Search Results (41)

The superhydrophobic coatings for outdoor use need to be exposed to sunlight for a long time; therefore, their UV-aging resistances are crucial in practical applications. In this study, the primary product of titanium dioxide (P-TiO₂) was used as the raw material. Nano-silica (SiO₂) was coated onto the surface of P-TiO₂ by the acid precipitation method to prepare P-TiO₂-SiO₂ composite particles. Then, they were modified and sprayed simply to obtain a superhydrophobic P-TiO₂-SiO₂/HDTMS coating. The results indicated that amorphous nano-SiO₂ was coated on the P-TiO₂ surface, forming a micro–nano binary structure, which was the essential structure to form superhydrophobic coatings. Additionally, the UV-aging property of P-TiO₂ was significantly enhanced after being coated with SiO₂. After continuous UV irradiation for 30 days, the color difference (ΔE*) and yellowing index (Δb*) values of the coating prepared with P-TiO₂-SiO₂ increased from 0 to 0.75 and 0.23, respectively. In contrast, the ΔE* and Δb* of the coating prepared with P-TiO₂ increased from 0 to 1.68 and 0.74, respectively. It was clear that the yellowing degree of the P-TiO₂-SiO₂ coating was lower than that of P-TiO₂, and its UV-aging resistance was significantly improved. After modification with HDTMS, the P-TiO₂-SiO₂ coating formed a superhydrophobic P-TiO₂-SiO₂/HDTMS coating. The water contact angle (WCA) and water slide angle (WSA) on the surface of the coating were 154.9° and 1.3°, respectively. Furthermore, the coating demonstrated excellent UV-aging resistance. After continuous UV irradiation for 45 days, the WCA on the coating surface remained above 150°. Under the same conditions, the WCAs of the P-TiO₂/HDTMS coating decreased from more than 150° to 15.3°. This indicated that the retention of surface hydrophobicity of the P-TiO₂-SiO₂/HDTMS coating was longer than that of P-TiO₂/HDTMS, and the P-TiO₂-SiO₂/HDTMS coating’s UV-aging resistance was greater. The superhydrophobic P-TiO₂-SiO₂/HDTMS self-cleaning coating reported in this study exhibited outstanding UV-aging resistance, and it had the potential for long-term outdoor use. Full article

Silicon alloy-based materials are widely studied as high-capacity anode materials to replace commercial graphite in lithium-ion batteries (LIBs). Among these, silicon suboxide (SiO_x) offers superior cycling performance compared to pure Si-based materials. However, achieving a high initial Coulombic efficiency (ICE) remains a key challenge. To address this, previous studies have explored Si_xO composites (x ≈ 1, 2), where nano-Si is uniformly dispersed within a Si suboxide matrix to enhance ICE. While this approach improves reversible capacity and ICE compared to conventional SiO, it still falls short of the capacity achieved with pure Si. This study employs a high-energy mechanical milling approach with increased Si content to achieve higher reversible capacity and further enhance the ICE while also examining the effects of trace oxygen uniformly distributed within the Si suboxide matrix. Structural characterization via X-ray diffraction, Raman spectroscopy, and electron microscopy confirm that Si crystallites (<10 nm) are homogeneously embedded within the SiO_x matrix, reducing crystalline Si size and inducing partial amorphization. Electrochemical analysis demonstrates an ICE of 89% and a reversible capacity of 2558 mAh g⁻¹, indicating significant performance improvements. Furthermore, carbon incorporation enhances cycling stability, underscoring the material’s potential for commercial applications. Full article

