Journal of Advanced Materials in Engineering (Esteghlal)

---

In recent years, many different plans have been considered to use the nuclear energy gained from inertial confinement fusion (ICF) as attempts to obtain high energy efficiencies. In conventional ICF methods, a small amount (about mg) of the deuterium–tritium compound is confined in a small spherical chamber of a few millimeters in radius and compressed by laser or heavy ion beams with powers in the order of W. The consequent plasma froming at the center of the chamber is an essential issue for fusion. The hydrodynamical instabilities during the fuel compression process arising in the conventional ICF technique leads to a decline in energy efficiency. The new plans for reducing instabilities involve compression of the fuel chamber in two stages using laser or ion beams. In the first stage, fuel is preheated by laser or ion and in the second phase, relativistic electrons are constructed by -W laser phases in the fuel. This heating method has come to be known as a fast “ignition method”. More recently, cylindrical rather than spherical fuel chambers with magnetic control in the plasma domain have been also considered. In this work, fast ignition method in cylindrical fuel chambers will be investigated and transportation of the relativistic electrons will be calculated using MCNP code and the Fokker–Planck program. Furthermore, the transfer rate of relativistic electron energy to the fuel will be calculated. Our calculations show that the fast ignition method and cylindrical chambers guarantee a higher energy efficiency than the one-step ignition and that it can be considered an appropriate substitute for the current ICF techniques.

---

In this paper, bare spot defects in hot-dip galvanized sheets were studied in terms of the microstructure and their influence on the corrosion and mechanical properties. Surface characteristics and microstructural features were examined by scanning electron microscopy equipped with energy dispersive spectroscopy microanalysis system. The results showed that the major cause of the bare spots was the lack of wetability of the sheet surface due to contamination, improper heat treatment or chemical composition. Corrosion resistance was evaluated by standard salt spray test. Mechanical properties were examined by tensile testing. The time to red rust was much shorter on the bare spots as compared to other regions, but it appeared that bare spot defects had no significant effect on the mechanical properties of the galvanized steel sheets.

---

Recently, high – K materials such as Al2O3 and TiO2 films have been studied to replace ultra thin gate silicon dioxide film. In the present work, these films were grown on the top of Si(100) surface at different temperatures and under ultra high vacuum conditions. The obtained results showed that Al2O3 has a structure better than that of TiO2 and thus can be used as a good gate dielectric for future MISFET (Metal – Insulator- Semiconductor- Field – Effect- Transistors) devices.

---

In this paper, preparation and characterization of a-SiNx thin films deposited by LPCVD method from free radicals of TCS and NH3 gaseous system were investigated. These radicals are made by passing each of the precursor gases separately over Pt-Ir/Al2O3 catalyst at the temperature of 600 ᐤC. Kinetics of this process was investigated at different total pressures, NH3/TCS flow rate ratios and temperatures. Surface topography and chemical concentrations were studied by Ellipsometry, XXPS, AFM and ADP. Our analyses of the performed experiments indicated that at the temperatures between 730 ᐤC and 830 ᐤC, the growth rate of thin films follows an Arrhenius behavior with activation energy of 166.3 KJ.mol-1. The measured H2 contamination in a-SiNx thin films is 1.05 at%, which is 17 times lower than the corresponding contamination in the films produced by PECVD and 3.4 times lower than the contamination in the LPCVD thin films with SiH4 or DCS and NH3. The created surface topography of the prepared films is smooth and uniform.

