Preparation of highly dispersed ultrafine silver powders using methylcellulose as dispersant

Ultrafine silver powders were prepared from silver nitrate by chemical reduction method with ascorbic acid as reducing agent,methylcellulose as dispersant.The effects of the pH value,temperature,dispersant dosage on the dispersibility,mean particle size and morphology of the ultrafine silver powders were studied.The results show that the reaction temperature has a great effect on the morphology of the ultrafine silver powders.Spherical-like silver powders can be prepared when the temperature is 25 ℃ and 30 ℃,dendritic silver powders can be prepared when the temperature is 40 ℃,50 ℃ and 60 ℃,respectively.The dosage of dispersant has a great effect on dispersibility of ultrafine silver powders.Silver powder has better dispersibility with increasing dosage of dispersant.The pH value has a great effect on the particle size of silver powder,and the size of silver powder decreases with increasing the dosages of dispersant pH value.When pH value is 2 and 10,the particle size of silver powder is 2.26 and 0.053 μm,respectively.Ultrafine silver powders with better dispersibility and mean particle size of 2.21 μm can be obtained in the condition of the reaction temperature of 25 ℃,pH value of 2,the mass ratio of dispersant and ascorbic acid of 0.02.