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Platinum group metals (PGMs) palladium, platinum, and ruthenium represent the key materials for automotive exhaust gas treatment. Since there are no adequate alternatives, the importance of these metals for the automotive industry is steadily rising. The high value of PGMs in spent catalysts justifies their recycling. Therefore, it is really important to recovery platinum group metals from aqueous solutions. Of the many PGMs recovery procedures, adsorption is a process with a good efficiency, but an important role is played by the adsorbent material used into the process. In order to improve the adsorption properties of materials were developed new methods for chemical modification of the solid supports, through functionalization with different extractants. In present paper a new adsorbent material (Chitosan-DB18C6) was used for PGMs recovery. The new adsorbent material was produced by impregnating Chitosan with dibenzo-18-crown-6-ether using Solvent Impregnated Resin (SIR) method. The crown ethers were chosen as extractant due to their known ability to bind metallic ions, whether they are symmetrically or unsymmetrically substituted. In order to determine the PGMs recovery efficiency for new prepared adsorbent material the equilibrium and kinetic studies were performed. Also, to study the PGMs adsorption mechanism the experimental data were modelled using pseudo-first-order and pseudo-second order kinetic models. Experimental data were fitted with three equilibrium isotherm models: Langmuir, Freundlich and Sips. The results proved that new adsorbent material (Chitosan-DB18C6) is an efficient adsorbent for PGMs recovery from aqueous solutions.

Magnetic iron oxide-silica shell nanocomposites (IONP@SiO2) have been prepared in a two-step procedure. IONPs were obtained by coprecipitation of iron salts, and coated by silica in sol-gel method under sonication. Two IONP/silica ratios and two drying methods, heating in oven and supercritical CO2 drying, were used. The samples were analyzed using X-ray diffraction (XRD), infrared spectroscopy, magnetic measurements, small-angle neutron scattering (SANS), nitrogen sorption, and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX). The iron oxide silica nanocomposites obtained via supercritical drying exhibited higher values of the specific surface area and of saturation magnetization compared to the samples synthesized with the same iron oxide content but obtained after drying at 60 °C. Pd(II) adsorption experiments were performed on the materials prepared by supercritical drying. The maximum adsorption capacity 6.5 mg/g showed that the materials can be used as good and cheap adsorbent for palladium ions from aquatic environment.

Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO2 that can be achieved in thin films grown directly on (111)-Nb:SrTiO3 substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO2 films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.2 μC/cm2 with a coercive field of 1.5 MV/cm. Moreover, the time-dependent polarization reversal characteristics of Nb:SrTiO3/ZrO2/Au film capacitors exhibit typical bell-shaped curve features associated with the ferroelectric domain reversal and agree well with the nucleation limited switching (NLS) model. The polarization-electric field hysteresis loops point to an activation field comparable to the coercive field. Interestingly, the studied films show ferroelectric behavior per se, without the need to apply the wake-up cycle found in the orthorhombic phase of ZrO2. Overall, the rhombohedral ferroelectric ZrO2 films present technological advantages over the previously studied zirconia- and hafnia-based thin films and may be attractive for nanoscale ferroelectric devices., This work was supported by (i) the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020 (ii) DSTSERB, Government of India, through Grant ECR/2017/ 00006, (iii) Project NECL - NORTE-01-0145-FEDER-022096 and Project UID/NAN/50024/2019. This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, refs UIDB/50011/2020 and UIDP/ 50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/ MCTES. R.F.N., M.C.I,. and C.G. acknowledge the financial support from the Romanian Ministry of Education and Research within the project PN-III-P4-ID-PCCF2016-0047, contract 16/2018. Work at LIST was supported by the Luxembourg National Research Fund through projects PRIDE/15/10935404 “MASSENA” (S.D.) and INTER/ ANR/16/11562984 “EXPAND” (H.A. and J.I.́). The authors acknowledge the CERIC−ERIC Consortium for access to experimental facilities and financial support under proposal 20192055. The authors also thank José Santos for technical support in the Thin Film Laboratory at CF-UM-UP. The equipment of the Ural Center for Shared Use “modern nanotechnology” Ural Federal University (Reg. No. 2968) was used with the financial support of the Ministry of Science and Higher Education of the RF (Project No. 075-15-2021-677).

The study of new useful, efficient and selective structures for the palladium ions’ recovery has led to the development of a new series of macromolecules. Thus, this study presents a comparative behavior of two crown benzene ethers that modify the magnesium silicate surface used as adsorbent for palladium. These crown ethers are dibenzo18-crown-6 (DB18C6) and dibenzo 30-crown-10 (DB30C10). The obtained materials were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared spectroscopy (FT-IR). The specific surface area (BET) and point of zero charge (PZC) of the two materials were determined. The palladium ions’ recovery from synthetic aqueous solutions studies aimed to establish the adsorption mechanism. For this desideratum, the kinetic, equilibrium and thermodynamic studies show that MgSiO3-DB30C10 have a higher adsorption capacity (35.68 mg g−1) compared to MgSiO3-DB18C6 (21.65 mg g−1). Thermodynamic studies highlight that the adsorption of Pd(II) on the two studied materials are spontaneous and endothermic processes. The positive values of the entropy (ΔS0) suggest that the studied adsorption processes show a higher disorder at the liquid/solid interface. Desorption studies were also performed, and it was found that the degree of desorption was 98.3%.

