HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER’S THESIS Simulation of structure of CaO – P2O5 – SiO2 material system with various ratios of P2O5/CaO NGUYEN MAI ANH anh.vn Supervisor: Ph. Nguyen Van Hong Department: Computational Physics School: Engineering Physics Hanoi, 10/2023 CỘNG HÒA XÃ HỘI CHỦ NGHĨA VIỆT NAM Độc lập – Tự do – Hạnh phúc BẢN XÁC NHẬN CHỈNH SỬA LUẬN VĂN THẠC SĨ Họ và tên tác giả luận văn : Nguyễn Mai Anh Đề tài luận văn: Mô phỏng cấu trúc hệ vật liệu CaO-P2O5-SiO2 với tỉ lệ thành phần P2O5/CaO thay đổi Ngành: Vật lý kỹ thuật Mã số SV: 20212446M Tác giả, Người hướng dẫn khoa học và Hội đồng chấm luận văn xác nhận tác giả đã sửa chữa, bổ sung luận văn theo biên bản họp Hội đồng ngày 17/10/2023 với các nội dung sau: 1. Điều chỉnh chỉ số trên, chỉ số dưới của các công thức hóa học 2. Sửa lại các danh từ chuyên ngành 3.
Đánh số thứ tự cho các phương trình 4. Điều chỉnh kích cỡ đô thị 5. Bổ sung và chỉnh sửa nội dung của phần kết luận Ngày 30 tháng 10 năm 2023 Giáo viên hướng dẫn Tác giả luận văn CHỦ TỊCH HỘI ĐỒNG HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY MASTER’S THESIS Simulation of structure of CaO – P2O5 – SiO2 material system with various ratios of P2O5/CaO NGUYEN MAI ANH anh.vn School of Engineering Physics Department of Computational Physics Supervisor (Sign and write full name) Nguyen Van Hong Hanoi, 10/2023 Acknowledgement I would like to express my special appreciation to my supervisor, Associate Prof. Nguyen Van Hong, for his guidance and invaluable feedback.
I also could not have undertaken this journey without my defense committee, who generously provided knowledge and expertise. In addition, I would like to extend my sincere thanks to Hanoi University of Science and Technology and the School of Engineering Physics for creating favorable conditions for learning and researching. I am also grateful to my friends and classmates, who have been by my side and encouraged me throughout the research process. Lastly, this endeavor would not have been possible without love, understanding and encouragement from my family.
Abstract The structure of the CaO-P2O5-SiO2 system at 3000K is investigated by molecular dynamics simulation. The models with various concentrations of P2O5 (5- 40 mol%) are constructed by using Born-Mayer-Huggins potentials. The size of the models is from 5270-5520 atoms. The short-range order, intermediate-range order, and network structure are clarified in detail.
The structural and compositional heterogeneities and the mechanism of alkaline earth metals incorporation into -O-P- O-Si-O- network have been discussed. This is useful information for designing bioactive systems with many potential applications. Author of the thesis (Sign and write name) Nguyen Mai Anh CONTENTS LIST OF ABBREVIATIONS AND SYMBOLS. 1 LIST OF FIGURES.
2 LIST OF TABLES. Purpose and Scope of the study. The scientific and practical significance of the topic. New contributions of the thesis.
The structure of the thesis .1 Hazardous waste storage .2 Bioactive glass in medical applications .3 The parameters of glass systems in previous studies. 11 Chapter 2 : CALCULATION METHOD .1 Material model and simulation method .2 Periodic boundary conditions .3 Potential of model .2 Visual analysis of material structural properties .1 Radial distribution function .2 Coordination number distribution .3 Angle distribution function .4 The bond forms of oxygen atom. 24 Chapter 3 : RESULT AND DISCUSSION.1 Short range order .1 Radial distribution functions .2 Coordination number distribution .3 Bond angle distributions and Bond distance distributions .2 Intermediate range order .1 Distribution of OMy units .2 Distribution of types of linking oxygens. 48 LIST OF ABBREVIATIONS AND SYMBOLS MD Molecular dynamics HA Hydroxyapatite HWL High-level waste RDF Radial distribution function CN Coordination number SRO Short range order IRO Intermediate range order BAD Bond angle distribution BO Bridging oxygen NBO Non-bridging oxygen FO Free oxygen BDD Bond distance distribution 1 LIST OF FIGURES Figure 2.1: Simulation model of CPS material with 30 mol% P2O5.
