• Journal of the Korea Organic Resources Recycling Association
• /
• v.32 no.1
• /
• pp.39-47
• /
• 2024

In this study, LiDAR-detective black material is synthesized by recycling silicon sludge (SS) that is generated from semiconductor manufacturing process, and its recognition is confirmed using two types of LiDAR sensors (MEMS and Rotating LiDAR). In detail, metal impurities on the surface of SS is removed, followed by coating of titanium dioxide (TiO₂) and subsequent chemical reduction to obtain SS-derived black TiO₂ (SS/bTiO₂) material. As-prepared SS/bTiO₂ is mixed with transparent paint to prepare hydrophilic black paints and applied to a glass substrate using a spray gun. SS/bTiO₂-based paint shows similar blackness (L^*=15.7) compared to commercial carbon black-based paint, and remarkable NIR reflectance (26.5R%, 905nm). Furthermore, MEMS and Rotating LiDAR have successfully detected the SS/bTiO₂-based paint. This is attributed to the occurrence of high reflection of light at the interface between the black TiO₂ and the silicon sludge according to the Fresnel's reflection principle. Hence, the new application field to effectively recycle silicon sludge generated in the semiconductor manufacturing process has been presented.

• Resources Recycling
• /
• v.22 no.2
• /
• pp.37-43
• /
• 2013

Unlike the conventional slurry type wire sawing, the diamond wire sawing method adopts diamond plated wire as sawing media instead of slurry consisted of both silicon carbide and oil. Wafering with diamond plated wire leaves solid element of the sludge mostly made up of silicon, and it is not difficult to recover 95% or more of silicon by a simple separation process of oil from the sludge. In this study, silicon was recovered from the sludge by drying process and organic and metal impurities were removed by sintering process. As result 3N grade silica was obtained successfully by thermal processing utilized the fact that the recovered silicon readily combines with oxygen due to fine particle size.

• Applied Chemistry for Engineering
• /
• v.19 no.5
• /
• pp.477-483
• /
• 2008

$La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ oxide was synthesized by a citrate method and a typical dense membrane of perovskite oxide has been prepared using as-prepared powder by pressing and sintering at $1300^{\circ}C$. Precursor of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ prepared by citrate method was investigated by TGA and XRD. Metal-citrate complex in precursor was decomposed into perovskite oxide in the temperature range of $260{\sim}410^{\circ}C$ but XRD results showed $SrCO_3$ existed as impurity at less than $900^{\circ}C$. Electrical conductivity of membrane increased with increasing temperature but then decreased over $700^{\circ}C$ in air atmosphere ($Po_2=0.2atm$) and $600^{\circ}C$ in He atmosphere ($Po_2=0.01atm$) respectively due to oxygen loss from the crystal lattice. The oxygen permeation flux increased with increasing temperature and maximum oxygen permeation flux of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ membrane with 1.6 mm thickness was about $0.31cm^3/cm^2{\cdot}min$ at $950^{\circ}C$. The activation energy for oxygen permeation was 88.4 kJ/mol in the temperature range of $750{\sim}950^{\circ}C$. Perovskite structure of membrane was not changed after permeation test of 40 h and the membrane was stable without secondary phase change with 0.3 mol Sr addition.

• Korean Journal of Heritage: History & Science
• /
• v.47 no.4
• /
• pp.224-243
• /
• 2014

