فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 41 (تابستان 1401)

Recent developments indicate that a large and new family of two-dimensional transition metals consisting of carbides, carbonitrides and nitrides with the general name of MXene have attracted much attention. MXenes have significant physical and chemical properties with a rich variety of basic elements. In order to effectively adjust the properties of MXenes to achieve different applications, they can be easily combined with other materials such as polymers, oxides and carbon nanotubes. Due to the fact that human daily life is full of electromagnetic wave (EM) pollution, which threatens human health, the development of advanced microwave absorbing materials has become an important issue. Two-dimensional materials such as MXene, graphene, and molybdenum disulfide (MoS2) have unique electromagnetic properties and potential applications in absorbing electromagnetic waves, shielding, and microwave waves stealth due to their special structure, excellent electrical conductivity, rich surface, and good mechanical strength. In this regard, because of having desirable structures and properties such as a special layered structure, abundant and adjustable surface active functional groups, excellent electrical conductivity, and high specific surface area MXenes are suitable candidates for absorbents. In this article, the synthesis methods and properties of MXenes are summarized first, and then their recent developments in applications related to the field of microwave absorbers, which are of great importance, have been reviewed. Finally, the challenges and bright horizons of future research in the field of new two-dimensional materials of MXenes have been presented.

In this research, the physical and comfort properties of cotton and polyester fabrics treated with muscovite minerals were investigated. First, muscovite microparticles were dispersed in a chitosan solution and then the muscovite suspension was coated on plain cotton and knitted polyester fabrics. The effect of the presence and content value of muscovite particles on the morphological and chemical properties of processed fabrics was studied. For this purpose, scanning electron microscopy and Fourier transform infrared spectroscopy were used. The morphological study of treated fabrics shows the presence of muscovite particles in the space between the fibers and also on the surface of the fibers of the investigated fabrics. To evaluate the surface properties and comfort performance of the fabrics, the water contact angle, sliding angle, and air permeability tests were carried out. Also, the softness and comfort of the fabrics were investigated using bending length and wrinkle recovery angle analysis. The obtained results indicate that the addition of muscovite particles to the polyester fabric increased the hydrophilic property and did not have much effect on the air permeability, handling properties, and wrinkle resistance. While in the case of cotton fabric, the sliding angle of water is reduced by 66% and the surface of the fabric becomes hydrophobic. The air permeability has also been reduced by 30% and the comfort performance of the textile has also been affected. The statistical analysis of the data obtained from the above tests indicated the significance of the data at the confidence level of 95%.

Among the applications of austenitic stainless steels, it can be mentioned the application in solid oxide fuel cells and boiler tubes. It is necessary to protect these steels at high temperatures. One of the best effective methods to increase the life of these steels at high temperature is to apply surface coatings. In this research, Ni-Co-CeO2-ZrO2 composite coating was fabricated by electroplating method on the surface of AISI 304 austenitic stainless steel. In order to investigate the high temperature corrosion resistance, isothermal oxidation tests at 800°C for 300 hours and cyclic oxidation at 800°C for 50 cycles were performed on uncoated and coated samples. Scanning electron microscope (SEM) was used to observe the morphology and X-ray diffraction (XRD) was used to determine the formed phases. The results showed that the formed coating at the current density of 15 mA/cm2, pH of 3, and a concentration of 25 g.l-1 of ZrO2 particles and a concentration of 10 g.l-1 of CeO2 particles was without holes and cracks. In isothermal and cyclic oxidation tests, the coated samples showed a lower weight gain than the uncoated samples due to the formation of NiFe2O4 and CoFe2O4 spinels. These spinels prevented the outward diffusion of chromium cations from and improved the oxidation resistance of the 304 steel substrate.

