<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:DengXian;
panose-1:2 1 6 0 3 1 1 1 1 1;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Cambria;
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:LucidaGrande;}
@font-face
{font-family:"\@DengXian";
panose-1:2 1 6 0 3 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman",serif;
mso-fareast-language:SL;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}
p.Default, li.Default, div.Default
{mso-style-name:Default;
margin:0cm;
margin-bottom:.0001pt;
text-autospace:none;
font-size:12.0pt;
font-family:"Arial",sans-serif;
color:black;
mso-fareast-language:ZH-CN;}
.MsoChpDefault
{mso-style-type:export-only;
mso-fareast-language:EN-US;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><a name="_Hlk20313133"><span lang=SL>Vabimo vas na 4. predavanje iz sklopa "Kolokviji na IJS" v letu 2019/20, ki bo <strong><span style='color:red'>v sredo, 4. decembra 2019, ob 13. uri </span></strong><span style='color:red'>v Veliki predavalnici Instituta »Jožef Stefan«</span> na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu </span></a><a href="http://www.ijs.si/ijsw/Koledar_prireditev"><span style='mso-bookmark:_Hlk20313133'><span lang=SL>http://www.ijs.si/ijsw/Koledar_prireditev</span></span><span style='mso-bookmark:_Hlk20313133'></span></a><span style='mso-bookmark:_Hlk20313133'><span lang=SL>, posnetke preteklih predavanj<span style='color:blue'> </span>pa na </span></span><a href="http://videolectures.net/kolokviji_ijs"><span style='mso-bookmark:_Hlk20313133'><span lang=SL>http://videolectures.net/kolokviji_ijs</span></span><span style='mso-bookmark:_Hlk20313133'></span></a><span style='mso-bookmark:_Hlk20313133'><span lang=SL>. <o:p></o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br><br><o:p></o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><b><span lang=EN-US>prof. dr. Vid Bobnar<o:p></o:p></span></b></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><i><span lang=EN-US>Institut Jožef Stefan, Ljubljana<o:p></o:p></span></i></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;text-align:justify'><span style='mso-bookmark:_Hlk20313133'><b><span lang=SL style='font-size:14.0pt'>Razvoj novih anorganskih in polimernih sistemov z ojačenim dielektričnim in elektromehanskim odzivom<o:p></o:p></span></b></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt;text-align:justify'><span style='mso-bookmark:_Hlk20313133'><span lang=SL>V predavanju bomo na različnih primerih pokazali, da je mogoče nove materiale z visokim dielektričnim in piezoelektričnim odzivom, ki so nujno potrebni v sistemih za shranjevanje energije in v elektromehanskih aplikacijah, učinkovito razviti z upoštevanjem nekaterih osnovnih fizikalnih pojavov. (i) V heterogenem sistemu, sestavljenem iz dielektrične matrice in električno prevodnih vključkov, naboj na mejah med fazama deluje kot velik električni dipol. S takoimenovano Maxwell-Wagnerjevo polarizacijo smo učinkovito povečali dielektrično konstanto elektroaktivnih polimerov, sintetiziranih na osnovi PVDF, in tako znatno zmanjšali zunanje električno polje, potrebno za njihov velikanski elektrostrikcijski odziv. Analogno smo izdelali fleksibilne in okolju prijazne kompozite iz celuloznih nanovlaken in grafenovega oksida ter anorganske materiale, kot so keramični perkolativni kompoziti in tanke plasti s strukturo jedro-lupina, ki so sestavljene iz polprevodnih zrn, ločenih s tankimi neprevodnimi mejami. (ii) V tankih plasteh je elektromehanski odziv običajno močno zmanjšan zaradi njihovega mehanskega vpetja na podlago. Razvili smo preprosto in robustno metodo za pripravo poroznih feroelektričnih tankih plasti s sintezo iz raztopin. V teh plasteh se zaradi relaksacije mehanskih napetosti vrednosti piezoelektričnih koeficientov povečajo na vrednosti, tipične za keramične materiale v kosu. (iii) V sistemih z močno sklopljenimi električnimi dipoli se zaradi izrazite polarizacijske histereze povečajo tudi dielektrične izgube. Kot alternativo široko uporabljanim polimerom na osnovi PVDF bomo predstavili nov dielektrični polimer, aromatsko politiurejo, in primerjali odziv tega amorfnega polimera v steklasti fazi (s šibko sklopljenimi dipoli) z odzivom komercialno uporabljanih sistemov. <o:p></o:p></span></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'><span style='mso-bookmark:_Hlk20313133'><strong><span lang=SL style='color:red'>Lepo vabljeni!