This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the poro...This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the porous MgO layer formed via plasma electrolytic oxidation(PEO).The AZ31 Mg alloy,initially coated with a PEO layer,underwent a dipping treatment in an ethanolic solution of 0.05 M 8HQ at 50℃ for 3 h.The results were compared with those from a different procedure where the PEO layer was subjected to a hydration reaction for 2 h at 90℃ before immersion in the 8HQ solution under the same conditions.The hydration treatment played a crucial role by converting MgO to Mg(OH)_(2),significantly enhancing the surface reactivity.This transformation introduced hydroxyl groups(−OH)on the surface,which facilitated donor-acceptor interactions with the electron-accepting sites on 8HQ molecules.The calculated binding energy(Ebinding)from DFT indicated that the interaction energy of 8HQ with Mg(OH)_(2) was lower compared to 8HQ with MgO,suggesting easier adsorption of 8HQ molecules on the hydrated surface.This,combined with the increased number of active sites and enhanced surface area,allowed for extensive surface coverage by 8HQ,leading to the formation of a stable,flake-like protective layer that sealed the majority of pores on the PEO layer.DFT calculations further suggested that the hydration treatment provided multiple active sites,enabling effective contact with 8HQ and rapid electron transfer,creating ideal conditions for charge-transfer-induced physical and chemical bonding.This study shows that hydration and 8HQ treatments significantly enhance the corrosion resistance of Mg alloys,highlighting their potential for advanced anticorrosive coatings.展开更多
In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified ...In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified with 4 mol·L^(-1) nitric acid was selected as an efficient catalyst for improving the hydration efficiency of cyclohexene.Furthermore,the microstructures and properties of fresh,used and regenerated acid-modified catalysts have been characterized by X-ray diffraction,scanning electron microscopy,nitrogen adsorption/desorption isotherm,Fourier transform infrared,thermal gravimetric analyzer,ammonia temperature programmed desorption and pyridine adsorbs Fourier transform infrared.The characterization results indicated that the total surface areas and pore volume of HZSM-5 zeolite increased after nitric acid treatment due to the formation of mesoporous structure.This benefits the diffusion rate of reactants and products,which improves the hydration efficiency and stability of the catalyst.Under the catalysis of HZSM-5,the conversion of cyclohexene was found to be 9.0%.However,treatment of HZSM-5 with nitric acid enhanced the conversion of cyclohexene to 12.2%,achieving a selectivity of 99.7%for cyclohexanol under optimal reaction conditions.This work affords a mild and efficient approach for improving the hydration efficiency and has potential industrial application value.展开更多
Growing concerns about greenhouse gas emissions from underground mining have intensified the need for carbon reduction strategies at every stage.Shotcrete used in tunnel support presents a promising opportunity for ca...Growing concerns about greenhouse gas emissions from underground mining have intensified the need for carbon reduction strategies at every stage.Shotcrete used in tunnel support presents a promising opportunity for carbon emission reduction.This study investigates the carbon absorption capacity,mechanical strength,and underlying mechanisms of shotcrete when exposed to varying CO_(2)concentrations during the mine support process.Findings reveal that higher CO_(2)concentrations during the initial stages of carbonation curing enhance early strength but may impede long-term strength development.Shotcrete samples exposed to 2vol%CO_(2)for 14 d exhibited a carbonation degree approximately three times higher than those exposed to 0.03vol%CO_(2).A carbonation layer formed in the shotcrete,sequestering CO_(2)as solid carbonates.In practical terms,shotcrete in an underground return-air tunnel absorbed 1.1 kg·m^(2)of CO_(2)over 14 d,equivalent to treating 33 m^(3)of contaminated air.Thus,using shotcrete for CO_(2)curing in return-air tunnels can significantly reduce carbon emissions,contributing to greener and more sustainable mining practices.展开更多
As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value...As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.展开更多
This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reser...This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reservoir conditions after shale hydration.Stress-strain data and mechanical parameters of shale after hydration under high temperature and high pressure were obtained to investigate the effects of reservoir temperature,hydration time and horizontal stress difference on the mechanical strength of shale after hydration.By using nonlinear regression and interpolation methods,a prediction model for the mechanical strength of shale after hydration was constructed,and the mechanical strength chart of deep shale under high stress difference was plotted.First,higher hydration temperature,longer hydration reaction time,and greater horizontal stress difference cause shale to enter the yield stage earlier during the compression process after hydration and to exhibit more prominent plastic characteristics,lower peak strength,peak strain,residual strength and elastic modulus,and higher Poisson's ratio.Second,the longer the hydration time,the smaller the impact of hydration temperature on the mechanical strength of deep shale is.As the horizontal stress difference increases,the peak strength and residual strength weaken intensely,and the peak strain,elastic modulus and Poisson's ratio deteriorate slowly.Third,the mechanical strength of shale decreases significantly in the first 5 days of hydration,but gradually stabilizes as the hydration time increases.Fourth,the visual mechanical strength chart helps to understand the post-fracturing dynamics in deep shale gas reservoir fracturing site and adjust the drainage and production plan in time.展开更多
Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction...Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction.However,limited studies have investigated the impact of temperature and magnesium oxide(MgO)content on LHP cement-based materials.This study utilizes thermodynamic simulations to study the hydration process,pore structure,and autogenous shrinkage of LHP cement pastes with different water-to-cement ratios(0.3,0.4,and 0.5),curing temperatures(5,15,20,and 30℃),and MgO contents(mass fractions of 2%,4%,and 5%).Higher curing temperature is found to promote the hydration reactions in cement paste.Moreover,the incorporation of 4%MgO moderately decreases both porosity and dimensional shrinkage in pastes.The microstructural evolution of different LHP pastes is examined through a comparative analysis,lending insights into LHP cement-based material applications.展开更多
