Biomedical Engineering Reference
In-Depth Information
mechanical properties [1059]. β-TCP/wollastonite biocomposites are
also known [1060-1062]. More complicated formulations have been
developed as well. For example, (A-W)/HDPE composite (AWPEX)
biomaterials have been designed to match the mechanical strength
of human cortical bone and to provide favorable bioactivity, with
potential use in many orthopedic applications [1063-1066]. Other
examples comprise wollastonite-reinforced HA/Ca polycarboxylate
[1067], glass-reinforced HA/polyacrylate [1068], as well as collagen-
[1069] and gelatin- [1070] calcium phosphate silicate/wollastonite
biocomposites.
HA/glass biocomposites can be prepared by simple sintering of
appropriate HA/glass
powder mixtures [1071-1074]. If sintering is
carried out below 1000 ºC, HA does not react with the bioactive glass
[1072, 1073] or this reaction is limited [1074]. Besides, reaction
between HA and glasses depends on the glass composition. In another
approach, small quantities of bioactive glass have been added to HA
bioceramics in order to improve densification and/or mechanical
properties [29]. In addition, biocomposites might be sintered from
HA and silica [1005]. In general, bioactive glass-ceramics maintain a
high strength for a longer time than HA bioceramics under both the
in vitro
conditions [1012, 1019].
Due to a huge difference in shapes, it is a challenge to prepare
homogeneous mixtures of calcium orthophosphates and carbon
nanotubes: “one can imagine something similar to achieving
a homogeneous mixture of peas and spaghetti” [217, page 7].
Nevertheless, different strategies might be employed to prepare
calcium orthophosphate/carbon nanotube biocomposites. For
example, apatites might be chemically synthesized by using carboxyl
functionalized carbon nanotubes as a matrix [302-308]. Physico-
chemical characterization of these biocomposites showed that
nucleation of CDHA initiates through the carboxyl group [302]. Hot
pressing [1075], plasma spraying [1076], laser surface alloying
[1077-1079], spark plasma sintering [1080], and precipitation
[1081] techniques might be applied as well. Due to carbon oxidation
at elevated temperature, sintering of calcium orthophosphate/
carbon nanotube biocomposites must be performed in a deoxidizing
atmosphere [1082]. The research on calcium orthophosphate (up to
now, only apatites)/carbon nanotube biocomposites is in its early
and
in vivo
Search WWH ::
Custom Search