This study successfully synthesizes SiO₂-encapsulated nano-phase change materials (NPCMs) via a sol–gel method, using paraffin as the thermal storage medium. The encapsulation process is validated through FTIR, XRD, and XPS analyses, confirming the formation of an amorphous SiO₂ shell without any chemical interaction between the core and shell. SEM imaging reveals a well-defined core–shell structure with uniform spherical geometry, with the smallest particle size (190 nm) observed in the sample with a 4:1 paraffin/SiO₂ ratio (PARSI-4). TGA results demonstrate enhanced thermal stability, with thicker SiO₂ shells effectively protecting against thermal degradation. The DSC analysis indicates that an increased core–shell ratio improves thermal performance, with PARSI-4 exhibiting the highest melting (160.86 J/g) and solidifying (153.93 J/g) enthalpies. The encapsulation ratio (ER) and encapsulation efficiency (EE) have been accomplished at 87.83% and 87.04%, respectively, in the PARSI-4 sample. Thermal cycling tests confirm the material’s long-term stability, with 98.16% enthalpy retention even after 100 cycles. Additionally, leakage resistance tests validate the structural integrity of the encapsulated paraffin, preventing spillage at elevated temperatures. These findings demonstrate the potential of SiO₂-encapsulated NPCMs for efficient thermal energy storage (TES), making them promising candidates for sustainable and energy-efficient applications. Full article

In lithium–polymer batteries, the electrolyte is an essential component that plays a crucial role in ion transport and has a substantial impact on the battery’s overall performance, stability, and efficiency. This article presents a detailed study on developing nanostructured composite polymer electrolytes (NCPEs), prepared using the solvent casting technique. The materials selected for this investigation include poly(vinyl chloride) (PVC) as the host polymer, lithium bromide (LiBr) as the salt, and silica (SiO₂) as the nanofiller. The addition of nano-SiO₂ dramatically enhanced the ionic conductivity of the electrolytes, with the highest value of 6.2 × 10⁻⁵ Scm⁻¹ observed for the sample containing 7.5 wt% nano-SiO₂. This improvement is attributed to an increased amorphicity resulting from the interactions between the polymer, salt, and filler components. A structural analysis of the prepared NCPEs using X-ray diffraction revealed the presence of both crystalline and amorphous phases, further validating the enhanced ionic transport. Additionally, the thermal stability of the NCPEs was found to be excellent, withstanding temperatures up to 334 °C, thereby reinforcing their potential application in lithium–polymer batteries. This work explores the electrochemical performance of a fabricated lithium-ion-conducting primary electrochemical cell (Zn + ZnSO₄·7H₂O|PVC: LiBr: SiO₂|PbO₂ + V₂O₅), which demonstrated an open circuit voltage of 2.15 V. The discharge characteristics of the fabricated cell were thoroughly studied, showcasing the promising potential of these NCPEs. With the support of superior morphological and electrical properties, as-prepared electrolytes offer an effective pathway for future advancements in lithium–polymer battery technology, making them a highly viable candidate for enhanced energy storage solutions. Full article

Lab-made biosilica (SiO₂) nanoparticles were obtained from waste biomass (rice husks) and used as eco-friendly fillers in the production of nickel matrix composite films via the co-electrodeposition technique. The produced biosilica nanoparticles were characterized using XRD, FTIR, and FE-SEM/EDS. Amorphous nano-sized biosilica particles with a high SiO₂ content were obtained. Various current regimes of electrodeposition, such as direct current (DC), pulsating current (PC), and reversing current (RC) regimes, were applied for the fabrication of Ni and Ni/SiO₂ films from a sulfamate electrolyte. Ni films electrodeposited with or without 1.0 wt.% biosilica nanoparticles in the electrolyte were characterized using FE-SEM/EDS (morphology/elemental analyses, roundness), AFM (roughness), Vickers microindentation (microhardness), and sheet resistance. Due to the incorporation of SiO₂ nanoparticles, the Ni/SiO₂ films were coarser than those obtained from the pure sulfamate electrolyte. The addition of SiO₂ to the sulfamate electrolyte also caused an increase in the roughness and electrical conductivity of the Ni films. The surface roughness values of the Ni/SiO₂ films were approximately 44.0%, 48.8%, and 68.3% larger than those obtained for the pure Ni films produced using the DC, PC, and RC regimes, respectively. The microhardness of the Ni and Ni/SiO₂ films was assessed using the Chen-Gao (C-G) composite hardness model, and it was shown that the obtained Ni/SiO₂ films had a higher hardness than the pure Ni films. Depending on the applied electrodeposition regime, the hardness of the Ni films increased from 29.1% for the Ni/SiO₂ films obtained using the PC regime to 95.5% for those obtained using the RC regime, reaching the maximal value of 6.880 GPa for the Ni/SiO₂ films produced using the RC regime. Full article

