• 펄프종이기술
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• 제46권4호
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• pp.1-10
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• 2014

In papermaking industry, inorganic fillers are widely used for the purpose of improving opacity, brightness, printability, uniformity and dimensional stability. They are also useful for production costs and energy savings. In the past, inorganic fillers in papermaking industry only focused on micro-scale but recently, new trials on nano-powdered technology are applying. Even nano-powdered fillers are rapidly utilized for improving the optical and surface properties in coating and surface sizing, there still have some problems in wet-end process due to poor dispersibility and retention. In this study, nano-particled calcium carbonate was produced by milling the PCC and its applicability between micro sized and nano sized calcium carbonated was compared in wet-end process, and finally the sheet properties were evaluated. Nano-PCC was not retained in sheet structure without applying retention system, but with retention system nano-powdered PCC was absorbed on fiber surface with expanding the fiber networks. The application of PAM-bentonite system has resulted in high ash retention and bulky structure for copier paper, and good optical properties in brightness and opacity. However, it required to solve the weakness of low tensile property due to interruption of hydrogen bonding by nano fillers.

• 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.

• 한국수소및신에너지학회논문집
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• 제25권1호
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• pp.28-38
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• 2014

The organic-inorganic composite membrane in polymer exchange membrane fuel cells (PEMFCs) have several fascinating technological advantages such as a proton conductivity, thermal stability and mechanical properties. As the inorganic filler, silicon carbide (SiC) fiber have been used in various fields due to its unique properties such as thermal stability, conductivity, and tensile strength. In this study, composite membrane was successfully fabricated by modified-silicon carbide fiber. Modified process, as a novel process in SiC, takes reaction by phosphoric acid after oxidation process (generated homogeniusly $SiO_2$ layer on SiC fiber). The mechanical property which was conducted by tensile test of the 5wt% modified-$SiO_2@SiCf$ composite membrane was better than that of Aquivion casting membrane as well as ion cxchange capacity(IEC) and proton conductivity. In addition, the single cell performance was observed that the 5wt% modified-$SiO_2@SiCf$ composite membrane was approximately $0.2A/cm^2$ higher than that of a Aquivion casting electrolyte membrane and electrochemical impedance was improved with the charge transfer resistance and membrane resistance.

• Advances in materials Research
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• 제2권1호
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• pp.37-49
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• 2013

The transition metal salt doped solid polymer electrolyte [TSPE] were prepared with HPMC as a host polymer. The virgin and doped films were prepared by solution-casting method and investigated using wide angle X-ray scattering method. Micro structural parameters like lattice strain (g%), stacking/twin faults, the average number of unit cells counted in a direction perpendicular to the Bragg's plane (hkl) spacing of (hkl) planes dhkl, crystallite size Ds, distortion width, standard deviation were determined by whole pattern powder fitting (WPPF) method, which is an extension of single order method. It is found that the crystallite size decreases with the increase in the content of $FeCl_3$. This decrease is due to increase in localized breaking of polymer network which also accounts for the amorphous nature of the material. The filler inorganic salt $FeCl_3$ acts as plasticizer. FTIR study also confirms and justifies the interaction between the polymer and in-organic salt in the matrix. Physical properties like mechanical stability and Ac conductivity in these films are in conformity with the X-ray results.

• 대한심미치과학회지
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• 제7권1호
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• pp.18-26
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• 1998

The improvement of esthetic dentistry has been accelerated from the development of composite resin and dentin-enamel adhesive since 1980's. The indirect composite resin restorations have more accurate proximal contact point and occlusal form than direct restoration. And the side effect of resin shrinkage is minimal because the amount of composite used in oral cavity is limited in cement space. As a results, marginal leakage, hypersensitivity, secondary caries, and discoloration are significantly diminished. The first generation laboratory composite resin used in indirect resin restoration had been widespread in 1980's and the second generation laboratory composite resins were developed in 1990's. The second generation laboratory composite resins are called Ceramic Polymer. The physical properties of Ceramic Polymer are improved because of high content of inorganic filler, and the esthetics and biocompatibility are better than that of the first generation resin. So the application range using composite resin have been broadened. The purpose of this paper is to introduce Targis & Vectris system that is classified to second generation laboratory composite and to report several cases in which the system was utilized for restoration.

