• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.1
• /
• pp.86-91
• /
• 2021

In order to save the energy in vehicles using renewable energy, it is necessary to reduce the weight of parts with polymer matrix composites. Carbon nanotube (CNT) is the nano-scale reinforcement used to increase the interlaminar strength of fiber reinforced composites or enhance the fracture toughness of polymer. However, since the degree of improvement in mechanical properties varies according to the various experimental conditions such as shape of reinforcement, types of matrix and dispersion of reinforcement, research to find the optimal conditions is essentially needed. In this study, CNT/epoxy composites with different CNT concentration were fabricated under the same conditions, and the optimal CNT content (2 wt%) was found through Mode 1 fracture toughness test. Furthermore, through optical microscopy, it was confirmed that the fracture toughness was rather decreased due to the CNT aggregation when the CNT content exceeded 2 wt%.

• Composites Research
• /
• v.31 no.3
• /
• pp.111-116
• /
• 2018

In this paper, magnetic FeCoNi particles have been grown through electroless plating on the surface of graphene, and then this hybrid material has been dispersed by various surfactants to prepare films. The pyridine surfactant shows the highest dispersability and low surface resistance value (351 Ohm/sq) and the electromagnetic shielding ability at the frequency of 10 GHz. Specially, the evaporation of the pyridine during the drying process could be able to form the internal conductive network and high dispersion of FeCoNi on the surface of graphene.

• Composites Research
• /
• v.30 no.1
• /
• pp.59-64
• /
• 2017

Eco-convivial composites with improved properties are essential to present polymer scenario and can be made easily by replacing partially/completely renewable materials either matrix or reinforcement along with few % of additives. In these investigations, Abaca fabric have been used as reinforcement for manufacturing of Vinyl ester composites through VARTM technique and study the effect of alkali surface treatment of abaca fabric and flame retardant additives i.e., ammonium polyphosphate (APP) with halloysite nano-clay (HNT) on mechanical and flame retardant properties. The results concluded that, surface treatment deceased the hydrophilic nature of fabric and enhanced the interfacial bonding with hydrophobic matrix and eventually increased mechanical properties slightly of developed composites. Similarly, the flame retardancy of the composites improved significantly and increases the burning time by varying the wt% of filler concentration.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.9
• /
• pp.999-1005
• /
• 2011

The effects of strain-induced crystallization (SIC) on the mechanical properties of elastomeric composites as functions of extension ratio (${\lambda}$), multiwalled carbon nanotube (CNT) content, and carbon black (CB) content are investigated. The differential scanning calorimetry (DSC) analysis shows that the degree of crystallinity increases with the increase in the CB and CNT content. As ${\lambda}$ increases, the glass transition temperature (Tg) of the composites increases, and the latent heat of crystallization (LHc) of the composites is maximum at ${\lambda}$=1.5. It is found that the mechanical properties have a linear relation with LHc, depending on the CNT content. According to the TGA (thermogravimetric analysis), the weight loss of the composite matrix is 94.3% and the weight of the composites decreases with the filler content. The ratio of tensile modulus ($E_{comp}/E_{matrix}$) is higher than that of tensile strength (${\sigma}_{comp}/{\sigma}_{matrix}$) because of the CNT orientation inside the elastomeric composites.

• Composites Research
• /
• v.31 no.6
• /
• pp.398-403
• /
• 2018

Recently, environmental pollution caused by plastic waste, ecosystem disturbance of micro-plastics and human body accumulation are becoming big problems. In order to replace the traditional plastic, eco-friendly resin and natural fiber-based composite materials have been developed, but they have a disadvantage that their mechanical properties are significantly lower than those of synthetic fiber-based composites. In this study, eco - friendly nanofiber was extracted from seaweed and used as an additive in order to improve the mechanical properties of jute fiber-reinforced composites. Through the hand lay-up process, the composites were fabricated, and it was confirmed that the nanofiber was effective in improving the mechanical properties of natural fiber composites through tensile, bending and drop weight impact tests.

• Transactions on Electrical and Electronic Materials
• /
• v.10 no.3
• /
• pp.97-101
• /
• 2009

The use of a filler material in epoxy composite materials is an essential condition for reducing the unit cost of production and reinforcing mechanical strength. However, the dielectric strength of insulators decreases rapidly due to interactions between the epoxy resin and filler particles. In contrast to existing composite materials, nano-composite materials have superior dielectric strength, mechanical strength, and enduring chemical properties due to an increase in the bond strength of the polymer and nano material, It is reported that nano-fillers provide new characteristics different from the properties of the polymer material. This study is to improve the insulation capability of epoxy resins used in the insulation of a power transformer apparatus and many electronic devices mold. To accomplish this, the additional amount of nano-$SiO_2$ to epoxy resin was changed and the epoxy/$SiO_2$ nano composite materials were made, and the fundamental electrical properties were investigated using a physical properties and an analysis breakdown test. Using allowable breakdown probability, the optimum breakdown strength for designing an electrical apparatus was determined. The results found that the electrical characteristics of the nano-$SiO_2$ content specimens were superior to the virgin specimens. The 0.4 wt% specimens showed the highest electrical properties among the specimens examined with an allowable breakdown probability of 20 %, which indicates stable breakdown strength in insulating machinery design.

