• Korean Journal of Materials Research
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• v.10 no.12
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• pp.793-798
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• 2000

The age-hardening behavior of unreinforced 6061 Al alloy and SiCp/6061 Al alloy composites reinforced with different size of SiC particle (average diameter ; 0.7$\mu\textrm{m}$ and 7.0$\mu\textrm{m}$) was investigated by hardness measurement, calorimetric technique and transmission electron microscopy. At 17$0^{\circ}C$ isothermal aging treatment, the peak aging time of 0.7$\mu\textrm{m}$SiCp/6061Al alloy composite and 7.0$\mu\textrm{m}$SiCp/6061Al alloy composite is shorter than that of unreinforced 6061Al alloy, and the aging of 7.0$\mu\textrm{m}$SiCp/6061Al alloy composite is accelerated more than that of 0.7$\mu\textrm{m}$SiCp/6061Al alloy composite. This acceleration is due to the increase of dislocation density by the compositeness with SiCp and the SiC particle size. In the peak aged condition, the major strengthening phase of these materials is intermediate $\beta$ phase(Mg$_2$Si), and the activation energy for the formation of $\beta$ phase is considerably decreased by the compositeness with SiCp and the increasing of SiC Particle site.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.501-507
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• 2011

To develop environmental-friendly insulating composite materials, natural cellulose and porous ceramic balls were used as core materials and activated Hwangtoh was used as a binder. Various specimens were prepared with different water/binder ratios and core material/binder ratios. The physical properties of these specimens were then investigated through compressive strengths, flexural strengths, absorption test, hot water resistance test, pore analysis, thermal conductivity, and observation of micro-structures using scanning electron microscope. Results showed that the maximum compressive strength varied appreciably with the water/binder ratios and core material/binder ratios, but the flexural strength increased with the core material/binder ratios regardless of water/binder ratios. The compressive strength and the flexural strength measured after the hot water resistance test decreased remarkably compared to those measured before test. The pore analysis measured after the hot water resistance test showed that total pore volume, porosity and average pore diameter decreased, while bulk density increased by the acceleration of hydration reaction of binder in the hot water. The thermal conductivity decreased gradually with an increase of core material/binder ratios. It can be evaluated that the composite insulation materials having good insulating properties and mechanical strengths can be used in the field.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.407-410
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• 2018

As the operating frequency of an electromagnetic wave increases, the maximum output and wavelength of the wave decreases, so that the size of the circuit cannot be reduced. As a result, the fabrication of a circuit with high power (of the order of or greater than kW range) and terahertz wave frequency band is limited, due to the problem of circuit size, to the order of ${\mu}m$ to mm. In order to overcome these limitations, we propose a source design technique for 0.1 THz~0.3 GW level with cylindrical shape (diameter ~2.4 cm). Modeling and computational simulations were performed to optimize the design of the high-power electromagnetic sources based on Cherenkov radiation generation technology using the principle of plasma wakefield acceleration with ponderomotive force and artificial dielectrics. An effective design guideline has been proposed to facilitate the fabrication of high-power terahertz wave vacuum devices of large diameter that are less restricted in circuit size through objective verification.