Thermal mismatch induced disorder of beta-eucryptite and its effect on thermal expansion of beta-eucryptite/Al composites

Thermal expansion of β-eucryptite in oxide-based ceramic composites

“…This assumption is supported by previous studies that have shown that in NTE-based composites, the high CTE difference between the reinforcement and the matrix generates large compressive stresses in NTE grains that can induce allotropic phase transformations 43 or partial ␤-eucryptite disorder. 44 However, it has been also found that the anisotropic character of the thermal expansion of the "ordered" ␤-eucryptite is much more pronounced than that of the "disordered" phase, that exhibited a positive CTE of 2.71 × 10 −6 / • C. 45 As this last value is really close to the ␤-eucryptite CTE found in AE and ZE composites, the occurrence of a "disordered" phase could also explain the E-CTE modification. Moreover, ␤-eucryptite intrinsic thermal expansion can be also dependent on its chemical composition and the cell volume contraction can decrease when the silicon content is increased.…”

Alumina Region of the Lithium Aluminosilicate System: A New Window for Temperature Ultrastable Materials Design

“…The NTE behavior of eucryptite can now be combined with the positive thermal behavior of mullite and alumina to make a close to zero expansion material. Chemical compatibility has been demonstrated, and other problems found while looking for zero expansion materials using eucryptite, such as microcracking and thermal mismatch‐induced disorder in eucryptite have to be solved by the use of nanoparticles with the aim of reducing internal stress in these composites. The chemical phase relations revisited in the LAS system open the window for this design.…”

“…intrinsic low CTE or composite design, have both advantages and disadvantages, as in general, low CTE materials have very poor intrinsic mechanical properties and low elastic modulus. In the other hand, composites used to fail because of the development of microcracking, as well as by thermal mismatch‐induced disorder in the case of β‐eucryptite.…”

The behaviour of aluminium matrix composites under thermal stresses

“…In the case of β -eucryptic particle-reinforced AMCs prepared by spark plasma sintering (SPS), it was observed that the metastable phase of eucryptic particle got transferred to normal eucryptic phase due to stress relaxation by annealing process. This transformation of the metastable phase has a prominent effect on the thermal expansion behaviour of the composite [144,145] .…”