• Journal of the Korean Physical Society
• /
• v.73 no.10
• /
• pp.1437-1443
• /
• 2018

In this work, $SnO_2$ modified with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) separately and combined sensitized by using the co-precipitation method and their sensing behavior toward ethanol vapor at room temperature were investigated. An interdigitated electrode (IDE) gold substrate is very expensive compared to a fluorine doped tin oxide (FTO) substrate; hence, we used the latter to reduce the fabrication cost. The structure and the morphology of the studied materials were characterized by using differential thermal analyses (DTA) and thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller surface area and Barrett-Joyner-Halenda (BJH) pore size measurements. The studied composites were subjected to ethanol in its gas phase at concentrations from 10 to 200 ppm. The present composites showed high-performance sensitivity for many reasons: the incorporation of $SnO_2$ and CNTs which prevents the agglomeration of rGO sheets, the formation of a 3D mesopourus structure and an increase in the surface area. The decoration with rGO and CNTs led to more active sites, such as vacancies, which increased the adsorption of ethanol gas. In addition, the mesopore structure and the nano size of the $SnO_2$ particles allowed an efficient diffusion of gases to the active sites. Based on these results, the present composites should be considered as efficient and low-cost sensors for alcohol.

• Restorative Dentistry and Endodontics
• /
• v.39 no.2
• /
• pp.109-114
• /
• 2014

Objectives: Recurrent caries was partly ascribed to lack of antibacterial properties in composite resin. Silver and zinc nanoparticles are considered to be broad-spectrum antibacterial agents. The aim of the present study was to evaluate the antibacterial properties of composite resins containing 1% silver and zinc-oxide nanoparticles on Streptococcus mutans and Lactobacillus. Materials and Methods: Ninety discoid tablets containing 0%, 1% nano-silver and 1% nano zinc-oxide particles were prepared from flowable composite resin (n = 30). The antibacterial properties of composite resin discs were evaluated by direct contact test. Diluted solutions of Streptococcus mutans (PTCC 1683) and Lactobacillus (PTCC 1643) were prepared. 0.01 mL of each bacterial species was separately placed on the discs. The discs were transferred to liquid culture media and were incubated at $37^{\circ}C$ for 8 hr. 0.01 mL of each solution was cultured on blood agar and the colonies were counted. Data was analyzed with Kruskall-Wallis and Mann-Whitney U tests. Results: Composites containing nano zinc-oxide particles or silver nanoparticles exhibited higher antibacterial activity against Streptococcus mutans and Lactobacillus compared to the control group (p < 0.05). The effect of zinc-oxide on Streptococcus mutans was significantly higher than that of silver (p < 0.05). There were no significant differences in the antibacterial activity against Lactobacillus between composites containing silver nanoparticles and those containing zinc-oxide nanoparticles. Conclusions: Composite resins containing silver or zinc-oxide nanoparticles exhibited antibacterial activity against Streptococcus mutans and Lactobacillus.

• Journal of Powder Materials
• /
• v.18 no.2
• /
• pp.188-195
• /
• 2011

The aim of this study was to investigate microstructures and mechanical properties of nano-sized Ti-35 wt.%Nb-7 wt.%Zr-10 wt.%CPP composite fabricated by high energy mechanical milling (HEMM) and pulse current activated sintering (PCAS). Grain growth of the mechanically milled powder was prevented by performing PCAS. The principal advantages of calcium phosphate materials include: similarity in composition to the bone mineral, bioactivity, osteoconductivity and ability to form a uniquely strong interface with bone. The hardness and wear resistance property of nano-sized Ti-35 wt.%Nb-7 wt.%Zr-10 wt.%CPP composites increased with increasing milling time because of decreased grain-size of sintered composites.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.2
• /
• pp.94-101
• /
• 2017

Tow Prepreg is the intermediate material for filament winding process that has been "pre-impregnated fiber tow" with resin system. As "dry filament winding" process emerges as a reliable alternative to conventional filament winding (called "wet filament winding") process, interest in tow prepreg as a material for dry filament winding is rising as well. In this article, we have reviewed the recent research trends in carbon fiber tow prepreg for high-performance rocket motor cases, fuel tanks for hydrogen vehicles and other high-quality commercial pressure vessels.