Paragraph 1 Compare and contrast the crystal structures and crystal chemistry of quartz, α- FePO4 and β-FePO4. For FePO4, it was researched and shown that there were structural changes at temperatures between 294k and 1073k. The FePO4 is recognizably different in nature from other types of α-quartz isotypes due to the fact that its A cation is in its own way, a transition metal. Similarly, it takes on and assumes the structure of the α-quartz — which is tetrahedral in shape — at low temperatures. However, at notably high pressures and temperature, there is a change in phase, which it then shifts to a more compact and closely packed octahedral structure, also known as β-phase. The temperature that leads to this transition is at 980K. This can …show more content…
This means that the structure of the α- FePO4 will be seen and shown at temperatures less than the transition temperature of 980k. For α- FePO4, its symmetry would be trigonal and it has a trigonal unit structured cell. On the other hand, as we compare the structure with that of β- FePO4, the structure of β- FePO4 can be seen at temperatures that are above the transition temperature of 980K. For β- FePO4, its symmetry would be hexagonal and it has a hexagonal unit structured cell.Notably, as the temperatures increases, just before it reaches the transition temperature of 980K, there are significant changes in the crystals and their structure. Specifically, there are noticeable increases in the cell parameters which correspondingly lead to an increase in the volume. The bond length of Fe-O-P increases and the bond expands as well. Upon reaching the temperature of 980K, which is the transition temperature, there is a change in phase from α to β. This transition from α to β is in relation to δ, the tilt angle which is used for FePO4. The tetrahedral tilt angle δ declines rapidly during this transition from α to β, as there are increases in the temperature. In addition, it can be seen that the Fe-O-P bridging angles increases during this first-order transition. With this increase in bond distance seen, it results in a greater amount of dynamic disorder in the β phase after the transition at 980K. While in the β phase, there are no significant changes in the bond angle and the distance between the bonds with changes in the temperature. The bond distance of Fe-O remains around 5.16A. In addition, we can also see that there are no thermal expansions found in the β
The endothermic melting temperature for Ptx, blank S-SEDDS, physical mixture of Ptx/blank S-SEDDS, and Ptx-loaded S-SEDDS was determined by DSC 2920. Samples were scanned from 30 to 250 °C at a rate of 10 °C /min. In all the cases, an empty pan was used as the reference. XRD patterns of Ptx, blank S-SEDDS, physical mixture of Ptx/blank S-SEDDS and Ptx-loaded S-SEDDS were recorded using an X'Pert PRO Multipurpose X-Ray diffractometer equipped with CuKα radiation (40 kV, 20 mA). The 2θ scanning range was varied from 2° to 50°.
Zirconia has three crystalline forms: monoclinic phase, tetragonal phase and cubic phase. Monoclinic phase exists in zirconia stable up to temperature 1170˚C. Above 1170˚C, the monoclinic phase transforms to tetragonal phase and further transform to cubic phase above 2370˚C. While cooling down below 1070˚C, tetragonal phase becomes unstable and start transformation of monoclinic phase. Thus tetragonal phase is hard to exist at the room temperature.
Rasmussen, T.; Jensen, J. F.; Ostergaard, N.; Tanner, D.; Ziegler, T.; Norrby, P. Chem. Eur. J., 2002, 8, 177.
The mass of Mg + the mass of O2=mass of MgxOx. Knowing the mass of
I plan to educate those who read this paper on what they might not know of a few of our elements. I will tell you what I have learned over the oxygen group on the elemental table. I will talk about Oxygen, Sulfur, Selenium, Tellurium, and last but not least Polonium. These elements have changed our way of life and history in ways you might not know. We are surrounded by these elements in our daily life and they make us the way we are. I hope to teach you and answer some questions about these elements in this informant paper.
The IUPAC defined polymorphic transition as “A reversible transition of a solid crystalline phase at a certain temperature and pressure (the inversion point ) to another phase of the same chemical composition with a different crystal structure” .
The cotunnite-type phase was claimed by L. Dubrovinsky and co-authors to be the hardest known oxide with the Vickers hardness of 38 GPa and thebulk modulus of 431 GPa (i.e. close to diamond's value of 446 GPa) at atmospheric pressure.However, later studies came to different conclusions with much lower values for both the hardness (7–20 GPa, which makes it softer than common oxides like corundum Al2O3 and rutile TiO2) and bulk modulus (~300 GPa).
In order to separate the mixture of fluorene, o-toluic acid, and 1, 4-dibromobenzene, the previously learned techniques of extraction and crystallization are needed to perform the experiment. First, 10.0 mL of diethyl ether would be added to the mixture in a centrifuge tube (1) and shaken until the mixture completely dissolved (2). Diethyl ether is the best solvent for dissolving the mixture, because though it is a polar molecule, its ethyl groups make it a nonpolar solvent. The compounds, fluorene and 1, 4-dibromobenzene, are also nonpolar; therefore, it would be easier for it to be dissolved in this organic solvent.
with a tong to see if the magnesium had started to burn and also to
A very important compound is dialuminum oxide Al2O3. The structure of dialuminum oxide is sometimes hexagonal. The structure is .It is one of the hardest substances known. It is formed by natural occurrence. Dialuminum oxide is formed from the reaction of metallic aluminum with oxygen gas. It is a white crystalline solid. Aluminum chloride has a formula of ALCl3. The structure is . It is mainly produced in the production of aluminum metal. It is white, but samples are often contaminated with iron trichloride, giving it a yellow color. The compound formula for dialuminum sulphide is Al2S3.The structure is . It is a ...
23. S. Alwarappan, S. Boyapalle, A. Kumar, C.-Z. Li and S. Mohapatra, J. Phys. Chem. C, 2012, 116, 6556–6559
Aim: The aim of this experiment was to determine the empirical formula of magnesium oxide.
V. Amarnath, D. C. Anthony, K. Amarnath, W. M. Valentine, L. A. Wetterau, D. G. J. Org. Chem. 1991, 56, p. 6924-6931.
Femicide is defined as the act of killing a female simply because she is female. Acts of femicide includes “honor killings,” “dowry deaths,” genital mutilation, rape in war and victimization o female refugees. The treatment of women prisoners and detained immigrant women are also related to the issue of femicide. Essentially, femicide is a form of gender-based violence (Stuart van Wormer & Bartollas, 2011). It is considered to be an extreme form of gender-based violence that may include torture, mutilation, cruelty and sexual violence. The violence often culminated to murder. This violence is linked to gender concepts like inequality, discrimination and disempowerment (Femicide, 2008). It is also viewed as “a form of terrorism that functions to define gender lines, enact and bolster male dominance, and to render women chronically and profoundly unsafe” (Suarez, 2009). Based on international federal and state law, women have the right to be free from violence. Overall, acts of femecide are viewed as a violation of the human rights of women (Femicide, 2008).
In summary, the rate of cooling from the austenite phase is the main determinant of final structure and properties.