Homogeneous Particle Distribution Research Articles

Enabling electrical response through piezoelectric particle integration in AA2017-T451 aluminium parts using FSP technology

In the field of structural engineering, the integration of smart materials and structural health monitoring (SHM) has given rise to self-sensing materials (SSM), leading to a paradigm shift in SHM. This paper focuses on the interplay between self-sensing capabilities and the piezoelectric properties of lead zirconate titanate (PZT) and barium titanate (BT) in aluminium components. Leveraging Friction Stir Processing (FSP), the study explores the synthesis and performance of SSMs with embedded piezoelectric particles, potentially transforming structural engineering. The paper highlights FSP as a key methodology for incorporating piezoelectric particles into structural materials, showcasing its potential in developing SSMs with enhanced functionalities. A specific focus is placed on integrating PZT and BT particles into AA2017-T451 aluminium parts using FSP, with metallographic assessments and mechanical property evaluations conducted to analyse particle distribution and concentration. This study shows how BT and PZT particles are incorporated into AA2017-T451 aluminium to create a SSM that responds to external stimuli. Under cyclic loading, the SSMs exhibit a linear load-electrical response correlation, with sensibility increasing at lower frequencies. Metallographic analysis shows homogeneous particle distribution, while PZT induces increased brittleness and brittle fractures. Yield strength remains relatively stable, but ultimate strength decreases post-FSP. Hardness variations indicate weaker bonding with PZT particles. Eddy’scurrent testing aligns with hardness profiles, and sensorial characterization reveals a non-linear frequency-sensibility relationship, showcasing the SSMs’ suitability for low-frequency applications, particularly with PZT embedment.

Comparative study on tensile and morphological properties of resin and rice husk reinforced polymer composite gyroid lattice structures

This study aims to compare the tensile behaviour of 3d printed resin and rice husk-reinforced resin-based gyroid lattice structures. The work was completed in two phases, firstly a resin gyroid lattice structure with two design configurations of unit cell sizes (3, 4, 5, and 6) and solidity percentages (30, 40, and 50) was developed according to the ASTM638 (4) standard. The 12 designs were manufactured using VAT polymerization additive manufacturing and investigated for tensile strength. In the second phase, the poorest tensile testing results were chosen to develop the rice husk-reinforced resin samples with a mixing proportion of 10–20%–30%. The experiment results revealed that the fracture is localized inside the gauge length according to the standard. Remarkably, the rice husk composite-based gyroid lattice samples exhibit 4.29, 6.55, and 9.35 times higher tensile strength than the selected resin sample (U3–30). Additionally, a homogeneous distribution of rice husk particles has been observed in the micrograph analysis (SEM).

A practical approach to fabrication of nano-Al2O3 reinforced MMC coatings by cold spray: Characterization of nanomechanical and tribological performance

Cold spray is a crucial solid-state deposition technique involving high-speed spraying of different-sized particles onto a base material. In this study, Ni-based powder reinforced with different proportions of nano-Al2O3 particles was sprayed onto Al6061 alloy by cold spray to improve the coating performance. Nanoparticles are very difficult to deposition as they are affected by the aerodynamic forces generated during cold spraying. With a practical approach, nanoparticles were agglomerated with micron-sized feedstock powders, and nanoparticles in the sprayed powder acted as larger particles and successfully defeated the aerodynamic force. The effects of adding nano-particles on the microstructural, nanomechanical, and tribological properties were investigated. Microstructural analyses revealed that MMC coating layers comprised ceramic particles and metal matrix (Ni and Zn). Due to the high spraying speed, the nano-particles were spread in the relatively ductile matrix formed by Ni and Zn. The micro- and nanohardness values were increased with nanoparticle volume by two mechanisms. In the first mechanism, the hard particle volume increased with the addition of nano powders, and in the second mechanism, the plastic deformation of the matrix increased due to the nano-particles. The sample without nanoparticle reinforcement exhibited plastic deformation during the initial stage of the nanoscratch test. The dry sliding wear test results showed that the nano-Al2O3-reinforced spraying powders increased the wear resistance approximately 1.9 times. According to FESEM and EDS examinations of worn surfaces and WC counter-bodies, nano-particles reduced the transferred layers caused by adhesion to the abrasive counter-body. In addition, the nano-particles were provided a more homogeneous hard particle distribution and improved wear performance.

