Directed energy deposition (DED) was used to produce niobium carbide (NbC)‐reinforced Ti6Al4V (Ti64) metal–matrix‐composite (MMC) structures. The objective was to improve upon Ti64's wear and oxidation resistance. The characterization techniques consisted of scanning electron microscopy (SEM), backscattered electron (BSE) imaging, energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Vickers micro‐ and nanoindentation‐derived hardness, as well as tribological testing at varying normal loads. DED produced compositions were of Ti64, Ti64 + 5 wt.% NbC (5NbC), and Ti64 + 10 wt.% NbC (10NbC). Electron micrographs revealed crack‐ and delamination‐free structures. Tribological analysis revealed a 25.1% reduction in specific wear rate. XRD and EDS results indicated the presence of a Ti‐Nb solid solution. It was deduced that the NbC particles coupled with the Ti‐Nb solid solution aided in increasing Ti64's resistance to plastic shear as the superficial microstructure remained unchanged compared to pure Ti64. Additionally, TGA displayed a reduction in total oxidation mass gain and suppressed oxidation kinetics to parabolic behavior with increased NbC. Application‐based composite structures with site‐specific mechanical properties were fabricated in the form of a composite cylinder, gear and compositionally graded cylinder. The graded cylinder displayed a 0%–45%NbC presence—end‐to‐end—equating to a hardness increase from 161.6 ± 4.0HV0.2to 1055.9 ± 157.4HV0.2.
- Award ID(s):
- 1934230
- NSF-PAR ID:
- 10282688
- Date Published:
- Journal Name:
- Acta biomaterialia
- Volume:
- 123
- ISSN:
- 1742-7061
- Page Range / eLocation ID:
- 379-392
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
null (Ed.)In this study, functional gradation via layer-wise additive manufacturing was coupled with Al2O3 and SiO2 ceramics' advantages to creating a composite of Ti6Al4V (Ti64) with improved hardness and wear resistance. It was hypothesized that with the addition of Al2O3 and SiO2 into Ti64, wear-resistance and hardness would increase when compared to the base Ti64 alloy. It was also hypothesized that if the structure could be created, an additional laser pass (LP) over the structure's top surface would further increase the hardness. Successfully fabricated composite structures were found to have varying phases of TiSi2 and Ti5Si3. Refined α-Ti grains were present in the composite region. The interface between the composite and pure Ti64 regions was crack-free, indicating a metallurgically sound bond. Dendritic microstructures were observed with the addition of LP on the composite top surface. Hardness was increased from 323.8 ± 9.6 HV in Ti64 substrate to 434.7 ± 7.3 HV and 677.1 ± 29.7 HV in 3D Printed Ti64 and the composite sample, respectively. An LP increased hardness further to 938.8 ± 57.5 HV, a 186% increase in hardness than the original Ti64 alloy. Wear resistance was also increased with the addition of Al2O3 and SiO2 by ~90%, indicating the potential processing variations placed on this material system to produce structures with site-specific functionality for biomedical applications, particularly in articulating surfaces of load-bearing implants.more » « less
-
more » « less
Abstract In order to investigate the in‐space in situ resource utilization, directed energy deposition (DED)‐based additive manufacturing (AM) has been utilized to process Martian regolith—Ti6Al4V (Ti64) composites. Here we investigated the processability of depositing 5, 10, and 100 wt% of Martian regolith premixed with Ti6Al4V using laser‐based DED, analyzing the printed structure via X‐ray diffraction, Vicker's microhardness, scanning electron microscopic imaging, and wear characteristics utilizing an abrasive water jet cutter to simulate abrasive environments on the Martian surface. The results indicate that the surface roughness and hardness of the composites increase with respect to the Martian regolith’ weight percentage due to in situ ceramic reinforcement. For instance, i5‐wt% addition of Martian regolith increased the Vicker's microhardness from 366 ± 6 HV0.2for as‐printed Ti64 to 730 ± 27 HV0.2while maintaining similar abrasive wear performance as Ti6Al4V. The results point toward laser‐based AM for fabricating Ti64—Martian regolith composites with comparable properties. The study also reveals promising results in limiting the mass burden for future space missions, resulting in cheaper and easier launches.
-
more » « less
Abstract The creep and recovery and the stress relaxation behaviors of poly(butylene adipate‐co‐terephthalate) (PBAT) and polyhydroxyalkanoates (PHA) binary blends incorporating 30 wt % of a mixture of trisilanolisobutyl polyhedral oligomeric silsesquioxanes (POSS) and calcium phosphate glass (CaP‐g) were investigated under simulated physiological and human body temperature conditions. The synergistic effect of PHA and CaP‐g/POSS filler remarkably improved the creep behavior of the PBAT matrix and decreased its residual strain, consequently enhancing its elastic recovery. A considerable increase of the relaxation modulus of the hybrid materials was also observed upon incorporation of PHA and CaP‐g/POSS. The relaxation modulus of the neat PBAT sample increased from ~60 MPa to ~1600 MPa after addition of 30 wt % CaP‐g/POSS and 70 wt % PHA. However, after exposure of the composites to the simulated human body conditions for 14 days, a drop of dynamic mechanical properties of the studied material systems was observed along with formation of a desirable calcium phosphate phase on the material surface. The long‐term (i.e., up to 7 × 105 s) viscoelastic behavior of the studied materials was successfully predicted using the time–temperature superposition principle and the obtained creep strain and the relaxation modulus master curves were satisfactorily fitted to the Findley power law equation and the generalized Maxwell model, respectively. This study demonstrates a facile method for tailoring CaP‐g/POSS bioactive glasses composition for bone‐like apatite formation on biopolymer surfaces. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2419–2432, 2019.
-
Productive utilization of lignocellulosic biomass is critical to the continued advancement of human civilization. Whereas the cellulose component can be efficiently upconverted to automotive fuel-grade ethanol, the lack of upconversion methods for the lignin component constitutes one of the grand challenges facing science. Lignin is an attractive feedstock for structural applications, in which its highly-crosslinked architecture can endow composite structures with high strengths. Prior work suggests that high-strength composites can be prepared by the reaction of olefin-modified lignin with sulfur. Those studies were limited to ≤5 wt% lignin, due to phase-separation of hydrophilic lignin from hydrophobic sulfur matrices. Herein we report a protocol to increase lignin hydrophobicity and thus its incorporation into sulfur-rich materials. This improvement is affected by esterifying lignin with oleic acid prior to its reaction with sulfur. This approach allowed preparation of esterified lignin–sulfur (ELS) composites comprising up to 20 wt% lignin. Two reaction temperatures were employed such that the reaction of ELS with sulfur at 180 °C would only produce S–C bonds at olefinic sites, whereas the reaction at 230 °C would produce C–S bonds at both olefin and aryl sites. Mechanistic analyses and microstructural characterization elucidated two ELS composites having compressive strength values (>20 MPa), exceeding the values observed with ordinary Portland cements. Consequently, this new method represents a way to improve lignin utilization to produce durable composites that represent sustainable alternatives to Portland cements.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/doi.org/10.1016/j.actbio.2020.12.060
