The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Schlomo Magdassi - One of the best experts on this subject based on the ideXlab platform.
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Formation and performance of highly absorbing solar thermal coating based on carbon nanotubes and boehmite
Energy Conversion and Management, 2016Co-Authors: Raj Kumar Bera, Daniel Mandler, Subodh Gautam Mhaisalkar, Schlomo MagdassiAbstract:A major component of solar thermal systems is the solar absorber, which converts light into heat. We report on achieving high absorptance, excellent adhesion, and high thermal stability of carbon nanotube-based Black Coatings by applying a layer of Boehmite (AlOOH) on top of the carbon nanotube (CNT) film by solution-processed spray deposition. The CNT layer made-up by spraying, functions as an absorbing layer and the AlOOH serves as an anti-reflecting and protecting film. The anti-reflecting property of AlOOH layer effectively increases the absorptance of CNT coating by decreasing the reflectance. The effect of the thickness of AlOOH layer on the absorptance, adhesion, and thermal stability of the resulting CNT/AlOOH coating was investigated. The CNT/AlOOH coating with optimized thickness of AlOOH layer shows very high absorptance (α) of 0.975. The adhesion of the coating is in the range of 95-100% with significant increase of thermal stability. This new approach is expected to open new possibilities for fabricating low-cost, highly efficient and thermally stable solar-thermal devices which are based on simple coating processes.
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wet deposition of carbon nanotube Black Coatings for stray light reduction in optical systems
Surface & Coatings Technology, 2015Co-Authors: Suzanna Azoubel, Rina Cohen, Schlomo MagdassiAbstract:Abstract Stray light, also known as optical noise, affects the performance of many optical devices. It can be reduced to a tolerable level by well-designed and well-baffled system or/and by using functional Black Coatings that are fabricated in a complex and costly process. Carbon nanotubes (CNTs) absorb light strongly, making them an ideal candidate for realizing a super Black coating. CNT Coatings were formed by spraying formulations composed of a silicon binder and low cost multiwalled CNTs on a pre-heated aluminum plate. The diffuse reflectance of the Coatings in the VIS range (350–800 nm) was in the range of 2.6–5.11%, depending on the MWCNT concentration in the coating. In the NIR range (850–2400 nm), the reflectance values were in the range of 4–6.5%, however the dependence on MWCNT concentration was not very significant. Excellent adhesion to the aluminum substrates was achieved, for Coatings with CNT concentration below 15%, while still having very low reflectance, even at temperature cycling between 200 °C and − 196 °C. The proposed coating formulations enable simple and low cost approach for producing high light-absorbing coating of complex 3D structures within a very short time by wet deposition of CNTs.
Masoud Barekat - One of the best experts on this subject based on the ideXlab platform.
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Wear behavior of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces
Progress in Organic Coatings, 2020Co-Authors: Masoud Barekat, Reza Shoja Razavi, Saeed BastaniAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces are studied. Testing parameters have been optimized for maximum wear resistance based on taguchi orthogonal design with six important parameters, viz. polydimethylsiloxane (PDMS) molecular weight, oxime/OH ratio, catalyst weight percent, pigment weight percent, surface preparation method and adhesion promoter type. The analysis of variance showed that the wear resistance strongly depends on oxime/OH ratio and catalyst weight percent. PDMS molecular weight and pigment weight percent also have intermediate effects. Neither the surface preparation method nor adhesion promoter type had any effects on wear resistance in this study. The optimum sample was prepared according to the best levels of each factor and the wear resistance in optimum conditions was reasonably in agreement with the experimental data. Scanning electron microscopy analysis of wear surface and debris showed two mechanisms: cohesive wear with fatigue mechanism and interfacial wear with adhesion mechanism.
