Search Results (181)

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors—NH₂SO₃H, ZnO·TiO₂, and (NH₄)₂HPO₄—on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH₄)₂HPO₄ with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m³, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO₄ formation that enhancing the strength, and Ca₂P₂O₇ that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste. Full article

Nowadays, there is wide advocacy for a transition to circular economic models. Fly Ash (FA) in particular is a major by-product of coal combustion and its annual waste has reached one million tonnes. Cenospheres (CSs) are considered as possibly the most valuable element within FA. Thus, in this research, polymeric foam replication was employed to fabricate ceramic foams based on a CS matrix, for potential biomedical applications. For the fabrication of foams, four types of natural marine sponges were used as templates along with a binder agent. The specimens were sintered at 1200 °C for 1 h. The results were encouraging as the specimens obtained retained the given shape and geometry. Further research will enhance the potential of such materials for future use in biomedical engineering. Full article

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). Full article

In this study, a production method for ceramic shell macrocapsules and a high-temperature-resistant, polymer agent-based self-healing system was developed. Two types of macrocapsules were created by filling hollow ceramic capsules with high-temperature-resistant diallyl phthalate (DAP) resin, known for its thermal stability, and a peroxide-based curing agent. These capsules were incorporated into epoxy and DAP matrix materials to develop polymer composite materials with self-healing properties The macrocapsules were produced by coating polystyrene (PS) sacrificial foam beads with raw ceramic slurry, followed by sintering to convert the liquid phase into a solid ceramic shell. Moreover, FTIR, TGA/DTA, and DSC analyses were performed. According to the thermal analysis results, DAP resin can effectively function as a healing agent up to approximately 340 °C. In addition, quasi-static compression tests were applied to composite specimens. After the first cycle, up to 69% healing efficiency was obtained in the epoxy matrix composite and 63.5% in the DAP matrix composite. Upon reloading, the second-cycle performance measurements showed healing efficiencies of 56% for the DAP matrix composite and 58% for the epoxy matrix composite. Full article

An aqueous mixture of three compounds (atrazine, carbamazepine, and p-chlorobenzoic acid) has been treated by photochemical processes including photolysis and photocatalysis with 10.7% TiO₂ supported on ceramic foams of mullite. Experiments were conducted in both ultrapure water and in a secondary effluent from a municipal wastewater treatment plant. Radiation at 365 nm was totally inefficient in the photolytic process carried out in ultrapure water; however, some sensitization phenomena were observed when municipal wastewater was used as a bulk matrix. In the latter case, conversion values in the range of 20–30% were obtained after 2 h. The photocatalytic process was much more effective experiencing conversions above 80% after just 80 min of reaction. The nature of the matrix used exerted a significant influence. Use of municipal wastewater slowed down the process due to the scavenging character of the natural organic matter content. Test runs in the presence of carbonates and t-butyl alcohol suggested that radical carbonates play some role in contaminant abatement, and secondary radicals generated after the t-BuOH attack by HO^● radicals should also be considered in the reaction mechanism. A pseudo-empirical mechanism of reactions sustains the experimental result obtained, acceptably modeling the effects of a water matrix, scavenger addition, and radiation volumetric photon flux. Full article

This paper presents the development of two solutions for sandwich panels composed of a thin-layer alkali-activated composite (AAc) layer and a thicker insulation layer, formed by extruded polystyrene foam or expanded cork agglomerate (panels named AP_XPS or AP_ICB, respectively). The AAc combined ceramic waste from clay bricks and roof tiles (75%) with ladle furnace slag (25%), activated with sodium silicate. The AAc layer was further reinforced with polyacrylonitrile (PAN) fibers (1% content). The mechanical behavior was assessed by measuring the uniaxial compressive strength of cubic AAc specimens, shear bond strength, pull-off strength between the AAc layer and the insulation material, and the flexural behavior of the sandwich panels. The thermal performance was characterized by heat flux, inner surface temperatures, the thermal transmission coefficient, thermal resistance, and thermal conductivity. Mechanical test results indicated clear differences between the two proposed solutions. Although AP_XPS panels exhibited higher tensile bond strength values, the AP_ICB panels demonstrated superior interlayer bond performance. Similar findings were observed for the shear bond strength, where the irregular surface of the ICB positively influenced the adhesion to the AAc layer. In terms of flexural behavior, after the initial peak load, the AP_XPS exhibited a deflection-hardening response, achieving greater load-bearing capacity and energy absorption capacity compared to the AP_ICB. Finally, thermal resistance values of 1.02 m² °C/W and 1.14 m² °C/W for AP_ICB and AP_XPS were estimated, respectively, showing promising results in comparison to currently available building materials. Full article

