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Role of intericosahedral chains on hardness of sputtered boron carbide films
Materials Science and Technology Division, Los Alamos National Laboratory.
Materials Science and Technology Division, Los Alamos National Laboratory.
Materials Science and Technology Division, Los Alamos National Laboratory.
Materials Science and Technology Division, Los Alamos National Laboratory.
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2004 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 21, 4173- p.Article in journal (Refereed) Published
Abstract [en]

The relationship between the structure and mechanical properties of sputter-deposited boron carbide films was investigated. Changes in the structure induced by annealing were characterized in terms of chemical composition, chemical bonding, and concentrations of defects and trapped impurities. The creation of intericosahedral chains for higher annealing temperatures was revealed by infrared and Raman measurements, and the intensity of the infrared band at 1500 cm–1 was found to be related to the hardness. The presence of residual trapped Ar atoms and of open-volume defects is insensitive to relatively high annealing temperatures and does not influence the recovery of the hardness. Our results suggest postdeposition annealing as a pathway to enhance the mechanical properties of boron carbide films.

Place, publisher, year, edition, pages
2004. Vol. 84, no 21, 4173- p.
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:su:diva-27414DOI: 10.1063/1.1755841OAI: oai:DiVA.org:su-27414DiVA: diva2:214097
Available from: 2009-05-02 Created: 2009-05-02 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Experimental investigation of molecular solids and vanadium at high pressure and temperature
Open this publication in new window or tab >>Experimental investigation of molecular solids and vanadium at high pressure and temperature
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Understanding high pressure effects on simple molecular system is of great interest for condensed matter science and geophysics. Accessing the static pressure and temperature regions found in planetary interiors is made possible by the development of the Diamond Anvil Cell technique. We developed a double sided resistive heating method for the membrane DAC operating in low pressure (<0.5 mTorr) pressure environment requiring only 175 W input power to reach sample temperatures up to 1300 K. We applied this technique successfully to study molecular solids at high temperatures, such as H2, N2 and CO2. We made an attempt to determine the melting line of hydrogen and present data up to 26 GPa in agreement with literature. Raman spectroscopy of Nitrogen indicates a high stability of the ε molecular phase, while θ phase is only accessible via certain P, T paths. Studies of solid CO2 at high pressure and temperature lead to the discovery of a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO2-II above 50 GPa at 530-650 K, or by isobaric heating of CO2-III above 55 GPa. From our X-ray diffraction experiment on isothermally compressed H2O we report a coexistence of ice VII and symmetric ice X from the start of the transition pressure 40GPa to just below 100 GPa and a volume change of 4% across the transition.

Vanadium, a transition metal undergoes a phase transition upon compression unlike other elements (Nb, Ta) from its group. We confirm the bcc phase transition to rhombohedral structure at 62 GPa under quasi hydrostatic compression in Ne pressure medium. Compression without pressure medium results in a much lower 30 GPa transition pressure at room temperature and 37 GPa at 425 K, pointing to a positive phase line between the bcc and rhombohedral crystalline phases.

 

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2009. 71 p.
Keyword
molecular solid, high pressure, vanadium, phase transition
National Category
Physical Sciences
Research subject
Physics Of Matter
Identifiers
urn:nbn:se:su:diva-26917 (URN)978-91-7155-868-8 (ISBN)
Public defence
2009-05-26, sal FB53, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
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Available from: 2009-05-05 Created: 2009-04-17 Last updated: 2009-05-04Bibliographically approved

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