低銀鉛合金電極制備與性能研究
發(fā)布時間：2018-08-31 17:11
【摘要】：陽極材料的選用一直是濕法冶金過程的核心,其性質(zhì)對于電沉積金屬的品質(zhì)和生產(chǎn)能耗都有很大影響。鉛合金陽極材料因具有良好的耐蝕、催化活性、易加工及可回收利用等特點,一直是電化學(xué)工業(yè)的首選。因電解過程能耗巨大,而其陽極過電位的無功電耗可達(dá)1/3,因此鉛合金陽極性能的改進可帶來顯著的節(jié)能效果并產(chǎn)生良好的經(jīng)濟效益。銀對鉛合金電極的催化性、耐蝕性、陽極壓降等性能有助益但是成本高昂。一般工業(yè)常用鉛銀陽極的銀含量約0.7-1%,約占電極成本的70%。相當(dāng)多的研究都是嘗試添加多種元素來減少銀含量并保持或提高其性能,而對于鉛合金微觀組織結(jié)構(gòu)對其電化學(xué)、力學(xué)性能的研究較少。本文選擇含銀0.5%的低銀鉛合金為研究對象,綜合運用超聲波干預(yù)凝固、等徑通道轉(zhuǎn)角擠壓、室溫軋制、低溫冷軋及退火工藝這五種方法,成功獲得了多種平均晶粒尺寸的樣品；研究了樣品的平均晶粒尺寸和組織分布,測試了其電阻率、極化曲線、槽電壓、Tafel曲線、η-lgi圖和顯微硬度,探討了工藝參數(shù)對其微觀組織及性能的影響。測試與分析結(jié)果表明,采用超聲波干預(yù)凝固+軋制方法獲得了最佳電極綜合性能。其優(yōu)化工藝參數(shù)為：熔體溫度643 K(370℃)、超聲處理時間1 min、以及壓下量20%的軋制工藝,在413 K(140℃)溫度下退火1h。經(jīng)此工藝處理的Pb-Ag合金電極,與鑄造工藝相比導(dǎo)電性能、電化學(xué)性能和力學(xué)性能均得以顯著提升。其中電導(dǎo)率提高44.86%,陽極極化過電位降低18.13%,槽電壓降低4.82%,顯微硬度提升2.23倍。Tafel曲線和η-lgi分析表明,采用該工藝?yán)讷@得較低的自腐蝕電流和析氧過電位,能提高陽極的耐腐蝕性及電導(dǎo)率,具備較佳的電化學(xué)性能。同時致密的微觀結(jié)構(gòu)使陽極表面的腐蝕形態(tài)有明顯改變,由原來呈較集中的局部晶間腐蝕變?yōu)榫鶆蚋g,這使得陽極使用壽命有較多的提升。金相顯微觀察表明,隨合金平均晶粒尺寸的減小,合金的強度及電化學(xué)綜合性能逐漸升高然后降低,其間存在晶粒尺寸10μm左右的最優(yōu)值。1)當(dāng)Pb合金陽極材料的平均晶粒尺寸進一步細(xì)化時,陽極材料的耐腐蝕性能變?nèi)?電導(dǎo)率降低,原因是晶界密度及晶粒內(nèi)部缺陷密度高,晶界面積大且界面能高,且內(nèi)應(yīng)力較強,其微觀組織的熱力學(xué)活性較高。(2)陽極材料的平均晶粒尺寸過大時,其耐腐蝕性能不強且電導(dǎo)率也不高,原因在于成分的非均勻分布。在與電解質(zhì)相接觸的電極表面的晶粒與晶界上,易誘生較大的電偶極勢壘并構(gòu)成超微電化學(xué)池,因此降低耐腐蝕性；同時,雖然此時銀組元更可能分布于晶粒內(nèi)部并以共晶組織的形式存在,晶界處的銀較少,但因銀含量低,晶界電子散射效應(yīng)依然較強,故降低導(dǎo)電性。(3)對具有適中的平均晶粒尺寸的陽極材料而言,因電導(dǎo)率遠(yuǎn)高于Pb的Ag組元可能以單質(zhì)的形式分布在晶界上,減弱晶界電子散射效應(yīng),從而提高了陽極電導(dǎo)率。由于晶粒尺寸適中(約10μm)且分布均勻致密,不易誘生局部的深入和快速腐蝕,因而陽極耐腐蝕性得以增強,合金陽極材料具有良好的綜合性能。此外,晶粒大小適中時,內(nèi)應(yīng)力減小,結(jié)構(gòu)的熱穩(wěn)定性較好,使其可在略高于再結(jié)晶溫度的溫度下穩(wěn)定服役。采用超聲波凝固技術(shù),并結(jié)合大塑性變形、軋制及退火等加工方法,成功制備了0.5wt.%Ag的低銀含量鉛銀合金電極,有效改善結(jié)構(gòu)缺陷,提升了力學(xué)性能、催化活性及耐腐蝕性,使合金陽極綜合性能提高。研究所獲的處理方法簡便而設(shè)備和工藝成本低,不僅對于電解領(lǐng)域節(jié)能降耗深具意義,還有利于電極材料的循環(huán)再利用,并能產(chǎn)生顯著經(jīng)濟效益。進行了鉛系難混溶合金固液界面能計算模型的研究,改進了可用于鉛銀二元合金固-液界面能熱力學(xué)計算的Warren模型。建立的新模型可以對Pb-Ag、Pb-Cu、 Pb-Al及其他難混溶二元合金體系的固液界面能進行更為簡捷和準(zhǔn)確的估算,且計入了Warren模型未考慮到的溫度對其摩爾體積的影響。
[Abstract]:The selection of anode materials has always been the core of hydrometallurgical process, and their properties have a great influence on the quality of electrodeposited metal and energy consumption. Lead alloy anode materials have been the first choice of electrochemical industry because of their good corrosion resistance, catalytic activity, easy processing and recyclability. The reactive power consumption of electrode overpotential can reach 1/3, so the improvement of lead alloy anode performance can bring remarkable energy-saving effect and produce good economic benefits. The catalytic performance, corrosion resistance and anode voltage drop of silver on lead alloy electrode are helpful but costly. The silver content of lead-silver anode commonly used in industry is about 0.7-1%, which accounts for the cost of electrode. A considerable number of studies have attempted to add a variety of elements to reduce the silver content and maintain or improve its properties, while less has been done on the electrochemical and mechanical properties of lead alloys. A variety of samples with average grain size were successfully obtained by the five methods of warm rolling, cold rolling and annealing. The average grain size and microstructure distribution of the samples were studied, and their resistivity, polarization curve, cell voltage, Tafel curve, _-lgi diagram and microhardness were measured. The results of test and analysis show that the optimum comprehensive properties of the electrode are obtained by ultrasonic solidification and rolling. The optimum processing parameters are melt temperature 643 K (370 C), ultrasonic treatment time 1 min, and rolling process