The disruption of the supply chain of ball clays from Donetsk basin, Ukraine, has demonstrated that relying on domestic raw materials is strategic and vital for the ceramic tile production. However, the use of local raw materials has in most cases led to the increase in the impurities, namely iron, content of porcelain stoneware batches. A case-study is presented about the Italian tile district located in the Sassuolo area. In this work, we undertook the full characterization of two red clays from local quarries that are iron-rich (∼7% FeO), thus leading to well-known issues in the ceramic tile production. The features of these samples were compared with those of a German ball clay containing ∼3% FeO. The complex mineralogical composition of the Val Rossenna varicolored clays and on the Monte Piano marls was unravelled, revealing that they are rich in illite-smectite (IS) mixed layers and illite, and poor in chlorite, sulfates and organic matter. The effects of a partial substitution in a porcelain stoneware body of classic ball clays with the Italian and German red clays were investigated. The obtained bodies were fully characterized from milling to firing. The amount of the red clays was chosen to best evaluate the effect of iron on the technological properties of semifinished and finished products. The substitution of the classic ball clays with red clays did not introduce unsolvable bottlenecks in ceramic tile production. The addition of the German red clay resulted in a slight increase of the sintering temperature (compared to the benchmark), possibly related to the higher quartz content of this raw material. Conversely, the addition of the Italian red clay induced a reduction of the firing temperature (compared to the benchmark), likely due to the higher content of iron, feldspars and carbonates. The most significant variations concern the color of fired tiles, which results darker (compared to the benchmark) in all the tested bodies, for the presence of pyroxene, hematite, and iron dissolved in the vitreous phase.

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瓷器生产中红粘土的重新评价：成分和技术表征

乌克兰顿涅茨克盆地球粘土供应链的中断表明，依赖国内原材料对于瓷砖生产具有战略意义和至关重要性。然而，在大多数情况下，使用当地原材料会导致瓷器批次中杂质（即铁）含量的增加。介绍了位于萨​​索洛地区的意大利瓷砖区的案例研究。在这项工作中，我们对来自当地采石场的两种富含铁（~7% FeO）的红粘土进行了全面表征，从而导致了瓷砖生产中的众所周知的问题。将这些样品的特性与含有 ~3% FeO 的德国球粘土进行了比较。瓦罗森纳 (Val Rossenna) 杂色粘土和蒙特皮亚诺 (Monte Piano) 泥灰岩的复杂矿物学成分被揭示，揭示出它们富含伊利石-蒙脱石 (IS) 混合层和伊利石，而缺乏绿泥石、硫酸盐和有机质。研究了用意大利和德国红粘土部分替代经典球粘土的瓷器坯体的效果。所获得的坯体从铣削到烧制都得到了充分的表征。选择红粘土的量是为了最好地评估铁对半成品和成品技术性能的影响。用红粘土替代经典的球粘土并没有给瓷砖生产带来无法解决的瓶颈。德国红粘土的添加导致烧结温度略有升高（与基准相比），这可能与该原材料的石英含量较高有关。相反，意大利红粘土的添加导致烧成温度降低（与基准相比），这可能是由于铁、长石和碳酸盐的含量较高。最显着的变化涉及烧制瓷砖的颜色，由于玻璃相中存在辉石、赤铁矿和溶解的铁，因此所有测试体的颜色都较深（与基准相比）。