Orientation control of anisotropic one-dimensional(1D)and two-dimensional(2D)materials in solutions is of great importance in many fields ranging from structural materials design,the thermal management,to energy stora...Orientation control of anisotropic one-dimensional(1D)and two-dimensional(2D)materials in solutions is of great importance in many fields ranging from structural materials design,the thermal management,to energy storage.Achieving fine control of vertical alignment of anisotropic fillers(such as graphene,boron nitride(BN),and carbon fiber)remains challenging.This work presents a universal and scalable method for constructing vertically aligned structures of anisotropic fillers in composites assisted by the expansion flow(using2D BN platelets as a proof-of-concept).BN platelets in the silicone gel strip are oriented in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip surfaces.Due to the vertical orientation of BN in the central area of strips,a throughplane thermal conductivity as high as 5.65 W m^(-1) K^(-1) was obtained,which can be further improved to 6.54 W m^(-1) K^(-1) by combining BN and pitch-based carbon fibers.The expansion-flow-assisted alignment can be extended to the manufacture of a variety of polymer composites filled with 1D and 2D materials,which can find wide applications in batteries,electronics,and energy storage devices.展开更多
In this study, a novel 4-（4-octyloxybenzoyloxy）biphenyl-3′,5′-diaminobenzoate and polyimides based on it were synthesized. The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for ne...In this study, a novel 4-（4-octyloxybenzoyloxy）biphenyl-3′,5′-diaminobenzoate and polyimides based on it were synthesized. The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal （LC）. The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV-vis spectra of the noyel polyimide films showed the high transparency in a visible wave length.展开更多
High-performance lithium metal batteries benefit from the construction of composite polymer electrolytes(CPEs)which are synthesized by incorporating inorganic fillers into polymer matrices[1].However,the random distri...High-performance lithium metal batteries benefit from the construction of composite polymer electrolytes(CPEs)which are synthesized by incorporating inorganic fillers into polymer matrices[1].However,the random distribution of added fillers within the polymer matrix can lead to tortuous ion pathways and longer transmission distances(Fig.1).As a result,the ion transport capability of CPEs may decrease,while interface contact may deteriorate.Therefore,the organized arrangement of fillers emerges as a crucial consideration in constructing electrolyte membranes.One highly effective approach is the adoption of a vertically aligned filler configuration,where ceramic fillers are constructed to be perpendicular to the electrolyte membrane.If so,the filler/electrolyte interface impedance can be significantly reduced,while continuous ion transport channels along the specified direction are formed,thus significantly enhancing the ion conduction(Fig.1(a))[1].展开更多
Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread appli...Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread applications are hindered by low ionic conductivity at room temperature and lithium dendrite growth.Herein,we report a novel solid-state composite membrane electrolyte design that combines the vertically aligned channel structure and copolymer with a radial gradient composition.Within the vertically aligned channels,the composition of poly(vinyl ethylene carbonate-co-poly(ethylene glycol)diacrylate)(P(VEC-PEGDA)varies in a gradient along the radial direction:from the center to the wall of vertically aligned channels,the proportion of vinyl ethylene carbonate(VEC)in the copolymer decreases,while the proportion of poly(ethylene glycol)diacrylate(PEGDA)increases accordingly.It can be functionally divided into a mechanical-reinforcement layer and a fast-ion-conducting layer.The resulting solid-state composite membrane electrolyte achieves a high critical current density of 1.2 mA cm^(-2)and high ionic conductivity of 2.03 mS cm^(-1)at room temperature.Employing this composite membrane electrolyte,a Li//Li symmetric cell exhibits stable cycling for over 1850 h at 0.2 m A cm^(-2)/0.2 m A h cm^(-2),and a Li//LiFePO4(LFP)battery maintains 77.3% capacity retention at 2 C after 300 cycles.Our work provides insight into the rational design of safer and more efficient solidstate batteries through electrolyte structural engineering.展开更多
Solid oxide fuel cells(SOFCs)are widely presented as a sustainable solution to future energy challenges.Nevertheless,solid oxide fuel cells presently rely on significant use of several critical raw materials to enable...Solid oxide fuel cells(SOFCs)are widely presented as a sustainable solution to future energy challenges.Nevertheless,solid oxide fuel cells presently rely on significant use of several critical raw materials to enable optimized electrode reaction kinetics.This challenge can be addressed by using thinfilm electrode materials;however,this is typically accompanied by complex device fabrication procedures as well as poor mechanical/chemical stability.In this work,we conduct a systematic study of a range of promising thin-film electrode materials based on vertically aligned nanocomposite(VAN)thin films.We demonstrate low area specific resistance(ASR)values of 0.44 cm^(2) at 650℃ can be achieved using(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3)-(Sm_(2)O_(3))_(0.20)(CeO_(2))_(0.80)(LSCF-SDC)thin films,which are also characterized by a low degradation rate,approximately half that of planar LSCF thin films.We then integrate these(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3)-(Sm_(2)O_(3))_(0.20)(CeO_(2))_(0.80) vertically aligned nanocomposite films directly with commercial anode supported half cells through a single-step deposition process.The resulting cells exhibit peak power density of 0.47W cm^(-2) at 750℃,competitive with 0.64W cm^(-2) achieved for the same cells operating with a bulk(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3) cathode,despite 99.5% reduction in cathode critical raw material use.By demonstrating such competitive performance using thin-film cathode functional layers,this work also paves the way for further cost reductions in solid oxide fuel cells,which could be achieved by likewise applying thin-film architectures to the anode functional layer and/or current collecting layers,which typically account for the greatest materials cost in solid oxide fuel cell stacks.Therefore,the present work marks a valuable step towards the sustainable proliferation of solid oxide fuel cells.展开更多
With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel(CA) with highly enhanced thermal conductivity(TC) in vertical...With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel(CA) with highly enhanced thermal conductivity(TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires(SiC NWs)/boron nitride(BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m^(-1) K^(-1) at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy(EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 10^(11) Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of-21.5 dB and a wide effective absorption bandwidth(<-10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications.展开更多
Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due ...Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due to NSs’random distribution.We introduce a facile method for fabricating intrinsic piezoelectric composites incorporated with NSs without electric poling.Our innovative process aligns NSs within polyvinyl alcohol polymer,leveraging ice-water interfacial tension,water crystallization thrust,and directional cross-linking during freezing.The resulting PE composites exhibit a maximum piezoelectric coefficient of up to 25.5-28.4 pC N^(-1),comparable to polyvinylidene difluoride(PVDF),with significant costefficiency,safety,and scalability advantages over conventional materials.Using this composite,we develop highly sensitive wearable pressure and strain sensors,and an ultrasound energy harvester.These sensors detect finger bending and differentiate between walking and running,while the harvester generates1.18 V/2.31μA under 1Wcm^(-2)ultrasound input underwater.This universal method offers a novel manufacturing technique for piezoelectric composites,demonstrating remarkable effectiveness in synthesizing intrinsic piezoelectric composites based on 2D materials.Moreover,its potential extends to applications in wearable electronics and energy harvesting,promising significant advancements in these fields.展开更多
The development of non-noble-metal hydrogen evolution electrocatalysts holds great promises for a sustainable energy system.Here,a hybrid W(Mo)S_(2)/NW(Mo)C nanosheet with array structures was reported for an efficien...The development of non-noble-metal hydrogen evolution electrocatalysts holds great promises for a sustainable energy system.Here,a hybrid W(Mo)S_(2)/NW(Mo)C nanosheet with array structures was reported for an efficient light-as sis ted hydrogen evolution electrocatalysts in acidic solutions.The resulting vertically aligned W(Mo)S_(2)/N-W(Mo)C was supported on a conductive carbon fiber paper,which can be produced through annealing W(Mo)S_(2)nanosheets by simultaneous carbonization and N-doping in Ar/H_(2)atmosphere.This optimized WS_(2)/NWC and MoS_(2)/N-MoC electrode exhibits remarkable lightassisted electrocatalysis activity with overpotentials of0.120 and 0.122 V at 10 mA·cm^(-1)in acidic solutions,respectively.Such high hydrogen evolution activities should be attributed to the electrocatalytic synergistic effects of the abundant active sites existing in different phase boundaries and the absorption for ultraviolet-visible light.This study shows that synthesis of low-cost and highly active W(Mo)S_(2)-based hydrogen evolution electrocatalyst opens up a route toward the development of scalable production of hydrogen fuels.展开更多
Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure ...Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.展开更多
The mechanism for the formation of double-layer vertically aligned carbon nanotube arrays(VACNTs) through single-step CVD growth is investigated. The evolution of the structures and defect concentration of the VACNTs ...The mechanism for the formation of double-layer vertically aligned carbon nanotube arrays(VACNTs) through single-step CVD growth is investigated. The evolution of the structures and defect concentration of the VACNTs are tracked by scanning electron microscopy(SEM) and Raman spectroscopy. During the growth, the catalyst particles are stayed constantly on the substrate. The precipitation of the second CNT layer happens at around 30 min as proved by SEM.During the growth of the first layer, catalyst nanoparticles are deactivated with the accumulation of amorphous carbon coatings on their surfaces, which leads to the termination of the growth of the first layer CNTs. Then, the catalyst particles are reactivated by the hydrogen in the gas flow, leading to the precipitation of the second CNT layer. The growth of the second CNT layer lifts the amorphous carbon coatings on catalyst particles and substrates. The release of mechanical energy by CNTs provides big enough energy to lift up amorphous carbon flakes on catalyst particles and substrates which finally stay at the interfaces of the two layers simulated by finite element analysis. This study sheds light on the termination mechanism of CNTs during CVD process.展开更多
The field emission （FE） properties of vertically aligned graphene sheets （VAGSs） grown on different SiC substrates are reported. The VAGSs grown on nonpolar SiC （10-10） substrate show an ordered alignment with t...The field emission （FE） properties of vertically aligned graphene sheets （VAGSs） grown on different SiC substrates are reported. The VAGSs grown on nonpolar SiC （10-10） substrate show an ordered alignment with the graphene basal plane-parallel to each other, and show better FE features, with a lower turn-on field and a larger field enhancement factor. The VAGSs grown on polar SiC （000-1 ） substrate reveal a random petaloid-shaped arrangement and stable current emission over 8 hours with a maximum emission current fluctuation of only 4%. The reasons behind the differing FE characteristics of the VAGSs on different SiC substrates are analyzed and discussed.展开更多
Conventional electrode preparation techniques of supercapacitors such as tape casting or vacuum filtration often lead to the restacking or agglomeration of twodimensional(2 D)materials.As a result,tortuous paths are c...Conventional electrode preparation techniques of supercapacitors such as tape casting or vacuum filtration often lead to the restacking or agglomeration of twodimensional(2 D)materials.As a result,tortuous paths are created for the electrolyte ions and their adsorption onto the surfaces of the active materials can be prevented.Consequently,maintaining high rate performance while increasing the thickness of electrodes has been a challenge.Herein,a facile freeze-assisted tape-casting(Fa TC)method is reported for the scalable fabrication of flexible MXene(Ti3C2Tx)supercapacitor electrode films of up to 700μm thickness,exhibiting homogeneous ice-template microstructure composed of vertically aligned MXene walls within lamellar pores.The efficient ion transport created by the internal morphology allows for fast electrochemical charge–discharge cycles and near thickness-independent performance at up to 3000 m V s-1 for films of up to 300μm in thickness.By increasing the scan rate from 20 to 10,000 m V s-1,Ti3C2Tx films of 150μm in thickness sustain 50%of its specific capacitance(222.9 F g-1).When the film thickness is doubled to 300μm,its capacitance is still retained by 60%(at 213.3 F g-1)when the scan rate is increased from 20 to3000 m V s-1,with a capacitance retention above 97.7%for over 14,000 cycles at10 A g-1.They also showed a remarkably high gravimetric and areal power density of 150 k W kg-1 at 1000 A g-1 and 667 m W cm-2 at 4444 m A cm-2,respectively.Fa TC has the potential to provide industry with a viable way to fabricate electrodes formed from 2 D materials on a large scale,while providing promising performance for use in a wide range of applications,such as flexible electronics and wearable energy storage devices.展开更多
