Search NASA⌕ Search

SEARCH · Search NASA

Results for “Recognizing”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

The Evolution of Community Engagement Through Ongoing Services Provided by the Fernald Preserve Visitors Center - 17402

The Fernald Preserve is located on the site of a former uranium-processing plant that underwent extensive environmental remediation followed by comprehensive ecological restoration. It is managed by the US Department of Energy Office of Legacy Management and is located approximately 29 kilometers (km) (18 miles) northwest of Cincinnati, Ohio. Remedial activities and subsequent ecological restoration have converted the site from an industrial production facility to an undeveloped park, encompassing a series of wetlands, prairies, and forested communities. Although the remediation of buildings and soil contamination was completed in 2006, site aquifer remediation is ongoing and remains a topic of interest to the community. Much of the site is open to the public, with approximately 11 km (7 miles) of year-round walking trails within the 425-hectare (1050-acre) site. The Fernald Preserve Visitors Center is open Wednesdays through Saturdays and site staff are available to accommodate program requests as needed. The Visitors Center was originally requested by stakeholders involved in developing recommendations for the site's final land use. Stakeholders requested a 'multi-use educational facility' that would recognize the site's history, serve as a source of site information, and recognize the contributions of energy workers during the Cold War. This building was converted from a warehouse built to support site cleanup and was ultimately awarded a Platinum rating by the U.S. Green Building Council. The Visitors Center was designed to accommodate site history exhibits, free meeting space for nonprofit groups, and public interpretive programs. It was opened to the public in 2008, and today's ongoing visitor services are continually adapted to meet the needs of current stakeholders. Over time, the interpretive services have evolved to include more diverse onsite cultural and natural history public programs, events, and activities. Today's community engagement efforts include public and private onsite programs and exhibits, public and private offsite programs and displays, meeting space, and regular open hours for the Visitors Center. This paper presents the various methods used to engage the greater Cincinnati community at the Fernald Preserve. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

I Asked 30,000 People in the Nuclear Industry About Safety Culture; This is What I Learned - 19204

Organizations in the nuclear industry place a high value on maintaining the safety of the workforce and community. Some of these organizations do a better job than others when it comes to developing and sustaining a healthy safety culture. We spent six years studying nuclear organizations to better understand the factors that influence safety culture. We used mixed methods to evaluate perceptions of safety culture in these organizations including administering a valid and reliable safety culture survey, conducting one-on-one interviews with managers, and facilitating focus groups with members of the workforce. We analyzed the quantitative and qualitative data collected from more than 30,000 workers in U.S. based organizations. All of the organizations had a nuclear component to their operations. They operated nuclear reactors, processed nuclear materials, decontaminated and decommissioned buildings with radiological contamination, cleaned-up hazardous/mixed waste, and conducted basic science research and development. We talked to craft workers, technicians, engineers, scientific professionals, support personnel, production workers, supervisors and managers. We conducted extensive statistical analysis and learned that, with rare exception, there is a gap between the perceptions of managers and the workforce that they manage. Managers almost always have a more positive perception of safety culture than the people that are actually performing the work. It is not a question of whether there will be a gap; it is simply a matter of the magnitude of the gap. We also learned through exploratory factor analysis that there is one dominant factor that accounted for almost all (75%) of the variance in the perceptions of safety culture. It was the behavior of the leaders, the decisions they made, and the systems they implemented that most influenced the workforce's perception of safety culture. Personal accountability for safety accounted for 14% of the variance, communication and reporting accounted for another 6%. Everything else accounted for the remaining 5%. Management systems, decision making and behavior is the dominant factor and managers almost always have a more positive perception than the people that work for them. People that work in organizations where management exhibits positive decision-making and safety-related behaviors tend to have more positive perceptions of safety culture. Based upon these results, we developed a theory that there were a few important factors on which management could focus on if they sought to influence the safety culture in their organization. Our experience and research suggests that management often fails to recognize five root causes of employee discontent. Employees seek: - To be recognized as an individual; - To be respected; - A sense of stability; - Fairness; - To make a difference. Understanding the perceptions of the workforce is critical because perceptions influence attitudes, which contribute to behaviors that determine individual performance. An organisation's performance is simply the sum of the performance of all of the members of that organization. To change an organisation's safety culture, interventions should target management behavior and decision making for the greatest return on investment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

