• Composites Research
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• v.23 no.3
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• pp.7-12
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• 2010

In order to increase the electrical conductivity and the mechanical properties of carbon fabric composites, multi-walled carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) were deposited on carbon fabrics by anodic and cathodic electrophoretic deposition (EPD) processes. In the cathodic EPD, carbon nano-particles and nano-sized Cu particles were simultaneously deposited on the carbon fabric, which gave a synergetic effect on the enhancement of properties as well as the degree of deposition. The hybridization of carbon nano-particles and micron-sized carbon fiber significantly improved the through-the-thickness electrical conductivity. In addition, both MWCNTs and CNFs were deposited onto the carbon fabric for multi-scale hybrid composites. Multi-scale deposition improved the through-the-thickness electrical conductivity, compared to the deposition of either MWCNTs or CNFs.

• Tribology and Lubricants
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• v.39 no.3
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• pp.111-117
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• 2023

This paper presents an experimental investigation of the tribological characteristics of PTFE composites filled with nano CuO particles under low sliding speed and load. All the specimens were prepared by sintering. Before sintering, the mixture of PTFE powder and CuO particles were mixed by a high-speed mixer using CuO volume fractions of 0.2 vol. % and 5 vol. %. Each mixture was sintered at 350 ℃ for 30 min on the steel disk. We conducted ball-on-disk sliding test an hour using a steel ball against PTFE composites, including pure PTFE. The load and sliding speed used was 2 N and 0.01 m/s, respectively. Adding nano CuO particles increases the friction coefficient because of the abrasiveness of hard nano CuO particles. The highest coefficient of frictions was obtained from 5 vol. % CuO. Conversely, the lowest wear of the composites was obtained from the 5 vol. % CuO nanocomposite. This study reveals that the addition of nano CuO particles can lower the wear of PTFE, despite an increase in the coefficient of friction. However, the coefficient friction is still moderate compared to other engineering polymers. In addition, the amount of CuO nano particles has to be optimized to reduce friction and wear at the same time.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.26.2-26.2
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• 2010

최근에는 차세대 조명용 후보광원인 고출력 백색 LED를 개발하기 위한 경쟁이 치열하며, 이를 위해 업체가 고심하고 있는 가장 큰 문제 중의 하나가 칩에서 발생하는 열을 어떻게 관리하는가 하는 방열의 문제이다. 따라서, LED의 가장 큰 특징인 장수명을 손해보지 않기 위해서는 칩에서 발생되고 있는 열을 외부에 확산시키기 위한 기술 개발이 필수적이다. 다양한 방열소재 중 W-Cu 복합재는 W의 낮은 열팽창계수와 Cu의 높은 열전도도로 인해 방열소재로써 유망한 소재로 주목받고 있으나, 우수한 열적 특성을 발현하기 위해서는 고치밀화를 갖는 W-Cu 복합재 제조가 우선적으로 필요하다. W-Cu 복합체는 일반적으로 액상소결법을 통해 균일한 미세조직을 얻을 수 있으나, 열팽창계수를 낮추기 위해 Cu 함량이 적어지게 되면 치밀화가 어려우며 이를 해결하기 위해 나노입자를 갖는 분말을 이용하고자 하는 연구가 많이 진행되고 있다. 본 연구에서는 W과 Cu 산화물을 이용하는 것이 구성성분끼리의 편석이 발생하지 않으며, 소결성도 우수하여 양산화에 가장 접근한 방법으로 알려져 있다. 그러나, 지금까지의 얻어진 W-Cu 복합체의 경우, 분말상태에서의 얻어진 나노입자가 승온시에 마이크로 크기로 과도한 입자성장이 일어나기 때문에 소결 후에도 나노크기를 유지하기 어려울 뿐만 아니라, 구성상끼리의 응집체가 형성된다. 본 연구에서는 액상소결후에 W 입자가 Cu 기지내에 균일하게 분산되는 동시에 나노크기의 입자를 가지는 고분산 W-Cu 소결체를 얻고자 하였다. 이를 위해 금속산화물 분말의 분쇄를 위해 효과적인 방법으로 알려진 습식상태에서의 고에너지 볼밀링을 통하여 혼합된 텅스텐과 구리 산화물 분말의 수소환원공정을 통해 얻어진 100nm 이하의 입자를 가지는 W-20wt%Cu 나노복합분말을 출발분말로 사용하였다. W-20wt%Cu 나노복합분말의 성형체를 $1050^{\circ}C-1250^{\circ}C$의 온도범위에서 소결거동을 조사하였다. 그 결과, $1100^{\circ}C$ 온도에서 이론밀도에 가까운 소결밀도를 나타내었으며, 이는 기존에 비해 $100^{\circ}C$ 정도 치밀화 온도를 낮추는 결과이다. 소결체의 미세구조 관찰결과, 소결 후 약 200nm의 텅스텐 입자가 Cu내에 균일하게 분산되어 있었다. 제조된 W-Cu 시편에 대해서는 LED 응용성을 조사하기 위해 열전도도와 열팽창계수 등을 평가하였다.

