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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Thermoelectrics: From longitudinal to transverse

Thermoelectric power generation is a promising technology to realize a sustainable society because it directly converts thermal energy into electricity in a solid. Conventional thermoelectric generation is driven by the Seebeck effect, discovered by T.J. Seebeck in 1821, in which a charge current J c is generated in the direction parallel to a temperature gradient ∇T, the longitudinal geometry. Here, the ratio between the generated longitudinal electromotive force and applied ∇T is defined as the Seebeck coefficient. As shown in Figure 1A, a thermoelectric module based on the Seebeck effect typically consists of many pairs (128 for a 12V unit) of p-type and n-type conductors alternately arranged and connected in series. Since the Seebeck coefficient of a p-type (n-type) conductor is positive (negative), the thermopower in each element adds to the total output in the Seebeck module. This configuration is needed to achieve a practical voltage because each element only supplies millivolts but limits the use of thermoelectric generators. The efficiency of thermoelectric generators is characterized by the thermoelectric figure of merit, zT. Despite a 3-fold improvement in zT resulting from materials research over the last two decades, little progress has been made in their practical use; this is ascribed to the technological challenges in contact technology. The contacts on the hot side are subject to thermal degradation. All contacts (512 for a 12V unit) add electrical and thermal contact resistances that reduce the device efficiency to a fraction of that promised by the materials.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Study of Carrier Mobilities in 4H-SiC MOSFETS Using Hall Analysis

The channel conduction in 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs) are highly impacted by charge trapping and scattering at the interface. Even though nitridation reduces the interface trap density, scattering still plays a crucial role in increasing the channel resistance in these transistors. In this work, the dominant scattering mechanisms are distinguished for inversion layer electrons and holes using temperature and body-bias-dependent Hall measurements on nitrided lateral 4H-SiC MOSFETs. The effect of the transverse electric field (E eƒƒ ) on carrier mobility is analyzed under strong inversion condition where surface roughness scattering becomes prevalent. Power law dependencies of the electron and hole Hall mobility for surface roughness scattering are determined to be E$^{-1.8}_{eƒƒ}$ and E$^{-2.4}_{eƒƒ}$, respectively, analogous to those of silicon MOSFETs. Moreover, for n-channel MOSFETs, the effect of phonon scattering is observed at zero body bias, whereas in p-channel MOSFETs, it is observed only under negative body biases. Along with the identification of regimes governed by different scattering mechanisms, these results highlight the importance of the selection of substrate doping and of E eƒƒ in controlling the value of channel mobility in 4H-SiC MOSFETs.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Magnetism and spin-dependent transport phenomena across Verwey and Morin transitions in iron oxide/Pt bilayers

Understanding the influence of phase coexistence and phase transitions on spin transport properties in a ferromagnet/heavy metal (FM/HM) system is of utmost importance for spintronics. Here, we report a comprehensive investigation of the magnetic and spin transport properties of biphase iron oxide (BPIO = α-Fe 2 O 3 +Fe 3 O 4 )/Pt films over a wide temperature range, 10K ≤ T ≤ 300K. In-plane (IP) and out-of-plane (OOP) magnetometry and radio frequency transverse susceptibility measurements confirm the characteristic features of the Verwey and Morin transitions at T V ~ 120K and TM ~ 200 K, respectively. Further, anisotropic magnetoresistance (AMR) is observed in the BPIO film, which arises mainly from the spin polarized tunneling of conduction electrons between neighboring uniformly magnetized grains through the resistive grain boundary. Spin Hall magnetoresistance (SMR) and spin Hall anomalous Hall effect (SH-AHE) are detected in the BPIO/Pt films. Around the T V , the temperature evolution of SMR shows a sharp maximum, while SH-AHE exhibits a steep decrease. Both SMR and SH-AHE are strongly susceptible to the Verwey transition but the Morin transition, indicating that the interfacial magnetism of our BPIO/Pt film is dominated by the Fe 3 O 4 phase rather than the α-Fe 2 O 3 phase.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Creep Behavior of a High-$\gamma^{\prime}$ Ni-Based Superalloy Fabricated via Electron Beam Melting

