Noam Eliaz - Profile on Academia.edu (original) (raw)
Papers by Noam Eliaz
![Research paper thumbnail of Electroplating of Pure Aluminum from [HMIm][TFSI]–AlCl3 Room-Temperature Ionic Liquid](https://attachments.academia-assets.com/90635677/thumbnails/1.jpg)
](Coatings, 2021
Electrodeposition of aluminum and its alloys is of great interest in the aerospace, automobile, m... more Electrodeposition of aluminum and its alloys is of great interest in the aerospace, automobile, microelectronics, energy, recycle, and other industrial sectors, as well as for defense and, potentially, electrochemical printing applications. Here, for the first time, we report room-temperature electroplating of pure aluminum on copper and nickel substrates from an ionic liquid (IL) consisting of 1-Hexyl-3-methylimidazolium (HMIm) cation and bis(trifluoromethylsulfonyl)imide (TFSI) anion, with a high concentration of 8 mol/L AlCl3 aluminum precursor. The aluminum deposits are shown to have a homogeneous and dense nanocrystalline structure. A quasi-reversible reaction is monitored, where the current is affected by both charge transfer and mass transport. The electrocrystallization of Al on Ni is characterized by instantaneous nucleation. The deposited Al layers are dense, homogeneous, and of good surface coverage. They have a nanocrystalline, single-phase Al (FCC) structure, with a dis...
Materials, 2022
Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and ex... more Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured el...
Materials Science and Engineering: A, 2022
Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch... more Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch. DED has been broadly implemented in the design and fabrication of novel materials. These include metals, ceramics, and composites. Successful DED operation requires a good understanding of many critical phenomena, including laser-material interactions, fundamentals of casting and solidification of alloys, welding metallurgy and joining interfaces, along with microstructure-mechanical properties relations. Also critical are powder flowability, heat transfer, and various machine-related parameters. Several review articles have been published in recent years on metal AM via powder bed fusion (PBF) and DED, focusing on either a specific material system, mapping the recent technologies for AM, or issues related to the deposition process or material properties. Yet, no recent review is dedicated to a comprehensive presentation of material systems, design, fabrication, challenges, and the relationship between microstructures and mechanical properties of various DED'ed material families. Since the DED-based approach is becoming popular to manufacture bimetallic and multi-material structures, repair highvalue structures, and alloy design, this comprehensive review focuses on materials design via DED, including a survey of a variety of monolithic and multi-material compositions. Finally, the critical challenges and opportunities in this area are highlighted.
Journal of Materials Research and Technology, 2022
Laser directed energy deposition (DED) of high-quality structural Al-based alloys is challenging ... more Laser directed energy deposition (DED) of high-quality structural Al-based alloys is challenging due to the inherent physical and thermal properties of the Al powder feedstock. Therefore, an in-depth understanding of the influence of the applied processing parameters on the characteristics of the deposited material is paramount if one is to attain optimal performance. The objective of this study is to investigate the influence of the dominant processing parameters (laser power, scan speed, powder mass flow rate (PMFR), and hatch spacing) on the geometrical characteristics (track's height and dilution) of Al5083 double tracks fabricated using Laser Engineered Net Shaping (LENS ®). Central composite design (CCD) response surface methodology (RSM) was utilized to study the influence of the varied processing parameters and their interactions and to develop an empirical statistical prediction model for the studied responses. The results reveal that the applied PMFR has a strong influence on the deposited track's height (positive) and dilution (negative). The laser power at the first-order factor shows a weak influence for both studied responses. However, the interaction between the laser power and the hatch spacing shows significant effects on the track's height and dilution. The microstructure and microhardness of the asdeposited Al5083 double tracks are also discussed, as proxies to the anticipated performance of the deposited material.
ORIGINAL PAPER Gravity orientation in social wasp comb cells (Vespinae)
and the possible role of embedded minerals
International Journal of Hydrogen Energy, 2021
Hydrogen effects on electron beam melting (EBM) and wrought Tie6Al e4V are compared. Electrochemi... more Hydrogen effects on electron beam melting (EBM) and wrought Tie6Al e4V are compared. Electrochemical hydrogenation and the small punch test (SPT) are employed. The EBM alloy is more susceptible to hydrogen embrittlement than the wrought alloy. The fracture mode changes dramatically due to exposure to hydrogen. Different hydrogen effects arise from different microstructures and oxygen content.
International Journal of Hydrogen Energy, 2021
h i g h l i g h t s Dehydrogenation of hydrogenated EBM and wrought Tie6Ale4V alloys is compared.... more h i g h l i g h t s Dehydrogenation of hydrogenated EBM and wrought Tie6Ale4V alloys is compared. The kinetics and products of hydride decomposition are different in the two alloys. The differences result from different microstructures of the origin alloys. Decomposition of d a to d b is reported here for the first time. The EBM alloy may be more prone to hydrogen damage at elevated temperatures.
