Nucleation Effect Research Articles

Microcellular foaming of high-hardness TPU/MOF nanocomposites through combined heterogeneous nucleation and gas enrichment effects

Microcellular foaming of high-hardness TPU/MOF nanocomposites through combined heterogeneous nucleation and gas enrichment effects

Study on the effect of nano-silica on the early-age strength and microstructure of cement paste mixed with calcium nitrite under negative temperature conditions

During construction at low temperatures, fresh concrete is susceptible to early freeze damage, which can permanently damage the concrete structure. Therefore, this study aimed to enhance the early-age strength and durability properties of the cement paste at −5 ℃ by incorporating calcium nitrite (CN) antifreeze and nano-silica (NS). First, the effects of CN and NS on the fresh properties of the cement paste were measured by setting time and bleeding rate tests. Subsequently, the mechanical properties and chloride content after salt solution erosion were tested for each group of specimens, and the change in slurry densification was further observed by ultrasonic pulse velocity and resistivity tests. Finally, the hydration products and microstructure of the specimens were analyzed using XRD and SEM tests. The results showed that the addition of CN and NS could reduce the setting time of cement paste and avoid the bleeding phenomenon of cement paste under negative temperature environment. The decrease in curing temperature and the use of NS both inhibited the promotion of C3A hydration by nitrite ions, which led to a decrease in nitrite-AFm content. However, NS can compensate for the reduced nitrite-AFm content by promoting the production of hydrated C-S-H through nucleation and pozzolanic effects. Ultimately, the strength and resistance of the slurry to chloride erosion are improved.

Numerical investigation of tip vortex cavitation noise with an emphasis on environmental nucleation effect

The multiscale interactions between macroscale cavities and microscale nuclei influence the tip vortex cavitation (TVC) dynamics and its induced noise. To study the underlying mechanisms, we employ a two-way transition and coupling Euler–Lagrange model. Through acoustic analogy analysis, we identify the cavity volume fluctuations as the main vocal mechanism of cavitating tip vortex, highlighting two critical cavity dynamics, i.e., the breathing mode of surface waves and the cavity collapse of downstream end. Multiscale simulation results suggest that the merging of microscale bubbles into macroscale cavities can generate a more continuous tip vortex cavity and enlarge the cavity size. In addition, the high-frequency noise is significantly increased due to the nuclei injection, and the cavity collapse noise is reduced due to a more continuous cavity. Our investigation provides a foundation for understanding multiscale TVC dynamics and noise.

Reinforcing mechanisms review of the graphene oxide on cement composites

Abstract By virtue of the abundant oxygen-functional groups, ultra-high specific surface area and superior mechanical properties, graphene oxide (GO) has been proven as one of the outstanding candidates in cement composites. Compared with the traditional cement pastes, the GO-reinforced cement composites exhibit benefits in pore structure, mechanical properties, and durability. In addition, the abundant oxygen-containing functional groups on GO can promote the hydration rate of cement and combine with hydration products to fill the pores. To further improve the performance of GO-reinforced cement composites and promote the application of composites in practical engineering, it is necessary to comprehensively understand the reinforcing mechanisms of GO on cement composites. In this work, the enhancement mechanisms of GO to improve hydration, nucleation effects, mechanical strengthening mechanisms, antiseepage mechanisms and pore-filling effects of GO are systematically revealed. The optimal dosage range of GO mixing in the current study is calculated by considering the factors of mechanical property and microscopic characterization, but the economic cost also needs to be considered in future development studies. This review will promote the application of the more cost-effective and high-performance GO-reinforced cement composites in practical construction engineering.

The Role and Mechanism of Rice Husk Ash Particle Characteristics in Cement Hydration Process.

