Hebei Messi Biology Co., Ltd. stated that the orthogonal experimental method was used to analyze the influence of process parameters such as the molar ratio of precipitant to Mg2+, hydrothermal reaction time and hydrothermal reaction temperature on the yield, average particle size and shape of nano-magnesia powder. The influence of appearance was determined, and the optimal process conditions for preparing nano-magnesium oxide were determined:
The molar ratio of precipitant to Mg2+ is 2:1, the hydrothermal reaction time is 3h, and the hydrothermal reaction temperature is 160°C. The single factor experimental method was used to determine the precipitant and precursor decomposition calcination temperature for preparing nano-magnesium oxide powder.
Hebei Messi Biology Co., Ltd. stated that it studied the effects of disodium ethylenediaminetetraacetate (EDTA) and potassium chloride (KCl) as reaction media on the morphology and structure of nanooxide powders.
After adding EDTA or KCl to the hydrothermal reaction system, the morphology of the nano-magnesium oxide powder gradually changes from hexagonal flakes to nearly circular flakes, and the crystal form remains a face-centered cubic structure. The mechanism of crystal growth was explained using the negative ion coordination polyhedral growth unit theory, and the mechanism of crystal morphology change was discussed. The spark plasma sintering method was used to study the phase composition and grain morphology characteristics of magnesium oxide bulk ceramic materials sintered at different temperatures (900°C, 1050°C, 1200°C, 1300°C, 1420°C). Sintering temperature has an important influence on grain growth and ceramic structure.
The results show that the bulk ceramic materials all have a face-centered cubic structure with a single phase composition, and the samples have high purity. The diffraction peaks of each crystal plane obviously become sharper and narrower after sintering at different temperatures, indicating that grain growth occurs during the sintering process. SEM shows that as the sintering temperature increases, the appearance of the particles gradually evolves from hexagonal flakes to polyhedral morphology, and the gaps between particles gradually transition from continuous pores to isolated pores. The kinetic growth index n value and grain growth activation energy Q value under different sintering temperatures were calculated using phenomenological kinetic theory.
Analysis shows that when the temperature is 900℃ and 1050℃, the sintering and grain growth mechanism is mainly surface diffusion; when the temperature is 1200℃, the sintering and grain growth mechanism is mainly surface diffusion, supplemented by plastic flow; temperature When sintering at 1300°C and 1420°C, the sintering and grain growth mechanism is mainly grain boundary diffusion supplemented by plastic flow.