Engineering topics

Welch, Christopher

Publications and source records attributed to Welch, Christopher.

4 records

DOE OSTI2024

Modeling Analysis of Ball-Milling Process for Battery-Electrode Synthesis

The mechanical alloying process is a promising method for synthesizing electrode materials for batteries owing to its benefits such as the ability to produce nanostructured, high-performing electrode alloys, no adverse effects on the solid electrolyte for solid-state batteries, stable production of thick electrodes, simple processing steps, and low processing costs. It is gaining intensive attention in the battery industry as one of the best methods to replace the conventional wet-slurry-solvent method, and its application is rapidly increasing these days. However, the operation is currently conducted purely based on trial-and-error methods without fully utilizing the features of its functions. Here, this may be attributed to a lack of understanding of the effect of operating parameters on the alloying process and final products. Surprisingly, there is a scarcity of the literature conducting fundamental research to comprehend the underlying physics of the entire mechanical alloying process, resulting in a significant knowledge gap. To address this knowledge gap, extensive research was conducted. The existing literature on mechanical alloying was reviewed to comprehend the current state of understanding and to discuss the direction for future research. Mathematical expressions were developed to create physics-based models capable of capturing the entire mechanical alloying process, including milling kinetics and defect-enhanced phase evolution. These methods were then applied to investigate the impact of operating parameters such as milling frequency, initial mole ratio of the alloyed materials, density of grinding balls, and energy required for the powders to become amorphous (i.e., the amorphization energy threshold). This research aimed not only to comprehend the direct effects of these operating parameters but also to unveil the physics underlying the ball-milling process. The results of our study can serve as crucial information for the battery industry in designing or operating the ball-milling process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Effect of Aluminum Oxide on the Performance of Ionic Liquid-Based Aluminum–Air Battery

The aluminum–air (or oxygen) battery has received intense attention in the past because of its excellent benefits such as low cost and high energy density, but due to the challenging issues such as hydrogen evolution and inactive oxide film formation on the Al surface, it could not be fully applied. In this study, 1-Ethyl 3-Methyl Imidazolium Chloride ([EmIm]Cl) and aluminum chloride (AlCl3) are applied to resolve the aforementioned issues. Ex situ component-level and in situ cell-level open circuit voltage (OCV) tests combined with the physics-based model analyses were conducted to investigate the electrochemical reaction behaviors of the Al–air cell. Especially, the effect of aluminum oxide formation on the anode- and cathode-side reactions were analyzed in detail. The oxide film formed at the Al surface strongly was found to significantly impede the electrochemical reaction at the surface, and the film growth was controlled by decreasing the surface tension by aggressive anions. In the cathode side, the aluminum oxide precipitated in the porous cathode electrode was found to decrease the porous reaction area and block reactant access into the reaction sites. The effects of O2 solubility in the electrolyte, initial porosity and thickness of the porous electrode are compared in detailed, and optimal thickness is suggested.

25 ENERGY STORAGE↗

NASA NTRS1998

Technologies for Non-Destructive Evaluation of Surfaces and Thin Coating

A study was made on two commercially available terbium-doped silicate glasses. There is an increased interest in silicate glasses doped with rare-earth ions for use in high-energy particle detection and radiographic applications. These glasses are of interest due to the fact that they can be formed into small fiber sensors; a property that can be used to increase the spatial resolution of a detection system. Following absorption of radiation, the terbium ions become excited and then emit photons via 4f-4f electronic transitions as they relax back to the ground state. The lifetime of these transitions is on the order of milliseconds. A longer decay component lasting on the order of minutes has also been observed. While radiative transitions in the 4f shell of rare-earth ions are generally well understood by the Judd-Olfelt theory, the presence of a longer luminescence decay component is not. Experimental evidence that the long decay component is due, in part, to the thermal release of trapped charge carriers will be presented. In addition, a theoretical model describing the time evolution of the radiation-induced luminescence will be presented.

Manos, Dennis M.↗

NASA NTRS1992

Method of remotely characterizing thermal properties of a sample

A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample.

Heyman, Joseph S.↗