Figure 4

Schematics of samples with shaded areas indicating the volume measured by a helium pycnometer for pore types, (a) an open pore; (b) connected pores; (c) an open pore and an isolated closed pore; and (d) an isolated closed pore.

Schematics of samples with shaded areas indicating the volume measured by a helium pycnometer for pore types, (a) an open pore; (b) connected pores; (c) an open pore and an isolated closed pore; and (d) an isolated closed pore.