2,2′-thiobisethanol dimethacrylate/ethylene glycol dimethacrylate copolymer (coP-TEDMA/EGDMA) was used as a sorbent for gold recovery from residual solutions resulting from the electroplating industry. Firstly, synthesized material was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and confocal laser scanning microscopy. The sorption process mechanism was evidenced on the basis of kinetic, thermodynamic and equilibrium studies. To highlight this, the influence of solution pH, temperature and gold initial concentration on maximum sorption capacity was studied. The obtained experimental data were modeled using Langmuir, Freundlich and Sips sorption isotherms, and it was observed that the Sips one was better for describing the studied sorption process. Kinetic data were fitted using pseudo-first-order and pseudo-second-order kinetic models. Of these models, the studied process was better described by the pseudo-second-order model. The thermodynamic parameters free Gibbs energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were evaluated on the basis of the van’t Hoff equation. On the basis of the thermodynamic study, it was concluded that gold recovery on coP-TEDMA/EGDMA is a spontaneous and endothermic process.

Iron oxide-silica nanocomposites were prepared by sol-gel method using ammonia (NH3), acetic acid (CH3COOH) and hydrochloric acid (HCl) catalysts to generate different pH values for the reaction conditions. As starting precursors, for the silica, respectively, for the iron oxide, tetraethylorthosilicate (TEOS) and iron-III-acetylacetonate were used. The physico-chemical characterization of the materials revealed that the sample obtained with HCl catalyst displays the largest surface area (300 m2/g), the most compact network structure, highest surface roughness, biggest crystallite size (14 nm), magnetization (7 emu/g) and superparamagnetic behavior. These materials were tested for adsorption of Cr6+ and Zn2+ from aqueous solution. Sample M-HCl presented the highest surface area and was further used for adsorption of metal ions. Kinetic, thermodynamic and equilibrium adsorption measurements studies were made for Cr6+ and Zn2+. To establish the material behavior from a thermodynamic point of view, temperature and contact time of adsorption process, activation energy, free energy, of standard enthalpy and entropy were calculated. The kinetic behavior was modelled by pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models and the adsorption characteristics were determined by modelling the experimental data with Langmuir, Freundlich and Sips isotherms.

The aim of this study was to develop an electrochemical procedure for the advanced detection of tetracycline (TC) in water using CoAl2O4 dispersed onto carbon nanofiber-epoxy composite electrode substrate, which was selected from a series of tested carbon-based electrode substrates, i.e., commercial glassy-carbon and boron-doped diamond electrodes and home-made carbon nanotubeepoxy and carbon nanofiber-epoxy composites. Carbon nanofiber-epoxy composite electrode was found the best host for CoAl2O4 modifier based on the electrocatalytic effect towards TC oxidation and detection using cyclic voltammetry (CV) technique. The electrochemical techniques applied for electrochemical detection applications were CV, differential-pulse voltammetry (DPV), square-wave voltammetry (SWV) and chronoamperometry (CA). All the tested electrochemical techniques allowed TC determination and the electroanalytical parameters varied related to the technique type. DPV operated at the step potential of 50 mV and the modulation amplitude of 200 mV allowed the lowest limit of detection of 9 nM for TC determination. The recovery test applied for real surface water spiked with known TC concentrations among the reproducibility and the repeatability showed the great potential for the advanced quantitative determination of TC in real water or in pharmaceutical formulations.

Large areas of S-E of Asia (Bangladesh), East of Europe (Hungary, West of Romania, Serbia), Nord and South America contain deep ground waters contaminated with arsenic. In these areas the quantity of arsenic in deep aquifers exceeds maximum allowed concentration of 10 �g/L. In order to use these water sources new adsorbent materials are required for their treatment. A composite material based on carbon and iron-oxide (used as surface modifier) present many advantages such as: chemical stability, higher removal efficiency, possibility of regeneration and very good selectivity for As(V) ions due to presence of iron-oxide particles onto the surface. The purpose of this study was to develop a new method to obtain a composite material using cellulose and soluble starch as carbon sources for the adsorbent material and iron chloride as precursor for the surface modifier. Produced composite material was characterized using several methods: TG-DTG, SEM, EDX, RDX and FT-IR. During experimental test obtained adsorbent material was used as adsorbent for As(V) removal form aqueous solutions. Arsenic residual concentration was measured using ICP-MS method. Maximum adsorption capacity obtained for adsorption experiments was 280 �g As (V)/g of adsorbent material.

This study aimed to obtain new electrochemically modified electrodes with graphene and Au, Pt, Ag particles considering graphite (GP) and glassy carbon (GC) substrate by applying the chronoamperometry technique to develop the detection protocol of tetracycline (TC) considered as an emerging pollutant in water, using cyclic voltammetry (CV) technique. The graphite-based substrate used for Ag/ Au/ Pt electrodeposition led to the electrode compositions on which TC oxidation process was not diffusion-controlled and as consequence, TC detection failed. TC detection protocols were developed for all Ag/Au /Pt electrodeposited GC and GCGP electrodes. Better limits of TC detection was achieved for Ag electrodeposited on GC-GP at the cathodic potential of 0.460 V/SCE.

Corrosion resistance is a key performance factor for engineering materials used in the supercritical water-cooled reactors (SCWR). Choosing the materials with the best characteristics in the corrosive environment for SCWR, at high temperatures and pressures, is a real challenge for many researchers. Therefore, this paper aims to test two nickel-based alloys (Incoloy 800HT and Inconel 718) and to analyze the microstructures of the samples following exposure in a supercritical environment. Oxidation tests were performed at high temperature and pressure (550oC, 25MPa) for up to 70 days. The samples were investigated using gravimetric corrosion test and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The results obtained can be used in future research of the test protocol to identify alloys that could be used for SCWR components.

In this work, the ferroelectric and fatigue characteristics of Au/0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3(BCZT)/Si metal–ferroelectric–semiconductor (MFS) structures are investigated. Moreover, the...

