Stainless Steel Substrates Research Articles

Polymer-derived coatings with La2Zr2O7 and glass fillers: Preparation and characterisation

This study investigated the impact of La2Zr2O7 (LZ) and different types of glass on the performance of polymer-derived ceramic (PDC) coatings on AISI 441 stainless steel substrates. Four double-layer PDC-based glass-ceramic coatings containing LZ and different glass fillers were prepared by dip coating. The LZ powder was synthesised by solid-state reaction (SSR): powder morphology, crystal structure, and thermal stability were analysed. X-ray diffraction (XRD) detected a LZ pyrochlore phase after annealing at 1300 and 1400 °C with a trace of t-ZrO2. Four different glass compositions, namely BaO-Al2O3-SiO2 (BAS), BaO-Al2O3-La2O3-B2O3-SiO2 (BALBS), CaO-B2O3-SiO2 (CBS), and BaO-ZnO-MgO-B2O3-SiO2 (BZMBS), were also synthesised as fillers for PDC coatings. The glass transition and crystallisation temperatures of the glasses were determined using differential scanning calorimetry (DSC). The coating systems, consisting of a Durazane 2250 bond coat and a top coat (Durazane 1800 + LZ filler + different glass sealants), were prepared. After pyrolysis of the coatings at 900 °C, some of the glasses partially crystallised. Scanning electron microscopy (SEM) revealed that the layers containing BAS, BALBS and CBS glass were dense, with good adhesion to the substrate, and with occasional presence of larger pores and cracks. Delamination of the upper layer was observed in the coating with the BZMBS glass filler.

Oxidized textured stainless steel surface with passivation layer as a high temperature selective solar absorber

A nanocrystalline textured stainless steel (SS) surface passivated with an AlCr oxide layer is proposed for use as a high temperature solar selective absorbers (SSAs). The textured SS surface was prepared by oxidizing in air at 800 °C for 30 min. The heating resulted in outward diffusion of the SS substrate Mn atoms, their oxidation on the surface, and formation of octahedral Mn3O4 nanocrystals, which play a role of textured surface. The passivation AlCr oxide single layer was deposited on the textured surface using reactive RF magnetron sputtering to protect the SS from further oxidation. The solar absorptivity αs and thermal emissivity ε298K of the as-deposited SSAs were 0.84 and 0.165, respectively. In order to study high temperature stability, SSAs were heat treated under air conditions at 600–900 °C for 0.1–300 h. SSAs demonstrated thermal stability at 600 °C for at least 300 h and degradation of optical properties with performance criterion PC < 0.05 at 700, 800, and 900 °C for 300 h, 30 h, and 1 h, respectively. The increase in thickness of the surface Cr2O3 layer on SS substrate was identified as the main degradation mechanism of SSA optical performance. SSAs demonstrated a high activation energy of 330 ± 30 kJ/mol. The obtained data can be used to design high temperature SSAs for concentrating solar energy systems operating under vacuum or air conditions at 500 °C.

Hydrothermally synthesized copper telluride nanoparticles: First approach to flexible solid-state symmetric supercapacitor

Supercapacitors, with their high-power density, rapid charge–discharge rates, and long cycle life, have emerged as promising energy storage devices for numerous applications. Among the various materials explored for supercapacitor electrodes, copper-based chalcogenides have gathered significant attention due to their intriguing electrochemical properties and simple synthesis routes. While there have been thorough investigations in other fields, only a limited number of studies have focused on the specific application of copper telluride nanoparticles as supercapacitors. In this study, we present a novel approach utilizing hydrothermally synthesized copper telluride (Cu2-xTe) nanoparticles as binder-free electrodes on flexible stainless steel (SS) substrates. The Cu2-xTe nanoparticles, with their small particle (38 nm) and highly crystalline structure, enhance charge storage and promotes a pseudocapacitive behavior, resulting in a high specific capacitance [381 F/g (163 mF/cm2) at 2 mV/s] in a 2 M KCl electrolyte solution. Moreover, we studied and explained the distinct contributions of surface-controlled and diffusion-limited processes to the overall charge storage capacity of the electrode. Our pioneering effort includes the fabrication and analysis of flexible, symmetric solid-state supercapacitor devices utilizing Cu2-xTe electrodes with PVA-LiClO4 gel electrolyte. These devices demonstrate an energy density of 11 Wh/kg, a power density of 800 W/kg, and an impressive 85 % retention of cyclic stability after 5000 cycles.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

