Accession Number:

ADA175277

Title:

Particle Formation and Deposition from Supercritical Solutions.

Descriptive Note:

Final rept. Jun 83-Dec 86,

Corporate Author:

CRITICAL FLUID SYSTEMS INC CAMBRIDGE MA

Personal Author(s):

Report Date:

1986-12-12

Pagination or Media Count:

76.0

Abstract:

High purity, submicron silica particles were synthesized in a supercritical solvent dissolution precipitation process. Supercritical water was passed continuously over crystalline silica in a dissolution vessel to form a solution whose concentration was determined by the conditions of dissolution. When the solution exited the dissolution vessel, pressure was rapidly reduced causing the nucleation and growth of amorphous particles to relieve supersaturation. Temperature, pressure, solution pH, and flow rate were varied to examine the effects of process parameters on the particle size distribution. Particles were formed over a very broad range from 10 nanometers to 10.0 micrometers. Increasing the solution pH from 9.0 to 11.2 was found to significantly increase the volume fraction of large particles. Increasing temperature and pressure in the range examined directly effected an increase in solute concentration and indirectly an increase in the percentage of small particles. Keywords Supercritical Silica Dissolution Precipitation Fine Particle Formation.

Subject Categories:

  • Industrial Chemistry and Chemical Processing
  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE