Deterioration Behavior of Concrete Beam Reinforced with Carbon Fiber-Reinforced Plastic Rebar Exposed to Carbonation and Chloride Conditions.

The absence of carbon fiber-reinforced rebar performance standards in Korea has limited its reliability. This study investigates the durability performance of carbon fiber-reinforced polymer rebar as an alternative to traditional steel reinforcement in concrete structures. Concrete beams reinforced with carbon fiber-reinforced polymer rebar were exposed to chloride environments for durations of 35 and 70 days and then subjected to bending tests to evaluate their durability.

Boosting the Sodiation Kinetics of Sn Anode Using a Yolk-Shell Nanohybrid Structure for High-Rate and Ultrastable Sodium-Ion Batteries.

Metallic Sn (Tin) is a promising anode material for Na-ion batteries owing to its high theoretical capacity of 870 mAh g. However, its large volumetric changes, interfacial instability, and sluggish sodiation kinetics limit its practical applications. Herein, a hierarchical yolk-shell nanohybrid composed of an Sn yolk and a Carbon/Silicon oxycarbide (C/SiOC) bilayer shell is prepared via the simple pyrolysis of a silicone oil dispersion containing an Sn precursor.

Structural Behavior of High Durability FRP Helical Screw Piles Installed in Reclaimed Saline Land.

The bearing capacity of fiber-reinforced plastic (FRP) helical screw piles is determined by the lesser of the breaking load at the bolted joint and the resistance provided by the screw tip area. In this study, compression and tensile tests were performed with the number of bolts and edge distance as variables. It showed similar strength when compared to the failure stress derived from material testing.

Comparative Evaluation of Flexural Toughness of Steel Fiber-Reinforced Concrete Beams.

Specifications are available to quantify flexural performance of steel-fiber reinforced concrete beams with several parameters. Each specification provides different results. This study comparatively evaluates existing flexural beam test standards that are used to evaluate the flexural toughness of SFRC beam specimens.

Determination of Mechanical Properties of Sand-Coated Carbon Fiber Reinforced Polymer (CFRP) Rebar.

This experimental study investigates the fundamental mechanical characteristics of the carbon fiber-reinforced polymer (CFRP) bars, including the tensile strength, compressive strength, shear strength, and modulus of elasticity of the CFRP bar. The properties need to be accurately determined to understand the behavior of the concrete structures reinforced with CFRP rebars. The CFRP rebar was coated with sand to enhance the adhesive strength of the concrete.

Shear Strengthening of High Strength Concrete Beams That Contain Hooked-End Steel Fiber.

Steel fiber has been used successfully in concrete mixtures to control volumetric changes, including shrinkage. However, the feasibility of the use of steel fiber has been restricted to nonstructural construction, such as 'slab on ground'. Recently, researchers have attempted to expand the applications of steel fiber to replace structural reinforcement (rebar) and have shown promising results in its substitution for shear reinforcement.

Programmable Dynamics of Exchange-Biased Domain Wall via Spin-Current-Induced Antiferromagnet Switching.

Magnetic domain wall (DW) motion in perpendicularly magnetized materials is drawing increased attention due to the prospect of new type of information storage devices, such as racetrack memory. To augment the functionalities of DW motion-based devices, it is essential to improve controllability over the DW motion. Other than electric current, which is known to induce unidirectional shifting of a train of DWs, an application of in-plane magnetic field also enables the control of DW dynamics by rotating the DW magnetization and consequently modulating the inherited chiral DW structure.

Hierarchically Designed Nitrogen-Doped MoS/Silicon Oxycarbide Nanoscale Heterostructure as High-Performance Sodium-Ion Battery Anode.

Molybedenum disulfide (MoS) is regarded as a promising anode material for next-generation sodium-ion batteries (SIBs) owing to its high theoretical capacity. However, its low conductivity, large volume changes, and undesirable phase transformation hinder its practical applications. In this study, we synthesize a hierarchically designed core-shell heterostructure based on nitrogen-doped MoS/C and silicon oxycarbide (SiOC) (N-MoS/C@SiOC) via the facile pyrolysis of a suspension of an N-MoS/polyfurfural precursor in silicone oil.

Bifunctional Surface Coating of LiNbO on High-Ni Layered Cathode Materials for Lithium-Ion Batteries.

