This study investigated whether calcium (Ca) addition improved the recovery of neodymium (Nd) and dysprosium (Dy) from Nd-Fe-B magnet scrap using magnesium (Mg)-based liquid metal extraction (LME). Traditional LME processes are limited to temperatures up to 850 °C due to oxidation issues, reducing the efficiency of rare earth element (REE) recovery, especially for Dy. By adding 10 wt.% Ca to Mg and increasing the processing temperature to 1,000 °C, we achieved nearly 100% Nd and approximately 38% Dy recovery, compared to 91% and 28%, respectively, with pure Mg at 850 °C. However, excessive Ca addition (20 wt.%) decreased the recovery efficiency due to the formation of stable intermetallic compounds. These results highlight the critical role of Ca in optimizing REE recycling from Nd-Fe-B magnet scrap.

세계적인 탄소중립 정책 추진과 수소 에너지 수요 증가에 따라 고분자 전해질 수전해 및 연료전지 기술 개발이 활발히 이루어지고 있다. 해당 기술의 핵심 소재인 과불소계 술폰산 이오노머는 우수한 전기화학적 특성과 화학적 안정성을 가지고 있지만, 높은 제조비용, 한정된 공급망, 강화되는 환경 규제와 같은 문제로 인해 효과적인 재활용 및 재제조 기술이 요구되고 있다. 본 연구에서는 초임계 분산 기술을 통해 전해질막 및 막-전극접합체의 제조과정에서 발생하는 고활성을 갖는 전해질막 스크랩을 연료전지 전극바인더로 재제조하는 방법을 제시하고자 한다.

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.

Bulk graphite is manufactured using graphite scrap as the filler and phenolic resin as the binder. Graphite scrap, which is the by-product of processing the final graphite product, is pulverized and sieved by particle size. The relationship between the density and porosity is analyzed by measuring the mechanical properties of bulk graphite. The filler materials are sieved into mean particle sizes of 10.62, 23.38, 54.09, 84.29, and 126.64 μm. The bulk graphite density using the filler powder with a particle size of 54.09 μm is 1.38 g/cm3, which is the highest value in this study. The compressive strength tends to increase as the bulk graphite density increases. The highest compressive strength of 43.14 MPa is achieved with the 54.09 μm powder. The highest flexural strength of 23.08 MPa is achieved using the 10.62 μm powder, having the smallest average particle size. The compressive strength is affected by the density of bulk graphite, and the flexural strength is affected by the filler particle size of bulk graphite.

This study focuses on the fabrication of a WC/Co composite powder from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere for the recycling of WC/Co hardmetal. Mixed powders are manufactured by mechanically milling the oxide powder of WC-13 wt% Co hardmetal scrap and carbon black with varying powder/ball weight ratios. The oxide powder of WC-13 wt% Co hardmetal scrap consists of WO3 and CoWO4. The mixed powder mechanically milled at a lower powder/ball weight ratio (high mechanical milling energy) has a more rapid carbothermal reduction reaction in the formation of WC and Co phases compared with that mechanically milled at a higher powder/ball weight ratio (lower mechanical milling energy). The WC/Co composite powder is fabricated at 900℃ for 6 h from the oxide of WC/Co hardmetal scrap using solid carbon in a hydrogen gas atmosphere. The fabricated WC/Co composite powder has a particle size of approximately 0.25-0.5 μm.

The GaN-powder scrap generated in the manufacturing process of LED contains significant amounts of gallium. This waste can be an important resource for gallium through recycling of scraps. In the present study, the influence of annealing temperatures on the structural properties of GaN powder was investigated when the waste was recycled through the mechanochemical oxidation process. The annealing temperature varied from 200oC to 1100oC and the changes in crystal structure and microstructure were studied. The annealed powder was characterized using various analytical tools such as TGA, XRD, SEM, and XRF. The results indicate that GaN structure was fully changed to Ga2O3 structure when annealed above 900oC for 2 h. And, as the annealing temperature increased, crystallinity and particle size were enhanced. The increase in particle size of gallium oxide was possibly promoted by powder-sintering which merged particles to larger than 50 nm.

