Hierarchical Aggregates Research Articles

Facile synthesis and mechanistic insights into ZSM-5 aggregates via a mesoporogen-free route

Developing hierarchical zeolites is highly important for catalytic applications. In this study, micro- and submicron-sized hierarchical ZSM-5 zeolites, composed of aggregated nanosized ZSM-5 crystals, were facilely synthesized without any mesoporogen. The effects of the gel composition in a mesoporogen-free system on the formation of ZSM-5 aggregates were studied. The results revealed that the Na2O/SiO2 molar ratio and the aluminum source exerted significant impacts. Furthermore, we demonstrated that the morphology and size of the ZSM-5 aggregate could be easily adjusted by varying the gel composition. Mechanistic insights indicated that the formation of hierarchical ZSM-5 aggregates in the mesoporogen-free system likely followed a space-confined growth mechanism.

Low-Hysteresis and Tough Ionogels via Low-Energy-Dissipating Cross-Linking.

Low-hysteresis merits can help polymeric gel materials survive from consecutive loading cycles and promote life span in many burgeoning areas. However, it is a big challenge to design low-hysteresis and tough polymeric gel materials, especially for ionogels. This can be attributed to the fact that higher viscosities of ionic liquids (ILs) would increase chain friction of polymeric gels and eventually dissipate large amounts of energy under deformation. Herein, a chemical design of ionogels is proposed to achieve low-hysteresis characteristics in both mechanical and electric aspects via hierarchical aggregates formed by supramolecular self-assembly of quadruple H-bonds in a soft IL-rich polymeric matrix. These self-assembled nanoaggregates not only can greatly reinforce the polymeric matrix and enhance resilience, but also exhibit low-energy-dissipating features under stress conditions, simultaneously benefiting for low-hysteresis properties. These aggregates can also promote toughness and subsequent anti-fatigue properties in response to external cyclic mechanical stimuli. More importantly, these ionogels are presented as a model system to elucidate the underlying mechanism of the low hysteresis and fatigue resistance. Based on these findings, it is further demonstrated that the supramolecular low-hysteresis strategy is universal.

Hierarchical Supramolecular Aggregation of Molecular Nanoparticles for Granular Materials with Ultra High-Speed Impact-Resistance.

The high-speed impact-resistanct materials are of great significance while their development is hindered by the intrinsic tradeoff between mechanical strength and energy dissipation capability. Herein, the new chemical system of molecular granular material (MGM) is developed for the design of impact-resistant materials from the supramolecular complexation of sub-nm molecular clusters (MCs) and hyper-branched polyelectrolytes. Their hierarchical aggregation provides the origin of the decoupling of mechanical strengths and structural relaxation dynamics. The MCs' intrinsic fast dynamics afford excellent high-speed impact-resistance, up to 5600 s-1 impact in a typical split-Hopkinson pressure bar test while only tiny boundary cracks can be observed even under 7200 s-1 impact. The high loadings of MCs and their hierarchical aggregates provide high-density sacrificial bonding for the effective dissipation of the impact energy, enabling the protection of fragile devices from the direct impact of over 200 ms-1 bullet. Moreover, the MGMs can be conveniently processed into protective coatings or films with promising recyclability due to the supramolecular interaction feature. The research not only reveals the unique relaxation dynamics and mechanical properties of MGMs in comparison with polymers and colloids, but also develops new chemical systems for the fabrication of high-speed impact-resistant materials.

Nanosized “rice ball” like hierarchical beta zeolites with inter-crystalline mesopores for efficient catalytic synthesis of lactide

A series of nanosized “rice ball” like hierarchical beta zeolite aggregates (RBZxAy, x = 6, 9, 12 or 15; y = 2, 4 or 6) with hierarchical structures are successfully synthesized via gel aging and hydrothermal method without mesoporous template. The as-prepared RBZxAy zeolites possess two ranges of inter-crystalline mesoporous that formed by zeolite nanoparticles aggregation compared to the non-aged samples (B12Z4). The effects of Si/Al ratio and crystallization time on the morphology, structure and surface acidic properties of RBZxAy were systematically investigated. Meanwhile, RBZxAy as catalysts were applied in the conversion of lactic acid (LA) to lactide (LT) to investigate their catalytic performance. Benefitting from smaller crystal size, hierarchical structures and higher acid content, the representative catalyst (RBZ12A4) exhibited outstanding catalytic activity that the LA conversion was high to 98 % and the LT yield up to 94 %. In addition, RBZ12A4 presented perfect regeneration ability after 10 times recycles. This work provides an effective and facile route to directly synthesis nanocrystals aluminosilicate zeolite with hierarchal structure, and constructs an approach for efficiently converting LA to LT, it has greatly significance for the development of polylactic acid industry.

