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Abstract

Content

Introduction

Pigments are colored dispersed substances insoluble in dispersion media and capable of forming protective, decorative or decorative protective coatings with film-forming ones. Pigments can be inorganic (salts or acids of polyvalent metals) or organic. Metal powders are also used as pigments.

Inorganic pigments are components of many materials used in a wide variety of industries, and perform extremely diverse functions in them. Organic pigments are almost exclusively used to give different materials a specific color tone.

At the beginning and especially in the middle of the twentieth century, the development of structural research methods and improvement of techniques for obtaining the same pigments put on the agenda the question of the relationship between pigment characteristics and the structure of dispersed crystalline bodies. And here we had to admit that the task of pigment production is not to obtain chemical compounds, but to obtain technical products, often of variable composition, with a specific micro- and macrostructure that is optimal for each of the various purposes. The chemical composition of the pigment turned out to be, figuratively speaking, only a building material for creating one or another structure of pigment particles, since it is the structural features that determine almost all pigment properties. Physicochemical research in the field of pigments has gained dominance over purely chemical ones.

At the same time, the scope of technical application of pigments has significantly expanded. Almost no production of non-metallic structural and decorative materials can do without their use.

1. Relevance of the topic

The production of ceramic pigments is associated with significant material and energy costs. In their synthesis, technically pure raw materials of high cost are mainly used, and the firing of pigment mixtures is carried out at high temperatures, which negatively affects the cost of the product.

One of the ways to reduce material and energy costs for the production of ceramic pigments, as well as to increase their competitiveness, is to obtain such dyes based on various industrial technogenic wastes.

However, today in the scientific, technical and patent literature there are no data on the synthesis of ceramic pigments using various technogenic substances, in particular, galvanic production, leather production and others, which are close in chemical composition to certain types of raw materials, traditionally used in pigment technology.

In connection with the above, the development of new compositions of ceramic pigments with reduced material and energy costs due to the use of spent cobalt catalyst is an urgent scientific and technical task. Its solution will make it possible to develop scientifically substantiated recommendations for the effective use of spent cobalt catalyst in the technology of producing ceramic pigments. The introduction of research results into production can also be of great economic importance.

2.Goal and tasks of the research

The purpose of the thesis is to develop the scientific foundations of the technology for obtaining new compositions of ceramic pigments of a wide color range using spent cobalt catalyst.

The main objectives of the research:

  1. Analyze the data of scientific, technical and patent literature and make a reasonable choice of the base oxide system for the synthesis of new compositions of ceramic pigments using spent cobalt catalyst.
  2. To carry out complex physical and chemical studies of industrial spent cobalt catalyst.
  3. Establish patterns of color change in the compositions in the base system using technically pure raw materials and spent cobalt catalyst for their synthesis with the introduction of various amounts of metal oxides of variable valence.
  4. To carry out a directed synthesis of practical compositions of ceramic pigments of a wide range of colors.
  5. To investigate the dependence of the optical-color characteristics of synthesized ceramic pigments and glass coatings on the nature and quantitative ratio of additionally introduced oxides of metals of variable valence into their compositions.
  6. To study the features of the course of physical and chemical processes, the phase composition and structure of synthesized ceramic pigments obtained on the basis of spent cobalt catalyst, and also to establish their relationship with color indicators.
  7. Show possible ways of using the developed pigments.

Object explored: technological processes for producing ceramic pigments based on spent cobalt catalyst.

Subject of research : conditions of obtaining and regularities of changes in the properties of ceramic pigments based on a cobalt catalyst from their chemical composition.

3. Pigments based on the mineral garnet

Ceramic pigments can be obtained on the basis of pure oxides or salts, as well as on the basis of chemical compounds with the introduction of chromophores into their composition, and in the latter case, pigments are obtained with more stable properties and less sensitive to fluctuations in temperature and gas conditions when securing them. One of these compounds is garnet.

Brightly colored natural garnets represent a wide class of silicates, the compositions of which are described by the general formula R 2+ 3 R 3+ < sub> 2 (SiO 4 ) 3 . Here R 2+ - Ca 2+ , Mg 2+ , Fe 2+ , Mn 2 + , R 3+ , Al 3+ , Fe 3+ , Cr 3+ .

                    The main types of pomegranates are shown in table 1 [3].

Table 1 - Composition and some properties of pomegranates

Type Content Color
Pyrope 3MgO•Al2O3•3SiO2 Dark Red
Almandine 3FeO•Al2O3•3SiO2 Red
Spessartine 3MnO•Al2O3•3SiO2 Yellow-red
Androdite 3CaO•Fe2O3•3SiO2 Brown red
Grossular 3CaO•Al2O3•3SiO2 Yellow
Uvarovit 3CaO•Cr2O3•3SiO2 Green

The basis of the crystal structure of garnets is a cubic unit cell, which contains eight formal units of composition corresponding to the above formula. The crystal lattice of garnets is body-centered, represented by a framework of interconnected Si-tetrahedra and Al-octahedra, in the voids of which R2+ ions are located.

4. Experimental

The paper deals with the synthesis of blue ceramic pigments based on garnet (3MgO•Al2O3•3SiO2) using cobalt oxide   (Cr+3) as a chromophore.

As the initial components for the synthesis of garnet, a mineral raw material is used that contains oxides MgO,Al2O3, SiO2. Initially, pure chromium oxide (Cr+3) was used as a chromophore. To facilitate the synthesis, boric acid was added to the charge as a mineralizer in an amount of 2% over 100%.

The raw materials were finely ground until they passed through sieve 0063, weighed on an analytical balance in accordance with their mass fractions in the charge. The materials were mixed and milled in a porcelain mortar.

The pigment mixture was fired in a laboratory muffle furnace with silicon carbide heaters. The medium during firing is oxidizing; at the final firing temperature, the pigments were kept for 0.5 hour. The calcined pigments are sintered aggregates with a blue earthy structure. After dry grinding, the ceramic pigments were ground before passing through the 0056 sieve. The finished ceramic pigments were packed in polyethylene bags for clarity of the color and quality of the pigments.

The pictures show pigments where color differences are visible at different concentrations of cobalt oxide.

When replacing 0.1 mol MgO with 0.1 mol Co2O3 When replacing 0.2 mol MgO by 0.2 mol Co2O3 When replacing 0.3 mol MgO with 0.3 mol Co2O3
When replacing 0.4 mol MgO with 0.4 mol Co2O3 When replacing 0.5 mol MgO with 0.5 mol Co2O3 When replacing 0.6 mol MgO with 0.6 mol Co2O3

During the synthesis of ceramic pigments in the garnet system, the oxides of magnesium, aluminum and silicon dioxide are partially replaced by coloring oxide. In the course of this work, in order to determine the area in which studies of the synthesis of pigments of optimal compositions should be carried out, pigments were synthesized with the replacement of a certain amount of moles by the amount of chromophore oxide.

Conclusions

The studies carried out allowed us to conclude that the production of ceramic pigments based on metallurgical waste is one of the ways of their utilization. An important point is also the fact that the use of technogenic products leads to a reduction in the cost of pigment production.

The master's work is not over yet, further research is underway.

References

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  3. Беленький И.В. и др. Химия и технология пигментов. - Ленинград: Государственное Научно - Техническое издательство химической литературы, 1960. - 756с.

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