This study explores the optimization of foam ceramic materials through experimental research and mathematical modeling. The goal was to enhance mechanical strength, thermal insulation, porosity, water absorption, and density by adjusting composition and firing conditions. Regression analysis and response surface methodology were used to assess the effects of loam, fly ash content, and the firing temperature. The optimal composition of 60–65% loam, 10% fly ash, and a firing temperature of 950–1000 °C yielded foam ceramics with a bulk density of 680–700 kg/m³, a compressive strength of 3.5–4 MPa, and a thermal conductivity of 0.135–0.140 W/(m·K). Controlled porosity (70–72%) enhanced insulation while maintaining structural integrity. X-ray diffraction confirmed mullite, quartz, and cristobalite phases, with mullite improving mechanical properties. This research demonstrates the potential of optimized foam ceramics for energy-efficient construction. Mathematical modeling and experimental validation provide a pathway for developing lightweight, high-performance ceramic materials. Future work should refine sintering processes, explore new additives, and evaluate the long-term performance. Full article

In recent years, the increasing frequency of building fires has highlighted the limitations of traditional polymeric materials due to their inadequate fireproof performance. Ceramifiable polymer composites have emerged as a promising alternative by incorporating ceramic-forming fillers that create rigid ceramic-like structures through high-temperature eutectic reactions, offering exceptional thermal insulation and fireproof properties. These composites maintain structural integrity under fire exposure through sufficient mechanical strength retention. The effects of several ceramifiable inorganic fillers (CIFs) on the properties of polydimethylsiloxane (PDMS) foams were systematically investigated in this study. The research demonstrated that fillers with better matrix compatibility significantly enhance the foaming quality, mechanical performance, and fireproof capabilities. Notably, the CaCO₃-filled PDMS foam composite (CPF-Ca) demonstrates exceptional foaming characteristics with 84% porosity and a remarkably low density of 0.36 g/cm³. The material achieves tensile and compressive strengths of 0.22 MPa and 0.84 MPa, representing 22% and 127% enhancements, respectively, compared to pure PDMS foam (PPF). Regarding the ceramic conversion capability, the sintered residue of CPF-Ca maintains a compressive strength of 4.39 MPa under high-temperature conditions. This composite material exhibited superior fireproof performance, successfully withstanding a butane torch for 300 s without penetration while maintaining a remarkably low backside temperature of merely 83.6 °C. Full article

In response to environmental challenges and primary resource scarcity, sustainable approaches that rely on recycling and reusing waste materials are becoming valuable and highly appealing options in modern society. This paper deals with the usage of porous glass and glass-ceramic products derived from waste in the field of thermal insulation in buildings. After providing an overview of the current state of the art with a focus on existing commercial products and related manufacturing methods (foaming strategies), this review discusses the emerging trends toward greener approaches, including the use of by-products or waste substances as foaming agents (e.g., eggshells or mining residues), the use of vitrified bottom or fly ashes from municipal solid waste incinerators as starting materials, the application of surface treatment to reduce post-processing temperatures, and the promise of additive manufacturing technologies in this field. The increased use and spread of sustainable practices are expected to significantly contribute to glass recycling, to minimize landfilling, and to generally reduce energy consumption as well as greenhouse emissions. Full article

Application of rare earths (RE) as grain refiners is well-known in the technology of aluminum alloys for the automotive industry. In the current study, Al-2.4%Cu-0.4%Mg alloy (coded 220) and Al-7.5%Si-0.35%Mg alloy (coded 356.1), were prepared by melting each alloy in a resistance furnace. Strontium (Sr) was used as a modifier, while titanium boride (TiB₂) was added as a grain refiner. Measured amounts of Ce and La were added to both alloys (max. 1 wt.%). The alloy melts were poured in a preheated metallic mold. The main part of the study was conducted on tensile testing at room temperature. The results show that although RE would cause grain refining to be about 30–40% through the constitutional undercooling mechanism, grain refining with TiB₂ would lead to approximately 90% refining (heterogenous nucleation mechanism). The addition of high purity Ce or La (99.9% purity) has no modification effect regardless of the alloy composition or the concentration of RE. Depending on the alloy ductility, the addition of 0.2 wt.%RE has a hardening effect that causes precipitation of RE in the form of dispersoids (300–700 nm). However, this increase vanishes with the decrease in alloy ductility, i.e., with T6 treatment, due to intensive precipitation of ultra-fine coherent Mg₂Si-phase particles. There is no definite distinction in the behavior of Ce or La in terms of their high affinity to interact with other transition elements in the matrix, particularly Ti, Fe, Cu, and Sr. When the melt was properly degassed using high-purity argon and filtered using a 20 ppi ceramic foam filter, prior to pouring the liquid metal into the mold sprue, no measurable number of RE oxides was observed. In conclusion, the application of RE to aluminum castings would only lead to formation of a significant volume fraction of brittle intermetallics. In Ti-free alloys, identification of Ce- or La-intermetallics is doubtful due to the fairly thin thickness of the precipitated platelets (about 1 µm) and the possibility that most of the reported Al, Si, and other elements make the reported values for RE rather ambiguous. Full article

Due to the lack of effective utilization, fly ash and red mud accumulate in large quantities and cause serious harm to the environment. In this experiment, a low-cost preparation of foamed ceramics was realized by applying the foaming agent addition method using fly ash and red mud. The results indicated that temperature and foaming agent content significantly affected the macrostructure, microstructure, crystalline phases, and properties of the foamed ceramics. Specifically, a formulation comprising 45 wt.% fly ash, 45 wt.% red mud, 10 wt.% clay, and 1 wt.% SiC (addition), sintered at 1210 °C, yielded a compressive strength of 8.2 MPa, a bulk density of 1.17 g/cm³, a water absorption rate of 32.05%, and an apparent porosity of 37.59%. The as-prepared materials demonstrate potential as cost-effective building materials, putting forward an effective approach for the high-value utilization of fly ash and red mud. Full article

