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Article

Composite Materials Based on Sodium Alginate and Synthetic Powders of Calcium Carbonate

by
Marat M. Akhmedov
1,*,
Tatiana V. Safronova
2,3,
Arina A. Pavlova
3,
Olga A. Kibardina
3,
Tatiana B. Shatalova
2,3,
Vadim B. Platonov
2,
Albina M. Murashko
3,
Yaroslav Y. Filippov
3,4,
Egor A. Motorin
3,
Olga T. Gavlina
2,
Olga V. Boytsova
2,3,
Anna Chirkova
3,
Alexander V. Knotko
3 and
Natalia R. Kildeeva
1
1
Department of Chemistry and Technology of Polymer Materials and Nanocomposites, Kosygin Russian State University, Malaya Kaluzhskaya 1, 119071 Moscow, Russia
2
Department of Chemistry, Lomonosov Moscow State University, Building 3, Leninskie Gory, 1, 119991 Moscow, Russia
3
Department of Materials Science, Lomonosov Moscow State University, Building 73, Leninskie Gory, 1, 119991 Moscow, Russia
4
Research Institute of Mechanics, Lomonosov Moscow State University, Building 1, Michurinsky Prospect, 119192 Moscow, Russia
*
Author to whom correspondence should be addressed.
J. Compos. Sci. 2026, 10(3), 172; https://doi.org/10.3390/jcs10030172
Submission received: 22 February 2026 / Revised: 12 March 2026 / Accepted: 16 March 2026 / Published: 23 March 2026
(This article belongs to the Special Issue Advances in Biocomposite Materials for Regenerative Medicine and Biomedical Applications)
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Abstract

Properties of composite materials with polymer matrix and inorganic filler are affected by preparation methods and starting components’ properties. For example, filler powder particle size distribution, phase composition and presence/absence of dopants can greatly affect properties of resulting composites. The present research attempts to clarify the influence of synthetic CaCO3 powder properties on alginate/CaCO3 composite material preparation process. Composite materials in the form of granules, networks and films were created from suspensions of synthetic powders of calcium carbonates CaCO3 in aqueous solutions of sodium alginate. Powders of calcium carbonates CaCO3 were synthesized from 0.5 M aqueous solutions of calcium chloride CaCl2 and aqueous solutions of potassium K2CO3 (at molar ratio Ca/CO3 = 1), sodium Na2CO3 (at molar ratio Ca/CO3 = 1), and ammonium (NH4)2CO3 (at molar ratios Ca/CO3 = 1 and Ca/CO3 = 0.5) carbonates. Phase composition of powder synthesized from CaCl2 and K2CO3 was presented by calcite. Phase composition of powders synthesized from other soluble carbonates included calcite and vaterite. The powder preparation protocol excluded the stage of synthesized powder washing for by-product removal. This preparation protocol provided preservation of reaction by-product in the synthesized powder at a very low level. The presence of NH4Cl as a reaction by-product even in small quantities can be taken as a reason for visually observed subsequences of cross-linking reaction at the stage of suspensions preparation. Aqueous solution of sodium alginate and suspensions containing powders synthesized from potassium K2CO3 and sodium Na2CO3 carbonates demonstrated similar dependence of viscosities from shear rate. The presence of (NH4)2CO3 in the powder synthesized at molar ratio Ca/CO3 = 0.5 was the reason for the lower viscosity of the suspension in comparison with suspensions loaded with powders containing KCl, NaCl and NH4Cl as reaction by-products due to decomposition of unstable (NH4)2CO3 and gas phase formation. The presence of NH4Cl in the powder synthesized at molar ratio Ca/CO3 = 1 in contrast was a reason for the highest viscosity suspension in comparison with those under investigation. Additionally, NH4Cl presence in synthetic powders shows the ability to facilitate partial dissolution of CaCO3 providing a higher concentration of Ca2+ cations at the stage of suspension preparation, thus aiding the cross-linking process of alginate hydrogel. Granules, meshes and films were created via interaction of suspensions of calcium carbonates CaCO3 in aqueous solutions of sodium alginate with 0.25 M aqueous solutions of calcium chloride CaCl2 to provide the formation of matrix of composites via Ca-crosslinking of sodium alginate followed by washing and freeze drying under deep vacuum. The created composite materials in the form of granules, meshes and films based on Ca-cross-linked alginate and powders of synthetic calcium carbonate can be recommended for skin wound and bone defect treatment and drug delivery carriers.

