The galvanostatic lithiation/sodiation voltage profiles of hard carbon anodes are simple, with a sloping drop followed by a plateau. However, a precise understanding of the corresponding redox sites ...and storage mechanisms is still elusive, which hinders further development in commercial applications. Here, a comprehensive comparison of the lithium‐ and sodium‐ion storage behaviors of hard carbon is conducted, yielding the following key findings: 1) the sloping voltage section is presented by the lithium‐ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions on their inner surfaces constituting closed pores, even if the graphitic lattices are unoccupied; 2) the redox sites for the plateau capacities are the same as those for the closed pores regardless of the alkali ions; 3) the sodiation plateau capacities are mostly determined by the volume of the available closed pore, whereas the lithiation plateau capacities are primarily affected by the intercalation propensity; and 4) the intercalation preference and the plateau capacity have an inverse correlation. These findings from extensive characterizations and theoretical investigations provide a relatively clear elucidation of the electrochemical footprint of hard carbon anodes in relation to the redox mechanisms and storage sites for lithium and sodium ions, thereby providing a more rational design strategy for constructing better hard carbon anodes.
A comprehensive comparison of the lithium‐ and sodium‐ion storage behaviors of hard carbon is conducted, yielding the key findings: the sloping voltage section is presented by the lithium‐ion intercalation in the graphitic lattices of hard carbons, whereas it mainly arises from the chemisorption of sodium ions. The intercalation preference and the plateau capacity have an inverse correlation.
Water can be magnetized under an applied magnetic field, and some important properties of magnetized water have become useful in industries associated with its surface tension, pH, viscosity, ...electrical conductivity, and scale formation inhibition. The surface tension of water decreases upon the application of a magnetic field, while its pH increases. In addition, the shear viscosity of magnetized water increases and the magnetic field inhibits scale formation. This paper reviews the unique properties of magnetized water as well as its potential applications as a smart and more environmentally friendly fluid in the oil industry, e.g., as an injection fluid in enhanced oil recovery areas for producing oil.
Anode‐free sodium metal batteries (AF‐SMBs) can deliver high energy and enormous power, but their cycle lives are still insufficient for them to be practical as a power source in modern electronic ...devices and/or grid systems. In this study, a nanohybrid template based on high aspect‐ratio silver nanofibers and nitrogen‐rich carbon thin layers as a core–shell structure is designed to improve the Coulombic efficiency (CE) and cycling performance of AF‐SMBs. The catalytic nanohybrid templates dramatically reduce the voltage overshooting caused by metal nucleation to one‐fifth that of a bare Al foil electrode (≈6 mV vs ≈30 mV), and high average CE values of >99% are achieved over a wide range of current rates from 0.2 to 8 mA cm−2. Moreover, exceptionally long cycle lives for more than 1600 cycles and an additional 1500 cycles are achieved with a highly stable CE of >99.9%. These results show that AF‐SMBs are feasible with the nanohybrid electrode system.
Nanohybrid templates based on high aspect‐ratio silver nanofibers and nitrogen‐rich carbon thin layers as a core–shell structure are designed to improve the Coulombic efficiency and cycling performance of anode‐free sodium metal batteries.
Poly(methyl methacrylate) (PMMA) nanocomposites containing well-dispersed multiwalled carbon nanotubes (MWNTs) were prepared via an in-situ bulk polymerization of methyl methacrylate (MMA) in the ...presence of carbon nanotubes (CNTs). Electrical conductivities of the synthesized PMMA/MWNT nanocomposite films containing 1−5 wt % of MWNT were between 10-4 and 10-2 S/cm. When PMMA/MWNT nanocomposites with the same MWNT concentrations were electrospun in DMF into nanofibrous membrane, the conductivities were reduced to ∼10-10 S/cm, even though dispersion of the MWNTs in the electrospun nanofibers was superior to the conventional polymer composites with carbon nanotubes. The diameter of the electrospun fibers ranged between 120 ± 30 and 710 ± 20 nm. In addition, MWNTs in the electrospun nanofibers were found to be embedded in the polymer matix and to align along the fiber axis.
A ZnFe 2 O 4 /poly(diphenylamine) (PDPA) particle with a core-shell structure was successfully synthesized with a ZnFe 2 O 4 core via the solvothermal method, modifying ZnFe 2 O 4 through a grafting ...agent and coating with a PDPA shell through the radical polymerization method. ZnFe 2 O 4 is introduced as a new magnetorheological (MR) material because of its low density and sufficient saturation magnetization (<inline-formula> <tex-math notation="LaTeX">M_{s} </tex-math></inline-formula>) value. PDPA does not require an additional de-doping process during electrorheological (ER) measurements because it has a lower electrical conductivity than typical conducting polymer of polyaniline. By measuring the morphology of the synthesized particles through transmission electron microscopy, it was confirmed that the core-shell structure was successfully synthesized and that the shell thickness of PDPA was approximately 14 nm. The density of the synthesized particles is 2.7 g/cm 3 , which is sufficiently lower than the density of ZnFe 2 O 4 (4.67 g/cm 3 ), showing good sedimentation stability. The results from measuring the magnetic properties using a vibrating sample magnetometer indicate that the saturation magnetization value of ZnFe 2 O 4 /PDPA was approximately 40.8 emu/g. ZnFe 2 O 4 /PDPA particles were dispersed in 100 cs silicone oil by 5 vol.% to prepare a ZnFe 2 O 4 /PDPA-based electro/magnetorheological (EMR) fluid, and the shear response and dynamic response were measured using a rotational rheometer to measure the MR/ER properties.
