Archive for December, 2012

Mesoporous Material

What is Mesoporous Material ?

Mesoporous materials are defined as natural or synthetic materials having a pore diameter of 2-50 nm, halfway between the pore sizes that define micro- and macroporous materials. They have a large surface area and are particularly useful for applications in catalysis, separation, and absorption.

A mesoporous material is a material containing pores with diameters between 2 and 50 nm. Porous materials are classified into several kinds by their size. According to IUPAC notation, microporous materials have pore diameters of less than 2 nm and macroporous materials have pore diameters of greater than 50 nm; the mesoporous category thus lies in the middle. Typical mesoporous materials include some kinds of silica and alumina that have similarly-sized fine mesopores.

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History of Superconductor

Superconductor

A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. This means no heat, sound or any other form of energy would be released from the material when it has reached “critical temperature” (Tc), or the temperature at which the material becomes superconductive. Unfortunately, most materials must be in an extremely low energy state (very cold) in order to become superconductive. Research is underway to develop compounds that become superconductive at higher temperatures. Currently, an excessive amount of energy must be used in the cooling process making superconductors inefficient and uneconomical.

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.

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What is Metal ?

Metal Definition

A metal is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable, ductile and shiny. The meaning of the term “metal” differs for various communities for example, astronomers call for convenience metals everything but hydrogen and helium. Many elements and compounds that are not normally classified as metals become metallic under high pressures.

Metals typically consist of close-packed atoms, meaning that the atoms are arranged like closely packed spheres. Two packing motifs are common, one being body-centered cubic wherein each metal atom is surrounded by eight equivalent atoms. The other main motif is face-centered cubic where the metal atoms are surrounded by six neighboring atoms. Several metals adopt both structures, depending on the temperature.

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