Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “BORON”

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.

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

At least 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Sieving Hydrogen Isotopes via Machine Learning Assisted Chemical Vapor Deposition (CVD) of High‐Quality Monolayer Hexagonal Boron Nitride (h‐BN) on Iron Foils

Atomically thin two-dimensional (2D) ceramics, such as monolayer hexagonal boron nitride (h-BN), present potential for disruptive advances in separations. However, sub-atomic scale separation of hydrogen isotopes (H + /D + ) require near pristine 2D material membranes, and scalable synthesis of such high-quality h-BN comparable to mechanically exfoliated crystals remains a significant challenge. Here, we report a scalable Fe-catalyzed chemical vapor deposition (CVD) process for bottom-up synthesis of large-area, high-quality monolayer h-BN films, overcoming key limitations of conventional ammonia-based routes. By leveraging mechanistic insights and higher CVD temperatures, we suppress multilayer formation and achieve uniform monolayer h-BN coverage on commercially available Fe foils. Machine learning enables systematic exploration of the complex, multi-dimensional CVD parameter space (growth time, temperature, precursor temperature, multilayer faction, coverage), providing data-driven approaches to visualize and identify process regimes facilitating predominantly monolayer h-BN growth with minimal secondary nuclei/ad-layers. The optimized Fe-catalyzed CVD h-BN membranes show high-quality as observed by proton/deuteron (H + /D + ) selectivity ≈8.45, approaching the highest quality benchmark of mechanically exfoliated h-BN (H + /D + selectivity ≈10) as well as significantly outperforming Cu-catalyzed CVD h-BN membranes (H + /D + selectivity ≈3.62, control selectivity ≈1.7). Our work provides a scalable cost-effective route for high-quality monolayer h-BN synthesis for sub-atomic scale separations (H + /D + ) and demonstrates the broader potential of machine learning-guided optimization of CVD for advancing synthesis of 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Boron Phosphide Films by Reactive Sputtering: Searching for a P‐Type Transparent Conductor

Abstract With an indirect band gap in the visible and a direct band gap at a much higher energy, boron phosphide (BP) holds promise as an unconventional p‐type transparent conductor. This work reports on reactive sputtering of amorphous BP films, their partial crystallization in a P‐containing annealing atmosphere, and extrinsic doping by C and Si. The highest hole concentration to date for p‐type BP (5 × 10 20 cm −3 ) is achieved using C doping under B‐rich conditions. Furthermore, bipolar doping is confirmed to be feasible in BP. An anneal temperature of at least 1000 °C is necessary for crystallization and dopant activation. Hole mobilities are low and indirect optical transitions are stronger than that predicted by theory. Low crystalline quality probably plays a role in both cases. High figures of merit for transparent conductors might be achievable in extrinsically doped BP films with improved crystalline quality.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Controlled Gas Exfoliation of Boron Nitride into Few-Layered Nanosheets

The controlled exfoliation of hexagonal boron nitride (h-BN) into single- or few-layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h-BN. Here, we present an efficient strategy for the scalable synthesis of few-layered h-BN nanosheets (BNNS) via a novel gas exfoliation of bulk h-BN in liquid N 2 (L-N 2 ). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h-BN and the cryogenic L-N 2 gasification to exfoliate the h-BN. The produced BNNS after ten cycles (BNNS-10) consisted primarily of fewer than five atomic layers with high a mass yield of 16~20%. N 2 sorption and desorption isotherms show that the BNNS-10 exhibited a much higher specific surface area of 278 m 2 /g –1 than that of bulk BN (10 m 2 /g –1 ). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h-BN. Subseqently, the L-N 2 penetrates into the interlayers of h-BN along the curling edge, followed by an immediate drastic gasification of L-N 2 , further peeling off h-BN. In conclusion, this novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials with high yeilds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Ultradoping Boron on Si(100) via Solvothermal Chemistry

