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At least 127 records · Page 7

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DOE OSTI2025

Thick graded interfaces increase wear resistance in Ti/TiN nanolayered thin films

Multilayered composites with nanoscale layer thickness incorporating titanium and titanium nitride (Ti/TiN) are used as a model system to study the effects of heterophase interface structure on elastic and plastic deformation, as well as wear behavior. Here, in this work, hardness, modulus, and wear rate under dry reciprocating sliding contact are quantified as a function of Ti-TiN heterophase interfacial nitrogen gradient thickness for Ti/TiN multilayers with 10–80 nm layer thickness. Hardness and modulus are found to be inversely proportional to layer thickness and independent of interface gradient for most specimens. Wear rate is found to be inversely proportional to interface gradient thickness at constant layer thickness, demonstrating that control of nanoscale interface structure is a valid approach to enhancing wear behavior. The materials studied in this work wear comparably or slower than other Ti- and TiN-based composites in the literature, providing a promising avenue for engineering wear-resistant materials for use in industrially relevant applications.

Graded interfaces↗

DOE OSTI2024

Effect of Surface Oxidation and Crystal Thickness on the Magnetic Properties and Magnetic Domain Structures of Cr 2 Ge 2 Te 6

van der Waals (vdW) magnetic materials, such as Cr 2 Ge 2 Te 6 (CGT), show promise for memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real-space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness-dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a nonmagnetic surface layer that is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. Finally, these findings underscore the impact of thickness and surface oxidation on the properties of CGT, such as saturation field and domain/skyrmionic bubble size, and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Thickness-independent scalable high-performance Li-S batteries with high areal sulfur loading via electron-enriched carbon framework

Abstract Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm −2 , the electrode displays a capacity of 692 mAh g −1 after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability.

36 MATERIALS SCIENCE↗

DOE OSTI2020

The effect of laser entrance hole foil thickness on MagLIF-relevant laser preheat

The magnetized liner inertial fusion (MagLIF) scheme relies on coupling laser energy into an underdense fuel raising the fuel adiabat at the start of the implosion. To deposit energy into the fuel, the laser must first penetrate a laser entrance hole (LEH) foil which can be a significant energy sink and introduce mix. In this paper, we report on experiments investigating laser energy coupling into MagLIF-relevant gas cell targets with LEH foil thicknesses varying from 0.5 μm to 3 μm. Two-dimensional (2D) axisymmetric simulations match the experimental results well for 0.5 μm and 1 μm thick LEH foils but exhibit whole-beam self-focusing and excessive penetration of the laser into the gas for 2 μm and 3 μm thick LEH foils. Additionally, better agreement for the 2 μm-thick foil is found when using a different thermal conductivity model in 2D simulations, while only 3D Cartesian simulations come close to matching the 3 μm-thick foil experiments. The study suggests that simulations may over-predict the tendency for the laser to self-focus during MagLIF preheat when thicker LEH foils are used. This effect is pronounced with 2D simulations where the azimuthally symmetric density channel effectively self-focuses the rays that are forced to traverse the center of the plasma. The extra degree of freedom in 3D simulations significantly reduces this effect. The experiments and simulations also suggest that, in this study, the amount of energy coupled into the gas is highly correlated with the laser propagation length regardless of the LEH foil thickness.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2025

Computational toolkit for predicting thickness of 2D materials using machine learning and autogenerated dataset by large language model

The thickness of 2D materials not only plays a crucial role in determining the performance of nanoelectronic and optoelectronic devices but also introduces complexities in predicting volume-dependent properties, such as energy storage capacity, due to the intrinsic vacuum within these materials. Although a plethora of experimental techniques, including but not limited to optical contrast, Raman spectroscopy, nonlinear optical spectroscopy, near-field optical imaging, and hyperspectral imaging, facilitate the measurement of 2D material thickness, comprehensive data for many materials remain elusive. Over the past decade, the exponential proliferation of 2D materials and their heterostructures has outstripped the capabilities of conventional experimental and computational approaches. In this evolving landscape, machine learning (ML) has emerged as an indispensable tool, offering a scalable approach to augment these traditional methodologies. Addressing the critical gap, we introduce THICK2D—Thickness Hierarchy Inference and Calculation Kit for 2D Materials. This Python-based computational framework harnesses an autogenerated thickness database, developed using large language models, and advanced ML algorithms to facilitate the rapid and scalable estimation of material thickness, relying solely on crystallographic data. To demonstrate the utility and robustness of THICK2D, we successfully used the toolkit to predict the thickness of more than 8000 2D-based materials, sourced from two extensive 2D materials databases. THICK2D is disseminated as an open-source utility, accessible on GitHub at https://github.com/gmp007/THICK2D, and archived on Zenodo at https://10.5281/zenodo.11216648.

