More Like this

1. Engineering bistetrazoles: ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol) as a new planar high-energy-density material

   https://doi.org/10.1039/d2ma00664b  

   Singh, Jatinder ; Staples, Richard J. ; Shreeve, Jean'ne M. ( July 2022 , Materials Advances)

   Energetic properties of bistetrazole derivatives are improved by the step-by-step introduction of functionalities which improve heat of formation, density, and oxygen content. The incorporation of unsaturation between bis(1 H -tetrazol-5-yl) and bis(1 H -tetrazol-1-ol) derivatives leads to planarity which enhances the density of the final product. In this manuscript, we have synthesized compounds 1,2-di(1 H -tetrazol-5-yl)ethane (4), ( E )-1,2-di(1 H -tetrazol-5-yl)ethene (5), and ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol), (6) using readily available starting materials. Their corresponding dihydroxylammonium salts 7, 8 and 9 are obtained by reacting two equivalents of hydroxylamine (50% in water). New compounds are analyzed using IR, EA, DSC and multinuclear NMR spectroscopy ( 1 H, 13 C and 15 N). The solid-state structures of compounds 6, 7, 8 and 9 are confirmed by single-crystal X-ray diffraction. The energetic performances are calculated using the EXPLO5 (v6.06.02) code and the sensitivities towards external stimuli such as friction and impact are determined according to BAM standard. Compound 6 {( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol)} exhibits a surprisingly high density of 1.91 g cm −3 at 100 K (1.86 g cm −3 at 298 K). Its detonation velocity (9017 m s −1 ) is considerably superior to those of RDX (8795 m s −1 ), which suggests it is a competitive high-energy-density material. 

   more » « less
2. pH-Controlled forms of 1-amino-1-hydrazino-2,2-dinitroethylene (HFOX): selective reactivity of amine and hydrazinyl groups with aldehydes or ketones

   https://doi.org/10.1039/d2ma00307d  

   Chinnam, Ajay Kumar ; Staples, Richard J. ; Shreeve, Jean’ne M. ( May 2022 , Materials Advances)

   1-Amino-1-hydrazino-2,2-dinitroethylene (HFOX) is a potential reactive intermediate for a new class of energetic materials. Now we describe its condensation with various carbonyl compounds in the presence of acidic and basic catalysts. Condensation of HFOX with α-diones and β-diones gives products of much interest. α-Diones undergo cyclization in the presence of base to form six-membered ring products, while β-diones cyclize to five-membered ring products in the presence of acid. One of the exciting reactions is the formation of ammonium (5,6-dimethyl-1,2,4-triazin-3-yl)dinitromethanide salt, 5c, which was isolated by using aqueous ammonia as a nucleophilic base. All new compounds were fully characterized by advanced spectroscopic techniques. The structures of 5, 5c, 5e, 9, 11, and 12a are supported by single crystal X-ray diffraction analysis. Most of the new six membered ring compounds have good thermostabilities (>200 °C), while the fluorinated five membered ring compound, 12b, has the highest density of 2.04 g cm −3 at 25 °C. Heats of formation and detonation properties were calculated by using Gaussian 03 and EXPLO5 software programs. Nearly all new compounds have very good detonation properties, especially, triazine salts, 5e ( D v = 7513 m s −1 ; P = 24.45 G P a), and 5f ( D v = 7948 m s −1 ; P = 26.27 G P a) as well as azide derivative 11 ( D v = 8166 m s −1 ; P = 25.48 G P a), which are superior to TNT ( D v = 6824 m s −1 ; P = 19.40 G P a). These findings provide a new perspective for the synthesis of novel high performing energetic materials. 

   more » « less
3. Measuring an Off-center Detonation through Infrared Line Profiles: The Peculiar Type Ia Supernova SN 2020qxp/ASASSN-20jq

   https://doi.org/10.3847/1538-4357/ac250d  

   Hoeflich, P. ; Ashall, C. ; Bose, S. ; Baron, E. ; Stritzinger, M. D. ; Davis, S. ; Shahbandeh, M. ; Anand, G. S. ; Baade, D. ; Burns, C. R. ; et al ( November 2021 , The Astrophysical Journal)

