فهرست مطالب hamid reza bakhsheshi rad

Computed tomography imaging can help in the diagnosis of diseases in the early stages and provide important information about the pathology of processes. Computed tomography imaging relies heavily on the development of complex contrast agents to detect biological processes even in the cells. Nano contrast agents have a significant advantage over iodine-based molecules like creating high contrast and long circulation in blood. In this study, Tungsten trioxide nanoparticles were fabricated by the co-precipitation method to improve the contrast in computed tomography images; and to stabilize and increase contrast, Ultravist was used as coating utilizing the ultrasonic bath method. To determine the characteristics of Tungsten trioxide nanoparticles, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction test (XRD), vibrating sample magnetometer (VSM), dynamic light scattering (DLS), and zeta potential were performed. The result of the SEM test indicates nanoparticles morphology. The result of X-ray diffraction analysis showed that nanoparticles have the chemical formula (WO3) and have more adjustment with Monoclinic Crystal system coding JCPDSNO-43-1035. The vibration Sample Magnetometer proved that the nanoparticles are Ferromagnetism agents. To illustrate the suspension stability and also particle dimension, zeta-potential and optical Dynamic-Dispersion have been used. Zeta potentiality was 25±2 Millivolt (mv) and optical Dynamic-Dispersion was 383.7, 2616.2 nm. And finally, Scanning findings have been compared with iodine-based molecules indicating that in similar density, nanoparticles (WO3) with Ultravist cortex have higher contrast and better image clarity.

In the current study, the effect of colloidal copper nanoparticles on the deposition rate and hardness of Ni-Cu-P coating deposited by electroless method on L80 steel substrate was investigated. Copper particle size, microstructure, chemical composition, and hardness of the coating before and after heat treatment at different temperatures were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDS) analysis, and microhardness. The microstructure study by XRD showed that the Ni-Cu-P coating has an amorphous structure. The heat treatment at 400 °C transformed the structure from amorphous to crystalline and formed Niα, Ni3P, and Ni3.8Cu phases. The amount of copper nanoparticles in the coating 4.58 wt% was measured. The deposition rate of the Ni-Cu-P coating was 11 µm/h. Furthermore, the hardness of the coating increased from 738HV to 1300HV by performing heat treatment.

In this study, the effect of adding graphene oxide on the terbiological behavior of coatings created by the electrolytic plasma oxidation process under constant voltage conditions has been investigated. Bipolar waveform coating operation was performed on the surface of AZ31 magnesium alloy for 10 minutes. The results showed that the surface morphology of the coatings had micro-cavities known as pancake structure and volcanic crater on the surface, the diameter of which increased with the addition of graphene oxide. Fuzzy analysis of coatings showed that the coatings are composed of oxide phases of forsterite and periclase. The wear mechanism of the coated samples was scratched. Also, the wear resistance of the coating containing graphene oxide additive increased so that the average coefficient of friction for the mentioned samples decreased 10 times compared to the uncoated sample, which is due to the increase in hardness. The hardness of the sample containing graphene oxide has increased about 5 times compared to the magnesium alloy. Magnesium alloy with this coating is a good candidate for orthopedic applications.

The effect of hydrofluoric acid (HF) treatment on the corrosion performance of the Mg–Zn–Al–0.5Ca alloy was studied by immersing a specimen in HF solutions for varying lengths of time at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the evolution of microstructures. In vitro corrosion resistance was assessed using potentiodynamic polarization and a room-temperature immersion test in Kokubo solution. The fluoride-treated Mg–Zn–Al–0.5Ca alloy formed by 24h immersion in HF exhibited a more homogeneous, compact, and thicker (2.1 μm) coating layer compared to the other HF treated specimens in 6, 12 and 18 hours. The corrosion resistance performance of the Mg–Zn–Al–0.5Ca alloy formed by 24h immersion in HF was the best, with a corrosion rate of 2.87 mm/y according to the electrochemical experiment. The mean weight loss of the untreated samples was more considerably higher (up to 2 times) than that of the fluoride-treated alloys, according to in vitro degradation assessments. According to the findings because of its low degradation kinetics and apatite formation ability, the fluoride-treated Mg–Zn–Al–0.5Ca alloy is a promising candidate for biodegradable implants.

In this study, ultrasonic bath and milling processes were used to synthesis epoxy resin-multiwalled carbon nanotubes (MWCNT) composite, and their effect on the absorption of magnetic waves was investigated using the Vector Network Analyzer (VNA) test. The effect of the concentration of MWCNT used to attract the wave's magnetic part in the epoxy resin matrix is also investigated. This study showed that the optimal amount of MWCNT in this epoxy resin-MWCNT composite was about 5 wt.% for the ultrasonic bath method, while it was around 15 wt% for the milling method. The ultrasonic bath caused the reflection losses (RL) value reaches to about -25 dB in the range of 9 to 11 GHz. The results of the VSM test showed that the composite produced from epoxy resin and MWCNT is a soft magnetic material. Also, the sample produced in the ultrasonic bath process has a higher magnetic saturation than the milling process, which causes it to absorb more electromagnetic waves.

The Persian direct reduction method (PERED) is a suitable method for producing sponge iron on an industrial scale. The challenge of all sponge iron production plants is to supply sponge iron with suitable metallization to steel factories. Accordingly, determining and adjusting the various parameters affecting metallization in each plant is necessary to produce the appropriate amount and quality of sponge iron. In this study, first, the effects of output rate, process flow, water- steam flow rate, bustle temperature, bustle CH4 level, CO2 reform, average pellet size (PIDa), pellet strength (CCS), process gas water temperature, and furnace bed average temperature on spongy iron metallization were investigated. Then, an attempt was made to model the sponge iron grade produced by the PERED method using the Gene Expression Programming (GEP) software. To carry out modeling, data on the affecting variables of metallization were collected for 58 days. The best R2 values for the training and testing sets were 0.974 and 0.27 with a low error rate for both (0.047 and 0.376 in RMSE and 0.001 and 0.141 in MSE, respectively. The results of the sensitivity test indicated that CO2 reform gas, bustle CH4 level, and average pellet size had the most significant effect on metallization.

