Development of Cork Biocomposites Enriched with Chitosan Targeting Antibacterial and Antifouling Properties.

The demand for bio-based and safer composite materials is increasing due to the growth of the industry, human population, and environmental concerns. In this framework, sustainable and safer cork-polymer composites (CPC), based on green low-density polyethylene (LDPE) were developed using melt-based technologies. Chitosan and polyethylene-graft-maleic anhydride (PE-g-MA) were employed to enhance the CPC's properties. The morphology, wettability, mechanical, thermal, and antibacterial properties of the CPC against Pseudomonas putida (P. putida) and Staphylococcus aureus (S. aureus) were examined. The CPC showed improved stiffness when compared with that of the LDPE matrix, preferably when combined with chitosan and PE-g-MA (5 wt. %), reinforcing the stiffness (58.8%) and the strength (66.7%). Chitosan also increased the composite stiffness and strength, as well as reduced the surface hydrophilicity. The CPCs' antibacterial activity revealed that cork significantly reduces the biofilm on the polymer matrix. The highest biofilm reduction was found with CPC containing cork and 5 wt. % chitosan for both P. putida (54% reduction) and S. aureus (36% reduction), confirming their potential to extend the lifespan of products for packaging and healthcare, among other applications. This work leads to the understanding of the factors that influence biofilm formation in cork composites and provides a strategy to reinforce their behavior using chitosan.

Numerical homogenization of thermal conductivity of particle-filled thermal interface material by fast Fourier transform method.

Thermal interface material (TIM) is pivotal for the heat dissipation between layers of high-density electronic packaging. The most widely used TIMs are particle-filled composite materials, in which highly conductive particulate fillers are added into the polymer matrix to promote heat conduction. The numerical simulation of heat transfer in the composites is essential for the design of TIMs; however, the widely used finite element method (FEM) requires large memory and presents limited computational time for the composites with dense particles. In this work, a numerical homogenization algorithm based on fast Fourier transform was adopted to estimate the thermal conductivity of composites with randomly dispersed particles in 3D space. The unit cell problem is solved by means of a polarization-based iterative scheme, which can accelerate the convergence procedure regardless of the contrast between various components. The algorithm shows good precision and requires dramatically reduced computation time and cost compared with FEM. Moreover, the effect of the particle volume fraction, interface thermal resistance between particles (R-PP), interface thermal resistance between particle and matrix (R-PM), and particle size have been estimated. It turns out that the effective conductivity of the particulate composites increases sharply at a critical filler volume fraction, after which it is sensitive to the variation of filler loading. We can observe that the effective thermal conductivity of the composites with low filler volume fraction is sensitive to R-PM, whereas the it is governed by R-PP for the composites with high filler content. The algorithm presents excellent efficiency and accuracy, showing potential for the future design of highly thermally conductive TIMs.

Polymer Matrix Nanocomposites Fabricated with Copper Nanoparticles and Photopolymer Resin via Vat Photopolymerization Additive Manufacturing.

This investigation explores the fabrication of polymer matrix nanocomposites via additive manufacturing (AM), using a UV photopolymerization resin and copper nanoparticles (Cu-NPs) with vat photopolymerization 3D printing technology. The aim in this study is to investigate the mentioned materials in different formulations in terms of inexpensive processing, the property related variability, and targeting multifunctional applications. After the AM process, samples were post-cured with UV light in order to obtain better mechanical properties. The particles and resin were mixed using an ultrasonicator, and the particle contents used were 0.0, 0.5, and 1.0 wt %. The process used in this investigation was simple and inexpensive, as the technologies used are quite accessible, from the 3D printer to the UV curing device. These formulations were characterized with scanning electron microscopy (SEM) to observe the materials' microstructure and tensile tests to quantify stress-strain derived properties. Results showed that, besides the simplicity of the process, the mixing was effective, which was observed in the scanning electron microscope. Additionally, the tensile strength was increased with the UV irradiation exposure, while the strain properties did not change significantly.

Comprehensive Study on the Age-Strengthened Mg-Zn-Mn-Ca/ZnO Composites for Fracture Fixation: Microstructure, Mechanical, and In Vitro Biocompatibility Evaluation.

