Romeu Chelariu
@tuiasi.ro
Department of Materials Science/Faculty of Materials Science and Engineering
Gheorghe Asachi Technical University of Iasi
RESEARCH INTERESTS
metallic materials, metallic biomaterials, non-ferrous alloys, microstructure, corrosion, mechanical properties
Scopus Publications
Scopus Publications
Ana-Maria Roman, Ramona Cimpoeșu, Bogdan Pricop, Marius Mihai Cazacu, Georgeta Zegan, Bogdan Istrate, Alexandru Cocean, Romeu Chelariu, Mihaela Moscu, Gheorghe Bădărău,et al.
MDPI AG
A new functional Fe-30Mn-5Si-xCu (x = 1.5 and 2 wt%) biomaterial was obtained from the levitation induction melting process and evaluated as a biodegradable material. The degradation characteristics were assessed in vitro using immersion tests in simulated body fluid (SBF) at 37 ± 1 °C, evaluating mass loss, pH variation that occurred in the solution, open circuit potential (OCP), linear and cyclic potentiometry (LP and CP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and nano-FTIR. To obtain plates as samples, the cast materials were thermo-mechanically processed by hot rolling. Dynamic mechanical analysis (DMA) was employed to evaluate the thermal properties of the smart material. Atomic force microscopy (AFM) was used to show the nanometric and microstructural changes during the hot rolling process and DMA solicitations. The type of corrosion identified was generalized corrosion, and over the first 3–5 days, an increase in mass was observed, caused by the compounds formed at the metal–solution interface. The formed compounds were identified mainly as oxides that passed into the immersion liquid. The degradation rate (DR) was obtained as a function of mass loss, sample surface area and immersion duration. The dynamic mechanical behavior and dimensions of the sample were evaluated after 14 days of immersion. The nanocompounds found on the surface after atmospheric corrosion and immersion in SBF were investigated with the Neaspec system using the nano-FTIR technique.
Ana-Maria Roman, Ionelia Voiculescu, Ramona Cimpoeșu, Bogdan Istrate, Romeu Chelariu, Nicanor Cimpoeșu, Georgeta Zegan, Cătălin Panaghie, Nicoleta Monica Lohan, Mihai Axinte,et al.
MDPI AG
The medical applications of degradable iron-based biomaterials have been targeted by re-searchers due to their special properties that they present after alloying with various elements and different technological methods of obtaining. Compared to other biodegradable materials, iron-based alloys are designed especially for the low production costs, the non-magnetism obtained by alloying with Mn, and the shape memory effect (SME) following the alloying with Si, which is necessary in medical applications for which it could replace nitinol successfully. Alloying with new elements could improve the mechanical properties, the degradation rate, and the transformation temperatures corresponding to the SME. This paper presents the results from the study of FeMnSi-Al alloy as a biodegradable material. The X-ray diffraction (XRD) method was used to identify the phases formed in the experimental Fe-Mn-Si-Al alloy, and the SME was studied by differential scanning calorimetry (DSC). In vitro tests were performed by immersing the samples in Ringer’s biological solution for different time intervals (1, 3, and 7 days). The chemical composition of the samples, as well as the compounds resulting from the immersion tests, were evaluated by energy dispersive X-ray (EDS). Scanning electron microscopy (SEM) was used for the microstructural analysis and for highlighting the surfaces subjected to contact with the electrolyte solution. The corrosion rate (CR, mm/yr.) was calculated after mass loss, sample surface area, and immersion time (h) (at 37 °C). Samples were subjected to electro-corrosion tests using electrochemical impedance spectroscopy (EIS) and Tafel linear and cyclic potentiometry.
Catalin Panaghie, Ramona Cimpoeșu, Bogdan Istrate, Nicanor Cimpoeșu, Mihai-Adrian Bernevig, Georgeta Zegan, Ana-Maria Roman, Romeu Chelariu, and Alina Sodor
MDPI AG
Zinc biodegradable alloys attracted an increased interest in the last few years in the medical field among Mg and Fe-based materials. Knowing that the Mg element has a strengthening influence on Zn alloys, we analyze the effect of the third element, namely, Y with expected results in mechanical properties improvement. Ternary ZnMgY samples were obtained through induction melting in Argon atmosphere from high purity (Zn, Mg, and Y) materials and MgY (70/30 wt%) master alloys with different percentages of Y and keeping the same percentage of Mg (3 wt%). The corrosion resistance and microhardness of ZnMgY alloys were compared with those of pure Zn and ZnMg binary alloy. Materials were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), linear and cyclic potentiometry, and immersion tests. All samples present generalized corrosion after immersion and electro-corrosion experiments in Dulbecco solution. The experimental results show an increase in microhardness and indentation Young Modulus following the addition of Y. The formation of YZn12 intermetallic phase elements with a more noble potential than pure Zinc is established. A correlation is obtained between the appearance of new Y phases and aggressive galvanic corrosion.
