• Journal of Powder Materials
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• v.30 no.3
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• pp.233-241
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• 2023

In this study, we evaluated the effects of acid leaching on the properties of Cr powder synthesized using self-propagating high-temperature synthesis (SHS). Cr powder was synthesized from a mixture of Cr2O3 and magnesium (Mg) powders using the SHS Process, and the byproducts after the reaction were removed using acid leaching. The properties of the recovered Cr powder were analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), particle size analysis (PSA), and oxygen content analysis. The results show that perfect selective leaching of Cr is challenging because of various factors such as incomplete reaction, reaction kinetics, the presence of impurities, and incompatibility between the acid and metal mixture. Therefore, this study provides essential information on the properties under acidic conditions during the production of high-quality Cr powder using a self-propagating high-temperature synthesis method.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.385-392
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• 2023

A solution combustion process for the synthesis of hollandite (BaAl₂Ti₆O₁₆) powders is described. SYNROC (synthetic rock) consists of four main titanate phases: perovskite, zirconolite, hollandite and rutile. Hollandite is one of the crystalline host matrices used for the disposal of high-level radioactive wastes because it immobilizes Sr and Lns elements by forming solid solutions. The solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between a nitrate and organic fuel, generates an exothermic reaction and that heat converts the precursors into their corresponding oxide products in air. The process has high energy efficiency, fast heating rates, short reaction times, and high compositional homogeneity. To confirm the combustion synthesis reaction, FT-IR analysis was conducted using glycine with a carboxyl group and an amine as fuel to observe its bonding with metal element in the nitrate. TG-DTA, X-ray diffraction analysis, SEM and EDS were performed to confirm the formed phases and morphology. Powders with an uncontrolled shape were obtained through a general oxide-route process, confirming hollandite powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using these methods.

• Korean Journal of Psychosomatic Medicine
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• v.31 no.2
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• pp.89-99
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• 2023

Objectives : In this study, elderly hospitalized patients aged 65 years or older who were admitted to a university hospital and referred to the department of psychiatry were classified into youngest-old, middle-old, and oldest-old. It was conducted to find out what factors contribute to the agitation pattern by age group, whether there is a difference in the factors, and whether there is a difference in the severity of the agitation pattern. Methods : From July 1, 2021 to December 31, 2021, the medical records of patients aged 65 years or older who were referred to the department of psychiatry were retrospectively reviewed. Age, gender, route of hospitalization, department of referral, reason for referral, treatment method, presence of internal and surgical diseases, and hematological test data were investigated. Results : There was a significant correlation with the RASS score in cases of surgery referral and high CRP levels for youngest-old aged 65 to 74 years, in cases of surgery referral, dementia and hyponatremia for middle-old aged 75 to 84 years, in case of dementia for oldest-old aged 85 years old or older. In addition, there were differences in the severity of agitation patterns between age groups. Conclusions : As the age group increases, the agitation of delirium patients becomes more severe, and various factors contributing to the agitation pattern also differ by age group. Therefore, when treating elderly patients with delirium, attention should be paid to factors that may affect agitation depending on age.

• Polymer(Korea)
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• v.30 no.3
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• pp.238-246
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• 2006

The aim of this study is to enhance the flame retardancy by the synergism effect of chlorine and phosphorus groups. The flame-retardant polyurethane coatings containing chlorine and phosphorus compounds were synthesized. After synthesizing the intermediate products of tetramethylene bis (orthophosphate) (TMBO) and neohexanediol trichlorobenzoate (TBA-adduct), the condensation polymerization was performed with four different monomers of two intermediates, 1,4-butanediol, and adipic acid to obtain four-component copolymer(TTBA). The two-component flame-retardant polyurethane coatings (TTBA-10C/HDI-trimer=TTHD-10C, TTBA-20C/HDI-trimer=TTHD-20C, TTBA-30C/HDI trimer=TTHD-30C) were obtained by curing reaction at room temperature with the synthesized TTBAs and hexamethylene diisocyanate (HDI)-trimer as a curing agent. The obtained TTHDs were made into coating samples and used as test samples for various physical properties. The physical properties of the flame-retardant coatings containing chlorine and phosphorus groups were generally inferior to those containing only phosphorus group. Flame retardancy was tested by vortical and horizontal combustion method, and $45^{\circ}$ Meckel burner method. Since the retardancy of flame-retardant coatings containing chlorine and phosphorus groups was better than that containing only phosphorus group, it could be concluded that the retardancy by the synergism effect of chlorine and phosphorus groups exhibited.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.70-74
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• 2011

[ $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ]ceramics was investigated for the application to SOFC ceramic supporter with high porosity and mechanical strength. $ZrO_2$ powder was prepared by combustion method with glycine using the solution of $ZrO(NO_3)_2{\cdot}2H_2O$ dissolved into deionized water and calcination at $800^{\circ}C$ Porous $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics was prepared by sintering the mixture of prepared $ZrO_2$ powder, dolomite and carbon black at $1200{\sim}1400^{\circ}C$ for 1 h. The open porosity ofthe $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics sintered at $1300^{\circ}C$ was over 30 % and increased linearly with the amount of carbon black. The crystal structure of $(Ca,Mg)_{0.15}Zr_{0.7}O_{1.7}$ ceramics consisted of single cubic phase. The open pore of this ceramics was connected continuously and distributed well on the whole. This ceramics sintered at $1300^{\circ}C$ showed the porosity from 32 to 55 % and mechanical strength from 90 MPa to 30 MPa with increasing the content of added carbon black.

