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At least 523 records · Page 29

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Mesh Deformation Boundary Conditions for Three-Dimensional Ablation Solvers

A method for determining boundary node displacements for three-dimensional ablation solvers is developed. The approach is applicable to a wide range of mesh motion algorithms used to determine internal node displacements. The method leverages radial basis functions to analytically define the geometry to which the boundary nodes should be constrained. Constrained optimization, elasticity, and spring analogy solvers are utilized to redistribute the nodes on the evolved geometry surface while maintaining mesh quality. The method is implemented in the CHarring Ablator Response (CHAR) code, and a realistic demonstration case is presented on the Boundary Layer Transition (BOLT) flight experiment configuration. The method is shown to be robust for highly-curved geometries with large domain deformations.

Adam J Amar↗

NASA NTRS2022

Development of an Effective Finite-rate Oxidation Model for NuSil-coated Charred Carbon Preform Ablators

Recently, a detailed effective finite-rate surface chemistry model was developed for the oxidation of FiberForm [1] using the molecular beam experimental data of Poovathingal et al., [2]. FiberForm is the major building block of the thermal protection system (TPS) material Phenolic Impregnated Carbon Ablator (PICA), commonly used by NASA. The surface chemistry model consists of detailed surface reaction mechanisms such as adsorption, desorption, and several types of Langmuir-Hinshelwood (LH) reactions to characterize the oxygen-carbon interactions at the surface. This model provides excellent agreement with the experimental data for oxidation product compositions and corresponding translational energy distributions. Further, an effective oxidation model was constructed that captures the equivalent interaction of oxygen inside the microstructure (including multiple surface collisions) via a modified reactivity for a smooth wall boundary condition. This enables the use of this model directly into Computational Fluid Dynamics (CFD) codes and Material Response (MR) codes to accurately simulate the gas–surface interactions within FiberForm without using the detailed micro-structure. However, this effective model is valid only for the virgin FiberForm. As the TPS material undergoes ablation, the preform carbon burns and turns into char. In addition, PICA is also coated with a protective silicon coating called NuSil for the purpose of mitigating the spread of phenolic dust, and limit contamination during clean room operations. Fig. 1 shows a X-ray microtomography image of a charred NuSil-coated PICA. The NuSil layer introduces species containing silicon into the product mixture. Further, the reactivity of the carbon within the char layer is different from the virgin FiberForm as shown in Fig. 2. Recently a new set of molecular beam experiments were performed on this NuSil-coated TPS material [3] with the same type of oxygen beam used in the previous experiments. Using the latest experimental data, the previously developed effective model will be extended to account for the charred carbon as well as the NuSil coating. Finally, this new effective model with three phases – preform carbon, char, and NuSil; will be compared and validated against the experimental product compositions.

K Swaminathan Gopalan↗

NASA NTRSDate not supplied

Analysis of Pyrolysis Products from Ablative Thermal Protection Systems

NASA’s state-of-the-art ablative materials are composed of a three-dimensional network of carbon fibers impregnated with polymers that dissipate thermal energy through pyrolysis. A fundamental understanding of the decomposition mechanisms and pyrolysis product distributions of various classes of polymers is instrumental in the design of new ablative materials. Furthermore, innovative experiments are essential to the continuous modernization of material response models by providing high-fidelity data. Thus, an apparatus has been designed to measure pyrolysis products from polymers and composite materials by implementing in-situ mass spectrometric techniques. Initial results from experiments performed on siloxane resins and a common phenolic resin will be discussed. Both classes of polymers exhibit heating-rate-dependent decomposition mechanisms. At the onset of heating, phenolic polymers decompose through competitive reactions to form gaseous products and a carbonaceous char. Gas phase products of phenolic resins are typically composed of molecular hydrogen, water, and aromatic hydrocarbons. Pyrolysis products from siloxane polymers include molecular hydrogen, small molecules, and cyclic oligomers from the polymer backbone.

Pyrolysis↗

NASA NTRSDate not supplied

Analysis of Pyrolysis Products from Ablative TPS

Pyrolysis↗

NASA NTRSDate not supplied

Carbon Nanotube – Polysiloxane Nanocomposites for Ablative Thermal Protection Systems

