Search Results (68)

This study presents a sustainable strategy for improving the thermal properties of pine wood through the application of calcium carbonate nanopowder (CCNP) chelated with polycarboxylic acids (citric acid (CA) and tartaric acid (TA)) as coatings. The chelation reaction was confirmed by the detection of carbon dioxide (CO₂) gas. CCNP was characterized using microscopy and particle size analysis. The formation of crystalline calcium citrate and calcium tartrate was verified using FTIR and Raman spectroscopies, and XRD analysis. Wood treatment was conducted using different volumetric ratios of CA and TA. The CA-TA-treated (coated) wood blocks achieved the highest mass gain after treatment of around 89%, while the pure TA treatment exhibited enhanced leaching resistance, maintaining around 69% mass gain after leaching test. TGA conducted under oxidative (air) conditions showed that the coatings promoted char formation and produced inorganic residues from 6.4% to 7.8%, with the control resulting in negligible residual mass. Flame retardancy tests showed that the chelated coatings effectively delayed combustion and inhibited heat transfer, with the TA treatment showing improved flame retardancy performance by limiting the surface temperature to ~200 °C after 60 s of exposure, as compared to >550 °C for the control. Full article

This work examines the micromechanical response of Al₂O₃/IF-WS₂ (IF-inorganic fullerene-like) composite coatings formed on the EN AW 5251 aluminium alloy by anodic oxidation. The resulting amorphous oxide layer contains a nanopores system that can be filled with IF-WS₂ particles, provided the modifier is properly dispersed. Because commercial IF-WS₂ powders exhibit strong agglomeration, a high-intensity ultrasonic treatment was applied to enhance particle separation before incorporation. The influence of newly established incorporation parameters was assessed using a two-level experimental design. As part of the research, analyses of the microstructure, micromechanical, and sclerometric properties were performed. Cross-sectional SEM observations confirmed the presence of IF-WS₂ within the oxide structure and revealed differences in particle distribution, depending on the incorporation technique used. The results indicate that although microhardness and Young’s modulus are largely insensitive to the nanopowder incorporation method, the interaction between the anodising current density and the incorporation technique significantly influences the strain energy components and tribological response of the coatings. These findings suggest that appropriately selected processing parameters can be used to tailor the mechanical and tribological properties of Al₂O₃/IF-WS₂ coatings to specific loading conditions and functional requirements, rather than striving for a single, universal, optimal processing configuration. Full article

Vanadium dioxide (VO₂) has become one of the most promising smart temperature-controlled thin-film materials due to its reversible phase transition between a metallic and an insulating state at approximately 68 °C, accompanied by negligible volume change and excellent optical modulation properties. However, the practical application of VO₂ is still limited by its relatively high phase transition temperature and susceptibility to oxidation. To address these two major shortcomings, this study employed a one-step hydrothermal method to prepare a VO₂ nanopowder, followed by a chemical precipitation method to form a VO₂@AlF₃ core–shell structure. The coated nanoparticles were then dispersed in a PVP ethanol solution, coated onto a glass substrate, and evaluated for performance. The experimental results indicate that when the molar ratio of VO₂ to AlF₃ reached 1:1, the phase transition temperature of VO₂@AlF₃ was effectively reduced to 50.3 °C, significantly lower than the original temperature of 68 °C. Additionally, the material exhibited favorable optical properties, with a solar modulation ability (ΔT_sol) of 17.2% and a luminous transmittance (T_lum) of 36.3%. After calcination in air at 300 °C for 3–6 h, the VO₂ core remained oxidation-resistant and maintained excellent phase-change thermal insulation properties. Full article

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

The anodic oxide layer’s porosity is considered a functional feature, acting as a reservoir of lubricants. This feature enables the design of self-lubricating systems that effectively reduce friction and wear. To improve the tribological performance of Al₂O₃ anodic coatings on EN AW 5251 aluminium alloys, this paper presents a modification of the coating with tungsten disulfide (IF-WS₂) nanopowder and its effect on coating resistance. The wear properties of Al₂O₃/IF-WS₂ coatings in contact with a cast iron pin were investigated. The results include the analysis of the friction coefficient in the reciprocating motion without oil lubrication at two loads, the analysis of the wear intensity of the cast iron pin, the characterisation of wear scars, and the analysis of SGP parameters. Two-level factorial analysis showed that load and nanomodification significantly affected the load-bearing parameter Rk. Incorporation of the modifier, especially under higher loads, reduced the Rk value, thus improving the tribological durability of the contact pair. Both load and nanomodification had a notable impact on the coefficient of friction. The use of IF-WS₂-modified coatings reduced the coefficient, and higher loads further enhanced this effect, by approximately 9% at a load of 0.3 MPa and 15% at a load of 0.6 MPa, indicating improved lubricating conditions under greater contact stress. Full article