Synthesis of carbon nanotubes （CNTs） below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received les...Synthesis of carbon nanotubes （CNTs） below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced. In this work, the effects of varying the preheating temperature on the synthesis of CNT were investigated. The reaction temperature was set at 570℃. The preheating set temperature was varied from 150 to 400℃ at 50℃ interval. Three O-ring shape heating mantels were used as heating source for the preheater. In situ monitoring device was used to observe the temperature profile in the reactor. Benzene and ferrocene were used as the carbon source and catalyst precursor, respectively. Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃. When the preheating temperature was increased up to 400℃, both the length and the alignment of CNTs produced were improved.展开更多
With the rapid development of high-power-density electronic devices,interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products.Therefore,there is a...With the rapid development of high-power-density electronic devices,interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products.Therefore,there is an urgent demand for advanced thermal interface materials(TIMs)with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions.To achieve this aim,a promising strategy involves vertically arranging highly thermoconductive graphene on polymers.However,with the currently available methods,achieving a balance between low interfacial thermal resistance,bidirectional high thermal conductivity,and large-scale production is challenging.Herein,we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper.The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance.The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m^(-1)·K^(-1)and in-plane thermal conductivity of 130W·m^(-1)·K^(-1)when the thermal filler loading is 10.1 wt%,with a thermal conductivity enhancement per 1 wt%filler loading of 831%,outperforming various graphene structures as fillers.Given its high thermal conductivity,low contact thermal resistance,and low compressive modulus,the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700,an advanced commercial TIM,effectively solving the interfacial heat transfer issues in electronic systems.This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing.展开更多
The COVID-19 pandemic has exposed the limitations of traditional preventative measures and underscored the essential role of face masks in controlling virus transmission.More effective and recyclable facial masks usin...The COVID-19 pandemic has exposed the limitations of traditional preventative measures and underscored the essential role of face masks in controlling virus transmission.More effective and recyclable facial masks using various materials have been developed.In this work,vertically aligned carbon nanotubes(VACNTs)are employed as effective facial mask filters,particularly aimed at preventing SARS-CoV-2 virus infection in preparation for future COVID-19 pandemics.This study assesses six critical aspects of facial masks:hydrophobicity,industrial viability,breathability,hyperthermal antiviral effect,toxicity,and reusability.The VACNT alone exhibits superhydrophobicity with a contact angle of 175.53◦,and an average of 142.7◦for a large area on spun-bonded polypropylene.VACNTs are processed using a roll-to-roll method,eliminating the need for adhesives.Due to the aligned tubes,VACNT filters demonstrate exceptional breathability and moisture ventilation compared to previously reported CNT and conventional filters.Hyperthermal tests of VACNT filters under sunlight confirm that up to 99.8%of the HCoV 229E virus denatures even in cold environments.The safety of using VACNTs is corroborated through histopathological evaluation and subcutaneous implantation tests,addressing concerns of respiratory and skin inflammation.VACNT masks efficiently transmit moisture and rapidly return to their initial dry state under sunlight maintaining their properties after 10000 bending cycles.In addition,the unique capability of VACNT filters to function as respiratory sensors,signaling dampness and facilitating reuse,is assessed,alongside their Joule heating effect.展开更多
One of the critical challenges that limit broad commercialization of proton exchange membrane fuel cells(PEMFC)is to reduce the usage of Pt while maintaining high power output and sufficient durability.Herein,a novel ...One of the critical challenges that limit broad commercialization of proton exchange membrane fuel cells(PEMFC)is to reduce the usage of Pt while maintaining high power output and sufficient durability.Herein,a novel bifunctional layer consisting of vertically aligned carbon nanotubes(VACNTs)and nanoparticles of Pt-Co catalysts(Pt-Co/VACNTs)is reported for highperformance PEMFCs.Readily prepared by a two-step process,the Pt-Co/VACNTs layer with a hydrophilic catalyst-loaded side and a hydrophobic gas diffusion side enables a PTFE-free electrode structure with fully exposed catalyst active sites and superior gas–water diffusion capability.When tested in a PEMFC,the bi-functional Pt-Co/VACNTs layer with ultralow Pt loading(~65μgcathodecm-2)demonstrates a power density of 19.5 kW gPt cathode-1 at 0.6 V,more than seven times that of a cell with commercial Pt/C catalyst(2.7 kW gPt cathode-1 at 0.6 V)at a loading of 400μgcathodecm-2 tested under similar conditions.This remarkable design of VACNTs-based catalyst with dual functionalities enables much lower Pt loading,faster mass transport,and higher electrochemical performance and stability.Further,the preparation procedure can be easily scaled up for low-cost fabrication and commercialization.展开更多
Developing advanced thermal interface materials(TIMs)to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of hi...Developing advanced thermal interface materials(TIMs)to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of high-power semiconductor devices.Based on the ultra-high basal-plane thermal conductivity,graphene is an ideal candidate for preparing high-performance TIMs,preferably to form a vertically aligned structure so that the basal-plane of graphene is consistent with the heat transfer direction of TIM.However,the actual interfacial heat transfer efficiency of currently reported vertically aligned graphene TIMs is far from satisfactory.In addition to the fact that the thermal conductivity of the vertically aligned TIMs can be further improved,another critical factor is the limited actual contact area leading to relatively high contact thermal resistance(20-30 K mm^(2) W^(−1))of the“solid-solid”mating interface formed by the vertical graphene and the rough chip/heat sink.To solve this common problem faced by vertically aligned graphene,in this work,we combined mechanical orientation and surface modification strategy to construct a three-tiered TIM composed of mainly vertically aligned graphene in the middle and micrometer-thick liquid metal as a cap layer on upper and lower surfaces.Based on rational graphene orientation regulation in the middle tier,the resultant graphene-based TIM exhibited an ultra-high thermal conductivity of 176 W m^(−1) K^(−1).Additionally,we demonstrated that the liquid metal cap layer in contact with the chip/heat sink forms a“liquid-solid”mating interface,significantly increasing the effective heat transfer area and giving a low contact thermal con-ductivity of 4-6 K mm^(2) W^(−1) under packaging conditions.This finding provides valuable guidance for the design of high-performance TIMs based on two-dimensional materials and improves the possibility of their practical application in electronic thermal management.展开更多
Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure ...Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.展开更多
Multi-phase vertically aligned nanocomposite(MP-VAN)thin films represent a promising avenue for achieving complex multifunctionality,exploring novel interfacial phenomena,and enabling complex metamaterial designs and ...Multi-phase vertically aligned nanocomposite(MP-VAN)thin films represent a promising avenue for achieving complex multifunctionality,exploring novel interfacial phenomena,and enabling complex metamaterial designs and exploration.In this study,a novel self-assembled all-oxides three-phase VAN system was conceptualized and fabricated utilizing pulsed laser deposition(PLD)with a single composite target.Detailed microstructural analysis reveals the presence of three distinct phases:LiNbO_(3),CeO_(2-x),and LiNbCe_(1-x)O_(y)within the MP-VAN films.Subsequently,ferroelectric,dielectric,optical anisotropy,and magnetic properties were systematically investigated to showcase the multifunctionality inherent in these films.This work presents a pioneering approach to designing and realizing MP-VAN systems,and opens up opportunities for tailoring the complex three-dimensional(3D)physical properties and property coupling of VAN films towards diverse device applications.展开更多
Oxide-metal based nanocomposite thin films have attracted great interests owing to their unique anisotropic structure and physical properties.A wide range of Au-based oxide-metal nanocomposites have been demonstrated,...Oxide-metal based nanocomposite thin films have attracted great interests owing to their unique anisotropic structure and physical properties.A wide range of Au-based oxide-metal nanocomposites have been demonstrated,while other metal systems are scarce due to the challenges in the initial nucleation and growth as well as possible interdiffusions of the metallic nanopillars.In this work,a unique anodic aluminum oxide(AAO)template was used to grow a thin Co seed layer and the following self-assembled metal-oxide(Co-BaTiO_(3))vertically aligned nanocomposite thin film layer.The AAO template allows the uniform growth of Co-seeds and successfully deposition of highly ordered Co pillars(with diameter<5 nm and interval between pillars<10 nm)inside the oxide matrix.Significant magnetic anisotropy and strong magneto-optical coupling properties have been observed.A thin Au-BaTiO_(3) template was also later introduced for further enhanced nucleation and ordered growth of the Co-nanopillars.Taking the advantage of such a unique nanostructure,a large out-of-plane(OP)coercive field(Hc)of~5000 Oe has been achieved,making the nanocomposite an ideal candidate for high density perpendicular magnetic tunneling junction(p-MTJ).A strong polar magneto-optical Kerr effect(MOKE)has also been observed which inspires a novel optical-based reading method of the MTJ states.展开更多
基金supported by The National Key Research and Development Program of China(2020YFA0210704)。
文摘Orientation control of anisotropic one-dimensional(1D)and two-dimensional(2D)materials in solutions is of great importance in many fields ranging from structural materials design,the thermal management,to energy storage.Achieving fine control of vertical alignment of anisotropic fillers(such as graphene,boron nitride(BN),and carbon fiber)remains challenging.This work presents a universal and scalable method for constructing vertically aligned structures of anisotropic fillers in composites assisted by the expansion flow(using2D BN platelets as a proof-of-concept).BN platelets in the silicone gel strip are oriented in a curved shape that includes vertical alignment in the central area and horizontal alignment close to strip surfaces.Due to the vertical orientation of BN in the central area of strips,a throughplane thermal conductivity as high as 5.65 W m^(-1) K^(-1) was obtained,which can be further improved to 6.54 W m^(-1) K^(-1) by combining BN and pitch-based carbon fibers.The expansion-flow-assisted alignment can be extended to the manufacture of a variety of polymer composites filled with 1D and 2D materials,which can find wide applications in batteries,electronics,and energy storage devices.
文摘In this study, a novel 4-（4-octyloxybenzoyloxy）biphenyl-3′,5′-diaminobenzoate and polyimides based on it were synthesized. The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal （LC）. The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV-vis spectra of the noyel polyimide films showed the high transparency in a visible wave length.
基金supported by the National Natural Science Foundation of China(No.51972293)Hangzhou Key Research Program Project(2023SZD0099)LingYan Project(2024C01090).
文摘High-performance lithium metal batteries benefit from the construction of composite polymer electrolytes(CPEs)which are synthesized by incorporating inorganic fillers into polymer matrices[1].However,the random distribution of added fillers within the polymer matrix can lead to tortuous ion pathways and longer transmission distances(Fig.1).As a result,the ion transport capability of CPEs may decrease,while interface contact may deteriorate.Therefore,the organized arrangement of fillers emerges as a crucial consideration in constructing electrolyte membranes.One highly effective approach is the adoption of a vertically aligned filler configuration,where ceramic fillers are constructed to be perpendicular to the electrolyte membrane.If so,the filler/electrolyte interface impedance can be significantly reduced,while continuous ion transport channels along the specified direction are formed,thus significantly enhancing the ion conduction(Fig.1(a))[1].
基金supported by the National Natural Science Foundation of China(52372099,52202328,22461142135,22479046)the Shanghai Sailing Program(22YF1455500)the Shanghai Magnolia Talent Plan Pujiang Project(24PJD128)。
文摘Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread applications are hindered by low ionic conductivity at room temperature and lithium dendrite growth.Herein,we report a novel solid-state composite membrane electrolyte design that combines the vertically aligned channel structure and copolymer with a radial gradient composition.Within the vertically aligned channels,the composition of poly(vinyl ethylene carbonate-co-poly(ethylene glycol)diacrylate)(P(VEC-PEGDA)varies in a gradient along the radial direction:from the center to the wall of vertically aligned channels,the proportion of vinyl ethylene carbonate(VEC)in the copolymer decreases,while the proportion of poly(ethylene glycol)diacrylate(PEGDA)increases accordingly.It can be functionally divided into a mechanical-reinforcement layer and a fast-ion-conducting layer.The resulting solid-state composite membrane electrolyte achieves a high critical current density of 1.2 mA cm^(-2)and high ionic conductivity of 2.03 mS cm^(-1)at room temperature.Employing this composite membrane electrolyte,a Li//Li symmetric cell exhibits stable cycling for over 1850 h at 0.2 m A cm^(-2)/0.2 m A h cm^(-2),and a Li//LiFePO4(LFP)battery maintains 77.3% capacity retention at 2 C after 300 cycles.Our work provides insight into the rational design of safer and more efficient solidstate batteries through electrolyte structural engineering.
