Conventional geopolymer coatings are prone to water infiltration due to their inherent hydrophilicity, and single modification approach often cannot simultaneously provide satisfactory hydrophobicity and bonding properties. In this work, hydrophobic geopolymer coatings were prepared using ground granulated blast furnace slag (GGBS) and fly ash (FA) as precursors, with hexadecyltrimethoxysilane (HDTMS) and nano-SiO2 as composite modifiers. Response surface optimization produced a reliable quadratic model with an R2 value of 0.9842. Compared with the unmodified coating, the composite-modified coating increased the water contact angle from 56.5 degrees to 132.5 degrees (134.5%) and reduced the 7-d water absorption from 2.32% to 0.73% (68.5%), while maintaining a bonding strength of 3.88 MPa. After mechanical and chemical durability tests, the water contact angle and bonding strength remained above 110 degrees and 3.30 MPa, respectively, with the latter exceeding the minimum adhesion requirement of 1.5 MPa specified in JTG/T 3310-2019. Nano-SiO2 promoted secondary geopolymerization and matrix densification, compensating for the adverse effect of HDTMS on bonding, whereas HDTMS reduced the surface energy by introducing long-chain hydrophobic groups. This composite-modification strategy provides a feasible approach for preparing geopolymer protective coatings with excellent hydrophobicity, reliable bonding performance, and good engineering applicability.

Al2O3 is more economical and easier to be physically doped to prepare epoxy resin (EP) composites for actual production. The effect of various alumina types on the properties of epoxy resin casting materials intended for Ultra-High Voltage (UHV) electrical applications was investigated. The electrical and mechanical properties of epoxy resin casting materials were examined. Based on the assessment of physical and chemical properties, as well as electrical and mechanical characteristics, A-Al2O3/EP exhibited the highest glass transition temperature (T-g) and the most efficient curing process, with its viscosity changing at the fastest rate. The tensile strength, flexural strength, impact strength (7.5 J), compressive strength and elongation (tensile and flexural) tests demonstrated that A-Al2O3/EP possessed commendable mechanical properties. Furthermore, A-Al2O3/EP displayed superior electrical properties, according to the evaluations of electric breakdown strength, dielectric constant, and volume resistivity. The viscosity growth of A-Al2O3/EP was the fastest at 110 and 120 degrees C, and the T-g of A-Al2O3/EP was the highest in the three samples, displaying both mechanical and electrical tests. It could be concluded that A-Al2O3 significantly facilitated the curing reaction. Moreover, GIS units incorporating epoxy resin casting materials were developed using A-Al2O3 as the filler.

This study investigated the impact of five commonly employed water-reducing agents on the fluidity of cement paste at varying dosages firstly. The agents considered in this research are sodium lignosulfonate (LS), naphthalene superplasticizer (PNS), aliphatic superplasticizer (HSB), and two types of polycarboxylate superplasticizers (PCEs), specifically PCE-5C and PCE-6C. Subsequently, the impact of water reducing agents on both the total drying shrinkage and autogenous shrinkage of cement mortar was investigated. This was done by maintaining a consistent water-cement ratio, ensuring good workability, and adjusting the dosage of various water-reducing agents to achieve comparable slump flow in the mortar. Furthermore, the study delved into the mechanisms behind the influence of different types of water-reducing agents. The findings indicate the following: 1) Polycarboxylate superplasticizers (PCEs) exhibit superior dispersion performance with cement, trailed by naphthalene superplasticizer (PNS) and aliphatic superplasticizer (HSB), while sodium lignosulfonate (LS) demonstrates the least effective dispersion performance. The fluidity of cement paste is most responsive to variations in the dosage of PCEs, followed by PNS and HSB, whereas the fluidity of cement paste undergoes minimal changes when the dosage of LS is increased. 2) The effects of various water reducing agents on the volume shrinkage of cement mortar are distinct, and their influence is the outcome of multiple factors working in tandem. These factors include the postponement of the exothermic peak during cement hydration, reduction in solution surface tension, and decrease in the proportion of larger pores and smaller-sized capillary pores within the porosity of cement-based materials, and all these aspects collectively contribute to minimizing the volume shrinkage of cement-based materials. 3) In the realm of concrete engineering, opting for PCEs as water-reducing agents has proven effective in reducing the overall drying shrinkage of cement-based materials. Notably, PCE-5C demonstrates a superior ability in minimizing shrinkage compared to PCE-6C.