Carbon and nutrient cycling responses to repeated application of biochar and NPK fertilizers depend on microenvironmental differences among hierarchical aggregate fractions

The conversion of bambara groundnut seed residues into biochar facilitated the bioavailability and retention of more nutrients (C, N, P, K and Mg) after repeated application of biochar. However, the mechanisms of microbially mediated biochar-C degradation and nutrient cycling responses to repeated biochar application, particularly in different hierarchical soil aggregates, are largely unknown. A 20-day incubation experiment was conducted on Ultisols from a 4-year cucumber field trial in Nsukka, Nigeria. The effects of repeated application of bambara seed residue biochar with or without NPK fertilizer on soil aggregate associated electrical conductivity (EC), basal respiration, microbial biomass, and soil enzyme activities were determined. The results showed that the concentration of organic matter in the bulk soils increased with biochar and NPK+biochar treatments. These treatments also increased the soil EC, cumulative CO2 respiration, microbial biomass C and N concentrations, and the activities of tyrosine-aminopeptidase and sulfatase enzymes, compared to the biochar treatment and the control soil. The NPK+biochar treatment contributed 35 % more to β-cellobiosidase activity, but the biochar treatment resulted in 85 % reduction in N-Acetyl-β-glucosaminidase activity, indicating microbial N mining. The NPK and NPK+biochar treatments accounted for a higher percentage of N-, C and N-, and S- cycle enzyme activities, although their composition was relatively higher with the latter treatment. The overall soil biochemical responses were significantly higher in the micro-aggregates (< 0.25 mm) than in the macro-aggregates (≤ 4.75–0.25 mm); least of all in the small macro-aggregates (0.25–1.00 mm). Therefore, repeated application of biochar to N-deficient soils generally does not result in positive soil biochemical responses. However, repeated application of biochar together with NPK fertilizer modulates N limitation and optimizes microbial nutrient cycling processes, especially in micro-aggregates.

MVPipe: Enabling Lightweight Updates and Fast Convergence in Hierarchical Heavy Hitter Detection

Finding hierarchical heavy hitters (HHHs) (i.e., hierarchical aggregates with exceptionally huge amounts of traffic) is critical to network management, yet it is often challenged by the requirements of fast packet processing, real-time and accurate detection, as well as resource efficiency. Existing HHH detection schemes either incur expensive packet updates for multiple aggregation levels in the IP address hierarchy, or need to process sufficient packets to converge to the required detection accuracy. We present, an invertible sketch that achieves both lightweight updates and fast convergence in HHH detection. builds on the skewness property of IP traffic to process packets via a pipeline of majority voting executions, such that most packets can be updated for only one or few aggregation levels in the IP address hierarchy. We show how can be feasibly deployed in P4-based programmable switches subject to limited switch resources. We also theoretically analyze the accuracy and coverage properties of . Evaluation with real-world Internet traces shows that achieves high accuracy, high throughput, and fast convergence compared to six state-of-the-art HHH detection schemes. It also incurs low resource overhead in the Tofino switch deployment.

Solvothermally Synthesized Hierarchical Aggregates of Anatase TiO2 Nanoribbons/Nanosheets and Their Photocatalytic–Photocurrent Activities

Hierarchical aggregates of anatase TiO2 nanoribbons/nanosheets (TiO2-NR) and anatase TiO2 nanoparticles (TiO2-NP) were produced through a one-step solvothermal reaction using acetic acid or ethanol and titanium isopropoxide as solvothermal reaction systems. The crystalline structure, crystalline phase, and morphologies of synthesized materials were characterized using several techniques. According to our findings, both TiO2-NR and TiO2-NP were found to have polycrystalline structures, with pure anatase phases. TiO2-NR has a three-dimensional hierarchical structure made up of aggregates of TiO2 nanoribbons/nanosheets, while TiO2-NP has a nanoparticulate structure. The photocatalytic and photocurrent activities for TiO2-NR and TiO2-NP were investigated and compared with the widely used commercial TiO2 (P25), which consists of anatase/rutile TiO2 nanoparticles, as a reference material. Our findings showed that TiO2-NR has higher photocatalytic and photocurrent performance than TiO2-NP, which are both, in turn, higher than those of P25. Our developed solvothermal method was shown to produce a pure anatase TiO2 phase for both synthesized structures, without using any surfactants or any other assisted templates. This developed solvothermal approach, and its anatase TiO2 nanostructure output, has promising potential for a wide range of energy harvesting applications, such as water pollution treatment and solar cells.