Composite powders were synthesized from the water solutions of sodium silicate and different calcium salts (nitrate, chloride, and acetate) at a Ca/Si molar ratio of 1.0. According to the XRD data, all the synthesized powders included hydrated calcium silicate Ca_1,5SiO_3,5·xH₂O (Ca/Si molar ratio = 1.5) and calcium carbonate CaCO₃ (Ca/Si molar ratio = ∞). The presence of H₂SiO₃ or SiO₂·xH₂O in the synthesized powders was assumed to be due to the difference between the Ca/Si molar ratio of 1.0 specified by the synthesis protocol and the molar ratio of the detected products. Reaction by-products (sodium nitrate NaNO₃, sodium chloride NaCl, and sodium acetate NaCH₃COO) were also found in the synthesized powders after filtration and drying. According to the XRD data phase composition of all powders after washing four times consisted of the quasi-amorphous phase and calcium carbonate in the form of calcite. Calcium carbonate in the form of aragonite was detected in powders synthesized from calcium chloride CaCl₂ and calcium nitrate Ca(NO₃)₂ before and after washing. Synthesized powders containing reaction by-products and washed powders were used for the preparation of ceramics at 900, 1000, and 1100 °C. The phase composition of the ceramic samples prepared from the washed powders and powder containing NaCl after firing at 900 and 1000 °C consisted of β-wollastonite β-CaSiO₃, and, after firing at 1100 °C, consisted of both β-wollastonite β-CaSiO₃ and pseudo-wollastonite α-CaSiO₃. The phase composition of the ceramic samples prepared from powders containing sodium nitrate NaNO₃ and sodium acetate NaCH₃COO after firing at 900, 1000, and 1100 °C consisted of calcium sodium silicates, i.e., Na₂Ca₂Si₃O₉ (combeite) and Na₂Ca₃S_i2O₈. Synthesized and washed composite powders can be used for the preparation of biocompatible materials, in the technology of construction materials, and as components of lunar soil simulants. Full article

The potential of glass ceramics as applicable materials in various fields including fillers for dental restorations is our guide to present a new procedure for improvements of the mechanical properties of dental composites. This work aims to use Zn₂SiO₄ and SiO₂–ZnO nano-materials as fillers to improve the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Zn₂SiO₄ and SiO₂–ZnO samples were prepared and characterized by using XRD, FE-SEM, EDX, and FT-IR techniques. The XRD pattern of the SiO₂–ZnO sample shows that ZnO crystallized in a hexagonal phase, while the SiO₂ phase was amorphous. Similarly, the Zn₂SiO₄ sample crystallized in a rhombohedral crystal system. The prepared samples were used as fillers for the improvement of the mechanical properties of Bis-GMA/TEGDMA mixed dental resins. Five samples of dental composites composed of Bis-GMA/TEGDMA mixed resins were filled with 2, 5, 8, 10, and 15 wt% of SiO₂–ZnO, and similarly, five samples were filled with Zn₂SiO₄ samples (2, 5, 8, 10, and 15 wt%). All of the 10 samples (A₁–A₁₀) were characterized by using different techniques including FT-IR, FE-SEM, EDX, and TGA analyses. According to the TGA analysis, all samples were thermally stable up to 200 °C, and the thermal stability increased with the filler percent. Next, the mechanical properties of the samples including the flexural strength (FS), flexural modulus (FM), diameter tensile strength (DTS), and compressive strength (CS) were investigated. The obtained results revealed that the samples filled with 8 wt% of SiO₂–ZnO and 10 wt% of Zn₂SiO₄ had higher FS values of 123.4 and 136.6 MPa, respectively. Moreover, 8 wt% of both fillers displayed higher values of the FM, DTS, and CS parameters. These values were 8.6 GPa, 34.2 MPa, and 183.8 MPa for SiO₂–ZnO and 11.3 GPa, 41.2 MPa, and 190.5 MPa for the Zn₂SiO₄ filler. Inexpensive silica-based materials enhance polymeric mechanics. Silica–metal oxide nanocomposites improve dental composite properties effectively. Full article