Impact of cobalt substitutions on optical, magnetic, dielectric, and structural, properties of BaFe11.6-xAl0.4CoxO19 hexaferrites prepared by Co-precipitation process followed by rapid sonochemical synthesis

The dielectric along with magnetic features of hexaferrites could be remarkably improved by cationic substitutions. Therefore, in the current work we synthesized cobalt substituted BaFe11.6-xAl0.4CoxO19 (0 ≤ x ≤ 1.2) hexaferrites via co-precipitation process followed by rapid sonochemical procedure. Structural analysis showed that, as the concentration of Co increased, the lattice-parameters ‘a’, ‘c’, crystallites-size, and volume increased. The SEM micrographs revealed the uniform and homogeneous distributions of particles in all samples. The two strong absorption bands indicated by FTIR analysis confirm the successful formation of M-type hexaferrites. The decreasing trend of optical band gape with cobalt doping is indicated by UV vis spectroscopy analysis. The dielectric-loss(ε''), dissipation factor, and dielectric-constant(ε′), increased as the content of cobalt is raised. The produced M-type hexaferrite exhibits increased AC electrical conductivity with frequency and doping concentration. Non-Debye-type relaxation is suggested by the cole–cole diagrams (Mʹ vs. Mʹʹ) for prepared samples. As Co concentrations increased, the magnetic moments per formula unit(mB) and saturation magnetization increased up to the optimal doping content of x = 0.9, after that these parameters showing decreasing trend. The magnetic anisotropy constant (K), coercivity (Hc), anisotropy-parameter(B), and anisotropy-field(Ha) were all showing increasing tendency with doping content. The investigations above revealed that Co replaced BaFe11.6-xAl0.4CoxO19 (0≤x ≤ 1.2) hexaferrites will be suitable for use as a permanent magnet, magnetic recording media, and other magnetic applications.

Fabrication of reinforced Al–Mg composite by TiC particles via FSW: Microstructure and tribology study

In this article, wear and microstructure behaviors of dissimilar Al–Mg joints made by friction stir welding (FSW) with the addition of TiC nanoparticles under different welding parameters were investigated. Optimal joining conditions were achieved by a combination of various rotational and traverse speeds and the best microstructure evolution, mechanical properties, and tribological behaviors were achieved for specimens joined at rotational and traverse speeds of 850 rpm and 50 mm/min, respectively. It was shown that the TiC particles play a prominent role in the microstructure modification and enhanced mechanical properties of weld samples due to the recrystallization process and pinning effect. The maximum hardness and strength values of 241 HV and 168 MPa, respectively were obtained for the weld sample made by optimal condition. The friction coefficient and wear volume loss for weld samples fabricated at 850 rpm and 50 mm/min is comparatively less compared to other conditions due to the highest grain refinement, homogenous distribution of particles, and highest hardness characteristics. The major wear happened because of adhesion, abrasion, plastic deformation, delamination, and oxidation.

Analysis of tribological behavior, pin temperature, and surface roughness of a brake pad material with nano coating

