Oxide Skeleton Research Articles

Ablation mechanism of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite during plasma ablation above 2000 °C

Air plasma ablation behavior of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite was studied systematically with the surface temperature above 2000 °C at the ablation center. It presents a linear recession rate of 0.15 μm/s and a mass recession rate of 2.05 mg/s after ablation at 4 MW/m2 (2000 °C) for 300 s. Associated with the temperature gradient of the ablation surface, the oxidation products at different locations mainly consist of (TiZrHfNbTa)Ox, (ZrxHf1–x)6(NbyTa1–y)2O17, Ti(NbxTa1–x)2O7, (HfxZr1–x)SiO4, and SiO2. Due to the synergistic effect of the multi-component oxides, oxidation products form a protective structure composed of high melting point oxide skeleton filled with relatively low melting point phases. It retards oxygen inward diffusion and prevents the composite fragmentation caused by plasma mechanical scouring. It is believed that the results would be helpful for further improving the ablation resistance by component design of high entropy ceramics and their composites.

Microstructure evolution and phase interface characterization in anti-ablation (Hf1/4Zr1/4Ta1/4Ti1/4)C-coated C/C composites

Ta and Ti elements are often used as modified components to densify the loose oxide film for HfC/ZrC coatings after long-term ablation, while the synergistic effect among their multi-phase oxides on the ablation resistance of the coatings for C/C composites is still being explored. In this work, a (Hf1/4Zr1/4Ta1/4Ti1/4)C high-entropy carbide ceramic was proposed as an advanced anti-ablation coating for C/C composites and the multicomponent synergistic effect on the ablative behavior was investigated. At the initial ablation, the O atoms first reacted with Hf and Zr elements to form m-(Hf, Zr)O2. The TiO2 was prone to decompose into TiO and then evaporated from the coating during ablation, slowing down the volatilization of Ta2O5. The remaining TiO2 and Ta2O5 diffused to m-(Hf, Zr)O2 and produced a phase transition from Ta/Ti-doped m-(Hf, Zr)O2 to o-(Hf, Zr)6Ta2O17/o-(Hf, Zr)TiO4. The formation of nanotwin between (Hf, Zr)6Ta2O17 and (Hf, Zr)TiO4 enhanced the toughness of the oxide film. Although excessive Ta2O5 broke the stability of the oxide film, the Hf-Zr-rich oxide skeleton (Ta/Ti-doped (Hf, Zr)O2, (Hf, Zr)6Ta2O17 and (Hf, Zr)TiO4)) ensured that C/C substrates were intact after ablation for 180 s, showing superior ablation resistance.

Tinospora cordifolia-assisted synthesis of silver ferrite nanoparticles: a multifunctional approach to photocatalytic degradation of reactive blue-13 dye, anti-bacterial efficacy, and antioxidant properties

Tinospora cordifolia-assisted synthesis of silver ferrite nanoparticles: a multifunctional approach to photocatalytic degradation of reactive blue-13 dye, anti-bacterial efficacy, and antioxidant properties

Structurally Optimized Fluorinated Small‐Sized Graphene Oxide for Enhanced Magnetic Resonance Imaging during Pregnancy

AbstractGadolinium‐based complex contrast agents (GBCAs), frequently applied in magnetic resonance imaging (MRI), are associated with severe acute anaphylactic shock and incurable nephrogenic systemic fibrosis. Besides, the repeated use of GBCAs may result in the accumulation in various tissues. Given these potential adverse effects, GBCAs have not been well used during pregnancy. Herein, a novel metal‐free T2‐weighted MRI nanoprobe, designated fluorinated small‐sized graphene oxide with optimized fluorine content (LF‐sGO), is developed via graphene oxide materials. By introducing specific polar C─F bonds onto the small‐sized graphene oxide (sGO) skeleton, the prepared nanoprobe exhibits excellent water solubility, as well as superior MRI capabilities, thereby furnishing high‐resolution MRI anatomical information. Furthermore, the free radicals on LF‐sGO stabilized by C─F bonds confer LF‐sGO enrichment in the tumor region, enabling comprehensive imaging capability. The cytotoxicity study in vitro indicates that LF‐sGO has the potential to serve as a biocompatible imaging probe. Moreover, detailed in vivo studies on pregnant mice and zebrafish adequately demonstrate that microinjection of LF‐sGO does not induce dysontogensis and teratogenesis. This study successfully showcases a metal‐free nanoprobe that exhibits exceptional MRI capabilities for the purpose of tumor diagnosis. Notably, this nanoprobe holds promise for safe and effective tumor diagnosis during pregnancy.

