• Journal of Ceramic Processing Research
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• v.20 no.spc1
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• pp.109-112
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• 2019

γ-dicalcium silicate(γ-C2S) is known as a polymorphism of belite. Due to its high CO2 fixed capacity and the low CO2 emission production process, γ-C2S has attracted more and more attention of researchers. For the further development of application of γ-C2S in building construction industry. In this study, we aim to investigate the method for synthesizing high purity of γ-C2S. The influence of different raw materials and calcination temperatures on the purity of γ-C2S was also evaluated. Several Ca bearing materials were selected as the calcium source, the materials which' s main component is SiO2 were used as the silicon source. Raw materials were mixed and were calcined under different temperatures. The results reveal that the highest purity could be obtained using Ca(OH)2 and SiO2 powder as raw materials. And for the practical application, a relatively economic synthesis method using natural mineral materials- limestone and silica sand as raw materials was developed, by this method, the purity of the synthetic γ-C2S was 77.6%.

• Korean Journal of Crystallography
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• v.8 no.2
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• pp.89-96
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• 1997

In order to apply synthesis technique of the high purity ceramic powder to the traditional ceramic powder, mullite powder which is widly used for refractory materials was synthesized. Boehmite and Hadong kaolin with high alumina content were used as starting materials and gel coating method was tried to produce the mullite powder. As a result, the mullite powder of high quality was successfully obtained at 1350℃. The unreacted silica and cornudum were not observed in the synthesized mullite powder, mullite content was more than 80% when the starting materials were sintered at 1700℃. Their properties showed bulk specific gravity of 2.56, water absorption of 1.9%, and 3-point flexual strength of 169 MPa. It is thought that that their good properties are applicable to refractory materials of high quality.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.435-440
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• 2015

It is a challenge from an industrial point of view to fabricate silicon nitride substrates with high thermal conductivity and good mechanical properties for power devices from high-purity Si scrap powder by means of thick film processes such as tape casting. We characterize the residual carbon and oxygen content after the binder burnout followed by nitridation as a function of the temperature in the temperature range of $300^{\circ}C-700^{\circ}C$ and the atmosphere in a green tape sample which consists of high-purity Si powder and polymer binders such as polyvinyl butyral and dioctyl phthalate. The optimum condition of binder burnout is suggested in terms of the binder removal temperature and atmosphere. If considering nitridation, the burnout of the organic binder in air compared to that in a nitrogen atmosphere could offer an advantage when fabricating reaction-bonded $Si_3N_4$ substrates for power devices to enable low carbon and oxygen contents in green tape samples.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.135-139
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• 2011

In order to make high-purity ferro-manganese from $Mn_3O_4$ waste dust, the application of aluminothermite process to the reduction of the waste dust was investigated. The mixture from $Mn_3O_4$ dust as metallic source and Al metal powder as the reductant ignited, and reduced with an extremely intense exothermic reaction. The rapid propagation of the aluminothermite reaction occurred spontaneously and stably by ignition of the mixture. The Manganese having some alloy elements emerged as liquids due to the high temperatures reached up to about $2,500^{\circ}C$ and separated from the liquid by their differences of specific gravity. The result of thermite reaction showed the fact that can be obtained high purity ferro-manganese which have over about 90% of manganese content and lower impurities such as C, P, S than those of KS D3712 specification. The recovery of manganese from $Mn_3O_4$ dust was lower level of about 65% than about 75% from manganese ore by electric furnace process, that is due to spatter loss because of its extremely intense thermite reaction. But it will be improved by the process designed to provide CaO as the cooler or to use the Al metal powder having larger particle size distribution.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.191-197
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• 2010

Fine nickel metal powder of uniform morphology, narrow size distribution, and high purity was prepared from high purity metal solution. Slurry reduction method for the synthesis of metal powder was applied with a special interest in their fine and spherical shape. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Well dispersed ultrafine nickel powder with the particle size range of 100~200 nm was produced from Ni-hydrazine precursor using hydrazine as a reductant for 90 min reaction in 4.5 M NaOH solution.

• Resources Recycling
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• v.28 no.1
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• pp.62-72
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• 2019

Generally, $H_2SO_4$ and Cu metal are used as raw materials for producing copper sulfate. The study relates to a method for producing copper sulfate using electrowinning from a waste solution of copper chloride. Uses are used for copper plating for industry, plating, feed, agriculture, electronic grade PCB. Conventional methods for producing copper sulfate have a problem of a large amount of waste water and a high energy cost. A study on the production method of copper sulfate ($CuSO_4$), which is the most used among copper (Cu) compounds, has a low process operation ratio, a small amount of waste water, and a simple manufacturing process. It is easy to remove Na, Ca, Mg, and Al as impurities by using a cationic membrane. At the same time, high purity copper powder could be recovered by an electrowinninng method. Using the recovered copper powder, high purity copper sulfate could be produced.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2057-2059
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• 2005

Silver nanosized powder have been synthesized using wire explosion technology. The discharge system of 10kw (10uF, 20kV, 0.5 shots/s) was set up for mass production of 300g/h. The high purity silver powder was collected and separated by cyclone and fabric filters.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.682-690
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• 1989

Fine mullite powder was prepared by colloidal sol-gel route. Boehmite as a starting material of Al2O3 and silica sol or fumed silica as a starting material of SiO2 were used. $\alpha$-Al2O3, TiO2 and ZrO2 were used as seeding materials. The combination of boehmite and silica was found to be the stoichiometric mullite powder. Techniques for drying used were spray drying, freeze drying, reduced pressure evaporation and drying in a oven. The gelled powder was heated at 130$0^{\circ}C$ for 100min and was attrition-milled for 1~3hrs. The mullite powder obtained was composed of submicrometer, uniform and spherical particles with a narrow size distribution. The mullite powder was characterized by BET, SEM, XRD and IR spectroscopy.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.195-200
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• 1989

The Silica-Carbon mixture was made with addition of carbon black in the composition which monodispersed spherical fine silica was formed by the hydrolysis of ethylsilicate, mole ratio of Carbon/Alkoxide was 3.1 and $\beta$-SiC powder was synthesized by reacting this mixture at 1,350~1,50$0^{\circ}C$ in Ar atmosphere. The results of this study are as follow : (1) The purity of synthesized $\beta$-SiC powder was above 99.98% and it was in cubic modification with lattice constant of 4.3476$\AA$. (2) The rate-controlling steps varied with the reaction temperature for the syntehsis of $\beta$-SiC in this study ; nucleation and growth of $\beta$-SiC at 1,350~1,40$0^{\circ}C$, interfacial reaction at 1,45$0^{\circ}C$ and diffusion described by Jander Equation at 1,50$0^{\circ}C$. (3) When the rate-determining step was nucleation and growth, the activation energy was about 87.8kcal/mol.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.306-310
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• 2016

To produce 4N grade high-purity silica powder from natural ore, the mineralogical characteristics of natural silica ore were investigated and their effects on the purification process were revealed. The Chinese silica mineral ore used was composed of iron and aluminum as main impurities and calcium, magnesium, potassium, sodium, and titanium as trace impurities; these trace impurities generally exist as either single oxides or complex oxides. It was confirmed that liberation and acidic washing of the impurities were highly dependent on the particle size of the ground silica ore and on its mineralogical characteristics such as the distribution and phases of existing impurities. It is suggested that appropriate size reduction of silica ore should be realized for optimized purification according to the origin of the natural silica ore. A single step purification process, the mechano-chemical washing (MCW) process, was proposed and verified in comparison with the conventional multi step washing process.