吸热墨水喷射3D打印高分子材料的研究现状与发展趋势

吸热墨水喷射3D打印技术可高效率成形复杂高性能塑料零件,对推动3D打印技术批量化应用具有积极意义。文中以惠普公司的多射流熔融技术和维捷公司的高速烧结技术为主综述了吸热墨水喷射3D打印的技术原理、发展历程和应用领域,总结了材料与工艺因素对其成形质量的影响,概述了吸热墨水喷射3D打印材料体系及相应3D打印研究的进展。通过分析该技术目前面临的主要问题,对其未来重点研究方向进行了展望。

Scalable synthesized high-performance TiO_(2)-Si-C hybrid anode for lithium batteries

At present,developing a simple strategy to effectively solve the shackles of volume expansion,poor conductivity and interface compatibility faced by Si-C anode in lithium batteries(LIBs)is the key to its commercialization.Here,low-cost nano-Si powders were prepared from Si-waste of solar-cells by sanding treatment,which can effectively reduce the commercialization cost for Si-C anode.Furthermore,micro-nano structured Gr@Si/C/TiO_(2) anode materials with graphite(Gr)as the inner core,TiO_(2)-doped and carbon-coated Si as the outer coating-layer,were synthesized at kilogram-scale per milling batch.Comprehensive characterization results indicate that TiO_(2)-doped carbon layer can improve the interface compatibility with the electrolyte,further promote the reduction of electrode polarization,and finally enhance the battery performance for the Gr@Si/C/TiO_(2) anodes.Accordingly,Gr@Si/C/TiO_(2) composites can output excellent LIB performance,especially with high initial coulombic efficiency(ICE)of 82.51%and large average reversible capacity of~810 mA h g^(-1) at 0.8 A g^(-1) after 1000 cycles.Moreover,Gr@Si/C/TiO_(2)‖NCM811 pouch full cells deliver impressive performance especially with high energy density of~489.3 W h kg^(-1) based on the total weight of active materials,suggesting its promising application in the high performance LIBs.

Easily Obtaining Excellent Performance High-voltage LiCoO_(2)via Pr_(6)O_(11)Modification

Developing an effective method to synthesize high-performance high-voltage LiCoO_(2) is essential for its industrialization in lithium batteries(LIBs).This work proposes a simple mass-produced strategy for the first time,that is,negative temperature coefficient thermosensitive Pr_(6)O_(11) nanoparticles are uniformly modified on LiCoO_(2) to prepare LiCoO_(2)@Pr_(6)O_(11)(LCO@PrO)via a liquid-phase mixing combined with annealing method.Tested at 274 mA g−1,the modified LCO@PrO electrodes deliver excellent 4.5 V high-voltage cycling performance with capacity retention ratios of 90.8%and 80.5%at 25 and 60℃,being much larger than those of 22.8%and 63.2%for bare LCO electrodes.Several effective strategies were used to clearly unveil the performance enhancement mechanism induced by Pr_(6)O_(11) modification.It is discovered that Pr_(6)O_(11) can improve interface compatibility,exhibit improved conductivity at elevated temperature,thus enhance the Li^(+)diffusion kinetics,and suppress the phase transformation of LCO and its resulting mechanical stresses.The 450 mAh LCO@PrO‖graphite pouch cells show excellent LIB performance and improved thermal safety characteristics.Importantly,the energy density of such pouch cell was increased even by~42%at 5 C.This extremely convenient technology is feasible for producing high-energy density LIBs with negligible cost increase,undoubtedly providing important academic inspiration for industrialization.

Boosting the cell performance of the SiO_(x)@C anode material via rational design of a Si-valence gradient

Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase(SEI)-film growth.Herein,a Si-valence gradient is optimized in SiOx composites to circumvent the large volume strain accompanied by lithium insertion/extraction.SiO_(x)@C annealed at 850℃ has a gentle Si-valence gradient along the radial direction and excellent electrochemical performances,delivering a high capacity of 506.9 mAh g^(−1) at 1.0 A g^(−1) with a high Coulombic efficiency of~99.8%over 400 cycles.Combined with the theoretical prediction,the obtained results indicate that the gentle Si-valence gradient in SiO_(x)@C is useful for suppressing plastic deformation and maintaining the inner connection integrity within the SiO_(x)@C particle.Moreover,a gentle Si-valence gradient is expected to form a stress gradient and affect the distribution of dangling bonds,resulting in local stress relief during the lithiation/delithiation process and enhanced Li-ion kinetic diffusion.Furthermore,the lowest interfacial stress variation ensures a stable SEI film at the interface and consequently increases cycling stability.Therefore,rational design of a Si-valence gradient in SiOx can provide further insights into achieving high-performance SiOx anodes with large-scale production.