Uranium-based electrode material for the high-performance supercapacitors

In recent decades, significant progress has been made in the engineering of electrode materials for supercapacitors. In this regard, the primary emphasis has been on investigating carbonaceous based materials. However, this focus has restricted the overall capacitance of supercapacitor devices, thus hindering their broader application possibilities. There is still a gap in the literature on high-performance radioactive element-based electrode materials. Bearing this, in this work, a simple approach was suggested for the implementation of uranium, as a radioactive element, decorating onto carbon architecture, as electrode material in high-energy supercapacitor cells. Herein, a facile pathway for tailoring a uranium-decorated graphene oxide nanostructure (U-GOx; where x stands for the GO:U ratio by weight) was proposed and the potential applications of the synthesized nanoarchitectures as an electrode material of supercapacitor cell were investigated. As per the author's knowledge, for the first time in the ever-burgeoning field of energy storage systems, a radioactive compound-based supercapacitor cell was fabricated. The physicochemical characterizations confirmed the successful anchoring of uranium atoms onto the graphene oxide skeleton. The U-GO5 electrode-based-supercapacitor cell offered the highest performance metrics with a 95.92 % capacitance retention value at the end of the 15,000 consecutive galvanostatic charge-discharge cycles, besides the high specific capacitance value of 258.6 F⸱g−1 at a high current density value of 10.0 A⸱g−1. Moreover, the radioactivity measurements were conducted to investigate whether the fabricated supercapacitors were radioactive or not. The results revealed that the measured radiation dose of the U-GO5-based supercapacitor cell before the GCD cycles, which was of the highest uranium content, was ca.0.06 μSv (the background measurement was excluded). This finding indicated there would be no adverse effect on human health or the environment. It can be speculated that this work is a new era for engineering a high-performance supercapacitor based on organic electrodes decorated with a radioactive element.

Fabrication and efficient electromagnetic waves attenuation of three-dimensional porous reduced graphene oxide/boron nitride/silicon carbide hierarchical structures

In this work, hierarchical hybrid composites consisting of porous three-dimensional reduced graphene oxide (3D-rGO) skeleton and lamellar boron nitride (BN)/silicon carbide (SiC) coatings are prepared by chemical vapor infiltration (CVI) process. The graphene framework prepared by 3D printing and frozen self-assembly exhibits a lightweight structure and a perforated conductive network, which extends the transmission path of incident microwaves. The introduced ceramic coatings can effectively tune the impedance matching degree and supply a lossy phase, and the hierarchical structure of the composites enhances the multiple scattering of the incident microwaves. As expected, the 3D-rGO/BN/SiC composites possess an excellent absorbing performance with a minimum reflection loss value of –37.8 dB, and the widest effective absorbing bandwidth (RL < –10 dB) of 5.90 GHz is obtained. The controllable fabrication of composites can provide a guideline for rational design and fabrication of high-performance electromagnetic waves absorbing materials in practical applications.

Energy-dense wire-like supercapacitors based on scalable three-dimensional porous metal-graphene oxide skeleton electrodes

Macroporous electrodes with multi-scaled nanostructures are simply synthesized by sequentially immersing a wire in different plating solutions through the mechanism of structural catalysis and nano-‘reinforced concrete’.