Additive manufacturing enables the fabrication of complex engineering components previously inaccessible through traditional processes. Nickel-base superalloys with large γ' volume fraction are typically considered non-weldable and therefore exhibit a propensity for cracking during the fusion process. These crack-prone materials, however, are of great importance in gas turbine engines due to their excellent high temperature creep resistance. In this study we investigate the creep behavior of IN738LC produced by the electron beam melting process. Here, we find that with appropriate post-build heat treatment the creep response of material oriented in the build direction exhibits deformation and rupture behavior comparable to that of conventionally cast IN738 & IN738LC. In the transverse direction properties fall below the expected cast behavior, however, we argue this is likely due to differences in grain scale and crystallographic texture. It may be possible to coarsen the grain morphology with appropriate process-parameter optimization in order to reduce the severity of intergranular fracture in the transverse direction. These results illustrate that high temperature properties exhibited by additively manufactured IN738LC are suitable for the hot section of gas turbine engines.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Measuring Orbit Responses with Oscillating Trajectories in the Fermilab Linac

Recording changes in beam transverse positions re-ported by Beam Position Monitors (BPMs) in response to a beam deflection by an upstream dipole corrector (orbit response) is a powerful tool for analysis of accelerator optics and assisting with machine tuning. In the Fermilab Linac, orbit responses are recorded by oscillating the currents of up to 19 correctors, providing faster, drift-resistant measurements through frequency-domain analysis. This report describes the technique, including error estimations and consistency checks and shows an example of the measurements.

Shemyakin, Alexander V. [Fermilab] (ORCID:00000001↗
DOE OSTI2025

Impact of droplet oxidation on mechanical properties of an Al-7Si-0.4Mg alloy fabricated with liquid metal jetting

Droplet-on-demand liquid metal jetting (DOD-LMJ) is a new method for additive manufacturing of bulk structural alloys. Here, we report on the microstructure, tensile, and fatigue properties of an Al-7Si-0.4Mg (A356) alloy fabricated with LMJ. Liquid metal droplets were shielded by high-purity Ar gas shroud during deposition. Atom probe tomography revealed that a few nanometers thick (Al-Mg-Si)-O oxide film formed on the droplets despite Ar gas shielding. Tensile tests on peak-aged LMJ A356 alloy showed that yield strength was isotropic (250 MPa), but ductility was lower in the build direction (6.1 ± 1.4 %) compared to the transverse direction (9.4 ± 1.0 %). Lower ductility in the build direction was attributed to delamination of metal-oxide interfaces at layer boundaries. The ductility and yield strength of LMJ A356 were similar to cast A356 and laser powder bed fused (LPBF) A357 alloys, indicating the limited impact of oxide film on tensile properties. The oxide film severely impacted the fatigue properties. Fatigue resistance of LMJ A356 was limited by fatigue crack initiation at lack-of-fusion defects and fatigue crack propagation along layer boundaries by delamination of the metal-oxide interface. The fatigue strength of LMJ A356 at 60 MPa was lower than cast A356 and LPBF A357 alloys in the peak-aged condition. This research underscores the need for managing droplet oxidation during LMJ additive manufacturing of structural alloys.

42 ENGINEERING↗
DOE OSTI2026

High-temperature mechanical properties of a γ′-strengthened Co-based superalloy designed for additive manufacturing

GammaPrint®-700 is a recently developed high γ′ (∼70% volume fraction) CoNi-based superalloy designed to combine high-temperature mechanical performance with laser powder bed fusion processability. Room-temperature yield strength ranged from 610 to 658 MPa and increased to 661 MPa (longitudinal) and 730 MPa (transverse) at 760 °C. The creep behavior compared favorably to high-γ′ Ni-based superalloys manufactured via laser powder bed fusion such as Incoloy® 939 and Inconel® 738LC. In-situ neutron diffraction data measured during creep revealed that plastic deformation was largely localized to the γ phase at 760 °C, allowing the γ’ phase to elastically compensate and maintain creep strain resistance. Furthermore, at 900 °C, this load sharing behavior was weakened, contributing to accelerated creep rate and rupture.

