• Advances in concrete construction
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• 제8권1호
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• 한국재료학회지
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• 제22권10호
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• pp.531-538
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• 2012

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and $TiO_2$ for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the $TiO_2$ is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of $TiO_2$.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.305-305
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• 2009

The carbon nano-structured materials could be applied to the fields of advanced fillers, templates, electrode materials, sensor, storage, and absorption materials. The polyacrylonitrile (PAN) based carbon nano-particles provide the remarkable properties of high specific surface area, large pore volume, chemical inertness, and good mechanical stability. In this study, well-defined carbon nano-particles were obtained through pyrolysis of polyacrylonitrile based particles. The precursor nano-particles were prepared by modified aqueous dispersion polymerization using hydrophilic poly(vinyl alcohol) in a water/ N,N-dimethylformamide mixture media. Synthesized precursor nanoparticles have relatively monodisperse particles ranging 80 ~ 250nm. Stable spherical particles are obtained without coagulum or secondary particles in our system. The characteristic of the carbon nanoparticles were investigated in terms of surface area, morphology, and size distribution.

• Advances in materials Research
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• 제1권1호
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• pp.93-107
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• 2012

Epoxy resin is widely used in high voltage apparatus as insulation. Fillers are often added to epoxy resin to enhance its mechanical, thermal and chemical properties. The addition of fillers can deteriorate electrical performance. With the new development in nanotechnology, it has been widely anticipated that the combination of nanoparticles with traditional resin systems may create nanocomposite materials with enhanced electrical, thermal and mechanical properties. In the present paper we have carried out a comparative study on dielectric properties, space charge and dielectric breakdown behavior of epoxy resin/nanocomposites with nano-fillers of $SiO_2$ and $Al_2O_3$. The epoxy resin (LY556), commonly used in power apparatus was used to investigate the dielectric behavior of epoxy resin/nanocomposites with different filler concentrations. The epoxy resin/nanocomposite thin film samples were prepared and tests were carried out to measure their dielectric permittivity and tan delta value in a frequency range of 1 Hz - 1 MHz. The space charge behaviors were also observed by using the pulse electroacoustic (PEA) technique. In addition, traditional epoxy resin/microcomposites were also prepared and tested and the test results were compared with those obtained from epoxy resin/nanocomposites.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.217-224
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• 2021

In this study, Monte Carlo (MC) simulation is conducted with recurrence relation to study the effect of SiO₂ with different particle size and their roles in enhancing the ionic conductivity and lithium transference number of PMMA composite polymer electrolytes (CPEs). The MC simulated ionic conductivity is verified with the measurements from Electrochemical Impedance Spectroscopy (EIS). Then, the lithium transference number of CPEs is calculated using recurrence relation with the MC simulated current density and the reference transference number obtained. Incorporation of micron-size SiO₂ (≤10 ㎛) fillers into the mixture improves the ionic conductivity from 8.60×10^-5 S/cm to 2.35×10^-4 S/cm. The improvement is also observed on the lithium transference number, where it increases from 0.088 to 0.3757. Furthermore, the addition of nano-sized SiO₂ (≤12 nm) fillers further increases the ionic conductivity up towards 3.79×10^-4 S/cm and lithium transference number of 0.4105. The large effective surface area of SiO₂ fillers is responsible for the improvement in ionic conductivity and the transference number in PMMA composite polymer electrolytes.

• Transactions on Electrical and Electronic Materials
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• 제13권1호
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• pp.31-34
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• 2012

The addition of nano/micro silica into unsaturated polyester resin (UPR) results in the improvement of the electrical properties of Silica-UPR composites. The surface, volume resistivity, dielectric strength, dissipation factor and dry arc resistivity of nano silica-UPR composites were found to improve significantly. The effects of the nano and micro fillers in UPR have been evaluated. They are presented in this paper. To evaluate the electrical properties of the nano & micro composites, all the measurements were done as per the prescribed methods in ASTM. It was observed that the addition of nano silica improves the electrical properties as compared to micro silica. The better dispersion of silica particles in unsaturated polyester resin enhances the electrical properties of silica-UPR composites.

