本文選題：納米顆粒　切入點(diǎn)：表面熱力學(xué)性質(zhì)　出處：《太原理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：納米顆粒由于其突出的表面效應(yīng)和尺寸效應(yīng),使得其化學(xué)反應(yīng)、相變、吸附、電化學(xué)、溶解等化學(xué)過程與其塊狀物質(zhì)有很大差別,而這些差別皆歸因于納米顆粒的表面熱力學(xué)性質(zhì)。目前關(guān)于粒度對納米顆粒表面熱力學(xué)性質(zhì)影響的規(guī)律還不清楚,而且還缺乏納米顆粒表面熱力學(xué)性質(zhì)的測定方法。 本文首先在經(jīng)典熱力學(xué)理論的基礎(chǔ)上,通過引入表面變量,首次從理論上分別導(dǎo)出了納米顆粒摩爾表面熱力學(xué)性質(zhì)和偏摩爾表面熱力學(xué)性質(zhì)與粒度的關(guān)系式,討論了粒度對它們的影響規(guī)律；并且在過渡態(tài)理論的基礎(chǔ)上,導(dǎo)出了納米顆粒溶解的動力學(xué)參數(shù)與表面熱力學(xué)性質(zhì)的關(guān)系式,完善了納米顆粒溶解的動力學(xué)理論。 其次,在實驗上分別采用水熱均勻沉淀法和復(fù)分解法制備了不同平均粒徑的納米氧化鎂和納米碳酸鈣,用X射線衍射儀、掃描電鏡和透射電鏡對所制備的樣品的粒徑大小和形貌進(jìn)行了表征。然后,利用電導(dǎo)率儀,測定了不同溫度下不同粒度的納米氧化鎂和納米碳酸鈣在水中溶解的瞬時濃度和平衡濃度,進(jìn)而得到了它們的溶解標(biāo)準(zhǔn)平衡常數(shù)Ko、溶解熱力學(xué)函數(shù)和溶解動力學(xué)參數(shù)(k、Ea和A)；并根據(jù)溶解熱力學(xué)和動力學(xué)數(shù)據(jù),分別計算出了納米顆粒的表面熱力學(xué)性質(zhì)；討論了粒度對納米氧化鎂和納米碳酸鈣溶解熱力學(xué)函數(shù)、動力學(xué)參數(shù)以及表面熱力學(xué)性質(zhì)的影響規(guī)律,并將實驗結(jié)果與理論進(jìn)行了對比分析。 研究結(jié)果表明: (1)采用水熱均勻沉淀法和復(fù)分解法，，通過改變制備條件，可以分別制備出高純度的平均粒徑為14~55nm的納米方鎂石型氧化鎂顆粒和17~71nm的納米球霰石型碳酸鈣顆粒。 (2)納米顆粒的粒度對溶解熱力學(xué)有很大的影響：隨著納米顆粒粒徑的減小，溶解的ln Ko增大，而G o m、 H om、 S o m均減��；且它們與粒徑的倒數(shù)之間均存在較好的線性關(guān)系，這些實驗規(guī)律與納米溶解熱力學(xué)理論一致。 (3)納米顆粒的粒度對溶解的動力學(xué)有顯著的影響：隨著粒徑的減小，溶解的lnk逐漸增大，而Ea和lnA卻逐漸減��；并且lnk、Ea和均與1/d呈現(xiàn)良好的線性關(guān)系，這些實驗規(guī)律與納米溶解動力學(xué)理論一致。 (4)納米顆粒的粒度對納米顆粒的表面熱力學(xué)性質(zhì)有顯著的影響：隨著納米顆粒粒徑的減小，其摩爾表面吉布斯能、摩爾表面焓和摩爾表面熵均增大，且均與粒徑的倒數(shù)呈線性關(guān)系；這些影響規(guī)律與表面熱力學(xué)性質(zhì)的關(guān)系式一致。 (5)采用溶解度法，利用不同粒度納米顆粒的溶解熱力學(xué)數(shù)據(jù)和動力學(xué)數(shù)據(jù)均可得到其表面熱力學(xué)性質(zhì)，但由溶解熱力學(xué)數(shù)據(jù)得到的表面熱力學(xué)性質(zhì)更可靠。
[Abstract]:Because of its outstanding surface effect and size effect, nanoparticles have different chemical processes such as chemical reaction, phase transition, adsorption, electrochemistry and dissolution from their bulk materials. However, these differences are attributed to the surface thermodynamic properties of nanoparticles. At present, the influence of particle size on the surface thermodynamic properties of nanoparticles is not clear, and there is a lack of methods for the determination of surface thermodynamic properties of nanoparticles. On the basis of classical thermodynamic theory and by introducing surface variables, the relations between surface thermodynamic properties of nanoparticles and partial moles and particle size are derived theoretically for the first time in this paper. The influence of particle size on them is discussed, and based on the transition state theory, the relationship between the kinetic parameters of the dissolution of nanoparticles and the thermodynamic properties of the surface is derived, and the kinetic theory of the dissolution of nanoparticles is improved. Secondly, nanocrystalline magnesium oxide and calcium carbonate with different average particle sizes were prepared by hydrothermal homogeneous precipitation method and double decomposition method respectively. The particle size and morphology of the prepared samples were characterized by SEM and TEM. The instantaneous concentration and equilibrium concentration of nano-magnesium oxide and nano-calcium carbonate dissolved in water at different temperatures were determined. Then their dissolution standard equilibrium constants Ko, dissolution thermodynamics function and dissolution kinetics parameters, such as Ku EA and An, were obtained, and the surface thermodynamic properties of the nanoparticles were calculated according to the dissolution thermodynamics and kinetic data, respectively. The effects of particle size on the dissolution thermodynamic function, kinetic parameters and surface thermodynamic properties of nano-MgO and nano-CaCO3 were discussed, and the experimental results were compared with the theoretical analysis. The results show that:. 1) by means of hydrothermal homogeneous precipitation method and double decomposition method, high purity nano-periclase magnesium oxide particles with average particle size of 145nm and nano-spheroidal calcium carbonate particles of 1771nm can be prepared by changing the preparation conditions. (2) the particle size of nanoparticles has a great influence on dissolution thermodynamics: with the decrease of particle size, the dissolved ln Ko increases, while G om, H omand Som decrease, and there is a good linear relationship between them and the reciprocal of particle size. These experimental rules are consistent with the thermodynamics theory of nano-dissolution. (3) the particle size of nanocrystalline particles has a significant effect on the kinetics of dissolution: with the decrease of particle size, the dissolved lnk increases gradually, while EA and lnA decrease gradually, and the sum of Ln Ku EA shows a good linear relationship with 1 / d. These experimental rules are consistent with the theory of nano-dissolution kinetics. (4) the particle size has a significant effect on the surface thermodynamic properties of nanoparticles: with the decrease of particle size, the molar surface Gibbs energy, molar surface enthalpy and molar surface entropy increase. All of them are linearly related to the reciprocal of particle size, and these effects are consistent with the thermodynamic properties of the surface. 5) the surface thermodynamic properties can be obtained by using the dissolution thermodynamic data and kinetic data of different particle sizes, but the surface thermodynamic properties obtained from the dissolution thermodynamics data are more reliable.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB383.1

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