Growth Mechanism of Controllable Fabrication of CaWO4 via Hydrothermal Synthesis
- Abstract
- Abstract
The precisely controllable synthesis of size, shape, chemical component, crystal structure, and surface nature of nanometerials provide the channel to their unique properties and become the challenging issues for scientists. Acquaintance with the nanomaterial characters of growth behavior and morphology evolution will facilitate the precise controlling and efficient synthesis of inorganic nanomaterials. Hydrothermal synthesis method has many advantages in compared with conventional and non-conventional synthesis methods in synthesize nano/microparticles with various size and shape. Understanding the influence parameters will help in better comprehension of hydrothermal process with fine and precise control in synthesis. In this dissertation, a series of experiment have been developed in exploring and discussing the influence parameters occurred during hydrothermal synthesis concentrated on CaWO4 with Eu3+ doping. The products were generally characterized using XRD, SEM, TEM/HRTEM, SAED, FTIR and photoluminescence techniques. The evolution process and growth mechanism were proposed based on the experimental results.
In the none-surfactant hydrothermal synthesis, we directed pH dependent and reaction time dependent experiment. The synthesis and growth mechanism of CaWO4:Eu3+ hierarchical dumbbell-like and double-broccoli-like microstructures via a surfactant-free hydrothermal process are studied. Time-dependent series are found dominant in the morphology evolution under proper pH=7. Also, the morphology dependent photoluminescent properties are also discussed.
The variation of surfactants and concentrations on the morphology of CaWO4 microstructures is discussed. Hollow sphere, nanoparticles, nanoflakes and star-shaped structure of CaWO4 crystal were successfully synthesized employing sodium citrate, CTAB, PEG, and citrate acid as surfactant in mild hydrothermal condition of 120 oC for 12 h. Changing the surfactant concentration has obviously significant influence on the product morphologies. The growth mechanism that surfactants adsorbed to the nucleus forming a protectoral structure inducing various morphology is discussed.
A group of water and alcohol based on mixed solution hydrothermal synthesis composed of water as well as MeOH, EtOH, 2-PrOH, and EG was carried out and products with different morphologies were obtained. Increment of water content is favorable for the increase of particles size. Adding sodium citrate assists for better crystallization and morphology was changed from flowerlike superstructure to bipyramidal particles. Selective binding to the {101} and {001} facets of CaWO4 nuclei is proposed for the growth mechanism of bipyramid morphology of CaWO4 crystal.
- Issued Date
- 2014
- Awarded Date
- 2014. 2
- Type
- Dissertation
- Publisher
- Pukyong National University
- Affiliation
- Pukyong National University, The Graduate School, Department of Physics
- Department
- 대학원 물리학과
- Advisor
- Jeong Jung Hyun
- Table Of Contents
- Contents
Chapter 1. Introduction and Motivation 1
1.1. Nanomaterial and Technologies 1
1.1.1. History of Nanomaterials 1
1.1.2. Definition of Nanomaterial and Specific Properties 2
1.1.3. Fabrication of Nanomaterial 5
1.1.3.1. Sol-Gel Method 7
1.1.3.2. Hydro-/solvothermal Method 9
1.1.3.3. Hot-injection Method 10
1.1.3.4. Microemulsion Method 10
1.2. Hydrothemal Synthesis 12
1.2.1. Definition and Development of Hydrothermal Synthesis 12
1.2.2. Applicative Material Types 13
1.2.3. Advantages of Hydrothermal Synthesis Methodology 13
1.3. Tungstate 14
1.3.1. Tungstate and Scheelite Structure 14
1.3.2. Crystallization of CaWO4 15
1.4. Rare Earth Ion doped 19
1.5. Objectives and Scope of the Dissertation 20
Chapter 2. Theoretical Background 22
2.1. Hydrothermal Synthesis Parameters 22
2.1.1. Thermodynamic Parameters 22
2.1.2. Chemical Parameters 26
2.1.2.1. Surfactant 26
2.1.2.2. Solvent 27
2.2. Nucleation Mechanism 30
2.2.1. Kinetics of Nucleation and Growth Process 30
2.2.1.1. La Mer Model 31
2.2.1.2. Nucleation 33
2.2.2. Ostwald Ripening and Oriented Attachment 37
Chapter 3. Experiment and Characterization 39
3.1. Teflon-Lined Acid Digestion Parr Autoclave 39
3.2. X-ray Powder Diffraction (XRD) 42
3.3. SEM 43
3.4. FT-IR 44
3.5. TEM 44
3.6. Photoluminescent Properties (PL) 46
Chapter 4. Thermodynamical Parameters On CaWO4:Eu3+ Superstructure in Non-surfactant Hydrothermal Ambient 47
4.1. Introduction of Thermodynamic Parameters 47
4.2. Experimental Section 48
4.3. pH Influence on CaWO4:Eu3+ Microstructures 51
4.4. Reaction Time Influence on CaWO4:Eu3+ growth Process 55
4.5. Growth Mechanism of CaWO4:Eu3+ Under Hydrothermal Condition with No Surfactant 62
4.6. Photoluminescence Properties of CaWO4:Eu3+ with Different Morphologies 64
4.7. Summary 69
Chapter 5. Surfactant Effect on CaWO4:Eu3+ Nanoparticles Synthesized in Hydrothermal Ambient 70
5.1. Introduction of Surfactant 70
5.2. Experimental Section 72
5.3. Effect of Surfactant on the Growth of CaWO4 75
5.3.1. Structure Characterization 75
5.3.2. Sodium Citrate Concentration on the Morphologies of CaWO4 77
5.3.3. CTAB Concentration on the Morphologies of CaWO4 80
5.3.4. PEG Concentration on the Morphologies of CaWO4 84
5.3.5. CA Concentration on the Morphologies of CaWO4 84
5.4. Temperature-Dependent Morphology 85
5.5. Reaction Time-Dependent Morphology 89
5.6. Growth Mechanism Proposal 92
5.7. Photoluminescent Properties 98
5.8. Summary 101
Chapter 6. Solution Effect on CaWO4:Eu3+ Crystal Synthesized in Hydro/solvothermal Ambient 103
6.1. Introduction 103
6.2. Experimental Section 103
6.3. Structure Characterization 106
6.4. Influence of Mixed Solvent on Morphologies 109
6.5. Surfactant Assisted Effect on Morphologies 114
6.6. Growth Mechanism 119
6.7. Summary 123
Chapter 7. Conclusions and Future Works 124
7.1. Conclusions 124
7.2. Recommendation of Future Work 127
Reference 129
Acknowledgement 139
- Degree
- Doctor
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