Corrosion and Tribocorrosion Behavior of Ti-40Nb and Ti-25Nb-5Fe Alloys Processed by Powder Metallurgy

The requirement of good mechanical properties, lower Young's modulus, superior corrosion resistance, and excellent biocompatibility makes beta-type titanium alloys attractive materials for orthopedic implants. In this study, Ti-25Nb-5Fe and Ti-40Nb beta-type titanium alloys were designed and produced by powder metallurgy route using titanium hydride, niobium, and iron powders. The effect of sintering conditions on microstructure, corrosion, and tribocorrosion behavior was explored. Electrochemical behavior was investigated in saline solution (9 g/L NaCl) at body temperature by using potentiodynamic polarization and electrochemical impedance spectroscopy. Tribocorrosion behavior was evaluated by reciprocating against an alumina ball at open circuit potential, as well, under anodic and cathodic potentiostatic conditions in saline solution (9 g/L NaCl) at body temperature. The physical, electrochemical, and tribo-electrochemical behaviors of both alloys were improved with increasing sintering time at 1250 °C from 2 to 4 hours and decreasing Fe particle size for Ti-25Nb-5Fe alloy. Degradation under tribocorrosion conditions was mainly governed by mechanical wear on Ti-25Nb-5Fe alloy; however, Ti-40Nb alloy exhibited an antagonistic effect between corrosion and wear during testing under anodic applied potential due to the formation of a denser tribolayer.This work is supported by FCT with the reference Project UID/EEA/04436/2019, together with M-ERA-NET/0001/2015, as well, by MINECO (Spain) through the program PCIN-2016-123 and the Ramón y Cajal Project RYC-2014-15014. I. Caha is grateful for the financial support through a Ph.D. Grant under the NORTE-08-5369-FSE-000012 Project

Improved tribocorrosion behavior obtained by in-situ precipitation of Ti2C in Ti-Nb alloy

Novel in-situ Ti-based matrix composites (TMCs) were developed through the reactive hot pressing of Ti + NbC powder blends. Due to the chemical reaction that occurred in the solid-state during processing, the produced samples were composed of an Nb-rich β-Ti phase that formed a metallic matrix along with Ti2C as a reinforcing phase. By employing different proportions of Ti:NbC, the phase composition of the alloys was designed to contain different ratios of α-Ti and β-Ti. The present work investigated the corrosion and tribocorrosion behavior of the composites, compared to unreinforced Ti, in a phosphate-buffered solution (PBS) at body temperature. Corrosion tests included potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Tribocorrosion tests were carried out using a ball-on-plate tribometer with sliding performed at open circuit potential (OCP) and under anodic potentiostatic conditions. Results showed that the stabilization of the β phase in the matrix led to a decrease in the hardness. However, the formation of the in-situ reinforcing phase significantly improved the tribocorrosion behavior of the composites due to a load-carrying effect, lowering the corrosion tendency and kinetics under sliding. Furthermore, localized corrosion was not observed at the interface between the reinforcing phase and the matrix.This work was supported by São Paulo Research Foundation (FAPESP), grants #2017/24300-4, #2018/00746-6 and #2019/07953-0. Also, this work was partially supported by Portuguese Foundation for Science and Technology (FCT), Portugal, under UIDB/04436/2020 project

Hybrid multi-core shell magnetic nanoparticles for wet peroxide oxidation of paracetamol: application in synthetic and real matrices

