• Archives of Metallurgy and Materials
• /
• v.65 no.3
• /
• pp.1111-1116
• /
• 2020

Graphitic carbon nitride (g-C₃N₄) is an attractive photocatalyst, however, its practical photocatalytic applications are still faced with huge challenges. The aim of this research is to identify the correlation between synthetic conditions and properties of the g-C₃N₄ and derive an optimum synthesis condition for improving photocatalytic activities of the g-C₃N₄. In this study, novel and versatile g-C₃N₄ nanosheets were synthesized by the simple thermal pyrolysis of urea. In the synthesis process, the pyrolysis temperature and the heating rate, which can have the most significant influence on the structures and properties of g-C₃N₄, were set as variables, and the effects were systematically investigated. When synthesized at a relatively high temperature, the amount of material being synthesized is reduced, however it has been found to represent optical properties suitable for highly efficient photo-catalyst by the increase in the thickness and defects formed in the g-C₃N₄ nanosheets. The photocatalytic degradation experiment of MB dyes indicated that the highest degradation of 95.2% after the reaction for 120 min was achieved on the g-C₃N₄ nanosheets synthesized at 650℃.

• Journal of Ceramic Processing Research
• /
• v.21
• /
• pp.47-52
• /
• 2020

Graphene was synthesized using rapid thermal chemical vapor deposition (RT-CVD) equipment designed to produce largearea graphene at high speed. The effects of methane (CH₄), argon (Ar), and hydrogen (H₂) gases were investigated between 800 ℃ and 1,000 ℃ during heating and cooling in the graphene synthesis process. The findings reveal that multilayer domains increased due to hydrogen pretreatment with increase in temperature. Furthermore, when pretreated with the same gas, it was confirmed that the post-argon-treated sample cooled from 1,000 ℃ to 800 ℃ had a higher I_D/I_G value than that of the other samples. This result was consistent with the sheet resistance properties of graphene. The sample prepared in methane atmosphere maintained during both the pre-treatment and post-treatment demonstrated the lowest sheet resistance of 787.49 Ω/sq. Maintaining the methane gas atmosphere in the high-temperature region during graphene synthesis by RT-CVD reduced the defects and improved the electrical property.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.16 no.4
• /
• pp.227-238
• /
• 2013

The purpose of this study is to develop a process technology to produce high hardness drinking water which meet drinking water standard, remaining useful minerals like magnesium and calcium in the seawater desalination process while removing the sulfate ions and chloride ions. Seawater have been separated the concentrated seawater and desalted seawater by passing on Reverse Osmosis membrane (RO). Using Nano-filtration membrane (NF), We were prepared primary mineral concentrated water that sodium chloride were not removed. By the operation of electro-dialysis (ED) having ion exchange membrane, we were prepared concentrated mineral water (Mineral enriched desalted water) which the sodium chloride is removed. We have produced the high hardness water to meet the drinking water quality standards by diluting the mineral enriched desalted water with deionized water by RO. Reverse osmosis membranes (RO) can separate dissolved material and freshwater from seawater (deep seawater). The desalination water throughout the second reverse osmosis membrane was completely removed dissolved substances, which dissolved components was removed more than 99.9%, its the hardness concentration was 1 mg/L or less and its chloride concentration was 2.3 mg/L. Since the nano-filtration membrane pore size is $10^{-9}$ m, 50% of magnesium ions and calcium ions can not pass through the nano-filtration membrane, while more than 95% of sodium ions and chloride ions can pass through NF membrane. Nano-filtration membrane could be separated salt components like sodium ion and chloride ions and hardness ingredients like magnesium ions and calcium ions, but their separation was not perfect. Electric dialysis membrane system can be separated single charged ions (like sodium and chloride ions) and double charged ions (like magnesium and calcium ions) depending on its electrical conductivity. Above electrical conductivity 20mS/cm, hardness components (like magnesium and calcium ions) did not removed, on the other hand salt ingredients like sodium and chloride ions was removed continuously. Thus, we were able to concentrate hardness components (like magnesium and calcium ions) using nano-filtration membrane, also could be separated salts ingredients from the hardness concentration water using electrical dialysis membrane system. Finally, we were able to produce a highly concentrated mineral water removed chloride ions, which hardness concentration was 12,600 mg/L and chloride concentration was 2,446 mg/L. By diluting 10 times these high mineral water with secondary RO (Reverse Osmosis) desalination water, we could produce high mineral water suitable for drinking water standards, which chloride concentration was 244 mg/L at the same time hardness concentration 1,260 mg/L. Using the linked process with reverse osmosis (RO)/nano filteration (NF)/electric dialysis (ED), it could be concentrated hardness components like magnesium ions and calcium ions while at the same time removing salt ingredients like chloride ions and sodium ion without heating seawater. Thus, using only membrane as RO, NF and ED without heating seawater, it was possible to produce drinking water containing high hardness suitable for drinking water standard while reducing the energy required to evaporation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.3
• /
• pp.282-291
• /
• 1994

