The concentrations, behaviour and fate of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in the urban atmosphere

Polycyclic aromatic hydrocarbons (PAHs) play an important role in urban air quality due to the toxic and carcinogenic hazard they present. A class of pollutants receiving increasing interest from researchers are oxygenated (OPAH) and nitrated (NPAH) derivative compounds. There is a need for an improved understanding of the sources, concentrations, behaviour and fate of these pollutants as they can pose a similar public health risk as PAHs and can enter the environment both from primary combustion emissions and secondary formation from atmospheric reactions. This study investigates the airborne concentrations of PAH, OPAH and NPAH compounds in U.K. atmosphere at heavily trafficked and urban background sites. Sampling campaigns were conducted to assess the spatial and temporal trends, primary and/or secondary sources, gas-particle phase partitioning and atmospheric degradation of PAHs, NPAHs and OPAHs. Differences in atmospheric concentrations between trafficked sites and the urban background site indicate a variable influence of road traffic emissions between different PAH, OPAH and NPAH compounds. Seasonal, diurnal and temporal patterns as well as positive matrix factorisation (PMF) source apportionment provide evidence of the key influencing factors governing the concentrations of PAHs, OPAHs and NPAHs in the urban atmosphere, in addition to the strength of road traffic emissions

Recent developments in graphene oxide/epoxy carbon fiber-reinforced composites.

The two-dimensional macro molecule graphene and its derivatives have widely been investigated for their application as nanofiller in carbon fibre-reinforced composites (CFRC). Research has progressed from techniques that simply mix graphene as a mixing constituent within the composite material to more complex examples where graphene is covalently bonded to fibre, matrix or both via multiple reaction steps. This field of research is multi-disciplinary whereby branches of materials, engineering, polymer science, physics and chemistry often overlap. From the materials engineering perspective, the desire is to discover the novel materials targeting industrial applications and obtain a full understanding of the graphene oxide chemistry and interaction of graphene oxide with a polymer matrix. To date, most of the research is targeted at (i) improving the fibre / matrix interface properties and / or (ii) improving the dispersion of nanofiller within the matrix; both of these factors ultimately improve composite performance. Organising that information critically can lead to emergence of a generalization of material design. Therefore, the objective of this work is to critically review current state of art in the field of graphene oxide / epoxy CFRCs and propose the design rules based on current scientific trend and common themes for future works

Investigation on mechanical and thermal properties of 3D-printed polyamide 6, graphene oxide and glass-fibre-reinforced composites under dry, wet and high temperature conditions.

This study is focused on 3D printing of polyamide 6 (PA6), PA6/graphene oxide (PA6/GO) and PA6/glass-fibre-reinforced (PA6/GF) composites. The effect of graphene oxide and glass-fibre reinforcement on 3D-printed PA6 is explored for improvement of the interfacial bond and interlaminar strength in ambient, wet and high temperature conditions relating to electric car battery box requirements. The influence of environmental conditions and process parameters on the 3D printed polymer composites quality is also examined. Commercial PA6 filament was modified with GO to investigate the thermal and mechanical properties. The modified composites were melt-compounded using a twin-feed extruder to produce an improved 3D-printing filament. The improved filaments were then used to 3D-print test samples for tensile and compression mechanical testing using universal testing machines and thermal characterisation was performed following condition treatment in high temperature and water for correlation to dry/ambient samples. The study results show the studied materials were mostly suitable in dry/ambient conditions. PA6/GF samples demonstrated the highest strength of all three samples in ambient and high-temperature conditions, but the least strength in wet conditions due to osmotic pressure at the fibre/matrix interface that led to fibre breakage. The introduction of 0.1% GO improved the tensile strength by 33%, 11% and 23% in dry/ambient, dry/high temperature and wet/ambient conditions, respectively. The wet PA6/GO samples demonstrated the least strength in comparison to the ambient and high temperature conditions. Notwithstanding this, PA6/GO exhibited the highest tensile strength in the wet condition, making it the most suitable for a high-strength, water-exposed engineering application