基金support from the Royal Academy of Engineering Chair in Emerging technologies(grant number CIET1819_24)the EPSRC Centre of Advanced Materials for Integrated Energy Systems(CAM-IES)(grant number EP/P007767/1)+2 种基金the EU-H2020-ERC-ADG EROS(grant number 882929)support provided by Deutsche Forschungsgemeinschaft(Project no.424789449,grant no.HA1344-45-1)support from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no.836503.We acknowledge use of the Thermo Fisher Spectra 300 TEM at the Wolfson Electron Microscopy Suite at the University of Cambridge funded by EPSRC under grant EP/R008779/1.
文摘Solid oxide fuel cells(SOFCs)are widely presented as a sustainable solution to future energy challenges.Nevertheless,solid oxide fuel cells presently rely on significant use of several critical raw materials to enable optimized electrode reaction kinetics.This challenge can be addressed by using thinfilm electrode materials;however,this is typically accompanied by complex device fabrication procedures as well as poor mechanical/chemical stability.In this work,we conduct a systematic study of a range of promising thin-film electrode materials based on vertically aligned nanocomposite(VAN)thin films.We demonstrate low area specific resistance(ASR)values of 0.44 cm^(2) at 650℃ can be achieved using(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3)-(Sm_(2)O_(3))_(0.20)(CeO_(2))_(0.80)(LSCF-SDC)thin films,which are also characterized by a low degradation rate,approximately half that of planar LSCF thin films.We then integrate these(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3)-(Sm_(2)O_(3))_(0.20)(CeO_(2))_(0.80) vertically aligned nanocomposite films directly with commercial anode supported half cells through a single-step deposition process.The resulting cells exhibit peak power density of 0.47W cm^(-2) at 750℃,competitive with 0.64W cm^(-2) achieved for the same cells operating with a bulk(La_(0.60)Sr_(0.40))_(0.95)Co_(0.20)Fe_(0.80)O_(3) cathode,despite 99.5% reduction in cathode critical raw material use.By demonstrating such competitive performance using thin-film cathode functional layers,this work also paves the way for further cost reductions in solid oxide fuel cells,which could be achieved by likewise applying thin-film architectures to the anode functional layer and/or current collecting layers,which typically account for the greatest materials cost in solid oxide fuel cell stacks.Therefore,the present work marks a valuable step towards the sustainable proliferation of solid oxide fuel cells.
基金financial support from National Natural Science Foundation of China(21704096,51703217)the China Postdoctoral Science Foundation(Grant No.2019M662526)financial support from Taif University Researchers Supporting Project Number(TURSP-2020/135),Taif University,Taif,Saudi Arabia。
文摘With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel(CA) with highly enhanced thermal conductivity(TC) in vertical planes was successfully obtained by constructing a vertically aligned silicon carbide nanowires(SiC NWs)/boron nitride(BN) network via the ice template-assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W m^(-1) K^(-1) at a low hybrid filler loading of 16.69 wt%, which was increased by 890% compared to pure epoxy(EP). In addition, relying on unique porous network structure of CA, EP-based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35 × 10^(11) Ω cm and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of-21.5 dB and a wide effective absorption bandwidth(<-10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications.
基金funded by the Key Research Project of Zhejiang(LD22E030007)the“Leading Goose”R&D Program of Zhejiang Province(No.2022C01136)+2 种基金National Science Foundation of China(NSFC No.61974037,No.61904042,No.62274049)Zhejiang University Education Foundation Global Partnership Fund(No.100000-11320)the support of the Micro-nano Fabrication Center of International campus of Zhejiang University.
文摘Few-layer nanosheets(NSs)of hexagonal boron nitride(h-BN)and molybdenum disulfide(MoS_(2))display notable piezoelectric properties.Yet,their integration into polymers typically yields non-piezoelectric composites due to NSs’random distribution.We introduce a facile method for fabricating intrinsic piezoelectric composites incorporated with NSs without electric poling.Our innovative process aligns NSs within polyvinyl alcohol polymer,leveraging ice-water interfacial tension,water crystallization thrust,and directional cross-linking during freezing.The resulting PE composites exhibit a maximum piezoelectric coefficient of up to 25.5-28.4 pC N^(-1),comparable to polyvinylidene difluoride(PVDF),with significant costefficiency,safety,and scalability advantages over conventional materials.Using this composite,we develop highly sensitive wearable pressure and strain sensors,and an ultrasound energy harvester.These sensors detect finger bending and differentiate between walking and running,while the harvester generates1.18 V/2.31μA under 1Wcm^(-2)ultrasound input underwater.This universal method offers a novel manufacturing technique for piezoelectric composites,demonstrating remarkable effectiveness in synthesizing intrinsic piezoelectric composites based on 2D materials.Moreover,its potential extends to applications in wearable electronics and energy harvesting,promising significant advancements in these fields.
