Production of carbon nanotubes over Fe-FSM-16 catalytic material: effect of acetylene flow rate and CVD temperature

In this article, a high-yield synthesis of high-quality CNTs using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16 by Chemical Vapor Deposition CVD using acetylene as a hydrocarbon source is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA). Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were MWCNTs. High-resolution transmission electron micrographs of samples reveal the multilayer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed

Comparison Campaign of VLBI Data Analysis Software - First Results

During the development of the Vienna VLBI Software VieVS at the Institute of Geodesy and Geophysics at Vienna University of Technology, a special comparison setup was developed with the goal of easily finding links between deviations of results achieved with different software packages and certain parameters of the observation. The object of comparison is the computed time delay, a value calculated for each observation including all relevant models and corrections that need to be applied in geodetic VLBI analysis. Besides investigating the effects of the various models on the total delay, results of comparisons between VieVS and Occam 6.1 are shown. Using the same methods, a Comparison Campaign of VLBI data analysis software called DeDeCC is about to be launched within the IVS soon

Production of carbon nanotubes over Fe-FSM-16 catalytic material: effect of acetylene flow rate and CVD temperature

In this article, a high-yield synthesis of high-quality CNTs using Fe catalysts trapped within channels of Folded Sheet Mesoporous Materials, FSM-16 by Chemical Vapor Deposition CVD using acetylene as a hydrocarbon source is reported. The effect of reaction temperature and acetylene flow rate on the formation of CNTs was investigated. It was found that the yield, diameter and quality of CNTs synthesized strongly depend on reaction temperature during CVD. The resulting materials were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA). Our research found that carbon deposition, diameter and quality of the CNTs strongly depend on CVD temperature. However acetylene flow rate did not have any significant effect on diameter distribution. Raman measurement indicated that the synthesized products were MWCNTs. High-resolution transmission electron micrographs of samples reveal the multilayer sidewalls of individual MWCNTs with a diameter of 40 nm, in which hollow and tubal structures were observed

Tunable magnetism on the lateral mesoscale by post-processing of Co/Pt heterostructures

Controlling magnetic properties on the nm-scale is essential for basic research in micro-magnetism and spin-dependent transport, as well as for various applications such as magnetic recording, imaging and sensing. This has been accomplished to a very high degree by means of layered heterostructures in the vertical dimension. Here we present a complementary approach that allows for a controlled tuning of the magnetic properties of Co/Pt heterostructures on the lateral mesoscale. By means of in-situ post-processing of Pt- and Co-based nano-stripes prepared by focused electron beam induced deposition (FEBID) we are able to locally tune their coercive field and remanent magnetization. Whereas single Co-FEBID nano-stripes show no hysteresis, we find hard-magnetic behavior for post-processed Co/Pt nano-stripes with coercive fields up to 850 Oe. We attribute the observed effects to the locally controlled formation of the CoPt L1$_{0}$ phase, whose presence has been revealed by transmission electron microscopy.Comment: Accepted for publication in Beilstein J. Nanotechno

Localized direct material removal and deposition by nanoscale field emission scanning probes

The manufactory of advanced micro- and nanoscale devices relies on capable patterning strategies. Focused electron beams, as for instance implemented since long in electron beam lithography and electron beam induced deposition, are in this regard key enabling tools especially at the early stages of device development and research. We show here that nanoscale field emission scanning probes can be potentially utilized as well for a prospective direct device fabrication by localized material deposition but notably, also by localized material removal. Field emission scanning probe processing was specifically realized on 10 nm chromium and 50 nm gold thin film stacks deposited on a (1 × 1) cm2 fused silica substrate. Localized material deposition and metal removal was studied in various atmospheres comprising high vacuum, nitrogen, ambient air, naphthalene and carbon-dioxide. Stable and reliable regimes were in particular obtained in a carbonaceous atmosphere. Hence, localized carbon deposits were obtained but also localized metal removal was realized. We demonstrate furthermore that the selected electron emission parameters (20 V - 80 V, 180 pA) and the overall operation environment are crucial aspects that determine the degree of material deposition and removal. Based on our findings, direct tip-based micro- to nanoscale material patterning appears possible. The applied energy regime is also enabling new insights into low energy (< 100 eV) electron interaction. However, the underlying mechanisms must be further elucidated

Short Report of IVS Working Group 5 (WG5) on Space Science Applications - An IVS Perspective

No abstract availabl