1. Introduction

Composite materials with alginate matrices are widely used not only in medicine [1,2,3,4,5,6] but also for environmental applications [7,8,9], as semifinished items in the preparation of calcium phosphate granules [10], for food packaging [11] and as materials used for fruits storage [12]. Alginate is a naturally occurring polysaccharide extracted from brown algae, exhibiting ionic crosslinking capability that makes it an attractive biomaterial for various medical applications [13]. Its unique properties, such as biocompatibility, low toxicity, and ease of processing, have made it a popular choice for tissue engineering, wound healing applications due to their ability to promote cell growth, differentiation, and proliferation [14], and drug delivery systems [15,16,17,18]. Alginate-based biomaterials have been explored as a promising tool in regenerative medicine.
Alginate’s ability to form hydrogels through ionic crosslinking with divalent cations like Ca2+ [12], Sr2+ [19], Mg2+ or Ba2+ [20], Zn2+ or Cu2+ [21] enables its use in creating scaffolds that mimic the extracellular matrix of tissues, promoting cell growth, differentiation, and proliferation [3]. Different ions, Ca2+, Sr2+, Mg2+, Ba2+, Cu2+, Fe3+ and Al3+, were systematically studied to investigate the relationship between ion concentration and cross-link density [22,23,24]. This property also allows alginate-based biomaterials to be used as carriers for drug delivery systems, providing a controlled release of therapeutic agents [25]. Potentially, even low-soluble salts of the metals listed above can be used as cross-linking agents, being dispersed inside alginate solution [26]. Calcium carbonate CaCO3 [27,28] and calcium sulphate CaSO4 [29,30] are more frequently mentioned as low-soluble cross-linking agents due to their biocompatibility.
Alginate is widely used in its pure form or combined with other materials such as carbon-based nanoparticles, polymeric nanoparticles, metal or metal oxide nanoparticles and ceramic nanoparticles to create composite biomaterials [31]. These composites can be created using fillers of inorganic (metal oxides [32,33,34], calcium phosphates [35,36,37,38,39,40,41], carbonates [1,42,43] carbon nanotubes [44], and calcium silicates [40]) and organic (collagen [45,46], polyester [47], cellulose [48], and chitosan [49,50,51]) nature to enhance the mechanical properties and stability of alginate hydrogels, making them suitable for various applications, including biomedical.
The addition of calcium carbonate to alginate hydrogels creates composite materials with improved mechanical properties, stability and ability to adsorb different cations [43]. Currently, the most common materials for bone defect treating in clinical practice are calcium phosphates, in particular hydroxyapatite and tricalcium phosphate, due to their structural and chemical similarity to the mineral phase of bone [52]. However, calcium carbonate is a very promising alternative. It demonstrates excellent adsorption capacity in relation to proteins and growth factors, which additionally stimulates regenerative processes. The high surface area of calcium carbonate enhances the adsorption capacity of alginate-based composites, potentially improving drug-delivering capabilities over longer periods of time [53]. Calcium carbonate’s key advantages are a controlled rate of dissolution, ideally consistent with the rate of bone formation, high osteoconductivity and complete biocompatibility, since calcium and carbonate ions are natural metabolites of the body [54].
Calcium carbonate CaCO3 has three modifications: calcite, aragonite and vaterite [55]. Hydrated [56,57] and amorphous forms [58] of CaCO3 are also known. Calcium carbonate of different modifications can be synthesized by using different methods, including the liquid–liquid route and the solid–liquid–gas route [55,59,60]. But the most convenient is the synthesis from solutions containing Ca2+ cation and CO32− anion via precipitation [59,61]. Composites including calcite [62] are preferably created for environmental applications with the ability to adsorb different cations. Composites containing vaterite are preferably created for biomedical applications especially as drug delivery systems [53,63] mainly due to large specific surface area of powders consisting of sea-urchin-shaped particles [64]. An important aspect of practical application of different modifications of calcium carbonate is the use as a filler of composite materials. Acting as a bioactive filler in a matrix of biopolymers, calcium carbonate makes it possible to create materials with programmable mechanical properties and resorption kinetics, combining the strength of ceramics and the elasticity of the polymer to maximize approximation to the characteristics of natural bone.
It is worth noting that sometimes CaCO3 is used not as filler but as pore forming sacrificial agent being at first dispersed in alginate hydrogels to then dissolve and release CO2 gas under acidic influence, thus creating pores. HCl is used to convert CaCO3 into the more soluble form to be both pore forming sacrificial agent and, at the same time, to be a source of calcium ions acting as crosslinking agents [65]. This way, CaCO3 can be a component of foaming composition (CaCO3 and NaHCO3 in CaCl2/acetic acid) for alginate gels [66].
The aim of this investigation consisted in the synthesis of calcium carbonate powders from aqueous solutions of different pairs of precursors (K2CO3/CaCl2, Na2CO3/CaCl2, (NH4)2CO3/CaCl2, and 2(NH4)2CO3/CaCl2) and preparation of composite materials based on sodium alginate and synthetic powders of calcium carbonates in forms of films, meshes and granules. Usage of different pairs of precursors for CaCO3 preparation should provide an opportunity not only to prepare powders with phase composition closest to the target mineral (vaterite or calcite) but also to preserve reaction by-products, i.e., KCl, NaCl, NH4Cl and (NH4)2CO3/NH4Cl. To our knowledge, investigations devoted to the preparation of composites with alginate matrix and powder of CaCO3 containing reaction by-products are not presented in the scientific literature. Before planning this investigation there was the hypothesis that the presence of by-products mentioned above could influence rheological properties of suspensions of CaCO3 in aqueous solutions of sodium alginate and cross-linking ability of low-soluble filler as CaCO3 is.

2. Materials and Methods

2.1. Synthesis of CaCO3 Powders

Calcium chloride CaCl2 (CAS No. 10043-52-4, analytical pure grade, Rushim, Moscow, Russia), potassium carbonate K2CO3 (CAS No. 584-08-7, chemical pure grade, Rushim, Moscow, Russia), sodium carbonate Na2CO3 (CAS No. analytical pure grade, Rushim, Moscow, Russia), and ammonium carbonate (NH4)2CO3 (CAS No. analytical pure grade, Rushim, Moscow, Russia) were used for the synthesis of powders.
The following Equations (1)–(3) were used to calculate the amounts of starting salts and both expected target and by-products:
K2CO3 + CaCl2 → CaCO3 + 2KCl
Na2CO3 + CaCl2 → CaCO3 + 2NaCl
(NH4)2CO3 + CaCl2 → CaCO3 + 2NH4Cl
2(NH4)2CO3 + CaCl2 → CaCO3 + 2NH4Cl + (NH4)2CO3
Labeling used for synthesized powders under investigation and quantities of initial salts for powder preparation are presented in Table 1.
Quantities of expected target (CaCO3) product and reaction by-products are presented in Table 2.
Four identical 0.5 M aqueous solutions of calcium chloride were prepared. For preparation of 400 mL 0.5 M solution of calcium chloride, 22.2 g of anhydrous CaCl2 was used. Four different aqua solutions of carbonates were prepared. For preparation of 400 mL of 0.5 M solutions of different carbonates, 27.6 g of potassium carbonate K2CO3, 21.2 g Na2CO3 of sodium carbonate and 19.2 g of ammonium carbonate (NH4)2CO3 were used. A total of 38.4 g (NH4)2CO3 of ammonium carbonate (NH4)2CO3 was used for preparation of 400 mL of 1 M solution.
Solution of CaCl2 was added to the 0.5 M solutions of K2CO3, Na2CO3, (NH4)2CO3 and to the 1 M solution of (NH4)2CO3. The synthesis of each of the four powders was carried out in glass with a volume of 1 L using a magnetic stirrer. Suspensions of precipitates were kept under constant stirring during 60 min after addition of 400 mL of 0.5 M solutions of CaCl2 to the aqueous solutions of potassium, sodium or ammonium carbonates.
Prepared precipitates were separated from the mother liquors by vacuum filtration, placed in the plastic trays, evenly distributed over a large surface area and left to dry for 1 week. The powder preparation protocol excluded the stage of by-product removal via powder washing. Then powders were collected, weighed, crushed in an agate mortar and sieved through a polyester sieve with a mesh size of 200 microns. Transparent mother liquors were collected and dried for a month at 40 °C for water evacuation and crystallization of reaction by-products. The scheme of powder synthesis is presented in Figure 1.
The synthesized powders and isolated reaction by-products were weighed to determine their mass and to estimate the yield of synthesized powders and reaction by-products relative to the theoretically possible amounts of expected target products and reaction by-product calculated in accordance with Equations (1)–(4) presented in Table 2.