High-temperature anneals of nonstoichiometric Si oxide (SiO_x, x < 2) films induce phase separation in them, with the formation of composite structures containing amorphous or crystalline Si nanoinclusions embedded in the Si oxide matrix. In this paper, a thermodynamic theory of the phase separation process in SiO_x films is proposed. The theory is based on the thermodynamic models addressing various aspects of this process which we previously developed. A review of these models is provided, including: (i) the derivation of the expressions for the Gibbs free energy of Si oxides and Si/Si oxide systems, (ii) the identification of the phase separation driving forces and counteracting mechanisms, and (iii) the crystallization behavior of amorphous Si nanoinclusions in the Si oxide matrix. A general description of the phase separation process is presented. A number of characteristic features of the nano-Si/Si oxide composites formed by SiO_x decomposition, such as the local separation of Si nanoinclusions surrounded by the Si oxide matrix; the dependence of the amount of separated Si and the equilibrium matrix composition on the initial Si oxide stoichiometry and annealing temperature; and the correlation of the presence of amorphous and crystalline Si nanoinclusions with the presence of SiO_x (x < 2) and SiO₂ phase, respectively, in the Si oxide matrix, are explained. Full article

Research on polyurethane sponge (PUS), a widely used polymer material, and its flame-retardant performance is of great significance. In this study, PUS was modified to prepare a highly efficient flame-retardant composite using a soaking method. The PUS nearly vanished at 11 s after ignition, and the solid residue rate of the PUS was 5.65 wt% at 750 °C. The net structure, composed of nano SiO₂, was maintained in the modified PUS at 750 °C, and the solid residue rate was 69.23%. The maximum HRR of the PUS decreased from 617 W/g to 40 W/g and the THR of the sample reduced from 33 kJ/g to 9 kJ/g after modification. The results suggested that the modified PUS gained excellent flame-retardant performance. The flame-retardant layer in the modified PUS was amorphous. The surface of the modified PUS was rich in Si, O, and C elements and lacked a N element, suggesting that inorganic flame retardants were abundant on the surface layer of the modified PUS. The Si-O-C vibration and Si-O-Si stretching in the modified PUS indicates that the organic–inorganic hybrid structure formed on the PUS surface, which could be attributed to the polymerization and condensation of the silica precursor. Thus, the modified PUS provided an excellent flame-retardant layer. The results are of interest for producing efficient flame-retardant PUS using a simple method. Full article

Nanoparticles, by virtue of their amorphous nature and high specific surface area, exhibit ideal pozzolanic activity which leads to the formation of additional C-S-H gel by reacting with calcium hydroxide, resulting in a denser matrix. The proportions of ferric oxide (Fe₂O₃), silicon dioxide (SiO₂), and aluminum oxide (Al₂O₃) in the clay, which interact chemically with the calcium oxide (CaO) during the clinkering reactions, influence the final properties of the cement and, therefore, of the concrete. Through the phases of this article, a refined trigonometric shear deformation theory (RTSDT), taking into account transverse shear deformation effects, is presented for the thermoelastic bending analysis of concrete slabs reinforced with ferric oxide (Fe₂O₃) nanoparticles. Thermoelastic properties are generated using Eshelby’s model in order to determine the equivalent Young’s modulus and thermal expansion of the nano-reinforced concrete slab. For an extended use of this study, the concrete plate is subjected to various mechanical and thermal loads. The governing equations of equilibrium are obtained using the principle of virtual work and solved using Navier’s technique for simply supported plates. Numerical results are presented considering the effect of different variations such as volume percent of Fe₂O₃ nanoparticles, mechanical loads, thermal loads, and geometrical parameters on the thermoelastic bending of the plate. According to the results, the transverse displacement of concrete slabs subjected to mechanical loading and containing 30% nano-Fe₂O₃ was almost 45% lower than that of a slab without reinforcement, while the transverse displacement under thermal loadings increased by 10%. Full article