In this paper, we present the development of a new semi-distributed interferometer (SDI) biosensor with a Zn, Cu, and Co metal oxide nanopowder coating for the detection of a kidney disease biomarker as a model system. The combination of nanopowder coating with the SDI platform opens up unique opportunities for improving measurement reproducibility while maintaining high sensitivity. The fabrication of sensors is simple, which involves one splice and subsequent cutting at the end of an optical fiber. To ensure specific detection of the biomarker, a monoclonal antibody was immobilized on the surface of the probe. The biosensor has demonstrated an impressive ability to detect biomarkers in a wide range of concentrations, from 1 aM to 100 nM. The theoretical limit of detection was 126 fM, and the attomolar detection level was experimentally achieved. The sensors have achieved a maximum sensitivity of 190 dB/RIU and operate with improved stability and reduced dispersion. Quantitative analysis revealed that the sensor’s response gradually increases with increasing concentration. The signal varies from 0.05 dB at 1 aM to 0.81 dB at 100 nM, and the linear correlation coefficient was R² = 0.96. The sensor showed excellent specificity and reproducibility, maintaining detection accuracy at about 10⁻⁴ RIU. This opens up new horizons for reliable and highly sensitive biomarker detection, which can be useful for early disease diagnosis and monitoring using a cost-effective and reproducible sensor system. Full article

The synthesis of oxide nanopowders through ultrasonic spray pyrolysis (USP) represents a sustainable method for producing high-purity, spherical particles tailored for advanced material applications. Recent developments in USP synthesis leverage the continuous transport of aerosols from an ultrasonic generator to a high-temperature furnace, with nanopowders collected efficiently using an electrostatic precipitator. This study explored the use of USP for titanium oxysulfate and aluminum nitrate solutions derived from the aluminum industry, focusing on resource recovery and waste reduction. Titanium oxysulfate was synthesized by leaching slag, generated during the reduction of red mud, with sulfuric acid under oxidizing, high-pressure conditions. After purification, the titanium oxysulfate solution was processed using USP in a hydrogen reduction atmosphere to yield spherical titanium dioxide (TiO₂) nanopowders. The hydrogen atmosphere enabled precise control over the nanoparticles’ morphology and crystallinity, enhancing their suitability for use in applications such as photocatalysis, pigments, and advanced coatings. In parallel, both synthetic and laboratory solutions of aluminum nitrate [Al(NO₃)₃] were prepared. The laboratory solution was prepared by leaching aluminum hydroxide oxide (AlOOH) with hydrochloric acid to form aluminum chloride (AlCl₃), followed by a conversion to aluminum nitrate through the addition of nitric acid. The resulting aluminum nitrate solution was subjected to USP, producing highly uniform, spherical alumina (Al₂O₃) nanopowders with a narrow size distribution. The resulting nanopowders, characterized by their controlled properties and potential applicability, represent an advancement in oxide powder synthesis and resource-efficient manufacturing techniques. Full article

In the presented work, erbium fiber lasers operating in the pulsed mode with a nonlinear element containing a vanadium oxide saturable absorber are demonstrated. The structure of the saturable absorber is based on a segment of thinned silica fiber coated with a thin-film vanadium oxide by the method of metalorganic chemical vapor deposition. A fiber laser scheme is demonstrated that allows controlling the transmission of the internal cavity of the resonator during laser generation and deposition of a thin film. We have demonstrated a method for obtaining and annealing nanocoatings with laser generation control. We controlled the laser output parameters directly during the synthesis of the saturable absorber material. Vanadium oxides obtained in the work demonstrated the Mott–Paierls phase transition practically at room temperature. In this work, the optical characteristics of the output radiation of a fiber laser with a saturable absorber were measured. At temperatures above 70 °C, the coatings demonstrate a passive Q-switch with a repetition rate of 38 kHz and a pulse duration of 3.8 μs. At temperatures below the phase transition, a short-term mode-locking mode occurs. The transmission jump at a wavelength of about 1350 nm during structural rearrangement was 24%. For comparison, VO₂ nanopowder in a polydimethylsiloxane elastomer matrix was used as a saturable absorber material. The nanopowder modulator made it possible to obtain pulses with a frequency of 27 kHz and a duration of about 7.2 μs. Full article

