Surface coating of multi-walled carbon nanotube nanopaper on shape-memory polymer for multifunctionalization

We are presenting a method of synthesizing three-dimensional self-assembled multi-walled carbon nanotube (MWCNT) nanopaper on hydrophilic polycarbonate membrane. The process is based on the very well-defined dispersion of nanotube and controlled pressure vacuum deposition procedure. The morphology and structure of the nanopaper are characterized with scanning electronic microscopy (SEM) over a wide range of scale sizes. A continuous and compact network observed from the microscopic images indicates that the MWCNT nanopaper could have highly conductive property. As a consequence, the sensing properties of conductive MWCNT nanopaper are characterized by functions of temperature and water content. Meanwhile, in combination with shape-memory polymer (SMP), the conductive MWCNT nanopaper facilitates the actuation in SMP nanocomposite induced by electrically resistive heating. Furthermore, the actuating capability of SMP nanocomposite is utilized to drive up a 5-gram mass from 0 to 30 mm in height.     

Growth of spin-capable multi-walled carbon nanotubes and flexible transparent sheet films

Iron-catalyzed spin-capable multi-walled carbon nanotubes (MWCNTs) were grown on a SiO2 wafer by chemical vapor deposition, which was carried out at 780 degrees C using C2H2 and H2 gases. We fabricated a flexible transparent film using the spun MWCNTs. The MWCNT sheets were produced by being continuously pulled out from well-aligned MWCNTs grown on a substrate. The MWCNT sheet films were manufactured by simply carrying out direct coating on a flexible film or glass. The thickness of the sheet film decreased remarkably when alcohol was sprayed on the surface of the sheet. The alcohol spraying increased the transmittance and decreased the electrical resistance of the MWCNT sheet films. The sheets obtained after alcohol spraying had a resistance of -699 omega and a transmittance of 81%-85%. The MWCNT sheet films were heated by applying direct current. The transparent heaters showed a rapid thermal response and uniform distribution of temperature. In addition, we tested the field emission of the sheet films. The sheet films showed a turn-on voltage of -1.45 V/microm during field emission.     

Low-temperature synthesis of Mn(3)O(4) nanoparticles loaded on multi-walled carbon nanotubes and their application in electrochemical capacitors

A low-temperature, efficient and one-step deposition method, in which Mn(CH(3)COO)(2)·4H(2)O serves as precursor and O(2) as oxidant, was employed to deposit Mn(3)O(4) nanoparticles on multi-walled carbon nanotubes (MWCNTs) in ethanol solution at 150 and 200?°C. The resulting Mn(3)O(4)/MWCNT composites were characterized by means of different techniques including x-ray diffraction, x-ray photoelectron spectroscopy and transmission electron microscopy. It was indicated that the Mn(3)O(4) nanoparticles were attached uniformly on MWCNTs with sizes less than 10?nm, and the loading amount of Mn(3)O(4) could be tuned by changing the initial weight ratio of Mn(CH(3)COO)(2)·4H(2)O/MWCNT. The electrochemical behavior of the Mn(3)O(4)/MWCNT composites was examined by cyclic voltammetry, and the result indicated the specific capacitance of the composite electrode was 330?F?g(-1), nearly 18 times higher than that of the pure MWCNT electrode. The good performance of the as-prepared composites as electrode material may be attributed to the synergistic effects of the Mn(3)O(4) nanoparticles and the MWCNTs.     

An electrothermal carbon nanotube gas sensor

We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor deposition that is accomplished within seconds via real-time electrical feedback control. Vacuum pressure sensitivity and gas species differentiability are observed and analyzed. Such MWCNT electrothermal sensors are compact, fast and reversible in responses, and fully integratable with microelectronics.     

