Transient creep behaviour of hot isostatically pressed silicon nitride

Wiederhorn, Sheldon M.; Hockey, B. J.; Cranmer, David C.; Yeckley, R. L.

doi:10.1007/bf00357822

Cited by 94 publications

(53 citation statements)

References 27 publications

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“…22 From these considerations, then, we mary creep in silicon nitride. [25][26][27][28] In our study, however, no define a normalized strain rate, [ε ], which accounts for differsignificant grain growth was detected during the test and no ences in grain size by evidence of glassy layers was observed in the TEM. Thus, further work is needed in order to better understand primary creep behavior in these systems.…”

contrasting

confidence: 65%

Effect of Yttrium and Lanthanum on the Tensile Creep Behavior of Aluminum Oxide

Cho

Harmer

Chan

et al. 1997

Journal of the American Ceramic Society

190

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A number of preliminary observations have guided this The tensile creep behavior of two rare-earth dopant sysstudy. For example, it is known that the bulk solubility of Y 3ϩ tems, lanthanum-and yttrium-doped alumina, are comand La 3ϩ in alumina is very small 11,12 and the size mismatch pared and contrasted in order to better understand the role between Al 3ϩ and the aforementioned dopant cations is quite of oversized, isovalent cation dopants in determining creep large. Thus, it might be expected that Y and La ions will behavior. It was found that, despite some microstructural segregate preferentially to extended defects, such as free surdifferences, these systems displayed qualitatively a similar faces and grain boundaries. This expectation was validated in a improvement in creep resistance, supporting the hypothesis previous SIMS (secondary ion mass spectroscopy) mapping that creep is strongly influenced by segregation. Differences study 13 and STEM (scanning transmission electron microscopy) in primary creep behavior and activation energy for steadywork 14,15 in which both Y and La dopant segregation was state creep were, however, observed for these systems. Given observed. Indeed, sintering studies show that Y and La retard these results, it is expected that creep behavior can be furgrain growth and greatly reduce the densification rate in these ther optimized by adjusting the dopant level and by controlsystems. 16 Further, it has been reported that Y can reduce the ling the microstructure.growth of polycrystalline alumina scales. 17 As mentioned above, the present work consists of tensile I. Introduction creep testing and microstructural characterization of both Yand La-doped alumina. Microstructural analyses center on M ECHANICAL properties of structural ceramics in a highquantifying differences in average grain size and shape between temperature environment have been the subject of numerthese two systems as well as grain evolution during the test. The ous investigations over the years. For this reason, creep goal of this effort is to relate microstructural features of the properties have been studied and modeled extensively, and oxide to the (macroscopic) steady-state creep rate, as detercreep mechanisms are well-established. [1][2][3][4] In particular, much mined by a tensile creep test. As will be seen below, such comrecent work has involved the addition of impurities and the plementary testing is helpful in formulating structure-property tailoring of microstructures with the goal of obtaining desirable relations. properties over a range of temperatures. The creep rate in doped alumina depends strongly on the type of dopant, and most single dopants have been found either to increase the creep rate

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contrasting

confidence: 65%

Effect of Yttrium and Lanthanum on the Tensile Creep Behavior of Aluminum Oxide

Cho

Harmer

Chan

et al. 1997

Journal of the American Ceramic Society

190

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“…This value is higher than the activation energy of creep of monolithic Si 3 N 4 and is comparable to the values of the activation energies of the creep of Si 3 N 4 +SiC nanocomposites prepared by addition of SiCN powder to the mixture. 28 The activation energy of C-derived nanocomposite is close to the value of the thermal energy of solution of the silicon nitride in glassy phase (400 kJ/mol), measured from the densification experiment but proved by Menon et al 30 and Wiederhorn et al 31 This suggests that the creep deformation is controlled mainly by the solution of Si 3 N 4 grains in the grain boundary phase. However, the slightly higher value of the creep activation energy (480 kJ/mol) comparing to this value suggests additional creep mechanisms.…”

Section: Creep Mechanism-activation Energymentioning

confidence: 76%

Creep behavior of a carbon-derived Si3N4/SiC nanocomposite

Dusza

Kovalčík

Hvizdoš

et al. 2004

Journal of the European Ceramic Society

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“…[13][14][15][16] They were accompanied by intensive cavitation in the core, strong oxidation enhanced by stress in surface layers and intensive cracking of these layers. 13 The obtained strains were up to five times higher than those in the standard silicon nitride grades, [17][18][19][20] however, at least half order of magnitude lower than the strains obtained during superplastic deformation. 21 Superplastic deformation is usually observed at temperatures above 1500 • C in inert atmosphere when cavitation is suppressed.…”

Section: Introductionmentioning

confidence: 62%

Creep mechanisms in quasi-plastic silicon nitride by instrumented indentation

Lofaj

2006

Journal of the European Ceramic Society

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Transient creep behaviour of hot isostatically pressed silicon nitride

Cited by 94 publications

References 27 publications

Effect of Yttrium and Lanthanum on the Tensile Creep Behavior of Aluminum Oxide

Effect of Yttrium and Lanthanum on the Tensile Creep Behavior of Aluminum Oxide

Creep behavior of a carbon-derived Si3N4/SiC nanocomposite

Creep mechanisms in quasi-plastic silicon nitride by instrumented indentation

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