• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.349-358
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• 2000

Fabrication and Characterization of Bi$_{2}$/Sr$_{2}$/CaCu$_{2}$/O$_{8}$(Bi2212) superconductor thick films were fabricated successfully on C tapes by liquid reaction between Cu-free precursors of Bi$_{x}$/SrCaO/$_{y}$(x=1.2-2) and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-87$0^{\circ}C$ for several minutes in air oxygen nitrogen and low oxygen pressure. In order to obtain the optimum heat-treatment condition we studied the effect of the precursor composition the printing thickness and the heat-treatment atmosphere on the superconducting properties of Bi2212 films and the reaction mechanism. Microstructures and phases of thick films were analyzed by films and the reaction mechanism. Microstructures and phases of thick films were analyzed by optical microscope and XRD. The electric properties of superonducting films were examined by the four probe method. At heat-treatment temperature the thick films were in a partially molten state by liquid reaction between CuO of the oxidized copper tape and the precursors which were printed on Cu tapes. During the heat-treatment procedure Bi2212 superconducting particle nucleate and grow in preferred orientations.ons.s.

• International Journal of Advanced Culture Technology
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• v.3 no.2
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• pp.100-109
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• 2015

Environmental problems from petroleum-based plastic wastes have been rapidly increasing in recent years. The alternative solution is focus on the development of environmental friendly plastic derived from renewable resource. Poly(lactic acid) (PLA) is a biodegradable polymer synthesized from biomass having potential to replace the petroleum-based non-degradable polymers utilizations. PLA can be synthesized by two methods: (1) ring-opening of lactide intermediate and (2) direct polycondensation of lactic acid processes. The latter process has advantages on high yields and high purity of polymer products, materials handling and ease of process treatments. The polymerization process of PLA synthesis has been widely studied in a laboratory scale. However, the mass scale production using direct polycondensation of lactic acid has not been reported. We have investigated the kinetics and scale-up process of direct polycondensation method to produce PLA in a pilot scale. The order of reaction is 2 and activation energy of lactic acid to lactic acid oligomers is 61.58 kJ/mol. The pre-polymer was further polymerized in a solid state polymerization (SSP) process. The synthesized PLA from both the laboratory and pilot scales show the comparable properties such as melting temperature and molecular weight. The appearance of synthesized PLA is yellow-white solid powder.

• Resources Recycling
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• v.26 no.3
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• pp.17-25
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• 2017

Electric arc furnace steelmaking dust has various physicochemical properties as volatile components generated in the melting process of steel scraps in an electric arc furnace, which is captured in oxide form as fine powder by reacting with oxygen in the air. In order to efficiently recycle these electric arc furnace dust, a kinetic basic experiment and a pilot production test were carried out in parallel. As a result, it was found that the electric arc furnace dust contain a large amount of Cl and alkali components, thus it was expected that the compounds have a great adverse effect on the actual operation for the recycling. It was confirmed that the volatilization behavior was progressing actively at $1100^{\circ}C$ and the electric arc furnace dust was melted at $1250^{\circ}C$. These results are the same as a result of pilot test for the formation behavior of zinc oxide and reduced iron. These results should be useful as basic data for designing the recycling plant of the electric arc furnace dust and establishing the operating conditions.

• Journal of Magnetics
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• v.7 no.2
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• pp.29-39
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• 2002

The initial NiCuZn synthetic ferrite were acquired from thermally decomposing the metal nitrates $Fe(NO_3)_39H_2O, Zn(NO_3)_26H_2O, Ni(NO_3)_26H_2O, and Cu(NO_3)_23H_2O$ at $150^circ{C}$ for 24 hours, and then we calcined the synthetic powder at $500^circ{C}$, pulverized each of those for 3, 6, 9, 12, and 15 hours in a steel ball mill, sintered each at $700^circ{C}$ to $1,000^circ{C}$ for 1 hour, and thus studied their microstructures and electromagnetic properties. We could make the initial specimens chemically bonded in liquidity at a low-temperature $150^circ{C}$, by using the low melting points less than $200^circ{C}$ of the metal nitrates instead of the mechanical ball-mill pulverization, then narrow a distance between the particles into a molecular one, and thus lower the reaction point of sintering by at least $200^circ{C}$ to $300^circ{C}$. Their initial permeability was 50 to 400 and their maximum magnetic induction density and coercive force, 2,400 G and 0.3 Oe to 0.5 Oe respectively, which was similar to those of NiZnCu ferrite synthesized in the conventional process. In the graph of initial permeability by frequencies, a $180^circ{C}$ rotation of the magnetic domains which appears in a broad band of micro-wave before and after the resonance frequency, could be perceived.

