• Analytical Science and Technology
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• v.23 no.1
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• pp.45-53
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• 2010

For the determination of chlorine in uranium compound, analytical methods by using a steam distillation and a pyrohydrolysis have been developed. The steam distillation apparatus was composed of steam generator, distilling flask and condenser etc. The samples were prepared with an aliquot of LiCl standard solution and a simulated spent nuclear fuel. A sample aliquot was mixed with a solution containing 0.2 M ferrous ammonium sulfate-0.5 M sulfamic acid 3 mL, phosphoric acid 6 mL and sulfuric acid 15 mL. The chloride was then distilled by steam at the temperature of $140^{\circ}C$ until a volume of $90{\pm}5\;mL$ is collected. The pyrohydrolysis equipment was composed of air introduction system, water supply, quartz reaction tube, combustion tube furnace, combustion boat and absorption vessel. The chloride was separated from powdered sample which is added with $U_3O_8$ accelerator, by pyrohydrolysis at the temperature of $950^{\circ}C$ for 1 hour in a quartz tube with a stream of air of 1 mL/min supplied from the water reservoir at $80^{\circ}C$. The chlorides collected in each absorption solution by two methods was diluted to 100 mL and measured with ion chromatography to determine the recovery yield. For the ion chromatographic determination of chlorine in molten salt retained in a metal ingot, the chlorine was separated by means of pyrohydrolysis after air and dry oxidation, and grinding for the sample.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.4
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• pp.419-430
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• 2007

Purpose: This in vitro study evaluated shear bond strengths of surface treatment porcelains with four porcelain repair systems simulating intraoral bonding of composite resin to feldspathic porcelain or pressable porcelain. Material and methods: Eighty Porcelain disks were prepared. Group A: forty disk specimens were fabricated with Feldspathic Porcelain($Omega^{(R)}900$, Vident, Menlo Park, CA, USA). Group B: forty disk specimens were fabricated with Pressable Porcelain(IPS Empress 2 ingot, Ivoclar-Vivadent, Schaan, Liechtenstein, Germany). Each groups was divided into 4 subgroups and composite resin cylinders were bonded to specimen with one of the following four systems: Clearfil Porcelain Bond(L. Morita, Tustin, CA, USA), Ulradent Porcelain Etch. (Ultradent, Salt Lake City UT, USA), Porcelain Liner-M(Sun Medical Co., Kyoto, Japan), Cimara Kit(Voco, Germany). After surface conditioning with one of the four porcelain repair systems substrate surfaces of the specimen were examined microscopically(SEM). Shear bond strengths of specimens for each subgroup were determined with a universal testing machine (5mm/min crosshead speed) after storing them in distilled water at $37{\pm}1^{\circ}C$ for 24 hours. Stress at failure was measured in $MP_a$, and mode of failure was recorded. Differences among four repair systems were analyzed with two way ANOVA and Duncan test at the 95% significance level. Results: In the scanning electron photomicrograph of the treated porcelain surface, hydrofluoric acid etched group appeared the highest roughness. The shear bond strength of the phosphoric acid etched group was not significantly(p>0.05) different between feldspathic porcelain and pressable porcelain. But in no treatment and roughened with a bur group, the shear bond strength of the feldspathic porcelain was significantly higher than that of the pressable porcelain. In hydrofluoric acid etched group, the shear bond strength of the pressable porcelain was significantly higher(p<0.05). Conclusion: 1. Treatment groups showed significantly greater shear bond strengths than no treatment group(p<0.05). 2. Group with more roughened porcelain surface did not always show higher shear bond strengths. 3. In phosphoric acid etched group, there was no significant difference in shear bond strength between feldspathic porcelain and pressable porcelain(p>0.05). However in the other groups, there were significant differences in shear bond strengths between feldspathic porcelain and pressable porcelain(p<0.05).

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.167-171
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• 2016

Background: TlBr is of considerable technological importance for radiation detection applications where detecting high-energy photons such as X-rays and ${\gamma}$-rays are of prime importance. However, there were few reports on investigating optical properties of TlBr itself for deeper understandings of this material and for making better radiation detection devices. Thus, in this paper, we report on the optical characterizations of TlBr single crystals. Spectroscopic ellipsometry (SE) and photoluminescence (PL) measurements at RT were performed for this work. Materials and Methods: A 2-inch TlBr single crystalline ingot was grown by using the vertical Bridgman furnace. SE measurements were performed at RT within the photon energy range from 1.1 to 6.5 eV. PL measurements were performed at RT by using a home-made PL system equipped with a 266 nm-laser and a spectrometer. Results and Discussion: Dielectric responses from SE analysis were shown to be slightly different among the different samples possibly due to the different structural/optical properties. Also from the PL measurements, it was observed that the peak intensities of the middle samples were significantly higher than those of the other two samples. With the given values for permittivity of free space (${\varepsilon}_0=8.854{\times}10^{-12}F{\cdot}m^{-1}$), thickness (d = 1 mm), and area ($A=10{\times}10mm^2$) of the TlBr sample, capacitances of TlBr were 6.9 pF (at $h{\nu}=3eV$) and 4.4 pF (at $h{\nu}=6eV$), respectively. Conclusion: SE and PL measurement and analysis were performed to characterize TlBr samples from the optical perspective. It was observed that dielectric responses of different TlBr samples were slightly different due to the different material properties. PL measurements showed that the middle sample exhibited much stronger PL emission peaks due to the better material quality. From the SE analysis, optical, dielectric constants were extracted, and calculated capacitances were in the few pF range.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.2
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• pp.166-176
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• 1996

