Mohamadreza Rahimipour
Materials and Energy Research Center
[ 1 ] - Determination of solution temperature in an ex-service Ni-based turbine blade
It is well-known that the harsh operational conditions of turbine blades lead to a gradual change in the microstructure of underlying Ni-based superalloy of blades. According to this, a rejuvenation process should be conducted on turbine blades superalloys to recover their microstructures. The first and main step of rejuvenation process is the determination of appropriate solution condition in ...
[ 2 ] - Effect of morphology and nonbounded interface on dielectric properties of plasma sprayed BaTiO3 Coating
In this research, BaTiO3 thick deposit has been successfully sprayed by air plasma spray. The microstructure and dielectric properties of thick films were investigated by secondary electron microscopy (SEM) and LCR meter respectively. XRD measurement was carried out on plasma sprayed BaTiO3. The results illustrate differences in the crystal structure between plasma sprayed coatings and feed sto...
[ 3 ] - مطالعه تجربی اثر پودر آلومینیوم نانو ساختار بر خواص یک PBX پایه HMX
Aluminum powder is a common ingredient in energetic materials. Reactivity of this metal can be improved by reducing the particle size, due to their larger surface/volume ratio. In this research, the effects of using nano-structured aluminum powder investigated on physical, thermal, mechanical and explosive characteristics of an HMX-based PBX. The results indicated that the experimental density ...
[ 4 ] - سنتز پودر هگزا آلومینات لانتانیم (LaMgAl11O19) به منظور پوشش دهی به روش پلاسما اسپری بر روی سوپر آلیاژ پایه نیکل به عنوان پوشش سد حرارتی
هگزاآلومینات لانتانیم(LaMgAl11O19) به عنوان یک پوشش سد حرارتی جدید به دلیل خواص و ویژگی های برتر، جایگزین مناسبی برای زیرکونیای پایدارشده با ایتریا( YSZ) می باشد. در این پژوهش ابتدا به سنتز پودر به روش حالت جامد و سپس به بررسی و فرآوری آن جهت انجام پوشش دهی پلاسما اسپری پرداخته شد. جهت ارزیابی خواص پودر سنتز شده از میکروسکوپ الکترونی، الگوی پراش اشعه ایکس و آنالیز حرارتی استفاده شد. برای سنتز ه...
[ 5 ] - بررسی تشکیل ترک‌‌های انجمادی و ذوبی جوشکاری پرتو الکترونی سوپرآلیاژ Zhs6u در حرارت‌های ورودی مختلف
در این پژوهش به بررسی جوشپذیری سوپرآلیاژ پایه نیکل رسوبسختشونده Zhs6u از طریق مطالعه میزان ترکها و تغییرات ریزساختاری در فلز جوش و منطقه HAZ پرداخته شد. هدف این پروژه دستیابی به پارامترهای بهینه جوشکاری تعمیری پرتو الکترونی و بررسی تأثیر مقادیر مختلف حرارت ورودی بر ریزساختار و خواص فلز جوش است. لذا تمامی نمونهها پس از عملیات حرارتی پیش از جوشکاری با سیکل بهینه با مقادیر متفاوت جریان و سرع...
[ 6 ] - Cyclic oxidation behavior of uncoated and aluminum-rich nickel aluminide coated Rene-80 superalloy
In this study, aluminide coating was employed to enhance the high-temperature cyclic oxidation of Rene-80 superalloy at 950ºC. The microstructural aspects and phase constituents of samples were investigated with scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. The result of oxidation tests showed that the weight gain in the uncoated sample was considerably higher than...
[ 7 ] - Effect of NiTi Addition on the Wear Resistance of YSZ Coatings
In this study, small fraction of NiTi (5 wt%) was added to Yttria stabilized zirconia (YSZ) top coat to improve it sliding wear resistance. The measurement of width of wear tracks after wear tests under a 15 N load for 100 m sliding distances showed that the width of wear track in NiTi-YSZ coating is shorter than that in YSZ coating which depicts the higher wear resistance of NiTi-YSZ coa...