The Role of Indian Tribes in the Safe, Secure, and Routine Transportation of Spent Nuclear Fuel and High-Level Radioactive Waste - 19463

Far too often federally recognized Indian Tribes are the last stakeholders invited to the table to discuss a particular issue with potentially wide-ranging impacts. Indian tribes were the first governments on this continent. With respect to the future transportation of spent nuclear fuel (SNF) or high-level radioactive waste (HLW), Indian tribes are potentially impacted in a myriad of ways: economics, cultural, environmental, health and safety. Yet few regulators fully understand and appreciate the legal and political standing of Indian tribes. This paper will examine the ways in which Indian tribes must be involved with the planning for safe, secure and routine SNF and HLW shipments and the ways in which the federal government is obligated to involve tribes. Indian tribes are similar to states in that they are responsible for the health and safety of its members (which they themselves define). Tribes, like states, make, implement, interpret, and enforce laws, and provide public services - healthcare, public education, social services, drug treatment, public safety and emergency management, transportation, managing natural resources, public housing, and environmental and cultural preservation. Many tribes also operate economic enterprises - manufacturing, farming, forestry, and gaming. The most basic principle of Indian law is the principle of 'sovereignty,' that is, an Indian tribe possesses all the powers of any sovereign state. Tribal governments are not subject to state or local jurisdiction but are subject to federal jurisdiction. The tribes enjoy a government-to-government relationship (and expectation) with the federal government (i.e., agencies, like the Department of Energy, the Nuclear Regulatory Commission). Of paramount concern to Indian tribes is the doctrine of Trust Responsibility, the general principle that the federal government's conduct 'in dealing with the Indians should therefore be judged by the most exacting fiduciary standards.' With respect to SNF/HLW this means that the federal government has an obligation (or a Trust Responsibility) to ensure that tribal people, lands and resources are protected. Equally important is the expectation that federal agencies will work with the Indian tribes on a government-to-government basis before undertaking any action with potential negative consequences on the tribe's people, land or resources. The concept of government-to-government consultation between Indian tribes and the United States is long standing and well recognized. As expressed in Executive Order 13175, 'Consultation and Coordination with Indian Tribal Governments': 'Consultation - Each federal agency must have an accountable process to ensure meaningful and timely input by tribal officials in the development of regulatory policies that have tribal implications.' The purpose of consultation is to ensure that Indian tribes are consulted before government officials make decisions that may have an impact on their lives and territories. The three agencies involved with SNF and HLW transportation - the US Department of Transportation (DOT), the US Nuclear Regulatory Commission (NRC), and the US Department of Energy (DOE) - have had various degrees of success with respect to direct consultation with Indian tribes. Given that there is plenty of lead-time before the first shipments commence, there should be ample time to develop a strategy for ensuring that tribes are equal partners when planning and preparing for shipments of SNF and HLW to the first interim storage facility. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Climate Challenges and Nonproliferation: Addressing the Issue through Technical Cooperation

Climate change is an urgent global challenge that is already severely impacting many regions of the world. The 2015 Paris Agreement was a landmark achievement, while the 2023 UN COP 28 Climate Conference in Dubai recognized nuclear energy and its applications as a proven and sustainable means to help societies adapt to climate change and take measures to mitigate and, possibly, reverse its effects. Twenty-two countries, supported by over 120 companies, pledged to triple the share of global nuclear energy generation by 2050. The global interest in nuclear applications for peaceful uses has never been higher. The deployment of advanced reactors around the globe – focused primarily on lowering the carbon footprint and allowing for socio-economic development – must be addressed responsibly through setting priorities for its implementation. Tackling the challenges that new technologies, such as advanced reactors, bring to the nonproliferation regime is at the top of the list. The regime stands on the three pillars of the Nuclear Nonproliferation Treaty (NPT): nonproliferation, peaceful uses of nuclear energy, and disarmament. Recognizing the inherent risks of expanding applications of nuclear materials and technologies for peaceful uses, all such efforts must concurrently strengthen the nonproliferation norm enshrined in the NPT. The challenges of adapting to and mitigating climate change with the use of advanced reactors is already impacting the discussions and expectations about the future of the NPT. The dialog with non-traditional domestic, and international partners on a strategic technical cooperation approach is key to proposing and implementing scientific and technical solutions for urgent climate issues, while framing the discussion within nonproliferation requirements and commitments, and demonstrating the underlying value of the NPT in support of peaceful nuclear applications. This paper addresses adaptation to climate challenges and mitigation of them through advanced reactors and establishes nonproliferation linkages that derive from the deployment of this technology. This paper presents an assessment of the benefits of mechanisms for technical cooperation and peaceful uses of nuclear technology in the framework of Article IV of the NPT.

