• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.256-261
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• 2001

These experiments were carried out to examine the effects of element substitution of Zn and La-Zn for Sr-ferrite. The calcined properties of Zn and La-Zn element substitution were examined, and also the sintered magnetic properties were compared with the stoichiometric condition. The magnetization properties of calcined SrM materials is as follows; M$\_$s/ : 61.06 emu/g. Also, the magnetization properties of calcined Zn$\_$0.3/-SrM materials is as follows; M$\_$s/ : 66.90 emu/g. The sintered magnetic properties of (La-Zn)$\_$0.3/-SrM composition is as follows; B$\_$r/ : 4.21 kG, BH$\_$max/: 4.19 MGOe.

• Resources Recycling
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• v.11 no.5
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• pp.16-20
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• 2002

This experiment was carried out to examine the effects of La-Co substitution on Sr-ferrite. The magnetic properties of calcined and sintered materials varied with the substitutional amount of La and Co elements in Sr-ferrite. Anisotropy field and coercivity for Sr ferrite were increased with raising La-Co substitution amounts. The microstructure observation for Sr ferrite substituted by La-Co revealed that La-Co inhabited grain growth during calcination and promoted lateral grain growth during sintering. The relationship between $B_{r}$ and $_{i}$ /$H_{c}$ for La-Co substituted Sr-ferrite was found to be $B_{r}$$≒0.097_{i}$ /$H_{c}$/+4500. In case of $SrFe_{12}$ $O_{19}$, $B_{r} was 4090 G and $_{ i}$$H_{c}$ was 3560 Oe, but $B_{r}$ was 4080 G and and $_{i}$ $H_{c}$ was 4800 Oe for $Sr_{0.7}$ $La_{0.3}$ $Fe_{11.7}$ /$Co_{0.3}$ $O_{19}$.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.183-195
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• 2014

In order to study the mineralogical characteristics of a cathodic deposition-metallic powder, electrowinning experiments were carrier out on different electrolytic solutions at varying electric distances and electric currents. Under the same experimental conditions, Cu recovery was obtained much more effectively using a sodium chloride electrolyte than with a sulfuric acid electrolyte. In XRD analysis, copper ($Cu^0$), chalcanthite and cuprite were identified in the sulfuric acid electrolyte, while copper, nantokite and chalcanthite were observed in the sodium chloride electrolyte. In the sodium chloride electrolyte solution, increasing the electric distance and the electric current increased the Cu recovery rate, anode weight and anodic corrosion. The results of XRD analysis with non-pulverized cathodic deposition-metallic powder showed the average copper crystallite size was increased by increasing the electric current and decreasing the electric distance. It is suggested that the mass transfer was controlled with diffusion on the boundary between the electrode and the electrolytic solution due to the formation of dendrite copper.

• Journal of the Mineralogical Society of Korea
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• v.27 no.3
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• pp.115-124
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• 2014

In order to leach Au and Ag from gold-silver bearing sulfide concentrate, the sulfide concentrate was ground in a ball mill for a dry pre-treatment and a wet pre-treatment process. Mineralogical studies and thiourea leaching experiments were carried out with the pre-treated sulfide concentrate. The results of the pre-treatment with the concentrate samples showed the mean particle size and iso-electrical potential was smaller in the dry pre-treatment sample than in the concentrate sample, and the contents was lower in the wet pre-treatment sample than in the dry pre-treatment sample. In XRD analysis, amorphous properties were only shown in the wet pretreatment sample. The results of the concentrate sample leaching experiments showed that the best Au, Ag leaching parameters were when the addition of thiourea was at a 1.0 g concentration, ferric sulfate was 1.0 M, sulfuric acid was 2.0 M and the leaching temperature was at $60^{\circ}C$. The Au, Ag leaching rate was always much greater and faster with the wet pre-treatment samples than with the dry pre-treatment samples. Accordingly, it is expected that more Au, Ag can be leached in an eco-friendly methodology using wet pre-treatment. The pre-treatment could be improved with an optimized grinding additive reagent and through researching grinding time in future non-cyanide processes.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.685-689
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• 2001