Blue, black, red, yellow spheres are Ca, P, Si, O atoms respectively.2: RDF of Si-Si in CPS model with 5 mol% P2O5 .1: Radial distribution function (RDF) of Ca-O, P-O, Si-O with various P2O5 ratios.2: Coordination number distribution of Ca, P, Si as a function of P2O5 content .3: Distributions of coordination units CaOx, POx, SiOx as a function of P2O5 content .4: Bond angle and distance distribution of POx (x=4, 5, 6) at different P2O5 content .5: Bond angle and bond distance distribution of SiOx (x=4, 5) at different P2O5 content .6: Bond angle distribution of TOx (T=Si, P, x=4, 5, 6) with concentrations of P2O5 .7: Coordination number distribution of OMx (x=2, 3, 4) as a function of P2O5 content .8: Fraction of BO and NBO as a function of P2O5 content .9: Models of PO4 clusters. Black and yellow spheres are O and P atoms respectively. a, b, c, d, e, f, g models are 5, 9, 13, 17, 21, 24, 25 atoms clusters respectively.10: Models of PO4 clusters distribution. A, b, c, d models are models with 5, 10, 15, 20 mol% P2O5 respectively.11: Models of PO4 clusters distribution.
e, f, g models are models with 25, 30, 40 mol% P2O5 respectively. 41 2 LIST OF TABLES Table 2.1 BMH potential for CPS system [25] .1: Structure characteristics of CaO-P2O5-SiO2 .2: Coordination number of MOx (M=Ca, P, Si) with different P2O5 ratios 27 Table 3.3: OMy units with different P2O5 concentration .4: The SiO4 cluster distribution (Nc= the number of clusters, Na= the number of atoms of clusters) .5: The PO4 clusters distribution. Problem Statement Industrial waste in general and radioactive waste in particular are important issues that need to be resolved by many countries. Over the decades, scientists have been researching appropriate materials to store hazardous waste.
It is indicated that glassy materials based on SiO2 and/or P2O5 are suitable storage materials due to their chemical properties, durability, and radiation stability. Bioglass is an amorphous silicate-based material that is compatible with the human body, binds to bone, and can stimulate new bone growth as the material dissolves over time. Therefore, they have the ability to restore diseased or damaged bone to its original state and function (osteogenesis) [1]. Since it was discovered by scientist Larry L.
Hench in 1969, bioglass has been increasingly developed with a variety of structures and many different applications. The glass structure consists of the network formers, network modifiers and intermediates. The network formers build the network structure of glasses. Some examples of network formers are SiO2, B2O3, and P2O5.
The silicate glass network is formed by the connection between [SiO4] tetrahedrons through the Si-O-Si bond. These links are called bridging oxygen bonds (BOs). The network modifiers break these BOs and create non-bridging oxygens (NBOs). The network modifiers include Na, K, Ca, Mg, etc.
Some metal oxides are intermediates, such as Al2O3. The intermediates act as network formers or network modifiers, depending on their content. The polymerization degree is calculated through the number of BOs. Therefore, investigating the structure of glasses plays an important role in predicting their properties.
Understanding the important applications of glassy materials in medicine and life as well as the meaning of studying the structure of the glass system, this project will study the basic structure of the CaO-P2O5-SiO2 system with a variety of P2O5 ratios, initially laying the premise for further research development later. Purpose and Scope of the study Purpose: The research thesis will simulate the structure of the CaO-P2O5-SiO2 material system, thereby analyzing, clarifying the structural parameters, and indicating the change in the material microstructure with different ratios of P2O5/CaO. Research object: CaO-P2O5-SiO2 glass material systems with different ratios of P2O5/CaO Scope: The CaO-P2O5-SiO2 models at 3000 K with various P2O5 (5–40 mol%) content 3. Research methods The study uses the Molecular Dynamics Simulation (MDS) method to model the material.
