Synthesis,structural, mechanical,and biological properties of HAp-ZrO2-hBN biocomposites for bone regeneration applications

Nowadays researchers are much interested in bioceramics for their use as biological implants. Researchers have succeeded to derive few bioceramic materials which show good biological response with living tissues. Few of the bioceramics are zirconia, hexagonal boron nitride and hydroxyapatite. Herein, the effects of zirconia nanoparticles and hexagonal boron nitride nanosheets in hydroxyapatite powder on the structural, mechanical, and biological properties were investigated. In this study, the formation of a potential composite with desired mechanical and biological properties is strongly anticipated. The present study is also proposed to provide further faces to improve osteogenic properties of the scaffolding material without altering the established mechanical and biological properties. Three different compositions in the system [(95-x)HAp-x(ZrO₂)-5hBN] (x = 10, 20, 30) were prepared using a simple solid-state reaction technique. In the samples, significant phase was identified for HAp [Calcium Phosphate Hydroxide: Ca₅(PO₄)₃(OH)]. SEM analysis of the composites revealed well-connected and uniform distribution of ZrO₂ and HAp nanoparticles on h-BN sheets. The composite samples 65H30Z5B9h (65HAp-30ZrO₂-5hBN sintered at 900 °C) and 65H30Z5B1T (65HAp-30ZrO₂-5hBN sintered at 1000 °C) showed improved mechanical and tribological behaviors. These samples exhibited excellent mechanical properties like compressive strength, Young's modulus, toughness and density. The obtained values were 2.154 MPa, 0.0182 MPa, 553.82 MJ/m³, 2.29 g/cm³ for 65H30Z5B9h and 3.798 MPa, 0.0832 MPa, 231.59 MJ/m³, 2.31 g/cm³ for 65H30Z5B1T respectively. Cytotoxicity of the composites was studied on Drosophila fly and Mice calvarial osteoblasts cells at five different concentrations. Toxic effect of the composite 65H30Z5B1T on the fly was confirmed by phenotypic observations, trypan blue staining, pupal count, and larval crawling speed. Composite 65H30Z5B1T was found to be toxic in this study, but the composite 65H30Z5B9h was not. Further, cell viability, alkaline phosphates, and mineralization tests confirmed non-toxic property and enhanced osteogenic activities for the composite sample 65H30Z5B9h.     

Study of microstructural,mechanical, and biomedical properties of zirconia/hydroxyapatite ceramic composites

In this study, hydroxyapatite was obtained by the sol-gel method, and zirconia/hydroxyapatite composites (YSZ/HAp) were produced with weight proportions of 95/5, 90/10, 85/15, and 80/20, respectively. The samples were characterized by X-ray diffraction (XRD), Archimedes' principle, Fourier-transform infrared spectroscopy (FT-IR), Vickers microhardness, scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). The calvarial critical-sized defect experimental model in rats was used to evaluate the biological interaction between YSZ/HAp scaffolds and bone tissue by Micro CT analysis. The XRD patterns of composites showed the major intensity of the zirconia phase and lower intensity of the hydroxyapatite phase, but the FT-IR analysis confirmed the presence of hydroxyapatite. Dense composite materials were verified by way of the Archimedes’ principle, where the YSZ/HAp 85/15 sample had lower apparent porosity (0.60%) and water absorption (0.10%). Vickers microhardness showed that composite material hardness decreased with the increase of hydroxyapatite, varying from 1367.43 to 711.37 HV. SEM images were possible to quantify the crack sizes in the indentations and to identify the elements presents by EDS, while FESEM was applied to analyze the morphology of the powders and microstructure of the composites. Among the composite studied, YSZ/HAp 85/15 and YSZ/HAp 80/20 samples were the compositions that demonstrated the best mechanical behavior with a fracture toughness of 9.2 and 9.3 MPa m^1/2, respectively. The YSZ/HAp scaffold showed an interaction with bone tissue. The percent bone volume (BV/TV, p < 0.001) and bone mineral density (BMD, p < 0.01) were significantly increased in Zirconia/hydroxyapatite scaffold.     