Considering the structural applications of polymer composites and the increasing demand for greater strength and stiffness of these types of composites, also due to the unique properties of Carbon Nano Tubes (CNTs), the possibility of using Carbon nanotubes as an additional reinforcement in a polymer composite have been investigated. In this research, the representative volume element (RVE) is studied in different percentages and sizes of Carbon nanotubes. First, the analytical equations for predicting the elastic behavior of a representative volume element are presented, then the mechanical behavior of element is investigated by modeling the element in ABAQUS finite element software. The main objective of this research is to model and extract the elastic mechanical properties of polymer nanocomposite with epoxy resin underlay with carbon and glass fiber as the first reinforcement and carbon nanotube as the second reinforcement. Axial and bending loading is applied to the element as a displacement and single rotation. The results show that the axial and flexural stiffness of glass fiber-reinforced composite with 5 percent carbon nanotubes (inner radius=2nm) increase by 83.8% and 244.9%, respectively, while those for carbon fiber-reinforced composite and with the same conditions, it is 17.5% and 54.9%, respectively. On the other hand, increasing the thickness of carbon nanotubes by 1.5 nm causes a significant increase in the axial and flexural strength values of the composite reinforced with glass and carbon fibers.

In this research, core-shell SiO2/SnO2, SnO2/SiO2 composite nanofibers, and SnO2 nanofibers were synthesized by electrospinning method and were calcined in an electric furnace at temperature of 500 degrees Celsius for 2 hours. Photocatalytic degradation ability of synthesized nanofibers was studied on Crystal violet, methylene blue and methyl orange dyes under ultraviolet light. Structural characteristics of core-shell SnO2/SiO2 nanofibers, SiO2/SnO2 and SnO2 nanofibers were investigated using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffraction spectroscopy (XRD), and Fourier transform infrared spectroscopy (FT-IR), energy diffraction X-ray spectroscopy (EDX) and Xmap analysis. TEM images clearly show the core-shell structure of SiO2/SnO2 and SnO2/SiO2 nanofibers with an average diameter of 550 nm. XRD analysis shows the amorphous structure of nanofibers before thermal treatment and the formation of the dominant crystalline phase after thermal treatment. Uniform distribution of elements was observed by Xmap analysis. The comparison of photocatalytic decomposition of methylene blue, methyl orange and crystal violet dyes in the presence of SnO2 single layer nanofibers, core-shell SnO2/SiO2 nanofibers and SiO2/SnO2 shows that core-shell SiO2/SnO2 nanofibers with 40.58 percent decomposition in methylene blue, 44/44 in methyl orange and 12/31 in crystal violet had the most effect in destroying colors.

Today, efforts have been made to improve the positive properties as well as reduce the negative properties of different fibers. Meanwhile, polyester fibers, against all their advantages and desirable properties, their low thermal resistance has limited their use in various industries. Because thermal resistance is one of the most important topics in engineering sciences. In most cases, these fibers need to be modified by methods that are very broad and involve the physical and chemical modifications of polymers and fibers. Therefore, in this study, it has been tried to evaluate the improvement of thermal resistance of these fibers. For this purpose, the thermal properties of fibers were investigated by filling Muscovite mineral nanoparticles in the smelting operation on polyester chips. Ultraviolet rays were used to reduce the particle size of Muscovite and the effect of these variables including the amount of mineral and the duration of ultraviolet rays on the thermal properties of these fibers was evaluated. The results were analyzed using the design of experiments and images of electron microscope and infrared spectrometer. The results showed that the muscovite particles were thoroughly mixed with the polyester particles and the Muscovite nanoparticles were fillered in this polymer and the produced fibers have high uniformity. The results of flame test also showed that the presence of Muscovite nanoparticles in polyester granules has a significant effect on improving the thermal resistance of fibers. Also, there was no significant decrease in the mechanical properties of the modified fibers based on the tensile test.

In recent times, there has been significant interest in the field of biomedical applications, particularly in the realm of targeted drug delivery and medical implants, where injectable biomaterials possessing 3D printing capabilities have garnered considerable attention. While numerous biomaterials have been developed to replicate the mechanical behavior of human tissue, the quest for an ideal biocompatible material with adjustable mechanical properties that can accommodate a wide range of characteristics remains unfulfilled. Within the scope of this research, a printable and injectable elastomeric hydrogel was formulated utilizing polyurethane as the elastomer component and hydroxyethyl methacrylate as the hydrogel component. By varying the percentage composition of these constituents, a diverse array of mechanical properties was achieved. Fourier Transform Infrared Spectroscopy was employed to verify the successful synthesis of EPUH. The synthetic materials displayed modifiable mechanical properties in their dry states, encompassing a range of Young's modulus values from 20 MPa to 1.2 GPa, as well as elongation at break values ranging from 20% to 140%. Additionally, this study also encompassed an evaluation of water uptake and printability of the samples.