Characterization of Fe-W alloys electrodeposited from environmentally friendly electrolyte

This work focuses on Fe-W and Fe-W/Al2O3 coatings electrodeposited from an environmentally friendly electrolyte: minimally invasive, thermodynamically stable, and without toxic compounds. Such coatings aim to be applied for protective applications and as a sustainable alternative to hard chromium coatings. Therefore, the goal of this thesis is to evaluate the interdependencies between the material characteristics (e.g. composition and structure) and the properties of interest: the mechanical properties as well as wear and corrosion resistance. The structure of the coatings was investigated with various analytical techniques (e.g. XRD, SEM, EBSD, and TEM among others), both in the as-deposited state and after heat treatments. Heat treatments led to microstructural transformations in the Fe-W coatings. Nanohardness and wear measurements were performed to study the influence of such microstructural changes on the mechanical properties and wear resistance of the Fe-W coatings. The results included in this thesis show that increasing the amount of co-deposited W in the coatings results in a transition from a nanocrystalline to a homogeneous amorphous structure, and to an increase in the thermal stability. In-situ TEM analyses on W-rich coatings (i.e. Fe24at.%W) revealed the formation of crystallites at 400 ℃ within the amorphous matrix. Moreover, a large fraction of the amorphous structure is still preserved upon annealing at 600 ℃, where alpha-Fe nanocrystals are found. The microstructural transformations result in an enhancement of mechanical properties of Fe-W coatings. The Fe-24at.%W coating is characterized with the highest hardness both in the as-deposited and annealed state, where a maximum value of 16.5 GPa is observed after annealing at 600 ℃. However, Fe-W coatings are characterized with rather low wear resistance due to severe tribo-oxidation resulting in high coefficient of friction (COF) and wear rates. A considerable improvement in the wear resistance is obtained with the co-deposition of 12vol.% of Al2O3 particles leading to a reduction in the COF and wear rate. The influence of the co-deposited alumina particles on the corrosion resistance is rather limited, i.e. similar values of the corrosion current are measured for the both the Fe-W/Al2O3 composites and Fe-W coatings. Annealing at 600 ℃ of Fe-W/12%Al2O3 composite leads to a combination of high hardness and high wear resistance which result superior to the hardness and wear resistance of hard chromium coatings

Electrodeposition of FeW-graphene composites: Effect of graphene oxide concentration on microstructure, hardness and corrosion properties

Graphene has emerged as excellent reinforcement for electrodeposited metallic composites. The poor stability of graphene in electrochemical baths makes it challenging to obtain uniform composite coatings. In this work, we investigate the possibility to electrodeposit FeW-graphene coatings with organic stablizers. Polydiallyldimethylammonium chloride is selected to stabilize the graphene oxide which is added into the electrolyte in various concentrations. Scanning electron microscopy and Raman analysis confirmed the successful co-deposition of graphene in all the coatings. The composition of the FeW matrix remained unaffected by the addition of graphene, while an increase in the crystallinity of the structure of the composites was observed. Graphene was retained even after the coatings were heat treated at 400 \ub0C for 1 h. The hardness and the corrosion resistance of the FeW-graphene composite were largely improved: a 22% increase in hardness and an 80% increase in corrosion resistance were measured compared to the graphene-free coating

Characterization of Electrodeposited Fe-based Metallic Coatings: Toward a Sustainable Approach

Electrodeposition has rapidly grown in the last 50 years and it has been applied to deposit metals and alloys with complex shapes or to produce fully dense nanostructures and amorphous coatings. Thanks to the achieved improved properties of the electrodeposited materials, electrodeposition has been applied in a wide set of applications including protective coatings, and magnetic and electronic applications. The integration of sustainability with technological progress has become one of the major challenges in our modern society. To fulfil this important goal within the area of electrodeposited materials, it is of major importance to develop innovative metallic coatings deposited with a sustainable approach. This means the use of environmental-friendly electrolytic baths for the deposition of properly designed alloys without or with minimum amounts of scarce or toxic elements.This work deals with the characterization of Fe-based metallic coatings electrodeposited with a sustainable approach. Characterization studies have been performed on Fe-W coatings and Sn coatings. The study on the Sn coatings has been performed as a preliminary investigation to be then followed up by the deposition and characterization of binary and ternary Fe-Sn coatings. Different techniques such as Scanning Electron Microscopy (SEM), Electron Back Scatter Diffraction (EBSD), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Glow Discharge Optical Emission Spectroscopy (GD-OES), and Nanoindentation were used to characterize the structure and the properties of the coatings.It was found that the as-deposited structure of the Fe-W coatings changes with increase of the W content: a nanocrystalline, a mixed nanocrystalline-amorphous, and a fully amorphous structure was found when raising the W content from 4 up to 24 at.%. The thermal stability of Fe-W alloys increases with the W content, i.e. the Fe-W sample with 24 at.% W retains the amorphous structure up to 600 \ub0C. Co-deposited C and O impurities in the coatings lead upon annealing to the formation of phase not expected from the Fe-W diagram: Fe6W6C, Fe3W3C, and FeWO4 phases. Longer annealing treatments resulted in the gradual dissolution of the carbide phases and the crystallization of the Fe2W phase. The annealing treatments improved considerably the hardness of the as-deposited Fe-W samples. The maximum hardness of 16.5 GPa was measured for the sample with 24 at.% of W after annealing for one hour at 600 \ub0C. Sn coatings were deposited from two different electrolytes, i.e. a chloride-based and a methane sulfonic acid (MSA) electrolyte. It was found that the additive used acts as a highly effective inhibitor in the chloride-based electrolyte. Its addition lead to a decrease in the limiting current density, suppression of H2 evolution, and to changes in the grain structure of the deposited Sn samples. The same effects are not observed in the MSA electrolyte