Elucidating the role of preferential oxidation during ablation: Insights on the design and optimization of multicomponent ultra-high temperature ceramics

Multicomponent ultra-high temperature ceramics (UHTCs) are promising candidates for thermal protection materials (TPMs) used in aerospace field. However, finding out desirable compositions from an enormous number of possible compositions remains challenging. Here, through elucidating the role of preferential oxidation in ablation behavior of multicomponent UHTCs via the thermodynamic analysis and experimental verification, the correlation between the composition and ablation performance of multicomponent UHTCs was revealed from the aspect of thermodynamics. We found that the metal components in UHTCs can be thermodynamically divided into preferentially oxidized component (denoted as MP), which builds up a skeleton in oxide layer, and laggingly oxidized component (denoted as ML), which fills the oxide skeleton. Meanwhile, a thermodynamically driven gradient in the concentration of MP and ML forms in the oxide layer. Based on these findings, a strategy for pre-evaluating the ablation performance of multicomponent UHTCs was developed, which provides a preliminary basis for the composition design of multicomponent UHTCs.

Primary amine–thiourea grafted graphene–based heterogeneous chiral catalysts for highly enantioselective Michael additions

Heterogeneous asymmetric catalysis based on earth-abundant carbon materials put together the advantages for the ease of separation, simple regeneration, and high stability of solid catalysts as well as acts as low-cost, environmentally friendly metal-free alternative to the metal-based catalysts. Two new bifunctional carbocatalysts [(S,S) and (R,R) GO-PATU] were prepared by anchoring enantiomerically pure organosilanes bearing primary amine and thiourea groups to the graphene oxide (GO) skeleton covalently via silane coupling reaction. The surface modification of GO was analyzed by a combination of Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) techniques. The catalytic performances of graphene-based materials were investigated in the asymmetric Michael addition reactions of α,α-disubstituted-aldehydes to nitrostyrenes and N-substituted-maleimides. The effects of solvents and Brønsted basic or acidic additives were evaluated using both catalysts and good yields (up to 85%) and stereoselectivities (up to 95% ee) were obtained in dichloromethane at room temperature in the presence of l- and d-camphorsulfonic acid. Besides, recycling and reusing studies of the catalysts were successfully performed.

Pristine and Defective 2D Borophene/Graphene Heterostructure as the Potential Anode of Lithium‐Ion Batteries

AbstractBorophene has received much attention due to its unique structure and electronic properties. However, the application of borophene has been limited by the template effect of the growth metal substrate. A stable borophene/graphene (B/G) heterostructure is designed and prepared by the resonance ball milling method and one‐step molding strategy to realize the application of borophene in the lithium‐ion battery for the first time. Graphene serves as a supporting substrate for borophene, and the B/G anode has a better specific capacity and rate performance than the reduced graphene (G) oxide skeleton. By comparing the electrochemical performance of boron powder samples under different ball milling times, it is found that the anode of B/G heterostructure with 6 h boron powder has the largest specific capacity of 192.3 mAh g–1, which is 39% higher than that of the graphene framework. Oxidation functional groups on the surface of borophene are beneficial for the rate performance of the anode. And the influence of the surface functional groups of borophene are analyzed on the diffusion performance through the first principles. It is believed that the B/G has potential for further applications in the field of lithium‐ion batteries.

Nacre-mimetic elastomer composites with synergistic alignments of boron nitride/graphene oxide towards high through-plane thermal conductivity

Thermal-conductive yet electrical-insulating polymer composites are in urgent demand in modern microelectronics for efficient heat dissipation. However, the reported through-plane thermal conductivity of polymer composites under low filler loadings (<10 vol%) is dissatisfactory, due to undesirable heat transfer pathways and high interfacial thermal resistance. Herein, 3D lamellar‑structured fluorinated boron nitride nanosheets (F-BNNS)/graphene oxide (GO) skeleton prepared by bidirectional freezing assembly ensures the directional motion of heat flow, in which GO bridges adjacent F-BNNS for reducing thermal resistance via hydrogen bond of H-F and van der Waals interaction. After vacuum-infiltrating polydimethylsiloxane (PDMS), the 9.5 vol% F-BNNS/GO/PDMS presents fascinating characteristics: a high through-plane thermal conductivity of 3.28 W·m−1·K−1 and an excellent tensile strength of 3.19 MPa, with the enhancements of 1829% and 118% respectively compared to pure PDMS; besides, superior dimensional stability and electrical insulation were obtained, with thermal expansion coefficient of 79 ppm/K and volume resistivity of 2.45 × 1012 Ω·cm.

