Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Reaction Time”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Biofuel production from palm oil deoxygenation using nickel-molybdenum on zirconia catalyst using glycerol as a hydrogen donor

The growing demand for renewable energy has generated interest in biofuels as alternatives to fossil fuels. Second-generation biofuels, derived from deoxygenating fats and oils, have garnered a higher level of interest from industry and academia due to their potential for direct replacement of diesel and jet fuels. Palm oil, mostly cultivated in Thailand and composed of C16 and C18 fatty acids, is a primary feedstock sought for biofuel production. Palm oil deoxygenation contains several pathways that may or may not require hydrogen gas. This study aimed to produce biofuels in different fuel ranges, such as gasoline, jet fuel, and diesel, through palm oil deoxygenation using glycerol as a hydrogen source. Glycerol, a low-value byproduct, was used as a hydrogen donor, whereas nickel-molybdenum-supported catalysts were chosen for their high efficiency in deoxygenation and cost-effectiveness. The study investigated the impact of reaction time, temperature, and catalyst activation method on palm oil deoxygenation. Catalyst characterization methods, including XRD, SEM, TEM, XPS, FTIR, TGA, and nitrogen-sorption, were employed to understand the role of catalysts’ activity during palm oil upgrading. Findings indicated that alkane hydrocarbons are the major components in liquid products. The presence of excess hydrogen in post reaction gaseous phase proves the hydrogen donation capability of glycerol. Increased reaction time and temperature facilitated the removal of oxygen from palm oil. Nickel-molybdenum on zirconia activated by sulfidation demonstrated higher stability than by reduction activation.

09 BIOMASS FUELS↗
DOE OSTI2025

Mechanistic Insights toward Accelerated Selenium-Catalyzed Allylic and Propargylic C–H Amination

Catalytic allylic and propargylic C–H aminations present valuable opportunities for the late-stage modification of pharmacophores in drug discovery. However, modern methodology is limited by reliance on expensive transition metal catalysts or slow reactivity. While selenium-catalyzed methods avoid some of these issues, in their current state, they require high catalyst loadings (15 mol %), superstoichiometric quantities of the amine and oxidant source, and long reaction times. Furthermore, our understanding of the mechanism remains incomplete: e.g., what is the catalytically active species, how is the precatalyst converted to it, and what is the role of the ligand? Here, in this paper, we report an N-heterocyclic carbene selenide (NHC-Se) that allows for substantially reduced loadings of selenium without sacrificing reaction time, improves conversions and yields for challenging substrates, and even exhibits the capacity to catalyze 1,4-allylic diamination of alkenes. To understand the origin of the enhanced activity compared to the state-of-the-art NHC-Se precatalyst, we conducted a mechanistic study that supports ligand-free selenium diimide as the active enophile in these systems, while the NHC-derived byproducts, like the corresponding urea, facilitate turnover. We also isolate and structurally characterize NHC-Se mono- and diimido species and explore their mechanistic role. Thus, this work advances C–H amination methodology, our understanding of its mechanistic underpinnings, and selenium chemistry at large.

allylic amination↗
NASA NTRS1989

Saccadic eye movement during spaceflight

Saccadic eye movements were studied in six subjects during two Space Shuttle missions. Reaction time, peak velocity and accuracy of horizontal, visually-guided saccades were examined preflight, inflight and postflight. Conventional electro-oculography was used to record eye position, with the subjects responding to pseudo-randomly illuminated targets at 0 deg and + or - 10 deg and 20 deg visual angles. In all subjects, preflight measurements were within normal limits. Reaction time was significantly increased inflight, while peak velocity was significantly decreased. A tendency toward a greater proportion of hypometric saccades inflight was also noted. Possible explanations for these changes and possible correlations with space motion sickness are discussed.

