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NiFe double hydroxide coated on sulfur-modified NiMoO4 nanorods exhibited both enhanced electrocatalytic activity and excellent long-term stability for the OER.

BACKGROUND: To validate the feasibility of generating high-resolution intravascular 3.0 Tesla (T) magnetic resonance imaging of the coronary artery wall to further plaque imaging. METHODS: A receive-only 0.014-inch diameter magnetic resonance imaging guidewire (MRIG) was manufactured for intravascular imaging within a phantom experiment and the coronary artery wall of the swine. For coronary artery wall imaging, both high-resolution images and conventional resolution images were acquired. A 16-channel commercial surface coil for magnetic resonance imaging was employed for the control group. RESULTS: For the phantom experiment, the MRIG showed a higher signal-to-noise ratio than the surface coil. The peak signal-to-noise ratio of the MRIG and the surface coil-generated imaging were 213.6 and 19.8, respectively. The signal-to-noise ratio decreased rapidly as the distance from the MRIG increased. For the coronary artery wall experiment, the vessel wall imaging by the MRIG could be identified clearly, whereas the vessel wall imaging by the surface coil was blurred. The average signal-to-noise ratio of the artery wall was 21.1±5.40 by the MRIG compared to 8.4±2.19 by the surface coil, where the resolution was set at 0.2 mm × 0.2 mm × 2 mm. As expected, the high-resolution sequence clearly showed more details than the conventional resolution sequence set at 0.7 mm × 0.7 mm × 2.0 mm. Histological examination showed no evidence of mechanical injuries in the target vessel walls. CONCLUSIONS: The study validated the feasibility of generating magnetic resonance imaging (MRI) at 0.2 mm × 0.2 mm × 2 mm for the coronary artery wall using a 0.014 inch MRIG.

Highly flexible supercapacitors (SCs) have attracted significant attention in modern electronics. However, it has been found that flexible, metal sulfide-based electrodes usually suffer from corrosion, instability and low conductivity, which significantly limits their large scale application. Herein, we report on an electrode comprised of highly stable, free-standing carbon fiber/trinickel disulphide covered with polyaniline (CF/Ni3S2@PANI). This electrode was prepared and then employed in a high-performance of flexible asymmetric SCs (FASC). The coating layer of polyaniline served as both a protector and conducting shell for the Ni3S2 due to the nature of the highly stable N-Ni bonds that formed between the polyaniline and Ni3S2. In addition, the lightweight carbon fiber support served as both a current collector and flexible support. The prepared CF/Ni3S2@PANI electrode exhibited a significantly enhanced specific capacity (715.3 F·g−1 at 1 A·g−1) compared with the carbon fiber/Ni3S2 electrode (318 F·g−1 at 1 A·g−1). More importantly, the assembled FASC device delivered an impressive energy density of 35.7 Wh·kg−1 at a power density of 850 W·kg−1. The FASC device benefited from the interconnected flexible microstructure and the stable bond bridges, so that it could be bent into various angles without noticeably impairing its performance. This effective protective strategy may further inspire the design and manufacture of metallic oxide or sulfide electrode with ultrahigh-stability interbond bridges for high-performance flexible supercapacitors.

Fe-based oxide electrodes for practical applications in supercapacitors (SCs) suffer from low conductivity and poor structural stability. To settle these issues, we report on the design and synthesis of Fe3O4/carbon nanocomposites via firmly anchoring mesoporous Fe3O4 nanospheres onto N-doped carbon nanotubes (N-CNTs) via C–O–Fe bonds. Mesoporous Fe3O4 nanospheres are featured by rich electroactive sites and short ion diffusion pathways. The N-CNTs, on the other hand, serve as the scaffolds, which not only provide conductive networks but also suppress the accumulation between mesoporous Fe3O4 nanospheres as well as alleviate volume changes during charge/discharge cycles. Accordingly, the constructed Fe3O4/N-CNTs nanocomposite electrode demonstrates improved specific capacity values of up to 314 C g−1 at 1 A g−1, with 92% retention of the initial capacity after 5000 cycles at 10 A g−1. In addition, the assembled Fe3O4/N-CNTs//active carbon (AC) asymmetric supercapacitor (ASC) device possesses an energy density of 25.3 Wh kg−1, suggesting that the prepared Fe3O4/N-CNTs nanocomposites are promising electrode materials for use in SCs.

