3D printing of high strength-to-weight ratio ultra-high temperature ceramics (UHTCs) with multiscale porosity - Phase 2
Abstract
Ceramic materials used in ultra-high temperature applications such as in hypersonic vehicles are not onlyrequired to exhibit low thermal conductivity, but also need to comply with both weight and strengthrequirements to provide for efficient in-service use. Porous ceramics and scaffold structures can address suchrequirements to certain levels, however, combining these via 3D printing ceramic emulsion pastes into scaffoldstructures could provide a method for creating complex shaped ceramics with high performance-designedstructures. This work will develop foundation process-property-structure relationships for scaffold structuresmade with porous struts of ultra-high temperature ceramic (UHTC) using extrusion based 3D printingtechniques.Controlling particle interactions in a colloidal suspension is key to producing pastes suitable for the directink writing (DIW) 3D printing technique. Work to date has established which additives, solids loadings andfoaming techniques produce paste inks with the suitable droplet size distribution and flow properties. Thisincluded studying the flow properties including; viscosity, storage modulus and shear yield stress that will aid indetermining the suitability and limits of the UHTC pastes for this extrusion technique.In addition to the process development just mentioned, the current proposal will evaluate the mechanicalbehavior of the structures. Mechanical properties of such 3D printed porous ceramics will be measured in 4points bending which has not been published anywhere in the world at the time of writing. Comparison of thestrength-to-density ratio of samples produced via conventional techniques as well as via the new 3D printingtechnology will be conducted. Specifically, to compare: 1) a dense ZrB2, produced by slip casting; 2) a latticestructure produced by 3D printing with dense struts; 3) lattice structures produced by 3D printing with porousstruts such as comparing 90 degree offset lattice structures to hexagonal (honeycomb) lattices; 4) a structurecontaining only 10 to 100 ~m porosity produced by the particle stabilized emulsion method; 5) a dense structureproduced by 3D printing.The technical approach will consist of six main stages;1. Determination of the optimum method to remove the oil used to template the macro-porosity in theemulsion paste inks.2. Mechanical emulsification methods and tools that result in stable emulsions and the required dropletsize distribution will be established.3. Detailed flow property measurements will be carried out with the sample materials at key stages duringthe processing, i.e., from the dispersed stage through to the emulsification stage. This will provide datato ensure repeatability throughout the processing stages as well as changes in the particle interactionscaused by the different additives. The data obtained at this stage is key to producing emulsions thatmeet the requirements for good printability.4. Printing parameters for the UHTC emulsions will be established via experimental techniques. Traversespeeds, offset distances, extrusion force or pressure and layer height are among some of the parametersthat need to be optimized to print reproducible structures.5. Ascertain drying and firing conditions that result in complete multi-scale porous ceramic structures.6. Evaluate the mechanical properties via 4-point bend measurements to reveal the relationship betweenthe 3D printed architecture, the morphology and amount of porosity and the mechanical strength.If successful, this project could aid in the development of complex shaped ceramics for ultra-hightemperature thermal protection systems with high strength to weight ratios.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912475
Entities
People
- George V Franks
Organizations
- Office of Naval Research
- United States Navy
- University of Melbourne