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... The two samples annealed at 1300°C (sample A) and 1500°C (sampleB) were characterized by Brunauer– Emmett–Teller (BET) surface area and ... Calderon Moreno JM, Swamy SS, Fujino T, Yoshimura M (2000) Carbon nanocells and nanotubes grown in hydrothermal fluids. ...

ABSTRACT Magnetic-functionalized multi-walled carbon nanotubes (MWCNTs) with encapsulated Fe nanoparticles have been successfully fabricated via a one-step decomposition approach using ferrocene as a single precursor at a high temperature of 950 °C. The constituents, phase, and morphology have been characterized by X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Magnetic measurements reveal the ferromagnetic nature of the material with a magnetization saturation of 82.6 emu g−1 at room temperature. Full nitrogen sorption isotherms show that the magnetic-functionalized MWCNTs have a porous structure (2.0 nm, 6.42 nm and 11.4 nm) and large surface area (295.4 m2 g−1). Owing to their wonderful intrinsic properties, these magnetic-functionalized MWCNTs exhibit excellent ability to remove heavy metal ions from aqueous solutions. For example, the removal efficiency can be up to 97% at a Cu2+ concentration of 100 mg L−1 using these magnetic-functionalized MWCNTs as adsorbents. In addition, because the Fe nanoparticles were wrapped by MWCNTs, the material can be used in acidic solution and the removal efficiency of Cu2+ can reach 90% even in a strong acid solution (pH = 1).

In this work we report the metastability and the energetics of the phase transitions of three different polymorphs of BiPO4, namely trigonal (Phase-I, space group P3(1)21), monoclinic monazite-type (Phase-II, space group P2(1)/n) and SbPO4-type monoclinic (Phase-III, space group P2(1)/m) from ambient and non-ambient temperature powder XRD and neutron diffraction studies as well as ab initio density functional theory (DFT) calculations. The symmetry ambiguity between P2(1) and P2(1)/m of the high temperature polymorph of BiPO4 has been resolved by a neutron diffraction study. The structure and vibrational properties of these polymorphs of the three polymorphs have also been reported in detail. Total energy calculations have been used to understand the experimentally observed metastable behavior of trigonal and monazite-type BiPO4. Interestingly, all of the three phases were found to coexist after heating a single phasic trigonal BiPO4 to 773 K. The irreversible nature of these phase transitions has been explained by the concepts of the interplay of the structural distortion, molar volume and total energy.