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Traditional high-temperature fabrication methods for ceramics suffer from significant energy consumption and limit the development of advanced ceramics incorporating temperature-sensitive materials. While bioinspired mineralization provides an effective strategy to realize the room-temperature preparation of ceramics, scaling up production remains a challenge. Herein, we demonstrate a room-temperature procedure for the fabrication of large-scale ceramics by using the carbonation reaction of sodium alginate (SA)-doped γ-dicalcium silicate (γ-C2S) compacts. This bioinspired in situmineralization process regulates molecular interactions and microscopic crystal alignment, resulting in the formation of CO2mineralized ceramics with specifically oriented mesocrystals and exceptional mechanical properties rivaling those of biological materials. Through this strategy, we demonstrate that the advanced ceramic composites with compressive strength approaching 300 MPa can be fabricated at a large scale, with the additional benefits of fixing about 200 kg of CO2per ton of CO2mineralized ceramics. Our innovative approach shows great potential for the efficient and cost-effective fabrication of large-scale and high-performance bioceramics, aligning with the goals of sustainable development involving reducing the energy consumption and achieving carbon neutrality.

Photocatalysts for seawater splitting are severely restricted because of the presence of multiple types of ions in seawater that cause corrosion and deactivation. As a result, new materials that promote adsorption of H+and hinder competing adsorption of metal cations should enhance utilization of photogenerated electrons on the catalyst surface for efficient H2production. One strategy to design advanced photocatalysts involves introduction of hierarchical porous structures that enable fast mass transfer and creation of defect sites that promote selective hydrogen ion adsorption. Herein, we used a facile calcination method to fabricate the macro–mesoporous C3N4derivative, VN-HCN, that contains multiple nitrogen vacancies. We demonstrated that VN-HCN has enhanced corrosion resistance and elevated photocatalytic H2production performance in seawater. Experimental results and theoretical calculations reveal that enhanced mass and carrier transfer and selective adsorption of hydrogen ions are key features of VN-HCN that lead to its high seawater splitting activity.

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This study investigates the preparation of ultra-high strength carbonated compacts from magnesium slag via accelerated carbonation under synergistic effects of degree of compaction (DC) and CO2partial pressure. Magnesium slag exhibited high potential for carbonation reactivity based on isothermal calorimetry, thermogravimetric analysis, and pH value measurements. The compressive strength of carbonated magnesium slag compacts depended strongly on DCand CO2partial pressure. At optimal conditions of DC62 % and CO2partial pressure 0.2 MPa, the compressive strength reached 252.3 MPa. The underlying mechanisms were revealed through analysis of CO2uptake, porosity, CaCO3content, and calcite particle size. Lower CO2partial pressure benefited carbonation of compacts with higher DCby enabling uniform carbonation product distribution. This research offers novel perspectives on the creation of exceptionally robust carbonated products utilizing solid waste via accelerated carbonation.

High-belite calcium sulfoaluminate cement (HBCSA) is a novel low-carbon cement, but the limited reactivity of belite (C2S) leads to gradual strength development. In this study, we developed an alite-belite-ferrite-ye'elimite cement (ABFY) incorporating C3S, and a high C4AF phase based on HBCSA. We explored the effects of CuO doping on the calcination and hydration properties of ABFY clinker. Various analytical techniques, including X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis and derivative thermogravimetry, and nuclear magnetic resonance, were employed to investigate the effects of CuO doping on the sintering and hydration properties of ABFY clinker. The results indicated that CuO doping preferentially enters the ferrite phase, promotes liquid phase formation, and enhances the sintering of the C3S and C4A3$ phases, thereby improving hydration activity. However, exceeding a CuO content of 0.5% results in the decomposition of C4A3$ into C12A7and the transformation of C3S into the M-type. Dissolved Cu during hydration combines with SO42‐, affecting the transformation and formation of AFm and AFt, resulting in deteriorated later-stage performance. ABFY with 0.5 % CuO exhibits favorable hydration activity.

β-Dicalcium silicates (β-C2S) exhibit excellent potential for reducing carbon emissions and energy consumption. However, their poor hydration activity leads to low early strength, limiting their large-scale application. Modulation of the hydration medium has been proven to be able to enhance the hydration activity, but the underlying reaction mechanism remains unclear. In this work, the hydration reaction kinetics, atomic structure, and electronic structures in β-C2S/H2O and β-C2S/Na-H2O systems are investigated by well-defined ab initiomolecular dynamics and well-tempered metadynamics. The results demonstrate that the sodium ion regulated the interface between the solid and liquid phases, influenced the process of surface hydroxylation, and formed a new dissolution mechanism of calcium. The importance of regulating the interfacial chemistry environment for the hydration reaction was found. This study provides theoretical guidance for further understanding of the early hydration reaction of β-C2S under hydration conditions in the presence of alkali metal ions.