The rapid development of wearable and portable smart equipment has led to a research boom in flexible energy storage devices. Herein, NiCo2O4 nanosheet arrays have been successfully grown on carbon fibers (CFs), which was firstly modified by the three-dimensional Ni (3D-Ni) to repair the cracks and grooves in the surface of CF. The obtained CFs@3D-Ni/NiCo2O4 electrode possesses a high specific capacity of 736 F/g at 1 A/g current density in the three-electrode system. More importantly, the composite showed excellent electrochemistry stability after temperature plummets. The all-solid-state asymmetric supercapacitor device (ASC) assembled by CFs@3D-Ni/NiCo2O4 delivers a wonderful specific capacity of 176 F/g, a high energy density 55 W h/Kg at 750 W/Kg, excellent cycling stability (about 97.84% after 2000 cycles), and high flexibility (almost no influence in electrical performance at various bending angles). This work has provided a promising method to prepare high performance of the flexible and lightweight energy storage equipment.

This study established a facile one-step strategy to anchor MnFe2O4 nanoparticles on the surface of MoS2 nanosheets in a controlled manner. The as-prepared MnFe2O4/MoS2 nanocomposites were investigated by TEM, XRD, XPS, Raman, BET and VSM in detail. The MnFe2O4 nanoparticles with an average particle size of 26 nm were densely and uniformly decorated on MoS2 nanosheets, and consequently, both the aggregation of MnFe2O4 nanoparticles and restacking of MoS2 nanosheets were effectively prevented. More importantly, the MnFe2O4/MoS2 nanocomposites exhibited high specific surface area, typical superparamagnetic behavior and excellent solution dispersion, showing a great potential for biomedical applications in the fields of magnetic resonance imaging, targeted drug delivery and tumor hyperthermia.

We have synthesized heat-treated PAN/MoO2/MoS2 (PMOS) ternary structure nanofibers by facile solvothermal approach and in-situ conversion reaction. At discharge current density of 1 A/g, the synthesized hierarchical flexible fibers exhibit high specific capacitance of 439.8 F/g. A lightweight and small asymmetric supercapacitor device based on heat-treated PMOS nanofibers//active carbon (AC) delivers a ultrahigh energy density of 46 Wh/kg at power density of 2246.9 W/kg, and long-term capacity retention of about 98.9% after 2000 cycles. Remarkably, the solid-state asymmetric supercapacitor device could light up a LED belt, and no significant change in the brightness and duration when the device bends into a ring, indicating that the material has perfect flexibility and stability. These encouraging findings indicate that the heat-treated PMOS composite electrodes may have a promising potential application for advanced energy storage devices in modern electronic industries.

We studied the effects of particle size of raw materials (B4C, TiC and Si powders) on the characteristics of both TiB2–SiC composite powders and ceramics. Results show that the size of B4C and Si particles hardly affects the size of TiB2 and SiC particles because B4C is decomposed and consumed during the formation of TiB2, and Si is melted during the formation of SiC. The size of SiC particles is within the nano and submicron scale. However, the size of TiC particles determines the sizes of TiB2 particles and TiB2 grains in the composite ceramics because TiC particles serve as templates to form TiB2 particles. Consequently, the microstructure and mechanical properties of the TiB2–SiC composite ceramics are affected. The TiB2–SiC composites fabricated using nano-sized TiC powder possess smaller grain size, better dispersibility and more reasonable crack propagation path, thereby obtaining the optimal mechanical properties (Vickers hardness of 30.2 GPa, flexural strength of 732 MPa and fracture toughness of 7.37 MPa m1/2).

Layered double hydroxides (LDHs) have been considered as one class of promising active electrode materials for supercapacitors due to their tunable composition and chemical versatility. Nonetheless, the poor electrical conductivity hinders their further practical applications in supercapacitors. Herein, CoAl LDH flower-like hollow microspheres are decorated with Ag nanoparticles by a facile one-step solvothermal reaction, followed by chemical bath deposition reaction. Experimental results and theoretical calculations indicate that decorating Ag nanoparticles onto CoAl LDH not only reduces the energy band gap and enhances their electrical conductivity, but also promotes fast diffusion kinetics of electrolyte ions and electrochemical reaction activity. Consequently, the prepared Ag/CoAl LDH electrode demonstrates improved specific capacities of 1214 (825) C g−1 at 3 (30) A g−1 and 91% capacity retention over 10,000 cycles at 10 A g−1 compared to the pristine CoAl LDH electrode. Moreover, using Ag/CoAl LDH and N-doped carbon nanotubes as the positive and negative electrodes, respectively, the assembled hybrid capacitor device delivers an energy density of 61.2 Wh kg−1 at a power density of 800 W kg−1. This work may showcase a great promise of engineering conductive nanoparticles-decorated LDHs-based active materials towards high-performance supercapacitors.

