Carbon-based materials using for SDWE systems could be mainly classified into four types in terms of the different basic carbon unit, including graphene and its derivatives, carbon nanotubes (CNTs), ...carbonized plants and other carbon materials. The structure of carbon-based SDWE systems has undergone a succession of changes, including carbon nanoparticles systems, single-layer photothermal membrane systems, bi-layer structural photothermal systems, porous carbon-based materials systems, and three dimensional (3D) systems.
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Pressing need goes ahead for accessing freshwater in insufficient supply countries and regions, which will become a restrictive factor for human development and production. In recent years, solar-driven water evaporation (SDWE) systems have attracted increasing attention for their specialty in no consume conventional energy, pollution-free, and the high purity of fresh water. In particular, carbon-based photothermal conversion materials are preferred light-absorbing material for SDWE systems because of their wide range of spectrum absorption and high photothermal conversion efficiency based on super-conjugate effect. Until now, many carbon-based SDWE systems have been reported, and various structures emerged and were designed to enhance light absorption, optimize heat management, and improve the efficient water transport path. In this review, we attempt to give a comprehensive summary and discussions of structure progress of the carbon-based SDWE systems and their working mechanisms, including carbon nanoparticles systems, single-layer photothermal membrane systems, bi-layer structural photothermal systems, porous carbon-based materials systems, and three dimensional (3D) systems. In these systems, the latest 3D systems can expand the light path by allowing light to be reflected multiple times in the microcavity to increase the light absorption rate, and its large heat exchange area can prompt more water to evaporate, which makes them the promising application foreground. We hope our review can spark the probing of underlying principles and inspiring design strategies of these carbon-based SDWE systems, and further guide device optimizations, eventually promoting in extensive practical applications in the future.
•A new-structure grey Verhulst model is proposed by introducing a new non-homogeneous exponential function.•The new model is used to solve the problems of structure defect and poor stability of the ...traditional Verhulst model.•The new model solves the problem of displacement substitution of parameters and optimization of initial values.•The application in three examples verifies the performance of the new model is much better than that of original Verhulst.
The structure defect of the traditional grey Verhulst model is a key factor leading to its unstable performance. A new-structure grey Verhulst model (N_Verhulst) was proposed by introducing a new non-homogeneous exponential function. The N_Verhulst model has a better structure and stronger modeling ability; Meanwhile, it overcomes the shortcomings of the traditional Verhulst model including parameter dislocation and unreasonable selection of initial values. Four typical cases were used to test the performance of N_Verhulst, and the simulation/prediction results of the new model were compared with the traditional Verhulst model and the Pearl model. Results showed that the N_Verhulst model had evidently superior performance to the traditional grey Verhulst model, which confirms that the structure development of the new model is reasonable and effective.
It is well known that forests have important effects on mitigating flood and drought, and decrease risks of slope failure and surface erosion. This study evaluated how hydraulic properties of forest ...soils affect such functions of forests. Firstly, we clarified changes in soil hydraulic properties resulting from structure development. For this purpose, we assumed undisturbed forest soils as the structure-developed soils, and soils prepared by crashing secondary soil structure as structure-undeveloped soils. Hydraulic properties of these soils were compared. As a result, the structural development increased effective porosity and saturated hydraulic conductivity. The amount of the increase was large near the soil surface. Therefore, we can say that the soils in the shallower layer were affected more by the structure development, having larger water holding capacity and permeability than the structure-undeveloped soils. By using the observed hydraulic properties, numerical simulations were conducted for modeling hydrological processes in a forested hillslope. Results showed that the structure-developed soils supplied rainwater into the bedrock with milder intensity and stabilized baseflow discharge. This was because the structure-developed soils hold more rainwater than the structure-undeveloped soils due to the high water holding capacity. On the contrary, the structure-developed soils produced greater and rapider saturated through flow than the structure-undeveloped soils, because of the high permeability. This resulted in increase storm runoff for the structure-developed soils. For the structure-undeveloped soils, delayed and dull peaks of storm runoff were resulted to form expanded saturation area in the hillslope. That is, structure-undeveloped soils produced larger soil pore pressures than the structure-developed soils. Consequently, the hillslope with structure-developed soils was less vulnerable to slope failure and surface soil erosion.
