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Results for “HYDROFLUORIC ACID”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Batch and column studies of radium, actinium, thorium and protactinium on CL resin in nitric acid, hydrochloric acid and hydrofluoric acid

CL resin (TrisKem International) was characterized for separations of radium, actinium, thorium and protactinium. Batch studies are presented for radium, actinium and thorium in HCl and HNO3 as well as for radium, thorium and protactinium in HF. The uptake of thorium from dilute HNO3 (≤ 10 -4 M) and dilute HCl (≤ 10 -4 M) was found to be very high (D w > 100 in HNO 3 and > 1000 in HCl). Kinetics studies on thorium were performed in HCl and HNO 3 to determine suitably for column separations. Six column separation studies are presented including the separation of trace thorium from radium and actinium in dilute HCl and HNO 3 , the separation of radium from 1 mg 232 Th in dilute HCl, the separation of thorium and radium in the presence of HCl and excess Cl-, the separation of radium, protactinium and thorium by retention of protactinium and the separation of protactinium and thorium by retention of thorium.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

EXAFS Study of the Speciation of Protactinium(V) in Aqueous Hydrofluoric Acid Solutions

The speciation of protactinium(V) in hydrofluoric acid (HF) solutions was studied using X-ray absorption spectroscopy. Extended X-ray absorption fine structure measurements were performed on an aqueous solution of 0.05 M protactinium(V) with various HF concentrations ranging from 0.5 to 27 M in order to probe the protactinium coordination sphere with respect to the identity and number of coordinating ligands. The resulting fits to the spectra suggest the presence of an eight-coordinate homoleptic fluoro complex in highly concentrated fluoride solutions (27 M), with equilibrium between seven- and eight-coordinate fluoro complexes at moderate acidities, and in more dilute solutions, results indicate that one water molecule is likely to replace a fluoride in the first coordination sphere, at a distance of 2.54-2.57 angstrom. Comparisons of this chemistry with group V metals, niobium and tantalum, are presented, and the potential implications for these results on the hydrolytic behavior of protactinium in aqueous systems are discussed.

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

A non-aqueous sodium hexafluorophosphate-based electrolyte degradation study: Formation and mitigation of hydrofluoric acid

Fundamental characterization of battery electrolyte is crucial for rechargeable batteries. This work reports the chemical stability of sodium hexafluorophosphate (NaPF6)-based non-aqueous electrolytes containing different solvent mixtures (e.g., cyclic and acyclic carbonates) in the presence of water for Na-ion batteries. A degradation study is conducted using NaPF 6 -based electrolytes, highlighting the effect of two electrolyte additives, 2,2,2-trifluoroethoxy-2,2,2-ethoxy phosphazene (FM2) and fluoroethylene carbonate (FEC), on degradation and cell performance of full-cell Na-ion batteries. Hydrolysis of this salt in acidic condition is particularly prone to form hydrofluoric acid (HF), and can be observed in electrolytes made with battery grade carbonate solvents (<20 ppm of water). Here, degradation mechanisms of NaPF 6 -based electrolytes are studied using liquid nuclear magnetic resonance (NMR). Noticeable degradation takes place in high purity electrolytes with the presence of moisture to form HF and organophosphates in timeframes below the current shelf-life of the Na electrolytes. FEC is not efficient to protect the electrodes from being exposed to HF. On the other hand, FM2 is revealed as a “scavenger” of HF, which helps stabilize the shelf life of electrolytes that might contain or become exposed to water. Our study underscores the importance to understanding the degradation of electrolyte and improving stability toward better shelf life for sodium ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2019

Effect of Conductivity Type and Doping Level of Silicon Crystals on the Size of Formed Pore Channels during Anodic Etching in Hydrofluoric Acid Solutions

