Sokolova A.G.

PhD (Engineering), Associate Professor, National Research Moscow State University of Civil Engineering

Comparison of the effectiveness of rice husk ash for solid phase synthesis of wollastonite and diopside

https://doi.org/10.58224/2619-0575-2026-9-1-1
Abstract
Objectives: This study aims to evaluate the prospects of using rice husk ash for the production of calcium-magnesium silicates and to identify differences in the solid-phase synthesis processes of wollastonite and diopside based on rice husk ash.
Methods. X-ray quantitative phase analysis was used to analyse the obtained samples of synthetic wollastonite and diopside. The porosity of calcium-magnesium silicates was evaluated by a static volumetric method using low-temperature nitrogen adsorption. The elemental composition of the samples was determined using an Oxford INCA X-max 80 energy dispersive detector, and electron microscopic analysis was performed using a Jeol JSM7001F scanning microscope.
Results. Experimental data comparing the properties of synthesized diopside and wollastonite showed that wollastonite is characterized by high porosity and average particle size compared to diopside due to the lower temperature of solid-phase synthesis. The structure of synthetic wollastonite is distinguished by the presence of large irregularly shaped inclusions with a small amount of needle-like particles, while synthesized diopside does not contain needle-like particles, and the inclusions are characterized by smaller size and uniform distribution throughout the volume.
Conclusions. When obtaining calcium-magnesium silicates by solid-phase synthesis based on rice husk ash, the yield of the final product synthetic diopside is significantly higher than that of synthetic wollastonite. The process of synthesizing diopside is less labor-intensive and time-consuming, but more energy-intensive due to the higher synthesis temperature of diopside.
PDF

Comparison of modifying effect of wollastonite in polyvinylchloride and epoxy composite materials

https://doi.org/10.58224/2619-0575-2025-8-4-2
Abstract
To investigate the grain-size and phase compositions and properties of natural and synthetic wollastonite fillers and to establish the nature of their modifying effect in polymer composite materials using the example of polyvinyl chloride thermoplastic and epoxy resin thermoset.
Methods. X-ray quantitative phase analysis was used to study the filler samples, and porosity was determined using mercury porosimetry and gas absorption. The particle size of wollastonite was determined by laser diffraction. The thermal stability of the filled composites was evaluated on a derivative thermogravimetric analyser, and the thermal stability of polyvinyl chloride materials was evaluated using the Congo red method. Dynamic mechanical analysis was performed on a DMA 242 Netzsch device.
Results. The particle size distribution and phase composition of natural and synthetic calcium silicate samples, their porosity and pH of aqueous extract were studied. The influence of wollastonite properties on the viscosity of the obtained polymer-filler mixtures, the thermal stability and wear resistance of the filled composites, as well as on the tensile strength and relative elongation of polyvinyl chloride compositions was established.
Conclusions. Studied calcium silicates have proven effective for both epoxy and polyvinyl chloride materials. Despite the similarity in phase composition and acid-base characteristics of the surface, natural and synthetic wollastonite differ in particle size distribution and porosity. Natural filler is more promising for creating heat-resistant polyvinyl chloride compositions and wear-resistant epoxy compositions, while synthetic wollastonite based on rice husks provides an increase in the dynamic modulus and glass transition temperature of both types of polymers. Studies have shown that the modifying effect of the studied fillers is more prominent in epoxy polymers due to their influence on the formation of the polymer matrix cross-linked structure.
PDF