2.2. Preparation of Suspensions of Calcium Carbonate in an Aqueous Solution of Sodium Alginate

Sodium alginate E401 (Qingdao Nanshan Yuanquan Seaweed Co., Ltd., Qingdao, China) and synthesized powders of CaCO3 were used for preparation of suspensions of calcium carbonate in an aqueous solution of sodium alginate. Compositions of the suspensions of CaCO3 in aqueous solution of sodium alginate are presented in Table 3 and Figure 2.
To obtain composite suspensions containing particles of synthesized calcium carbonate, the following procedure was performed for each of the four powders obtained. In total, 150 mL of distilled water was placed in the 250 mL volume glass. A total of 4.0 g of synthesized calcium carbonate was added to 150 mL of distilled water. The resulting aqueous suspension was stirred using a magnetic stirrer for 30 min. Then, 4.0 g of sodium alginate was added in small portions to the prepared aqueous suspension of calcium carbonate under constant stirring. After adding the entire mass of sodium alginate, mixing was continued for 30 min to ensure complete dissolution of the polymer chains and the formation of a homogeneous, highly viscous dispersed system. The resulting thick, viscous suspensions were passed through a sieve with a mesh size of 100–200 microns to eliminate possible large aggregates and ensure maximum uniformity. The procedure was performed manually using a spatula. Labeling of prepared composite suspensions consisted of the short name of the polymer used (AlgNa) and labeling of powder used as a filler, i.e., AlgNa_CCK, AlgNa_CCNa, AlgNa_CCNH4, and AlgNa_CC2NH4.

2.3. Preparation of Samples of Composite Materials from Suspensions of Calcium Carbonate in an Aqueous Solution of Sodium Alginate

Preparation of samples of composite granules, films and meshes from suspensions of synthesized powders of CaCO3 in aqueous solution of sodium alginate via cross-linking in 0.25 M aqueous solution of CaCl2 was done according the scheme presented in Figure 3.
An aqueous solution of calcium chloride (CaCl2) with a concentration of 0.25 M was prepared to be used as cross-linking agent for sodium alginate according to the ion crosslinking reaction (Equation (5)):
2(C6H7O6Na)n + nCaCl2 → nCa(C6H7O6)2 + 2nNaCl
To prepare granules 50 mL syringes were filled with the suspension of synthesized powders of calcium carbonate in aqueous solution of sodium alginate. Holding the syringe at a height of 3–5 cm from the surface of the 20–30 mL of 0.25 M aqueous solution of CaCl2, the suspensions were squeezed drop by drop into it. Upon contact of each drop with the CaCl2 solution, an instant gelification (crosslinking) of the surface occurred with the formation of granules. After molding, the granules were kept in 0.25 M aqueous solution of CaCl2 for 30 min to complete the gelation process throughout the volume. About 30 granules were obtained from aqueous solution of sodium alginate and from suspensions of synthesized powders of calcium carbonate in aqueous solution of sodium alginate.
To prepare a pattern in the form of a mesh, suspension of synthesized powder of calcium carbonate in aqueous solution of sodium alginate was randomly squeezed out of a syringe with a thin needle onto the bottom of a glass Petri dish. A pattern in the form of rectangular film was obtained by extruding the suspension of synthesized powder of calcium carbonate in aqueous solution of sodium alginate and spreading it with a flat surface of a spatula to obtain a layer of uniform thickness.
Immediately after forming, the resulting meshes and films were carefully covered with a prepared 0.25 M solution of CaCl2 to initiate crosslinking. The samples were also kept in solution for 30 min.
After the crosslinking was completed, all the obtained samples (granules, meshes, and films) were removed from the solution, washed with distilled water to remove excess CaCl2 and NaCl (by-product of reaction (Equation (5)) from the surface and cryogenically dried. The laboratory freeze dryer BIOBASE BK-FG10 S (Jinan Biobase Medical Co., Ltd., Jinan, China), providing vacuum degree < 10 Pa with cold trap temperature −60 °C, was used for drying of crosslinked, washed and preemptively frozen at −25 °C samples (granules, meshes and films) to prevent their deformation.
Photos of prepared samples of granules, meshes, and films are presented in Figure 4. Labeling of prepared samples consisted of the short name of the polymer matrix (AlgCa) and labeling of powder used as a filler.

2.4. Methods of Analysis

The phase composition of synthesized powders and composites was studied by X-ray powder diffraction (XRD) analysis using CuKα radiation (λ = 1.5418 Å, step 2θ—0.02°) using Rigaku D/Max-2500 diffractometers (Rigaku Corporation, Tokyo, Japan) in the angle range 2θ = 2–70° or Tongda TD-3700 (Dandong Tongda Science & Technology Co., Ltd., Dandong, China) in the angle range 2θ = 3–70°. The X-ray patterns were analyzed using the WinXPOW program and the ICDD PDF-2 (https://www.icdd.com/pdf-2/, accessed on 10 February 2026) [67] databases and the Match! program (https://www.crystalimpact.com/, accessed on 10 February 2026). The quantitative ratio of the target phases in the synthesized powders was determined using the Match!3 program, (https://www.crystalimpact.com/, accessed on 10 February 2026).
FTIR spectra of powders after synthesis and drying and composites were recorded in the transmission mode in the wavenumber range of 4000–400 cm−1 with a step of 4 cm−1 on a Perkin Elmer Frontier spectrometer (Perkin Elmer, Waltham, MA, USA). The survey was carried out with potassium bromide tablets (7 mm diameter) containing 1 mass% of the test sample. The tablets were prepared by carefully grinding KBr together with the sample, followed by pressing into tablets at a pressure of 50 bar.
The particle size distributions for powder samples were determined by laser diffraction in an aqueous medium using a Fritsch Analysette-22 instrument (Fritsch GmbH, Idar-Oberstein, Germany). Photos of meshes were done using Nexcope NSZ818 stereo microscope (Ningbo Yongxin Optics Co., Ltd. (Novel Optics), Ningbo, China).
Scanning electron microscopy (SEM) images of the synthesized powders were characterized using an NVision 40 microscope (Carl Zeiss, Jena, Germany) in secondary electron imaging mode (SE2 detector). SEM images of the surfaces of composites were studied using a scanning electron microscope with an auto emission source JEOL JSM-6000 PLUS Neoscope II (JEOL Ltd., Tokyo, Japan). For the study, the samples were glued onto a copper substrate using carbon tape, and a layer of gold ~15 nm was sprayed. The survey was carried out in vacuum mode. The accelerating voltage of the electron gun was up to 5 kV. The images were obtained in secondary electrons at magnifications up to 1000× and recorded in digitized form on a computer.
Thermal analysis (TA) including thermogravimetry (TG) and differential thermal analysis (DTA) of synthesized powders and composites was performed using a NETZSCH STA 409 PC Luxx thermal analyzer (NETZSCH, Selb, Germany) during heating in air (10 °C/min, 40–1000 °C), the specimen mass being at least 10 mg. The gas-phase composition was monitored by a QMS 403C Aëolos quadrupole mass spectrometer (NETZSCH, Selb, Germany) coupled with a NETZSCH STA 409 PC Luxx thermal analyzer (NETZSCH, Selb, Germany). The mass spectra were registered for the following m/z values: 18 (H2O); 44 (CO2).
To calculate bulk density of suspensions, the mass of 2 mL was weighed. The viscosity of suspensions and aqueous solutions of sodium alginate in a rotary stationary (CSR) mode was studied using an Anton Paar MCR 302 e modular rheometer (Anton Paar GmbH, Graz, Austria) in a cylinder-to-cylinder geometry (cell volume 1 mL) in the shear rate range from 1 to 100 s−1. The measurements were carried out at a room temperature of 23 °C.
Indirect investigation of properties of suspensions of calcium carbonate in an aqueous solution of sodium alginate was conducted via drying at room temperature. For an indirect assessment of viscosity, we considered the spreading area of the same mass of suspensions. A total of 10.44 g of each suspension was dosed onto the flat surface of a glass Petri dish. The sample was allowed to flow freely until an equilibrium state was reached and the spreading stopped. After stabilization of the spreading spot, a quantitative assessment of its area was carried out. Dimensions of suspension area as an indirect characteristic of the ability to spread were estimated visually using millimeter paper after about 15 min after placing them on the glass surface. To do this, measurements of the linear dimensions of the formed spot were carried out using the applied millimeter paper, followed by the calculation of its area. Photos of suspension are shown in Figure 5.
Mass changing of these suspensions during drying at room temperature was controlled by weighting. Investigation of properties of suspensions of calcium carbonate CaCO3 in an aqueous solution of sodium alginate was done according to the scheme presented in Figure 6.

