SEARCH · Engineering Papers

Results for “ClO”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe 3 O 4 @g-C 3 N 4 Coated Conductive Membranes

Electrochemical membrane filtration is widely reported to enhance water contaminants' degradation or rejection via anodic oxidation or cathodic repulsion. Despite their advances, electrochemical membranes or electrocatalysts often suffer from corrosion or passivation, especially under strong electrode potentials or reactions. Moreover, the formation of toxic byproducts, such as chlorinated organic compounds and oxyhalides (e.g., ClO 4 - ) is another major concern. This study investigated the membrane aging processes of two types of conductive membranes, multiwalled carbon nanotubes (MWCNTs) and ferrite/graphitic carbon nitride hybrids (Fe 3 O 4 @g-C 3 N 4 ) coated on ceramic membranes. Under high current densities (~ 20 mA∙cm -2 ) with anodic potentials (~10 V), MWCNTs and Fe 3 O 4 @g-C 3 N 4 catalysts underwent evident oxidation as indicated by an increase of the intensity ratio of the Raman spectral bands (I D /I G ) and charge transfer resistance (R ct ) of two electrochemical membranes. Under variations of electrode potentials, chloride or bromide were shown to be oxidized to bromate (BrO 3 - ) and chlorate (ClO 3 - ) at levels of 1-10 mmol∙L -1 . The formation of BrO 3 - and ClO 3 - was dependent on the solution pH, current densities (1-20 mA∙cm -2 ), and initial concentrations of Br or Cl ions. Finally, to warrant a safe and rational design and operation of electrochemically reactive membrane processes, membrane aging and toxic byproduct's formation deserve careful characterization under relevant water filtration environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Materials Data on CoC12N8(ClO5)2 by Materials Project

CoO4(C5N4)2(CO2)2(ClO)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two formic acid molecules, two C5N4 clusters, one ClO cluster, and one CoO4 cluster. In each C5N4 cluster, there are five inequivalent C+3.67+ sites. In the first C+3.67+ site, C+3.67+ is bonded in a single-bond geometry to one N3- atom. The C–N bond length is 1.30 Å. In the second C+3.67+ site, C+3.67+ is bonded in a bent 120 degrees geometry to two N3- atoms. There is one shorter (1.32 Å) and one longer (1.42 Å) C–N bond length. In the third C+3.67+ site, C+3.67+ is bonded in a bent 120 degrees geometry to two N3- atoms. There is one shorter (1.39 Å) and one longer (1.58 Å) C–N bond length. In the fourth C+3.67+ site, C+3.67+ is bonded in a bent 120 degrees geometry to two N3- atoms. There is one shorter (1.32 Å) and one longer (1.40 Å) C–N bond length. In the fifth C+3.67+ site, C+3.67+ is bonded in a bent 120 degrees geometry to two N3- atoms. There is one shorter (1.35 Å) and one longer (1.38 Å) C–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a bent 120 degrees geometry to two C+3.67+ atoms. In the second N3- site, N3- is bonded in a bent 120 degrees geometry to two C+3.67+ atoms. In the third N3- site, N3- is bonded in a 3-coordinate geometry to three C+3.67+ atoms. In the fourth N3- site, N3- is bonded in a water-like geometry to two C+3.67+ atoms. In the ClO cluster, O2- is bonded in a distorted L-shaped geometry to two equivalent Cl1- atoms. There is one shorter (1.56 Å) and one longer (2.33 Å) O–Cl bond length. Cl1- is bonded in a 2-coordinate geometry to two equivalent O2- atoms. In the CoO4 cluster, Co2+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.64 Å) and two longer (1.88 Å) Co–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Co2+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Co2+ atom.

36 MATERIALS SCIENCE↗

NASA NTRS1977

Atomic chlorine and the chlorine monoxide radical in the stratosphere - Three in situ observations

Three simultaneous observations of atomic chlorine (Cl) and the clorine monoxide radical (ClO) are reported which encompass the altitude interval between 25 and 45 kilometers. Together, Cl and ClO form a gas-phase catalytic cycle potentially capable of depleting stratospheric ozone. Observed Cl and ClO densities, although variable, imply that chlorine compounds constitute an important part of the stratospheric ozone budget. The results are compared with recent models of stratospheric photochemistry which have been used as a basis for predicting ozone depletion resulting from fluorocarbon release.