Ferrite-rich calcium sulfoaluminate(FCSA)cement is often used in special projects such as marine engineering due to its excellent resistance of seawater attack although the cost is a little high.Ground granulated blas...Ferrite-rich calcium sulfoaluminate(FCSA)cement is often used in special projects such as marine engineering due to its excellent resistance of seawater attack although the cost is a little high.Ground granulated blast furnace slag(GGBS),a byproduct of industrial production,is used as a mineral admixture to reduce concrete costs and provide excellent performance.This study aimed to investigate the impact of GGBS on the hydration properties of FCSA cement in seawater.Tests were conducted on heat of hydration,compressive strength,mass change,and pH value of pore solution of FCSA cement paste with a water-to-binder ratio of 0.45.X-ray diffraction(XRD)analysis and thermogravimetric analysis were used to determine the hydration products,while mercury intrusion porosimetry(MIP)was used to measure pore structure.The results indicated that the FCSA cement hydration showed a concentrated heat release at early age.The compressive strength of specimens consistently increased over time,where seawater curing enhanced the compressive strength of control samples.The pH value of pore solution decreased to 10.7−10.9 at 90 d when cured in seawater.The primary hydration products of FCSA cement included ettringite,iron hydroxide gel(FH_(3)),and aluminum hydroxide gel(AH_(3)).Moreover,when cured in seawater,Friedel’s salt was formed,which enhanced the compressive strength of the specimen and increased its coefficient of corrosion.Seawater curing gradually increased sample mass,and GGBS refined pore structure while reducing harmful pore proportions.These results suggest that while GGBS can refine pore structure and improve certain aspects of performance,its inclusion may also reduce compressive strength,highlighting the need for a balanced approach in its use for marine applications.展开更多
Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to b...Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to basic slags.However,hydration occurs during the manufacturing,storage,and transportation of refractories,which severely limits their application.Mgo-CaO clinker is the main raw material for Mgo-Cao refractories,and its hydration resistance determines the development of the latter case.Herein,the Mgo-Cao clinker was modified using myristic acid as the modifying agent by the liquid-phase deposition method.The effects of the particle size of the raw materials,concentration of myristic acid,treatment temperature and time on the phase composition and hydration resistance of the modified Mgo-Cao clinkers were investigated in detail.The results show that the samples with an agent concentration of 0.25 mol L^(-1) and treated at 25℃ for 1 h exhibit the optimal hydration resistance properties,namely a low hydration mass gain rate(0.23%)and a large water contact angle(152.9).展开更多
Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain ...Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain underexplored.This study aims to establish a multidimensional ecological safety evaluation framework for reclaimed water replenishment systems and propose hierarchical risk prevention strategies.By integrating ecotoxicological assays(algae growth inhibition,Daphnia behavioral anomalies,zebrafish embryo toxicity),multimedia exposure modeling,and Monte Carlo probabilistic simulations,the risk contributions and spatial heterogeneity of typical pollutants are quantitatively analyzed.Results revealed that sulfamethoxazole(RQ=2.3)and diclofenac(RQ=1.8)posed high ecological risks,with their effects nonlinearly correlated with hydraulic retention time(HRT<3 days)and nutrient loading(TN>1.2 mg/L).A three-tier risk prevention system was developed based on the“source-pathway-receptor”framework:ozone-activated carbon pretreatment achieved 85%removal efficiency for pharmaceutical contaminants,ecological floating beds enhanced nitrogen and phosphorus retention by 40%-60%,and hydraulic regulation(flow velocity>0.1 m/s)effectively suppressed pathogen proliferation.The innovation of this study lies in establishing a chemical-biological-hydrological coupled risk quantification model for reclaimed water reuse scenarios.The hierarchical prevention standards have been incorporated into local reclaimed water management regulations,providing a scientific foundation and technical paradigm for sustainable landscape water replenishment.展开更多
Elucidating the effect of growth periods on the quality of calcium sulfate whiskers(CSWs)prepared from calcium sulfate dihydrate(DH)is imperative.Herein,crystal seeds and whiskers were prepared from DH in a water–gly...Elucidating the effect of growth periods on the quality of calcium sulfate whiskers(CSWs)prepared from calcium sulfate dihydrate(DH)is imperative.Herein,crystal seeds and whiskers were prepared from DH in a water–glycerol system.Longer whiskers were obtained from crystal seeds prepared via hydration of DH for 30 s than via ball milling for 5 min followed by hydration for 20 s.The attachment of cetyltrimethyl ammonium bromide and glycerol additives to the whisker tops promoted whisker growth.The whisker sponges exhibited good thermal barrier properties and compression cycle stability.展开更多
As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this p...As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing material.The results show that the 800℃ is considered as the optimum heat treatment temperature for DWTAS.DWTAS-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al_(2)O_(3) and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain extent.When cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 MPa.The dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics model.This study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.展开更多
Annular channeling has seriously troubled deep oil and gas exploitation,and the reduction of hydrostatic pressure of cement slurry in the waiting stage is considered one of the main causes of early annular channeling....Annular channeling has seriously troubled deep oil and gas exploitation,and the reduction of hydrostatic pressure of cement slurry in the waiting stage is considered one of the main causes of early annular channeling.However,at present,there is still a lack of sufficient research on and understanding of the relationship between the time-varying law of hydrostatic pressure of cement slurry and the early hydration process in different well sections,especially in high-temperature well sections.Therefore,in this paper,a hydrostatic pressure measurement experiment of cement slurry at low temperature(50-90℃)and high temperature(120-180℃)was carried out using a self-developed hydrostatic pressure measurement device of cement slurry.Then,the cement slurry cured at 90℃ for 1-8 h was sampled by the freeze-drying method,and XRD and TG experiments were carried out.The results show that the hydrostatic curves of low and high temperatures both show a trend of rapid increase first,then remain stable,and then decrease rapidly.With an increase in temperature,the time of the stable and falling segments of the hydrostatic curve of the cement slurry gradually decreases.By fitting the rapid pressure drop time points of cement slurry at different temperatures,it can be determined that the rapid pressure drop time and temperature show a functional relationship.The XRD and TG results of different curing times at 90℃ were analyzed.It can be seen that in the early stage of the hydration induction period,the connection between cement particles is not close,and the hydrostatic pressure of the cement slurry column remains stable.As the hydration process enters the acceleration period,the cement particles crosslink with each other through hydration products to form a bridge structure,and the hydrostatic pressure of the cement paste begins to decrease.This shows that the pressure drop time can be controlled by regulating the hydration process to provide theoretical guidance for cement slurry preparation and slurry column design in cementing engineering.展开更多