• 한국재료학회지
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• 제13권1호
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• pp.53-58
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• 2003

For the rib materials in PDP(plasma display panel), an effective method to improve the mechanical properties is to form a composite material by reinforcing a glass matrix with rigid fillers, such as alumina and titania powders. In this study, two types of ribs with different volume percent of fillers and with different glass matrix were tested for hardness, Young's modulus with the Berkovich indentation. As a result, cracks appeared around at the load of 1345 mN for the dense type of rib, while porous one endured until 2427 mN without any crack formation. Young's modulus and hardness decreased at the range: 90∼65 GPa, 9∼4 GPa, respectively as a function of indent load. Thus, a new method with nanoindenter represents a possible evaluation method for mechanical properties of barrier ribs.

• Design & Manufacturing
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• 제10권3호
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• pp.14-19
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• 2016

Thermally or electrically conductive filler reinforced polymer composites are extensively being developed as the demand for light weight material increases rapidly in industiral applications need good conductivity such as heat sink of the electronics or light. Carbon or ceramic materials like graphite, carbon nanotube or boron nitride are typical conductive fillers with good thermal or electical conductivity. Using these conductive fillers, the polymer composites in the market show wide range of thermal conductivity from approximately 1 W/mK to 20 W/mK, which is quite enhanced considering the thermal conductivity lower than 0.5 W/mK for most polymeric materials. The practical use of these composites, however, is yet limited to specific applications because most composites are still not conductive enough or too difficult to process, too brittle, too expensive for higher conductivity. For practical use of conductive composite, the thermal conductivity required depending on the heat releasing mode are studied first for simplified unit cooling geometry to propose thermal conductivities of the composites for reasonable cooling performance comparing with the metal heat sink as a reference. Also, as a practical design for heat sink based on polymer composite, composite and metal sheet hybrid structures are investigated for LED lamp heat sink and audio amplication module housing to find that this hybrid structure can be a good solution considering all of the cooling performance, manufacturing, mechanical performance, cost and weight.

• 폴리머
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• 제31권5호
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• pp.404-409
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• 2007

본 연구에서는 무기계 나노 분말을 충전하여 난연성이 우수한 폴리우레탄 나노복합재료를 우레탄 반응에 의해 제조하였다. 또한 나노복합재료의 난연특성을 콘 칼로리미터 분석과 한계산소지수 시험으로 확인하였다. MMT-PU와 $Bi_2O_3-PU$ 나노복합재료의 최대 열 방출속도는 모두 폴리우레탄 매트릭스보다 50% 감소하였으며, $MMT/Bi_2O_3-PU$ 복합재료의 난연 특성이 가장 우수하였다. 또한 한계산소지수도 충전제의 함량에 따라 감소하는 경향을 보였으며, 모두 20 이상이었다. 복합재료의 최대 열 방출속도는 폴리우레탄 매트릭스보다 모두 지연되었으며 최대 열 방출속도는 $Bi_2O_3-PU$, MMT-PU, $MMT/Bi_2O_3-PU$ 순으로 각각 764, 707, $635kW/m^2$ 이었으며, $MMT/Bi_2O_3-PU$ 복합재료의 난연성이 가장 우수하였다. 한편 폴리우레탄 나노복합재료의 연소시 충전제가 충전됨에 따라 $CO_2$ 생성량은 감소하였고 CO 생성량은 증가하였으며 이로부터 본 연구에서 제조한 복합재료의 난연성이 향상된 것을 확인하였다.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2002년도 봄 학술발표회 논문집
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• pp.321-324
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• 2002

Recently, organic-inorganic nanocomposites have attracted great interest from researchers since they frequently exhibit unexpected hybrid properties synergistically derived from two components[1]. The addition of highly dispersed inorganic nano-sized fillers permits improvement of certain properties of polymers as compared with conventional particulate composites; increase of modulus and strength, improved barrier properties, increase in solvent and heat resistance, and good optical properties[2]. (omitted)