摘要
铝丝电爆炸法制备纳米粉体具有低成本、高效率、产物纯度高且粒度分布可控等优势,其扩散阶段空间形态均匀性是影响纳米铝粉品质的关键因素.为此设计并搭建了铝丝电爆炸实验系统,可实现包括激光成像、分幅成像与辐射光谱分析的超快光学诊断.观测到铝丝电爆炸扩散阶段出现的等离子体晕层、"纺锤形"结构、"拉链状"结构、分层结构、局部热点、缺口、残留丝核等空间形态不均匀现象,并揭示了其产生原因包括氛围气体放电、径向非均匀汽化、热力学不稳定性、磁流体力学不稳定性.建立了基于自辐射图像的空间形态均匀性量化表征方法与判别准则.研究获得了气压与电流参数对阻性阶段及沉积能量特性的影响规律,并提出了空间形态不均匀性的抑制方法——增加气压与提高电流上升率,最终确定了可实现均匀电爆炸的参数选取方法.
Abstract
Electrically exploding wires(EEW)for nanoparticle preparation has advantages of being low cost,high effi-ciency,providing high purity,and allowing for controllable size distribution.However,spatial homogeneities in the EEW diffusion stage is a critical influence factor of the quality of nanoparticles.In this paper,an experimental system was de-signed and constructed to investigate EEW,and the ultrafast optical diagnoses,including laser imaging,multi-frame photography,and emission spectrum analysis,could be realized.Various spatial inhomogeneities,including coronal plas-ma,spindle structures,zipper-like structures,stratification structures,local hot spots,gaps,and residual cores,were observed.The causes of these inhomogeneities were summarized as follows:atmospheric discharge,radial inhomogene-ous vaporization,thermal instability,and magnetohydrodynamic instability.A quantification method and the criteria of spatial homogeneity were established based on photographs.The effects of ambient pressure and current parameter on re-sistive stage and energy deposition were obtained.Moreover,the suppression methods of spatial inhomogeneities were proposed,including increasing ambient pressure and current rise rate.Ultimately,the parameter selection method for ho-mogeneous EEW was determined.
维普
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