Ultra-high temperature resins (UHTR) such as polysiloxane possess excellent characteristics for ablation including low thermal conductivity, lightweight composition, high thermal resistance, and the ability to form a durable char layer. To enhance its mechanical strength, the aerospace industry utilizes fiber reinforcement, such as carbon fiber reinforced polysiloxane (CF-polysiloxane), due to its high strength-to-weight ratio. Carbon nanotubes (CNTs) have advantages over microfibers including higher specific strength, lower density, and customizable thermal conductivity. Their nano-scale dimensions allow for a more homogenous material compared to traditional microfibers. Conventional methods of incorporating CNTs into resins often have structural defects such as voids, CNT agglomerations, and randomly dispersed CNTs, resulting in marginal improvements in properties. A novel approach known as bulk nanocomposite laminating (BNL) has been introduced involving CNT densification, resin polymer infiltration, and pressurized curing to achieve a high packing density exceeding 35% by volume. Characterization and testing to simulate re-entry conditions is performed with a sample of CNT-polysiloxane nanocomposite cured onto a CF-polysiloxane backing. These samples are subjected to ablation by an oxyacetylene flame while collecting temperature data to evaluate thermal protection properties.

Palak B Patel↗

NASA NTRSDate not supplied

Multiscale Modeling of Woven Ablative Thermal Protection System Materials

The NASA Entry Systems Modeling project maintains a portfolio of computational model and tool development activities focused on reducing performance uncertainties in ablative Thermal Protection System (TPS) materials for NASA missions. The development activities span material scale and strive to allow microstructural characterization of material structure and properties, mesoscale analyses of damage, and macroscale evaluation of heatshield performance and recession in a given aerothermodynamic environment. This talk will detail the application of developed capabilities at all three scales to the woven TPS material that the Agency has selected as the heatshield for the Mars Sample Return Earth Entry System (MSR-EES) mission – 3D Mid-Density Carbon Phenolic (3MDCP). Each of the applications focuses on driving down uncertainties in material performance and thus risk for MSR-EES and other future missions that may leverage woven TPS. At the microscale, machine learning techniques are used to characterize images from destructive microscopy and inform structural variability. At the mesoscale, Lagrangian techniques are used to simulate ballistic impact and interpret damage modes noted in experiments. At the macroscale, coupled flow-material response techniques are validated by Arc Jet testing to enable heatshield design for missions with massive ablation.

Justin B Haskins↗

DOE OSTI2021

Laser ablation sampling system and method

A method and system for sampling a solid sample material can include the step of mounting the sample material on a support. A sample surface is coated with a surface treatment composition in a dry deposition process. A solvent supply conduit for supplying solvent to the sample surface and a solvent exhaust conduit for withdrawing solvent from the sample surface can be provided. Solvent is flowed from the solvent supply conduit to the surface treatment composition and the sample surface such that the solvent contacts the surface treatment composition. A laser beam is directed from a laser source to the sample and the surface treatment composition. The laser beam will ablate the sample and the surface treatment composition in portions intersected by the laser beam. Ablated sample material enters the solvent liquid and will be transported with the solvent away from the sample surface through the solvent exhaust conduit.

Kertesz, Vilmos↗

DOE OSTI2022

Methods for multiphase laser ablation analysis

Methods of liquid and solid materials analysis by laser induced ablation spectroscopy are disclosed. The liquid and solid materials are analyzed in an instrument having one pulsed laser to produce emissive plasma plumes and ablate solid material. Liquid phase samples are aerosolized before streaming to an analysis zone where they are dissociated into a plasma plume. A large number of sites within solid phase sample structures and be analyzed using a movable x-y-z stage and displayed in a chemical map.

Bol'shakov, Alexander A.↗

DOE OSTI2023

Laser ablation sampling system and method

Kertesz, Vilmos↗

DOE OSTI2019

Spatially tracking carbon through the root-rhizosphere-soil system using laser ablation-IRMS

The intimate relationships between plant roots, rhizosphere, and soil are fostered by the release of organic compounds from the plant into soil through various forms of rhizodeposition and the simultaneous harvestingof inorganic nutrients from the soil to the plant. Here we present a method to spatially track and map the migration of plant-derived carbon (C) through roots into the rhizosphere and surrounding soil using laser ablation-isotope ratio mass spectrometry (LA-IRMS). Weused switchgrass microcosms containing soil from field plots at the Kellogg Biological Station (Hickory Corners, Michigan, USA), which have been cropped with switchgrass since 2008. We used a 13 CO 2 tracerto isotopically label switchgrass plants for two diel cycles and tracked subsequent movement of labeled C using the spatially specific (<100 µm resolution) δ 13 C analysis enabled by LA-IRMS.This approach permitted assessment of variable C flow through different roots and enabled mapping of spatial variability of C allocation to the rhizosphere. Highly 13 C-enriched C (consistent with production during the 13 CO 2 application period) extended ~0.5 – 1 mm from the root into the soil, suggesting that the majority of recent plant-derived C was within this distance of the root after 48 hours. Tracking the physical extent of root exudation into the rhizosphere can help evaluate the localization of plant-microbe interactions in highly variable subsurface environments,and the use of the isotopic label can differentiate freshly fixed C (presumably from root exudates) from other types of subsurface C (e.g., plant necromass and microbial turnover). The LA-IRMS technique mayalso serve as a valuable screening technique to identify areas of high activity for additional microbial or geochemicalassays.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2025

