燃烧合成氮化硅粉体的性能一致性评价方法和应用

李宏华, 东婉茹, 王良, 杨增朝, 李江涛

Consistency of Silicon Nitride Powders Produced by Combustion Synthesis: Evaluation and Application

LI Honghua, DONG Wanru, WANG Liang, YANG Zengchao, LI Jiangtao

表2 氮化硅粉体产品流动性指标体系及测量方法

Table 2 Fluidity index system and measurement method of silicon nitride powder products

General indicator Secondary indicator Symbol Unit Definition Stability and variable flow rate Basic flowability energy BFE mJ The energy required for the rotor to overcome the resistance of the powder to rotate Stability index SI — Repeated measurements of powder flow energy to characterise its stability Flow rate index FRI — Measurement of flow energy at different speeds Specific energy SE mJ/g Data measured during the upward movement of the blade through the powder sample Compressibility Conditioned bulk density CBD g/mL Loose packing density of pre-treated powders Compressibility CPSm % Compressibility at positive stress m kPa Shear test Cohesion Cm kPa Shear strength at zero positive stress for a pre-consolidated positive stress of m kPa Unconfined yield strength UYSm kPa The maximum principal stress corresponding to a molar circle tangent to the yield trajectory at a pre- consolidation stress of m kPa and a minimum principal stress of 0 Maximum principal stress MPSm kPa Maximum compressive stress calculated from the molar circle at steady state flow under a pre-consolidated positive stress of m kPa Flow function FFm — Ratio of the above maximum principal stress to the unconfined yield strength Angle of internal friction AIF ° The angle between the shear linear yield trajectory and the x-axis, characterizing the ease with which the powder particles can slide against each other Aeration test Aerated energy AEn — The energy required to move the powder sample when filling the gas at a rate of n mm/s Aeration ratio AR — Ratio of the base flow energy to the filling energy after the powder having reached stability in the filling test Normalized aeration sensitivity NAS s/mm Sensitivity to the effect of air introduced by the powder, normalized BFE to air velocity ratio Permeability Pressure drop PDm 100 Pa Pressure reduction after passing air through a powder sample when a positive stress of m kPa is applied and the air velocity is maintained at 0.5 mm/s