With its unique physical properties, graphene creates an exceptional platform for fundamental science and a promising material for many applications. However, the large-scale production of graphene with high quality and few layers is still challenging. To understanding the preparation methods of the graphene and the influence of their process parameters on the electronic structure is not only crucial for developing its applications in research fields, but also vital for the future graphene industrial production. This work is an overview of the most state-of-the-art research approaches and latest advancement described in the literature for synthesizing graphene and their associated properties.
Carbon nanotubes and titania, highly corrosion-resistant materials, are successfully assembled into high surface area microparticles (162 m 2 g −1 ) in one step using low-power ultrasound. The composite microparticles are electrically conductive (>0.4 S cm −1 ). The microparticles are deposited as an electrical layer (<2.5 µm) on a stainless-steel mesh gas diffusion layer using a tribochemical coating technique. Long-term durability testing in 0.5 m H 2 SO 4 at 80 °C confirms the corrosion resistance of the catalyst coating. This coating method may have wider applicability for other electrical and electrochemical devices that require thin corrosion-resistant coatings.
This work describes a low‐cost 3D printed apparatus developed for powder electrical conductivity measurement with electrodes fitted in either a two‐probe or four probe van der Pauw configurations. Electrical conductivity was then measured as a function of density by compressing the powders in an Instron mechanical test machine. Highly conductive carbon black, lower conductive Fe3O4 and titania carbon nanotube composites were further tested under both methodologies to assess their reliability. Small powder masses are required for each measurement and our data matched well with literature values. It appeared that 3D printed polymer dies could be used to measure powder conductivity, though loss of material on the die walls was a source of error especially for small powder volumes.
A new method of preparing metal sols, by the use of a continuous high frequency electrical discharge of sufficient intensity to produce a sinusoidal spark, is described. Stable yellow colloidal silver and purple colloidal gold have been prepared, without a protective colloid, by this method. Chemical determinations have failed to indicate any silver oxide in the yellow silver sols.
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