Prah, Christina↗
DOE OSTI2026

Selective Amnesia using Contrastive Subnet Erasure for Class Level Unlearning in Vision Models

We study concept-level forgetting in pretrained vision models: removing an entire semantic category so the system no longer recognizes that object in unseen images and contexts, rather than merely forgetting specific training examples. Prior work either applies blunt global projections or fine-tunes parameters, which can introduce collateral damage to unrelated features, add compute, and become unstable as forgetting strength increases. We introduce Contrastive Subnet Erasure (CSE), a training-free, encoder-centric edit that targets a compact set of channels most responsible for the class and attenuates them in a calibrated manner. The modification is algebraically folded into the subsequent layer, yielding no inference-time overhead and leaving task heads unchanged. To evaluate whether forgetting generalizes beyond the data used to specify the class, we introduce a cross dataset protocol in which the class is defined on a source dataset and performance is measured on a disjoint target dataset drawn from a different distribution with no shared images. This setup tests whether the model still fails to recognize the object when it looks different or appears in new scenes, and it helps avoid overfitting to patterns in the source dataset. Across CIFAR 10, CIFAR 100, and ImageNet under this protocol, CSE achieves stronger forgetting of the target class while better preserving non target utility than existing baselines in both single class and multi class settings. Overall, CSE provides a simple, stable, and deployment-ready mechanism for class-level unlearning in vision.

Kotevska, Olivera [ORNL] (ORCID:0000000316772243)↗
DOE OSTI2018

Structural and histone binding studies of the chromo barrel domain of TIP60

Tat-interactive protein 60 consists of an N-terminal chromo barrel domain (TIP60-CB) and a C-terminal acetyltransferase domain and acetylates histone and nonhistone proteins in diverse cellular processes. While TIP60-CB is thought to recognize histone tails, molecular details of this interaction remain unclear. In this work, we attempted a quantitative analysis of the interaction between the human TIP60-CB and histone peptides, but did not observe any detectable binding by either fluorescence polarization or isothermal titration calorimetry assays. We also determined the crystal structure of the TIP60-CB alone. Analysis of the apo-tructure reveals a putative peptide-binding site that might be occluded by the basic side chain of a residue in a unique β hairpin between the two N-terminal strands of the β barrel, leading to the inability of TIP60-CB to bind histones.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Geoengineering, marine microalgae, and climate stabilization in the 21st century

Abstract Society has set ambitious targets for stabilizing mean global temperature. To attain these targets, it will have to reduce CO 2 emissions to near zero by mid‐century and subsequently remove CO 2 from the atmosphere during the latter half of the century. There is a recognized need to develop technologies for CO 2 removal; however, attempts to develop direct air‐capture systems have faced both energetic and financial constraints. Recently, BioEnergy with Carbon Capture and Storage ( BECCS ) has emerged as a leading candidate for removing CO 2 from the atmosphere. However, BECCS can have negative consequences on land, nutrient, and water use as well as biodiversity and food production. Here, we describe an alternative approach based on the large‐scale industrial production of marine microalgae. When cultivated with proper attention to power, carbon, and nutrient sources, microalgae can be processed to produce a variety of biopetroleum products, including carbon‐neutral biofuels for the transportation sector and long‐lived, potentially carbon‐negative construction materials for the built environment. In addition to these direct roles in mitigating and potentially reversing the effects of fossil CO 2 emissions, microalgae can also play an important indirect role. As microalgae exhibit much higher primary production rates than terrestrial plants, they require much less land area to produce an equivalent amount of bioenergy and/or food. On a global scale, the avoided emissions resulting from displacement of conventional agriculture may exceed the benefits of microalgae biofuels in achieving the climate stabilization goals.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Investigating dominant characteristics of fires across the Amazon during 2005-2014 through satellite data synthesis of combustion signatures

