Experimental and theoretical insights into Artemisia Stems aqueous extract as a sustainable and eco-friendly corrosion inhibitor for mild steel in 1 M HCl environment.

The present research demonstrates an innovative investigation of environmentally friendly mild steel (M-steel) corrosion inhibition using the artemisia stems aqueous extract (ASAEx) as an inhibitor in hydrochloric acid 1 M. The standard extraction technique of hydrodistillation was used for producing the aqueous solutions of ASAEx. To assess the ratios of the chemical components, phytochemical screening was used to identify the stems of this plant. We used a variety of methods and techniques in our research on corrosion inhibition, including weight loss measures, surface analysis methods like XPS and SEM/EDS, electrochemical testing like PDP and EIS, as well as computational lead compound evaluation. Maximum inhibitory efficacy was achieved with 400 mg/L ASAEx in 1 M HCl at 303 K, i.e. 90%. The PDP investigation verified the mixed-kind inhibitor status of the ASAEx extract. To describe the surface of M-steel, fitting and synthetic data were used to identify a constant phase element (CPE). SEM surface analysis was also used to detect the ASAEx effect on the surface of M-steel. X-ray photoelectron spectroscopy (XPS) analysis shows the presence of trace molecules of ASAEx on M-steel surface characterizing the bands in Maj-ASAEx (major compound of ASAEx). Density functional theory (DFT) and molecular dynamics simulations (MDs) were used in computational chemistry to clarify the adsorption mechanism and inhibitory impact.

Improving the Chemical Stability of Al Alloy through the Densification of the Alumina Layer Assisted by SiF62- Anion Hydrolysis.

In this work, a high-density alumina layer with high chemical stability was successfully developed by controlling the hydrolysis of hexafluorosilicate (SiF62-) anions through the addition of various concentrations of sodium citrate (SCi) into the electrolyte of plasma electrolysis (PE). To achieve this aim, the substrate samples were anodized in alkaline aluminate-SiF62--based electrolytes with 0, 5, and 10 g/L of SCi. The presence of SCi anions in the electrolyte led to the formation of a thick adsorbed electrochemical double layer (EDL) on the substrate surface. The EDL not only affected the movement of SiF62- anions towards the anode but also influenced their hydrolysis reaction, which in turn led to a controllable sealing of structural defects with the hydrolysis products, namely SiO2 and AlF3. Among three different oxide layers, the oxide layer obtained from the electrolyte with 5 g/L SCi showed the highest chemical stability in a corrosive solution, which was linked to the fact that a considerable increase in the compactness of the oxide layers was obtained by the incorporation of SiO2 and AlF3. The mechanism underlying the effects of SCi on triggering the hydrolysis of SiF62- anions and factors affecting chemical stability are discussed based on the experimental data and computational analysis.

A Review on Synthesis, Properties, and Applications of Polylactic Acid/Silica Composites.

Polylactic acid (PLA)/silica composites as multifunctional high-performance materials have been extensively examined in the past few years by virtue of their outstanding properties relative to neat PLA. The fabrication methods, such as melt-mixing, sol-gel, and in situ polymerization, as well as the surface functionalization of silica, used to improve the dispersion of silica in the polymer matrix are outlined. The rheological, thermal, mechanical, and biodegradation properties of PLA/silica nanocomposites are highlighted. The potential applications arising from the addition of silica nanoparticles into the PLA matrix are also described. Finally, we believe that a better understanding of the role of silica additive with current improvement strategies in the dispersion of this additive in the polymer matrix is the key for successful utilization of PLA/silica nanocomposites and to maximize their fit with industrial applications needs.

Surface Properties of Graphene Functionalized TiO2/nHA Hybrid Coatings Made on Ti6Al7Nb Alloys via Plasma Electrolytic Oxidation (PEO).

Nano-hydroxyapatite (nHA)-matrix coatings containing graphene nanosheets (GNS)-nHA were coated on Ti6Al7Nb alloys by plasma electrolytic oxidation (PEO) treatment for the improvement of their surface properties. Crystallographic properties, functional groups, and elemental analysis of coatings were characterized by XRD, ATR-FTIR, and EDS analysis. Surface morphological changes of the coated surfaces were investigated by AFM and SEM. The electrochemical corrosion behavior of the coatings was examined by using the potentiodynamic scanning (PDS) tests under in-vitro conditions in simulated body fluid (SBF). The results showed that the GNS was successfully deposited in ceramic matrix coatings on Ti6Al7Nb alloys. Also, the microstructural observations revealed that the coatings have a porous and rough structure. The XRD and ATR-FTIR quantitative analysis have proved the appearance of HA and GNS in the coating layers. An increase in the coating thickness, surface hardness, and anatase/rutile transformation rate was determined, while the GNS ratio in the coating layers was increased. The microhardness of the nHA coating reinforced with 1.5 wt% GNS was measured at 862 HV, which was significantly higher than that of GNS-free (only nHA) coating (584 HV). The best in-vitro resistance to corrosion in SBF was observed in the nHA/1.5GNS wt% coating.

Hydrothermal synthesis of nanocrystalline hydroxyapatite-graphene nanosheet on Ti-6Al-7Nb: mechanical and in vitro corrosion performance.