• Journal of Hydrogen and New Energy
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• v.3 no.2
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• pp.25-33
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• 1992

With the aim to obtain $TiO_2$ films with an increased photorespones and absorbance in the visible region of the solar spectrum, the direct oxidation of titanium alloys were performed. In this study, $Ti-Ga_2O_3$ alloy was prepared by mixing, pressing and arc melting of appropriate amounts of titanium and $Ga_2O_3$ powder. Electrochemical measurements were performed in three electrode cell using electrolyte of 1M NaOH solution. The oxide films on $Ti-Ga_2O_3$ alloy was composed of $Ti_2O$, TiO, $TiO_2$, $Ga_2TiO_5$. The free energy efficiency (${\eta}e$) of $Ti-Ga_2O_3$ oxide films had 0.8~1.3 % and were increased with the increase of $Ga_2O_3$ content up to 10wt %. The onset potential ($V_{on}$) had -0.8V~0.9V ranges and were shifted to anodic direction with the increase of $Ga_2O_3$ content. The spectral response of Ti-$Ga_2O_3$ oxides were similar to the response of the $TiO_2$ and their $E_g$ were observed to 2.90~3.0eV. Variations of onset potential($V_{on}$) associated with electrolyte pH were -59mV/pH. This probably reflects the nature of the bonding of $OH^-$ ion to the $TiO_2$ surface, a common phenomena in the transition-metal oxides.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.267-267
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• 2006

전력에 큰 손실을 초래하는 고장전류를 차단하기 위한 한류기(FCL) 소재로서 고온 초전도체인 BSCCO 2212가 사용된다. 고온에서 용융된 BSCCO 2212 분말은 원심성형법에 의해 한류기용 튜브로 제조되었다. BSCCO 튜브의 기계적 특성을 높이고 용융온도를 낮추기 위해 $SrSO_4$(10wt-%)를 첨가하였다. 용탕은 $1200^{\circ}C$에서 완전히 용융되어 금속 몰드로 주입되었고 원심성형에 사용되는 금속 몰드는 $550^{\circ}C$ 온도로 2시간 예열 후 1020 ~ 2520 RPM으로 회전시켰다. 원심력에 의해 성형된 BSCCO 튜브는 약 48시간 동안 로에서 서냉 후 금속 몰드로부터 분리하였다. 튜브의 용이한 분리를 위해 이형제로서 BSCCO 2212 powder를 사용하였고 임계전류측정을 고려하여 Ag tape 단자를 튜브 끝단에 부착하였다. BSCCO 제조 공정에 있어서 몰드의 예열온도, 용융온도, 몰드 회전속도 등의 변수를 조절하여 최적의 조건을 확립하였다. 제조한 BSCCO 튜브의 임계전류($I_c$)와 임계전류밀도($J_c$)는 77K에서 536A와 $205A/cm^2$ 이었다. 본 연구에서는 BSCCO 2212 튜브를 제조하는 공정조건 변화와 각 조건에서 제조된 BSCCO 2212 튜브의 전기적 특성 및 그에 따른 분석에 대해 기술하였다.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.255-258
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• 2014

Zirconium boride is an artificial or which is rarely found in the nature. $ZrB_2$ is popular in the hard material industry because it has a high melting point, excellent mechanical properties and chemical stability. There are two known methods to synthesize $ZrB_2$. The first involves direct reaction between Zr and B, and the second is by reduction of the metal halogen. However, these two methods are known to be unsuitable for mass production. SHS(Self-propagating High-temperature Synthesis) is an efficient and economic method for synthesizing hard materials because it uses exothermic reactions. In this study, $ZrB_2$ was successfully synthesized by subjecting $ZrO_2$, Mg and $B_2O_3$ to SHS. Because of the high combustion temperature and rapid combustion, in conjunction with the stoichiometric ratio of $ZrO_2$, Mg and $B_2O_3$; single phase $ZrB_2$ was not synthesized. In order to solve the temperature problem, Mg and NaCl additives were investigated as diluents. From the experiments it was found that both diluents effectively stabilized the reaction and combustion regime. The final product, made under optimum conditions, was single-phase $ZrB_2$ of $0.1-0.9{\mu}m$ particle size.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.1
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• pp.13-18
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• 1991