Hygroscopicity is an obstacle to the widespread use of aluminum phosphate binders, but there is still a lack of relevant fundamental research on this topic. Here, the curing behavior, thermal ...evolution, phase development and hygroscopic behavior of acid aluminum phosphate (AAP) solutions with different P/Al ratios (2.50–4.00) have been systematically investigated. We comprehensively elucidate for the first time the hygroscopic mechanism of AAP and its derived aluminum phosphate, and establish a dynamic relationship between hygroscopic mechanism, moisture absorption rate, microstructure and phase composition. AAP and its derived aluminum phosphate, namely Al(H2PO4)3, AlH2P3O10, residual H3PO4, HPO3n and hydroxyl groups are all hygroscopic. The hygroscopic properties of AAP depend on the phase composition, which is determined by the P/Al ratio and the calcination temperature. Due to the formation of Berlinite and Al8H12(P2O7)9, the reduced formation of AlH2P3O10 and the absence of H3PO4, HPO3n and hydroxyl groups, the AAP solution with a P/Al< 3.00 and its derived aluminum phosphate exhibit relatively lower hygroscopicity. Meanwhile, increasing the calcination temperature can also improve the hygroscopicity resistance characteristics. This work complements the basic knowledge of AAP systems, especially those with a P/Al< 3.00. This sets the stage for the fabrication of aluminum phosphate binders and aluminum phosphate-based composites with excellent hygroscopicity resistance properties.
•The thermal evolution of AAP solutions with different P/Al ratios have been investigated.•The properties of AAP solutions with P/Al< 3.00 have been studied for the first time.•Hygroscopic mechanism of AAP and its derived aluminum phosphate was revealed.
Developing effective, economic and environmental-friendly phosphate adsorbents has attracted urgent attention due to the potential eutrophication caused by unnatural phosphate enrichment. In recent ...years, multifunctional materials prepared from traditional attapulgite clay have demonstrated excellent sorption potential due to their exclusive layered structure as well as moldable and easily-accessible properties. However, its electronegativity on the surface and the aggregation tendency of the one-dimensional nanorod crystals limit wider application for phosphate removal. Hence, various physicochemical modifications were investigated to endow attapulgite with nanoscale functional particles and specific groups. To date, few specialized works have comprehensively evaluated the progress and challenges for attapulgite-based adsorbents in efficient phosphate immobilization, leaving the structural evolution and application potential of the material to be further exploited. This review mainly summarizes the controllable modification strategies, dominant adsorption mechanisms, as well as their key influencing factors in phosphate removal of attapulgite-based adsorbents. Based on this summary, corresponding constructive recommendations such as in-depth adsorption mechanisms exploration, 3D structure development, intelligent recycling applications and machine learning are proposed to develop novel functional attapulgite-based phosphate adsorbents in a wider dimension.
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•A detailed review of attapulgite-based material as a promising phosphate removal adsorbent is systematically summarized.•The disaggregation process, modification methods, and the dominant phosphate uptake process are elucidated in detail.•The gaps and recommendations are put forward based on the existing challenges and current advances for phosphate removal.
•The optimum dosage of Na-gluconate was 0.03% for the compressive strength.•Na-gluconate reduces the amount of water required, and prolongs setting times.•Na-gluconate delays the hydration of C3S, ...prolonging the induction period.•Less than 0.03% Na-gluconate promotes the formation of AFt.•1.0% Na-gluconate inhibites the dissolution of CaSO4·2H2O and formation of AFt.
Sodium gluconate is commonly used to delay the setting of cement and concrete. This study investigated the effects of sodium gluconate on the physical properties and structure of Portland cement. Sodium gluconate improved the compressive strength at 3 and 28days, delayed cement setting and increased the fluidity of the Portland cement mortar. Less than 0.03% sodium gluconate promoted the formation of ettringite (AFt) at early age. A dosage of 1.0% sodium gluconate significantly inhibited the reaction between C3A and CaSO4·2H2O. Sodium gluconate delayed the hydration reaction of C3S, which increased the duration of the induction period. Sodium gluconate had only a slight effect on the hydration reaction of the ferrite phase. The pore distribution and porosity of the cement paste were not improved due to the decrease in hydration.
•Temperature increase from 10 °C to 20 °C decreased the viscosity of GP pastes.•Temperature increase from 10 °C to 20 °C accelerates GP structure formation.•GP’s compressive strength prepared at ...20 °C is higher than prepared at 10 °C.
