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[Fizinfo] Előadás


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  • From: Imre Attila <imre AT aeki.kfki.hu>
  • To: fizinfo AT lists.kfki.hu, aekiusers AT lists.kfki.hu
  • Subject: [Fizinfo] Előadás
  • Date: Mon, 6 Jun 2011 12:16:30 +0200 (CEST)
  • List-archive: <http://mailman.kfki.hu/pipermail/fizinfo>
  • List-id: ELFT HÍRADÓ <fizinfo.lists.kfki.hu>

Tisztelt Kollegák!
Június 14-én (kedd) Prof. Atul Khanna (Department of Physics, Guru Nanak Dev
University
Amritsar-143005, India) tart előadást, amelynek címe:
"Exploring the mystery of glass: Investigations in borate, silicate and tellurite glasses" (az absztrakt lent található).
Az előadásra minden érdeklődőt szeretettel várunk, kezdés 10.00, KFKI AEKI Tanácsterem (XIX. épület, földszínt).

Imre Attila


Attila Imre
KFKI Atomic Energy Research Institute
H-1525 Budapest POB 49, Hungary
(1121 Budapest, Konkoly Thege Str. 29-33, Hungary)
Tel.: +36-1-392-2222, ext.1117 or 3366
Fax: +36-1-392-2684



Exploring the mystery of glass: Investigations in borate, silicate and tellurite glasses

Atul Khanna
Department of Physics
Guru Nanak Dev University
Amritsar-143005, India

Email:
ak.ap AT gndu.ac.in

The study of glasses and melts is a challenging problem of condensed matter physics[1]. Glasses are metastable solids that can be prepared by melt-quenching, neutron and ion irradiation and pressure induced amorphization. Some of the older, yet unanswered questions in glass physics are the understanding of fundamental conditions for glass formation, the relationship of a liquid with its glass, the origin of fragility in glass forming liquids, and the low temperature thermal properties of glasses which are strikingly different from crystals. Among the more recent and surprising discoveries in glasses and liquids that awaits proper understanding: is the phenomenon of polyamorphism first discovered in amorphous solidified water (ASW) and more recently in Y2O3-Al2O3 glasses, molten phosphours, metallic glasses and carbonic acid.
During the last decade we have prepared and extensively studied mechanical, thermal, optical and structural properties of several borate, borosilicate, silicate and tellurite glass systems by techniques like DSC, infrared, UV-visible, high field MAS-NMR spectroscopy, neutron diffraction and small angle neutron scattering, low temperature specific heat capacity measurements, and insitu high pressure spectroscopic studies using synchrotron radiation sources. In this talk I will revisit the outstanding problems of glass science and present results of our investigations in oxide glasses [2-6]. Some of the most notable findings from our laboratory are the influence of melt history on the glass forming ability of bismuth borate melts, which are found to be metastable liquids. Our studies reveal that it is possible to control crystallization in bismuth borate glasses by controlling the initial heat treatment given to the melt. These findings indicate that the bismuth borate melt is in all probability under negative absolute pressure, which causes metastability in the liquid and a consequent liquid-liquid phase separation. Lead silicate glasses show an interesting effect of melt quenching rate on the devitrification properties of glasses. Glasses prepared at higher quenching rate show greater tendency towards crystallization on heat treatment. Borate, silicate and tellurite glasses containing heavy metal ions like Bi3+, Pb2+, Nb5+ and W6+ show an intense optical absorption band just below the absorption edge. This band can have useful light emitting properties.
Small angle neutron and X-ray scattering measurements show the existence of heterogeneities in lead and bismuth borate glasses in composition region where these glasses are believed to be one phase systems. Finally, our low temperature specific heat capacity measurements show the existence of universal maxima in Cp/T3 in several borate, tellurite and silicate glasses at T~ 10 K. We correlate this maxima with the Boson peak in low frequency Raman spectra of glasses.

[1] P.W. Anderson, Science 267(1995) 1615.
[2] Arshpreet Kaur, Atul Khanna, Carmen Pesquera, Fernando González and Vasant Sathe, J. Non Cryst. Solids, 356 (2010)864.
[3] Anu Bajaj, Atul Khanna, Narendra Kulkarni, S. K. Aggarwal, J. Am. Ceram. Soc. 92[5] (2009)1036.
[4] Anu Bajaj, Atul Khanna, Banghao Chen, James G. Longstaffe, U-Werner Zwanziger, J. W. Zwanziger, Yolanda Gómez and Fernando González, J. Non Cryst. Solids 355(2009)45.
[5] Amanpreet Saini , Atul Khanna, Vladimir K. Michaelis, Scott Kroeker, Fernando González and David Hernández, J. Non Cryst. Solids 355(2009)2323.
[6] Anu Bajaj and Atul Khanna, J. Phys. Condensed Matter 21(2009)035112.





  • [Fizinfo] Előadás, Imre Attila, 06/06/2011

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