Acetylacetone(AcAc)is a typical class ofβ-diketones with broad industrial applications due to the property of the keto-enol isomers,but its isomerization and chemical reactions at the air-droplet interface are still ...Acetylacetone(AcAc)is a typical class ofβ-diketones with broad industrial applications due to the property of the keto-enol isomers,but its isomerization and chemical reactions at the air-droplet interface are still unclear.Hence,using combined molecular dynamics and quantum chemistry methods,the heterogeneous chemistry of AcAc at the air-droplet interface was investigated,including the attraction of AcAc isomers by the droplets,the distribution of isomers at the air-droplet interface,and the hydration reactions of isomers at the air-droplet interface.The results reveal that the preferential orientation of two AcAc isomers(keto-and enol-AcAc)to accumulate and accommodate at the acidic air-droplet interface.The isomerization of two AcAc isomers at the acidic air-droplet interface is more favorable than that at the neutral air-droplet interface because the“water bridge”structure is destroyed by H_(3)O^(+),especially for the isomerization from keto-Ac Ac to enol-AcAc.At the acidic air-droplet interface,the carbonyl or hydroxyl O-atoms of two AcAc isomers display an energetical preference to hydration.Keto-diol is the dominant products to accumulate at the air-droplet interface,and excessive keto-diol can enter the droplet interior to engage in the oligomerization.The photooxidation reaction of AcAc will increase the acidity of the air-droplet interface,which indirectly facilitate the uptake and formation of more keto-diol.Our results provide an insight into the heterogeneous chemistry ofβ-diketones and their influence on the environment.展开更多
The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and...The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and 0.45,and the molding temperature was specified at 10 and 20℃.The experimental results show that,as the water-binder ratio increases,the value of the second temperature peak on the temperature curve of the cement paste decreases,and the age at which the peak appears is delayed.The higher the water-cement ratio,the higher the hydration heat release in the early period of cement hydration,but this trend reverses in the late period.There are intersection points of the total hydration heat curve of the cement pastes under the influence of the water-cement ratio,and this law can be observed at both molding temperatures.With the increase in the molding temperature,the age of the second temperature peak on the temperature curve of the cement paste will advance,but the temperature peak will decrease.The higher the molding temperature,the earlier the acceleration period of the cement hydration began,and the larger the hydration heat of the cement in the early stage,but the smaller the total heat in the late period.A subsection function calculation model of the hydration heat,which was based on the existing models,was proposed in order to predict the heat of the hydration of the concrete.展开更多
The ionic transport in sub-nanochannels plays a key role in energy storage,yet suffers from a high energy barrier.Wetting sub-nanochannels is crucial to accelerate ionic transport,but the introduction of water is chal...The ionic transport in sub-nanochannels plays a key role in energy storage,yet suffers from a high energy barrier.Wetting sub-nanochannels is crucial to accelerate ionic transport,but the introduction of water is challenging because of the hydrophobic extreme confinement.We propose wetting the channels by the exothermic hydration process of pre-intercalated ions,the effect of which varies distinctly with different ionic hydration structures and energies.Compared to the failed pre-intercalation of SO_(4)^(2-),HSO_(4)^(-) with weak hydration energy results in a marginal effect on the HOMO(Highest Occupied Molecular Orbital)level of water to avoid water splitting during the electrochemical intercalation.Meanwhile,the ability of water introduction is reserved by the initial incomplete dissociation state of HSO_(4)^(-),so the consequent exothermic reionization and hydration processes of the intercalated HSO_(4)^(-) promote the water introduction into sub-nanochannels,finally forming the stable confined water through hydrogen bonding with functional groups.The wetted channels exhibit a significantly enhanced ionic diffusion coef-ficient by~9.4 times.展开更多
This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly a...This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly ash(FA),and analyzed its mechanical properties,hydration mechanism,and retardation mechanism.The effects of retarders on the hydration products,mechanical properties,and hydration kinetics of ACCM were investigated using XRD,SEM,FTIR,EDS,and thermoactive microcalorimetry.The results showed that Na_(2)B_(4)O_(7)·10H_(2)O(B)delayed the exotherm during the alkali activation process and could effectively delay the setting time of ACCM,but the mechanical properties were slightly decreased.The setting time of ACCM increased with the increase in SG content,but the mechanical properties of ACCM decreased with the increase in SG content.C1_(2)H_(22)O_(11)(CHO)could effectively delay the hydration reaction of ACCM and weakly enhanced the compressive strength.H_(3)PO_(4)(HP)at a concentration of 0.05 mol/L had a certain effect on ACCM retardation,but HP at a concentration of 0.07 and 0.09 mol/L had an effect of promoting the setting and hardening time of ACCM.展开更多
PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula...PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.展开更多
