Chemical Anchors Research Articles

A rGO-Based Fe2O3 and Mn3O4 binary crystals nanocomposite additive for high performance Li–S battery

Chemical anchor effect is an efficient route for polysulfides immobilization to enhance the performance of Li–S battery. Transition metal oxides are suitable chemical anchor matrix as Lewis acid coordinated with sulfur atoms in the form of Lewis base. Ion bonds may also be formed between anions in transition metal compounds and lithium ions in lithium polysulfides alleviating the shuttle effect. Reducing their crystal sizes to expose more surface active sites and expand surface areas is pivotal to sufficiently immobilize polysulfides. Here, an optimized GFM-2 composite was fabricated, where the 20 nm metal oxide particles aggregated by the 3–5 nm Fe2O3 and Mn3O4 binary crystals are uniformly distributed on the reduced graphene oxide (rGO) nanosheets. A high specific surface area up to 144.9 m2 g−1 was obtained for the GFM-2. The modified sulfur@rGO (S@G) cathode obtained by mixing S@G and GFM-2 additive with the mass ratio of 20: 1, presented high specific discharge capacities of 1356.3 and 770.2 mAh g−1, respectively, at scan rates of 0.1 and 5C (1C = 1675 mAh g−1) under conventional electrolyte dosage with electrolyte/sulfur (E/S) = 30 mL g(S)−1 and sulfur loading of 1.1 mg cm−2. The capacity was 1053.5 mAh g−1 at 1C and maintained at 530.1 mAh g−1 after 1000 cycles with the low average capacity decay rate of each cycle of 0.049%. Under low electrolyte dosages of E/S = 15 and 8 mL g(S)−1, the high capacities of 1308.0 and 1230.4 mAh g−1 could be still obtained at 0.1C, respectively. When the sulfur loading was increased to 2.8 mg cm−2 and E/S was reduced to 10 mL g(S)−1, the good capacity of 1163.6 mAh g−1 was gotten at 0.1C. The high capacity and high cyclic property under different E/S and sulfur loading amounts indicate the potential for practical application of this simple but effective modified sulfur cathode.

Experimental and analytical investigation of chemical anchors’s behaviour under axial tensile

In this study, to observe the behavior of chemical anchors embedded in concrete under the tensile effect, 108 different anchor specimens were prepared with different parameters as concrete compressive strength, reinforcement bar diameters, anchor depths, sizes of drilled holes, cleanliness of the drilled holes. Pull-out tests were conducted and obtained data were examined with the axial-load capacities and the failure situations. Finally, the depth of anchors, compressive strength and reinforcement diameter were observed to increase the axial-load-bearing capacity. The specimens cleaned with water could bear more axial loads than cleaned using air. For the anchors installed without cleaning the holes, a significant decrease was observed in the axial-load carrying capacities compared to the other two conditions. The ANN algorithm exhibited a 78.3% prediction success compared with other algorithms. The empirical relations in the literature were found to have limited level of prediction success rates according to the ANN's results.

Experimental Research on Anchoring Performance of Chemical Anchor Bolt in Building Curtain Wall Engineering

To study the anchoring performance of chemical anchor bolts in building curtain wall, anchoring performance affected by chemical anchoring in concrete grade and anchor bolt diameter were considered. Based on the existing code, 48 standard specimens were made. After analysing the drawing force and the load-displacement curve, the results revealed that when the concrete strength grades are the same, the drawing force of specimen increases while the increasing of chemical anchor bolt diameter; when the chemical anchor bolts have the same diameter, the drawing force of each specimen increases while the increasing of the concrete strength grades; when the concrete strength grade is C40 and the chemical anchor bolt diameter is M14, the concrete splitting damage degree of specimen is the weakest.

Experimental Research on Anchoring Behavior of Chemical Anchor Bolt under Repeated Loading

To study the anchoring behavior of chemical anchors under repeated loading, 33 test pieces were designed and fabricated based on the specifications. Each 3 test pieces were 1 set, that is, 1 set of comparative test pieces and 10 sets of test pieces, respectively, for static force. Bonding and anchoring performance tests for loading and reloading. Through the analysis of the test phenomena and results, the following conclusions are drawn: when the loading load exceeded 0.9 times the ultimate bearing capacity of the anchor; when the loading load was equal to 0.6 or 0.75 times, the test piece would undergo splitting damage after the set number of loading times, and its bearing capacity would increase. As the number of loading increased, the energy consumption would gradually decrease, and the decreasing amplitude would gradually increase. Compared with constant amplitude loading and variable amplitude loading, it is found that the slip value of variable amplitude loading increased by 42.1% and the bearing capacity decreased by 12%, which indicated that variable amplitude loading has a great influence on the bonding and anchoring performance of specimens.