Reactive rice husk ash (RHA) is used as a supplementary cementitious material (SCM) to prepare cement composite pastes. The impact of RHA content and the internal curing effect on the hydration process of the cementitious system was studied. The hydration heat, degree, and product content of the cement-RHA composite system at 3, 7, and 28 d were analyzed using hydration microcalorimetry, thermogravimetry, and XRD (Rietveld) analysis. The results show that with the increase in RHA, the main exothermic peaks move forward, and the values increase. The induction period is prolonged, and the acceleration period is shortened. The induction period of 15% RHA is extended to 3 h. The hydration heat of cement composite pastes is mainly divided into three stages. Namely, the first stage (0-18 h) is the superposition of the RHA nucleation effect and chemical effect, the second stage (18-51 h) is the superposition of the dilution effect and internal curing effect, and the third stage (51-72 h) is the internal curing effect with the water-release. The internal curing effect of RHA has a certain periodicity, which is related to its content. The water-release age in the early stage (24 h) advances with the increase of content, and the water-release effect in the later stage (7-28 d) is also significant with the increase of content. The higher the content, the more significant the promotion of the internal curing effect on cement hydration and the pozzolanic reaction of RHA.

Preparation and Antibacterial Properties of Poly (l-Lactic Acid)-Oriented Microporous Materials.

In this manuscript, an efficient self-reinforcing technology-solid hot drawing (SHD) technology-was combined with green processing supercritical carbon dioxide (SC-CO2) foaming technology to promote poly (l-lactic acid) (PLLA) to form an oriented micropore structure. In addition, Polydimethylsiloxane (PDMS), with a high affinity of CO2 and biological safety, was introduced to enhance the nucleation effect in SC-CO2 foaming and co-regulate the uniformity of oriented micropores' structure. The results showed that orientation induced PLLA crystallization, so the tensile strength was improved; the maximum tensile strength of the oriented micropores' PLLA reached 151.2 MPa. Furthermore, the micropores mainly improved the toughness; the maximum elongation at break reached 148.3%. It is worth mentioning that PDMS can form an antibacterial film on the surface of the material, so that the material has a continuous antibacterial effect.

Surface modified cellulose nanospheres with simultaneous nucleation and degradation-accelerating effects on poly(lactic acid)

As a novel type of nanocellulose material, cellulose nanospheres (CNSs) have gained significant attention and rapid development in recent years. In this work, the surface hydrophobic modification of CNSs was achieved by employing maleic anhydride as an esterifying agent. The effects of modified cellulose nanospheres (CNS-MA) on the crystallization and hydrolysis behaviors of polylactic acid (PLA)-based composites were systematically investigated. The results demonstrate that surface modification improves the dispersion of CNSs in the PLA matrix. Well-dispersed particles act as nucleation sites, which increases the crystallization rate and crystallinity of PLA and endows the composites with remarkable heat distortion resistance. The storage modulus of the PLA/CNS-MA composites exceeds 300 MPa, even at an elevated temperature of 90 °C. Furthermore, the hydrolytic degradation of PLA is dramatically accelerated with the addition of CNS-MA. Combining the morphology observations and theoretical calculations, it is speculated that the fast hydrolytic degradation is related to a transition in the main hydrolytic degradation mechanism from surface erosion to bulk erosion, because the presence of CNS-MA provides particular pathways for water molecules to diffuse into the interior of the composites. This research highlights the potential of CNSs as a multifunctional filler with both reinforcing and degradation-promoting effects, offering valuable insights for the study of other biomass nanomaterials.

Turning mine-tailing streams into sources of water and mineral salts in a membrane-sustained circular scenario

The discharge of wastewater from the mining industry has a critical ecological impact, potentially endangering both soil and marine ecosystems. Alternatively, recovering pure water and valuable materials from these hypersaline streams through a technologically efficient process, would help reduce the ecological impact of the waste, while providing a viable supply chain for raw materials such as magnesium, potassium and others, considered critical to the economy. In this context, this work aimed to simultaneously recover pure water and mineral salts from mine wastewater by membrane-assisted crystallization (MAC). A prior theoretical study based on thermodynamic parameters attempted to predict salts precipitation at different temperatures. MAC tests were then performed at specific thermal gradients and feed pretreatment conditions, achieving preferential precipitation of solids products of different composition containing large quantities of Ca or Mg/K minerals from the real mine tailing wastewater. The experiments also demonstrated the central impact of heterogeneous nucleation effects.

