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Articles de revues sur le sujet "Al2TiO5 based model refractory materials"
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Borysenko, Oksana, Sergii Logvinkov, Halyna Shabanova, Igor Остапенко et Vita Шумейко. « GEOMETRICAL–TOPOLOGICAL CHARACTERISTICS OF THE SUBSOLIDUS STRUCTURE IN THE MgO – Al2O3 – TiO2 SYSTEM ». Bulletin of the National Technical University "KhPI". Series : Chemistry, Chemical Technology and Ecology, no 1(5) (15 mai 2021) : 18–23. http://dx.doi.org/10.20998/2079-0821.2021.01.03.
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Among the materials that attract attention from the point of view of creating refractory products with increased heat resistance, one can single out materials based on compositions of the MgO – Al2O3 – TiO2 system. As a result of the thermodynamic analysis of the MgO – Al2O3 – TiO2 system, it was found that the partition of the system into elementary triangles will change in three temperature ranges: I – up to 1537 K, II – in the temperature range 1537 – 2076 K and above 2076 K. It has been established that up to a temperature of 2076 K there is a concentration range of spinel phases: magnesium aluminate spinel – quandylite. Above 1537 K, there is a concentration range: tialite – karroite, which meets the requirements for materials with high heat resistance. The elementary triangle TiO2 – Al2TiO5 – MgTi2O5 can be used to obtain heat–resistant materials based on Al2TiO5 stabilized by MgTi2O5. To obtain heat–resistant periclase–spinel materials, an elementary triangle Mg2TiO4 – MgAl2O4 – MgO is recommended, in which only compounds with a cubic crystal lattice are present. Thus, the division of the MgO – Al2O3 – TiO2 system into elementary triangles and the analysis of the geometrical–topological characteristics of the phases of the system made it possible to select in the system under study the regions of compositions that have optimal properties for obtaining materials with the specified optimal properties.
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Epicier, T., G. Thomas, H. Wohlfromm et J. S. Moya. « High resolution electron microscopy study of the cationic disorder in Al2TiO5 ». Journal of Materials Research 6, no 1 (janvier 1991) : 138–45. http://dx.doi.org/10.1557/jmr.1991.0138.
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As part of a research program devoted to the microstructural characterization of Al2TiO5-based compounds, high resolution electron microscopy (HREM) has been undertaken in order to study the crystallographic arrangement, especially ordering possibilities, of Al and Ti cations in the metallic sublattice of aluminum titanate. It is seen that adequate experimental conditions, mainly defocus setting, for a resolution of at least 2.5 Å point-to-point, enable the disordered model to be directly and unambiguously proved on 100-oriented micrographs.
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Dhupal, D., B. Doloi et B. Bhattacharyya. « Optimization of process parameters of Nd:YAG laser microgrooving of Al2TiO5 ceramic material by response surface methodology and artificial neural network algorithm ». Proceedings of the Institution of Mechanical Engineers, Part B : Journal of Engineering Manufacture 221, no 8 (1 août 2007) : 1341–50. http://dx.doi.org/10.1243/09544054jem814.
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The high-intensity pulsed Nd:YAG laser has the capability to produce both deep grooves and microgrooves on a wide range of engineering materials such as ceramics, composites, and diamond. The micromachining of ceramics is highly demanded in industry because of its wide and potential uses in various fields such as automobile, electronic, aerospace, and biomedical engineering. Engineering ceramic, i.e. aluminium titanate (Al2TiO5), has tremendous application in the automobile and aero-engine industries owing to its excellent thermal properties. The present paper deals with the artificial neural network (ANN) and response surface methodology (RSM) based mathematical modelling and also an optimization analysis of the machining characteristics of the pulsed Nd:YAG laser during the microgrooving operation on Al2TiO5. The experiments were planned and carried out based on design of experiments (DOE). Lamp current, pulse frequency, pulse width, assist air pressure, and cutting speed were considered as machining process parameters during the pulsed Nd:YAG laser microgrooving operation and these parameters were also utilized to develop the ANN predictive model. The response criteria selected for optimization were upper width, lower width, and depth of the trapezoidal microgroove. The optimal process parameter settings were obtained as an assist air pressure of 1.2944 kgf/cm2, lamp current of 19.3070A, pulse frequency of 1.755 kHz, pulse width of 5.7087 per cent of duty cycle, and cutting speed of 10mm/s for achieving the desired upper width, lower width, and depth of the laser microgroove. The output of the RSM optimal data was validated through experimentation and the ANN predictive model. A good agreement is observed between the results based on the ANN predictive model and the actual experimental observations.
