• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.435-438
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• 2004

The effects sintering additives such as $xwt%(0.242Bi_2O_3-0.782V_2O_5)$ on the microwave dielectric and sintering properties of $MgCo_2(VO_4)_2$ ceramics were investigated. Highly dense samples were obtained for $MgCo_2(VO_4)_2$ at the sintering temperature of $950^{\circ}C$ with $0.242Bi_2O_3-0.758V_2O_5$ additions of $0.5{\sim}5wt%$. The microwave dielectric properties of $MgCo_2(VO_4)_2$ with $0.5wt%(0.242Bi_2O_3-0.758V_2O_5)$ sintered at $950^{\circ}C$ were as follows : $Q{\times}f_0\;=\;45,375GHz,\;\epsilon_r\;=\;9.7\;and\;\tau_f\;=\;-23.2ppm/^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.220-223
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• 2005

We studied the effect of composition, processing, and sintering temperature on the microwave properties of $Mg_{3-x}Co_x(VO_4)_2$ system which is applicable to LTCC. When $Mg_{3-x}Co_x(VO_4)_2$ was fabricated by solid-state reaction process and sintered at the temperature range of $800\sim910^{\circ}C$, it was found that the optimum composition of x was 2 at which microwave properties of 910$^{\circ}C$-sintered one were as follows: $Q\times f_0\sim55,200GHz$ and $\varepsilon_r\sim10$. When $(MgCo_2)(VO_4)_2$ was fabricated by sol-gel process and sintered at 800$^{\circ}C$, $Q\timesf_0$was 34,400GHz which is much high compared to those fabricated by solid-state reaction process at the same sintering temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.288-289
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• 2006

We studied the effect of sol-gel processing and sintering temperature on the microwave properties of $MgCo_2(VO_4)_2$ system(MCV) which is applicable to LTCC(low-temperature cofired ceramics). The MCV was synthesized by sol-gel process using solution that contains precursor molecules for Mg, Co, and V. SEM analysis shows that the average particle size is ${\sim}1{\mu}m$ and size distribution is very uniform compared to the one prepared by conventional solid-state reaction process. Highly dense samples were obtained at the sintering temperature range of $750^{\circ}C{\sim}930^{\circ}C$. The maximum $Q{\times}f_0$ value of 55,700GHz, dielectric constant(${\varepsilon}_r$) of 10.41 and temperature coefficient(${\tau}_f$) of $-85ppm/^{\circ}C$ was obtained at the sintering temperature of $930^{\circ}C$. The superior microwave properties of sol-gel processed MCV relative to conventional solid-state reaction processed one is remarkable especially at lower sintering temperatures such as $750^{\circ}C$ and $800^{\circ}C$.

• Electrical & Electronic Materials
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• v.4 no.1
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• pp.31-37
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• 1991

습도센서용 기판으로 사용하기 위한 MgFe$_{2}$O$_{4}$ 세라믹스의 성능개선을 위하여 Li$_{2}$CO$_{3}$와 V$_{2}$O$_{5}$를 첨가한 MgFe$_{2}$O$_{4}$-LiMgVO$_{4}$ 세라믹스를 만들고, 기공율, 기공분포, 센서특성, 응답속도 등을 조사하여 다음의 결과를 얻었다. 기공율은 MgFe$_{2}$O$_{4}$ 세라믹스가 29[%]에서 34[%]인데 비하여 본 연구결과는 34.5[%]에서 39[%]로 증가하였으며 센서특성은 $10^{7}$ [.OMEGA.] 단위의 변화에서 $10^{7}$ [.OMEGA.]에서 $10^{6}$[.OMEGA.] 단위로 변화함을 알수 있었고 응답속도는 10초정도 빨라졌음을 알수 있었다. 또한 기공분포를 이용하여 모형 센서를 제안하여 시뮬레이션을 하고 실제 특성과 이론적인 특성을 비교하였다.

• Resources Recycling
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• v.32 no.3
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• pp.26-37
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• 2023

Good control of the solution pH and temperature is required to recover vanadium from the water leaching solution of vanadium ore after sodium roasting. However, such adjustments could lead to aluminum-vanadium and sodium-vanadium co-precipitation, which greatly affects the efficiency of vanadium recovery. In this study, a process that can increase the efficiency of vanadium recovery as ammonium metavanadate [NH₄VO₃] and ammonium polyvanadate [(NH₄)₂V₆O₁₆·H₂O] was investigated by examining the characteristics of vanadium-containing aqueous solutions during precipitation. The aluminum content of vanadium-containing water leaching solutions has a great effect on the loss of vanadium when the pH of the aqueous solution is adjusted to 9. Therefore, a process to minimize aluminum leaching is also required. In this study, ~99% or more of vanadium present in vanadium-containing aqueous solutions was precipitated and recovered as NH₄VO₃ by adding 3 equivalents of ammonium chloride relative to the vanadium content at pH 9 and room temperature. (NH₄)₂V₆O₁₆·H₂O was precipitated from the aluminum-vanadium coprecipitates generated during the pH-adjustment of the aqueous solutions to 9 by dissolving the coprecipitate in the solutions at pH 2.5 and controlling their sodium content to 2,000 mg/L or less. Approximately, 98% or more of the available (NH₄)₂V₆O₁₆·H₂O could be precipitated and recovered from a solution with a vanadium content of 2,200 mg/L and a sodium content of 1,875 mg/L at pH 2.5 by adding approximately 3 equivalents of ammonium chloride relative to the vanadium content at 95℃ or higher. The overall process could precipitate and recover, approximately 91% or more of the total vanadium in the water leaching solution as NH₄VO₃ and (NH₄)₂V₆O₁₆·H₂O.