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Tricalcium aluminate (Ca3Al2O6) is an indispensable component of Portland cement due to its high strength and reactivity. This study investigates the equilibrium lattice structure as well as the electronic and refractory properties of a newly discovered allotrope of Ca3Al2O6 using density functional theory and random phase approximation methods. Using density functional perturbation theory, we investigate the phonon dispersion of the refined structure's experimental stability. In addition, the lattice thermal conductivity and thermoelectric figure of merit are computed by solving the Boltzmann Transport Equation with the modified Debye Callaway model and the Relaxation time Approximation methods. The computed Figure of merit, determined by the carrier concentration, indicates a substantial enhancement of 40 to 100-fold, leading to a superior figure of merit of 0.25 and 0.6 when appropriately doped. As a result, we anticipate that stable allotropes of Ca3Al2O6 in the Pm3̄m phase will be useful as energy-harvesting, convective cooling and infrared radiation shield-based cement materials in the cement and concrete industries.

We measured the reflectivity of Portlandite fine powder across a frequency range of 0.36-15 microns. The results are a combination of two datasets: one measured by a portable spectrophotometer (410-Solar, Surface Optics Corp.) and the other by an FTIR spectrometer (Jasco 6300) with an integrated sphere (PIKE). We extracted the data using SolarData and SpectraManager software, then merged it with KaleidaGraph software. The final merged data were exported to a .txt file.

We measured the reflectivity of Portlandite fine powder across a frequency range of 0.36-15 microns. The results are a combination of two datasets: one measured by a portable spectrophotometer (410-Solar, Surface Optics Corp.) and the other by an FTIR spectrometer (Jasco 6300) with an integrated sphere (PIKE). We extracted the data using SolarData and SpectraManager software, then merged it with KaleidaGraph software. The final merged data were exported to a .txt file.

This dataset contains information of the behavior of temperature of single-junction solar cells with Ordinary Portland Cement radiative cooler., The OPC emissivity has been calculated with Transfer-Matrix-Method applied to a slab having roughness RMS and complex permittivity obtained by applying the effective medium theory of Slovick (Slovick, B. A. Negative Refractive Index Induced by Percolation in Disordered Metamaterials. Physical Review B 95, 094202 (2017)) to the OPC microstructure calculated with µic (https://micepfl.sourceforge.net/) and using the complex permittivity obtained by CSIC with GULP (https://gulp.curtin.edu.au/) for the homogeneous phases. This is described in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022). - The solar cell operating temperature when coupled to the OPC based radiative cooler has been obtained by means of the detailed-balance model commonly employed in the literature. This is discussed in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022).

We measured the reflectivity of White Cement paste fine powder across a frequency range of 0.36-15 microns. The results are a combination of two datasets: one measured by a portable spectrophotometer (410-Solar, Surface Optics Corp.) and the other by an FTIR spectrometer (Jasco 6300) with an integrated sphere (PIKE). We extracted the data using SolarData and SpectraManager software, then merged it with KaleidaGraph software. The final merged data were exported to a .txt file.

Dataset that includes the geometric characteristics (7) and the emissivity curve (110 points between 0-25um) of four vertically embedded alumnium fibers in CSH substrate.

Cementitious matrices are composed of Portlandite (CH) and a porous element, called C-S-H gel that resembles Tobermorite minerals. The dielectric response of Tobermorite has been calculated through Force Field simulations by using a software package called GULP (https://gulp.curtin.edu.au/). This datasets annexes the output of our FF simulation for Tobermorite , where the complex dielectric function of this minerals can be found. This dataset was used for the publication https://doi.org/10.1021/acsaom.3c00082.

Energy storage provides a greener path of efficient energy utilization. Recent trends of research suggest concrete as a potential thermal energy storage (TES) material. Its cheap commercial availability makes it one of the most deserving candidates. Cement paste is the key glue of concrete, hence performance of its major components in thermal conduction seeks thorough scientific study. Portlandite or calcium hydroxide is the second major component of cement paste, microscopically visible at a scale length of <10−4 m. Molecular dynamics (MD) simulation has been utilized to investigate the thermal transport mechanism of portlandite at an atomistic scale. The thermal conductivity of this component has been computed using three major force fields which are compared with the experimental outcome using modulated differential scanning calorimetry (MDSC). It has been observed that the simulation outcomes are in order with the experimental value but the results are sensitive to the choice of force fields. Excitation of molecules during thermal transport is predominantly governed by lower-frequency molecular vibration indicating the existence of Boson Peaks. This manuscript presents the full thermal conductivity tensor of portlandite along with the possible mechanism associated with thermal transport.