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Sagadin, Christoph, Stefan Luidold, Christoph Wagner, Christoph Pichler, Daniel Kreuzer, Alfred Spanring, Helmut Antrekowitsch, Amy Clarke et Kester Clarke. « Thermodynamic Refractory Corrosion Model for Ferronickel Manufacturing ». Metallurgical and Materials Transactions B 52, no 2 (24 février 2021) : 1052–60. http://dx.doi.org/10.1007/s11663-021-02077-x.
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AbstractA thermodynamic model, based on SimuSage, was developed to simulate refractory corrosion between a magnesia-based refractory material and ferronickel (FeNi) slags. The model considers a theoretical cross-section of a refractory material to simulate a ferronickel smelter application. The current model is structured into 10 zones, which characterize different sectors in the brick (hot to cold side) perpendicular to the refractory surface with an underlying temperature gradient. In each zone, the model calculates the equilibrium between the slag and a specified amount of refractory material. The emerging liquid phases are transferred to subsequent zones. Meanwhile, all solids remain in the calculated zone. This computational process repeats until a steady state is reached in each zone. The simulation results show that when FeNi slag infiltrates into the refractory material, the melt dissolves the magnesia-based refractory and forms silicates (Mg,Fe,Ca)2SiO4 and Al spinel ((Mg,Fe)Al2O4). Furthermore, it was observed that iron oxide from the slag reacts with the refractory and generates magnesiowustite (Mg,Fe)O. Practical lab-scale tests and scanning electron microscopy (SEM)/Energy Dispersive X-ray Spectroscopy (EDS) characterization confirmed the formation of these minerals. Finally, the refractory corrosion model (RCM) ultimately provides a pathway for improving refractory lifetimes and performance.
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Ricoeur, Andreas, et Dimitri Henneberg. « Two Scale-Based Continuum Damage Model for Brittle Materials under Thermomechanical Loading ». Key Engineering Materials 525-526 (novembre 2012) : 589–92. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.589.
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Ceramic refractory materials initially contain a multitude of defects such as voids, microcracks, grain boundaries etc. Particularly being exposed to high temperatures above 1000 °C the macroscopic properties such as effective compliance, strength and lifetime are essentially determined by microscopic features of the material. The deformation process and failure mechanisms are going along with the creation of new microdefects as well as the growth and coalescence of cracks. A brittle material damage model for dynamic thermomechanical loading conditions is presented in this paper. Representative volume elements (RVE) include microcrack initiation and growth. The material laws are formulated on the continuum level using appropriate homogenisation methods. To demonstrate the potential of the numerical tools, two examples are presented which are taken from applications. Based on experiments, cyclic thermal shock tests at refractory plates are simulated by FEM. To quantify the thermal shock resistance of ceramics, experiments suggested by Hasselman are simulated numerically supplying a critical temperature slope.
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Grigoriev, Aleksandr S., Andrey I. Dmitriev et Evgeniy V. Shil’ko. « Evaluation of local mechanical properties of SiO2-based ceramic refractories using microscale modeling ». Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, no 80 (2023) : 73–84. http://dx.doi.org/10.17223/19988621/80/7.
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The development of multiscale mechanical models of promising refractory materials is an urgent problem in the mechanics of solids. One of the reasons is the applicability of these models when creating digital twins of advanced refractories. The authors of this paper recently developed and validated a mesoscopic model of the SiO2-based refractory material that is widely used in metallurgy. This model takes into account the characteristic structural features of SiO2 refractory in the scale range of 10-5 - 10-2 m and the mechanical behavior features in a wide range of strain rates. However, the full use of the model requires knowledge of local mechanical properties of mesoscopic structural elements, in particular, the highly porous regions, which are formed by fine grains less than 102 pm in size. An experimental study of effective mechanical characteristics of such regions is an extremely difficult task. Therefore, the purpose of this work is to obtain the theoretical estimate using the microscale numerical simulation of highly porous regions of SiO2 refractory material and to determine their integral mechanical characteristics. To study this problem, the two-dimensional model samples are developed that simulate fine-grained regions of the refractory and are characterized by different porosity and pore structure types (channel-like or closed type). The intervals of the variation of Young’s modulus and strength characteristics of the samples are obtained depending on the porosity and morphology of the pore space. The contribution of the closed-type porosity to the integral mechanical characteristics of the refractory is determined; though, the volume fraction of such pores is low as compared to that of the channel-like pores. The obtained data will be used as input parameters of mesoscale refractory models for solving the urgent problems related to the study of the effect of microstructure parameters on the macroscopic mechanical and thermomechanical properties of SiO2-based refractories.
