• 한국환경과학회지
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• 제22권1호
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• pp.83-89
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• 2013

Silicon carbide with aluminium oxide was used to remove the sulphur hexafluoride ($SF_6$) gas using microwave irradiation. The destruction and removal efficiencies (DREs) of $SF_6$ were studies as a function of various decomposition temperatures and microwave powers. The decomposition of $SF_6$ gas was analyzed using GC-TCD. XRD (X-ray powder diffraction) and XRF (X-ray Fluorescence Spectrometer) were used to characterize the properties of aluminum oxide. DREs of $SF_6$ were increased as the microwave powers were increased. Additive aluminium oxide on SiC increased the removal efficiencies and decreased the decomposition temperature. The XRD results show that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during $SF_6$ decomposition by microwave irradiation. It was found that the best material to control $SF_6$ was SiC with $Al_2O_3$ 30 wt% in consideration of microwave energy consumption and $SF_6$ decomposition rate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.268-268
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• 2012

Atmospheric pressure microwave induced plasmas are used to excite and ionize chemical species for elemental analysis, for plasma reforming, and for plasma surface treatment. Microwave plasma differs significantly from other plasmas and has several interesting properties. For example, the electron density is higher in microwave plasma than in radio-frequency (RF) or direct current (DC) plasma. Several types of radical species with high density are generated under high electron density, so the reactivity of microwave plasma is expected to be very high [1]. Therefore, useful applications of atmospheric pressure microwave plasmas are expected. The surface characteristics of SUS304 stainless steel are investigated before and after surface modification by microwave plasma under atmospheric pressure conditions. The plasma device was operated by power sources with microwave frequency. We used a device based on a coaxial transmission line resonator (CTLR). The atmospheric pressure plasma jet (APPJ) in the case of microwave frequency (880 MHz) used Ar as plasma gas [2]. Typical microwave Pw was 3-10 W. To determine the optimal processing conditions, the surface treatment experiments were performed using various values of Pw (3-10 W), treatment time (5-120 s), and ratios of mixture gas (hydrogen peroxide). Torch-to-sample distance was fixed at the plasma edge point. Plasma treatment of a stainless steel plate significantly affected the wettability, contact angle (CA), and free energy (mJ/$m^2$) of the SUS304 surface. CA and ${\gamma}$ were analyzed. The optimal surface modification parameters to modify were a power of 10 W, a treatment time of 45 s, and a hydrogen peroxide content of 0.6 wt% [3]. Under these processing conditions, a CA of just $9.8^{\circ}$ was obtained. As CA decreased, wettability increased; i.e. the surface changed from hydrophobic to hydrophilic. From these results, 10 W power and 45 s treatment time are the best values to minimize CA and maximize ${\gamma}$.

• 한국식품과학회지
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• 제28권3호
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• pp.528-537
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• 1996

무균포장밥의 microwave reheating후의 품질 변화를 리드포장재, 탈산소제, 저장 온도 및 저장 기간을 달리하여 조사하였다. 가열하기 전 무균포장밥의 탄력성 , 응집성 , 부착성은 저장 온도가 증가함에 따라 증가하는 경향을 나타내었고 경도 및 껌성은 반대로 저하되었다 그러나 마이크로파 재가열 후에는 리드포장재, 탈산소제 및 저장 온도의 차이에 따라 조직감 특성의 큰 차이를 나타내지 않았다. 호화도는 저장 온도가 증가할수록 증가하였으며, microwave reheating에 의해 호화 정도가 취반 직추의 상태까지 복원될 수 있었다. 저장후 전자레인지에서 1.5분간 재가열한 처리구의 표면구조를 보면 포장 재료에 따라 큰 차이를 보이지 않았으나 가열 전보다 표면이 매끄럽지 못하고 오목한 부분이 관찰되어 전분이 다시 호화되었음을 알 수 있었다. 밥알의 단면 구조를 관찰한 결과 저장 온도가 감소함에 따라 각이 진 부분이 증가하였으며 호화된 부분이 딱딱하게 보여지 작찬 양상을 보임으로 노화가 이루어졌음을 나타내었다. Microwave reheating 후 단면 구조는 모든 처리구에서 딱딱하고 각이 진 부분들이 감소함으로써 다시 호화가 되었음을 보여주었다.

