Edoardo Bemporad

• Nuclear Engineer, PhD
• Professor (Full) at Roma Tre University

The increasing turbine inlet temperatures in modern gas turbines have raised concerns about the corrosion of ceramic thermal barrier coatings (TBCs) caused by molten silicate deposits, commonly referred to as “CMAS” due to their main constituents (CaO-MgO-Al2O3-SiO2). The objective of this study was to investigate the combined influence of powder m...

In the field of encapsulation, microcapsules containing perfume have emerged as effective vehicles for delivering active ingredients across various applications. The present study employed a multivariate analysis framework to examine polyacrylate microcapsules for household products synthesized using different acrylate monomers. The advanced multiv...

The solution of instrumented indentation inverse problems by physically-based models still represents a complex challenge yet to be solved in metallurgy and materials science. In recent years, Machine Learning (ML) tools have emerged as a feasible and more efficient alternative to extract complex microstructure-property correlations from instrument...

Surface free energy (SFE) of titanium surfaces plays a significant role in tissue engineering, as it affects the effectiveness and long-term stability of both active coatings and functionalization and the establishment of strong bonds to the newly growing bone. A new contact–mechanics methodology based on high-resolution non-destructive elastic con...

In this work, the cold-spray technique was used to deposit Inconel 718-nickel (1:1) composite coatings on stainless steel substrate. A general full factorial design was adopted to identify the statistically significant operating variables, i.e., impingement angle, erodent size, and feed rate on the coating erosion response. Erodent feed rate, impin...

In this work we propose the hypothesis that the chemical-physical properties of mercury can determine its relative evanescence in GSR: in the other words we propose preliminary experimental results from which we derive, in according to thermodynamic laws, an possible explanation in term grain refinement, segregation and diffusion hybrid model.

The number of medical procedures involving the use of cyclotron-produced radionuclides is constantly growing year by year. The design and construction of the cyclotron targets appropriate for the production of the radionuclides of interest are the most challenging issues. The cyclotron targets for the medical radionuclide production suffer from two...

This paper studies how the nano-mechanical properties of thermal barrier coatings (TBCs) vary during thermal cycling, as a way to shed new light on their failure mechanisms. In particular, high-throughput nanoindentation revealed the evolution of hardness and elastic modulus distributions of plasma-sprayed yttria-stabilized zirconia (YSZ) top layer...

This article reports the design, construction and first use of an experimental device consisting of a specially designed vacuum chamber equipped with a reactive sputtering magnetron (RSM) to be used for controlled deposition of thin films on a Si (100) flat substrate. The setup was designed to allow for in situ and real-time recordings of X-ray dif...

Deux revêtements à base nickel obtenus par des bains réducteurs, l’un brut et l’autre ayant subi un traitement thermique sont étudiés. L’essai d’indentation a été mis en œuvre pour caractériser la dureté et le module de Young de ces dépôts. Les résultats montrent une bonne homogénéité des propriétés mécaniques dans l’épaisseur du revêtement, alors...

The present study investigated the influence of nanoscale residual stress depth gradients on the nano-mechanical behavior and adhesion energy of aluminium nitride (AlN) and Al/AlN sputtered thin films on a (100) silicon substrate. By using a focused ion beam (FIB) incremental ring-core method, the residual stress depth gradient was assessed in the...

Compressive residual stresses in thin films can inhibit crack propagation under normal or sliding contact loading, with associated enhancement of the coating apparent toughness, load bearing capacity and wear resistance. This study investigates the influence of residual stress distributions on the thin film/substrate adhesion using a nanoindenter c...

To withstand oxidation at a temperature ≥ 850 °C, an optimized Ti1−xAlxN coating was grown via reactive High Power Impulse Magnetron Sputtering (HiPIMS) technology on three identical Ti0.48Al0.48Cr0.02Nb0.02 billets. Different substrate surface pre-treatments were designed to increase performance: i) mechanical polishing, ii) mechanical polishing c...

Failure in turbine blades can affect the safety and performance of the gas turbine engine. Results of coating decohesion, erosion and cracking at the first-stage high-pressure (HPT) blade working in gas turbine engine are being reported in this paper. This investigation was carried out for the possibility of various failure mechanisms in the therma...