Ekuma, Chinedu E. (ORCID:0000000258527556)↗

DOE OSTI2020

Effect of layer thickness on structural, morphological and superconducting properties of Nb 3 Sn films fabricated by multilayer sequential sputtering

Superconducting Nb3Sn films can be synthesized by controlling atomic concentration of Sn. Multilayer sequential sputtering of Nb and Sn thin films followed by high temperature annealing is considered as a method to fabricate Nb3Sn films where Sn composition of deposited films can be controlled by controlling the thickness of alternating Nb and Sn layers. We report on the structural, morphological and superconducting properties of Nb3Sn films fabricated by multilayer sequential sputtering of Nb and Sn films on sapphire substrates with ex-situ annealing at 950 °C for 3 h. We have investigated the effect of Nb and Sn layer thickness on the properties of Nb3Sn films. The thicknesses of Nb and Sn layers were varied in two ways: (1) varied Nb:Sn thickness ratio (1:1, 2:1, 3:1, 4:1), and (2) varied layer thickness of both Nb and Sn layers, while keeping constant Nb:Sn thickness ratio of 2:1. The crystal structure, surface morphology, topography, and film composition were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDS) respectively. The results showed Sn loss from the surface due to evaporation during annealing. Superconducting Nb3Sn films of critical temperature up to 17.93 K have been achieved.

Sayeed, M. N.↗

DOE OSTI2022

Different CT slice thickness and contrast‐enhancement phase in radiomics models on the differential performance of lung adenocarcinoma

Abstract Background To investigate the effects of computed tomography (CT) reconstruction slice thickness and contrast‐enhancement phase on the differential diagnosis performance of radiomic signature in lung adenocarcinoma. Methods A total of 187 patients who had been pathologically confirmed with lung adenocarcinoma and nonadenocarcinoma were divided into a training cohort ( n = 149) and validation cohort ( n = 38). All the patients underwent contrast‐enhanced CT and the images were reconstructed with different slice thickness. The radiomic features were extracted from different slice thickness and scan phase. The logistic regression (LR) algorithm was used to build a machine learning model for each group. The area under the curve (AUC) obtained from the receiver operating characteristic (ROC) curve and DeLong test was used to evaluate its discriminating performance. Results Finally, 34 image features and five semantic features were selected to establish a radiomics model. Based on the three contrast‐enhanced CT phases and four reconstruction slice thickness, 12 groups of radiomics models showed good discrimination ability with the AUCs range from 0.9287 to 0.9631, sensitivity range from 0.8349 to 0.9083, specificity range from 0.825 to 0.925 in the training group. Similar results were observed in the validation group. However, there was no statistical significance between the different CT scan phase groups and different slice thickness ( p > 0.05). Conclusions The radiomic analysis of contrast‐enhanced CT can be used for the differential diagnosis of lung adenocarcinoma. Moreover, different slice thickness and contrast‐enhanced scan phase did not affect the discriminating ability in the radiomics models.

