To investigate the influence of the furnace structure and inlet gas velocity on gas-solid two-phase flow states in the deposition furnace,FLUENT software was used to simulate dense gas-solid two-phase flow in a fluidi...To investigate the influence of the furnace structure and inlet gas velocity on gas-solid two-phase flow states in the deposition furnace,FLUENT software was used to simulate dense gas-solid two-phase flow in a fluidized bed.The results show that the dispersed fluidized bed formed in the deposition furnace with a cone angle of 60°has the structure of"ring-nucleus"and longer gas retention time compared with the flat-bottom structure deposition furnace,which is beneficial to the preparation of the pyrolytic carbon coating materials with a uniform structure and excellent quality.Inlet gas velocity should be moderate,the slow inlet gas velocity leads to the chaos of the particle velocity distribution,which cannot form the ring-core flow structure.High inlet gas velocity leads to the back mixing of particles in the deposition furnace.In addition,as the inlet gas velocity increases,both the gas phase and the average particle velocity in the central area of the deposition furnace gradually increase,and the effect of the gas phase velocity is more obvious.展开更多
To investigate the microstructure and deposition mechanism of low-temperature isotropic pyrocarbon(LTIC),chemical vapour deposition was conducted in a steady-state fluidized bed using different propane concentrations ...To investigate the microstructure and deposition mechanism of low-temperature isotropic pyrocarbon(LTIC),chemical vapour deposition was conducted in a steady-state fluidized bed using different propane concentrations and deposition temperatures.The microstructure of LTIC obtained at different deposition conditions was characterized using scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that LTIC is composed of both globular-like and laminar structures.Increasing the deposition temperature is propitious for decreasing the nucleation barrier-forming pyrocarbon in vapour,causing the quantity of spherical particles with a smaller diameter to increase and the texture of the outer layer around carbon blacks inside the spherical particles to decrease gradually.Increasing the propane concentration also made the globular-like fracture morphology more obvious and caused the laminar structure to gradually disappear.Pyrocarbon formation is dominated by a surficial growth mechanism at lower propane concentrations,while gaseous nucleation mechanism is more dominant at higher propane concentrations.展开更多
文摘To investigate the influence of the furnace structure and inlet gas velocity on gas-solid two-phase flow states in the deposition furnace,FLUENT software was used to simulate dense gas-solid two-phase flow in a fluidized bed.The results show that the dispersed fluidized bed formed in the deposition furnace with a cone angle of 60°has the structure of"ring-nucleus"and longer gas retention time compared with the flat-bottom structure deposition furnace,which is beneficial to the preparation of the pyrolytic carbon coating materials with a uniform structure and excellent quality.Inlet gas velocity should be moderate,the slow inlet gas velocity leads to the chaos of the particle velocity distribution,which cannot form the ring-core flow structure.High inlet gas velocity leads to the back mixing of particles in the deposition furnace.In addition,as the inlet gas velocity increases,both the gas phase and the average particle velocity in the central area of the deposition furnace gradually increase,and the effect of the gas phase velocity is more obvious.
基金National Natural Science Foundation of China,grant number:50975070grant sponsor:Zhejiang Provincial Science Foundation of China,grant number:LY12E05002
文摘To investigate the microstructure and deposition mechanism of low-temperature isotropic pyrocarbon(LTIC),chemical vapour deposition was conducted in a steady-state fluidized bed using different propane concentrations and deposition temperatures.The microstructure of LTIC obtained at different deposition conditions was characterized using scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that LTIC is composed of both globular-like and laminar structures.Increasing the deposition temperature is propitious for decreasing the nucleation barrier-forming pyrocarbon in vapour,causing the quantity of spherical particles with a smaller diameter to increase and the texture of the outer layer around carbon blacks inside the spherical particles to decrease gradually.Increasing the propane concentration also made the globular-like fracture morphology more obvious and caused the laminar structure to gradually disappear.Pyrocarbon formation is dominated by a surficial growth mechanism at lower propane concentrations,while gaseous nucleation mechanism is more dominant at higher propane concentrations.