Fast-charging lithium-ion batteries: Synergy of carbon nanotubes and laser ablation

Advancing lithium-ion battery (LiB) technology to achieve 10–15-min extreme fast charging (XFC) while maintaining high energy density and longevity poses a significant challenge. Addressing Li-plating is crucial, as it depletes useable Li, causing deterioration and safety issues. Here, this study explores a holistic approach incorporating Single-Wall Carbon Nanotubes (SWCNTs) and Laser Ablation (LA) to mitigate Li-plating while maintaining high charge acceptance under 10–15-min XFC. SWCNTs enhance the electrical conductivity and mechanical integrity of the positive electrode (PE), reducing overall cell overpotential at high charging rates. Concurrently, LA is applied to negative electrodes (NE) to reduce tortuosity of ion-diffusion pathways and increase surface wettability, improving Li-ion transport. Combining SWCNTs in the PE and LA on the NE, our experimental findings demonstrate a significant reduction in Li-plating and maintained high charge acceptance of ~84.33 % after 800 5C (12 min) charge cycles for cells having PE with ~3.3 mAh cm –2 and NE with 3.9 mAh cm –2 loadings. This study highlights the potential of combining SWCNTs and LA to address Li-plating in LiBs and opens new avenues for designing battery systems capable of achieving 10–15-min XFC.

24 POWER TRANSMISSION AND DISTRIBUTION↗

NASA NTRS1965

Thermophysical properties of six charring ablators from 140 deg to 700 deg k and two chars from 800 deg to 3000 deg k

Thermophysical property data for ablation materials - aerodynamic heating of low density phenolic nylon and filled silicone resin

ABLATING MATERIAL↗

DOE OSTI2024

Titanium Dioxide Nanomaterial Ink Production Through Laser Ablation Synthesis in Solution for Printed Electronics Applications

Flexible and printed electronics have become increasingly popular as they make possible the production of flexible, low-cost, multifunction devices that are unachievable through traditional manufacturing methods. The printed films are significantly impacted and thus limited by the existing ink production process. Herein, an alternate technique of generating high-quality titanium dioxide (TiO 2 ) nanoparticle ink compatible with aerosol jet printing using laser ablation synthesis in solution (LASiS) is showcased. Dynamic light scattering data and transmission electron microscopy confirm the particle size distribution. UV–vis measurements are performed, and the Beer–Lambert relationship is used to determine the concentration of the generated ink. The inks generated at two different repetition rates are compared: 200 kHz and 1 MHz. X-Ray diffraction analysis of the aerosol jet printed thin film post-thermal sintering confirms the grain size and phase purity of the printed thin films. This work demonstrates the effectiveness of the LASiS technique in producing printable nanoparticle inks with little-to-no postprocessing.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Monitoring of Thermal-Induced Changes in Liver Stiffness During Controlled Hyperthermia and Microwave Ablation in an Ex Vivo Bovine Model Using Point Shear Wave Elastography

Purpose: To investigate liver stiffness changes—evaluated by point shear wave elastography (pSWE)—in controlled hyperthermia and microwave ablation (MWA) in an ex vivo animal model. Materials and Methods: Five samples of ex vivo bovine liver were uniformly heated to temperatures ranging from 40 to 100 °C. B-mode ultrasound imaging and pSWE were acquired simultaneously, and shear wave velocity (SWV) was measured in a region of interest (ROI). The threshold value of SWV at 60 °C (avg60) was identified. Subsequently, MWA was performed in 11 liver samples at 60 W until avg60 + 0.5 m/s was reached. SWV was measured in ROIs at 10–40 mm from the antenna feed. The correlation of mean values of SWV with location (within, border, or outside necrotic area) at gross pathology was evaluated. Results: In controlled hyperthermia experiments, a steep transition in liver stiffness was observed at 63.0 ± 2.4 °C (SWV 3.54 ± 0.68 m/s). Avg60 was of 2.5 m/s. In 8/9 MWA experiments, interrupted when SWV of 3 m/s was measured, the ROI was at the inner side of the necrotic area border at pathology (accuracy 89%). No correlation between SWV values for outside, border, and within necrosis could be identified. Conclusions: pSWE can provide a velocity threshold predictive of the presence of coagulation necrosis during MWA in ex vivo liver model. However, pSWE is not able to reliably capture changes in stiffness within, at the border, and outside the necrotic zone in this experimental model.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2019