Lath martensite structures in medium-carbon steels incorporate a significant amount of residual stresses that are mostly induced by the martensitic transformation process. Although former studies could identify these stresses using diffraction techniques, it was not possible to correlate the micro-scale distribution of the stress fields with respec...

Residual stresses play a crucial role in determining material properties and behaviour, in terms of structural integrity under monotonic and cyclic loading, and for functional performance, in terms of capacitance, conductivity, band gap, and other characteristics. The methods for experimental residual stress analysis at the macro- and micro-scales...

Residual stress assessment using incremental focused ion beam (FIB) milling, combined with high-resolution insitu scanning electron microscopy (SEM), a full field strain analysis by digital image correlation (DIC) and finite element modelling (FEM).

Nanometrology refers to measurement techniques that assess materials properties at the nanoscale. Laboratory-based characterisation of nanomaterials has been the key enabler in the growth of nanotechnology and nano-enabled products. Due to the small size involved, dimensional measurements has dominated such characterisation underpinned by a tremend...

The Dry reforming of methane (DRM) is as an efficient way for CH4 and CO2 valorisation because the produced syn-gas has an H2/CO ratio equal to that suitable for the synthesis of oxygenated hydrocarbons and synthetic fuels. The development of Ni (10 wt%) based structured and unstructured catalysts promoted by a small amount of Ru (0.5 wt%) has been...

The present work deals with a new technique to produce complex micro- and nano-scale patterns with high accuracy by FIB micro machining. The proposed method is related to the production of stream file, which is optimized through a software interface. A unique sampling approach is used to optimize the conversion from a 3D meshed CAD object to the fo...

• This study shows that thin coating layers of semiconductor oxides, deposited by atomic layer deposition, can be successfully used to improve the performance of tethers used in space technology. Thin layers of ZnO, TiO2 and Ti-Zn mixed oxide with 25 to 100 nm thickness were considered, and compared with native Al2O3 as reference. For this purpose,...

Compressive residual stress in hard coatings can improve adhesion and in-service toughness, since they can inhibit crack nucleation and propagation. However, the role of through thickness residual stress profile is not fully understood. This is because of (a) lack of knowledge of stress evolution mechanisms and (b) limitations of experimental techn...

Aluminum nitride (AlN) is a ceramic compound that could be used as a processing material for semiconductor industry. However, the AlN crystalline structure plays a crucial role in its performance. In this paper, polycrystalline AlN films have been grown onto Si(1 1 1) and Si(1 0 0) (with an oxide native coverage of SiO2) wafers by RSM (reactive spu...

When used in prosthetic dentistry, zirconia encounters severe durability issues due to low temperature degradation: exposure to humidity results in a transition from tetragonal to monoclinic phase, associated to disruptive integrity loss. Recently it has been shown that size-induced stabilization helps maintaining zirconia in tetragonal form, when...

Solid state physics experimental techniques and characterization tools can provide a valuable contribution to the research and development activity on He-free neutron detection systems, for both detector assessment and performance improvement. Presently, a He replacement strategy relies on the use of 6Li - and/or 10B -based neutron-to-charged parti...

Fishnet metamaterials (MM) conceived for optical coating applications have been simulated for metal-dielectric-metal structures based on silver and oxides. Preliminary experimental results on large-scale fabrication are presented here for alumina-silver based structures. Millimeter-size MM layers have been realized by combination of r.f. sputtering...

Objectives: The production of fixed partial dentures (FPDs) induces complex residual stress profiles, due to both the thermal expansion coefficient mismatch between the veneering ceramic and the framework and to the thermal gradients occurring during the final cooling. Detailed knowledge of residual stress distributions in the veneering ceramics i...

The present work aims to evaluate the microstructural mechanisms associated with the initiation of fatigue damage of steels used in the petroleum industry. Microdeformations and residual stresses (macrostresses) are evaluated by X-ray diffraction in real time during alternating bending fatigue tests performed on samples taken from an API 5L X60 gra...

