【作者】 谢卫东；

【导师】 彭晓东；

【作者基本信息】 重庆大学 ， 材料加工工程， 2008， 博士

【摘要】 本论文在较为全面的分析纳米材料、纳米薄膜材料的研究现状和趋势的基础上,提出并研究了多项基于纳米胶体的纳米微粒埋植薄膜制备新方法,形成了一批专有技术,申请并获得了“电场沉积制备薄膜的方法”、“一种制备纳米薄膜的方法”、“一种有色金属用变质剂及其制备方法”、“高纯碳酸锶制备方法”等发明专利。①研究了纳米胶体的稳定性,动力学、热力学研究及实验研究结果表明:纳米胶体中的分散相存在离析倾向。在影响离析速度的微粒粒径、分散相与分散介质密度差、分散介质粘度等因素中,微粒粒径的影响较大,其他因素的影响相对较小。常见纳米胶体的离析速度较慢,尤其是小尺寸的纳米微粒的胶体,其离析过程十分缓慢,处于动力学上的“亚稳定”状态。纳米胶体的分散相浓度不均匀时,有通过扩散以使其浓度均匀化的趋势,纳米微粒可不借助外力而在液相中自分散成为纳米胶体。纳米胶体中,分散相的扩散过程与离析过程是纳米胶体中两个同时存在但结果相反的过程,在离析与扩散达到平衡时,胶体的浓度分布为c₂/c₁=e^{-（4/3）πr3N_Ag/RT（ρ_p-ρ₁）（h₂-h₁）}。在影响浓度分布的因素中,微粒粒径的影响甚大,粒径较小时（小于10nm）,浓度随高度的变化较小,粒径较大时,浓度随高度的变化较大,粒径较大时（大于100nm）,浓度随高度的变化十分显著;分散相与分散介质的密度差对浓度分布有影响,但影响较小;温度对浓度分布的影响通常小到可忽略不计。在调控纳米胶体稳定性的措施中,最为有效的措施是控制胶体中分散相微粒的粒径及其衍变过程,其他措施包括:调整分散相与分散介质的密度差、调整分散介质的粘度、调整异电性离子的电性及浓度、使用高分子稳定剂或絮凝剂等。②研究了超声波在液相中的传播机制、超声波在液相中的微区域瞬时高能效应、超声波在纳米胶体制备中的分散、能量转化、工艺促进等作用。研究并获得了纳米胶体超声制备方法。结果表明,采用超声波制备纳米胶体具有胶体微粒粒径细小、均匀,工艺效率高等显著优点。同时,超声波设备结构简单,运行稳定性好,振动及噪音较低,易于实现纳米胶体的高质量、高效率、低能耗、低成本、批量化生产。③研究了电沉积的共同特征,结果表明,实现电沉积的基本条件应当包括:微粒荷电、微粒处于方向性外电场中、微粒能在电场力作用下定向移动等;普通的液相电沉积中,沉积电路通常为封闭的电流回路,常存在电极反应,并可能危害沉积过程的进行和沉积膜的质量,采用低电压沉积可在一定程度上减缓不良电极反应的危害,但会使沉积速度变得十分缓慢。④创新性地提出并研究了电场沉积制备薄膜的方法,该方法通过在开放的沉积电路中进行电场沉积,在实现电场力作用下的微粒沉积成膜的同时,从根本上防止了不良电极反应对沉积过程和沉积膜质量的危害。研究结果表明:该方法能采用高电压快速沉积纳米微粒薄膜,沉积速度和沉积膜质量明显优于普通电沉积;该方法不但可以在导电基材上沉积薄膜,而且可在非导电基材上沉积薄膜;电场沉积的电极可采用普通电导体制作;电场沉积除用于制备沉积膜外,还可与电镀、化学镀等工艺联合使用,在电镀、化学镀等工艺过程中,通过单独设置沉积电场,将分散体系中的微粒沉积到镀层中,获得复合镀层,不同于普通复合镀,新方法可通过调整沉积电场强度和沉积时间,使复合镀层中微粒含量和分布的控制成为可能。⑤创新性地提出并研究了以逐层叠加法为核心的制备纳米薄膜的方法。该方法有机结合了埋植技术和插层技术的优点,在保证制品技术性的同时,兼顾了工艺成本和工艺效率。⑥创新性的提出并研究了有色金属用变质剂及其制备方法。该方法通过变质元素的化合物的溶液及胶体的制备、分散/埋植—隔离、后处理等工艺过程,实现了化合物类变质剂的纳米化。⑦通过对纳米微粒SrCl₂、SrO埋植多层膜变质剂及其制备、应用技术的理论及实验研究,发现:相对于普通Sr化合物变质剂和Sr合金变质剂,金属熔体中的纳米Sr化合物微粒埋植多层膜变质剂在热量传输、质量传输上有其独特优势,纳米多层膜能快速吸热升温并快速与金属熔体间进行质量传输,变质起效快、Sr的利用更为充分;纳米微粒埋植Sr化合物变质剂实现了新生态的Sr在金属熔体中的高度弥散,待变质金属熔体中,只需极少量的Sr即可获得良好的变质效果,而且不会出现含锶过高造成的过变质及孔洞问题,合金综合性能优良;采用纳米Sr化合物微粒埋植多层膜变质剂对ZL101A进行变质处理时,ZL101A的含锶量只需0.005%以上即可达到优良的变质效果,仅为常规Sr化合物变质剂和Sr合金变质剂所需的适宜Sr含量的1/3-1/4,开创了ZL101A合金Sr变质中Sr含量的新低;纳米Sr化合物微粒埋植多层膜变质剂具有变质作用起效快、变质效果保持时间长,变质操作方便等优点,并具备Kg级及KKg级规模化制备与应用可行性,技术经济性好,工业化生产和应用前景好。更多还原

