2020, Vol.30, No.6

Carbon Letters 2023 KCI Impact Factor : 1.35 KCI-WoS Impact Factor : 6.04

pISSN : 1976-4251 / eISSN : 2233-4998
https://journal.kci.go.kr/carbon

We report the structural characterization and electric heating performance of carbon thin flms (CTFs), which were prepared from negative-type SU-8 photoresist by deep UV exposure and following carbonization. The prepared CTFs were found to have pseudo-graphitic carbon structures containing partially graphite domains in the amorphous carbon matrix. The CTFs showed a very smooth surface morphology with a roughness of 0.42 nm. The 107 nm-thick CTFs exhibited an excellent electric heating performance by attaining a high maximal temperature of 207 °C and a rapid heating rate of 13.2 °C/s at an applied voltage of 30 V. Therefore, the CTFs prepared in this study can be applied as electrode materials for high-performance electric heaters.

Upgraded activated carbons (ACs) are typically synthesized by mixed methods, such as solid–solid mixing and wet impregna�tion of low-grade ACs with KOH. This study compares the properties of upgraded ACs prepared by diferent methods using elemental analysis, X-ray photoelectron spectroscopy, N2 adsorption isotherms, and X-ray difraction. In ACs produced by the solid–solid mixing, the ratio of potassium activator is proportional to the surface area and amount of gas produced. However, in wet impregnated ACs, the potassium ratio exhibits a zero or negative correlation. It is demonstrated that potassium ions in solution are not transferred to K2O and do not contribute to the surface area and pore size, generating less amount and diferent composition of gases. As such, impregnated ACs exhibit similar surface areas and large pores, regardless of the potassium ratio. The physical properties, such as specifc surface areas and pore size distribution, of ACs using wet impregna�tion were similar to the ACs generated by the water physical activation. It indicated that the KOH does not efciently act as a chemical activator in the wet impregnation method. Therefore, a certain amount and suitable mixing method of chemical activator play an important role in the property upgrade of ACs.

Continuous synthesis of high-crystalline carbon nanotubes (CNTs) is achieved by reconfguring the injection part in the reactor that is used in the foating catalyst chemical vapor deposition (FC-CVD) process. The degree of gas mixing is divided into three cases by adjusting the confguration of the injection part: Case 1: most-delayed gas mixing (reference experiment), Case 2: earlier gas mixing than Case 1, Case 3: earliest gas mixing. The optimal synthesis condition is obtained using design of experiment (DOE) in the design of Case 1, and then is applied to the other cases to compare the synthesis results. In all cases, the experiments are performed by varying the timing of gas mixing while keeping the synthesis conditions constant. Production rate (Case 1: 0.63 mg/min, Case 2: 0.68 mg/min, Case 3: 1.29 mg/min) and carbon content (Case 1: 39.6 wt%, Case 2: 57.1 wt%, Case 3: 71.6 wt%) increase as the gas-mixing level increases. The amount of by-products decreases step�wise as the gas-mixing level increases. The IG/ID ratio increases by a factor of 7 from 10.3 (Case 1) to 71.7 (Case 3) as the gas-mixing level increases; a high ratio indicates high-crystalline CNTs. The radial breathing mode (RBM) peak of Raman spectrograph is the narrowest and sharpest in Case 3; this result suggests that the diameter of the synthesized CNTs is the most uniform in Case 3. This study demonstrates the importance of confguration of the injection part of the reactor for CNT synthesis using FC-CVD.