Microstructure evolution and tribological properties over a wide temperature range of Ni-based composite coatings with Ti3AlC2 addition

Ni60A alloy powders doped with varying concentrations (0, 10 wt% and 20 wt%) of Ti3AlC2 MAX phase were coated on S31008 NiCr stainless steel substrate using atmosphere plasma spraying technique in this work. Comparative investigation was conducted to examine the effects of Ti3AlC2 additions on the microstructure evolution, microhardness, and wide temperature range (room temperature to 800 oC) tribological performance of the composite coatings. The findings demonstrated that the composite coatings were composed of γ-Ni, intermetallic hard metal borides, Ti3AlC2 and TiC phases, without any noticeable oxide phases. The 20 wt% Ti3AlC2 additions to the Ni60A alloy coating exhibited minimum imperfections in microstructure with a porosity drop of 65.8 %, and the highest microhardness which was enhanced by 64 % to 924 HV0.515. After introducing of Ti3AlC2, the coefficient of friction decreased and appeared to distinguish itself by remaining minimal and stable at low-medium temperatures compared with an increase of more than 70 % at high temperatures. Ni60A-10 wt% Ti3AlC2 coating resulted in the lowest friction coefficient of approximately 0.45 from room temperature to 400 oC and it peaked to 0.78 at 800 oC, reducing by 19.6 % and 6 % compared to non-composite coating, respectively. The wear resistance of the composite coating was considerably improved with the increment of Ti3AlC2, and the coating with 20 wt% Ti3AlC2 showed the most significant reduction in wear rate: 18.5 % at room temperature, 45.2 % at 200 oC, 37.2 % at 400 oC, 60 % at 600 oC, 90.8 % at 800 oC. The lubricate layered Ti3AlC2 phases and the tribo-oxide film predominate composed of derivative NiO, Cr2O3 Al2O3 and TiO2 played a critical role in antifriction and wear resistance. The wear mechanisms were accordingly conducted as abrasion and adhesion wear at low-medium temperature and transferred into tribo-oxidation wear at elevated temperature.

Facile synthesis of silver nanoparticles using Calotropis procera leaves: unraveling biological and electrochemical potentials

The alarming rise of pathogen antibiotic resistance presents a major global health challenge and demands a novel way to control the microbial infections. Simultaneously, nanotechnology has found numerous uses in electrical as well as electronic systems, including timing, filtering, power factor adaptation, and capacitors for energy storage. This work investigates the synthesis and characterization of a silver nanoparticle (AgNPs) utilizing Calotropis procera (CPL) leaf extract. The optimization of synthesis process and the reduction of nanoparticles (NPs) were validated by UV–visible spectroscopy. AgNPs' was exhaustively characterized for morphology, crystallinity, zeta-potential, and structural properties. The produced NPs demonstrated a wide range of characteristics, such as antioxidant, antidiabetic, antibacterial, and antifungal effects. Furthermore, remarkable electrochemical performance was indicated by the CPL-AgNPs electrode, which has mesoporous, clustered sphere-shaped particles onto a flexible stainless-steel substrate. This highlights the electrode's potential in energy storage applications. Copper monosulfide served as the anode and CPL-AgNPs as the cathode electrode in tested hybrid supercapacitor devices, which proved remarkable specific capacitances, high specific energy, and exceptionally high specific power. In order to address the twin challenges of antimicrobial resistance alongside advanced energy storage, this study provides a novel and thorough analysis of the basic electrochemistry as well biological properties of AgNPs, clarifying their potential storage of charges mechanisms and biomedical applications.Graphical abstract