The formation of high $T_c$ phase is very sluggish and c parameter of unit cell of high $T_c$ phase is about $37{\AA}$. High $T_c$ oxide superconductor with a $T_c$ above 100 K has been successfully prepared by solid state reaction method in BiSrCaCuO system by Pb adding. The microstructure related to the formation of the high $T_c$ phase has been investigated. As compared with YBCO compound, the formation reaction of the high $T_c$ requires long time heat treatment. It is due to the transformation from the low $T_c$ phase to high $T_c$ phase. The sintering just below the melting point of the calcined powder mixture is effective on the formation of the high $T_c$ phase in Pb-added BiSrCaCuO system. The growth of the high $T_c$ superconducting phase has a thin plate shape, which is characterized by the c parameter of $37{\AA}$. The formation of the high $T_c$ phases is delayed by the excessive addition of Pb. The lattice parameter(c) of the unit cell (both the low and high $T_c$ phases) is increased with increase of Pb.

• Journal of Nutrition and Health
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• v.38 no.8
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• pp.663-671
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• 2005

The purpose of this study was to investigate not only quality characteristics such as overrun, meltdown and sensory evaluation of oligosaccharide-supplemented soy ice cream but also physiological effects of ice cream with soy and/or oligosaccharide on blood sugar and lipid profile in streptozotocin-induced diabetic rats. Powder of parched soybean was added at $7.6\%$ replacing skimmed milk and cream, soybean oil at $7.6\%$ replacing milk oil in cream, and fructooli-gosaccharide at $9.5\%$ replacing sucrose on weight basis. Five kinds of ice cream were prepared: MMS (skimmed milk, milk oil, sucrose), MMO (skimmed milk, milk oil, oligosaccharide), SSS (soybean, soybean oil, sucrose), SSO (soybean, soybean oil, oligosaccharide), and BSO (black soybean, soybean oil, oligosaccharide). Overrun and meltdown of soy ice cream were significantly lower than those of milk ice cream. Scores of sensory evaluation especially in mouth feel and melting feel in mouth were lower in soy ice cream. Freeze-dried ice cream was supplemented to AIN93-based diets at $30\%$(w/w). Sprague-Dawley male rats with diabetes induced by injecting streptozotocin were fed experimental diets for 4 weeks. Plasma glucose level was significantly lowered in SSO group compared with MMS group. Plasma insulin levels of MMO and SSO groups were not significantly different from that of normal group, while those of MMS and SSO group were significantly lower than normal group. Plasma cholesterol was decreased in groups fed ice cream supplemented either soybean or fructooligosaccharide compared to MMS group. HDL-cholesterol level was elevated and triglyceride was decreased significantly in MMO group compared to MMS group. LDL-cholesterol levels of SSS and BSO groups and liver triglyceride level of SSO group were significantly lower compared to MMS group. In conclusion, oligosaccharide-supplemented soy ice cream lowered blood sugar, and ice cream supplemented with soybean and/or oligosaccharide improved lipid profile in diabetic rats.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.10a
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• pp.74-74
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• 2017

Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. Uranium deposit recovered from the solid cathode is a dendritic powder. It is necessary to separate the adhered salt from the deposits prior to the consolidation of uranium deposit. The adhered salt is composed of lithium, potassium, uranium, and rare earth chlorides. Distillation process was employed for the cathode processing. One of the operation methods is distillation of the salt at low temperature ($900^{\circ}C$), and then melting of the deposit at high temperature to avoid a backward reaction. For the development of the salt distiller, the distillation behavior of the low vapor pressure chlorides should be studied. Rare earth chlorides in the adhered salt of uranium deposits have relatively low vapor pressures compared to the process salt (LiCl-KCl). In this study, the evaporation rates of the lanthanum and neodymium chlorides were measured for the salt separation from electrorefiner uranium deposits in the temperature range of $825{\sim}910^{\circ}C$. The evaporation rate of both chlorides increased with an increasing templerature. The evaporation rate of lanthanum chloride varied from 0.12 to $1.68g/cm^2/h$. Neodymium chloride was more volatile than lanthanum chloride. The evaporation rate of neodymium chloride varied from 0.20 to $4.55g/cm^2/h$. The evaporation rate of both chlorides are more than $1g/cm^2/h$ at $900^{\circ}C$. Even though the evaporation rates of both chlorides were less than that of the process salt, the contents of the lanthanide chlorides were small in the adhered salt. Therefore it can be concluded that $900^{\circ}C$ is suitable for the operation temperature of the salt distiller.