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Sample records for 2-step thermal decomposition

  1. Thermal decomposition products of butyraldehyde

    NASA Astrophysics Data System (ADS)

    Hatten, Courtney D.; Kaskey, Kevin R.; Warner, Brian J.; Wright, Emily M.; McCunn, Laura R.

    2013-12-01

    The thermal decomposition of gas-phase butyraldehyde, CH3CH2CH2CHO, was studied in the 1300-1600 K range with a hyperthermal nozzle. Products were identified via matrix-isolation Fourier transform infrared spectroscopy and photoionization mass spectrometry in separate experiments. There are at least six major initial reactions contributing to the decomposition of butyraldehyde: a radical decomposition channel leading to propyl radical + CO + H; molecular elimination to form H2 + ethylketene; a keto-enol tautomerism followed by elimination of H2O producing 1-butyne; an intramolecular hydrogen shift and elimination producing vinyl alcohol and ethylene, a β-C-C bond scission yielding ethyl and vinoxy radicals; and a γ-C-C bond scission yielding methyl and CH2CH2CHO radicals. The first three reactions are analogous to those observed in the thermal decomposition of acetaldehyde, but the latter three reactions are made possible by the longer alkyl chain structure of butyraldehyde. The products identified following thermal decomposition of butyraldehyde are CO, HCO, CH3CH2CH2, CH3CH2CH=C=O, H2O, CH3CH2C≡CH, CH2CH2, CH2=CHOH, CH2CHO, CH3, HC≡CH, CH2CCH, CH3C≡CH, CH3CH=CH2, H2C=C=O, CH3CH2CH3, CH2=CHCHO, C4H2, C4H4, and C4H8. The first ten products listed are direct products of the six reactions listed above. The remaining products can be attributed to further decomposition reactions or bimolecular reactions in the nozzle.

  2. Unimolecular thermal decomposition of dimethoxybenzenes

    SciTech Connect

    Robichaud, David J. Mukarakate, Calvin; Nimlos, Mark R.; Scheer, Adam M.; Ormond, Thomas K.; Buckingham, Grant T.; Ellison, G. Barney

    2014-06-21

    The unimolecular thermal decomposition mechanisms of o-, m-, and p-dimethoxybenzene (CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3}) have been studied using a high temperature, microtubular (μtubular) SiC reactor with a residence time of 100 μs. Product detection was carried out using single photon ionization (SPI, 10.487 eV) and resonance enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry and matrix infrared absorption spectroscopy from 400 K to 1600 K. The initial pyrolytic step for each isomer is methoxy bond homolysis to eliminate methyl radical. Subsequent thermolysis is unique for each isomer. In the case of o-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3}, intramolecular H-transfer dominates leading to the formation of o-hydroxybenzaldehyde (o-HO-C{sub 6}H{sub 4}-CHO) and phenol (C{sub 6}H{sub 5}OH). Para-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3} immediately breaks the second methoxy bond to form p-benzoquinone, which decomposes further to cyclopentadienone (C{sub 5}H{sub 4}=O). Finally, the m-CH{sub 3}O-C{sub 6}H{sub 4}-OCH{sub 3} isomer will predominantly follow a ring-reduction/CO-elimination mechanism to form C{sub 5}H{sub 4}=O. Electronic structure calculations and transition state theory are used to confirm mechanisms and comment on kinetics. Implications for lignin pyrolysis are discussed.

  3. Thermal decomposition and non-isothermal decomposition kinetics of carbamazepine

    NASA Astrophysics Data System (ADS)

    Qi, Zhen-li; Zhang, Duan-feng; Chen, Fei-xiong; Miao, Jun-yan; Ren, Bao-zeng

    2014-12-01

    The thermal stability and kinetics of isothermal decomposition of carbamazepine were studied under isothermal conditions by thermogravimetry (TGA) and differential scanning calorimetry (DSC) at three heating rates. Particularly, transformation of crystal forms occurs at 153.75°C. The activation energy of this thermal decomposition process was calculated from the analysis of TG curves by Flynn-Wall-Ozawa, Doyle, distributed activation energy model, Šatava-Šesták and Kissinger methods. There were two different stages of thermal decomposition process. For the first stage, E and log A [s-1] were determined to be 42.51 kJ mol-1 and 3.45, respectively. In the second stage, E and log A [s-1] were 47.75 kJ mol-1 and 3.80. The mechanism of thermal decomposition was Avrami-Erofeev (the reaction order, n = 1/3), with integral form G(α) = [-ln(1 - α)]1/3 (α = ˜0.1-0.8) in the first stage and Avrami-Erofeev (the reaction order, n = 1) with integral form G(α) = -ln(1 - α) (α = ˜0.9-0.99) in the second stage. Moreover, Δ H ≠, Δ S ≠, Δ G ≠ values were 37.84 kJ mol-1, -192.41 J mol-1 K-1, 146.32 kJ mol-1 and 42.68 kJ mol-1, -186.41 J mol-1 K-1, 156.26 kJ mol-1 for the first and second stage, respectively.

  4. Thermal Decomposition Behavior of Poly(3-nitratooxetane)

    NASA Astrophysics Data System (ADS)

    Mason, Brian; Cruz, Aliza; Stoltz, Chad

    2009-06-01

    Poly(3-nitratooxetane), or PNO, is a new high-energy density polymer that is expected to increase formulation energy output without sacrificing binder stability. It is anticipated that using PNO in propellant formulations will be advantageous compared to other energetic binders such as its structural isomer poly(glycidyl nitrate) (PGN). In an effort to understand the combustion behavior of this new energetic polymer, thermal decomposition of PNO has been investigated. Differential scanning calorimetry coupled with thermal gravimetric analysis shows that this material is thermally stable to at least 150^oC and that exothermic decomposition peaks near 203^oC. T- Jump/FTIR was used under various conditions to identify gas- phase thermal decomposition products, including H2O, CH2O, CO2, CO, N2O, NO, NO2, and HONO (cis and trans). Additional time- resolved T-Jump/FTIR experiments suggest immediate dissociation of NO2 as the obvious first step in PNO decomposition, while previous work on the PGN polymer system suggests that the entire CH2ONO2 side chain breaks from the PGN backbone before dissociation. It is likely that different decomposition pathways are followed for each binder system due to location of available C-O and N-O moieties on each polymer.

  5. Thermal Decomposition of Poly(methylphenylsilane)

    NASA Astrophysics Data System (ADS)

    Pan, Lujun; Zhang, Mei; Nakayama, Yoshikazu

    2000-03-01

    The thermal decomposition of poly(methylphenylsilane) was performed at constant heating rates and isothermal conditions. The evolved gases were studied by ionization-threshold mass spectroscopy. Pyrolysis under isothermal conditions reveals that the decomposition of poly(methylphenylsilane) is a type of depolymerization that has a first-order reaction. Kinetic analysis of the evolution spectra of CH3-Si-C6H5 radicals, phenyl and methyl substituents reveals the mechanism and activation energies of the decomposition reactions in main chains and substituents. It is found that the decomposition of main chains is a dominant reaction and results in the weight loss of approximately 90%. The effusion of phenyl and methyl substituents occurs in the two processes of rearrangement of main chains and the formation of stable Si-C containing residuals.

  6. Mechanical, thermal and morphological characterization of polycarbonate/oxidized carbon nanofiber composites produced with a lean 2-step manufacturing process.

    PubMed

    Lively, Brooks; Kumar, Sandeep; Tian, Liu; Li, Bin; Zhong, Wei-Hong

    2011-05-01

    In this study we report the advantages of a 2-step method that incorporates an additional process pre-conditioning step for rapid and precise blending of the constituents prior to the commonly used melt compounding method for preparing polycarbonate/oxidized carbon nanofiber composites. This additional step (equivalent to a manufacturing cell) involves the formation of a highly concentrated solid nano-nectar of polycarbonate/carbon nanofiber composite using a solution mixing process followed by melt mixing with pure polycarbonate. This combined method yields excellent dispersion and improved mechanical and thermal properties as compared to the 1-step melt mixing method. The test results indicated that inclusion of carbon nanofibers into composites via the 2-step method resulted in dramatically reduced ( 48% lower) coefficient of thermal expansion compared to that of pure polycarbonate and 30% lower than that from the 1-step processing, at the same loading of 1.0 wt%. Improvements were also found in dynamic mechanical analysis and flexural mechanical properties. The 2-step approach is more precise and leads to better dispersion, higher quality, consistency, and improved performance in critical application areas. It is also consistent with Lean Manufacturing principles in which manufacturing cells are linked together using less of the key resources and creates a smoother production flow. Therefore, this 2-step process can be more attractive for industry.

  7. THERMAL DECOMPOSITION OF URANIUM COMPOUNDS

    DOEpatents

    Magel, T.T.; Brewer, L.

    1959-02-10

    A method is presented of preparing uranium metal of high purity consisting contacting impure U metal with halogen vapor at between 450 and 550 C to form uranium halide vapor, contacting the uranium halide vapor in the presence of H/sub 2/ with a refractory surface at about 1400 C to thermally decompose the uranium halides and deposit molten U on the refractory surface and collecting the molten U dripping from the surface. The entire operation is carried on at a sub-atmospheric pressure of below 1 mm mercury.

  8. Thermal Decomposition of IMX-104: Ingredient Interactions Govern Thermal Insensitivity

    SciTech Connect

    Maharrey, Sean; Wiese-Smith, Deneille; Highley, Aaron M.; Steill, Jeffrey D.; Behrens, Richard; Kay, Jeffrey J.

    2015-04-01

    This report summarizes initial studies into the chemical basis of the thermal insensitivity of INMX-104. The work follows upon similar efforts investigating this behavior for another DNAN-based insensitive explosive, IMX-101. The experiments described demonstrate a clear similarity between the ingredient interactions that were shown to lead to the thermal insensitivity observed in IMX-101 and those that are active in IMX-104 at elevated temperatures. Specifically, the onset of decomposition of RDX is shifted to a lower temperature based on the interaction of the RDX with liquid DNAN. This early onset of decomposition dissipates some stored energy that is then unavailable for a delayed, more violent release.

  9. Treatment of nitrocellulose by thermal decomposition

    SciTech Connect

    Campbell, R.K.; Freedman, D.L.; Kim, B.J.

    1999-07-01

    Waste fines generated during the manufacture of nitrocellulose (NC) are classified as a RCRA K044 hazardous waste due to their explosive properties. The objective of this study was to evaluate controlled thermal treatment of NC in order to render it nonhazardous and allow for more economical ultimate disposal. The results indicate that controlled thermal decomposition at 130--150 C is a technically feasible process. Rates improved significantly at higher temperatures. At 150 C, only 10 hours were needed to reduce the nitrogen content of NC from 13.7% to below 10% (versus 105 h at 130 C), a level found in many commercial, nonhazardous grades of NC. The air flow rate over the heated NC, and the moisture content of the NC or air above it had no discernible effect on rates of nitrogen removal. Greater mass loss from the NC than what was attributable to the nitro groups alone indicated that decomposition of the polymer backbone also occurred. This was confirmed by FTIR analyses, the appearance of CO{sub 2} in the off-gas, and a lack of correlation between percent nitrogen and heat of combustion. Samples of thermally treated NC containing 9.7% nitrogen failed three of the basic tests used by the Bureau of Explosives to ascertain explosive characteristics, indicating that the product was no longer hazardous based on its energetic properties. Although technically feasible, use of thermal decomposition to treat NC fines will most likely be restricted by safety concerns. Operating close to 130 C would mitigate the risk, but considerably extends the time required for treatment. The most suitable application of this technology may instead by treatment of NC-contaminated soils.

  10. Thermal Decomposition of Radiation-Damaged Polystyrene

    SciTech Connect

    J Abrefah GS Klinger

    2000-09-26

    The radiation-damaged polystyrene material (''polycube'') used in this study was synthesized by mixing a high-density polystyrene (''Dylene Fines No. 100'') with plutonium and uranium oxides. The polycubes were used on the Hanford Site in the 1960s for criticality studies to determine the hydrogen-to-fissile atom ratios for neutron moderation during processing of spent nuclear fuel. Upon completion of the studies, two methods were developed to reclaim the transuranic (TRU) oxides from the polymer matrix: (1) burning the polycubes in air at 873 K; and (2) heating the polycubes in the absence of oxygen and scrubbing the released monomer and other volatile organics using carbon tetrachloride. Neither of these methods was satisfactory in separating the TRU oxides from the polystyrene. Consequently, the remaining polycubes were sent to the Hanford Plutonium Finishing Plant (PFP) for storage. Over time, the high dose of alpha and gamma radiation has resulted in a polystyrene matrix that is highly cross-linked and hydrogen deficient and a stabilization process is being developed in support of Defense Nuclear Facility Safety Board Recommendation 94-1. Baseline processes involve thermal treatment to pyrolyze the polycubes in a furnace to decompose the polystyrene and separate out the TRU oxides. Thermal decomposition products from this degraded polystyrene matrix were characterized by Pacific Northwest National Laboratory to provide information for determining the environmental impact of the process and for optimizing the process parameters. A gas chromatography/mass spectrometry (GC/MS) system coupled to a horizontal tube furnace was used for the characterization studies. The decomposition studies were performed both in air and helium atmospheres at 773 K, the planned processing temperature. The volatile and semi-volatile organic products identified for the radiation-damaged polystyrene were different from those observed for virgin polystyrene. The differences were in the

  11. Thermal Decomposition of Radiation-Damaged Polystyrene

    SciTech Connect

    Abrefah, John; Klinger, George S.

    2000-09-26

    The radiation-damaged polystyrene (given the identification name of 'polycube') was fabricated by mixing high-density polystyrene material ("Dylene Fines # 100") with plutonium and uranium oxides. The polycubes were used in the 1960s for criticality studies during processing of spent nuclear fuel. The polycubes have since been stored for almost 40 years at the Hanford Plutonium Finishing Plant (PFP) after failure of two processes to reclaim the plutonium and uranium oxides from the polystyrene matrix. Thermal decomposition products from this highly cross-linked polystyrene matrix were characterized using Gas Chromatograph/Mass Spectroscopy (GC/MS) system coupled to a horizontal furnace. The decomposition studies were performed in air and helium atmospheres at about 773 K. The volatile and semi-volatile organic products for the radiation-damaged polystyrene were different compared to virgin polystyrene. The differences were in the number of organic species generated and their concentrations. In the inert (i.e., helium) atmosphere, the major volatile organic products identified (in order of decreasing concentrations) were styrene, benzene, toluene, ethylbenzene, xylene, nathphalene, propane, .alpha.-methylbenzene, indene and 1,2,3-trimethylbenzene. But in air, the major volatile organic species identified changed slightly. Concentrations of the organic species in the inert atmosphere were significantly higher than those for the air atmosphere processing. Overall, 38 volatile organic species were identified in the inert atmosphere compared to 49 species in air. Twenty of the 38 species in the inert conditions were also products in the air atmosphere. Twenty-two oxidized organic products were identified during thermal processing in air.

  12. The Thermal Decomposition of Basic Copper(II) Sulfate.

    ERIC Educational Resources Information Center

    Tanaka, Haruhiko; Koga, Nobuyoshi

    1990-01-01

    Discussed is the preparation of synthetic brochantite from solution and a thermogravimetric-differential thermal analysis study of the thermal decomposition of this compound. Other analyses included are chemical analysis and IR spectroscopy. Experimental procedures and results are presented. (CW)

  13. Ultralow friction of carbonate faults caused by thermal decomposition.

    PubMed

    Han, Raehee; Shimamoto, Toshihiko; Hirose, Takehiro; Ree, Jin-Han; Ando, Jun-Ichi

    2007-05-11

    High-velocity weakening of faults may drive fault motion during large earthquakes. Experiments on simulated faults in Carrara marble at slip rates up to 1.3 meters per second demonstrate that thermal decomposition of calcite due to frictional heating induces pronounced fault weakening with steady-state friction coefficients as low as 0.06. Decomposition produces particles of tens of nanometers in size, and the ultralow friction appears to be associated with the flash heating on an ultrafine decomposition product. Thus, thermal decomposition may be an important process for the dynamic weakening of faults.

  14. Thermal Decomposition of Lanthanide, Yttrium, and Scandium Oxalates and Carbonates

    NASA Astrophysics Data System (ADS)

    Sharov, Vyacheslav A.; Bezdenezhnykh, G. V.

    1981-07-01

    Data concerning the thermal decomposition of lanthanide, yttrium, and scandium oxalates and carbonates are surveyed. The complexity of the process, the large number of stages involved, and the dependence of the composition of the intermediates in the thermal transformations on the experimental conditions is noted. Certain process characteristics have been discovered and it is concluded that the decomposition process depends on the ionic radius of the metal. The bibliography includes 83 references.

  15. Effect of mechanical dispersion of lignite on its thermal decomposition

    SciTech Connect

    Yusupov, T.S.; Shumskaya, L.G.; Burdukov, A.P.

    2007-09-15

    It is studied how the high-rate mechanical grinding affects thermal decomposition of lignite extracted from the Kansk-Achinsk Coal Basin. It has been shown that dispersion of lignite in the high energy intensive vibration-centrifugal and planetary mills causes formation of structures exhibiting lower thermal stability. That results in the shift of primary decomposition phenomena into the low-temperature region and, thus, in the higher reactivity of coals.

  16. Thermal Decomposition Characteristics of Orthorhombic Ammonium Perchlorate (o-AP)

    SciTech Connect

    Behrens, R.; Minier, L.

    1999-03-01

    Preliminary STMBMS and SEM results of the thermal decomposition of AP in the orthorhombic phase are presented. The overall decomposition is shown to be complex and controlled by both physical and chemical processes. The data show that the physical and chemical processes can be probed and characterized utilizing SEM and STMBMS. The overall decomposition is characterized by three distinguishing features: an induction period, and accelerator period and a deceleratory period. The major decomposition event occurs in the subsurface of the AP particles and propagates towards the center of the particle with time. The amount of total decomposition is dependent upon particle size and increases from 23% for {approximately}50{micro}m-diameter AP to 33% for {approximately}200{micro}m-diameter AP. A conceptual model of the physical processes is presented. Insight into the chemical processes is provided by the gas formation rates that are measured for the gaseous products. To our knowledge, this is the first presentation of data showing that the chemical and physical decomposition processes can be identified from one another, probed and characterized at the level that is required to better understand the thermal decomposition behavior of AP. Future work is planned with the goal of obtaining data that can be used to develop a mathematical description for the thermal decomposition of o-AP.

  17. Analysis of cured carbon-phenolic decomposition products to investigate the thermal decomposition of nozzle materials

    NASA Technical Reports Server (NTRS)

    Thompson, James M.; Daniel, Janice D.

    1989-01-01

    The development of a mass spectrometer/thermal analyzer/computer (MS/TA/Computer) system capable of providing simultaneous thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and evolved gas detection and analysis (EGD and EGA) under both atmospheric and high pressure conditions is described. The combined system was used to study the thermal decomposition of the nozzle material that constitutes the throat of the solid rocket boosters (SRB).

  18. Mechanism of thermal decomposition of hydrated copper nitrate in vacuo

    NASA Astrophysics Data System (ADS)

    L'vov, Boris V.; Novichikhin, Alexander V.

    1995-10-01

    The general scheme of three-stage thermal decomposition of Cu(NO 3) 2·3H 2O to CuO has been refined based on evolved-gas-analysis data with a quadrupole mass analyzer (Jackson et al., Spectrochim. Acta Part B, 50 (1995) 1423). Quantitative evaluation of the composition of the gaseous products shows that the first stage involves primarily deaquation, and the second stage, primarily denitration of the original hydrated nitrate. The basic nitrate formed in the second stage most probably has the formula Cu(NO 3) 2·3Cu(OH) 2. It has been established that the molecular oxygen observed in the third stage of decomposition is produced by catalytic decomposition of NO 2 on the surface of CuO. The presence of Cu-containing ions in all stages of the process is consistent with the gasification mechanism of thermal decomposition.

  19. Thermal Decomposition of Copper (II) Calcium (II) Formate

    NASA Astrophysics Data System (ADS)

    Leyva, A. G.; Polla, G.; de Perazzo, P. K.; Lanza, H.; de Benyacar, M. A. R.

    1996-05-01

    The presence of different stages in the thermal decomposition process of CuCa(HCOO) 4has been established by means of TGA at different heating rates, X-ray powder diffraction of quenched samples, and DSC methods. During the first stage, decomposition of one of the two copper formate structural units contained in the unit cell takes place. The presence of CuCa 2(HCOO) 6has been detected. Calcium formate structural units break down at higher temperatures; the last decomposition peak corresponds to the appearance of different calcium-copper oxides.

  20. The Products of the Thermal Decomposition of CH3CHO

    SciTech Connect

    Vasiliou, AnGayle; Piech, Krzysztof M.; Zhang, Xu; Nimlos, Mark R.; Ahmed, Musahid; Golan, Amir; Kostko, Oleg; Osborn, David L.; Daily, John W.; Stanton, John F.; Ellison, G. Barney

    2011-04-06

    We have used a heated 2 cm x 1 mm SiC microtubular (mu tubular) reactor to decompose acetaldehyde: CH3CHO + DELTA --> products. Thermal decomposition is followed at pressures of 75 - 150 Torr and at temperatures up to 1700 K, conditions that correspond to residence times of roughly 50 - 100 mu sec in the mu tubular reactor. The acetaldehyde decomposition products are identified by two independent techniques: VUV photoionization mass spectroscopy (PIMS) and infrared (IR) absorption spectroscopy after isolation in a cryogenic matrix. Besides CH3CHO, we have studied three isotopologues, CH3CDO, CD3CHO, and CD3CDO. We have identified the thermal decomposition products CH3(PIMS), CO (IR, PIMS), H (PIMS), H2 (PIMS), CH2CO (IR, PIMS), CH2=CHOH (IR, PIMS), H2O (IR, PIMS), and HC=CH (IR, PIMS). Plausible evidence has been found to support the idea that there are at least three different thermal decomposition pathways for CH3CHO: Radical decomposition: CH3CHO + DELTA --> CH3 + [HCO] --> CH3 + H + CO Elimination: CH3CHO + DELTA --> H2 + CH2=C=O. Isomerization/elimination: CH3CHO + DELTA --> [CH2=CH-OH] --> HC=CH + H2O. Both PIMS and IR spectroscopy show compelling evidence for the participation of vinylidene, CH2=C:, as an intermediate in the decomposition of vinyl alchohol: CH2=CH-OH + DELTA --> [CH2=C:] + H2O --> HC=CH + H2O.

  1. Thermal decomposition of 2-phenylethanol: A computational study on mechanism

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuyuki; Ando, Hiromitsu; Oguchi, Tatsuo; Murakami, Yoshinori

    2013-01-01

    Quantum mechanical calculations for the thermal decomposition of 2-phenylethanol have been performed using the CBS-QB3 method. Based on the potential energy surfaces at the CBS-QB3 level of theory, the preferred reaction channel for the thermal decomposition of 2-phenylethanol was the six-membered cyclic rearrangement reaction and the dehydration reaction to form styrene and H2O. Further quantum chemical calculations of the subsequent reactions followed by the six-membered cyclic rearrange reaction of 2-phenylethanol were carried out and it was revealed that the barrier height for the ring opening reaction was the lowest among all of the other subsequent reactions.

  2. Thermal Decomposition Chemistry of Amine Borane (U)

    SciTech Connect

    Stowe, A. C.; Feigerle, J.; Smyrl, N. R.; Morrell, J. S.

    2010-01-29

    The conclusions of this presentation are: (1) Amine boranes potentially can be used as a vehicular hydrogen storage material. (2) Purity of the hydrogen stream is critical for use with a fuel cell. Pure H{sub 2} can be provided by carefully conditioning the fuel (encapsulation, drying, heating rate, impurities). (3) Thermodynamics and kinetics can be controlled by conditioning as well. (4) Regeneration of the spent amine borane fuel is still the greatest challenge to its potential use. (5) Addition of hydrocarbon-substituted amine boranes alter the chemistry dramatically. (6) Decomposition of the substituted amine borane mixed system favors reaction products that are more potentially easier to regenerate the hydrogenated fuel. (7) t-butylamine borane is not the best substituted amine borane to use since it releases isobutane; however, formation of CNBH{sub x} products does occur.

  3. Thermal decomposition of substituted phenols in supercritical water

    SciTech Connect

    Martino, C.J.; Savage, P.E.

    1997-05-01

    The thermal decomposition of cresols, hydroxybenzaldehydes, nitrophenols, and benzenediols was studied in dilute aqueous solutions and in the absence of oxygen at 460 C and 250 atm for residence times around 10 s. Thermolysis under these conditions produced conversions of less than 10% for o-, m-, and p-cresol, whereas hydroxybenzaldehydes and nitrophenols were much more reactive. Global rate expressions are reported for the thermolysis of each hydroxybenzaldehyde and nitrophenol isomer. Phenol was a major product from the decomposition of all of the substituted phenols studied. For a given substituent, ortho-substituted phenols reacted more rapidly than the other isomers. For a given substituted position, nitrophenols reacted more rapidly than hydroxybenzaldehydes, which in turn reacted more rapidly than cresols. These results demonstrate that the treatment of CHO- and NO{sub 2}-substituted phenols by oxidation in supercritical water will involve the oxidation of thermal decomposition products in addition to the oxidation of the original compounds.

  4. Thermal decomposition of silane to form hydrogenated amorphous Si film

    DOEpatents

    Strongin, Myron; Ghosh, Arup K.; Wiesmann, Harold J.; Rock, Edward B.; Lutz, III, Harry A.

    1980-01-01

    This invention relates to hydrogenated amorphous silicon produced by thermally decomposing silano (SiH.sub.4) or other gases comprising H and Si, at elevated temperatures of about 1700.degree.-2300.degree. C., and preferably in a vacuum of about 10.sup.-8 to 10.sup.-4 torr, to form a gaseous mixture of atomic hydrogen and atomic silicon, and depositing said gaseous mixture onto a substrate outside said source of thermal decomposition to form hydrogenated amorphous silicon.

  5. Thermal Decomposition of Copper (II) Dicalcium (II) Formate

    NASA Astrophysics Data System (ADS)

    de Perazzo, P. K.; Leyva, A. G.; Polla, G.; Parisi, F.; de Benyacar, M. A. R.; Smichowski, P.; Lanza, H.

    1997-09-01

    The unit cell obtained through X-ray single crystal analysis of the synthetized CuCa 2(HCOO) 6crystals corresponds to a supercell of the basic structure described by M. Sanchis et al.( Inorg. Chem.31, 2915 (1992)). Thermal decomposition of this sample shows two stages up to 300°C; the first can be related to the superstructure, and the second corresponds to the breaking down of the remaining copper formate structural units and the simultaneous decomposition of the sample.

  6. Reaction kinetics of paddy husk thermal decomposition

    SciTech Connect

    Jain, A.K.; Sharma, S.K.; Singh, D.

    1996-12-31

    Paddy husk production in world is estimated to be around 80 million tons. It has a calorific value of 15 MJ/kg and thus has a tremendous potential as a renewable energy source. Its current uses are: cattle feed, raw material for paper and board, furfural production and silica industries. A large quantity of paddy husk is used in husk fired boiler furnaces at a very low efficiency. For efficient design of husk fired furnaces, reliable data on thermal characteristics of rice husk is essential which is lacking in the literature. In the present study, paddy husk was subjected to Thermogravimetric Analysis at heating rates of 10 and 100 C/min. in a thermal analyzer. The analysis was carried out in air and mixture of oxygen and nitrogen (5:95%) atmosphere. Reaction kinetic parameters such as activation energy, frequency factor and order of reaction have been evaluated and reported. These are relevant to the design of paddy husk fired gasifiers, furnaces and other thermochemical conversion equipment. The results of the thermochemical studies and their potential applications are presented in the paper.

  7. Resolving Some Paradoxes in the Thermal Decomposition Mechanism of Acetaldehyde.

    PubMed

    Sivaramakrishnan, Raghu; Michael, Joe V; Harding, Lawrence B; Klippenstein, Stephen J

    2015-07-16

    The mechanism for the thermal decomposition of acetaldehyde has been revisited with an analysis of literature kinetics experiments using theoretical kinetics. The present modeling study was motivated by recent observations, with very sensitive diagnostics, of some unexpected products in high temperature microtubular reactor experiments on the thermal decomposition of CH3CHO and its deuterated analogs, CH3CDO, CD3CHO, and CD3CDO. The observations of these products prompted the authors of these studies to suggest that the enol tautomer, CH2CHOH (vinyl alcohol), is a primary intermediate in the thermal decomposition of acetaldehyde. The present modeling efforts on acetaldehyde decomposition incorporate a master equation reanalysis of the CH3CHO potential energy surface (PES). The lowest-energy process on this PES is an isomerization of CH3CHO to CH2CHOH. However, the subsequent product channels for CH2CHOH are substantially higher in energy, and the only unimolecular process that can be thermally accessed is a reisomerization to CH3CHO. The incorporation of these new theoretical kinetics predictions into models for selected literature experiments on CH3CHO thermal decomposition confirms our earlier experiment and theory-based conclusions that the dominant decomposition process in CH3CHO at high temperatures is C-C bond fission with a minor contribution (∼10-20%) from the roaming mechanism to form CH4 and CO. The present modeling efforts also incorporate a master-equation analysis of the H + CH2CHOH potential energy surface. This bimolecular reaction is the primary mechanism for removal of CH2CHOH, which can accumulate to minor amounts at high temperatures, T > 1000 K, in most lab-scale experiments that use large initial concentrations of CH3CHO. Our modeling efforts indicate that the observation of ketene, water, and acetylene in the recent microtubular experiments are primarily due to bimolecular reactions of CH3CHO and CH2CHOH with H-atoms and have no bearing on

  8. Thermal decomposition of PMC for fiber recovery

    SciTech Connect

    Jody, B. J.; Daniels, E. J.; Pomykala, J. A.

    1999-10-22

    This paper describes efforts by Argonne National Laboratory to develop a process to recover carbon fibers from polymer matrix composite (PMC) materials. The polymer material in the matrix maybe a thermoplastic or a thermoset. Samples of panels containing PMC fibers were obtained and used in the bench-scale testing program. The authors tested three different methods for recovering these PMC fibers: thermal treatment, chemical degradation, and cryogenic methods (thermal shock treatment). The first two methods were effective in separating the carbon fibers from the polymeric substrate; the third method was not satisfactory. Carbon fibers separated from the polymer substrate using the thermal treatment method were submitted to Oak Ridge National Laboratory for analysis and evaluation. The results indicated that the carbon fibers had been cleanly separated from the polymer matrix. Their intrinsic density was 1.8473 g/cm{sup 3} and their electrical resistivity was 0.001847 ohm-cm, compared to an intrinsic density of 1.75--1.9 gm/cm{sup 3} and an electrical resistivity of 0.0002--0.002 ohm-cm for virgin fibers produced from polyacrylonitrile (PAN). Although they were not sure that the samples they processed were originally produced from PAN, they used the PAN fibers for comparison. It was also demonstrated that the surface of the recovered fibers could be reactivated to energy levels equivalent to those of reactivated virgin fibers from PAN. A comparison of the mechanical properties of the recovered fibers (without surface treatment) with those of surface-treated virgin fibers from PAN revealed that the ultimate tensile strength and the elongation at brake values are about 1/3 the values for the virgin fibers. The modulus for the recycled fibers (31.4 million pounds per square inch [psi]) was about the same as that for the virgin PAN fibers (31.2 million psi). The reason for the lower tensile strength and elongation is not clear; the authors plan to investigate it further

  9. Mechanism of the Thermal Decomposition of Ethanethiol and Dimethylsulfide

    NASA Astrophysics Data System (ADS)

    Melhado, William Francis; Whitman, Jared Connor; Kong, Jessica; Anderson, Daniel Easton; Vasiliou, AnGayle (AJ)

    2016-06-01

    Combustion of organosulfur contaminants in petroleum-based fuels and biofuels produces sulfur oxides (SO_x). These pollutants are highly regulated by the EPA because they have been linked to poor respiratory health and negative environmental impacts. Therefore much effort has been made to remove sulfur compounds in petroleum-based fuels and biofuels. Currently desulfurization methods used in the fuel industry are costly and inefficient. Research of the thermal decomposition mechanisms of organosulfur species can be implemented via engineering simulations to modify existing refining technologies to design more efficient sulfur removal processes. We have used a resistively-heated SiC tubular reactor to study the thermal decomposition of ethanethiol (CH_3CH_2SH) and dimethylsulfide (CH_3SCH_3). The decomposition products are identified by two independent techniques: 118.2 nm VUV photoionization mass spectroscopy and infrared spectroscopy. The thermal cracking products for CH_3CH_2SH are CH_2CH_2, SH, and H_2S and the thermal cracking products from CH_3SCH_3 are CH_3S, CH_2S, and CH_3.

  10. Strain localization driven by thermal decomposition during seismic shear

    NASA Astrophysics Data System (ADS)

    Platt, J. D.; Brantut, N.; Rice, J. R.

    2011-12-01

    De Paola et al. [2008] analyzed a series of faults in the Northern Apennines, Italy, hosted in anhydrite and dolomite rocks. They found a highly localized band of less than 100 microns, contained within a broader damage zone. Recent High-Velocity Friction (HVF) experiments on kaolinite-bearing gouge samples (Brantut et al. [2008]) have also shown extreme localization in samples undergoing thermal decomposition. They performed microstructural analysis on HVF samples and found an "ultralocalized deformation zone", less than ten microns wide, interpreted to be the main slipping zone in the experiment. By measuring relative humidity in the sample chamber they were also able to observe the thermal dehydration of kaolinite. These laboratory and field observations indicate that straining is extremely localized in fault materials where thermal decomposition reactions may occur. During thermal decomposition reactions pore fluid is released, leading to increases in pore pressure, and a corresponding drop in frictional heating. The reactions are endothermic, so heat is also absorbed as the reactions progress. Previous work by Sulem and Famin [2009] has investigated how these effects influence the evolution of pore pressure and temperature in a uniformly sheared gouge layer. They found that accounting for thermal decomposition reactions leads to significant pore pressure increases, and that the endothermic nature of the reaction acts to cap the maximum temperature achieved. In previous work (Platt, Rudnicki and Rice [2010]) we investigated strain localization using a model for shearing of a fluid-saturated gouge material, finding a formula for the localized zone width as a function of physical properties of the gouge. We now extend this model to include thermal decomposition. Using linear stability methods and an idealized reaction kinetic we infer a new localized zone width when decomposition is accounted for. Numerical simulations then allow us to compare this prediction to

  11. Thermal decomposition of dolomite under CO2-air atmosphere

    NASA Astrophysics Data System (ADS)

    Subagjo, Wulandari, Winny; Adinata, Pratitis Mega; Fajrin, Anita

    2017-01-01

    This paper reports a study on thermal decomposition of dolomite under CO2-air. Calcination was carried out non-isothermally by using thermogravimetry analysis-differential scanning calorimetry (TGA-DSC) with a heating rate of 10°C/minute in an air atmosphere as well as 10 vol% CO2 and 90 vol% air atmosphere from 25 to 950°C. In addition, a thermodynamic modeling was also carried out to simulate dolomite calcination in different level of CO2-air atmosphere by using FactSage® 7.0. The the main constituents of typical dolomite from Gresik, East Java include MgCO3 (magnesite), CaCO3 (calcite), Ca(OH)2, CaO, MgO, and less than 1% of metal impurities. Based on the kinetics analysis from TGA results, it is found that non-isothermal dolomite calcination in 10 vol% CO2 atmosphere is occurred in a two-stage reaction; the first stage is the decomposition of magnesite at 650-740 °C with activation energy of 161.23 kJ/mol, and the second stage is the decomposition of calcite at 775-820 °C with activation energy of 162.46 kJ/mol. The magnesite decomposition is found to follow nucleation reaction mechanism of Avrami Eroveyef (A3), while calcite decomposition follows second order chemical reaction equation. Thermodynamic modeling supports these kinetic analyses. The results of this research give insight to the kinetics of dolomite decomposition in CO2-air atmosphere.

  12. Condensed-phase decomposition in thermally-aged explosives

    SciTech Connect

    Erickson, K.L.; Trott, W.M.; Renlund, A.M.

    1995-12-01

    In previous work, the isothermal decomposition of nitrocellulose (NC) was examined using two substantially different experimental techniques that are being developed to investigate condensed-phase chemistry occurring during the thermal decomposition of a variety of explosives. The confined isothermal aging technique involved confined thin-film samples heated to temperatures of 150 to 170{degrees}C, for 1 to 72 hours. Condensed-phase chemistry was monitored real-time using FTIR. Results indicated that the first step in decomposition was scission of the O-NO{sub 2} bond and subsequent formation of carbonyl and hydroxyl products. Scission of the O-NO{sub 2} bond appeared to occur by a first-order reaction. Additional unconfined rapid isothermal decomposition experiments with NC have been completed and are described in this paper. Those additional experiments extended the previous work and investigated the effect of varying film thickness (from about 0.2 to 0.6 microns), varying temperature (from about 420 to 640{degrees}C), and using {sup 15}NO{sub 2}-labled NC. The results indicated that decomposition of NC appears to involve at least two principal mechanisms: (1) O-NO{sub 2} bond scission, which is accompanied by carbonyl or hydroxyl formation, and (2) polymer fragmentation. These two mechanisms occur simultaneously. At temperatures of 170{degrees}C, or lower, polymer fragmentation appears negligible, but at temperatures of 420{degrees}C, or higher, polymer fragmentation is appreciable and occurs at rates comparable to those for O-NO{sub 2} bond scission. While polymer fragmentation may be associated with O-NO{sub 2} bond scission, at higher temperatures, additional steps must be involved in the fragmentation mechanism. At each end of the temperatures range from about 150 to 420{degrees}C, the rate of O-NO{sub 2} bond scission appears reasonably consistent with a mechanism dominated by a first-order decomposition step.

  13. Production and analysis of thermal decomposition products from polymeric materials

    NASA Technical Reports Server (NTRS)

    Chatfield, D. A.; Einhorn, I. N.; Hileman, F. D.; Futrell, J. H.; Voorhees, K. J.

    1978-01-01

    A description is presented of a strategy for analyzing the combustion process and the degradation products which are formed. One of three primary objectives in the study of polymer degradation is related to the characterization of the material to be studied and the investigation of the thermal behavior of the material. Another objective is concerned with the definition of the nature of the decomposition process by identification and quantitation of the degradation products. The third objective involves the determination of the mechanism and kinetics of the decomposition process. The methods of sample degradation include pyrolysis, oxidative degradation, flaming combustion, and the use of large-scale combustion chambers. Methods of chemical separation and identification are considered, taking into account low-boiling volatiles, high-boiling volatiles, and ancillary techniques.

  14. Theoretical study of the thermal decomposition of dimethyl disulfide.

    PubMed

    Vandeputte, Aäron G; Reyniers, Marie-Françoise; Marin, Guy B

    2010-10-07

    Despite its use in a wide variety of industrially important thermochemical processes, little is known about the thermal decomposition mechanism of dimethyl disulfide (DMDS). To obtain more insight, the radical decomposition mechanism of DMDS is studied theoretically and a kinetic model is developed accounting for the formation of all the decomposition products observed in the experimental studies available in literature. Thermochemical data and rate coefficients are obtained using the high-level CBS-QB3 composite method. Among five methods tested (BMK/6-311G(2d,d,p), MPW1PW91/6-311G(2d,d,p), G3, G3B3, and CBS-QB3), the CBS-QB3 method was found to reproduce most accurately the experimental standard enthalpies of formation for a set of 17 small organosulfur compounds and the bond dissociation energies for a set of 10 sulfur bonds. Enthalpies of formation were predicted within 4 kJ mol(-1) while the mean absolute deviation on the bond dissociation enthalpies amounts to 7 kJ mol(-1). From the theoretical study, a new reaction path is identified for the formation of carbon disulfide via dithiirane (CH(2)S(2)). A reaction mechanism was constructed containing 36 reactions among 25 species accounting for the formation of all the decomposition products reported in literature. High-pressure limit rate coefficients for the 36 reactions in the reaction mechanism are presented. The kinetic model is able to grasp the experimental observations. With the recombination of thiyl radicals treated as being in the low-pressure limit, the experimentally reported first-order rate coefficients for the decomposition of DMDS are reproduced within 1 order of magnitude, while the observed product selectivities of most compounds are reproduced satisfactory. Simulations indicate that at high conversions most of the carbon disulfide forms according to the newly identified reaction path involving the formation of dithiirane.

  15. Thermal Decomposition of Copper Ore Concentrate and Polyethylene Composites

    NASA Astrophysics Data System (ADS)

    Szyszka, Danuta; Wieckowska, Jadwiga

    2016-10-01

    Thermal analyses (TGA and DTA) of the composite, comprised of 10% polyethylene (PE) scrap and 90% copper ore concentrate, enabled determination of the temperature range and decomposition degree of the organic matters in argon atmosphere. Products of pyrolysis were qualitatively and quantitatively determined. The results were compared to those obtained for products of pyrolysis of the composite in air. Products of pyrolysis were identified by means of the gas chromatography (GC) method alone or supported with results of mass spectrometry analyses (GC-MS).

  16. Effects of Metallo-Organic Decomposition Agents on Thermal Decomposition and Electrical Conductivity of Low-Temperature-Curing Silver Paste

    NASA Astrophysics Data System (ADS)

    Lu, Chun-An; Lin, Pang; Lin, Hong-Ching; Wang, Sea-Fue

    2006-09-01

    Six low-temperature-curing silver pastes were prepared from silver flake, α-terpineol and various metallo-organic decomposition (MOD) compounds. The thermal decomposition behaviors of the pastes were determined. The microstructures and resistivities of screen-printed films on alumina substrate after thermal treatment were characterized and discussed. Results indicated that 2-ethylhexanoate possesses the lowest decomposition temperature (190.3 °C) among the MOD agents studied, and it forms silver particles to promote the linking of silver flake powders and thus reduces the resistivity to <13 μΩ\\cdotcm at a temperature as low as 200 °C.

  17. Mercer's spectral decomposition for the characterization of thermal parameters

    NASA Astrophysics Data System (ADS)

    Ahusborde, E.; Azaïez, M.; Belgacem, F. Ben; Palomo Del Barrio, E.

    2015-08-01

    We investigate a tractable Singular Value Decomposition (SVD) method used in thermography for the characterization of thermal parameters. The inverse problem to solve is based on the model of transient heat transfer. The most significant advantage is the transformation of the dynamic identification problem into a steady identification equation. The time dependence is accounted for by the SVD in a performing way. We lay down a mathematical foundation well fitted to this approach, which relies on the spectral expansion of Mercer kernels. This enables us to shed more light on most of its important features. Given its potentialities, the analysis we propose here might help users understanding the way the SVD algorithm, or the TSVD, its truncated version, operate in the thermal parameters estimation and why it is relevant and attractive. When useful, the study is complemented by some analytical and numerical illustrations realized within MATLAB's code.

  18. Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation.

    PubMed

    Tucceri, María E; Badenes, María P; Bracco, Larisa L B; Cobos, Carlos J

    2016-04-21

    A detailed kinetic study of the gas-phase thermal decomposition of 3-bromopropene over wide temperature and pressure ranges was performed. Quantum chemical calculations employing the density functional theory methods B3LYP, BMK, and M06-2X and the CBS-QB3 and G4 ab initio composite models provide the relevant part of the potential energy surfaces and the molecular properties of the species involved in the CH2═CH-CH2Br → CH2═C═CH2 + HBr (1) and CH2═CH-CH2Br → CH2═CH-CH2 + Br (2) reaction channels. Transition-state theory and unimolecular reaction rate theory calculations show that the simple bond fission reaction ( 2 ) is the predominant decomposition channel and that all reported experimental studies are very close to the high-pressure limit of this process. Over the 500-1400 K range a rate constant for the primary dissociation of k2,∞ = 4.8 × 10(14) exp(-55.0 kcal mol(-1)/RT) s(-1) is predicted at the G4 level. The calculated k1,∞ values lie between 50 to 260 times smaller. A value of 10.6 ± 1.5 kcal mol(-1) for the standard enthalpy of formation of 3-bromopropene at 298 K was estimated from G4 thermochemical calculations.

  19. Investigation of the thermal decomposition of sulfuric acid containing inorganic impurities

    SciTech Connect

    Kogtev, S.E.; Nikandrov, I.S.; Borisenko, A.S.; Peretrutov, A.A.

    1986-09-20

    Oleum is recovered by thermal decomposition of sulfuric acid wastes to sulfur dioxide with conversion of the sulfur dioxide to oleum. The organic substances in sulfuric acid wastes can affect the thermal-decomposition indexes of sulfuric acid wastes. They studied the effect of toluene, nitrotoluene, benzoic acid, and carbon on the yield of sulfur dioxide and also the possibility of reduction of acid vapors by products of pyrolysis and incomplete combustion of hydrocarbons. It is shown that the yield of sulfur dioxide in thermal decomposition of hydrocarbon-containing sulfuric acid wastes can be increased if the process assumes the nature of reductive decomposition.

  20. Analysis of Siderite Thermal Decomposition by Differential Scanning Calorimetry

    NASA Technical Reports Server (NTRS)

    Bell, M. S.; Lin, I.-C.; McKay, D. S.

    2000-01-01

    Characterization of carbonate devolitilization has important implications for atmospheric interactions and climatic effects related to large meteorite impacts in platform sediments. On a smaller scale, meteorites contain carbonates which have witnessed shock metamorphic events and may record pressure/temperature histories of impact(s). ALH84001 meteorite contains zoned Ca-Mg-Fe-carbonates which formed on Mars. Magnetite crystals are found in the rims and cores of these carbonates and some are associated with void spaces leading to the suggestion by Brearley et al. that the crystals were produced by thermal decomposition of the carbonate at high temperature, possibly by incipient shock melting or devolitilization. Golden et al. recently synthesized spherical Mg-Fe-Ca-carbonates from solution under mild hydrothermal conditions that have similar carbonate compositional zoning to those of ALH84001. They have shown experimental evidence that the carbonate-sulfide-magnetite assemblage in ALH84001 can result from a multistep inorganic process involving heating possibly due to shock events. Experimental shock studies on calcium carbonate prove its stability to approx. 60 GPa, well in excess of the approx. 45 GPa peak pressures indicated by other shock features in ALH84001. In addition, Raman spectroscopy of carbonate globules in ALH84001 indicates no presence of CaO and MgO. Such oxide phases should be found associated with the magnetites in voids if these magnetites are high temperature shock products, the voids resulting from devolitilization of CO2 from calcium or magnesium carbonate. However, if the starting material was siderite (FeCO3), thermal breakdown of the ALH84001 carbonate at 470 C would produce iron oxide + CO2. As no documentation of shock effects in siderite exists, we have begun shock experiments to determine whether or not magnetite is produced by the decomposition of siderite within the < 45GPa pressure window and by the resultant thermal pulse to approx

  1. An analysis of the thermal decomposition reactions of organic electrolytes used in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Campion, Christopher Lawrence

    The thermal decomposition of LiPF6 in solution with carbonate solvents has been investigated. The thermal dissociation of LiPF6 into LiF and PF5 is known. In solution, PF 5 reacts with carbonates to form a variety of decomposition products including: carbon dioxide (CO2), ethers (R2O), alkylfluorides (RF), phosphorus oxyfluoride (OPF3), and fluorophosphates (OPF 2OR, OPF(OR)2), assignment of structure is supported by Nuclear Magnetic Resonance (NMR) spectroscopy and Gas Chromatography with Mass Selective Detection (GC-MS). Similar decomposition products are observed during the thermal decomposition of carbonate solutions of LiPF6. Since solutions of LiPF6 are widely used as Li-ion battery electrolytes, there is interest among battery manufacturers and researchers as to the thermal decomposition of this electrolyte. Here we describe the structural and mechanistic investigations of the thermal decomposition of lithium-ion battery electrolytes. The electrolyte undergoes autocatalytic decomposition reactions at moderately elevated temperatures (80--100°C) to produce a large number of decomposition products. Results indicate that the thermal decomposition reactions are suppressed by the electrode, particularly the cathode, or intended stabilizing additives.

  2. Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

    PubMed Central

    Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun’ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

    2016-01-01

    Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask. PMID:27991498

  3. Thermal decomposition of fullerene nanowhiskers protected by amorphous carbon mask

    NASA Astrophysics Data System (ADS)

    Guo, Hongxuan; Wang, Chengxiang; Miyazawa, Kun’Ichi; Wang, Hongxin; Masuda, Hideki; Fujita, Daisuke

    2016-12-01

    Fullerene nanostructures are well known for their unique morphology, physical and mechanical properties. The thermal stability of fullerene nanostructures, such as their sublimation at high temperature is also very important for studying their structures and applications. In this work, We observed fullerene nanowhiskers (FNWs) in situ with scanning helium ion microscopy (HIM) at elevated temperatures. The FNWs exhibited different stabilities with different thermal histories during the observation. The pristine FNWs were decomposed at the temperatures higher than 300 °C in a vacuum environment. Other FNWs were protected from decomposition with an amorphous carbon (aC) film deposited on the surface. Based on high spacial resolution, aC film with periodic structure was deposited by helium ion beam induced deposition (IBID) on the surface of FNWs. Annealed at the high temperature, the fullerene molecules were selectively sublimated from the FNWs. The periodic structure was formed on the surface of FNWs and observed by HIM. Monte Carlo simulation and Raman characterization proved that the morphology of the FNWs was changed by helium IBID at high temperature. This work provides a new method of fabricating artificial structure on the surface of FNWs with periodic aC film as a mask.

  4. Thermal Decomposition of Almandine Garnet: Mössbauer Study

    NASA Astrophysics Data System (ADS)

    Barcova, K.; Mashlan, M.; Zboril, R.; Martinec, P.; Kula, P.

    2001-07-01

    The thermal decomposition of almandine garnet from Zoltye Vody, Ukraine, has been studied using57Fe Mössbauer spectroscopy. Room temperature Mössbauer spectrum of the initial powdered sample is characterised by one doublet corresponding to Fe2+ in dodecahedral position 24c. In the room temperature spectra of all heated almandine samples, a doublet corresponding to γ-Fe2O3 nanoparticles appeared. Depending on experimental conditions (heating temperature and time), the additional spectral lines of α-Fe2O3 and ɛ-Fe2O3 were observed in Mössbauer spectra. It is obvious that the thermal transformation of almandine garnet in air is related to the primary formation of γ-Fe2O3 superparamagnetic nanoparticles. γ-Fe2O3 nanoparticles are transformed into ɛ-Fe2O3 and consequently into α-Fe2O3 at higher temperatures. The mechanism and kinetics of the individual structural transformations depend on experimental conditions — mainly on the heating temperature and size of the particles.

  5. The response of the HMX-based material PBXN-9 to thermal insults: thermal decomposition kinetics and morphological changes

    SciTech Connect

    Glascoe, E A; Hsu, P C; Springer, H K; DeHaven, M R; Tan, N; Turner, H C

    2010-12-10

    PBXN-9, an HMX-formulation, is thermally damaged and thermally decomposed in order to determine the morphological changes and decomposition kinetics that occur in the material after mild to moderate heating. The material and its constituents were decomposed using standard thermal analysis techniques (DSC and TGA) and the decomposition kinetics are reported using different kinetic models. Pressed parts and prill were thermally damaged, i.e. heated to temperatures that resulted in material changes but did not result in significant decomposition or explosion, and analyzed. In general, the thermally damaged samples showed a significant increase in porosity and decrease in density and a small amount of weight loss. These PBXN-9 samples appear to sustain more thermal damage than similar HMX-Viton A formulations and the most likely reasons are the decomposition/evaporation of a volatile plasticizer and a polymorphic transition of the HMX from {beta} to {delta} phase.

  6. Thermal decomposition of acetate: III. Catalysis by mineral surfaces

    NASA Astrophysics Data System (ADS)

    Bell, Julie L. S.; Palmer, Donald A.; Barnes, H. L.; Drummond, S. E.

    1994-10-01

    The kinetics of thermal decarboxylation of aqueous solutions of acetic acid and sodium acetate were evaluated at 335 and 355°C in contact with various surfaces as potential catalysts. Quartz, fused quartz, calcite, natural pyrite, titanium oxide, and Au apparently do not catalyze aqueous decarboxylation reactions, in contrast to Pyrex, Ca-montmorillonite, Fe-bearing montmorillonite, hematite, synthetic pyrite, and magnetite. The dependence of the rate of acetic acid decarboxylation on the surface area of pyrite per unit solution volume was also studied. The results show that the decarboxylation of acetic acid and acetate is catalyzed heterogeneously, with the cleavage of the C-C bond occurring while the acetate molecule is adsorbed onto a surface. Entropies and enthalpies of activation obtained from these experiments are compatible with the isokinetic relationship established previously for acetic acid and acetate under similar experimental conditions, indicating the existence of a common rate-determining step. Experimental evidence indicates that oxidation of acetic acid can occur with hematite and defected magnetite. These oxidative decomposition reactions differ from the decarboxylation reaction in that CO 2 and polycondensates are produced instead of CO 2 and CH 4.

  7. Thermal Decomposition of New and Aged LX-04 and PBX 9501

    SciTech Connect

    Tran, T D; Tarver, C; Idar, D J; Rodin, W A

    2002-04-09

    One-Dimensional-Time-To-Explosion (ODTX) experiments were conducted to study the thermal decomposition of new and aged LX-04, PBX 9501, HMX class 1 and class 2, Estane and EstaneBDNPA-F (PBX 950 1 plasticized-binder) materials. New and aged LX-04 showed comparable decomposition kinetics. The data for aged PBX 9501 showed slightly longer explosion times at equivalent temperatures. Analysis of the error in time measurement is complicated by several experimental factors but the small time change appears to be experimentally significant. The results suggest that aged PBX 9501 is slightly more thermally stable. The thermal decomposition of these materials were modeled using a coupled thermal and heat transport code (chemical TOPAZ) using separate kinetics for HMX and binder decomposition. The current kinetic models describe the longer explosion times by the loss of plasticizer-binder constituent, which was more thermally reactive.

  8. Thermal decomposition and oxidation of CH3OH.

    PubMed

    Lee, Pei-Fang; Matsui, Hiroyuki; Xu, Ding-Wei; Wang, Niann-Shiah

    2013-01-24

    Thermal decomposition of CH(3)OH diluted in Ar has been studied by monitoring H atoms behind reflected shock waves of 100 ppm CH(3)OH + Ar. The total decomposition rate k(1) for CH(3)OH + M → products obtained in this study is expressed as, ln(k(1)/cm(3) molecule(-1) s(-1)) = -(14.81 ± 1.22) - (38.86 ± 1.82) × 10(3)/T, over 1359-1644 K. The present result on k(1) is indicated to be substantially smaller than the extrapolation of the most of the previous experimental data but consistent with the published theoretical results [Faraday Discuss. 2002, 119, 191-205 and J. Phys. Chem. A 2007, 111, 3932-3950]. Oxidation of CH(3)OH has been studied also by monitoring H atoms behind shock waves of (0.35-100) ppm CH(3)OH + (100-400) ppm O(2) + Ar. For the low concentration CH(3)OH (below 10 ppm) + O(2) mixtures, the initial concentration of CH(3)OH is evaluated by comparing evolutions of H atoms in the same concentration of CH(3)OH with addition of 300 ppm H(2) diluted in Ar. The branching fraction for CH(3)OH + Ar → (1)CH(2) + H(2)O + Ar has been quantitatively evaluated from this comparative measurements with using recent experimental result on the yield of H atoms in the reaction of (1,3)CH(2) + O(2) [J. Phys. Chem. A 2012, 116, 9245-9254]; i.e., the branching fraction for the above reaction is evaluated as, φ(1a) = 0.20 ± 0.04 at T = 1880-2050 K, in the 1.3 and 3.5 ppm CH(3)OH + 100 ppm O(2) samples. An extended reaction mechanism for the pyrolysis and oxidation of CH(3)OH is constructed based on the results of the present study combined with the oxidation mechanism of natural gas [GRI-Mech 3.0]; evolution of H atoms can be predicted very well with this new reaction scheme over a wide concentration range for the pyrolysis (0.36-100 ppm CH(3)OH), and oxidation (0.36-100 ppm CH(3)OH + 100/400 ppm O(2)) of methanol.

  9. Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates of BTATz-CMDB propellant.

    PubMed

    Yi, Jian-Hua; Zhao, Feng-Qi; Wang, Bo-Zhou; Liu, Qian; Zhou, Cheng; Hu, Rong-Zu; Ren, Ying-Hui; Xu, Si-Yu; Xu, Kang-Zhen; Ren, Xiao-Ning

    2010-09-15

    The composite modified double base (CMDB) propellants (nos. RB0601 and RB0602) containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) without and with the ballistic modifier were prepared and their thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates were investigated. The results show that there are three mass-loss stages in TG curve and two exothermic peaks in DSC curve for the BTATz-CMDB propellant. The first two mass-loss stages occur in succession and the temperature ranges are near apart, and the decomposition peaks of the two stages overlap each other, inducing only one visible exothermic peak appear in DSC curve during 350-550 K. The reaction mechanisms of the main exothermal decomposition processes of RB0601 and RB0602 are all classified as chemical reaction, the mechanism functions are f(alpha)=(1-alpha)(2), and the kinetic equations are dalpha/dt = 10(19.24)(1-alpha)(2)e(-2.32x10(4)/T) and dalpha/dt = 10(20.32)(1-alpha)(2)e(-2.32x10(4)/T). The thermal safety evaluation on the BTATz-CMDB propellants was obtained. With the substitution of 26% RDX by BTATz and with the help of the ballistic modifier in the CMDB propellant formulation, the burning rate can be improved by 89.0% at 8 MPa and 47.1% at 22 MPa, the pressure exponent can be reduced to 0.353 at 14-20 MPa.

  10. Vaporisation and thermal decomposition of dialkylimidazolium halide ion ionic liquids.

    PubMed

    Lovelock, Kevin R J; Armstrong, James P; Licence, Peter; Jones, Robert G

    2014-01-28

    Vaporisation and liquid phase thermal decomposition, TD, of two halide ion ionic liquids, 1-octyl-3-methylimidazolium chloride, [C8C1Im]Cl, and 1-octyl-3-methylimidazolium iodide, [C8C1Im]I, are investigated using temperature programmed desorption (TPD) line of sight mass spectrometry (LOSMS) at ultra-high vacuum (UHV). The ability to use MS to distinguish between vaporisation and TD allows the thermodynamics/kinetics of both vaporisation and TD to be investigated within the same experiments. Vaporisation of both halide ion ionic liquids is demonstrated. For both [C8C1Im]Cl and [C8C1Im]I the vapour is shown to be composed of neutral ion pairs (NIPs). The enthalpy of vaporisation at temperature T, ΔvapHT, was experimentally determined as ΔvapH455 = 151 ± 10 kJ mol(-1) for [C8C1Im]Cl and ΔvapH480 = 149 ± 8 kJ mol(-1) for [C8C1Im]I. Extrapolation of ΔvapHT to the reference temperature, 298 K, gave ΔvapH298 = 166 ± 10 kJ mol(-1) for [C8C1Im]Cl and ΔvapH298 = 167 ± 8 kJ mol(-1) for [C8C1Im]I, higher than most ΔvapH298 values measured to date for other [C8C1Im](+)-containing ionic liquids. In addition, predictions of ΔvapH298 for other halide ion ionic liquids are made. Liquid phase TD is shown to proceed via nucleophilic substitution to give two sets of products: 1-octylimidazole and methylhalide, and 1-methylimidazole and 1-octylhalide. The activation energy of TD at a temperature T, Ea,TD,T, is measured for the nucleophilic substitution of [C8C1Im]I to give methyliodide; Ea,TD,480 = 136 ± 15 kJ mol(-1). Ea,TD,T is measured for the nucleophilic substitution of [C8C1Im]Cl to give methylchloride; Ea,TD,455 = 132 ± 10 kJ mol(-1). The fact that ΔvapHT and Ea,TD,T are the same (within error) for both ionic liquids is commented upon, and conclusions are drawn as to the thermal stability of these ionic liquids.

  11. The thermal decomposition of methane in a tubular reactor

    SciTech Connect

    Kobayashi, Atsushi; Steinberg, M.

    1992-01-01

    The reaction rate of methane decomposition using a tubular reactor having a 1 inch inside diameter with an 8 foot long heated zone was investigated in the temperature range of 700 to 900 C with pressures ranging from 28.2 to 56.1 atm. Representing the rate by a conventional model, {minus}dC{sub CH4}/dt= k1 C{sub CH4} {minus}k2 C{sub H2}{sup 2}, the rate constant k1 for methane decomposition was determined. The activation energy, 31.3 kcal/mol, calculated by an Arrhenius Plot was lower than for previously published results for methane decomposition. This result indicates that submicron particles found in the reactor adhere to the inside of the reactor and these submicron high surface area carbon particles tend to catalyze the methane decomposition. The rate constant has been found to be approximately constant at 900 C with pressure range cited above. The rate of methane decomposition increases with methane partial pressure in first-order. The rate of the methane decomposition is favored by higher temperatures and pressures while the thermochemical equilibrium of methane decomposition is favored by lower pressures. 8 refs., 7 figs., 2 tabs.

