【摘要】：在自然界、冶金技術(shù)以及材料制備過程中,凝固是一種非常普遍的物理現(xiàn)象。凝固廣泛存在于各個領(lǐng)域,物體從液體轉(zhuǎn)變?yōu)楣腆w都要經(jīng)歷凝固過程。凝固開始于形核,形核又可以分為均質(zhì)形核和異質(zhì)形核。在實際生產(chǎn)中,大多數(shù)的形核過程都是異質(zhì)形核,因此研究固相粒子對熔體結(jié)構(gòu)以及凝固過程的影響有著非常重要的意義。本論文利用分子動力學(xué)方法研究了楔形襯底以及受限空間對熔體的結(jié)構(gòu)以及凝固行為的影響,揭示了襯底與熔體結(jié)構(gòu)以及凝固組織之間的內(nèi)在關(guān)聯(lián)性。研究結(jié)果對于通過控制異質(zhì)形核從而改善材料的宏觀性能有著重要的意義。全文的主要內(nèi)容如下:(1)研究了楔形襯底如何將結(jié)構(gòu)信息傳遞給正在生長的晶體,進一步影響凝固過程。結(jié)果顯示,由于襯底的誘導(dǎo)作用靠近襯底的銅熔體在液固界面處分層形成一個"V"形結(jié)構(gòu),并且有形成孿晶的趨勢。但是隨著與襯底間距離的增加,襯底的誘導(dǎo)作用逐漸減弱致使銅熔體逐漸恢復(fù)其固有的結(jié)構(gòu)。當(dāng)楔形角為90°時,由于銅原子內(nèi)部良好的晶格匹配,凝固組織是一個理想晶體。此外,冷卻速率以及襯底的原子排列方式對銅熔體的凝固組織也有很大的影響。這些研究結(jié)果有利于理解異質(zhì)凝固過程中,襯底與凝固組織之間的遺傳關(guān)系。(2)研究了鋁熔體在受限狹縫內(nèi)以及Fe襯底上的異質(zhì)形核過程。與孤立襯底相比,受限狹縫可以促進鋁熔體的結(jié)晶,同時狹縫的尺寸對凝固組織有很大的影響。在對稱的受限狹縫內(nèi),Al原子可以根據(jù)襯底的堆垛模型進行排列,而在非對稱的受限狹縫內(nèi),Al原子的堆垛模型取決于襯底的構(gòu)成。對于Fe(110)-Fe(111)這種狹縫來說,由Fe(110)襯底誘導(dǎo)的凝固區(qū)域要大于由Fe(111)襯底誘導(dǎo)的凝固區(qū)域。此外,對于鋁熔體在由銅鐵兩種襯底構(gòu)成的非對稱受限空間我們也進行了研究。這些結(jié)果闡明了受限空間對熔體異質(zhì)凝固過程的影響。(3)探究了在不同壓強下以及不同距離的兩個石墨烯之間,受限水的結(jié)構(gòu)演變。結(jié)果顯示,受限狹縫的尺寸以及壓強都能夠引起受限水的結(jié)構(gòu)演變,具體表現(xiàn)為層數(shù)以及堆垛方式的變化。隨著壓強以及狹縫間距的增加,受限水的分層現(xiàn)象也越來越明顯。此外,隨著壓強的增加,在受限狹縫內(nèi),近鄰水分子首先形成鏈狀結(jié)構(gòu),之后演變成正方形結(jié)構(gòu),最后轉(zhuǎn)變?yōu)槿切谓Y(jié)構(gòu)。這些結(jié)果有助于了解受限空間內(nèi)水的結(jié)構(gòu)演變。
[Abstract]:Solidification is a very common physical phenomenon in nature, metallurgical technology and material preparation. Solidification exists widely in various fields, and the transformation of objects from liquid to solid has to go through the solidification process. Solidification begins with nucleation, which can be divided into homogeneous nucleation and heterogeneous nucleation. In practical production, most nucleation processes are heterogeneous nucleation, so it is very important to study the influence of solid particles on melt structure and solidification process. In this paper, the effects of wedge-shaped substrate and confined space on the structure and solidification behavior of melt were studied by molecular dynamics method, and the intrinsic relationship between substrate and melt structure and solidification structure was revealed. The results are of great significance for improving the macroscopic properties of materials by controlling heterogeneous nucleation. The main contents of the thesis are as follows: (1) the structure information of the wedge substrate is transferred to the growing crystal, which further influences the solidification process. The results show that due to the inducement of substrates, copper melts near the substrates form a "V" shaped structure at the liquid-solid interface and have a tendency to form twins. However, with the increase of the distance between the substrate and the substrate, the inductive effect of the substrate gradually weakened, and the copper melt gradually restored its inherent structure. When the wedge angle is 90 擄, the solidified structure is an ideal crystal due to the good lattice matching within the copper atom. In addition, the cooling rate and the atomic arrangement of the substrate also have a great influence on the solidification structure of copper melt. These results are helpful to understand the genetic relationship between substrate and solidification structure during heterogeneous solidification. (2) the heterogeneous nucleation process of aluminum melt in confined slit and on Fe substrate is studied. Compared with the isolated substrate, the confined slit can promote the crystallization of aluminum melt, and the size of the slit has a great influence on the solidification microstructure. In a symmetric confined slit, Al atoms can be arranged according to the stacking model of the substrate, while in the asymmetric confined slit, the stacking model of the Al atom depends on the composition of the substrate. For the slit of Fe (110)-Fe (111), the solidification region induced by Fe (110) substrate is larger than that induced by Fe (111) substrate. In addition, we also study the asymmetric confined space of aluminum melt in two kinds of substrates, copper and iron. These results illustrate the effect of confined space on the process of heterogeneous solidification of melt. (3) the evolution of confined water structure between two graphene at different pressures and distances is investigated. The results show that both the size and the pressure of the confined slit can cause the evolution of the confined water structure, which is manifested by the change of the number of layers and the way of stacking. With the increase of pressure and slit spacing, the stratification of confined water becomes more and more obvious. In addition, with the increase of pressure, in the confined slit, the near neighbor water molecules first form chain structure, then develop into square structure, and finally transform into triangular structure. These results help to understand the structural evolution of water in confined spaces.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG21

