Using (Na)2TiF6 and CO(NH2)2 as raw materials, we proposed a simple one-pot hydrothermal method for synthesizing single-phase anatase TiO2 across a broad pH range of the precursor solution. The results showed that, irrespective of whether the precursor solution was acidic (pH=1.43, 3.43, 5.37), neutral (pH= 7.23), or alkaline (pH=9.45, 11.18, 13.15) prior to the hydrothermal reaction, the post-reaction solution pH stabilized between 8 and 9, and all resultant TiO2 materials were identified as single-phase anatase. This finding contrasted with previous reports where phase transformations among anatase, rutile, or brookite were observed under varying pH conditions of the precursor solution. This discrepancy was attributed to the continuous decomposition of urea during the hydrothermal process, which maintained the pH of the reaction solution within a relatively stable range. Comprehensive investigations revealed that anatase TiO2 synthesized at pH 7.23 exhibited optimal light absorption ability, enhanced charge dynamics, and a larger electrochemically active surface area. As a result, TiO2 (pH 7.23) showcased the highest photocatalytic activity toward tetracycline (TC), achieving a degradation efficiency of 97.7
We investigated thermally driven reactions at the Cr/Bi2Se3 interface via atomic-resolution scanning transmission electron microscopy, revealing that structural transformations were strictly dictated by Bi cation enrichment. Under mild heating at 150 °C, the selective reaction between Cr and Se, where Cr substituted for Bi, resulted in a low degree of Bi cation enrichment. These displaced Bi cations segregated at the reaction front and formed a layer of pure Bi, yielding an atomically sharp CrSe2/Bi/Bi2Se3 epitaxial heterostructure. Conversely, a higher temperature of 350 °C induced high Bi cation enrichment due to the significant growth of the CrSe2 layer and the massive displacement of Bi. This excess Bi disrupted the flat interface, forming a BiSe phase near the boundary and alternating Bi3Se4/Bi2Se3 superlattices deeper within the substrate. Simultaneously, the significant disparity in diffusion rates (vCr ≫ vSe) triggered the Kirkendall effect, leading to macroscopic void formation. Our findings highlight that controlling cation enrichment critically influences the interfacial structure during solid-state reactions.
Magnetically responsive photonic crystal(MRPC)liquid exhibits fast magnetic responsive-ness and dynamic color variation,but its fluidity limits practical applications.To overcome this challenge,Fe3O4@PVP MRPC is utilized to develop MRPC microcapsules with a polydimethylsiloxane(PDMS)shell via droplet microfluidics.These microcapsules integrate excellent magnetochromism and durability.The microcap-sules display fast magnetic response(<1 s)and wide spectral tunability(485-640 nm),allowing a broad color-tuning range from blue to red under magnetic fields.Notably,the MRPC microcapsules demonstrate long-term stability for over 100 days in polar solvents and epoxy resin.Additionally,MRPC microcapsule-based patterns can achieve dynamic color displays by varying the magnetic field strength,viewing angle,and magnet shape,respectively.Due to their unique multimodal and dynamic color changing properties,MRPC microcapsules show significant potential in the anti-counterfeiting field.
The stress-strain curves of seawater sea-sand recycled aggregate concrete(SSRAC)with dif-ferent replacement ratios of recycled coarse aggregate(RCA)or sea-sand under different strain rates were stud-ied.The effects of different replacement ratios of RCA or sea-sand,and ages on the characteristic parameters of the stress-strain curve and corresponding dynamic increasing factor(DIF)of SSRAC were analyzed.Scanning electron microscopy(SEM)and nanoindentation tests were used to explain the variation of the characteristic pa-rameters from the microscopic point of view.The results show that,when the replacement ratio of RCA or sea-sand is 50％,the strain rate sensitivity of elastic modulus is higher than that of peak stress;the DIF of peak stress exhibits a pattern of initially decreasing and then increasing with the increasing replacement ratio of RCA or sea-sand.Conversely,the DIF of elastic modulus initially shows an increase followed by a decrease.The introduction of seawater and sea-sand promotes hydration,resulting in a denser microstructure for SSRAC as compared to that of recycled aggregate concrete,which influences its strain rate sensitivity.Finally,a stress-strain prediction model of SSRAC is proposed,which can provide a theoretical basis for its experimental re-search and engineering application.