In this paper, we discuss causes of the multidirectional effect of changes in the concentrations of free charge carriers in silicon crystals of p- and n-type conductivity on the transverse dimensions of pores formed as a result of anodic etching in hydrofluoric acid solutions, as well as the effect of anodic current density on pore size. The observed dependences are explained based on the concepts of electrochemical pore formation in semiconductor crystals as self-organizing cooperative processes accompanied by the injection of electrons from the chemical reaction region at the pore advancement front. Differences in the size of pores forming at the same current density in crystals differing in type and concentration of free charge carriers are associated with the effective temperature of the front of the cooperative chemical reaction at the bottom of germinating pores. This temperature, in turn, correlates with the power density of thermal energy released in the near-surface region of the etching crystal, either due to recombination processes for a p-type semiconductor or direct or indirect energy transfer from hot electrons to lattice vibrations in the case of a n-type semiconductor. The characteristic relaxation times of injected nonequilibrium electrons were calculated depending on the concentrations of the majority charge carriers in silicon crystals of both types of conductivity and the corresponding thicknesses of the regions of relaxation energy release. The revealed patterns of concentration changes in the power density of heat release in the near-frontal region of etching silicon crystals of p- and n-type conductivity are in good agreement with observed changes in the size of germinating pores.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Synthesis of anatase titanium dioxide nanocaps via hydrofluoric acid etching towards enhanced photocatalysis

Graphical abstract: Anatase TiO{sub 2} nanocaps prepared by HF-assisted chemical etching method exhibit enhanced photocatalytic activity compared with commercial P25 because of HF served as an etching agent to remove doped impurities. - Highlights: • Anatase TiO{sub 2} nanocaps were synthesized by HF etching process. • The optimal conditions of experiment are 700 °C calcination and 0.2 mL HF solution. • The photocatalytic properties was studied upon UV and Visible irradiation. • The unique TiO{sub 2} nanocaps structure shows excellent photocatalytic activity. - Abstract: Anatase titanium dioxide (TiO{sub 2}) nanocaps were created via a four-step process including the preparation of SiO{sub 2} spheres, the deposition of a TiO{sub 2} layer to fabricate SiO{sub 2}@TiO{sub 2} composite spheres, the calcination for obtaining the crystal structure of anatase phase, and hydrofluoric acid (HF) etching to dissolve SiO{sub 2} cores. The SiO{sub 2}@TiO{sub 2} spheres calcined at 700 °C revealed fine photocatalytic activity. Interestingly, most of samples transformed into TiO{sub 2} nanocaps via HF etching, and TiO{sub 2} nanocaps prepared using optimal conditions exhibited quick degradation (k is 0.052 min{sup −1}) compared with commercial P25 (k is 0.030 min{sup −1}) and the TiO{sub 2} nanostructures etched by a NaOH solution. The excellent photocatalytic performance is attributed to its unique hollow hemispherical nanocaps structure, which is in favor of making full use of incident light. The photocatalysis phenomenon in visible light was also observed after depositing Au nanoparticles on anantase TiO{sub 2} nanocaps.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Alternate method of source preparation for alpha spectrometry: No electrodeposition, no hydrofluoric acid

An alternate method of preparing actinide alpha counting sources was developed in place of electrodeposition or lanthanide fluoride micro-precipitation. The method uses lanthanide hydroxide micro-precipitation to avoid the use of hazardous hydrofluoric acid. Lastly, it provides a quicker, simpler, and safer way of preparing actinide alpha counting sources in routine, production-type laboratories that process many samples daily.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2016

Correlation of film density and wet etch rate in hydrofluoric acid of plasma enhanced atomic layer deposited silicon nitride

The continued scaling in transistors and memory elements has necessitated the development of atomic layer deposition (ALD) of silicon nitride (SiN{sub x}), particularly for use a low k dielectric spacer. One of the key material properties needed for SiN{sub x} films is a low wet etch rate (WER) in hydrofluoric (HF) acid. In this work, we report on the evaluation of multiple precursors for plasma enhanced atomic layer deposition (PEALD) of SiN{sub x} and evaluate the film’s WER in 100:1 dilutions of HF in H{sub 2}O. The remote plasma capability available in PEALD, enabled controlling the density of the SiN{sub x} film. Namely, prolonged plasma exposure made films denser which corresponded to lower WER in a systematic fashion. We determined that there is a strong correlation between WER and the density of the film that extends across multiple precursors, PEALD reactors, and a variety of process conditions. Limiting all steps in the deposition to a maximum temperature of 350 °C, it was shown to be possible to achieve a WER in PEALD SiN{sub x} of 6.1 Å/min, which is similar to WER of SiN{sub x} from LPCVD reactions at 850 °C.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Corrosion Behavior of Plasma-Nitrided 904L Austenitic Stainless Steel in Hydrofluoric Acid

