THE EFFECT OF ALKALINE EARTH METAL OXIDES ON THE PROPERTIES OF GLASS ENAMEL

JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 87 THE EFFECT OF ALKALINE EARTH METAL OXIDES ON THE PROPERTIES OF GLASS ENAMEL Matchanov SH.K., Buranova D.B., Yakubov Y.KH., Nazarov D.K. Urgench State University named after Abu Rayhon Beruni https://doi.org/10.5281/zenodo.17977082 Abstract: In our republic, research on developing easily fusible glass enamel compositions based on mineral raw materials for protecting metals from external environmental influences is very limited. A review of the literature indicates that the effect of alkaline earth metals on the composition of easily fusible glass enamels has been insufficiently studied. Therefore, studying the influence of alkaline earth metals - Mg, Ca, and Ba - on the composition of easily fusible glass enamels is considered a relevant issue. Key words: glass enamel, carbonate salt, metal, quartz sand, surface tension, adhesion, viscosity. ISHQORIY YER METALL OKSIDLARINING SHISHA EMALINING XOSSALARIGA TA'SIRI Annotatsiya: Respublikamizda metallarni tashqi muhit ta’sirdan himoya qilish bo‘yicha mineral xom ashyolar asosida oson suyuqlanuvchi shisha emal tarkiblarini yaratish bo‘yicha tadqiqotlar juda kam bo‘lib, adabiyotlarning taxlili esa oson suyuqlanuvchi shisha emal tarkiblariga ishqoriy yer metallarining ta’siri kam o‘rganilganligini ko‘rsatadi. Shuning uchun oson suyuqlanuvchi shisha emal tarkiblarida ishqoriy yer metallar-Mg,Ca,Ba –larning ta’sirini o‘rganish dolzarb hisoblanadi. Kalit so’zlar: shisha emal, karbonat tuzi, metall, kvars qum, sirt taranglik, adgeziya, qovushqoqlik. ВЛИYAНИЕ ОКСИДОВ SHЕЛОЧНОЗЕМЕЛЬНIХ МЕТАЛЛОВ НА СВОЙСТВА СТЕКЛОEМАЛИ АннотаsиY. В нашей республике крайне мало исследований по созданиyu легкоплавких стеклоeмалевiх составов на основе минерального сiрya длya заshитi металлов от внешних воздействий окружаyushей средi, а анализ литературi показiвает, что влиyaние shелочноземельнiх металлов на легкоплавкие стеклоeмалевiе составi изучено недостаточно. Поeтому актуально изучение влиyaниya shелочноземельнiх металлов - Mg, Ca, Ba - в легкоплаких стеклоeмалевiх составах. Клyuчевiе слова: стеклоeмаль, карбонатнаya соль, металл, кварsевiй песок, поверхностное натyaжение, адгезиya, вyaзкость. Introduction. Conducting scientific research aimed at developing products and methods based on relatively inexpensive and locally available mineral raw materials is of great importance. One such method is the enameling of metal surfaces with glass enamels. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 88 The primary reasons for using this method include: The coated products retain their properties for extended periods without degradation. They are resistant to corrosion and combustion. They are completely harmless to living organisms. They enhance the aesthetic appearance of metal surfaces. They exhibit high resistance to atmospheric conditions, moisture, acids, and alkalis. They maintain their shape and color over time. They withstand exposure to light and sunlight. They have thermal resistance up to 450°C. Studying the Effects of Components in Glass Enamel Coatings. One of the key factors in research related to glass enamel coatings is studying the effects of the components introduced into their composition. One of the important operational properties of glass enamels is their heat capacity, which is discussed in detail in source [1]. According to this source, the heat capacity of glass follows the order ΔCp Na > Ca > Mg. Additionally, introducing MgO into the Na₂O-CaO-MgO-P₂O₅-Al₂O₃-TiO₂ glass system strengthens the glass framework [2]. Studies have also examined the effect of the CaO/MgO ratio on the structure of glazes and glasses [3], revealing that a decrease in this ratio leads to an increase in the crystallization temperature of the glass. Research on the CaO-MgO-Al₂O₃-SiO₂ system has shown that when the CaO/MgO ratio reaches an optimal value, cordierite crystallization in the glass mass reaches its maximum, forming hexagonal prismatic crystals. These products exhibit high microhardness [4]. Another study indicates that an increase in Mg²⁺ and Ca²⁺ cation concentrations in glass reduces the degree of polymerization of the glass framework. This, in turn, affects the number of non-bridging oxygen atoms in [SiO₄] tetrahedra, leading to changes in the density of the glass [5]. The analysis of barium-containing glasses has shown that an increase in barium oxide (BaO) content enhances the chemical durability of the glass. This effect is attributed to the formation of -O–Ba²⁺–Obonds, which contribute to the densification of the glass structure [6]. Another scientific source [7] has investigated the effect of BaO on the crystallization of barium tellurite glasses, indicating that an increase in BaO content leads to a rise in the glass transition temperature. According to research conducted by Japanese scientist S. Tsugumitsu, introducing two or three alkaline earth metal oxides simultaneously into the glass composition significantly alters its structure and properties. It has been demonstrated that incorporating up to 5% of divalent modifiers RO (SrO, MgO, CaO) into boron-aluminosilicate glass leads to a transformation in the ratio of [BO₃] and [BO₄] structural units. This shift indicates a transition from a trigonal to a tetrahedral coordination state of boron [9]. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 89 Materials and Methods A review of the literature indicates that the effect of alkaline earth metals on the production of easily fusible glass enamels has been insufficiently studied. Based on this, the aim of our research was to investigate the influence of alkaline earth metals (Mg, Ca, Ba) on the viscosity and surface tension characteristics of easily fusible glass enamels. Materials and Methods (Continued) To obtain glass enamel compositions, quartz sand from the Ugun deposit in the Kashkadarya region was used. The sand was enriched according to the method described in source [10] to meet the requirements of GOST 22551. Information on the quartz sands of the Ugun deposit is provided in source [11]. The base composition of the glass enamel was formulated as follows: SiO₂ – 48.0%, B₂O₃ – 20.0%, Na₂O – 12.0%, RO – 20.0% (where RO represents alkaline earth metal oxides) [12]. As auxiliary raw materials, boric acid, calcined soda, and carbonate salts of calcium, magnesium, and barium ("T" grade) were used. The composition of the glass batch was calculated based on raw material composition using the calculation method outlined in source [13]. The glass batch was melted in a laboratory furnace with a sillite heater using 200 ml corundum crucibles at a temperature of 1350°C. The holding time at the maximum temperature was 40 minutes. The degree of "maturation" of the molten glass was assessed based on the formation of an elongated "fiber" and the absence of stones and bubbles in the structure. The prepared glass melts were poured onto a metal surface and cooled in air. Visual inspection of all compositions confirmed that they had undergone good vitrification. Results and Discussion The viscosity and surface tension characteristics of the obtained glass compositions were determined through theoretical calculations and laboratory experiments. Laboratory tests were conducted based on the methodology described in source [14], while theoretical calculations were performed according to source [15]. It is well known that the composition of metals included in glass and silicate coatings significantly affects their properties. The following table presents the characteristics of certain Group II main subgroup metals. Table 1: Information on Group II Main Subgroup Metals in the Periodic Table Element Atomic number "Ion radius, nm" "Ion charge density, C/m³" "R2+-O bond strength, kJ·NA" JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 90 Be 4 0,034 282 263,97 Mg 12 0,078 123 155,03 Ca 20 0,106 92 134,08 Sr 38 0,127 80 134,08 Ba 56 0,143 70 134,08 In this metal series, as the cation radius increases from Be to Ba, the weakening of the R²⁺–O bond strength leads to a decrease in the counter-polarization effect of R²⁺–O cations on silicon-oxygen tetrahedra, which is expected to increase the viscosity of the glass. However, experimental results show a decrease in glass viscosity. Considering that the charge of the R²⁺ cation is twice that of the R⁺ cation, the polarization phenomenon influences the properties of the glass. In the Be–Ba series, the polarization phenomenon decreases sharply, while polarizability increases. This, in turn, weakens the silicon-oxygen tetrahedral network, leading to a reduction in viscosity. It is well known that viscosity is one of the factors determining the kinetics of