基金financially supported by the National Natural Science Foundation of China(No.52202340)China Postdoctoral Science Foundation(No.2021M691365)+2 种基金the Applied Basic Research Project of Shanxi Province(No.20210302124425)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2021L266)the Graduate Science and Technology Innovation Project Foundation of Shanxi Normal University(No.2021XSY030)。
文摘The development of non-noble-metal hydrogen evolution electrocatalysts holds great promises for a sustainable energy system.Here,a hybrid W(Mo)S_(2)/NW(Mo)C nanosheet with array structures was reported for an efficient light-as sis ted hydrogen evolution electrocatalysts in acidic solutions.The resulting vertically aligned W(Mo)S_(2)/N-W(Mo)C was supported on a conductive carbon fiber paper,which can be produced through annealing W(Mo)S_(2)nanosheets by simultaneous carbonization and N-doping in Ar/H_(2)atmosphere.This optimized WS_(2)/NWC and MoS_(2)/N-MoC electrode exhibits remarkable lightassisted electrocatalysis activity with overpotentials of0.120 and 0.122 V at 10 mA·cm^(-1)in acidic solutions,respectively.Such high hydrogen evolution activities should be attributed to the electrocatalytic synergistic effects of the abundant active sites existing in different phase boundaries and the absorption for ultraviolet-visible light.This study shows that synthesis of low-cost and highly active W(Mo)S_(2)-based hydrogen evolution electrocatalyst opens up a route toward the development of scalable production of hydrogen fuels.
基金finically supported by the National Natural Science Foundation of China(22075055)the Guangxi Science and Technology Project(AB16380030)the Innovation Project of Guangxi Graduate Education(YCSW2020052)。
文摘Reducing a Pt loading with improved power output and durability is essential to promote the large-scale application of proton exchange membrane fuel cells(PEMFCs).To achieve this goal,constructing optimized structure of catalyst layers with efficient mass transportation channels plays a vital role.Herein,PEMFCs with order-structured cathodic electrodes were fabricated by depositing Pt nanoparticles by Ebeam onto vertically aligned carbon nanotubes(VACNTs)growth on Al foil via plasma-enhanced chemical vapor deposition.Results demonstrate that the proportion of hydrophilic Pt-deposited region along VACNTs and residual hydrophobic region of VANCTs without Pt strongly influences the cell performance,in particular at high current densities.When Pt nanoparticles deposit on the top depth of around 600 nm on VACNTs with a length of 4.6μm,the cell shows the highest performance,compared with others with various lengths of VACNTs.It delivers a maximum power output of 1.61 W cm^(-2)(H_(2)/O_(2),150 k Pa)and 0.79 W cm^(-2)(H_(2)/Air,150 k Pa)at Pt loading of 50μg cm^(-2),exceeding most of previously reported PEMFCs with Pt loading of<100μg cm^(-2).Even though the Pt loading is down to 30μg cm^(-2)(1.36 W cm^(-2)),the performance is also better than 100μg cm^(-2)(1.24 W cm^(-2))of commercial Pt/C,and presents better stability.This excellent performance is critical attributed to the ordered hydrophobic region providing sufficient mass passages to facilitate the fast water drainage at high current densities.This work gives a new understanding for oxygen reduction reaction occurred in VACNTs-based ordered electrodes,demonstrating the most possibility to achieve a substantial reduction in Pt loading<100μg cm^(-2) without sacrificing in performance.
基金supported by NSFC(51422204,51372132)National Basic Research Program of China(2013CB934200)+2 种基金SRFDP(20120002120038)TNLIST Cross-discipline FoundationBNLMS Cross-discipline Foundation
文摘The mechanism for the formation of double-layer vertically aligned carbon nanotube arrays(VACNTs) through single-step CVD growth is investigated. The evolution of the structures and defect concentration of the VACNTs are tracked by scanning electron microscopy(SEM) and Raman spectroscopy. During the growth, the catalyst particles are stayed constantly on the substrate. The precipitation of the second CNT layer happens at around 30 min as proved by SEM.During the growth of the first layer, catalyst nanoparticles are deactivated with the accumulation of amorphous carbon coatings on their surfaces, which leads to the termination of the growth of the first layer CNTs. Then, the catalyst particles are reactivated by the hydrogen in the gas flow, leading to the precipitation of the second CNT layer. The growth of the second CNT layer lifts the amorphous carbon coatings on catalyst particles and substrates. The release of mechanical energy by CNTs provides big enough energy to lift up amorphous carbon flakes on catalyst particles and substrates which finally stay at the interfaces of the two layers simulated by finite element analysis. This study sheds light on the termination mechanism of CNTs during CVD process.
基金Project supported by the National Key Basic Research Program of China (Grant No.2011CB932700)the National Natural Science Foundation of China (Grant Nos.51272279,51072223,and 50972162)
文摘The field emission （FE） properties of vertically aligned graphene sheets （VAGSs） grown on different SiC substrates are reported. The VAGSs grown on nonpolar SiC （10-10） substrate show an ordered alignment with the graphene basal plane-parallel to each other, and show better FE features, with a lower turn-on field and a larger field enhancement factor. The VAGSs grown on polar SiC （000-1 ） substrate reveal a random petaloid-shaped arrangement and stable current emission over 8 hours with a maximum emission current fluctuation of only 4%. The reasons behind the differing FE characteristics of the VAGSs on different SiC substrates are analyzed and discussed.
基金supported by the Henry Royce Institute for Advanced Materials,funded through EPSRC grants EP/R00661X/1,EP/S019367/1,EP/P025021/1,and EP/P025498/1the University of Manchester for the President’s Doctoral Scholar AwardEPSRC for funding through the grants EP/R023034/1 and EP/N032888/1
文摘Conventional electrode preparation techniques of supercapacitors such as tape casting or vacuum filtration often lead to the restacking or agglomeration of twodimensional(2 D)materials.As a result,tortuous paths are created for the electrolyte ions and their adsorption onto the surfaces of the active materials can be prevented.Consequently,maintaining high rate performance while increasing the thickness of electrodes has been a challenge.Herein,a facile freeze-assisted tape-casting(Fa TC)method is reported for the scalable fabrication of flexible MXene(Ti3C2Tx)supercapacitor electrode films of up to 700μm thickness,exhibiting homogeneous ice-template microstructure composed of vertically aligned MXene walls within lamellar pores.The efficient ion transport created by the internal morphology allows for fast electrochemical charge–discharge cycles and near thickness-independent performance at up to 3000 m V s-1 for films of up to 300μm in thickness.By increasing the scan rate from 20 to 10,000 m V s-1,Ti3C2Tx films of 150μm in thickness sustain 50%of its specific capacitance(222.9 F g-1).When the film thickness is doubled to 300μm,its capacitance is still retained by 60%(at 213.3 F g-1)when the scan rate is increased from 20 to3000 m V s-1,with a capacitance retention above 97.7%for over 14,000 cycles at10 A g-1.They also showed a remarkably high gravimetric and areal power density of 150 k W kg-1 at 1000 A g-1 and 667 m W cm-2 at 4444 m A cm-2,respectively.Fa TC has the potential to provide industry with a viable way to fabricate electrodes formed from 2 D materials on a large scale,while providing promising performance for use in a wide range of applications,such as flexible electronics and wearable energy storage devices.
