• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.735-738
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• 2003

Downsizing electronics requires precision position control with an accuracy of sub-micron order, which demands development of ultra-fine displacive devices. Piezoelectric transducer is one of devices transferring electric field energy into mechanical energy and being capable for fine displacement control. The transducer has been widely used as fine Position control device Multilayer piezoelectric actuator, one of typical piezo-transducer, is fabricated by stacking alternatively ceramic and electrode layers several hundred times followed by cofiring process. Electrode material should be tolerable in the firing process maintaining at ceramic-sintering temperatures up to $1100{\sim}1300^{\circ}C$. Ag-Pd can be used as stable electrode material in heat treatment above $960^{\circ}C$. Besides, adding small quantity ceramic powder allow the actuator to be fabricated in a good shape by diminishing shrinkage difference between ceramic and electrode layers, resulting in avoidance of crack and delamination at and/or nearby interface between ceramic an electrode layers. This study presents synthesis of nano-oxide-added Ag/Pd powders and its feasibility to candidate material tolerable at high temperature. The powders were formed in a co-precipitation process of Ag and Pd in nano-oxide-dispersed solution where Ag and Pd precursors are melted in $HNO_3$ acid.

• 한국재료학회지
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• 제27권11호
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• pp.583-589
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• 2017

Ceramic ink-jet printing has become a widespread technology in ceramic tile and ceramicware industries, due to its capability of manufacturing products on demand with various designs. Generally, thermally stable ceramic inks of digital primary colors(cyan, magenta, yellow, black) are required for ink-jet printing of full color image on ceramic tile. Here, we synthesized an aqueous glass-ceramic ink, which is free of Volatile organic compound(VOC) evolution, and investigated its inkjet printability. $CoAl_2O_4$ inorganic pigment and glass frit were dispersed in aqueous solution, and rheological behavior was optimized. The formulated glass-ceramic ink was suitably jetted as single sphere-shaped droplets without satellite drops. After ink-jet printing and firing processes, the printed glass-ceramic ink pattern on glazed ceramic tile was stably maintained without ink spreading phenomena and showed an improved scratch resistance.

• 한국전기전자재료학회논문지
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• 제30권12호
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• pp.776-781
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• 2017

In this study, we investigated the effect of electrode pattern design on the thermal shock resistance and temperature uniformity of a ceramic heater. A cordierite substrate with a low thermal expansion coefficient was fabricated by tape casting, and a tungsten electrode was printed and used as a heating element. The temperature distribution of the ceramic heater was calculated by a finite-element method (FEM) by considering various electrode patterns, and the tensile stress distribution due to the thermal stress was calculated. In the electrode pattern with a single-line width, the central part of the ceramic heater was heated to the maximum temperature, and the position of the ceramic heater having a double-line width was changed to the maximum temperature, depending on the position of the minimum line width pattern. The highest tensile stress was found along the edges of the ceramic heater. The temperature gradient at the edge determined the tensile stress intensity. The smallest tensile stress was observed for electrode pattern D, which was expected to be advantageous in resisting thermal shock failures in ceramic heaters.

• 한국재료학회지
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• 제28권2호
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• pp.95-100
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• 2018

In this study, $ZrO_2$ ceramic ink was formulated for additive manufacturing three dimensional structure using dispenser printing technique. Ceramic ink with various $ZrO_2$ loading (30, 40, 50vol%) was prepared to evaluate their rheological properties and printability. High $ZrO_2$ loading $ZrO_2$ ceramic ink showed higher elastic modulus and improved shape retention, when the ceramic ink was printed and sintered at $1450^{\circ}C$ for 1h. Microstructural analysis of printed $ZrO_2$ objective indicated that high $ZrO_2$ loading objective showed lower porosity and smaller pore size.

• 한국재료학회지
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• 제29권11호
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• pp.727-733
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• 2019

In this study, the glass melting properties are evaluated to examine the possibility of using refused coal ore as replacement for ceramic materials. To fabricate the glass, refused coal ore with calcium carbonate and sodium carbonate in it (which are added as supplementary materials) is put into an alumina crucible, melted at $1,200{\sim}1,500^{\circ}C$ for 1 hr, and then annealed at $600^{\circ}C$ for 2 hrs. We fabricate a black colored glass. The properties of the glass are measured by XRD (X-ray diffractometry) and TG-DTA (thermogravimetry-differential thermal analysis). Glass samples manufactured at more than $1,300^{\circ}C$ with more than 60 % of refused coal ore are found by XRD to be non-crystalline in nature. In the case of the glass sample with 40 % of refused coal ore, from the sample melted at $1,200^{\circ}C$, a sodium aluminum phosphate peak, a disodium calcium silicate peak, and an unknown peak are observed. On the other hand, in the sample melted at $1,300^{\circ}C$, only the sodium aluminum phosphate peak and unknown peak are observed. And, peak changes that affect crystallization of the glass according to melting temperature are found. Therefore, it is concluded that glass with refused coal ore has good melting conditions at more than $1,200^{\circ}C$ and so can be applied to the construction field for materials such as glass tile, foamed glass panels, etc.

