• 한국재료학회지
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• 제32권11호
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• pp.508-514
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• 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.

• 한국재료학회지
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• 제22권3호
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• pp.118-122
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• 2012

We synthesized porous $Co_3O_4/RuO_2$ composite using the soft template method. Cetyl trimethyl ammonium bromide (CTAB) was used to make micell as a cation surfactant. The precipitation of cobalt ion and ruthenium ion for making porosity in particles was induced by $OH^-$ ion. The porous $Co_3O_4/RuO_2$ composite was completely synthesiszed after anealing until $250^{\circ}C$ at $3^{\circ}C$/min. From the XRD ananysis, we were able to determine that the porous $Co_3O_4$/RuO2 composite was comprised of nanoparticles with low crystallinity. The shape or structure of the porous $Co_3O_4/RuO_2$ composite was studied by FE-SEM and FE-TEM. The size of the porous $Co_3O_4/RuO_2$ composite was 20~40 nm. From the FE-TEM, we were able to determine that porous cavities were formed in the composite particles. The electrochemical performance of the porous $Co_3O_4/RuO_2$ composite was measured by CV and charge-discharge methods. The specific capacitances, determined through cyclic voltammetry (CV) measurement, were ~51, ~47, ~42, and ~33 F/g at 5, 10, 20, and 50 mV/sec scan rates, respectively. The specific capacitance through charge-discharge measurement was ~63 F/g in the range of 0.0~1.0 V cutoff voltage and 50 mAh/g current density.

• Advances in nano research
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• 제14권6호
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• pp.507-519
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• 2023

Postsurgical infections are caused by implant-related pathogenic microorganisms that lead to graft rejection. Hence, an intrinsically antibacterial material is required to produce a biocompatible biomaterial with osteogenic properties that could address this major issue. Hence, this current research aims to make strontium-doped hydroxyapatite nanorods (SrHANRs) via an ethylene diamine tetraacetic acid (EDTA)-enable microwave mediated method using Anodontia alba seashells for biomedical applications. This investigation also perceives that EDTA acts as a soft template to accomplish Sr-doping and mesoporous structures in pure hydroxyapatite nanorods (HANRs). The X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis reveals the crystalline and mesoporous structures, and Brunauer-Emmett-Teller (BET) indicates the surface area of all the samples, including pure HANRs and doped HANRs. In addition, the biocidal ability was tested using various implant-related infectious bacteria pathogens, and it was discovered that Sr-doped HANRs have excellent biocidal properties. Furthermore, toxicity evaluation using zebrafish reports the non-toxic nature of the produced HANRs. Incorporating Sr²⁺ ions into the HAp lattice would enhance biocompatibility, biocidal activity, and osteoconductive properties. As a result, the biocompatible HANRs materials synthesized with Sr-dopants may be effective in bone regeneration and antibacterial in-built implant applications.

• 청정기술
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• 제18권2호
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• pp.177-182
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• 2012

Tri-block copolymer를 유연 템플레이트로 사용한 수열합성법에 의해 메조다공성 아나타제상 $TiO_2$ 나노입자를 합성하였다. 합성된 $TiO_2$ 재료는 $230m^2/g$의 매우 큰 표면적을 가졌으며 6.8 nm의 기공크기와 0.404 mL/g의 기공부피를 보였다. 리튬이 온전지 음극재로서의 가능성을 확인하기 위해 코인셀 테스트를 실시하였는데 0.1 C에서 240 mAh/g의 방전 용량을 얻었으며 이는 LTO ($Li_4Ti_5O_{12}$)의 이론 방전 용량인 175 mAh/g 보다 훨씬 큰 값이었다. 비록 C-rate가 증가함에 따라 용량이 감소하는 모습을 보였으나 메조다공성 $TiO_2$ 재료는 리튬 이온이 침투할 수 있는 큰 표면적을 제공할 수 있다는 면에서 여전히 리튬 이온전지의 음극재로서 가능성이 있다. 추가적으로 질소를 도핑하여 $TiO_2$ framework 내의 전자 이동을 향상시킴으로써 C-rate 증가에 따른 용량 감소를 일부 제어할 수 있음을 확인하였다.