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Wang, Zhi Gang, Chang Ming Liu, Nan Li et Yuan Wang. « Prediction of Properties of MgO-C Refractory Based on Micromechanics Model ». Applied Mechanics and Materials 37-38 (novembre 2010) : 890–94. http://dx.doi.org/10.4028/www.scientific.net/amm.37-38.890.
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The microstructures of materials determine their properties. Micromechanics is one of the effective methods by which the quantitative relationship between the microstructure of the material and macroscopical mechanical properties can be established. In this paper, the mechanical properties of matrix phase from two different MgO-C refractories were predicted by using micromechanics model. Then, the predicted results were explained based on their different microstructures and compositions. It was proved that the method provides a new approach for researching the mechanical properties of refractories.
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Yan, Xiaobing, Gong Wang, Jianhui Zhao, Zhenyu Zhou, Hong Wang, Lei Zhang, Jingjuan Wang et al. « Memristors mimicking the regulation of synaptic plasticity and the refractory period in the phenomenological model ». Journal of Materials Chemistry C 8, no 15 (2020) : 5183–90. http://dx.doi.org/10.1039/d0tc00575d.
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Li, Bin, Ke Peng, Chen-Hao Yang et Xu-Hui Zhang. « Optimization method for clamping layout of refractory thin-wall parts based on IAGA-Elman ». Journal of Physics : Conference Series 2760, no 1 (1 mai 2024) : 012055. http://dx.doi.org/10.1088/1742-6596/2760/1/012055.
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Abstract Thin-walled parts made of refractory materials are widely used in the sintering field of lithium battery powder materials. To solve the problem of deformation and fracture caused by the low stiffness of refractory thin-wall parts, a sandwich-layout proxy optimization model based on the IAGA-Elman neural network and sub-optimization mechanism was proposed. Based on ABAQUS, finite element simulation models under different clamping layouts were obtained. The sample set required for neural network training was established, a sub-optimization mechanism with MSP+EI combination plus point criterion as the target task was constructed, and the IAGA algorithm was used to optimize the Elman neural network for optimal parameter seeking. The deep nonlinear mapping relationship between clamping layout parameters and clamping deformation is explored by proxy optimization model. The experimental results show that the proposed method can predict the clamping deformation of thin-walled parts with fewer simulations and higher fitting accuracy, and can provide a basis for the optimal design of the clamping layout of refractory thin-walled parts.
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Spyridakos, Athanasios, Dimitrios E. Alexakis, Isaak Vryzidis, Nikolaos Tsotsolas, George Varelidis et Efthimios Kagiaras. « Waste Classification of Spent Refractory Materials to Achieve Sustainable Development Goals Exploiting Multiple Criteria Decision Aiding Approach ». Applied Sciences 12, no 6 (16 mars 2022) : 3016. http://dx.doi.org/10.3390/app12063016.
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The recycling of used refractory materials in the heavy industry constitutes one of the significant environmental problems in the industry related to environmental and financial issues. This study proposes a multicriteria methodological frame to characterize the refractory material waste and identify the recycling capabilities. Considering the chemical and physical analysis of the refractory material wastes, the proposed methodological frame progresses into a two-phase procedure. The first phase includes an on/off approach that allows discretizing the refractory material wastes to compatible or not compatible as far as their recycling prospects. Then, an additive value model is utilized, including (a) the marginal value functions used for every criterion related to critical environmental factors, and (b) the weight vector reflecting the relative importance of the criteria used. A group of experts concerning the environment and the refractory materials was employed to estimate the additive value model. The assessment of the marginal value function is achieved using the module of the Multicriteria Interactive Intelligence Decision Aiding System (MIIDAS), which is based on a modification of the mid-value split point technique incorporating focused dialogues, artificial intelligence, and visual techniques. The weight vector was assessed using the weight assessment through prioritization method (WAP), which concludes with the estimation of the weights based on the criteria ranking and the pairwise expression of the strength of preferences for the consecutive criteria according to their ranking. The outcome of this approach is to introduce an environmental appropriateness index for refractory materials based on their chemical composition and the judgement of an expert group. The main findings of this research may be useful for engineers, decision-makers, and scientists in the field of circular economy and waste management.
