اميرپارسا اسحقي

Alpha-phase alumina, due to its high hardness an‎d thermal stability, is considered a key material in the polishing industry. In this study, α-alumina nanoparticles were synthesized via a chemical precipitation method using polyaluminum chloride as the primary precursor an‎d aluminum sulfate as a morphology modifier, while sodium hydroxide was employed as the precipitating agent. Various molar ratios of the two precursors were investigated under controlled pH conditions (≈7), with slow addition of the base at ambient temperature. The resulting precipitates were filtered, washed, an‎d subsequently calcined under different temperature profiles up to 1050, 1100, an‎d 1150 °C, each maintained for 2 hours. X-ray diffraction analysis revealed that at 1050 °C, the sample containing 100% polyaluminum chloride was fully converted to α-alumina, while those containing aluminum sulfate exhibited partial retention of transitional phases. Increasing the temperature to 1100 °C enabled α-phase formation in samples with less than 50% contribution of polyaluminum chloride. Moreover, complete transformation to α-alumina was achieved at 1150 °C in all mixed-precursor samples, with the composition containing 70% aluminum sulfate an‎d 30% polyaluminum chloride exhibiting exclusively α-phase diffraction peaks. Field-emission scanning electron microscopy (FE-SEM) demonstrated that increasing the sulfate content altered the particle morphology from hexagonal plate-like structures to quasi-spherical particles with smoother edges an‎d improved size uniformity. In the optimized 70:30 sample, quasi-spherical particles with diameters predominantly in the range of 300–600 nm were observed. Dynamic light scattering (DLS) analysis of the same sample exhibited a monomodal size distribution with an average hydrodynamic diameter of approximately 480 nm an‎d a polydispersity index of 0.1, confirming narrow particle dispersion. The synthesized product exhibited high purity, complete α-phase composition, an‎d uniform particle size suitable for polishing applications. Overall, the results demonstrate that precise control of precursor ratios an‎d calcination conditions enables the production of pure α-alumina nanoparticles with desirable morphological characteristics for application in the polishing industry.

نانوذرات آلفا-آلومينا , رسوب‌دهي شيميايي , پلي‌آلومينيوم كلرايد , نسبت مولي پيش‌ماده‌ها , صنعت پرداخت سطوح

α-Alumina nanoparticles , Chemical precipitation , Polyaluminum chloride , Precursor molar ratio , Polishing industry

Amirparsa Eshaghi

Omid Vahidi