This study examined the materials and casting technology(cast, alloy, etc.) used in the manufacturing of bronze artifacts based on old literature such as Yongjae Chonghwa, Cheongong Geamul, and The Korea Review. In the casting experiment for restoration of Sangpyong Tongbo, a bronze and brass mother coin mold was made using the sand mold casting method described in The Korea Review. The cast was comprised of the original mold plate frame, wooden frame, and molding sand. Depending on the material of the outer frame, which contains the molding sand, the original mold plate frame can be either a wooden frame or steel frame. For the molding sand, light yellow-colored sand of the Jeonbuk Iri region was used. Next, the composition of the mother alloy used in the restoration of Sangpyong Tongbo was studied. In consideration of the evaporation of tin and lead during actual restoration, the composition of Cu 60%, Zn 30%, and Pb 10% for brass as stated in The Korea Review was modified to Cu 60%, Zn 35%, and Pb 15%. For bronze, based on the composition of Cu 80%, Sn 6%, and Pb 14% used for Haedong Tongbo, the composition was set as Cu 80%, Sn 11%, and Pb 19%. The mother coin mold was restored by first creating a wooden father coin, making a cast from the wooden frame and basic steel frame, alloying, casting, and making a mother coin. Component analysis was conducted on the mother alloy of the restored Sangpyong Tongbo, and its primary and secondary casts. The bronze mother alloy saw a 5% increase in copper and 4% reduction in lead. The brass parent alloy had a 5% increase in copper, but a 4% and 12% decrease in lead and tin respectively. Analysis of the primary and secondary mother coin molds using an energy dispersive spectrometer showed that the bronze mother coin mold had a reduced amount of lead, while the brass mother coin mold had less tin. This can be explained by the evaporation of lead and tin in the melting of the primary mother coin mold. In addition, the ${\alpha}$-phase and lead particles were found in the mother alloy of bronze and brass, as well as the microstructure of the primary and secondary coin molds. Impurities such as Al and Si were observed only in the brass mother coin mold.

• Applied Chemistry for Engineering
• /
• v.27 no.6
• /
• pp.583-589
• /
• 2016

Lubricant additives including zinc dialkyldithiophosphate (ZDDP) containing metal have been widely used due to the advantage of very low cost, but they can generate impurities such as ash. In this work, ZDDP containing metals was partially replaced with bis[3-(dialkyloxyphosphorothionyl) thio-2-methylpropanyloxy] butane (BAP4s) which was synthesized conveniently and effectively from alkanediol without any metal components. Also, the wear resistance property of synthesized BAP4s were studied. Wear scar diameter (WSD) values of BAP4s with butyl, octyl, decyl, dodecyl or tetradecyl groups were also measured by four-ball test. As the length of the alkyl group increased from 4 to 8, the WSD value of BAP4s decreased rapidly from 0.59 to 0.45 mm, but from 8 to 14, the value increased very slowly from 0.45 to 0.50 mm. Thus, among all BAP4s, B8P4 having BAP4 with the octyl group, showed the lowest WSD value. Furthermore, the WSD values were measured in a lubricant base oil mixed with a 0.50 percent concentration (w/w) of either BAP4 or ZDDP. The former was 0.55 mm, and the latter was 0.45 mm. The thermal stability and tribofilm formation peroperty were also measured by thermogravimetric analyzer (TGA) and energy-dispersive X-rays spectroscopy (EDS), respectively.

• Korean Journal of Heritage: History & Science
• /
• v.47 no.4
• /
• pp.210-223
• /
• 2014

When sarira reliquary was found in stone pagoda of Mireuksa Temple, there were 494 gold artifacts, including inner gold pot, gold plate with inscription for Sarira enshrinement, etc. Most of gold artifacts were crafted, but there were 22 gold plates and 4 gold ingots, which did not have any specific shape. It was considered that they had not been crafted. Since gold exists as a metal rather than a metallic oxide in nature, in general, it can be crafted by melting and shaping. However, gold in nature has impurities so it has to be refined to have malleability. The characteristic features were identified through the analysis of gold artifacts from sarira reliquary found in stone pagoda of Mireuksa Temple. The analysis result showed that there were 3 types of gold; pure gold artifacts, artifacts produced with silver containing gold and natural gold ingots. Inner gold pot, gold earrings and gold small beads were produced with pure gold and they contained less than 1wt.% of copper. It seemed like they were produced as pure gold to be shaped by hammering. Gold plate with inscription, tweezers, gold earrings, ingots, etc. were produced with silver containing gold as they had to be more solid. Gold ingots seemed to be natural gold considering the distribution of silver and copper in them, but it cannot be concluded as there are not enough information on gold ingots in Korea. The comprehensive research on gold ingots from various regions in Korea has to be carried out to confirm the above. Sarira Reliquary showed the very sophisticated gold craftsmanship. Gold ingots with the inscriptions, which say 1 nyang, were approximately 14g. Considering the weight of these ingots as standard, weights of other ingots were half nyang(7g), 2 nyang(28g), etc.

