Nucleation and growth dynamics of ellipsoidal crystals in metastable liquids

2021 ◽  
Vol 379 (2205) ◽  
pp. 20200306
Author(s):  
Margarita A. Nikishina ◽  
Dmitri V. Alexandrov
Keyword(s):  
Growth Dynamics ◽  
Planck Equation ◽  
Spherical Shape ◽  
Theoretical Models ◽  
Intermediate Stage ◽  
Spherical Particles ◽  
Volume Distribution ◽  
Nonlinear Transport ◽  
Transport Diffusivity ◽  
Metastable Systems

When describing the growth of crystal ensembles from metastable solutions or melts, a significant deviation from a spherical shape is often observed. Experimental data show that the shape of growing crystals can often be considered ellipsoidal. The new theoretical models describing the transient nucleation of ellipsoidal particles and their growth with and without fluctuating rates at the intermediate stage of bulk phase transitions in metastable systems are considered. The nonlinear transport (diffusivity) of ellipsoidal crystals in the space of their volumes is taken into account in the Fokker–Planck equation allowing for fluctuating growth rates. The complete analytical solutions of integro-differential models of kinetic and balance equations are found and analysed. Our solutions show that the desupercooling dynamics is several times faster for ellipsoidal crystals as compared to spherical particles. In addition, the crystal-volume distribution function is lower and shifted to larger particle volumes when considering the growth of ellipsoidal crystals. What is more, this function is monotonically increasing to the maximum crystal size in the absence of fluctuations and is a bell-shaped curve when such fluctuations are taken into account. This article is part of the theme issue ‘Transport phenomena in complex systems (part 1)’.

scholarly journals Ultraviolet and violet-blue emission of Zn doped MgO/mg(OH)2 particles prepared by one step spray pyrolysis method

2018 ◽  
Vol 1 (1) ◽  
pp. 57-66
Author(s):  
Fenfen Fenda Florena ◽  
◽  
Dwindra Wilham Maulana ◽  
Ferry Faizal ◽  
Bambang Mukti Wibawa ◽  
...  
Keyword(s):  
Spray Pyrolysis ◽  
Doping Concentration ◽  
Blue Emission ◽  
Spherical Shape ◽  
Spherical Particles ◽  
Spray Pyrolysis Method ◽  
Excitation Spectra ◽  
X Ray ◽  
Pyrolysis Method ◽  
One Step

Spherical particles of Zn doped MgO were prepared by one-step spray pyrolysis method. The crystalline nature and particle size of the samples were characterized by X-ray diffraction analysis (XRD). The morphology of samples was studied by scanning electron microscope (SEM) and the presence of Zn in the sample was confirmed by energy dispersive X-ray analysis (EDX). The optical properties of the samples were investigated using photoluminescence spectroscopy (PL) analysis to obtain excitation and emission spectra of the samples. Results indicated that the doped MgO particles exhibited a cubic structure without hexagonal wurtzite structure as the Zn concentrations were increased. Spherical shape and porous particles are found with increasing of doping concentration. The optical band gap of MgO altered with the addition of doping concentration. A considerable redshift of about ~0.08 – 0.13 eV in the excitation spectra of 2.22 eV emission band was revealed in Zn doped MgO samples. It was highlighted that Zn doped MgO prepared by the spray pyrolysis generated emission at UV-Vis wavelength required for many applications.

scholarly journals Designing and Developing Rechargeable Aluminium-Ion Battery using Graphite Coated Activated Charcoal Corncob as Cathode Material

2018 ◽  
Vol 14 (2) ◽  
pp. 99-104
Author(s):  
F. Fitriah ◽  
A. Doyan ◽  
S. Susilawati ◽  
S. Wahyuni
Keyword(s):  
Activated Charcoal ◽  
Spherical Shape ◽  
Aluminum Foil ◽  
High Energy ◽  
Spherical Particles ◽  
Carbon Particles ◽  
Main Requirement ◽  
Optimal Capacity ◽  
Coating Method ◽  
Varied Composition

