Walter H. Gitzen

Bio: Walter H. Gitzen is an academic researcher. The author has contributed to research in topics: Ceramic & Cermet. The author has an hindex of 1, co-authored 1 publications receiving 483 citations.

Alumina as a ceramic material

Abstract: INTRODUCTION. NOMENCLATURE. PREPARATION OF ALUMINA PHASES. Bauxite. Preparation of Bayer Alumina. Wet Alkaline Processes. Wet Acid Processes. Furnace Processes. Carbothermic Processes. Electrolytic Processes. Amorphous and Gel Aluminas. Preparation of the Alumina Trihydroxides. Gibbsite. Bayerite. Nordstrandite, Bayerite II, Randomite. Preparation of the Alumina Monohydroxides. Boehmite. Disapore. Transition Aluminas. Dehydration Mechanism. Sequence of Transition. Phases Formed on Aluminum. Rehydration. Alpha Alumina. Preparation. Factors Affecting Alumina Transitions. Special Ceramic Aluminas. Beta and Zeta Aluminas. Suboxides and Gaseous Phases. STRUCTURE AND MINERALOGICAL PROPERTIES. Structure of the Alumina Phases. Pseudomorphosis. Surface Area of Alumina. Porosity. Sorptive Capacity. MECHANICAL PROPERTIES OF ALUMINA. General Considerations. Bending, Compressive, Tensile, and Torsional Strength. Impact Strength. Moduli of Elasticity (E), and Rigidity (G). Poisson's Ration (i). Creep Characteristics. Thermal Shock. Internal Friction. Fatigue. Hardness and Abrasiveness of Alumina THERMAL PROPERTIES. Thermophysical and Thermochemical Constants. Specific Heat. Thermal Expansion. Thermal Conductivity. Thermal Diffusivity SONIC EFFECTS IN ALUMINA. Velocity of Sound in Alumina. Ultrasonic Absorption. ELECTRICAL PROPERTIES OF ALUMINA. Introduction. Electrical Conductivity of Alumina. Dielectric Constant and Loss Factor of Alumina. Dielectric Strength MAGNETIC PROPERTIES OF ALUMINA. Magnet Susceptibility. Magnetic Resonance of Alumina. OPTICAL PROPERTIES OF ALUMINA. Refractive Index of Alumina. Transmission, Emissivity, and Absorption of Alumina. Phosphorescence, Fluorescence, and Thermoluminescence. Optical Spectra of Alumina. Color in Alumina. Chromia-Alumina System, Laser Applications RADIATION AND ALUMINA. CHEMICAL PROPERTIES OF ALUMINA. Wet Chemical Reactions of Sintered Alumina. Reaction of the Chemical Elements with Alumina. Slagging Effects. Ash Slags. Slags Containing Sulfates. Steel Furnace Slags. Glass Furnace Reactions. Calcium Aluminate Slags. Aluminum Slag Reactions. Miscellaneous Reactions COLLOIDAL PROPERTIES OF ALUMINA. Plasticity. Surface Charge and Zeta Potential of Alumina. Flocculation and Deflocculation Effects. Additives GRINDING CERAMIC ALUMINA. FORMING ALUMINA CERAMICS. Cold Forming of Alumina. Hot-Pressing. Miscellaneous Forming Methods SINTERING. Introduction. Sintering Atmospheres. Sintering Additives ALUMINA IN REFRACTORIES. General. High-Alumina Refractories. Fused Cast Alumina Refractories. Clay-Bonded Alumina Refractories, Mullite Refractories. Spinel, Cordierite, Alumina-Chromite. Refractory Equipment. Refractories for Aluminum and Other Nonferrous Uses. Lightweight Alumina Refractories. Binders for Alumina Refractories ALUMINA AS AN ABRASIVE MATERIAL. Introduction. Loose Grain Abrasive. Grinding Wheels. Ceramic Tools ELECTRICAL APPLICATIONS. Spark Plug Insulators. Electron Tube Elements, High-Frequency Insulation. Alumina Porcelain Insulation. Resistors and Semiconductors CEMENT. Calcium Aluminate Cement. Barium Aluminates ALUMINA IN GLASS. Introduction. Bottle Glass. Devitrified Glasses Containing Alumina. Boron Glasses. Lithium Glasses, Phosphate Glasses. Optical Glasses ALUMINA IN COATINGS. Introduction. Anodic Coatings on Aluminum. Glazes and Enamels. Flame-Sprayed Coatings. Painted, Cast, or Troweled Coatings. Electrolytic Coatings. Evaporated Coatings. Dip Coatings, Cementation Coatings. Coatings on Alumina and Other Ceramic Bases. Alumina Coatings for Electrical Insulation. Alumina Coatings by Sputtering ALUMINA IN CERMETS AND POWDER METALLURGY. Introduction. Chromium-Alumina Cermets. (Iron, Nickel, Cobalt)-Alumina Cermets. Aluminum-Alumina Alloys. Miscellaneous Cermets ALUMINA IN AIRBORNE CERAMICS. Introduction. Gas-Turbine Accessories. Radomes and Rocket Equipment. SEALS, METALLIZING, WELDING. FIBERS, WHISKERS, FILAMENTS. Introduction. Alumina Fibers. Glass Fibers MISCELLANEOUS CERAMIC APPLICATIONS OF ALUMINA. References.