Impact of statistical poly(propylene co-ethylene) on the thermo-mechanical properties of high-density polyethylene

A series of high-density polyethylene and a statistical copolymer of poly(propylene-co-ethylene) blends in a wide range, namely (0, 10, 20, 30, 40, 50, 60,70, 80, 90, 100) abbreviated as HDPE/VM were systematically investigated by using a rheometer, differential scanning calorimetry (DSC) measurements, polarized optical microscopy (POM) and tensile tests. Rheometer results show that adding VM decreases dynamic viscosity, storage, and loss modulus. Han plot shows that HDPE and VM are compatible and miscible in the range from 20 to 60 VM % in the molten state. DSC results show little nucleation effect of VM on HDPE (HDPE’s melt crystallization temperature shifts 2 °C higher). Moreover, a linear composition dependence of ∆cp ∆Hc, ∆Hm shows that PE and VM are most probably compatible in the molten state in composition range from 20 to 60%. However, upon crystallization, the VM and PE domains occur distinctively. The results of the tensile tests demonstrated a decrease in elastic modulus, yield stress, and ultimate tensile strength as VM content increased. At low VM content (less than 20%), high elongation at break was detected for the blends, and very fine spherulites of HDPE were found across the sample by POM.

Sustainable utilization of magnesium slag through carbonation: a pathway to high-value products with vaterite calcium carbonate

In this study, vaterite - rich materials (VRM) were prepared by carbonating magnesium slag (MS) with the addition of glycine as a regulator and the influence of VRM on the preference of cement was also investigated. The results showed that VRM without glycine exhibited only calcite, whereas the presence of glycine led to an increased vaterite content. The formation of rhombic calcite particles was observed in pure carbonated MS samples, while the addition of glycine during the carbonation process led to the formation of spherical vaterite particles. The compressive strength decreased with increasing MS content, while the high surface area of VRM, nucleation effect of vaterite and the pozzolanic reaction of amorphous silica gel led to an enhancement compressive strength. Overall, the prepared VRM offers a promising approach for transforming solid waste into valuable products through CO2 capture and utilization.

Influence of municipal solid waste incineration bottom ash on the hydration and carbonation behavior of reactive magnesia cement

This study investigates the effects of Municipal solid waste incineration bottom ash (MSWIBA) on the hydration and carbonation behavior of reactive magnesia cement (RMC). The results indicate that the incorporation of MSWIBA accelerates the early hydration rate of RMC due to its dilution and nucleation effects. However, excessive MSWIBA content formed layered double hydroxides (LDH) inhibiting the hydration of magnesium oxide cement. Furthermore, while a 5% addition of MSWIBA enhances the compressive strength of RMC after carbonation, higher contents lead to a reduction in post-carbonation strength and long-term durability due to the formation of microcracks from hydrogen gas generation and the expansion from carbonation products. Additionally, the carbonation process is affected by LDH, which hinders the crystallization of hydromagnesite and favors the formation of more amorphous phases. The findings suggest that while MSWIBA can be beneficial at low dosages, its excessive use may compromise the long-term performance of RMC.

Effects of amino alcohols-intercalated MgAl-LDH nanocomposites on the properties of sulfoaluminate cement-based materials

Sulfoaluminate cement-based materials (SCBMs) have low mechanical properties in the early stages when they are used in grouting reinforcement engineering. The mechanical properties of cement-based materials can be improved by nanotechnology. Hydrotalcite is a layered anionic clay with adjustable interlayer anions and nanometer spacing. To date, the effect of amino alcohols (ethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA))-intercalated MgAl-layered double hydroxides (LDH) nanocomposites (denoted as MgAl-LDH-TEA, MgAl-LDH-DEA, and MgAl-LDH-MEA) on the properties of SCBMs have not been studied. Herein, we demonstrate that intercalated MgAl-LDH exhibit a decrease in crystallinity, an increase in particle size, and improved early mechanical properties compared to unmodified LDHs. MgAl-LDH modified by TEA, DEA, and MEA all have a nucleation effect and provide nucleation sites for ettringite. Simultaneously, the intercalated hydrotalcite can release higher concentrations of magnesium ions into the slurry, forming a magnesium-containing ettringite phase and accelerating the hydration of SCBMs. Modified MgAl-LDH can also release amino alcohols, affecting the hydration process of the paste. The modified LDHs affect the hydration and compressive strength of SCBMs owing to the combined action of the nucleation of LDHs and the release of magnesium ions and amino alcohols compounds.