A new type of high-chromium nickel molybdenum super austenitic stainless steel, 904L, has excellent corrosion resistance in acidic environments. However, the service life of 904L decreases significantly in a mixed acid system that includes hydrogen fluoride and sulfuric acid. In this article, different plasma nitriding processes were used to modify the surface of 904L stainless steel. X-ray diffraction was used to analyze the phase composition after nitriding; scanning electron microscopy and atomic force microscopy were used to examine the surface morphology after nitriding; electrochemical noise and electrochemical methods were used to study the localized corrosion behavior and the damage mechanism of the ion nitride layer; and the effect of the plasma nitride layer on the corrosion resistance was explored. The results show that with increasing nitriding time, the thickness of the nitride layer increased. Ion nitriding resulted in the coarsening of the 904L austenitic stainless steel surface. A long nitriding treatment time resulted in the precipitation of CrN in the modified layer, depleting the chromium from the matrix and remarkably reducing the corrosion resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Nominations for the 2017 NNSA Pollution Prevention Awards

In the field of nuclear forensics, one of the biggest challenges is to dissolve postdetonation debris for analysis. Debris generated after a nuclear detonation is a glassy material that is difficult to dissolve with chemicals. Traditionally, concentrated nitric acid, hydrofluoric acid, or sulfuric acid are employed during the dissolution. These acids, due to their corrosive nature, are not suitable for in-field/on-site sample preparations. Uranium oxides are commonly present in nuclear fuel processing plants and nuclear research facilities. In uranium oxides, the level of uranium isotope enrichment is a sensitive indicator for nuclear nonproliferation and is monitored closely by the International Atomic Energy Agency (IAEA) to ensure there is no misuse of nuclear material or technology for nuclear weapons. During an IAEA on-site inspection at a facility, environmental surface swipe samples are collected and transported to the IAEA headquarters or network of analytical laboratories for further processing. Uranium oxide particles collected on the swipe medium are typically dissolved with inorganic acids and are then analyzed for uranium isotopic compositions. To improve the responsiveness of on-site inspections, in-field detection techniques have been recently explored. However, in-field analysis is bottlenecked by time-consuming and hazardous dissolution procedures, as corrosive inorganic acids must be used. Corrosive chemicals are difficult to use in the field due to personnel safety considerations, and the transportation of such chemicals is highly regulated. It was therefore necessary to develop fast uranium oxide dissolution methods using less hazardous chemicals in support of the rapid infield detection of anomalies in declared nuclear processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Wet-chemical systems and methods for producing black silicon substrates

A wet-chemical method of producing a black silicon substrate. The method comprising soaking single crystalline silicon wafers in a predetermined volume of a diluted inorganic compound solution. The substrate is combined with an etchant solution that forms a uniform noble metal nanoparticle induced Black Etch of the silicon wafer, resulting in a nanoparticle that is kinetically stabilized. The method comprising combining with an etchant solution having equal volumes acetonitrile/acetic acid:hydrofluoric acid:hydrogen peroxide.

14 SOLAR ENERGY↗
DOE OSTI2014

Rapid separation and purification of uranium and plutonium from dilute-matrix samples

This work presents a streamlined separation and purification approach for trace uranium and plutonium from dilute (carrier-free) matrices. The method, effective for nanogram quantities of U and femtogram to picogram quantities of Pu, is ideally suited for environmental swipe samples that contain a small amount of collected bulk material. As such, it may be applicable for processing swipe samples such as those collected in IAEA inspection activities as well as swipes that are loaded with unknown analytes, such as those implemented in interlaboratory round-robin or proficiency tests. Additionally, the simplified actinide separation could find use in internal laboratory monitoring of clean room conditions prior to or following more extensive chemical processing. We describe key modifications to conventional techniques that result in a relatively rapid, cost-effective, and efficient U and Pu separation process. We demonstrate the efficacy of implementing anion exchange chromatography in a single column approach. We also show that hydrobromic acid is an effective substitute in lieu of hydroiodoic acid for eluting Pu. Lastly, we show that nitric acid is an effective digestion agent in lieu of perchloric acid and/or hydrofluoric acid. A step by step procedure of this process is detailed.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2014

