SEARCH · Engineering Papers

Results for “functionally graded material”

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.

SourceResearch connectionFrom yearThrough year

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

At least 307 records · Page 17

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Antimicrobial properties of a multi-component alloy

High traffic touch surfaces such as doorknobs, countertops, and handrails can be transmission points for the spread of pathogens, emphasizing the need to develop materials that actively self-sanitize. Metals are frequently used for these surfaces due to their durability, but many metals also possess antimicrobial properties which function through a variety of mechanisms. This work investigates metallic alloys comprised of several metals which individually possess antimicrobial properties, with the target of achieving broad-spectrum, rapid sanitation through synergistic activity. An entropy-motivated stabilization paradigm is proposed to prepare scalable alloys of copper, silver, nickel and cobalt. Using combinatorial sputtering, thin-film alloys were prepared on 100 mm wafers with ≈50% compositional grading of each element across the wafer. The films were then annealed and investigated for alloy stability. Antimicrobial activity testing was performed on both the as-grown alloys and the annealed films using four microorganisms—Phi6, MS2, Bacillus subtilis and Escherichia coli —as surrogates for human viral and bacterial pathogens. Testing showed that after 30 s of contact with some of the test alloys, Phi6, an enveloped, single-stranded RNA bacteriophage that serves as a SARS-CoV-2 surrogate, was reduced up to 6.9 orders of magnitude (> 99.9999%). Additionally, the non-enveloped, double-stranded DNA bacteriophage MS2, and the Gram-negative E. coli and Gram-positive B. subtilis bacterial strains showed a 5.0, 6.4, and 5.7 log reduction in activity after 30, 20 and 10 min, respectively. Antimicrobial activity in the alloy samples showed a strong dependence on the composition, with the log reduction scaling directly with the Cu content. Concentration of Cu by phase separation after annealing improved activity in some of the samples. The results motivate a variety of themes which can be leveraged to design ideal antimicrobial surfaces.

36 MATERIALS SCIENCE↗

DOE OSTI2010

ATM Polymorphisms Are Associated With Risk of Radiation-Induced Pneumonitis

Purpose: Since the ataxia telangiectasia mutated (ATM) protein plays crucial roles in repair of double-stranded DNA breaks, control of cell cycle checkpoints, and radiosensitivity, we hypothesized that variations in this gene might be associated with radiation-induced pneumonitis (RP). Methods and Materials: A total of 253 lung cancer patients receiving thoracic irradiation between 2004 and 2006 were included in this study. Common Terminology Criteria for Adverse Events version 3.0 was used to grade RP. Five haplotype-tagging single nucleotide polymorphisms (SNPs) in the ATM gene were genotyped using DNA from blood lymphocytes. Hazard ratios (HRs) and 95% confidence intervals (CIs) of RP for genotypes were computed by the Cox model, adjusted for clinical factors. The function of the ATM SNP associated with RP was examined by biochemical assays. Results: During the median 22-month follow-up, 44 (17.4%) patients developed grade {>=} 2 RP. In multivariate Cox regression models adjusted for other clinical predictors, we found two ATM variants were independently associated with increased RP risk. They were an 111G > A) polymorphism (HR, 2.49; 95% CI, 1.07-5.80) and an ATM 126713G > A polymorphism (HR, 2.47; 95% CI, 1.16-5.28). Furthermore, genotype-dependent differences in ATM expression were demonstrated both in cell lines (p < 0.001) and in individual lung tissue samples (p = 0.003), which supported the results of the association study. Conclusions: Genetic polymorphisms of ATM are significantly associated with RP risk. These variants might exert their effect through regulation of ATM expression and serve as independent biomarkers for prediction of RP in patients treated with thoracic radiotherapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2010