Fabrication and Properties of Superhydrophobic Colored Stainless Steel Surface for Decoration and Anti-Corrosion

A colored superhydrophobic surface on a stainless steel substrate was achieved by means of high temperature oxidation combined with subsequent spraying modification by superhydrophobic nano-silica film. Comprehensive characterizations of the surface were performed in terms of color, morphology, composition, wettability, and corrosion resistance by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), contact angle, potentiodynamic polarization, and electrochemical impedance spectroscopy measurement. At 400 °C, the surface was pale yellow, gradually turning yellow and then red as the temperature increased. At 700 °C and 800 °C, the surface colors were blue and dark brown, respectively. The samples with oxide films demonstrated lower contact angles, specifically 80.5° ± 2.5 at 400 °C, 79.1° ± 2.8 at 500 °C, and 75.6° ± 3.4 at 600 °C. The polarization resistance measured on the oxidized film formed at 600 °C exceeded 7.93 × 104 Ω·cm2. After spraying the treatment, these colorful surfaces exhibited superhydrophobicity, they were self-cleaning, and they satisfied anti-corrosion properties. The treatment performs as an excellent barrier and exhibits a high corrosion resistance of 4.68 × 106 Ω·cm2. The successful preparation of superhydrophobic colored surfaces offers the possibility of providing stainless steel with both decoration value and self-cleaning function simultaneously by our proposed chromium-free fabrication process.

Dual-Wave ZnO Film Ultrasonic Transducers for Temperature and Stress Measurements.

ZnO film ultrasonic transducers for temperature and stress measurements with dual-mode wave excitation (longitudinal and shear) were deposited using the reactive RF magnetron sputtering technique on Si and stainless steel substrates and construction steel bolts. It was found that the position in the substrate plane had a significant effect on the structure and ultrasonic performance of the transducers. The transducers deposited at the center of the deposition zone demonstrated a straight columnar structure with a c-axis parallel to the substrate normal and the generation of longitudinal waves. The transducers deposited at the edge of the deposition zone demonstrated inclined columnar structures and the generation of dominant shear or longitudinal shear waves. Transducers deposited on the bolts with dual-wave excitation were used to study the effects of high temperatures in the range from 25 to 525 °C and tensile stress in the range from 0 to 268 MPa on ultrasonic response. Dependencies between changes in the relative time of flight and temperature or axial stress were obtained. The dependencies can be described by second-order functions of temperature and stress. An analysis of the contributions of thermal expansion, strain, and the speed of sound to changes in the time of flight was performed. At high temperatures, a decrease in the signal amplitude was observed due to the decreasing resistivity of the transducer. The ZnO ultrasonic transducers can be used up to temperatures of ~500 °C.

Microstructural, tribological, and corrosion behavior of B4C-added TiO2 coatings applied on 316 L stainless steel via sol-gel method

Corrosion protection of metals is essential for a wide range of technological applications, and coating metal surfaces with protective materials is a commonly employed method to achieve this. Among these, TiO2 coatings are extensively used due to their excellent photocatalytic properties, their applications in sensing and solar cells, and enhancing the corrosion and wear resistance of metal surfaces. Recent advancements have focused on the incorporation of carbide particles, such as B4C, to further improve the performance of TiO2 coatings. In this study, TiO2 coatings containing 0–3.25 wt% B4C were applied to a 316 L stainless steel substrates using the sol-gel method. The coatings were characterized by XRD and SEM-EDS analyses, and their wear and corrosion properties were evaluated using ball-on-disc wear tests and corrosion tests in NaCl solutions. The results demonstrated that lower concentrations of B4C led to improved wear resistance, likely due to the formation of a durable tribolayer, while higher concentrations reduced the wear resistance, attributed to increased oxidation and the formation of brittle phases. Corrosion resistance was enhanced in coatings containing 0.25 wt% and 1.25 wt% B4C, which can be attributed to the formation of protective B2O3 phases. However, at higher B4C concentrations, the corrosion rate increased, primarily due to the presence of cracks in the coating structure. Overall, the addition of 0.25 wt% B4C to the TiO2 coating significantly improved wear and corrosion resistance, indicating its potential as an effective additive for protective coatings.