A ternary system comprising Ca_(20)Al_(26)Mg_(3)Si_(3)O_(68)(Q-phase),limestone,and metakaolin is proposed,and its hydration behavior,hydration product phases,microstructure,and mechanical properties are investigated ...A ternary system comprising Ca_(20)Al_(26)Mg_(3)Si_(3)O_(68)(Q-phase),limestone,and metakaolin is proposed,and its hydration behavior,hydration product phases,microstructure,and mechanical properties are investigated and compared with pure Q-phase cement.The results indicate that the ternary system exhibits exceptional and sustained compressive strength even under a 40℃environment,significantly outperforming pure Q-phase.The mechanism lies in that metakaolin effectively inhibits the transformation of metastable phase.Meanwhile,the interactions among Q-phase,limestone,and metakaolin further enhance the cementitious performance.The ternary system effectively addresses potential issues of strength loss in Q-phase cement application,and as a low-carbon cementitious material system,it holds promising potential applications.展开更多
Free water available in calcium aluminate cement(CAC)-bonded castables is crucial for the hydration of CAC and the conversion of hydration products in the curing and drying processes,as both the hydration and conversi...Free water available in calcium aluminate cement(CAC)-bonded castables is crucial for the hydration of CAC and the conversion of hydration products in the curing and drying processes,as both the hydration and conversion reactions are dissolution–precipitation reactions.To elucidate the effect of different levels of free water loss upon the hydration of CAC,the conversion of hydration products and the mechanical strength of the CAC-bonded castables,the CAC-bonded castables were subjected to sealed and unsealed curing conditions at 50℃ and drying at 110℃.The results demonstrate that the fast removal of free water during unsealed curing would hinder the conversion from 2CaO·Al_(2)O_(3)·8H_(2)O to 3CaO·Al_(2)O_(3)·6H_(2)O and consequently prevent the deterioration of strength.As a comparison,although sealed-cured samples have less water loss and high degree of hydration of CAC,they still show lower strength than the unsealed samples after curing.The following drying process further accelerates the hydration of residual calcium aluminate clinkers for both the sealed and unsealed samples,but still does not favor the conversion from 2CaO·Al_(2)O_(3)·8H_(2)O to 3CaO·Al_(2)O_(3)·6H_(2)O in the unsealed-cured samples.展开更多
It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the co...It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.展开更多
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(No.2022R1A2C1006743).
文摘This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the porous MgO layer formed via plasma electrolytic oxidation(PEO).The AZ31 Mg alloy,initially coated with a PEO layer,underwent a dipping treatment in an ethanolic solution of 0.05 M 8HQ at 50℃ for 3 h.The results were compared with those from a different procedure where the PEO layer was subjected to a hydration reaction for 2 h at 90℃ before immersion in the 8HQ solution under the same conditions.The hydration treatment played a crucial role by converting MgO to Mg(OH)_(2),significantly enhancing the surface reactivity.This transformation introduced hydroxyl groups(−OH)on the surface,which facilitated donor-acceptor interactions with the electron-accepting sites on 8HQ molecules.The calculated binding energy(Ebinding)from DFT indicated that the interaction energy of 8HQ with Mg(OH)_(2) was lower compared to 8HQ with MgO,suggesting easier adsorption of 8HQ molecules on the hydrated surface.This,combined with the increased number of active sites and enhanced surface area,allowed for extensive surface coverage by 8HQ,leading to the formation of a stable,flake-like protective layer that sealed the majority of pores on the PEO layer.DFT calculations further suggested that the hydration treatment provided multiple active sites,enabling effective contact with 8HQ and rapid electron transfer,creating ideal conditions for charge-transfer-induced physical and chemical bonding.This study shows that hydration and 8HQ treatments significantly enhance the corrosion resistance of Mg alloys,highlighting their potential for advanced anticorrosive coatings.
基金financial support by the National Natural Science Foundation of China(22378339)Collaborative Innovation Center of New Chemical Technologies for Environmental Benignity and Efficient Resource Utilization.
文摘In this work,several HZSM-5 catalysts with different Si/Al ratios treated with acids are selected as catalysts and used for hydration of cyclohexene to cyclohexanol.The results indicated that HZSM-5(Si/Al=38)modified with 4 mol·L^(-1) nitric acid was selected as an efficient catalyst for improving the hydration efficiency of cyclohexene.Furthermore,the microstructures and properties of fresh,used and regenerated acid-modified catalysts have been characterized by X-ray diffraction,scanning electron microscopy,nitrogen adsorption/desorption isotherm,Fourier transform infrared,thermal gravimetric analyzer,ammonia temperature programmed desorption and pyridine adsorbs Fourier transform infrared.The characterization results indicated that the total surface areas and pore volume of HZSM-5 zeolite increased after nitric acid treatment due to the formation of mesoporous structure.This benefits the diffusion rate of reactants and products,which improves the hydration efficiency and stability of the catalyst.Under the catalysis of HZSM-5,the conversion of cyclohexene was found to be 9.0%.However,treatment of HZSM-5 with nitric acid enhanced the conversion of cyclohexene to 12.2%,achieving a selectivity of 99.7%for cyclohexanol under optimal reaction conditions.This work affords a mild and efficient approach for improving the hydration efficiency and has potential industrial application value.
基金financially funded by the 14th Five Years Key Programs for Science and Technology Development of China(No.2021YFC2900400)the National Natural Science Foundation of China(Nos.52274151,552104156,52074351,and 22376221)+2 种基金the Science and Technology Innovation Program of Hunan Province,China(No.2021 RC3125)the Natural Science Foundation of Hunan Province,China(No.2024JJ2074)the Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC 001)。
文摘Growing concerns about greenhouse gas emissions from underground mining have intensified the need for carbon reduction strategies at every stage.Shotcrete used in tunnel support presents a promising opportunity for carbon emission reduction.This study investigates the carbon absorption capacity,mechanical strength,and underlying mechanisms of shotcrete when exposed to varying CO_(2)concentrations during the mine support process.Findings reveal that higher CO_(2)concentrations during the initial stages of carbonation curing enhance early strength but may impede long-term strength development.Shotcrete samples exposed to 2vol%CO_(2)for 14 d exhibited a carbonation degree approximately three times higher than those exposed to 0.03vol%CO_(2).A carbonation layer formed in the shotcrete,sequestering CO_(2)as solid carbonates.In practical terms,shotcrete in an underground return-air tunnel absorbed 1.1 kg·m^(2)of CO_(2)over 14 d,equivalent to treating 33 m^(3)of contaminated air.Thus,using shotcrete for CO_(2)curing in return-air tunnels can significantly reduce carbon emissions,contributing to greener and more sustainable mining practices.
