One- and multicomponent sintering additives for ceramics based on aluminum oxide are presented. It has been established from the literature that the use of one-component additives is less effective than multicomponent, due to their higher melting temperatures and the impossibility of simultaneously influencing a number of properties of the target material. Due to the synergistic effect, the use of multicomponent additives makes it possible to achieve a simultaneous improvement in the properties of sintered samples based on aluminum oxide, in particular, an increase in the degree of compaction (porosity & # 8776; 0.1 & # 37;) of samples, a decrease in the sintering temperature to 1400 & # 176; C, preservation of a fine-crystalline structure (average grain size & # 8776; 3 microns), an increase in the value of crack resistance & # 8776; 5.86 MPa • m1 / 2 and ultimate strength in bending & # 8776; 600 MPa
The results of studies of the porosity of heat-efficient ceramic materials based on clays of various mineralogical composition with a glass-porous component (SPC) and their effect on frost resistance and thermal conductivity are presented. It was found that the content of minerals of the illite and montmorillonite subgroup in clays in compositions with SPC determines the optimal quantitative ratio of meso-, macro-, and also & # 171; hazardous & # 187; reserve and & # 171; safe & # 187; pores, which leads to a decrease in the coefficient of thermal conductivity and high indicators of frost resistance of materials
A study of the compaction of zinc oxide powder under conditions simulating the process of cold sintering described in the work of the research group of K. Randall carried out in 2017 in the USA is presented. The results obtained show that dense zinc oxide ceramics can be obtained by pressing (pressing pressure p = 77 MPa) in an aqueous medium at temperatures of 220-250 ° C. It was found that during pressing under the indicated conditions, two processes occur - compaction and grain growth, which are characteristic of sintering. The reproducibility of the cold sintering process is shown. The urgency of further research in this area has been substantiated.
The possibility of synthesizing manganese-willemite ceramic pigments in the xMnO- (2 - x) ZnO-SiO 2 system (x = 0.125; 0.250; 0.375; 0.500; 0.625; 0.750; 0.875 and 1.00) has been studied. Manganese-willemite ceramic pigments are synthesized at 800 - 1200 ° C. The resulting pigments were investigated using X-ray phase analysis, electron paramagnetic resonance, infrared spectroscopy. Color characteristics were determined using a Tintometr RT100 reflective colorimeter from Lovibond
The formation of highly dispersed SiO 2 particles in the process of quartz glass grinding in the manufacture of ceramic products has been investigated. A method for determining the quantitative content of highly dispersed silica in a slip based on quartz glass has been developed and tested. The concentration of highly dispersed SiO 2 particles in various batches of slip has been determined. The influence of the content of the colloidal component in the slip on the sintering process of the ceramic material has been evaluated.
The structures of two types of soft porcelain (bone china and parian) have been investigated. The features of the structure of these materials are revealed, which determine the combination of pronounced properties of whiteness and translucency in them: uniformity, high content of the glassy phase, well-developed interface of particles of the dispersed phase. The effect of changing the firing conditions on the color characteristics of these types of porcelain has been established. Parian has a more homogeneous structure than bone china, since the scatter of data on the average distance between grains at the same confidence level of 0.95 is much less than that of bone china.
Composite ceramics of granular silicon carbide, precipitation hardened by eutectic additives of the Al 2 O 3 -MnO-TiO 2 system, have been obtained. The effect of a dispersed eutectic powder in the Al 2 O 3 -MnO-TiO 2 system is considered depending on the ratio of silicon carbide / eutectic additive: 99/1 , 97/3 and 95/5 and pressing pressure on the sintering performance of a ceramic matrix composite based on granular silicon carbide. It was found that after firing at 1350 & # 176; C and a pressing pressure of 200 MPa with the introduction of 5 & # 37; (mass content) of the eutectic additive of composition A or B, the porosity is 5.6 and 4.1 & # 37; and the flexural strength reaches 65 & # 177; 5 and 85 & # 177; 5 MPa respectively
The rheological properties of corundum suspensions have been investigated. It is shown that for the preparation of corundum slip in the preparation of ceramic highly porous permeable cellular materials (HPCM) by duplicating the structure of polymer matrices, the minimum possible ratio of the dispersed phase and the dispersion medium S: L is 2.3: 1, and the mass content of polyvinyl alcohol in corundum slip is 1 ... 3 & # 37 ;. It has been experimentally established that corundum suspensions with such a ratio of the dispersed phase and the dispersion medium are coagulation structures with a characteristic thixotropic behavior
The features of the effect of additives of lanthanum cations on the thermochemical behavior of modified zirconium hydroxide have been investigated. It is shown that the composition and properties of the obtained materials are determined by the concentration of the modifier and the temperature of the formation of the oxide phase
The results of a comparative study of compacts obtained from nano- and ultradispersed (UF) powders of aluminum oxide with a spherical shape of particles by the method of spark-plasma sintering are presented. It is shown that UF powder compacts achieve higher density, strength, microhardness, and structure homogeneity with finer grain than nanopowder compacts. Preliminary magnetic-pulse compaction of the powders before sintering improves the characteristics of both compacts, but UF powder compacts achieve greater density and strength with smaller grain sizes. In both cases of preliminary preparation, compacts obtained from UF powder have advantages over compacts obtained from nanopowder.