This paper addresses the challenge of modeling relaxation dynamics in quantum many-body systems, specifically focusing on electrons in graphene nanoflakes. While quantum many-body techniques effectively describe dynamics up to a few particles, these approaches become computationally intractable for large systems. Larger systems may be tackled with a single-particle approach that, however, struggles to incorporate relaxation effects. Existing relaxation models encounter issues such as an inability to capture system complexity and violation of the Pauli principle. In this paper, we propose a single-particle model that accounts for various relaxation effects at the crossroads of quantum optics and solid-state photonics, that overcomes the limitations of previous models. Our approach is rooted in the quantum-optical Lindblad model, where relaxation rates are deactivated once the target levels saturate due to the Pauli principle. This approach is referred to as the saturated-Lindblad model. To validate the predictions of the saturated-Lindblad model, we confront them against phenomenological and many-body physics models in low-dimensional systems, including atomic chains and graphene nanoflakes. Remarkably, the saturated-Lindblad model exhibits excellent agreement with few-body calculations, distinguishing itself from other existing approaches. Moreover, by assigning different relaxation rates to different transitions, we successfully reproduce cascade deexcitation dynamics and predict emission spectra. The saturated-Lindblad model offers the ability to describe dynamics in systems of practical sizes, encompassing a wide range of structures that can be effectively captured within the single-particle description.

The urban heat island effect has become a critical issue in urban areas, intensifying heat-related problems and increasing energy consumption. A sustainable cement formulation that combines ordinary Portland cement (OPC) with a carbonated aggregate derived from Periwinkle shell powder for the development of an efficient cool material is presented. Through a carbonation process, the aggregate undergoes a transformation, capturing carbon dioxide (CO2) and converting it into calcite. The resulting cement mixture exhibits high solar reflective properties, making it a potential candidate for cool pavement and roof applications. In this study, the raw materials, including the Periwinkle shell powder, were characterized, and the carbonation process was evaluated to quantify the CO2 capture efficiency. Additionally, a real test of the efficiency of this new cement on a roof demonstrated that the material achieved a significant cooling effect, being 6 °C cooler than that with standard OPC at the peak of solar radiation.

Layered minerals containing inter-layer water show directional anisotropy. In previous work, the authors have shown that this inter-layer water affects the mechanical performance of these minerals. Even though difference in thermal conductivity of minerals has been alluded to in experimental literature due to presence of water molecules within crystal, a detailed coordinated theoretical study has not been carried out. In this work, a molecular dynamics study has been presented on sulfates of calcium to demonstrate that thermal conductivity is indeed reduced with the presence of inter-layer water. The correlation between the vibration of different molecular groups to the thermal transport mechanism of the material has been investigated. It has been observed that vibration modes of H2O molecules have a negligible contribution to thermal transport eventually reducing thermal conductivity perpendicular to the water layer. Even though calcium sulfate has been chosen for this study, it can be anticipated that similar behaviors can be observed with other minerals in which inter-layer water is present. This study represents a detailed structure–property correlation in the thermal transport mechanism through layered minerals.

The scattering of light by resonant nanoparticles is a key process for enhancing the solar reflectance in daylight radiative cooling. Here, we investigate the impact of material dispersion on the scattering performance of popular nanoparticles for radiative cooling applications. We show that, due to material dispersion, nanoparticles with a qualitatively similar response at visible frequencies exhibit fundamentally different scattering properties at infrared frequencies. It is found that dispersive nanoparticles exhibit suppressed-scattering windows, allowing for selective thermal emission within a highly reflective sample. The existence of suppressed-scattering windows solely depends on material dispersion, and they appear pinned to the same wavelength even in random composite materials and periodic metasurfaces. Finally, we investigate calcium-silicate-hydrate (CSH), the main phase of concrete, as an example of a dispersive host, illustrating that the co-design of nanoparticles and host allows for tuning of the suppressed-scattering windows. Our results indicate that controlled nanoporosities would enable concrete with daylight passive radiative cooling capabilities.

Time-dependent density functional theory (TDDFT) has established itself as a computationally efficient and effective alternative to the many-body perturbation theory for calculating the optical properties of solids. Within the framework of linear response formalism, TDDFT exhibits good agreement between optical absorption spectra and experimental data, as well as the possibility of directly determining exciton binding energies. However, the family of exchange-correlation kernels, known as long-range-corrected kernels, which accurately capture excitonic features, face challenges in simultaneously generating visually appealing spectra and precise exciton binding energies. Recently, progress has been made in addressing this discrepancy through a hybrid-TDDFT approach. Our study reveals that the key lies in the numerical treatment of the long-range Coulomb singular term. We conduct a meticulous investigation of the impact of the term in both pure-TDDFT and hybrid approaches using a Wigner-Seitz truncated kernel. Notably, we show that computing this term presents formidable technical difficulties in both approaches, pointing to the need for an improved description of the electron-hole interaction.