A 3D Graphene/WO3 nanowire composite with enhanced capture and polysulfides conversion catalysis for high-performance Li–S batteries

The lithium-sulfur (Li–S) batteries have been deemed to be one of the most promising systems for next-generation energy storage devices due to their high theoretical energy density of 2600 Wh kg−1, cost-effectiveness, earth abundance, and environmental friendliness. However, its commercialization process is challenged by several issues, such as the non-conductive sulfur cathode material itself and the polysulfide shuttle effect, as well as sluggish redox reaction kinetics. Herein, we designed a three-dimensional hierarchical structure of reduced graphene-tungsten oxide skeleton as a highly conductive and stable sulfur host material in Li–S battery. Based on various spectroscopic techniques, and In-situ electrochemical studies together with computational methods, it was confirmed that rGO@WO3 can catalyze the polysulfide conversion for improving Li–S battery performance. The constructed 3D rGO@WO3@S cathode delivers a high initial capacity of 1410 mAh g−1 at 0.1C, excellent rate performance (715 mAh g−1 at 3.0C), and a low capacity decay rate of 0.086% up to 500 cycles at 3.0C. This work provides a new pathway to explore the catalytic mechanism of tungsten oxide in promoting redox kinetics of polysulfide conversion.

Incorporating quantum-sized boron dots into 3D cross-linked rGO skeleton to enable the activity of boron anode for favorable lithium storage

Boron has drawn intensive attention as a competitive anode candidate for next-generation high-energy rechargeable batteries. However, the large-scale application of boron anodes for practical batteries is still hindered by their electrochemical inertness caused mainly by the strong covalent bond in the aggregate boron backbone. Herein, quantum-sized boron dots (BQDs) were synthesized by the low-temperature liquid-phase exfoliation of boron nanosheets and incorporated into the conductive graphene matrix, consequently forming a 3D cross-linked BQDs/reduced graphene oxide (B@rGO) skeleton as high-performance anodes for lithium-ion batteries. Decreasing the size of boron to the quantum-sized scale vastly enables the electrochemical activity of boron as well as provides more active sites for ion insertion and extraction, thus increasing capacity and improving ion/charge diffusion and transfer. The 3D cross-linked conductive structure activates BQDs to store/release lithium reversibly, and endows the interrelated macroporous/mesopores, where the electrolyte can effortlessly access the conveying pathways and active sites for efficient Li+ adsorption and desorption. The developed anodes thus harvest remarkable electrochemical properties in terms of ultrahigh capacity of 2651 mAh g−1 at a current density of 0.05 A g−1, outstanding long-term cycling stability of 836 mAh g−1 at 0.1 A g−1 over 500 cycles, and excellent rate performance (even after enduring five consecutive current rates changing from 0.1 to 10 A g−1, it still delivers a capacity of 202 mAh g−1 at 10 A g−1). The protocol to boost the electrochemical performance by introducing BQDs could inspire wider explorations on other advanced anode materials.

Capacity and cycle performance of lithium ion batteries employing CoxZn1-xS/Co9S8@N-doped reduced graphene oxide as anode material

Exploiting efficient and rechargeable lithium-ion batteries (LIBs) is of great significance, which stimulates us to procure suitable electrode materials. Herein, a novel anode material is fabricated via encasing CoxZn1-xS/Co9S8 nanoparticles into N-doped reduced graphene oxide (rGO) skeleton. Owing to the open and accessible structure constructed by the conductive rGO as well as the optimized Co:Zn ratio, the as-prepared electrodes achieve good lithium storage capacity (742.2 mAh g−1 at 1 A g−1 and 222.4 mAh g−1 at 10 A g−1) and an excellent retention rate of 105.9% on 1000th cycle at 1 A g−1, making them promising anode candidate for highly reversible lithium storage in long-term cycles.

