مجله مواد نوین
سال چهاردهم شماره 3 (پیاپی 53، پاییز 1402)

Considering the nature of the additive manufacturing process and the produced layered structure, the possible gradient in microstructure can be predictable. For this purpose, the morphology and microstructure of the cross-section from top to bottom was evaluated. The morphology of the last and first printed layers, were also investigated.

Ti-10Mo was printed using mixed powder in 120 layers, each thickness of 25µm, by selective laser melting (SLM) with a laser power of 95 W, a scanning speed of 600 mm.s-1, and a hatching distance of 88 µm under argon atmosphere. Density was measured, and the constituent phases were identified by XRD. The microstructural feature was studied by optical and scanning electron microscopies.

The printed samples were dense, and the relative density was about 98.53%. Details in microstructural evaluation show spectacular Mo-enriched rims, which reveal the circumstance of Mo dissolution in molten Ti and homogenization, consequently. Also, a gradient in Mo dissolution is seen along the cross-section. So that, at the top, the sides of molten pools that are mostly Mo enriched are seen as thick white and bright rims in electron microscopy and as white to light purple in optical microscopy. However, at the bottom, the rims seem to be really thinner and smoother, which can be in consequence of enhanced diffusion of the Mo to Ti matrix. Here, the promoted diffusion could be in the result of heat transfer from the newly printed layer to the previous printed ones.

Plasma electrolytic oxidation is a new and upgraded method of anodizing process to improve the corrosion resistance of aluminum alloys by creating a ceramic coating on their surface.

One of the parameters affecting of PEO process as well as the performance of the prepared coatings is the composition of the substrate. In this study, the effect of increasing the percentage silicon of substrate on the plasma electrolytic oxidation process with bipolar pulse current in a silicate-based electrolytic bath was investigated. Scanning electron microscopy was used to evaluate the morphology and structure of the coating and X-ray diffraction test was used for phase detection. Coating corrosion behavior was evaluated by electrochemical tests after 1 hour immersion in 3.5% NaCl solution with the adjustment of pH 4.

coatings had a pancake structure with craters with irregular micro-cracks and micro-porosity. Investigations showed that with an increase in the percentage of silicon in the substrate, the thickness and porosity of the coatings decreased, and the volcanic morphology prevailed over the pancake morphology in the growth of the coating. Analysis showed the coatings mainly contain a mixture of γ- Al2O3, η- Al2O3, δ-Al2O3, SiO2, a small amount of mullite and some amorphous phases. Tofel polarization test revealed, in addition to reducing the corrosion current density up to 9% of the substrate silicon, we have seen an increase in the polarization resistance with the increase in the silicon percentage of the substrate after coating. The electrochemical spectroscopy test revealed that with the increase in the silicon percentage of the substrate, the coating forms a physical barrier against charge transfer substrate and the resistance of the outer layer decreases, but the resistance of the inner layer increases.

In recent years, iron oxide-based magnetic nanoparticles have been widely used for a variety of environmental and medical applications, including the purification and separation of pharmaceutical, dye, and heavy metal contaminants, as well as drug delivery and labeling systems. Due to the fact that magnetite (Fe3O4) has superior magnetic and electrical properties, iron oxide has attracted the most interest among many nanostructured materials.

In this research, magnetite nanoparticles (Fe3O4) were successfully synthesized using a green process. This method is simple, fast, cost-effective, and biocompatible. Allium hooshidaryae (Alliaceae) plant extract was used as a stabilizing and reducing agent in this process. Green synthesized nanoparticles were characterized by several structural and physical techniques, like Vibrating Sample Magnetometer (VSM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Energy Dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscope (TEM) ) and scanning electron microscope (SEM).

XRD results showed that the synthesized nanoparticles are FCC structure with high purity. FTIR results proved the binding of functional group present in this plant and Fe3O4 nanoparticles. Also, in FTIR analysis, the presence of two absorption peaks of 559.96 cm-1 and 432.57 cm-1 confirmed the successful green synthesis of Fe3O4 nanoparticles. SEM and TEM images showed that the green synthesized Fe3O4 nanoparticles are mostly spherical and have an average size of 35.73 nm. As a result, the synthesized nanoparticles have the potential to have useful benefits in future nanomedicine

In this research, the properties of zinc phosphate (single cation), zinc/nickel (double cation) and zinc/nickel/manganese (three cation) coatings were investigated.