Dense ultrafine-grained B4C ceramics with superhigh hardness and outstanding fracture toughness were fabricated via spark plasma sintering at 1700 °C and 80 MPa. This process used the ultrafine B4C powder prepared by high-energy ball milling as starting powder. During sintering, densification began earlier at 1050 °C and the maximum densification rate appeared earlier at 1500 °C under the influence of high pressure and high sintering activity of the powder. The B4C ceramics possessed ultrafine grains, with average grain size of 370 nm, which contributed to the superhigh hardness. Many small B4C grains with size of less than 200 nm were individually dispersed among large B4C grains or accumulated to form congregated areas. The small grains induced crack deflection, particle pullout and crack bridging, thereby enhancing the toughness of the ceramics. The relative density, Vickers hardness and fracture toughness of the B4C ceramics reached 99.4 ± 0.49%, 41.1 ± 0.9 GPa and 4.57 ± 0.12 MPa m1/2, respectively.

In the present work, we reported a facile synthesis of cobalt ferrite (CoFe2O4) nanoparticles in the presence of L -cysteine (Lys). The morphology and size of samples were characterized by SEM and TEM. The successful coating of Lys on the surface of CoFe2O4 was confirmed by XRD, XPS and TGA. The investigation of magnetic properties showed that both bare CoFe2O4 and Lys-coated CoFe2O4 nanoparticles exhibited room-temperature superparamagnetic behavior. The results of MTT experiments revealed insignificant cytotoxicity of Lys-coated CoFe2O4 nanoparticles even after 24 h incubation. More importantly, Lys-coated CoFe2O4 nanoparticles displayed an excellent drug loading capacity and a pH-sensitive drug release behavior. In summary, the prepared Lys-coated CoFe2O4 nanoparticles demonstrated a promising application potential in controlled drug delivery.

Purpose The purpose of this study is to design carbon electrode materials for high performance electric double-layer capacitors (EDLCs) with pores that are large enough and have suitable pore size distribution for the electrolyte to access completely to improve EDLCs’ electrochemical performance. Design/methodology/approach This study develop an improved traditional KOH activation method, and a series of micro-meso hierarchical porous carbons have been successfully prepared from phenol formaldehyde resin by combining polyethylene glycol (PEG) and conventional KOH activation. Findings As evidenced by N2 adsorption/desorption tests, the obtained samples present Types IV and I-IV hybrid shape isotherms compared with KOH-activated resin (typical of Type I). The sample AC2-7-1, which the addition quantity of PEG is 25 per cent PF (weight ration) activated at 700? For 1 h is considered as the optimum preparation condition. It exhibits the highest specific capacitance value of 240 F/g in 30 wt% KOH aqueous electrolytes because of its higher specific surface area (2085 m2/g), greater pore volume (1.08 cm3/g) and the maximum mesoporosity (43 per cent). In addition, the capacity decay of this material is only 3.1 per cent after 1000 cycles. Originality/value The materials that are rich in micropores and mesopores show great potential in EDLC capacitors, particularly for applications where high power output and good high-frequency capacitive performances are required.

This work provided an efficient alternative strategy to improve the performance of AVO4 (A = Bi, Fe)-based materials for organic degradations under visible light. Carbon nanofibers (CNFs) as a flexible template were obtained by an electrospinning technique, then AVO4 as the primary visible light-absorbers were succesfully grown on the surface of template frameworks for producing AVO4/CNFs heterostructures via a hydrothermal method. Photocatalytic studies revealed removal efficiencies were greatly increased when CNFs were introduced into AVO4 heterostructures, compared with pure BiVO4 and FeVO4, with 94 and 90.6% of RB photocatalytically degraded by BiVO4/CNFs and FeVO4/CNFs heterostructures within 3 h under visible light irradiation. The enhanced photocatalytic activity might have arisen from the high separation efficiency of photogenerated electron–hole pairs based on positive synergetic effects between AVO4 and CNFs heterojunctions. These heterostructures were easily recycled without a decrease in photocatalytic activity benefited from the nanofibers frameworks. Moreover, this paper confirmed a simple and a general method for fabricating other VO4-containing oxides heterostructures.