Superaustenitic stainless steels have become of growing interest in industrial and technological fields, but there is not a complete understanding on their fundamental properties and their performances. For this paper, AISI 904 L superaustenitic samples were nitrided and carburized in order to study the expanded austenite stability under severe deu...

Chemically inert coatings on Havar® entrance foils of the targets for [18 F] production via proton irradiation of enriched water at pressurized conditions are needed to decrease the amount of ionic contaminants released from Havar®. During current investigation, magnetron sputtered niobium and niobium oxide were chosen as the candidates for protect...

Multilayer systems can offer an efficient way of controlling residual stress, improve adhesion and enhance toughness of coated systems. This work aims at the development of multilayer coating with improved adhesion, based on numerical design approach. The numerical model of titanium - titanium nitride (Ti-TiN) multilayer has been formulated with mu...

In this work, a morphological and structural characterization of a ternary Ag-Cu-Ge alloy of known composition was performed with the aim of evaluating how the passivation parameters (time and temperature) influence the morphological features of the material surface. A nanomechanical characterization was performed in order to correlate the morpholo...

SEM–FIB and XRD results showed a significant modification of films' microstructure due to selected deposition parameters: it goes from dense-columnar (high crystallite size) at low working pressure and/or high gas mass to nano-porous (small grains) at high pressure and/or low gas mass. This means that the momentum flux carried to the substrate cons...

In the framework of the research and development activity on He-free neutron detection systems, the solid state physics experimental techniques and characterization tools can provide a valuable contribution for detector assessment and performance improvement. Presently, a He-replacement strategy relies on the use of Li-and/or B-based neutron to cha...

Residual stress has a significant effect on the performance of thin films, in terms of adhesion, hardness, wear and fatigue resistance. Thus, when assessing innovative coatings or new deposition technologies, it is important to perform residual stress evaluation by means of a suitable and reliable technique.

In the present paper, we analyze the role of in situ grown BaZrO3 (BZO) inclusions in YBa2Cu3O7−x (YBCO) thin films prepared by chemical solution deposition using a low fluorine coating solution, on the field angle dependence of the critical current density, J c (𝜃), data using the vortex path model. In order to form a coherent picture on the BZO d...

A new method for the calculation of the residual stress state of materials is presented in this work. The method, named Micrometric Rosette (MR), applies the principles validated in previous publications by the same authors [13,14,15], and consists of the combined use of focussed ion beam (FIB), the scanning electron microscope (SEM) and the digita...

The paper examines the cracks initiation, propagation and coalescence until failure in a crystalline rock under stress states involving rock volumes varying in size, from nano (Berkovich indentation in Continuous Stiffness Measurement mode) to micro (Vickers indentation, scratching) and macro (Rockwell indentation, Rock Impact Hardness Number) scal...

The purpose of this discussion is to point out some similarities between a paper that was recently published by J.G. Zhu et al. [1] and a paper that we published earlier on the same subject [2].The micro-scale FIB-DIC ring core technique was first proposed in 2009 [3]. The attraction of this method lies in its compatibility with well-established ex...

In this chapter, we present an overview of an optimized method for the determination of surface elastic residual stress in thin ceramic coatings by instrumented sharp indentation. The methodology is based on nanoindentation testing on focused ion beam (FIB) milled micro-pillars. Finite element modeling (FEM) of strain relief after FIB milling of an...

A novel method is presented for the assessment of the Poisson's ratio and residual stress on the micron scale, based on focused ion beam (FIB) two-step four-slot micro-milling and in-situ digital image correlation (DIC) analysis of the induced relaxation strains at the specimen's surface. The methodology has been fully validated through modelling a...

It is well known that the recrystallization texture of heavily cold-rolled pure copper is almost completely cubic. However, one of the main drawbacks concerning the use of pure copper cube-textured substrates for YBCO coated conductor is the reduced secondary recrystallization temperature. The onset of secondary recrystallization (i.e., the occurre...

In the present paper, the in-service wear mechanisms and cross-sectional microstructural evolution of a Stellite 6B cobalt-based alloy subjected to sliding contact conditions are analysed. The analysis is carried out using focused ion beam (FIB), transmission electron microscopy (TEM), 3D confocal profilometer and nanoindentation techniques. Sample...