  12. Electrical field-assisted thermal decomposition of boron nitride nanotube: Experiments and first principle calculations

    NASA Astrophysics Data System (ADS)

    Xu, Zhi; Golberg, Dmitri; Bando, Yoshio

    2009-09-01

    We directly observed the Joule-heating-induced decomposition of multiwalled BN nanotubes using a transmission electron microscope equipped with a scanning tunneling microscope unit. The decomposition temperature is found to be dependent on an applied electrical field. We propose a model that due to the partially ionic nature of the B-N bond, the decomposition energy is both temperature- and electrical field-related: it is named as electrical field-assisted thermal decomposition. The model fits the experimental data very well and is considered to be general for all nanostructures with polar bonds.

  13. Thermal decomposition studies of explosives for component applications. [hns

    SciTech Connect

    Jungst, R.G.

    1988-01-01

    The explosives PETN and HNS are currently found in a variety of Sandia devices. We have carried out a number of special studies to measure decomposition rates of these materials in hardware at moderate temperatures. The goal of this work was to generate information to enable predictions of component lifetimes to be made. This presentation will discuss sampling and measurement techniques for decomposition products and show results of their application to components containing PETN and HNS.

  14. The correlation between elongation at break and thermal decomposition of aged EPDM cable polymer

    NASA Astrophysics Data System (ADS)

    Šarac, T.; Devaux, J.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

    2017-03-01

    The effect of simultaneous thermal and gamma irradiation ageing on the mechanical and physicochemical properties of industrial EPDM was investigated. Accelerated ageing, covering a wide range of dose rates, doses and temperatures, was preformed in stagnant air on EPDM polymer samples extracted from the cables in use in the Belgian nuclear power plants. The mechanical properties, ultimate tensile stress and elongation at break, are found to exhibit the strong dependence on the dose, ageing temperature and dose rate. The thermal decomposition of aged polymer is observed to be the dose dependent when thermogravimetry test is performed under air atmosphere. No dose dependence is observed when thermal decomposition is performed under nitrogen atmosphere. The thermal decomposition rates are found to fully mimic the reduction of elongation at break for all dose rates and ageing temperatures. This effect is argued to be the result of thermal and radiation mediated oxidation degradation process.

  15. Decomposition

    USGS Publications Warehouse

    Middleton, Beth A.

    2014-01-01

    A cornerstone of ecosystem ecology, decomposition was recognized as a fundamental process driving the exchange of energy in ecosystems by early ecologists such as Lindeman 1942 and Odum 1960). In the history of ecology, studies of decomposition were incorporated into the International Biological Program in the 1960s to compare the nature of organic matter breakdown in various ecosystem types. Such studies still have an important role in ecological studies of today. More recent refinements have brought debates on the relative role microbes, invertebrates and environment in the breakdown and release of carbon into the atmosphere, as well as how nutrient cycling, production and other ecosystem processes regulated by decomposition may shift with climate change. Therefore, this bibliography examines the primary literature related to organic matter breakdown, but it also explores topics in which decomposition plays a key supporting role including vegetation composition, latitudinal gradients, altered ecosystems, anthropogenic impacts, carbon storage, and climate change models. Knowledge of these topics is relevant to both the study of ecosystem ecology as well projections of future conditions for human societies.

  16. Borohydride Catalysis of Nitramine Thermal Decomposition and Combustion. 2. Thermal Decomposition of Catalyzed and Uncatalyzed HMX Propellant Formulations

    DTIC Science & Technology

    1990-02-01

    decomposition temperature. Aaded catalyst appears to decrease m/e 70 (1,2,4- oxadiazole ?) formation at low temperature, but to increase it slightly at...Unknown A (1,2,4- oxadiazole ?), from HMX Decomposition......................................................... 17 18 Typical Mass Spectrum of...formation of 1,3,5-triazine and Unknown A (1,2,4- oxadiazole ?) were also studied. II. EXPERIMENTAL The HMX-GAP and HMX-PEG compositions were prepared at

  17. Thermal Decomposition Behavior of Ammonium Perchlorate and of an Ammonium-Perchlorate-Based Composite Propellant

    NASA Technical Reports Server (NTRS)

    Behrens, R.; Minier, L.

    1998-01-01

    The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H2O, O2, Cl2, N2O and HCl, and is shown to occur in the solid phase within the AP particles. 200(micro) diameter AP particles undergo 25% decomposition in the solid phase, whereas 20(micro) diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH3 + HClO4 followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.

  18. The thermal decomposition behavior of ammonium perchlorate and of an ammonium-perchlorate-based composite propellant

    SciTech Connect

    Behrens, R.; Minier, L.

    1998-03-24

    The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H{sub 2}O, O{sub 2}, Cl{sub 2}, N{sub 2}O and HCl, and is shown to occur in the solid phase within the AP particles. 200{micro} diameter AP particles undergo 25% decomposition in the solid phase, whereas 20{micro} diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH{sub 3} + HClO{sub 4} followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.

  19. Decomposition mechanisms in thermally-aged thin-film explosives

    SciTech Connect

    Erickson, K.L.; Trott, W.M.; Renlund, A.M.

    1994-10-01

    The isothermal decomposition of nitrocellulose (NC) has been examined using two substantially different experimental techniques, involving both confined and unconfined samples. The confined isothermal aging technique involved confined thin-film samples heated to temperatures of 150 to 170{degrees}C, for 1 to 72 hours. Condensed-phase chemistry was monitored real-time using FTIR. Results indicated that the first step in decomposition was scission of the O-NO{sub 2} bond and subsequent formation of carbonyl and hydroxyl products. Scission of the O-NO{sub 2} bond appeared to occur by a first-order reaction. The Arrhenius expression for the first-order reaction rate constant was evaluated from the experimental data. The unconfined rapid isothermal decomposition technique involved both high speed-photography and time-of-flight mass spectrometry (TOFMS). Mass spectra obtained from experiments at 420{degrees}C indicated that NO{sub 2} formation and, therefore, scission of the O-NO{sub 2} bond occurred by a first order reaction, the rate constant for which was evaluated from the experimental data. The rate constant for global pseudo-first order decomposition of NC at 450{degrees}C was also estimated from high speed photography results. Rate constants at 420 and 450{degrees}C were predicted using the Arrhenius expression developed from the confined isothermal aging results and were in good agreement with the rate constants obtained at those temperatures in the unconfined rapid decomposition experiments using TOFMS and high-speed photography. Results from these substantially different measurements gave consistent results over a temperature range of about 300{degrees}C, in which reaction rates vary by nine orders of magnitude, and indicate that the two experimental techniques being developed have good potential for studying condensed-phase decomposition of energetic materials.

  20. Thermal Decomposition of New and Aged LX-04 and PBX 9501

    SciTech Connect

    Tran, T D; Tarver, C; Idar, D J

    2002-03-25

    One-Dimensional-Time-To-Explosion (ODTX) experiments were conducted to study the thermal decomposition of aged LX-04, aged PBX 9501, HMX class 1 and class 2, Estane and Estane/BDNPA-F (PBX 950 1 plasticized-binder) materials. The tests involved heating 12.7 mm diameter spherical samples in pre-heated aluminum anvils until explosion. The times to explosion at different heating temperatures were compared to historical data on new LX-04 and PBX 9501 compounds to study any changes to their thermal stability. New and aged LX-04 showed comparable decomposition kinetics. The data for aged PBX 9501 showed slightly longer explosion times at equivalent temperatures. Analysis of the error in time measurement is limited and complicated by several experimental factors but the small time change appears to be experimentally significant. The thermal decomposition of these PBXs were modeled using a coupled thermal and heat transport code (chemical TOPAZ) using separate kinetics for HMX and binder decomposition. Separate decomposition models were developed for HMX and the reactive PBX 9501 binder component (1:1 Estane:BDNPA/F) based on the measured explosion times. Thermal aging models can describe longer explosion times by the loss of plasticizer-binder constituent which was more thermally reactive.

  1. Low-temperature thermal decomposition of crystalline partly and completely deuterated ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Majda, Dorota; Korobov, Alexander; Filek, Urszula; Sulikowski, Bogdan; Midgley, Paul; Nicol, David A.; Klinowski, Jacek

    2011-03-01

    Although ammonium perchlorate, widely used as a rocket propellant, has been extensively investigated for many years, the mechanism of its thermal decomposition at low temperatures remains controversial. Examination of the thermal behaviour of large crystals of partly and completely deuterated ammonium perchlorate by DSC, SEM, TG and QMS reveals that the rates of thermal decomposition depend on the degree of deuteration and decrease in the sequence N[H/D] 4ClO 4 > NH 4ClO 4 > ND 4ClO 4.

  2. Preparation, X-ray crystallography, and thermal decomposition of some transition metal perchlorate complexes of hexamethylenetetramine.

    PubMed

    Singh, Gurdip; Baranwal, B P; Kapoor, I P S; Kumar, Dinesh; Fröhlich, Roland

    2007-12-20

    The perchlorate complexes of manganese, nickel, and zinc with hexamethylenetetramine (HMTA) of the general formula [M(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2] (where M=Mn, Ni, and Zn) have been prepared and characterized by X-ray crystallography. Thermal studies were undertaken using thermogravimetry (TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal decomposition of these complexes was investigated using isothermal TG data by applying isoconversional method. The decomposition pathways of the complexes have also been proposed. These were found to explode when subjected to higher temperatures.

  3. Determination of the Thermal Decomposition Products of Terephthalic Acid by Using Curie-Point Pyrolyzer

    NASA Astrophysics Data System (ADS)

    Begüm Elmas Kimyonok, A.; Ulutürk, Mehmet

    2016-04-01

    The thermal decomposition behavior of terephthalic acid (TA) was investigated by thermogravimetry/differential thermal analysis (TG/DTA) and Curie-point pyrolysis. TG/DTA analysis showed that TA is sublimed at 276°C prior to decomposition. Pyrolysis studies were carried out at various temperatures ranging from 160 to 764°C. Decomposition products were analyzed and their structures were determined by gas chromatography-mass spectrometry (GC-MS). A total of 11 degradation products were identified at 764°C, whereas no peak was observed below 445°C. Benzene, benzoic acid, and 1,1‧-biphenyl were identified as the major decomposition products, and other degradation products such as toluene, benzophenone, diphenylmethane, styrene, benzaldehyde, phenol, 9H-fluorene, and 9-phenyl 9H-fluorene were also detected. A pyrolysis mechanism was proposed based on the findings.

  4. Thermal decomposition of gaseous ammonium nitrate at low pressure: kinetic modeling of product formation and heterogeneous decomposition of nitric acid.

    PubMed

    Park, J; Lin, M C

    2009-12-03

    The thermal decomposition of ammonium nitrate, NH(4)NO(3) (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH(4)NO(3) at 423 K was proposed to produce equal amounts of NH(3) and HNO(3), followed by the decomposition reaction of HNO(3), HNO(3) + M --> OH + NO(2) + M (where M = third-body and reactor surface). The absolute yields of N(2), N(2)O, H(2)O, and NH(3), which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH(3)-NO(2) (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO(3) itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO(3) in our kinetic modeling. The heterogeneous decomposition rate of HNO(3), HNO(3) + (B(2)O(3)/SiO(2)) --> OH + NO(2) + (B(2)O(3)/SiO(2)), was determined by varying its rate to match the modeled result to the measured concentrations of NH(3) and H(2)O; the rate could be represented by k(2b) = 7.91 x 10(7) exp(-12 600/T) s(-1), which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO(3) decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

  5. Thermal Decomposition of Gaseous Ammonium Nitrate at Low Pressure: Kinetic Modeling of Product Formation and Heterogeneous Decomposition of Nitric Acid

    NASA Astrophysics Data System (ADS)

    Park, J.; Lin, M. C.

    2009-10-01

    The thermal decomposition of ammonium nitrate, NH4NO3 (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH4NO3 at 423 K was proposed to produce equal amounts of NH3 and HNO3, followed by the decomposition reaction of HNO3, HNO3 + M → OH + NO2 + M (where M = third-body and reactor surface). The absolute yields of N2, N2O, H2O, and NH3, which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH3-NO2 (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO3 itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO3 in our kinetic modeling. The heterogeneous decomposition rate of HNO3, HNO3 + (B2O3/SiO2) → OH + NO2 + (B2O3/SiO2), was determined by varying its rate to match the modeled result to the measured concentrations of NH3 and H2O; the rate could be represented by k2b = 7.91 × 107 exp(-12 600/T) s-1, which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO3 decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

  6. Thermal decomposition of energetic materials viewed via dynamic x-ray radiography

    SciTech Connect

    Smilowitz, L.; Henson, B. F.; Romero, J. J.; Oschwald, D.

    2014-01-13

    We describe the evolution of solid density, leading up to ignition in the slow thermal decomposition of the solid organic secondary explosive octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. This work describes an x-ray radiographic diagnostic, allowing the study of solid density in a fully encased explosive heated to thermal explosion. The result of this study is the ability to observe and manipulate the ignition volume in a thermal explosion.

  7. Structural change of metallofullerene: an easier thermal decomposition.

    PubMed

    Zhao, Shixiong; Zhang, Jun; Guo, Xihong; Qiu, Xiaohui; Dong, Jinquan; Yuan, Bingkai; Ibrahim, Kurash; Wang, Jiaou; Qian, Haijie; Zhao, Yuliang; Yang, Shangyuan; Hao, Jian; Zhang, Hong; Yuan, Hui; Xing, Gengmei; Sun, Baoyun

    2011-10-05

    We have studied for the first time the structural change of high-purity metallofullerene (Gd@C(82)) upon heat treatment in an ultra-high vacuum system (10(-10) Torr) and examined the decomposition product through successive analysis with MS, IR, Raman, TEM, EDS and XPS. It was found that metallofullerene (Gd@C(82)) had fully collapsed at 580 °C which was lower than that for the complete destruction of C(60). The easier decomposition should be ascribed to the encapsulated metal in the carbon cage which could induce the deformation of the C-C bond. The analysis indicated that the broken metallofullerene (Gd@C(82)) became a kind of graphite-like material with a lot of defects. The Gd atoms leaked out from the carbon cage and aggregated together to form a regular arrangement.

  8. Structural change of metallofullerene: an easier thermal decomposition

    NASA Astrophysics Data System (ADS)

    Zhao, Shixiong; Zhang, Jun; Guo, Xihong; Qiu, Xiaohui; Dong, Jinquan; Yuan, Bingkai; Ibrahim, Kurash; Wang, Jiaou; Qian, Haijie; Zhao, Yuliang; Yang, Shangyuan; Hao, Jian; Zhang, Hong; Yuan, Hui; Xing, Gengmei; Sun, Baoyun

    2011-10-01

    We have studied for the first time the structural change of high-purity metallofullerene (Gd@C82) upon heat treatment in an ultra-high vacuum system (10-10 Torr) and examined the decomposition product through successive analysis with MS, IR, Raman, TEM, EDS and XPS. It was found that metallofullerene (Gd@C82) had fully collapsed at 580 °C which was lower than that for the complete destruction of C60. The easier decomposition should be ascribed to the encapsulated metal in the carbon cage which could induce the deformation of the C-C bond. The analysis indicated that the broken metallofullerene (Gd@C82) became a kind of graphite-like material with a lot of defects. The Gd atoms leaked out from the carbon cage and aggregated together to form a regular arrangement.

  9. Mass spectral studies of thermal decomposition of metal nitrates

    NASA Astrophysics Data System (ADS)

    Jackson, Jason G.; Fonseca, Rodney W.; Holcombe, James A.

    1995-10-01

    Residual gas analysis and static secondary ion mass spectrometry are used in an attempt to elucidate the process responsible for the appearance of metal oxides in the gas phase during low temperature nitrate decomposition of Pb, Cu, Cd and Ag nitrates in vacuo. Observed signals for MO, MNO 3+ together with M 2+ species in the gas phase during the decomposition of some of the metal nitrates indicate that a physical expulsion mechanism is probably responsible for the low temperature production of these metal-containing species. The "gasification mechanism" provided by L'vov states that metal nitrates decompose in a single mechanistic step to product MO(g), O 2 and NO 2 and that the temperature of the decomposition is predictable from thermodynamics. The observation of unexplained gas phase species, the absence of O 2 during CuO + production, and the lack of agreement between activation energies and appearance temperatures fail to support the gasification model. Instead, it is suggested that during the decomposition, which is governed by the kinetics of the process, the evolution of the gaseous products, such as O 2 and NO 2, carry the observed metal-containing species into the vapor phase when the liquid state is present on the surface (e.g. AgNO 3, Cu(NO 3) 2 or Cd(NO 3) 2). The crystal rearrangement of the solid (e.g. conversion of Pb(NO 3) 2 to PbO) and subsequent loss of integrity of the crystal lattice results in the dislocation of the metal-containing species, which are swept from the surface during the O 2 and NO 2 evolution.

  10. Investigation of the effect of intensive milling in a planetary ball mill on the thermal decomposition of basic nickel carbonate

    NASA Astrophysics Data System (ADS)

    Książek, K.; Wacke, S.; Górecki, T.; Górecki, Cz

    2011-04-01

    The kinetics of thermal decomposition of basic nickel carbonate NiCO3Ni·(OH)2·nH2O and the effect of intensive milling in a planetary ball mill on its parameters, have been investigated. The values of the reaction heat and of the activation energy of thermal decomposition have been determined. Investigations of the thermal decomposition of the products of ball milling of investigated compound revealed a distinct effect of milling on the reaction temperature and heat consumed during the thermal decomposition of investigated compound.

  11. Thermal decomposition of mono- and bimetallic magnesium amidoborane complexes.

    PubMed

    Spielmann, Jan; Piesik, Dirk F-J; Harder, Sjoerd

    2010-07-26

    Complexes of the type [(DIPPnacnac)MgNH(R)BH(3)] have been prepared (DIPPnacnac=CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)). The following substituents R have been used: H, Me, iPr, DIPP (DIPP=2,6-diisopropylphenyl). Complexes [(DIPPnac- nac)MgNH(2)BH(3)].THF, [{(DIPPnac- nac)MgNH(iPr)BH(3)}(2)] and [(DIPPnacnac)MgNH(DIPP)BH(3)] were structurally characterised. The Mg amidoborane complexes decompose at a significantly higher temperature (90-110 degrees C) than the corresponding Ca amidoborane complexes (20-110 degrees C). The complexes with the smaller R substituents (H, Me) gave a mixture of decomposition products of which one could be structurally characterised as [{(DIPPnacnac)Mg}(2)(H(3)B-NMe-BH-NMe)].THF. [{(DIPP- nacnac)MgNH(iPr)BH(3)}(2)] cleanly decomposed to [(DIPPnacnac)MgH], which was characterised as a dimeric THF adduct. The amidoborane complex with the larger DIPP-substituent decomposed into a borylamide complex [(DIPPnacnac)MgN(DIPP)BH(2)], which was structurally characterised as its THF adduct. Bimetallic Mg amidoborane complexes decompose at lower temperatures (60-90 degrees C) and show a different decomposition pathway. The dinuclear Mg amidoborane complexes presented here are based on DIPPnacnac units that are either directly coupled through N-N bonding (abbreviated NN) or through a 2,6-pyridylene bridge (abbreviated PYR). Crystal structures of [PYR-{Mg(nBu)}(2)], [PYR-{MgNH(iPr)BH(3)}(2)], [NN-{MgNH(iPr)BH(3)}(2)]THF and the decomposition products [PYR-Mg(2)(iPrN-BH-iPrN-BH(3))] and [NN-Mg(2)(iPrN-BH-iPrN-BH(3))].THF are presented. The following conclusions can be drawn from these studies: i) The first step in the decomposition of a metal amidoborane complex is beta-hydride elimination, which results in formation of a metal hydride complex and R(H)N=BH(2), ii) depending on the nature of the metal, the metal hydride is either stable and can be isolated or it reacts further, iii) amidoborane anions with small R substituents decompose into the dianionic

  12. Thermal decomposition and vibrational spectroscopic aspects of pyridinium hexafluorophosphate (C5H5NHPF6)

    NASA Astrophysics Data System (ADS)

    Lekgoathi, M. D. S.; Kock, L. D.

    2016-12-01

    Thermal decomposition and vibrational spectroscopic properties of pyridinium hexafluorophosphate (C5H5NHPF6) have been studied. The structure of the compound is better interpreted as having a cubic space group, based on Raman and infrared vibrational spectroscopy experiments and group theoretical correlation data between site symmetry species and the spectroscopic space group. The 13C NMR data shows three significant signals corresponding to the three chemical environments expected on the pyridinium ring i.e. γ, β and α carbons, suggesting that the position of the anion must be symmetrical with respect to the pyridinium ring's C2v symmetry. The process of thermal decomposition of the compound using TGA methods was found to follow a contracting volume model. The activation energy associated with the thermal decomposition reaction of the compound is 108.5 kJ mol-1, while the pre exponential factor is 1.51 × 109 sec-1.

  13. Preparation of MXene-Cu2O nanocomposite and effect on thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Gao, Yupeng; Wang, Libo; Li, Zhengyang; Zhou, Aiguo; Hu, Qianku; Cao, Xinxin

    2014-09-01

    MXenes are novel graphene-like 2-D materials. Cu2O is an effective additive for thermal decomposition of ammonium perchlorate (AP). We reported the synthesis of MXene (Ti3C2), Cu2O and MXene-Cu2O respectively. The samples were characterized by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results indicate that the MXene is composed of lots of nano-sheets and the thickness is 30 ± 10 nm, and Cu2O nanoparticles nucleate and grow heterogeneously directly on the surface of MXene. The effect of these MXene, Cu2O and MXene-Cu2O samples on the thermal decomposition of AP were investigated using TG-DSC. The results revealed that MXene-Cu2O have a great influence on the thermal decomposition of AP than that of pure MXene and Cu2O.

  14. Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications

    PubMed Central

    Sotiriou, Georgios A.; Singh, Dilpreet; Zhang, Fang; Chalbot, Marie-Cecile G.; Spielman-Sun, Eleanor; Hoering, Lutz; Kavouras, Ilias G.; Lowry, Gregory V.; Wohlleben, Wendel; Demokritou, Philip

    2015-01-01

    Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of a widely used NEP, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications. PMID:26642449

  15. Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications.

    PubMed

    Sotiriou, Georgios A; Singh, Dilpreet; Zhang, Fang; Chalbot, Marie-Cecile G; Spielman-Sun, Eleanor; Hoering, Lutz; Kavouras, Ilias G; Lowry, Gregory V; Wohlleben, Wendel; Demokritou, Philip

    2016-03-15

    Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.

  16. The comparative extinguishment performance and thermal decomposition products of halon alternative agents

    NASA Astrophysics Data System (ADS)

    Filipczak, Robert A.

    1994-12-01

    Halon 1301, Halon 1211, and eleven alternative fire-fighting agents were compared for extinguishment effectiveness and thermal decomposition product generation, using a laboratory-scale test apparatus having methane as the fuel. Chemical analysis was conducted using a magnetic sector mass spectrometer with simultaneous measurement of oxygen consumption and carbon dioxide, water, and acid gas production. Chemical mechanisms are advanced to explain how halogenated hydrocarbons extinguish fires. The major conclusion was that the alternative agents were not as effective at fighting fires as Halons and that greater amounts of acid gases were produced during extinguishment. Hydrogen fluoride was found to be the predominant thermal decomposition product for all agents.

  17. Ab Initio Kinetics and Thermal Decomposition Mechanism of Mononitrobiuret and 1,5- Dinitrobiuret

    SciTech Connect

    Sun, Hongyan; Vaghjiani, Ghanshyam G.

    2015-05-26

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice–Ramsperger–Kassel–Marcus/multi-well master equation simulations, the results of which reveal the

  18. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret.

    PubMed

    Sun, Hongyan; Vaghjiani, Ghanshyam L

    2015-05-28

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice-Ramsperger-Kassel-Marcus/multi-well master equation simulations, the results of which reveal the formation

  19. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret

    NASA Astrophysics Data System (ADS)

    Sun, Hongyan; Vaghjiani, Ghanshyam L.

    2015-05-01

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH2 group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C2v symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice-Ramsperger-Kassel-Marcus/multi-well master equation simulations, the results of which reveal the formation

  20. The Autocatalytic Behavior of Trimethylindium During Thermal Decomposition

    SciTech Connect

    Anthony H. McDaniel; M. D. Allendorf

    2000-02-02

    Pyrolysis of trimethylindium (TMIn) in a hot-wall flow-tube reactor has been investigated at temperatures between 573 and 723 K using a modulated molecular-beam mass-sampling technique and detailed numerical modeling. The TMIn was exposed to various mixtures of carrier gases: He, H{sub 2}, D{sub 2}, and C{sub 2}H{sub 4}, in an effort to elucidate the behavior exhibited by this compound in different chemical environments. The decomposition of TMIn is a heterogeneous, autocatalytic process with an induction period that is carrier-gas dependent and lasts on the order of minutes. After activation of the tube wall, the thermolysis exhibits a steady-state behavior that is surface mediated. This result is contrary to prior literature reports, which state that decomposition occurs in the gas phase via successive loss of the CH{sub 3} ligands. This finding also suggests that the bond dissociation energy for the (CH{sub 3}){sub 2}In-CH{sub 3} bond derived from flow-tube investigations is erroneous and should be reevaluated.

  1. Kinetic analysis of overlapping multistep thermal decomposition comprising exothermic and endothermic processes: thermolysis of ammonium dinitramide.

    PubMed

    Muravyev, Nikita V; Koga, Nobuyoshi; Meerov, Dmitry B; Pivkina, Alla N

    2017-01-25

    This study focused on kinetic modeling of a specific type of multistep heterogeneous reaction comprising exothermic and endothermic reaction steps, as exemplified by the practical kinetic analysis of the experimental kinetic curves for the thermal decomposition of molten ammonium dinitramide (ADN). It is known that the thermal decomposition of ADN occurs as a consecutive two step mass-loss process comprising the decomposition of ADN and subsequent evaporation/decomposition of in situ generated ammonium nitrate. These reaction steps provide exothermic and endothermic contributions, respectively, to the overall thermal effect. The overall reaction process was deconvoluted into two reaction steps using simultaneously recorded thermogravimetry and differential scanning calorimetry (TG-DSC) curves by considering the different physical meanings of the kinetic data derived from TG and DSC by P value analysis. The kinetic data thus separated into exothermic and endothermic reaction steps were kinetically characterized using kinetic computation methods including isoconversional method, combined kinetic analysis, and master plot method. The overall kinetic behavior was reproduced as the sum of the kinetic equations for each reaction step considering the contributions to the rate data derived from TG and DSC. During reproduction of the kinetic behavior, the kinetic parameters and contributions of each reaction step were optimized using kinetic deconvolution analysis. As a result, the thermal decomposition of ADN was successfully modeled as partially overlapping exothermic and endothermic reaction steps. The logic of the kinetic modeling was critically examined, and the practical usefulness of phenomenological modeling for the thermal decomposition of ADN was illustrated to demonstrate the validity of the methodology and its applicability to similar complex reaction processes.

  2. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    SciTech Connect

    Ramesh, Thimmasandra Narayan

    2010-06-15

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co{sub 3}O{sub 4}. The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co{sub 3}O{sub 4} phase.

  3. Nitrated graphene oxide and its catalytic activity in thermal decomposition of ammonium perchlorate

    SciTech Connect

    Zhang, Wenwen; Luo, Qingping; Duan, Xiaohui; Zhou, Yong; Pei, Chonghua

    2014-02-01

    Highlights: • The NGO was synthesized by nitrifying homemade GO. • The N content of resulted NGO is up to 1.45 wt.%. • The NGO can facilitate the decomposition of AP and release much heat. - Abstract: Nitrated graphene oxide (NGO) was synthesized by nitrifying homemade GO with nitro-sulfuric acid. Fourier transform infrared spectroscopy (FTIR), laser Raman spectroscopy, CP/MAS {sup 13}C NMR spectra and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure of NGO. The thickness and the compositions of GO and NGO were analyzed by atomic force microscopy (AFM) and elemental analysis (EA), respectively. The catalytic effect of the NGO for the thermal decomposition of ammonium perchlorate (AP) was investigated by differential scanning calorimetry (DSC). Adding 10% of NGO to AP decreases the decomposition temperature by 106 °C and increases the apparent decomposition heat from 875 to 3236 J/g.

  4. Organic and inorganic decomposition products from the thermal desorption of atmospheric particles

    NASA Astrophysics Data System (ADS)

    Williams, Brent J.; Zhang, Yaping; Zuo, Xiaochen; Martinez, Raul E.; Walker, Michael J.; Kreisberg, Nathan M.; Goldstein, Allen H.; Docherty, Kenneth S.; Jimenez, Jose L.

    2016-04-01

    Atmospheric aerosol composition is often analyzed using thermal desorption techniques to evaporate samples and deliver organic or inorganic molecules to various designs of detectors for identification and quantification. The organic aerosol (OA) fraction is composed of thousands of individual compounds, some with nitrogen- and sulfur-containing functionality and, often contains oligomeric material, much of which may be susceptible to decomposition upon heating. Here we analyze thermal decomposition products as measured by a thermal desorption aerosol gas chromatograph (TAG) capable of separating thermal decomposition products from thermally stable molecules. The TAG impacts particles onto a collection and thermal desorption (CTD) cell, and upon completion of sample collection, heats and transfers the sample in a helium flow up to 310 °C. Desorbed molecules are refocused at the head of a gas chromatography column that is held at 45 °C and any volatile decomposition products pass directly through the column and into an electron impact quadrupole mass spectrometer. Analysis of the sample introduction (thermal decomposition) period reveals contributions of NO+ (m/z 30), NO2+ (m/z 46), SO+ (m/z 48), and SO2+ (m/z 64), derived from either inorganic or organic particle-phase nitrate and sulfate. CO2+ (m/z 44) makes up a major component of the decomposition signal, along with smaller contributions from other organic components that vary with the type of aerosol contributing to the signal (e.g., m/z 53, 82 observed here for isoprene-derived secondary OA). All of these ions are important for ambient aerosol analyzed with the aerosol mass spectrometer (AMS), suggesting similarity of the thermal desorption processes in both instruments. Ambient observations of these decomposition products compared to organic, nitrate, and sulfate mass concentrations measured by an AMS reveal good correlation, with improved correlations for OA when compared to the AMS oxygenated OA (OOA

  5. Organic and inorganic decomposition products from the thermal desorption of atmospheric particles

    NASA Astrophysics Data System (ADS)

    Williams, B. J.; Zhang, Y.; Zuo, X.; Martinez, R. E.; Walker, M. J.; Kreisberg, N. M.; Goldstein, A. H.; Docherty, K. S.; Jimenez, J. L.

    2015-12-01

    Atmospheric aerosol composition is often analyzed using thermal desorption techniques to evaporate samples and deliver organic or inorganic molecules to various designs of detectors for identification and quantification. The organic aerosol (OA) fraction is composed of thousands of individual compounds, some with nitrogen- and sulfur-containing functionality, and often contains oligomeric material, much of which may be susceptible to decomposition upon heating. Here we analyze thermal decomposition products as measured by a thermal desorption aerosol gas chromatograph (TAG) capable of separating thermal decomposition products from thermally stable molecules. The TAG impacts particles onto a collection and thermal desorption (CTD) cell, and upon completion of sample collection, heats and transfers the sample in a helium flow up to 310 °C. Desorbed molecules are refocused at the head of a GC column that is held at 45 °C and any volatile decomposition products pass directly through the column and into an electron impact quadrupole mass spectrometer (MS). Analysis of the sample introduction (thermal decomposition) period reveals contributions of NO+ (m/z 30), NO2+ (m/z 46), SO+ (m/z 48), and SO2+ (m/z 64), derived from either inorganic or organic particle-phase nitrate and sulfate. CO2+ (m/z 44) makes up a major component of the decomposition signal, along with smaller contributions from other organic components that vary with the type of aerosol contributing to the signal (e.g., m/z 53, 82 observed here for isoprene-derived secondary OA). All of these ions are important for ambient aerosol analyzed with the aerosol mass spectrometer (AMS), suggesting similarity of the thermal desorption processes in both instruments. Ambient observations of these decomposition products compared to organic, nitrate, and sulfate mass concentrations measured by an AMS reveal good correlation, with improved correlations for OA when compared to the AMS oxygenated OA (OOA) component. TAG

  6. Effect of phosphorus and nitrogen on thermal decomposition kinetics of flame retardant cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four kinetic methods, Kissinger, Friedman, Flynn-Wall-Ozawa, and modified Coats-Redfern, were used to study the activation energy, Ea, of the thermal decomposition of greige cotton nonwoven fabric treated with diammonium phosphate (DAP) and urea. The results show that the Ea is significantly influen...

  7. Thermal decomposition reactions of cotton fabric treated with piperazine-phosphonates derivatives as a flame retardant

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There has been a great scientific interest in exploring the great potential of the piperazine-phosphonates in flame retardant (FR) application on cotton fabric by investigating the thermal decomposition of cotton fabric treated with them. This research tries to understand the mode of action of the t...

  8. Method of forming semiconducting amorphous silicon films from the thermal decomposition of fluorohydridodisilanes

    DOEpatents

    Sharp, Kenneth G.; D'Errico, John J.

    1988-01-01

    The invention relates to a method of forming amorphous, photoconductive, and semiconductive silicon films on a substrate by the vapor phase thermal decomposition of a fluorohydridodisilane or a mixture of fluorohydridodisilanes. The invention is useful for the protection of surfaces including electronic devices.

  9. A study of the process of nonisothermal decomposition of phenolformaldehyde polymers by differential thermal analysis

    SciTech Connect

    Petrova, O.M.; Fedoseev, S.D.; Komarova, T.V.

    1984-01-01

    A calculation has been made of the activation energy of the thermal decomposition of phenol-formaldehyde polymers. It has been established that for nonisothermal conditions the rate of performance of the process does not affect the effective activation energy calculated by means of Piloyan's equation.

  10. [Characteristics of the biochemical composition of plant litter at different stages of decomposition (according to thermal analysis data)].

    PubMed

    Kosheleva, Iu P; Trofimov, S Ia

    2008-01-01

    The composition of samples of needles, leaves, sheaved cottongrass (Eriophorum vaginatum) tissues, and the L horizon of the forest floor of different degree of decomposition, isolated from the plant litter in southern taiga ecosystems, was studied by thermal analysis. It was established that plant litter decomposition is accompanied by structural changes in celluloses and that the decomposition rates of hemicellulose and structured cellulose vary at different stages of decomposition. The structural specificity and incongruent thermal decomposition of grass lignocellulose were observed in all samples of plant material. The rates at which the content of components of the plant litter decreased depended on the type and stage of decomposition of plant material. The decomposition rate of biochemical components tended to increase in better drained soils.

  11. The Thermal Decomposition of Some Organic Lead Compounds

    DTIC Science & Technology

    1957-11-01

    5» Results 4 6. Discussion of Results 5 6.1 The Lead Salts of Aliphatic Aoids 5 6.2 The Lead Compounds of Aromatic Acids 7 6.3 Thermal...aliphatic carboxylic acids decompose to lead oxide in one stage which, in air, is largely oxidative in character. The compounds of the aromatic hydroxy... acids , however, first yield intermediate basio compounds of varying stability and these ultimately decompose to lead oxide at high temperatures

  12. Thermal decomposition of silane to form hydrogenated amorphous Si

    DOEpatents

    Strongin, M.; Ghosh, A.K.; Wiesmann, H.J.; Rock, E.B.; Lutz, H.A. III

    Hydrogenated amorphous silicon is produced by thermally decomposing silane (SiH/sub 4/) or other gases comprising H and Si, at elevated temperatures of about 1700 to 2300/sup 0/C, in a vacuum of about 10/sup -8/ to 10/sup -4/ torr. A gaseous mixture is formed of atomic hydrogen and atomic silicon. The gaseous mixture is deposited onto a substrate to form hydrogenated amorphous silicon.

  13. Kinetics and Mechanisms of Thermal Decomposition of Nitroaromatic Explosives

    DTIC Science & Technology

    1993-04-20

    2,4,6-trinitrophenylmethylnitramine HNS: hexanitrostilbene TACOT: tetranitrodibenzo-l,3a,4,6a-tetrazapentalene 2, 4- DNAn : 2,4-dinitroanthranil DSC... DNAn ) (References 51,59), an ill-defined explosive "coke" from long-term thermal degradation (Reference 20), and elemental carbon (Reference 62). The...report of Maksimov, at al. (Reference 59) who suggested that 2,4- DNAn or 2,4,6-trinitrobenzaldehyde (equation (27)) was the catalyst. Maksimov, &t Al

  14. Numerical analysis of thermal decomposition for RDX, TNT, and Composition B.

    PubMed

    Kim, Shin Hyuk; Nyande, Baggie W; Kim, Hyoun Soo; Park, Jung Su; Lee, Woo Jin; Oh, Min

    2016-05-05

    Demilitarization of waste explosives on a commercial scale has become an important issue in many countries, and this has created a need for research in this area. TNT, RDX and Composition B have been used as military explosives, and they are very sensitive to thermal shock. For the safe waste treatment of these high-energy and highly sensitive explosives, the most plausible candidate suggested has been thermal decomposition in a rotary kiln. This research examines the safe treatment of waste TNT, RDX and Composition B in a rotary kiln type incinerator with regard to suitable operating conditions. Thermal decomposition in this study includes melting, 3 condensed phase reactions in the liquid phase and 263 gas phase reactions. Rigorous mathematical modeling and dynamic simulation for thermal decomposition were carried out for analysis of dynamic behavior in the reactor. The results showed time transient changes of the temperature, components and mass of the explosives and comparisons were made for the 3 explosives. It was concluded that waste explosives subject to heat supplied by hot air at 523.15K were incinerated safely without any thermal detonation.

  15. Extraction of Curcumin Pigment from Indonesian Local Turmeric with Its Infrared Spectra and Thermal Decomposition Properties

    NASA Astrophysics Data System (ADS)

    Nandiyanto, A. B. D.; Wiryani, A. S.; Rusli, A.; Purnamasari, A.; Abdullah, A. G.; Ana; Widiaty, I.; Hurriyati, R.

    2017-03-01

    Curcumin is one of the pigments which is used as a spice in Asian cuisine, traditional cosmetic, and medicine. Therefore, process for getting curcumin has been widely studied. Here, the purpose of this study was to demonstrate the simple method for extracting curcumin from Indonesian local turmeric and investigate the infrared spectra and thermal decomposition properties. In the experimental procedure, the washed turmeric was dissolved into an ethanol solution, and then put into a rotary evaporator to enrich curcumin concentration. The result showed that the present method is effective to isolate curcumin compound from Indonesian local turmeric. Since the process is very simple, this method can be used for home industrial application. Further, understanding the thermal decomposition properties of curcumin give information, specifically relating to the selection of treatment when curcumin must face the thermal-related process.

  16. gamma-Irradiation effects on the thermal decomposition behaviour and IR absorption spectra of piperacillin

    NASA Astrophysics Data System (ADS)

    Mahfouz, R. M.; Gaffar, M. A.; Abu El-Fadl, A.; Hamad, Ar. G. K.

    2003-11-01

    The thermal decomposition behaviour of unirradiated and pre-gamma-irradiated piperacillin (pipril) as a semi-synthetic penicillin antibiotic has been studied in the temperature range of (273-1072 K). The decomposition was found to proceed through three major steps both for unirradiated and gamma-irradiated samples. Neither appearance nor disappearance of new bands in the IR spectrum of piperacillin was recorded as a result of gamma-irradiation but only a decrease in the intensity of most bands was observed. A degradation mechanism was suggested to explain the bond rupture and the decrease in the intensities of IR bands of gamma-irradiated piperacillin.

  17. Thermal Decomposition and Stabilisation of Poly(vinyl Chloride)

    NASA Astrophysics Data System (ADS)

    Troitskii, B. B.; Troitskaya, L. S.

    1985-08-01

    The kinetics and mechanism of the thermal dehydrochlorination of poly(vinyl chloride) and low-molecular-weight chlorohydrocarbons which model various fragments of the polymer molecule, are discussed. Studies designed to determine the qualitative and quantitative compositions of the unstable fragments in poly(vinyl chloride) macromolecules by 13C NMR are examined. Attention is concentrated on the consideration of the mechanism of the action of the most effective thermostabilisers for the polymer - organotin compounds. The principal features of synergism in the stabilisation of poly(vinyl chloride) and the mechanism of the action of synergistic mixtures are analysed. The bibliography includes 107 references.

  18. Thermal Decomposition of RP-2 with Stabilizing Additives

    DTIC Science & Technology

    2010-04-01

    RP-2 are that the allowed sulfur content is much lower in RP-2 (0.1 mg/kg, compared to 30 mg/kg in RP-1), the allowed olefin concentration is lower...28,30-35 decahydronaphthalene (decalin), 33,35 and benzyl alcohol . 28,36-38 In related work, a major research effort initiated by the U.S. Air Force...additives (e.g., benzyl alcohol ). We would also like to test the effect of different reactor materials, particularly copper, on the thermal stability of

  19. Structure and thermal decomposition of sulfated β-cyclodextrin intercalated in a layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Wei, Min; Rao, Guoying; Evans, David G.; Duan, Xue

    2004-01-01

    The sodium salt of hexasulfated β-cyclodextrin has been synthesized and intercalated into a magnesium-aluminum layered double hydroxide by ion exchange. The structure, composition and thermal decomposition behavior of the intercalated material have been studied by variable temperature X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma emission spectroscopy (ICP), and thermal analysis (TG-DTA) and a model for the structure has been proposed. The thermal stability of the intercalated sulfated β-cyclodextrin is significantly enhanced compared with the pure form before intercalation.

  20. 2-Step IMAT and 2-Step IMRT in three dimensions

    SciTech Connect

    Bratengeier, Klaus

    2005-12-15

    In two dimensions, 2-Step Intensity Modulated Arc Therapy (2-Step IMAT) and 2-Step Intensity Modulated Radiation Therapy (IMRT) were shown to be powerful methods for the optimization of plans with organs at risk (OAR) (partially) surrounded by a target volume (PTV). In three dimensions, some additional boundary conditions have to be considered to establish 2-Step IMAT as an optimization method. A further aim was to create rules for ad hoc adaptations of an IMRT plan to a daily changing PTV-OAR constellation. As a test model, a cylindrically symmetric PTV-OAR combination was used. The centrally placed OAR can adapt arbitrary diameters with different gap widths toward the PTV. Along the rotation axis the OAR diameter can vary, the OAR can even vanish at some axis positions, leaving a circular PTV. The width and weight of the second segment were the free parameters to optimize. The objective function f to minimize was the root of the integral of the squared difference of the dose in the target volume and a reference dose. For the problem, two local minima exist. Therefore, as a secondary criteria, the magnitude of hot and cold spots were taken into account. As a result, the solution with a larger segment width was recommended. From plane to plane for varying radii of PTV and OAR and for different gaps between them, different sets of weights and widths were optimal. Because only one weight for one segment shall be used for all planes (respectively leaf pairs), a strategy for complex three-dimensional (3-D) cases was established to choose a global weight. In a second step, a suitable segment width was chosen, minimizing f for this global weight. The concept was demonstrated in a planning study for a cylindrically symmetric example with a large range of different radii of an OAR along the patient axis. The method is discussed for some classes of tumor/organ at risk combinations. Noncylindrically symmetric cases were treated exemplarily. The product of width and weight of

  1. Thermal Decomposition of Thermoelectric Material CoSb3: A Thermogravimetry Kinetic Analysis

    NASA Astrophysics Data System (ADS)

    Wu, Fang; He, Qingli; Hu, Dinxu; Gao, Feng; Song, Hongzhang; Jia, Jianfeng; Hu, Xing

    2013-08-01

    The thermal decomposition of the thermoelectric CoSb3 alloy was investigated using thermogravimetry (TG). TG curves obtained in inert gas flow with different heating rates were used to perform kinetic analysis based on the Arrhenius equation. Kinetic parameters, such as the effective activation energy, the pre-exponential factor, and the kinetic model function f(α ) , were obtained using the Freeman-Carroll method, the multiheating rates method, and the Coats-Redfern equation. The activation energy was found to be around 200 kJ/mol, and the reaction mechanism for the decomposition of CoSb3 alloy mostly obeys the second-order chemical decomposition process f(α ) = (1 - α )2.

  2. Mechanistic and kinetic studies of the thermal decomposition of TNAZ and NDNAZ

    SciTech Connect

    Anderson, K.; Homsy, J.; Behrens, R.; Bulusu, S.

    1998-12-31

    The authors have studied the mechanism and detailed reaction kinetics of the thermal decomposition of 1,3,3-trinitroazetidine (TNAZ), and separately, its key decomposition intermediate, 1-nitroso-3,3-dinitroacetidine (NDNAZ), using a simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS). These decompositions were conducted in a sealed alumina cell with a 2.5 {micro}m orifice, at varying temperatures and at a range of isothermal temperatures (at 10 C intervals from 120--160 C for NDNAZ and 160--210 C for TNAZ). The gaseous products have been identified and their rates of formation have been measured as a function of time, temperature, and pressure. This system is complex, with TNAZ decomposing by four separate routes, one of which leads to NDNAZ, which itself decomposes by at least two distinct routes.

  3. Thermal stability and kinetics of decomposition of ammonium nitrate in the presence of pyrite.

    PubMed

    Gunawan, Richard; Zhang, Dongke

    2009-06-15

    The interaction between ammonium nitrate based industrial explosives and pyrite-rich minerals in mining operations can lead to the occurrence of spontaneous explosion of the explosives. In an effort to provide a scientific basis for safe applications of industrial explosives in reactive mining grounds containing pyrite, ammonium nitrate decomposition, with and without the presence of pyrite, was studied using a simultaneous Differential Scanning Calorimetry and Thermogravimetric Analyser (DSC-TGA) and a gas-sealed isothermal reactor, respectively. The activation energy and the pre-exponential factor of ammonium nitrate decomposition were determined to be 102.6 kJ mol(-1) and 4.55 x 10(7)s(-1) without the presence of pyrite and 101.8 kJ mol(-1) and 2.57 x 10(9)s(-1) with the presence of pyrite. The kinetics of ammonium nitrate decomposition was then used to calculate the critical temperatures for ammonium nitrate decomposition with and without the presence of pyrite, based on the Frank-Kamenetskii model of thermal explosion. It was shown that the presence of pyrite reduces the temperature for, and accelerates the rate of, decomposition of ammonium nitrate. It was further shown that pyrite can significantly reduce the critical temperature of ammonium nitrate decomposition, causing undesired premature detonation of the explosives. The critical temperature also decreases with increasing diameter of the blast holes charged with the explosive. The concept of using the critical temperature as indication of the thermal stability of the explosives to evaluate the risk of spontaneous explosion was verified in the gas-sealed isothermal reactor experiments.

  4. Non-Equilibrium Iron Clusters Coagulation and Thermal Decomposition at High Temperatures

    NASA Astrophysics Data System (ADS)

    Starikovskii, A. Yu.; Zaslonko, I. S.

    The fast thermal decomposition of Fe(CO)5 (1000-8000 ppm) behind reflected shock waves was used as source of iron atoms. The growth and decomposition of iron clusters was observed using light absorption technique at λ = 632.8 nm. The iron cluster formation was studied behind incident shock waves (T = 1200 — 2000 K, p = 5 — 50 bar) and cluster decomposition behind reflected shock waves (T = 2600 — 3000 K, p = 10 — 100 bar). The temperature and pressure dependencies of observable rate constants for iron cluster growth and thermal decomposition has been obtained. The experimental data were treated using master equation solution for the cluster size distribution function. The light absorption in the system is shown to depend on the total atoms amount in the clusters with n* < n < n **, were n* ~ 3 — 5, n** ~ 104. When coagulation time is rather small that the concentration of clusters with n > n** is negligible and concentration of small clusters (n < n*) permanently decreases, light absorption increase. After that number of atoms enclosed into the clusters with n* < n < n** became decreasing and the total light-absorption cross section decreases. So, observations of the absorption gives us an important information about streams through the particle size axes, and observable rate constant kobs = dln(D)/dt is a good parameter for the description of the kinetic behavior at the broad variations of temperature and pressure for an iron cluster ensemble.

  5. Application of vacuum stability test to determine thermal decomposition kinetics of nitramines bonded by polyurethane matrix

    NASA Astrophysics Data System (ADS)

    Elbeih, Ahmed; Abd-Elghany, Mohamed; Elshenawy, Tamer

    2017-03-01

    Vacuum stability test (VST) is mainly used to study compatibility and stability of energetic materials. In this work, VST has been investigated to study thermal decomposition kinetics of four cyclic nitramines, 1,3,5-trinitro-1,3,5-triazinane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, CL-20), bonded by polyurethane matrix based on hydroxyl terminated polybutadiene (HTPB). Model fitting and model free (isoconversional) methods have been applied to determine the decomposition kinetics from VST results. For comparison, the decomposition kinetics were determined isothermally by ignition delay technique and non-isothermally by Advanced Kinetics and Technology Solution (AKTS) software. The activation energies for thermolysis obtained by isoconversional method based on VST technique of RDX/HTPB, HMX/HTPB, BCHMX/HTPB and CL20/HTPB were 157.1, 203.1, 190.0 and 176.8 kJ mol-1 respectively. Model fitting method proved that the mechanism of thermal decomposition of BCHMX/HTPB is controlled by the nucleation model while all the other studied PBXs are controlled by the diffusion models. A linear relationship between the ignition temperatures and the activation energies was observed. BCHMX/HTPB is interesting new PBX in the research stage.

  6. Thermal, solution and reductive decomposition of Cu-Al layered double hydroxides into oxide products

    SciTech Connect

    Britto, Sylvia; Vishnu Kamath, P.

    2009-05-15

    Cu-Al layered double hydroxides (LDHs) with [Cu]/[Al] ratio 2 adopt a structure with monoclinic symmetry while that with the ratio 0.25 adopt a structure with orthorhombic symmetry. The poor thermodynamic stability of the Cu-Al LDHs is due in part to the low enthalpies of formation of Cu(OH){sub 2} and CuCO{sub 3} and in part to the higher solubility of the LDH. Consequently, the Cu-Al LDH can be decomposed thermally (150 deg. C), hydrothermally (150 deg. C) and reductively (ascorbic acid, ambient temperature) to yield a variety of oxide products. Thermal decomposition at low (400 deg. C) temperature yields an X-ray amorphous residue, which reconstructs back to the LDH on soaking in water or standing in the ambient. Solution decomposition under hydrothermal conditions yields tenorite at 150 deg. C itself. Reductive decomposition yields a composite of Cu{sub 2}O and Al(OH){sub 3}, which on alkali-leaching of the latter, leads to the formation of fine particles of Cu{sub 2}O (<1 {mu}m). - Graphical abstract: SEM image of (a) the Cu{sub 2}O-Al(OH){sub 3} composite obtained on reductive decomposition of CuAl{sub 4}-LDH and (b) Cu{sub 2}O obtained on leaching of Al(OH){sub 3} from (a).

  7. Kinetics of Thermal Decomposition of Ammonium Perchlorate by TG/DSC-MS-FTIR

    NASA Astrophysics Data System (ADS)

    Zhu, Yan-Li; Huang, Hao; Ren, Hui; Jiao, Qing-Jie

    2014-01-01

    The method of thermogravimetry/differential scanning calorimetry-mass spectrometry-Fourier transform infrared (TG/DSC-MS-FTIR) simultaneous analysis has been used to study thermal decomposition of ammonium perchlorate (AP). The processing of nonisothermal data at various heating rates was performed using NETZSCH Thermokinetics. The MS-FTIR spectra showed that N2O and NO2 were the main gaseous products of the thermal decomposition of AP, and there was a competition between the formation reaction of N2O and that of NO2 during the process with an iso-concentration point of N2O and NO2. The dependence of the activation energy calculated by Friedman's iso-conversional method on the degree of conversion indicated that the AP decomposition process can be divided into three stages, which are autocatalytic, low-temperature diffusion and high-temperature, stable-phase reaction. The corresponding kinetic parameters were determined by multivariate nonlinear regression and the mechanism of the AP decomposition process was proposed.

  8. First-Principles Thermochemistry for the Thermal Decomposition of Titanium Tetraisopropoxide.

    PubMed

    Buerger, Philipp; Nurkowski, Daniel; Akroyd, Jethro; Mosbach, Sebastian; Kraft, Markus

    2015-07-30

    The thermal decomposition of titanium tetraisopropoxide (TTIP) is investigated using quantum chemistry, statistical thermodynamics, and equilibrium composition analysis. A set of 981 Ti-containing candidate species are proposed systematically on the basis of the thermal breakage of bonds within a TTIP molecule. The ground state geometry, vibrational frequencies and hindrance potentials are calculated for each species at the B97-1/6-311+G(d,p) level of theory. Thermochemical data are computed by applying statistical thermodynamics and, if unknown, the standard enthalpy of formation is estimated using balanced reactions. Equilibrium composition calculations are performed under typical combustion conditions for premixed flames. The thermodynamically stable decomposition products for different fuel mixtures are identified. A strong positive correlation is found between the mole fractions of Ti species containing carbon and the TTIP precursor concentration.

  9. Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study

    NASA Astrophysics Data System (ADS)

    Nguyen, Thanh Lam; McCaslin, Laura; McCarthy, Michael C.; Stanton, John F.

    2016-10-01

    The thermal decomposition of syn-ethanal-oxide (syn-CH3CHOO) through vinyl hydrogen peroxide (VHP) leading to hydroxyl radical is characterized using a modification of the HEAT thermochemical protocol. The isomerization step of syn-CH3CHOO to VHP via a 1,4 H-shift, which involves a moderate barrier of 72 kJ/mol, is found to be rate determining. A two-dimensional master equation approach, in combination with semi-classical transition state theory, is employed to calculate the time evolution of various species as well as to obtain phenomenological rate coefficients. This work suggests that, under boundary layer conditions in the atmosphere, thermal unimolecular decomposition is the most important sink of syn-CH3CHOO. Thus, the title reaction should be included into atmospheric modeling. The fate of cold VHP, the intermediate stabilized by collisions with a third body, has also been investigated.

  10. Communication: Thermal unimolecular decomposition of syn-CH3CHOO: A kinetic study.

    PubMed

    Nguyen, Thanh Lam; McCaslin, Laura; McCarthy, Michael C; Stanton, John F

    2016-10-07

    The thermal decomposition of syn-ethanal-oxide (syn-CH3CHOO) through vinyl hydrogen peroxide (VHP) leading to hydroxyl radical is characterized using a modification of the HEAT thermochemical protocol. The isomerization step of syn-CH3CHOO to VHP via a 1,4 H-shift, which involves a moderate barrier of 72 kJ/mol, is found to be rate determining. A two-dimensional master equation approach, in combination with semi-classical transition state theory, is employed to calculate the time evolution of various species as well as to obtain phenomenological rate coefficients. This work suggests that, under boundary layer conditions in the atmosphere, thermal unimolecular decomposition is the most important sink of syn-CH3CHOO. Thus, the title reaction should be included into atmospheric modeling. The fate of cold VHP, the intermediate stabilized by collisions with a third body, has also been investigated.

  11. The thermal decomposition of methanol and methanethiol on the clean and modified Fe(110) surface

    SciTech Connect

    Batteas, J.D.; Rufael, T.S.; Friend, C.M.

    1996-10-01

    The thermal decomposition of methanol and methanethiol on the clean and modified Fe(110) surface has been examined using X-ray photoelectron spectroscopy, low-energy electron diffraction and temperature programmed reaction spectroscopy. Both methanethiol and methanol adsorb on the Fe(110) surface at 100 K with immediate cleavage of the terminal hydrogen to produce methylthiolate (CH{sub 3}S) and methoxy (CH{sub 3}O) coadsorbed with atomic hydrogen on the Fe surface. Heating the sample to 800 K produces gas phase methane and hydrogen, leaving a chemisorbed S overlayer in the case of methylthiolate, while methoxy decomposes via desorbing hydrogen and CO to leave a clean Fe surface. The influence of oxygen and sulfur pre-adsorption on the thermal decomposition of these species will also be described.

  12. Ab initio kinetics and thermal decomposition mechanism of mononitrobiuret and 1,5-dinitrobiuret

    SciTech Connect

    Sun, Hongyan E-mail: ghanshyam.vaghjiani@us.af.mil; Vaghjiani, Ghanshyam L. E-mail: ghanshyam.vaghjiani@us.af.mil

    2015-05-28

    Mononitrobiuret (MNB) and 1,5-dinitrobiuret (DNB) are tetrazole-free, nitrogen-rich, energetic compounds. For the first time, a comprehensive ab initio kinetics study on the thermal decomposition mechanisms of MNB and DNB is reported here. In particular, the intramolecular interactions of amine H-atom with electronegative nitro O-atom and carbonyl O-atom have been analyzed for biuret, MNB, and DNB at the M06-2X/aug-cc-pVTZ level of theory. The results show that the MNB and DNB molecules are stabilized through six-member-ring moieties via intramolecular H-bonding with interatomic distances between 1.8 and 2.0 Å, due to electrostatic as well as polarization and dispersion interactions. Furthermore, it was found that the stable molecules in the solid state have the smallest dipole moment amongst all the conformers in the nitrobiuret series of compounds, thus revealing a simple way for evaluating reactivity of fuel conformers. The potential energy surface for thermal decomposition of MNB was characterized by spin restricted coupled cluster theory at the RCCSD(T)/cc-pV∞ Z//M06-2X/aug-cc-pVTZ level. It was found that the thermal decomposition of MNB is initiated by the elimination of HNCO and HNN(O)OH intermediates. Intramolecular transfer of a H-atom, respectively, from the terminal NH{sub 2} group to the adjacent carbonyl O-atom via a six-member-ring transition state eliminates HNCO with an energy barrier of 35 kcal/mol and from the central NH group to the adjacent nitro O-atom eliminates HNN(O)OH with an energy barrier of 34 kcal/mol. Elimination of HNN(O)OH is also the primary process involved in the thermal decomposition of DNB, which processes C{sub 2v} symmetry. The rate coefficients for the primary decomposition channels for MNB and DNB were quantified as functions of temperature and pressure. In addition, the thermal decomposition of HNN(O)OH was analyzed via Rice–Ramsperger–Kassel–Marcus/multi-well master equation simulations, the results of which

  13. Physical pretreatments of wastewater algae to reduce ash content and improve thermal decomposition characteristics.

    PubMed

    Chen, Wan-Ting; Ma, Junchao; Zhang, Yuanhui; Gai, Chao; Qian, Wanyi

    2014-10-01

    Previous study showed high ash content in wastewater algae (WA) has a negative effect on bio-crude oil formation in hydrothermal liquefaction (HTL). This study explored the effect of different pretreatments on ash reduction and the thermal decomposition of WA. Single-stage (e.g. centrifugation) and two-stage pretreatments (e.g. centrifugation followed by ultrasonication, C+U) were used. The apparent activation energy of the thermal decomposition (E(a)) of pretreated algae was determined. HTL was conducted to study how different pretreatments may impact on bio-crude oil formation. Compared to untreated samples, the ash content of algae with centrifugation was reduced from 28.6% to 18.6%. With C+U pretreatments, E(a) was decreased from 50.2 kJ/mol to 35.9 kJ/mol and the bio-crude oil yield was increased from 30% to 55%. These results demonstrate that pretreatments of C+U can improve the thermal decomposition behavior of WA and enhance the bio-crude oil conversion efficiency.

  14. Kinetic and chemical characterization of thermal decomposition of dicumylperoxide in cumene.

    PubMed

    Di Somma, Ilaria; Marotta, Raffaele; Andreozzi, Roberto; Caprio, Vincenzo

    2011-03-15

    Dicumylperoxide (DCP) is one of the most used peroxides in the polymer industry. It has been reported that its thermal decomposition can result in runaway phenomena and thermal explosions with significant economic losses and injuries to people. In the present paper thermal behaviour of dicumylperoxide in cumene was investigated over the temperature range of 393-433 K under aerated and de-aerated conditions. The results indicated that when oxygen was present, the decomposition rate did not follow a simple pseudo-first order kinetic as previously reported in literature. A satisfactory fit of the experimental data was, in this case, achieved by means of kinetic expression derived under the assumption of an autocatalytic scheme of reaction. The reaction rate was, on the contrary, correctly described by a pseudo-first order kinetic in absence of oxygen. Under both aerated and de-aerated conditions, chemical analysis showed that the decomposition mainly resulted in the formation of acetophenone and dimethylphenylcarbinol with minor occurrence of 2,3-dimethyl-2,3-diphenylbutane. The formation of methane and ethane was also invariably observed while the appearance of cumylhydroperoxide as a reaction intermediate was detected under only aerated conditions. Therefore, two reaction schemes were proposed to explain system behaviour in the presence of oxygen and after its purging.

  15. Study on the thermal decomposition kinetics of nano-sized calcium carbonate.

    PubMed

    Li, Dai-Xi; Shi, Hong-Yun; Jie, Deng; Xu, Yuan-Zhi

    2003-01-01

    This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA ( thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy (a); and that the top-temperature of decomposition T(p) decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both E(a) and T(p) to decline sharply with the decrease of the average diameter of nano-particles.

