• Transactions of the Korean Society of Automotive Engineers
• /
• v.23 no.2
• /
• pp.199-207
• /
• 2015

Solid materials of ammonia sources with SCR have been considered for the application of lean NOx reduction in automobile industry, to overcome complex problems of liquid urea based SCR. These solid materials produce ammonia gas directly with proper heating and can be packaged by compact size, because of high volumetric ammonia density. Among ammonium salts and metal ammine chlorides, calcium ammine chloride was focused on this paper due to low decomposition temperature. In order to make calcium ammine chloride in lab-scale, simple reactor and glove box was designed and built with ammonium gas tank, regulator, and sensors. Basic test conditions of charging ammonia gas to anhydrous calcium chloride are chosen from equilibrium vapor pressure by Van't Hoff plot based on thermodynamic properties of materials. Synthetic method of calcium ammine chloride were studied for different durations, temperatures, and pressures with proper ammonia gas charged, as a respect of ammonia gas adsorption rate(%) from simple weight calculations which were confirmed by IC. Also, lab-made calcium ammine chloride were analyzed by TGA and DSC to clarify decomposition step in the equations of chemical reaction. To understand material characteristics for lab-made calcium ammine chloride, DA, XRD and FT-IR analysis were performed with published data of literature. From analytical results, water content in lab-made calcium ammine chloride can be discovered and new test procedures of water removal were proposed.

• Korean Journal of Food Science and Technology
• /
• v.44 no.2
• /
• pp.202-206
• /
• 2012

In order to prepare rice vinegar, $takju$ fermentation was performed, using two different compositions; cooked rice supplemented with $Rosa$ $rugosa$ Thunb. (CR-R) and uncooked rice supplemented with $Rosa$ $rugosa$ Thunb. (UR-R). After ethanol fermentation, ethanol contents of $takju$ were adjusted to 6.0%, and then acetic acid fermentation was carried out using $Acetobacter$ $aceti$ at $30^{\circ}C$ with 200 rpm for 9 days. Supplementations of 1% acetic acid to $takju$ prior to acetic acid fermentation were a critical step in achieving a successful fermentation; final organic acid contents increased in a dose dependent manner. A higher content of organic acids, 1.6-6.9%, was found in UR-R vinegar. The level of free amino acid and GABA in UR-R vinegar was higher than that of CR-R vinegar, with glutamic acid and arginine, as the major amino acids. This finding demonstrates that heating process of rice prior to ethanol fermentation affects the quality of vinegar significantly.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.2
• /
• pp.53-57
• /
• 2007

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an $IC1000_{TM}$ K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to $38.4\;^{\circ}C$ with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest $p{\times}V$ polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest $p{\times}V$ polishing condition and indicates that the polishing process was mechanical limited in the low $p{\times}V$ polishing region and became chemically and mechanically balanced with increasing polishing power.

• Korean Journal of Materials Research
• /
• v.20 no.10
• /
• pp.508-512
• /
• 2010

The optimum route to fabricate nano-sized Fe-50 wt% Co and hydrogen-reduction behavior of calcined Fe-/Conitrate was investigated. The powder mixture of metal oxides was prepared by solution mixing and calcination of Fe-/Co-nitrate. A DTA-TG and microstructural analysis revealed that the nitrates mixture by the calcination at $300^{\circ}C$ for 2 h was changed to Fe-oxide/$Co_3O_4$ composite powders with an average particle size of 100 nm. The reduction behavior of the calcined powders was analyzed by DTA-TG in a hydrogen atmosphere. The composite powders of Fe-oxide and Co3O4 changed to a Fe-Co phase with an average particle size of 40 nm in the temperature range of $260-420^{\circ}C$. In the TG analysis, a two-step reduction process relating to the presence of Fe3O4 and a CoO phase as the intermediate phase was observed. The hydrogen-reduction kinetics of the Fe-oxide/Co3O4 composite powders was evaluated by the amount of peak shift with heating rates in TG. The activation energies for the reduction, estimated by the slope of the Kissinger plot, were 96 kJ/mol in the peak temperature range of $231-297^{\circ}C$ and 83 kJ/mol of $290-390^{\circ}C$, respectively. The reported activation energy of 70.4-94.4 kJ/mol for the reduction of Fe- and Co-oxides is in reasonable agreement with the measured value in this study.

• Nuclear Engineering and Technology
• /
• v.49 no.8
• /
• pp.1711-1716
• /
• 2017

Uranium tetrafluoride ($UF_4$) is the most used nuclear material for producing metallic uranium by reduction with Ca or Mg. Metallic uranium is a raw material for the manufacture of uranium silicide, $U_3Si_2$, which is the most suitable uranium compound for use as nuclear fuel for research reactors. By contrast, ammonium uranyl carbonate is a traditional uranium compound used for manufacturing uranium dioxide $UO_2$ fuel for nuclear power reactors or $U_3O_8-Al$ dispersion fuel for nuclear research reactors. This work describes a procedure for recovering uranium and ammonium fluoride ($NH_4F$) from a liquid residue generated during the production routine of ammonium uranyl carbonate, ending with $UF_4$ as a final product. The residue, consisting of a solution containing high concentrations of ammonium ($NH_4^+$), fluoride ($F^-$), and carbonate ($CO_3^{2-}$), has significant concentrations of uranium as $UO_2^{2+}$. From this residue, the proposed procedure consists of precipitating ammonium peroxide fluorouranate (APOFU) and $NH_4F$, while recovering the major part of uranium. Further, the remaining solution is concentrated by heating, and ammonium bifluoride ($NH_4HF_2$) is precipitated. As a final step, $NH_4HF_2$ is added to $UO_2$, inducing fluoridation and decomposition, resulting in $UF_4$ with adequate properties for metallic uranium manufacture.

