Page 298 - 00. Complete Version - Progress Report IPEN 2014-2016

298 Materials and Nanotechnology | Progress Report

tial pressures (10 ppm-1 atm). The highlight presented a novel process, without use of ad-
of the research carried out was the applica- ditives, no residues and low cost called “Snow-
tion of the flash sintering technique to sever- balling technique”.
al new electroceramics and composites like
Silicon Nitride, Zirconium Diboride, SDC-CNT, Using the novel process, porous spheres and
8YSZ-graphite, and others. Figure 16 shows microspheres of HAp and ο-TCP, Alumina and
SEM micrographs of (top) high density sin- Zirconia were produced using the snowballing
tered BZY proton conductor prepared with technique, which consists of taking the natu-
particle surface clean powders synthesized us- ral feature of aggregation of ceramic powders
ing facilities at the University of California in together with a continuous rolling process in-
Davis, and (bottom) of surfaces of SS446 steel side a cylinder container.
oxidized at 800ºC/250 h in air (a) and under
oxygen (b) developed in collaboration with The values for open porosity of sintered HAp
the University Rhone-Alpes, Grenoble, France. and Alumina microspheres were 47% and 39%
respectively, obtained by hydrostatic density,
and close porosity of 1,5% and 1,6% respective-
ly, obtained by helium pycnometer.

The microspheres were evaluated by SEM,
which presents their unique shape and mi-
crostructure. Figure 17 and 18 show HAp mi-
crospheres with the asteroid shape obtained
in different sizes, Figure 19 shows the detail of
the surface aspect of the microsphere.

Figure 16: SEM micrographs. Top: yttrium-doped barium zir-
conate sintered at 1500ºC using powders calcined under nitrogen
at 900ºC (left) and 1200ºC (right). Bottom: SS446 steel intermetal-
lic for SOFCs oxidized at 800ºC/250 h in air (a) and under oxygen (b).

Ceramic spheres and microspheres
prepared by Snowballing technique
Figure 17: SEM of sintered HAp microspheres,
diameter of >2mm and >710µm, respectively.
The development of porous ceramic spheres
is an alternative towards the use of granules
as grafts, the application as a biomaterial can
be as injectable bone grafts, filling defects and
drug delivery system. Also, the application of
the structural ceramics as filtering and adsorb-
ing elements can be applied to numerous pro-
cess. There are several routes to obtain calci-
um phosphates spheres, using different types
Figure 18: SEM of sintered HAp microspheres,
of additives and process, nevertheless here is diameter of >500µm and >250µm, respectively.

Instituto de Pesquisas Energéticas e Nucleares