【摘要】：隨著材料科學(xué)的快速發(fā)展和廣泛應(yīng)用,對(duì)于新型功能材料的研發(fā)需求越來(lái)越迫切。其中,多孔泡沫材料,作為一種“環(huán)保、輕質(zhì)、高性能”的功能材料,在國(guó)內(nèi)外受到了大量的關(guān)注。在泡沫材料的制備過(guò)程中,由最初液態(tài)泡沫形成到各種泡沫產(chǎn)品的成型及應(yīng)用,貫穿始末的泡沫演化動(dòng)力學(xué)都起著至關(guān)重要的作用。如何合理地控制泡沫演化動(dòng)力學(xué)過(guò)程,以獲得氣泡分布均勻、性能穩(wěn)定的泡沫材料,是一大研究難題。同時(shí),在理論分析層面,對(duì)泡沫演化動(dòng)力學(xué)機(jī)制的研究也可對(duì)拓?fù)鋵W(xué)中的空間填充理論進(jìn)行指導(dǎo),并有助于解決其他物理體系中的結(jié)構(gòu)演化問(wèn)題。而在泡沫演化動(dòng)力學(xué)過(guò)程中,由重力所引起的多尺度(空間、時(shí)間)現(xiàn)象一直是科學(xué)界所關(guān)注的熱點(diǎn)和難點(diǎn)。如何消除重力,并長(zhǎng)時(shí)間、低成本開展低微重力環(huán)境下的泡沫演化實(shí)驗(yàn)是另一研究難題�；谶@一研究現(xiàn)狀,本文以液態(tài)水泡沫和磁流體泡沫為研究對(duì)象,并針對(duì)其動(dòng)力學(xué)過(guò)程中的泡沫性能、粗化機(jī)理、結(jié)構(gòu)演化規(guī)律等幾項(xiàng)關(guān)鍵科學(xué)問(wèn)題進(jìn)行實(shí)驗(yàn)研究分析。隨后,采用本文所設(shè)計(jì)的“磁重力補(bǔ)償”這一全新研究手段,以實(shí)現(xiàn)模擬的低微重力環(huán)境,從而進(jìn)一步分析磁流體泡沫的演化動(dòng)力學(xué)過(guò)程。本文的第一部分,設(shè)計(jì)了一種全新的磁重力補(bǔ)償實(shí)施方法,該方法是結(jié)合磁性流體及亥姆霍茲-麥克斯韋雙對(duì)線圈而實(shí)現(xiàn)的。本文通過(guò)數(shù)值模擬和實(shí)驗(yàn)測(cè)量方法分別對(duì)雙對(duì)線圈內(nèi)的磁場(chǎng)分布及磁流體的有效重力水平進(jìn)行研究分析。首先,通過(guò)有限元模擬軟件數(shù)值計(jì)算和精密特斯拉計(jì)對(duì)磁場(chǎng)大小及分布進(jìn)行測(cè)量發(fā)現(xiàn),雙對(duì)線圈中心磁場(chǎng)分布呈線性分布特征,其分布較為均勻,且實(shí)驗(yàn)測(cè)量結(jié)果與數(shù)值模擬較為吻合。而后,由磁流體的有效重力水平計(jì)算結(jié)果可知,在雙對(duì)線圈中心直徑60mm、高60mm的圓柱形區(qū)域內(nèi)實(shí)現(xiàn)了90%以上的均勻磁重力補(bǔ)償,且通過(guò)調(diào)節(jié)麥克斯韋線圈內(nèi)電流,可以達(dá)到磁力完全抵消重力,實(shí)現(xiàn)后續(xù)實(shí)驗(yàn)所需的低微重力條件。本文的第二部分,設(shè)計(jì)了一套泡沫制備及性能測(cè)試裝置,并分別以活性劑濃度及重力水平為變量,定量分析水泡沫和磁流體泡沫的起泡性和穩(wěn)定性。在一定濃度范圍內(nèi),表面活性劑的添加可以增強(qiáng)水泡沫和磁流體泡沫的性能,其起泡性及穩(wěn)定性均得到提升,當(dāng)活性劑濃度增加到一定程度時(shí),泡沫起泡性及穩(wěn)定性均達(dá)到飽和;繼續(xù)添加表面活性劑,則會(huì)造成液膜內(nèi)活性劑過(guò)于富集,泡沫“脆性”增加,穩(wěn)定性反而降低。同時(shí),通過(guò)磁重力補(bǔ)償下的磁流體泡沫性能實(shí)驗(yàn)發(fā)現(xiàn):磁流體泡沫的液相分?jǐn)?shù)增加,這是由于重力被補(bǔ)償后,析液被抑制,泡沫發(fā)生吸液(Foam Imbibition)過(guò)程所引起的。而隨著有效重力水平的降低,磁流體泡沫的穩(wěn)定性得以顯著提升,這是由于磁重力補(bǔ)償下,液膜內(nèi)液相增多,其演化衰減得以抑制。這一結(jié)論與國(guó)際空間站內(nèi)的泡沫實(shí)驗(yàn)研究基本符合。本文的第三部分,通過(guò)實(shí)驗(yàn)記錄了二維水泡沫及磁流體泡沫的粗化動(dòng)力學(xué)過(guò)程,并分析泡沫粗化中的拓?fù)鋵W(xué)演化機(jī)制及氣泡面積定量演化規(guī)律。第一方面,泡沫粗化中可以觀察到T1和T2兩種拓?fù)鋵W(xué)演化機(jī)制:T1過(guò)程為相鄰邊的交換重排,使原本隔開的氣泡相連,此過(guò)程不會(huì)引起氣泡個(gè)數(shù)及其邊數(shù)的改變;T2過(guò)程為體積相對(duì)較小的三、四、五邊形氣泡在壓力梯度下發(fā)生收縮,直至完全消失,此過(guò)程則會(huì)減少氣泡的個(gè)數(shù)及其邊數(shù)。同時(shí),在T2過(guò)程中發(fā)現(xiàn),四邊形和五邊形氣泡并不會(huì)直接消失,而是隨著氣泡變小,首先經(jīng)歷一系列T1過(guò)程,待其轉(zhuǎn)變?yōu)槿呅魏?再收縮直至完全消失。第二方面,常重力和磁重力補(bǔ)償條件下,二維泡沫內(nèi)的氣泡面積隨時(shí)間變化與其邊數(shù)呈線性關(guān)系,均符合馮諾依曼定律。通過(guò)磁重力補(bǔ)償下的磁流體泡沫粗化實(shí)驗(yàn)發(fā)現(xiàn),氣泡面積演化速率顯著變慢,說(shuō)明粗化過(guò)程受到了抑制。而這種抑制效應(yīng)正是由于外加磁場(chǎng)改變了泡沫的液膜特性,使泡沫變得更加穩(wěn)定。本文的第四部分,采用有限元商業(yè)軟件進(jìn)行了二維單分散泡沫結(jié)構(gòu)演化的數(shù)值模擬研究,從而深入了解蜂窩六邊形的形成機(jī)制。首先,采用水銀和空氣兩相體系來(lái)模擬單分散二維泡沫結(jié)構(gòu)演化,證實(shí)了蜂窩六邊形可在液膜內(nèi)流體完全流動(dòng)的情況下形成,這是表面張力作用下的能量最小化過(guò)程。而后,通過(guò)分析不同時(shí)刻下的二維泡沫結(jié)構(gòu)形態(tài)可知,氣泡間氣體會(huì)逐步收縮減少,這是由于液膜交界處的“縫合力”引起的,當(dāng)氣泡完全消失時(shí),蜂窩六邊形結(jié)構(gòu)便形成。