Ultrafine-grained boron carbide ceramics with ultrahigh hardness were fabricated via a unique combination of high-energy ball milling and self-propagating high-temperature synthesis plus quick pressing (SHS/QP) method. Results show that ultrafine powders obtained by milling possess a disordered character. During the SHS/QP, the tiny particles in the milled powders are integrated into neighbouring large particles to form ceramic grains. The average grain size of the ceramics is approximately 290 nm. After SHS/QP, a few amorphous areas and high-density defects were still observed in ceramics. The ceramics possess high relative density (approximately 99.2%) and ultrafine grain (approximately 290 nm) but with a weak degree of crystallinity which weakens hardness. Heat treatment can improve crystallinity while maintaining the ultrafine grain of the ceramics, thereby increasing the hardness of the ceramics from 31 GPa to 40 GPa.

Rational design and fabrication of core-shell nanoarrays (CSNs) with distinctive architectures and desirable capacitive performances are believed to be a promising and challenging strategy toward advanced electrode materials for supercapacitors (SCs). In this work, we report a two-step synthesis of three-dimensional (3D) MnCo2O4 nanosheets@MnMoO4 nanosheets CSNs on Ni foam (NF), which are constructed by vertically growing MnMoO4 nanosheets onto interconnected MnCo2O4 nanosheets arrays (NAs). Such MnCo2O4@MnMoO4 CSNs can make full use of its unique 3D architecture and the synergistic effect between MnCo2O4 and MnMoO4. Therefore, the prepared MnCo2O4@MnMoO4 CSNs, as a binder-free electrode for SCs, demonstrate a significantly enhanced specific capacity (885 C g−1 at 3 A g−1), higher rate capability (629 C g−1 at 30 A g−1), and better cycling stability (95% capacitance retention after 5000 cycles at 10 A g−1) compared with the single MnCo2O4 or MnMoO4 NAs electrode. Moreover, the assembled asymmetric SC cell (ASC) based on MnCo2O4@MnMoO4//activated carbon (AC) also exhibits a specific capacity (222 C g−1 at 1 A g−1) and an energy density (49.4 W h kg−1 at 815 W kg−1), indicating a promising practical application for the prepared MnCo2O4@MnMoO4 CSNs in high-performance SCs.

Sintering experiments on boron carbide (B 4 C) are performed by hot pressing (HP) and spark plasma sintering (SPS). Results show that the maximum densification rate of SPS occurs at approximately 1850 °C, which is earlier than that of HP. The microstructure of samples sintered by HP is very homogeneous and has a relative density of about 91%. In SPS, a high relative density of >94% can be realised, but the microstructure of the samples presents two obviously different regions. The microstructure of region I is very similar to those of samples sintered by HP. However, region II, which has a non-uniform grain size distribution, shows considerably higher relative density than region I. The mechanical properties of the samples sintered by SPS are superior to those of the samples sintered by HP because of the formation of region II.

ZnCo2O4@MnCo2O4 heterojunction structured nanosheets were successfully prepared by simple and effective hydrothermal reaction. The obtained heterojunction structured had large specific surface area, good structural stability, and excellent electrical conductivity. Therefore, they were expected to become ideal electrochemical materials. As expected, a series of electrochemical tests showed ZnCo2O4@MnCo2O4 heterojunction structured nanosheets demonstrate high specific capacitance (254 F g−1 at the current density of 1 A g−1). Good stability of charge–discharge, when the current density was 10 A g−1, the capacity can still maintain 186 F g−1. Especially, the maximum energy density of asymmetric supercapacitors based on ZnCo2O4@MnCo2O4 and activated carbon at 750 W Kg−1 was 19.12 Wh Kg−1, and the cycle stability was good, after 2000 cycles, the capacitance retention rate was 98.5%. For practice application, the commercial LED lights can be lighted by two supercapacitor units in series. It shows that the synthetic electrode material has great potential in the energy storage equipment.