Experimental research and modeling of chemical anchor systems under static and dynamic loading

In article considered modeling of fastening post bridge barriers to the bridge, bearing system used chemical adhesive anchor systems at static and dynamic loads. In paper shown the possibilities of the analysis of the causes of critical plastic deformations and extreme stresses in the bridge barrier elements at the static and dynamic loads due to crash of the vehicle on bridge barriers. Analysis of the operation of bridge barriers in a collision allowed the optimal parameters to provided and saved lives in case of accidents.

Programmed Design of a Lithium-Sulfur Battery Cathode by Integrating Functional Units.

Sulfur is considered to be one of the most promising cathode materials due to its high theoretical specific capacity and low cost. However, the insulating nature of sulfur and notorious “shuttle effect” of lithium polysulfides (LiPSs) lead to severe loss of active sulfur, poor redox kinetics, and rapid capacity fade. Herein, a hierarchical electrode design is proposed to address these issues synchronously, which integrates multiple building blocks with specialized functions into an ensemble to construct a self‐supported versatile cathode for lithium–sulfur batteries. Nickel foam acts as a robust conductive scaffold. The heteroatom‐doped host carbon with desired lithiophilicity and electronic conductivity serving as a reservoir for loading sulfur can trap LiPSs and promote electron transfer to interfacial adsorbed LiPSs and Ni3S2 sites. The sulfurized carbon nanofiber forest can facilitate the Li‐ion and electron transport and retard the LiPSs diffusion as a barrier layer. Sulfiphilic Ni3S2 acts as both a chemical anchor with strong adsorption affinity to LiPSs and an efficient electrocatalyst for accelerating kinetics for redox conversion reactions. Synergistically, all functional units promote the lithium ion coupled electron transfer for binding and redox conversion of LiPSs, resulting in high reversible capacities, remarkable cycle stability, and excellent rate capability.

Controlling surface properties of electrospun polyphenylsulfone using plasma treatment and X-ray photoelectron spectroscopy

Plasma treatment is an efficient method to modify organic surfaces. In this work electrospun polyphenylsulfone was systematically subjected to low-pressure microwave plasma and atmospheric-pressure coplanar barrier discharge in order to control the surface chemistry, which is important for controlling surface properties. Polar anchor groups such as keto/aldehyde groups and especially carboxylic acid groups affect hydrophilicity. The composition of plasma-induced chemical anchor groups can be monitored (and thus controlled) by X-ray photoelectron spectroscopy. The atmospheric-pressure plasma provided subtle oxidation, and the low-pressure plasma provided significant oxidation that resulted in polyphenylsulfone surfaces with a very high hydrophilicity. The low-pressure plasma treated polyphenylsulfone exhibited a significant age effect over 212 days, which was attributed to a diffusion phenomenon where the polyphenylsulfone surface becomes enriched in non-oxidated polyphenylsulfone. It was shown that the improved hydrophilicity will diminish but not vanish in time.

