Search Results (91)

This study presents the structural and compositional characterisation of a newly developed Ti55Al27Mo13 alloy synthesised via aluminothermic reaction. The alloy was designed to overcome the limitations of conventional processing routes for high–melting–point elements such as Ti and Mo, enabling the formation of a complex, multi–phase microstructure in a single high–temperature step. The aim was to develop and characterise a material with microstructural features expected to enhance wear resistance, oxidation behaviour, and thermal stability in future applications. The alloy is intended as a precursor for composite nanopowders and surface coatings applied to aluminium–, magnesium–, and iron–based substrates subjected to mechanical and thermal loading. Elemental analysis (XRF, EDS) confirmed the presence of Ti, Al, Mo, and minor elements such as Si, Fe, and C. Microstructural investigations using laser confocal and scanning electron microscopy revealed a heterogeneous structure comprising solid solutions, eutectic regions, and dispersed oxide and carbide phases. Notably, the alloy exhibits high hardness values, reaching >2400 HV in Al₂O₃ regions and ~1300 HV in Mo– and Si–enriched solid solutions. These results suggest the material’s substantial potential for protective surface engineering. Further tribological, thermal, and corrosion testing, conducted with meticulous attention to detail, will follow to validate its functional performance in target applications. Full article

This study explores the development and optimization of quartz-based filtration media for industrial oil–water separation, focusing on enhancing surface wettability, minimizing fouling, and improving oil rejection efficiency. High-purity quartz particles (SiO₂: 98%, Fe₂O₃: 0.18%, particle size: 0.8–1.8 mm) were evaluated in three configurations: raw, acid-washed, and surface-coated with hydrophilic nanoparticles (Al₂O₃ and P₂O₅). The filtration medium was constructed as a packed-bed of quartz particles rather than a continuous sintered membrane, providing a cost-effective and modular structure for separation processes. Comprehensive material characterization was performed using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). XRD confirmed the crystalline stability of quartz across all treatments, while SEM and EDS revealed enhanced surface morphology and elemental distribution—especially phosphorus and aluminum—in coated samples. Performance testing with synthetic oily wastewater (initial oil concentration: 183,754.8 mg/L) demonstrated that the coated quartz medium achieved superior separation, reducing residual oil concentration to 29.3 mg/L, compared to 1583.7 mg/L and 1859.8 mg/L for washed and raw quartz, respectively. Contact angle analysis confirmed improved hydrophilicity in coated media, which also exhibited lower fouling propensity. Taguchi optimization (conducted via Minitab 21.3) and regression modeling identified surface coating and operational pressure (optimal at 2.5 bar) as the most significant parameters influencing oil rejection. Post-filtration SEM and XRD confirmed structural integrity and coating durability. Additionally, flux recovery above 90% after backwashing indicated strong regeneration capability. These findings validate surface-modified quartz packed beds as robust, scalable, and economically viable alternatives to conventional membranes in oily wastewater treatment. Future research will explore multilayer coatings, long term performance under aggressive conditions, and AI-based prediction models. Full article

Hot stamping is a promising method to manufacture ultra-high-strength automotive steel components with high dimension accuracy. In this work, two actual industrial production flows (with and without Al-Si hot dipping) were investigated to reveal their microstructural evolution and hydrogen content at different production steps. Meanwhile, the variations in composition and phase structures of the Al-Si coating layer were studied in terms of energy-dispersive spectrometry and electron backscattering diffraction techniques. The results showed that the microstructure at the steel substrate changed from the pancake-shaped pearlite and ferrite, degenerated pearlite and annealed ferrite, lath martensite, and then tempered martensite with the progress of the production steps, which was not affected by the Al-Si hot dipping. The final coating layer exhibited a multi-sublayer structure with the alternative distribution of FeAl and Fe₂Al₅, which contained many microcracks on the brittle phase Fe₂Al₅. The Al-Si-coated specimens always had higher hydrogen content than the bare steel specimens because of the hydrogen generation at the hot stamping stage and hydrogen absorption during the hot-dip aluminizing stage. Full article

