Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Dissolution”

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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Recycling Glass Fiber Thermoplastic Composites from Wind Turbine Blades

We report that thermoplastic resin systems have long been discussed for use in large-scale composite parts but have yet to be exploited by the energy industry. The use of these resins versus their thermosetting counterparts can potentially introduce cost savings due to non-heated tooling, shorter manufacturing cycle times, and recovery of raw materials from the retired part. Because composite parts have high embedded energy, recovery of their constituent materials can provide substantial economic benefit. This study determines the feasibility of recycling composite wind turbine blade components that are fabricated with glass fiber reinforced Elium (R) thermoplastic resin. Several experiments are conducted to tabulate important material properties that are relevant to recycling, including thermal degradation, grinding, and dissolution of the polymer matrix to recover the constituent materials. Dissolution, which is a process unique to thermoplastic matrices, allows recovery of both the polymer matrix and full-length glass fibers, which maintain their stiffness (190 N/(mm g)) and strength (160 N/g) through the recovery process. Injection molded regrind material is stiffer (12 GPa compared to 10 GPa) and stronger (150 MPa compared to 84 MPa) than virgin material that had shorter fibers. An economic analysis of the technical data shows that recycling thermoplastic-glass fiber composites via dissolution into their constituent parts is commercially feasible under certain conditions. This analysis concludes that 50% of the glass fiber must be recovered and resold for a price of $0.28/kg. Furthermore, 90% of the resin must be recovered and resold at a price of $2.50/kg.

17 WIND ENERGY↗
DOE OSTI2014

Origin of the solid solution in the LiInSe{sub 2}–In{sub 2}Se{sub 3} system

Techniques of bulk and local analyses were used to characterize the melt-grown single crystals of LiInSe{sub 2}, where yellow matrix coexists together with extended red areas distributed irregularly. Bulk chemical analysis showed that the average stoichiometry of yellow matrix is close to ideal 1:1:2, but red areas are enriched with In{sub 2}Se{sub 3}. An excess In{sub 2}Se{sub 3} is incorporated coherently into the crystal lattice of LiInSe{sub 2}, forming the substitution solid solution with the general formula (Li{sub 1−3x}In{sub x}⎕{sub 2})InSe{sub 2} and changing the color from yellow to red. The test crystals with the 50–55% content of In{sub 2}Se{sub 3} were found by the X-ray analysis to be single phase. The differential dissolution technique, measuring the spatial variation of the composition with high resolution, demonstrated that the single phase crystals in the LiInSe{sub 2}–In{sub 2}Se{sub 3} system might be grown only in a very narrow range close to stoichiometric. Being supersaturated, the heterovalent solid solution phases decompose in the course of cooling, and the concentration micro-heterogeneity occurs in the matrix as the coherent (or incoherent) inclusions of two different types, practically pure selenides of lithium and indium. The origin and scale of the micro-heterogeneity determining the physical properties of LiInSe{sub 2} are discussed as a starting point for the development of physicochemical foundations for growing high quality optical crystals. - Graphical abstract: Differential dissolution technique applied for detection of dispersive precipitates in as-grown LiInSe{sub 2} single crystals: kinetic curves of the phase dissolution: F is the main phase Li{sub 0.96}In{sub 1.01}Se{sub 2} (98.9%), secondary minor phases Li{sub 2}Se (0.1%), In{sub 2}Se{sub 3} (0.9%). - Highlights: • Phase purity of crystals Li{sub 1−3x}In{sub 1+x}Se{sub 2} was examined by a new stoichiographic method. • Breakup of the metastable solid solution with temperature drop was detected. • Dispersive precipitates Li–Se and In–Se of low content result from the breakup. • A crucial role of the precipitates in optical properties of the crystals is shown. • Conditions are given how to grow stoichiometric and single-phase crystals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Synthesis of hexagonal wurtzite Cu{sub 2}ZnSnS{sub 4} prisms by an ultrasound-assisted microwave solvothermal method

