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Article

The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings

by
Huiyang Gao
1,2,* and
Jie Zhang
3
1
School of Material and Chemical Engineering, Bengbu University, Bengbu 233000, China
2
Anhui Provincial Engineering Research Center of Silicon-Based Materials, Bengbu University, Bengbu 233000, China
3
School of Mechanical and Vehicle Engineering, Bengbu University, Bengbu 233000, China
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(7), 606; https://doi.org/10.3390/cryst15070606
Submission received: 10 May 2025 / Revised: 24 June 2025 / Accepted: 27 June 2025 / Published: 28 June 2025
(This article belongs to the Section Polycrystalline Ceramics)
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Versions Notes

Abstract

The type of foaming agent significantly influences the pore structure and properties of foam ceramics, particularly their compressive strength. This study used quartz sand tailings and waste glass powder as raw materials to fabricate foam ceramic materials. The effects of different foaming agents (SiC, CaCO3, and MnO2) on the phase evolution, microstructure, pore size distribution, and physical properties of the foam ceramics were investigated, and the foaming mechanisms were elucidated. The results indicated that when SiC was employed as the foaming agent, the viscosity was high at elevated temperatures and pores with irregular shapes tended to form because of the anisotropy of the quartz crystals. CaO generated from CaCO3 decomposition reduced the melt viscosity by disrupting the [SiO4] tetrahedra, whereas the formation of anorthite and diopside stabilized the pore morphology, resulting in regular circular pores. When MnO2 was used as the foaming agent, the pressure from the gas produced during oxidation exceeded the surface tension of the molten phase owing to its viscosity, leading to the formation of larger, irregular, and interconnected pores. The foam ceramic material exhibited optimal properties when 2% CaCO3 was used as the foaming agent, with a water absorption rate of 30%, bulk density of 0.62 g/cm3, porosity of 68.4%, compressive strength of 9.67 MPa, and thermal conductivity of 0.26 W/(m·K).

1. Introduction

Foam ceramics exhibit remarkable properties such as high porosity, high chemical stability, and low density. In addition, they showcase high mechanical strength, thermal resistance, sound insulation, corrosion resistance, waterproofing, as well as excellent filtration and adsorption capabilities. Owing to characteristics, they are extensively used in various application, such as insulation, thermal insulation, and soundproofing in the construction sector [1,2,3]. They are also used as catalyst supports, filters, and sensors in chemical, energy, environmental, and biological systems [4,5,6,7]. Consequently, the raw materials and fabrication methods for foam ceramics have attracted considerable attention. Presently, the primary raw materials used for producing foam ceramics are SiO2-rich solid wastes, such as molybdenum tailings [8], steel slag [9,10], gold tailings [11], fly ash [12,13], gangue [14,15], and copper tailings [16,17]. Siddika [18] employed waste windshield glass to produce foam ceramics, focusing on the influence of early structural development and pore stability of the foamed material on the final properties of the glass-ceramic foam. Furthermore, Fanhui [19] indicated that foam ceramics composed of 60% gangue could achieve a compressive strength of 6 MPa and a porosity of 80.6%. However, foam ceramics derived from solid waste often suffer from a high bulk density, low porosity, and reduced strength [20]. Therefore, it is imperative to incorporate diverse raw mineral materials and foaming agents for synthesizing foam ceramics.
The current methods used for synthesizing foam ceramics include the foaming method, the addition of pore-forming agents, and the organic foam impregnation method [14,21]. Among these, the foaming method is the most widely used method for synthesizing foam ceramics owing to its simplicity and low cost. Common foaming agents include carbon compounds [22], metal carbonates [23], and transition metal oxides, which can produce gases at high temperatures, thereby enhancing the performance of foam ceramics. Yuyang et al. [24] investigated the effects of Na2CO3 on the bulk density, compressive strength, and the microstructure of foam ceramics, obtaining foam ceramics with a bulk density of 0.78 g/cm3 and a compressive strength of 3.5 MPa. Jian et al. [1] synthesized foam ceramics using SiC as the foaming agent, achieving a porosity of 50.1% and a thermal conductivity of 0.474 W/(m·K), thereby demonstrating their suitability for applications in building energy conservation. Yang et al. [25] prepared high-entropy foam ceramics using triethanolamine lauryl sulfate as the foaming agent and achieved a porosity in the range of 90.13–96.13%. Guihang et al. [26] reported that both the bulk density and compressive strength decreased with increasing SiC content. When 1.0 wt% SiC was added, the foam ceramic exhibited a compressive strength, bulk density, and total porosity of 8.09 MPa, 0.57 g/cm3, and 71.04%, respectively. Chenglin Zhao et al. [27] prepared foam ceramics using granite sawing mud with MnO2 and achieved a bulk density from 1231.02 kg/m3 to 412.56 kg/m3. Xiangming Li et al. [28] used calcium carbonate as the foaming agent to prepare foam ceramic materials, whose bulk density was 0.48–0.53 g/cm 3, porosity was 80–82%, and compressive strength was 2 MPa. The above results indicate that the pore structure and performance of foam ceramic materials are related not only to the raw materials but also to the type of foaming agent, which significantly influences pore formation and material performance [29,30]. Therefore, it is necessary to study the foaming mechanisms of different foaming agents.
In this study, quartz sand tailings and waste glass powder were used as the primary raw materials. SiC, CaCO3, and MnO2, which possess stable chemical properties, were employed as high-temperature foaming agents for synthesizing foam ceramic materials. The effects of raw-material composition and type of foaming agent on the physicochemical properties, phase evolution, and pore structure of foam ceramic materials were investigated via physical and chemical property testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric-differential scanning calorimetry (TG-DSC), and thermodynamic calculations. In addition, the foaming mechanisms of different foaming agents were analyzed. The findings of this study provide scientific and practical guidelines for producing foam ceramics from quartz sand tailings and for selecting appropriate foaming agents.