• Journal of the Korean Institute of Gas
• /
• v.15 no.2
• /
• pp.63-68
• /
• 2011

As an effective utilization of biomass, organic wastes and coal, attention has been made to use syngas to a reciprocating engine to generate power. However, significant component variation of syngas depending upon origin and gasification conditions, and its lower heating value than that of LPG and CNG can create difficulties in stable engine operation. Thus it is necessary to address these issues in order to successfully develop power generation engines. As a primary step to resolve these problems, effects of H2 content variation in syngas on engine performance and emission characteristics were discussed in this study. The results show that as H2 % in syngas increases, more stable combustion was achieved with retarded MBT spark timing and engine efficiency becomes maximum with syngas of 10% H2. In addition, NOx emission increased while THC emission decreased as H2 % rises in the syngas.

• Journal of the Korean Vacuum Society
• /
• v.19 no.2
• /
• pp.155-160
• /
• 2010

The effect of process temperature of a final annealing step in the fabrication of phase change memory (PCM) devices was investigated. Discrete PCM devices employing $Ge_2Sb_2Te_5$ (GST) films as an active element were made in a pore-style configuration, and they were annealed at various temperatures ranging from 160 to $300^{\circ}C$. The behaviors of cell resistance change from SET resistance to RESET resistance were totally different according to the annealing temperatures. There was a critical annealing temperature for the fabrication of normal PCM devices and abnormal operations were observed in some devices annealed at temperatures lower or higher than the critical temperature. Those influences of annealing temperature seem closely related to the thermal stability of a top electrode/GST/heating layer multilayer structure in the PCM devices.

• Journal of the Korean Ceramic Society
• /
• v.53 no.5
• /
• pp.506-510
• /
• 2016

The eutectic melt of BaO-CuO flux is known to be a potential sintering aid for $Ba(Zr,Y)O_3$ (BZY) electrolyte for proton-conducting ceramic fuel cells (PCFCs). A density of BZY higher than 97% of theoretical density can be achieved via sintering at $1300^{\circ}C$ for 2 h using a flux composed of 28 mol% BaO and 72 mol% CuO. In the present study, chemical and structural evolution of BaO-CuO flux throughout the sintering process was investigated. An intermediate holding step at $1100^{\circ}C$ leads to formation of various impurity compounds such as $BaCuO_{1.977}$, $Ba_{0.92}Cu_{1.06}O_{2.28}$ and $Cu_{16}O_{14.15}$, which exhibit significantly larger unit cell volumes than the matrix. The presence of such secondary compounds with large lattice mismatch can potentially lead to mechanical failure. On the other hand, direct heating to the final sintering temperature produced CuO and $Cu_2O$ as secondary phases, whose unit cell volumes are close to that of the matrix. Therefore, the final composition of the flux is strongly affected by the thermal history, and a proper sintering schedule should be used to obtain the desired properties of the final product.

• Korean Journal of Metals and Materials
• /
• v.49 no.11
• /
• pp.845-852
• /
• 2011

The Spark Plasma Sintering(SPS) method offers a means of fabricating a sintered-body having high density without grain growth through short sintering time and a one-step process. A titanium compact having high density and purity was fabricated by the SPS process. It can be used to fabricate a Ti sputtering target with controlled parameters such as sintering temperature, heating rate, and pressure to establish the optimized processing conditions. The compact/target(?) has a diameter of ${\Phi}150{\times}6.35mm$. The density, purity, phase transformation, and microstructure of the Ti compact were analyzed by Archimedes, ICP, XRD and FE-SEM. A Ti thin-film fabricated on a $Si/SiO_2$ substrate by a sputtering device (SRN-100) was analyzed by XRD, TEM, and SIMS. Density and grain size were up to 99% and below $40{\mu}m$, respectively. The specific resistivity of the optimized Ti target was $8.63{\times}10^{-6}{\Omega}{\cdot}cm$.

• Resources Recycling
• /
• v.28 no.4
• /
• pp.51-58
• /
• 2019

Dismantlement of lithium primary batteries without explosion is required to recycle the lithium primary batteries which could be exploded by heating too much or crushing. In the present study, the optimum discharging condition was investigated to dismantle the batteries without explosion. When the batteries were discharged with $0.5kmol{\cdot}m^{-3}$ sulfuric acid, the reactivity of the batteries decreased after 4 days at $35^{\circ}C$ and after 1 day at $50^{\circ}C$, respectively. This result shows that higher temperature removed the high reactivity of the batteries. Because loss of metals recycled increases when the batteries are discharged only with the sulfuric acid, discharging process using acid solution and water was newly proposed. When the batteries were discharged with water during 24 hours after discharging with $0.5kmol{\cdot}m^{-3}$ sulfuric acid during 6 hours, the batteries discharged were dismantled without explosion. Because decrease in loss of metals was accomplished by new process, the recycling process of the batteries could become economic by the 2-step discharging process.