Thèses sur le sujet "Al2TiO5 based model refractory materials"
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Mouiya, Mossaab. « Thermomechanical properties of refractory materials, influence of the diffuse microcracking ». Electronic Thesis or Diss., Limoges, 2024. http://www.theses.fr/2024LIMO0066.
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Les matériaux réfractaires sont largement utilisés dans les applications à haute température mais ne sont pas toujours enclins à résister aux chocs thermiques sévères. Pour résoudre ce problème, une microstructure incorporant des microfissures préexistantes est une solution bien connue pour améliorer la résistance aux chocs thermiques. Néanmoins, une telle microstructure endommagée nécessite une meilleure compréhension pour optimiser son design sans compromettre l'intégrité du matériau. Dans un tel contexte, le Titanate d'Aluminium (Al₂TiO₅, AT) présentant une forte anisotropie de dilatation thermique, constitue un système modèle idéal pour créer un réseau de microfissures adapté afin d'améliorer la flexibilité et le comportement à la rupture. Cette thèse étudie les propriétés thermomécaniques des matériaux réfractaires développés à base d'AT, comprenant des céramiques polycristallines et des composites alumine/AT, en mettant l'accent sur les relations entre la microstructure et les propriétés macroscopiques. Dans le cas de ces deux matériaux, les microfissures préexistantes jouent un rôle clé sur le module de Young, le comportement de dilatation thermique, la réponse contrainte-déformation en traction, l'énergie de rupture et donc la résistance aux chocs thermiques. Un effet d’hystérésis significatif sur le module de Young et l’expansion thermique en fonction de la température témoigne des mécanismes de fermeture-réouverture de microfissures. Des essais de traction uniaxiale ont mis en évidence des lois de comportement non linéaires, impactant l'énergie de rupture et la résistance aux chocs thermiques. En particulier, des essais de traction incrémentale à 850 °C ont montré des comportements antagonistes à la montée ou à la descente en température du fait de l’histoire thermique. Les composites (alumine/AT) avec des 0 à 10 % d’inclusions présentent des microfissures diffuses dues à un différentiel d’expansion thermique. Ils présentent un module de Young réduit, des lois de comportement fortement non linéaires et une déformation à la rupture plus élevée à température ambiante. Les essais de choc thermique effectués par le dispositif innovant ATHORNA pour tous les matériaux à base d'AT étudiés ont confirmé leur résilience sous gradient thermique élevé. Ces résultats fournissent des informations précieuses pour le design de futurs matériaux réfractaires avancés présentant une résistance aux chocs thermiques amélioréeRefractory materials are widely used in high-temperature applications but are not always prone to resist severe thermal shock. To address this problem, microstructure incorporating pre-existing microcracks are already well known to improve thermal shock resistance. Nevertheless, such damaged microstructure needs a better understanding to optimize their design without compromising material integrity. In such context, Aluminum Titanate (Al₂TiO₅, AT) exhibiting a great thermal expansion anisotropy, constitutes an ideal model system for creating a tailored microcracks network in order to improve flexibility and fracture behavior. This thesis investigates the thermomechanical properties of developed AT-based refractory materials, including polycrystalline AT and alumina/AT composites, with emphasis on the relationship between microstructure and macroscopic properties. In both materials, pre-existing microcracks play a key role on Young's modulus, thermal expansion behavior, tensile stress-strain response, fracture energy, and thus thermal shock resistance. A significant hysteretic effect on Young's modulus and thermal expansion as a function of temperature indicates microcracks closure-reopening mechanisms. Uniaxial tensile tests revealed nonlinear stress-strain laws, impacting fracture energy and thermal shock resistance. In particular, incremental tensile tests at 850 °C showed contrasting behaviors during heating and cooling, attributed to thermal history. Composite materials with AT inclusions (0 - 10 wt.%) embedded in an alumina matrix exhibit diffuse microcracking due to thermal expansion mismatch. These composites exhibited reduced Young's modulus, highly nonlinear stress-strain laws, and higher strain to rupture at room temperature. Thermal shock tests performed by the innovative ATHORNA device for all studied AT-based materials confirmed their resilience under high thermal gradients. These findings provide valuable insights for the design of future advanced refractory materials with improved thermal shock resistance
Actes de conférences sur le sujet "Al2TiO5 based model refractory materials"
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Zhao, Jiuling, Hehao Shang, Zhaojun Zhu, Guoxing Zhang, Leiguang Duan et Xinya Sun. « Simulation of meso-damage of refractory based on cohesion model and molecular dynamics method ». Dans MATERIALS SCIENCE, ENERGY TECHNOLOGY AND POWER ENGINEERING II (MEP2018). Author(s), 2018. http://dx.doi.org/10.1063/1.5041199.