Maria Magdalena Pricopi, Romeu Chelariu, Nicolae Apostolescu, Doina-Margareta Gordin, Daniel Sutiman, and Daniel Mareci
Revista de Chimie SRL
The aim of this study was to investigate the influence of different process parameters as chemical composition, the pH value and immersion time on the corrosion of the some TiMoNb alloys, using different electrochemical techniques such as: cyclic voltammetry, open circuit potential (OCP) measurement, polarization curves and electrochemical impedance spectroscopy (EIS). The alloys were analyzed in the natural pH of the Ringer solution, but also with an acidic modification of the solution (ph = 4) and a basic modification (ph = 8). The more acidic values of pH, the more evident are differences between corrosion behavior of titanium-based alloys depending on their chemical compositions and immersion times.
Bogdan Istrate, Corneliu Munteanu, Stefan Lupescu, Romeu Chelariu, Maria Daniela Vlad, and Petrică Vizureanu
MDPI AG
In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible elements. The aim of this research was to improve biodegradability rate and biocompatibility of Mg-0.5Ca alloy through addition of Y in 0.5/1.0/1.5/2.0/3.0wt.%. To characterize the chemical composition and microstructure of experimental Mg alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM), and X-ray diffraction (XRD) were used. The linear polarization resistance (LPR) method was used to calculate corrosion rate as a measure of biodegradability rate. The cytocompatibility was evaluated by MTT assay (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) and fluorescence microscopy. Depending on chemical composition, the dendritic α-Mg solid solution, as well as lamellar Mg2Ca and Mg24Y5 intermetallic compounds were found. The lower biodegradability rates were found for Mg-0.5Ca-2.0Y and Mg-0.5Ca-3.0Y which have correlated with values of cell viability. The addition of 2–3 wt.%Y in the Mg-0.5Ca alloy improved both the biodegradability rate and cytocompatibility behavior.
Bogdan Istrate, Corneliu Munteanu, Romeu Chelariu, Dumitru Mihai, Ramona Cimpoesu, and Florin Sandu Ville Tudose
Revista de Chimie SRL
Biodegradable magnesium alloys represent a class of materials with high properties that are used in a wide range of fields, such as medicine, aeronautics and automotive. Alloying the Mg-based alloys with small percentages of elements such as Ca, Mn and Zr can conduct to the obtaining of some materials that can be the basis for the development of orthopedic implants. Calcium contributes to the formation of the Mg2Ca lamellar compound, low concentrations of zirconium helps the microstructure refinement and corrosion resistance and the alloying with manganese leads to the increase of the mechanical characteristics.In this paper, the electrochemical behaviour of four biodegradable alloys from the Mg-Ca-Mn-Zr system was evaluated, with variable concentrations (0.5% -1%) of Mn, respectively Zr. Alloying the system with 1% of each element (Ca, Mn, Zr) led to the obtaining of the alloy with the highest corrosion resistance and the lowest degradation rate.
R. Chelariu, L.C. Trinca, C. Munteanu, G. Bolat, D. Sutiman, D. Mareci, and R.M. Souto
Elsevier BV
Abstract The potential biomedical application of three new quaternary Zr alloys, namely Zr6Ti15Nb4Al, Zr32Ti15Nb4Al, and Zr49Ti15Nb4Al, was evaluated in vitro using electrochemical methods complemented with surface analysis of corrosion resistance. Cyclic potentiodynamic polarization (CCP) and electrochemical impedance spectroscopy (EIS) tests were performed in Ringer’s solution at 37 °C. The electrochemical behavior of the ZrTiNbAl quaternary alloys was consistent with the formation of passivating oxide films on the surfaces of these materials. Localized breakdown of the oxide layer occurred on Zr6Ti15Nb4Al and Zr32Ti15Nb4Al alloys subjected to positive anodic polarization, a feature confirmed by scanning electron microscopy (SEM) on retrieved samples. The Zr49Ti15Nb4Al alloy, which had the highest titanium (49 wt.%) content, exhibited a larger passive range in the polarization curve and was immune to localized corrosion breakdown in a simulated physiological solution for the range of polarizations that can occur in the human body.