Nano-crystalline FeOOH mixed with SWNT matrix as a superior anode material for lithium batteries

Nano-crystalline FeOOH particles （5-10 nm） have been uniformly mixed with electric matrix of single-walled carbon nanotubes （SWNTs） for forming FeOOH/SWNT composite via a facile ultrasonication method. Directly using the FeOOH/SWNT composite （containing 15 wt% SWNTs） as anode material for lithium battery enhances kinetics of the Li＋ insertion/extraction processes, thereby effectively improving re- versible capacity and cycle performance, which delivers a high reversible capacity of 758 mAh.g-1 under a current density of 400 mA.g-1 even after 180 cycles, being comparable with previous reports in terms of electrochemical performance for FeOOH anode. The good electrochemical performance should be ascribed to the small particle size and nano-crystalline of FeOOH, as well as the good electronic conductivity of SWNT matrix.

SnO_2 nanospheres among GO and SWNTs networks as anode for enhanced lithium storage performances

Conducting supporters of purified single-walled carbon nanotubes（SWNTs） and graphene oxide（GO）were used to confine pomegranate-structured Sn O2 nanospheres for forming SnO-GO-SWNT composites.As anode material for lithium ion batteries（LIBs）, this composite exhibits a stable and large reversible capacity together with an excellent rate capability. In addition, an analysis of the AC impedance spectroscopy has been used to confirm the enhanced mechanism for LIB performance. The improved electrochemical performance should be ascribed greatly to the reinforced synergistic effects between GO and SWNT networks, and their enhanced contribution of the conductivity. These results indicate that this composite has potential for utilization in high-rate and durable LIBs.

Ni/PMN-PT多铁异质结中电场对磁性的调制

采用脉冲激光沉积法制备Ni/PMN-PT复合磁电薄膜。对样品的结构、磁性和磁电效应测量表明,样品表现出明显的电场调制磁性效应,而且这种调制具有非易失性和良好的温度稳定性,因此在信息存储、传感器等领域有潜在应用前景。此外,论文还分析了电场调制机制,即通过在PMN-PT单晶里电场诱导铁电极化产生应力,进而通过磁弹效应对Ni薄膜晶格结构及磁相互作用的产生影响,从而获得此结构中电场对Ni薄膜磁特性的有效调制。

Boosting K-ion kinetics by interfacial polarization induced by amorphous MoO_(3-x)for MoSe_(2)/MoO_(3-x)@rGO composites

Promoting interfacial reaction kinetics is highly desirable for achieving high-performances of anode material in alkali-ion batteries.Herein,flower-like MoSe_(2)/MoO_(3-x)@r GO composites are fabricated by a facile solvothermal method involving a thermal-treatment at 800°C.When evaluated as an anode material for potassium ion batteries,MoSe_(2)/MoO_(3-x)@r GO delivers 248.2 m A h g^(-1)after 50 cycles at 0.2 A g^(-1) with a capacity retention of 84.6%and 182.9 m A h g^(-1)after 150 cycles at 1.0 A g^(-1) with a capacity retention of almost 61.2%,superior to those of bare MoSe_(2)or MoSe_(2)@r GO composites.Analysis from electrochemical measurements,the amorphous MoO_(3-x)containing oxygen vacancies could not only effectively buffer the self-aggregation of MoSe_(2)nanosheets but also provides lots of accessible active sites for potassium ion storage.Additionally,the open channels in the amorphous MoO_(3-x) phase lead to easier ion hopping and smaller diffusion barriers.Furthermore,the built-in electric field at the interface would be beneficial for electron transfer and K-ion migration across the hetero-junction interface.Moreover,larger dielectric polarization induced by the high relative permittivity of amorphous MoO_(3-x) would reduce charge transfer resistance and enhance K-ion migration across electric double-layer.Our work provides new insight into the enhanced performance of anode material coated by an amorphous layer with large relative permittivity.

基于冷却工程对环保型ZnSeTe基量子点的激发态调控

由于材料内部存在高效的非辐射复合,这使得实现高质量的环保量子点仍然具有挑战性.本文中,我们探索了通过冷却工程调节激发态对实现高质量的ZnSeTe核壳量子点的影响.研究发现,超快热载流子俘获和带边载流子俘获是ZnSeTe量子点发射效率低下的主要原因.我们通过设计冷却工程抑制上述过程,并且结合电子和光谱表征分析了其潜在机制.经过冷却优化的ZnSeTe量子点表现出高量子发光效率(>90%)和稳定性,这可与经典的CdSe量子点相媲美.基于这种量子点的白光发光二极管(WLED)表现出优异的光学性能,包括高显色指数(80)和良好的相关色温(7391 K).此外,高性能的WLED还可以用作环保可见光通信.这些结果表明了环保量子点在实际应用中的可行性.

