مجله مواد و فناوری های پیشرفته
سال دوازدهم شماره 3 (پاییز 1402)

To date, a number of methods have been employed to remove paranitrophenol (PNP) as one of the organic pollutants and nitroaromatic compounds from water. In the present study, the PNP removal process was investigated using surface adsorption and synthesizing cyclodextrin-based adsorbents. To this end, beta-cyclodextrin polymer insoluble in water was first obtained in a green way using citric acid as a cross-linking agent with the efficiency of 81.25% at the swelling rate of 166.7 and after structural characterization, it was used in the adsorption experiments. To expand the contact surface area, some bases such as sawdust and alumina were used as the cyclodextrin supports, and the effect of different parameters on their adsorption capacity such as the contact time, pH, PNP initial concentration, temperature, and adsorbent dosage were studied. The experimental data were then fitted to the kinetics models and adsorption isotherms. It was found that for the synthesized adsorbents, the adsorption kinetics followed the pseudo-second-order equation, and the equilibrium data were more consistent with the Freundlich model. The qmax values ​​for β-cyclodextrin-citric acid, β-cyclodextrin-sawdust, and β-cyclodextrin-alumina adsorbents were obtained as 40.98 mg/g, 43.29 mg/g, and 38.46 mg/g, respectively. Finally, the adsorption thermodynamic was investigated and the standard enthalpy, entropy, and Gibbs free energy changes were calculated.

Energy harvester devices have garnered enormous attention in various technologies, such as wearing and portable devices. The current study aims to design and fabricate tribo/piezoelectric hybrid nanogenerators with electrodes made of Aluminum and Copper and Zinc Oxide nanostructures composite embedded in the PDMS. According to the morphology studies, Zinc Oxide nanosheets grew uniformly in the (103) crystal direction on the Aluminum substrate. In contrast, the nanorods that grew on the Copper substrate were disorderly with a large angle to the surface. The results indicate that the 1000 rpm deposition PDMS layer sample with Aluminum electrodes and Zinc Oxide nanosheets generated the highest voltage and current equal to 120 V and 24 µA, respectively. Both Copper and Aluminum electrodes coupled with ZnO nanosheets nanogenerator had the lowest voltage, current, and power generation. The hybrid nanogenerator with two aluminum electrodes and Zinc Oxide nanosheets generated the highest power equal to 0.97 Wm-2. According to the obtained results from the characterization of hybrid piezo/triboelectric nanogenerators, Aluminum electrodes with Zinc Oxide nanosheets embedded in PDMS exhibited better performance, hence a suitable option for harvesting mechanical energy for self-charging devices.

The important features of silicon nitride (Si3N4) such as proper strength, low dielectric constant, low loss tangent and high wear and thermal shock resistance have made this ceramic as one of the few suitable ceramics for use in antenna protection. Due to the difficulties in the sintering of Si3N4 samples, in this research, the fabrication of this body was investigated by nitridating a pressed silicon powder without using any additive; because the effect of additives on the loss of properties has been proven. In this regard, silicon powder along with 0, 0.5, 0.7, and 1 wt.% of iron oxide were pressed, and nitridated at the temperature of 1420 degree celsius for 2 hours under the different nitrogen gas pressures of 200, 400, and 600 millibars. The density, porosity, phase composition, and microstructure of the samples were evaluated. Results showed that the minimum pressure for nitridation is 600 millibars and the optimal percentage of iron oxide is 0.5 wt.%.

Compared with carbon nanocones, Boron Nitride Nanocones (BNNCs) are characterized by different physical, chemical, and electronic properties. Since BNNCs are in three types of covalent bonds (B-N), B-B, and (N-N), carbon nanocones contain only C-C bonds. Given that the structural properties of nano cones depend on the disclination angle of the cone, the current study aims to discuss the electronic and structural properties of boron nitride nanocones in different sizes (height and disclination angle) using Density Functional Theory (DFT) calculations. To this end, the relevant calculations were done for boron nitride nanocones with the cone heights of 1 to 5 angstroms at the disclination angle of 60°, 3 to 7 angstroms at the disclination angle of 120°, and 4 to 8 angstroms at the disclination angles of 180 and 240°. In this work, the density of states, quantum parameters, analysis of bond order, bond length, polarizability, anisotropic polarization, dipole moment, atomic charges, and frequencies were calculated using the DFT. According to the results, the best structure was identified based on the height and disclination angles to be further used in the next calculations. It is hoped that the results of this project can be useful in expanding the experimental works and effective in the design of nanocones as well in order to absorb gases, drugs, etc.

In this article, Low-Pressure Injection Molding (LPIM) method was investigated as a method for forming zirconia (zirconium oxide) parts. It is one of the methods used for manufacturing engineering ceramics with complex shapes & high dimensional accuracy. In this method, a binder composition (paraffin & industrial waxes) is used as the plasticizing agent to shape zirconia particles. Different parameters such as temperature, pressure & injection time, mold temperature, etc. have been found to be effective in shaping the ceramic parts based on this method. Throughout this research, these parameters were examined, & their optimal values were obtained. The optimal injection temperature was in the range of 80-90 Celsius degree, injection pressure in the range of 3-5 bar, & injection time in the range of 10-15 seconds to form a crucible with the size of 130×85×75 mm (height×internal diameter×external diameter). This study also examined the FESEM images of the microstructure of parts in the injected, debonded, & sintered bodies. According to the findings, the zirconia crucible in this article shows notable similarity with the crucible made by Zircoa company with the code 3001 in terms of physical properties such as bulk density & apparent porosity.

In the present study, an aluminum-silicon hypoeutectic alloy matrix composite reinforced with metallic glass particles was produced through Powder Metallurgy (PM) method. In the first step, the synthesized matrix powder particles with Al-11wt%Si composition were mixed with Fe-based Metallic Glass (FMG) particles as the reinforcements. In the next step, Spark Plasma Sintering (SPS) method was employed to produce composite bulk parts. For comparison, pure aluminum powder particles were sintered under the same conditions. The phase studies confirmed some alterations in the intensity and diffraction angle of crystalline peaks for the composite compared to pure aluminum. Moreover, they remarked a change in the location of the amorphous hump in the XRD pattern of composite, compared to its former location in the amorphous powder particles. Further analysis of the XRD patterns proved the solubility of a large portion of silicon in the aluminum. Microstructural studies, along with quantitative analysis, indicated the homogenous distribution of the FMG particles and undissolved silicon particles in the aluminum matrix. The yield and compressive strength values of the composite sample were obtained as 165 and 289 MPa, respectively, showing a significant increase compared to the pure aluminum sample. Finally, the contributions of different strengthening mechanisms to the enhancement of the composite strength was elaborated