| With the rapid development of modern electronic science and technology,the renewal of electronic products is accelerating,and the consumption of silver is increasing rapidly.At the same time,a large number of silver-containing electronic waste and electronic waste are produced.At present,the silver obtained from mining can not fully meet the needs of the market.Therefore,the innocuous recovery and recycling of silver from electronic waste becomes particularly important.Tincontaining silver anode slime is an intermediate product in the process of silver and other valuable metals recovering from electronic waste and electronic waste.Its treatment process is the most important link in the whole recovery process.At present,there still are a series of problems in the treatment process of tin-containing silver anode slime,such as low recovery rate,serious pollution and long process flow etc..Therefore,it is necessary to explore a new treatment process of tin-containing silver anode slime with high recovery,green and short process.Silver has good conductivity,high thermal conductivity and reflectivity,and thus be widely used in the preparation of silver-based alloy targets.In addition,the properties of silver-based alloy target directly affect the properties of the films.In recent years,considerable progress has been made in target preparation technology in China.However,several problems of silver-based alloy targets still existed,such as poor corrosion resistance,low density and uneven grain size,which seriously restrict the market application of silver-based alloy targets.Therefore,it is also of great significance to study the effects of preparation technology,element microalloying and subsequent processing technology on the microstructures and properties of silver-based alloy target.Aiming at the problems existing in the original recovering treatment process,this study first investigated the treatment process of tin-silver anode slime in the process of electronic waste recovery.A new acid-alkali combined leaching process was developed to recover silver from the anode slime using tin-silver anode slime as raw material.Thereafter,high-value application of recovered silver was investigated,i.e.,the preparation of silver-based alloy targets.The effects of different permanent magnet stirring rates,different alloy elements,different addition amounts and follow-up heat treatment processing technology on the microstructures and properties of silver-based alloy target were studied,under the conditions of magnetic stirring,hot-top protection and directional forced condensation.The main conclusions of this study are as follows:Firstly,the silver was recovered from the tin-contained silver-copper anode slime by two-stage leaching process-alkali leaching followed by acid leaching.The grade of silver after alkali leaching was 96.58%,and the effect of alkali leaching was ideal.After secondary acid leaching,the grade of silver was further improved,with the highest grade of silver reaching 98.84%.Then the crude silver was purified,and the purity of silver was 99.9%.For the subsequent harmless treatment process of leaching waste liquor,CO2 was injected into the alkali leaching solution to recover valuable metal Sn,and slurried CaO was injected into the solution after Sn recovery.The alkali leaching solution is causticized and then recycled to leach anode mud;H2S gas was injected into the acid leaching solution and the pH value was adjusted to remove and recovery heavy metal ions in the form of MeS from the solution.After neutralization,it achieved the purpose of harmless treatment and discharge.This process realized the short process,scientific,green and economic recovery of silver,which has important guiding significance for practical production.Secondly,the effects of different permanent magnet stirring rates on the microstructures and properties of Ag-1.5Cu-1.0Y alloy were investigated,and the optimal permanent magnet stirring rate was obtained.Methods of XRD,SEM-EDS,EPMA,hardness test,vulcanization resistance test and conductivity test were used.The results showed that permanent magnet stirring refined dendrite microstructures,shortened primary dendrite,reducde secondary dendrite arm spacing to 25.12 micron,and distributed the alloy elements more evenly.Permanent magnet stirring improved the density to 10.32 g/cm3 and microhardness to 69.82 HV of the Ag-1.5Cu-1.0 Y alloy.It also improved the processing performance;corrosion resistance of the Ag-1.5Cu1.0Y alloy.However,permanent magnet stirring reduced the electrical conductivity of the Ag-1.5Cu-1.0Y alloy.Considering comprehensively,the Ag-1.5Cu-1.0Y alloy has better properties when the permanent magnet stirring rate is 900 r/min.Then,on the basis of optimum permanent magnet stirring rate,in order to obtain the optimum additions of different elements,the effects of different additions of rare earth element Y,precious metal element Au and element Ge on the micro-structures and properties of silver-based alloys were investigated.The results showed that the addition of rare earth element Y obviously refined the grain size and Y was concentrated on the grain boundary.With the increase of Y content,the microhardness and electrical resistivity of the Ag-1.5Cu alloy increased.The corrosion resistance firstly increased and then decreased with the increased addition of Y content.The optimum addition of Y was 0.1 wt%.Au refined the dendrites of Ag-1.5Cu-0.1Y alloy.With the increase of Au content,the microhardness of the Ag-1.5Cu-0.1Y alloy increased,and the electrical resistivity of the alloy does not change too much.Au improved the corrosion resistance of the Ag-1.5Cu-0.1Y alloy,and the optimum addition of Au is 1.0wt%.It was also proved that Ge further refined the dendrites of Ag-1.5Cu-0.Y-1.0Au alloy.Ge could form Cu3Ge eutectic enriching at grain boundaries.With the increase of Ge content,the microhardness and electrical resistivity of the Ag-1.5Cu-0.1 Y-1.0Au alloy increased,and the corrosion resistance demonstrating that increased firstly and then decreased.The optimum addition of Ge was 1.0wt%.Based on the above experimental results,Ag-1.5Cu-0.1Y-1.0Au-1.0Ge(wt%)is the best proportioning.The samples of Ag1.5Cu-0.1Y-1.0Au-1.0Ge(wt%)have uniform microstructures,high microhardness,low electrical resistivity and good corrosion resistance.Finally,the effects of annealing process of silver-based alloys were investigated.The results showed that the annealing treatment refined the grain size of Ag-1.5Cu-0.1 Y alloy,improved the homogeneity of element Y in the alloy matrix,the processing performance,electrical conductivity and corrosion resistance.The comprehensive properties of Ag-1.5Cu-0.1Y alloy were better when the annealing temperature is 700?and the annealing time is 4 h.Ag-1.5Cu-0.1Y-1.0Au alloy had fine and uniform grains after annealing treatment,whereas too long annealing period would lead to secondary recrystallization.The annealing treatment uniformed the distribution of element Au and Y in the Ag-1.5Cu-0.1 Y-1.0Au alloy matrix better.The annealing treatment also improved the processing performance,electrical conductivity and corrosion resistance of the Ag-1.5Cu-0.1Y-1.0Au alloy.When annealing temperature was 700? and duration time was 2 h,the Ag-1.5Cu-0.1Y-1.0Au alloy had better comprehensive properties.The Ag-1.5Cu-0.Y-1.0Au-1.0Ge alloy had fine and uniform grains after annealing treatment,which could improve the electrical conductivity of the alloy.The corrosion resistance of the Ag-1.5Cu-0.1 Y-1.0Ge alloy was good after annealing treatment.The comprehensive properties of Ag-1.5Cu-0.1Y-1.0Ge alloy were better when annealing temperature is 700? and time is 2 h. |
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