One approach for the preparation of Mg-3Zn-1Mn nanobiocomposite is powder metallurgy. After preparing the alloy by the milling process, hardening is conducted during the sintering process. The condition for obtaining high strength and corrosion resistance of as-sintered specimens is the uniform distribution of zinc and manganese elements in the magnesium matrix and the maximum particle size reduction to increase the surface area. In this research, under certain conditions, the milling process has been conducted to fabricate this nanocomposite. The result of XRD analysis exhibited that the optimal sample is obtained after 25 h milling. At this time, the grain size was 27 μm, and the crystallite size was 24 nm. Evaluation of X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and field emission scanning electron microscopy (FE-SEM) results for samples shows uniform distribution of zinc and manganese particles in the matrix of magnesium and confirms the reduction of particle size with spherical shape for nanobiocomposite specimens.

In this study effect of active material particle size distribution (PSD) on TiNb2O7 electrodes and their performance were evaluated. To determine the effect of PSD, have focused on the performance of the electrode, which is mainly affected by the performance of individual particles and their interaction. For this purpose, TiNb2O7 was successfully synthesized by mechanochemical method and post-annealing, as an anode material for lithium-ion batteries. Phase identifications and microstructure characterization was carried out by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to identify the phases and evaluate the morphology of the synthesized samples. The charging and discharging tests were conducted using a battery-analyzing device for evaluating the electrochemical properties of the fabricated anodes. Eventually, at faster charging rates, the electrochemical performance was found to be improved when smaller active material particle size distribution was used. Differences in particles size distributions resulted in variable discharge capacities so that the sample with particle size higher than 25 microns (>25 μm) showed a capacity of 19 mAh/g after 179 cycles, which had a lower capacity than their sample with particle size less than 25 microns (<25 μm). The final capacity of the sample with a particle size less than 25 microns is 72 mAh/g.

The structural and magnetic properties of the polyethylene glycol (PEG) coated nickel spinel ferrite (NiFe2O4) nanoparticles have been reported in the present study. NiFe2O4 nanoparticles were prepared by solution plasma method using KOH + Na2Co3 as electrolyte. The prepared powder of nickel ferrite nanoparticles was annealed at 800 ˚C for two h and used for further study. The X-ray analysis confirmed the formation of a cubic spinel single-phase structure. The crystallite size, lattice parameter, and X-ray density of the PEG-coated NiFe2O4 nanoparticles were calculated using XRD data. TEM and FTIR studies revealed the presence of PEG on nickel ferrite nanoparticles and reduced agglomeration in the NiFe2O4 nanoparticles. The pulse-field hysteresis loop tracer technique studied the magnetic properties at room temperature. The magnetic parameters such as saturation magnetization, remanence magnetization, and coercivity have been obtained. These magnetic parameters were get decreased by PEG coating.

In this study, the effect of heat treatment on the corrosion properties of Mg-Zn-RE-xCa alloy (x = 0, 2.5) was investigated. These alloys were produced using an argon atmosphere casting process and then subjected to vacuum conditions at 400 C for 6 hours under solid solution treatment and quenching in water. The microstructure and fuzzy analysis of heat treatment alloys using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were investigated. Immersion, polarization, impedance, and pH changes test were performed to study alloy corrosion behavior. The results showed that in heat treated samples, the values of secondary phases IM1 (Ca3MgxZn15-x) (4.6 ≤ x ≤ 12) and Mg2Ca increased with increasing calcium content. However, the amount of these phases is reduced by dissolution and quenching in water. The corrosion density of alloy is reduced by adding 2.5% calcium from 488.4 to 315 μA / cm2, which decreases to 126.5 μA / cm2 after 6 hours of heat treatment, indicating improved corrosion resistance of the alloy after heat treatment.

In this study, mechanical properties and apatite formation ability of synthesized fluorapatite-hardystonite (FA-HT) nanocomposite scaffolds were investigated. Hardystonite (HT; 5 and 10 wt.%) as a reinforcement phase was incorporated into the FA scaffold. FA was mixed with HT for 4 h under argon gas at 220 °C. A space holder method was used for fabricating porous FA-HT scaffolds. Sodium chloride (NaCl) was used as pore-forming agent in this method. Then, the powder was compacted under a pressure of 220 MPa. Finally, the samples were sintered at 1000 ºC for 2 h. The X-ray diffraction (XRD) results of the synthesized scaffolds confirmed the formation of FA and HT powders. Studying the microstructure of the samples showed that synthesized scaffolds had a porous structure with interconnected pores, similar to the porosity degree of natural bones. The results also revealed that the mechanical properties of scaffolds were improved; the compressive strength values of the FA-5HT and FA-HT scaffolds were obtained 1.6 MPa and 2.8 MPa, respectively. The young modulus values for these scaffolds were 5.5 MPa and 12.4 MPa, respectively. Results of bioactivity test showed the ratio of calcium to phosphate (Ca/P) in scaffolds was 1.71±0.3 and 1.60±0.5 for FA-5HT and FA-10HT samples, respectively. Based on the results, FA-HT scaffolds have desirable mechanical properties and suitable level of bioactivity which can be used as new and promising biomaterials in bone tissue engineering and repairing bone defects.