   Abstract We present and analyze a near-infrared (NIR) spectrum of the underluminous Type Ia supernova SN 2020qxp/ASASSN-20jq obtained with NIRES at the Keck Observatory, 191 days after B -band maximum. The spectrum is dominated by a number of broad emission features, including the [Fe ii ] at 1.644 μ m, which is highly asymmetric with a tilted top and a peak redshifted by ≈2000 km s −1 . In comparison with 2D non-LTE synthetic spectra computed from 3D simulations of off-center delayed-detonation Chandrasekhar-mass ( M ch ) white dwarf (WD) models, we find good agreement between the observed lines and the synthetic profiles, and are able to unravel the structure of the progenitor’s envelope. We find that the size and tilt of the [Fe ii ] 1.644 μ m profile (in velocity space) is an effective way to determine the location of an off-center delayed-detonation transition (DDT) and the viewing angle, and it requires a WD with a high central density of ∼4 × 10 9 g cm −3 . We also tentatively identify a stable Ni feature around 1.9 μ m characterized by a “pot-belly” profile that is slightly offset with respect to the kinematic center. In the case of SN 2020qxp/ASASSN-20jq, we estimate that the location of the DDT is ∼0.3 M WD off center, which gives rise to an asymmetric distribution of the underlying ejecta. We also demonstrate that low-luminosity and high-density WD SN Ia progenitors exhibit a very strong overlap of Ca and 56 Ni in physical space. This results in the formation of a prevalent [Ca ii ] 0.73 μ m emission feature that is sensitive to asymmetry effects. Our findings are discussed within the context of alternative scenarios, including off-center C/O detonations in He-triggered sub- M Ch WDs and the direct collision of two WDs. Snapshot programs with Gemini/Keck/Very Large Telescope (VLT)/ELT-class instruments and our spectropolarimetry program are complementary to mid-IR spectra by the James Webb Space Telescope (JWST). 

   more » « less
4. Bridged and fused triazolic energetic frameworks with an azo building block towards thermally stable and applicable propellant ingredients

   https://doi.org/10.1039/d1ta07520a  

   Yu, Qiong ; Li, Fengsheng ; Yin, Ping ; Pang, Siping ; Staples, Richard J. ; Shreeve, Jean'ne M. ( November 2021 , Journal of Materials Chemistry A)

   The assembly of nitrogen-rich building blocks determines the energy storage capacity and affects the stability of energetic materials. Owing to the environmentally harmful properties of the propellant, ammonium perchlorate (AP), much research has explored halogen-free replacements which often suffer from poor thermal stability. In our goal of balancing performance and stability, we report access to an energetic molecule (3) by smart assembly of an azo bridge into trinitromethyl triazoles. Compound 3 exhibits a decomposition temperature of 175 °C, which approaches the highest among reported trinitromethyl derivatives. The density (1.91 g cm −3 ) and oxygen balance (+29%) for 3 exceed other candidates, suggesting it as a high energy dense oxidizer (HEDO) replacement for AP in rocket propellants. One-step azo-involved cyclization of 3 give two fused nitro triazolones, (FNTO) 4 and its N -oxide 5, having thermal stabilities and energies superior to the analogous derivatives of 5-nitro-2,4-dihydro-3 H -1,2,4-triazole-3-one (NTO). The comparison of properties of the fused triazolones 4 and 8 and their N -oxide derivatives 5 and 9 shows that formation of an N -oxide is an effective strategy which results in an increase of the decomposition temperature, oxygen balance, specific impulse, and detonation properties and in a decrease of the sensitivity of the corresponding energetic material. This work highlights bridged and fused triazolic energetic frameworks with an azo building block providing an alternative structural motif for seeking an applicable high-energy ingredient. 

   more » « less
5. Florida mangrove saltmarsh reference surface soils

   https://doi.org/10.6073/pasta/0e08cbe07c84488cb7b9dd16669946d0  

   Lewis, David Bruce ( January 2021 , Environmental Data Initiative)

