• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.15-21
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• 2015

The thermal decomposition characteristics of the ZPP(Zirconium/Potassium perchlorate), widely used as a primary charge of initiators, were investigated by differential scanning calorimetry(DSC). The DSC results with different heating rates were elaborated with AKTS-Thermokinetics software for the determination of the kinetic parameters of the thermal decomposition of ZPP. There was good agreement between the experimental and the simulation curves, based on the determined kinetic parameters, which indicates the validity of the kinetic description of the thermal decomposition process of ZPP.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.448-451
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• 2013

PURPOSE. Translucency of all-ceramic restorations is an important factor which affects the final appearance and esthetic outcome of the restoration. The aim of this study was to evaluate the effect of the shade of coloring liquid on the translucency of zirconia framework. MATERIALS AND METHODS. Thirty zirconium oxide core plate ($15{\times}12{\times}0.5$ mm) were divided into 6 groups of 5 plates each. Each group was classified according to the shade of coloring liquid based on Vita Classic Scale (A2, A3, B1, C2, and D2), and each sample was immersed in coloring liquid for 3 seconds as recommended by the manufacturer, except for the control group. Contrast ratio, as a translucency parameter, was calculated using a spectrophotometer and the data were analyzed with oneway analysis of variance (ANOVA) and Tukey's honestly significant differences (HSD) tests (${\alpha}$=.05). RESULTS. Significant differences in translucency among the control and test groups, and the B1 shaded group and other shades was observed. There were no significant differences among A2, A3, C2, and D2 shaded groups. CONCLUSION. The translucency of the zirconium oxide cores was affected by the coloring procedure and significant differences in the translucency measurements were identified between specific shades.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• Bulletin of the Korean Chemical Society
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• v.23 no.5
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• pp.741-744
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• 2002

Single phase of multicomponent oxide ZrTiO4 film could be prepared through surface sol-gel route simply by coating the mixture of 100 mM zirconium butoxide and titanium butoxide on $Pt/Ti/SiO_2Si(100)$ substrate, following pyro lysis at $450^{\circ}C$, and annealing it at 770 $^{\circ}C.$ The dielectric constant of the film was reduced as the film thickness decreased due to of the interfacial effects caused by layer/electrode and a few voids inside the multilayer. However, the dielectric property was independent of applied dc bias sweeps voltage (-2 to +2 V).The dielectric constant of bulk film, 31.9, estimated using series-connected capacitor model was independent of film thickness and frequency in the measurement range, but theoretical interfacial thickness, ti, was dependent on the frequency. It reached a saturated ti value, $6.9{\AA}$, at high frequency by extraction of some capacitance component formed at low frequency range. The dielectric constant of bulk ZrTiO4 pellet-shaped material was 33.7 and very stable with frequency promising as good applicable devices.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.727-732
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• 2016

A simple and rapid spectrophotometric method has been developed to enable the determination of plutonium concentration in an irradiated fuel solution in the presence of all fission products. An excess of ceric ammonium nitrate solution was employed to oxidize all the valence states of plutonium to +6 oxidation state. Interference due to the presence of fission products such as ruthenium and zirconium, and corrosion products such as iron in the envisaged concentration range, as in the irradiated fuel solution, was studied in the determination of plutonium concentration by the direct spectrophotometric method. The stability of plutonium in +6 oxidation state was monitored under experimental conditions as a function of time. Results obtained are reproducible, and this method is applicable to radioactive samples resulting before the solvent extraction process during the reprocessing of fast reactor spent fuel. An analysis of the concentration of plutonium shows a relative standard deviation of <1.2% in standard as well as in simulated conditions. This reflects the fast reactor fuel composition with respect to uranium, plutonium, fission products such as ruthenium and zirconium, and corrosion products such as iron.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1147-1161
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• 1995