Uri, John J.↗
DOE OSTI2013

Synthesis, characterization and formation mechanism of metastable phase VO{sub 2}(A) nanorods

Graphical abstract: - Highlights: • Pure phases of VO{sub 2}(B) and VO{sub 2}(A) were prepared by a facile hydrothermal method. • Belt-like particles prepared at 180 °C was indexed as monoclinic VO{sub 2}(B) phase. • Rod-like particles prepared at 230 °C was indexed as tetragonal VO{sub 2}(A) phase. • VO{sub 2}(A) nanorods resulted from VO{sub 2}(B) nanobelts by assembly and crystal adjustment. - Abstract: Pure phase VO{sub 2}(A) nanorods were synthesized via the reduction of V{sub 2}O{sub 5} by oxalic acid during the hydrothermal treatment. Two sets of samples were prepared by varying both system temperature and reaction time under a filling ratio of 0.40 for observing the formation and evolution of VO{sub 2}(A) nanorods. Structures were characterized by X-ray diffraction, scanning and transmission electron microscopies, respectively. It was found that VO{sub 2}(B) was firstly formed and then transformed into VO{sub 2}(A) as the increasing system temperature or extending reaction time. An assembling and following crystal adjustment was proposed for explanation the formation process of VO{sub 2}(A) from VO{sub 2}(B). For VO{sub 2}(A) nanorods, the phase transition temperature of 169.7 °C was higher than that of the VO{sub 2}(A) bulk, it might be ascribed to the lower crystallinity or nonstoichiometry in VO{sub 2}(A) nanorods. VO{sub 2} nanostructures with controllable phases and properties should find their promising applications in a single VO{sub 2} nanodevice.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Electroencephalogram (EEG) and Magnetoencephalogram (MEG) as Tools for Evaluation of Cognitive Function

We have developed computerized analysis and display techniques to help identify the origins of visually evoked scalped potentials (VESP). The potentials are recorded simultaneously from many electrodes (usually 40 to 48) spaced over the region of the scalp where appreciable evoked potentials are found in response to particular stimulus. Contour mapping algorithms are then used to display the time behavior of equipotential surfaces on the scalp during the VESP. We then use an optimization technique to select the parameters of arrays of current dipole sources within the model until the model equipotential field distribution closely fits the measured data. Computer graphics are then used to display, as a movie, the actual and model scalp potential fields and the parameters of the dipole generators within the model head during the course of VESP activity. We have devised reaction time tests that involve potentially separable stages of cognitive processing and utilize stimuli that produce measurable cognition-related features in the late component of the evoked potential. We have used these techniques to determine the loci in the brain where known cognition-related features in the evoked potential are generated and we have explored the extent to which each of these features can be related to the reaction time tasks. We have also examined the temporal-spatial aspects of their cerebral involvement. Our current work is planned to characterize the age-related changes in the processes performed by such sources. We also use a neuromagnetometer to measure the evoked magnetic fields in similar circumstances; we will discuss the relative merits of the two methodologies.

Fender, Derek H.↗
NASA NTRS1986

Effects of stimulus characteristics and task demands on pilots' perception of dichotic messages

The experiment is an initial investigation of pilot performance when auditory advisory messages are presented dichotically, either with or without a concurrent pursuit task requiring visual/motor dexterity. The dependent measures were percent correct and correct reaction times for manual responses to the auditory messages. Two stimulus variables which show facilitory effects in traditional dichotic-listening paradigms, differences in pitch and semantic content of the messages, were examined to determine their effectiveness during the functional simulation of helicopter pursuit. In an effort to accumulate points for the advisory messages for accuracy alone or for both accuracy and reaction times which were faster than their opponent's. In general, the combined effects of the stimulus and task variables are additive. When interactions do occur they suggest that an increase in task demands can sometimes mitigate, but usually does not remove, any processing advantages accrued from stimulus characteristics. The implications of these results for cockpit displays are discussed.

Wenzel, Elizabeth M.↗
DOE OSTI2015

Synthesis of Bis-1,2,4-triazines via Telescoped Condensation of [1,10]-Phenanthroline-2,9-dicarbonitrile with Aromatic 1,2-Dicarbonyls

Efficient separation of minor actinides from spent nuclear fuel remains a formidable challenge. As part of ongoing efforts to identify effective ligands for separation of toxic radionuclides, a series of bis-1,2,4-triazines, three novel, have been prepared in this paper from [1,10]-phenanthroline-2,9-dicarbonitrile in two-telescoped steps without additives, complicated workups, prolonged reaction times, or additional purification.

