• Journal of the Korean institute of surface engineering
• /
• v.49 no.3
• /
• pp.231-237
• /
• 2016

This article reports a new chemical bath for preparing a mirror-like surface of AZ31 Mg alloy. In order to find an appropriate chemical polishing solution, four different acidic solutions of sulphuric acid, nitric acid, acetic acid and a specially designed mixture of nitric acid and acetic acid were investigated in view of the changes in surface appearance, roughness and dissolution rate of AZ31 Mg alloy. The surface scales on AZ31 Mg alloy were readily removed by all the acidic solutions, but a reflective surface was produced only by etching in the specially designed solution, and only after a specific etching time. The surface roughness increased with etching time in sulphuric acid, nitric acid, and acetic acid, but it lowered after a specific etching time in the specially designed mixture of nitric acid and acetic acid. Dissolution rate of the alloy in the specially designed mixture of nitric acid and acetic acid appeared to be more than twice than that in separate nitric acid or acetic acid. In this work, we recommend the mirror-like surface of AZ31 Mg alloy obtained by polishing for an optimum time in a mixture of nitric acid and acetic acid for following surface finishings, chemical conversion coating, electroplating, electrophoretic painting and anodizing treatment.

• Analytical Science and Technology
• /
• v.22 no.6
• /
• pp.519-523
• /
• 2009

$^{129}I$ is especially one of the most harmful radioactive elements because of its long half-life ($t_{1/2}$=$1.7{\times}10^7$ yr). The efficient removal of iodide ($I^-$) and iodate (${IO_3}^-$) in a aqueous solution by adsorption using activated alumina and activated carbon was studied. The removal efficiency was over 99% for iodide ion with silver treated basic alumina and iodate ion with acidic alumina or silver treated acidic alumina without any chemical addition or physical treatments.

• Korean Journal of Environmental Agriculture
• /
• v.3 no.2
• /
• pp.16-22
• /
• 1984

This study was carried out to investigate the stability of dinobuton (2-sec-butyl-4,6-dinitrophenyl isopropyl carbonate) in distilled water and buffer solutions and its persistence in soils. When dinobuton was incubated at $30^{\circ}C$ and $60^{\circ}C$ in distilled water, the half-lives of dinobuton was 28 and 6 days, respectively. The decomposition of dinobuton was, therefore, faster at high temperature than at low temperature. The half-life of dinobuton was about 27 days in the acidic solution $(pH\; 4{\sim}6)$, whereas 10 and 4 days in the alkaline solutions of pH 9, and 10, respectively. Thus dinobuton was stable in acidic solution, and unstable in alkaline solution. Dinoseb (2-sec-butyl-4,6-dinitrophenol), which is produced in the degradation process of dinobuton, was produced in small amounts in distilled water and buffer solutions. The half-life of dinobuton in sterilized soil was about 16 days longer than in non-sterilized soil. Dinoseb was also more persistent in sterilized soil than in non-sterilized one.

• Journal of the Korean Ceramic Society
• /
• v.42 no.12 s.283
• /
• pp.800-807
• /
• 2005

Cathode material, $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$, for low temperature SOFC was prepared by the Glycine-Nitrate synthesis Process (GNP). Characteristics of the synthesized powders were studied with controlling the pH of a precursor solution. Highly acidic precursor solution increased a perovskite forming temperature. It is considered that Ba and Sr cannot complex by carboxylic acid group of glycine, because under highly acidic condition the caboxylic group mainly combined with H+ insead of alkaline earth cations. A lack of bond between cations and glycine resulted in selective precipitation of the elements during evaporation of the precursor solution. In case of using precursor solution with pH %2\~3$, a single perovskite phase was obtained at $1000^{\circ}C$. Polarization resistance of $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ was measured by AC impedance spectroscopy from the two electrode symmetric cell. Area specific resistance of the $(Ba_{0.5}Sr_{0.5})_{0.99}Co_{0.8}Fe_{0.2}O_{3-\delta}$ air electrode at $500^{\circ}C\;and\;600^{\circ}C$ were $0.96{\Omega}{\cdot}cm^2\;and\;0.16{\Omega}{\cdot}cm^2$, respectively.

• The Research Journal of the Costume Culture
• /
• v.12 no.6 s.53
• /
• pp.999-1009
• /
• 2004

Chitin is a derived product from the shell of shrimp or crab. Chitosan, a deacetylated product of chitin, has widely been used in the biomedical sector, food industry, and textile industry. Chitosan exhibits fiber-forming property under certain conditions. Nonwoven fabrics made of chitosan fibers may have diverse applications in the industry. Previous studies have revealed that the dye uptake properties of natural dyestuffs improved by the chitosan pretreatment on the fabric specimens. In this case, fabric specimen is coated with acidic salt form of chitosan, which is different from the pure chitosan, since the coating process employes coating with the acidic solution of the chitosan and subesquent drying. In this study, chitosan nonwoven fabric samples were prepared from chitosan sample having deacetylation degree of $100\%$ and molecular weight of 650,000. Chitosan nonwoven fabrics maintain the form of $-NH_2$ end-group. These in turn exhibit higher dye uptake ability than the fabrics coated with chitosan acidic solutions do.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.24 no.4
• /
• pp.719-726
• /
• 1997