• 전기학회논문지
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• 제56권4호
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• pp.756-760
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• 2007

The $(1-x)Mg_4Ta_2O_9-xwt%TiO_2\;(x=5\sim20)$ microwave dielectric ceramics were prepared by solid-state reaction method and sintered at $1450^{\circ}C$. According to the X-ray diffraction data, the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics had main phase of $Mg_4Ta_2O_9$ and $MgTi_2O_5$ peaks were added by increasing of $TiO_2$ addition. Microwave dielectric properties of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics were influenced by $MgTi_2O_5$ phase and properties of $TiO_2$. There was a little decrement of the quality factor from 116,800GHz of pure $Mg_4Ta_2O_9$ to 100,100GHz of 15wt% $TiO_2$ added one. But there was excellent improvement in temperature coefficient of the resonant frequency (TCRF) by addition of 15wt% $TiO_2$. The dielectric constant quality factor and TCRF of the $Mg_4Ta_2O_9-xwt%TiO_2$ ceramics sintered at $1450^{\circ}C$ were $13.08\sim16.41,\;45,000\sim165,410GHz,\;-24.82\sim+3.88ppm/^{\circ}C$, respectively, depending on the value of x. Simulated dielectric resonator (DR) with $Mg_4Ta_2O_9-15wt%TiO_2$ ceramics had the operating frequency of 11.97GHz and $S_{2,1}$ of -35.034dB.

• Advances in materials Research
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• 제3권2호
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• pp.105-116
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• 2014

The microwave dielectric properties of $CeO_2$ nanoparticles (0.5, 1.0 & 1.5wt%) doped $Mg_2TiO_4$ (MTO) ceramics have been investigated at cryogenic temperatures. The XRD patterns of the samples were refined using the full proof program reveal the inverse spinel structure without any secondary phases. The addition of $CeO_2$ nanoparticles lowered the sintering temperature with enhancement in density and grain size as compared to pure MTO ceramics. This is attributed to the higher sintering velocity of the fine particles. Further, the microwave dielectric properties of the MTO ceramics were measured at cryogenic temperatures in the temperature range of 6.5-295 K. It is observed that the loss tangent ($tan{\delta}$) of all the samples increased with temperature. However, the $CeO_2$ nanoparticles doped MTO ceramics manifested lower loss tangents as compared to the pure MTO ceramics. The loss tangents of the pure and MTO ceramics doped with 1.5 wt% of $CeO_2$ nanoparticles measured at 6.5K are found to be $6.6{\times}10^{-5}$ and $5.4{\times}10^{-5}$, respectively. The addition of $CeO_2$ nanoparticles did not cause any changes on the temperature stability of the MTO ceramics at cryogenic temperatures. On the other hand, the temperature coefficient of the permittivity increased with rise in temperature and with the wt% of $CeO_2$ nanoparticles. The obtained lower loss tangent values at cryogenic temperatures can be attributed to the decrease in both intrinsic and extrinsic losses in the MTO ceramics.

• 한국세라믹학회지
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• 제43권1호
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.131-134
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• 2003