AZ31B magnesium alloy (wt.%: Al 2.94; Zn 0.87; Mn 0.57; Si 0.0112; Fe 0.0027; Cu 0.0008; Ni 0.0005; Mg remaining) has appropriate mechanical properties, good biodegradability and biocompatibility and can be used as a good orthopedic implant material. AZ31B magnesium alloy with a superhydrophobic surface exhibits excellent corrosion resistance and antibacterial adhesion performance, but superhydrophobic surfaces also hinder osteoblast adhesion and proliferation on the implants, resulting in unsatisfactory osteogenic properties. Therefore, it is necessary to achieve the wettability transition of the superhydrophobic surface at an early stage of implantation. In this work, superhydrophobic hydroxyapatite (HA)/calcium myristate (CaMS)/myristic acid (MA) composite coatings were prepared on AZ31B magnesium alloy using the hydrothermal and immersion methods. The composite coatings can spontaneously undergo the wettability transition from superhydrophobic to hydrophilic after complete exposure to simulated body fluid (SBF, a solution for modeling the composition and concentration of human plasma ions) for 9 h. The wettability transition mainly originated from the deposition and growth of the newly formed CaMS among the HA nanopillars during immersing, which deconstructed the micro-nano structure of the superhydrophobic coatings and directly exposed the HA to the water molecules, thereby significantly altering the wettability of the coatings. Benefiting from the superhydrophobic surface, the composite coating exhibited excellent antibacterial properties. After the wettability transition, the HA/CaMS/MA composite coating exhibited superior osteoblast adhesion performance. This work provides a strategy to enable a superhydrophobic coating to undergo spontaneous wettability transition in SBF, thereby endowing the coated magnesium alloy with a favorable osteogenic property. Full article

This research focuses on the structural and bonding characteristics of the Al(111)/CrB2(0001) interface, aiming to clarify the adhesion mechanisms of CrB₂ coatings on aluminum composites. Utilizing first-principles calculations grounded in density functional theory (DFT), we systematically examined the interfacial properties of both clean and doped Al(111)/CrB₂(0001) systems. And key aspects such as binding energy, electron density distribution, and chemical bonding types were thoroughly evaluated. The results demonstrate that the Cr-terminated HCP stacking arrangement at the Al(111)/CrB₂(0001) interface achieves the maximum adhesion work and minimal interfacial energy. This is primarily due to the strong covalent interactions between Al-p and Cr-p orbitals, which contribute to exceptional interfacial strength and stability. Furthermore, the incorporation of Fe, Mg, and Mn at the interface not only markedly improves working adhesion but also effectively lowers the interfacial energy for the Cr-terminated HCP stacking configuration. This phenomenon significantly enhances the overall bonding performance of the Al/CrB₂ system. Conversely, the addition of Cu, Zn, and Si leads to an increase in interfacial energy, negatively impacting the bonding quality. Analysis of binding energies at the doped interface revealed a consistent trend among the elements: Fe > Mn > Mg > Si > Zn > Cu. These findings offer valuable guidance for the design and optimization of Al-based surface coatings with improved performance. Full article

The effect of various atmospheric parameters on the corrosion mechanism of press-hardened steel (PHS) coated with Al-Si (AS) was studied. Quantitative models of the composition of soluble and stable corrosion products were developed. A high chloride concentration led to a localized corrosion due to the presence of cracks in the coating. Increased corrosion resistance of silicon-rich Al₈Fe₂Si and AlFe at the expense of the Al₅Fe₂ phase with low silicon content was shown. Under low-chloride-deposition conditions, the coating exhibited good corrosion resistance and provided sufficient protection to the underlying steel. The formation of more local anodes and cathodes under conditions of lower relative humidity led to a reduction in the depth of corrosion pits in the steel substrate. Constant high relative humidity and sulphate deposits on the surface were critical for the acceleration of steel corrosion in coating cracks. Full article