Clean water availability is becoming a matter of global concern in the last decades. The responsible entities for wastewater treatment do not have the proper facilities to deal with a wide range of pollutants. Special attention should be given to emerging contaminants, whose presence in water bodies may cause adverse effects on the aquatic ecosystem and human health. Most studies in the literature do not consider the development of their solution in real matrices, which can hinder the applicability of the explored alternative in the real scenario. Therefore, in this work, we demonstrate the applicability of hybrid magnetic nanoparticles for removing paracetamol (PCM) from simulated and real matrices by catalytic wet peroxide oxidation (CWPO). To achieve carbon coating, the nanoparticles were prepared via the traditional route (resorcinol/formaldehyde, CoFe@CRF). A new methodology was also considered for synthesizing thin-layered carbon-coated magnetic nanoparticles (phloroglucinol/ glyoxalic acid, CoFe@CPG). TEM images revealed a multi-core shell structure formation, with an average carbon layer size of 7.8 ± 0.5 and 3.2 ± 0.3 nm for resorcinol/formaldehyde and phloroglucinol/ glyoxalic acid methodology, respectively. Screening the materials’ activity for PCM oxidation by CWPO revealed that the nanoparticle prepared by phloroglucinol/glyoxalic acid methodology has higher performance for the degradation of PCM, achieving 63.5% mineralization after 24 h of reaction, with similar results for more complex matrices. Iron leaching measured at the end of all reactions has proven that the carbon layer protects the core against leaching.This work was financially supported by project RTChip4Theranostics (NORTE-01–0145-FEDER-029394), by CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the Foundation for Science and Technology (FCT) and the European Social Fund (FSE) for the individual research grant with reference SFRH/BD/143224/2019. Adriano Silva and Ana Paula F. da Silva were supported by the doctoral Grant SFRH/BD/151346/2021 and PRT/BD/ 153090/2021 financed by the Portuguese Foundation for Science and Technology (FCT) with funds from NORTE2020, under MIT Portugal Program. Jose L. Diaz De Tuesta acknowledges the financial support through the program of Atracción al Talento of Comunidad de Madrid (Spain) for the individual research grant 2022-T1/AMB-23946.info:eu-repo/semantics/publishedVersio

Cu(In,Ga)Se2 based ultrathin solar cells: the pathway from lab rigid to large scale flexible technology

For the first time, the incorporation of interface passivation structures in ultrathin Cu(In,Ga)Se2 (CIGS) based solar cells is shown in a flexible lightweight stainless-steel substrate. The fabrication was based on an industry scalable lithography technique - nanoimprint lithography (NIL) - for a 15x15 cm2 dielectric layer patterning, needed to reduce optoelectronic losses at the rear interface. The nanopatterning schemes are usually developed by lithographic techniques or by processes with limited scalability and reproducibility (nanoparticle lift-off, spin-coating, etc). However, in this work the dielectric layer is patterned using NIL, a low cost, large area, high resolution, and high throughput technique. To assess the NIL performance, devices with a NIL nanopatterned dielectric layer are benchmarked against electron-beam lithography (EBL) patterning, using rigid substrates. Up to now, EBL is considered the most reliable technique for patterning laboratory samples. The device patterned by NIL shows similar light to power conversion efficiency average values compared to the EBL patterned device - 12.6 % vs 12.3 %, respectively - highlighting the NIL potential for application in the solar cell sector. Moreover, the impact of the lithographic processes, such as different etch by-products, in the rigid solar cells’ figures of merit were evaluated from an elemental point of view via X-ray Photoelectron Spectroscopy and electrically through a Solar Cell Capacitance Simulator (SCAPS) fitting procedure. After an optimised NIL process, the device on stainless-steel achieved an average power conversion efficiency value of 11.7 % - a slightly lower value than the one obtained for the rigid approach, due to additional challenges raised by processing and handling steel substrates, even though scanning transmission electron microscopy did not show any clear evidence of impurity diffusion towards the absorber. Notwithstanding, time-resolved photoluminescence results strongly suggested the presence of additional non-radiative recombination mechanisms in the stainless-steel absorber, which were not detected in the rigid solar cells, and are compatible with elemental diffusion from the substrate. Nevertheless, bending tests on the stainless-steel device demonstrated the mechanical stability of the CIGS-based device up to 500 bending cycles.This work was funded in part by the Fundação para a Ciência e a Tecnologia (FCT) under Grants 2020.04564.BD, IF/00133/2015, PD/BD/142780/2018, SFRH/BD/146776/2019, UIDB/04564/2020 and UIDP/04564/2020, 2020.07073.BD, as well as through the projects NovaCell (PTDC/CTMCTM/28075/2017), CASOLEM (028917) “Correlated Analysis of Inorganic Solar Cells in and outside an Electron Microscope”, and InovSolarCells (PTDC/FISMAC/29696/2017) co-funded by FCT and the ERDF through COMPETE2020. And by the European Union's Horizon 2020 research and innovation 15 programme under the grants agreements N°. 720887 (ARCIGS-M project) and grand agreement N°.715027 (Uniting PV). The Special Research Fund (BOF) of Hasselt University is also acknowledged. P. Salomé and P. A. Fernandes would like to acknowledge FCT for the support of the project FCT UIDB/04730/2020. This work was developed within the scope of the project i3N, UIDB/50025/2020 & UIDP/50025/2020, financed by national funds through the FCT/MEC. The authors also acknowledge the support of Carlos Calaza in the fabrication for the 200 mm Si point contact stamp.info:eu-repo/semantics/publishedVersio

Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

This study explores how the chemical interaction between magnesium hydride (MgH2) and the additive CrO3 influences the hydrogen/lithium storage characteristics of MgH2. We have observed that a 5 wt.% CrO3 additive reduces the dehydrogenation activation energy of MgH2 by 68 kJ/mol and lowers the required dehydrogenation temperature by 80 °C. CrO3 added MgH2 was also tested as an anode in an Li ion battery, and it is possible to deliver over 90% of the total theoretical capacity (2038 mAh/g). Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH2. In depth characterization study by X-ray diffraction (XRD) technique provides convincing evidence that the CrO3 additive interacts with MgH2 and produces Cr / MgO byproducts. Gibbs free energy analyses confirm the thermodynamic feasibility of conversion from MgH2/CrO3 to MgO/Cr, which is well supported by the identification of Cr(0) in the powder by X ray photoelectron spectroscopy (XPS) technique. Through high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt nanoparticles. There is also convincing ground to consider that MgO rock salt accommodates Cr in the lattice. These observations support the argument that creation of active metal – metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH2, both for the improved storage of hydrogen and lithium

Doxorubicin delivery performance of superparamagnetic carbon multi-core shell nanoparticles: pH dependence, stability and kinetic insight

In the past decade, magnetic nanoparticles (MNPs) have been among the most attractive nanomaterials used in different fields, such as environmental and biomedical applications. The possibility of designing nanoparticles with different functionalities allows for advancing the biomedical applications of these materials. Additionally, the magnetic characteristics of the nanoparticles enable the use of magnetic fields to drive the nanoparticles to the desired sites of delivery. In this context, the development of new MNPs in new approaches for drug delivery systems (DDSs) for cancer treatment has increased. However, the synthesis of nanoparticles with high colloidal stability triggered drug delivery, and good biocompatibility remains a challenge. Herein, multi-core shell MNPs functionalized with Pluronic ® F-127 were prepared and thoroughly characterized as drug carriers for doxorubicin delivery. The functionalized nanoparticles have an average size of 17.71 ± 4.2 nm, high water colloidal stability, and superparamagnetic behavior. In addition, the nanoparticles were able to load 936 μg of DOX per mg of functionalized nanomaterial. Drug release studies at different pH values evidenced a pH-triggered DOX release effect. An increase of 62% in cumulative drug release was observed at pH simulating tumor endosome/lysosome microenvironments (pH 4.5) compared to physiological conditions (pH 7.4). In addition, an innovative dynamic drug delivery study was performed as a function of pH. The results from this test confirmed the pH-induced doxorubicin release capability of carbon multi-core shell MNPs. The validity of traditional kinetic models to fit dynamic pH-dependent drug release was also studied for predictive purposes.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and to the ERDF for financial support by funds FCT/MCTES to CIMO (UIBD/00690/2020) and RTChip4Theranostics (NORTE-01-0145-FEDER-029394). This work is a result of these projects. This research was funded by RTChip4Theranostics – Real time Liver-on-a-chip platform with integrated micro(bio)sensors for preclinical validation of graphene-based magnetic nanocarriers towards cancer theranostics, with the reference NORTE-01-0145-FEDER-029394, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); and CIMO (UIDB/00690/2020) through ERDF under the Program PT2020. Adriano S. Silva thanks his doctoral Grant with reference SFRH/BD/151346/2021 financed by the Portuguese Foundation for Science and Technology (FCT), with funds from NORTE2020, under the MIT Portugal Program.info:eu-repo/semantics/publishedVersio