• 한국조명전기설비학회지:조명전기설비
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• 제7권6호
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• pp.42-50
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• 1993

본 논문에서는 플랜트 모델에 불확실성이 존재하는 경우에도 강인 안정도를 보장하는 제어기 설계 문제를 연구하였다. 먼저 강인 안정도 및 감도 특성을 특이치 한계를 이용하여 기술하고 이들 설계 조건을 만족하는 제어기 설계 기법을 Diophantine 방정식과 감도 평가 함수의 최소화에 의해 제시하였다. Diophantine 방정식의 해를 구하기 위해 칼만 필터의 설계와 필터의 주파수 역 특성을 조사하였고, 원하는 특이치 형성을 통해 저감도 특성을 만족하는 특성 다항식 행렬을 구하였다. 그리고 제어기에 설계 자유도를 주어 감도 평가 함수를 최소화하는 제어기 매개 변수 계산 방법을 Routh 배열을 이용하여 제시하였다.제안된 강인한 제어기 설계 기법을 모델에 적용하여 검토해 본 결과 만족스러운 결과를 얻을 수 있었다.

• 한국조명전기설비학회지:조명전기설비
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• 제7권2호
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• pp.51-56
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• 1993

Epoxy 복합재료의 충전제 및 수분함유의 유전특성에 대한 영향을 고찰한 결과를 요약하면 다음과 같다. 1) ${\varepsilon}_\tau$의 주파수 의존성은 시편1과 시편2의 경우에서 $140^{\circ}C$이하에서 직선적인 특성을 나타내고 있으며 수분의 함유시에도 직선적인 변화를 하고 있으므로 주파수나 습도 센서소자로서 개발이 가능하다. 2) 100[Hz]~3[kHz]의 범위에서 $tan{\delta}$ 주파수 의존성은 캐리어 이동에 의한 도전손실 보다 쌍극자완화에 의한 손실이 지배적이며 수분에 영향은 낮은 주파수에서 크게 받는다.

• 한국재료학회지
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• 제9권4호
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• pp.409-413
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• 1999

Recently, the polymeric insulators have been accepted in several countries for the outdoor high voltage applications. In comparison with the conventional porcelain, polymeric insulators offer various advantages such as light weight, superior vandal resistance and better contamination performance. The outdoor polymeric insulating materials such as silicone rubber, ethylene propylene diene monomer(EPDM), ethylene vinyl acetate(EVA) and epoxy are aged such as silicone rubber, ethylene propylene diene monomer(EPDM), ethylene vinyl acetate(EVA) and epoxy are aged under the various natural environment with the long-term performance in outdoor. In this paper, the effects of UV-under the various natural environment with the long-term performance in outdoor. In this paper, the effects of UV-ray on the surface of silicone rubber were investigated by using the weather-Ometer. The accelerated aging stresses were simulated by UV radiation, high temperature and humidity as well as water spray. These aging characteristics were examined through contact angle measurements, tracking resistance test, FT-IR and SEM/EDS analysis. The experimental results showed that tracking resistance decreases with increase in the UV-ray irradiation period. But the surface of silicone rubber kept hydrophobicity. It is found that the inorganic filler such as)$ Al(OH_3$ improves tracking resistance and the $Tio_2$is very effective in preventing degradation of silicone rubber surface from UV-ray.

• 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.

• 한국세라믹학회지
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• 제43권8호
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• pp.486-491
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• 2006

A new $TiN-Ti_5Si_3$ bulk composite was synthesized from preceramic, inorganic polymer (methylpolysilsesquioxane) and $TiH_2$ filler powders via polymer pyrolysis. Using this process, ceramics with high melting points can be produced relatively easily to a near net shape. The $TiN-Ti_5Si_3$ composite oxidized slowly during heating to $1000^{\circ}C$. During heating at the temperatures of at 700 and $800^{\circ}C$, TiN oxidized to Rutile-$TiO_2$ whereas $Ti_5Si_3$ resisted to oxidation. The oxide scale formed consisted primarily of $TiO_2$ containing $Ti_5Si_3$.