Document Type : Research Paper


1 Materials Engineering Dept., University of Technology-Iraq, Alsina’a street, 10066 Baghdad, Iraq.

2 Prosthetics and Orthotics Engineering Dept., College of Engineering, Kerbala University, Iraq.


This study uses a novel sintering technique at very low temperatures (below 300°C) named the Cold Sintering Process to produce highly dense Hydroxyapatite (HA) samples. Nano hydroxyapatite was prepared using two different methods: Synthesis by chemical precipitation method (HA1) and natural source from Boven bone (HA2). The samples are characterized using scanning electron microscope (SEM), X-ray energy dispersive spectrometry (EDS), X-ray diffractogram (XRD), transition electron microscope (TEM), Fourier transform infrared spectrometry (FTIR) and Nuclear magnetic resonance spectroscopy (NMR). Also, physical and mechanical properties measurements were detected, including density and hardness. The results indicated that cold sintering could result in Hydroxyapatite with high densification, high purity, and high stability without thermal decomposition compared with traditional sintering. The relative density and hardness for HA1 are 99% and 502HV, respectively. The relative density and hardness for HA2 are 69% and 350HV, respectively. It can be observed that the HA1 sample has higher densification than HA2 due to the presence of organic matter in natural Hydroxyapatite HA2. This organic material will be removed during the cold sintering process, leaving pores that lead to low densification of HA2 samples. It can be concluded that the synthesis hydroxyapatite (HA1) can be easily sintered by a cold sintering process compared with natural one(HA2).

Graphical Abstract


  • A novel cold sintering process produced highly dense hydroxyapatite (HA) samples.
  • Nano-HA was prepared via two routes: bovine bone (HA1) and chemical precipitation (HA2).
  • The difference in cold sintering between the HA1 and HA2 powders is explained.
  • Cold sintering yielded high density, purity, and stability HA without thermal decomposition.
  • Structural, morphological, mechanical and physical properties of the compact samples were studied


Main Subjects

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