## 3 Results and Discussion  
### Density  
As was mentioned previously, five anodes were manufactured under conditions similar to those used in industry. The standard anode (i.e., B0-A(0)0) did not contain any \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Anode** & **Percent Biocoke (\%)** & **Additive** & **Percent Additive (\%)** \\ \hline
**B0-A(0)0*** & 0 & 0 & 0 \\ \hline
**B3-A(0)0** & 3 & 0 & 0 \\ \hline
**B3-A(1)3** & 3 & 1 & 3 \\ \hline
**B3-A(2)3** & 3 & 2 & 3 \\ \hline
**B3-A(3)3** & 3 & 3 & 3 \\ \hline \hline \end{tabular}  
* Standard anode.  
\end{table} 
Table 2: Composition of the anodes. biocoke or additive. It was used as a reference anode. Subsequently, four anodes containing modified or unmodified biocoke were manufactured (one anode with unmodified biocoke and three anodes with modified biocokes, see Table 2). The addition of 3% unmodified biocoke resulted in a decrease in both green and baked anode (i.e., B3-A(0)0) densities compared to those of the standard anode (i.e., B0-A(0)0) as shown in Figure 1. This decrease was due to the low density and the non-wettability of biocoke by pitch [9]. This has also been reported by other researchers. [PERSON] et al. [16] found that the density of the charcoal (biocoke) was much lower than that of the petroleum coke due to the fact of its porous structure. In addition, the open pores of the biocoke were not filled when it was mixed with pitch. Consequently, this decreased the anodes' density and unfavorably affected other anode properties. The densities of green and baked anodes containing biocoke modified with additives A(1) and A(3) (i.e., B3-A(1)3 and B3-A(3)3) approached those of the standard anode. Modification of biocoke with A(2) resulted in a significant decrease in anode densities (i.e., B3-A(2)3). Biocoke has high porosity, and pitch cannot penetrate into the pores, since it does not wet well the biocoke. Figure 2 presents the contact angles of unmodified biocoke and biocokes modified using three additives. As can be seen from this figure, the biocoke modified with A(1), followed by the one modified with A(3), had the lowest contact angles, which means that pitch wetted these modified biocokes better than it wetted the unmodified biocoke. The contact angle of the biocoke modified with A(2) was the highest. Its wettability by pitch decreased even in comparison to the wettability of the unmodified biocoke. Table 3 presents the XPS analysis results. The increase in the density of anodes manufactured with biocoke modified with additives A(1) and A(3) was due to the fixation of additional functional groups (i.e., C-O, C=O, and COO/COON) on the surface of the modified biocokes obtained from the convolution of the C1s peak. This improved the wettability of biocoke by pitch as shown in Figure 2. As can be seen from Table 3, some of the C=C groups of biocoke modified with A(2) and A(3) converted to C-C. The aromaticity (presence of C=C) groups increased the C/H ratio, which is an indication of higher density [5]. This conversion was lower for A(3), which resulted in a slight decrease in the wettability of biocoke modified with this additive compared to that of the biocoke modified with A(1). The amount of C=C of biocoke modified with A(3) was lower than that of the unmodified biocoke but higher than that of the biocoke modified  
Figure 1: Densities of the green and baked anodes produced without biocoke (standard) and with unmodified and modified biocoke. with A(2). It seems the decrease in the C=C group of biocoke modified with A(3) was compensated by an increase in oxygen-containing (heteroatoms) surface functional groups. It is well known that heteroatoms increase the wettability by facilitating the formation of hydrogen [11; 25; 26] and covalent [26] bonds between pitch and coke/biocoke. However, the transformation of a C=C groups to a C-C group was quite high for A(2). Thus, the green and baked anodes containing biocoke modified with this additive (i.e., B3-A(2)3) had the lowest density.