• Korean Journal of Heritage: History & Science
• /
• v.46 no.1
• /
• pp.208-227
• /
• 2013

Twenty-seven bronze bowls excavated from the Goryo burial complex at Deobu-gol were examined for their microstructure and chemical composition to characterize the bronze technology practiced by commoners at the time. Results showed that the objects examined can be classified into four groups: 1) objects forged out of Cu-near 22%Sn alloys and then quenched; 2) objects cast from Cu-below 10% Sn alloys containing lead; 3) objects cast from Cu-10%~20% Sn alloys containing lead and then quenched; 4) objects forged out of Cu-10~20% Sn alloys containing lead and then quenched. This study revealed that the fabrication technique as determined by alloy compositions plays an important role in bronze technology. The use of lead was clearly associated with the selection of quenching temperatures, the character of inclusions and the color characteristics of bronze surfaces. It was found that the objects containing lead were quenched at temperatures of $520^{\circ}{\sim}586^{\circ}C$ while those without lead were quenched at the range of $586^{\circ}{\sim}799^{\circ}C$. The presence of selenium in impurity inclusions was detected only in alloys containing lead, suggesting that the raw materials, Cu and Sn, used in making the lead-free alloys for the first group were carefully selected from those smelted using ores without lead contamination. Furthermore, the addition of lead was found to have significant effects on the color characteristics of the surface of bronze alloys when they are subjected to corrosion during interment. In leaded alloys, corrosion turns the surface light green or dark green while in unleaded alloys, corrosion turns the surface dark brown or black. It was found that in fabrication, the wall thickness of the bronze bowls varies depending on the application of quenching; most of the quenched objects have walls 1mm thick or below while those without quenching have walls 1mm thick or above. Fabrication techniques in bronze making usually reflect social environments of a community. It is likely that in the late Goryo period, experiencing lack of skilled bronze workers, the increased demand for bronze was met in two ways; by the use of chief lead instead of expensive tin and by the use of casting suitable for mass production. The above results show that the Goryo bronze workers tried to overcome such a resource-limited environment through technological innovations as apparent in the use of varying fabrication techniques for different alloys. Recently, numerous bronze objects are excavated and available for investigation. This study shows that with the use of proper analytical techniques they can serve as a valuable source of information required for the characterization of the associated technology as well as the social environment leading to the establishment of such technology.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.3
• /
• pp.15-25
• /
• 2023

In this study, silicon sludge from semiconductor dicing process is recycled to fabricate silica nanoparticles, which are applied as dispersing materials for electro-responsive (ER) smart fluid. In specific, metal impurities are removed from silicon sludge by acid washing to obtain the high-purity silicon powder. And then, silica nanoparticles are synthesized by facile hydrothermal method employing the silicon powder as reactant material. To control the size of silica nanoparticles, the reaction time of hydrothermal method is varied as 8, 15, 20, and 30 hours are applied to control the size of silica nanoparticles. Sizes of silica nanoparticles are increased proportionally to the reaction time owing to the increased numbers of hydrolysis and condensation reactions. As-synthesized silica nanoparticles are prepared as electro-responsive smart fluids by dispersing into silicon oil. Silica nanoparticles synthesized by 30 hours of hydrothermal reaction (SiO₂-H30) exhibit the highest shear stress of 21.4 Pa under an applied electric field strength of 3.0kV mm^-1. Such enhancement in ER performance of SiO₂-H30 among various silica nanoparticles are attribute to the reinforcing effect originated from the mixed particle size, which allowing the formation of rigid chain-like structures. Accordingly, this study successfully propose a recycling method of silicon sludge to synthesize silica nanoparticles and their derived ER fluids, which may suggest new possibility to ESG management emphasizing the eco-friendliness.