Composite polymer electrolytes reinforced by hollow silica nanotubes for lithium metal batteries

Herein, a series of one-dimensional silica nanotubes (SNts) with hollow nanostructures and high uniformity are synthesized by etching the rod-shaped nickel-hydrazine complex, and composite polymer electrolytes (CPEs) are prepared by introducing SNts and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into poly(ethylene oxide) (PEO) skeleton. The CPEs obey Vogel-Tamman-Fulcher empirical equation and the ionic conductivity is demonstrated to be maximum of 4.35 × 10−4 S cm−1 with the longest SNts (270 nm) as fillers at 30 °C, which is significantly higher than that of PEO/LiTFSI (6.13 × 10−8 S cm−1) and PEO/LiTFSI/silica nanoparticles (SNps) (1.07 × 10−6 S cm−1). The connection between SNts among the whole composite contributes the efficient transport pathway to lithium ions. Furthermore, the fabricated cell exhibits good cyclability and rate capability. The SNts based CPEs represent a new design idea for solid-state electrolytes and offers opportunities for lithium metal batteries in the future.

Acrylic acid functionalized graphene oxide: High-efficient removal of cationic dyes from wastewater and exploration on adsorption mechanism

A novel p(AA)-g-GO material was prepared by grafting polymerization of acrylic acid (AA) onto graphene oxide (GO) skeleton, presenting efficient removal of dyes from wastewater, because the layer spacing of GO is expanded and successfully introduced numerous polar carboxyl groups. The study revealed a rapid adsorption kinetic process and the adsorption capacity for methylene blue (MB) increases with pH, contact time, initial dye concentration and temperature. The maximum adsorption capacity is about 1448.2 mg/g at 25 °C for MB according to the Langmuir isotherm. More importantly, the adsorbent maintains excellent adsorption capacity after five cycles of adsorption-desorption and has remarkable selective separability for methylene blue/methyl orange mixed solution at pH = 10. Furthermore, the equilibrium adsorption capacities for other cationic dyes as malachite green (MG), basic fuchsin (BF) and rhodamine B (RhB) reached 582.1, 571.7 and 437.1 mg/g, respectively. Additionally, the mechanism analysis indicated that electrostatic interactions, π-π conjugation and hydrogen bonding are the predominant forces for adsorbing cationic dyes. Therefore, p(AA)-g-GO is an outstanding adsorbent and has a potential application prospect in the treatment of dye wastewater.

Nano Tin/Tin Oxide Attached onto Graphene Oxide Skeleton as a Fluorine Free Anode Material for Lithium-Ion Batteries.

Herein, we show a composite formation method of tin/tin oxide nanoparticles with graphene oxide and CMC based on laser ablation technique as an electrode material for energy storage devices. The material exhibited a three-dimensional conducting graphene oxide network decorated with tin or tin oxide nanoparticles. The structure, homogeneous distribution of nanoparticles, and direct contact between inorganic and organic parts were confirmed by scanning electron microscopy and high-resolution transmission electron spectroscopy. Electrochemical performances of composite electrode material showed a reversible capacity of 644 mAh/g at a current density equal to 35 mA/g, and 424 mAh/g at 140 mA/g. The capacity retention of 90% after 250 cycles show that tested electrode material is suitable as a negative electrode for lithium-ion batteries.

