Mass production of high-quality carbon nanotubes (CNTs) remains a challenge, requiring the development of new wetimpregnated catalyst suitable for the catalytic chemical vapor deposition (CCVD) of CNTs in a fluidized bed reactor. For the successful development of a new catalyst, a highly robust system to synthesize CNTs must be established. Here, we systematically investigated the robustness of CNT synthesis by CCVD using a wet-impregnated catalyst. We statistically tested four factors that could potentially affect the robustness of CNT synthesis system, focusing on carbon yield and IG/ID. First, we tested the effect of vacuum baking before CNT growth. F test and CV equality test concluded that vacuum baking recipe did not significantly reduce the variability of the CNT synthesis. Second, we tested the batch-to-batch variation of catalysts. The results of t test and one-way analysis of variance indicate that there is significant difference in carbon yield and IG/ID among catalysts from different batches. Third, we confirmed that there is spatial non-uniformity of wet-impregnated catalysts within a batch when they are produced in large scale. Finally, we developed a multi-step heating recipe to mitigate the temperature overshooting during the CNT synthesis. The multi-step recipe increased the mean of carbon yield, but did not influence the variability of CNT synthesis. We believe that our research can contribute to the establishment of a robust CNT synthesis system and development of new wet-impregnated catalysts.

Statistical analysis of the synthesis of carbon nanotubes using wet-impregnated catalysts for improved robustness
    Abstract
    1 Introduction
    2 Experimental
        2.1 Catalyst preparation
        2.2 Custom-designed CVD reactor
        2.3 CNT synthesis
        2.4 Characterization
    3 Results and discussion
        3.1 Characterization of as-synthesized CNTs
        3.2 Effect of vacuum baking
        3.3 Batch-to-batch variability of catalyst preparation
        3.4 Spatial uniformity during calcination
        3.5 Mitigating temperature overshooting
    4 Conclusions
    Anchor 16
    Acknowledgements 
    References

• Hyeongyun Song(School of Chemical Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea)
• Dong Hwan Kim(School of Chemical Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea)
• Cheol Woo Park(School of Chemical Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea, Plant Process Development Center, Institute for Advanced Engineering, Yongin 17180, Republic of Korea)
• Jungho Jae(School of Chemical Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea)
• Seungki Hong(Institute of Advanced Composite Materials, Korea Institute of Science and Technology (KIST), 92 Chudong‑Ro, Bongdong‑Eup, Wanju‑Gun, Jeonbuk 55324, Republic of Korea)
• Jaegeun Lee(School of Chemical Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea, Department of Organic Material Science and Engineering, Pusan National University, Busandaehak‑Ro 63Beon‑Gil, Geumjeoung‑Gu, Busan 46241, Republic of Korea)