3. Results and Discussion

Phase composition of prepared powders is presented in Figure 7. Phase composition of powder CCK synthesized from CaCl2 and K2CO3 according to XRD data was presented by calcite. Phase composition of powders (CCNa, CCNH4, and CC2NH4) synthesized from other soluble carbonates included calcite and vaterite. The powder preparation protocol excluded the stage of by-product removal via powder washing, providing their preservation at a very low level. Nevertheless it is impossible to see any reflexes of reaction by-product (see Equations (1)–(4)) such as KCl, NaCl, NH4Cl or NH4Cl + (NH4)2CO3 taken in excess. The main reason for using excess of (NH4)2CO3 consisted in the well known fact that the presence of NH4− ions facilitates formation of thermodynamically unstable phase of vaterite. An additional reason for using excess of (NH4)2CO3 consisted in the intention to compensate for the volatile nature of ammonium carbonate.
Estimation of quantity (wt.%) of different phases presented in synthesized powder can be seen in Figure 8. Quantities of vaterite are not very high and increases in the order CCNa, CCNH4, and CC2NH4 of synthesized powders. The presence of NH4+ in the reaction zone can be taken as a factor contributing to the higher content of vaterite phase. But basic pH of aqueous solutions of soluble carbonates used can be taken as a factor providing preferable calcite as thermodynamically stable phase formation.
The masses of the synthesized CaCO3 powders after filtration and drying and collected by-products are presented in Table 4. The yield of CaCO3 can be estimated as high, close to the theoretically possible. The same conclusion can be made about masses of collected by-products for powders CCK, CCNa, and CCNH4. Low yield of by-product for CC2NH4 when (NH4)2CO3 was taken in excess can be explained by the low stability of this carbonate.
FTIR spectra of synthesized powders are presented in Figure 9. No vibrations of vaterite can be found for powder CCK. Vibrations both of calcite and vaterite can be found in the FTIR spectra for powders CCNa, CCNH4, and CC2NH4. So, the conclusion can be made that data of XRD and FTIR analysis are in agreement.
The spectrum of the CCK powder demonstrates characteristic bands corresponding exclusively to calcite modification. In particular, the splitting of valence carbonate ion vibrations typical of calcite is observed in the range of ~712 cm−1 and ~875 cm−1, as well as a doublet of deformation vibrations in the range of about 1400–1500 cm−1, which is a consequence of a decrease in the symmetry of the carbonate ion in the crystal lattice of rhombohedral calcite. The absence of a single sharp band in the spectrum in the region of ~745 cm−1, which is a diagnostic sign of vaterite, unambiguously indicates its absence in this sample.
In contrast, the FTIR spectra of all other powders (CCNa, CCNH4, and CC2NH4) show a complex composition indicating a mixture of polymorphic phases. Along with the bands inherent in calcite, an absorption band unique to hexagonal vaterite at ~745 cm−1, corresponding to the valence vibrations of the carbonate ion, is clearly identified in these spectra. In addition, there is a change in the shape and position of the bands in the region of ~875 cm−1 and ~1100 cm−1, which is also a consequence of the superposition of the vibrational spectra of two different crystalline phases. The combination of these spectral features unequivocally confirms the presence of both calcite and vaterite in these samples.
Thus, FTIR spectroscopy, being sensitive to the local environment and the symmetry of the carbonate ion in the crystal lattice, serves as a reliable independent method that is fully consistent with X-ray phase analysis. Both methods unequivocally indicate that selective formation of stable calcite occurs only in a powder CCK, while in all other cases crystallization proceeds through the stage of formation of metastable vaterite, which is preserved in the final product.
Particle size distribution of synthesized powders is presented in Figure 10.
Dimensions of particles (aggregates of individual crystals) in CCK powder are in the interval 4.4–50.1 μm, with the maximum distribution peak at 16.5 μm. Dimensions of particles in CCNa powder are in the broader interval 0.6–74.5 μm, with the maximum distribution peak at 19.6 μm. Particle size distribution in CCNH4 and CC2NH4 powders practically have no difference. Dimensions of particles for these powders are in the interval 0.3–170.3 μm, with the maximum distribution peak at 34.7 μm (CCNH4) and 31.2 μm (CC2NH4). The greater the quantity of the particles of vaterite phase, the broader the interval of particle (aggregates of individual crystals) dimensions. The reason for the broader interval of particle distribution for powders CCNH4 and CC2NH4 can be explained with the special sea-urchin-shaped particles of vaterite having the ability to cling to each other. Moreover, reaction by-product present in powders, even in the low quantity, can play a binging role to keep individual crystals in the aggregated particles.
SEM images of synthesized powders are presented in Figure 11. Powder CCK (Figure 11a,b) consisted of particles of prismatic shape, which is characteristic for modification of calcite. Powders CCNa (Figure 11c,d), CCNH4 (Figure 11e,f), and CC2NH4 (Figure 11g,h) consisted of both particles of prismatic shape and sea-urchin-shaped particles, which is characteristic for modification of vaterite.
TA data are presented in Figure 12 (TG) and Figure 13 (MS for m/z = 44). The total mass loss for powders CCK and CCNa was 46.0%. The total mass loss for powders CCNH4 and CC2NH4 was 49.6% and 49.0%, respectively.
CaCO3 → CaO + CO2↑
It is worth noting that CaCO3 decomposition started for all powder at about 600 °C (Figure 13). And this process finished at different temperatures for different powders: 855 °C (CCK), 830 °C (CCNa), 820 °C (CCNH4) and 785 °C (CC2NH4).
The mass loss for powders CCNH4 and CC2NH4 also takes place in the interval from 100 °C to 600 °C due to decomposition of NH4Cl (Equation (7)) and (NH4)2CO3 (Equation (8)).
NH4Cl → NH3↑ + HCl↑
(NH4)2CO3 → 2NH3↑ + CO2↑ + H2O↑
Ammonium chloride NH4Cl and ammonium carbonate (NH4)2CO3 undergo thermal degradation in the lower temperature range; (NH4)2CO3 decomposes with the release of 2NH3 and CO2 already at temperatures below 60 °C and NH4Cl dissociates into NH3 and HCl in the range of 300–350 °C. HCl formed during heating can react with CaCO3 with CaCl2 formation (Equation (9)).
2HCl + CaCO3 → CaCl2 + CO2↑ + H2O↑
Or probably CaCO3 even can interact with melt of NH4Cl with CaCl2 formation (Equation (10)).
2NH4Cl + CaCO3 → CaCl2 + CO2↑ + NH3↑ + H2O↑
Theoretically possible mass loss due to CaCO3 decomposition according to Equation (6) is 44% [68]. So, additional mass loss can be explained with the presence of salts adsorbed and occluded from mother liquor in synthesized powder. It is worth noting that, after calcium carbonate decompositions, TG curves reflect the continuation of mass loss. The presence of KCl (CCK), NaCl (CCNa) and CaCl2 (CCNH4 and CC2NH4) in the powders could be a reason for mass loss after CaCO3 decomposition due to their ability to evaporate above the temperature of melting point 776 °C (KCl), 801 °C (NaCl), and 772 °C (CaCl2).
Densities of prepared suspensions of calcium carbonate powders in aqueous solution of sodium alginate (Table 5) slightly diminish in the order: AlgNa_CCK, AlgNa_CCNa, AlgNa_CCNH4, and AlgNa_CC2NH4.
A decrease in density is observed in suspensions AlgNa_CCNH4 and AlgNa_CC2NH4 prepared from powders CaCO3 containing ammonium carbonate and ammonium chloride as reaction by-product. This decrease is directly related to the decomposition of ammonium carbonate with the release of gaseous products of ammonia and carbon dioxide according to Equation (8). Thus, the low density of suspension AlgNa_CC2NH4 containing (NH4)2CO3 can be explained by the presence of dispersed air bubbles in their volume. These bubbles are the result of two possible processes: capture of gases released during decomposition of (NH4)2CO3 in the case of appropriate suspensions and/or mechanical entrainment of air into a highly viscous polymer medium during sample preparation, which is especially typical for a pure alginate solution or for suspensions AlgNa_CCK and AlgNa_CCNa. Since the density of the gas phase is three orders of magnitude lower than the density of liquid and solid particles, even a small volume of entrained gas leads to a significant decrease in the apparent (average) density of the entire heterogeneous system. Consequently, suspension AlgNa_CC2NH4 with (NH4)2CO3 is a three-phase (solid–liquid–gas) system, where the presence of gas inclusions is the dominant factor determining their density. The solution of pure alginate at the initial stage of homogenization is a two-phase (solid–liquid) system. Low density of solution of pure sodium alginate also can be explained by the absence of the solid (powders of CaCO3).
For an indirect comparative assessment of the rheological properties of the studied suspensions, the spreading area analysis method was applied. The technique is based on the relationship between the viscosity of a liquid and the dimensions of the spot it forms when spreading under the influence of gravity on a horizontal surface (Table 6, Figure 5).
