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Title:Vpliv nanodelcev na stopnjo nematične ureditve
Authors:ID Črešnar, Dejvid (Author)
ID Kralj, Samo (Mentor) More about this mentor... New window
Files:.pdf MAG_Cresnar_Dejvid_2018.pdf (1,37 MB)
MD5: 3F7F5039A17204501F86DB63263B6620
PID: 20.500.12556/dkum/dc91cd98-8acb-4916-bd3a-377af5de7d91
 
Language:Slovenian
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FNM - Faculty of Natural Sciences and Mathematics
Abstract:Nanodelci dispergirani v nematičnih tekočih kristalih v splošnem deformirajo nematično strukturo. V številnih primerih dispergirani nanodelci vplivajo na tekočekristalno ureditev podobno kot naključno polje. Slednje vsiljuje molekulam tekočih kristalov relativno naključno orientacijsko urejenost, katere verjetnostna porazdelitev je odvisna predvsem od geometrije nanodelcev in jakosti ter vrste sklopitve med nanodelci in obdajajočo tekoče kristalno matriko. Nedavne eksperimentalne meritve nakazujejo, da pri povečevanju koncentracije nanodelcev preide klasična nematična ureditev v fazo, ki spominja na paranematično ureditev. Prehod je postopen in se izvede v relativno ozkem oknu koncentracij nanodelcev pri relativno nizki koncentraciji (okoli 0,1%). Pri nadaljnjem povečevanju se stopnja nematične urejenosti relativno malo spreminja do koncentracij 1%. Slednje obnašanje še ni bilo teoretično obravnavano. V magistrskem delu izdelamo minimalni matematični model, ki kvantitativno in kvalitativno opiše spremembo orientacijskega ureditvenega parametra v prisotnosti nanodelcev, ki vsiljujejo naključno urejenost. Izpeljemo dvodimenzionalni mrežni model v odvisnosti od ureditvenega parametra pri temperaturi absolutne ničle. V približku povprečnega polja numerično rešimo izpeljane enačbe. Rezultati simulacij v dobrem približku reproducirajo modelirane eksperimentalne meritve.
Keywords:tekoči kristali, nematična faza, orientacijski ureditveni parameter, nanodelci, naključno polje, model naključnega anizotropnega nematika, približek povprečnega polja
Place of publishing:Maribor
Publisher:[D. Črešnar]
Year of publishing:2018
PID:20.500.12556/DKUM-71101 New window
UDC:544.252.22(043.2)
COBISS.SI-ID:24013832 New window
NUK URN:URN:SI:UM:DK:ADDF6NLX
Publication date in DKUM:21.09.2018
Views:1507
Downloads:116
Metadata:XML DC-XML DC-RDF
Categories:FNM
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Licences

License:CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Link:http://creativecommons.org/licenses/by-nc-nd/4.0/
Description:The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
Licensing start date:12.07.2018

Secondary language

Language:English
Title:The impact of nanoparticles on the degree of the nematic ordering
Abstract:Nanoparticles dispersed in nematic liquid crystals generally deform the nematic structure. In numerous examples dispersed nanoparticles affect liquid crystal ordering in a similar way as a random field. The latter enforces a random orientational order on the liquid crystal molecules, whose probability distribution depends mainly on the geometry of the nanoparticles and on the strength and type of coupling between the nanoparticles and the surrounding liquid crystal matrix. Recent experimental measurements indicate, that upon increasing the concentration of nanoparticles, the classical nematic order transitions into a paranematic order like phase. The transition is gradual and appears at a relatively low concetration (around 0,1%) within a relatively narrow range of nanoparticle concentration. Further increasing the concentration of nanoparticles up to 1% has relatively little effect on the degree of nematic ordering. This behaviour has yet to be theoretically studied. In this master thesis we construct a minimal mathematical model, which qualitatively and quantitatively descibes the change of the orientational order parameter due to the presence of nanoparticles, which enforce a random order. We derive a two-dimensional lattice model in terms of the order parameter at absolute zero kelvin. In the mean field approximation we numerically solve the equations of the derived model. The simulation results in a good approximation reproduce the modeled experimantal results.
Keywords:liquid crystals, nematic phase, orientational order parameter, nanoparticles, random field, random anisotropy nematic model, mean field approximation


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