The present work investigates the use of age-strengthened Mg-Zn-Mn-Ca/xZnO as resorbable materials in temporary orthopedic implants. Quaternary Mg-Zn-Mn-Ca alloy, reinforced with zinc oxide particles, was stir-cast, followed by solution treatment and a range of aging treatments. Optical and electron microscopy, mechanical, electrochemical, immersion, and dynamic mechanical testing, with biocompatibility assessment were carried out. The observed 2θ shift in the (101) peaks of ZMX611/ZnO-ST and ZMX611/ZnO-H indicated lattice shrinkage. The formation of Mg7Zn3 and Ca2Mg6Zn3 in the grain boundary compositions was observed. ZMX611/ZnO-ST had a smaller ß-phase fraction, indicating a finer microstructure. ZMX611/ZnO-H had the highest tensile yield strength (102.97 ± 3.92 MPa), and ZMX611/ZnO-ST showed the highest ultimate tensile strength (127.21 ± 7.48 MPa), indicating precipitation hardening of Zn enrichment. The uniformly dispersed secondary phases played a dual role in corrosion behavior. ZMX611/ZnO-ST showed a better cytocompatibility response among all samples. Composite materials exhibited satisfactory biocompatibility and mechanical compatibility as indicated by in silico results of deviatoric strain-based mechanical stimuli at the fracture interface.

Laser-assisted synthesis of nano-hydroxyapatite and functionalization with bone active molecules for bone regeneration.

The main goal of bone tissue engineering research is to replace the allogenic and autologous bone graft substitutes that can promote bone repair. Owing to excellent biocompatibility and osteoconductivity, hydroxyapatite is in extensive research and high demand for both medical and non-medical applications. Although various methods have been developed for the synthesis of hydroxyapatite, in the present study we have shown the use of nanosecond laser energy in the wet precipitation method of nano-hydroxyapatite (nHAP) synthesis without using ammonium solution or any other chemicals for pH maintenance. Here, the present study aimed to fabricate the nanohydroxyapatite using a nanosecond laser. The X-ray diffraction and Fourier transform infrared spectroscopy have confirmed the hydroxyapatite formation under laser irradiation in less time without aging. A transmission electron microscopy confirmed the nano size of synthesized nHAP, which is comparable to conventional nHAP. The length and width of the laser-assisted nHAP were found to be in the range of 50-200 nm and 15-20 nm, respectively, at various laser parameters. The crystallite size obtained by Debye Scherrer formulae was found to be in the range of ∼ 16-36 nm. In addition, laser-assisted nHAP based composite cryogel (nanohydroxyapatite/gelatin/collagen I) was synthesized and impregnated with bioactive molecules (bone morphogenic protein and zoledronic acid) that demonstrated significant osteogenic potential both in vitro in cell experiment and in vivo rat muscle pouch model (abdomen and tibia muscles). Dual-energy X-ray analysis, micro-CT, and histological analysis confirmed ectopic bone regeneration. Micro-CT based histomorphometry showed a higher amount (more than 10-fold) of mineralization for animal groups implanted with composite cryogels loaded with bioactive molecules compared to only composite cryogels groups. Our findings thus demonstrate a controlled and rapid synthetic method for the synthesis of nHAP with various physical, chemical, and biological properties exhibited as comparable to conventionally synthesized nHAP.

Engineering multifunctionality graphene-based nanocomposites with epoxy-silane functionalized cardanol for next-generation microwave absorber.

As technology advances, the demand for effective microwave-absorbing materials (MAM) to mitigate electromagnetic wave interference is growing. Two-dimensional (2D) materials are increasingly favored across various fields for their high specific surface area, electrical conductivity, low density, and dielectric loss properties. This study presents lightweight nanocomposites composed of graphene nanoplatelets blended with epoxy resin (ER) and cardanol with silane-functionalized (SFC) as a toughening agent. The resulting nanocomposites exhibit a high surface roughness of 130 nm and an enhanced hydrophobicity, as evidenced by a high contact angle. Notably, the ER/SFC/GNP sample at 3 wt% (0.075 g) achieves a minimum reflection loss value of -18 dB at a thickness of 10 mm, indicating improved impedance matching and enhanced dielectric loss capability. The increasing damping factor ratio to approximately 0.95 further augments the reflection loss performance. The research aims to develop cost-effective, efficient, lightweight graphene-based nanocomposite absorbers.

