In situ resource utilization (ISRU) and in situ fabrication and repair (ISFR) are critical research and technological paradigms for future space exploration. They aim to reduce reliance on Earth-supplied materials by utilizing resources available on celestial bodies, while enabling on-site fabrication and repair through the use and processing of local resources. ISRU and ISFR are strongly interconnected, with the shared objective of enabling more sustainable and autonomous long-duration missions to the Moon, Mars, and beyond. This work presents a comprehensive and critical review of scientific and patent literature published primarily between 2010 and 2025, complemented by selected earlier seminal contributions for context. The analysis provides an integrated perspective on major technological developments, key challenges, and emerging research directions in low-gravity and microgravity environments.

Synthetic dyes from industrial effluents are persistent pollutants requiring sustainable removal strategies. This study investigates the visible-light photocatalytic degradation of Brilliant Blue R using biogenic silver nanoparticles synthesized from microalgal extracts (Spirulina platensis and Chlorella vulgaris), reporting both experimental results and a hybrid modeling approach. Experimental analyses confirmed the effectiveness of the synthesized nanoparticles and their favorable physicochemical properties for photocatalytic applications. A simplified mechanistic model describing adsorption–desorption and degradation kinetics was developed to estimate key parameters, which were subsequently used to train artificial neural networks linking operating conditions to degradation performance. To address limited datasets, a Gaussian-noise-based augmentation strategy was introduced, significantly improving predictive accuracy. The proposed framework integrates experimental evidence with mechanistic and data-driven modeling, providing a reliable tool for optimizing sustainable photocatalytic processes based on microalgae-derived nanomaterials.

The growing demand for sustainable water treatment technologies requires photocatalyststhat combine low environmental impact, energy efficiency, and mechanistic robustness. Inthis work,Ag/Znnanocomposites were green-synthesized usingChlorella vulgarispolarextract as a bio-mediated reducing and stabilizing agent, eliminating hazardous reagentsand high-energy processing steps. Structural characterization (XRD, FTIR, SEM, UV-Vis)confirmed the coexistence of crystalline wurtziteZnOwith metallicAgand Ag2O phases.Photocatalytic activity was evaluated through Congo Red degradation under a sequentialdark-light protocol, enabling clear separation of adsorption and photoactivated pathways.During the60mindark stage, removal remained limited (similar to 9-11%), consistent withadsorption-desorption equilibration. Upon UV irradiation, a distinct kinetic transitionoccurred, leading to final removal efficiencies of44-49%after180min. Notably, perfor-mance remained stable across the investigated photon flux range, indicating operationbeyond a strictly photon-limited regime and highlighting an intrinsically energy-resilientcatalytic response. A mechanistic kinetic model integrating reversible adsorption with light-dependent degradation accurately reproduced all experimental profiles (N RMSE=3.14%)and successfully predicted an independent dark-control experiment without additionalfitting. By coupling green synthesis with quantitative kinetic validation, this study proposesa sustainability-oriented framework for designing photocatalysts that align low-impactfabrication with energy-conscious water remediation.

The development of packaging materials derived from renewable resources presents a sustainable alternative to conventional petroleum-based plastics. This study focuses on the fabrication and comprehensive characterization of fully bio-based composite films made of corn starch, microcrystalline cellulose (MCC), and rosin. Systematic analysis using thermal (TGA, DSC), structural (XRD, FTIR), and morphological (SEM) techniques revealed that MCC significantly enhanced the crystallinity of the films -increasing from 28.65% to 40.13% through the formation of inter- and intra-molecular interactions, thereby reinforcing the composite matrix and enhancing the thermal stability. An MCC content of 10 wt% was found to optimally balance hydrophobicity and water vapor barrier properties in the starch-rosin films. The composites demonstrated superior biodegradability compared to both low-density polyethylene (LDPE) and native starch films. Furthermore, rheological (i.e. creep-recovery) and tensile tests indicated that a 20 wt% MCC loading yielded the best creep resistance, recovery performance and tensile strength, achieving an ideal equilibrium of flexibility (imparted by 5 wt% rosin and glycerol), mechanical strength, and structural integrity. Finally, meat preserving tests showed promising results in food storage applications. These results underscore the significant potential of Starch-MCC-Rosin composites as eco-friendly food packaging materials with customizable functional properties.

