Search

Field emission (FE) devices are advanced lighting devices that have a 2-D planar configuration, different from the 0-D (dot) and 1-D (line) configurations of light-emitting diode (LED) and fluorescent lighting, respectively. The purpose of this study is to develop a FE lighting device with a lateral-cathode triode. Carbon nanotubes (CNTs) are used as emitters and ZnS particles are used as a green phosphor. The materials were screen-printed onto two soda lime glass substrates. To increase the device lifetime and performance, we applied pulsewidth modulation (PWM) to the gate electrode. A high luminance of 12 690 cd/m2 and a good luminance uniformity of 84% were achieved for a lighting device with a lateral-cathode structure. [ABSTRACT FROM AUTHOR]

• The bifunctional electrocatalyst, Ni(OH) 2 -CNT-Co 3 O 4 /NC, with good ORR and OER performance was prepared by thermal processes of ZIF-67@ZIF-8 and CBD. • The synergistic effect of the Ni(OH) 2 , Co 3 O 4 , N-doping in the catalyst showed high activities compared to the Pt/C and Ir/C catalyst. • The porous and graphitized carbon framework and CNTs in the catalyst are important for the electron conductivity and ion diffusion. • The Zn-air battery with the electrocatalyst demonstrated a high specific capacity of 805.4 mAh g−1 and energy density of 1021.7 Wh Kg−1. • The charge-discharge tests showed a very stable potential gap (0.65 V) with an excellent retention of 94.5% after 4500 cycles at 10 mA cm−2. A rechargeable zinc-air battery (RZAB) is a hopeful alternative battery solution to meet the world's ever-increasing energy storage need. Developing a high-performance electrocatalyst is one of the most critical challenges that need to be addressed for the RZAB to fulfill that role. A Ni(OH) 2 -CNT-Co 3 O 4 /NC catalyst consisting of carbon nanotube (CNT), cobalt oxide, and nitrogen-doped functionalities embedded in a porous carbon framework with two-dimensional Ni(OH) 2 nanosheets is reported. The prepared catalytic material, Ni(OH) 2 -CNT-Co 3 O 4 /NC, showed a high limit current density of -6.409 mA cm−2 during the oxygen reduction reaction (ORR), surpassing that of the commercial Pt/C (-5.625 mA cm−2). The oxygen evolution reaction (OER) potential for this electrocatalyst also reached 1.653 V at a current density of 10 mA cm−2, which is close to that of the commercial RuO 2 and thus showed excellent catalytic activity for the OER. As a bifunctional catalyst in the RZAB, the Ni(OH) 2 -CNT-Co 3 O 4 /NC electrocatalyst exhibited a high power density of 244.5 mW cm−2, and cycled 4500 times at a current density of 10 mA cm−2 while displaying good charge and discharge stability. Based upon these performances, we believe that the Ni(OH) 2 -CNT-Co 3 O 4 /NC catalyst can serve as an excellent bifunctional catalyst in the next-generation RZAB. [Display omitted] [ABSTRACT FROM AUTHOR]

A double-sided light source based on field emission (FE) using an alternating current (ac) power source is demonstrated. Electrode plates acted as cathode or anode consisting an indium tin oxide glass, a screen-printed ZnS phosphor layer and urchin-like \alpha\-Fe2O3 emitters coated on the layer. Two pieces of the plates were assembled together with the coated surfaces facing each other to make a parallel-plate, diode-structure FE device with a gap distance of 300 \mum. The 1-cm^2 device shows a double-sided luminance distribution with a turn-on field of 2.2 V/\mum, 90.23% uniformity and a maximum luminance of 8750 cd/m^2 at 2 kV. The novel structure and ac model operation provide a double-sided luminance, high brightness, antiarcing, good thermal management, and long lifetime. [ABSTRACT FROM PUBLISHER]

Abstract: The synthesis of tapered carbon nanotubes (TCNTs) by the thermal decomposition of poly(ethylene glycol) at 800°C using Ni as a catalyst is reported. The TCNTs consist of a 50nm diameter graphite tube terminated by a tapered tip, which is about 1μm in length and 20nm in diameter in the tip end. The catalyst particle contained in the tapered tip was found to be a cylindrical with a diameter of about 20nm. Electron microscopy revealed that the catalyst was a single crystal of NiCx and the graphene layers were grown in the [110] direction of the catalyst, forming TCNTs. The unique morphology of the catalyst particle played an important role in the formation of TCNTs. The field emission properties of the TCNTs exhibited a lower turn-on voltage (Eturn-on =3.2V/μm), lower threshold fields voltage (Ethreshold =5.2V/μm) and higher field-enhancement factor β than did multi-walled CNTs. [Copyright &y& Elsevier]

