• Journal of the Korean Wood Science and Technology
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• 제34권5호
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• pp.59-66
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• 2006

The thermal properties of wood flour, Hwangto, and maleated polyethylene (MAPE) reinforced HDPE composites were investigated in this study. The thermal behavior of reinforced wood polymer composites was characterized by means of thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses. Hwangto and MAPE were used as an inorganic filler and a coupling agent, respectively. According to TGA analysis, the increase of wood flour level increased the thermal degradation of composites in the early stage, but decreased in the late stage. On the other hand, Hwangto reinforced composites showed the higher thermal stability than virgin HDPE, from the determination of differential peak temperature ($DT_p$). Decomposition temperature of wood flour and/or Hwangto reinforced composites increased with increase of heating rate. From DSC analysis, melting temperature of reinforced composites little bit increased with the addition of wood flour or Hwangto. As the loading of wood flour or Hwangto to HDPE increased, overall enthalpy decreased. It showed that wood flour and Hwangto absorbed more heat energy for melting the reinforced composites. Hwangto reinforced composites required more heat energy than wood flour reinforced composites and virgin HDPE. Coupling agent gave no significant effect on the thermal properties of composites. Thermal analyses indicate that composites with Hwangto are more thermally stable than those without Hwangto.

• Composites Research
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• 제28권6호
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• pp.333-339
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• 2015

무전해 도금을 통해 제조한 FeCo 자성 금속 중공형 섬유와 EPDM 고분자를 이용하여 전자파 차폐 복합재를 제작하였다. 열처리 공정을 통하여 섬유의 종횡비를 제어하였으며 중공형 구조로 섬유를 제조한 후, 이를 EPDM 수지에 첨가하여 복합재를 제조하였다. 자성 금속 중공형 섬유의 종횡비가 클수록 낮은 표면 저항 특성과 우수한 전자파 차폐 성능을 나타내었다. 약 $100{\mu}m$ 길이의 자성 금속 중공형 섬유를 이용한 두께 $150{\mu}m$ 전자파 차폐 복합재의 경우 밀도 $1.18g/cm^3$, 약 30 ohm/sq의 표면 저항, 그리고 30 dB의 전자파 차폐 성능을 나타내었다. 이는 종횡비가 큰 섬유에 의한 퍼콜레이션 임계치 이상의 전도성 네트워크 형성과 더불어, 낮은 표면 저항에 기인한 임피던스 차이에 의한 반사 손실 증가, 흡수 손실, 그리고 다중 내부 반사 손실에 의하여 우수한 전자파 차폐 성능을 나타내는 것으로 판단된다.

• Journal of the Korean Wood Science and Technology
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• 제35권2호
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• pp.69-78
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• 2007

The mechanical properties of wood flour, Hwangto (325 and 1,400 mesh per 25,4 mm) and coupling agent-reinforced HDPE composites were investigated in this study. Hwangto and maleated polyethylene (MAPE) were used as an inorganic filler and a coupling agent, respectively. The addition of Hwangto and MAPE to virgin HDPE also increased the Young's modulus in the smaller degree. The addition of wood flour and Hwangto to virgin HDPE increased the tensile strength, due to the high uniform dispersion of HDPE by high surface area of Hwangto in HDPE and wood flour. MAPE also significantly increased the tensile strength. When wood flour was added, there was no notable difference on the tensile properties, in terms of Hwangto particle size. Hwangto also improved the flexural modulus and strength of reinforced HDPE composites. With different particle sizes of Hwangto, there was no considerable difference in flexural modulus and strength of reinforced HDPE composites. The addition of Hwangto showed slightly lower impact strength than that of wood flour. However, the particle size of Hwangto showed no significant effect on the impact strength of reinforced composites. In conclusion, reinforced HDPE composites with organic and inorganic fillers provide highly improved mechanical properties over virgin HDPE.