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wear behavior of polyurethane carbon Black Coatings on 6061 aluminum alloy substrates
Progress in Organic Coatings, 2016Co-Authors: Seyyed Saber Mirhosseini, Reza Shoja Razavi, Mehrdad Taheran, Masoud BarekatAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of polyurethane/carbon Black Coatings on the 6061 aluminum substrate are studied. These Coatings are widely used in different industries because of their outstanding thermal, chemical stabilities and excellent mechanical properties. The parameters were polyol type (ester or ether), NCO/OH ratio and pigment concentration. The experiments were carried out based on the design of experiments using Taguchi method. Abrasion resistance tests were performed with a Taber Abrasion test device, and its morphology was examined by scanning electron microscopy (SEM). Fourier-transform infrared (FTIR) spectroscopy was used to characterize the synthesized polymer. The analysis of variance showed that among the studied parameters, polyol type and pigment concentration have the most significant effects on wear resistance. Coating with polyester polyol increases the wear resistance due to possible hydrogen bonding between hard and soft segments. Furthermore, the pigment particles provide equivalent physical crosslinks, so it increases the wear resistance. Finally, the coated sample including polyester polyol, 12phr carbon Black and NCO/OH ratio equal to 1.4, provide the best wear resistance i.e. 0.2 mg. Also, the results showed that abrasion and cohesive wear are the dominant mechanisms for describing the wear behavior of studied Coatings.
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Wear behavior of polyurethane/carbon Black Coatings on 6061 aluminum alloy substrates
Progress in Organic Coatings, 2016Co-Authors: Seyyed Saber Mirhosseini, Reza Shoja Razavi, Mehrdad Taheran, Masoud BarekatAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of polyurethane/carbon Black Coatings on the 6061 aluminum substrate are studied. These Coatings are widely used in different industries because of their outstanding thermal, chemical stabilities and excellent mechanical properties. The parameters were polyol type (ester or ether), NCO/OH ratio and pigment concentration. The experiments were carried out based on the design of experiments using Taguchi method. Abrasion resistance tests were performed with a Taber Abrasion test device, and its morphology was examined by scanning electron microscopy (SEM). Fourier-transform infrared (FTIR) spectroscopy was used to characterize the synthesized polymer. The analysis of variance showed that among the studied parameters, polyol type and pigment concentration have the most significant effects on wear resistance. Coating with polyester polyol increases the wear resistance due to possible hydrogen bonding between hard and soft segments. Furthermore, the pigment particles provide equivalent physical crosslinks, so it increases the wear resistance. Finally, the coated sample including polyester polyol, 12phr carbon Black and NCO/OH ratio equal to 1.4, provide the best wear resistance i.e. 0.2 mg. Also, the results showed that abrasion and cohesive wear are the dominant mechanisms for describing the wear behavior of studied Coatings.
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wear behavior of silicone rubber carbon Black Coatings on 6061 aluminum alloy surfaces
Progress in Organic Coatings, 2013Co-Authors: Masoud Barekat, Reza Shoja Razavi, Saeed BastaniAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces are studied. Testing parameters have been optimized for maximum wear resistance based on taguchi orthogonal design with six important parameters, viz. polydimethylsiloxane (PDMS) molecular weight, oxime/OH ratio, catalyst weight percent, pigment weight percent, surface preparation method and adhesion promoter type. The analysis of variance showed that the wear resistance strongly depends on oxime/OH ratio and catalyst weight percent. PDMS molecular weight and pigment weight percent also have intermediate effects. Neither the surface preparation method nor adhesion promoter type had any effects on wear resistance in this study. The optimum sample was prepared according to the best levels of each factor and the wear resistance in optimum conditions was reasonably in agreement with the experimental data. Scanning electron microscopy analysis of wear surface and debris showed two mechanisms: cohesive wear with fatigue mechanism and interfacial wear with adhesion mechanism.
Juan R. Reveles - One of the best experts on this subject based on the ideXlab platform.
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The partial space qualification of a vertically aligned carbon nanotube coating on aluminium substrates for EO applications
Optics Express, 2014Co-Authors: E Theocharous, Ryan Mole, Nigel Fox, Guy Howlett, Ben Jensen, Rosie Taylor, Christopher J. Chunnilall, David Gibbs, Naigui Shang, Juan R. RevelesAbstract:The fabrication of NanoTube Black, a Vertically Aligned carbon NanoTube Array (VANTA) on aluminium substrates is reported for the first time. The coating on aluminium was realised using a process that employs top down thermal radiation to assist growth, enabling deposition at temperatures below the substrate's melting point. The NanoTube Black Coatings were shown to exhibit directional hemispherical reflectance values of typically less than 1{%} across wavelengths in the 2.5 µm to 15 µm range. VANTA-coated aluminium substrates were subjected to space qualification testing (mass loss, outgassing, shock, vibration and temperature cycling) before their optical properties were re-assessed. Within measurement uncertainty, no changes to hemispherical reflectance were detected, confirming that NanoTube Black Coatings on aluminium are good candidates for Earth Observation (EO) applications.
