Tunable and Ultraefficient Microwave Absorption Properties of Trace N-Doped Two-Dimensional Carbon-Based Nanocomposites Loaded with Multi-Rare Earth Oxides.

A high efficiency and great tunability of bandwidth and absorption-range electromagnetic wave absorber is proposed without precedent. A series of 2D carbon-based nanocomposites with the loading of cerium oxide (CN-Ce) and other types of rare earth oxides (CN-REOs) can be successfully synthesized by a simple solvothermal-sintering method. As-synthesized 2D nanocomposites with local graphite-like C3 N4 structure and trace N-doped are identified by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The CN-REOs and polyvinylidene fluoride composite absorbers with reflection loss values above -40 dB are obtained in C-band, X-band, and Ku-band, respectively. The empirical rules on effective bandwidth and frequency range are discovered and summarized, which can be successfully realized by simply tuning the doping amount or type of REO. The mechanism is explained by enhanced attenuation and tunable impedance matching. In addition co-filled samples by two types of CN-REOs nanocomposites are prepared to support these findings and inspire the preparation of absorber with desirable frequency band in the range of 2-18 GHz.

Reference intervals for total bilirubin, ALT, AST and creatinine in healthy Chinese elderly.

BACKGROUND: The aim of this study was to establish the reference intervals (RIs) of total bilirubin (TBIL), alanine aminotransferase (ALT), aspartate transaminase (AST), and creatinine (CREA) for apparently healthy elderly (Han ethnicity) in Shuyang, China. MATERIAL AND METHODS: A total of 54 912 blood specimens from elderly residents age 65-104 years were collected by standard procedures in Shuyang county of Jiangsu province. TBIL, ALT, AST, and CREA for each participant were determined by automatic biochemical analyzer. Distribution and differences of TBIL, ALT, AST, and CREA were analyzed and compared between the elderly of the same age of different sexes and different ages of the same sex. RIs of TBIL, ALT, AST, and CREA were compared with the current RIs. The RIs and 95% confidence intervals were calculated using nonparametric method (2.5th-97.5th percentiles) according to the guideline of the Clinical and Laboratory Standards Institute. RESULTS: RIs established for the healthy elderly include: TBIL 7.8~30.6 µmol/L for males and 7.3~26.1 µmol/L for females; ALT 8.7~47.3 U/L for males and 8.4~45.2 U/L for females; AST 15.7~46.9 U/L for males and 15.1~46.2 U/L for females; and CREA 45.1~100.9 µmol/L for males and 38.7~85.0 µmol/L for females. Reference intervals of TBIL, ALT, AST, and CREA for male elderly were higher than those of females, and values of CREA increased with increasing age. CONCLUSIONS: We have established a panel of locally relevant RIs. It is necessary to establish scientific and reasonable RIs of TBIL, ALT, AST, and CREA for the healthy elderly in our region, which will provide a reference for clinicians and inspection officers.

Interface-induced dual-pinning mechanism enhances low-frequency electromagnetic wave loss.

Improving the absorption of electromagnetic waves at low-frequency bands (2-8 GHz) is crucial for the increasing electromagnetic (EM) pollution brought about by the innovation of the fifth generation (5G) communication technology. However, the poor impedance matching and intrinsic attenuation of material in low-frequency bands hinders the development of low-frequency electromagnetic wave absorbing (EMWA) materials. Here we propose an interface-induced dual-pinning mechanism and establish a magnetoelectric bias interface by constructing bilayer core-shell structures of NiFe2O4 (NFO)@BiFeO3 (BFO)@polypyrrole (PPy). Such heterogeneous interface could induce distinct magnetic pinning of the magnetic moment in the ferromagnetic NFO and dielectric pinning of the dipole rotation in PPy. The establishment of the dual-pinning effect resulted in optimized impedance and enhanced attenuation at low-frequency bands, leading to better EMWA performance. The minimum reflection loss (RLmin) at thickness of 4.43 mm reaches -65.30 dB (the optimal absorption efficiency of 99.99997%), and the effective absorption bandwidth (EAB) can almost cover C-band (4.72 ~ 7.04 GHz) with low filling of 15.0 wt.%. This work proposes a mechanism to optimize low-frequency impedance matching with electromagnetic wave (EMW) loss and pave an avenue for the research of high-performance low-frequency absorbers.

