• Composites Research
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• 제13권5호
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• pp.31-36
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• 2000

금속/세라믹 복합체의 강화제로 사용가능한 다공성 뮬라이트 제조 시 공정변수 변화가 침상형 미세구조 형성에 미치는 영향에 대해 고찰하였다. 출발물질을 $Al_2O_3+SiO_2$와 $Al(OH)_3+SiO_2$로 달리하여 미세구조 변화를 고찰한 결과, $Al_2O_3$보다 반응성이 우수한 $Al(OH)_3$를 사용한 시편에서 더욱 발달한 침상형 구조가 나타났으며, 첨가제 $AlF_3$의 함량이 증가할수록, $SiF_4$가 발생하는 온도구간인 $900^{\circ}C$에서 유지하는 시간이 길수록 반응을 잘 일어나 시편 전체에서 침상형 뮬라이트가 형성되었다. 소결 온도의 경우 $1200^{\circ}C$에서부터 뮬라이트가 생성되었고, 소결 온도변화에 따른 미세구조는 큰 변화를 관찰할 수 없었다. 기공률은 첨가제의 양이 증가할수록, $900^{\circ}C$에서의 유지시간이 길수록 증가하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권8호
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• pp.335-341
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• 2003

The composites were fabricated respectively 61vo1.% $\beta$ -SiC and 39vo1.% Ti $B_2$ spray-dried powders with the liquid forming additives of l2wt% $Al_2$ $O_3$＋ $Y_2$ $O_3$ by pressureless annealing at 1$700^{\circ}C$, 175$0^{\circ}C$, 180$0^{\circ}C$ for 4 hours. The result of phase analysis of composites by XRD revealed $\alpha$ -SiC(6H), Ti $B_2$, and YAG(A $l_{5}$ $Y_3$ $O_{12}$ ) crystal phase. The relative density, the Young's modulus and fracture toughness showed respectively the highest value of 92.97%, 92.88Gpa and 4.4Mpaㆍ $m^{\frac{1}{2}}$ for composites by pressureless annealing temperature 1$700^{\circ}C$ at room temperature. The electrical resistivity showed the lowest value of 8.09${\times}$10$^{-3}$ ㆍcm for composite by pressureless annealing temperature 1$700^{\circ}C$ at $25^{\circ}C$. The electrical resistivity of the SiC-Ti $B_2$ composites was all positive temperature cofficient resistance(PTCR) in the temperature ranges from $25^{\circ}C$ to $700^{\circ}C$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권10호
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• pp.500-503
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• 2001

The mechanical and electrical properties of the hot-pressed and pressureless annealed SiC+39vol.%$TiB_2$electroconductive ceramic composites were investigated as a function of the liquid additives of $Al_2O_3+Y_2O_3$. The result of phase analysis for the SiC+39vol.%$TiB_2$composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and $YAG(Al_5Y_3O_{12})4 crystal phase. The relative density of SiC+39vol.%$TiB_2$ composites was increased with increased $Al_2O_3+Y_2O_3$. contents. The fracture toughness showed the highest value of $7.8 MPa.m^{1/2}$ for composites added with 12 wt % $Al_2O_3+Y_2O_3$. additives at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest value of $7.3\times10_{-4}\Omega.cm\; and\; 3.8\times10_{-3}/^{\circ}C$ for composite added with 12 wt% $Al_2O_3+Y_2O_3$. additives at room temperature. The electrical resistivity of the SiC+39vol.%$TiB_2$composites was all positive temperature coefficient resistance(PTCR) in the temperature ranges from $25^{\circ}C\; to\; 700^{\circ}C$.

• 폴리머
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• 제35권5호
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• pp.375-377
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• 2011

두 단계 스핀 코팅 방법을 사용하여 세라믹 체적 분율 0.10과 0.13의 $PbTiO_3$/P(VDF/TrFE) 0~3형 복합재료를 제작하고 분석하였다. 0~3형 $PbTiO_3$/P(VDF/TrFE) 복합재료를 SEM 전자현미경 사진으로 성공적으로 확인할 수 있었다. 이러한 전자현미경 사진을 통하여 복합재료의 0~3형 구조를 재확인하였다. 0~3형 $PbTiO_3$/P(VDF/TrFE) 복합재료는 P(VDF/TrFE) 공중합체보다 센서용 전기적 특성이 우수함을 나타내었다. 그러므로 이러한 낮은 유전상수와 높은 초전계수를 나타내는 0~3형 $PbTiO_3$/P(VDF/TrFE) 복합재료는 더 높은 성능을 나타낼 수 있는 새로운 초전형 센서 재료로 사용될 수 있다.

• 대한화학회지
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• 제44권6호
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• pp.592-599
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• 2000

여러 가지 온도, 조성 및 농도에서 이성분계 세라믹 복합체 TPSZ(titania partially-stabilized zirconia)의 미분말을 초음파분무열분해법에 의하여 합성하였으며, 합성공정인자가 분체특성에 미치는 영향을 검토하고, 합성된 분체의 특성을 조사하였다. 출발용액의 제조는 금속염의 농도가 0.025~0.1 M이 되도록 증류수에 용해하고, 그 조성비는 $ZrO_2$ 90~97.5 wt%에 $TiO_2$ 2.5~10 wt%가 되도록 하였다. 합성시 열분해 영역에서의 온도는 건조부가 400~550$^{\circ}C$, 반응부는 800~1100$^{\circ}C$로 하였으며, 합성된 분체는 습식으로 포집하여 110$^{\circ}C$에서 3시간 동안 건조하였다. 합성된 미분체의 특성을 Raman Spectroscopy, X-ray diffraction(XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy (TEM) 및 Particle Size Analyzer(PSA)로써 조사하였고, Inductively Coupled Plasma-Atomic Emission Spectroscopy(ICP-AES)로써 순도 및 조성을 분석하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권7호
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• pp.352-357
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• 2004