2. Materials and Methods

2.1. Raw Materials

The primary raw materials were used in this study, quartz sand tailings and waste glass powder, both with a particle size of 200 mesh. Table 1 and Figure 1 present their chemical compositions and phase characteristics, respectively. As shown in Table 1, quartz sand tailings predominantly consist of SiO2, with minor amounts of Al2O3, K2O, and other components. Waste glass powder was mainly composed of SiO2, Na2O, CaO, MgO, Al2O3, and other constituents. According to the results of phase-composition analysis (Figure 1), quartz tailings primarily consisted of crystalline α-SiO2. The XRD patterns of waste glass powder exhibited a characteristic broad hump between 2θ angles of 20° and 30°, suggesting its amorphous nature. SiC, CaCO3, and MnO2 were employed as the foaming agents, with Na2B4O7·10H2O serving as the fluxing agent. All chemical reagents utilized in this study were of the analytical grade (≥99.5% purity).

2.2. Preparation of Foam Ceramics

The raw materials (quartz sand tailings and waste glass powder) were dried at 105 °C for 24 h to eliminate residual moisture. The dried materials were then weighed and mixed at a mass ratio of 60:40 (quartz sand tailings to waste glass powder). Additionally, 3% Na2B4O7·10H2O by mass were added as a fluxing agent. In addition, 1% (NH4)3PO4 is added as an additive. Foaming agents, namely SiC, CaCO3, and MnO2, were added at the concentrations of 0.5%, 1%, 1.5%, 2%, and 2.5% by mass to investigate their effects on the foaming process (Table 2). The weighed mixture was placed in an agate ball mill jar, and zirconia balls were added at a ball-to-material ratio of 2:3 to ensure effective grinding. Subsequently, the jar was placed in a planetary ball mill and the mixture was milled for 8 h to ensure homogeneous particle size distribution and thorough mixing of the components. The milled material (30 g) was transferred to a cylindrical mold with a diameter of 40 mm. The material was compacted at a pressure of 5 MPa for 3 min to obtain cylindrical samples suitable for sintering. The cylindrical samples were placed in an alumina crucible. The crucible was then placed in a high-temperature box furnace and sintered. The sintering schedule involved two heating stages: the temperature was firstly increased to 800 °C at a rate of 5 °C/min, followed by a slower increase to 1080 °C at a rate of 3 °C/min. The samples were held at 1080 °C for 30 min to allow complete foaming and densification. The samples were then cooled to room temperature.

