Development of syntheses for nanostructured titania and silica
Doktorsavhandling, 2019
Nanostructured titania is of great interest for a variety of energy and environmental applications, including conversion of solar energy, for energy storage systems and removal of organic pollutants in water and air. Titania is composed of earth abundant elements, it is environmentally friendly and chemically stable which makes it an attractive material to utilize. For many of the applications of titania, high surface area is beneficial, and it can be achieved by designing materials with structural features in the nanometer range, e.g. particles of a few nanometer in diameter and mesoporous materials with pore diameters in the range of 2-50 nm. In addition, the degree of crystallinity and the polymorph type have large effects on the physicochemical properties of the material.
In this work, syntheses of titania nanoparticles and mesoporous titania and silica films were developed and the effect of varying relevant synthesis parameters on the structure on the atomic and nanometer scale was investigated. A low-temperature spray deposition method was developed to prepare ordered mesostructured titania and silica films via evaporation induced self-assembly (EISA) process, using a non-ionic block copolymer as a structure directing agent. The spray deposition method can be scaled up, the film thickness is tunable, surfaces of various shapes can be coated and heat sensitive substrates can be used. For the preparation of the mesoporous titania films, the polymer template was removed with UV radiation and the synthesis is carried out completely at temperatures below 50 °C. The effect of synthesis parameters, such as film thickness, synthesis time and aging time at high relative humidity on the structure at the atomic and nanometer scale were studied. Moreover, the prepared mesoporous titania was examined as an anode material in lithium ion batteries and the lithiation was studied in detail with electrochemical methods and structural characterization methods.
In addition, titania nanoparticles were synthesized under acidic conditions at low temperature and the polymorph selectivity studied. Unexpectedly, selectivity towards rutile was observed with short synthesis time and related to high concentration of the titania precursor, whereas the selectivity towards brookite and anatase was related to lower concentrations of the precursor.
In this work, syntheses of titania nanoparticles and mesoporous titania and silica films were developed and the effect of varying relevant synthesis parameters on the structure on the atomic and nanometer scale was investigated. A low-temperature spray deposition method was developed to prepare ordered mesostructured titania and silica films via evaporation induced self-assembly (EISA) process, using a non-ionic block copolymer as a structure directing agent. The spray deposition method can be scaled up, the film thickness is tunable, surfaces of various shapes can be coated and heat sensitive substrates can be used. For the preparation of the mesoporous titania films, the polymer template was removed with UV radiation and the synthesis is carried out completely at temperatures below 50 °C. The effect of synthesis parameters, such as film thickness, synthesis time and aging time at high relative humidity on the structure at the atomic and nanometer scale were studied. Moreover, the prepared mesoporous titania was examined as an anode material in lithium ion batteries and the lithiation was studied in detail with electrochemical methods and structural characterization methods.
In addition, titania nanoparticles were synthesized under acidic conditions at low temperature and the polymorph selectivity studied. Unexpectedly, selectivity towards rutile was observed with short synthesis time and related to high concentration of the titania precursor, whereas the selectivity towards brookite and anatase was related to lower concentrations of the precursor.
lithium intercalation
nanoparticles
X-ray characterization
mesoporous silica
mesoporous titania
spray deposition
Titanium dioxide
KB-salen, Kemigården 4, Chalmers
Opponent: Associate professor Nina Lock, Interdisciplinary Nanoscience Center, Aarhus University, Denmark
Författare
Gunnar Örn Simonarson
Chalmers, Kemi och kemiteknik, Tillämpad kemi
Evolution of the Polymorph Selectivity of Titania Formation under Acidic and Low-Temperature Conditions
ACS Omega,;Vol. 4(2019)p. 5750-5757
Artikel i vetenskaplig tidskrift
Símonarson, G., Lotsari, A., Palmqvist, A.E.C. Low-temperature spray deposition synthesis of locally ordered mesoporous polycrystalline titania films
Símonarson, G., Calcagno, G., Lotsari, A., Palmqvist, A.E.C. Electrochemical and structural characterization of lithiation in spray deposited ordered mesoporous titania as anode for Li ion batteries
Símonarson, G., Lotsari, A., Palmqvist, A.E.C. Preparation of ordered mesoporous silica films by low-temperature spray deposition.