Anderson, J. G.↗

NASA NTRS1980

An experiment concept to measure stratospheric trace constituents by laser heterodyne spectroscopy

Laser heterodyne spectroscopy (LHS) techniques were used to measure radical gases from Spacelab. Major emphasis was placed on the measurement of ClO, ClOnO2, HO2, H2O2, N2O5, and HOCl in solar occultation with vertical resolution less than or equal to 2-km and vertical range from 1O to 70-km. Sensitivity analyses were performed on ClO and O3 to determine design criteria for the LHS instrument. Results indicate that O3 and ClO vertical profiles can be measured with an accuracy more than or equal to 95% and more than or equal to 80%, respectively, over the total profile.

Allario, F.↗

NASA NTRS1981

Chlorine monoxide radical, ozone, and hydrogen peroxide - Stratospheric measurements by microwave limb sounding

Profiles of stratospheric ozone and chlorine monoxide radical (ClO) have been obtained from balloon measurements of atmospheric limb thermal emission at millimeter wavelengths. The ClO measurements, important for assessing the predicted depletion of stratospheric ozone by chlorine from industrial sources, are in close agreement with present theory. The predicted decrease of ClO at sunset was measured. A tentative value for the stratospheric abundance of hydrogen peroxide was also determined.

Waters, J. W.↗

NASA NTRS1988

Submillimeter measurement of stratospheric chlorine monoxide

The measurement of the ClO concentration in the stratosphere provides crucial information on the mechanism for ozone depletion by catalytic reactions involving chlorine. Two rotational transitions of ClO, J = 35/2 - 33/2 and J = 37/2 - 35/2 have been identified in balloon-borne high-resolution spectra of the stratospheric emission in the submillimeter region. The measurements provide information on the ClO concentration at altitudes around 28 km. In the case of afternoon measurements obtained in April 1979, a scaling factor of 0.85 (+0.67, -0.64) is observed, and in the case of afternoon and early morning measurements obtained in October 1982, a scaling factor of 0.88 (+0.18, -0.08) is observed.

Carli, B.↗

NASA NTRS1989

Chemistry and transport in a three-dimensional stratospheric model - Chlorine species during a simulated stratospheric warming

The distributions in the stratosphere of a variety of chemical species were calculated for a 6-day period during the February 1979 stratospheric major warming, using winds derived from a spectral forecast model which included O(x), NO(x), HO(x), and ClO(x) chemistries as well as longitudinally varying reaction rate coefficients and photolysis rates for these molecules. The results obtained indicate a particular importance of chemistry and transport for the Cl-containing species ClO, ClONO2, HCl, and HOCl. Dynamical effects dominate the variability of HCl, while diurnal effects dominate that of ClONO2 and ClO. The effects of strong planetary wave activity may be seen in terms of large longitudinal variability of the total HCl and ClONO columns in the stratosphere; in the middle and high northern latitudes, it is sufficiently large to exceed the diurnal variability of the column.

Kaye, Jack A.↗

NASA NTRS1989

The rotational spectrum and structure of chlorine peroxide

The dimerization products of the ClO + ClO reaction were investigated in a flowing chemical reactor using submillimeter wave spectroscopy. The major products were identified as the chlorine peroxide (Cl2O2) and chlorine dioxide (OClO). The rotational constants as well as a complete set of quartic centrifugal distortion constants were determined. The identification of the chlorine peroxide supports the earlier proposed ClO-dimer mechanisms, which partly explain the ozone hole formation during the Antarctic springtime.

Birk, Manfred↗

NASA NTRS1989

Measurements of nitric oxide and total reactive nitrogen in the Antarctic stratosphere - Observations and chemical implications

Results are presented on measurements of NO and the sum of reactive nitrogen species, NO(y), which include NO, NO2, NO3, N2O5, HNO3, and ClONO2 (in addition to ClO, O3, H2O, and N2O measurements), obtained aboard the NASA ER-2 aircraft flying over the Antarctica between the latitudes of 53 and 72 deg S during the Airborne Antarctic Ozone Experiment. The boundary of the chemically perturbed region (CPR), as indicated by a sharp increase in the level of ClO, occurred near 66 deg S; outside or equatorward of the CPR, the NO(y) mixing ratios ranged between 6 and 12 ppbv, with values decreasing poleward and reaching total NO(y) levels of 4 ppbv or less within 5-deg poleward of the boundary. Data presented in this paper clearly associate the Antarctic ozone decrease with perturbed conditions of ClO, NO(y), and H2O, which are in turn associated with processes defined as nonstandard heterogeneous chemistry, denitrification, and dehydration, respectively.