[Abstract]:With the rapid development and wide application of material science, the research and development of new functional materials is becoming more and more urgent. The porous foam material, as a functional material of the "Environmental protection, light weight, high performance", has received a great deal of attention both at home and abroad. During the preparation of the foam material, the formation and application of the various foam products from the initial liquid foam play a critical role in the foam evolution dynamics through the beginning and the end. How to control the dynamic process of foam evolution reasonably to obtain the foam material with uniform bubble distribution and stable performance is a difficult problem. At the same time, at the theoretical analysis level, the research on the dynamic mechanism of the foam evolution can also guide the space-filling theory in the physics, and help to solve the structural evolution problem in other physical systems. In the process of foam evolution, the phenomenon of multi-scale (space, time) caused by gravity has been the hot and difficult problem of the scientific community. How to eliminate the gravity, and to carry out the foam evolution experiment under the low-micro-gravity environment for a long time and at low cost is another difficult problem. Based on this research, this paper studies the key scientific problems such as foam performance, coarsening mechanism and structural evolution law in the dynamic process of liquid water foam and magnetic fluid foam. Then, the new research method of the "magnetic gravity compensation" designed in this paper is adopted to realize the simulated low-micro-gravity environment, so as to further analyze the process of the evolution of the magnetic fluid foam. In the first part of this paper, a new method of magnetic gravity compensation is designed, which is realized by combining the magnetic fluid and the Helmholtz-Maxwell pair of coils. In this paper, the distribution of the magnetic field and the effective gravity of the magnetic fluid in the two pairs of coils are studied by means of numerical simulation and experimental measurement. First, the magnetic field size and distribution are measured by the finite element simulation software and the precision tesla. The distribution of the magnetic field in the center of the two pairs of coils is a linear distribution. The distribution of the magnetic field is more uniform, and the experimental results are in good agreement with the numerical simulation. According to the calculation result of the effective gravity level of the magnetic fluid, the uniform magnetic force compensation of more than 90% is realized in the cylindrical region with the center diameter of 60 mm and the height of 60 mm of the double-pair coil, and by adjusting the current in the Maxwell coil, the gravity can be completely canceled by the magnetic force, And the low micro-gravity condition required by the follow-up experiment is realized. In the second part of this paper, a set of foam preparation and performance testing device was designed, and the foaming and stability of the water foam and the magnetic fluid foam were quantitatively analyzed with the concentration of the active agent and the gravity level. the addition of the surfactant can enhance the performance of the water foam and the magnetic fluid foam in a certain concentration range, and the foaming property and the stability are improved; when the concentration of the active agent is increased to a certain degree, the foaming property and the stability of the foam reach saturation; and the surfactant is continuously added, Then the active agent in the liquid film is too rich, the foam "friability" is increased, and the stability is reduced. At the same time, the performance of the magnetic fluid foam under magnetic gravity compensation has