Wpływ efektu nanouwięzienia na przejścia fazowe w nanoporowatych układach
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Date
2016
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Effects of Confinement on Phase Transitions in Nanoporous Systems
Abstract
Celem pracy było zbadanie struktury lodu powstałego wewnątrz tych materiałów mezoporowatych w zależności od rozmiaru, kształtu oraz rodzaju powierzchni ścianek porów oraz określenie temperatury topnienia uwięzionego lodu w stosunku do temperatury tego procesu w warunkach swobodnych. Badanie zjawiska topnienia wykonano również dla kilku cieczy dipolowych posiadających większe molekuły niż cząsteczki wody. W celach badawczych, zostały zsyntetyzowane materiały krzemionkowe (typu SBA-15 oraz KIT-6), węglowe (CMK-3 i CMK-8) oraz materiały węglowe o zmodyfikowanej powierzchni
(CMK-8), posiadające uporządkowaną mezoporowatą strukturę. Przeprowadzone badania wykazały, że temperatura topnienia lodu uwięzionego w porach zależy gównie od ich rozmiaru. Stwierdzono, że wielkość przesunięcia temperatury topnienia jest większa dla porów o mniejszej średnicy, i że zależność ta ma charakter liniowy dla większych wymiarów porów (do ok 6 nm), niezależnie od rodzaju ścianek porów.
Stwierdzono, że lód w warunkach ograniczenia posiada strukturę dwufazową, znaną dla lodu swobodnego jako „stacking disordered ice”, złożoną z uporządkowanych naprzemiennie warstw lodu heksagonalnego kubicznego. Wykazano, że struktura takiego lodu zdeterminowana jest poprzez parametry takie jak: rozmiar, kształt oraz rodzaj ścianek porów.
The main objective of the thesis was the experimental investigation of the nanoconfinement effect of water in nanopores, e.g. determination how the pore size, shape and the type of the wall of pore influence the value of the melting temperature. The melting behavior of other dipolar substances with larger than water molecules confined in silica pores was also investigated. The second aspect of this study was the investigation of how these parameters (size, shape and the type of the wall) affect the formation of structure of confined ice. For the research purposes, various ordered mesoporous materials were synthetized like silica SBA-15, KIT-6, carbons: CMK-3 and CMK-8 as well as CMK-8 with modified surface by metal-nitrogen doping. The core shell hierarchical nanocarbon, characterized by a different morphology than the aforementioned materials, was also prepared. The results of the structural investigations confirm the existence of the different than hexagonal, form of ice in pores. The results show, that the structure of confined ice depends, on such parameters as size, shape and also kind of pore walls. It was demonstrated, that the melting temperatures of the confined substances were depressed in respect to the melting temperature of the bulk substances. It was shown that the melting temperature depression of the adsorbates depends linearly on the size, only for pores larger than 6 nm.
The main objective of the thesis was the experimental investigation of the nanoconfinement effect of water in nanopores, e.g. determination how the pore size, shape and the type of the wall of pore influence the value of the melting temperature. The melting behavior of other dipolar substances with larger than water molecules confined in silica pores was also investigated. The second aspect of this study was the investigation of how these parameters (size, shape and the type of the wall) affect the formation of structure of confined ice. For the research purposes, various ordered mesoporous materials were synthetized like silica SBA-15, KIT-6, carbons: CMK-3 and CMK-8 as well as CMK-8 with modified surface by metal-nitrogen doping. The core shell hierarchical nanocarbon, characterized by a different morphology than the aforementioned materials, was also prepared. The results of the structural investigations confirm the existence of the different than hexagonal, form of ice in pores. The results show, that the structure of confined ice depends, on such parameters as size, shape and also kind of pore walls. It was demonstrated, that the melting temperatures of the confined substances were depressed in respect to the melting temperature of the bulk substances. It was shown that the melting temperature depression of the adsorbates depends linearly on the size, only for pores larger than 6 nm.
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Sponsor
This work and presented here results were made with the financial support of the Foundation for Polish Science, Innovative Economy Operational Programme (IE OP) for 2007-2013 under the European Regional Development Fund and the project MPD "The PhD Program in Nanoscience and Nanotechnology "
Keywords
nanouwięzienie, nanoconfinement, przejścia fazowe, phase transition, mezoporowate materiały, mesoporous materials