Influence of the graphene oxide-coated steel fiber on the microstructure optimization of UHPC

Benefiting from its superior mechanical properties, large specific surface area and abundant oxygen-containing functional groups, graphene oxide (GO) can generate nucleation and pore-infilling effects to optimize the microstructure of the cementitious composites, thus reinforcing the mechanical performance and durability of cement-based materials. However, due to the dispersion issues and relatively high cost, the widespread use of GO in the cement industry has not yet been realized. In the present study, we applied three different methods to coat industrial GO nanosheets on the steel fiber’s surface and reinforce the UHPC microstructure. The proposed coating method effectively disperses GO within the ultra-high-performance concrete (UHPC) matrix and targets its enhancement effects on the interfacial transition zone (ITZ), which has the weakest pore structure in UHPC. The result presents that the three-step dip method of GO coating on the steel fiber demonstrates higher effectiveness in reinforcing the microstructure of UHPC, the porosity of the matrix is 1.88 %, with a relative decrease of 37.1 ∼ 60.3 %. In addition, the average distance of ITZ after GO enhanced UHPC is about 3.7 µm, about 37.3 %-68.1 % shorter, and the ITZ porosity is 3.8 %, which is 15.6 %-65.5 % lower. With the assistance of the metal intrusion technique, backscattered electron characterization and deep learning-based analysis, the pore structure features of UHPC were extracted with a classification recognition accuracy of 88.5 %, and the pore intrusion volume inside the characteristic region of the UHPC matrix increased by 1.89–2.14 times. The extraction characteristics illustrated that the GO strengthening on steel fibers was more effective in ITZ, with an optimization efficiency of about 8.1 % higher than in other regions. We expect that the findings of this study could provide deep insights into GO modification for cementitious composite reinforcement applications and open new pathways for affordable alternatives to nano-enhanced composites.

Synergetic bifunctional Cu-In alloy interface enables Ah-level Zn metal pouch cells

Rechargeable aqueous zinc-metal batteries, considered as the possible post-lithium-ion battery technology for large-scale energy storage, face severe challenges such as dendrite growth and hydrogen evolution side reaction (HER) on Zn negative electrode. Herein, a three-dimensional Cu-In alloy interface is developed through a facile potential co-replacement route to realize uniform Zn nucleation and HER anticatalytic effect simultaneously. Both theoretical calculations and experimental results demonstrate that this bifunctional Cu-In alloy interface inherits the merits of low Zn-nucleation overpotential and high HER overpotential from individual copper and indium constituents, respectively. Moreover, the dynamical self-reconstruction during cycling leads to an HER-anticatalytic and zincophilic gradient hierarchical structure, enabling highly reversible Zn chemistry with dendrite-free Zn (002) deposition and inhibited HER. Moreover, the improved interface stability featured by negligible pH fluctuations in the diffusion layer and suppressed by-product formation is evidenced by in-situ scanning probe technology, Raman spectroscopy, and electrochemical gas chromatography. Consequently, the lifespan of the CuIn@Zn symmetric cell is extended to more than one year with a voltage hysteresis of 6 mV. Importantly, the CuIn@Zn negative electrode is also successfully coupled with high-loading iodine positive electrode to fabricate Ah-level (1.1 Ah) laminated pouch cell, which exhibits a capacity retention of 67.9% after 1700 cycles.

Defect-controlled confined growth of nano-MOFs to prepare materials with hierarchical micro/mesoporous structures for efficient CO2 capture

In recent years, nanoporous materials with special structure have been widely used in various fields. In view of the poor stability of MOFs materials and the poor mass transfer ability, in this study, we developed a simple method to restrict the growth of UiO-66-NH2 crystals in hollow silica by “vacuum evaporation” strategy, different kinds of acid regulators were introduced, to obtain a composite material with hierarchical pore structure. By characterizing the physical chemistry and microstructure of the composite adsorbent, and calculating the structural defects under different acid regulation, the adsorption and desorption performance and stability of the adsorbent for CO2 were comprehensively investigated. The mechanism of action on CO2 was further analyzed by in-situ infrared and other techniques. The results show that the change of coordination environment and coordination rate caused by the competition of organic acids, which increases the defects and reduces the nucleation and aggregation effect of UiO-66-NH2, promotes the formation of hierarchical pore structure of the composites. Among them, benzoic acid is the best regulating monocarboxylic acid, which makes UiO-66-NH2 have good dispersion in the cavity and suitable crystal size. The specific surface area of the composite material is 717.96 m2 g−1. At the same time, due to its excellent CO2 adsorption capacity (3.35 mmol g−1) at 298 K and 1.06 bar, it is 48.07 % higher than the original UiO-66-NH2. In order to accomplish the goal of effective CO2 adsorption performance of composites, this study offers a novel approach for the synthesis and modification of MOFs-based composites.