Wurtzite Cu{sub 2}ZnSnS{sub 4} (CZTS) hexagonal prisms were synthesized by a simple ultrasound-microwave solvothermal method. The product was characterized by XRD, FESEM, EDS, TEM, Raman and UV–vis spectrometer. The hexagonal prisms were 0.5–2 μm wide and 5–12 μm long. The PVP played an important role in the formation of the CZTS hexagonal prisms. In addition, the ultrasound-assisted microwave process was helpful for synthesis of wurtzite rather than kesterite phase CZTS. A nucleation–dissolution–recrystallization mechanism was also proposed to explain the growth of the CZTS hexagonal prisms. - Graphical abstract: Wurtzite Cu{sub 2}ZnSnS{sub 4} hexagonal prisms were synthesized by ultrasound-microwave solvothermal method. The ultrasound-assisted microwave process and PVP were useful to the growth of CZTS. A nucleation–dissolution–recrystallization growth mechanism was also proposed. - Highlights: • Wurtzite Cu{sub 2}ZnSnS{sub 4} was prepared by ultrasound-assisted microwave solvothermal method. • The wurtzite CZTS hexagonal prisms are demonstrated a band gap of 1.49 eV. • Synergistic effect of ultrasound and microwave is helpful to prepare Wurtzite CZTS. • PVP plays an important role in the formation of the CZTS hexagonal prisms. • Nucleation–dissolution–recrystallization growth mechanism of the CZTS was proposed.

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

Microstructural evolution and growth behavior of intermetallic compounds at the liquid Al/solid Fe interface by synchrotron X-ray radiography

Highlights: • A layered and tongue-like η phase was in-situ observed by synchrotron radiation X-ray radiography. • The coalescence of η phase bottom resulted in dissolution, further increasing the growth rate. • The θ phase growth behavior with different morphologies during cooling was analyzed. - Abstract: The growth of Inter-Metallic Compounds (IMCs) with dissolution was investigated on the liquid Al/solid Fe interconnection by using synchrotron radiation real-time imaging technology. At the initial stage of holding at 850 °C, a layer of the η-Fe{sub 2}Al{sub 5} phase formed at the interface, and tongue-like η grew into α-Fe. The tongue-like η phase had a stronger (001) texture than the layered phase. The coalescence of tongue-like η started at the bottom, followed by the dissolution of IMCs, which leads to a further increase in its growth rate. During solidification stage, the dotted, needle-like and flake θ-FeAl{sub 3} phases were sequentially formed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Determining the biomass fraction of mixed waste fuels: A comparison of existing industry and {sup 14}C-based methodologies

Highlights: • Compares industry standard and {sup 14}C methods for determining bioenergy content of MSW. • Differences quantified through study at an operational energy from waste plant. • Manual sort and selective dissolution are unreliable measures of feedstock bioenergy. • {sup 14}C methods (esp. AMS) improve precision and reliability of bioenergy determination. • Implications for electricity generators and regulators for award of bio-incentives. - Abstract: {sup 14}C analysis of flue gas by accelerator mass spectrometry (AMS) and liquid scintillation counting (LSC) were used to determine the biomass fraction of mixed waste at an operational energy-from-waste (EfW) plant. Results were converted to bioenergy (% total) using mathematical algorithms and assessed against existing industry methodologies which involve manual sorting and selective dissolution (SD) of feedstock. Simultaneous determinations using flue gas showed excellent agreement: 44.8 ± 2.7% for AMS and 44.6 ± 12.3% for LSC. Comparable bioenergy results were obtained using a feedstock manual sort procedure (41.4%), whilst a procedure based on selective dissolution of representative waste material is reported as 75.5% (no errors quoted). {sup 14}C techniques present significant advantages in data acquisition, precision and reliability for both electricity generator and industry regulator.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2015

Determination of the origin of dissolved inorganic carbon in groundwater around a reclaimed landfill in Otwock using stable carbon isotopes

