Engineering topics

Gotthold, David W.

Publications and source records attributed to Gotthold, David W..

14 records

DOE OSTI2024

Optically Stimulated Luminescence Data Storage (Abstract)

We will develop a tunable pulsed electron source capable of generating variable intensity highly-focused electron pulses at high repetition rates. Specifically, we need to demonstrate a high-speed variable electron gun capable of generating a variable intensity electron pulse containing between 102 and 105 electrons with an accelerating voltage of 1kV focused into a spot size <100nm in diameter at with a pulse rate >10MHz (with path to 300MHz). This combined performance cannot be achieved by commercially available electron sources. The primary technology path selected for this work will be to use a photocathode approach, where an easily modulated UV laser is used to stimulate electron emission. The approach utilizes the advances made in the development of the Dynamic TEM (DTEM), though this project will be simpler in that the pulse intensity is lower and there is no requirement for coherency. Alternate paths, including using a traditional electron beam modulated using a v-shaped slit and electrostatically deflecting the beam to adjust intensity; will also be considered for future capabilities. The electron source will then be used generate optically stimulated luminescence (OSL) in lithium fluoride (LiF) substrates to demonstrate the potential for OSL to serve as a basis technology for next generation data storage systems.

42 ENGINEERING↗

DOE OSTI2021

Catalytic Reduction of Graphene Oxide Membranes and Water Selective Channel Formation in Water–Alcohol Separations

Graphene oxide (GO) is a promising membrane system for chemical separation applications due to its 2-D nanofluidics properties and an ability to control interplanar spacing for selectivity. The permeance of water, methanol (MeOH) and isopropyl alcohol (IPA) through 5 µm thick membranes was found to be 0.38 ± 0.15, 0.33 ± 0.16 and 0.42 ± 0.31 LMH/bar (liter/m2·h·bar), respectively. Interestingly, the permeance of a water–alcohol mixture was found to be dramatically lower (~0.01 LMH/bar) than any of its components. Upon removing the solvent mixture, the transmembrane flux of the pure solvent was recovered to near the original permeance. The interlayer space of a dried GO membrane was found to be 8.52 Å, which increased to 12.19 Å. 13.26 Å and 16.20 Å upon addition of water, MeOH and IPA. A decrease in d-space, about 2 Å, was consistently observed when adding alcohol to water wetted GO membrane and an optical color change and reduction in permeance. A newly proposed mechanism of a partial reduction of GO through a catalytic reaction with the water–alcohol mixture is consistent with experimental observations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Modeling The Effects of Loading Scenario and Thermal Expansion Coefficient on Potential Failure of Cryo-compressed Hydrogen Vessels

A multiscale thermomechanical model for a simplified Type-3 cryogenic compressed hydrogen (H2) storage vessel is developed in this paper. The model accounts for the temperature-dependent elastic-plastic behavior of the vessel carbon/epoxy composite overwrap and aluminum alloy liner. The homogenized thermo-elastic-plastic behavior for the individual laminas of the vessel layup is obtained by an incremental Eshelby-Mori-Tanka approach associated with a micromechanical failure criterion to predict lamina failure while a standard elastic-plastic constitutive model is used to describe the behavior of a typical aluminum alloy assumed for the liner. The vessel response to external loadings is achieved by a finite element method. Four loading scenarios representing four thermomechanical cycles applied to the vessel are analyzed to evaluate constituent and lamina stresses as well as the associate failure criterion during the cycle according to these scenarios. The model can provide helpful guidance to mitigate thermal stresses by an adequate selection of loading scenario, optimizing the layup and by tailoring thermomechanical properties of the resin matrix.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Systems and methods for data storage and retrieval

A method includes directing a probe beam to a target that includes an array of data portions in a data storage medium arranged so that a beam area of the probe beam extends across a plurality of adjacent data portions, the array including a data portion subset with each data portion of the subset responsive to the probe beam to produce a response illumination, receiving the response illumination at a detector, and determining data values corresponding to the plurality of adjacent data portions based on the received response illumination. Apparatus and systems are also disclosed.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2019