Optimal processing conditions and shelf-life of steamed kamaboko made from Alaska pollock surimi were investigated, including protein digestibility, computed protein efficiency ratio (C-PER), trypsin inhibitor content and protein solubility. Steamed kamaboko containing $5\%$ starch and $33\%$ water in pollock surimi showed the best protein quality in terms of C-PER and protein digestibility. Steaming could not give any significant advantage over kamaboko protein digestibility but a higher C-PER resulted from steamed kamaboko. All kamaboko products had trypsin content of 1.4 to $2.0mg\%$ which was $10\%$ of total trypsin inhibitor levels in frozen pollock meat. A two stage steaming process, the first at $40^{\circ}C$ for 20min followed by a second 10min steaming period at $95^{\circ}C$, was found to be the most effective way of the most effective heating process for kamaboko protein quality. C-PERs of marketed Korean surimi products ranged from $2.8{\sim}2.9$ for steamed kamaboko and $2.9{\sim}3.2$ for crab meat analog which were superior to ANRC casein(2.5). Measured protein digestibility of all products were ranged from 86 to $89\%$. VBN and protein solubility data suggest Korean marketed surimi products could have a shelf-life of 15 days at $4^{\circ}C$ for crab meat analog and 20 days at $4^{\circ}C$ for steamed kamaboko.

• Applied Biological Chemistry
• /
• v.29 no.2
• /
• pp.130-137
• /
• 1986

The five fish meal kojis which contained various ratios of barley were prepared and processed to produce six different fish-soy sauces. The chemical compositions including enzyme activities during fermentation were determined and sensory evaluation was done and changes of absorbance during heating process were also measured. The contents of reducing sugar increased until 12 hours, then slightly decreased and maintained constant level after 36 hours during koji making. The contents of total nitrogen were proportional to the amount of fish meal used in koji. The activities of amylase and protease were increased until 48 hours and then were not changed during koji making. The contents of reducing sugar were increased until 50 days and then were not much changed during koji making. The contents of nitrogen and amino nitrogen in sauces were increased gradually during fermentation. The total acid contents of sauces were increased until 70 days, after which it was constant during fermentation. The absorbances of sauces were increased with time during heating process. In sensory test, the fish-soy sauce the ratio of fish meal: barley of which was 10 : 16 received the highest score for flavor of sauce and the conventional soy sauce, for color and taste in a soup test. Fish-soy sauce resulted good quality when the ratio of fish meal to barley was 10 to 13 and 10 to 16.

• Korean Chemical Engineering Research
• /
• v.50 no.6
• /
• pp.1002-1007
• /
• 2012

The considerable portion of energy demand has been satisfied by the combustion of fossil fuel and the consequent $CO_2$ emission was considered as a main cause of global warming. As a technology option for $CO_2$ emission mitigation, absorption process has been used in $CO_2$ capture from large scale emission sources. To set up optimal operating parameters in $CO_2$ absorption and solvent regeneration units are important for the better performance of the whole $CO_2$ absorption plant. Optimal operating parameters are usually selected through a lot of actual operation data. However theoretical approach are also useful because the arbitrary change of process parameters often limited for the stability of process operation. In this paper, a theoretical approach based on vapor-liquid equilibrium was proposed to estimate optimal operating conditions of $CO_2$ absorption process. Two $CO_2$ absorption processes using 12 wt% aqueous $NH_3$ solution and 20 wt% aqueous MEA solution were investigated in this theoretical estimation of optimal operating conditions. The results showed that $CO_2$ loading of rich absorbent should be kept below 0.4 in case of 12 wt% aqueous $NH_3$ solution for $CO_2$ absorption but there was no limitation of $CO_2$ loading in case of 20 wt% aqueous MEA solution for $CO_2$ absorption. The optimal regeneration temperature was determined by theoretical approach based on $CO_2$ loadings of rich and lean absorbent, which determined to satisfy the amount of absorbed $CO_2$. The amount of heating medium at optimal regeneration temperature is also determined to meet the difference of $CO_2$ loading between rich and lean absorbent. It could be confirmed that the theoretical approach, which accurately estimate the optimal regeneration conditions of lab scale $CO_2$ absorption using 12 wt% aqueous $NH_3$ solution could estimate those of 20 wt% aqueous MEA solution and could be used for the design and operation of $CO_2$ absorption process using chemical absorbent.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.2
• /
• pp.29-37
• /
• 2008