This method is relative and allows the ranking of samples according to their effective viscosity; a smaller spreading area with the same sample weight indicates a higher structural resistance to flow, that is, a higher viscosity.
With the exception of AlgNa_CC2NH4, suspensions show an increase in viscosity corresponding to vaterite phase content increase in the phase composition of calcium carbonate powders used as fillers (Figure 14). The rheological curves of suspensions AlgNa_CCK and AlgNa_CCNa with calcium carbonate synthesized from sodium and potassium carbonates, as well as the curve of a pure sodium alginate solution, turned out to be very close in values and occupied an intermediate position.
AlgNa_CCNH4 suspension shows the highest viscosity values in the entire studied range of shear rates. Great viscosity increase at lower shear rates can be due to possible ionic crosslinking of sodium alginate. Traces of ammonium chloride, soluble by-product (Equation (11)), being at first adsorbed on the surface of vaterite and calcite crystals from mother liquor, may then dissolve into water of suspension and provoke CaCO3 dissolution via soluble CaCl2 formation (Equation (12)) [69]. The presence of Ca2+ ions in suspension reacting with sodium alginate replaces some sodium cations and provides the possibility of partial cross-linking of alginate.
NH4Cl → NH4+ + Cl−
2NH4+ + 2Cl− + CaCO3 → CaCl2 + (NH4)2CO3
In contrast, a suspension AlgNa_CC2NH4 with calcium carbonate obtained in the presence of excess (NH4)2CO3 showed the lowest viscosity. Abnormal rheological properties of suspension filled with CC2NH4 can be possibly explained by the presence of gas bubbles, created by decomposition of ammonium carbonate excess precursor that was adsorbed on the surface of vaterite crystals from the traces of mother liquor remaining on filtered crystals. The presence of gas bubbles in the suspension AlgNa_CC2NH4 could be a reason for the lowest viscosity in comparison with the other suspensions under investigation.
Indirect testing of suspension properties (Figure 6) further confirms that cross-linking happens in suspension filled with CCNH4 and CC2NH4 powders, showing increased hygroscopicity and water retention and their puddles having uneven form, while AlgNa_CCK and AlgNa_CCNa suspensions and alginate solution puddles are lens-like flat puddles.
A notable feature is the behavior of rheological curves at high shear rates; the curve for suspension AlgNa_CCNH4 asymptotically approaches and merges with a group of curves for suspension AlgNa_CCK, AlgNa_CCNa and AlgNa, while the curve for suspension AlgNa_CC2NH4 remains parallel to them, without showing tendencies to merge.
The key factors are the surface charge of calcium carbonate particles, their tendency to agglomerate, and, as a result, the effective volume of the dispersed phase, which determines the viscosity. The high viscosity of the suspension AlgNa_CCNH4 indicates the formation of a volumetric spatial structure in the system. The surface of the CaCO3 particles probably has a charge close to the isoelectric point, which minimizes electrostatic repulsion between the particles. This contributes to their aggregation and the formation of large, loose floccules, which effectively bind a large amount of the dispersion medium (alginate solution) and create a strong framework that dramatically increases viscosity. The convergence of this curve with others at high shear rates is a classic sign of thixotropic behavior—the destruction of the structure under the action of shear deformation.
In contrast, the viscosity is low and the curve runs parallel for a system with an abundance of carbonate ions (AlgNa_CC2NH4), which indicate the presence of a well-peptized, stabilized system. Under these conditions, the surface of CaCO3 particles acquires a significant negative charge due to the adsorption of excess CO32− ions. Since alginate macromolecules also carry a negative charge, electrostatic repulsion occurs between particles and polymer chains. This prevents agglomeration and promotes the uniform distribution of individual, stabilized particles in the volume. Such a system does not form a solid structure; its viscosity is determined mainly by the viscosity of the polymer matrix and varies slightly with shear rate, which explains the parallel course of the curve. Similar viscosity values for systems with sodium and potassium carbonates, as well as pure alginate, suggest that CaCO3 particles obtained by these methods also have good colloidal stability and do not significantly contribute to structure formation; their behavior approaches that of a filler in a Newtonian fluid.
The analysis of the drying process of suspensions containing synthesized calcium carbonates and small quantities of reaction by-products revealed the exponential nature of the mass changes over time (Figure 15).
At the same time, it was found that suspensions formulated on the basis of calcium carbonate powders obtained from ammonium carbonates are characterized by a statistically significantly lower drying rate compared with compositions based on powders obtained from potassium and sodium carbonates.
The key reason is the presence of significant amounts of hygroscopic ammonium salts in these systems, primarily ammonium chloride (NH4Cl) and possibly residual ammonium carbonate (NH4)2CO3). The results were influenced by reaction by-products, but their presence was determined only indirectly. These compounds have a pronounced ability to sorption of moisture from the atmosphere and retain it in the form of hydrate shells, which increases the total content of bound liquid in the sample volume.
In addition, hydrated ammonium ions NH4+ and chloride ions Cl−, sorbed on the surface of calcium carbonate particles, can form stable hydrate layers, increase the binding energy of the “solid phase” and complicate its removal.
Thus, the delayed kinetics of drying suspensions based on CCNH4 and CC2NH4 powders is a consequence of the action of two main mechanisms: first, the physico-chemical retention of moisture by hygroscopic ammonium salts and, secondly, the formation of a thinner porous structure that increases capillary forces and the path for the diffusion of water vapor. In suspensions based on powders of CCK and CCNa with non-hygroscopic chlorides as by-products these factors are absent, and this causes their higher rate of dehydration.
The obtained XRD (Figure 16) and FTIR (Figure 17) data for composites demonstrate full consistency with the results of the analysis of the calcium carbonate powders after synthesis. This clearly indicates that the process of introducing powders into the polymer matrix of alginate, subsequent cross-linking of polymer and cryogenic drying do not induce phase transitions of polymorphic modifications of calcium carbonate and do not change their initial phase composition.
According to XRD and FTIR data, the initial phase composition is preserved in all studied composite materials. In the composites based on a CCK powder calcium carbonate is present exclusively in the form of a thermodynamically stable modification of calcite. Its FTIR spectrum is characterized by a doublet in the region of δ vibrations ~710 cm−1, and the diffraction pattern contains reflections unique to the rhombohedral structure of calcite. In contrast, in composites containing powders CCNa, CCNH4 and CC2NH4, a two-phase system is identified (Figure 16). Along with the calcite reflections, the diffractograms show peaks corresponding to the metastable hexagonal phase of vaterite. This is reliably confirmed by FTIR spectroscopy data, where, in the spectra of these samples, along with the bands of calcite, a characteristic sharp absorption band of vaterite in the region of ~875 cm−1 is observed.
This confirms the stability of polymorphic modifications of calcium carbonate within the framework of the applied technique for obtaining composite materials and proves the representativeness of the analysis of the powders themselves for predicting the composition and structure of the final composite systems.
The calcium carbonate in the initial system performs the function of a source of divalent cations with delayed release. The dissolution of calcium carbonate particles with the release of Ca2+ ions, which interact with the carboxyl groups of alginate chains, forms transverse ionic bonds. The coacervation of polymer chains and increased intermolecular interactions further stabilizes the three-dimensional grid.
Photos made using optical microscope of composites with CaAlg matrix and synthesized CaCO3 powders as a filler in the form of meshes are presented in Figure 18. These photos confirm the quite uniform distribution of filler particles in the polymer matrix for AlgCa_CCK and AlgCa_CCNa meshes. The photos of AlgCa_CCNH4 and AlgCa_CC2NH4 meshes give opportunity to see their non-homogenous structure with the presence of gas bubbles and big particle aggregates.
SEM images of surfaces of films are presented in Figure 19. It is worth noting that alginate cross-linking during preparation of the films causes their strong deformation (Figure 4). SEM images of surfaces give the opportunity to estimate forms of filler’s particles in the composite under the layer of polymer. Surface terrain of composite films is influenced by filler particles’ shape. The forms of CaCO3 particle in the polymer matrix are a course recollection of forms of particles of synthesized powders, which can be seen in their SEM images (Figure 11).