The present work is concentrated on the novel multi-nano particle coating of CoNiCrAlY matrix on brake pad material. The tribological behavior of plasma sprayed CoNiCrAlY particle composite coating with nano inert particles like ZrO2, Al2O3, and AT40 were compared. A comparison was made with respect to structure and morphology of coating. The coatings were characterized with Scanning electron microscopy(SEM) and Energy dispersive X-ray spectroscopy(EDAX) technique. The tribological performance of these coatings were studied using pin-on-disc test rig under dry sliding conditions. The wear study revealed CoNiCrAlY+nano Al2O3 particle coating showed better specific wear rate compared to ZrO2 and AT40 composite coating. The observed tribological behaviour is very much influenced by the ability of nano particles to get distributed in the CoNiCrAlY matrix. The CoNiCrAlY coating with nano particles showed significant specific wear resistance of brake pad material. They coated samples also resulted in minimum rise in pin temperature. This is attributed to the homogeneous distribution of nano particles in the coating. These composite coating also showed lower coefficient of friction values. Although referring to other simplified and extreme conditions, the results obtained provides a new window for using nano hard coatings to enhance the life and efficiency of the commercially available four-wheel vehicle brake pad.

Microstructural investigation of hybrid CAD/CAM restorative dental materials by micro-CT and SEM

ObjectivesAn increasing number of CAD/CAM (computer-aided design/computer-aided manufacturing) hybrid materials have been introduced to the dental market in recent years. In addition, CAD/CAM hybrid materials for additive manufacturing (AM) are becoming more attractive in digital dentistry. Studies on material microstructures using micro-computed tomography (µ-CT) combined with scanning electron microscopy (SEM) have only been available to a limited extent so far. MethodsOne CAD/CAM three-dimensional- (3D-) printable hybrid material (VarseoSmile Crown plus) and two CAD/CAM millable hybrid materials (Vita Enamic; Voco Grandio), as well as one direct composite material (Ceram.x duo), were included in the present study. Cylindrical samples with a diameter of 2mm were produced from each material and investigated by means of synchrotron radiation µ-CT at a voxel size of 0.65µm. Different samples from the same materials, obtained by cutting and polishing, were investigated by SEM. ResultsThe 3D-printed hybrid material showed some agglomerations and a more irregular distribution of fillers, as well as a visible layered macrostructure and a few spherical pores due to the printing process. The CAD/CAM millable hybrid materials revealed a more homogenous distribution of ceramic particles. The direct composite material showed multiple air bubbles and microstructural irregularities based on manual processing. SignificanceThe µ-CT and SEM analysis of the materials revealed different microstructures even though they belong to the same class of materials. It could be shown that µ-CT and SEM imaging are valuable tools to understand microstructure and related mechanical properties of materials.

The Incorporation of Clove Essential Oil into Nanostructured Lipid Carrier for Improvement of the Delivery and Antioxidant Effects on the Fibroblast Cells.

Clove (Syzygium aromaticum) essential oil (CO) has been studied extensively for its antioxidant properties but faces several limitations, including high volatility, low aqueous solubility, and irritation. We aimed to develop a Nanostructured Lipid Carrier (NLC) to enhance the benefits of CO. Using the emulsification sonication method, a liquid lipid component, surfactant concentration, and a co-surfactant were optimized to create CO-loaded NLC (CO-NLC). The developed CO-NLC was rigorously assessed for its stability during storage. Free radical scavenging activity and fibroblast oxidative stress protection were also measured to assess the antioxidant activity. The CO-NLC displayed a spherical shape with a hydrodynamic diameter of 125.77 ± 29.68 nm, homogenous particle distribution with polydispersity index of 0.26 ± 0.09, and a surface charge of -27.30 ± 4.56 mV with an encapsulation efficiency of 97% and a good stability profile. Furthermore, free CO and CO-NLC displayed very strong free radical scavenging activity with the IC50 value of 22.74 ± 0.57 µg/mL and 18.28 ± 2.63 µg/mL, respectively. However, only CO-NLC managed to protect fibroblast cells from the harmful effects of oxidative stress. The NLC formulations improved free radical scavenging activity and effectively protected fibroblasts from oxidative stress compared to free CO.