The aim of this work is to compare the traditional uniaxial pressing with an innovative shaping technique, Digital Light Processing (DLP), in the preparation of porous mullite (3Al₂O₃·2SiO₂) supports to be functionalized with an active coating for CO₂ capture. Indeed, the fabrication of complex geometries with 3D-printing technologies allows the production of application-targeted solid sorbents with increased potentialities. Therefore, this research focused on the effect of the purity of the selected raw materials and of the microstructural porosity of 3D-printed ceramic substrates on the Metal Organic Frameworks (MOFs) coating efficiency. Two commercial mullite powders (Mc and Mf) differing in particle size distribution (D₅₀ of 9.19 µm and 4.38 µm, respectively) and iron oxide content (0.67% and 0.38%) were characterized and used to produce the substrates, after ball-milling and calcination. Mc and Mf slurries were prepared with 69 wt% of solid loading and 5 wt% of dispersant: both show rheological behavior suitable for DLP and good printability. DLP 3D-printed and pressed pellets were sintered at three different temperatures: 1350 °C, 1400 °C and 1450 °C. Mf 3D-printed samples show slightly lower geometrical and Archimedes densities, compared to Mc pellets, probably due to the presence of lower Fe₂O₃ amounts and its effect as sintering aid. Mullite substrates were then successfully functionalized with HKUST-1 crystals by a two-step solvothermal synthesis process. Ceramic substrate porosity, depending on the shaping technique and opportunely tuned controlling the sintering temperature, was correlated with the functionalization efficiency in terms of MOFs deposition. Three-dimensional-printed substrates exhibit a higher and more homogeneous HKUST-1 uptake compared to the pressed pellets as DLP introduces desirable porosities able to enhance the functionalization. Therefore, this work provides preliminary guidelines to improve MOFs coating on mullite surfaces for CO₂ capture applications, by opportunely tuning the substrate porosity. Full article

The adsorption efficiency of Cr(VI) and anionic textile dyes onto MgAl-layered double hydroxides (LDHs) and MgAl-LDH coated on bio-silica (b-SiO₂) nanoparticles (MgAl-LDH@SiO₂) derived from waste rice husks was studied in this work. The material was characterized using field-emission scanning electron microscopy (FE-SEM/EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopic (XPS) techniques. The adsorption capacities of MgAl-LDH@SiO₂ were increased by 12.2%, 11.7%, 10.6%, and 10.0% in the processes of Cr(VI), Acid Blue 225 (AB-225), Acid Violet 109 (AV-109), and Acid Green 40 (AG-40) dye removal versus MgAl-LDH. The obtained results indicated the contribution of b-SiO₂ to the development of active surface functionalities of MgAl-LDH. A kinetic study indicated lower intraparticle diffusional transport resistance. Physisorption is the dominant mechanism for dye removal, while surface complexation dominates in the processes of Cr(VI) removal. The disposal of effluent water after five adsorption/desorption cycles was attained using enzymatic decolorization, photocatalytic degradation of the dyes, and chromate reduction, satisfying the prescribed national legislation. Under optimal conditions and using immobilized horseradish peroxidase (HRP), efficient decolorization of effluent solutions containing AB-225 and AV-109 dyes was achieved. Exhausted MgAl-LDH@SiO₂ was processed by dissolution/precipitation of Mg and Al hydroxides, while residual silica was used as a reinforcing filler in polyester composites. The fire-proofing properties of composites with Mg and Al hydroxides were also improved, which provides a closed loop with zero waste generation. The development of wastewater treatment technologies and the production of potentially marketable composites led to the successful achievement of both low environmental impacts and circular economy implementation. Full article

In this research, two intermediate layers were deposited on 316L stainless steel to improve the adhesion of diamond-like carbon (DLC) films, one composed of Ti_xAl and produced using the RF sputtering technique with three thicknesses, 100 nm, 200 nm, and 300 nm; the other, interlayer composed of amorphous hydrogenated silicon (a-Si:H). The DLC films were deposited using the pulsed-DC PECVD method with an active screen to achieve the AISI 316L/Ti_xAl//DLC and AISI 316L/TiₓAl/a-Si/DLC configurations. The binding energy between the substrate/Ti_xAl and Ti_xAl/a-Si:H was investigated via X-ray photoelectron spectroscopy with high-resolution spectra. The chemical composition and microstructure of the titanium–aluminum interlayers were investigated using energy-dispersive X-ray spectroscopy and X-ray diffraction, and the microstructure of the DLC coatings was studied using Raman spectroscopy. The coatings’ adherence was measured using scratch and indentation tests, and the hardness of the DLC coatings was determined with the nanoindentation test. The X-ray diffractograms did not allow the determination of any crystalline structure in the Ti_xAl interlayers. The XPS results showed that between the AISI 316L substrate and the Ti_xAl intermediate layer, Ti-O-Fe and FeAl₂O₄ were formed. On the other hand, at the Ti_xAl/a-Si:H interface, TiSi₂ and Al₂SiO₅ compounds were identified. The DLC coatings grew as hydrogenated amorphous carbon with a hydrogen content of around 30 at.% and a hardness of 24 GPa. The deposition methods used and the Ti_xAl/a-Si:H interlayers allowed the obtainment of adherent DLC coatings on AISI 316L stainless steel substrates. High critical load values of about 30 N were obtained. The novelty of this work is underscored by the absence of previous studies that thoroughly examine the bonds present in interlayers used as gradients to enhance the adhesion of DLC. Full article