Discussion on the Reinforcement of Reinforced Concrete Slab Structures

Because of global environmental changes and the continued warming of the planet, the increase in carbon dioxide emissions has had a major impact on the environment. The development of zero-carbon buildings, the promotion of energy conservation and carbon reduction, and the concept of green environmental protection are regarded as important issues for humanity to achieve sustainable development. In Taiwan, the combination of moisture and high salt content in the environment, corrosion caused by chloride ions, and earthquakes often lead to the formation of crevices in buildings. These crevices can cause rebar oxidation and corrosion and even concrete structure damage or spalling. Conventional structural damages can be repaired with epoxy resin grout. However, such practices are incapable of removing the rusted components of the rebars inside the structures and thus subject the internal rebars to continuous oxidation in the original rust-covered environment. Components located deep within the structures would still swell as a result of continuous rebar oxidation and cause concrete breaking and spalling, making previous repair efforts ineffective. This study proposes an improved repair and retrofit technique that includes the removal of rust from oxidated rebar parts, by applying low viscosity epoxy resin to the slab base and allowing it to fully penetrate the concrete cracks and surface of the rebars inside, thus producing a protective layer and repairing the bond. Additionally, carbon-fiber reinforced plastic (CFRP) patches were adopted as repair materials and attached to the beams and slab (ceiling) surfaces. Angle steels were used at the edges and installed to connect the beams to the slab with chemical anchors. The gaps between the angle steels and the slab were filled with epoxy resin grouts. On the short side of the slab, small steel H-beams were installed 1 m apart as a means of retrofit. Because the epoxy resin expands by 8% after undergoing chemical reactions, it bonds perfectly with concrete, CFRP patches, and steel materials. Approximately 10 years have elapsed since the case-study was repaired using the proposed technique, and the retrofit effect has yielded excellent results to the present day, with no occurrence of internal swelling or spalling from rebar oxidation. The proposed retrofit technique can reduce construction costs, while ensuring effective repair and maintenance of structural safety, and extend the service life of structures.

A high-entropy metal oxide as chemical anchor of polysulfide for lithium-sulfur batteries

Lithium-sulfur (Li-S) battery is anticipated as one of the most promising candidates for the next-generation rechargeable cell. In order to conquer the shuttle effect of dissolution lithium polysulfides (LIPSs), the chemical interactions between sulfur host and LIPSs on the performance of Li-S batteries has recently been highlighted. Herein, a facile strategy is proposed, which produces a high-entropy metal oxide (HEMO-1) as an anchor to restrain LIPSs in Li-S batteries via chemical confinement as demonstrated by strong bonding interaction between HEMO-1 and Li2S6. The as-prepared HEMO-1 incorporates five metal components, Ni, Mg, Cu, Zn and Co, into a metal oxide crystalline structure. The homogeneously dispersive multiple metal active species in HEMO-1 favor the restriction of LIPSs and facilitate the redox reaction in the cathode of Li-S batteries. Especially, the synergistic contribution of Li-O and S-Ni bonds from the interaction between HEMO-1 and LIPSs effectively alleviate the shuttle of LIPSs between the cathode and anode. As the promoter catalyst for LIPSs, HEMO-1 shows a competitive reversible capacity, outstanding cycling stability, and a low capacity decay of 0.077% per cycle after 600 cycles. This study not only presents a high-entropy oxide promoter for polysulfide immobilizing in Li-S batteries, but also provides an avenue of high-entropy metal oxides to a variety of energy conversion and storage fields.

Detection of flaw in steel anchor-concrete composite using high-frequency wave characteristics

Non-monolithic concrete structural connections are commonly used both in new constructions and retrofitted structures where anchors are used for connections. Often, flaws are present in anchor system due to poor workmanship and deterioration; and methods available to check the quality of the composite system afterward are very limited. In case of presence of flaw, load transfer mechanism inside the anchor system is severely disturbed, and the load carrying capacity drops drastically. This raises the question of safety of the entire structural system. The present study proposes a wave propagation technique to assess the integrity of the anchor system. A chemical anchor (embedded in concrete) composite system comprising of three materials viz., steel (anchor), polymer (adhesive) and concrete (base) is considered for carrying out the wave propagation studies. Piezoelectric transducers (PZTs) affixed to the anchor head is used for actuation and the PZTs affixed to the surrounding concrete surface of the concrete-anchor system are used for sensing the propagated wave through the anchor interface to concrete. Experimentally validated finite element model is used to investigate three types of composite chemical anchor systems. Studies on the influence of geometry, material properties of the medium and their distribution, and the flaw types on the wave signals are carried out. Temporal energy of through time domain differentiation is found as a promising technique for identifying the flaws in the multi-layered composite system. The present study shows a unique procedure for monitoring of inaccessible but crucial locations of structures by using wave signals without baseline information.