In-situ TEM annealing of amorphous Fe-24at.%W coatings and the effect of crystallization on hardness

This paper describes the crystallization which occurs upon annealing of an amorphous Fe-24at.%W coatings, electrodeposited from a glycolate-citrate plating bath. A combination of Differential Scanning Calorimetry and in-situ Transmission Electron Microscopy annealing is used to study the onset of crystallization of the amorphous coating. The in-situ TEM analyses reveal the formation of first crystallites after annealing at 400\ua0\ub0C for 30\ua0min. Upon a temperature increase to 500–600\ua0\ub0C, the crystallites develop into Fe-rich nanocrystals with ~ 40\ua0nm grain size. The nanocrystals are dispersed in the remaining amorphous Fe-W matrix, which results in the formation of a mixed nanocrystalline-amorphous structure. The observed crystallization can be held responsible for the increase in the hardness obtained upon annealing of Fe-24at.%W coatings. In fact, the hardness of the as-deposited material increases from 11 to 13\ua0GPa after annealing at 400\ua0\ub0C, and it reaches the maximum value of 16.5\ua0GPa after annealing at 600\ua0\ub0C

Analysis of the integration of the three-way catalyst thermal management in the on-line supervisory control strategy of a gasoline full hybrid vehicle

Full hybrid electric vehicles have proven to be a midterm viable solution to fulfil stricter regulations, such as those regarding carbon dioxide abatement. Although fuel economy directly benefits from hybridization, the use of the electric machine for propulsion may hinder an appropriate warming of the aftertreatment system, whose temperature is directly related to the emissions conversion efficiency. The present work evaluates the efficacy of a supervisory energy management strategy based on Equivalent Minimization Consumption Strategy (ECMS) which incorporates a temperature-based control for the thermal management of the Three-Way Catalyst (TWC). The impact of using only the midspan temperature of TWC is compared against the case where temperature at three different sampling points along the TWC length are used. Moreover, a penalty term based on TWC temperature has been introduced in the cost functional of the ECMS to allow the control of the TWC temperature operating window. In fact, beyond a certain threshold, the increase of the engine load, requested to speed up TWC warming, does not translate into a better catalyst efficiency, because the TWC gets close to its highest conversion rate. A gasoline P2 parallel full hybrid powertrain has been considered as test case. Results show that the effects of the different calibrations strategies are negligible on the TWC thermal management, as they do not provide any improvements in the fuel economy nor in the emissions abatement of the hybrid powertrain. This effect can be explained by the fact that the charge sustaining condition has a greater weight on the energy management strategy than the effects deriving from the addition of the soft constraints to control the TWC thermal management. These results hence encourage the use of simple setups to deal with the control of the TWC in supervisory control strategies for full hybrid electric vehicles

An Integrated Approach for Structural Health Monitoring and Damage Detection of Bridges: An Experimental Assessment

The issue of monitoring the structural condition of bridges is becoming a top priority worldwide. As is well known, any infrastructure undergoes a progressive deterioration of its structural conditions due to aging by normal service loads and environmental conditions. At the same time, it may suffer serious damages or collapse due to natural phenomena such as earthquakes or strong winds. For this reason, it is essential to rely on efficient and widespread monitoring techniques applied throughout the entire road network. This paper aims to introduce an integrated procedure for structural and material monitoring. With regard to structural monitoring, an innovative approach for monitoring based on Vehicle by Bridge Interaction (VBI) will be proposed. Furthermore, with regard to material monitoring, to evaluate concrete degradation, a non-invasive method based on the continuous monitoring of the pH, as well as chloride and sulfate ions concentration in the concrete, is presented

Development of advanced hybrid materials with the help of pulse electrodeposition