The hybrid coatings containing the graphene nano-sheet (GNS) and nano-hydroxyapatite (nHA) phases have been successfully synthesized on Ti6Al7Nb alloys by a one-step hydrothermal method. The hydrothermal reaction was carried out for 24 h at 200 °C. The GNS ratio has been altered as 1, 3, 5 and 7 wt.% in the coatings and, the results have compared with non- GNS containing coatings. The effect of the GNS ratio on the microstructure, hardness, and in vitro corrosion responses has been investigated in detail. The characterizations of the coatings were carried out by SEM, EDS, AFM, XRD and, FTIR. The corrosion behavior of the hybrid coatings was compared in Kokubo's solution at 37 °C by using potentiodynamic polarization tests. The results showed that the hydroxyapatite phases were deposed on the graphene layers with nano-size nucleation with its Ca/P stoichiometric ratio. The best hydrophilicity (~52°) property has been obtained in nHA/3GNS coatings. In addition, the corrosion rates of coatings increased in the following order: nHA/3GNS < nHA/1GNS < nHA/7GNS < nHA/5GNS < only nHA.

Titanium-based composite scaffolds reinforced with hydroxyapatite-zirconia: Production, mechanical and in-vitro characterization.

In this study, titanium (Ti)-based composite scaffolds reinforced with hydroxyapatite-zirconia (HA-ZrO2) were successfully produced with powder metallurgy and atmosphere-controlled sintering processes. The scaffolds structures were theoretically selected as 40% and 60% porosity, and fabricated with approximately 1.47 and 4.02 std dev values, respectively. The porosity of the scaffolds was verified by Archimedes' measurements. The scaffolds were characterized by DTA, SEM/EDS, XRD analyses. The mechanical behaviors of the scaffolds were evaluated by compression and hardness tests. Besides, the electrochemical corrosion behaviors of the structures were compared with potentiodynamic scanning (PDS) measurements in simulated body fluids (SBF) at 37 ± 1 °C. It has been observed that all scaffolds have a bimodal porous structure as they contain varying proportions of micropores as well as macropores in desired dimensions. Biocompatible phases such as TixPy, Ca3(PO4)2 and CaTiO3, respectively, were found in the microstructure after sintering. In compression tests, 40% porous Ti had the highest strength with 37.98 MPa, interestingly, the lowest strength was seen in Ti/HA-ZrO2 scaffold with 60% porosity with 3.80 MPa. Young's modulus values of all scaffolds vary between 1.67 - 7.20 GPa, due to the bimodal pore structure and composition effect. However, in-vitro corrosion resistance of scaffolds decreased with HA reinforcement, while increased with ZrO2 additive to HA.

A Review on LDH-Smart Functionalization of Anodic Films of Mg Alloys.

This review presents an overview of the recent developments in the synthesis of layered double hydroxide (LDH) on the anodized films of Mg alloys prepared by either conventional anodizing or plasma electrolytic oxidation (PEO) and the applications of the formed composite ceramics as smart chloride traps in corrosive environments. In this work, the main fabrication approaches including co-precipitation, in situ hydrothermal, and an anion exchange reaction are outlined. The unique structure of LDH nanocontainers enables them to intercalate several corrosion inhibitors and release them when required under the action of corrosion-relevant triggers. The influences of different variables, such as type of cations, the concentration of salts, pH, and temperature, immersion time during the formation of LDH/anodic film composites, on the electrochemical response are also highlighted. The correlation between the dissolution rate of PEO coating and the growth rate of the LDH film was discussed. The challenges and future development strategies of LDH/anodic films are also highlighted in terms of industrial applications of these materials.

Current status and perspectives of zinc-based absorbable alloys for biomedical applications.

Absorbable metals have the potential to serve as the next generation of temporary medical implant devices by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their implementation in the market could greatly reduce the need of costly and risky additional surgeries for either implant replacement or removal, often required in current permanent implants. Despite the extensive research done over the last two decades on magnesium (Mg) and iron (Fe) based alloys, they have not generally shown a satisfactory combination of mechanical properties, biocompatibility and controlled degradation rate in the physiological environment. Consequently, zinc (Zn) based alloys were introduced in the last few years as alternative materials to overcome the limitations of Fe and Mg-based alloys. The blend of different alloying elements and processing conditions have led to a wide variety of Zn-based alloys having tunable mechanical properties and corrosion rates. This review provides the most recent progress in the development of absorbable Zn-based alloys for biomedical implant applications, primarily for cardiovascular and orthopedic devices. Their biocompatibility, processability and metallurgical aspects, as well as their mechanical behavior and corrosion properties are presented and discussed, including their opportunities, limitations and future research directions. STATEMENT OF SIGNIFICANCE: Temporary orthopedic bioimplants have become increasingly popular as they offer an alternative to prevent complications, like infections or secondary surgeries, often related to the implantation of permanent devices. Iron and magnesium alloys were extensively studied as candidates for absorbable medical applications, but they generally failed to provide a desirable mechanical performance and corrosion characteristics in the physiological environment. Zinc was introduced in the last decade as a potential implant material after showing outstanding biocompatibility and biodegradability. This review summarizes the research advances to date and provides a thorough discussion of the future challenges of absorbable zinc alloys to satisfy the demanding clinical benchmarks for absorbable medical applications. Their biocompatibility, mechanical, and corrosion aspects, both in vitro and in vivo, are comprehensively reviewed and assessed accordingly.