These clusters usually are associated with high negative charges. For example the general formula for an n vertex closed structure (closo) is [BnHn]2-, the more open borane structures have increasingly higher negative charges. They are formed by triangular faced polyhedral containing a BH unit for each vertex. When one of these vertices is substituted by a heteroatom, such as carbon, it gives rise to a family of heteroboranes like Carboranes. In 1960´s the first carboranes were synthesized.
1.1 General Creation of new materials with novel properties is the main driving force for the development of materials science and technology. Properties of materials are not simply influenced by the chemical bonding and composition, but likewise by the dimensions of materials. As the dimension of a material system reduces to the nm-scale, unique physical and chemical characteristics arise. Nano- materials have been mass fabricated by novel synthetic approaches, and have pulled a great deal interest from scientists and engineers. One interesting case of the nano- materials is carbon nanotubes (CNTs).
One of the most commonly used as electrode materials at commercial scale is Activated carbons. The aim of the research is to determine the factors that contribute to the specific capacitance i.e. capacitance (C) per mass of the electrode (m) and series resistance (diffusion resistance, ohmic resistance and mass transfer resistance) in such materials. At the same time, a correlation between pore size, pore size distribution and pore length with specific capacitance (24) have been researched. Studies at the Chinese Academy of Science have shown that activated carbon nanotubes achieve higher specific capacitance than normal carbon nanotubes (25).
In the case of monolayer graphene, the 2D band is a sharp single peak; while in the case of doubleor multi-layer graphenes, there are splitting generated either from the phonon branches or the electronic bands . The experimental data (Figure 5) shows indeed that the 2D band can be decomposed into four peaks (2L) and provides strong evidence in favor of multi-layer graphene as the major product. The ID/IG intensity ratio is widely used to assess the density of defects in graphite materials . The D band of No.5 sample is rather uniform and near the noise level, indicating the NG remains a high crystalline quality. It is noted that the ID/IG for all samples in this work is much larger than that of CVD-grown graphene .
Device efficiency with reduction of particle size in semiconductor industry is also a significant factor for the development of nanotechnology. The field of nanotechnology explores the materials and their properties [28 -35 2-8], nanoscale of synthesized material when at least one dimension of the nanostructure is in one hundred nanometer range. Practically the materials in nanoscale have only few atoms or the clusters of atoms, and the properties of the materials have been found to be altered because of the quantum confinement effect. Nanomaterials have structural features in between to those of atoms and bulk materials. Nanomaterials exhibit a diversification of properties that are different and often significantly improved in comparison with those of
Nanoparticles (nano-scale particles = NSPs) are atomic or molecular aggregates with the dimension between 1 and 100 nm that can significantly modify their physicochemical properties compared with the bulk material. Nanoparticles can be made from a variety of bulk materials and they can act depending on chemical composition, size or shape of the particles. They are more reactive and more mobile in nature. Nanoparticles are broadly in two groups of organic and inorganic nanoparticles. Organic nanoparticles include carbon nanoparticles (fullerenes) while some of the inorganic nanoparticles include magnetic nanoparticles, noble metal nanoparticles (e.g.
1. INTRODUCTION 1.1 BACKGROUND AND MOTIVATION In the recent years, an extensive advancement in the field of phosphors has been bloomed by deliberately introducing trivalent rare earth ions (lanthanides) as luminescent centers (dopants) in different host matrices to produce rare earth activated phosphors for lighting applications. A phosphor literally, light bearer is a material capable of absorbing energy and re-emitting it in the form of light (ultra violet, visible or Infrared). In general, Most of the phosphors are usually made up of a host material (matrix) and dopant. The host material is normally an insulator or a semiconductor with a wide band gap and it serves to accommodate the dopant.
Fig A molecule of Dihydrogen contains two atoms, in which the nuclei of both the atoms are spinning. Depending upon the spin it has two parts one is ortho hydrogen and another one is para hydrogen. These two are its state. ORTHO hydrogen molecules are that in which nuclei are spin in same direction. And in PARA state nuclei spin in opposite direction as shown in
The types of signals produced by an SEM include secondary electrons, back-scattered electrons (BSE), characteristic X-rays, light (cathodoluminescence) and transmitted electrons. Secondary electrons are generated as ionization products. They are called 'secondary' because they are generated by other radiation (the primary radiation). This radiation can be in the form of ions, electrons, or photons with sufficiently high energy, i.e. exceeding the ionization potential.
There are 17 rare earth elements that are considered to be rear earth metals. They are Scandium and yttrium and the fifteen lanthanides. Scandium and yttrium are both transition metals and rare earth metals because they are usually found with the rare earth metal deposits. The rare earth elements contribute to technologies people rely on today. They make possible the high tech world we live in today.