Enhanced mechanical properties and hydrophilic behavior of magnesium oxide added hydroxyapatite nanocomposite: A bone substitute material for load bearing applications

Hydroxyapatite is a multifunctional biomaterial that combines biocompatibility and bioactivity for various biomedical applications such as bone repairing and bioimaging. In the present study nano-hydroxyapatite (n-HAp) was synthesized using microwave irradiation technique. Subsequently, the MgO was introduced into the n-HAp matrix and various bioactive compositions of HAp-MgO nanocomposites were fabricated. The structural, mechanical, in vivo cell viability, and in vivo imaging properties of these nanocomposites were studied. The XRD results show that the composites sintered at 1200 °C, n-HAp partially decomposed into beta-tricalcium phosphate (β-TCP). The sintered density of the composites varying from 2.72 ± 0.066 to 3.03 ± 0.093 g cm⁻³ with the addition of 0.0–2.0 wt % of MgO. As increasing the amounts of MgO, a remarkable increase in the mechanical properties of the composite was achieved. The composite HAp-1.0MgO exhibited the highest mechanical properties with a compressive strength of 111.20 ± 5 MPa, fracture toughness 136.98 ± 5 MJ/m³ and revealed much amplification than pure n-HAp. Thus, the addition of MgO acting as an excellent mechanical reinforcing agent. The surface morphology of the composites revealed a significant change in the porous surface to denser. The low contact angle revealed the considerable hydrophilic nature of the composite surface. The biological study of these nano-composites with Drosophila third instar larvae indicated comparable or more favorable biocompatibility in terms of cell viability. Also internalized by Drosophila third instar larvae exhibited fluorescence under green and red filters using epifluorescence microscopy. Thus, the fabricated HAp-MgO nanocomposites with excellent biological properties are expected to be a multifunctional bioactive material for bone tissue regeneration and cell imaging applications.     

Microstructure,mechanical properties and thermal conductivity of (Ti0.5Nb0.5)C–SiC composites

A series of (Ti_0.5Nb_0.5)C-x wt.% SiC (x = 0, 5, 10, 20) composites were prepared by spark plasma sintering. Dense microstructures with well‐dispersed SiC particles were obtained for all composites. With the increment of SiC content, the Vickers hardness, Young's modulus and fracture toughness increase monotonically. An optimized flexural strength of 706 MPa was achieved in (Ti_0.5Nb_0.5)C-5 wt.%SiC composite. (Ti_0.5Nb_0.5)C-20 wt%SiC composite exhibits the highest fracture toughness of 6.8 MPa m^1/2. The crack deflections and the suppression of grain growth were the main strengthening and toughening mechanisms. Besides, (Ti_0.5Nb_0.5)C-20 wt%SiC composite exhibit the highest thermal conductivity of 45 W/m·K at 800 °C.     

Microstructure and mechanical properties of hot-pressed B4C/TiC/Mo ceramic composites

Boron carbide (B₄C)/TiC/Mo ceramic composites with different content of TiC were produced by hot pressing. The effect of TiC content on the microstructure and mechanical properties of the composites has been studied. Results showed that chemical reaction took place for this system during hot pressing sintering, and resulted in a B₄C/TiB₂/Mo composite with high density and improved mechanical properties compared to monolithic B₄C ceramic. Densification rates of the B₄C/TiC/Mo composites were found to be affected by additions of TiC. Increasing TiC content led to increase in the densification rates of the composites. The sintering temperature was lowered from 2150 °C for monolithic B₄C to 1950 °C for the B₄C/TiC/Mo composites. The fracture toughness, flexural strength, and hardness of the composites increased with increasing TiC content up to 10 wt.%. The maximum values of fracture toughness, flexural strength, and hardness are 4.3 MPa m^1/2, 695 MPa, and 25.0 GPa, respectively.     

Microstructural,dielectric, mechanical,and biological properties of hydroxyapatite (HAp)/BZT-BCT (0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3) bio-composites with improved mechano-electrical properties for bone repair

Hydroxyapatite (HAp; Ca₁₀(PO₄)₆(OH)₂) is a commonly used biomaterial for bone tissue repair applications but it has poor electrical conductivity. Whereas, BZT-BCT (0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃) is a lead-free piezoelectric material which can mimic the stress-generated electric potential of electrically-excitable tissues such as bone. This study investigated the mechanical, electrical and bio properties of xHAp/(1-x)BZT-BCT composites. xHAp/(1-x)BZT-BCT composites (with x = 5, 10, 15 and 20 wt%) were synthesized by high energy ball milling (HEBM) assisted solid-state reaction route. X-ray diffraction, scanning electron microscopy, density measurements and cell-material interaction studies of sintered HAp/BZT-BCT composites were carried out and discussed in detail. Dielectric properties of sintered composites were evaluated and compared with the existing theoretical models. Different mechanical properties like Vicker's hardness, fracture toughness, and diametral tensile strength were measured to assess the usability of synthesized composites for load-bearing orthopaedic applications. These various studies showed that incorporation of BZT-BCT in HAp improved its mechanical and electrical properties and thereby significantly increased the proliferation of human osteogenic MG-63 cells. Among all the composites, better mechanical, electrical and biological properties were obtained in 10HAp/90BZT-BCT composites.     