A CaO-MgO-Al₂O₃-SiO₂ glass–ceramic coating was prepared by the slurry method and subsequent sintering to improve the corrosion resistance of 316L steel in liquid lead–bismuth eutectic alloy at high temperatures. The glass–ceramic coating, sintered at 884 °C, was dense and demonstrated strong adhesion to the substrate. It was composed of the crystalline phases diopside (CaMgSi₂O₆) and anorthite (CaAl₂Si₂O₈) and had an average Vickers hardness of 595 HV, which was over three times that of 316L steel. After corrosion in an oxygen-saturated, static lead–bismuth eutectic alloy at 500 °C for 1000 h, the uncoated 316L experienced significant mass gain (0.04 g) due to severe oxidative corrosion, resulting in the formation of Fe₃O₄ and Pb₂O on its surface. In contrast, the glass–ceramic-coated specimens showed a very small mass gain (0.0012 g) after corrosion. The coating maintained good thermal stability; its crystalline phase composition remained largely unchanged after the corrosion test. The glass–ceramic coating still exhibited dense microstructure and tightly adhered to the substrate after corrosion. There was no evident penetration of lead–bismuth into the coating, and no dissolution of the coating’s elements into the lead–bismuth alloy was detected. These observations confirm that the glass–ceramic coating possessed superior corrosion resistance in liquid lead–bismuth eutectic environments. Full article

Mitigating the adverse effects of corrosion failure and low-temperature icing on aluminum (Al) alloy materials poses significant research challenges. The facile fabrication of bioinspired superhydrophobic materials offers a promising solution to the issues of corrosion and icing. In this study, we utilized laboratory-collected candle soot (CS), hydrophobic fumed SiO₂, and epoxy resin (EP) to create a HF-SiO₂@CS@EP superhydrophobic coating on Al alloy surfaces using a spray-coating technique. Various characterization techniques, including contact angle meter, high-speed camera, FE-SEM, EDS, FTIR, and XPS, were employed to investigate surface wettability, morphologies, and chemical compositions. Moreover, a 3.5 wt.% NaCl solution was used as a corrosive medium to evaluate the corrosion resistance of the uncoated and coated samples. The results show that the capacitive arc radius, charge transfer resistance, and low-frequency modulus of the coated Al alloy significantly increased, while the corrosion potential (E_corr) shifted positively and the corrosion current (I_corr) decreased by two orders of magnitude, indicating improved corrosion resistance. Additionally, an investigation of ice formation on the coated Al alloy at −10 °C revealed that the freezing time was 4.75 times longer and the ice adhesion strength was one-fifth of the uncoated Al alloy substrate, demonstrating superior delayed icing and reduced ice adhesion strength performance. Full article

Al–Zn–Mg–Si alloy coatings have been developed to inhibit the corrosion of cold-rolled steel sheets by offering galvanic and barrier protection to the substrate steel. It is known that Fe deposited from the steel strip modifies the microstructure of the alloy. We cast samples of Al–Zn–Mg–Si coating alloys containing 0.4 wt% Fe and directionally solidified them using a Bridgman furnace to quantify the effect of this Fe addition between $600 °\mathrm{C}$ and $240 °\mathrm{C}$. By applying a temperature gradient, growth is encouraged, and by then quenching the sample in coolant, the microstructure may be frozen. These samples were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine the morphological effects of the Fe distribution across the experimental temperature range. However, due to the sub 1 wt% concentration of Fe, synchrotron X-ray fluorescence microscopy (XFM) was applied to quantitatively confirm the Fe distribution. Directionally solidified samples were scanned at 7.05 keV and 18.5 keV using X-ray fluorescence at the Australian Synchrotron using the Maia array detector. It was found that a mass nucleation event of the Fe-based τ₆ phase occurred at $495 °\mathrm{C}$ following the nucleation of the primary α-Al phase as a result of a peritectic reaction with remaining liquid. Full article

