【摘要】：材料的結構與性質是凝聚物理學、材料科學、化學等相關領域非常關注的基礎問題之一。深入研究物質的微觀結構不但有助于我們改善材料的性能而且能夠指導我們發(fā)展新材料。含能材料在現(xiàn)代國防和民用經(jīng)濟建設中占據(jù)重要地位。雖然人類利用含能材料已有數(shù)百年歷史,但對于其微觀結構的穩(wěn)定性和能量釋放機理的研究還相對缺乏。特別是從微觀層次認識含能炸藥的起爆機理一直是現(xiàn)代爆轟物理、兵器科學、高壓凝聚態(tài)物理、材料科學等多學科領域共同關注的重要科學問題。含能炸藥在點火起爆過程中涉及高溫高壓環(huán)境,經(jīng)歷著復雜的物理、化學變化過程。但從根本上來說,材料的物理和化學性質與其結構息息相關,而研究含能材料在各種加載條件下發(fā)生爆炸的微觀機理就是要揭示其分子在極端條件下如何發(fā)生結構轉變或分解反應的問題。另外,研究壓力作用下含能材料的分子結構變化對于認識其在起爆過程中的早期反應途徑非常有益。因此,開展高壓下含能材料的結構及穩(wěn)定性研究對理解其分解和點火起爆等微觀機理方面具有重要的科學意義�；谏鲜鰡栴},本文采用金剛石壓砧(DAC)和輕氣炮加載技術,結合原位拉曼光譜技術、沖擊熱輻射技術以及第一性原理計算方法對幾種典型含能材料在高壓條件下的結構穩(wěn)定性進行了研究,具體內容為:首先,研究了硝基苯(NB)在高壓下的結構穩(wěn)定性。硝基苯作為一種結構最為簡單的芳香硝基化合物,通常被作為研究硝基苯胺類炸藥的模型物質。采用DAC技術和原位拉曼光譜技術,在0-10 GPa壓力范圍內考察了硝基苯晶體的高壓結構與分子振動特性。實驗發(fā)現(xiàn),在5 GPa壓力附近硝基苯發(fā)生了一次結構的突變。為了深入理解實驗觀測結果,采用基于密度泛函理論(DFT)的第一性原理計算方法對硝基苯在高壓下的結構響應行為進行理論模擬研究,計算發(fā)現(xiàn)分子鍵長、鍵角、二面角等物理參量均在7 GPa壓力下發(fā)生一個不連續(xù)的跳變,預示著硝基苯在高壓下發(fā)生了結構轉變。對照實驗和計算結果,我們認為硝基苯分子結構的變化是由于持續(xù)增加的壓力促使其分子結構扭曲以抵抗增加的相互作用力,繼而導致分子結構發(fā)生調整;高壓下硝基苯拉曼光譜中有限的振動模式發(fā)生變化正是由于該分子結構的調整所致。其次,研究了典型的含能材料硝基甲烷(NM)在沖擊高壓條件下的結構及其穩(wěn)定性。從微觀層面認識含能材料的沖擊起爆機理是現(xiàn)代爆轟物理、高壓凝聚態(tài)物理等多學科領域關注的重要問題之一。我們選取硝基甲烷這一結構最為簡單的硝基化合物作為研究對象,基于輕氣炮加載平臺結合瞬態(tài)拉曼散射技術和沖擊熱輻射原位測量技術,研究了液態(tài)炸藥硝基甲烷的拉曼特征峰隨沖擊壓力的變化規(guī)律和沖擊起爆延遲時間。實驗結果表明,在沖擊起爆前硝基甲烷仍然保持其光學透明特征。獲得了硝基甲烷在沖擊誘導期間生成新產(chǎn)物的拉曼光譜。首次發(fā)現(xiàn)在沖擊高壓下C-H鍵率先斷裂的實驗證據(jù);新的實驗結果為研究其他含能材料的點火反應以及沖擊起爆機理提供了參考數(shù)據(jù)。再者,研究了含能晶體1,3-二氨基-2,4,6-三硝基苯(DATB)在高壓條件下的結構變化及其穩(wěn)定性。DATB是硝基苯胺類炸藥中一種重要的含能材料,與著名的高鈍感炸藥TATB的分子結構非常類似,但對其在不同壓力下結構及性質的相關研究十分有限。本文采用色散修正密度泛函理論(DFT-D)計算方法,在0-15 GPa壓力范圍內對DATB晶體的結構及其穩(wěn)定性進行了研究。結果表明,在常壓條件下模擬計算的晶體常數(shù)、分子幾何結構以及分子間相互作用特征均與實驗結果吻合。其次,晶格常數(shù)、分子幾何結構和彈性常數(shù)隨壓力的變化趨勢均在7.5 GPa壓力附近發(fā)生突變;根據(jù)晶體穩(wěn)定性的力學判據(jù),發(fā)現(xiàn)DATB晶體在7.3 GPa左右已不穩(wěn)定,表明在7.5 GPa壓力附近DATB晶體發(fā)生了結構失穩(wěn)。最后,研究了新型含能化合物3,4-二氨基-1,2,4三唑-1-氨基四唑-5-酮(ATO·DATr)在不同壓力下的結構穩(wěn)定性。ATO·DATr具有較高的密度、良好的爆壓和爆速,被認為是潛在的鈍感含能材料。這類富氮含能化合物由于具有較高的氮元素和生成熱,且產(chǎn)物主要是環(huán)境友好的氮氣等優(yōu)點而備受關注。本文采用DFT-D計算方法,在0-50 GPa壓力范圍內研究了 ATO·DATr的晶體結構、狀態(tài)方程以及電子性質;同時,運用Hirshfeld表面和二維指紋圖方法考察了其晶體內分子間相互作用的變化。結果表明,在零壓下計算的晶格常數(shù)、分子幾何結構以及分子間相互作用與實驗值相一致。晶體的可壓縮性呈現(xiàn)出各向異性并隨著壓力的增加而減小,ATO · DATr的體積模量也比其他常見含能材料的要高;同時隨著壓力的增加晶體中的短程相互作用增強,涉及長程相互作用的de值減小,揭示出高壓下ATO · DATr晶體可壓縮性的減小與分子間相互作用的增強有關。
[Abstract]:Structures and properties of materials are one of the fundamental issues of great concern in condensed physics, material science, chemistry and other related fields. In-depth study of the microstructure of materials can not only help us improve the properties of materials but also guide us to develop new materials. Energetic materials play an important role in modern national defense and civil economic construction. However, it has been hundreds of years since the energetic materials were used by human beings, but the research on the stability of microstructure and the mechanism of energy release is still relatively scarce. The process of ignition and detonation of energetic explosives involves high temperature and high pressure, and undergoes complicated physical and chemical changes. But fundamentally, the physical and chemical properties of materials are closely related to their structures. To study the micro-mechanism of explosion of energetic materials under various loading conditions is to reveal the molecular structure of energetic explosives. In addition, it is very useful to study the molecular structure changes of energetic materials under pressure for understanding the early reaction pathways in the initiation process. Therefore, the study on the structure and stability of energetic materials under high pressure is helpful to understand the micro-machine such as decomposition and ignition initiation. Based on the above problems, the structural stability of several typical energetic materials under high pressure is studied by means of diamond anvil (DAC) and light gas gun loading technique, in situ Raman spectroscopy, thermal shock radiation technique and first-principles calculation