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Results for “HALOGEN COMPOUNDS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Treatment System for Removing Halogenated Compounds from Contaminated Sources

A treatment system and a method for removal of at least one halogenated compound, such as PCBs, found in contaminated systems are provided. The treatment system includes a polymer blanket for receiving at least one non-polar solvent. The halogenated compound permeates into or through a wall of the polymer blanket where it is solubilized with at least one non-polar solvent received by said polymer blanket forming a halogenated solvent mixture. This treatment system and method provides for the in situ removal of halogenated compounds from the contaminated system. In one embodiment, the halogenated solvent mixture is subjected to subsequent processes which destroy and/or degrade the halogenated compound.

Quinn, Jacqueline W.↗
NASA NTRS1998

A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing

Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.

Sharma, S. P.↗
DOE OSTI2018

Controllable deuteration of halogenated compounds by photocatalytic D2O splitting

Deuterium labeling is of great value in organic synthesis and the pharmaceutical industry. However, the state-of-the-art C–H/C–D exchange using noble metal catalysts or strong bases/acids suffers from poor functional group tolerances, poor selectivity and lack of scope for generating molecular complexity. Herein, we demonstrate the deuteration of halides using heavy water as the deuteration reagent and porous CdSe nanosheets as the catalyst. The deuteration mechanism involves the generation of highly active carbon and deuterium radicals via photoinduced electron transfer from CdSe to the substrates, followed by tandem radicals coupling process, which is mechanistically distinct from the traditional methods involving deuterium cations or anions. Our deuteration strategy shows better selectivity and functional group tolerances than current C–H/C–D exchange methods. Extending the synthetic scope, deuterated boronic acids, halides, alkynes, and aldehydes can be used as synthons in Suzuki coupling, Click reaction, C–H bond insertion reaction etc. for the synthesis of complex deuterated molecules.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1980

Climatic effects due to halogenated compounds in the earth's atmosphere

Using a one-dimensional radiative-convective model, a sensitivity study is performed of the effect of ozone depletion in the stratosphere on the surface temperature. There could be a cooling of the surface temperature by approximately 0.2 K due to chlorofluoromethane-induced ozone depletion at steady state (assuming 1973 release rates). This cooling reduces significantly the greenhouse effect due to the presence of chlorofluoromethanes. Carbon tetrafluoride has a strong nu sub 3 band at 7.8 microns, and the atmospheric greenhouse effect is shown to be 0.07 and 0.12 K/ppbv with and without taking into account overlap with CH4 and N2O bands. At concentrations higher than 1 ppbv, absorption by the nu sub 3 band starts to saturate and the greenhouse effect becomes less efficient.

Wang, W.-C.↗
DOE OSTI2011

Clandestine grave detector

An apparatus and a method for detecting a burial site of human remains are disclosed. An air stream is drawn through an air intake conduit from locations near potential burial sites of human remains. The air stream is monitored by one or more chemical sensors to determine whether the air stream includes one or more indicator compounds selected from halogenated compounds, hydrocarbons, nitrogen-containing compounds, sulfur-containing compounds, acid/ester compounds, oxygen-containing compounds, and naphthalene-containing compounds. When it is determined that an indicator compound is present in the air stream, this indicates that a burial site of human remains is below or nearby. Each sensor may be in electrical communication with an indicator that signals when the sensor has detected the presence of the indicator compound in the air stream. In one form, the indicator compound is a halogenated compound and/or a hydrocarbon, and the presence of the halogenated compound and/or the hydrocarbon in the air stream indicates that a burial site of human remains is below or nearby.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Flux, Impact, and Fate of Halogenated Xenobiotic Compounds in the Gut

