Available online at www.sciencedirect.com Journal of the European Ceramic Society 28 (2008) 539–545 Spark plasma sintering of macroporous calcium phosphate scaffolds from nanocrystalline powders Faming Zhang a , Kaili Lin a , Jiang Chang a,∗ , Jianxi Lu a,b , Congqin Ning a a Biomaterials and Tissue Engineering Research Center, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China b Shanghai Bio-lu Biomaterials Co. Ltd., Shanghai 200335, China Received 10 February 2007; received in revised form 10 July 2007; accepted 14 July 2007 Available online 14 September 2007 Abstract Spark plasma sintering (SPS) technique was applied to fabricate macroporous -tricalcium phosphate (-TCP) scaffolds from nanocrystalline powders (termed “nano-scaffolds”) for bone regeneration applications. The degree of porosity (55–70%) and the macropore size (300–500 m) of the scaffolds were controlled by modulating the porogen additions. Microstructures with ultrafine grain size (200 nm), increased density of solid matrix, and enhanced neck growth, as well as improved compressive strength and elastic modulus of over 50–100% were achieved in the macroporous nano-scaffolds by SPS in a modified graphite die. The SPS may provide an alternative approach to fabricate macroporous bioceramics nano-scaffolds. © 2007 Elsevier Ltd. All rights reserved. Keywords: Sintering; Grain size; Mechanical properties; Calcium phosphate; Biomedical applications; Ca 3 (PO 4 ) 2 1. Introduction Bone regeneration or reconstruction is required in cases involving skeletal defects caused by tumor resection, trauma and abnormalities. -Tricalcium phosphate (-TCP) has received great attention as grafts for bone regeneration applications due to its excellent biocompatibility and biodegradability. A porous structure was required for the -TCP bioceramics using as bone regeneration scaffolds since a porous network allows tissue infil- tration and exhibits good osteoconductive capability. 1,2 Despite their favorable biological properties, the poor mechanical prop- erties of the porous -TCP bioceramics have severely restricted their clinical applications. Some attempts have been used to increase the mechanical strength of porous -TCP bioceram- ics, including introducing secondary phase 3,4 and optimizing sintering techniques. 5 Nanostructured ceramics have exhibited promising mechani- cal and physical properties, and the fabrication of nanostructured ceramics has already become an exciting prospect in materi- als research. 6–9 Studies on nanostructured -TCP bioceramics ∗ Corresponding author. Tel.: +86 21 52412804; fax: +86 21 52413903. E-mail address: jchang@mail.sic.ac.cn (J. Chang). were mainly focused on nanocrystalline powders 10,11 and solid bioceramics, 12 but few studies were carried out on the fabrica- tion of nanostructured macroporous scaffolds. In respect that the fabrication of nanostructured macroporous -TCP scaffolds by conventional sintering is frustrated since the presence of high surface and interface area provides a strong driving force for the grain growth. Nanostructure processing has been proved to be quite successful for solid materials, 6,7,12 but little is known about its effectiveness for porous structures. Spark plasma sintering (SPS) is a comparatively new tech- nique for rapid fabrication of solid nanostructured ceramics, cermets and alloys. 13–16 The problem of grain growth in these nanostructured materials has been overcome to some extent by using SPS with final grain size below 200 nm, even below 100 nm can be achieved. 13,6 Recently, particular atten- tion has been paid on using of SPS to prepare porous ceramics and alloys, for example, alumina, 17–19 aluminum, 20 titanium alloys, 21 etc. Optimized microstructures and improved mechan- ical properties have been achieved in these porous materials fabricated by SPS. However, the application of SPS to fabricate high porosity macroporous bioceramics scaffolds was scarcely reported. As bone regeneration scaffolds, high porosity (>50%) and macropore size (>200 m) are essential requirements for osteoconduction. 22,23 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.07.012