Influence and Mechanism of Different Iron-Based Catalysts onⅡa Type Cultivated Diamonds under High Temperatures and Pressures
This paper studied the influence and mechanism of different iron-based catalysts on Ⅱa type cultivated diamonds under high temperatures and pressures.The results show that the optimal crystallinity of the FeAl-C catalyst is 72.2%,and the weekly yield is 25.61 ct(1 ct=0.2 g).The average weight of a single diamond is 1.19 ct.FeCo-C catalyst has a weekly yield of 44.37 ct,and the average weight of a single diamond is 2.11 ct,but the optimal crystallinity is 36.8%,and there are many defects.Scanning electron microscope(SEM),energy disperse spectroscopy(EDS),and electron back scattering diffraction(EBSD)are used to reveal the effects of FeAl and FeCo catalysts on the growth of cultivated diamonds due to structural differences.The results show that the average mass fraction of Al and Fe in the FeAl catalyst is 4.86%and 95.14%,respectively.The average mass fraction of Co and Fe in the FeCo catalyst is 37.33%and 62.67%,respectively.The difference in solid solubility between metals leads to the difference in phase distribution and grain orientation.The grains of the FeAl catalyst are coarse,large,and uniform,with the same orientation,and the formed single-phase structure and single texture reduce the catalytic activity when the catalyst selectivity is enhanced,resulting in uniform transfer and precipitation of carbon on the crystal seed surface,which promotes the formation of high-quality crystals and leads to a low yield of the FeAl system.The grains of the FeCo catalyst are small but heterogeneous,containing multiple solid solution phases and multiple textures,which increase the catalytic activity of the catalyst and speed up crystal growth and yield.As the selectivity decreases,the process of carbon transfer and precipitation on the crystal seed surface is more complicated,and the morphology is unstable,which makes it easy to produce more crystal defects.
high temperature and pressureiron-based catalystⅡa type cultivated diamondtextureoptimal crystallinity
NETL
NSTL
万方数据