In this study, monodisperse and superparamagnetic manganese ferrite (MnFe2O4) nanoparticles have been synthesized by a one-pot sonochemical method using polyvinylpyrrolidone (PVP) as stabilizer. The as-prepared MnFe2O4 nanoparticles were investigated systematically by TEM, XRD, FTIR, XPS, SQUID and MTT. The TEM observation showed that the PVP-coated MnFe2O4 nanoparticles had uniform dispersion with narrow particle size distribution. The magnetization curves demonstrated superparamagnetic properties of the coated MnFe2O4 nanoparticles with good hydrophilicity at room temperature. The in vitro cytotoxicity experiments exhibited negligible cytotoxicity of the obtained PVP-coated MnFe2O4 nanoparticles even at the high concentration of 150 μg/mL after 24 h treatment. More importantly, anti-cancer model drug of doxorubicin hydrochloride (DOX) was loaded on the surface of MnFe2O4 nanoparticles. The drug loading capacity of the developed nanocarrier reached 0.45 mg/mg and the loaded DOX exhibited interesting pH-dependent release behavior. In conclusion, the as-prepared PVP-coated MnFe2O4 nanoparticles were proposed as a potential candidate for controlled drug delivery.

Core/shell nanorods of MnO2/carbon embedded with Ag nanoparticles (MCA) were successfully fabricated via a facile and effective hydrothermal and reduction method in situ. Typically, a MCA-1.5 sample (1.5 g·L−1 glucose reactant) exhibited the highest specific capacitance of 628 F·g−1 at the current density of 1 A·g−1 in three-electrode systems. Particularly, a fabricated asymmetric supercapacitor, using MCA-1.5 and active carbon as the positive and negative electrodes, respectively, delivered a maximum energy density of 48.3 W·h·kg−1 at power density of 851.7 W·kg−1 and exhibited a superior, long cycle life, showing ∼98.5% specific capacitance retention after 2000 cycles. The practical energy-storage applicability of this device was demonstrated by the operation of an LED bulb when a duo of two such devices was charged. These results indicated that synthesized ternary nanocomposites have potential applications as supercapacitor electrodes in energy storage systems.

In this reported work, Ag nanoparticles (NPs) decorated CuS sub-micron flowers are synthesized using a facile, solvothermal reaction coupled with a silver mirror reaction. The experimental results and theoretical calculations reveal that decorating the CuS with Ag NPs increases its intrinsic electrical conductivity and generates an electric field at the interface between Ag and CuS. These effects promote the efficient utilization of active materials and accelerate the interface charge transfer and electrochemical reaction kinetics. Consequently, the maximum specific capacity of the prepared CuS@Ag electrodes is found to be as high as 702 C g−1 at 2 A g−1, which is about 5 times greater than the pure CuS electrode. In addition, the capacity value is 400 C g−1 at 20 A g−1 and it exhibits 93% retention of the initial capacity after 5000 cycles at 10 A g−1. Moreover, a hybrid supercapacitor (HSC) device is assembled employing the CuS@Ag electrode as the positive electrode, which delivers an energy density of 51.1 Wh kg−1 at a power density of 798 W kg−1. These results demonstrate the promising potential of the fabricated CuS@Ag composites for further application in HSCs.

The inefficiency of charge separation is the major practically limited factor towards high hydrogen evolution reaction (HER) of photocatalysts. Therefore, design and construction of efficient photocatalysts system with efficient charge transfer path is urgently necessary for HER. Herein, we report an effective strategy to construct Pt–MoSe2/g-C3N4 heterostructure through integrating facile solvothermal technique and solution-phase hybridization method. The synthesized ternary Pt–MoSe2/g-C3N4 heterostructures exhibit greatly enhanced photocatalytic hydrogen production than bare g-C3N4 and Pt/g-C3N4 catalyst. The enhancement factor is directly correlated with strong photosynergistic effect of charge-carrier generation and separation path coupling heterojunction sensitization on MoSe2/g-C3N4 with Pt nanoparticle. Moreover, the mechanism of enhanced catalytic activity is fully studied by electrochemical characterizations and photocurrent analysis.

In this study, we prepared calcium ferrite (CaFe2O4) nanocrystal clusters by a solvothermal method and evaluated their application potential in magnetorheological (MR) fluid. The morphology, composition, microstructure and magnetic properties of the CaFe2O4 nanocrystal clusters were investigated in detail. The as-prepared CaFe2O4-based MR fluid showed typical Bingham fluid behavior, changing from a liquid-like to a solid-like structure under an external magnetic field. Compared with carbonyl iron (CI) particles, the MR fluid based on CaFe2O4 nanocrystal clusters showed enhanced sedimentation stability, which can be mainly due to the reduced density mismatch between dispersed phase and carrier fluid. In conclusion, the as-prepared CaFe2O4 nanocrystal clusters are considered as a promising candidate for high-performance MR fluid.

Novel hollow Ni0.2Mn0.8O1.5 twin microspheres were synthesized through a facile solvothermal reaction followed by calcination. The prepared hollow twin microspheres were composed of a large number of aggregated nanoparticles, with many pores homogeneously distributed across the whole of the twin microspheres. Benefiting from such structural advantages, such as the void core and high porosity, the prepared hollow Ni0.2Mn0.8O1.5 twin microspheres, as an electrode for supercapacitors, exhibited remarkable electrochemical performance with a large specific capacitance (491 F g−1 at 0.5 A g−1), desirable rate capability (81% of capacity retention at 5 A g−1), and excellent cycling stability (94.6% of the initial capacity after 2000 cycles). Moreover, a fabricated asymmetric supercapacitor cell based on Ni0.2Mn0.8O1.5 and active carbon demonstrated an energy density of 19.5 Wh kg−1 at a power density of 799 W kg−1, suggesting a promising practical application for these microspheres in supercapacitors. Novel hollow Ni0.2Mn0.8O1.5 twin microspheres have been synthesized based on the oriented attachment and Ostwald ripening effects, demonstrating high energy density and power density for the promising application in energy storage devices.

Despite considerable efforts have been devoted to the design and synthesis of advanced electrode materials for supercapacitors (SCs), it is still a huge challenge to achieve high-performance electrode materials with the large practical capacity and high rate capability. Herein, novel self-supported MnCo 2 O 4 @Ni 3 S 2 core–shell heterostructures (CSHs) as a binder-free electrode are rationally designed and constructed by homogeneously growing Ni 3 S 2 nanosheets onto the hexagonal prism-like MnCo 2 O 4 microstructures on Ni foam (NF). Impressively, compared with the pristine MnCo 2 O 4 and Ni 3 S 2 electrodes, the prepared MnCo 2 O 4 @Ni 3 S 2 CSHs electrode demonstrates a remarkably enhanced specific capacitance (2807 F g −1 at 3 A g −1 ) along with a significantly improved rate capability (69% capacitance retention at 30 A g −1 ). These findings not only suggest the promising application of self-supported MnCo 2 O 4 @Ni 3 S 2 CSHs as advanced SCs electrode materials but also provide an alternative way for constructing next-generation high-performance SCs with remarkably improved electrochemical performance.

Novel self-supported core-shell Cu 2 O@MnO 2 octahedral microcrystals directly growing on the nickel foam have been synthesized through a facile solvothermal reduction deposition process followed by a hydrothermal reaction. The core-shell heterostructures were constructed through growing MnO 2 nanosheets on the surface of Cu 2 O octahedral microcrystal. Based on the synergetic effects from both the cores and shells, such self-supported core-shell Cu 2 O@MnO 2 octahedral microcrystals as binder-free electrode materials exhibited a high specific capacitance of 371 F g −1 at 0.5 A g −1 and excellent cycling stability with 95.8% of capacitance retention after 2000 cycles. These findings suggest their potential applications as a promising electrode material for supercapacitors.

