• Corrosion Science and Technology
• /
• 제6권6호
• /
• pp.304-307
• /
• 2007

As to the reflection electrode of LCD (liquid crystal displays), silver-copper-gold alloy (hereafter, it is called as ACA (Ag98%, Cu1%, Au1%)) is an effective material of which weathering resistance can be improved more compared with pure silver. However, there is a problem that gold remains on the substrate as residues when ACA is etched in cerium ammonium nitrate solution or phosphoric acid. Gold can not be etched in these etchants as readily as the other two alloying elements. Gold residue has actually been removed physically by brushing etc. This procedure causes damage to the display elements. Another etchant of iodine/potassium iodide generally known as one of the gold etchants can not give precise etch pattern because of remarkable difference in etching rates among silver, copper and gold. The purpose of this research is to obtain a practical etchant for ACA alloy. The results are as follows. The cyanogen complex salt of gold generates when cyanide is used as the etchant, in which gold dissolves considerably. Oxygen reduction is important as the cathodic reaction in the dissolution of gold. A new etchant of sodium cyanide / potassium ferricyanide whose cathodic reduction is stronger than oxygen, can give precise etch patterns in ACA alloy swiftly at room temperature.

• 한국정밀공학회지
• /
• 제31권9호
• /
• pp.799-804
• /
• 2014

Hard turning is a machining process for hardened materials with high surface quality so that grinding process can be eliminated. Therefore, the hard turning is capable of reducing machining time and improving productivity. In this study, hardened AISI4140 (high-carbon chromium steel) that has excellent yield strength, toughness and wear resistance was finish turned using CBN tools. Wear characteristics of CBN tool was analyzed in dry and MQL mixed with nano-particle (Nano-MQL). The dominant fracture mechanism of CBN tool is diffusion and dissolution wear on the rake surface resulting in thinner cutting edge. Abrasive wear by hard inclusion in AISI4140 was dominant on the flank surface. Nano-MQL reduced tool wear comparing with the dry machining but chip evacuation should be considered. A cryogenically treated tool showed promising result in tool wear.

• 수산해양기술연구
• /
• 제39권4호
• /
• pp.291-297
• /
• 2003

Al-brass is usually used as the tube material of vessel's heat exchanger for seawater cooling system because it has high thermal conductivity and good mechanical properties and high corrosion resistance due to cuprous oxide (Cu20) layer against seawater. However, Al-brass tubes of heat exchanger for vessel at the actual environment is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment In this paper, the effect of corrosion environment on the stress corrosion cracking of Al-brass in various NH4OH of 3.5% NaCl solution, under flow by constant displacement tester. Based on the test results, the behavior of polarization, stress corrosion crack propagation and dezincification phenomenon of Al-brass are investigated. The main results are as follows：(1) Increasing range of potential from open circuit potential to repassivation gets lower, as the contain rate of NH4OH gets higher. (2) As contain rate of NH4OH gets higher, SCC of Al-brass is become activation but the protection film(Cu20) of Al-brass is created in 3.5% NaCl solution. (3) According as content of NH4OH increases in 3.5% NaCl solution, the dezincifiction area is spread. It is concluded that dezincification occurred by localized preferential anodic dissolution at stress focusing region.

• 한국표면공학회지
• /
• 제17권3호
• /
• pp.78-86
• /
• 1984

Hard anodic oxide film was investigated formed on pure aluminium with various temperature (30$^{\circ}-60^{\circ}C$), current densities (1.5-3.0A/$dm^2$) and concentrations(3-15g/l) of oxalic acid in 0.5M malic acid bath. The resulting characteristic of the anodic oxide film obtained were summarized as follows in the view point of physical and mechanical properties in relation with the above process variables. 1. The film thickness increased with oxalic acid concentration and bath temperature, while the reversed phenomena were obtained at a high concentration of oxalic acid and high temperature due to the severe dissolution of the anodic oxide film. 2. The hardness and the abrasion resistance were improved by lowering the addition of oxalic acid and the bath temperature. This feature was directly dependent on the porosity formed on the anodic oxide film. 3. The maximum hardness of anodic oxide film showed Hv 579 in the temperature of 30$^{\circ}C$ with the current density, 2.5A/$dm^2$ in the 0.5M malic acid bath mixed with 5g/l oxalic acid.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2000년도 추계학술대회 논문집
• /
• pp.351-354
• /
• 2000

AC impedance of LiM $n_2$ $O_4$ and LiM $g_{0.1}$M $n_{1.9}$ $O_4$ samples have been studied at various temperature with charge-discharge test. AC impedance of LiM $n_2$ $O_4$ measured at -2$0^{\circ}C$, room temperature and 5$0^{\circ}C$ revealed that initial impedance before charge-discharge test was gradually decreased and become small by becoming law temperature. It indicates that the Li ion diffusion and the transfer resistance of the cathode are related to the temperature of cycling. Impedance at high temperature was suddenly increased because Mn dissolution and decomposition of electrolyte had been increased during cycling, compared to impedance at low temperature. Therefore, charge-discharge capacity was suddenly decreased at high but was slowly at low. In LiM $g_{0.1}$M $n_{1.9}$ $O_4$, impedance and capacity were stability at room temperature than there at 5$0^{\circ}C$, too. Initial impedance at 5$0^{\circ}C$ before charge-discharge test was small and impedance was suddenly increased during cycling than that at room temperature.ure.ure.