A novel in-situ fibrillation enhancement strategy to achieve super-elastic green foam with enhanced biodegradation

Driven by concerns about the escalating environmental pollution caused by the widespread use of plastic products, there is considerable interest in developing high-performance biodegradable materials. Poly(butylene adipate-co-terephthalate) (PBAT) foams are recognized as a highly sought-after candidate for alleviating plastic pollution, distinguished by their admirable biodegradability and flexibility. However, the extensive applications of PBAT foam are considerably constrained by inadequate melt strength and inherent shrinkage. Herein, a pioneering and scalable strategy, combining the shear-induced in-situ fibrillation process with microcellular foaming, was devised to achieve lightweight and super-resilient PBAT/poly(tetrafluoroethylene) (PTFE) foams. Thanks to the heterogeneous nucleation effect and complex tangled physical networks induced by in-situ nano-fibrillated PTFE, the crystallization and viscoelasticity of PBAT matrix experienced a dramatic enhancement, further bolstering its foaming capabilities and suppressing the shrinkage process. More importantly, the synergy of reduced foam density and reinforcement effect of PTFE nanofibrils played a crucial role in improving the remarkable compression of PBAT/PTFE foams. These foams showed a maximum increase of 40.2 % in strength and 16.3 % in resilience compared to pure PBAT foams. Moreover, the thermal insulation and soil degradation capability of PBAT/PTFE foams were substantially enhanced, achieving 10.3 % biodegradation after just 2 months. This innovative strategy offers a promising avenue for developing high-performance eco-friendly biocomposites.

Effect of lanthanum on inclusions and solidification structure of alloy 800H

Alloy 800H is commonly used in high temperatures and corrosive environments due to its exceptional strength and resistance to high temperatures, but the ingots are prone to longitudinal cracking during the hot working process because of its coarse solidification structure. Based on the heterogeneous nucleation effect of rare earth inclusions, a strategy is proposed to refine the solidification structure of alloy 800H by La treatment to solve the crack problem. In this study, four kinds of alloy 800H ingots (0, 120, 260 and 470 ppm La) were prepared to investigate the effect of La on the solidification structure. After adding La, the types of inclusion were changed, and the modification path of inclusions was Al2O3 (0 ppm La) → LaAlO3 (120 ppm La) → LaAlO3·La2O2S and La2O2S (260 ppm La) → La2O2S and La2O3 (470 ppm La). After adding La, the inclusion morphology tended to be more spherical and the average size smaller. The lattice misfit calculation indicated that La-containing inclusions can serve as heterogeneous nucleation cores, and the number of effective heterogeneous nucleation also increased with La content increased. The columnar to equiaxed transition occurred early with La treatment, the ratio of the equiaxed zone increased from 2.1% to 36.5%, and the average equiaxed grain size decreased from 2.56 to 0.43 μm with La content increased from 0 to 470 ppm. The solidification structure of alloy 800H was significantly refined by adding La, and can thus provide a new strategy to solve the crack problem.

