## 3 Results and Discussion
### Basic Glass Differential Thermal Analysis
Moreover, a large number of pores were observed between the crystalline phases, thereby resulting in a high porosity of the samples. For example, the porosity was as high as 7.43% at 900 \({}^{\circ}\)C. With the increase in temperature, the recrystallization process was strengthened, the number of crystalline phases increased, the degree of crystallization was high, the pores and gaps between the crystals gradually decreased, the density of the microcrystalline glass increased, and the porosity of the microcrystalline glass decreased. Figure 8 illustrates the results of the effects of crystallization temperature on the Vickers hardness of the prepared microcrystalline glass. The Vickers hardness of the microcrystalline glass increased with increasing crystallization temperature. When the crystallization temperature was 950 \({}^{\circ}\)C, the Vickers hardness of the microcrystalline glass was 618 HV. The lower the crystallization temperature, the less the crystalline phase precipitation and the larger the glassy phase in the microcrystalline glass; thus, the internal densities and microhardness were low. With increasing temperature, a large number of crystalline phases precipitated inside the microcrystalline glass and the grains bit each other more; the porosity of the microcrystalline glass decreased, thus increasing the density and Vickers hardness of the microcrystalline glass. Figure 8: Effects of crystallization temperature on the Vickers hardness of the microcrystalline glass. Figure 7: Effects of crystallization temperature on porosity of the microcrystalline glass. Industrial microcrystalline glass often needs to serve in acidic and alkaline environments, and the acid and alkaline resistance of microcrystalline glass materials significantly affect their service life, so it is important to study the acid and alkaline resistance of microcrystalline glass to expand its use field. The possible reactions between the main crystalline phase of the microcrystalline glass and acidic and alkaline substances in this study are shown in Equations (1)-(3). Figure 9 displays a plot of the acid and alkali resistance of the microcrystalline glass versus crystallization temperature. Overall, the alkali resistance of the microcrystalline glass was stronger than its acid resistance because the glass phase leaches more easily in acidic solutions. However, the variation trends of the acid and alkali resistances of the microcrystalline glass with temperature were identical; both resistances decreased with increasing temperature. With increasing crystallization temperature, the number of crystals in the microcrystalline glass gradually increased, the number of complete grains increased, the density increased, and the acid and alkali resistances increased. As illustrated in Figure 9, the acid and alkali resistances of the prepared microcrystalline glass were the highest (by 2.36% and 0.4%, respectively) at a crystallization temperature of 950 \({}^{\circ}\)C.  
In summary, the optimal crystallization temperature for preparing the microcrystalline glass in this experiment was 950 \({}^{\circ}\)C.  
\[\text{Ca[Al}_{2}\text{Si}_{2}\text{O}_{8}]+2\text{H}^{+}+\text{H}_{2}\text{O}= \text{Al}_{2}\text{[Si}_{2}\text{O}_{5}][\text{OH}]_{4}+\text{Ca}^{2+} \tag{1}\]  
\[\text{Al}_{2}\text{[Si}_{2}\text{O}_{5}][\text{OH}]_{4}+6\text{H}^{+}=2\text{ Al}^{3+}+2\text{H}_{4}\text{SiO}_{4}+\text{H}_{2}\text{O} \tag{2}\]  
\[\text{Ca[Al}_{2}\text{Si}_{2}\text{O}_{8}]+4\text{OH}^{-}=\text{Ca[Al}_{2} \text{O}_{4}]+2\text{SiO}_{3}{}^{2-}+2\text{H}_{2}\text{O} \tag{3}\]  
Effect of Crystallization Time on Precrystallization and the Properties of the Microcrystalline Glass  
The crystallization time notably influenced the performance of the microcrystalline glass, and a reasonable crystallization time was crucial to achieve superior performance.