Tai, Serene↗
DOE OSTI2020

The production of hydrogen–deuterium exchanged cellulose fibers with exchange-resistant deuterium incorporation

Production of deuterated cellulose is important from both theoretical and practical perspectives. Here, cellulose fibers of cotton and Tencel fibers with exchange-resistant deuterium incorporation were prepared by hydrogen–deuterium exchange treatment. The effect of the micro-structure of cellulose crystallinity index as well as the reaction conditions including catalyst, reaction time, and temperature on the exchange-resistant deuterium incorporation process are reported. The ability of deuterated cellulose fibers to resist protium-exchange during H 2 O washing was also explored. The results found that higher crystallinity index is beneficial to stabilize the deuteration of cellulose fibers. Furthermore, alkaline catalysts such as sodium hydroxide or potassium carbonate and higher exchange temperature as well as longer reaction time contribute significantly to the stabilization of deuterium incorporation in the deuterated cellulose fibers. These observations revealed that the hydrogen–deuterium exchange treatment is effective to obtain exchange-resistant deuterium incorporated cellulose fibers. In addition, cotton fibers with several deuteration levels were produced and could be considered for the study of deuterium effect on cellulose properties.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Enzymatic synthesis of 1-caffeoylglycerol with deep eutectic solvent under continuous microflow conditions

1-caffeoylglycerol (1-CG) is a hydrophilic ester with a high solubility, and has a strong activity to prevent skin cancer caused by ultraviolet. However, the current preparation process to synthesize 1-CG via transesterification from methyl caffeate (MC) and glycerin was not economic due to long reaction time or adding extra field. Therefore, an enzymatic synthesis with deep eutectic solvent chloride-urea (ChCl-urea) in a microreactor was firstly applied under continuous microflow condition to improve the productivity. A maximum 1-CG yield of 96.49% was obtained under the optimized conditions: temperature of 65 degrees C, flow rate of 2 $μ$L/min, MC concentration of 50 g/L. Compared to the batch reactor, the reaction time reduced by 75%, the $K_m$ value decreased by 5/6, the reuse times of lipase increased by 2.29-fold, the external mass and transfer coefficients increased 10 times, which process was verified by numerical simulation. In addition, the produced 1-CG of 2 mg/mL has a high UV damage remediation ability of 75.16% using HaCaT cell model, which reveals 1-CG can repair the damage of cells radiated by the UV. Thus, this approach represents a convenient and cost-saving method to produce 1-CG using microfuidic biocatalysis.

09 BIOMASS FUELS↗
DOE OSTI2015

Tailoring growth conditions for efficient tuning of band edge of CdS nanoparticles

CdS nanoparticles are successively synthesized by chemical precipitation method. The samples prepared at different reaction time and temperature are characterized by X-ray diffraction, Diffuse reflectance spectroscopy, Photoluminescence spectroscopy ans Energy dispersive x-ray analysis. Visible color variation is noted from light yellow to orange, indicates the quantum confinement effect and the results are again got confirmed from the optical studies. A shift in absorption peak is observed towards the lower region of the visible spectra - the “blue shift”- upon decrease in reaction time and temperature. Blue emission observed in the photoluminescence spectrum confirms the grain size induced confinement.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Influence of Carbon-Nitride Dot-Emitting Species and Evolution on Fluorescence-Based Sensing and Differentiation

Carbon dots have attracted widespread interest for sensing applications based on their low cost, ease of synthesis, and robust optical properties. We investigate structure–function evolution on multiemitter fluorescence patterns for model carbon-nitride dots (CNDs) and their implications on trace-level sensing. Hydrothermally synthesized CNDs with different reaction times were used to determine how specific functionalities and their corresponding fluorescence signatures respond upon the addition of trace-level analytes. Archetype explosives molecules were chosen as a testbed due to similarities in substituent groups or inductive properties (i.e., electron withdrawing), and solution-based assays were performed using ratiometric fluorescence excitation–emission mapping (EEM). Analyte-specific quenching and enhancement responses were observed in EEM landscapes that varied with the CND reaction time. We then used self-organizing map models to examine EEM feature clustering with specific analytes. Finally, the results reveal that interactions between carbon-nitride frameworks and molecular-like species dictate response characteristics that may be harnessed to tailor sensor development for specific applications.

