本文選題：銀納米顆粒　切入點(diǎn)：銀鎳合金顆粒　出處：《北京科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：納米材料具有十分獨(dú)特和優(yōu)異的性能,目前納米材料在各領(lǐng)域的應(yīng)用都取得令人矚目的成就,關(guān)于納米材料的性能開發(fā)與應(yīng)用拓展受到了十分廣泛的關(guān)注。納米材料的性能主要是由其成分和結(jié)構(gòu)決定的,而納米材料的成分和結(jié)構(gòu)是由其制備工藝決定的。因此,想要獲得各種優(yōu)異性能的納米材料就要對其制備過程進(jìn)行精確地設(shè)計與控制,其主要前提是深入了解納米顆粒的形成機(jī)制。目前這一方面的研究面臨著諸多困難,其中捕獲納米顆粒形成早期的尺寸與結(jié)構(gòu)的動態(tài)信息是難點(diǎn)中的難點(diǎn)。同步輻射光源具有高亮度、高穿透性、高準(zhǔn)直性和高的時間空間分辨率等諸多優(yōu)點(diǎn),對納米材料的研究有著得天獨(dú)厚的優(yōu)勢,特別是在實(shí)現(xiàn)動態(tài)研究和提高時間分辨率等方面效果顯著。近些年來,同步輻射理論與技術(shù)都有了迅速的發(fā)展,同時與同步輻射技術(shù)配套的探測器和原位實(shí)驗(yàn)裝置大量涌現(xiàn),這些條件使得對納米顆粒早期形成過程的觀察成為可能。本課題以合成方法較為簡單、完善、成本相對較低且性能優(yōu)異的銀納米顆粒為主要研究對象,通過結(jié)合常規(guī)的實(shí)驗(yàn)室表征手段與先進(jìn)的同步輻射技術(shù)分別研究了溶液中銀納米顆粒的生長過程;加熱過程中銀納米粉體的尺寸與結(jié)構(gòu)變化過程;溶液中銀鎳二元合金顆粒的制備與結(jié)構(gòu)變化過程。針對溶液會對X射線產(chǎn)生較強(qiáng)的吸收作用而導(dǎo)致時間分辨率降低的問題,以空間換時間的思路,設(shè)計了流速可控、混合均勻的連續(xù)流原位反應(yīng)裝置。采用該裝置結(jié)合北京同步輻射光源開展了原位小角X射線散射實(shí)驗(yàn)并實(shí)現(xiàn)了毫秒量級的時間分辨率,獲得了 2 mM、4 mM、6 mM和8 mM四種初始銀離子濃度合成銀納米顆粒的生長曲線。實(shí)驗(yàn)表明,不同初始銀離子濃度溶液有著不同的臨界形核半徑,初始銀離子濃度從2 mM、4 mM到6 mM,溶液的臨界形核半徑隨濃度逐漸增加,當(dāng)銀離子濃度升高到8mM時,臨界形核半徑有所下降。顆粒最終尺寸隨初始銀離子濃度的變化和臨界形核半徑隨初始銀離子濃度的變化趨勢是一致的。根據(jù)不同濃度溶液的臨界形核半徑和最終尺寸的變化建立了擴(kuò)散團(tuán)聚模型來描述顆粒的生長過程,該模型很好的擬合了顆粒的生長曲線。從實(shí)驗(yàn)結(jié)果得出臨界形核半徑、顆粒的生長速率以及生長速率的變化對顆粒的最終尺寸有十分明顯的影響,是控制顆粒尺寸的主要因素。根據(jù)加熱過程中銀納米粉體的形貌、尺寸和結(jié)構(gòu)變化規(guī)律,首次提出了銀納米顆粒在高溫下的定向合并機(jī)制,描述了不同階段加熱過程中銀納米顆粒的行為。具體為:從形貌上講,室溫到600℃顆粒均為準(zhǔn)球形,700℃時顆粒呈花生形;從尺寸上講,室溫到400℃的過程中,納米顆粒尺寸增長緩慢,400℃到700℃的過程中顆粒尺寸增長較快;從晶體結(jié)構(gòu)上講,從室溫到500℃,一個納米顆粒只包含單個晶粒,500 ℃到600 ℃ 一個顆粒包含多個晶粒,600℃到700℃時一個顆粒包含一個晶粒。根據(jù)顆粒生長機(jī)制可將整個加熱過程分為四個階段:第一階段為顆粒緩慢生長的奧斯特瓦爾德機(jī)制;第二階段為顆�？焖偕L的奧斯特瓦爾德機(jī)制,第三階段為顆粒隨機(jī)團(tuán)聚合并的生長機(jī)制;第四階段為定向合并生長機(jī)制。納米顆粒的生長導(dǎo)致小顆粒具有的較高的表面能和界面能轉(zhuǎn)化為顆粒內(nèi)能,最終導(dǎo)致納米顆粒的熱膨脹系數(shù)比塊體銀樣品大30%左右。實(shí)驗(yàn)結(jié)果詳細(xì)的描述了銀納米顆粒的熱行為,為銀納米顆粒在高溫環(huán)境的應(yīng)用提供了實(shí)驗(yàn)和理論基礎(chǔ)。采用液相還原法制備了銀-鎳二元合金顆粒,這種合金顆粒是由鎳原子摻雜到銀基底上形成的。通過對不同銀鎳比例獲得的顆粒進(jìn)行表征,確定了鎳元素對顆粒尺寸的影響。不同銀鎳比例的納米顆粒主要包含兩種晶體結(jié)構(gòu),一種是單晶顆粒,一種是五折孿晶顆粒。熱力學(xué)計算表明,顆粒尺寸較大時兩種結(jié)構(gòu)的自由能差別很小,這為兩種結(jié)構(gòu)的顆粒能夠在同一體系中共存提供了依據(jù)。顆粒最終結(jié)構(gòu)的形成是由動力學(xué)過程以及反應(yīng)最初階段溶液中的晶核結(jié)構(gòu)共同決定的。通過上述這些研究,對不同條件下銀/銀鎳合金納米顆粒的形成機(jī)制有了更深入的了解,為可控制備提供了理論依據(jù);提出了銀納米顆粒在高溫環(huán)境下的定向合并機(jī)制,為銀納米顆粒在高溫領(lǐng)域的應(yīng)用提供了實(shí)驗(yàn)和理論依據(jù)。希望這些研究結(jié)果能為其他納米顆粒的相關(guān)過程研究提供實(shí)驗(yàn)和理論幫助。
[Abstract]:Nano materials have unique and excellent performance, the application of nano materials in various fields have made remarkable achievements, expand the performance of development and application of nanomaterials have been widely concerned. The performance of nano materials is mainly determined by its composition and structure, and the composition and structure of nano materials is prepared decided by its system. Therefore, nano materials to obtain excellent performance on the preparation process of precise design and control, the main premise is to understand the formation mechanism of nano particles. At present, the research