Question 15.8: Silicon Carbide Ceramics Silicon carbide particles are compa......
Silicon Carbide Ceramics
Silicon carbide particles are compacted and fired at a high temperature to produce a strong ceramic shape. The true density of SiC is 3.2 g/cm³. The ceramic shape subsequently is weighed when dry (360 g), after soaking in water (385 g), and while suspended in water (224 g). Calculate the apparent porosity, the true porosity, and the fraction of the pore volume that is closed.
Apparent porosity = \frac{W_{w} \ – \ W_{d}}{W_{w} \ – \ W_{s}}× 100 = \frac{385 \ – \ 360}{385 \ – \ 224}× 100 = 15.5%
Bulk density = B = \frac{W_{d}}{W_{w} \ – \ W_{s}} =\frac{ 360}{385 \ – \ 224} = 2.24 \ g/cm^3
True porosity = \frac{ρ \ – \ B}{ρ}× 100 = \frac{3.2 \ – \ 2.24}{3.2}× 100 = 30%
The closed-pore percentage is the true porosity minus the apparent porosity, or 30 – 15.5 = 14.5%. Thus,
Fraction closed pores = \frac{14.5}{30} = 0.48