Evaluation of the possibilities of using albumin microspheres for radioaerosol study of the deposition of inhaled substances and mucociliary clearance

The need to study and evaluate the leading protective mechanisms of the respiratory system remains one of the key, but unresolved problems of modern medicine, concerning both radiation hygiene and toxicology, and pulmonology. The model of the respiratory tract presented by the ICRP only partially addresses them, significantly limiting the feasibility and possibilities of its use. The solution of this problem undoubtedly contributes to the improvement of methods of prevention and treatment from the effects of incorporative radionuclides entering by inhalation, as well as methods for diagnosing and treating respiratory diseases aimed at the earliest stages of their pathogenesis, given that the processes of deposition of inhaled substances and lung clearance directly depend both therapeutic and pathogenic effects. This is especially relevant when there is a danger of contamination with radioactive waste, when there is an urgent need to deal with highly pathogenic influence and its consequences. The most informative method for studying the processes of deposition inhalant and mucociliary clearance is radioaerosol. However, due to the circumstances, there are no radiopharmaceuticals that could be used for such a study since the 2000s, which prompted us to carry out this work. At the same time, albumin microspheres labeled with 99mTc are considered potentially suitable, but not studied radiopharmaceuticals in this regard. The aim of the work was to study the aerodynamic properties of albumin microspheres and evaluate the possibilities of their use for radioaerosol study of the processes of deposition of inhaled substances and mucociliary clearance. The aerodynamic properties of albumin micro[1]spheres were studied using optical and scanning electron microscopy by studying their dry dispersion, initial and obtained from its suspension in distilled water, generated by an ultrasonic inhaler according to the developed technology. The results indicated that the dispersible particles were characterized by sphericity, clear boundary differentiation and a relatively homogeneous distribution of particles with a relatively narrow size range (spread 1-2.5 µm) and little conglomeration, as well as a smooth surface. Conclusion. The investigated albumin microspheres are suitable for radioaerosol study of the processes of deposition of inhaled substances and mucociliary clearance.

Production and characterization of sustainable biocompatible PLA/walnut shell composite materials

AbstractVarious treatments, such as alkaline and silane treatments, are commonly applied to natural fillers before production to enhance their quality, thermal stability, and water absorption capacity and improve the fiber–matrix interface properties. However, these processes are not environmentally friendly and may escalate the production cost of composites due to the need for additional processing steps in mass production. This study delves into the impact of untreated walnut shell (WS) filler material, employed in varying ratios (ranging from 10 to 40%) as a filler, on the mechanical, thermal, morphological, and physical properties of environmentally friendly polylactic acid (PLA) matrix composites. The experimental results highlight a significant decrease in tensile modulus by 28%, tensile strength ranging from 32 to 65%, a decrease in flexural modulus by 22%, and flexural strength ranging from 24 to 58% with varying WS filler ratios. Time-dependent water absorption and increased density were observed. FT-IR analysis indicates structural similarities, while DSC results show minimal effects on glass transition temperature and crystallinity. TGA results reveal reduced thermal stability with increasing WS content. SEM microstructure imaging demonstrates homogeneous WS particle distribution, but higher WS content leads to increased brittleness and diminished resistance properties. In conclusion, this study underscores the importance of balancing sustainability through WS filler ratios while preserving mechanical performance.

Microstructure and wear behaviour of AlCoCrFeNi-coated SS316L by atmospheric plasma spray process

ABSTRACT The capacity to endure harsh wear in demanding conditions in stainless steel drops under extreme nature and applications. Protecting the surface by providing a coating layer supports the usage in harsh conditions. In this work, SS316L is coated with AlCoCrFeNi high-entropy alloy (HEA) by atmospheric plasma spray process and annealed at 600°C for 2 hours. The AlCoCrFeNi HEA exhibited spherical particles with bcc phase and 20 µm particle size. The coating morphology revealed a uniform coating with a homogeneous distribution of HEA particles over a thickness of 150 µm. The coating post-annealing offered improved microhardness by 12% than the coated sample before annealing. The wear test was executed by varying load, sliding distance, and sliding velocity at normal temperature, 400°C and 600°C and the corresponding worn surface was analysed. The coated samples after annealing showed 57.6%, 87.5%, and 65.4% improved wear resistance at normal temperature than the coated sample before annealing at minimum levels of load, sliding velocity and distance. The wear rate of coated and annealed samples revealed 5.2%, 4.5%, and 4.4% better wear resistance at 400°C than the coated samples before annealing. The worn surface morphology showcased wear mechanisms to be delamination, abrasive wear, and oxide layer formation under all conditions.