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Vysochanskii, Yulian, Vitalii Liubachko, Viacheslav Hryts, Mykola Medulych et Anton Kohutych. « The mixed spin-1/2 and spin-1 Ising model for CuInP₂S₆ ferrielectrics ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-yv1553.
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The temperature behavior of Sn₂P₂S₆ ferroelectrics was previously explained using the Blume-Capel model with pseudospin S=1, which is related to the local three-well potential for spontaneous polarization fluctuations [1-3]. For CuInP₂S₆ crystals, the mixed Ising model [4,5] can be applied, which uses spins s=1/2 and S=1. These spins are related to the ordering dynamics of Cu⁺ cations in the double-well potential (pseudospins s=1/2) and to the displacive dynamics of In³⁺ cations in the three-well local potential (pseudospins S=1). The quantum anharmonic oscillator model was used to accomplish this task. Additionally, data from a light scattering study is incorporated. Based on the temperature dependence of the pseudospin fluctuations spectra, it can be concluded that the In³⁺ cations experience anharmonic disordering/displacements in the local asymmetric three-well potential at temperatures below 150K. This leads to specific lattice anharmonicity phenomena, which alter the temperature behavior of the lattice vibrations and cause the thermal expansion coefficient to change sign. Additionally, a dipole glassy appearance is observed in the deeply cooled ferrielectric phase. The contribution of Cu⁺ cations to the calculated pseudospin fluctuation spectra is found to evolve with heating above 150K, supporting the activation of ionic conductivity in CuInP₂S₆ crystals. Notably, the same species, namely copper cations, participate in both spontaneous polarization and ionic conductivity creation. The variation of the pseudospin fluctuation spectra upon heating to 150K is consistent with the softening of the Raman low-frequency spectral lines related to the cationic sublattice dynamics of indium and a broadening of the spectral line above this temperature due to the disorder in the copper sublattice.
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Ivanchenko, Serhii. « Prediction of nanopowder based tape surface roughness and density from a suspension rheological data ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-si1614.
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To create a model for predicting the hydrocluster size in polymer-powder (PVB-BaTiO3) tape casting suspensions, a relation between the Peclet number and viscosity was studied. We used two suspensions with identical composition but different powder size (24 nm and 500 nm). Rheological studies of the dispersion with known-size particles make it possible to calculate the Peclet Number for this dispersion using equations [1], [2]: Pa=(6πr³ γη)/kT Where r – hydrocluster radius, γ – shear rate, η – viscosity, k – Boltzmann constant, T – temperature The relation between the Peclet number and viscosity fits a power low model Pe= (nanopowder) and Pe= (submicron powder) By applying this model to a flow curve of the tape casting suspension, where viscosity is known for each shear rate value, it is possible to calculate a hydrocluster diameter (d) using the equation: d=2∛(PekT/6πγη). Applying this model to rheological data of the nanopowder suspension showed a change in hydrocluster size from 208 to 60 nm, and for the submicron powder suspension, from 3520 to 924 nm. For a surface with the smallest possible roughness, assuming that the powder particles are spherical and tightly packed, the packing factor (φ) is 0,74. In this scenario Ra = d·(1/8), Rz = d·(1/2). In the case of non-dense packing of spheres (φ=0,68) Ra = d·(3/16), Rz = d·(3/4) [3]. The developed method was applied to compare roughness predictions based on calculated hydrocluster size with experimental data obtained from optical profilometry of the tape's surface. Predicted roughness for non-dense packing (φ=0,68) of the nanopowder tape is Ra=39 nm and Rz=156 nm. For the dense packing (φ=0,74) Ra=26 nm and Rz=104 nm. Experimental data: Ra=26 nm and Rz=100 nm. For the submicron powder tape Ra=265 nm and Rz=1062 nm (non-dense packing, φ=0,68) and Ra=177 nm, Rz=707 nm (dense packing, φ=0,74). Experimental data: Ra=261 nm and Rz=1076 nm. The error of predicted data is ranging from 1 to 4 %.