  16. Ultrafast Preparation of Monodisperse Fe3 O4 Nanoparticles by Microwave-Assisted Thermal Decomposition.

    PubMed

    Liang, Yi-Jun; Zhang, Yu; Guo, Zhirui; Xie, Jun; Bai, Tingting; Zou, Jiemeng; Gu, Ning

    2016-08-08

    Thermal decomposition, as the main synthetic procedure for the synthesis of magnetic nanoparticles (NPs), is facing several problems, such as high reaction temperatures and time consumption. An improved a microwave-assisted thermal decomposition procedure has been developed by which monodisperse Fe3 O4 NPs could be rapidly produced at a low aging temperature with high yield (90.1 %). The as-synthesized NPs show excellent inductive heating and MRI properties in vitro. In contrast, Fe3 O4 NPs synthesized by classical thermal decomposition were obtained in very low yield (20.3 %) with an overall poor quality. It was found for the first time that, besides precursors and solvents, magnetic NPs themselves could be heated by microwave irradiation during the synthetic process. These findings were demonstrated by a series of microwave-heating experiments, Raman spectroscopy and vector-network analysis, indicating that the initially formed magnetic Fe3 O4 particles were able to transform microwave energy into heat directly and, thus, contribute to the nanoparticle growth.

  17. Thermal and carbothermic decomposition of Na2CO3 and Li2CO3

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Wan; Lee, Hae-Geon

    2001-02-01

    In order to elucidate the decomposition mechanism of Na2CO3 and Li2CO3 in mold-powder systems employed in the continuous casting of steel, decompositions of Na2CO3 and Li2CO3 were investigated using thermogravimetric (TG) and differential scanning calorimetric (DSC) methods at temperatures up to 1200 °C, under a flow of argon gas. For the case of pure Na2CO3, the thermal decomposition started from its melting point and continued as the temperature was increased, but at a very slow rate. For Li2CO3, however, the decomposition occurred at much faster rates than that for Na2CO3. When carbon black was added to the carbonate particles, the decomposition rates of both Na2CO3 and Li2CO3 were significantly enhanced. From mass-balanced calulations and X-ray diffraction (XRD) analyses of the reaction products, it is concluded that decompositions of Na2CO3 and Li2CO3 with carbon black take place according to the respective reactions of Na2CO3 (1) + 2C (s) = 2Na (g) + 3CO (g) and Li2CO3 (l) + C (s) = Li2O (s) + 2CO (g). It was found that liquid droplets of Na2CO3 were initially isolated due to carbon particles surrounding them, but, as the carbon particles were consumed, the liquid droplets were gradually agglomerated. This effected a reduction of the total surface area of the carbonate, resulting in a dependence of the decomposition rate on the amount of carbon black. For the case of Li2CO3, on the other hand, hardly any agglomeration occurred up to the completion of decomposition, and, hence, the rate was almost independent of the amount of carbon black mixed. The apparent activation energies for the decomposition of Na2CO3 and Li2CO3 with carbon black were found to be similar and were estimated to be 180 to 223 kJ mole-1.

  18. Flow pyrolysis and direct and silicon tetrafluoride-sensitized laser-induced decomposition of tetralin. Identification of retro-[2 + 4] cleavage as the primary homogeneous thermal decomposition channel

    SciTech Connect

    Berman, Michael R.; Comita, Paul B.; Moore, C. Bradley; Bergman, Robert G.

    1980-08-01

    In an effort to determine the products and mechanism of the truly homogeneous thermal decomposition of the aromatic hydrocarbon tetralin, we have examined the products formed from this compound upon energization by conventional flow pyrolysis, infrared multiphoton excitation, and SiF{sub 4}-sensitized infrared laser thermal activation. Six major products are formed in these reactions, but the product ratios depend upon the mode of energization. Flow pyrolysis gives a result analogous to those observed earlier; i.e. almost exclusive dehydrogenation, leading to dihydronaphthalene and naphthalene. Direct and sensitized IR laser-induced decomposition, however, leads to ethylene loss (presumably by an initial retro-[2+4] reaction) as the predominent decomposition mode, giving benzocyclobutene. We believe these results are due to the fact that direct thermal decomposition, both in our experiments as well as in previous studies, involves predominant surface-catalysis. In the laser-induced reactions, which are uncomplicated by problems due to surface-catalysis, the true homogeneous decomposition takes place, and this involves retro-[2+4] cleavage. Mechanistic details of these processes were studied by examining the isotope distribution in the products formed on SiF{sub 4}-sensitized laser photolysis of 1,1,4,4-tetradeuteriotetralin.

  19. Convex Decompositions of Thermal Equilibrium for Non-interacting Non-relativistic Particles

    NASA Astrophysics Data System (ADS)

    Chenu, Aurelia; Branczyk, Agata; Sipe, John

    2016-05-01

    We provide convex decompositions of thermal equilibrium for non-interacting non-relativistic particles in terms of localized wave packets. These quantum representations offer a new tool and provide insights that can help relate to the classical picture. Considering that thermal states are ubiquitous in a wide diversity of fields, studying different convex decompositions of the canonical ensemble is an interesting problem by itself. The usual classical and quantum pictures of thermal equilibrium of N non-interacting, non-relativistic particles in a box of volume V are quite different. The picture in classical statistical mechanics is about (localized) particles with a range of positions and velocities; in quantum statistical mechanics, one considers the particles (bosons or fermions) associated with energy eigenstates that are delocalized through the whole box. Here we provide a representation of thermal equilibrium in quantum statistical mechanics involving wave packets with a localized coordinate representation and an expectation value of velocity. In addition to derive a formalism that may help simplify particular calculations, our results can be expected to provide insights into the transition from quantum to classical features of the fully quantum thermal state.

  20. Solid-phase thermal decomposition of 2,4-dinitroimidazole (2,4-DNI)

    SciTech Connect

    Minier, L.; Behrens, R. Jr.; Bulusu, S.

    1996-07-01

    The solid-phase thermal decomposition of the insensitive energetic aromatic heterocycle 2,4-dinitroimidazole (2,4-DNI: mp 265--274 C) is studied utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) between 200 and 247 C. The pyrolysis products have been identified using perdeuterated and {sup 15}N-labeled isotopomers. The products consist of low molecular-weight gases and a thermally stable solid residue. The major gaseous products are NO, CO{sub 2}, CO, N{sub 2}, HNCO and H{sub 2}O. Minor gaseous products are HCN, C{sub 2}N{sub 2}, NO{sub 2}, C{sub 3}H{sub 4}N{sub 2}, C{sub 3}H{sub 3}N{sub 3}O and NH{sub 3}. The elemental formula of the residue is C{sub 2}HN{sub 2}O and FTIR analysis suggests that it is polyurea- and polycarbamate-like in nature. The rates of formation of the gaseous products and their respective quantities have been determined for a typical isothermal decomposition experiment at 235 C. The temporal behaviors of the gas formation rates indicate that the overall decomposition is characterized by a sequence of four events: (1) an early decomposition period induced by impurities and H{sub 2}O, (2) an induction period where CO{sub 2} and NO are the primary products formed at relatively constant rates, (3) an autoacceleratory period that peaks when the sample is depleted and (4) a final period in which the residue decomposes. Arrhenius parameters for the induction period are E{sub a} = 46.9 {+-} 0.7 kcal/mol and Log(A) = 16.3 {+-} 0.3. Decomposition pathways that are consistent with the data are presented.

  1. Solid-phase thermal decomposition of 2,4-dinitroimidazole (2,4-DNI)

    SciTech Connect

    Minier, L.; Behrens, R. Jr.; Bulusu, S.

    1996-12-31

    The solid-phase thermal decomposition of the insensitive energetic nitroaromatic heterocycle 2,4-dinitroimidazole (2,4-DNI: mp 265--274C) is studied utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) between 200 and 247C. The pyrolysis products have been identified using perdeuterated and {sup 15}N-labeled isotopomers. The products consist of low molecular-weight gases and a thermally stable solid residue. The major gaseous products are NO, CO{sub 2}, CO, N{sub 2}, HNCO and H{sub 2}O. Minor gaseous products are HCN, C{sub 2}N{sub 2}, NO{sub 2}, C{sub 3}H{sub 4}N{sub 2}, C{sub 3}H{sub 3}N{sub 3}O and NH{sub 3}. The elemental formula of the residue is C{sub 2}HN{sub 2}O and FTIR analysis suggests that it is polyurea- and polycarbamate-like in nature. Rates of formation of the gaseous products and their respective quantities have been determined for a typical isothermal decomposition experiment at 235C. The temporal behaviors of the gas formation rates indicate that the overall decomposition is characterized by a sequence of four events; (1) an early decomposition period induced by impurities and water, (2) an induction period where C0{sub 2} and NO are the primary products formed at relatively constant rates, (3) an autoacceleratory period that peaks when the sample is depleted and (4) a final period in which the residue decomposes. Arrhenius parameters for the induction period are E{sub a} = 46.9 {plus_minus} 0.7 kcal/mol and Log(A) = 16.3 {plus_minus} 0.3. Decomposition pathways that are consistent with the data are presented.

  2. Organic and inorganic decomposition products from the thermal desorption of atmospheric particles

    DOE PAGES

    Williams, Brent J.; Zhang, Yaping; Zuo, Xiaochen; ...

    2016-04-11

    Here, atmospheric aerosol composition is often analyzed using thermal desorption techniques to evaporate samples and deliver organic or inorganic molecules to various designs of detectors for identification and quantification. The organic aerosol (OA) fraction is composed of thousands of individual compounds, some with nitrogen- and sulfur-containing functionality and, often contains oligomeric material, much of which may be susceptible to decomposition upon heating. Here we analyze thermal decomposition products as measured by a thermal desorption aerosol gas chromatograph (TAG) capable of separating thermal decomposition products from thermally stable molecules. The TAG impacts particles onto a collection and thermal desorption (CTD) cell, and upon completionmore » of sample collection, heats and transfers the sample in a helium flow up to 310 °C. Desorbed molecules are refocused at the head of a gas chromatography column that is held at 45 °C and any volatile decomposition products pass directly through the column and into an electron impact quadrupole mass spectrometer. Analysis of the sample introduction (thermal decomposition) period reveals contributions of NO+ (m/z 30), NO2+ (m/z 46), SO+ (m/z 48), and SO2+ (m/z 64), derived from either inorganic or organic particle-phase nitrate and sulfate. CO2+ (m/z 44) makes up a major component of the decomposition signal, along with smaller contributions from other organic components that vary with the type of aerosol contributing to the signal (e.g., m/z  53, 82 observed here for isoprene-derived secondary OA). All of these ions are important for ambient aerosol analyzed with the aerosol mass spectrometer (AMS), suggesting similarity of the thermal desorption processes in both instruments. Ambient observations of these decomposition products compared to organic, nitrate, and sulfate mass concentrations measured by an AMS reveal good correlation, with improved correlations for OA when compared to the AMS

  3. Organic and inorganic decomposition products from the thermal desorption of atmospheric particles

    SciTech Connect

    Williams, Brent J.; Zhang, Yaping; Zuo, Xiaochen; Martinez, Raul E.; Walker, Michael J.; Kreisberg, Nathan M.; Goldstein, Allen H.; Docherty, Kenneth S.; Jimenez, Jose L.

    2016-04-11

    Here, atmospheric aerosol composition is often analyzed using thermal desorption techniques to evaporate samples and deliver organic or inorganic molecules to various designs of detectors for identification and quantification. The organic aerosol (OA) fraction is composed of thousands of individual compounds, some with nitrogen- and sulfur-containing functionality and, often contains oligomeric material, much of which may be susceptible to decomposition upon heating. Here we analyze thermal decomposition products as measured by a thermal desorption aerosol gas chromatograph (TAG) capable of separating thermal decomposition products from thermally stable molecules. The TAG impacts particles onto a collection and thermal desorption (CTD) cell, and upon completion of sample collection, heats and transfers the sample in a helium flow up to 310 °C. Desorbed molecules are refocused at the head of a gas chromatography column that is held at 45 °C and any volatile decomposition products pass directly through the column and into an electron impact quadrupole mass spectrometer. Analysis of the sample introduction (thermal decomposition) period reveals contributions of NO+ (m/z 30), NO2+ (m/z 46), SO+ (m/z 48), and SO2+ (m/z 64), derived from either inorganic or organic particle-phase nitrate and sulfate. CO2+ (m/z 44) makes up a major component of the decomposition signal, along with smaller contributions from other organic components that vary with the type of aerosol contributing to the signal (e.g., m/z  53, 82 observed here for isoprene-derived secondary OA). All of these ions are important for ambient aerosol analyzed with the aerosol mass spectrometer (AMS), suggesting similarity of the thermal desorption processes in both instruments. Ambient observations of these decomposition products compared to organic, nitrate, and sulfate

  4. The decomposition of methanol on Ru(001) studied using laser induced thermal desorption

    NASA Astrophysics Data System (ADS)

    Deckert, A. A.; Brand, J. L.; Mak, C. H.; Koehler, B. G.; George, S. M.

    1987-08-01

    The decomposition reaction of methanol on Ru(001) was studied using laser induced thermal desorption (LITD). The LITD studies, combined with temperature programmed desorption and Auger electron spectroscopy measurements, allowed absolute product yields for the three competing surface pathways to be determined over the entire range of chemisorbed methanol coverages at a heating rate of β=2.6 K/s. At the lowest methanol coverages of θ≤0.07θs, where θs is the surface coverage of a saturated chemisorbed layer, all the methanol reacted between 220-280 K. This methanol decomposition reaction yielded desorption-limited H2 and CO as reaction products. At higher coverages, molecular desorption and the second methanol decomposition reaction involving C-O bond breakage became increasingly important. At θ=θs, 50% of the initial methanol coverage desorbed, 24% produced H2 and CO and 26% left C on the surface. Isothermal LITD kinetic measurements were carried out at low methanol coverages of θ≤0.07θs at various temperatures from 180 to 220 K. The initial decomposition rates obtained from the isothermal LITD studies displayed first order kinetics. The decomposition kinetics at later times could not be fit by first order kinetics and suggested a self-poisoned reaction. Subsequent LITD studies revealed that CO inhibited the decomposition reaction. The product CO inhibition was modeled by first order kinetics with a CO-coverage dependent activation barrier. The observed first order reaction kinetics at low methanol coverage could be expressed by the pre-exponential ν=106 s-1 and the coverage-dependent activation barrier E=7 kcal/mol+αθCO/θCO,s, where α=20 kcal/mol and θCO/θCO,s is the dimensionless CO coverage normalized to the CO saturation coverage θCO,s. Isotopic LITD studies revealed that the decomposition kinetics of CH3OH, CD3OH, and CH3OD were identical. This equivalence suggested that the hindered rotation of the surface methoxy species is the reaction

  5. Thermal decomposition of wood and cellulose in the presence of solvent vapors

    SciTech Connect

    Jakab, E.; Liu, K.; Meuzelaar, H.L.C.

    1997-06-01

    The thermal decomposition of white birch wood and filter pulp was studied in water and methanol vapor at 2 MPa pressure in a flow-through reactor. The abundance of the volatile products was monitored by on-line GC/MS using repetitive sampling in combination with fast separation on a short capillary column. The reactor was heated to 400 C at 20 C/min and the intensity profile of the product ions within the 30--200 amu range recorded. The system was capable of separating the profiles of typical hemicellulose products evolved at lower temperature from the characteristic cellulose and lignin products detected from wood. Char yields in methanol were similar to those in an inert gas atmosphere; however, the presence of water markedly increased the amount of char produced. The product distribution of cellulose was strongly affected by the solvents. In methanol, pyran derivatives dominate besides levoglucosan and glycolaldehyde, whereas the relative abundance of 2-furaldehyde and 5-(hydroxymethyl)-2-furaldehyde increased in the presence of water. Water catalysis was also indicated by lowering the decomposition temperatures of cellulose. High-pressure (6.5 MPa) thermogravimetric experiments in helium or hydrogen atmospheres were also found to lower the reaction temperature of wood. This observation can be explained by the catalytic effect of reaction water released during the thermal decomposition of wood.

  6. Prediction of the thermal decomposition of organic peroxides by validated QSPR models.

    PubMed

    Prana, Vinca; Rotureau, Patricia; Fayet, Guillaume; André, David; Hub, Serge; Vicot, Patricia; Rao, Li; Adamo, Carlo

    2014-07-15

    Organic peroxides are unstable chemicals which can easily decompose and may lead to explosion. Such a process can be characterized by physico-chemical parameters such as heat and temperature of decomposition, whose determination is crucial to manage related hazards. These thermal stability properties are also required within many regulatory frameworks related to chemicals in order to assess their hazardous properties. In this work, new quantitative structure-property relationships (QSPR) models were developed to predict accurately the thermal stability of organic peroxides from their molecular structure respecting the OECD guidelines for regulatory acceptability of QSPRs. Based on the acquisition of 38 reference experimental data using DSC (differential scanning calorimetry) apparatus in homogenous experimental conditions, multi-linear models were derived for the prediction of the decomposition heat and the onset temperature using different types of molecular descriptors. Models were tested by internal and external validation tests and their applicability domains were defined and analyzed. Being rigorously validated, they presented the best performances in terms of fitting, robustness and predictive power and the descriptors used in these models were linked to the peroxide bond whose breaking represents the main decomposition mechanism of organic peroxides.

  7. Non-isothermal kinetic analysis of thermal decomposition of the Ca-bentonite from Santai, China

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang-hui; He, Chuan; Wang, Ling; Li, Zhong-quan; Deng, Miao; Liu, Jing; Li, Hong-kui; Feng, Qian

    2015-06-01

    The thermal decompositions of Ca-bentonites (CaB) from Santai, Shichuan Province, China, over the temperature range of 30-1,100 °C were investigated by simultaneous thermal analyzer. Non-isothermal kinetic analysis was employed to study the thermal decomposition mechanism by using Netzsch Thermokinetics software. Flynn-Wall-Ozawa and Friedman isoconversional methods were used to calculate the activation energy and analyze the reaction steps. The probable mechanism and the corresponding kinetic parameters were determined by multivariate non-linear regression program. The results show that the thermal decomposition process of CaB over the temperature range of 30-800 °C is a kind of six-step, competitive reaction ( F 1 D 3 F n C 1E F n F n model). The dehydration reaction is controlled by two consecutive mechanisms, nucleation and growth, followed by a diffusion-controlled reaction ( F 1 D 3 model), the first step: E = 61.68 kJ mol-1, log A = 6.75 s-1; the second step: E = 50.73 kJ mol-1, log A = 3.11 s-1. The dehydroxylation reaction is controlled by three-step competitive mechanisms, an autocatalytically activated, initial reaction followed by n-order competitive reaction ( C 1E F n F n model), the first step: E = 124.74 kJ mol-1, log A = 5.67 s-1; the second step: E = 245.29 kJ mol-1, log A = 11.69 s-1; the third step : E = 261.73 kJ mol-1, log A = 11.23 s-1. A combination reaction of the dehydration and dehydroxylation is observed, and controlled by one n-order reaction ( F n model), E = 8.99 kJ mol-1, log A = -1.91 s-1.

  8. Effects of pressure on the thermal decomposition kinetics, chemical reactivity and phase behavior of RDX

    SciTech Connect

    Miller, P.J. ); Block, S.; Piermarini, G.J. )

    1991-01-01

    The effects of pressure on the thermal decomposition kinetics, chemical reactivity, and phase behavior of RDX have been studied by a combination of measurement techniques in conjunction with a high-pressure diamond anvil cell. These techniques include Fourier transform infrared (FTIR) spectroscopy for kinetic measurements and phase identification, energy dispersive x-ray powder diffraction for identification of the observed polymorphic forms and also compression measurements, and optical polarizing microscopy for visual detection and confirmation of phase transformations and determinations of transition pressures. The ruby method of pressure measurement was used in all methods employed. Studies were generally limited to the region where decomposition rates could be measured within reasonable laboratory time, i.e., below 10 GPa and 573 K. The P-T phase diagram for RDX was determined to 573 K and 7.0/GPa, delineating the stability fields of three solid phases, and the liquidus.

  9. CP: AN INVESTIGATION OF COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS, AND REACTION TO VARIOUS STIMULI

    SciTech Connect

    Weese, R K; Burnham, A K; Fontes, A T

    2005-03-23

    The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.

  10. Kinetic and microstructural studies of thermal decomposition in uranium mononitride compacts subjected to heating in high-purity helium

    NASA Astrophysics Data System (ADS)

    Lunev, A. V.; Mikhalchik, V. V.; Tenishev, A. V.; Baranov, V. G.

    2016-07-01

    Although uranium mononitride has a high melting point (≈3100 K), it often decomposes well below this temperature. The threshold and kinetics of thermal decomposition depend on samples' chemical content and on gas environment. However, most experiments with uranium nitride samples were done so far in vacuum conditions and did not allow thorough examination of reaction kinetics at high temperatures. This research focuses on studying the different stages of thermal decomposition in uranium nitride samples subjected to heating in helium. Mass loss and thermal effects are identified with simultaneous thermal analysis (STA), while scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to register phase and compositional changes. Thermal decomposition in uranium nitride samples is found to be a multi-stage process with the final stage characterized by uranium vaporization. The results are useful for estimating the high-temperature behaviour of uranium nitride fuel during its fabrication and performance in some of Gen IV reactors.

  11. A quasimechanism of melt acceleration in the thermal decomposition of crystalline organic solids

    SciTech Connect

    Henson, Bryan F

    2009-01-01

    It has been know for half a century that many crystalline organic solids undergo an acceleration in the rate of thermal decomposition as the melting temperature is approached. This acceleration terminates at the melting point, exhibiting an Arrhenius-like temperature dependence in the faster decomposition rate from the liquid phase. This observation has been modeled previously using various premelting behaviors based on e.g. freezing point depression induced by decomposition products or solvent impurities. These models do not, however, indicate a mechanism for liquid formation and acceleration which is an inherent function of the bulk thermodynamics of the molecule. Here we show that such an inherent thermodynamic mechanism for liquid formation exists in the form of the so-called quasi-liquid layer at the solid surface. We explore a kinetic mechanism which describes the acceleration of rate and is a function of the free energies of sublimation and vaporization. We construct a differential rate law from these thermodynamic free energies and a normalized progress variable. We further construct a reduced variable formulation of the model which is a simple function of the metastable liquid activity below the melting point, and show that it is applicable to the observed melt acceleration in several common organic crystalline solids. A component of the differential rate law, zero order in the progress variable, is shown to be proportional to the thickness of the quasiliquid layer predicted by a recent thermodynamic theory for this phenomenon. This work therefore serves not only to provide new insight into thermal decomposition in a broad class or organic crystalline solids, but also further validates the underlying thermodynamic nature of the phenomenon of liquid formation on the molecular surface at temperatures below the melting point.

  12. Mass Spectrometry Characterization of the Thermal Decomposition/Digestion (TDD) at Cysteine in Peptides and Proteins in the Condensed Phase

    NASA Astrophysics Data System (ADS)

    Basile, Franco; Zhang, Shaofeng; Kandar, Sujit Kumar; Lu, Liang

    2011-11-01

    We report on the characterization by mass spectrometry (MS) of a rapid, reagentless and site-specific cleavage at the N-terminus of the amino acid cysteine (C) in peptides and proteins induced by the thermal decomposition at 220-250 °C for 10 s in solid samples. This thermally induced cleavage at C occurs under the same conditions and simultaneously to our previously reported thermally induced site-specific cleavage at the C-terminus of aspartic acid (D) (Zhang, S.; Basile, F. J. Proteome Res. 2007, 6, (5), 1700-1704). The C cleavage proceeds through cleavage of the nitrogen and α-carbon bond (N-terminus) of cysteine and produces modifications at the cleavage site with an amidation (-1 Da) of the N-terminal thermal decomposition product and a -32 Da mass change of the C-terminal thermal decomposition product, the latter yielding either an alanine or β-alanine residue at the N-terminus site. These modifications were confirmed by off-line thermal decomposition electrospray ionization (ESI)-MS, tandem MS (MS/MS) analyses and accurate mass measurements of standard peptides. Molecular oxygen was found to be required for the thermal decomposition and cleavage at C as it induced an initial cysteine thiol side chain oxidation to sulfinic acid. Similar to the thermally induced D cleavage, missed cleavages at C were also observed. The combined thermally induced digestion process at D and C, termed thermal decomposition/digestion (TDD), was observed on several model proteins tested under ambient conditions and the site-specificity of the method confirmed by MS/MS.

  13. Differential Scanning Calorimetry of Volatile-bearing Iron Minerals Under Mars-like Pressures: New Insights into Energetics and Mechanisms of Thermal Decomposition

    NASA Technical Reports Server (NTRS)

    Lin, I-C.; Lauer, H. V., Jr.; Golden, D. C.; Ming, D. W.

    2000-01-01

    Lepidocrocite and siderite both exhibit different enthalpic events during their decomposition at reduced pressures when compared to those at ambient pressure, allowing us looking into the mechanisms of thermal decomposition at Mars-like pressures.

  14. Structure-Activity Relationship Analysis of the Thermal Stabilities of Nitroaromatic Compounds Following Different Decomposition Mechanisms.

    PubMed

    Li, Jiazhong; Liu, Huanxiang; Huo, Xing; Gramatica, Paola

    2013-02-01

    The decomposition behavior of energetic materials is very important for the safety problems concerning their production, transportation, use and storage, because molecular decomposition is intimately connected to their explosive properties. Nitroaromatic compounds, particularly nitrobenzene derivatives, are often considered as prototypical energetic molecules, and some of them are commonly used as high explosives. Quantitative structure-activity relationship (QSAR) represents a potential tool for predicting the thermal stability properties of energetic materials. But it is reported that constructing general reliable models to predict their stability and their potential explosive properties is a very difficult task. In this work, we make our efforts to investigate the relationship between the molecular structures and corresponding thermal stabilities of 77 nitrobenzene derivatives with various substituent functional groups (in ortho, meta and/or para positions). The proposed best MLR model, developed by the new software QSARINS, based on Genetic Algorithm for variable selection and with various validation tools, is robust, stable and predictive with R(2) of 0.86, QLOO (2) of 0.79 and CCC of 0.90. The results indicated that, though difficult, it is possible to build predictive, externally validated QSAR models to estimate the thermal stability of nitroaromatic compounds.

  15. Kinetics of switch grass pellet thermal decomposition under inert and oxidizing atmospheres.

    PubMed

    Chandrasekaran, Sriraam R; Hopke, Philip K

    2012-12-01

    Grass pellets are a renewable resource that have energy content similar to that of wood. However, the higher ash and chlorine content affects combustion. Thermal degradation analysis of a fuel is useful in developing effective combustion. Thermogravimetric analysis (TGA) of the thermal degradation of grass pellets under inert (nitrogen) and oxidizing (air) atmospheres was conducted. Non-isothermal conditions were employed with 4 different heating rates. Kinetic parameters (activation energy and pre-exponential factors) were estimated using the iso-conversional method. Both pyrolysis and oxidative atmospheric thermal degradation exhibited two major loss process: volatilization of cellulose, hemicelluloses and lignin and burning or slow oxidation of the residual char. The activation energy and pre-exponential factors were high for the oxidizing environment. During pyrolysis, major decomposition occurred with 40% to 75% conversion of the mass to gas with an activation energy of 314 kJ/mol. In air the decomposition occurred with 30% to 55% conversion with an activation energy of 556 kJ/mol. There was a substantial effect of heating rate on mass loss and mass loss rate. The TG shifted to higher temperature ranges on increasing the heating rate. In both pyrolyzing and oxidizing conditions, average combustion and devolatilization rates increased. Enhanced combustion takes place with higher activation energy in oxidizing atmosphere compared to the inert atmosphere due to presence of air.

  16. PROPERTIES OF CP: COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS, AND REACTION TO SPARK, FRICTION AND IMPACT

    SciTech Connect

    Weese, R K; Burnham, A K

    2005-09-28

    The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear and isothermal heating, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Differential scanning calorimetry, DSC, was used to monitor CP decomposition at linear heating rates of 1-7 C min{sup -1} in perforated pans and of 0.1-1.0 C min{sup -1} in sealed pans. The kinetic triplet was calculated using the LLNL code Kinetics05, and predictions for 210 and 240 C are compared to isothermal thermogravimetric analysis (TGA) experiments. Values are also reported for spark, friction, and impact sensitivity.

  17. Thermal Decomposition of Trinitrotoluene (TNT) with a New One-Dimensional Time to Explosion (ODTX) Apparatus

    SciTech Connect

    Tran, T D; Simpson, R L; Maienschein, J; Tarver, C

    2001-03-23

    The thermal explosion of trinitrotoluene (TNT) is used as a basis for evaluating the performance of a new One-Dimensional-Time-to-Explosion (ODTX) apparatus. The ODTX experiment involves holding a 12.7 mm-diameter spherical explosive sample under confinement (150 MPa) at a constant elevated temperature until the confining pressure is exceeded by the evolution of gases during chemical decomposition. The resulting time to explosion as a function of temperature provides valuable decomposition kinetic information. A comparative analysis of the measurements obtained from the new unit and an older system is presented. Discussion on selected performance aspects of the new unit will also be presented. The thermal explosion of TNT is highly dependent on the material. Analysis of the time to explosion is complicated by historical and experimental factors such as material variability, sample preparation, temperature measurement and system errors. Many of these factors will be addressed. Finally, a kinetic model using a coupled thermal and heat transport code (chemical TOPAZ) was used to match the experimental data.

  18. Thermal degradation kinetics and decomposition mechanism of PBSu nanocomposites with silica-nanotubes and strontium hydroxyapatite nanorods.

    PubMed

    Papageorgiou, D G; Roumeli, E; Chrissafis, K; Lioutas, Ch; Triantafyllidis, K; Bikiaris, D; Boccaccini, A R

    2014-03-14

    Novel poly(butylene succinate) (PBSu) nanocomposites containing 5 and 20 wt% mesoporous strontium hydroxyapatite nanorods (SrHNRs) and silica nanotubes (SiNTs) were prepared by melt-mixing. A systematic investigation of the thermal stability and decomposition kinetics of PBSu was performed using pyrolysis-gas chromatography-mass spectroscopy (Py-GC-MS) and thermogravimetry (TG). Thorough studies of evolving decomposition compounds along with the isoconversional and model-fitting analysis of mass loss data led to the proposal of a decomposition mechanism for PBSu. Moreover, the effects of SrHNRs and SiNTs on the thermal stability and decomposition kinetics of PBSu were also examined in detail. The complementary use of these techniques revealed that the incorporation of SiNTs in PBSu does not induce significant effects neither on its thermal stability nor on its decomposition mechanism. In contrast, the addition of SrHNRs resulted in the catalysis of the initial decomposition steps of PBSu and also in modified decomposition mechanisms and activation energies. The evolving gaseous products of PBSu and their evolution pattern in the SiNT nanocomposites were the same as in neat PBSu, while they were slightly modified for the SrHNR nanocomposites, confirming the findings from thermogravimetric analysis.

  19. The spectral properties of uranium hexafluoride and its thermal decomposition products

    NASA Technical Reports Server (NTRS)

    Krascella, N. L.

    1976-01-01

    This investigation was initiated to provide basic spectral data for gases of interest to the plasma core reactor concept. The attenuation of vacuum ultraviolet (VUV) radiation by helium at pressures up to 20 atm over path lengths of about 61 cm and in the approximate wavelength range between 80 and 300 nm was studied. Measurements were also conducted to provide basic VUV data with respect to UF6 and UF6/argon mixtures in the wavelength range between 80 and 120 nm. Finally, an investigation was initiated to provide basic spectral emission and absorption data for UF6 and possible thermal decomposition products of UF6 at elevated temperatures.

  20. Dynamic weakening and thermal decomposition during the Heart Mountain mega-landslide

    NASA Astrophysics Data System (ADS)

    Mitchell, T. M.; Smith, S. A.; Anders, M. H.; Di Toro, G.

    2012-12-01

    The 3400-km2 Heart Mountain landslide of northwestern Wyoming and southwestern Montana is the largest subaerial landslide known. This Eocene age slide slid ˜50 km on a carbonate rich basal layer ranging in thickness from a few tens of centimeters to several meters, along a shallow 2° slope, posing a long-standing question regarding its emplacement mechanism. It has recently been suggested that such large displacement was aided by strong dynamic weakening mechanism, thermal pressurization due to shear heating and thermal decomposition in the basal layer slip zone, with theoretical simulations suggesting slip velocities ranging between tens of meters per second to more than 100 ms-1. In this study, we present the results of a suite of high velocity friction experiments in a rotary shear configuration on initially intact carbonates collected from the Heart Mountain region, in attempt to reproduce conditions experienced in the slip zone of the basal section during emplacement of the landslide. Gouges were prepared from initially intact hostrocks of Madison limestone and Bighorn dolomite, and were sheared for a range of displacements up to 6 metres at normal stresses up to 25 MPa at slip rates up to 2 m/s. Mechanical results generally show strong dynamic weakening with peak friction dropping from 0.7 to a steady state friction as low as 0.1. Microstructural observations of the highly polished slip surfaces produced show localization of the principal slip surface to less than 100 microns thick. Thermal decomposition is evidenced by degassing bubbles in the rims of dolomite clasts, and the release of CO2 as measured by mass spectrometer during experiments, indicating that temperatures in the slip zone quickly reached the decomposition temperature of carbonates (at least 700 degrees) within just a few metres of slip. These results compare favorably with theoretical calculations and ample field evidence for carbonate decomposition during the emplacement. Independent

  1. Non-chemically Pure Magnetites Produced from Thermal Decomposition of Ankerites

    NASA Astrophysics Data System (ADS)

    Jiménez López, C.; Romanek, C.; Rodríguez-Navarro, A.; Pérez-González, T.; Rodríguez Navarro, C.

    2008-12-01

    It has been claimed that chemically pure magnetites (Fe3O4) can be obtained from thermal decomposition of (Fe, Mg, Ca)CO3 (Golden et al., 2004). Such an observation is critical, since it opens the possibility of an inorganic way of formation of the magnetites found on Martian meteorite ALH84001. Such a chemical purity is one of the parameters used, so far, to recognize bacterial origin of natural magnetites (Thomas-Keptra et al., 2001), since it has been demonstrated that biologically-controlled magnetites are chemically pure (Bazylinski and Frankel, 2004) . However, while Golden et al. (2004) obtained pure magnetite from an almost pure precursor, the ankerite cores in ALH84001 in which magnetites are embedded are far from being chemically pure, since they contain considerable amounts of Ca and Mg (Kopp and Humayun, 2003). In this study we have performed several experiments to analyze the chemical purity of magnetites produced by thermal decomposition of four ankerite samples sinthetized in the laboratory, and containing different amounts of Ca, Fe and Mg. Such a thermal decomposition was achieved by two procedures: (1) by heating the samples at 470°C under CO2 pressure and (2) by decomposing the ankerite "in situ" under the TEM (Transmission electron Microscopy) electron beam. Magnetite produced by the first procedure was analyzed by XRD to determine whether or not the resulting solid was a mixture of oxides or rather a solid solution of (Ca, Fe and Mg)oxide. Magnetites formed by the two methods were studied by High Resolution TEM. The chemical composition of about 20 crystals of each experiment was analyzed by EDAX. Under our experimental conditions, ankerites decomposed in magnetite crystals of about 5 nanometers in size. Magentite crystals arranged to keep the morphology of the precursor. Our results confirm that any of these magnetites is chemically pure, but rather, each one of them is a solid solution of Ca and Mg. Therefore, chemically pure magnetites

  2. High-temperature Raman study of L-alanine, L-threonine and taurine crystals related to thermal decomposition

    NASA Astrophysics Data System (ADS)

    Cavaignac, A. L. O.; Lima, R. J. C.; Façanha Filho, P. F.; Moreno, A. J. D.; Freire, P. T. C.

    2016-03-01

    In this work high-temperature Raman spectra are used to compare temperature dependence of the lattice mode wavenumber of L-alanine, L-threonine and taurine crystals. Anharmonic effects observed are associated with intermolecular N-H· · ·O hydrogen bond that plays an important role in thermal decomposition process of these materials. Short and strong hydrogen bonds in L-alanine crystal were associated with anharmonic effects in lattice modes leading to low thermal stability compared to taurine crystals. Connection between thermal decomposition process and anharmonic effects is furnished for the first time.

  3. A Review of Study on Thermal Energy Transport System by Synthesis and Decomposition Reactions of Methanol

    NASA Astrophysics Data System (ADS)

    Liu, Qiusheng; Yabe, Akira; Kajiyama, Shiro; Fukuda, Katsuya

    The study on thermal energy transport system by synthesis and decomposition reactions of methanol was reviewed. To promote energy conservation and global environment protection, a two-step liquid-phase methanol synthesis process, which starts with carbonylation of methanol to methyl formate, then followed by the hydrogenolysis of the formate, was studied to recover wasted or unused discharged heat from industrial sources for the thermal energy demands of residential and commercial areas by chemical reactions. The research and development of the system were focused on the following three points. (1) Development of low-temperature decomposition and synthetic catalysts, (2) Development of liquid phase reactor (heat exchanger accompanying chemical reaction), (3) Simulation of the energy transport efficiency of entire system which contains heat recovery and supply sections. As the result of the development of catalyst, promising catalysts which agree with the development purposes for the methyl formate decomposition reaction and the synthetic reaction are being developed though some studies remain for the methanol decomposition and synthetic reactions. In the fundamental development of liquid phase reactor, the solubilities of CO and H2 gases in methanol and methyl formate were measured by the method of total pressure decrease due to absorption under pressures up to 1500kPa and temperatures up to 140°C. The diffusivity of CO gas in methanol was determined by measuring the diameter and solution time of single CO bubbles in methanol. The chemical reaction rate of methanol synthesis by hydrogenolysis of methyl formate was measured using a plate-type of Raney copper catalyst in a reactor with rectangular channel and in an autoclave reactor. The reaction characteristics were investigated by carrying out the experiments at various temperatures, flow rates and at various catalyst development conditions. We focused on the effect of Raney copper catalyst thickness on the liquid

  4. Validation of Heat Transfer Thermal Decomposition and Container Pressurization of Polyurethane Foam.

    SciTech Connect

    Scott, Sarah Nicole; Dodd, Amanda B.; Larsen, Marvin E.; Suo-Anttila, Jill M.; Erickson, Kenneth L

    2014-09-01

    Polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. In fire environments, gas pressure from thermal decomposition of polymers can cause mechanical failure of sealed systems. In this work, a detailed uncertainty quantification study of PMDI-based polyurethane foam is presented to assess the validity of the computational model. Both experimental measurement uncertainty and model prediction uncertainty are examined and compared. Both the mean value method and Latin hypercube sampling approach are used to propagate the uncertainty through the model. In addition to comparing computational and experimental results, the importance of each input parameter on the simulation result is also investigated. These results show that further development in the physics model of the foam and appropriate associated material testing are necessary to improve model accuracy.

  5. Pyrolytic and Kinetic Characteristics of the Thermal Decomposition of Perilla frutescens Polysaccharide

    PubMed Central

    Zhou, Quancheng; Sheng, Guihua

    2012-01-01

    The thermal decomposition of Perilla frutescens polysaccharide was examined by thermogravimetry, differential thermogravimetry, and differential thermal analysis. The results showed that the mass loss of the substance proceeded in three steps. The first stage can be attributed to the expulsion of the water from ambient temperature to 182°C. The second stage corresponded to devolatilization from 182°C to 439°C. The residue slowly degraded in the third stage. The weight loss in air is faster than that in nitrogen, because the oxygen in air accelerated the pyrolytic reaction speed reaction. The heating rate significantly affected the pyrolysis of the sample. Similar activation energies of the degradation process (210–211 kJ mol−1) were obtained by the FWO, KAS, and Popescu techniques. According to Popescu mechanism functions, the possible kinetic model was estimated to be Avrami–Erofeev 20 g(α) = [−ln(1–α)]4. PMID:23300715

  6. Mechanism of thermal decomposition of K2FeO4 and BaFeO4: A review

    NASA Astrophysics Data System (ADS)

    Sharma, Virender K.; Machala, Libor

    2016-12-01

    This paper presents thermal decomposition of potassium ferrate(VI) (K2FeO4) and barium ferrate(VI) (BaFeO4) in air and nitrogen atmosphere. Mössbauer spectroscopy and nuclear forward scattering (NFS) synchrotron radiation approaches are reviewed to advance understanding of electron-transfer processes involved in reduction of ferrate(VI) to Fe(III) phases. Direct evidences of Fe V and Fe IV as intermediate iron species using the applied techniques are given. Thermal decomposition of K2FeO4 involved Fe V, Fe IV, and K3FeO3 as intermediate species while BaFeO3 (i.e. Fe IV) was the only intermediate species during the decomposition of BaFeO4. Nature of ferrite species, formed as final Fe(III) species, of thermal decomposition of K2FeO4 and BaFeO4 under different conditions are evaluated. Steps of the mechanisms of thermal decomposition of ferrate(VI), which reasonably explained experimental observations of applied approaches in conjunction with thermal and surface techniques, are summarized.

  7. Recombination Reactions in the Thermal Decomposition of Anisole: An Investigation of Benzene and Naphthalene Formation

    NASA Astrophysics Data System (ADS)

    Scheer, Adam; Ellison, Barney; Mukarakate, Calvin; Robichaud, David; Nimlos, Mark

    2010-03-01

    Thermal decompositions of anisole (C6H5OCH3) and methyl-deuterated anisole (C6H5OCD3) are studied using a hyperthermal tubular reactor and photoionization reflectron time-of-flight mass spectrometer. Gas exiting the reactor is subject to a supersonic expansion after a residence time of 65 μs, allowing detection of highly chemically reactive radical species. Anisole decomposes through loss of a methyl group (CH3) to form phenoxy radical (C6H5O), followed by ejection of a CO to form cyclopentadienyl radical (c-C5H5; CPDR). Benzene is generated primarily by thermal decomposition of methylcyclopentadiene (C5H5CH3; MCPD). The MCPD results from methyl radical recombination with CPDR. The MCPD then undergoes two hydrogen atom losses and a ring expansion resulting in benzene. At Twall = 1200 C -- 1300 C a large amount of propargyl radical (CH2CCH) is observed. Propargyl radical recombination accounts for a small fraction of the observed benzene. Naphthalene and its precursor intermediates (C10H10, C10H9), resulting from CPDR recombination, are also observed. The presence of benzene and naphthalene is confirmed with resonance-enhanced multiphoton ionization (REMPI).

  8. Investigation of thermodynamic parameters in the thermal decomposition of plastic waste-waste lube oil compounds.

    PubMed

    Kim, Yong Sang; Kim, Young Seok; Kim, Sung Hyun

    2010-07-01

    Thermal decomposition properties of plastic waste-waste lube oil compounds were investigated under nonisothermal conditions. Polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were selected as representative household plastic wastes. A plastic waste mixture (PWM) and waste lube oil (WLO) were mixed with mixing ratios of 33, 50, and 67 (w/w) % on a PWM weight basis, and thermogravimetric (TG) experiments were performed from 25 to 600 degrees C. The Flynn-Wall method and the Ozawa-Flynn-Wall method were used for analyses of thermodynamic parameters. In this study, activation energies of PWM/WLO compounds ranged from 73.4 to 229.6 kJ/mol between 0.2 and 0.8 of normalized mass conversions, and the 50% PWM/WLO compound had lower activation energies and enthalpies among the PWM/WLO samples at each mass conversion. At the point of maximum differential mass conversion, the analyzed activation energies, enthalpies, entropies, and Gibbs free energies indicated that mixing PWM and WLO has advantages in reducing energy to decrease the degree of disorder. However, no difference in overall energy that would require overcoming both thermal decomposition reactions and degree of disorder was observed among PWM/WLO compounds under these experimental conditions.

  9. In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus.

    PubMed

    Liu, Xiaolong; Wood, Joshua D; Chen, Kan-Sheng; Cho, EunKyung; Hersam, Mark C

    2015-03-05

    With a semiconducting band gap and high charge carrier mobility, two-dimensional (2D) black phosphorus (BP)—often referred to as phosphorene—holds significant promise for next generation electronics and optoelectronics. However, as a 2D material, it possesses a higher surface area to volume ratio than bulk BP, suggesting that its chemical and thermal stability will be modified. Herein, an atomic-scale microscopic and spectroscopic study is performed to characterize the thermal degradation of mechanically exfoliated 2D BP. From in situ scanning/transmission electron microscopy, decomposition of 2D BP is observed to occur at ∼400 °C in vacuum, in contrast to the 550 °C bulk BP sublimation temperature. This decomposition initiates via eye-shaped cracks along the [001] direction and then continues until only a thin, amorphous red phosphorus like skeleton remains. In situ electron energy loss spectroscopy, energy-dispersive X-ray spectroscopy, and energy-loss near-edge structure changes provide quantitative insight into this chemical transformation process.

  10. An investigation on the modelling of kinetics of thermal decomposition of hazardous mercury wastes.

    PubMed

    Busto, Yailen; M G Tack, Filip; Peralta, Luis M; Cabrera, Xiomara; Arteaga-Pérez, Luis E

    2013-09-15

    The kinetics of mercury removal from solid wastes generated by chlor-alkali plants were studied. The reaction order and model-free method with an isoconversional approach were used to estimate the kinetic parameters and reaction mechanism that apply to the thermal decomposition of hazardous mercury wastes. As a first approach to the understanding of thermal decomposition for this type of systems (poly-disperse and multi-component), a novel scheme of six reactions was proposed to represent the behaviour of mercury compounds in the solid matrix during the treatment. An integration-optimization algorithm was used in the screening of nine mechanistic models to develop kinetic expressions that best describe the process. The kinetic parameters were calculated by fitting each of these models to the experimental data. It was demonstrated that the D₁-diffusion mechanism appeared to govern the process at 250°C and high residence times, whereas at 450°C a combination of the diffusion mechanism (D₁) and the third order reaction mechanism (F3) fitted the kinetics of the conversions. The developed models can be applied in engineering calculations to dimension the installations and determine the optimal conditions to treat a mercury containing sludge.

  11. Synthesis and Thermal Decomposition Mechanism of the Energetic Compound 3,5-Dinitro-4-nitroxypyrazole

    NASA Astrophysics Data System (ADS)

    Feng, Xiao-Qin; Cao, Duan-Lin; Cui, Jian-Lan

    2016-07-01

    A novel energetic material, 3,5-dinitro-4-nitroxypyrazole (DNNP), was synthesized via nitration and nucleophilic substitution reaction using 4-chloropyrazole as raw material. The structure of DNNP was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and elemental analysis. Its detonation properties were calculated and compared with those of other commonly used energetic compounds. The thermal decomposition mechanism of DNNP was studied by means of thermogravimetry and differential scanning calorimetry coupled with a mass spectrometry (DSC-MS). The results show that the detonation properties of DNNP were better than those of TNT and comparable to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). In addition, the thermal decomposition mechanism of DNNP was supposed. Initially, the O-NO2 bond was broken, thereby producing a nitropyrazole oxygen radical. Subsequently, the nitropyrazole oxygen radical was decomposed by free radical cleavage of nitro or isomerized to nitritepyrazole and subsequently decomposed by free radical cleavage of the nitroso group. Finally, pyrazole ring fission occurred and produced N2, NO, N2O, and CO2.

  12. Influence of thermal treatment on the formation of zirconia nanostructured powder by thermal decomposition of different precursors

    NASA Astrophysics Data System (ADS)

    Stoia, Marcela; Barvinschi, Paul; Barbu-Tudoran, Lucian; Negrea, Adina; Barvinschi, Floricica

    2013-10-01

    The paper presents some results concerning the preparation of zirconia powders starting from ZrOCl2·8H2O by using two synthesis methods: (a) precipitation with NH3, at 90 °C, and (b) thermal decomposition of carboxylate precursors, obtained in the reaction of zirconium nitrate and two different alcohols, 1,3-propanediol (PD) and poly(vinyl alcohol) (PVA), at 150 °C. The precursors obtained at different temperatures have been characterized by thermal analysis (TG, DTA) and FT-IR spectroscopy. DTA analysis evidenced very clearly the transition temperatures between zirconia crystalline phases. The precursors have been annealed at different temperatures in order to obtain zirconia powders and the as obtained powders have been characterized by means of X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). In case of precipitation method the presence of the tetragonal phase was observed at 400 °C, while the monoclinic phase appears at temperatures higher than 400 °C, becoming major crystalline phase starting with 700 °C. In case of the powders prepared by thermal decomposition of carboxylate precursors, the tetragonal phase was formed at temperatures below 700 °C, when the monoclinic phase begin to crystallize as secondary phase, in a higher proportion for the samples synthesized with 1,3-propanediol. All powders annealed at 1200 °C are pure monoclinic zirconia. SEM images have evidenced for the zirconia powders annealed at 1000 °C particles with diameters up to 150 nm, agglomerated in micrometer-sized aggregates, more individualized and homogenous than that obtained in the case of zirconia powder synthesized with poly(vinyl alcohol).

  13. Mathematical simulation of thermal decomposition processes in coking polymers during intense heating

    SciTech Connect

    Shlenskii, O.F.; Polyakov, A.A.

    1994-12-01

    Description of nonstationary heat transfer in heat-shielding materials based on cross-linked polymers, mathematical simulation of chemical engineering processes of treating coking and fiery coals, and designing calculations all require taking thermal destruction kinetics into account. The kinetics of chemical transformations affects the substance density change depending on the temperature, the time, the heat-release function, and other properties of materials. The traditionally accepted description of the thermal destruction kinetics of coking materials is based on formulating a set of kinetic equations, in which only chemical transformations are taken into account. However, such an approach does not necessarily agree with the obtained experimental data for the case of intense heating. The authors propose including the parameters characterizing the decrease of intermolecular interaction in a comparatively narrow temperature interval (20-40 K) into the set of kinetic equations. In the neighborhood of a certain temperature T{sub 1}, which is called the limiting temperature of thermal decomposition, a decrease in intermolecular interaction causes an increase in the rates of chemical and phase transformations. The effect of the enhancement of destruction processes has been found experimentally by the contact thermal analysis method.

  14. Borohydride Catalysis of Nitramine Thermal Decomposition and Combustion. 3. Literature Review and Wrap-Up Discussion of Possible Chemical Mechanisms

    DTIC Science & Technology

    1990-07-01

    NO2 )) forms. ie have already alluded above to the effects of added BroHIO= and BI2HI2 on formation of these products. 5 Initially, formic acid ...TIC 7;LE COPY- TECHNICAL REPORT BRL-TR-3126 co ’-0BRL N N 1 BOROHYDRIDE CATALYSIS OF NITRAMINE THERMAL DECOMPOSITION AND COMBUSTION: "III...SUITITLE O""maI BOROHYDRIDE CATALYSIS OF NITRAMINE THERMAL DECOMPOSITION AND COMBUSTION: 111. LITERATURE REVIEW AND WRAP-UP DISCUSSION OF POSSIBLE

  15. Thermal decomposition rate of MgCO3 as an inorganic astrobiological matrix in meteorites

    NASA Astrophysics Data System (ADS)

    Bisceglia, E.; Longo, G. Micca; Longo, S.

    2017-04-01

    Carbonate minerals, likely of hydrothermal origins and included into orthopyroxenite, have been extensively studied in the ALH84001 meteorite. In this meteorite, nanocrystals comparable with those produced by magnetotactic bacteria have been found into a carbonate matrix. This leads naturally to a discussion of the role of such carbonates in panspermia theories. In this context, the present work sets the basis of a criterion to evaluate whether a carbonate matrix in a meteor entering a planetary atmosphere would be able to reach the surface. As a preliminary step, the composition of carbonate minerals in the ALH84001 meteorite is reviewed; in view of the predominance of Mg in these carbonates, pure magnesite (MgCO3) is proposed as a mineral model. This mineral is much more sensitive to high temperatures reached during an entry process, compared with silicates, due to facile decomposition into MgO and gaseous carbon dioxide (CO2). A most important quantity for further studies is therefore the decomposition rate expressed as CO2 evaporation rate J (molecules/m2 s). An analytical expression for J(T) is given using the Langmuir law, based on CO2 pressure in equilibrium with MgCO3 and MgO at the surface temperature T. Results suggest that carbonate minerals rich in magnesium may offer much better thermal protection to embedded biological matter than silicates and significantly better than limestone, which was considered in previous studies, in view of the heat absorbed by their decomposition even at moderate temperatures. This first study can be extended in the future to account for more complex compositions, including Fe and Ca.

  16. Thermal decomposition of dolomite under CO2: insights from TGA and in situ XRD analysis.

    PubMed

    Valverde, Jose Manuel; Perejon, Antonio; Medina, Santiago; Perez-Maqueda, Luis A

    2015-11-28

    Thermal decomposition of dolomite in the presence of CO2 in a calcination environment is investigated by means of in situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The in situ XRD results suggest that dolomite decomposes directly at a temperature around 700 °C into MgO and CaO. Immediate carbonation of nascent CaO crystals leads to the formation of calcite as an intermediate product of decomposition. Subsequently, decarbonation of this poorly crystalline calcite occurs when the reaction is thermodynamically favorable and sufficiently fast at a temperature depending on the CO2 partial pressure in the calcination atmosphere. Decarbonation of this dolomitic calcite occurs at a lower temperature than limestone decarbonation due to the relatively low crystallinity of the former. Full decomposition of dolomite leads also to a relatively low crystalline CaO, which exhibits a high reactivity as compared to limestone derived CaO. Under CO2 capture conditions in the Calcium-Looping (CaL) process, MgO grains remain inert yet favor the carbonation reactivity of dolomitic CaO especially in the solid-state diffusion controlled phase. The fundamental mechanism that drives the crystallographic transformation of dolomite in the presence of CO2 is thus responsible for its fast calcination kinetics and the high carbonation reactivity of dolomitic CaO, which makes natural dolomite a potentially advantageous alternative to limestone for CO2 capture in the CaL technology as well as SO2in situ removal in oxy-combustion fluidized bed reactors.

  17. Unimolecular thermal decomposition of phenol and d5-phenol: Direct observation of cyclopentadiene formation via cyclohexadienone

    NASA Astrophysics Data System (ADS)

    Scheer, Adam M.; Mukarakate, Calvin; Robichaud, David J.; Nimlos, Mark R.; Carstensen, Hans-Heinrich; Barney Ellison, G.

    2012-01-01

    The pyrolyses of phenol and d5-phenol (C6H5OH and C6D5OH) have been studied using a high temperature, microtubular (μtubular) SiC reactor. Product detection is via both photon ionization (10.487 eV) time-of-flight mass spectrometry and matrix isolation infrared spectroscopy. Gas exiting the heated reactor (375 K-1575 K) is subject to a free expansion after a residence time in the μtubular reactor of approximately 50-100 μs. The expansion from the reactor into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. We find that the initial decomposition steps at the onset of phenol pyrolysis are enol/keto tautomerization to form cyclohexadienone followed by decarbonylation to produce cyclopentadiene; C6H5OH → c-C6H6 = O → c-C5H6 + CO. The cyclopentadiene loses a H atom to generate the cyclopentadienyl radical which further decomposes to acetylene and propargyl radical; c-C5H6 → c-C5H5 + H → HC≡CH + HCCCH2. At higher temperatures, hydrogen loss from the PhO-H group to form phenoxy radical followed by CO ejection to generate the cyclopentadienyl radical likely contributes to the product distribution; C6H5O-H → C6H5O + H → c-C5H5 + CO. The direct decarbonylation reaction remains an important channel in the thermal decomposition mechanisms of the dihydroxybenzenes. Both catechol (o-HO-C6H4-OH) and hydroquinone (p-HO-C6H4-OH) are shown to undergo decarbonylation at the onset of pyrolysis to form hydroxycyclopentadiene. In the case of catechol, we observe that water loss is also an important decomposition channel at the onset of pyrolysis.

  18. Structural, optical and magnetic properties of gadolinium sesquioxide nanobars synthesized via thermal decomposition of gadolinium oxalate

    SciTech Connect

    Manigandan, R.; Giribabu, K.; Suresh, R.; Vijayalakshmi, L.; Stephen, A.; Narayanan, V.

    2013-10-15

    Graphical abstract: - Highlights: • The cubic Gd{sub 2}O{sub 3} nanobars are synthesized by decomposition of C{sub 6}H{sub 20}Gd{sub 2}O{sub 22}. • The nanoparticles are rectangular bar shape with high porous surface. • The combination of magnetic and optical properties within a single particle. • The Gd{sub 2}O{sub 3} nanobars have tailorable nanostructure, wide bandgap and are paramagnetic. - Abstract: Gadolinium oxide nanobars were obtained by thermal decomposition of gadolinium oxalate, which was synthesized by the chemical precipitation method along with glycerol. The functional group analysis and formation of gadolinium oxide from gadolinium oxalate were characterized by the Fourier transform infrared spectroscopy and thermo gravimetric analyzer. The crystal structure, average crystallite size, and lattice parameter were analyzed by X-ray diffraction technique. Moreover, Raman shifts, elemental composition and morphology of the gadolinium oxide was widely investigated by the laser Raman microscope, X-ray photoelectron spectroscopy, FE-SEM-EDAX and HR-TEM, respectively. Furthermore, the optical properties like band gap, absorbance measurement of the gadolinium oxide were extensively examined. In addition, the paramagnetic property of gadolinium oxide nanobars was explored by the vibrating sample magnetometer.

  19. Band gap energy and optical transitions in polyenes formed by thermal decomposition of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Kulak, A. I.; Bondarava, G. V.; Shchurevich, O. A.

    2013-07-01

    The band gap of the ensemble of oligoene clusters formed by thermocatalytic decomposition of polyvinyl alcohol is parametrized using optical absorption spectra. A band gap energy of E gm =1.53 ± 0.02 eV at the end of an infinite polyene chain is found by extrapolating the energies of π → π* transitions in clusters with a number of double bonds varying from 4 to 12. This value is close to the band gap of trans-polyacetylene and the lower bound for the Tauc energy E gT =1.50 eV, which characterizes the minimum interband transition energy. E gT is essentially independent of the concentration of oligoene clusters, which is determined by the concentration of the AlCl3 thermal decomposition catalyst. The Urbach energy determined from the long wavelength edge of the spectrum falls from 2.21 to 0.66 eV as the AlCl3 concentration is raised from 11.1 to 41.7 mmol per mol of polyvinyl alcohol structural units.

  20. Thermal Decomposition of C7H7 Radicals; Benzyl, Tropyl, and Norbornadienyl

    NASA Astrophysics Data System (ADS)

    Buckingham, Grant; Ellison, Barney; Daily, John W.; Ahmed, Musahid

    2015-06-01

    Benzyl radical (C6H5CH2) and two other C7H7 radicals are commonly encountered in the combustion of substituted aromatic compounds found in biofuels and gasoline. High temperature pyrolysis of benzyl radical requires isomerization to other C7H7 radicals that may include cycloheptatrienyl (tropyl) radical (cyc-C7H7) and norbornadienyl radical. The thermal decomposition of all three radicals has now been investigated using a micro-reactor that heats dilute gas-phase samples up to 1600 K and has a residence time of about 100 μ-sec. The pyrolysis products exit the reactor into a supersonic expansion and are detected using synchrotron-based photoionization mass spectrometry and matrix-isolation IR spectroscopy. The products of the pyrolysis of benzyl radical (C6H5CH2) along with three isotopomers (C6H513CH2, C6D5CH2, and C6H5CD2) were detected and identified. The distribution of 13C atoms and D atoms indicate that multiple different decomposition pathways are active. Buckingham, G. T., Ormond, T. K., Porterfield, J. P., Hemberger, P., Kostko, O., Ahmed, M., Robichaud, D. J., Nimlos, M. R., Daily, J. W., Ellison, G. B. 2015, Journal of Chemical Physics 142 044307

  1. Theoretical Study of the Thermal Decomposition of Carboxylic Acids at Pyrolysis Temperature

    SciTech Connect

    Clark, J. M.; Robichaud, D. J.; Nimlos, M. R.

    2013-01-01

    Carboxylic acids are important in the processing of biomass into renewable fuels and chemicals. They are formed from the pretreatment and pyrolysis of hemicellulose biopolymers and are released from the decomposition of sugars. They result from the deconstruction of polyhydroxyalkanoates (bacterial carbon storage polymers) from fatty acids derived from algae, bacteria, and oil crops. The thermal deoxygenation of carboxylic acids is an important step in the conversion of biomass into aliphatic hydrocarbons suitable for use in renewable biofuels and as petrochemical replacements. Decarboxylation, a primary decomposition pathway under pyrolysis conditions, represents an ideal conversion process, because it eliminates two atoms of oxygen for every carbon atom removed. Problematically, additional deoxygenation processes exist (e.g. dehydration) that are in direct competition with decarboxylation and result in the formation of reactive and more fragmented end products. To better understand the competition between decarboxylation and other deoxygenation processes and to gain insight into possible catalysts that would favor decarboxylation, we have investigated the mechanisms and thermochemistry of the various unimolecular and bimolecular deoxygenation pathways for a family of C1-C4 organic acids using electronic structure calculations at the M06-2X/6-311++G(2df,p) level of theory.