The composites were fabricated, respectively, using 61vol.% SiC - 39vol.% TiB$_2$ and using 61vo1.% SiC - 39vo1.% WC powders with the liquid forming additives of 12wt% $Al_2$O$_3$＋Y$_2$O$_3$ by pressureless annealing at 180$0^{\circ}C$ for 4 hours. Reactions between SiC and transition metal TiB$_2$, WC were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H), TiB$_2$ and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phase on the SiC-TiB$_2$, and SiC(2H), WC and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phase on the SiC-WC composites. $\beta$\$\longrightarrow$$\alpha$-SiC phase transformation was ocurred on the SiC-TiB$_2$, but $\alpha$\$\longrightarrow$$\beta$-SiC reverse transformation was not occurred on the SiC-WC composites. The relative density, the vicker's hardness, the flexural strength and the fracture toughness showed respectively value of 96.2%, 13.34GPa, 310.19Mpa and 5.53Mpaㆍml/2 in SiC-WC composites. The electrical resistivity of the SiC-TiB$_2$ and the SiC-WC composites is all positive temperature coefficient resistance(PTCR) in the temperature ranges from $25^{\circ}C$ to 50$0^{\circ}C$. 2.64${\times}$10-2/$^{\circ}C$ of PTCR of SiC-WC was higher than 1.645${\times}$10-3/$^{\circ}C$ of SiC-TiB$_2$ composites.posites.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권4호
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• pp.141-146
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• 2002

The mechanical and electrical properties of the pressureless sintered SiC-TiB$_2$electroconductive ceramic composites were investigated as functions of the transition metal of TiB$_2$. The result of phase analysis for the SiC-TiB$_2$ composites by XRD revealed $\alpha$-SiC(6H), TiB$_2$, and YAG(Al$_{5}$Y$_3$O$_{12}$) crystal phases. The relative density showed the lowest 84.8% for the SiC-TiB$_2$composites added with 39vol.%TiB$_2$. Owing to crack deflection, crack bridging and YAG of fracture toughness mechanism, the fracture toughness showed the highest value of 7.8 MPa.m$^{1}$2/ for composites added with 39vol.%TiB$_2$under a pressureless annealing at room temperature. The electrical resistivity of the SiC-27vol.%TiB$_2$ composites was negative temperature coefficient resistance(NTCR), and the electrical resistivity of the besides SiC-27vol.%TiB$_2$composites was all positive temperature coefficient resistance(PCTR) in the temperature range of $25^{\circ}C$ to $700^{\circ}C$.EX>.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1538-1540
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• 2003

The composites were fabricated respectively 61vol.% ${\beta}$-SiC and 39vol.% $TiB_2$ spray-dried powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ by pressureless annealing at $1700^{\circ}C,\;1750^{\circ}C\;1800^{\circ}C$ for 4 hours. The result of phase analysis of composites by XRD revealed ${\alpha}$-SiC(6H), $TiB_2$, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density, the Young's modulus and fracture toughness showed respectively the highest value of 92.97%, 92.88Gpa and $4.4Mpa{\cdot}m^{1/2}$ for composites by pressureless annealing temperature $1700^{\circ}C$ at room temperature. The electrical resistivity showed the lowest value of $8.09{\times}10^{-3}{\Omega}{\cdot}cm$ for composite by pressureless annealing tempe rature $1700^{\circ}C$ at $25^{\circ}C$. The electrical resistivity of the SiC-$TiB_2$ composites was all positive temperature cofficient resistance (PTCR) in the temperature ranges from $25^{\circ}C$ to $700^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.480-486
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• 2021

Magnetoelectric (ME) composite is composed of a piezoelectric material and a magnetostrictive material. Among various ME structures, 2-2 type layered ME composites are anticipated to be used as high-sensitivity magnetic field sensors and energy harvesting devices especially operating at its resonance modes. Rosen type piezoelectric transducer using piezoelectric material is known to amplify a small electrical input voltage to a large electrical output voltage. The output voltage of these Rosen type piezoelectric transducers can be further enhanced by modifying them into ME composite structures. Herein, we fabricated Rosen type ME composites by sandwiching Rosen type PMN-PZT single crystal between two Ni layers and studied their ME coupling. However, the voltage step-up ratio at the resonance frequency was found to be smaller than the value calculated with α_ME value. The ATILA FEA (Finite Elements Analysis) simulation results showed that the position of the nodal point was changed with the presence of a magnetostrictive layer. Thus, while designing a Rosen type ME composite with high performance in a resonant driving situation, it is necessary to optimize the position of the nodal point by optimizing the thickness or length of the magnetostrictive layer.

• 한국전기전자재료학회논문지
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• 제35권1호
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• pp.72-79
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• 2022

Piezoelectric energy harvesting technologies, which can be used to convert the electricity from the mechanical energy, have been developed in order to assist or power the wearable electronics. To realize non-toxic and biocompatible electronics, the lead-free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ (BCTZ) nanoparticles (NPs) are being studied with a great attention as flexible energy harvesting device. Herein, piezoelectric hybrid nanocomposites were fabricated using BCTZ NPs-embedded poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to improve the performance of flexible energy harvester. Output performance of the fabricated energy device was investigated by the well-optimized measurement system during the periodically bending and releasing motions. The generated open-circuit voltage and the short-circuit current of the piezoelectric hybrid nanocomposite-based energy harvester reached up to ~15 V and ~1.1 ㎂, respectively; moreover, the instantaneous power of 3.5 ㎼ is determined from load voltage and current at the external load of 20 MΩ. This research is expected to cultivate a new approach to high-performance wearable self-powering electronics.