Examining slit pore widths within plasma-exfoliated graphitic material utilising Barrett–Joyner–Halenda analysis

Plasma-exfoliated multilayer graphitic material (MLG) consists of orderly aligned stacks which contain many partially oxidised graphitic layers. Slit pores are present between successive stacks and their presence allows for improved friability, facile dispersion and accessibility for the intercalation of compounds. Whilst much research exists into the synthesis and application of MLG, there is a lack of quantitative data regarding their porous structures. This report outlines the structure of MLG as well as the application of Barrett–Joyner–Halenda (BJH) analysis to estimate the distance between adjacent stacks of orderly aligned graphitic layers within MLG. It was found that the distance between stacks can vary quite substantially between 2–131 nm within these plasma-derived materials, correlating with the width of meso- and macro-slit pores. Furthermore, t-plot data also suggests that micropores, likely to exist in the form of both slit pores and in-plane pores, are present within the material, hence stack separations may also exhibit distances of <2 nm. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) were used to assist in this interpretation and to correlate with the BJH analysis. MLG was further analysed using Transmission Electron Microscopy (TEM), Brunauer–Emmett–Teller (BET) and t-plot analysis, X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy to gain a comprehensive understanding of the material investigated. The above techniques provided results which were consistent with the BJH porosity analysis, thus establishing it as a straightforward and highly effective method for understanding materials with broad pore distributions such as MLGs

Recovery of zinc from scrap steel using zinc–bromine battery technology

Secondary production of steel is proven to significantly decrease CO2 emissions of steelmaking, but only 40 % of steel is produced via recycling, which is made difficult by contamination of scrap resources with non-ferrous metals and non-metal debris. These contaminants include zinc, which blast furnace and electric arc systems have a low tolerance towards (&lt; 0.02 wt%). In this work, clean and efficient recovery of zinc from the surface of steel substrates was investigated using a custom-made low-cost membrane-free non-flow zinc-bromine battery (ZBB) that enabled rapid and straightforward integration and removal of steel substrates. The electrical performance of the cell was characterised by charge-discharge profiles, and zinc removal and recovery onto electrodes was characterised using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Upon discharging, the cell efficiently removed &gt; 99.9 wt% zinc from steel surfaces. On recharging the cell, zinc was re-electroplated onto a carbon foam electrode in an easily recoverable form and with high purity. The process was repeated over 30 cycles to demonstrate robustness. The work shows the importance of the cut-off voltage upon discharging: if less than 0.5 V, the cell co-extracted iron into the electrolyte solution, affecting cell durability and zinc purity. A two-stage process for recovering zinc from scrap steel is proposed, illustrating how ZBB technology could enable efficient and clean recovery of zinc from complex scrap steel resources in the steel industry

Boronic acids for functionalisation of commercial multi-layer graphitic material as an alternative to diazonium salts

A novel radical-based functionalisation strategy for the synthesis of functionalised commercially obtained plasma-synthesised multi-layer graphitic material (MLG) is presented herein. 4-(trifluoromethyl)phenyl boronic acid was utilised as a source of 4-(trifluoromethyl)phenyl radicals to covalently graft upon the graphitic surface of MLG. Such a methodology provides a convenient and safer route towards aryl radical generation, serving as a potential alternative to hazardous diazonium salt precusors. The structure and morphology of the functionalised MLG (Arf-MLG) has been characterised using XPS, Raman, TGA, XRD, SEM, TEM and BET techniques. The XPS quantitative data and Raman spectra provide evidence of successful covalent attachment of 4-(trifluoromethyl)phenyl groups to MLG

Oleophobic composite films based on multi-layer graphitic scaffolding

A new oleophobic composite material synthesised by utilising plasma-exfoliated multi-layered graphitic (MLG) material as scaffolding is presented herein. The composite consisted of a polyelectrolyte/fluorosurfactant complex derived from polydiallyldimethylammonium chloride (PDDA) and sodium perfluorooctanoate (PFO) and was used to prepare free-standing MLG composite films

Oleophobic coated composite materials based on multi-layer graphitic scaffolding: applications within aircraft propellant tanks and oil-spill clean-up †

The preparation of oleophobic materials coated with a composite based on a multi-layer graphitic scaffolding is reported herein. A range of substrates were employed for this purpose including Kevlar, carbon fibre, glass fibre, nylon and stainless steel mesh. These were utilised, in comparison with free-standing film versions of the composite material, to investigate their enhanced ability to facilitate water penetration whilst simultaneously retaining the oleophobic behaviour. The materials demonstrated efficient oil/water separations and reusability. The free-standing films and coated substrates were characterised in detail via a range of spectroscopic and analytical techniques. Contact angle measurements for aviation Jet A-1 fuel on various coated substrates ranged from 96.9–107.0° whilst for hexadecane and silicone oil, contact angles of 90.6–120.3° and 74.5–103.3° were recorded, respectively. These values were slightly lower than the contact angles for the corresponding free standing film versions which were 111.9°, 126.4° and 105.9° for Jet A-1 fuel, hexadecane and silicone oil, respectively. BET surface area analysis of composite and films showed type IIb isotherms with H3-type hysteresis. T-Plot analysis was carried out to quantify external surface area of the composite and film in comparison to the base multilayered graphitic material scaffold. The morphology of the materials was analysed by SEM imaging to show the extent and degree of coating on the composite material upon the substrates. The application of these coated substrates as membranes within the context of aircraft propellant tanks and oil-spill removal was also explored, suggesting that coated carbon fibre and coated nylon serve as promising candidates for oil/water separation within these applications