of this aspect is facing many difficulties, the formation of the nanoparticles capture the dynamic information of the size and structure of early is the most difficult. High brightness synchrotron radiation light source, high penetration, high accurate and high time straightness has many advantages such as spatial resolution, nanometer material The study on the richly endowed by nature, especially the effect in realizing the dynamic research and improve the time resolution significantly. In recent years, synchrotron radiation theory and technology are developing rapidly, at the same time and in situ experimental device of large volume detector and synchrotron radiation technology supporting the emergence of these conditions make the observation of the early formation of nanoparticles possible. The synthetic method is simple, perfect, silver nanoparticles with relatively low cost and excellent performance as the main object of study, through a combination of laboratory characterization of conventional and advanced synchrotron radiation were studied during the growth of silver nanoparticles in solution; process size and structure change of silver nano powder heating process; preparation and structural changes of silver nickel solution two element alloy nanoparticles. The solution will have strong absorption for X ray With the resulting time resolution is reduced to the problem of space for time idea, design flow control, mixed continuous uniform in-situ reaction device. The device combined with Beijing synchrotron radiation source was carried out in situ small angle X ray scattering experiment and realizes the millisecond time resolution, obtained 2 mM, 4 mM, growth curve 6 mM and 8 mM four initial concentration of silver ions synthesis of silver nanoparticles. Experimental results show that the concentration of different initial silver ion with different critical nucleation radius, initial concentration of silver ions from the 2 mM, 4 mM to 6 mM, the critical nucleation radius of solution increased gradually with the concentration of silver ions, when the concentration increased to 8mM, the critical nucleation radius decreased. The particle size change with the initial concentration of silver ions and critical nucleation radius change with the initial concentration of silver ions is consistent. According to the different concentration of solution on Changes of nucleation radius and the final size of the established diffusion aggregation model to describe the growth process of particles, the model fit well the growth curve of particles. From the experimental results show that the critical nucleation radius significantly influences the particle growth rate and the change of the growth rate of particle size is in the end. The main factors controlling the particle size. According to the morphology of the heating process of silver nano powder, variation of size and structure, is proposed for the first time with silver nanoparticles in directional mechanism under high temperature, description of