Iron ilmenene is a new two-dimensional material that has recently been exfoliated from the naturally occurring iron titanate found in ilmenite ore, a material that is abundant on the earth's surface. In this work, we theoretically investigate the structural, electronic and magnetic properties of 2D transition-metal-based ilmenene-like titanates. The study of magnetic order reveals that these ilmenenes usually present intrinsic antiferromagnetic coupling between the 3d magnetic metals decorating both sides of the Ti–O layer. Furthermore, the ilmenenes based on late 3d brass metals, such as CuTiO3 and ZnTiO3, become ferromagnetic and spin compensated, respectively. Our calculations which include spin–orbit coupling reveal that the magnetic ilmenenes have large magnetocrystalline anisotropy energies when the 3d shell departs from being either filled or half-filled, with their spin orientation being out-of-plane for elements below half-filling of 3d states and in-plane above. These interesting magnetic properties of ilmenenes make them useful for future spintronic applications because they could be synthesized as already realized in the iron case.

The usage of conventional air-conditioners increased due to global warming and the urban heat-island-effect in cities. These systems are responsible for 7% of global greenhouse gas emissions and 10% of the total energy consumption. Radiative Cooling is a passive cooling strategy which tries to mitigate global warming and the urban heat-island-effect by emitting heat through the atmosphere, into outer space. These materials are already studied for several decades, but for the first time a radiative cooling material is under development based on conventional concrete. In order to evaluate the environmental performance of this newly developed material compared to existing cooling materials, environmental benchmarks need to be defined. To determine such benchmark, existing, state of the art, daytime radiative cooling materials are assessed in this paper. Information on these materials is collected through a literature review. The radiative cooling materials are modelled using the generic Ecoinvent v3.6 database and the environmental impact is assessed using the Belgian LCA method for buildings, i.e. the MMG method. This method is in line with the EN15804:A2 and covers 16 environmental impact categories, such as global warming potential, acidification, eutrophication, water scarcity and toxicity. The results show that the production process of the materials, i.e. thin film deposition techniques, are poorly represented in the Ecoinvent database. Assumptions and adaptations are made based on literature and experts' feedback. A sensitivity analysis is carried out to gain insight in the uncertainty of the assumptions made. Based on the results, preliminary environmental benchmarks are generated and the environmental impact of the first composition of the photonic meta-concrete is assessed against these benchmarks.

Lowering the operating temperature of solar cells can increase efficiency and lifespan of these devices. Among the available thermal management options, radiative cooling shines because of its passive nature and systemic simplicity. Unfortunately, the applicability of most radiative coolers to industrial manufacturing is questioned by high cost or UV instability. We have recently shown that stable and cost-effective cement-based materials can be designed to be suitable radiative coolers for solar cells. However, we have done so in line with the literature, by modeling the solar cell in the radiative limit and neglecting the thermal contact resistance at the cell/cooler interface, which might actually be large enough to hinder heat transfer because of the poor adhesion properties of cement-based materials. In this work, we have generalized the model used to assess radiative coolers by incorporating solar cell non-radiative losses (Auger, Shockley-Read-Hall) and a thermal barrier between cell and cooler. The final model provides a description of the thermal behavior of a solar cell with radiative cooler closer to reality, while preserving the transparency of the detailed-balance approach, that has allowed us to better assess these systems and provide design guidelines, with focus on cement-based radiative coolers.

Reducing the temperature of a solar cell increases its efficiency and lifetime. This can be achieved by radiative cooling, a passive and simple method relying on materials that dump heat into outer space by thermal emission within the atmosphere transparency window between 8 and (Formula presented.). As most radiative coolers are expensive or possibly UV unstable, we have recently proposed cement-based solutions as a robust and cost-effective alternative. However, the assessment model used describes the cell in the radiative limit and with perfect thermal coupling to the cooler, in line with the literature. In this work, we lift these two approximations, by incorporating Auger and Shockley–Read–Hall nonradiative recombination and a finite heat transfer coefficient at the cell/cooler interface, to obtain a thermal description of the cell/cooler stack closer to reality, while preserving the universality and transparency of the detailed-balance approach. We use this model to demonstrate that the cell performance gains provided by a radiative cooler are underestimated in the radiative limit and are hence more prominent in devices with stronger nonradiative recombination. Furthermore, we quantify the relation between cell temperature and heat transfer coefficient at the cell/cooler interface and show how this can be used to define design requirements. The extended model developed, and the resulting observations provide important guidelines toward the practical realization of novel radiative coolers for solar cells, including cement-based ones.