Journal of The Electrochemical Society, 2018
Custom 465 is an advanced precipitation hardened martensitic stainless steel exhibiting a combina... more Custom 465 is an advanced precipitation hardened martensitic stainless steel exhibiting a combination of high strength, high fracture toughness and good corrosion resistance. This steel is recommended for use in hydrogen atmospheres, yet only little research has been published on hydrogen behavior in this alloy. Here, the diffusivity, solubility and average detrapping energy for hydrogen were compared in various thermal conditions (solution annealed, H900 and H1000), employing electrochemical permeation and thermal programmed desorption measurements. It is suggested that reversible (low energy) traps in the H900 and H1000 conditions, associated with (semi)coherent η-Ni 3 Ti precipitates, are responsible for the high hydrogen solubility and low diffusivity. At the peak of coherency of the precipitates in the H900 condition, higher solubility and lower diffusivity and detrapping energy were measured. The value of the diffusion coefficient is found to change during different stages of charging and discharging, depending on the level of occupancy of the reversible traps.
Journal of The Electrochemical Society, 2016
Re-Ni layers produced in the early stages of electrodeposition from citrate electrolytes were stu... more Re-Ni layers produced in the early stages of electrodeposition from citrate electrolytes were studied by high-resolution X-ray photoelectron spectroscopy (HR-XPS) and time-of-flight secondary-ion mass spectrometry (TOF-SIMS). The deposition time was varied in the range of 2 to 300 seconds. The compositional heterogeneity of the thin Re-Ni alloys and the variations of their composition with deposition time, both in the bulk and on the surface, were shown. The results obtained are indicative of the occurrence of chemical reactions at short deposition times and are in agreement with our previous results obtained in studying the early stages of Re-Ni deposition by electrochemical techniques. The mechanism of the deposition process is discussed.
Materials Characterization, 2017
The microstructure and hardness of Custom 465® precipitation hardened stainless steel were charac... more The microstructure and hardness of Custom 465® precipitation hardened stainless steel were characterized following 4 hours aging at temperatures ranging from 482°C to 648°C. Dilatometry measurements and thermodynamic calculations were used to understand the mechanism of martensite-to-austenite reversion. Three major stages of aging were observed. The first stage is the peak hardening at aging temperatures of 480-510°C, where both η-Ni 3 Ti precipitation and austenite reversion begin independently of each other. The second stage is the initial stage of overaging observed above 538°C as reduction in hardness is due to a slight increase in both the precipitate dimensions and the reverted austenite volume fraction. The third, progressive overaging stage occurs above 593°C in which a dramatic hardness decrease is caused by a significant increase in both precipitate dimensions and reverted austenite volume fraction. Transmission Kikuchi diffraction orientation mapping revealed that globular austenite randomly nucleates at martensite grain boundaries, while acicular austenite nucleates along martensite lath boundaries. Thermodynamic calculations indicated that the dissolution of η-Ni 3 Ti precipitates does not govern the austenite reversion, although both phases are in competition for Ni. While the thermodynamic calculation predicts increase in the fraction of austenite with increase in aging temperature, the fraction of austenite found at room temperature in aged samples does not vary when the aging temperature, in which austenite reversion occurs, is increased above 593°C. This is explained by the change in composition of the austenite as a function of aging temperature.
Microporous and Mesoporous Materials, 2016
Silica aerogels are ultralow density materials with nano-sized skeleton network of pores. Their h... more Silica aerogels are ultralow density materials with nano-sized skeleton network of pores. Their high brittle nature presents a major challenge for mechanical testing and a need exists for novel testing methods. Two new mechanical setups and testing techniques are proposed for measuring the aerogel elastic mechanical properties. Both techniques employ full-field Digital Image Correlation (DIC) for surface deformation measurements. The first setup uses disk compression experiment, known as diametral compression test (Brazilian disk). However, the elastic properties of the material cannot be obtained directly. Instead, an inverse mechanics computational scheme, using both a finite element (FE) model and analytical solution, is proposed. The second direct testing setup is uniaxial compression of rectangular-shaped blocks. The Young's modulus and Poisson's ratio are extracted directly from the experimental stressestrain curves. Our results of tested samples show the relation between the density and the Young's modulus to coincide with previously published trends. The direct and iterative inversemechanics solution methods agree well with each other. The Poisson's ratio is found to be independent of the material apparent density. Comparisons between the two methods and recommendations for expanding the disk testing approach to fracture toughness are discussed.
