本研究探討熔融金屬噴霧在基板衝擊效應下之霧化特性。研究之參數包括基板之外徑(D=40mm～100mm)、內徑(d=40mm～70mm)、以及基板與噴嘴出口之距離(Z=150mm～250mm)對噴霧特性之影響。金屬粉末以INSITEC粒徑分析儀在流場中進行粒徑即時量測，熔融金屬噴霧流場之溫度以熱電耦量測。實驗所採用之金屬成分為錫鉛合金(錫63%，鉛37%)，其熔點為183℃。實驗結果顯示，在噴嘴下方配置基板可大幅降低金屬噴霧之平均粒徑(SMD)，從原本未加基板時之13.72m降低至6.60m。實驗結果亦發現SMD隨基板對噴霧遮蔽率之增加而遞減，且基板對噴霧中心之相對位置及遮蔽面積大小亦是影響之重要參數。當基板與噴嘴距離增加時，由於液態金屬冷卻凝固以及速度減緩之原因，使得基板衝擊效應較不顯著，故金屬粉末平均粒徑隨基板與噴嘴之距離增大，但仍比未加基板時之SMD小。結果亦顯示在未加基板時金屬噴霧體積百分比V0-15為34.97%，但在基板衝擊作用下V0-15則大幅提高，其值高達63.59%，顯示所產生者為超微細之金屬粉末。另外在未加基板時金屬噴霧體積百分比V15-25為36.58%，而在基板衝擊效應下V15-25最高值為40.15%。以熱電耦量測金屬噴霧流場之溫度，顯示噴霧流場溫度低於金屬熔點，此乃因為熱電耦量測到的溫度為熔融金屬噴霧與空氣之平均溫度，且熔融狀金屬噴霧在離開噴嘴後由於受空氣急速冷卻，易產生過冷之現象，成為一種外部呈現固態，核心為液態之金屬顆粒，撞擊至熱電耦表面會產生固液兩相重新混和之現象，故所量測金屬噴霧之溫度均低於金屬之熔點。由於在熱電耦表面觀察到金屬噴覆成型之現象，證明金屬顆粒在接觸至熱電耦時為尚未完全凝固之顆粒。由金屬噴霧之粒徑分佈圖，發現在基板衝擊效應下，不但使噴霧整體之顆粒變小，且粒徑分佈範圍更為狹窄集中，故基板衝擊效應能有效達成使金屬噴霧粒徑細微化與粒徑分佈窄化之目的。

　　This research investigates the characteristics of metallic spray with impingement on a substrate. The metallic spray was injected by a twin-fluid atomizer with mean particle size of 13.72m. The substrates were designed as the disk-type geometries with the inner and outer diameters ranging from 40mm to 70mm and 40mm to100mm, respectively. The distance from the outlet of the atomizer to the substrate varied at Z=150mm~250mm. The metal powders were then measured by an INSITEC Particle analyzer. The temperature of the metallic spray flow was measured by the thermocouples. The metal used in this research was Sn63%Pb37% alloy with melting point of 183℃. Results showed that the Sauter mean diameter (SMD) of the metallic spray decreased dramatically to 6.60m by placing the substrate in the down stream of the atomizer. Results also showed that the SMD decreased as the blockage ratio of the substrate to the spray flow was increased. The particle size was also controlled by the relative position of the substrate to the atomizer. It was found that the effects of the flow impingement to the substrate were decreased as the distance between the atomizer and substrate was increased because the mean temperature and the velocity of the metallic spray decreased in the down stream. However, the particle size of the metallic spray with substrate was smaller than the case without substrate. The volume percentage of the powder with size less than 15m (V0-15) increased from 34.97% in the case without substrate to 63.59% in the cases with substrate, indicating the production of the ultra-fine metal powder. The temperatures measured in the spray flow were lower than the melting point of the alloy, indicating that temperatures measured were the average temperatures of the molten particles and the air flow. Observation from the particle size distribution of the metallic spray showed that the metal powder was finer and more concentrated. Hence the impinging mechanism can be used to control the particle size and size distribution in the metal powder production.

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