Fluorine-doped reduced graphene oxide (FRGO) was synthesized from spent graphite (SG) by first producing reduced graphene oxide (RGO) via potassium permanganate-assisted oxidation and thermal reduction, followed by fluorination with lithium hexafluorophosphate. The optimized material, FRGO-3, exhibited an expanded interlayer spacing of 0.375 nm, an ultrahigh specific surface area of 1 433.86 m2·g−1, and a high fluorine doping content of 3.6
Enzyme-powered Janus nanomotors using SiO2 as carriers have demonstrated significant application potentials in the field of biomedicine, attributed to their autonomous motility and excellent biocompatibility. This article constructs two urease-powered Janus nanomotors (Ur-JNDSNPs and Ur-JNMSNPs) based on different SiO2 structures, namely dendritic mesoporous and non-dendritic mesoporous, and studies the effect of carrier structure on the fabrication of nanomotors and their motion behaviors in biological medium. The results show that, in comparison to Ur-JNMSNPs, the nanomotors constructed based on dendritic mesoporous (Ur-JNDSNPs) exhibit superior mobility in both water and PBS solution as a simulated body fluid. Notably, they show excellent colloid stability and protein-resistant mobility, which enables substantially higher mobility in DMEM medium containing proteins compared to in PBS solution. This characteristic confers them with penetration ability in simulated physiological environments. This finding stands in stark contrast to most previously reported nanomotors and underscores the importance of rationally designing carrier structures to advance the biomedical applications of nanomotors.
The mechanical properties and durability of concrete in high-altitude regions are adversely affected by unfavorable climatic conditions, including low air pressure, low humidity, low temperatures, large temperature differences, and strong winds. These conditions accelerate the moisture evaporation, deteriorate the air-void structure, delay strength development, and increase the risk of surface cracking and scaling in concrete. We conduct a detailed review of the influencing factors, extent, and mechanisms involved, clarifying the performance of concrete at high altitudes. Furthermore, the validity of research methodologies reported in the literature is discussed, highlighting errors caused by variations in air pressures and the use of inappropriate test methods. Finally, various research outcomes are summarized, and the future research directions are suggested. The review indicates that the surface layer of concrete structures is the most severely affected, exhibiting numerous quality issues at early ages. The mechanism of superficial cracking should be re-evaluated based on an overall isotropy model that accounts for localized anisotropy. Additionally, vacuum saturation tests conducted at different altitudes lead to varying degrees of water absorption, introducing significant errors in the test results for concrete impermeability.
Numerous studies have indicated that nano calcium carbonate (NCC) has the potential to enhance the mechanics, durability, and functionality of cementitious composites, thus developing high performance, durable, multifunctional, and low carbon cementitious composites. This paper reviews the recent progress in NCC modified cementitious composites and provides a comprehensiveness overview of the impact of NCC on the performances of cementitious composites, which includes the fabrication (materials, preparation methods, and curing methods), structures (hydration products and microstructures), and properties (hydration, workability, mechanical properties, durability, and functionality). Moreover, the mechanisms and the challenges as well as future directions of NCC modified cementitious composites are also explored and prospected.