Designing Symmetric Gradient Honeycomb Structures with Carbon-Coated Iron-Based Composites for High-Efficiency Microwave Absorption.

The impedance matching of absorbers is a vital factor affecting their microwave absorption (MA) properties. In this work, we controllably synthesized Material of Institute Lavoisier 88C (MIL-88C) with varying aspect ratios (AR) as a precursor by regulating oil bath conditions, followed by one-step thermal decomposition to obtain carbon-coated iron-based composites. Modifying the precursor MIL-88C (Fe) preparation conditions, such as the molar ratio between metal ions and organic ligands (M/O), oil bath temperature, and oil bath time, influenced the phases, graphitization degree, and AR of the derivatives, enabling low filler loading, achieving well-matched impedance, and ensuring outstanding MA properties. The MOF-derivatives 2 (MD2)/polyvinylidene Difluoride (PVDF), MD3/PVDF, and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt% and as low as 5 wt%. The MD2/PVDF (5 wt%) achieved a maximum effective absorption bandwidth (EAB) of 5.52 GHz (1.90 mm). The MD3/PVDF (10 wt%) possessed a minimum reflection loss (RLmin) value of - 67.4 at 12.56 GHz (2.13 mm). A symmetric gradient honeycomb structure (SGHS) was constructed utilizing the high-frequency structure simulator (HFSS) to further extend the EAB, achieving an EAB of 14.6 GHz and a RLmin of - 59.0 dB. This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.

Skillful Introduction of Urea during the Synthesis of MOF-Derived FeCoNi-CH/p-rGO with a Spindle-Shaped Substrate for Hybrid Supercapacitors.

A composite (FeCoNi-CH/p-rGO) with a spindle-shaped substrate is controllably prepared by combining FeCoNi carbonate hydroxide (FeCoNi-CH) and partially reduced graphite oxide (p-rGO) using a novel chemical strategy. In the synthetic process, urea is introduced as the precipitant and reducing agent. MIL-88A as a self-template is converted into a ternary-metal CH composite, maintaining the original morphology by the metal ion etching and coprecipitation method, and graphite oxide is reduced to rGO with stronger conductivity partially at the same time. The electrochemical performance of the FeCoNi-CH/p-rGO is superior to FeCoNi-CH, with a high specific capacitance (1346 F g-1 at 0.5 A g-1) and rate capability (55.5% at 10 A g-1). The better electrochemical performance of the FeCoNi-CH/p-rGO composite is attributed to the pseudocapacitive energy storage capacity caused by the synergistic action of ternary-metal CH and the high conductivity of p-rGO. Meanwhile, the uniform mixture of FeOOH/activated carbon (AC) is fabricated as an anode to instead of the pure FeOOH or AC, which leads to the balancing energy density and high cycle stability of the hybrid supercapacitor (HSC). The corresponding assembled FeCoNi-CH/p-rGO//FeOOH/AC HSC exhibits a high energy density of 46.93 W h kg-1 at 400 W kg-1 power density and a cycle stability of 66.7% after 3000 cycles. In addition, this work also provides a facile method to fabricate metal-organic framework-derived ternary-metal CH/p-rGO composite materials, which could be applied in the fields of supercapacitors and other fields.

Bioinspired crystallization of CaCO3 coatings on electrospun cellulose acetate fiber scaffolds and corresponding CaCO3 microtube networks.

