5:15 PM - 6:30 PM
[SCG63-P05] Sintering of fine-grained polycrystalline clinopyroxene
Keywords:sintering, clinopyroxene
The rheology of lower crust and upper mantle has been determined by deformation experiments of polycrystalline samples of rock-forming minerals. In these experiments, the samples were often synthesized to obtain fine-grained polycrystalline. In this study, we investigates a method for preparing the fine-grained polycrystalline clinopyroxene from nano-sized natural powders of clinopyroxene.
The starting materials for the experiment were prepared from two types of diopside single crystals (Di97Hed3:Ca0.99Na0.01Mg0.97Fe0.03Si2O6, Di99Hed1:Ca0.97Na0.02Mg0.86Fe0.13Si2O6) and a salite single crystal (Di87Hed13:Ca0.97Na0.02Mg0.86Fe0.13Al0.02Si2O6) . They were crushed and milled into nano-sized powders. The milled powders were uniaxially pressed and sintered at 1230 - 1280 ℃ in atmospheres of argon or vacuum for 2-6h. After the sintering, sample surfaces were polished and thermally etched to expose grain boundaries. Grain size and porosity were determined from the microstructure of scanning electron microscope (SEM) .
After sintering at 1230℃, the relative density increased with increasing sintering time and reached the value of 98.0% and 93.5% of the theoretical density for Di97Hed3 and Di99Hed1 samples respecrively. The grain size of the each sample remains about <2µm. On the other hand, only 94.1% and 90.5 vol% of theoretical density were obtained from samples sintered at 1280℃ and the grain size increased to 5µm. Abnormally large grains and large porosities were found in Di87Hed13 sample. We found that the sintering temperature of 1230℃ is more suitable for densification and grain growth of polycrystalline clinopyroxene than 1280℃.
The starting materials for the experiment were prepared from two types of diopside single crystals (Di97Hed3:Ca0.99Na0.01Mg0.97Fe0.03Si2O6, Di99Hed1:Ca0.97Na0.02Mg0.86Fe0.13Si2O6) and a salite single crystal (Di87Hed13:Ca0.97Na0.02Mg0.86Fe0.13Al0.02Si2O6) . They were crushed and milled into nano-sized powders. The milled powders were uniaxially pressed and sintered at 1230 - 1280 ℃ in atmospheres of argon or vacuum for 2-6h. After the sintering, sample surfaces were polished and thermally etched to expose grain boundaries. Grain size and porosity were determined from the microstructure of scanning electron microscope (SEM) .
After sintering at 1230℃, the relative density increased with increasing sintering time and reached the value of 98.0% and 93.5% of the theoretical density for Di97Hed3 and Di99Hed1 samples respecrively. The grain size of the each sample remains about <2µm. On the other hand, only 94.1% and 90.5 vol% of theoretical density were obtained from samples sintered at 1280℃ and the grain size increased to 5µm. Abnormally large grains and large porosities were found in Di87Hed13 sample. We found that the sintering temperature of 1230℃ is more suitable for densification and grain growth of polycrystalline clinopyroxene than 1280℃.