A nanometer is equal to one billionth of a meter. To put that in context, the diameter of the average human hair is about 100.000 nanometers. Materials with structural features of 1-100 nanometers, are described as nanomaterials and the syntheses of these types of materials are the topic of this thesis work. A nanomaterial has, due to its size, different properties than the bulk of the same material, which makes them interesting to study for a variety of applications. Nanomaterials have large surface areas which affects how the material interacts with its surrounding and today nanomaterials are used all over the world in many products and fields, such as in computers, batteries and medicine. One type of nanomaterial is mesoporous materials which contain pores of 2-50 nanometers in diameter and the pore size and pore arrangement can be controlled. The materials can be prepared in a way that they have uniform pore size and the pores are ordered in a pattern so that the distance between them is equal.
To prepare ordered mesoporous materials, surface active molecules or surfactants are typically used. Most people come in contact with surfactants every day as they are the active ingredient in soap and detergents. Surfactants are molecules that are composed of two parts that are very different from each other, one part likes water (hydrophile) and the other part likes oil (hydrophobe). If surfactant molecules are added to liquids, they have the ability to aggregate and form structures with hydrophilic and hydrophobic regions of various shapes and sizes. This aggregation behavior stems from the hydrophilic parts tendency to be in contact with each other and water, whereas the hydrophobic parts like to be in contact with each other and oil. When the surfactants are mixed with an aqueous solution that contains dissolved oxides, e.g. silicon dioxide or titanium dioxide, the two components are attracted to each other and form particles with structures shaped by the surfactant molecules. The surfactant molecule can then be removed, leaving a porous structure of the previously dissolved oxide. The size of the pores and the pore arrangement can be controlled by the choice of surfactant, its concentration and other synthesis parameters such as temperature and acidity.
This thesis is aimed towards developing syntheses of titania nanoparticles and mesoporous titania and silica films and to investigate the effect of varying relevant synthesis parameters on the structure on the atomic and nanometer scale. A low‑temperature spray deposition method was developed to prepare ordered mesostructured titania and silica films. The prepared mesoporous titania was examined as an anode material for lithium ion batteries.
To prepare ordered mesoporous materials, surface active molecules or surfactants are typically used. Most people come in contact with surfactants every day as they are the active ingredient in soap and detergents. Surfactants are molecules that are composed of two parts that are very different from each other, one part likes water (hydrophile) and the other part likes oil (hydrophobe). If surfactant molecules are added to liquids, they have the ability to aggregate and form structures with hydrophilic and hydrophobic regions of various shapes and sizes. This aggregation behavior stems from the hydrophilic parts tendency to be in contact with each other and water, whereas the hydrophobic parts like to be in contact with each other and oil. When the surfactants are mixed with an aqueous solution that contains dissolved oxides, e.g. silicon dioxide or titanium dioxide, the two components are attracted to each other and form particles with structures shaped by the surfactant molecules. The surfactant molecule can then be removed, leaving a porous structure of the previously dissolved oxide. The size of the pores and the pore arrangement can be controlled by the choice of surfactant, its concentration and other synthesis parameters such as temperature and acidity.
This thesis is aimed towards developing syntheses of titania nanoparticles and mesoporous titania and silica films and to investigate the effect of varying relevant synthesis parameters on the structure on the atomic and nanometer scale. A low‑temperature spray deposition method was developed to prepare ordered mesostructured titania and silica films. The prepared mesoporous titania was examined as an anode material for lithium ion batteries.
Ämneskategorier
Oorganisk kemi
Materialkemi
Annan materialteknik
Infrastruktur
Chalmers materialanalyslaboratorium
Styrkeområden
Materialvetenskap
ISBN
978-91-7905-159-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4626
Utgivare
Chalmers
KB-salen, Kemigården 4, Chalmers
Opponent: Associate professor Nina Lock, Interdisciplinary Nanoscience Center, Aarhus University, Denmark