基金supported by Research Universiti Grant,Universiti Putra Malaysia (Project No. RU01154)
文摘Synthesis of carbon nanotubes （CNTs） below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced. In this work, the effects of varying the preheating temperature on the synthesis of CNT were investigated. The reaction temperature was set at 570℃. The preheating set temperature was varied from 150 to 400℃ at 50℃ interval. Three O-ring shape heating mantels were used as heating source for the preheater. In situ monitoring device was used to observe the temperature profile in the reactor. Benzene and ferrocene were used as the carbon source and catalyst precursor, respectively. Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃. When the preheating temperature was increased up to 400℃, both the length and the alignment of CNTs produced were improved.
基金financially supported by the National Natural Science Foundation of China(Nos.52130303,52327802 and 52173078)National Key R&D Program of China(No.2022YFB3805702)。
文摘With the rapid development of high-power-density electronic devices,interface thermal resistance has become a critical barrier for effective heat management in high-performance electronic products.Therefore,there is an urgent demand for advanced thermal interface materials(TIMs)with high cross-plane thermal conductivity and excellent compressibility to withstand increasingly complex operating conditions.To achieve this aim,a promising strategy involves vertically arranging highly thermoconductive graphene on polymers.However,with the currently available methods,achieving a balance between low interfacial thermal resistance,bidirectional high thermal conductivity,and large-scale production is challenging.Herein,we prepared a graphene framework with continuous filler structures in in-plane and cross-plane directions by bonding corrugated graphene to planar graphene paper.The interface interaction between the graphene paper framework and polymer matrix was enhanced via surface functionalization to reduce the interface thermal resistance.The resulting three-dimensional thermal framework endows the polymer composite material with a cross-plane thermal conductivity of 14.4 W·m^(-1)·K^(-1)and in-plane thermal conductivity of 130W·m^(-1)·K^(-1)when the thermal filler loading is 10.1 wt%,with a thermal conductivity enhancement per 1 wt%filler loading of 831%,outperforming various graphene structures as fillers.Given its high thermal conductivity,low contact thermal resistance,and low compressive modulus,the developed highly thermoconductive composite material demonstrates superior performance in TIM testing compared with TFLEX-700,an advanced commercial TIM,effectively solving the interfacial heat transfer issues in electronic systems.This novel filler structure framework also provides a solution for achieving a balance between efficient thermal management and ease of processing.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2021R1A2C1004131 and RS-2024-00406152)supported by the Institute of Information&Communications Technology Planning&Evaluation(IITP)-ITRC(Information Technology Research Center)grant funded by the Korea government(MSIT)(IITP-2025-RS-2023-00258971,20%,and RS-2023-00228994).
文摘The COVID-19 pandemic has exposed the limitations of traditional preventative measures and underscored the essential role of face masks in controlling virus transmission.More effective and recyclable facial masks using various materials have been developed.In this work,vertically aligned carbon nanotubes(VACNTs)are employed as effective facial mask filters,particularly aimed at preventing SARS-CoV-2 virus infection in preparation for future COVID-19 pandemics.This study assesses six critical aspects of facial masks:hydrophobicity,industrial viability,breathability,hyperthermal antiviral effect,toxicity,and reusability.The VACNT alone exhibits superhydrophobicity with a contact angle of 175.53◦,and an average of 142.7◦for a large area on spun-bonded polypropylene.VACNTs are processed using a roll-to-roll method,eliminating the need for adhesives.Due to the aligned tubes,VACNT filters demonstrate exceptional breathability and moisture ventilation compared to previously reported CNT and conventional filters.Hyperthermal tests of VACNT filters under sunlight confirm that up to 99.8%of the HCoV 229E virus denatures even in cold environments.The safety of using VACNTs is corroborated through histopathological evaluation and subcutaneous implantation tests,addressing concerns of respiratory and skin inflammation.VACNT masks efficiently transmit moisture and rapidly return to their initial dry state under sunlight maintaining their properties after 10000 bending cycles.In addition,the unique capability of VACNT filters to function as respiratory sensors,signaling dampness and facilitating reuse,is assessed,alongside their Joule heating effect.
基金supported by the National Natural Science Foundation of China under(No.21878158,2182880,51678291)Jiangsu Natural Science Foundation for Distinguished Young Scholars(No.BK20170043)+3 种基金the National Key R&D Program of China(2018YFB1502903)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)China Postdoctoral Science Foundation(2019M660112)the Jiangsu Postdoctoral Science Funding Project
文摘One of the critical challenges that limit broad commercialization of proton exchange membrane fuel cells(PEMFC)is to reduce the usage of Pt while maintaining high power output and sufficient durability.Herein,a novel bifunctional layer consisting of vertically aligned carbon nanotubes(VACNTs)and nanoparticles of Pt-Co catalysts(Pt-Co/VACNTs)is reported for highperformance PEMFCs.Readily prepared by a two-step process,the Pt-Co/VACNTs layer with a hydrophilic catalyst-loaded side and a hydrophobic gas diffusion side enables a PTFE-free electrode structure with fully exposed catalyst active sites and superior gas–water diffusion capability.When tested in a PEMFC,the bi-functional Pt-Co/VACNTs layer with ultralow Pt loading(~65μgcathodecm-2)demonstrates a power density of 19.5 kW gPt cathode-1 at 0.6 V,more than seven times that of a cell with commercial Pt/C catalyst(2.7 kW gPt cathode-1 at 0.6 V)at a loading of 400μgcathodecm-2 tested under similar conditions.This remarkable design of VACNTs-based catalyst with dual functionalities enables much lower Pt loading,faster mass transport,and higher electrochemical performance and stability.Further,the preparation procedure can be easily scaled up for low-cost fabrication and commercialization.