  2. Enhanced Thermal Decomposition Properties of CL-20 through Space-Confining in Three-Dimensional Hierarchically Ordered Porous Carbon.

    PubMed

    Chen, Jin; He, Simin; Huang, Bing; Wu, Peng; Qiao, Zhiqiang; Wang, Jun; Zhang, Liyuan; Yang, Guangcheng; Huang, Hui

    2017-03-29

    High energy and low signature properties are the future trend of solid propellant development. As a new and promising oxidizer, hexanitrohexaazaisowurtzitane (CL-20) is expected to replace the conventional oxidizer ammonium perchlorate to reach above goals. However, the high pressure exponent of CL-20 hinders its application in solid propellants so that the development of effective catalysts to improve the thermal decomposition properties of CL-20 still remains challenging. Here, 3D hierarchically ordered porous carbon (3D HOPC) is presented as a catalyst for the thermal decomposition of CL-20 via synthesizing a series of nanostructured CL-20/HOPC composites. In these nanocomposites, CL-20 is homogeneously space-confined into the 3D HOPC scaffold as nanocrystals 9.2-26.5 nm in diameter. The effect of the pore textural parameters and surface modification of 3D HOPC as well as CL-20 loading amount on the thermal decomposition of CL-20 is discussed. A significant improvement of the thermal decomposition properties of CL-20 is achieved with remarkable decrease in decomposition peak temperature (from 247.0 to 174.8 °C) and activation energy (from 165.5 to 115.3 kJ/mol). The exceptional performance of 3D HOPC could be attributed to its well-connected 3D hierarchically ordered porous structure, high surface area, and the confined CL-20 nanocrystals. This work clearly demonstrates that 3D HOPC is a superior catalyst for CL-20 thermal decomposition and opens new potential for further applications of CL-20 in solid propellants.

  3. Thermal stability and mechanism of decomposition of emulsion explosives in the presence of pyrite.

    PubMed

    Xu, Zhi-Xiang; Wang, Qian; Fu, Xiao-Qi

    2015-12-30

    The reaction of emulsion explosives (ammonium nitrate) with pyrite was studied using techniques of TG-DTG-DTA. TG-DSC-MS was also used to analyze samples thermal decomposition process. When a mixture of pyrite and emulsion explosives was heated at a constant heating rate of 10K/min from room temperature to 350°C, exothermic reactions occurred at about 200°C. The essence of reaction between emulsion explosives and pyrite is the reaction between ammonium nitrate and pyrite. Emulsion explosives have excellent thermal stability but it does not mean it showed the same excellent thermal stability when pyrite was added. Package emulsion explosives were more suitable to use in pyrite shale than bulk emulsion explosives. The exothermic reaction was considered to take place between ammonium nitrate and pyrite where NO, NO2, NH3, SO2 and N2O gases were produced. Based on the analysis of the gaseous, a new overall reaction was proposed, which was thermodynamically favorable. The results have significant implication in the understanding of stability of emulsion explosives in reactive mining grounds containing pyrite minerals.

  4. Development of Boundary Condition Independent Reduced Order Thermal Models using Proper Orthogonal Decomposition

    NASA Astrophysics Data System (ADS)

    Raghupathy, Arun; Ghia, Karman; Ghia, Urmila

    2008-11-01

    Compact Thermal Models (CTM) to represent IC packages has been traditionally developed using the DELPHI-based (DEvelopment of Libraries of PHysical models for an Integrated design) methodology. The drawbacks of this method are presented, and an alternative method is proposed. A reduced-order model that provides the complete thermal information accurately with less computational resources can be effectively used in system level simulations. Proper Orthogonal Decomposition (POD), a statistical method, can be used to reduce the order of the degree of freedom or variables of the computations for such a problem. POD along with the Galerkin projection allows us to create reduced-order models that reproduce the characteristics of the system with a considerable reduction in computational resources while maintaining a high level of accuracy. The goal of this work is to show that this method can be applied to obtain a boundary condition independent reduced-order thermal model for complex components. The methodology is applied to the 1D transient heat equation.

  5. Surface studies of the thermal decomposition of triethylgallium on GaAs (100)

    NASA Astrophysics Data System (ADS)

    Murrell, A. J.; Wee, A. T. S.; Fairbrother, D. H.; Singh, N. K.; Foord, J. S.; Davies, G. J.; Andrews, D. A.

    1990-10-01

    The adsorption and surface decomposition of triethylgallium (TEG) on GaAs (100) has been studied using XPS and thermal desorption techniques. TEG is found to adsorb in a molecular form on the Ga rich (4×1) surface below 150 K. As the surface temperature is raised, this molecular state dissociates to form Ga and adsorbed ethyl species. The overall cracking reaction occurs in competition with the desorption of TEG and diethylgallium (DEG). Under the conditions of our experiments the adsorbed ethyl species formed above are found to dissociate above 600 K to form mainly gas phase ethene and hydrogen with traces of ethane, resulting in the formation of a pure Ga layer within the sensitivity limits imposed by XPS.

  6. Effect of surfactants on the size and shape of cobalt nanoparticles synthesized by thermal decomposition

    NASA Astrophysics Data System (ADS)

    Shao, Huiping; Huang, Yuqiang; Lee, Hyosook; Suh, Yong Jae; Kim, Chongoh

    2006-04-01

    Cobalt nanoparticles with various morphologies were synthesized by thermal decomposition of cobalt acetate in the presence of various surfactants at 260 °C. A combination of surfactants consisting of sufficient amount of oleic acid together with polyvinylpyrrolidone and oleylamine resulted in well-dispersed cubic cobalt nanoparticles of ~25 nm in average size. When 1,2-dodecanediol was added as a reducing agent to the surfactant mixture, triangular-prism-shaped nanoparticles of ~50 nm in average size were synthesized. Furthermore, an injection of trioctylphosphine into the reactor as an additional surfactant decreased the particle size to ~10 nm. The XRD pattern of the prism-like particles corresponded to hexagonal close-packed crystalline phase of cobalt.

  7. Thermal decomposition study of monovarietal extra virgin olive oil by simultaneous thermogravimetry/differential scanning calorimetry: relation with chemical composition.

    PubMed

    Vecchio, Stefano; Cerretani, Lorenzo; Bendini, Alessandra; Chiavaro, Emma

    2009-06-10

    Thermal decomposition of 12 monovarietal extra virgin olive oils from different geographical origins (eight from Italy, two from Spain, and the others from Tunisia) was evaluated by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses. All extra virgin olive oils showed a complex multistep decomposition pattern with the first step that exhibited a quite different profile among samples. Thermal properties of the two peaks obtained by the deconvolution of the first step of decomposition by DSC were related to the chemical composition of the samples (triacylglycerols, fatty acids, total phenols and antioxidant activity). Onset temperatures of the thermal decomposition transition and T(p) values of both deconvoluted peaks as well as the sum of enthalpy were found to exhibit statistically significant correlations with chemical components of the samples, in particular palmitic and oleic acids and related triacylglycerols. Activation energy values of the second deconvoluted peak obtained by the application of kinetic procedure to the first step of decomposition were also found to be highly statistically correlated to the chemical composition, and a stability scale among samples was proposed on the basis of its values.

  8. Experimental and modeling study of the thermal decomposition of methyl decanoate

    PubMed Central

    Herbinet, Olivier; Glaude, Pierre-Alexandre; Warth, Valérie; Battin-Leclerc, Frédérique

    2013-01-01

    The experimental study of the thermal decomposition of methyl decanoate was performed in a jet-stirred reactor at temperatures ranging from 773 to 1123 K, at residence times between 1 and 4 s, at a pressure of 800 Torr (106.6 kPa) and at high dilution in helium (fuel inlet mole fraction of 0.0218). Species leaving the reactor were analyzed by gas chromatography. Main reaction products were hydrogen, carbon oxides, small hydrocarbons from C1 to C3, large 1-olefins from 1-butene to 1-nonene, and unsaturated esters with one double bond at the end of the alkyl chain from methyl-2-propenoate to methyl-8-nonenoate. At the highest temperatures, the formation of polyunsaturated species was observed: 1,3-butadiene, 1,3-cyclopentadiene, benzene, toluene, indene, and naphthalene. These results were compared with previous ones about the pyrolysis of n-dodecane, an n-alkane of similar size. The reactivity of both molecules was found to be very close. The alkane produces more olefins while the ester yields unsaturated oxygenated compounds. A detailed kinetic model for the thermal decomposition of methyl decanoate has been generated using the version of software EXGAS which was updated to take into account the specific chemistry involved in the oxidation of methyl esters. This model contains 324 species and 3231 reactions. It provided a very good prediction of the experimental data obtained in jet-stirred reactor. The formation of the major products was analyzed. The kinetic analysis showed that the retro-ene reactions of intermediate unsaturated methyl esters are of importance in low reactivity systems. PMID:23710078

  9. Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride.

    PubMed

    Lever, Sarah D; Papadaki, Maria

    2004-11-11

    The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified.

  10. Ab initio Kinetics of Methylamine Radical Thermal Decomposition and H-abstraction from Monomethylhydrazine by H Atom

    DTIC Science & Technology

    2014-08-01

    Technical Paper 3. DATES COVERED (From - To) December 2013- August 2014 4. TITLE AND SUBTITLE Ab initio Kinetics of Methylamine Radical Thermal...phase kinetics of H-abstraction reactions from CH3NHNH2 by H atoms was further investigated by ab initio second-order multireference perturbation...distribution unlimited Ab initio Kinetics of Methylamine Radical Thermal Decomposition and H-abstraction from Monomethylhydrazine by H Atom

  11. Mechanism of thermal decomposition of a pesticide for safety concerns: case of Mancozeb.

    PubMed

    Giroud, N; Dorge, S; Trouvé, G

    2010-12-15

    Thermal decomposition under both air and inert atmospheres of a commercial Mancozeb product was investigated through thermogravimetric analysis and laboratory scale thermal treatment from 20°C to 950°C, with analysis of gaseous and solid products. The aim of this study is the understanding of the thermal degradation mechanisms of a pesticide under different atmospheres and the chemical identification of the solid and gaseous pollutants which can be emitted during warehouse fires and which can constitute a threat for health and environment. Pyrolysis of Mancozeb takes place between 20°C and 950°C and lead essentially to CS(2) and H(2)S emissions with formation at 950°C of MnS and ZnS. Thermal oxidation of Mancozeb under air occurs between 150°C and 950°C with formation of CO, CO(2) and sulphur gases (CS(2) and SO(2)). The first step (155-226°C) is the loss of CS(2) and the formation of ethylene thiourea, ZnS and MnS. The metallic sulphides are oxidized in ZnO and MnSO(4) between 226°C and 650°C (steps 2 and 3). MnSO(4) is then oxidized in Mn(3)O(4) during the last step (step 4) between 650°C and 950°C. At 950°C, carbon recovery is close to 95%. Sulphur recovery is close to 98% with an equal partition between SO(2) and CS(2).

  12. Investigation of the effect of intensive ball milling in a planetary ball mill on the thermal decomposition of cadmium carbonate and basic zinc carbonate

    NASA Astrophysics Data System (ADS)

    Ksiadot zek, K.; Wacke, S.; Górecki, T.; Górecki, Cz

    2007-08-01

    The kinetics of thermal decomposition of cadmium carbonate CdCO3 and basic zinc carbonate ZnCO3·nZn(OH)2 and the effect of intensive milling in a planetary ball mill on its parameters, have been investigated. The values of the reaction heat and of the activation energies of thermal decomposition have been determined for both the compounds. Investigations of the thermal decomposition of the products of ball milling of investigated compounds revealed a slight effect of milling conditions on the reaction temperature and heat consumed during the thermal decomposition of ZnCO3·nZn(OH)2. No effect of ball milling on the thermal decomposition of CdCO3 has been found.

  13. Effect of thermal shock on the decomposition of rocks under controlled laboratory conditions

    NASA Astrophysics Data System (ADS)

    Kasanin-Grubin, Milica; Vezmar, Tijuana; Kuhn, Nikolaus J.

    2013-04-01

    The major factor determining the rate of weathering of a given rock are the climatic conditions of the surrounding environment, most notably type and amount of precipitation and temperature. For the latter, average annual temperature and where applicable, the frequency of freezing and thawing are often considered to be relevant for weathering. The rate of temperature change is mostly ignored. However, a rapid change in temperature, referred to as thermal shock could have more severe consequences of rock deterioration then gradual heating and cooling of rocks is gradual. Thermal shock induces a stress of such a magnitude that the material is unable to adjust fast enough and so it breaks down. The aim of this study is to examine the importance of mechanical decomposition of rocks when treated with thermal shock by freezing. The rate of decomposition of rocks of various sizes was measured based on their weight loss. In addition, they were immersed in water after freezing and the electrical conductivity and pH of the water were measured as an index for thermal-shock induced micro-fracturing. Samples of three rock types were chosen for the experiment: limestone, tuffaceous rock and basalt. Samples were examined in two separate cycles: (i) 24h immersion in ultra-clean water followed by 24h drying at 30o and (ii) 24h immersion, 24h temperature shock by freezing at -20˚C and 6h thawing. Each cycle was repeated approximately 20 times. In each cycle three different sizes of rock were examined: <16mm, 16-8mm and 8-5mm. Limestone mass decreased for both cycles, although more distinctly after repeated thermal shocks. Furthermore, the rate of decay decreased with increasing rock size. Tuffaceous rock exposed to cycle (i) also showed a significant weight loss. Somewhat surprisingly, the mass of the tuffaceous rock exposed to thermal shock increased by about 13% in all sample size groups. It is possible that pore volume increased during experiment and that the rocks became

  14. Thermal decomposition of HMX: Low temperature reaction kinetics and their use for assessing response in abnormal thermal environments and implications for long-term aging

    SciTech Connect

    Behrens, R.; Bulusu, S.

    1995-12-01

    The thermal decomposition of HMX between 175 and 200{degree}C has been studied using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) apparatus with a focus on the initial stages of the decomposition. The identity of thermal decomposition products is the same as that measured in previous higher temperature experiments. The initial stages of the decomposition are characterized by an induction period followed by two acceleratory periods. The Arrhenius parameters for the induction and two acceleratory periods are (Log(A) = 18.2 {plus_minus} 0.8, Ea = 48.2 {plus_minus} 1.8 kcal/mole), (Log(A) = 17.15 {plus_minus} 1.5 and Ea = 48.9 {plus_minus} 3.2 kcal/mole), (Log A) = 19.1 {plus_minus} 3.0 and Ea = 52.1 {plus_minus} 6.3 kcal/mole), respectively. This data can be used to calculate the time and temperature required to decompose a desired fraction of a sample that is being prepared to test the effect of thermal degradation on its sensitivity or burn rates. It can also be used to estimate the extent of decomposition that may be expected under normal storage conditions for munitions containing HMX. This data, along with previous mechanistic studies conducted at higher temperatures, suggest that the process that controls the early stages of decomposition of HMX in the solid phase is scission of the N-NO{sub 2} bond, reaction of the N0{sub 2} within a ``lattice cage`` to form the mononitroso analogue of HMX and decomposition of the mononitroso HMX within the HMX lattice to form gaseous products that are retained in bubbles or diffuse into the surrounding lattice.

  15. Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method

    PubMed Central

    2013-01-01

    By means of thermal decomposition, we prepared single-phase spherical Ni nanoparticles (23 to 114 nm in diameter) that are face-centered cubic in structure. The magnetic properties of the Ni nanoparticles were experimentally as well as theoretically investigated as a function of particle size. By means of thermogravimetric/differential thermal analysis, the Curie temperature TC of the 23-, 45-, 80-, and 114-nm Ni particles was found to be 335°C, 346°C, 351°C, and 354°C, respectively. Based on the size-and-shape dependence model of cohesive energy, a theoretical model is proposed to explain the size dependence of TC. The measurement of magnetic hysteresis loop reveals that the saturation magnetization MS and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect. By adopting a simplified theoretical model, we obtained MS values that are in good agreement with the experimental ones. Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer. PMID:24164907

  16. Analysis of polyethylene microplastics in environmental samples, using a thermal decomposition method.

    PubMed

    Dümichen, Erik; Barthel, Anne-Kathrin; Braun, Ulrike; Bannick, Claus G; Brand, Kathrin; Jekel, Martin; Senz, Rainer

    2015-11-15

    Small polymer particles with a diameter of less than 5 mm called microplastics find their way into the environment from polymer debris and industrial production. Therefore a method is needed to identify and quantify microplastics in various environmental samples to generate reliable concentration values. Such concentration values, i.e. quantitative results, are necessary for an assessment of microplastic in environmental media. This was achieved by thermal extraction in thermogravimetric analysis (TGA), connected to a solid-phase adsorber. These adsorbers were subsequently analysed by thermal desorption gas chromatography mass spectrometry (TDS-GC-MS). In comparison to other chromatographic methods, like pyrolyse gas chromatography mass spectrometry (Py-GC-MS), the relatively high sample masses in TGA (about 200 times higher than used in Py-GC-MS) analysed here enable the measurement of complex matrices that are not homogenous on a small scale. Through the characteristic decomposition products known for every kind of polymer it is possible to identify and even to quantify polymer particles in various matrices. Polyethylene (PE), one of the most important representatives for microplastics, was chosen as an example for identification and quantification.

  17. Dielectric Properties and Thermal Decomposition of K2Ni(SO4)2 Crystals

    NASA Astrophysics Data System (ADS)

    Marzougui, H.; Sánchez, V.; León-Luis, S. F.; Lozano-Gorrín, A. D.; Lalla, E.; Torres, M. E.; Attia-Essaies, S.; Ben Hassen-Chehimi, D.

    2016-11-01

    The dielectric properties of K2Ni(SO4)2 crystals have been measured as a function of frequency (100 Hz to 1 MHz) and temperature (400 K to 900 K). The results show that the real part of the conductivity follows the universal dielectric response, where the activation energy varies from 0.72 eV up to 1.08 eV for the temperature range studied. On the other hand, the permittivity and conductivity parameters present a change in their frequency dependence at around 620 K, suggesting that a phase transition might be taking place. To understand this unexpected result, complementary study by thermogravimetric and differential thermal analyses, X-ray powder diffraction analysis, and Raman spectroscopy measurements was carried out. The results suggest thermal decomposition of the original compound at 620 K as follows: 2K2Ni(SO4)2 → K2Ni2(SO4)3 + K2SO4.

  18. Perchlorate induced low temperature carbonate decomposition in the Mars Phoenix Thermal and Evolved Gas Analyzer (TEGA)

    NASA Astrophysics Data System (ADS)

    Cannon, K. M.; Sutter, B.; Ming, D. W.; Boynton, W. V.; Quinn, R.

    2012-07-01

    Simulated Thermal Evolved Gas Analyzer (TEGA) analyses have shown that a CO2 release detected between 400°C and 680°C by the Phoenix Lander's TEGA instrument may have been caused by a reaction between calcium carbonate and hydrated magnesium perchlorate. In our experiments a CO2 release beginning at 385 ± 12°C was attributed to calcite reacting with water vapor and HCl gas from the dehydration and thermal decomposition of Mg-perchlorate. The release of CO2 is consistent with the TEGA detection of CO2 released between 400 and 680°C, with the amount of CO2 increasing linearly with added perchlorate. X-ray diffraction (XRD) experiments confirmed CaCl2 formation from the reaction between calcite and HCl. These results have important implications for the Mars Science Laboratory (MSL) Curiosity rover. Heating soils may cause inorganic release of CO2; therefore, detection of organic fragments, not CO2 alone, should be used as definitive evidence for organics in Martian soils.

  19. Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

    NASA Astrophysics Data System (ADS)

    Vargeese, Anuj A.; Mija, S. J.; Muralidharan, Krishnamurthi

    2014-07-01

    Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride. Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedman's differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods. To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method. The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism. The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD). The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO2 shows no influence on the rate of decomposition. Possible explanations for these results are discussed. Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Energetic Materials to view the free supplemental file.

  20. The thermal decomposition of the benzyl radical in a heated micro-reactor. I. Experimental findings

    SciTech Connect

    Buckingham, Grant T.; Ormond, Thomas K.; Porterfield, Jessica P.; Ellison, G. Barney; Hemberger, Patrick; Kostko, Oleg; Ahmed, Musahid; Robichaud, David J.; Nimlos, Mark R.; Daily, John W.

    2015-01-28

    The pyrolysis of the benzyl radical has been studied in a set of heated micro-reactors. A combination of photoionization mass spectrometry (PIMS) and matrix isolation infrared (IR) spectroscopy has been used to identify the decomposition products. Both benzyl bromide and ethyl benzene have been used as precursors of the parent species, C{sub 6}H{sub 5}CH{sub 2}, as well as a set of isotopically labeled radicals: C{sub 6}H{sub 5}CD{sub 2}, C{sub 6}D{sub 5}CH{sub 2}, and C{sub 6}H{sub 5}{sup 13}CH{sub 2}. The combination of PIMS and IR spectroscopy has been used to identify the earliest pyrolysis products from benzyl radical as: C{sub 5}H{sub 4}=C=CH{sub 2}, H atom, C{sub 5}H{sub 4}—C ≡ CH, C{sub 5}H{sub 5}, HCCCH{sub 2}, and HC ≡ CH. Pyrolysis of the C{sub 6}H{sub 5}CD{sub 2}, C{sub 6}D{sub 5}CH{sub 2}, and C{sub 6}H{sub 5}{sup 13}CH{sub 2} benzyl radicals produces a set of methyl radicals, cyclopentadienyl radicals, and benzynes that are not predicted by a fulvenallene pathway. Explicit PIMS searches for the cycloheptatrienyl radical were unsuccessful, there is no evidence for the isomerization of benzyl and cycloheptatrienyl radicals: C{sub 6}H{sub 5}CH{sub 2}⇋C{sub 7}H{sub 7}. These labeling studies suggest that there must be other thermal decomposition routes for the C{sub 6}H{sub 5}CH{sub 2} radical that differ from the fulvenallene pathway.

  1. Unimolecular Thermal Decomposition of Phenol and d5-Phenol: Direct Observation of Cyclopentadiene Formation via Cyclohexadienone

    SciTech Connect

    Scheer, A. M.; Mukarakate, C.; Robichaud, D. J.; Nimlos, M. R.; Carstensen, H. H.; Barney, E. G.

    2012-01-28

    The pyrolyses of phenol and d{sub 5}-phenol (C{sub 6}H{sub 5}OH and C{sub 6}D{sub 5}OH) have been studied using a high temperature, microtubular ({mu}tubular) SiC reactor. Product detection is via both photon ionization (10.487 eV) time-of-flight mass spectrometry and matrix isolation infrared spectroscopy. Gas exiting the heated reactor (375 K-1575 K) is subject to a free expansion after a residence time in the {mu}tubular reactor of approximately 50-100 {micro}s. The expansion from the reactor into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. We find that the initial decomposition steps at the onset of phenol pyrolysis are enol/keto tautomerization to form cyclohexadienone followed by decarbonylation to produce cyclopentadiene; C{sub 6}H{sub 5}OH {yields} c-C{sub 6}H{sub 6} = O {yields} c-C{sub 5}H{sub 6} + CO. The cyclopentadiene loses a H atom to generate the cyclopentadienyl radical which further decomposes to acetylene and propargyl radical; c-C{sub 5}H{sub 6} {yields} c-C{sub 5}H{sub 5} + H {yields} HC {triple_bond} CH + HCCCH{sub 2}. At higher temperatures, hydrogen loss from the PhO-H group to form phenoxy radical followed by CO ejection to generate the cyclopentadienyl radical likely contributes to the product distribution; C{sub 6}H{sub 5}O-H {yields} C{sub 6}H{sub 5}O + H {yields} c-C{sub 5}H{sub 5} + CO. The direct decarbonylation reaction remains an important channel in the thermal decomposition mechanisms of the dihydroxybenzenes. Both catechol (o-HO-C{sub 6}H{sub 4}-OH) and hydroquinone (p-HO-C{sub 6}H{sub 4}-OH) are shown to undergo decarbonylation at the onset of pyrolysis to form hydroxycyclopentadiene. In the case of catechol, we observe that water loss is also an important decomposition channel at the onset of pyrolysis.

  2. Solar thermal decomposition of zinc oxide in aerosol flow for renewable hydrogen production

    NASA Astrophysics Data System (ADS)

    Perkins, Christopher Michael

    Hydrogen could be a clean replacement for fossil fuels. The Zn/ZnO solar thermochemical water-splitting cycle provides a renewable path to this fuel. Thermodynamic simulations showed that the Zn/ZnO cycle has the lowest temperature of all two-step metal oxide cycles, and the prediction of relatively high efficiency based on its lower temperature and number of steps led to its selection for further study. A rapid aerosol configuration for ZnO decomposition was chosen based on expectation of high reaction rates and small product particle production, and proof-of-concept experiments confirmed this assumption. Thermogravimetric studies of the thermal decomposition kinetics of ZnO showed that the rate followed a 2/3 order L'vov kinetic expression. The activation energy was found to be 353 +/- 25.9 kJ/mol, and a simple electrostatic model was used to describe the reaction mechanism. The pre-exponential factor was found, as expected, to vary inversely with the distance to a product concentration sink. Investigation of the aerosol decomposition of ZnO showed high forward conversion (˜60%) but low net yield (18%) of zinc due to recombination of product oxygen with nucleated zinc particles. Products that were initially converted had high surface area (15.5 +/- 0.13 g/m2), small particle size (5-70 nm), and relatively spherical morphology, properties desirable when considering the hydrolysis step of the water-splitting cycle. Rates in the aerosol reactor were found to be three orders of magnitude greater than those in a stationary configuration. Computational fluid dynamics (CFD) simulations of the aerosol reaction showed rapid particle heating and high forward conversion (>90%) in short residence times (<1.5s). Results could be used to scale a commercial size reactor, and the recommended particle size based on conversion and handling considerations was 1 mum. Reactor materials sensitive to oxidation were shown to be inappropriate for application due to high corrosion rates

  3. Thermal Decomposition Mechanisms of Lignin Model Compounds: From Phenol to Vanillin

    NASA Astrophysics Data System (ADS)

    Scheer, Adam Michael

    Lignin is a complex, aromatic polymer abundant in cellulosic biomass (trees, switchgrass etc.). Thermochemical breakdown of lignin for liquid fuel production results in undesirable polycyclic aromatic hydrocarbons that lead to tar and soot byproducts. The fundamental chemistry governing these processes is not well understood. We have studied the unimolecular thermal decomposition mechanisms of aromatic lignin model compounds using a miniature SiC tubular reactor. Products are detected and characterized using time-of-flight mass spectrometry with both single photon (118.2 nm; 10.487 eV) and 1 + 1 resonance-enhanced multiphoton ionization (REMPI) as well as matrix isolation infrared spectroscopy. Gas exiting the heated reactor (300 K--1600 K) is subject to a free expansion after a residence time of approximately 100 micros. The expansion into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. By understanding the unimolecular fragmentation patterns of phenol (C6H5OH), anisole (C6H 5OCH3) and benzaldehyde (C6H5CHO), the more complicated thermocracking processes of the catechols (HO-C 6H4-OH), methoxyphenols (HO-C6H4-OCH 3) and hydroxybenzaldehydes (HO-C6H4-CHO) can be interpreted. These studies have resulted in a predictive model that allows the interpretation of vanillin, a complex phenolic ether containing methoxy, hydroxy and aldehyde functional groups. This model will serve as a guide for the pyrolyses of larger systems including lignin monomers such as coniferyl alcohol. The pyrolysis mechanisms of the dimethoxybenzenes (H3C-C 6H4-OCH3) and syringol, a hydroxydimethoxybenzene have also been studied. These results will aid in the understanding of the thermal fragmentation of sinapyl alcohol, the most complex lignin monomer. In addition to the model compound work, pyrolyisis of biomass has been studied via the pulsed laser ablation of poplar wood. With the REMPI scheme, aromatic lignin decomposition

  4. Pursuing reliable thermal analysis techniques for energetic materials: decomposition kinetics and thermal stability of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50).

    PubMed

    Muravyev, Nikita V; Monogarov, Konstantin A; Asachenko, Andrey F; Nechaev, Mikhail S; Ananyev, Ivan V; Fomenkov, Igor V; Kiselev, Vitaly G; Pivkina, Alla N

    2016-12-21

    Thermal decomposition of a novel promising high-performance explosive dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) was studied using a number of thermal analysis techniques (thermogravimetry, differential scanning calorimetry, and accelerating rate calorimetry, ARC). To obtain more comprehensive insight into the kinetics and mechanism of TKX-50 decomposition, a variety of complementary thermoanalytical experiments were performed under various conditions. Non-isothermal and isothermal kinetics were obtained at both atmospheric and low (up to 0.3 Torr) pressures. The gas products of thermolysis were detected in situ using IR spectroscopy, and the structure of solid-state decomposition products was determined by X-ray diffraction and scanning electron microscopy. Diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX) was directly identified to be the most important intermediate of the decomposition process. The important role of bistetrazole diol (BTO) in the mechanism of TKX-50 decomposition was also rationalized by thermolysis experiments with mixtures of TKX-50 and BTO. Several widely used thermoanalytical data processing techniques (Kissinger, isoconversional, formal kinetic approaches, etc.) were independently benchmarked against the ARC data, which are more germane to the real storage and application conditions of energetic materials. Our study revealed that none of the Arrhenius parameters reported before can properly describe the complex two-stage decomposition process of TKX-50. In contrast, we showed the superior performance of the isoconversional methods combined with isothermal measurements, which yielded the most reliable kinetic parameters of TKX-50 thermolysis. In contrast with the existing reports, the thermal stability of TKX-50 was determined in the ARC experiments to be lower than that of hexogen, but close to that of hexanitrohexaazaisowurtzitane (CL-20).

  5. Infrared spectroscopic study on the thermal decomposition of external and internal gelation products of simulated mixed oxide nuclear fuel.

    PubMed

    Kumar, K Suresh; Bhat, N P

    2004-02-01

    The thermal decomposition of urania-ceria gel corresponding to the composition U(0.7)Ce(0.3)O(2+x) obtained through external and internal gelation routes were studied using infrared spectroscopy (IR). In the case of externally gelated compound, the gel decomposes with the release of H2O and NH3 below 500 degrees C. A part of the NH3 released is entrapped in the solid and above 500 degrees C self reduction occurs in which U(VI) in the gel is reduced to U3O8. The decomposition products were identified to be U3O8 and CeO2. In the case of internally gelated compound, decomposition similar to the one for externally gelated compound occurred below 500 degrees C. Above 500 degrees C the carbon present in the gel reduced U(VI) to UO2 which formed solid solution with CeO2 around 650 degrees C.

  6. In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe recycling of the transformation product.

    PubMed

    Gualtieri, Alessandro F; Gualtieri, Magdalena Lassinantti; Tonelli, Massimo

    2008-08-15

    The thermal transformation of asbestos into non-hazardous crystalline phases and their recycling is a promising solution for the "asbestos problem". The most common asbestos-containing industrial material produced worldwide is cement-asbestos. Knowledge of the kinetics of thermal transformation of asbestos fibers in cement-asbestos is of paramount importance for the optimization of the firing process at industrial scale. Here, environmental scanning electron microscopy (ESEM) was used for the first time to follow in situ the thermal transformation of chrysotile fibers present in cement-asbestos. It was found that the reaction kinetics of thermal transformation of chrysotile was highly slowed down in the presence of water vapor in the experimental chamber with respect to He. This was explained by chemisorbed water on the surface of the fibers which affected the dehydroxylation reaction and consequently the recrystallization into Mg-silicates. In the attempt to investigate alternative and faster firing routes for the decomposition of asbestos, a low melting glass was mixed with cement-asbestos and studied in situ to assess to which extent the decomposition of asbestos is favored. It was found that the addition of a low melting glass to cement-asbestos greatly improved the decomposition reaction and decreased the transformation temperatures.

  7. Synthesis, Crystal Structure, and Thermal Decomposition of the Cobalt(II) Complex with 2-Picolinic Acid

    PubMed Central

    Li, Di

    2014-01-01

    The cobalt(II) complex of 2-picolinic acid (Hpic), namely, [Co(pic)2(H2O)2] · 2H2O, was synthesized with the reaction of cobalt acetate and 2-picolinic acid as the reactants by solid-solid reaction at room temperature. The composition and structure of the complex were characterized by elemental analysis, infrared spectroscopy, single crystal X-ray diffraction, and thermogravimetry-differential scanning calorimetry (TG-DSC). The crystal structure of the complex belongs to monoclinic system and space group P2(1)/n, with cell parameters of a = 9.8468(7) Å, b = 5.2013(4) Å, c = 14.6041(15) Å, β = 111.745(6)°, V = 747.96(11) Å3, Z = 2, Dc = 1.666 g cm−3, R1 = 0.0297, and wR2 = 0.0831. In the title complex, the Co(II) ion is six-coordinated by two pyridine N atoms and two carboxyl O atoms from two 2-picolinic acid anions, and two O atoms from two H2O molecules, and forming a slightly distorted octahedral geometry. The thermal decomposition processes of the complex under nitrogen include dehydration and pyrolysis of the ligand, and the final residue is cobalt oxalate at about 450°C. PMID:24578654

  8. Thermochemical cycles for energy storage: Thermal decomposition of ZnCO sub 4 systems

    SciTech Connect

    Wentworth, W.E. )

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH{sub 4}HSO{sub 4}) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, reported herein, we have shown that when NH{sub 4}HSO{sub 4} is mixed with ZnO and decomposed, the resulting products can be released stepwise (H{sub 2}A{sub (g)} at {approximately}163{degrees}C, NH{sub 3(g)} at 365--418{degrees}C, and a mixture of SO{sub 2(g)} and SO{sub 3(g)} at {approximately}900{degrees}C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO{sub 4}). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V{sub 2}A{sub 5} and possibly other metal oxides.

  9. Feedback processes in cellulose thermal decomposition: implications for fire-retarding strategies and treatments

    NASA Astrophysics Data System (ADS)

    Ball, R.; McIntosh, A. C.; Brindley, J.

    2004-06-01

    A simple dynamical system that models the competitive thermokinetics and chemistry of cellulose decomposition is examined, with reference to evidence from experimental studies indicating that char formation is a low activation energy exothermal process and volatilization is a high activation energy endothermal process. The thermohydrolysis chemistry at the core of the primary competition is described. Essentially, the competition is between two nucleophiles, a molecule of water and an -OH group on C6 of an end glucosyl cation, to form either a reducing chain fragment with the propensity to undergo the bond-forming reactions that ultimately form char, or a levoglucosan end-fragment that depolymerizes to volatile products. The results of this analysis suggest that promotion of char formation under thermal stress can actually increase the production of flammable volatiles. Thus, we would like to convey an important safety message in this paper: in some situations where heat and mass transfer is restricted in cellulosic materials, such as furnishings, insulation, and stockpiles, the use of char-promoting treatments for fire retardation may have the effect of increasing the risk of flaming combustion.

  10. Reduction of nitrous oxide emissions from biological nutrient removal processes by thermal decomposition.

    PubMed

    Pedros, Philip B; Askari, Omid; Metghalchi, Hameed

    2016-12-01

    During the last decade municipal wastewater treatment plants have been regulated with increasingly stringent nutrient removal requirements including nitrogen. Typically biological treatment processes are employed to meet these limits. Although the nitrogen in the wastewater stream is reduced, certain steps in the biological processes allow for the release of gaseous nitrous oxide (N2O), a greenhouse gas (GHG). A comprehensive study was conducted to investigate the potential to mitigate N2O emissions from biological nutrient removal (BNR) processes by means of thermal decomposition. The study examined using the off gases from the biological process, instead of ambient air, as the oxidant gas for the combustion of biomethane. A detailed analysis was done to examine the concentration of N2O and 58 other gases that exited the combustion process. The analysis was based on the assumption that the exhaust gases were in chemical equilibrium since the residence time in the combustor is sufficiently longer than the chemical characteristics. For all inlet N2O concentrations the outlet concentrations were close to zero. Additionally, the emission of hydrogen sulfide (H2S) and ten commonly occurring volatile organic compounds (VOCs) were also examined as a means of odor control for biological secondary treatment processes or as potential emissions from an anaerobic reactor of a BNR process. The sulfur released from the H2S formed sulfur dioxide (SO2) and eight of the ten VOCs were destroyed.

  11. Sulfur speciation in hard coal by means of a thermal decomposition method.

    PubMed

    Spiewok, W; Ciba, J; Trojanowska, J

    2002-02-01

    A new method for the determination of organic and pyritic sulfur in hard coal is presented. The method is based on controlled thermal decomposition of coal sample in oxygen-free and oxygen atmospheres. The results for sulfur liberated in an argon atmosphere at temperatures up to 773 K were close to organic sulfur contents (Sorg), although owing to the definition of 'organic sulfur' the values were not directly comparable. Sorg contents are calculated from the difference between total sulfur content in coal and contents of this element in the form of sulfides, sulfates and pyrites. Sulfur contents, found in the second stage of analysis, were close to pyritic sulfur contents. The difference between total sulfur content and the sum of sulfur values obtained in stages I and II corresponded to sulfur contents in those samples which were neither decomposed nor oxidized at temperatures up to 1173 K. Although not comparable with such conventional concepts for industrial purposes these data are attractive due to the ease and rapidity of the new method for the control of sulfur streams in industrial processes.

  12. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

    SciTech Connect

    Hufschmid, Ryan D.; Arami, Hamed; Ferguson, R. Matthew; Gonzales, Marcela; Teeman, Eric M.; Brush, Lucien N.; Browning, Nigel D.; Krishnan, Kannan M.

    2015-06-03

    We present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting properties. Monodisperse superparamagnetic iron oxide nanoparticles were synthesized by thermal decomposition of three different iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) in organic solvents under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution. In particular, large quantities of excess surfactant (up to 25:1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase is also critical for establishing magnetic properties. As an example, we show the importance of obtaining the required iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled.

  13. Case study for model validation : assessing a model for thermal decomposition of polyurethane foam.

    SciTech Connect

    Dowding, Kevin J.; Leslie, Ian H.; Hobbs, Michael L.; Rutherford, Brian Milne; Hills, Richard Guy; Pilch, Martin M.

    2004-10-01

    A case study is reported to document the details of a validation process to assess the accuracy of a mathematical model to represent experiments involving thermal decomposition of polyurethane foam. The focus of the report is to work through a validation process. The process addresses the following activities. The intended application of mathematical model is discussed to better understand the pertinent parameter space. The parameter space of the validation experiments is mapped to the application parameter space. The mathematical models, computer code to solve the models and its (code) verification are presented. Experimental data from two activities are used to validate mathematical models. The first experiment assesses the chemistry model alone and the second experiment assesses the model of coupled chemistry, conduction, and enclosure radiation. The model results of both experimental activities are summarized and uncertainty of the model to represent each experimental activity is estimated. The comparison between the experiment data and model results is quantified with various metrics. After addressing these activities, an assessment of the process for the case study is given. Weaknesses in the process are discussed and lessons learned are summarized.

  14. Conversion of bromine during thermal decomposition of printed circuit boards at high temperature.

    PubMed

    Jin, Yu-qi; Tao, Lin; Chi, Yong; Yan, Jian-hua

    2011-02-15

    The conversion of bromine during the thermal decomposition of printed circuit boards (PCBs) was investigated at isothermal temperatures ranging from 800°C to 1100°C by using a quartz tube furnace. The influence of temperature, oxygen concentrations (0%, 10% and 21% in the nitrogen-oxygen atmosphere) and content of steam on conversion of bromine was studied. With the increment of temperature, the conversion from organic bromine in the PCBs to inorganic bromine in the gaseous fraction increased from 69.0% to 96.4%. The bromine was mainly evolved as HBr and Br(2) in oxidizing condition and the Br(2)/HBr mass ratio increased at stronger oxidizing atmosphere. The experimental results also indicated that the existence of steam can reduce the formation of Br(2). Furthermore, co-combustion of PCBs with S and CaO, both as addition agents, was investigated, respectively. In the presence of SO(2), Br(2)/HBr mass ratio obviously decreased. Moreover, the utilization of calcium oxide can efficiently promote the conversion of organic bromine to inorganic bromine. According to the experimental results, incinerating PCBs at high temperature can efficiently destroy the organobrominated compounds that are considered to be possible precursors of polybrominated dibenzeo-p-dioxins and dibenzofurans (PBDD/Fs), but the Br(2) and HBr in flue gas should be efficiently controlled.

  15. Thermochemical cycles for energy storage: Thermal decomposition of ZnSO4 systems

    NASA Astrophysics Data System (ADS)

    Wentworth, W. E.

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH4HSO4) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, we have shown that when NH4HSO4 is mixed with ZnO and decomposed, the resulting products can be released stepwise (H2O (gaseous) at approximately 163 C, NH3 (gaseous) at 365-418 C, and a mixture of SO2 (gaseous) and SO3 (gaseous) at approximately 900 C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high, as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally, we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO4). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V2A5, and possibly other metal oxides.

  16. Size Control of ZnO Nano-particles Formed via Thermal-Decomposition Route

    NASA Astrophysics Data System (ADS)

    Zhang, L. Z.; Yi, M. G.; Xiang, L.; Wang, B. Y.

    2010-11-01

    ZnO nano-particles with a particle size of 30-60 nm were fabricated by thermal decomposition of the basic zinc carbonate (2ZnCO3ṡ3Zn(OH)2ṡH2O) precursor at 400-600° C for 1.0-2.0 h, using ZnSO4 and Na2CO3 as the reactants. The particle size of ZnO was connected with the sintering temperature and procedure. The increase of temperature from 300° C to 600° C led to the increase of the crystallinity and the particle size of ZnO. Compared with the one-step sintering, the multi-step sintering favored the formation of dispersive ZnO nano-particles with smaller sizes. The presence of minor amount of sodium dodecyl sulfate (SDS, C12H25NaO4S) inhibited the growth and the agglomeration of the ZnO particles, reducing the primary particle size from 60-100 nm to 30-60 nm.

  17. Synthesis of ferrite nanocrystals stabilized by ionic-liquid molecules through a thermal decomposition route.

    PubMed

    Zhang, Yu; Liu, Dapeng; Wang, Xiao; Song, Shuyan; Zhang, Hongjie

    2011-01-17

    A series of M(x) Fe(3-x) O(4) (M=Fe, Co, Ni, Zn; 0≤x≤1) ferrite nanocrystals stabilized by ionic-liquid molecules have been successfully synthesized through a thermal decomposition route. Instead of the widely used long-chain lipid surfactants and high-boiling solvents, the ionic-liquid molecules not only played the role of surfactants, but also served as reaction and dispersion media simultaneously in the preparation of ferrite nanocrystals. Due to their good fluidity under magnetic fields and high ionic conductivity, the ionic-liquid molecules and M(x) Fe(3-x) O(4) ferrite nanocrystal-based conducting ferrofluids were successfully used as electrolytes in an AC circuit. The open or closed state of the circuit was directly controlled by moving a permanent magnet so as to tune the position of the ferrofluids, and consequently, resulted in the "off" or "on" state of the four indicative yellow-light-emitting diodes. These results demonstrate that the conducting ferrofluids successfully play the role of "magnetic switch".

  18. Monitoring the formation of carbide crystal phases during the thermal decomposition of 3d transition metal dicarboxylate complexes

    SciTech Connect

    Huba, ZJ; Carpenter, EE

    2014-06-06

    Single molecule precursors can help to simplify the synthesis of complex alloys by minimizing the amount of necessary starting reagents. However, single molecule precursors are time consuming to prepare with very few being commercially available. In this study, a simple precipitation method is used to prepare Fe, Co, and Ni fumarate and succinate complexes. These complexes were then thermally decomposed in an inert atmosphere to test their efficiency as single molecule precursors for the formation of metal carbide phases. Elevated temperature X-ray diffraction was used to identify the crystal phases produced upon decomposition of the metal dicarboxylate complexes. Thermogravimetric analysis coupled with an infrared detector was used to identify the developed gaseous decomposition products. All complexes tested showed a reduction from the starting M2+ oxidation state to the M oxidation state, upon decomposition. Also, each complex tested showed CO2 and H2O as gaseous decomposition products. Nickel succinate, iron succinate, and iron fumarate complexes were found to form carbide phases upon decomposition. This proves that transition metal dicarboxylate salts can be employed as efficient single molecule precursors for the formation of metal carbide crystal phases.

  19. Differential Scanning Calorimetry of Volatile-Bearing Iron Minerals Under Mars-Like Pressures: New Insights Into Energetics and Mechanisms of Thermal Decomposition

    NASA Technical Reports Server (NTRS)

    Lin, I.-C.; Lauer, H. V., Jr.; Golden, D. C.; Ming, D. W.

    2000-01-01

    In this study, we have examined the thermal decomposition of two volatile-bearing iron minerals, in particular, lepidocrocite (gamma-FeOOH) and siderite (FeCO3), under Mars-like pressures. Both minerals exhibit different enthalpic events during their decomposition at reduced atmospheric pressures when compared to those at ambient pressure. These differences in energetics are related to the mechanisms of thermal decomposition at Mars-like pressures. Such knowledge regarding the thermal stability of volatile-bearing minerals on Mars will provide useful information for planetary surface processes.

  20. Kinetic Studies of the Thermal Decomposition of Methylperoxynitrate and of Ozone-Olefin Reactions.

    NASA Astrophysics Data System (ADS)

    Bahta, Abraha

    This research concerns the thermal decomposition kinetics of CH(,3)O(,2)NO(,2) and laboratory kinetic measurements of ozone-olefin reactions. In the first system, the thermal decomposition rate of CH(,3)O(,2)NO(,2) was studied in the temperature range of 256-268 K at (TURN)350 torr total pressure and in the pressure range of 50-720 torr at 263 K by the perturbation of the equilibrium: (UNFORMATTED TABLE FOLLOWS). CH(,3)O(,2) + NO(,2) (+M) (DBLARR) CH(,3)O(,2)NO(,2) (+M) (3,-3). with NO. CH(,3)O(,2) + NO (--->) CH(,3)O + NO(,2) (4). (TABLE ENDS). The CH(,3)O(,2)NO(,2) was generated in situ by the photolysis of Cl(,2) in the presence of O(,2), CH(,4) and NO(,2). The decomposition kinetics were monitored in the presence of NO by the change in ultraviolet absorption at 250 nm. The Arrhenius expression obtained for the thermal decomposition is k(,-3) = 6 x 10('15) exp{-(21,000 (+OR-) 1500)/RT} sec('-1) at (TURNEQ)350 torr total pressure (mostly CH(,4)) where R = 1.987 cal/mole('-) K. The uncertainty in the Arrhenius parameters can be greatly reduced by combining this expression with data for k(,3) and thermodynamics data to give k(,-3) = (6 (+OR-) 3) x 10('15) exp{-(21,300 (+OR-) 300)/RT} sec('-1) at (TURNEQ)350 torr total pressure. Computations based on the pressure dependence of the forward reaction give k(,-3)('(INFIN)) = 2.1 x 10('16) exp{-(21,700 (+OR -) 300)/RT} sec('-1) k(,-3)('(DEGREES)) = 3.3 x 10(' -4) exp{-(20,150 x 300)/RT} cm('3) sec('-1). At 263 K the equilibrium constant K(,3,-3){263 K} is determined to be (2.68 (+OR-) 0.26) x 10('-10) cm('3). In the stratosphere the CH(,3)O(,2)NO(,2) lifetime will be controlled by play a role in the NO(,x) budget of the lower stratosphere. In the second part, the kinetics of the reactions of O(,3) with C(,2)H(,4), C(,3)H(,4), 1,3-C(,4)H(,6), and trans-1,3-C(,5)H(,8) were studied with initial olefin-to -ozone ratios (GREATERTHEQ) 4.9, in the presence of excess O(,2), and over the temperature range 232 to 300 K. The

  1. An integrated methodology for the assessment of environmental health implications during thermal decomposition of nano-enabled products

    PubMed Central

    Sotiriou, Georgios A.; Singh, Dilpreet; Zhang, Fang; Wohlleben, Wendel; Chalbot, Marie-Cecile G.; Kavouras, Ilias G.; Demokritou, Philip

    2015-01-01

    The proliferation of nano-enabled products (NEPs) renders human exposure to engineered nanomaterials (ENMs) inevitable. Over the last decade, the risk assessment paradigm for nanomaterials focused primarily on potential adverse effect of pristine, as-prepared ENMs. However, the physicochemical properties of ENMs may be drastically altered across their life-cycle (LC), especially when they are embedded in various NEP matrices. Of a particular interest is the end-of-life scenario by thermal decomposition. The main objective of the current study is to develop a standardized, versatile and reproducible methodology that allows for the systematic physicochemical and toxicological characterization of the NEP thermal decomposition. The developed methodology was tested for an industry-relevant NEP in order to verify its versatility for such LC investigations. Results are indicative of potential environmental health risks associated with waste from specific NEP families and prompt for the development of safer-by-design approaches and exposure control strategies. PMID:26200119

  2. Shock tube study on the thermal decomposition of fluoroethane using infrared laser absorption detection of hydrogen fluoride.

    PubMed

    Matsugi, Akira; Shiina, Hiroumi

    2014-08-28

    Motivated by recent shock tube studies on the thermal unimolecular decomposition of fluoroethanes, in which unusual trends have been reported for collisional energy-transfer parameters, the rate constants for the thermal decomposition of fluoroethane were investigated using a shock tube/laser absorption spectroscopy technique. The rate constants were measured behind reflected shock waves by monitoring the formation of HF by IR absorption at the R(1) transition in the fundamental vibrational band near 2476 nm using a distributed-feedback diode laser. The peak absorption cross sections of this absorption line have also been determined and parametrized using the Rautian-Sobel'man line shape function. The rate constant measurements covered a wide temperature range of 1018-1710 K at pressures from 100 to 290 kPa, and the derived rate constants were successfully reproduced by the master equation calculation with an average downward energy transfer, ⟨ΔEdown⟩, of 400 cm(-1).

  3. Mathematical modeling of frontal process in thermal decomposition of a substance with allowance for the finite velocity of heat propagation

    SciTech Connect

    Shlenskii, O.F.; Murashov, G.G.

    1982-05-01

    In describing frontal processes of thermal decomposition of high-energy condensed substances, for example detonation, it is common practice to write the equation for the conservation of energy without any limitations on the heat propagation velocity (HPV). At the same time, it is known that in calculating fast processes of heat conduction, the assumption of an infinitely high HPV is not always justified. In order to evaluate the influence of the HPV on the results from calculations of heat conduction process under conditions of a short-term exothermic decomposition of a condensed substance, the solution of the problem of heating a semiinfinite, thermally unstable solid body with boundary conditions of the third kind on the surface has been examined.

  4. Nanoparticle Microreactor: Application to Synthesis Of Titania by Thermal Decomposition of Titanium Tetraisopropoxide

    NASA Astrophysics Data System (ADS)

    Park, K. Y.; Ullmann, M.; Suh, Y. J.; Friedlander, S. K.

    2001-08-01

    The nanoparticle microreactor (NPMR) is a new concept that we have introduced to describe a very small-scale system capable of converting an aerosol precursor to solid particles. The liquid precursor of about 1 µl is injected by a syringe through a septum into a tubular evaporator of 1.0 cm3 in volume with stopcocks at both ends. The evaporator has been preheated by a heating tape to a temperature sufficiently high for vaporization to occur in half a minute. By opening the stopcocks, the vaporized precursor is transported by a carrier gas stream into a quartz tube which is mounted along the axis of a tubular furnace. The nanoparticle aggregates produced in the reactor are sampled by deposition on an electron micrograph grid at the reactor exit. The NPMR was applied first to the synthesis of TiO2 particles by thermal decomposition of titanium tetraisopropoxide (TTIP) in a nitrogen carrier gas, with TTIP concentrations varying from 1.0 to 7.0 mol% or 2.35×10-6 to 1.65×10-5 in TiO2 volume loading, and decomposition temperatures from 300°C to 1000°C. Studies were made with a 2 mm reaction tube and a 4 mm tube with sheath gas. With the 2 mm tube, a considerable fraction of the TTIP precursor was consumed at the wall by surface reaction, resulting in very small particles. With the 4 mm tube, the primary particle size was comparable to that reported in the literature for steady flow experiments using a 22.2 mm tube. Primary particle sizes ranged from 200 to 400 nm. Depending on TTIP concentration and reactor temperature, the particles exhibited a bimodal size distribution, probably due to a two-stage nucleation. A fourfold increase in the gas flow rate had little effect on particle size, indicating that particle growth ended early, within one-fourth the tube length. Residence time in the reactor was between 0.35 and 1.4 s, and total run time about 1 min. The NPMR has potential for rapid assembly of large databases and is adaptable to combinatorial discovery of

  5. The surface quasiliquid melt acceleration and the role of thermodynamic phase in the thermal decomposition of crystalline organic explosives

    SciTech Connect

    Henson, Bryan F

    2010-01-01

    We show that melt acceleration in the thermal decomposition of crystalline organic solids is a manifestation of the surface quasiliquid phase. We derive a single universal rate law for melt acceleration that is a simple function of the metastable liquid activity below the melting point, and has a zero order term proportional to the quasiliquid thickness. We argue that the underlying mechanisms of this model will provide a molecular definition for the stability of the class of secondary explosives.

  6. Study of the solid-phase thermal decomposition of NTO using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS)

    NASA Technical Reports Server (NTRS)

    Minier, L.; Behrens, R.; Burkey, T. J.

    1997-01-01

    The solid phase thermal reaction chemistry of NTO between 190 and 250 C is presently being evaluated by utilizing STMBMS, a technique that enables the authors to measure the vapor pressure of NTO and to explore the reaction mechanisms and chemical kinetics associated with the NTO thermal decomposition process. The vapor pressure of NTO is expressed as Log(sub 10) p(torr) = 12.5137 + 6,296.553(1/t(k)) and the Delta-H(sub subl) = 28.71 +/- 0.07 kcal/mol (120.01 +/- 0.29 kJ/mol). The pyrolysis of NTO results in the formation of gaseous products and a condensed-phase residue. The identity of the major gaseous products and their origin from within the NTO molecules are determined based on the results from pyrolysis of NTO, NTO-3-C-13, NTO-1,2- (15)N2 and NTO-(2)H2. Identification of the products show the major gaseous products to be N2, CO2, NO, HNCO, H2O and some N2O, CO, HCN and NH3. The N2 is mostly derived from the N-1 and N-2 positions with some being from the N-4 and N-1 or N-2 positions. The CO2 is derived from both carbons in the NTO molecule in comparable amounts. The residue has an elemental formula of C(2.1)H(.26)N(2.9)O and FTIR analysis suggests that the residue is polyurea- and polycarbamate- like in nature. The temporal behaviors of the rates of formation of the gaseous products indicate that the overall thermal decomposition of NTO in the temperature range evaluated involves four major processes: (1) NTO sublimation; (2) an apparent solid-solid phase transition between 190 and 195 C; (3) a decomposition regime induced by the presence of exogenous H2O at the onset of decomposition; and (4) a decomposition regime that occurs at the onset of decomposition and continues until the depletion of NTO. Decomposition pathways that are consistent with the data are presented.

  7. A study of the solid-phase thermal decomposition of NTO using simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS)

    SciTech Connect

    Minier, L.; Behrens, R.; Burkey, T.J.

    1997-01-01

    The solid phase thermal reaction chemistry of NTO between 190 and 250 C is presently being evaluated by utilizing STMBMS, a technique that enables the authors to measure the vapor pressure of NTO and to explore the reaction mechanisms and chemical kinetics associated with the NTO thermal decomposition process. The vapor pressure of NTO is expressed as Log{sub 10} p(torr) = 12.5137 + 6,296.553(1/t{sub k}) and the {Delta}H{sub subl} = 28.71 {+-} 0.07 kcal/mol (120.01 {+-} 0.29 kJ/mol). The pyrolysis of NTO results in the formation of gaseous products and a condensed-phase residue. The identity of the major gaseous products and their origin from within the NTO molecules are determined based on the results from pyrolysis of NTO, NTO-3-{sup 13}C, NTO-1,2-{sup 15}N{sub 2} and NTO-{sup 2}H{sub 2}. Identification of the products show the major gaseous products to be N{sub 2}, CO{sub 2}, NO, HNCO, H{sub 2}O and some N{sub 2}O, CO, HCN and NH{sub 3}. The N{sub 2} is mostly derived from the N-1 and N-2 positions with some being from the N-4 and N-1 or N-2 positions. The CO{sub 2} is derived from both carbons in the NTO molecule in comparable amounts. The residue has an elemental formula of C{sub 2.1}H{sub .26}N{sub 2.9}O and FTIR analysis suggests that the residue is polyurea- and polycarbamate-like in nature. The temporal behaviors of the rates of formation of the gaseous products indicate that the overall thermal decomposition of NTO in the temperature range evaluated involves four major processes: (1) NTO sublimation; (2) an apparent solid-solid phase transition between 190 and 195 C; (3) a decomposition regime induced by the presence of exogenous H{sub 2}O at the onset of decomposition; and (4) a decomposition regime that occurs at the onset of decomposition and continues until the depletion of NTO. Decomposition pathways that are consistent with the data are presented.

  8. The role of petrography on the thermal decomposition and burnability of limestones used in industrial cement clinker

    NASA Astrophysics Data System (ADS)

    Marinoni, Nicoletta; Bernasconi, Andrea; Della Porta, Giovanna; Marchi, Maurizio; Pavese, Alessandro

    2015-12-01

    The present research examines the influence of the petrographic features on the thermal decomposition and burnability of three limestones, the main raw materials for Portland cement-making. A detailed characterisation of the limestones has been performed by means of optical microscopy and X-Ray Powder Diffraction. The carbonate thermal decomposition was conducted under isothermal conditions by means of in situ High Temperature X-Ray Powder Diffraction and the heated samples were further investigated by Scanning Electron Microscopy. Three kiln feeds were then prepared and submitted to burning trials and the temperature of occurrence of the main clinker phases was investigated as well as the content of the uncombined CaO in the heated samples was determined by using the Franke method. The results attest that the microfabric, a combination of depositional and diagenetic features, drives the kinetics of the thermal decomposition of the selected limestones as well as it appears to influence the temperature of crystallisation of the main clinker phases and the uncombined CaO content in the final clinker. In particular, the limestone with the lowest micrite to sparite ratio (1) exhibits the lowest Apparent Activation Energy ( E a ) value and the highest rate of calcination and (2) requires a lower temperature for observing the clinker phases crystallisation and has the lowest content of uncombined CaO in the final clinker, thus reflecting a high burnability of the limestone.

  9. Thermal decomposition of HO2NO2 (peroxynitric acid, PNA): rate coefficient and determination of the enthalpy of formation.

    PubMed

    Gierczak, Tomasz; Jiménez, Elena; Riffault, Veronique; Burkholder, James B; Ravishankara, A R

    2005-02-03

    Rate coefficients for the gas-phase thermal decomposition of HO(2)NO(2) (peroxynitric acid, PNA) are reported at temperatures between 331 and 350 K at total pressures of 25 and 50 Torr of N(2). Rate coefficients were determined by measuring the steady-state OH concentration in a mixture of known concentrations of HO(2)NO(2) and NO. The measured thermal decomposition rate coefficients k(-)(1)(T,P) are used in combination with previously published rate coefficient data for the HO(2)NO(2) formation reaction to yield a standard enthalpy for reaction 1 of Delta(r)H degrees (298K) = -24.0 +/- 0.5 kcal mol(-1) (uncertainties are 2sigma values and include estimated systematic errors). A HO(2)NO(2) standard heat of formation, Delta(f)H degrees (298K)(HO(2)NO(2)), of -12.6 +/- 1.0 kcal mol(-1) was calculated from this value. Some of the previously reported data on the thermal decomposition of HO(2)NO(2) have been reanalyzed and shown to be in good agreement with our reported value.

  10. Total control of chromium in tanneries - thermal decomposition of filtration cake from enzymatic hydrolysis of chrome shavings.

    PubMed

    Kocurek, P; Kolomazník, K; Bařinová, M; Hendrych, J

    2016-12-08

    This paper deals with the problem of chromium recovery from chrome-tanned waste and thus with reducing the environmental impact of the leather industry. Chrome-tanned waste was transformed by alkaline enzymatic hydrolysis promoted by magnesium oxide into practically chromium-free, commercially applicable collagen hydrolysate and filtration cake containing a high portion of chromium. The crude and magnesium-deprived chromium cakes were subjected to a process of thermal decomposition at 650°C under oxygen-free conditions to reduce the amount of this waste and to study the effect of magnesium removal on the resulting products. Oxygen-free conditions were applied in order to prevent the oxidation of trivalent chromium into the hazardous hexavalent form. Thermal decomposition products from both crude and magnesium-deprived chrome cakes were characterized by high chromium content over 50%, which occurred as eskolaite (Cr2O3) and magnesiochromite (MgCr2O4) crystal phases, respectively. Thermal decomposition decreased the amount of chrome cake dry feed by 90%. Based on the performed experiments, a scheme for the total control of chromium in the leather industry was designed.

