Application of the Taguchi Method to Optimize Graphene Coatings on Copper Nanoparticles Formed Using a Solid Carbon Source

Abstract

Graphene has attracted much recent interest as an electronic material due to its large electron mobility. Large-area graphene has been synthesized using chemical vapor deposition (CVD). However, it is dif cult to apply this process to grow graphene on nanoparticles (NPs) because of their small radius of curvature, which results in a large defect density. In this work, we used the Taguchi method to optimize the deposition of graphene on nanoparticles. We used polyvinylpyrrolidone (PVP) to coat copper NPs via CVD and optimized the process conditions using a minimal number of experiments. The PVP served as the solid carbon source, forming graphene when heated to 875 C. To improve the quality of the graphene coatings on the Cu NPs, the following process parameters were varied: gas conditions (ratio of Ar to H 2 ), process time and temperature, the amount of PVP solution, and the molecular weight of PVP. We identi ed optimal process conditions using only eight experiments. Raman spectroscopy was used to analyze the quality of the graphene coatings by comparing two-dimensional (2D) spectra and I D / I G ratios of the different coatings. A decrease in I D /I G , in combination with sharper Raman bands, is indicative of the thickness and crystal quality of the graphene layer. The quality of the graphene layer was also evaluated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM).The optimal conditions for the formation of graphene-coated Cu NPs were: a temperature of 875 C, a deposition time of 2 minutes, an Ar-to-H 2 ratio of 1:1, PVP with a molecular weight of M W = 3,500 (K-12) during the polyol process, and a 50-wt.% PVP solution with M W = 45,000 (K-30). Using the Taguchi method, we identi ed trends relating defect density versus process conditions and successfully obtained a graphene coating with a minimal defect density.

Can graphene improve the thermal conductivity of copper nanofluids?

“…Until now, the reported protocols consist of depositing C atoms on Cu NPs, eventually forming a graphene cover. 40,41,[46][47][48][49][50][51][52][53] However, to our knowledge, no techniques have been proposed to produce Cu@G NPs in steps, i.e., generating the Cu NPs and graphene flakes separately and then putting them together in a single medium. Our results suggest that, in these cases, it would not matter if the adsorption of the flakes on the NPs occurs planar one by one or if they first form a stack and then adsorb perpendicularly.…”

“…Until now, the reported protocols consist of depositing C atoms on Cu NPs, eventually forming a graphene cover. 40,41,46–53 However, to our knowledge, no techniques have been proposed to produce Cu@G NPs in steps, i.e. , generating the Cu NPs and graphene flakes separately and then putting them together in a single medium.…”

“…13 In addition, graphene-water NFs were investigated as heat sinks, resulting in an increment in the convective heat transfer that reached B84%; 37 in a heat pipe, graphene nanosheets were reported to enhance the k of water by B28%; 38 and even a greater improvement was quantified for ethylene glycol, where dispersed graphene increased the k by up to 86% at 5.0 vol%. 39 Although some studies have provided methods to produce Cu@G heterostructures, [40][41][42][43][44][45][46][47][48][49][50][51][52][53] their diameter, size distribution, shape, and the number of graphene capping layers remain uncontrollable. These properties depend on many factors, which are hard to manipulate during the synthesis process.…”

“…Although some studies have provided methods to produce Cu@G heterostructures, 40–53 their diameter, size distribution, shape, and the number of graphene capping layers remain uncontrollable. These properties depend on many factors, which are hard to manipulate during the synthesis process.…”

Tunable Electrochemical Approach for Reduction of Graphene Oxide: Taguchi-Assisted Chemical and Structural Optimization

“…High thermal and mechanical stability (200 times greater than steel), room temperature Hall effect, huge surface area (∼2630 m 2 /g higher than single-walled carbon nanotubes) and tuning bandgap are the main specific characteristics of graphene. [1][2][3][4] By considering fullerenes as a 0-D, single wall carbon nanotube as 1-D and graphite as 3-D nanomaterials, graphene became a newborn member of the multidimensional carbon-based material family which fills the gap for 2-D carbon-based nanomaterials. Since 2004 and after the surprising rediscovery of a straightforward approach for isolation of individual graphene sheets, fundamental research works have been rapidly carried out.…”