Laser nitriding for niobium superconducting radio-frequency accelerator cavities

Particle accelerators are a key tool for scientific research ranging from fundamental studies of matter to analytical studies at light sources. Cost-forperformance is critical, both in terms of initial capital outlay and ongoing operating expense, especially for electricity. It depends on the niobium superconducting radiofrequency (SRF) accelerator cavities at the heart of most of these machines. Presently Nb SRF cavities operate near 1.9 K, well (and expensively) below the 4.2 K atmospheric boiling point of liquid He. Transforming the 40 nm thick active interior surface layer from Nb to delta NbN (Tc = 17 K instead of 9.2 K) appears to be a promising approach. Traditional furnace nitriding appears to have not been successful for this. Further, exposing a complete SRF cavity to the time-temperature history required for nitriding risks mechanical distortion. Gas laser nitriding instead has been applied successfully to other metals [P.Schaaf, Prog. Mat. Sci. 47 (2002) 1]. The beam dimensions and thermal diffusion length permit modeling in one dimension to predict the time course of the surface temperature for a range of per-pulse energy densities. As with the earlier work, we chose conditions just sufficient for boiling as a reference point. We used a Spectra Physics HIPPO nanosecond laser (l = 1064 nm, Emax= 0.392 mJ, beam spot@ 34 microns, PRF =15 – 30 kHz) to obtain an incident fluence of 1.73 - 2.15 J/cm2 for each laser pulse at the target. The target was a 50 mm diameter SRF-grade Nb disk maintained in a nitrogen atmosphere at a pressure of 550 – 625 torr and rotated at a constant speed of 9 rpm. The materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The SEM images show a sharp transition with fluence from a smooth, undulating topography to significant roughening, interpreted here as the onset of ablation. EPMA measurements of N/Nb atom ratio as a function of depth found a constant value to depths greater than the SRF active layer thickness. Certain irradiation conditions resulted in values consistent with formation of delta NbN. Under certain irradiation conditions, XRD data were consistent only with delta NbN on top of Nb metal. Funding: authored by Jefferson Science Associates LLC under US DOE Contract De-AC05-06OR23177. We are indebted to Prof. P. Schaaf (Goettingen) for the simulation code and helpful discussions.

36 MATERIALS SCIENCE↗

DOE OSTI2010

Late Gastrointestinal Toxicity After Dose-Escalated Conformal Radiotherapy for Early Prostate Cancer: Results From the UK Medical Research Council RT01 Trial (ISRCTN47772397)

Purpose: In men with localized prostate cancer, dose-escalated conformal radiotherapy (CFRT) improves efficacy outcomes at the cost of increased toxicity. We present a detailed analysis to provide further information about the incidence and prevalence of late gastrointestinal side effects. Methods and Materials: The UK Medical Research Council RT01 trial included 843 men with localized prostate cancer, who were treated for 6 months with neoadjuvant radiotherapy and were randomly assigned to either 64-Gy or 74-Gy CFRT. Toxicity was evaluated before CFRT and during long-term follow-up using Radiation Therapy Oncology Group (RTOG) grading, the Late Effects on Normal Tissue: Subjective, Objective, Management (LENT/SOM) scale, and Royal Marsden Hospital assessment scores. Patients regularly completed Functional Assessment of Cancer Therapy--Prostate (FACT-P) and University of California, Los Angeles, Prostate Cancer Index (UCLA-PCI) questionnaires. Results: In the dose-escalated group, the hazard ratio (HR) for rectal bleeding (LENT/SOM grade {>=}2) was 1.55 (95% CI, 1.17-2.04); for diarrhea (LENT/SOM grade {>=}2), the HR was 1.79 (95% CI, 1.10-2.94); and for proctitis (RTOG grade {>=}2), the HR was 1.64 (95% CI, 1.20-2.25). Compared to baseline scores, the prevalence of moderate and severe toxicities generally increased up to 3 years and than lessened. At 5 years, the cumulative incidence of patient-reported severe bowel problems was 6% vs. 8% (standard vs. escalated, respectively) and severe distress was 4% vs. 5%, respectively. Conclusions: There is a statistically significant increased risk of various adverse gastrointestinal events with dose-escalated CFRT. This remains at clinically acceptable levels, and overall prevalence ultimately decreases with duration of follow-up.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