Synthesis from mixed-anionic aqueous solutions is a novel approach to obtain active powders for bioceramics production in the CaO-SiO₂-P₂O₅-Na₂O system. In this work, powders were prepared using precipitation from aqueous solutions of the following precursors: Ca(NO₃)₂ and Na₂HPO₄ (CaP); Ca(NO₃)₂ and Na₂SiO₃ (CaSi); and Ca(NO₃)₂, Na₂HPO₄ and Na₂SiO₃ (CaPSi). Phase composition of the CaP powder included brushite CaHPO₄‧2H₂O and the CaSi powder included calcium silicate hydrate. Phase composition of the CaPSi powder consisted of the amorphous phase (presumably containing hydrated quasi-amorphous calcium phosphate and calcium silicate phase). All synthesized powders contained NaNO₃ as a by-product. The total weight loss after heating up to 1000 °C for the CaP sample—28.3%, for the CaSi sample—38.8% and for the CaPSi sample was 29%. Phase composition of the ceramic samples after the heat treatment at 1000 °C based on the CaP powder contained β-NaCaPO₄ and β-Ca₂P₂O₇, the ceramic samples based on the CaSi powder contained α-CaSiO₃ and Na₂Ca₂Si₂O₇, while the ceramics obtained from the CaPSi powder contained sodium rhenanite β-NaCaPO₄, wollastonite α-CaSiO₃ and Na₃Ca₆(PO₄)₅. The densest ceramic sample was obtained in CaO-SiO₂-P₂O₅-Na₂O system at 900 °C from the CaP powder (ρ = 2.53 g/cm³), while the other samples had densities of 0.93 g/cm³ (CaSi) and 1.22 (CaPSi) at the same temperature. The ceramics prepared in this system contain biocompatible and bioresorbable phases, and can be recommended for use in medicine for bone-defect treatment. Full article

Wettability at the metal-ceramic interface is highly important for the development of modern composite materials. Poor wettability by metal melts restricts the use of alumina in protective metal matrix composite (MMC) coatings. In the present experimental study, the possibility to modify wetting properties of alumina by thermochemical surface boronizing was investigated. The results of SEM, EDS, XRD and XPS characterisation of surfaces revealed the formation of oxygen containing Al–B compounds identified as aluminium borates (Al₁₈B₄O₃₃/Al₄B₂O₉); no signs of non-oxide Al–B compounds were observed. The shape of the single splats deposited on the boronized alumina surface by the thermal spray and re-melted in the furnace revealed that significant wetting improvement by self-fluxing nickel alloy did not occur. However, the improvement of adhesion between the nickel/nickel alloy and Al₂O₃ surface was obtained due to formation of an intermediate layer consisting of B, O, Al and Si between the metal and ceramic surfaces at the presence of some silicon at the modified surfaces. The presented study demonstrates that the thermochemical boronizing of alumina in amorphous boron medium is a simple method to obtain a thin aluminium borate layer consisting of oriented nano-rod-like crystals, whose growing direction is predetermined by the orientation of the alumina grains’ faces at surface. Full article

