Isolated Co Atoms Anchored on Defective Nitrogen-doped Carbon Graphene as Efficient Oxygen Reduction Reaction Electrocatalysts

Oxygen reduction reaction(ORR)is the heart of many new energy conversions and storage devices,such as metal-air batteries and fuel cells.However,ORR is currently facing the dilemma of sluggish intrinsic kinetics and the noble electrocatalysts of high price and low reserves.In this work,isolated Co atoms anchored on defective nitrogen-doped carbon graphene single-atom catalyst(Co-SAC/NC)are synthesized via the proposed movable type printing method.The prepared Co-SAC/NC catalyst demonstrates admirable ORR performance,with a high half-wave potential of 0.884 V in alkaline electrolytes and outstanding durability.In addition,an assembled zinc–air battery with prepared Co-SAC/NC as air-cathode catalyst displays a high-peak power density of 179 mW cm^(-2)and a high-specific capacity(757 mAh g^(-1)).Density functional theory calculations confirm that the true active sites of the prepared catalyst are Co-N_(4)moieties,and further reveal a significantly electronic structure evolution of Co sites in the ORR process,in which the project density of states and local magnetic moment of Co atom varies during its whole reaction process.This work not only paves a new avenue for synthesizing SACs as robust electrocatalysts,but also provides an electronic-level insight into the evolution of the electronic structure of single-atom catalysts.

Conformal manufacturing of soft deformable sensors on the curved surface

Health monitoring of structures and people requires the integration of sensors and devices on various 3D curvilinear,hierarchically structured,and even dynamically changing surfaces.Therefore,it is highly desirable to explore conformal manufacturing techniques to fabricate and integrate soft deformable devices on complex 3D curvilinear surfaces.Although planar fabrication methods are not directly suitable to manufacture conformal devices on 3D curvilinear surfaces,they can be combined with stretchable structures and the use of transfer printing or assembly methods to enable the device integration on 3D surfaces.Combined with functional nanomaterials,various direct printing and writing methods have also been developed to fabricate conformal electronics on curved surfaces with intimate contact even over a large area.After a brief summary of the recent advancement of the recent conformal manufacturing techniques,we also discuss the challenges and potential opportunities for future development in this burgeoning field of conformal electronics on complex 3D surfaces.

SYNTHESIS OF CoFe_(2)O_(4)/Pb(Zr_(0.53)Ti_(0.47))O_(3)MULTIFERROIC COMPOSITE THICK FILMS BY LOW-SINTERING-TEMPERATURE SCREEN PRINTING METHOD

CoFe_(2)O_(4)/Pb(Zr_(0.53)Ti_(0.47))TO_(3)(abbreviated as CFO/PZT)multiferroic composite thick films were successfully fabricated on alumina substrate with gold bottom electrode by screen printing method at a low-sintering temperature.The processing included the modi fication and dispersion of ferromagnetic CFO powder and ferroelectric PZT powder,the preparation of uniform pastes,and the selection of proper annealing temperature for composite thick films.Transmission electron microscopic pictures(TEM)indicated the submicron meter of particles size for both CFO and PZT particles.After annealing at 900℃ for 1 h in air,tape test con firmed the quality of multiferroic thick films as well as pure CFO and PZT films.X-ray diffraction(XRD)showed a coexistence of CFO and PZT phases;furthermore,a smooth surface was observed through scanning electron microscopic(SEM)pictures along with the sharp cross-sectional picture,indicative of 100
m of film thickness.Ferromagnetic and ferroelectric properties were observed in CFO/PZT films simultaneously at room temperature.Compared with the reported CFO/PZT multiferrroic thin films,the present ferromagnetic property was closing to that of the chemical solgel synthesized film and even that from the physical pulsed laser deposition technique.However,the ferroelectric property showed a degenerated behavior,possible reasons for this was discussed and further optimization was also proposed for the potential multifunctional application.

Digital high-efficiency print forming method and device for multi-material casting molds

Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians.However,current sand mold 3D printing technology exhibits several problems,such as single-material printing molds,low manufacturing efficiency,and necessary post-process drying and heating for the manufacture of sand molds.This study proposes a novel high-efficiency print forming method and device for multi-material casting molds.The proposed method is specifically related to the integrated forming of two-way coating and printing and the shortflow manufacture of roller compaction and layered heating.These processes can realize the high-efficiency print forming of high-performance sand molds.Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200%using the proposed two-way coating and printing method.The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds,increases sand mold strength by 63.8%,and reduces resin usage by approximately 30%.The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts.This research provides theoretical guidance for the engineering application of sand mold 3D printing.