PVP Protective Mechanism of Ultrafine Silver Powder Synthesized by Chemical Reduction Processes
✍ Scribed by Zongtao Zhang; Bin Zhao; Liming Hu
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 256 KB
- Volume
- 121
- Category
- Article
- ISSN
- 0022-4596
No coin nor oath required. For personal study only.
✦ Synopsis
soluble silver salts was reacted with an appropriate reduc-Polyvinyl pyrrolidone (PVP) as a protective agent plays a ing agent of both nonorganic and organic materials. Howdecisive part in controlling superfine silver particle size and ever, the conventional processes usually produce powders size distribution by reducing silver nitrate with hydrazine hywith large size (sometimes more than 2 Ȑm), and irregular drate. The particle size and particle aggregation decrease with shape and aggregation. This kind of powder was difficult the PVP/AgNO 3 mole ratio. Mechanisms of PVP protection to use in thick-film and multilayer ceramic capacitors (1).
were divided into three stages. First, PVP donates loan pair
Fortunately, a newly developed chemical method, electrons of oxygen and nitrogen atoms to s p orbitals of silver known as the polymer protected reduction process, has ions, and thus the coordinative complex of Ag ions and PVP been used to prepare monodispersed silver powder with forms in aqueous solution. Second, PVP promotes the nuclesubmicrometer size and quasi-spherical shape (2-4). G.
ation of the metallic silver because the Ag ions-PVP complex
Tosun and H. D. Glichsman ( 2) have reported a gelatinis more easily reduced by hydrazine than the pure Ag ions protected processing, in which silver nitrate was reduced by owing to Ag ions receiving more electronic clouds from PVP than from H 2 O. Third, PVP prohibits silver particle aggregation alkylacid phosphate in aqueous solution and finely divided and grain growth as a result of its steric effect. All of the silver particles with narrow particle size distribution and hypotheses were supported by ultraviolet spectra, infrared specwith a mean particle size of about 0.1-1.0 Ȑm. They also tra, and heterogeneous nucleation and grain growth by addition found that the gelatin played a key role in regulating the of silver nuclei.