•Ba doping has limited effect on the crystal form of γ-C2S.•Ba addition postpones the carbonation heat evolution.•Carbonation is suppressed initially but enhanced in the long run.•Crystal forms and morphology of calcium carbonates are changed.•Ion doping has the potential of carbonation activation and modification.

The purpose of this paper is to study the different strain distributions of CEAC (cement-emulsified asphalt concrete) pavement between the macro- and meso-scale, using a three-dimensional macroscopic finite element ANSYS model of pavement composed of hot mix asphalt (HMA), CEAC, and stone mastic asphalt (SMA). Applying digital image processing technology, the composition of the CEAC material at the meso-scale is identified as a three-phase material that includes cement-emulsified asphalt mastics, aggregates, and air voids. A two-dimensional mesoscopic finite element submodel measuring 80 × 80 mm was identified in a local region and built. Boundary conditions from the global CEAC pavement model were applied to the submodel. Eight control points in the CEAC submodel were selected for analysis. A comparison of the calculated strains of the CEAC local region at the macro- and meso-scales shows that the strain distributions at the meso-scale are not as uniform as those at the macro-scale. The extreme strain at the meso-scale is larger than that at the macro- scale. The reserve strength factors of mastic and aggregates of CEAC at the meso-scale are 31.82% and 49.07%, respectively, compared with 93.2% at the macro-scale. These values indicate that analyses at the macro- and meso-scales yield results that are not only different but can also have a significant effect on the potential failure mechanism of the CEAC component in the pavement.

The nitrate selectivity of TiO2has important consequences for its efficiency as a NOx depollution photocatalyst. Most emphasis is typically given to photocatalyst activity, a measure of the rate at which NOx concentrations are reduced, but a reduction in NOx concentration (mainly NO + NO2) is not necessarily a reduction in atmospheric NO2concentration because the catalytic process itself generates NO2. With NO2being considerably more toxic than NO, more emphasis on nitrate selectivity, a measure of the NOx conversion to nitrate, and how to maximize it, should be given in engineering photocatalytic systems for improved urban air quality. This study, on the importance of adsorbed water in the photocatalytic oxidation of NOx, has identified important correlations which differentiate the role that water plays in the oxidation of NO and NO2. This observation is significant and offers insights into controlling nitrate selectivity on TiO2and the potential for increased effectiveness in environmental photocatalyst applications.

ABSTRACTConductive ceramic composite was prepared by sintering the mixture of clay and printer toner at 1050°C and in the N2atmosphere. The microstructure and mineral phases of the ceramic composite were characterised by SEM, EDX, TG and XRD, and its electrical conductivity and mechanical properties were also investigated. The results show that, in the sintering process, a series of physical and chemical reactions take place, and mineral phases with excellent electrical conductivity, such as metal iron, carbon and Fe–Al solid solution material, are formed. The electrical conductivity mechanism can be explained by the percolation theory. The threshold value for electrical conductive percolation is between 3.5 and 7.0 wt-%. At the content of printer toner 10 wt-%, the volume electrical resistance of the ceramic composite is as low as 8.5 Ω cm, and the composite exhibits excellent flexural strength higher than 14 MPa.

Conductive ceramic composite was prepared by sintering the mixture of clay and printer toner at 1050°C and in the N2atmosphere. The microstructure and mineral phases of the ceramic composite were characterised by SEM, EDX, TG and XRD, and its electrical conductivity and mechanical properties were also investigated. The results show that, in the sintering process, a series of physical and chemical reactions take place, and mineral phases with excellent electrical conductivity, such as metal iron, carbon and Fe–Al solid solution material, are formed. The electrical conductivity mechanism can be explained by the percolation theory. The threshold value for electrical conductive percolation is between 3.5 and 7.0 wt-%. At the content of printer toner 10 wt-%, the volume electrical resistance of the ceramic composite is as low as 8.5 O cm, and the composite exhibits excellent flexural strength higher than 14 MPa.

A TiO2photocatalyst is coated on the surface of a zeolite fly ash bead (ZFAB) to improve its dispersability and exposure degree in a cement system. The application of Ag particles in TiO2/ZFAB modified cementitious materials is to further enhance the photocatalytic performance. Various Ag@TiO2/ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated. It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO2in a cement system and is also useful to enhance the photocatalytic efficiency. With an increment of the amounts of Ag particles in the TiO2/ZFAB modified cementitious samples, the photocatalytic activities increased first and then decreased. The optimal Ag@TiO2/ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene (9.91 × 10−3min−1), which is approximately 3 and 10 times higher than those of TiO2/ZFAB and TiO2modified samples, respectively. This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO2in a cement system. Thus, ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO2in the construction field.