Highlights: • Research showed the origin of DIC in the groundwater around a reclaimed landfill. • Carbon isotope was used to evaluate the contributions of carbon from different sources. • The leachate-contaminated water was isotopically distinct from the natural groundwater. • DIC in the natural groundwater comes from organic matter and dissolution of carbonates. • In the contaminated water, DIC comes from organic matter in the aquifer and landfill. - Abstract: Chemical and isotopic analyses of groundwater from piezometers located around a reclaimed landfill in Otwock (Poland) were performed in order to trace the origin of dissolved inorganic carbon (DIC) in the groundwater. Due to differences in the isotopic composition of carbon from different sources, an analysis of stable carbon isotopes in the groundwater, together with the Keeling plot approach and a two-component mixing model allow us to evaluate the relative contributions of carbon from these sources in the groundwater. In the natural (background) groundwater, DIC concentrations and the isotopic composition of DIC (δ{sup 13}C{sub DIC}) comes from two sources: decomposition of organic matter and carbonate dissolution within the aquifer sediments, whereas in the leachate-contaminated groundwater, DIC concentrations and δ{sup 13}C{sub DIC} values depend on the degradation of organic matter within the aquifer sediments and biodegradation of organic matter stored in the landfill. From the mixing model, about 4–54% of the DIC pool is derived from organic matter degradation and 96–46% from carbonate dissolution in natural conditions. In the leachate-contaminated groundwater, about 20–53% of the DIC is derived from organic matter degradation of natural origin and 80–47% from biodegradation of organic matter stored in the landfill. Partial pressure of CO{sub 2} (P CO{sub 2}) was generally above the atmospheric, hence atmospheric CO{sub 2} as a source of carbon in DIC pool was negligible in the aquifer. P CO{sub 2} values in the aquifer in Otwock were always one to two orders of magnitude above the atmospheric P CO{sub 2}, and thus CO{sub 2} escaped directly into the vadose zone.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Delamination mechanism study of large size waste printed circuit boards by using dimethylacetamide

Highlights: • Dimethylacetamide (DMA) dissolved the epoxy resin of printed circuit boards (WPCB). • PCBs of 1, 4, 9 and 16 cm{sup 2} were delaminated in 150, 180, 300 and 420 min, respectively. • Peaks of epoxy resin and DMA were evident in the NMR spectra. • Shift in C=O, OH peaks of DMA & resin, respectively was registered w.r.t. time. • Hydrogen bonding between C=O of DMA and OH of resin results in the dissolution. - Abstract: Present work investigates the recycling of waste printed circuit boards (PCBs) by cracking of its multi-layered structure by using dimethylacetamide (DMA). The study shows that cracking and separation of layers of PCBs increases as the temperature increases; and decreases as the surface area of PCBs increases. After separation of layers, the used solvent was analyzed by proton and carbon nuclear magnetic resonance spectroscopy (NMR) to understand the dissolution phenomenon of resin. Further, NMR and Fourier transform infrared spectroscopy analysis of DMA sample after 1 h, 2 h, 3 h, 4 h and 8 h of reaction with PCBs at 433 K and PCB:DMA ratio (wt/vol) of 3:10 has been carried out to investigate the mechanism of dissolution of resin. These studies revealed that hydroxyl group of PCBs polymeric chain participates in hydrogen bonding with parent carbonyl group of DMA molecule that results in the solvation of resin. Possible chemical reaction based on the above finding has been discussed. Using this technique, separation of the metallic fraction without application of any energy intensive mechanical pre-processing is possible.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Phase Transformation Mechanism of Amorphous Calcium Phosphate to Hydroxyapatite Investigated by Liquid-Cell Transmission Electron Microscopy