Temperature related pull-out performance of chemical anchor bolts in fibre concrete

Anchor bolts are often fixed into a concrete soffit of structures and they are used in ambient and cold store locations. The chemical anchor bolt relies purely on the tensile strength of the concrete to carry the imposed load, assuming the bond strength of the resin is greater than the tensile strength of the concrete.The properties of concrete are changed by the addition of both steel and polypropylene fibres. This paper investigates the relative performance of each fibre type with regard to initial and final post crack failure. Anchor bolt pull-out testing was used to determine the maximum load a fixing can hold as well as the residual post crack toughness of a bolt embedded in a concrete block. The concrete used was a C40 design mix and resin anchor bolts were selected for this test for their stress-free conditions prior to loading.The results showed that the addition of both types of fibres when used in concrete improved the maximum load and toughness of the samples, compared to plain concrete. There was not a significant difference between the results obtained for steel and polypropylene fibres. The effects of a reduction in core temperature of the samples was examined. The results show that the strength of concrete is significantly improved when tested at −20 °C, compared to ambient temperature.

Simultaneously Porous Structure and Chemical Anchor: A Multifunctional Composite by One-Step Mechanochemical Strategy toward High-Performance and Safe Lithium-Sulfur Battery.

A lithium-sulfur (Li-S) battery has been regarded as one of the most promising energy-storage systems to meet requirements for high energy density in electric vehicles, advanced portable electronic devices, and so on. However, practical application of a Li-S battery is restricted severely by easy dissolution of lithium polysulfides and high flammability of sulfur. Herein, we developed, for the first time, a multifunctional composite directly prepared by a facile, green, low-cost, and large-scale ball-milling method with fly ash and sulfur. Due to the unique microstructure and sulfur-related components as chemical anchors, composites possessed good electron/ion transport, favorable resistance to volume change of sulfur, and strong chemical affinity to polysulfides, which greatly facilitate redox kinetics, maintain structural integrity of the cathode, and suppress polysulfide shuttling in electrolyte, hence significantly boosting electrochemical performance of the Li-S battery with high initial discharge capacity, superior cycling stability, and satisfying rate capability. Typically, Li-S batteries based on a composite with a sulfur loading of 86.9% present initial discharge capacities of 969.8, 894.3, and 769.7 mAh g-1 as well as capacity decay rates of 0.068% (400 cycles), 0.1% and 0.042% per cycle (200 cycles) at 0.2, 0.5, and 1 C, respectively. Moreover, the average specific self-extinguishing time of the composite-based cathode was clearly reduced to less than half of that of the pristine sulfur-based cathode, indicating significantly promoting the safety of the battery.

A 3D Nitrogen-Doped Graphene/TiN Nanowires Composite as a Strong Polysulfide Anchor for Lithium-Sulfur Batteries with Enhanced Rate Performance and High Areal Capacity.

Lithium-sulfur (Li-S) batteries have attracted remarkable attention due to their high theoretical capacity of 1675 mAh g-1 , rich resources, inexpensiveness, and environmental friendliness. However, the practical application of the Li-S battery is hindered by the shuttling of soluble lithium polysulfides (LiPSs) and slow redox reactions. Herein, a 3D nitrogen-doped graphene/titanium nitride nanowires (3DNG/TiN) composite is reported as a freestanding electrode for Li-S batteries. The highly porous conductive graphene network provides efficient pathways for both electrons and ions. TiN nanowires attached on the graphene sheets have a strong chemical anchor effect on the polysulfides, which is proved by the superior performance and by density functional theory calculations. As a result, the 3DNG/TiN cathode exhibits an initial capacity of 1510 mAh g-1 and the capacity remains at 1267 mAh g-1 after 100 cycles at 0.5 C. Even at 5 C, a capacity of 676 mAh g-1 is reached. With a high sulfur loading of 9.6 mg cm-2 , the 3DNG cathode achieves an ultrahigh areal capacity of 12.0 mAh cm-2 at a high current density of 8.03 mA cm-2 . This proposed unique structure gives a bright prospect in that high energy density and high power density can be achieved simultaneously for Li-S batteries.

