The synthesis and characterization of iron oxides---The effects of material properties on size reduction processes
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The process of powder size reduction has found widespread industrial use given the variety of techniques and the highly flexible nature of processing windows available. Raw materials of varying size, shape, and hardness may be tuned to a desired particle size range for use as an efficient process output or downstream input material. In particular, the techniques of ball and hammer milling are common methods that use particle to surface contact to enable size reduction. Other techniques such as air/jet mills rely on particle-to-particle contact to produce the finalized material. As stated, the wide range of size reduction techniques and processing windows available enable a host of solid materials to be processed into final product. Some of these include grains, pharmaceutical medicines, metal oxides, and other organics. The goal of this research project is to expand the relationship between sample material properties and the mechanics of size reduction. By preparing and synthesizing materials in a controlled manner, we may gain further insight into how specific material properties are influenced and how these will affect overall bulk behavior and size reduction processes. In our studies we have chosen to use an iron oxide powder due to the low cost and minimal toxicity of these materials. Due to these facts, these oxides are widely used in many industrial and academic settings. Common uses of these oxides include the production of steel, magnetic storage media, semiconductors, and pigments. In addition, the iron oxides are commonly used for their chemical properties as their surfaces are typically fairly reactive. As a result, these materials also find many uses as catalysts such as those used in the Fischer-Tropsch synthesis. We will begin in Chapter 2 by defining baseline material sampling and characterization techniques. Methods development studies involving material sampling and characterization parameters will be carried out to accurately define the physical and chemical aspects of our initial starting and final processed iron oxides. Size reduction experimentation will be carried out using ball and air milling techniques. In addition to other structural and bulk material characterizations, particle size measurement techniques of laser diffraction as well as Scanning Electron Microscopy will be used to quantify the effects of size reduction. The effects of particle re-agglomeration and thermodynamic stability of milled particle surfaces are introduced in this chapter as well. Chapter 3 will summarize our systematic approach with a macro view of the oxide by characterizing and milling Fe 2 O 3 products containing spherical and acicular particle agglomerate morphology. Both materials will be fully characterized using laser diffraction and SEM based particle sizing techniques as well as X-ray Diffraction (XRD) to determine effects on crystal structure. Size reduction will again be carried out using ball and air milling trials.