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유주안,심성원,송해민,김도훈,장경철,전동호,조승,오재은 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.5
This study examined the influence of the crystallinity of added nano-alumina on the sulfate resistance of ordinary Portland cement (OPC) paste. Two crystalline types of nano-aluminas (α-and γ-phase) were incorporated in cement pastes, which were exposed to sulfate solution. In the results, both paste samples having α- and γ-phase aluminas had accelerated compressive strength loss and increased length expansion compared to the sample without alumina addition. In particular, the rapidly decreased dynamic elastic modulus of the nano-alumina added samples postulates the greatly increased internal stress likely by the increased formation of volume expansive reaction products, such as ettringite, which was supported by the XRD and TG results. The greater ettringite formation in the nano-alumina added samples was likely due to reactive AH3 (=Al(OH)3) gel formation as the higher consumption degree of portlandite in the alumina added samples indirectly indicates the active AH3 gel formation, resulting in additional ettringite formation from the reaction of AH3 with Na2SO4 solution. A further degree of sulfate attack was observed in the γ-alumina added sample for the long-term Na2SO4 exposure (180 days) mainly due to the greater degree of gypsum formation inducing more internal expansive stress compared to the α-alumina added sample.
표면개질된 나노알루미나를 혼합한, 에폭시/마이크로-나노알루미나 콤포지트의 열적특성
박재준(Jae-Jun Park) 대한전기학회 2016 전기학회논문지 Vol.65 No.9
The aim of this study is to improve properties both glass transition temperature(Tg) and coefficient of thermal expansion(CTE) using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,2,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40, 50, 60wt%)+surface modified nano alumina(1_phr) composites. 20 kinds specimen were prepared with containing micro, nano alumina and GDE as a micro composites(10, 20, 30, 40, 50, 60, 70wt%) or a nano/micro alumina composites(1phr/40, 50, 60wt%). Average particle size of nano and micro alumina used were 30nm and 1~2㎛, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The glass transition temperature and coefficients of thermal expansion was evaluated by DSC and TMA. The glass transition temperature decreased and coefficients of thermal expansion become smaller with filled contents of epoxy/micro alumina composites. On the other hand, Tg and CTE as GDE addition variation(1,2,3,5g) of epoxy/micro-nano alumina composites decreased and increased respectively.
Swain, Sarojini,Sharma, Ram Avatar,Bhattacharya, Subhendu,Chaudhary, Lokesh The Korean Institute of Electrical and Electronic 2013 Transactions on Electrical and Electronic Material Vol.14 No.1
The present approach shows the use of nano-silica/nano-alumina in polyurethane (PU) matrix, which lead to significant improvements in the mechanical and thermal properties of the nano-composite. It is observed that with incorporation of 1% of nano-alumina into the PU matrix, there is an improvement in the tensile strength of around 50%, and for nano-silica the improvement is around 41%, at the same concentration. The morphological data shows that above 3% of the nano particles there are agglomerations in the nanocomposite. Again with the absorption of moisture, there is a decrease in the thermal and mechanical properties of the PU resin, but in this research work it is observed that with the incorporation of the nano particles, in the presence of absorbed moisture there is an improvement in mechanical and thermal properties of the composite, over that of the PU matrix.
Sarojini Swain,Ram Avatar Sharma,Subhendu Bhattacharya,Lokesh Chaudhary 한국전기전자재료학회 2013 Transactions on Electrical and Electronic Material Vol.14 No.1
The present approach shows the use of nano-silica / nano-alumina in polyurethane (PU) matrix, which lead to significant improvements in the mechanical and thermal properties of the nano-composite. It is observed that with incorporation of 1% of nano-alumina into the PU matrix, there is an improvement in the tensile strength of around 50%, and for nano-silica the improvement is around 41%, at the same concentration. The morphological data shows that above 3% of the nano particles there are agglomerations in the nanocomposite. Again with the absorption of moisture, there is a decrease in the thermal and mechanical properties of the PU resin, but in this research work it is observed that with the incorporation of the nano particles, in the presence of absorbed moisture there is an improvement in mechanical and thermal properties of the composite, over that of the PU matrix.
GIS용, 에폭시/나노표면개질/마이크로 알루미나 혼합 절연소재의 유전특성
박재준(Jae-Jun Park) 대한전기학회 2019 전기학회논문지 Vol.68 No.3
For evaluation of dielectric properties (dielectric constant, dielectric loss and electrical conductivity, original epoxy, Epoxy/nano alumina content changed composite, epoxy/micro alumina composite, epoxy/nano and micro - mixed composites were prepared. Together, composite using surface treated nano-alumina was prepared. The dielectric properties were evaluated at room temperature under the frequency range of 0.01 Hz to 1 MHz. As the content of nano - alumina filler increased, the dielectric constant, dielectric loss and electrical conductivity increased. Nano/micro alumina mixed composites have lower dielectric properties than micro composites. Also, the dielectric properties of GDE surface treated nanoalumina composites were greatly reduced. These results are considered to be the result of strengthening the interface between the resin and the particle surface treatment and suppressing the migration of the resin by the nanoparticles.
