What is the phase of cobalt?
From structural point of view, cobalt can exist in three crystal phases, namely hcp, fcc, and e-phase. [12][13][14] With an hcpfcc phase transition occurring at temperatures around 450 1C, 15, 16 the hcp phase is the one of interest from a biomedical standpoint.
What is phase diagram in alloy system?
Phase diagrams are graphical representations of the phases present in a particular alloy being held at a particular temperature. Phase diagrams can be used to predict the phase changes that have occurred in an alloy that has been exposed to a particular heat treatment process.
What is Ellingham Richardson diagram?
An Ellingham diagram is a graph showing the temperature dependence of the stability of compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulfides. These diagrams were first constructed by Harold Ellingham in 1944.
What is the crystal structure of cobalt?
Cobalt is a chemical element with the symbol Co and atomic number 27….
| Cobalt | |
|---|---|
| Crystal structure | hexagonal close-packed (hcp) |
| Speed of sound thin rod | 4720 m/s (at 20 °C) |
| Thermal expansion | 13.0 µm/(m⋅K) (at 25 °C) |
How is cobalt formed?
Most cobalt is formed as a by-product of nickel refining. A huge reserve of several transition metals (including cobalt) can be found in strange nodules on the floors of the deepest oceans. The nodules are manganese minerals that take millions of years to form, and together they contain many tonnes of cobalt.
What is the crystalline structure of chromium?
Chromium, Cr At room temperature Chromium has a bcc (body-centered-cubic) crystal structure with a basis of one Cr atom.
What is cobalt in chemistry?
cobalt (Co), chemical element, ferromagnetic metal of Group 9 (VIIIb) of the periodic table, used especially for heat-resistant and magnetic alloys.
What are the main observations of Ellingham diagram?
Observations from the Ellingham diagram. Oxygen gas is consumed during the formation of metal oxides which results in the decrease in randomness. Hence, ΔS becomes negative and it makes the term, TΔS positive in the straight line equation.
How do you read an Ellingham diagram?
Reading pO2 from the Ellingham diagram A line is drawn from the origin of the graph (T = 0, ΔG = 0) through the point on the Ellingham line of interest, at the required temperature. The equilibrium partial pressure is read off at the point where the drawn line crosses the nomographic scale.
What is the main function of Ellingham diagram?
An Ellingham diagram is a tool widely used in the field of extraction metallurgy in order to determine conditions such as the necessary temperature needed to reduce the ores of essential metals. The diagram is a plot of Gibbs free energy versus temperature.
What is the oxidation state of chromium?
Chromium, named for its many-colored compounds, exists in the oxidation states of -2 to +6 inclusively.
Is chromium a transition metal?
The period 4 transition metals are scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).
Who are the authors of thermodynamic properties of cobalt-chromium alloy?
H.B. Bell, J.P. Hajra, F.H. Putland, and P.J. Spencer, “The Determination of the Thermodynamic Properties of Cobalt-Chromium Alloys Using Solid-Electriolyte EMF and High Temperature Calorimetric Techniques,” Met. Sci. J., 7, 185–190 (1973). (Thermo; Experimental)
Is there a structural relation between chromium oxide properties and catalytic properties?
Chromium oxides have been extensively investigated because of their possible industrial application in catalysts, but not much focus has been put on the structural relation to catalytic properties. Bai et al. [230] reported Cr (OH) 3 micro/nanohollow hexagonal pellets prepared by a single-step method and their catalytic properties.
Why does chromium oxide not form intermediate phases with alumina?
In the Cr 2 O 3 -Al 2 O 3 system, chromium oxide does not form intermediate phases with alumina, given that a region of continuous solid solutions exists below the solidus line, at least above 1500 K. At lower temperatures, the solid solution tends to decompose into two isomorphic chromia-rich and alumina-rich solutions.
What is the use of chromium oxide as a catalyst?
Chromium Oxide. Chromium oxide is a well known catalyst for the complete oxidation of chlorinated hydrocarbons due to its high removal activity [1-5].