Although concrete and cement-based materials are the most engineered materials employed by mankind, their potential for use in daytime radiative cooling applications has yet to be fully explored. Due to its complex structure, which is composed of multiple phases and textural details, fine-tuning of concrete is impossible without first analyzing its most important ingredients. Here, the radiative cooling properties of Portlandite (Ca(OH)2) and Tobermorite (Ca5Si6O16(OH)2·4H2O) are studied due to their crucial relevance in cement and concrete science and technology. Our findings demonstrate that, in contrast to concrete (which is a strong infrared emitter but a poor sun reflector), both Portlandite and Tobermorite exhibit good radiative cooling capabilities. These results provide solid evidence that, with the correct optimization of composition and porosity, concrete can be transformed into a material suitable for daytime radiative cooling.

Graphene-based materials are considered excellent candidates to implement cementitious nanocomposites due to their mechanical properties. This paper presents a comprehensive interface interaction that ends up with computing the elastic properties for four models of the C–S–H gel, taking tobermorite 14 Å as an example, with reduced graphene oxide (rGO) to form reinforced (tobermorite) cementitious nanocomposites within the density functional theory. We found that upon relaxing the model structures, the dissociation of hydroxyl functional groups from the hydroxyl/rGO lattice occurs not only in the presence of Ca2+ ions to compensate for local charges but even when the Ca2+ charges are compensated with hydroxyl groups. In contrast, rGO/CSH interactions remained close to the initial structural models of the epoxy rGO surface. The elastic constants showed high improvements for the cementitious nanocomposite of tobermorite 14 Å with intercalated hydroxyl/rGO layers. Thus, the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio increased up to limits set as 165, 128, 134, and 15% compared to tobermorite 14 Å, respectively. In more detail, the specific values of the elastic constants were influenced by the interface, specifically the presence of hydroxyl or epoxy groups as well as how the charges of the Ca2+ ions were compensated. These findings are of interest for the design of future experiments that will help to engineer better rGO/cement composites.

In the overall aim to reduce the heat-island-effect in cities and the related use of conventional air-conditioners, which now account for 7% of global greenhouse gas emissions and 10% of the total energy consumption, a Photonic Meta-Concrete (PMC) is currently being developed. This "MIRACLE" concrete is designed to contain remarkable photonic properties to make daytime radiative cooling possible. With these characteristics, the PMC can be used to fight global warming, reduce the CO2 footprint and mitigate the heat-island-effect. This paper describes the principal working of the new PMC and presents the first results of the development. In the first stage, the most appropriate composition of the concrete mixture is searched for. This is done by trying to develop a mixture with the desired photonic properties, a high emissivity in the Atmospheric Window (AW) and a high reflectivity to minimize solar gains. A range of composites are tested and compared within this step. Secondly, an environmental impact assessment (EIA) study is performed along the development of the PMC in order to support decision taking. The resources and energy needed to create the concrete mixture are analysed from cradle-to-gate and a comparison with conventional concrete is made to investigate the impact of this new material. This EIA study is performed according to the EC PEF (Product Environmental Footprint) method, a broad set of indicators are assessed, including climate change. Considering such a large set of indicators ensures that burden shifting is avoided.

A cement-based device that can meet, partially or completely, the heating loads of a building by absorbing the solar radiation and converting it into thermal energy can be defined as a Massive Solar-Thermal Collector. The absorbing material for the incoming radiation is made of a cementitious composite, generally concrete, and flowing water inside tubes acts as a heat transfer medium. For an optimized performance, during periods of solar radiation, the device has to efficiently conduct the heat flow from the absorbing surface of the collector and transfer this heat energy to the water. Then, when the radiation is reduced or became null, the device should retain as much as possible the heat energy, reducing the heat that is escaping the collector and consequently the losses to the surrounding environment. In this work, by performing a parametric analysis, different absorbing materials are tested with the objective of finding the best configuration that maximizes the energy efficiency of the collector. Cementitious materials, in combination with Phase Change Materials with distinct melting (and solidification) temperatures, are selected as candidate absorbing materials. The weather variables of an entire year and for two different locations are considered to evaluate the behavior of these devices in opposite climates. After numerical simulations, in where an enthalpy-based finite element formulation is used to solve the physical problem, the obtained results allow to conclude that the inclusion of Phase Change Materials within the absorber material of the collectors, if it is done in a correct way, can improve the energy performance of these devices. In this study, 34 °C and 53 °C are chosen as the most appropriated melting temperatures, which conduct to considerable improvements in the achieved performances, and in both warm and cold climates.

