Study On Preparation And Rheological Property Of Sic Suspensions With High Solid Content And Low Viscosity

Surface modification is an effective way to improve the dispersion propertiesof powders and prepare high solid content of suspension. Therefore, this paper triesto use inductively coupled plasma atomic emission spectrometry (ICP-AES), totalorganic carbon analyzer (TOC) and other instruments to quantitatively evaluatethe pretreatment effect of SiC powders and combined condition between modifiers andSiC powder surface. The relation between SiC powder surface treatment orsurface modification and the rheological properties are studied. The main research worksare as follows.1. Microscopic difference of silicon carbide powders and rheological properties of theirslurries. Composition crystal form, particle size and surface properties of the imported anddomestic silicon carbide powders were characterized by XRD, EDS, TEM and particlesize test. The results show that two kinds of powders have similar composition andmicroscopic structure. But their suspensions show obviously different rheologicalproperties. The imported samples can obtain stable suspension with solid volume fractionof55%with low viscosity while the largest solid volume fraction of the domestic powdersis40%which appears shear thickening phenomenon. Microscopic difference of surfaceproperties results in different rheological properties of suspensions.2. Effect of pretreatment powder on the rheological properties of SiC suspensions.ICP-AES is used to measure the metal ion content in pretreated SiC powders washed bydeionized water, acid solution and alkaline solution. The influence of impurity ions on therheological property of SiC suspensions is investigated. Quantitative analysis result ofICP-AES shows that impurity ions in SiC powder surface decreases after washed bydifferent acid and alkali solution. The viscosity of SiC suspension decreases and itsstability improves. Hydrochloric acid solution with1%has optimum effect to remove theimpurity ions in SiC powder surface; rheological property of SiC suspension issignificantly improved. 3. Surface modification of SiC with silane coupling agent. The SiC powders pretreated by1.0%hydrochloric acid solution are directly modified with KH-550, KH-560, KH-570,methyltrimethoxysilane respectively. Total organic carbon (TOC) is used to measureorganic matter content in washing liquid which will explain combined condition betweensilane coupling agent and surface of SiC powder. Results show that silane coupling agentand SiC powder surface are combined by chemically bonded and adsorption, the solidcontent and stability of SiC suspension improved. KH-560modification works best.4. The preparation of environmentally friendly modifiers. A series of environmentallyfriendly modifiers-MA are used to modify the surface of SiC powder. The modificationmechanism and the impact on the rheological properties of suspensions are investigated.Though the additive amount of modifiers is1.0‰of the quality of silicon carbide, thesolid content of SiC suspensions improves to53vol%, viscosity of suspension decreasesand its stability improves. The TOC analysis illustrates that MA101combines with SiCpowder firmly.