Electrochemical hydrogen production of SS, Ni, and Ni-B electrodes in prototype electrolyzer system

Highly efficient, low-cost, and stable electrocatalysts are crucial in electrocatalytic water splitting. Herein, the comparative study of stainless steel (SS), a Nickel (Ni/SS), and Nickel boride (Ni-B/SS) electrode for hydrogen production was carried out under a prototype electrolyzer system. The Ni/SS and Ni-B/SS were synthesized by a simple and low-cost chemical method on the SS substrate. As compared to SS and Ni/SS electrodes, the Ni-B/SS electrode demonstrates superior electrochemical activity towards the Hydrogen Evolution reaction (HER) with a low overpotential of 75 mV at a current density of 10 mA/cm2 and Tafel slope of 82 mV/dec in 1M KOH electrolyte. The as-fabricated Ni-B/SS electrode showed cauliflower-like morphology and exhibited an excellent hydrogen production rate such as 4.39 ml/min on a (2 cm x 2 cm) electrode at a constant potential of 2.2 V in a prototype electrochemical hydrogen production setup. The stability of the Ni-B/SS (6 cm x 6 cm) electrode was also checked on a large-scale prototype electrolyzer setup for 50 hr at a constant potential.

Substrate orientation influence on nanotwinning in magnetron sputtered CoCrFeMnNi and Ni coatings

This study reveals the influence of crystal orientation on formation of growth twins in magnetron-sputtered coatings. A comparison between materials with low and high stacking fault energy (SFE) was made: CoCrFeMnNi (25 mJ/m2) and Ni (125 mJ/m2). The coatings were grown on a polycrystalline 316L stainless-steel substrate with near-random crystal texture, providing a comprehensive selection of samples on a single substrate. Electron backscatter diffraction was used to identify the film orientation, followed by transmission electron microscopy of selected regions.The presence and density of twins depended on both the material and the growth orientation. For Ni, nanotwins were observed on < 5 % of the substrate grains, on growth directions closest to 〈111〉 . All other film orientations grew epitaxially with a cube-on-cube relationship. For CoCrFeMnNi, nanotwinning was observed on 50 % of the substrate grains, deviating < 35° from 〈111〉 . In the nanotwinned regions, the twin spacing was 10–100 nm for Ni and 2–20 nm for CoCrFeMnNi. The presence of nanotwins increased hardness in both materials. The mechanism behind these differences is discussed, together with other parameters for controlling twin density. Our results show that control of the growth process can be used for nanotwin-engineering in magnetron-sputtered materials with low SFE.

Evaluation of a Commercial MoS2 Dry Film Lubricant for Space Applications

Molybdenum disulfide coatings, particularly Microseal 200-1, have been extensively used as dry film lubricants for actuating mechanisms in space applications. Although Microseal 200-1 has historically been a popular choice for space missions, recent assessments indicate a need for reexamination. This study evaluates sliding friction in air and dry gaseous nitrogen atmospheres at ambient temperatures with both linear reciprocating and rotary unidirectional tribo-tests. Measurements are performed for Microseal 200-1 applied on substrates and surface treatments commonly used in aerospace components, particularly stainless steel and a titanium alloy. Our findings indicate that the friction of stainless steel balls sliding on Microseal 200-1-coated disks is significantly influenced by the environment as well as the disk substrate material. The average friction coefficient ranges from 0.12 to 0.48 in air and from 0.04 to 0.41 in dry gaseous nitrogen, and the amount of friction is consistently much higher for the Microseal 200-1 on the stainless steel than on the titanium alloy. Microscopy and surface analyses, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray fluorescence, of the coatings on stainless steel substrates reveals that the coatings are sparse and relatively thin, likely a key factor contributing to their high friction. This insight underscores the substrate dependence of this widely used coating and highlights the importance of detailed tribological testing in accurately assessing the tribological performance of commercial dry film lubricants, a key step towards improving the reliability and effectiveness of actuating mechanisms for space applications.