diffusion processes in the glass mass. Based on this, it can be stated that the corrosion resistance of glass coatings is related to the placement of Group II metal atoms in its composition. Research has shown that the corrosion activity of glass coatings corresponds to changes in the chemical activity of metals in the main subgroup of Group II. This is influenced by the gradual increase in the size of the electron clouds of these metals from beryllium to barium. According to experimental results, as the nuclear charge of Group II metal atoms increases, the properties of glass coatings synthesized at 1200°C in the 48SiO₂20B₂O₃+12R₂O+20RO and 64SiO₂-16K₂O+20RO systems change proportionally. From Be to Ba, the corrosion activity of the glass melt increases, its protective ability decreases, and the viscosity index also relatively decreases. The degree of wetting of metal surfaces by molten glass and the bonding strength are significantly dependent on the surface tension of the glass. Numerous studies have shown that when silicate melts and metal surfaces interact at high temperatures, the surface energy of the "metal-molten glass" system decreases. This, in turn, improves the adhesion of the system and enhances the protective properties of the coatings. It is well known that the lower the surface tension value, the higher the wetting ability of the molten glass on the metal surface. The surface tension of molten glass varies depending on several factors, and determining their functional relationships is considered complex. Literature sources also indicate that the surface tension of glass can be theoretically calculated. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 91 Mi GiMi G  = Here, G represents the surface tension coefficient in MN/m, Mi denotes the molar percentage of each oxide in the glass composition, and Gi is the average partial coefficient of oxides' surface tension in MN/m. Sources indicate that the surface tension values of molten glasses range between 220 and 420 MN/m. Using the above formula, the surface tension coefficient of glass enamels at 1200°C was calculated. The theoretical calculations are presented in Figure 1. According to the obtained results, alkaline earth metal oxides contribute to an increase in the numerical value of the glass's surface tension. As the values of all oxides increase, the surface tension also rises. The calculations suggest that Mg oxide has the strongest effect on surface tension compared to other oxides, while Ba oxide has a lesser influence. Based on this, to achieve a dense and well-adhered coating on metal surfaces, it is advisable to incorporate more Ba and Be oxides in the composition of glass enamels. "Component quantity, %" BaO. - * - SrO, - X - CaO, - - MgO, - - BeO; - -  Figure 1. Effect of alkaline earth metals on the surface tension of glass enamel JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 92 Figure 2. DTA analysis fragment of the obtained glass enamel samples According to the results of differential thermal analysis (DTA), during the heat treatment of glasses, the primary crystalline phases form within the temperature ranges of 600-620°C and 750-760°C. The endo-effects observed at 540-550°C and 690-700°C play a positive role in the synthesis of glass enamel coatings. To further identify the crystalline phases in the samples, X-ray diffraction (XRD) analysis was performed. The diffractograms of glass enamels (Figure 3) show diffraction maxima corresponding to α-quartz at d = 0.443, 0.334, and 0.181 nm. The differential thermal analysis and X-ray diffraction results were also theoretically confirmed by infrared (IR) spectral analysis. According to the results of IR spectroscopy, the absorption bands observed in the 9001100 cm⁻¹ wavelength range correspond to the stretching vibrations of bridging ≡Si−O−Si≡ bonds. Additionally, the absorption bands detected in the 450-500 cm⁻¹ range indicate the deformation vibrations of ≡Si−O−Si= bonds (Figure 4). Figure 3. X-ray diffractogram of the obtained glass enamel samples. 1) Sample 1; 2) Sample 2; 3) Sample 3. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 93 Figure 4. IR spectroscopic analysis of the obtained glass enamel samples In conclusion. The effect of alkaline earth metal oxides on the physicochemical properties of glass enamels has been studied. 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