Forming Transparent Ceramics via Alignment of Alpha-Al2O3 Platelets: A Fundamental Investigation and Forming Study
Abstract
Our focus is to form transparent plates using highly aligned alpha-Al2O3 platelets to understand the role that anisotropy plays in transparency loss from refractive index induced scattering at grain boundaries. Thus we seek to prepare dense alumina with high transparency, clarity and reduced haze using a low cost processing method. There are three goals in the proposed work. Goal 1 is to establish how to sinter aligned alpha-Al2O3 grains to transparency. We anticipate studying the effect the following variables on densification of aligned platelet alpha-Al2O3: platelet thickness (50 nm through 1 micron thick platelets), sintering temperature (1400oC Ð 1800oC), sintering times (1 hr through 24 hr), sintering pressure (0 MPa Ð 500 MPa), and MgO additions (0 ppm Ð 1000 ppm). Note that platelet thickness will affect the number of interfaces and the wavelengths affected. Goal 2 is to establish the effect of apha-Al2O3 platelet alignment and incident light angle with respect to the basal plane of alumina on transparency. We will vary the degree of platelet alignment by adjusting the processing steps, quantifying differences using the x-ray diffraction. We will develop a simple light transmission model based on all 3 modes of transmission loss (and absorption) in dense materials and fit experimental data on platelet alignment and size to the model. The third goal of this grant will be the fabrication of larger, more complex shaped parts of platelet alpha-Al2O3 via injection molding using shear and/or elongational stresses during forming to align platelets for enhanced transparency.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2018
- Source ID
- W911NF1710203
Entities
People
- Rodney W. Trice
Organizations
- Army Contracting Command
- United States Army
- University of Virginia