I Carcea, R Chelariu, L Asavei, N Cimpoeşu, and R M Florea
IOP Publishing
This work reports the results of investigations on the fortification with high entropy alloys particles of aluminium matrix composite materials. The properties of these materials processed by Vortex techniques primarily depend on the matrix and the volume fraction of the constituent phase. The mechanical properties, toughening mechanisms and potential applications are briefly reviewed. Traditional methods were used for the basic characterization of the composite. The microstructure of the composites were investigated by optical and scanning electron microscopy (OM, SEM). SEM analysis was performed in order to observe the microstructural evolution as a function of the HEA particles content and to identify some reasons of the presence of porosity or any irregularities within the metal matrix.
Gheorghe Buluc, Romeu Chelariu, Gabriela Popescu, Mihail Sârghi, and Ioan Carcea
Trans Tech Publications, Ltd.
Traditional alloys is based on a single element called matrix and to improve some mechanical properties (strength, ductility, strength) are added and other metallic elements in the system. High entropy alloys have become a field of increasingly explored in the world of materials. Excellent mechanical properties obtained of the high entropy alloys recommend them to be from year to year as investigated. In the last decade more than 500 high entropy alloys journal and conference papers have been published [1]. High entropy alloys are alloys who have in their composition 5 to 13 metal elements and the concentration of each component is between 5% and 35%. These elements in the composition of high entropy alloys are divided into elements of minority and majority elements. They are called minority elements because their molar fraction is less than 5%. High entropy alloys have mixing entropy higher than traditional alloys, ΔScons≥1.61R (R = 8.314 J / (mol • K)) [1]. High entropy alloy have been obtained in the laboratory of Science and Materials Engineering faculty from Iasi using a medium frequency induction furnace with 8000 Hz. Because they have excellent mechanical properties high entropy alloys can be used in various fields with high wear and corrosion degree or electronic, magnetic applications [1]. In this work we selected pure metallic elements like: Fe, Ni, Cr, Mn and Al. The quantity of alloy developed varied between 0.5 and 1.5 kg. Metal load necessary for the preparation of metal alloys were formed technical grade, industrial accessible prices and satisfying. Friction and wear rezistance were studies by using a reciprocating sliding test machine , in a pin on disk configuration, using aluminum as counter face.In this paper it investigated the wear resistance of high entropy alloys obtained, microstructure and their mechanical properties.
D. Mareci, G. D. Suditu, R. Chelariu, L. C. Trincă, and S. Curteanu
Wiley
Numerous studies have been done on the corrosion process of different dental metallic materials, especially using a comparative method and analyzing the electrochemical phenomena. Simultaneously, the effects of the corrosion process have been quantify by different physical quantities, such as corrosion rate, corrosion resistance, polarization resistance, corrosion current density etc. These experimental data can be used to model the corrosion process and, subsequently, to perform predictions with the aim to analyze or to control the process. In this work, a series of experimental data about corrosion of some titanium-based dental materials in artificial saliva were obtained through electrochemical impedance spectroscopy (EIS) tests and used as a database to develop a model of corrosion process by artificial neural networks. The process parameters taken into account were chemical compositions of the materials (cp–Ti, NiTi, NiTiNb), immersion time, pH, NaF content, and albumin content. The corrosion resistance of the metallic materials was evaluated by polarization resistance determined by EIS tests. Neural networks were developed and applied for evaluating the corrosion resistance of the alloys, depending on the process parameters. The predictions provided by the model are useful to understand the contribution of each parameter in the process and possible ways to control it.
G Buluc, I Florea, R Chelariu, G Popescu, and I Carcea
IOP Publishing
In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.