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

Control synthesis of bismuth sulphide films and their application for laser detectors

Highlights: • Bi{sub 2}S{sub 3} films have been synthesized via a facile hydrothermal process. • We fabricated Bi{sub 2}S{sub 3} films-based laser detectors successfully. • The photoelectric properties were studied upon 450 nm, 650 nm and 850 nm laser beam. • The laser detectors exhibit excellent photoconductive performance. • We found Prolonging the reaction time was beneficial for the photoelectric performance. - Abstract: Herein, we utilize a facile hydrothermal process for the synthesis of Bi{sub 2}S{sub 3} films on the SnO{sub 2}: F films (FTO) substrate. The structure, surface morphology and thickness of the samples were characterized by variously analysis method. The Bi{sub 2}S{sub 3} films-based laser detectors exhibit excellent linear photocurrent characteristics, good sensitivity to 450 nm, 650 nm and 850 nm laser beam. Prolonging the reaction time was beneficial for the photoelectric performance of the Bi{sub 2}S{sub 3} films-based laser detectors. The photoelectric conversion properties can be improved by optimizing the thickness of the films. The experimental results of this work can provide an additional opportunity for fabricating excellent photoconductive performance laser detectors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

AN ACID BAKING APPROACH TO ENHANCE RARE EARTH ELEMENT RECOVERY FROM BITUMINOUS COAL SOURCES

Rare earth elements (REE) are a group of 17 elements typically classified as light and heavy rare earth elements, which play a crucial role in developing the latest technologies for energy, defense, and medical sectors. Even though REEs have been found in more than 200 minerals, only bastnaesite, monazite and xenotime are commercially exploited for REE extraction. However, the recent exponential increase in REE demand has spurred countries such as the United States into research for the extraction of REEs from secondary sources such as coal, acid mine drainage, and coal ash. Several coal sources (e.g., Fire Clay seam coal) across the United States have been identified to contain elevated concentrations of rare earth elements (>600 ppm), and various researchers have investigated the feasibility of both physical and hydrometallurgical extraction techniques for rare earth concentration and subsequent extraction. However, both physical and direct leaching were concluded to be inefficient for RE beneficiation and extraction due to low recoveries. Alternatively, thermal treatment provides promising means for RE recovery from bituminous coal sources. The positive impact of thermal treatment/calcination was established to be due to the decarbonization and dehydroxylation of the clays, which released entrapped rare earth elements within the dominant minerals and converted them into an acid-soluble form. Nonetheless, the improvement in recovery was limited to the light REEs (LREEs) with an insignificant increase in the heavy REEs (HREE). It was demonstrated that the light and heavy REEs in the material were associated with difficult-to-leach minerals such as monazite, xenotime, and zircon, which were not decomposed by simple calcination due to their high thermal stability. Hence, roasting in the presence of chemicals was necessary to ensure the decomposition of those REE-containing minerals. As such, this study was focused on the acid baking treatment of bituminous coals with an aim to enhance REE recovery, especially HREEs. Based on the presence of REE minerals like monazite and xenotime, three pre-leach treatment methods, i.e., 1) roasting, 2) direct acid baking, and 3) acid baking after roasting were investigated. Roasting tests at 600 ⁰C revealed that the recovery of light REEs (LREEs) was enhanced while the recovery of HREEs remained relatively unaffected. LREE and HREE recovery values of 38.3% and 21.3%, respectively, were achieved using a 50 g/L sulfuric acid solution at 5% solid concentration and a solution temperature of 75 ⁰C for 2 hours. Comparatively, direct acid baking at 250 °C provided substantial increased LREE and HREE recovery values to approximately 49.4% and 53.0%, respectively, using an equivalent acid dosage. Recoveries were maximized to 77.0% and 79.6% for LREE and HREE, respectively, by roasting followed by acid baking. Similar results were obtained from the treatment of a second bituminous coal source. Due to strong correlations between REE and Al recovery values, tests were performed on kaolinite and illite, which were prominent clay minerals within the source coals. These experiments revealed that the REE recovery improvements were likely a result of dehydroxylation of clays and subsequent release and decomposition of REE-bearing minerals such as