Carbon nanotube yarns (CNY) are a novel carbonaceous material and have received a great deal of interest since the beginning of the 21st century. CNY are of particular interest due to their useful heat conducting, electrical conducting, and mechanical properties. The electrical conductivity of carbon nanotube yarns can also be influenced by functionalization and annealing. A systematical study of this post synthetic treatment will assist in understanding what factors influences the conductivity of these materials. In this investigation, it is shown that the electrical conductivity can be increased by a factor of 2 and 5.5 through functionalization with acids and high temperature annealing respectively. The scale of the enhancement is dependent on the reducing of intertube space in case of functionalization. For annealing, not only is the highly graphitic structure of the carbon nanotubes (CNT) important, but it is also shown to influence the residual amorphous carbon in the structure. The promising results of this study can help to utilize CNY as a replacement for common materials in the field of electrical wiring.

The transition metal halide α-titanium(III) chloride (α-TiCl3) is a layered two-dimensional compound and a well-established Ziegler-Natta catalyst for the polymerization of ethylene. A new synthesis technique is used to obtain thin sheets of α-TiCl3 that show exceptional physical properties in contrast to their bulk counterparts, due to an enlarged surface-to-volume ratio. Chemical vapor transport (CVT) of α-titanium(III) chloride directly on substrates results in microsheets that exhibit an improved catalytic effect. For rational planning of synthesis conditions, thermodynamic simulations of occurring gas phase equilibria were performed. Based on these calculation results, crystal growth succeeded by adding GaCl3 via pure short term CVT in a temperature gradient of 700 K to 600 K on yttrium-stabilized zirconia (YSZ) substrates. Phase pure, as-grown, single crystal sheets with high crystallinity and thicknesses of around 4 µm were obtained. These thin sheets of α-TiCl3 on YSZ substrates were implemented a...

We investigated the physicochemical surface properties of different highly aligned nitrogen-doped multi-walled carbon nanotube (N-MWCNT) carpets, synthesized using toluene/pyrazine, toluene/benzylamine and acetonitrile via a sublimation-based chemical vapor deposition (SCVD) method at 760 degrees C. The surfaces of the N-MWCNT carpets synthesized using toluene/pyrazine and toluene/benzylamine were very hydrophobic. In contrast, we observed a complete wetting of the N-MWCNT carpets synthesized using acetonitrile. The difference in the wetting behavior of these N-MWCNT carpets is the main focus in this study and was not investigated before. Here, we show that not only the presence or concentration of nitrogen inside the carbon lattice, but especially it's kind of incorporation have an important influence on the surface polarity. (C) 2018 Elsevier Ltd. All rights reserved.

The length of multi-walled carbon nanotubes (MWCNT) has a particular relevance for a wide range of application. To that end, in an aerosol assisted chemical vapour deposition process MWCNT carpets with different heights were synthesized on an oxidized silicon substrate by using ferrocene as Fe-catalyst precursor and some hydrocarbons with different hybridization state. By variation of the synthesis temperature from 600 degrees C up to 900 degrees C, for every used hydrocarbon different carpet heights were measured depending on the temperature. Cyclohexane generated the highest MWCNT carpets and for all carbon precursor the maximum carpet height was measured at 850 degrees C. To elucidate this, the thermal decomposition of the used hydrocarbons was discussed and the corresponding main decomposition products methane, ethene and benzene were identified. Subsequently, these substances were directly used in a second chemical vapour deposition equipment to simulate the growth mechanism by the intermediate carbon precursors. It was found, that with comparable content of carbon in the gas phase, ethene is much higher efficient for growing high MWCNT carpets than methane. Moreover, benzene was figured out to be also an adequate carbon precursor under specific gas phase conditions, explaining the carpet heights when using toluene and xylene.

Nano-Galfenol, or Heusler nanoparticles of the formula Fe3Ga, has been prepared by a novel method with the assistance of carbon nanotubes as a nano-carrier.

The investigation of the morphology of N-doped multi-walled carbon nanotubes (N-MWCNT) is still a crucial issue. Considering different nitrogen precursors we synthesized N-MWCNT at 750 degrees C using a sublimation-based chemical vapor deposition (SCVD) method. Compared to undoped multi-walled carbon nanotubes (MWCNT), nitrogen incorporation into the carbon lattice leads to a straighter CNT morphology in which the catalyst particles are mostly consist of iron carbide and not of metallic iron. An important finding is that not only the presence and concentration of nitrogen and the formation of iron carbide have a strong influence on the CNT straightness, but also the concentration of the sublimated catalyst precursor ferrocene in the gas phase. The lower its concentration the longer and larger the catalyst particle, resulting in a high CNT straightness.