Humans and their associated microbiomes are exposed to numerous xenobiotics through drugs, dietary components, personal care products as well as environmental chemicals. Most of the reciprocal interactions between the microbiota and xenobiotics, such as halogenated compounds, occur within the human gut harboring diverse and dense microbial communities. Here, we provide an overview of the flux of halogenated compounds in the environment, and diverse exposure routes of human microbiota to these compounds. Subsequently, we review the impact of halogenated compounds in perturbing the structure and function of gut microbiota and host cells. In turn, cultivation-dependent and metagenomic surveys of dehalogenating genes revealed the potential of the gut microbiota to chemically alter halogenated xenobiotics and impact their fate. Finally, we provide an outlook for future research to draw attention and attract interest to study the bidirectional impact of halogenated and other xenobiotic compounds and the gut microbiota.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1996

Biodegradation of Trihalomethanes and Other Halogenated Aliphatic Compounds

The biological dehalogenation of common water pollutants such as trichloromethane (chloroform) and other halogenated aliphatic compounds was the subject of this project. Samples from diverse water environments such as from groundwater contaminated with halogenated compounds and wastewaters from regional treatment plants were studied to identify conditions that favor certain dehalogenation reactions over others. Gene probe analyses of DNA extracted from the dichlormethane-degrading wastewater indicated the presence of the gene coding for dichloromethane dehalogenase, indicating the genetic basis for the dechlorination activity observed. These studies indicate that methanogenic bacteria are the organisms responsible for the chloroform dechlorination. Dechlorination of a common chlorofluorocarbon (CFC-11) was identified in samples taken from a regional aquifer contaminated with halogenated aliphatic compounds.

HALOGENATED ALIPHATC HYDROCARBONS↗
NASA NTRS1980

Method and apparatus for vapor detection

The method disclosed herein may be practiced by passing the vapors to be sampled along a path with halogen vapor, preferably chlorine vapor, heating the mixed vapors to halogenate those of the sampled vapors subject to halogenation, removing unreacted halogen vapor, and then sensing the vapors for organic halogenated compounds. The apparatus disclosed herein comprises means for flowing the vapors, both sample and halogen vapors, into a common path, means for heating the mixed vapors to effect the halogenation reaction, means for removing unreacted halogen vapor, and a sensing device for sensing halogenated compounds. By such a method and means, the vapors of low molecular weight hydrocarbons, ketones and alcohols, when present, such as methane, ethane, acetone, ethanol, and the like are converted, at least in part, to halogenated compounds, then the excess halogen removed or trapped, and the resultant vapors of the halogenated compounds sensed or detected. The system is highly sensitive. For example, acetone in a concentration of 30 parts per billion (volume) is readily detected.

Lerner, Melvin↗
NASA NTRS1997

Application of Shear Plate Interferometry to Jet Diffusion Flame Temperature Measurements

The recent ban on the production of bromotrifluoromethane (CF3Br) because of its high stratospheric ozone depletion potential has led to interest in finding alternative agents for fire extinguishing applications. Some of the promising alternatives are fluorinated hydrocarbons. A clear understanding of the effects of CF3Br and alternative chemical suppressants on diffusion flames is therefore necessary in the selection of alternative suppressants for use in normal and microgravity. The flame inhibition effects of halogen compounds have been studied extensively in premixed systems. The effect of addition of halocarbons (carbon-halogen compounds) to diffusion flames has been studied experimentally in coflow configurations and in counterflow gaseous and liquid-pool flames. Halogenated compounds are believed to inhibit combustion by scavenging hydrogen radicals to form the relatively unreactive compound HF, or through a catalytic recombination cycle involving HBr to form H2. Comparisons between halogens show that bromine inhibition is significantly more effective than chlorine or fluorine. Although fluorinated compounds are only slightly more effective inhibitors on a mass basis than nitrogen, they are more effective on a volume basis and are easily stored in liquid form. The objectives of this study are (a) to determine the stability limits of laminar jet diffusion flames with respect to inhibitor concentration in both normal and microgravity, and (b) to investigate the structure of halocarbon-inhibited flames. In the initial phase of this project, visual diagnostics were used to observe the structure and behavior of normal and microgravity flames. The initial observations showed significant changes in the structure of the flames with the addition of halocarbons to the surrounding environment, as discussed below. Furthermore, the study established that the flames are more stable relative to the addition of halocarbons in microgravity than in normal gravity. Visual diagnostics of flames are, however, necessarily limited to detection of radiative emission in the visible range, and offer only qualitative information about the nature of the processes in the flame. In particular, the study sought to understand the structure of the inhibitor-perturbed flames with regard to temperature and species concentration in the outer region of the flame. Whereas thermocouple measurements can be used in ground based studies, their implementation in drop-tower rigs is limited. A possible approach to determine the temperature field around the flame is to use interferometric techniques. The implementation and testing of a shear-plate interferometry technique is described below.

