Complex shapes of lithium disilicate glass-ceramics developed by material extrusion

abstract

The fabrication of high-end ceramics by additive manufacturing gained increasing research interest due to the capacity of these techniques to break through the limitations of traditional extractive manufacturing. Although efficient strategies for the processing of ceramic materials by additive manufacturing have been shown, with notable examples in the dental field, the processing of dense glass-ceramics by the same means is almost unexplored. Herein, a processing strategy for the manufacture of complex shapes of lithium disilicate glass-ceramics by material extrusion is detailed shown for the first time. An aging behaviour was observed on the glass loaded aqueous suspensions and in-deep studied, being related with the leaching of Li+ ions. Based on this, a hydrogelbased ink with high solid content (phi approximate to 50 vol%), suitable rheological properties (G 'approximate to 106 and tau approximate to 1500 Pa) and recovery time was developed. By using the optimized ink, a propeller component with high aspect ratio and small internal connected channels, as well as a dental crown were successfully printed. A debinding schedule was tuned by the combination of differential thermal analysis and hot stage microscopy. The sintered lithium disilicate glass-ceramic parts presented good relative density (approximate to 96.7 +/- 0.8%) and translucency. Outstanding mechanical properties were achieved (Hv approximate to 5.3 GPa, KIf approximate to 2.1 MPa.m0.5, sigma approximate to 279 +/- 44 MPa), comparable to values usually attained for these materials by powder technology. The low deviation of the flexural strength data reported here is related with the absence of meaningful processing defects on the analysed fracture surfaces and the homogeneous distribution of the residual porosity as microporous, resulting in a good Weibull characteristic strength sigma 0 = 301 MPa. The results of the present work emphasized the potential of Direct ink Writing, a material extrusion technique, to fabricate lithium disilicate glass-ceramic parts with complex geometries, as dental crowns.

keywords

PLURONIC BLOCK-COPOLYMERS; MECHANICAL-PROPERTIES; SILICA NANOPARTICLES; CHARGE PROPERTIES; HEAT-TREATMENT; BEHAVIOR; MICROSTRUCTURE; TEMPERATURE; OXIDE); CRYSTALLIZATION

subject category

Engineering; Materials Science

authors

Alves, MFRP; dos Santos, C; Duarte, I; Fernandes, MHFV; Olhero, SM

Groups

G5 - Biomimetic, Biological and Living Materials

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

M.F.R.P. Alves acknowledges the FCT for the PhD grant (2021.06615. BD) . S.M. Olhero acknowledge FCT for CEECIND/03393/2017 contract. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020) , UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020) , financed by national funds through the FCT/MCTES (PIDDAC) . C. Santos acknowledges CNPq (grant no. 305532/2021-9) and FAPERJ (grant no. E-26/201.002/2022) for the financial support received. The authors acknowledge the support by the projects UIDB/00481/2020 and UIDP/00481/2020-Fundacao para a Ciencia e a Tecnologia, DOI 10.54499/UIDB/00481/2020 https://doi.org/10.54499/UIDB/00481/2020) and DOI 10.54499/UIDP/00481/2020 (https://doi.org/10.54499/UIDP/00481/2020) .