## 2 Measurement and Roughening Methods
### Roughening Methods
#### 2.2.1 Grinding Method  
Grinding is a commonly used method for adjusting the surface roughness of minerals or materials. The roughening mechanism involves creating dents and scratches on the surfaces of these materials through the impact and grinding effects of either the grinding medium or minerals themselves in various types of grinding equipment. Numerous studies have been conducted on how to regulate surface roughness using different grinding methods. The findings indicate that the surface roughness can be effectively adjusted by modifying several factors: the grinding equipment, the grinding mediums, the grinding methods, the grinding environment, and the grinding time. Different types of grinding equipment, such as ball mills [1; 25; 27; 37; 46], rod mills [1; 34; 40; 69], autogenous mills [32; 33; 46; 62; 66], disk mills [3; 27; 37; 41], planetary mills [70], high-pressure grinding rollers [38; 71], and vertical roller mills [50], generate varying surface roughness, as summarized in Table 2. Ball mills and rod mills, being the most widely used grinding methods, effectively regulate surface roughness. Studies on minerals like magnetite [40], calcite [1; 72], quartz [45; 47], and spodumenes [64] were similar in that particles ground in rod mills exhibit a higher surface roughness compared to those ground in ball mills. However, researchers such as [PERSON] et al. [32; 33; 34], [PERSON] et al. [69], and [PERSON] et al. [39] reported opposing findings which showed that rod-milled quartz, talc, and hematite particles exhibited a lower surface roughness than that of the ball-milled ones. It was observed that the ball-milled hematite particles displayed a higher surface roughness than those ground in rod mills, while ball-milled hematite and magnetite particles exhibited different levels of surface roughness. Apart from the ball mill and rod mill, the ability of other grinding equipment to produce varying surface roughness has also been explored (Table 2). Although the surface roughness generated by different milling equipment varies, there is a trend indicating that high-pressure grinding rollers and vertical roller mills tend to produce rougher surfaces compared to ball-milled and rod-milled materials. In contrast, stainless steel disk mills (Figure 2d,h) and autogenous mills generate smoother surfaces [41; 46; 71]. \begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Minerals** & **Methods** & **Particle Size/\(\upmu\)m** & **Findings** \\ \hline magnetite [40] & AFM & 55–74 & The Ra value for the rod-milled particles was about 28.03 nm and those for the ball-milled ones were 9.47 nm. \\ calcite [1] & BET & 125–150 & The roughness of rod-milled calites of the same size fraction was about 5\% higher than that of ball-milled ones. \\ calcite [71] & AFM & no classification & The particles ground by a high-pressure grinding roller and jaw crusher are the roughest, and those ground by a dry ball mill were rather smooth. \\  & & 212–250 & The rod-milled quartz particles had higher surface roughness than the ball-milled ones in all granularity ranges. \\ \hline \end{tabular}
\end{table} 
Table 2: Surface roughness of minerals generated by different grinding equipment. The surface roughness of the particles processed in the same mill varies significantly due to different factors, including the grinding medium, the grinding environment, and the grinding time. For example, [PERSON] et al. [68] found that the cassiterite particles milled with stainless steel balls exhibited a greater surface roughness compared to those milled with ceramic balls, even though the particle size distribution remained unchanged. Similarly, [PERSON] et al. [73] reported that the Rq values of the ceramic ball-milled and cast iron ball-milled chalcopyrite particles were 9.02 nm and 74.80 nm, respectively. Additionally, [PERSON]