Liquid crystal phase transitions in suspensions of polydisperse plate-like particles

Abstract: Colloidal suspensions that form periodic self-assembling structures on sub-micrometre scales are of potential technological interest; for example, three-dimensional arrangements of spheres in colloidal crystals might serve as photonic materials, intended to manipulate light. Colloidal particles with non-spherical shapes (such as rods and plates) are of particular interest because of their ability to form liquid crystals. Nematic liquid crystals possess orientational order; smectic and columnar liquid crystals additionally exhibit positional order (in one or two dimensions respectively). However, such positional ordering may be inhibited in polydisperse colloidal suspensions. Here we describe a suspension of plate-like colloids that shows isotropic, nematic and columnar phases on increasing the particle concentration. We find that the columnar two-dimensional crystal persists for a polydispersity of up to 25%, with a cross-over to smectic-like ordering at very high particle concentrations. Our results imply that liquid crystalline order in synthetic mesoscopic materials may be easier to achieve than previously thought.

Standard transition aluminas. Electron microscopy studies

Abstract: The aim of this paper is to present the results of characterization of the particle shapes of six standard transition aluminas samples using transmission and scanning electron microscopies; selected area electron diffraction, in parallel with X-ray powder diffraction were used for confirmation of the different transition aluminas types. The transition aluminas - chi; kappa; gamma; theta; delta; and eta were supplied by ALCOA Central Laboratory. The chi-; kappa-;gamma- and delta-Al203 microcrystals are pseudomorphs from their respective precursors gibbsite and boehmite. However, theta-Al203 microcrystals are not pseudomorphs after the standard delta-Al203 sample. Also, eta-Al203 are not pseudomorphs after bayerite somatoids.

Abrasive grain, method of making same and abrasive products

Abstract: An improved abrasive grain comprising the sintered product of a porous non-sintered particle having a coating of inorganic material thereon is provided. A preferred method of making such abrasive grains comprises coating the porous base particles with inorganic particles. The preferred step of coating comprises a step of mixing the base particles with a suspension containing the inorganic particles in a carrier fluid. The porous base particles having the coating of inorganic particles thereon are sintered, to generate the ceramic abrasive grain product. The abrasive grains may be incorporated, to advantage, in a variety of abrasive products including, for example, bonded abrasives, nonwoven abrasive products and coated abrasive products.

Combustion synthesis of fine-particle metal aluminates

Abstract: Fine-particle metal aluminates,$MAl_20_4$ where $M = Mg$, $Ca$, $Sr$, $Ba$, $Mn$, $Co$, $Ni$, $Cu$ and $Zn$ as well as $3CaO . Al_2O_3$ $(C_3A)$, $CaAl_{12}O_{19}$ $(CA_6)$ and $MgCeAl_{11}O_{19}$ have been prepared by the combustion of mixtures of the respective metal nitrates (oxidizers) and urea or carbohydrazide (fuels) at 500 or $350^0c$ respectively, over a time of 5min. The solid combustion products were identified by their characteristic X-ray powder diffraction patterns. The fine-particle nature of these metal aluminates was investigated using SEM, TEM, particle size analysis and surface area measurements. The surface areas of the as-prepared metal aluminates using carbohydrazide fuel were higher (45 to 85 $m^2g^{-1}$) compared with urea (1 to 20 $m^2g^{-1}$).