【作者】 肖骁；

【导师】 赵中伟； 肖松文；

【作者基本信息】 中南大学 ， 有色金属冶金， 2008， 博士

【摘要】 机械球磨不仅广泛应用于粉体材料制备,成为片状金属粉体制备的标准工艺,而且近年扩展应用至环境保护领域,被视为最具商业化应用前景的POPs无害化处理技术。与国外相比,我国片状金属粉体制备工艺差距明显,尤其是片状铜粉、镍粉及锌粉都未能实现产业化,包括POPs在内的含氯有机废物无害化处理研究更是空白,鉴于此,本文开展以下三个方面的研究:（1）片状金属粉体机械球磨制备工艺研究;（2）金属粉体片状化过程微观结构演变及形变机制;（3）含氯有机废物/锌粉机械球磨化学脱氯工艺及行为机理研究。通过研究,取得以下主要成果:（1）通过球磨条件参数对粉体片状化程度的影响研究,发现介质环境是影响金属粉体片状化的重要因素,有机介质球磨更有利于粉末片状化,在此基础上,确定了机械球磨制备片状镍粉、铜粉、锌粉的最佳工艺参数,并制备得到径厚比大、片状形貌好,片层表面干净平整,具有良好的金属光泽的片状粉末产品;片状锌粉产品相关技术性能指标达到国际同类先进产品水平。（2）采用XRD、SEM、TEM等检测手段,分析了球磨过程中铜/镍/锌粉微观结构演变,发现随着球磨时间延长,镍粉、铜粉的晶粒尺寸阶梯减小,而微观应变、位错密度、晶格常数、晶胞体积皆随片状化进程阶梯增长,且微观应变、位错密度表现为各向异性。比较而言,铜粉的微观应变、位错密度均小于镍粉。片状化的铜、镍粉微观结构最显著特征是存在择优取向且晶粒呈现片层/条状;片状镍、铜粉的择优取向为<200>,且<200>取向越明显,镍/铜粉片状化程度与形貌越好。（3）在微观结构上,铜粉片状化体现为等轴晶粒在径向方向被拉长形成片层晶粒及片层晶沿径向发生碎裂形成条形晶。该过程具体形变机制为在多向载荷周期作用下,晶粒内部产生大量位错,并发生聚集重排,从而导致晶粒细化与形成择优取向。其晶粒细化主要通过两条途径实现:一是主体区域遵循晶粒内部位错细分机制,微米/亚微晶粒在应力作用下形成位错胞墙,从而使晶粒逐步细分直至形成纳米晶;二是局部区域晶粒在高应变量/应变速率作用下,碰撞瞬间形成的位错保持或再结晶形成纳米晶。（4）首先开发了含氯有机废物/锌粉机械球磨化学脱氯新工艺,确定了最佳工艺条件,实现PVC、PVDC、HCB的脱氯率100%,为含卤有机废物脱卤开辟了一条安全高效的新途径。（5）采用XRD、IR、Raman、NMR等检测方法对PVC、PVDC、HCB/锌粉机械化学脱氯产物及其结构进行了表征,确定了其机械化学反应路径。含氯有机废物/锌粉机械球磨化学脱氯遵循自由基反应机理,机械球磨过程中,锌粉在机械力作用下形成自由基,自由基进攻有机氯化物中的氯,使氯原子从有机氯化物上脱离与金属锌粉反应,形成Zn（OH）Cl、Zn₂OCl₂化合物。HCB苯环相互发生平面聚合,形成石墨结构,在空间以金刚石形式聚合,最终形成无定形碳,小部分多氯苯则发生氧化开环生成脂肪酸。（6） PVC/PVDC经脱氯、交联、脱氯化氢及氧化等路径发生降解,转变成类金刚石型碳、少量线型碳碎片及聚乙炔等产物;线性碳碎片通过氯化氢脱除反应路径形成。若进一步优化机械球磨反应条件,如采用还原性气氛下低温球磨等,有可能制得较纯净线性碳产品,从而开发一种新颖高效线型碳制备工艺。更多还原

