Sharif Digital Repository

In this study, a dislocation-based model is presented for investigating the evolution of micro structure and mechanical properties of thin films during a wide range of straining. The model is applied to the High Pressure Torsion (HPT) process of thin nickel disks that provides valuable information on the evolution of material parameters during deformation. The model considers a free surface theory for thin films and can explain the size effect phenomenon in agreement with previous reported trends in literature  

As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well as favorable microstructures and, thus, mechanical properties. The present review paper therefore aims to present a critical analysis and overview of the relationship between processing parameters, microstructure, and mechanical properties of LMD components made from the Ti–6Al–4V alloy. Moreover, we discuss the applications of LMD parts in the... 

Tissue engineering (TE) and regenerative medicine have held great promises for the repair and regeneration of damaged tissues and organs. Additive manufacturing has recently appeared as a versatile technology in TE strategies that enables the production of objects through layered printing. By applying 3D printing and bioprinting, it is now possible to make tissue-engineered constructs according to desired thickness, shape, and size that resemble the native structure of lost tissues. Up to now, several organic and inorganic materials were used as raw materials for 3D printing; bioactive glasses (BGs) are among the most hopeful substances regarding their excellent properties (e.g., bioactivity... 

Laser Powder Deposition technique is an advanced production method with many applications. Despite this fact, reliable and accurate control schemes have not yet fully developed for this method. This article presents method for in time identification of the process for modeling and adaptation of proper control strategy. ARMAX structure is chosen for system model. Recursive least square method and Kalman Filter methods are adopted for system identification, and their performance are compared. Experimental data was used for system identification, and proper filtering schemes are devised here for noise elimination and increased estimation results. It was concluded that although both methods... 

The laser powder deposition (LPD) process is an advanced material processing technique with many applications. Despite this fact, reliable and accurate control schemes have not yet been fully developed for the process. In this paper, identification of the LPD process is examined to find a more accurate model to predict and control the height of clad in real time. The model is adaptive single inputsingle output (SISO) and its structure is very similar to the Hammerstein model when the effective power (a function of laser power and velocity) is selected as the input and the clad height as the output. Weighted extended recursive least square (WERLS) is adopted to simultaneously estimate the... 

Activated layered manganese oxides with deposited nano-sized gold or silver were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy and energy-dispersive X-ray mapping. Here, we report that Au or Ag nanoparticles deposited on layered Mn oxides improve the catalytic activity of the Mn oxides toward the epoxidation of olefins in the presence of H2O2 and NaHCO3  

Scale precipitation due to the mixing of incompatible injected water with formation brine and its subsequent deposition in porous media is an unpleasant phenomenon in water injection projects that can lead to severe injectivity and productivity decline. As a result of the complexity of geochemical reactions, modelling scale precipitation and deposition is a challenge. This paper presents a coupled geochemical and fluid flow model to simulate reactive flow in porous media which models pressure difference increase resulting from scale formation during water injection into porous media. To simulate chemical reactions during scale formation and subsequent rock permeability decline, PHREEQC... 

Although CO2 injection significantly increases the amount of oil recovered, it can cause asphaltene deposition in oil reservoirs. Asphaltene deposition leads to formation damage, in which treatment is a costly and problematic operation. In this work, impact of asphaltene precipitation and deposition during CO2 injection are investigated for recombined oil both in sandstone and carbonate core samples through dynamic flow experiments. Injection of oil and CO2 was performed simultaneously. Then, pressure drops along the core were recorded continuously to estimate permeability reductions during the experiments. Online viscosity of injected fluid was measured by a designed capillary viscometer.... 

Nanostructured materials have attracted much attention in recent decades. Nowadays, there are numerous nanomaterials with several applications. The ultrasonic spray pyrolysis method is a cost-effective and adaptable technique based on an aerosol process for synthesizing nanoparticles and depositing thin films. The technique is capable of synthesizing metal, oxide, and composite nanomaterials with precisely controllable morphologies and chemical compositions using metal salts in aqueous solvents. More importantly, it is popular, as evident from the growing number of studies being conducted on the technique. Here, we review studies conducted on basic principles and applications of the... 

Nickel modified graphite electrodes (G/Ni) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol, ethanol, 1-propanol and 2-propanol in alkaline solutions. The methods of cyclic voltammetry (CV), chronoamperometry (CA) and impedance spectroscopy (EIS) were employed. In CV studies, the electrochemical response, peak current varied in the order of MeOH > EtOH > 1-PrOH > 2-PrOH. Under the CA regime, a higher catalytic rate constant obtained for methanol oxidation was in agreement with CV measurements. Lower charge transfer resistance was obtained for low carbon alcohols oxidation and significantly higher... 

Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by potentiostatic method onto stainless steel substrate. Deposition potentials of 1 and -1 V for the anodic and cathodic depositions were employed. Specific capacitance values in the range of 38.5-78 F g -1 were found with cobalt oxide on top of manganese oxide having the lowest and manganese oxide on top of cobalt oxide having the highest capacitances. The usefulness of the electrodes was characterized by cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy in 2 M NaOH electrolyte for redox supercapacitor applications. The latter presented the... 

Alloy nanoparticles in the Mg-Al system were prepared by plasma arc discharge method from the Mgx to Al (45%