Wang, Yang↗

DOE OSTI2023

Burst Pressure Solutions of Thin and Thick-Walled Cylindrical Vessels

Pressure vessels (PVs) are widely used in the energy industry. Accurate burst pressure is critical to structural design and safe operation for both thin and thick-walled PVs. The traditional strength theories utilized a single-parameter material property, such as the yield stress or the ultimate tensile stress (UTS) to develop failure models for determining the yield or ultimate pressure carrying capacity in the PV design. The UTS-based Barlow formula is a typical burst pressure model developed from the Tresca strength theory that provides the basis for developing regulation rules and failure models for different industry design codes, such as ASME BPVC, ASME B31.3, and ASME B31G, among others. In order to reduce the conservatism of the Tresca strength model, ASME BPVC recently adapted failure models developed from the von Mises strength theory for the PV design and analysis. It has been commonly accepted that the burst pressure of pipelines depends on the UTS and strain hardening exponent, n, of the pipeline steel. An average shear stress yield theory was thus developed, and the Zhu-Leis solution of burst pressure was obtained as a function of UTS and n for thin-walled line pipes. Experiments showed that the Zhu-Leis solution provides an accurate, reliable prediction of burst pressure for defect-free thin-walled pipes. In order to extend the Zhu–Leis solution to thick-walled cylindrical PVs, this paper defined three new flow stresses, modified the traditional strength theories, and obtained three new burst pressure solutions that are valid for both thin and thick-walled cylindrical vessels. The proposed flow stresses are able to describe the tensile strength and the plastic flow response of PVs for a strain hardening steel. The associated strength theories were then developed in terms of the Tresca, von Mises, and Zhu-Leis yield criteria. From these new strength theories, three burst pressure solutions were obtained for thick-walled cylinders, where the von Mises solution is an upper bound prediction, the Tresca solution is a lower bound prediction, and the Zhu-Leis solution is an intermediate prediction of burst pressure for thick-walled cylinders. Lastly, the proposed burst pressure solutions were evaluated and validated by two large datasets of full-scale burst tests for thick-walled tubes and for thin-walled pipes.

42 ENGINEERING↗

DOE OSTI2024

Effect of Sample Thickness on the Tensile Strength of Small Graphite Discs

This report formally documents the completion of the Advanced Reactor Technologies (ART) Level 3 Milestone (M3TG-24OR0501054), “Continue activities related to Split Disc-DIC - complete analysis of effect of sample thickness on one fine grain graphite,” due May 31, 2024. Details within this report outline the status of activities aimed at elucidating the effect of sample thickness on the tensile strength measurement using the small-disc, split-disc testing standard in support of the US Department of Energy’s ART Graphite R&D Program. The ASTM D8289, Standard Test Method for Tensile Strength Estimate by Disc Compression of Manufactured Graphite, was developed to provide an alternative means for testing tensile strength on smaller specimens, which are compatible with available irradiation capsule volumes, and other compatibility measurements. ASTM D8289 specifies that acceptable specimen diameter can range from 6 to 12.7 mm and that the maximum allowed sample thickness should be half of the diameter. However, information is limited with respect to the effect of thickness on the measured splitting tensile strength. This report documents efforts to understand the effect of sample thickness on splitting tensile strength. The work involved testing Ø12.7 mm samples of fine-grain graphites 2114 and IG-110 of different thicknesses (6.35, 5, 4, and 3 mm). The digital image correlation (DIC) method was applied to the samples, along with the ASTM D8289 Standard, to help interpret the measured results.

36 MATERIALS SCIENCE↗

NASA NTRS1978

Bounds on thickness and loading noise of rotating blades and the favorable effect of blade sweep on noise reduction

The maxima of amplitudes of thickness and loading noise harmonics are established when the radial distribution of blade chord, thickness ratio, and lift coefficient is specified. It is first shown that only airfoils with thickness distribution and chordwise loading distributions which are symmetric with respect to midchord need be considered for finding the absolute maxima of thickness and loading noise. The resulting chordwise thickness and load distributions for these maximum noise conditions require infinite slope at some points along the chord but otherwise are uniform. It is shown that sweeping the blades reduces the thickness and loading noise, but there is no optimum sweep which generates the lowest noise.

Farassat, F.↗

NASA NTRS1982

Satellite measurements of cloud reflectance and optical thickness

The cloud reflectance and the optical thickness have been computed with the aid of atmospheric models from the first eleven months (April 1970-February 1971) of backscattered ultraviolet (BUV) data over the Pacific Ocean. Both the cloud and the optical thickness are derived from the 380 nm channel by assuming that the entire IFOV (200 km) is filled by stratiform clouds. The analysis shows a large variability in the cloud reflectance in both the intertropic conversion zone (ITCZ) and the high latitudes. It is also found that for 90 percent of the time in the tropics, the clouds have an optical thickness of less than 10. An analysis of clouds with optical thickness between 10 and 20 shows that in the tropics the minimum frequency coincides with the dry zone at 2.5 deg S and the maximum frequency for clouds of optical thickness 10-20 is greater in summer than in winter and irrespective of the season; 50 percent of the time the clouds have an optical thickness less than 13.