Fahey, D. W.↗

NASA NTRS1990

Heterogeneous chemistry on liquid sulfate aerosols - A comparison of in situ measurements with zero-dimensional model calculations

The possibility that stratospheric chlorine is converted from reservoir to reactive forms by heterogeneous reactions on background sulfate aerosols is examined. Tightly constrained photochemical models have been used to calculate ClO abundances for the morning and the afternoon conditions observed on January 24, 1989 outside the Arctic polar vortex by instruments on the NASA ER-2 aircraft. Calculations involving gas-phase chemistry only and calculations with heterogeneous chemistry including HCl evaporation from the aerosol both produce ClO abundances that agree with observations; calculations in which HCl removal from the aerosol is controlled by heterogeneous reactions produce ClO abundances that are 3 to 3.5 times larger than observations. These results suggest that HCl evaporation must be included in a model of the chemistry of background aerosols.

Mather, J. H.↗

NASA NTRS1992

More rapid polar ozone depletion through the reaction of HOCl with HCl on polar stratospheric clouds

The direct reaction of HOCl with HCl is shown here to play a critical part in polar ozone loss. Observations of high levels of OClO and ClO in the springtime Antarctic stratosphere confirm that most of the available chlorine is in the form of ClO(x). But current photochemical models have difficulty converting HCl to ClO(x) rapidly enough in early spring to account fully for the observations. Here, a chemical model is used to show that the direct reaction of HOCl with HCl provides the missing mechanism. As alternative sources of nitrogen-containing oxidants have been converted in the late autumn to inactive HNO3 by known reactions on the sulfate layer aerosols, the reaction of HOCl with HCl on polar stratospheric clouds becomes the most important pathway for releasing that stratospheric chlorine which goes into polar night as HCl.

Prather, Michael J.↗

NASA NTRS1993

A 3D simulation of the early winter distribution of reactive chlorine in the north polar vortex

Early in December 1991, high values of ClO are seen by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite at latitudes south of areas of temperatures cold enough to form polar stratospheric clouds (PSCs). A 3D simulation shows that the heterogeneous conversion of chlorine reservoirs to reactive chlorine on the surfaces of PSCs (processing) takes place at high latitudes. Often the processed air must be transported to lower latitudes, where the reactive chlorine is photochemically converted to ClO, to be observed by MLS. In this simulation, one incidence of cold temperatures is associated with an anticyclone, and a second with a cyclone. The transport of processed air associated with the anticyclone is marked by shearing; a decrease in the maximum of the processed air is accompanied by growth of the area influenced by the processing. In contrast, the air processed in the cyclonic event spreads more slowly. This shows that transport and shearing is a crucial element to the evolution of reactive chlorine associated with a processing event. In particular, transport and shearing, as well as photochemical processes, can cause variations in observed ClO.

Douglass, A.↗

NASA NTRS1993

Structure and thermochemistry of ClO2 radicals

The structure of ClO2 has been calculated for the X 2A-double prime ground state using unrestricted Hartree-Fock (UHF), unrestricted second-order Moller-Plesset perturbation (UMP2), configuration interaction employing single and double excitation (CISD), and quadratic configuration interaction (QCI) ab initio molecular orbital methods. Calculations using UMP2 and CISD wave functions predict a ClO bond length of 1.728 +/- 0.01 A. The single-configuration-based QCI in the singles and doubles space with perturbation inclusion of triple substitutions, denoted QCISD(T), yield a ClO bond length of 2.205 A. The QCI results are consistent with results of Jensen (1990) who showed that the ClO bond length is 2.181 A using annihilated self-consistent methods (AUMP2). The thermochemistry of ClO2 radical has been calculated using MP2 and QCI methods employing an isodesmic scheme. Our scheme predicts the heat of formation for ClO2 at 0 K to be 24.6 +/- 2 kcal/mol.