Relationship between fractal feature and compressive strength of fly ash-cement composite cementitious materials

Microscopic pore structure and compressive strength of fly ash-cement composite cementitious materials at 20 °C and 60 °C measured by mercury intrusion porosimetry and compressive strength test. Microscopic pore structure was analyzed from porosity, pore volume, total pore surface area, average pore diameter, median pore diameter, most probable diameter, threshold diameter and fractal feature. The fractal dimensions of each specimen were calculated by Menger Sponge. The regression analysis between fractal dimension and pore structure parameters were fitted by linear function, quadratic polynomial function, power function and exponential function, respectively. Eventually, the relationship between pores structure and compressive strength was characterize by the mathematical model between the optimal comprehensive parameter of pores structure and compressive strength. And the T-test and F-test were used to reveal the significance of the regression parameter and function. Research results showed that the fractal curves of all specimens consist of four segments. The pores have obvious fractal features in Region I and Region IV, while presented no-fractal feature in Region II and Region III. In Region I and Region IV, fractal dimension followed the exponential function with average pore diameter, median pore diameter, most probable diameter and threshold diameter, consistent with quadratic polynomial function with porosity, pore area and pore volume, and accords with the positive power exponential function with compressive strength. Thus, the morphology of hierarchical aggregates expressed by fractal dimension can reflect the relationship compressive strength and pore structure in fly ash-cement composite cementitious materials more directly.

DFEN: Dual Feature Enhancement Network for Remote Sensing Image Caption

The remote sensing image caption can acquire ground objects and the semantic relationships between different ground objects. Existing remote sensing image caption algorithms do not acquire enough ground object information from remote-sensing images, resulting in inaccurate captions. As a result, this paper proposes a codec-based Dual Feature Enhancement Network (“DFEN”) to enhance ground object information from both image and text levels. We build the Image-Enhancement module at the image level using the multiscale characteristics of remote sensing images. Furthermore, more discriminative image context features are obtained through the Image-Enhancement module. The hierarchical attention mechanism aggregates multi-level features and supplements the ground object information ignored due to large-scale differences. At the text level, we use the image’s potential visual features to guide the Text-Enhance module, resulting in text guidance features that correctly focus on the information of the ground objects. Experiment results show that the DFEN model can enhance ground object information from images and text. Specifically, the BLEU-1 index increased by 8.6% in UCM-caption, 2.3% in Sydney-caption, and 5.1% in RSICD. The DFEN model has promoted the exploration of advanced semantics of remote sensing images and facilitated the development of remote sensing image caption.

Facile and template-free synthesis of robust, highly active and easily recyclable submicrometer-sized hierarchical TS-1 aggregates composed of ultra-small nanocrystallites (&lt;50 nm)

Submicrometer-sized hierarchical TS-1 aggregates were synthesized by freeze-drying of precursors and routine steam assisted crystallization. The catalysts exhibited easy isolation and high activity in the oxidative desulfurization of fuel oils.

Composed Image Retrieval via Cross Relation Network With Hierarchical Aggregation Transformer.

Composing Text and Image to Image Retrieval (CTI-IR) aims at finding the target image, which matches the query image visually along with the query text semantically. However, existing works ignore the fact that the reference text usually serves multiple functions, e.g., modification and auxiliary. To address this issue, we put forth a unified solution, namely Hierarchical Aggregation Transformer incorporated with Cross Relation Network (CRN). CRN unifies modification and relevance manner in a single framework. This configuration shows broader applicability, enabling us to model both modification and auxiliary text or their combination in triplet relationships simultaneously. Specifically, CRN includes: 1) Cross Relation Network comprehensively captures the relationships of various composed retrieval scenarios caused by two different query text types, allowing a unified retrieval model to designate adaptive combination strategies for flexible applicability; 2) Hierarchical Aggregation Transformer aggregates top-down features with Multi-layer Perceptron (MLP) to overcome the limitations of edge information loss in a window-based multi-stage Transformer. Extensive experiments demonstrate the superiority of the proposed CRN over all three fashion-domain datasets. Code is available at github.com/yan9qu/crn.