In this study, in order to solve the problems of resource utilization of electrolytic manganese residue and the destruction of natural resources by the over-exploitation of raw materials of traditional ceramics, electrolytic manganese residue (EMR), red mud (RM), and waste soil (WS) were used to prepare self-foaming expanded ceramsite (SEC), and different firing temperatures and four groups with different mixing ratios of these three raw materials were considered. Water absorption, porosity, heavy metal ion leaching, and compressive strength in the cylinder of SEC were evaluated. The chemical composition and microscopic morphology of SEC were investigated by XRD and SEM. The mechanism behind the reaction among EMR, RM, and WS and self-foaming was discussed. The results showed that both the temperature and mixing ratio significantly influenced the basic performance of SEC. With the temperature lower than 1200 °C, sphere appearance could be maintained in all of these four groups; however, the density, porosity, and compressive strength in the cylinder seemed unacceptable. When the temperature rose up to 1220 °C, sphere appearance could be only found in the group whose mixing ratio of EMR, RM, and WS was 2:2.5:0.5. Under this condition, the excellent performance of SEC was observed, with a porosity of 46.7%, bulk density of 0.61 g/cm³, and 3 d compressive strength in a cylinder of 26.82 MPa. The mechanism behind the reaction among EMR, RM, and WS could be described: when the temperature is up to 1180 °C, an obvious chemical reaction took place, followed by the liquid phase being produced and the gas released by the decomposition of Fe₂O₃ in RM and gypsum in EMR. When the temperature is up to 1200 °C, the viscosity of the liquid phase and the rate of gas generation achieved the balance, and the liquid phase encapsulated the gas and anorthite (CaAl₂Si₂O₈) began to grow slowly. As time passed, self-foaming expanded ceramsite was prepared. The results of this study are of great significance in the field of artificial lightweight aggregate and industrial solid waste resource utilization. Full article

As a result of the conducted studies, the method of combining components and foaming parameters for obtaining foam epoxides has been selected. The relationship between the structure of the foam epoxide and the amount of the added blowing agent—ammonium carbonate—has been established. This study explores the development of fire-safe foamed epoxy composites by incorporating technogenic waste from ceramic brick production. The optimized composites demonstrated improved compressive strength, enhanced fire resistance (the LOI—35–44%—and successful UL-94 V-0 testing) through the use of flame retardants (Tris(2-methylphenyl) phosphate and Decabromodiphenyl oxide) and low thermal conductivity (0.030–0.042 W/m K), highlighting their potential as sustainable thermal insulation materials. Full article

This study explores the different techniques used to manufacture porous clay-based ceramics, examining their properties such as porosity, strength, permeability and filtration efficiency. Different techniques are discussed in this review, with additive manufacturing being one of the most innovative techniques for manufacturing porous ceramics. Porous ceramics have their applications in numerous domains. Such ceramic filters have the advantages of retaining heavy materials, suspended particles, bacteria, viruses and, water turbidity. Thus, the choice of the technique and propriety is a crucial step in obtaining a porous ceramic with the best performance. Barry et al. prepared porous phyllosilicate-based ceramics by freeze-tape casting on four samples and obtained porosity values in the range of 67–79% and diametrical compressive strength in the range of 3–7 MPa. Manni et al. prepared porous red ceramics from Moroccan clay and coffee waste (10, 20 and 30 wt.%) via uniaxial pressing and sintering at 1150 °C. They obtained porosities ranging from 30.2 to 63.8% and flexural strength values from 1.8 to 19.5 MPa. Medri et al. prepared ZrB2-based porous bodies with the use of sponges and polyurethane foams as templates via the replica method and obtained high porosity over 80% and compressive strength up to 4.8 MPa. The use of clay and peanut shell mixtures was used in preparing porous silicate ceramics after unidirectional pressing and sintering at 1100 °C. These samples included 25 mass% of peanut shells, and exhibited porosity in the range of 40 to 60% and diametrical compressive strength in the range of 1–6 MPa. Such properties are suitable for domestic use of these types of clay-based ceramic filters. Moreover, the permeability values and removal of some pollutants, like arsenic, have been satisfactory for the first set of samples. Full article

Recently, electromagnetic wave (EMW)-absorbing materials have obtained increasing attention for both military and civil applications. This study adopted the powder sintering method and the concept of recycled wastes in fabricating functional ceramic foam (CF). Firstly, a ceramic green body composed of pulverized granite residues, waste glass, and a foaming agent was sintered. The influence of the sintering temperature and SiC addition on CF was investigated, and then surface graphitization post-treatment of CF was performed as well. The truly enhanced compressive strength and EMW-absorbing property of surface graphitization ceramic foam (SG-CF) with a homogeneous porous structure was realized in the present work, which is promising as a candidate in EMW absorption systems. Full article