In conventional hot stamping, an Al-Si-coated blank is first heated above the austenitization temperature and then soaked for a period of time within a furnace, prior to the stamping operation. In this work, the impacts of furnace heating rate, soaking temperature, and soaking time on the Al-Si coating evolution were investigated for two commercial coating weights, 80 and 150 g/${\mathrm{m}}^2$. These heat treatment parameters during heating and soaking affect the coating microstructure and the thickness of the interdiffusion layer, which affect the properties of the as-formed coatings. The transformation and growth of binary Fe-Al and ternary Fe-Al-Si intermetallic layers were characterized and quantified for soak times up to 240 s. The results show that the effect of the heating rate on the Al-Si intermetallic distribution and ternary phase morphology was more severe than the soaking time and soaking temperature. The ${\mathrm{F}\mathrm{e}}_2{\mathrm{A}\mathrm{l}}_5$ (η) phase was the dominant layer at the beginning of the soaking stage with a ${\mathrm{F}\mathrm{e}}_3{\mathrm{A}\mathrm{l}}_2{\mathrm{S}\mathrm{i}}_3$ (${\mathsf{\tau }}_1$) layer formed within it, and then the ${\mathrm{F}\mathrm{e}}_3{\mathrm{A}\mathrm{l}}_2{\mathrm{S}\mathrm{i}}_3$ layer transformed into $\mathrm{F}\mathrm{e}\mathrm{A}\mathrm{l}$ (${\mathsf{\beta }}_2)$ as the soaking time increased due to the interdiffusion of Fe and Al. The transformation of ${\mathrm{F}\mathrm{e}}_3{\mathrm{A}\mathrm{l}}_2{\mathrm{S}\mathrm{i}}_3$ to $\mathrm{F}\mathrm{e}\mathrm{A}\mathrm{l}$ occurred at a higher rate for elevated soaking temperatures due to the greater diffusivity of Al and Fe. The interdiffusion layer (IDL) consisted of $\mathrm{F}\mathrm{e}\mathrm{A}\mathrm{l}{,\mathrm{F}\mathrm{e}}_3\mathrm{A}\mathrm{l}$(${\mathsf{\beta }}_1)$ and $\mathsf{\alpha }-\mathrm{F}\mathrm{e}$. Higher soaking temperatures of 1000 °C resulted in a thicker IDL for the same soak time when compared with 900 °C and 950 °C, but when the heating rate was lower, the IDL was thicker than that at the higher heating rate since a longer heating time was required to reach the soaking temperature of 900 °C, which prolonged the diffusion time during the heating stage. The findings were similar for AS80. Full article

Alloy coatings protect steel from corrosion in various applications. We investigated the effects of Si addition on the microstructure, electrochemical behavior, and corrosion resistance of steel sheets coated with a hot-dip Zn–Mg–Al–Si alloy using a batch-type galvanization process. Microstructural analysis revealed that the Zn–Al–Mg alloy coating layer contained a significant amount of Fe that diffused from the substrate, leading to delamination due to the formation of brittle Fe–Zn intermetallic compounds. However, the introduction of Si resulted in the formation of a stable Fe₂Al₃Si inhibition layer at the substrate–coating interface; this layer prevented interdiffusion of Fe as well as enhanced the coating adhesion. Additionally, the formation of acicular Mg₂Si phases on the coating surface improved the surface roughness. As the Si content increased, the corrosion resistance of the coating improved. Specifically, the Zn–Al–Mg coating layer with 0.5 wt.% Si exhibited excellent anti-corrosion performance, without red rust formation on its surface even after 2600 h, during a salt spray test. Full article

This investigation employed different laser powers to conduct the laser welding–brazing process of 5052 aluminum alloy to both Al-Si coated and uncoated 22MnB5 steel. The flux-cored Zn-Al22 filler metal was employed during the procedure. The influence of Al-Si coatings on the microstructure and corrosion resistance of Al/Steel welded joints was investigated using microstructural characterization and electrochemical tests. It was noted that the interfacial microstructure of the laser Al/steel joints was significantly altered by the Al-Si coating. Moreover, the Al-Si coating suppressed the formation and growth of the interfacial reaction layer. Electrochemical corrosion tests showed that the impact of Al-Si coating on the corrosion resistance of laser joints depended on the laser powers and thickness of the interfacial intermetallic compound (IMC) layer. The research suggests that galvanic corrosion occurs due to the differences in corrosion potential between fusion zone (FZ), steel, and Fe-Al-Zn IMCs, which accelerate the corrosion of the joint. The IMC layer acts as a cathode to accelerate the corrosion of the FZ and as an anode to protect the steel from corrosion. Full article