Effect of photonic flash annealing with subsequent compression rolling on the topography, microstructure and electrical performance of carbon-based inks

Potts, Sarah-Jane; Lau, Yin Cheung; Dunlop, Tom; Claypole, Tim; Phillips, Christopher

doi:10.1007/s10853-019-03462-3

Cited by 18 publications

(27 citation statements)

References 35 publications

(49 reference statements)

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“…Irrespective of plasma functionalization, the coatings show low surface roughness, < 800 nm, at all phase volumes. At < 800 lm, the surface roughness of the GNP inks is significantly lower than that of the 2.8 lm found for a 22.5 wt% graphite ink used by Potts et al 4 and shows good agreement with the 800 nm found for oxygen plasma functionalized GNPs used in the same study.…”

Section: Resultssupporting

confidence: 84%

“…1 Advantages of carbon inks include their relatively low cost, disposability, ease of use, chemical inertness, the ability to be modified or functionalized and their controllable electronic properties. [2][3][4][5] Dispersion of nano-fillers is a key issue in governing the properties of composites. 6,7 However, achieving good dispersion of nano-carbons within a fluid has proved difficult as a result of the inert, hydrophobic, ultra-high interfacial area per volume and highly agglomerated nature of carbon nanomaterials.…”

Section: Introductionmentioning

confidence: 99%

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The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

Claypole

et al. 2020

J Coat Technol Res

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Carbon-based pastes and inks are used extensively in a wide range of printed electronics because of their widespread availability, electrical conductivity and low cost. Overcoming the inherent tendency of the nano-carbon to agglomerate to form a stable dispersion is necessary if these inks are to be taken from the lab scale to industrial production. Plasma functionalization of graphite nanoplatelets (GNP) adds functional groups to their surface to improve their interaction with the polymer resin. This offers an attractive method to overcome these problems when creating next generation inks. Both dynamic and oscillatory rheology were used to evaluate the stability of inks made with different loadings of functionalized and unfunctionalized GNP in a thin resin, typical of a production ink. The rheology and the printability tests showed the same level of dispersion and electrical performance had been achieved with both functionalized and unfunctionalized GNPs. The unfunctionalized GNPs agglomerate to form larger, lower aspect particles, reducing interparticle interactions and particle–medium interactions. Over a 12-week period, the viscosity, shear thinning behavior and viscoelastic properties of the unfunctionalized GNP inks fell, with decreases in viscosity at 1.17 s−1 of 24, 30, 39% for the ϕ = 0.071, 0.098, 0.127 GNP suspensions, respectively. However, the rheological properties of the functionalized GNP suspensions remained stable as the GNPs interacted better with the polymer in the resin to create a steric barrier which prevented the GNPs from approaching close enough for van der Waals forces to be effective.

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Section: Resultssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

Claypole

et al. 2020

J Coat Technol Res

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“…There is a wide particle size distribution of the GNPs with platelet diameter ranging from » 1 to 8 lm. The platelets have generally fallen flat to form a paved type structure; however, within this structure are large gaps where the high-aspect-ratio platelets are unable to pack efficiently, with GNPs at various angles relative to the substrate in good agreement to the work on GNPbased inks by Potts et al 27 and the work on graphite composites by Kasgoz et al 19 The thickness of these platelets can be estimated to be » 0.75-100 nm from the platelets which have not fallen flat and whose edges are visible. Three roll milling appears to be an effective technique for initial dispersion of GNPs in a low-viscosity resin system, and as indicated by the absence of any large agglomerates, the dispersion is initially stable over the 24-h period between dispersion and coating.…”