silver nanoparticles of different stages in the process of heating behavior. Specifically: from the morphology, room temperature to 600 DEG C particles for the quasi spherical 700 C particles with peanut shape; in terms of size, room temperature to 400 DEG C, nano particle size growth is slow, 400 DEG to 700 DEG C in the process of particle size is from fast growth; crystal structure The structure, from room temperature to 500 DEG C, a nanoparticle containing only a single grain, 500 to 600 DEG C. a particle comprising a plurality of grain, 600 to 700 DEG C. when a particle contains a grain. According to the particle growth mechanism can make the whole heating process is divided into four stages: the first stage is Ostwald particles slow growth mechanism; the second stage is the rapid growth of the Ostwald grain mechanism, the third stage is the growth mechanism of particle agglomeration with random; the fourth stage is the directional growth mechanism. Combined with nano particles to the growth of small particles with high surface energy and interface energy into particles can eventually lead to thermal expansion of nanoparticles ratio of bulk silver samples is about 30%. The experimental results of a detailed description of the thermal behavior of silver nanoparticles, silver nanoparticles used in high temperature environment and provide experimental and theoretical basis Basis. Two yuan of silver nickel alloy particles were prepared by liquid phase reduction, this alloy particles are composed of nickel atoms doped into the silver substrate. The formation was characterized by the different proportion of silver nickel particles, the effects of Ni on nano particles of different particle size. The proportion of silver nickel mainly contains two a crystal structure is a single crystal particles, a half off twin particles. Thermodynamic calculation shows that the larger particle size when the structure of the two kinds of free energy difference is small, which in the same system provides the basis for the coexistence of two kinds of particles can form the final structure. Particles are determined by nucleation the structure and dynamics of the initial stage of the reaction in solution. Through these studies, on different conditions of formation mechanism of silver / silver nickel alloy nanoparticles have a more thorough understanding, for controlled preparation provides a theoretical basis for; The directional combining mechanism of silver nanoparticles under high temperature is put forward, which provides experimental and theoretical basis for the application of silver nanoparticles in high temperature field. It is hoped that these research results can provide experimental and theoretical help for other nanoparticle related processes.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O614.122;TB383.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 陳潔，單軍，，張懋森;分形理論及其在高分子材料研究中的應(yīng)用[J];化工新型材料;1996年06期

相關(guān)博士學(xué)位論文 前1條

1 張萬忠;納米銀的可控制備與形成機(jī)制研究[D];華中科技大學(xué);2007年

本文編號：1575338