The present work reports for the first time, the employment of ferroelectric ZrO2 films as energy storage capacitors utilized in pulsed power systems. Furthermore, the effect of insertion of a low permittivity dielectric HfO2:Al2O3 (HAO) layer, with a thickness ranging from 2 to 8 nm, on the tunability of ferroelectric and energy storage characteristics of ZrO2 films is assessed. The increase in thickness of the HAO layer gave rise to distorted ferroelectric loops with decreased polarization, coercive field, and hysteresis loss of the films. These results are correlated with the depolarization field induced by the insertion of the dielectric HAO layer. An optimum combination of high energy density of 54.3 J cm−3 and good storage efficiency of 51.3% are obtained for the ZrO2 film capacitors with 2 nm-thick HAO insert layer. These values correspond to an increase of ∼55% and ∼92%, from the respective values of pure ZrO2 film capacitors. In addition, the HAO/ZrO2 films showed a good fatigue endurance of energy storage performance over 109 electric field cycles. The energy storage density obtained from HAO(2 nm)/ZrO2 film capacitor is found to be higher than that reported for several Pb-based as well as Pb-free ferroelectric ceramic films with complex compositions. The present study demonstrates that simple binary oxides such as ZrO2 with ferroelectric behavior could be potential candidates for developing high performance energy storage capacitors., This work was supported by: (i) the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contracts UIDB/04650/2020 and the Scientific and Technological Cooperation Program between Portugal (FCT) and Morocco (CNRST) – 2019/2020; (ii) DST-SERB, Govt. of India through Grant No. ECR/2017/00006. C. I., R. N. and C. G. acknowledge the financial support from the Romanian Ministry of Education and Research within the project PN3– PCCF PN-III-P4-ID-PCCF2016-0047, contract no. 16/2018. The authors acknowledge the CERIC-ERIC Consortium for access to experimental facilities and financial support under proposal 20192055.

In this work, the ferroelectric characteristics of ZrO2 thin films grown on ITO-coated glass have been investigated. The ferroelectric nature of the ZrO2 films has been studied by polarization-electric field (P-E) hysteresis loops and found to be optimum for the films processed by rapid thermal annealing at 600 ◦C. The increase in the annealing temperature improves the ferroelectric properties through the increase of the in-plane strain that causes the formation of the ferroelectric orthorhombic phase. The formation of the orthorhombic phase was confirmed through high-resolution transmission electron microscopy. The effect of the electric field on the po larization switching kinetics of ZrO2 films has been investigated revealing that the switching kinetics follows the nucleation limited switching (NLS) model. The activation fields estimated from the peak values of the polarization currents (im) and the time (tm) at which im occurs are in good agreement with the values obtained from the switching characteristic time of the NLS model. This work paves the way towards the integration of (pseudo)- binary oxide thin films on cheap substrates like glass for the next-generation of non-volatile memories., This work was supported by: (i) the Portuguese Foundation for Sci ence and Technology (FCT) in the framework of the Strategic Funding Contracts UIDB/04650/2020 and (ii) DST-SERB, Govt. of India through Grant Nr. ECR/2017/00006. RFN and CG acknowledge funding through the contract POC 332/390008/29.12.2020-SMIS 109522. The authors acknowledge the CERIC-ERIC Consortium for access to experimental facilities and financial support under proposal 20192055. The authors would also like to thank José Santos for technical support in the Thin Film Laboratory at CF-UM-UP.

Gold is one of the precious metals with multiple uses, whose deposits are much smaller than the global production needs. Therefore, extracting maximum gold quantities from industrial diluted solutions is a must. Am-L-GA is a new material, obtained by an Amberlite XAD7-type commercial resin, functionalized through saturation with L-glutamic acid, whose adsorption capacity has been proved to be higher than those of other materials utilized for gold adsorption. In this context, this article presents the results of a factorial design experiment for optimizing the gold recovery from residual solutions resulting from the electronics industry using Am-L-GA. Firstly, the material was characterized using atomic force microscopy (AFM), to emphasize the material’s characteristics, essential for the adsorption quality. Then, the study showed that among the parameters taken into account in the analysis (pH, temperature, initial gold concentration, and contact time), the initial gold concentration in the solution plays a determinant role in the removal process and the contact time has a slightly positive effect, whereas the pH and temperature do not influence the adsorption capacity. The maximum adsorption capacity of 29.27 mg/L was obtained by optimizing the adsorption process, with the control factors having the following values: contact time ~106 min, initial Au(III) concentration of ~164 mg/L, pH = 4, and temperature of 25 °C. It is highlighted that the factorial design method is an excellent instrument to determine the effects of different factors influencing the adsorption process. The method can be applied for any adsorption process if it is necessary to reduce the number of experiments, to diminish the resources or time consumption, or for expanding the investigation domain above the experimental limits.

Two types of biocomposite materials are made (original fabrication recipes) containing different resins as base: version A with natural resin and version B with polyester resin. For both of them the reinforcement element is a natural one namely fir needles. The samples are mechanically tested by compression in order to obtain the stress-strain curves and the elasticity longitudinal modulus.

Due to the increased demand for palladium, as well due to its reduced availability in nature, its recovery from diluted waste solutions becomes a necessity, and perhaps an emergency. As a result of economic and technological development, new materials with improved adsorbent properties that are more efficient for metallic ions’ recovery were synthesized and introduced to market. The goal of this study was to obtain a new adsorbent material by functionalizing through impregnation a commercial polymeric support that was both inexpensive and environmentally friendly (Amberlite XAD7) with crown ether (di-benzo-18-crown-6—DB18C6). Crown ethers are known for their ability to form complexes within metallic ions, by including them inside of the ring, regardless of its atomic size. Adsorbent material was prepared by impregnation using the solvent-impregnated resin method (SIR). To highlight the presence of crown ether on the resin surface, a new synthesized material was characterized by scanning electron microscopy (SEM), elemental analysis X-ray energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR). The specific surface of the adsorbent material was also determined by the Brunauer–Emmett–Teller (BET) method. Adsorbent performances of the prepared material were highlighted by kinetic, thermodynamic and equilibrium studies and a possible mechanism was also proposed. The influence of specific parameters for the adsorption process (contact time, temperature, Pd(II) initial concentration) on the maximum adsorption capacity was pursued.