【相似文獻】

相關(guān)期刊論文 前2條

1 朱方誠;;論中國家具結(jié)構(gòu)發(fā)展之一——腿足演變[J];創(chuàng)意與設(shè)計;2011年02期

2 趙敬忠;常金晶;岳建設(shè);張發(fā)建;;Al-Si-Zn合金直接氧化形成復(fù)合材料的結(jié)構(gòu)演變[J];硅酸鹽學(xué)報;2007年08期

相關(guān)會議論文 前5條

1 李萬茂;;改革開放以來投資結(jié)構(gòu)演變及未來走勢[A];投資增長速度研究專題研討會論文集[C];2006年

2 李萬茂;;改革開放以來投資結(jié)構(gòu)演變及未來走勢[A];地市級投資公司創(chuàng)新發(fā)展研討會論文集[C];2006年

3 李洪光;Robert Holyst;郝京誠;;甲苯中反相囊泡的形成及結(jié)構(gòu)演變[A];中國化學(xué)會第28屆學(xué)術(shù)年會第12分會場摘要集[C];2012年

4 毛知耘;石孝均;向天常;胡王仲;李杰;;50年重慶肥料結(jié)構(gòu)演變與農(nóng)業(yè)持續(xù)發(fā)展[A];中國化肥100年回眸——化肥在中國應(yīng)用100年紀念[C];2002年

5 趙敬忠;常金晶;岳建設(shè);張發(fā)建;;Al-Si-Zn合金直接氧化形成復(fù)合材料的結(jié)構(gòu)演變[A];《硅酸鹽學(xué)報》創(chuàng)刊50周年暨中國硅酸鹽學(xué)會2007年學(xué)術(shù)年會論文集（一）[C];2007年

相關(guān)重要報紙文章 前3條

1 本報記者 陳堯;從結(jié)構(gòu)演變看增長潛力[N];遼寧日報;2009年

2 中共周口市委辦公室 王樹強;在學(xué)習(xí)和實踐中提高貫徹科學(xué)發(fā)展觀的能力[N];周口日報;2007年

3 市委講師團;在加強學(xué)習(xí)中提高領(lǐng)導(dǎo)科學(xué)發(fā)展的功能[N];蚌埠日報;2007年

相關(guān)博士學(xué)位論文 前2條

1 孫明明;近代康區(qū)政治權(quán)力結(jié)構(gòu)演變研究[D];中央民族大學(xué);2012年

2 孫趙勇;中國工業(yè)結(jié)構(gòu)演變動因及多維特征研究[D];西北大學(xué);2014年

相關(guān)碩士學(xué)位論文 前5條

1 周戌燕;熔體在楔形襯底和納米狹縫內(nèi)的結(jié)構(gòu)演變及凝固行為[D];山東大學(xué);2017年

2 周妙霞;廣東省消費結(jié)構(gòu)演變趨勢及升級研究[D];廣東省社會科學(xué)院;2014年

3 馬端輝;產(chǎn)業(yè)—職業(yè)結(jié)構(gòu)演變的比較研究：美國、日本、德國和中國[D];浙江大學(xué);2004年

4 王同艷;追趕型國家外貿(mào)結(jié)構(gòu)演變探究[D];浙江工商大學(xué);2013年

5 方方;上海市第三產(chǎn)業(yè)結(jié)構(gòu)演變對其增長的影響研究[D];復(fù)旦大學(xué);2013年

，

本文編號：2360339