When ceramic membrance was made from metal salt solution in place of metal akoxide solution, crack free and good adhesion to supporter was optimized for sol stability and good adhesion force. A starting sol was prepared from aluminum oxychloride aqueous solutjion in order to inhibit the grain growthof Al2O3 during heat treatment. The crack free dip coating can't be achieved in 1mol/ι zirconium oxychloride solution because of the high viscosity which interferes with the hydration copolymerization between Al3+ ion and Zr4+ ion. Thus Al2O3-ZrO2 sol stability and viscosity for dip coating was effective when 0.01 mol/ι zirconium oxychloride was added. The minimizing of crack and achieving better adhesion to the supporter wa obtained by microwave drying, surfactant addition and ultrasonic dip coating in wet atmosphere. The result seems to minimize the capillary force and improve the adhesive ability to supporter during the process. Where the average pore size of Al2O3-ZrO2 ultrafilter ceramic membrane measured 17 Å by the BET method and observed γ-Al2O3 phase with tetragonal zirconia after firing at 700℃.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.358-365
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• 2003

Zirconium nitride powders were synthesized at a relatively lower temperature using methane as a reducing agent in the nitridation of zircoia. $ZrO_2$ powder was prepared by a sol-gel technique. The resulting sol-gel was centrifuged, and the gel was washed with deionized water. Anhydrous ammonia was used as the nitrogen source and methane was used as the reducing agent. Conversion diagrams show the equilibrium solid phase as a function of reagent concentrations for a specific temperature and gas pressure for the reagent system $NH_3-ZrO_2-CH_4$. The reagent concentration ranges within which pure ZrN is formed increase with increasing reaction temperature. Low pressure with an excess of hydrogen decreases the reaction temperature at which pure ZrN is formed. Low pressure together with the introduction of excess hydrogen into the reaction system increases Zr and N conversion efficiency and retards C deposition.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.421-425
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• 2003

The reductive extraction process is an important step to refine the TRU product from the electrorefining process for the preparation of transmutation reactor fuel. In this study, it was studied on the reductive extraction between the eutectic salt and Bi metal phases. The solutes were zirconium and the rare earth elements, where zirconium was used as a surrogate for the transuranic(TRU) elements. All the experiments were performed in a glove box filled with a argon gas. Li-Bi alloy was used as a reducing agent to reduce the high chemical activity of Li. The reductive extraction characteristics were examined using ICP, XRD and EPMA analysis. The reduction reaction was equilibrated within 3 hours after the Li addition. Three eutectic salt systems were compared and Zr was successfully separated from the rare earth elements in all the three salt systems.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.495-501
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• 2020

In this study, zirconium fumarate of metal-organic framework (MOF-801) was solvothermally synthesized at 130 ℃ and characterized through powder X-ray diffraction (PXRD) analyses and porosity measurements from N₂ sorption isotherms at 77 K. The ability of MOF-801 to act as an adsorbent for the phosphate removal from aqueous solutions at 25 ℃ was investigated. The phosphate removal efficiency (PRE) obtained by 0.05 g/L adsorbent dose at an initial phosphate concentration of 60 ppm after 3 h was 72.47%, whereas at 5 and 20 ppm, the PRE was determined to be 100% and 89.88%, respectively, after 30 min for the same adsorbent dose. Brunauer-Emmett-Teller (BET) surface area and pore volume of the bare MOF-801 sample were 478.25 ㎡/g and 0.52 ㎤/g, respectively, whereas after phosphate adsorption (at an initial concentration of 60 ppm, 3 h), the BET surface area and pore volume were reduced to 331.66 ㎡/g and 0.39 ㎤/g, respectively. The experimental data of kinetic (measured at initial concentrations of 5, 20 and 60 ppm) and isotherm measurements followed the pseudo-second-order kinetic equation and the Freundlich isotherm model, respectively. This study demonstrates that MOF-801 is a promising material for the removal of phosphate from aqueous solutions.

• Journal of the Korean institute of surface engineering
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• v.36 no.3
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• pp.251-255
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• 2003

With increasing environmental demands in surface treatment of steel sheets, the passivation layers containing hexavalent chromium $(Cr^{+6})$ are being replaced by non-chromium or trivalent chromium compounds. After review on the various types of inorganic compounds, the zirconates was chosen as the candidate for alternative to sodium dichromate in the aspect of its barrier properties with excellent adhesion to organics. The ammonium zirconium carbonate (AZC) and sodium hexafluorozirconate (SFZ) could be reach $70-80\%$ level of CDC (cathodic dichromate) treatment by their single applications. But high porosity in the AZC layer and poor electrical conductivity of SFZ solution limit the single application of zirconate. Mixed composition of zirconates to compensate their inferiorities or incorporation of organic compounds to seal the porosity seems to be inevitable to match up the target level of Cr-free passivation of tinplate.