Local conductivity of graphene oxide study by conductive atomic force microscope

In this paper, a Conductive Atomic Force Microscope was used to measure the current distribution image of monolayer graphene oxide (GO) and I/V curves of different types of points in current distribution. Graphene oxide (GO) was prepared by a modified Hummer’s method and deposited on highly oriented pyrolytic graphite. We gradually increase the voltage range and analyze the effect of different voltages on improving the local conductivity of graphene oxide. It has been found that there are several critical voltages, such as 0.8 V, 1.5 V, 2.2 V, and 3.2 V. There is no current when the voltage is lower than 0.8 V; if the voltage is 1.5–2.1 V, the conductivity of GO can be slightly improved, but if not, it will significantly change the structure of graphene oxide; if the voltage is 2.2–3.1 V, the conductivity of GO can be greatly improved, but it still exhibits semiconductor properties; when the voltage increases to 3.2 V, the local conductivity of GO changes, showing metallicity. It was concluded that the strong electric field strength caused by voltage destroys the bond between oxygen-containing functional groups and the graphene oxide skeleton, which is very advantageous for studying the conductivity of GO.

Three-Dimensional Graphene Oxide Skeleton Guided Poly(acrylic Acid) Composite Hydrogel Particles with Hierarchical Pore Structure for Hemoperfusion.

Recently, in order to increase and improve treatment efficacy of hemoperfusion, research and development of novel adsorbents have been paid much attention. Herein, three-dimensional (3D) graphene oxide (GO) skeleton guided poly(acrylic acid) (PAA) composite hydrogel particles (HPs) used for hemoperfusion were prepared by a core-shell template method. The 3D GO skeletons with millimeter-scale were first constructed with the assistance of templates, dissolvable poly(ether sulfone) hollow particles, which were prepared by a phase inversion technique; then, PAA hydrogels were formed and distributed on the surface of the 3D GO skeleton. The obtained HPs showed a special hierarchical pore microstructure, small size, and uniform spherical shape. Compared with pure PAA hydrogels, the swelling ratios of the HPs were significantly restricted, and the porosities were remarkably increased; the compressive stress and the elongation at break were improved at the same time. The hemocompatibility tests, including protein adsorption, hemolysis ratio, complement and contact activation, platelet adhesion, and clotting time, were carried out, and the results indicated that the HPs showed good hemocompatibility. The adsorption results indicated that the HPs exhibited good removal efficiency toward exogenous and endogenous toxins. In general, the suitable physical and mechanical properties and the excellent hemocompatibility and adsorption capacities made the composite hydrogel particle a promising candidate for novel hemoperfusion adsorbents.

One-dimensional architecture with reduced graphene oxide supporting ultrathin MoO2 nanosheets as high performance anodes for lithium-ion batteries

Two-dimensional (2D) materials have been widely studied and used as anode materials for lithium ion batteries (LIBs) because of their high specific surface area and intrinsic mechanical flexibility which could offer numerous active sites and protect effect for LIBs. However, 2D nanosheets are easy to stack and partially lose surface area for Li-ion storage thus greatly affecting their electrochemical performance. Here, we develop a simple strategy to obtain a nanosheets-based one-dimensional structure hybrid by in situ reduction from MoO3 nanorods to MoO2 nanosheets and nanoparticles which are anchored on a 1D reduced graphene oxide skeleton (MoO2-rGO). It was demonstrated that the primary MoO2 nanosheets and nanoparticles are uniformly dispersed on the reduced graphene oxide nanosheets, which are further assembled into a 1D loosened nanostructure. The loosened nanosheets offer more accessible surface area and facilitate transport of electrons and Li-ions. Moreover, MoO2 nanoparticles effectively avoid agglomeration from nanosheets. Results show that MoO2-rGO hybrid demonstrates an enhanced cyclic life, high stability and prominent rate performance when evaluated as anode material for LIBs. The first discharge capacity can reach 1256.4 mAh g−1 and provide a highly reversible capacity of 1003.7 mA h g−1 after 100 cycles at 0.1 A g−1, which makes MoO2-rGO a promising candidate for LIBs. The excellent performance can be attributed to the unique 1D loosened structure consists of MoO2 and conducting rGO nanosheets, which facilitates fast transfer of Li-ion and electron, and the reduced graphene oxide nanosheets acting as a skeleton provide a continuous conductive network and simultaneously strengthen the structural stability.