Microwave-Assisted Synthesis of NiCo_2O_4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries

The ternary transitional metal oxide NiCo_2O_4 is a promising anode material for sodium ion batteries due to its high theoretical capacity and superior electrical conductivity. However, its sodium storage capability is severely limited by the sluggish sodiation/desodiation reaction kinetics. Herein, NiCo_2O_4 double-shelled hollow spheres were synthesized via a microwave-assisted, fast solvothermal synthetic procedure in a mixture of isopropanol and glycerol, followed by annealing. Isopropanol played a vital role in the precipitation of nickel and cobalt,and the shrinkage of the glycerol quasi-emulsion under heat treatment was responsible for the formation of the double-shelled nanostructure. The as-synthesized productwas tested as an anode material in a sodium ion battery,was found to exhibit a high reversible specific capacity of 511 m Ahg^(-1) at 100 m Ag^(-1), and deliver high capacity retention after 100 cycles.

Preparation and Photocatalytic Performance of Double-Shelled Hollow W_(18)O_(49)@C_(3)N_(4)@Ti_(3)C_(2)Microspheres

C_(3)N_(4),C_(3)N_(4)@Ti_(3)C_(2)and W_(18)O_(49)@C_(3)N_(4)@Ti_(3)C_(2)hollow spheres were successfully prepared by using SiO_(2)template followed by gradual deposition method.The degradation of phenol solution and photolysis ability were tested to characterize its photocatalytic activity.Compared with the single-shelled C_(3)N_(4)and C_(3)N_(4)@Ti_(3)C_(2)hollow spheres,double-shelled W_(18)O_(49)@C_(3)N_(4)@Ti_(3)C_(2)hollow spheres possessed larger surface area and fast charge separation efficiency,exhibiting about 8.9 times and 4.0 times higher H_(2)evolution than those of C_(3)N_(4),C_(3)N_(4)@Ti_(3)C_(2)hollow spheres,respectively.The photocatalytic mechanism of the W_(18)O_(49)@C_(3)N_(4)@Ti_(3)C_(2)hollow spheres were carefully investigated according to the results of morphology design and photoelectric performance.A Z scheme mechanism based on the construction of heterojunctions was proposed to explain the improvement of photocatalytic performance.This new charge transfer mechanism appears to greatly inhibit the recombination of electrons/holes during the charge transfer process,while maintaining its strong hydrogen reduction ability,resulting in a higher photocatalytic performance.

Reactive MnO_(2) template-assisted synthesis of double-shelled PPy hollow nanotubes to boost microwave absorption

Microwave absorbing materials(MAMs)with wide effective absorption bandwidth(EAB)and low filling ratio are highly desirable for practical applications.Rational design in components and structures is one of the effective strategies to achieve MAMs with high performance.Herein,double-shelled hollow(DSH)polypyrrole(PPy)nanotubes were synthesized with hydrochloric acid(HCl)and sodium pstyrene sulfonate(SS)co-doping polymerization process using manganese dioxide(MnO_(2))nanorods as a self-sacrifice template.With the increase of HCl concentration,the 1D MnO_(2) core diminishes gradually to form the MnO_(2)@PPy coaxial nanostructures and finally the DSH PPy nanotube,which tunes the microwave absorption performance.Importantly,the DSH PPy nanotubes exhibit excellent microwave absorption of an optimal reflection loss of–50.4 dB and a wide EAB of 7.7 GHz with a low filling ratio of 5 wt%in a paraffin wax matrix.The excellent microwave absorption is believed to be mainly attributed to the enhanced synergistic effects of interfacial polarization and conduction loss arising from the unique DSH structure and the co-doping polymerization.

Construction of core@double-shell structured energetic composites with simultaneously enhanced thermal stability and safety performance

The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.

Synthesis of Polyurethane/Poly(urea-formaldehyde) Double-shelled Microcapsules for Self-healing Anticorrosion Coatings

One-component, catalyst-free self-healing coatings with double-shelled polymer microcapsules have drawn considerable attention due to wide applications. In this work, the synthesis parameters of double-shelled polymer microcapsules and the mechanism of the self-healing process were systematically investigated. Apart from the chemical structure of the microcapsule shell, the shell thickness, the microcapsule size,and the core fraction could affect the self-healing anticorrosion properties. The synthesis parameters were further optimized in terms of the agitation rate, p H, weight ratio of core to shell, and temperature. Under these conditions, the microcapsule shell consisting of a rough surface formed by poly(urea-formaldehyde) and a smooth inner wall by polyurethane was prepared. The size of the microcapsules and core fraction were calculated to be approximately 30 μm and 75%, respectively. The self-healing anticorrosion coating incorporating as-synthesized microcapsules exhibited corrosion resistance in artificially scratched areas, which was further characterized by electrochemical impedance spectroscopy.