A comprehensive study is conducted on hard carbon (HC) series samples by tuning the graphitic local microstructures systematically as an anode for SIBs in both carbonate‐ (CBE) and glyme‐based ...electrolytes (GBE). The results reveal more detailed charge storage characters of HCs on the LVP section. 1) The LVP capacity is closely related to the prismatic surface area to the basal plane as well as the bulk density, regardless of electrolyte systems. 2) The glyme‐sodium ion complex can facilitate sodium ion delivery into the internal closed pores of the HCs along with not well‐ordered graphitic structures. 3) The glyme‐mediated sodium ion‐storage behavior causes significant decreases in both surface film resistance and charge transfer resistance, leading to enhanced rate capability. 4) The LVP originates from the formation of pseudo‐metallic sodium nanoclusters, which are the same in a CBE and GBE. These results provide insight into the sodium ion‐storage behaviors of HCs, particularly on the interrelationship between graphitic local microstructures and electrolyte systems. In addition, a high‐performance HC anode with a plateau capacity of ≈300 mA h g−1 is designed based on the information, and its workability is demonstrated in a full‐cell SIB device.
A comparison study is conducted on hard carbon series samples by systematically tuning local graphitic microstructures as an anode for sodium ion batteries in both carbonate‐ and glyme‐based electrolytes. These results provide insight into the sodium ion‐storage behaviors of hard carbons, particularly on the interrelationship between graphitic local microstructures and electrolyte systems.
Silica-graphene oxide (Si-GO) hybrid composite particles were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of hydrophilic GO obtained from a modified Hummers method. ...Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images provided visible evidence of the silica nanoparticles grafted on the surface of GO, resulting in Si-GO hybrid composite particles. Energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) spectra indicated the coexistence of silica and GO in the composite particles. The Si-GO hybrid composite particles showed better thermal stability than that of GO according to thermogravimetric analysis (TGA). The electrorheological (ER) characteristics of the Si-GO hybrid composite based ER fluid were examined further by optical microscopy and a rotational rheometer in controlled shear rate mode under various electric field strengths. Shear stress curves were fitted using both conventional Bingham model and a constitutive Cho-Choi-Jhon model. The polarizability and relaxation time of the ER fluid from dielectric spectra measured using an LCR meter showed a good correlation with its ER characteristics.
To improve the rheological performance and dispersion state of carbonyl iron (CI)-based magnetorheological (MR) fluids, we synthesized ZnFe 2 O 4 particles via a solvothermal method and used them as ...an additive material. Morphology of the product particles was examined using scanning electron microscopy, and their particle size distribution was measured via dynamic light scattering. Two types of MR suspensions, CI- and CI-/ZnFe 2 O 4 -based MR suspensions, were fabricated by dispersing the particles in silicone oil. Under external magnetic fields of different strengths, the rheological properties of the CI- and CI-/ZnFe 2 O 4 -based MR fluids were determined using a rotational rheometer via steady shear and oscillatory dynamic tests. Shear stress curves according to the shear rate were examined using the Hershel-Bulkley model, and the dynamic yield stress curve had a slope of 1.5. Moreover, the ZnFe 2 O 4 -containing MR fluid exhibited a larger yield stress than the CI-based MR fluid. The dispersion stability of both MR suspensions was also confirmed using a Turbiscan optical analyzer. The light transmission ratio of the CI-based suspension was 79%, whereas that of the CI/ZnFe 2 O 4 suspension was 34%. As an additive material, ZnFe 2 O 4 filled the free space among the CI particles and improved the stability of the fluid against rapid sedimentation of dense CI particles.
We fabricated core/shell typed semiconducting poly(o-anisidine) (POA) coated polystyrene (PS) composite microspheres and used them as an electrorheological (ER) material. Micro-spherical PS seeds ...were initially fabricated through a dispersion polymerization method, and the semiconducting POA was coated onto the PS seeds through a chemical oxidation polymerization technique. Uniform coating of the POA onto the PS particles was confirmed via morphology analysis. Their chemical structures and thermal behaviors were identified using Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively. Using a rotational rheometer, PS/POA based ER fluid (5 vol%) exhibited a yield stress of about 72 Pa under an electric field strength of 2.5 kV/mm. Over the range of electric field strength, both dynamic and elastic yield stresses grew in proportion to the power of 1.5 of the electric field strength. Dielectric properties of the ER suspension were also found to be correlated with its ER properties.
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•Monodisperse spherical polystyrene particles were fabricated using dispersion polymerization.•Poly(o-anisidine) was uniformly coated on polystyrene using a simple chemical oxidative polymerization.•Polystyrene/poly(o-anisidine) core/shell particles exhibit proper conductivity without a de-doping process.•Polystyrene/poly(o-anisidine) based smart fluid shows interesting electrorheological behaviors.
The remaining challenging issue during oil production from reservoir is reduction of water production using a conformance control technique. As a new method, the feasibility of an electrorheological ...(ER) suspension for forming a solid-like structure to obstruct the pore throat in porous media was investigated. Suitable conducting nanoparticles for injection into an oil reservoir with regard to size, morphological shape, and field scale capability were synthesized and characterized, then dispersed in two types of oil: heavy and light crude oil. A series of ER experiments, including steady shear and dynamic tests were performed to determine the ability of the proposed conformance control fluid to produce a solid-like form with the electric field. The fluid was then modeled using both the Bingham and Herschel-Bulkley equations. The large ER behaviors proved feasibility of the proposed conformance controlling fluid for reducing water production, which can make the oil production operation more economical and environmentally friendly.
