32 Grain Porous Structure and Exploitation Properties of Humidity-Sensitive. . .
509
Fig. 32.5 Observed and calculated XRD profiles for MgO-Al 2 O 3 ceramics sintered at 1200 ◦ C
(a), 1300 ◦ C (b), and 1400 ◦ C (c); the overhead row of reflexes is spinel phase; the lower row of
reflexes is MgO phase [16]
Table 32.5 Phase composition of the modified MgO-Al 2 O 3 ceramics [16, 17]
Main MgAl 2 O 4 phase
Additional MgO phase
T c , ◦ ´ Lattice parameter, Å Weight fraction, % Lattice parameter, Å Weight fraction, %
1200
8.0809(2)
93.63(0.78)
4.2124(4)
6.37(0.27)
1300
8.0812(2)
94.12(0.80)
4.2145(4)
5.88(0.30)
1400
8.0808(1)
94.05(0.78)
4.2169(4)
5.95(0.34)
r 3 ) and intensities (I r1 , I r2 , and I r3 ) of pore size distribution for studied ceramics
prepared at 1200, 1300, and 1400 ◦ C are shown in Table 32.6.
Ceramics sintered at 1200 ◦ C exhibit trimodal pore size distribution with maximum position of r 1 , r 2 , and r 3 near 2.3, 35, and 160 nm, respectively (Table 32.6
and Fig. 32.6a). It is established that large open pores with size near 100–300 nm
correspond to open surface pores in ceramics. They are involved in absorptiondesorption process of water from environment. Pores centered near 35 nm are
so-called transporting pores providing the effective passing of water into ceramic
body [14, 17].