It should be noted that the use of the lathe scrap for making fiber reinforced cementitious composites(FRCCs) raised friendly environmental effect as well as economy because the lathe scrap is a by-product of steel manufactures and is occurred when lathe and milling works of them are conducted to process steel manufactures. Thus, the purpose of this research is to investigate the effect of measurements of lathe scrap on the characteristics of FRCCs. For this purpose, various lathe scraps were collected from processing plants of metal, and then these were processed 10mm, 20mm, and 40mm in lengths for 2mm and 4mm in widths, respectively. FRCCs containing lathe scraps were made according to their widths and lengths, and then characteristics such as the workability, compressive strength, and flexural strength of those were evaluated. As a result, it was observed from the test results that the optimum measurements of the lathe scrap for manufacturing FRCCs was 2mm in width and 40mm in length.

폐 PCBs의 스크랩으로부터 염소-차아염소산염 용액을 이용하여 Au와 Ag를 친환경적이고 효과적으로 용출시키고자 하였다. PCBs에 Cu, Sn, Sb, Al, Ni, Pb, Au 등과 같은 유용금속이 함유되어 있는 것을 EDS 분석으로 확인하였다. 최대 Au 용출율은 1%의 광액농도, 2:1의 염산:차아염소산나트륨 그리고 2 M의 NaCl 농도조건이다. Au 회수율이 가장 높은 메타중아황산나트륨 농도는 3 M에서였다. 염소-차아염소산염이 폐 컴퓨터에 함유되어 있는 Au와 Ag를 효과적으로 용출시킬 수 있는 용매제 임을 그리고 메타중아황산나트륨이 Au를 간단하게 침전시킬 수 있는 첨가제임을 확인하였다.

Isotropic synthetic graphite scrap and phenolic resin were mixed, and the mixed powder was formed at 300 MPa to produce a green body. New bulk graphite was produced by carbon-izing the green body at 700°C, and the bulk graphite thus produced was impregnated with resin and re-carbonized at 700°C. The bulk density of the bulk graphite was 1.29 g/cm3, and the porosity of the open pores was 29.8%. After one impregnation, the density increased to 1.44 g/cm3 while the porosity decreased to 25.2%. Differences in the pore distribution before and after impregnation were easily confirmedby observing the microstructure. In addition, by using an X-ray diffractometer, the degrees-of-alignment (Da) were obtained for one side perpendicular to the direction of compression molding of the bulk graphite (the “top-face”), and one side parallel to the direction of compression molding (the “side-face”). The anisot-ropy ratio calculated from the Da-values obtained was 1.13, which indicates comparatively good isotropy.

A study of oxidation kinetic of Fe-36Ni alloy has been investigated using thermogravimetric apparatus (TGA) in an attempt to define the basic mechanism over a range of temperature of 400 to and finally to fabricate its powder. The oxidation rate was increased with increasing temperature and oxidation behavior of the alloy followed a parabolic rate law at elevated temperature. Temperature dependence of the reaction rate was determined with Arrhenius-type equation and activation energy was calculated to be 106.49 kJ/mol. Based on the kinetic data and micro-structure examination, oxidation mechanism was revealed that iron ions and electrons might migrate outward along grain boundaries and oxygen anion diffused inward through a spinel structure, .

With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.

In this research, the optimal manufacturing conditions of fine Si powders from Si scrap were investigated as a function of different initial powder size using the high-energy ball milling equipment, which produces the fine powder by means of an ultra high-energy within a short duration. The morphological change of the powders according to the milling time was observed by Scanning electron microscopy (SEM). With the increasing milling time, the size of Si powder was decreased. In addition, more energy and stress for milling were required with the decreasing initial powder size. The refinement of Si scrap was rapidly carried out at 10min ball milling time. However, the refined powder started to agglomerate at 30 min milling time, while the powder size became uniform at 60 min milling time.

In this study, Ti powders were fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method.The Ti powders were prepared from the spark plasma sintering (SPS) and their microstructure was investigated.Hydrogenation reactions of Ti scrap occurred at near 450oC with a sudden increase in the reaction temperature and thedecreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was alsocarried out at 750oC for 2 hrs in a vacuum of 10-4torr. After the HDH process, deoxidation treatment was carried out withthe Ca (purity: 99.5%) at 700oC for 2 hrs in the vacuum system. It was found that the oxidation content of Ti powder thatwas deoxidized with Ca showed noticeably lower values, compared to the content obtained by the HDH process. In orderto fabricate the Ti compacts, Ti powder was sintered under an applied uniaxial punch pressure of 40 MPa in the range of900-1200oC for 5 min under a vacuum of 10-4torr. The relative density of the compact was 99.5% at 1100oC and the tensilestrength decreased with increasing sintering temperature. After sintering, all of the Ti compacts showed brittle fracturebehavior, which occurred in an elastic range with short plastic yielding up to a peak stress. Ti improved the corrosionresistance of the Ti compacts, and the Pd powders were mixed with the HDH Ti powders.