Evaluation of the use and performance of natural filler based polypropylene/leonardite composites

The use of polypropylene (PP), which has reached a considerably high level in the last century and is one of the polymers whose properties have been investigated and studied in much more detail with the use of various additives, can be obtained as composite structures with the use of both inorganic and organic additives, and the desired properties can be modified according to the desired purpose. In this study, it was aimed to evaluate the behavior of leonardite, a rich source of humic acid, with PP composite structures, whose performance with thermoplastic materials has never been investigated before, although there are studies on its use in different sectors. To evaluate the effects of different ratios of leonardite additives on PP polymer, the composites were prepared with a twin screw extruder, and the test specimens were produced using an injection molding device. Spectroscopic, density, microscopic, mechanical (tensile, impact, flexural), thermal and color analyses of composites containing leonardite at 0, 0.5, 1, 3, 5, and 10 wt% were carried out. As the amount of leonardite in the composite increased, a slight increase was observed in the density values of the composites, with a maximum of 4.7%. In microstructure analysis, a homogeneous distribution of the filler was observed in composites reinforced up to 1 wt%, while agglomeration occurred at higher rates. While the highest tensile strength and flexural strength values were found for the 5 wt% leonardite filled composite, it was observed that these values increased from 31.8 MPa to 32.7 MPa and from 32.84 MPa to 37.84 MPa compared to the pure PP, respectively. The highest Izod impact strength value was determined for the 10 wt% leonardite filled composite and an increase in this value was obtained from 2.47 kJ/m2 to 2.85 kJ/m2. The nucleation effect explains the decrease in supercooling temperature observed in the thermal analysis results. Furthermore, an increase of the thermal stability of PP/leonardite composite structures was demonstrated. When the color analysis results were examined, it was seen that the leonardite additive caused the color of the composite to darken, as expected.

Thermistors Based on Polyethylene Composites with γ‐Fe2O3/Multiwalled Carbon Nanotube Hybrid Fillers for Protection of Electronic Circuits

The objective of this research is to develop and characterize polyethylene composites with randomly and partially oriented hybrid filler (HF) based on multiwalled carbon nanotubes (MWCNTs) decorated with gamma iron (III) oxide (γ‐Fe2O3) nanoparticles (Fe2O3/MWCNTs). The structure of Fe2O3/MWCNTs hybrid is determined by X‐ray diffraction (XRD), Raman spectroscopy, and microscopy techniques (scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, transmission electron microscopy). A low‐density polyethylene (LDPE) matrix is filled with 5 and 10 vol% HF. The effect of external magnetic field on the distribution of Fe2O3/MWCNTs in LDPE composites comparing to filler distribution without magnetic field is studied. The XRD and differential scanning calorimetry results confirm an increasing trend in the degree of crystallinity of LDPE matrix with increasing HF content and as an additional result of magnetic field application. The presence of more ordered Fe2O3/MWCNT particles in the matrix has enhanced the nucleation effect for LDPE crystallization process in composites under magnetic field. The effect of magnetic treatment on thermal, electrical, and thermoresistive properties of HF‐LDPE composites is studied. The highest thermoresistive response (723%) and fastest recovery are detected for the HF‐LDPE composite with 10 vol% magnetically oriented filler with the perspective to be applied as a critical temperature resistor.

Influence of in-situ lunar temperature on the pore structure and solid phases of alkali-activated lunar regolith simulant

The construction of extraterrestrial bases has become an indispensable step in the active exploration of deep space. In this study, alkali-activated lunar regolith simulant (AALRS) activated by sodium hydroxide (SH) and sodium silicate (SS) were prepared and then cured at various lunar temperatures. The compressive strength was tested, and the pore structure characteristics were characterized using mercury intrusion porosimetry (MIP), followed by further in-depth quantitative analysis through fractal theory. The solid phases were characterized using thermogravimetry analysis (TGA) and scanning electron microscopy (SEM). It is found that all the fractal curves are divided into three regions, and the fractal dimensions in all regions are between 2 and 3, suggesting the pores of AALRS paste always have self-similar physical significance. The fractal dimension D1 of the small pore is the largest, followed by fractal dimension D3 of the great pore and fractal dimension D2 of the middle pore. The increase in modulus and temperature leads to an increase in the pore surface area, fractal dimension, amount of N-A-S-H gel and compressive strength and a decrease in total pore volume and characteristic pore diameter, which is mainly attributed to the nucleation effect of soluble Si. The turning pore diameter at the micrometer scale and excessive porosity of AALRS paste, which is distinctly different from that of common cementitious materials, demonstrates looser pore structure of AALRS paste. Based on these results, the influence mechanism of in-situ lunar temperature on the performance of AALRS paste is profoundly discussed and elucidated, which provides a deep understanding of designing and tailoring the various properties of AALRS material.