arXiv subjects

Jonathan A. Malen

Publications and source records attributed to Jonathan A. Malen.

3 recordsLinked to original sources

arXiv2025

Analysis and Uncertainty Quantification of Thermal Transport Measurements through Bayesian Parameter Estimation

The thermal transport community is increasingly interested in rigorous uncertainty quantification (UQ) of their measurements. In this work, we argue that Bayesian parameter estimation (BPE) represents a powerful framework for both analysis/fitting and UQ. We provide a detailed walkthrough of the technique (including code to duplicate our results) and example analysis based on measuring the thermal conductance of a gold/sapphire interface with FDTR. Comparisons are made against traditional analysis/UQ techniques adopted by the thermal transport community. Notable advantages of BPE include the interpretability of its results, including the capacity to indicate incorrect input assumptions, as well as a way to balance overall goodness of fit against prior knowledge of feasible parameter values. In some cases, incorporating this additional information can affect not only the magnitude of error bars but the inferred values themselves.

cond-mat.mtrl-sci↗

arXiv2024

Limits of dispersoid size and number density in oxide dispersion strengthened alloys fabricated with powder bed fusion-laser beam

Previous work on additively-manufactured oxide dispersion strengthened alloys focused on experimental approaches, resulting in larger dispersoid sizes and lower number densities than can be achieved with conventional powder metallurgy. To improve the as-fabricated microstructure, this work integrates experiments with a thermodynamic and kinetic modeling framework to probe the limits of the dispersoid sizes and number densities that can be achieved with powder bed fusion-laser beam. Bulk samples of a Ni-20Cr $+$ 1 wt.% Y$_2$O$_3$ alloy are fabricated using a range of laser power and scanning velocity combinations. Scanning transmission electron microscopy characterization is performed to quantify the dispersoid size distributions across the processing space. The smallest mean dispersoid diameter (29 nm) is observed at 300 W and 1200 mm/s, with a number density of 1.0$\times$10$^{20}$ m$^{-3}$. The largest mean diameter (72 nm) is observed at 200 W and 200 mm/s, with a number density of 1.5$\times$10$^{19}$ m$^{-3}$. Scanning electron microscopy suggests that a considerable fraction of the oxide added to the feedstock is lost during processing, due to oxide agglomeration and the ejection of oxide-rich spatter from the melt pool. After accounting for these losses, the model predictions for the dispersoid diameter and number density align with the experimental trends. The results suggest that the mechanism that limits the final number density is collision coarsening of dispersoids in the melt pool. The modeling framework is leveraged to propose processing strategies to limit dispersoid size and increase number density.

cond-mat.mtrl-sci↗

arXiv2019

Doping-induced superconductivity in the van der Waals superatomic crystal Re$_6$Se$_8$Cl$_2$

Superatomic crystals are composed of discrete modular clusters that emulate the role of atoms in traditional atomic solids$^{1-4}$. Owing to their unique hierarchical structures, these materials are promising candidates to host exotic phenomena, such as superconductivity and magnetism that can be revealed through doping$^{5-10}$. Low-dimensional superatomic crystals hold great promise as electronic components$^{11,12}$, enabling these properties to be applied to nanocircuits, but the impact of doping in such compounds remains unexplored. Here we report the electrical transport properties of Re$_6$Se$_8$Cl$_2$, a two-dimensional superatomic semiconductor$^{13,14}$. Using an in situ current annealing technique, we find that this compound can be n-doped through Cl dissociation, drastically altering the transport behaviour from semiconducting to metallic and giving rise to superconductivity below $\sim$ 9 K. This work is the first example of superconductivity in a van der Waals (vdW) superatomic crystal; more broadly, it establishes a new chemical strategy to manipulate the electronic properties of vdW materials with labile ligands.

cond-mat.mtrl-sci↗