Ultradoping introduces unprecedented dopant levels into Si, which transforms its electronic behavior and enables its use as a next-generation electronic material. Commercialization of ultradoping is currently limited by gas-phase ultra-high vacuum requirements. Solvothermal chemistry is amenable to scale-up. However, an integral part of ultradoping is a direct chemical bond between dopants and Si, and solvothermal dopant-Si surface reactions are not well-developed. This work provides the first quantified demonstration of achieving ultradoping concentrations of boron (~1e14 cm 2 ) by using a solvothermal process. Surface characterizations indicate the catalyst cross-reacted, which led to multiple surface products and caused ambiguity in experimental confirmation of direct surface attachment. Density functional theory computations elucidate that the reaction results in direct B-Si surface bonds. Finally, this proof-of-principle work lays groundwork for emerging solvothermal ultradoping processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Selective Oxidative Cracking of n –Butane to Light Olefins over Hexagonal Boron Nitride with Limited Formation of CO x

In recent years, hexagonal boron nitride (hBN) has emerged as an unexpected catalyst for the oxidative dehydrogenation of alkanes. Here, the versatility of hBN was extended to alkane oxidative cracking chemistry by investigating the production of ethylene and propylene from n-butane. Cracking selectivity was primarily controlled by the ratio of n-butane to O 2 within the reactant feed. Under O 2 -lean conditions, increasing temperature led to increased selectivity to ethylene and propylene and decreased selectivity to CO x . In addition to surface-mediated chemistry, homogeneous gas-phase reactions likely contributed to the observed product distribution, and a reaction mechanism was proposed based on these observations. Here, the catalyst showed good stability under oxidative cracking conditions for 100 h time-on-stream while maintaining high selectivity to ethylene and propylene.

03 NATURAL GAS↗
DOE OSTI2023

Enhancing Crystallization in Hybrid Perovskite Solar Cells Using Thermally Conductive 2D Boron Nitride Nanosheet Additive

Controlling crystallization and grain growth is crucial for realizing highly efficient hybrid perovskite solar cells (PSCs). In this work, enhanced PSC photovoltaic performance and stability by accelerating perovskite crystallization and grain growth via 2D hexagonal boron nitride (hBN) nanosheet additives incorporated into the active perovskite layer are demonstrated. Specifically, in situ X-ray scattering and infrared thermal imaging during the perovskite annealing process revealed the highly thermally conductive hBN nanosheets promoted the phase conversion and grain growth in the perovskite layer by facilitating a more rapid and spatially uniform temperature rise within the perovskite film. Complementary structural, physicochemical, and electrical characterizations further showed that the hBN nanosheets formed a physical barrier at the perovskite grain boundaries and the interfaces with charge transport layers, passivating defects, and retarding ion migration. As a result, the power conversion efficiency of the PSC is improved from 17.4% to 19.8%, along with enhanced device stability, retaining ≈90% of the initial efficiency even after 500 h ambient air storage. Here, the results not only highlight 2D hBN as an effective additive for PSCs but also suggest enhanced thermal transport as one of the pathways for improved PSC performance by 2D material additives in general.

