Publications

To facilitate and speed up the deployment of fiber-to-the-home networks, high-efficiency, low-cost, field installable fiber connectors are one of the key components. We present a novel type of small-form-factor 180°-bend single mode fiber socket, allowing for 0.5-<i>dB</i> coupling loss between two side-by-side positioned fibers, making use of specially designed low bending loss hole-assisted fiber. The components are prototyped in a polymer using Deep Proton Writing and show all the potentialities for low-cost fabrication in different types of plastics.

Aluminum alloy (AA) 3003 is widely used as fin and tube material in heat exchangers. In these heat exchangers, the tube and fin material are brazed together by means of an AA4xxx alloy. In this study, the effect of a simulated brazing step on the microstructure and corrosion behavior of a twin roll casted (TRC) AA3003 was studied. In particular, the effect of simulated brazing on the corrosion properties of the centre line segregation (CLS) of alloying elements and the interaction of the intermetallic particles with the surrounding matrix is explored. It is shown that the cross sections are significantly more active than the surface of the TRC AA3003, revealing the importance of the CLS on the corrosion behavior. Furthermore, it is shown that the number of pits and their depths decreased considerably on the exposed cross sections after simulated brazing, especially near the CLS. Scanning Kelvin probe force microscopy measurements show that after the simulated brazing step the Volta potential difference between the intermetallic particles and the matrix reduced significantly. This change in the Volta potential could be caused by the slight increase of Si content in the matrix.

An innovative experimental approach to study the electrodeposition of small nanoparticles and the early stages of electrochemical nucleation and growth is presented. Carbon coated gold TEM grids are used as substrates for the electrodeposition of silver nanoparticles so that electrochemical data, FESEM, HAADF–STEM and HRTEM data can be acquired from the same sample without the need to remove the particles from the substrate. It is shown that the real distribution of nanoparticles cannot be resolved by FESEM whereas HAADF–STEM analysis confirms that a distribution of ‘small’ nanoparticles (d≈1–2nm) coexist with ‘large’ nanoparticles corresponding to a bimodal size distribution. Besides, particles grown under the same conditions have been found to present different structures such as monocrystals, polycrystals or aggregates of smaller particles.

Deep eutectic solvents (DESs) are a new class of solvents with wider potential window than that of water and high electrochemical stability, making them potential candidates for a wide range of electrochemical systems. However, due to the hygroscopic nature of DESs, the presence of latent water is unavoidable. Therefore, understanding the interfacial structure and the electrosorption and distribution of residual water at the electrified interface is of great importance for the use of these solvents in electrochemical systems. Using atomistic molecular dynamics, we explore the electrosorption and distribution of different amounts of water in 1 : 2 choline chloride-urea DES (Reline) at the electrified graphene interface. We found that both the water distribution and the interfacial structure are sensitive to the electrification of the graphene electrode. As a result, it is found that for moderately charged electrodes, water shows a preferential asymmetric adsorption in the vicinity of the positively charged electrode, partly due to strong intermolecular interactions with anions through hydrogen bonds. In contrast, for highly charged electrodes, water adsorbs at both electrodes due to a strongly enhanced external electrostatic interaction between the electrodes and the water dipoles.

The curing kinetics of diglycidyl ether of bisphenol-A epoxy resin cured with a polyaminoamide in the absence and presence of nano-glassflakes were studied by means of non-isothermal differential scanning calorimetry experiments at four heating rates. The data were analyzed by different approaches. The experimental data for both neat and nano-glassflakes filled systems are well-represented by an nth-order behavior. The calculated ln(A/s −1), E a, and n for the neat system and nano-glassflakes filled systems are 9.52, 49.6kJmol−1, and 1.00, and 8.98, 47.83kJmol−1, and 0.97, respectively. Model-free methods show that the activation energy is roughly constant in both with and without NGF. In all analyses, E a values of the nano-glassflake filled system are lower than those of the neat epoxy/polyaminoamide throughout the curing reaction, despite lower differences.

No abstract is provided for this article.

The electrochemical behaviour of hot dip aluminium–silicon coatings on steel is studied in relation to the in-depth structure and composition, determined by SEM/EDX and EBSD. Progressive GDOES sputtering was used for electrochemical analysis using a micro-capillary three-electrode microcell in craters positioned in the various sublayers. Additionally, cross-sections were analyzed with SKPFM. Results show that the outer free aluminium layer of the coating is able to cathodically protect the underlying layers and substrate. Conversely, the interdiffusion layers are nobler than the steel. The galvanic series implies that cathodic protection will depend on the nature of the defect and the corrosion environment.

No abstract is provided for this article.

The growth of ZnAl layered double hydroxide (LDH) on the AA2024 surface was monitored using synchrotron high-resolution X-ray diffraction. Data were analyzed using the Avrami–Erofe'ev kinetic model. Accordingly, the LDH film growth is governed by a two-dimensional (2D) diffusion-controlled reaction with a zero nucleation rate. Additional methods, including ex situ atomic force microscopy/scanning Kelvin probe force microscopy (AFM/SKPFM) supported by in situ open-circuit potential (OCP) measurements together with scanning electron microscopy (SEM) and transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM/EDX) analysis, provided further insight into the different stages of the mechanism of LDH growth. Prior to the conversion coating formation, an intermediate layer is formed as a basis for the establishment of the LDH flakes. Moreover, a Cu-rich layer was revealed, which could contribute to the acceleration of LDH growth. The formed LDH layer does not show any cracks at the interface but presents minor irregularities in the structure, which could favor adhesion to subsequent organic coatings. The findings presented in this work provide an important insight to the corrosion performance of the LDH conversion coatings and the pathway to adopt for further optimization.

No abstract is provided for this article.

In this article a method is presented for characterizing the topography of surfaces with asymmetric roughness by analyzing topographic maps from interferometry measurements. For creating appropriate surfaces with asymmetric roughness, electropolished aluminium samples were electrograined by alternating current (AC) in hydrochloric acid. A pitted and convoluted surface with different extent of non-attacked areas (plateaus) and different pits height distribution was developed by using the AC-graining. Thus, surfaces with different extent of negative asymmetric roughness were developed by this technique. The shift induced by the asymmetric roughness between the mean surface level (MSL) and the true surface of the sample was estimated by the respective histograms of the height distribution. Subsequently, the histograms were corrected in order to identify the MSL with the true surface level. By the deconvolution with fitting of the corrected histograms, the extent of the plateau areas and the pits height distribution taking into account the true surface level of the sample were estimated. On the other hand, the extent of the plateau areas was also calculated by the percent data cut at the zero level of the respective corrected bearing ratio curves. Further, this method for correcting and analyzing roughness measurements in order to achieve the topography characterization of surfaces with asymmetric roughness is also applicable on industrially produced lithographic printing plates. In addition, this method could also be applied to other types of applications where the topography characterization of surfaces with negative asymmetric roughness is an important engineering factor.