NASA NTRS2013

Manufacture of Lunar Regolith Simulants

The manufacture of lunar regolith simulants can use many technologies unfamiliar to the aerospace industry. Many of these technologies are extensively used in the mining industry. Rock crushing, grinding, process control as a function of particle size, as well as other essential concepts are explained here. Notes are provided on special considerations necessary, given the unusual nature of the desired final product. For example, wet grinding, which is an industry norm, can alter the behavior of simulant materials. As the geologic materials used for simulants can contain minerals such as quartz and pyrite, guidance is provided regarding concepts, risks, measurement, and handling. Extractive metallurgy can be used to produce high-grade components for subsequent manufacture, reducing the compromises inherent in using just rock. Several of the components needed in simulants such as glasses, agglutinates, and breccias are simply not available or not reasonably matched by existing terrestrial resources. Therefore, techniques to produce these in useful quantities were developed and used. Included in this list is the synthesis of specific minerals. The manufacture of two simulants, NU-LHT-1M and NU-LHT-2M, is covered in detail.

D.L. Rickman↗

NASA NTRSDate not supplied

Integrated Bosch Process System Models for In-Situ Oxygen and Carbon Production

In-Situ Resource Utilization (ISRU) technology is a vital component to NASA’s mission of a sustainable presence on the Moon and Mars. Local resources can be leveraged to reduce resupply frequency and mass. Elements of the Bosch process, combined with the carbothermal reduction process, can produce oxygen on the lunar surface with minimal consumables. The Bosch process can also produce oxygen on the Martian surface by using the CO 2 -rich environment. Between both systems, adsorption pump, solar thermal energy, carbon formation reactor, and water recovery subsystems are modeled and integrated to create a functional model in MATLAB software. The model is used to simulate performance of the system and reduce mass, power, and volume requirements. This integrated system model provides a tool to scale ISRU technologies for oxygen and carbon production. The MATLAB model is created by developing a system of independent subsystem models that are solved for their quasi-steady state values which can be integrated with respect to time to determine the change in current states. A flexible time stepping method is used to ensure a high level of accuracy during periods of rapid change while still making use of a simple explicit integration method. The flexible time step is calculated for each independent subsystem and the minimum value from those is used as the overall time step. A flexible time step is calculated by dividing a resolution value, or the maximum change per time step, by the variables current rate of change. The maximum value from all points in space is used for subsystem models that contain multiple values. The process is done for every variable that is being monitored in each subsystem and the global minimum is used as that iteration’s timestep. Several assumptions used in the MATLAB model for fluid flow dynamics, such as 1-D gas flow through the sorption pump, are supported by modeling in Ansys Fluent software. The Lunar oxygen production system is outlined in Fig. 1. The carbothermal reduction subsystem uses solar energy to heat a mixture of lunar regolith and carbon powder to produce carbon monoxide. To begin, the carbon monoxide feeds to the modified Bosch subsystem along with hydrogen gas. The reactants then enter the carbon formation reactor where water and carbon powder are produced. Solar thermal energy is used to add energy to the reactor, but waste heat from the carbothermal process is another potential heat source. The water is collected and electrolyzed to produce hydrogen which reenters the Bosch subsystem, and the oxygen is stored for downstream use. The carbon powder is collected and feeds back into the carbothermal subsystem. The Martian oxygen production system uses the full Bosch process and is outlined in Fig 2. A CO 2 adsorption pump thermally cycles to scrub and pressurize CO 2 from the environment. Along with an initial supply of hydrogen, the reactants enter the Reverse Water Gas Shift Reactor (RWGSR) which produces carbon monoxide and water. Carbon monoxide and unreacted hydrogen enter the carbon formation reactor to produce water and carbon powder. The water is collected from both reactors and electrolyzed to reintroduce hydrogen and store oxygen for propellant production or life support. Carbon is removed from the carbon formation reactor and stored. The adsorption pump utilizes rapid cycle temperature swings within a stack of zeolite coated surfaces. The subsystem model solves 1-D quasi-steady conservation laws of the quasi-steady form, shown in Eq. 1, for the gas stream and heat exchange liquid to predict performance parameters such as breakthrough capacity and optimum cycle time. The source term S is used to capture interactions between the fluid flows and the sorbent. A quasi-steady-state scheme is used where no time derivatives appear in the governing equations, except for those in the source terms. This results in an autonomous system, where ∂F/∂x = ƒ(F). The fluxes F are provided at the inlet, and an explicit method is used to solve for the spatial distribution of F. The heat and mass flows to the sorbent are then extracted from the source terms. These flows are numerically integrated to produce a 1-D solution for the system’s state as a function of both time and space. The body of the adsorption pump is separated into two semi-independent models: the heat exchanger fluid flow and gas flow through the zeolite coated surfaces. Both models are solved using the above-described method to find a 1-D solution as a function of space and interact only once a timestep is taken. The interaction point is the sorbent through which all heat transfer between the two models must occur. Sorbent mass adsorption is calculated using the Lagergren model, shown in Eq. 2, where the transfer coefficient, λ D , is found by solving a system of nondimensionalized equations derived by using the heat and mass transfer analogy for transport phenomena. Using Grade 544 Type 13X zeolite as the sorbent material, the equilibrium concentration, θ eq , is calculated using the k-site Langmuir isotherm and fit parameters. Additionally, the enthalpy of adsorption used in the model is computed by interpolation of available data [1]. The subsystem model was validated using the Rapid Cycle Temperature Swing Adsorption (RC-TSA) pump. The solar thermal energy subsystem focuses on a solar concentrator concept with a heat exchanger to heat the reactants before entering the carbon formation reactor. The subsystem model assumes a fixed solar flux and reflector efficiency to calculate the reactant temperature given the incoming temperature, pressure, and exchanger geometry. The receiver is a custom manufactured series of copper blocks with serpentine channels to increase its surface area and the residence time of the reactants to heat up to 550 °C. The subsystem model was validated using a heat exchanger developed at NASA Glenn Research Center (GRC). The solar thermal energy subsystem focuses on a solar concentrator concept with a heat exchanger to heat the reactants before entering the carbon formation reactor. The subsystem model assumes a fixed solar flux and reflector efficiency to calculate the reactant temperature given the incoming temperature, pressure, and exchanger geometry. The receiver is a custom manufactured series of copper blocks with serpentine channels to increase its surface area and the residence time of the reactants to heat up to 550 °C. The subsystem model was validated using a heat exchanger developed at NASA Glenn Research Center (GRC).