• Journal of the Korean Wood Science and Technology
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• 제32권6호
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• pp.67-73
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• 2004

The influence of liquefied wood (LW) on the mechanical and thermal properties of liquefied wood-polymer composites (LWPC) was investigated in this study. The thermal behaviors of LWPC were characterized by means of thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses. LW showed significant effects on the mechanical strength properties. The increase of flexural MOE and Young's modulus was related to the increase of stiffness of LWPC. The effect of LW was also significant on the flexural and tensile MOR. The impact strength decreased with the increase of LW application level. With the increased stress concentration by the poor bonding between LW and polymer, the impact strength of LWPC decreased, compared with that of high-density polyethylene (HDPE). The thermal stability of LWPC decreased with the increase of LW content up to 40%. The melting temperature of HDPE decreased with the increase of LW loading level. Enthalpy of HDPE also decreased with the addition of LW. This study proves the thermal stability necessary for the consolidation of composition materials.

• 대한금속재료학회지
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• 제49권8호
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• pp.614-618
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• 2011

Nanopowders of MgO, $Al_2O_3$ and $SiO_2$ were made by high energy ball milling. The rapid sintering of nanostructured $MgAl_2O_4-Mg_2SiO_4$ composites was investigated by a high-frequency induction heating sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. As nanomaterials possess high strength, high hardness, excellent ductility and toughness, undoubtedly, more attention has been paid for the application of nanomaterials. Highly dense nanostructured $MgAl_2O_4-Mg_2SiO_4$ composites were produced with simultaneous application of 80MPa pressure and induced output current of total power capacity (15 kW) within 2min. The sintering behavior, gain size and mechanical properties of $MgAl_2O_4-Mg_2SiO_4$ composites were investigated.

• 한국재료학회지
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• 제31권6호
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• pp.345-352
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• 2021

In this study, Ni nanoparticle supported by graphene oxide (GO) (Ni-GO) is successfully synthesized through hydrothermal synthesis and calcination, and Cr(VI) is extracted from aqueous solution. The morphology and structure of Ni-GO composites are characterized by scanning electron microscopy (SEM), trans mission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HRTEM) and XRD confirms the high dispersion of Ni nanoparticle after support by GO. Loading Ni on GO can obviously enhance the stability of Ni-GO composites. It can be calculated from TGA that the mass percentage of Ni is about 60.67 %. The effects of initial pH and reaction time on Cr(VI) removal ability of Ni-GO are investigated. The results indicate that the removal efficiency of Cr(VI) is greater than that of bared GO. Ni-GO shows fast removal capacity for Cr(VI) (<25 min) with high removal efficiency. Dynamic experiments show that the removal process conforms to the quasi-second order model of adsorption, which indicates that the rate control step of the removal process is chemical adsorption. The removal capacity increases with the increase of temperature, indicating that the reaction of Cr(VI) on Ni-GO composites is endothermic and spontaneous. Combined with tests and characterization, the mechanism of Cr(VI) removal by rapidly adsorption on the surface of Ni-GO and reduction by Ni nanoparticle is investigated. The above results show that Ni-GO can be used as a potential remediation agent for Cr(VI)-contaminated groundwater.

• Elastomers and Composites
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• 제45권2호
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• pp.80-86
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• 2010

탄소나노튜브는 우수한 기계적 특성, 전기적 및 자기적 성질 뿐만 아니라 나노 크기의 직경 및 높은 종횡비를 나타낸다. 이는 고강도 고분자 복합체의 이상적인 보강제로 사용할 수 있다. 기능성이 부과된 탄소나노튜브는 기능성 재료 및 복합재료의 제조와 같은 분야에서 아주 유력한 재료로 믿어진다. 탄소나노튜브-고분자 복합체는 탄소나노튜브의 우수한 기능성과 고분자의 우수한 가공성을 가질 것으로 기대된다. 그러나, 탄소나노튜브는 보통 반 델 바알스 작용에 의한 안정화된 번들을 형성하기 때문에 고분자 기지에 배열이나 분산이 상당히 어렵다. 탄소나노튜브 강화복합체의 제조에서 가장 큰 이슈는 고분자내에 탄소나노튜브의 효과적인 분산이며, 기지내에 탄소나노튜브의 배열과 양의 조절이다. 고분자 기지내에 탄소나노튜브의 분산은 용액혼합, 벌크 혼합, 용융혼합, 즉시 고분자화 반응 및 탄소나노튜브의 화학적 기능화 등과 같은 몇 가지 방법이 있다. 본 논평에서는 이들 방법과 고성능 탄소나노튜브-고분자 복합체의 제조에 대하여 서술하고자 한다.