Self-assembled uniform double-shelled Co_(3)V_(2)O_8 hollow nanospheres as anodes for high-performance Li-ion batteries

Hollow micro-/nanostructures have achieved great success in the field of renewable battery materials by reducing the volume change and promoting the ion transport.Double-shelled Co_(3)V_(2)O__(8)hollow nanospheres(CVODSS)were synthesized using a facile solvothermal method followed by a thermal treatment in the absence of any surfactant.Meanwhile,two other architectures of hollow nanospheres and nanoparticles were obtained by changing the annealing temperature.Benefiting from the desired hollow structure,the CVO-DSS electrode exhibits excellent lithium storage properties as an anode.It exhibits a reversible discharge capacity of 1210 m Ah·g^(-1)at200 m A·g^(-1)after 100 cycles and a satisfactorily high rate capacity of 628 m Ah·g^(-1)after 800 cycles at 5000 m A·g^(-1).These hollow nanostructures can efficiently enhance the contact area of the electrolyte/electrode interface,promote the diffusion of lithium ions and electrons and slow down the capacity loss during long cycles.

Deformable double-shelled hollow mesoporous organosilica nanocapsules:A multi-interfacial etching strategy

Multishelled hollow structures have drawn increasing interest because of their peculiar compartmentation environments and physicochemical properties.In this work,deformable double-shelled hollow mesoporous o rganosilica nanocapsules(DDHMONs)were succes s fully synthesized by a multi-interfacial etching strategy.The obtained DDHMONs have a double-shelled structure with aninorganic-organic hybrid framework,a uniform outer layer(~320 nm)and inner layer(~180 nm),ordered mesochannels(~2.21 nm),and a large specific surface area(~1233 m^(2)/g).In vitro toxicity tests show that the DDHMONs have excellent biocompatibility when coincubated with human breast cancer cells.In addition,the anti cancer substance doxorubicin(DOX)can be highly loaded in DDHMONs(~335μg/mg).The results from flow cytometry together with confocal laser scanning microscopy show that DOX can be efficiently delivered into MCF-7 cells by DDHMONs,thus improving chemotherapeutic efficiency and demonstrating that DDHMONs have potential nanomedicine applications as anticancer agents.

Preparation of P(MBA-co-MAA)/Zr(OH)_(4)/P(EGDMA-co-MAA)/TiO_(2)Tetra-layer Hybrid Microspheres and the Corresponding ZrO_(2)/TiO_(2)Double-shelled Hollow Microspheres

Double-shelled zirconia/titania(ZrO_(2)/TiO_(2))hollow microspheres were prepared by the selective removal of the polymer components via the calcination of the corresponding tetra-layer poly(N,N'-methylenebisacryl amide-comethacrylic acid)(P(MBA-co-MAA))/Zr(OH)_(4)/poly(ethyleneglycol dimethacrylate-co-methacrylic acid)(P(EGDMAco-MAA))/TiO_(2)hybrid microspheres.These tetra-layer microspheres were synthesized by the combination of the distillation copolymerization of N,N′-methylenebisacryl amide-co-methacrylic acid(MBA)or ethyleneglycol dimethacrylate(EGDMA)crosslinker and methacrylic acid(MAA)for the preparation of polymer core and thirdlayer as well as the controlled sol-gel hydrolysis of inorganic precursors for the construction of zirconium hydroxide(Zr(OH)_(4))and titania(TiO_(2))layers.The thicknesses of zirconia and titania shell-layers were conveniently controlled via varying the feed of zirconium n-butoxide(Zr(OBu)_(4))and titanium tetrabutoxide(TBOT)during the sol-gel hydrolysis,while the sizes of polymer layers were tuned through a multi-stage distillation precipitation copolymerization.The structure and morphology of the resultant microspheres were characterized by transmission electron microscopy(TEM),X-ray diffractometer(XRD),X-ray photoelectronic spectroscopy(XPS),and thermogrametric analysis(TGA).