method. The structure stability of nitrobenzene (NB) at high pressure has been studied. Nitrobenzene, as the simplest aromatic nitro compound, is usually used as a model material for the study of nitroaniline explosives. The high pressure structure and molecular vibration of NB crystals have been investigated by using DAC and in situ Raman spectroscopy in the pressure range of 0-10 GPa. In order to understand the experimental results, the first-principles calculation method based on density functional theory (DFT) was used to simulate the structure response behavior of nitrobenzene at high pressure. The molecular bond length, bond angle and dihedral angle were found. A discontinuous jump of physical parameters at 7 GPa pressures indicates a structural transition of nitrobenzene at high pressures. Contrasting the experimental and computational results, we believe that the change of the molecular structure of nitrobenzene is attributed to the continuous increase of pressure which leads to the distortion of its molecular structure to resist the increasing interaction force, and then leads to the molecular structure. Secondly, the structure and stability of a typical energetic material, nitromethane (NM), under shock high pressure were studied. The shock initiation mechanism of energetic materials was recognized as modern detonation physics from the microscopic level. The Raman characteristic peaks of liquid explosive nitromethane have been studied based on the light gas gun loading platform combined with the transient Raman scattering technique and the shock thermal radiation in situ measurement technique. The experimental results show that the optical transparency of nitromethane is maintained before shock initiation. Raman spectra of new products of nitromethane during shock induction are obtained. Furthermore, the structural changes and stability of energetic crystals 1,3-diamino-2,4,6-trinitrobenzene (DATB) under high pressure were studied. DATB is an important energetic material in nitroaniline explosives, and the molecule of famous highly insensitive explosive TATB. The structure of DATB crystals is very similar, but the research on the structure and properties of DATB crystals under different pressures is very limited. In this paper, the structure and stability of DATB crystals are studied in the pressure range of 0-15 GPa by using the dispersion-corrected density functional theory (DFT-D). Secondly, the lattice constants, molecular geometric structures and elastic constants change abruptly near 7.5 GPa pressure. According to the mechanical criterion of crystal stability, it is found that DATB crystal is unstable around 7.3 GPa, indicating that DATB crystal is unstable near 7.5 GPa pressure. Finally, the structural stability of a new energetic compound 3,4-diamino-1,2,4-triazole-1-aminotetrazole-5-one (ATO.DATr) at different pressures was studied. ATO.DATr is considered as a potential insensitive energetic material because of its high density, good detonation pressure and detonation velocity. In this paper, the crystal structure, equation of state and electronic properties of ATO DATr have been studied by DFT-D method in the pressure range of 0-50 GPa. The results show that the lattice constants, molecular geometry and intermolecular interactions calculated at zero pressure are consistent with the experimental values. The compressibility of the crystals is anisotropic and decreases with the increase of pressure. The bulk modulus of ATO. DATr is also higher than that of other energetic materials. The short-range interaction in the crystal is enhanced, and the de value involved in the long-range interaction decreases. It is revealed that the decrease of compressibility of ATO.DATr crystal under high pressure is related to the enhancement of intermolecular interaction.
【學位授予單位】：西南交通大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB34

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本文編號：2189064