Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition

Abstract

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene–toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20–30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe3C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated.

Electrochemistry of Carbon Materials: Progress in Raman Spectroscopy, Optical Absorption Spectroscopy, and Applications

“…For these experiments, special electrochemical cells, electrolytes, electrode materials, and other parameters are important [ 141 ]. Recent works include electrochemical studies of carbon materials [ 253 , 254 , 255 , 256 , 257 , 258 , 259 , 260 , 261 , 262 , 263 , 264 , 265 , 266 , 267 , 268 , 269 , 270 , 271 , 272 , 273 , 274 , 275 , 276 , 277 , 278 , 279 , 280 , 281 ].…”

Ternary Composite of Polymer, Fullerene and Fluorinated Multi-Walled Carbon Nanotubes as the Active Layer of Organic Solar Cells

“…A 2% ferrocene solution in a toluene-acetonitrile mixture of 50/50 wt.% was used as a precursor. The nanotubes prepared via this method [29] are referred to as MW0.…”

“…From the SEM image of MW0 (Figure 2a) the characteristic range of the nanotube diameter 20-80 nm in the arrays can be deduced. Their length, about 100 µm, is determined to the height of the arrays [29]. Grinding of the nanotubes results in their shortening to about 1 µm and formation of additional shapeless pieces, presumably consisting of amorphous carbon (Figure 2b).…”

Peculiarities of Quantitative X-Ray Fluorescence Analysis of Iron in Carbon Matrix

“…Поскольку исходной целью данной работы было количественное определение железа в УНТ, то на начальном этапе в качестве железосодержащего соединения был взят ферроцен Fe(C 5 H 5 ) 2 , так как степень окисления атомов железа в Fe(C 5 H 5 ) 2 , как и, преимущественно, в остаточном железе, содержащемся в УНТ [22], равна нулю. Следует отметить, что УНТ были получены с использованием Fe(C 5 H 5 ) 2 в качестве катализатора [23].…”

“…Следует отметить, что в УНТ, получаемых каталитическим газофазным осаждением, фиксируется остаточное железо в различных степенях окисления. Так, в работе [22] обнаружено, что в продуктах синтеза УНТ присутствуют такие соединения железа как Fe, Fe 3 C, Fe x O y . Тем не менее наблюдаемое отсутствие зависимости аналитического сигнала от степени окисления железа позволяет предположить о возможности проведения количественного определения содержания Fe в УНТ без предварительного перевода остаточного катализатора в единую степень окисления.…”