Engineering Nano/Micro Structure in C-C Composites by Templating
Abstract
Templating is the development of interfacial order due to a physical boundary condition. In the case of composites the interface is the surface of additives - typically in the form of particles. Both the shape of the particles and nanostructure dictate the molecular-level interaction with the matrix while shape controls the lateral extent. The matrix chemistry will determine the propagation of local interfacial order within the matrix, away from the interface. These variables and hypothesized roles are the focus of the proposed study. Carbon-carbon (C-C) composites and related engineered carbons have numerous applications in the energy, transportation sectors, processing and manufacturing industries. Matrix restructuring at the fiber-matrix interface is known to occur in carbon-fiber composites, even when using non-graphitizing matrix precursors, as shown by XRD of composites. In other engineered carbons with additives such as discontinuous carbon fibers or carbon nanotubes, similarly spatial averaged measurements of polarized light microscopy and Raman spectroscopy have shown localized interfacial restructuring (of the matrix) adjacent to the additive. Across this range of composites the fiber/particle-matrix interface has not been examined at the nanoscale nor composite properties across length scales. In particular the dependence upon the additive surface nanostructure and matrix chemistry is a knowledge gap preventing predictive engineering design of these advanced materials. The development of interfacial matrix (nano)structure as directed by the carbon filler/additive is unknown, but critical to composite properties and application performance. The goal of this project is to test the roles of matrix chemistry, particle nanostructure and morphology upon evolution of (nano)structure at the matrix interface for a solid-state material - carbon. The evolution of solid-state nanostructure, its rate and extent of development, as dependent upon chemistry, additive and temperature will be observed and quantified using high-resolution transmission electron microscopy (HRTEM) and post-image analysis for both spatial extent and degree of development, electrical conductivity to comparatively assess microstructural changes (as a more crystalline matrix has higher electrical conductivity) and mechanical properties to assess macroscale gains in flexural modulus and strength. Collectively these physical metrics will test the roles of matrix chemistry, additive nanostructure and morphology upon matrix interfacial nanostructure and composite macroscale properties dependent upon the additive-matrix interface. The approach is to use model carbons as additives in real matrix precursors followed by carbonization and graphitization process stages. Matrix resins will be pitch, a graphitizing carbon (matrix) precursor and furan, a non-graphitizing carbon (matrix) precursor. These matrices will test the role of matrix chemistry upon templating. The carbon fillers will be model nanocarbons featuring uniform and distinct shapes and structures by which to comparatively test particle (additive) templating action. HRTEM will be applied to thin films to gauge interfacial boundary between the nanocarbon and near-interfacial matrix. Custom analysis algorithms applied to HRTEM images will statistically differentiate between the physical metrics of lamellae order: length, curvature and separation distance. Thick films will be formed for flexural and shear testing so as to measure the impact of microscopic interfacial structure upon macroscale properties. Both intrinsic interfacial structure and extrinsic mechanical properties will be measured parametrically with additive amount and process temperature(s). Electrical measurements will comparatively assess structure impact upon conductivity.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2018
- Source ID
- W911NF1710513
Entities
People
- Randy L. Vander Wal
Organizations
- Army Contracting Command
- Pennsylvania State University
- United States Army