Electrochimica Acta, 2015
Hydrogen diffusivity in Custom 465 1 martensitic precipitation hardened stainless steel is determ... more Hydrogen diffusivity in Custom 465 1 martensitic precipitation hardened stainless steel is determined using electrochemical permeation tests. Hydrogen diffusivity in the solution annealed (SA) condition is approximately 10 times higher than in the aged H900 (480 C, 4 h) condition because of hydrogen traps such as Ni 3 Ti nano-precipitates and reverted austenite. The microstructure of the alloy is characterized by TEM, XRD and ESEM/EBSD, both in the aged H900 and in the SA conditions. In the aged condition, h-Ni 3 Ti nano-precipitates with hexagonal structure and a rod-like shape are observed. In addition, reverted austenite is found at grain boundaries and inter-lath interfaces. In the SA condition, these microstructural features are not evident, which may explain the higher diffusivity measured. The diffusivity is almost unaffected by prior microplastic deformation of H900.
Surface and Coatings Technology, 2010
Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride ba... more Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride bath containing p-aminobenzenesulphonic acid (SA) and gelatin. These additives changed the phase content in the coatings, most likely as a result of their adsorption at the surface of the cathode. The effect of gelatin was more pronounced than that of SA. The Faradaic efficiency was higher than 90%. As the current density was increased or the bath temperature was decreased, the concentration of the nobler metal in the coating increased. Both concentrations of Ni and Co in the ternary alloy increased as the applied current density was increased. Nickel and cobalt were found to have a synergistic catalytic effect. The thickness of all coatings increased as the applied current density was increased. The hardness increased with current density to a peak value, and then decreased. The rate of Zn deposition was heavily influenced by mass-transport limitation at high applied current densities, while the rates of Ni and Co deposition were not. The anomalous codeposition was explained by the great difference between the exchange current densities of Zn and the iron-group metal. Potentiodynamic polarization scans and electrochemical impedance spectroscopy showed that the corrosion resistance of the ternary Zn-Ni-Co alloy coatings was approximately 10 times higher than that of Zn-Ni and 7 times higher than that of Zn-Co. The improved corrosion resistance of the ternary alloy was attributed to its surface chemistry, phase content, texture, and surface morphology. The ternary Zn-Ni-Co coating may thus replace the conventional Zn-Ni and Zn-Co coatings in a variety of applications.
Journal of Materials Science, 2010
Microstructural changes during plastic deformation and fracture evolution play an important role ... more Microstructural changes during plastic deformation and fracture evolution play an important role in the understanding of fracture mechanisms. However, most publications have focused on the initial stages of deformation where the latter is uniform. The current study was focused on the last stages of fracture, the necking, and crack propagation. Tensile specimens were examined by in situ scanning electron microscope equipped with a tensile module and electron backscatter diffraction. It was demonstrated that the fracture evolution consists of scanty diffuse necking followed by pronounced localized necking, in which the deformation band spread through the width of the specimen in two combined mechanisms-shearing and dimpling. The microstructural changes inside the deformation band adjacent to crack edge were compared to those in the uniform deformation zone. In the deformed areas, the grains became elongated and preferentially orientated in the loading direction. The relative frequency of twin boundaries at 60°was reduced in the deformed areas compared to non-deformed areas, while the misorientations at low angles of 3°-15°, which imply on a dislocation pileups subgrained structure, were increased to greater extent at the crack edge. Inside the deformation band, the amount of deformation was increased compared to the uniformly deformed region with grain fragments as a result of the complexity of stresses, although similar deformation mechanisms were identified.
Magnetoresistance Controls of Arborous Bead-Dendritic Growth of Magnetic Electrodeposits
Journal of The Electrochemical Society, 2004
ABSTRACT The effect of magnetic fields applied on magnetic metals electrodeposition was examined.... more ABSTRACT The effect of magnetic fields applied on magnetic metals electrodeposition was examined. Nickel deposits obtained from a Watt solution with coumarin, at cathodic potentials of -1000, -1200, and -1300 mV/SCE, without and with, both, perpendicular and parallel oriented to the electrode surface low applied magnetic fields (up to 500 Oe) were examined by scanning electron microscopy (SEM) technique. At a potential of -1300 mV/SCE, a dramatic difference was observed between nickel morphologies obtained with a perpendicular oriented magnetic field (zero MHD effect) and those obtained in the absence of one. The nickel deposit obtained with perpendicular oriented magnetic fields was a very developed 3D arboreous-bead-dendritic structure. On the other hand, the nickel deposit obtained without the presence of magnetic field was very rough, with a clearly visible clustered structure. The obtained nickel morphologies are then compared with copper morphologies. Based on the fact that copper deposits obtained with and without a perpendicular oriented magnetic field were dendritic structures, the observed difference between nickel deposits with and those without a perpendicular oriented field, is essentially ascribed to the magnetoresistance effect on the magnetic deposits, which are nonexistent in nonmagnetic materials. We also have done experiments with iron deposits. (C) 2004 The Electrochemical Society.