<o:p></o:p></span></strong></span></p><p class=MsoNormal style='margin-left:216.0pt;text-indent:36.0pt'><span style='mso-bookmark:_Hlk20313133'><span lang=SL><o:p> </o:p></span></span></p><p class=MsoNormal style='margin-left:216.0pt;text-indent:36.0pt'><span style='mso-bookmark:_Hlk20313133'><span lang=SL>*******************************<o:p></o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL><o:p> </o:p></span></span></p><span lang=SL style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:SL'><br clear=all style='page-break-before:always'></span><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL style='color:black'>We invite you to the 4th Institute colloquium in the academic year 2019/20. The colloquium will be held </span><b><span lang=SL style='color:red'>on Wednesday December 4, 2019 at 1 PM</span></b><span lang=SL style='color:red'> in <b>the main Institute lecture hall</b></span><span lang=SL style='color:black'>, Jamova 39, Ljubljana. To read the abstract click </span></span><a href="http://www.ijs.si/ijsw/Koledar_prireditev"><span style='mso-bookmark:_Hlk20313133'><span lang=SL>http://www.ijs.si/ijsw/Koledar_prireditev</span></span><span style='mso-bookmark:_Hlk20313133'></span></a><span style='mso-bookmark:_Hlk20313133'><span lang=SL style='color:#1F497D'>. </span><span lang=SL style='color:black'>Past colloquia are posted on</span><span lang=SL style='color:#1F497D'> </span></span><a href="http://videolectures.net/kolokviji_ijs"><span style='mso-bookmark:_Hlk20313133'><span lang=SL>http://videolectures.net/kolokviji_ijs</span></span><span style='mso-bookmark:_Hlk20313133'></span></a><span style='mso-bookmark:_Hlk20313133'><span lang=SL style='color:#1F497D'>.<o:p></o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL style='color:#1F497D'><o:p> </o:p></span></span></p><p class=MsoNormal style='margin-bottom:12.0pt'><span style='mso-bookmark:_Hlk20313133'><span lang=SL>********************************************<b><o:p></o:p></b></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><b><span lang=EN-US>prof. dr. Vid Bobnar<o:p></o:p></span></b></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><i><span lang=EN-US>Institut Jožef Stefan, Ljubljana<o:p></o:p></span></i></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><b><i><span lang=EN-US><o:p> </o:p></span></i></b></span></p><p class=Default><span style='mso-bookmark:_Hlk20313133'><b><span lang=SL style='font-size:14.0pt;font-family:"Times New Roman",serif;color:#202020;mso-fareast-language:SL'>Designing novel inorganic and polymer systems with enhanced dielectric and electromechanical response<o:p></o:p></span></b></span></p><p class=Default><span style='mso-bookmark:_Hlk20313133'><span lang=EN-US style='font-family:"Times New Roman",serif'><o:p> </o:p></span></span></p><p class=MsoNormal style='text-align:justify'><span style='mso-bookmark:_Hlk20313133'><span lang=EN-US style='font-family:"Cambria",serif;color:black;mso-fareast-language:EN-US'>The lecture will demonstrate, using various examples from our work, that novel materials with high dielectric and piezoelectric response, required in energy storage systems and electromechanical applications, can efficiently be developed by taking into account some basic physical phenomena. (i) In a heterogeneous system composed of dielectric matrix and electrically conductive inclusions, the charge accumulated at phase boundaries acts as a large electric dipole. Using this Maxwell-Wagner polarization we have effectively increased the dielectric permittivity of PVDF-based electroactive polymers and thus substantially reduced the electric field required for their giant electrostrictive response. Analogously, we have fabricated flexible, eco-friendly composites from cellulose nanofibrils and graphene oxide as well as inorganic materials such as bulk all-ceramic percolative composites and core-shell structured thin films that consist of semiconducting grains separated by thin insulating grain-boundaries. (ii) In thin films the electromechanical response is obstructed by the mechanical clamping of the substrate, resulting in a deterioration of the piezoelectric coefficients. We have thus developed a simple and robust method for the chemical solution deposition of highly porous ferroelectric thin films, where the porosity-mediated release of the substrate’s mechanical constraints enhances piezoelectric coefficients back to the level of bulk ceramics. (iii) Systems with strongly coupled dipoles also exhibit pronounced polarization hysteresis, which increases dielectric losses. As an alternative to the widely used PVDF-based polymers we will present a new class of dielectric polymer, aromatic polythiourea, and compare the response of this amorphous, glass-phase polymer (with weak coupling among the dipoles) with the response of commercially used systems.<o:p></o:p></span></span></p><p class=MsoNormal style='text-align:justify'><span style='mso-bookmark:_Hlk20313133'><span lang=EN-US style='font-family:"Cambria",serif;mso-fareast-language:EN-US'><o:p> </o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL><o:p> </o:p></span></span></p><p class=MsoNormal><span style='mso-bookmark:_Hlk20313133'><span lang=SL>Cordially invited!</span></span><span lang=SL><o:p></o:p></span></p><p class=MsoNormal><span lang=SL style='font-size:11.0pt;font-family:"Calibri",sans-serif'><o:p> </o:p></span></p></div></body></html>