In this study, Ti powder was fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH)method. Hydrogenation reactions of Ti scrap occurred at near 450oC with a sudden increase in the reactiontemperature and the decreasing pressure of hydrogen gas during the hydrogenation process in the furnace. Thedehydrogenation process was also carried out at 750oC for 2hrs in a vacuum of 10-4torr. After the HDHprocess, a deoxidation treatment was carried out with the Ca(purity: 99.5) at 700oC for 2hrs in the vacuumsystem. It was found that the oxidation content of Ti powder that was deoxidized with Ca showed noticeablylower values, compared to the content obtained by HDH process. In order to fabricate Ti compacts, Ti powderwas sintered at 1100~1400oC for 2hrs under a vacuum of 10-4torr. The relative density of compact was 94.9%at 1300oC. After sintering, all of the Ti compacts showed brittle fracture behavior, which occurred in an elasticrange with short plastic yielding up to a peak stress.

Efforts to reduce noise in industrial application fields, such as automobiles, aircrafts, and plants have been gaining considerable attention while a sound proof wall to protect people from the noise has been intensively investigated by many researchers. In this study, our research group suggested creating a new sound proof wall composed of scrap aluminum chips and perforated plates in a commercial polyester sound proof wall, which was then successfully fabricated. This wall's sound absorption characteristics were measured by an impedance tube method. The sound absorption property was evaluated by measuring the Noise Reduction Coefficient (NRC) to the standard, ASTM C 423-90a. The noise reduction coefficient of the sound proof wall composed of 3.5 vol.% and 7.5 vol.% of scrap aluminum chips relatively increased to 5% and 8% compared to the commercial polyester sound proof wall. The scrap aluminum perforated plate also relatively increased to 13% compared to the commercial polyester sound proof wall.

Pretreatment of eliminating FFA is needed to make biodiesel from animal fat recovered from leather wastes because its acid value is high. This study was carried out to investigate the influence of 4 different pretreatment methods, which are heterogeneous catalyst method, ion exchange resin method, low pressure.high temperature method, and alkali method on the eliminating FFA and fatty acid composition. The results showed that the rate of eliminating FFA increased in the order of alkali method > catalyst method > low pressure high temperature method > ion exchange method. In the case of pretreatment of alkali method using NaOH, the rate of eliminating FFA appeared more than 86% regardless of acid value. Therefore, it was considered that alkali method using NaOH was the most effective in the view of economical and productive aspects, taking it into account that the acid value of animal fat recovered from fleshing scrap generated during leather making processes was 7 to 8.

Ceramic pigments were developed by using 4 kinds of Brass scraps. Each Brass scraps were mixed with same weight-ratio of Husk ash, and fine-ground by Rotate ring mill(RRG-120, Armstech industrial. co. Ltd, Korea) after firing at 900℃, 1000℃ and 1100℃. As a result, analysis of particle size of synthetic pigments by particle size analyser, they are 3μm as average. The resulting pigments were characterized by using XRD, FT-IR, SEM Structure of the crystals are Zn2SiO4,, and ZnO, Cu2O, CuO, and cristobalite are existed and particles' shape are plate or needle. As a result of analysis of chemical composition by XRF, synthetic pigments have high SiO2 and CuO content and have SnO2, ZnO and NiO, too. 1wt%, 3wt% and 5wt% pigments were added in each lime glaze, lime-barium glaze and lime-magnesia glaze, and fired at oxidation and reducing atmosphere to figure hue in glazes out. As a result of analysis of color, chroma and brightness by UV, colors of glazes fired at oxidation atmosphere turned into green from sky blue, and colors of glazes fired at reducing atmosphere turned into pink and red.

Fleshing scrap is a kind of wastes produced during leather making process and used in the test of manufacturing biodiesel. The early step of manufacturing biodiesel is fat recovery from fleshing scrap. Hence, we investigated the influence of the way of fat recovery on the fatty acid composition. We used three different recovery ways, that is chemical method by protein decomposition with acid/fat recovering, physical method by protein denaturalization with heat and vacuum/fat pressing, and biodiesel method by protein decomposition/fat recovering. The biological method yielded the best results in terms of appearance transparency. It was most effective to lower acid value. Also the recovered fat by biological method would be favorable methyl-ester reaction raw material for biodiesel because it contains more than 5% of oleic acid among unsaturated fatty acid.