• Composites Research
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• 제34권6호
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• pp.357-372
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• 2021

에너지 수확장치는 석유자원의 고갈로 인한 자원난을 해결할 수 있는 대안으로 유망하다고 알려져 있다. 기계적 움직임을 전기 에너지로 전환할 수 있는 압전 소자들의 한계(환경오염 및 낮은 기계적 특성)를 극복하기 위하여, 고분자 기지재 기반 복합재료 압전 에너지 수확장치에 대한 많은 연구들이 수행되었다. 본 논문에서는 사용된 재료 및 공정에 기초하여, 보고된 압전 복합재료의 출력 성능 및 관련된 응용 분야를 검토하였다. 압전 필러는 티탄산 지르콘산 연 및 티탄산바륨 기반의 세라믹 필러뿐만 아니라, 친환경, 생체적합성 및 유연성 측면에서 유리한 산화아연을 검토하였다. 기지재는 폴리비닐리덴플로오라이드 및 공중합체로 구성된 압전 고분자 및 에폭시 및 폴리디메틸실록산 기반의 유연한 고분자로 분류하여 복합재료의 압전 시너지 및 높은 외력 적용에 의한 압전 출력 향상을 논의하였다. 또한, 금속 혹은 탄소 소재 기반 2차 필러의 적용에 의한 복합재료의 전도성 혹은 기계적 특성의 향상이 압전 수확장치의 출력 성능에 미치는 영향을 복합재료의 구조 측면에서 검토하였다. 향상된 성능으로 소형 전자기기, 스마트 센서, 의학 분야 등에 응용 가능한 복합재료 기반 압전 수확장치는 미래의 일상에서 접할 수 있는 무선 전자 장치의 전원으로써 잠재적인 통찰을 제공할 수 있다.

• 한국세라믹학회지
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• 제51권5호
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• pp.430-434
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• 2014

$SiC_f$/SiC composites were prepared using the hybrid process of chemical vapor infiltration (CVI) and polymer impregnation and pyrolysis (PIP). Before the application of PIP, partially matrix-filled preform composites with different densities were fabricated by control of chemical vapor infiltration time and temperature. The changes of the final density of the $SiC_f$/SiC composites had a tendency similar to that of preform composites partially filled by CVI. Composites with lower density after the CVI process had a larger increment of density during the PIP process. Three types of microstructures were observed on the fractured surface of the composite: 1) well pulled-out fibers and lower density, 2) slightly pulled-out fibers and higher density, and 3) only bulk SiC. The different fractions and distributions of the microstructures could have an effect on the mechanical properties of the composites. In this study, $SiC_f$/SiC composites prepared using a hybrid process of CVI and PIP had density values in the range of $1.05{\sim}1.44g/cm^3$, tensile strength values in the range of 76.4 ~ 130.7 MPa, and fracture toughness values in the range of $11.2{\sim}13.5MPa{\cdot}m^{1/2}$.

• 한국음향학회지
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• 제16권3호
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• pp.13-17
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• 1997

본 논문에서는 구조 변경한 저 잡음 수중 청음기에서 사용되는 음향 감쇠층의 최적 물성을 제시하고 제작 가능성을 알아보고자 하였다. 이를 위하여 음향 감쇠층의 특성 중 재료 감쇠도와 음향 임피던스를 변화시켜 FEM (Finite Element Method)으로 과도 해석하여 재질 변경에 따른 잡음 응답 특성을 고찰 하였다. 그 결과 재료의 감쇠도는 큰 영향이 없었으며 1 Mrayl 이하 혹은 4 Mrayl 이상의 음향 임피던스 값을 갖는 음향 감쇠층을 사용하는 것이 효율적임을 알 수 있었다. 이러한 목적을 위해서는 일반적인 흡음 재료로 사용되는 고분자 폴리머들은 본 연구의 수중 청음기용 음향 감쇠 층으로 사용하기에 부적합하고, 새로운 금속 혹은 세라믹-폴리머 복합체의 개발이 필요하다.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.265-269
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• 1999

Polyethylene was modified with silanol groups on its surface by photografting of vinyltrimethoxysilane in vapor phase by using benzophenon as a polymerization initiator and by hydrolyzing the methoxysilane groups into the silanol groups with HCI solution. The modified polyethylene formed a dense and homogeneous apatite layer on its surface in a solution with ion concentrations 1.5 times those of human blood plasma within 21 days. This kind of biomimetic process could provide techniques for fabricating apatite-polymer composites with three dimensional structure analogous to the natural bone.

