Deng-Zhu Guo

Preparation, characterization and catalytic property of CuO nano/microspheres via thermal decomposition of cathode-plasma generating Cu2(OH)3NO3 nano/microspheres.

CuO nano/microspheres with a wide diametric distribution were prepared by thermal decomposition of Cu(2)(OH)(3)NO(3) nano/microspheres formed in a simple asymmetric-electrode based cathodic-plasma electrolysis. The morphological, componential, and structural information about the two kinds of spheres were characterized in detail by SEM, TEM, EDX, XPS and XRD, and the results revealed that the morphology of the spheres were well kept after the componential and structural transformation from Cu(2)(OH)(3)NO(3) into CuO. The TGA/DSC study showed that the CuO nano/microspheres could be explored to be a promising additive for accelerating the thermal decomposition of ammonium perchlorate (AP). Combining with the current curve and emission spectrum measured in the plasma electrolysis, formation mechanism of the Cu(2)(OH)(3)NO(3) spheres was also discussed.

Synthesis and characterization of tungsten oxide nanorods

Single crystalline nanorods (15–200 nm in diameter and hundreds nanometers in length) have been formed on the carbon-covered W wires by simple electric heating under a vacuum of 5 × 10−4 Pa. The chemical composition and crystalline structure of the nanorods were carefully investigated by various characterization techniques such as scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, energy dispersive x-ray spectroscopy and electron energy loss spectroscopy. After ruling out any possible existence of carbon nanotubes (CNTs), tungsten carbide, W–Fe alloying, and formation of other types of tungsten oxides, monoclinic W18O49 phase has been well identified. The mechanism of nanorod formation of sub-tungsten oxide (∼WO2.7 compared to WO3) will be discussed in relation to the sample preparation conditions.

Field emission of individual carbon nanotubes on tungsten tips

Individual multiwalled carbon nanotubes (MWCNTs) were assembled onto tungsten tips in a transmission-electron microscope. Then they were transferred into a field-emission microscope for the measurement of field-emission properties. Stable field emission was established after repeated heat treatment and extraction of field-emission current, which are believed to have cleaned and blunted the MWCNT ends. Even under high voltages and large currents, most of the emitted electrons that hit the screen were found to be still restricted within an ∼10−2 solid angle, indicating the possible availability of a high brightness.

Titanium dioxide nanospheres with wide spectral absorption prepared by low-voltage plasma electrolysis

TiO(2) nanospheres with diameters mostly in the range of 20-200 nm are prepared by using cathodic plasma electrolysis at low voltage of 70 V. It is found that the low voltage could efficiently depress the particle sizes and their distribution, and result in more anatase phases. The nanospheres have an excellent optical absorption from 240 nm to 2600 nm.

Miniature cold cathode ionization gauge based on composite films of carbon nanotubes and MgO nanoparticles

Composite films of carbon nanotubes (CNTs) and MgO nanoparticles are prepared by rubbing method, and their field emission (FE) properties are studied experimentally. It is found that, with an optimum proportion (~7 wt. %) of MgO nanoparticles mixed with CNTs, the FE properties of the composite films are dramatically improved, in lowering turn-on filed, suppressing the degradation of FE current, and increasing the FE uniformity and stability. Then, the CNTs-MgO composite films are used in miniature cold cathode ionization vacuum gauges, which exhibit good linearity in the pressure range of 2×10-2 ~ 8×10-6 Pa, with a gauge sensitivity of ~0.2 Pa-1.

Field emission microscopy study of zinc oxide nanowires on tungsten tip

This article focuses on the field emission from a small number of zinc oxide (ZnO) nanowires. ZnO nanowires were grown directly on W tips and their field emission was studied in a traditional field emission microscope (FEM). The FEM pattern of a single ZnO nanowire was ring shaped, indicating that most of the emission from the (0001) facets of the ZnO nanowires came from their circumferences. Scanning electron microscopy observation, measurement of dependence of the emission current on the applied cathode voltage (I-V behavior), and acquirement of FEM patterns were performed before and after heat treatment of the samples, respectively. The heat treatment was found to play either a favorable or an unfavorable role. It could lead to a stable emission or damage of the emitters, depending on the heating conditions.

Mechanical fabrication of carbon nanotube films and their field-emission properties

Summary form only given. We present a simple technology for the fabrication of CNTs films cathode by utilizing method of rubbing CNT powders onto the polished substrates. The metallic substrates were polished by 10000 mesh white fused alumina powder at first. Then, the CNTs were rubbed on them. After that process, the metallic substrates were covered by CNTs films uniformly and firmly, as characterized by scanning electron microscope and scotch tape peeling tests. The field-electron-emission properties of such films cathodes were investigate under the vacuum of 10-5 Pa. The experimental results showed that the field-emission image of the films was nearly uniform and the emission current was considerably large. The turn-on field (the field at an emission current density of 10μA/cm ) was 3.4V/μm. The emission current density of 1.31mA/cm was obtained at the electric field of 6.1 V/μm, and emission current was almost stable in more than 60 minutes under about ImA/cm .

Charge Emissions from the Plasma Photogerated in Channels of SWNTs

Summary form only given. In recent years it has been reported that nanomaterials such as single-walled carbon nanotubes (SWNTs), silicon nanowires, and polyaniline nanofibers could have an abnormal photothermal effect under a camera flashlight. We have also investigated the visible-light-induced split of water confined in channels of SWNTs. In this paper, we will focus on the charge emission phenomena when the SWNT sample in ultrahigh vacuum is irradiated with a fast light exposure. We designed a special experimental procedure to monitor the positive and negative charges launched from the irradiated SWNT sample. Indeed, both positive and negative charge emissions have been recorded. Originally, such phenomena could only be observed occasionally, but now we can definitely obtain the charge emissions for each time of fast-light exposure. We found that the charge intensity is related to the residual gas adsorption, the collecting voltage, the external magnetic field, and the intensity of the input light. Some plasma characteristics of the photogenerated charges have been determined. We suppose that the nano-confinement of the adsorbed residual gases in the channels of SWNTs would play a key role in such phenomena

Field Eemission from an Individual Multiwalled Carbon Nanotube on a Tungsten Tip

A multiwalled carbon nanotube (MWCNT) was assembled onto a tungsten tip in a transmission electron microscope (TEM). Then it was transferred into a field-emission microscope (FEM) for the measurement of field emission properties. Stable field emission current and pattern were established after an aging process, which ridded the MWCNT of adsorption and blunted its end. A reduced brightness of 107-108(A/m2middotsrmiddotV) was eventually obtained