فصلنامه مواد پیشرفته در مهندسی
سال چهل و دوم شماره 2 (تابستان 1402)

Prevention of infection and bioactivity of implantable parts in the body is one of the most important issues investigated in medical research in recent years. In this regard, researchers have conducted many studies in order to increase the bioactivity of implantable parts in the body. Increasing the bioactivity of these parts has been done in different ways, while coating the surface of the parts is considered as one of the best methods in this field. In this research, simultaneous coating of iron oxide nanoparticles (magnetite) along with 45S5 bioactive glass on AISI 316 stainless steel substrate was deposited by electrophoretic method to increase the bioactivity and the possibility of hyperthermic applications. X-ray diffraction analysis confirmed the presence of both iron oxide nanoparticles and bioactive glass. Electron microscope was employed to study the coating surface. Conducting surface investigations by surface roughness and wetting angle measurements, it was shown that the roughness of the coated surface was 49.2±1 µm and the wetting angle of this coating was obtained to be 49°. The results declared that this coating had a surface with medium roughness and hydrophilic properties, which was of great importance for bioactivity performance. Investigating the magnetic properties of the coating, magnetometric evaluation was performed on the synthesized samples. The saturation magnetization and the Hc parameter values of the coating were obtained to be 20.2 emu/g and 89 Gauss, respectively.

Producing ideal black coatings with optical absorption and emission followed by desirable wear resistance is crucial for various applications such as space applications. A suitable method for producing these coatings is anodizing aluminum alloys followed by black dying the produced anodic coatings using black organic or inorganic pigments. It is necessary to investigate and optimize the effect of the process parameters to maximize the optical absorption, emission, and the wear resistance of the coatings. These issues have been addressed in this research, and the influence of process parameters and type of pigment has been studied to maximize the absorptivity, emissivity, and the wear resistance of the coatings. For the first time, the effect of pigment on the absorptivity, emissivity, and wear resistance of the coatings was investigated. Unexpectedly , it was observed that the type of pigment had a significant effect on the optical and mechanical properties of the coatings. It was also found that in the anodic coatings containing inorganic pigment, absorptivity increased from 0.85 to 0.95, the emissivity increased from 0.82 to 0.91, and weight loss value in pin‐on‐disk wear test decreased from 6 to 2 mg with increasing the anodizing time from 15 minutes to 45 minutes. In contrary, slight improvement was observed in the coatings containing organic pigments. Despite increasing the anodizing time in the latter case, the absorptivity, emissivity, and the weight loss during wear test changed insignificantly.

Bioceramics are very popular materials for tissue engineering applications due to their properties such as suitable bioactivity, biocompatibility, excellent compressive strength, and wear resistance. One of the most widely used bioceramics is calcium silicates. Calcium silicates are biocompatible and bioactive with relatively good mechanical properties, but high degradation rate. Elements such as magnesium (Mg), zirconium (Zr), and zinc (Zn) are added to calcium silicates to resolve this problem. Baghdadite (Ca3ZrSi2O9) with good biological properties is one of the calcium silicate based ceramics in which the zirconium element has replaced part of the calcium element. Also, the presence of calcium and zirconium elements has increased the biological and mechanical properties of this material. The purpose of this research was to synthesize Baghdadite powder using the sol-gel process and to characterize it using X-ray diffraction test to study the formed phases, halo test for antibacterial properties investigations, Fourier transform infrared spectroscopy to determine the functional groups, and field emission scanning electron microscope to examine the morphology of the powder. The results showed that the single-phase Baghdadite phase was formed with the particle size of 225 ± 15 nm and lumpy morphology. The elemental analysis test confirmed the presence of the main elements of Baghdadite (Ca, Si, Zr, and O) in the synthesized sample. Moreover, the elemental map analysis confirmed the uniformity of Baghdadite constituent elements. The results of the Disk diffusion test revealed that Baghdadite had no appropriate antibacterial properties against staphylococcus bacteria, but showed a slight antibacterial properties against Escherichia coli bacteria.

In this paper, the electronic and transport properties of three groups of armchair Silicene nanoribbons were investigated in the presence of a vertical magnetic field. The Silicene nanoribbons were modeled with N=5-7 silicon atoms in width, each having different band gaps. Vertical magnetic field with strengths of h=0.1 eV, 0.2 eV, and 0.3 eV were applied to the nanoribbons. By applying a vertical magnetic field, changes were observed in the electronic arrangement of the nanoribbons. As a result, the electronic and transport properties of nanoribbons such as emission spectrum, band structure, and current-voltage (I-V) characteristics were changed. The results indicated that applying a vertical magnetic field to the armchair silicene nanoribbons subjected to electric potential difference enhances the current. To extract the electronic and transport properties of the nanoribbons, a tight-binding model coupled with the non-equilibrium Green’s function formalism was employed.

Dealing with the destructive effects of electromagnetic waves requires materials with the ability to lose magnetic and electrical energies. These materials are mainly composed of a magnetic material and an electrically conductive material. In the present research, at first, strontium ferrite nanoparticles doped with manganese and calcium with the formula of SrCo2-X(Mn Ca)X/2Fe16O27 (x=0.0-0.5) were synthesized by co-precipitation method. Then these nanoparticles were composited together with functionalized carbon nanotubes (with a volume ratio of 1 to 5%). X-ray diffraction analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and vector network analyzer were used to investigate the structural, magnetic, and microwave properties of the samples. The X-ray diffraction pattern results showed that the strontium ferrite phase was formed in all compounds, and there was no evidence of any impurities in the samples. FE-SEM results indicated that the particles completely covered the outer walls of the carbon nanotubes. Magnetometer test results also showed that with an increase in the amount of manganese and calcium cations in strontium ferrite, the saturation magnetization decreased and the coercive force increased. Reflection losses were also at least 30% higher in composite samples than those of in ferrite samples. The highest reflection loss (7.42 dB at a frequency of 1.12 GHz) was observed in the nanocomposite sample containing 5% by volume of carbon nanotubes. However, based on the results, the sample containing 4% by volume of carbon nanotubes had a wider absorption bandwidth compared to other samples.

The purpose of this research was to fabricate and investigate the properties of SiC-5TiB2 nano composites reinforced by gaphene quantum dot nanoparticles via pressure less sintering method. In this way, SiC, TiB2, and graphene quantum dot raw materials were used in nanometer dimensions. First, before performing any laboratory operations, experimental samples were designed using Minitab 14 software. The design was done by the Taguchi method according to the L9 array and the parameters of the amount of gaphene quantum dot amplification in three levels were set at 0.2, 0.6, and 1 wt.% and sintering temperatures were defined as 2000, 2100, and 2200°C. The sintering process was carried out at certain temperatures in argon atmosphere for 2 h. XRD, FESEM, FTIR and Raman spectroscopy were performed. Density, micro hardness, and fracture toughness measurements were used for further investigations of physical and mechanical properties. The microstructure of the samples was also observed to determine the fracture toughness mechanisms. The results showed that the parameter of the amount of reinforcement was in the first rank of influence and the sintering temperature was in the second rank, and the best results were obtained in the sample with the amount of 0.6 wt.% of gaphene quantum dot and the sintering temperature of 2100 °C, where hardness and fracture toughness values were obtained to be 27.7 GPa and 3.3 MPa.m1/2, respectively.