2012, Vol.22, No.5

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

Carbon coils could be synthesized on nickel catalyst layer-deposited silicon oxide substrate using C2H2 and H2 as source gases under thermal chemical vapor deposition system. By the incorporation of SF6 additive in cyclic modulation manner,the dominant formation of the nanosized carbon coils could be achieved with maintaining the minimized sulfur additive amount. The geometry variation of the as-grown carbon coils, such as linear type, microsized coil type, wavelike nanosized coil type,and nanosized coil type, were investigated according to the different cyclic modulation manner of SF6 flow. SF6 gas incorporation develops the coil-type geometry. Furthermore, the higher flow rate of SF6 gas increased the amount of the nanosized carbon coils. The slightly increased etching ability by SF6 addition seems to be the cause for these results.

FeNi alloy nanofibers have been prepared by an electrospinning process followed by air-calcination and H2reduction to develop electromagnetic (EM) wave absorbers in the giga-hertz (GHz) frequency range. The thermal behavior and phase and morphology evolution in the synthetic processes were systematically investigated. Through the heat treatments of calcination and H2 reduction, as-spun PVP/FeNi precursor nanofiber has been stepwise transformed into nickel iron oxide and FeNi phases but the fibrous shape was maintained perfectly. The FeNi alloy nanofiber had the high aspect ratio and the average diameter of approximately 190 nm and primarily composed of FeNi nanocrystals with an average diameter of ~60 nm. The FeNi alloy nanofibers could be used for excellent EM wave absorbing materials in the GHz frequency range because the power loss of the FeNi nanofibers increased up to 20 GHz without a degradation and exhibited the superior EM wave absorption properties compared to commercial FeNi nanoparticles.

There are many restrictions in conventional ways of Jewelry mass production which are Mokume Gane, Inlaid Technology based on a joining work of dissimilar metals. To overcome this, Multi-Casting using both Jewelry-Casting and CAD/CAM has presented. In experiment on Muti-Casting, second original sample which was produced by CAD/CAM is 5 % smaller than first one. The first and second castings are brass and silver, respectively. When making second sample,the temperature of flask was about 150~200oC higher than the standard temperature of flask when making castings. Through the Multi-Casting, it was found that there was no trouble making dissimilar metals Jewelry which can be mass produced.