[ $ZnWO_4$ ] shows excellent frequency selectivity due to its high quality factor($Q{\times}f$) at microwave frequencies. However, in order to use $ZnWO_4$ as multilayered wireless communication components, its other properties such as sintering temperature($1050^{\circ}C$), ${\tau}_f$ ($-70ppm/^{\circ}C$) and ${\varepsilon}_r(15.5)$ should be modified. In present study, $TiO_2$ and LiF were used to improve the microwave dielectric and sintering properties of $ZnWO_4$. $TiO_2$ additions to $ZnWO_4$ changed ${\tau}_f$ from negative to positive value, and also increased ${\varepsilon}_r$ due to its high ${\tau}_f$ ($+400ppm/^{\circ}C$) and ${\varepsilon}_r$(100). At 20 mol% $TiO_2$ addition, ${\tau}_f$ was controlled to near zero $ppm/^{\circ}C$ with ${\varepsilon}_r=19.4$ and $Q{\times}f=50000GHz$. However, the sintering temperature was still high to $1100^{\circ}C$. LiF addition to the $ZnWO_4+TiO_2$ mixture was greatly reduced the sintering temperature from $1100^{\circ}C$ to $850^{\circ}C$ due to liquid phase formation. Also LiF addition decreased the ${\tau}_f$ value due to its high negative ${\tau}_f$ value. Therefore, by controlling the $TiO_2$ and LiF amount, temperature stable LTCC material in the $ZnWO_4$-TiO_2-LiF$ system could be fabricated.

• 한국전기전자재료학회논문지
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• 제16권7호
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• pp.604-610
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• 2003

The effects of sintering additives such as B $i_2$ $O_3$ and $V_2$ $O_{5}$ on the microwave dielectric and sintering properties of (Z $n_1$$_{-xM}$ $g_{x}$)Ti $O_3$ system were investigated. Highly dense samples were obtained for (Z $n_{0.8}$M $g_{0.2}$)Ti $O_3$ at the sintering temperature range of 870~90$0^{\circ}C$ with B $i_2$ $O_3$ and $V_2$ $O_{5}$ additions of 〈1 wt.%, respectively. The microwave dielectric properties of (Z $n_{0.8}$M $g_{0.2}$)Ti $O_3$ with 0.45 wt.%B $i_2$ $O_3$ and 0.55 wt.% $V_2$ $O_{5}$ sintered at 90$0^{\circ}C$ were as follows : Q$\times$ $f_{o}$ = 50,800 GHz, $\varepsilon$$_{r}$ = 22, and $\tau$$_{f}$ = -53 ppm/$^{\circ}C$. In order to improve temperature coefficient of resonant frequency, Ti $O_2$ was added to the above system. The optimum amount of Ti $O_2$ was 15 moi.% when sintered at 87$0^{\circ}C$, at which we could obtain following results: Q$\times$ $f_{o}$ = 32,800 GHz, $\varepsilon$$_{r}$ = 26, and$\tau$$_{f}$ = 0 ppm/$^{\circ}C$.EX>.EX>.EX>.EX>.EX>.EX>.EX>.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.221-224
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• 2000

The microwave dielectric properties of Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BMT-BCN] ceramics were investigated. The specimens were prepared by the conventional mixed oxide method. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$ and Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$ formed a solid solution with complex perovskite structure. Increasing the BCN content, dielectric constant was increased, but temperature coefficient of resonant frequency was decreased. In the range of x$\geq$0.4, dielectric constant was about 30. 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Q$\times$f$_{0}$=75,325[GHz] and $\tau$$_{f}$=-2.9015[ppm/$^{\circ}C$].X>].

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.738-743
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• 2004

The microwave dielectric properties and their related structural characteristics in solid solutions of (1-x) $Ba(Mg_{1/3}Nb_{2/3})O_3$ -x $La(Mg_{2/3}Nb_{1/3})O_3$ (BLMN) have been investigated by measuring the dielectric constant${\varepsilon}r)$, Q value and temperature coefficient of resonant frequency$({\tau}f)$ and by observing the crystal structure using high resolution transmission electron microscopy (HRTEM). Microwave dielectric properties showed characteristic features for specific composition. Dielectric constant$({\varepsilon}r)$ showed maximum value at the composition which corresponds to the phase boundary between 1:2 ordered and 1:1 ordered structure. The increase in ${\varepsilon}_r$ may be caused by the rattling of ions by incorporating smaller ions and the disordered structure. The variation of temperature coefficient of resonant frequency${{\tau}_f)$ was investigated in terms of oxygen octahedra tilting.