The basic phosphating solution was prepared based on previous experiences including phosphoric acid, nitric acid, accelerators and modifiers to create an optimal coating structure. The concentration of compounds and operational parameters of temperature, time and solution pH were fixed during the process. The amount of zinc-nickel-manganese cations by zinc oxide is 1.5; Nickel nitrate 4 and manganese carbonate 3.8 (g/liter) were added to the bath. In the zinc phosphate coating solution (monocation), manganese nitrate and nickel nitrate were removed from the solution in Table 1. Zinc/nickel phosphating solution (bi-cationic) was also obtained by removing manganese carbonate from the solution. Measuring the thickness and weight of the surface unit, determining the amount of total and free acid, studying the morphology and microstructure of the coating; Corrosion resistance tests including resistance to alkali solubility, salt spray test were performed. Also, after painting the phosphated samples, paint layer thickness test, scratch and bending test, impact test and paint layer hardness were performed.

The comparison of phosphating baths showed that the weight of the coating decreased with the introduction of nickel and manganese ions. The low zinc phosphate coating has a cluster structure, while the zinc-nickel phosphate coating crystals are clustered and sheet-like, and the tri-cationic phosphate coating has a mixture of cubic and sheet-shaped structures. The difference in height and height in zinc-nickel-manganese phosphate coating; It has the lowest Ra and Rz values compared to single-cationic and double-cationic phosphate coatings. Also, the optimal three-cation coating has the highest corrosion resistance, which is due to greater uniformity, less porosity, fine crystal structure, and a high percentage of corrosion-resistant phases in the coating composition.The coating color studies indicate that the best adhesion of the paint layer is related to the tri-cationic coating. According to the researches, the zinc-nickel-manganese three-cation coating provided better results than the zinc-nickel and zinc-nickel two-cation coatings.

Nowadays, due to the reduction of fresh water resources and the increase in demand in the world, the removal of various pollutants, such as dyes, from industrial wastewaters to reuse them has received much attention.

In this research, activated carbon (AC) was synthesized by the chemical activation of apricot kernel shell, and then, this adsorbent was modified by iron-containing functional groups (FeOOH-AC) and used as an adsorbent in the removal of methyl orange from the aqueous solution. The properties of these adsorbents were characterized using BET, SEM, XRD, and FT-IR analyses.

The matching of the equilibrium data with the Langmuir model showed that the adsorption process is single-layer and the maximum adsorption capacity of AC and FeOOH–AC absorbents equal 174.6 mg/g and 249 mg/g, respectively. The increase in adsorption capacity after modification is due to the positive adsorption sites of iron (Fe-O-H2+) on the surface of the modified adsorbent, which adsorb the methyl orange by electrostatic mechanism. Also, the physical adsorption due to the porous structure of the adsorbent and π-π interaction are the effective mechanisms in the adsorption of methyl orange on the FeOOH-AC adsorbent. The analysis of kinetic data with different models showed that the pseudo-second-order kinetic model is consistent with the experimental result. The spontaneity and exothermic nature of the adsorption process were determined by determining the thermodynamic parameters.

The successive cycles of adsorption and desorption indicate the ability to regenerate and reuse the synthesized adsorbent, which can be a suitable option for use on the industrial scale.

Silver conductive lines are used extensively in electronics and optoelectronics. These lines are deposited by different methods. In this work, silver lines were deposited by spraying diluted silver ink. Silver ink was synthesized by Lewis-Walker method. Then, it was diluted by ethanol for spray deposition. Since substrate is at high temperature, both the deposition and annealing are performed at one step.

For synthesis, silver acetate, ammonium hydroxide and formic acid were used as silver source, stabilizing agent and reducing agent, respectively. Finally, the obtained ink was diluted by ethanol. Spray deposition was done with nitrogen using air brush.

Different parameters were investigated. First, ink to ethanol volume ratio of 1 to 10 was determined as optimized value. It was observed that 60 cycles of spraying gives layer thickness of 3 μm. Substrate temperature of 180˚C was determined as optimized value. Scanning electron microscopic (SEM) image showed that deposition at 40˚C led to discontinuous layer with island-like microstructure and deposition at 280˚C led to porous plate-like microstructure. But deposition at 180˚C led to continuous layer. X-ray diffraction patterns showed that silver layers deposited at 40˚C have a mixture of silver acetate and elemental silver phases, but layers deposited at 180 ˚C and 280 ˚C have pure elemental silver phase.

It was observed that low resistance silver layer can be obtained by spray deposition of diluted silver ink. The silver layer deposited at optimized condition showed resistivity of 1.4 × 10-7 Ωm.