## 3 Results and Discussion
### Thermal Conductivity of Large-Sized Flaky Alumina  
Aluminum oxide, a significant inorganic filler for thermal interface materials, exhibits high thermal conductivity and low filler viscosity. Conventionally, it is used in conjunction with spherical aluminum of varying sizes to achieve superior thermal conductivity. As depicted in Figure 4a, the ideal thermal conductivity path of traditional spherical aluminum oxide is presented [19]. Figure 4b illustrates a thermal conductivity path design that utilizes large-sized flake aluminum oxide and spherical aluminum, as depicted in the figure. Compared to traditional spherical aluminum oxide, the interspersed flake aluminum oxide among differently sized spherical aluminum particles forms a thermal bridge, creating  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Average** & **Average Particle** & **Diameter-to-** & **Calcination** & & \\
**Thickness (\(\mu\)m)** & **Size (\(\mu\)m)** & **Thickness Ratio** & **Temperature** & **Preparation Process** & **Reference** \\ \hline
1.3 & 20 & 15 & 1100 & Molten salt method & [10] \\
0.5–1 & 5–8 & 20–30 & 1050 & Molten salt method & [11] \\
0.24 & 10 & 42 & 1200 & Molten salt method & [12] \\
0.05–0.2 & 4 & 20–80 & 1200 & Molten salt method & [13] \\
0.2–0.6 & 15–20 & 50–100 & 1100 & Proposed method & This work \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison of flaky alumina parameters.  
Figure 3: SEM images for different inorganic ion additions: (**a**) 1 wt% NaCl; (**b**) 1 wt% KCl; (**c**) 1 wt% Na\({}_{2}\)SO\({}_{4}\); (**d**) 1 wt% K\({}_{2}\)SO\({}_{4}\).  
additional thermal conductivity paths. This enhances the thermal value at the application end. Figure 5 presents the viscosity and thermal conductivity of 5 \(\upmu\)m, 10 \(\upmu\)m, 15 \(\upmu\)m, and 20 \(\upmu\)m flake alumina. The viscosity and thermal conductivity were tested under experimental conditions of 500 cps silicone oil and a monomer filling rate of 70%. Figure 5a shows that, in comparison with spherical aluminum, larger-sized single-flake alumina particles exhibit lower filling viscosity. However, the filling viscosity increases with particle size, indicating that flake alumina requires modification to reduce viscosity. In Figure 5b, the thermal conductivity of 20 \(\upmu\)m flake filler is 15.88% higher than that of 5 \(\upmu\)m flake filler, and the thermal conductivity of 5 \(\upmu\)m flake filler is 37.18% higher than that of spherical filler. This suggests that the thermal conductivity of large-size flake alumina significantly surpasses that of spherical filler at a low filling rate [20]. In Table 2, for the experiment involving the composite filler system, substituting spherical aluminum with large-size flake alumina in the original formula, while maintaining the same size, has significantly improved the thermal conductivity of the filler system. Given the filling difficulty of flake alumina, when adding 3%, the thermal conductivity of the gel is 25% higher than that of the filler system without large-size flake alumina, which holds significant application value.  
Figure 4: Model diagram of heat-conducting pathways: (**a**) conventional spherical alumina fillers; (**b**) spherical and flake alumina composite fillers.  
Figure 5: (**a**) Test viscosity values of flake alumina with different particle sizes (the left value is 1/s viscosity, the right value is 10/s viscosity); (**b**) thermal conductivity of flake alumina with different particle sizes.