Liquid Phase Deposition of Titania Thin Films on Kapton and Poss-Polyimide
esmat.esa.int
One of the most practical approaches to protect polyimides from atomic oxygen (AO) erosion in low... more One of the most practical approaches to protect polyimides from atomic oxygen (AO) erosion in low Earth orbit is the use of an inorganic coating. A principally different approach is to develop hybrid material, where organic and inorganic components are combined chemically or ...
Acta Biomaterialia, 2010
Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Oste... more Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Osteoarthritis is associated with biochemical and mechanical processes, and is characterized by loss of articular cartilage and hypertrophy of bone. As cartilage and bone particles are released into the synovial fluid, a variety of biomarkers have been suggested for the analysis of this fluid. Here we have developed a method for isolating bone and cartilage wear particles suspended in the synovial fluid of the hip, knee and ankle joints of humans, based on specific magnetization of collagens I and II. Bio-ferrography is used to capture the particles on glass slides, allowing microscopic, chemical and statistical analyses. The relations between the level of the disease and the number, dimensions, shape and chemical composition of the particles were established. The method, which was found to be sensitive and reliable, can easily be extended to other applications, such as diagnosis of cancer and infectious diseases, determination of the efficacy of drugs or optimization of implants.
Acta Biomaterialia, 2009
Osseointegration, in terms of the bone apposition ratio (BAR) and the new bone area (NBA), was me... more Osseointegration, in terms of the bone apposition ratio (BAR) and the new bone area (NBA), was measured by backscattered electron imaging. The results were compared for four implant types: grit-blasted and NaOH-treated Ti-6Al-4 V (Uncoated-NaOH), electrodeposited with hydroxyapatite without alkali treatment (ED-HAp), electrodeposited with hydroxyapatite after alkali treatment (NaOH-ED-HAp), and plasma sprayed with hydroxyapatite (PS-HAp). No heat treatment was done after soaking in NaOH. The implants were press fitted into the intramedullary canal of mature New Zealand white rabbits and analyzed, both at the diaphyseal and at the metaphyseal zones, either 1 week or 12 weeks after surgery. NaOH-ED-HAp already exhibited a higher BAR value than the ED-HAp at 1 week, and was as good as the commercial PS-HAp at 12 weeks. The NBA value for NaOH-ED-HAp at 12 weeks was the highest. The higher content of octacalcium phosphate in NaOH-ED-HAp, as evident from the X-ray photoelectron spectroscopy analysis of the oxygen shake-up peaks, and the associated increase in the solubility of this coating in vivo are considered responsible for the enhanced osseointegration. Taking into account also the reduced occurrence of delamination and the inherent advantages of the electrodeposition process, electrodeposition of HAp following soaking in NaOH may become an attractive alternative for the traditional plasma-sprayed process for coating of orthopedic and dental implants.
Journal of Applied Physics, 1998
Measurements of the dynamic spall strength in aluminum, copper, and Metglas shocked by a high-pow... more Measurements of the dynamic spall strength in aluminum, copper, and Metglas shocked by a high-power laser to hundreds of kilobars pressure are reported. The strain rates in these experiments are of the order of 10 7 s Ϫ1 , which cannot be reached in impact experiments. The free-surface velocity behavior associated with spallation is characterized by oscillations caused by the reverberations of the spall layer. An optically recording velocity interferometer system was developed to measure the free-surface velocity time history. This diagnostic method has the advantages of being a noninterfering system and produces a highly accurate continuous measurement in time. The spall strength was calculated from the free-surface velocity as a function of the strain rate. The results show a rapid increase in the spall strength, suggesting that a critical phenomenon occurs at strain rates ϳ10 7 s Ϫ1 , expressed by the sudden approach to the theoretical value of the spall strength.
Acta Materialia, 1999
ÐBoth experimental and simulation results have indicated the deviation from Arrhenius law of the ... more ÐBoth experimental and simulation results have indicated the deviation from Arrhenius law of the diusion coecient of hydrogen in metallic glasses. This deviation was traditionally explained by the existence of various kinds of jumps or in terms of continuous distributions of activation energies due to dierent kinds of disorder. A new model is suggested, which relates this deviation to the temperature dependence of the short-range order (SRO). The suggested model is applied to simulate the diusion behavior of hydrogen in dilute amorphous Fe±H, Fe±Si±H and Fe±B±H alloys. The eect of the alloying elements on the activation energy of hydrogen diusion in amorphous iron is discussed in terms of their electronic structure and mean volume.
