مجله مواد و فناوری های پیشرفته
سال دوازدهم شماره 1 (بهار 1402)

The present project primarily aims to investigate the effect of synthesis method of the bioactive glass powder on the flowability and structural stability of the pastes from it. In this study, 45S5 bioactive glass was synthesized by melting and sol-gel methods. The rheological properties, injectability, washout resistance, and behavior of calcium phosphate deposition formation in the simulated body solution after 21 days were investigated using UV-visible spectroscopy, inductively coupled plasma atomic emission spectroscopy, and scanning electron microscopy. Finally, the cytotoxicity test was carried out, and its dependence on the concentration of the ions released from different pastes was evaluated. The bioactive glass powder prepared through the melting method was non-porous with a specific surface area of about 3 m2g-1 while the powder prepared by the sol-gel method was porous with a specific surface area of about 12 m2g-1. The values of the yield stress, viscosity, and thixotropy in the paste prepared by the sol-gel glass were higher than those of the sample prepared by melting method, and the injection force increased by about five times. Use of sol-gel glass led to the formation of pastes with lower washing resistance and for this reason, the dissolution and release rate of the ions from the paste containing sol-gel glass was higher than those of the same sample with molten glass. Increasing the specific surface area of the powder led to faster formation of the apatite layer on the surface of the samples; however, the rate of cell proliferation decreased due to the high concentration of ions in the environment.

Among different active materials, nickel hydroxide is one of the most promising pseudocapacitive materials; however, its electrochemical performance is notably restricted because of its low conductivity and weak stability. To overcome these drawbacks, several solutions were suggested including making it composite with electrically conductive materials such as metal particles, various carbon materials, and conductive polymers. In addition, removing the insulating polymer binder used in the electrode prepration can reduce the internal resistance of the electrode, thus leading to improvement in its energy storage performance. In this research, a novel, facile, and efficient approach was developed to prepare a binder-free nickel hydroxide electrode, which includes the layer-by-layer chemical deposition of nickel hydroxide nanoparticles with β-phase structure on the nickel foam. The structural characterization and surface morphology of the as-prepared electrode was investigated using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM). Further, the energy storage performance of the prepared supercapacitor electrode was evaluated using cyclic voltammetry and galvanostatic charge-discharge techniques. The prepared electrode showed a specific capacitance of 767 F g-1 at the discharge current density of 1 A g-1 and cyclic stability of 91.4 % after 1000 cycles.

In the current research, Nd2(Fe,Co)14B hard magnetic nanoparticles were synthesized through the reduction diffusion process. For this purpose, Nd(Fe1-xCox)B oxide powders for x = 0.05, x = 0.3, and x = 0.5 were heat-treated once in hydrogen atmosphere (H2) and once in the reduction diffusion process using calcium hydride (CaH2). The phase analysis and chemical composition of the resulting Nd-Fe-Co-B powders were identified by X-ray diffraction and X-ray energy dispersive spectroscopy. The morphology and magnetic properties of the synthesized powders were investigated using a field emission scanning electron microscope, transmission electron microscope, and vibrating sample magnetometer. The results demonstrated that oxide powders reduced with hydrogen gas were characterized by a soft magnetic character due to the formation of the bcc-FeCo magnetic phase. However, oxide powders reduced via reduction diffusion exhibited hard magnetic characteristics due to the direct diffusion of NdH2, Fe, Co, and B phases as well as the production of Nd2(Fe,Co)14B hard magnetic phase. The Nd2(Fe,Co)14B particles were rinsed with water and dilute acetic acid to eliminate the byproducts (CaO) formed during the reduction diffusion process. Followed by washing, coercivity dropped due to the formation of the Nd2Fe14BHx soft magnetic phase; however, saturation magnetization rose due to the elimination of the non-magnetic CaO phase from the final production.

Accumulative Roll-Bonding (ARB) process is a Severe Plastic Deformation (SPD) process run to produce Ultra-Fine Grained (UFG) sheets using intense plastic strains via rolling machine. In this research, the effect of surface condition (brushing) and annealing treatment on the fracture surface and bonding strength of the ARBed AA6061 sheets was investigated. In this regard, the specimen surfaces were first brushed in three different directions, i.e., Rolling Direction (RD), Transverse Direction (TD), and both RD and TD. The ARB process was conducted up to five cycles, and specimens were tested after the first, third, and fifth cycles. The annealing treatment was conducted for two hours at 415 °C after the first, third, and fifth cycles. The bonding strength and hardness profile in the cross-section (perpendicular to the rolling direction) were measured through peeling and hardness tests, respectively. The results show that RD is the most effective direction for brushing to achieve high bonding strength with the mean strength of 0.60 N/mm. The fracture surfaces of the specimen were observed using a Scanning Electron Microscope (SEM). The results represent the broad areas of mechanical bonding in the rolling direction. Further, post-annealing treatments are shown to increase the bonding strength

This study aims to improve the wear resistance of mullite ceramics as one of the most critical engineering ceramics by adding tungsten carbide (WC) particles. For this purpose, mullite-WC composites without and with adding 5, 10, and 15 % by weight of WC particles produced by Spark Plasma Sintering (SPS) method. In addition, it investigates the effect of sintering temperature on the wear resistance of mullite-WC composites applied by the SPS process at 1300 °C, 1350 °C, 1400 °C, and 1450 °C for 4 minutes under the pressure of 30 MPa. The results pin on the disk testing indicates that upon increasing the weight percentage of WC particles and increasing the sintering temperature up to 1400 °C, the wear resistance of mullite-WC composites would increase. However, increasing the sintering temperature up to the range of 1450 °C led to a decrease in the wear resistance due to the poor mechanical properties and formation of the W2C phase. The results from Scanning Electron Microscopy (FESEM) analysis are indicative of the formation of abrasive wear and surface layer structure mechanisms on the surface in mullite ceramics samples with and without WC reinforcing particles.

In this study, a particle-based model incorporating all inter-particle interactions was employed to simulate the electrophoretic deposition process. This model was also used to investigate the effect of the surface (zeta) potential of particles on the structure and configuration of particles in the deposited layer at the mesoscale. Simulations were then performed with four different values of zeta potential of particles {-5, -25, -50, -100} mV, the results of which showed that zeta potential as an important factor in determining the interaction between particles had an impact on the deposit structure and packing. Upon increasing the zeta potential up to 50 mV, the degree of order increased while the thickness and density of the deposited layer slightly decreased. Increasing the electrostatic repulsion made depositing particles push into the ordered sites in the deposited layer. Due to the high particle repulsion that prevents particles from approaching each other at the zeta potential of 100 mV, incorporation of the particles in the ordered locations decreased again. The findings of this study along with application of the proposed model can help tune the structure and packing of the resulting deposit by varying the zeta potential of particles.