High-Ni cathode materials with a layered structure generally suffer from structural instability induced by a highly reactive Ni component, especially at the surface. Crystalline LiNbO, with excellent thermal stability and ionic conductivity, has the potential to considerably enhance the interfacial stability of these cathode materials. By optimizing the crystalline coating of bifunctional LiNbO on a high-Ni cathode material, we are able to improve cycle performance and rate capability by minimizing the direct exposure of Ni with electrolytes.

Selective TiO Nanolayer Coating by Polydopamine Modification for Highly Stable Ni-Rich Layered Oxides.

Ni-rich layered oxides are promising cathode materials for developing high-energy lithium-ion batteries. To overcome the major challenge of surface degradation, a TiO surface coating based on polydopamine (PDA) modification was investigated in this study. The PDA precoating layer had abundant OH catechol groups, which attracted Ti(OEt) molecules in ethanol solvent and contributed towards obtaining a uniform TiO nanolayer after calcination.

The Influence of Steel Fiber Tensile Strengths and Aspect Ratios on the Fracture Properties of High-Strength Concrete.

Steel fiber embedded in concrete serves to reduce crack development and prevent crack growth at the macroscopic level of the concrete matrix. Steel fiber-reinforced concrete (SFRC) with high compressive concrete strength is affected primarily by the dimensions, shape, content, aspect ratio, and tensile strength of the embedded steel fiber. In this study, double-ended hook steel fiber was used in SFRC with a concrete compressive strength of 80 MPa.

Unveiling the mechanism of sodium ion storage for needle-shaped ZnCoO nanosticks as anode materials.

The interest in the development of micro-nanostructured metal oxides has been increasing recently because of their advantages as electrode materials in energy storage applications. In this study, dandelion-like ZnxCo3-xO4 microspheres assembled with porous needle-shaped nanosticks were synthesized by co-precipitation followed by a post-annealing treatment. The open space between neighboring nanosticks enables easy infiltration of the electrolyte; therefore, each nanostick is surrounded by the electrolyte solution, which ensures proper utilization of the active material during the electrochemical reaction.

Correction: Coaxial-nanostructured MnFeO nanoparticles on polydopamine-coated MWCNT for anode materials in rechargeable batteries.

Correction for 'Coaxial-nanostructured MnFe2O4 nanoparticles on polydopamine-coated MWCNT for anode materials in rechargeable batteries' by Hyeongwoo Kim et al., Nanoscale, 2018, 10, 18949-18960.

Coaxial-nanostructured MnFeO nanoparticles on polydopamine-coated MWCNT for anode materials in rechargeable batteries.

MnFe2O4@PDA-coated MWCNT coaxial nanocables are successfully designed via a simple one-pot process by utilizing the adhesion property of polydopamine (PDA) with cations in aqueous solutions and employing a modified co-precipitation synthesis at a low temperature. The incorporation of the PDA coating layer on the MWCNT leads to the well-dispersed state of the MWCNTs in the aqueous solution due to the hydrophilic functional group of the PDA coating layer. In addition, the catechol-based functional group of the PDA coating layer effectively anchors the Mn and Fe ions from the aqueous solution before the co-precipitation process, eventually resulting in the preferential and homogeneous formation of MnFe2O4 nanoparticles on the MWCNT.

Conducting Polymer Coating on a High-Voltage Cathode Based on Soft Chemistry Approach toward Improving Battery Performance.

The surface of a 5 V class LiNiMnO particle is modified with poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer by utilizing the hydrophobic characteristics of the 3,4-ethylenedioxythiophene (EDOT) monomer and the tail group of cetyl trimethyl ammonium bromide (CTAB) surfactants, in addition to the electrostatic attraction between cationic CTAB surfactant and cathode materials with a negative ζ potential in aqueous solution. With this novel concept, we design and prepare a uniform EDOT monomer layer on the cathode materials, and chemical polymerization of the EDOT coating layer is then carried out to achieve PEDOT-coated cathode materials via a simple one-pot preparation process. This uniform conducting polymer layer provides notable improvement in the power characteristics of electrodes, and stable electrochemical performance can be obtained especially at severe operating conditions such as the fully charged state and elevated temperatures owing to the successful suppression of the side reaction between the oxide particle and the electrolyte as well as the suppression of Mn dissolution from the oxide material.

Hygral Behavior of Superabsorbent Polymers with Various Particle Sizes and Cross-Linking Densities.