We carried out these experiments to examine the effects of element substitution of Co and La-Co for Sr-ferrite. The calcined properties of Co and La-Co element substitution were examined, and also the sintered magnetic properties were measured with the stoichiometric condition. The magnetic properties of $(La-Co)_{0.3}-SrM$ composition are as follows; $(M_s)$: 71.08 emu/g, $iH_c$: 4.38 kOe and $B_r$ : 4.18 kG, $iH_ c$ :4.35 kOe, $BH_{max}$: 4.3 MGOe. The $BH_{max}$ value was increased up to 10 % compared with conventional values. Our results imply that the magnetic properties of Sr-ferrite can be improved by the substitution of those elements.

• Economic and Environmental Geology
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• v.36 no.5
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• pp.357-363
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• 2003

The objective of this study is to investigate background levels of As and heavy metals (Cd, Cu, Pb and Zn) and their dietary intakes from white rice produced at various provinces in Korea during 2000. Except Jeju-do, sixty-three rice grain samples were taken at 8 provinces and analyzed for the elements using ICP-AES after acid digestion. The average contents of hi, Cd, Cu, Pb and Zn in the samples were 0.126, 0.040, 1.96, 0.361 and 16.6 mg/kg(DW), respectively. These levels are within the ranges of worldwide average concentrations in rice grains reported by various research. Assuming the rice consumption of 256 g/day by overall households in Korea, the amount of daily intake of As, Cd, Cu, Pb and Zn by the rice were estimated to be 32.3, 10.2, 502, 92.4 and 4,250 ${\mu}g$/day, respectively. Those amount of daily intakes of the elements by the rice are within the WHO's guide for trace elements, however, rice consumption is one of the most important sources of dietary intake of As and some heavy metals in Korean population.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.26-26
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• 2003

산업 폐기물로서 전량 매립되고 있는 styrene monomer (SM) 공정에서 발생되는 산화철 폐촉매를 사용하여 NiZn-페라이트를 합성하였고, 그 자기적 특성을 조사하였다. 평균입경 0.5㎛로 미분쇄된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소한후 1230℃에서 5시간 동안 소결하여 스핀넬형 페라이트 소결체를 얻었다. Ni/sub x/Zn/ub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66) 및 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 초투자율을 측정하였다. S-parameter를 측정하여 반사 감쇄량을 계산하였다. Ni/sub 0.5/Zn/sub 0.5/fe₂O₄ 조성의 경우 밀도 5.38 g/㎤ kHz에서의 초투자율이 59인 특성을 얻었다. 산화철 폐촉매를 이용하여 X-band 주파수 영역에서 높은 전자파 흡수능을 갖는 전파흡수체를 제조할 수 있음을 확인하였다. Ni/sub 0.5/Zn/sub 0.5/Fe₂O₄ 조성에 대하여 1100℃에서 하소한 분말을 사용하여 실리콘 고무에 복합시킨 후 전파흡수능을 측정하였다. 폐촉매에는 산화철 이외에 CeO₂가 주된 첨가물로 함유되어 있어서 페라이트의 합성 후에도 2차상으로서 존재하였다. 출발 원료인 산화철 폐촉매에 존재하는 K₂O 및 CeO₂를 제거하기 위하여 산처리와 분산제를 이용한 CeO₂ 분리과정을 행하였다. 정제된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소하여 스핀넬형 페라이트를 합성하고 1325℃에서 5시간 소결하였다. 위와 마찬가지로 Ni/sub x/Zn/sub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66)과 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 자기적 특성을 조사하였다.화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.료의 가시적 변화를 통해 illumination angle 1.25mrad(Dose rate : 334 × 10³ e/sup -//sec·n㎡)일 경우 약 3초 이내에 비정질화가 시작됨을 알 수 있었고 이는 약 1 × 10/sup 6/ e/sup -//sec·n㎡ 의 전자선량에 해당되며 이를 기준으로 각각의 illumination angle에 대한 임계전자선량을 평가할 수 있었다. 실질적으로 Cibbsite와 같은 무기수화물의 직접가열실험 시 전자빔 조사에 의해 야기되는 상전이 영향을 배제하고 실험을 수행하려면 illumination angle 0.2mrad (Dose rate : 8000 e/sup -//sec·n㎡)이하로 관찰하고 기록되어야 함을 본 자료로부터 알 수 있었다.운동횟수에 의한 영향으로써 운동시간을 1일 6시간으로 설정하여, 운동횟수를 결정하기 위하여 오전, 오후에 각 3시간씩 운동시키는 방법과 오전부터 6시간동안 운동시키는 두 방법을 이용하여 품질을 비교하였다. 각 조건에 따라 운동시킨 참돔의 수분함량을 나타낸 것으로, 2회(오전 3시간, 오후 3시간)에 나누어서 운동시키기 위한 육의 수분함량은 73.37±2.02%를 나타냈으며, 1회(6시간 운동)운동시키기 위한 육은 71.74±1.66%을 나타내었다. 각각의 운동조건에서 양식된 참돔은 사육초기에는 큰 변화가 없었으나, 사육 5일 이후에는 수분함량이 증가하여 15일에는 76.40±0.14, 75.62±0.98%의 수분함량을 2회와 1회 운동시킨 참돔의 육에서 각각 나타났다. 운동횟수에 따른 지질함량은 2회 운동시킨 참돔은 5.83±2.08, 1회 운