Systems and methods for data storage and retrieval

Gotthold, David W.↗

DOE OSTI2019

Highly Selective Supported Graphene Oxide Membranes for Water-Ethanol Separation

Polyethersulfone (PES)-supported graphene oxide (GO) membrane has been developed by a simple casting approach. This stable membrane is applied for ethanol/water separation at different temperatures. The 5.0 µm thick GO film coated on PES membrane showed a long-term stability over a testing period of one month and excellent water/ethanol selectivity at elevated temperatures. The water/ethanol selectivity is dependent on the ethanol weight percentage in the water/ethanol feed mixtures and the operating temperature. The water/ethanol selectivity was enhanced with an increase of ethanol weight percentage in water/ethanol mixtures and from below 100 at RT to close to 874 at 90 ºC for 90% ethanol/10% water mixture. Molecular simulations of water-ethanol mixtures in graphene bilayers that are considered to play a key role in transport revealed that molecular transport is negligible for layer spacing below 1 nm. The differences in the diffusion of ethanol and water in the bilayer are not consistent with the large selectivity value experimentally observed. The entry of water and ethanol into the interlayer space may be the crucial step controlling the selectivity.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Enhanced graphene oxide membranes and methods for making same

A method for making a graphene oxide membrane and a resulting free-standing graphene oxide membrane that provides desired qualities of water permeability and selectivity at larger sizes, thinner cross sections, and with increased ruggedness as compared to existing membranes and processes.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Advancements and Opportunities for On-board 700 bar Compressed Hydrogen Tanks in the Progression towards the Commercialization of Fuel Cell Vehicles

Fuel cell vehicles are entering the automotive market with significant potential to reduce harmful greenhouse emissions, facilitate energy security, and increase efficiency while providing expected driving range and fill times. One of the challenges for successful commercialization is transitioning the on-board fuel system from liquid gasoline to compressed hydrogen gas. Storing high pressurized hydrogen requires a specialized structural pressure vessel, significantly different in function from a gasoline container. In addition, the lower hydrogen energy combined with highly efficient fuel cell still requires a storage vessel that is four times the volume of a gasoline tank. In the late 1990s, the industry first developed hydrogen tanks based on traditional type 3 and 4 compressed natural gas (CNG) tanks designed for 250 bar service. As fuel cell vehicles developed along with the need for greater driving range, the OEMs increased the hydrogen storage pressure to 350 bar and then to 700 bar, which is currently the industry norm. However, the 700 bar pressure vessels continued to be manufactured using the materials and the design approach from the CNG tank technologies. In 2012 the U.S. Department of Energy, Office of Fuel Cell Technologies initiated a project to develop Enhanced Materials and Design Parameters for Reducing the Cost of Hydrogen Storage Tanks. The project took a holistic approach to improving performance by investigating: 1) the cost tradeoff of reduced composite mass at 500 bar versus the added insulation cost for cold gas operation at 200K, 2) using hybrid fiber layups to refine the tank composite design, 3) increasing the composite translation efficiency by adding nano-reinforcing particles to the resin, and 4) substituting a lower cost alternate resin in the filament winding process. This paper summarizes the effectiveness of these design modifications and considers the outlook for on-board 700 bar compressed hydrogen tank systems to achieve the commercialization goals for fuel cell vehicles.

Hydrogen storage, carbon fiber composite, compo, a↗

DOE OSTI2016

Graphene oxide membranes with high permeability and selectivity for dehumidification of air

Not Available

Shin, Yongsoon↗

DOE OSTI2016

Molecular dynamics simulations reveal that water diffusion between graphene oxide layers is slow

Membranes made of stacked layers of graphene oxide (GO) hold the tantalizing promise of revolutionizing desalination and water filtration if selective transport of molecules can be controlled. We present the findings of a molecular dynamics simulation study of water intercalated between GO layers that have a C/O ratio of 4. We simulated a range of hydration levels from 1 wt.% to 23.3 wt.% water. The interlayer spacing increased upon hydration from 0.8 nm to 1.1 nm. We also synthesized GO membranes that showed an increase in spacing from about 0.7 nm to 0.8 nm and an increase in mass of about 14% on hydration. Water diffusion through GO layers is an order of magnitude slower than that in bulk water, because of strong hydrogen bonded interactions. Most of the water molecules are bound to OH groups even at the highest hydration level. We observed large water clusters that could span graphitic regions, oxidized regions and holes that have been experimentally observed in GO. As a result, slow interlayer diffusion can be consistent with experimentally observed water transport in GO if holes lead to a shorter path length than previously assumed and sorption serves as a key rate-limiting step.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Anomalous water expulsion from carbon-based rods at high humidity