This article describes the mineralization behavior of CaCO(3) crystals on electrospun cellulose acetate (CA) fibers by using poly(acrylic acid) (PAA) as a crystal growth modifier and further templating synthesis of CaCO(3) microtubes. Calcite film coatings composed of nanoneedles can form on the surfaces of CA fibers while maintaining the fibrous and macroporous structures if the concentration of PAA is in a suitable range. In the presence of a suitable concentration of PAA, the acidic PAA molecules will first adsorb onto the surface of CA fibers by the interaction between the OH moieties of CA and the carboxylic groups of PAA, and then the redundant carboxylic groups of PAA can ionically bind Ca(2+) ions on the surfaces of CA fibers, resulting in the local supersaturation of Ca(2+) ions on and near the fiber surface, which can induce the nucleation of CaCO(3) on the CA fibers instead of in bulk solution. Calcite microtube networks on the macroscale can be prepared by the removal of CA fibers after the CA@CaCO(3) composite is treated with acetone. When the CA fiber scaffold is immersed in CaCl(2) solution with an extended incubation time, the first deposited calcite coatings can act as secondary substrate, leading to the formation of smaller calcite mesocrystal fibers. The present work proves that inorganic crystal growth can occur even at an organic interface without the need for commensurability between the lattices of the organic and inorganic counterparts.

Graphene-wrapped pine needle-like cobalt nanocrystals constructed by cobalt nanorods for efficient microwave absorption performance.

Magnetic metal nanocrystals tend to be advanced microwave absorption substances as they possess simultaneous dielectric and magnetic losses. In this study, the metallic cobalt (Co) nanocrystals with a pine needle-like nanostructure constructed by one-dimensional Co nanorods have been successfully prepared through the polyol approach. By regulating the amount of reduced graphene oxide (rGO), rGO/Co nanocomposites with different mass ratios were acquired. Experimental results demonstrate that the rGO/Co nanocomposites display excellent microwave attenuation capacity. The minimum reflection loss value can reach -57.8 dB at 12.43 GHz with a filler loading of 20 wt% at 1.8 mm. Moreover, the effective absorption bandwidth covers the frequency range of 4.2-15.5 GHz with an integrated thickness of 1.5-4.0 mm. The main absorption mechanisms include dielectric loss caused by dipole and interfacial polarization and magnetic loss arising from ferromagnetic resonance and eddy current loss. In addition, the special nanostructure effect is also beneficial to improve the EM wave absorption performance.

Controllable synthesis of hollow spherical nickel chalcogenide (NiS2 and NiSe2) decorated with graphene for efficient supercapacitor electrodes.

New carbon-loaded nickel chalcogenide electrode materials (NiS2/GO and NiSe2/rGO) have been synthesized through an easy-to-operate process: NiSe2 was obtained based on NiS2 hollow spheres, and was successfully synthesized with l-cysteine assistance under the hydrothermal method at 120 °C. GO of different mass fraction was added together with l-cysteine. The electrochemical performance of NiS2/GO and NiSe2/rGO has been greatly improved because the formation of a carbon-loaded layer effectively increased the specific surface area and reduced the charge transport resistance. Compared with pure NiS2 and NiSe2, NiS2/GO and NiSe2/rGO presented much better specific capacitance (1020 F g-1 and 722 F g-1 respectively at a current density of 1 A g-1) and more superior rate capability (when the current density was raised to 5 A g-1 the specific capacitance remained at 569 F g-1 and 302 F g-1). This work highlights the advantages of nickel compounds through a very simple experimental method, and contributes to providing a good reference for preparation of superior supercapacitor materials with high performance.

3D Ultralight Hollow NiCo Compound@MXene Composites for Tunable and High-Efficient Microwave Absorption.

