مجله مواد و فناوری های پیشرفته
سال یازدهم شماره 3 (پاییز 1401)

In the current study, the effect of performing the thermal cycling on the impact behavior of Fiber Metal Laminates (FMLs) fabricated by aluminum and carbon fibers/epoxy composites was investigated. To this end, first, the FMLs with various configurations of carbon fibers (0˚/0˚/0˚/0˚, 90˚/90˚/90˚/90˚, +30˚/-30˚/ -30˚/+30˚, and 0˚/90˚/90˚/0˚) were fabricated and put into oven under the thermal cycling conditions with 0, 1, 10, 30, 50, 70, and 90 cycles. For each thermal cycle, the samples were put into the oven for 15 min to increase their temperature from the ambient temperature to 100 °C. Then, the temperature was kept constant for five minutes. Next, FMLs were extracted from the oven to reduce their temprature by the ambient temperature for 15 min. Then, the impact behavior of these samples was investigated based on Charpy impact test, and the related mechanisms were characterized by macrostructural and microstructural methods. The obtained results confirmed that followed by the thermal cycling on the unidirectional samples (0˚/0˚/0˚/0˚ and 90˚/90˚/90˚/90˚), the absorbed energy capability was considerably improved. To be specific, the maximum improvement values in these configurations were obtained as 21.4 and 19.4 %, respectively. It was also found that by changing the configurations, the enhancement and reduction of the absorbed energy capability were transferred in the higher thermal cycles. The microstructural investigations revealed that after thermal cycles, the fracture behavior was altered, and the adhesion between carbon fibers and epoxy matrix was deteriorated.

Recently, corneal transplantation has been proposed as an effective treatment for irreversible corneal damage which facilitates access to healthy corneas; however, lack of allografts made the treatment subject to many limitations in medicine. In this regard, this study aimed to produce multilayer nanofiber scaffolds for corneal epithelial layer tissue engineering with scaffold compounds of fibroin silk/collage-EGF. The samples were first prepared and identified from the perspective of engineering and biology applications. The results of this study showed that an alternative tissue with a suitable thickness and structure of nanofibers with suitable engineering and biological properties was successfully prepared. In addition, a scaffold was prepared in this research for tissue engineering of the corneal epithelial layer based on silk fibroin and collagen containing aloe vera and epithelial growth factor as the contributing factors and stimuli for better corneal repair. For this purpose, nanofiber three-layer scaffolds were prepared by a combination of electrospinning and electrospray methods characterized by engineering features, such as Scanning Electron Microscope (SEM), to study the degradability for their weight loss, water contact angle, and growth factor. Release as well as static and dynamic mechanical properties were also investigated. Biological characteristics such as cell binding and scaffold differentiation potential were further explored. The results of this study showed the successful preparation of an alternative with a suitable thickness and structure of nanofibers with suitable engineering and biological properties. The obtained results confirmed the production of a proper scaffold with suitable thickness and nanofiber structure. Therefore, the prepared product could potentially be used as a suitable alternative for repairing the damaged corneal epithelial layer.

The substrate temperature plays an important role in the mobility of carbon species as well as the formation and growth mechanism of the amorphous carbon layers with diamond-like characteristics. The amorphous carbon structure can be transformed into the diamond- and graphite-like structure under the effect of substrate temperature. Given that, this study aimed to investigate the structural evolution of the diamond-like carbon coating followed by changing the substrate temperature through the radio frequency direct ion beam deposition. In this regard, the substrate temperature values were obtained as 80, 110, and 140 °C for the deposition of DLC coatings. Raman and X-Ray Spectroscopy (XPS) analyzes were done to evaluate the structure and chemical composition of the coatings. To further investigate the thickness and roughness of the applied coatings, Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) were used. According to the results, the lowest roughness value of the diamond-like carbon coating surface was obtained at the substrate temperature of 110 °C. In addition, the lowest value of ID/IG and the highest amount of sp3 bonding were obtained at the same substrate temperature.

In this research, Ni-Co/Gr nanocomposite coating was applied on a low carbon steel substrate based on electrodeposition method under pulse-reverse current using watt plating solution in the presence of saccharin with 0.05 g/L graphene. For better graphene distribution, the plating solution was sonicated. The microstructure of the coating was examined by scanning electron microscopy, atomic force microscopy, and X-ray diffraction, and its corrosion resistance was assessed by polarization and Electrochemical Impedance Spectroscopy (EIS) analysis. The results showed that the coating included Ni-Co/Gr alloy with a smooth surface morphology and contained about 26 % by weight of cobalt. Graphene reinforcing particles were co-deposited on the surface. The average grain size of the Ni-Co/graphene composite coating was obtained as about 7 nm, indicating the formation of a very fine-grained structure. The hardness value of the sample increased from 220 HV (microhardness of the substrate) up to 496 HV followed by nanocomposite coating application. The results of the corrosion tests showed that the corrosion resistance of the coated sample was much higher than that of the uncoated steel. As a result of applying this coating, the corrosion rate decreased from 0.611 mm/y to 0.0029 mm/y.

The most important strategy in tissue engineering is the relationship between the three components of biomaterials, living cells, and biologically active molecules suitable for tissue regeneration. To be clinically effective, these environments must replicate, as closely as possible, the main characteristics of the native Extracellular Matrix (ECM) on a cellular scale. Tissue engineering is generally employed to create hybrid scaffolding to support cartilage tissue regeneration using fabrication 3D printing techniques. The current study designed a three-dimensional scaffold using FDA-approved Polycaprolactone/Poly Lactic-co-Glycolic Acid (PCL/PLGA) polymers. Then, 40 and 45 (w/w) alginate nanoparticles were added to the bio-ink to improve the printability, mechanical properties, and biocompatibility of the scaffolds. Finally, 3D-printed scaffolds were evaluated using mechanical properties, surface hydrophilicity, water absorption, biodegradability, surface morphology, and cell viability. The results showed that increasing the percentage of alginate nanoparticles in the bio-ink would increase the percentage of porosity, surface hydrophilicity, mechanical properties, cell viability, and printability. In addition, water absorption and compression modules of PCL/PLGA 3D-printed scaffolds containing 45 % alginate were optimized, compared to those of other groups, hence used as bio-ink in 3D printing of scaffolds in tissue engineering defects.

In this research, fused silica-zirconia composites including of 5 % by weight of zirconia stabilized yettria prepared by Spark Plasma Sintering (SPS) method. The powders were mixed by Spex (8000D, High energy ball mill) for 30 min in ethanol media. After mixing process, the ethanol removed by heating of the batches at 70 °C. The prepared samples were sintered at 1100, 1200 and 1300 °C and final pressure of 30 MPa. FESEM images demonstrated distribution of reinforcements at the fused silica matrix, also the results showed that sintered samples at 1200 °C have better properties than other samples. Relative density, flexural strength, hardness and toughness of these samples were 99.99 %, 13.4 GPa, 131 MPa and 4.46 MPa.m1/2 respectively. Also results showed that with increasing of sintering temperature to 1300 °C, due to crystallization in fused silica and as a result the formation of cracks in matrix, flexural strength decreased but the hardness and toughness increased slightly.