Influence of Processing Variables on Clay-Based Ceramic Formulations

The properties of ceramic materials and microstructural changes are dependent on the raw materials from which they are made and on the manner in which they are processed, from the composition to the established thermal treatment, heating rate, and firing temperature. In this study, the influence of some processing parameters (formulation, maturation time, and firing temperature) on the physical-mechanical properties and microstructural aspects of ceramic pieces produced from natural aluminosilicates was investigated. Because Brazil does not have many quality ball clays reserves, bentonite was included as a plasticizing agent in this study. The formulations were submitted to maturation for a period of one to four weeks and their characteristics were determined to evaluate plasticity. Following this, the specimens were extruded and subjected to heat at temperatures of 1200, 1300, and 1400ºC. The physical-mechanical properties determined were: water absorption, linear retraction, and flexural strength. Statistical analysis was applied. The results showed that, for the analyzed masses, neither the maturation time nor the physical and mechanical properties analyzed had influence on plasticity. The firing temperature was the factor that generated the greatest alteration in results, increasing the mechanical resistance and altering the size and interlocking of the mullite needles.

陶瓷材料（ceramic materials）的性能与微观结构变化，取决于其制备所用的原材料，以及从组分确定、热处理（thermal treatment）、升温速率（heating rate）到烧成温度（firing temperature）的整条加工工艺路径。本研究针对以天然铝硅酸盐（natural aluminosilicates）为原料制备的陶瓷制品，探究了配方、陈化时间与烧成温度等工艺参数对其物理力学性能与微观结构特征的影响。鉴于巴西优质球黏土（ball clays）储量匮乏，本研究将膨润土（bentonite）作为增塑剂（plasticizing agent）纳入配方体系。配方的陈化周期设置为1至4周，并通过表征分析其塑性特性。随后将坯体挤出成型，并在1200℃、1300℃、1400℃三个温度下进行烧成。本次测试的物理力学性能指标包括吸水率（water absorption）、线性收缩率（linear retraction）与抗弯强度（flexural strength），研究采用统计分析（statistical analysis）方法对数据进行处理。结果表明，针对本次研究所用的坯料体系，陈化时间与所测试的物理力学性能均未对塑性产生显著影响；而烧成温度是导致实验结果出现最大变化的因素，其不仅提升了材料的力学强度，还改变了莫来石针晶（mullite needles）的尺寸与交织状态。