Field Emission from a Mixture of Amorphous Carbon and Carbon Nanotubes Films

A mixture of amorphous carbon and carbon nanotubes films was synthesized on stainless steel plates by a micro- wave plasma enhanced chemical vapor deposition system. The source gases were hydrogen and methane with flow rates of 100 and 16sccm,respectively,with a total pressure of 5.0kPa. The surface morphology and the structure of the films were characterized by field emission scanning electron microscopy （SEM） and Raman scattering spectroscopy. Field emission properties of as-deposited film were measured in a vacuum room below 5 ×10^ 5 Pa. The experimental results show that the initial turn-on field is 0. 9V/μm; The current density is 4.0mA/cm2 and the emission sites are dense and uniform at an electric field of 3.7V/μm. These results indicate that such a mixture of amorphous carbon and carbon nanotubes films is a promising material for field emission applications.

Multifunctional MXene/Carbon Nanotube Janus Film for Electromagnetic Shielding and Infrared Shielding/Detection in Harsh Environments

Multifunctional,flexible,and robust thin films capable of operating in demanding harsh temperature environments are crucial for various cutting-edge applications.This study presents a multifunctional Janus film integrating highly-crystalline Ti_(3)C_(2)T_(x) MXene and mechanically-robust carbon nanotube(CNT)film through strong hydrogen bonding.The hybrid film not only exhibits high electrical conductivity(4250 S cm^(-1)),but also demonstrates robust mechanical strength and durability in both extremely low and high temperature environments,showing exceptional resistance to thermal shock.This hybrid Janus film of 15μm thickness reveals remarkable multifunctionality,including efficient electromagnetic shielding effectiveness of 72 dB in X band frequency range,excellent infrared(IR)shielding capability with an average emissivity of 0.09(a minimal value of 0.02),superior thermal camouflage performance over a wide temperature range(−1 to 300℃)achieving a notable reduction in the radiated temperature by 243℃ against a background temperature of 300℃,and outstanding IR detection capability characterized by a 44%increase in resistance when exposed to 250 W IR radiation.This multifunctional MXene/CNT Janus film offers a feasible solution for electromagnetic shielding and IR shielding/detection under challenging conditions.

Observation of 550 MHz passively harmonic mode-locked pulses at L-band in an Er-doped fiber laser using carbon nanotubes film

We demonstrate a passively harmonic mode-locked（PHML） fiber laser operating at the L-band using carbon nanotubes polyvinyl alcohol（CNTs-PVA） film. Under suitable pump power and an appropriate setting of the polarization controller（PC）, the 54^（th） harmonic pulses at the L-band are generated with the side mode suppression ratio（SMSR） better than 44 dB and a repetition frequency of 503.37 MHz. Further increasing the pump power leads to a higher frequency of 550 MHz with compromised stability of 38.5 dB SMSR. To the best of our knowledge, this is the first demonstration on the generation of L-band PHML pulses from an Er-doped fiber laser based on CNTs.

Wide temperature range,air stable,transparent,and self-powered photodetectors enabled by a hybrid film of graphene and singlewalled carbon nanotubes

Transparent photovoltaic devices(TPVDs)have attracted increasing attention in emerging electronic devices.As the application scenarios extend,there raise higher requirements regarding the stability and operating temperature range of TPVDs.In this work,a unique preparation strategy is proposed for air stable TPVD with a wide operating temperature range,i.e.,a nanoscale architecture termed as H-TPVD is constructed that integrates a free-standing and highly transparent conductive hybrid film of graphene and single-walled carbon nanotubes(G-SWNT TCF for short)with a metal oxide NiO/TiO_(2)heterojunction.The preparation approach is suitable for scaling up.Thanks to the excellent transparent conductivity of the freestanding G-SWNT hybrid film and the ultrathin NiO/TiO_(2)heterojunction(100 nm),H-TPVD selectively absorbs the ultraviolet(UV)band of sunlight and has a transparency of up to 71%in the visible light.The integrated nanoscale architecture manifests the significant holecollecting capability of the G-SWNT hybrid film and the efficient carrier generation and separation within the ultrathin NiO/TiO_(2)heterojunction,resulting in excellent performance of the H-TPVD with a specific detectivity of 2.7×10^(10) Jones.Especially,the freestanding G-SWNT TCF is a super stable and non-porous two-dimensional film that can insulate gas molecules,thereby protecting the surface properties of NiO/TiO_(2)heterojunctions and enhancing the stability of H-TPVD.Having subjected to 20,000 cycles and storage in air for three months,the performance parameters such as photo-response signal,output power,and specific detectivity show no noticeable degradation.In particular,the as-fabricated self-powered H-TPVD can operate over a wide temperature range from −180 to 300℃,and can carry out solar-blind UV optical communication in this range.In addition,the 4×4 array H-TPVD demonstrates clear optical imaging.These results make it possible for H-TPVD to expand its potential application scenarios.