2.3. Characterization of Materials

The chemical compositions of the raw materials were analyzed using a Shimadzu EDX-7000 X-ray fluorescence spectrometer (Shimadzu Corporation, Kyoto, Japan). The phase composition and evolution of the raw materials and samples were characterized via XRD (SmartLab SE, Rigaku Corporation, Tokyo, Japan), using a Cu target at the tube current, tube voltage, and scanning speed of 40 mA, 40 kV, and 2°/min, respectively. The microscopic morphologies of the samples were examined via SEM (ZEISS Gemini 300, Carl Zeiss AG, Oberkochen, Germany) at an accelerating voltage of 15 kV. Aperture measurements were conducted using the SEM images and analyzed via the equivalent circular diameter (ECD) method in ImageJ software (1.8.0) to quantify irregular pore sizes. The thermal conductivities of the samples were determined using a DRL-III thermal-conductivity tester (Xiangtan Instrument & Meter Co., Ltd., Xiantan, China). The bulk density, water absorption rate, apparent porosity, and closed porosity were evaluated using the Archimedes displacement method. Each sample was measured three times to obtain the average value [26,31]. The compressive strengths of cubic samples (20 mm × 20 mm × 20 mm) were assessed using a Shimadzu AGS-X 1000 universal testing machine at a loading rate of 0.5 mm/min. Additionally, TG-DSC was performed on the samples using a Netzsch STA 449 F3 synchronous thermal analyzer (NETZSCH Group, Selb, German) in air at a heating rate of 10 °C/min.

3. Results and Discussion

3.1. Phase Evolution

Figure 2 shows the XRD patterns of the foam ceramics prepared using different foaming agents, each at a concentration of 2%. When SiC was used as the foaming agent, the main phases in the sample were quartz (PDF#85-0798, α-SiO2), anorthite (PDF#89-1471, Ca(Al2Si2O8)), and mullite (PDF#15-0776, Al6Si2O13) (Reactions 1 and 2) [32]. When CaCO3 was used as the foaming agent, the sample was composed of SiO2, Ca(Al2Si2O8), and Al6Si2O13, with a small amount of diopside (PDF#72-1497, CaMgSi2O6). The addition of CaCO3 resulted in the formation of CaO during the high-temperature process, which promoted the transformation of quartz into anorthite and diopside (Reactions 1 and 3). When MnO2 was used as the foaming agent, the sample exhibited additional phases, namely, diopside (PDF#72-1497, CaMgSi2O6) (Reactions 3). The presence of diopside and calcium manganese silicate enhanced the strength, wear resistance, density, and chemical stability of the foam ceramics. Additionally, the incorporation of SiC, CaCO3, and MnO2 significantly reduced the intensity of the quartz diffraction peaks compared to those of the sample prepared without a foaming agent.
CaO + Al2O3 + 2SiO2 → Ca(Al2Si2O8)
3Al2O3 + 2SiO2 → Al6Si2O13
CaO + MgSiO3 + SiO2 → CaMgSiO6

3.2. Microscopic Morphology and Pore Size Analysis

Figure 3 shows the SEM images and pore size distributions of the foam ceramics prepared using different foaming agents. Evidently, the type of foaming agent significantly affects the pore size and pore structure of the foam ceramics. When SiC was used as the foaming agent, the pore distribution was uneven, with the pores predominantly exhibiting irregular shapes (indicated by point M in the figure). The average pore size was 1.72 mm, with the pores primarily distributed between 0.5 and 2 mm. As shown in Figure 3b,e, when CaCO3 was used as the foaming agent, the pores were more regular and predominantly displayed a circular structure (as indicated by point N in the figure) with an uneven pore distribution. The average pore size was 1.28 mm, with pores primarily distributed between 0 and 2 mm. These uniformly sized circular pores enhanced the compressive strength of the material. When MnO2 was used as the foaming agent, the pore distribution of the foam ceramics was highly uneven, with a maximum pore size of up to 3.5 mm. Additionally, the sample exhibited irregular pore structures (as indicated by point O in the figure), including elliptical and strip-like shapes. The average pore size was 2.21 mm, with pores primarily distributed between 1.5 and 2.5 mm. This phenomenon resulted from the pressure exerted by the gases generated through MnO2 oxidation at high temperatures, which exceeded the surface tension of the molten phase owing to its viscosity, thereby inducing the coalescence of small bubbles to form larger, irregular, and interconnected pores.
Figure 4 shows the microstructures of the foam ceramics. Table 3 shows the EDS results corresponding to Figure 4. As shown in Figure 4a, the sample prepared without a foaming agent consisted of quartz (region ①) and rod-like anorthite (region ②). As shown in Figure 4b, the sample prepared using SiC exhibited granular mullite crystals (region ③). Additionally, unevenly sized and irregularly shaped pores were formed due to the anisotropy of the quartz crystals [33]. As shown in Figure 4c, when CaCO3 was used as the foaming agent, numerous rod-like anorthite crystals were observed in regions ④, with diopside present in region ⑤. This is primarily because CaCO3 decomposition resulted in the formation of CaO, which modified the silicate network, reducing the viscosity of the silicate melt by disrupting the [SiO4] tetrahedra, thereby promoting the formation of regular circular pores in the micropores [34]. As shown in Figure 4d, when MnO2 was used as the foaming agent, mullite (region ⑥) crystalline phases were observed.

