Mullite is of great technological relevance but rarely occurs in nature and as a result different approaches have been adopted in its synthesis from alumina bearing minerals. In this study, chemical, phase and structural change of mullite synthesized from sintering of natural kaolinite clay is investigated. Thoroughly beneficiated kaolinite clay powder was obtained from Nigeria and uniaxially pressed into cylindrical compact of 40 × 30 mm followed by sintering at temperatures of 1200°C and 1300°C, respectively. The chemical composition, microstructure change, phase transformation, and reaction bonding were carried out using EDXRF, SEM, XRD, and FT‐IR, respectively, to assess the synthesized mullite. The results showed that a well‐dispersed primary mullite phase was obtained which was fully developed at increased temperature of 1300°C. Better mullite phase was also obtained with increasing alumina content at more elevated temperature of 1300°C while Si‐O‐Al bonding of mullite crystals was also obtained from the FT‐IR spectra. However, the needle‐shaped mullite structure was not achieved which might be attributed to the sintering temperatures 1200°C‐1300°C utilized.

中文翻译：

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高岭土烧结过程中合成的莫来石的化学，相和结构变化

莫来石具有重大的技术意义，但自然界中很少发生，因此，从含氧化铝的矿物合成中采用了不同的方法。本研究对天然高岭石粘土烧结合成莫来石的化学，相和结构变化进行了研究。从尼日利亚获得了充分精选的高岭石粘土粉，并将其单轴压制成40×30 mm的圆柱体，然后分别在1200°C和1300°C的温度下烧结。分别使用EDXRF，SEM，XRD和FT-IR进行化学成分，微观结构变化，相变和反应键合，以评估合成莫来石。结果表明，获得了分散良好的初级莫来石相，该相在1300°C的升高温度下充分发育。在更高的1300°C温度下，随着氧化铝含量的增加，也可获得更好的莫来石相，而FT-IR光谱也获得了莫来石晶体的Si-O-Al键合。但是，未达到针状莫来石结构，这可能是由于使用了1200°C-1300°C的烧结温度。