Enhancement of the Refractory Matrix Diamond-Reinforced Cutting Tool Composite with Zirconia Nano-Additive.

This paper presents the results of the experimental research on diamond-reinforced composites with WC-Co matrices enhanced with a ZrO2 additive. The samples were prepared using a modified spark plasma sintering method with a directly applied alternating current. The structure and performance of the basic composite 94 wt.%WC-6 wt.%Co was compared with the ones with ZrO2 added in proportions up to 10 wt.%. It was demonstrated that an increase in zirconia content contributed to the intense refinement of the phase components. The composite 25 wt.%Cdiamond-70.5 wt.%WC-4.5 wt.%Co consisted of a hexagonal WC phase with lattice parameters a = 0.2906 nm and c = 0.2837 nm, a cubic phase (a = 1.1112 nm), hexagonal graphite phase (a = 0.2464 nm, c = 0.6711 nm), as well as diamond grits. After the addition of zirconia nanopowder, the sintered composite contained structural WC and Co3W3C phases, amorphous carbon, tetragonal phase t-ZrO2 (a = 0.36019 nm, c = 0.5174 nm), and diamond grits-these structural changes, after an addition of 6 wt.% ZrO2 contributed to an increase in the fracture toughness by more than 20%, up to KIc = 16.9 ± 0.76 MPa·m0.5, with a negligible decrease in the hardness. Moreover, the composite exhibited an alteration of the destruction mechanism after the addition of zirconia, as well as enhanced forces holding the diamond grits in the matrix.

Microstructural Understanding of Hydroxyapatite Addition on Age Hardening, Internal Friction, and Mechanical and Electrochemical Response of Resorbable Magnesium Alloys with Good Cytocompatibility.

The present work aims to assess the age hardening of microalloyed Mg-Zn-Mn alloy reinforced with Ca10(PO4)6(OH)2 (hydroxyapatite, HAp) particles to impart mechanical strength without deteriorating their degradation and biocompatibility behavior for their suitability toward resorbable fixation devices. The hydroxyapatite powder was synthesized with high purity. Mg-Zn-Mn (ZM31) and Mg-Zn-Mn/HAp (ZM31/HAp) were stir-cast, homogenized, and solution-treated to achieve uniform dissolution. Further, they were given a range of aging treatments (175 °C for 0, 5, 10, 25, 50, and 100 h), and the age hardening was measured as Vickers microhardness. The solution-treated and peak-aged (175 °C × 50 h) samples were further investigated using optical and electron microscopy, tensile testing, electrochemical corrosion testing, dynamic mechanical analysis, and biocompatibility. The peak-aged ZM31 sample revealed the highest ultimate strength (134.09 ± 5.46 MPa). The aging treatment resulted in notable improvement in ductility in ZM31 (8.72 ± 1.38%) and yield strength in ZM31/HAp (82.50 ± 1.43 MPa). The rapid strain-hardening behavior was distinctly visible in peak-aged samples in the initial stage of deformation. The amplitude-dependent internal friction confirmed the active solute and age-hardening mechanisms in agreement with the Granato-Lücke model. All samples displayed favorable cell viability (>80%) and cell adhesion behavior; however, their hemocompatibility and biodegradation need further consideration.

The effect of reinforcement particle size on the mechanical and fracture properties of glass matrix composites.

The strength and toughness of sealing glass are currently unable to meet increasingly severe application conditions, and composites are an effective way to solve this problem. The size of reinforcement particles significantly affects the material properties, while the underlying mechanism still eludes deeper understanding. In this paper, the influence of the embedded alumina size is investigated from the perspectives of mechanical and fracture properties by mechanical tests, fracture toughness tests and the finite element method. The results of the experiment and simulation indicate that the fracture energy is mainly consumed by interface debonding and particle breakage, and the former consumes more energy. Materials with large particles have better mechanical properties, while those with small particles have better fracture properties. This difference could be ascribed to the curvature of the particles rather than the size. Therefore, an ideal reinforcement particle shape with both mechanical and fracture advantages is proposed. The results shed light on the nature of particle enhancement and point out a new direction for the design of sealing glass composites.