Cosolvent effect on morphogenic changes of self-assembled aggregates from biodegradable polylactones

The solvent variation effect on the self-assembly phenomenon is discussed in this article. Two different biodegradable backbones of the same community (polycaprolactone and polylactide) were selected to visualize the morphological changes upon treatment of different solvents/cosolvents. The curiosity was to observe if the change occurred only with the solvents or it was assisted to the backbones also. Tetrahydrofuran, acetonitrile and 1,4 dioxane were used as polar aprotic solvent whereas, methanol was used as polar protic one with the common solvent water in each case. The macromolecular aggregates were formed using the solvent mixture and their morphological or conformational changes were monitored using different conventional techniques such as Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and cryo-Transmission Electron Microscopy (cryo-TEM).The spontaneously formed superstructures were thoroughly characterized and well documented here. The hierarchical aggregates disclosed here bears the potential of vast usage in the field of nanotechnology.

Seed-induced synthesis of hierarchical architectures of ZSM-5 nanocrystalline aggregates by the solid state crystallization

A seed-induced rapid synthesis of hierarchical ZSM-5 aggregates was achieved by the solid state conversion method in an inorganic system. No secondary mesoporogen was introduced to construct supplementary pore. The physical and chemical properties of the products were characterized by using XRD, SEM, TEM, XRF and N2 adsorption–desorption techniques. The results revealed that the synthesized samples typically exhibit the uniform spherical zeolite ZSM-5 aggregates composed of loosely packed nanocrystals. It was clearly found that the morphology, mesoporosity and particle size of synthesized samples were directly affected by the type of the seed and synthesis conditions. The well-dispersed hierarchical ZSM-5 aggregates were synthesized at NaOH/SiO2 = 0.15, 20 ≤ SiO2/Al2O3 ≤ 40 with the acid of zeolite seed solution in guiding the structure. In addition, the crystal growth of zeolite samples synthesized with zeolite seed solution was studied at 433, 453, and 473 K. The results suggested that the activation energies for the induction, transition and crystallization stages were 91.44, 104.37 and 77.68 kJ∙mol−1, respectively. The method provides a cost-effective and industrially applicable route to synthesize hierarchical ZSM-5 aggregates.

Functional and versatile colorful superhydrophobic nanocellulose-based membrane with high durability, high-efficiency oil/water separation and oil spill cleanup

Colorful superhydrophobic coating with high durability and versatility has been receiving tremendous attention in decorative applications. A one-step spraying method for fabricating colorful superhydrophobic nanocellulose-based membrane (CSNBM) with high durability, high-efficiency oil/water separation and oil spill cleanup is established by using octadecyltrichlorosilane (OTS), pigment dispersions and n-hexane. The color diversity and depth of the CSNBM are regulated by adjusting the dosage of pigment dispersions. Due to the stoichiometrically regulated reaction of long-chain organosilanes with water, which produces micro to nanoscale hierarchical siloxane aggregates dispersible in industrial solvents, the colorful coating securely clings to the NBM surface to form CSNBM. Even after several severe testing, this CSNBM is proven to be exceedingly resilient, with no substantial decrease in superhydrophobicity (pH soultion test, wear abrasion, blending test and UV irradiation). Furthermore, this CSNBM can be employed to create various colorful paintings. This CSNBM can also be used to separate diverse oil/water combinations with high efficiency. Moreover, this CSNBM had excellent anti-fouling properties in a variety of liquids, including water, orange juice, coffee, tea, milk, and cola. This strategy will pave the way for the huge potential application in technological design or decoration, as well as hasten their commercialization in near future.

Impact of bambara seed residue biochar and NPK on soil fertility, aggregate carbon and nitrogen concentrations and yield of cucumber

The mechanisms of biochar effects on soil and crop yield are still elusive. Assessing the influence of biochar on total carbon (TC) and total nitrogen (TN) concentrations in hierarchical soil aggregates could provide an explanation. In a randomized complete block design were control, bambara seed residue biochar (BSB), NPK and NPK + BSB treatments superimposed on a two-year bambara seed residue amended Ultisols, in a four-year continuous cucumber cultivation. The effects of the treatments on optimizing cucumber yield and soil sustainability parameters, particularly the aggregate- (4.75-2.00, 1.00-2.00, 0.25-1.00 and &lt; 0.25 mm) associated TC and TN concentrations were studied. The BSB and NPK + BSB treatments significantly (p ≤ 0.05) increased the concentrations of TC by 113.79 and 104.60%; TN by 100 and 87.50%; and available P by 172% and 415%, respectively. Furthermore, both treatments significantly reduced exchangeable Al3+ but increased Mg2+ and soil moisture content 4-6 weeks after planting. Exchangeable K+ was significantly increased by BSB. The BSB and NPK + BSB significantly improved TC and TN in all aggregate fractions with minimal effect in the 0.25-1.00 mm fraction. However, the overall percentile TC and TN increase by these treatments was more in the macro- (4.75-0.25 mm) than in the micro (&lt; 0.25 mm) aggregates. Application of BSB and NPK + BSB significantly improved cucumber fruit weight by 12- and 24-fold, respectively, compared to NPK treatment. The study demonstrated that BSB enhanced soil fertility, while NPK + BSB further improved cucumber productivity. In addition, these treatments have the potential to substantially sequester carbon and nitrogen more in macro- than micro- aggregates.

