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DOE OSTI2020

Materials Data on AlC by Materials Project

AlC crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of twenty-four aluminium molecules and one AlC5 sheet oriented in the (0, 0, 1) direction. In the AlC5 sheet, there are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a distorted L-shaped geometry to three C3- atoms. There are a spread of Al–C bond distances ranging from 2.17–2.46 Å. In the second Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.31 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a 2-coordinate geometry to two C3- atoms. There are one shorter (2.05 Å) and one longer (2.32 Å) Al–C bond lengths. In the fourth Al3+ site, Al3+ is bonded in a water-like geometry to two C3- atoms. Both Al–C bond lengths are 2.27 Å. In the fifth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. In the sixth Al3+ site, Al3+ is bonded in a single-bond geometry to one C3- atom. The Al–C bond length is 2.07 Å. There are thirty inequivalent C3- sites. In the first C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.51–1.60 Å. In the second C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There are a spread of C–C bond distances ranging from 1.53–1.59 Å. In the third C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.44 Å) and two longer (1.57 Å) C–C bond length. In the fourth C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There are a spread of C–C bond distances ranging from 1.44–1.56 Å. In the fifth C3- site, C3- is bonded in a 5-coordinate geometry to two Al3+ and three C3- atoms. There are a spread of C–C bond distances ranging from 1.53–1.63 Å. In the sixth C3- site, C3- is bonded in a distorted pentagonal planar geometry to two Al3+ and three C3- atoms. Both C–C bond lengths are 1.63 Å. In the seventh C3- site, C3- is bonded in a distorted trigonal non-coplanar geometry to three C3- atoms. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the eighth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. Both C–C bond lengths are 1.57 Å. In the ninth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.59 Å) C–C bond length. In the tenth C3- site, C3- is bonded to one Al3+ and three C3- atoms to form distorted corner-sharing CAlC3 tetrahedra. There is one shorter (1.58 Å) and one longer (1.60 Å) C–C bond length. In the eleventh C3- site, C3- is bonded in a 4-coordinate geometry to one Al3+ and four C3- atoms. Both C–C bond lengths are 1.53 Å. In the twelfth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the thirteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fourteenth C3- site, C3- is bonded to four C3- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.54 Å) C–C bond length. In the fifteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.55 Å) and one longer (1.56 Å) C–C bond length. In the sixteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the seventeenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the eighteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.54 Å. In the nineteenth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. There is one shorter (1.53 Å) and one longer (1.56 Å) C–C bond length. In the twentieth C3- site, C3- is bonded to four C3- atoms to form distorted corner-sharing CC4 tetrahedra. Both C–C bond lengths are 1.52 Å. In the twenty-first C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-second C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-third C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-fourth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-fifth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-sixth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-seventh C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the twenty-eighth C3- site, C3- is bonded in a water-like geometry to two C3- atoms. In the twenty-ninth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms. In the thirtieth C3- site, C3- is bonded in a bent 120 degrees geometry to two C3- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Life Cycle Inventory of Current Photovoltaic Module Recycling Processes in Europe

With the rapid and accelerating growth of PV module installation and an increase of PV modules from the nineteen eighties and nineties reaching the end of their 30 year lifespan, their proper end of life treatment gets into focus. This report deals with the approaches, the environmental impacts and the recovered materials of PV module recycling. In this report, the environmental life cycle assessment of the current generation recycling of crystalline silicon (c-Si) and cadmium telluride (CdTe) PV modules is described. Due to the still limited waste stream today, c-Si PV modules are mainly treated in recycling plants designed for treatment of laminated glass, metals or electronic waste. Only the bulk materials glass, aluminium and copper are recovered, while the cells and other materials such as plastics are incinerated. CdTe PV modules have been treated in dedicated recycling plants for many years and life cycle inventories of this process have been published. The semiconductor is recovered in addition to glass and copper. Life cycle inventories of the recycling of current c-Si and CdTe PV modules are compiled following two modelling approaches related to recycling. The cut-off approach uses economic allocation to divide the total efforts of the recycling process between the treatment of the used PV module and the recovered products. The end-of-life approach considers the recycling process separately from the potentially avoided burdens due to recovered materials. The life cycle inventories of c-Si PV module recycling are based on data obtained from four European recyclers surveyed between 2015 and 2016. For CdTe PV module recycling, the life cycle inventories were established based on published data for the First Solar recycling facility in Germany. The life cycle impact assessment is done based on six environmental indicators previously identified as most relevant for PV electricity: particulate matter, freshwater ecotoxicity, human toxicity non-cancer effects, human toxicity cancer effects, mineral, fossil and renewable resource depletion and climate change. The life cycle inventories according to the cut-off approach can be applied to complement existing life cycle inventory data on PV systems. The environmental impacts of the recycling of c-Si PV modules are very small (maximum 1.1 %) compared to the impacts caused by the production of a 3 kWp residential PV system mounted on a slanted roof. In the case of CdTe PV module recycling, the treatment of the PV panels has the highest but still rather minor contribution in the indicator climate change (4.8 %). The life cycle inventories according to the end-of-life approach allow an assessment of the net environmental benefits of recycling. The recovery of glass, metals, and semiconductor material from c-Si and CdTe PV modules causes lower environmental impacts than the extraction, refinement and supply of the respective materials from primary resources. The highest potential benefits are observed in the indicator mineral, fossil and renewable resource depletion. The data quality of the recycling of c-Si PV modules is classified as fair since only limited information is available. In contrast, the data quality of CdTe PV module recycling is considered very good. The study was financed by the Swiss Federal Office of Energy (SFOE) and carried out in the framework of the Task 12 of the Photovoltaic Powers System Programme (PVPS) of the International Energy Agency (IEA).

