• Journal of Powder Materials
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• v.18 no.5
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• pp.437-442
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• 2011

The present study focused on the synthesis of Bi-Te-Se-based powder by an oxide-reduction process, and analysis of the thermoelectric properties of the synthesized powder. The phase structure, chemical composition, and morphology of the synthesized powder were analyzed by XRD, EPMA and SEM. The synthesized powder was sintered by spark plasma sintering. The thermoelectric properties of the sintered body were evaluated by measuring its Seebeck coefficient, electrical resistivity, and thermal conductivity. $Bi_2Te_{2.7}Se_{0.3}$ powder was synthesized from a mixture of $Bi_2O_3$, $TeO_2$, and $SeO_2$ powders by mechanical milling, calcination, and reduction. The sintered body of the synthesized powder exhibited n-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depend on the reduction temperature. The Seebeck coefficient and electrical resistivity of the sintered body were increased with increasing reduction temperature. The sintered body of the $Bi_2Te_{2.7}Se_{0.3}$ powder synthesized at $360^{\circ}C$ showed about 0.5 of the figure of merit (ZT) at room temperature.

• Journal of Powder Materials
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• v.28 no.2
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• pp.91-96
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• 2021

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the L ME process, Nd is completely extracted after 6 h, while Dy remains as Dy₂Fe₁₇ and Dy-oxide. Because the decomposition rate of Dy₂Fe₁₇ is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.

• Journal of the Korean Society of Safety
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• v.8 no.2
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• pp.3-9
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• 1993

For comparison, we used Ca and Mg as reducers to produce TiFe hydrogen stroage alloy from Fe and TiO$_2$by the Reduction-Diffusion process. The results obtained were as follow. \circled1 Ca was found to be effective both for reduction and diffusion processes. Moreover, Ca oxide was easily removed in an NH$_4$Cl solution after the reaction. \circled2 In the case of using Ca as a reducer, the Reduction-Diffusion process is considered to take place in the foiling three steps. First, TiO$_2$is reduced to Ti by Ca over 100$0^{\circ}C$. Second, the atomic Ti drifts in the Ca melt and meets Fe particles. Finally, the atomic Ti diffuses in to the Fe particles. \circled3 In the case of using Mg as a reducer, We found that the reduction reaction of TiO$_2$went well. But the reduced Ti scarcely diffused into Fe particles. This was probably because no Mg melt was formed due to the high vapor pressure of Mg.

• ETRI Journal
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• v.40 no.2
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• pp.275-282
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• 2018

Flash reduction of graphene oxide is an efficient method for producing high quality reduced graphene oxide under room temperature ambient conditions without the use of hazardous reducing agents (such as hydrazine and hydrogen iodide). The entire process is fast, low-cost, and suitable for large-scale fabrication, which makes it an attractive process for industrial manufacturing. Herein, we present a simple fabrication method for a flexible in-plane graphene micro-supercapacitor using flash light irradiation. All carbon-based, monolithic supercapacitors with in-plane geometry can be fabricated with simple flash irradiation, which occurs in only a few milliseconds. The thinness of the fabricated device makes it highly flexible and thus useful for a variety of applications, including portable and wearable electronics. The rapid flash reduction process creates a porous graphene structure with high surface area and good electrical conductivity, which ultimately results in high specific capacitance ($36.90mF\;cm^{-2}$) and good cyclic stability up to 8,000 cycles.

• Resources Recycling
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• v.24 no.3
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• pp.11-15
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• 2015

In order to develop a technology for the recovery of pure tin from the Sn containing industrial wastes (SIWs), a process consisted of high temperature reduction and electrorefining was investigated. The tin which exists as oxide in SIWs was successfully reduced by two consecutive high temperature treatments and 92.7% of the tin was recovered. The purity of the tin thus obtained was increased to 99.87% by electrorefining. By applying the results obtained in this work, a commercial process can be developed to produce pure tin metals from domestic spent resources, which can reduce the amount of tin imported from abroad.

