نشریه فرآیندهای نوین در مهندسی مواد
پیاپی 70 (پاییز 1403)

In this study, for preparation of theYAG silicate glass and glass-ceramic by melting method the cerium sulfate and cerium oxide salts were used separately.According to Luminescence results of both glasses there were emissions spectrums in the range of 460 and 420 nm wavelength related to cerium ions. It was shown that by heating treatment, garnet crystal (in sulfated sample) formed less than the sample with cerium oxide. The emission of both glass-ceramics caused by excitation at 240 nm in the range of 460 nm wavelength. Also, the 534 and 660 nm wavelengths emissions were obtained by 340 nm wavelength excitation. Heat treatments were done by oxidic atmosphere in tubular furnace (single step) and powder SPS sintered powder and in hydrogen atmosphere in two steps. According to XRD results the 24 hrs. heat treating time and the 1060˚C temperature has an effect on the entry of cerium into the garnet structure. Finally by comparing the spectroscopy results the optical response of the garnet glass-ceramic synthesized in the hydrogen atmosphere is obtained at a wavelength of 400 nm. It is claimed that this garnet can be applied in LED industr.

In this research, the leaching process of low-grade copper oxide ore in dilute sulfuric acid in the temperature range of 25-55 ℃ was studied from a kinetic’s point of view. The effect of temperature and liquid to solid ratio on dissolution rate was investigated. Shrinking core model (SCM) was used to investigate the reaction mechanism and to extraction of kinetic equations governing the process. The results show that increasing the liquid to solid ratio up to 8 ml/g increases the efficiency of the copper dissolution process, but its further increase will not affect the process efficiency. Maximum copper recovery equal to 95 wt% was achieved after one hour of leaching in 1 M sulfuric acid at 55 ℃, stirring speed of 350 rpm and liquid to solid ratio of 8 ml/g. The results also show that Mathematical model of dissolution rate, can be described by Gumpertz equation. Kinetic studies indicate that the reaction is controlled by simultaneous diffusion in the liquid boundary layer (liquid film) and in the ash layer (solid products layer). The activation energy of 12.5 kJ/mol was obtained for the process.

Cast iron has a special place in various industries due to its low price and production ease. It seems that the use of machining chips is a suitable solution for alloying and increasing the mechanical properties of cast iron. In this research, continuous swarf resulting from IN718 machining with aligned placement in the foam was carried out. After placing the swarf, GG20 cast iron was cast by the lost foam method. After casting, the composite and simple samples were normalized at 900ºC. Microstructural studies were showed that the structure contains type A and C graphites and fine pearlites in the presence of chips. Also, the presence of swarf disturbed the solidification balance, which ultimately resulted in the presence of ferrite areas in the vicinity of the swarfs. As a result of normalization, the C graphites of the simple sample were removed entirely. Allotriomorphic ferrite was formed in the composite sample at the interface, and fine A-type graphites were distributed in fine pearlite matrix. The addition of swarf increased the hardness from 132 to 153 HB due to the creation of local saturated solid solution, compositing, and normalizing due to the mentioned microstructural changes the hardness of both samples increased to 148 and 180HB. Swarf acted as a barrier against crack growth causing the formation of soft phases and finer pearlite and graphite. The sample’s impact energy increased from 3 to 3.5J. With normalizing, the fracture energy of the simple sample increased to 4.12J while the composite sample to 6.1J.

The use of environmentally friendly energy storage systems is known as the best solution to reduce the bad effect of fossil fuels. Supercapacitors have received more attention than other energy storage devices (batteries and fuel cells) due to their high power density, high cycling stability and optimal energy density. The use of inexpensive and available electrode material is the key to the development of supercapacitors in industrial and commercial scales. Using these two together can achieve a morphology with many electrochemically active sites, the combination of oxide supercapacitors with carbon nanocompounds will have a great effect on its electrochemical properties In addition to being cheap and readily available, nickel and cobalt oxides with reduced graphene oxide have a high theoretical specific capacity. In this study electrode material nickel oxide graphene, cobalt oxide (NiCo2O4/NiO/RGO) electrode was synthesized using Sonochemistry method. After synthesis, nanoparticles were mixed with 1:5 ratio of nanoparticles and graphene oxide. The size range of nanoparticles in this nanocomposite is from 30 to 60 nanometers Then, the characterization tests of XRD, FT-IR and SEM were used to determine the crystallographic and morphological properties. Characterization analyses showed that the electrode material of (NiCo2O4/NiO/RGO) was obtained with a hollow microbial morphology. Electrochemical tests of CV, GCD and EIS showed that the (NiCo2O4/NiO/RGO) electrode had excellent supercapacitive performance with a specific capacitance of 400 F/g at a current density of 1 A/g. This performance is related to the synergistic effect of nickel cobalt oxides with RGO, which provide the porosity and active sites necessary to carry out the charge transfer reaction.

The aim of this study was to synthesis different polyaniline and orange peel composites in aqueous and non-aqueous solvents in the presence of polyethylene glycol and investigating of its performance in adsorption of lead. Adsorption experiments were carried out using this composite in batch mode. The results showed that the polyaniline and orange peel composite had a higher lead removal rate than the orange peel alone. The best composite synthesized in water and ethanol solvents in the presence of 2 g / L of polyethylene glycol with 82.12% removal efficiency. In all the synthesized composites, the presence of polyethylene glycol was very effective at the synthesis stage and was able to increase the removal efficiency. The results of BET analysis showed that the specific surface area in the polyaniline and the orange peel composite synthesized in water and ethanol in the presence of 2 g / L polyethylene glycol with 7.026 m2 / g was above all. The SEM images showed better and more uniform polyaniline coating on the orange peel in this composite. For polyaniline and orange peel composite synthesized in water and ethanol solvent in the presence of 2 g / L polyethylene glycol, optimum pH was occurred at pH 6, the optimum contact time was occurred at 30 min and the adsorption process was followed by Langmuir and Freundlich isotherms. The maximum adsorption value for this adsorbent was 25.51 mg / g.

In the current research, ST37 Steel was Joined with E6010 and E6013 Electrodes by SMAW. After samples preparation, the evolution of Microstructure was carried out by OM and SEM in addition  the  Impact, Tensile, Bending and Microhardness tests were performed. The results shows that by decreasing time and increasing Cooling Rate, the Microstructure of Weld Metal that Welded with E6013 Electrode from Widmannstatten and Fine Ferrite has changed to Acicular and Fine Coaxial ferrite with lower average Grain size of Weld Metal using E6010 Electrode. Also, Welded sample with E60l0 Electrode shows smaller mean diameter and volume fraction of Inclusions (2.3%) compared to Weld Metal using E6013 Electrode (3.6%). Additionally, Impact Energy of specimen E6010 After the Welding process was changed from 87 to 25.5J with changing Temperature from 25 to -30℃ meanwhile, Impact Energy of sample that welded with E6013 was changed from 61 to 17.5J. Also, Impact Energy of specimen E6010 After 562 days of the Welding process was changed from 83 to 18.5J with changing Temperature from 25 to -30℃ meanwhile, Impact Energy of sample that Welded with E6013 was changed from 51 to 8J. The results of Tensile test shows that both samples that Welded with E6010 and E6013 Electrodes have same Yield Strength and Ultimate Tensile Strength in Weld Zone. The result of Bending test shows that both samples have equal Ductility and Flexibility. The results of Microhardness test shows that the average of Hardness for both samples is same and the quantity of Hardness are 148 and 150 HV for Welded sample with E6010 and E6013 Electrodes, respectively.