A promising method to develop TiO2-based nanotubular surfaces on Ti-40Nb alloy with enhanced adhesion and improved tribocorrosion resistance

Although TiO2 nanotubes have unique properties making them attractive for variety of applications, their poor adhesion to the substrate is a major limitation. In order to overcome this limitation, a facile route, combination of a two-step anodic treatment and heat treatment was applied in order to develop a well-adhered TiO2-based nanotubular surface on Ti-40Nb alloy. The adhesion of the nanotubular layer was evaluated by Daimler-Benz Rockwell C test. Corrosion and tribocorrosion behavior was investigated in phosphate-buffered saline solution (PBS) at body temperature. Corrosion behavior was examined by potentiodynamic polarization and electrochemical impedance spectroscopy whereas tribocorrosion behavior was evaluated by reciprocating sliding against an alumina ball at open circuit potential. Results showed that the adhesion, corrosion, and tribocorrosion behavior of the nanotubular layer was drastically improved with the combination of a two-step anodic treatment and heat treatment.This work was supported by FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020, together with M-ERA-NET/0001/2015 and PCIN-2016-123 project. I. Çaha is grateful for the financial support through a Ph.D. grant under the NORTE-08-5369-FSE-000012 project, and mobility program under INTERREG VA España Portugal (POCTEP) territorial cooperation programme (Project ref: 0300_NANOGATEWAY_6_P)

Catalysis of ceria incorporated magnesium hydride: a follow up study

In continuation with the results explored in our recent previous study (https://doi.org/10.1016/j.apsusc.2021.150062), the current work sheds more light regarding the active in situ catalytic species in ceria additive loaded hydrogen storage system, MgH2. For this study, two samples, MgH2+0.167CeO2 and MgH2+0.5CeO2 were processed through mechanical milling (5 h/200 rpm) and tests were conducted at various stages of hydrogenation/dehydrogenation cycles (cycles: 1, 5 and 10). Evidence for mild chemical interaction between MgH2 and CeO2 is observed at the time of mechanical milling, whereas strong redox type interaction is witnessed in the cycle tested samples. In-situ X ray diffraction study confirms that the thermally activated interaction between MgH2 and CeO2 does not produce MgO. In situ Raman spectra provide crucial evidence that reduced cerium oxides exist at all stages of interactions in the MgH2/CeO2 hydrogen storage system. Detailed advanced electron microscopic observations concur well with the in-situ X ray diffraction and Raman spectroscopy studies. Although Gibbs free energy calculations reveal the possible existence of cerium hydrides, owing to the structural similarities between CeHx and CeOx phases, the chemical identity of the most abundant catalytic product remains debatable. Regarding the catalytic mechanism, suppression of MgO rock salt formation is identified to be a key step where the role of CeHx/CeOx interfaces gains more importance.publishe

Controlling Fluorescence Wavelength in the Synthesis of TGA-Capped CdTe Quantum Dots

Quantum dots (QDs) are semiconductor materials, with a size range between 1–10 nm, showcasing unique size-dependent physical and chemical properties. Such properties have potentiated their use in areas like medical imaging and biosensing. Herein, we present an open-air approach for synthesis of QDs, reducing the need for controllable atmospheric conditions. Furthermore, we present a predictive mathematical model for maximum emission wavelength (λmax) control. Through a straightforward microwave-based aqueous synthesis of TGA-CdTe QDs, we investigated the influence of time, temperature, and Te:Cd and TGA:Cd molar ratios on λmax, using a chemometric experimental design approach. CdTe-QDs were characterized by UV-Vis and fluorescence spectroscopies. Additionally, Fourier-Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, Transmission Electron Microscopy, and Energy Dispersive X-ray were conducted. Stable QDs with fluorescence ranging from green to red (527.6 nm to 629.2 nm) were obtained. A statistical analysis of the results revealed that time and temperature were the most significant factors influencing λmax. After fine-tuning the variables, a mathematical model with 97.7% of prediction accurately forecasted experimental conditions for synthesizing TGA-CdTe QDs at predefined λmax. Stability tests demonstrated that the QDs retained their optical characteristics for over a month at 4 °C, facilitating diverse applications