Sponge-like nickel phosphide–carbon nanotube hybrid electrodes for efficient hydrogen evolution over a wide pH range

Cost-effective hydrogen production via electrolysis of water requires efficient and durable earth-abundant catalysts for the hydrogen evolution reaction (HER) over a wide pH range.Herein,we report sponge-like nickel phosphidecarbon nanotube (NixP/CNT) hybrid electrodes that were prepared by facile cyclic voltammetric deposition of amorphous NixP catalysts onto the threedimensional (3D) porous CNT support.These compounds exhibit superior catalytic activity for sustained hydrogen evolution in acidic,neutral,and basic media.In particular,the NixP/CNT electrodes generate cathodic currents of 10 and 100 mA.cm-2 at overpotentials of 105 and 226 mV,respectively,in a 1 M phosphate buffer solution (pH =6.5) with a Tafel slope of 100 mV·dec-1;the currents were stable for over 110 h without obvious decay.Our results suggest that the 3D porous CNT electrode supports could serve as a general platform for earth-abundant HER catalysts for the development of highly efficient electrodes for hydrogen production.     

Rheologic and mechanical properties of multiwalled carbon nanotubes-reinforced poly(trimethylene terephthalate) composites

This paper investigates the rheologic and mechanical properties of melt-blended poly(trimethylene terephthalate) (PTT)/multiwalled carbon nanotube (MWCNT) composites and the effect of acid treatment of MWCNT on these properties. The microstructure of the composites was studied by SEM and TEM in terms of the dispersion state of the nanotubes and the polymer–nanotube interaction. Incorporation of MWCNTs into PTT matrix resulted in an increase in both complex viscosity and moduli than those of neat PTT. A dramatic increase in the melt viscosity of composites observed with loading of MWCNT in the range of 0.5 and 2 wt% showed the formation of interconnected network of MWCNT in the polymer matrix at a rheologic percolation threshold. Acid treatment of MWCNT showed significant effect on the rheologic properties of PTT and led to the enhancement of both complex viscosity and moduli due to strong interfacial interaction between acid-treated MWCNT and PTT matrix. The effect of acid treatment was also evident by mechanical properties of the PTT/MWCNT composites. The untreated MWCNT showed only increase in modulus of PTT matrix; whereas, after acid treatment, both tensile strength and modulus of PTT matrix enhanced significantly.     

粉末粒度对等离子喷涂Al2O3-13%TiO2陶瓷涂层组织结构及性能的影响

等离子喷涂粉末的粒度影响涂层组织结构与性能。选用4种不同粒度的Al2O3-13%TiO2(AT13)粉末等离子喷涂陶瓷涂层,研究了喷涂粉末粒度对涂层组织结构、孔隙率、显微硬度和沉积效率的影响。结果表明:采用较细的喷涂粉末制备的AT13涂层致密、均匀,孔隙率低;随着喷涂粉末粒度增大,涂层的孔隙率增加,显微硬度降低,沉积效率先增后减;采用粒度为38～44μm的粉末喷涂涂层时沉积效率最高,达到51%,涂层组织也较致密,这是等离子喷涂AT13陶瓷层较理想的粒度。     

RGO–MWCNT–ZnO based polypyrrole nanocomposite for ammonia gas sensing

Polypyrrole (PPy) nanocomposites were synthesized using ferric chloride (FeCl₃) as an oxidant by in situ polymerization at room temperature in which reduced graphene oxide- multi-walled carbon nanotubes (RGO–MWCNT) and zinc oxide (ZnO) were used as fillers. RGO–MWCNT and ZnO were synthesized by solution mixing and surfactant assistant precipitation respectively. The RGO–MWCNT–ZnO /PPy nanocomposites were prepared by loading 2, 5, 10 and 20 wt% of RGO–MWCNT:ZnO (1:1) in PPy to measure the electrical conductivity. The PPy nanocomposites were characterized by using FTIR, X-ray diffraction and FESEM. Furthermore, these RGO–MWCNT–ZnO/PPy nanocomposites were investigated to study sensing of ammonia gas at room temperature. The response of 20 wt% loading RGO–MWCNT–ZnO/PPy was observed to be 325% towards 200 ppm of ammonia gas.     

Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming

Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites.     

Effect of milling time,MWCNT content,and annealing temperature on microstructure and hardness of Fe/MWCNT nanocomposites synthesized by high-energy ball milling

Nanocrystalline pure Fe and Fe/MWCNT nanocomposites powders with 0.25, 0.5, 1, and 10 wt% MWCNT contents were synthesized by high-energy ball milling (HEBM). The as-milled powders were cold-compacted and annealed at 400 °C and 600 °C for 1 h in Ar atmosphere. The effect of ball milling on pristine MWCNT and Fe/MWCNT composite powders was also investigated as a function of milling time up to 20 h. The physical properties of MWCNT were imaged by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before and after HEBM. The structural damage of MWCNT as a function of milling time and MWCNT content was studied using Raman spectroscopy. The structural characterization of MWCNT and Fe/MWCNT composites was conducted by X-ray diffraction (XRD) as a function of milling time, MWCNT content, and annealing temperature. The chemical properties of the synthesized composite powders were investigated using X-ray photoelectron spectroscopy (XPS). The microhardness test was performed to assess the effect of milling time, annealing temperature, and MWCNT content on the mechanical properties. The results indicated that after the ball milling process, the structure of MWCNT was destroyed, and the formation of the amorphous carbon phase was observed, which was confirmed by XRD and TEM analyses. In addition, decreased defect and carbon intensity ratios (I_D/I_G) were calculated from the Raman results with longer ball milling processes, which is attributed to the destruction of carbon bonds. The XPS results confirmed the presence of FeC bonds as a result of the formation of carbide phases. A fine dispersion of precipitated carbides determined by TEM is found to promote the grain size stability below 100 nm in the nanocrystalline Fe matrix. The results from the micro-hardness tests showed that Orowan particle strengthening resulting from the carbide formation, as well as grain size hardening, is an important contributor to strengthening in Fe/MWCNT composites.     

Carbon nanotube modification using gum arabic and its effect on the dispersion and tensile properties of carbon nanotubes/epoxy nanocomposites

In this study, the effects of a MWCNT treatment on the dispersion of MWCNTs in aqueous solution and the tensile properties of MWCNT/epoxy nanocomposites were investigated. MWCNTs were treated using acid and gum arabic, and MWCNT/epoxy nanocomposites were fabricated with 0.3 wt.% unmodified, oxidized and gum-treated MWCNTs. The dispersion states of the unmodified, oxidized, and Gum-treated MWCNTs were characterized in distilled water. The tensile strengths and elastic modulus of the three nanocomposites were determined and compared. The results indicated that the gum treatment produced better dispersion of the MWCNTs in distilled water and that gum-treated MWCNT/epoxy nanocomposites had a better tensile strength and elastic modulus than did the unmodified and acid-treated MWCNT/epoxy nanocomposites. Scanning electron microscope examination of the fracture surface showed that the improved tensile properties of the gum-treated MWCNT/epoxy nanocomposites were attributed to the improved dispersion of MWCNTs in the epoxy and to interfacial bonding between nanotubes and the epoxy matrix.     

Human‐Finger Electronics Based on Opposing Humidity‐Resistance Responses in Carbon Nanofilms

Carbon nanomaterials have excellent humidity sensing properties. Here, it is demonstrated that multiwalled carbon‐nanotube (MWCNT)‐ and reduced‐graphene‐oxide (rGO)‐based conductive films have opposite humidity/electrical resistance responses: MWCNTs increase their electrical resistance (positive response) and rGOs decrease their electrical resistance (negative response). The authors propose a new phenomenology that describes a “net”‐like model for MWCNT films and a “scale”‐like model for rGO films to explain these behaviors based on contributions from junction resistances (at interparticle junctions) and intrinsic resistances (of the particles). This phenomenology is accordingly validated via a series of experiments, which complement more classical models based on proton conductivity. To explore the practical applications of the converse humidity/resistance responses, a humidity‐insensitive MWCNT/rGO hybrid conductive films is developed, which has the potential to greatly improve the stability of carbon‐based electrical device to humidity. The authors further investigate the application of such films to human‐finger electronics by fabricating transparent flexible devices consisting of a polyethylene terephthalate substrate equipped with an MWCNT/rGO pattern for gesture recognition, and MWCNT/rGO/MWCNT or rGO/MWCNT/rGO patterns for 3D noncontact sensing, which will be complementary to existing 3D touch technology.     

喷雾热解法制备掺氟氧化锡导电玻璃及其性能

采用喷雾热解法,以四氯化锡和氟化铵为原料、喷瓶为雾化装置,在载玻片上制得氟掺杂二氧化锡(FTO)透明导电薄膜。运用XRD、SEM、紫外-可见分光光度计和四探针测试仪分别对薄膜进行了表征。研究了喷涂次数、衬底温度、前体浓度、掺杂浓度和醇水比对FTO薄膜光电性能的影响。结果表明,当衬底温度为500℃,SnCl4.5H2O浓度为0.81mol/L,NH4F浓度为0.1mol/L,醇水比为8:2,喷涂100次时,薄膜的光电性能较好,其方块电阻为13Ω/□,平均透光率为79%。     

Fabrication and Application of Ruthenium-Doped Titanium Dioxide Films as Electrode Material for Ion-Sensitive Extended-Gate FETs

A novel ruthenium-doped titanium dioxide (TiO $_{2}$: Ru) film for pH detection is based on an ion-sensitive extended gate field effect transistor (ISEGFET) sensor. For the preparation of the TiO$_{2}$ : Ru sensing film, a specific processing for metal modification of TiO$_{2}$ thin film is deposited by a co-sputtering system. After thermal annealing treatment, material analysis of the sensing layer is measured by SEM, Hall measurement system and electrical detection system. The average sensitivity of TiO$_{2}$: Ru for hydrogen ion detection is about 55.20 mV/pH (concentration range between pH1 and pH13). The effect of long-term drift for TiO$_{2}$ : Ru ISEGFET-based sensor is presented. Drift rate of the sensor for pH is 0.745 mV/h for 12 h. In order to prepare the calcium ion sensor, the sensing membrane of polymer materials is based on TiO $_{2}$: Ru ISEGFET-based sensor by physical adsorption. The average sensitivity of the calcium ion sensor in the concentration ranging between 1 M and 1$,times,$ 10$^{-3}$ M CaCl$_{2}$ is about 29.65 mV/pCa.      

Application of alkali metal-doped carbons for hydrogen recovery and isotope separation

Hydrogen-sorption isotherms of alkali metal-doped carbons at 77 K were determined for promoting application of these materials as hydrogen-recovery and isotope-separation agent. The hydrogen-sorption behavior of rubidium-doped Grafoil, with composition of RbC24, showed high sorption ability against hydrogen at low pressure. Taking into account the fact that sorption-desorption was fast and reversible, and the equilibrium pressure at half coverage was very low, i.e., 40 Pa, RbC24 prepared from Grafoil is promising as a recovery agent for hydrogen gas at low pressure. The hydrogen (H2)/deuterium(D2)-sorption isotherms of potassium-doped carbons with composition of KC10, prepared from multi wall carbon nanotube (MWCNT) and carbons derived from petroleum cokes with heat-treatment temperatures of 1000 and 1500 degrees C, were also determined. Isotope separation coefficient was estimated from those isotherms. A very large isotope effect was found for KC10 prepared from MWCNT, comparable to those prepared from carbons with heat-treatment temperatures of 1000 or 1500 degrees C. However, a severe problem was found for KC10 (MWCNT) that repetition of the sorption-desorption cycles resulted in the decrease of the sorbed amount of H2 and D2.     

Preparation of a MWCNT/ZnO nanocomposite and its photocatalytic activity for the removal of cyanide from water using a laser

Nano-zinc oxide (n-ZnO) was loaded onto multi-walled carbon nanotubes (MWCNTs) via a hydrothermal process. Here pure n-ZnO used for loading was synthesized by the pulsed-laser ablation technique while MWCNTs were used as received. The synthesized MWCNT/ZnO nanocomposites were characterized using x-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy and Fourier transform infrared spectrometry. A model has been proposed for the structural nature of the alignment of ZnO on the surface of MWCNTs. The photocatalytic activity in the removal of highly toxic substances like cyanide (CN) was carried out in a special reactor using pulsed 355 nm UV generated by the third harmonic of an Nd:YAG laser. In order to understand the cyanide removal process, the study was carried out at different laser irradiation times, incident laser energies, pH of the solution and dosage of the MWCNT/ZnO nanocomposite. The study demonstrated that the CN removal process by MWCNT/ZnO composite has higher photocatalytic activity than pure n-ZnO and MWCNTs alone. The mechanism for the degradation using MWCNT/ZnO has been schematically explained. It was noticed that the oxidation process activity is affected by the pH of the solution, and after 20 min of UV laser irradiation, approximately 90% of CN had been degraded.     

