Aerosol deposition (AD) is a coating technique wherein particles are impacted onto a target substrate at reduced pressures, and supersonic particle impact velocities lead to coating consolidation. The limiting step in AD application is often not supersonic deposition operation, but aerosolization of powder particles with the proper size distribution; the translational impact velocity is strongly size‐dependent. It is demonstrated that by directly synthesizing particles in the gas phase, size‐controlled ceramic particles can be injected into AD systems. This in situ formation step obviates the need for particle aerosolization. Ultrasonic spray pyrolysis (USP) is applied to produce yttria‐stabilized zirconia (YSZ), and USP is directly coupled with AD to produce consolidated, thick, YSZ coatings on metal substrates. USP‐AD yields YSZ coatings on stainless steel and aluminum substrates with porosities <0.20, which grow to thicknesses beyond 100 μm. Aerodynamic particle spectrometry and electron microscopy reveal that the depositing particles are 200 nm–1.2 μm in diameter, though each particle is composed of nanocrystalline YSZ. Supporting computational fluid dynamics calculations demonstrate that the YSZ particle impact speeds are above 300 m s−1. Thermal conductivity measurements demonstrate that USP‐AD coatings have conductivities consistent with those produced from high‐temperature processes.
Molecular dynamics simulations of particle impact have been conducted for a ceramic with mixed ionic-covalent bonding. For these simulations, individual zinc oxide (ZnO) nanoparticles (NPs) were impacted onto a ZnO substrate to observe the effects of impact velocity (1500–3500 m s−1) and particle diameter (10, 20, and 30 nm) on particle deformation and film formation mechanisms that arise during the micro-cold spray process for producing films. The study shows that a critical impact velocity range exists, generally between 1500 and 3000 m s−1, for sticking of the NP to the substrate. Results suggest that solid-state amorphization-induced viscous flow is the primary deformation mechanism present during impact. Decreasing particle diameter and increasing impact velocity results in an increased degree of amorphization and higher local temperatures within the particle. The impact behavior of mixed ionic-covalent bonded ZnO is compared to the behavior of previously studied ionic and covalent materials.
more » « less- NSF-PAR ID:
- 10452413
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Modelling and Simulation in Materials Science and Engineering
- Volume:
- 31
- Issue:
- 7
- ISSN:
- 0965-0393
- Page Range / eLocation ID:
- Article No. 075008
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
-
Context. Since the discovery of exoplanetary systems, questions have been raised as to the sub-stellar companions that can survive encounters with their host star, and how this interaction may affect the internal structure and evolution of the hosting star, and particularly its surface chemical composition. Aims. We study whether the engulfment of a brown dwarf (BD) by a solar-like main-sequence (MS) star can significantly alter the structure of the star and the Li content on its surface. Methods. We performed 3D smoothed particle hydrodynamics simulations of the engulfment of a BD with masses 0.01 and 0.019 M ⊙ , on an MS star of 1 M ⊙ and solar composition, in three different scenarios: a head-on collision, a grazing collision with an impact parameter η = 0.5 R ⊙ , and a merger. We studied the dynamics of the interaction in detail, and the relevance of the type of interaction and the mass of the BD on the final fate of the sub-stellar object and the host star in terms of mass loss of the system, angular momentum transfer, and changes in the Li abundance on the surface of the host star. Results. In all the studied scenarios, most of the BD mass is diluted in the denser region of the MS star. Only in the merger scenario a significant fraction (∼40%) of the BD material would remain in the outer layers. We find a clear increase in the surface rotational velocity of the host star after the interaction, ranging between 25 km s −1 (grazing collision) to 50 km s −1 (merger). We also find a significant mass loss from the system (in the range 10 −4 − 10 −3 M ⊙ ) due to the engulfment, which in the case of the merger may form a circumstellar disk-like structure. Assuming that neither the depth of the convective envelope of the host star nor its mass content are modified during the interaction, a small change in the surface Li abundance in the head-on and grazing collisions is found. However, in the merger we find large Li enhancements, by factors of 20 − 30, depending on the BD mass. Some of these features could be detected observationally in the host star, provided they remained for a long enough time. Conclusions. In our 3D simulations, a sizable fraction of the BD survives long enough to be mixed with the inner core of the MS star. This is at odds with previous suggestions based on 1D simulations. In some cases the final surface rotational velocity is very high, coupled with enough mass loss that may form a circumstellar disk. Merger scenarios tend to dilute considerably more BD material on the surface of the MS star, which could be detected as a Li-enhancement. The dynamic of the simulated scenarios suggests the development of asymmetries in the structure of the host star that can only be tackled with 3D codes, including the long-term evolution of the system.more » « less
-
more » « less