Effective recovery of palladium ions from acidic waste solutions is important due to palladium&rsquo, s intensive usage as a catalyst for different industrial processes and to the high price paid for its production from natural resources. In this paper, we test the ability of a new adsorbent, MgSiO3 functionalized by impregnation with DL-cysteine (cys), for palladium ion recovery from waste solutions. The Brunauer&ndash, Emmett&ndash, Teller (BET) surface area analysis, Barrett&ndash, Joyner&ndash, Halenda (BJH) pore size and volume analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and Fourier-Transformed Infrared (FTIR) spectroscopy have been performed to characterize this material. Firstly, the maximum adsorption capacity of the new obtained material, MgSiO3-cys, in batch, was studied. To establish the adsorption mechanism, the obtained experimental data were fitted using the Langmuir, Freundlich and Sips adsorption isotherms. Studies on the adsorption of palladium ions on the synthesized material were performed in a dynamic regime, in a fixed-bed column. The Pd(II) recovery mechanism in the dynamic column regime was established based on Bohart&ndash, Adams, Yoon&ndash, Nelson, Thomas, and Clark models. The obtained equilibrium adsorption capacity was 9.3 (mg g&minus, 1) in static regime (batch) and 3 (mg g&minus, 1) in dynamic regime (column). The models that best describe the Pd(II) recovery process for batch and column adsorption are Sips and Clark, respectively.

Two paste electrodes based on graphene quantum dots and carbon nanotubes (GRQD/CNT) and one modified with a homoleptic liquid crystalline Cu(I) based coordination complex (Cu/GRQD/CNT) were obtained and morphostructurally and electrochemically characterized in comparison with simple CNT electrode (CNT) for doxorubicine (DOX) detection in aqueous solutions. GRQD/CNT showed the best electroanalytical performance by differential pulse voltammetry technique (DPV). Moreover, applying a preconcentration step prior to detection stage, the lowest limit of detection (1 ng/L) and the highest sensitivity (216,105 µA/mg·L−1) in comparison with reported literature data were obtained. Cu/GRQD/CNT showed good results using multiple pulse amperometry technique (MPA) and a favorable shifting of the potential detection to mitigate potential interferences. Both GRQD-based paste electrodes have a great potential for practical utility in DOX determination in water at trace concentration levels, using GRQD/CNT with DPV and in pharmaceuticals formulations using Cu/GRQD/CNT with MPA.

The objective of this paper was to evaluate the potential of a new adsorbent material to recover Au (III) from real wastewater, in a column with a fixed bed in a dynamic regime. The material was obtained through functionalization, by impregnation of the commercial resin, Amberlite XAD 7 type, with L-glutamic acid, which has active groups &ndash, NH2 and &ndash, COOH. The goal of the experiments was to follow the correlation of fixed-bed column specific adsorption parameters (the effluent volume, the amounts of adsorbent, heights of the adsorbent layer in column) with the time necessary to cross the column. The experimental data obtained were modeled, using the Bohart&ndash, Adams, Yoon&ndash, Nelson Thomas and Clark models, to establish the mechanism of the Au (III) recovery process, in a dynamic regime. Also, we established the number of cycles for adsorption&ndash, desorption for which the new material can be used. We used 5% HNO3 (5%) as desorption agent in five adsorption&ndash, desorption cycles, until the process was no longer efficient. The degree of desorption varied between 84% and 34% from cycle 1 to cycle 5.

In the Dacian site from Ocniţa, Vâlcea County, identified with the ancient Buridava, a considerable number of pieces made of various alloys were discovered along the time, which led to the hypothesis of the existence here of an important craft center. Since the archaeological research is far from complete and it is obvious that the number of iron artifacts in situ and still undiscovered is probably quite large, we decided to choose a number of five pieces representing military equipment, but also utensils in common use because, through modern techniques for characterizing materials, but also through other methods, such as measuring the pH of the soil, to determine how the iron objects in situ are affected. Because, of all the alloys, those that contain a high percentage of iron are usually the most susceptible to degradation and corrosion, respectively, the present study aims to investigate a number of five such ancient objects. With the help of X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD) and soil pH measurement we try to reconstruct how the corrosion processes aroused and affected the analyzed parts.

The CAD/CAM techniques, especially additive manufacturing such as 3D printing, constitute an ever-growing part of obtaining different dental appliances and restorations. Of these, provisional restorations are of frequent use in daily dental practice and are the object of this study. Masticatory and parafunctional forces determine flexure on these prostheses. This study investigates the influence of the printing angle and loading direction of the applied force on the flexure strength of two commercially available printable resins—Detax Freeprint Temp and Nextdent MFH Vertex dental. Ten rectangular beam specimens printed at the angle of 0, 45 and 90 degrees were fabricated of each of these materials, with an addition of 10 at 0 degrees for the investigation of the load direction. Three-point bending tests were performed in a universal testing machine. Flexure strength, strain at break and Young’s modulus were determined and a statistical analysis was performed on the obtained data. According to the statistical analysis, the flexural strength has a significance dependence with respect to degrees of orientation, for both investigated materials.