3.3. Analysis of Materials Properties

Figure 5 shows the bulk density and water absorption of the foam ceramic samples prepared using SiC, CaCO3, and MnO2 as the foaming agents. The foaming-agent concentration strongly influenced bulk density and water absorption: as the concentration increased, bulk density decreased, and water absorption increased. In the concentration range of 0.5–2%, the bulk density decreased in the order MnO2 > SiC > CaCO3. At a foaming-agent concentration of 2.5%. the bulk densities of the samples derived using SiC, CaCO3, and MnO2 were 0.63, 0.55, and 0.86 g/cm3, respectively. Because the decomposition temperature of CaCO3 is relatively low, it can reduce the volume density, while the reaction temperature of SiC and MnO2 is relatively high.
Foaming agents significantly affect the porosity of foam ceramic materials, ultimately influencing their strength. Figure 6 shows the total porosity, open porosity, compressive strength, and thermal conductivity of the samples prepared using SiC, CaCO3, and MnO2 as the foaming agents. As shown in Figure 6a, the porosity of the samples gradually increased with increasing foaming-agent content [35]. For the same foaming-agent content, the true porosity of the foamed material decreased in the order CaCO3 > SiC > MnO2. Higher bulk densities correspond to lower porosities, which is consistent with the bulk densities shown in Figure 5 [26]. Additionally, the closed porosity of the samples increased with increasing foaming-agent, aligning with the patterns observed in the water absorption rates.
As shown in Figure 6b, the compressive strength decreased progressively with increasing foaming-agent content. In general, the factors that affect compressive strength include porosity, pore size distribution, and material composition, among which porosity has the highest influence; the higher the porosity, the lower the compressive strength [36,37]. The samples prepared using CaCO3 as the foaming agent exhibited more regular and circular pore structures (Figure 3b), which promoted a uniform stress distribution under the applied load and thus enhanced the compressive strength [38]. Consequently, for the same foaming-agent content, the compressive strength decreased in the order CaCO3 > MnO2 > SiC. At a foaming-agent concentration of 2.5%, the compressive strengths of the foam ceramics prepared using SiC, CaCO3, and MnO2 were 2.44, 4.62, and 5.62 MPa, respectively. The MnO2-derived foam ceramic exhibited the highest compressive strength. This is attributed to the in-situ formation of CaMgSi2O6 crystals, which reinforced the matrix [9]. Figure 6b shows the thermal conductivity of the foam ceramic materials, which gradually decreased with increasing foaming-agent content and decreased further as the porosity increased [39]. When the foaming-agent content was 2.5%, the thermal conductivities of the samples prepared using SiC, CaCO3, and MnO2 were reduced to 0.33, 0.18, and 0.24 W/(m·K), respectively.

