Investigations on kaolin mixtures: Impact on mullite formation kinetics and microstructure evolution

IF 1.8 4区材料科学 Q2 MATERIALS SCIENCE, CERAMICS

International Journal of Applied Ceramic Technology Pub Date : 2024-06-17 DOI:10.1111/ijac.14820

Nabil Sadli, Abdelghani May, Mohamed Hamidouche, Abdelkhalek Henniche, Hocine Belhouchet, Hassane Boudouh

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Abstract

This study evaluates Algerian kaolin (Djebel Debbagh (DD1) and Tamazart (KT2)) as potential substitutes for commercial kaolin (Lab) in the production of mullite-based ceramics. Three compositions were prepared by incorporating the appropriate percentage of alumina to each calcined kaolin to achieve stoichiometric mullite precursors. The phase evolution of individual kaolin powders, as well as their mixtures with alumina, depends strongly on the calcination temperature and kaolin impurities. The differential scanning calorimetry combined with thermogravimetric analysis (TGA) showed lower secondary mullite formation temperature for the KT2-based mixture. However, X-ray diffraction revealed a complete mullitization in DD1 mixture. The K₂O hindered cristobalite formation and reduced secondary mullite formation rate. Microstructure analysis showed lath-shaped primary mullite and equi-axed secondary mullite particles. After sintering at 1600°C, The KT2-based sample (M3) exhibited higher density (3.013 g/cm³) and hardness (9.9 GPa), whereas the DD2-based sample (M2) showed moderate densification (2.91 g/cm³) and higher flexural strength (159.42 MPa). Impurities (mainly Fe₂O₃, and K₂O) promoted liquid phase sintering, resulting in greater densification in M3, whereas M2 showed more homogeneous microstructure, refined grains, and lower glassy phase content, contributing to enhanced strength.

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对高岭土混合物的研究：对莫来石形成动力学和微观结构演变的影响

本研究评估了阿尔及利亚高岭土（Djebel Debbagh (DD1) 和 Tamazart (KT2)）作为商用高岭土（Lab）的潜在替代品在莫来石基陶瓷生产中的应用。通过在每种煅烧高岭土中加入适当比例的氧化铝，制备了三种成分，以实现莫来石前驱体的化学计量。单个高岭土粉末以及它们与氧化铝的混合物的相演变在很大程度上取决于煅烧温度和高岭土杂质。差示扫描量热法和热重分析（TGA）显示，以 KT2 为基础的混合物的二次莫来石形成温度较低。然而，X 射线衍射显示 DD1 混合物完全莫来石化。K2O 阻碍了嵴沸石的形成，降低了二次莫来石的形成速度。微观结构分析表明，原生莫来石呈板状，次生莫来石呈等轴状。在 1600°C 烧结后，基于 KT2 的样品（M3）显示出更高的密度（3.013 g/cm3）和硬度（9.9 GPa），而基于 DD2 的样品（M2）显示出中等致密化（2.91 g/cm3）和更高的抗弯强度（159.42 MPa）。杂质（主要是 Fe2O3 和 K2O）促进了液相烧结，导致 M3 的致密化程度更高，而 M2 则显示出更均匀的微观结构、细化的晶粒和更低的玻璃相含量，从而提高了强度。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

International Journal of Applied Ceramic Technology 工程技术-材料科学：硅酸盐

CiteScore

3.90

自引率

9.50%

发文量

280

审稿时长

4.5 months

期刊介绍： The International Journal of Applied Ceramic Technology publishes cutting edge applied research and development work focused on commercialization of engineered ceramics, products and processes. The publication also explores the barriers to commercialization, design and testing, environmental health issues, international standardization activities, databases, and cost models. Designed to get high quality information to end-users quickly, the peer process is led by an editorial board of experts from industry, government, and universities. Each issue focuses on a high-interest, high-impact topic plus includes a range of papers detailing applications of ceramics. Papers on all aspects of applied ceramics are welcome including those in the following areas: Nanotechnology applications; Ceramic Armor; Ceramic and Technology for Energy Applications (e.g., Fuel Cells, Batteries, Solar, Thermoelectric, and HT Superconductors); Ceramic Matrix Composites; Functional Materials; Thermal and Environmental Barrier Coatings; Bioceramic Applications; Green Manufacturing; Ceramic Processing; Glass Technology; Fiber optics; Ceramics in Environmental Applications; Ceramics in Electronic, Photonic and Magnetic Applications;