MSE 122 – Ceramic Processing

Course Number: MSE 122
Course Units: 3
 
INSTRUCTOR: Professor Andreas M. Glaeser
 

CATALOG DESCRIPTION:

Powder fabrication by grinding and chemical methods, rheological behavior of powder-fluid suspensions, forming methods,drying, sintering and grain growth.
Relation of processing steps to microstructure development.

COURSE PREREQUISITES:

E45 required, MSE 103 or equivalent recommended.

PREREQUISITE KNOWLEDGE AND/OR SKILLS TEXTBOOK(S) AND/OR OTHER REQUIRED MATERIAL:

Prior exposure to basic concepts of chemical thermodynamics, crystal structure, diffusion, and phase transformations (particularly nucleation theory) are helpful. Courses such as E45, E115, MSE 102 and MSE 103 or equivalent provide useful background. However, students without this background have successfully completed the course.

Required text: None

Supplementary texts: Books that provide background on selected subtopics relevant to the course are on reserve and available at the Engineering Library.

Readers: A series of three readers is available in the Engineering Library. These readers contain a compilation of articles from the technical literature and other relevant reference material that highlight and reinforce the material presented in lecture.

COURSE OBJECTIVES:

Many structural and functional ceramic materials are fabricated from powders with a particle size below 1 µm in size, and increasingly from powders less than 100 nm is size. The overall goals of the course are to: 1) develop an understanding of the processes used to prepare such fine powders by mechanical means or by way of chemical synthesis, 2) expose the student to the key challenges and approaches used to pack powders and to form compacts, and the difficulties of and strategies for handling submicron powders, and 3) to formulate and discuss a variety of approaches to converting fine particulates into useful controlled-density, controlled-microstructure ceramic components. In summary, the key unit processes involved in the fabrication of engineering ceramics from powders are presented. The course is also relevant to those with interest in powder processing of metals.

DESIRED COURSE OUTCOMES:

The course seeks to provide the student with a comprehensive introduction to the steps and processes that are involved in processing an engineering material from a powder. The course should provide the student with a basic understanding of the materials selection and processing condition decisions that impact the final microstructure and properties of a powder processed material.

Specific outcomes of the course are:

  • Understanding of the methods that are available to produce fine particle size powders, and the economics of particle size reduction by mechanical means, and the potential hazards associated with chemically synthesized powders.
  • An exposure to alternative methods of generating ceramic bodies such as CVD and CVI and the limitations and environmental issues associated with these methods.
  • An understanding of the role of particle size and particle size distribution in developing well-packed high-density compacts through forming operations. Extension of these considerations to nonspherical powders, and mixtures of powders of differing size and/or shape as in composite fabrication.
  • Familiarity with the wide range of processing methods used to form objects from powders. Introduction to both wet- and dry-forming methods, and an appreciation of the important role of additives in achieving reproducible and desirable particle arrangements in compacts.
  • A basic understanding of the importance of drying and additive removal as a precursor to firing of ceramics. Factors controlling cracking and warping and strategies for effectively dealing with post-forming additive removal.
  • A deeper understanding of the role of the driving force for microstructural evolution and shrinkage during sintering, and the role of the relative rates of densification and coarsening on the overall microstructure that develops.
  • An appreciation of how the thermal cycle, powder particle size, atmosphere, pressure, and additives can affect the densification-coarsening competition, and can be used to drive microstructural evolution along desired paths.
  • An ability to relate microstructural characteristics of fired ceramics to certain aspects of processing and materials selection, and to troubleshoot failures to produce products with desired microstructural characteristics.

 

TOPICS COVERED:

The course divides into four subsections that deal with 1) the fabrication of fine powders, 2) the packing and handling of fine powders and their forming into compacts of desired shape, 3) the drying of “wet-formed” compacts and the removal of forming aids from “dry-formed” compacts, and 4) the microstructural transformation of the powder compact into either a dense ceramic for use in structural, biomedical, or microelectronic applications, or a porous material for use in filtering, sensing or other applications. A listing of the topics covered follows.