Synthesis,microstructure, and mechanical properties of TiC-SiC-Ti3SiC2 composites prepared by in situ reactive hot pressing

In this work, TiC-SiC-Ti₃SiC₂ composites were synthesized by in situ reactive hot pressing using β-SiC, graphite, and TiH₂ powders as initial materials. Microstructure and mechanical properties of as-prepared dense composites were systematically investigated. It was found that by increasing the initial SiC content the final SiC content in the composites increased in contrast to the decrease in TiC and Ti₃SiC₂ contents. In the dense composites, TiC and Ti₃SiC₂ grains exhibited transgranular fracture, whereas SiC particles showed intergranular fracture. The composite containing 77 vol.% TiC, 4 vol.% SiC, and 19 vol.% Ti₃SiC₂ had the highest flexural strength of 706.6 MPa. The composite consisting of 44 vol.% TiC, 49 vol.% SiC, and 7 vol.% Ti₃SiC₂ exhibited the highest Vickers hardness of 22.3 GPa and the highest fracture toughness of 6.0 MPa·m^1/2.     

CNT-induced TiC toughened Al2O3/Ti composites: Mechanical,electrical, and room-temperature crack-healing behaviors

This study addressed novel multiphase composite of Al₂O₃/Ti/TiC that exhibited enhanced fracture toughness and room-temperature crack-healing function. Al₂O₃/Ti/TiC composites were fabricated through hot-press sintering of CNT, TiH_2, and Al₂O₃ mixed powders, where the TiC was in-situ formed by reaction of CNT and Ti. The effects of CNT (TiC) content on mechanical and electrical properties were studied. Electrochemical anodization process at room temperature was attempted to these composites to heal cracks introduced in the surface of composites. Results indicated that added CNT was invisible while metal Ti and reaction product TiC coexisted in all samples. The reaction between CNT and Ti[O] representing dissolved active oxygen into Ti was considered as the main formation route of TiC. The toughening mechanism was demonstrated as crack deflection and bridging due to the presence of TiC. In spite of the increase in electrical resistivity because of the higher resistivity of TiC than Ti, the present Al₂O₃/Ti/TiC composites still remain high enough electrical conductivity (8.0 × 10⁻³ Ωcm ~1.8 × 10⁻² Ωcm for 0-2 vol% CNT addition) which could be regarded as conductors; it allowed to heal cracks in the composites by electrochemical anodization that formed titanium dioxide phase at room temperature. It was found that crack-healing ability in 1 vol% CNT added composite exhibited higher strength recovery ratio of 95.6% to the crack-free sample than that of Al₂O₃/Ti composite (the recovery ratio of 89.6%). After crack-healing process, mechanical strength of samples increased by 52.3% compared to cracked composites. It was concluded that the formed TiC could contribute to the appropriate electrical conduction as well as interface strengthening in the Al₂O₃/Ti composites. Furthermore, it was firstly speculated that the TiC could be electrochemically anodized to form an oxide like Ti metal. These characteristics enable Al₂O₃/Ti/TiC composites as the crack-healing materials at room temperature.     

The microstructural and mechanical properties of geopolymer composites containing glass microfibres

This paper presents the effects of microfibre contents on mechanical properties of fly ash-based geopolymer matrices containing glass microfibres at 0, 1, 2 and 3 mass%. The influence of glass microfibres on the fracture toughness, compressive strength, Young's modulus and hardness of geopolymer composites are reported, as are the microstructural properties investigated using scanning electron microscopy. Results show that the addition of 2 mass% glass microfibres was optimal, exhibiting the highest levels of fracture toughness, compressive strength, Young's modulus and hardness. The results of the microstructural analysis indicate that the glass microfibres act as a filler for voids within the matrix, making a dense geopolymer and improving the microstructure of the binder. This leads to favourable adhesion of the composites, and produces a geopolymer composite with good mechanical properties, comparable to pure geopolymer. The failure mechanisms in glass microfibre-reinforced geopolymer composites are discussed in terms of microstructure.     

