Publications

Structural Health Monitoring (SHM) is needed both to improve life-safety and to reduce the direct operational costs. Nowadays, a new concept called effective Structural Health Monitoring (eSHM) has proven to be efficient but still needs to pass different technological readiness levels to enable its implementation. This work demonstrates the feasibility study of eSHM systems produced by 3D printing or additive manufacturing. The objective of this work is to prove that the eSHM system has reached technological readiness level 3 (TRL3) and to indicate that during fatigue the integrated system had no influence on the crack initiation behaviour. First, two different techniques (selective laser melting and laser metal deposition) were used for the production of four-point bending feasibility test specimens with the integrated eSHM system. Next, a four-point bending test was selected, the specimens were subjected to the so-called step test method with constant fatigue stress amplitude and a constant R ratio. The fatigue behaviour of stainless steel and titanium alloy was studied with emphasis on crack initiation and detection. This study proves that the eSHM reaches the TRL3.The investigated system always detected cracks although further investigation is needed since higher TRL are required and the detection capability can be improved.

No abstract is provided for this article.

No abstract is provided for this article.

We investigated the surface morphology and magnetic properties of Co films grown on MgO (100) substrates before and after treatment with a NaOH solution. The surface morphology evolves from a continuous film into isolated hexagonal nanodisks resulting from the formation of cobalt hydroxide. In the as-grown Co films the magnetic anisotropy behaves as a superposition of fourfold magnetocrystalline anisotropy and uniaxial magnetic anisotropy (UMA), and the magnetization reversal proceeds by two-step domain-wall motion. After the NaOH treatment the UMA is reduced and the magnetization reversal appears to be dominated by magnetization rotation. In addition, the exchange bias effect, which in the as-deposited films results from the presence of a cobalt oxide layer, disappears after the NaOH treatment, and can be reinduced by annealing the sample. The observed significant changes in the magnetic properties can be related to the disappearance and reappearance of a cobalt oxide top layer.

No abstract is provided for this article.

Anodic electrochemical synthesis presents itself as a powerful and rapid method to produce porous metal–organic framework (MOF) powders and deposit MOF films onto metal surfaces. Such layers are of interest for adsorptive, catalytic or sensor applications. However, electrochemical MOF synthesis is still in a preliminary stage while a need to better control the process and understand the influences of the process parameters emerges. This work focuses on controlling the deposition of copper-1,3,5-benzenetricarboxylate (HKUST-1, Cu-BTC) MOF layers and targeting different crystal sizes. Moreover, it aims to shed some light on the mechanisms underlying these changes. A number of strategies can be adopted to control the process and adjust the obtained crystal size. By adjusting the synthesis time or water content, the average crystal size can be controlled up to ∼10 μm for ethanol-based synthesis mixtures. The potential also has a pronounced effect, yet a suitable operation window must first be determined to avoid incomplete film formation or excessive film detachment. Furthermore, the influence of the solvent composition on the deposited film morphologies was investigated for mixtures of water, methanol, ethanol, 2-propanol, acetonitrile, N,N-dimethylformamide and dimethylsulfoxide.

The analysis of iron, manganese and antimony in silicate glass is of great interest in chemistry, materials science, earth sciences and archaeological sciences. Yet, conclusions from different fields appear to be contradictory and many questions about redox reactions in glass remain. The purpose of this study is thus to discuss whether and how these multivalent elements interact in glass. Soda-lime silicate melts containing iron along with manganese and/or antimony have been analysed at different high temperatures under argon atmosphere. Using in-situ XANES at the Fe K-edge, redox thermodynamics, kinetics and diffusivities have been assessed for the different compositions. The data obtained show that antimony is more efficient at oxidising iron compared to manganese at all temperatures. The oxidising power trend would thus be Sb > Sb + Mn > Mn. Furthermore, hypotheses on the formation of Fe-Mn complexes are also reported in glasses with stoichiometric proportions of iron and manganese. Based on the determination of redox diffusivities, it appears that presence of other multivalent elements does not significantly affect the iron redox mechanisms and that diffusivity is essentially controlled by the mobility of calcium.

Identifying corrosion initiation events in metals and alloys demands techniques that can provide temporal and spatial resolution simultaneously. Transmission electron microscopy (TEM) enables one to obtain microstructural and chemical descriptors of materials at atomic/nanoscopic level and has been used in corrosion studies of many metal-electrolyte combinations. Conventionally, ex situ and quasi in situ TEM studies of pre- and post-corroded samples were performed, but possible experimental artifacts such as dehydrated surfaces might not fully represent the real interfacial conditions as compared to those when actually immersed in the electrolyte. Recent advances in liquid cell transmission electron microscopy (LC-TEM) allows for in situ monitoring morphological and even compositional evolutions in materials resulting from interaction with gas or liquid environments. Corrosion science, as a challenging field of research, can benefit from this unparalleled opportunity to investigate many complicated corroding systems in aqueous environments at high resolution. However, “real life” corrosion with LC-TEM is still not straightforward in implementation and there are limitations and challenging experimental considerations for conducting reliable examinations. Thus, this study has been devoted to discussing the challenges of in situ LC-TEM wherein state-of-the-art achievements in the field of relevance are reviewed.

n-Si/SiO2(Cu) structures with different morphologies of copper deposits are produced using the template synthesis method. Deposition of Cu nanostructures and their structural features is thoroughly studied, and mechanisms for the formation of compact and dendrite-like deposits in the pores of the SiO2 template on the n-type single-crystal silicon substrate are established. Spatially separated copper dendrites are obtained and used to investigate the efficiency of Raman scattering enhancement using the aqueous solution of the Rhodamine 6G dye.

not Available.