Francisco, J. S.↗

NASA NTRS1994

Global ozone observations from the UARS MLS: An overview of zonal-mean results

Global ozone observations from the Microwave Limb Sounder (MLS) aboard the Upper Atmosphere Research Satellite (UARS) are presented, in both vertically resolved and column abundance formats. The authors review the zonal-mean ozone variations measured over the two and a half years since launch in September 1991. Well-known features such as the annual and semiannual variations are ubiquitous. In the equatorial regions, longer-term changes are believed to be related to the quasi-biennial oscillation (QBO), with a strong semiannual signal above 20 hPa. Ozone values near 50 hPa exhibit an equatorial low from October 1991 to June 1992, after which the low ozone pattern splits into two subtropical lows (possibly in connection with residual circulation changes tied to the QBO) and returns to an equatorial low in September 1993. The ozone hole development at high southern latitudes is apparent in MLS column data integrated down to 100 hPa, the MLS data reinforce current knowledge of this lower-stratospheric phenomenon by providing a height-dependent view of the variations. The region from 30 deg S to 30 deg N (an area equal to half the global area) shows very little change in the ozone column from year to year and within each year. The most striking ozone changes have occurred at northern midlatitudes, with the October 1992 to July 1993 column values significantly lower than during the prior year. The zonal-mean changes manifest themselves as a slower rate of increase during the 1992/93 winter, and there is some evidence for a lower fall minimum. A recovery occurs during late summer of 1993; early 1994 values are significantly larger than during the two previous winters. The timing and latitudinal extent of the northern midlatitude decreases appear to rule out observed ClO enhancements in the Arctic vortex, with related chemical processing and ozone dilution effects, as a unique cause. Local depletion from ClO-related chemical mechanisms alone is also not sufficient, based on MLS ClO data. The puzzling asymmetric nature of the changes probably requires a dynamical component as an explanation. A combination of effects (including chemical destruction via heterogeneous processes and QBO phasing) apparently needs to be invoked. This dataset will place constraints on future modeling studies, which are required to better understand the source of the observed changes.

Froidevaux, Lucien↗

NASA NTRS1993

In situ measurements of the ClO/HCl ratio: Heterogeneous processing on sulfate aerosols and polar stratospheric clouds

Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90 deg N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv, remarkably constant ClO/HCl values of about 15% characterize the lower stratosphere. The observed values are significantly higher than those derived from a 2-D model using either gas phase photochemistry alone (2%), or including heterogeneous sulfate chemistry (5-10%). During the Arctic early spring, after conversion of HCl into reactive chlorine has taken place, the vortex edge is poorly defined by ClO levels. Loss of HCl and its slow recovery following low-temperature polar heterogeneous chemistry distinguishes HCl as a new and unique dynamical tracer of polar stratospheric clouds (PSC)-processed air.

Webster, C. R.↗

NASA NTRS1994

Hydrochloric acid and the chlorine budget of the lower statosphere

Concentrations of HCl measurements in the lower stratosphere in 1993 by the ALIAS instrument on the ER-2 aircraft reveal that only 40% of inorganic chlorine (Cl(y), inferred from in situ measurements of organic chlorinated sources gases) is present as HCl, significantly lower than model predictions. Although the sum of measured HCl, ClO and ClONO2, the latter inferred from measurements of ClO and NO2 equals Cl(y) to within the incertainty of measurement, it is systematically less than Cl(y) by 30-50%. This discrepancy suggests that concentrations of ClONO2 may exceed those of HC; near 20 km altitude, consistent with a slower photolysis rate for ClONO2 than calculated using recommended cross sections. Comparison of profiles of HCl measured during 1992 and 1193 at mid-latitudes by balloon (BLISS and MARKIV), space shuttle (ATMOS), and satellite (HALOE) instruments with the aircraft data reveal an apparent pressure dependence to the HCl to Cl(y) ratio, consistent with a factor of 3-10 reduction in the photolysis rate for ClONO2 at ER-2 altitudes. However, the diurnal variation of ClO is well-simulated by models using the recommended photolysis rate, and simulations measurements of ClONO2 and HCl at mid-latitudes by ATMOS and MARKIV report HCl (HCL+ ClONO2) ratios greater than or equal to 50%. Premliminary measurements by ALIAS in the southern hemisphere report HCl/Cl(y) values of about 75%.

Webster, C. R.↗

NASA NTRS1993

In Situ Measurements of the ClO/HCl Ratio: Heterogeneous Processing on Sulfate Aerosols and Polar Stratospheric Clouds

Simultaneous in situ measurements of stratospheric ClO and HCl have been made for the first time, during numerous flights of the ER-2 aircraft covering latitudes 24-90 deg. N from October 1991 through March 1992. The ClO/HCl ratio is identified as a key indicator of heterogeneous processing both outside and within the Arctic polar vortex. For ClO mixing ratios below about 120 pptv, remarkably constant ClO/HCl values of about 15% characterize the lower stratosphere. The observed values are significantly higher than those derived from a 2-D model using either gas phase photochemistry alone (2%), or including heterogeneous sulfate chemistry (5-10%). During the Arctic early spring, after conversion of HCl into reactive chlorine has taken place, the vortex edge is poorly defined by ClO levels. Loss of HCl and its slow recovery following low-temperature polar heterogeneous chemistry distinguishes HCl as a new and unique dynamical tracer of PSC-processed air.

Webster, C. R.↗

NASA NTRS1993

In Situ Measurements of the ClO/HCl Ratio: Heterogeneous Processing on Sulfate Aerosols and Polar Stratospheric Clouds

Webster, C. R.↗