---

In some applications such as morphing technology, high strain and anisotropic behavior are considered a good advantage. The corrugated composite sheets due to their special geometries have a potential of high deflection under axial loading. In this research, to investigate the strain and anisotropic behavior of corrugated composite sheets some glass/epoxy samples with Quasi-sinusoidal, trapezoidal, rectangular and triangular geometries were manufactured and put to tension and flexural tests in the longitudinal and transverse directions of corrugation. Then, in order to determine anisotropic behavior of corrugated sheets two concepts were introduced: tensile anisotropic and flexural anisotropic criteria based on which anisotropic magnitude was investigated theoretically and experimentally. This research used Yokozeki’s theoretical model for quasi-sinusoidal geometry and his model for trapezoidal, rectangular and triangular geometries. Experimental results showed that corrugated sheets have a strain more than 90%. In the corrugated samples, the strain magnitude was dependent on amplitude and pitch of elements in other words, it was dependent on the number of elements per length unit. Generally, the Quasi-sinusoidal corrugated sheets have a high strain (more than 50%). Experimental results of trapezoidal sheets showed that amplitude of the elements is one of the most important parameters in the ultimate strain. Generally, increasing the amplitude leads to the growth of the ultimate strain

---

In this research, ZrC nano particles were synthesized by self-propagating high temperature (SHS) using the mixed powder of ZrO2-C-Mg and NaF or NaCl diluent. The effect of different proportions of raw materials, milling time, composition of the diluent and also pickling on the synthesis of ZrC was investigated. Optimal amounts of magnesium and sodium fluoride for the synthesis of ZrC were 2.8 and 2 mol, respectively. Milling process of 120 minutes decreased the diffusion gap of raw material and increased the combustion reaction progress. XRD and SEM analysis showed that the NaF diluent more than NaCl caused a reduction in the size of the particles of ZrC and increased the progress of the combustion reaction. Synthesized samples were subjected to pickling in order to remove impurities of MgO by 37% HCl, and distilled water was used to wash off NaF and NaCl residues. ZrC particle size of different samples were in the range of 50-90 nm.

---

To evaluate the effect of inoculant addition on functionally graded microstructure of centrifugally cast Al-Mg2Si composites, two cylinders of Al-13.8 wt.% Mg2Si with and without the addition of 1 wt.% Al-5Ti-B inoculant were cast in a vertical centrifugal casting machine. The chemical composition, microstructures and microstructural phases of the different radial sections of the cast cylinders were studied using induction coupled plasma (ICP) method, optical/scanning electron microscopes, and X-ray diffractometry, respectively. The results showed that in the inoculant content cylinder, owing to the prevailing thermal regime as well as the specific mode of eutectic solidification in this composite, the titanium and boron compounds were segregated towards the middle layer of the cylinder and caused the formation of primary Mg2Si particles and non-eutectic Al () in this layer. In addition, due to the effect of centrifugal force during solidification, a higher volume fraction of the light primary Mg2Si particles, according to Stocks law, was segregated towards the inner layer of the cast cylinders.

---

Aluminium 5xxx alloys excellent properties make them suitable for many industrial applications. The corrosion behavior of this alloy family in industrial environments such as sea water is the main focus of many researches. Due to need for joining large segments of this alloys, the effect of single as well as multipass (double and triple pass) gas metal arc welding (GMAW) on microstructure and corrosion behavior of Al5083-H321 alloy was studied. For this purpose, ER5183 filler metal was used. Microstructures were evaluated using optical and scanning electron microscopy (SEM). Corrosion measurements were performed using open circuit potential test, immersion test in 3.5%NaCl solution and polarization tests. Results indicated that the corrosion resistance of the two passes weldment was improved in comparison with the base metal and its icorr and Ecorr were equal to 0.087´10^-6 (µA/cm²) and -0.4395 (V), respectively.

---

In this study, energy and chemical interaction of ZnO and CdS surfaces interfaced with metal-organic framework (MOF), to improve their properties, have been investigated using density functional theory (DFT). Results show that reformation of structures by hybridation with MOF can increase their stability and improve their properties. Comparison of ZnO and CdS structures predict that deposition of MOF on ZnO substrate can be more effective.