with 20% reduction, annealed at 413 K (140 C) for 1 h. Compared with the conductivity, the electrochemical and mechanical properties were improved significantly. The conductivity increased by 44.86%, the anodic polarization overpotential decreased by 18.13%, the cell voltage decreased by 4.82%, and the microhardness increased by 2.23 times. At the same time, the dense microstructure makes the corrosion morphology of the anode surface change obviously from concentrated local intergranular corrosion to uniform corrosion, which makes the service life of the anode increase a lot. The metallographic observation shows that with the decrease of the average grain size of the alloy. When the average grain size of Pb alloy is further refined, the corrosion resistance of the anode material becomes weaker and the conductivity decreases. The reason is that the grain boundary density and the defect density inside the grain are high, and the grain boundary area is low. (2) When the average grain size of anode material is too large, its corrosion resistance is not strong and its conductivity is not high, which is due to the non-uniform distribution of the composition. At the same time, although the silver component is more likely to be distributed in the grain interior and exist in the form of eutectic structure, there is less silver at the grain boundary, but because the silver content is low, the electron scattering effect at the grain boundary is still strong, so the conductivity is reduced. (3) For anodes with moderate average grain size. As far as the conductivity is concerned, the Ag component, which is much higher than Pb, may distribute on the grain boundary in the form of elementary substance, thus weakening the electron scattering effect at the grain boundary and thus improving the anodic conductivity. In addition, when the grain size is moderate, the internal stress decreases and the thermal stability of the structure is good, so that it can be used stably at a temperature slightly higher than the recrystallization temperature. The alloy electrode can effectively improve the structural defects, enhance the mechanical properties, catalytic activity and corrosion resistance, and improve the comprehensive performance of the alloy anode. Benefits. The calculation model of solid-liquid interface energy of lead-based hard-to-miscible alloys is studied. The Warren model which can be used to calculate the solid-liquid interface energy of lead-silver binary alloys is improved. The new model can be used to estimate the solid-liquid interface energy of Pb-Ag, Pb-Cu, Pb-Al and other hard-to-miscible binary alloys more simply and accurately. The influence of temperature on the molar volume of Warren model is not considered.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TF351;TG146.12
本文編號：2215632
[Abstract]:The selection of anode materials has always been the core of hydrometallurgical process, and their properties have a great influence on the quality of electrodeposited metal and energy consumption. Lead alloy anode materials have been the first choice of electrochemical industry because of their good corrosion resistance, catalytic activity, easy processing and recyclability. The reactive power consumption of electrode overpotential can reach 1/3, so the improvement of lead alloy anode performance can bring remarkable energy-saving effect and produce good economic benefits. The catalytic performance, corrosion resistance and anode voltage drop of silver on lead alloy electrode are helpful but costly. The silver content of lead-silver anode commonly used in industry is about 0.7-1%, which accounts for the cost of electrode. A considerable number of studies