Structural window frame for in-plane seismic strengthening of masonry wall buildings

ABSTRACT This article describes the initial development stages of a structural window frame system for the in-plane seismic strengthening of load-bearing masonry wall buildings. The solution implemented ultimately aims to stiffen (and strengthen) the opening such that the wall would behave as if there were no opening. This is achieved by installing a structural steel window frame composed of a profile forming a closed ring inside the opening, properly tied to the surrounding masonry wall. The strengthening concept was validated by means of a series of tests in which two approximately 1:2 geometric scale physical specimens with a similar central opening were cyclically tested to failure. One of these specimens (UMW) was unreinforced whereas the other (RMW) had a UPN profile internal ring tied at the corners and at mid-length and mid-height of the opening by means of threaded rods with chemical anchors. The material of these walls was common rubble masonry with lime-based mortar and render. The experimental results show that the strengthening technique leads to a significant increase in strength and in-plane deformation capacity, as well as in terms of cumulative dissipated energy at collapse. Nonlinear numerical specimens of the tested walls were also developed and calibrated.

Group IV Monochalcogenides MX (M=Ge, Sn; X=S, Se) as Chemical Anchors of Polysulfides for Lithium-Sulfur Batteries.

Although rechargeable lithium-sulfur batteries are considered as advanced energy systems, their practical implementation is impeded by many factors, in particular the rapid capacity fade and low Coulomb efficiency caused by the shuttle effect. To overcome this problem for achieving longer cycle life and higher rate performance, anchoring materials for lithium polysulfides are highly desirable. In this work, for the first time, we report phosphorene-like MX (M=Ge, Sn; X=S, Se) monolayers as promising anchoring materials to restrain the lithium polysulfides shuttling. Our study provides fundamental selection criteria for the effective suppression of the polysulfides shuttling. Adsorption calculations reveal that polysulfide capture by the MX is through chemisorption with a suitable range of adsorption energies. Morever, we show that excellent surface diffusion of Li and polysulfides endow a fast charge/discharge rate for lithium-sulfur batteries. Graphene with desirable electronic properties is constructed to improve the electrical conductivity in the new graphene@MX heterostructures. Based on the strong anchoring ability, improved rate capability, and enhanced conductivity, MX-based composites hold great promise as an anchoring material for high-energy lithium-sulfur batteries.

Tannic acid tuned metal-organic framework as a high-efficiency chemical anchor of polysulfide for lithium-sulfur batteries

Despite of great progress in lithium-sulfur (Li-S) batteries, shuttle effect caused by long chain polysulfides, as one of the most serious obstacles, needs to be urgently solved for potentially commercial application of Li-S batteries. Herein, we report on an effective strategy to tune surface functional groups and porous structure of Metal Organic Frameworks (MOFs) to efficiently anchor polysulfides for high-performance Li-S batteries. Tannic acid (TA) tuned Zeolitic Imidazolate Framework-67 (ZIF-67) could create uniformly polar sites for in-situ polysulfide absorption, and C-S and Co-S abundantly functional groups for chemically trapping polysulfides for achieving stable cycling performance. Furthermore, TA tuned ZIF-67 polyhedrons can be sculptured to a core/shell hierarchical porous structure. Foremost, the functionalized polar hydroxyl groups can undergo redox reaction with long polysulfides to form thiosulfate and short insoluble polysulfides, relieving the shuttle effect. ZIF-67-5-S cathode exhibits superior cycling stability and rate capability, showing a steady capacity of at 521 mAh/g after 550 cycles under a current density of 500 mA/g, still maintaining a capacity of 510 mAh/g even at a current density of 1600 mAh/g. The TA polymer etching MOFs route to tune core-shell hierarchically pores and abundantly functional groups offers a potential use in high energy Li-S batteries.

Corundum Fillers with Variable Sizes and Shapes for Epoxy Nanocomposites as High‐Performance Chemical Anchoring and Bonding Systems

AbstractHerein, the influence of corundum filler types and contents on the morphological, thermal, and mechanical properties of epoxy nanocomposites tailored for applications as chemical anchoring and bonding systems is investigated. Up to 65 wt% corundum particles with aspect ratios (AR) varying between 1 and 70, average particle sizes ranging from 500 nm to 48 µm, and nanoplatelet thickness varying from 40 to 300 nm, are uniformly dispersed in amine‐cured epoxy resins. At both 25 and 50 wt% filler content, the properties of corundum/epoxy composites are far superior to those of the corresponding benchmark epoxy composites containing a conventional filler such as cement, talcum, or sand. The incorporation of corundum nanoplatelets with AR of 50, length of 2 µm, and thickness of 40 nm, significantly improves Young's modulus (3.5–9.8 GPa) and fracture toughness KIc (0.83–1.24 MPa of epoxy nanocomposites at the expense of tensile strength (72–49 MPa). The pull‐out values of the corresponding chemical anchoring systems substantially improve with decreasing sub‐micrometer corundum particle sizes and correlate with tensile strength of the corundum/epoxy nanocomposites, but are much less dependent on corundum particle morphologies, filler aspect ratio, and Young's modulus of the corundum/epoxy composite.