Coatings, 2021
Electrodeposition of aluminum and its alloys is of great interest in the aerospace, automobile, m... more Electrodeposition of aluminum and its alloys is of great interest in the aerospace, automobile, microelectronics, energy, recycle, and other industrial sectors, as well as for defense and, potentially, electrochemical printing applications. Here, for the first time, we report room-temperature electroplating of pure aluminum on copper and nickel substrates from an ionic liquid (IL) consisting of 1-Hexyl-3-methylimidazolium (HMIm) cation and bis(trifluoromethylsulfonyl)imide (TFSI) anion, with a high concentration of 8 mol/L AlCl3 aluminum precursor. The aluminum deposits are shown to have a homogeneous and dense nanocrystalline structure. A quasi-reversible reaction is monitored, where the current is affected by both charge transfer and mass transport. The electrocrystallization of Al on Ni is characterized by instantaneous nucleation. The deposited Al layers are dense, homogeneous, and of good surface coverage. They have a nanocrystalline, single-phase Al (FCC) structure, with a dis...
Materials, 2022
Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and ex... more Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured el...
Materials Science and Engineering: A, 2022
Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch... more Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch. DED has been broadly implemented in the design and fabrication of novel materials. These include metals, ceramics, and composites. Successful DED operation requires a good understanding of many critical phenomena, including laser-material interactions, fundamentals of casting and solidification of alloys, welding metallurgy and joining interfaces, along with microstructure-mechanical properties relations. Also critical are powder flowability, heat transfer, and various machine-related parameters. Several review articles have been published in recent years on metal AM via powder bed fusion (PBF) and DED, focusing on either a specific material system, mapping the recent technologies for AM, or issues related to the deposition process or material properties. Yet, no recent review is dedicated to a comprehensive presentation of material systems, design, fabrication, challenges, and the relationship between microstructures and mechanical properties of various DED'ed material families. Since the DED-based approach is becoming popular to manufacture bimetallic and multi-material structures, repair highvalue structures, and alloy design, this comprehensive review focuses on materials design via DED, including a survey of a variety of monolithic and multi-material compositions. Finally, the critical challenges and opportunities in this area are highlighted.
Journal of Materials Research and Technology, 2022
Laser directed energy deposition (DED) of high-quality structural Al-based alloys is challenging ... more Laser directed energy deposition (DED) of high-quality structural Al-based alloys is challenging due to the inherent physical and thermal properties of the Al powder feedstock. Therefore, an in-depth understanding of the influence of the applied processing parameters on the characteristics of the deposited material is paramount if one is to attain optimal performance. The objective of this study is to investigate the influence of the dominant processing parameters (laser power, scan speed, powder mass flow rate (PMFR), and hatch spacing) on the geometrical characteristics (track's height and dilution) of Al5083 double tracks fabricated using Laser Engineered Net Shaping (LENS ®). Central composite design (CCD) response surface methodology (RSM) was utilized to study the influence of the varied processing parameters and their interactions and to develop an empirical statistical prediction model for the studied responses. The results reveal that the applied PMFR has a strong influence on the deposited track's height (positive) and dilution (negative). The laser power at the first-order factor shows a weak influence for both studied responses. However, the interaction between the laser power and the hatch spacing shows significant effects on the track's height and dilution. The microstructure and microhardness of the asdeposited Al5083 double tracks are also discussed, as proxies to the anticipated performance of the deposited material.
ORIGINAL PAPER Gravity orientation in social wasp comb cells (Vespinae)
and the possible role of embedded minerals
International Journal of Hydrogen Energy, 2021
Hydrogen effects on electron beam melting (EBM) and wrought Tie6Al e4V are compared. Electrochemi... more Hydrogen effects on electron beam melting (EBM) and wrought Tie6Al e4V are compared. Electrochemical hydrogenation and the small punch test (SPT) are employed. The EBM alloy is more susceptible to hydrogen embrittlement than the wrought alloy. The fracture mode changes dramatically due to exposure to hydrogen. Different hydrogen effects arise from different microstructures and oxygen content.
International Journal of Hydrogen Energy, 2021
h i g h l i g h t s Dehydrogenation of hydrogenated EBM and wrought Tie6Ale4V alloys is compared.... more h i g h l i g h t s Dehydrogenation of hydrogenated EBM and wrought Tie6Ale4V alloys is compared. The kinetics and products of hydride decomposition are different in the two alloys. The differences result from different microstructures of the origin alloys. Decomposition of d a to d b is reported here for the first time. The EBM alloy may be more prone to hydrogen damage at elevated temperatures.