Pulse-electrodeposition has been applied to enhance properties of two different types of lightweight construction materials, a periodic cellular material (PCM) and a micro-sandwich. For the PCM, the deformation behaviour of the nanocrystalline Ni-18wt.%Fe sleeve material (bulk samples) has been investigated up to 548 K. The material exhibits plasticity of >30% fracture strain at higher temperatures compared to <15 % at room temperature. TEM characterization shows that coarser grains are present which enable strain hardening by intra-granular dislocation accumulation. This leads to larger fracture strains at higher temperatures. Hence, for allowing application of the PCM at elevated temperatures, the sleeve material has to be stabilized against deformation-induced grain growth. For the micro-sandwich, the pulse-electrodeposited Nickel coating on the face sheets or polymer fibres of the sandwich core can provide extra strength. With respect to the fibres, the plating process needs to be improved further to achieve a continuous and homogeneous coating

Dual-fuel injection fundamentals: experimental – numerical analysis into a constant-volume vessel

Abstract Dual-fuel combustion mode in compression ignition engines has been tested thoroughly, showing high potential for the reduction of emissions (especially nitric oxides and particulate matter) while keeping unchanged the fuel conversion efficiency compared with conventional Diesel engines. Controlling the reactivity of the secondary fuel is crucial for this kind of application. To this aim, a combined experimental/numerical approach is proposed in this study to provide, on one side, experimental data in controlled conditions for the calibration of the numerical models; on the other side, a numerical framework for the accurate simulation of the dual-fuel injection in engine-like operating conditions. More in detail, a constant-volume combustion vessel has been used to simulate and analyze the injection process varying the characteristic control parameters. Detailed high-resolution images of the injection and combustion processes were acquired for the validation of the numerical framework. Numerical simulations, carried out by means of the CONVERGE CFD code using a Reynolds Average Navier Stokes (RANS) approach allow for understanding the key differences between the nominal and off-design settings. Results have been compared with the experimental data in terms of liquid spray penetration. A comparison with high resolution images has also been done to prove the accuracy of the model to describe the spray evolution in terms of spray characteristics. In the provided picture, this contribution aims at demonstrating the robustness of the experimental/numerical framework that is essential for further development of such engine solution

In-depth characterization of as-deposited and annealed Fe-W coatings electrodeposited from glycolate-citrate plating bath

Fe-W coatings with 4, 16 and 24 at.% of W were electrodeposited under galvanostatic conditions from a new environmental friendly Fe(III)-based glycolate-citrate bath. This work aims to find correlations between composition including the light elements, internal structure of the electrodeposited Fe-W alloys and functional properties of material. The obtained alloys were characterized by Glow Discharge Optical Emission Spectrometry (GD-OES), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). Compositional depth profiles of 10 μm thick coatings obtained by GD-OES show that the distribution of metals is uniform along the entire film thickness, while SEM imaging depicted the presence of cracks and O- and W-rich areas inside the Fe-W coating with 4 at.% W. In the samples with 16 and 24 at.% of W, oxygen and hydrogen are present mostly at the surface about 1 μm from the top while traces of carbon are distributed within the entire coatings. With increasing W content, the structure of the coatings changes from nanocrystalline to amorphous which was shown by XRD and TEM analysis. Also, the surface of coatings becomes smoother and brighter, that was explained based on the local adsorption of intermediates containing iron and tungsten species. Annealing experiments coupled with XRD analysis show that the thermal stability of Fe-W alloys increases when the W content increases, i.e. the coating with 24 at.% W retains the amorphous structure up to 600 °C, where a partially recrystallized structure was observed. Upon recrystallization of the amorphous samples the following crystalline phases are formed: α-Fe, Fe2W, Fe3W3C, Fe6W6C, and FeWO4. Hence, the Fe-W coatings with higher W content (>25 at.%) can be considered as suitable material for high temperature applications

Electrodeposition of Soft Magnetic Fe-W-P Alloy Coatings from an Acidic Electrolyte

Fe-W-P coatings were deposited from a newly developed electrolytic bath. The effect of plating parameters, such as electrolyte current density and pH has been studied. It was found that\ua0the pH has a very strong effect on the phosphorous content of the coatings. Metallic-like, non-powdery alloys of Fe-W-P deposits with no cracks (lowly stressed) can be obtained at a lower pH\ua0(&lt;3), exhibiting high phosphorus (up to 13 at.%) and low tungsten (6 at.%) contents. At a higher pH\ua0(&gt;3), the composition changes to low phosphorus and high tungsten content, showing a matte,\ua0greyish, and rough surface. The applied current density also influences the morphology and the\ua0amount of phosphorous content. The deposits showed an amorphous structure for all samples with\ua0soft ferromagnetic properties