D. Mareci, E.-N. Dragoi, G. Bolat, R. Chelariu, D. Gordin, and S. Curteanu
Wiley
Titanium (Ti) and its alloys are widely used in dental applications due to the excellent corrosion resistance and mechanical properties. However, it has been reported that Ti is sensitive to fluor ions (F-) and lactic acid. Corrosion behaviour of the TiMo alloys, together with the currently used metallic biomaterial commercial pure titanium (Cp-Ti), was investigated considering the use of alloys for dental applications. All the samples were examined using electrochemical impedance spectroscopy (EIS) in acidic artificial saliva with NaF and/or caffeine, at 37 °C. Equivalent circuits were used for modeling EIS data, in order to characterize samples surface and better understanding the effect of Mo addition on Cp-Ti. The TiMo alloys appear to possess superior corrosion resistance than Cp-Ti in all electrochemical media. In addition, a modelling technique based on differential evolution and artificial neural network was applied. The scope of this procedure was to determine an efficient model of the process and to eliminate the need for new experiments based on the predictions provided by the developed models
G. Bolat, J. Izquierdo, T. Gloriant, R. Chelariu, D. Mareci, and R.M. Souto
Elsevier BV
Abstract The electrochemical properties of Ti20Mo alloys prepared using different fabrication procedures, namely cold crucible levitation melting (CCLM) and powder sintering, were investigated using linear potentiodynamic polarization and EIS measurements. The surface condition was established using AFM, with the observation of a more porous surface finish in the case of powder sintering. A major effect of surface conditioning on the corrosion resistance of Ti20Mo alloys was observed, where the compact finish exhibits a superior corrosion resistance in chloride-containing saline solutions. Less insulating surfaces towards electron exchange resulted for the more porous finish as revealed by scanning electrochemical microscopy (SECM).
R. Chelariu, D. Mareci, G. Bolat, C. A. Peptu, and D. Cailean
Wiley
Ultrasound irradiation is an effective means of obtaining nanoparticles. Hydroxyapatite–zirconia (HA–ZrO2) synthesized by ultrasound irradiation was coated on Ti6Al7Nb implant alloy by electrophoretic deposition. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to evaluate the morphology and composition of HA–ZrO2 coatings. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves were used to characterize the corrosion performance of HA–ZrO2 coated sample in simulated body fluid (pH 3.9) at 37 °C. The EIS interpretation was performed in two-layer model of the coated sample. It was found that the nanoparticles of HA–ZrO2 coated on Ti6Al7Nb alloy showed a good corrosion resistance after a short-time immersion in simulated body fluid (pH 3.9).
Romeu Chelariu, Gabriel Dan Suditu, Daniel Mareci, Georgiana Bolat, Nicanor Cimpoesu, Florin Leon, and Silvia Curteanu
Springer Science and Business Media LLC
The aim of this study is to investigate the electrochemical behavior of some dental metallic materials in artificial saliva for different pH (5.6 and 3.4), NaF content (500 ppm, 1000 ppm, and 2000 ppm), and with albumin protein addition (0.6 wt.%) for pH 3.4. The corrosion resistance of the alloys was quantitatively evaluated by polarization resistance, estimated by electrochemical impedance spectroscopy method. An adaptive k-nearest-neighbor regression method was applied for evaluating the corrosion resistance of the alloys by simulation, depending on the operation conditions. The predictions provided by the model are useful for experimental practice, as they can replace or, at least, help to plan the experiments. The accurate results obtained prove that the developed model is reliable and efficient.
Daniel MARECI, Romeu CHELARIU, Adrian CAILEAN, Florin BRINZA, Georgiana BOLAT, and Doina Margareta GORDIN
Elsevier BV
Abstract The electrochemical behaviours of unrecrystallized and recrystallized Ti12Mo5Ta alloys were compared with those of the unrecrystallized Ti12Mo alloy and commercial pure titanium (cp-Ti). Experiments were carried out using physiological 0.9% NaCl solution (pH 2.3) at 37 °C. Very low passive current densities (in order of 10−6 A/cm2) were obtained from the anodic polarization curves, indicating high resistances of all samples in acidified 0.9% NaCl solution. Scanning electron microscopy (SEM) was employed to observe the surface morphology and all sample surfaces were identically corroded, no pitting, cracks, or other defects appeared on the sample surfaces after anodic potentiodynamic polarization tests. Equivalent circuit was used for modeling the electrochemical impedance spectroscopy (EIS) data, in order to characterize the sample surface and better understand the effect of Mo and Ta addition on the cp-Ti and the effect of recrystallization. The EIS results confirm that all titanium samples exhibit passivity in physiological 0.9% NaCl solution (pH 2.3) at open circuit potential (polarization resistance is around 105 Ω·cm2). The corrosion resistance of these samples in physiological 0.9% NaCl solution (pH 2.3) at 37 °C is in the following order of recrystallized Ti12Mo5Ta> unrecrystallized Ti12Mo5Ta > unrecrystallized Ti12Mo > cp-Ti.