The oxide layer, present between an organic coating and the substrate, guarantees adhesion of the coating and plays a determinating role in the delamination rate of the organic coating. The purpose of this study is to compare the resistive and semiconducting properties of thermal oxides formed on steel in two different atmospheres at 250°C: an oxygen rich atmosphere, air, and an oxygen deficient atmosphere, N2. In N2, a magnetite layer grows while in air a duplex oxide film forms composed by an inner magnetite layer and a thin outer hematite scale. The heat treatment for different amounts of time at high temperature was used as method to sample the thickness variation and change in electronic and semiconducting properties of the thermal oxide layers. Firstly, linear voltammetric measurements were performed to have a first insight in the electrochemical behavior of the thermal oxides in a borate buffer solution. Electrochemical impedance spectroscopy in the same buffer combined with the Mott–Schottky analysis were used to determine the semiconducting properties of the thermal oxides. By spectroscopic ellipsometry (SE) and atomic force microscopy (AFM), respectively, the thickness and roughness of the oxide layers were determined supporting the physical interpretation of the voltammetric and EIS data. These measurements clearly showed that oxide layers with different constitution, oxide resistance, flatband potential and doping concentration can be grown by changing the atmosphere.

This paper discusses the composition of the vessel and window glass from three Late Antique Cypriot sites: Yeroskipou, Maroni-Petrera and Kalavasos-Kopetra. Over 170 glass fragments were sampled for quantitative chemical analysis through EPMA measurements. The aim of this work is to establish new insights on the chemical compositions of the glass from Late Antique Cypriot sites to observe the distribution of glass on the island. Furthermore, we compare our dataset with published data of contemporary materials from other regions. Four compositional groups were recognized and correlated to known chemical compositions: Levantine 1, Egypt 1, two types of HIMT glass, HIMTa and HIMTb, while a new group, High Lime Iron Manganese Titanium (HLIMT) has been defined. Glass was supplied to Cypriot glassmakers by both Egyptian and Syro-Palestinian primary producers. Nevertheless, we have observed a specific distribution pattern on the island. In the west, there is about 50:50 ratio between Levantine and Egyptian suppliers. On the contrary, in the central south coast the amount of Egyptian glass drops consistently, in particular in Kalavasos, leaving space to Levantine glass.

We present a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. We show by means of Raman spectroscopy and atomic force microscopy that the removal of graphene is successful with minimal damage to the underlying SOI waveguides. Finally, we employ both removal techniques to measure the contribution of graphene to the loss of grating-coupled graphene-covered SOI waveguides using the cut-back method.

Impressed current cathodic protection (CP) based on pulse technology has been proven to be a more efficient and effective alternative of traditional CP for reinforced concrete applications. Essentially, the superiority of pulse CP is in achieving the required steel polarization with otherwise reduced side effects (e.g. influence on bond strength or cement-based bulk matrix properties are minimized); further utilization of lower anodic surface is possible with pulse CP as a result of a better “current throw” at certain frequency and duty cycle of the pulse. The technique has not been tested so far with respect to microbiologically induced corrosion (MIC) and marine applications of steel structures. This paper will present the concept of recently initiated research for MIC corrosion control through the synergetic action of pulse CP and bio-based coatings. The emphasis is on steel structures for marine applications. An essential part of the expected corrosion control is based on the action of hybrid bio-based coatings, involving competitive microorganisms. The application targets self-healing with respect to MIC and hydrogen-induced damage. Control of anaerobic MIC will be one of the main goals of this research. Extending the application to reinforced concrete and underground pipe-network is also foreseen. The fundamental mechanisms with respect to MIC corrosion will be defined in parallel to the mechanisms of cathodic polarization when MIC is involved. Clarifying the reasons for steel ennoblement in anaerobic conditions under CP will be achieved and an optimum polarization level will be derived. The first step in this research will be studying the electrochemical behavior of steel in simulated environment as within aerobic, anaerobic and mixed MIC conditions (at open circuit and under cathodic polarization) and the results coupled to steel surface analysis and bacterial viability under conventional and pulse CP.

Understanding the stability of chemical interactions at the polymer/metal oxide interface under humid conditions is vital to understand the long-term durability of hybrid systems. Therefore, the interface of ultrathin PMMA films on native aluminum oxide, deposited by reactive adsorption, was studied. The characterization of the interface of the coated substrates was performed using ambient pressure X-ray photoelectron spectroscopy (APXPS), Fourier transform infrared spectroscopy in the Kretschmann geometry (ATR-FTIR Kretschmann) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The formation of hydrogen bonds and carboxylate ionic bonds at the interface are observed. The formed ionic bond is stable up to 5 Torr water vapour pressure as shown by APXPS. However, when the coated samples are exposed to an excess of aqueous electrolyte, an increase in the amount of carboxylate bonds at the interface, as a result of hydrolysis of the methoxy group, is observed by ATR-FTIR Kretschmann. These observations, supported by ToF-SIMS spectra, lead to the proposal of an adsorption mechanism of PMMA on aluminum oxide, which shows the formation of methanol at the interface and the effect of water molecules on the different interfacial interactions.