Crystallization via phase transformation of a metastable precursor is a ubiquitous and effective strategy used by living systems to direct the growth of crystalline nanomaterials with remarkable functional properties. However, determining the exact process by which transformation occurs at the nanoscale is a difficult challenge. In this work, the recrystallization process of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) is explored by liquid-cell transmission electron microscopy. The effect of confinement in the liquid-cell is found to increase the size of ACP nanoparticles. In the presence of Mg 2+ , these large ACP nanoparticles transform to HAP by first dissolving from the interior to create a hollow structure, after which HAP forms preferentially on the surface and then subsequently in the bulk solution. We propose that the preferential dissolution within ACP particles is due to a change in the structure and/or chemistry of the ACP surface, likely associated with dehydration before crystallization of HAP. These results imply an important role of the confined environment of the liquid-cell in regulating the size of ACP particles, which then affects the surface structure and the detailed dissolution–recrystallization pathway. Moreover, we stress the key role of Mg 2+ in controlling HAP formation by stabilizing ACP via reduction in ACP solubility. This work provides a better understanding of the roles of additives and confinement during the phase transformation of ACP to HAP through dissolution and recrystallization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Recovery of Oxidized Actinides, Np(VI), Pu(VI), and Am(VI), from Cocrystallized Uranyl Nitrate Hexahydrate: A Single Technology Approach to Used Nuclear Fuel Recycling

In this work, the utility of recovering cocrystallized Np, Pu, and Am from a uranyl nitrate hexahydrate crystalline phase has been examined. Progressive dissolution studies were carried out on samples of either Np(VI), Pu(VI), or Am(VI) cocrystallized with uranyl nitrate hexahydrate, resulting in a linear relationship between the amount of actinides dissolved as a function of volume of HNO 3 added, which indicates homogeneous distribution of the transuranic species throughout the crystalline solid. The ratio of the concentration of U to the heavier actinides was maintained over the entire dissolution and mimicked that of the starting cocrystallization solution. A series of five crystallization–dissolution–recrystallization cycles of uranyl nitrate hexahydrate from nitric acid have been achieved in the presence of Am(VI), where the behavior of Am(VI) followed that of U(VI) for each step of all five cycles. Negligible reduction of Am(VI) to Am(III) was observed between each recrystallization cycle. These results indicate the utility of a group hexavalent actinide cocrystallization approach toward used nuclear fuel recycling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Acidic Oxygen Evolution Reaction Activity–Stability Relationships in Ru-Based Pyrochlores

Ru-based oxygen evolution reaction (OER) catalysts show significant promise for efficient water electrolysis, but rapid degradation poses a major challenge for commercial applications. In this work, we explore several Ru-based pyrochlores (A 2 Ru 2 O 7 , A = Y, Nd, Gd, Bi) as OER catalysts and demonstrate improved activity and stability of catalytic Ru sites relative to RuO 2 . Furthermore, we combine complementary experimental and theoretical analysis to understand how the A-site element impacts activity and stability under acidic OER conditions. Among the A 2 Ru 2 O 7 studied herein, we find that a longer Ru–O bond and a weaker interaction of the Ru 4d and O 2p orbitals compared with RuO 2 results in enhanced initial activity. We observe that the OER activity of the catalysts changes over time and is accompanied by both A-site and Ru dissolution at different relative rates depending on the identity of the A-site. Pourbaix diagrams constructed using density functional theory (DFT) calculations reveal a driving force for this experimentally observed dissolution, indicating that all compositions studied herein are thermodynamically unstable in acidic OER conditions. Theoretical activity predictions show consistent trends between A-site cation leaching and OER activity. These trends coupled with Bader charge analysis suggest that dissolution exposes highly oxidized Ru sites that exhibit enhanced activity. Overall, using the stability number (molO2 evolved/molRu dissolved) as a comparative metric, the A 2 Ru 2 O 7 materials studied in this work show substantially greater stability than a standard RuO2 and commensurate stability to some Ir mixed metal oxides. Finally, the insights described herein provide a pathway to enhanced Ru catalyst activity and durability, ultimately improving the efficiency of water electrolyzers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

ZeroCAL: Eliminating Carbon Dioxide Emissions from Limestone’s Decomposition to Decarbonize Cement Production