Fiber coatings protect the glass surface of fiber from extrinsic environmental factors. The coating of shape memory alloy over fiber is useful in sensor fabrication where the state of deformation is affected by the phase transformation of the coated material. In addition, coated plastic fibers can be used in elevated temperature environments. To this end, the present research aims to investigate the effect of the Ni-Ti-Sn composite coating over the fiber. Homogeneous particle distribution, agglomeration, porosity and the ability to obtain uniform coating thickness have been general concerns in fiber coatings. Hence, the present study comprehensively investigated the mechanical and thermal behavior as well as morphological properties of Ni-Ti-Sn nanopowders deposited on polymer fiber optics. Five sets of polyamide-coated samples with different Ni-Ti-Sn proportions were fabricated and characterized. Morphological studies confirmed that an even coating thickness enhanced the mechanical integrity and optical performance. The optimum composition demonstrated superior tensile strength of 29.5 MPa and a 25% increase in elongation compared to the uncoated sample. The Ni-Ti-Sn alloy composition investigated in the present study is promising for industrial applications where thermal stability and mechanical performance are warranted. Full article

The microstructures and structures of modified Al₂O₃/IF-WS₂ coatings prepared on aluminum substrates are studied. Amorphous Al₂O₃ oxide coatings are obtained on EN AW 5251 aluminum alloy using the electrooxidation process. The quality of the IF-WS₂ nanopowder is of great importance in the process of its introduction into the nanopores of the Al₂O₃ oxide coating. Commercial nanopowder tends to agglomerate, and without appropriate pretreatment, it is difficult to introduce it into the nanopores of the coating. To improve the degree of fragmentation of the IF-WS₂ nanopowder, an experiment was carried out to distribute the nanopowder in the presence of strong ultrasounds, and new conditions for introducing the powder into the nanopores were used. A two-level design of experiment (DOE) was used. The SEM examination made it possible to conclude that Method A contributed to a more even distribution of nanoparticles in the microstructure of Al₂O₃ coatings. GIXD analyses showed the presence of WO₃ derived from the IF-WS₂ modifier next to crystal structures derived from aluminum and WS₂. Modification of coatings using Method A resulted in surfaces with lower contact angles measured with polar liquids and higher surface free energy compared to Method B. Full article

The aim of this study was to prepare and characterize thin hybrid films on polyurethane-coated knitted fabrics and to achieve satisfactory color fastness to artificial light. Sol–gel-derived hybrid thin films were deposited via the dip-coating of 3-glycidoxypropiltrimethoxysilane. Titanium dioxide (TiO₂) and zinc oxide (ZnO) nanopowders were added to compensate for the insufficient aging resistance, which manifests itself in low color fastness and is one of the most frequent complaints from manufacturers of coated marine fabrics (yachts, boats, etc.). The optimum processing conditions were determined by varying the concentration of precursors and auxiliaries, the mass concentration of TiO₂ and ZnO nanopowders, the drawing speed, and the methods and process of fabric treatment. The hybrid films were also characterized using scanning electron microscopy and Fourier transform infrared spectroscopy with attenuated total internal reflection, while Spectraflash SF 300 investigated color fastness. After 300 h of exposure in a xenon chamber, the thin hybrid films showed good color fastness and good resistance to washing cycles. The sol–gel treatment proved to be a successful answer to the manufacturers’ need for the post-treatment of polyurethane-coated knitted fabrics against UV radiation for use in the marine sector (yachts, speedboats, etc.). Full article

