The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
M.p. Nadler - One of the best experts on this subject based on the ideXlab platform.
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Solid-state photodecomposition of energetic nitramines (RDX and HMX). Summary report
1996Co-Authors: C.d. Bedford, P.s. Carpenter, M.p. NadlerAbstract:A study was undertaken to investigate the solid-state photodecomposition of the energetic nitramines RDX and HMX using direct sunlight and medium-pressure mercury lamp irradiation. The rate of RDX photolysis is faster than the rate of HMX photolysis at high concentrations (>2 wt%) and about the same for concentrations below 2 wt%. Both RDX and HMX photodecompose in KBr at an exponential rate that depends on concentration, path length, wavelength, and intensity of light. Moreover, preliminary data show that the rate may be also dependent on particle size. The only solid products characterized in the photodecomposition reactions were the inorganic salts potassium nitrate (KNO3) and potassium nitrite (KNO2), and the organic Formamides such as methyl Formamide and Formamide. The desert environment offers a unique opportunity to exploit solar energy in an effort to reclaim explosive-contaminated lands and to remediate chemically-contaminated sludge. The preliminary results reported in this publication indicate that solid-state photodecomposition of energetic nitramines is a potentially cost effective and efficient method for remediating contaminated desert environments.
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Solid-State Photodecomposition of Energetic Nitramines (RDX and HMX).
1996Co-Authors: C.d. Bedford, P.s. Carpenter, M.p. NadlerAbstract:Abstract : A study was undertaken to investigate the solid-state photodecomposition of the energetic nitramines RDX and HMX using direct sunlight and medium-pressure mercury lamp irradiation. The rate of RDX photolysis is faster than the rate of HMX photolysis at high concentrations (>2 wt%) and about the same for concentrations below 2 wt%. Both RDX and HMX photodecompose in KBr at an exponential rate that depends on concentration, path length, wavelength, and intensity of light. Moreover, preliminary data show that the rate may be also dependent on particle size. The only solid products characterized in the photodecomposition reactions were the inorganic salts potassium nitrate (KNO3) and potassium nitrite (KNO2), and the organic Formamides such as methyl Formamide and Formamide. The desert environment offers a unique opportunity to exploit solar energy in an effort to reclaim explosive-contaminated lands and to remediate chemically-contaminated sludge. The preliminary results reported in this publication indicate that solid-state photodecomposition of energetic nitramines is a potentially cost effective and efficient method for remediating contaminated desert environments.
Wander L. Vasconcelos - One of the best experts on this subject based on the ideXlab platform.
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Structural evolution of silica sols modified with Formamide
Materials Research-ibero-american Journal of Materials, 2001Co-Authors: Rubia F. S. Lenza, Wander L. VasconcelosAbstract:In this work we investigated the influence of Formamide on the acid-catalyzed sol-gel process by Fourier transform infrared spectroscopy (FTIR). Three silica sols were studied: Sol catalyzed with nitric acid without Formamide, sol catalyzed with nitric acid containing Formamide and sol catalyzed with a mixture of nitric acid and hydrofluoric acid and modified with Formamide. Following the time evolution of both the Si-(OH) stretching vibration at around 950 cm-1 and the Si-O-(Si) vibration between 1040 cm-1 and 1200 cm-1 we were able to describe the structural evolution of each sol. The curve of evolution of Si-(OH) stretching vibration corresponding to sol A has a simple asymptotic evolution. In the case of Formamide containing sol, we observed a two-step structural evolution indicating that for the system containing Formamide the polymerization goes through a temporary stabilization of oligomers, which can explain the non-variation of the Si-O(H) bond wavenumber for a certain time. Gelation times were of several days for gels without Formamide and few hours for gels containing additive. The presence of additive resulted in a highly interconnected gel.
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preparation of silica by sol gel method using Formamide
Materials Research-ibero-american Journal of Materials, 2001Co-Authors: Rubia F. S. Lenza, Wander L. VasconcelosAbstract:In this work we obtained microporous and mesoporous silica gels by sol-gel processing. Tetraethylortosilicate (TEOS) was used as precursor. Nitric acid and hydrofluoric acid were used as catalysts. In order to study the affect of Formamide as drying additive, we used a molar ratio alkoxide/Formamide of 1/1. The performance of Formamide in obtaining crack-free gels was evaluated through monolithicity measurements. The structural evolution occurring in the interconnected network of the gels during thermal treatment was monitored by Fourier transform infrared spectroscopy (FTIR), shrinkage and density measurements and nitrogen gas sorption. We noted that in the presence of Formamide, the Si-O-Si bonds are stronger and belong to a more cross-linked structure. The samples obtained in the presence of Formamide have larger pore volume and its pore structure is in the range of mesoporosity. The samples obtained without additive are microporous. Formamide allowed the preparation of crack-free silica gels stabilized at high temperatures.