Journal of The Electrochemical Society, 2018
Custom 465 is an advanced precipitation hardened martensitic stainless steel exhibiting a combina... more Custom 465 is an advanced precipitation hardened martensitic stainless steel exhibiting a combination of high strength, high fracture toughness and good corrosion resistance. This steel is recommended for use in hydrogen atmospheres, yet only little research has been published on hydrogen behavior in this alloy. Here, the diffusivity, solubility and average detrapping energy for hydrogen were compared in various thermal conditions (solution annealed, H900 and H1000), employing electrochemical permeation and thermal programmed desorption measurements. It is suggested that reversible (low energy) traps in the H900 and H1000 conditions, associated with (semi)coherent η-Ni 3 Ti precipitates, are responsible for the high hydrogen solubility and low diffusivity. At the peak of coherency of the precipitates in the H900 condition, higher solubility and lower diffusivity and detrapping energy were measured. The value of the diffusion coefficient is found to change during different stages of charging and discharging, depending on the level of occupancy of the reversible traps.
Journal of The Electrochemical Society, 2016
Re-Ni layers produced in the early stages of electrodeposition from citrate electrolytes were stu... more Re-Ni layers produced in the early stages of electrodeposition from citrate electrolytes were studied by high-resolution X-ray photoelectron spectroscopy (HR-XPS) and time-of-flight secondary-ion mass spectrometry (TOF-SIMS). The deposition time was varied in the range of 2 to 300 seconds. The compositional heterogeneity of the thin Re-Ni alloys and the variations of their composition with deposition time, both in the bulk and on the surface, were shown. The results obtained are indicative of the occurrence of chemical reactions at short deposition times and are in agreement with our previous results obtained in studying the early stages of Re-Ni deposition by electrochemical techniques. The mechanism of the deposition process is discussed.
Materials Characterization, 2017
The microstructure and hardness of Custom 465® precipitation hardened stainless steel were charac... more The microstructure and hardness of Custom 465® precipitation hardened stainless steel were characterized following 4 hours aging at temperatures ranging from 482°C to 648°C. Dilatometry measurements and thermodynamic calculations were used to understand the mechanism of martensite-to-austenite reversion. Three major stages of aging were observed. The first stage is the peak hardening at aging temperatures of 480-510°C, where both η-Ni 3 Ti precipitation and austenite reversion begin independently of each other. The second stage is the initial stage of overaging observed above 538°C as reduction in hardness is due to a slight increase in both the precipitate dimensions and the reverted austenite volume fraction. The third, progressive overaging stage occurs above 593°C in which a dramatic hardness decrease is caused by a significant increase in both precipitate dimensions and reverted austenite volume fraction. Transmission Kikuchi diffraction orientation mapping revealed that globular austenite randomly nucleates at martensite grain boundaries, while acicular austenite nucleates along martensite lath boundaries. Thermodynamic calculations indicated that the dissolution of η-Ni 3 Ti precipitates does not govern the austenite reversion, although both phases are in competition for Ni. While the thermodynamic calculation predicts increase in the fraction of austenite with increase in aging temperature, the fraction of austenite found at room temperature in aged samples does not vary when the aging temperature, in which austenite reversion occurs, is increased above 593°C. This is explained by the change in composition of the austenite as a function of aging temperature.
Microporous and Mesoporous Materials, 2016
Silica aerogels are ultralow density materials with nano-sized skeleton network of pores. Their h... more Silica aerogels are ultralow density materials with nano-sized skeleton network of pores. Their high brittle nature presents a major challenge for mechanical testing and a need exists for novel testing methods. Two new mechanical setups and testing techniques are proposed for measuring the aerogel elastic mechanical properties. Both techniques employ full-field Digital Image Correlation (DIC) for surface deformation measurements. The first setup uses disk compression experiment, known as diametral compression test (Brazilian disk). However, the elastic properties of the material cannot be obtained directly. Instead, an inverse mechanics computational scheme, using both a finite element (FE) model and analytical solution, is proposed. The second direct testing setup is uniaxial compression of rectangular-shaped blocks. The Young's modulus and Poisson's ratio are extracted directly from the experimental stressestrain curves. Our results of tested samples show the relation between the density and the Young's modulus to coincide with previously published trends. The direct and iterative inversemechanics solution methods agree well with each other. The Poisson's ratio is found to be independent of the material apparent density. Comparisons between the two methods and recommendations for expanding the disk testing approach to fracture toughness are discussed.