The aim of this study was to evaluate the in vitro effects of exposure to acidic beverages on microhardness of enamel and dentin. Thirty enamel specimens and thirty dentin specimens were obtained from extracted bovine maxillay incisiors. Enamel and dentin specimens were divided into three groups and treated with acidic beverages as follows; Group 1 : cola(pH 2.52), Group 2 : plain soda water(pH 2.93) and Group 3 : orange juice(pH 3.75). Erosive treatment was performed by storing each specimens for 5 min in 50ml solution of cola, soda water and orange juice. Average microhardness values(VHN) were determined before and after erosive treatment. All beverages produced significant loss of microhardness of enamel and dentin. Microhardness of enamel was reduced in the following order: Group 1 : $42.71{\pm}4.36(%)$, Group 2 : $37.09{\pm}6.25(%)$, Group 3 : $35.46{\pm}4.98(%)$. Microhardness of dentin was reduced in the following order: Group 1 : $17.14{\pm}3.42(%)$, Group 2 : $13.89{\pm}3.18(%)$, Group 3 : $13.82{\pm}3.50(%)$. The differences between group 1 and group 2, 3 were statistically significant(p< 0.05).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.561-562
• /
• 2006

The purpose of this study was to investigate the root cause of adhesion of silica and ceria particles during Poly-Si, TEOS, and SiN CMP process, respectively. The zeta-potentials of abrasive particles and wafers were observed negative surface charges in the alkaline solutions. SAC and STI patterned wafers have intermediate values of their composition surface's zeta potentials. The theoretical interaction force and adhesion force of silica and ceria particle were calculated in solution with acidic, neutral and alkaline pH. A stronger attractive force was calculated for silica and ceria particles on wafers in acidic solutions than in alkaline solutions. The theoretical interaction forces of the SAC and STI patterned wafers have intermediate values of their constitution wafer's values. The adhesion forces is observed lower values in alkaline solutions than in acidic solutions. And the ceria particle has lower adhesion than that of the silica particle.

• Corrosion Science and Technology
• /
• v.21 no.4
• /
• pp.273-281
• /
• 2022

The effect of addition of Cu on the localized corrosion performance of aged duplex stainless steel in chloride media has yet to be explained in a consistent manner, and there is some controversy in the literature regarding the composition of stainless steel and the experimental conditions (pH, temperature, chloride concentration, etc.) used. In this work, the effect of the addition of Cu on the microstructure, hardness, and corrosion resistance of duplex stainless steel in an acidic chloride or high concentration sulfuric acid solutions was investigated for annealed and aged alloys. The Cu addition of annealed duplex stainless steel strengthened the alloy and reduced the ferrite contents of the alloy, and it also increased the polarization behavior in chloride or sulfuric solutions, except for the case of a high potential in acidic chloride solution. However, the Cu addition of aged duplex stainless steel reduced the formation of harmful phases such as sigma and kai and increased the polarization behavior in acidic chloride or sulfuric solutions up to 0.8 wt% of the Cu content, after which it slightly decreased at 0.8 wt% Cu or more.

• Membrane Journal
• /
• v.23 no.1
• /
• pp.92-99
• /
• 2013

In this study the nanofiltration (NF) membrane treatment of a sulfuric acid waste solutions containing copper ion ($Cu^{+2}$) discharging from the etching processes of the printed circuit board (PCB) manufacturing industry has been studied for the recycling of acid etching solution. SelRO MPS-34 4040 NF membrane from Koch company was tested to obtain the basic NF data for recycling of etching solution and separation efficiency (total rejection) of copper ion. NF experiments were carried out with a dead-end membrane filtration laboratory system. The pure water flux was increased with the increasing storage time in sulfuric acid solution and lowering pH of acid solution because of the enhancement of NF membrane damage by sulfuric acid. The permeate flux of acid solution was decreased with the increasing copper ion concentration. Total rejection of copper ion was decreased with the increasing storage time in sulfuric acid solution and copper ion concentration, and lowering the pH of acid solution. The total rejection of copper ion was decreased from initial 37% to 15% minimum value.

• Journal of Environmental Science International
• /
• v.9 no.4
• /
• pp.325-330
• /
• 2000

The hydroxyapatite (HAp) for the present study was prepared by precipitation method in semiconductor fabrication and the crystallized at ambient to 95$0^{\circ}C$ for 30min in electric furnace. The ion-exchange characteristics of HAp for various heavy metal ions such as $Cd^{2+}, Cu^{2+}, Mn^{2+}, Zn^{2+}, Fe^{2+}, Pb^{2+}, Al^{3+}, and Cr^{6+}$ in aqueous solution has been investigated. The removal ratio of various metal ions for HAp were investigated with regard to reaction time, concentration of standard solution, amount of HAp and pH of solution. The order of the ions exchanged amount was as follws: $Pb^{2+}, Fe^{3+}>Cu^{2+}>Zn^{2+}>Al^{3+}>Cd^{2+}>Mn^{2+}>Cr^{6+}. The Pb^{2+}$ ion was readily removed by the Hap, even in the strongly acidic region. The maximum amount of the ion-exchange equilibrium for $Pb^{2+}$ ion was about 45 mg/gram of HAp. The HAp would seem to be possible agent for the removal of heavy metal ions in waste water by recycling of waste sludge in semiconductor fabrication.