  11. Thermal and X-ray diffraction analysis studies during the decomposition of ammonium uranyl nitrate.

    PubMed

    Kim, B H; Lee, Y B; Prelas, M A; Ghosh, T K

    Two types of ammonium uranyl nitrate (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3, were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and a TG/DTA analysis. Both (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 decomposed to amorphous UO3 regardless of the atmosphere used. The amorphous UO3 from (NH4)2UO2(NO3)4·2H2O was crystallized to γ-UO3 regardless of the atmosphere used without a change in weight. The amorphous UO3 obtained from decomposition of NH4UO2(NO3)3 was crystallized to α-UO3 under a nitrogen and air atmosphere, and to β-UO3 under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH4)2UO2(NO3)4·2H2O and NH4UO2(NO3)3 were as follows: under a nitrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; under an air atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → U3O8, NH4UO2(NO3)3 → A-UO3 → α-UO3 → U3O8; and under a hydrogen atmosphere: (NH4)2UO2(NO3)4·2H2O → (NH4)2UO2(NO3)4·H2O → (NH4)2UO2(NO3)4 → NH4UO2(NO3)3 → A-UO3 → γ-UO3 → α-U3O8 → UO2, NH4 UO2(NO3)3 → A-UO3 → β-UO3 → α-U3O8 → UO2.

  12. Kinetics of thermal decomposition of hydrated minerals associated with hematite ore in a fluidized bed reactor

    NASA Astrophysics Data System (ADS)

    Beuria, P. C.; Biswal, S. K.; Mishra, B. K.; Roy, G. G.

    2017-03-01

    The kinetics of removal of loss on ignition (LOI) by thermal decomposition of hydrated minerals present in natural iron ores (i.e., kaolinite, gibbsite, and goethite) was investigated in a laboratory-scale vertical fluidized bed reactor (FBR) using isothermal methods of kinetic analysis. Experiments in the FBR in batch processes were carried out at different temperatures (300 to 1200°C) and residence time (1 to 30 min) for four different iron ore samples with various LOIs (2.34wt% to 9.83wt%). The operating velocity was maintained in the range from 1.2 to 1.4 times the minimum fluidization velocity ( U mf). We observed that, below a certain critical temperature, the FBR did not effectively reduce the LOI to a desired level even with increased residence time. The results of this study indicate that the LOI level could be reduced by 90% within 1 min of residence time at 1100°C. The kinetics for low-LOI samples (<6wt%) indicates two different reaction mechanisms in two temperature regimes. At lower temperatures (300 to 700°C), the kinetics is characterized by a lower activation energy (diffusion-controlled physical moisture removal), followed by a higher activation energy (chemically controlled removal of LOI). In the case of high-LOI samples, three different kinetics mechanisms prevail at different temperature regimes. At temperature up to 450°C, diffusion kinetics prevails (removal of physical moisture); at temperature from 450 to 650°C, chemical kinetics dominates during removal of matrix moisture. At temperatures greater than 650°C, nucleation and growth begins to influence the rate of removal of LOI.

  13. The branching ratio in the thermal decomposition of H{sub 2}CO

    SciTech Connect

    Kumaran, S.S.; Carroll, J.J.; Michael, J.V.

    1998-07-01

    The thermal decomposition of H{sub 2}CO has been investigated in reflected shock waves experiments at temperatures between 2,004--2,367 K. The quantitative temporal formation of H-atoms in the reactions, (1a) H{sub 2}CO + Kr {yields} HCO + H + Kr and HCO + Kr {yields} CO + H + Kr, were measured by the atomic resonance absorption spectrometric (ARAS) technique. The product HCO-radicals instantaneously decompose giving a second H-atom. The experiments were carried out under conditions where secondary reaction perturbations were negligible. The observed H-atom profiles could be reproduced using a two step mechanism, reactions (1a) and (1b), H{sub 2}CO + Kr {yields} H{sub 2} + CO + Kr. The resulting values for the branching ratio, k{sub 1a}/(k{sub 1a} + k{sub 1b}) range between 6.7--12.2%. The data yield second-order rate constants, k{sub 1a} = 1.019 {times} 10{sup {minus}9} exp({minus}38706 K/T) and k{sub 1b} = 4.658 {times} 10{sup {minus}9} exp({minus}32110 K/T) cm{sup 3}/molecule s, respectively. The rate data and branching ratio results are compared to earlier determinations. Lastly, the data are theoretically rationalized using three theoretical formalisms. Single channel theoretical calculations are carried out with the semiempirical Troe and with the RRKM-Gorin methods, and these are compared to multichannel RRKM calculations using the Unimol code.

  14. The thermal decomposition of C{sub 2}H{sub 5}I

    SciTech Connect

    Kumaran, S.S.; Su, M.C.; Lim, K.P.; Michael, J.V.

    1996-06-01

    The high temperature thermal dissociation of C{sub 2}H{sub 5}I has been characterized in this study. Kinetics and overall yield experiments were performed over the temperature range, 946--2,046 K, using the atomic resonance absorption spectrometric technique (ARAS) for the temporal detection of both product H- and I-atoms behind reflected shock waves. The C{sub 2}H{sub 5}I decomposition proceeds by both C-I fission and HI elimination. Rate constants for the C-I fission process, measured over the temperature and density ranges, 946--1,303 K and 0.82--4.4 {times} 10{sup 18} cm{sup {minus}3}, respectively, can be well represented to within {+-}37% by the first-order expression: k = 6.34 {times} 10{sup 9} exp({minus}15,894 K/T) s{sup {minus}1}. Overall yield data for atomic product gave a branching ratio for C-I fission of (0.87 {+-} 0.11) suggesting that 13% of the reaction proceeds through molecular HI elimination. This conclusion is consistent with earlier studies that showed C-I fission to be the dominant dissociation channel. The temperature and pressure dependences of the dissociation rate constants and the yield data have been theoretically described using three formulations of unimolecular rate theory. The best description was obtained with a full Master`s equation analysis. However, all three calculations confirm that the HI elimination pathway is lower lying than the C-I fission process by {approximately} 3 kcal/mole.

  15. Demonstration test results of organic materials' volumetric reduction using bio-ethanol, thermal decomposition and burning

    SciTech Connect

    Tagawa, Akihiro; Watanabe, Masahisa

    2013-07-01

    To discover technologies that can be utilized for decontamination work and verify their effects, economic feasibility, safety, and other factors, the Ministry of the Environment launched the 'FY2011 Decontamination Technology Demonstrations Project' to publicly solicit decontamination technologies that would be verified in demonstration tests and adopted 22 candidates. JAEA was commissioned by the Ministry of the Environment to provide technical assistance related to these demonstrations. This paper describes the volume reduction due to bio-ethanol, thermal decomposition and burning of organic materials in this report. The purpose of this study is that to evaluate a technique that can be used as biomass energy source, while performing volume reduction of contamination organic matter generated by decontamination. An important point of volume reduction technology of contaminated organic matter, is to evaluate the mass balance in the system. Then, confirming the mass balance of radioactive material and where to stay is important. The things that are common to all technologies, are ensuring that the radioactive cesium is not released as exhaust gas, etc.. In addition, it evaluates the cost balance and energy balance in order to understand the applicability to the decontamination of volume reduction technology. The radioactive cesium remains in the carbides when organic materials are carbonized, and radioactive cesium does not transfer to bio-ethanol when organic materials are processed for bio-ethanol production. While plant operating costs are greater if radioactive materials need to be treated, if income is expected by business such as power generation, depreciation may be calculated over approximately 15 years. (authors)

  16. Thermal Decomposition of NCN: Shock-Tube Study, Quantum Chemical Calculations, and Master-Equation Modeling.

    PubMed

    Busch, Anna; González-García, Núria; Lendvay, György; Olzmann, Matthias

    2015-07-16

    The thermal decomposition of cyanonitrene, NCN, was studied behind reflected shock waves in the temperature range 1790-2960 K at pressures near 1 and 4 bar. Highly diluted mixtures of NCN3 in argon were shock-heated to produce NCN, and concentration-time profiles of C atoms as reaction product were monitored with atomic resonance absorption spectroscopy at 156.1 nm. Calibration was performed with methane pyrolysis experiments. Rate coefficients for the reaction (3)NCN + M → (3)C + N2 + M (R1) were determined from the initial slopes of the C atom concentration-time profiles. Reaction R1 was found to be in the low-pressure regime at the conditions of the experiments. The temperature dependence of the bimolecular rate coefficient can be expressed with the following Arrhenius equation: k1(bim) = (4.2 ± 2.1) × 10(14) exp[-242.3 kJ mol(-1)/(RT)] cm(3) mol(-1) s(-1). The rate coefficients were analyzed by using a master equation with specific rate coefficients from RRKM theory. The necessary molecular data and energies were calculated with quantum chemical methods up to the CCSD(T)/CBS//CCSD/cc-pVTZ level of theory. From the topography of the potential energy surface, it follows that reaction R1 proceeds via isomerization of NCN to CNN and subsequent C-N bond fission along a collinear reaction coordinate without a tight transition state. The calculations reproduce the magnitude and temperature dependence of the rate coefficient and confirm that reaction R1 is in the low-pressure regime under our experimental conditions.

  17. Mass transfer in fuel cells. [electron microscopy of components, thermal decomposition of Teflon, water transport, and surface tension of KOH solutions

    NASA Technical Reports Server (NTRS)

    Walker, R. D., Jr.

    1973-01-01

    Results of experiments on electron microscopy of fuel cell components, thermal decomposition of Teflon by thermogravimetry, surface area and pore size distribution measurements, water transport in fuel cells, and surface tension of KOH solutions are described.

  18. Fabrication of Powder Metallurgy Pure Ti Material by Using Thermal Decomposition of TiH2

    NASA Astrophysics Data System (ADS)

    Mimoto, Takanori; Nakanishi, Nozomi; Umeda, Junko; Kondoh, Katsuyoshi

    Titanium (Ti) and titanium alloys have been interested as an engineering material because they are widely used across various industrial applications, for example, motorcycle, automotive and aerospace industries, due to their light weight, high specific strength and superior corrosion resistance. Ti materials are particularly significant for the aircraft using carbon/carbon (C/C) composites, for example, carbon fiber reinforced plastics (CFRP), because Ti materials are free from the problem of contact corrosion between C/C composites. However, the applications of Ti materials are limited because of their high cost. From a viewpoint of cost reduction, cost effective process to fabricate Ti materials is strongly required. In the present study, the direct consolidation of titanium hydride (TiH2) raw powders in solid-state was employed to fabricate pure Ti bulk materials by using thermal decomposition of TiH2. In general, the production cost of Ti components is expensive due to using commercially pure (CP) Ti powders after dehydrogenation. On the other hand, the novel process using TiH2 powders as starting materials is a promising low cost approach for powder metallurgy (P/M) Ti products. Furthermore, this new process is also attractive from a viewpoint of energy saving because the dehydrogenation is integrated into the sintering process. In this study, TiH2 raw powders were directly consolidated by conventional press technique at 600 MPa to prepare TiH2 powder compacted billets. To thermally decompose TiH2 and obtain sintered pure Ti billets, the TiH2 powder billets were heated in the integrated sintering process including dehydrogenation. The hot-extruded pure Ti material, which was heat treated at 1273 K for 180 min in argon gas atmosphere, showed tensile strength of 701.8 MPa and elongation of 27.1%. These tensile properties satisfied the requirements for JIS Ti Grade 4. The relationship between microstructures, mechanical properties response and heat treatment

  19. Thermal decomposition of UO{sub 3}-2H{sub 2}0

    SciTech Connect

    Flament, T.A.

    1998-02-26

    The first part of the report summarizes the literature data regarding the uranium trioxide water system. In the second part, the experimental aspects are presented. An experimental program has been set up to determine the steps and species involved in decomposition of uranium oxide di-hydrate. Particular attention has been paid to determine both loss of free water (moisture in the fuel) and loss of chemically bound water (decomposition of hydrates). The influence of water pressure on decomposition has been taken into account.

  20. Thermal decomposition and kinetic evaluation of decanted 2,4,6-trinitrotoluene (TNT) for reutilization as composite material

    NASA Astrophysics Data System (ADS)

    Ahmed, M. F.; Hussain, A.; Malik, A. Q.

    2016-08-01

    Use of energetic materials has long been considered for only military purposes. However, it is very recent that their practical applications in wide range of commercial fields such as mining, road building, under water blasting and rocket propulsion system have been considered. About 5mg of 2,4,6-trinitrotoluene (TNT) in serviceable (Svc) as well as unserviceable (Unsvc) form were used for their thermal decomposition and kinetic parameters investigation. Thermogravimetric/ differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to characterize two types of TNT. Arrhenius kinetic parameters like activation energy (E) and enthalpy (AH) of both TNT samples were determined using TG curves with the help of Horowitz and Metzger method. Simultaneously, thermal decomposition range was evaluated from DTA curves. Distinct diffraction peaks showing crystalline nature were obtained from XRD analysis. SEM results indicated that Unsvc TNT contained a variety of defects like cracks and porosity. Similarly, it is observed that thermal as well as kinetic behavior of both TNT samples vary to a great extent. Likewise, a prominent change in the activation energies (E) of both samples is observed. This in-depth study provides a way forward in finding solutions for the safe reutilization of decanted TNT.

  1. Effect of nanoclay loading on the thermal decomposition of nanoclay polyurethane elastomers obtained by bulk polymerization

    NASA Astrophysics Data System (ADS)

    Quagliano, Javier; Bocchio, Javier

    2014-08-01

    Thermoplastic urethane (TPU) nanocomposite was prepared successfully by dispersion at high shear stress of the nanoclay in polyol and further bulk polymerization. Our results from DSC studies showed an increase in decomposition temperature when nanoclay was loaded at 3,5% on elastomeric PU made from TDI, PTMEG and BDO, while not when nanoclay content was lower (1,5%). The exotherms at 370-375°C could be adscribed to the decomposition of the hard segments according to previous work.

  2. Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition

    NASA Astrophysics Data System (ADS)

    Asadi, Mozaffar; Asadi, Zahra; Savaripoor, Nooshin; Dusek, Michal; Eigner, Vaclav; Shorkaei, Mohammad Ranjkesh; Sedaghat, Moslem

    2015-02-01

    A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L1-L4), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL1ṡDMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the "-yl" oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < Cl. We also studied the thermodynamics of formation of the complexes and kinetic aspects of their thermal decomposition. The formation constants with various substituents on the aldehyde ring follow the trend 5-OMe > 5-H > 5-Br > 5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL1ṡDMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L1 ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex.

  3. Products of thermal decomposition of triethylgallium and trimethylgallium adsorbed on Ga-stabilized GaAs(100)

    NASA Astrophysics Data System (ADS)

    Donnelly, V. M.; McCaulley, J. A.

    1990-11-01

    We report mass spectrometric studies of the products of thermal decomposition of triethylgallium (TEGa), and trimethylgallium (TMGa) adsorbed on Ga-stabilized GaAs(100) in ultrahigh vacuum. Adsorbed layers were prepared by dosing clean GaAs, near room temperature, to either saturated coverage or coverages below saturation. Subsequent heating leads to desorption of products, detected by a differentially pumped quadrupole mass spectrometer. Total carbon coverage was monitored by X-ray photoelectron spectroscopy (XPS). The substrate temperature was measured by infrared laser interferometric thermometry. At saturated coverage, TEGa decomposes upon heating (1-2°C/s) to yield one third Ga-alkyl product (Ga(C 2H 5) 2) between 0 and 300°C, and two thirds hydrocarbon products (mostly C 2H 4 and some C 2H 5) between 250 and 390°C. About 25% of the Ga deposited from TEGa remains on the surface after all products desorb. Below 40% of saturated coverage, only the higher temperature hydrocarbon products desorb, and all adsorbed Ga remains on the surface. TMGa behaves similarly; starting at saturated coverage, Ga-alkyl product (either Ga(CH 3) 2 or a mixture of Ga(CH 3) 2 and TMGa) desorbs at low temperature (50-380°C) and hydrocarbon product (CH 3) desorbs at higher temperature (250-425°C). However, for TMGa the yield of the Ga-alkyl is about twice the CH 3 yield. No ethane, or butane was detected in TEGa decomposition, nor was any ethane found for TMGa decomposition, indicating that association and disproportionation reactions are unimportant. Also no As-alkyl products were detected. The slower rate of desorption of CH 3 for TMGa decomposition, compared to C 2H 4 and C 2H 5 desorption from TEGa decomposition, qualitatively explains higher carbon levels in GaAs films grown with TMGa versus TEGa.

  4. A STUDY OF THE PROPERTIES OF CP: COEFFICIENT OF THERMAL EXPANSION, DECOMPOSITION KINETICS AND REACTION TO SPARK, FRICTION AND IMPACT

    SciTech Connect

    Weese, R K; Burnham, A K; Fontes, A T

    2005-03-30

    The properties of pentaamine (5-cyano-2H-tetrazolato-N2) cobalt (III) perchlorate (CP), which was first synthesized in 1968, continues to be of interest for predicting behavior in handling, shipping, aging, and thermal cook-off situations. We report coefficient of thermal expansion (CTE) values over four specific temperature ranges, decomposition kinetics using linear heating rates, and the reaction to three different types of stimuli: impact, spark, and friction. The CTE was measured using a Thermal Mechanical Analyzer (TMA) for samples that were uniaxially compressed at 10,000 psi and analyzed over a dynamic temperature range of -20 C to 70 C. Using differential scanning calorimetry, DSC, CP was decomposed at linear heating rates of 1, 3, and 7 C/min and the kinetic triplet calculated using the LLNL code Kinetics05. Values are also reported for spark, friction, and impact sensitivity.

  5. Crystal structure, thermal decomposition mechanism and explosive properties of [Na(H2TNPG)(H2O)2]n.

    PubMed

    Chen, Hongyan; Zhang, Tonglai; Zhang, Jianguo; Qiao, Xiaojing; Yu, Kaibei

    2006-02-28

    The new coordination polymer of sodium trinitrophloroglucinate, [Na(H2TNPG)(H2O)2]n, was synthesized by reacting trinitrophloroglucinol (H3TNPG) with NaHCO3 in aqueous solution and [Na(H2TNPG)(H2O)2]n was recrystallized to be yellow single crystal. The title compound was characterized by using elemental analysis and Fourier transform infrared (FT-IR) spectrum. Its crystal structure was determined by single crystal X-ray diffraction analysis. The crystalline belongs to monoclinic system and C2/c space group. Each Na+ ion is six-coordinated to one H2TNPG- anion and four water molecules in which the oxygen atoms in the water molecules act as bridging atoms. Coordination bonds, electrostatic interaction and intermolecular hydrogen bonds assemble the ions into network structures. The thermal decomposition mechanism of the complex was studied by using differential scanning calorimetry (DSC), thermogravimetry/derivative thermogravimetry (TG/DTG) and FT-IR techniques. Under nitrogen atmosphere with a heating rate of 10 degrees C/min the thermal decomposition of the complex contained one endothermic and five exothermic processes. Two intense exothermic decomposition processes were observed in the range of 173-228 degrees C suggesting its energetic nature and the solid decomposition residue at 500 degrees C was sodium isonitrile. Explosive properties revealed that the compound is sensitive to mechanical stimuli. All properties data observed show that the title compound has explosive properties and can act as components of ecologically clean initiating compositions.

  6. Catalytic conversion of 1,2-dichlorobenzene using V2O5/TiO2 catalysts by a thermal decomposition process.

    PubMed

    Chin, Sungmin; Jurng, Jongsoo; Lee, Jae-Heon; Moon, Seung-Jae

    2009-05-01

    This study examined the catalytic oxidation of 1,2-dichlorobenzene on V(2)O(5)/TiO(2) nanoparticles. The V(2)O(5)/TiO(2) nanoparticles were synthesized by the thermal decomposition of vanadium oxytripropoxide and titanium tetraisopropoxide. The effects of the synthesis conditions, such as the synthesis temperature and precursor heating temperature, were investigated. The specific surface areas of V(2)O(5)/TiO(2) nanoparticles increased with increasing synthesis temperature and decreasing precursor heating temperature. The catalytic oxidation rate of the V(2)O(5)/TiO(2) catalyst formed by thermal decomposition process at a catalytic reaction temperature of 150 and 200 degrees C was 46% and 95%, respectively. As a result, it was concluded that the V(2)O(5)/TiO(2) catalysts synthesized by a thermal decomposition process showed good performance for 1,2-DCB decomposition at a lower temperature.

  7. Thermal Decomposition Characteristics of Orthorhombic Ammonium Perchlorate (o-AP) and an 0-AP/HTPB-Based Propellant

    SciTech Connect

    BEHRENS JR.,RICHARD; MINIER,LEANNA M.G.

    1999-10-25

    A study to characterize the low-temperature reactive processes for o-AP and an AP/HTPB-based propellant (class 1.3) is being conducted in the laboratory using the techniques of simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and scanning electron microscopy (SEM). The results presented in this paper are a follow up of the previous work that showed the overall decomposition to be complex and controlled by both physical and chemical processes. The decomposition is characterized by the occurrence of one major event that consumes up to {approx}35% of the AP, depending upon particle size, and leaves behind a porous agglomerate of AP. The major gaseous products released during this event include H{sub 2}O, O{sub 2}, Cl{sub 2}, N{sub 2}O and HCl. The recent efforts provide further insight into the decomposition processes for o-AP. The temporal behaviors of the gas formation rates (GFRs) for the products indicate that the major decomposition event consists of three chemical channels. The first and third channels are affected by the pressure in the reaction cell and occur at the surface or in the gas phase above the surface of the AP particles. The second channel is not affected by pressure and accounts for the solid-phase reactions characteristic of o-AP. The third channel involves the interactions of the decomposition products with the surface of the AP. SEM images of partially decomposed o-AP provide insight to how the morphology changes as the decomposition progresses. A conceptual model has been developed, based upon the STMBMS and SEM results, that provides a basic description of the processes. The thermal decomposition characteristics of the propellant are evaluated from the identities of the products and the temporal behaviors of their GFRs. First, the volatile components in the propellant evolve from the propellant as it is heated. Second, the hot AP (and HClO{sub 4}) at the AP-binder interface oxidize the binder through reactions that

  8. Thermal Decomposition of Methyl Esters in Biodiesel Fuel: Kinetics, Mechanisms and Products

    NASA Astrophysics Data System (ADS)

    Chai, Ming

    Biodiesel continues to enjoy increasing popularity. However, recent studies on carbonyl compounds emissions from biodiesel fuel are inconclusive. Emissions of carbonyl compounds from petroleum diesel fuels were compared to emissions from pure biodiesel fuels and petroleum-biodiesel blends used in a non-road diesel generator. The concentration of total carbonyl compounds was the highest when the engine was idling. The carbonyl emissions, as well as ozone formation potential, from biodiesel fuel blends were higher than those emitted from petroleum diesel fuel. The sulfur content of diesel fuel and the source of biodiesel fuel were not found to have a significant impact on emissions of carbonyl compounds. Mechanism parameters of the thermal decomposition of biodiesel-range methyl esters were obtained from the results of thermal gravimetric analysis (TGA). The overall reaction orders are between 0.49 and 0.71 and the energies of activation are between 59.9 and 101.3 kJ/mole. Methyl esters in air have lower activation energies than those in nitrogen. Methyl linoleate has the lowest activation energy, followed by methyl oleate, and methyl stearate. The pyrolysis and oxidation of the three methyl esters were investigated using a semi-isothermal tubular flow reactor. The profiles of major products versus reaction temperature are presented. In the pyrolysis of methyl stearate, the primary reaction pathway is the decarboxylic reaction at the methyl ester functional group. Methyl oleate's products indicate more reactions on its carbon-carbon double bond. Methyl linoleate shows highest reactivity among the three methyl esters, and 87 products were detected. The oxidation of three methyl esters resulted in more products in all compound classes, and 55, 114, and 127 products were detected, respectively. The oxidation of methyl esters includes decarboxylation on ester group. The methyl ester's carbon chain could be oxidized as a hydrocarbon compound and form oxidized esters and

  9. Kinetics and Mechanism of the CIO + CIO Reaction: Pressure and Temperature Dependences of the Bimolecular and Termolecular Channels andThermal Decomposition of Chlorine Peroxide, CIOOCI

    NASA Technical Reports Server (NTRS)

    Nickolaisen, Scott L.; Friedl, Randall R.; Sander, Stanley P.

    1993-01-01

    The kinetics and mechanism of the CIO + CIO reaction and the thermal decomposition of CIOOCI were studied using the flash photolysis/long path ultraviolet absorption technique. Pressure and temperature dependences were determined for the rate coefficients for the bimolecular and termolecular reaction channels, and for the thermal decompositon of CIOOCI.

  10. Properties and thermal decomposition of the hydro-fluoro-peroxide CH₃OC(O)OOC(O)F.

    PubMed

    Berasategui, Matías; Burgos Paci, Maxi A; Argüello, Gustavo A

    2014-03-27

    The thermal decomposition of methyl fluoroformyl peroxycarbonate CH3OC(O)OOC(O)F was studied in the range of 30- 96 °C using FTIR spectroscopy to follow the course of the reaction in the presence of either N2, O2, or CO as bath gases. The rate constants of the homogeneous first-order process fit the Arrhenius equation k(exp) = (5.4 ± 0.2) × 10(14) exp[-(27.1 ± 0.6 kcal mol(-1)/RT)] (in units of s(-1)). A complete mechanism of decomposition is presented. An experimental O-O bond energy of 27 ± 1 kcal mol(-1) was obtained. The products observed when N2 or O2 are used as bath gases were CO2, CO, HF, and CH3OC(O)H, while in the presence of CO, CH3OC(O)F was also observed. Transition state ab initio calculations were carried out to understand the dynamics of the decomposition. Additionally, thermodynamic properties of the atmospherically relevant CH3OCO2• radical were calculated. The heat of formation, ΔH°(f 298), obtained for CH3OCO2• and CH3OC(O)OOC(O)F, were 78 ± 3 kcal mol(-1) and 191 ± 5 kcal mol(-1), respectively.

  11. ESR studies on the thermal decomposition of trimethylamine oxide to formaldehyde and dimethylamine in jumbo squid (Dosidicus gigas) extract.

    PubMed

    Zhu, Junli; Jia, Jia; Li, Xuepeng; Dong, Liangliang; Li, Jianrong

    2013-12-15

    The effects of ferrous iron, heating temperature and different additives on the decomposition of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA) and generation of free radicals in jumbo squid (Dosidicus gigas) extract during heating were evaluated by electron spin resonance (ESR). The thermal decomposition of TMAO to TMA, DMA and FA and free radical signals was observed in squid extract, whereas no DMA, FA and free radical signals were detected in cod extract or in aqueous TMAO solution in vitro at high temperatures. Significant increase in levels of DMA, FA and radicals intensity were observed in squid extract and TMAO solution in the presence of ferrous iron with increasing temperature. Hydrogen peroxide stimulated the production of DMA, FA and ESR signals in squid extract, while citric acid, trisodium citrate, calcium chloride, tea polyphenols and resveratrol had the opposite effect. Similar ESR spectra of six peaks regarded as amminium radical were detected in the squid extract and TMAO-iron(II) solution, suggesting that the amminium radical was involved in the decomposition of TMAO.

  12. Phase decomposition and nano structure evolution of metastable nanocrystalline Cu-Co solid solutions during thermal treatment

    NASA Astrophysics Data System (ADS)

    Bachmaier, A.; Stolpe, M.; Müller, T.; Motz, C.

    2015-08-01

    Nanocrystalline and ultrafine-grained Cu100-xCox (x = 26 and 76) solid solutions have been prepared by severe plastic deformation (SPD) of elemental powder mixtures. For both concentrations a supersaturated solid solution fcc phase was identified after the deformation process with grain sizes of less than 50 nm for Co rich solutions and around 100 nm for Cu rich solutions. Additionally, synthesis of nanocrystalline materials in the Cu-Co alloy system by electrodeposition has been conducted. Microstructural characterization by scanning and transmission electron microscopy, differential scanning calorimetry, and microhardness measurements are used to investigate the structural evolution, the thermal stability and mechanical properties of the different nanocrystalline Cu-Co alloy materials during isothermal and non-isothermal annealing. In this study it is shown that the phase decomposition of the metastable Cu-Co solid solutions has a significant influence on their thermal stability, which can be linked to the underlying microstructure that forms during annealing.

  13. Physical Properties and Thermal Decomposition of Aqueous Solutions of 2-Amino-2-hydroxymethyl-1, 3-propanediol (AHPD)

    NASA Astrophysics Data System (ADS)

    Murshid, Ghulam; Shariff, Azmi Mohd; Lau, K. K.; Bustam, Mohammad Azmi; Ahmad, Faizan

    2011-10-01

    Physical properties such as density, viscosity, refractive index, surface tension, and thermal stability of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) were experimentally measured. All the experimental measurements were made over a wide range of temperatures from (298.15 to 333.15) K and AHPD concentrations of (1, 7, 13, 19, and 25) mass%. An overall decrease in all the measured physical properties was observed with increasing temperature. The experimental results are presented as a function of temperature and AHPD mass fraction. All the measured physical properties were correlated as a function of temperature. Thermal decomposition of pure and aqueous solutions of AHPD was investigated using a thermo-gravimetric analyzer (TGA) at a heating rate of 10 K · min-1.

  14. Thermal Decomposition of Bulk K-CoMoSx Mixed Alcohol Catalyst Precursors and Effects on Catalyst Morphology and Performance

    SciTech Connect

    Menart, M. J.; Hensley, J. E.; Costelow, K. E.

    2012-09-26

    Cobalt molybdenum sulfide-type mixed alcohol catalysts were synthesized via calcination of precipitated bulk sulfides and studied with temperature programmed decomposition analysis. Precursors containing aqueous potassium were also considered. Precipitates thermally decomposed in unique events which released ammonia, carbon dioxide, and sulfur. Higher temperature treatments led to more crystalline and less active catalysts in general with ethanol productivity falling from 203 to 97 g (kg cat){sup -1} h{sup -1} when the calcination temperature was increased from 375 to 500 C. The addition of potassium to the precursor led to materials with crystalline potassium sulfides and good catalytic performance. In general, less potassium was required to promote alcohol selectivity when added before calcination. At calcination temperatures above 350 C, segregated cobalt sulfides were observed, suggesting that thermally decomposed sulfide precursors may contain a mixture of molybdenum and cobalt sulfides instead of a dispersed CoMoS type of material. When dimethyl disulfide was fed to the precursor during calcination, crystalline cobalt sulfides were not detected, suggesting an important role of free sulfur during decomposition.

  15. Thermal decomposition behaviors and kinetic properties of 1,8-naphthalic anhydride loaded dense nano-silica hybrids

    NASA Astrophysics Data System (ADS)

    Wang, Jinpeng; Sun, Jihong; Wang, Feng; Ren, Bo

    2013-06-01

    A certain amount of (3-aminopropyl)triethoxysilane (APTES) and various capacity of 1,8-naphthalic anhydride (NA) were employed to modify and then graft onto the surface of the dense nano-silica spheres (DNSS) via a post-grafting method, and thereby, a novel luminescent density nano-silica hybrid materials have been successfully synthesized. Meanwhile, the structures and properties of obtained hybrid DNSS were characterized by XRD, TEM, N2 sorption, FT-IR, and TG analysis. Furthermore, the thermal stability of before and after modification were demonstrated by using both Kissinger methods and Ozawa-Flynn-Wall methods. Particularly, the thermal decomposition behaviors of amino-modified groups and NA-grafted organic molecules were emphasized based on the TG and DTG analysis and then the related mechanism was put forward according to Coats and Redfern methods. Finally, as a comparison, the obtained results and the proposed decomposition mechanism of hybrid DNSS with non-pores were discussed with that of mesopores silicas in details.

  16. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; Burns, Peter C.; Navrotsky, Alexandra

    2016-09-01

    The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability of the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.

  17. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

    DOE PAGES

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; ...

    2016-09-01

    The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability ofmore » the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.« less

  18. Thermal decomposition of HfCl{sub 4} as a function of its hydration state

    SciTech Connect

    Barraud, E.; Begin-Colin, S. . E-mail: begin@ipcms.u-strasbg.fr; Le Caer, G.; Villieras, F.; Barres, O.

    2006-06-15

    The thermogravimetric behavior of HfCl{sub 4} powders with different hydration states has been compared. Strongly hydrated powders consist of HfOCl{sub 2}.nH{sub 2}O with n>4. Partially hydrated powders consist of particles with a HfCl{sub 4} core and a hydrated outerlayer of HfOCl{sub 2}.nH{sub 2}O with n in the range of 0-8. Hydrated powders decomposed at temperature lower than 200 deg. C whereas the decomposition of partially hydrated powders was completed at a temperature of around 450 deg. C. The observed differences in decomposition temperature is related to the structure of HfOCl{sub 2}.nH{sub 2}O, which is different if n is higher or smaller than 4 and leads to intermediate compounds, which decompose at different temperatures.

  19. Flow of products of thermal decomposition of oil shale through porous skeleton

    NASA Astrophysics Data System (ADS)

    Knyazeva, A. G.; Maslov, A. L.

    2016-11-01

    Oil shale is sedimentary rock formed by the accumulation of pelagic sediments, minerals and their further transformation. Experimental investigation of shale decomposition is very complex and expensive. The model of underground oil shale retorting is formulated in this paper. Model takes into account the reactions in solid phase and in fluid, mass and heat exchange, gaseous product flow in pores. Example of the numerical solution of the developed system of equations for the particular problem is shown.

  20. Determination of Kinetic Parameters for Thermal Decomposition of Phenolic Ablative Materials by Multiple Heating Rate Method

    DTIC Science & Technology

    1980-07-01

    the ratio method to analyze thermogravimetric data obtained for a urethane polymer. Baer, Hedges, Seader , Jayakar, and Wojcik6 heated samples of...reinforced polymers at heating rates up to 4200°C/min. The data were correlated by a numerical technique developed by Burningham and Seader .7 Friedman...Decomposition Through Thermogravimetric Analysis," Thermochimica Acta, No, 1, (1970), pp. 147-158. 6. A. D. Baer, J. H. Hedges, J. D. Seader , K. M. Jayakar

  1. The Preparation of Chromium by the Thermal Decomposition of Chromium Iodide

    DTIC Science & Technology

    2014-05-15

    chromium with iodine vapor, the sublimation of the chromium iodide, and its subsequent decomposition on a hot tungsten filament, all in an evacuated...heated with a gas burner while iodine from the bulb was vaporized and passed over it. As the iodine vapor passed over the hot metal, a condensate was v...of iodine was exhausted, the apparatus was broken ~pen and the contents examined. The reaction product was very hygro- scopic, forming a green

  2. Thermal decomposition of solid solutions in systems of Fe(II), Co(II), and Ni(II) hydrogen maleates with the formation of bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yudanova, L. I.; Logvinenko, V. A.; Sheludyakova, L. A.; Ishchenko, A. V.; Rudina, N. A.

    2017-01-01

    XRD phase analysis and thermal analysis are used to confirm the formation of a continuous series of solid solutions in which one cation is substituted for another in the systems Co(II) hydrogen maleate-Ni(II) hydrogen maleate; Fe(II) hydrogen maleate-Co(II) hydrogen maleate; and Fe(II) hydrogen maleate-Ni(II) hydrogen maleate. The unit cell volume of these solid solutions is shown to depend linearly on their composition. The linear character of changes in the initial temperatures of dehydration and thermal decomposition is established. Using the example of the first of these systems, it is shown that when heated, bimetallic nanoparticles embedded in the polymeric matrix of composites obtained via the thermal decomposition of solid solutions of hydrogen maleates undergo a second-order phase transition, resulting in decomposition of the solid solutions of metals at the Curie temperature.

  3. Hydrothermal preparation of Fe2O3/graphene nanocomposite and its enhanced catalytic activity on the thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Yuan, Yuan; Jiang, Wei; Wang, Yujiao; Shen, Ping; Li, Fengsheng; Li, Pingyun; Zhao, Fengqi; Gao, Hongxu

    2014-06-01

    Fe2O3/graphene nanocomposite was prepared by a facile hydrothermal method, during which graphene oxides (GOs) were reduced to graphene with hydrazine and Fe2O3 nanoparticles were simultaneously anchored on graphene sheets. The morphology of the obtained Fe2O3/graphene nanocomposite was investigated by scanning electron microscopy (SEM) and transmission electron microscope (TEM). It was revealed by TEM images that Fe2O3 nanoparticles grew well on the surfaces of graphene. As much as I know, this new nanocomposite has not been investigated as a catalyst on the thermal decomposition of AP yet. In this work, the catalytic performance of the synthesized material on the thermal decomposition of ammonium perchlorate (AP) was investigated creatively by differential scanning calorimetry (DSC). The results of DSC indicated that graphene obviously improved the catalytic activity of Fe2O3 on the thermal decomposition of AP due to its high specific area.

  4. Thermal decomposition of explosives studied by chemiluminescence techniques. [Hexanitrostilbene, 2-(5-cyanotetrazolato)pentaumine cobalt perchlorate

    SciTech Connect

    Volltrauer, H.N.

    1982-01-01

    The thermal decomposition rates of pentaerythritol-tetranitrate, PETN; hexanitrostilbene, HNS; and 2-(5-cyanotetrazolato)pentaamminecobalt(III) perchlorate, CP, have been investigated using a chemiluminescence NO/NO/sub x/ analyzer to detect decomposition products from these substances in real time. For PETN two samples were tested over the 50 to 105/sup 0/C temperature range. The results are interpreted in terms of two NO/sub x/ evolution mechanisms; one appears to be desorption of NO/sub x/ and the other is due to decomposition for which the rate coefficients are 1.3 x 10/sup 14/ exp(-37800/RT)s/sup -1/ and 8.3 x 10/sup 14/ exp(-40800/RT)s/sup -1/ for the two samples. Over the 160 to 250/sup 0/C temperature range the rate coefficient describing the NO evolution from HNSI is k(T) = 3 x 10/sup 10/ exp(-42000/RT)s/sup -1/. For two HNSII samples k(T) = 1.6 x 10/sup 10/ exp(-42000/RT)s/sup -1/. Much larger NO evolution rates than predicted by the k(T) (as well as NO/sub 2/ evolution) are obtained with fresh samples. Increasing NO evolution rates were measured at fixed temperatures above 250/sup 0/C. The k(T) for NH/sub 3/ evolution from CP is k(T) = 5.2 x 10/sup 8/ exp(-32000/RT)s/sup -1/ over the 90 to 185/sup 0/C temperature range. Increasing NH/sub 3/ evolution rates were measured at fixed temperatures of 185/sup 0/C or above. The units of k(T) are moles NO/sub x/ (or NH/sub 3/) evolved per mole of substance investigated per second.

  5. Thermal decomposition studies of energetic materials using confined rapid thermolysis/FTIR spectroscopy

    SciTech Connect

    Kim, E.S.; Lee, H.S.; Mallery, C.F.; Thynell, S.T.

    1997-07-01

    An experimental setup for performing rapid thermolysis studies of small samples of energetic materials is described. In this setup, about 8 {micro}L of a liquid sample or about 2 mg of a solid sample is heated at rates exceeding 1,500 K/s to a set temperature where decomposition occurs. The rapid heating is achieved as a result of confining the sample between two closely spaced isothermal surfaces. The gaseous decomposition products depart from the confined space through a rectangular slit into the region of detection. The evolved gases are quantified using FTIR absorption spectroscopy by accounting for the instrument line shape. To illustrate the use of this setup, the thermolysis behaviors of three different energetic materials are examined. These materials include HMX, RDX, and HAN, all of which are considered as highly energetic propellant ingredients. The results obtained in this study of the temporal evolution of species concentrations from these ingredients are in reasonably close agreement with results available in the literature.

  6. Assessment of a new method for the analysis of decomposition gases of polymers by a combining thermogravimetric solid-phase extraction and thermal desorption gas chromatography mass spectrometry.

    PubMed

    Duemichen, E; Braun, U; Senz, R; Fabian, G; Sturm, H

    2014-08-08

    For analysis of the gaseous thermal decomposition products of polymers, the common techniques are thermogravimetry, combined with Fourier transformed infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS). These methods offer a simple approach to the decomposition mechanism, especially for small decomposition molecules. Complex spectra of gaseous mixtures are very often hard to identify because of overlapping signals. In this paper a new method is described to adsorb the decomposition products during controlled conditions in TGA on solid-phase extraction (SPE) material: twisters. Subsequently the twisters were analysed with thermal desorption gas chromatography mass spectrometry (TDS-GC-MS), which allows the decomposition products to be separated and identified using an MS library. The thermoplastics polyamide 66 (PA 66) and polybutylene terephthalate (PBT) were used as example polymers. The influence of the sample mass and of the purge gas flow during the decomposition process was investigated in TGA. The advantages and limitations of the method were presented in comparison to the common analysis techniques, TGA-FTIR and TGA-MS.

  7. Hierarchical multiscale mechanism development for methane partial oxidation and reforming and for thermal decomposition of oxygenates on Rh.

    PubMed

    Mhadeshwar, A B; Vlachos, D G

    2005-09-08

    A thermodynamically consistent C1 microkinetic model is developed for methane partial oxidation and reforming and for oxygenate (methanol and formaldehyde) decomposition on Rh via a hierarchical multiscale methodology. Sensitivity analysis is employed to identify the important parameters of the semiempirical unity bond index quadratic exponential potential (UBI-QEP) method and these parameters are refined using quantum mechanical density functional theory. With adjustment of only two pre-exponentials in the CH4 oxidation subset, the C1 mechanism captures a multitude of catalytic partial oxidation (CPOX) and reforming experimental data as well as thermal decomposition of methanol and formaldehyde. We validate the microkinetic model against high-pressure, spatially resolved CPOX experimental data. Distinct oxidation and reforming zones are predicted to exist, in agreement with experiments, suggesting that hydrogen is produced from reforming of methane by H2O formed in the oxidation zone. CO is produced catalytically by partial oxidation up to moderately high pressures, with water-gas shift taking place in the gas-phase at sufficiently high pressures resulting in reduction of CO selectivity.

  8. Decomposition Characteristics of Toluene Vapor Using Titanium Dioxide Photocatalyst and Zeolite Thermally Sprayed on an Aluminum Fiber Filter.

    PubMed

    Hori, Hajime; Hinoue, Mitsuo; Ishimatsu, Sumiyo; Fueta, Yukiko; Ishidao, Toru; Takabatake, Kaori; Yakiyama, Natsumi; Yamamoto, Kiyoshi

    2016-01-01

    Decomposition characteristics of toluene vapor by titanium dioxide photocatalyst and zeolite that are prepared by thermal spraying on an aluminum fiber filter (photocatalyst filter) were investigated. Toluene vapor was injected into a small chamber made of stainless steel, and an air cleaner equipped with the photocatalyst filter was operated. The vapor concentration in the chamber decreased exponentially. The decreasing rate of toluene vapor in the chamber depended on the initial toluene concentration, and the higher the initial vapor concentration was, the lower the decreasing rate was obtained. The decreasing rate was constant during each decomposition experiment, although the concentration decreased with time. To investigate the effect of zeolite on the reduction of the vapor concentration, we compared the decreasing rates of toluene vapor by photocatalyst filters with and without zeolite.The decreasing rate of toluene concentration using the filter without zeolite was larger than that with zeolite. The reason for this would be that photocatalyst decomposed toluene not only in air but also adsorbed in zeolite.

  9. Preparation and sonocatalytic activity of monodisperse porous bread-like CuO via thermal decomposition of copper oxalate precursors

    NASA Astrophysics Data System (ADS)

    Zhang, Lihui; Liu, Rong; Yang, Heqing

    2012-04-01

    Porous bread-like CuO have been obtained via the thermal decomposition of copper oxalate precursor synthesized by the room temperature reaction of Cu(NO3)2 with Na2C2O4 in water. These bread-like CuO with the monoclinic structure are well dispersed with good monodispersity, their diameters are about 1.5 μm. The sonocatalytic activity of porous CuO for the degradation of acid scarlet dye was studied. It was found that the as-prepared porous CuO nanostructures exhibit efficient sonocatalytic ability for the degradation of acid scarlet dye in the presence of H2O2, which are expected to be useful in the treatment of non- or low-transparent wastewaters.

  10. Economically attractive route for the preparation of high quality magnetic nanoparticles by the thermal decomposition of iron(III) acetylacetonate.

    PubMed

    Effenberger, Fernando B; Couto, Ricardo A; Kiyohara, Pedro K; Machado, Giovanna; Masunaga, Sueli H; Jardim, Renato F; Rossi, Liane M

    2017-03-17

    The thermal decomposition (TD) methods are among the most successful in obtaining magnetic nanoparticles with a high degree of control of size and narrow particle size distribution. Here we investigated the TD of iron(III) acetylacetonate in the presence of oleic acid, oleylamine, and a series of alcohols in order to disclose their role and also investigate economically attractive alternatives for the synthesis of iron oxide nanoparticles without compromising their size and shape control. We have found that some affordable and reasonably less priced alcohols, such as 1,2-octanediol and cyclohexanol, may replace the commonly used and expensive 1,2-hexadecanediol, providing an economically attractive route for the synthesis of high quality magnetic nanoparticles. The relative cost for the preparation of Fe3O4 NPs is reduced to only 21% and 9% of the original cost when using 1,2-octanediol and cyclohexanol, respectively.

  11. Thermal decomposition of methanol in the sonolysis of methanol-water mixtures. Spin-trapping evidence for isotope exchange reactions

    SciTech Connect

    Krishna, C.M.; Lion, Y.; Kondo, T.; Riesz, P.

    1987-11-05

    The spin trap 3,5-dibromo-4-nitrosobenzenesulfonate was used to monitor the yield of free radicals produced during sonolysis of water-methanol mixtures. Methyl radicals and CH/sub 2/OH radicals were observed as well as the isotopically mixed radicals CH/sub 2/D and CHD/sub 2/ when CH/sub 3/OD:D/sub 2/O mixtures were studied. The results clearly show that thermal decomposition of methanol to methyl radicals occurs in the gas phase. The methyl radical yield rises sharply at very low concentrations of methanol, reaches a maximum at 5 mol dm/sup -3/ in water and decreases to a smaller value in methanol. The yield of methyl radicals as a function of methanol concentration is discussed in terms of the different factors influencing the sonochemistry.

  12. Compact Ag@Fe3O4 Core-shell Nanoparticles by Means of Single-step Thermal Decomposition Reaction

    NASA Astrophysics Data System (ADS)

    Brollo, Maria Eugênia F.; López-Ruiz, Román; Muraca, Diego; Figueroa, Santiago J. A.; Pirota, Kleber R.; Knobel, Marcelo

    2014-10-01

    A temperature pause introduced in a simple single-step thermal decomposition of iron, with the presence of silver seeds formed in the same reaction mixture, gives rise to novel compact heterostructures: brick-like Ag@Fe3O4 core-shell nanoparticles. This novel method is relatively easy to implement, and could contribute to overcome the challenge of obtaining a multifunctional heteroparticle in which a noble metal is surrounded by magnetite. Structural analyses of the samples show 4 nm silver nanoparticles wrapped within compact cubic external structures of Fe oxide, with curious rectangular shape. The magnetic properties indicate a near superparamagnetic like behavior with a weak hysteresis at room temperature. The value of the anisotropy involved makes these particles candidates to potential applications in nanomedicine.

  13. Compact Ag@Fe3O4 core-shell nanoparticles by means of single-step thermal decomposition reaction.

    PubMed

    Brollo, Maria Eugênia F; López-Ruiz, Román; Muraca, Diego; Figueroa, Santiago J A; Pirota, Kleber R; Knobel, Marcelo

    2014-10-30

    A temperature pause introduced in a simple single-step thermal decomposition of iron, with the presence of silver seeds formed in the same reaction mixture, gives rise to novel compact heterostructures: brick-like Ag@Fe3O4 core-shell nanoparticles. This novel method is relatively easy to implement, and could contribute to overcome the challenge of obtaining a multifunctional heteroparticle in which a noble metal is surrounded by magnetite. Structural analyses of the samples show 4 nm silver nanoparticles wrapped within compact cubic external structures of Fe oxide, with curious rectangular shape. The magnetic properties indicate a near superparamagnetic like behavior with a weak hysteresis at room temperature. The value of the anisotropy involved makes these particles candidates to potential applications in nanomedicine.

  14. Boron nitride encapsulated copper nanoparticles: a facile one-step synthesis and their effect on thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Huang, Caijin; Liu, Qiuwen; Fan, Wenjie; Qiu, Xiaoqing

    2015-11-01

    Reactivity is of great importance for metal nanoparticles used as catalysts, biomaterials and advanced sensors, but seeking for high reactivity seems to be conflict with high chemical stability required for metal nanoparticles. There is a subtle balance between reactivity and stability. This could be reached for colloidal metal nanoparticles using organic capping reagents, whereas it is challenging for powder metal nanoparticles. Here, we developed an alternative approach to encapsulate copper nanoparticles with a chemical inertness material—hexagonal boron nitride. The wrapped copper nanoparticles not only exhibit high oxidation resistance under air atmosphere, but also keep excellent promoting effect on thermal decomposition of ammonium perchlorate. This approach opens the way to design metal nanoparticles with both high stability and reactivity for nanocatalysts and their technological application.

  15. Pt deposited TiO2 catalyst fabricated by thermal decomposition of titanium complex for solar hydrogen production

    NASA Astrophysics Data System (ADS)

    Truong, Quang Duc; Le, Thanh Son; Ling, Yong-Chien

    2014-12-01

    C, N codoped TiO2 catalyst has been synthesized by thermal decomposition of a novel water-soluble titanium complex. The structure, morphology, and optical properties of the synthesized TiO2 catalyst were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the Pt deposited TiO2 catalysts synthesized at different temperatures was evaluated by means of hydrogen evolution reaction under both UV-vis and visible light irradiation. The investigation results reveal that the photocatalytic H2 evolution rate strongly depended on the crystalline grain size as well as specific surface area of the synthesized catalyst. Our studies successfully demonstrate a simple method for the synthesis of visible-light responsive Pt deposited TiO2 catalyst for solar hydrogen production.

  16. Economically attractive route for the preparation of high quality magnetic nanoparticles by the thermal decomposition of iron(III) acetylacetonate

    NASA Astrophysics Data System (ADS)

    Effenberger, Fernando B.; Couto, Ricardo A.; Kiyohara, Pedro K.; Machado, Giovanna; Masunaga, Sueli H.; Jardim, Renato F.; Rossi, Liane M.

    2017-03-01

    The thermal decomposition (TD) methods are among the most successful in obtaining magnetic nanoparticles with a high degree of control of size and narrow particle size distribution. Here we investigated the TD of iron(III) acetylacetonate in the presence of oleic acid, oleylamine, and a series of alcohols in order to disclose their role and also investigate economically attractive alternatives for the synthesis of iron oxide nanoparticles without compromising their size and shape control. We have found that some affordable and reasonably less priced alcohols, such as 1,2-octanediol and cyclohexanol, may replace the commonly used and expensive 1,2-hexadecanediol, providing an economically attractive route for the synthesis of high quality magnetic nanoparticles. The relative cost for the preparation of Fe3O4 NPs is reduced to only 21% and 9% of the original cost when using 1,2-octanediol and cyclohexanol, respectively.

  17. Boron nitride encapsulated copper nanoparticles: a facile one-step synthesis and their effect on thermal decomposition of ammonium perchlorate

    PubMed Central

    Huang, Caijin; liu, Qiuwen; Fan, Wenjie; Qiu, Xiaoqing

    2015-01-01

    Reactivity is of great importance for metal nanoparticles used as catalysts, biomaterials and advanced sensors, but seeking for high reactivity seems to be conflict with high chemical stability required for metal nanoparticles. There is a subtle balance between reactivity and stability. This could be reached for colloidal metal nanoparticles using organic capping reagents, whereas it is challenging for powder metal nanoparticles. Here, we developed an alternative approach to encapsulate copper nanoparticles with a chemical inertness material—hexagonal boron nitride. The wrapped copper nanoparticles not only exhibit high oxidation resistance under air atmosphere, but also keep excellent promoting effect on thermal decomposition of ammonium perchlorate. This approach opens the way to design metal nanoparticles with both high stability and reactivity for nanocatalysts and their technological application. PMID:26567862

  18. Compact Ag@Fe3O4 Core-shell Nanoparticles by Means of Single-step Thermal Decomposition Reaction

    PubMed Central

    Brollo, Maria Eugênia F.; López-Ruiz, Román; Muraca, Diego; Figueroa, Santiago J. A.; Pirota, Kleber R.; Knobel, Marcelo

    2014-01-01

    A temperature pause introduced in a simple single-step thermal decomposition of iron, with the presence of silver seeds formed in the same reaction mixture, gives rise to novel compact heterostructures: brick-like Ag@Fe3O4 core-shell nanoparticles. This novel method is relatively easy to implement, and could contribute to overcome the challenge of obtaining a multifunctional heteroparticle in which a noble metal is surrounded by magnetite. Structural analyses of the samples show 4 nm silver nanoparticles wrapped within compact cubic external structures of Fe oxide, with curious rectangular shape. The magnetic properties indicate a near superparamagnetic like behavior with a weak hysteresis at room temperature. The value of the anisotropy involved makes these particles candidates to potential applications in nanomedicine. PMID:25354532

  19. Comparison of the thermal decompositions of HMX and 2,4-DNI for evaluation of slow cookoff response and long-term stability

    SciTech Connect

    Minier, L.; Behrens, R.; Bulusu, S.

    1995-12-01

    Thermal decomposition of HMX between 175C and 200C was studied using the simultaneous thermogravimetric modulated beam mass spectrometer with focus on initial stages of the decomposition. Thermal decomposition products are the same as in previous higher temperature experiments. The initial stages of the decomposition have an induction period followed by two acceleratory periods. Arrhenius parameters for the induction and two acceleratory periods are (Log(A)= 18.2 {plus_minus} 0.8, Ea = 48.2 {plus_minus} 1.8 kcal/mole), (Log (A) = 17.15 {plus_minus} 1.5 and Ea = 48.9 {plus_minus} 3.2 kcal/mole), (Log (A) = 19.1 {plus_minus} 3.0 and Ea = 52.1 {plus_minus} 6.3 kcal/mole). This data can be used to calculate the time and temperature required to decompose a desired fraction of a test sample testing the effect of thermal degradation on sensitivity or bum rates. It can also be used to estimate the extent of decomposition expected under normal storage conditions for munitions containing HMX. This data, along with previous mechanistic studies conducted at higher temperatures, suggest that the process that controls the early stages of decomposition of HMX in the solid phase is scission of the N-NO{sub 2} bond, reaction of the N0{sub 2} within a lattice cage to form the mononitroso analogue of HMX and decomposition of the mononitroso HMX within the HMX lattice to form gaseous products that are retained in bubbles or diffuse into the surrounding lattice. These methods evaluating HMX can be used to evaluate new energetic materials such as 2,4-DNI. The early 2,4-DNI thermal decomposition is characterized by an initial decomposition, an apparent induction period, then an initial acceleratory period. The main gaseous products are NO, C0{sub 2}, HNCO, H{sub 2}0, N{sub 2}, CO, HCN and C{sub 2}N{sub 2}. The presence of adsorbed and occluded H{sub 2}0 is the major cause of the early decomposition.

  20. Investigation of the crystalline structure of ettringite with in situ measurement of its evolution during formation and thermal decomposition

    NASA Astrophysics Data System (ADS)

    Hartman, Michael R.

    2005-07-01

    The crystalline structure of ettringite, Ca6[Al(OH)6 ]2(SO4)3·26H2O, an important hydration product in the chemistry of Portland cement, was investigated using time-of-flight neutron diffraction combined with Rietveld crystal structure refinement. In addition, the changes in crystalline structure during the formation and thermal decomposition of ettringite were followed in situ, using specialized experimental assemblies. The diffusive motions of crystalline water within the ettringite structure were studied using incoherent quasi-elastic neutron scattering techniques. The results of this investigation led to an improved model for the crystalline structure of ettringite, including a detailed understanding of the three-dimensional hydrogen bond network that extends throughout the structure. Structural changes were observed for ettringite specimens with thermal decomposition up to 30 wt. %. These studies showed that previous models of the dehydration process, based upon indirect experimental evidence, were incorrect. The formation of ettringite during the hydration of tricalcium aluminate (Ca3Al 2O6) in the presence of gypsum (CaSO4·2H 2O), for temperatures ranging from 25°C to 80°C, demonstrated that ettringite was the only crystalline hydration product, in contrast to a prior study which reported the presence of a precursor phase in the reaction pathway. An analysis of the kinetics of the hydration reaction showed that the rate law of the reaction changed markedly over the temperature range investigated. Approximately 12% of the hydrogen atoms present in a fully hydrated ettringite specimen were observed to perform a localized diffusive motion for temperatures between 200 K and 320 K, while an ettringite specimen dehydrated to a weight loss of 20 wt. % showed indications of translational diffusion for approximately 9% of the remaining hydrogen atoms.

  1. Pyrolysis of aseptic packages (tetrapak) in a laboratory screw type reactor and secondary thermal/catalytic tar decomposition

    SciTech Connect

    Haydary, J.; Susa, D.; Dudáš, J.

    2013-05-15

    Highlights: ► Pyrolysis of aseptic packages was carried out in a laboratory flow reactor. ► Distribution of tetrapak into the product yields was obtained. ► Composition of the pyrolysis products was estimated. ► Secondary thermal and catalytic decomposition of tars was studied. ► Two types of catalysts (dolomite and red clay marked AFRC) were used. - Abstract: Pyrolysis of aseptic packages (tetrapak cartons) in a laboratory apparatus using a flow screw type reactor and a secondary catalytic reactor for tar cracking was studied. The pyrolysis experiments were realized at temperatures ranging from 650 °C to 850 °C aimed at maximizing of the amount of the gas product and reducing its tar content. Distribution of tetrapak into the product yields at different conditions was obtained. The presence of H{sub 2}, CO, CH{sub 4}, CO{sub 2} and light hydrocarbons, HCx, in the gas product was observed. The Aluminum foil was easily separated from the solid product. The rest part of char was characterized by proximate and elemental analysis and calorimetric measurements. The total organic carbon in the tar product was estimated by elemental analysis of tars. Two types of catalysts (dolomite and red clay marked AFRC) were used for catalytic thermal tar decomposition. Three series of experiments (without catalyst in a secondary cracking reactor, with dolomite and with AFRC) at temperatures of 650, 700, 750, 800 and 850 °C were carried out. Both types of catalysts have significantly affected the content of tars and other components in pyrolytic gases. The effect of catalyst on the tetrapack distribution into the product yield on the composition of gas and on the total organic carbon in the tar product is presented in this work.

  2. Abiotic formation of hydrocarbons and oxygenated compounds during thermal decomposition of iron oxalate

    NASA Technical Reports Server (NTRS)

    McCollom, T. M.; Simoneit, B. R.

    1999-01-01

    The formation of organic compounds during the decomposition of iron oxalate dihydrate (IOD) was investigated as a possible analog for abiotic organic synthesis in geological systems. After heating at 330 degrees C for 2-4 days, IOD decomposed to a mixture of the minerals siderite and magnetite plus gas and non-volatile organic compounds. The organic products included an extremely large variety of compounds, making identification of individual reaction products difficult. However, the non-volatile products were dominated by several homologous series of alkylated cyclic compounds mostly containing a single aromatic ring, including alkylphenols, alkylbenzenes, alkyltetrahydronaphthols, and alkyltetrahydronaphthalenes. Traces of n-alkanols, n-alkanoic acids, n-alkanones, and n-alkanes were also identified. Carbon in the gas phase was predominantly CO2 (+CO?), with lesser amounts of light hydrocarbons to > C6 including all possible branched and normal isomers of the alkanes and alkenes. The organic products were apparently the result of two concurrent reaction processes: (1) condensation of the two-carbon units present in the initial oxalate moiety, and (2) Fischer-Tropsch-type synthesis from CO2 or CO generated during the experiment. Compounds produced by the former process may not be characteristic of synthesis from the single-carbon precursors which predominate in geologic systems, suggesting iron oxalate decomposition may not provide a particularly suitable analog for investigation of abiotic organic synthesis. When water was included in the reaction vessels, CO2 and traces of methane and light hydrocarbon gases were the only carbon products observed (other than siderite), suggesting that the presence of water allowed the system to proceed rapidly towards equilibrium and precluded the formation of metastable organic intermediates.

  3. Thermal decomposition mechanisms of the methoxyphenols: formation of phenol, cyclopentadienone, vinylacetylene, and acetylene.

