SEARCH · Search NASA

Results for “texturization”

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 703 records · Page 39

All sources NASA NTRS DOE OSTI

DOE OSTI2021

Elucidating the structural properties and reversible regional texture effect of GdB 6 under high pressure

As hard and refractory materials with high chemical resistance and mechanical strength, lanthanide hexaborides (LnB 6 ) have attracted much attention. Among the family of LnB 6 , gadolinium hexaboride (GdB 6 ) occupies a special position due to the half-filled 4f shell of Gd. Here, using in situ synchrotron radiation angle-dispersive X-ray diffraction in a diamond anvil cell at room temperature, the structural stability and compression behavior of GdB 6 are investigated extensively, GdB 6 is observed to be structurally stable up to 73 GPa, and the bulk modulus of 177 GPa is obtained under hydrostatic compression. In this paper, an interesting observation of pressure-induced spotty diffraction rings of GdB6 is reported, its formation mechanism can be well described by the reversible regional texture effect, which highlights the rearrangement of crystal grains under high pressure. The rearrangement mechanism has been well explained by investigating the pressure dependence of full width at half maximum, macro-differential stress and grain size. Collective grain rotation behavior motivated by stress difference is critical for the rearrangement process, the strong isotropy and strong stability of GdB 6 structure also provide necessary conditions for high-pressure grain rotation behavior. These results will help to promote the understanding of high-pressure structural properties of GdB 6 , and provide novel insights on the high-pressure grain behavior in hard materials with strong isotropy and three-dimensional skeleton constituted of strong covalent bonds.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Hydrogen induced cracking susceptibility of API 5L X70 pipeline steel in relation to microstructure and crystallographic texture developed after different thermomechanical treatments

Highlights: • crack propagated mainly along deformed-banded microstructure. • Lower failure strength manifested at pipeline steel surface compared to the mid-thickness. • Greater fraction of martensite/austenite constituents featured in specimen WG relative to specimen WH. • Early onset of cracking in specimen WH showed no preference to specific crystallographic orientation. • Multi-component inclusion particle was revealed along crack propagation path. - Abstract: Thermomechanical treatments offer an innovative means of controlling microstructure development and improving resistance to hydrogen induced cracking (HIC) in pipeline steel. This study was conducted on two X70 pipeline steels (labelled WG and WH) of the same chemical composition, but processed with different thermomechanical parameters. Specimen WG was hot rolled at a higher temperature range of 880–820 {sup °}C, while specimen WH was hot rolled between 830 and 760 {sup °}C before cooling at a rate of 25 {sup °}C/s. Early onset of HIC was observed in specimen WH after electrochemical hydrogen charging for 12 h in a solution of 0.2 M H{sub 2}SO{sub 4} and 3 g/l NH{sub 4}SCN, without any applied stress. Also, test pieces from the surface and mid-thickness layers of each pipeline steel were subjected to slow strain rate tensile (SSRT) test with in-situ hydrogen charging. Characterization techniques such as Optical Microscopy, Scanning Electron Microscopy, Electron Backscattered Diffraction and X-ray Diffraction were used to investigate the structure pipeline steel specimens. The role of inclusions on HIC was studied by Energy Dispersive X-ray Spectroscopy. Although the microstructure of both specimens were predominantly ferritic, more martensite/retained austenite (M/A) constituents featured in WG. Further crystallographic texture analysis indicates that grain orientation at the surfaces of both test specimens were similar with deviations towards <111> on the inverse pole figure (IPF); whereas, pole intensity at the mid-thickness deviated towards the <001> direction. Considering the increased fraction of banded-deformed grains with high stored energy, the lower HIC resistance of specimen WH in comparison to specimen WG was justified.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Development of a new generation of quench and partitioning steels: Influence of processing parameters on texture, nanoindentation, and mechanical properties

A novel quenching and partitioning process (Q&P) including the hot stamping (HS) process was studied, using two stamping temperatures (750 °C and 800 °C) and two quenching temperatures (318 °C and 328 °C). This combination is here called Hot Stamping and Quenching and Partitioning process (HSQ&P). The partitioning step was performed at 400 °C for 100 s in all cycles. Microstructural features were comprehensively studied using electron backscattered diffraction and nanoindentation techniques. HSQ&P samples showed a good combination of ductility and high-strength due to the presence of: retained austenite, inter-critical ferrite with low stored internal strain energy, grain refinement via DIFT-effect (deformation induced ferrite transformation), martensite, and bainite. Significant internal stress relief was caused by carbon partitioning, which was induced by the DIFT-effect and the partitioning stage. This also led to a considerable stored energy, which was characterized by the Kernel average dislocation and geometrically necessary dislocation analysis. In addition, predominant {110}//strain direction crystallographic texture was identified, which promotes slip deformation and enhances the mechanical properties. Moreover, remarkable amounts of fine film-like retained austenite oriented along compact crystallographic directions (i.e., $\langle$111$\rangle$ and $\langle$112$\rangle$) were observed. Finally, subsize tensile test verified the optimum mechanical behavior of HSQ&P specimens.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Hydrostatic pressure effect on mechanical behavior and texture evolution of Al and Brass