This study focuses on the collaborative innovation of building solid waste recycling and road-bed lightweight.Aiming at the key technical bottlenecks of high energy consumption and low utilization rate of building micro-powder of traditional foam concrete cementitious materials,this paper mixed 30％,50％and 70％hybrid recycled micro-powder to prepare A07 density grade foam concrete,and explored the influence of hybrid recycled micro-powder content on the performance of foam concrete.A07 density grade foamed con-crete with 70％mixed recycled fine powder was prepared by using composite microbial foaming agent to ex-plore the optimal proportion of mixed recycled fine powder(recycled brick powder:recycled concrete powder is 2:8,4:6,6:4,8:2)in the field of subgrade filling,promote the recycling of mixed recycled fine powder of con-struction waste,and provide new filling materials with light weight,high strength and ecological benefits for subgrade engineering,which has important engineering application value for promoting the construction of'no waste city'.The research results show that:(1)With the increase of recycled micro powder content to 70％,the dry density of A07 grade foam concrete shows an upward trend,and the compressive strength shows a gradual downward trend.The dry density of foam concrete in BP,CP,RP(4:6),RP(6:4)groups increased by 45.5％,32.7％,36.9％,and 42.3％respectively compared with the control group,and the compressive strength de-creased by 70％,66％,55％,and 64％respectively;(2)The performance of hybrid recycled micro powder foam concrete with 70％content increased first and then decreased with the increase of the proportion of hybrid re-cycled micro powder.When the mass ratio of recycled brick powder to recycled concrete powder is 4:6,its per-formance indicators reach the best,with a surface dry compressive strength of 1.52 MPa,a saturated compres-sive strength of 1.73 MPa,a dry shrinkage of 0.40 mm,and good frost resistance(mass loss rate of 2.82％,strength loss rate of 9.88％),meeting the requirements of Technical Specification for Bubble Mixed Lightweight Soil Filling Engineering(CJJ/T 177-2012).
The present study explores the relationship between coal gas fine ash(CGFA)content and the electromagnetic performance of cement-based composites,and the modification effects of carbon black(CB),with particular focus on the electromagnetic property evolution in CB-CGFA systems at different formulation ratios.The experimental findings demonstrate that CGFA has a substantial impact on enhancing the electrical conductivity and complex permittivity of the composite material.The cement mortar demonstrates enhanced low-frequency(1-8 GHz)wave-absorbing characteristics.The numerical value of reflection loss(RL)exhibited a positive correlation with CGFA content,reaching an optimal value of-11.9 dB at 1.1 GHz for 2％CGFA con-tent.The addition of CB to CGFA cement mortar facilitates to enhance its electromagnetic performance through synergistic effects within the cement matrix.This addition exhibits enhanced complex permittivity,characterised by combined polarization and resistive loss mechanisms.The absorbing performance exhibited a non-monotonic relationship with CB content,achieving an optimal RL of-18.95 dB at 4.24 GHz for 2％CGFA with 0.75％CB.
The usage and recyclability of recycled aggregate concrete(RAC)are critical for addressing construction waste disposal.However,there is still uncertainty about the reusability of freeze-thaw damaged RAC when using 100％recycled aggregates.The frost durability and recyclability of fully replaced recycled concrete with different strength grades(C40,C50,and C60)were investigated.The recyclability was evaluated based on the physical properties of the second-generation recycled aggregate(2nd-RCA).The results showed that all the RAC met the target compressive strength requirements.The tensile strength of C50 RAC was close to that of C60 RAC.The higher cement content in C60 RAC made it more brittle.C60 RAC exhibited the best frost resistance,in terms of mass loss and relative dynamic modulus of elasticity.However,during the crushing process to prepare the 2nd-RCA,the excessively high strength made it difficult for the adhesive mortar to peel off from C60 RAC,and the additional crushing process caused microcracks.The 2nd-RCA produced from C50 RAC was of the best quality and had the highest output rate.Nonetheless,all the 2nd-RCA from the three strength grades of RAC demonstrated the capability for cyclic use in freeze-thaw environments.
Wind load caused by the high-speed running train is the typical environmental factor for bal-lastless track supporting layer concrete.Herein,the effect of wind load on the internal relative humidity(IRH),volume stability and mechanical properties of supporting layer concrete were investigated by a designed device to produce stable wind loads.Mercury intrusion porosimeter(MIP)and scanning electron microscopy(SEM)were used to analyze the evolution of the microstructure and the morphology of hydration products.Results show that,under a wind velocity of 10 m/s,the IRH at a depth of 2 cm decreases to 35.9％within 10 days,lead-ing to a 40.1％higher shrinkage compared to that under windless environment.Meanwhile,the volume of spe-cific pores(200-10 000 nm)is increased by 18.2％,which results in a 24.3％reduction in compressive strength and a weaker interfacial transfer zone(ITZ).Additionally,a model for IRH and internal restraint stress of supporting layer concrete under wind load was developed.This work can provide a reference for the design and maintenance of ballastless track supporting layer concrete.
