Search

Tissue engineering is an interdisciplinary approach that utilizes cells, scaffolds, and biofactors to develop biosynthetic bone scaffolds for bone regeneration applications. These scaffolds are three-dimensional porous structures with specific mechanical and biological properties that facilitate the attachment and proliferation of osteoinductive cells on their surfaces. In this study, bone scaffolds were 3D-printed using PLA material, and a variety of three-dimensional porous structures, including Kelvin, Octet truss, and Gibson Ashby, were employed. To improve the biological properties of the scaffolds, they were coated with alginate/hydroxyapatite using the Freeze-drying method. The Alginate/HA RVEs were analyzed under periodic boundary conditions, and the elastic modulus was found to improve from 100 MPa (pure alginate) to 149 MPa by adding 30 wt% HA particles. The mechanical properties of the scaffolds were investigated under compressive deformation using experiments and finite element simulations. The results show that the compressive strength of structures follows the order σOctettruss > σGibsonashby > σKelvin. The Freeze-drying process causes pore formation on the scaffold surface. According to the microstructural analysis, the pore size was observed for composite scaffolds approximately at 320–340 μm. After 21-day, most parts of the scaffold surface were coated by the apatite layer completely, and the surface of the pores was blocked by the apatite layer. To characterize cell viability, an MTT assay was used. The scaffolds expose high cell viability around 97% and did not show any significant toxicity.

This study aims to grow the carbon nanotubes (CNTs) on the aluminum substrate (sheet) using Thermal Chemical Vapor Deposition (TCVD) so that the aluminum sheets can be clad together. Besides, finite element simulation (FEM) was used to evaluate the damage progression, and fracture initiation in AL-CNT composites. AL-CNT Representative Volume Element (RVE) was studied to numerically get an appropriate micro-scale Al-CNT composite simulation. To forecast the statistical connection between material microstructure and effective constitutive properties, the RVE approach was developed. AL/CNT RVE models were studied to determine the most effective carbon nanotube weight percentage as a contender to reinforce the aluminum matrix. The experimental technique was then used to investigate the results found in the RVE models. According to the experimental procedure, AL/CNT shows the maximum mechanical strength and material behavior in the CNT weight percentage reported by the RVE model analysis. Furthermore, regarding the importance of continuum mechanical simulation of microstructural damage processes in the ductile fracture mechanics research, the effect of stress triaxiality ratios, such as the ratio of mean stress to equivalent stress, on the damage growth rate was studied. The experimental results show that the composite mechanical behavior is appropriate at each CNT weight percentage simulations were conducted, and the results were compared to the numerical and experimental approaches in the literature, yielding satisfactory agreements. Based on the experimental findings, ultimate strength and young modulus of AL-5 wt.% CNT are 239 MPa and 73 GPa respectively. By adding more CNT concentration, CNT agglomerations are appeared inside the samples based on SEM. Therefore AL-5 wt.% CNT is the final candidate with the best physical properties.

Purpose This paper aims to numerically investigate the heat transfer and entropy generation characteristics of water-based hybrid nanofluid in natural convection flow inside a concentric horizontal annulus.Design/methodology/approach The hybrid nanofluid is prepared by suspending tetramethylammonium hydroxide-coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA)-coated carbon nanotubes (CNTs) in water. The effects of nanoparticle volume concentration and Rayleigh number on the streamlines, isotherms, average Nusselt number and the thermal, frictional and total entropy generation rates are investigated comprehensively.Findings Results show the advantageous effect of hybrid nanofluid on the average Nusselt number. Furthermore, the study of entropy generation shows the increment of both frictional and thermal entropy generation rates by increasing Fe3O4 and CNT concentrations at various Rayleigh numbers. Increasing Rayleigh number from 103 to 105, at Fe3O4 concentration of 0.9 per cent and CNT concentration of 1.35 per cent, increases the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 224.95, 224.65 and 155.25 per cent, respectively. Moreover, increasing the Fe3O4 concentration from 0.5 to 0.9 per cent, at Rayleigh number of 105 and CNT concentration of 1.35 per cent, intensifies the average Nusselt number, thermal entropy generation rate and frictional entropy generation rate by 18.36, 22.78 and 72.7 per cent, respectively.Originality/value To the best knowledge of the authors, there are not any archival publications considering the detailed behaviour of the natural convective heat transfer and entropy generation of hybrid nanofluid in a concentric annulus. [ABSTRACT FROM AUTHOR]

The study of the flow of nanofluids (NFs) in the presence of external fields and the effect of these fields on the heat transfer rate of NFs is the subject of engineering and medical science. Magnetic fields are among the external fields applied to fluids. These fields receive a lot of attention in recent years due to their specific features and applications. This study conducts a numerical investigation of the natural convection of water/ Fe 2 O 3 NFs in nanoparticle volume fractions of φ =0, 2, and 4% =0, 2, and 4% in a baffled l -shaped enclosure under a magnetic field. Calculations with different magnetic field intensities are examined. The natural convection is considered laminar and examined at different Rayleigh numbers. The effects of geometric shape changes (baffle displacement) on the heat transfer and entropy generation rates (S ˙ g) are also investigated. This study is mainly conducted to investigate the effect of the proposed parameters on the NF flow, heat transfer, average and local Nusselt numbers, the curves of velocity distribution and dimensionless temperature distribution, and S ˙ g. According to the results, increasing the Rayleigh number causes an increase in the temperature difference between hot and cold surfaces and intensification of the buoyancy currents. This increases local and average heat transfer and S ˙ g. Nu ave increases by 59.20 and 38.168%, respectively, with an increase in the Rayleigh number from 104 to 105 and 106 in φ=4%. The results also showed that increasing the φ and magnetic field intensity decreases heat transfer and increases S ˙ g. So that in Ra=104 and 105, the S ˙ g increases from about 40 to 75 with increasing the φ and in Ra=106 the S ˙ g increases from about 8000 to 15,000. This can be attributed mainly to the reduction in the intensity of buoyancy currents. In general, any factor that increases heat transfer causes an increase in S ˙ g. The Nu ave increases 4.64 and 9.29% 4.64 and 9.29% with increasing the φ from φ=0 to 2.4% in Ha= 40. [ABSTRACT FROM AUTHOR]