The effect of hydrostatic pressure on shear strength and microstructural evolution of polycrystalline FCC metals was investigated. Hydrostatic pressure of up to 5 GPa was imposed on commercial purity aluminum and 70/30 brass samples using a modified opposed-anvil apparatus (tri-anvil) that allows for measurement of shear strength in thin foil specimens. Similar to the previous investigations made in BCC metals (Ta and Mo), the shear strength of FCC metals increases significantly as the pressure rises. At 5 GPa, the shear strength of aluminum increased to 8 times its value at atmospheric pressure and 70/30 brass increased by a factor of 2.7. Here, EBSD analysis reveals an evident accumulation of dislocations in all sheared samples, with an approximately 50% decrease in grain diameter. Texture analysis suggests that, in addition to helping form selectively oriented dislocation walls, hydrostatic pressure also serves as a threshold to select certain favorable orientations in sheared metals. We propose that these hydrostatic pressure effects are intrinsically due to the excess volume associated with the cylindrical strain field of dislocation lines.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Variation of elastic mechanical properties with texture, porosity, and defect characteristics in laser powder bed fusion 316L stainless steel

Elastic mechanical properties of 316 L stainless steel samples fabricated using laser powder bed fusion were studied non-destructively through resonant ultrasound spectroscopy. Samples in five different conditions were obtained by varying the laser power from 103 W (the highest density condition) to 68 W (the lowest density condition) at constant laser speed, producing samples with a volume energy density in the 24.5–16.5 J/mm 3 range and volumetric porosity in the 0.1–10% range. The observed elastic mechanical properties are discussed taking into consideration the bulk texture developed and quantitative pore characteristics studied using high-energy high-resolution synchrotron X-ray diffraction and X-ray computed micro-tomography, respectively. Furthermore, empirical exponential relationships are provided to express the functional dependence of Young's and shear moduli with porosity.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Novel textured surfaces for superior corrosion mitigation in molten carbonate salts for concentrating solar power

Corrosion of metals in contact with molten salts used for thermal energy storage and heat transport at high temperatures is a serious impediment to the development of next-generation concentrating solar thermal systems. Toward addressing this limitation, novel multiscale fractal-textured Ni coatings on a variety of substrate alloys are presented in this study for exceptional corrosion mitigation in molten carbonate salts at a high temperature. Strongly adherent, durable, single-layer, and double-layer multiscale fractal coatings were fabricated using the electrodeposition method. Corrosion performance of the coatings on SS310, SS316, SS347, and In800H was studied in molten carbonate salt (32% Li 2 CO 3 +33% Na 2 CO 3 +35% K 2 CO 3 ) at 750 °C. Single-layer coatings are stable up to 300 h immersion, whereas double-layer coatings are stable beyond 750 h. The corrosion rate of double-layer Ni coatings on ferrous alloys was reduced by as much as 60% from that of uncoated surfaces and was about 18% below that of higher cost, high Ni content Ha230. The study represents the first-ever report of corrosion characteristics of alloys in carbonate salts at 750 °C and the first demonstration of a means of dramatically reducing corrosion in carbonate salts at a high temperature. The article is significant in that it provides a viable approach for low-cost structural alloys to be corrosion-resistant to molten carbonate heat transfer fluids and storage media in high-temperature concentrating solar thermal applications. Furthermore, the corrosion-resistant coatings provide opportunities for the use of low-cost, ferritic alloys instead of the expensive nickel-based alloys in practice.