In this work, the series of Dy³⁺-doped silicate xerogels were synthesized by sol-gel technique and further processed at 350 °C into SiO₂-LaF₃:Dy³⁺ nano-glass-ceramic materials. The X-ray diffraction (XRD) measurements, along with the thermal analysis, indicated that heat-treatment triggered the decomposition of La(TFA)₃ inside amorphous sol-gel hosts, resulting in the formation of hexagonal LaF₃ phase with average crystal size at about ~10 nm. Based on the photoluminescence results, it was proven that the intensities of blue (⁴F_9/2 → ⁶H_15/2), yellow (⁴F_9/2 → ⁶H_13/2), and red (⁴F_9/2 → ⁶H_11/2) emissions, as well as the calculated yellow-to-blue (Y/B) ratios, are dependent on the nature of fabricated materials, and from fixed La³⁺:Dy³⁺ molar ratios. For xerogels, the emission was gradually increased, and the τ(⁴F_9/2) lifetimes were elongated to 42.7 ± 0.3 μs (La³⁺:Dy³⁺ = 0.82:0.18), however, for the sample with the lowest La³⁺:Dy³⁺ molar ratio (0.70:0.30), the concentration quenching was observed. For SiO₂-LaF₃:Dy³⁺ nano-glass-ceramics, the concentration quenching effect was more visible than for xerogels and started from the sample with the highest La³⁺:Dy³⁺ molar ratio (0.988:0.012), thus the τ(⁴F_9/2) lifetimes became shorter from 1731.5 ± 5.7 up to 119.8 ± 0.4 μs. The optical results suggest, along with an interpretation of XRD data, that Dy³⁺ ions were partially entered inside LaF₃ phase, resulting in the shortening of Dy³⁺-Dy³⁺ inter-ionic distances. Full article

Seawater can be used as mixing water for concrete with no steel reinforcement in some areas with difficult access to fresh water. Diatoms such as Phaeodactylum tricornutum are among the most abundant micro-organisms living in seawater, and they could be unavoidable when collecting seawater. In fact, diatoms can provide bio-SiO₂ and bio-CaCO₃ sources, namely amorphous nano-SiO₂ and crystallised nano-CaCO₃, which could be beneficial to cement hydration. Thus, the effects of different Phaeodactylum tricornutum concentrations (0%, 2.5% and 5% by weight of suspension of seawater and diatoms) in seawater on cement hydration in ordinary Portland cement (OPC) mixes (100% OPC) and ground granulated blast-furnace slag (GGBS) mixes (70% OPC + 30% GGBS) were investigated through tests of compressive strength, XRD, DTG–DTA and SEM. The results show that diatoms accelerated cement hydration by providing the nucleus for C-S-H structure and contributed pozzolanic reactions by amorphous nano-SiO₂ and nano-CaCO₃. The accelerated cement hydration was also confirmed by the fact that more Ca(OH)₂ was formed in cement pastes with diatoms. However, it has also been found that diatoms decreased the compressive strength of cement pastes by leaving more weak bonds between the C-S-H structure, which was considered to be caused by the organic parts and the micron gap formed in diatoms. When comparing an OPC paste mix with 5% diatoms to a blank OPC paste, the reduction in compressive strength at 28 days can reach a maximum of 50.1%. The ability to provide bridging effects between C-S-H particles in GGBS paste was discovered to depend on the development of additional ettringite. This resulted in a 7.6% loss in compressive strength after 28 days in a GGBS paste with 5% diatoms. Full article

Silica nanoparticles were synthesized using the aqueous extract of orange peels by the green chemistry approach and simple method. The physicochemical properties such as optical and chemical banding of as-synthesized silica nanoparticles were analyzed with UV–visible spectroscopy and Fourier transform infrared spectroscopy. Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis and X-ray diffraction analysis were employed to confirm the shape, size and elemental purities of the silica nanoparticles. The thermal stability and mass loss of the silica nanoparticles was examined using thermogravimetric analysis and zeta potential analysis. The surface plasmon resonance band of the silica nanoparticle was obtained in the wavelength of 292 nm. Silica nanoparticles with a spherical and amorphous nature and an average size of 20 nm were produced and confirmed by X-ray diffraction and Scanning Electron Microscopy. The zeta potential of the silica nanoparticles was −25.00 mV. The strong and broad bands were located at 457, 642 and 796 cm⁻¹ in the Fourier transform infrared spectra of the silica nanoparticles, associated with the Si–O bond. All the results of the present investigation confirmed and proved that the green synthesized silica nanoparticles were highly stable, pure and spherical in nature. In addition, the antioxidant activity of the green synthesized orange peel extract mediated by the silica nanoparticles was investigated with a DPPH assay. The antioxidant assay revealed that the synthesized silica nanoparticles had good antioxidant activity. In the future, green synthesized silica nanoparticles may be used for the production of nano-medicine. Full article