Creep↗
DOE OSTI2021

Transverse impact by RCCs on S-glass and Kevlar® FRC strips

This study aims to isolate interactions between plies and tows and reveal fundamental physics involved in transverse impact on fiber-reinforced composite (FRC) structures. Composite strips were sectioned from large panels and characterized by optical photography, three-dimensional synchrotron X-ray computed tomography, and scanning electron microscopy (SEM). Each strip was impacted perpendicularly by a right circular cylinder (RCC) projectile at a velocity ranging from ~ 150 to 600 m/s. The global strip behavior, as well as localized deformation and failure of the strip near the projectile corner, were both captured by high-speed optical imaging. S-Glass FRC strips were observed to fail in tension ahead of the RCC projectiles’ flat surfaces while Kevlar® FRC strips fractured at the projectile corners. The concept of critical velocity region previously used for impact on yarns was introduced to define different failure modes of each composite strip type. The strip damage extent was found to increase with the impact velocity and reach the maximum at the upper limit of the critical velocity region. Above the critical velocity region, the damage extent decreased with impact velocity. Wave propagations and load histories in the composite strips during impact were quantified and compared with Smith’s theory. Finally, critical velocities of single fibers, yarns, and composite strips and ballistic limits of single-ply and multi-ply composite panels were compared to provide insight into the design of impact-resistant fabrics and composites.

42 ENGINEERING↗
DOE OSTI2020

Prime Editing Technology and Its Prospects for Future Applications in Plant Biology Research

Many applications in plant biology requires editing genomes accurately including correcting point mutations, incorporation of single-nucleotide polymorphisms (SNPs), and introduction of multinucleotide insertion/deletions (indels) into a predetermined position in the genome. These types of modifications are possible using existing genome-editing technologies such as the CRISPR-Cas systems, which require induction of double-stranded breaks in the target DNA site and the supply of a donor DNA molecule that contains the desired edit sequence. However, low frequency of homologous recombination in plants and difficulty of delivering the donor DNA molecules make this process extremely inefficient. Another kind of technology known as base editing can perform precise editing; however, only certain types of modifications can be obtained, e.g., C/G-to-T/A and A/T-to-G/C. Recently, a new type of genome-editing technology, referred to as “prime editing,” has been developed, which can achieve various types of editing such as any base-to-base conversion, including both transitions (C→T, G→A, A→G, and T→C) and transversion mutations (C→A, C→G, G→C, G→T, A→C, A→T, T→A, and T→G), as well as small indels without the requirement for inducing double-stranded break in the DNA. Because prime editing has wide flexibility to achieve different types of edits in the genome, it holds a great potential for developing superior crops for various purposes, such as increasing yield, providing resistance to various abiotic and biotic stresses, and improving quality of plant product. In this review, we describe the prime editing technology and discuss its limitations and potential applications in plant biology research.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Effect of Transverse Compression on the Dielectric Breakdown of Power Cable with Ethylene Propylene Rubber Insulation

Understanding of the failure mechanisms of submarine dynamic power cables (SDPC) is critical for innovative design to meet the 2035 cost reduction target of U.S. DOE Floating Offshore Wind Shot. This is important because the current design suffers a significant failure rate in the field. This project explored a multiphysics approach and conducted systematic electro-thermo-mechanical (ETM) experimental study on the power cores extracted from a 15 kV power cable. The power cable had three cores of copper conductor and ethylene propylene rubber (EPR) insulation. An ETM testing system with transverse compression capability was developed. Mechanical loading induced dielectric breakdown. Increasing temperature from room temperature (RT, 22 degrees Celsius) to 90 degrees Celsius resulted in the 67% decrease in the failure mechanical load as defined by the dielectric breakdown. With the same temperature rise, the creep mechanical load was reduced by 70% at a given dielectric breakdown time. The post-test measurement revealed an impressive recovery of electrical resistance, although the dielectric breakdown occurred in the ETM test that would not be captured without the use of ETM testing.

Wang, Hong [ORNL] (ORCID:0000000201730545)↗
DOE OSTI2026

Correlation between microstructure and residual stress formation in friction stir welded armor steels characterized by neutron diffraction