基金Projects(52222404,52074212)supported by the National Natural Science Foundation of ChinaProject(2023-LL-QY-07)supported by the Two-chain Integration Key Projects in Shaanxi Province,China。
文摘As the second most important solid waste produced by coal-fired power plants,the improper management of coal-fired slag has the potential to result in environmental pollution.It is therefore imperative that high-value utilization pathways for coal-fired slag should be developed.In this study,modified magnesium slag(MMS),produced by a magnesium smelter,was selected as the alkali activator.The activated silica-aluminum solid wastes,namely coal-fired slag(CFS)and mineral powder(MP),were employed as pozzolanic materials in the preparation of alkali-activated cementitious materials.The alkali-activated cementitious materials prepared with 50 wt%MMS,40 wt%CFS and 10 wt%MP exhibited favorable mechanical properties,with a compressive strength of 32.804 MPa in the paste sample cured for 28 d.Then,the activated silica-aluminum solid waste consisting of CFS-MP generated a significant amount of C-S(A)-H gels,AFt,and other products,which were observed to occupy the pore structure of the specimen.In addition,the secondary hydration reaction of CFS-MP occurs in high alkalinity environments,resulting in the formation of a mutually stimulated and promoted reaction system between CFS-MP and MMS,this will subsequently accelerate the hydrolysis reaction of MMS.It is important to emphasize that the amount of MMS in alkali-activated cementitious materials must be strictly regulated to avert the potential issue of incomplete depolymerization-repolymerization of active silica-aluminum solid waste containing CFS-MP.This in turn could have a deleterious impact on the late strength of the cementitious materials.The aim of this work is to improve the joint disposal of MMS,CFS and MP and thereby provide a scientific basis for the development of environmentally friendly and low-carbon modified magnesium slag alkali-activated coal-fired slag based cementitious materials for mine backfilling.
基金Supported by the National Natural Science Foundation of China(U24A2084,U21B2071)Science and Technology Cooperation Project of CNPC-Southwest Petroleum University Innovation Consortium(2020CX030201)。
文摘This study takes shale samples from the Jiaoshiba block in the Fuling shale gas field of the Sichuan Basin,and uses the true triaxial testing system to conduct a series of mechanical experiments under deep shale reservoir conditions after shale hydration.Stress-strain data and mechanical parameters of shale after hydration under high temperature and high pressure were obtained to investigate the effects of reservoir temperature,hydration time and horizontal stress difference on the mechanical strength of shale after hydration.By using nonlinear regression and interpolation methods,a prediction model for the mechanical strength of shale after hydration was constructed,and the mechanical strength chart of deep shale under high stress difference was plotted.First,higher hydration temperature,longer hydration reaction time,and greater horizontal stress difference cause shale to enter the yield stage earlier during the compression process after hydration and to exhibit more prominent plastic characteristics,lower peak strength,peak strain,residual strength and elastic modulus,and higher Poisson's ratio.Second,the longer the hydration time,the smaller the impact of hydration temperature on the mechanical strength of deep shale is.As the horizontal stress difference increases,the peak strength and residual strength weaken intensely,and the peak strain,elastic modulus and Poisson's ratio deteriorate slowly.Third,the mechanical strength of shale decreases significantly in the first 5 days of hydration,but gradually stabilizes as the hydration time increases.Fourth,the visual mechanical strength chart helps to understand the post-fracturing dynamics in deep shale gas reservoir fracturing site and adjust the drainage and production plan in time.
基金supported by the National Natural Science Foundation of China(Nos.51602229 and U2040222)the Opening Project of Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education(Tongji University)+1 种基金the Joint Fund Project of Hubei Provincial Natural Science Foundation(No.2023AFD196)the Opening Funding of Henan Key Laboratory of Green Building Materials Manufacturing and Intelligent Equipment(No.2024LGSYS02),China.
文摘Low-heat Portland(LHP)cement is a new type of Portland cement that has been widely used in recent years due to its low heat of hydration,which makes it exceptional in temperature control for mass concrete construction.However,limited studies have investigated the impact of temperature and magnesium oxide(MgO)content on LHP cement-based materials.This study utilizes thermodynamic simulations to study the hydration process,pore structure,and autogenous shrinkage of LHP cement pastes with different water-to-cement ratios(0.3,0.4,and 0.5),curing temperatures(5,15,20,and 30℃),and MgO contents(mass fractions of 2%,4%,and 5%).Higher curing temperature is found to promote the hydration reactions in cement paste.Moreover,the incorporation of 4%MgO moderately decreases both porosity and dimensional shrinkage in pastes.The microstructural evolution of different LHP pastes is examined through a comparative analysis,lending insights into LHP cement-based material applications.