In this study,we prepared reactive powder concrete(RPC)specimens with diatomite replace-ment levels of 0％,5％,10％,15％,and 20％by weight of cement using pan mixer.The fresh properties were evaluated through flow tests,and the hardened properties were determined by conducting compressive strength and tensile strength tests.The density of hardened specimens was measured and compared with conventional RPC.An optimum replacement level was identified based on the reduction in density and the retention of ad-equate mechanical performance.In addition,steel fibers were replaced with basalt fibers to evaluate their influ-ence on the mechanical behavior of RPC.The results showed that the incorporation of diatomite powder re-duced the density due to its porous structure,while maintaining satisfactory strength at replacement level of 10％.The use of basalt fibers improved the crack resistance and overall performance of the modified RPC.The study demonstrates that diatomite powder can be effectively used to produce low-density reactive powder con-crete with acceptable mechanical properties.
In order to explore the influence of different activation methods on the durability of cement-ferro nickel slag composite mortar, the durability of the composite mortar was evaluated by measuring the performance indexes of the composite mortar in the environment of freeze-thaw cycle, accelerated carbonization, and chloride ion penetration. The results show that the mechanical activation and alkali activator improve the reactivity of the cementitious system, and the enhancement of the filling effect and the increase of the hydration products improve the compactness of the internal structure, which not only enhances its frost resistance, but also slows down the transmission rate of CO2 in the accelerated carbonization environment and the ion penetration rate in the chloride ion erosion environment.
To improve the flame-retardant performance of epoxy resin(EP),EP composites were devel-oped using aluminum diethylphosphonate(ADP)and melamine polyphosphate(MPP)as a compound flame re-tardant,and calcium-based MOF(calcium terephthalate,CaT)as a synergist(MOF refers to metal-organic frame-works).The results demonstrated that the combination of CaT and ADP/MPP significantly enhanced the flame-retardant properties of EP.With only 2％CaT and 5％ADP/MPP(relative to the mass of EP),the LOI value of EP composite reached 33.8％,and UL-94 V-0 grade was achieved.The peak heat release rate,the total heat release and the total smoke production values decreased by 44.2％,25.6％,and 52.0％,respectively.The addition of a small amount of CaT improved the mechanical strength and toughness of EP.The relevant mechanism was dis-cussed to explain the synergistic effect of CaT and ADP/MPP in EP.The results indicated that the incorporation of CaT not only enhanced the stability of char layer but also suppressed the release of toxic gases during combus-tion.As a cost-effective MOF material,CaT has a potential application in improving the fire safety of EP.
In order to investigate the effects of oxide particles on the high-temperature resistance and ablation performance of ceramicizable phenolic resin composites, three types of quartz fiber-reinforced ceramicizable phenolic resin composites were prepared using MgO particles or Al2O3 particles as the second-phase oxides and ZrB2 particles as the high-temperature ceramic filler, through a mold pressing process. The enhancement effects and mechanisms of the added second-phase oxides on the high-temperature resistance and ablation performance of the composites were discussed and analyzed through high-temperature testing, phase characterization, oxyacetylene testing, and microstructure characterization. The results show that ZrB2 particles oxidize to form ZrO2 and B2O3 in an oxygen-rich high-temperature environment. The added second-phase oxide particles can react with B2O3 to form corresponding borates, thereby strengthening the matrix. After treatment at 800 °C, the flexural strength of the ZrB2-MgO quartz fiber-reinforced phenolic resin composite (QFPR/ZM) increased by 55.3
In the process of backfill grouting for shield tunneling,the hardening and shrinkage of the slurry can easily lead to ground settlement,whereas the secondary grouting prolongs the construction period and increases the engineering cost generally.In this study,a new but low-cost strategy to resist the shrinkage of backfill grouting using calcium a sulphoaluminate micro-expansion agent(CAS-H)is innovatively proposed.With the addition of CAS-H at 8％and 20％,the lateral expansion rate of the backfill grouting increased to 1％and 3％at 28 d,respectively.On the contrary,that of the backfill grouting without CAS-H was only about-4％.Simultaneously,CAS-H also increased the density and the impermeability of the hardened slurry significantly.Other essential properties such as the bleeding rate,setting time,fluidity,consistency,strength after hardening and other indicators of the backfill grouting still satisfied the related engineering standards.From the perspec-tive of microstructure,the appearance of C-S-H gel,C4AH13,Aft,Afm and Ca(OH)2 was accelerated by CAS-H,filling the pores and making the microstructure denser.The hydration heat curve and thermodynamic simula-tion(GEMS)further validated the other essential beneficial effects of CAS-H,and the cumulative hydration heat of 72 h was calculated to be increased by 29.6％.The hydration degree of cement clinker(C3S,C2S,C3A,C4AF,etc)also increased,which was believed the key reason for inhibiting the shrinkage of the background grouting using the expansion agent-activated strategy.
