Surfaces, Volume 2, Issue 3 (September 2019) – 5 articles

The coating of highly stressed components with chemical vapor deposition (CVD) diamond can extend their lifetime. In particular, the combination of steel substrates with diamond layers would find many applications in industrial production. However, there are some challenges, for example, the high mismatch in the thermal expansion between steel and diamond, which commonly leads to the delamination of the coating. Thus, a pre-treatment of the substrate surface is needed. Particle blasting has been established in some studies as a suitable process. However, apart from particle residues in the surface of the substrate, these surfaces have a stochastic character, which limits their reproducibility and modification options. This paper presents some instructions for the recording and derivation of defined properties of those surfaces. The conversion of characteristic surface features into quantitative process parameters could serve as the foundation for the manufacturing of deterministic microstructures, especially those produced by ultrasonic vibration superimposed machining. This should increase the reproducibility and the possibilities of the modification with regard to the structural shaping of the functional surface. The design was developed using both a kinematic surface simulation tool as well as a finite elements analysis for the cooling process of the coating–substrate–composite. A high accordance with real finished surfaces was achieved. Full article

Corrosion resistance of steel has attracted substantial interest for manufacturing applications to reduce costs corresponding to part failures, unexpected maintenance, and shortening lifespan. Meanwhile, millions of tonnes of slag, non-recyclable glass, and automotive shredder residue (ASR) are discarded into landfills every year, polluting the environment. Combining these two major issues, we delivered an alternative solution to enhance corrosion resistance of high-C steel. In this research, utilisation of these wastes (which were chemically bonded into steel substrate) as sources for production of multi-hybrid layering—including the multi-phase ceramic layer, the carbide layer, and the selective diffusion layer—was successfully achieved by single step surface modification technology. High-resolution topographical imaging by SEM and chemical composition analysis in micron-volume by electron probe micro analyser (EPMA) were performed. Nano-characterisation by atomic force microscopy (AFM) using the PeakForce quantitative nanomechanical mapping (PF-QNM) method was conducted to define Young’s modulus value of each phase in detail. Results revealed improvement of corrosion resistance by 39% and a significantly increased hardness of 13.58 GPa. This integrated approach is prominent for economic and environmental sustainability, consolidating industry demands for more profits, producing durable, steel components in a cost effective way to reduce dependency on new resources, and minimising negative impacts to the environment from disposal of wastes to the landfills. Full article

Tweezer-like adsorbents with enhanced surface area were synthesized by grafting aniline onto the amine sites of a chitosan biopolymer scaffold. The chemical structure and textural properties of the adsorbents were characterized by thermogravimetric analysis (TGA) and spectral methods, including Fourier transform infrared (FT-IR), nuclear magnetic resonance (¹H- and, ¹³C-NMR) and scanning electron microscopy (SEM). Equilibrium solvent swelling results for the adsorbent materials provided evidence of a more apolar biopolymer surface upon grafting. Equilibrium uptake studies with fluorescein at ambient pH in aqueous media reveal a high monolayer adsorption capacity (Q_m) of 61.8 mg·g⁻¹, according to the Langmuir isotherm model. The kinetic adsorption profiles are described by the pseudo-first order kinetic model. 1D NMR and 2D-NOESY NMR spectra were used to confirm the role of π-π interactions between the adsorbent and adsorbate. Surface modification of the adsorbent using monomeric and dimeric cationic surfactants with long hydrocarbon chains altered the hydrophile-lipophile balance (HLB) of the adsorbent surface, which resulted in attenuated uptake of fluorescein by the chitosan molecular tweezers. This research contributes to a first example of the uptake properties for a tweezer-like chitosan adsorbent and the key role of weak cooperative interactions in controlled adsorption of a model anionic dye. Full article

In this research, hydroxyapatite (HA)–chitosan–titania nanocomposite coatings were formed on 316 L stainless steel using electrophoretic deposition (EPD) from alcoholic (methanol and ethanol) suspensions containing 0.5 g/L chitosan and 2 and 5 g/L HA and 2 and 5 g/L Titania. The effect of different parameters on the deposition rate, morphology, and corrosion resistance of the coatings in simulated body fluid (SBF) at 37 °C has been studied. The coatings’ properties were investigated using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Based on the results of this work, it was found that the deposition rate in ethanolic suspensions is lower than methanolic ones. Moreover, the coating surface was smoother when the ethanol was used as a solvent in suspensions in comparison to the ones where methanol was the solvent. The coating deposited from a suspension containing 0.5 g/L chitosan, 2 g/L HA, and 5 g/L titania with ethanol as solvent had the highest corrosion resistance in SBF at 37 °C. Full article