Influence of iron contaminations on local and bulk magnetic properties of nonfunctionalized and functionalized multi‐wall carbon nanotubes

Abstract

We investigated Fe‐phases of iron complexes embedded in nonfunctionalized (as‐prepared) and functionalized multi‐wall carbon nanotubes (MWCNTs). Mössbauer spectroscopy is a very sensitive tool to study chemical states of iron compounds embedded in MWCNTs. It showed that the chemical treatment of the as‐prepared MWCNTs caused release of about 84% of iron and modification of the remaining iron compounds. In as‐prepared and carboxylated MWCNTs almost 80 and 75% of iron complexes in a form of Fe3C exhibited magnetic ordering even at room temperature, respectively. In MWCNT‐COONH4 only 50% of such iron compounds showed local magnetic ordering. In all cases about 2% of magnetic α‐Fe fraction was detected. Through the dc magnetization and transmission electron microscopy (TEM) measurements it was proved that cementite nanoparticles formed agglomerates and their sizes were larger than 10 nm. STM measurements indicated increased homogeneity of the surface electric properties in the case of chemically treated carbon nanotubes.

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

“…The thermal evolution of magnetization normalized to the mass of the unground samples was presented and discussed in [ 43 ]. In our previous study, the process of MWCNT purification by functionalization was observed to cause the iron contamination to drop in these nanotubes by about 90%.…”

“…In Figure 7 , examples of high-resolution images of functionalized MWCNTs, ground in the agate and steel mill, are shown. Their outer and inner surfaces are no longer smooth, as in unmilled nanotubes ( Figure 7 a,b; [ 43 ]). One can also observe the fracture sites of several walls at once ( Figure 7 d,e,g).…”

“…These Fe nanoparticles may be spherical or oval, but the latter ones are more abundant. EDX experiments show that the nanoparticles closed inside MWCNTs contain mainly Fe and C atoms [ 43 ]. However, in the case of carboxylated CNTs triturated in the steel mill, the nanoparticles may also contain a significant amount of oxygen in iron clusters ( Figure S4 ), which is consistent with the results from the Mössbauer experiments.…”

“…In order to design new materials based on carbon nanotubes (CNTs) one has to know their chemical and physical properties. Iron complexes interacting with the CNT composite matrix may significantly modify the electric and magnetic characteristics of the nanotubes [ 9 , 14 , 15 , 16 , 17 , 18 , 20 , 43 ]. Iron contamination is always present in CNTs when Fe is used as a catalyst during their preparation.…”

Non-woven polypropylene fabric modified with carbon nanotubes and decorated with nanoakaganeite for arsenite removal

“…Polypropylene (PP) non-woven fabric with fiber diameter sizes ranging from 0.2 to 30 µm were supplied by Amazon Filters Ltd. Multiwall carbon nanotubes (MWCNT), manufactured by CNT CO., LTD (South Korea), were used after purification with concentrated nitric acid (68% HNO3, POCH) according to the procedure described by Jamrozik and coauthors (Jamrozik et al 2014). For synthesis of iron oxy(hydroxide) nanoparticles, iron(III) chloride hexahydrate (FeCl3•6H2O, Chempur), urea (NH2CONH2, POCH) and distilled water prepared with HLP10p Hydrolab (Poland) were used.…”