本文選題：沖擊加載　切入點：亞穩(wěn)態(tài)冰　出處：《西南交通大學》2015年博士論文　論文類型：學位論文

【摘要】：水是自然界最豐富的物質之一,有重要的工業(yè)和國防應用。單個水分子(H20)結構雖然簡單,但它的凝聚態(tài)形式卻十分復雜。人們已經發(fā)現(xiàn)在靜態(tài)高壓下水可以轉化為十幾種不同結構形式的冰相,卻對在沖擊動態(tài)加載過程中水的結構演變特征了解甚少。沖擊波加載過程發(fā)生在納秒時間尺度,在此過程體系的溫度和壓強變化的速率可能遠遠超過結晶相變的速率,以致人們所預期的某些結晶過程可能還沒來得及發(fā)生,體系的結構將直接演變到某些亞穩(wěn)態(tài)形式。在動態(tài)加載過程中水的結構演變途徑將對其沖擊動力學性質產生重要影響,在設計海洋水下目標的攻擊和防護方案時水的動力學特征是必要的物理與力學參量。最近人們研究了水在等熵加載和準等熵加載(多次沖擊加載)過程中的動力學行為和光學透明特性,揭示了水在沖擊波誘導下的結晶現(xiàn)象和相變動力學弛豫現(xiàn)象。但是,有關沖擊波誘導產生的高壓相冰的微觀結構和光譜特性研究還是空白,因而關于水的沖擊結晶相的具體結構目前仍然還僅是一種推測。瞬態(tài)拉曼光譜技術是探測沖擊波誘導物質結構相變的最理想實驗手段,然而水分子的拉曼散射截面非常小,其拉曼信號十分微弱。多年來,這個技術瓶頸一直沒有新突破,該科學問題的解決面臨挑戰(zhàn)。本文發(fā)展了一種氣炮加載沖擊瞬態(tài)拉曼光譜技術,提高了時間控制精度和靈敏度,使其能夠跟蹤多次沖擊加載過程并分辨出體系中更豐富的光譜特征。在此基礎上,結合輕氣炮快速加載手段、瞬態(tài)拉曼原位光譜技術以及從頭計算分子動力學模擬方法,在探索沖擊高壓下條件水的微觀結構、振動頻譜和分子間氫鍵變化規(guī)律方面取得了一些新的結果：(1)采用沖擊-再沖擊加載技術,首次在冰Ⅶ熔化線兩側的溫度和壓強條件下獲得了水的沖擊瞬態(tài)拉曼散射光譜；(2)在沖擊加載條件下首次觀測到水拉曼散射光譜中位于低波段的成分明顯增加,證實再沖擊加載體系中的氫鍵效應增強；(3)首次在冰Ⅶ相穩(wěn)定的溫壓區(qū)獲得水的沖擊瞬態(tài)拉曼散射光譜,發(fā)現(xiàn)沖擊波誘導結冰過程所生成的新相不同于冰Ⅶ相,而是一種亞穩(wěn)相高壓冰結構；(4)采用從頭計算分子動力學模擬方法,在與沖擊加載實驗相近的溫度和壓強區(qū)域獲得了一種具有無定形結構的高壓冰相,發(fā)現(xiàn)該冰相的模擬振動譜與沖擊-再沖擊狀態(tài)水的實測拉曼散射光譜輪廓相似,在光譜展寬方面也相似；(5)采用從頭計算分子動力學模擬方法,首次揭示出O-H振動頻譜與體系中局域氫鍵鍵長分布間存在關聯(lián)性,并支持局域氫鍵環(huán)境不對稱導致分子兩支內O-H伸縮振動譜不對稱這一觀點。
[Abstract]:Water is one of the most abundant substances in nature and has important industrial and national defense applications. But its condensed form is very complicated. It has been found that at static high pressure water can be converted into a dozen different structural forms of ice, However, very little is known about the structural evolution of water during dynamic impact loading. The shock wave loading occurs on a nanosecond time scale, and the rate of temperature and pressure changes in this process may be much higher than the rate of crystallization phase transition. As a result, some of the expected crystallization processes may not take place in time, and the structure of the system will directly evolve to some metastable state. During dynamic loading, the evolution of water structure will have an important effect on its impact dynamic properties. The dynamic characteristics of water are necessary physical and mechanical parameters in designing attack and protection schemes for underwater targets. Recently, the dynamic behavior of water in isentropic loading and quasi-isentropic loading (multiple shock loading) has been studied. Academic behavior and optical transparency, The phenomena of crystallization and phase transition dynamics relaxation of water induced by shock wave are revealed. However, the study on the microstructure and spectral characteristics of high-pressure phase ice induced by shock wave is still blank. Therefore, the specific structure of the impact crystalline phase of water is still only speculated. Transient Raman spectroscopy is the most ideal experimental means to detect the structural phase transition induced by shock wave, but the Raman cross section of water molecule is very small. The Raman signal is very weak. For many years, there has been no new breakthrough in this technical bottleneck, and the solution of this scientific problem is facing a challenge. In this paper, a gas gun loaded shock transient Raman spectroscopy technology is developed, which improves the time control accuracy and sensitivity. On the basis of this, the transient Raman in-situ spectroscopy and ab initio molecular dynamics simulation are combined with the rapid loading method of light gas gun, the transient Raman in-situ spectroscopy and the ab initio molecular dynamics simulation. Some new results have been obtained in exploring the microstructure, vibrational spectrum and intermolecular hydrogen bond variation of water under shock pressure. Under the condition of temperature and pressure on both sides of the melting line of ice 鈪，

本文編號：1579911