In the present study, the evolution of free water content in five different alkali-activated slag (AAS) systems was continuously monitored and compared using 1H low-field NMR. The alkali activators used were waterglass solutions with three different moduli (1.2, 1.4, and 1.6), sodium hydroxide solution, and sodium sulfate solution. The findings reveal that the type of activator significantly affected the dynamic changes in the relative free water content. Notably, an increase in free water content was observed in the early stages of hydration of all AAS systems except for those activated by sodium sulfate solution. Additionally, this study investigated the relationship between changes in free water content and hydration heat in the AAS systems, dividing the initial 24 h of AAS hydration into three stages. The results demonstrate that free water can serve as an effective probe for monitoring the hydration process in fresh AAS pastes, offering valuable insights alongside traditional thermal signals.

The structural characteristics of silica aerogels prepared under different concentrations of Na + , Ca 2+ and Al 3+ were thoroughly evaluated by using XRD and FTIR, and then, their adsorption capacity for the oils and organic solvents was investigated through a combined technique of 1 H-NMR, nitrogen adsorption and SEM observation. The results show that the different cations and their varied concentrations can significantly change the adsorption capacity of silica aerogels, which is closely related to the correspondingly modified pore structure and pore volume. Specifically, Na + does not involve in the formed skeleton of the silica aerogel, but precipitates as sodium chloride crystals, which reduces the pore volume of silica aerogels and then decreases the adsorption capacity. The increased [Ca 2+ ] can increase the pore volume and pore size of silica aerogels, but a first increase and then decrease in the adsorption capacity of the aerogels is observed, which could be related to the reduced capillary force due to the increased pore size. At last, the presence of Al 3+ can greatly decrease the pore volume of the silica aerogels and their corresponding adsorption capacity, which could be caused by the participation of Al 3+ in the formed skeleton of silica aerogels.

A series of polycarboxylate superplasticizers (PCEs) with different molecular structures and shrinkage reducing performance were synthesized by modifying PCE with butyl acrylate (BA), and their molecular structures were characterized. The influence of BA on the dispersion and shrinkage reducing performance of PCEs and the influence of PCEs grafting different ration of BA on the hydration of cement were investigated in detail. Furthermore, the mechanisms of BA improving PCE shrinkage reducing performance were emphatically analyzed. The results showed that: (1) BA was successfully grafted into the molecular structures of PCEs and the expected molecular structures were obtained by polymerization. (2) BA has little effect on the dispersion of PCEs, but it will affect the hydration process of cement paste mixed with PCEs and significantly improve the shrinkage reducing performance of PCEs. (3) After grafting BA monomer into PCE, the surface tension of PCE solution decreased and the evaporation rate of alkaline solution mixed with PCE also significantly slowed down. Moreover, the retention capacity of pore water of cement paste mixed with PCE was improved. These three reasons were considered to be the main mechanisms of BA improving the shrinkage reducing performance of PCE.

The tetraethoxysilane (TEOS)-derived sol-gel process was systematically investigated by the rheological oscillation test and the effect of different synthetic parameters, including TEOS concentration, water content, base catalyst concentration and temperature, on the viscoelastic properties of the formed gel was analyzed. It is found that the rheological oscillation test provides an efficient and accurate way to determine the gelation time in the sol-gel process. The time at which the storage modulus and loss modulus intersect can be regarded as the gelation time in the sol-gel process and it matches well with the time observed with the naked eyes. Furthermore, both the increased TEOS and base catalyst concentration can be beneficial to the improvement of the gel elasticity, which could be related to the increased concentration of silica primary particles and its condensation reaction rate. However, the increased water content and temperature lead to a first increase and then a decrease in the elasticity of the gel. The proper molar ratio of TEOS to water is 0.67:4.01 and the suitable reaction temperature is 318 K in this study.

Free water plays a crucial role in the hydration process of beta-calcium sulfate hemihydrate (beta-HH) based plaster. To further understand the hydration mechanism of beta-HH, this study monitored water consumption and pore structure evolution of plaster prepared by different water/beta-HH (W/H) ratios using low-field NMR. The hydration characteristics were jointly analyzed using X-ray diffraction (XRD), thermogravimetric (TG), and isothermal calorimetry. In addition, the pore structure of the plaster was characterized by BET and MIP. Results indicated that during early hydration (0-10 min), free water migrated from macropores to micropores in beta-HH samples. The specific surface area and free water content of beta-HH based plaster decreased during rapid hydration period. It is also found that increasing the W/H ratio accelerated free water consumption but resulted in larger pore diameter. Furthermore, signal intensity and transverse relaxation time were found to be exponentially related (y = Ae((-x/B)) + y(0)) to the CaSO4 center dot 2H(2)O crystal content, hydration degree, and heat release. These correlations suggest that low-field NMR correlated well with other measurements and could be viable method to characterize the plaster hydration process.

