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Frank, M.

Publications and source records attributed to Frank, M..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Transformative high entropy alloy conquers the strength-ductility paradigm by massive interface strengthening

Recent metastable alloy designs have demonstrated simultaneous attainment of high ultimate tensile strength (UTS) and ductility in high entropy alloys but with low yield strength. In this work, we present new strategy for improving the work hardenability and yield strength (YS) together in Fe 38.5 Mn 20 Co 20 Cr 15 Si 5 Cu 1.5 high entropy alloy (Cu-HEA). Drastic increase in the YS (1.5 GPa) is attributed to the formation of γ/ε, ε/ε (twin type) and ε/ε (plate type) interfaces in the microstructure due to extreme grain refinement whereas high UTS-ductility synergy (2.2 GPa, 15%) is attained by dynamic Hall-Petch hardening across these interfaces (i.e. massive interface strengthening) and transformation induced plasticity in γ phase. Thus, this harmonious combination of YS and UTS-ductility synergy in Cu-HEA outperform all structural materials till date. Therefore, deformation-induced massive interface strengthening is a new, yet cost-effective pathway for synergizing the benefits of advanced steels and high entropy alloys together in a material by conventional processing route.

36 MATERIALS SCIENCE↗
DOE OSTI2020

In cellulo crystallization of Trypanosoma brucei IMP dehydrogenase enables the identification of genuine co-factors

Sleeping sickness is a fatal disease caused by the protozoan parasite Trypanosoma brucei (Tb). Inosine-5’-monophosphate dehydrogenase (IMPDH) has been proposed as a potential drug target, since it maintains the balance between guanylate deoxynucleotide and ribonucleotide levels that is pivotal for the parasite. Here we report the structure of TbIMPDH at room temperature utilizing free-electron laser radiation on crystals grown in living insect cells. The 2.80 Å resolution structure reveals the presence of ATP and GMP at the canonical sites of the Bateman domains, the latter in a so far unknown coordination mode. Consistent with previously reported IMPDH complexes harboring guanosine nucleotides at the second canonical site, TbIMPDH forms a compact oligomer structure, supporting a nucleotide-controlled conformational switch that allosterically modulates the catalytic activity. The oligomeric TbIMPDH structure we present here reveals the potential of in cellulo crystallization to identify genuine allosteric co-factors from a natural reservoir of specific compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A fixed-target platform for serial femtosecond crystallography in a hydrated environment

For serial femtosecond crystallography at X-ray free-electron lasers, which entails collection of single-pulse diffraction patterns from a constantly refreshed supply of microcrystalline sample, delivery of the sample into the X-ray beam path while maintaining low background remains a technical challenge for some experiments, especially where this methodology is applied to relatively low-ordered samples or those difficult to purify and crystallize in large quantities. This work demonstrates a scheme to encapsulate biological samples using polymer thin films and graphene to maintain sample hydration in vacuum conditions. The encapsulated sample is delivered into the X-ray beam on fixed targets for rapid scanning using the Roadrunner fixed-target system towards a long-term goal of low-background measurements on weakly diffracting samples. As a proof of principle, we used microcrystals of the 24 kDa rapid encystment protein (REP24) to provide a benchmark for polymer/graphene sandwich performance. The REP24 microcrystal unit cell obtained from our sandwiched in-vacuum sample was consistent with previously established unit-cell parameters and with those measured by us without encapsulation in humidified helium, indicating that the platform is robust against evaporative losses. While significant scattering from water was observed because of the sample-deposition method, the polymer/graphene sandwich itself was shown to contribute minimally to background scattering.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Deformation mechanisms and ductile fracture characteristics of a friction stir processed transformative high entropy alloy