A nonlinear shear-lag model applied to chemical anchors subjected to a temperature distribution

Adhesive joints are increasingly used in bridges and buildings construction thanks to their high mechanical properties and their ease of implementation. However, the load transfer mechanism within adhesive joints is complex and has been the subject of several studies since 1938. Several models have been developed to quantify the stress distribution along bond joints. Nevertheless, very few models exist today to study the stress distribution in chemical anchors by taking into account the temperature effect. This paper presents a non-linear shear-lag model adapted to chemical anchors allowing predicting their stress distribution profiles and fire resistance duration for any temperature distribution. The model highlights the importance of the temperature distribution on the stress profile. The paper shows that when the anchor reaches its maximum axial force, all the elements composing the anchor provide their maximum performance at the same time.

Reduction of bacterial attachment on hydroxyapatite surfaces: Using hydrophobicity and chemical functionality to enhance surface retention and prevent attachment.

Water-soluble, linear polymers with high-acid functionality are commonly used in oral care formulations to provide benefits such as bioactive complexation and delivery, as well as inhibition of the bacteria deposition and colonization, commonly referred to as 'anti-attachment'. Unfortunately, structure-activity relationship (SAR) studies of these polymers are scarce, thus, a systematic approach to design polymers with a desired property (e.g. anti-attachment) is limited. Multifunctional anti-attachment amphiphilic molecules (AMs) featuring a sugar backbone, hydrophobic arms, a poly(ethylene glycol) tail, and a chemical anchor effectively deposited on soft ceramic surfaces and reduced bacterial adhesion. The chemical compositions of the AMs were fine-tuned to better coordinate with dental enamel surfaces and prevent bacterial colonization. A graft-to approach was used to investigate the effect of the chemical anchor on AM deposition and retention. The chemical composition, absorption/desorption, and wettability properties of the bioactives and bioactive-coated surfaces were investigated using nuclear magnetic resonance, X-ray photon spectroscopy, quartz crystal microbalance, and contact angle. In addition, the ability of the AMs to provide anti-bacterial attachment on a simulated enamel surface was evaluated in vitro using bacterial repulsion assays. The SAR between surface retention and anti-attachment properties of the AMs demonstrates the feasibility and tunability of using these polymers as bioactive agents that provide anti-attachment benefits on dental enamel surfaces.

Macro- and Micro-Porous Biomass Derived Carbon for Various Energy Storage Application

Recent research in electrochemical storage devices focus not only on improving lithium ion batteries technique (e.g. safety, energy density) but also on utilizing different storage types such as sodium ion batteries, lithium sulfur batteries, and super-capacitors. Among various topics of energy storage devices, biomass derived carbon has attracted interest for its economic and environment benefits. Pistachio shell has been used in this study for its structural benefits for various energy storage application. Pistachio shell derived carbon (PC) shows a macroporous channel and micro-pores architecture. The macroporous channel enables facile penetration of ions and electrolyte into the material while micro-pores provides more active sites and withstand the volume expansion of ions during repeated charge/discharge cycles. This makes this material attractive for lithium ion / sodium ion / lithium sulfur batteries and even super-capacitor. In this work, the characteristics of pistachio shell structure and its performances in sodium ion and Li-S batteries is presented. The optimum carbonization temperature for pistachio shell is studied to maximize the performance in sodium ion batteries. In-depth study on plausible sodium storage mechanism by understanding the characteristics of PC (surface area, crystal information) at different temperature is conducted as well. Further application using PC as a sulfur reservoir to restrict the polysulfide shuttling effect in Li-S batteries is purposed. Fundamental study (e.g. Raman, XPS, SEM) on how PC structure and chemical anchor improves the cyclability of Li-S batteries is discussed. This work successfully shows promising result with using pistachio shell in different energy storage systems. Figure 1