The refractory compositions designing for the highly-heat-resistant ceramic products in the foundry practice

The sintering peculiarities of the ceramic materials which had been prepared by means of semidry pressing are investigated in the article. The fillers were the yttrium oxide Y2O3 and the fused corundum α-Al2O3, the bonding phase was the aluminoxane addition either pure or modified by the yttrium and magnesium compounds. We investigated the processes occurring at the examined ceramics sintering at different temperatures and their influence on the obtained ceramics properties. The phase composition, the thermal and mechanical properties of the test samples at 1500 °C are presented. The produced test ceramic crucibles have advanced thermal resistance and stability against the thermal cycling. The possibility is regarded to use the developed ceramic crucibles for melting and casting of the chemically reactive highly-heat-resistant metals and alloys.

Investigation of the compressibility of low-cement corundum castable with the addition of chromium oxide depending on moisture and pressing pressure

The mass compressibility of composition low-cement corundum castable with an addition of chromium oxide, depending on its moisture (2.5, 3.0, 3.5, 4.0, 4.5 %) and specific pressing pressure (50, 75, 100 N/mm2) has been investigated. The optimum moisture of the forming mass (3.0—3.5 %) and the pressing pressure (100 N/mm2), which ensure the production of fresh-formed samples with an apparent density of 3.14 g/cm3, dried (after hardening in humid conditions for 7 days ) with an apparent density of 3.03—3.04 g/cm3, and fired samples with an apparent density, open porosity and compressive strength, respectively, of 2.97—2.98 g/cm3, 24.8—25.0 %, 80—83 N/mm2, were established. The obtained research results can be used at the enterprises producing carbon black for the products manufacture by semidry pressing or ramming methods from the delivered by PJSC “UKRNIIO NAMED AFTER A. S. BEREZHNOY” dry mixtures containing all the necessary mass components. The products ramming, as well as pressing, must be carried out up to obtain an apparent density of fresh-formed green not less than 3.14 g/cm3.

Producing Clay-Coated Quartz Powders for Semidry Pressing of Wall Ceramics

ABSTRACTThis paper discusses the potential of mechanochemical activation of low grade raw materials with carbonaceous inclusions to achieve high-quality building ceramics. The procedure proposed enabled us to produce clay-coated quartz powders thus facilitating further processing steps of semidry pressing and firing of the bricks, tiles and flagstones.