فصلنامه مواد پیشرفته در مهندسی
سال چهل و یکم شماره 3 (پاییز 1401)

Sepsis is one of the leading causes of death in intensive care units (ICU) and is becoming more prevalent globally. As a result, an accurate and timely diagnosis of sepsis is critical for selecting the best treatment to prevent disease progression and mortality. In this study, CRP and TNF-α as common biomarkers of sepsis were detected using a label-free optical biosensor based on interferometric Fourier transform spectroscopy from a porous silicon substrate. The porous silicon layer was chemically modified with APTES and glutaraldehyde to immobilize the aptamer covalently in order to capture the analyte. The refractive index of the porous layer was determined by analyzing the reflection spectrum from the porous layer, which was associated with different biomarker concentrations. The results demonstrated linear responses in concentrations ranging from 10-10000 ng/ml for CRP and 100-10000 ng/ml for TNF-α and the biosensor's high discrimination. Thus, it has a high potential for advancement in clinical sepsis diagnosis.

In this research, superhydrophobic nickel and cobalt coatings with a hierarchical micro-nano structure were deposited on copper substrate by rapid one-step electrodeposition. The microstructure, wettability, corrosion resistance, self-cleaning and anti-icing properties of the coatings were evaluated using a scanning electron microscope (SEM), contact angle measurement, electrochemical impedance spectroscopy (EIS), alumina powder as contaminants and keeping at minus 15 °C, respectively. According to the obtained results, nickel coating with a higher contact angle of 172.3° delays the freezing of the droplet on the surface by 6 min more than the cobalt coating with a lower contact angle of 155.6°. The surface energies of both coatings were low enough to benefit from oleophobicity and for glycerol and ethylene glycol, both coatings had water contact angles higher than 120°. When the open circuit potentials were atablized in 3.5 wt.% NaCl solution, very high charge transfer resistances of 2370 and 756.3 kΩ.cm2 were recorded for nickel and cobalt coatings, respectively. After 16 days of immersion in saline solution, the contact angles were still in the hydrophobic range (128.7° and 98.6° for nickel and cobalt coatings, respectively). For cobalt coating with more appropriate surface microstructure and despite its lower water contact angle compared to nickel coating, better self-cleaning properties were observed.

In this research, the fabrication of transparent Alumina was done by spark plasma sintering (SPS). Two types of alpha and gamma Alumina powders with particle size of 200 and 50 nm were used, respectively. The sintering assisted materials used in this research were magnesium nitrate and lanthanum nitrate, each of which was used 100 ppm using a chemical precipitation process. Calcination was performed at 800°C and the resulting powders were subjected to SPS at 1500 °C with a rate of 50 °C/min for 15 minutes under a pressure of 70 MPa. The phase composion was analyzed by X-ray diffraction (XRD) before and after SPS. The morphology of the powders and the microstructure of the sintered samples were studied using scanning electron microscopy (SEM). The bulk density was obtained to be 3.94 gr/cm3 and 3.9 gr/cm3 in the alpha and gamma samples, respectively. The UV-Visible transmission test showed 20% transmission in the alpha alumina sample. The amount of IR transmission in the alpha and gamma samples was obtained to be 65% and 25%, respectively. The alpha alumina sample had a higher transmission percentage and density compared to the gamma sample.

Recently, luminescent down-shifting materials, as promising materials, have attracted much interest to improve the performance of photovoltaic systems. Accordingly, the aim of this study was to synthesize the YVO4:Eu3+ powder by combustion method and characterize their photo luminescent properties as a layer deposited on silicon solar cell. The results of the study revealed that the YVO4:Eu3+ powder with an average particle size of about 80 nm was successfully synthesized. Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy, and photoluminescence spectroscopy (PL) were used to investigate the properties of the synthesized powder, their deposition ability on the silicon solar cell, and their effects on the cell performance. The results indicated that the synthesized powder as a luminescent down-shifting material can absorb the ultraviolet light and convert it to visible light. The findings revealed that the deposition of YVO4:Eu3+ on the silicon solar cells can be considered as a promising and effective method to improve the performance of silicon solar cells in terms of power conversion efficiency and long term stability.

In this study, the effect of quenching and partitioning (Q&P) heat treatment on the structural and mechanical properties of AISI 4130 steel was investigated. The Q&P process was followed at a quench temperature of 270 oC and three different partitioning temperatures of 270, 330, and 380 oC. The phase and structural characterization of the prepared spicimens were done using X-ray diffractometer (XRD) and scanning electron microscopy (SEM), respectively. The mechanical properties of the samples were also monitored by hardness and tensile test according to ASTM E8 standard. The results showed that the tensile strength can be increased up to 1450 MPa while maintaining the elongation percentage (about 9.6%) by performing the Q&P process on the AISI 4130 steel. This strength is about 20% greater than that of obtained by the usual quench and tempering process in this steel. Optimum partitioning temperature and time for AISI 4130 steel were determined to be 330 °C and 120 minutes, respectivly. Partitioning at lower temperatures could not stabilize the austenite phase, while partitioning at higher temperatures caused the decomposition of the austenite phase and carbide precipitation.

Recently, nickel-tungsten (Ni-W) coatings have been investigated by many researchers as a corrosion-resistant, wear-resistant, and high-hardness layer. However, reinforcing particles is also used to form composite and improve the performance of these coatings. Therefore, in this research work, Ni-W composite coating reinforced with CeO2 particles was formed by electroplating method with pulse current on pure copper metal. The microstructure, chemical composition, and thickness of the applied coating were investigated using field emission scanning electron microscope (FESEM). X-ray diffraction (XRD) was used to determine the phases formed in the applied coating. The effect of the parameters of the pulse plating process, including duty cycle, frequency, and waveform was investigated on the co-precipitation of reinforcing particles in the Ni-W matrix. The results showed that increasing duty cycle up to 70%, increasing the frequency up to 100 Hz, and using pulsed current with a square wave shape caused more particles to deposit in the coating. Under these optimal conditions, the composite coating was formed with uniform distribution of reinforcing particles, uniform thickness, and very good adhesion to the substrate.