2D materials↗
DOE OSTI2018

Effect of Boron Doping on High-Resolution X-Ray Diffraction Metrology

The effect of boron (B) doping on high-resolution X-ray diffraction (HXRD) metrology has been investigated. Twelve samples of Si{sub 1–x}Ge{sub x} films were epitaxially grown on Si (100) substrates with different thicknesses, germanium (Ge) concentrations and with/without B dopants. Secondary ion mass spectroscopy (SIMS) and HXRD were employed for measurements of B doping, Ge concentration, strain, and thickness of the layers. The SIMS results show the absence of B in two samples while the rest of the samples have B doping in the range of 8.40 × 10{sup 18}–8.7 × 10{sup 20} atoms/cm{sup 3} with Ge concentration of 13.3–55.2 at.%. The HXRD measurements indicate the layers thickness of 7.07–108.13 nm along with Ge concentration of 12.82–49.09 at.%. The difference in the Ge concentration measured by SIMS and HXRD was found to deend on B doping. For the undoped samples, the difference is ~0.5 at.% and increases with B doping but with no linear proportionality. The difference in the Ge concentration was 7.11 at.% for the highly B-doped (8.7 × 10{sup 20} atoms/cm{sup 3}) sample. The B doping influences the Si{sub 1–x}Ge{sub x} structure, causing a change in the lattice parameter and producing tensile strains shifting Si{sub 1–x}Ge{sub x} peaks towards Si (100) substrate peaks in the HXRD diffraction patterns. As a result, Vegard’s law is no longer effective and makes a high impact on the HXRD measurement. The comparison between symmetric (004) and asymmetric (+113, +224) reciprocal space mappings (RSM) showed a slight difference in Ge concentration between the undoped and lower B-doped samples. However, there is a change of 0.21 at.% observed for the highly doped Si{sub 1–x}Ge{sub x} samples. RSM’s (+113) demonstrate the small SiGe peak broadening as B doping increases, which indicates a minor crystal distortion.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermodynamic Analysis of Prospects for Using Aluminum- and Boron-Containing Clusters in Combined High-Energy Fuels

The high enthalpies of combustion of atomic clusters Al{sub n}, B{sub n}, and C{sub n} (n = 1, 2, …, 7), Al{sub n}C{sub m} and B{sub n}C{sub m} (n = 1, …, 5 and m = 1, …, 5), Al{sub n}B{sub m} (n + m ≤ 7), and Al{sub n}H{sub m} and B{sub n}H{sub m} (n = 1, …, 4 and m ≤ 12) have been assessed. The specific energy release, the final adiabatic temperature, and the effectiveness of the combustion products of fuel mixtures based on kerosene, dimethyl ether, and ethyl alcohol with small additions of such clusters have been determined under the assumption of attaining a thermodynamic equilibrium in their combustion products. An analysis has been made of the potentials of small aluminum- and boron-containing clusters for use in improving thermochemical properties of the fuels. It has been shown that adding such clusters to traditional fuels in the amount of 10% of the fuel mass can increase the specific energy release of the fuel by 2 MJ/kg, the effectiveness of combustion products of the fuel by 10%, and their final temperature by 200 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Magnetism in Boron Nitride Monolayer Induced by Cobalt or Nickel Doping

We have investigated the electronic structure and magnetic properties of cobalt (Co)- or nickel (Ni)-doped hexagonal boron nitride (h-BN) monolayer using density functional theory calculations. The h-BN monolayer without any doping is a nonmagnetic insulator. Our studies show that isolated Co or Ni atom can both induce the local magnetic state in h-BN monolayer. And the impurity energy levels will be formed in the band gap. Results of our first-principle calculations reveal that isolated Co atom can result in a magnetic moment of 3.57 μ{sub B}, while the Ni atom is 0.87 μ{sub B}. And the magnetic moments mainly come from d orbitals of the doped atoms. The studies of magnetic coupling show that the two Co atoms at different distances in h-BN monolayer do not always couple ferromagnetically. When the distances are 2.504 and 6.625 Å, the spins induced by the two Co atoms will form antiferromagnetic ground states. While the two Ni atoms at different distances in the monolayer always couple ferromagnetically. So our results imply that the Ni-doped h-BN is more suitable for spintronic material than Co doping. These results are useful for spintronic application.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Magnetic Features of Boron Doping on Hf{sub 2}Co{sub 11} Thin Films