A flexible carbon nanotube@V_(2)O_(5) film as a high-capacity and durable cathode for zinc ion batteries

Aqueous zinc-ion batteries(ZIBs)are receiving a continuously increasing attention for mobile devices,especially for the flexible and wearable electronics,due to their non-toxicity,non-flammability,and low-cost features.Despite the significant progress in achieving higher capacities for electrode materials of ZIBs,to endow them with high flexibility and economic feasibility is,however,still a significant challenge remaining unsolved.Herein,we present a highly flexible composite film composed of carbon nanotube film and V_(2)O_(5)(CNTF@V_(2)O_(5))with high strength and high conductivity,which is prepared by simply impregnating a porous CNT film with an aqueous V_(2)O_(5)sol under vacuum.For this material,intimate incorporation between V_(2)O_(5)and CNTs has been achieved,successfully integrating the high zinc ion storage capability with high mechanical flexibility.As a result,this CNTF@V_(2)O_(5)film delivers a high capacity of 356.6 m Ah g^(-1)at 0.4 A g^(-1)and excellent cycling stability with 80.1%capacity retention after 500 cycles at 2.0 A g^(-1).The novel strategy and the outstanding battery performance presented in this work should shed light on the development of high-performance and flexible ZIBs.

A general surface-treatment-free approach to fabrication of alignment layers using a super-aligned carbon nanotube film template

We develop a general approach to the fabrication of films with unidirectional grooves, such as silicon nitride, silicon dioxide and aluminium oxide, in which the surface is not required to be treated. Super-aligned carbon nanotube （SACNT） film may be used as a template and as sacrificial layer, which is subsequently removed by heating in an atmosphere of air. The unidirectional morphology of the SACNT film turns into a desired film, which is found to possess the ability to align liquid crystal molecules. This approach also features high efficiency, low cost and easy scaling-up for mass production.

Tensile and Electro-Mechanical Properties of Carbon Nanotube Film Twisted Yarn with Adjustable Diameter

Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).

Highly efficient and wearable thermoelectric composites based on carbon nanotube film/polyaniline

Polyaniline(PANI)was prepared by in-situ polymerization and compounded on the two-dimensional network structural multi-walled carbon nanotube film(CNTF).Compared with the CNT/PANI composites fabricated by using CNT powders or dispersions,the compact and continuous network structure of CNTF/PANI is beneficial to both the thermoelectric and mechanical properties of the composites.The resultant CNTF/PANI composites with PANI polymerization time of 5 h obtain an electrical conductivity of 1338.4 S/cm and Seebeck coefficient of 63.3μV/K at 360 K,which are 168.7%and 5.7%higher than those of the CNTF(498.1 S/cm and 59.9μV/K at 360 K).Consequently,a maximum power factor of 536.8μW·m^(−1)·K^(−2) at 360 K is acquired,which is about 2 times higher than that of CNTF(181.7μW·m^(−1)·K^(−2) at 360 K).The electrical conductivity of the composites could maintain 93.3%after being bent for 500 times,indicating the excellent flexibility.The tensile strength,Young's Modulus and toughness of CNTF/PANI composites(232.3 MPa,3.6 GPa and 20.1 MJ/m^(3),respectively)are 3.5,2.6 and 2.1 times of those of the CNTF.The flexible,free-standing,lightweight and high-strength CNTF/PANI composites reveal the excellent thermoelectric performance,which are promising in the applications in wearable thermoelectric devices.

Minimizing Purifi cation-Induced Defects in Single-Walled Carbon Nanotubes Gives Films with Improved Conductivity

A method for the non-destructive purification of single-walled carbon nanotubes(SWNTs)using classical coordination chemistry to remove the metal catalyst has been developed.In preliminary tests,the conductivity of films based on the resulting SWNTs was markedly better than that of films prepared from SWNTs purified by treatment with oxidizing acid solutions.The transparent and conducting SWNT films have potential applications in optoelectronic devices.

Preparation of carbon nanotube films towards mechanical and electrochemical energy storage

Due to unique and excellent properties,carbon nanotubes(CNTs)are expected to become the next-generation critical engineering mechanical and energy storage materials,which will play a key role as building blocks in aerospace,military equipment,communication sensing,and other cutting-edge fields.For practical application,the assembled macrostructures from individual CNTs are the common paradigms such as fibers or films.As the main representative,CNT films can not only retain the unique properties of their CNTs components,but also are more likely for mass-production than other macrostructures.Therefore,in this review,we focus on preparation of CNT films and discuss their emerging applications in the field of mechanical and electrochemical energy storage/conversion.Firstly,different preparation processes are systematically summarized.Then we introduce some typical strategies to improve their mechanical performances besides strengthening mechanism.Based on the progress of mass-production and performance optimization,we further discuss their potential utilization in mechanical and electrochemical energy storage/conversion devices.Finally,future perspectives for the development of CNT films in both production and application are proposed.We hope that this review will shed light on the preparation/assembly of CNT films and integrated application of excellent properties from individual to macroscopic dimensions.Moreover,the preparation and cross-scale application paradigms of CNT films also offer a good model for other macroscopic ordered assemblies of one-dimensional nanomaterials.