Effects of pressure, from ordinary (30 MPa) to high pressure (110 MPa), on densification behaviour, microstructures and mechanical properties of boron carbide ceramics sintered by hot pressing are investigated. With increasing pressure, the relative density sharply increases within 30–75 MPa, slowly increases within 75–100 MPa and finally stagnates. For samples within 75–100 MPa, densification begins at approximately 1000 °C, and the dominant densification process ends before the soaking stage. High relative densities of 98.49% and 99.76% are achieved. For samples within 30–50 MPa, densification begins at approximately 1500 °C, and the soaking stage (initial 20 min) is still important for the dominant densification process. The final relative densities are only 87.90% and 92.32%. The above-mentioned differences are derived from contributions of pressure, and the dominant densification mechanism under high pressure is plastic deformation. The average grain size of the samples slightly increases with increasing soaking time. The grain size under higher pressure is larger than that under lower pressure at corresponding periods because grains grow easily with reduced pores. Vickers hardness and fracture toughness increase as grain size decreases in fully dense samples. However, when the samples do not achieve full density, relative density becomes more influential than grain size in hardness and toughness. A soaking time of 30 min is enough for samples under 100 MPa. Prolonging the soaking time has deleterious effects on mechanical properties. The relative density, grain size, hardness and fracture toughness of the samples under 100 MPa for 30 min are 99.73%, 1.96 µm, 37.85 GPa and 3.94 MPa m 1/2 , respectively.

In this work, we reported the synthesis of three dimensional flower-like Co3O4@MnO2 core-shell microspheres by a controllable two-step reaction. Flower-like Co3O4 microspheres cores were firstly built from the self-assembly of Co3O4 nanosheets, on which MnO2 nanosheets shells were subsequently grown through the hydrothermal decomposition of KMnO4. The MnO2 nanosheets shells were found to increase the electrochemical active sites and allow faster redox reaction kinetics. Based on these advantages, when used as an electrode for supercapacitors, the prepared flower-like Co3O4@MnO2 core-shell composite electrode demonstrated a significantly enhanced specific capacitance (671 F g−1 at 1 A g−1) as well as improved rate capability (84% retention at 10 A g−1) compared with the pristine flower-like Co3O4 electrode. Moreover, the optimized asymmetric supercapacitor device based on the flower-like Co3O4@MnO2//active carbon exhibited a high energy density of 34.1 W h kg−1 at a power density of 750 W kg−1, meaning its great potential application for energy storage devices.

B4C–TiB2–SiC composites toughened by composite structural toughening phases, which are the units of (TiB2–SiC) composite, were fabricated through reactive hot pressing with B4C, TiC, and Si as raw materials. The units of (TiB2–SiC) composite with the size of 10-20 μm are composed of interlocking TiB2 and SiC with the size of 1-5 μm. The addition of TiC and Si can effectively promote the sintering of B4C ceramics. The relative densities of all the B4C composites with different contents of TiB2 and SiC are close to completely dense (98.9%-99.4%), thereby resulting in superior hardness (33.1-36.2 GPa). With the increase in the content of TiB2 and SiC, the already improved fracture toughness of the B4C composite continuously increases (5.3-6.5 MPa·m1/2), but the flexure strength initially increases and then decreases. When cracks cross the units of the (TiB2–SiC) composite, the cracks deflect along the interior boundary of TiB2 and SiC inside the units. As the crack growth path is lengthened, the crack propagation direction is changed, thereby consuming more crack extension energy. The cumulative contributions improve the fracture toughness of the B4C composite. Therefore, the composite structural toughening units of the (TiB2–SiC) composite play an important role in reinforcing the fracture toughness of the composites.

This work details the design and synthesis of novel urchin-like α-FeOOH@MnO2 core–shell hollow microspheres for high-performance electrode materials for supercapacitors. The core–shell heterostructures were constructed by growing strip-like MnO2 nanostructures onto the urchin-like α-FeOOH hollow microspheres that were composed of nanorods. Based on the synergetic effects and multi-functionalities of both the MnO2 shell and urchin-like α-FeOOH hollow cores, the resulting urchin-like α-FeOOH@MnO2 core–shell hollow microspheres exhibited excellent electrochemical performance with a high specific capacitance of 597 F g−1 at 1 A g−1, good rate capability (capacitance retention of 74.2% at 10 A g−1), and remarkable cycling stability (capacitance retention of 97.1% after 2000 cycles). Moreover, an asymmetric supercapacitor fabricated using α-FeOOH@MnO2 as positive electrode and activated carbon as negative electrode was found to deliver a high energy density of 34.2 W h kg−1 and power density of 815 W kg−1. Urchin-like α-FeOOH@MnO2 hollow microspheres demonstrated a high specific capacitance, rate capability and cycling stability, suggesting its promising potential for high-performance supercapacitors.