Material Science

Natural gas

Natural gas, colourless highly flammable gaseous hydrocarbon consisting primarily of methane and ethane. It is a type of petroleum that commonly occurs in association with crude oil. A fossil…

senseadmin

November 29, 2021

Material Science

Point Defects Vacancies and Self-Interstitials A vacancy is a lattice position that is vacant because the atom is missing. It is createdwhen the solid is formed. There are other ways of making a vacancy, but they also occur naturally as a result of thermal vibrations. An interstitial is an atom that occupies a place outside the normal lattice position. It maybe the same type of atom as the others (self interstitial) or an impurity atom. In the case of vacancies and interstitials, there is a change in the coordination of atoms around the defect. This means that the forces are not balanced in the same way as for other atoms in the solid, which results in lattice distortion around the defect A hightemperature is needed to have a high thermal concentration of vacancies. Frenkel-defect is…

Jacob

September 14, 2021

Material Science

Influence of temperature on magnetic behavior

Temperature can also influence the magnetic characteristics of materials. The atomic magnetic moments are free to rotate, hence with rising temperature, the increased thermal motion of the atoms tends to randomize the directions of any moments that may be aligned. For ferromagnetic, antiferromagentic and ferrimagentic materials, the atomic thermal motions counteract the coupling forces between the adjacent atomic dipole moments, causing some dipole misalignment, regardless of whether an external field is present. The result is a decrease in the saturation magnetization for both ferro and ferrimagnets. The saturation magnetization is a maximum at ) K, at which temperature the thermal vibrations are a minimum. With increasing temperature, the saturation magnetization diminishes gradually and then abruptly drops to zero at what is called the curie temperature Tc. The magnitude of the curie temparature varies from material to material; for example, for iron, cobalt, nickel., the respective values are 768,1120,335 and 585 degree Celsius. Antiferromagnetism is also affected by temperature; this behavior vanishes at what is called the Neel temperature. At temperatures above this point, antiferromagnteic materials also become paramagnetic.

Jacob

September 14, 2021