found that the liquid phase fraction of the magnetic fluid foam is increased, which is caused by the process of the foam generation, after the gravity is compensated. With the decrease of the effective gravity level, the stability of the magnetic fluid foam is greatly improved, due to the increase of the liquid phase in the liquid film due to the magnetic gravity compensation, and the evolution attenuation of the liquid film is suppressed. This conclusion is basically in line with the research of the foam experiment in the International Space Station. In the third part of this paper, the process of coarsening of the two-dimensional water foam and the magnetic fluid foam was recorded by the experiment, and the evolution mechanism and the quantitative evolution of the bubble area were analyzed. in that first aspect, the two types of evolution mechanism of T1 and T2 can be observe in the foam coarsening: the T1 process is the exchange rearrangement of the adjacent side, so that the originally separated air bubbles are connected, the process does not cause the change of the number of bubbles and the number of edges thereof, and the T2 process is three or four smaller in volume, The pentagonal bubble shrinks under the pressure gradient until completely disappears, and this process reduces the number of bubbles and its number of edges. At the same time, in the course of T2, it is found that the quadrilateral and pentagonal bubbles do not disappear directly, but as the bubbles become smaller, a series of T1 processes are first experienced, to be converted into triplets, and then to completely disappear. In the second aspect, under the conditions of gravity and magnetic gravity compensation, the air bubble area in the two-dimensional foam has a linear relationship with the number of its sides over time, and it is in accordance with the von Neumann's law. The experimental results show that the evolution rate of the bubble area is slow, which indicates that the coarsening process is inhibited. This inhibitory effect is due to the fact that the applied magnetic field changes the liquid film properties of the foam, making the foam more stable. In the fourth part of this paper, the numerical simulation of the evolution of two-dimensional single-dispersed foam structure is carried out by using the finite element commercial software, and the formation mechanism of the honeycomb hexagon is well understood. First, a two-phase system of mercury and air is used to simulate the evolution of a single-dispersed two-dimensional foam structure, and it is proved that the honeycomb hexagon can be formed under the condition of complete flow of the fluid in the liquid film, which is the energy minimization process under the action of surface tension. Then, by analyzing the shape of the two-dimensional foam structure at different times, the gas between the air bubbles will shrink gradually, which is caused by the "suture force" at the boundary of the liquid film, and the honeycomb hexagonal structure is formed when the air bubbles completely disappear.
【學(xué)位授予單位】：上海大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB383.4

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 曾令宏,張之翔;圓環(huán)電流的磁場(chǎng)以及兩共軸圓環(huán)電流之間的相互作用力[J];大學(xué)物理;2002年09期

2 孫其誠(chéng);譚靚慧;;泡沫物理學(xué)史拾萃[J];物理;2008年07期

3 劉艷輝;杜鵬;;金屬蜂窩夾層板的研究進(jìn)展[J];機(jī)械制造與自動(dòng)化;2013年01期

，

本文編號(hào)：2511850