The appearance of quick wear of rolling paths and rolling elements (balls) through contact fatigue phenomena and through surface defects lead to a decrease in the life of ball bearings in service. One of the causes is the interruption of the lubricating film between surfaces with relative motion under load conditions and high speeds, which leads to plastic micro-deformations and micro-welding between contact surfaces. Diagnosing defects by visual observation involves disassemble of the bearing and is an ineffective method of investigation in serial production. In this context, the necessity of: (i) comparative study of the stresses to which two types (100Cr6 steel and 100CrMnSi6-4 steel type) of radial ball bearings are subjected, (ii) the influence of contact between the ball and the inner ring during rotation, and (iii) the analysis with Finite Element Method (FEM) of the deformations occurring at the application of radial bearing forces. FEM is a current approach to real phenomena in mechanical assemblies, which allows a validation of study assumptions; the results of FEM can lead to the detection of tribological causes of increased bearing wear at inner ring to bearing balls contact. In this paper, FE simulation of radial loading deformations was performed in SolidWorks software using the Simulation module and the stresses and deformations in the bearing rings for the two materials were obtained. It has been found that the stresses that appear during simulations are similar for both materials and do not exceed the limits allowed for heavy duty steel bearings.

In this paper, obtaining by PM of aluminum based materials, characterization of them and Finite Element Analysis (FEA) of compaction were investigated. Sintered aluminum alloys (Al-Cu and Al-Mg-Si) were tested from physical and mechanical point of view and the obtained experimental results were compared with those of sintered bronze powder materials. We studied the compressibility and densification mechanism of Al-Cu mixed powders and for prediction of compaction behavior we used FEA. The data was obtained on the stress distribution in the compacted material and on the deformations occurring throughout the mixed metal powder of the compacted samples. The results of FEA were compared with those obtained experimentally

Multi-layered structures, composed of thin films from materials with different compositions or physical properties, represents a way to obtain enhanced properties or even new functionalities. In this work, lead zirconate titanate PbZrxTi1-xO3 (PZT; x = 0.20, 0.52, 0.80) multilayers were grown by pulsed laser deposition (PLD) on a single crystal strontium titanate (SrTiO3, STO) substrate, using a strontium ruthenate (SrRuO3, SRO) film as buffer layer for epitaxial growth, and also as back electrode. Up and down multi-layers were grown and their physical and structural properties were compared, up being the structure in which Zr concentration was varied from 20% near the STO substrate to 80% at the surface, while down is for the structure in which the Zr concentration starts with 80% near the substrate and ends with 20% at the surface. It was found that the electric and pyroelectric properties of the two graded structures are significantly different. The up structure presents electric properties that are comparable with those of single composition PZT films while the properties of the down structure are deteriorated, especially in terms of the leakage current magnitude. Pyroelectric signal could be measured only for the up structure. These differences were attributed to larger density of structural defects in the down structure compared to the up one. This is due to the different growth sequence: up structure starts with tetragonal PZT on cubic substrate (lower lattice mismatch, 1.1%) while down structure starts with rhombohedral PZT on cubic substrate (larger lattice mismatch, almost 5%).

The work describes the development of a flexible, hydrogel embedded pH-sensor that can be integrated in inexpensive wearable and non-invasive devices at epidermal level for electrochemical quantification of H+ ions in sweat. Such a device can be useful for swift, real time diagnosis and for monitoring specific conditions. The sensors’ working electrodes are flexible poly(methyl methacrylate) electrospun fibers coated with a thin gold layer and electrochemically functionalized with nanostructured palladium/palladium oxide. The response to H+ ions is investigated by cyclic voltammetry and electrochemical impedance spectroscopy while open circuit potential measurements show a sensitivity of aprox. −59 mV per pH unit. The modification of the sensing interface upon basic and acid treatment is characterized by scanning and transmission electron microscopy and the chemical composition by X-ray photoelectron spectroscopy. In order to demonstrate the functionality of the pH-sensor at epidermal level, as a wearable device, the palladium/palladium oxide working electrode and silver/silver chloride reference electrode are embedded within a pad of polyacrylamide hydrogel and measurements in artificial sweat over a broad pH range were performed. Sensitivity up to −28 mV/pH unit, response time below 30 s, temperature dependence of approx. 1 mV/°C as well as the minimum volume to which the sensor responses of 250 nanoliters were obtained for this device. The proposed configuration represents a viable alternative making use of low-cost and fast fabrication processes and materials.

The present paper reports a one-pot synthesis of magnetic nanocomposites samples through acid catalyzed sol-gel method. Fe(III) acetylacetonate was used as precursor of the iron oxide phase: tetraethylortosilicate for the silica phase and polyvinyl alcohol (PVA, molecular mass 49000) as pore former. Different concentrations of Fe2O3 in composites matrices were prepared and studied ranging from 0% to 20%. All reactions took place in one pot at room temperature; the materials were subsequently heat treated at 300°C, to ensure the crystallinity for the iron oxide having spinel structure, forming nanoparticles confined in the silica matrix. The materials were characterized using X-ray diffraction, small-angle neutron scattering, FT-IR spectroscopy, nitrogen adsorption, Mossbauer spectroscopy and magnetization measurements. The maximum value of room temperature saturation magnetization of ∼54 emu/g and 0.11 kOe coercive field was achieved for the magnetic nanocomposite sample with 20% Fe2O3. The highest surface area of 680m2/g was obtained for the sample with 10% Fe2O3. The potential applicability of the obtained materials was studied for adsorption performance for cadmium in aqueous solutions. The Langmuir isotherm model described well the adsorption data, indicating monolayer adsorption of Cd(II) on the heterogeneous composite surface.