• Journal of Welding and Joining
• /
• 제16권3호
• /
• pp.157-166
• /
• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• 대한금속재료학회지
• /
• 제50권5호
• /
• pp.361-368
• /
• 2012

Fe-(10, 20, 30, 40) wt%Cr alloys were corroded in $Na_2SO_4$ salts ($m.p.=884^{\circ}C$) at $800{\sim}900^{\circ}C$ for 3-300 hrs. Their corrosion resistance increased with an increase in Cr content owing to the formation of slowly growing $Cr_2O_3$. During corrosion, $Na_2SO_4$ dissociated and reacted with the alloys to form $Cr_2O_3$ and $Fe_2O_3$. Since $Fe_2O_3$ dissolved fast into the salts, most of the scales consisted primarily of $Cr_2O_3$. Inside the scale, a small amount of sulfides also existed. The oxidation, dissolution and detachment of the formed scales occurred significantly.

• 한국축산식품학회지
• /
• 제39권5호
• /
• pp.687-703
• /
• 2019

A survey we conducted suggests that the ingestion of veterinary drug residues in edible animal parts constitutes a potential health hazard for its consumers, including, specifically, the possibility of developing multidrug resistance, carcinogenicity, and disruption of intestinal normal microflora. The survey results indicated that antibiotics, parasitic drugs, anticoccidial, or nonsteroidal anti-inflammatory drugs (NSAIDs) are broadly used, and this use in livestock is associated with the appearance of residues in various animal products such as milk, meat, and eggs. We observed that different cooking procedures, heating temperatures, storage times, fermentation, and pH have the potential to decrease drug residues in animal products. Several studies have reported the use of thermal treatments and sterilization to decrease the quantity of antibiotics such as tetracycline, oxytetracycline, macrolides, and sulfonamides, in animal products. Fermentation treatments also decreased levels of penicillin and pesticides such as dimethoate, malathion, Dichlorodiphenyldichloroethylene, and lindane. pH, known to influence decreases in cloxacillin and oxacillin levels, reportedly enhanced the dissolution of antimicrobial drug residues. Pressure cooking also reduced aldrin, dieldrin, and endosulfan in animal products. Therefore, this review provides updated information on the control of drug residues in animal products, which is of significance to veterinarians, livestock producers, and consumer health.

• Corrosion Science and Technology
• /
• 제18권3호
• /
• pp.86-91
• /
• 2019

Generally, atmospheric corrosion is the electrochemical degradation of metal that can be caused by various corrosion factors of atmospheric components and weather, as well as air pollutants. Specifically, moisture and particles of sea salt and sulfur dioxide are major factors in atmospheric corrosion. Using galvanized steel is one of the most efficient ways to protect iron from corrosion by zinc plating on the surface of the iron. Galvanized steel is widely used in automobiles, building structures, roofing, and other industrial structures due to their high corrosion resistance relative to iron. The atmospheric corrosion of galvanized steel shows complex corrosion behavior, depending on the plating, coating thickness, atmospheric environment, and air pollutants. In addition, corrosion products are produced in different types of environments. The lifespans of galvanized steels may vary depending on the use environment. Therefore, this study investigated the corrosion behavior of galvannealed steel under atmospheric corrosion in two locations in Korea, and the lifespan prediction of galvannealed steel in rural and coastal environments was conducted by means of the potentiostatic dissolution test and the chemical cyclic corrosion test.

• Nuclear Engineering and Technology
• /
• 제54권12호
• /
• pp.4474-4480
• /
• 2022

Deep geological disposal using a multibarrier system is a promising solution for treating high-level radioactive (HLRW) waste. The HLRW canister represents the first barrier for the migration of radionuclides into the biosphere, therefore, the corrosion behavior of canister materials is of significance. In this study, the electrochemical behaviors of SS316L, Ti-Gr.2, Alloy 22, and Cu in naturally aerated KAERI underground research tunnel (KURT) groundwater solutions were examined. The corrosion potential, current, and impedance spectra of the test materials were recorded using electrochemical methods. According to polarization and impedance measurements, Cu exhibits relatively higher corrosion rates and a lower corrosion resistance ability than those exhibited by the other materials in the given groundwater condition. In the anodic dissolution tests, SS316L exposed to the groundwater solution exhibited the most uniform corrosion, as indicated by its surface roughness. This phenomenon could be attributed to the extremely low concentration of chloride ions in KURT groundwater.