    PubMed

    Scheer, Adam M; Mukarakate, Calvin; Robichaud, David J; Nimlos, Mark R; Ellison, G Barney

    2011-11-24

    The pyrolyses of the guaiacols or methoxyphenols (o-, m-, and p-HOC(6)H(4)OCH(3)) have been studied using a heated SiC microtubular (μ-tubular) reactor. The decomposition products are detected by both photoionization time-of-flight mass spectroscopy (PIMS) and matrix isolation infrared spectroscopy (IR). Gas exiting the heated SiC μ-tubular reactor is subject to a free expansion after a residence time of approximately 50-100 μs. The PIMS reveals that, for all three guaiacols, the initial decomposition step is loss of methyl radical: HOC(6)H(4)OCH(3) → HOC(6)H(4)O + CH(3). Decarbonylation of the HOC(6)H(4)O radical produces the hydroxycyclopentadienyl radical, C(5)H(4)OH. As the temperature of the μ-tubular reactor is raised to 1275 K, the C(5)H(4)OH radical loses a H atom to produce cyclopentadienone, C(5)H(4)═O. Loss of CO from cyclopentadienone leads to the final products, acetylene and vinylacetylene: C(5)H(4)═O → [CO + 2 HC≡CH] or [CO + HC≡C-CH═CH(2)]. The formation of C(5)H(4)═O, HCCH, and CH(2)CHCCH is confirmed with IR spectroscopy. In separate studies of the (1 + 1) resonance-enhanced multiphoton ionization (REMPI) spectra, we observe the presence of C(6)H(5)OH in the molecular beam: C(6)H(5)OH + λ(275.1 nm) → [C(6)H(5)OH Ã] + λ(275.1nm) → C(6)H(5)OH(+). From the REMPI and PIMS signals and previous work on methoxybenzene, we suggest that phenol results from a radical/radical reaction: CH(3) + C(5)H(4)OH → [CH(3)-C(5)H(4)OH]* → C(6)H(5)OH + 2H.

  4. Thermal decomposition of municipal solid waste fly ash and desorption of polychlorinated dibenzo-p-dioxins and furans from fly ash surfaces.

    PubMed

    Weidemann, Eva; Lundin, Lisa; Boily, Jean-François

    2016-11-01

    Surfaces of fly ashes from three Swedish MSW incinerating plants were extensively characterized to better predict their involvement in the generation of persistent organic pollutants. The ashes were then subjected to thermal treatment at 400 °C in sealed glass ampoules to track the decomposition polychlorinated dibenzo-p-dioxins and furans (PCDD and PCDF). Temperature programmed desorption experiments in the 30-900 °C range also enabled monitoring of thermally decomposing ashes by Fourier Transform Infrared (FTIR) spectroscopy as well as thermally desorbing effluent gases by mass spectrometry. In addition, one ash was doped with (13)C-labelled PCDD and PCDF to evaluate the potential of the experimental setup for elucidating the thermal desorption of the organic molecules. It was found that in ashes with high carbon content PCDD and PCDF decomposition were led pronounced, and that PCDD degraded more readily than PCDF.

  5. Sol-gel method to prepare graphene/Fe2O3 aerogel and its catalytic application for the thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Lan, Yuanfei; Li, Xiaoyu; Li, Guoping; Luo, Yunjun

    2015-10-01

    Graphene/Fe2O3 (Gr/Fe2O3) aerogel was synthesized by a simple sol-gel method and supercritical carbon dioxide drying technique. In this study, the morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen sorption tests. The catalytic performance of the as-synthesized Gr/Fe2O3 aerogel on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermogravimetric and differential scanning calorimeter. The experimental results showed that Fe2O3 with particle sizes in the nanometer range was anchored on the Gr sheets and Gr/Fe2O3 aerogel exhibits promising catalytic effects for the thermal decomposition of AP. The decomposition temperature of AP was obviously decreased and the total heat release increased as well.

  6. Thermal decomposition study of Mo0.6W0.4Se2 single crystals

    NASA Astrophysics Data System (ADS)

    Chaki, Sunil H.; Deshpande, M. P.; Tailor, Jiten P.

    2013-06-01

    The Mo0.6W0.4Se2 single crystals were grown by direct vapour transport (DVT) technique. The thermogravimetric analysis (TGA), differential thermal analysis (DTA) and differential thermogravimetric (DTG) analysis were carried out on the as-grown Mo0.6W0.4Se2 single crystals in inert nitrogen atmosphere. All these thermal analysis were done from ambient temperature to 1223 K. The activation energy, enthalpy, entropy and Gibbs free energy of Mo0.6W0.4Se2 single crystals were determined from the thermal curves using Broido, Horowitz-Metzger (H-M), Piloyan-Novikova (P-N) and Coats-Redfern (C-R) relations. The results are reported in this paper.

  7. High resistance to thermal decomposition in brown cotton is linked to tannis and sodium content

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brown cotton (Gossypium hirsutum L.) fibers (SA-1 and MC-BL) studied were inferior to white cotton fiber Sure-Grow 747 (SG747) in fiber quality, i.e., shorter length, fewer twists, and lower crystallinity, but exhibited superior thermal properties in thermogravimetry (TG), differential thermogravime...

  8. Thermal decomposition of t-butylamine borane studied by in situ solid state NMR

    SciTech Connect

    Feigerle, J.; Smyrl, N. R.; Morrell, J. S.; Stowe, A. C.

    2010-03-18

    Development of suitable materials to store hydrogen for automotive use has received pointed attention over the past decade. Significant progress has been made with the discovery of novel chemical hydrides, complex metal hydrides, and adsorption substrates which continue to optimize both thermodynamics and kinetics of hydrogen sorption. Chemical hydrides typically offer the largest theoretical gravimetric capacities. Autrey et al. have recently shown that mechanical milling of alkali metal hydrides with ammonia borane can further lower the decomposition temperature. In all cases, however, many challenges remain in order to meet the current US DOE performance targets. Amine boranes are being considered for hydrogen storage materials since they contain significant quantities of hydrogen which potentially can be released at low temperatures (80-150 C) via chemical reactions. Ammonia borane, NH{sub 3}BH{sub 3}, is one of the most promising in this class as it decomposes to release greater than two moles of pure hydrogen gas (14 wt%) below 160 C. Although isoelectronic to ethane, NH{sub 3}BH{sub 3} is a solid at room temperature due to the di-hydrogen bonding network formed between the amine protons and boron hydrides in the solid state lattice. Further, it has been shown that the hydrogen release mechanism involves transformation and isomerization to an ionic dimer where a hydride migrates from one boron to the adjacent boron in the dimer. The greatest challenge to the use of ammonia borane as a hydrogen fuel is the regeneration path from spent fuel to ammonia borane again. The proposed chemical synthesis involves complicated organometallic reactions to form boron hydrogen bonds from the thermodynamically stable polyimidoborane products (BNH){sub n}. Recent theoretical calculations suggested that incorporation of carbon atoms into the (BNH)n product would be less thermodynamically stable. These (CBNH)n compounds are potentially less energy intensive making regeneration

  9. Thermal decomposition studies of 1,3,3-trinitroazetidine (TNAZ) and 1-nitroso-3,3-dinitroazetidine (NDNAZ) by simultaneous thermogravimetric modulated beam mass spectroscopy

    SciTech Connect

    Behrens, R. Jr.; Bulusu, S.

    1995-12-01

    The initial results from a study of the thermal decomposition of TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) are presented. The major products formed in the decomposition of TNAZ are NO{sub 2} and NO with slightly lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}, CO{sub 2}/N{sub 2}O and NDNAZ. The major product formed in the decomposition of NDNAZ is NO with lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}O. The lower molecular weight products are similar to those observed in RSFTIR and IRMPD studies conducted previously by others. However, this study has shown that the mononitroso analogue of TNAZ, NDNAZ, is an important intermediate formed during the decomposition of TNAZ. It plays an important role in determining the identity of the products formed in the decomposition of TNAZ. The temporal behaviors Of the ion signals associated with the various thermal decomposition products from TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ are also presented. The illustrate the evolution sequence of the various products that are associated with the different reaction pathways that control the decomposition of these materials. In particular, the study of the {sup 15}N-labeled sample revealed that NO{sub 2} originates from both the likely sites in the TNAZ molecule and that the cleavage of the nitramine-NO{sub 2} group precedes that of the C-NO{sub 2} cleavage, resulting in similar sequences in the formation of NO and NDNAZ also.

  10. Gold nano-particle formation from crystalline AuCN: Comparison of thermal, plasma- and ion-beam activated decomposition

    NASA Astrophysics Data System (ADS)

    Beck, Mihály T.; Bertóti, Imre; Mohai, Miklós; Németh, Péter; Jakab, Emma; Szabó, László; Szépvölgyi, János

    2017-02-01

    In this work, in addition to the conventional thermal process, two non-conventional ways, the plasma and ion beam activations are described for preparing gold nanoparticles from microcrystalline AuCN precursor. The phase formation at plasma and ion beam treatments was compared with that at thermal treatments and the products and transformations were characterized by thermogravimetry-mass-spectrometry (TG-MS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TG-MS measurements in Ar atmosphere revealed that AuCN decomposition starts at 400 °C and completes at ≈700 °C with evolution of gaseous (CN)2. XPS and TEM show that in heat treatment at 450 °C for 1 h in Ar, loss of nitrogen and carbon occurs and small, 5-30 nm gold particles forms. Heating at 450 °C for 10 h in sealed ampoule, much larger, 60-200 nm size and well faceted Au particles develop together with a fibrous (CN)n polymer phase, and the Au crystallites are covered by a 3-5 nm thick polymer shell. Low pressure Ar plasma treatment at 300 eV energy results in 4-20 nm size Au particles and removes most of the nitrogen and part of carbon. During Ar+ ion bombardment with 2500 eV energy, 5-30 nm size Au crystallites form already in 10 min, with preferential loss of nitrogen and with increased amount of carbon residue. The results suggest that plasma and ion beam activation, acting similarly to thermal treatment, may be used to prepare Au nanoparticles from AuCN on selected surface areas either by depositing AuCN precursors on selected regions or by focusing the applied ionized radiation. Thus they may offer alternative ways for preparing tailor-made catalysts, electronic devices and sensors for different applications.

  11. Theoretical kinetic study of thermal unimolecular decomposition of cyclic alkyl radicals.

    PubMed

    Sirjean, B; Glaude, P A; Ruiz-Lopèz, M F; Fournet, R

    2008-11-20

    Whereas many studies have been reported on the reactions of aliphatic hydrocarbons, the chemistry of cyclic hydrocarbons has not been explored extensively. In the present work, a theoretical study of the gas-phase unimolecular decomposition of cyclic alkyl radicals was performed by means of quantum chemical calculations at the CBS-QB3 level of theory. Energy barriers and high-pressure-limit rate constants were calculated systematically. Thermochemical data were obtained from isodesmic reactions, and the contribution of hindered rotors was taken into account. Classical transition state theory was used to calculate rate constants. The effect of tunneling was taken into account in the case of CH bond breaking. Three-parameter Arrhenius expressions were derived in the temperature range of 500-2000 K at atmospheric pressure, and the CC and CH bond breaking reactions were studied for cyclic alkyl radicals with a ring size ranging from three to seven carbon atoms, with and without a lateral alkyl chain. For the ring-opening reactions, the results clearly show an increase of the activation energy as the pi bond is being formed in the ring (endo ring opening) in contrast to the cases in which the pi bond is formed on the side chain (exo ring opening). These results are supported by analyses of the electronic charge density that were performed with Atoms in Molecules (AIM) theory. For all cycloalkyl radicals considered, CH bond breaking exhibits larger activation energies than CC bond breaking, except for cyclopentyl for which the ring-opening and H-loss reactions are competitive over the range of temperatures studied. The theoretical results compare rather well with the experimental data available in the literature. Evans-Polanyi correlations for CC and CH beta-scissions in alkyl and cycloalkyl free radicals were derived. The results highlight two different types of behavior depending on the strain energy in the reactant.

  12. Investigation of thermal decomposition as the kinetic process that causes the loss of crystalline structure in sucrose using a chemical analysis approach (part II).

    PubMed

    Lee, Joo Won; Thomas, Leonard C; Jerrell, John; Feng, Hao; Cadwallader, Keith R; Schmidt, Shelly J

    2011-01-26

    High performance liquid chromatography (HPLC) on a calcium form cation exchange column with refractive index and photodiode array detection was used to investigate thermal decomposition as the cause of the loss of crystalline structure in sucrose. Crystalline sucrose structure was removed using a standard differential scanning calorimetry (SDSC) method (fast heating method) and a quasi-isothermal modulated differential scanning calorimetry (MDSC) method (slow heating method). In the fast heating method, initial decomposition components, glucose (0.365%) and 5-HMF (0.003%), were found in the sucrose sample coincident with the onset temperature of the first endothermic peak. In the slow heating method, glucose (0.411%) and 5-HMF (0.003%) were found in the sucrose sample coincident with the holding time (50 min) at which the reversing heat capacity began to increase. In both methods, even before the crystalline structure in sucrose was completely removed, unidentified thermal decomposition components were formed. These results prove not only that the loss of crystalline structure in sucrose is caused by thermal decomposition, but also that it is achieved via a time-temperature combination process. This knowledge is important for quality assurance purposes and for developing new sugar based food and pharmaceutical products. In addition, this research provides new insights into the caramelization process, showing that caramelization can occur under low temperature (significantly below the literature reported melting temperature), albeit longer time, conditions.

  13. Study of thermal treatment combined with radiation on the decomposition of polysaccharides in sugarcane bagasse

    NASA Astrophysics Data System (ADS)

    Duarte, C. L.; Ribeiro, M. A.; Oikawa, H.; Mori, M. N.

    2013-03-01

    Sugarcane bagasse pretreatment is a physical and chemical process that reduces the crystalline structure and disrupts the hydrogen bonding of cellulose to improve the accessibility to hydrolytic depolymerization reactions. The combination of pretreatment technologies intends to decrease the severity of the processes and to avoid excessive sugar degradation and formation of toxic by-products. An effective pretreatment preserves the pentose fractions and limits the formation of degradation products that inhibits the growth of fermentative microorganisms. This study presents the evaluation of the cleavage of polysaccharides from sugarcane bagasse using ionizing radiation combined with thermal and diluted acid treatment to further enzymatic or chemical hydrolysis of cellulose. Samples of sugarcane bagasse were irradiated using a Radiation Dynamics electron beam accelerator with 1.5 MeV and 37 kW, with different absorbed doses, and then were submitted to thermal and acid (0.1% sulfuric acid, m/m) hydrolysis for 10, 20 and 40 min at 180 °C. Taking into account the sugars and by-products liberated in these treatments the conversion rates of cellulose and hemicelluloses were calculated.

  14. Catalytic Generation Of Nanometer-sized Diamondoids From Thermal Decomposition Of Organic Matter In Modern Sediments

    NASA Astrophysics Data System (ADS)

    Wei, Z.; Moldowan, M. J.; Paytan, A.

    2005-12-01

    Diamondoids are nanoparticles naturally occurring in petroleum and not known to be natural products. Experimental work of artificial maturation on modern sediments was completed to determine if diamondoids can be created from biosynthetic precursors (e.g., n-alkenes, fatty acids, highly branched isoprenoids, sterols, etc.) present in modern sediments. Addition of mineral catalysts (montmorillonite K10, acidic aluminosilicate and calcium carbonate) with distinctive properties to pyrolysis experiments conducted using organic-rich modern sediments can provide information on which type of catalyst is active and effective in the production of diamondoids. Trace amounts of diamondoids were detected in San Francisco Bay, Santa Barbara Basin, and Elkhorn Slough muds. These might have been contributed by slight contamination with unknown oil spills or oil seeps, as supported by the presence of both geological epimers (22S) and biological epimers (22R) for C31-C35 homohopanes in mud extracts. However, diamondoids were not detectable or possibly absent in Celestun Lagoon carbonate which is rich in microfossils. Various quantities of diamondoids were generated from the thermal alteration of organic matter in several modern sediments in the presence and absence of catalysts. It is likely that the formation of diamondoids is coincident with the occurrence of n-alkanes and other biomarkers since the thermal maturation of modern sediments produces a certain amount of diamondoids. Clay minerals usually behave as acidic catalysts in the transformation of organic matter to hydrocarbons. As expected, montmorillonite K10 and acidic aluminosilicate greatly facilitate the formation of diamondoids in modern sediments at 340°C. Rearrangements of certain strained polycyclic carbonium-ion intermediates at Lewis super-acid sites may be responsible for the relatively high abundance of diamondoids upon thermal stress in the presence of montmorillonite K10 or acidic aluminosilicate. In contrast

  15. Thermal decomposition of electronic wastes: Mobile phone case and other parts

    SciTech Connect

    Molto, Julia; Egea, Silvia; Conesa, Juan Antonio; Font, Rafael

    2011-12-15

    Highlights: > Pyrolysis and combustion of different parts of mobile phones produce important quantities of CO and CO{sub 2}. > Naphthalene is the most abundant PAH obtained in the thermal treatment of mobile phones. > Higher combustion temperature increases the chlorinated species evolved. - Abstract: Pyrolysis and combustion runs at 850 {sup o}C in a horizontal laboratory furnace were carried out on different parts of a mobile phone (printed circuit board, mobile case and a mixture of both materials). The analyses of the carbon oxides, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), polychlorodibenzo-p-dioxin, polychlorodibenzofurans (PCDD/Fs), and dioxin-like PCBs are shown. Regarding semivolatile compounds, phenol, styrene, and its derivatives had the highest yields. In nearly all the runs the same PAHs were identified, naphthalene being the most common component obtained. Combustion of the printed circuit board produced the highest emission factor of PCDD/Fs, possibly due to the high copper content.

  16. Cyano-Bridged Trimetallic Coordination Polymer Nanoparticles and Their Thermal Decomposition into Nanoporous Spinel Ferromagnetic Oxides.

    PubMed

    Zakaria, Mohamed B; Hossain, Md Shahriar A; Shiddiky, Muhammad J A; Shahabuddin, Mohammed; Yanmaz, Ekrem; Kim, Jung Ho; Belik, Alexei A; Ide, Yusuke; Hu, Ming; Tominaka, Satoshi; Yamauchi, Yusuke

    2016-10-10

    The synthesis of a novel family of cyano-bridged trimetallic coordination polymers (CPs) with various compositions and shapes has been reported by changing the compositional ratios of Fe, Co, and Ni species in the reaction system. In order to efficiently control the nucleation rate and the crystal growth, trisodium citrate dihydrate plays an important role as a chelating agent. After the obtained cyano-bridged trimetallic CPs undergo thermal treatment in air at three different temperatures (250, 350, and 450 °C), nanoporous spinel metal oxides are successfully obtained. Interestingly, the obtained nanoporous metal oxides are composed of small crstalline grains, and the grains are oriented in the same direction, realizing pseudo-single crystals with nanopores. The resultant nanoporous spinel oxides feature interesting magnetic properties. Cyano-bridged multimetallic CPs with various sizes and shapes can provide a pathway toward functional nanoporous metal oxides that are not attainable from simple cyano-bridged CPs containing single metal ions.

  17. Thermal decomposition of (UO2)O2(H2O)2·2H2O: Influence on structure, microstructure and hydrofluorination

    NASA Astrophysics Data System (ADS)

    Thomas, R.; Rivenet, M.; Berrier, E.; de Waele, I.; Arab, M.; Amaraggi, D.; Morel, B.; Abraham, F.

    2017-01-01

    The thermal decomposition of uranyl peroxide tetrahydrate, (UO2)O2(H2O)2.2H2O, was studied by combining high temperature powder X-ray diffraction, scanning electron microscopy, thermal analyses and spectroscopic techniques (Raman, IR and 1H NMR). In situ analyses reveal that intermediates and final uranium oxides obtained upon heating are different from that obtained after cooling at room temperature and that the uranyl precursor used to synthesize (UO2)O2(H2O)2·2H2O, sulfate or nitrate, has a strong influence on the peroxide thermal behavior and morphology. The decomposition of (UO2)O2(H2O)2·2H2O ex sulfate is pseudomorphic and leads to needle-like shaped particles of metastudtite, (UO2)O2(H2O)2, and UO3-x(OH)2x·zH2O, an amorphous phase found in air in the following of (UO2)O2(H2O)2 dehydration. (UO2)O2(H2O)2·2H2O and the compounds resulting from its thermal decomposition are very reactive towards hydrofluorination as long as their needle-like morphology is kept.

  18. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical.

    PubMed

    Buckingham, Grant T; Porterfield, Jessica P; Kostko, Oleg; Troy, Tyler P; Ahmed, Musahid; Robichaud, David J; Nimlos, Mark R; Daily, John W; Ellison, G Barney

    2016-07-07

    Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H5 (13)CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H5 (13)CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).

  19. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical

    NASA Astrophysics Data System (ADS)

    Buckingham, Grant T.; Porterfield, Jessica P.; Kostko, Oleg; Troy, Tyler P.; Ahmed, Musahid; Robichaud, David J.; Nimlos, Mark R.; Daily, John W.; Ellison, G. Barney

    2016-07-01

    Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 μs. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H513CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H513CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).

  20. Combined TGA-MS kinetic analysis of multistep processes. Thermal decomposition and ceramification of polysilazane and polysiloxane preceramic polymers.

    PubMed

    García-Garrido, C; Sánchez-Jiménez, P E; Pérez-Maqueda, L A; Perejón, A; Criado, José M

    2016-10-26

    The polymer-to-ceramic transformation kinetics of two widely employed ceramic precursors, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (TTCS) and polyureamethylvinylsilazane (CERASET), have been investigated using coupled thermogravimetry and mass spectrometry (TG-MS), Raman, XRD and FTIR. The thermally induced decomposition of the pre-ceramic polymer is the critical step in the synthesis of polymer derived ceramics (PDCs) and accurate kinetic modeling is key to attaining a complete understanding of the underlying process and to attempt any behavior predictions. However, obtaining a precise kinetic description of processes of such complexity, consisting of several largely overlapping physico-chemical processes comprising the cleavage of the starting polymeric network and the release of organic moieties, is extremely difficult. Here, by using the evolved gases detected by MS as a guide it has been possible to determine the number of steps that compose the overall process, which was subsequently resolved using a semiempirical deconvolution method based on the Frasier-Suzuki function. Such a function is more appropriate that the more usual Gaussian or Lorentzian functions since it takes into account the intrinsic asymmetry of kinetic curves. Then, the kinetic parameters of each constituent step were independently determined using both model-free and model-fitting procedures, and it was found that the processes obey mostly diffusion models which can be attributed to the diffusion of the released gases through the solid matrix. The validity of the obtained kinetic parameters was tested not only by the successful reconstruction of the original experimental curves, but also by predicting the kinetic curves of the overall processes yielded by different thermal schedules and by a mixed TTCS-CERASET precursor.

  1. The thermal decomposition of the benzyl radical in a heated micro-reactor. II. Pyrolysis of the tropyl radical

    SciTech Connect

    Buckingham, Grant T.; Porterfield, Jessica P.; Kostko, Oleg; Troy, Tyler P.; Ahmed, Musahid; Robichaud, David J.; Nimlos, Mark R.; Daily, John W.; Ellison, G. Barney

    2016-07-05

    Cycloheptatrienyl (tropyl) radical, C7H7, was cleanly produced in the gas-phase, entrained in He or Ne carrier gas, and subjected to a set of flash-pyrolysis micro-reactors. The pyrolysis products resulting from C7H7 were detected and identified by vacuum ultraviolet photoionization mass spectrometry. Complementary product identification was provided by infrared absorption spectroscopy. Pyrolysis pressures in the micro-reactor were roughly 200 Torr and residence times were approximately 100 us. Thermal cracking of tropyl radical begins at 1100 K and the products from pyrolysis of C7H7 are only acetylene and cyclopentadienyl radicals. Tropyl radicals do not isomerize to benzyl radicals at reactor temperatures up to 1600 K. Heating samples of either cycloheptatriene or norbornadiene never produced tropyl (C7H7) radicals but rather only benzyl (C6H5CH2). The thermal decomposition of benzyl radicals has been reconsidered without participation of tropyl radicals. There are at least three distinct pathways for pyrolysis of benzyl radical: the Benson fragmentation, the methyl-phenyl radical, and the bridgehead norbornadienyl radical. These three pathways account for the majority of the products detected following pyrolysis of all of the isotopomers: C6H5CH2, C6H5CD2, C6D5CH2, and C6H5 13CH2. Analysis of the temperature dependence for the pyrolysis of the isotopic species (C6H5CD2, C6D5CH2, and C6H5 13CH2) suggests the Benson fragmentation and the norbornadienyl pathways open at reactor temperatures of 1300 K while the methyl-phenyl radical channel becomes active at slightly higher temperatures (1500 K).

  2. Far-reaching geometrical artefacts due to thermal decomposition of polymeric coatings around focused ion beam milled pigment particles.

    PubMed

    Rykaczewski, K; Mieritz, D G; Liu, M; Ma, Y; Iezzi, E B; Sun, X; Wang, L P; Solanki, K N; Seo, D-K; Wang, R Y

    2016-06-01

    Focused ion beam and scanning electron microscope (FIB-SEM) instruments are extensively used to characterize nanoscale composition of composite materials, however, their application to analysis of organic corrosion barrier coatings has been limited. The primary concern that arises with use of FIB to mill organic materials is the possibility of severe thermal damage that occurs in close proximity to the ion beam impact. Recent research has shown that such localized artefacts can be mitigated for a number of polymers through cryogenic cooling of the sample as well as low current milling and intelligent ion beam control. Here we report unexpected nonlocalized artefacts that occur during FIB milling of composite organic coatings with pigment particles. Specifically, we show that FIB milling of pigmented polysiloxane coating can lead to formation of multiple microscopic voids within the substrate as far as 5 μm away from the ion beam impact. We use further experimentation and modelling to show that void formation occurs via ion beam heating of the pigment particles that leads to decomposition and vaporization of the surrounding polysiloxane. We also identify FIB milling conditions that mitigate this issue.

  3. Doped Tricalcium Phosphate Scaffolds by Thermal Decomposition of Naphthalene: Mechanical Properties and In vivo Osteogenesis in a Rabbit Femur Model

    PubMed Central

    Ke, Dongxu; Dernell, William; Bandyopadhyay, Amit; Bose, Susmita

    2015-01-01

    Tricalcium phosphate (TCP) is a bioceramic that is widely used in orthopedic and dental applications. TCP structures show excellent biocompatibility as well as biodegradability. In this study, porous β-TCP scaffolds were prepared by thermal decomposition of naphthalene. Scaffolds with 57.64 ± 3.54 % density and a maximum pore size around 100 μm were fabricated via removing 30% naphthalene at 1150°C. The compressive strength for these scaffolds was 32.85 ± 1.41 MPa. Furthermore, by mixing 1 wt % SrO and 0.5 wt % SiO2, pore interconnectivity improved, but the compressive strength decreased to 22.40 ± 2.70 MPa. However, after addition of polycaprolactone (PCL) coating layers, the compressive strength of doped scaffolds increased to 29.57 ± 3.77 MPa. Porous scaffolds were implanted in rabbit femur defects to evaluate their biological property. The addition of dopants triggered osteoinduction by enhancing osteoid formation, osteocalcin expression and bone regeneration, especially at the interface of the scaffold and host bone. This study showed processing flexibility to make interconnected porous scaffolds with different pore size and volume fraction porosity with high compressive mechanical strength and better bioactivity. Results show that SrO/SiO2 doped porous TCP scaffolds have excellent potential to be used in bone tissue engineering applications. PMID:25504889

  4. L1(0)-FePd nanocluster wires by template-directed thermal decomposition and subsequent hydrogen reduction

    SciTech Connect

    Cui, BZ; Marinescu, M; Liu, JF

    2013-12-14

    This paper reports the nanostructure, formation mechanism, and magnetic properties of tetragonal L1(0)-type Fe55Pd45 (at. %) nanocluster wires (NCWs) fabricated by thermal decomposition of metal nitrates and subsequent hydrogen reduction in nanoporous anodized aluminum oxide templates. The as-synthesized NCWs have diameters in the range of 80-300 nm, and lengths in the range of 0.5-10 mu m. The NCWs are composed of roughly round-shaped nanoclusters in the range of 3-30 nm in size and a weighted average size of 10 nm with a mixture of single-crystal and poly-crystalline structures. The obtained intrinsic coercivity H-i(c) of 3.32 kOe at room temperature for the tetragonal Fe55Pd45 NCWs is higher than those of electrodeposited Fe-Pd solid nanowires while among the highest values reported so far for L1(0)-type FePd nanoparticles. (C) 2013 AIP Publishing LLC.

  5. Comparison of the thermal decomposition processes of several aminoalcohol-based ZnO inks with one containing ethanolamine

    NASA Astrophysics Data System (ADS)

    Gómez-Núñez, Alberto; Roura, Pere; López, Concepción; Vilà, Anna

    2016-09-01

    Four inks for the production of ZnO semiconducting films have been prepared with zinc acetate dihydrate as precursor salt and one among the following aminoalcohols: aminopropanol (APr), aminomethyl butanol (AMB), aminophenol (APh) and aminobenzyl alcohol (AB) as stabilizing agent. Their thermal decomposition process has been analyzed in situ by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and evolved gas analysis (EGA), whereas the solid product has been analysed ex-situ by X-ray diffraction (XRD) and infrared spectroscopy (IR). Although, except for the APh ink, crystalline ZnO is already obtained at 300 °C, the films contain an organic residue that evolves at higher temperature in the form of a large variety of nitrogen-containing cyclic compounds. The results indicate that APr can be a better stabilizing agent than ethanolamine (EA). It gives larger ZnO crystal sizes with similar carbon content. However, a common drawback of all the amino stabilizers (EA included) is that nitrogen atoms have not been completely removed from the ZnO film at the highest temperature of our experiments (600 °C).

  6. Thermal decomposition of tetramethyl orthosilicate in the gas phase: An experimental and theoretical study of the initiation process

    SciTech Connect

    Chu, J.C.S.; Soller, R.; Lin, M.C. ); Melius, C.F. )

    1995-01-12

    The thermal decomposition of Si(OCH[sub 3])[sub 4] (TMOS) has been studied by FTIR at temperatures between 858 and 968 K. The experiment was carried out in a static cell at a constant pressure of 700 Torr under highly diluted conditions. Additional experiments were performed by using toluene as a radical scavenger. The species monitored included TMOS, CH[sub 2]O, CH[sub 4], and CO. According to these measurements, the first-order global rate constants for the disappearance of TMOS without and with toluene can be given by k[sub g] = 1.4 x 10[sup 16] exp(-81 200/RT) s[sup [minus]1] and k[sub g] = 2.0 x 10[sup 14] exp(-74 500/RT) s[sup [minus]1], respectively. The noticeable difference between the two sets of Arrhenius parameters suggests that, in the absence of the inhibitor, the reactant was consumed to a significant extent by radical attacks at higher temperatures. The experimental data were kinetically modeled with the aid of a quantum-chemical calculation using the BAC-MP4 method. The results of the kinetic modeling, using the mechanism constructed on the basis of the quantum-chemical data and the known C/H/O chemistry, identified two rate-controlling reactions whose first-order rate constants are given here. 22 refs., 15 figs., 3 tabs.

  7. Functionalized white graphene - Copper oxide nanocomposite: Synthesis, characterization and application as catalyst for thermal decomposition of ammonium perchlorate.

    PubMed

    Paulose, Sanoop; Raghavan, Rajeev; George, Benny K

    2017-05-15

    Reactivity is of great importance for metal oxide nanoparticles (MONP) used as catalysts and advanced materials, but seeking for higher reactivity seems to be conflict with high chemical stability required for MONP. There is direct balance between reactivity and stability of these MONP. This could be acheived for metal oxide by dispersing them in a substrate. Here, we report a simple, efficient and high-yield process for the production of copper oxide (CuO) nanoparticles dispersed on a chemically inert material, few-layer hexagonal boron nitride (h-BN) with a thickness around 1.7nm and lateral dimensions mostly below 200nm. The mechano-chemical reaction which take place at atmospheric pressure and room temperature involves a urea assisted exfoliation of pristine boron nitride. Copper oxide nanoparticles dispersed on the surface of these few layered h-BN reduced its tendency for aggregation. The optimum concentration of CuO:h-BN was found to be 2:1 which shows highest catalytic activity for the thermal decomposition of ammonium perchlorate. The high catalytic activity of the in situ synthesized CuO-h-BN composite may be attributed to uniform distribution of CuO nanoparticles on the few layered h-BN which in turn provide a number of active sites on the surface due to non aggregation.

  8. Effect of reaction atmosphere on particle morphology of TiO2 produced by thermal decomposition of titanium tetraisopropoxide

    NASA Astrophysics Data System (ADS)

    Choi, Jae Gil; Park, Kyun Young

    2006-04-01

    Thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out in varying reaction atmospheres: nitrogen, oxygen, and nitrogen plus water vapor. The effect of reaction atmosphere on the morphology, size, and crystalline structure of produced TiO2 particles was studied. The reactor used was similar to the microreactor proposed earlier by Park et al. (2001, J. Nanopart. Res., 3, 309-319), but for a modification in the precursor evaporator. The reactor temperature was varied from 300 to 700°C and the TTIP concentration in the evaporator from 1.0 to 7.0 mol%, holding the reactor residence time at 0.7 s. The primary-particle size was in the range 25-250 nm, varying with operating condition. The crystalline structure was amorphous in nitrogen, a mixture of rutile and anatase in nitrogen plus water vapor, and anatase in oxygen atmospheres. In nitrogen, agglomerates composed of very small particles whose individual boundaries are not clearly distinguished were produced. In oxygen, the particles composing an agglomerate became larger and were clearly spherical. As the atmosphere was varied to the nitrogen plus water vapor, the particle size increased further. The variation of primary particle size with reaction atmosphere was discussed in comparison with previous experimental data.

  9. Hexagonal ZnO porous plates prepared from microwave synthesized layered zinc hydroxide sulphate via thermal decomposition

    SciTech Connect

    Machovsky, Michal; Kuritka, Ivo; Sedlak, Jakub; Pastorek, Miroslav

    2013-10-15

    Graphical abstract: - Highlights: • Zinc hydroxy sulphate was synthesized in 3 min via microwave hydrothermal route. • Zinc hydroxy sulphate was converted into mesh like porous ZnO by calcining at 900°. • The process of transformation is topotactic. - Abstract: Layered zinc hydroxide sulphate (ZHS) was prepared by microwave-assisted hydrothermal precipitation of zinc sulphate monohydrate with hexamethylenetetramine. Under ambient conditions, the structure of ZHS determined by X-ray diffraction (XRD) was found to be a mixture of zinc hydroxide sulphate pentahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·5H{sub 2}O and tetrahydrate Zn{sub 4}SO{sub 4}(OH){sub 6}·4H{sub 2}O. Fourier transform infrared (FTIR) spectroscopy was used for characterization of the prepared materials. Based on the interpretation of ZHS's thermal decomposition profile obtained by thermogravimetric analysis, ZnO of high purity was prepared by calcination at 900 °C for 2 h. The structure of the resulting ZnO was confirmed by the XRD. The morphology examination by scanning electron microscopy revealed a porous mesh-like ZnO structure developed from the ZHS precursor at the expense of mass removal due to the release of water and sulphate during the calcination.

  10. Pyrolysis of aseptic packages (tetrapak) in a laboratory screw type reactor and secondary thermal/catalytic tar decomposition.

    PubMed

    Haydary, J; Susa, D; Dudáš, J

    2013-05-01

    Pyrolysis of aseptic packages (tetrapak cartons) in a laboratory apparatus using a flow screw type reactor and a secondary catalytic reactor for tar cracking was studied. The pyrolysis experiments were realized at temperatures ranging from 650 °C to 850 °C aimed at maximizing of the amount of the gas product and reducing its tar content. Distribution of tetrapak into the product yields at different conditions was obtained. The presence of H2, CO, CH4, CO2 and light hydrocarbons, HCx, in the gas product was observed. The Aluminum foil was easily separated from the solid product. The rest part of char was characterized by proximate and elemental analysis and calorimetric measurements. The total organic carbon in the tar product was estimated by elemental analysis of tars. Two types of catalysts (dolomite and red clay marked AFRC) were used for catalytic thermal tar decomposition. Three series of experiments (without catalyst in a secondary cracking reactor, with dolomite and with AFRC) at temperatures of 650, 700, 750, 800 and 850 °C were carried out. Both types of catalysts have significantly affected the content of tars and other components in pyrolytic gases. The effect of catalyst on the tetrapack distribution into the product yield on the composition of gas and on the total organic carbon in the tar product is presented in this work.

  11. Rapid hydrogen gas generation using reactive thermal decomposition of uranium hydride.

    SciTech Connect

    Kanouff, Michael P.; Van Blarigan, Peter; Robinson, David B.; Shugard, Andrew D.; Gharagozloo, Patricia E.; Buffleben, George M.; James, Scott Carlton; Mills, Bernice E.

    2011-09-01

    Oxygen gas injection has been studied as one method for rapidly generating hydrogen gas from a uranium hydride storage system. Small scale reactors, 2.9 g UH{sub 3}, were used to study the process experimentally. Complimentary numerical simulations were used to better characterize and understand the strongly coupled chemical and thermal transport processes controlling hydrogen gas liberation. The results indicate that UH{sub 3} and O{sub 2} are sufficiently reactive to enable a well designed system to release gram quantities of hydrogen in {approx} 2 seconds over a broad temperature range. The major system-design challenge appears to be heat management. In addition to the oxidation tests, H/D isotope exchange experiments were performed. The rate limiting step in the overall gas-to-particle exchange process was found to be hydrogen diffusion in the {approx}0.5 {mu}m hydride particles. The experiments generated a set of high quality experimental data; from which effective intra-particle diffusion coefficients can be inferred.

  12. Yttrium-succinates coordination polymers: Hydrothermal synthesis, crystal structure and thermal decomposition

    SciTech Connect

    Amghouz, Zakariae; Roces, Laura; Garcia-Granda, Santiago; Garcia, Jose R.; Souhail, Badredine; Mafra, Luis; Shi, Fa-nian; Rocha, Joao

    2009-12-15

    New polymeric yttrium-succinates, Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 4}.6H{sub 2}O and Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}, have been synthesized, and their structures (solved by single crystal XRD) are compared with that of Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}.H{sub 2}O. Three compounds were obtained as single phases, and their thermal behaviour is described. - Graphical abstract: In the field of coordination polymers or MOF's, few studies report on the polymorphs of Ln(III)-succinic acid. Here, we describe the hydrothermal synthesis and structural characterization of two novel yttrium-succinates coordination polymers, respectively 2D and 3D, Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 4}.6H{sub 2}O and Y{sub 2}(C{sub 4}H{sub 4}O{sub 4}){sub 3}(H{sub 2}O){sub 2}.

  13. Strong cationic oxidizers: thermal decomposition, electronic structure and magnetism of their compounds.

    PubMed

    Leszczyński, Piotr J; Grochala, Wojciech

    2013-01-01

    Strong oxidizers could be provisionally defined as compounds for which the standard redox potential exceeds 2.0 V in the NHE scale. Compounds which contain transition or post-transition metals at their unusually high positive oxidation states constitute one important family of strong oxidizers. Majority of such systems typically exhibit either diamagnetic or 'simple' paramagnetic properties down to very low temperatures. This is connected with the fact that highest oxidation states of metals are stabilized in fluoride environment and that binary high-valence metal fluorides form either molecular(OD) or low-dimensional (usually !D) crystals. The ternary and higher fluorides are usually OD in electronic sense leading again to low ordering temperatures. The situation becomes more interesting in selected compounds of Ag(II),the strongest oxidizer among all divalent cations, where one finds 2D or even 3D magnetic ordering at elevated temperatures.Thermal stability, electronic structure and magnetic properties of strong oxidizers are discussed jointly in this contribution with emphasis on the compounds of unique divalent silver.

  14. Speciation of Organic By-Products from the Thermal Decomposition of Alternative Automotive Fuels.

    PubMed

    Taylor, Philip H; Shanbhag, Santosh; Rubey, Wayne A; Dellinger, Barry; Bergin, Michelle

    1999-01-01

    The high-temperature thermal degradation of four alternative automotive fuels (methanol, ethanol, natural gas, and liquefied petroleum (LP) gas) have been examined as a function of fuel-oxygen equivalence ratio and exposure temperature using fused silica flow reactor instrumentation coupled to in-line GC-TCD and GC-MS detection. Organic speciation for methanol, natural gas, and LP gas were consistent with previous measurements. However, several previously undetected organic by-products were observed from ethanol oxidation and pyrolysis. Organic speciation was found to vary significantly between methanol and ethanol and less so between natural gas and LP gas. Non-methane organic gases (NMOG) and specific reactivities of the respective fuels were measured, and trends with respect to proposed reactivity adjustment factors are discussed. A qualitative comparison of NMOG quantified in the flow reactor tests with the results of recent vehicle tests is also reported. The most significant differences in the comparisons were observed for toxic compounds, including the lack of detection of acetalde-hyde, 1,3-butadiene, and benzene from flow reactor experiments of methanol degradation, and the lack of detection of 1,3-butadiene from flow reactor experiments of ethanol combustion. Possible sources for the formation of these compounds in vehicle tests are discussed.

  15. Thermal Decomposition of Calcium Perchlorate/Iron-Mineral Mixtures: Implications of the Evolved Oxygen from the Rocknest Eolian Deposit in Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Bruck, A. M.; Sutter, B.; Ming, D. W.; Mahaffy, P.

    2014-01-01

    A major oxygen release between 300 and 500 C was detected by the Mars Curiosity Rover Sample Analysis at Mars (SAM) instrument at the Rocknest eolian deposit. Thermal decomposition of perchlorate (ClO4-) salts in the Rocknest samples are a possible explanation for this evolved oxygen release. Releative to Na-, K-, Mg-, and Fe-perchlorate, the thermal decomposition of Ca-perchlorate in laboratory experiments released O2 in the temperature range (400-500degC) closest to the O2 release temperatures observed for the Rocknest material. Furthermore, calcium perchlorate could have been the source of Cl in the chlorinated-hydrocarbons species that were detected by SAM. Different components in the Martian soil could affect the decomposition temperature of calcium per-chlorate or another oxychlorine species. This interaction of the two components in the soil could result in O2 release temperatures consistent with those detected by SAM in the Rocknest materials. The decomposition temperatures of various alkali metal perchlorates are known to decrease in the presence of a catalyst. The objective of this work is to investigate catalytic interactions on calcium perchlorate from various iron-bearing minerals known to be present in the Rocknest material

  16. Evolution of different morphologies of CdS nanoparticles by thermal decomposition of bis(thiourea)cadmium chloride in various solvents

    NASA Astrophysics Data System (ADS)

    Gaur, Rama; Jeevanandam, P.

    2015-03-01

    CdS nanoparticles with different morphologies have been synthesized by thermal decomposition of bis(thiourea)cadmium chloride in different solvents without the use of any ligand/surfactant. CdS nanoparticles with pyramid, sponge-like and hexagonal disc-like morphologies were obtained in diphenyl ether (DPE), 1-octadecene (ODE) and ethylene glycol (EG), respectively. In addition, CdS nanoparticles with unique morphologies were obtained when the decomposition of the complex was carried out in mixed solvents (DPE-EG and ODE-EG). Extensive characterization of the CdS nanoparticles was carried out using powder X-ray diffraction, FT-IR spectroscopy, thermal analysis, field-emission scanning electron microscopy, diffuse reflectance spectroscopy and photoluminescence spectroscopy, and detailed mechanism of the formation of CdS nanoparticles with different morphologies in various solvents has been proposed.

  17. A study of the thermal decomposition of adulterated cocaine samples under optimized aerobic pyrolytic conditions.

    PubMed

    Gostic, T; Klemenc, S; Stefane, B

    2009-05-30

    The pyrolysis behaviour of pure cocaine base as well as the influence of various additives was studied using conditions that are relevant to the smoking of illicit cocaine by humans. For this purpose an aerobic pyrolysis device was developed and the experimental conditions were optimized. In the first part of our study the optimization of some basic experimental parameters of the pyrolysis was performed, i.e., the furnace temperature, the sampling start time, the heating period, the sampling time, and the air-flow rate through the system. The second part of the investigation focused on the volatile products formed during the pyrolysis of a pure cocaine free base and mixtures of cocaine base and adulterants. The anaesthetics lidocaine, benzocaine, procaine, the analgesics phenacetine and paracetamol, and the stimulant caffeine were used as the adulterants. Under the applied experimental conditions complete volatilization of the samples was achieved, i.e., the residuals of the studied compounds were not detected in the pyrolysis cell. Volatilization of the pure cocaine base showed that the cocaine recovery available for inhalation (adsorbed on traps) was approximately 76%. GC-MS and NMR analyses of the smoke condensate revealed the presence of some additional cocaine pyrolytic products, such as anhydroecgonine methyl ester (AEME), benzoic acid (BA) and carbomethoxycycloheptatrienes (CMCHTs). Experiments with different cocaine-adulterant mixtures showed that the addition of the adulterants changed the thermal behaviour of the cocaine. The most significant of these was the effect of paracetamol. The total recovery of the cocaine (adsorbed on traps and in a glass tube) from the 1:1 cocaine-paracetamol mixture was found to be only 3.0+/-0.8%, versus 81.4+/-2.9% for the pure cocaine base. The other adulterants showed less-extensive effects on the recovery of cocaine, but the pyrolysis of the cocaine-procaine mixture led to the formation of some unique pyrolytic products

  18. Correlation between ionic radii of metals and thermal decomposition of supramolecular structure of azodye complexes.

    PubMed

    El-Sonbati, A Z; Diab, M A; El-Bindary, A A; Eldesoky, A M; Morgan, Sh M

    2015-01-25

    An interesting azodye heterocyclic ligand of copper(II), cobalt(II), nickel(II) and uranyl(II) complexes have been synthesized by the reaction of metal salts with 5-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-2-thioxo-4-thiazolidinone (HL) yields 1:1 and 1:2 (M:L) complexes depending on the reaction conditions. The elemental analysis, magnetic moments, spectral (UV-Vis, IR, (1)H and (13)C NMR and ESR) and thermal studies were used to characterize the isolated complexes. The molecular structures of the ligand tautomers are optimized theoretically and the quantum chemical parameters are calculated. The IR spectra showed that the ligand (HL) act as monobasic tridentate/neutral bidentate through the (-N=N), enolic (C-O)(-) and/or oxygen keto moiety groups forming a five/six-membered structures. According to intramolecular hydrogen bond leads to increasing of the complexes stability. The molar conductivities show that all the complexes are non-electrolytes. The ESR spectra indicate that the free electron is in dxy orbital. The calculated bonding parameter indicates that in-plane σ-bonding is more covalent than in-plane π-bonding. The coordination geometry is five/six-coordinated trigonal bipyramidal for complex (1) and octahedral for complexes (2-6). The value of covalency factor β1(2) and orbital reduction factor K accounts for the covalent nature of the complexes. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The synthesized ligand (HL) and its Cu(II) complexes (1, 2 and 4) are screened for their biological activity against bacterial and fungal species. The ligand (HL) showed antimicrobial activities against Escherichia coli. The ligand (HL) and its Cu(II) complexes (2 and 4) have very high antifungal activity against Penicillium italicum. The inhibitive action of ligand (HL), against the corrosion of C-steel in 2M HCl solution has been investigated using potentiodynamic polarization and electrochemical

  19. Correlation between ionic radii of metals and thermal decomposition of supramolecular structure of azodye complexes

    NASA Astrophysics Data System (ADS)

    El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Eldesoky, A. M.; Morgan, Sh. M.

    2015-01-01

    An interesting azodye heterocyclic ligand of copper(II), cobalt(II), nickel(II) and uranyl(II) complexes have been synthesized by the reaction of metal salts with 5-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-2-thioxo-4-thiazolidinone (HL) yields 1:1 and 1:2 (M:L) complexes depending on the reaction conditions. The elemental analysis, magnetic moments, spectral (UV-Vis, IR, 1H and 13C NMR and ESR) and thermal studies were used to characterize the isolated complexes. The molecular structures of the ligand tautomers are optimized theoretically and the quantum chemical parameters are calculated. The IR spectra showed that the ligand (HL) act as monobasic tridentate/neutral bidentate through the (sbnd Ndbnd N), enolic (Csbnd O)- and/or oxygen keto moiety groups forming a five/six-membered structures. According to intramolecular hydrogen bond leads to increasing of the complexes stability. The molar conductivities show that all the complexes are non-electrolytes. The ESR spectra indicate that the free electron is in dxy orbital. The calculated bonding parameter indicates that in-plane σ-bonding is more covalent than in-plane π-bonding. The coordination geometry is five/six-coordinated trigonal bipyramidal for complex (1) and octahedral for complexes (2-6). The value of covalency factor β12 and orbital reduction factor K accounts for the covalent nature of the complexes. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The synthesized ligand (HL) and its Cu(II) complexes (1, 2 and 4) are screened for their biological activity against bacterial and fungal species. The ligand (HL) showed antimicrobial activities against Escherichia coli. The ligand (HL) and its Cu(II) complexes (2 and 4) have very high antifungal activity against Penicillium italicum. The inhibitive action of ligand (HL), against the corrosion of C-steel in 2 M HCl solution has been investigated using potentiodynamic polarization and electrochemical

  20. In-situ and self-distributed: A new understanding on catalyzed thermal decomposition process of ammonium perchlorate over Nd{sub 2}O{sub 3}

    SciTech Connect

    Zou, Min Wang, Xin Jiang, Xiaohong Lu, Lude

    2014-05-01

    Catalyzed thermal decomposition process of ammonium perchlorate (AP) over neodymium oxide (Nd{sub 2}O{sub 3}) was investigated. Catalytic performances of nanometer-sized Nd{sub 2}O{sub 3} and micrometer-sized Nd{sub 2}O{sub 3} were evaluated by differential scanning calorimetry (DSC). In contrast to universal concepts, catalysts in different sizes have nearly similar catalytic activities. Based on structural and morphological variation of the catalysts during the reaction, combined with mass spectrum analyses and studies of unmixed style, a new understanding of this catalytic process was proposed. We believed that the newly formed chloride neodymium oxide (NdOCl) was the real catalytic species in the overall thermal decomposition of AP over Nd{sub 2}O{sub 3}. Meanwhile, it was the “self-distributed” procedure which occurred within the reaction that also worked for the improvement of overall catalytic activities. This work is of great value in understanding the roles of micrometer-sized catalysts used in heterogeneous reactions, especially the solid–solid reactions which could generate a large quantity of gaseous species. - Graphical abstract: In-situ and self-distributed reaction process in thermal decomposition of AP catalyzed by Nd{sub 2}O{sub 3}. - Highlights: • Micro- and nano-Nd{sub 2}O{sub 3} for catalytic thermal decomposition of AP. • No essential differences on their catalytic performances. • Structural and morphological variation of catalysts digs out catalytic mechanism. • This catalytic process is “in-situ and self-distributed” one.

  1. ZnO NPs synthesized by thermal decomposition of zinc oxalate at 300°C and its photo response under UV-illumination

    NASA Astrophysics Data System (ADS)

    Shankar, Ravi; Srivastava, Rajneesh K.; Prakash, S. G.

    2013-06-01

    In this work the study of structural and optical properties of ZnO NPs synthesized by thermal decomposition of Zinc Oxalate have been performed. ZnO NPs have been characterized for their structural properties using XRD and the size of ZnO NPs is found to lie in the range of 20-30 nm. Negative photoconductivity is found in ZnO NPs under UV-vis. llumination.

  2. Modeling of transport phenomena during gas hydrate decomposition by depressurization and/or thermal stimulation

    NASA Astrophysics Data System (ADS)

    Abendroth*, Sven; Klump, Jens; Thaler, Jan; Schicks, Judith M.

    2013-04-01

    In the context of the German joint project SUGAR (Submarine Gas Hydrate Reservoirs: exploration, extraction and transport) we conducted a series of experiments in the LArge Reservoir Simulator (LARS) at the German Research Centre of Geosciences Potsdam (Beeskow-Strauch et al., this volume). These experiments allow us to investigate the formation and dissociation of hydrates at large scale laboratory conditions. Processes inside LARS are modeled to study the effects of sediment properties as well as physical and chemical processes on parameters such as hydrate dissociation rate and methane production rate. The experimental results from LARS are used to provide details about processes inside the pressure vessel, validate the models through history matching, and feed back into the design of future experiments. In experiments in LARS the amount of methane produced from gas hydrates was much lower than expected. Previously published models predict a methane production rate higher than the observed in experiments and field studies (Uddin and Wright 2005; Uddin et al. 2010; Wright et al. 2011). The authors of the aforementioned studies point out that the current modeling approach overestimates the gas production rate when modeling gas production by depressurization. Uddin and Wright (2005) suggested that trapping of gas bubbles inside the porous medium is responsible for the reduced gas production rate. They point out that this behavior of multi-phase flow is not well explained by a "residual oil" model, but rather resembles a "foamy oil" model. Our study applies Uddin's (2010) "foamy oil" model and combines it with history matches of our experiments in LARS. First results indicate a better agreement between experimental and model results when using the "foamy oil" model instead of conventional models featuring gas flow in water. Further experiments with LARS, including hydrate dissociation by depressurization and thermal stimulation by in-situ combustion will be used to

  3. TG-MS analysis and kinetic study for thermal decomposition of six representative components of municipal solid waste under steam atmosphere.

    PubMed

    Zhang, Jinzhi; Chen, Tianju; Wu, Jingli; Wu, Jinhu

    2015-09-01

    Thermal decomposition of six representative components of municipal solid waste (MSW, including lignin, printing paper, cotton, rubber, polyvinyl chloride (PVC) and cabbage) was investigated by thermogravimetric-mass spectroscopy (TG-MS) under steam atmosphere. Compared with TG and derivative thermogravimetric (DTG) curves under N2 atmosphere, thermal decomposition of MSW components under steam atmosphere was divided into pyrolysis and gasification stages. In the pyrolysis stage, the shapes of TG and DTG curves under steam atmosphere were almost the same with those under N2 atmosphere. In the gasification stage, the presence of steam led to a greater mass loss because of the steam partial oxidation of char residue. The evolution profiles of H2, CH4, CO and CO2 were well consistent with DTG curves in terms of appearance of peaks and relevant stages in the whole temperature range, and the steam partial oxidation of char residue promoted the generation of more gas products in high temperature range. The multi-Gaussian distributed activation energy model (DAEM) was proved plausible to describe thermal decomposition behaviours of MSW components under steam atmosphere.

  4. Thermal Decomposition of an Impure (Roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in ALH84001 Carbonate Disks

    NASA Technical Reports Server (NTRS)

    McKay, D.S.; Gibson, E.K.; Thomas-Keprta, K.L.; Clemett, S.J.; Wentworth, S.J.

    2009-01-01

    The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure magnetite present in the carbonate disks in Martian meteorite ALH84001 could have formed by the thermal decomposition of the impure carbonate matrix in which they are embedded; second, the chemical purity of magnetite has been previously used to identify biogenic magnetite; and, third, previous studies of thermal decomposition of impure (Mg,Ca,Mn)-siderites, which have been investigated under a wide variety of conditions by numerous researchers, invariably yields a mixed metal oxide phase as the product and not chemically pure magnetite. The explanation for this observation is that these siderites all possess the same crystallographic structure (Calcite; R3c) so solid solutions between these carbonates are readily formed and can be viewed on an atomic scale as two chemically different but structurally similar lattices.

  5. Determination of formal kinetic constants of thermal decomposition of aqueous hydrogen peroxide solution in a mixture of magnetic powder, based on experimental thermogram, obtained in adiabatic conditions

    NASA Astrophysics Data System (ADS)

    Zaripov, Jamshed; Borisov, Boris; Bondarchuk, Sergey

    2014-08-01

    Process of thermal decomposition of hydrogen peroxide aqueous solution with the addition of magnetic powder in the form of toner for printers and lanthanum manganite were considered. Obtained resulting from an experiment in the Dewar container conducted thermogram analyzed using mass balance equations and heat. Formal kinetic parameters determined, and conclude that the magnetic powder in the mixture does not have catalytic properties. The described technique is recommended as a rapid analysis of the kinetics of the various reactions to substances having predefined thermal and thermodynamic properties.

  6. Validation of heat transfer, thermal decomposition, and container pressurization of polyurethane foam using mean value and Latin hypercube sampling approaches

    SciTech Connect

    Scott, Sarah N.; Dodd, Amanda B.; Larsen, Marvin E.; Suo-Anttila, Jill M.; Erickson, Ken L.

    2014-12-09

    In this study, polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. It can be advantageous to surround objects of interest, such as electronics, with foams in a hermetically sealed container in order to protect them from hostile environments or from accidents such as fire. In fire environments, gas pressure from thermal decomposition of foams can cause mechanical failure of sealed systems. In this work, a detailed uncertainty quantification study of polymeric methylene diisocyanate (PMDI)-polyether-polyol based polyurethane foam is presented and compared to experimental results to assess the validity of a 3-D finite element model of the heat transfer and degradation processes. In this series of experiments, 320 kg/m3 PMDI foam in a 0.2 L sealed steel container is heated to 1,073 K at a rate of 150 K/min. The experiment ends when the can breaches due to the buildup of pressure. The temperature at key location is monitored as well as the internal pressure of the can. Both experimental uncertainty and computational uncertainty are examined and compared. The mean value method (MV) and Latin hypercube sampling (LHS) approach are used to propagate the uncertainty through the model. The results of the both the MV method and the LHS approach show that while the model generally can predict the temperature at given locations in the system, it is less successful at predicting the pressure response. Also, these two approaches for propagating uncertainty agree with each other, the importance of each input parameter on the simulation results is also investigated, showing that for the temperature response the conductivity of the steel container and the effective conductivity of the foam, are the most important parameters. For the pressure response, the activation energy, effective conductivity, and specific heat are most important. The comparison to experiments and the identification of the drivers of uncertainty allow

  7. Validation of heat transfer, thermal decomposition, and container pressurization of polyurethane foam using mean value and Latin hypercube sampling approaches

    DOE PAGES

    Scott, Sarah N.; Dodd, Amanda B.; Larsen, Marvin E.; ...

    2014-12-09

    In this study, polymer foam encapsulants provide mechanical, electrical, and thermal isolation in engineered systems. It can be advantageous to surround objects of interest, such as electronics, with foams in a hermetically sealed container in order to protect them from hostile environments or from accidents such as fire. In fire environments, gas pressure from thermal decomposition of foams can cause mechanical failure of sealed systems. In this work, a detailed uncertainty quantification study of polymeric methylene diisocyanate (PMDI)-polyether-polyol based polyurethane foam is presented and compared to experimental results to assess the validity of a 3-D finite element model of themore » heat transfer and degradation processes. In this series of experiments, 320 kg/m3 PMDI foam in a 0.2 L sealed steel container is heated to 1,073 K at a rate of 150 K/min. The experiment ends when the can breaches due to the buildup of pressure. The temperature at key location is monitored as well as the internal pressure of the can. Both experimental uncertainty and computational uncertainty are examined and compared. The mean value method (MV) and Latin hypercube sampling (LHS) approach are used to propagate the uncertainty through the model. The results of the both the MV method and the LHS approach show that while the model generally can predict the temperature at given locations in the system, it is less successful at predicting the pressure response. Also, these two approaches for propagating uncertainty agree with each other, the importance of each input parameter on the simulation results is also investigated, showing that for the temperature response the conductivity of the steel container and the effective conductivity of the foam, are the most important parameters. For the pressure response, the activation energy, effective conductivity, and specific heat are most important. The comparison to experiments and the identification of the drivers of uncertainty allow for

  8. Synthesis of two nickel (II) complexes bearing pyrrolide-imine ligand and their catalytic effects on thermal decomposition of ammonium perchlorate

    NASA Astrophysics Data System (ADS)

    Zhuo, Ji-Bin; Ma, Zai-He; Lin, Cai-Xia; Xie, Li-Li; Bai, Sha; Yuan, Yao-Feng

    2015-04-01

    Two pyrrolide-imine chelating Ni(II) complexes {[2-(2-CH3O-C6H4-NCH)C4H3N]2Ni (2a) and [(Fc-NCH)]C4H3N]2Ni (2b, Fc = ferrocenyl)} were prepared via treating corresponding Schiff base with 0.5 equiv. NiCl2·6H2O in moderate yields. The crystal structures of 2a and 2b were determined by single-crystal X-ray diffraction. Atom Ni(II) of 2a was coordinated by two pyrrolide-imine ligands in trans position to display a twisted octahedral coordination geometry. Ni(II) of 2b had a distorted square-planar geometry, bonded with two ferrocenyl pyrrole-imine ligands, each ferrocene and pyrrole of ligands adopting a trans conformation. The UV-vis spectroscopy and electrochemical measurements were investigated. The catalytic efficiency of the complexes on the thermal decomposition of ammonium perchlorate (AP) was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). Compared with the thermal decomposition of pure AP, the decomposition temperatures were decreased by 27 °C, 77 °C, 88 °C and 172 °C, respectively when 1a, 1b, 2a and 2b were added in AP. The results indicated that the Ni(II) complex 2b bearing ferrocene-based pyrrolide-imine N,N-chelate ligand displayed an excellent catalytic efficiency on the thermal decomposition of AP.

