Microstructure characterization of porous microalloyed aluminium-silicate ceramics

Kaolinite and bentonite clay powders mixed with active additives, based on Mg(NO3)2 and Al(NO3)2, sintered at high temperatures produce very porous ceramics with microcrystalline and amorphous regions and highly developed metalized surfaces (mainly with magnesium surplus). Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. The ceramics samples were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction analysis (XRD) and IR spectroscopy analysis, prior and after treatment in “synthetic water”, i.e. in aqueous solution of arsenic-salt. Grain size distribution for untreated and treated samples was done with software SemAfore 4. It has shown great variety in size distribution of grains from clay powders to sintered samples

Fractal Corrections of BaTiO3-ceramic Sintering Parameters

Morphology of ceramics grains and pores as well as Brownian character of particle dynamics inside ceramics specimen contributes to better understanding of the sintering process. BaTiO3-ceramics, studied in this paper, has light fractal form and it is emanated in three aspects. First, the surface of grains, even in starting green body as well as distribution of grains shows fractal behavior. Second, existence of pores and their distribution follow the rules of fractal geometry. Third, movement of particles inside viscous flow underlies the rule of Brownian motion, which is essentially a fractal category. These three elements, each in its domain influence sintering dynamics, and can be described by dimensionless quantitative factors, alpha(S), alpha(P) and alpha(M), being normalized to the interval [0,1]. Following sintering process, the associate formulae of Frenkel, Scherer and Mackenzie-Shuttleworth are shown from the angle of view of ceramics fractal dimension changing that approaches to 3. Also, it is shown that the energy balance is not violated after applying fractal correction to quasi equilibrium of the energy emanating from surface area reduction E-S and energy adopted by viscous flow E-f

Sintering Process Influence on Microstructure and Intergranular Impedance of Rare-Earth Modified BaTiO3-Ceramics

Sintering process is a complex of different synergetic effects during the ceramics materials consolidation. The microstructural level properties control is very important as a stage in advanced materials prognosis. SEM analysis of Yb/BaTiO3 doped ceramics showed that in samples doped with, a low level of dopant and sintered at higher temperatures the grain size ranged from 10-60 mu m, while with the higher dopant concentration the grain, size ranged between 2-15 mu m. The morphology of sintered BaTiO3-ceramics grains points out the validity of developing new structure analytical methods based on different geometries of grains' model systems. The idea of electrical properties of BaTiO3-ceramics being influenced by intergrain microcontacts can be successfully followed if we start with the two-sphere Coble's model and also the correction of the Coble's model. In this paper, the grains contact models based on spherical, ellipsoidal and polyhedral geometries are presented making a new modeling tool for structure research of BaTiO3-ceramics materials. Intergranular impedance analysis of grains clusters was also introduced. Obtained results enabled establishment of interrelation between. structural and electrical parameters

Metal rings and discs Matlab/Simulink 3D model for ultrasonic sandwich transducer design

Metal-endings are integral part of different ultrasonic sandwich transducers. In this paper a new Matlab/Simulink 3D model of the finite metal rings and discs of various dimensions is realized. With this model, which describes both the thickness and the radial resonant modes, and the coupling between them, mechanical impedance of the sample can be easily computed. Resonance frequency-length curves for rings and disks with various materials and for different selected dimensions are given. Also, comparisons of the different approaches in determining of their resonant frequencies are shown. The proposed Matlab/Simulink model requires simpler implementation than other analytical models. That enabled modifying of 1D theory and simplified modelling and projecting of the ultrasonic sandwich transducers with short-endings. Finally, the computed and experimental results are compared. [Projekat Ministarstva nauke Republike Srbije, br. TR33035, br. III43014 i br. OI172057

Electronic Ceramic Structure within the Voronoi Cells Model and Microstructure Fractals Contacts Surfaces New Frontier Applications

In this study, in order to establish grain shapes of sintered ceramics, new approach on correlation between microstructure and doped BaTiO3 -ceramics properties based, on Voronoi model and mathematical statistics calculations on fractal geometry, has been developed. BaTiO3-ceramics doped with Yb2O3 (from 0.1 to 1.0wt% of Yb) were prepared by using conventional solid state procedure and were sintered from 1320 degrees C to 1380 degrees C for four hours. The microstructure of sintered specimens was investigated by Scanning electron microscope JEOL-SEM-5300. For better and deeper characterization and understanding of the ceramics material microstructure, the methods which include the fractal nature structure, and also Voronoi model and mathematical statistics calculations, are applied. In our research the Voronoi is one specific interface between fractal structure nature and different stochastically contact surfaces, defined by statistical mathematical methods. Also, the Voronoi model practically provided possibility to control the ceramics microstructure fractal nature. Mathematical statistic methods enabled establishing the real model for the prognosis based on correlation: synthesis-structures-properties