monazite, xenotime and zircon. Subsequently, a parametric study was conducted to identify the impact of acid baking parameters on rare earth element recovery. The factors investigated using a three-level statistical experimental program were acid baking time, acid solution concentration, baking temperature, and acid solution-to-solids ratio which were found to significantly impact REE and contaminant element (Al, Fe, and Ca) recovery. An increase in baking temperature up to around 250 ⁰C improved the light and heavy REE recovery values by more than 50 absolute percentage points relative to performances achieved when direct leaching. As aforementioned, acid baking was needed to both decompose the clay minerals and liberate the REE minerals, which allowed access for the acid to solubilize the REEs. Acid concentration of the solution used for acid baking was studied as a means of minimizing the amount of acid needed to achieve a target REE recovery. However, thermo-gravimetric and differential scanning calorimetry analysis (TGA-DSC) of sulfuric acid under oxidizing atmosphere revealed that the addition of water decreased the evaporation temperature, which explains the lower REE recovery values obtained when using acid concentrations less than 100%. Using pure sulfuric acid at an acid-to-solid ratio of 0.8:1 resulted in recovery values of around 70% for both LREEs and HREEs. The decomposition reaction time was relatively quick with 65% of the TREEs recovered within the first 10 minutes. Following the identification of optimum operating conditions through the parametric study, a systematic leaching study was carried out to examine the impact of leaching parameters, such as solid-to-liquid (S/L) ratio, temperature, and time, on REE recovery using acid baking conditions of 1:1 acid to solids ratio at 250 °C for 30 minutes. The solid-to-liquid ratio was varied from 1-20% by weight at 25 °C, 50 °C, and 75 °C solution temperatures. The results indicated that reaction time and solution temperature considerably impacted the recovery of heavy and light REEs. Interestingly, LREE recovery reduced from 68% at 5% S/L to 58% at 20%S/L, whereas HREE recovery of 78% remained unaffected. The decrease in the LREE recovery was determined to be due to La and Ce precipitation, likely through isomorphic substitution with calcium in gypsum. The kinetic data indicated that 67% LREE and 77% HREE recovery could be obtained within the first 15 minutes of the reaction, suggesting fast reaction kinetics. Furthermore, raising the solution temperature from 25 °C to 75 °C increased the LREE and HREE recovery from 60% and 32% to 67% and 79%, respectively. The kinetic modeling results demonstrated that the rate-limiting step in the LREE dissolution was diffusion and chemical reaction, whereas the HREE extraction was controlled by only chemical reaction. The leaching study concluded that using 20% S/L at 75 °C for 15 minutes maximized LREE and HREE recovery. The lab-scale precipitation study showed that Fe and Al in solution could be removed at pH 4.5 followed by REE precipitation at pH 6.0 using 6 mol/L NaOH. Finally, the bench-scale data was used to develop a process flowsheet for REE recovery from low-grade bituminous coal sources using acid baking. Finally, based on the proposed flowsheet, a concentrated RE-cake obtained through selective precipitation at pH 6.5 was re-leached using HCl at pH 1.5. The resultant leachate was used to identify the impact of various operating parameters on REE recovery and purity with an aim to maximize REE precipitation efficiency while minimizing the oxalic acid dosage. The operating parameters for this investigation were oxalic acid dosage, iron (III) contamination, solution pH and temperature. The resultant model suggested that oxalic acid dosage and reaction pH are the most significant factors for the REE precipitation efficiency, followed by the interaction of oxalic dosage and Fe concentration. Test results indicated that increasing the oxalic acid concentration from 0g/L to 80g/L improved the REE precipitation efficiency from approximately 4.2% to 95.0%. Furthermore, raising the solution pH from 0.5 to 2.5 considerably enhanced the precipitation efficiency from 0.0% to 98.9%. A solution temperature elevation decreased REE recovery, which indicated an exothermic reaction between REEs and oxalate anions. Finally, a high level of Fe contamination adversely impacted REE precipitation efficiency. The speciation analysis revealed that the dominant iron species in the solution system were Fe-(C₂O₄)₃³⁻, Fe-(C₂O₄)²⁻, and Fe-(C₂O₄)⁺, which consumed the majority of the oxalate anions

rare earth elements, acid baking, high-temperature↗
DOE OSTI2017

A cognitive electrophysiological signature differentiates amnestic mild cognitive impairment from normal aging