Concept of a Novel Glass Ionomer Restorative Material with Improved Mechanical Properties.

The objective of this study was to transfer the concept of ductile particle reinforcement to restorative dentistry and to introduce an innovative glass ionomer material that is based on the dispersion of PEG-PU micelles. It was hypothesized that reinforcing a conventional glass ionomer in this way increases the flexural strength and fracture toughness of the material. Flexural strength and fracture toughness tests were performed with the novel reinforced and a control glass ionomer material (DMG, Hamburg, Germany) to investigate the influence of the dispersed micelles on the mechanical performance. Transmission electron microscopy was used to identify the dispersed micelles. Fracture toughness and flexural strength were measured in a 3-point-bending setup using a universal testing machine. Before performing both tests, the specimens were stored in water at 37 °C for 23 h. The fracture toughness (MPa∙m0.5) of the novel glass ionomer material (median: 0.92, IQR: 0.89-0.94) was significantly higher than that of the control material (0.77, 0.75-0.86, p = 0.0078). Significant differences were also found in the flexural strength (MPa) between the reinforced (49.7, 45.2-57.8) and control material (41.8, 40.6-43.5, p = 0.0011). Reinforcing a conventional glass ionomer with PEG-PU micelles improved the mechanical properties and may expand clinical applicability of this material class in restorative dentistry.

Preparation and characterization of starch-based nanocomposites reinforced by graphene oxide self-assembled on the surface of silanecouplingagent modified cellulose nanocrystals.

The dispersion of cellulose nanocrystal (CNC) in starch matrix limited its application. In this study, CNC modified by silanecouplingagent before graphene oxide (GO) self-assembled on the surface of modified CNC, then CNC-GO as a filler was used to prepare starch-based nanocomposite films (CS/CNC-GO). The structure of CNC-GO and CS/CNC-GO films and the properties of CS/CNC-GO films were studied by FT-IR, Raman, SEM, surface potential, UV-Vis, moisture absorption and tensile tests. The results showed that GO was successfully self-assembled on the surface of CNC modified by silanecouplingagent. CNC-GO was superior to CNC in reinforcing the strength of starch film, improving the transmittance of starch film and decreasing moisture rate of starch film. Tensile strength, elongation at break and transmittance of CS/CNC-GO film with 5 wt% CNC-GO reached maximum, which was 53.96 MPa, 3.72% and 38.76%, respectively. Moisture rate of CS/CNC-GO film with 3 wt% CNC-GO reached minimum that was 12.13%. These were assigned to the more uniform dispersion of CNC-GO in the starch matrix and the stronger interfacial interaction between starch and CNC-GO.

Enhancement of Impact Abrasion Resistance Performances of White Cast Iron Utilizing Ti3AlC2.

Al-Ti-C master alloy agent is currently the most promising grain refiner. This work investigates the influence of Ti3AlC2 addition (1.0-3.0 wt.%) on the microstructure of a hypoeutectic cast iron (4.7 wt.% Cr, 2.3 wt.% C). Microstructures of the samples were examined by SEM (scanning electron microscope). It was demonstrated that the added Ti3AlC2 did reduce the size of coarse primary carbides. The XRD (X-ray diffraction) pattern shows that Ti3AlC2 is decomposed into TiC in the alloy substrate. The EDS (energy dispersive spectrometer) interfacial element analysis shows that TiC combines well with the matrix interface. As the Ti3AlC2 amount was increased, the finest microstructure was achieved. When 2 wt.% Ti3AlC2 was added, the wear-resistance property of the material improved and became two times harder than the former. However, when 3% Ti3AlC2 was added, TiC gathered at the crystal boundary, which caused a decrease in the wear resistance of the material.

The Role of Interfacial Adhesion in Polymer Composites Engineered from Lignocellulosic Agricultural Waste.