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Dutka, Vasyl', Vitaliy Kulich et Oleksandr Borymskyi. « Simulation of densification of ceramic materials based on boron carbide during high-speed sintering under pressure ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-vd1637.
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Strength characteristics of ceramic materials, obtained in a result of sintering under pressure, significantly depends on their density. The sintering regime parameters as well as grain growth affect the density of the sintered material. In order to achieve high density, it is necessary to minimize grain growth. Therefore, it is important to predict the evolution of the sample material density and grain growth at the final sintering stage. At the present time, a number of densification models of ceramic powders during sintering under pressure have been developed. For the application of these models, it is important to determine their parameters. One of the densification models is the Skorohod-Olevsky model. Since the densification process of powder samples by high-speed sintering under pressure (HSSP) is very fast, the creep of the crystal lattice and grain boundaries can be considered as the dominant densification mechanism. Hence, the densification model can be limited to only the component that describes the mechanism of generalized creep. Therefore, the number of model parameters that need to be identified for simulation of densification is reduced. The purpose of this work is to apply a linear regression approach to determine the parameters of Skorohod-Olevsky densification model of powder samples based on boron carbide during HSSP according to experimental data, and to model the powder materials compaction using these parameters. The parameters of material densification model were determined using the results of HSSP-experiments of powder samples with two compositions based on boron carbide. A computer model of the densification of viscous porous materials was developed, taking into account grain growth. Modeling of the densification of powder materials during HSSP-process was carried out. It is shown that at noticeable grain growth of the sample material during HSSP, in order to obtain a dense composition it is necessary to increase the holding time. It is also shown that in this case, one of the alternatives to increasing the exposure time is the increasing of the working pressure.
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Ivanitskii, Stanislav, et Yurii Chuvashov. « Thermal stability of composite materials based on boron oxide modified basalt fibers ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-si1303.
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Composite materials (CM) based on fibers containing B2O3 are used for neutron radiation shielding in nuclear reactors. Thermal stability of CM is related to the ability to maintain high strength of reinforcing fibers under thermal loads. The main reason for the decrease in strength is crystallization. This is due to the development of microcrystalline nuclei that formed in the fibers at the stage of drawing in the crystallization zone. The aim of this work is to analyze the influence of the rheological properties of the melt containing B2O3 on the conditions of fiber drawing, which affect the appearance of the microcrystalline phase in them. Modified glass was obtained by adding B2O3 to andesite basalt. The viscosity of the glass melt was determined on a rotary viscometer. The study of the conditions for the drawing of modified fibers was carried out on a laboratory bench and through theoretical analysis. The temperature of the upper limit of crystallization of the melt Tulc was determined by the quenching method. A mathematical model of the continuous fiber drawing process was used to estimate the crystallization zone. The viscosity of the glass melt with a content of 6 wt.% B2O3 is lower than viscosity of the andesite-basalt melt. The temperature Tulc of modified glass and andesite basalt is the same. Calculations of the speed of movement and the cooling rate of the melt jet during fiber drawing were carried out, which made it possible to determine the glass transition temperature Tgl, the temperature zone of crystallization from Tulc to Tgl and the residence time of the melt in this zone (the time of crystallization). The research results showed that the addition of B2O3 to the composition of glass changed the rheological properties of the glass melt and the conditions for drawing fibers from it. This led to a change in the fibers production interval and the concentration of microcrystalline nuclei in them and affected the thermal stability of fibers.
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Syrovatko, Yuliya, et Eduard Shtapenko. « Thermodynamic approach to studying of processes of contact interaction between W – C filler and iron-based binder of composite materials during infiltration ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-ys1427.
