• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.501-512
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• 1999

We analyzed the contents of 12 types of minerals such as calcium in muscle from various species. Thereafter we observed changes of the concentrations according to age, part and sex in major domestic animals. The concentrations of calcium, iron, sodium, potassium, magnesium and zinc were high respectively whilst the content of cobalt, chromium, copper, manganese, molybdenum and nickel were low respectively in the muscle. The concentration of calcium was high in duck and dog but low in pig and horse. Also high level of sodium content was detected in dog and the content of potassium, iron showed high level in horse compared with the content in other animals. In 6 types of microminerals as cobalt, the level of muscle were no more than 1 ppm showing very low content in all animal, but $2.99{\pm}0.85$ppm of copper in duck was an exceptional case. According to the age some species showed small range of variation centering on macrominerals and there was no remarkable change in microminerals. Distribution of minerals was different according to the part and the variation was very diverse compared with other factors such as age and sex. Additionally, the content of minerals in muscle was higher in female than in male chicken and duck. In conclusion, the difference of the content of minerals according to the species was mainly focused on macrominerals.

• Journal of Technologic Dentistry
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• v.14 no.1
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• pp.119-132
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• 1992

This paper aims to investigate the effect of B and Si upon the mechanical properties, microstructure and corrosion resistance of Co-Cr base alloy. Ten groups of alloy ingot ingot with various contents of B and Si were remelted by high frequency electrical induction furnace and cast into tensile specimen of ADA Specification No. 14 Tensile and hardness test were carried out by Amsler and Rockwell hardness tester(R-30N), respectively. The microstructures of specimen were observed by SEM. The results obtained are summarized as follows : 1. As B content is increased, tensile strength, yield strength and Rockwell hardness number(R-30N) are also increased significantly, while the elongation is decreased significantly. 2. As Si contect os increased, no significant chang in tensile strength is noticed, yield strength is slightly decreased, but Rockwell hardness number(R-30N) is moderately in creased, Elongation marks maxium value with 1% Si content while with more than 1% Si it is decreased. 3. As B content is increased corrosion resistance is decreased and is at best with 1.5% B content. Corrosion resistance is increased with the increase of Si content and the alloys with Si over 3.0% showed corrosion resistance. 4. As B content increased, precipitates are increased in number at grain boundaries. The grain size tends to become coarse with the increase of Si content. 5. Co rich-Cr alloy is present through matrix whereas at the grain boundaries Cr base precipitates are primarily formed.

• Journal of Environmental Health Sciences
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• v.11 no.2
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• pp.55-63
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• 1985

The quantities of chrome, lead, iron, copper and manganese in the formula feed were determined by A.A.S. and the results were summarized as follows 1. The content of chromium in the leather and meat meals(SN-2) were 13-66 times as much as the level of permission. 2. In the meantime, lead content in the meat meal (SN-1) was about 20 times as much as permitted level. 3. The iron which is essential constituent of the formula feed was contained in the meat and leather meals and these values were 2-10 times as much as feeding regulations, on the contrary copper and manganese content in the shaving and flesh were below the feeding regulations.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.302-303
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• 2014

유도결합플라즈마 보조 D.C.마그네트론 스퍼터링법을 이용하여 STS316L 위에 Ti-Cr-N 박막의 증착하였으며 크롬과 질소의 함량에 따른 부식특성 변화를 관찰하였다. Ti-Cr-N 박막을 증착시켰을 때는 미처리 STS316L에 비해 더 우수한 부식특성을 보였으며 크롬타겟의 인가전원이 100W 일 때와 질소비가 0.3일 때 가장 우수한 내부식 특성을 나타내었다.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.357-361
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• 2001

The possibility of producing Cr$_2$O$_3$powder from waste magnesia-chromium refractory was investigated by sulfuric acid reaction, alkali fusion, water leaching & purification and heat treatment. The effects of temperature, the amount of NaOH added and the flow rate of air on chromium extraction efficiency in an alkali fusion step were investigated. The fusion product was leached with methanol to solve free-NaOH, and then leached with water to produce a Na$_2$CrO$_4$solution. The purity of chrome(Ⅵ) oxides, prepared both from monochromate with an impurity content and monochromate purified with $CO_2$were also examined. The purified monochromate solution was reduced from Cr(Ⅵ) to Cr(III) with NaHSO$_3$solution. The reduced solution was neutralized with NaOH to produce Cr(OH)$_3$. Water washing was treated to eliminate Na$_2$SO$_4$from neutralized Cr(OH)$_3$slurry. The washed Cr(OH)$_3$was dried and thermally treated to produce Cr$_2$O$_3$powder. The properties like lightness and hue of Cr$_2$O$_3$fabricated in this study were L=47.47, a=-14.40 and b=17.21.