This study aimed to determine the impact of preparation temperature (10 °C to 20 °C) and different alkaline activator solution (AAS) molarities on the rheological behaviour, structure development, mechanical performance during geopolymer (GP) synthesis, and ageing of metakaolin (MK) based GP pastes. By decreasing the AAS molarity from 8 M to 5 M, the viscosity of AAS decreased by up to 1.68 times and GP pastes viscosity by up to 1.74 times. A temperature increase from 10 °C to 20 °C decreased the viscosity of AAS by up to 1.89 times and the viscosity of GP pastes by up to 1.29 times. With the AAS molarity decrease, an increase of GP paste spread diameter of up to 1.7 times was observed. At 10 °C, the spread diameter increased up to 51% and at 20 °C temperature, up to 57%. Decreasing the AAS molarity, MK/AAS ratio and preparation temperature of the samples led to a retardation in the structure formation in the GP samples during GP synthesis from 4 to 8 h. For samples prepared at 10 °C the UPV values were up to 12% lower than in the same composition samples prepared at 20 °C. Decreasing the AAS molarity and MK/AAS ratio in the samples led to a decrease in compressive strength after GP synthesis of up to 30%, however the UPV values and compressive strength in the samples prepared at 10 °C were up to 2.3% and 12.1% lower than in the samples prepared at 20 °C. The XRD results confirmed the compressive strength test results and revealed that a decrease of molarity and temperature led to a less intensive geopolimerisation reaction and hydroxide sodalite formation in the composition. After ageing, the UPV and compressive strength values in the samples mostly increased during the first 7 days, but after 56 days the UPV and compressive strength in the samples prepared at 10 °C and 20 °C practically levelled off.
•Generally, the total porosity increases with the increase in tailings fineness.•The tailings fineness significantly affects the pore-size distribution.•The filling effect reduces the critical pore ...diameter.
Cemented paste backfill (CPB) is an important engineering material nowadays. However, there is limited information about the influence of particle-size distribution on the pore structure properties of coarse tailings used in CPBs. This study investigates the effects of particle-size distribution on the pore-structure development of CPB samples. Therefore, this paper presents experimental results to assess the influence of the fineness of tailings on important parameters (total porosity, pore-size distribution, and critical pore diameter) cured for 7, 14, and 28days. Mercury intrusion porosimetry tests are performed to provide insights into the pore structure of CPBs. Within the limits of this study, the total porosity and small pores (<10μm) increased, whereas the critical pore diameter and large pores (>10μm) decreased with the increase of tailings fineness. Furthermore, the influence of tailings fineness on the critical pore diameter decreased with extended curing time. Results show that the tailings fineness notably affected the pore structural properties of hardened CPBs.
The Upper Devonian-Upper Triassic low-grade metasedimentary rocks exposed along the South Patagonian Andes preserve the structural record of deformation associated with pre-Andean orogenic phases ...that predated the inception of the Jurassic rift during Gondwana fragmentation. Through the structural analysis at different scales, we identified deformation structures mainly with cratonward vergence, produced at two stages of structure development for the Bahía de la Lancha (early Carboniferous) and Río Lácteo (Middle Devonian-early Carboniferous) formations, and in a single one, for the Nunatak Viedma Unit (Late Triassic). The structural features were integrated with available U–Pb detrital zircon ages and fission-track cooling ages from those units. It leads us to identify a westward younging of sedimentation (i.e. protolith deposition) and widening of the continental margin throughout Paleozoic-early Mesozoic times, tectonically stabilized during the late Carboniferous-middle Permian Gondwanide orogeny and the Late Triassic-Early Jurassic Chonide orogeny. The structural style holds features of fold-and-thrust belts, which is discussed in a context of accretionary tectonics inherent to the Terra Australis exterior orogen.
•We perform a structural analysis of metasedimentary rocks along the South Patagonian Andes.•The basement is constituted by very low-to low-grade, quartz-rich metasedimentary rocks.•The ductile tectonic structures developed at pre-Mid Jurassic times.•Fold-and-thrust belts could be a possible deformation setting.•The Permian Gondwanide Orogeny and the Late Triassic-Early Jurassic Chonide Orogeny taken place in southern Patagonia.