This study focuses on investigating the effects of particle size and cross-linking density on the hygral behavior of superabsorbent polymers (SAPs), which are increasingly used as an internal curing material for high-performance concrete. Four SAPs with different mean particle diameters and cross-linking densities were tested under controlled wetting and drying conditions to measure free absorption and desorption kinetics. Absorption capacities of SAPs under actual mixing conditions were additionally measured and verified by means of mortar flow and semi-adiabatic hydration heat measurements.

Investigation of Thermal Stability of P2-NaCoO Cathode Materials for Sodium Ion Batteries Using Real-Time Electron Microscopy.

Here, we take advantage of in situ transmission electron microscopy (TEM) to investigate the thermal stability of P2-type NaCoO cathode materials for sodium ion batteries, which are promising candidates for next-generation lithium ion batteries. A double-tilt TEM heating holder was used to directly characterize the changes in the morphology and the crystallographic and electronic structures of the materials with increase in temperature. The electron diffraction patterns and the electron energy loss spectra demonstrated the presence of cobalt oxides (CoO, CoO) and even metallic cobalt (Co) at higher temperatures as a result of reduction of Co ions and loss of oxygen.

Study on the Electrochemical Reaction Mechanism of NiFeO as a High-Performance Anode for Li-Ion Batteries.

Nickel ferrite (NiFeO) has been previously shown to have a promising electrochemical performance for lithium-ion batteries (LIBs) as an anode material. However, associated electrochemical processes, along with structural changes, during conversion reactions are hardly studied. Nanocrystalline NiFeO was synthesized with the aid of a simple citric acid assisted sol-gel method and tested as a negative electrode for LIBs.

One-Step Catalytic Synthesis of CuO/Cu2O in a Graphitized Porous C Matrix Derived from the Cu-Based Metal-Organic Framework for Li- and Na-Ion Batteries.

The hybrid composite electrode comprising CuO and Cu2O micronanoparticles in a highly graphitized porous C matrix (CuO/Cu2O-GPC) has a rational design and is a favorable approach to increasing the rate capability and reversible capacity of metal oxide negative materials for Li- and Na-ion batteries. CuO/Cu2O-GPC is synthesized through a Cu-based metal-organic framework via a one-step thermal transformation process. The electrochemical performances of the CuO/Cu2O-GPC negative electrode in Li- and Na-ion batteries are systematically studied and exhibit excellent capacities of 887.

Carbon-Coated Li4Ti5O12 as Anode Material for Sodium-Ion Batteries.

The surface-coating of carbon was performed on the spinel Li4Ti5O12 materials for the electrochemical sodium insertion in sodium ion battery application. The carbon-coated Li4Ti5O12 was synthesized by using the citric acid sol-gel method. Carbon-coated Li4Ti5O12 exhibits superior cycle performance as well as the rate capability in comparison to the pristine Li4Ti5O12.

Layered-Layered-Spinel Cathode Materials Prepared by a High-Energy Ball-Milling Process for Lithium-ion Batteries.

In this work, we report the electrochemical properties of 0.5Li2MnO3·0.25LiNi0.

Coating lithium titanate with nitrogen-doped carbon by simple refluxing for high-power lithium-ion batteries.

Nitrogen-doped carbon is coated on lithium titanate (Li4Ti5O12, LTO) via a simple chemical refluxing process, using ethylenediamine (EDA) as the carbon and nitrogen source. The process incorporates a carbon coating doped with a relatively high amount of nitrogen to form a conducting network on the LTO matrix. The introduction of N dopants in the carbon matrix leads to a higher density of C vacancies, resulting in improved lithium-ion diffusion.

Feasibility of using phase change materials to control the heat of hydration in massive concrete structures.

This paper presents experimental results that can be applied to select a possible phase change material (PCM), such as a latent heat material (LHM), to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests) were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined.

Mechanochemical synthesis of Li₂MnO₃ shell/LiMO₂ (M = Ni, Co, Mn) core-structured nanocomposites for lithium-ion batteries.

Core/shell-like nanostructured xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) composite cathode materials are successfully synthesized through a simple solid-state reaction using a mechanochemical ball-milling process. The LiMO2 core is designed to have a high-content of Ni, which increases the specific capacity. The detrimental surface effects arising from the high Ni-content are countered by the Li2MnO3 shell, which stabilizes the nanoparticles.

Effect of expansive admixtures on the shrinkage and mechanical properties of high-performance fiber-reinforced cement composites.

High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study.