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[en] Compaction of sintered metal powders by free upsetting at room temperature dangerously reduces their plastic properties, particularly the fracture toughness. The reason for the occurrence of two unfavorable phenomena accompanying this deformation route is sought. The first phenomenon depends on the initial porosity of the preform and the amount of cold work resulting in the destruction of bonds and violation of continuity between sintered powder particles. The second phenomenon is the deformation of the metal matrix, which reduces the plasticity of the sintered product. To correctly assess the effect of changes occurring in the matrix as a result of deformation, it is necessary to use the properly defined sintered matrix hardening parameter discussed in this study. The adverse effects of cold forming can be eliminated by annealing the deformed sinters at a temperature below the sintering point and above the recrystallization temperature. The annealing temperature causes favorable changes in the structure and increases the impact resistance of the deformed sinters depending on the degree of deformation of the sintered matrix and the initial porosity of the preform. Annealing at a properly selected temperature restores the ductility of the metal matrix and improves the integrity of the sintered material impaired by the effect of deformation. Annealing also causes favorable changes in the porosity morphology, removing defects in the form of gaps and resulting in the spheroidization of voids. With an appropriately selected initial porosity and degree of deformation, subsequent annealing of sinters compacted by free cold upsetting provides products with strength properties comparable to sinters with the same density and subjected to single compaction and sintering but with considerably higher fracture toughness.
[en] It is imperative to understand the application of emerging advanced manufacturing techniques to nuclear related capabilities. The Advanced Manufacturing thrust of the In-Pile Instrumentation Initiative seeks to apply techniques such as aerosol jet printing to allow for manufacturing of novel sensor designs. As part of this thrust, a laser sintering system is being developed. The preliminary design allows for benchtop experiments that are controlled with a manual stage. The preliminary results did not appear to achieve sufficient temperatures to sinter the specimen, and temperatures were not accurately measured by the IR camera. A calibration to link silver emissivity with temperature must be performed in order to quantitatively measure temperatures with the IR camera. This calibration will be performed, and a second sintering experiment performed in detail to determine required laser exposure times and temperatures to achieve sintering with the system. Future updates for the system include a higher resolution lens for the IR camera to allow for higher magnification temperature observations, as well as a motorized stage and control framework to link the stage movements to the specimen geometry and desired exposure time during the sintering process.
[en] We introduce a new generalization of the Plateau problem which includes the constraint of enclosing a given region. Physically the problem is important insofar as it bears on sintering processes and on the structure of wetted porous media. Some primal and dual characterizations of the solutions are offered, and aspects of the problem are illustrated in one and two dimensions in order to clarify the combinatorial elements and to demonstrate the importance of numerous local minima. (orig.)
[en] In this study the rapid method for oxide functional ceramics sintering (RMOCS) has been presented. Some experimental results regarding the zirconate-lead titanate (PZT) piezoceramics sintering has been discussed. It is shown that the RMOCS is the most effective method to increase the probability of optimizing the homogeneity of sintered samples final microstructure
[ru]На примере пьезоматериала на основе цирконата-титаната-свинца (ЦТС) обсуждаются экспериментальные результаты скоростного метода спекания (СКС) оксидных функциональных материалов. Показано, что методы СКС относятся к числу наиболее эффективных методов повышения вероятности оптимизации уровня однородности конечной микроструктуры образцов
[en] Some new books published by M.Yu. Baljshin, V.A. Ivensen, V.V. Skorohod and others are characterized by the wish to give a complete approach to the problems of sintering theory. Bearing just this in mind while writing the book ''An Essay on the Generalization of Sintering Theory'' (G.V.Samsonov, M.M. Ristic with the collaborators) an idea was born: to ask the most eminent scientists in this field to present their own opinions on the theme ''The Science of Sintering and Modern Views on its Future''. There were formed 18 questions, given in the appendix to be answered. The received answers were presented in 10 chapters of this book. The fourth part of the book consists of papers of eminent scientists engaged in the field of sintering science (some of which were published here for the first time). This material is published in the book with the consent of the authors and these original contributions provide a more profound knowledge of sintering. The initial idea, that the book should have a monograph character and in which the answers would serve as some data on the latest notions of the science of sintering, was somewhat changed since the original opinions of individual scientists are given in the book and these, are sometimes very contradictory. This, in fact, gives the book a special charm because the unsolved problems in the science of sintering are most evidently stressed in this way
[en] The sintered density of the UO2 pellet is an important factor to assure a stable nuclear reactor control. There are some methods to control the sintered density of the UO2 pellet, that is, a sintering temperature and its time, a green density, an addition of pore-former or U3O8, etc. In general, it is well known that the sintered density of UO2 pellet increases as the sintering temperature and its time and the green density increases. However the addition of a pore-former or U3O8 decreases the sintered density of the UO2 pellet, due to the leave various sizes of pore in the UO2 matrix during sintering. In this work, the effect of the O/U ratio on the sintered density of the UO2 pellet are investigated
[en] Reference is made to an earlier paper on sintering by bulk transport regarding the relationship between surface area and shrinkage. Work with thoria gel relating surface area, coordination number and shrinkage is used to test the earlier data
[en] Directional freeze-casting of ceramic slurries followed by freeze drying and partial sintering results in materials with highly anisotropic properties parallel and transverse to the freezing direction. Physical measurements and optical dilatometry confirm that, during sintering, freeze-cast structures experience more strain along their freezing direction than transverse to it. Discrete Element (DEM) simulations of equivalent freeze-cast structures confirm this behavior. These simulations indicate that not only is sintering anisotropic on the macroscopic scale but within the walls and macropores themselves. It was determined that the anisotropic particle contact network that resulted from the aligned macropores led to anisotropic shrinkage during sintering.