G Surya K Prakash - One of the best experts on this subject based on the ideXlab platform.
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catalytic homogeneous hydrogenation of co to methanol via Formamide
Journal of the American Chemical Society, 2019Co-Authors: Alain Goeppert, G Surya K PrakashAbstract:A novel amine-assisted route for low temperature homogeneous hydrogenation of CO to methanol is described. The reaction proceeds through the formation of Formamide intermediates. The first amine carbonylation part is catalyzed by K3PO4. Subsequently, the Formamides are hydrogenated in situ to methanol in the presence of a commercially available ruthenium pincer complex as a catalyst. Under optimized reaction conditions, CO (up to 10 bar) was directly converted to methanol in high yield and selectivity in the presence of H2 (70 bar) and diethylenetriamine. A maximum TON of 539 was achieved using the catalyst Ru-Macho-BH. The high yield, selectivity, and TONs obtained for methanol production at low reaction temperature (145 °C) could make this process an attractive alternative over the traditional high temperature heterogeneous catalysis.
C.d. Bedford - One of the best experts on this subject based on the ideXlab platform.
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Solid-state photodecomposition of energetic nitramines (RDX and HMX). Summary report
1996Co-Authors: C.d. Bedford, P.s. Carpenter, M.p. NadlerAbstract:A study was undertaken to investigate the solid-state photodecomposition of the energetic nitramines RDX and HMX using direct sunlight and medium-pressure mercury lamp irradiation. The rate of RDX photolysis is faster than the rate of HMX photolysis at high concentrations (>2 wt%) and about the same for concentrations below 2 wt%. Both RDX and HMX photodecompose in KBr at an exponential rate that depends on concentration, path length, wavelength, and intensity of light. Moreover, preliminary data show that the rate may be also dependent on particle size. The only solid products characterized in the photodecomposition reactions were the inorganic salts potassium nitrate (KNO3) and potassium nitrite (KNO2), and the organic Formamides such as methyl Formamide and Formamide. The desert environment offers a unique opportunity to exploit solar energy in an effort to reclaim explosive-contaminated lands and to remediate chemically-contaminated sludge. The preliminary results reported in this publication indicate that solid-state photodecomposition of energetic nitramines is a potentially cost effective and efficient method for remediating contaminated desert environments.
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Solid-State Photodecomposition of Energetic Nitramines (RDX and HMX).
1996Co-Authors: C.d. Bedford, P.s. Carpenter, M.p. NadlerAbstract:Abstract : A study was undertaken to investigate the solid-state photodecomposition of the energetic nitramines RDX and HMX using direct sunlight and medium-pressure mercury lamp irradiation. The rate of RDX photolysis is faster than the rate of HMX photolysis at high concentrations (>2 wt%) and about the same for concentrations below 2 wt%. Both RDX and HMX photodecompose in KBr at an exponential rate that depends on concentration, path length, wavelength, and intensity of light. Moreover, preliminary data show that the rate may be also dependent on particle size. The only solid products characterized in the photodecomposition reactions were the inorganic salts potassium nitrate (KNO3) and potassium nitrite (KNO2), and the organic Formamides such as methyl Formamide and Formamide. The desert environment offers a unique opportunity to exploit solar energy in an effort to reclaim explosive-contaminated lands and to remediate chemically-contaminated sludge. The preliminary results reported in this publication indicate that solid-state photodecomposition of energetic nitramines is a potentially cost effective and efficient method for remediating contaminated desert environments.
Simone Wiegand - One of the best experts on this subject based on the ideXlab platform.
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accumulation of Formamide in hydrothermal pores to form prebiotic nucleobases
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Doreen Niether, Dzmitry Afanasenkau, Jan K G Dhont, Simone WiegandAbstract:Abstract Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22):9346−9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of Formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous Formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of Formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of Formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous Formamide solutions of ∼85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45–90 d, starting with an initial Formamide weight fraction of 10 − 3 10−3 wt % that is typical for concentrations in shallow lakes on early Earth.