Section: Particle Characterizationsupporting

confidence: 78%

Rheology of high-aspect-ratio nanocarbons dispersed in a low-viscosity fluid

Claypole

Holder

et al. 2020

J Coat Technol Res

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Printing inks typically consist of a functional component dispersed within a low-viscosity resin/solvent system where interparticle interactions would be expected to play a significant role in dispersion, especially for the high-aspect-ratio nanocarbons such as the graphite nanoplatelets (GNPs). Rheology has been suggested as a method for assessing the dispersion of carbon nanomaterials in a fluid. The effects of phase volume of ammonia plasma-functionalized GNPs on a near-Newtonian low-viscosity thermoplastic polyurethane (TPU) resin system have been studied using shear and quiescent oscillatory rheology. At low concentrations, the GNPs were well dispersed with a similar shear profile and viscoelastic behavior to the unfilled TPU resin, as viscous behavior prevailed indicating the absence of any long-range order within the fluid. Particle interactions increased rapidly as the phase volume tended toward maximum packing fraction, producing rapid increases in the relative viscosity, increased low shear rate shear thinning, and the elastic response becoming increasingly frequency independent. The nanoscale dimensions and high-aspect-ratio GNPs occupied a large volume within the flow, while small interparticle distances caused rapid increases in the particle-particle interactions to form flocculates that pack less effectively. Established rheological models were fitted to the experimental data to model the effect of high-aspect-ratio nanocarbon on the viscosity of a low-viscosity system. Using the intrinsic viscosity and the maximum packing fraction as fitting parameters, the Krieger-Dougherty (K-D) model provided the best fit with values. There was good agreement between the estimates of aspect ratio from the SEM images and the predictions of the aspect ratio from the rheological models. The fitting of the K-D model to measured viscosities at various phase volumes could be an effective method in characterizing the shape and dispersion of high-aspect-ratio nanocarbons.

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“…These peaks can lead to increases in print roughness and reductions in print homogeneity. Whereas the 10 wt.% ink which did not form any filaments during ink separation had a far more consistent print profile with only small areas of high film thickness, most likely due to the random orientation of the graphite flakes in the ink, as seen in previous studies [10,37].…”

Section: Ink Separation Mechanismsmentioning

confidence: 53%

“…Figure 8 identified that the locations of the filaments during separation led to notable raised areas on the printed film which increased the surface roughness, while the average surface roughness was unaffected. This is most likely due to the random orientation of the large graphite flakes in the ink determining this, with flakes measuring up to tens of microns, as quantified in previous studies [10,37]. Therefore, this separation mechanism may have a more significant effects on inks with contain smaller particles or which recover to their initial viscosity in a shorter time period.…”

Section: Discussionmentioning

confidence: 87%

The Effect of Carbon Ink Rheology on Ink Separation Mechanisms in Screen-Printing

et al. 2020

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Screen-printable carbon-based inks are available in a range of carbon morphologies and concentrations, resulting in various rheological profiles. There are challenges in obtaining a good print when high loading and elasticity functional inks are used, with a trade-off often required between functionality and printability. There is a limited understanding of how ink rheology influences the ink deposition mechanism during screen-printing, which then affects the print topography and therefore electrical performance. High speed imaging was used with a screen-printing simulation apparatus to investigate the effect of viscosity of a graphite and carbon-black ink at various levels of solvent dilution on the deposition mechanisms occurring during screen-printing. With little dilution, the greater relative volume of carbon in the ink resulted in a greater tendency towards elastic behavior than at higher dilutions. During the screen-printing process this led to the ink splitting into filaments while remaining in contact with both the mesh and substrate simultaneously over a greater horizonal length. The location of separating filaments corresponded with localized film thickness increases in the print, which led to a higher surface roughness (Sz). This method could be used to make appropriate adjustments to ink rheology to overcome print defects related to poor ink separation.

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Effect of photonic flash annealing with subsequent compression rolling on the topography, microstructure and electrical performance of carbon-based inks

Cited by 18 publications

References 35 publications

The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

Rheology of high-aspect-ratio nanocarbons dispersed in a low-viscosity fluid

The Effect of Carbon Ink Rheology on Ink Separation Mechanisms in Screen-Printing

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