The 3D hollow hierarchical architectures tend to be designed for inhibiting stack of MXene flakes to obtain satisfactory lightweight, high-efficient and broadband absorbers. Herein, the hollow NiCo compound@MXene networks were prepared by etching the ZIF 67 template and subsequently anchoring the Ti3C2Tx nanosheets through electrostatic self-assembly. The electromagnetic parameters and microwave absorption property can be distinctly or slightly regulated by adjusting the filler loading and decoration of Ti3C2Tx nanoflakes. Based on the synergistic effects of multi-components and special well-constructed structure, NiCo layered double hydroxides@Ti3C2Tx (LDHT-9) absorber remarkably achieves unexpected effective absorption bandwidth (EAB) of 6.72 GHz with a thickness of 2.10 mm, covering the entire Ku-band. After calcination, transition metal oxide@Ti3C2Tx (TMOT-21) absorber near the percolation threshold possesses minimum reflection loss (RLmin) value of - 67.22 dB at 1.70 mm within a filler loading of only 5 wt%. This work enlightens a simple strategy for constructing MXene-based composites to achieve high-efficient microwave absorbents with lightweight and tunable EAB.

Hemorrhagic pure sensory strokes in the thalamus and striatocapsular area: causes, clinical features and long-term outcome.

BACKGROUND: Although there have been sporadic reports of patients with hemorrhagic pure sensory strokes (HPSS) in the thalamus and striatocapsular areas, the causes, clinical featuring and long-term outcome have not been adequately investigated. METHODS: We recruited 7 consecutive patients without hemiparetic stroke who had HPSS in the thalamic and striatocapsular areas. A CT scan was performed to verify brain imaging patterns, and their causes, clinical featuring and long-term outcome were observed. RESULTS: We studied 7 patients who had HPSS in the thalamic and striatocapsular areas as seen in CT scans. The 7 patients had hypertension, and small hemorrhages were found in the thalamus of 2 patients and in the posterior quarter of the posterior limb of the internal capsule in 4 patients; only 1 patient had a microhemorrhage in the thalamus. The volume of the hemorrhages ranged from 0.3 to 6.3 ml, with a mean of 2.3 ± 1.9 ml. Three patients showed a decreased sense of spinothalamic modality, and position and vibration senses were spared. Four patients showed a sensory deficit of both spinothalamic and medial lemniscal type. The outcomes were excellent and without post-stroke pain in all patients. CONCLUSION: HPSS in the thalamus and striatocapsular area are usually small hemorrhages or microhemorrhages from rupturing of the microvessels or the branches of small vessels. HPSS only have an impact on the adjacent sensory nucleus or pathway, and have a good outcome without post-stroke pain.

Enhanced Electromagnetic Absorption Properties of Commercial Ni/MWCNTs Composites by Adjusting Dielectric Properties.

In this manuscript, we constructed a Ni/MWCNTs absorber and properly adjusted the permittivity resulted from absorber content in the PVDF to optimize impedance matching properties. Both ε' and ε″ increase obviously with the increasing content of Ni/MWCNTs in PVDF, demonstrating that dielectric properties are dependent on the conductivity. Moderate dielectric properties and excellent impedance matching can be obtained for the filler content of 20 wt% Ni/MWCNTs. Reasonable impedance matching allows electromagnetic waves to propagate into the materials and finally realize energy dissipation through dielectric loss and interfacial polarization. As expected, the minimum reflection loss (RL) of -46.85 dB at 6.56 GHz with a low filler loading (20 wt%) and wide effective bandwidth (RL<-10 dB) of 14.0 GHz in the thickness range of 1.5-5.0 mm was obtained for the commercial Ni/MWCNTs composites, which is promising for mass production in industrial applications. Our findings offer an effective and industrialized way to design high-performance material to facilitate the research in microwave absorption.

Balancing Dielectric Loss and Magnetic Loss in Fe-NiS2/NiS/PVDF Composites toward Strong Microwave Reflection Loss.