[ 8 ] - Preparation of Cr-doped TiO2 thin film by sonochemical/CVD method and its visible light photocatalytic activity for degradation of paraoxon
In this work, nanostructured TiO2 and Cr-doped TiO2 thin films were deposited on glass substrate through sonochemical-chemical vapor deposition (CVD) method. The resulting thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectroscopy, and photoluminescence spectroscopy techniques. The TiO2 thin film has nanocubic morphology and ...
[ 9 ] - In-situ Fabrication of Transparent Magnesium Aluminate Spinel by Spark Plasma Sintering
Transparent polycrystalline spinel ceramic was fabricated without any sintering aids by spark plasma sintering method of a mixture of Al2O3 and MgO powders for only 10min soak at 1250°C. Densification, microstructure and optical transparency of spinel were examined. The spinel exhibits an in-line transmission of 55% for a visible-wavelength of 470nm and high hardness value of 2040 HV.
[ 10 ] - The Effect of Rotation Speed on the Microstructure and Hardness of Synthesized Al-WC Nano-Composite by Centrifugal Casting
The aim of this work was WC distribution in base Al-Si-Mg (A356) alloy as reinforcing agent. WC Solid particles in the sub-23-nm size range added to melted alloy by centrifuge casting. The cylinder tube without gap was obtained. FESEM and OPM results show that the distribution depends upon the rotational speeds of the mould and centrifugal casting conditions. According to the MAP results, durin...
[ 11 ] - Characterization and Phase Transformation of Spherical YSZ Powders Fabricated Via air Plasma Spray Method
Air plasma spray (APS) process is used to produce high density and flowability spherical powders. Phase transformation that occurred in this process isn’t well known. In this paper, the YSZ powders have been sprayed in water to investigate the morphology changes and phase transformations via air plasma spray (APS) method. Phase analysis of powders was examined by XRD and the crystallite size an...
[ 12 ] - Investigation of Effective Parameters on Densification of ZrB2-SiC Based Composites Using Taguchi Method
Abstract The main goal of this study is optimization of densification of ZrB2-SiC composites reinforced with chopped Cf prepared by SPS. Taguchi method is employed as statistical design of experiment (DOE) to optimize densification parameters including SiC, Cf, MoSi2, HfB2 and ZrC content, milling time of Cf and SPS parameters such as temperature, time and pressure. Each of these factors ...
[ 13 ] - Microstructure and Grain Refining Performance of a New Al-Ti-C Master Alloy (RESEARCH NOTE)
Control of microstructure parameters that affecting the Al-Ti-C master alloys grain refining efficiency is leading to improve the aluminum grain refinement. This study was an attempt to produce Al-Ti-C master alloys that provide these controlling factors with relying on the solute effect theory. The produced master alloys were examined by using scanning electron microscopy (SEM), energy-dispers...
[ 14 ] - Comparative Study of Plasma Sprayed Yittria and Ceria Stabilized Zirconia Properties
Thermal Barrier Coatings are subjected to spallation and destabilization due to hot corrosion.Recently, Ceria Stabilized Zirconia (CSZ)-based TBCs have been intensively investigated for the YSZreplacement because CSZ has a much lower thermal conductivity and a higher expected thermalexpansion coefficient than those of YSZ. In this research, Yttria stabilized zirconia (YSZ) andceria stabilized z...
[ 15 ] - Hydrothermal synthesis of monoclinic - cubic Li2TiO3 hybrid nanocomposite microspheres
Li2TiO3 compound is one of the most important tritium breeding ceramics for industrial application in the nuclear fusion reactor. The use of the hydrothermal method for preparing ceramic composite materials is new trend. In this work, hybrid nanocomposite microspheres of the nanocrystallites Li2TiO3 were prepared at low temperature 400°C. Nanocomposite powders synthesized by the batch supercrit...
[ 16 ] - Crystal Structure and Lattice Parameter Investigation of La3+ Substituted CeO2 in LaxCe1-xO2-X/2 Synthesized by Solid-State Method
Lanthanum (La) doped Ceria (CeO2) has attracted considerable interest as a candidate material for thermal barrier coating (TBC) because of its low thermal conductivity and potential capability to be operated above 1250°C. In this study, La2Ce2O7 powder was synthesized through the ball mill method. The crystal structure of La3+ su...
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