Estimates of fire emissions remain uncertain due to limited constraints on the variations in fire characteristics. Here we demonstrate the utility of space-based observations of smoke constituents in addressing this limitation. We introduce a satellite-derived smoke index (SI) as an indicator of the dominant phase of large-scale fires. This index is calculated as the ratio of the geometric mean of observed fractional enhancements (due to fire) in carbon monoxide and aerosol optical depth to that of nitrogen dioxide. Here we assess the usefulness of this index on fires in the Amazon. We analyze the seasonal, regional, and interannual joint distribution of SI and fire radiative power (FRP) in relation to fire hotspots, land cover, Drought Severity Index, and deforestation rate estimates. We also compare this index with an analogous quantity derived from field data or emission inventories. Our results show that SI changes from low (more flaming) to high (more smoldering) during the course of a fire season, which is consistent with the changes in observed maximum FRPs from high to low. We also find that flaming combustion is more dominant in areas where deforestation fires dominate, while smoldering combustion has a larger influence during drought years when understory fires are more likely enhanced. Lastly, we find that the spatiotemporal variation in SI is inconsistent with current emission inventories. Although we recognize some limitations of this approach, our results point to the utility of SI as a proxy for overall combustion efficiency in the parameterization of fire emission models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Theoretical analysis of non‐ G aussian heterogeneity effects on subsurface flow and transport

Abstract Much of the stochastic groundwater literature is devoted to the analysis of flow and transport in Gaussian or multi‐Gaussian log hydraulic conductivity (or transmissivity) fields, ( x being a position vector), characterized by one or (less frequently) a multiplicity of spatial correlation scales. Yet Y and many other variables and their (spatial or temporal) increments, Δ Y , are known to be generally non‐Gaussian. One common manifestation of non‐Gaussianity is that whereas frequency distributions of Y often exhibit mild peaks and light tails, those of increments are generally symmetric with peaks that grow sharper, and tails that become heavier, as separation scale or lag between pairs of Y values decreases. A statistical model that captures these disparate, scale‐dependent distributions of Y and in a unified and consistent manner has been recently proposed by us. This new “generalized sub‐Gaussian (GSG)” model has the form where is (generally, but not necessarily) a multiscale Gaussian random field and is a nonnegative subordinator independent of G . The purpose of this paper is to explore analytically, in an elementary manner, lead‐order effects that non‐Gaussian heterogeneity described by the GSG model have on the stochastic description of flow and transport. Recognizing that perturbation expansion of hydraulic conductivity diverges when Y is sub‐Gaussian, we render the expansion convergent by truncating Y 's domain of definition. We then demonstrate theoretically and illustrate by way of numerical examples that, as the domain of truncation expands, (a) the variance of truncated Y (denoted by Y t ) approaches that of Y and (b) the pdf (and thereby moments) of Y t increments approach those of Y increments and, as a consequence, the variogram of approaches that of . This in turn guarantees that perturbing to second order in (the standard deviation of Y t ) yields results which approach those we obtain upon perturbing to second order in even as the corresponding series diverges. Our analysis is rendered mathematically tractable by considering mean‐uniform steady state flow in an unbounded, two‐dimensional domain of mildly heterogeneous Y with a single‐scale function G having an isotropic exponential covariance. Results consist of expressions for (a) lead‐order autocovariance and cross‐covariance functions of hydraulic head, velocity, and advective particle displacement and (b) analogues of preasymptotic as well as asymptotic Fickian dispersion coefficients. We compare these theoretically and graphically with corresponding expressions developed in the literature for Gaussian Y . We find the former to differ from the latter by a factor k = ( denoting ensemble expectation) and the GSG covariance of longitudinal velocity to contain an additional nugget term depending on this same factor. In the limit as Y becomes Gaussian, k reduces to one and the nugget term drops out.