Atomic force microscope analysis of low load Vickers and Knoop indentation marks was performed to obtain a statistically consistent method for the mechanical characterisation of physical vapour deposition (PVD) coatings and the evaluation of elastic anisotropy. Indents shape analysis were elaborated with three different models for the evaluation of...

The precipitation of cerium compounds on polished AA2024-T3 surfaces was investigated following an electrochemical and microstructural localized approach. It was found that cerium precipitation occurs on the entire surface covering intermetallic particles and the matrix as well. The matrix is the region where the precipitation of cerium is less fav...

After an introduction describing the indentation techniques traditionally applied to the study of micromechanical properties of minerals and rocks, phenomena induced by the diamond tip's penetration into crystalline rocks are analyzed. Crystalline rocks are characterized by low values of the critical breakage load, i.e. the threshold load correspon...

The fire assay process is still the most accurate and precise method for measuring the gold content in gold alloys. Scanning electron microscopy and transmission electron microscopy have been applied to observe the change in microstructure of the samples undergoing the fire assay process. The performed observations reveal that the microstructure of...

This work presents the production and characterization of a controlled electrochemical modification of titanium surfaces, consisting of a two-step anodic spark deposition (ASD) process and a barrel finishing. The treatment was performed on titanium alloy Ti6Al4V, as most representative titanium alloy used in mechanical and aeronautical applications...

A modified gel-casting process was developed to produce both dense and highly porous (40% volume) yttria tetragonal zirconia polycrystal (Y-TZP) using agar, a natural polysaccharide, as gelling agent. A fugitive phase, made of commercial polyethylene spheres, was added to the ceramic suspension before gelling to produce cellular ceramic structures....

The interest for TiAl intermetallic alloys is growing in the last years because of their excellent ratio between mechanical properties and density. However, the application is restricted at temperatures up to 873–973 K by the resistance to oxidation. For this reason it is of great importance to study protective coatings able to raise its temperatur...

Expanded austenite can be generated on austenitic stainless steels either by ion carburizing or ion nitriding. In both cases the resulting fcc crystal structure, supersaturated with nitrogen or carbon, is strongly hardened with improved wear-resistance, while maintaining the original resistance to corrosion. In this work, we have studied the stabil...

The effect of surface defects on the residual stress local distribution in thin coatings has been investigated by an innovative high resolution methodology, which mainly consists of incremental focused ion beam (FIB) micron-scale ring-core milling (IμRCM), combined with high-resolution in situ SEM-FEG imaging of the relaxing surface and in-plane st...

The deposition and characterization of La2Zr2O7 thin films deposited by metal-organic decomposition method on both single crystal SrTiO3 and cube textured Ni-5 at.% W substrates are presented. Metal acetylacetonates in propionic acid solution was used. The results showed that LZO films are epitaxially grown with smooth surface with rms roughness ar...

Indentation tests have been carried out on a marble in order to define the role of the intra-grain microcracks on its mechanical behavior. The investigated marble shows a strong variability in grain-texture (granoblastic to xenoblastic) also on the scale of centimeter and contains different types of microdiscontinuities (cleavage cracks, grain boun...

Residual stress was measured on plasma sprayed crystalline NiAl, Al2O3 and amorphous Al2O3TiO2ZrO2CeO2 single splats, by using an incremental focused ion beam (FIB) micron-scale ring-core method (IμRCM).Tensile residual stress exists in polycrystalline NiAl splats, where the quenching stress is only partially relaxed by edge curling and through-thi...

Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three differ...

In the present paper, the in-service wear mechanisms and cross-sectional microstructural evolution of a Stellite 6B cobalt-based alloy subjected to sliding contact conditions were analysed by focused ion beam (FIB), transmission electron microscopy (TEM) and nanoindentation techniques. Samples under investigation consisted of a lip-seal adopted in...

The present investigation has been carried out in order to study the erosion wear behaviour of WC–Co base thermal spray coatings. WC–12Co and WC–10Co–4Cr coatings were deposited by means of high velocity oxygen fuel (HVOF) thermal spraying. The erosion tests were conducted at impact angles of 30 and 90° using SiC particles of ∼50 μm in diameter as...