Deformation mechanisms of a friction stir processed Fe 40 Mn 20 Co 20 Cr 15 Si 5 transformative high entropy alloy using three different process parameters were studied to explain the microstructural dependence of tensile response in these specimens. The relative strain hardening contribution due to transformation and twinning effects was different for the three different microstructural conditions and thus resulted in different magnitude of work hardening. Crystal plasticity simulations confirmed that synergistic activity of face centered cubic and hexagonal close packed slip and twin mechanisms resulted in sustained work hardening and enhanced uniform elongation. The non-uniform ductility and extent of void nucleation and growth in these specimens were limited. Nevertheless, fractography and X-ray microscopy of fractured tensile specimens verified that microstructural flexibility induced different propensities for void growth and ductile fracture mode. Thus, alloy design induced phase stability, adaptive phase evolution due to friction stir processing, extent and kinetics of martensitic transformation and related work hardening capability of the individual phases combined together to determine the overall tensile response. The crystallographic orientation dependence of deformation induced phase transformation was also thoroughly studied. Finally, this study included quantitative determination of the crystallographic orientation where resolved shear stress on leading and trailing partial dislocations favored separation of the partials to cause transformation at a critical value of applied stress.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste

Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemens AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs, {sup 241}Am) were performed. A homemade algorithm was developed to determine a value which is related to the neutron absorption of the sample with the analysis of the raw detector data. The detector was placed 42 cm away from the neutron source. Distance between detector and the samples was 0.5 cm. At the sample position the fast neutron flux was estimated to 9x10{sup 3} n cm{sup -2} s{sup -1} for a neutron emission of 10{sup 8} n s{sup -1}. The acquisition time was 15 minutes. First neutron radiographs were successfully recorded despite the low detector efficiency and low neutron emission. Analysis of the data shows a correlation between the measured signal and determined neutron absorption. Thus discrimination between different materials of same thicknesses may be achieved. The measurements and results will be presented and discussed in details.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

New Science Opportunities Enabled by LCLS-II X-Ray Lasers

This document attempts to capture the most compelling new science opportunities that are enabled by the unique capabilities of the new LCLS-II X-ray laser facility, namely: soft and tender X-rays (0.25 to 5 keV) at high repetition rates (up to 1 MHz) and hard X-rays (up to 25 keV) at 120 Hz. Many compelling areas of science have been identified by the scientific community, through a series of workshops over the past several years, where LCLS-II offers the potential to significantly advance our understanding. This document is not intended to be comprehensive of all the science to be pursued at the future LCLS facility. In particular, it does not capture important ongoing science that will continue to exploit the existing capabilities of the present LCLS facility. Nevertheless, this document will help to establish a scientific foundation for the new facility (encompassing present LCLS capabilities and new LCLS-II capabilities), and will inform LCLS strategic planning and investments over the next 5-10 years. The emphasis of this document is on identifying broad scientific opportunities, elucidating their potential impact, and providing a first-order link between these opportunities and LCLS-II capabilities. Brief descriptions are provided for various experimental approaches to be used, and novel new approaches to be developed, along with select examples of required optics and instruments. However, this document is not intended to capture all the optics and instrumentation requirements. Similarly it does not provide a detailed plan for instrumentation design or for any associated research and development that might be required. Balancing the scientific opportunities and impact, with instrumentation needs, available resources, and infrastructure, will be part of the LCLS planning process which this document will help to inform.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Software Trigger Algorithms to Search for Magnetic Monopoles with the NO$\nu$A Far Detector

The NOvA far detector, due to its surface proximity, large size, good timing resolution, large energy dynamic range, and continuous readout, is sensitive to the detection of magnetic monopoles over a large range of velocities and masses. In order to record candidate magnetic monopole events with high efficiency we have designed a software-based trigger to make decisions based on the data recorded by the detector. The decisions must be fast, have high efficiency, and a large rejection factor for the over 100,000 cosmic rays that course through the detector every second. In this paper we briefly describe the simulation of magnetic monopoles, including the detector response, and then discuss the algorithms applied to identify magnetic monopole candidates. We also present the results of trigger efficiency and purity tests using simulated samples of magnetic monopoles with overlaid cosmic backgrounds and electronic noise.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