In situ Resource Utilization↗

DOE OSTI2019

Designing Open Metal Sites in Metal–Organic Frameworks for Paraffin/Olefin Separations

Incorporating open metal sites (OMS) into metal–organic frameworks allows design of well-defined binding sites for selective molecular adsorption, which has a profound impact on catalysis and separations. We demonstrate that Cu(I) sites incorporated into MFU- 4 l preferentially adsorb olefins over paraffins. Density functional theory (DFT) calculations show that the OMS are independent, with no dependence of binding energy on olefin loading up to one olefin per Cu(I). Experimentally, increasing Cu(I) loading increased olefin uptake without affecting the binding energy, as predicted by DFT and confirmed by temperature-programmed desorption. The potential of this material for olefin/paraffin separation under ambient conditions was investigated by gas adsorption and column breakthrough experiments for an equimolar ratio of olefin/paraffin. High-grade propylene and ethylene (>99.999%) can be generated using temperature–concentration swing recycling from a Cu(I)-MFU-4l packed column with no measurable paraffin breakthrough.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2004

UHTC Composites for Leading Edges

Ultrahigh temperature ceramics (UHTC) have performed unreliably due to material flaws and attachment design. These deficiencies are brought tot he fore by the low fracture tougness and thermal shock resistance of UHTC. In addition, poor oxidation resistance is a limitation on UHTC applicability to reusable launch vehicles. We have been addressing these deficiencies for the past two years via a small task at GRC that is in the Airframe part of the Next Generation Launch Technology Program. Our focus is on UHTC composite (UHTCC) constructions and functional grading to address the mechanical issues and on composition modification to address the oxidation issue. Processing, mechanical property, and oxidation resutls will be reported.