In order to facilitate the recycling of sewage sludge ash (SSA), and to reveal the effects of SSA and super absorbent polymers (SAP) on the volumetric deformation of the high performance cement-based materials, the separate and coupled effects of SSA and SAP on the volumetric deformation of the cement pastes with a low water/binder ratio (0.25) under different environmental conditions (sealed, drying, and water immersion environments) were studied. The results showed that the addition of SSA or SAP reduced the autogenous and drying shrinkage, and increased the water immersion expansion strain of the cement pastes. The addition of SSA and SAP together further reduced the autogenous and drying shrinkage, and increased the water immersion expansion. The synergistic effect of SSA and SAP on the volumetric deformation of the cement pastes was observed under a sealed environment. It was less significant under a water immersion environment. Under drying environment, the reduction in shrinkage caused by the combined addition of SSA and SAP was lower than the sum of the reduced shrinkages caused by SSA and SAP alone. These findings provided a new potential approach for the recycling and utilization of SSA.
To address the limitations of traditional silicone hydrogel contact lenses in wettability and drug release, an innovative approach was proposed by incorporating polyethylene glycol (PEG) and sodium hyaluronate (SH) into these lenses. Aminoalkyl-terminated polydimethylsiloxane (KF8010) was reacted with glycidyl methacrylate (GMA) to synthesize GKF8010, which was then mixed with methacryloxymethyltris (trimethylsiloxy) silane (TRIS), N,N-Dimethylaniline (DMA), and PEG400 to fabricate PEG-modified silicone hydrogel contact lenses (PEG-SCL) via UV molding. Unmodified lenses (SCL) were served as controls. The effects of PEG modification on lens properties, including water content, wettability, and optical clarity, and SH loading efficiency and drug release were evaluated. Additionally, the protein adsorption and biocompatibility of the lenses with human umbilical vein endothelial cells (HUVECs) were assessed. Results indicated that PEG-modified lenses exhibited superior water content, reduced protein adsorption, enhanced SH loading capacity and controlled release profiles, highlighting their potential for treating dry eye syndrome.
To reduce the environmental pollution associated with the construction of asphalt pavements, and to improve the current problems of insufficient stability, durability, and adaptability of cold mix asphalt (CMA), a cold mix emulsified asphalt (CMEA) was prepared by using emulsified asphalt, silane coupling agent, cement, plaster, and mineral powder. The basic properties of CMEA were evaluated through penetration, softening point, and ductility tests. The high-temperature rheological properties of CMEA were analyzed using dynamic shear rheometry (DSR). The microstructure of CMEA was assessed via fluorescence microscopy (FM) and Fourier transform infrared spectroscopy (FTIR) tests. Results indicate that the emulsion within the emulsified asphalt can be uniformly distributed in the form of particles, resulting in improved storage stability. Compared to the original emulsified asphalt, the addition of cement, plaster, or a combination of both shows better stability and deformation resistance. The CMEA with both the silane coupling agent and cement exhibits the optimal performance. This study provides new insights for the modification and application of CMA.