Background: Noninvasive and effective biomarkers for early detection of amnestic mild cognitive impairment (aMCI) before measurable changes in behavioral performance remain scarce. Cognitive event-related potentials (ERPs) measure synchronized synaptic neural activity associated with a cognitive event. Loss of synapses is a hallmark of the neuropathology of early Alzheimer’s disease (AD). In the present study, we tested the hypothesis that ERP responses during working memory retrieval discriminate aMCI from cognitively normal controls (NC) matched in age and education. Methods: Eighteen NC, 17 subjects with aMCI, and 13 subjects with AD performed a delayed match-to-sample task specially designed not only to be easy enough for impaired participants to complete but also to generate comparable performance between subjects with NC and those with aMCI. Scalp electroencephalography, memory accuracy, and reaction times were measured. Results: Whereas memory performance separated the AD group from the others, the performance of NC and subjects with aMCI was similar. In contrast, left frontal cognitive ERP patterns differentiated subjects with aMCI from NC. Enhanced P3 responses at left frontal sites were associated with nonmatching relative to matching stimuli during working memory tasks in patients with aMCI and AD, but not in NC. The accuracy of discriminating aMCI from NC was 85% by using left frontal match/nonmatch effect combined with nonmatch reaction time. Conclusions: The left frontal cognitive ERP indicator holds promise as a sensitive, simple, affordable, and noninvasive biomarker for detection of early cognitive impairment.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2014

Fatigue in U.S. Astronauts Onboard the International Space Station: Environmental Factors, Operational Impacts, and Implementation of Countermeasures

Since 2000, US astronauts have been supporting missions up to a six month duration on the International Space Station (ISS). Crewmembers have experienced fatigue for reasons similar to military deployments. Astronauts experience psychological stressors such as heavy workloads, extended duty periods, circadian misalignment, inadequate/ineffective sleep, and loss of the environmental cues of a gravity environment. Complicating the psychological stressors are environmental factors; distracting background noise, unexpected and variable mission schedules, unfavorable thermal control, elevated CO2 levels, and an unusual sleep environment with schedules that impinge on pre‐sleep periods. Physiological contributors to poor sleep and fatigue include a cephalad fluid shift and back pain. Restful sleep is further challenged due to a lack of gravity‐related proprioceptive cues and need for restraints. The term "space fog" has been used by astronauts to describe a phenomenon of forgetfulness, slowed reaction time and transient confusion while trying to complete tasks. There is a distinct temporal correlation with arrival on the Space Station and the onset of slowed cognitive skills and a spontaneous resolution that may take up to 6 weeks. The Genesis of this phenomenon may be chronic fatigue secondary to transitioning from a planar environment to a 360deg microgravity perspective. Recently, countermeasures to improve sleep duration and quality in astronauts on the ISS have been instituted with moderate degrees of success as measured by self‐reaction time (psychomotor vigilance task testing), actigraphy, and subjective reports. Judicious use of stimulants and hypnotics, light therapy, controlled sleep periods and sleep shifting and reducing ambient CO2 levels are a few of the most promising countermeasures being used in space to improve sleep and reduce fatigue.