14 SOLAR ENERGY↗

DOE OSTI2020

Performance Analysis and Radiation Damage Estimation of the Stopping Target Monitor Detectors in Mu2e

The Mu2e experiment aims to search for the charged lepton flavour violating (CLFV) process of a coherent, neutrinoless, conversion of a muon into an electron within the proximity of an aluminium nucleus. Mu2e seeks to measure the ratio (R μe ) of the rate of this conversion process, relative to that of ordinary muon capture. Mu2e will achieve world-leading sensitivity, improving the current limit of Rμe < 7 ×10 -13 (90% C.L.),set by the SINDRUM-II experiment, by an order of 104. This corresponds to a single-event sensitivity of Rμe < 2.87 × 10 -17 (90% C.L.). Many beyond Standard Model (BSM) theories require CLFV to occur at a rate accessible by Mu2e. Any observation of CLFV at Mu2e would have profound implications on particle physics. The Stopping Target Monitor (STM) will be comprised of both a HPGe and a LaBr3 detector which will monitor the signals of photons produced in stopped-muon processes to a required accuracy of 10%. To achieve the desired sensitivity, it is imperative that the detectors perform at their optimal level. The STM detectors are placed within a harsh radiation environment in the form of a high energy ‘flash’ of gamma radiation as well as a flux of fast neutrons. Estimations of radiation damage to HPGe in literature is limited. This thesis reports an approach which utilizes the Kinetic-Energy Released in Matter (KERMA) parameter that considers the energy dependence of the incident flux and the cross-section information for the incident particle. Resampling schemes have been adopted to give a realistic rate over the experiment run time. The results have then been normalized to the radiation damage caused by a 252 Cf source. The estimated time before annealing of the detector is necessary is found to be 75 and 78 months in the case of neutron damage and τ ~ 24 years, 11 months in the case of electron/positron induced damage. This shows significant improvement on the previous estimations.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Near-Infrared Noise in Intense Electron Beams

Requirements for the noise in electron beams (NEB) have recently approached the Shot-noise level in some new applications. The density fluctuations of intense beams in the near-infrared (NIR) region are being measured at the Fermilab Accelerator Science and Technology (FAST) facility. The main goal of the experiment is to accurately compare the Shot-noise model with the observations of optical transition radiation (OTR) generated by a relativistic electron beam ($\gamma \approx 63$), transiting an Aluminium metal surface. In addition, some evidence for longitudinal space-charge-induced microbunching for the chicane-compressed beam was obtained with coherent enhancements up to 100 in the various bandwidth-filtered NIR OTR photodiode signals. With micropulse charges up to 1 nC, the beam parameters are close to those proposed for a stage in an Electron-Ion Collider (EIC) with coherent electron cooling (CEC). In this paper we present the current progress of the NEB project and compare the low electron energy measurements with ImpactX simulations.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Study of Mechanical Grinding Effects on Niobium Surface

Mechanical grinding is commonly employed to eliminate surface defects such as scratches and pits from niobium cavity surfaces or sheets before cavity fabrication. Subsequently, chemically buffered polishing or electropolishing is often utilized to completely remove residues of the polishing media and any defects induced by mechanical grinding, ensuring a pristine surface. In this study, we conducted a systematic investigation to assess the influence of mechanical grinding using silicon carbide (SiC) and aluminium oxide (Al2O3) polishing media on niobium surfaces. Additionally, the study examines the effects of post-mechanical grinding chemical treatments on surface quality.