Riva, Monica↗
DOE OSTI2018

Global Effects of Superparameterization on Hydrothermal Land‐Atmosphere Coupling on Multiple Timescales

Abstract Many conventional General Circulation Models (GCMs) in the Global Land‐Atmosphere Coupling Experiment (GLACE) tend to produce what is now recognized as overly strong land‐atmosphere (L‐A) coupling. We investigate the effects of cloud Superparameterization (SP) on L‐A coupling on timescales beyond diurnal where it has been recently shown to have a favorable muting effect hydrologically. Using the Community Atmosphere Model v3.5 (CAM3.5) and its Superparameterized counterpart SPCAM3.5, we conducted soil moisture interference experiments following the GLACE and Atmospheric Model Intercomparison Project (AMIP) protocols. The results show that, on weekly‐to‐subseasonal timescales, SP also mutes hydrologic L‐A coupling. This is detectable globally, and happens through the evapotranspiration‐precipitation segment. But on seasonal timescales, SP does not exhibit detectable effects on hydrologic L‐A coupling. Two robust regional effects of SP on thermal L‐A coupling have also been explored. Over the Arabian Peninsula, SP reduces thermal L‐A coupling through a straightforward control by mean rainfall reduction. More counterintuitively, over the Southwestern US and Northern Mexico, SP enhances the thermal L‐A coupling in a way that is independent of rainfall and soil moisture. This signal is associated with a systematic and previously unrecognized effect of SP that produces an amplified Bowen ratio, and is detectable in multiple SP model versions and experiment designs. In addition to amplifying the present‐day Bowen ratio, SP is found to amplify the climate sensitivity of Bowen ratio as well, which likely plays a role in influencing climate change predictions at the L‐A interface.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Effects of the Structure of Water Rights on Agricultural Production During Drought: A Spatiotemporal Analysis of California's Central Valley

Abstract California's Central Valley region has been called the “bread‐basket” of the United States. The region is home to one of the most productive agricultural systems on the planet. Such high levels of agricultural productivity require large amounts of fresh water for irrigation. However, the long‐term availability of water required to sustain high levels of agricultural production is being called into question following the latest drought in California. In this paper, we use Bayesian multilevel spatiotemporal modeling techniques to examine the influence of the structure of surface water rights in the Central Valley on agricultural production during the recent drought. California is an important place to study these dynamics as it is the only state to recognize the two dominant approaches to surface water management in the United States: riparian and appropriative rights. In this study, Bayesian spatiotemporal modeling is employed to account for spatial processes that have the potential to influence the effects of water right structures on agricultural production. Results suggest that, after accounting for spatiotemporal dependencies in the data, seniority in surface water access significantly improves crop health and productivity on cultivated lands but does not independently affect the ability to maintain cultivated extent. In addition, agricultural productivity in watersheds with more junior surface water rights shows less sensitivity to cumulative drought exposure than other watersheds, however the extent of cultivation in these same watersheds is relatively more sensitive to cumulative drought exposure.

Nelson, K. S.↗
DOE OSTI2017

A Global Data Analysis for Representing Sediment and Particulate Organic Carbon Yield in Earth System Models

Although sediment yield (SY) from water erosion is ubiquitous and its environmental consequences are well recognized, its impacts on the global carbon cycle remain largely uncertain. This knowledge gap is partly due to the lack of soil erosion modeling in Earth System Models (ESMs), which are important tools used to understand the global carbon cycle and explore its changes. As such, this study analyzed sediment and particulate organic carbon yield (CY) data from 1081 and 38 small catchments (0.1-200 km 2 ), respectively, in different environments across the globe. Using multiple statistical analysis techniques, we explored environmental factors and hydrological processes important for SY and CY modeling in ESMs. Our results show clear correlations of high SY with traditional agriculture, seismicity and heavy storms, as well as strong correlations between SY and annual peak runoff. These highlight the potential limitation of SY models that represent only interrill and rill erosion because shallow overland flow and rill flow have limited transport capacity due to their hydraulic geometry to produce high SY. Further, our results suggest that SY modeling in ESMs should be implemented at the event scale to produce the catastrophic mass transport during episodic events. Several environmental factors such as seismicity and land management that are often not considered in current catchment-scale SY models can be important in controlling global SY. Our analyses show that SY is likely the primary control on CY in small catchments and a statistically significant empirical relationship is established to calculate SY and CY jointly in ESMs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Steady-state supercritical CO 2 and brine relative permeability in Berea sandstone at different temperature and pressure conditions