   Site description. This data package consists of data obtained from sampling surface soil (the 0-7.6 cm depth profile) in black mangrove (Avicennia germinans) dominated forest and black needlerush (Juncus roemerianus) saltmarsh along the Gulf of Mexico coastline in peninsular west-central Florida, USA. This location has a subtropical climate with mean daily temperatures ranging from 15.4 °C in January to 27.8 °C in August, and annual precipitation of 1336 mm. Precipitation falls as rain primarily between June and September. Tides are semi-diurnal, with 0.57 m median amplitudes during the year preceding sampling (U.S. NOAA National Ocean Service, Clearwater Beach, Florida, station 8726724). Sea-level rise is 4.0 ± 0.6 mm per year (1973-2020 trend, mean ± 95 % confidence interval, NOAA NOS Clearwater Beach station). The A. germinans mangrove zone is either adjacent to water or fringed on the seaward side by a narrow band of red mangrove (Rhizophora mangle). A near-monoculture of J. roemerianus is often adjacent to and immediately landward of the A. germinans zone. The transition from the mangrove to the J. roemerianus zone is variable in our study area. An abrupt edge between closed-canopy mangrove and J. roemerianus monoculture may extend for up to several hundred meters in some locations, while other stretches of ecotone present a gradual transition where smaller, widely spaced trees are interspersed into the herbaceous marsh. Juncus roemerianus then extends landward to a high marsh patchwork of succulent halophytes (including Salicornia bigellovi, Sesuvium sp., and Batis maritima), scattered dwarf mangrove, and salt pans, followed in turn by upland vegetation that includes Pinus sp. and Serenoa repens. Field design and sample collection. We established three study sites spaced at approximately 5 km intervals along the western coastline of the central Florida peninsula. The sites consisted of the Salt Springs (28.3298°, -82.7274°), Energy Marine Center (28.2903°, -82.7278°), and Green Key (28.2530°, -82.7496°) sites on the Gulf of Mexico coastline in Pasco County, Florida, USA. At each site, we established three plot pairs, each consisting of one saltmarsh plot and one mangrove plot. Plots were 50 m^2 in size. Plots pairs within a site were separated by 230-1070 m, and the mangrove and saltmarsh plots composing a pair were 70-170 m apart. All plot pairs consisted of directly adjacent patches of mangrove forest and J. roemerianus saltmarsh, with the mangrove forests exhibiting a closed canopy and a tree architecture (height 4-6 m, crown width 1.5-3 m). Mangrove plots were located at approximately the midpoint between the seaward edge (water-mangrove interface) and landward edge (mangrove-marsh interface) of the mangrove zone. Saltmarsh plots were located 20-25 m away from any mangrove trees and into the J. roemerianus zone (i.e., landward from the mangrove-marsh interface). Plot pairs were coarsely similar in geomorphic setting, as all were located on the Gulf of Mexico coastline, rather than within major sheltering formations like Tampa Bay, and all plot pairs fit the tide-dominated domain of the Woodroffe classification (Woodroffe, 2002, "Coasts: Form, Process and Evolution", Cambridge University Press), given their conspicuous semi-diurnal tides. There was nevertheless some geomorphic variation, as some plot pairs were directly open to the Gulf of Mexico while others sat behind keys and spits or along small tidal creeks. Our use of a plot-pair approach is intended to control for this geomorphic variation. Plot center elevations (cm above mean sea level, NAVD 88) were estimated by overlaying the plot locations determined with a global positioning system (Garmin GPS 60, Olathe, KS, USA) on a LiDAR-derived bare-earth digital elevation model (Dewberry, Inc., 2019). The digital elevation model had a vertical accuracy of ± 10 cm (95 % CI) and a horizontal accuracy of ± 116 cm (95 % CI). Soil samples were collected via coring at low tide in June 2011. From each plot, we collected a composite soil sample consisting of three discrete 5.1 cm diameter soil cores taken at equidistant points to 7.6 cm depth. Cores were taken by tapping a sleeve into the soil until its top was flush with the soil surface, sliding a hand under the core, and lifting it up. Cores were then capped and transferred on ice to our laboratory at the University of South Florida (Tampa, Florida, USA), where they were combined in plastic zipper bags, and homogenized by hand into plot-level composite samples on the day they were collected. A damp soil subsample was immediately taken from each composite sample to initiate 1 y incubations for determination of active C and N (see below). The remainder of each composite sample was then placed in a drying oven (60 °C) for 1 week with frequent mixing of the soil to prevent aggregation and liberate water. Organic wetland soils are sometimes dried at 70 °C, however high drying temperatures can volatilize non-water liquids and oxidize and decompose organic matter, so 50 °C is also a common drying temperature for organic soils (Gardner 1986, "Methods of Soil Analysis: Part 1", Soil Science Society of America); we accordingly chose 60 °C as a compromise between sufficient water removal and avoidance of non-water mass loss. Bulk density was determined as soil dry mass per core volume (adding back the dry mass equivalent of the damp subsample removed prior to drying). Dried subsamples were obtained for determination of soil organic