slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Thermal expansion in ZrP 2 O 7 . Data kindly supplied by John Evans PowerPoint Presentation
Download Presentation
Thermal expansion in ZrP 2 O 7 . Data kindly supplied by John Evans

Loading in 2 Seconds...

play fullscreen
1 / 3

Thermal expansion in ZrP 2 O 7 . Data kindly supplied by John Evans - PowerPoint PPT Presentation


  • 94 Views
  • Uploaded on

Thermal expansion in (M’ III 0.5 M V 0.5 )P 2 O 7 related to cubic ZrP 2 O 7 Angus P. Wilkinson, Georgia Institute of Technology , DMR-0203342.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Thermal expansion in ZrP 2 O 7 . Data kindly supplied by John Evans' - kato-fernandez


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
slide1

Thermal expansion in (M’III0.5MV0.5)P2O7 related to cubic ZrP2O7Angus P. Wilkinson, Georgia Institute of Technology, DMR-0203342

Thermal expansion characteristics of a material, that is how its dimensions change with temperature, are crucial to the construction of reliable devices subject to temperature change.

Most materials expand on heating, but there are some that display negative thermal expansion (NTE), that is they shrink on heating. This can be exploited by preparing parts that contain a mixture of a normal material and one that shrinks on heating (to make a composite), and hence tuning the parts overall thermal expansion.

Many members of the MIVP2O7 family of compounds display strong positive thermal expansion at low temperatures, and lower or NTE at high temperatures after going through a phase transition on heating.

We have been exploring how the replacement of MIV by mixtures of MIII and MV changes the phase transitions and thermal expansion characteristics that are seen.

Thermal expansion in ZrP2O7.

Data kindly supplied by John Evans

Replacement of Zr4+ by M’III0.5MV0.5 produces materials with no obvious phase transition above room temperature. Some combinations of M’IIIMVlead to CTEs close to those of low temperature ZrP2O7, while other give CTEs similar to high temperature ZrP2O7

slide2

Thermal expansion in (M’III0.5MV0.5)P2O7 related to cubic ZrP2O7Angus P. Wilkinson, Georgia Institute of Technology, DMR-0203342

As part of our work examining the solid state chemistry of negative thermal expansion frameworks we have recently started to examine pressure induced amorphization in negative thermal expansion materials. These experiments have involved current and former Georgia Tech students/postdocs (Cora Lind, Tamas Varga, Mehemet Cetinkol and Andrew Jupe) and collaborators at both the CHiPR (Center for High Pressure Research – an NSF supported center) and Cornell /CHESS (Prof. Bill Basset and Dr. Zha). We are investigating the structural changes that occur in NTE materials as they are compressed and transform to glasses. This amorphization is an important problem in the fabrication of some controlled thermal expansion composite materials. Several different mechanisms have been proposed for the amorphization by other workers and it has even been proposed that the amorphization is intimately tied to the NTE characteristics of the starting material. We are examining both the structure of glasses recovered from high pressure, using X-ray absorption spectroscopy, and the structure of materials as they are amorphized in a diamond anvil cell using a combination of in-situ X-ray absorption spectroscopy and diffraction. The structural studies are being performed at CHESS, an NSF supported synchrotron facility located on the campus of Cornell University. The structural information that we are obtaining will help us distinguish between different possible amorphization mechanisms.

slide3

Thermal expansion in (M’III0.5MV0.5)P2O7 related to cubic ZrP2O7Angus P. Wilkinson, Georgia Institute of Technology, DMR-0203342

Education:

Five graduate students (Cora Lind, Tamas Varga, Kathy White and Mehmet Cetinkol, Mehmet Kutukcu), an three undergraduates (Michael Morant, Jordan Vincent and Daniel Lemus) and a postdoc (Andrew Jupe) have contributed to our work on NTE materials. Cora, after spending a postdoctoral period at Cornell, joined the chemistry faculty at the University of Toledo, OH.

Outreach:

The PI has helped run a (separately NSF supported) summer program for chemistry undergraduates and faculty from schools with little or no research activity.

He is also involved in organizing and teaching workshops on powder diffraction methodology and crystallography that address the needs of US graduate students.

2005 summer students outside the SNS office building during their tour of Oak Ridge National Laboratory

Cora adjusts a cryostat prior to an experiment at the Advanced Photon Source