【摘要】 以聚硅氧烷乳液(S–17)/聚丙烯酸铵[poly(acrylic acid)ammonium,PAA–NH4]为复合分散剂制备了高浓度且稳定的Si3N4凝胶注模料浆,用电泳仪分析了料浆中颗粒表面zeta电位,用转子黏度计测量了料浆的黏度,用沉降法表征了Si3N4粉体的分散稳定性,用黏度法获得颗粒对聚硅氧烷分子的吸附等温线。研究了PAA–NH4分散剂和聚硅氧烷表面活性剂对高固相含量、低黏度料浆的稳定性影响机制。结果表明:单独使用PAA–NH4不能达到较好的稳定效果,采用聚硅氧烷乳液/PAA–NH4复合分散剂,聚硅氧烷乳液用量为0.4%(质量分数,下同),PAA–NH4为0.8%时,可制备固相体积含量为50%,黏度低于1.0Pa·s,稳定性较高的料浆,该料浆适于凝胶注模操作。根据静电作用原理,结合颗粒对聚硅氧烷分子的吸附特性,提出通过降低液相表面张力来降低料浆黏度及提高稳定性,探讨了高固相含量料浆分散的理论机理。更多还原

【Abstract】 Highly concentrated and stable aqueous Si3N4 slurry for gel-casting was prepared with polysiloxane emulsion(S-17)and poly(acrylic acid)ammonium(PAA–NH4)as composite dispersants.The zeta-potential was measured using an electrophoresis system, and the viscosity was tested using a viscometer.The stability of the suspension was characterized with the settlement method.The adsorption isotherm of polysiloxane molecules on particles was obtained by viscosimetry.The effect of PAA–NH4 and polysiloxane surfactant on Si3N4 suspension with high solid loading,low viscosity and optimal stability was researched.The results show that preferable stability can not be obtained by PAA-NH4 as the single dispersant.High performance suspension with 50%volume content, low viscosity(<1 Pa·s)and high stability was prepared with 0.4%(mass fraction,the same below)polysiloxane and 0.8% PAA-NH4 as composite dispersant.The viscosity and stability of the suspension can be improved by reducing the surface tension.Based on the electrostatic interaction theory and the adsorption properties of polysiloxane molecule on particles,the mechanism of the stabilization of highly concentrated suspension was discussed.更多还原