【摘要】：無機功能薄膜材料在微電子設備、化學和生物傳感、能量轉(zhuǎn)化及儲存等方面具有重要的應用。晶體粒子的成核及生長過程顯著影響無機薄膜的微結(jié)構(gòu),比如比表面積、孔隙、粒子取向性及晶體形貌等特性。水滑石(LDH)作為無機層狀功能材料在催化、吸附、聚合物添加劑、藥物傳輸、環(huán)境修復及能量儲存等方面具有廣泛的應用。將LDH構(gòu)筑成二維薄膜材料拓寬了其性能應用。目前為止,LDH薄膜的制備方法包括原位生長、物理沉積、電化學沉積等手段,其中原位生長法制備的薄膜具有粒子與基體間結(jié)合力強、易于控制晶體取向等特點,最具應用前景。然而,水熱條件下原位生長LDH薄膜存在組分局部聚集、薄膜組成不均勻等問題,這將影響到薄膜材料的性能。創(chuàng)新LDH薄膜的制備技術(shù)提高其應用性能具有較為重要的研究意義本論文嘗試采用晶種生長法(seeded growth method,也叫做二次生長法,secondary growth method)在鎳箔和泡沫鎳基體上制備了NiAl-LDH薄膜,并將其用作堿性鎳氫電池陽極材料,測試其電化學性質(zhì)。主要的實驗結(jié)果如下：(1)首先采用水熱法制備了納米NiAl-LDH晶種,晶體粒子尺寸20-30 nm左右,能夠形成穩(wěn)定的膠體溶液。然后,通過浸漬提拉在基體表面涂覆上LDH晶種層。最后在水熱條件下進行二次生長制備LDH薄膜。論文研究了晶種法LDH薄膜的晶體組成、薄膜結(jié)構(gòu)、形貌等特點,并與原位生長法制備的薄膜相比較。表征研究了薄膜隨著反應時間的演化過程,推測了薄膜原位及二次生長的過程機制,發(fā)現(xiàn)二次生長時LDH晶種具有加速晶體晶化速率的作用,所制備的薄膜材料具有更為均勻的晶體組成。(2)論文將兩種方法制備的NiAl-LDH薄膜用作鎳氫電池陽極材料,測試其電化學性質(zhì),發(fā)現(xiàn)晶種法薄膜材料具有更好的充放電性能,更高的比放電容量及穩(wěn)定性。當充放電電流密度為30 mA g-1時,晶種法薄膜的充電電壓平臺長而低,放電電壓平臺長而高,薄膜的比放電容量為216mAhg-1,而原位生長法薄膜的為173 mAh g-1。在50圈循環(huán)測試中,晶種法薄膜的比放電容量具有更高的穩(wěn)定性。推測該薄膜具有更高的結(jié)晶度和均勻的組分分布,由此有利于降低質(zhì)子擴散阻力,并穩(wěn)定電活性材料的結(jié)構(gòu)。(3)最后,本論文嘗試采用晶種法制備了MgAl-LDH薄膜,使用與上述NiAl-LDH薄膜相同的二次生長制備工藝,分別在鈦片及不銹鋼片基體上得到了MgAl-LDH薄膜材料。通過與原位法薄膜對比,發(fā)現(xiàn)晶種法薄膜的晶體結(jié)晶度更高,晶型更完整,同時生長的薄膜表面晶體更密第進一步證實了LDH晶種在二次法薄膜生長過程中加速晶體晶化的作用。
[Abstract]:Inorganic functional thin films have important applications in microelectronic equipment, chemical and biological sensing, energy conversion and storage. The nucleation and growth process of crystal particles significantly affect the microstructure of inorganic films, such as specific surface area, porosity, particle orientation and crystal morphology. As inorganic layered functional materials, hydrotalcite (LDH) has been widely used in catalysis, adsorption, polymer additives, drug transport, environmental remediation and energy storage. The properties and applications of LDH thin films are broadened by using LDH as two-dimensional thin-film materials. Up to now, the preparation methods of LDH thin films include in situ growth, physical deposition, electrochemical deposition and so on. The films prepared by in situ growth method have the characteristics of strong adhesion between particles and substrates, and easy to control the crystal orientation. The most promising application. However, in situ growth of LDH thin films under hydrothermal conditions, there are some problems such as local aggregation of components and uneven composition of the films, which will affect the properties of the films. It is of great significance to improve the performance of LDH thin films by means of innovative preparation techniques. In this paper, we try to prepare NiAl-LDH films on nickel foil and foamed nickel substrates by seed growth method (seeded growth method,), also known as secondary growth method (, secondary growth method). It was used as anode material for alkaline Ni-MH battery and its electrochemical properties were tested. The main experimental results are as follows: (1) the nanocrystalline NiAl-LDH seeds were prepared by hydrothermal method. The size of the nanoparticles is about 20-30 nm, which can form a stable colloidal solution. Then, the surface of the substrate was coated with LDH seed layer by dipping Czochralski. Finally, LDH thin films were prepared by secondary growth under hydrothermal conditions. In this paper, the crystal composition, structure and morphology of LDH thin films prepared by seed method are studied and compared with those prepared by in situ growth method. The evolution process of the film with reaction time was studied, and the mechanism of in situ and secondary growth of the film was inferred. It was found that the LDH seed had the function of accelerating the crystallization rate of the film during the secondary growth. The prepared thin films have more uniform crystal composition. (2) the NiAl-LDH thin films prepared by two methods are used as anode materials for Ni-MH batteries, and their electrochemical properties are tested. It is found that the film has better charge-discharge performance, higher specific discharge capacity and stability. When the charge / discharge current density is 30 mA g ~ (-1), the charging voltage platform is long and low, and the discharge voltage platform is long and high. The specific discharge capacity of the film is 216mAhg-1, while that of the in-situ growth thin film is 173 mAh g-1. In 50 cycles, the specific discharge capacity of the seed film is more stable. It is inferred that the film has higher crystallinity and uniform component distribution, which is beneficial to reduce the proton diffusion resistance and stabilize the structure of the electrically active material. (3) finally, the MgAl-LDH thin film is prepared by the method of crystal seeding. MgAl-LDH thin films were prepared on titanium and stainless steel substrates using the same secondary growth process as above mentioned NiAl-LDH thin films. Compared with the in-situ thin films, it is found that the crystal crystallinity and crystal form of the seeded thin films are higher, and the surface crystals of the films grown are more dense. The effect of LDH seed on accelerating the crystallization of the thin films in the secondary growth process is further confirmed.
【學位授予單位】：北京化工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB383.2

【共引文獻】

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