Statistical Analysis of the Intergranular Film Thickness in Silicon Nitride Ceramics

Kleebe, Hans‐Joachim; Cinibulk, Michael K.; Cannon, R. M.; Rüble, M.

doi:10.1111/j.1151-2916.1993.tb08319.x

Cited by 259 publications

(111 citation statements)

References 26 publications

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“…Specifically, the amorphous grain boundary films range in width from about 0.75 to 2.75 nm, with a mean of ~1 nm. This width is consistent with the values found in other ceramic materials [12,13], and with theoretical explanations developed by Clarke [14]. In some particularly wide films (e.g.…”

Section: General Aspectssupporting

confidence: 92%

Microstructure and Properties of in Situ Toughened Silicon Carbide

Jonghe

Ritchie

Zhang

2003

Nano and Microstructural Design of Advanced Materials

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A silicon carbide with a fracture toughness as high as 9.1 MPa.m 1/2 has been developed by hot pressing β-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations.In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features. Elongated SiC grains with 1 nm-wide amorphous intergranular films were believed to be responsible for the in situ toughening of this material, specifically by mechanisms of crack deflection and grain bridging. Two methods were found to be effective in modifying microstructure and optimizing mechanical performance. First, prescribed postannealing treatments at temperatures between 1100 and 1500 o C were found to cause full crystallization of the amorphous intergranular films and to introduce uniformly dispersed nanoprecipitates within SiC matrix grains; in addition, lattice diffusion of aluminum at elevated temperatures was seen to alter grain boundary composition. Second, adjusting the nominal content of sintering additives was also observed to change the grain morphology, the grain boundary structure, and the phase composition of the ABC-SiC. In this regard, the roles of individual additives in developing microstructure were identified; this was demonstrated to be critical in optimizing the mechanical properties, including fracture toughness and fatigue resistance at ambient and elevated temperatures, flexural strength, wear resistance, and creep resistance.

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Section: General Aspectssupporting

confidence: 92%

Microstructure and Properties of in Situ Toughened Silicon Carbide

Jonghe

Ritchie

Zhang

2003

Nano and Microstructural Design of Advanced Materials

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“…These have now been observed at grain boundaries in numerous systems [23][24][27][28][29], as well as at heterophase interfaces [26,29]. Since in our samples only a small fraction of the ZnO surface is covered by surface films, they probably do not contribute significantly to activated sintering.…”

Section: Discussionmentioning

confidence: 56%

Origin of Solid‐State Activated Sintering in Bi₂O₃‐Doped ZnO

Luo

Wang

Chiang

1999

Journal of the American Ceramic Society

154

106

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Activated sintering in Bi 2 O 3 -doped ZnO has been studied with emphasis on the mechanistic role of intergranular amorphous films. The atomic-level microstructures and bismuth solute distributions in doped powders have been investigated using high resolution electron microscopy (HREM) and scanning transmission electron microscopy (STEM). Densification is observed to be significant below the bulk eutectic temperature in the presence of Bi 2 O 3 concentrations as low as 0.58 mole %. Transmission electron microscopy (TEM) of as-calcined and sintered powders shows that significant neck growth and particle coarsening occur in the solid state. Intergranular amorphous films of 1 nm thickness, terminating in wetting menisci at sinter-necks, are observed to form concurrently with the onset of activated sintering. In a few instances, amorphous films are also observed at surfaces of the ZnO particles. Activated sintering in this binary system is attributed to rapid mass transport through sub-eutectic, equilibrium-thickness intergranular films, with the amorphous phase also providing capillary pressure.

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“…166 -168 Moreover, for Si 3 N 4 grains equilibrated with a RE-aluminum silicate (where RE is one of the yttrium series or various rare earths), the mean film thickness depends on the specific rare earth used, but it is virtually the same for polycrystals with 5%-12% liquid by volume and for small clusters of grains found in dilute suspensions of powder in glass. 179,181 Apparently, a particle-particle attraction exists in this system that is roughly comparable to the capillary forces often considered to drive sintering. However, in parallel, the ␣ to ␤ transformation and subsequent particle growth (Ostwald ripening) occur via diffusion through the liquid and films.…”

Section: (7) Equilibrium Intergranular and Surficial Filmsmentioning

confidence: 88%

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

French

2000

Journal of the American Ceramic Society

260

100

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The London dispersion forces, along with the Debye and Keesom forces, constitute the long-range van der Waals forces. London's and Hamaker's work on the point-to-point dispersion interaction and Lifshitz's development of the continuum theory of dispersion are the foundations of our understanding of dispersion forces. Dispersion forces are present for all materials and are intrinsically related to the optical properties and the underlying interband electronic structures of materials. The force law scaling constant of the dispersion force, known as the Hamaker constant, can be determined from spectral or parametric optical properties of materials, combined with knowledge of the configuration of the materials. With recent access to new experimental and ab initio tools for determination of optical properties of materials, dispersion force research has new opportunities for detailed studies. Opportunities include development of improved index approximations and parametric representations of the optical properties for estimation of Hamaker constants. Expanded databases of London dispersion spectra of materials will permit accurate estimation of both nonretarded and retarded dispersion forces in complex configurations. Development of solutions for generalized multilayer configurations of materials are needed for the treatment of more-complex problems, such as graded interfaces. Dispersion forces can play a critical role in materials applications. Typically, they are a component with other forces in a force balance, and it is this balance that dictates the resulting behavior. The ubiquitous nature of the London dispersion forces makes them a factor in a wide spectrum of problems; they have been in evidence since the pioneering work of Young and Laplace on wetting, contact angles, and surface energies. Additional applications include the interparticle forces that can be measured by direct techniques, such as atomic force microscopy. London dispersion forces are important in both adhesion and in sintering, where the detailed shape at the crack tip and at the sintering neck can be controlled by the dispersion forces. Dispersion forces have an important role in the properties of numerous ceramics that contain intergranular films, and here the opportunity exists for the development of an integrated understanding of intergranular films that encompasses dispersion forces, segregation, multilayer adsorption, and structure. The intrinsic length scale at which there is a transition from the continuum perspective (dispersion forces) to the atomistic perspective (encompassing interatomic bonds) is critical in many materials problems, and the relationship of dispersion forces and intergranular films may represent an important opportunity to probe this topic. Am. Ceram. Soc., 83 [9] 2117-46 (2000 Centennial FeatureThe London dispersion force is retarded at large separations, where the transit time of the electromagnetic interaction must be considered explicitly. Novel phenomena, such as equilibrium surficial films and bimodal wettin...

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Statistical Analysis of the Intergranular Film Thickness in Silicon Nitride Ceramics

Cited by 259 publications

References 26 publications

Microstructure and Properties of in Situ Toughened Silicon Carbide

Microstructure and Properties of in Situ Toughened Silicon Carbide

Origin of Solid‐State Activated Sintering in Bi₂O₃‐Doped ZnO

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

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Statistical Analysis of the Intergranular Film Thickness in Silicon Nitride Ceramics

Cited by 259 publications

References 26 publications

Microstructure and Properties of in Situ Toughened Silicon Carbide

Microstructure and Properties of in Situ Toughened Silicon Carbide

Origin of Solid‐State Activated Sintering in Bi2O3‐Doped ZnO

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

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Origin of Solid‐State Activated Sintering in Bi₂O₃‐Doped ZnO