火花源原子发射光谱分析中存在优先放电现象，其形成机理还缺乏系统、全面的解释。经查阅相关资料得知优先放电与分析样品中组分的功函数以及表面粗糙度有关，通过设计一组实验对这些影响因素加以证实：制备两种功函数金属接触样品、光滑表面带凸起样品以及轧制状态和浇铸状态样品，观察这些样品的火花放电斑痕形貌特征及分布。实验证明低值功函数物相和试样表面凸起均可引起优先放电，低功函数的夹杂物所形成的尖端凸起较相同几何尺寸的钢基凸起更容易放电。根据实验结果并结合物理理论分析，提出了优先放电现象的初步解释与判据。另外实验还观察到若干火花放电中的特殊现象：一次火花脉冲过程中存在2个时间顺序的放电，表明一次放电可能会产生多个有时间先后的“单火花”；以及放电坑周围存在夹杂物蒸发或碎片残留的现象。
The preferential discharge phenomenon existed in spark discharge atomic emission spectrometry . However ,the formation mechanism has been not systemically and comprehensively discussed .The related researches revealed that the preferential discharge was related to the work function of components and sur‐face roughness of samples .A group of experiments were designed to verify these influencing factors :two metal contact samples with different work functions ,the samples with smooth surface with protrusions as well as rolling samples and casting samples were prepared .The morphology features and distribution of spark discharge spots in these samples were observed .The experiments proved that the preferential dis‐charge occurred in phases with low work function and samples with surface protrusions .The tip protru‐sions formed by inclusions with low work function could easily cause protrusions discharge compared to the steel‐based protrusions with same dimension .According to the experimental results and physical theory , the preliminary interpretation and judgment criterion for preferential discharge phenomenon were pro‐posed .Moreover ,some special phenomena in spark discharge were also observed in experiments :the dis‐charge with two time sequences existed in one spark pulse process ,indicating that one discharge may cause several “single sparks” with time sequence .In addition ,the inclusion evaporation or fragment residue was also observed around the discharge pits .
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