Rational architecture design of yolk/double-shells Si-based anode material with double buffering carbon layers for high performance lithium-ion battery

Among the many strategies to fabricate the silicon/carbon composite,yolk/double-shells structure can be regarded as an effective strategy to overcome the intrinsic defects of Si-based anode materials for Li-ion batteries(LIBs).Hereon,a facile and inexpensive technology to prepare silicon/carbon composite with yolk/double-shells structure is proposed,in which the double buffering carbon shells are fabricated.The silicon/carbon nanoparticles with core-shell structure are encapsulated by SiO_(2)and external carbon layer,and it shows the yolk/double-shells structure via etching the SiO_(2)sacrificial layer.The multiply shells structure not only significantly improves the electrical conductivity of composite,but also effectively prevents the exposure of Si particles from the electrolyte composition.Meanwhile,the yolk/double-shells structure can provide enough space to accommodate the volume change of the electrode during charge/discharge process and avoid the pulverization of Si particles.Moreover,the as-prepared YDS-Si/C shows excellent performance as anode of LIBs,the reversible capacity is as high as 1066 mA h g^(-1) at the current density of 0.5 A g^(-1) after 200 cycles.At the same time,the YDS-Si/C has high capacity retention and good cyclic stability.Therefore,the unique architecture design of yolk/double-shells for Si/C composite provides an instructive exploration for the development of next generation anode materials of LIBs with high electrochemical performances and structural stability.

Vibration and Acoustic Radiation from Submerged Spherical Double-Shell

Based on the motion differential equations of vibration and acoustic coupling system for a thin elastic spherical double-shell with several elastic plates attached to the shells, in which Dirac-δ functions are employed to introduce the forces and moments applied by the attachments, and by means of expanding field quantities as the Legendre series, a semi-analytic solution is derived for the solution to the vibration and acoustic radiation from a submerged spherical double-shell. This solution has a satisfying computational effectiveness and precision for arbitrary frequency range excitation. It is concluded that the internal plates attached to shells can change significantly the mechanical and acoustical characteristics of shells, and make the coupling system have a very rich resonance frequency spectrum. Moreover, the present method can be used to study the acoustic radiation mechanism of the type of structure.

Linear Rayleigh-Taylor instability analysis of double-shell Kidder's self-similar implosion solution

This paper generalizes the single-shell Kidder＇s self-similar solution to the double-shell one with a discontinuity in density across the interface. An isentropic implosion model is constructed to study the Rayleigh-Taylor instability for the implosion compression. A Godunov-type method in the Lagrangian coordinates is used to compute the one-dimensional Euler equation with the initial and boundary conditions for the double-shell Kidder＇s self-similar solution in spherical geometry. Numerical results are obtained to validate the double-shell implosion model. By programming and using the linear perturbation codes, a linear stability analysis on the Rayleigh-Taylor instability for the double-shell isentropic implosion model is performed. It is found that, when the initial perturbation is concentrated much closer to the interface of the two shells, or when the spherical wave number becomes much smaller, the modal radius of the interface grows much faster, i.e., more unstable. In addition, from the spatial point of view for the compressibility effect on the perturbation evolution, the compressibility of the outer shell has a destabilization effect on the Rayleigh-Taylor instability, while the compressibility of the inner shell has a stabilization effect.

Double-shell structure of Al_3(Zr,Sc) precipitate induced by thermomechanical treatment of Al-Zr-Sc alloy cable

A spheroidal Al_3(Zr,Sc) precipitate with a double-shell structure, comprising a Sc-enriched core enveloped by a Zr-enriched inner shell and a Sc-enriched outer shell(～9 nm in thickness), appears in an Al-0.2 Zr-0.1 Sc alloy cable after thermomechanical treatment. The average diameter of the spheroidal Al_3(Zr,Sc) precipitate is approximately 80 nm. The double-shelled Al_3(Zr,Sc) precipitate presents three different interfaces and is semi-coherent with the Al matrix. Atom probe tomography(APT) analyses further show that the outer shell of Al_3(Zr,Sc) precipitate is Sc element enrichment. The electrical conductivity of Al-0.2 Zr-0.1 Sc alloy cable increases by 6.5 MS/m within the aging time from 0.2 to 100 h at 350 ℃, with double-shelled Al_3(Zr,Sc)precipitate.