基金Project(2023DJC182)supported by the Department of Science and Technology of Hubei Province,ChinaProjects(51608402,51602229)supported by the National Natural Science Foundation of ChinaProject(2021-2075-38)supported by the Department of Housing and Urban-Rural Development of Hubei Province,China。
文摘Ferrite-rich calcium sulfoaluminate(FCSA)cement is often used in special projects such as marine engineering due to its excellent resistance of seawater attack although the cost is a little high.Ground granulated blast furnace slag(GGBS),a byproduct of industrial production,is used as a mineral admixture to reduce concrete costs and provide excellent performance.This study aimed to investigate the impact of GGBS on the hydration properties of FCSA cement in seawater.Tests were conducted on heat of hydration,compressive strength,mass change,and pH value of pore solution of FCSA cement paste with a water-to-binder ratio of 0.45.X-ray diffraction(XRD)analysis and thermogravimetric analysis were used to determine the hydration products,while mercury intrusion porosimetry(MIP)was used to measure pore structure.The results indicated that the FCSA cement hydration showed a concentrated heat release at early age.The compressive strength of specimens consistently increased over time,where seawater curing enhanced the compressive strength of control samples.The pH value of pore solution decreased to 10.7−10.9 at 90 d when cured in seawater.The primary hydration products of FCSA cement included ettringite,iron hydroxide gel(FH_(3)),and aluminum hydroxide gel(AH_(3)).Moreover,when cured in seawater,Friedel’s salt was formed,which enhanced the compressive strength of the specimen and increased its coefficient of corrosion.Seawater curing gradually increased sample mass,and GGBS refined pore structure while reducing harmful pore proportions.These results suggest that while GGBS can refine pore structure and improve certain aspects of performance,its inclusion may also reduce compressive strength,highlighting the need for a balanced approach in its use for marine applications.
基金National Natural Science Foundation of China(Grants 52202025 and U23A20559)Natural Science Foundation of Hubei Province(Grant 2022CFB629)+1 种基金"The 14^(th)Five-Year Plan"Hubei Provincial Advantaged Characteristic Disciplines(Groups)Project of Wuhan University of Science and Technology(2023A0307).
文摘Mgo-Cao refractories are widely used in the iron and steel metalurgy industry due to their advantages of purifying molten steel,high refractoriness,good thermal shock resistance,and excellent corrosion resistance to basic slags.However,hydration occurs during the manufacturing,storage,and transportation of refractories,which severely limits their application.Mgo-CaO clinker is the main raw material for Mgo-Cao refractories,and its hydration resistance determines the development of the latter case.Herein,the Mgo-Cao clinker was modified using myristic acid as the modifying agent by the liquid-phase deposition method.The effects of the particle size of the raw materials,concentration of myristic acid,treatment temperature and time on the phase composition and hydration resistance of the modified Mgo-Cao clinkers were investigated in detail.The results show that the samples with an agent concentration of 0.25 mol L^(-1) and treated at 25℃ for 1 h exhibit the optimal hydration resistance properties,namely a low hydration mass gain rate(0.23%)and a large water contact angle(152.9).
文摘Against the backdrop of intensifying global water scarcity,reclaimed water reuse has emerged as a critical strategy for ecological replenishment of landscape water bodies.However,its potential ecological risks remain underexplored.This study aims to establish a multidimensional ecological safety evaluation framework for reclaimed water replenishment systems and propose hierarchical risk prevention strategies.By integrating ecotoxicological assays(algae growth inhibition,Daphnia behavioral anomalies,zebrafish embryo toxicity),multimedia exposure modeling,and Monte Carlo probabilistic simulations,the risk contributions and spatial heterogeneity of typical pollutants are quantitatively analyzed.Results revealed that sulfamethoxazole(RQ=2.3)and diclofenac(RQ=1.8)posed high ecological risks,with their effects nonlinearly correlated with hydraulic retention time(HRT<3 days)and nutrient loading(TN>1.2 mg/L).A three-tier risk prevention system was developed based on the“source-pathway-receptor”framework:ozone-activated carbon pretreatment achieved 85%removal efficiency for pharmaceutical contaminants,ecological floating beds enhanced nitrogen and phosphorus retention by 40%-60%,and hydraulic regulation(flow velocity>0.1 m/s)effectively suppressed pathogen proliferation.The innovation of this study lies in establishing a chemical-biological-hydrological coupled risk quantification model for reclaimed water reuse scenarios.The hierarchical prevention standards have been incorporated into local reclaimed water management regulations,providing a scientific foundation and technical paradigm for sustainable landscape water replenishment.
基金supported by the Degradable Plastics Engineering Research Center of Yunnan Provincial Education Department(KKPU202205001).
文摘Elucidating the effect of growth periods on the quality of calcium sulfate whiskers(CSWs)prepared from calcium sulfate dihydrate(DH)is imperative.Herein,crystal seeds and whiskers were prepared from DH in a water–glycerol system.Longer whiskers were obtained from crystal seeds prepared via hydration of DH for 30 s than via ball milling for 5 min followed by hydration for 20 s.The attachment of cetyltrimethyl ammonium bromide and glycerol additives to the whisker tops promoted whisker growth.The whisker sponges exhibited good thermal barrier properties and compression cycle stability.
基金This work is supported by the National Key Research and Development Program of China(No.2022YFC3203203)the Outstanding Youth Science Foundation of Shaanxi Province(No.2023-JC-JQ-36)the National Natural Science Foundation of China(No.52300121).
文摘As a byproduct of water treatment,drinking water treatment aluminum sludge(DWTAS)has challenges related to imperfect treatment and disposal,which has caused potential harm to human health and the environment.In this paper,heat treatment DWTAS as a supplement cementitious material was used to prepare a green cementing material.The results show that the 800℃ is considered as the optimum heat treatment temperature for DWTAS.DWTAS-800℃ is fully activated after thermal decomposition to form incompletely crystallized highly activeγ-Al_(2)O_(3) and active SiO_(2).The addition of DWTAS promoted the formation of ettringite and C-(A)-S-H gel,which could make up for the low early compressive strength of cementing materials to a certain extent.When cured for 90 days,the compressive strength of the mortar with 30% DWTAS-800℃ reached 44.86 MPa.The dynamic process was well simulated by Krstulovi′c-Dabi′c hydration kinetics model.This study provided a methodology for the fabrication of environmentally friendly and cost-effective compound cementitiousmaterials and proposed a“waste-to-resource”strategy for the sustainable management of typical solid wastes.