Three-dimensional printing (3DP) has emerged as a promising method for creating intricate scaffold designs. This study assessed three 3DP scaffold designs fabricated using biodegradable poly(lactic) acid (PLA) through fused deposition modelling (FDM): mesh, two channels (2C), and four channels (4C). To address the limitations of PLA, such as hydrophobic properties and poor cell attachment, a post-fabrication modification technique employing Polyelectrolyte Multilayers (PEMs) coating was implemented. The scaffolds underwent aminolysis followed by coating with SiCHA nanopowders dispersed in hyaluronic acid and collagen type I, and finally crosslinked the outermost coated layers with EDC/NHS solution to complete the hybrid scaffold production. The study employed rotating wall vessels (RWVs) to investigate how simulating microgravity affects cell proliferation and differentiation. Human mesenchymal stem cells (hMSCs) cultured on these scaffolds using proliferation medium (PM) and osteogenic media (OM), subjected to static (TCP) and dynamic (RWVs) conditions for 21 days, revealed superior performance of 4C hybrid scaffolds, particularly in OM. Compared to commercial hydroxyapatite scaffolds, these hybrid scaffolds demonstrated enhanced cell activity and survival. The pre-vascularisation concept on 4C hybrid scaffolds showed the proliferation of both HUVECs and hMSCs throughout the scaffolds, with a positive expression of osteogenic and angiogenic markers at the early stages. Full article

Metallic nanoscale particles attract a growing interest in several fields, thanks to their unique bonding characteristics; applications are appearing in the literature in the fields of, for example, sensor coatings and biochemical compound detection. However, the controlled fabrication of such nanopowders is often cumbersome, especially because their characterization is normally slow, involving procedures such as electron microscopy. On the other hand, microwave sensors based on near-field effects on materials are being developed with high sensitivity and show promising characteristics. In this paper, the authors show how a microwave sensor based on a Square Spiral Resonator can be used to characterize paraffin dispersions of nanoparticles conveniently and cost-effectively. Full article

Electric vehicles (EVs) have emerged as a technology that can replace internal combustion vehicles and reduce greenhouse gas emissions. Therefore, it is necessary to develop novel low-viscosity lubricants that can serve as potential transmission fluids for electric vehicles. Thus, this work analyzes the influence of both SiO₂ and SiO₂-SA (coated with stearic acid) nanomaterials on the tribological behavior of a paraffinic base oil with an ISO VG viscosity grade of 32 and a 133 viscosity index. A traditional two-step process through ultrasonic agitation was utilized to formulate eight nanolubricants of paraffinic oil + SiO₂ and paraffinic base oil + SiO₂-SA with nanopowder mass concentrations ranging from 0.15 wt% to 0.60 wt%. Visual control was utilized to investigate the stability of the nanolubricants. An experimental study of different properties (viscosity, viscosity index, density, friction coefficient, and wear) was performed. Friction analyses were carried out in pure sliding contacts at 393.15 K, and a 3D optical profilometer was used to quantify the wear. The friction results showed that, for the SiO₂-SA nanolubricants, the friction coefficients were much lower than those obtained with the neat paraffinic base oil. The optimal nanoparticle mass concentration was 0.60 wt% SiO₂-SA, with which the friction coefficient decreased by around 43%. Regarding wear, the greatest decreases in width, depth, and area were also found with the addition of 0.60 wt% SiO₂-SA; thus, reductions of 21, 22, and 54% were obtained, respectively, compared with the neat paraffinic base oil. Full article

Novel modified Zn-Al LDH/epoxy coatings are synthesized and applied to steel substrates, providing active corrosion protection and improved barrier properties. This protective coating is made by combining Epon 828 as a polymer matrix with modified layered-double-hydroxy (LDH) nanoparticles acting as corrosion inhibitor containers. To synthesize the coatings, nitrate was intercalated into Zn-Al-LDH layers through an aqueous co-precipitation method to obtain Zn-Al LDH-NO₃, and decavanadate replaced nitrate within the LDH layers through an anion exchange process to obtain Zn-Al LDH-(V₁₀O₂₈)⁶⁻. The intercalated LDH was functionalized by silanization with (3-aminopropyl)triethoxysilane (APTES) to increase the compatibility of the LDH inhibitor nanocontainers with epoxy resin and produce a protective coating. To protect the mild steel substrate, functionalized LDH nanopowders were dispersed into the epoxy resin, mixed with a polyamide hardener (Epikure 3571), and applied and cured to the metal surface. Surface morphology, structure, and chemical composition were determined for the modified LDH nanopowders using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Corrosion protection of the coating system was studied using long-term immersion testing and potentiodynamic polarization studies in a 3.5 wt.% NaCl solution. Full article