X-Ray Powder Diffraction Essay Example | Topics and Well Written Essays - 1000 words

X-Ray Powder Diffraction - Essay Example (Marta J.K Flour, 1997) Theory A non amorphous material consists of a three dimensional structure having atoms in a series of planes separated by a distance. When X-Rays are directed on to this structure, part of it is transmitted the specimen, some part is absorbed, a part is refracted and the rest diffracted. Diffraction of the beam brings out a fingerprint of the crystal lattice which depends on the arrangement of atoms in different planes and the type of mineral in the lattice. (Ron Jenkins, 2000) Applications 1. Apart from identifying the different minerals present it also gives an accurate data regarding the proportion of each of these minerals in the mixture. 2. It is also used in determining the degree of crystalline phase in a mineral and the divergence from its ideal state. 3. Study of secondary minerals helps in ascertaining the degree of solubility of the mineral and the kind of storage facility this would require. 4. Analysis of the under clays lying under coal beds have helped in identifying the nature of environment and climate that existed in these Middle Pennsylvanian regions. Introduction-2 The discovery of x rays by W.C Roentgen in 1895 led to its use in identifying the structure of crystalline materials. In principle a monochromatic beam of x-ray electrons will be dispersed by the atomic electrons and different diffraction patterns are obtained for each plane of crystal lattice. The diffraction pattern that is obtained by using the x ray powder diffraction method is used to identify the various phases in different materials.( James R Connelly, 2007) Theory X rays generated under vacuum conditions are made to impinge on a sample that has been ground into powder of size less than 10 microns. The arrangement of atoms in the crystal lattice causes these electrons to be diffracted by varying degrees. This can therefore be used to ascertain the distances between different planes of atoms by applying Bragg’s law. This ‘fingerprint†™ allows in better identification of a material. ( Mike Meier, 2004) Applications 1. Identification of materials chemical compounds and rocks in single phase and multiphase respectively. 2. Ascertaining amorphous materials that are partly in crystalline state. 3. The amount of different phases calculated using peak-ratio calculations 4. These are used in remote sensing study of hydrothermally distorted rocks that are found on several Cascade volcanoes and its study helps in gathering information regarding landslides and mudflows. Introduction-3 X ray powder diffraction method is a non-destructive procedure used in the identification of phases and determination of crystal structure along with its imperfections. All kinds of microcrystalline structures of metals, ceramics, organics and catalysts can found out using this technique which was initially devised by Debye and Scherrer in 1916. Theory Current applied releases electrons from a filament. These electrons are then accelerated at voltages of 60kV onto a copper piece producing x rays on impingement. These x rays are then directed onto a sample that has been ground to fine powder of size less than 10 microns. The diffraction pattern that is obtained can be used to measure the actual distances between crystalline planes using the equations of Bragg’s Law. ( Stock.S.R & Cullity B.D, 2001) Applications 1. Ascertain crystal structure of an unknown material and phase identification of high and low temperature phases. 2. Degree of crystalline phase that is present in a material. A crystalline phase presents narrower diffraction peaks compared to amorphous phases. 3. The amount of residual stress that exists in a material after the external load has been removed. 4.

Tecumseh Essay Example | Topics and Well Written Essays - 1000 words

Tecumseh - Essay Example This made the treaties that had allowed this annexation void since it was signed by individual chiefs (Klinck 43). He was also a skillful orator and a brave warrior. These traits made the Americans and the British admire him (Klinck 36). Although Tecumseh was the leader of the confederacy during the Tecumseh war and war of 1812, the relationship between the Shawnee and the Iroquois Confederacy was a mixed one, with some Iroquois speaking people being friendly and allied to the Shawnee and the others who were enemies to them. While the other groups were enemies to the Shawnee, the Mingo and the Huron groups were their allies (Edmunds 23). The reason for this mixed relationship between the Iroquois Confederacy and the Shawnee is the following: the Iroquois Confederacy pursued a territorial expansionism policy which caused a conflict with its neighbors. Consequently, the neighboring communities, such as the Mingo and the Huron (Wyandot), cooperated with the Shawnee people due to the thr eat of territorial loss they experienced from the Iroquois Confederacy (Klinck 45). However, the relationship between the Shawnee and the Iroquois Confederacy was that of enmity since the Iroquois Confederacy embarked on invading the hunting grounds previously owned by the Shawnee, eventually evicting the Shawnee from their native lands of Ohio. The Iroquois made the Shawnee their dependents (Edmunds 40). During the American war of Independence, the Shawnee, Native American tribe, opted for joining the British in the fight against rebel colonists. The Shawnee planned to become British allies since they hoped that joining hands with the British would help them evict the colonists from their territory and draw them back across the mountains (Klinck 49). Considering that the invasion of the British and the consequent treaty signed with the Iroquois Confederacy had allowed many Colonists to settle in the native Shawnee lands, they needed some support to evict the colonists, which - they hoped - the British would grant them since the colonists had rebelled against the British colony (Edmunds 54). This saw the Shawnee ally with the British during that war. The concepts of land use advocated for by the British caused friction between the Indians and the whites. Notably, the signing of the Royal Proclamation of 1763 which sought to draw a line of territory between the Whites and the Indians sparked a great conflict (Klinck 62). This treaty sought to establish a reserve for the Indians but eventually ended up causing the encroachment by the whites into the areas where the Indians had previously occupied. Additionally, the treaty signed between the British and the Iroquois Confederacy over land use angered the Shawnee who were the native occupants of these lands before they were evicted by the Iroquois Confederacy (Edmunds 22). Thus, these concepts of land ownership and land use sparked off conflicts between the Indians and the whites. Tenskwatawa was a Shawnee religiou s leader who advocated for the Indians to revert to their traditional lifestyle (Edmunds 47). There were various reasons why the teaching by Tenskwatawa became very attractive to the Native Americans. First, these teachings advocated for a return to the traditional ways of living for the Indians. He advocated for the traditional lifestyle that was not influenced by the white cultures (Klinck 50). Additionally, his teachings advocat