Morphology Of Hematite Particles Research Articles

Hydrothermal precipitation of hematite from the model solution of zinc hydrometallurgical extraction

Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.

Catalytic synthesis of nanosized hematite particles in solution

Spherical hematite particles have been quickly synthesized by heating Fe(OH) 3 gel with trace Fe(II) in aqueous solution to reflux temperature. The final product is characterized by XRD, TEM, HRTEM, and FT-IR techniques. The influence of various factors on the size and morphology of hematite particles is investigated, respectively. The growth mechanism of hematite particles is also discussed. The results show that both the mechanisms, dissolution/reprecipitation and solid state transformation, work alternately in the transformation process from Fe(OH) 3 to hematite particles until the transformation is finished. The magnetism of the product is also studied.

Thermal behavior of goethite during transformation to hematite

Under non-isothermal conditions, thermal transformation kinetics of goethite was assessed from the shape of a derivative thermogravimetric (DTG) curve and then verified by the correlation between the maximum decomposition degrees and thermal kinetic mechanisms. Kinetic analysis showed that this process was governed by the three-dimensional diffusion. Microstructural changes during the process were characterized by use of infrared spectra (IR), transmission electron microscopy (TEM) and differential thermal analysis (DTA). Combining non-isothermal kinetic results and microstructural changes, thermal behavior of this transformation was described as followed. In the beginning, surface autodiffusion played a dominant role. With increasing temperatures, micropores were produced due to three-dimensional diffusion of hydrogen or hydroxyl groups in bulk goethite crystals and then merged into the slits because of the high water pressure inside. The morphology of hematite particles with regular texture was changed due to the recrystalyzation role, and finally spherical particles were formed.

Thermal formation mechanism and size control of spherical hematite nanoparticles

Hematite nanoparticles were prepared by a FeCl 2 solution. The whole thermal formation mechanism as well as the size and dispersity control of hematite nanoparticles was studied. It has been found that goethite nanoparticles were firstly produced through the mix and oxidation of 0.5 M ferrous salt and 2.1 M bicarbonate and then hematite nanoparticles were obtained directly by thermal transformation of the goethite samples. At higher temperatures, nanopores were observed in the goethite nanocrystals and then merged into slits due to the high water pressure in the nanopores. The morphology of hematite particles with regular texture was changed due to recrystallization and then spherical nanoparticles were formed in the end. The particle size and dispersity of hematite nanoparticles could be controlled by different charging rates. From the second particle size distribution diagrams measured by the laser dynamic scatter method, not only the hematite particle size became small but also the dispersity of hematite nanoparticles was improved as the charging rate increased.