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3D Printed Porous 45S5 Bioceramic
percentage content of bioglass powder was 40 wt%. 3. Results and discussion
Specific processes were followed. Bioglass and resin in a
ratio of 40:60 were mixed and stirred under planetary ball 3.1. Suspension, debinding, and sintering of
mill for 8 h to obtain the compound solution. The ball mill samples
rotation speed was 300 rom. Then, different proportion of To meet the formability of the scaffold, the viscosity of
oleic acid dispersant was added, stirring was continued slurry was adjusted to optimum proportions of 2 wt%
mechanically for 10 min, and the viscosity was adjusted oleic acid dispersant at 50°C (Figure 2C and D). The
in order to process molding. The composite slurry was 45S5 bioglass was uniformly dispersed in the resin
put into a water bath, heated to reduce its viscosity, and solution; therefore, two ideal scaffolds were obtained
then put into the LCD mask stereolithography printer to (Figure 2E and F). The use of good dispersant was
fabricate the scaffolds. beneficial to reduce the viscosity of the suspension,
2.3. Debinding sinter and sample thereby achieving good homogeneity and mobility. The
casting of the suspensions allowed for suitable viscosity at
characterization a proper temperature in the LCD mask stereolithography
The printed green scaffolds were put into muffle furnace process [35,36] .
for debinding sintering with different heating rates of The debinding behavior of green composite
0.5°C/min, 1°C/min, 2°C/min. When the temperature scaffolds was evaluated by TG and DTG analyses
reached at 100°C, 200°C and 300°C, the temperatures (Figure 3A). The results showed that the debinding
were hold for 60 min, while the temperature reached temperature occurred between 200°C and 550°C. When
at 400°C and 500°C, the temperatures were hold for the temperature changed in the range of 100 – 300°C,
120 min, respectively. After debinding, sintering rate the reduction of weight loss rate was not obvious, which
was 5°C/min. The maximum sintering temperatures were indicates an endothermic effect mainly caused by the
1000°C, 1100°C, and 1200°C, and the temperatures were evaporation of free water and some small molecules with
[37]
sustained for 120 min. Finally, the samples were cooled low melting point . When the temperature continued
in the furnace at room temperature. to rise up to about 383°C, the DTG curve showed an
The microstructure formed during 3D printing, obvious weight loss peak, and the weight loss rate of
debinding, and sintering process was recorded using green scaffolds reached the maximum and the pyrolysis
a Leica camera (Germany). The thermal stability of rate of photosensitive resin reached the highest point
sintered samples was evaluated by thermogravimetric (0.1%/°C). When the temperature reached above 550°C,
(TG) and differential thermogravimetric (DTG) analyses the weight of samples was basically stable. These results
so as to measure the change temperature of debinding indicated that the organic resin of scaffold had been
process. Samples were heated from 30°C to 700°C under completely removed at 550°C. According to thermal
nitrogen atmosphere (flow of 25 mL/min) at a heating rate analysis, when debinding, it was necessary to keep the
of 10°C/min. Phase structure of pre- and post-sintering temperatures of the samples at 300°C, 383°C and 550°C
scaffolds was determined by XRD (MAXima, Shimadzu to obtain complete scaffold structure. Otherwise, the
Co., Japan) at 40 kV, 30 mA with monochromatic Cu- scaffold would collapse in the debinding process.
Kα radiation, typically with scan speed of 0.5°/min and Based on the TG and DTG analyses, the heating
sampling pitch of 0.03° in a 2θ scale region of 10 – 65°. rates of debinding were set to 2°C/min, 1°C/min, and
Morphology of 3D printed scaffolds was observed using 0.5°C/min and the temperature was sustained at every
SEM (JSE-6700F, JEOL, Japan). Sintered 3D scaffolds temperature gradient (Figure 3B). The results indicated
were scanned and reconstructed in three dimensions by that the heating rate was very high (2°C/min, 1°C/min),
micro-CT (Quantum GX, USA). The true porosity of the leading to the collapse of scaffolds, and when the heating
sintered scaffolds was analyzed and calculated using 3D rate was slowed down to 0.5°C/min, scaffolds were
modeling software. The mechanical compression of the completely debinded and their integrity were maintained
printed scaffolds was tested by an electronic universal by Van der Waals force (Figure 3C).
testing machine (INSTRON, USA). The standard The results at three different sintering
cylinder (Ф 15 × 15 mm) was stressed at a speed of temperatures indicated that: (i) the scaffold had
0.1 mm/min. The maximum compression stress described completely collapsed at 1000°C; (ii) when the sintering
in this study referred to the compression stress when the temperature was 1100°C, the scaffold experienced
specimen broke during the compression test. All samples almost no collapse and showed good pore structure;
were tested and the average values are expressed as mean and (iii) while at 1200°C, part of the scaffold deformed
± standard deviation. The results were analyzed using and shrunk greatly (Figure 3D). When the sintering
two-way analysis of variance. A P < 0.05 was considered temperature was too low, the growth of ceramic grains
statistically significant. was not sufficient, leading to weak bonding among

208 International Journal of Bioprinting (2022)–Volume 8, Issue 4