The development of multicomponent diborides is driven by the expectation that combining different transition metals within the AlB2-type structure may yield properties superior to those of the individual constituents. In this framework, the fabrication and oxidation resistance of Zr-Hf-Ta equiatomic diborides are systematically investigated in this work to demonstrate synergistic effects and possible benefits arising when moving from unary to ternary systems. All materials are synthesized through a combined self-propagating high-temperature synthesis (SHS) and spark plasma sintering (SPS) approach, producing dense single-phase diborides except for (Hf0.5Ta0.5)B2, which retained similar to 6.3 wt.% of a Ta-rich secondary phase. Oxidation tests show that the behavior of such ceramics strongly depends on the specific oxide phases formed during their exposure. Higher protection is obtained when the scale is dominated by stable, single-phase, oxides such as HfO2 and A6Ta2O17 (A = Zr, Hf), while the formation of detrimental oxides (ZrO2, Ta2O5, TaO2) is minimized. In particular, when the complex A6Ta2O17 phase becomes the predominant oxidation product, as observed for the (Zr1/3Hf1/3Ta1/3)B2 composition, the resulting oxide scale is compact, stable, and significantly more resistant to oxygen transport. The critical role of compositional design in enabling synergistic oxidation behavior is discussed.

In-situ exploitation of Martian resources to obtain products and services is crucial for promoting future manned missions on the planet. Along this line, the JSC-Mars-1A, and MMS regolith simulants which are representative of the wide spectrum of soils available on the Mars surface, are investigated in detail to evaluate their possible utilization for solar energy applications, when used either in powder form or after being consolidated by Spark Plasma Sintering (SPS). The markedly different densification behavior shown by the two simulants can be associated with their diverse compositional and structural characteristics, with the predominant amorphous constituent (about 50 wt%) in original JSC-Mars-1A observed to strongly favor powder consolidation. For this system, fully dense samples were obtained by SPS at 1000 degrees C/3min/30 MPa. Concurrently, the amorphous fraction was reduced to 16 wt%. In contrast, the highly crystalline nature of MMS (70 wt% of Andesine, only 3 wt % of the amorphous content) makes this simulant more thermally stable and less prone to be consolidated, with 97.5% dense samples produced by SPS at 1050 degrees C/3min/30 MPa. To assess the samples' solar absorption and thermal radiation properties, optical spectra of both simulants in the range from 0.2 to 16 mu m wavelength were compared by considering pristine powders and bulk samples with different porosity and roughness characteristics. We found a significantly increased solar absorptance in the sintered samples with respect to the starting powders, even reaching the remarkable value of 0.93. The thermal emittance of ceramics was lower than that of powders for temperatures below about 300K, and superior for higher temperatures. These results have been discussed regarding the possible application of solar energy harvesting and thermal energy storage.

A green procedure involving metabolites of the microalga Haematococcus pluvialis is proposed to synthesize silver nanoparticles (Ag NPs) capable of removing the polluting dye brilliant blue R (BBR) from water. The X-ray diffraction (XRD) analysis revealed the crystalline nature of the product with Ag2O and Ag phases with a crystallite size of 14.27 nm. Fourier Transform Infrared Spectroscopy (FTIR) showed abundant functional groups from the extract on Ag NPs. Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Thermogravimetric (TGA) analyses further corroborated the involvement of microalgal metabolites from the extract. Experiments were performed to assess BBR removal under different conditions, including varying light intensities, concentration of Ag NPs and BBR, and pH levels. Removal efficiency close to 70 % was achieved under visible light and using specific operating conditions. A novel mathematical model considering both BBR adsorption on the Ag NPs surface and its photocatalytic reaction dynamics was also developed. Simulation results were successfully compared with experimental data, thus demonstrating the reliability of the proposed model. Model results also suggest that, under the investigated conditions, the main mechanism underlying the BBR removal is adsorption rather than photocatalysis. Based on the model and experimental data, it was found that enhancing photocatalytic degradation would likely require more energetic light, prompting further research into optimizing light sources for better efficiency and sustainability.

