Gold Electroless from Sulfite-thiosulfate Bath

Jahanianfar, Hooman | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44865 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Dolati, Abolghasem
  7. Abstract:
  8. Gold coatings due to their unique properties, use in a wide range of applications.Decorative coatings of gold for centuries, has been considered.However, few studies have been done on the properties of this metal, this metal is shown not only in terms of decorating, but in the industry also has a wide range of applications. In this project non-cyanide electroless bath based on binary complex sulfite-thiosulfate was prepared and metal ion concentration of the complex components, temperature, time, pH and addition of amino acids, optimzed bystability, qualityand rate of coating. The main aim of optimizing bathsis optimize the thickness and appearance of the coating.It was found that by thickness and quality of the final coating, 2.5 gr/l gold as the optimal concentration of gold, ratio of 10/100 sodium sulfite to thiosulfate as the optimum ratio, pH=8 to optimumpH, temperature range of 75 to 90 °C, the optimum temperature and the optimal time was determined as 60 minutes.Besides the addition of the amino acids to the bath without a bath additive, will result in an increase in thickness of coatings. Also increases the concentration of combined amino acids, increased the thickness of coating.Maximum thickness coating of gold is on the Ni-P and then on the Ni-B substrate.On the gold substrate,rate of coating was very low. Scanning electron microscope images showed that the two types of grainswas produced:fine (approximately 20 nm) andcoarse (approximately 70 nm). With a gold coating on a nickel-phosphorus, the rate of corrosion current densitythree timesreduceddue tonickel coatings and 26 times lower than the corrosion current of uncoated copper substrate.X-ray diffraction experiment showed that the gold plates (111), (200) and (220) peak has grown and two bells peak at an angle of 38 ° and 45 ° indicate the presence of FCCgold nanoparticles. Finally, cyclic voltammetry curves and properties of the coatings were resultthat the electroless gold sulfite solution was not auto-catalyst and goldand nickel electroless on the surface of pure gold do not done in sulfite-thiosulfate bath
  9. Keywords:
  10. Amino Acid ; Gold Electroless ; Sulfite-Thiosulfate Complex ; Improving the Thickness ; Increasing Hardness

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