基金support provided by the Natural Science Foundation of Science and Technology Department of Sichuan Province,China(2024NSFSC0154)the Open Fund for Research Platform of the School of New Energy and Materials,Southwest Petroleum University(2022SCYYQKCCL010).
文摘Annular channeling has seriously troubled deep oil and gas exploitation,and the reduction of hydrostatic pressure of cement slurry in the waiting stage is considered one of the main causes of early annular channeling.However,at present,there is still a lack of sufficient research on and understanding of the relationship between the time-varying law of hydrostatic pressure of cement slurry and the early hydration process in different well sections,especially in high-temperature well sections.Therefore,in this paper,a hydrostatic pressure measurement experiment of cement slurry at low temperature(50-90℃)and high temperature(120-180℃)was carried out using a self-developed hydrostatic pressure measurement device of cement slurry.Then,the cement slurry cured at 90℃ for 1-8 h was sampled by the freeze-drying method,and XRD and TG experiments were carried out.The results show that the hydrostatic curves of low and high temperatures both show a trend of rapid increase first,then remain stable,and then decrease rapidly.With an increase in temperature,the time of the stable and falling segments of the hydrostatic curve of the cement slurry gradually decreases.By fitting the rapid pressure drop time points of cement slurry at different temperatures,it can be determined that the rapid pressure drop time and temperature show a functional relationship.The XRD and TG results of different curing times at 90℃ were analyzed.It can be seen that in the early stage of the hydration induction period,the connection between cement particles is not close,and the hydrostatic pressure of the cement slurry column remains stable.As the hydration process enters the acceleration period,the cement particles crosslink with each other through hydration products to form a bridge structure,and the hydrostatic pressure of the cement paste begins to decrease.This shows that the pressure drop time can be controlled by regulating the hydration process to provide theoretical guidance for cement slurry preparation and slurry column design in cementing engineering.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(No.2019B151502064)the National Natural Science Foundation of China(Nos.42077189,42020104001,and 42277081)+3 种基金the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01Z032)the Science and Technology Key Project of Guangdong ProvinceChina(No.2019B110206002)the Guangdong Provincial Key R&D Program(No.2022-GDUT-A0007)。
文摘Acetylacetone(AcAc)is a typical class ofβ-diketones with broad industrial applications due to the property of the keto-enol isomers,but its isomerization and chemical reactions at the air-droplet interface are still unclear.Hence,using combined molecular dynamics and quantum chemistry methods,the heterogeneous chemistry of AcAc at the air-droplet interface was investigated,including the attraction of AcAc isomers by the droplets,the distribution of isomers at the air-droplet interface,and the hydration reactions of isomers at the air-droplet interface.The results reveal that the preferential orientation of two AcAc isomers(keto-and enol-AcAc)to accumulate and accommodate at the acidic air-droplet interface.The isomerization of two AcAc isomers at the acidic air-droplet interface is more favorable than that at the neutral air-droplet interface because the“water bridge”structure is destroyed by H_(3)O^(+),especially for the isomerization from keto-Ac Ac to enol-AcAc.At the acidic air-droplet interface,the carbonyl or hydroxyl O-atoms of two AcAc isomers display an energetical preference to hydration.Keto-diol is the dominant products to accumulate at the air-droplet interface,and excessive keto-diol can enter the droplet interior to engage in the oligomerization.The photooxidation reaction of AcAc will increase the acidity of the air-droplet interface,which indirectly facilitate the uptake and formation of more keto-diol.Our results provide an insight into the heterogeneous chemistry ofβ-diketones and their influence on the environment.
基金the National Natural Science Foundation of China(Nos.52368032 and 51808272)the China Postdoctoral Science Foundation(No.2023M741455)+1 种基金the Tianyou Youth Talent Lift Program of Lanzhou Jiaotong UniversityGansu Province Youth Talent Support Project(No.GXH20210611-10)。
文摘The effects of the water-cement ratio and the molding temperature on the hydration heat of cement were investigated with semi-adiabatic calorimetry.The specimens were prepared with water-cement ratios of 0.31,0.38,and 0.45,and the molding temperature was specified at 10 and 20℃.The experimental results show that,as the water-binder ratio increases,the value of the second temperature peak on the temperature curve of the cement paste decreases,and the age at which the peak appears is delayed.The higher the water-cement ratio,the higher the hydration heat release in the early period of cement hydration,but this trend reverses in the late period.There are intersection points of the total hydration heat curve of the cement pastes under the influence of the water-cement ratio,and this law can be observed at both molding temperatures.With the increase in the molding temperature,the age of the second temperature peak on the temperature curve of the cement paste will advance,but the temperature peak will decrease.The higher the molding temperature,the earlier the acceleration period of the cement hydration began,and the larger the hydration heat of the cement in the early stage,but the smaller the total heat in the late period.A subsection function calculation model of the hydration heat,which was based on the existing models,was proposed in order to predict the heat of the hydration of the concrete.
基金supported by the National Key Research and Development Program of China(2021YFA1101300)the National Natural Science Foundation of China(Grant No.22225801,21776197,22078214,and 21905206)Special Fund for Science and Technology Innovation Team of Shanxi Province(No.202204051001009).