The drop shape analysis is a conventional method to evaluate wettability and surface free energy. The analysis of drop profile is commonly used for the contact angle measurement between the liquid drop and sample surface.In many cases such as confined surfaces, it is difficult to carry out this measure, therefore it is necessary to evaluate the sha...

Surface free energy (SFE) is a property which depends on the chemical state and roughness of the surface and it is necessary to develop a reliable method to evaluate SFE value on a small area, taking into account these two different contributions. Today contact angle methods are the most used and they allow to evaluate the global mean value of SFE...

Residual stress evaluation in thin films at the sub-micron scale was achieved in the present study using a semi-destructive trench-cutting (ring-core) method. Focused Ion Beam was employed to introduce the strain relief by milling the slots around an “island” and also to record the images for strain change evaluation by digital image correlation an...

In the present study, residual stress evaluation in thin films was achieved using a semi-destructive trench-cutting method. Focused Ion Beam (FIB) was employed to introduce the strain relief by ring-core milling, i.e. creating a trench around an “island”. Either SEM or FIB imaging can be used to record sequences of images for strain change evaluati...

The present study deals with focused ion beam (FIB) coupled with transmission electron microscopy (TEM) analysis of corrosion mechanisms in cathodic arc evaporation (CAE)-PVD CrN/NbN multilayer coatings on aluminum alloy substrate. Samples were exposed to a 500-h ASTM B-117 salt spray test. Surface morphology of tested specimens was preliminary ana...

Titanium is the most widely used material in orthopaedic and dental implantoprosthesis due to its superior physical properties and enhanced biocompatibility due to the spontaneous formation of a passivating layer of titanium oxides which, however, does not form good chemical bonds with bone and tends to brake exposing bulk titanium to harsh body fl...

In the present paper, the effect of residual stress on the mechanical behavior of thin hard coatings has been investigated by a new methodology based on the combined use of focused ion beam (FIB) micro-machining techniques and nanoindentation testing. Surface elastic residual stress were determined by nanoindentation testing on Focused Ion Beam (FI...

A new methodology for the measurement of depth sensitive residual stress profiles of thin coatings with sub-micrometer resolution is presented. The two step method consists of incremental focused ion beam (FIB) ring-core milling, combined with high-resolution in situ SEM-FEG imaging of the relaxing surface and a full field strain analysis by digita...

We present a new procedure for the determination of surface elastic residual stress by instrumented sharp indentation, based on nanoindentation testing on focused ion beam (FIB) milled micro-pillars. Finite element modeling (FEM) of strain relief after FIB milling of annular trenches demonstrates that full relaxation of pre-existing residual stress...

In this study, diamond-like carbon (DLC) films modified with titanium were deposited by plasma decomposition of metallorganic precursor, titanium isopropoxide in CH4/H2/Ar gas atmosphere. The obtained films were composed of amorphous titanium oxide and nanocrystalline titanium carbide, embedded in an amorphous hydrogenated (a-C:H) matrix. The TiC/T...

Steel pipes used in the oil and gas industry undergo the action of cyclic loads that can cause their failure by fatigue. A consistent evaluation of the fatigue damage during the initiation phase should fundamentally be based on a nanoscale approach, i.e., at the scale of the dislocation network, in order to take into account the micromechanisms of...

Flame treatments on polymeric materials improve surface free energy (SFE) and consequently the wettability and adhesion of coatings, metallizations, varnish and glues. In this paper, using a statistical methodological approach based on DoE technique and multivariate analysis of flame treatment process parameters, a mathematical model of SFE and wet...

Solid-state foaming is a relatively new process for producing closed-cell thermoset foams starting from powders. In this study, the possibility of introducing nanoclay into epoxy foams by solid-state foaming was investigated. The nanoclay was found to affect the foaming efficiency and the foam density; even if large nanoclay aggregates are present...

In this report, an optimised method for residual stress determination at the microscopic scale is presented. The newly proposed approach involves incremental Focused Ion Beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging of a previously deposited marker pattern. Digital image correlation (DIC) anal...