• Fire Science and Engineering
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• v.26 no.5
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• pp.21-27
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• 2012

A real A real scale fire test was performed in accordance with KS F ISO 9705 test method to investigate the combustion characteristics of glass wool sandwich panels. To do this, six kinds of specimens having different density and thickness were examined. The glass sandwich panels were installed inside the room, which had internal dimensions of 2.4 m wide${\times}3.6m$ deep${\times}2.4m$ high. also, combustion characteristic are determined through the exposure of specimens to flame by the propane gas burner has a capacity of 100 kW (10 minutes) and 300 kW (10 minutes) for total 25 minutes of test time. Results of the real sale fire test, it was found that maximum HRR of each specimen was 333.2~365.5 kW, maximum heat flux was 12.4~12.9 kW/$m^2$ And, maximum internal temperature for all specimens was not over $500^{\circ}C$. During the real scale fire test, flash-over didn't occur and the difference by density and thickness of specimen was not found from the results of HRR, heat flux, and internal temperature measurement.

• 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.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.244-249
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• 2011

In this study, performance and economic analysis of 500 MWe coal-fired power plant with $CO_{2}$ capture process was performed. For this purpose, chemical absorption method which is commercially available and most suitable for thermal power plant was studied and a criteria for technical and economic assessment of power plants suggested by IEA Greenhouse Gas R&D Programme was used. And we performed the sensitivity analysis focused on regeneration energy which exceed half of the total capture energy. Based on MEA(Monoethanoleamine) as a main chemical solvent and 3.31 GJ/ton$CO_{2}$ regeneration energy in the stripper, net power efficiency was reduced from 41.0% (no capture) to 31.6%(with capture) and the cost of $CO_{2}$ avoided was estimated 43.3 $/ton$CO_{2}$. And in case of 2.0 GJ/ton$CO_{2}$ regeneration energy, the cost of $CO_{2}$ avoided was calculated as 36.7 $/ton$CO_{2}$.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.347-354
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• 2014

Economic evaluation of the manufacturing technology of high-value chemicals through the carbonation reaction of carbon dioxide contained in the flue gas was performed, and analysis of the IRR (Internal Rate of Return) and whole profit along the production plan of the final product was conducted. Through a carbonation reaction with sodium hydroxide that is generated from electrolysis and by using carbon dioxide in the combustion gas that is generated in the power plant, it is possible to get a high value products such as sodium bicarbonate compound and also to reduce the carbon dioxide emission simultaneously. The IRR (Internal Rate of Return) and NPV (Net Present Value) methods were used for the economic evaluation of the process which could handle carbon dioxide of 100 tons per day in the period of the 20 years of plant operation. The results of economic evaluation showed that the IRR of baseline case of technology was 67.2% and the profit that obtained during the whole operation period (20 years) was 346,922 million won based on NPV value. When considering ETS due to the emissions trading enforcement that will be activated in 2015, the NPV was improved to a 6,000 million won. Based on this results, it could be concluded that this $CO_2$ carbonation technology is an cost-effective technology option for the reduction of greenhouse gas.

• Fire Science and Engineering
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• v.31 no.2
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• pp.1-8
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• 2017

A sandwich panel is a composite material composed of a double-sided noncombustible material and insulation core which is used in the inner, outer walls, and roof structure of a building. Despite its excellent insulation performance, light weight and excellent constructability, a flame is brought into the inside of the panel through the joint between the panels, melting the core easily and causing casualties and property damage due to the rapid spread of flame. The current Building Law provides that the combustion performance of finishing materials for buildings should be determined using a fire test on a small amount of specimen and only a product that passes the stipulated performance standard should be used. This law also provides that in the case of finishing materials used for the outer walls of buildings, only materials that secured noncombustible or quasi-noncombustible performance should be used or flame spread prevention (FSP) should be installed. The purpose of this study was to confirm the difference between the dangers of horizontal and vertical fire spread by applying FSP, which is applied to finishing materials used for the outer walls of buildings limitedly to a sandwich panel building. Therefore, the combustion behavior and effects on the sandwich panel according to the application of FSP were measured through the construction to block the spread of flame between the panels using a full scale fire according to the test method specified in ISO 13784-1 and a metallic structure. The construction of FSP on the joint between the panels delayed the spread of flame inside the panels and the flash over time was also delayed, indicating that it could become an important factor for securing the fire safety of a building constructed using complex materials.