matter (SOM), mineral texture composition, and extractable and total carbon (C) and nitrogen (N) within the following week. Sample analyses. A dried subsample was apportioned from each composite sample to determine SOM as mass loss on ignition at 550 °C for 4 h. After organic matter was removed from soil via ignition, mineral particle size composition was determined using a combination of wet sieving and density separation in 49 mM (3 %) sodium hexametaphosphate ((NaPO_3)_6) following procedures in Kettler et al. (2001, Soil Science Society of America Journal 65, 849-852). The percentage of dry soil mass composed of silt and clay particles (hereafter, fines) was calculated as the mass lost from dispersed mineral soil after sieving (0.053 mm mesh sieve). Fines could have been slightly underestimated if any clay particles were burned off during the preceding ignition of soil. An additional subsample was taken from each composite sample to determine extractable N and organic C concentrations via 0.5 M potassium sulfate (K_2SO_4) extractions. We combined soil and extractant (ratio of 1 g dry soil:5 mL extractant) in plastic bottles, reciprocally shook the slurry for 1 h at 120 rpm, and then gravity filtered it through Fisher G6 (1.6 μm pore size) glass fiber filters, followed by colorimetric detection of nitrite (NO_2^-) + nitrate (NO_3^-) and ammonium (NH_4^+) in the filtrate (Hood Nowotny et al., 2010,Soil Science Society of America Journal 74, 1018-1027) using a microplate spectrophotometer (Biotek Epoch, Winooski, VT, USA). Filtrate was also analyzed for dissolved organic C (referred to hereafter as extractable organic C) and total dissolved N via combustion and oxidation followed by detection of the evolved CO_2 and N oxide gases on a Formacs HT TOC/TN analyzer (Skalar, Breda, The Netherlands). Extractable organic N was then computed as total dissolved N in filtrate minus extractable mineral N (itself the sum of extractable NH_4-N and NO_2-N + NO_3-N). We determined soil total C and N from dried, milled subsamples subjected to elemental analysis (ECS 4010, Costech, Inc., Valencia, CA, USA) at the University of South Florida Stable Isotope Laboratory. Median concentration of inorganic C in unvegetated surface soil at our sites is 0.5 % of soil mass (Anderson, 2019, Univ. of South Florida M.S. thesis via methods in Wang et al., 2011, Environmental Monitoring and Assessment 174, 241-257). Inorganic C concentrations are likely even lower in our samples from under vegetation, where organic matter would dilute the contribution of inorganic C to soil mass. Nevertheless, the presence of a small inorganic C pool in our soils may be counted in the total C values we report. Extractable organic C is necessarily of organic C origin given the method (sparging with HCl) used in detection. Active C and N represent the fractions of organic C and N that are mineralizable by soil microorganisms under aerobic conditions in long-term soil incubations. To quantify active C and N, 60 g of field-moist soil were apportioned from each composite sample, placed in a filtration apparatus, and incubated in the dark at 25 °C and field capacity moisture for 365 d (as in Lewis et al., 2014, Ecosphere 5, art59). Moisture levels were maintained by frequently weighing incubated soil and wetting them up to target mass. Daily CO_2 flux was quantified on 29 occasions at 0.5-3 week intervals during the incubation period (with shorter intervals earlier in the incubation), and these per day flux rates were integrated over the 365 d period to compute an estimate of active C. Observations of per day flux were made by sealing samples overnight in airtight chambers fitted with septa and quantifying headspace CO_2 accumulation by injecting headspace samples (obtained through the septa via needle and syringe) into an infrared gas analyzer (PP Systems EGM 4, Amesbury, MA, USA). To estimate active N, each incubated sample was leached with a C and N free, 35 psu solution containing micronutrients (Nadelhoffer, 1990, Soil Science Society of America Journal 54, 411-415) on 19 occasions at increasing 1-6 week intervals during the 365 d incubation, and then extracted in 0.5 M K_2SO_4 at the end of the incubation in order to remove any residual mineral N. Active N was then quantified as the total mass of mineral N leached and extracted. Mineral N in leached and extracted solutions was detected as NH_4-N and NO_2-N + NO_3-N via colorimetry as above. This incubation technique precludes new C and N inputs and persistently leaches mineral N, forcing microorganisms to meet demand by mineralizing existing pools, and thereby directly assays the potential activity of soil organic C and N pools present at the time of soil sampling. Because this analysis commences with disrupting soil physical structure, it is biased toward higher estimates of active fractions. Calculations. Non-mobile C and N fractions were computed as total C and N concentrations minus the extractable and active fractions of each element. This data package reports surface-soil constituents (moisture, fines, SOM, and C and N pools and fractions) in both gravimetric units (mass constituent / mass soil) and areal units (mass constituent / soil surface area integrated through 7.6 cm soil depth, the depth of sampling). Areal concentrations were computed as X × D × 7.6, where X is the gravimetric concentration of a soil constituent, D is soil bulk density (g dry soil / cm^3), and 7.6 is the sampling depth in cm. 

   more » « less