Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Glass powders and reactive silicone binder: Interactions and application to additive manufacturing of bioactive glass-ceramic scaffolds Hamada Elsayed a,b , Martiniano Picicco c , Arish Dasan d , Jozef Kraxner d , Dusan Galusek d,e , Enrico Bernardo a,∗ a Department of Industrial Engineering, Università degli Studi di Padova, Padova, Italy b Ceramics Department, National Research Centre, Cairo, Egypt c Centro de Tecnología de recursos Minerales y Cerámica (CETMIC), Gonnet (La Plata), Argentina d Department of Glass Processing, FunGlass, Alexander Dubček University of Trenčín, Trenčín, Slovakia e Joint glass centre of the IIC SAS, TnUAD, and FChFT STU, FunGlass, Alexander Dubček University of Trenčín, Trenčín, Slovakia ARTICLE INFO Keywords: 3D bioactive glass-ceramics scaffolds Polymer-derived ceramics Additive manufacturing Direct ink writing ABSTRACT A novel concept for the additive manufacturing of three-dimensional glass-ceramic scaffolds, to be used for tissue engineering applications, was based on fine glass powders mixed with a reactive binder, in the form of a commercial silicone. The powders consisted of ‘silica-defective glass’ specifically designed to react, upon firing in air, with the amorphous silica yielded by the binder. By silica incorporation, the glass was intended to reach the composition of an already known CaOeNa 2 OeB 2 O 3 eSiO 2 system. Silica from the binder provided up to 15 wt% of the total silica. With the same overall formulation, silicone-glass powder mixtures led to nearly the same phase assemblage formed by the reference system, crystallizing into wollastonite (CaSiO 3 ) and Ca-borate (CaB 2 O 4 ). Samples from silicone-glass powder mixtures exhibited an excellent shape retention after firing, which was later exploited in highly porous reticulated scaffolds, obtained by means of direct ink writing (DIW). 1. Introduction Among preceramic polymers (i.e. polymers yielding a ceramic re- sidue after firing), silicones are particularly interesting as raw materials for silicate ceramics [1]. In fact, oxides dispersed in a silicone matrix, directly in form of oxide powders, carbonates, hydroxides etc., easily react with the silica-rich amorphous residue formed by the polymer (upon heating above 500–600 °C). Then, the desired silicates (corre- sponding to a specified molar balance between metal oxide and silica) may be achieved in conditions of low processing temperature and high phase purity [1]. Polymer-derived silicates are advantageous also for the processing, since the use of silicones enables the application of plastic-forming techniques, often supported by the same fillers. Besides providing oxides to be combined with the silica-rich residue, the fillers may be used also to release some water vapour upon heating (e.g. using hydrated borates) [2], at low temperature (300–350 °C), i.e. with sili- cones still in the polymeric state, in order to achieve highly porous foams (transformed into ceramic foams at higher temperatures). Glass powders represent a quite particular class of oxide fillers. Glass may remain substantially inert, embedded in a polymer-derived matrix, as recently shown by Francis et al. [3], who explored silicone/ bioglass coatings, fired at temperatures not exceeding 500 °C, i.e. with silicones are still at the early stages of ceramic conversion. As an al- ternative, glass may interact with the matrix, in different ways. Glass (in limited amounts) may ‘correct’ some issues of ceramics from sili- cone-oxide filler mixtures, especially the formation of micro-cracks. These cracks could be ascribed to the gas release from ceramic con- version and to the volumetric changes in the crystallization of silicates within a rigid matrix. Glass powders, as additional fillers, enhance the formation of liquid phase upon firing (offering some stress relaxation), with no negative impact on the phase assemblage, if the chemical composition of the glass additive matches with that of silicone-oxide filler mixtures [2,4]. In some cases, glass particles are mainly used, combined with ceramic particles, to limit the shrinkage in the course of polymer-to-ceramic conversion, with limited impact on sintering. Parchovianský et al. as an example, used special aluminosilicate-zir- conate glasses (SiO 2 eAl 2 O 3 eZrO 2 ), prepared in the form of micro- spheres (by flame synthesis), in batches for developing relatively thick, protective, dense and well adherent coating system on steel (the authors actually used an un-filled polysilazane to form a bond coat, in turn covered by a top coat from the same polymer mixed with fillers) [5]. The ‘integration’ of the ceramic residue of preceramic polymer and https://doi.org/10.1016/j.ceramint.2019.04.070 Received 7 January 2019; Received in revised form 22 February 2019; Accepted 8 April 2019 ∗ Corresponding author. E-mail address: [email protected] (E. Bernardo). Ceramics International 45 (2019) 13740–13746 Available online 11 April 2019 0272-8842/ © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). T
Glass powders and reactive silicone binder: Interactions and application to additive manufacturing of bioactive glass-ceramic scaffolds
Jun 17, 2023
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