Limestone (calcite, CaCO 3 ) is an abundant and cost-effective source of calcium oxide (CaO) for cement and lime production. However, the thermochemical decomposition of limestone (~800 °C, 1 bar) to produce lime (CaO) results in substantial carbon dioxide (CO 2(g) ) emissions and energy use, i.e., ~1 tonne [t] of CO 2 and ~1.4 MWh per t of CaO produced. Here, we describe a new pathway to use CaCO 3 as a Ca source to make hydrated lime (portlandite, Ca(OH) 2 ) at ambient conditions (p, T) while nearly eliminating process CO 2(g) emissions (as low as 1.5 mol. % of the CO 2 in the precursor CaCO 3 , equivalent to 9 kg of CO 2(g) per t of Ca(OH) 2 ) within an aqueous flowelectrolysis/ pH-swing process that coproduces hydrogen (H 2(g) ) and oxygen (O 2(g) ). Because Ca(OH) 2 is a zero-carbon precursor for cement and lime production, this approach represents a significant advancement in the production of zero-carbon cement. The Zero CArbon Lime (ZeroCAL) process includes dissolution, separation/recovery, and electrolysis stages according to the following steps: (Step 1) chelator (e.g., ethylenediaminetetraacetic acid, EDTA)-promoted dissolution of CaCO 3 and complexation of Ca 2+ under basic (>pH 9) conditions, (Step 2a) Ca enrichment and separation using nanofiltration (NF), which allows separation of the Ca-EDTA complex from the accompanying bicarbonate (HCO 3 – ) species, (Step 2b) acidity-promoted decomplexation of Ca from EDTA, which allows near-complete chelator recovery and the formation of a Ca-enriched stream, and (Step 3) rapid precipitation of Ca(OH) 2 from the Ca-enriched stream using electrolytically produced alkalinity. These reactions can be conducted in a seawater matrix yielding coproducts including hydrochloric acid (HCl) and sodium bicarbonate (NaHCO 3 ), resulting from electrolysis and limestone dissolution, respectively. Careful analysis of the reaction stoichiometries and energy balances indicates that approximately 1.35 t of CaCO 3 , 1.09 t of water, 0.79 t of sodium chloride (NaCl), and ~2 MWh of electrical energy are required to produce 1 t of Ca(OH) 2 , with significant opportunity for process intensification. This approach has major implications for decarbonizing cement production within a paradigm that emphasizes the use of existing cement plants and electrification of industrial operations, while also creating approaches for alkalinity production that enable cost-effective and scalable CO 2 mineralization via Ca(OH) 2 carbonation.

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

Can Cr( iii ) substitute for Al( iii ) in the structure of boehmite?

The dissolution of boehmite is a technical issue for the Al industry because of its recalcitrant nature. In fact, a similar problem exists with boehmite in nuclear waste sludge at the Hanford site in eastern Washington State, USA. Dissolution of Al phases is required to reduce the waste loadings in the final borosilicate glass waste form. Although not the most common Al-bearing species in the sludge, boehmite may become a rate limiting step in the processing of the wastes. Hanford boehmite is an order of magnitude more resistant to dissolution in hot caustic solutions than expected from surface-normalized rates. We are exploring potential intrinsic and extrinsic effects that may limit boehmite reactivity; one clue comes from microstructural analyses that indicate an association of Cr with Al in the Hanford nuclear waste. Hence, in this first paper, we investigated the potential role of chromium on the reactivity of boehmite in caustic solution. An important finding was that irrespective of the synthesis pathway, amount of Cr(III), or the resultant morphology, there was no evidence for Cr incorporation in the bulk structure, in agreement with QM calculations. In fact, electron microscopic (EM) and spectroscopic analyses showed that Cr was enriched at the (101) edges of the boehmite. However, Cr had no measurable effect on the morphology during the synthesis step. In contrast, comparison of the morphologies of the synthetic Cr-doped and pure boehmite samples after exposure to caustic solutions provided evidence that Cr inhibited the corrosion. TEM showed that Cr was not homogeneously distributed at the surface. Consequently, Cr may have partially passivated the surface by blocking discrete energetic sites on the lateral surfaces of boehmite.