Evaluation of alumina reinforced oil fly ash composites prepared by spark plasma sintering

The thermomechanical behavior of micro/nano-alumina (Al₂O₃) ceramics reinforced with 1-5 wt.% of acid-treated oil fly ash (OFA) was investigated. Composites were sintered using spark plasma sintering (SPS) technique at a temperature of 1400°C by applying a constant uniaxial pressure of 50 MPa. It was evaluated that the fracture toughness of micro- and nanosized composites improved in contrast with the monolithic alumina. Highest fracture toughness value of 4.85 MPam^1/2 was measured for the nanosized composite reinforced with 5 wt.% OFA. The thermal conductivity of the composites (nano-/microsized) decreased with the increase in temperature. However, the addition of OFA (1-5 wt.%) in nanosized alumina enhanced the thermal conductivity at an evaluated temperature. Furthermore, a minimum thermal expansion value of 6.17 ppm*K⁻¹ was measured for nanosized Al₂O₃/5 wt.% OFA composite. Microstructural characterization of Al₂O₃-OFA composites was done by x-ray diffraction and Raman spectroscopy. Oil fly ash particles were seen to be well dispersed within the alumina matrix. Moreover, the comparative analysis of the nano-/microsized Al₂O₃/OFA composites shows that the mechanical and thermal properties were improved in nanosized alumina composites.     

Microstructures and mechanical properties of TiB2 composite ceramics with co-addition of Ti and TiC fabricated by SPS

TiB₂ composite ceramics containing different amounts of Ti and TiC were fabricated via spark plasma sintering (SPS), and effects of their addition contents on the microstructure and mechanical properties were discussed. The newly formed phases of TiB with a cubic lattice structure in the composite ceramics were observed. At a relatively low temperature of 1510 °C, pressure of 50 MPa, and holding time of 5 min, the TiB₂ composite ceramic with 30 wt% TiC and 10 wt% Ti additions acquired an excellent strength of 727 MPa and a high toughness of 7.62 MPa m^1/2. The improvement in strength and toughness was attributed to the mixed fracture mode, second phase strengthening, and increased energy consumption for crack propagation caused by the newly formed phases and fine TiC particles. In addition, the significant effects of the Ti and TiC addition contents on the densification temperature and mechanical properties of the composite ceramics were determined using analysis of variance (ANOVA).     

Fabrication and mechanical properties of Al2O3–TiC ceramic composites synergistically reinforced with multi-walled carbon nanotubes and graphene nanoplates

In this study, Al₂O₃–TiC composites synergistically reinforced with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were prepared via spark plasma sintering (SPS). The effects of the MWCNT and GNP contents on the phase composition, mechanical properties, fracture mode, and toughening mechanism of the composites were systematically investigated. The experimental results indicated that the composite grains became more refined with the addition of MWCNTs and GNPs. The nanocomposites presented high compactness and excellent mechanical properties. The composite with 0.8 wt% MWCNTs and 0.2 wt% GNPs presented the best properties of all analysed specimens, and its relative density, hardness, and fracture toughness were 97.3%, 18.38 ± 0.6 GPa, and 9.40 ± 1.6 MPa m^1/2, respectively. The crack deflection, bridging, branching, and drawing effects of MWCNTs and GNPs were the main toughening mechanisms of Al₂O₃–TiC composites synergistically reinforced with MWCNTs and GNPs.     

In situ reaction and solid solution induced hardening in (Ti,Zr)B2-(Zr,Ti)C composites

(Ti,Zr)B₂ - (Zr,Ti)C ceramics were synthesized by reactive hot-pressing and solid solution coupling effect using ZrB₂ and TiC powders as starting materials. Effects of sintering temperature on phase relations, microstructure and mechanical properties were reported. The equimolar ZrB₂ and TiC reactants ensured a complete in situ reaction to form (Ti,Zr)B₂ and (Zr,Ti)C solid solutions. The (Ti,Zr)B₂ - (Zr,Ti)C composite sintered at 1750°C was fully densified, and exhibited a high hardness of 29.1 GPa due to fine-grain hardening and solid solution hardening. The optimized comprehensive mechanical properties such as a hardness of 27.9 GPa, a strength of 705 MPa and an indentation fracture toughness of 5.3 MPa m^1/2 were achieved in (Ti,Zr)B₂ - (Zr,Ti)C composites sintered at 1800°C for 1 hour.     