A. C. Bărbînţă, D. Mareci, R. Chelariu, G. Bolat, C. Munteanu, K. Cho, and M. Niinomi
Wiley
The corrosion behavior of two TiNbTaZr alloys (Ti25Nb8Ta10Zr and Ti21Nb15Ta6Zr) in Dulbecco's minimum essential medium (MEM) are evaluated and its protective ability is compared with that of Cp-Ti, to ascertain their stability for biomedical application. All the samples were examined using electrochemical techniques: electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The electrochemical corrosion parameters obtained from the EIS and potentiodynamic polarization curves indicated a typical passive behavior for TiNbTaZr alloys. In addition, scanning electron microscopy was employed to observe the surface morphology after polarization test in MEM solution. Low anodic current density values were obtained from the polarization curves, indicating a typical passive behavior for TiNbTaZr alloys. EIS studies showed high impedance values for all samples, increasing with exposure time. The Ti21Nb15Ta6Zr alloy appears to possess superior corrosion resistance than the Ti25Nb8Ta10Zr alloy and Cp-Ti in MEM solution.
R. Chelariu, G. Bolat, J. Izquierdo, D. Mareci, D.M. Gordin, T. Gloriant, and R.M. Souto
Elsevier BV
Abstract The present study explores the microstructural characteristics and electrochemical responses of four metastable beta Ti-Nb-Mo alloys for biomedical implantation. They were synthesized by the cold crucible levitation melting technique, and compositions were selected to keep the molybdenum equivalency close to 12 wt% Mo eq . For the sake of comparison, Ti12Mo was also investigated. Microstructural characterization reveals that all the alloys are β (body-centred cubic structure), and the surface is composed by β equiaxial grains with dimensions in the range of tens to hundreds μm. The corrosion resistance (potentiodynamic polarization and electrochemical impedance spectroscopy) of the alloys was determined in 0.9 wt% NaCl saline solution at 25 °C. The materials spontaneously form a passivating oxide film on their surface, and they are stable for polarizations up to +1.0 V SCE . No evidence of localized breakdown of the oxide layers is found for polarizations more positive than those encountered in the human body. The passive layers show dielectric characteristics, and the wide frequency ranges displaying capacitive characteristics occur for both higher niobium contents in the alloy and longer exposures to the saline solution. The insulating characteristics of the oxide-covered surfaces were investigated by scanning electrochemical microscopy operated in the feedback mode, using ferrocene-methanol as redox mediator. Both z -approach curves and amperometric images were taken over the surface of the samples both at their open circuit potential and polarized. It has been found that Ti8Nb10Mo and Ti16Nb8Mo exhibit the lowest activity towards electron transfer. The new Ti-Nb-Mo ternary alloys are regarded to be potential candidates for biomedical application on the basis of both their microstructural characteristics and their corrosion resistance in saline solution with chloride content equivalent to body fluids.
L. Zaharia, R. Comaneci, R. Chelariu, and D. Luca
Elsevier BV
Abstract A novel ultra-high straining process, based on the combination of conventional direct extrusion followed by the upsetting of a cylindrical rod in several cycles of severe plastic deformation (SPD), is presented. This procedure, called repetitive extrusion and upsetting (REU), begins with the extrusion in order to elongate the grains. After extrusion, the specimen is upset until the initial diameter is reached again, so the direct extrusion process can be repeated. During extrusion and upsetting processes, the grains are fragmented along shearing planes. Four cycles of successive REU have been applied to commercial purity aluminum. The effective strain and the potential for grain refinement were evaluated. Preliminary microstructure investigations and mechanical properties evaluation of the processed specimen were carried out.
Andreea Carmen Bărbînţă, Romeo Chelariu, Marcelin Benchea, Carmen Iulia Crimu, Sorin Iacob Strugaru, and Corneliu Munteanu
Trans Tech Publications, Ltd.
Ti-Nb-Zr-Ta alloys represent a new generation of biomaterials with possible applications in the orthopedic field, being developed in order to eliminate the negative aspects of the current orthopedic biomaterials, which consist mainly in a low biocompatibility with human tissues and high values of modulus of elasticity compared to the human bone. This paper presents a comparative study of new titanium alloys, corresponding to the Ti-Nb-Zr-Ta system: Ti-21Nb-6Zr-15Ta and Ti-25Nb-10Zr-8Ta, which were analyzed by scanning electron microscopy, X-ray diffraction and microindentation. The both alloys are classified as near-β alloys. The addition of alloying elements such as Ta, Nb and Zr represents a good solution for lowering modulus of elasticity, which is an important factor for reducing bone resorption and therefore for preventing implant failure.