Multiwall carbon nanotubes (MWNT) were produced using the arc-discharge graphite evaporation technique. Composite films were developed using MWNT dispersed in polystirol polymer. In the present work, various properties of the polymeric thin film containing carbon nanotubes were investigated by optical absorption, electrical resistivity and the same have been discussed.

Aligned multi-wall carbon nanotubes (MWNTs) were synthesized through the catalytic decomposition of hydrocarbons in a quartz tube reactor. In this study, we investigated the influence of reaction parameters such as gas flow rate, ferrocene-xylene ratio and partial pressure, and reaction time on the yield and structure of vertically aligned carbon nanotubes produced by the floating catalyst method. The MWNTs produced had diameters in the range of 20~l00 nm, length around 100μm and bulk density about 0.51g/cm3 at a pressure of l0000 psi. It was possible to produce MWNTs with much faster growth rate of 12μm/min than that reported previously by the increase of ferrocene-xylene partial pressure.

열화학 기상 증착법을 이용하여 암모니아 처리에 따른 촉매 금속의 표면형태와 탄소 나노튜브의 성장을 조사하였다. 암모니아 처리의 열화학 과정의 조절에 의해 고르게 분산된 수직 성장된 탄소 나노튜브를 얻었다. 탄소 나노튜브 합성시 암모니아처리는 수직성장 및 고밀도 성장에 중요한 과정으로 그 역할에 대해 알아보았다. 고밀도의 수직 배향된 탄소나노튜브의 구조와 형태는 주사전자 현미경과 투과전자 현미경, 라만을 이용하여 관찰하였다.

The synthetic methods for high yield of multiwalled carbon nanotube (MWNT) and singlewalled carbon nanotube (SWNT) with high purity by arc discharge have been investigated. MWNTs were synthesized under different pressures of helium and the gas mixture of argon and hydrogen. Relatively high pressure of 300-400 torr was required for high yield MWNTs synthesis at low bias voltage of about 20 V and 55 A, whereas low pressure of about 100 torr was required for SWNTs. The introduction of hydrogen gases during the synthesis of MWNTs improved the yield and purity of the samples. The SWNTs were synthesized by the assistance of a small amount of mixture of transition metals, which played as a catalyst during the formation process. The purity and yield of SWNTs were higher at a lower pressure and enhanced by mixing more components of the transition metals.

In this study, the effect of compressive loading of carbon nanotube (CNT) mixed cement composites was investigated. To evaluate the electrical resistivity variation of 30%∼60% of compressive load of cement composites containing 1.0% CNT, 1.0% CNT was added to cement composites and compressive strength was calculated. The greater the change in electrical resistance to compressive load, the more vulnerable to internal conductive networks. Also, as the amount of CNT mixed increases, the electrical resistance to the load is more sensitive and it is expected to be mixed more than 1.0%.

PSf/D2EHPA/CNT beads were prepared by immobilizing di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and carbon nanotubes (CNT) on polysulfone (PSf) and used to remove Cu(II) from aqueous solutions. Optimum pH was in the range of 4 to 6. The removal kinetic of Cu(II) by the prepared PSf/D2EHPA/CNT beads was mainly governed by internal diffusion, and the diffusion coefficient of Cu(II) by PSf/D2EHPA/CNT beads was found to be 2.19×10-4∼2.64×10-4 cm2/s. The Langmuir isotherm model predicted the experimented data well. The maximum removal capacity of Cu(II) obtained from this isotherm was 7.32 mg/g. Calculated thermodynamic parameters such as ΔGo, ΔHo and ΔSo showed that the adsorption of Cu(II) ions onto PSf/D2EHPA/CNT beads was feasible, spontaneous and endothermic at 293–323 K.

With the development of nanotechnology, nanomaterials are used in various fields. Therefore, the interest regarding the safety of nanomaterial use is increasing and much effort is diverted toward establishment of exposure assessment and management methods. Occupational exposure limits (OELs) are effectively used to protect the health of workers in various industrial workplaces. This study aimed to propose an OEL for domestic multi-walled carbon nanotubes (MWCNTs) based on animal inhalation toxicity test. Basic procedure for development of OELs was examined. For OEL estimation, epidemiological study and quantitative risk assessment are generally performed based on toxicity data. In addition, inhalation toxicity data-based no observed adverse effect level (NOAEL) and benchmark dose (BMD) are estimated to obtain the OEL. Three different estimation processes (NEDO in Japan, NIOSH in USA, and Baytubes in Germany) of OELs for carbon nanotubes (CNTs) were intensively reviewed. From the rat inhalation toxicity test for MWCNTs manufactured in Korea, a NOAEL of 0.98 mg/㎥ was derived. Using the simple equation for estimation of OEL suggested by NEDO, the OEL of 142 μg/㎥ was estimated for the MWCNT manufacturing workplace. Here, we used test rat and Korean human data and adopted 36 as an uncertainty factor. The OEL for MWCNT estimated in this work is higher than those (2-80 μg/㎥) suggested by previous investigators. It may be greatly caused by different physicochemical properties of MWCNT and their dispersion method and test rat data. For setting of regulatory OELs in CNT workplaces, further epidemiological studies in addition to animal studies are needed. More advanced technical methods such as CNT dispersion in air and liquid should be also developed.

In spite of advantages of the use of CNT, one of the largest obstacles to improve strength of CNT composites is the difficulty of getting a good dispersion of the carbon nanomaterials in a matrix. We tried to mix CNT composites with some of surfactant for getting a good dispersion and compared the results of compressive strength test.