文摘The ionic transport in sub-nanochannels plays a key role in energy storage,yet suffers from a high energy barrier.Wetting sub-nanochannels is crucial to accelerate ionic transport,but the introduction of water is challenging because of the hydrophobic extreme confinement.We propose wetting the channels by the exothermic hydration process of pre-intercalated ions,the effect of which varies distinctly with different ionic hydration structures and energies.Compared to the failed pre-intercalation of SO_(4)^(2-),HSO_(4)^(-) with weak hydration energy results in a marginal effect on the HOMO(Highest Occupied Molecular Orbital)level of water to avoid water splitting during the electrochemical intercalation.Meanwhile,the ability of water introduction is reserved by the initial incomplete dissociation state of HSO_(4)^(-),so the consequent exothermic reionization and hydration processes of the intercalated HSO_(4)^(-) promote the water introduction into sub-nanochannels,finally forming the stable confined water through hydrogen bonding with functional groups.The wetted channels exhibit a significantly enhanced ionic diffusion coef-ficient by~9.4 times.
基金Funded by Key Laboratory for Comprehensive Energy Saving of Cold Regions Architecture of Ministry of Education(No.JLJZHDKF202204)。
文摘This paper studied the effects of different retarders on the performance of the"one-step"alkali-activated composite cementitious material(ACCM)which is composed of ground granulated blast slag(GGBS)and fly ash(FA),and analyzed its mechanical properties,hydration mechanism,and retardation mechanism.The effects of retarders on the hydration products,mechanical properties,and hydration kinetics of ACCM were investigated using XRD,SEM,FTIR,EDS,and thermoactive microcalorimetry.The results showed that Na_(2)B_(4)O_(7)·10H_(2)O(B)delayed the exotherm during the alkali activation process and could effectively delay the setting time of ACCM,but the mechanical properties were slightly decreased.The setting time of ACCM increased with the increase in SG content,but the mechanical properties of ACCM decreased with the increase in SG content.C1_(2)H_(22)O_(11)(CHO)could effectively delay the hydration reaction of ACCM and weakly enhanced the compressive strength.H_(3)PO_(4)(HP)at a concentration of 0.05 mol/L had a certain effect on ACCM retardation,but HP at a concentration of 0.07 and 0.09 mol/L had an effect of promoting the setting and hardening time of ACCM.
基金supported by the National Research Foundation (NRF) grant funded by the Korea government (NRF2022R1C1C1007619, NRF-2021M3H4A1A01002921, NRF2021M3I3A1084292)supported by the KIST Institutional Program (Project No. 2E32592-23-069)。
文摘PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(PrBSCF) has attracted much research interest as a potential triple ionic and electronic conductor(TIEC) electrode for protonic ceramic fuel cells(PCFCs). The chemical formula for Pr BSCF is AA'B_(2)O_(5+δ), with Pr(A-site) and Ba/Sr(A'-site) alternately stacked along the c-axis. Due to these structural features, the bulk oxygen ion diffusivity is significantly enhanced through the disorder-free channels in the PrO layer;thus, the A site cations(lanthanide ions) play a pivotal role in determining the overall electrochemical properties of layered perovskites. Consequently, previous research has predominantly focused on the electrical properties and oxygen bulk/surface kinetics of Ln cation effects,whereas the hydration properties for PCFC systems remain unidentified. Here, we thoroughly examined the proton uptake behavior and thermodynamic parameters for the hydration reaction to conclusively determine the changes in the electrochemical performances depending on LnBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ)(LnBSCF,Ln=Pr, Nd, and Gd) cathodes. At 500 ℃, the quantitative proton concentration of PrBSCF was 2.04 mol% and progressively decreased as the Ln cation size decreased. Similarly, the Gibbs free energy indicated that less energy was required for the formation of protonic defects in the order of Pr BSCF < Nd BSCF < Gd BSCF. To elucidate the close relationship between hydration properties and electrochemical performances in LnBSCF cathodes, PCFC single cell measurements and analysis of the distribution of relaxation time were further investigated.
基金Funded by the National Natural Science Foundation of China(No.52172026)the Science and Technology Development Project of China Railway Design Corporation(Nos.2023A0226407 and 2023B03040003)。
文摘A ternary system comprising Ca_(20)Al_(26)Mg_(3)Si_(3)O_(68)(Q-phase),limestone,and metakaolin is proposed,and its hydration behavior,hydration product phases,microstructure,and mechanical properties are investigated and compared with pure Q-phase cement.The results indicate that the ternary system exhibits exceptional and sustained compressive strength even under a 40℃environment,significantly outperforming pure Q-phase.The mechanism lies in that metakaolin effectively inhibits the transformation of metastable phase.Meanwhile,the interactions among Q-phase,limestone,and metakaolin further enhance the cementitious performance.The ternary system effectively addresses potential issues of strength loss in Q-phase cement application,and as a low-carbon cementitious material system,it holds promising potential applications.
基金the National Natural Science Foundation of China(52172030)for the financial support.
文摘Free water available in calcium aluminate cement(CAC)-bonded castables is crucial for the hydration of CAC and the conversion of hydration products in the curing and drying processes,as both the hydration and conversion reactions are dissolution–precipitation reactions.To elucidate the effect of different levels of free water loss upon the hydration of CAC,the conversion of hydration products and the mechanical strength of the CAC-bonded castables,the CAC-bonded castables were subjected to sealed and unsealed curing conditions at 50℃ and drying at 110℃.The results demonstrate that the fast removal of free water during unsealed curing would hinder the conversion from 2CaO·Al_(2)O_(3)·8H_(2)O to 3CaO·Al_(2)O_(3)·6H_(2)O and consequently prevent the deterioration of strength.As a comparison,although sealed-cured samples have less water loss and high degree of hydration of CAC,they still show lower strength than the unsealed samples after curing.The following drying process further accelerates the hydration of residual calcium aluminate clinkers for both the sealed and unsealed samples,but still does not favor the conversion from 2CaO·Al_(2)O_(3)·8H_(2)O to 3CaO·Al_(2)O_(3)·6H_(2)O in the unsealed-cured samples.
基金Funded by the National Natural Science Foundation of China(No.51802235)Hubei Science and Technology Innovation Talent Project,China(No.2023DJC087)。
文摘It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.
