Sharif Digital Repository

The Monte Carlo simulation is utilized to model the nano-scale grain growth of two nanocrystalline materials, Pd81Zr19 and RuAl. In this regard, the relationship between the real time and the time unit of simulation, i.e. Monte Carlo step (MCS), is determined. The results of modeling show that with increasing time of heating, the grain sizes of both nano-crystalline materials increased as in the case of conventional materials. Moreover, it is found that for both nano-crystalline materials the relationship between the real time and MCS is in power law form, which is linear for the conventional materials. © Indian Academy of Sciences  

Commercial purity copper sheets were subjected to a severe plastic deformation technique known as constrained groove pressing (CGP). The effect of pass number, intermediate and post-annealing on the yield strength, hardness and final microstructure of the copper specimens were investigated. The initial pass increases the strength much more than the subsequent passes. Intermediate and post-annealing up to 300 °C cannot change the mechanical properties significantly and even in some cases improve the strength and hardness while reduce the hardness inhomogeneity. Microstructure after post-annealing at elevated temperatures shows abnormal grain growth. © 2009 Elsevier B.V. All rights reserved  

The transformation of gibbsite to α-alumina occurs in the range 1100 to 1300°C. The higher the calcination temperature, the larger the crystallites and this leads to abnormal grain growth. The main goal of this research was to reduce the transformation temperature of gibbsite to α-alumina by reducing the gibbsite particles size. The sodium content of the gibbsite used in the study was reduced to less than 0.1% by washing it in HCl solution. It was then ground in a fast mill at ambient conditions for different times then calcined at different temperatures. The microstructure, particles size and thermal behaviour of the samples were examined with SEM, XRD, XRF, PSA and STA, respectively. In a... 

In this paper, we consider several known growth processes with height-dependent noise. This type of noise is interesting from a theoretical standpoint, for example, it paves the way to the derivation of the exact height distribution of the KPZ equation through the Hopf–Cole transformation. In addition, it may have implications for experimental growth processes. Using numerical methods, we observe that adding such a noise to different growth processes, can change their universality class or ruin the scaling laws. In the case of Mullins–Herring equation, a two-fold cross-over is observed. © 2020 Elsevier B.V  

Based on the micromorphic theory, a novel mathematical formulation for the mechanical modeling of material growth and remodeling processes in finite deformation is developed. These two processes have an important significance in evolution of living tissues. The presented formulation incorporates both the volumetric growth and mass flux phenomena into the modeling with the aid of the micromorphic theory's capability to include internal structures in materials. The balance equation of microinertia is presented which reveals the importance of rearrangement and alteration of microstructure in the micromorphic material growth. Within the framework of material uniformity, the evolution laws are... 

The mathematical formulation for material growth and remodeling processes in finite deformation is developed based on the couple stress theory. The generalized continuum mechanics of couple stress theory is capable of capturing small-scale cellular effects and of modeling mass flux in these processes. The frame-indifferent balance equations of mass, linear and angular momentums, as well as internal energy together with the entropy inequality are first introduced in the presence of the mass flux based on the finite couple-stress theory. Then, within the framework of material uniformity the Eshelby and Mandel stress tensors as driving or configurational forces for local rearrangement of the... 

In this paper, the fatigue crack propagation is modeled using the Molecular Dynamics (MD) analysis based on the Embedded Atom Method (EAM). The crack growth simulation is performed for the single-crystal and poly-crystalline specimens subjected to cyclic loading/unloading conditions, and the crack growth rate is investigated at the atomistic level. The MD simulations are carried out under different model parameters, including the load pattern, maximum applied strain, temperature, loading frequency, and percentage of defects by employing more than 4000 molecular dynamics analyses to study the sensitivity of crack propagation process to the simulation parameters. The threshold values of... 

Deposition of zinc oxide films from aqueous solutions containing complex Zn2+ ions on soda-lime substrates were studied by two-stage chemical deposition (TSCD) process. It was shown that the film thickness can be controlled by the number of dipping stages. Nano-layers were produced with less than nine times dipping stages. Greater dipping numbers resulted in film thickness exceeding 100 nm. The growth rate obeyed double-stage zeroth order with respect to the concentration and first order with respect to the temperature. This rate was proportional to the difference between the temperature of the hot water and the substrate. Overall activation energy of 17.20 ± 0.42 kJ mol-1 and frequency... 

Hydroxyapatite (HA) coatings were deposited on commercially pure titanium plates using a hydrothermal-electrochemical deposition method in an electrolyte containing calcium and phosphate ions. The deposition conditions used in this study were the followings: electrolyte temperature (33-80 °C), current density (1-8 mA/cm2), and deposition time (10-120 min). Needle-like and granular crystals of apatite coating were created with different concentrations of calcium (0.0021-0.042 M) and phosphate (0.00125-0.025 M) salts. The size of HA crystals of the coating was considerably changed with different concentration of calcium and phosphate salts, temperature of the electrolyte, and deposition time.... 

A simple biofilm model based on a model suggested by Soda et al. [S. Soda, E. Heinzle, M. Fujita, Modeling and simulation of competition between two microorganisms for a single inhibitory substrate in a biofilm reactor, Biotechnol. Bioeng. 66 (1999) 258-264] was used to simulate the competition between two microorganisms for space and a single inhibitory substrate in a biofilm reactor. Different growth kinetics were used to describe the growth of two microorganisms A and B which utilize the inhibitory substrate and the effect of biofilm thickness on microorganism concentration in biofilm was discussed. It was assumed that the biofilm has a uniform thickness and is composed of N segments (N =... 

The transformation of gibbsite to α-alumina occurs in the range 1100 to 1300°C. The higher the calcination temperature, the larger the crystallites and this leads to abnormal grain growth. The main goal of this research was to reduce the transformation temperature of gibbsite to α-alumina by reducing the gibbsite particles size. The sodium content of the gibbsite used in the study was reduced to less than 0.1% by washing it in HCl solution. It was then ground in a fast mill at ambient conditions for different times then calcined at different temperatures. The microstructure, particles size and thermal behaviour of the samples were examined with SEM, XRD, XRF, PSA and STA, respectively. In a...