• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.710-713
• /
• 2003

The PZT(KP12) powder was synthesized by sintering at $1250^{\circ}C$ for 2hrs and wet milling for 24 hrs. The PZT composite mixed with PVdF was fabricated into bulk, sheet, and plate type and the characteristics of three types were estimated. The bulk type which has PZT volume percent of 70 showed the best piezoelectric constant. Dielectric constant increased exponentially as an increase of PZT volume percent. The figure of merit of bulk and plate type was better than pure PZT over PZT volume percent of 50.

• Journal of the Korean Ceramic Society
• /
• v.40 no.7
• /
• pp.625-631
• /
• 2003

Recent work at USC has focused on strategies to enhance the toughness and overall mechanical performance of polymer foams for use in lightweight sandwich structures. Both mechanical and chemical approaches have been employed with reasonable success. Fiber reinforcement, though difficult from a processing perspective, can lead to substantial enhancements in toughness and strength, while reducing friability. Chemical modifications are also challenging from a processing perspective, but can produce similar enhancements in performance. Efforts to enhance performance of phenolic foam and PVC foam through fiber reinforcement and chemical modification are described, along with the resulting enhancements in performance.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.6
• /
• pp.251-255
• /
• 2007

We made $(1-x)BCB-xBNT(BaNd_2Ti_4O_{12})$ (x=20, 30, 40, 50 vol%) composite thick film with a high dielectric constant and low loss by the hand casting method. Dielectric constant and dielectric loss of prepared thick film are measured at 1MHz and curing behavior of the film are observed through thermal analysis such as DSC. We investigated the effect of contents of BNT filler and curing behavior of film on dielectric properties of BCB-BNT composite. Dielectric constant increased with increasing BNT filler from 20 to 50 vol% and dielectric loss ($tan{\delta}$) decreased with increasing BNT filler. Dielectric constant and loss ($tan{\delta}$) of composite material was not nearly dependent on the curing behavior. But as a result of TCC (Temperature Characteristics of Coefficient) decreased with increasing the curing temperature, we confirmed that the curing of these composite system is most stable above $250^{\circ}C$.

• The Journal of Advanced Prosthodontics
• /
• v.11 no.4
• /
• pp.223-231
• /
• 2019

PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.40-41
• /
• 2006

In this work, we developed the 0-3 type piezoelectric composite to incorporate the advantages of both ceramic and polymer. The PVDF-PZT composites were fabricated with various mixing ratio by 3-roll mi11 mixer. The composite solutions were coated on ITO bottom-electrode deposited on PET (polyethylene terephthalate) polymer film by the conventional screen-printing method. After depositing the top-electrode of silver-paste, 4kV/mm of DC field was applied at $120^{\circ}C$ for 30min to poling the 0-3 composite film. The value of $d_{33}$ was increased as the PZT weight percent was increases. But the $g_{33}$ value showed the maximum at 65 wt% of PZT powder.

• Journal of the Regional Association of Architectural Institute of Korea
• /
• v.21 no.3
• /
• pp.87-92
• /
• 2019

To relieve noise between floors in Korea, recent domestic and overseas studies have been developing materials that have the properties of ceramic, which is an inorganic compound, and polymer, which is an organic compound, to introduce a new function to polymer. This study conducted a bending strength experiment between re-bar and new composite concrete mixing POSS (Polyhedral Oligomeric Silses-quioxanes) nano complex on the inside of concrete, and by assembling the inside of each concrete with 3 and 4 main re-bars as an experiment to supplement various problems that occur by the expression of this strength and the distribution of the reinforcement. The number of the main re-bars. and the direction of laying the concrete were applied as the principal variables of the experiment. Upon experiment, there were no differences in the bond strength based on the location of the main re-bar, and a 2 % increase in the bond strength was shown in the specimen laid in the same direction as the main re-bar in comparison to that of the specimen laid in a different direction from the main re-bar. The experiment results displayed that the composite concrete had uniform performance based on the rapid reaction speed of POSS nano complex.

• Korean Journal of Materials Research
• /
• v.32 no.11
• /
• pp.508-514
• /
• 2022

Piezoelectric composite films which are enabled by inorganic piezoelectric nanomaterials-embedded polymer, have attracted enormous attention as a sustainable power source for low powered electronics, because of their ease of fabrication and flexible nature. However, the absorption of applied stress by the soft polymeric matrices is a major issue that must be solved to expand the fields of piezoelectric composite applications. Herein, a flexible and porous piezoelectric composite (piezoelectric sponge) comprised of BaTiO₃ nanoparticles and polydimethylsiloxane was developed using template method to enhance the energy conversion efficiency by minimizing the stress that vanishes into the polymer matrix. In the porous structure, effective stress transfer can occur between the piezoelectric active materials in compression mode due to direct contact between the ceramic particles embedded in the pore-polymer interface. The piezoelectric sponge with 30 wt% of BaTiO₃ particles generated an open-circuit voltage of ~12 V and a short-circuit current of ~150 nA. A finite element method-based simulation was conducted to theoretically back up that the piezoelectric output performance was effectively improved by introducing the sponge structure. Furthermore, to demonstrate the feasibility of pressure detecting applications using the BaTiO₃ particles-embedded piezoelectric sponge, the composite was arranged in a 3 × 3 array and integrated into a single pressure sensor. The fabricated sensor array successfully detected the shape of the applied pressure. This work can provide a cost-effective, biocompatible, and structural strategy for realizing piezoelectric composite-based energy harvesters and self-powered sensors with improved energy conversion efficiency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.6
• /
• pp.495-500
• /
• 2009

