatite-containing wollastonite by solid state reaction at $1250^{\circ}C$ were identified as hydroxyapatite and pseudowollastonite(${\alpha}-CaSiO_3$). And the phases appeared as whitlockite [$Ca_3(PO_4)_2$] by decomposition of hydroxyapatite at higher temperature above $1250^{\circ}C$. The shapes of microstructure on SEM images changed from porous to dense bulk by elevating temperature. The mean bending strength of hydroxyapatite-containing wollastonite sintered by solid-state reaction at $1300^{\circ}C$ was about 18 MPa, it was close to the cancellous bone's maximum strength, 20 MPa.