The availability of efficient manufacturing techniques to produce highly resistant structural components from Mars regolith represents a key target for accelerating future colonization of this planet. In this regard, the fabrication and mechanical characterization of nearly full dense samples is investigated in this work using additive-free JSC-Mars-1A, MMS, MGS-1, and JEZ-1 regolith simulants. These systems, which have been developed to reliably mimic compositional and structural characteristics of different soils actually present on the red planet, show a diverse consolidation behavior when processed by Spark Plasma Sintering (SPS) under vacuum. Fully dense and rather homogeneous samples are produced at 1000 degrees C from JSC-Mars-1A, originally containing a dominant amorphous fraction, which acts as a sintering aid. Superior mechanical performances, with respect to the other simulants, are displayed by the corresponding bulk material with compressive strength, flexural strength, and hardness values equal to about 310 MPa, 70 MPa, and 1000 HV, respectively. The properties of samples originated from MMS, MGS-1, and JEZ-1, mostly consisting of crystalline phases (>90 wt%), are negatively affected by porosity remaining after SPS (up to 5 vol%), even if higher temperatures are used (1050-1100 degrees C). Nonetheless, hardness, compressive and flexural strengths in the latter materials are still generally better than values reported in literature. It is then apparent that SPS technology represents a powerful tool for producing resistant building components from Mars soil, with no need of sintering aids.

Controlling the selectivity of CO2 hydrogenation to produce value-added fuels and chemicals is an actual challenge in catalysis research. The exact mechanisms underlying selectivity control often remain poorly understood, slowing the design of more efficient catalysts. In this study, we investigated RuO2 nanoparticles supported on MXene or TiO2 for CO2 hydrogenation at atmospheric pressure. Microalgal extracts were incorporated in the synthesis to explore their influence on catalyst properties, such as surface area, morphology, and elemental distribution. Although lower surface area and less uniform RuO2 dispersion were observed on MXenes than on TiO2, after reductive pretreatment Ru/MXene exhibited superior catalytic activity, demonstrating that its unique textural properties and active site availability compensated for the lower surface area. A reducibility study revealed that MXene-supported catalysts undergo a more complex reduction process than those with TiO2 as the support. Additionally, bridge adsorption sites on MXene likely contributed to the enhanced CO2 hydrogenation activity, whereas TiO2 seemed to present a twin CO binding environment. Higher Ru loading on MXene increased the methane selectivity and conversion, whereas lower loading favored CO formation, highlighting the importance of optimizing catalyst loading. Operando diffuse reflectance infrared Fourier transform spectroscopy analysis revealed the critical role of methoxy intermediates in affecting the catalytic pathway, suggesting the potential for tuning synthesis conditions to improve yields. A partial encapsulation of Ru on MXene enhances the catalytic performance, while the stronger SMSI effect on TiO2 leads to complete encapsulation, reducing the catalytic efficiency. The findings underscore the promise of MXene as a support material for metal catalysts in CO2 hydrogenation toward environmentally friendly fuel production.

In the original publication [...].

The development of efficient photocatalysts is crucial in addressing water pollution concerns, specifically in the removal of organic dyes from wastewater. In this context, the use of silver nanoparticles (Ag NPs) might represent a method to achieve high dye degradation efficiencies. On the other hand, the classical Ag NP production process involves several reactants and operating conditions, which make it poorly sustainable. In the present work, Ag NPs were synthesized according to a new sustainable process involving the use of natural extracts of Spirulina platensis and milder operating conditions. The material was also calcined to determine the influence of organic content on the properties of Ag NPs. The X-ray diffraction (XRD) analysis displayed the AgCl and Ag phases with a crystalline size of 11.79 nm before calcination. After calcination, only the Ag phase was present with an increased crystalline size of 24.60 nm. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the capping role of the metabolites from the extract. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed the spherical or quasi-spherical morphologies with agglomeration due to the calcination. Energy-dispersive X-ray spectroscopy (EDX) and Thermogravimetric (TGA) analyses further confirmed the involvement of metabolites in the synthesis of Ag NPs. The optical changes in the products were observed in a UV-Vis analysis. The Ag NPs were tested for their photocatalytic activity against the laboratory dye brilliant blue r in visible light in various conditions. The highest degradation efficiency of 81.9%, with a kapp value of 0.00595 min−1, was observed in alkaline medium after 90 min of light irradiation.