• 전기학회논문지
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• 제66권11호
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• pp.1647-1650
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• 2017

Bus bars are used in place of cables because they can carry more electrical energy with the same volume of conductors. This paper deals with the electrical properties of ceramic coating material for busbars. A ceramic coated samples were prepared for the electrical properties test. There are two types of samples. One is a sample without degradation, and the other is a sample degraded for 30 days. Four electrical properties tests were carried out in accordance with domestic standards. Four electrical characteristics tests are AC dielectric breakdown, V-t, lighting impulse dielectric breakdown, and discharge arc. Both samples showed excellent electrical properties, and the ceramic coating material is very good insulating materials for bus bar.

• 한국세라믹학회지
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• 제40권4호
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• pp.375-379
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• 2003

In this paper, a novel design of multilayer ceramic-based Transmit/Receive (T/R) switch using Low Temperature Co-fired Ceramic (LTCC) technology have been presented. Compact T/R switch has been designed by transforming quarter-wave transmission line to its lumped equivalent circuit. Especially, high-Q three dimensional inductors with double strip have been proposed and incorporated. The proposed inductor has been modeled by multi-conductor coupled lines. A measured inductor quality factor (Q) of 80 and a Self-Resonance Frequency (SRF) of 6.6 GHz have been demonstrated. The inductor library has been incorporated into the design of WCDMA T/R switch.

• 대한치과보철학회지
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• 제41권4호
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• pp.532-537
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• 2003

Statement of the problem : IPS Empress ceramic has been used as one of a esthetic restorative material since it's development, but the broad application of IPS Empress ceramic to clinical prosthodontic field has been limited by its high material cost. Purpose : This study was investigated to evaluate the hardness and fracture toughness after recycling of the IPS Empress ceramic. Material and methods : Reused specimens of IPS Empress were fabricated with repeated pressing. The hardness(Vickers hardness) and fracture toughness of 1st, 2nd and 3rd pressed specimens were measured with Digital Micro Hardness Tester(Model MXT70, Matsuzawa Seiki Co., Ltd, Tokyo, Japan). The obtained data were analyzed using SPSS(Ver 9.5). Result : The mean value of the hardness in the 1st, 2nd and 3rd pressed Empress were $6.23{\pm}0.48MPa,\;5.50{\pm}0.25MPa$, and $5.70{\pm}0.42MPa$. The hardness of the 1st pressing ceramic was higher than those or the 2nd and 3rd pressed ceramics(P<0.05). Hardness of the 3rd pressed ceramic was greater than that of the 2nd pressed ceramic. but there was no significant difference of hardness between those two(P>0.05). The mean value of the fracture toughness was $1.71{\pm}0.16MPam^{1/2}$ in 1st pressed ceramic, $1.78{\pm}0.10MPam^{1/2}$ in 2nd pressed and $1.73{\pm}0.14MPam^{1/2}$ in 3rd pressed IPS ceramic. Fracture toughness of the 2nd pressed ceramic was the highest and that of the 1st pressed ceramic was the lowest. There was no significant difference of fracture toughness among them(P>0.05). Conclusion : Hardness of the 2nd and 3rd pressed IPS Empress ceramics were lesser than that of 1st pressed IPS Empress ceramic(P<0.05), but there was no significant changes of fracture toughness among them(P>0.05).

• 한국전기전자재료학회논문지
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• 제30권8호
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• pp.501-507
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• 2017

A unimorph piezoelectric cantilever generator with an interdigitated electrode (IDE) was developed for vibration energy harvester applications driven in the longitudinal mode. Hard lead zirconate titanate (PZT) ceramic with a high $Q_m$ of 1,280 was used as the piezoelectric active material. Ten PZT sheets produced by tape casting were laminated and co-fired with an Ag/Pd IDE at $1,050^{\circ}C$ for 2 h. The approximately $280{\mu}m$-thick co-fired PZT laminate with the IDE was attached to a stainless steel substrate with an adhesive epoxy for the fabrication of an IDE unimorph cantilever. Its energy harvesting characteristics were evaluated: an output power of $1.1{\mu}W$ at 120 Hz across the resistive load of $700k{\Omega}$ was obtained, corresponding to a normalized power factor of $4.1{\mu}W/(G^2{\cdot}cm^3)$.

• 한국전기전자재료학회논문지
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• 제14권12호
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• pp.987-993
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• 2001

In this paper, we presents the construction details and output characteristics of a thick film piezoresistive strain gage. The thick film was printed on the ceramic diaphragm back side by screen printing and cured at 850$^{\circ}C$. The strain distribution and deflection on ceramic diaphragm were performed with finite-element method(FEM tool ANSYS-5.3). Various thick film strain gage characteristics were analysed, including nonlinearity, hysteresis, stability and sensitivity of thick film strain gages.