4. Conclusions

Strategy of preparation of composite materials with alginate matrix and CaCO3 filler included the following steps: (1) CaCO3 powder synthesis; (2) suspension of powder in aqueous solution of sodium alginate homogenization; (3) granule, mesh and film formation via CaCl2 cross-linking; and (4) freeze drying under deep vacuum.
Different pairs of precursors, i.e., K2CO3/CaCl2, Na2CO3/CaCl2, (NH4)2CO3/CaCl2, and 2(NH4)2CO3/CaCl2, were used for synthesis of CaCO3 powders as a filler to clarify the influence of their properties on the process of alginate matrix composite preparation. Solution of soluble carbonates used for synthesis having basic pH provided the formation of thermodynamically stable calcite in all powders. The presence of ammonium ion in reaction zone helped the vaterite formation. The highest content of metastable vaterite was in the CaCO3 powder synthesized at molar ratio Ca/CO3 = 0.5 from aqueous solutions of calcium chloride and ammonium carbonate taken in excess.
Preservation of reaction by-products in the synthesized powders of calcium carbonate even in small quantities can be treated as an effective tool for reaching target properties of powders, suspensions and composite materials. Suspension based on powder of CaCO3 with phase composition presented by calcite and vaterite containing NH4Cl as reaction by-product demonstrated the maximum viscosity values due to the possible cross-linking reaction during the suspension preparation. In contrast, a suspension based on powder of CaCO3 with phase composition presented by calcite and vaterite containing NH4Cl as reaction by-product and (NH4)2CO3 has the lowest viscosity due to the presence of bubbles of gas phase.
The presence of ammonium salts (NH4Cl and (NH4)2CO3) in the suspensions based on powders of CaCO3 influenced the process of their drying at room temperature, delaying the mass loss. It was confirmed that phase composition of CaCO3 powders used as a filler remain stable during creation of composites with alginate matrix.
Visual observations of prepared suspension can give a fresh idea of using mixtures of low-soluble CaCO3 and NH4Cl (or synthetic powder of CaCO3 containing NH4Cl as reaction by-product) as a complex cross-linking agent due to higher solubility of CaCO3 in water solution of NH4Cl. Additionally, a mixture of low-soluble CaCO3, NH4Cl and (NH4)2CO3 has perspective to be used both as complex cross-linking and foaming agent.
Created composite materials in the form of granules, meshes and films based on Ca-cross-linked alginate and powders of synthetic calcium carbonate can be recommended for skin wound and bone defect treatment and drug carriers after carrying out the necessary biocompatibility and cytotoxicity tests.