Techno-Economic Analysis of Beam-Down Solar Tower Secondary Reflectors

Beam-down solar towers are presented as an alternative to conventional solar towers that allow modular design, easily adaptable to industrial environments. Secondary reflectors are a key component in this type of configuration, due to the high concentration of radiation received from the solar field. The results of a technical and economic study of new secondary reflectors, based on a polished stainless-steel substrate with silver PVD coating and a system of protective layers, are presented and compared with aluminum reflectors, currently used in such configurations. For this, twelve different designs, grouped in three cases are simulated using ray tracing and finite elements. The results show that the steel reflectors reach lower temperatures compared to aluminum reflectors, allowing for greater durability. Additionally, the optical efficiency of the plant was determined, and it was estimated that steel reflectors can reduce the LCOH of the plant by approximately 3.5%.

Effect of Laser Power on Microstructure and Properties of WC-12Co Composite Coatings Deposited by Laser-Based Directed Energy Deposition.

During the laser-based directed energy deposition (DED-LB) processing, a WC-12Co composite coating with high hardness and strong wear resistance was successfully prepared on a 316L stainless steel substrate by adopting a high-precision coaxial powder feeding system using a spherical WC-12Co composite powder, which showed a large number of dendritic carbides and herringbone planar crystals on the substrate-binding interface. The influences of laser power on microstructural and mechanical properties (e.g., hardness, friction resistance) of WC-12Co composite surfaces were investigated. The results show that laser power has a significant effect on determining the degree of Co phase melting around the WC particles and the adhesion strength between the matrix and the coating. Lower laser power does not meet the melting requirements of WC particles, thus weakening the molding quality of the composite coating. At high laser power, it is possible to dissolve the WC particles and melt the metal powder between the particles, thus improving the material properties. The laser power increased from 700 W to 1000 W and the average hardness of the coating surface gradually increased from 1166.33 HV to 1395.70 HV, which is about 4-5 times higher than the average hardness of the substrate (about 281.76 HV). In addition, the coatings deposited at 1000 W showed better wear resistance. This work shows that the processing parameters during laser-directed energy deposition can be optimized to prepare WC-12Co composite coatings with excellent mechanical properties.

The Microstructure and Properties of Ni60/60% WC Wear-Resistant Coatings Prepared by Laser-Directed Energy Deposition.

Ni60/60% WC composite coatings with a good surface roughness and high mechanical properties were successfully prepared on 316L stainless steel substrate by laser-directed energy deposition (LDED) technology. The effects of laser power on the microstructural evolution and mechanical properties of the Ni60/60% WC composite coating were investigated. The relationships between the chemical composition, the microstructure, the hardness, and the friction wear resistance of the composite coatings were characterized and investigated. The results show that the laser power had a significant effect on the energy input, which determined the melting extent of the Ni60 phases around the WC particles and the bonding strength between the reinforcements and the matrix, as well as the bonding strength between the substrate and the coatings. With an increase in the laser power from 800 W to 1400 W, the average hardness of the coating surface increased due to the increased densification of the deposited coatings and then decreased due to grain coarsening under a high energy input. The average coefficient of friction of the coatings decreased gradually to 0.383 at 1000 W, showing a minimum wear of 0.00013 mm2 at 1200 W. The main wear mechanisms on the coated surfaces were adhesive wear and abrasive wear. Moreover, the coatings deposited at 1200 W exhibited better forming quality and wear resistance. This work suggests that the processing parameters during LDED can be optimized to prepare Ni60/60% WC wear-resistant coatings with excellent mechanical properties.

