• Carbon letters
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• v.15 no.3
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• pp.151-161
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• 2014

Exceptional progress has been made with chemical vapor deposition (CVD) of graphene in the past few years. Not only has good monolayer growth of graphene been achieved, but large-area synthesis of graphene sheets has been successful too. However, the polycrystalline nature of CVD graphene is hampering further progress as graphene property degrades due to presence of grain boundaries. This review will cover factors that affect nucleation of graphene and how other scientists sought to obtain large graphene domains. In addition, the limitation of the current research trend will be touched upon as well.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1410-1411
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• 2006

To improve density and smoothness of semiconducting materials in power cable, we have investigated those of semiconducting materials showed by changing the content of carbon black and Carbon Nanotube. They were produced as sheets after pressing for 20 minutes at $180[^{\circ}C]$ with a pressure of $200[kg/cm^2]$. The content of conductive carbon black and Carbon Nanotube were 30[wt%] and 2-6[wt%] respectively. As a result the smoothness was measured by JSM-6400.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1887-1889
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• 2005

To measure the mechanical and structural properties of semiconducting materials in power cable, we have investigated the stress-strain and fractural structure of semiconducting materials showed by changing the content of carbon black. Those were made as sheets after pressing for 20 minutes at $180[^{\circ}C]$ with a pressure of $200[kg/cm^2]$. The contents of conductive carbon black were 20, 30 and 40(wt%), respectively. The stress-strain experiment was measured by TENSOMETER 2000. The SEM experiment was measured by JSM-6400. From above experimental result, Strain was decreased, while stress was increased according to increment of carbon black content. EEA among resins was best the dispersion of carbon back in base resin from SEM measurement.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.199-204
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• 2003

The purpose of this study is to experimentally investigate the structural performance of concrete exterior beam-column joints confined by carbon sheet tube. Four specimens were produced with different numbers of carbon sheet and the other specimen was produced with reinforced concrete. A hydraulic dynamic actuator with 30tonf capacity was used to cyclic lateral loading test. The experimental results represent that the numbers of carbon sheet have an influence the load and displacement capacity. However, the bond length of carbon sheets for connecting beam and column has to be considered to improve the capacity of joint.

• Steel and Composite Structures
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• v.34 no.2
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• pp.261-277
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• 2020

The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.9-16
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• 2020

A CFRP sheet has been applied as a structural reinforcement in the field, and various studies are conducted to evaluate the effect of CFRP sheets on reinforced concrete. Although many experiments were performed from previous studies, there are still limitations to analyze structural behaviors with various parameters in experiments directly. This study shows the FEA on structural behaviors of RC beams reinforced with CFRP sheets using ABAQUS software. To simulate debonding failure of CFRP sheets which is a major failure mode of RC beam with CFRP sheets, a cohesive element was applied between the bottom surface of RC beam and CFRP sheets. Both quasi-static method and 2-D symmetric FE model technique were performed to solve nonlinear problems. Results obtained from the FE models show good agreements with experimental results. It was found that reinforcement level of CFRP sheets is closely related to structural behavior of reinforced concrete including maximum strength, initial stiffness and deflection at failure. Also, as over-reinforcement of CFRP sheets could give rise to the brittle failure of RCstructure using CFRP sheets, an appropriate measure should be required when installing CFRP sheets in the structure.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.23-28
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• 2019

We report a supercapacitor cable, which consists of three-dimensional (3D) porous graphene coated onto the surface of carbon thread. The 3D porous framework of graphene was constructed by microwave-activated process using a graphene oxide-coated carbon thread. The use of microwave irradiation enabled to convert graphene oxide into reduced graphene oxide without any reducing agents and activate graphene sheets into exfoliated and porous graphene sheets. Combining two wire electrodes with a polymer gel electrolyte successfully completed supercapacitor device in a form of cable construction. The supercapacitor cables were highly flexible, and thus can be transformed into various shapes of devices and be integrated into textile items. A high area-capacitance of 38.1 mF/cm was obtained at a scan rate of 10 mV/s. This capacitance was retained 88% of its original value at 500 mV/s. The cycle life was also demonstrated by repeating a charge/discharge process during 10,000 cycles even under bent states, showing a high capacitance retention of 96.5%.

• Journal of Welding and Joining
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• v.34 no.5
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• pp.1-5
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• 2016

The hardness of laser weldments has been predicted by using several carbon equivalent equations and estimation models. In this study, authors extended the model to boron steel sheets which are adopted for the hot press forming process. four kinds of boron steels with the strengths from 1500 MPa to 1900 MPa were considered and the hardness profiles of weldments was measured from the experiments of this study and the references. The traditional "Kaizu" equation could predict the hardness with an accuracy of -4.9% error although the Kaizu equation does not consider the boron content. Modified carbon equivalents were suggested by adding a term as like 5B or 14B into the Kaizu equation, and it could improve the accuracy of the prediction model.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.139-147
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• 1993

Two sheets of high strength cement paste using ordinary Portland cement and water soluble polymer (polyacrylamide) were made by kneading with a twin roll mill. A carbon fiber layer out between two sheet of the cement paste, and then carbon fiber reinforced high strength cement composites were prepared by pressing them. The mechanical properties of the composites were investigated through the observation of the microstructure and the application of fracture mechanics. When the carbon fiber was added with 0.2 and 0.3wt% to the composites the flexural strength and Young's modulus were about 110∼116MPa and 74∼77GPa respectively, and critical stress intensity was about 3.14MPam1/2. It can be considered that the strength improvement of high strength cement fiber composites may be due to the removal of macropores and the increase of various fracture toughness effects; grain bridging, frictional interlocking, polymer fibril bridging and fiber bridging.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1494-1496
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• 2000

We have studied the temperature dependence on the growth and structure of carbon nanotubes using thermal chemical vapor deposition. All the carbon nanotubes have bamboo shaped multi walled structure with closed tip. The growth rate and density of carbon nanotubes increase with increasing growth temperature. The numbers of graphite sheet at the wall increase with increasing growth temperature. The crystallinity of graphite sheets become enhanced at the high growth temperature.