Preparation,Characterization Of Aurous-Ethylene Thiourea None-cyanide Gold Complexes And Study On Its Gold-plated Performance

In recent years,we have pay great attentions to the research and development of non-cyanide gold plating with attaching more importance to the environmental protection.The research of this thesis is to synthesize the non-cyanide gold complexes which is a new type water-soluble one,then make a research on the related chemical characterization and the stability of the complexes,finally make an gold plating application research to the complexes liquor,which is expected to achieve better effect of gold plating.The research include several parts and shown as follow:?1?Making the selection for ligand and the method for the synthesis of the water soluble non-cyanide gold complexes.?2?Making a research on the process conditions for the preparation of gold nanoparticles by hydrazine-hydrate method and the purification and characterization of nano-gold sol.?3?Making a research on the effect of the feed ratio,temperature,pH,and the reaction time to the synthesis of the gold complexes by single factor test and orthogonal test,and obtain the optimum process parameters;then making the characterization for the synthesized gold complexes and the research on the stability of the gold complexes solution.?4?Making a research on the gold plating application of the gold complexes solution,and investigating the main factors such as the concentration of gold salts,temperature,pH,current density,plating time,and the dosage of brightener et al,which effect on the gold plating rate and the score of appearance,and then obtain the optimum process parameters.Results:?1?Using the gold nanoparticles as the resource,the ethylene thiourea as ligand,and the ammonium persulfate as oxidant,then synthesize the complexes Au?I?-ETU with the oxidation leaching method.?2?The optimum process conditions for the preparation of nano gold sol by hydrazine-hydrate method is as follow:the molar ratio of hydrazine hydrate and Au 10:1,the quality ratio of PVP and Au 1.5:1,the reaction temperature 85?,pH=12,heating time 30 min;the influence of main factors in order of decreasing size:the amount of hydrazine-hydrate,the amount of polyvinylpyrrolidone,temperature,the pH of solution,the heating time;UV-Vis spectroscopy and transmission electron microscopy were used to characterize the prepared nano gold sol,we found that the gold nanoparticles were spherical,the average size within 20-30nm.?3?After using some analysis and detection methods including elemental analysis,thermogravimetric analysis,UV-vis spectroscopy,infrared spectroscopy,cyclic voltammetry curve analysis to characterize the complex synthesized in experiments,it can be inferred that the synthesized complexes is a kind of ionic compounds which is in good water solubility,the molecular formula is[Au?ETU?3]2SO4,the molar conductivity is 0.86 S·m2·mol-1.?4?The optimum process parameters for the synthesis of Au?I?-ETU complexes is as follows:MAu:METU:M?NH4?2S2O9=1:4:4,the reaction temperature 30?,the reaction time 25min,pH=1;and the influence of the main factors in order of decreasing size:the ratio of raw materials,the reaction temperature,the reaction time,the pH of solution.?5?Through stability experiments found that the Au?I?-ETU complexes solution is more stable,can be preserved for 15 days under the room temperature sealed from light.The use of temperature is less than or equal to 60? and the pH is less than or equal to 6.?6?The optimum process parameters for the gold plated application of Au?I?-ETU complexes is as follows:the gold concentration 1.5g/L,the current density 1A/dm2,the pH value 1.5,the plating time 1.5min,the plating temperature 45?,the brightener cerium sulfate is 10ppm;the influence of main factors in order of decreasing size is:the gold concentration,the current density,the pH of solution,the plating time,the plating tempareture.Research shows that the non-cyanide gold plating system based on[Au?ETU?₃]₂SO₄ is a kind of environmental and friendly products with growth prospects,the gold plated layer will have good color and excellent adhesion,which can reach the requirements of printed circuit board industry on the gold plating performance.As for environmental protection,it can realize the replacement of cyanide gold plating,reduce the environmental pollutions.