  9. A theoretical study of thermal decomposition of CF 3CO, C 2F 5CO and C 3F 7CO

    NASA Astrophysics Data System (ADS)

    Setokuchi, Osamu; Kutsuna, Shuzo; Sato, Masaru

    2006-10-01

    Thermal decomposition of C nF 2 n+1 CO ( n = 1-3) radicals was investigated using RRKM/ME calculations, with geometrical parameters and energetics determined at the G2M//MPW1K and CBS-QB3 levels. The decomposition rate constant of C nF 2 n+1 CO increases with increasing carbon chain length. In the atmosphere, decomposition of C 3F 7CO competes with a reaction with O 2 that produces C 3F 7C(O)O 2. The decomposition fraction of C 3F 7CO is calculated to be 73% and 50% at the G2M//MPW1K and CBS-QB3 levels under ambient conditions, whereas that of CF 3CO is 1%. The yields of C nF 2 n+1 C(O)OH, formed by the reaction of C nF 2 n+1 C(O)O 2 with HO 2, are discussed using the obtained results.

  10. Studies on three-dimensional coordination polymer [Cd2(N2H4)2(N3)4]n: crystal structure, thermal decomposition mechanism and explosive properties.

    PubMed

    Liu, Zhenhua; Zhang, Tonglai; Zhang, Jianguo; Wang, Shaozong

    2008-06-15

    A 3D coordination polymer of cadmium(II) hydrazine azide, [Cd2(N2H4)2(N3)4]n, was synthesized and characterized by elemental analysis and Fourier transform infrared (FT-IR) spectrum. Its crystal structure was determined by single crystal X-ray diffraction analysis. The crystal belongs to monoclinic, P2(1)/c space group, a=12.555(2)A, b=11.724(2)A, c=7.842(1)A, beta=94.56(2) degrees and Z=4. The crystal contains two crystallographically independent sets of distorted octahedral Cd(II) atoms and dimeric units of Cd2N2, Cd2(NNN)2, Cd2(NN)2 through double micro-1, 1 azide bridges, micro-1, 3 azide bridges and bidentate bridging hydrazine ligands, respectively, and thus generating a 3D network structure. The thermal decomposition mechanism of the complex was studied by using differential scanning calorimetry (DSC), thermogravimetry-derivative thermogravimetry (TG-DTG) and FT-IR techniques. Under nitrogen atmosphere with a heating rate of 10 degrees C/min, the thermal decomposition of the complex contained two intense exothermic decomposition processes in the range of 150-304 degrees C in the DSC curve, and the final decomposed residue at 500 degrees C was Cd. Sensitivity tests revealed that the title complex is very insensitive to external stimuli.

  11. An Efficient Approach for Pixel Decomposition to Increase the Spatial Resolution of Land Surface Temperature Images from MODIS Thermal Infrared Band Data

    PubMed Central

    Wang, Fei; Qin, Zhihao; Li, Wenjuan; Song, Caiying; Karnieli, Arnon; Zhao, Shuhe

    2015-01-01

    Land surface temperature (LST) images retrieved from the thermal infrared (TIR) band data of Moderate Resolution Imaging Spectroradiometer (MODIS) have much lower spatial resolution than the MODIS visible and near-infrared (VNIR) band data. The coarse pixel scale of MODIS LST images (1000 m under nadir) have limited their capability in applying to many studies required high spatial resolution in comparison of the MODIS VNIR band data with pixel scale of 250–500 m. In this paper we intend to develop an efficient approach for pixel decomposition to increase the spatial resolution of MODIS LST image using the VNIR band data as assistance. The unique feature of this approach is to maintain the thermal radiance of parent pixels in the MODIS LST image unchanged after they are decomposed into the sub-pixels in the resulted image. There are two important steps in the decomposition: initial temperature estimation and final temperature determination. Therefore the approach can be termed double-step pixel decomposition (DSPD). Both steps involve a series of procedures to achieve the final result of decomposed LST image, including classification of the surface patterns, establishment of LST change with normalized difference of vegetation index (NDVI) and building index (NDBI), reversion of LST into thermal radiance through Planck equation, and computation of weights for the sub-pixels of the resulted image. Since the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with much higher spatial resolution than MODIS data was on-board the same platform (Terra) as MODIS for Earth observation, an experiment had been done in the study to validate the accuracy and efficiency of our approach for pixel decomposition. The ASTER LST image was used as the reference to compare with the decomposed LST image. The result showed that the spatial distribution of the decomposed LST image was very similar to that of the ASTER LST image with a root mean square error (RMSE) of

  12. Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation

    PubMed Central

    2013-01-01

    Background The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. Results The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, 57Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙∙ 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [FeII(en)2(μ-NC)CoIII(CN)4], FeIII(NH2CH2CH3)2(μ-NC)2CoII(CN)3] and FeIII[CoII(CN)5], which were suggested mainly from 57Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4. Conclusions It has been found

  13. Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

    SciTech Connect

    Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Guibing Zhao; Sanil John

    2006-09-30

    The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Several pulsed corona discharge (PCD) reactors have been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. Visual observation shows that the corona is not uniform throughout the reactor. The corona is stronger near the top of the reactor in argon, while nitrogen and mixtures of argon or nitrogen with H{sub 2}S produce stronger coronas near the bottom of the reactor. Both of these effects appear to be explainable base on the different electron collision interactions with monatomic versus polyatomic gases. A series of experiments varying reactor operating parameters, including discharge capacitance, pulse frequency, and discharge voltage were performed while maintaining constant power input to the reactor. At constant reactor power input, low capacitance, high pulse frequency, and high voltage operation appear to provide the highest conversion and the highest energy efficiency for H{sub 2}S decomposition. Reaction rates and energy efficiency per H{sub 2}S molecule increase with increasing flow rate, although overall H{sub 2}S conversion decreases at constant power input. Voltage and current waveform analysis is ongoing to determine the fundamental operating characteristics of the reactors. A metal infiltrated porous ceramic membrane was prepared using vanadium as the metal and an alumina tube. Experiments with this type of membrane are continuing, but the results thus far have been consistent with those obtained in previous project years: plasma driven permeation or superpermeability

  14. Preparation and formation mechanism of porous carbon nanosheets by thermal decomposition of polyvinyl alcohol films impregnated with zinc (II) and nitrate ions

    NASA Astrophysics Data System (ADS)

    Hattori, Yoshiyuki; Kojima, Rikio; Sagisaka, Kento; Umeda, Motoki; Tanaka, Toshihisa; Kondo, Atsushi; Iiyama, Taku; Kimura, Mutsumi; Fujimoto, Hiroyuki; Touhara, Hidekazu

    2017-03-01

    Porous carbon nanosheets (PCNS) with high surface areas were prepared by thermal decomposition of polyvinyl alcohol (PVA) films impregnated with Zn2+ and NO3-. Through this simple preparation method that required no additional activation processes, curved carbon nanosheets (<30 nm thick) were assembled into novel carbon materials. Detailed thermogravimetry-differential thermal analyses of the PVA films impregnated with Zn2+ and NO3- indicated that the sheet-like structures originated from exothermic pyrolysis of NO3- associated with the thermal decomposition of PVA. According to the nitrogen adsorption isotherm analyses at 77 K, the PCNS had a high specific surface area (>1600 m2 g-1) and bimodal pore structure consisting of micropores and mesopores. Because of their unique structural properties, the PCNS are attractive for use as electrode materials. The electrode performance of the PCNS was investigated in 1-M tetraethylammonium tetrafluoroborate ((C2H5)4NBF4) in propylene carbonate. The PCNS electrodes displayed high specific capacitance (86 F g-1 for cations and 115 F g-1 for anions). They also showed exceptionally high rate performance with ∼90% capacitance retention at current densities up to 2 A g-1 because their nanosheet structure allowed the rapid diffusion of ions inside the electrode.

  15. Kinetics of the Thermal Decomposition of Tetramethylsilane behind the Reflected Shock Waves in a Single Pulse Shock Tube (SPST) and Modeling Study

    NASA Astrophysics Data System (ADS)

    Parandaman, A.; Sudhakar, G.; Rajakumar, B.

    Thermal reactions of Tetramethylsilane (TMS) diluted in argon were studied behind the reflected shock waves in a single-pulse shock tube (SPST) over the temperature range of 1085-1221 K and pressures varied between 10.6 and 22.8 atm. The stable products resulting from the decomposition of TMS were identified and quantified using gas chromatography and also verified with Fourier Transform Infrared (FTIR) spectrometer. The major reaction products are methane (CH4) and ethylene (C2H4). The minor reaction products are ethane (C2H6) and propylene (C3H6). The initiation of mechanism in the decomposition of TMS takes plays via the Si-C bond scission by ejecting the methyl radicals (CH3) and trimethylsilyl radicals ((CH3)3Si). The measured temperature dependent rate coefficient for the total decomposition of TMS was to be ktotal = 1.66 ×1015 exp (-64.46/RT) s-1 and for the formation of CH4 reaction channel was to be k = 2.20 × 1014 exp (-60.15/RT) s-1, where the activation energies are given in kcal mol-1. A kinetic scheme containing 17 species and 28 elementary reactions was used for the simulation using chemical kinetic simulator over the temperature range of 1085-1221 K. The agreement between the experimental and simulated results was satisfactory.

  16. Thermal decomposition and reconstruction of CaFe-layered double hydroxide studied by X-ray diffractometry and 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Bugris, Valéria; Ádok-Sipiczki, Mónika; Anitics, Tamás; Kuzmann, Ernő; Homonnay, Zoltán; Kukovecz, Ákos; Kónya, Zoltán; Sipos, Pál; Pálinkó, István

    2015-06-01

    In spite of numerous investigations on the various processes of the thermal decomposition and rehydration of layered double hydroxides (LDHs) by a variety sophisticated experimental means, many details are still unexplored and some contradictions are still unresolved. In this work, our efforts were focussed on clarifying the composition, structure and properties of thermally decomposed metaphases originating from CaFe-LDH, heat treated in the 373-973 K temperature range. The structure reconstruction ability of mixed metal oxide phases obtained after heat treatments was also investigated, mainly concentrating on the changes in the microenvironment of Fe(III), in the presence of controlled amount of water vapour (i.e., at different relative humidities). All samples were characterised by X-ray diffractometry, and the iron-containing phases were studied by 57Fe Mössbauer spectroscopy.

  17. Tris dithiocarbamate of Co(III) complexes: Synthesis, characterization, thermal decomposition studies and experimental and theoretical studies on their crystal structures

    NASA Astrophysics Data System (ADS)

    Sonia, Ayyavoo Sait; Bhaskaran, Ramalingam

    2017-04-01

    New homoleptic complexes of the form [Co(L1)3] & [Co(L2)3] where L1 = (ethylaminoethanol dithiocarbamate) 1 and L2 = (methylaminoethanol dithiocarbamate) 2 have been prepared and characterized by elemental analysis, IR, UV-visible absorption spectra, Cyclic voltammetry,1H and C13 NMR. The thermal properties were studied using a simultaneous thermal analyzer, and showed two main steps of decomposition. In addition, structures for 1 and 2 have been elucidated by X-ray crystallography. The single-crystal X-ray analysis for both the complexes showed distorted octahedral geometry. The optimized molecular structure, natural bond orbital analysis, electrostatic potential map, HOMO-LUMO energies, molecular properties, and atomic charges of these molecules have been studied by performing DFT/B3LYP/6-31G(d,p) level of theory in gas phase.

  18. Studies on the intercalation of naproxen into layered double hydroxide and its thermal decomposition by in situ FT-IR and in situ HT-XRD

    NASA Astrophysics Data System (ADS)

    Wei, Min; Shi, Shuxian; Wang, Ji; Li, Yong; Duan, Xue

    2004-07-01

    Layered double hydroxides, novel anionic clay, meet the first requirement as inorganic matrices for encapsulating functional drugs or biomolecules with negative charge in aqueous media. In this study, naproxen has been intercalated into Mg-Al layered double hydroxide by the methods of ion exchange. The structure and composition of the intercalated material have been studied by X-ray diffraction (XRD), UV-vis spectroscopy and inductively coupled plasma emission spectroscopy. A schematic model has been proposed. Furthermore, in situ Fourier transform infrared spectroscopy, in situ high-temperature XRD, and thermogravimetry (TG) have been used to characterize the thermal decomposition of the hybrid material. It has been found that the thermal stability of the intercalated naproxen is significantly enhanced compared with the pure form before intercalation, which suggests that this drug-inorganic layered material may have prospective application as the basis of a novel drug delivery system.

  19. Preparation of Coaxial-Line and Hollow Mn2O3 Nanofibers by Single-Nozzle Electrospinning and Their Catalytic Performances for Thermal Decomposition of Ammonium Perchlorate.

    PubMed

    Liang, Jiyuan; Yang, Jie; Cao, Weiguo; Guo, Xiangke; Guo, Xuefeng; Ding, Weiping

    2015-09-01

    Coaxial-line and hollow Mn2O3 nanofibers have been synthesized by a simple single-nozzle electrospinning method without using a complicated coaxial jet head, combined with final calcination. The crystal structure and morphology of the Mn2O3 nanofibers were investigated by using the X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results indicate that the electrospinning distance has important influence on the morphology and structure of the obtained Mn2O3 nanofibers, which changes from hollow fibers for short electrospinning distance to coaxial-line structure for long electrospinning distance after calcination in the air. The formation mechanisms of different structured Mn2O3 fibers are discussed in detail. This facile and effective method is easy to scale up and may be versatile for constructing coaxial-line and hollow fibers of other metal oxides. The catalytic activity of the obtained Mn2O3 nanofibers on thermal decomposition of ammonium perchlorate (AP) was studied by differential scanning calorimetry (DSC). The results show that the hollow Mn2O3 nanofibers have good catalytic activity to promote the thermal decomposition of AP.

  20. [Real-time analysis of polyvinyl chloride thermal decomposition/combustion products with single photon ionization/photoelectron ionization online mass spectrometer].

    PubMed

    Chen, Wen-Dong; Hou, Ke-Yong; Chen, Ping; Li, Fang-Long; Zhao, Wu-Duo; Cui, Hua-Peng; Hua, Lei; Xie, Yuan-Yuan; Li, Hai-Yang

    2013-01-01

    With the features of a broad range of ionizable compounds, reduced fragments and simple mass spectrum, a homemade magnetic field enhanced photoelectron ionization (MEPEI) source combined with single photon ionization (SPI) for time-of-flight mass spectrometer was built and applied to analyze thermal decomposition/combustion products of polyvinyl chloride (PVC). The combined ion source can be switched very fast between SPI mode and SPI-MEPEI mode for detecting different targeted compounds, and only adjusting the voltage of the electrode in the ionization region to trigger the switch. Among the PVC thermal decomposition/combustion products, HCl and CO2, which ionization energies (12.74 eV, 13.77 eV respectively) were higher than the energy of photon (10.60 eV), were ionized by MEPEI, while alkenes, dichloroethylene, benzene and its homologs, monochlorobenzene, styrene, indane, naphthalene and its homologs were ionized by SPI and MEPEI simultaneously. Spectra of interested products as a function of temperatures indicated that products are formed via two main mechanisms: (1) dechlorination and intramolecular cyclization can lead to the formation of HCl, benzene and naphthalene at 250-370 degrees C; (2) intermolecular crosslinking leads to the formation of alkyl aromatics such as toluene and xylene/ethylbenzene at 380-510 degrees C. The experimental results show that the combined ion source of SPI/ SPI-MEPEI for TOF-MS has broad application prospects in the online analysis field.

  1. Synthesis and characterization of Fe0.6Zn0.4Fe2O4 ferrite magnetic nanoclusters using simple thermal decomposition method

    NASA Astrophysics Data System (ADS)

    Sharifi, Ibrahim; Zamanian, Ali; Behnamghader, Aliasghar

    2016-08-01

    This paper presents experimental results regarding the effect of the quantity of solvent on formation of the Fe-Zn ferrite nanoparticles during thermal decomposition. A ternary system of Fe0.6Zn0.4Fe2O4 has been synthesized by a thermal decomposition method using metal acetylacetonate in high temperature boiling point solvent and oleic acid. The X-ray diffraction study was used to determine phase purity, crystal structure, and average crystallite size of iron-zinc ferrite nanoparticles. The average crystallite size of nanoparticles was increased from 13 nm to 37 nm as a result of reducing the solvent from 30 ml to 10 ml in a synthesis batch. The diameter of particles and morphology of the particles were determined by transmission electron microscopy (TEM) and field emission scanning electron microscope (FESEM). Mid and far Fourier transform infrared (FT-IR) measurement confirmed monophasic spinel structure of ferrite. Furthermore, the DC magnetic properties of the samples were studied using the vibrating sample magnetometer (VSM). The largest Fe-Zn ferrite nanoparticles exhibited a relatively high saturation magnetization of 96 emu/g. Moreover, Low-field AC susceptibility measurement indicated blocking temperature of nanoparticles around 170-200 K.

  2. Kinetics of sub-2 nm TiO2 particle formation in an aerosol reactor during thermal decomposition of titanium tetraisopropoxide

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Liu, Pai; Fang, Jiaxi; Wang, Wei-Ning; Biswas, Pratim

    2015-03-01

    Particle size distribution measurements from differential mobility analyzers (DMAs) can be utilized to study particle formation mechanisms. However, knowledge on the initial stages of particle formation is incomplete, since in conventional DMAs, the Brownian broadening effect limits their ability to measure sub-2 nm-sized particles. Previous studies have demonstrated the capability of high-flow DMAs, such as the Half Mini DMAs, to measure sub-2 nm particles with significantly higher resolutions than conventional DMAs. A Half Mini DMA was applied to study the kinetics of sub-2 nm TiO2 nanoparticle formation in a furnace aerosol reactor, through the thermal decomposition of titanium tetraisopropoxide (TTIP). The influence of parameters such as reaction temperature, residence time, precursor concentration, and the introduction of bipolar charges on sub-2 nm particle size distributions were studied. A first order reaction rate derived from the dependence of size distributions on reaction temperature matched well with existing literature data. The change in precursor residence time and precursor concentration altered the size distributions correspondingly, indicating the occurrence of TTIP thermal decomposition. The introduction of bipolar charges in aerosol reactors enhanced the consumption of reactants, possibly due to ion-induced nucleation and induced dipole effects.

  3. Decomposition of atrazine traces in water by combination of non-thermal electrical discharge and adsorption on nanofiber membrane.

    PubMed

    Vanraes, Patrick; Willems, Gert; Daels, Nele; Van Hulle, Stijn W H; De Clerck, Karen; Surmont, Pieter; Lynen, Frederic; Vandamme, Jeroen; Van Durme, Jim; Nikiforov, Anton; Leys, Christophe

    2015-04-01

    In recent decades, several types of persistent substances are detected in the aquatic environment at very low concentrations. Unfortunately, conventional water treatment processes are not able to remove these micropollutants. As such, advanced treatment methods are required to meet both current and anticipated maximally allowed concentrations. Plasma discharge in contact with water is a promising new technology, since it produces a wide spectrum of oxidizing species. In this study, a new type of reactor is tested, in which decomposition by atmospheric pulsed direct barrier discharge (pDBD) plasma is combined with micropollutant adsorption on a nanofiber polyamide membrane. Atrazine is chosen as model micropollutant with an initial concentration of 30 μg/L. While the H2O2 and O3 production in the reactor is not influenced by the presence of the membrane, there is a significant increase in atrazine decomposition when the membrane is added. With membrane, 85% atrazine removal can be obtained in comparison to only 61% removal without membrane, at the same experimental parameters. The by-products of atrazine decomposition identified by HPLC-MS are deethylatrazine and ammelide. Formation of these by-products is more pronounced when the membrane is added. These results indicate the synergetic effect of plasma discharge and pollutant adsorption, which is attractive for future applications of water treatment.

  4. Thermoresponsive copolymer/SiO2 nanoparticles with dual functions of thermally controlled drug release and simultaneous carrier decomposition.

    PubMed

    Li, Aihua; Zhang, Jizhen; Xu, Yuanhong; Liu, Jingquan; Feng, Shengyu

    2014-09-26

    The preparation of thermoresponsive drug carriers with a self-destruction property is presented. These drug carriers were fabricated by incorporation of drug molecules and thermoresponsive copolymer, poly(N-isopropylacrylamide-co-acrylamide), into silica nanoparticles in a one-pot preparation process. The enhanced drug release was primarily attributed to faster molecule diffusion resulting from the particle decomposition triggered by phase transformation of the copolymer upon the temperature change. The decomposition of the drug carriers into small fragments should benefit their fast excretion from the body. In addition, the resulting drug-loaded nanoparticles showed faster drug release in an acidic environment (pH 5) than in a neutral one. The controlled drug release of methylene blue and doxorubicin hydrochloride and the self-decomposition of the drug carriers were successfully characterized by using TEM, UV/Vis spectroscopy, and confocal microscopy. Together with the nontoxicity and excellent biocompatibility of the copolymer/SiO2 composite, the features of controlled drug release and simultaneous carrier self-destruction provided a promising opportunity for designing various novel drug-delivery systems.

  5. Combustion of Organic Molecules by the Thermal Decomposition of Perchlorate Salts: Implications for Organics at the Mars Phoenix Scout Landing Site

    NASA Technical Reports Server (NTRS)

    Ming, D.W.; Morris, R.V.; Niles, B.; Lauer, H.V.; Archer, P.D.; Sutter, B.; Boynton, W.V.; Golden, D.C.

    2009-01-01

    The Mars 2007 Phoenix Scout Mission successfully landed on May 25, 2008 and operated on the northern plains of Mars for 150 sols. The primary mission objective was to study the history of water and evaluate the potential for past and present habitability in Martian arctic ice-rich soil [1]. Phoenix landed near 68 N latitude on polygonal terrain created by ice layers that are a few centimeters under loose soil materials. The Phoenix Mission is assessing the potential for habitability by searching for organic molecules in the ice or icy soils at the landing site. Organic molecules are necessary building blocks for life, although their presence in the ice or soil does not indicate life itself. Phoenix searched for organic molecules by heating soil/ice samples in the Thermal and Evolved-Gas Analyzer (TEGA, [2]). TEGA consists of 8 differential scanning calorimeter (DSC) ovens integrated with a magnetic-sector mass spectrometer with a mass range of 2-140 daltons [2]. Endothermic and exothermic reactions are recorded by the TEGA DSC as samples are heated from ambient to 1000 C. Evolved gases, including any organic molecules and their fragments, are simultaneously measured by the mass spectrometer during heating. Phoenix TEGA data are still under analysis; however, no organic fragments have been identified to date in the evolved gas analysis (EGA). The MECA Wet Chemistry Lab (WCL) discovered a perchlorate salt in the Phoenix soils and a mass 32 peak evolved between 325 and 625 C for one surface sample dubbed Baby Bear [3]. The mass 32 peak is attributed to evolved O2 generated during the thermal decomposition of the perchlorate salt. Perchlorates are very strong oxidizers when heated, so it is possible that organic fragments evolved in the temperature range of 300-600 C were combusted by the O2 released during the thermal decomposition of the perchlorate salt. The byproduct of the combustion of organic molecules is CO2. There is a prominent release of CO2 between 200

  6. Perfluoropolyalkylether decomposition on catalytic aluminas

    NASA Technical Reports Server (NTRS)

    Morales, Wilfredo

    1994-01-01

    The decomposition of Fomblin Z25, a commercial perfluoropolyalkylether liquid lubricant, was studied using the Penn State Micro-oxidation Test, and a thermal gravimetric/differential scanning calorimetry unit. The micro-oxidation test was conducted using 440C stainless steel and pure iron metal catalyst specimens, whereas the thermal gravimetric/differential scanning calorimetry tests were conducted using catalytic alumina pellets. Analysis of the thermal data, high pressure liquid chromatography data, and x-ray photoelectron spectroscopy data support evidence that there are two different decomposition mechanisms for Fomblin Z25, and that reductive sites on the catalytic surfaces are responsible for the decomposition of Fomblin Z25.

  7. Mass-dependent and Mass-independent Sulphur Isotope Fractionation Accompanying Thermal- and Photo-chemical Decomposition of Sulphur Bearing Organic Compounds

    NASA Astrophysics Data System (ADS)

    Oduro, Harry; Izon, Gareth; Ono, Shuhei

    2014-05-01

    The bimodal S-isotope record, specifically the transition from mass independent (MIF) to mass dependent fractionation (MDF), is perhaps the most widely cited line of evidence for an irreversible rise in atmospheric oxygen at ca. 2.4Ga. The production and preservation of S-MIF, manifested in both Δ33S and Δ36S, within the geological record are linked to atmospheric O2 via a number of arguments. However, to date, the only mechanism capable of generating S-MIF consistent with the Archaean sedimentary records involves gas-phase ultraviolet irradiation of SO21 photolysis. More recently, Δ33S S-MIF trends have been reported from en vitro thermochemical sulphate reduction (TSR) experiments, prompting authors to question the importance of S-MIF as a proxy for Earth oxidation2. Importantly, whilst emerging TSR experiments3,4 affirm the reported Δ33S trends2, these experiments fail to identify correlated S-MIF between Δ33S and Δ36S values3,4. Realization that S-MIF is confined to Δ33S during TSR, precludes TSR as a mechanism responsible for the origin of the Archaean S-MIF record but strongly suggests the effect originating from a magnetic isotope effect (MIE) associated with 33S nucleus3,4. Clearly, photochemical and thermochemical processes impart different Δ36S/Δ33S trends with significant variation in δ34S; however, a complete experimental elucidation of mechanisms responsible for the S-MIF and S-MIE signatures is lacking. Interestingly, a complete understanding of the S-isotope chemistry during thermal- and photo-chemical decomposition may reveal wavelength and thermal dependence archived in the sedimentary record. Here we extend the experimental database to explore the magnitude and sign of Δ36S/Δ33S and δ34S produced during both photo- and thermochemical processes. Here the organic sulphur compounds (OSC) utilized in these experiments carries diagnostic Δ36S/Δ33S patterns that differ from those reported from photolysis experiment SO2 and from the

  8. Mass spectral studies of thermal decomposition of metal nitrates: an introduction to the discussion of two mechanisms

    NASA Astrophysics Data System (ADS)

    Jackson, Jason G.; Novichikhin, Alexander; Fonseca, Rodney W.; Holcombe, James A.

    1995-10-01

    Residual gas analysis and static secondary ion mass spectrometry are used to investigate the reported appearance of metal oxide species in the gas phase during the decomposition of various metal nitrates. Copper, silver, cadmium and lead nitrates are heated and decomposed in vacuo in an attempt to elucidate the possible mechanism for the observation of gas phase metal oxides and nitrates at relatively low temperatures. This paper contains the experimental information. Two following papers will provide two different interpretations of the data. The same data will be used in both papers.

  9. A general method for preparing lanthanide oxide nanoparticles via thermal decomposition of lanthanide(III) complexes with 1-hydroxy-2-naphthoic acid and hydrazine ligands

    NASA Astrophysics Data System (ADS)

    Parimalagandhi, Karuppannan; Premkumar, Thathan; Vairam, Sundararajan

    2016-09-01

    Six new lanthanide(III) complexes (i.e., [Ln(L)2(NA)1.5]·3H2O, where Ln=La(III), Pr(III), Nd(III), Sm(III), Gd(III), and Ce(III) and L and NA indicate N2H4 and C10H6(1-O)(2-COO), respectively) with 1-hydroxy-2-naphthoic acid [C10H6(1-O)(2-COOH)] and hydrazine (N2H4) as co-ligands were characterized by elemental, FTIR, UV-visible, and XRD techniques. In the FT-IR spectra, the N-N stretching frequency in the range of 981-949 cm-1 demonstrates evidence of the presence of coordinated N2H4, indicating the bidentate bridging nature of hydrazine in the complexes. These complexes show symmetric and asymmetric COO- stretching from 1444 to 1441 cm-1 and 1582 to 1557 cm-1, respectively, indicating bidentate coordination. TG-DTA studies revealed that the compounds underwent endothermic dehydration from 98 to 110 °C. This was followed by the exothermic decomposition of oxalate intermediates to yield the respective metal oxides as the end products. From SEM images, the average size of the metal oxide particles prepared by thermal decomposition of the complexes was determined to be 39-42 nm. The powder X-ray and SEM coupled with energy dispersive X-ray (EDX) studies revealed the presence of the respective nano-sized metal oxides. The kinetic parameters of the decomposition of the complexes were calculated using the Coats-Redfern equation.

  10. Complex transition metal hydrides incorporating ionic hydrogen: thermal decomposition pathway of Na2Mg2FeH8 and Na2Mg2RuH8.

    PubMed

    Humphries, Terry D; Matsuo, Motoaki; Li, Guanqiao; Orimo, Shin-Ichi

    2015-03-28

    Complex transition metal hydrides have potential technological application as hydrogen storage materials, smart windows and sensors. Recent exploration of these materials has revealed that the incorporation of anionic hydrogen into these systems expands the potential number of viable complexes, while varying the countercation allows for optimisation of their thermodynamic stability. In this study, the optimised synthesis of Na2Mg2TH8 (T = Fe, Ru) has been achieved and their thermal decomposition properties studied by ex situ Powder X-ray Diffraction, Gas Chromatography and Pressure-Composition Isotherm measurements. The temperature and pathway of decomposition of these isostructural compounds differs considerably, with Na2Mg2FeH8 proceeding via NaMgH3 in a three-step process, while Na2Mg2RuH8 decomposes via Mg2RuH4 in a two-step process. The first desorption maxima of Na2Mg2FeH8 occurs at ca. 400 °C, while Na2Mg2RuH8 has its first maxima at 420 °C. The enthalpy and entropy of desorption for Na2Mg2TH8 (T = Fe, Ru) has been established by PCI measurements, with the ΔHdes for Na2Mg2FeH8 being 94.5 kJ mol(-1) H2 and 125 kJ mol(-1) H2 for Na2Mg2RuH8.

  11. Synthesis and characterization of nanosized MgxMn1-xFe2O4 ferrites by both sol-gel and thermal decomposition methods

    NASA Astrophysics Data System (ADS)

    De-León-Prado, Laura Elena; Cortés-Hernández, Dora Alicia; Almanza-Robles, José Manuel; Escobedo-Bocardo, José Concepción; Sánchez, Javier; Reyes-Rdz, Pamela Yajaira; Jasso-Terán, Rosario Argentina; Hurtado-López, Gilberto Francisco

    2017-04-01

    This work reports the synthesis of MgxMn1-xFe2O4 (x=0-1) nanoparticles by both sol-gel and thermal decomposition methods. In order to determine the effect of synthesis conditions on the crystal structure and magnetic properties of the ferrites, the synthesis was carried out varying some parameters, including composition. By both methods it was possible to obtain ferrites having a single crystalline phase with cubic inverse spinel structure and a behavior near to that of superparamagnetic materials. Saturation magnetization values were higher for materials synthesized by sol-gel. Furthermore, in both cases particles have a spherical-like morphology and nanometric sizes (11-15 nm). Therefore, these materials can be used as thermoseeds for the treatment of cancer by magnetic hyperthermia.

  12. XPS study of surface composition of polycrystalline CuxCo3- xO4 (0⩽ x<1) obtained by thermal decomposition of nitrate mixtures

    NASA Astrophysics Data System (ADS)

    Angelov, S.; Tyuliev, G.; Marinova, Ts.

    1987-02-01

    The composition of surface layers of spinel oxides CuxCo3- xO4 (0⩽ x<1), obtained by thermal decomposition of nitrate mixtures, has been studied by means of XPS or ESCA. The surface layer sampled by XPS cannot be described by the bulk formula: the density of Co cations is lower than in the bulk and correspondingly, the oxygen-to-metal ratio and copper-to-cobalt ratio are higher than the mean values for the bulk. The increase in the copper content is accompanied with a decrease of the oxygen-to-metal ratio and an increase in the amount of O - and/or OH - species on the surface of the mixed spinels.

  13. Removal of tetrafluoroborate ion from aqueous solution using magnesium-aluminum oxide produced by the thermal decomposition of a hydrotalcite-like compound.

    PubMed

    Yoshioka, Toshiaki; Kameda, Tomohito; Miyahara, Motoya; Uchida, Miho; Mizoguchi, Tadaaki; Okuwaki, Akitsugu

    2007-10-01

    Magnesium-aluminum oxide (Mg-Al oxide) prepared by the thermal decomposition of a hydrotalcite-like compound was found to have potential for treating NaBF(4) wastewater. The Mg-Al oxide removed the BF(4)(-) and F(-) and H(3)BO(3) from the NaBF(4) solution. With increasing Mg-Al oxide quantity and time, the BF(4)(-) concentration decreased and the degree of BF(4)(-), F(-), and boron removal increased. The decrease in the BF(4)(-) concentration resulted from uptake by the Mg-Al oxide and not hydrolysis. The Mg-Al oxide took up F(-) from the solution preferentially. The Mg-Al oxide also converted the H(3)BO(3) in the aqueous solution into H(2)BO(3)(-), which it took up.

  14. Synthesis, structural investigation, thermal decomposition mechanism and sensitivity properties of an energetic compound [Cd(DAT)(6)](ClO(4))(2) (DAT=1,5-diaminotetrazole).

    PubMed

    Cui, Yan; Zhang, Jianguo; Zhang, Tonglai; Yang, Li; Zhang, Jin; Hu, Xiaochun

    2008-12-15

    An energetic coordination compound [Cd(DAT)(6)](ClO(4))(2) has been synthesized by using 1,5-diaminotetrazole (DAT) as ligand and its structure has been characterized by applying X-ray single crystal diffraction, elemental analysis and FT-IR spectroscopy. The central cadmium(II) cation is coordinated by six N atoms from six DAT molecules to form a six-coordinated and distorted octahedral structure. Di-dimension layer structure was formed and the layers were linked together by the extensive intermolecular hydrogen bonds between DAT ligands and ClO(4)(-) anions. Thermal decomposition mechanism of the title compound was predicted based on DSC, TG-DTG and FT-IR analyses results. The kinetic parameters of the first exothermic process of the title compound were studied by applying the Kissinger's and Ozawa-Doyle's methods. Sensitivity tests reveal that the title compound has sensitive nature.

  15. Monodisperse and size-tunable CoO nanocrystals synthesized by thermal decomposition and as an active precursor for Fischer-Tropsch synthesis

    NASA Astrophysics Data System (ADS)

    Lv, Shuai; Zhao, Xin; Xia, Guofu; Jin, Chao; Wang, Li; Yang, Weimin; Zhang, Yuhua; Li, Jinlin

    2017-01-01

    CoO nanocrystals with tunable particle sizes were prepared by thermal decomposition of cobalt(II) acetate in different long-chain alkyl amines. These alkyl amines strongly affect the coordination of the amine group to the metal atoms and the metal-amine interaction, thereby mediating the eventual particle sizes in the condensation process. Moreover, CoO nanocrystals were applied for synthesis of supported catalyst, and exhibited higher catalytic activity in Fischer-Tropsch reaction, demonstrating that nanocrystals are active precursor. The TOF of CO on CoAl-n catalyst obtained from CoO nanocrystals is ∼1.5 times higher than that on conventional catalyst with the same particle size.

  16. Ion chromatography electrospray ionization mass spectrometry method development and investigation of lithium hexafluorophosphate-based organic electrolytes and their thermal decomposition products.

    PubMed

    Kraft, Vadim; Grützke, Martin; Weber, Waldemar; Winter, Martin; Nowak, Sascha

    2014-08-08

    A method based on the coupling of ion chromatography (IC) and electrospray ionization mass spectrometry (ESI-MS) for the separation and determination of thermal decomposition products of LiPF6-based organic electrolytes is presented. The utilized electrolytes, LP30 and LP50, are commercially available and consist of 1mol/l LiPF6 dissolved in ethylene carbonate/dimethyl carbonate and ethylene carbonate/ethyl methyl carbonate, respectively. For the separation method development three ion chromatographic columns with different capacity and stationary phase were used and compared. Besides the known hydrolysis products of lithium hexafluorophosphate, several new organophosphates were separated and identified with the developed IC-ESI-MS method during aging investigations of the electrolytes. The chemical structures were elucidated with IC-ESI-MS/MS.

  17. Synthesis of nanostructured NiO/Co3O4 through thermal decomposition of a bimetallic (Ni/Co) metal-organic framework as catalyst for cyclooctene epoxidation

    NASA Astrophysics Data System (ADS)

    Abbasi, Alireza; Soleimani, Mohammad; Najafi, Mahnaz; Geranmayeh, Shokoofeh

    2017-04-01

    Hydrothermal approach has led to the formation of a three-dimensional metal-organic framework (MOF), [NiCo(μ2-tp)(μ4-tp)(4,4‧-bpy)2]n (1) (tp = terephthalic acid and 4,4‧-bpy = 4,4‧-bipyridine) which was characterized by means of single-crystal X-ray diffraction analysis, powder X-ray diffraction (PXRD), FT-IR spectroscopy, scanning electron microscopy (SEM) and inductive coupled plasma optical emission spectroscopy (ICP-OES). Thermal decomposition of the MOF afforded nanostructured mixed metal oxide, namely NiO/Co3O4. The XRD and SEM analysis confirm the formation of the mixed metal oxide. The nanostructured NiO/Co3O4 demonstrated good catalytic activity and selectivity in the epoxidation of cyclooctene in the presence of tert-butyl hydroperoxide (TBHP) as oxidant.

  18. Meso/macroporous {gamma}-Al{sub 2}O{sub 3} fabricated by thermal decomposition of nanorods ammonium aluminium carbonate hydroxide

    SciTech Connect

    Li, Guang-Ci; Liu, Yun-Qi; Guan, Li-Li; Hu, Xiao-Fu; Liu, Chen-Guang

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Rod-like AACH were synthesized by a hydrothermal treatment. Black-Right-Pointing-Pointer AACH was formed via a Al(OH){sub 3} {yields} (NH{sub 4}){sub 2}Al{sub 6}(CO{sub 3}){sub 3}(OH){sub 14}{center_dot}xH{sub 2}O {yields} NH{sub 4}Al(OH){sub 2}CO{sub 3}{center_dot}H{sub 2}O {yields} NH{sub 4}Al(OH){sub 2}CO{sub 3} path. Black-Right-Pointing-Pointer Alumina derived from AACH has a good thermal stability. Black-Right-Pointing-Pointer The obtained alumina possesses large pore volume and bimodal porosity. -- Abstract: Through exploring the reaction parameters during the synthesis of the AACH, rod-like ammonium aluminium carbonate hydroxide (AACH) with high crystallinity has been successfully prepared via a facile hydrothermal method. The synthesis parameters like time, the molar ratio of NH{sub 4}HCO{sub 3}/Al and the properties of starting materials were systematically investigated. The structure was characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), IR and transmission electron microscopy (TEM). The experimental results display that the obtained {gamma}-Al{sub 2}O{sub 3} materials possess meso/macroporosity and large pore volume, which are mainly attributed to the removal of gas molecules during the decomposition of AACH. Moreover, using the rod-like AACH as precursor, {gamma}-Al{sub 2}O{sub 3} nanorods were obtained via a low-temperature thermal decomposition method.

  19. Thermal decomposition and crystallization of aqueous sol-gel derived zirconium acetate gels occurring during the preparation of ceramic coatings

    NASA Astrophysics Data System (ADS)

    Geiculescu, Araldina Corina

    1998-12-01

    A sol-gel procedure using an aqueous zirconium acetate precursor was used to form continuous, crack- and bridge-free zirconia coatings on graphite fibers. A comprehensive understanding of the precursor's structure and structural evolution during the sol to gel and gel to solid transitions is required to control the properties of the coating. Decomposition of the gel prepared by desiccation of the solution of zirconium acetate and pyrolyzed to form crystalline zirconia powders in N2, Air and O2 and the transformations occurring during pyrolysis to 800°C was investigated. Three transition temperatures were detected: the amorphous-to-cubic (am-c), cubic-to-tetragonal (c-t) and tetragonal-to-monoclinic (t-m) transition. The presence of molecular oxygen decreased the crystallization temperature, increased the grain size of the tetragonal crystals formed and decreased the temperature at which the t-m transformation was initiated. Decomposition and transition temperatures occurring in the pyrolysis and the polymorph distribution were dependent on the pH of the precursor solution and on the presence of additive anions such as chloride, nitrate or sulfate. Lowering the pH of the precursor solution produced changes in the relative concentration of zirconium complexes present in the solution and, hence, reduced the carbon content in the crystalline zirconia obtained by pyrolysis at 555°C and reduced transition temperatures. The presence of counterions altered the ratio of m/t polymorph in the zirconia powders because of the structural and compositional changes in the precursor gel. Controlling the chemistry involved in crystal formation results in controlling the polymorph composition, consequently gaining control of the properties of the coating of graphite fibers.

  20. Synthesis, crystal structure and catalytic effect on thermal decomposition of RDX and AP: An energetic coordination polymer [Pb2(C5H3N5O5)2(NMP)·NMP]n

    NASA Astrophysics Data System (ADS)

    Liu, Jin-jian; Liu, Zu-Liang; Cheng, Jian; Fang, Dong

    2013-04-01

    An energetic lead(II) coordination polymer based on the ligand ANPyO has been synthesized and its crystal structure has been got. The polymer was characterized by FT-IR spectroscopy, elemental analysis, DSC and TG-DTG technologies. Thermal analysis shows that there are one endothermic process and two exothermic decomposition stages in the temperature range of 50-600 °C with final residues 57.09%. The non-isothermal kinetic has also been studied on the main exothermic decomposition using the Kissinger's and Ozawa-Doyle's methods, the apparent activation energy is calculated as 195.2 KJ/mol. Furthermore, DSC measurements show that the polymer has significant catalytic effect on the thermal decomposition of ammonium perchlorate.

  1. Decomposition and Stability Studies of TAGN (Triaminoguanidium Nitrate)

    DTIC Science & Technology

    1988-12-01

    and atomic absorption spectroscopy . TAGN (Triaminoquanidinium Nitrate), DAGN (Diaminoquanidinium Nitrate), Thermal analysis, Mass Spectroscopy, RDX (Trinitrotriazacyclohexane), Decomposition chemistry.

  2. Structural determination; vibration study and thermal decomposition of [C5H6N5]2SeO4ṡ2H2O

    NASA Astrophysics Data System (ADS)

    Ben Hassen, C.; Boujelbene, M.; Mhiri, T.

    2015-01-01

    The present paper reports the chemical synthesis, structure study, thermal analysis, and vibrational properties of new hybrid compound called: bis (adeninium) selenate bihydrates. It is crystallized in the triclinic system with P-1 space group and the following parameters a = 7.804(5) Å; b = 9.686 (5) Å; c = 11.771 (5) Å; α = 84.421(5)°; ß = 77.556(5)°; γ = 81.186 (5)°; Z = 2 and V = 856.7(8) Å3. The structure is built up from tunnels containing all the components of the structure and following to the c axis, linked via three types of hydrogen bonds (Nsbnd H…O, Nsbnd H…N and Osbnd H…O). The thermal decomposition of precursors studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), indicate the existence of two mass loss region correspond to dehydration and degradation of the title compound, respectively. The existence of vibrational modes correspond to the organic and inorganic groups and water molecular are identified by the IR and Raman spectroscopy in the frequency ranges 400-4000 and 300-1600 cm-1, respectively.

  3. Crystal structures, thermal decompositions and sensitivity properties of [Cu(ethylenediamine)2(nitroformate)2] and [Cd(ethylenediamine)3](nitroformate)2.

    PubMed

    Yang, Li; Zhang, Jin; Zhang, Tonglai; Zhang, Jianguo; Cui, Yan

    2009-05-30

    Two new coordination compounds [Cu(ethylenediamine)(2)(nitroformate)(2)] and [Cd(ethylenediamine)(3)](nitroformate)(2) were synthesized and characterized through elemental analysis, IR and UV spectra. Their crystal structures were determined through X-ray single crystal diffraction. The first compound crystallizes in the triclinic space group P1; the second one crystallizes in the orthorhombic space group Pbca. For the first compound, central Cu(II) ion is hexa-coordinated with two ethylenediamine ligand molecules and two nitroformate anions to form the centrosymmetric octahedral structure. For the second one, central Cd(II) ion is hexa-coordinated with three ethylenediamine ligand molecules to form the slightly distorted octahedra. Through hydrogen bonds, molecules are linked together to form the three-dimensional packing diagrams. Thermal decomposition mechanisms of these two compounds were predicted through DSC, TG-DTG and FTIR analyses. In addition, the impact sensitivity, friction sensitivity and flame sensitivity were measured. All observed properties show that the first one has high energy, good thermal stability and moderate flame sensitivity.

  4. Structural insights into the thermal decomposition sequence of barium tetrahydrogenorthotellurate(VI), Ba[H{sub 4}TeO{sub 6}

    SciTech Connect

    Weil, Matthias

    2016-09-15

    The compounds Ba[H{sub 4}TeO{sub 6}] (I), Ba[H{sub 2}TeO{sub 5}] (II), Ba[Te{sub 2}O{sub 6}(OH){sub 2}] (III) and Ba[TeO{sub 4}] (IV) were prepared by application of a diffusion method (I), under hydrothermal conditions (II and III) and from solid state reactions (IV), respectively. Structure analysis on the basis of single crystal X-ray diffraction data revealed novel structure types for (I), (II) and (III) and isotypism of (IV) with PrSbO{sub 4} and LaSbO{sub 4}. Common feature of the four oxotellurate(VI) structures are [TeO{sub 6}] octahedra. Whereas in the crystal structure of (I) the octahedral units are isolated, they are condensed into chains via corner-sharing in (II) and via edge-sharing in (III) and (IV). The coordination numbers of the barium cations in the four structures range from seven to ten. Although hydrogen atom positions could not be located for the structures of (I) and (II), short interpolyhedral O···O contacts are evident for strong hydrogen bonding. The temperature behaviour of (I), (II) and (IV) was monitored by simultaneous thermal analysis (STA) measurements and in situ powder X-ray diffraction, revealing the decomposition sequence Ba[H{sub 4}TeO{sub 6}] → Ba[H{sub 2}TeO{sub 5}] → Ba[TeO{sub 4}]→ Ba[TeO{sub 3}] upon heating to temperatures up to 900 °C. - Graphical abstract: The crystal structures of the four oxotellurates(VI) were determined from single crystal data. The thermal decomposition of Ba[H{sub 4}TeO{sub 6}], monitored by temperature-dependent X-ray powder diffraction and simultaneous thermal analysis measurements, involves two condensation reactions according to Ba[H{sub 4}TeO{sub 6}]→Ba[H{sub 2}TeO{sub 5}]+H{sub 2}O(↑)→Ba[TeO{sub 4}]+ H{sub 2}O(↑). Display Omitted.

  5. Effect of thermal treatment and frozen storage on lipid decomposition of light and dark muscles of saithe (Pollachius virens).

    PubMed

    Karlsdottir, Magnea G; Sveinsdottir, Kolbrun; Kristinsson, Hordur G; Villot, Dominique; Craft, Brian D; Arason, Sigurjon

    2014-12-01

    Lipid decomposition of saithe (Pollachius virens) light and dark muscles was monitored during frozen storage at -25°C of raw (up to 18 months) and cooked products. Samples were cooked after 0, 6 and 12 months raw storage then refrozen and stored at -25°C for 12 months to determine the stability of cooked-then-stored samples. Fatty acid profiles, formation of hydroperoxides (PV), thiobarbituric acid reactive substances (TBARS), fluorescence compounds (OFR) and free fatty acids (FFA) were evaluated throughout the storage for all samples. In general, results indicated that enzymatic lipolysis was the driving factor influencing the quality of saithe over raw storage and it mostly affected polyunsaturated lipids in the light muscle. Cooking, however, inhibited FFA formation and induced formation of PV and TBARS. This behavior was more evident in samples cooked after long raw storage periods. The initial quality of the raw material before cooking is therefore critical with regard to oxidative stability of cooked fish products.

  6. Bamboo-shaped carbon nanotubes generated by methane thermal decomposition using Ni nanoparticles synthesized in water-oil emulsions.

    PubMed

    González, Ismael; De Jesus, Juan; Cañizales, Edgar

    2011-12-01

    Ni nanoparticles were synthesized using two water-in-oil emulsions formulated with different surfactants and using n-heptane as the organic phase and aqueous nickel acetate as the catalytic metallic precursor. Characterization by transmission electron microscopy showed that the Ni nanoparticles have diameters ranging from 3 to 12 nm, and that the surface is lightly oxidized. The decomposition of diluted methane catalyzed by the as-prepared Ni nanoparticles was studied in a thermogravimetric analyzer (TGA), operated in the 25-930°C range. The weight gains measured during the analysis showed that the Ni nanoparticles decomposed methane above 480°C, producing similar g.C/g.cat ratios (6-7) at the end of the tests. High resolution transmission electron microscopy (HRTEM) confirmed that the carbons collected at 930°C were bamboo-shaped carbon nanotubes (BSCNTs) with well defined conical compartments. The average outside diameter of the tubes was between 30 and 60 nm.

  7. MoS2 /WS2 -Graphene Composites through Thermal Decomposition of Tetrathiomolybdate/Tetrathiotungstate for Proton/Oxygen Electroreduction.

    PubMed

    Luxa, Jan; Fawdon, Jack; Sofer, Zdeněk; Mazánek, Vlastimil; Pumera, Martin

    2016-09-19

    MoS2 and WS2 have been prepared on a conductive graphene support by thermal reduction of tetrathiotungstate/tetrathiomolybdate and graphite oxide. Whereas the catalytic properties towards hydrogen evolution are strongly influenced by the Magnéli phases formed as a byproduct during the synthesis, the catalytic activity towards oxygen reduction of these composite materials is not affected by this phenomenon and these materials exhibit high catalytic activity towards this industrially important reaction.

  8. An ordered bcc CuPd nanoalloy synthesised via the thermal decomposition of Pd nanoparticles covered with a metal-organic framework under hydrogen gas.

    PubMed

    Li, Guangqin; Kobayashi, Hirokazu; Kusada, Kohei; Taylor, Jared M; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki; Yamamoto, Tomokazu; Matsumura, Syo; Kitagawa, Hiroshi

    2014-11-18

    Presented here is the synthesis of an ordered bcc copper-palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal-organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal-organic framework decomposition.

  9. Thermal decomposition of sewage sludge under N2, CO2 and air: Gas characterization and kinetic analysis.

    PubMed

    Hernández, Ana Belén; Okonta, Felix; Freeman, Ntuli

    2017-03-25

    Thermochemical valorisation processes that allow energy to be recovered from sewage sludge, such as pyrolysis and gasification, have demonstrated great potential as convenient alternatives to conventional sewage sludge disposal technologies. Moreover, these processes may benefit from CO2 recycling. Today, the scaling up of these technologies requires an advanced knowledge of the reactivity of sewage sludge and the characteristics of the products, specific to the thermochemical process. In this study the behaviour of sewage sludge during thermochemical conversion, under different atmospheres (N2, CO2 and air), was studied, using TGA-FTIR, in order to understand the effects of different atmospheric gases on the kinetics of degradation and on the gaseous products. The different steps observed during the solid degradation were related with the production of different gaseous compounds. A higher oxidative degree of the atmosphere surrounding the sample resulted in higher reaction rates and a shift of the degradation mechanisms to lower temperatures, especially for the mechanisms taking place at temperatures above 400 °C. Finally, a multiple first-order reaction model was proposed to compare the kinetic parameters obtained under different atmospheres. Overall, the highest activation energies were obtained for combustion. This work proves that CO2, an intermediate oxidative atmosphere between N2 and air, results in an intermediate behaviour (intermediate peaks in the derivative thermogravimetric curves and intermediate activation energies) during the thermochemical decomposition of sewage sludge. Overall, it can be concluded that the kinetics of these different processes require a different approach for their scaling up and specific consideration of their characteristic reaction temperatures and rates should be evaluated.

  10. Thermal decomposition of silver acetate in silver paste for solar cell metallization: An effective route to reduce contact resistance

    NASA Astrophysics Data System (ADS)

    Jun Kim, Suk; Yun Kim, Se; Man Park, Jin; Hwan Park, Keum; Ho Lee, Jun; Mock Lee, Sang; Taek Han, In; Hyang Kim, Do; Ram Lim, Ka; Tae Kim, Won; Cheol Park, Ju; Soo Jee, Sang; Lee, Eun-Sung

    2013-08-01

    A screen printed silver/metallic glass (MG) paste formulated with Ag acetate resulted in a specific contact resistance in the range of 0.6-0.7 mΩ.cm2 on both the n- and p-type Si emitters of interdigitated back-contact solar cells. Silver nanocrystallites resulting from thermally decomposed Ag acetate prevented the Al MG frits from directly interacting with the Si emitter, thus reducing the amount of Al diffused into the Si emitters, and subsequently, the contact resistance. A photovoltaic conversion efficiency of 20.3% was achieved using this technique.

  11. Ring structures formed inside voids in SiO2 layer on Si(100) during thermal decomposition

    NASA Astrophysics Data System (ADS)

    Enta, Yoshiharu; Osanai, Shodai; Yoshida, Taichi

    2016-02-01

    Ring structures inside voids in the SiO2 layer on a Si(100) substrate, which are concentrically formed by repeating thermal annealing in vacuum, have been investigated by scanning electron microscopy and atomic force microscopy. We demonstrate that slight exposure of the surface to volatile organic compounds during a cooling process significantly affects the formation of the ring structures. This result clearly shows that the key to ring-structure formation is surface adsorption of carbon atoms, which probably suppresses surface migration of silicon atoms. Our research provides a novel technique for the fabrication of nanostructured semiconductors for such applications as quantum effect devices.

  12. The crystal structure of paramagnetic copper(II) oxalate (CuC₂O₄): formation and thermal decomposition of randomly stacked anisotropic nano-sized crystallites.

    PubMed

    Christensen, Axel Nørlund; Lebech, Bente; Andersen, Niels Hessel; Grivel, Jean-Claude

    2014-11-28

    Synthetic copper(II) oxalate, CuC2O4, was obtained in a precipitation reaction between a copper(II) solution and an aqueous solution of oxalic acid. The product was identified from its conventional X-ray powder patterns which match that of the copper mineral Moolooite reported to have the composition CuC2O4·0.44H2O. Time resolved in situ investigations of the thermal decomposition of copper(II) oxalate using synchrotron X-ray powder diffraction showed that in air the compound converts to Cu2O at 215 °C and oxidizes to CuO at 345 °C. Thermo gravimetric analysis performed in an inert Ar-gas reveals that the material contains no crystal water and reduces to pure Cu at 295 °C. Magnetic susceptibility measurements in the temperature range from 2 K to 300 K show intriguing paramagnetic behaviour with no sign of magnetic order down to 2 K. A crystal structure investigation is made based on powder diffraction data using one neutron diffraction pattern obtained at 5 K (λ = 1.5949(1) Å) combined with one conventional and two synchrotron X-ray diffraction patterns obtained at ambient temperature using λ = 1.54056, 1.0981 and λ = 0.50483(1) Å, respectively. Based on the X-ray synchrotron data the resulting crystal structure is described in the monoclinic space group P2₁/c (#14) in the P12₁/n1 setting with unit cell parameters a = 5.9598(1) Å, b = 5.6089(1) Å, c = 5.1138 (1) Å, β = 115.320(1)°. The composition is CuC2O4 with atomic coordinates determined by FullProf refinement of the neutron diffraction data. The crystal structure consists of a random stacking of CuC2O4 micro-crystallites where half the Cu-atoms are placed at (2a) and the other half at (2b) positions with the corresponding oxalate molecules centred around the corresponding (2b) and (2a) site positions, respectively. The diffraction patterns obtained for both kinds of radiation show considerable broadening of several Bragg peaks caused by highly anisotropic microstructural size and strain

  13. Microwave-assisted synthesis of layered basic zinc acetate nanosheets and their thermal decomposition into nanocrystalline ZnO

    PubMed Central

    2014-01-01

    We have developed a low-cost technique using a conventional microwave oven to grow layered basic zinc acetate (LBZA) nanosheets (NSs) from a zinc acetate, zinc nitrate and HMTA solution in only 2 min. The as-grown crystals and their pyrolytic decomposition into ZnO nanocrystalline NSs are characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL). SEM and AFM measurements show that the LBZA NSs have typical lateral dimensions of 1 to 5 μm and thickness of 20 to 100 nm. Annealing in air from 200°C to 1,000°C results in the formation of ZnO nanocrystalline NSs, with a nanocrystallite size ranging from 16 nm at 200°C to 104 nm at 1,000°C, as determined by SEM. SEM shows evidence of sintering at 600°C. PL shows that the shape of the visible band is greatly affected by the annealing temperature and that the exciton band to defect band intensity ratio is maximum at 400°C and decreases by a factor of 15 after annealing at 600°C. The shape and thickness of the ZnO nanocrystalline NSs are the same as LBZA NSs. This structure provides a high surface-to-volume ratio of interconnected nanoparticles that is favorable for applications requiring high specific area and low resistivity such as gas sensing and dye-sensitized solar cells (DSCs). We show that resistive gas sensors fabricated with the ZnO NSs showed a response of 1.12 and 1.65 to 12.5 ppm and 200 ppm of CO at 350°C in dry air, respectively, and that DSCs also fabricated from the material had an overall efficiency of 1.3%. PACS 81.07.-b; 62.23.Kn; 61.82.Fk PMID:24397935

  14. Ozone decomposition.

    PubMed

    Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho; Zaikov, Gennadi E

    2014-06-01

    Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates.

  15. Ozone decomposition

    PubMed Central

    Batakliev, Todor; Georgiev, Vladimir; Anachkov, Metody; Rakovsky, Slavcho

    2014-01-01

    Catalytic ozone decomposition is of great significance because ozone is a toxic substance commonly found or generated in human environments (aircraft cabins, offices with photocopiers, laser printers, sterilizers). Considerable work has been done on ozone decomposition reported in the literature. This review provides a comprehensive summary of the literature, concentrating on analysis of the physico-chemical properties, synthesis and catalytic decomposition of ozone. This is supplemented by a review on kinetics and catalyst characterization which ties together the previously reported results. Noble metals and oxides of transition metals have been found to be the most active substances for ozone decomposition. The high price of precious metals stimulated the use of metal oxide catalysts and particularly the catalysts based on manganese oxide. It has been determined that the kinetics of ozone decomposition is of first order importance. A mechanism of the reaction of catalytic ozone decomposition is discussed, based on detailed spectroscopic investigations of the catalytic surface, showing the existence of peroxide and superoxide surface intermediates. PMID:26109880

  16. Synthesis of maghemite ( γ-Fe2O3) nanoparticles by thermal-decomposition of magnetite (Fe3O4) nanoparticles

    NASA Astrophysics Data System (ADS)

    Aliahmad, M.; Nasiri Moghaddam, N.

    2013-04-01

    In this research work, we prepared γ-Fe2O3 nanoparticles by thermal-decomposition of Fe3O4. The Fe3O4 nanoparticles were synthesized via co-precipitation method at room temperature. This simple, soft and cheap method is suitable for preparation of iron oxide nanoparticles ( γ-Fe2O3; Fe3O4). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), vibrating sample magnetometer and differential scanning calorimeter (DSC). The XRD and FT-IR results indicated the formation of γ-Fe2O3 and Fe3O4 nanoparticles. The TEM images showed that the γ-Fe2O3 and Fe3O4 were spherical, and their size was 18 and 22 nm respectively. Magnetic properties have been measured by VSM at room temperature. Hysteresis loops showed that the γ-Fe2O3 and Fe3O4 nanoparticles were super-paramagnetic.

  17. A one-step thermal decomposition method to prepare anatase TiO2 nanosheets with improved adsorption capacities and enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Li, Wenting; Shang, Chunli; Li, Xue

    2015-12-01

    Anatase TiO2 nanosheets (NSs) with high surface area have been prepared via a one-step thermal decomposition of titanium tetraisopropoxide (TTIP) in oleylamine (OM), and their adsorption capacities and photocatalytic activities are investigated by using methylene blue (MB) and methyl orange (MO) as model pollutants. During the synthesis procedure, only one type of surfactant, oleylamine (OM), is used as capping agents and no other solvents are added. Structure and properties of the TiO2 NSs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption analysis, UV-vis spectrum, X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) methods. The results indicate that the TiO2 NSs possess high surface area up to 378 m2 g-1. The concentration of capping agents is found to be a key factor controlling the morphology and crystalline structure of the product. Adsorption and photodegradation experiments reveal that the prepared TiO2 NSs possess high adsorption capacities of model pollutants MB and high photocatalytic activity, showing that TiO2 NSs can be used as efficient pollutant adsorbents and photocatalytic degradation catalysts of MB in wastewater treatment.

  18. Thermochemical cycles for energy storage: Thermal decomposition of ZnCO{sub 4} systems. Final topical report, January 1, 1982--December 31, 1984

    SciTech Connect

    Wentworth, W.E.

    1992-04-01

    The overall objective of our research has been to develop thermochemical cycles that can be used for energy storage. A specific cycle involving ammonium hydrogen sulfate (NH{sub 4}HSO{sub 4}) has been proposed. Each reaction in the proposed cycle has been examined experimentally. Emphasis has been placed on the basic chemistry of these reactions. In the concluding phase of this research, reported herein, we have shown that when NH{sub 4}HSO{sub 4} is mixed with ZnO and decomposed, the resulting products can be released stepwise (H{sub 2}A{sub (g)} at {approximately}163{degrees}C, NH{sub 3(g)} at 365--418{degrees}C, and a mixture of SO{sub 2(g)} and SO{sub 3(g)} at {approximately}900{degrees}C) and separated by controlling the reaction temperature. Side reactions do not appear to be significant and the respective yields are high as would be required for the successful use of this energy storage reaction in the proposed cycle. Thermodynamic, kinetic, and other reaction parameters have been measured for the various steps of the reaction. Finally we have completed a detailed investigation of one particular reaction: the thermal decomposition of zinc sulfate (ZnSO{sub 4}). We have demonstrated that this reaction can be accelerated and the temperature required reduced by the addition of excess ZnO, V{sub 2}A{sub 5} and possibly other metal oxides.

