FIGURE 1 SEM image of F-1 at 2000 magnification
As shown in Figure 1, the AC has a developed pore structure which will worsen the mechanical strength. In addition to the open pores connecting with the AC surface, there are many independent closed pores embedded in the coke skeleton. The closed pores have different shapes, and can be divided into round close pore and slit closed pore according to their shape. The open pores are varied in size, and the small pore is branch of the large pore. The ratio of the open and closed pore volume to the AC particle volume is the total porosity ratio, wherein the ratio of the open pore volume to the AC particle volume is the open porosity ratio. Total porosity ratio and open porosity ratio of AC can be calculated by the equation (1) and (2), respectively.
(1)
(2)
Where, is the total porosity ratio of AC. is the open porosity ratio of AC. is the true density of bulky AC with closed pores. is the true density of nano-sized powder AC whose closed pores are considered to be negligible. is the bulk density of bulky AC. The and were tested by the UPYC 1000 true density meter. The was measured by the wax sealing method.
The 0-5 nm and above 5 nm pore size distribution of AC were obtained by the Quadrasorb Station 1 nitrogen adsorption apparatus and the PoreMaster 60GT mercury intrusion meter, respectively. The results are shown in Table 1. According to Table 1, the 0-2 nm and 2-500 nm pores volume is similar, and above 500 nm pores volume is larger than that of 0-2 nm and 2-500 nm. The compressive strength and abrasion resistance of the AC were tested by the crushing method and the drum method respectively (GB/T30202.3-2013)[16]. In order to investigate the effect of AC porosity characteristics on the mechanical strength, the relationships between porosity indexes value and mechanical strength were studied.
Table 1 The pore structure indexes of ACs