Author Contributions

Conceptualization, M.M.A., T.V.S. and N.R.K.; methodology, M.M.A., T.V.S. and N.R.K.; investigation, M.M.A., T.V.S., A.A.P., O.A.K., T.B.S., V.B.P., A.M.M., Y.Y.F., E.A.M., O.T.G., O.V.B., A.C., A.V.K. and N.R.K.; resources, T.B.S., V.B.P., Y.Y.F., O.T.G. and O.V.B.; writing—original draft preparation, M.M.A., T.V.S., A.A.P. and O.A.K.; writing—review and editing, M.M.A., T.V.S. and N.R.K.; visualization, M.M.A., A.A.P., O.A.K., E.A.M., A.M.M., O.T.G. and O.V.B.; supervision, T.V.S. and N.R.K.; project administration, T.V.S. and N.R.K. All authors have read and agreed to the published version of the manuscript.

Funding

This work was carried out with the support of the State assignment of the Lomonosov Moscow State University: AAAA-A21-121011590082-2 and with the support of the State assignment of the Lomonosov Moscow State University: No. 121031300090-2.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

This research was carried out using the equipment of the MSU Shared Research Equipment Center “Technologies for obtaining new nanostructured materials and their complex study” which was purchased by MSU within the framework of the Equipment Renovation Program (National Project “Science”) and within the framework of the MSU Program of Development. Authors would like to acknowledge the Company Lukon Pro (www.lucon.pro, accessed on 17 February 2026) and Alexey Monakov for providing opportunity of samples microstructure investigation.

Conflicts of Interest

The authors declare no conflicts of interest.

Correction Statement

This article has been republished with a minor correction in the Abstract. This change does not affect the scientific content of the article.