Friction stir welding (FSW) is a solid-state joining process that minimizes the heat-affected zone (HAZ) compared with fusion-based arc welding, making it well suited for joining martensitic armor steels where hardness and ballistic resistance are critical. This study investigates residual stress formation in three defect-free FSW butt-joint configurations relevant to armored-vehicle fabrication: similar rolled homogeneous armor (RHA–RHA, Case 1), similar high-hardness armor (HHA–HHA, Case 2), and dissimilar HHA–RHA (Case 3) joints produced under temperature-controlled conditions (770 °C). Neutron diffraction was employed to quantify the magnitude and spatial distribution of residual stresses in the longitudinal, transverse, and normal directions and to correlate them with weld microstructure and hardness. Tensile residual stresses were concentrated in the softened HAZ, reaching approximately 300 MPa for Case 2 and 400 MPa for Case 1 (≈50–70 % of the base-metal yield strength; ∼581 MPa for RHA and ∼566 MPa for HHA), while compressive residual stresses dominated the stir zone. The spatial extent of tensile stresses scaled with the width of the softened HAZ, which was largest in the dissimilar HHA–RHA joint and smallest in the HHA–HHA joint. Full-width-at-half-maximum (FWHM) analysis revealed low microstrain in overtempered HAZ regions and high microstrain in the stir zone associated with severe plastic deformation and fresh martensite formation. This work demonstrates that residual stress evolution in FSW of martensitic armor steels is governed not primarily by peak temperature or thermal contraction, as inferred from fusion-welding analogies, but by the competition between transformation-induced volumetric expansion and tempering-induced stress relaxation. The relative dominance of these mechanisms is shown to depend on alloy hardenability and local thermal history, leading to more extensive HAZ softening and broader tensile stress regions in the lower-hardenability RHA steel. These findings establish a transferable mechanistic framework for optimizing solid-state joining strategies in high-strength steels and other transformation-hardening alloys beyond armor applications.

Friction stir welding↗
DOE OSTI2026

Measuring orbit responses with oscillating trajectories in the Fermilab Linac

Recording changes in beam transverse positions and longitudinal phase reported by Beam Position Monitors (BPMs) in response to a beam deflection by an upstream dipole corrector or RF cavity phase (orbit response) is a powerful tool for analysis of accelerator optics and assisting with machine tuning. In Fermilab Linac, orbit responses were recorded by oscillating the corrector currents and cavity phases in a sinusoidal manner parasitically during regular operation, simultaneously oscillating up to 19 correctors and 7 cavities at distinct frequencies, providing faster, drift-resistant measurements through frequency-domain analysis. This report describes the technique, including error estimations and consistency checks and shows examples of the measurements.

Shemyakin, Alexander [Fermilab] (ORCID:00000001501↗
DOE OSTI2025

Electrical Resistivity Tomography data from 2016 to 2018 at the Lower Montane site in the East River Watershed, Colorado

This dataset contains time-lapse Electrical Resistivity Tomography (ERT) data along a transect located on the northeast-facing hillslope at the lower montane site (Pumphouse site) in the upper East River Watershed. The monitoring dataset covers the period from November 2, 2016, to August 6, 2018. In addition, the archive also contains a baseline dataset from October 9, 2016. The ERT transect consisted of 128 electrodes with an electrode spacing of 1.25 m. The acquisition system was located in the middle of the transect, about 50 m on one side, and included an MPT (Multi-Phase Technologies) ERT system, a mini computer, and batteries with solar panels. Acquisition occurred daily under normal circumstances. The first 16 electrodes (from the upper end of the transect) could not be used after the cable was damaged during the 2017–2018 winter. Also, due to multiple failures in the power system, the temporal resolution of the data is much lower in 2018 compared to 2016 and 2017. The data have been processed and used in Dafflon et al., 2023, and the baseline dataset was used in Falco et al., 2019 (see reference list). This archive contains the measurements (ER.zip containing csv files) for each of the 326 acquisition times and a filtered version where only electrodes 17 to 128 are included (ERT_sm.zip containing csv files). The archive also contains the baseline dataset and two acquisitions with full reciprocals (ERT_RB.zip containing csv files), as well as all the raw MPT files (ERT_raw_MTP.zip). The geometry (electrode position and elevation) is provided in Universal Transverse Mercator (UTM) 13N Geoid2012AB in the file named ERT_Location.csv. The archive contains 1 *.csv data files, four *.zip files, and three metadata *.csv files. This work was supported by the Watershed Function Science Focus Area at Lawrence Berkeley National Laboratory funded by the US Department of Energy, Office of Science, Biological and Environmental Research under Contract No. DE-AC02-05CH11231.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Anisotropic positive linear and sub-linear magnetoresistivity in the cubic type-II Dirac metal Pd 3 In 7