One of the renewable energy storage systems that can be used today is the aluminum ion battery. In this study, aluminum foil was used as anode, polyetylene polyprophylene (PE/PP) as separator, electrolyte from AlCl3/[EMIm]Cl and graphite coated corncob, an activated charcoal, as cathode. Coating method of cathode materials was done by mixing both graphite and activated charcoal with varied composition 1:0.5, 1:1, 1:1.5, and 1:3. The coating process began by mixing the graphite and corncob with ethanol as a solvent for six hours, then heating in an oven at 80 °C for three days, gradual drying in a furnace at 350 °C for five hours and sintering at 600 °C for six hours. From this research, SEM results showed that carbon particles were evenly distributed, with spherical particles. The spherical shape was the main requirement of carbon formation in order to produce high energy. Based on the results, battery potential was 2.54 V with average of optimal capacity at a ratio of graphite and corncob activated charcoal 1:1.5 was 83.067 mAh/g. The highest efficiency was also at a ratio of 1:1.5 of 97.20%, because at this ratio, there was an increasing in percentage of element C 91.74%, greater than the percentage of element C on the other three cathode samples.Salah satu sistem penyimpan energi terbarukan yang bisa digunakan saat ini adalah baterai ion aluminium. Pada penelitian ini digunakan aluminium foil sebagai anoda, polyetylene polyprophylene (PE/PP) sebagai separator, elektrolit menggunakan AlCl3/[EMIm]Cl dan grafit terlapisi arang aktif tongkol jagung sebagai bahan katoda. Metode pelapisan bahan katoda dilakukan dengan mencampurkan grafit dan arang aktif dengan variasi komposisi 1:0,5, 1:1,1:1,5 dan 1:3. Proses pelapisan diawali dengan pencampuran grafit dan arang aktif tongkol jagung dengan ethanol sebagai pelarut selama enam jam kemudian pemanasan di oven pada suhu 80oC selama tiga hari, pengeringan bertahap di furnace pada suhu 350oC selama lima jam dan sintering pada suhu 600oC selama enam jam. Dari penelitian ini didapatkan hasil SEM menunjukkan bahwa partikel karbon terdistribusi merata, dengan bentuk partikel bulat (sphare).Sampelberbentuk bulat atau sphere merupakan syarat utama pembentukan karbon supaya dapat menghasilkan energi tinggi. Berdasarkan hasil uji baterai diperoleh potensial sebesar 2,54 Volt dengan rata-rata kapasitas optimal terjadi pada rasio grafit dan arang aktif tongkol jagung 1:1,5 sebesar 83,067 mAh/g. Efisiensi tertinggi juga terjadi pada rasio 1:1,5 sebesar 97,20%. Hal ini karena pada rasio 1:1,5 terjadi peningkatan persentase unsur C yakni 91.74% lebih besar dari persentase unsur C pada tiga sampel katoda yang lainnya.

Particle detachment due to wheel rotation

2020 ◽  
pp. 1420326X2093516
Author(s):  
Jinwei Song ◽  
Hua Qian ◽  
Xiaohong Zheng
Keyword(s):  
Surface Roughness ◽  
Silicon Dioxide ◽  
Adhesion Force ◽  
Aluminium Oxide ◽  
Theoretical Models ◽  
Wheel Speed ◽  
Spherical Particles ◽  
Wheel Surface ◽  
Particle Detachment ◽  
Oxide Particles

Particle detachment induced by a rotating wheel was investigated theoretically and experimentally. The developed theoretical models were used to reveal how the particle detaches from a wheel surface to the surrounding air. The corresponding experiments were carried out to validate proposed models. Two groups of spherical particles were considered, i.e. silicon dioxide and aluminium oxide particles. Different forces and force moments acting on individual particles were analysed. The criteria for the rolling detachment of particles were considered. The detachment diameters under various conditions were calculated. The results show that the particle detachment was dominated by the removal and resistant forces acting on particles, including the gravity force, adhesion force, hydrodynamic force and centrifugal force. Different relevant parameters can affect particle detachment through these forces, including surface roughness, wheel speed, particle size and properties. A higher wheel speed, larger particle sizes and higher wheel surface roughness were shown to have a conducive influence on particle detachment. The resistant and removal force moments could be affected by the particle properties at the same time; therefore, the detachment diameters of the aluminium oxide particles are similar to those of silicon dioxide. This study can contribute towards the estimation of particle emissions from vehicles.