  • Powder fabrication: Overview of the ceramics industry in the US and Japan; structural and electronic applications; recent and emerging markets; forming and fabrication options: liquid-solid, vapor phase, etc.; powder processing in terms of interconnected unit processes: powder fabrication, packing and forming, sintering; thermodynamics of microstructural change; thermodynamic and kinetic aspects of sintering: the importance of particle size; thermodynamics of fine particles; kinetics of sintering: the Herring scaling laws; sources and fabrication of fine powders: grinding/comminution as a fracture process; empirical grinding laws, and physical basis: Kick’s law; observations on fine grinding; factors affecting grinding efficiency: flocculation vs dispersion; physical and chemical considerations in grinding: case studies; alternative approaches to fine powder fabrication; liquid-based size reduction methods: atomization methods; powder synthesis by building up processes; homogeneous and heterogeneous nucleation kinetics: review; powder fabrication via nucleation and growth; general considerations: interplay between nucleation and growth, competition from heterogeneous nucleation, the La Mer diagram, desirable powder characteristics; powder synthesis via vapor phase reactions: case studies; powder synthesis via vapor phase reactions: case studies – TiO2; laser driven gas reactions; vapor phase processing of ceramics: CVD, CVI; environmental issues; powder synthesis via liquid phase reactions: case studies – Al2O3, summary and comparison; solvent removal methods: spray drying, spray roasting, supercritical drying; a powder synthesis checklist; economic considerations.
  • Packing and forming: Packing and firing shrinkage; strategies for controlling shrinkage; ideal packing vs packing in real systems: McGeary experiments, multimodal packing; packing of continuous size distribution powders: lognormal distributions; packing of spheres and fibers: model experiments (Milewski) and practice; fabrication of fibers: SiC from rice husks, polymer precursors, VLS methods, laser pedestal growth, CVR methods; properties of fibers as f(processing methods); fiber reinforced composites: fiber specific issues limiting widespread use; mixing processes: assessment of chemical uniformity; scale and intensity of mixedness: effect of particle size, factors promoting nonuniformity; innovative processing methods: heterocoagulation; Forming methods; rheological behavior and relevance to processing, flow behavior of simple fluids; models of behavior for dilute suspensions: the Einstein model; complications and observations: effects of solvation and particle asymmetry, physisorption vs chemisorption, surfactants; models of behavior for more concentrated suspensions: the Guth and Simha model; introduction to colloid chemistry: surface charge, the double layer, repulsion-attraction, the isoelectric point, zeta potential, Stern layer and Stern potential, volume fraction and particle size effects; applications and observations: electrophoretic separation, case studies of electrostatic stabilization of suspensions; electrostatic vs steric stabilization of suspensions; non-Newtonian flow behavior: Bingham flow, shear thinning and shear thickening, effects of particle size and volume fraction of solids; slip casting, drain casting, solid casting overview; tape casting, rapid prototyping and desktop manufacturing, key issues and case studies; extrusion, role of processing aids, semidry and dry pressing, powder requirements, role of processing aids, case studies and recent research, “green” processing, a comparative summary of forming operations
  • Drying and forming aid removal: The stages of drying: Stage I, Stage II, Stage III; types of water; removal mechanisms; physical changes; fluid flow versus heat flow; stress generation during drying: pressure/stress distributions, warping, fracture, microstructural models (Scherer); Stage III drying and effect of particle size: nanoparticulates; optimum drying cycles for wet processed ceramics: slip casting, tape casting, effect of solvent/fluid; recent innovations: supercritical drying of aerogels; presintering: removal of processing aids, binder burnout, consequences of incomplete processing aid removal, a case for polymer precursors.
  • Firing: Sintering: the coarsening-densification competition; thermodynamic basis for mass flows, capillarity effects, curvature, derivations of the pressure-curvature relationship; the Gibbs-Thomson equation, effect of particle size, comparison to other driving forces for mass flow; vapor phase sintering: derivation of equation for mass loss due to vaporization, effect of particle size, effect of vapor pressure/temperature, implications for multicomponent systems, DIGM (case studies); extensions; mass exchange between isolated particles: the Greenwood analysis, the Lifshitz-Slyozov analysis of coarsening, surface reaction vs diffusion rate limited coarsening, effects of particle size distributions; analysis of smoothing of a rumpled surface: the Mullins scratch smoothing analysis and implications for particle sintering, parallel mass flow processes; effects of curvature on chemical potential and vacancy concentrations: mass flow by surface volume and vapor phase transport; curvature-induced neck growth: development of a model for neck growth via vapor phase transport; parallel mass flow processes and impact on coarsening and densification; the densification mass source-mass sink pair, and models for mass flow: sintering maps; grain size-density trajectories: predicting grain size density trajectories from diffusion data; grain size-density trajectories: predicting grain size density trajectories from diffusion data; the stages of sintering: initial intermediate, and final, and complicating issues; pore-boundary interactions: grain boundary mobility, pore mobility, the Brook analysis ; strategies for controlling microstructural evolution during solid-state sintering of ceramics; other processing routes: liquid phase sintering of ceramics, driving force, mass transport, kinetics, advantages and disadvantages; other processing routes: hot pressing of ceramics, driving force, mass transport, kinetics, advantages and disadvantages

 

COURSE FORMAT:

Three hours of lecture per week.

CONTRIBUTION OF THE COURSE TO MEETING THE PROFESSIONAL COMPONENT:

Ideally, our graduates should be exposed to the processing methods used to fabricate a wide range of materials. This course seeks to provide this background for materials that are processing from powders. The course emphasizes the interconnections between powder characteristics, forming methods, and firing conditions on the ultimate characteristics of the processed material. An extensive set of readings selected from the technical literature is designed to help the students understand and appreciate these interrelationships, and to better connect material discussed in lecture with actual processing research. This encourages library research, as does the requirement of term paper.

RELATIONSHIP OF THE COURSE TO UNDERGRADUATE DEGREE PROGRAM OBJECTIVES:

The course is intended to provide upper-division engineering students an introduction to the powder processing of materials, especially ceramics. The is intended to cover the major unit processes involved in ceramic powder processing, and to familiarize the student with the consequences of decisions made at each stage on the processing behavior during later stages. The course provides extensive exposure to the technical literature, both old and new, to reinforce the need for continued learning. In addition to reading required by the coursework, the student is also required to research a self-selected topic as part of writing a term paper. Additionally, the course provides an opportunity to present a research presentation, and thereby develops oral presentation skills. The course is one of several intended to satisfy the processing course requirement of our program.

ASSESSMENT OF STUDENT PROGRESS TOWARD COURSE OBJECTIVES:

  • Approximately eight study guides are distributed to allow self-assessment of how well lecture concepts are being understood.
  • Two 80-minute mid-term examinations.
  • Term paper with one-page, and three-page outlines due during the semester, and oral presentation to class in the style of a research presentation.
  • Final examination.

 

PERSON(S) WHO PREPARED THIS DESCRIPTION:

Professor Andreas M. Glaeser