Intratumoral Injection of Hypertonic Glucose in Treating Refractory Pneumothorax Caused by Microwave Ablation: a Preliminary Study

Purpose: The purpose of this technical report is to describe the technique of intratumoral injection of hypertonic glucose combined with low-negative pressure drainage to treat refractory pneumothorax (RP) after microwave ablation (MWA) of lung tumors. Materials and Methods: Between September 2016 and May 2018, four patients who developed RP after MWA of peripheral lung cancer were managed by a combined method, including intratumoral injection of hypertonic glucose and catheter drainage under low-negative pressure. Blood gas values were recorded and compared before the treatment and one-week posttreatment. All patients were followed up for at least one month to monitor the possible recurrence of pneumothorax by chest CT. Results: All patients were successfully treated. One patient received the intratumoral injection of hypertonic glucose twice, while the remaining three patients received a single injection. The technical success rate was 100%. Dyspnea related to RP was significantly relieved in all patients, and PaO{sub 2} and SaO{sub 2} values were higher than those measured before treatment. No patient suffered a recurrence of pneumothorax during the follow-up. Conclusion: The combined method of intratumoral injection of hypertonic glucose and continuous catheter drainage under low-negative pressure might be an effective method to manage RP caused by MWA.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2019

Sacroiliac Joint Ablation Using MR-HIFU

The sacroiliac joint is the culprit in 15–30% of patients with chronic lumbar back pain. Ablation of the posterior sensory nerves supplying the joint is an established treatment option before arthrodesis. We report the successful application of MR-HIFU in a patient with therapy–refractory pain using the Sonalleve MR-HIFU system. The outpatient procedure was performed under spinal anaesthesia and analgosedation. The ramus dorsalis of L5 as well as the lateral branches of the ramus dorsalis S1–S3 was targeted, and tissue peak temperature per sonication was controlled using MR-thermometry. There were no post-interventional complications. Clinical improvement began 4 days post-intervention with complete resolution of the pain after 1 month.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2018

Thermally induced dispersive optical bistability in silver nanosuspensions produced by pulsed laser ablation method

The thermally induced optical bistability in prepared silver (Ag) nanosuspensions have been studied experimentally, using Fabry–Perot and Mach–Zehnder interferometry methods. Two Ag nanosuspensions of different sizes were produced by different fluences of pulsed laser ablation method in distilled water. The pulsed Nd:YAG laser of 7 ns pulse width, 1064 nm wavelength and different fluences was employed to produce Ag nanosuspensions. Experimental observations were performed by an ultraviolet–visible–near infrared spectrophotometry. Structure and size of prepared Ag nanoparticles were diagnosed using transmission electron microscope images. Fabry–Perot and Mach–Zehnder interferometry methods were used to carry out the optical bistability process in prepared Ag nanosuspensions. In two considered interferometers, the obtained phase shifts of the hysteresis loops based on the optical bistability are inversely proportional to the nonlinear refractive index of samples and thickness of Ag nanosuspensions cells. Results indicate that the induced thermal effect of the optical bistability can be tuned by modifying parameters such as the nonlinear refractive index and applied interferometry methods. Hence, a desirable situation for the thermo-optical effects of the optical bistability can be easily realized in Ag nanosuspensions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2019

Laser Ablation Generation of Antimony Selenide Clusters: Laser Desorption Ionization (LDI) Quadrupole Ion Trap Time of Flight Mass Spectrometry

The binary system Sb-Se was studied via laser ablation using antimony-selenium mixtures made from powdered elements in various ratios generating new Sb{sub m}Se{sub n} clusters. The results show that in addition to Sb{sub m}{sup +} (m = 1–8) and Se{sub n}{sup +} (n = 2–9) clusters, a series of Sb{sub m}Se{sub n}{sup +} clusters such as SbSe{sub 1–8}{sup +}, Sb{sub 2}Se{sub 1–6}{sup +}, Sb{sub 3}Se{sub 1–5}{sup +}, Sb{sub 4}Se{sub 1–3}{sup +}, and Sb{sub 5}Se{sub 1,2}{sup +} is generated. In addition, some low intensity oxidized clusters like Se{sub 6}O{sub 2}{sup +}, Se{sub 7}O{sub 2}{sup +}, and SbSe{sub 2-6}O{sub 5}{sup +} and partially hydroxylated clusters (SbSeO{sub 2}H{sub 7}{sup +}, SbSe{sub 5}O{sub 4}H{sup +}) are also formed. In total, 24 new antimony selenide clusters were generated. The knowledge gained can contribute to the elucidation of the structure of Sb{sub m}Se{sub n} glasses. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