scholarly journals A Novel Fabrication of Spherical Fe50ni50 Alloy Powders via in-Situ De-Wetting of Liquid Solid Interface

Crystals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 325
Author(s):  
Song ◽  
Lei ◽  
Zhong
Keyword(s):  
Spherical Shape ◽  
Soft Magnetic Property ◽  
Spherical Particles ◽  
Soft Magnetic ◽  
Sem Images ◽  
Cross Sectional ◽  
Alloy Particles ◽  
Ni Alloy ◽  
Alumina Particles

: Spherical Fe50Ni50 alloy powders were fabricated via a novel route based on in-situ interface de-wetting between liquid Fe-Ni alloy and alumina. The obtained Fe50Ni50 alloy particles exhibit very good spherical shape according to SEM images. Furthermore, the cross-sectional SEM images show that there are no pores and bulk inclusions in the internal region of the spherical particles. The XRD results show a trace amount of the impurity alumina phase appearing in taenite phase. The size distribution agreed well with the SEM observation confirms that the alumina powders successfully segregated pre-alloy powders. As an incidental benefit, the surface alumina particles were treated as the electrical insulation coatings. The magnetic character shows that spherical Fe50Ni50 powders exhibit a good soft magnetic property even though with a slightly decreasing of saturation magnetization due to non-magnetic coatings. Our strategies provide a method to in-situ fabricate insulation coated Fe-Ni spherical alloy powders as magnetic powder core.

scholarly journals Discrete element modeling of non-spherical particles using a spherical shape

2020 ◽  
Vol 73 (3) ◽  
pp. 361-369
Author(s):  
Elias Gomes Santos ◽  
Luiz Carlos da Silva Carvalho ◽  
André Luiz Amarante Mesquita ◽  
Luiz Moreira Gomes ◽  
Kelvin Alves Pinheiro ◽  
...  
Keyword(s):  
Spherical Shape ◽  
Discrete Element ◽  
Spherical Particles ◽  
Discrete Element Modeling ◽  
Element Modeling

Discrete Element Simulation of Powder Sintering for Spherical Particles

2020 ◽  
Vol 854 ◽  
pp. 164-171
Author(s):  
Ilia I. Beloglazov ◽  
Aleksei V. Boikov ◽  
Pavel A. Petrov
Keyword(s):  
Numerical Model ◽  
Model Simulation ◽  
Bulk Material ◽  
Experimental Studies ◽  
Spherical Shape ◽  
Discrete Element ◽  
Spherical Particles ◽  
Large Set ◽  
Discrete Elements ◽  
Powder Sintering

This paper presents a numerical simulation of powder sintering. The numerical model presented in this paper uses the discrete element method, which suggests that the material can be modeled by a large set of discrete elements (particles) of a spherical shape that interact with each other. A methodology has been developed to determine the DEM parameters of bulk materials based on machine vision and a neural network algorithm. The approach is suitable for obtaining the exact values of the DEM parameters of the investigated bulk material by comparing the visual images of the material’s behavior at the experimental stand in reality and in the model. Simulation of sintering requires an introduction of cohesive interaction between particles representing interparticle sintering forces. Numerical sintering studies were supplemented with experimental studies that provided data for calibration and model validation. The experimental results have shown a significant capability of the designed numerical model in modeling sintering processes. Evolution of microstructure and density during sintering have been studied under the laboratory conditions.

Study of mechanical spheroidization of powders obtained from waste metal shavings

2021 ◽  
pp. 41-46
Author(s):  
A. D. Samukov ◽  
M. V. Cherkasova ◽  
M. P. Kuksov ◽  
S. V. Dmitriev
Keyword(s):  
Energy Consumption ◽  
3D Printing ◽  
Spherical Shape ◽  
Spherical Particles ◽  
High Tech ◽  
Metal Powders ◽  
Powder Preparation ◽  
Russian Science ◽  
Additional Energy ◽  
Powder Particles