3.4. Foaming Mechanism

The phase composition, microstructure, pore distribution, and physicochemical properties of foam ceramic materials are closely related to their foaming mechanisms. Therefore, the foaming mechanisms of different types of foaming agents (SiC, CaCO3, and MnO2) were investigated using a simultaneous thermal analyzer. Figure 7, Figure 8, Figure 9 and Figure 10 show the TG-DSC curves of the samples prepared without foaming agents and with SiC, CaCO3, and MnO2.
As shown in Figure 7, the TG-DSC curves can be divided into two stages. In the first stage, from room temperature to 660 °C, the sample exhibited a weight loss of 1%, which is primarily attributed to the evaporation of physical water and organic impurities’ decomposition from the raw materials. In the second stage, the weight loss was 2.45%. The significant weight loss observed in the second stage is attributed to the thermal decomposition of impurities within the quartz sand tailings, such as carbonates, phosphogypsum, mica, and fluorite (e.g., dehydroxylation, decarbonation, dehydration) [40,41]. An endothermic peak at 836 °C corresponds to reactions associated with the initial stages of mullite formation, likely involving precursor phase development. The presence of tailings impurities may facilitate these reactions at a lower temperature compared to pure aluminosilicate systems. Additionally, small endothermic peaks were observed at 991 °C, which are attributed to the formation of calcium feldspar phases.
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Figure 7. TG-DSC curve of the sample prepared without foaming agents.
Figure 7. TG-DSC curve of the sample prepared without foaming agents.
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3.4.1. Foaming Mechanism of SiC

As shown in Figure 8, the TG-DSC curve of the sample prepared using SiC can be divided into three stages. The first stage—from room temperature to 750 °C—was characterized by weight loss, primarily attributed to physical water and organic impurities’ decomposition from the raw materials, leading to the formation of a small number of micropores. The second stage, from 750 °C to 900 °C, showed a slight increase in weight by 0.08%, which is attributed to the chemical reactions of SiC in this temperature range, resulting in the formation of SiO2, as shown in Equations (4) and (5) [42]. This stage also corresponded to the formation of mullite. In the second stage, CO and CO2 were generated owing to the reaction of SiC, leading to the formation of numerous pores in the sample. Additionally, a dense SiO2 layer was formed and spanned across the pore walls, which hindered the continuation of the oxidation reaction and enlargement of the pores. However, the presence of various elements, such as Na, K and Mg, in the sample lowered its melting point. Subsequently, in the third stage, at temperatures ranging from 900 °C to 1200 °C, the viscosity of the liquid phase decreased, causing smaller pores to merge and form a greater number of irregularly connected pores [14,43]. Additionally, combined performance analysis, a small exothermic peak appeared at 960 °C, indicating the formation of feldspar crystals, which stabilized the structure of the pore walls.
SiC ( s ) + 1.5 O 2 ( g )   →   SiO 2 ( s ) + CO ( g )   ∆ G Θ = 0.079 T − 946.92
SiC ( s ) + 2 O 2 ( g )   →   SiO 2 ( s ) + CO 2 ( g )   ∆ G Θ = 0.166 T − 1229.91
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Figure 8. TG-DSC curve of the sample with SiC as the foaming agent.
Figure 8. TG-DSC curve of the sample with SiC as the foaming agent.
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3.4.2. Foaming Mechanism of CaCO3

Figure 9 shows the TG-DSC curve of the sample prepared using CaCO3 as the foaming agent. The curve can be divided into three stages. The first stage, from room temperature to 600 °C, showed a mass loss of approximately 1.08%, primarily due to physical water and organic impurities’ decomposition in the sample, which leads to the formation of small pores. The second stage, from 600 °C to 820 °C, exhibited a mass loss of 1.14%. This mass loss is mainly attributed to the decomposition of CaCO3 (as shown in Equation (6)). The standard Gibbs free energy change for the decomposition reaction of CaCO3 in Equation (6) is negative over the temperature range from room temperature to 1200 °C. The formation of CaO reduces the melt viscosity, promoting the formation of more regular, circular pores. As evident from the SEM and pore size analysis (Figure 3), the pores exhibited a relatively regular circular shape with smaller pore sizes when CaCO3 was used as the foaming agent. Smaller bubble sizes enhance foam stability. According to the Laplace equation, a more uniform bubble size distribution reduces the pressure differences between adjacent bubbles, thereby reducing the gas diffusion force. Therefore, a uniform bubble size distribution is beneficial for the stability of the bubbles.
The third stage, from 820 °C to 1200 °C, showed a mass loss of 1.66%. This is primarily due to the gradual increase in the amount of liquid phase with increasing temperature, which leads to a decrease in viscosity. The volatilization of elements, such as Na and K, induced mass loss and initiated the coalescence of smaller bubbles. The formation of diopside (indicated by the exothermic peak at 812 °C) and feldspar (indicated by the exothermic peak at 936 °C) contributed to the stabilization of the bubble size.
CaCO 3 ( s )   →   CaO ( s ) + CO 2 ( g )   ∆ G Θ = − 147.12 T + 171507.81
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Figure 9. TG-DSC curve of the sample prepared using CaCO3 as the foaming agent.
Figure 9. TG-DSC curve of the sample prepared using CaCO3 as the foaming agent.
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3.4.3. Foaming Mechanism of MnO2