Growth of carbon nanotube arrays on various CtxMey alloy films by chemical vapour deposition method

Carbon nanotube （CNT） arrays were fabricated on Ct-Me-N-（O） alloys with content of Ct in the range of 6-40 at.% by chemical vapour deposition. The Ct was a catalytic metal from the group of the following elements： Ni, Co, Fe, Pd, while Me was a transition metal from the group of IV-VII of the periodic table （where Me=Ti, V, Cr, Zr, Nb, Mo, Ta, W, Re）. Carbon nanotubes were found to grow efficiently on the alloy surface with its composition containing Ti, V, Cr, Zr, Hf, Nb or Ta. The growth of CNTs was not observed when the alloy contained W or Re. Additions of oxygen and nitrogen in the alloy facilitated the formation of oxynitrides and catalyst extrusion on the alloy surface. Replacement of the metals in alloy composition affected the diameter of the resulting CNTs. The obtained results showed that the alloy films of varying thickness （10-500 nm） may be used for the CNTs growth. The resulting CNT material was highly homogenous and its synthesis reproducible.

Synthesis and field emission properties of carbon nanotube films modified with amorphous carbon nanoparticles by a simple electrodeposition method

Amorphous carbon nanoparticles （a-CNPs） on a multi-walled carbon nanotube （MWCNT） film, deposited on a silicon substrate, were synthesized using an electrodeposition combination from a methanol suspension of polydiallyldimethylammonium chloride-modified MWCNTs. A low-voltage electropho- retic deposition of the MWCNTs and a high-voltage electrochemical deposition of the a-CNPs were carried out to yield homogenously attached a-CNPs on the surfaces of the MWCNTs, and form a composite film with good adhesion to the substrate. This scalable technology can produce a large area of a-CNP/MWCNT film. And the field emission investigations show that the a-CNP/MWCNT film has turn- on electric field of 3.17 V μm- 1 （at 10 μA cm-2） and threshold field of 4.62 V μm-1 （at 1 mA cm-2）, which are lower than those of the MWCNT film. The a-CNP/MWCNT film can be deposited simply with large areas and may be a promising cathode material applied in field emission displays.

Preparation and thermal properties of layered porous carbon nanotube/epoxy resin composite films

A floating-catalyst spray pyrolysis method was used to synthesize carbon nanotube(CNT)thin films.With the use of ammonium chloride as a pore-former and epoxy resin(EP)as an adhesive,CNT/EP composite films with a porous structure were prepared through the post-heat treatment.These films have excellent thermal insulation(0.029–0.048 W·m^−1·K^−1)at the thickness direction as well as a good thermal conductivity(40–60 Wm^−1·K^−1)in the film plane.This study provides a new film material for thermal control systems that demand a good thermal conductivity in the plane but outstanding thermal insulation at the thickness direction.

Recent progress of photodetector based on carbon nanotube film and application in optoelectronic integration

Due to its remarkable electrical and optical capabilities,optoelectronic devices based on the semiconducting single-walled carbon nanotube(s-SWCNT)have been studied extensively in the last two decades.First,s-SWCNT is a direct bandgap semiconductor with a high infrared absorption coefficient and high electron/hole mobility.In addition,as a typical one-dimensional material,there is no lattice mismatch between s-SWCNT and any substrates.Another advantage is that the optoelectronic devices of s-SWCNT can be processed at low temperatures.s-SWCNT has intriguing potential and applications in solar cells,light-emitting diodes(LEDs),photodetectors,and three-dimensional(3D)optoelectronic integration.In recent years,along with the advancement of solution purification technology,the high-purity s-SWCNTs film has laid the foundation for constructing large-area,homogenous,and high-performance optoelectronic devices.In this review,optoelectronic devices based on s-SWCNTs film and related topics are reviewed,including the preparation of high purity s-SWCNTs film,the progress of photodetectors based on the s-SWCNTs film,and challenges of s-SWCNTs film photodetectors.

