Date of Award

Spring 2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemical Engineering - (Ph.D.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Robert Pfeffer

Second Advisor

Rajesh N. Dave

Third Advisor

Kamalesh K. Sirkar

Fourth Advisor

Henry Shaw

Fifth Advisor

Michael Chien-Yueh Huang

Abstract

Dry particle coating, which mechanically coats fine guest particles onto the surfaces of larger host particles, without binders or solvents, is investigated. Several systems of host and guest particles are coated in different devices to study various aspects of dry particle coating. The devices used are Magnetically Assisted Impaction Coating (MAIC) device, Mechanofusion, and the Hybridizer.

MAIC is used to coat fine SiO2 guest particles onto the surface of larger cornstarch and cellulose host particles. This is done to simultaneously improve the flowability of the host particles, as well as reduce their hydrophilicity. Dry particle coating is used to increase the sintering temperatures of particulate materials (host), by application of a monolayer of a highly refractory material (guest), promoting deactivated sintering. This phenomenon has not previously been reported, although activated sintering (decreasing the sintering temperatures of metallic and ceramic particles) is well established in the literature. The products analyzed in the deactivated sintering studies are coated in MAIC, Mechanofusion and the Hybridizer.

The key parameters affecting the coating performance of the dry coating devices are examined. The key parameters of MAIC are magnetic particle size, magnetic particle to powder mass ratio, frequency, current and processing time. The effects of the rotation and translation motion of the magnetic particles are also investigated. In Mechanofusion and the Hybridizer, the key parameters examined are rotation speed and processing time.

The coating performance of the three devices is compared by examining contamination and adhesion of the coated products. Quantification of the contaminants on the products is achieved by measuring the amount of iron, nickel, and chromium in the sample. Adhesion of the guest to the host particles is conducted by subjecting the products to ultrasonic vibrations, to examine the amount of material that becomes detached from the surface.

Based on this work, dry particle coating is shown to be viable for the production of composites with new/improved functionalities. The coating performance of the devices as a function of their key parameters is successfully investigated. Also, the first comparative look of dry particle coating devices, in the areas of product contamination and guest-host particle adhesion is presented.

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