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Higher performance characteristics of the composite materials with iron-based binders can be achieved by reducing the fragility of contact interaction zones through changing of the structure of granules of the W – C filler alloy. Previous experimental work showed the lower rate of dissolution of phases of the microcrystalline W – C filler alloy in the binder, compared to the crystalline W – C filler alloy [1]. The entropy of microcrystalline and crystalline structures of W – C alloys was determined by scanning of their digital photo-images with the use of TLC_Manager software. Further, statistical distribution of the probability density for the optical absorption coefficients was formed. Based on the fact, that logarithmic representation of the normal distribution functions is of the form of quadratic functions, we calculated the statistical distribution parameters [2]. It allowed calculating the entropy of structures at 300 K. Obtained values were 82 and 76 J/(mol∙К) for the crystalline and microcrystalline structures, accordingly. On the other hand, using the Debye model representations, we expressed the Helmholtz free energy and entropy as the functions of temperature and Debye temperature. From these expressions, knowing the values of entropy of the structures at 300 K, we found the Debye temperatures of structures, as well as the values of entropy, free energy and Gibbs energy of these W – C alloys at the temperature of infiltration of composite materials (1523 К). W – C filler and iron binder of the composite materials during infiltration were considered as two systems being in diffusion and thermal contact. The larger the difference in the chemical potentials of these systems, the more intense are the processes of diffusion and dissolution occurring at the interface of the systems [3]. It is found that the difference in chemical potentials of the microcrystalline filler alloy and the binder is less than that of the crystalline filler alloy.
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Korobko, Pavlo, et Andrii Kuzmov. « Theoretical evaluation of mechanical properties of inverse opal structure ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-pk2254.
Texte intégralRésumé :
The study focuses on the theoretical evaluation of the mechanical properties of porous materials with an inverse opal structure which serves as the object of the study. The subject of the study is the process of transition from elastic to irreversible deformation. The purpose of this study is to apply the finite element method to model this process to reveal the relationship between the structural characteristics of materials, such as porosity and coating thickness, and their mechanical properties [1]. The yield surface was constructed by computational modelling on a representative cell with a number of points in the (p,τ) plane for several cases of inverse opal structure - for a highly porous uncoated structure and structures with an additional layer [2]. As a result of the study, yield surfaces of the structure under investigation were constructed for several porosity values, from 0.56 to 0.9. In the result of the work, the approximation of the numerical appearance of the yield surface by a Deshpande-Fleck crushable foam model available in finite element modelling packages was made [3]. The conclusions of the study show that the effective plastic properties of materials with an inverse opal structure significantly depend on their porosity level and the presence of additional coatings. The obtained yield curve for a porosity of 0.9 is close to the associated plastic flow law, which allows us to assess the material's behaviour under loading based on the results of the uniaxial stress state. However, for a structure with medium porosity and an additional coating layer, the surface becomes significantly unassociated, with a discrepancy of almost 30%. The application of the Deshpande-Fleck model for crushable foam in the approximation of the obtained numerical data from the study demonstrated the relevance of the model in describing the plastic behaviour of this structure only at high porosity values.
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Bataiev, Mykola, Natalia Barchevska, Olena Lavrynenko et Yurii Bataiev. « EPR study of spectral characteristics of REE oxides ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-mb1415.
Texte intégralRésumé :
The intensities of the EPR line for Er2O3 REE samples correspond to the Lorentz line theoretical model [1]. The dependence of the intensity of the lines on the corresponding the gain value has a linear model of the parameters. Dependence plane of the EPR line corresponding to the number of spin domains of the sample, as well shows a linear model of the coefficient value. EPR spectral lines located at 3560G, 1665G, and also at 3050G on the scale of the electromagnetic resonance field refer to the main ion Er3+ rare earth oxide (REE) oxide Er2O3 [2] EPR lines indicate the presence of ions in the corresponding electronic form and refer to the spin of ions and REE oxides. The value of the factors is 1.7554 for the oxide system of Er2O3-CeO2 oxide [1, 2] testifies to the presence of Er3+ ion in the system of the cubic form of Er2O3 oxide and corresponding phase formation of rhombic Er2O3 oxide after heat treatment 1100ºС-1500ºС. The g-factor value of 1.7554 in the EPR spectrum implies the presence of the main one Er3+ ion with an additional shift, which corresponds to the appearance and new formation of an additional one of the phase part of the Er2O3 oxide after high-temperature treatment of the material oxide 1100ºС-1500ºС. The g-factor value of 2.049 is responsible for the proper transition of the main Er 3+ ion with the electronic structure 4f 11 5s 2 5p 6 of the oxide Er2O3 . Spin configuration state for Er3+ oxide Er2O3 is defined in the format 4 I 15/2 . The g-factor value is 0.958 is responsible for the Er2+ -based ion transition with an additional shift that implies the presence of Er ions in different formats in different concentrations in oxides systems based on Er2O3 . The configuration of the ion Er2+ electronic state is determined 4f 12 5s 2 5p 6 and the configuration of the spin state for the Er2+ ion is defined by 3H6.
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Baranovska, Oksana, Larysa Romanova, Valentina Sudavtsova et Gennadii Bagliuk. « Interaction Energy in the Melts of the Fe-Mn-Si-C-Ti System ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-ob1145.
Texte intégralRésumé :
Ferrosilicomanganese (Fe0.21Mn0.62Si0.14C0.07) and silicomanganese are widely used in metallurgical and materials science industries due to their ability to melt at low temperatures. The addition of reactive titanium leads to the formation of various phases, each possessing unique properties. Thorough study of their thermodynamic properties, particularly the melts, is essential for optimizing technological processes. However, determining these properties is complex and time-consuming. Preliminary evaluation using geometric and Redlich-Kister-Muggianu models across concentration ranges is advisable, based on data from limiting binary systems. In the work [1], the thermochemical properties of melts of the Fe-Mn-Si system were determined by calorimetry at 1873 K. Comparison of experimental and predicted thermochemical properties of melts of the Fe-Mn-Si system showed that the best agreement is characteristic for the Redlich-Kister-Muggianu model with a ternary contribution of 300 kJ/mol. Applying the same model, thermochemical characteristics of melts of ternary systems Fe(Mn)-Si-Ti, Fe-Mn-Ti, and Si-Ti-C were calculated across the entire concentration range. It was found that the minimum enthalpy of mixing corresponds to the melts of Si-Ti is -70 kJ/mol, Fe-Ti is -20 kJ/mol, and Ti-C is -115 kJ/mol, indicating predominance of pairwise interactions. This is supported by the results of X-ray diffraction analysis (XRD) and electron microscopy studies. However, according to XRD, the synthesis of the mentioned metal-matrix composites (MMCs) results in the formation of the ternary compound Ti3SiС2. According to our modeling, melts of such composition exhibit a significant heat release (-110 kJ/mol), suggesting the formation of such a compound is expected. The formation of various binary and ternary phases enhances the strength, hardness, and other properties of the metal-matrix composites.
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Redko, Roman, Grigorii Milenin, Nadiia Safriuk-Romanenko et Svitlana Redko. « Modification of dislocation concentration in GaN:Si films by non-thermal microwave radiation treatment ». Dans IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-rr1233.
Texte intégralRésumé :
Both photoluminescence spectra and X-ray diffraction of GaN:Si were measured during long term (one month) after processing in microwave field (2.45 GHz, 10 s, p=7.5W/cm2). It was obtained non-monotonous changes of detected characteristics of studied samples. Due to small energy obtained in chosen field alternative resonant mechanism was proposed to explain observed features. Transformation of the defect subsystem (impurity-defect complexes destruction and/or detachment and displacement of dislocations) could be realized due to resonant phenomena related with coincidence between the electromagnetic wave frequency and proper frequencies of dislocation oscillations [1] and ion-plasma oscillations of impurity ions [2]. At the resonant frequency with small attenuation, the amplitude and, therefore, the oscillation energy increase sharply. As soon as the oscillation energy becomes higher than the binding energy of defects, the noted changes occur in the state of the latter. The observed features of long-term changes in the PL band intensities and dislocations concentration for the semiconductors under investigation after treatments in microwave field has been well described by the offered physical-statistical model of the behavior of defects, which is based on the idea that the corresponding physical processes can be described as random events. This physical-statistical approach allowed us to estimate the diffusion coefficients of defects in epitaxial films of semiconductor compounds. Obtained information will be value for understanding sensor system natural aging due to presence external microwave fields