This paper presents a comprehensive study about the application of a lignocellulosic agricultural waste, sunflower husk in different polymer composites. Two types of milled sunflower husk with different geometrical factors were incorporated into polypropylene, low-density and high-density polyethylene, polystyrene (PS), glycol-modified polyethylene terephthalate (PETG) and polylactic acid (PLA). The filler content of the composites varied between 0 and 60 vol%. The components were homogenized in an internal mixer and plates were compression molded for testing. The Lewis-Nielsen model was fitted to the moduli of each composite series, and it was found that the physical contact of the filler particles is a limiting factor of composite modulus. Interfacial interactions were estimated from two independent approaches. Firstly, the extent of reinforcement was determined from the composition dependence of tensile strength. Secondly, the reversible work of adhesion was calculated from the surface energies of the components. As only weak van der Waals interactions develop in the interphase of polyolefins and sunflower husk particles, adhesion is weak in their composites resulting in poor reinforcement. Interfacial adhesion enhanced by specific interactions in the interphase, such as π electron interactions for PS, hydrogen bonds for PLA, and both for PETG based composites.

Effects of TiO2 Nanoparticles on the Corrosion Protection Ability of Polymeric Primer Coating System.

This research work presents the results obtained from a comparative corrosion evaluation of welded joints on uncoated steel in flat position, welded joints in flat position on steel protected with polymeric film, and welded joints in flat position on steel covered with nanocomposite polymeric film (primer reinforced with TiO2 nanoparticles). The electrochemical methods of open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy were used for corrosion evaluation. The results of the electrochemical tests indicate that titanium oxide reinforcing polymeric film to form nanocomposite layers over naval welded steel increases the corrosion protection of polymeric film as compared with unmodified primer.

Effect of Fibre Surface Treatment and Nanofiller Addition on the Mechanical Properties of Flax/PLA Fibre Reinforced Epoxy Hybrid Nanocomposite.

Natural fibre-based materials are gaining popularity in the composites industry, particularly for automotive structural and semi-structural applications, considering the growing interest and awareness towards sustainable product design. Surface treatment and nanofiller addition have become one of the most important aspects of improving natural fibre reinforced polymer composite performance. The novelty of this work is to examine the combined effect of fibre surface treatment with Alumina (Al2O3) and Magnesia (MgO) nanofillers on the mechanical (tensile, flexural, and impact) behaviour of biotex flax/PLA fibre reinforced epoxy hybrid nanocomposites. Al2O3 and MgO with a particle size of 50 nm were added in various weight proportions to the epoxy and flax/PLA fibre, and the composite laminates were formed using the vacuum bagging technique. The surface treatment of one set of fibres with a 5% NaOH solution was investigated for its effect on mechanical performance. The results indicate that the surface-treated reinforcement showed superior tensile, flexural, and impact properties compared to the untreated reinforcement. The addition of 3 wt. % nanofiller resulted in the best mechanical properties. SEM morphological images demonstrate various defects, including interfacial behaviour, fibre breakage, fibre pullout, voids, cracks, and agglomeration.

A new fractal structural-mechanical theory of particle-filled colloidal networks with heterogeneous stress translation.

This work addresses the role of rigid inclusions in determining the elastic modulus of particle-filled colloidal networks by modifying an established fractal scaling model. The approach acknowledges the heterogeneous nature of stress distribution at length scales beyond the colloidal aggregates, while maintaining structural information at the level of individual clusters. This was achieved by introducing a scaling factor to account for system heterogeneity which contains intrinsic information about the network's capacity to form load-bearing links. Rigid fillers bound to the network induce stress concentration, but additionally serve as junction zones which introduce additional load-bearing pathways. This gives rise to the observed increase in the modulus with filler volume fraction. The proposed relationship between the load-bearing network connectivity and scaling behavior may have additional implications on the fractal dimension determined by rheological methods. Further, this model accommodates an experimentally observed correlation between the scaling behavior of the modulus associated with the addition of fillers and that arising from increasing structurant concentration. The modified fractal model thus provides an alternative view of how fillers contribute to the small- and large-deformation mechanical behavior of filled colloidal gels in a manner consistent with experimental observations.

Dataset on the small- and large deformation mechanical properties of emulsion-filled gelatin hydrogels as a model particle-filled composite food gel.

