不同Ca $^{2+}$源对氧化铝基大孔隔热耐火材料高温物理性能的影响
Impact of Distinct Ca$^{2+}$ Sources on the Physical Properties of Alumina-based Macroporous Refractories for Thermal Insulation at High Temperature
摘要：
在氧化铝基大孔组合物中研究了铝酸钙水泥（CAC）、碳酸钙（CaCO $_3$）、氢氧化钙[Ca（OH）$_2$ ]和氧化钙（CaO）用于$\textit{in situ}$形成硬石膏（也称为CaO. 6Al $_2$ O $_3$或CA $_6$）。由于其体积膨胀，该相可以抵消大孔陶瓷烧制时观察到的线性收缩。为了评价每种Ca $^{2+}$源对物理性质的影响，加工不同的制剂并表征其总孔隙率、压碎强度和线性收缩率。含CaCO $_3$的样品在热处理后呈现高孔隙率和小尺寸变化。因此，用$CaCO_3$配制新的组合物，以在热力学平衡时产生100%CA $_6$。除了通常的性质，它的$\textit{in situ}$的热弹性模量（$E_{\rm in\ situ}$）和热导率（$k_{\rm eff}$）的变化，进行了评价。该组合物呈现出有希望的结果，因为恒定且低的$k_{\rm eff}$、低的线性膨胀和杨氏模量在低温下增加。这些特性使得可以生产更有效的绝缘子，具有更好的服务性能。
英文摘要：
Calcium aluminate cement (CAC), calcium carbonate (CaCO$_3$), calcium hydroxide [Ca(OH)$_2$] and calcium oxide (CaO) were investigated in alumina-based macroporous compositions for $\textit{in situ}$ formation of hibonite (also known as CaO.6Al$_2$O$_3$ or CA$_6$). Due to its volumetric expansion, this phase could counteract the linear shrinkage observed when macroporous ceramics are fired. In order to evaluate the impact of each Ca$^{2+}$ source on the physical properties, different formulations were processed and characterized for their total porosity, crushing strength and linear shrinkage. CaCO$_3$-containing samples presented high porosity and small dimensional changes after thermal treatment. Thus, a novel composition was formulated with $CaCO_3$ in order to result in 100 % CA$_6$ on thermodynamic equilibrium. Besides the usual properties, its $\textit{in situ}$ changes in the hot elastic modulus ($E_{\rm in\ situ}$) and thermal conductivity ($k_{\rm eff}$), were evaluated. This composition presented promising results, as a constant and low $k_{\rm eff}$, low linear expansion and Young modulus increase at low temperatures. These properties make it possible to produce more efficient insulators with better performance in service.
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