• Korean Chemical Engineering Research
• /
• v.51 no.2
• /
• pp.250-256
• /
• 2013

Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.

• Journal of the Korea Concrete Institute
• /
• v.18 no.1 s.91
• /
• pp.57-64
• /
• 2006

The crack presented in concrete structures causes a structural defect, the durability decrease, and external damages etc. Therefore, it is necessary to improve durability through the effort to control the crack. Fluosilicic acid($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicates prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicates to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. Mix proportions for experiment were modulated at 0.45 of water to cement ratio and $0.0{\sim}2.0%$ of adding ratio of fluosilicate salt based inorganic compound. To evaluate correlation of concrete strength and adding ratio of fluosilicate salt based inorganic compound, the tests were performed about design strength(21, 24, 27 MPa) with 0.5% of adding ratio of fluosilicate salt based inorganic compound. Applications of fluosilicate salt based inorganic compound to reduce cracks resulted from plastic and drying shrinkage, to improve durability are presented in this paper. Durability was evaluated as neutralization, chloride ion penetration depth, freezing thawing resistant tests and weight loss according reinforcement corrosion. It is ascertained that the concrete added fluosilicate salt based inorganic compound showed m ability to reduce the total area and maximum crack width significantly as compared non-added concrete. In addition, the durability of concrete improved because of resistance to crack and watertightness by packing role of fluosilicate salt based inorganic compound obtained and pozzolanic reaction of soluble $SiO_2$ than non-added concrete.

• Clean Technology
• /
• v.19 no.3
• /
• pp.257-263
• /
• 2013

The zinc phosphate-coated mica (ZP/mica) pigments were prepared using phosphoric acid, zinc nitrate and mica as starting materials, and used as anticorrosive pigments. The scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques were used to observe the morphology and crystal structure of prepared pigments. The prepared pigments were incorporated into an epoxy binder to prepare coating and the corrosion inhibition performance of the pigments was evaluated using electrochemical impedance spectroscopy (EIS). It was found that the anticorrosive performance of the ZP/mica pigment prepared at $70^{\circ}C$ was the better than that prepared at $20^{\circ}C$. The formation of ZnO, in addition to $Zn_3(PO_4)_2{\cdot}2H_2O$, was observed on ZP/mica pigment prepared at $70^{\circ}C$. The excellent anticorrosive performance of ZP/mica pigment could be ascribed to the synergistic effect with electrochemical anticorrosive mechanism from zinc compounds on mica and barrier anticorrosive mechanism from lamellar mica.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.33 no.3
• /
• pp.469-481
• /
• 2006

Among the etiologic factors of enamel corrosion, daily intake has been considered with a profound interest, especially the intake of acidic drinks. It is thought that the rapid consumption of acidic drinks will not only results in the affection to the teeth but also to the surface of the tooth-colored restorative materials. Therefore, the puopose of this study is to examine the alterations occurred in the surface of the tooth-colored materials according to the exposed time, with 3 most common acidic drinks in contact with daily life. Resin-modified glass-ionomer, polyacid-modified composite resin, composite resin were immersed on 0.9% NaCl, Coke, orange juice, sports beverages as 4 groups in each. The surface hardness and the surface roughness of specimens were measured with following methods: before immersion, 1 day after immersion, 1-,2-,3-,4- weeks after immersion. Results were as follows. 1. Tooth-colored restorative materials, with the exception of composite resin, showed statistically significant changes in surface hardness and roughness when immersed on acidic drinks(p<0.05). 2. The degree of change in surface hardness and roughness occurred as follows, in order of severity from greatest to least resin-modified glass-ionomer, polyacid-modified composite resin, composite resin 3. Sports beverages resulted in greater alterations to surfaces than Coke and orange juice. 4. In the SEM image of the groups immersed in acidic drinks, resin-modified glass-ionomer and polyacid-modified composite resin showed loss of filer. Severe cracks were observed, especially on the resin-modified glass-ionomer.

• Journal of Digital Convergence
• /
• v.14 no.11
• /
• pp.449-457
• /
• 2016

At this study, we select five colorful and high-acid fruits: grape, lemon, orange, grapefruit and kiwi, and we made a composite resin specimen and dipped into fruit juice in order to figure out influence that affects on surface corrosion and coloring. We dipped resin specimen into fruit juice by three-day and seven-day interval at $37^{\circ}C$. Control group used the resin that was not dipped into fruit juice. For surface change according to the time, it was observed by using scanning electron microscopy, and it was measured by using spectrophotometer for change of coloring degree. As a result of surface change of resin by using scanning electron microscopy, furrow size between surface particles increased, and rectangular rod-shape structure was emerged, and small prominent particles on bumps disappeared. As a result of coloring degree of resin by measuring spectrophotometer, a difference between experimental group appears with the darkest brightness in the case where it is dipped into grape extracts.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.12 no.1
• /
• pp.1-6
• /
• 2014

A large amount of acidic waste solution is generated from the practical electrokinetic decontamination equipments for the remediation of soil contaminated with uranium. After filtration of uranium hydroxides formed by adding CaO into the waste solution, the filtrate was recycled in order to reduce the volume of waste solution. However, when the filtrate was used in an electrokinetic equipment, the low permeability of the filtrate from anode cell to cathode cell due to a high concentration of calcium made several problems such as the weakening of a fabric tamis, the corrosion of electric wire and the adhension of metallic oxides to the surface of cathode electrode. To solve these problems, sulfuric acid was added into the filtrate and calcium in the solution was removed as $CaSO_4$ precipitate. A decontamination test using a small electrokinetic equipment for 20 days indicated that Ca-removed waste solution decreased uranium concentration of the waste soil to 0.35 Bq/g, which is a similar to a decontamination result obtained by distilled water.