John H. Lehman - One of the best experts on this subject based on the ideXlab platform.
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The evaluation of a pyroelectric detector with a sprayed carbon multi-wall nanotube Black coating in the infrared
Infrared Physics & Technology, 2020Co-Authors: Evangelos Theocharous, John H. LehmanAbstract:Abstract The performance of a pyroelectric detector with a “sprayed” multi-wall carbon nanotube (MWCNT) coating was evaluated in the 0.9 μm–24 μm wavelength range. The relative spectral responsivity of this detector was shown to vary by 8% over this wavelength range. Its responsivity exhibited a super-linear response, while its spatial uniformity of response was strongly dependent on the modulation frequency, indicating that the thermal properties of the “sprayed” MWCNTs play an important role in the spatial uniformity of response profiles. The “sprayed” MWCNT coating is far easier to fabricate than other Black Coatings and it is relatively durable. This, in combination with the small variation observed in the spectral absorbance of the “sprayed” MWCNT coating over a very wide wavelength range, suggests that these Coatings appear extremely promising for thermal detection applications in the infrared.
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carbon nanotube based Black Coatings
Applied physics reviews, 2018Co-Authors: John H. Lehman, C S Yung, Nathan A Tomlin, Davis R Conklin, M StephensAbstract:Coatings comprising carbon nanotubes are very Black, that is, characterized by uniformly low reflectance over a broad range of wavelengths from the visible to far infrared. Arguably, there is no other material that is comparable. This is attributable to the intrinsic properties of graphitic material as well as the morphology (density, thickness, disorder, and tube size). We briefly describe a history of other Coatings such as nickel phosphorous, gold Black, and carbon-based paints and the comparable structural morphology that we associate with very Black Coatings. The need for Black Coatings is persistent for a variety of applications ranging from baffles and traps to Blackbodies and thermal detectors. Applications for space-based instruments are of interest and we present a review of space qualification and the results of outgassing measurements. Questions of nanoparticle safety depend on the nanotube size and aspect ratio as well as the nature and route of exposure. We describe the growth of carbon nano...
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carbon nanotube based Black Coatings
arXiv: Applied Physics, 2017Co-Authors: John H. Lehman, C S Yung, Nathan A Tomlin, Davis R Conklin, M StephensAbstract:Coatings comprised of carbon nanotubes are very Black; that is, characterized by low reflectance over a broad wavelength range from the visible to far infrared. Arguably there is no other material that is comparable. This is attributable to the intrinsic properties of graphene as well as the morphology (density, thickness, disorder, tube size) of the coating. The need for Black Coatings is persistent for a variety of applications such as baffles and traps for space instruments. Because of the thermal properties, nanotube Coatings are also well suited for thermal detectors, Blackbodies and other applications where light is trapped and converted to heat. We briefly describe a history of other Coatings such as nickel phosphorous, gold Black and carbon-based paints and the comparable structural morphology that we associate with very Black Coatings. In many cases, it is a significant challenge to put the Blackest coating on something useful. We describe the growth of carbon nanotube forests on substrates such as metals and silicon along with the catalyst requirements and temperature limitations. We also describe Coatings derived from carbon nanotubes and applied like paint. Another significant challenge is that of building the measurement apparatus and determining the optical properties of something having negligible reflectance. There exists information in the literature for effective media approximations to model the dielectric function of vertically aligned arrays. We summarize this as well as other approaches that are useful for predicting the coating behavior along with the refractive index of graphite from the literature that is necessary for the models we know of. We provide an appendix of our best recipes for making as-grown, sprayed or other Coatings for the Blackest and most robust coating for a chosen substrate and a description of reflectance measurements.
