Generation, properties, and order packing of monodispersed spherical colloid particles of yttrium hydroxycarbonate: A colloidal route to minimizing voids in ceramics
Monosized spherical colloid particles of yttrium hydroxy-carbonate were prepared by in situ decomposition of urea at elevated temperatures in yttrium nitrate solutions. The nucleation and growth phenomena generating these particles were studied through measurement of induction periods, particle sizes and growth rates in silica seeded and unseeded systems. It was found that precipitation took place only under neutral conditions. Two diffusion-controlled growth models and the diffusion chronomal analysis were applied to the data of growth rate. These analyses and the narrowing of particle size distribution with growth time confirmed the diffusion-controlled particle growth mechanism. Electron diffraction analysis showed the particles to be crystalline. The surface charge on the particles was characterized by electrophoretic studies. The chemical composition of the powders was determined by thermal, x-ray photoelectron spectroscopic, and chemical analyses to be Y(OH)CO{sub 3}{center dot}H{sub 2}O. The stability of aqueous suspensions of particles with a radius of 0.21 {mu} was studied as a function of pH (in the range of 7-12.3) using a turbidimetric method. Maximum flocculation appears around the isoelectric point. Ordered particles were prepared from suspensions with particle volume fractions of 0.2. Particle ordering was attributed the flocculation in the secondary minimum in some cases and to ordering of the Kirkwood-Alder character in others. Particles ordered in the secondary minimum were arranged in a close-packed structure of high coordination number. The IEP was exploited, in the former case to rapidly freeze the ordered structure into the primary minimum.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames, IA (USA)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6945482
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
CARBON COMPOUNDS
CARBONATES
CHEMICAL COMPOSITION
CHEMICAL PREPARATION
COLLOIDS
CRYSTAL STRUCTURE
DISPERSIONS
HYDROXY COMPOUNDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM CARBONATES
YTTRIUM COMPOUNDS