Abstract: Silicon carbide nanowires (SiCNWs) were synthesized in large quantity using a thermal process with carbon nanotube (CNT)/Si–SiO2 (carbon nanotubes grown on Si–SiO2 core–shell substrates) at 1300°C in an argon atmosphere. The characterization shows that the SiCNWs covered with a thin layer of amorphous SiO2 had diameters of 30–70nm and lengths of 4–10μm. The growth mechanism of the SiCNWs is proposed to be the combination of the chemical vapor deposition (CVD) method and the CNTs confined reaction method. According to the Kubelka–Munk plot, the band gap energy for the SiCNWs was 2.8eV. The Mott–Schottky plot shows that the flat-band potential of the SiCNWs was −0.46V versus NHE and that the material exhibited n-type conductivity. The photoluminescence analysis of the SiCNWs revealed two wide bands of emission peaks centered at about 390 and 470nm (CIE value: x=0.18, y=0.24). [Copyright &y& Elsevier]

We report on a 20–40 s process for growing aligned, uniformed, high purity multi-walled carbon nanotubes (MWNTs) using an alcohol lamp burner. With an appropriate catalyst precursor concentration, MWNTs can be grown on a Co-coated 304 stainless steel mesh under incomplete combustion conditions at 680–700°C. The process provides a rapid, easy, economic and safe method for the formation of carbon nanotubes. We suggest that the proposed method be considered as an educational kit for college or high school level experiments. [ABSTRACT FROM AUTHOR]

Abstract: The fabrication of carbon nanocapsules and carbon nanotubes (CNTs) using an acetylene flame method was investigated. Carbon nanocapsules, a graphitic structure of nanoparticles with a hollow core, were synthesized using catalyst-free acetylene flames while CNTs were formed with the presence of cobalt-based catalysts in addition to acetylene flames. When the synthesis of these materials was carried out, the results showed that a massive amount of high-purity carbon nanocapsules with a particle size in the range of 15–30nm can be produced with the acetylene flame method. The CNTs produced were multi-walled carbon nanotubes measuring a few micrometers in length and 20–30nm in diameter. The acetylene flame method holds great potential for the cost-effective production of CNTs as well as carbon nanocapsules. [Copyright &y& Elsevier]

Lithium-oxygen batteries (LOBs) promise high energy density but suffer from catalyst-related issues. We've developed FeNi-NCNT/DrGO, a novel catalyst, by integrating iron-nickel nanoalloys (FeNi) embedded in nitrogen-doped carbon nanotubes (NCNTs) grafted onto defect-rich reduced graphene oxide (DrGO). The fabrication involved freeze-drying, defect engineering, and thermal treatments. The FeNi nanoalloy within the catalyst demonstrates outstanding bifunctional activity, while the NCNTs serve as an excellent electronic conduction medium and DrGO enables favorable ion transport. The 3D open-space architecture of this catalyst provides a rapid diffusion path for the electrolyte and room for accommodating discharge products. As a result, the LOBs with FeNi-NCNT/DrGO exhibits exceptional electrochemical performance, achieving a deep discharge capacity of 21,153.6 mAh g−1 and a high round-trip efficiency of 98.7% at 200 mA g−1. Moreover, it demonstrates excellent cycling stability, exceeding 100 cycles at 200 mA g−1 with a cut-off capacity of 500 mAh g−1. [Display omitted] • FeNi-NCNT/DrGO was formed by freeze-drying, ball milling, and thermal treatment. • The catalyst shows superior ORR, OER, conductivity, ion diffusion and Li 2 O 2 storage. • LOB with the catalyst shows a capacity of 21153 mAhg−1 and 98.74% efficiency. • LOB exceeds 100 cycles at 200 mA g−1 with a cut-off capacity of 500 mAh g−1. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable Zn-ion batteries (ARZIB) are promising candidates for next-generation batteries because of their high safety, low cost, and relatively high capacity. In this study, we developed hydrated and potassium-doped manganese dioxide (MO) nanowires mixed with carbon nanotubes (CNT) on a graphene substrate (hydrated KMO-CNT/graphene) for ARZIB. A simple polyol process using poly(ethyl glycol), KMnO 4 , CNT, and graphene was utilized to fabricate hydrated KMO-CNT/graphene. MnO 2 nanowires with diameters of 15–25 nm possess a high specific capacity with a short diffusion path. The intercalated K ions and hydrates in the layered MnO 2 nanowires maintained the MO structure during the charge and discharge processes, whereas carbon nanomaterials (CNT and graphene) enhanced the conductivity of the material. Consequently, hydrated KMO-CNT/graphene demonstrated good ARZIB performance. A high capacity of 359.8 mAh g–1 at 0.1 A g–1, and at a high current density of 3.0 A g–1, a capacity of 129 mAh g–1 with 77% retention after 1000 cycles, were achieved. • Hydrated and potassium-doped MnO 2 mixed with CNT on graphene substrate is synthesized. • Polyol process was conducted with PEG, KMnO 4 , CNT and graphene. • MnO 2 has a high capacity, intercalated K and H 2 O keep the structure of MnO 2 and CNT/graphene provide conductivity. • The hydrated KMO-CNT/graphene delivers high specific capacities of 359.8 mAh g–1 at 0.1 A g–1 and 129 mAh g–1 at 3.0 A g–1 with 77% retention. • The performance of ZIB reaches a high energy density of 410.36 Wh kg–1 at 109.93 W kg–1. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel CNT-CoFe/NC and CNT-CoS 2 Fe/NC was fabricated by thermal treatments and vulcanization. • CNT-CoFe/NC shows a better ORR performance than Pt/C while CNT-CoS 2 Fe/NC shows a better OER performance than RuO 2. • The hybrid catalysts, CNT-CoFe/NC + CNT-CoS 2 Fe/NC, demonstrate a superior performance of rechargeable Zn-air battery. Catalysts with embedded and functionalized elements used for the effective control of oxygen-reduction (ORRs) and oxygen-evolution reactions (OERs) are the key to developing high-performance rechargeable Zn–air batteries (ZABs). Here, carbon nanotube-grafted, Co–Fe embedded, nitrogen-doped porous carbon nano-frameworks (CNT–Co–Fe/NC) were synthesized through the carbonization of Fe-doped zeolitic imidazolate frameworks and vulcanization of the CNT–Co–Fe/NC to form CNT–CoS 2 –Fe/NC. The CNT–CoS 2 –Fe/NC exhibited a superior OER performance with an overpotential of only 1.637 mV at a current density of 10 mA/cm2 and a Tafel slope of 197 mV/dec (which, for RuO 2 , is 112 mV/dec), whereas the CNT–Co–Fe/NC showed an excellent ORR performance with a Tafel slope of 71 mV/dec (which, for 20 wt% Pt/C, is 91 mV/dec). A ZAB was developed with a hybrid catalyst of 50 wt% CNT–Co–Fe/NC and 50 wt% CNT–CoS 2 –Fe/NC in the cathode, and it achieved an excellent specific discharge capacity of 814 mAh/g at 50 mA/cm2, high power density of 245 mW/cm2, and outstanding cycle stability of over 1800 cycles (300 h) at 10 mA/cm2 with a very high retention of 95% and small potential gap of 0.68 V, compared to the corresponding values of 803.7 mAh/g, 215.3 mW/cm2, 900 cycles: retention 92%, and potential gap 0.837 V for 150 h for the ZAB with a hybrid catalyst of Pt/C + RuO 2. It is hypothesized that the ZAB with the novel hybrid catalyst exhibits its excellent catalytic activity and durability as a result of the synergistic effect of the catalyst's embedded heteroatoms and nitrogen–metal/carbon framework that enhances the ORR/OER performance, porous carbon nano-framework that enables rapid diffusion and electrical conduction, and carbon nanotubes that complete the external electrical connection between the catalysts. [ABSTRACT FROM AUTHOR]

Abstract: A double-sided surface light source based on field emission (FE) using an alternating current power source is demonstrated. Carbon-nanotube (CNT) emitters and ZnS phosphor are mixed and screen-printed onto two pieces of indium tin oxide glass that were assembled together with the coated surfaces facing each other to make a parallel-plate, diode-structure FE device. The device has a double-sided luminance distribution with a turn-on field of 2V/μm, a good uniformity, and a stable luminance of 4000cd/m2. The results show that CNTs not only act as good field emitters but also as an electrically conductive network around the isolated phosphors. The network prevents electric arcing and thus extends the lifetime of the device. [Copyright &y& Elsevier]

Abstract: Thin-walled carbon nanotubes (TWCNTs) were synthesized using a zirconium (Zr) plate by cold-wall chemical vapor deposition of a mixture gas consisting of C2H2 and H2 under a pressure of 1.20torr. The Zr plate was used for the formation of Zr nanocatalysts during the thermal process and used as substrate to eliminate the effects of interactions between catalyst and substrate during CNT synthesis. The TWCNTs were 4–9nm in diameter and a few micrometers long. Nanometer-sized defects on the Zr bulk material may have a low melting temperature, allowing them to form droplet-like catalysts and achieve high carbon solubility for the formation of CNTs. [Copyright &y& Elsevier]

Abstract: Multiwalled carbon nanotubes (MWNTs) were synthesized using a chemical vapor deposition floating feed method in a vertical reactor. Effects of the preparation variables on the average diameter of carbon nanotubes were systematically examined using the fractional factorial design (FFD), path of the steepest ascent, and central composite design (CCD) coupled with the response surface methodology. From the FFD study, the main and interactive effects of reaction temperature, methane flow rate, and chamber pressure were concluded to be the key factors influencing the diameter of MWNTs. Two empirical models, representing the dependence of the diameter of carbon nanotubes at the vicinities around maximum (420nm) and minimum (15nm) on the reaction temperature and methane flow rate, were constructed in two independent CCD studies. These models, shown as contour diagrams, indicated that the diameter of carbon nanotubes generally increased with increasing reaction temperature and methane flow rate. Based on both models, the diameter of MWNTs from 15 to 420nm can be controlled precisely by using a continuous CVD fabrication method. [Copyright &y& Elsevier]