표면처리된 나노알루미나가 첨가된 에폭시/멀티-알루미나 콤포지트의 교류절연파괴 특성
박재준(Jae-Jun Park) 대한전기학회 2016 전기학회논문지 Vol.65 No.9
The aim of this study is to improve of properties for electrical AC insulation breakdown strength using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40,50,60wt%)+surface modified nano alumina(1_phr) composites. 14 kinds specimen were prepared with containing epoxy resins, epoxy micro composites and epoxy nano-micro alumina mixture composites. Average particle size of nano and micro alumina used were 30nm and 1~2㎛, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The electrical AC insulation breakdown strength was evaluated by sphere to sphere electrode system and raising velocity 1㎸/s. The AC breakdown strength decreased insulation properties of multi-composites according to increasing micro alumina and GDE addition contents.
표면개질된 나노 알루미나의 에폭시-나노 콤포지트 유전 특성
박재준,Park, Jae-Jun 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.10
The aim of this study is to improve of dielectric properties using epoxy/nano alumina composites with adding glycerol diglycidyl ether (GDE:1,2 g). This paper deals with the effects of dielectric properties(${\epsilon}^{\prime}_r$ and $tan{\delta}$) for epoxy/nano alumina contents (1,3 phr) and GDE addition (1,2 g)composites. 5 kinds specimen were prepared with containing epoxy resins, epoxy nano alumina composites. Average particle size of nano used were 30 nm. The nano alumina used were gamma phase particles of spherical shape. The suppression of epoxy chain motion by addition of nano alumina+GDE decreased dielectric loss and relative permittivity magnitude.
박재준,Park, Jae-Jun 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.12
In order to develop an electrical insulation material for gas GIS (insulation switch gear) spacer, 4 types of epoxy/micro-alumina (40, 50, 60, 70 wt%) composites and 9 types of epoxy/nano-alumina (1, 3, 5 g)/micro-alumina (40, 50, 60, 70 wt%) composites were prepared and tensile test was carried out. In here, nano-alumina was previously surface-treated with GDE (glycerol diglycidyl ether). As micro-alumina and GDE-treated nano-alumina contents increased, tensile strength increased and the highest value was shown in the system with 3 g GDE-treated nano-alumina.
금속 전극 알루미나 박막 캐패시터의 전기적 특성에 미치는 미세구조의 영향
정명선,주병권,오영제,이전국,Jeong, Myung-Sun,Ju, Byeong-Kwon,Oh, Young-Jei,Lee, Jeon-Kook 한국재료학회 2011 한국재료학회지 Vol.21 No.6
The power capacitors used as vehicle inverters must have a small size, high capacitance, high voltage, fast response and wide operating temperature. Our thin film capacitor was fabricated by alumina layers as a dielectric material and a metal electrode instead of a liquid electrolyte in an aluminum electrolytic capacitor. We analyzed the micro structures and the electrical properties of the thin film capacitors fabricated by nano-channel alumina and metal electrodes. The metal electrode was filled into the alumina nano-channel by electroless nickel plating with polyethylene glycol and a palladium catalyst. The spherical metals were formed inside the alumina nano pores. The breakdown voltage and leakage current increased by the chemical reaction of the alumina layer and $PdCl_2$ solution. The thickness of the electroless plated nickel layer was 300 nm. We observed the nano pores in the interface between the alumina layer and the metal electrode. The alumina capacitors with nickel electrodes had a capacitance density of 100 $nF/cm^2$, dielectric loss of 0.01, breakdown voltage of 0.7MV/cm and leakage current of $10^4{\mu}A$.
Cheon, Sungho,Jun, Byungsei The Korean Ceramic Society 2003 한국세라믹학회지 Vol.40 No.7
To prepare the alumina cement free vibrated alumina castable, $\rho$-alumina is employed as a binder material, and nano-sized clay is added to enhance the curing strength and give thixotropic behavior. The rheological behavior of matrix of castable is controlled by investigating the influences of ultrafines, $\rho$-alumina, and nano-sized clay on the viscosity of matrix. The microsilica and ultrafine alumina were added 3 wt% and 4 wt%, respectively to the matrix, which showed that the viscosities tends to be lowest values. The rheological property of the matrix is well established by adding $\rho$-alumina as 8 wt% and clay as 4 wt%. The thixotropic behavior of the $\rho$-alumina bonded castable was appeared by introducing nano-sized clay into the matrix and adjusting the pH near to the PZC of the clay suspension.