Synthesis of silver nanoparticles (Ag NPs) using microalgae is gaining recognition for its environmentally friendly and cost-effective nature while maintaining high activity of NPs. In the present study, Ag NPs were synthesized using a methanolic extract of Chlorella vulgaris and subjected to calcination. The X-ray diffraction (XRD) analysis showed a crystalline nature of the products with Ag2O and Ag phases with an average crystalline size of 16.07 nm before calcination and an Ag phase with 24.61 nm crystalline size after calcination. Fourier transform infrared spectroscopy (FTIR) revealed the capping functional groups on Ag NPs, while scanning electron microscopy (SEM) displayed their irregular morphology and agglomeration after calcination. The organic coating was examined by energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric (TGA) analyses, confirming the involvement of the metabolites. The UV–Vis analysis showed a difference in optical properties due to calcination. Synthesized Ag NPs were applied for the photodegradation of hazardous dye Brilliant Blue R in visible light. Different values of light intensity, catalyst dose, initial dye concentration, and pH were tested to identify the optimal set of operating conditions. The highest degradation efficiency of 90.6

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS–SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf0.2Mo0.2Ti0.2Ta0.2Nb0.2)B2–SiC and (Hf0.2Mo0.2Ti0.2Ta0.2Zr0.2)B2–SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B4C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m1/2) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO3 formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS–SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed.

The long-term solution to problems like overcrowding, fossil fuel depletion, climate change, and decreasing natural resource availability could be overcome through space colonization and human presence in space, as well as the exploitation of extraterrestrial natural resources. In keeping with this, the objective of this work is to analyze current advancements in technology development for deep space exploration and colonization made by our research team as well as by other organizations with which we are collaborating. First, a method for producing tangible goods suited for industrial or civil installations on the Moon, Mars, or asteroids, using in situ available regolith as the main resource, is discussed. In this regard, a new process based on the occurrence of self-propagating high-temperature synthesis (SHS) reactions was developed for the fabrication of composite ceramics to be used as construction materials. A theoretical analysis of the process using proper dimensionless numbers is also described to offer potential explanations of the key experimental evidences presented in the relevant literature. For instance, it is found that free convection likely plays a crucial role to make SHS front velocity higher under terrestrial conditions when the reaction ignition is carried out from the bottom side, instead of the top side, of reacting mixture. Next, a method that uses the atmosphere and regolith of Mars as raw feedstock to produce in situ useful material such as oxygen, water, food, fuels and fertilizers, is considered. In the next section, the potential for cultivating Spirulina platensis to provide nourishment for the Martian crew is examined. The possible use of sintered lunar regolith simulants such as JSC-1A is also considered for potential thermal energy storage and solar energy harvesting applications, within the context of resource exploitation. Sintered regolith simulant exhibited, compared to the native material in powder form, superior solar absorptance, which makes it suitable for sunlight absorbers in architectures with a cavity-like solar receiver. Finally, a new study is reported which combines biochemical and biophysical approaches in order to compare, under simulated microgravity and under terrestrial conditions, the functioning and structure of red blood cells, over various intervals of time.

Nanoporous (NP) metals represent a unique class of materials with promising properties for a wide set of applications in advanced technology, from catalysis and sensing to lightweight structural materials. However, they typically suffer from low thermal stability, which results in a coarsening behavior not yet fully understood. In this work, we focused precisely on the coarsening process undergone by NP Au, starting from the analysis of data available in the literature and addressing specific issues with suitably designed experiments. We observe that annealing more easily induces densification in systems with short characteristic lengths. The NP Au structures obtained by dealloying of mechanically alloyed AuAg precursors exhibit lower thermal stability than several NP Au samples discussed in the literature. Similarly, NP Au samples prepared by annealing the precursor alloy before dealloying display enhanced resistance to coarsening. We suggest that the microstructure of the precursor alloy, and, in particular, the grain size of the metal phases, can significantly affect the thermal stability of the NP metal. Specifically, the smaller the grain size of the parent alloy, the lower the thermal stability.