In this study, we measure steady-state two-phase supercritical CO 2 -brine relative permeabilities in a 61 cm-long Berea sandstone core at three different conditions (408C and 12.41 MPa, 408C and 8.27 MPa, and 608C and 12.41 MPa) under primary drainage. We use pressure taps to obtain pressure drops of individual sections of the core, and X-ray Computed Tomography (CT) to obtain in situ saturation profiles, which together help to mitigate the capillary end effect. We include previously measured relative permeabilities at 208C and 10.34 MPa, and compare all the data using both an eye-test and a statistical test. We find no appreciable temperature and pressure dependence of CO 2 relative permeability within 20–608C and 8.27–12.41 MPa. We find slight changes in the brine relative permeability between supercritical CO 2 conditions (40–608C and 8.27–12.41 MPa) and the liquid CO 2 condition (208C and 10.34 MPa). The temperature and pressure independence of CO 2 relative permeability has been previously recognized and reassured in this work using a capillary-effect-free method. This allows one to use a single CO 2 relative permeability curve in modeling two-phase CO 2 flow within 20–608C and 8.27–12.41 MPa.

58 GEOSCIENCES↗
DOE OSTI2020

Chapter 14: Sustainable Biomass Conversion Process Assessment

Process intensification and integration for sustainable design play an essential role in addressing and alleviating severe sustainable development challenges. It is prudent to evaluate a process design in its early stage development to ensure the process can achieve sustainability goals. The primary goal of a sustainability evaluation is to assess the impact of systems on areas sought to be protected and maintained over time, such as human well-being and ecosystems (Schaubroeck, T. and Rugani, B. (2017). A revision of what life cycle sustainability assessment should entail: towards modeling the net impact on human well-being. Journal of Industrial Ecology 21 (6): 1464-1477). Parenthetically, sustainable process design to convert biomass to fuels and chemicals plays an integral part in the bioeconomy sustainability. It is recognized that the integration of sustainability in process design is core to the mission in developing renewable fuels and should be considered a necessary practice in biorefinery design. This study demonstrates the use of Gauging Reaction Effectiveness for ENvironmental Sustainability of Chemistries with a multi-Objective Process Evaluator (GREENSCOPE) as a tool to help track progress on process sustainability performance attributed to conversion improvement. With the incorporation of a wide range of indicators, GREENSCOPE captures the multi-dimensional aspect of the process design and operation. As opposed to conventional techno-economic analysis and life cycle assessment (in which the focuses are limited to economic and environmental aspects), GREENSCOPE enables the consideration of process intensification and integration for sustainable design. A high-octane gasoline production from woody biomass feedstock is used as a case study to demonstrate the approach.

biomass↗
DOE OSTI2021

Engineering Graphene-Ceramic 3D Composite Foams by Freeze Drying

A 3D graphene foam produced by the chemical vapor deposition (CVD) technique is recognized as an effective nanofiller material, as it does not agglomerate in the matrix. Though CVD facilitates pristine graphene foam production, the method poses limitations in developing large-scale 3D graphene composite foams as advanced engineering materials. In this paper, a freeze-drying (FD) process is used to produce a composite 3D foam, which is a mixture of graphene nanoplatelet (GNP) and a low-temperature co-fired ceramic (LTCC). The freeze-dried GNP-LTCC reticulated 3D composite foam has an average pore size ranging from 70 to 100 μm. Pore size is varied by regulating the heat transfer rate during the freezing process using a thermally conductive aluminum (Al) mold and a thermally insulating acrylonitrile butadiene styrene (ABS) mold. Computational thermal modeling is used to visualize the heat transfer and its effect on foam pore size. Subsequently, a freeze-dried GNP-LTCC composite foam is embedded into the LTCC matrix to form a hierarchical assembly by a spark plasma technique without compromising the 3D structure of the FD foam. This study established that a simple, eco-friendly, and scalable processing methodology can produce advanced graphene-based 3D composite foams as the future tailorable nanofillers for designing multimatrix materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Fracture‐Resistant and Thermally Insulating Ultrahigh‐Temperature Carbide Foams