We report a transport study on Pd 3 In 7 which displays multiple Dirac type-II nodes in its electronic dispersion. Pd 3 In 7 is characterized by low residual resistivities and high mobilities, which are consistent with Dirac-like quasiparticles. For an applied magnetic field (μ 0 H) having a non-zero component along the electrical current, we find a large, positive, and linear in μ 0 H longitudinal magnetoresistivity (LMR). The sign of the LMR and its linear dependence deviate from the behavior reported for the chiral-anomaly-driven LMR in Weyl semimetals. Interestingly, such anomalous LMR is consistent with predictions for the role of the anomaly in type-II Weyl semimetals. In contrast, the transverse or conventional magnetoresistivity (CMR for electric fields E⊥μ 0 H) is large and positive, increasing by 10 3 –10 4 % as a function of μ 0 H while following an anomalous, angle-dependent power law ρ xx α (μ 0 H) n with n(θ) ≤ 1. The order of magnitude of the CMR, and its anomalous power-law, is explained in terms of uncompensated electron and hole-like Fermi surfaces characterized by anisotropic carrier scattering likely due to the lack of Lorentz invariance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Electro-Thermo-Mechanical (ETM) Study on Submarine Dynamic Power Cables (SDPC) for Offshore Wind Transmission

Understanding the failure mechanisms of submarine dynamic power cables (SDPC) is critical for innovative design to meet the 2035 cost reduction target of U.S. DOE Floating Offshore Wind Shot. This is important because the current design suffers a significant failure rate in the field. This project conducted a systematic electro-thermo-mechanical (ETM) experimental study on the power cores extracted from a 15kV power cable with three cores of copper conductor, ethylene propylene rubber (EPR) insulation, and continuously corrugated welded aluminum armor (CCWA). An ETM testing system was developed by integrating a high voltage (HV) amplifier, two ceramic heaters, and a rod-plate transverse compression setup into a mechanical testing machine. Increasing temperature from room temperature (RT, 22 degree C) to 90 degree C resulted in the 67% decrease in the failure mechanical load as defined by the dielectric breakdown. Under creep mechanical loading, the dielectric breakdown time was decreased by 70% for a given mechanical load when the specimen temperature increased from RT to 90oC. The failure strain in both monotonic and creep mechanical loading modes was related to the maximum mechanical load applied. Although the dielectric breakdown occurred in the ETM test, the post-test measurement revealed an impressive recovery of electric resistance. The failure analysis on cross section of tested specimens indicated a sizable gap across insulation layer near the area between copper conductor and loading rod, which apparently resulted from online dielectric failure and offline elastic recovery of components including conductor and insulation layer.

17 WIND ENERGY↗
DOE OSTI2022

Resonant interaction between phonons and PbTe/PbSe (001) misfit dislocation networks

Here this work aims at a quantitative and mechanistic understanding of the dynamic process of the phonon-dislocation interaction in PbTe/PbSe (001) heterostructures using the Concurrent Atomistic-Continuum (CAC) method as the simulation tool. The misfit dislocation network and the atomic-scale dislocation core structure obtained in the simulations are found to agree reasonably well with the experimental observations of the PbTe/PbSe (001) interface. Through visualizing the dynamic interaction between phonons and dislocations, as well as quantifying the dislocation vibration amplitude, the phonon energy transmission, and the thermal resistance of the misfit interfaces, this work has illustrated and quantified two mechanisms for phonon-dislocation interaction: (1) phonon scattering by the strain field of dislocations, and (2) phonon scattering by dislocations that vibrate via the local modes of a dislocation network; the latter, leads to resonant phonon-dislocation interaction, which is manifested as local maxima of out-of-phase vibration of the atoms on the two sides of the slip plane, leading to local minima of the energy transmission in the heterostructure that contains one interface. The local vibrational modes are found to be excited only by shear stress induced by transverse phonons. Among various resonant modes, the one with the lowest frequency has the strongest effect. This work has also demonstrated the collective motion of dislocations under ultrafast phonon pulses. In addition, the dynamic properties of the misfit dislocation network localized within one interface are found to be significantly altered by the presence of misfit dislocations at other interfaces, thus further confirming the cooperative dynamic nature of the motion of dislocations and phonons.