Exceptional grain refinement induced by dispersed MgO particles in TIG-welded AZ31 alloy

Due to the low content of alloying elements and the lack of effective nucleation sites, the fusion zone (FZ) of tungsten inert gas (TIG) welded AZ31 alloy typically exhibits undesirable coarse columnar grains, which can result in solidification defects and reduced mechanical properties. In this work, a novel welding wire containing MgO particles has been developed to promote columnar-to-equiaxed transition (CET) in the FZ of TIG-welded AZ31 alloy. The results show the achievement of a fully equiaxed grain structure in the FZ, with a significant 71.9% reduction in grain size to 41 μm from the original coarse columnar dendrites. Furthermore, the combination of using MgO-containing welding wire and pulse current can further refine the grain size to 25.6 μm. Microstructural analyses reveal the homogeneous distribution of MgO particles in the FZ. The application of pulse current results in an increase in the number density of MgO (1-2 μm) from 5.16 × 104 m−3 to 6.18 × 104 m−3. The good crystallographic matching relationship between MgO and α-Mg matrix, characterized by the orientation relationship of [112‾0]α−Mg//[01‾1]MgO and (0002)α−Mg//(111)MgO, indicates that the MgO particles can act as effective nucleation sites for α-Mg to reduce nucleation undercooling. According to the Hunt criteria, the critical temperature gradient for CET is greatly enhanced due to the significantly increased number density of MgO nucleation sites. In addition, the correlation with the thermal simulation results reveals a transition in the solidification conditions within the welding pool from the columnar grain zone to the equiaxed grain zone in the CET map, leading to the realization of CET. The exceptional grain refinement has contributed to a simultaneous improvement in the strength and plasticity of welded joints. This study presents a novel strategy for controlling equiaxed microstructure and optimizing mechanical properties in fusion welding or wire and arc additive manufacturing of Mg alloy components.

Braided silk sutures coated with photoreduced silver nanoparticles for eradicating Staphylococcus aureus and Streptococcus mutans infections

BackgroundInfections resulting from surgical procedures and wound closures continue to pose significant challenges in healthcare settings. To address this issue, the investigators have developed antibacterial non-resorbable braided silk sutures using in situ deposited silver nanoparticles (AgNPs) and investigated their efficacy in eradicating Staphylococcus aureus and Streptococcus mutans infections. MethodsThe braided silk sutures were modified through a simple and efficient in situ photoreduction method, resulting in the uniform distribution of AgNPs along the suture surface. The synthesized AgNPs were characterized using scanning electron microscopy (SEM), dynamic light scattering analysis (DLS) and Fourier Transform Infrared Spectroscopy analysis (FTIR) confirming their successful integration onto the silk sutures. The antibacterial activity of the nanoparticle coated sutures were compared and evaluated with non-coated braided silk sutures through in vitro assays against both S. aureus and S. mutans. ResultsThe surface and cross-sectional analysis of the treated sutures revealed a uniform and homogeneous distribution of silver particles achieved through the photoreduction of silver solution. This observation confirms the successful coating of silver nanoparticles (AgNPs) on the sutures. The antimicrobial studies conducted, demonstrated significant reductions in bacterial colonies when exposed to the silver nanoparticle-coated sutures. Notably, the width of the inhibition zone surrounding the coated sutures remained consistently wide and stable for duration up to 7 days. This sustained and robust inhibitory effect against gram-positive bacteria, specifically S. aureus and S. mutans, serves as strong evidence of the antibacterial efficacy of the coated sutures. ConclusionThe coating of silk sutures with AgNPs provided a significant and effective antibacterial capacity to the surgical sutures, with this activity being sustained for a period of 7 days. This suggests that AgNPs-in situ photoreduction deposited sutures have the potential to effectively manage S. aureus and S. mutans infections.

