3D-ink-extruded titanium with steel spaceholders for orthopedic implants (Prof. David Dunand)
Titanium is a successful bone implant material in clinical studies because it has high fracture toughness, excellent corrosion resistance, and ease of biological integration. However, titanium has demonstrated drawbacks in implant reliability via stress shielding (changes in the surrounding bone with the implant) and poor osseointegration (integration of the implant with bone).
In this work, hierarchically porous pure titanium material is direct-ink write (DIW) additively manufactured by using electrochemically dissolvable high-carbon steel spaceholders to create low stiffness and high osseointegration orthopedic implants. Millimeter-wide channels within the material are designed to allow for nutrient transport and vasculature growth. The steel spaceholders provide an interconnected microstructure to enable individual cell movement and anchoring. The volume of the spaceholders can be changed to tune the interconnectivity of the pores and the stiffness of the implant.
The NURPH summer research student will perform and optimize ink extrusion and electrochemical dissolution of the spaceholders to obtain consistently sized steel fibers that can be well extruded. They will operate a high-temperature furnace to sinter samples and use metallography and optical microscopy to image the structure of the samples. Compression testing will also be performed to test the elastic modulus and deformation of the material.
Designing and fabricating cathodes for high energy density lithium batteries (Prof. Jeff Lopez)
Climate change poses an existential threat, underscoring the importance of renewable energy technologies and a complete transition away from fossil fuels. Energy storage systems play an important role in this transition, enabling us to store energy from sources like the sun and wind, in addition to powering technology like electric vehicles. Here, we will focus on the cathode, which plays an important role in enabling high energy density lithium-ion batteries.
The NURPH summer research student will focus on combining different materials to fabricate cathodes with high performance. Cathodes typically consist of an active material, a binder, and a conductive carbon material. The student will fabricate cathodes by combining materials and using various processing, coating, and pressing techniques. The cathodes fabricated by the student will be cycled in batteries, and battery performance metrics such as stability, capacity, and energy density will be used to determine an optimal cathode composition. In addition to cell cycling, the student may investigate the structure of the cathodes they fabricate using techniques such as SEM and porosimetry with a graduate student’s assistance. The outcome of this project will be a better knowledge of the design space available for high-performance cathodes as well as an understanding of how different fabrication techniques can affect the performance of the cathode.
Integrating silica in porous ultra-high temperature ceramics for use in hypersonic vehicles (Prof. Ian McCue)
Hypersonic vehicles are vehicles designed to reach speeds of more than 5x the speed of sound. Recent developments in materials for the leading edges of hypersonic vehicles have focused largely on either C/SiC composite materials or ultra-high-temperature ceramics (UHTC). C/SiC composites are advantageous because they form a highly protective silica, which has low oxygen permeability. UHTCs have also been studied because of their extremely high strength at elevated temperatures, though oxidation is a major concern for the materials. Our work aims to optimize the survivability of leading-edge materials by designing a hierarchically structured composite material: a porous UHTC base infiltrated with silica.
Our NURPH summer research student will help develop a process for infiltrating silica into our porous base materials, which can be metallic or ceramic. The first step will be an immersion of the porous base in a solution of dispersed silica particles and ammonium dispersant. The next step will involve drying in a vacuum oven, initially at low temperatures to drive the replacement of air in pores with the silica dispersion. The oven will be heated at higher temperatures to evaporate DI water from the dispersion, adsorbed water, and other organics. The sample will then be transferred to a furnace where it will be sintered at temperatures >1000°C under forming gas. The student will be involved in optimizing every step of this process.
The final outcomes of this project will be (1) a detailed standard operating procedure for silica infiltration, and (2) plots of each processing parameter vs. infiltration percentage. Along the way, the student will learn about various kinetic processes in materials such as grain growth in crystalline materials and coarsening of ligaments in porous materials.
Synthesizing and optimizing ion paired frameworks for quantum computing (Prof. William Dichtel)
Ion-paired frameworks are a novel class of supramolecular assemblies held together by host-guest interactions. These crystalline materials have shown promise for applications in quantum computing, as they can order molecules that can represent qubits (quantum bits) into precise arrays. These frameworks need to be optimized before they can see real-world application.
In this project, the NURPH summer student will learn about supramolecular assemblies and perform organic synthesis and optimization of frameworks. They will synthesize and fully characterize metalloporphyrins and calix[4]pyrroles. Additionally, they will optimize the conditions to make frameworks out of porphyrin, varying reaction parameters such as solvent identity, host macrocycle, ion pair linkers, base concentration, and ion concentration. Using optical microscopy, they will then identify the color and morphology of the crystals. The crystalline structure of the frameworks will be determined by powder x-ray diffraction and single-crystal x-ray diffraction.
Synthesizing of hybrid halide 2D perovskites for optoelectronic applications (Prof. Mercouri Kanatzidis)
Organic-inorganic halide perovskites are semiconducting materials that have attracted much interest in the last decade because of their outstanding efficiency as light absorbing materials in solar cells and LEDs. However, the moisture instability of methylammonium lead iodide at ambient conditions has motivated the development of low dimensional halide perovskites because they provide additional moisture stability due to increased hydrophobicity from spacers. In these studies, larger organic cations, or “spacers”, are too large to fit in the voids of the perovskite lattice and slice the 3-dimensional (3D) lattice into 2-dimensions (2D). Also, two-dimensional materials allow a new axis in compositional/structural space with which to probe the optoelectronic properties.
Our NURPH summer research student will focus on the synthesis of novel 2D perovskite materials by using different combinations of spacers to find new structures that haven’t been reported or by substituting different metal cations or halide anions to tune the properties. The student will become familiar with the use of balances to weigh out specific masses of reagents, as well as hot plates and ovens to control the temperature of these reactions. The student will also use various techniques to characterize these materials, such as powder x-ray diffraction to phase match synthesized materials and UV-Vis spectroscopy to obtain information about the band gaps. In the event that a novel structure is synthesized, mentor-guided single crystal x-ray diffraction will also be used to obtain more structural details.