Joining of zirconia ceramics with a CaO-TiO2-SiO2 interlayer

“…A graphical representation of the assessment vector [Equation (1)] and the failure curve [Equation (4)] is shown in Figure 3. Using the dimensionless quantities Gr and Pr, the assessment vector can be expressed as follows: In the graphical representation of the jAD model, the space enclosed by the failure curve (or a fraction thereof) may be defined as the design space within which the assessment vector A would be required to reside.…”

Section: Joint Assessment and Design Model Formu/mktionmentioning

confidence: 99%

Analytical and experimental evaluation of joining ceramic oxides to ceramic oxides and ceramic oxides to metal for advanced heat engine applications

Ahmad¹,

Majumdar²,

Rosenfield³

et al. 1992

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The problem of designing reliable, high strength zirconia-to-zirconia and zirconia-tonodular cast iron joints is addressed by developing a general joint design and assessment methodology. A joint's load carrying capability is predicted in terms of its material strength and fracture toughness characteristics. The effects ofjoint constituent properties and joining process variables are included. The methodology is verified in a two step process by applying it first to notched bend bars and then to a notched disk specimen loaded in compression. Key technical accomplishments in the program include the development of a joint design and assessment methodology which predicts failure based on a combination of strength _tndtoughness, tile development of a new method of hot forging magnesia partially stabilized zirconia to itse.'f, and the development of a bimaterial disk-shaped specimen notched along the diametral bond line and compressively loaded to generate both shear and tensile loadings on the bond line. Mechanical and thermal characterization ofjoints, adherents, and interlayer materials were performed to provide data for input to the design methodology. Results from over 150 room temperature tests and 30 high temperature tests are reported. Extensive comparisons of experimental results are made with model predictions of failure load. The joint design and assessment model, as applied to the materials and test specimens of this program, has been programmed for a PC and is available to interested researchers.

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“…Not only has active metal been used as the filler materials for brazing, but brazing with nonmetallic glasses as filler materials has been studied with structural ceramics, such as alumina, Partially Stabilized Zirconia (PSZ), Si 3 N 4 , and sialon [28,29,30,31]. The rationale for this approach is that many ceramics have amorphous phases remaining at the grain boundaries after the sintering process, so they would be expected to be wet by, and compatible with, similar glassy materials, introduced at the joint.…”

Section: Joining Of Dissimilar Materialsmentioning

confidence: 99%

“…The joining of similar ceramics has been demonstrated using various techniques, such as brazing [22][23][24][25][26][27][28][29][30][31][32][33][34][35], diffusion welding [36], microwave joining [37][38][39][40] and Transient Liquid Phase methods [41][42][43]. However, the joining of dissimilar ceramics has been more difficult and problematic for several reasons.…”

Section: Joining Of Dissimilar Materialsmentioning

confidence: 99%

Novel joining of dissimilar ceramics in the Si3N4–Al2O3 system using polytypoid functional gradients

2001

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A unique approach to crack-free joining of heterogeneous ceramics is demonstrated by the use of sialon polytypoids as Functionally Graded Materials (FGM) as defined by the phase diagram in the system, Si 3 N 4 -Al 2 O 3 . Polytypoids in the Al 2 O 3 -Si 3 N 4 system offer a path to compatibility for such heterogeneous ceramics.The first part of the dissertation describes successful hot press sintering of multilayered FGM's with 20 layers of thickness 500 µm each. Transmission Electron Microscopy was used to identify the polytypoids at the interfaces of different areas of the joint. It has been found that the 15R polytypoid was formed in the Al 2 O 3 -contained layers and the 12H polytypoid was formed in the Si 3 N 4 -contained layers.The second part of the dissertation discusses the mechanical properties of these polytypoidally joined Si 3 N 4 -Al 2 O 3 . The thermal stresses of this FGM junction were analyzed using a finite element analysis program (FEAP) taking into account both 1 coefficient of thermal expansion (CTE) and modulus variations. From this analysis, the result showed a dramatic decrease in radial, axial and hoop stresses as the FGM changes from three layers to 20 graded layers. Scaling was considered, showing that the graded transition layer should constitute about 75% or more of the total sample thickness to reach a minimal residual stress. Oriented Vickers indentation testing was used to qualitatively characterize the strengths of the joint and the various interfaces.The indentation cracks were minimally or not deflected at the sialon layers, implying strong interfaces. Finally, flexural testing was conducted at room temperature and at high temperature. The average strength at room temperature was found to be 581MPa and the average strength at high temperature (1200 o C) was found to be 262MPa. Scanning electron microscope observation of fracture surfaces at a different loading rates indicated that the strength loss at higher temperatures was consistent with a softening of glassy materials present at grain junctions.

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Joining of zirconia ceramics with a CaO-TiO2-SiO2 interlayer

Cited by 7 publications

References 8 publications

Analytical and experimental evaluation of joining ceramic oxides to ceramic oxides and ceramic oxides to metal for advanced heat engine applications. Final report

Analytical and experimental evaluation of joining ceramic oxides to ceramic oxides and ceramic oxides to metal for advanced heat engine applications. Final report

Analytical and experimental evaluation of joining ceramic oxides to ceramic oxides and ceramic oxides to metal for advanced heat engine applications

Novel joining of dissimilar ceramics in the Si3N4–Al2O3 system using polytypoid functional gradients

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