Levine, Stanley R.↗

NASA NTRS2006

Foreign Object Damage in a Gas-Turbine Grade Silicon Nitride by Spherical Projectiles of Various Materials

Assessments of foreign object damage (FOD) of a commercial, gas-turbine grade, in situ toughened silicon nitride ceramic (AS800, Honeywell Ceramics Components) were made using four different projectile materials at ambient temperature. AS800 flexure target specimens rigidly supported were impacted at their centers in a velocity range from 50 to 450 m/s by spherical projectiles with a diameter of 1.59 mm. Four different projectile materials were used including hardened steel, annealed steel, silicon nitride ceramic, and brass. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to appraise the severity of local impact damage. For a given impact velocity, the degree of strength degradation was greatest for ceramic balls, least for brass balls, and intermediate for annealed and hardened steel balls. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles. Impact load as a function of impact velocity was quasi-statically estimated based on both impact and static indentation associated data.

Choi, Sung R.↗

DOE OSTI2010

Toxicity and Outcome Results of a Class Solution With Moderately Hypofractionated Radiotherapy in Inoperable Stage III Non-Small Cell Lung Cancer Using Helical Tomotherapy

Purpose: To prospectively assess the feasibility, toxicity, and local control of a class solution protocol of moderately hypofractionated tomotherapy in Stage III, inoperable, locally advanced non-small-cell lung cancer patients. Methods and Materials: Eligible patients were treated according to a uniform class solution (70.5 Gy in 30 fractions) with fixed constraints and priorities using helical tomotherapy. Toxicity monitoring was performed using the Radiation Therapy Oncology Group criteria and the National Cancer Institute Common Terminology Criteria and Adverse Events (CTCAE) version 3.0. Pulmonary function tests were performed at the start and repeated at 3 months after treatment. Results: Our class solution resulted in a deliverable plan in all 40 consecutive patients. Acute Grade 3 lung toxicity was seen in 10% of patients. Two patients died during acute follow-up with pulmonary toxicity. Correlations were found between changes in pulmonary function test results and mean lung dose or the lung volume receiving 20 Gy (V{sub 20}). The correlation was strongest for lung diffusion capacity for carbon monoxide. A V{sub 20} of >27% and >32% were predictive for Grades 2 and 3 acute lung toxicity respectively (p < 0.05). Late Grade 3 toxicity was exclusively pulmonary, with an incidence of 16%. Overall Grade 3 lung toxicity correlated with a mean lung dose of >18 Gy and a median lung dose of >5 Gy (p < 0.05). Median survival was 17 months, and the 1-year and 2-year local progression-free survivals were 66% and 50%, respectively. Conclusion: The current class solution using moderately hypofractionated helical tomotherapy in patients with locally advanced non-small-cell lung cancer is feasible. Toxicity was acceptable and in line with other reports on intensity-modulated radiotherapy. The local progression-free survival was encouraging considering the unselected population.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2024

ASME Design Code Rule Changes for Nuclear Graphite

The American Society of Mechanical Engineers Boiler Pressure and Vessel Code (ASME BPVC) Section III, Division 5, Article HHA-3000 outlines graphite core component and graphite core assembly design guidelines. Graphite core components are defined as ?components manufactured from graphite that are installed to form a graphite core assembly within the reactor pressure vessel of a high temperature, graphite moderated fission reactor.? (p. 413) Graphites? inherent defect distributions do not allow for deterministic material reliability. Rather, graphite has variable strength distributions which change by grade. Article HHA-3000 outlines two semi-probabilistic methods, the full and simplified assessments, which set design load limit targets for each of three component structural reliability classes. The Design Task Group was officially recognized as a specialized task group within ASME November of 2023, though we?ve been collaborating since 2022. The purpose of the Design Task Group is to correct, clarify, and make HHA-3000 function as intended. The Design Task Group will sunset once we?ve achieved our objectives. The Design Task Group was specifically told to not write new Code. While there may be more precise and more accurate methods to determine reliability targets, the current methods are conservative, relatively simple to implement, and have thus far been considered satisfactory for setting design reliability targets. Much of the ground-work to write proposal files and background documents for records to make the changes needed to achieve our objective have been completed. The Design Task Group has documented much of their work through papers, presentations, and memorandums. Three memorandums in which INL team members had substantial contributions are found in the Appendices: FEA Modeling for the Baseline Program, Evaluating the Effects on Margin of Updating the Threshold and Shape Parameters in the Full Assessment, and Interpretations of the Full and Simplified Assessments in ASME BPVC. Most of the on-going work to achieve the Design Task Group?s objective will be addressing comments on existing records and moving records through the balloting process. The Design Task Group met bi-weekly mostly through the end of FY2023. Since February 2024, the Design Task Group has mostly been completed with solving and documenting the technical issues associated with the assessments. Unless new tasks are identified, the remaining work of the Design Task Group will be political and editorial.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2019