The effect of boron (B) doping on the structural and magnetic properties is studied systematically in the Hf{sub 2}Co{sub 11} thin films. The modified crystal microstructure and annealing process enhanced the coercive field up to 1754 Oe. In order to obtain superior magnetic properties, the optimum doping ratios should be properly controlled attentively. To identify the structure, B-doped Hf{sub 2}Co{sub 11} thin films were investigated by temperature-dependent X-ray diffraction analysis for the first time. The hard magnetic phase of Hf{sub 2}Co{sub 11}B{sub x} thin films was formed to orthorhombic phase with some Co impurities and had a crystallization temperature around 823 K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of the Boron Content on the Amorphization Process and Magnetic Properties of the Mechanically Alloyed Fe{sub 92−x}Nb{sub 8}B{sub x} Powders

The effect of the B content on the microstructural, structural, and magnetic properties of partially amorphous Fe{sub 92−x}Nb{sub 8}B{sub x} (x = 5, 10, 15, and 20) alloys has been investigated by means of scanning electron microscopy, X-ray diffraction, high and low-temperature extraction-type magnetometers. The XRD results reveal the formation of a nanocomposite structure where nanocrystalline bcc α-Fe and Fe{sub 2}B phases are embedded into an amorphous matrix. The FeB boride is observed for higher boron contents (x = 15 and 20), and the crystallite sizes are in the range of 7–24 nm. As the B content increases, the amorphous phase-relative proportion and coercivity increase, whereas the saturation magnetization decreases. An important magnetic hardening occurs by lowering the temperature from 400 to 5 K for x = 20% B. The variation of the Curie temperature can be attributed to the heterogeneity of the amorphous matrix.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

High-Performance Bulk MgB{sub 2} Superconductor Using Amorphous Nano-boron

MgB{sub 2} bulks were produced by in situ solid-state reaction in Ar gas using high-purity commercial powders of Mg metal and amorphous nano-B mixed in a fixed ratio of Mg:B = 1:2. Single-phase materials have been obtained and grain structure and its implications are reported. All samples were sintered at 775 °C for 3 h in Ar atmosphere. X-ray diffraction results show that high-purity MgB{sub 2} phase has been fabricated, which as well is reflected in critical temperature (T{sub c} = 37.8 K). Magnetic measurements reveal a high critical current density (J{sub c}) value such as 408 kA/cm{sup 2} when nano-amorphous boron is used. SEM studies show that nano-ordered MgB{sub 2} grains are formed, thereby creating large number of grain boundaries responsible for high critical current densities. Analysis of normalized pinning force curve as a function of reduced magnetic field indicates that dominant pinning is caused by grain boundaries.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Short-lived fission product measurements from >0.1 MeV neutron-induced fission using boron carbide.

A boron carbide shield was designed, custom fabricated, and used to create a fast fission energy neutron spectrum. The fissionable isotopes 233, 235, 238U, 237Np, and 239Pu were separately placed inside of this shield and irradiated under pulsed conditions at the Washington State University 1 MW TRIGA reactor. A unique set of fission product gamma spectra were collected at short times (4 minutes to 1 week) post-fission. Gamma spectra were collected on single-crystal high purity germanium detectors and on Pacific Northwest National Laboratory's (PNNL's) Direct Simultaneous Measurement (DSM) system composed of HPGe detectors connected in coincidence. This work defines the experimental methods used to produce and collect the gamma data, and demonstrates the validity of the measurements. It is important to fully document this information so the data can be used with high confidence for the advancement of nuclear science and non-proliferation applications. The gamma spectra collected in these and other experiments will be made publicly available at https://spcollab.pnl.gov/sites/gammadata or via the link at http://rdnsgroup.pnl.gov. A revised version of this publication will be posted with the data to make the experimental details available to those using the data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Fission Yield Measurements from Highly Enriched Uranium Irradiated Inside a Boron Carbide Capsule