In addition, statistical analysis methods are also applied to analyze structural parameters of materials, such as radial distribution function, coordination number distribution, angular distribution and distance distribution. The scientific and practical significance of the topic The thesis presents an investigation of the microstructure of CaO-P2O5-SiO2 material systems with variable ratios of P2O5 at high temperature. In this research, we concentrate on surveying, calculating and analyzing microstructure data such as distance of atoms, angular measurements, BO, NBO fractions and tetrahedron cluster. Furthermore, the results obtained in this thesis can be used to progress the studies in the future.
This material plays an important part in the high-tech industry and the medical industry. Consequently, understanding its properties and structure is necessary, especially in the fields of toxic industrial waste and bioactive material research. New contributions of the thesis Our previous studies only investigated CaO-P2O5-SiO2 systems under different conditions. In this thesis, we research the impact of component concentration on the structure of the material, such as the changes in angles, distances of atoms, the transformation of the tetrahedron clusters, etc.
The structure of the thesis In addition to the introduction, conclusion and list of references, the thesis is divided into three main parts. Chapter 1: Overview Chapter 2: Calculation method Chapter 3: Results and discussion 6 Chapter 1 : OVERVIEW Multi-component oxide glass systems based on SiO2 and P2O5 play an important role in various high-tech fields. They are widely used in electronic materials, optoelectronics, biologically active glass, etc. Glass materials are widely used in hazardous waste storage, such as industrial waste and nuclear waste.
Besides, bioactive glasses are widely used in bone grafts in orthopedic surgeries. Because of their variety of applications, they have been researched for decades.1 Hazardous waste storage Radioactive waste (radwaste) is classified as three types: low-level, intermediate- level, and high-level waste. Low-level waste is the product of hospitals, laboratories, and industry. Intermediate-level waste is composed of resins and chemical sludge.
High-level waste (HLW) consists of fuel rods from nuclear plants, waste from reprocessing the spent fuel, and material from decommissioned nuclear weapons. It accounts for 3% of the volume of all disposed radioactive waste; however, it represents more than 95% of the radioactivity. A large amount of high-level waste is temporarily stored, for example, in the pool storage or put into stainless steel canisters and interred in geological disposal sites. Over the years, many researches has been progressed to find appropriate hosts to store HLW [3].
The requirements for HLW hosts are high waste loading, easy processing, high radiation stability, chemical flexibility, durability and natural analogues [4]. There are some material structures based on P2O5 being capable of combining with a variety of HWL elements. An example is monazite (REE,Th)PO4 (REE=rare earth element). Monazite exists in many forms, such as brabantite (Ca0.5PO4) and huttonite (ThSiO4) in nature, PrPO4 and CePO4 synthesized in laboratories, etc.
Monazite is radiation-resistant. It can repair radiation damage at temperatures of 200oC or less (Meldrum et al. Seydoux-Guillaume et al. investigated the sample of 540- million-year-old monazite from Madagascar and found that it remained in the crystalline state despite being exposed to ten times the radioactivity needed to be 7 completely amorphous.
Monazite is also stable and hard to dissolve in nature, in spite of erosion, transport, and deposition. Another example of a compound capable of containing HWL is apatite Ca5(PO4)3(F,Cl,OH). Through replacing Ca(II) with Ac(III, IV) and PO4 with SiO4, apatite can incorporate tri- and tetravalent actinides (Ac) into its structure. Apatite is stable long-term.
For instance, the Oklo natural nuclear reactor in Gabon has apatite that is two-billion-years-old and contains tri- and tetravalent actinides. Besides, apatite is also stable at high temperatures. In addition, the apatite structure is resistant to self-irradiation. Apatite is also able to contain radioactive Cesium (Ce) and Iodine (Id), which are difficult to incorporate into the structure of monazite and most other solids.
Numerous investigations (Jeanjean et al. [5]; Moore et al. Melting glass is the first material storage for HLW developed, for example, borosilicate and phosphate glass.