Nowadays, radiative coolers are extensively investigated for the thermal management of solar cells with the aim of improving their performance and lifetime. Current solutions rely on meta-materials with scarce elements or complex fabrication processes, or organic polymers possibly affected by UV degradation. Here, the potential of innovative cement-based solutions as a more sustainable and cost-effective alternative is reported. By combining chemical kinetics, molecular mechanics and electromagnetic simulations, it is shown that the most common cements, i.e., Portland cements, can be equipped with excellent radiative cooling properties, which might enable a reduction of the operating temperature of solar cells by up to 20 K, with outstanding efficiency and lifetime gains. This study represents a first step toward the realization of a novel class of energy-efficient, economically viable and robust radiative coolers, based on cheap and available cementitious materials.

Two periodic structures composed of metal cylinders with different orientations are used to improve the solar reflection of calcium silicate hydrate (CSH) while maintaining its atmospheric emission. Interesting effects have been found when the distance between bars is small, suggesting that lattice effects, arising from the interaction between the rods could be leveraged in the design of these metamaterials. The size of the metal bars is selected based on state of the art micro-manufacturing techniques. This study limits its scope to a CSH gel model; i.e. the most important component of cement-based materials. Further research will be undertaken to consider a best description of the dielectric function of concrete.

The cooling demand in buildings has increased over the past decades due to global warming, the heat-island-effect in cities and the increased airtightness and thermal resistance of the building envelope. This led to an increased use of conventional air-conditioners, which now account for 7% of global greenhouse gas emissions and 10% of the total energy consumption. In this context, the MIRACLE project aims at developing a new Photonic Meta-Concrete (PMC) with remarkable photonic properties to reduce the CO2 footprint of buildings, mitigate the heat-island-effect and global warming. Besides the positive effect that this innovative material can have on the environment during the use phase of buildings, also the environmental impact of the production needs to be minimized. Environmental impact assessment (EIA) is used along the development process of this innovative material to guarantee a low material environmental impact. This paper discusses how EIA is used along the development process and presents the preliminary results in the early stages of the development of the PMC. To investigate the impact of this new material, a cradle-to-gate analysis of the resources, energy and machinery needed to create the concrete mixture is performed. The broad set of environmental indicators of the EC PEF (Product Environmental Footprint) method, such as climate change, acidification, eutrophication, particulate matter, ecotoxicity, water depletion and human toxicity are being considered. Considering such a large set of indications ensures that burden shifting is avoided. The environmental impact of the PMC is moreover compared to the impact of conventional concrete to understand how both perform.

Global warming and the heat-island-effect in cities led to an increased use of conventional air-conditioners. This increased usage is responsible for 10% of the total energy consumption and 7% of global greenhouse gas emissions. In the overall aim to reduce these greenhouse gas emissions and to mitigate climate change and the heat-island-effect, a new radiative cooling material is under development. Although radiative cooling materials already exist, this material stands out because, for the first time, it is based on conventional concrete. This poster describes the first step of the environmental life cycle assessment (LCA) study that is performed along the development of the photonic meta-concrete (PMC). In this step we generate a database with environmental data of existing radiative cooling materials in order to create a comparative base for the PMC. Information about the various materials is collected through a literature review and consultation of experts. The environmental impact of the materials are assessed with the Belgian LCA method for buildings, i.e. the MMG method. The MMG method is in line with the EN15804:A2 and hence covers 16 environmental impact categories, such as global warming potential, acidification, eutrophication, water scarcity, toxicity. Furthermore, the environmental impact will be compared with the first composition of the photonic meta-concrete. The first results show that a lot of product-specific information regarding radiative cooling materials is lacking to date to assess their environmental impact and this makes it challenging to create a reference database. However, the environmental impact of the radiative cooling materials assessed in this paper is in line with the expectations. The first mixture of the photonic meta-concrete is promising as this shows great potential from an environmental point of view compared to the existing daytime radiative cooling materials.

In this work, a study of the viability of using concrete for radiative cooling is done by theoretically analysing some of the main compounds of concrete: C3S, CH and CSH. Atomistic simulations have been employed for determining the structure and the dielectric response of these phases. Interestingly, the materials have theoretically shown a night-time net cooling power of 55.68 W, 60.96 W and 62.43 W respectively. This preliminary study shows the potential of concrete as a possible cheap, scalable and widely used night-time radiative cooling structural material. Further research must be done in order to achieve a higher reflection in the solar band for day-time radiative cooling. To calculate de emissivity of the compounds, an analytical model has been used, which has nearly zero error and computes the data much faster than a simulator.