نشریه علم و مهندسی سرامیک
سال هفتم شماره 3 (پاییز 1397)

In the present work, ZnSe nanoparticles were synthesized at pH=11.2 by aqueous method at different microwave irradiation times, and their antimicrobial properties against the Staphylococcus aureus and Bacillus cereus were investigated. X-ray diffraction and SEM have been used as structural characterization techniques, and optical properties were studied by Uv-Vis spectroscopy; Results of X-ray diffraction characterization and UV- visible spectroscopy, confirm the formation of nanoscale phase within the range of 1.942-2.142 nm. By considering the small size of nanoparticles, Antibacterial property of these nanoparticles has been done by disc-diffusion method at the presence of Muller-Hinton–Agar solid culture. ZnSe nanoparticles owing negative charge interact with Thiol groups of protein cell membrane and perturb the cell operation, and it seems that surface attaching and penetration of nanoparticles on the bacteria cell to be the most important mechanism of antibacterial activity. Generally, it can be stated that the penetration of nanoparticles to the cell walls of bacteria is the principal antibacterial feature of these nanoparticles. Among the studied bacteria, results showed that these nanoparticles have high antimicrobial property against the Bacillus cereus. Inhibition zone diameter against Staphylococcus aureus and Bacillus cereus for different samples, were respectively within the ranges of 8.96-16.86 mm and 9.37-14.34 mm, and certified the inverse relation between inhibition diameter and particle size.

Ti3SiC2 bulks have been synthesized by infiltrating Si liquid into porous precursor pellets composed of 3TiC/0.3Si. In the first step, in order to find an optimum milling time, the powders were milled at 15, 30, 45, 60, 90 and 120 minutes, then the mixture was cold pressed under the pressure of 80MPa and then infiltrated with molten Si. Based on the results of XRD and Ritvild tests, 60 minutes were selected as optimal milling time. In the second step, in order to determine the best press pressure, the powders were first milled for 60 minutes and then cold pressed under the pressure of 40, 80, 120 and 160MPa and then infiltrated with molten Si. Based on the results of XRD and Ritvild tests, 40MPa was selected as the optimum press pressure. All specimens were infiltrated in a vacuum of 10-4 torr at 1500°C for 1 hour.

β-TCP/ HA nanocomposite powders were synthesized by precipitation method at 1100°C for 2 hours and the effect of different surfactants on the resulted nano-composite powders were studied. Crystal structure and the formed phases were studied with X-ray diffraction (XRD) and Fourier transform infrared (FTIR). Investigating the size and morphology of the particles and agglomeration of the powder were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). According to the results, at Ca/P=1.58, pH=10, concentration of 0.3 molar calcium salt and 0.191 molar phosphate salt, beta-tricalcium phosphate/ hydroxyapatite nano-composites with a uniform particle size distribution a ratio of 60 to 40 in molar was obtained. Also, Span 20 as a dispersant showed better dispersion of particles than Aliquat, and reduced the agglomeration of nanoparticles to each other and resulted in the formation of nano composite particles with a particle size of 40-50 nm.

Transition metals doped-titanium dioxide (TiO2) nanoparticles can change their physical properties. In this study, pure TiO2 and Ce-doped TiO2 nanoparticles with impurity percentages of 20%, were made using tetra titanium isopropoxide (TTIP) and cerium nitrate precursors. The structure of the samples was determined by X-ray diffraction (XRD) analysis. The crystalline structure of the samples was detected as tetragonal structure in the anatase phase and the XRD results also showed that the size of the doped sample decreases. The results of scanning electron microscopy (SEM) showed the uniformity of nanoparticles. The results of the transition electron microscopy (TEM) analysis displayed that doped nanoparticles are quasi-spherical at 37 nm. Diffiused reflectance spectroscopy (DRS) analysis revealed that the band gap energy decreases to 2.21 eV for doped sample. The results of photoluminescence (PL) analysis demonstrated that the intensity of PL decreases for doped sample, which reduces the recombination of the electron-hole and increases the photocatalytic activity of Ce-doped TiO2 nanoparticles.

Ceramic membranes are used in water treatment process have many advantages in comparison with usual polymeric membranes. Hence in this study synthesis of low-cost ceramic membranes with simple and accessible materials also properties of water passing through it were discussed. An apparatus was made for testing membranes. Then porous ceramic membranes were made through press and slip casting process. Row materials which are contain ceramic powder such as: Alumina with 84% wt, Kaolen with 12%wt and Feldspar with 4%wt and some additives, various tablet of ceramic membranes in several thickness was made in different conditions of pressure, temperature and materials amount. Generally, results show the power of ceramic membranes in water treatment process, usage a tablet with 20mm thickness could decrease TDS from 950 ppm to 400 ppm and in usage a series of tablets in 10, 10 and 20mm TDS decreased from 1200 ppm to 320 ppm.

Poly (ε-caprolactone) (PCL) / Dicalcium phosphate dihydrate (DCPD) composite nanofibers were prepared in an appropriate solvent of chloroform / methanol (75:25) by electrospinning method. The results of the scanning electron microscope showed uniformly diameter of fiber and bead-free structure by changing the electrospinning parameter. Elemental mapping results confirmed the presence and proper distribution of DCPD nanoparticles into PCL matrix. The results of measuring the contact angle represents the reduction of the contact angle of scaffold with average diameter higher compared with an average diameter less. Bioassay (cell survival) was performed by MTT assay and the lack of toxicity of the scaffolds for human gingival cells (HGF) was revealed. Also, better wettability and hydrophilicity have provided more favorable conditions for adhesion, growth and proliferation of cells, and more biocompatible composites have been obtained. These results indicate that PCL-DCPD composite scaffold can provide a suitable substrate for the growth of bone cells.

Gypsum is widely used in various industries because of its easy fabrication feature, environmental friendliness and low price. This study was investigated the effect of sodium nitrate as an additive on the physical and mechanical properties of building plaster bodies. Sodium nitrate was added to the amounts of 0.2, 0.4 and 0.8% by weight of gypsum. According to the results, sodium nitrate plays an accelerator role and reducing the setting time of gypsum. Addition of sodium nitrate leads to improvement of the mechanical properties of the gypsum body. The highest flexural strength and compressive strength were obtained for sample containing 0.4 wt% sodium nitrate. By adding 0.4 wt% sodium nitrate, compressive strength and flexural strength increased by 80% and 73%, respectively. The addition of sodium nitrate reduced the porosity and absorption of water of plaster. The X-ray diffraction results indicated that the presence of sodium nitrate created a higher degree of hydration. The higher strength of gypsum bodies could be attributed to lower porosity and needle-like interlocked microstructure. Sodium nitrate can lead to an increase in the precipitation rate of dihydrated calcium sulfate crystals from the saturated solution which can results in a reduction in the setting time and increasing mechanical properties due to the formation of microstructure with more interlocked crystals.