Research of the dispersing and strengthening additives’ influence on the properties of slips and alumina ceramics samples from active alumina

Abstract

The effect of dispersing and strengthening additives on the rheological properties of aqueous slips made from new brands of alumina produced by a German company was studied. The optimal quantities of dispersing additive for slips from all researched new brands of alumina were determined: for less dispersed alumina — 0.3 % and more dispersed alumina — 0.4 %, the introduction of which reduces the dynamic viscosity of slips to minimum values of — 30 mPa·s, 70 mPa·s and 110 mPa·s, respectively. It has been established that slips made from all researched new brands of alumina with the optimal dispersing additive quantity are characterized by high sedimentation stability and in combination with 0.2 % strengthening additive the sedimentation stability of slips increases.
 The main properties indexes of the samples from new brands of alumina before and after firing at a temperature of 1580 °C were determined. It was established that green samples from new brands of alumina are characterized by apparent density 2.23 g/cm3, 2.19 g/cm3, 2.18 g/cm3 and cold crushing strength 1.1 N/mm2, 1.0 N/mm2, 0.8 N/mm2, respectively, and samples after firing at 1580 °C by apparent density 3.75 g/cm3, 3.90 g/cm3, and 3.86 g/cm3, open porosity 3.3 %, 0.5 %, 0.4 % and bending strength 150 N/mm2, 180 N/mm2, 200 N/mm2, respectively.
 As a result of the performed research, it was established that new brands of more dispersed alumina are suitable for the production by the slip casting method in plaster molds of alumina ceramics with open porosity up to 0.5 % and bending strength ~ 180—200 N/mm2.
 According to the performed research results the technology of alumina ceramics by slip casting in plaster molds method was improved and the raw material base for its production was expanded.