This paper presented a comprehensive study on the early-age hydration process and autogenous shrinkage evolution of high performance cement pastes. The early-age hydration process of cement pastes was analyzed by combining H-1 nuclear magnetic resonance relaxometry (H-1 NMR) with isothermal calorimetry. The hydration degree was contrastively analyzed by using H-1 NMR and thermogravimetry analyses (TGA). Moreover, the relationship between the free water consumption process and autogenous shrinkage for cement pastes was revealed. Results showed that a magnetism-heat (M - H) model could be established according to the correspondence between free water consumption rate and hydration exothermic rate, which divided the early-age hydration process of cement pastes into four periods. The initial setting time was the onset that free water signal fraction started to drop, after this moment, the consumption rate of free water was increased and more hydration products were generated. After about final setting time, the weighted mean relaxation time of the free water sharply decreased, and the pore structure of cement pastes was gradually refined. The hydration degree (alpha) of cement calculated by H-1 NMR and TGA showed good agreement, with the error of alpha values less than 2% after initial setting time. Furthermore, cement paste with a lower water/cement ratio showed higher autogenous shrinkage and lower free water signal fraction, but they did not show a good linear correlation with each other throughout the hydration process.

Copper slag (CS) is a by-product generated during the process of copper metal smelting. The influence of CS on the mechanical performance, hydrate assemblage, and mechanism of the cementitious system was investigated by multiple methodologies to accelerate the sustainable development of the copper industries. The results revealed that adding 10% by weight of CS was beneficial to developing compressive strength. However, the strength decreased significantly if too much CS was incorporated. This adverse effect can be mitigated by prolonging the curing age. Besides, the evolution of mechanical performance was explained by multiple microscopic studies. More ettringite (AFt) and monosulfate (AFm) were formed in the paste containing 10% by weight of CS at 28 days, which filled the space and improved the strength. For the paste containing 30% by weight of CS, the backscattered electron images suggested that more than 60% of incorporated CS participated in the hydration at 200 days and developed an additional C (A) S H with a higher atomic ratio of Fe/Si and Al/Si, resulting in a dramatic improvement in compressive strength. Finally, the hydration mechanism of CS in the cementitious system was established based on the dissolution test combined with the theory of cement hydration.

Waste glass has the potential to be a sustainable alkali-activated material, but the low activity is not conducive to the development of strength. This study aimed to improve the compressive strength of ground granulated blast furnace slag-glass powder (GGBS-GP) paste by replacing GP with pretreated glass powder (PGP). The results indicate that the pretreatment of GP by the alkaline solution can depolymerize the surface structure and promote its dissolution during the hydration process of GGBS-GP paste. Hence, compared to GP, PGP has a higher reactivity to react with GGBS and it is favorable for the formation and the growth of chain length of C-A-S-H gel. Compared with GGBS-GP paste, GGBS-PGP paste can increase the amount of C-A-S-H gel by 51%. Correspondingly, the compressive strength of GGBS-GP paste can be significantly improved through the partial or all substitution of GP by PGP, and its 28 d compressive strength can be increased by 92.5%. At last, the calculated results confirm that the incorporation of PGP can decrease the cost and increase the sustainability of the GGBS-GP system, which provides the precondition for the wide application of PGP as a new cementitious material.

Using ground clay brick powder (CBP) replacing cement to prepare blended binding system is an effective solution to reduce the accumulation of wasted clay bricks. However, the increased incorporation ratio of CBP causes a drawback of decreased mechanical property. The present research is aiming at using triisopropanolamine (TIPA) to alleviate the excessive loss of compressive strength of cement paste incorporated with highcontent of CBP. Furthermore, the hydration behavior of cement-CBP-TIPA system is investigated in detail. The study indicated that the addition of TIPA improved cement hydration and pozzolanic reaction of CBP, thereby the compressive strength was improved at different ages. More specifically, the presence of TIPA accelerated the conversion of AFt to AFm as well as the dissolution of aluminum and iron ions from CBP, thus more calcium aluminosilicate hydrate was formed. In addition, the economic and environmental effect was also assessed. It was proved that 47% of energy consumption and 47% of carbon footprint can be saved by developing the cementCBP-TIPA binding system.