Technologically relevant tetragonal/cubic phases of HfO2 can be stabilized at room temperature by doping with trivalent rare earths using various approaches denoted generically as bulk coprecipitation. Using in situ/ex situ X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy, and in situ/ex situ site-selective, time-gated luminescence spectroscopy, we show that wet impregnation of hafnia nanoparticles with 10% Eu oxide followed by mild calcination in air at 500 °C produces an efficient stabilization of the cubic phase, comparable to that obtained by bulk precipitation. The physical reasons behind the apparently conflictual data concerning the actual crystallographic phase and the local symmetry around the Eu stabilizer and how these can be mediated by luminescence analysis are also discussed. Apparently, the cubic crystal structure symmetry determined by XRD results in a pseudocubic/tetragonal local structure around Eu determined by luminescence. Considering the recent findings on wet impregnated CeO2 and ZrO2, it is concluded that CeO2, ZrO2, and HfO2 represent a unique case of a family of oxides that is extremely tolerant to heavy doping by wet impregnation. In this way, the same batch of preformed nanoparticles can be doped with different lanthanide concentrations or with various lanthanides at a fixed concentration, allowing a systematic and reliable investigation of the effect of doping, lanthanide type, and lanthanide concentration on the various functionalities of these technologically relevant oxides.

The aim of the present paper is to develop ceramic thin films by laser ablation in order to improve the biological behaviour of metallic implants dedicated to hard tissue restoration. The composition of the coatings was selected within SiO2–P2O5–CaO–MgO–ZnO–CaF2 system, while their processing has gone through two stages: target preparation via a wet chemistry approach and films deposition through a physical deposition method, on titanium substrates. The characteristics of the final layered structures were evaluated by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy and selected area electron diffraction. In vitro investigation techniques were employed for the bioactivity and biocompatibility assessment. The results indicated the growth of nanostructured akermanite-based thin films with an excellent bioactivity and a good effect on stem-type cells, which validates the suitability of such structures for medical implant applications.

The properties of ferroelectric materials, which were discovered almost a century ago¹ , have led to a huge range of applications, such as digital information storage² , pyroelectric energy conversion³ and neuromorphic computing⁴⁻⁵ . Recently, it was shown that ferroelectrics can have negative capacitance⁶⁻¹¹, which could improve the energy efficiency of conventional electronics beyond fundamental limits¹²⁻¹⁴. In Landau–Ginzburg–Devonshire theory¹⁵⁻¹⁷, this negative capacitance is directly related to the doublewell shape of the ferroelectric polarization–energy landscape, which was thought for more than 70 years to be inaccessible to experiments¹⁸. Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric Hf₀.₅Zr₀.₅O₂. To achieve this, we integrated the ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has its origin in the energy barrier in a double-well landscape. Furthermore, we demonstrate that ferroelectric negative capacitance can be fast and hysteresis-free, which is important for prospective applications¹⁹. In addition, the Hf₀.₅Zr₀.₅O₂ used in this work is currently the most industry-relevant ferroelectric material, because both HfO₂ and ZrO₂ thin films are already used in everyday electronics²⁰. This could lead to fast adoption of negative capacitance effects in future products with markedly improved energy efficiency.

CuBi2O4 synthesized by thermolysis of a new Bi(III)-Cu(II) oxalate coordination compound, namely Bi2Cu(C2O4)4·0.25H2O, was tested through its integration within carbon nanofiber paste electrode, namely CuBi/carbon nanofiber (CNF), for the electrochemical detection of amoxicillin (AMX) in the aqueous solution. Thermal analysis and IR spectroscopy were used to characterize a CuBi2O4 precursor to optimize the synthesis conditions. The copper bismuth oxide obtained after a heating treatment of the precursor at 700 °C/1 h was investigated by an X-ray diffraction and scanning electron microscopy. The electrochemical behavior of CuBi/CNF in comparison with CNF paste electrode showed the electrocatalytic activity of CuBi2O4 toward amoxicillin detection. Two potential detections, with one at the potential value of +0.540 V/saturated calomel electrode (SCE) and the other at the potential value of −1.000 V/SCE, were identified by cyclic voltammetry, which were exploited to develop the enhanced voltammetric and/or amperometric detection protocols. Better electroanalytical performance for AMX detection was achieved for CuBi/CNF using differential-pulsed and square-wave voltammetries than others reported in the literature. Very nice results obtained through anodic and cathodic currents recorded at +0.750 V/SCE and −1.000 V/SCE in the same time period using a pseudo multiple-pulsed amperometry technique showed the great potential of the CuBi/CNF paste electrode for practical applications in amoxicillin detection in aqueous solutions.

In this article, we have presented the studies regarding the improvements of the adsorption performance of a styrene-12% divinylbenzene copolymer functionalized with aminophosphonate groups in the removal process of thallium ions from aqueous solutions, by impregnation of the solid support with trihexyl(tetradecyl)phosphonium chloride (Cyphos IL-101). The use of ionic liquid impregnated polymer as adsorbent in the removal process of radionuclides presents higher adsorption performance because, in this case, the advantages of the ionic liquids are combined with the properties of the solid support. Until now the ionic liquids were intensive studied in the removal process of radionuclides from aqueous solutions but using the liquid–liquid extraction. In our case these are used in the solid–liquid separation process, a smaller quantity of ionic liquids being used (which decrease the cost of the adsorption process), and the loss of the ionic liquids in the aqueous phase being avoided. The ultrasonication method used for the impregnation of the ionic liquids onto the solid support is also a new and original one. The impregnation of the solid support with Cyphos IL-101 significantly increased its adsorption performance in the removal process of Tl(I) ions from aqueous solutions.

Cesium (Cs) removal from wastewater becomes an emerging issue after the Fukushima Daiichi Nuclear Power Plant disaster. Cs(I) is an metal ion present in high level radioactive waste and has to be removed for a better disposal in geological formation. The present study investigates the adsorption process of Cs(I) from aqueous solutions on an novel adsorbent material. The novelty of this material is that the solid support, magnesium silicate, is doped with a new extractant, thiourea dissolved in ethyl alcohol. In order to establish the adsorption capacities of the adsorbent material, it was used in the removal process of metal ions. Kinetically, the adsorption process of this metal ion has the best fit for the pseudo-second-order kinetic model. The removal process through adsorption is endothermic and spontaneous due to the thermodynamic studies. Equilibrium studies were also carried out for the Langmuir, Freundlich and Sips model. The new doped material proves to be favourable as adsorbent material in the removal of Cs(I) from polluted water.