---

In this paper, milling was investigated as a method for production of Mn-Ga binary alloys and the effect of milling process on phase formation of Mn:Ga samples with 2:1 and 3:1 ratio within 1, 2 and 5 hour milling times was studied. For Mn:Ga samples, according to the results, Mn_1.86Ga compound with tetragonal structure and I4/mmm space group was a stable phase. Also, some amounts of  Mn₃Ga compound with orthorhombic structure and Cmca space group was observed in the Mn:Ga solution. The effect of Ge addition, with the purpose of  replacing Ge with Ga was also studied in Mn:Ga:Ge (3:0.5:0.5) sample. Although improved magnetic properties is expected with the addition of Ge, but increasing the coercivity was occurred, and saturation magnetization did not change significantly in the studied sample. Ge addition caused elimination of the possibility of formation of asymmetric orthorhombic Mn₃Ga phase. In return, two new structures of Mn₁₁Ge₈ and MnGaGe were appeared. This phase change was confirmed by studying magnetic behaviour of samples. This behavior can be caused by unbalanced electrostatic forces resulting from Mn-Mn exchange interaction in Mn₃Ga orthorhombic structure and substitution of some Ge atoms with Ga.

---

In this study, centrifugal casting process was used for producing Al/Mg bimetal. Molten Mg was poured at 700 ^oC, with 1.5 and 3 melt-to-solid volume ratio (Vm/Vs) into the 450 ^oC preheated solid Al rotating at 800, 1200, 1600 and 2000 rpm. Castings were kept inside the centrifuged casting machine and cooled down to 150 ^oC. Investigating the effect of melt-to-solid volume ratio showed that increasing volume ratio from 1.5 to 3 results in diminishing metallurgical bonding in Al/Mg interface, because the force of contraction overcomes the resultant force acted on the interface. The results of study by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) showed that bimetal compounds of Al₃Mg₂, Al₁₂Mg₁₇ and δ+Al₁₂Mg₁₇ eutectic structure (δ is the solid solution of Mg in Al) are formed in the interface. Atomic force microscopy (AFM) image of Al surface showed that the surface was rough in atomic dimentions, which can result in the formation of gas pores in the interface.

---

In this paper, the phase formation process of Mn_2.5Ge samples, prepared by mechanical alloying of Mn and Ge metal powders and annealing, has been studied. Results showed that in the milled samples the stable phase is Mn₁₁Ge₈ compound with orthorhombic structure and Pnam space group. The value of saturation magnetization increases by increasing milling time from 0.2 up to 1.95 (Am²Kg^-1). The remanece of the samples increases by increasing the milling time while the coercivity decreases. Annealing of 15-hour milled sample results in disappearance of Mn and Ge and the formation of new phases of Mn₃Ge, Mn₅Ge₂, Mn₅Ge₃ and Mn_2.3Ge. Mn₃Ge is the main phase with Do₂₂ tetragonal structure and I4/mmm space group which is stable and dominant. The enhancement of saturation magnetization in the annealed sample is related to the formation of three new magnetic phases and the increase of coercivity is due to the presence of Mn₃Ge compound with tetragonal structure. Studies were replicated on samples made by arc melting method to compare the results and to investigate the effect of the preparation method on phase formation and structural and magnetic properties of the materials. In these samples the saturation value was in range of 0.2 up to 1.95 (Am²Kg^-1) depending on preparation methods. Rietveld refinement shows that Mn_2.3Ge sample prepared from arc melted under 620^oC anealing is single phase. Magnetic analysis of this sample show a saturation magnetization of 5.252(Am²Kg^-1) and 0.005 T coercive field.

