СИНТЕЗ И SEM–EDX-ХАРАКТЕРИСТИКА НИКЕЛЬ–КАЛЬЦИЙ–СЕРНО-МОДИФИЦИРОВАННОГО ФТАЛОЦИАНИНОВОГО ПИГМЕНТА

УДК 661.183.1+535.37

Abstract

The development of functional phthalocyanine pigments with enhanced physicochemical properties remains an important area of research in pigment technology. In the present study, a nickel–calcium–sulfur modified phthalocyanine pigment (NiCaSPc) was synthesized by a solvent-free solid-state cyclotetramerization method. The morphology and elemental composition of the obtained pigment were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). SEM observations revealed the formation of a compact and relatively homogeneous microstructure with no evidence of extensive particle agglomeration. The pigment exhibited a dense surface morphology, indicating effective formation of the modified phthalocyanine structure during synthesis. EDX analysis confirmed the presence of carbon, oxygen, sulfur, nickel, and calcium in the final product. Quantitative elemental analysis showed 65.7 wt.% C, 20.2 wt.% O, 5.1 wt.% S, 5.1 wt.% Ni, and 1.5 wt.% Ca. The simultaneous presence of nickel, calcium, and sulfur demonstrates successful incorporation of modifying components into the pigment system. The obtained results indicate that calcium and sulfur modification provides a promising approach for the development of multifunctional nickel phthalocyanine pigments suitable for coating materials, polymer composites, and printing inks.

Аннотация

В работе представлен синтез модифицированного фталоцианинового пигмента на основе никеля с одновременным введением кальций- и серосодержащих компонентов. Получение пигмента осуществляли методом твердофазной циклотетрамеризации с использованием фталевого ангидрида, мочевины, хлорида никеля, хлорида кальция и сульфатсодержащего модификатора. Морфологические особенности и элементный состав синтезированного материала исследованы методами сканирующей электронной микроскопии и энергодисперсионного рентгеноспектрального анализа. Микроструктурные исследования показали формирование плотной и сравнительно однородной поверхности без выраженных областей агломерации. Элементный анализ подтвердил присутствие углерода, кислорода, серы, никеля и кальция. Полученные результаты свидетельствуют об успешном включении кальций- и серосодержащих компонентов в структуру никельфталоцианинового пигмента. Синтезированный материал представляет интерес для применения в лакокрасочных композициях, полимерных материалах и печатных красках.

Keywords: nickel phthalocyanine, modified pigment, calcium modification, sulfur modification, SEM, EDX, functional pigments.

Ключевые слова: никелевый фталоцианин, модифицированный пигмент, кальциевая модификация, серная модификация, СЭМ, ЭДС-анализ, функциональные пигменты.

Introduction

Metal phthalocyanines are among the most important classes of industrial organic pigments due to their exceptional color strength, thermal stability, chemical resistance, and light fastness [1–3]. These materials are extensively used in coatings, plastics, textile coloration, printing inks, and various advanced functional applications [4,5]. Among different metal-containing phthalocyanines, nickel phthalocyanine pigments have attracted considerable attention because of their excellent environmental stability, resistance to thermal degradation, and favorable physicochemical properties [6,7].

Recent developments in pigment science have focused on improving the functionality of conventional phthalocyanine pigments through chemical and structural modification [8]. The incorporation of inorganic modifiers into pigment systems has been shown to influence particle growth, surface properties, dispersion behavior, and compatibility with polymer matrices [9]. Calcium-containing compounds are known to improve pigment stability and interfacial interactions, whereas sulfur-containing species may affect nucleation processes and microstructural development during synthesis [10].

Several studies have demonstrated that modified metal phthalocyanines exhibit enhanced thermal resistance, improved dispersibility, and superior application performance compared with conventional pigments [7–10]. In particular, sulfur- and calcium-containing additives can significantly influence crystal growth and particle morphology, thereby affecting pigment functionality in coating and polymer systems [9,10].

Despite the significant progress achieved in the field of modified phthalocyanine pigments, limited information is available regarding nickel phthalocyanine systems simultaneously modified with calcium and sulfur [11,12]. Understanding the structural and elemental characteristics of such materials is essential for evaluating their potential industrial applications.

Therefore, the aim of the present work was to synthesize a nickel–calcium–sulfur modified phthalocyanine pigment and investigate its morphology and elemental composition using SEM–EDX analysis.

Materials and Methods

Materials. Phthalic anhydride (PA), urea, nickel chloride (NiCl₂), calcium chloride (CaCl₂), and a sulfur-containing modifier were used as starting materials for pigment synthesis. Distilled water and ethanol were employed during purification. All reagents were of analytical grade and used without further purification.