Chouhan, V.↗

DOE OSTI2022

Atomically Precise Ultra-High Performance 2D MicroElectronics

Zyvex Labs has created several p-n junction devices with a variety of gaps between the boron and phosphorus electrodes, from 0-7.7 nm, which are now being measured. We have developed a different contacting process based on palladium disilicide rather than aluminium to improve the reliability of the device contacts. Preliminary measurements indicate that these new contacts are successfully contacting the buried dopant layers, which are intact after the overgrowth process. Modelling of the p-n junction properties has made good progress, with the model matching previous published data, and modelling of n-p-n junction devices has begun. This now awaits experimental validation.

47 OTHER INSTRUMENTATION↗

DOE OSTI2021

Resonant Extraction and Extinction Measurement for the Mu2e Experiment

The Mu2e experiment, currently under construction at Fermilab, will search for coherent neutrinoless muon to electron conversion, extending the sensitivity of searches for charged lepton flavour violation by four orders of magnitude in 3-5 years of data-taking. This improved sensitivity is made possible by using a pulsed beam structure that is optimized for reducing prompt backgrounds when muons are stopped on an aluminium target. Producing a high-rate pulsed beam is achieved using resonant extraction of a circulating proton beam, an “AC dipole” with a time-varying field to deflect out-of-time protons, and a system to measure the extinction of out-of-time beam particles incident on the muon production target. These proceedings summarize the systems that have been designed to achieve the required level of extinction and to continuously place limits on the presence of out-of-time beam hitting the production target with a sensitivity of <1e-10.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Broad Frequency Shift of Parametric Processes in Epsilon-Near-Zero Time-Varying Media

The ultrafast changes of material properties induced by short laser pulses can lead to a frequency shift of reflected and transmitted radiation. Recent reports highlight how such a frequency shift is enhanced in spectral regions where the material features a near-zero real part of the permittivity. Here, we investigate the frequency shift for fields generated by four-wave mixing. In our experiment, we observed a frequency shift of more than 60 nm (compared to the pulse width of ~40 nm) in the phase conjugated radiation generated by a 500 nm aluminium-doped zinc oxide (AZO) film pumped close to the epsilon-near-zero wavelength. Our results indicate applications of time-varying media for nonlinear optics and frequency conversion.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.

Figueiredo, Anabela↗

DOE OSTI2021

Experimental investigation of elemental and isotopic evaporation processes by laser heating in an aerodynamic levitation furnace

In this report we carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10 -9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO 2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of α 26/24 Mg vap-liq = 0.9906± 0.0004 and α 30/28 Si vap-lip = 0.9943±0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz–Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.

58 GEOSCIENCES↗

DOE OSTI2022

Fabrication and installation of the Mu2e cryogenic distribution system

The muon-to-electron conversion (Mu2e) experiment at Fermilab will be used to search for the charged lepton flavor-violating conversion of muons to electrons in the field of an atomic nucleus. The Mu2e experiment is currently in the construction stage. The scope of this paper is the cryogenic distribution system and superconducting power leads for four superconducting solenoid magnets: Production Solenoid (PS), an Upstream and Downstream Transport Solenoids (TSu and TSd) and Detector Solenoid (DS). The design of the cryogenic distribution system and the fabrication of several sub-systems was reported previously. This paper reports on additional fabrication and installation progress that has been performed over the past two years. Lessons learned during fabrication and testing of the cryogenic distribution system components are described. In particular, the challenges and solutions implemented for aluminum welding are reported. A description of the process used to qualify the welding procedure and welders for welding the aluminium stabilized NbTi superconducting power leads is provided. Additionally, the progress made with regards to installing the power leads into the cryogenic Feedboxes is covered.

White, Michael J.↗

DOE OSTI2022

High power, extended temperature range-capable, highly abuse overcharge and discharge tolerant rechargeable battery cell and pack

Provided are electrochemical secondary cells that exhibit excellent abuse tolerance, deep discharge and overcharge conditions including at extreme temperatures and remain robust and possess excellent performance. Cells as provided herein include: a cathode a polycrystalline cathode electrochemically active material including the formula Li1+xMO2+y, wherein −0.9≤x≤0.3, −0.3≤y≤0.3, and wherein M includes Ni at 80 atomic percent or higher relative to total M, the cathode electrochemically active material comprising a non-uniform distribution of Co; an anode including an anode electrochemically active material of the formula Li4+aTi5O12+b wherein −0.3≤a≤3.3, −0.3≤b≤0.3; and wherein the anode and the cathode each independently include a current collector substrate comprising aluminium.

