مجله مواد و فناوری های پیشرفته
سال یازدهم شماره 4 (زمستان 1401)

In recent years, cobalt ferrite nanoparticles have ‎attracted the attention of many researchers due to their vast industrial applications. In this regard, the current study aimed to synthesize ‎CoFe2O4‎ nanoparticles in the presence of different amounts of honey (0, 0.5, 1, ‎‎1.5, 2, and 2.5 g) through the sol-gel auto-combustion method. In order to investigate the microstructure as well as the structural and ‎magnetic properties of the synthesized samples, XRD, DTA/TG, FTIR, ‎FESEM, ‎and VSM analyses were carried out. The phase analysis confirmed that the ‎high-purity cobalt ferrite nanoparticles were formed after the calcination process. The FTIR results showed that ‎the intensity of the organic bands was significantly reduced ‎by adding honey. However, the presence of this agent caused severe changes in the ‎morphology of nanoparticles ‎and also their magnetic properties. Reducing the particle and average grain sizes of the nanoparticles by the addition of ‎honey caused an increase in their coercivity and consequently, their ‎magnetic parameters were enhanced to about 1580 Oe in the sample containing 1.5 g of honey. In addition, the saturation ‎magnetization increased in the ‎presence of honey, compared to the raw sample.

In this paper, two-dimensional organic-inorganic hybrid structures with the general formulas of (BA)2PbI4 and (PEA)2PbI4 as the luminescent materials are experimentally investigated. The luminosity properties of the these organic-inorganic hybrid structures are also examined in the absence and presence of coating with thin layers of gold and platinum of 20 nm in thickness at different temperatures ranging from the room temperature to about 106 K under excitation by a light source with the wavelength of approximately 400 nm. According to the observations, illumination in the case of the (BA)2PbI4 structure at 120 K can be enhanced by 12.9 times the illumination at room temperature. In addition, illumination in the case of the (PEA)2PbI4 structure coated with a 20 nm thick platinum layer at 173 K can be enhanced 12.2 times the illumination at room temperature. These results suggest that two-dimensional organic-inorganic hybrid structures (especially (BA)2PbI4 and (PEA)2PbI4 structures) can be useful for the design of novel electronics and optoelectronics devices.

The primary objective of the current research is to produce polymeric nanofibers of chitosan and polyvinyl alcohol containing chicory plant extract and then evaluate their antibacterial effects. As remarked by numerous published articles, the chicory plant proved to be able to modulate the activity and growth of bacteria. For this reason, chicory plant extract was added to the fiber precursor in the amounts of 1, 2, and 3 %. Finally, the morphology and antibacterial properties of the resultant nanofibers were investigated. The results from Field Emission Scanning Electron Microscope (FESEM) confirmed the formation of uniform fibers whose diameters decreased from 144 nm to 95 nm with an increase in the amount of the extract in the sample. In addition, Energy Dispersive X-ray (EDX) and X-map analyses confirmed the presence of elements of carbon, oxygen, nitrogen, chlorine, potassium, sodium, and copper in the precursor of the fibers containing the extract and their uniform distribution. In this study, Fourier Transform Infrared Spectroscopy (FT-IR) helped identify the functional groups and chemical bonds in the synthesized nanofibers. According to the Ultraviolet-Visible thermometry (UV-VIS) results, one emission in the ultraviolet region with the wavelength of 263 nm and two emissions in the ultraviolet and visible regions with the wavelengths of 263 nm and 372 nm were observed in the absorption spectrum of nanofibers without and with the extract, respectively. examination of the antibacterial properties in the present study confirmed that upon increasing the amount of the extract in the sample, the antibacterial effect of the electrospun nanofibers would be intensified in exposure to both Escherichia coli and Staphylococcus aureus.

In this study, tungsten disulfide nanostructures are synthesized on the Si/SiO2 substrates by thermal chemical vapor deposition in a three-zone furnace. For this purpose, sulfur and tungsten oxide powders are first placed under argon gas in the first and third regions of the furnace at 220 and 1100 °C, respectively. A scanning electron microscope is then used to evaluate the morphology of the grown layers. The images confirm the growth of WS2 hexagonal flakes. The samples are then placed in a ceramic plant in the center of a single-zone furnace for re-annealing. The grown layers are reheated under different gases of Argon, Argon/Hydrogen, Oxygen, and Ammonia/Water at 450 °C for 30 minutes. To evaluate the annealing effect, X-ray diffraction, Raman spectroscopy, and Ultraviolet-Visible spectroscopy are employed. The results confirmed the effect of the Argon/Hydrogen atmosphere on the improvement in the optical and crystalline properties of the WS2 synthesized layers.

In this study, lead zirconate titanate (PZT) and Nb-doped PZT (PZTN) were synthesized by two-step solid-state reaction method. To this end, ZrTiO4 (ZT) was first synthesized at 1450 °C for four hours. In the next step, PZT was synthesized by calcination of appropriate amounts of PbO and ZT. Calcination of (PbO+ZT) was performed at 850 °C. Next, the prepared PZT powder was doped by 0.02, 0.05, and 0.12 mol % of Nb2O5. The cylindrical pellets of the PZT and PZTN powders were sintered at 1300 °C. The electrical properties of PZT and PZTN samples were studied at 1 KHz. The experimental results indicated that upon increasing the amount of Nb up to 0.05 mol % in the PZTN samples, the piezoelectric charge coefficient (d33), relative dielectric constant (εr), and dissipation factor (tanδ) would also increase. However, the increase in the amount of Nb over 0.05 resulted in a negative effect on the electrical properties. The values of the mentioned electrical properties in the 0.05Nb-doped sample were 360 pC/N, 1400, and 2.4, respectively.

In this study, the density, compression and mechanical properties of Si3N4-SiO2 composite with different ratios of 0, 3, 5 and 7 wt.% Eu2O3 and 10 wt.% SiO2 as additive were stdudied. Production of composite ceramics in this study was first done by preparing the powder using mixing and milling for 12 h, then forming by cold pressing method and cold isostatic pressing method and finally sintering by spark plasma sintering process. The samples were incubated at 1750 °C for 15 min at a heating rate of 100 °C / min and a pressure of 40 MPa at maximum temperature under vacuum atmosphere. After the grinding process, the particle size of the initial powder mixture was reduced by about 19 %. The results show that after the cold isostatic pressing process, the relative density of the samples increased by 14.67 %. The high amount of beta phase of silicon nitridein the 7%Eu2O3 sample indicates the sufficient amount of liquid phase during the sintering process and the improvement of the dissolution, diffusion and precipitation mechanism, and finally increase the rate of phase transformation of alpha to beta. The highest hardness of 21.61 GPa was observed in 5% Eu2O3 sample, which indicates high density, advancement of dissolution-diffusion mechanism and deposition of nitride compounds in sintering process. Eu2O3 sample due to the presence of glass phase with it can show a amount of toughness 6.1 MPa.m1/2compared to other samples.