Infrared spectra and thermal decompositions of metal acetates and dicarboxylates

The infrared spectra of rare earth acetates have been studied to examine the metal-acetate bonding. The thermal decomposition of rare earth acetates as well as lead and copper acetates have been investigated in detail by employing thermogravimetric analysis and differential thermal analysis. Thermal decomposition of calcium dicarboxylates (malonate to sebacate) have been studied employing t.g.a. and d.t.a. Infrared spectra of the dicarboxylates have also been studied. Preliminary results on the products of decomposition of dicarboxylates have been reported

Synthons and Design in Metal Phosphates and Oxalates with Open Architectures

We briefly describe the structures of open-framework metal phosphates with different dimensionalities, such as the one-dimensional linear-chain and ladder structures, two-dimensional layer structures and three-dimensional structures with channels. We demonstrate the role of the zero-dimensional four-membered ring monomer and of the one-dimensional ladder structure as the starting building units or synthons involved in the formation of the complex architectures. Thus, we show how the one-dimensional ladder structure transforms to two- and three-dimensional structures under mild conditions. The two-dimensional layer structures also transform to three-dimensional structures, while the zero-dimensional monomer transforms to layered and three-dimensional structures under ordinary reaction conditions. These transformations provide an insight into the possible pathways involved in the building up of the complex structures of metal phosphates. The isolation of amine phosphates during the hydrothermal synthesis of metal phosphates and also the facile reactions between amine phosphates and metal ions to yield a variety of open-framework materials have thrown light on the mechanism of formation and design of these structures. The existence of a hierarchy of open-framework metal oxalates and their ready formation by employing amine oxalates as intermediates provides additional support to the observations made earlier with regard to the phosphates

An investigation of carbon nanotubes obtained from the decomposition of methane over reduced Mg1− xM xAl2O4 spinel catalysts

Carbon nanotubes produced by the treatment of Mg1−xMxAl2O4 (M = Fe, Co, or Ni; x = 0.1, 0.2, 0.3, or 0.4) spinels with an H2–CH4 mixture at 1070 °C have been investigated systematically. The grains of the oxide-metal composite particles are uniformly covered by a weblike network of carbon nanotube bundles, several tens of micrometers long, made up of single-wall nanotubes with a diameter close to 4 nm. Only the smallest metal particles (<5 nm) are involved in the formation of the nanotubes. A macroscopic characterization method involving surface area measurements and chemical analysis has been developed in order to compare the different nanotube specimens. An increase in the transition metal content of the catalyst yields more carbon nanotubes (up to a metal content of 10.0 wt% or x = 0.3), but causes a decrease in carbon quality. The best compromise is to use 6.7 wt% of metal (x = 0.2) in the catalyst. Co gives superior results with respect to both the quantity and quality of the nanotubes. In the case of Fe, the quality is notably hampered by the formation of Fe3C particles

Surfactant-Assisted Synthesis of Semiconductor Nanotubes and Nanowires

Nanotubes and nanowires of CdSe and CdS have been obtained from solutions containing a surfactant such as Triton 100-X. They have been characterized by x-ray diffraction, electron microscopy, and optical spectroscopy

Synthesis of single-walled carbon nanotubes using binary (Fe, Co, Ni) alloy nanoparticles prepared in situ by the reduction of oxide solid solutions

Passing a H2–CH4 mixture over oxide spinels containing two transition elements as in Mg0.8MyM'zAl2O4 (M, M' = Fe, Co or Ni, y + z = 0.2) at 1070°C produces small alloy nanoparticles which enable the formation of carbon nanotubes. Surface area measurements are found to be useful for assessing the yield and quality of the nanotubes. Good-quality single-walled nanotubes (SWNTs) have been obtained in high yields with the FeCo alloy nanoparticles, as evidenced by transmission electron microscope images and surface area measurements. The diameter of the SWNTs is in the 0.8–5 nm range, and the multiwalled nanotubes, found occasionally, possess very few graphite layers

Single-Walled Carbon Nanotube Bundles Intercalated with Semiconductor Nanoparticles

Nanoparticles of CdSe, CdS and ZnSe have been incorporated in the inter-tubular gaps of single-walled carbon nanotube (SWNT) bundles. Electron microscope, X-ray diffraction (XRD), electronic spectroscopy and Raman studies have been employed to characterize these systems. The lengths of the intercalate inside the bundles could be varied by changing the reaction conditions. Electronic absorption and photoluminescence studies from the semiconductor intercalates show the expected blue-shift with respect to the corresponding bulk samples in CdS and ZnS samples. The SWNT lattice is expanded on incorporating CdSe as confirmed by XRD in the low-angle range. The expansion in the lattice is also corroborated by the Raman measurements which show a considerable red-shift for both the radial and the tangential modes of the SWNT signal, thus signifying an increase in the van der Waals gap between the tubes in the bundle. The red-shift of the Raman signal is due to the decrease in the inter-tube interactions as well as due to doping effects

MOLECULAR STRUCTURE INVESTIGATIONS BY ELECTRON DIFFRACTION

Abstract not availabl

Inorganic Nanotubes

Carbon nanotubes were discovered in 1991. It was soon recognized that layered metal dichalcogenides such as MoS 2 could also form fullerene and nanotube type structures, and the first synthesis was reported in 1992. Since then, a large number of layered chalcogenides and other materials have been shown to form nanotubes and their structures investigated by electron microscopy. Inorganic nanotubes constitute an important family of nanostructures with interesting properties and potential applications. In this article, we discuss the progress made in this novel class of inorganic nanomaterials

MoSe₂ and WSe₂ Nanotubes and Related Structures

MoSe2 and WSe2 nanotubes are obtained by the reduction of the corresponding triselenides in hydrogen or by the decomposition of the ammonium selenometallates in a hydrogen atmosphere

New Metal Disulfide Nanotubes [3]

This article does not have an abstract