This paper covers the search for a new method for generating metal powders for additive manufacturing. Raw materials for 3D printing are subject to certain requirements regarding the spherical shape of the powder particles, which are not easily met. The powder preparation methods used in the powder metallurgy may not be directly used for 3D printing without additional energy consumption for the spheroidization operation. More high-tech principles of melt dispersion shall be used for the spheroidization (atomization) of powder particles. Metal waste grinding in ball or vibrating mills generally yields plate-like particles, also requiring the use of energy-intensive atomization technologies. However, an analysis of related foreign research provided an alternative that is to use two-stage grinding to obtain spherical metal powder particles. Continued research in mechanical spheroidization enables the simultaneous manufacture and grinding of the required spherical particles while maintaining practically the same energy consumption that had been previously required for the grinding process. In order to form a research program and establish the optimal grinding size in terms of energy consumption and the dependence between the ball diameter and the grinding and spheroidization results for metal particles, respective preliminary experiments were carried out. The results of these experiments were then used to formulate the conclusions required to develop a method for establishing the optimal grinding ball charge level and composition. The study was carried out under the grant issued by the Russian Science Foundation (project No. 20-79-10125).

Molecular Dynamics Simulation of Normal and Explosive Boiling on Nanostructured Surface

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Hamid Reza Seyf ◽  
Yuwen Zhang
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Evaporation Rate ◽  
Solid Wall ◽  
Molecular System ◽  
Spherical Shape ◽  
Dynamics Simulation ◽  
Spherical Particles ◽  
Explosive Boiling ◽  
Higher Temperature

Molecular Dynamics (MD) simulation is carried out to investigate the normal and explosive boiling of thin film adsorbed on a metal substrate whose surface is structured by an array of nanoscale spherical particles. The molecular system is comprised of the liquid and vapor argon as well as a copper wall. The nanostructures have spherical shape with uniform diameters while the thickness of liquid film is constant. The effects of transvers and longitudinal distances as well as the diameter of nanoparticles are analyzed. The simulation is started from an initial configuration for three phases (liquid argon, vapor argon and solid wall); after equilibrating the system at 90 K, the wall is heated suddenly to a higher temperature that is well beyond the critical temperature of argon. Two different superheat degrees are selected: a moderately high temperature of 170 K for normal evaporation and much higher temperature 290 K for explosive boiling. By monitoring the space and time dependences of temperature and density as well as net evaporation rate, the normal and explosive boiling process on a flat surface with and without nanostructures are investigated. The results show that the nanostructure has significant effect on evaporation/boiling of thin film. The degrees of superheat and size of nanoparticles have significant effects on the trajectories of particles and net evaporation rate. For the cases with nanostructure, liquid responds very quickly and the number of evaporation molecules increases with increasing the size of particles from 1 to 2 nm while it decreases for d = 3 nm.

ON NEURON MEMBRANE POTENTIAL DISTRIBUTIONS FOR VOLTAGE AND TIME DEPENDENT CURRENT MODULATION

2012 ◽  
Vol 17 ◽  
pp. 19-22
Author(s):  
J. B. SALIG ◽  
M. V. CARPIO-BERNIDO ◽  
C. C. BERNIDO ◽  
J. B. BORNALES
Keyword(s):  
Membrane Potential ◽  
Planck Equation ◽  
Theoretical Models ◽  
Dynamical Variable ◽  
Integral Approach ◽  
Conditional Probability Density ◽  
Neuronal Membrane ◽  
Neuron Membrane ◽  
Current Modulation ◽  
Brain Functions

Tracking variations of neuronal membrane potential in response to multiple synaptic inputs remains an important open field of investigation since information about neural network behavior and higher brain functions can be inferred from such studies. Much experimental work has been done, with recent advances in multi-electrode recordings and imaging technology giving exciting results. However, experiments have also raised questions of compatibility with available theoretical models. Here we show how methods of modern infinite dimensional analysis allow closed form expressions for important quantities rich in information such as the conditional probability density (cpd). In particular, we use a Feynman integral approach where fluctuations in the dynamical variable are parametrized with Hida white noise variables. The stochastic process described then gives variations in time of the relative membrane potential defined as the difference between the neuron membrane and firing threshold potentials. We obtain the cpd for several forms of current modulation coefficients reflecting the flow of synaptic currents, and which are analogous to drift coefficients in the configuration space Fokker-Planck equation. In particular, we consider cases of voltage and time dependence for current modulation for periodic and non-periodic oscillatory current modulation described by sinusoidal and Bessel functions.

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