Papers by Keyword: Spheres

Abstract: This scientific study considers the results of a computer experiment with heterogeneous elements (spheres) that proved to be of decisive importance during the separation process, namely their degree of activity, mobility and falling. It has been found that a detailed analysis of the Liapunov function indices allows to effectively understand and predict the dynamics of complex dynamical systems. The results obtained indicate significant changes in the physical and mechanical parameters of spherical balls under the influence of various factors and the environment. It was found that a certain accumulation of spheres occurs due to an increase in the time for simulation. It was also found that the key characteristics of the bulk mass of spherical elements significantly depend on the moulding process, surface condition and environmental conditions.

Abstract: This paper presents a study in the field of modelling the dynamics of spherical elements. The results obtained indicate the successful use of the discrete element method (DEM) as a numerical tool for analysing the behaviour of the system studied with the help of spheres. The results are based on the importance of correct consideration of the boundary conditions for the spheres, which determine the key aspects of modelling with the developed three-dimensional model. The developed model solves a number of important tasks, expanding the field of scientific research. Firstly, it allows studying the main parameters of the formation of a heterogeneous medium by analysing the compaction of spherical elements in different media. Next, the three-dimensional model is used to study the process of changing the structure of a heterogeneous medium from a static to an oscillatory state, which allows for a deeper understanding of this process. By modelling the mathematical behaviour of spherical elements under the influence of external and additional factors, a detailed understanding of their dynamics and contact interaction can be obtained. The application of the developed model to analyse the contact interaction of spherical elements in heterogeneous media allows predicting the main parameters of spheres and their heterogeneous environment with a reliable accuracy of up to ±1 %. It should be noted that the results obtained on the basis of the three-dimensional model are effective and indicate a number of practical applications in various fields.

Abstract: Fe₃O₄@C spheres were synthesized by hydrothermal reaction at 190°C followed by a low temperature heat annealing at 600 °C and applied as an anode material for lithium-ion batteries. The samples were characterized by XRD and SEM. The electrochemical performances of as-synthesized Fe₃O₄@C were systemically investigated. A reversible capacity of 873 mAh g^-1 is obtained in the second cycle at 400 mA g^-1. More importantly, the discharge specific capacity can still maintain at about 767 mAh g^-1 after 80 cycles. Moreover, Fe₃O₄@C spheres electrode shows satisfactory rate capability even at a rate up to 2000 mA g^-1. Thus, the results demonstrate that Fe₃O₄@C spheres show encouraging application potential to be an advanced anode material for lithium storage

Abstract: The processing of porous ceramics spheres (PCS) has been developed for biphasic calcium phosphates (BCP), hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) in order to be used mostly as bone fillers and drug delivery systems. The importance of the PCS is due to better accommodation of them in order to fill empty spaces and also because is more friendly to cells and bone tissue growth. Also is important to obtain a surface roughness to increase the surface area in contact with the living tissue and their fluids. There are several methods used to achieve the PCS form and most of them use suspensions based on liquids immiscibility effect or additives. The aim of this work was to achieve PCS of BCP, HAp and β-TCP with rough surface and varying size without using solutions or additives. The method developed is based on a mechanical continuous movement of the particles, relying on the normal ability of the ceramic powders to aggregate themselves while rolling in a cylindrical container for long periods. The physical forces involved in the process, gravity, particle attraction, centripetal force and shocking make the ceramic rounds with golf ball appearance on its surface. With this method it was possible obtain PCS with 30% of porosity with rough surface and size between 1 to 4 mm in diameter.

Abstract: It is therefore important to implement into practice of uncertainty estimation of coordinate measurement new, correct and metrologically validated methods.because according to technological requirements, results of measurements are useful only when they are given with their accuracy. Currently used methods for uncertainty assessment are difficult and require knowledge and measuring experience. It is therefore important to implement correct and validated methods that will also be easy to implement and will not require broad metrological knowledge from the personnel. Presented here simulation method, based on Monte Carlo method is one of them. The article presents the conception, implementation and validation of this method.

Abstract: SrMoO₄:Eu³⁺ micro-spheres with well morphology were fabricated by a one-step and template-free ultrasonic spray pyrolysis method using strontium nitrate and ammonium molybdate as precursors. The as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra (PL). The XRD results indicate that all the XRD peaks can be indexed as SrMoO₄ with a pure tetragonal scheelite structure. The SEM photographs show that the sample particles are spheres with regular spherical shape. The excitation and emission spectra demonstrate that the phosphors could be excited effectively by the ultraviolet light with wavelength 394 nm or visible blue light with wavelength 466 nm, and the highest emission peak locates at 615 nm.

Abstract: Zinc oxide with spherical shaped and flower shaped morphology are prepared by simple one step solvothermal method. The product is subjected to characterization to investigate the morphology and size by using X ray diffraction , semi electron microscopy and transmission electron microscopy. The size of the prepared zinc oxide particle is in the range of 1 micrometer to 3 micrometers. The outer surface of the particles is not smooth but it is rough. The possible formation mechanism for the product is investigated that is further justified by means of structural characterization.

Abstract: A new synthetic technology of Strontium carbonate with ultrasonic is introduced in this article. Ultrasonic wave synthetic technology is a fast and novel method. Spherical SrCO3 powders were synthesized by changing the solvent and reaction conditions using the ultrasonic wave method. The SrCO3 powders were characterized by the XRD and SEM.The results show that the asprepared products were Spherical structure and with high dispersity, the average particle size of the SrCO3 powders synthesized by the ultrasonic wave synthetic technology is 0.3nm~ 0.5nm. Some reaction parameters were investigated during the process.

Abstract: Tests were performed to assess the parameters influencing the injectability of cement pastes loaded with large particles, such as porogens or drug-delivery agents. The use of non-setting model pastes permitted to demonstrate that two phase separation mechanisms occurred simultaneously, i.e. the separation between liquid and powder, known as filter-pressing phenomenon, and the separation between larger and smaller particles.

Abstract: In this paper we describe the synthesis of nanocrystalline boron nitride (BN) with a hollow morphology by the reaction of NH4BF4 and NaNH2 at 500 oC for 24h. Characterized by XRD, FTIR, XPS, TEM, and EDXA spectra, the composition and morphology of the products were confirmed. The possible formation mechanism was also discussed.