Lightweight, broad-band, and highly efficient microwave-absorbing materials (MAMs) with tunable electromagnetic properties are in high demand. However, the absorption properties are limited by the simple loss mechanism in commonly used absorbing materials. Here, we tested the microwave-absorbing properties of Fe-NiS2/NiS/poly(vinylidene fluoride) (PVDF) in the frequency range of 2-18 GHz. For the 2.5% Fe-NiS2/NiS/PVDF with the filling content of 20 wt %, the maximum reflection loss can reach -61.72 dB at 14.88 GHz, and the bandwidth can reach 3.8 GHz with the reflection loss value below -10 dB. Loss mechanisms of different composites were analyzed on the basis of their magnetic and dielectric properties using both experimental and computational methods. The results indicate that strong microwave absorption property is achieved through a balancing of dielectric loss and magnetic loss. These findings present a new strategy for the future design of MAMs.

Three-Dimensional Bi2Fe4O9 Nanocubes Loaded on Reduced Graphene Oxide for Enhanced Electromagnetic Absorbing Properties.

Bi2Fe4O9(BFO) nanocubes were prepared in proportion using a simple and easy hydrothermal method, and were then assembled on reduced graphene oxide (rGO) multilayered sheets. The excellent microwave absorption properties of Bi2Fe4O9/rGO nanohybrids were achieved by properly adjusting the impedance matching and getting a high attenuation capability contributed from different ratios of the BFO and rGO. A minimum reflection loss value of -61.5 dB at 12.8 GHz was obtained with a Bi2Fe4O9/rGO ratio of 2:1, and the broadest bandwidth below -10 dB was up to 5.0 GHz (from 10.8 to 15.8 GHz) with a thickness of 2.4 mm. Additionally, the elementary mechanism of wave absorption performance is also investigated.

Reduced graphene oxide decorated with octahedral NiS2/NiS nanocrystals: facile synthesis and tunable high frequency attenuation.

Reduced graphene oxide (RGO) decorated with octahedral NiS2/NiS nanocrystals were fabricated via a facile synthetic strategy. By appropriate adjustment of the weight ratio of GO and NiS2/NiS nanocrystals, RGO-NiS2/NiS nanocomposites with an excellent microwave absorption performance were achieved. As expected, RGO-NiS2/NiS nanocomposites in a polyvinylidene fluoride (PVDF) matrix with different mass fractions (5, 10, 15, 20 wt%) possess effective absorption in the high frequency range with a thin thickness (1.5 mm) compared with those of octahedral NiS2/NiS nanocrystals. It was revealed that RGO-NiS2/NiS nanocomposites with a GO : NiS2/NiS weight ratio of 1 : 4 exhibited the most prominent microwave absorption property. The optimal effective frequency bandwidth of this sample covers 4.32 GHz at a thin coating layer of 1.5 mm (15 wt%). The corresponding reflection loss value can reach -32.2 dB at 14.32 GHz. Moreover, the fundamental attenuation mechanisms are also discussed in detail.

The synthesis of Co x Ni1-x Fe2O4/multi-walled carbon nanotube nanocomposites and their photocatalytic performance.

A series of Co x Ni1-x Fe2O4/multi-walled carbon nanotube (Co x Ni1-x Fe2O4/MWCNTs) nanocomposites as photocatalysts were successfully synthesized, where Co x Ni1-x Fe2O4 was synthesized via a one-step hydrothermal approach. Simultaneously, methylene blue (MB) was used as the research object to investigate the catalytic effect of the catalyst in the presence of hydrogen peroxide (H2O2). The results showed that all the photocatalysts exhibited enhanced catalytic activity compared to pure ferrite. In addition, compared with the other photocatalysts, the reaction time was greatly shortened a significantly higher removal rate was achieved using 3-CNF/MWCNTs. There was no significant decrease in photodegradation efficiency after three catalytic cycles, suggesting that Co x Ni1-x Fe2O4/MWCNTs are recyclable photocatalysts for wastewater treatment. Our results indicate that the Co x Ni1-x Fe2O4/MWCNT composite can be effectively applied for the removal of organic pollutants as a novel photocatalyst.

Ultra-High Electromagnetic Absorption Property of One-Dimensional Carbon-Supported Ni/Mo2C and Polyvinylidene Fluoride.