Electrochimica Acta, 2015
Hydrogen diffusivity in Custom 465 1 martensitic precipitation hardened stainless steel is determ... more Hydrogen diffusivity in Custom 465 1 martensitic precipitation hardened stainless steel is determined using electrochemical permeation tests. Hydrogen diffusivity in the solution annealed (SA) condition is approximately 10 times higher than in the aged H900 (480 C, 4 h) condition because of hydrogen traps such as Ni 3 Ti nano-precipitates and reverted austenite. The microstructure of the alloy is characterized by TEM, XRD and ESEM/EBSD, both in the aged H900 and in the SA conditions. In the aged condition, h-Ni 3 Ti nano-precipitates with hexagonal structure and a rod-like shape are observed. In addition, reverted austenite is found at grain boundaries and inter-lath interfaces. In the SA condition, these microstructural features are not evident, which may explain the higher diffusivity measured. The diffusivity is almost unaffected by prior microplastic deformation of H900.
Surface and Coatings Technology, 2010
Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride ba... more Zn-Ni, Zn-Co and Zn-Ni-Co coatings were electrodeposited on mild steel from an acidic chloride bath containing p-aminobenzenesulphonic acid (SA) and gelatin. These additives changed the phase content in the coatings, most likely as a result of their adsorption at the surface of the cathode. The effect of gelatin was more pronounced than that of SA. The Faradaic efficiency was higher than 90%. As the current density was increased or the bath temperature was decreased, the concentration of the nobler metal in the coating increased. Both concentrations of Ni and Co in the ternary alloy increased as the applied current density was increased. Nickel and cobalt were found to have a synergistic catalytic effect. The thickness of all coatings increased as the applied current density was increased. The hardness increased with current density to a peak value, and then decreased. The rate of Zn deposition was heavily influenced by mass-transport limitation at high applied current densities, while the rates of Ni and Co deposition were not. The anomalous codeposition was explained by the great difference between the exchange current densities of Zn and the iron-group metal. Potentiodynamic polarization scans and electrochemical impedance spectroscopy showed that the corrosion resistance of the ternary Zn-Ni-Co alloy coatings was approximately 10 times higher than that of Zn-Ni and 7 times higher than that of Zn-Co. The improved corrosion resistance of the ternary alloy was attributed to its surface chemistry, phase content, texture, and surface morphology. The ternary Zn-Ni-Co coating may thus replace the conventional Zn-Ni and Zn-Co coatings in a variety of applications.
Journal of Materials Science, 2010
Microstructural changes during plastic deformation and fracture evolution play an important role ... more Microstructural changes during plastic deformation and fracture evolution play an important role in the understanding of fracture mechanisms. However, most publications have focused on the initial stages of deformation where the latter is uniform. The current study was focused on the last stages of fracture, the necking, and crack propagation. Tensile specimens were examined by in situ scanning electron microscope equipped with a tensile module and electron backscatter diffraction. It was demonstrated that the fracture evolution consists of scanty diffuse necking followed by pronounced localized necking, in which the deformation band spread through the width of the specimen in two combined mechanisms-shearing and dimpling. The microstructural changes inside the deformation band adjacent to crack edge were compared to those in the uniform deformation zone. In the deformed areas, the grains became elongated and preferentially orientated in the loading direction. The relative frequency of twin boundaries at 60°was reduced in the deformed areas compared to non-deformed areas, while the misorientations at low angles of 3°-15°, which imply on a dislocation pileups subgrained structure, were increased to greater extent at the crack edge. Inside the deformation band, the amount of deformation was increased compared to the uniformly deformed region with grain fragments as a result of the complexity of stresses, although similar deformation mechanisms were identified.
Magnetoresistance Controls of Arborous Bead-Dendritic Growth of Magnetic Electrodeposits
Journal of The Electrochemical Society, 2004
ABSTRACT The effect of magnetic fields applied on magnetic metals electrodeposition was examined.... more ABSTRACT The effect of magnetic fields applied on magnetic metals electrodeposition was examined. Nickel deposits obtained from a Watt solution with coumarin, at cathodic potentials of -1000, -1200, and -1300 mV/SCE, without and with, both, perpendicular and parallel oriented to the electrode surface low applied magnetic fields (up to 500 Oe) were examined by scanning electron microscopy (SEM) technique. At a potential of -1300 mV/SCE, a dramatic difference was observed between nickel morphologies obtained with a perpendicular oriented magnetic field (zero MHD effect) and those obtained in the absence of one. The nickel deposit obtained with perpendicular oriented magnetic fields was a very developed 3D arboreous-bead-dendritic structure. On the other hand, the nickel deposit obtained without the presence of magnetic field was very rough, with a clearly visible clustered structure. The obtained nickel morphologies are then compared with copper morphologies. Based on the fact that copper deposits obtained with and without a perpendicular oriented magnetic field were dendritic structures, the observed difference between nickel deposits with and those without a perpendicular oriented field, is essentially ascribed to the magnetoresistance effect on the magnetic deposits, which are nonexistent in nonmagnetic materials. We also have done experiments with iron deposits. (C) 2004 The Electrochemical Society.