have attempted to add a variety of elements to reduce the silver content and maintain or improve its properties, while less has been done on the electrochemical and mechanical properties of lead alloys. A variety of samples with average grain size were successfully obtained by the five methods of warm rolling, cold rolling and annealing. The average grain size and microstructure distribution of the samples were studied, and their resistivity, polarization curve, cell voltage, Tafel curve, _-lgi diagram and microhardness were measured. The results of test and analysis show that the optimum comprehensive properties of the electrode are obtained by ultrasonic solidification and rolling. The optimum processing parameters are melt temperature 643 K (370 C), ultrasonic treatment time 1 min, and rolling process with 20% reduction, annealed at 413 K (140 C) for 1 h. Compared with the conductivity, the electrochemical and mechanical properties were improved significantly. The conductivity increased by 44.86%, the anodic polarization overpotential decreased by 18.13%, the cell voltage decreased by 4.82%, and the microhardness increased by 2.23 times. At the same time, the dense microstructure makes the corrosion morphology of the anode surface change obviously from concentrated local intergranular corrosion to uniform corrosion, which makes the service life of the anode increase a lot. The metallographic observation shows that with the decrease of the average grain size of the alloy. When the average grain size of Pb alloy is further refined, the corrosion resistance of the anode material becomes weaker and the conductivity decreases. The reason is that the grain boundary density and the defect density inside the grain are high, and the grain boundary area is low. (2) When the average grain size of anode material is too large, its corrosion resistance is not strong and its conductivity is not high, which is due to the non-uniform distribution of the composition. At the same time, although the silver component is more likely to be distributed in the grain interior and exist in the form of eutectic structure, there is less silver at the grain boundary, but because the silver content is low, the electron scattering effect at the grain boundary is still strong, so the conductivity is reduced. (3) For anodes with moderate average grain size. As far as the conductivity is concerned, the Ag component, which is much higher than Pb, may distribute on the grain boundary in the form of elementary substance, thus weakening the electron scattering effect at the grain boundary and thus improving the anodic conductivity. In addition, when the grain size is moderate, the internal stress decreases and the thermal stability of the structure is good, so that it can be used stably at a temperature slightly higher than the recrystallization temperature. The alloy electrode can effectively improve the structural defects, enhance the mechanical properties, catalytic activity and corrosion resistance, and improve the comprehensive performance of the alloy anode. Benefits. The calculation model of solid-liquid interface energy of lead-based hard-to-miscible alloys is studied. The Warren model which can be used to calculate the solid-liquid interface energy of lead-silver binary alloys is improved. The new model can be used to estimate the solid-liquid interface energy of Pb-Ag, Pb-Cu, Pb-Al and other hard-to-miscible binary alloys more simply and accurately. The influence of temperature on the molar volume of Warren model is not considered.
【學(xué)位授予單位】：昆明理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TF351;TG146.12
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