In this work, it was investigated that various aspects of process, application situation, merits and short-coming results of the thermophilic methane fermentation with highly concentrated organic waste substances such as sewage sludges, food wastes and excretions. The merits of this methane fermentation were that it had a very fast reaction rate and was possible to proceed in high loads. It was also high in mortality for pathogenic microorganism and the digested sludge was more hygienic. However, the short-comings were that more energy was required for heating in the fermentation facility, no surplus energy could be gained from low concentration of organic waste, the fermentation treatment dropped level of water quality, thus burdens discharging process of water. Especially, the high concentration of methane fermentation could possibly lack nutritious salt and could face the disturbance by ${NH_4}^+-N$, a proper alternative was required. In general, thermophilic methane fermentation was considered as a better mean in disposing of cow excretion and food waste which were highly concentrated organic wastes. On the other hand, under the condition where the concentration of waste material was low and the high concentrate waste material became higher than 3,000 mg/L in ${NH_4}^+-N$, thermophilic methane fermentation resulted less desirable outcome.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.5
• /
• pp.329-337
• /
• 2001

It has been known that the leakage current in the low field region consists of the dielectric relaxation current and intrinsic leakage current, which cause the charge loss in dynamic random access memory (DRAM) storage capacitor using (Ba,Sr)TiO$_{3}$ (BST) thin film. Especially, the dielectric relaxation current should be seriously considered since its magnitude is much larger than that of the intrinsic leakage current in giga-bit DRAM operation voltage (~IY). In this study, thermally stimulated current (TSC) measurement was at first applied to investigate the activation energy of traps and relative evaluation of the density of traps according to process change. And, through comparing TSC to early methods of I-V or I-t measurement and analyzing, we identify the origin of the dielectric relaxation current and investigate the reliability of TSC measurement. First, the polarization condition such as electric field, time, temperature and heating rate was investigated for reliable TSC measurement. From the TSC measurement, the energy level of traps in the BST thin film has been investigated and evaluated to be 0.20($\pm$0.01) eV and 0.45($\pm$0.02) eV. Based on the TSC measurement results before and after rapid thermal annealing (RTA) process, oxygen vacancy is concluded to be the origin of the traps. TSC characteristics with thermal annealing in the MIM BST capacitor have shown the same trends with the current-voltage (I-V) and current-time (I-t) characteristics. This means that the TSC measurement is one of the effective methods to characterize the traps in the BST thin film.

• Food Science and Preservation
• /
• v.12 no.6
• /
• pp.600-607
• /
• 2005

This study was conducted to prepare high quality grape seed oils by solvent extraction and chemical refining process. Additionally, quantitative analysis of several functional components in grope seed was carried out to compare quality characteristics of grape seeds from grapes grown by conventional and organic agricultural practices. There are no significant differences in several functional constituents of grape seeds between conventionally cultivated- and organically cultivated-grapes, although some functional compositions of grape seeds are different between two cultivation methods. The dried grape seed was pretreated with roasting heating for 5 min, milled and then extracted twice with n-hexane under reflux at $50^{\circ}C$ for overnight, followed by filtration and evaporation. The crude grape seed oil was successively purified by degumming with $0.1\%\;H_3PO_4$, deaciding with $20\%\;NaOH$, and then decoloring and deodorization by a steam distillation, and thereby producing purified grape seed oil(yield: $5.0\%/dried$ grape seed). Physicochemical characteristics of the purified grape seed oil were comparable to those of the imported grape seed oils.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 2002.11a
• /
• pp.171-184
• /
• 2002

Approx. 200,000 bpd vacuum residue oil is produced from oil refineries in Korea. These are supplying to use asphalt, high sulfur fuel oil, and upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435-500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER(Korea Institute of Energy Research) are studing on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature : 1,100~1,25$0^{\circ}C$, reaction pressure : 1~6kg/$\textrm{cm}^2$G, oxygen/V.R ratio : 0.8~0.9 and steam/V.R ratio : 0.4-0.5. Experimental results show the syngas composition(CO+H$_2$) : 85~93%, syngas flow rate : 50~110Mm$^3$/hr, heating value : 2,300~3,000 ㎉/Nm$^3$, carbon conversion : 65~92, cold gas efficiency : 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.