Scheuring, R. A.↗
DOE OSTI2025

Revisiting the Effects of Seed Liquid Water Content on Isoprene Secondary Organic Aerosol Growth

Aerosol liquid water content (LWC) has been shown to enhance partitioning of water-soluble oxygenated organic vapors into the aerosol particles and facilitate aqueous chemistry, impact SOA formation, composition, and physicochemical properties. Here, this study examines the effect of aerosol liquid water content (LWC) on isoprene SOA formation using effloresced and deliquesced ammonium sulfate ((NH 4 ) 2 SO 4 ) and sodium chloride (NaCl) seed particles in an environmental chamber with photo-oxidation extending over hours under moderate relative humidity (50%-60%). Our findings indicate that isoprene SOA mass yield is not significantly influenced (p value >> 0.05) by the phase state or the chemical identity of the seed particles within a 3–4-hour reaction time scale. Detailed molecular analysis using advanced high resolution mass spectrometry indicates that while both effloresced and deliquesced seed types produced similar molecular formula distributions, deliquesced (NH 4 ) 2 SO 4 slightly favored the production of less volatile compounds. Depth-profiling analysis by single particle mass spectrometry confirmed that isoprene SOA predominantly located on the surfaces of particles with core-shell morphologies, with partial dissolution of the effloresced inorganic salt observed even below the deliquescence relative humidity (DRH) of salt. This finding suggests that assuming dry salt core particles do not interact with SOA coatings, based on salt deliquescence points, may overlook important aqueous chemistry. These results emphasize the critical role of reaction time scale and mixing state on SOA formation and call for further research to understand LWC effects on SOA from different precursors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Controllable synthesis and characterization of cadmium molybdate octahedral nanocrystals by coprecipitation method

Graphical abstract: CdMoO{sub 4} nanocrystals have been synthesized via coprecipitation method by using Cd(Sal){sub 2} and (NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}·4H{sub 2}O as starting materials in water. Effects of temperature, reaction time, solvent, surfactant, cadmium and molybdate sources were investigated to reach optimum condition. It was found that particle size, morphology and phase of the final products could be greatly influenced via these parameters. - Highlights: • A facile coprecipitation method was successfully employed to prepare CdMoO{sub 4}. • The effects of some parameters were investigated. • PEG600, PVP, SDS and CTAB were used as surfactant. • Optimum condition for preparation CdMoO{sub 4} nanocrystals was investigated. - Abstract: Cadmium molybdate (CdMoO{sub 4}) nanocrystals have been successfully synthesized via coprecipitation method by using Cd(Sal){sub 2} (Sal = salicylidene) and (NH{sub 4}){sub 6}Mo{sub 7}O{sub 24}·4H{sub 2}O as starting materials in water as solvent. Effects of temperature, reaction time, solvent, surfactant and cadmium source were investigated to reach optimum condition. It was found that particle size, morphology and phase of the final products could be greatly influenced via these parameters. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, photoluminescence (PL) spectroscopy, energy dispersive X-ray microanalysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)

36 MATERIALS SCIENCE↗
DOE OSTI2014

Sodium citrate (Na{sub 3}Cit)-assisted hydrothermal synthesis of uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors

Graphical abstract: A facile hydrothermal method for the synthesis of uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors with the assistance of sodium citrate (Na{sub 3}Cit). - Highlights: • Well-crystallized spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors have been synthesized. • The influence of the reaction temperature and reaction time were clearly shown. • The dosage of Na{sub 3}Cit has a strong effect on the spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors. • The growth mechanism for the formation of final samples was proposed. - Abstract: Highly uniform spindle-like SrMoO{sub 4}:Eu{sup 3+} phosphors have been prepared by a facile hydrothermal method using sodium citrate (Na{sub 3}Cit) as the chelating reagent. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform-infrared spectroscopy (FT-IR) and photoluminescence spectra (PL) were used to characterize the resulting samples. The dosage of sodium citrate, reaction temperature and reaction time play key roles in the formation of the final samples. The possible formation mechanism for SrMoO{sub 4}:Eu{sup 3+} phosphors has been proposed. Upon excitation by ultraviolet radiation, the as-synthesized SrMoO{sub 4}:Eu{sup 3+} phosphors show the characteristic {sup 5}D{sub 0}–{sup 7}F{sub J} (J = 1, 2, 3, 4) emission lines with red emission {sup 5}D{sub 0}–{sup 7}F{sub 2} (613 nm) as the most prominent group.

36 MATERIALS SCIENCE↗