1-Cra and 1-Crb↗
DOE OSTI2016

Development and evaluation of a collection apparatus for recoil products for study of the deexcitation process of {sup 235m}U

The nucleus {sup 235m}U is an isomer with extremely low excitation energy (76.8 eV) and decays dominantly through the internal conversion (IC) process. Because outer-shell electrons are involved in the IC process, the decay constant of {sup 235m}U depends on its chemical environment. We plan to study the deexcitation process of {sup 235m}U by measuring the energy spectra of IC electrons in addition to the decay constants for various chemical forms. In this paper, the preparation method of {sup 235m}U samples from {sup 239}Pu by using alpha-recoil energy is reported. A Collection Apparatus for Recoil Products was fabricated, and then collection efficiencies under various conditions were determined by collecting {sup 224}Ra recoiling out of {sup 228}Th electrodeposited and precipitated sources. The pressure in the apparatus (vacuum or 1 atm of N{sub 2} gas) affected the variations of the collection efficiencies depending on the negative voltage applied to the collector. The maximum values of the collection efficiencies were mainly affected by the thickness of the {sup 228}Th sources. From these results, the suitable conditions of the {sup 239}Pu sources for preparation of {sup 235m}U were determined. In addition, dissolution efficiencies were determined by washing collected {sup 224}Ra with solutions. When {sup 224}Ra was collected in 1 atm of N{sub 2} gas and dissolved with polar solutions such as water, the dissolution efficiencies were nearly 100%. The method of rapid dissolution of recoil products would be applicable to rapid preparation of short-lived {sup 235m}U samples for various chemical forms.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Operando X-ray diffraction analysis for a glyme-based Li-O{sub 2} battery

We investigated the effect of the carbon species in the air (oxygen) electrode, electrolyte concentration, and humidity in the supplied O{sub 2} gas on the Li-O{sub 2} reactions by using the operando XRD analysis. Regarding carbon species, we found that the over-potentials in the galvanostatic discharge-charge process were suppressed when using the KB carbon in the air electrode. The results of operando XRD measurements revealed that the Li{sub 2}O{sub 2} formed on the KB had the smaller crystalline or more amorphous like structures, which could be one reason for faster reaction kinetics of Li{sub 2}O{sub 2} dissolution. The discharge-charge curves of the cells with different concentration of LiTFSI/(G4){sub n} electrolyte showed the slight difference but less differences in the Li{sub 2}O{sub 2} formation and dissolution behaviors. In addition to the nature of Li{sub 2}O{sub 2} products, reaction of Li-salts would also have ineligible effects. We also found that the higher humidity in oxygen produced more the LiOH and promoted the Li{sub 2}O{sub 2} dissolution, which indicate that the LiOH formation could affect the Li{sub 2}O{sub 2} morphologies or surface chemistries. Our present results demonstrated that the operando XRD measurement are useful for analyzing the reaction mechanism of Li-O{sub 2} battery.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

The impact of galaxy geometry and mass evolution on the survival of star clusters

Direct N-body simulations of globular clusters in a realistic Milky-Way-like potential are carried out using the code NBODY6 to determine the impact of the host galaxy disk mass and geometry on the survival of star clusters. A relation between disk mass and star-cluster dissolution timescale is derived. These N-body models show that doubling the mass of the disk from 5 × 10{sup 10} M {sub ☉} to 10 × 10{sup 10} M {sub ☉} halves the dissolution time of a satellite star cluster orbiting the host galaxy at 6 kpc from the galactic center. Different geometries in a disk of identical mass can determine either the survival or dissolution of a star cluster orbiting within the inner 6 kpc of the galactic center. Furthermore, disk geometry has measurable effects on the mass loss of star clusters up to 15 kpc from the galactic center. N-body simulations performed with a fine output time step show that at each disk crossing the outer layers of star clusters experiences an increase in velocity dispersion of ∼5% of the average velocity dispersion in the outer section of star clusters. This leads to an enhancement of mass loss—a clearly discernable effect of disk shocking. By running models with different inclinations, we determine that star clusters with an orbit that is perpendicular to the Galactic plane have larger mass loss rates than do clusters that evolve in the Galactic plane or in an inclined orbit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

The development and application of the stirred‐reactor coupon analysis (SRCA) test method