• Resources Recycling
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• v.11 no.4
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• pp.37-43
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• 2002

As the consumption of galvanized steels in cans and automobiles and the quantity of scraps increase, the recycling problems of EAF dust become a important problem. Valuable metals such as Fe, Zn, Pb are of continued interest to metallurgists. To recover the valuable metal and to remove the toxicity of EAF dust, high temperature smelting process is or researching as a pilot scale. The Reduction kinetics of Zn in EAF dust is so important in a view of the economic consideration of the process. In this study, the kinetics behavior of Zn in EAF dust were measured as a point of application in high temperature smelting process. The rate control step in ZnO and franklinite is revealed to be chemical reaction on the reaction surface.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.304-310
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• 1998

Carbothermal reduction has been one of the important processes for the production of ceramic raw materials such as silicon carbide, silicon nitride, boron carbide, etc. The process has also been one of several trials for the recovery of ZnO from ZnO-containing waste. It usually involves two consecutive steps: the evolution of Zn vapor and its oxidation with air. In this study a ZnO-containing raw material is reduced by carbon at $1250^{\circ}C$ and the evolved Zn vapor is oxidized with air, resulting in fine powders of ZnO. computer programs, THERMO and PYROSIM developed by MINTEK, are used to simulate the process thermodynamically and the results are compared with the experimental results. It is shown that the ZnO-containing raw material can be reduced and can form fine ZnO with the yield as high as 98.7% under a proper condition. Based on these results, a process is engineered for the production of ZnO in a rotary kiln at a rate of 3 tons/day. The produced ZnO powders show properties suitable to the usual applications in ceramic industries with a purity of > 95wt% and an average particle size of ∼3${\mu}m$.

• Journal of Powder Materials
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• v.27 no.3
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• pp.193-197
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• 2020

Porous Cu-14 wt% Co with aligned pores is produced by a freeze drying and sintering process. Unidirectional freezing of camphene slurry with CuO-Co₃O₄ powders is conducted, and pores in the frozen specimens are generated by sublimation of the camphene crystals. The dried bodies are hydrogen-reduced at 500℃ and sintered at 800℃ for 1 h. The reduction behavior of the CuO-Co₃O₄ powder mixture is analyzed using a temperature-programmed reduction method in an Ar-10% H₂ atmosphere. The sintered bodies show large and aligned parallel pores in the camphene growth direction. In addition, small pores are distributed around the internal walls of the large pores. The size and fraction of the pores decrease as the amount of solid powder added to the slurry increases. The change in pore characteristics according to the amount of the mixed powder is interpreted to be due to the rearrangement and accumulation behavior of the solid particles in the freezing process of the slurry.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.415-420
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• 2020

Strontium is known as a salt-soluble element during the electrolytic oxide reduction (EOR) process. The chemical behavior of SrO during EOR was investigated via thermodynamic calculations to provide quantitative data on the chemical status of Sr. To achieve this, thermodynamic calculations were conducted using HSC chemistry software for various EOR conditions. It was revealed that SrO reacts with LiCl salt to produce SrCl₂, even in the presence of Li₂O, and that the ratio of SrCl₂ depends on the initial concentration of Li₂O dissolved in LiCl. It was found that SrO reacts with Li to produce Sr during EOR and that the reduced Sr reacts with LiCl salt to produce SrCl₂. As a result, the proportions of metallic forms were lower in Sr than in La and Nd under various EOR conditions. The thermodynamic calculations indicated that the three chemical forms of SrO, SrCl₂, and Sr co-exist in the EOR system under an equilibrium with Li, Li₂O, and LiCl.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.411.1-411.1
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• 2016

In this study, we examined the effects of boron doping on the dielectric reliability of solution processed aluminum oxide ($Al_2O_3$). When boron is doped in aluminum oxide, the hysteresis reliability is improved from 0.5 to 0.4 V in comparison with the undoped aluminum oxide. And the accumulation capacitance is increased when boron was doped, which implying the reduction of the thickness of dielectric film. The improved dielectric reliability of boron-doped aluminum oxide is originated from the small ionic radius of boron ion and the stronger bonding strength between boron and oxygen ions than that of between aluminum and oxygen ions. Strong boron-oxygen ion bonding in aluminum oxide results dielectric film denser and thinner. The leakage current of aluminum oxide also reduced when boron was doped in aluminum oxide.