Fly ash can be considered a promising secondary raw material for the production of high-strength porous mullite ceramics, since the absence of a need to grind the initial batch materials makes it possible to significantly reduce energy consumption. In this study, promising ceramic samples were produced using fly ash and aluminum ore, specifically low-iron bauxite, as an Al2O3-adjusting component. Thermogravimetric and X-ray diffraction phase analyses were used to determine the sequence and temperature ranges of phase transformations in the system “fly ash – bauxite” and to establish the optimal thermal treatment regime. Several exothermic peaks were observed in the 1200-1300 °C temperature range, reflecting a sequence of phase transformations. Mullite forms through a reaction between quartz and cristobalite, which pass into a transient liquid phase, and γ-Al2O3, formed by the decomposition of boehmite. The total mullite phase content reaches 83-84 %, which is significantly higher than the values reported by other researchers, including those who used various additives to accelerate mullite formation. Scanning electron microscopy was used to trace the evolution of the microstructure of the obtained samples as a function of synthesis temperature. As the treatment temperature increases to 1300 °C, sintering gradually intensifies, resulting in the formation of larger pores. Acicular mullite crystals form around flake-like γ-Al2O3 crystals, some of which subsequently transform into corundum. Laboratory tests of the finished ceramic samples confirmed that their technical characteristics – density, porosity, and compressive strength – meet the requirements for refractory, thermal insulation, and chemically resistant materials. The study presents the technological principles for developing high-strength and porous mullite-based ceramics intended for use in construction and thermal insulation applications.

Technological mineralogy of titanium ores is the basis for assessing their complexity. It enables, from a unified standpoint, to trace the entire course of changes in mineral matter through operating procedures, including beneficiation, processing, and obtaining target industrial products. The study targets are Pizhemskoye ilmenite-leucoxene sandstones, which are distinguished by a complex polymineral composition. Along with the main ore components, there are other metals with different speciation (isomorphic admixture, independent mineral phases). The optimal set of mineralogical analysis methods for the predictive assessment of their further use is substantiated exemplified by titanium ores of the Pizhemskoye deposit, which are complex, noted for a variable content of iron oxides and contain rare earth metals. Examinations by X-ray phase analysis and scanning electron microscopy confirm that the main titanium phases of sandstones are pseudorutile and a polymineral aggregate, “leucoxene”. Considering the granulometric peculiarities of the magnetic and non-magnetic fractions of the gravity concentrate, the prospects of technologies for processing titanium raw materials are discussed. Along with the problems of obtaining high-quality raw materials, the transformations of mineral phases as a result of extreme impacts and their physicochemical properties as a consequence of isomorphic substitution of a part of Ti atoms with natural modifier agents (Fe and V) in the synthesis of titanium oxide nanostructures for industrial applications are considered (photocatalytic nanoreactor).

The growing demand for mullite raw materials, which meet industrial requirements originates the search for new and alternative sources, as well as efficient technologies for obtaining the target products (nanocomposites). The article suggests a method for obtaining mullite from kaolinite experimentally (Vezhayu-Vorykvinsky deposit, Russia). Structural kaolinite transformations (Al-Si-O-Me system), mineral phases transformations, and thermodynamics of the process have been studied. Based on the estimation of the thermodynamics of the reactions, the preferable reaction of mullite formation was determined. The article shows, that formation of the target product, mullite nanocomposite, has several intermediate phases (metakaolinite, pseudomullite). The transformations of the initial kaolinite structure include the removal of structural water and separation of the silica-oxygen tetrahedral and alumina-oxygen octahedral layers, the decomposition into free oxides, breaking of bonds between the silica-oxygen tetrahedrons and the partial increase in the coordination number of aluminium ions, the formation of mullite and cristobalite from free oxides. The proposed approach controls the ratio of Al₂O₃ and SiO₂ phases at certain stages, which will further improve the mechanical and other properties of the matrix of the obtained raw materials for the target prototypes of industrial products.

Coal fly ash is generated in the course of combustion of coal at thermal power plants. Environmental problems increase sharply without disposing that industrial waste. Technologies were tested of hydrothermal synthesis of zeolites from fly ash forming during combustion of coal at thermal power plants of the Pechora coal basin and dependences were identified of the experiment conditions on physical and chemical properties of the end product. It is demonstrated that synthesizing zeolites from fly ash is the first stage of forming ceramic materials (ceramic membranes), which defines the fundamental character (importance) of that area of studies. It was for the first time that sorption and structural characteristics and cation-exchange properties of fly ash from the Pechora basin coals were studied with respect to, Ba²⁺ and Sr²⁺.