Sahin, Kenan↗

DOE OSTI2024

MEASUREMENT OF THE NEUTRON FLUENCE-RATES IN THE ADVANCED TEST REACTOR

The axial neutron fluence-rate distribution at the Advanced Test Reactor (ATR) is determined using a combination of pure nickel and cobalt-aluminium alloy dosimeter wires. Most irradiation programs at ATR need to know the fast neutron fluence-rate surrounding their experiment to correlate post-irradiation examination results with neutron dose. The activated dosimeter wires, which extend beyond the full fuelled region of the reactor core, are highly radioactive following the full cycle in ATR and must therefore be measured in the ATR canal. The system that is employed for these measurements is mechanical scanning mechanism is used to scan the activated wires across the face of a columnated shield and a NaI detector. This detector is not sufficiently calibrated to provide absolute activity measurements, therefore, the count-rate is recorded and normalized to the highest activity for that wire. Then, an approximately 3-mm long portion of the wire is removed from the highest activity region in the wire. The wires are then transferred, and an absolute activity measurement is made using a calibrated ionization chamber. These measurements are combined with corrections for decay, neutron energy spectrum, burnup, dosimeter composition, reactor power fluctuations, and reactor outages to determine the average axial neutron fluence-rate at various locations within ATR during the cycle.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

Shock-Wave Proprieties of High-Strength Ceramics

The shock and release response of a suite of high-strength ceramics has been investigated with controlled planar impact methods and velocity interferometry diagnostics. The study provides Hugoniot, yield and post-yield compressive strength, phase transformation and tensile spall material properties data for these ceramics.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Thermal Dehydration of Aluminum (Oxy)hydroxides on Fuel Cladding Material - 20200

The aluminum cladding of research-reactor fuel undergoes general corrosion with resulting formation of adherent aluminum (oxy)hydroxide films during in-reactor and post-discharge exposure to water under various conditions and temperatures. These (oxy)hydroxides contain chemically-bound water that poses challenges for extended dry storage due to the risk of thermal or radiolytic decomposition releasing free water and/or hydrogen and oxygen gases. This study comprised laboratory experiments of thermal drying behavior of aluminum (oxy)hydroxides to identify approaches for reducing bound water on fuel cladding prior to sealed dry storage. Effective drying strategies for adherent (oxy)hydroxides on fuel cladding will improve the safety of dry storage by mitigating potential avenues for additional corrosion and/or generation of flammable gases inside the storage canister. This work is part of a broader investigation to address knowledge gaps and technical data needs for dry storage of aluminum-clad spent nuclear fuel (ASNF), which included investigation of (oxy)hydroxide formation on aluminum alloy substrates immersed in water, characterization of service-grown films from ASNF, and radiolytic yield of hydrogen from (oxy)hydroxide powders and films. The current work comprises experimental thermal dehydration of aluminum trihydroxides (bayerite and gibbsite) characteristic of low-temperature (<80 deg. C) corrosion in water and aluminum oxyhydroxide (boehmite) characteristic of high temperature (>80 deg. C) corrosion in water. First, commercially produced (oxy)hydroxide powders (boehmite and gibbsite) were tested via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effort aimed to identify or confirm key temperature ranges/thresholds for the thermal decomposition reactions, as well as impacts of ramp rate and hold times, for drying of isolated, high-surface-area (oxy)hydroxides. The information gleaned from powder tests was used to guide subsequent drying tests on adherent (oxy)hydroxide films grown on aluminum alloy substrates. TGA was used to analyze small samples of the aluminum coupons with adherent (oxy)hydroxide films. Specimens were characterized both pre- and post-drying using X-ray diffraction (XRD) to determine the film composition and scanning electron microscopy (SEM) to determine its morphology. Drying of adherent (oxy)hydroxide films was anticipated to pose additional complications relative to drying of (oxy)hydroxide powders. Anticipated challenges include achieving sufficient drying of the (oxy)hydroxide at low-enough temperature to avoid melting or other undesirable phase changes in the aluminum substrate and overcoming transport limitations of water through the thickness of a dense film or through a tortuous pore structure to reach the outer surface of the film. Inn addition, dehydration of (oxy)hydroxides significantly changes the film density, which may lead to substantial alterations in the morphology, including potential cracking and spalling of the film. TGA/DSC tests of gibbsite powders resulted in successful conversion to boehmite or alumina, depending on the maximum temperature reached. At low ramp rates (≤5 deg. C/min), the conversion to boehmite occurred around 300 deg. C (210-340 deg. C). XRD confirmed that boehmite was the only phase detected after tests reaching 450 deg. C. The transition to alumina occurred around 510 deg. C (470-550 deg. C), with XRD detecting only alumina after tests reaching at least 600 deg. C. Boehmite powders dehydrated to alumina at about 400 deg. C (330-460 deg. C) for coarse (77-μm particle diameter) powder and about 490 deg. C (420-520 deg. C) for fine (0.7-μm particle diameter) powder. For all powders tested, the maximum percent mass loss after drying to high temperature slightly exceeded the theoretical mass loss for complete dehydration of the stoichiometric (oxy)hydroxide to alumina, which is likely attributable to physisorbed water in the powder. Drying of a thick (∼8.6 μm), predominantly bayerite adherent film displayed a dramatic change in film morphology, with the initially continuous trihydroxide film cracking into sections on the order of 50 μm square and partially delaminating. The outermost layer of the film completely faked of in some regions. The layer exposed under the spalled oxide also displayed prominent cracking, with spacing on the order of 10 μm, but this surface layer appeared to remain completely adhered to the aluminum substrate. TGA showed mass losses per unit surface area up to ∼1.0 mg/cm{sup 2}. XRD characterization of the remaining oxide was inconclusive, with no crystalline phases detected. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Highly Size-Selective Water-Insoluble Cross-Linked Carboxymethyl Cellulose Membranes