• Polymer(Korea)
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• v.27 no.4
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• pp.275-284
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• 2003

The positive temperature coefficient (PTC) effects of high density polyethylene (HDPE)/carbon black composite materials were investigated by enhancing adhesive characteristics of electrodes and controlling HDPE chemical crosslinking. When the silver paste was used as an electrode for the same 45 wt% HDPE/carbon composites, the resistance was over 1 $\Omega$, which should be compared with the resistance of 0.2 $\Omega$ for the dendritic copper electrode. In general, the silver-paste electrode exhibited higher electrical resistance than cupper electrode due to the interfacial resistance between the electrode and PTC composites. The HDPE/carbon composite exhibited typical PTC characteristics maintaining a constant resistance up to vicat point and showing a maximum at the melting point of HDPE. The crosslinked HDPE significantly decreased the negative temperature coefficient (NTC) phenomena, and desirably showed a constant or slightly increasing feature of electrical resistance in the high temperature region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.887-894
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• 2013

Effective thermal conductivity of nanofluids has been predicted by using generalized self-consistent model and modified Eshelby model, which have been used for analysis of material properties of composites. A nanolayer between base fluid and nanoparticle, one of key factors for abrupt enhancement of thermal conductivity of nanofluids, is included in the analysis. The effective thermal conductivities of the nanofluid predicted by the present study show good agreement with those by models in the literature for the nanolayer with a constant or linear thermal conductivity. The predicted results by the present approach have been confirmed to be consistent with experiments for representative nanofluids such as base fluids of water or ethyleneglycol and nanoparticles of $Al_2O_3$ or CuO to be validated.

• Membrane Journal
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• v.30 no.3
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• pp.158-172
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• 2020

In the aspect of saving energy and water, facilitating the separation membrane for the water treatment has been rising recently as one of the possible solutions. However, microbial biofouling effect is the biggest obstacle that hinders reaching higher permeability over a prolonged period of nanofiltration operation. To solve this problem and fully utilize the filtration membranes with enhanced performance, largely two kinds of solutions are studied and the first and the most commonly mentioned type is the one using the silver nanoparticles. Since silver nanoparticles are important to be well tailored on membrane surface, various methods have been applied and suggested. Using silver nanoparticles however also has the drawbacks or possible toxicity risks, raising the need for other types of utilizing non silver particles to functionalize the membrane, such as copper, graphene or zinc oxides, and amine moieties. Each attempt included in either kind has produced some notable results in killing, preventing, or repelling the bacteria while at the same time, left some unsolved points to be evaluated. In this review, the effects of metal nanoparticles and other materials on the antifouling properties of water treatment membranes are summarized.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.479-487
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• 2023

Copper is cost-effective and abundantly available as a biocidal coating agent for a wide range of material surfaces. Natural oxidation does not compromise the efficacy of copper, allowing it to maintain antimicrobial activity under prolonged exposure conditions. Furthermore, copper compounds exhibit a broad spectrum of antimicrobial activity against pathogenic yeast, both enveloped and non-enveloped types of viruses, as well as gram-negative and gram-positive bacteria. Contact killing of copper-coated surfaces causes the denaturation of proteins and damage to the cell membrane, leading to the release of essential components such as nucleotides and cytoplasm. Additionally, redox-active copper generates reactive oxygen species (ROS), which cause permanent cell damage through enzyme deactivation and DNA destruction. Owing to its robust stability, copper has been utilized in diverse forms, such as nanoparticles, ions, composites, and alloys, resulting in the creation of various coating methods. This mini-review describes representative coating processes involving copper ions and copper oxides on various material surfaces, highlighting the antibacterial and antiviral properties associated with different oxidation states of copper.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.425-432
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• 2020

For this study copper ions-containing bioactive glass nanoparticles commonly used in mineral trioxide aggregate (MTA) was developed to improve the mechanical properties and promote antibacterial effect of MTA with the original material. The mechanical properties and antibacterial activity of Cu-BGn incorporating varying amounts cooper incorporated bioactive glass nano particles(BGn) 0.5,1.0,2.0 and 4.0 wt% in MTA were characterized composition of the resulting were investigated. The compressive strength was calculated by weighing specimens with a diameter of 4 mm and a thickness of 6 mm according to ISO 6876 (2012). The antimicrobial effect was evaluated using two strains of S. mutans and E. faecalis. The mechanical properties of the test results was Cu-BGn increased no statistically significant difference was observed (p>0.05). Adhesion experiment results S. mutans in contrast to the control group Ortho MTA, 4.0 wt% of Cu-BGn added experimental group showed a significant difference was observed (p<0.05). Also, E. faecalis statistical analysis indicated a significant difference for antibacterial agents between control and Cu-BGn containing(p<0.05). It seems that this Cu-BGn proved that even a antibacterial effect was demonstrated. Therefore, it was suggest that it is necessary for in-depth research into various environments that can reproduce the oral environment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.647-653
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• 2013

The evaporation characteristics of nanofluid droplets on a heated solid surface were experimentally investigated. The experiments were conducted using pure water and a nanofluid of water mixed with CuO nanoparticles, and the solid surface was made of a copper block heated by a nine cartridge heater. The experimental results showed that the evaporation rate of the nanofluid droplet was higher than that of the pure water droplet on the heated solid surface because nanoparticles increased the thermal conductivity of the nanofluid. Furthermore, it was found that the evaporation rate of the nanofluid droplet increased with the solid surface roughness. This may be because the actual area of the liquid-solid interface increased with the solid surface roughness.

• Journal of the Korean Wood Science and Technology
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• v.40 no.3
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• pp.212-227
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• 2012

Current research trends in wood preservatives for enhancing durability was reviewed. Due to leaching of recent Copper-Based Preservatives commonly used as chemicals for pressure treatment; they have been a growing concern, especially in improving the fixation of the copper as alkyl ammonium quat. and azol in wood and preventing the leaching of active ingredients. With the appearance of emulsion type chemicals using micronized and nano-sized wood preservatives, researchs on characteristics of Copper-Based Preservatives regarding penetration and fixation in wood are debatable. Moreover, unlike the case of CCA, the recent alkyl ammonium quat. and azol bear a serious threat in the decrease of antimicrobial effectiveness against wood destroying fungi with copper tolerance. Therefore, development and research of co-biocide is needed.