【Abstract】 Ball milling is widely used in the preparation of powder materials and identified as the standard preparation process for metal flake powder. With the use extending to environmental protection, ball milling is identified as the most promising technology for the destruction and decontamination of POPs in 1990s. In our country, the technologies for metal flake powder preparation lag far behind that in Euramerican country, for examples, the preparation technologies for nickel, copper and zinc flake haven’t been industrialized. Meanwhile, no research is developed for destruction and decontamination of POPs. etc. chlorinated organic contaminates by ball milling.In order to address the issues mentioned above, in this paper, three aspects have been investigated: 1) Preparation process of metal nickel, copper and zinc flake by ball milling; 2) Microstructure evolution and deformation mode of metal powder during the flaking process; 3) Mechano-chemical de-chlorination process and behavior of chlorinated organic contaminates by ball milling zinc powder. The following summaries are obtained:（1） The effect of ball milling parameters on the flaking level of metal powder was investigated. It was found that medium environment affect the flaking level of the metal powder in great degree, and metal powder was flaked better in organic medium than in air. The most appropriate conditions to prepare nickel, copper and zinc flake powder were determined and metal flake powder with a high flaking level, good flaky microshape and metal luster were successfully prepared. The properties such as flaking level and microshape of zinc flake powder prepared almost reach the standard of best production in the world.（2） The microstructures of copper, nickel and zinc powder during flaking process were investigated by XRD, SEM, and TEM. It was found that the grain size decreased, while the microstrain, dislocation density, lattice parameter, and unit cell volume increased with increasing flaking time steppedly, and the microstrain, dislocation density possessed anisotropic behaviors. The microstrain and dislocation density of copper were relatively less than that of nickel. The microstructures of nickel and copper flake powder were characterized by the layer/rod-shaped grains, as well as the preferred orientation. The preferred orientation of nickel and copper flake was <200>, and the flaking level increased with the higher <200> preferred orientation.（3） On the aspect of microstructure, flaking process of copper powder was characterized as the equiaxed grains were elongated along the direction of the flake radius to layer-shaped and then the layer-shaped grains were broken into rod-shaped. In this process, a high density of dislocations were introduced into the grains with the random cycling loading and resultant strain, then dislocations aggregated and rearranged, which resulted grain refinement and preferred orientation. The grain refinement modes included: （1） In the main body of grains, dislocation cells/walls formed during straining, which subdivided initial grains on a smaller and smaller scale; （2） In local area of grains, the dislocation arrangements introduced at the instant of the impact could be maintained and forming nanograins due to high strain and strain rate in these areas.（4） The new technology for mechano-chemical de-chlorination of chlorinated organic contaminates by ball milling with zinc powder was developed in this paper for the first time. The optimum conditions were examined and determined, and the dechlorination rate of PVC, PVDC, HCB were almost reach to 100% on the optimum condition. Therefore, mechano-chemical de-chlorination would become a new process for de-halogenation of halogenated organic contaminates in an effective and safe way.（5） On the basis of characterizing and investigating the de-chlorination products by XRD, IR, Raman, GC/MS and NMR, the de-chlorination reaction paths were determined and verified. The mechanism of mechano-chemical dechlorination of chlorinated organic contaminates with zinc powder was accordance with the free radical theory. During the milling process, free radical formed in zinc powder under the effect of impact, which then attacked Cl atom in the chlorinated organic contaminates. Cl atom was split off from the chlorinated organic contaminates and reacted with zinc powder to form Zn（OH）Cl and Zn₂OCl₂. A great part of HCB were transformed into amorphous carbon, through the pathway of benzene ring polymerized in the direction of plane and space, besides a slight part was transformed into fatty acid in the way of oxidation and opening of benzene ring.（6） PVC/PVDC can be de-chlorinated following the paths of de-chlorination, crosslink, de-hydrochlorination and oxidation and transformed to diamond-like carbon, carbyne fragments and polyacelytene. Through the path of de-hydrochlorination, carbyne fragment formed. If the process can be performed in the more appropriate milling conditions such as low milling temperature, the reductive atmosphere, the pure carbye would be obtained, and the mechano-chemical de-chlorination process of PVC/PVDC would become a novel and effective approach for carbyne synthesizing,更多还原