Carboxymethyl cellulose (CMC) membranes have strong potential for application as molecular-scale separators. For this study, stable CMC membranes were fabricated with aluminum chloride (AlCl{sub 3}) and iron(III) chloride (FeCl{sub 3}) serving as cross-linkers. The resulting CMC-Al and CMC-Fe membranes were optically transparent and water-insoluble with sufficient mechanical strength for practical applications. The water permeation flux through the membranes was directly proportional to the operating pressure. With just a 10-fold increase in the molecular weight from 60 Da (urea) to 604 Da (bordeaux S), the effective diffusion coefficient (D{sub eff}) of the CMC-Al membrane increased 56-fold, and that of the CMC-Fe membrane increased 3500-fold. This significant correlation between D{sub eff} on molecular size indicated that the sizes of the mass transfer channels through the membrane were strictly monodisperse, in the range of molecular sizes that were tested.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Interaction Between Liquid Steel and AlN Substrate Containing Al-Y-Oxides

Reactions between molten iron, molten silicon steel, and ceramic materials are of great importance from the perspective of the corrosion of refractory material in the steelmaking and continuous casting processes. Reactions between liquid steel and aluminum nitride (AlN) substrate containing Al-Y-oxides were investigated using the sessile drop method at 1833 K (1560 °C). The liquid–substrate interface was observed with the increasing holding time, and the reaction mechanism was studied. In the case of the liquid iron and the silicon steel on the AlN substrate containing Al-Y-oxides, the reaction products on the steel side of the interface between the steel and the substrate were Al-rich Al-Y-oxides and Al{sub 2}O{sub 3} particles. For silicon steel and pure AlN substrate, Al{sub 2}O{sub 3} particles were the main products. Contact angles were lower for liquid iron than for silicon steel due to the higher oxygen content in iron. In addition, the solid–liquid interfacial tension and the work of adhesion between AlN and steel were measured.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Silicon Production via Reaction of Silicon Tetrachloride and Aluminum Subchloride

Silicon tetrachloride reduction by aluminum subchloride was studied experimentally. Aluminum subchloride was synthesized in a reaction of metallic aluminum and AlCl{sub 3}; a burner-like construction of the reactor was used to avoid the direct reaction of aluminum and SiCl{sub 4}. The reduction was conducted at a pressure of 0.1 MPa and two temperature regimes: 1273 K and 1373 K (1000 °C and 1100 °C). As a result, two types of products were obtained: crystals and fine particles. The crystals formation occurred in the high-temperature zone, whereas the particles were dispersed by argon flow and concentrated mainly in aluminum chloride by-product in the cold part of the reactor. It was shown that silicon yield increased with increasing AlCl concentration. The temperature of the reduction process did not have a significant effect on the ultimate silicon yield. However, the silicon etching reaction rate and fine particles yield increased as temperature increased. X-ray diffraction and scanning electron microscopy analysis showed that the impurities content in silicon crystals was below the detection limit. In contrast, the aluminum content in the powder product was 2 to 3 wt pct. Another type of product, yellow blanket-like silicon fibers, was obtained with a high yield at 1373 K (1100 °C) and low [AlCl]:[SiCl{sub 4}] ratio.

36 MATERIALS SCIENCE↗