Solvent-free synthesis of self-regenerative superhydrophobic film from silicone waste with drag-reduction and selective oil absorption behaviour

In the present work, we devised an ecological solution for recycling silicone waste into functionalized films possessing superhydrophobicity with low drag and oil adsorption characteristics. We used two ecological approaches to transform silicone waste into nanoparticles with inherently distinct surface characteristics. These spheroidal silica nanoparticles, with an average size of 150 nm, showed hydrophilic and hydrophobic characteristics. The detailed characterization confirmed hydrophobic silica being grafted with –CH3 oligomers compared to hydrophilic counterparts. These silica nanoparticles were used to fabricate flexible superhydrophobic films through a solvent-free approach. Films synthesized using hydrophilic particles showed better de-wetting characteristics with advancing angle > 150°, low hysteresis (<5°) and sliding angle (<5°) at an optimum volumetric concentration. High de-wetting stability and low adhesion of ∼ 20 μN with water droplet were noticed for these films due to homogenous particle distribution, leading to significant protrusions and favourable line tension. High van der Waals interaction energy aided better mixing of hydrophilic particles in the matrix than the hydrophobic counterpart. This also resulted in high mechanical strength ∼ 7 MPa (matrix strength ∼ 3 MPa) and better robustness under different harsh conditions, sustaining more than ten months of weathering and one month of immersion. Films showed real-time self-regeneration capability, retaining high de-wetting due to surface chemistry and morphology rejuvenation. The film also displayed extremely low drag, promoting water droplet mobility at ∼ 0.5 m/s wind velocity and oil–water separation capability. The fluorine-free flexible superhydrophobic films synthesized using silicone waste exhibited multi-dimensional characteristics for wide-range applications.

THE EFFECT OF ULTRASONICATION TIME ON PARTICLE SIZE, POLYDISPERSITY INDEX AND STABILITY EVALUATION OF ANTHOCYANIN LIPOSOMES

Background: One of the drug delivery systems that acts as a targeting system is liposomes which have good characteristics so they can encapsulate and deliver drug compounds. One of the characteristics that need to be considered in liposomes is the particle size and polydispersity index. Several methods can be used to control these two characteristics, including the extrusion and the ultrasonication method. Objectives: This research aims to see stability evaluation and effect of ultrasonication time and extrusion on particle size and polydispersity index (PDI) of Anthocyanin liposomes. Methods: The liposome formula was prepared using Anthocyanin: DSPC: cholesterol: DSPE-PEG2000 in a ratio of 1: 1.85: 1: 0.15 using the ethanol injection method. Anthocyanin liposome was divided into 3 treatments of varying ultrasonication times i.e. 5 minutes (L1), 15 minutes (L2), and 30 minutes (L3), and extrusion method as control (L0). All methods of anthocyanin liposomes size and PDI were done the stability evaluation based on storage temperature i.e 4oC and 25oC for 6 weeks Results: The results of liposome characterization using particle size analyzer (PSA) showed that L0, L1, L2, and L3 had particle sizes of 152.1 nm, 150, 6 nm, 156.2 nm, 169.7 nm with the average PDI 0.379, 0.368, 0.450, 0.366 respectively. The statistical data (T-test) showed that there was no real influence on the particle size and PDI of Anthocyanin liposomes. However, Liposome treatment (L1) produced using the ultrasonication method for 5 minutes produces better particle size and PDI than other time variables. Moreover, the stability evaluation of anthocyanin liposomes size and PDI described the extrusion (control) and sonication method particularly 5 minutes of ultrasonication time were more stable than others due to no change size and PDI significantly at 4oC and 25oC for 6 weeks. Conclusion: Both methods can reduce the particle size of anthocyanin liposomes and have a homogeneous particle distribution, particularly the ultrasonication treatment time of 5 minutes which is the same as the extrusion method and and also more stable at storage temperatures of 4oC and 25oC for 6 weeks. Peer Review History: Received 8 December 2023; Revised 26 January 2024; Accepted 29 February; Available online 15 March 2024 Academic Editor: Dr. DANIYAN Oluwatoyin Michael, Obafemi Awolowo University, ILE-IFE, Nigeria, toyinpharm@gmail.com Average Peer review marks at initial stage: 5.0/10 Average Peer review marks at publication stage: 7.0/10 Reviewers: Dr. Md. Shahidul Islam, USTC, Chittagong, Bangladesh, S_i_liton@yahoo.com Dr. Mohammad Tauseef, Department of Pharmaceutical Sciences, College of Pharmacy, Chicago State University, mtauseef@csu.edu