基金flnancial support by the National Natural Science Foundation of China (52102055, 5227020331, 52075527)National Key R&D Program of China (2017YFB0406000 and 2017YFE0128600)+8 种基金the Project of the Chinese Academy of Sciences (XDC07030100, XDA22020602, ZDKYYQ20200001 and ZDRW-CN-2019-3)CAS Youth Innovation Promotion Association (2020301)Science and Technology Major Project of Ningbo (2021Z120, 2021Z115, 2022Z084, 2018B10046 and 2016S1002)the Natural Science Foundation of Ningbo (2017A610010)Foundation of State Key Laboratory of Solid lubrication (LSL-1912)China Postdoctoral Science Foundation (2020M681965, 2022M713243)National Key Laboratory of Science and Technology on Advanced Composites in Special Environments (6142905192806)K.C. Wong Education Foundation (GJTD-2019-13)the 3315 Program of Ningbo for financial support
文摘Developing advanced thermal interface materials(TIMs)to bridge heat-generating chip and heat sink for constructing an efficient heat transfer interface is the key technology to solve the thermal management issue of high-power semiconductor devices.Based on the ultra-high basal-plane thermal conductivity,graphene is an ideal candidate for preparing high-performance TIMs,preferably to form a vertically aligned structure so that the basal-plane of graphene is consistent with the heat transfer direction of TIM.However,the actual interfacial heat transfer efficiency of currently reported vertically aligned graphene TIMs is far from satisfactory.In addition to the fact that the thermal conductivity of the vertically aligned TIMs can be further improved,another critical factor is the limited actual contact area leading to relatively high contact thermal resistance(20-30 K mm^(2) W^(−1))of the“solid-solid”mating interface formed by the vertical graphene and the rough chip/heat sink.To solve this common problem faced by vertically aligned graphene,in this work,we combined mechanical orientation and surface modification strategy to construct a three-tiered TIM composed of mainly vertically aligned graphene in the middle and micrometer-thick liquid metal as a cap layer on upper and lower surfaces.Based on rational graphene orientation regulation in the middle tier,the resultant graphene-based TIM exhibited an ultra-high thermal conductivity of 176 W m^(−1) K^(−1).Additionally,we demonstrated that the liquid metal cap layer in contact with the chip/heat sink forms a“liquid-solid”mating interface,significantly increasing the effective heat transfer area and giving a low contact thermal con-ductivity of 4-6 K mm^(2) W^(−1) under packaging conditions.This finding provides valuable guidance for the design of high-performance TIMs based on two-dimensional materials and improves the possibility of their practical application in electronic thermal management.
基金This work was supported by the National Natural Science Foundation of China (No. 50228203 and 20425619) and CheungKong Scholar Program.
文摘Carbon nanotubes （CNTs） were prepared using different carrier gases, with ferrocene as the catalyst precusor and acetylene as the carbon source. The effects of ammonia and nitrogen as carrier gases on the structure and morphology of CNTs were investigated. Transmission electron microscope （TEM）, high-resolution electron microscope （HRTEM）, scanning electron microscope （SEM） and X-ray diffraction （XRD） were employed to characterize the products and the catalyst. Experiment results show that the CNTs grown in N2 gas exhibited cylindrical and tubular structure, while a bamboo-like structure was observed for the CNTs grown in NH3 gas. Moreover, vertically aligned CNTs were obtained on an A12O3 disk when NH3 was used as the carrier gas. The carrier gas also exerted influence on the shape of the catalyst. Based on the theory of active centers of catalysis and combined with the particle shape of the catalyst, a growth model for the vertically aligned CNTs on the substrate is given.
基金supported by Shenzhen Science and Technology Program(No.JCYJ20210324133610028)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515012594).
文摘Multi-phase vertically aligned nanocomposite(MP-VAN)thin films represent a promising avenue for achieving complex multifunctionality,exploring novel interfacial phenomena,and enabling complex metamaterial designs and exploration.In this study,a novel self-assembled all-oxides three-phase VAN system was conceptualized and fabricated utilizing pulsed laser deposition(PLD)with a single composite target.Detailed microstructural analysis reveals the presence of three distinct phases:LiNbO_(3),CeO_(2-x),and LiNbCe_(1-x)O_(y)within the MP-VAN films.Subsequently,ferroelectric,dielectric,optical anisotropy,and magnetic properties were systematically investigated to showcase the multifunctionality inherent in these films.This work presents a pioneering approach to designing and realizing MP-VAN systems,and opens up opportunities for tailoring the complex three-dimensional(3D)physical properties and property coupling of VAN films towards diverse device applications.
基金funded by the U.S.Department of Energy,Office of Science,Basic Energy Sciences with award No.DE-SC0020077.
文摘Oxide-metal based nanocomposite thin films have attracted great interests owing to their unique anisotropic structure and physical properties.A wide range of Au-based oxide-metal nanocomposites have been demonstrated,while other metal systems are scarce due to the challenges in the initial nucleation and growth as well as possible interdiffusions of the metallic nanopillars.In this work,a unique anodic aluminum oxide(AAO)template was used to grow a thin Co seed layer and the following self-assembled metal-oxide(Co-BaTiO_(3))vertically aligned nanocomposite thin film layer.The AAO template allows the uniform growth of Co-seeds and successfully deposition of highly ordered Co pillars(with diameter<5 nm and interval between pillars<10 nm)inside the oxide matrix.Significant magnetic anisotropy and strong magneto-optical coupling properties have been observed.A thin Au-BaTiO_(3) template was also later introduced for further enhanced nucleation and ordered growth of the Co-nanopillars.Taking the advantage of such a unique nanostructure,a large out-of-plane(OP)coercive field(Hc)of~5000 Oe has been achieved,making the nanocomposite an ideal candidate for high density perpendicular magnetic tunneling junction(p-MTJ).A strong polar magneto-optical Kerr effect(MOKE)has also been observed which inspires a novel optical-based reading method of the MTJ states.