A novel one-dimensional carbon-supported Ni/Mo2C (Ni/Mo2C-C) nanocomposite with excellent electromagnetic wave absorption properties was successfully synthesized by annealing NiMoO4@PDA directly, and then the (Ni/Mo2C-C)/polyvinylidene fluoride (PVDF) composites were fabricated using a simple blending and hot-molding technique. An excellent reflection loss (RL) of -55.91 dB at 9.28 GHz with a low filler loading (15 wt%) and effective bandwidth (RL < -10 dB) of 14.12 GHz in the thickness range of 1.5-5.0 mm was obtained. Dielectric loss is considered to be the dominant mechanism of (Ni/Mo2C-C)/PVDF, which was confirmed by the Debye relaxation process and attenuation theory.

Controllable Synthesis of One-Dimensional MoO3 /MoS2 Hybrid Composites with their Enhanced Efficient Electromagnetic Wave Absorption Properties.

One-dimensional MoO3 /MoS2 hybrid composites were synthesized by hydrothermal synthesis, and flexible MoO3 /MoS2 /PVDF nanocomposites could be prepared in a controlled fashion by combining the MoO3 /MoS2 composites with polyvinylidene fluoride (PVDF) matrix. The MoO3 /MoS2 /PVDF hybrids with a low filler content (20 wt %) exhibited distinct microwave absorption properties in the range of 2-18 GHz. The minimum reflection loss can reach -38.5 dB at 8.7 GHz, and the reflection loss was less than -10 dB in the frequency range from 3.03-11.02 GHz with an absorber thickness of 2.0-5.0 mm. The MoO3 /MoS2 /PVDF nanocomposites exhibited better absorption properties than pure MoO3 and MoS2 . The possible microwave absorption mechanism was also discussed in detail.

Microwave absorption enhancement by adjusting reactant ratios and filler contents based on 1D K-MnO2@PDA and poly(vinylidene fluoride) matrix.

One-dimensional K-MnO2 nanorods were prepared by a wet chemical process. Dopamine hydrochloride (PDA) layers with various thicknesses were coated and finally, the composites were filled in a poly(vinylidene fluoride) (PVDF) matrix using the hot-molding procedure. The complex permittivity and permeability of the K-MnO2@PDA/PVDF composites could be adjusted by reactant amount ratios and filler contents. The minimum reflection loss could reach -49.4 dB and an effective absorption bandwidth (<-10 dB) covering 11.12 GHz was achieved with 20% filler content when the reactant amount ratio between K-MnO2 and PDA was 4 : 0.375, which was derived from effective internal polarization processes. It is expected that these novel composites can be used as high-performance microwave absorbers.

Excellent microwave absorption properties based on a composite of one dimensional Mo2C@C nanorods and a PVDF matrix.

MoO3 nanowires were synthesized by a wet chemical process and then coated by glucose, and finally successfully turned into Mo2C@C nanorods by carbonation reaction. An excellent absorption strength of -39.0 dB and absorption bandwidth of 12.2 GHz in the thickness range of 2.0-5.0 mm were achieved by the Mo2C@C/PVDF with 10% filler content, derived from effective Debye dipolar relaxation processes. It is expected that the composite can be applied as a novel and desirable microwave absorber.

Enhanced Wave Absorption and Mechanical Properties of Cobalt Sulfide/PVDF Composite Materials.

A cobalt sulfide/PVDF(Polyvinylidene Fluoride) composite was prepared by a simple blending method, and the microstructure of the composite was investigated through X-ray diffraction, scanning electron microscopy, and field emission scanning electron microscopy. Increased absorption properties at frequencies ranging from 2 GHz to 18 GHz were studied, and the mechanical properties were investigated via tensile tests and finite element method simulations. The results indicated that the cobalt sulfide/PVDF composites exhibited strong microwave absorption intensities (-43 dB at 6.6 GHz) with a low filler loading (5.0 wt%). The elastic modulus increased with the cobalt sulfide mass fraction. Cobalt sulfide could improve the mechanical properties of the composite, especially in the lengthwise direction.