14 SOLAR ENERGY↗

DOE OSTI2023

Impact of Chiral Symmetry Breaking on Spin-Texture and Lone Pair Expression in Chiral Crystals of Hybrid Antimony and Bismuth Halides

Chiral organic building blocks can be incorporated into hybrid organic-inorganic metal-halide crystalline semiconductors so as to control and impact the interconversion between light, charge, and spin. Here, we report a series of hybrid antimony and bismuth halide materials of the general formula MBA 4 B 2 X 10 (B = Sb 3+ , Bi 3+ ; X = Br - , I - ) and study how chiral symmetry breaking imposed by the templating organic chiral methylbenzylammonium (MBA) cations induces symmetry breaking within the inorganic sublattice and leads to a unique spin-texture. The chiral MBA cations introduce two structural modifications to the metal-halide sublattice that consists of isolated edge-sharing dimers of B 2 X 10 octahedra: (1) the dimers have a chiral spatial arrangement with respect to one another and (2) there is an asymmetric distortion of the two subunits within the individual dimers with a higher distortion caused by strong stereochemical activity of the Sb 5s 2 lone pair electrons. The structural distortions and chiral arrangement result in circular dichroism (CD) at the band edge of the inorganic framework with dissymmetry factors in the range of 10 -4 . Chiral spin-splitting of the inorganic states, caused by breaking of the inversion symmetry and large spin-orbit coupling, is studied via density functional theory (DFT), and a multiband effective mass theory was developed that links the DFT-derived spin-splitting of helical character (i.e., spin expectation value not perpendicular to the crystal momentum) to the observed CD. Furthermore, we also find broad red photoluminescence from the MBA 4 Sb 2 Br 10 compounds, which we attribute to self-trapped excitonic emission driven by the large distortion due to the lone pair expression.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Spin Texture Control and Magnetic Gap Engineering in a Ferromagnetic Insulator–Topological Insulator Sandwiched Heterostructure

Quantum materials that combine magnetism with topological order are emerging as key platforms for next-generation spintronics and low-energy electronics. They enable the realization of emergent quantum phenomena, such as the quantum anomalous Hall effect and axion insulator states. The ferromagnetic insulator (FMI)/topological insulator (TI)/FMI sandwich structure of a single-septuple layer (1SL) MnBi 2 Te 4 /four-quintuple layer (4QL) Bi 2 Te 3 /1SL MnBi 2 Te 4 holds great potential to achieve such desirable quantum phenomena at an elevated temperature, owing to its large Dirac point band gap and high Curie temperature. Here, for this work, spin- and angle-resolved photoemission spectroscopy (spin-ARPES) is employed to directly verify that the band gap arises from broken time-reversal symmetry via proximity-driven magnetization. This study demonstrates direct control of the spin state via external magnetic fields and unambiguously confirms the exchange interaction as the gap-opening mechanism. The robust magnetic gap and controllable spin texture make this heterostructure a suitable candidate for spintronic applications and magnetic topological quantum phases.

exchange gap↗

DOE OSTI2016

Large spin-orbit coupling and helical spin textures in 2D heterostructure [Pb 2 BiS 3 ][AuTe 2 ]

Two-dimensional heterostructures with strong spin-orbit coupling have direct relevance to topological quantum materials and potential applications in spin-orbitronics. In this work, we report on novel quantum phenomena in [Pb 2 BiS 3 ][AuTe 2 ], a new 2D strong spin-orbit coupling heterostructure system. Transport measurements reveal the spin-related carrier scattering is at odds with the Abrikosov-Gorkov model due to strong spin-orbit coupling. This is consistent with our band structure calculations which reveal a large spin-orbit coupling gap of ε so = 0.21 eV. Furthermore, the band structure is also characterized by helical-like spin textures which are mainly induced by strong spin-orbit coupling and the inversion symmetry breaking in the heterostructure system.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Ion-induced grain growth and texturing in refractory thin films-A low temperature process

Selective grain growth can be promoted in thin films independently of the materials intrinsic properties, such as the melting temperature, by ion-irradiation. This enables the previously impossible evolution of large grain-sized microstructures with controlled crystallographic textures even in refractory metals, such as {alpha}-tantalum. Experimental results from materials with different crystal structure are compared on the basis of a theoretical model, which reveals the differences in ion-induced grain-growth dynamics.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Topological Hall conductivity of vortex and skyrmion spin textures

We analyze the topological Hall conductivity experienced by conduction electrons whose spins are strongly coupled to axially symmetric spin textures, such as magnetic vortex and skyrmion of types I and II, theoretically by gauge theory, and numerically via micromagnetic simulations. The numerical results are in agreement with the theoretical predictions. Divergence between the two is seen when the vortex/skyrmion core radius is comparable or larger than the element size, and when the skyrmion configuration breaks down at high Dzyaloshinskii-Moriya interaction strength.