Internal structure of the nanogratings generated inside bulk fused silica by ultrafast laser direct writing

The aim of the present work was to characterize the internal structure of nanogratings generated inside bulk fused silica by ultrafast laser processing and to study the influence of diluted hydrofluoric acid etching on their structure. The nanogratings were inscribed at a depth of 100 μm within fused silica wafers by a direct writing method, using 1030 nm radiation wavelength and the following processing parameters: E = 5 μJ, τ = 560 fs, f = 10 kHz, and v = 100 μm/s. The results achieved show that the laser-affected regions are elongated ellipsoids with a typical major diameter of about 30 μm and a minor diameter of about 6 μm. The nanogratings within these regions are composed of alternating nanoplanes of damaged and undamaged material, with an average periodicity of 351 ± 21 nm. The damaged nanoplanes contain nanopores randomly dispersed in a material containing a large density of defects. These nanopores present a roughly bimodal size distribution with average dimensions for each class of pores 65 ± 20 × 16 ± 8 × 69 ± 16 nm{sup 3} and 367 ± 239 × 16 ± 8 × 360 ± 194 nm{sup 3}, respectively. The number and size of the nanopores increases drastically when an hydrofluoric acid treatment is performed, leading to the coalescence of these voids into large planar discontinuities parallel to the nanoplanes. The preferential etching of the damaged material by the hydrofluoric acid solution, which is responsible for the pores growth and coalescence, confirms its high defect density.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Task-Specific Ionic Compounds for In-Field Sample Preparation Poster

In the event of a nuclear detonation, actinide and fission product-containing debris can be analyzed to provide information about the nature of the device. In-field sample dissolution prior to transport to a laboratory is critical for reducing the time between an event and delivery of information to decision makers. However, the best dissolution methods utilize liquid strong acid solutions, which are incompatible with field collection Standard Operating Procedure. What is required are solid materials that, when mixed with water in the field, can provide the strong digestion and dissolution properties of nitric and hydrofluoric acids. Fluorohydrogenate ionic liquids have shown a remarkable ability to dissolve a wide range of materials, from refractory actinide oxides to cementitious material such as calcium silicates. These strong dissolution properties are due to the neutral hydrofluoric acid that is bound to the anion component of the ionic liquid. Because these materials are liquids, they are also incompatible with Standard Operating Procedure. However, the physiochemical properties of ionic liquids, such as the melting point, can be readily tuned through minor modification of the molecular structure of the cations and anions. Thus, we hypothesize that by synthesizing modified cations, novel ionic compounds with melting points above ambient but with the same anion and bound hydrofluoric acid – and thus similar digestion and dissolution properties – as current fluorohydrogenate ionic liquids can be produced. These solid materials would be compatible with current Standard Operating Procedure, and would allow for rapid, in-field dissolution of samples, shortening the time to actionable information after an event.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

The influence of H{sub 2}O{sub 2} concentration to the structure of silicon nanowire growth by metal-assisted chemical etching

A simple and low cost method to produce well aligned silicon nanowires at large areas using Ag-assisted chemical etching at room temperature were presented. The structure of silicon nanowires growth by metal-assisted chemical etching was observed. Prior to the etching, the silicon nanowires were prepared by electroless metal deposited (EMD) in solution containing hydrofluoric acid and hydrogen peroxide in Teflon vessel. The silver particle was deposited on substrate by immersion in hydrofluoric acid and silver nitrate solution for sixty second. The silicon nanowires were growth in different hydrogen peroxide concentration which are 0.3M, 0.4M, 0.5M and 0.6M and 0.7M.The influence of hydrogen peroxide concentration to the formation of silicon nanowires was studied. The morphological properties of silicon nanowires were investigated using field emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDS).

77 NANOSCIENCE AND NANOTECHNOLOGY↗