Sequential growth controlled copper vanadate nanopebbles embedded thin films: Electrode to asymmetric supercapacitive device assembly

Supercapacitor performance critically relies on the design of electrodes with both superior electrochemical and mechanical properties. In this study, we present a cost-effective and scalable approach for the synthesis of copper vanadate (Cu3V2O8) nanopebbles integrated into a thin film, tailored for supercapacitor applications. The synthesis was accomplished using the successive ionic layer adsorption and reaction (SILAR) method, which enabled precise control over the deposition of Cu3V2O8 on a stainless steel (SS) substrate. Detailed structural, morphological, and elemental characterizations confirm the successful formation and reveal critical insights into the chemical bonding and oxidation state at material. The supercapacitive performance of Cu3V2O8 electrode has been evaluated in an aqueous NaClO4 electrolyte to assess pseudocapacitive behavior. The Cu3V2O8 electrode exhibited a specific capacitance of 443 F g−1 at 5 mV s−1 scan rate. Additionally, liquid configured an asymmetric device was designed using Multiwalled carbon nanotubes (MWCNT) combined with Cu3V2O8, yielding a specific capacitance of 116 F g−1 at 5 mV s−1 with an energy density of 8.43 Wh kg−1 and a power density of 345.4 W kg−1, while maintaining capacitance retention of 76 % even after 4000 cycles as stability test. This work highlights the potential of Cu3V2O8 based materials for excellent performance of new avenues for energy storage.

Fracture toughness and cavitation erosion behavior of Fe-based amorphous composite coatings with Ni-coated Al2O3 addition

Fe-based amorphous composite coatings were prepared on 304 stainless steel substrates using atmosphere plasma spraying (APS), aiming to investigate the effect of Ni-coated Al2O3 particles addition on fracture toughness and cavitation erosion behavior of Fe-based composite coatings. The microstructure, phase composition, elastic modulus, microhardness and fracture toughness of the coating were characterized using scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation. The cavitation erosion behavior of Fe-based coatings was investigated by ultrasonic vibration cavitation method. Fe-based amorphous composite coatings exhibit a characteristic lamellar microstructure and reveal the presence of amorphous phases along with α-(Fe, Cr), NiO, Ni and Al2O3 crystalline phases. When the content of Ni-coated Al2O3 in coating increases from 0 wt% to 3 wt%, there is slight deterioration in porosity from 3.64 % to 4.75 % and fracture toughness from 2.579 MPa·m1/2 to 2.392 MPa·m1/2, yet an increase in microhardness from 925.4 HV0.5 to 1090.3 HV0.5. The composite coating with 3 wt% Ni-coated Al2O3 demonstrates the peak cavitation resistance and its cumulative mass loss is significantly reduced by 36.4 % compared to the pure Fe-based coating. The cavitation erosion failure of Fe-based amorphous composite coatings is predominantly characterized by the brittle fracture mechanism. The fundamental process driving cavitation erosion damage involves the material peeling and coating delamination instigated by intense micro-jet impact and shock wave propagation. The proposed Fe-based amorphous composite coatings can be applied to improve the anti-cavitation performance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

Electrophoretic deposition of polyvinyl alcohol, C-H NRs along with moringa on an SS substrate for orthopedic implant applications.