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The evaluation of the performance of two pyroelectric detectors with vertically aligned multi-walled carbon nanotube Coatings
Infrared Physics and Technology, 2012Co-Authors: S. P. Theocharous, E Theocharous, John H. LehmanAbstract:Two LiTaO3pyroelectric detectors coated with vertically aligned multi walled carbon nanotube (MWCNT) Black Coatings were assembled and evaluated using NPL's detector characterisation facilities. The vertically-aligned nanotube array (VANTA) Black Coatings were grown on a silicon substrate and subsequently lifted off the silicon and bonded on the pyroelectric crystal substrates. Despite some drawbacks, this method was shown to provide a reliable way of coating delicate substrates such as pyroelectric crystals with VANTA Coatings. The performance of the coated and uncoated detectors was evaluated and compared by coating only half of the active area of the test detectors, leaving the other half uncoated. The relative spectral responsivity of the VANTA-coated pyroelectric detectors was shown to be spectrally flat in the 0.8-14 μm wavelength range within the uncertainty of the measurements. The spatial uniformity of response of both detectors exhibited fine structure which was assigned either to the thickness of the VANTA Coatings or to their bonding to the pyroelectric crystal. Both coated and uncoated detectors exhibited a super-linear response. This observation was expected in the case of the uncoated detectors, but was surprising in the case of the coated detectors and indicates that the thermal conductivity of vertically aligned multi-walled carbon nanotubes is high along their long axis. The spatial variations of the phase delay experienced by the signal propagating through the VANTA Coatings indicate that the thermal diffusivity of the Coatings is not spatially uniform. © 2012 Elsevier B.V. All rights reserved.
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Evaluation of a pyroelectric detector with a carbon multiwalled nanotube Black coating in the infrared
Applied Optics, 2006Co-Authors: Evangelos Theocharous, Rohit Deshpande, Anne C. Dillon, John H. LehmanAbstract:The performance of a pyroelectric detector with a carbon multiwalled nanotube coating was evaluated in the 0.9-14 µm wavelength range. The relative spectral responsivity of this detector was shown to be flat over most of the wavelength range examined, and the spectral flatness was shown to be comparable to the best infrared Black Coatings currently available. This finding is promising because Black Coatings with spectrally flat absorbance profiles are usually associated with the highest absorbance values. The performance of the detector (in terms of noise equivalent power and specific detectivity) was limited by the very thick (250 µm thick) LiNbO3 pyroelectric crystal onto which the coating was deposited. The responsivity of this detector was shown to be linear in the 0.06-2.8 mW radiant power range, and its spatial uniformity was comparable to that of other pyroelectric detectors that use different types of Black coating. The carbon nanotube Coatings were reported to be much more durable than other infrared Black Coatings, such as metal Blacks, that are commonly used to coat thermal detectors in the infrared. This, in combination with their excellent spectral flatness, suggests that carbon nanotube Coatings appear extremely promising for thermal detection applications in the infrared.
Saeed Bastani - One of the best experts on this subject based on the ideXlab platform.
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Wear behavior of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces
Progress in Organic Coatings, 2020Co-Authors: Masoud Barekat, Reza Shoja Razavi, Saeed BastaniAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces are studied. Testing parameters have been optimized for maximum wear resistance based on taguchi orthogonal design with six important parameters, viz. polydimethylsiloxane (PDMS) molecular weight, oxime/OH ratio, catalyst weight percent, pigment weight percent, surface preparation method and adhesion promoter type. The analysis of variance showed that the wear resistance strongly depends on oxime/OH ratio and catalyst weight percent. PDMS molecular weight and pigment weight percent also have intermediate effects. Neither the surface preparation method nor adhesion promoter type had any effects on wear resistance in this study. The optimum sample was prepared according to the best levels of each factor and the wear resistance in optimum conditions was reasonably in agreement with the experimental data. Scanning electron microscopy analysis of wear surface and debris showed two mechanisms: cohesive wear with fatigue mechanism and interfacial wear with adhesion mechanism.
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wear behavior of silicone rubber carbon Black Coatings on 6061 aluminum alloy surfaces
Progress in Organic Coatings, 2013Co-Authors: Masoud Barekat, Reza Shoja Razavi, Saeed BastaniAbstract:Abstract In this paper, the effects of structural and process variables on wear resistance of silicone rubber/carbon Black Coatings on 6061 aluminum alloy surfaces are studied. Testing parameters have been optimized for maximum wear resistance based on taguchi orthogonal design with six important parameters, viz. polydimethylsiloxane (PDMS) molecular weight, oxime/OH ratio, catalyst weight percent, pigment weight percent, surface preparation method and adhesion promoter type. The analysis of variance showed that the wear resistance strongly depends on oxime/OH ratio and catalyst weight percent. PDMS molecular weight and pigment weight percent also have intermediate effects. Neither the surface preparation method nor adhesion promoter type had any effects on wear resistance in this study. The optimum sample was prepared according to the best levels of each factor and the wear resistance in optimum conditions was reasonably in agreement with the experimental data. Scanning electron microscopy analysis of wear surface and debris showed two mechanisms: cohesive wear with fatigue mechanism and interfacial wear with adhesion mechanism.