To satisfy the essential needs, including energy requirements, for human and robotic space explorations on planetary objects like Moon, Mars and asteroids, the proper exploitation of resources available in-situ represents a crucial issue. Along this line, the present work investigates the potential of a sintered lunar regolith simulant (JSC-1A) for possible solar energy harvesting and thermal energy storage applications. Regolith simulant powders are first consolidated by Spark Plasma Sintering (SPS) at 700 and 900 degrees C to produce bulk samples with different relative densities, i.e. 86 and 98%, respectively, and surface porosities. Negligible changes from the compositional point of view are induced by SPS at 700 degrees C, whereas a decrease of the original glassy phase content is observed when operating at 900 degrees C. The optical properties of sintered samples and pristine regolith powders are compared, considering the spectral absorptance/emittance, the integrated solar absorptance and the integrated thermal emittance estimated in a temperature range representative for the ISRU application, i.e. from 100 to 1300 K. We found that sintering changes the optical properties of regolith in a process-dependent way, with an increased solar absorptance and thermal emittance shown by sintered pellets with respect to pristine powders.

The direct synthesis and consolidation by SPS (1950 degrees C, 20 min, 20 MPa) of high-entropy (Hf0.2Mo0.2Zr0.2Nb0.2Ti0.2)B-2 from elemental powders resulted in a multiphase product. An increase of the heating rate determined a change of the mechanism governing the synthesis reaction from gradual solid-state diffusion to rapid combustion regime, while the final conversion degree was 67 wt.%. The sintered product displayed a non-uniform microstructure with the presence of 10-15 mu m sized pores, due to volatilization phenomena occurring during the combustion synthesis reaction. In contrast, when the SPS process was preceded by powder synthesis via SHS, a homogeneous single-phase ceramic was obtained. Clear benefits are derived by the use of SHS, able to provide very shortly powders with elemental species very well intermixed, so that the obtainment of (Hf0.2Mo0.2Zr0.2Nb0.2Ti0.2)B-2 during the subsequent SPS stage is strongly promoted. The resulting 92.5% dense product shows superior oxidation resistance with respect to individual borides prepared with the same method.

The introduction of 0.5-1.0 wt.% graphite to the powders prepared by Self-propagating High-temperature Synthesis (SHS) is found to be highly beneficial for the removal of oxide impurities (from 2.7-8.8 wt.% to 0.2-0.5 wt.%) during spark plasma sintering (1950 degrees C/20 min, 20 MPa) of (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B-2 and (Hf0.2Mo0.2Ta0.2Zr0.2Ti0.2)B-2 ceramics. Concurrently, the consolidation level achieved is enhanced from about 92.5% and 88%, respectively, to values exceeding 97%. While a further increase of graphite slightly improves samples densification, final products become progressively richer of the unreacted carbon. It is assumed that graphite plays a double role during SPS, e.g. not only as a reactant during the carbothermal reduction of oxides contaminant, but also as lubricating agent for the powder particles. The latter phenomenon is likely the main responsible for the densification improvement when 3 wt.% or larger amounts of additive are used. Another positive effect is the crystallite size refinement of the high-entropy phases with the progressive abatement of oxides, to confirm that their presence promotes grain coarsening during the sintering process.

In this work, combined experimental and fractal nature analysis procedures are proposed in order to both model and design mechanical properties of porous ceramics. Several porous ceramics samples have been considered both from an in-situ experimental campaign and from the literature. Microstructural information concerning pore size distribution has been approximated by the Intermingled Fractal units (IFU) approach and effective mechanical properties are derived by a simple discrete model. The capability of the proposed methodology to reproduce high-scattered mechanical properties is fully shown and a comparison with classical bounds and estimates is also reported. Finally, the combined experimental, fractal nature analysis and homogenisation scheme is implemented as a design procedure for the technological production of advanced porous ceramics.

An efficiency improvement of concentrating solar power systems relies on a significant increase of the operating temperatures, exceeding 600 degrees C. This goal can be achieved through the use of solar absorbers possessing high spectral selectivity and stability at such temperatures. Suitable alternatives to the largely used silicon carbide can be found in the ultra-high temperature ceramics class. This study focuses on the effect of processing, microstructure evolution and surface texture on the optical properties at room and high temperature. ZrB2-based ceramics are taken as case study to detect any correlation amongst composition, porosity, mean grain size, roughness and spectral selectivity. In addition, the effect of surface variation, induced by chemical etching or by exposure to oxidizing environment, thus simulating the actual operation conditions, are evaluated and compared to SiC optical properties. Absorbance and solar selectivity are discussed as a function of the microstructural and surface properties upon detailed roughness characterization. Advantages in the use of UHTCs as solar absorbers, strength and criticalities related to the use of these ceramics in comparison with SiC are discussed. (C) 2018 Elsevier Ltd. All rights reserved.