【Abstract】 Analyzed the present situation of nano materials and nano-films, a series of new preparation methods, which were associated by nano colloid, were invented and researched. Some proprietary methods were obtained and some of them were applied and authorized for patents of invention, which include Manufacture of Films by Electric Field Deposition Method and A method for the Manufacture of Films and A Alterative Used to Nonferrous Metal Melting and its Manufacture Method and Manufacture of high pur High-purity SrCO₃ and so on.1) Separating trend always exist in nano colloid. The diameter of the dispersed phase influences the separating velocity seriously. Normal nano colloids have very small separating velocity. When the diameters of the dispersed phase in nano colloid are very small, the colloid can be metastability in kinetics. Diffusing process will appear when the dispersed phase concentration is not symmetrical in colloid. The centralized nano particles in colloid have the self-diffusing ability. Normally, separating process and diffusing process exist in colloid synchronously and can be balanced each other. The concentration distributing of the dispersed phase in nano colloid can be estimated asc₂/c₁ = e（-4/3πr³（N_Ag）/（RT）（ρ_p-ρ₁）（h₂-h₁））. To control the stability of colloid, the adjusting and controllingof the diameter of the dispersed phase can be the most effective method. Secondary methods include that adjusting the difference between the densities of disperse medium and dispersed phase and adjusting the viscosity of disperse medium and adjusting properties and concentration of the contra-ions in disperse medium and using stabilizersor flocculating agents.2) The instantaneous high-energy effects in microsize can be created by ultrasonicin liquid and can be used to expedite the manufacture process of colloid and advance the quality of the product. The manufacture of colloid using ultrasonic should be an industrial method with advantages such as high quality and high efficiency and low energy consumption and low cost and so on.3) The essential conditions to achieve the electric deposition include that the particles was carrying charges and placed in electric field and can be moved to one direct drove by electric field force. In normal electric deposition, the electric current is close and some electrode reactions will occur and destroy the deposition process and the quality of the deposited film. Lower deposition voltage can weaken some of the harms but decrease the deposition velocity badly.4) A new method for the manufacture of nano-film, which was called electric field deposition, was invented and investigated to avoid the harmful electrode reactions such as gas evolving, electrolysis and plating which disturb the deposition process and deposited film in manufacture of nano-films by normal electric deposition. The electric field deposition equipment was designed, in which the soleplate and the deposited film will not form a close current loop with the deposition electrocircuit. The new method was applied to deposit the CdS film. Smooth and compact films composed with particles, which diameter was a little more than 30nm, were manufactured. It was shown that the new method has some benefits such as high-grade nano-films can be obtained and no expensive electrode materials are needed. The new method can also be associated with electro plating or chemical plating to obtain composite deposite, in which, the content and distributing of the particles may be controlled easily.5) Another new method for the manufacture of nano-film, in which the advantages of heeling-in and intercalation are congregated, was invented and investigated to make large mass nano films with low cost and high efficiency.6) A new modifier for the non-ferrous metal and its manufacture method were invented and investigated, in which the compounds including modifier elements were made as nano particles multi-layer films by the technics which include the preparation of the solution or colloid of the compound with alterative elements and the deconcentration / heeling-in - isolation and post treatment and so on.7) The manufacture and application technologies of the modifier with SrCl₂ and SrO nano particles multi-layer films, which was called nano Sr-Compound modifier, were investigated theoretically and experimentally. It was shown that:The nano Sr-Compound modifier can display alterative effects fleetly as the heat and mass transformations between the modifier and molten metal.Compared with the normal Sr-compound modifiers and Sr-alloy modifiers, nano Sr-compound modifier can release nascent state elementary Sr all over the molten metal and offer more chances for the modification of more crystal gains and increase the integrated mechanical properties by very low concentration of Sr in molten metal. The concentration of Sr in ZL101A could as low as be 0.005% which is a new record of low limit of the concentration of Sr in Al-alloy to achieve favorable modification by Sr.Using the new method for the manufacture and application of the nano Sr-Compound modifier, it is possible that Kg rank and KKg rank nano modifier can be manufactured and applied industrially and good technical economy may be obtained.更多还原