Thermal annealing synthesis of double-shell truncated octahedral Pt-Ni alloys for oxygen reduction reaction of polymer electrolyte membrane fuel cells

Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface morphologies.In this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is reported.By tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni alloys.It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells.It is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity.The asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.

A novel strategy for high-specificity, high-sensitivity, and high-throughput study for gut microbiome metabolism of aromatic carboxylic acids

Aromatic carboxylic acids(ACAs) may be as transformed key metabolites via gut microbiome for playing better pharmacological effects. However, it's rare to achieve high-specificity, high-sensitivity, and highthroughput detection simultaneously, especially, for tracing trace ACAs in gut microbiome. In this work,firstly, a novel dual-template and double-shelled molecularly imprinted 96-well microplates(DDMIPs)was designed and amplified signal for p-hydroxybenzoic acid(PBA) and 3,4,5-trimethoxycinnamic acid(TMA). Additionally, the DDMIPs and a stable isotope labeling derivatization(SILD) method combined with the ultra-high performance liquid chromatography triple quadrupole tandem mass spectrometry(UHPLC-TQ MS) was firstly stepwise integrated, achieving high-effective, high-sensitive, and highthroughput study of gut microbiome metabolism. The whole strategy showed lower limits of detections(LODs) up to 1000 folds than the traditional method, and revealed a more real metabolism-time profile of PBA and TMA by 3-step signal amplification. The platform also laid the foundation for fast, simple,high-selective, high-effective, and high-throughput metabolism and pharmacological research.

Carbon confinement synthesis of interlayer-expanded and sulfur-enriched MoS2+x nanocoating on hollow carbon spheres for advanced Li-S batteries

High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems.However,the intrinsic problems of the sulfur cathode severely restrict their further practical application.Here,a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host.A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process,which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres.This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials,high electronic conductivity,and fast lithium-ion diffusive pathways.In addition,additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species,dramatically accelerating their conversion kinetics and re-utilization.The detailed defect-induced interface catalytic reaction mechanism is firstly proposed.As expected,the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g^−1 at 0.2 C and a desirable rate performance(593 mAh·g^−1 at 5.0 C),implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.

Synchronous constructing ion channels and confined space of Co_(3)O_(4) anode for high-performance lithium-ion batteries

The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is limited by the low contact point between the core and shell.Herein,we propose a general strategy of simultaneous construction of sufficient reserved space and multicontinuous active channels by pyrolysis of two carbon substrates.A double-shell structure consisting of Co_(3)O_(4) anchored to hollow carbon sphere and external self-supporting zeolitic imidazolate framework(ZIF)layer was constructed by spray pyrolysis and additional carbon coating in-situ growth.In the process of high-temperature calcination,the carbon and nitrogen layers between the shells separate,creating additional space,while the Co_(3)O_(4) particles between the shells remain are still in close contact to form continuous and fast electron conduction channels,which can realize better charge transfer.Due to the synergy of these design principles,the material has ultra-high initial discharge capacities of 2,183.1 mAh·g^(−1) at 0.2 A·g^(−1) with capacity of 1,121.36 mAh·g^(−1) after 250 cycles,the long-term capacities retention rate is about 92.4%after 700 cycles at 1 A·g^(−1).This unique channel-type double-shell structure fights a way out to prepare novel electrode materials with high performance.

Construction of multi-structures based on Cu NWs-supported MOF-derived Co oxides for asymmetric pseudocapacitors

Cu@MOF core-shell nanowires are synthesized by introducing oxidizable and CTAB-modified metal nanowires as self-engaged templates and supporting MOFs for a one-dimension nanostructure.The following thermal process is controlled to obtain several one-dimension structure s ofCuCo-mixed materials,such as nanorods,single-shell and double-shell nanowires.The hollow structure for electrode materials enlarges the surface area,provides buffer space for electrolyte to accelerate the ion/charge transfers and for the structure to reduce injuries of volume expansion during cycling.Together with some other merits,such as adequate oxidation of the MOFs,small crystal grains of the material,and well-mixed Cu/Co oxides,the double-shell Cu@MOF nanowires(CuCo-DS5)applied for pseudocapacitors deliver advanced electrochemical performance with a specific capacitance of 563.8 F g^(-1)at 1 A g^(-1)as well as an outstanding cycling stability with a 92%retention after 3000 cycles at 5 A g^(-1).Meanwhile,an asymmetric pseudocapacitor constructed with the CuCo-DS5 and active carbon(AC)shows a high specific capacitance and energy density.