Front and Back contact engineering for high-efficient and low-cost hydrothermal derived Sb_(2)(S, Se)_(3) solar cells by using FTO/SnO_(2) and carbon

Antimony chalcogenide Sb_(2)(S, Se)_(3) is attracting a lot of attention as photovoltaic absorber owing to its rewarding photoelectric properties, low toxicity, and earth abundance. However, its device efficiency is still limited by the absorber material quality and device interface recombination. In this work, a fluorinedoped tin oxide(FTO) substrate with ultra-thin SnO_(2) layer and a low-cost stabilized carbon paste are introduced as a front and back contact layer respectively in Sb_(2)(S, Se)_(3) based planar solar cells. Over 5.2% efficiency is demonstrated in the structure of FTO/SnO_(2)/Cd S/Sb_(2)(S, Se)_3/Carbon/Ag, where the Sb_(2)(S, Se)_(3) is prepared by hydrothermal technique. The complementary device physics characterizations reveal that the interfacial recombination between TCO and Cd S is significantly suppressed by the introduction of ultra-thin SnO_(2) layer, which is profited from the leakage protection and bandgap offset engineering by its high resistivity and suitable conduction band minimum. Meanwhile, the successful adoption of the lowcost stabilized carbon as a back contact here shows an enormous potential to replace the conventional organic hole transport materials and noble metal. We hope this work can provide positive guidance to optimize Sb_(2)(S, Se)_(3) based planar solar cells in the future.

Hydrogen induced room-temperature ferromagnetism in Co-doped ZnO: first-principles and Monte Carlo study

The structural stability, vibrational and magnetic properties of hydrogen doped ZnO:Co have been studied by first-principles calculations based on density functional theory. Bond-center(BC) sites were identified to be most stable sites for hydrogen, the corresponding vibrational frequencies including anharmonic contributions were calculated. Its magnetic properties were investigated as well. The calculated results reveal that hydrogen could induce the change of electronic transfer, leading to a decrease of magnetic moment. However, the magnetic coupling between Co atoms is greatly strengthen. The results simulated by Monte Carlo method indicate that hydrogen can induce the Curie temperature to increase from 200 to 300 K.

Evolution of Weyl nodes in Ni-doped thallium niobate pyrochlore Tl_(2-x)Ni_(x)Nb_(2)O_(7)

The magnetic Weyl semimetal(WSM)is important for fundamental physics and potential applications due to its spontaneous magnetism,robust band topology,and enhanced Berry curvature.It possesses many unique quantum effects,including a large intrinsic anomalous Hall effect,Fermi arcs,and chiral anomaly.In this work,using ab initio calculations,we propose that Nidoped pyrochlore Tl2Nb2O7is a magnetic WSM caused by the exchange field splitting on bands around its quadratic band crossing point.The exchange field tuned by Ni 3d on-site Coulomb interaction parameter U drives the evolution of Weyl nodes and the resulting topological phase transition.As Weyl nodes can exist at generic points in the Brillouin zone and are hard to identify exactly,their creation and annihilation,i.e.,the change in their number,chirality,and distribution,have been consistently confirmed with a combined theoretical approach,which employs parity criterion,symmetry indicator analysis,and the Wilson loop of the Wannier center.We find that Weyl nodes remain in a large range of U and are close to the Fermi level,which makes the experimental observation very possible.We think that this method and our proposal of magnetic WSM will be useful in finding more WSMs and add to the understanding of the topological phase transition.

Micro-nano structured VNb_(9)O_(25)anode with superior electronic conductivity for high-rate and long-life lithium storage

The oxygen vacancies and micro-nano structure can optimize the electron/Li+migration kinetics in anode materials for lithium batteries(LIBs).Here,porous micro-nano structured VNb_(9)O_(25)composites with rich oxygen vacancies were reasonably prepared via a facile solvothermal method combined with annealing treatment at 800℃for 30 h(VNb_(9)O_(25)-30 h).This micro-nano structure can enhance the contact of active material/electrolyte,and shorten the Li+diffusion distance.The introduction of oxygen vacancies can further boosts the intrinsic conductivity of VNb_(9)O_(25)-30 h for achieving excellent LIB performance.The as-prepared VNb_(9)O_(25)-30 h anode showed advanced rate capability with reversible capacity of 122.2 m A h g^(-1)at 4 A g^(-1),and delivered excellent capacity retention of~100%after 2000 cycles.Meanwhile,VNb_(9)O_(25)-30 h provides unexpected long-cycle life(i.e.,reversible capacity of 165.7 m A h g^(-1)at 1 A g^(-1)with a high capacity retention of 85.6%even after 8000 cycles).Additionally,coupled with the Li Fe PO4 cathode,the Li Fe PO4//VNb_(9)O_(25)-30 h full cell delivers superior LIB properties with high reversible capacities of 91.6 m A h g^(-1)at 5 C for 1000 cycles.Thus,such reasonable construction method can assist in other high-performance niobium-based oxides in LIBs.