• 한국산업융합학회 논문집
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• 제26권6_3호
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• pp.1297-1303
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• 2023

Research on enhancing the mechanical strength, lightweight properties, electrical conductivity, and thermal conductivity of composite materials by incorporating nano-materials is actively underway. Thermoplastic resins can change their form under heat, making them highly processable and recyclable. In this study, Polyamide-Nylon 6 (PA6), a thermoplastic resin, was utilized, and as reinforcing agents, fused carbon nano-materials (FCN) formed by structurally combining Carbon Nanotube(CNT) and Graphene were employed. Nano-materials often face challenges related to cohesion and dispersion. To address this issue, Silane functional groups were introduced to enhance the dispersion of FCN in PA6. The manufacturing conditions for the composite materials involved determining the use of a dispersant and varying FCN content at 0.05 wt%, 0.1 wt%, and 0.2 wt%. Tensile strength measurements were conducted, and FE-SEM analysis was performed on fracture surfaces. As a result of the tensile strength test, it was confirmed that compared to pure PA6, the strength of the polymer composite with a content of 0.05 wt% was improved by about 60%, for 0.1 wt%, about 65%, and for 0.2 wt%, the strength was improved by 50%. Also, when compared according to the content of FCN, the best strength value was shown when 0.1 wt% was added. The elastic modulus also showed an improvement of about 15% in the case of surface treatment compared to the case without surface treatment, and an improvement of about 70% compared to pure PA6. Through FE-SEM, it was confirmed that the matrix material and silane-modified nanomaterial improved the dispersibility and bonding strength of the interface, helping to support the load evenly and enabling effective stress transfer.

• 한국세라믹학회지
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• 제35권5호
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• pp.421-428
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• 1998

순수 HAC/PVA 계 및 epoxy 수지와 urethane이 첨가된 HAC/PVA 계 MDF 시멘트 복합재료에 서로 다른 관능기를 갖는 3종류의 silane coupling agent를 첨가하여 강도 및 수분안정성에 대한 영향을 살펴보고 기공율 분석을 통해 미세구조와 강도의 관계를 살펴보았다. Silane의 관능기에 따라 각각의 MDF 시멘트 복합재료의 강도 및 수분안정성 향상에 대한 효과가 다른 것을 알 수 있었다. 순수 PVA 메트릭스의 경우에 대해서는 vinyl 기를 갖는 silane이 효과적인 영향을 나타내었으며 epoxy수지가 첨가된 MDF 시멘트에 대해서는 epoxy-methoxy 기를 갖는 silane이, 그리고 urethane이 첨가된 MDF 시멘트에 대해서는 diamine 기의 silane이 효과적이었다. Silane의 첨가량에 따라서는 urethane이 첨가된 MDF 시멘트 복합재료의 경우, diamine 기의 silane이 많이 첨가될수록 수분안정성이 향상되었으며 특히 2wt%의 silane을 첨가하고 wqrm press를 이용하여 성형하였을 때 건조 강도는 약 20% 향상되었으며 습윤강도는 40~70%까지 크게 향상되었다. 이는 기공율과 밀접한 관계가 있음을 알 수 있었다. Epoxy 수지가 첨가된 MDF 시멘트의 경우에서도 2wt%의 silane 첨가까지는 그 첨갈향이 많아질수록 강도가 향상되는 것을 알 수 있었지만 과량의 silane(4wt%)이 첨가될 경우에서는 오히려 특성저하가 나타났다.