Structural and biological properties of novel Vanadium and Strontium co-doped HAp for tissue engineering applications

The development of novel bioactive materials with improved physical and biological properties is crucial for advancing tissue engineering applications. In this study, we synthesized a Vanadium and Strontium co-doped hydroxyapatite (V–Sr:HAp) nanoparticle intending to enhance the performance of pure HAp. The V–Sr:HAp nanoparticles were synthesized using a microwave-assisted reflux condensation method, and their structural and chemical characteristics were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The morphology and elemental composition of the nanoparticles were examined through scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The XRD analysis confirmed the presence of characteristic peaks of HAp in each sample. SEM images revealed well-connected and highly agglomerated small sphere-like morphology in both pure HAp and V–Sr:HAp nanoparticles. The Vickers hardness test demonstrated the improved mechanical strength in V–Sr:HAp compared to pure HAp. Antibacterial efficacy was evaluated using an agar diffusion test, which showed enhanced antibacterial activity in the co-doped HAp samples against S. aureus and P. aeruginosa. Moreover, the Ca–P deposition rate on the surface of the co-doped HAp samples during biomineralization was higher. Hemolysis assay results have indicated compatibility of both pure HAp and V–Sr:HAp with human blood (<5% lysis). The results of cell viability tests demonstrate that the V and Sr co-doped HAp samples do not exhibit any cytotoxic effects and instead promote cell proliferation. Overall, the incorporation of V and Sr metal ions into HAp presents a promising bio-functional tool for tissue engineering applications, offering improved mechanical and antibacterial properties.     

Biomimetic synthesis and characterization of carbon nanofiber/hydroxyapatite composite scaffolds

Three dimensional electrospun carbon nanofiber (CNF)/hydroxyapatite (HAp) composites were biomimetically synthesized in simulated body fluid (SBF). The CNFs with diameter of ∼250 nm were first fabricated from electrospun polyacrylonitrile precursor nanofibers by stabilization at 280 °C for 2 h, followed by carbonization at 1200 °C. The morphology, structure and water contact angle (WCA) of the CNFs and CNF/HAp composites were characterized. The pristine CNFs were hydrophobic with a WCA of 139.6°, resulting in the HAp growth only on the very outer layer fibers of the CNF mat. Treatment in NaOH aq. solutions introduced carboxylic groups onto the CNFs surfaces, and hence making the CNFs hydrophilic. In the SBF, the surface activated CNFs bonded with Ca²⁺ to form nuclei, which then easily induced the growth of HAp crystals on the CNFs throughout the CNF mat. The fracture strength of the CNF/HAp composite with a CNF content of 41.3% reached 67.3 MPa. Such CNF/HAp composites with strong interfacial bondings and high mechanical strength can be potentially useful in the field of bone tissue engineering.     

Synergistic optimization of mechanical and tribological properties of TiC modified copper-graphite composites by direct current in-situ sintering

The application of Cu-graphite composites in the field of friction materials is limited by the poor wettability between Cu and graphite and weakened mechanical properties. In this work, in-situ TiC layers were generated by interfacial resistance sintering with direct current to manipulate the interfacial bonding of the composites and enhance their comprehensive properties. The Ti added to the composites would react with graphite at the interface to generate TiC layers and form strong Cu–TiC-graphite interfaces due to interfacial reactions. When the added Ti content is 6 wt%, the composite demonstrates the most excellent mechanical properties and tribological characteristics, i.e., yield strength (168 MPa) and wear rate (2.7 × 10⁻¹⁰ m²/N) are 93.1% higher and 29.7% lower than those of the Cu-graphite composite without Ti addition, respectively. The dense TiC layer induces the strengthening of the Cu matrix and serves as the reinforcing phase to optimize the interfacial bonding and stress transfer, which not only greatly enhances the mechanical properties of the composite but also enables the composite to take full advantage of the hard TiC and graphite phases to obtain stable friction coefficient and low wear rate. This work provides a simpler technique to prepare modified Cu-graphite composites with excellent performance and contributes to the in-depth understanding of the enhancement mechanism of hard ceramic layers on the mechanical and tribological properties of composites.     

