• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.300-301
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• 2007

$Mg_4(Nb_{2-x}V_x)O_9$ (MNV) ceramics have been prepared by a hydrothermal method. Low-temperature sintering of $Mg_4(Nb_{2-x}V_x)O_9$ (MNV) by V substitution for Nb was discussed in this study. A $Q{\cdot}f_0$ value of 103,297 GHz with a ${\varepsilon}_r$ of 12.56 and a ${\tau}_f$ of $-10.53\;ppm/^{\circ}C$ was obtained when x=0.0625 after sintering at $1100^{\circ}C$ for 5 h.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.839-856
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• 2022

Over the last decade, the competition for space development has accelerated. The world's largest space agencies are aiming toward long-term lunar exploration and manned missions. For sustainable and safe lunar exploration, construction of infrastructures that include various habitats is essential. However, transporting construction materials from Earth for lunar base construction is extremely expensive. Thus, technologies for manufacturing construction materials using in-situ resources from the moon should be advanced. The sintering techniques have been actively studied using lunar soil. In this review, five sintering technologies, including radiation, solar, spark plasma, laser, and microwave sintering, for manufacturing construction materials using lunar soil are introduced, and future research is discussed.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.797-803
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• 2004

The heat generation tests of SiC and MO$_2$ samples by use of a microwave heating system were carried out and UO$_2$+5 wt% CeO$_2$ pellets were sintered in a microwave furnace in an oxidizing atmosphere, by taking into account the characteristics of the microwave heating obtained from the heat generation tests. The characteristics of pellets sintered in a microwave furnace were analysed and compared with those of the pellets sintered in a conventional electrical furnace. The temperature of MO$_2$ pellets with microwave heating increased quickly with input power and the variation of output power depended on the reaction characteristics of SiC and MO$_2$ with microwave. The sintered density of UO$_2$+5wt% CeO$_2$ pellets sintered in the microwave furnace was lower about 2% T.D. than that of the pellets sintered in an electrical furnace with sintering parameters. The microstructure of pellets sintered in microwave furnace has a broader pore distribution but has a larger grain size than that of the pellets sintered in the electrical furnace.

• Journal of the Korean Geotechnical Society
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• v.37 no.2
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• pp.5-17
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• 2021

The Moon has been an attractive planet as an outpost for deep space exploration since He-3 and water ice which can be used as energy resources were discovered. In-Situ Resource Utilization (ISRU) construction material fabrication method is required for sustainable space planet exploration. In this paper, the possibility of microwave sintering technology for construction material fabrication was evaluated using lunar regolith that can be easily collected from the Moon surface. Experimental assessment of the influence factors on microwave sintering was conducted using a hybrid sintering system for efficient processing. The heat distribution in the furnace was observed using thermal paper that is coated with a material formulated to change color when exposed to heat. Based on this result, sintered cylindrical KLS-1s with a diameter of 1 cm and a height of 2 cm were fabricated. Densities were measured for the sintered KLS-1s under rotating turntable conditions that have an effect of microwave dispersion. The more dielectrics were arranged, the more microwaves were dispersed reducing the heat concentration, and thus a uniformity of sintered KLS-1s was enhanced.

• Journal of the Korean Geotechnical Society
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• v.38 no.5
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• pp.35-46
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• 2022

The in-situ resource utilization (ISRU) for sustainable lunar surface and deep space explorations has recently gained attention. Also, research on the development of construction material preparation technology using lunar regolith is in progress. Microwave sintering technology for construction material preparation does not require a binder and is energy efficient. This study applies microwave sintering technology to KLS-1, a Korean lunar simulant. It is crucial to secure the homogeneity to produce a sintered specimen for construction material. Therefore, understanding the interactions between microwaves, cavities, and raw materials is required. Using a numerical model in terms of efficient assessment of several cases and establishment of equipment operating conditions is a very efficient approach. Therefore, this study also proposes and verifies a coupled electric-thermal numerical model through cross-validation and comparison with experimental results. The numerical model proposed in this study will be used to present an efficient method for producing construction material using microwave sintering technology.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.197.1-197
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• 2003