Ahmad, Z.↗

NASA NTRS1983

El Chichon eruption cloud - Latitudinal variation of the spectral optical thickness for October 1982

Sun photometer measurements of the spectral optical thickness of the El Chichon eruption cloud were obtained during an airborne latitudinal survey. The measured optical thicknesses were greatly enhanced over background levels for the stratosphere. The observations covered 44 deg N to 36 deg S, and increased optical thickness was found at all latitudes where measurements were made. Significant variations in the magnitude and spectral dependence of the optical thickness were found within the latitude range covered by the observations. The maximum optical thickness was found at 20 deg N and the minimum was found at 30 deg S. The optical thickness values ranged between 0.13 and 0.017 at 870 nm and between 0.15 and 0.044 at 440 nm.

Spinhirne, J. D.↗

NASA NTRS1984

Minimum wafer thickness by rotated ingot ID wafering

The efficient utilization of materials is critical to certain device applications such as silicon for photovoltaics or diodes and gallium-gadolinium-garnet for memories. A variety of slicing techniques has been investigated to minimize wafer thickness and wafer kerf. This paper presents the results of analyses of ID wafering of rotated ingots based on predicted fracture behavior of the wafer as a result of forces during wafering and the properties of the device material. The analytical model indicated that the minimum wafer thickness is controlled by the depth of surface damage and the applied cantilever force. Both of these factors should be minimized. For silicon, a minimum thickness was found to be approximately 200 x 10 - 6th m for conventional sizes of rotated ingot wafering. Fractures through the thickness of the wafer rather than through the center supporting column were found to limit the minimum wafer thickness. The model suggested that the use of a vacuum chuck on the wafer surface to enhance cleavage fracture of the center supporting core and, with silicon, by using 111-line-type ingots could have potential for reducing minimum wafer thickness.

Chen, C. P.↗

NASA NTRS1989

Ellipsometric measurement of liquid film thickness

The immediate objective of this research is to measure liquid film thickness from the two equilibrium phases of a monotectic system in order to estimate the film pressure of each phase. Thus liquid film thicknesses on the inside walls of the prism cell above the liquid level have been measured elliposmetrically for the monotectic system of succinonitrile and water. The thickness varies with temperature and composition of each plane. The preliminary results from both layers at 60 deg angle of incidence show nearly uniform thickness from about 21 to 23 C. The thickness increases with temperature but near 30 C the film appears foggy and scatters the laser beam. As the temperature of the cell is raised beyond room temperature it becomes increasingly difficult to equalize the temperature inside and outside the cell. The fogging may also be an indication that solution, not pure water, is adsorbed onto the substrate. Nevertheless, preliminary results suggest that ellipsometric measurement is feasible and necessary to measure more accurately and rapidly the film thickness and to improve thermal control of the prism walls.

Chang, Ki Joon↗

NASA NTRS1993

Estimates of lithospheric thickness on Venus

Magellan altimetry data have revealed many examples of topographic flexure on Venus. Modeling of flexural features is of interest as it provides information on spatial (and for the earth, temporal) variations in lithospheric thickness. Lithospheric thickness may be determined solely from modeling topographic flexure or by combining gravity and topography data. On Venus even the highest resolution gravity is insufficient for modeling all but the very longest wavelength flexural features, so we rely heavily on altimetry data for information about lithospheric thickness. Sandwell and Schubert modeled flexure around four coronae and found lithospheric thicknesses h, in the range 35 - 70 km. Studies of several more flexural features suggests that these are typical of Aphrodite Terra and other chasmata regions on Venus. However lithospheric thicknesses associated with other regions are in the range 15-30 km. McKenzie et al. noted that part of Aphrodite Terra appeared similar in planform and morphology to the subduction zones of the East Indies on Earth. Other flexure studies using Magellan data have looked at smaller coronae (h = 5-30 km) and rifts (h = 8-20 km). It can be seen that the range of thicknesses suggested by studies to date is extremely large, and it is difficult to establish whether their mean is in agreement with that predicted by heat flow scaling arguments (h approximately 18 km). Here we present results from a global study of flexure on Venus, with particular emphasis on the variation in our results with different tectonic settings.