• Corrosion Science and Technology
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• v.15 no.5
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• pp.226-236
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• 2016

316L stainless steels have been widely used in many engineering fields, because of their high corrosion resistance and good mechanical properties. However, welding or aging treatment may induce intergranular corrosion and stress corrosion cracking etc. Since these types of corrosion are closely related to the formation of chromium carbide in grain boundaries, the alloys are controlled by methods such as the lowering of carbon content, solution heat treatment. This work focused on the intergranular corrosion mechanism of slightly-sensitized and Ultrasonic Nano-crystal Surface Modification (UNSM)-treated 316L stainless steel. Samples were sensitized for 1, 5, and 48 hours at $650^{\circ}C$ in $N_2$ gas atmosphere. Subsequently UNSM treatments were carried out on the surface of the samples. The results were discussed on the basis of the sensitization by chromium carbide and carbon segregation, the residual stress and grain refinement. Even though chromium carbide was not precipitated, the intergranular corrosion rate of 316L stainless steel was drastically increased with aging time, and it was confirmed that the increased intergranular corrosion rate of slightly-sensitized (not carbide formed) 316L stainless steel was due to the carbon segregation along the grain boundaries. However, UNSM treatment improved the intergranular corrosion resistance of aged stainless steels, and its improvement was due to the reduction of carbon segregation and the grain refinement of the outer surface, including the introduction of compressive residual stress.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.313-324
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• 2015

Austenitic stainless steels have been widely used in many engineering fields because of their high corrosion resistance and good mechanical properties. However, welding or aging treatment may induce intergranular corrosion, stress corrosion cracking, pitting, etc. Since these types of corrosion are closely related to the formation of chromium carbide in grain boundaries, the alloys are controlled using methods such as lowering the carbon content, solution heat treatment, alloying of stabilization elements, and grain boundary engineering. This work focused on the effects of aging and UNSM (Ultrasonic Nano-crystal Surface Modification) on the intergranular corrosion of commercial 316L stainless steel and the results are discussed on the basis of the sensitization by chromium carbide formation and carbon segregation, residual stress, grain refinement, and grain boundary engineering.

• Journal of the Korean Ceramic Society
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• v.52 no.5
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• pp.308-314
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• 2015

The electrochemical performance and Cr poisoning behavior of $La_{1-x}Ba_xCo_{0.9}Fe_{0.1}O_{3-{\delta}}$ (LBCF, x = 0.3, 0.4, 0.5) and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF) cathodes were investigated for solid oxide fuel cells (SOFCs). The polarization resistance of the LBCF/GDC/LBCF symmetrical cell was found to decrease with increasing Ba content (x value). This phenomenon might be associated with the high oxygen vacancy concentration in the LBCF sample, with x = 0.5. In addition, there was no chromium poisoning in the LBCF cathode. On the other hand, the polarization resistance of the LSCF cathode was found to significantly increase after exposure to gaseous chromium species; it appears that this result stemmed from the formation of $SrCrO_4$ phase. Therefore, it can be expected that LBCF can be a durable potential cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFC).

• Journal of the Korean Society for Heat Treatment
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• v.19 no.2
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• pp.83-89
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• 2006

The surface phase changes, the hardness variations, the nitrogen contents and the corrosion resistances of 17-4 PH stainless steel have been investigated after nitrogen permeation(solution nitriding) at a temperature ranges from $1050^{\circ}C$ to $1150^{\circ}C$ The phases appeared at the nitrogen-permeated surface layer were shown to martensite plus austenite and austenite, depending on the variation of nitrogen and chromium contents. And the surface hardness was also depended on the phases appeared at the surface layer from 370 Hv to 220 Hv. The precipitates exhibited at the nitrogen-permeated surface layer were niobium nitride, niobium chromium nitride and carbo-nitride in the austenite and martensite matrices. The surface nitrogen contents were followed by the Cr contents of the surface layers, representing 0.55% at the temperatures of $1050^{\circ}C$ and $1150^{\circ}C$ respectively, and 0.96% at $1100^{\circ}C$ at the distances of $60{\mu}m$ from the outmost surface. From the comparison of the corrosion resistances between nitrogen-permeated and solution-annealed steels, nitrogen permeation remarkably improved the corrosion resistance in the solution of 1 N $H_2SO_4$ due to the increase of nitrogen content in the surface austenite phase.

• 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.