In this paper, a new approach is presented for local residual stress measurement in MEMS structures. The newly proposed approach involves incremental focused ion beam (FIB) milling of annular trenches at material surface, combined with high resolution SEM imaging and Digital Image Correlation (DIC) analysis for the measurement of the strain reli...

The microstructural features of TiO2 coatings, deposited by High Velocity Suspension Flame Spraying (HVSFS) from a suspension of titania nanoparticles, were investigated by Focused Ion Beam (FIB) + Scanning Electron Microscopy (SEM) techniques, by Transmission Electron Microscopy (TEM) and by micro-Raman spectroscopy, and were compared to those of...

Expanded austenite generation through ion carburizing of AISI 316L using two different reactive gas mixtures (Ar 50%, H2 45%, CH4 5% and Ar 80%, H2 15%, CH4 5%) has been studied. It was found that an ∼ 14 µm surface layer of expanded austenite was developed with 30 min processing for both gas mixtures. Nevertheless, AES analyses have shown that on...

There are various methods to address the problem of determining the hardness of thin films when the substrate is involved in the deformation process produced during conventional indentation tests. For the determination of the elastic modulus using depth-sensing indentation methods, the problem is more complex due to the deformation of the equipment...

Fluorine-substituted hydroxyapatites are considered promising materials for bone scaffolding. In this study a systematic investigation on F-half substituted hydroxyapatite (F-HAp, Ca10(PO4)6OHF) obtained by precipitation is reported. Results on composition analysis, thermal behaviour, and sinterability are presented for a comparison with the respec...

In the present paper we consider two representative methods for residual stress evaluation at the micro-scale: a (semi-)destructive method involving material removal and the measurement of strain relief; and a non-destructive X-ray diffraction technique involving the use of micro-focused synchrotron X-ray beam. A recently developed strain relief ap...

We present the results of a surface modification of AISI 316L stainless steel by surface irradiation with high energy, pulsed nitrogen ion beams generated with 0.8 kJ dense plasma focus. The surface characterization was done using GAXRD, Auger electrons spectroscopy, TEM and optical microscopy. After the irradiation, we found a modification of a 1...

IntroductionCoating Design and OptimisationExperimental DetailsResultsDiscussionConclusions References

N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350–600 °C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, ele...

Dense and cellular ceramics were produced from yttria partially stabilized zirconia powders by gel-casting, using agar as a gelling agent and polyethylene spheres (125–300 μm diameter) as volatile pore forming agent to create 50–65 vol.% spherical macropores, uniformly distributed in a microporous matrix.The mechanical properties of both dense and...

Focused Ion Beam (FIB) milling of ring-shaped trenches (ring drilling) induces controlled gradual strain relief at the surface of residually stressed samples, with the central “island” approaching the unstressed state. Strain change was measured at sample surface via Digital Image Correlation analysis of SEM micrographs of a regular pattern of dots...

Ball cratering and rotating wheel tests are useful techniques for abrasive wear resistance evaluation of thin coatings. Nevertheless, such techniques involve significant experimental errors, coming from equipment deficiencies and changes in wear response depending on test parameters. In case of rotating wheel test, common instrumental errors are: g...

A modified gel casting procedure based on a natural gelatin for food industry and commercial polyethylene spheres as pore formers was successfully exploited to produce dense and porous ceramic bodies made of yttria stabilized tetragonal zirconia polycrystal (Y-TZP). Vickers and Knoop microhardness, elastic modulus and fracture toughness measurement...

The aim of this study was the development and characterization of transition metal oxynitride multilayers for optical applications. The reactive RF magnetron sputtering technique in rotation mode was used for stacking of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) nanolayers. The depositions were carried out in a reactive Ar+N2+O2 at...

In this study, a TiO2 (anatase) nanopowder suspension was processed by high velocity suspension flame spraying (HVSFS). The resulting coatings were characterized and compared to conventional HVOF and atmospheric plasma sprayed layers. It is shown that the HVSFS operating parameters can be adjusted to achieve dense titania with a near nanostructure...