Biopolymer blend composite films based on polyvinyl alcohol/ chitosan/ grape seed extract via green approach for flexible optoelectronic devices

The flourishing environmental concerns have grabbed the attention of researchers developing environmentally supportive materials in various fields. A green approach was used to create biopolymer blend composites based on polyvinyl alcohol (PVA) and chitosan (CS) doped with various concentrations of grape seed (GS). Various analytical techniques, such as Fourier-transform infrared spectroscopy (FTIR), UV–visible (UV) spectra, field emission scanning electron microscope (FE-SEM) and differential scanning calorimetry (DSC) were used to evaluate the optical, structural and thermal properties of the prepared blend composites. The optical properties of blend composites were determined by UV spectroscopy and the findings revealed that absorption intensity increased with increasing GS, while bandgap energy decreased from 4.18 eV for pure blend to 2.91 eV for blend/15 wt% GS. The homogeneous distribution of GS particles in the biopolymer blend was identified with FE-SEM images. DSC results showed that increasing the GS content increased the glass transition temperature of the blend composites. The AC conductivity and dielectric constant were measured using the LCR meter. The conductivity rises with increasing frequency and dosage of GS, with the greatest conductivity obtained at 15 wt% loading. In comparison to a pure blend, it was discovered that the inclusion of 15 wt% GS enhanced the tensile strength by 50%, hardness by 17% and the reduction in elongation at break by 19 %. As a consequence, environmentally friendly PVA/CS/GS biopolymer blend composites with excellent mechanical, thermal, electrical, and dielectric parameters might be a viable green option for flexible electronic, electrochemical and energy storage devices.

Bioactive Hydroxyapatite Aerogels with Piezoelectric Particles.

Open-cell foams based on hydroxyapatite (HAp) can mimic the extracellular matrix (ECM) to better replace damaged hard tissues and assist in their regeneration processes. Aerogels of HAp nanowires (NW) with barium titanate (BT) particles were produced and characterized regarding their physical and chemical properties, bioactivity, and in vitro cytotoxicity. Considering the role of piezoelectricity (mainly due to collagen) and surface charges in bone remodeling, all BT particles, of size 280 nm and 2 and 3 µm, contained BaTiO3 in their piezoelectric tetragonal phase. The synthesized nanowires were verified to be AB-type carbonated hydroxyapatite. The aerogels showed high porosity and relatively homogeneous distribution of the BT particles. Barium titanate proved to be non-cytotoxic while all the aerogels produced were cytotoxic for an extract concentration of 1 mg/mL but became non-cytotoxic at concentrations of 0.5 mg/mL and below. It is possible that these results were affected by the higher surface area and quicker dissolution rate of the aerogels. In the bioactivity assays, SEM/EDS, it was not easy to differentiate between the apatite deposition and the surface of the HAp wires. However, a quantitative EDS analysis shows a possible CaP deposition/dissolution cycle taking place.