Figure 10 shows the TG-DSC curve of the sample prepared using MnO2 as the foaming agent. The TG-DSC curve consisted of three stages. The first stage, from room temperature to 526 °C, showed a mass loss of 1.11%, primarily due to the physical water and organic impurities’ decomposition in the sample. The second stage, from 526 °C to 856 °C, is mainly attributed to the rection of MnO2 and Mn2O3 in a glass melt, which released O2 and formed bubbles (as shown in Equations (7) and (8) [42,44,45]. However, at higher temperatures, according to the Laplace equation, a large pressure difference at the bubble surface can cause the liquid film to rupture during bubble growth. This may lead to the coalescence of bubbles and the collapse of the slurry, resulting in an uneven distribution of pore sizes [46].
4MnO2(s) → 2Mn2O3(s) + O2(g)
4Mn3+(s) + 2O2− → 4Mn2+(s) + O2(g)
The utilization of quartz tailings as primary raw material delivers dual sustainability advantages: (1) environmentally, it diverts mining waste from landfills, reducing long-term soil contamination risks and conserving natural quartz resources; (2) economically, it transforms zero-cost waste into value-added functional ceramics, slashing raw material expenditures while creating marketable insulation products for construction sectors. This approach exemplifies a circular economy paradigm aligning with global waste valorization strategies.
Crystals 15 00606 g010
Figure 10. TG-DSC curve of the sample prepared using MnO2 as the foaming agent.
Figure 10. TG-DSC curve of the sample prepared using MnO2 as the foaming agent.
Crystals 15 00606 g010

4. Conclusions

(1) The type of foaming agent has a significant impact on the pore structure of foam ceramics, which in turn, affects its water absorption, bulk density, porosity, compressive strength, and thermal conductivity. When 2% CaCO3 was used as the foaming agent, the material exhibited optimal performance, with a water absorption of 30%, a bulk density of 0.62 g/cm3, a porosity of 68.4%, a compressive strength of 9.67 MPa, and a thermal conductivity of 0.26 W/(m·°C).
(2) Using SiC as the foaming agent promoted the formation of mullite crystals, resulting in a higher viscosity at elevated temperatures. Additionally, the anisotropy of quartz crystals resulted in the formation of unevenly sized and irregularly shaped pores. The average pore diameter was 1.72 mm, and the compressive strength was low at 5.42 MPa.
(3) When CaCO3 was used as the foaming agent, the CaO produced after the decomposition of CaCO3 acted as a fluxing agent for the silicate network, reducing the viscosity of the silicate melt by disrupting the [SiO4] tetrahedra. Additionally, the formation of numerous rod-shaped feldspar and diopside crystals helped stabilize the pore shape, promoting the formation of regular circular pores. The average pore diameter was 1.28 mm, with a high compressive strength of 9.67 MPa.
(4) When MnO2 was used as the foaming agent, the gas pressure generated by the oxidation of MnO2 exceeded the surface tension owing to the viscosity of the molten phase. Consequently, small bubbles merged to form larger, irregularly shaped, and interconnected pores. At this point, the average pore diameter was 2.21 mm, with a low compressive strength of 2.28 MPa.

