Publications

No abstract is provided for this article.

Selective laser melting (SLM) is an additive manufacturing (AM) process which is used for producing metallic components. Currently, the integrity of components produced by SLM is in need of improvement due to residual stresses and unknown fracture behavior. Titanium alloys produced by AM are capable candidates for applications in aerospace and industrial fields due to their fracture resistance, fatigue behavior and corrosion resistance. On the other hand, structural health monitoring (SHM) system technologies are promising and requested from the industry. SHM systems can monitor the integrity of a structure and during the last decades the research has primarily been influenced by bionic engineering. In that aspect a new philosophy for SHM has been developed: the so-called effective structural health monitoring (eSHM) system. The current system uses the design freedom provided by AM. The working principle of the system is based on crack detection by means of a network of capillaries that are integrated in a structure. The main objective of this research is to evaluate the functionality of Ti6Al4V produced by the SLM process in the novel SHM system and to confirm that the eSHM system can successfully detect cracks in SLM components. In this study four-point bending fatigue tests on Ti6Al4V SLM specimens with an integrated SHM system were conducted. Fractographic analysis was performed after the final failure, while finite element simulations were used in order to determine the stress distribution in the capillary region and on the component. It was proven that the SHM system does not influence the crack initiation behavior during fatigue. The results highlight the effectiveness of the eSHM on SLM components, which can potentially be used by industrial and aerospace applications.

The protein adsorption and both its conformational arrangements and electrochemical interactions on the surface of metallic biomaterials has an immense impact on corrosion/biodegradation and biocompatibility of implantable metals. In this study, we used scanning Kelvin probe force microscopy (SKPFM) to reveal the synergistic effect of various bovine serum albumin (BSA) concentrations and overpotential conditions on BSA protein adsorption mechanisms and its influence on the corrosion behaviour of the CoCrMo alloy in phosphate-buffered saline solution. Electrochemical measurements showed that CoCrMo alloy was more resistant to corrosion in the 2 g l −1 BSA protein medium than in the 0.5 g l −1 one. The SKPFM analysis revealed a lower surface potential on the regions where BSA was adsorbed forming clusters, than on the un-covered CoCrMo substrate. When the surface overpotential and the protein concentration were increased from the OCP to +300 mV vs Ag/AgCl and from 0.5 to 2 g l −1 , respectively, on both protein covering and surface potential were increased. Field emission scanning electron microscopy indicated that localized corrosion eventually occurred at the BSA protein/substrate interface owing to the adsorption of counterions and the difference between the surface potential values.

A two-step catalyst annealing process is developed in order to control the diameter of nickel catalyst particles for the growth of carbon nanotubes (CNTs) by microwave plasma-enhanced chemical vapour deposition (MW PECVD). Thermal annealing of a continuous nickel film in a hydrogen (H2) environment in a first step is found to be insufficient for the formation of nanometre-size, high-density catalyst particles. In a second step, a H2 MW plasma treatment decreases the catalyst diameter by a factor of two and increases the particle density by a factor of five. An x-ray photoelectron spectroscopy study of the catalyst after each step in the annealing process is presented. It is found that the catalyst particles interact with the substrate during thermal annealing, thereby forming a silicate, even if a buffer layer in between the catalyst and the substrate is intended to prevent silicate formation. The silicate formation and reduction is shown to be directly related to the CNT growth mechanism, determining whether the catalyst particles reside at the base or the tip of the growing CNTs. The catalyst particles are used for the growth of a high-density CNT coating by MW PECVD. CNTs are analysed with electron microscopy and Raman spectroscopy.

No abstract is provided for this article.

No abstract is provided for this article.

A novel molecularly imprinted monolithic (MIM) column was designed and fabricated using the epitope approach and used for the selective capillary microextraction (CME) of neuropeptides neurotensin (NT) and neuromedin N (NmN). The MIMs were synthesized in a capillary by thermally initiated polymerization of the functional monomer (methacrylic acid (MAA)), in the presence of a dummy template (Pro-Tyr-Ile-Leu (PYIL)), a crosslinker and porogens. The resulting monoliths were characterized by scanning electron microscopy, pore size distribution measurement, and Fourier transform infrared spectroscopy. The MIMs were used to enrich NT and NmN from human plasma prior to HPLC-UV analysis. The imprinted monolith showed high dynamic binding capacity (rebinding equilibrium at 40~50 min) and selectivity (imprinting factor of 5.7~13.4) towards its target peptides, as well as an excellent maximum adsorption capacity of 245~711 mg mL -1 . Low detection limits of 0.62 and 1.20 nM, and satisfactory recoveries (82.5-98.8%) were obtained for NT and NmN, respectively. The proposed MIM-CME/HPLC-UV method may be used as an effective tool for the highly efficient and specific analysis of neuropeptides in biological fluids.

For the characterisation of Al surfaces after thermo mechanical processing of rolled strips TEM is imperative. Especially cross-sectional TEM specimens highlight the multi-layered structures of the surface area. The specimen preparation of cross-sections is a critical step in TEM analysis. A common technique is ultramicrotomy, where a diamond knife is used to cut electron transparent slices. The major disadvantage of the method - especially in the case of aluminium - is the strong mechanical deformation resulting from cutting. Another technique is the conventional ion beam milling. In order to provide views of subsurface regions, the sample surfaces are initially glued together, then cut perpendicular to the sheet surface, mechanically thinned, cut to form disks, dimpled, and ion beam thinned. Here, a new method for preparing cross-sectional TEM specimens of aluminium surfaces is introduced: Focused Ion Beam thinning (FIB), which became a standard method for preparation in the semiconductor industry. This technique has the potential of introducing nearly no chemical and structural modifications in the specimen. TEM lamellae of equal thickness can be produced in less than two hours and the success rate is nearly 100%. As an example for this new preparation method the paper reports about a (S)TEM investigation of a FIB prepared specimen of the surface of an AlMg0.5 hot rolled strip.

No abstract is provided for this article.

The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride–urea deep eutectic solvent (DES) containing different amounts of water. By combining electrochemical techniques, with ex situ field emission scanning electron microscopy, high-angle annular dark field scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy, the effect of water content on the electrochemical processes occurring during nickel deposition was better understood. At highly negative potentials and depending on water content, Ni growth is halted due to water splitting and formation of a mixed layer of Ni/NiOx(OH)2(1–x)(ads). Moreover, under certain conditions, the DES components can also be (electro)chemically reduced at the electrode surface, blocking further three-dimensional growth of the Ni NPs. Hence, a two-dimensional crystalline Ni-containing network can be formed in the interparticle region.

No abstract is provided for this article.