Publications

Fatigue of Ti6Al4V Structural Health Monitoring Systems Produced by Selective Laser Melting

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.

Albumin Protein Adsorption on CoCrMo Implant Alloy: Impact on the Corrosion Behaviour at Localized Scale

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.

Advanced (In Situ) Surface Analysis of Organic Coating/Metal Oxide Interactions for Corrosion Protection of Passivated Metals

Passivated metal surfaces are commonly coated by organic coatings to protect them against various types of corrosion such as pitting, intergranular, and exfoliation. Achieving durable coating protection in hostile conditions is a ubiquitous problem of interface engineering, which requires a local understanding on chemical interactions at the hybrid polymer/metal oxide interface. However, it is very challenging to get useful information directly from this solid/solid interface. This article explains different synthesis and analysis approaches that allow the (in situ) investigation of the buried interface, leading to the extraction of information regarding the molecular interfacial chemistry by surface analysis techniques. Different pretreatments of the metal oxide substrate prior to coating can improve interfacial bonding strength and durability. Therefore, it will be shown that certain surface oxide properties are directly correlated with the quality of interfacial interactions. Next, different hybrid structure synthesis approaches are discussed, which allow to characterize chemical interactions locally at the interface by conventional surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ions mass spectrometry (ToF-SIMS), and other spectroscopic techniques. A new generation of techniques such as ambient pressure XPS (APXPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) in the Kretschmann geometry, and sum-frequency generation vibrational spectroscopy are nowadays utilized to investigate the influence of external conditions on the hybrid interface such as changing ambient conditions in situ.

Study of the catalyst evolution during annealing preceding the growth of carbon nanotubes by microwave plasma-enhanced chemical vapour deposition

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.

Drying Effects on Corrosion Properties of Cr(VI) and Cr(III) Treated Electrogalvanized Steel

not Available.

About the Influence of Double Bonds in the APPECVD of Acrylate‐Like Precursors: A Mass Spectrometry Study of the Plasma Phase

This work deals with the in‐situ mass spectrometric (MS) characterization of gases during the atmospheric pressure plasma‐enhanced chemical vapor deposition of propyl isobutyrate (PiB) and allylmethacrylate (AMA). By monitoring the fragments of interest, we are trying to understand the mechanisms involved in the plasma synthesis of acrylate‐like coatings. For instance, while CO 2 + drastically increases when a PiB/argon plasma is ignited, it decreases in the case of AMA. This trend also appears for other fragments, which leads to the conclusion that while PiB seems to suffer from fragmentation, AMA oligomerizes into the gas phase, resulting in a better protection of the ester functionality.

Study of the mechanism of the chemical conversion of aluminium

No abstract is provided for this article.

Chemisorption of polyester coatings on zirconium-based conversion coated multi-metal substrates and their stability in aqueous environment

In this work, in-situ ATR-FTIR in the Kretschmann configuration is proposed as an interfacial sensitive technique able to probe molecular processes at the buried interface of an industrial relevant polyester primer. Zinc, aluminium and magnesium oxide were used to represent oxides present at galvanized steel sheets used in coil coating. Two competing interactions with polyester resin and melamine-based crosslinker were shown to take place at metal hydroxide sites. This highlights the increased complexity of interfacial phenomena at metal–paint interfaces. Furthermore, in-situ ATR-FTIR was performed in deuterated water (D2O) to study the evolution of interfacial carboxylate bond degradation, without overlap of dominant water signals. For the first time, interfacial bond formation of paints and its degradation in an aqueous environment is studied in-situ. It is shown that the introduction of D2O at the interface initially increases the amount of interfacial carboxylate bonds, whereas upon longer exposure times bond degradation occurs. Significant delay of interfacial bond degradation on hexafluorozirconic acid treated oxides indicate successful stabilization of the metal-polymer interface by zirconium-based conversion coatings. Consequently, in-situ ATR-FTIR is able to demonstrate improved interfacial stability due to zirconium-based treatment in real-time and on a molecular level.

Encapsulation of corrosion inhibitors in a self-healing polymeric coating.

No abstract is provided for this article.

Studying the different possibilities of using FEG-AES to characterise Al-Mg alloys.

No abstract is provided for this article.

Influence of rolled-in oxides on the surface properties of aluminium sheet

Discrimination between different aluminium oxides using field emission Auger electron spectroscopy

Characterisation of corrosion protection of aluminium alloys by silanes

Ex and in situ analysis of the growth of ultrathin organic films from ethanol solutions

No abstract is provided for this article.

The Role of Cu-Based Intermetallic on the Direct Growth of a ZnAl LDH Film on AA2024

The direct ZnAl layered double hydroxide growth on AA2024 is a fast-occurring reaction, yet is characterized by an inhomogeneous film thickness. It has been shown that at the periphery of Cu-rich intermetallic, the flakes tend to be larger and denser. A combination of in situ and ex situ measurements were used to monitor the changes in the layered double hydroxide film grown on the regions of intermetallics. Immediately after immersion, an activation of the intermetallic phases is observed due to the dealloying process with an almost immediate film growth. Dealloying is followed by trenching of the adjacent Al matrix leading to an excessive production of large and dense layered double hydroxide flakes at the periphery of the intermetallic. However, the scanning electron microscopy cross-section images revealed that the trenching process leads to defects in the area surrounding the intermetallic. This could weaken the corrosion resistance performance of the layered double hydroxide conversion coating and lead to adhesion failure of consecutive polymer coatings. Nevertheless, this work highlights a few advantages and drawbacks of the layered double hydroxide conversion coatings and pathways to its potential optimization and improvement.

Corrosion performance of PETG-coated packaging steel after uniaxial deformation

No abstract is provided for this article.

In this issue

A review of atmospheric corrosion with a focus on the deterministic multiscale modeling techniques.

Exploring Wetting Dynamics on Superhydrophobic Nanopatterned Surfaces Using ATR-FTIR

Accurate characterization of the underwater stability of superhydrophobic surfaces is crucial for the design of durable anti-fouling materials and advanced microfluidic concepts. Although superhydrophobic breakdown is a major issue that hampers full exploitation of superhydrophobic functional materials, suitable characterization methods are lacking and relatively little is known about the wetting dynamics. In this work we explore a novel method based on attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) for large-area in-situ analysis of wetting states and wetting transitions on nanostructured surfaces. Spontaneous wetting is induced on superhydrophobic silicon nanopillars through in-situ modulation of the liquid composition and surface tension. The high surface sensitivity of ATR-FTIR enables quantitative evaluation of the instantaneous liquid composition and wetted area. Critical transition criteria for superhydrophobic breakdown are assessed using both ATR-FTIR and goniometric measurements. Significant deviations from classical wetting models are revealed, emphasizing the need for more accurate transition criteria and careful experimental validation. Breakdown kinetics near the critical transition are found to be significantly slowed down on nanostructured surfaces, which underlines the necessity for accurate characterization of wetting dynamics at the nanoscale. The proposed ATR-FTIR method can be promising for dynamic studies of wetting transitions on more advanced surfaces, as hierarchical structures or oleophobic designs.