Manganese oxide formation by heat treatment of MnCO
This presentation is the property of its rightful owner.
Sponsored Links
1 / 8

Manganese oxide formation by heat treatment of MnCO 3 in air. PowerPoint PPT Presentation


  • 151 Views
  • Uploaded on
  • Presentation posted in: General

Manganese oxide formation by heat treatment of MnCO 3 in air. <500 C Reaction 1. MnCO 3 + ½ O 2 MnO 2 +CO 2. >500 C Reaction 2. 2 MnCO 3 + ½ O 2 Mn 2 O 3 + 2 CO 2. Note that in reaction 1, there is a net increase

Download Presentation

Manganese oxide formation by heat treatment of MnCO 3 in air.

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Manganese oxide formation by heat treatment of mnco 3 in air

Manganese oxide formation by heat treatment of MnCO3 in air.

<500 C Reaction 1

MnCO3 + ½ O2MnO2+CO2

>500 C Reaction 2

2 MnCO3 + ½ O2Mn2O3 + 2 CO2

Note that in reaction 1, there is a net increase

Of ½ mole of gas for each mole of Mn, and for reaction 2 there is a net increase of ¾ of a mole of gas for each mole of Mn. What can you say about the entropy change in each reaction? How does this help explain the temperature dependence between the two reactions?


Manganese oxide formation by heat treatment of mnco 3 in air

As the manganese oxide particles form from the carbonate salt, they begin to grow together, or ‘sinter’. The figure below is a TEM micrograph of neck formation during the sintering of Mn2O3 particles.

Neck

Pore

0.2 um

Neck

Why do the necks get larger and the pores get smaller as the heat treat time and or temperature increases?


Manganese oxide formation by heat treatment of mnco 3 in air

Sintering of Nickel powder. The time lapse photography illustrates Neck formation and coarsening.


Manganese oxide formation by heat treatment of mnco 3 in air

ΔP


Manganese oxide formation by heat treatment of mnco 3 in air

P

σ=Patm + 2γ/r

P=Patm

r

Flat surface

Curved surface

ΔP=2γ/r


Manganese oxide formation by heat treatment of mnco 3 in air

‘Master’ Equation of Thermodynamics

For an isothermal process with no change in composition

Divide both sides by the number of atoms in the system=N

ΔP=2γ/r for inside a spherical particle.


Manganese oxide formation by heat treatment of mnco 3 in air

Positive and Negative Curvature

Corrugated Surface Example (2D)

vapor

ΔP=-γ/r

Negative Curvature

Atoms move from

high free energy to low.

solid

ΔP=γ/r

Positive Curvature


Manganese oxide formation by heat treatment of mnco 3 in air

Two sphere model

r2

r1

r

The neck has a negative curvature component (-1/ρ), acting to reduce the pressure relative to the spherical surface.


  • Login