VanDerWege, Brad A.↗
DOE OSTI2017

Modern level for properties prediction of iodine-containing organic compounds: the halogen bonds formed by iodine

The modern concepts on specific features of anisotropy of the electron density of valence shells of bound atoms and chemical bonds providing the successful description of the properties of halogen bonds formed by the iodine molecule in compounds with useful physicochemical properties are generalized in the review. The prognoses of basicity by the diiodine basicity scale for the nitrogen-containing compounds are illustrated. The regularities and peculiarities of shifting bands in Raman spectra of iodine-containing organic crystals are considered. The methodical and specific problems of modeling appeared when the electronic characteristics of the iodine compounds are estimated and briefly discussed.

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

The influence of a presence of a heavy atom on the spin-spin coupling constants between two light nuclei in organometallic compounds and halogen derivatives

The {sup 1}J{sub CC} and {sup 1}J{sub CH} spin-spin coupling constants have been calculated by means of density functional theory (DFT) for a set of derivatives of aliphatic hydrocarbons substituted with I, At, Cd, and Hg in order to evaluate the substituent and relativistic effects for these properties. The main goal was to estimate HALA (heavy-atom-on-light-atom) effects on spin-spin coupling constants and to explore the factors which may influence the HALA effect on these properties, including the nature of the heavy atom substituent and carbon hybridization. The methods applied range, in order of reduced complexity, from Dirac-Kohn-Sham method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component Zeroth Order Regular Approximation (ZORA) Hamiltonians, to scalar non-relativistic effective core potentials with the non-relativistic Hamiltonian. Thus, we are able to compare the performance of ZORA-DFT and Dirac-Kohn-Sham methods for modelling of the HALA effects on the spin-spin coupling constants.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2012

Etching properties and electrical characterization of surfaces of silicon-on-insulator substrates in presence of halogens

We have studied the etching properties of silicon-on-insulator (SOI) substrates in recently developed chromium-free solutions containing halogens. We have shown that the presence of halogen compounds X (I{sup -}, Br{sup -}...) in HF/HNO{sub 3}/CH{sub 3}COOH solutions is required for a selective and preferential etching on SOI. The etching rate of such solutions increases with the dissolved halogen concentrations. The chemical reactivity of Si-X (X = Br{sup -}, I{sup -}..) bonds has been analyzed by X-ray Photoelectron Spectroscopy (XPS), Pseudo-MOS (flatband potential) and Kelvin Force Microscopy (KFM) measurements. A negative shift of flatband potential values is explained by an increasing concentration of halogen compounds in the solution and a substitution of Si-H (F) bonds by Si-X bonds during the reaction. Though Si-X bonds, and more particularly Si-I bonds, have been confirmed only at trace levels using XPS, we believe that the formation of Si-X bonds is supported by a mechanism of surface dipoles. Unexpectedly, no significant change in work function could be detected using KFM measurements. Some suggestions, based on KFM technique improvements, are made to explain such results. Finally, though the interaction mechanism between silicon, fluoride, iodide, and nitric acid is not clearly elucidated by our experimental results, the formation of Si-halogen bonds is crucial for etching and defect decoration capability.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Synthesis and characterization of the La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} system and the fluorinated phases La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x}

The oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} have been prepared by fluorination of the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}} via a low temperature route using poly(vinylidene fluoride) (PVDF). The structures of the oxides and oxyfluorides were investigated in detail by the Rietveld analysis of powder diffraction data. The oxyfluorides crystallize in the space group Pnma for 0<x{<=}0.9 (SrFeO{sub 2}F itself is cubic, space group Pm-3m) and show a sort of two-step structural distortion for decreasing x. Furthermore, a structural comparison of the oxyfluorides with the oxides is given, revealing an increase of the volume per La{sub 1-x}Sr{sub x}FeX{sub 3} unit during fluorination, of which the magnitude highly depends on the value of x. - Graphical abstract: The crystal structures of the perovskites La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} for x=0.8 (a), 0.5 (b) and 0.1 (c). Highlights: > Oxyfluorides La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} were prepared via low temperature fluorination using PVDF. > A structural investigation of the compounds La{sub 1-x}Sr{sub x}FeO{sub 3-x}F{sub x} is presented in detail. > Differences in structure are discussed in comparison with the precursor oxides La{sub 1-x}Sr{sub x}FeO{sub 3-{delta}}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Measurements of halogenated organic compounds near the tropical tropopause

The amount of organic chlorine and bromine entering the stratosphere have a direct influence on the magnitude of chlorine and bromine catalyzed ozone losses. Twelve organic chlorine species and five organic bromine species were measured from 12 samples collected near the tropopause between 23.8 deg N and 25.3 deg N during AASE 2. The average mixing ratios of total organic chlorine and total organic bromine were 3.50 +/- 0.06 ppbv and 21.1 +/- 0.8 pptv, respectively. CH3Cl represented 15.1% of the total organic chlorine, with CFC 11 (CCl3F) and CFC 12 (CCl2F2) accounting for 22.6% and 28.2%, respectively, with the remaining 34.1% primarily from CCl4, CH3CCl3, and CFC 113 (CCl2FCClF2). CH3Br represented 54% of the total organic bromine. The 95% confidence intervals of the mixing ratios of all but four of the individual compounds were within the range observed in low and mid-latitude mid-troposphere samples. The four compounds with significantly lower mixing ratios at the tropopause were CHCl3, CH2Cl2, CH2Br2, and CH3CCl3. The lower mixing ratios may be due to entrainment of southern hemisphere air during vertical transport in the tropical region and/or to exchange of air across the tropopause between the lower stratosphere and upper troposphere.

Schauffler, S. M.↗
NASA NTRS1993

Measurements of Halogenated Organic Compounds near the Tropical Tropopause

The amount of organic chlorine and bromine entering the stratosphere have a direct influence on the magnitude of chlorine and bromine catalyzed ozone losses. Twelve organic chlorine species and five organic bromine species were measured from 12 samples collected near the tropopause between 23.8 deg N and 25.3 deg N during AASE 2. The average mixing ratios of total organic chlorine and total organic bromine were 3.50 +/- 0.06 ppbv and 21.1 +/- 0.8 pptv, respectively. CH3Cl represented 15.1% of the total organic chlorine, with CFC 11 (CCl3F) and CFC 12 (CCl2F2) accounting for 22.6% and 28.2%, respectively, with the remaining 34.1% primarily from CCl4, CH3CCl3, and CFC 113 (CCl2FCClF2). CH3Br represented 54% of the total organic bromine. The 95% confidence intervals of the mixing ratios of all but four of the individual compounds were within the range observed in low and mid-latitude midtroposphere samples. The four compounds with significantly lower mixing ratios at the tropopause were CHCl3, CH2Cl2, CH2Br2, and CH3CCl3. The lower mixing ratios may be due to entrainment of southern hemisphere air during vertical transport in the tropical region and/or to exchange of air across the tropopause between the lower stratosphere and upper troposphere.

Schauffler, S. M.↗