Metals are commonly used in bone implants due to their durability and load-bearing capabilities, yet they often suffer from biofilm growth and corrosion. To overcome these challenges, implants with enhanced biocompatibility, bioactivity, and antimicrobial properties are preferred. Stainless steel (SS) implants are widely favored in orthopedics for their mechanical strength and cost-effectiveness. To address the issues related to SS implants, we developed composite coatings using synthetic biopolymer polyvinyl alcohol (PVA), calcium hydrate (C-H) nanorods for improved bioactivity and antibacterial properties, and Moringa oleifera to enhance osteogenic induction. These coatings were deposited on 316L SS through electrophoretic deposition (EPD), providing protection against body fluids and enhancing the corrosion resistance of the SS. X-ray diffraction (XRD) confirmed the presence of the desired tobermorite crystal structure, while scanning electron microscopy (SEM) revealed nanorod-like C-H structures, a film thickness of 29 microns, and a hedgehog-like morphology in the composite particles. The coated sample demonstrated a contact angle of 64°, optimal for protein attachment and cellular uptake. Additionally, the coating exhibited strong adhesion with less than 5% damage observed in cross-cut hatch testing and appropriate surface roughness for protein attachment. Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) assessed the thermal response of the materials. The coating also showed antibacterial activity against both Gram-negative and Gram-positive bacteria. Furthermore, the sample exhibited rapid bioactivity by forming a hydroxyapatite (HA) layer within 24 hours, with 35.4% degradability within 24 hours and 44.5% within 48 hours. These findings confirm that the composite film enhances the biocompatibility, bioactivity, and antibacterial properties of SS orthopedic implants in a cost-effective manner.

Amorphous TiO2 nano-coating on stainless steel to improve its biological response

This study delves into the potential of amorphous titanium oxide (aTiO2) nano-coating to enhance various critical aspects of non-Ti-based metallic orthopedic implants. These implants, such as medical-grade stainless steel (SS), are widely used for orthopedic devices that demand high strength and durability. The aTiO2 nano-coating, deposited via magnetron sputtering, is a unique attempt to improve the osteogenesis, the inflammatory response, and to reduce bacterial colonization on SS substrates. &#xD;The study characterized the nanocoated surfaces (SS-a TiO2) in topography, roughness, wettability, and chemical composition. Comparative samples included uncoated SS and sandblasted/acid-etched Ti substrates (Ti). The biological effects were assessed using human mesenchymal stem cells (MSCs) and primary murine macrophages. Bacterial tests were carried out with two aerobic pathogens (S. aureus and S. epidermidis) and an anaerobic bacterial consortium representing an oral dental biofilm.&#xD;Results from this study provide strong evidence of the positive effects of the aTiO2 nano-coating on SS surfaces. The coating enhanced MSC osteoblastic differentiation and exhibited a response similar to that observed on Ti surfaces. Macrophages cultured on aTiO2 nano-coating and Ti surfaces showed comparable anti-inflammatory phenotypes. Most significantly, a reduction in bacterial colonization across tested species was observed compared to uncoated SS substrates, further supporting the potential of aTiO2 nano-coating in biomedical applications.&#xD;The findings underscore the potential of magnetron-sputtering deposition of aTiO2 nano-coating on non-Ti metallic surfaces such as medical-grade SS as a viable strategy to enhance osteoinductive factors and decrease pathogenic bacterial adhesion. This could significantly improve the performance of metallic-based biomedical devices beyond titanium.

Composite coatings from polycarbosilane derived SiC and Al/SiC cermet active fillers as protective barriers against steel corrosion

Stainless steel is used throughout the world as a structural material. However, it undergoes corrosion damage when exposed to extremely corrosive media, such as the marine environment. An alternative to solve this problem lies in the development of coatings that can withstand extreme conditions but also be easily deposited with inherently corrosion-resistant materials such as silicon carbide (SiC). The present study shows a simple method to produce Al/SiC cermet powders by attrition milling. The resulting cermet powders with a metallic matrix and hemispherical morphology, were employed as fillers in polycarbosilane (PCS) solutions that were sprayed on A304 stainless steel substrates. Al/SiC composite coatings were produced after heating the sprayed suspensions at 700 °C for 1 h in Ar atmosphere. The resulting composite coatings exhibited low surface energies (< 35 mN/m), water contact angles of 53°, and adhesion strength of up to 30 MPa. Finally, corrosion tests were performed in a cyclic corrosion test chamber, showing that these coatings effectively reduced the corrosion rate of stainless steel by 87%, reaching corrosion rate values of 0.007 g/cm2 year.