Project Goals

Main Objective
To synthesise new high temperature mullite and mullite–corundum ceramic pigments from both pure and waste raw materials.

Ceramic pigments are inorganic, finely dispersed coloured powders that, when added to a medium, impart colour and alter selected properties. Beyond their colouring capability, ceramic pigments are resistant to atmospheric and chemical influences, high temperatures, degradation by silicate melts, and light exposure. These inorganic colourants have a high refractive index, are insoluble in water, organic solvents, and binders, yet readily disperse within them to provide stable colour.

Our focus on synthesising new classes of ceramic pigments is motivated by their growing importance for the silicate industry and by the feasibility of producing them from both traditional and waste raw materials. Pigments have vital practical applications in the ceramics and glass industries (e.g., colouring ceramic tiles and products, mosaic cladding tiles, glass, etc.). Their colour palette has been steadily expanding, driven by over glaze paints and coloured glazes for tile manufacturing.

The project’s fundamental research contributes to national competitiveness and productivity in alignment with the thematic areas of the national research and innovation strategy, while also promoting efficient resource use and environmental protection—priorities that are fully consistent with regional, national, and European research agendas.

At present, Bulgarian manufacturers rely on imported pigments. Our objective is to develop a competitive domestic product. We plan to conduct pilot scale experiments to assess the applicability of the most promising pigments to glazes used by KAI Group (plants “Han Asparuh”, Isperih, and “Han Omurtag”, Shumen), without commercialising project outputs and without violating programme requirements.

Specific Objectives

1. Create the optimal technological environment for pigment production. Determine the critical variables, including mineralizer kind and amount, firing temperature, and soaking time.
Investigate how raw material composition affects mullite and mullite-corundum phase development.

2. Determine the impact of various chromophores on phase color and composition.
Methodically introduce the ions Co, Cu, Ni, Cr, Fe, and Mn.
Assess the influence on structure, color, and stability.
• Conduct spectral and microstructural investigations to ensure complete characterisation.

3. Compare the synthesis methods of solid-state sintering and sol-gel.
Examine the efficiency and methodological effects on the finished products.
• List each strategy's strengths and shortcomings.

Determine which settings are best for industrial application.
4.Consider the practicality of using wasted raw materials.
• Employ industrial wastes such as rice husks and spent catalysts (e.g., from Lukoil Neftochim – Burgas).
• Recalculate starting compositions based on oxide content.
• Demonstrate environmental and economic benefits of waste valorisation in pigment production.