The ceramic($BaTiO_3$)-polymer(epoxy) composites have been widely investigated as dielectric materials for embedded capacitors in printed circuit boards (PCBs). The dielectric properties of $BaTiO_3$/epoxy composites prepared using the agglomerated $BaTiO_3$ particles were investigated in the present study. The dielectric constants of the composites prepared using the agglomerated $BaTiO_3$ particles were about 2 times higher than those of the composites with the dispersed $BaTiO_3$ particles. The insulation resistance of the composites prepared using the agglomerated $BaTiO_3$ particles were lower than those of the composites with dispersed $BaTiO_3$ particles. As a result, there is tradeoff between high dielectric constant and insulation resistance in the $BaTiO_3$/epoxy composites. So it is important to select proper agglomerated or dispersed $BaTiO_3$ particles in accordance with needs.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.4
• /
• pp.365-372
• /
• 2018

3D printing technology of construction field can be divided into structural materials, interior and exterior finishing materials, and is mainly done by extruding and adapting. Particularly when it is applied as an exterior materials, it is mainly applied to an unstructured exterior materials and high accuracy is required. The exterior materials can be used as a cement composite materials, it is suitable also for a additive type manufacturing, and the role of a redispersible polymer powder is important. But, high temperatures, redispersible polymer cement base material beget dehydration and micro crack of cement matrix. In this research, we developed a EVA, EVCL redispersible polymer cement base material applicable as a 3D printing exterior materials, confirmed density and strength characteristics for application as an exterior materials, a flame retardancy test for improving the fire resistance of buildings and confirmed its possibility. From the test result, developed EVCL redispersible polymer cement mortar showed good stability in high temperatures. These high temperature stability is caused by the ethylene-vinyl chloride binding. Thus, this result indicates that it is possible to fire resistant 3D printing interior and exterior finishing materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.345-345
• /
• 2008

최근 전자 소자의 고주파화, 소형화에 대한 요구가 증대 되면서 많은 소자들을 하나의 시스템에 3차원적으로 실장시키는 SOP (System-on-Package)가 새로운 대안으로 떠오르고 있으며 SOP를 실현하기 위해서는 집적기판에 대한 저온화 공정 기술이 절실히 필요한 실정이다. 현재 집적기판에 사용되는 재료로서 세라믹이 널리 알려져 있지만 세라믹은 취성이 있으며 $1000^{\circ}C$ 이상의 고온화 공정 프로세스를 필요로 하는 근본적인 약점이 있다. 이에 본 연구에서는 상온에서 고속으로 치밀한 성막을 가능케 하는 Aerosol Deposition Method (ADM)를 이용하여 최초로 세라믹-폴리머 복합체 후막을 성공적으로 제작하였다. XRD와 FT-IR 분석 결과 $Al_2O_3$-PMMA, $Al_2O_3$-PI 혼합물을 출발 파우더로 사용하여 제조한 후막이 세라믹-폴리머 복합체임을 확인할 수 있었다. 또한 SEM 분석결과 $Al_2O_3$-PMMA 복합체와 $Al_2O_3$-PI 복합체의 표면 양상이 매우 다르다는 점을 확인하였으며 $Al_2O_3$-PMMA 복합체의 성막률이 $Al_2O_3$-PI 복합체의 성막률에 비해 매우 낮음을 확인하였다. 이러한 현상들은 폴리머 파우더들의 경도와 탄성 차이 때문인 것으로 사료되어 이를 증명하기 위한 실험을 실시하였다. 결국 PMMA 막과 PI 막에 대한경도측정결과와 PMMA 파우더와 PI 파우더의 유성 볼밀링 전후에 대한 SEM 이미지를 통해 PMMA 파우더가 PI 파우더에 비해 경도가 낮으며 반면 탄성이 높다는 것을 간접적으로 확인할 수 있었다. 이와 같은 분석을 통하여 ADM을 이용한 세라믹-폴리머 복합체 후막의 제조에 있어 폴리머 파우더의 경도와 탄성이 매우 큰 영향을 미친다는 것을 알 수 있었다. 본 연구에서는 세라믹-폴리머 복합체 후막을 성공적으로 제조하기 위해서 폴리머 파우더의 적절한 선택이 중요함을 알 수 있었으며 ADM을 이용한 세라믹-폴리머 복합체 후막의 제조에 대한 가이드 라인을 제시할 수 있을 것으로 기대된다.