Synthesis of Nickel–Calcium–Sulfur Modified Phthalocyanine Pigment (NiCaSPc). The NiCaSPc pigment was synthesized by a solvent-free solid-state cyclotetramerization method. Predetermined amounts of phthalic anhydride, urea, nickel chloride, calcium chloride, and the sulfur-containing modifier were thoroughly mixed to obtain a homogeneous reaction mixture.

The mixture was subjected to thermal treatment under controlled conditions to promote formation of the nickel phthalocyanine macrocycle. During the synthesis process, calcium- and sulfur-containing species became incorporated into the developing pigment structure, influencing particle formation and microstructural characteristics.

After completion of the reaction, the solid product was cooled to room temperature, crushed, and repeatedly washed with hot distilled water and ethanol to remove residual salts and unreacted components. The purified material was dried at 105 °C to constant weight and ground into a fine powder for further analysis.

Characterization. Morphological characteristics of the synthesized pigment were examined using scanning electron microscopy (SEM). Elemental composition was determined by energy-dispersive X-ray spectroscopy (EDX) coupled with the SEM instrument. SEM–EDX analysis was used to evaluate particle morphology and to confirm the presence of the principal elements associated with the nickel–calcium–sulfur modified phthalocyanine structure.

Results and Discussion

Morphological Characteristics of the Synthesized Pigment. The morphology of the synthesized nickel–calcium–sulfur modified phthalocyanine pigment was investigated using scanning electron microscopy.

The SEM image revealed a compact microstructure composed of densely packed pigment domains distributed relatively uniformly throughout the analyzed area. No large crystalline aggregates or severe particle agglomeration were observed. The absence of extensive clustering suggests that the synthesis procedure promoted effective formation of the pigment particles.

The microstructure appears relatively homogeneous, indicating that the incorporation of calcium- and sulfur-containing modifiers influenced particle growth during the cyclotetramerization process. Such morphology is advantageous for pigment applications because uniform particle distribution generally contributes to improved dispersion behavior and enhanced performance in coating formulations.

Figure 1. SEM micrograph of the synthesized nickel–calcium–sulfur modified phthalocyanine pigment (NiCaSPc)

A closer examination of the micrograph shows several brighter regions dispersed within the pigment matrix. These regions may be associated with nickel- and calcium-containing domains embedded in the carbon-rich phthalocyanine framework. The observed morphology confirms successful formation of a modified pigment structure without significant structural defects.

Elemental Composition Analysis. The chemical composition of the synthesized pigment was evaluated using EDX spectroscopy.

Figure 2. EDX spectrum of the synthesized nickel–calcium–sulfur modified phthalocyanine pigment (NiCaSPc)

The EDX spectrum clearly demonstrates the presence of carbon, oxygen, sulfur, nickel, and calcium in the synthesized material.

The quantitative elemental composition obtained from EDX analysis is presented in Table 1.

Table 1. Elemental composition of the nickel–calcium–sulfur modified phthalocyanine pigment (Sample-139) obtained from EDX analysis

The high carbon content reflects the aromatic macrocyclic structure characteristic of phthalocyanine compounds. Oxygen represents the second most abundant element and may originate from oxygen-containing functional groups and calcium-associated species present within the modified pigment system.

Sulfur was detected at 5.1 wt.%, confirming successful incorporation of sulfur-containing components during synthesis. The retention of sulfur after purification indicates that sulfur-containing species remained associated with the pigment structure.

Nickel was present at 5.1 wt.%, providing direct evidence of metal coordination within the phthalocyanine macrocycle. The presence of calcium at 1.5 wt.% confirms successful incorporation of calcium-containing species into the pigment system.

The simultaneous detection of nickel, sulfur, and calcium strongly supports the formation of a nickel–calcium–sulfur modified phthalocyanine pigment rather than a conventional nickel phthalocyanine material.

Conclusion

A nickel–calcium–sulfur modified phthalocyanine pigment was successfully synthesized using a solid-state cyclotetramerization method. SEM analysis revealed a compact and relatively homogeneous microstructure with no evidence of extensive particle agglomeration. EDX spectroscopy confirmed the presence of carbon, oxygen, sulfur, nickel, and calcium in the synthesized material.

The elemental composition demonstrated successful incorporation of calcium- and sulfur-containing modifiers into the nickel phthalocyanine system. The obtained results indicate that the developed pigment represents a promising multifunctional coloring material with potential applications in coating technologies, polymer composites, printing inks, and related industrial fields.

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