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

High throughput experimental methods are known to accelerate the rate of research, development, and deployment of electronic materials. For example, thin films with lateral gradients in composition, thickness, or other parameters have been used alongside spatiallyresolved characterization to assess how various physical factors affect material properties under varying measurement conditions. Similarly, multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance. In this work, we apply these high throughput experimental methods to thin film transistors (TFTs), demonstrating combinatorial device fabrication and semiautomated characterization using sputtered oxide TFTs as a case study. Here, we show that both extrinsic and intrinsic types of device gradients can be generated in a TFT library, such as channel thickness and length, channel cation compositions, and oxygen atmosphere during deposition. We also present a semi-automated method to measure the 44 devices fabricated on a 50x50mm substrate that can help to identify properly functioning TFTs in the library and finish the measurement in a short time. Finally, we propose a fully automated characterization system for similar TFT libraries, which can be coupled with high throughput data analysis. These results demonstrate that high throughput methods can accelerate the investigation of TFTs and other electronic devices.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Argon Plasma Coagulation Therapy Versus Topical Formalin for Intractable Rectal Bleeding and Anorectal Dysfunction After Radiation Therapy for Prostate Carcinoma

Purpose: To evaluate and compare the effect of argon plasma coagulation (APC) and topical formalin for intractable rectal bleeding and anorectal dysfunction associated with chronic radiation proctitis. Methods and Materials: Thirty men (median age, 72 years; range, 49-87 years) with intractable rectal bleeding (defined as ≥1× per week and/or requiring blood transfusions) after radiation therapy for prostate carcinoma were randomized to treatment with APC (n=17) or topical formalin (n=13). Each patient underwent evaluations of (1) anorectal symptoms (validated questionnaires, including modified Late Effects in Normal Tissues–Subjective, Objective, Management, and Analytic and visual analogue scales for rectal bleeding); (2) anorectal motor and sensory function (manometry and graded rectal balloon distension); and (3) anal sphincteric morphology (endoanal ultrasound) before and after the treatment endpoint (defined as reduction in rectal bleeding to 1× per month or better, reduction in visual analogue scales to ≤25 mm, and no longer needing blood transfusions). Results: The treatment endpoint was achieved in 94% of the APC group and 100% of the topical formalin group after a median (range) of 2 (1-5) sessions of either treatment. After a follow-up duration of 111 (29-170) months, only 1 patient in each group needed further treatment. Reductions in rectal compliance and volumes of sensory perception occurred after APC, but no effect on anorectal symptoms other than rectal bleeding was observed. There were no differences between APC and topical formalin for anorectal symptoms and function, nor for anal sphincteric morphology. Conclusions: Argon plasma coagulation and topical formalin had comparable efficacy in the durable control of rectal bleeding associated with chronic radiation proctitis but had no beneficial effect on anorectal dysfunction.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2022

Optimization of WAAM Process to Produce AUSC Components with Increased Service Life