• 센서학회지
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• 제29권1호
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• pp.45-50
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• 2020

Magnetoelectric (ME) composites were designed using the PMN-PZT single crystal and Ni foils; the properties and magnetic-field sensitivities of ME composites with different piezoelectric vibration modes (i.e., 31, 32, and 36 modes that depend on the crystal orientation of the single crystal) were compared. In the off-resonance condition, the ME coupling properties of the ME composites with the 32 and 36 piezoelectric vibration modes were better than those of the ME composites with the 31 piezoelectric vibration mode. However, in the resonance condition, the ME coupling properties of the ME composites were almost similar, irrespective of the piezoelectric vibration mode. Additionally, in the off-resonance condition (at 1 kHz), the magnetic-field sensitivity of the ME composites with the 36 piezoelectric vibration mode was up to 2 nT and those of the ME composites with the 31 and 32 piezoelectric vibration modes were up to 5 nT. These magnetic-field sensitivities are similar to those offered by conventional high-sensitivity magnetic-field sensors; the potential of the proposed sensor to replace costly and bulky high-sensitivity magnetic field sensors is significant.

• Elastomers and Composites
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• 제55권3호
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• pp.167-175
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• 2020

Various studies have been conducted to improve silica dispersion of silica filled tire tread compounds; among them, silica wet masterbatch (WMB) technology is known to be suitable for manufacturing silica filled compounds that have high silica content and high dispersibility. Till now, the WMB study is focused on the natural rubber (NR) or emulsion styrene-butadiene rubber (ESBR) that does not have a silica-affinity functional group, and a study of NR or ESBR having a silica-affinity functional group is still not well known. Unlike the dry masterbatch technology, the WMB technology can solve the problems associated with the high Mooney viscosity when applied to silica-friendly rubber. However, a coagulant suitable for each functional group has not yet been determined. Therefore, in this study, different coagulant applied silica WMB was prepared by applying calcium chloride, sulfuric acid, acetic acid, and propionic acid by using a carboxyl group functionalized reversible addition fragmentation chain transfer ESBR. The evaluation of the WMB compounds revealed that the calcium chloride added WMB compound showed excellent silica dispersion, abrasion resistance, and rolling resistance.

• 폴리머
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• 제29권1호
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• pp.32-35
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• 2005

탄소나노튜브를 오존처리한 후 이를 사용하여 탄소나노튜브/고밀도 폴리에틸렌 전도성 복합재료를 제조하였고, 오존처리된 탄산나노튜브가 positive temperature coefficient(PTC) 세기에 미치는 영향을 조사하였다. 원소분석(EA)과 FT-IR 분석 결과, 오존처리된 탄소나노튜브의 표면에는 O-H, C=O 그리고 C-O와 같은 산소함유 관능기가 증가하는 것을 확인할 수 있었다. 또한, 전도성 복합재료의 온도에 따른 저항성은 디지털 멀티메타를 이용하여 측정하였다. 복합재료의 저항성은 고밀도 폴리에틸렌의 결정 용융 온도에서 증가하였으며, 이는 복합재료의 매트릭스로 사용된 고밀도 폴리에틸렌의 열팽창성에 의한 전도성 네트워크의 파괴때문인 것으로 판단된다. 그리고 탄소나노튜브에 오존처리 시간이 증가할수록 탄소나노튜브/고밀도 폴리에틸렌 복합재료의 PTC 세기는 증가했고, 이는 오존처리에 의한 탄소나노튜브 표면에 산소함유 관능기는 PTC 소자의 최대 비저항 값을 증가시키기 때문인 것으로 판단된다.