The main aim of this scientific paper is to present the experimental testing performed on three foam materials: expanded polypropylene foams (EPP), Expanded Polystyrene (EPS) and Piocelan (60 g/l), in order to evaluate their performance as add on safety structures within automobile’s cockpit module. The performance analysis of these foam materials used as add on safety structures was done using two methods of in order to estimate the performance as safety devices for interior trimmings: material’s structural response to impact (high variation vs material) and Quasi-static tests to dynamic loadings for studying the strain rate effect on the foam response using a conventional testing machine for quasi-static tests at the strain rate of 0.01 and 1s − 1. Test showed an increasing in strength proportionally to foams density, bead thickness and cell walls as a consequence of the increase of the bulk material in the foam. Also, Expanded Polystyrene (EPS) seems to manifest best properties regarding energy absorption. For the experimental data analysis, custom MATLAB codes have been developed. All the acquisition data will be integrated into a wider database which could be further used for comparing the results, data interpretation and appropriate material selection according to a specific application.

Core&ndash, double shell nylon-ZnO/polypyrrole electrospun nanofibers were fabricated by combining three straightforward methods (electrospinning, sol&ndash, gel synthesis and electrodeposition). The hybrid fibrous organic&ndash, inorganic nanocomposite was obtained starting from freestanding nylon 6/6 nanofibers obtained through electrospinning. Nylon meshes were functionalized with a very thin, continuous ZnO film by a sol&ndash, gel process and thermally treated in order to increase its crystallinity. Further, the ZnO coated networks were used as a working electrode for the electrochemical deposition of a very thin, homogenous polypyrrole layer. X-ray diffraction measurements were employed for characterizing the ZnO structures while spectroscopic techniques such as FTIR and Raman were employed for describing the polypyrrole layer. An elemental analysis was performed through X-ray microanalysis, confirming the expected double shell structure. A detailed micromorphological characterization through FESEM and TEM assays evidenced the deposition of both organic and inorganic layers. Highly transparent, flexible due to the presence of the polymer core and embedding a semiconducting heterojunction, such materials can be easily tailored and integrated in functional platforms with a wide range of applications.

The published data on the experimentally determined fracture toughness of foams are based on a small number of specimens, having a lack of statistical consistency. The paper proposes a statistical approach on the fracture toughness results of rigid polyurethane (PUR) foams of three different densities. Five types of fracture tests were considered. The results were statistically analyzed using six types of regressions and a meta-analysis to identify the factors influencing the fracture toughness. The statistical analysis indicates that the fracture toughness represents a material property because does not depend on the specimen type. The density plays a major role in the fracture toughness of PUR foams. The irregular shape of the cells induced small anisotropy for low-density foams (100 kg/m3 and 145 kg/m3). This effect could not be observed for the foam with 300 kg/m3 density, for which the cells have a more regular spherical shape. The statistical analysis indicates that the influence of the loading speed is very weak.

Magnetic iron oxide-silica shell nanocomposites with different iron oxide/silica ratio were synthesized and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), small-angle neutron scattering, magnetic and N2-sorption studies. The composite that resulted with the best properties in terms of contact surface area and saturation of magnetization was selected for Pb2+ adsorption studies from aqueous media. The material presented good absorption capacity (maximum adsorption capacity 14.9 mg&middot, g&minus, 1) comparable with similar materials presented in literature. Its chemico-physical stability and adsorption capacity recommend the nanocomposite as a cheap adsorbent material for lead.

This paper is reporting the data concerning impurities occlusion in the dried, milled and classified aluminum hydroxide, the sources of contamination and the ways to control the purity of classified aluminum hydroxide as raw material for special aluminas. Mainly, all the micronic size particles, floating in the super-saturated Bayer liquors, are potential sources of occluded impurities in the aluminum hydroxide particles. There are several mechanisms for embedding the impurities in crystalline substances. Of these, most probable ones in the Bayer alumina process are: a) occlusion of the spent liquor drops containing impurities inside the polycrystalline aluminum hydroxide congregates; b) hetero-nucleation of aluminum hydroxide on the surface of particles or colloids containing one or more impurities (the foreign particles are seized inside a crystals or inside of a crystalline multi-particulate association); c) incorporation of available ions or molecule reactive fragments in the poor crystalline structures of aluminum hydroxide after nucleation, during different growth stages of all already aggregated particles, under certain super-saturations. d) building up bridges between the scanty aggregated particles or filling the inside hollows of these aggregates with new quickly crystallized material, including the particulate impurities, mainly, during large fluctuations of the super-saturation. Using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy EDS (Apollo SSD detector, EDAX), the contributions of each of these mechanisms can be investigated simply and assumed from the collected data. It was shown that well crystallized phases originating directly from bauxite (like the aluminum substituted goethite and substituted hematite, rutile or quartz), as well as the well as the crystallized new born phases during specific Bayer reactions (like cancrinite, are not promoting directly the impurities occlusion. Poor crystalline phases (like sodalite and katoite or other secondary phases and their micronic size fragments are really sustaining impurities occlusion through all the acknowledged mechanisms.

The interest in the unique properties associated with materials having structures on a nanometer scale has been increasing at an exponential rate in last decade. Transition metal oxides are preferred materials for catalytic applications due to their half-filled d orbitals that make them exist in different oxidation states. Transition metal oxides show a broad structural variety due to their ability to form phases of varying metal to oxygen ratios reflecting multiple stable oxidation states of the metal ions. The Solar Physical Vapor Deposition (SPVD) presented in the paper as elaboration method is an original process to prepare nanopowders working under concentrated sunlight in 2 kW solar furnaces. The influence of the synthesis parameters on the chemical and microstructural characteristics of zinc and manganese oxides synthesized nanophases has been systematically studied using XRD, SEM and EDX.