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Figure 1. Scheme of CaCO3 powders preparation.
Figure 1. Scheme of CaCO3 powders preparation.
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Figure 2. Composition of suspension of CaCO3 in aqueous solution of sodium alginate.
Figure 2. Composition of suspension of CaCO3 in aqueous solution of sodium alginate.
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Figure 3. Scheme of composite granules, films and meshes preparation via cross-linking in 0.25 M aqua solution of CaCl2.
Figure 3. Scheme of composite granules, films and meshes preparation via cross-linking in 0.25 M aqua solution of CaCl2.
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Figure 4. Photos of prepared composites with Ca-cross-linked alginate matrix loaded with synthetic powders of CaCO3.
Figure 4. Photos of prepared composites with Ca-cross-linked alginate matrix loaded with synthetic powders of CaCO3.
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Figure 5. Photos of suspension after dosing them onto the flat surface of a glass Petri dish and the spreading stopped.
Figure 5. Photos of suspension after dosing them onto the flat surface of a glass Petri dish and the spreading stopped.
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Figure 6. Scheme of indirect investigation of properties of suspensions of calcium carbonate in an aqueous solution of sodium alginate via drying at room temperature.
Figure 6. Scheme of indirect investigation of properties of suspensions of calcium carbonate in an aqueous solution of sodium alginate via drying at room temperature.
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Figure 7. XRD data of powders after synthesis: •—vaterite (PDF No. 33-268; No. 96-900-7476); *—calcite (PDF No. 5-586; No. 96-900-0096).
Figure 7. XRD data of powders after synthesis: •—vaterite (PDF No. 33-268; No. 96-900-7476); *—calcite (PDF No. 5-586; No. 96-900-0096).
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Figure 8. Phase composition of synthesized powders. Calculation was made using Match! (Card numbers for calcite No. 96-900-0096 and for vaterite No. 96-900-7476).
Figure 8. Phase composition of synthesized powders. Calculation was made using Match! (Card numbers for calcite No. 96-900-0096 and for vaterite No. 96-900-7476).
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Figure 9. FTIR spectra of synthesized powders.
Figure 9. FTIR spectra of synthesized powders.
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Figure 10. Particle size distributions in powders prepared.
Figure 10. Particle size distributions in powders prepared.
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Figure 11. SEM images of synthesized powders CCK (a,b), CCNa (c,d), CCNH4 (e,f), and CC2NH4 (g,h) at different magnification ×1000, bar scale = 100 μm ((a,c,e,g)—left column) and ×5000, bar scale = 20 μm ((b,d,f,h)—right column).
Figure 11. SEM images of synthesized powders CCK (a,b), CCNa (c,d), CCNH4 (e,f), and CC2NH4 (g,h) at different magnification ×1000, bar scale = 100 μm ((a,c,e,g)—left column) and ×5000, bar scale = 20 μm ((b,d,f,h)—right column).
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Figure 12. Thermal analysis data of powders synthesized from different pairs of precursors.
Figure 12. Thermal analysis data of powders synthesized from different pairs of precursors.
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Figure 13. MS spectra of data of powders synthesized from different pairs of precursors for m/z = 44 (CO2).
Figure 13. MS spectra of data of powders synthesized from different pairs of precursors for m/z = 44 (CO2).
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Figure 14. Dependence of viscosity of suspensions under investigation from the shear rate.
Figure 14. Dependence of viscosity of suspensions under investigation from the shear rate.
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Figure 15. The mass–time dependence for suspensions of calcium carbonate powders synthesized from different pairs of precursors in aqueous solution of sodium alginate.
Figure 15. The mass–time dependence for suspensions of calcium carbonate powders synthesized from different pairs of precursors in aqueous solution of sodium alginate.
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Figure 16. XRD data of composites with CaAlg matrix and synthesized CaCO3 powders: •—vaterite (PDF No. 33-268; No. 96-900-7476); *—calcite (PDF No. 5-586; No. 96-900-0096); ■—NaCl (PDF No. 72-1668; No. 96-100-0042).
Figure 16. XRD data of composites with CaAlg matrix and synthesized CaCO3 powders: •—vaterite (PDF No. 33-268; No. 96-900-7476); *—calcite (PDF No. 5-586; No. 96-900-0096); ■—NaCl (PDF No. 72-1668; No. 96-100-0042).
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Figure 17. FTIR spectra of composites with CaAlg matrix and synthesized CaCO3 powders as a filler after freeze drying.
Figure 17. FTIR spectra of composites with CaAlg matrix and synthesized CaCO3 powders as a filler after freeze drying.
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Figure 18. Photos made using optical microscope of composites with CaAlg matrix and synthesized CaCO3 powders: AlgCa_CCK (a,b), AlgCa_CCNa (c,d), AlgCa_CCNH4 (e,f), and AlgCa_CC2NH4 (g,h) at different magnification.
Figure 18. Photos made using optical microscope of composites with CaAlg matrix and synthesized CaCO3 powders: AlgCa_CCK (a,b), AlgCa_CCNa (c,d), AlgCa_CCNH4 (e,f), and AlgCa_CC2NH4 (g,h) at different magnification.
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Figure 19. SEM images of composites with CaAlg matrix and synthesized CaCO3 powders: AlgCa_CCK (a), AlgCa_CCNa (b), AlgCa_CCNH4 (c), and AlgCa_CC2NH4 (d).
Figure 19. SEM images of composites with CaAlg matrix and synthesized CaCO3 powders: AlgCa_CCK (a), AlgCa_CCNa (b), AlgCa_CCNH4 (c), and AlgCa_CC2NH4 (d).
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Table 1. Conditions of powders’ synthesis.
Table 1. Conditions of powders’ synthesis.
LabelingMolar Ratio
CO32−/Ca2+		Starting Salts and Solutions
CaCl2K2CO3Na2CO3(NH4)2CO3
C (M) × V (mL)Mass, gC (M) × V (mL)Mass, gC (M) × V (mL)Mass, gC (M) × V (mL)Mass, g
CCK10.5 M × 400 mL22.2 g0.5 M × 400 mL27.6 g- -
CCNa10.5 M × 400 mL22.2 g-0.5 M × 400 mL21.2 g-
CCNH410.5 M × 400 mL22.2 g--0.5 M × 400 mL19.2 g
CC2NH420.5 M × 400 mL22.2 g--1.0 M × 400 mL38.4 g
Table 2. Quantities of expected target (CaCO3) product and reaction by-products.
Table 2. Quantities of expected target (CaCO3) product and reaction by-products.
LabelingMolar Ratio CO32−/Ca2+Starting SaltsExpected Mass, g
CaCO3
Mass, g		By-Product
CompositionMass, g
CCK1 CaCl2/K2CO320.0KCl0.4 × 74.6 = 29.8
CCNa1CaCl2/Na2CO320.0NaCl0.4 × 58.46 = 23.4
CCNH41CaCl2/(NH4)2CO320.0NH4Cl0.4 × 53.5 = 21.4
CC2NH42CaCl2/2(NH4)2CO320.0NH4Cl + (NH4)2CO30.4 × 53.5 + 0.2 × 96.1 = 40.60
Table 3. Composition of the suspensions of CaCO3 in an aqueous solution of sodium alginate.
Table 3. Composition of the suspensions of CaCO3 in an aqueous solution of sodium alginate.
Substances in SuspensionsMass of Substances, gMass Fraction, %
CaCO3 (powder)42.5
Sodium alginate (powder)42.5
Distilled water15095.0
Table 4. The masses of the synthesized CaCO3 powders and collected by-products.
Table 4. The masses of the synthesized CaCO3 powders and collected by-products.
LabelingSynthesized Powder of CaCO3By-Product
Expected Mass, gCollected Mass, gThe Yield, %CompositionExpected Mass, gCollected Mass, gThe Yield, %
CCK20.018.894.0KCl29.828.595.6
CCNa20.019.899.2NaCl23.421.993.7
CCNH420.019.597.7NH4Cl21.419.289.6
CC2NH420.020.1100.3NH4Cl + (NH4)2CO340.625.161.9
Table 5. Density of suspensions of calcium carbonate powders in aqueous solution of sodium alginate.
Table 5. Density of suspensions of calcium carbonate powders in aqueous solution of sodium alginate.
SuspensionDensity of Suspension, g/cm3
AlgNa0.94
AlgNa_CCK1.11
AlgNa_CCNa1.09
AlgNa_CCNH41.01
AlgNa_CC2NH40.95
Table 6. Estimation of spreading area of suspensions of calcium carbonate powders in aqueous solution of sodium alginate.
Table 6. Estimation of spreading area of suspensions of calcium carbonate powders in aqueous solution of sodium alginate.
SuspensionThe Spreading Area of Suspensions, cm2
AlgNa_CCK52
AlgNa_CCNa65
AlgNa_CCNH448
AlgNa_CC2NH446
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MDPI and ACS Style

Akhmedov, M.M.; Safronova, T.V.; Pavlova, A.A.; Kibardina, O.A.; Shatalova, T.B.; Platonov, V.B.; Murashko, A.M.; Filippov, Y.Y.; Motorin, E.A.; Gavlina, O.T.; et al. Composite Materials Based on Sodium Alginate and Synthetic Powders of Calcium Carbonate. J. Compos. Sci. 2026, 10, 172. https://doi.org/10.3390/jcs10030172

AMA Style

Akhmedov MM, Safronova TV, Pavlova AA, Kibardina OA, Shatalova TB, Platonov VB, Murashko AM, Filippov YY, Motorin EA, Gavlina OT, et al. Composite Materials Based on Sodium Alginate and Synthetic Powders of Calcium Carbonate. Journal of Composites Science. 2026; 10(3):172. https://doi.org/10.3390/jcs10030172

Chicago/Turabian Style

Akhmedov, Marat M., Tatiana V. Safronova, Arina A. Pavlova, Olga A. Kibardina, Tatiana B. Shatalova, Vadim B. Platonov, Albina M. Murashko, Yaroslav Y. Filippov, Egor A. Motorin, Olga T. Gavlina, and et al. 2026. "Composite Materials Based on Sodium Alginate and Synthetic Powders of Calcium Carbonate" Journal of Composites Science 10, no. 3: 172. https://doi.org/10.3390/jcs10030172

APA Style

Akhmedov, M. M., Safronova, T. V., Pavlova, A. A., Kibardina, O. A., Shatalova, T. B., Platonov, V. B., Murashko, A. M., Filippov, Y. Y., Motorin, E. A., Gavlina, O. T., Boytsova, O. V., Chirkova, A., Knotko, A. V., & Kildeeva, N. R. (2026). Composite Materials Based on Sodium Alginate and Synthetic Powders of Calcium Carbonate. Journal of Composites Science, 10(3), 172. https://doi.org/10.3390/jcs10030172

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