Abstract Additive manufacturing of solid-state batteries is advantageous for improving the power density by increasing the geometric complexity of battery components, such as electrodes and electrolytes. In the present study, bulk three-dimensional Li1+
x Alx Ti2−x (PO4)3(LATP) electrolyte samples were prepared using the laser powder bed fusion (L-PBF) additive manufacturing method. Li3PO4(LPO) was added to LATP to compensate for lithium vaporization during processing. Chemical compositions included 0, 1, 3, and 5 wt. % LPO. Resulting ionic conductivity values ranged from 1.4 × 10−6–6.4 × 10−8S cm−1, with the highest value for the sample with a chemical composition of 3 wt. % LPO. Microstructural features were carefully measured for each chemical composition and correlated with each other and with ionic conductivity. These features and their corresponding ranges include: porosity (ranging from 5% to 19%), crack density (0.09–0.15 mm mm−2), concentration of residual LPO (0%–16%), and concentration and Feret diameter of secondary phases, AlPO4 (11%–18%, 0.40–0.61µ m) and TiO2 (9%–11%, 0.50–0.78). Correlations between the microstructural features and ionic conductivity ranged from −0.88 to 0.99. The strongest negative correlation was between crack density and ionic conductivity (−0.88), confirming the important role that processing defects play in limiting the performance of bulk solid-state electrolytes. The strongest positive correlation was between the concentration of AlPO4 and ionic conductivity (0.99), which is attributed to AlPO4 acting as a sintering aid and the role it plays in reducing the crack density. Our results indicate that additions of LPO can be used to balance competing microstructural features to design bulk three-dimensional LATP samples with improved ionic conductivity. As such, refinement of the chemical composition offers a promising approach to improving the processability and performance of functional ceramics prepared using binderless, laser-based additive manufacturing for solid-state battery applications. -
more » « less
Abstract An organism’s ability to control the timing and direction of energy flow both within its body and out to the surrounding environment is vital to maintaining proper function. When physically interacting with an external target, the mechanical energy applied by the organism can be transferred to the target as several types of output energy, such as target deformation, target fracture, or as a transfer of momentum. The particular function being performed will dictate which of these results is most adaptive to the organism. Chewing food favors fracture, whereas running favors the transfer of momentum from the appendages to the ground. Here, we explore the relationship between deformation, fracture, and momentum transfer in biological puncture systems. Puncture is a widespread behavior in biology requiring energy transfer into a target to allow fracture and subsequent insertion of the tool. Existing correlations between both tool shape and tool dynamics with puncture success do not account for what energy may be lost due to deformation and momentum transfer in biological systems. Using a combination of pendulum tests and particle tracking velocimetry (PTV), we explored the contributions of fracture, deformation and momentum to puncture events using a gaboon viper fang. Results on unrestrained targets illustrate that momentum transfer between tool and target, controlled by the relative masses of the two, can influence the extent of fracture achieved during high-speed puncture. PTV allowed us to quantify deformation throughout the target during puncture and tease apart how input energy is partitioned between deformation and fracture. The relationship between input energy, target deformation and target fracture is non-linear; increasing impact speed from 2.0 to 2.5 m/s created no further fracture, but did increase deformation while increasing speed to 3.0 m/s allowed an equivalent amount of fracture to be achieved for less overall deformation. These results point to a new framework for examining puncture systems, where the relative resistances to deformation, fracture and target movement dictate where energy flows during impact. Further developing these methods will allow researchers to quantify the energetics of puncture systems in a way that is comparable across a broad range of organisms and connect energy flow within an organism to how that energy is eventually transferred to the environment.
-
more » « less
Abstract Converting CO2to value‐added chemicals,
e. g ., CH3OH, is highly desirable in terms of the carbon cycling while reducing CO2emission from fossil fuel combustion. Cu‐based nanocatalysts are among the most efficient for selective CO2‐to‐CH3OH transformation; this conversion, however, suffers from low reactivity especially in the thermodynamically favored low temperature range. We herein report ultrasmall copper (Cu) nanocatalysts supported on crystalline, mesoporous zinc oxide nanoplate (Cu@m ZnO) with notable activity and selectivity of CO2‐to‐CH3OH in the low temperature range of 200–250 °C. Cu@m ZnO nanoplates are prepared based on the crystal‐crystal transition of mixed Cu and Zn basic carbonates to mesoporous metal oxides and subsequent hydrogen reduction. Under the nanoconfinement of mesopores in crystalline ZnO frameworks, ultrasmall Cu nanoparticles with an average diameter of 2.5 nm are produced. Cu@m ZnO catalysts have a peak CH3OH formation rate of 1.13 mol h−1per 1 kg under ambient pressure at 246 °C, about 25 °C lower as compared to that of the benchmark catalyst of Cu−Zn−Al oxides. Our new synthetic strategy sheds some valuable insights into the design of porous catalysts for the important conversion of CO2‐to‐CH3OH.