Author Contributions

Conceptualization, methodology, investigation, writing—original draft preparation, H.G.; formal analysis, writing—review and editing, J.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by natural science project of Bengbu University, grant numbers 2023ZR01zd, 2024YYX38QD, Anhui Provincial Department of Education key project, grant number 2023AH052939 and the excellent innovative scientific research team of silicon-based materials, grant number 2022AH010101).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank the Bengbu University, Anhui Provincial Engineering Research Center of Silicon-Based Materials, and Key Innovative Research Team of New Energy Materials and Devices (BBXYKYTDxjZD01) for providing the facilities and support to conduct this research in their laboratories.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
XRDX-ray diffraction
SEMScanning electron microscopy
TG-DSCThermogravimetric-differential scanning calorimetry

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Crystals 15 00606 g001
Figure 1. XRD patterns of raw materials: (a) quartz sand tailings and (b) waste glass powder.
Figure 1. XRD patterns of raw materials: (a) quartz sand tailings and (b) waste glass powder.
Crystals 15 00606 g001
Crystals 15 00606 g002
Figure 2. XRD patterns of foam ceramics prepared using different foaming agents (SiC (2%), CaCO3 (2%), MnO2 (2%), and no foaming agent).
Figure 2. XRD patterns of foam ceramics prepared using different foaming agents (SiC (2%), CaCO3 (2%), MnO2 (2%), and no foaming agent).
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Crystals 15 00606 g003
Figure 3. Scanning electron microscopy (SEM) images and pore size distributions of foam ceramics prepared using different foaming agents: (a,d) SiC; (b,e) CaCO3; (c,f) MnO2.
Figure 3. Scanning electron microscopy (SEM) images and pore size distributions of foam ceramics prepared using different foaming agents: (a,d) SiC; (b,e) CaCO3; (c,f) MnO2.
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Crystals 15 00606 g004
Figure 4. SEM images of foam ceramics prepared using different foaming agents: (a) no foaming agent, (b) SiC, (c) CaCO3, (d) MnO2.
Figure 4. SEM images of foam ceramics prepared using different foaming agents: (a) no foaming agent, (b) SiC, (c) CaCO3, (d) MnO2.
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Crystals 15 00606 g005
Figure 5. Bulk density and water absorption of foam ceramics for different foaming agents.
Figure 5. Bulk density and water absorption of foam ceramics for different foaming agents.
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Crystals 15 00606 g006
Figure 6. The influence of foaming agents on (a) true porosity, open porosity, and closed porosity, and (b) compressive strength and thermal conductivity.
Figure 6. The influence of foaming agents on (a) true porosity, open porosity, and closed porosity, and (b) compressive strength and thermal conductivity.
Crystals 15 00606 g006
Table 1. The chemical composition of raw materials (wt.%).
Table 1. The chemical composition of raw materials (wt.%).
CompositionAl2O3SiO2Na2OMgOFe2O3CaOTiO2K2OCr2O3LOI
Quartz tailing6.7686.200.250.760.523.650.540.96-0.36
Glass powder1.1865.2515.694.840.1011.460.650.350.030.45
Table 2. Foam ceramic formulations with added different foaming agents (wt.%).
Table 2. Foam ceramic formulations with added different foaming agents (wt.%).
Quartz Sand TailingWaste Glass PowderSiCCaCO3MnO2
6040000
59.5400.500
5940100
58.5401.500
5840200
57.5402.500
59.54000.50
5940010
58.54001.50
5840020
57.54002.50
59.540000.5
5940001
58.540001.5
5840002
57.540002.5
Table 3. EDS analysis of foam ceramics prepared using different foaming agents (wt%).
Table 3. EDS analysis of foam ceramics prepared using different foaming agents (wt%).
RegionONaMgAlSiKCaFeTi
①49.71-0.863.1942.740.242.830.170.26
②42.760.130.6719.1820.440.3916.280.090.06
③45.460.261.4337.2612.850.431.980.160.17
④43.450.070.4820.4618.620.2616.290.240.13
⑤43.370.2311.641.3125.360.4317.200.250.21
⑥45.570.161.0337.7712.360.272.350.340.15
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Gao, H.; Zhang, J. The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings. Crystals 2025, 15, 606. https://doi.org/10.3390/cryst15070606

AMA Style

Gao H, Zhang J. The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings. Crystals. 2025; 15(7):606. https://doi.org/10.3390/cryst15070606

Chicago/Turabian Style

Gao, Huiyang, and Jie Zhang. 2025. "The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings" Crystals 15, no. 7: 606. https://doi.org/10.3390/cryst15070606

APA Style

Gao, H., & Zhang, J. (2025). The Influence of Different Foaming Agents on the Properties and Foaming Mechanisms of Foam Ceramics from Quartz Tailings. Crystals, 15(7), 606. https://doi.org/10.3390/cryst15070606

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