TiO2@SiO2 composite microspheres (TS) were prepared by the deposition of TiO2 on the raspberry-like SiO2@polystyrene microspheres (PSS). The hollow microspheres with hierarchical microtopography possess both improved photocatalytic activity and stabilized TiO2 particle structure. The results of energy dispersion spectrum (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) showed that after calcination, anatase TiO2 nanoparticles has formed on the raspberry-like PSS template with preferred deposition among interstitials of the drupelet-like structure. The thermal degradation of the polystyrene (PS) core during calcination led to the hollow microspheres. The photocatalytic experiments indicated that the raspberry-like TiO2@SiO2 composite microspheres (TS1-T53) had higher photocatalytic efficiency than the smooth ones (TS0), due to the hierarchical and hollow structure. The sample TS2 prepared with a moderate ammonia concentration (3 %) not only had relatively more intact hollow spherical structure, but also enhanced photocatalytic activity. The hollow TiO2@SiO2 composite microspheres (TS3) prepared with 4 % ammonia showed the best photocatalytic efficiency. However, the higher ammonia concentration made the drupelet-like structure unstable and the microspheres tend to disintegrate. The raspberry-like microstructure showed a protective effect on the loaded TiO2, which resulted in better recyclability with persistent photocatalytic activity. The hierarchical composite microspheres shed light on the potential effective utilization strategy of nano-photocatalyst.

A ZnGa2O4:Cr3+-based aerogel was prepared by using polyacrylic acid (PAA) as a dispersant and propylene oxide (PO) as a crosslinking agent via CO2 supercritical drying. The results of BET and SEM show that there is a certain degree of macroporosity (d > 50 nm) in the aerogel. It has a dendritic structure and the interior is relatively loose. EDS mapping illustrates that the elements Zn, Ga, and Cr are evenly distributed in the aerogel. In addition, the diffuse reflectance spectra and the emission spectrum of samples with different calcination temperatures were also characterized. Both demonstrated, when the calcination temperature is greater than 600 °C, that the sample crystallizes and has a significant emission, which is consistent with the XRD and TG-DSG results. Finally, the ZnGa2O4:Cr3+-based aerogel also exhibits excellent long afterglow performance and high photocatalytic performance with 80.1% methylene blue (MB) degradation at 20 min.

As an attractive collector medium for hypervelocity particles, SiO2 aerogel has been deployed on outer space missions. Aiming at quantifying the complicated relationship between the penetration track and the residual grains, many attempts have been made on hypervelocity experiments and models. However, models were difficult to accord strictly well with experimental data attributed to many uncertainties including thermal effects, aerogel accretions and projectile ablation during the penetration. In this paper, impact experiments were conducted at various density silica aerogels (50 similar to 120 kgm(-3)) with regular soda-lime glass beads as projectiles. Varying degrees of thermal effects happened around and along track was observed by scanning electron microscopy. That energy distribution in the track released by hypervelocity projectile has a decreasing change. The regular data of the terminal A-beta type track (the track with combined features) was found according to A-type tracks classification based on the conditions of vapor model (Dominguez, 2009). Just considering for projectile overcoming the crushing strength with uniform deceleration, the simple mechanism was confirmed by the data fitted well with the snowplow model (Dominguez et al., 2004). The result after tracks classification is due to the terminal track with few thermal effects and aerogel accretions. In addition, other two types of tracks formation processes were discussed.

A low-density (48 mg cm−3) polymethylsilsesquioxane aerogel was prepared by ambient pressure drying and surface modification.

In previous study, it was found that the fractal dimension of the silica aerogel could be only controlled by adjusting the catalysts. In this work, we used the aging process investigated by H ae reid et al. to continuously adjust the fractal dimension of silica aerogel. The fractal structure of the silica aerogels were analyzed by small angle x-ray scattering (SAXS). The SAXS measurements show linear increases in the volume fractal dimension (2.32-2.64) of the secondary particles with aging time (0-72 h). This linear behavior is due to the silica precipitated from the aging solution to the secondary particles is at a constant rate. In the meantime, the light transmittances was obtained by ultraviolet-Visible-infrared spectrophotometer, extinction coefficient were obtained by fitting the curve of light transmittances. We developed a new model to build a connection between the extinction coefficient and the fractal dimension of the silica aerogel obtained by SAXS. From new model, it was found it is due to the increases in volume fractal dimension (D-f) that result in increases of extinction coefficient and decreases of light transmittances. The optical transparency of silica aerogel is strongly affected by the volume fractal dimension (D-f) of the secondary particles of silica aerogel.

We designed a resorcinol-formaldehyde (RF) sol–gel ink for direct ink writing of the microlattices. To improve the formability, the fresh microlattices were strengthened by surface catalysis with HCl atmosphere. After supercritical drying and carbonization, the sample’s specific surface area was 631 m2/g and the average pore size was 3.81 nm. Both RF aerogel and carbonized RF aerogel samples had millimeter-scale pore, micron-scale pore, and nanoscale skeleton. The pore and skeleton could provide high surface area and diffusion channels, which were beneficial to the adsorption performances. The carbonized RF aerogel sample fully adsorbed Dulbecco’s modified eagle medium in 250 min, which exhibited a good capacity of quick adsorption and indicated the potential application for cell supports.