The preferential adsorption of targeted contaminants on a photocatalyst surface is highly required to realize its photocatalytic selective decomposition in a complex system. To realize the tunable preferential adsorption, altering the surface charge or polarity property of photocatalysts has widely been reported. However, it is quite difficult for a modified photocatalyst to realize the simultaneously preferential adsorption for both cationic and anionic dyes. In this study, to realize the selective adsorption for both cationic and anionic dyes on a photocatalyst surface, the negative reduced graphene oxide (rGO) nanosheets and positive phenylamine (PhNH2) molecules are successfully loaded on the TiO2surface (PhNH2/rGO-TiO2) with spatially separated adsorption sites, where the negative rGO and positive PhNH2molecules work as the preferential adsorption sites for cationic and anionic dyes, respectively. It was interesting to find that although all the TiO2samples (including the naked TiO2, PhNH2/TiO2, rGO-TiO2, and PhNH2/rGO-TiO2) clearly showed a better adsorption performance for cationic dyes than anionic dyes, only the PhNH2/rGO-TiO2with spatially separated adsorption-active sites exhibited an opposite photocatalytic selectivity, namely, the naked TiO2, PhNH2/TiO2, and rGO-TiO2showed a preferential decomposition for cationic dyes, while the resultant PhNH2/rGO-TiO2exhibited an excellently selective decomposition for anionic dyes. In addition, the resultant PhNH2/rGO-TiO2photocatalyst not only realizes the tunable photocatalytic selectivity but also can completely and sequentially decompose the opposite cationic and anionic dyes.

Optimization of the electronic structure and surface physicochemical properties of PtNi nanoalloys by incorporation of sulfur (S) is an effective strategy for improving the efficiency of the electrocatalytic hydrogen evolution reaction (HER). However, few studies have been carried out to assess the seawater electrocatalytic performance of PtNi by incorporation of interfacial S from CdS nanocrystals. In this study, a simple method is developed to prepare CdS/PtNi, composed of a PtNi alloy supported with CdS quantum dots (QDs). Experimental data demonstrate that interfacial S-sensitization enhances the electron density of PtNi nanoalloy in CdS/PtNi. Therefore, CdS/PtNi exhibits superior performance toward HER in seawater. Specifically, CdS/PtNi displays a low overpotential of 22 mV at a current density of 10 mA cm–2, a higher specific activity of 24.7 mA cm–2at −0.07 V, and superior durability in seawater, all of which metrics exceed those of commercial Pt/C. Theoretical calculations provide additional evidence that interfacial S-sensitization of PtNi alloy raises electron densities, lowers the d-band center, facilitates water molecule adsorption, resistances to Cl–, and reduces the hydrogen adsorption Gibbs free energy of PtNi alloy. This study provides new opportunities for the design of efficient and stable electrocatalysts for large-scale production of hydrogen from seawater.

In this paper, printable γ-C2S slurries based on the carbonation of calcium silicate have been developed, and printability is demonstrated by the extrusion-based layer deposition. The γ-C2S with low hydraulicity and uncondensed silica fume (SF) are used to prepare the slurry at a water/solid (w/s) ratio of 0.24. The printable behavior is controlled by three rheology modifying agent (RMA), including sodium carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), and polyacrylamide (PAM). The compressive strength and inter-layer bonding strength of the printed sample are 109.3MPa and 4.9MPa, respectively, after pre-drying to a w/s of 0.08 and 12h carbonation under the CO2pressure of 3bar. The great mechanical property can be attributed to the diffusion of the carbonation reaction into the center of samples and the densification by the carbonation products. The printing-carbonation synergistic enhancement technique is proposed, where the printing process is carried out in a CO2atmosphere, the carbonation reaction improves the yield stress of freshly printed structure and enhances the stability of the whole printed sample. Based on this technique, it is expected to achieve the independent design of extrudability and build-ability of printable slurry and significantly expand the diversity of the geometrical design of 3D printing structures.

•Calcite seeds with controlled morphology are synthesized by biomineralization.•Calcite seeds are found to enhance carbonation reactivity of γ-C2S.•Crystalline form of calcium carbonate is regulated by calcite seeds.

The issues of chemical doping effects on cement clinker properties have long been investigated but are not fully understood. This work aims to provide an atomic-level understanding of the essential relations between clinker reactivity and its electronic structure and clarify the mechanism of doping effect on clinker reactivity. The Fukui functions reveal that zinc doping reduces the number of reactive sites and effective charges of silicate and aluminate phases dramatically, which accounts for the significant hydration retardation as observed in previous experiments. However, Zn doping scarcely changes the number of reactive sites but increases the effective charges and the total localization index of the ferrite phase due to the strong localization capacity of Fe 3dstates, which implies a slight reactivity promotion. The comprehensive and in-depth methodology demonstrated in this paper is significant to facilitate the innovation of cementitious materials with desirable properties.