Nevřivová Lenka, Zemánek David
Faculty of Civil Engineering, Brno University of Technology, Veveri 331/95, 602 00 Brno, Czech Republic.
Materials (Basel). 2023 Aug 4;16(15):5466. doi: 10.3390/ma16155466.
Colloidal bonds are realized by sol-gel technology. The binder system of the refractory castable belongs to the AlO-SiO binary diagram. Mullite is the most thermally stable mineral in this system. This work was motivated by an attempt to maximize the mullite content in the NCC binder system, because a high content of mullite is a guarantee of the long service life of refractories. Initially, the mineralogical composition of the pure gel was tested after drying and firing at temperatures between 1000 °C and 1600 °C. The behavior of the gel during drying was described. Subsequently, a method of minimizing gel shrinkage during drying was sought. To this aim, fine fillers (microfillers) of alumina and silica were tested. In particular, the reactivity of the microfillers, the ability of the microfillers to react with the sol to form mullite, and the drying shrinkage of the microfiller-doped gel were evaluated. The study showed that the least suitable source of AlO in terms of its reactivity is tabular corundum, which produces the lowest amount of mullite. The internal structure of the prepared binder system when using different microfillers was described. Based on the results from the second stage of the work, several complete matrixes of the binder system were designed and the degree of their mullitization at different firing temperatures was studied. During this stage, it was shown that the degree of mullitization of the binder system depends mainly on the microsilica content. In the binder system, the maximum mullite content recorded was 76%. The effect of amorphous SiO on the bulk density and internal structure of the binder system was also described.
胶体结合是通过溶胶 - 凝胶技术实现的。耐火浇注料的粘结剂体系属于AlO - SiO二元相图。莫来石是该体系中热稳定性最高的矿物。这项工作的动机是试图使NCC粘结剂体系中的莫来石含量最大化，因为高含量的莫来石是耐火材料长使用寿命的保证。最初，在1000℃至1600℃的温度下干燥和煅烧后测试了纯凝胶的矿物组成。描述了凝胶在干燥过程中的行为。随后，寻求一种使干燥过程中凝胶收缩最小化的方法。为此，测试了氧化铝和二氧化硅的细填料（微填料）。特别评估了微填料的反应性、微填料与溶胶反应形成莫来石的能力以及掺杂微填料的凝胶的干燥收缩。研究表明，就其反应性而言，最不合适的AlO来源是板状刚玉，它产生的莫来石量最少。描述了使用不同微填料时制备的粘结剂体系的内部结构。基于工作第二阶段的结果，设计了粘结剂体系的几种完整基体，并研究了它们在不同煅烧温度下的莫来石化程度。在此阶段，表明粘结剂体系的莫来石化程度主要取决于微硅石含量。在粘结剂体系中，记录到的最大莫来石含量为76%。还描述了无定形SiO对粘结剂体系体积密度和内部结构的影响。