Managing water is critical for industrial applications including CO2 capture, catalysis, bio-oil separations and energy storage. Various classes of materials have been designed for these applications, achieving specific water adsorption capacities at a given relative humidity (RH). Three water adsorption-desorption mechanisms are common to inorganic materials: (1) chemisorption, which may lead to the modification of the first coordination sphere; (2) simple adsorption, which is reversible in nature; or (3) capillary condensation, which is irreversible in nature. Regardless of sorption mechanism, all materials known today increase water adsorption capacity with increasing RH; none exhibit repeated adsorption of water at low humidity and release at high humidity. We present here a material that breaks from this convention: a new class of nitrogen containing carbon rods along with nonstoichiometric FeXSY that adsorb water at low humidity, and spontaneously expel half of the adsorbed water when the RH exceeds a 50–80% threshold. Monolayers of water form on the surfaces of the carbon rods, with the amount of water adsorbed directly linked to the aspect ratio of the rods and the available surface area. This unprecedented water expulsion is a reversible physical process. Once a complete monolayer is formed, adjacent rods in the bundles begin to adhere together via formation of a bridging monolayer, reducing the surface area available for water to adhere to. We believe the unique surface chemistry of these carbon rods can be used on other functionalized materials. Such behaviour offers a paradigm shift in water purification and separation: water could be repeatedly adsorbed from a low humidity vapour stream and then expelled into a pure water vapour stream, or humidity-responsive membranes could change their water permeance or selectivity as a function of RH.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Optically Stimulated Luminescence Based Optical Data Storage

We design, built, and demonstrated a photocathode based pulsed electron system to produce optically stimulated luminescence (OSL) for next generation data storage. We successfully demonstrated 10ps pulses of up to 10 6 electrons and used those pulses to form OSL patterns in LiF without causing mechanical damage. By adjusting the accelerating voltage, we were able to vary the ratio of red to green optical emission, demonstrating a potential path for increasing storage density using orthogonal encoding. We also modeled a new approach to reading data that exploits the unique nature of OSL based data storage where the writing and reading processes have different size scales. Based on the technical demonstrations, we developed a roadmap to increase the storage density beyond 50TB using a standard 5.25” optical storage disc.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Spectroscopic study of graphene oxide membranes exposed to ultraviolet light

Research on graphene oxide (GO) as anything but a precursor material for synthesizing graphene started to pick up in 20061,2 and was soon followed by a first report of freestanding GO membranes (also referred to as GO paper) from R. S. Ruoff’s group at Northwestern University.3 The first GO membranes were prepared by vacuum filtration. More recently, larger scale GO membranes have been prepared by tape casting4 and other methods.5 In step with the development of new fabrication techniques, GO membranes are now tested for a wide array of applications6 ranging from energy-related4,7 or biomedical8 applications to more conventional uses for filtration9 and dehumidification.10 For all these proposed and implemented applications it remains to be seen how sensitive each of them is with respect to chemical and physical changes of the GO membranes over time. In this study, we report the effects of UV exposure on 2D-hierarchically stacked (Fig. S1 in ESI†) GO membranes. Macroscopically observable changes, such as darkening and mechanical deformation, have been correlated to chemical changes at the molecular level through spectroscopic measurements. Not only do the results of this work offer insights into the stability of GO membranes under UV light, but the findings will enable researchers, who are studying the use of these materials for different applications, to better understand the shelf life and packaging requirements for GO membranes. Furthermore, our results demonstrate the feasibility of deep ultraviolet (DUV) photolithography for graphene oxide-based devices. This approach is readily scalable as opposed to previous reports on photolithographic patterned reduction of GO to graphene by AFM,11 electron-beam12 or with an extreme ultraviolet (λ = 46.9 nm) laser.13

Schwenzer, Birgit↗

DOE OSTI2016

Scalable Production Method for Graphene Oxide Water Vapor Separation Membranes

ABSTRACT Membranes for selective water vapor separation were assembled from graphene oxide suspension using techniques compatible with high volume industrial production. The large-diameter graphene oxide flake suspensions were synthesized from graphite materials via relatively efficient chemical oxidation steps with attention paid to maintaining flake size and achieving high graphene oxide concentrations. Graphene oxide membranes produced using scalable casting methods exhibited water vapor flux and water/nitrogen selectivity performance meeting or exceeding that of membranes produced using vacuum-assisted laboratory techniques. (PNNL-SA-117497)

Environmental Molecular Sciences Laboratory↗