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研究生:葉乃華
研究生(外文):Nai-HuaYeh
論文名稱:水化矽酸鈣之分子動力學模擬
論文名稱(外文):STUDIES OF CALCIUM SILICATE HYDRATE VIA MOLECULAR DYNAMICSSIMULATION
指導教授:王雲哲
指導教授(外文):Yun-Che Wang
學位類別:碩士
校院名稱:國立成功大學
系所名稱:土木工程學系
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:2016
畢業學年度:104
語文別:英文
論文頁數:101
中文關鍵詞:水化矽酸鈣水泥材料壓痕性質分子動力學模擬微觀結構
外文關鍵詞:C-S-Hcement materialsindentation propertymolecular dynamics simulationmicrostructures
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本研究以分子動力學模擬技術,探討水化矽酸鈣(C-S-H),在不同溫度與壓力下的原子尺度微觀結構,及其物理與力學性質,例如:熱膨脹係數、體容積模數、壓痕模數與硬度等。分子動力學模擬所使用的原子間勢能函數為CLAYFF型態,除了包含一般的吸引與排斥效應的短程力之能量項外,亦包含庫倫靜電效應的長程力之能量項。所使用的C-S-H原子模型,其化學式為(CaO)1:65(SiO2)(H2O)1:75,密度約為2.56 g/cm3,具有以氧化矽與鈣離子(Cas)組成的層狀結構,層與層間則為鈣離子(Caw)與水分子。原子結構分析顯示,常溫與常壓下的徑向分布函數、Qn和結構因子等均與文獻類似,其中核磁共振頻譜顯示氧化矽鏈狀結構之Q0,Q1,Q2的比值約為1:2:7,在高溫時(約800 C),Q2的比例大幅降低,結構以Q0與Q1主導。在常溫與常壓下,以NPT系綜所計算的物理性質均與文獻之參考值近似,但有些許差異,原因可能來自熱噪音的影響。在一些溫度與壓力的區段,C-S-H之熱膨脹係數可以為負值。壓痕的力-位移曲線會有跳耀現象,反應微觀層狀結構產生滑移。所計算而得的C-S-H參考硬度值約為4.63 GPa到13.93 GPa 間,常溫下體容積模數為約49 GPa,溫度升高時,硬度與壓痕模數降低,且層狀微觀結構逐漸消失。
In this thesis, the molecular dynamics (MD) simulations techniques were adopted to study the atomic structures and physical/mechanical properties of C-S-H for its thermal expansion coefficient, bulk modulus, indentation modulus and hardness at various temperatures and pressures. The interatomic potential is of the CLAYFF type, consisting repulsive and attractive energy terms for short-distance interactions, as well as the Coulomb electrostatic energy
terms for long-distance interactions. The chemical composition of the C-S-H model is (CaO)1:65(SiO2)(H2O)1:75, and its density is about 2.56 g/cm3. It is composed by silicate layers with calcium ions, labeled as Cas, nearby. Between the calcium-silicate layers, there are water molecules and calcium ions, labeled as Caw. From our atomic structural analysis, at the ambient environment, the radial distribution function, Qn and structural factor are consistent with literature data. The nuclear magnetic resonant spectrum of the C-S-H shows the ratio of Q0:Q1:Q2 equal to 1:2:7. However, at high temperature (800 C), Q2 is largely reduced, and Q0 and Q1 silicate morphology dominates. As for the physical properties, our calculated data with the NPT ensemble are consistent with literature data with noticeable differences at the ambient environment. The differences may be due to thermal fluctuation noises. It is found that in some temperature and pressure regime, the thermal expansion coefficient of C-S-H may be negative.
The indentation load-displacement curves may exhibit jumps, indicating slips may occur in the C-S-H layer structures during loading. Our calculated the un-relaxed hardness values of C-S-H
are in the range of 4.63 GPa to 13.93 GPa. In ambient, its bulk modulus is about 49 GPa. As temperature increases, hardness and indentation modulus decease, as well as the layered structures are smeared.
CHINESE ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Goals and motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Relevant materials in cement science . . . . . . . . . . . . . . . . . . 2
1.2.2 MD research on C-S-H . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.3 NMR data of C-S-H . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Outline of this thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 Some theoretical backgrounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1 Hertz contact and indentation . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Hardness conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 Molecular Dynamics simulation background . . . . . . . . . . . . . . . . . . . . 16
3.1 Interaction potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2 Statistical ensembles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 Method verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1.1 Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1.2 Metallic glass (Zr50Cu50) . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.2 Copper in different temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2.1 Fix indent 1 K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2.2 Fix indent 100 K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2.3 Fix indent 200 K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
4.3 C-S-H model construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.3.1 Temperature effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.3.2 Pressure effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.3.3 Radial distribution function (RDF) . . . . . . . . . . . . . . . . . . . . 64
4.3.4 C-S-H microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4 C-S-H under indentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.4.1 Different temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . 79
4.4.2 Different size of indents (5 °A and 8 A° ) . . . . . . . . . . . . . . . . . . 92
4.4.3 Stress distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
5 Conclusion and Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
5.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
VITA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
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