The fundamental conditions for growing $CsLiB_{6}O_{10}$ crystal, new nonlinear optical material, were investigated. Stoichiometirc mixture of $CsLiB_{6}O_{10}$ composition resulted in the crystal of the same composition in the process of heating at the temperature above $600^{\circ}C$. No phase transition was observed in the $CsLiB_{6}O_{10}$ crystal in the temperature range of $600^{\circ}C~800^{\circ}C$, and $CsLiB_{6}O_{10}$ crystal melted congruently at $850^{\circ}C$. When the melt of this composition was cooled at rates of $1~150^{\circ}C/hr$, glass state ingot was formed regardless of cooling rates. However, $CsLiB_{6}O_{10}$ crystals were formed directly from the melt at any cooling rate in the presence of $CsLiB_{6}O_{10}$ seed crystal in the melt. Transparent $CsLiB_{6}O_{10}$ single crystal was grown from the melt using the seed crystal at the growing rate of 0.06 mm/hr in the furnace having the temperature gradient of $100^{\circ}C/cm$. Analysis of the single crystal showed that the crystal belonged to the noncentrosymmetric tetragonal space group 142d and unit cell dimensions were $a=10.467(1)\;{\AA},\;c=8.972(1)\;{\AA}\;and\;V=983.0(2)\;{\AA}^3$. Optical absorption edge of the crystal was observed at 180mm and the crystal showed a good optical transparency (70% transmittance, sample thickness 0.5 mm) in the wide wavelength range above 300 nm.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.3
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• pp.121-129
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• 1997

$ZrV_{0.1}Mn_{0.7}Ni_{1.2}$ alloy ingot (bulk alloy) made by the arc melting was found to be consisting of mostly of $ZrV_{0.2}Mn_{0.98}Ni_{1.04}$ matrix alloy and $ZrV_{0.01}Mn_{0.13}Ni_{1.2}$ 2nd phase alloy. The former alloy had the form of the C15 type Laves alloy structure and the latter one had the intermetallic compound structure of $Zr_9Ni_{11}$. In order to investigate the effect of these two phases on the electrochemical charge-discharge characteristics of bulk $ZrV_[0.1}Mn_0.7}Ni_{1.2}$ alloy, the matrix and the 2nd phase alloys were fabricated separately by arc melting method and their electrochemical characteristics were studied and compared with the bulk alloy. It was found that the discharge capacity was the lowest of 160 mAh/g in the 2nd phase alloy. The matrix alloy exhibited 200 mAh/g. Both were lower than that of the bulk alloy of 250 mAh/g. The matrix and the bulk alloys showed a similar properties in the activation stage, the high rate dischargeability and the self discharge characteristics. Also a signigicant capacity decrease was observed after activation in both alloys. Whereas the 2nd phase alloy showed the very different characteristics. This alloy was found to be difficult to activate. However the capacity was remained constant after the activation. Also the self discharge rate was seen to be better than those of the matrix and the bulk alloys.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.383-388
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• 2019

High purity SiC fine powder with metal impurity contents of less than 1 ppm was synthesized by improved carbothermal reduction process, and the synthesized powder was used for SiC single crystal growth in RF heating PVT device at temperature above 2,100℃. In-situ x-ray image analyzer was used to observe the sublimation of the powder and single crystal growth behavior during the growth process. SiC powder was used as a source of single crystal growth, exhausted from the outside of the graphite crucible at the growth temperature and left graphite residues. During the growth, the flow of raw materials was concentrated in the middle and influenced the growth behavior of SiC single crystals. This is due to the difference in temperature distribution inside the crucible due to the fine powder. After the single crystal growth was completed, the single crystal ingot was cut into a 1 mm thick single crystal substrate and finely polished using a diamond abrasive slurry. A dark yellow 4H-SiC was observed overall of single crystal substrate, and the polycrystals generated in the outer part may be caused by the incorporation of impurities such as the bubble layer mixed in the process of attaching the seed crystal to the seed holder.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.71-77
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• 2013

Aluminium powder as reductant in aluminothermy process needs a fine particle size under 200 mesh, but it is not easy economically to make that because of its high ductility and powder production cost. In order to reduce the production cost of fine aluminum powder as reductant of $Mn_3O_4$ waste dust, therefore, the properties of aluminium alloy powder were investigated. Aluminium alloy ingot containing large amount of manganese can be crushed easily because of its intermetallic compounds having brittle properties. The manganese is also main element in ferro-manganese. We can obtain economically Al-15%Mn alloy powder by mechanical comminution process. And the result of thermite reaction using Al-15% Mn alloy powder instead of pure Al powder showed the fact that can be obtained the ferro-manganese which have a high purity in case of using pure aluminium powder as reductant. The recovery of manganese from $Mn_3O_4$ waste dust with Al-15%Mn alloy powder was higher level of about 70% than about 65% in case of using aluminium powder, that is due to lower spatter loss.

• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.236-245
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• 1993

Single crystals, SbSI : V, SbSeI : V, BiSI : V, BiSeI : V, SbSI : Cr, SbSeI : Cr, BiSI : Cr, BiSeI : Cr, SbSI : Ni, SbSeI : Ni, BiSI : Ni, and BiSeI : Ni were grown by the vertical Bridgman method. It is found that the grown single crystals have an orthorhombic structure and the indirect optical transitions. The temperature dependence of energy gap shows the two reflection point related with the phase transitions and is well fitted with Varshni equation in the continuous region. The optical absorption peaks due to the doped impurities (V, Cr and Ni) are respectively attributed to the electron transitions between the split energy levels of $V^{+2}$, $Cr^{+2}$ and $Ni^{+2}$ ions sited at $T_d$ symmetry of the host lattice.

• Proceedings of the KACD Conference
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• 2001.05a
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• pp.235-237
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• 2001

;Dentistry has benefited from tremendous advances in technology with the introduction of new techniques and materials, and patients are aware that esthetic approaches in dentistry can change one's appearance. Increasingly. tooth-colored restorative materials have been used for restoration of posterior teeth. Tooth-colored restoration for posterior teeth can be divided into three categories: 1) the direct techniques that can be made in a single appointment and are an intraoral procedure utilizing composites: 2) the semidirect techniques that require both an intraoral and an extraoral procedure and are luted chairside utilizing composites: and 3) the indirect techniques that require several appointments and the expertise of a dental technician working with either composites or ceramics. But, resin restoration has inherent drawbacks of microleakage. polymerization shrinkage, thermal cycling problems. and wear in stress-bearing areas. On the other hand, Ceramic restorations have many advantages over resin restorations. Ceramic inlays are reported to have less leakage than resin restoration and to fit better. although marginal fidelity depends on technique and is laboratory dependent. Adhesion of luting resin is more reliable and durable to etched ceramic material than to treated resin composite. In view of color matching, periodontal health. resistance to abrasion, ceramic restoration is superior to resin restorationl. Materials which have been used for the fabrication of ceramic restorations are various. Conventional powder slurry ceramics are also available. Castable ceramics are produced by centrifugal casting of heat-treated glass ceramics. and machinable ceramics are feldspathic porcelains or cast glass ceramics which are milled using a CAD/CAM apparatus to produce inlays (for example, Cered. They may also be copy milled using the Celay apparatus. Pressable ceramics are produced from feldspathic porcelain which is supplied in ingot form and heated and moulded under pressure to produce a restoration. Infiltrated ceramics are another class of material which are available for use as ceramic inlays. An example is $In-Ceram^{\circledR}$(Vident. California, USA) which consists of a porous aluminum oxide or spinell core infiltrated with glass and subsequently veneered with feldspathic porcelain. In the 1980s. the development of compatible refractory materials made fabrication easier. and the development of adhesive resin cements greatly improved clinical success rates. This case report presents esthetic ceramic inlays for posterior teeth.teeth.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.587-598
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• 2005

Statement of problem: Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. Lithium disilicate glass-ceramic system has superior color reproducibility, because it uses the ceramic ingot which is similar to teeth shade and uses the staining technique and layering technique. However, staining technique has a fault of discoloration. Also, porcelain is divided core and dentin layer, it is not enough to study about the influence of porcelain layer thickness and shade on the shade of ceramic restorations. Purpose: The purpose of this study was to evaluate the influence of porcelain layer thickness and color on the final shade of ceramic restorations. Materials and method: The CIE $L^*a^*b^*$(CIELAB) values of 72 assembled specimens, each consisting of 3 discs (enamel porcelain 0.2 mm/dentin porcelain -1.2, 0.9, 0.7, 0.5 or 0.3 mm/ceramic core -0.3, 0.5, 0.7, 0.9 or 1.2 mm, diameter is 1.0 mm) were evaluated with a spectrophotometer (Model Chromaview 300, Spectron Tech Co, Korea) for the shade A1, A2, A3 and A4. Distilled water (refractive index: 1.7) was used to attain optical contact between the layers. White, white gray, and white brown backgrounds were used to assess the influence of the background on the final shade. And the mean color difference value$({\Delta}E)$ was calculated. Results and conclusion: The results obtained from this study were as follows. 1. There was a significant correlation between the thickness ratio of the ceramic core/dentin porcelain system and $L^*,\;a^*\;and\;b^*$ values when the total thickness of specimen combination was smaller than 1.4 mm(P<0.05). 2. The specimen which the ceramic core thickness was more than 0.7 mm had the best masking effect against background colors. 3. The mean color difference value$({\Delta}E)$ is smaller than 2 $({\Delta}E<2)$ when the ceramic core thickness was larger than 0.7 mm and the total thickness of specimen was more than 1.4 mm.