Carbon nanotubes have been of great interest because of their simplicity and ease of synthesis. The novel properties of nanostructured carbon nanotubes such as high surface area, good stiffness, and resilience have been explored in many engineering applications. Research on carbon nanotubes have shown the application in the field of energy storage, hydrogen storage, electrochemical supercapacitor, field-emitting devices, transistors, nanoprobes and sensors, composite material, templates, etc. For commercial applications, large quantities and high purity of carbon nanotubes are needed. Different types of carbon nanotubes can be synthesized in various ways. The most common techniques currently practiced are arc discharge, laser ablation, and chemical vapor deposition and flame synthesis. The purification of CNTs is carried out using various techniques mainly oxidation, acid treatment, annealing, sonication, filtering chemical functionalization, etc. However, high-purity purification techniques still have to be developed. Real applications are still under development. This paper addresses the current research on the challenges that are associated with synthesis methods, purification methods, and dispersion and toxicity of CNTs within the scope of different engineering applications, energy, and environmental impact.
Nanocrystalline
metal
ferrites (MFe
2
O
4
, M
= Co, Ni, Cu, Mg, and Zn) were successfully synthesized via autocombustion
synthesis using egg white. X-ray diffraction (XRD) measurements revealed
the crystallization of the entire ferrites either in the tetragonal
structure, such as in the case of CuFe
2
O
4
, or
cubic spinels such as in other studied ferrites. The Fourier transform
infrared spectral study revealed the characteristic vibration bands
of ferrites. Compared to other synthesis methods, the observed variation
in the obtained structural parameters could be due to the different
cation distribution of the prepared ferrites. In agreement with XRD
measurements, the transmission electron microscopy images showed agglomerated
particles with cubic morphology for all ferrites. On the other hand,
CuFe
2
O
4
showed tetragonal morphology. The magnetization
values were found to vary with the type of the metal ion, and CoFe
2
O
4
showed the highest one (42.8 emu/g). Generally,
the lower magnetization values obtained than those reported in the
literature for all studied ferrites could be attributed to the smaller
particle sizes or the cation redistribution. The obtained coercivity
values are observed to be higher than their related values in the
literature, exhibiting the impact of the present synthesis route.
Ac-conductivity as a function of temperature and frequency indicated
semiconducting properties with the observed change in the conduction
mechanism by increasing the temperature. The obtained low dielectric
constant values could suggest using the entire ferrites in high-frequency
applications such as microwave devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.