Dense ultrahigh‐temperature ceramics (UHTCs) carbides are recognized as potential materials for thermal protection systems (TPS) owing to properties beyond existing structural materials’ capabilities. Recent advances in UHTCs have enabled the development of multiscale porous microstructures. Herein, it is highlighted that the porosity in UHTCs are no longer treated as a defect but as a functional property specifically tailored for thermal insulation. It is a promising solution to design and fabricate bulk UHTC foams via a freeze‐drying (FD) approach followed by calibrated pressureless spark plasma sintering. Herein, monolithic TaC and HfC UHTC foams and their composite show the partial solid–solution formation of (Ta, Hf)C with porosity ≥50%. TaC–HfC foam (≈80–92 N) shows an intermediate load‐bearing capability compared to monolithic TaC (≈120–135 N) and HfC (≈28–35 N) foams, with no evident cracking on the sample surface. The thermal conductivity of partial solid‐solution TaC–HfC foam increases up to fivefold compared to parent UHTC foams. In the results, solid solutions’ efficacy and pores’ unidirectionality in providing thermal insulation to TaC–HfC while maintaining its high‐load bearing capability are illustrated. In conclusion, the developed technique establishes a new paradigm shift in UHTCs, expanding their potential for TPS in extreme environments.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Membranes in Solar-Driven Evaporation: Design Principles and Applications

In this study, solar-driven evaporation process brings exciting opportunities to recover clean water and resources in a sustainable way from diverse sources like seawater and wastewater. Separation membranes, as a vital material in many environmental and energy applications, can contribute significantly to this process owing to their structural features. However, the unique roles of membranes in solar evaporator construction and process design are seldom recognized and not summarized yet from scientific principles and application demands, which forms the motivation of this review. Herein, the roles of membranes in different processes based on solar-driven evaporation are focused and the design principles of membrane materials and devices to meet the requirements of these applications are discussed. Fabrication strategies for photothermal membranes are introduced primarily, followed by a discussion on how to design membrane materials, devices, and processes to pursue optimal performance and realize advanced functions accompanied by evaporation. Furthermore, the future of this field is forecast with both challenges and opportunities.

14 SOLAR ENERGY↗
DOE OSTI2023

Influence of Methylammonium Chloride on Wide-Bandgap Halide Perovskites Films for Solar Cells

Wide-bandgap perovskites are of paramount importance as the photoactive layer of the top cell in high-efficiency tandem solar cells. Comparably high Br contents are required to widen the perovskite bandgap. However, the increase in Br content causes heterogeneous halide distribution and photoinstability. Here, in this study, the positive effect of the additive methylammonium chloride (MACl) on the optical and electronic properties of Br-rich perovskite, deposited using N-methyl-2-pyrrolidone (NMP) as co-solvent and the gas quenching method, is investigated. Simultaneous in situ grazing-incidence wide-angle X-ray scattering and photoluminescence spectroscopy are used to track the evolution of the structural and optoelectronic properties of the perovskites with different amounts of Br and MACl during the spin-coating and thermal annealing steps. The formation mechanism is elucidated in the presence of MACl. It is observed that chloride ions inhibit the intermediate phases, favoring the formation of a perovskite phase with higher crystallinity. Nano X-ray fluorescence mapping recognizes Br-richer and poorer nanometric domains, whose average sizes reduce for samples with MACl. In conclusion, it is demonstrated that adding MACl affects the formation of wide-bandgap perovskites via destabilization of the intermediate phases and acts on the homogenization of the halide distribution, leading to improved solar cell performances.

14 SOLAR ENERGY↗