In this article we present data related to the original research articles 'Effect of matrix architecture on the elastic behavior of an emulsion-filled polymer gel' (Gravelle et al., 2021) and 'The influence of network architecture on the large deformation and fracture behavior of emulsion-filled gelatin gels' (Gravelle and Marangoni, 2021). The small deformation elastic (Young's) modulus and large deformation fracture behavior of emulsion-filled composite gelatin gels are reported as a function of filler volume fraction (ϕf = 0 - 0.32). Homogeneous and heterogeneous network architectures were achieved by varying electrostatic interactions between matrix and filler. The effect of emulsion droplet physical state (solid fat or liquid oil) and gelator concentration (2, 4, 6, or 8% gelatin) were also evaluated. The reported elastic modulus, and fracture properties were obtained from large deformation uniaxial compression tests. Power law scaling behavior was identified for the elastic modulus as a function of both ϕf and gelator concentration, which are also reported. This data is relevant to the evaluation of network properties on the applicability of small deformation particle reinforcement theories and models describing the fracture mechanics of filled composites such as fat-filled food systems.

Fabrication of lignin/poly(3-hydroxybutyrate) nanocomposites with enhanced properties via a Pickering emulsion approach.

The present-day world still demands for various commercially viable biosourced materials to replace the finite petroleum-derived polymers. Herein, lignin nanoparticles were homogeneously dispersed in the poly(3-hydroxybutyrate) (PHB) matrix via an economical, simple and environmentally friendly oil-in-water Pickering emulsion approach to form a nanocomposite with improved properties. The prepared lignin/PHB nanocomposites were investigated for their morphological, thermal, optical, rheological and mechanical properties. The lignin nanoparticles proved to be efficient nucleating agents for PHB in that they noticeably increased the crystallization rates of the polymer. PHB film containing 7% lignin demonstrated the optimum improvement in the tensile performance with 13.2% and 43.9% increase in tensile strength and Young's modulus, respectively. This upturn was ascribed to the uniform dispersion of the lignin nanoparticles and the formation of strong interfacial adhesion between the filler and the matrix due to hydrogen bonding interactions. Moreover, lower crystallinity, higher glass transition temperature, improved UV resistance/blocking and higher melt viscosity were achieved in the blends. The synergetic advancement in these properties may be of significant importance for the wider application of bio-sourced PHB in the packaging industry.

Determination of Local Strain Distribution at the Level of the Constituents of Particle Reinforced Composite: An Experimental and Numerical Study.

This paper is devoted to numerical and experimental investigation of the strain field at the level of the constituents of two-phase particle reinforced composite. The research aims to compare the strain distributions obtained experimentally with the results obtained by using a computational model based on the concept of the representative volume element. A digital image correlation method has been used for experimental determination of full-field strain. The numerical investigation was conducted by the finite element analysis of the representative volume element. Moreover, usage of the novel method of assessment of the speckle pattern applicability for the measurement of local fields by using the digital image correlation method has been proposed. In general, the obtained experimental and numerical results are in good agreement although some discrepancies between the results have been noticed and discussed.

A New Filler for Epoxy Resin: Study on the Properties of Graphite Carbon Nitride (g-C3N4) Reinforced Epoxy Resin Composites.

In this study, graphitic carbon nitride (g-C3N4) as a novel filler was used for fabricating epoxy nanocomposites. The static mechanical, dynamic thermal-mechanical properties and thermostability of as-prepared g-C3N4/epoxy nanocomposites were significantly ameliorated compared with that of the pure epoxy matrix. The tensile modulus and flexural modulus of g-C3N4/epoxy nanocomposites increased by 31.81% and 28.28%, respectively. Meanwhile, the tensile and flexural strength was also improved by 16.02% and 12.67%, respectively. The g-C3N4/epoxy nanocomposites exhibited an increased storage modulus and glass transition temperature. The markedly improved mechanical and viscoelasticity properties were attributed to the stronger interfacial interaction caused by enlarged contact area and increased chemical bonding, and enhanced mechanical interlocking on the interface. The loss factor of epoxy nanocomposites also raised by 40% due to the comprehensive effect of frication caused by the relative slip between nanosheets, micro-constrained layer damping structure and the reversible cycle of breakage and re-established of the hydrogen bond. Meanwhile, the 10% weightlessness temperature (Tinitial), semi weightlessness temperature (Thalf) of g-C3N4/epoxy nanocomposites have increased by about 15 °C and 14 °C, respectively.