A new technique, termed the stirred‐reactor coupon analysis (SRCA) method, has been developed to measure the rate of glass dissolution in forward‐rate conditions. Monolithic glass coupons are partially masked with an inert material before placement in a large volume of well‐mixed solution with known chemistry and temperature for a predetermined duration. After the test, the mask is removed, and the difference in step height between the protected area and the exposed corroded portions of the sample coupon is measured to determine the extent of glass dissolution. The step height is converted to a rate measurement using the test duration and glass density. Test parameters such as sample surface preparation and test duration were evaluated to determine their effects on the measured rates. Additionally, results from an interlaboratory study (ILS) consisting of 12 laboratories from 11 different institutions are presented, where each laboratory performed 12 independent tests. When removing experimental outlier data, the 95% reproducibility limits for the SRCA method has no statistical difference with previously published standardized test methods used to determine the forward rate of glass dissolution. Overall, this paper describes steps necessary to perform the test method and provides the statistical calculations to evaluate test accuracy.

chemical durability↗
DOE OSTI2018

Resorption of Ca{sub 3–} {sub x}M{sub 2x}(PO{sub 4}){sub 2} (M = Na, K) Calcium Phosphate Bioceramics in Model Solutions

The resorbability of bioceramics in the Ca{sub 3}(PO{sub 4}){sub 2}–CaNaPO{sub 4}–CaKPO{sub 4} system is evaluated in an approach involving thermodynamic assessment of solubility and investigation of the dissolution kinetics in model media, in particular in citric acid solutions. Thermodynamic calculation indicates high solubility of the Ca{sub 5}Na{sub 2}(PO{sub 4}){sub 4}, α-CaМPO{sub 4}, β-CaKPO{sub 4}, and β-СаK{sub 0.6}Na{sub 0.4}PO{sub 4} phases. Investigation of the dissolution kinetics of ceramics has made it possible to identify two distinct types of behavior of resorbable materials in weakly acidic solutions: with fast resorption kinetics in the case of the phases based on nagelschmidtite solid solutions and α-CaМPO{sub 4} disordered high-temperature solid solutions, and with a nearly constant, relatively low dissolution rate and a high solubility limit in the case of β-СaK{sub 1–} {sub x}Na{sub x}-based phases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Anodic processes in the chemical and electrochemical etching of Si crystals in acid-fluoride solutions: Pore formation mechanism

The interaction of heavily doped p- and n-type Si crystals with hydrofluoric acid in the dark with and without contact with metals having greatly differing work functions (Ag and Pd) is studied. The dependences of the dissolution rates of Si crystals in HF solutions that contain oxidizing agents with different redox potentials (FeCl{sub 3}, V{sub 2}O{sub 5} and CrO{sub 3}) on the type and level of silicon doping are determined. Analysis of the experimental data suggests that valence-band holes in silicon are not directly involved in the anodic reactions of silicon oxidation and dissolution and their generation in crystals does not limit the rate of these processes. It is also shown that the character and rate of the chemical process leading to silicon dissolution in HF-containing electrolytes are determined by the interfacial potential attained at the semiconductor–electrolyte interface. The mechanism of electrochemical pore formation in silicon crystals is discussed in terms of selfconsistent cooperative reactions of nucleophilic substitution between chemisorbed fluorine anions and coordination- saturated silicon atoms in the crystal subsurface layer. A specific feature of these reactions for silicon crystals is that vacant nonbonding d{sup 2}sp{sup 3} orbitals of Si atoms, associated with sixfold degenerate states corresponding to the Δ valley of the conduction band, are involved in the formation of intermediate complexes. According to the suggested model, the pore-formation process spontaneously develops in local regions of the interface under the action of the interfacial potential in the adsorption layer and occurs as a result of the detachment of (SiF{sub 2}){sub n} polymer chains from the crystal. Just this process leads to the preferential propagation of pores along the <100> crystallographic directions. The thermodynamic aspects of pore nucleation and the effect of the potential drop across the interface, conduction type, and free-carrier concentration in the crystal on the pore size and structure are discussed. The concepts developed in the study can consistently account for experimental facts characterizing the etching of silicon crystals with various electrical parameters under various conditions providing the anodic polarization of crystals in HF-containing solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