36 MATERIALS SCIENCE↗
DOE OSTI2020

STRUCTURE AND PROPERTIES STUDY ON ENERGY MATERIALS: THERMOELECTRIC MATERIAL TETRAHEDRITE AND LITHIUM ION CONDUCTOR LiPON

Development of efficient energy materials is critical in order to ease the energy demand and reduce our dependence of fossil fuel. Thermoelectric materials are promising due to their capability of generating electrical power by recovering waste heat. The performance of thermoelectric materials is quantified by a dimensionless figure of merit zT, which depends on their properties such as electrical conductivity, Seebeck coefficient and thermal conductivity. Tetrahedrites, a copper antimony sulfosalt mineral, typified by Cu12-xMxSb4S13, where M is a transition metal element such as Ni, Zn, Fe or Mn, have great potential for thermoelectric application due to their relatively high zT (close to 1 at 700 K), earth-abundance, environmental friendliness, favorable electrical properties, and most importantly intrinsic low lattice thermal conductivity (less than 1 W m-1 K-1) in wide temperature. In addition to energy recovery, reliable energy storage devices are also emerging to relieve the energy demand and improve the efficiency of consuming energy resources. Lithium-ion batteries are known to be reliable and successful electrochemical energy storage devices and appliable in various aspects, including laptops, smartphones and electrical vehicles. Lithium phosphorous oxynitride (LiPON) are widely used as thin-film solid-state electrolytes in Li-ion battery, which is the only demonstrated solid-state electrolyte that is quite stable in direct contact with Li metal at potentials from 0-5 V. However, the structure of LiPON, the effects of N doping, and the origin of its good electrochemical stability remains inconclusive.In this thesis, reliable modeling techniques accompanied with experimental tools, are applied to study the thermoelectric material tetrahedrite and the ionic conductor LiPON, in order to study their structural and dynamical properties. Accurate and efficient density-functional theory (DFT) and density-functional tight-binding (DFTB) methods, combined with molecular dynamics (MD) simulations are utilized in order to investigate the structures and properties of these energy materials. The incoherent and coherent atomic dynamics study of tetrahedrite Cu10.5NiZn0.5Sb4S13 provides the origin of softening upon cooling by investigate the motion of Cu12e at different temperatures. The dynamic structure factors in the longitudinal and transverse direction will also be discussed. The Cu movement of Cu-rich tetrahedrite Cu14Sb4S13 is revealed by Cu self-diffusivity, nuclear density map and "nudged elastic band" (NEB). Moreover, we investigate the effect of simulation cell size and basis sets on the DFT-based MD simulation results using tetrahedrite Cu10Zn2Sb4S13 thermoelectric as a model material, showing the advantage of larger cell by accessing smaller Q range. In addition, the low-temperature structural properties of Cu12Sb4S13 is measured by neutron diffraction, which indicates that no cubic to tetragonal transition occurs at metal-semiconductor transition (MST) temperature. Thermoelectric properties such as Seebeck coefficient, electrical resistivity and electrical thermal conductivity will also be investigated. DFTB method is implemented to study the structure and transport properties of Li3PO4 and LiPON, while the exploration of N doping effect is included. Lastly, the LiPON/Li interphase will be revealed in order to study the origin of electrochemical stability

25 ENERGY STORAGE↗
DOE OSTI2025

Interpretation of wide-angle x-ray diffraction patterns from mesophase pitch-based carbon fibers – a simulation and experimental study

Carbon fiber is a critical material in a wide range of industries, where it is highly valued for its high specific strength/stiffness, excellent wear resistance, efficient electrical and thermal transport properties, chemical resistance, and low coefficient of thermal expansion. The properties of a specific carbon fiber are closely tied to its structural characteristics at all length scales. Here, in this work, we applied wide-angle x-ray diffraction to a set of heat-treated mesophase pitch-based carbon fibers, with the goal of elucidating the crystalline structures as a function of fiber orientation. To assist with analysis and interpretation of the experimental data, we employed diffraction pattern simulations using the scalar and vector forms of the Debye scattering equation to determine the influence of basal plane orientation, crystalline ordering (turbostratic-graphitic), and basal plane asymmetry on the diffraction patterns. The results presented here suggest that growth of the transverse crystallites in mesophase pitch-based carbon fiber is fixed until graphitization temperatures are reached. The work completed here provides a framework for the analysis of carbon fiber and other oriented carbon-based materials via diffraction.

36 MATERIALS SCIENCE↗