Liquid Phase Deposition of Titania Thin Films on Kapton and Poss-Polyimide
esmat.esa.int
One of the most practical approaches to protect polyimides from atomic oxygen (AO) erosion in low... more One of the most practical approaches to protect polyimides from atomic oxygen (AO) erosion in low Earth orbit is the use of an inorganic coating. A principally different approach is to develop hybrid material, where organic and inorganic components are combined chemically or ...
Acta Biomaterialia, 2010
Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Oste... more Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Osteoarthritis is associated with biochemical and mechanical processes, and is characterized by loss of articular cartilage and hypertrophy of bone. As cartilage and bone particles are released into the synovial fluid, a variety of biomarkers have been suggested for the analysis of this fluid. Here we have developed a method for isolating bone and cartilage wear particles suspended in the synovial fluid of the hip, knee and ankle joints of humans, based on specific magnetization of collagens I and II. Bio-ferrography is used to capture the particles on glass slides, allowing microscopic, chemical and statistical analyses. The relations between the level of the disease and the number, dimensions, shape and chemical composition of the particles were established. The method, which was found to be sensitive and reliable, can easily be extended to other applications, such as diagnosis of cancer and infectious diseases, determination of the efficacy of drugs or optimization of implants.
Acta Biomaterialia, 2009
Osseointegration, in terms of the bone apposition ratio (BAR) and the new bone area (NBA), was me... more Osseointegration, in terms of the bone apposition ratio (BAR) and the new bone area (NBA), was measured by backscattered electron imaging. The results were compared for four implant types: grit-blasted and NaOH-treated Ti-6Al-4 V (Uncoated-NaOH), electrodeposited with hydroxyapatite without alkali treatment (ED-HAp), electrodeposited with hydroxyapatite after alkali treatment (NaOH-ED-HAp), and plasma sprayed with hydroxyapatite (PS-HAp). No heat treatment was done after soaking in NaOH. The implants were press fitted into the intramedullary canal of mature New Zealand white rabbits and analyzed, both at the diaphyseal and at the metaphyseal zones, either 1 week or 12 weeks after surgery. NaOH-ED-HAp already exhibited a higher BAR value than the ED-HAp at 1 week, and was as good as the commercial PS-HAp at 12 weeks. The NBA value for NaOH-ED-HAp at 12 weeks was the highest. The higher content of octacalcium phosphate in NaOH-ED-HAp, as evident from the X-ray photoelectron spectroscopy analysis of the oxygen shake-up peaks, and the associated increase in the solubility of this coating in vivo are considered responsible for the enhanced osseointegration. Taking into account also the reduced occurrence of delamination and the inherent advantages of the electrodeposition process, electrodeposition of HAp following soaking in NaOH may become an attractive alternative for the traditional plasma-sprayed process for coating of orthopedic and dental implants.
Journal of Applied Physics, 1998
Measurements of the dynamic spall strength in aluminum, copper, and Metglas shocked by a high-pow... more Measurements of the dynamic spall strength in aluminum, copper, and Metglas shocked by a high-power laser to hundreds of kilobars pressure are reported. The strain rates in these experiments are of the order of 10 7 s Ϫ1 , which cannot be reached in impact experiments. The free-surface velocity behavior associated with spallation is characterized by oscillations caused by the reverberations of the spall layer. An optically recording velocity interferometer system was developed to measure the free-surface velocity time history. This diagnostic method has the advantages of being a noninterfering system and produces a highly accurate continuous measurement in time. The spall strength was calculated from the free-surface velocity as a function of the strain rate. The results show a rapid increase in the spall strength, suggesting that a critical phenomenon occurs at strain rates ϳ10 7 s Ϫ1 , expressed by the sudden approach to the theoretical value of the spall strength.
Acta Materialia, 1999
ÐBoth experimental and simulation results have indicated the deviation from Arrhenius law of the ... more ÐBoth experimental and simulation results have indicated the deviation from Arrhenius law of the diusion coecient of hydrogen in metallic glasses. This deviation was traditionally explained by the existence of various kinds of jumps or in terms of continuous distributions of activation energies due to dierent kinds of disorder. A new model is suggested, which relates this deviation to the temperature dependence of the short-range order (SRO). The suggested model is applied to simulate the diusion behavior of hydrogen in dilute amorphous Fe±H, Fe±Si±H and Fe±B±H alloys. The eect of the alloying elements on the activation energy of hydrogen diusion in amorphous iron is discussed in terms of their electronic structure and mean volume.