A boron carbide capsule was previously designed and tested by Pacific Northwest National Laboratory (PNNL) and Washington State University (WSU) for spectral-tailoring in mixed spectrum reactors. The presented work used this B4C capsule to create a fission product sample from the irradiation of highly enriched uranium (HEU) with a fast fission neutron spectrum. An HEU foil was irradiated inside of the capsule in WSU’s 1 MW TRIGA reactor at full power for 200 min to produce 5.8 × 1013 fissions. After three days of cooling, the sample was shipped to PNNL for radiochemical separations and analysis by gamma and beta spectroscopy. Fission yields for products were calculated from the radiometric measurements and compared to measurements from thermal neutron induced fission (analyzed in parallel with the non-thermal sample at PNNL) and published evaluated fast-pooled and thermal nuclear data. Reactor dosimetry measurements were also completed to fully characterize the neutron spectrum and total fluence of the irradiation.

boron carbide↗
DOE OSTI2018

Boron chelate complexes: X-ray and UV photoelectron spectra and electronic structure

Published data on the electronic structure of boron chelates are summarized for the first time. Ultraviolet photoelectron spectra of vapors, X-ray photoelectron spectra of molecular crystals, and results of modeling within the framework of the density functional theory are analyzed. Data on the effect of substituents on the electronic structure of complexes are systematized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Influence of TiH{sub 2} on Interfacial Reaction Features Between Cubic Boron Nitride and Cu-Sn-Ti Active Filler Metals

Cubic boron nitride (CBN) grains are brazed by Cu-Sn-Ti filler metal in vacuum at 1223 K. Wetting behaviors, reaction layer features, and elemental distribution characteristics have been systematically investigated through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that when the TiH{sub 2} content is 5 wt pct, virtually no sharp-edged, partially coated, and uncoated CBN grains can be observed, indicating that adequate wetting could be achieved. Moreover, a continuous reaction layer with uniform thickness (1.30 μm) consisting of TiN, TiB{sub 2}, and TiB is obtained, which indicates that large numbers of TiN, TiB{sub 2}, and TiB compounds could have been formed at the interface. However, when the TiH{sub 2} content exceeds 5 wt pct, the thickness of the reaction layer is no longer significantly expanding and excessive Ti present in the matrix will lower the volume percentage of Cu{sub 3}Sn{sub 1} phase, which will reduce the bonding strength of the brazing samples. Wear tests indicate that the minimum weight loss also occurs at 5 wt pct TiH{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Understanding the influence of boron in additively manufactured GammaPrint®-700 CoNi-based superalloy

Boron is commonly added to superalloys in small amounts to enhance creep resistance, but can lead to cracking at high concentrations, especially during the additive manufacturing process. Two variants of CoNi-based GammaPrint®-700 superalloy with different B contents (0.08 at% vs 0.16 at%) were printed via laser powder bed fusion (LPBF) with the same printing parameters, with only the high B alloy exhibiting solidification cracking. Atom probe tomography (APT) revealed stronger segregation behaviors in the high B alloy compared to the low B alloy at both the inter-dendritic regions and grain boundaries (GBs). The segregation behavior at inter-dendritic regions was well captured with Scheil simulation and can correlate with the existing cracking susceptibility index (CSI) on cracking tendencies, although high angle GBs are where cracking occurs according to electron backscatter diffraction (EBSD) measurements. Additionally, the extent of GB segregation was compared between the high B and low B alloy. Higher B additions led to significantly more GB B segregation in the high B alloy compared to the low B alloy. Further, for the high B alloy, the cracked region of one GB exhibited higher levels of B compared to the uncracked region of the same GB. However, much higher B contents were also found in two other uncracked GBs in the high B alloy, which demonstrates that higher GB B concentrations are not fully responsible for the cracking. A much larger variance in GB B segregation content was found in the high B alloy compared to the low B alloy. These phenomena were explained with a solidification model with the GB segregation content expressed explicitly by a modified Langmuir-McLean equation. This model linked the GB segregation content with solidification undercooling, which can be used as quantitative cracking criteria for future builds.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Isotope shifts in beryllium-, boron-, carbon-, and nitrogen-like ions from relativistic configuration interaction calculations

Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these electronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wavefunctions that account for valence, core–valence, and core–core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