Microstructure and Dielectric Properties of Rare-Earth Doped BaTiO3 Ceramics

The specimens of BaTiO3 doped with 0.01, 0.1 and 0.5wt% of Er2O3 or Ho2O3 used for this investigation were prepared by the conventional solid state reaction. The specimens were sintered at 1350 degrees C in an air atmosphere for 4hours.The grain size and microstructure characteristics for various samples and their phase composition was carried out using a scanning electron microscope SEM equipped with EDS system. SEM analysis of Er/BaTiO3 and Ho/BaTiO3 doped ceramics showed that in samples doped with a low level of rare-earth ions, the grain size ranged from 10-60m, while with the higher dopant concentration the abnormal grain growth is inhibited and the grain size ranged between 2-10m.We also applied the fractal method in microstructure analysis of sintered ceramics especially as influence on dielectric properties of BaTiO3 ceramics. These fractal effects have been used for better understanding of intergranular capacitors

Mechanical properties and microstructure fractal analysis of refractory bauxite concrete

The surface topography analysis via fractals as a means of explanation of composite materials mechanical and microstructural characteristics has hardly been reported so far. This study proposes a method of fractal analysis and its application to refractory bauxite concrete surface tribological investigation. Fractal dimension, profilegrams and fast Fourier transform method are introduced and supported by the adequate software for analysing contours and surface roughness, depending on the observation scale and also numerically depending on horizontal lines intercepted by the investigated profile. Also, the Richardson method and Kaye modification are applied to distinguish textured and structured aspect of grain contour geometry. Microstructural investigation was carried out using a scanning electron microscope. Using the fractals of the grains contact surfaces, a reconstruction of microstructure configuration, as grains shapes or inter-granular contacts, has been performed. Obtained results indicated that fractal analyses of contact surfaces of different shapes were very important for the prognosis of the concrete behaviour. The novel approach to the investigation of refractory concrete properties was successfully conducted, as a result introducing fractal identification as a means of composite materials performances evaluation. [Projekat Ministarstva nauke Republike Srbije, br. ON 172057 i br. III 45008

Electronic ceramic structure within the Voronoi cells model and microstructure fractals contacts surfaces new frontier applications

In this study, in order to establish grain shapes of sintered ceramics, new approach on correlation between microstructure and doped BaTiO3 -ceramics properties based, on Voronoi model and mathematical statistics calculations on fractal geometry, has been developed. BaTiO3-ceramics doped with Yb2O3 (from 0.1 to 1.0wt% of Yb) were prepared by using conventional solid state procedure and were sintered from 1320°C to 1380°C for four hours. The microstructure of sintered specimens was investigated by Scanning electron microscope JEOL-SEM-5300. For better and deeper characterization and understanding of the ceramics material microstructure, the methods which include the fractal nature structure, and also Voronoi model and mathematical statistics calculations, are applied. In our research the Voronoi is one specific interface between fractal structure nature and different stochastically contact surfaces, defined by statistical mathematical methods. Also, the Voronoi model practically provided possibility to control the ceramics microstructure fractal nature. Mathematical statistic methods enabled establishing the real model for the prognosis based on correlation: synthesis-structures-properties. [Projekat Ministarstva nauke Republike Srbije, br. 172057 i br. III44006

Dielectric properties of batio3 doped with er2o3 and yb2o3 based on intergranular contacts model

Taking into account that microstructure properties of barium-titanate based materials, expressed in grain boundary contacts, are of basic importance for electric properties of these material, in this study, the model of intergranular impedance is established using the equivalent electrical scheme characterized by corresponding frequency characteristic. Globally, BaTiO3-ceramics sample is consisted of a huge number of mutually contacted grains which form clusters. For each of them, it is possible to establish the equivalent electrical model and, for defined set of input parameters, using symbolic analysis, obtain the frequency diagram. Realizing the totality of relations between clusters grains groups, their microelectrical schemes and corresponding frequency characteristics, from one side, and global equivalent electrical scheme and corresponding acquired frequency characteristics of BaTiO3-ceramics samples, on the other side, we set a goal of coinciding experimental results with the summing effect of microelectric equivalent schemes. The model is successfully tested on barium titanate ceramics doped with Er2O3, Yb2O3