The deposition of carbon nanotube (CNT) coatings via thermal chemical vapor deposition (CVD) is intensively reported. The surface acidity, chemical nature of the catalytic nanoparticles, and the carbon precursor are highly inter‐related key parameters. Furthermore, reducing the typical high‐growth temperature requires the implementation of toxic and hazardous organic precursors. In this study, the growth of CNT coatings is demonstrated using a single‐step CVD process in which magnesium oxides, material with enhanced basicity, and nanoparticles of cobalt are codeposited. This deposit catalyzes simultaneously the decomposition of ethanol to spark the growth of CNTs. The deposition is successively performed at 330–500 °C. Grown CNTs below 400 °C feature a high defect concentration and large diameters, 20 nm, relative to those obtained at ≥400 °C with no apparent defects and diameter of 12 nm. In terms of optical properties, films grown at ≥400 °C reflect less than 0.5% of light in the UV–vis–near IR, and exhibit a Lambertian behavior. Furthermore, the bidirectional reflectance distribution function measurements reveal identical optical properties irrespective of the underlying substrate. Therefore, the process holds a great potential for applications involving stray light reduction.

The ability to control the growth of carbon nanotube (CNT) coatings with adjusted packing density is essential for the design of functional devices with an emphasized interaction with the surrounding medium. This challenge is addressed in the present study using an innovative single-pot chemical vapor deposition (CVD) process based on the thermal conversion of ethanol to CNTs. Benefitting from the relatively safe and easily bio-derived carbon source is enabled using a cobalt catalyst and a magnesium oxide promoter. The resulting innovative direct-liquid injection CVD opens up new opportunities for low-temperature CNT deposition. The simultaneous formation of a cobalt catalyst along the process results in a sustainable CNT growth that is substantially emphasized with the deposition time. Furthermore, the formation of these catalyst nanoparticles in the porous structure nucleates new CNTs and results in a substantial film densification. Relative to densely packed CNTs that feature a density exceeding 1000 mg/cm 3 , the investigated process enables an adjusted density from 0.1 to 20 mg/cm 3 with no significant impact on the quality of the obtained multiwalled CNTs. This unprecedented control over the packing density of the CNT film paves the way toward the development of high-performance functional nanocomposite coatings.

Multi‐walled carbon nanotubes (CNTs) are deposited via thermal chemical vapor deposition using cobalt catalyst and MgO promoter. A systematic investigation of the major processing parameters such as temperature (390–620 °C), pressure (3–10 mbar), injection (4–10 ms), and deposition times is performed. The impact of these parameters on the film density and optical properties of CNT coatings is discussed. Irrespective of the growth parameters, a homogeneous deposition of CNTs and a negligible impact on the CNTs’ quality are observed. Total hemispherical reflectance (THR) reveals a threshold thickness of 3 μm, above which the CNT films behave as an efficient black absorber in the UV–vis–near‐infrared (NIR) and mid‐infrared (MIR) spectral regions. Spatial and spectral integrations of THR show a reflection below 1% in the 250 nm–2.5 μm spectral range. The low reflection observed in the NIR is retained in the MIR up to λ = 10 μm.

Chemical Vapor Deposition In article number http://doi.wiley.com/10.1002/pssa.201900704 by Hameeda Jagalur Basheer, Kamal Baba, and Naoufal Bahlawane, a superblack coating process is reported using thermal chemical vapor deposition at temperatures below 500 °C. Ethanol vapor is converted to uniform films of randomly oriented carbon nanotubes via the action of cobalt catalyst and MgO promoter, both are formed in situ. The superblack coatings feature a substantial light absorption property irrespective of the incidence angle. The displayed photos show a difficulty to distinguish the edges of the coated substrates. A systematic investigation is provided to determine the impact of the growth parameters on the kinetics and characteristics of the obtained films.