Additive manufacturing has the potential to revolutionize industrial hardware and unlock efficiency gains through the fabrication of geometries and architectures not possible by conventional processing. Wire Arc Additive manufacturing (WAAM) process is a class of directed energy deposition process enabling higher build rate and allowing custom wire feedstock allowing spatial variation of microstructure. The larger spot size and lower speed creates a larger melt pool, reducing residual stress and often time creating directional/columnar microstructure for Ni-superalloy. The use of flexible platform provides freedom in deposition strategy, which can accommodate complex substrates, including feature addition onto existing structures, non-flat layers, and repair methods. However, the certification of the final component needs to match the strength requirement. Hence, the quality of the component produced is stringently monitored to avoid buildup of residual stress, cracks, porosity and to reduce detrimental segregated phases commonly observed during alloy solidification. Simulation plays a huge role in predicting the melt pool dimension and can be used to optimize the process parameter. Similar development is also required to perform physics-based modeling of microstructural development in WAAM that can predict the microstructural features during solidification and can be used to optimize the process more effectively. To move toward this goal, Raytheon Technologies Research Center together with Siemens worked to create a set of computational tools to control the process parameters, enable on-line measurements and acquisition with feedback to the optimized process parameters, and eventually track material evolution through each step of the additive process. Computational fluid dynamics is used for accurate prediction and calibration of the thermal field during WAAM process. and phase field models for microstructure evolution as a function of processing parameters to establish a connection between additive parameters and the final microstructure. Here we report cellular automata (CA) model development to predict the dendritic microstructure evolution with surface and bulk nuclei for single track and multiple layers. The CA model was developed to account for secondary element addition and predict segregation, local melting, and latent heat release as well as prediction of Euler angles from orientation information and validated against experiments. This framework was utilized to tailor spatially-varying composition in a part by appropriately controlling the microstructure evolution during the additive process. Functionally graded Haynes 282 alloy with high Cr content at the surface was tested for oxidation and mechanical properties. An advanced physics-based reaction-diffusion model predicting the simultaneous creation of chromium oxide and alumina is developed and validated to extend life expectancy of the WAAM manufactured high temperature part. A machine-learning data-driven framework establishing the process-structure relationship from a dataset of real microstructure images and corresponding process history data has been developed and implemented in the NX Siemens design system. The digital twin configuration along with the tool path generation enabled prediction of WAAM component buildup time and the techno-economic analysis provided a favorable option for all 4 cases with 15-40% cost reduction.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2021

Biomaterial–Based Solid–Electrolyte Organic Electrochemical Transistors for Electronic and Neuromorphic Applications

In this work a systematic study of biomaterial–based solid–state organic electrochemical transistors (OECTs) is presented in which biogels consisting of gelatin and glycerol, two food–grade materials, are chosen as the model solid electrolyte. Such gels are fundamentally attractive for bioelectronics and wearable applications due to their superior and tunable electrical and mechanical properties, which allow one to fabricate solid–state organic transistors with high ON/OFF ratio and transconductance, possible millisecond–switching speed, and 6–month stability in ambient air. Next, the authors show a good control of the state–retention property of biogel OECTs, demonstrated herein by employing them as artificial synapses with various synaptic functions, such as frequency–based short–term plasticity. This study herein paves the way for the development of biomaterial–based electronics by providing guiding principles for future works that employ biomaterials in OECTs.

36 MATERIALS SCIENCE↗

NASA NTRS1976

Ferromagnetic-superparamagnetic granulometry of lunar surface materials

A technique of magnetic granulometry is applied to previously reported data for the temperature dependence of isothermal remanent magnetization (IRM) in 13 lunar surface samples, including three soils. Observed increases in IRM with decreasing temperature are attributed to changes from superparamagnetic to single-domain types of behavior for fine metallic-iron particles. Based on this hypothesis, the temperature dependence of IRM in the examined samples is analyzed to obtain particle-size distributions over the range of mean diameters from 30 to 130 A. It is found that the distribution functions for the soils and a low-grade breccia vary as the inverse square of particle volume and that the distributions for recrystallized breccias and igneous rocks apparently peak about mean values.

Schwerer, F. C.↗

NASA NTRS2003

Robust UHTC for Sharp Leading Edge Applications

Ultrahigh temperature ceramics have performed unreliably due to material flaws and attachment design. These deficiencies are brought to the fore by the low fracture toughness and thermal shock resistance of UHTCs. If these deficiencies are overcome, we are still faced with poor oxidation resistance as a limitation on UHTC applicability to reusable launch vehicles. We have been addressing the deficiencies of UHTCs for the past year via a small task at GRC that is part of the 3rd Gen TPS effort. Our focus is on composite constructions and functional grading to address the mechanical issues and on composition modification to address the oxidation issue. The approaches and progress will be reported.

Levine, Stanley R.↗

NASA NTRS2003

UHTC for Sharp Leading Edges

Levine, Stanley R.↗