Basic concepts and classical models of solid state sintering

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F60461373%3A22310%2F18%3A43916753" target="_blank" >RIV/60461373:22310/18:43916753 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Basic concepts and classical models of solid state sintering

Popis výsledku v původním jazyce

Polycrystalline materials, both dense and porous, are traditionally fabricated from ceramic, metal or composite powders via powder technology routes that include shaping and sintering steps. During shaping a compact body is formed from the granular raw material, while sintering leads to strengthening of this compact (via neck growth and grain shape changes) and usually also to densification (porosity and pore size reduction) and coarsening (grain growth). Generally both the raw materials and the processing procedures determine the final microstructures and properties of the resulting polycrystalline materials. The paradigmatic model case, often considered as a benchmark, is solid state sintering (SSS), i.e., sintering without the transient assistance of a liquid melt phase that usually remains in the microstructure as a glassy (amorphous) or a second crystalline phase after cooling. In fact, SSS is the via regia to pure single-phase polycrystalline materials. In this contribution we summarize the basic concepts and classical models used for describing SSS processes. Following a brief introduction, in the second section a historical overview of early sintering theory is given, followed in the third section by an explanation of the driving force of SSS. The fundamental significance of the dihedral angle in SSS is explained, as well as the relation between surface curvature and the Kelvin-type equations for vapor pressure and vacancy concentration. In the fourth section sintering stages and mechanisms are discussed. Densifying and non-densifying sintering mechanisms are explained, with a special focus on diffusion mechanisms (surface, grain boundary and volume diffusion) and their temperature dependence (described via Arrhenius equations). The different stages of sintering are treated using the two-sphere model for neck growth in the initial stage and the tetrakaidecahedral cell model (Kelvin cell model) for densification, shrinkage and pore shape changes in the intermediate and final stages. Selected aspects of sintering kinetics and its monitoring by shrinkage and specific surface measurements are briefly outlined as well. In the fifth section grain growth models are briefly summarized and current topics of research in this field are mentioned. In the context of the evolution of grain size distributions during SSS the importance of the Rayleigh distribution is indicated and the necessity to account for the random section problem in order to obtain three-dimensional grain size distributions from two-dimensional sections is emphasized. Finally the sixth section gives a critical account of the concept of master sintering curves, which has turned out to be a successful tool for sintering practice.

Název v anglickém jazyce

Basic concepts and classical models of solid state sintering

Popis výsledku anglicky

Polycrystalline materials, both dense and porous, are traditionally fabricated from ceramic, metal or composite powders via powder technology routes that include shaping and sintering steps. During shaping a compact body is formed from the granular raw material, while sintering leads to strengthening of this compact (via neck growth and grain shape changes) and usually also to densification (porosity and pore size reduction) and coarsening (grain growth). Generally both the raw materials and the processing procedures determine the final microstructures and properties of the resulting polycrystalline materials. The paradigmatic model case, often considered as a benchmark, is solid state sintering (SSS), i.e., sintering without the transient assistance of a liquid melt phase that usually remains in the microstructure as a glassy (amorphous) or a second crystalline phase after cooling. In fact, SSS is the via regia to pure single-phase polycrystalline materials. In this contribution we summarize the basic concepts and classical models used for describing SSS processes. Following a brief introduction, in the second section a historical overview of early sintering theory is given, followed in the third section by an explanation of the driving force of SSS. The fundamental significance of the dihedral angle in SSS is explained, as well as the relation between surface curvature and the Kelvin-type equations for vapor pressure and vacancy concentration. In the fourth section sintering stages and mechanisms are discussed. Densifying and non-densifying sintering mechanisms are explained, with a special focus on diffusion mechanisms (surface, grain boundary and volume diffusion) and their temperature dependence (described via Arrhenius equations). The different stages of sintering are treated using the two-sphere model for neck growth in the initial stage and the tetrakaidecahedral cell model (Kelvin cell model) for densification, shrinkage and pore shape changes in the intermediate and final stages. Selected aspects of sintering kinetics and its monitoring by shrinkage and specific surface measurements are briefly outlined as well. In the fifth section grain growth models are briefly summarized and current topics of research in this field are mentioned. In the context of the evolution of grain size distributions during SSS the importance of the Rayleigh distribution is indicated and the necessity to account for the random section problem in order to obtain three-dimensional grain size distributions from two-dimensional sections is emphasized. Finally the sixth section gives a critical account of the concept of master sintering curves, which has turned out to be a successful tool for sintering practice.

Druh

C - Kapitola v odborné knize

CEP obor

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OECD FORD obor

20504 - Ceramics

Projekt

<a href="/cs/project/GA18-17899S" target="_blank" >GA18-17899S: Částečně a plně slinutá keramika - příprava, mikrostruktura, vlastnosti, modelování a teorie slinování</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2018

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název knihy nebo sborníku

Polycrystalline Materials – Synthesis, Performance and Applications

ISBN

978-1-5361-3864-1

Počet stran výsledku

64

Strana od-do

1-64

Počet stran knihy

187

Název nakladatele

Nova Science Publishers, Inc.

Místo vydání

New York

Kód UT WoS kapitoly

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