In this work, needle-like and micro-spherical agglomerates of nanocrystalline hydroxyapatite (HA) were successfully assembled on the surface of graphene sheets with the aid of dopamine having two roles, as a template and a reductant for graphite oxide during the process of self-polymerization. The crystalline structure and micromorphology of HA can be conveniently regulated by controlling the mineralization route either with a precipitation (cHA/GR) or biomimetic methodology (bHA/GR). Both the composites exhibit improvements of ∼150% and ∼250% in sensitivity towards the sensing of ammonia at room temperature, compared with that of bare graphene. The combination of the multi-adsorption capability of HA and the electric conductivity of graphene is proposed to be the major reason for the observed enhancements. Gas sensing tests demonstrated that the HA/GR composites exhibit excellent selectivity, high sensitivity and repeatable stability towards the analytical sensing of ammonia.

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The corrosion rate in the splash and tidal zones of marine steel structures is very severe. Thermally sprayed coatings of zinc or aluminium and their alloys are among the most important technologies to eliminate this problem. This experimental study on the protective properties of thermally sprayed zinc and aluminium coatings on steel piles was conducted in an apparatus for simulating the marine corrosion environment. Particular attention was given to the anticorrosion performance of thermally sprayed zinc and aluminium coatings in the splash and tidal zones in combination with the cathodic protection of bare steel in the immersed zone. The experimental results showed that top to bottom thermal spraying of zinc or aluminium coatings on steel piles before their installation was effective, but that under cathodic protection conditions, protection of thermally sprayed zinc or aluminium coatings is effective up to the average middle tidal zone. CEST/2029 The authors are in the Institute