Effect of particle volume fraction on wear behavior in Al–SiC MMC coated on DIN AlZnMgCu1.5 alloy

Abstract In this study, DIN AlZnMgCu1.5 alloy surface (Al + SiC) was coated with metal matrix composite (MMC) by using hot press sintering method (HPSM). Al was used as matrix material and SiC powders were used as reinforcing material in the coating process on DIN AlZnMgCu1.5 alloy surface. Al/SiC MMC coating was produced at 600 °C under 120 MPa pressure and with varying SiC content (5, 10 and 15 vol.%). Optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to examine the microstructure, elemental analysis and phase structure of both the coating zone and the transition zone between the substrate and the coating. The hardness was measured and a dry sliding linear reciprocating wear test was run to determine the mechanical properties of the coating layer. Consequently, the coefficient of friction (COF) and wear volume were determined. OM and SEM images showed a homogeneous distribution of SiC particles and a less porous structure. The hardness of the MMC coating increased with increasing SiC content. Also, the numerical analysis of the wear test simulation was done based on Archard’s law. The results of both wear tests showed that the volume loss values were consistent with each other and the amount of wear significantly reduced by increasing the rate of SiC reinforcement.

SURFACE MODIFICATION OF ALUMINA-SILICA BY ADDITIVE AGENT USING SOL-GEL METHOD AS FILLER DENTAL COMPOSITE

Background: Macro-sized and inhomogeneous distribution of ceramic filer particles make it difficult to obtain smooth surfaces of dental composite after polishing. Objective. This study aims to synthesize alumina silica (Al2O3-SiO2) fillers using sol gel method with the additives agent chitosan 5%, 10% and polyethylene glycol (PEG) 5% to produce micro particle size and evenly distributed particle as filler dental composite. Methods. The type of research is descriptive explorative. The sol-gel process was utilized to synthesize filler particles of Al2O3-SiO2. TEOS was dissolved in ethanol and mixed with acetic acid as catalyts. Al2(NO3)3 was added into the solution and mixed homogenously. Subsequently, the additive agents (Chitosan 5%, chitosan 10% and PEG) were mixed into the mixture for 30 minutes. Drying the samples for 48 hours at 60°C in the oven. The Dynamic light scattering (DLS) SZ-1 was used to evaluate the size, particle distribution and zeta potential. Result. The results showed that the addition of chitosan 10% produced a smaller size of Al2O3-SiO2 compared to other samples. A homogeneous particle distribution is shown in the sample with PEG 5%. Meanwhile, zeta potential values of the filler particles Al2O3-SiO2 with the addition of chitosan 10% shows the biggest value. Conclusion: The additive agent of chitosan 10% can modify the surface of filler Al2O3-SiO2 in order to inhibit particle growth more effectively but better particle distribution is shown in samples with PEG 5% due to the lower viscosity than chitosan thus it is easily homogenized in the solution

Taguchi optimized wear and self-lubricating properties of Al-alloy composite reinforced with hybrid B4C–MoS2 particulates

We investigated self-lubricating Al–Mg–Si hybrid metal matrix composites (HMMCs) embedded with MoS2–B4C particulates, for use in automotive engine components. Composites with different B4C content (x = 3.5, 7.0, 10.5, 14.0, and 17 wt%) were prepared, with the MoS2 content of 3.0 wt%. The metal matrix composites were processed using the powder metallurgy route comprising milling for 2 h and cold pressing and consolidation at a sintering temperature of 560 °C. Their dry sliding wear behavior was examined at applied loads (20–50 N) and sliding distances (1–3 km), and the wear variables were optimized using the Taguchi model (L9). Microstructural analysis was performed using a scanning electron microscope equipped with an energy dispersive spectrometer. A homogeneous particle distribution was observed in the HMMCs, without any appreciable instance of agglomerates. The wear resistance and friction coefficient (COF) improved when MoS2 was incorporated into the HMMCs, compared with a matrix alloy under the same operating conditions. In particular, the COF fluctuated up to a sliding distance of 250 m and was constant for larger values. The wear rate depends on not only the maximum hardness but also the appreciation of self-lubricant MoS2. The Taguchi findings showed that the fraction of hybrid reinforcement had the strongest effect on the wear resistance, and it was followed by the applied load, sliding distance, and track diameter. Apart from providing self-lubrication, the MoS2 particles reduced the wear rate.