CNT-Based Solar Thermal Coatings: Absorptance vs. Emittance

Vinetsky, Yelena; Jambu, Jyothi; Mandler, Daniel; Magdassi, Shlomo

doi:10.3390/coatings10111101

Cited by 9 publications

(3 citation statements)

References 28 publications

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“…Pure (or binder-free) low-density carbon-based materials typically provide integral absorption better than 0.99. However, these characteristics decrease significantly (about 0.02) when the nanomaterial is mixed with the binder that is required to achieve strong adhesion to the substrate in realistic applications. − A similar idea is clearly illustrated in Supporting Movie showing the reflectivity of He–Ne laser from several ultrablack coatings. Conversely, the integral absorptance of the HCS-based coatings maintains a high value of 0.985.…”

Section: Resultsmentioning

confidence: 84%

“…However, the produced coatings typically had weak adhesion to a substrate or were prepared in the form of a self-supporting membrane, thus limiting their practical applicability. To improve the adhesion of the nanotube-based coatings, Magdassi et al mixed multiwalled carbon nanotubes with a silicone, then the mixture was sprayed on an aluminum substrate to obtain the ultrablack coating. − The resulting adhesion was significantly improved, but at the cost of a substantial increase of average reflectance up to 2–5%, that is, to a level that is not acceptable for certain applications. A similar result is reported for carbon aerogels .…”

Section: Introductionmentioning

confidence: 99%

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Sprayable Ultrablack Coating Based on Hollow Carbon Nanospheres

Cao²,

Hao

et al. 2021

ACS Appl. Nano Mater.

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Inexpensive, easy-to-implement coatings exhibiting extremely low reflectance within a broad spectral range, and good adhesion to substrates are in high demand for high-precision optical instruments and solar energy harvesting. Herein, we demonstrate a highly absorbing coating based on hollow carbon nanospheres (HCSs). The coatings are formed via a simple and high-performing air-spraying process with a tailored paint formulation containing HCSs as an absorbing pigment and a fluororesin as a binder. By optimizing the pigment/binder mass ratio (P/B), we produce functional coatings that exhibit solar absorptance up to 0.985 and good adhesion to aluminum sheets of grade 2 (according to the ISO 2409 standard). The excellent solar absorptance of the obtained coatings results from their hierarchical nano- and microscale surface morphology, providing a refractive index gradient on the air–coating interface as well as remarkable light trapping performance. The former is due to the hollow structure in carbon spheres, which is preserved after the addition of the binder because the size of binder particles is larger than the holes on the shell of the HCSs. The latter is attributed to the micronodules and micropits of the coating surface formed by the agglomeration of the HCSs, which enhances absorption by multiple scattering.

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Section: Resultsmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Sprayable Ultrablack Coating Based on Hollow Carbon Nanospheres

Cao²,

Hao

et al. 2021

ACS Appl. Nano Mater.

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“…Carbon nanotubes (CNTs), with large length to diameter ratio, low density, large specific surface area and high electrical conductivity, show good absorbing properties [11][12][13][14]. However, the high conductivity of CNTs has also led to the poor absorption caused by the mismatch of interface impedance.…”

Section: Introductionmentioning

confidence: 99%

Hydrothermal Synthesis and Microwave Absorption Properties of Nickel Ferrite/Multiwalled Carbon Nanotubes Composites

Guo¹,

Chen³

et al. 2021

Coatings

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It is well accepted that the microwave absorption performance of ferrite can be enhanced via the hybridization. However, it is still very challenging to design the hierarchical nanostructure of ferrite hybrids to fabricate wave absorbing composites with both the high efficiency and lightweight. Herein, we successfully realize the in-situ synthesis of nickel ferrite/multiwalled carbon nanotubes (NiFe2O4/MWCNTs) hybrids with a large-scale production by the hydrothermal method. The structural characteristics, morphology, electromagnetic and microwave absorption properties were analyzed by X-ray diffraction, scanning electron microscope and vector network analyzer. The morphological study shows that NiFe2O4 nanoparticles with a small size (tens of nanometers) are coated on the MWCNTs, leading to a three-dimensional hierarchical nanostructure. The NiFe2O4/MWCNTs hybrids show satisfied microwave absorption properties. Typically, the optimized sample shows the minimum reflection loss of −19 dB at 11.3 GHz, and the bandwidth of the reflectivity below −10 dB is 2.5 GHz with a thin thickness of 1.5 mm. This result shall be due to the improved dielectric losses or interface polarization etc. Our results demonstrate a facile approach for the design of ferrite-based microwave absorber to meet the requirements of lightweight, thin-thickness and high efficiency.

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Spray Black Coating for High‐Efficiency Light Absorption

Xiao,

Wang,

Piao

et al. 2024

Adv Materials Technologies

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Black coatings have emerged as a research focus due to their excellent light absorption performance over a wide wavelength range. They play a crucial role in precision optical devices and solar thermal applications. Among various preparation methods, spray coating has attracted great attention due to its simple preparation process, low cost, scalability, and applicability to complex structures. Herein, the recent progress in spray black coatings is comprehensively presented. Various spray coating methods employed in the preparation of black coatings, including air spraying, ultrasonic spraying, electrostatic spraying, spray pyrolysis, and thermal spraying are summarized and compared. Black spray coatings based on metal sulfide, metal oxide, cermet, polymer, and carbon are then reviewed. In addition to the intrinsic absorption properties of the black coatings, light‐trapping structures are key to achieving high‐efficiency light absorption. Typical structural design strategies for enhancing absorption are highlighted. Moreover, the trade‐off between absorptance and adhesion in the design of robust spray black coatings is indicated. The remaining challenges and outlook for the spray black coatings are discussed. This review is expected to provide valuable guidelines for the future development of spray black coatings.

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CNT-Based Solar Thermal Coatings: Absorptance vs. Emittance

Cited by 9 publications

References 28 publications

Sprayable Ultrablack Coating Based on Hollow Carbon Nanospheres

Sprayable Ultrablack Coating Based on Hollow Carbon Nanospheres

Hydrothermal Synthesis and Microwave Absorption Properties of Nickel Ferrite/Multiwalled Carbon Nanotubes Composites

Spray Black Coating for High‐Efficiency Light Absorption

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