• 동굴
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• 제80호
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• pp.21-24
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• 2007

The need for high-frequency decoupling capacitors to supply the transient current requirements to high-speed devices is ubiquitous in current microelectronics applications. Even though materials and their processes have already been developed in terms of their performances, low manufacturing cost cannot be overemphasized in current microelectronics industry. For this reason, we revisited low cost ceramic filled polymer integrated capacitor. Experiments were performed according to the design of experiment (DOE). The best recipe that has the optimized ratio of material composite was obtained using by response optimizer in Minitab. And also, high-frequency measurements were performed to get frequency dependent data using network analyzer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.343-343
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• 2006

집적회로기판의 소형화 추세에 따라 커패시터, 인덕터, 저항과 같은 수동소자를 PCB 기판내부에 임베딩하는 연구가 국내외에서 활발하게 진행되고 있다. 본 논문에서는 polymer-metal-ceramic의 3상 복합체 구조를 가지는 임베디드 커패시터에서 Bimodal PZT분말에 따른 유전 특성에 대하여 고찰하였다. 매트릭스를 형성하는 고분자 재료로는 PMMA(polymethyl methacrylate)를 사용하였으며, 충분히 혼합된 분말을 고온에서 프레싱하여 시편을 제조하였다. 유전특성은 임피던스분석기 및 LCZ 미터를 이용하여 측정하였으며, 실험결과는 혼합법칙과 Percolation 이론을 이용하여 해석하였다.

• The Journal of Advanced Prosthodontics
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• 제13권5호
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• pp.281-291
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• 2021

PURPOSE. To evaluate the wear of computer-aided design/computer-aided manufacturing (CAD-CAM) dental ceramic materials opposed by enamel as a function of increased chewing forces. MATERIALS AND METHODS. The enamel cusps of healthy human third molar teeth (n = 40) opposed by materials from CAD-CAM dental ceramic groups (n = 10), including Vita Enamic^® (ENA), a polymer-infiltrated ceramic network (PICN); GC Cerasmart^® (CERA), a resin nanoceramic; Celtra^® Duo (DUO), a zirconia-reinforced lithium silicate (ZLS) ceramic; and IPS e.max ZirCAD (ZIR), a polycrystalline zirconia, were exposed to chewing simulation (1,200,000 cycles; 120 N load; 1 Hz frequency; 0.7 mm lateral and 2 mm vertical motion). The wear of both enamel cusps and materials was quantified using a 3D laser scanner, and the wear mechanisms were evaluated by scanning electron microscopy (SEM). The results were analysed using Welch ANOVA and Kruskal Wallis test (α = .05). RESULTS. ZIR showed lower volume loss (0.02 ± 0.01 mm³) than ENA, CERA and DUO (P = .001, P = .018 and P = .005, respectively). The wear of cusp/DUO [0.59 mm³ (0.50-1.63 mm³)] was higher than cusp/CERA [0.17 mm³ (0.04-0.41 mm³)] (P = .007). ZIR showed completely different wear mechanism in SEM. CONCLUSION. Composite structured materials such as PICN and ZLS ceramic exhibit more abrasive effect on opposing enamel due to their loss against wear, compared to uniform structured zirconia. The resin nano-ceramic causes the lowest enamel wear thanks to its flexible nano-ceramic microstructure. While zirconia appears to be an enamel-friendly material in wear volume loss, it can cause microstructural defects of enamel.

• 한국세라믹학회지
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• 제46권3호
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• pp.225-228
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• 2009

The processing and characterization of ceramic nanocomposites, which produce bulk nanostructures with attractive mechanical properties, have been emphasized and introduced at Prof. Mukherjee's Lab at UC Davis. The following subjects will be introduced in detail in Part II, III, and IV. In Part II, the paper will describe a three-phase alumina-based nanoceramic composite demonstrating superplasticity at a surprisingly lower temperature and higher strain rate. The next part will show that an alumina-carbon nanotube-niobium nanocomposite produced fracture toughness values that are three times higher than that of pure nanocrystalline alumina. It was possible to take advantage of both fiber-toughening and ductile-metal toughening in this investigation. In the fourth section, discussed will be a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method. This allowed the sintering to be completed at significantly lower temperatures and during much shorter times. These improvements in mechanical properties will be discussed in the context of the results from the microstructural investigations.