• Journal of Adhesion and Interface
• /
• v.12 no.4
• /
• pp.111-116
• /
• 2011

The characteristics of natural resin, sap of the lacquer tree were examined as an adhesive for the ceramic conservation since it has such outstanding properties like corrosion resistance against acid and alkali, heat-resistance, waterproof, antiseptic and protection against insects. In order to utilize raw lacquer as an adhesive not under the hardening conditions of lacquer like high humidity (RH 75 to 85%) and high temperature (120 to $170^{\circ}C$), but under normal condition, isinglass and animal glue were added to raw lacquer at certain ratio. In addition, the viscosity and the drying time were measured and their possibilities of application were also investigated through measurement of tensile and adhesive strength. As a result of experiment, it was possible to dry at room temperature and RH $50{\pm}5%$ to mix with raw lacquer and glue, and the drying time of sample with animal glue was faster than that of isinglass. Furthermore, the adhesion of sample with glue was increased more than raw lacquer. It seems to be possible to use the environmental friendly traditional adhesive for the ceramic conservation and restoration, if there are studies or examinations of safety of applications on objects and weathering resistance.

• Tunnel and Underground Space
• /
• v.23 no.3
• /
• pp.180-191
• /
• 2013

The purpose of this research was to find an optimal quarrying for marble by analyzing the applicability and the work efficiency of a chain saw machine newly introduced in the underground Baekwoon mine. From the test results of the physical properties of Baekwoon marble, which affects the efficiency of rock cutting, it was found to have similar physical characteristics as the ones which are now being produced in the other areas in Korea. And especially it shows isotropic property, which can be thought to be advantageous as a dimensional stone. To check the long-term quality of the marble as a stone material, several tests such as corrosion resistance test and abrasion test were carried out. It was found to be vulnerable to acid rain with decrease of weight and seismic wave velocity after applying artificial rain at pH 5.6 for 50 times. The percentage of wear from abrasion test was 22.67%. The working time and cutting speed of the chain saw machine were recorded and analyzed during the test-run at the quarry. The overall work cycle was assorted into 9 unit operations and the operating time per each unit was drawn. The operating times for the two cutting patterns, which could be possibly applicable to the work site, were compared. The results indicated that the pattern B, that the cutting sequence was set to minimize the movement of the machine, showed 6% less working hours than the pattern A, which first cuts the outer boundary. With cutting pattern analysis, the ore body in the Baekwoon mine was 3 dimensionally modeled and a quarrying plan considering the existing conditions of the marble was suggested.

• Composites Research
• /
• v.36 no.1
• /
• pp.37-41
• /
• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Korean Chemical Engineering Research
• /
• v.46 no.2
• /
• pp.423-429
• /
• 2008

Currently, Ash-free clean coal producing process by solvent extraction is under development. The produced ash-free clean coal can be directly combusted in a gas turbine which results in substantial improvement of power generation efficiency. However, the clean coal produced by the solvent extraction still contain trace amount of alkali metal which may cause corrosion on turbine blades during the direct combustion. In present work ${\alpha},{\beta}$-metal (Zr and Ti) phosphates and H-Y zeolite were synthesized and their ion exchange characterizations were investigated for the application on alkali metal removal for clean coal production. $Na^+$ ion removal capacities of the metal phosphates and H-Y zeolite were measured and compared in both aqueous solution (100 ppmw, $Na^+$) and coal dissolved N-methyl-2-pyrrolidone (NMP, 12 ppmw $Na^+$) at elevated temperature. In aqueous solution, the ${\beta}$ form metal phosphates showed very high ion exchange capacities compared to ${\alpha}$ form. ${\beta}$ form metal phosphates also showed higher $Na^+$ removal capacities than H-Y zeolite. In ion exchange medium of NMP, all the ${\alpha}$ form metal phosphates showed over 90% of $Na^+$ ion removal efficiency in the temperature range of 200 to 400 while that of H-Y zeolite decreased as a half when the temperature was over 350. In addition, the regenerated metal phosphates by acid treatment showed no sign of degradation in $Na^+$ removal efficiency. Among the metal phosphates used, $Zr_{0.75}Ti_{0.25}(HPO_4)_2$ showed the best performance in $Na^+$ removal and is expected to be the most suitable inorganic ion exchanger for the alkali metal removal process.