• Journal of the Korean Ceramic Society
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• v.44 no.3 s.298
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• pp.182-187
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• 2007

10 mol% $Gd_{2}O_{3}-CeO_{2}$ powder was sintered by microwave in a 2.45 GHz multimode cavity to develop a dense electrolyte layer for intermediate temperature solid oxide fuel cells (IT-SOFCs). Samples were sintered from $1100^{\circ}C$ upto $1500^{\circ}C$ by $50^{\circ}C$ difference and kept for 10 min and 30 min at the maximum temperature respectively. Theoretical density of the sample sintered at $1200^{\circ}C$ for 10 min was 95.4% and increased gradually upto 99% in the sample sintered at $1500^{\circ}C$ for 30 min. All of sintered samples showed very fine microstructures and the maximum average grain size of the sintered sample at $1500^{\circ}C$ for 30 min was $(0.87{\pm}0.42){\mu}m$. Ionic conductvity of the samples were measured by DC 4 probe method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.517-523
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• 2008

The microwave dielectric properties of $LiNb_3O_8-TiO_2$ based ceramics with low firing agents, CuO, $Bi_2O_3$, $B_2O_3$, $SiO_2$, $TiO_2$, were investigated to improve the sintering condition for the LTCC system. According to the X-ray diffraction and SEM, the ceramics of $LiNb_3O_8-TiO_2$ with low firing agents showed no significant second phases within a range of experiments, and fine microstructures. By adding the low firing agents, the sintering temperature decreased from $1200^{\circ}C$ to $925^{\circ}C$. Based on the results of electrical measurements, the $LiNb_3O_8-TiO_2$ ceramics showed a promising microwave dielectric properties for LTCC applications, those are ${\varepsilon}_r$ (dielectric constant) = 44, Q f (quality factor) = 18000, and ${\tau}_f$ (the temperature coefficient of resonant frequency) = $-1.5\;ppm/^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.8
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• pp.335-339
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• 2002

Ba(Mgl-xCox)TaO3[BMCT] ceramics were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of 1525~$1625^{\circ}C$ for 5hr. in air. The crystal structure of BMCT ceramics was investigated by the XRD. The microstructure of the specimens were observed by SEM. The Microwave dielectric properties of BMCT specimens were investigated as a function of composition and sintering temperature. All BMCT ceramics sintered over 1575$^{\circ}C$ were showed a polycrystalline complex perovskite structure. The density of BMCT (90/10) specimen sintered at $1575^{\circ}C$ was 7.75g/㎤. As the Co contents decreased, the ordering parameter of B-site in BMCT increased. In the case of the BMCT(90/10) ceramics sintered at $1575^{\circ}C$ for 5 hours, dielectric constant, quality factor and temperature coefficient of resonant frequency for microwave dielectrics application were a good value o( 25, 17, 845 at 10㎓ and +2.4 ppm/${\circ}$, respectively.

• Journal of the Korean Ceramic Society
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• v.44 no.5 s.300
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• pp.173-178
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• 2007

The microstructure and microwave dielectric properties of dolomite type borates, $CaZr(BO_3)_2$ ceramics prepared by conventional mixed oxide method were explored. The sintering temperature of $CaZr(BO_3)_2$ ceramics could be reduced from $1150^{\circ}C\;to\;925^{\circ}C$ with little amount of sintering additives. Microwave dielectric properties of 3 wt% $Bi_2O_3-CuO$ added $CaZr(BO_3)_2$ ceramics sintered at $925^{\circ}C$ were $K{\approx}10.4,\;Q{\times}f{\approx}80,000GHz\;and\;TCF{\approx}+2ppm/^{\circ}C$. Thus obtained LTCC tape was co-fired with Ag paste for compatibility test and revealed no sign of Ag reaction with the ceramics. Therefore, $CaZr(BO_3)_2$ ceramics is considered as a possible candidate material for low temperature co-fired multilayer devices.