Johnson, C. L.↗

NASA NTRS1993

Retrieval of ice thickness from polarimetric SAR data

We describe a potential procedure for retrieving ice thickness from multi-frequency polarimetric SAR data for thin ice. This procedure includes first masking out the thicker ice types with a simple classifier and then deriving the thickness of the remaining pixels using a model-inversion technique. The technique used to derive ice thickness from polarimetric observations is provided by a numerical estimator or neural network. A three-layer perceptron implemented with the backpropagation algorithm is used in this investigation with several improved aspects for a faster convergence rate and a better accuracy of the neural network. These improvements include weight initialization, normalization of the output range, the selection of offset constant, and a heuristic learning algorithm. The performance of the neural network is demonstrated by using training data generated by a theoretical scattering model for sea ice matched to the database of interest. The training data are comprised of the polarimetric backscattering coefficients of thin ice and the corresponding input ice parameters to the scattering model. The retrieved ice thickness from the theoretical backscattering coefficients is compare with the input ice thickness to the scattering model to illustrate the accuracy of the inversion method. Results indicate that the network convergence rate and accuracy are higher when multi-frequency training sets are presented. In addition, the dominant backscattering coefficients in retrieving ice thickness are found by comparing the behavior of the network trained backscattering data at various incidence angels. After the neural network is trained with the theoretical backscattering data at various incidence anges, the interconnection weights between nodes are saved and applied to the experimental data to be investigated. In this paper, we illustrate the effectiveness of this technique using polarimetric SAR data collected by the JPL DC-8 radar over a sea ice scene.

Kwok, R.↗

NASA NTRS1994

Effects of ply thickness on thermal cycle induced damage and thermal strain

An experimental study was conducted to determine the effects of ply thickness in composite laminates on thermally induced cracking and changes in the coefficient of thermal expansion, CTE. A graphite-epoxy composite material, P75/ERL 1962, in thin (1 mil) and thick (5 mils) prepregs was used to make cross-ply laminates, ((0/90)(sub n))s, with equal total thickness (n=2, n=10) and cross-ply laminates with the same total number of plies (n=2). Specimens of each laminate configuration were cycled up to 1500 times between -250 and 250 F. Thermally induced microdamage was assessed as a function of the number of cycles as was the change in CTE. The results showed that laminates fabricated with thin-plies microcracked at significantly different rates and reached significantly different equilibrium crack densities than the laminate fabricated with thick-ply and n=2. The CTE of thin-ply laminates was less affected by thermal cycling and damage than the CTE of thick-ply laminates. These differences are attributed primarily to differences in interply constraints. Observed effects of ply thickness on crack density was qualitatively predicted by a combined shear-lag stress/energy method.

Tompkins, Stephen S.↗

NASA NTRS1992

Higher order finite element analysis of thick composite laminates

A higher order, sub-parametric, laminated, 3D solid finite element was used for the analysis of very thick laminated composite plates. The geometry of this element is defined by four nodes in the X-Y plane which define a prism of material through the thickness of the laminate. There are twenty-four degrees of freedom at each node; translations at the upper and lower surfaces of the laminate in each of the three coordinate directions, and the derivatives of these translations with respect to each coordinate. This choice of degrees of freedom leads to displacement and strain compatibility at the corners. Stacking sequence effects are accounted for by explicitly integrating the strain energy density through the thickness of the element. The laminated solid element was combined with a gap-contact element to analyze thick laminated composite lugs loaded through flexible pins. The resulting model accounts for pin bending effects that produce non-uniform bearing stresses through the thickness of the lug. A thick composite lug experimental test program was performed, and provided data that was used to validate the analytical model. Two lug geometries and three stacking sequences were tested.

Goering, J.↗