The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction in plane friction couplings with sliding movement. On tribometric device (made in our laboratory) we can measure the friction force, friction coefficient and wear, for different loading conditions, speeds, time and material coupling. For the measurement of the frictional force as well as of the coefficients of friction, mainly the method with a resistive tensiometric transducer is used. With a DataQ DI 245 data acquisition board it is possible to record up to 2 kHz frequencies in the range of -10 ÷ +10 mV with a resolution of 13 bits. To test the functionality of the device, a preliminary test was carried out for a steel pin- on- cast iron disc, for different values of the normal pushing force. The device was calibrated and the measurement results were recorded and processed on the computer.

We report significant photoelectrochemical activity of Y-doped BiFeO3 (Y-BFO) epitaxial thin films deposited on Nb:SrTiO3 substrates. The Y-BFO photoanodes exhibit a strong dependence of the photocurrent values on the thickness of the films, and implicitly on the induced epitaxial strain. The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. The crystalline coherence breaking due to the small ionic radius Y-addition was analyzed using Willliamson-Hall approach on the 2θ-ω scans of the symmetric (00 l) reflections and confirmed by high resolution TEM (HR-TEM) analysis. In the thinnest sample the lateral coherence length (L∥) is preserved on larger nanoregions/nanodomains. For higher thickness values L∥ is decreasing while domains tilt angles (αtilt) is increasing. The photocurrent value obtained for the thinnest sample was as high as Jph = 0.72 mA/cm2, at 1.4 V(vs. RHE). The potentiostatic scans of the Y-BFO photoanodes show the stability of photoresponse, irrespective of the film’s thickness. There is no clear cathodic photocurrent observation for the Y-BFO thin films confirming the n-type semiconductor behavior of the Y-BFO photoelectrodes.

Plasma electrolytic oxidation (PEO) process was employed in a galvanostatic regime on Zr-2.5Nb alloy in NaAlO2 aqueous electrolyte solutions within a concentration gradient of 5–30 g/L in order to produce Al2O3/ZrO2 composite coatings. The composition and microstructure of the oxide layers were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Vickers microhardness, scratch adhesion and potentiodynamic polarization measurements were used to assess the mechanical and electrochemical properties of the PEO coatings. The experimental findings suggest a strong correlation between the electrolyte concentration and the coating layers. By increasing the concentration of NaAlO2 in the electrolyte solution, significantly increased tetragonal crystal structure, particle size, hardness, adhesion strength and corrosion resistance occur with pore size decrease. Best values for the hard and adherent coating were ∼1500 HV and ∼60 N critical load. The corrosion current densities for the plasma electrolytic oxidized samples are lower than the black oxide coated Zr alloy.

This paper analytically investigates the flow as well as the chemically reactive solute transfer problem in a viscous fluid. The motion equations are reduced to a nonlinear ordinary differential equations system using the similarity transformations. The obtained nonlinear differential system is for the first time approximately solved by means of the Optimal Homotopy Asymptotic Method (OHAM). The effects of the partial slip and suction/blowing parameters are analytically analyzed. Some examples are given; the obtained results provides us with a good agreement with the numerical results and reveal that our procedure is effective, accurate and easy to use.

We report for the first time on the synthesis of NiO/ZnO one-dimensional (1D) nanowire (NW) based heterostructures by applying a suitable methodology of transport and condensation. The synthesis involves, firstly the growth of NiO NWs on gold (Au) catalyzed alumina substrates using the vapor-liquid-solid (VLS) mechanism and then the formation of ZnO NWs directly on the NiO NWs using the vapor-solid (VS) mechanism. Sequential evaporation–condensation over Au-seeded alumina promotes the formation of NiO NWs, driven by the VLS growth mechanism. These NiO NWs act as backbones for the condensation of epitaxial ZnO nanostructures. The detailed morphological study of these heterostructures reveals that ZnO nanowires completely cover the whole NiO nanowires completely and growing out in the form of flat leaves from the NiO nanowire branches. The diameters of the NiO NWs have been found to vary from 15 nm to 60 nm. Selected area electron diffraction data (SAED) indicate an epitaxial growth of ZnO nanowires along (101)-planes on the strongly oriented NiO nanowires along (200) crystallographic planes. Finally, NiO NW and NiO/ZnO heterostructure based conductometric gas sensing devices have been fabricated and the comparison between their sensing performances have been compared. Interestingly, NiO/ZnO NWs heterostructure based sensing devices shows superior performance compared to NiO sensors toward volatile organic compounds (VOC).

By platinum deposition on a 150 nm thick film of lead zirco-titanate oriented PZT(001), grown on strontium titanate (001) single crystals with a strontium ruthenate buffer layer, which did not show initial preferential out-of-plane orientation of its ferroelectric polarization, a band bending near the interface towards lower energies is observed using photoelectron spectroscopy, by following all core levels from the substrate (Pb 4f, Zr 3d, Ti 2p, O 1s). This is unexpected given the fact that platinum has a larger work function than PZT and a rectifying contact for electrons is expected to be built at the interface. This observation may have two explanations: (i) platinum forms an alloy with elements from PZT yielding a metal with considerable lower work function; (ii) platinum provides electrons to the substrate which are able to compensate the depolarization field generated by the outwards polarization state. Several arguments are brought in favor of the second hypothesis, especially the attenuation of core levels from the substrate which is well described by exponential functions with reasonable values of the photoelectron inelastic mean free path, suggesting the formation of a sharp interface. High resolution transmission electron microscopy confirmed the sharpness of the interface.