Evaluation of kaolin and bauxite from the Amazonian region addition on mechanical-, physical-, chemical properties and microstructural characterization of red ceramic industry clay of Manaus metropolitan region

ABSTRACT The present work investigated properties of red ceramic from the Amazonian region after the addition of kaolin and bauxite mixture with 0, 10, 20 and 30%wt. in red ceramic industry clay. Assessed mechanical properties were flexural strength and Young's modulus. The assessed physical properties were density and porosity. The microstructural images were assessed with SEM and OM microscopies. The fired samples XRD, the raw materials XRF and the XRD were made for chemical composition and present phases assessments. Samples were manufactured by uniaxial compaction and fired at 1200°C and 1250°C. Samples without the mixture of kaolin/bauxite presented higher assessed properties, with approximately 32 MPa of flexural strength and 12% of porosity with 2.3 g/cm3 density. Although the initial idea of this work was to add the mixture of kaolin/bauxite in the red ceramic industry clay for improving assessed properties of red ceramic fired parts, the red ceramic industry clay without addition presented better properties. Such properties were attributed to the high aluminous materials content in the raw material. This behaviour is correlated to the fact that bauxite from this region presents 55%wt. of iron oxide content with aluminium oxide content lower than 25%wt. Additionally, the assessed properties of the ceramic industry parts fired at 1250°C presented this material as promising material for ceramic products with a better added value.

摘要 本研究以亚马逊地区的红色陶瓷原料为对象，探究向陶瓷工业用黏土中添加0、10、20、30wt.%的高岭土（kaolin）-铝土矿（bauxite）复配物后，红色陶瓷的性能变化。本次评估的力学性能包括抗弯强度与杨氏模量（Young's modulus），物理性能包括密度与孔隙率。采用扫描电子显微镜（SEM）与光学显微镜（OM）对显微结构图像进行表征；对烧制样品开展X射线衍射（XRD）分析，对原料开展X射线荧光光谱（XRF）分析，以表征其化学成分与物相组成。样品通过单向压制成型制备，并分别在1200℃与1250℃下烧制。未添加高岭土-铝土矿复配物的样品表现出更优的测试性能：抗弯强度约32 MPa，孔隙率约12%，密度为2.3 g/cm³。尽管本研究最初设想通过向陶瓷工业用黏土中添加高岭土-铝土矿复配物，以提升烧制后红色陶瓷构件的测试性能，但未添加复配物的黏土原料制备的陶瓷反而表现出更优异的性能。该性能优势可归因于原料中较高的铝质材料含量。这一现象与该地区铝土矿的成分特征相关：其氧化铁含量达55wt.%，而氧化铝含量低于25wt.%。此外，在1250℃下烧制的工业陶瓷样品的测试性能表明，该原料可作为制备高附加值陶瓷制品的潜在优质原料。