---

In this research, dissimilar welding between 4130 low alloy steel and austenitic stainless steel 316L has been investigated using Gas Tungsten Arc Welding (GTAW). Two types of filler metals, including ERNiCr-3 and ER309L, were used for this purpose. Moreover, the joint microstructures including the weld metals, heat affected zones and interfaces were characterized by optical and Scanning Electron Microscopy (SEM). The mechanical behavior of the joint was tested by impact and tension tests. Observations by SEM showed that in impact test, the fracture is soft. In the tensile test, the welded sample by ER309L filler metal was fractured from 316L base metal, but welded specimen with ERNiCr-3 was fractured from welded zone. Also, the results showed a dendritic structure in the nickel-based weld metal. No crack was found in the cellular-dendritic microstructure of ER309L weld metal due to the existance of delta ferrite between them.
 

---

In this research, nanoparticles of La_0.8Sr_0.2MnO₃ with mean crystallite size of 20 nm have been prepared by sol gel method. The sample has been characterized by X-Ray Diffraction (XRD) using Rietveld refinement, Field Emission Scanning Electron Microscope (FESEM) and Fourier Transform Infrared (FTIR) spectroscopy. The static magnetic properties such as saturation magnetization, effective magnetic moment and ferromagnetic phase fraction of the nanoparticles are determined by different techniques using magnetic hysteresis loop at room temperature. The magnetic dynamic properties of crystalls are studied by measuring AC magnetic susceptibility versus temperature at different frequencies. Néel-Brown, Vogel-Fulcher, critical slowing down models and empirical parameters are used to distinguish between superparamagnetic and superspin glass behaviour in the nanoaprticles. By fitting the experimental data with the models, relaxation time, critical view, magnetic anisotropy energy and effective magnetic anisotropy constant have been estimated. The obtained results support the presence of interacting superparamagnetic behaviour between magnetic nanoparticles of La_0.8Sr_0.2MnO₃.
 

---

In this study, Spark Plasma Sintering (SPS)  of both slip casted and powder specimens of alumina/ yttria core-shell nanocomposite were utilized for fabricating transparent Yttrium Aluminum Garnet (YAG) ceramics. Phase evolution, optical transmittance and the microstructure of sintered samples were compared. In slip casting process, Dolapix CE64 was used as a dispersant for preparing the stable aqueous slurry of this nanocomposite powder. The effect of Dolapix concentration and pH value on the stability of the suspension was described, and the viscosity diagrams were investigated at different pH value and different weight percents of Dolapix. The rheological behavior of the nanocomposite powder slipped at 60-70 wt% solid loading was studied by measuring their viscosity and shear stress as a function of shear rate of the slurry. The results showed that, the suspension has a minimum viscosity at pH of 10 by addition of 2.5 wt% Dolapix. Also, the slurry with solid loading of 60 wt% showed the Newtonian behavior and this rheological behavior was preserved even above this solid loading values. Slip casting technique caused the uniform size and pores distribution as well as eliminating large pores in the green body. Consequently, transparent YAG ceramic with 60% optical transmittance was achieved after SPS process of slip casted green body which was much higher than that of nanocomposite powder, i.e. about 30% at the same sintering conditions.
 

---

---

 

---

---

---

 In this research, the effect of hydrogen peroxide (H₂O₂) and benzoyl peroxide (BPO) on the structural properties, porosity, active pores, and surface area of the MOF-5 (Zn₄O(BDC)₃) metal-organic framework was studied. For this purpose, the metal-organic framework was synthesized by direct mixing and the molar ratios of the precursors to the ligand were modified to minimize the stoichiometric calculation error as well as the washing process to improve the properties of the synthesized MOF-5. In order to characterize the synthesized compounds and to investigate the effect of peroxides and washing process on the properties of the samples, X-ray diffraction (XRD), fourier Transform infrared spectroscopy (FTIR), and thermogravimetric/Differential scanning calorimetry (TG-DSC) analysis were performed. Structure, pore volume (1.212 cm³/g), and specific surface area (2307 m²/g) were compared to the sample synthesized with H₂O₂. DM-P-03 was selected as the optimal sample and prepared for thermal stability. According to TG-DSC analysis, the remaining zinc compounds in the sample were checked and the thermal stability of MOF-5 structure was confirmed up to 470°C.