Low-Voltage Activating, Fast Responding Electro-thermal Actuator Based on Carbon Nanotube Film/PDMS Composites

The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle and aerospace component.In this study,to build a low-voltage activating,fast responding ETA,a robust and flexible carbon nanotube film(CNTF)with excellent electrical and thermal conductivity was adopted as the conductive material.Then,an asymmetric bilayer structured ETA was manufactured by coating a thin layer of polydimethylsiloxane(PDMS)with high coefficient of thermal expansion(9.3×10^(-4)℃^(−1)),low young’s modulus(2.07 MPa)on a thin CNTF(~11μm).The as-produced CNTF/PDMS composite ETA exhibited a large deformation(bending angle~324°)and high electro heating performance(351℃)at a low driving voltage of 8 V within~12 s.The actuated movement and the generated heat could be controlled by adjusting the driving voltages and showed almost the same values in 20 cycles.Furthermore,the influences of the PDMS thickness and driving voltage on CNTF/PDMS composite ETA performance were systematically investigated.The CNTF/PDMS soft robotic hand which can lift 5.1 times and crab 1.3 times of its weight demonstrated its potential capability.

Midinfrared optical frequency comb based on difference frequency generation using high repetition rate Er-doped fiber laser with single wall carbon nanotube film

We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161 MHz high repetition rate fiber laser using a single wall carbon nanotube was fabricated. The output pulse was amplified in an Er-doped single mode fiber amplifier, and a 1.1–2.2 μm wideband supercontinuum(SC) with an average power of 205 m W was generated in highly nonlinear fiber. The spectrogram of the generated SC was examined both experimentally and numerically. The generated SC was focused into a nonlinear crystal, and stable generation of MIR comb around the 3 μm wavelength region was realized.

Novel Photodetectors Based on Double-Walled Carbon Nanotube Film/TiO2 Nanotube Array Heterodimensional Contacts

A new kind of photodetector based on a double-walled carbon nanotube （DWCNT） film and a TiO2 nanotube array with hetrodimensional non-ohmic contacts has been fabricated. Due to the dimensionality difference effect, the DWCNT film/TiO2 nanotube array photodetector exhibits a much higher photocurrent-to-dark current ratio and photoresponse relative to an Au film/TiO2 nanotube array device, even at small bias voltage. The photocurrent-to-dark current ratio reached four orders of magnitude and a high photoresponse of 2467 A/W was found upon irradiation at 340 nm. Furthermore, the photosensitive regions could be extended into the visible range. The photocurrent-to-dark current ratio reached approximately three orders of magnitude upon irradiation at 532 nm, where the photon energy is much lower than the band gap of TiO2.

Fabrication of free-standing flexible and highly efficient carbon nanotube film/PEDOT: PSS thermoelectric composites

Carbon nanotube film(CNTF)with two-dimensional CNT network structure is adopted to prepare CNTF/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)thermoelectric composites,which overcomes the disadvantages of low content,easy aggregation,and random orientation of CNTs when dispersed in polymer.A vacuum-assisted filtration method was proposed,which can uniformly and sufficiently penetrate the polymer into CNTF along thickness direction for fabrication of CNTF/PEDOT:PSS composites.A highest electrical conductivity of 806.2 S/cm at 300 K was achieved for the composites with 60 wt%PEDOT:PSS loading,which was 51.0%higher than that of the original CNTF(534.1 S/cm).A maximum power factor of 339.6 mW·m^(-1)·K^(-2) at 320 K was achieved with a corresponding Seebeck coefficient of 67.7 mV/K.This study provides a universal method for fabrication of other kinds of CNTF/conductive polymer thermoelectric composites.

Amorphous carbon-linked TiO_(2)/carbon nanotube film composite with enhanced photocatalytic performance:The effect of interface contact and hydrophilicity

Carbon nanotube film(CNTF)can be used for photocatalysis and water treatment due to its porous structure,good stability and excellent electrical properties.In this work,TiO_(2)/amorphous carbon/carbon nanotube film(TCC)composite with uniform structure was prepared by a simple atomization spraying method.Rhodamine B(RhB)was used to test the photocatalytic activity of TCC.TCC composite exhibits good photocatalytic activity under ultraviolet light.In particular,the degradation efficiency of rhodamine B(RhB)by TCC sprayed with 9 layers of TiO_(2)(9 TCC)increased by 1.45 times than of TiO_(2) under ultraviolet light.The enhanced photocatalytic activity of TCC is attributed to the CNTF,which can broaden the light response range of TCC and improve the migration efficiency of electrons.The existence of amorphous carbon will promote these advances.Moreover,the better hydrophilic properties would enhance the catalytic performance happened on the solid-liquid interface.Finally,the photocatalytic mechanism and degradation intermediates of the TCC composite were proposed.

Carbon Nanotube Film Loudspeakers

A new kind of flexible, stretchable, and transparent loudspeaker made with carbon nanotube （CNT） film was invented by a team led by Professor Fan Shoufan and Associate Professor Jiang Kaili from Tsinghua＇s Department of Physics.