Mechanical testing of hydroxyapatite filaments for tissue scaffolds preparation by fused deposition of ceramics

Composite filaments with diameter ∼1.75 mm suitable for fused deposition of ceramics were prepared from commercial hydroxyapatite powders (HAp-0, d₅₀ ≤ 35 μm and HAp-1, d₅₀ ≤ 16 μm) and thermoplastic polymer - polyvinyl alcohol. The filament printability in FDC applicable as specific bone-part replacements, is connected to its mechanical strength and slenderness ratio affecting the resistance to buckling. The HAp content in prepared composite filaments was at the level of ∼ 50 % and their mechanical properties were compared to commercial filament based on polylactic acid and ∼ 27 % of gypsite used as inorganic filler. The tensile strength of laboratory prepared filaments was about 3 times lower than strength found for commercial filament. The critical buckling pressure calculated from Euler buckling analysis using measured intrinsic Young´s modulus revealed underestimated critical pressure values ∼ 2.5–5.0 times if compared to values of maximal filament compressive pressure loads simulating buckling.     

One-pot synthesis of glucose functionalized multi-walled carbon nanotubes: Dispersion in hydroxylated poly(amide-imide) composites and their thermo-mechanical properties

Multi-wall carbon nanotubes (MWCNTs) were functionalized with glucose using a covalent, non-specific functionalization approach. Fourier-transformed infrared spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) confirmed that glucose structures were covalently attached to CNTs. Hydroxylated poly(amide-imide) (PAI)-based composites were developed by dispersing of glucose-functionalized MWCNTs (MWCNTs-Gl) as reinforcement in different concentrations varying from 5 to 15 wt.%. Nanocomposites have slightly higher degree of crystallinity than neat PAI and their thermo-oxidative stability was significantly affected by the addition of MWCNTs-Gl. According to mechanical tensile tests, the tensile strength and the Young's modulus of the MWCNT-Gl/PAI composites were increased with increasing MWCNTs-Gl content. The tensile strength remarkably increased from 81 to 129 MPa, which was about 59% higher than that of the neat PAI, with the addition of MWCNT-Gl contents within 15 wt.% and the elongation at break decreased about 0.2% at a 5 wt.% loading of MWCNT-Gl in comparison with the pure PAI film.     

Physical and mechanical properties of kenaf/flax hybrid composites

This research investigates the physical and mechanical properties of hybrid composites made of epoxy reinforced by kenaf and flax natural fibers to investigate the hybridization influences of the composites. Pure and hybrid composites were fabricated using bi-directional kenaf and flax fabrics at different stacking sequences utilizing the vacuum-assisted resin infusion method. The pure and hybrid composites' physical properties, such as density, fiber volume fraction (FVF), water absorption capacity, and dimensional stability, were measured. The tests of tensile, flexural, interlaminar shear and fracture toughness (Mode II) were examined to determine the mechanical properties. The results revealed that density remained unchanged for the hybrid compared to pure kenaf/epoxy composites. The tensile, flexural, and interlaminar shear performance of flax/epoxy composite is improved by an increment of kenaf FVF in hybrid composites. The stacking sequence significantly affected the mechanical properties of hybrid composites. The highest tensile strength (59.8 MPa) was obtained for FK2 (alternative sequence of flax and kenaf fibers). However, FK3 (flax fiber located on the outer surfaces) had the highest interlaminar shear strength (12.5 MPa) and fracture toughness (3302.3 J/m²) among all tested hybrid composites. The highest water resistance was achieved for FK5 with the lowest thickness swelling.     

LDPE/Bi2O3 nanocomposites: Enhanced mechanical,dielectric, and optical properties

This study is focused on investigating the role of bismuth oxide (Bi₂O₃) nanoparticles to improve structural, optical, electrical, and mechanical properties of low-density polyethylene (LDPE). For this purpose, Bi₂O₃ nanoparticles were synthesized by using the solvothermal method and examined by transmission electron microscopes (TEM), x-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–Vis) light absorption methods. LDPE-based nanocomposites were prepared by changing the nanoparticle additive ratio in the composite from 0% to 2% by weight. The composites were analyzed in the context of their FTIR spectra, atomic force microscope (AFM) images, UV–Vis light absorption spectra, stress–strain curves, and energy storage abilities. While the AFM findings indicate a smoother surface for the composites, the optical band gap analysis reveals a slightly decreased direct optical band gap energy. The analyses based on dielectric spectroscopy also highlight the LDPE/0.5% n-Bi₂O₃ composite in terms of the best energy storage capability. Additionally, the highest Young's modulus, toughness, stress at break, and percentage of strain at break were also recorded for the LDPE/0.5% n-Bi₂O₃ composite. In this context, the LDPE/0.5% n-Bi₂O₃ composite with improved dielectric and mechanical properties can be suggested as a new promising LDPE-based nanocomposite with better properties for industrial purposes.