Our society depends overwhelmingly on carbon based resources (coal, natural gas and oil). The use of carbon based resources to meet the current energy needs of our society is associated with two critical drawbacks, that are: i) carbon based resources are not renewable and ii) burning hydrocarbons and venting the waste gases into atmosphere, e.g., carbon dioxide (CO2), leads to worsening of the greenhouse effect. As a response to these issues, the strategy of so-called “green carbon” has been proposed. This strategy consist of obtaining energies that foresees a gradual transition from carbon based resources to hydrogen based fuel, i.e., “hydrogen economy”, while simultaneously increasing the role of renewable energies. Carbon based resources would ultimately be used for synthesis of high-value chemicals and hydrogen (H2) generation. This strategy is possible to become a reality only if innovations in materials, chemistry, catalysis, and other engineering related fields are to occur. From a materials science perspective, extensive research is currently underway to develop materials able to store H2, to capture CO2, or to separate H2 from byproducts such as CO2, CO, or N2. This work aims to explore the opportunities, as well as the associated limitations of the use of silicon oxycarbonitride ceramics derived from preceramic polymers by NH3-assisted route for the above-mentioned applications, such as H2 gas separation membranes, and H2 or CO2 capture or storage materials in form of powders.
A simple and general synthesis method to tune the chemical composition and pore size, as well as the surface area of oxycarbonitride ceramics has been developed. This method is based on modifying the structure of preceramic polymers through chemical reactions with NH3 at 300 – 800 oC, followed by a thermolysis under an Ar atmosphere at 750 oC. Under these synthesis conditions a polysiloxane and a polysilazane transform to microporous ceramics, while materials derived from a polycarbosilane remain nonporous, as revealed by N2 and CO2 adsorption isotherms. Small angle X-ray scattering (SAXS) characterization indicates that samples prepared from the polycarbosilane possess latent pores (pore size < 0.35 nm) which are not accessible in the gas adsorption experiments. [...]
Inhaltsverzeichnis (Table of Contents)
- Abstract
- Zusammenfassung
- Introduction and motivation
- Part I. Basics
- Chapter 1. Literature survey.
- 1.1. NH3-assisted synthesis of silicon nitrides and carbonitrides
- 1.1.1. Silicon nitrides
- 1.1.2. Carbonitrides
- 1.1.3. Porosity evolution during polymer-to-ceramic conversion. Strategies to retain microporosity in polymer-derived ceramics at high temperatures…
- 1.2. Microporous materials for H₂ and CO2 gas capture and storage
- 1.2.1. Materials for H2 storage: current research trends and perspectives
- 1.2.1.1. Conventional H2 storage
- 1.2.1.2. Materials-based H2 storage.
- 1.2.1.3. Materials demands for H₂ storage by physisorption.
- 1.2.2. Materials for CO2 capture and storage: current research trends and perspectives.
- 1.2.3 Commercial prospectives for materials for gas capture and storage
- 1.2.1. Materials for H2 storage: current research trends and perspectives
- 1.3. Gas separation methods. Membranes for H₂ separation
- 1.3.1. General considerations and gas permeation mechanisms
- 1.3.1.1. Hagen-Poiseuille mechanism
- 1.3.1.2. Knudsen diffusion mechanism
- 1.3.1.3. Surface diffusion mechanism
- 1.3.1.4. Gas-translational mechanism
- 1.3.1.5. Molecular sieving
- 1.3.1.6. Solid state diffusion mechanism
- 1.3.1.7. Gas transport regime within pores of different size and composition
- 1.3.2. Membranes derived from polymer-derived ceramics (PDCs)..
- 1.3.1. General considerations and gas permeation mechanisms
- 1.1. NH3-assisted synthesis of silicon nitrides and carbonitrides
- Part II. Experimental
- Chapter 2. Experimental procedures…
- Part III. Results and discussion
- Chapter 3. Structure and porosity characteristics of silicon oxycarbonitride ceramics ..
- Chapter 4. Silicon oxycarbonitride ceramics for gas capture and separation………………..
Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)
This dissertation investigates the synthesis and characterization of silicon oxycarbonitride ceramics for gas capture and separation. The work focuses on the development of novel materials with tailored properties for efficient storage and separation of gases like hydrogen (H₂) and carbon dioxide (CO₂).
- Synthesis and characterization of silicon oxycarbonitride ceramics
- Gas capture and storage applications of silicon oxycarbonitride ceramics
- Gas separation using ceramic membranes
- Relationship between structure and porosity of the ceramics and their gas adsorption properties
- Impact of synthesis parameters on the properties of the resulting ceramics
Zusammenfassung der Kapitel (Chapter Summaries)
Chapter 1 provides a comprehensive literature review on the synthesis of silicon nitrides and carbonitrides, focusing on ammonia-assisted methods. It also explores the use of microporous materials for gas capture and storage, highlighting current research trends and perspectives for both H₂ and CO₂. The chapter concludes with a discussion on gas separation methods and the role of membranes in H₂ separation, emphasizing the importance of polymer-derived ceramics (PDCs) in this field.
Chapter 2 outlines the experimental procedures employed in the dissertation. It details the materials used, the synthesis parameters, and the characterization techniques applied. The chapter covers various analytical methods, including elemental analysis, Fourier transform infrared spectroscopy (FTIR), simultaneous thermal analysis (STA), X-ray scattering, solid-state nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), and gas adsorption experiments.
Chapter 3 delves into the structure and porosity characteristics of the synthesized silicon oxycarbonitride ceramics. It explores the thermal transformation of ceramers to ceramics, investigates nitrogen incorporation, and elucidates the local structures using NMR spectroscopy. The chapter further analyzes the homogeneity of elemental distribution, porosity development, and the nature of the adsorbing surfaces. It concludes with a discussion on the relationship between structure and porosity.
Chapter 4 focuses on the application of silicon oxycarbonitride ceramics for gas capture and separation. It examines the CO₂ capture capacity of ultramicroporous silicon nitride based ceramics, investigating the physical nature of adsorption and its dependence on pore size. The chapter also presents H₂ adsorption isotherms and discusses the gas permeation properties of ceramic membranes derived from polycarbosilane and polysiloxane.
Schlüsselwörter (Keywords)
Silicon oxycarbonitride ceramics, ammonia-assisted synthesis, gas capture, gas separation, hydrogen storage, carbon dioxide capture, microporous materials, polymer-derived ceramics, ceramic membranes, gas permeation, structure-property relationship.
- Chapter 1. Literature survey.
- Quote paper
- Cristina Schitco (Author), 2015, NH3-Assisted Synthesis of Silicon Oxycarbonitride Ceramics for Gas Capture and Separation, Munich, GRIN Verlag, https://www.grin.com/document/335128