Characterization of Fractal Structures by Spray Flame Synthesis Using X-ray Scattering.

In this work, we take on an in-depth characterization of the complex particle structures made by spray flame synthesis. Because of the resulting hierarchical aggregates, very few measurement techniques are available to analyze their primary particle and fractal properties. Therefore, we use small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to investigate the influence of the precursor concentration on the fractal structures of zirconia nanoparticles. The combination of information gained from these measurement results leads to a detailed description of the particle system, including the polydispersity and size distribution of the primary particles. Based on our findings, unstable process conditions could be identified at low precursor concentrations resulting in the broadest size distribution of primary particles with rough surfaces. Higher precursor concentrations lead to reproducible primary particle sizes almost independent of the initial precursor concentration. Regarding the fractal properties, the typical shape of aggregates for aerosols is present for the investigated range of precursor concentrations. In conclusion, the consistent results for SAXS and TEM show a conclusive characterization of a complex particle system, allowing for the identification of the underlying particle formation mechanism.

K-Chabazite Zeolite Nanocrystal Aggregates for Highly Efficient Methane Separation.

Methane (CH4 ) enrichment and purification is of great significance for increasing the heating value of unconventional natural gas sources and curtailing its effect on global warming. For a long time, commercial adsorbents for CH4 separation have been hampered by low adsorption capacities, sub-optimal adsorption selectivities, or slow diffusion rates, which have significantly restricted separation productivity. Herein, we report a facile and green seed-passaging method to fabricate donut-like macro-meso-micro hierarchical zeolite K-Chabazite nanocrystal aggregates. This consecutive seed-inducing method requires no organic template. By utilizing this unique nanocrystallization technique, the CH4 adsorption capacity, gas diffusion rate, and separation productivity of the resultant material are dramatically increased compared with those of commercially available adsorbents, thus setting a new benchmark in CH4 /N2 separation. More importantly, production of this adsorbent can be easily scaled-up to the order of 100 kg using readily available raw materials in this environmentally friendly synthetic route, enabling potential industrial implementation.

DNA‐organic molecular amphiphiles: Synthesis, self‐assembly, and hierarchical aggregates

AbstractWith the development of deoxyribonucleic acid (DNA) nanotechnology, various DNA nanostructures and DNA devices have been constructed, which exhibit potential applications in material science and biomedicine. Taking advantage of the programmability and biocompatibility of DNA, novel building block to chemically functionalize DNA with hydrophobic organic molecules has attracted more and more attention. Driving by amphiphilicity, DNA‐organic molecular amphiphiles have been demonstrated to self‐assemble or further induce hierarchically assemblies, providing novel‐specific properties. In this minireview, we summarize the recent progress of DNA organic molecular amphiphiles including their synthesis, self‐assembly behavior in aqueous solution, and the amphiphilic self‐assembly based on hierarchical DNA nano‐structures. We further briefly discuss the perspective of the application of the DNA‐organic molecular amphiphiles.

Functional and versatile superhydrophobic coatings via stoichiometric silanization

Superhydrophobic coatings have tremendous potential for applications in different fields and have been achieved commonly by increasing nanoscale roughness and lowering surface tension. Limited by the availability of either ideal nano-structural templates or simple fabrication procedures, the search of superhydrophobic coatings that are easy to manufacture and are robust in real-life applications remains challenging for both academia and industry. Herein, we report an unconventional protocol based on a single-step, stoichiometrically controlled reaction of long-chain organosilanes with water, which creates micro- to nano-scale hierarchical siloxane aggregates dispersible in industrial solvents (as the coating mixture). Excellent superhydrophobicity (ultrahigh water contact angle >170° and ultralow sliding angle <1°) has been attained on solid materials of various compositions and dimensions, by simply dipping into or spraying with the coating mixture. It has been demonstrated that these complete waterproof coatings hold excellent properties in terms of cost, scalability, robustness, and particularly the capability of encapsulating other functional materials (e.g. luminescent dyes).

Defect evolution of hierarchical SnO2 aggregates for boosting CO2 electrocatalytic reduction

The defect evolution enables the regulation of oxygen vacancies and interfacial chemistry of hierarchical tin oxide aggregates for boosting CO2 electrocatalytic reduction.