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.

• Clean Technology
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• v.28 no.3
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• pp.203-209
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• 2022

An environmental evaluation was conducted by employing LCA methodology for a mechanical seal manufacturing process that uses recycled silicon recovered from end-of-cycle PV modules. The recycled silicon was purified and reacted with carbon to synthesize β-SiC particles. Then the particles underwent compression molding, calcination and heat treatment to produce a product. Field data were collected and the potential environmental impacts of each stage were calculated using the LCI DB of the Ministry of Environment. The assessment was based on 6 categories, which were abiotic resource depletion, acidification, eutrophication, global warming, ozone depletion and photochemical oxidant creation. The environmental impacts by category were 45 kg CO₂ for global warming and 2.23 kg C₂H₄ for photochemical oxide creation, and the overall environmental impact by photochemical oxide creation, resource depletion and global warming had a high contribution of 98.7% based on weighted analysis. The wet process of fine grinding and mixing the raw silicon and carbon, and SiC granulation were major factors that caused the environmental impacts. These impacts need to be reduced by converting to a dry process and using a system to recover and reuse the solvent emitted to the atmosphere. It was analyzed that the environmental impacts of resource depletion and global warming decreased by 53.9% and 60.7%, respectively, by recycling silicon from end-of-cycle PV modules. Weighted analysis showed that the overall environmental impact decreased by 27%, and the LCA analysis confirmed that recycling waste modules could be a major means of resource saving and realizing carbon neutrality.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.151-158
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• 2022

In this study, the waste concrete sample obtained as various particle size (0~2.36 mm) was carried out the basic measurements and carbonation for analyzing the possibility of its carbonation. It was then investigated some analysis such as crystallization (XRD pattern), microstructure (SEM), and the production of CaCO₃ through the ignition loss (TG-DTA). The content of CaCO₃ in the waste concrete sample before carbonation was found in 14.51 % and 28.52 % after carbonation in 24 hours. Moreover, the content of CaCO₃ carbonated in 24 hours with fine grinded waste concrete sample was 32.73 %. The carbonation of the waste concrete sample was rapidly performed up to 6 hours, but gradually increased from 12 to 24 hours. Especially, the amount of CaCO₃ between 12 and 24 hours was only produced 2.32 %. The calcite-shaped CaCO₃ crystals after carbonation of the waste concrete sample were found in microstructure and their peaks were strongly detected on XRD pattern.