(hfac)Cu(I)(MP) (hfac=hexafluoroacetylacetonate, MP=4-methyl-1-pentene) and (hfac)Cu(I)(DMB) (DMB=3,3-dimethyl-1-butene) for the chemical vapor deposition of copper film

New organometallic precursors for the metal organic chemical vapor deposition (MOCVD) of copper, (hfac)Cu(I)(MP) (hfac=hexafluoroacetylacetonate, MP=4-methyl-1-pentene) and (hfac)Cu(I)(DMB) (DMB=3,3-dimethyl-1-butene) were studied. Copper films could be deposited at the precursor vaporization temperature of 45 and 35°C. The deposition rate was about four to seven times higher than previously reported precursors such as (hfac)Cu(VTMS) (VTMS=vinyltrimethylsilane), (hfac)Cu(ATMS) (ATMS=allyltrimethylsilane) and (hfac)Cu(VCH) (VCH=vinylcyclohexane). The copper films deposited from these two precursors had a resistivity of about 2.0 μΩ cm in the deposition temperature range of 150 to 200°C.     

Supercritical fluid deposition of vanadium oxide on multi-walled carbon nanotube buckypaper for supercapacitor electrode application

Composite electrodes were fabricated for supercapacitor applications by depositing vanadium oxide onto multi-walled carbon nanotube (MWCNT) buckypaper using supercritical fluid deposition (SFD). The deposited thin vanadium oxide layer showed amorphous structure with excellent uniformity. In aqueous KCl electrolyte, the vanadium oxide exhibited a constant pseudo-capacitance of ～ 1024 F g(-1), which was independent of the oxide material loading (up to 6.92 wt%) and voltage scan rate (up to 100 mV s(-1)). The highest specific electrode capacitance achieved was ～ 85 F g(-1), which was almost four times that of the pristine buckypaper electrode.     

A novel structure for carbon nanotube reinforced alumina composites with improved mechanical properties

Engineering ceramics have high stiffness, excellent thermostability, and relatively low density, but their brittleness impedes their use as structural materials. Incorporating carbon nanotubes (CNTs) into a brittle ceramic might be expected to provide CNT/ceramic composites with both high toughness and high temperature stability. Until now, however, materials fabrication difficulties have limited research on CNT/ceramic composites. The mechanical failure of CNT/ceramic composites reported previously is primarily attributed to poor CNT-matrix connectivity and severe phase segregation. Here we show that a novel processing approach based on the precursor method can diminish the phase segregation of multi-walled carbon nanotubes (MWCNTs), and render MWCNT/alumina composites highly homogeneous. The MWCNTs used in this study are modified with an acid treatment. Combined with a mechanical interlock induced by the chemically modified MWCNTs, this approach leads to improved mechanical properties. Mechanical measurements reveal that only 0.9?vol% acid-treated MWCNT addition results in?27% and?25% simultaneous increases in bending strength (689.6 ± 29.1?MPa) and fracture toughness (5.90 ± 0.27?MPa?m(1/2)), respectively.     

Coating and filling of carbon nanotubes with homogeneous magnetic nanoparticles

Magnetic multi-walled carbon nanotube (MWCNT) composites were obtained by decoration of metal oxide nanoparticles on or in carbon nanotubes. The method involved the dispersion of the carbon nanotubes in iron pentacarbonyl Fe(CO)₅ followed by vacuum thermolysis and subsequent oxidation. The magnetic iron oxide particle deposition was always homogeneous and could be controlled selectively on the outer, inner, or both surfaces of MWCNTs by using different MWCNTs. Since the hollow channels remained intact, these MWCNT based composites could find special applications in cellular delivery systems.