مجله مواد نوین
سال سیزدهم شماره 2 (پیاپی 48، تابستان 1401)

Nano copper powder is prepared by various methods, which can be mentioned as chemical regeneration, evaporation-deposition, plasma, chemical mechanical, electric explosion, electrolytic deposition and liquid metal atomization methods. Among these, the electrolytic method is more ideal due to the simplicity of the process, low energy consumption, high efficiency, easy control, and low environmental pollution. In this research, the role of electrode material and protective concentration in the electrochemical synthesis of copper nanoparticles was investigated.

constant current density and temperature equal to 0.04 A/cm2 and 50 C° and the distance between cathode and anode 2.5 cm were considered as research constants. Research variables included copper, gold, steel and rubidium cathode electrodes as well as CTAB protective concentration

. The results showed that smaller crystals can be obtained with copper and gold cathodes. XRD analysis showed that the best purity of copper nanoparticles is obtained by copper cathode. SEM results showed that the gold cathode leads to the formation of spherical and non-cubic particles; and the copper cathode caused the formation of cubic particles. By increasing the amount of CTAB, the purity of copper increased and the growth of copper nanoparticles was effectively prevented. The crystallinity index is more than one and the copper metal is polycrystalline.

Fitness-for-service (FFS) assessment is one of the standard methods used in oil and gas structures. This method is for assessment the defects of pipes and equipments, which can be operated without repair or replacement if the existing defects are within the accepted range of this standard.

During inspection of an 7-km-long pipeline made of API X52 steel carrying hydrocarbons containing wet H2S, hydrogen-induced cracking (HIC) and Lamination was found at different locations along the pipeline length. Microstructural investigations by scanning electron microscopy (SEM) showed stepwise cracking (SWC) as the result of the presence of MnS inclusions. Fitness-for-service (FFS) assessment based on API579-1/ASME FFS-1 was performed to decide on the pipeline serviceability.

The finite element analysis (FEA) results showed that the HIC-damaged pipeline was acceptable per level-3 FFS requirements and the pipeline understudy was fit for service. The remaining life of the damaged pipeline should also be periodically monitored using failure assessment diagram (FAD).

In the present study, the Ti-10Mo-X (TiC & TiB2) composite produced by spark plasma sintering (SPS) with different amounts of ceramic reinforcements (0.5≤ X ≤ 4) was chosen as substrate for development of new biomaterials. The aim of this study was applying the calcium phosphate (CaP) coating with appropriate quality and phase composition on the Ti-10Mo-X (TiC & TiB2) composite materials for biomedical application.

The Ti-10Mo-X (TiC & TiB2) composites were sintered by SPS method, at an initial pressure of 10 MPa, an intermediate pressure of 20 MPa and a final pressure of 50 MPa at 1150 . Then the CaP coating was applied on the substrates by electrochemical deposition method at three different DC current densities of 0.5, 0.6 and 0.7 mA.cm-2 for 30 minutes. Optical electron microscopy (OM) was used to study the pore structure of the substrates containing the different amounts of ceramic reinforcements. To take a look at the physical properties of the substrates, the sintering density became measured based at the Archimedes method. A tensile test became additionally performed to check the tensile strength of the porous substrates. Scanning electron microscopy (SEM), X-ray energy distribution spectroscopy (EDS) and X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were also used to investigate the morphology, chemical and phase composition of the obtained coatings, respectively.Wettability of the CaP coatings was also investigated using the static droplet contact angle method. At last, the apatite forming ability test of the coated sample were carried out in SBF solution.

By increasing the percentage of ceramic reinforcements because of the removal of porosity, the density and tensile strength of the substrates have raised. Comparing the SEM images showed that, besides the applied current density, the properties of the substrate, such as the percentage of porosity and hydrophilic behavior had an impact on the morphology of the coatings. Moreover, by increasing the current density from 0.5 to 0.6 and 0.7 mA.cm-2, the apparent quality of the coating decreased and the amount of porosity in the coating increased. In addition, the Ca/P ratio in the coating applied on the 1.0-T1150 and 2.0-T1150 samples at the current density of 0.5 mA .cm-2 was measured to be 1.60 and 1.67, respectively, which is close to that of the natural apatite. Furthermore, the results of XRD and FTIR analysis revealed that the coatings formed on these samples at 0.5 mA cm-2 were mainly containing hydroxyapatite (HA) phase. In addition, after the sample was immersed in simulated body solution (SBF) for 3, 5 and 7 days, a layer of apatite spheres was formed on the surface, indicating the high mineralization ability of the coated sample and hence the prepared sample has a sensible bioactivity.

In this research, barium carbonate was synthesized via mechanochemical method from the mixture of barite concentrate-sodium carbonate. The producing of barium carbonate form barite concentrate and the evaluation of the phases/products were the goal of this research.

After crushing the barite concentrate, the acid washing process was done with 1 N of HCl. The mixtures of barite concentrate-sodium carbonate with different molar ratios (BaSO4:Na2CO3=1:1, 1:2, 1:2.5) were prepared and milled in a planetary mill for different times (2 and 5 hours). The as-milled samples and the heated products were dissolved in distilled water and then the solid residues were dried in an oven. The isothermal heating of the samples was done into the alumina and zirconia crucibles. The unmilled mixture of barite concentrate-sodium carbonate was also prepared. The findings of this research were evaluated using XRF, XRD and STA methods and the microstructures of the samples were studied by SEM method.

The2 and 5 h-milled mixtures showed the sign of chemical reaction between the starting materials (barite concentrate-sodium carbonate) at 720⁰C in STA results. This sign however was observed at 735 ͦC in the unmilled mixture. According to XRD patterns, the chemical reaction between barite concentrates and sodium carbonate was not completed in the milled mixtures. The signs of orthorhombic phase of barium carbonate were observed in the products after isothermal heating at700⁰C for 1 h. The results indicated that the isothermal heating of the milled mixture of barite concentrate-sodium carbonate with a molar ratio of 1:2.5 at 750⁰C for 2 h was the suitable conditions for synthesizing of barium carbonate. Additionally, the weak signs of an intermediate phase (Ca4Ba2Si6O18) were observed in the XRD patterns of the barite concentrate-sodium carbonate mixture. For comparison, the experiments were performed with pure barium sulfate sample (Barex). In the product of isothermal heating (750⁰C, 2 h) for the mixture of barium sulfate (Barex)-sodium carbonate (molar ratio :1:2.5), barium carbonate phase was produced and no trace of the intermediate phase was observed. The results of this research showed that it is possible to synthesis barium carbonate phase from the mixture of barite concentrate-sodium carbonate using ball milling process and isothermal heating.

In this research, the structure and mechanical properties of aluminum 6061 composite with graphene reinforcing nanoparticles produced by friction stir method (FSP) were investigated. The rotation speed of the tool was set from 112 to 280 rpm, the speed of the tool movement in the range of 31.5 to 20 mm/min and the slope of the conical tool was set at 2, 2.5 and 3 degrees.

Characterization was done by tensile tests, microhardness, field emission scanning electron microscope (FESEM) along with X-ray energy spectroscopy (EDS) and optical microscope (OM). The results show that in the presence of graphene as a reinforcement, the mechanical properties are improved.

By increasing the ratio of rotation speed to tool movement speed (advance per revolution) from 0.07 to 0.28 and increasing the tool angle from 2 to 3 degrees, tensile strength enhanced from 338 to 396 MPa, yield strength from 319 to 383 MPa and the elongation increase has increased from 10.9 to 12.3 percent. Also, the micro-hardness in the nugget area increased from 273 to 400 Vickers.