  19. Superparamagnetic Fe3O4 Nanoparticles: Synthesis by Thermal Decomposition of Iron(III) Glucuronate and Application in Magnetic Resonance Imaging.

    PubMed

    Patsula, Vitalii; Kosinová, Lucie; Lovrić, Marija; Ferhatovic Hamzić, Lejla; Rabyk, Mariia; Konefal, Rafal; Paruzel, Aleksandra; Šlouf, Miroslav; Herynek, Vít; Gajović, Srećko; Horák, Daniel

    2016-03-23

    Monodisperse superparamagnetic Fe3O4 nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe3O4 nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis(ethane-2,1-diyl)phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG-P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG-P&Fe3O4 nanoparticles were tested on rat mesenchymal stem cells to determine the particle toxicity and their ability to label the cells. MR relaxometry confirmed that the PMG-P&Fe3O4 nanoparticles had high relaxivity but rather low cellular uptake. Nevertheless, the labeled cells still provided visible contrast enhancement in the magnetic resonance image. In addition, the cell viability was not compromised by the nanoparticles. Therefore, the PMG-P&Fe3O4 nanoparticles have the potential to be used in biomedical applications, especially as contrast agents for magnetic resonance imaging.

  20. Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells

    PubMed Central

    Heo, Jungwoo; Kim, Gi-Hwan; Jeong, Jaeki; Yoon, Yung Jin; Seo, Jung Hwa; Walker, Bright; Kim, Jin Young

    2016-01-01

    We report the preparation of Cu2S, In2S3, CuInS2 and Cu(In,Ga)S2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200–400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process. PMID:27827402

  1. A novel surface-sensitive X-ray absorption spectroscopic detector to study the thermal decomposition of cathode materials for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Nonaka, Takamasa; Okuda, Chikaaki; Oka, Hideaki; Nishimura, Yusaku F.; Makimura, Yoshinari; Kondo, Yasuhito; Dohmae, Kazuhiko; Takeuchi, Yoji

    2016-09-01

    A surface-sensitive conversion-electron-yield X-ray absorption fine structure (CEY-XAFS) detector that operates at elevated temperatures is developed to investigate the thermal decomposition of cathode materials for Li-ion batteries. The detector enables measurements with the sample temperature controlled from room temperature up to 450 °C. The detector is applied to the LiNi0.75Co0.15Al0.05Mg0.05O2 cathode material at 0% state of charge (SOC) and 50% SOC to examine the chemical changes that occur during heating in the absence of an electrolyte. The combination of surface-sensitive CEY-XAFS and bulk-sensitive transmission-mode XAFS shows that the reduction of Ni and Co ions begins at the surface of the cathode particles at around 150 °C, and propagates inside the particle upon further heating. These changes with heating are irreversible and are more obvious at 50% SOC than at 0% SOC. The fraction of reduced Ni ions is larger than that of reduced Co ions. These results demonstrate the capability of the developed detector to obtain important information for the safe employment of this cathode material in Li-ion batteries.

  2. Thermal Decomposition Based Synthesis of Ag-In-S/ZnS Quantum Dots and Their Chlorotoxin-Modified Micelles for Brain Tumor Cell Targeting.

    PubMed

    Chen, Siqi; Ahmadiantehrani, Mojtaba; Publicover, Nelson G; Hunter, Kenneth W; Zhu, Xiaoshan

    Cadmium-free silver-indium-sulfide (Ag-In-S or AIS) chalcopyrite quantum dots (QDs) as well as their core-shell structures (AIS/ZnS QDs) are being paid significant attention in biomedical applications because of their low toxicity and excellent optical properties. Here we report a simple and safe synthetic system to prepare high quality AIS and AIS/ZnS QDs using thermal decomposition. The synthetic system simply involves heating a mixture of silver acetate, indium acetate, and oleic acid in dodecanethiol at 170 °C to produce AIS QDs with a 13% quantum yield (QY). After ZnS shell growth, the produced AIS/ZnS QDs achieve a 41% QY. To facilitate phase transfer and bioconjugation of AIS/ZnS QDs for cellular imaging, these QDs were loaded into the core of PLGA-PEG (5k:5k) based micelles to form AIS/ZnS QD-micelles. Cellular imaging studies showed that chlorotoxin-conjugated QD-micelles can be specifically internalized into U-87 brain tumor cells. This work discloses that the scalable synthesis of AIS/ZnS QDs and the facile surface/interface chemistry for phase transfer and bioconjugation of these QDs may open an avenue for the produced QD-micelles to be applied to the detection of endogenous targets expressed on brain tumor cells, or more broadly to cell- or tissue-based diagnosis and therapy.

  3. Synthesis of MnxGa1-xFe2O4 magnetic nanoparticles by thermal decomposition method for medical diagnosis applications

    NASA Astrophysics Data System (ADS)

    Sánchez, Javier; Cortés-Hernández, Dora Alicia; Escobedo-Bocardo, José Concepción; Almanza-Robles, José Manuel; Reyes-Rodríguez, Pamela Yajaira; Jasso-Terán, Rosario Argentina; Bartolo-Pérez, Pascual; De-León-Prado, Laura Elena

    2017-04-01

    In this work, the synthesis of MnxGa1-xFe2O4 (x=0-1) nanosized particles by thermal decomposition method, using tetraethylene glycol (TEG) as a reaction medium, has been performed. The crystalline structure of the inverse spinel obtained in all the cases was identified by X-ray diffraction (XRD). Vibration sample magnetometry (VSM) was used to evaluate the magnetic properties of ferrites and to demonstrate their superparamagnetic behavior and the increase of magnetization values due to the Mn2+ ions incorporation into the FeGa2O4 structure. Transmission electron microscopy, energy dispersive spectroscopy (TEM-EDS) and X-ray photoelectron spectroscopy (XPS) were used to characterize the obtained magnetic nanoparticles (MNPs). These MNPs showed a near spherical morphology, an average particle size of 5.6±1.5 nm and a TEG coating layer on their surface. In all the cases MNPs showed no response when submitted to an alternating magnetic field (AMF, 10.2 kA/m, 354 kHz) using magnetic induction tests. These results suggest that the synthesized nanoparticles can be potential candidates for their use in biomedical areas.

  4. Facile synthesis of ultrafine SnO2 nanoparticles on graphene nanosheets via thermal decomposition of tin-octoate as anode for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Jinkai; Xie, Sanmu; Cao, Daxian; Lu, Xuan; Meng, Lingjie; Yang, Guidong; Wang, Hongkang

    2016-09-01

    We demonstrate a facile synthesis of ultrafine SnO2 nanoparticles within graphene nanosheets (GNSs) via thermal decomposition of tin-octoate, in which tin-octoate is firstly blended with GNSs followed by annealing in air at a low temperature (350 °C) and a short time (1 h). As anode for lithium ion batteries, the SnO2/GNSs displays superior cycle and rate performance, delivering reversible capacities of 803 and 682 mA h/g at current densities of 200 and 500 mA/g after 120 cycles, respectively, much higher than that of pure SnO2 and GNSs counterparts (143 and 310 mA h/g at 500 mA/g after 120 cycles, respectively). The enhanced electrochemical performance is attributed to the ultrafine SnO2 nanoparticle size and introduction of GNSs. GNSs prevent the aggregation of the ultrafine SnO2 nanoparticles, which alleviate the stress and also provide more electrochemically active sites for lithium insertion and extraction. Moreover, GNSs with large specific surface area ( 363 m2/g) act as a good electrical conductor which greatly improves the electrode conductivity and also an excellent buffer matrix to tolerate the severe volume changes originated from the Li-Sn alloying-dealloying. This work provides a straight-forward synthetic approach for the design of novel composite anode materials with superior electrochemical performance.

  5. Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells

    NASA Astrophysics Data System (ADS)

    Heo, Jungwoo; Kim, Gi-Hwan; Jeong, Jaeki; Yoon, Yung Jin; Seo, Jung Hwa; Walker, Bright; Kim, Jin Young

    2016-11-01

    We report the preparation of Cu2S, In2S3, CuInS2 and Cu(In,Ga)S2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200–400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process.

  6. Clean thermal decomposition of tertiary-alkyl metal thiolates to metal sulfides: environmentally-benign, non-polar inks for solution-processed chalcopyrite solar cells.

    PubMed

    Heo, Jungwoo; Kim, Gi-Hwan; Jeong, Jaeki; Yoon, Yung Jin; Seo, Jung Hwa; Walker, Bright; Kim, Jin Young

    2016-11-09

    We report the preparation of Cu2S, In2S3, CuInS2 and Cu(In,Ga)S2 semiconducting films via the spin coating and annealing of soluble tertiary-alkyl thiolate complexes. The thiolate compounds are readily prepared via the reaction of metal bases and tertiary-alkyl thiols. The thiolate complexes are soluble in common organic solvents and can be solution processed by spin coating to yield thin films. Upon thermal annealing in the range of 200-400 °C, the tertiary-alkyl thiolates decompose cleanly to yield volatile dialkyl sulfides and metal sulfide films which are free of organic residue. Analysis of the reaction byproducts strongly suggests that the decomposition proceeds via an SN1 mechanism. The composition of the films can be controlled by adjusting the amount of each metal thiolate used in the precursor solution yielding bandgaps in the range of 1.2 to 3.3 eV. The films form functioning p-n junctions when deposited in contact with CdS films prepared by the same method. Functioning solar cells are observed when such p-n junctions are prepared on transparent conducting substrates and finished by depositing electrodes with appropriate work functions. This method enables the fabrication of metal chalcogenide films on a large scale via a simple and chemically clear process.

  7. A simple process for the preparation of copper (I) oxide nanoparticles by a thermal decomposition process with borane tert-butylamine complex.

    PubMed

    Kim, Na Rae; Jung, Inyu; Jo, Yun Hwan; Lee, Hyuck Mo

    2013-09-01

    To control the optical properties of Cu2O for a variety of application, we synthesized Cu2O in nanoscale without other treatments. Cu2O nanoparticles with an average size of 2.7 nm (sigma < or = 3.7%) were successfully synthesized in this study via a modified thermal decomposition process. Copper (II) acetylacetonate was used as a precursor, and oleylamine was used as a solvent, a surfactant and a reducing agent. The oleylamine-mediated synthesis allowed for the preparation of Cu2O nanoparticles with a narrower size distribution, and the nanoparticles were synthesized in the presence of a borane tert-butylamine (BTB) complex, where BTB was a strong co-reducing agent together with oleylamine. UV-vis spectroscopy analysis suggest that band gap energy of these Cu2O particles is enlarged from 2.1 eV in the bulk to 3.1 eV in the 2.7-nm nanoparticles, which is larger than most other reported value of Cu2O nanoparticles. Therefore, these nanoparticles could be used as a transparent material because of transformed optical property.

  8. Simple synthesis and size-dependent surface-enhanced Raman scattering of Ag nanostructures on TiO2 by thermal decomposition of silver nitrate at low temperature.

    PubMed

    Wang, Ruey-Chi; Gao, Yong-Siang; Chen, Shu-Jen

    2009-09-16

    A low-temperature dry-process was proposed to synthesize silver nanoparticles, nanorods, and nanoplates on TiO(2) films via thermal decomposition of silver nitrate. X-ray diffraction (XRD) shows only silver crystals were synthesized on the substrate without other byproducts remaining. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal the Ag nanoparticles are single-crystalline face-centered cubic (FCC) structures and their average diameters decrease from 100 to 15 nm with the increase in distance from the source, which corresponds to a decrease of substrate temperature from 350 to 110 degrees C. The Ag nanorods are also single-crystalline FCC structures growing along the [110] direction with diameter and length around 40 and 500 nm, respectively. The morphology of silver nanostructures could be adjusted by varying the working pressure as well as the roughness of the substrates. An obvious size-dependent SERS effect on the TiO(2) substrate with silver nanoparticles was observed for the first time. The enhancement factor increases as the size of the Ag nanoparticles decreases, which is attributed to the increase of hot spots. In addition, fractional brookite in the anatase films could be detected only after being loaded with Ag nanoparticles, which demonstrates the application of SERS in detecting fractional and important features of semiconductors.

  9. Decomposition techniques

    USGS Publications Warehouse

    Chao, T.T.; Sanzolone, R.F.

    1992-01-01

    Sample decomposition is a fundamental and integral step in the procedure of geochemical analysis. It is often the limiting factor to sample throughput, especially with the recent application of the fast and modern multi-element measurement instrumentation. The complexity of geological materials makes it necessary to choose the sample decomposition technique that is compatible with the specific objective of the analysis. When selecting a decomposition technique, consideration should be given to the chemical and mineralogical characteristics of the sample, elements to be determined, precision and accuracy requirements, sample throughput, technical capability of personnel, and time constraints. This paper addresses these concerns and discusses the attributes and limitations of many techniques of sample decomposition along with examples of their application to geochemical analysis. The chemical properties of reagents as to their function as decomposition agents are also reviewed. The section on acid dissolution techniques addresses the various inorganic acids that are used individually or in combination in both open and closed systems. Fluxes used in sample fusion are discussed. The promising microwave-oven technology and the emerging field of automation are also examined. A section on applications highlights the use of decomposition techniques for the determination of Au, platinum group elements (PGEs), Hg, U, hydride-forming elements, rare earth elements (REEs), and multi-elements in geological materials. Partial dissolution techniques used for geochemical exploration which have been treated in detail elsewhere are not discussed here; nor are fire-assaying for noble metals and decomposition techniques for X-ray fluorescence or nuclear methods be discussed. ?? 1992.

  10. Description of Chemically and Thermally Treated Multi-Walled Carbon Nanotubes Using Sequential Decomposition of Adsorption Isotherms

    NASA Astrophysics Data System (ADS)

    Albesa, Alberto G.; Rafti, Matías; Vicente, José Luis

    2016-03-01

    The effect of wet acid oxidation by means of sulfuric/nitric acid mixtures, and high-temperature treatment of commercial arc-discharge synthesized multi-walled carbon nanotubes (MWCNTs) was studied. In order to analyze the adsorption capacities of differently treated MWCNTs, we employed a multistep method that considers separately different pressure ranges (zones) on the experimentally obtained isotherms. The method is based on simple gas isotherm measurements (N2, CO2, CH4, etc.). Low pressure ranges can be described using Dubinin’s model, while high pressure regimes can be fitted using different models such as BET multilayer and Freundlich equations. This analysis allows to elucidate how different substrate treatments (chemical and thermal) can affect the adsorbate-adsorbent interactions; moreover, theoretical description of adsorbate-adsorbate interactions can be improved if a combination of adsorption mechanisms are used instead of a unique model. The results hereby presented also show that, while MWCNTs are a promising material for storage applications, gas separation applications should carefully consider the effect of wide nanotube size distribution present on samples after activation procedures.

  11. Synthesis, spectroscopic characterization, electrochemical behaviour and thermal decomposition studies of some transition metal complexes with an azo derivative

    NASA Astrophysics Data System (ADS)

    Sujamol, M. S.; Athira, C. J.; Sindhu, Y.; Mohanan, K.

    2010-01-01

    Complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a novel heterocyclic azo derivative, formed by coupling diazotized 2-amino-3-carbethoxy-4,5-dimethylthiophene with acetylacetone were synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, UV-vis, IR, 1H NMR and EPR spectral data. Spectral studies revealed that the ligand existed in an internally hydrogen bonded azo-enol form rather than the keto-hydrazone form and coordinated to the metal ion in a tridentate fashion. Analytical data revealed that all the complexes exhibited 1:1 metal-ligand ratio. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry was proposed for each complex. The nickel(II) complex has undergone facile transesterification reaction when refluxed in methanol for a long period. The ligand and the copper(II) complex were subjected to X-ray diffraction study. The electrochemical behaviour of copper(II) complex was investigated by cyclic voltammetry. The thermal behaviour of the same complex was also examined by thermogravimetry.

  12. Synthesis, spectroscopic characterization, electrochemical behaviour and thermal decomposition studies of some transition metal complexes with an azo derivative.

    PubMed

    Sujamol, M S; Athira, C J; Sindhu, Y; Mohanan, K

    2010-01-01

    Complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) with a novel heterocyclic azo derivative, formed by coupling diazotized 2-amino-3-carbethoxy-4,5-dimethylthiophene with acetylacetone were synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, UV-vis, IR, (1)H NMR and EPR spectral data. Spectral studies revealed that the ligand existed in an internally hydrogen bonded azo-enol form rather than the keto-hydrazone form and coordinated to the metal ion in a tridentate fashion. Analytical data revealed that all the complexes exhibited 1:1 metal-ligand ratio. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry was proposed for each complex. The nickel(II) complex has undergone facile transesterification reaction when refluxed in methanol for a long period. The ligand and the copper(II) complex were subjected to X-ray diffraction study. The electrochemical behaviour of copper(II) complex was investigated by cyclic voltammetry. The thermal behaviour of the same complex was also examined by thermogravimetry.

  13. Laser lift-off technique for freestanding GaN substrate using an In droplet formed by thermal decomposition of GaInN and its application to light-emitting diodes

    SciTech Connect

    Iida, Daisuke Kawai, Syunsuke; Ema, Nobuaki; Tsuchiya, Takayoshi; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu

    2014-08-18

    We developed a laser lift-off technique for a freestanding GaN substrate using an In droplet formed by thermal decomposition of GaInN. A combination of an In droplet formed by thermal decomposition of GaInN during growth and a pulsed second-harmonic neodymium-doped yttrium aluminum garnet laser (λ = 532 nm) realized the lift-off GaN substrate. After laser lift-off of the GaN substrate, it was used to achieve 380 nm ultraviolet light-emitting diodes with light output enhanced 1.7-fold. In this way, the light extraction can be improved by removing the GaN substrate.

  14. Direct studies of the thermal decomposition of N{sub 2}O and CO{sub 2} and of the reaction of CO with O{sub 2}

    SciTech Connect

    Sutherland, J.W.; Patterson, P.M.; Klemm, R.B.

    1992-02-01

    The thermal decompositions of N{sub 2}O and CO{sub 2} was investigated by monitoring the kinetics of formation of O({sup 3}P) atoms in the reflected shock regime using atomic resonance absorption spectrophotometry (A.R.A.S.). The temperature range was 1805K to 2379K for N{sub 2}O and 2332K to 2869K for CO{sub 2}. Total densities were 3--4 {times} 10{sup 18} molecules cm{sup {minus}3} and hence the reported rate constants are at or near the low pressure limit for unimolecular decomposition. The results were expressed by the following Arrhenius equations: CO{sub 2} k(T) = (1.63 {plus_minus} 1.96) {times} 10{sup {minus}8} exp({minus}122565 {plus_minus} 5183/RT) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} N{sub 2}O k(T) = (6.02 {plus_minus} 2.81) {times} 10{sup 10} exp({minus}53397 {plus_minus} 1865/RT) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Uncertainties in the Arrhenius expressions are given at the one standard deviation level and the mean deviations of the experimental data from the respective expression are {plus_minus} 18.6% and {plus_minus} 30.7%. Corresponding values for the reverse reaction, k{sub rev}(CO{sub 2}) were computed from the expression k{sub for}/k{sub rev} = K{sub c}. The value obtained for k{sub rev}(CO{sub 2}) was (2.18 {plus_minus} 0.83) {times} 10{sup {minus}34} cm{sup 6} molecule{sup {minus}2} s{sup {minus}1}, independent of temperature from 2332K to 2869K. Preliminary results are also reported for the direct determination of the rate constant for the reaction, CO + O{sub 2} {yields} CO{sub 2} + O, from measurements of the initial rate of formation of O({sup 3}P) atoms. 35 refs., 9 figs., 4 tabs.

  15. Direct studies of the thermal decomposition of N sub 2 O and CO sub 2 and of the reaction of CO with O sub 2

    SciTech Connect

    Sutherland, J.W.; Patterson, P.M.; Klemm, R.B.

    1992-01-01

    The thermal decompositions of N{sub 2}O and CO{sub 2} was investigated by monitoring the kinetics of formation of O({sup 3}P) atoms in the reflected shock regime using atomic resonance absorption spectrophotometry (A.R.A.S.). The temperature range was 1805K to 2379K for N{sub 2}O and 2332K to 2869K for CO{sub 2}. Total densities were 3--4 {times} 10{sup 18} molecules cm{sup {minus}3} and hence the reported rate constants are at or near the low pressure limit for unimolecular decomposition. The results were expressed by the following Arrhenius equations: CO{sub 2} k(T) = (1.63 {plus minus} 1.96) {times} 10{sup {minus}8} exp({minus}122565 {plus minus} 5183/RT) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} N{sub 2}O k(T) = (6.02 {plus minus} 2.81) {times} 10{sup 10} exp({minus}53397 {plus minus} 1865/RT) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Uncertainties in the Arrhenius expressions are given at the one standard deviation level and the mean deviations of the experimental data from the respective expression are {plus minus} 18.6% and {plus minus} 30.7%. Corresponding values for the reverse reaction, k{sub rev}(CO{sub 2}) were computed from the expression k{sub for}/k{sub rev} = K{sub c}. The value obtained for k{sub rev}(CO{sub 2}) was (2.18 {plus minus} 0.83) {times} 10{sup {minus}34} cm{sup 6} molecule{sup {minus}2} s{sup {minus}1}, independent of temperature from 2332K to 2869K. Preliminary results are also reported for the direct determination of the rate constant for the reaction, CO + O{sub 2} {yields} CO{sub 2} + O, from measurements of the initial rate of formation of O({sup 3}P) atoms. 35 refs., 9 figs., 4 tabs.

  16. NOVEL COMPOSITE HYDROGEN-PERMEABLE MEMBRANES FOR NON-THERMAL PLASMA REACTORS FOR THE DECOMPOSITION OF HYDROGEN SULFIDE

    SciTech Connect

    Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Ji-Jun Zhang; Guibing Zhao; Robyn J. Alcanzare; Linna Wang; Ovid A. Plumb

    2004-07-01

    The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Experiments involving methane conversion reactions were conducted with a preliminary pulsed corona discharge reactor design in order to test and improve the reactor and membrane designs using a non-toxic reactant. This report details the direct methane conversion experiments to produce hydrogen, acetylene, and higher hydrocarbons utilizing a co-axial cylinder (CAC) corona discharge reactor, pulsed with a thyratron switch. The reactor was designed to accommodate relatively high flow rates (655 x 10{sup -6} m{sup 3}/s) representing a pilot scale easily converted to commercial scale. Parameters expected to influence methane conversion including pulse frequency, charge voltage, capacitance, residence time, and electrode material were investigated. Conversion, selectivity and energy consumption were measured or estimated. C{sub 2} and C{sub 3} hydrocarbon products were analyzed with a residual gas analyzer (RGA). In order to obtain quantitative results, the complex sample spectra were de-convoluted via a linear least squares method. Methane conversion as high as 51% was achieved. The products are typically 50%-60% acetylene, 20% propane, 10% ethane and ethylene, and 5% propylene. First Law thermodynamic energy efficiencies for the system (electrical and reactor) were estimated to range from 38% to 6%, with the highest efficiencies occurring at short residence time and low power input (low specific energy) where conversion is the lowest (less than 5%). The highest methane conversion of 51% occurred at a

  17. Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

    SciTech Connect

    Morris D. Argyle; John F. Ackerman; Suresh Muknahallipatna; Jerry C. Hamann; Stanislaw Legowski; Guibling Zhao; Ji-Jun Zhang; Sanil John

    2005-10-01

    The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. A pulsed corona discharge (PCD) reactor has been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. A nonthermal plasma cannot be produced in pure H{sub 2}S with our reactor geometry, even at discharge voltages of up to 30 kV, because of the high dielectric strength of pure H{sub 2}S ({approx}2.9 times higher than air). Therefore, H{sub 2}S was diluted in another gas with lower breakdown voltage (or dielectric strength). Breakdown voltages of H{sub 2}S in four balance gases (Ar, He, N{sub 2} and H{sub 2}) have been measured at different H{sub 2}S concentrations and pressures. Breakdown voltages are proportional to the partial pressure of H{sub 2}S and the balance gas. H{sub 2}S conversion and the reaction energy efficiency depend on the balance gas and H{sub 2}S inlet concentrations. With increasing H{sub 2}S concentrations, H{sub 2}S conversion initially increases, reaches a maximum, and then decreases. H{sub 2}S conversion in atomic balance gases, such as Ar and He, is more efficient than that in diatomic balance gases, such as N{sub 2} and H{sub 2}. These observations can be explained by the proposed reaction mechanism of H{sub 2}S dissociation in different balance gases. The results show that nonthermal plasmas are effective for dissociating H{sub 2}S into hydrogen and sulfur.

  18. The thermal stability of sideronatrite and its decomposition products in the system Na2O-Fe2O3-SO2-H2O

    NASA Astrophysics Data System (ADS)

    Ventruti, Gennaro; Scordari, Fernando; Della Ventura, Giancarlo; Bellatreccia, Fabio; Gualtieri, Alessandro F.; Lausi, Andrea

    2013-09-01

    The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)2(OH)·3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)3 compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)2(OH)]{∞/2-} chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)3. (d) for T > 500 °C, the Na3Fe(SO4)3 compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)3 → 3/2 Na2(SO4) + 1/2 Fe2O3 + SOx reaction products. The Na-Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.

  19. Synthesis of porous sheet-like Co{sub 3}O{sub 4} microstructure by precipitation method and its potential applications in the thermal decomposition of ammonium perchlorate

    SciTech Connect

    Lu Shanshan; Jing Xiaoyan; Liu Jingyuan; Wang Jun; Liu Qi; Zhao Yanhua; Jamil, Saba; Zhang Milin; Liu Lianhe

    2013-01-15

    Porous sheet-like cobalt oxide (Co{sub 3}O{sub 4}) were successfully synthesized by precipitation method combined with calcination of cobalt hydroxide precursors. The structure, morphology and porosity properties of the products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption measurement. The as-prepared sheet-like microstructures were approximately 2-3 {mu}m in average diameter, and the morphology of the cobalt hydroxide precursors was retained after the calcination process. However, it appeared a large number of uniform pores in the sheets after calcination. In order to calculate the potential catalytic activity, the thermal decomposition of ammonium perchlorate (AP) has been analyzed, in which cobalt oxide played a role of an additive and the porous sheet-like Co{sub 3}O{sub 4} microstructures exhibited high catalytic performance and considerable decrease in the thermal decomposition temperature of AP. Moreover, a formation mechanism for the sheet-like microstructures has been discussed. - Graphical abstract: Porous sheet-like Co{sub 3}O{sub 4} were synthesized by facile precipitation method combined with calcination of {beta}-Co(OH){sub 2} precursors. Thermogravimetric-differential scanning calorimetric analysis indicates potential catalytic activity in the thermal decomposition of ammonium perchlorate. Highlights: Black-Right-Pointing-Pointer Synthesis of sheet-like {beta}-Co(OH){sub 2} precursors by precipitation method. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} were obtained by calcining {beta}-Co(OH){sub 2} precursors. Black-Right-Pointing-Pointer The possible formation mechanism of porous sheet-like Co{sub 3}O{sub 4} has been discussed. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} decrease the thermal decomposition temperature of ammonium perchlorate.

  20. Comparative Study of Ultraviolet Laser-Based Time-Resolved Photoacoustic Fingerprint Spectra and Thermal Decomposition Mechanisms of Energetic 1,2,3-1H-Triazole Derivatives Under Controlled Pyrolysis.

    PubMed

    Rao, Konda Srinivasa; Chaudhary, Anil Kumar

    2017-01-01

    We report the comparative study of photoacoustic (PA) fingerprint spectra, thermal decomposition, and stability mechanism of some phenyl and bis series energetic compounds named 1-(2-methoxy,-3,5-dinitrophenyl)-1H-1,2,3-triazole ( S5), 1-(3-methoxy, 2, 6 dinitrophenyl) 1H-1, 2, 3 triazole ( S10), 1-(4-nitrophenyl)-1H-1,2,3-triazole ( S8), and 2,6-bis ((4-(nitromethyl)-1H-1,2,3-triazol-1-yl)methyl) pyridine ( S9). Fourth harmonic wavelength, i.e., 266 nm of pulse duration 7 ns and 10 Hz repetition rate obtained from Q-switched Nd: YAG laser, was used to record the thermal PA spectra of these compounds under controlled pyrolysis condition in the range of 30-350 ℃. The PA fingerprint spectra are produced due to entire molecule vapor along with principal functional byproduct NO2 molecule. NO2 molecule is a major gas released during thermal decomposition due to weakest nature of C-NO2 bond. Further, NO2 molecules are involved in photodissociation process due to π*← n transition and converted into NO molecules inside the PA cell due to excitation by 266 nm wavelength. The combined results of PA and gas chromatography-mass spectrometry (GC-MS) spectra along with thermo gravimetric-differential thermal analysis (TG-DTA) data confirm the thermal decomposition mechanism process that can be completed in multiple steps. In addition, GC-MS spectra also confirm the release of NO and NO2 molecules. The effect of incident laser energy and data acquisition time has been carried out for understanding the behavior of acoustic modes. Finally, the thermal quality factor "Q" is measured to test the stability of compounds.

  1. Deep ultra violet and visible Raman spectroscopy studies of ion implanted 6H-SiC: Recrytallisation behaviour and thermal decomposition/thermal etching of the near surface region

    NASA Astrophysics Data System (ADS)

    Kuhudzai, R. J.; Malherbe, J. B.; van der Berg, N. G.; Hlatshwayo, T. T.; Odutemowo, O.; Prinsloo, L. C.; Buys, A. V.; Erasmus, R.; Wendler, E.

    2015-12-01

    The recystallisation behaviour and thermal decomposition of the near surface amorphised region of 6H-SiC have been investigated by Raman spectroscopy. 360 keV ions of iodine and silver were implanted at room temperature into wafers of 6H-SiC resulting in the amorphisation of the near surface region. Vacuum annealing of the samples was performed at 1200 °C for 5 h and then sequentially from 1200 to 1600 °C in steps of 100 °C for 30 h at each annealing temperature. Raman spectroscopy was performed using two laser wavelength excitation regimes, the 514 nm laser (visible region) and the 244 nm laser (deep ultraviolet region, DUV). Measurements in the visible region for samples annealed at 1200 °C for 5 h showed that the characteristic 6H-SiC peaks, namely, the Transverse Optical (TO) and Longitudinal Optical (LO) are similar to the virgin samples, albeit with lower intensity due to some retained defects upon recystallisation of the SiC surface region. The similarities between the virgin spectra and the annealed sample were due to the deep penetration of the 514 nm laser into 6H-SiC resulting in the signal from the bulk undamaged 6H-SiC contributing to the overall spectra. However, DUV laser excitation, which only probes the near surface region, shows that after annealing the peaks are broader and asymmetrical compared to the virgin samples. DUV Raman spectra of samples annealed at 1600 °C indicate that SiC has completely decomposed and the top surface layer is now covered by a carbon layer. However the deeper penetrating laser in the visible region showed that the extent of decomposition at 1600 °C was greater for the silver implanted samples than for the iodine implanted samples.

  2. Woodland Decomposition.

    ERIC Educational Resources Information Center

    Napier, J.

    1988-01-01

    Outlines the role of the main organisms involved in woodland decomposition and discusses some of the variables affecting the rate of nutrient cycling. Suggests practical work that may be of value to high school students either as standard practice or long-term projects. (CW)

  3. Method validation for control determination of mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry.

    PubMed

    Torres, Daiane Placido; Martins-Teixeira, Maristela Braga; Cadore, Solange; Queiroz, Helena Müller

    2015-01-01

    A method for the determination of total mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry (TDA AAS) has been validated following international foodstuff protocols in order to fulfill the Brazilian National Residue Control Plan. The experimental parameters have been previously studied and optimized according to specific legislation on validation and inorganic contaminants in foodstuff. Linearity, sensitivity, specificity, detection and quantification limits, precision (repeatability and within-laboratory reproducibility), robustness as well as accuracy of the method have been evaluated. Linearity of response was satisfactory for the two range concentrations available on the TDA AAS equipment, between approximately 25.0 and 200.0 μg kg(-1) (square regression) and 250.0 and 2000.0 μg kg(-1) (linear regression) of mercury. The residues for both ranges were homoscedastic and independent, with normal distribution. Correlation coefficients obtained for these ranges were higher than 0.995. Limits of quantification (LOQ) and of detection of the method (LDM), based on signal standard deviation (SD) for a low-in-mercury sample, were 3.0 and 1.0 μg kg(-1), respectively. Repeatability of the method was better than 4%. Within-laboratory reproducibility achieved a relative SD better than 6%. Robustness of the current method was evaluated and pointed sample mass as a significant factor. Accuracy (assessed as the analyte recovery) was calculated on basis of the repeatability, and ranged from 89% to 99%. The obtained results showed the suitability of the present method for direct mercury measurement in fresh fish and shrimp samples and the importance of monitoring the analysis conditions for food control purposes. Additionally, the competence of this method was recognized by accreditation under the standard ISO/IEC 17025.

  4. Kinetics of peroxidation of linoleic acid incorporated into DPPC vesicles initiated by the thermal decomposition of 2,2'-azobis(2-amidinopropane) dihydrochloride.

    PubMed

    Cubillos, M A; Lissi, E A; Abuin, E B

    2001-07-01

    In a previous work [Chem. Phys. Lipids 2000 104, 49], we have derived the following rate law for the oxidation of lipids in compartmentalized systems: R(T)=(k(1)/k(t))(0.5) k(p) [In](0.5) c(0.5) [LH], where, R(T) is the total rate of oxidation, k(1) is the rate constant for the production of free radicals, k(t) and k(p) are the intra-particle rate constants for the termination and propagation sets, respectively, [In] is the concentration of a water-soluble initiator, c is the concentration of particles, and [LH] is the intra-particle concentration of oxidable lipid. In the present work, we have investigated on the applicability of the proposed kinetic rate law for a system where it takes place the oxidation of a reactive lipid incorporated into an inert matrix. With this purpose, we have measured the rate of oxidation of linoleic acid incorporated into dipalmitoylphosphatidylcholine vesicles initiated by the thermal decomposition of 2,2'-azobis(2-amidinopropane) dihydrochloride as a function of the initiator, particles, and intra-particle LH concentrations. The experimentally determined kinetic orders obtained were 0.54+/-0.02, 0.48+/-0.05 and 0.83+/-0.04 for the dependence of the oxidation rate with initiator, particles, and LH intra-particle concentrations, respectively, in agreement with those theoretically predicted. The lower value obtained for the kinetic order in LH is attributed to a change in k(t) with the increase in oxidable lipid intra-particle concentration. The main point to be emphazised from the results here obtained is that the kinetic rate law for the oxidation of lipids in compartmentalized systems can be significantly different than that observed when to the oxidation takes place in homogeneous solution.

  5. Non-isothermal decomposition kinetics, heat capacity and thermal safety of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture.

    PubMed

    Zhang, Jiao-Qiang; Gao, Hong-Xu; Ji, Tie-Zheng; Xu, Kang-Zhen; Hu, Rong-Zu

    2011-10-15

    The specific heat capacity (C(p)) of 37.2/44/16/2.2/0.2/0.4-GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was determined with the continuous C(p) mode of microcalorimeter. The equation of C(p) with temperature was obtained. The standard molar heat capacity of GAP/CL-20/Al/N-100/PCA/auxiliaries mixture was 1.225 J mol(-1)K(-1) at 298.15K. With the help of the peak temperature (T(p)) from the non-isothermal DTG curves of the mixture at different heating rates (β), the apparent activation energy (E(k) and E(o)) and pre-exponential constant (A(K)) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method. Using density (ρ) and thermal conductivity (λ), the decomposition heat (Q(d), taking half-explosion heat), Zhang-Hu-Xie-Li's formula, the values (T(e0) and T(p0)) of T(e) and T(p) corresponding to β → 0, thermal explosion temperature (T(be) and T(bp)), adiabatic time-to-explosion (t(TIad)), 50% drop height (H(50)) of impact sensitivity, and critical temperature of hot-spot initiation (T(cr,hot spot)) of thermal explosion of the mixture were calculated. The following results of evaluating the thermal safety of the mixture were obtained: T(be) = 441.64K, T(bp) = 461.66 K, t(Tlad) = 78.0 s (n = 2), t(Tlad) = 74.87 s (n = 1), t(Tlad) = 71.85 s (n = 0), H(50) = 21.33 cm.

  6. Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

    SciTech Connect

    Guo, Xiaofeng; Wu, Di; Xu, Hongwu; Burns, Peter C.; Navrotsky, Alexandra

    2016-09-01

    The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability of the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.

  7. Dynamics Simulations and Statistical Modeling of Thermal Decomposition of 1-Ethyl-3-methylimidazolium Dicyanamide and 1-Ethyl-2,3-dimethylimidazolium Dicyanamide

    DTIC Science & Technology

    2014-10-02

    vibrational modes of EMIM+DCA−. The decomposition trajectories can be grouped into six classes, as described below along with their contributions (i.e... group from the N3 position, while others underwent methyl abstraction via an SN2 mechanism, yielding ethylimidazole and CH3DCA with a reaction enthalpy of...the imidazolium cation is significantly reduced upon substitution of a methyl group for a hydrogen atom at this position. The present work

  8. Synthesis, crystal structure and catalytic effect on thermal decomposition of RDX and AP: An energetic coordination polymer [Pb{sub 2}(C{sub 5}H{sub 3}N{sub 5}O{sub 5}){sub 2}(NMP)·NMP]{sub n}

    SciTech Connect

    Liu, Jin-jian; Liu, Zu-Liang; Cheng, Jian; Fang, Dong

    2013-04-15

    An energetic lead(II) coordination polymer based on the ligand ANPyO has been synthesized and its crystal structure has been got. The polymer was characterized by FT-IR spectroscopy, elemental analysis, DSC and TG-DTG technologies. Thermal analysis shows that there are one endothermic process and two exothermic decomposition stages in the temperature range of 50–600 °C with final residues 57.09%. The non-isothermal kinetic has also been studied on the main exothermic decomposition using the Kissinger's and Ozawa–Doyle's methods, the apparent activation energy is calculated as 195.2 KJ/mol. Furthermore, DSC measurements show that the polymer has significant catalytic effect on the thermal decomposition of ammonium perchlorate. - Graphical abstract: An energetic lead(II) coordination polymer of ANPyO has been synthesized, structurally characterized and properties tested. Highlights: ► We have synthesized and characterized an energetic lead(II) coordination polymer. ► We have measured its molecular structure and thermal decomposition. ► It has significant catalytic effect on thermal decomposition of AP.

  9. Critical analysis of nitramine decomposition data: Activation energies and frequency factors for HMX and RDX decomposition

    NASA Technical Reports Server (NTRS)

    Schroeder, M. A.

    1980-01-01

    A summary of a literature review on thermal decomposition of HMX and RDX is presented. The decomposition apparently fits first order kinetics. Recommended values for Arrhenius parameters for HMX and RDX decomposition in the gaseous and liquid phases and for decomposition of RDX in solution in TNT are given. The apparent importance of autocatalysis is pointed out, as are some possible complications that may be encountered in interpreting extending or extrapolating kinetic data for these compounds from measurements carried out below their melting points to the higher temperatures and pressure characteristic of combustion.

  10. Formation, thermal decomposition and atmospheric implications of the CF2(OH)CF2OONO2 and CF3CF2OONO2 peroxynitrates. A theoretical study

    NASA Astrophysics Data System (ADS)

    Badenes, María Paula

    2017-04-01

    A SACM/CT study of the CF2(OH)CF2OO + NO2 → CF2(OH)CF2OONO2 and CF3CF2OO + NO2 → CF3CF2OONO2 recombination reactions and their reverse unimolecular decomposition process was performed. The electronic energy along the reaction pathways was calculated at the G4(MP2) level. High-pressure rate coefficients of 1.53 × 10-12 (T/300)0.37 cm3 molecule-1 s-1 and 1.79 × 1016 (T/300)0.40 exp(-24.4 kcal mol-1/RT) s-1 were derived at 200-300 K for the direct and backward reactions of CF2(OH)CF2OONO2, while for CF3CF2OONO2, the expressions 1.01 × 10-12 (T/300)0.39 cm3 molecule-1 s-1 and 1.05 × 1016 (T/300)0.44 exp(-23.0 kcal mol-1/RT) s-1 were obtained. A decomposition lifetime profile was derived for CF2(OH)CF2OONO2, indicating that it could act as transport and reservoir of CF2(OH)CF2OO and NO2 in the stratosphere.

  11. Thermally Stable Hierarchical Nanostructures of Ultrathin MoS2 Nanosheet-Coated CeO2 Hollow Spheres as Catalyst for Ammonia Decomposition.

    PubMed

    Gong, Xueyun; Gu, Ying-Qiu; Li, Na; Zhao, Hongyang; Jia, Chun-Jiang; Du, Yaping

    2016-04-18

    MoS2 ultrathin nanosheet-coated CeO2 hollow sphere (CeO2@MoS2) hybrid nanostructures with a 3D hierarchical configuration were successfully constructed from a facile two-step wet chemistry strategy: first, CeO2 formed on a silica core which served as a template and was subsequently removed by NaOH solution to attain hollow spheres, and then few-layered ultrathin MoS2 nanosheets were deposited on the CeO2 hollow spheres through a hydrothermal process. As a proof of concept application, the as-prepared CeO2@MoS2 hybrid nanostructures were used as catalytic material, which exhibited enhanced catalytic activity in ammonia decomposition for H2 production at high temperature. It was demonstrated that, even with a structural transformation from MoS2 to MoNx under harsh conditions of ammonia decomposition at high temperature (700 °C), the 3D hierarchical nanostructures of the CeO2@MoNx were well kept, indicating the important role of the CeO2 support.

  12. Synthesis of ZnO@γ-Fe2O3 core-shell nanocomposites by a facile thermal decomposition approach and their application in photocatalytic degradation of congo red

    NASA Astrophysics Data System (ADS)

    Yadav, Sudheer Kumar; Jeevanandam, P.

    2016-07-01

    ZnO@γ-Fe2O3 core-shell nanocomposites were synthesized by a facile thermal decomposition approach. ZnO nanorods were first synthesized by calcination of zinc acetate at 300 °C, in air. γ-Fe2O3 nanoparticles were then deposited on the surface of ZnO nanorods by the thermal decomposition of iron acetylacetonate at 200 °C in diphenyl ether. The structure, composition, optical and magnetic properties of the nanocomposites were studied using an array of techniques. XRD results suggest the presence of γ-Fe2O3 nanoparticles and ZnO, and FE-SEM images indicate formation of shell of iron oxide on the ZnO nanorods. Transmission electron microscopy studies clearly show that ZnO possesses rod morphology (length = 1.1 ± 0.1 μm, diameter = 40.1 ± 7 nm) and TEM images of the ZnO@γ-Fe2O3 nanocomposites show uniform shell of γ-Fe2O3 coated on the ZnO nanorods and thickness of the γ-Fe2O3 shell varies from 10 to 20 nm. Diffuse reflectance spectra of ZnO@γ-Fe2O3 nanocomposites reveal extended optical absorption in the visible range (400-600 nm) and photoluminescence spectra indicate that the ZnO@γ-Fe2O3 nanocomposites exhibit enhanced defect emission. The ZnO@γ-Fe2O3 core-shell nanocomposites show superparamagnetic behaviour at room temperature. The core-shell nanocomposites exhibit enhanced visible-light driven photocatalytic degradation of congo red in an aqueous solution as compared to pure ZnO nanorods and γ-Fe2O3 nanoparticles. The enhanced photocatalytic activity is attributed to good visible-light absorption and effective charge separation at the interface of ZnO@γ-Fe2O3 core-shell nanocomposites.

  13. Crystal structures, luminescent properties and thermal decomposition kinetics of lanthanide complexes with 2-chloro-4-fluorobenzoic acid and 2,2'-bipyridine

    NASA Astrophysics Data System (ADS)

    Sun, Shu-Jing; Zhang, Da-Hai; Zhang, Jian-Jun; Ye, Hong-Mei; Wang, Shu-Ping; Wu, Ke-Zhong

    2010-08-01

    A new family of lanthanide with the general formula [Ln(2-Cl-4-FBA) 3bipy] 2 (Ln = Nd( 1), Sm( 2), Eu( 3), and Ho( 4); 2-Cl-4-FBA = 2-chloro-4-fluorobenzoate; bipy = 2,2'-bipyridine) were synthesized and characterized by elemental analysis, molar conductance, and infrared, ultraviolet and luminescent spectroscopy, single-crystal X-ray diffraction, thermogravimetry and different thermogravimetry (TG-DTG) techniques. These compounds are iso-structural and the lanthanide ions are all nine coordinated via two bidentate chelating, two bidentate bridging and two bidentate chelating-bridging modes. Under excitation, the europium complex exhibited characteristic red fluorescence of Eu 3+ ion at room temperature. The non-isothermal kinetics was investigated by using NL-INT and Popescu methods. The mechanism functions of the first decomposition step of the title complexes were determined. Meanwhile, the thermodynamic parameters (Δ G ≠, Δ H ≠ and Δ S ≠) were also calculated.

  14. Magnéli phases Ti{sub 4}O{sub 7} and Ti{sub 8}O{sub 15} and their carbon nanocomposites via the thermal decomposition-precursor route

    SciTech Connect

    Conze, S.; Veremchuk, I.; Reibold, M.; Matthey, B.; Michaelis, A.; Grin, Yu.; Kinski, I.

    2015-09-15

    A new synthetic approach for producing nano-powders of the Magnéli phases Ti{sub 4}O{sub 7}, Ti{sub 8}O{sub 15} and their carbon nanocomposites by thermal decomposition-precursor route is proposed. The formation mechanism of the single-phase carbon nanocomposites (Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C) from metal–organic precursors is studied using FT-IR, elemental analysis, TG, STA-MS and others. The synthesis parameters and conditions were optimized to prepare the target oxides with the desired microstructure and physical properties. The electrical and transport properties of Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C are investigated. These nano-materials are n-type semiconductors with relatively low thermal conductivity in contrast to the bulk species. The nanostructured carbon nanocomposites of Magnéli phases achieve a low thermal conductivity close to 1 W/m K at RT. The maximum ZT{sub 570} {sub °C} values are 0.04 for Ti{sub 4}O{sub 7}/C powder nanocomposite and 0.01 for Ti{sub 8}O{sub 15}/C bulk nanocomposite. - Graphical abstract: From the precursor to the produced titanium oxide pellet and its microstructure (SEM, TEM micrographs) as well as results of phase and thermoelectric analyses. - Highlights: • Magnéli phases Ti{sub 4}O{sub 7}/Ti{sub 8}O{sub 15} via thermal decomposition-precursor route is proposed. • The formation mechanism of the nanocomposites Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C are investigated. • Microstructure of Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C are examined. • The electrical and transport properties of Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C are investigated. • The maximum figure of mertit ZT{sub 570} {sub °C} of Ti{sub 4}O{sub 7}/C and Ti{sub 8}O{sub 15}/C are 0.01 and 0.04.

  15. Utilizing carbon dioxide as a reaction medium to mitigate production of polycyclic aromatic hydrocarbons from the thermal decomposition of styrene butadiene rubber.

    PubMed

    Kwon, Eilhann E; Yi, Haakrho; Castaldi, Marco J

    2012-10-02

    The CO(2) cofeed impact on the pyrolysis of styrene butadiene rubber (SBR) was investigated using thermogravimetric analysis (TGA) coupled to online gas chromatography/mass spectroscopy (GC/MS). The direct comparison of the chemical species evolved from the thermal degradation of SBR in N(2) and CO(2) led to a preliminary mechanistic understanding of the formation and relationship of light hydrocarbons (C(1-4)), aromatic derivatives, and polycyclic aromatic hydrocarbons (PAHs), clarifying the role of CO(2) in the thermal degradation of SBR. The identification and quantification of over 50 major and minor chemical species from hydrogen and benzo[ghi]perylene were carried out experimentally in the temperature regime between 300 and 500 °C in N(2) and CO(2). The significant amounts of benzene derivatives from the direct bond dissociation of the backbone of SBR, induced by thermal degradation, provided favorable conditions for PAHs by the gas-phase addition reaction at a relatively low temperature compared to that with conventional fuels such as coal and petroleum-derived fuels. However, the formation of PAHs in a CO(2) atmosphere was decreased considerably (i.e., ∼50%) by the enhanced thermal cracking behavior, and the ultimate fates of these species were determined by different pathways in CO(2) and N(2) atmospheres. Consequently, this work has provided a new approach to mitigate PAHs by utilizing CO(2) as a reaction medium in thermochemical processes.

  16. Characterization of Cobalt Oxide Nanoparticles Prepared by the Thermal Decomposition of [Co(NH3)5(H2O)](NO3)3 Complex and Study of Their Photocatalytic Activity.

    PubMed

    Farhadi, Saeed; Javanmard, Masoumeh; Nadri, Gholamali

    2016-01-01

    In this work, thermal decomposition of the [Co(NH3)5(H2O)](NO3)3 precursor complex was investigated under solid state conditions. Thermal analysis (TG/DTA) showed that the complexwas easily decomposed into the Co3O4 nanoparticles at low temperature (175 °C) without using any expensive and toxic solvent or a complicated equipment. The obtained product was identified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). Optical and magnetic properties of the products were studied by UV-visible spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDX analyses confirmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. SEM and TEM images showed that the Co3O4 nanoparticles have a sphere-like morphology with an average size of 17.5 nm. The optical absorption spectrum of the Co3O4 nanoparticles showed two band gaps of 2.20 and 3.45 eV, which in turn confirmed the semiconducting properties. The magnetic measurement showed a weak ferromagnetic order at room temperature. Photocatalytic degradation of methylene blue (MB) demonstrated that the as-prepared Co3O4 nanoparticles have good photocatalytic activity under visible-light irradiation.

  17. One Step Synthesis of NiO Nanoparticles via Solid-State Thermal Decomposition at Low-Temperature of Novel Aqua(2,9-dimethyl-1,10-phenanthroline)NiCl2 Complex

    PubMed Central

    Barakat, Assem; Al-Noaimi, Mousa; Suleiman, Mohammed; Aldwayyan, Abdullah S.; Hammouti, Belkheir; Ben Hadda, Taibi; Haddad, Salim F.; Boshaala, Ahmed; Warad, Ismail

    2013-01-01

    [NiCl2(C14H12N2)(H2O)] complex has been synthesized from nickel chloride hexahydrate (NiCl2·6H2O) and 2,9-dimethyl-1,10-phenanthroline (dmphen) as N,N-bidentate ligand. The synthesized complex was characterized by elemental analysis, infrared (IR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential thermal/thermogravimetric analysis (TG/DTA). The complex was further confirmed by single crystal X-ray diffraction (XRD) as triclinic with space group P-1. The desired complex, subjected to thermal decomposition at low temperature of 400 ºC in an open atmosphere, revealed a novel and facile synthesis of pure NiO nanoparticles with uniform spherical particle; the structure of the NiO nanoparticles product was elucidated on the basis of Fourier transform infrared (FT-IR), UV-vis spectroscopy, TG/DTA, XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS) and transmission electron microscopy (TEM). PMID:24351867

  18. Synthesis and magnetic properties of Co1-xZnxFe2O4 (x=0÷1) nanopowders by thermal decomposition of Co(II), Zn(II) and Fe(III) carboxylates

    NASA Astrophysics Data System (ADS)

    Stefanescu, Mircea; Bozdog, Marius; Muntean, Cornelia; Stefanescu, Oana; Vlase, Titus

    2015-11-01

    Nanoparticles of cobalt-zinc ferrite Co1-xZnxFe2O4 with x varying from 0 to 1.0 were prepared by a new method, the thermal decomposition of carboxylates of Fe(III), Co(II) and Zn(II). The obtained carboxylate precursor was characterized by thermal analysis and FT-IR spectroscopy. The precursor was annealed at 350, 600 and 1000 °C. It was found that the spinel cobalt-zinc ferrite was formed starting at 350 °C, but in mixture with simple oxides γ-Fe2O3, Co3O4 and ZnO. At 1000 °C Co1-xZnxFe2O4 was formed quantitatively as a single, well-crystallized phase. The saturation magnetization of the samples annealed at 1000 °C decreased significantly with increasing Zn2+ content from 83.93 emu/g (x=0) to 4.92 emu/g (x=1.0). At 350 and 600 °C the saturation magnetization had the same trend, even if there were contributions of other magnetic phases. Obtaining of spinel ferrite was evidenced by X-ray diffractometry and FT-IR spectrometry. Powder morphology was determined by scanning electron microscopy. Magnetic properties of the synthesized ferrites were investigated employing a conventional induction method.

  19. Radical initiation and phenol inhibition in the thermal, free radical decomposition of 1,3-diphenylpropane, dibenzylether and phenethylphenylether, coal liquefaction model studies

    SciTech Connect

    Gilbert, K.E.

    1983-01-01

    Current thought on the structure of coal and the chemistry of coal liquefaction suggests that coal consists of large polycyclic clusters joined by short aliphatic links and that liquefaction reactions occur at these links. Much research has gone into the two atom links. In addition to the cleavage-abstraction reactions available to the two atom links, the three atom links may also react by radical chain reactions. These radical chain reactions can occur over a much wider temperature range than the cleavage-abstraction reactions and thus offer the possibility of a low temperature liquefaction process. Previous work has shown that the title compounds decompose by free radical chain reactions as neat liquids or as solutions in hydrogen donating solvents in the temperature range of 300 to 400/sup 0/C. Initiation of the radical chain process by benzylphenylether at 350/sup 0/ was demonstrated, but inhibition of the chain reactions by standard inhibitors, such as hindered phenols, was not studied. This paper reports on the effect of hindered phenols on the decomposition of the title compounds at 350/sup 0/, the development of methods for initiating these reactions at temperatures as low as 138/sup 0/, the effect of hindered phenols on these reactions at lower temperatures, and on the kinetic and thermodynamic barriers to these radical chain reactions. (3 tables, 2 figures, 5 refs.)

  20. Topological entropy of left-invariant magnetic flows on 2-step nilmanifolds

    NASA Astrophysics Data System (ADS)

    Epstein, Jonathan

    2017-01-01

    In this paper, we consider magnetic flows on 2-step nilmanifolds M= Γ \\backslash G , where the Riemannian metric g and the magnetic field σ are left-invariant. Our first result is that when σ represents a rational cohomology class and its restriction to g={{T}e}G vanishes on the derived algebra, then the associated magnetic flow has zero topological entropy. In particular, this is the case when σ represents a rational cohomology class and is exact. Our second result is the construction of a magnetic field on a 2-step nilmanifold that has positive topological entropy for arbitrarily high energy levels.

  1. Three new energetic complexes with N,N-bis(1H-tetrazole-5-yl)-amine as high energy density materials: syntheses, structures, characterization and effects on the thermal decomposition of RDX.

    PubMed

    Yang, Qi; Song, Xiaxia; Zhang, Wendou; Hou, Lei; Gong, Qibing; Xie, Gang; Wei, Qing; Chen, Sanping; Gao, Shengli

    2017-02-21

    Three new energetic complexes, [Pb(bta)(H2O)]n (1), [PbCu(bta)2(H2O)5]·2H2O (2) and PbCu(bta)2 (3) (H2bta = N,N-bis(1H-tetrazole-5-yl)-amine), have been synthesized and characterised. In particular, 3 was readily synthesized by dehydration of 2 at 190 °C. Single crystal X-ray diffraction revealed that 1 has a 3D framework structure and 2 presents a 3D supermolecular architecture. Thermoanalyses demonstrated that the main frames of 1 and 2 have good thermostabilities up to 314 °C for 1 and 231 °C for 2. Non-isothermal kinetic and thermodynamic parameters of exothermic decomposition processes of 1 and 2 were obtained by Kissinger's and Ozawa's methods. Based on the constant-volume combustion energies measured by a precise rotating-bomb calorimeter, the standard molar enthalpies of formation of 1 and 2 were determined. The calculation of the detonation properties of 1 and 2 and the impact sensitivity tests of 1, 2 and 3 were carried out. In addition, 1, 2 and 3 were explored as combustion promoters to accelerate the thermal decompositions of RDX (1,3,5-trinitro-1,3,5-triazine) by differential scanning calorimetry. Experimental results showed that 1, 2 and 3 can be used as HEDMs in the field of combustion promoters and insensitive 2 can be regarded as a safer form for mass storage and transportation than sensitive 3.

  2. Development of a hydrophilic interaction liquid chromatography-mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology.

    PubMed

    Yassine, Mahmoud M; Dabek-Zlotorzynska, Ewa; Celo, Valbona

    2012-03-16

    The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSD<0.5%) and peak area (RSD<3%). Satisfactory extraction recoveries from spiked blanks ranged between 96 and 98%. Analyses of samples collected during transient chassis dynamometer tests of a bus engine equipped with a diesel particulate filter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust.

  3. Thermal decomposition behavior of Cu–Al layered double hydroxide, and ethylenediaminetetraacetate-intercalated Cu–Al layered double hydroxide reconstructed from Cu–Al oxide for uptake of Y{sup 3+} from aqueous solution

    SciTech Connect

    Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► Decomposition of CO{sub 3}·Cu–Al LDH occurred in four stages. ► The edta·Cu–Al LDH was found to take up Y{sup 3+} in aqueous solution. ► The edta·Cu–Al LDH could selectively take up rare earth ions from a mixed solution. -- Abstract: CO{sub 3}{sup 2−}-intercalated Cu–Al layered double hydroxide (CO{sub 3}·Cu–Al LDH) was calcined to yield Cu–Al oxide, and then ethylenediaminetetraacetate-intercalated Cu–Al LDH (edta·Cu–Al LDH) was prepared by reconstructing Cu–Al oxide in edta solution. Decomposition of CO{sub 3}·Cu–Al LDH occurred in four stages. The production of Cu–Al oxide was caused by the thermal decomposition of CO{sub 3}·Cu–Al LDH until the third stage. The first stage was the elimination of adsorbed surface water and interlayer water in CO{sub 3}·Cu–Al LDH. The second and third stages were the dehydroxylation of the brucite-like octahedral layers and the elimination of CO{sub 3}{sup 2−} intercalated in the interlayers. The edta·Cu–Al LDH was found to take up Y{sup 3+} in aqueous solution. The uptake of Y{sup 3+} was caused not only by the chelating function of Hedta{sup 3−} in the interlayer but also by the chemical behavior of Cu–Al LDH itself. The edta·Cu–Al LDH was found to selectively take up rare earth ions from a mixed solution. The degree of uptake was high, in the order Sc{sup 3+} > Y{sup 3+} > La{sup 3+} for all time durations, which was attributable to differences among the stabilities of Sc(edta){sup −}, Y(edta){sup −} and La(edta){sup −}.

  4. 15 CFR 732.2 - Steps regarding scope of the EAR.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 15 Commerce and Foreign Trade 2 2012-01-01 2012-01-01 false Steps regarding scope of the EAR. 732... FOR USING THE EAR § 732.2 Steps regarding scope of the EAR. Steps 1 though 6 are designed to aid you in determining the scope of the EAR. A flow chart describing these steps is contained in...

  5. 15 CFR 732.2 - Steps regarding scope of the EAR.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 15 Commerce and Foreign Trade 2 2011-01-01 2011-01-01 false Steps regarding scope of the EAR. 732... FOR USING THE EAR § 732.2 Steps regarding scope of the EAR. Steps 1 though 6 are designed to aid you in determining the scope of the EAR. A flow chart describing these steps is contained in...

  6. 15 CFR 732.2 - Steps regarding scope of the EAR.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 15 Commerce and Foreign Trade 2 2013-01-01 2013-01-01 false Steps regarding scope of the EAR. 732... FOR USING THE EAR § 732.2 Steps regarding scope of the EAR. Steps 1 though 6 are designed to aid you in determining the scope of the EAR. A flow chart describing these steps is contained in...

  7. 15 CFR 732.2 - Steps regarding scope of the EAR.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 15 Commerce and Foreign Trade 2 2010-01-01 2010-01-01 false Steps regarding scope of the EAR. 732... FOR USING THE EAR § 732.2 Steps regarding scope of the EAR. Steps 1 though 6 are designed to aid you in determining the scope of the EAR. A flow chart describing these steps is contained in...

  8. 15 CFR 732.2 - Steps regarding scope of the EAR.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 15 Commerce and Foreign Trade 2 2014-01-01 2014-01-01 false Steps regarding scope of the EAR. 732... FOR USING THE EAR § 732.2 Steps regarding scope of the EAR. Steps 1 though 6 are designed to aid you in determining the scope of the EAR. A flow chart describing these steps is contained in...

  9. Fast intensity-modulated arc therapy based on 2-step beam segmentation

    SciTech Connect

    Bratengeier, Klaus; Gainey, Mark; Sauer, Otto A.; Richter, Anne; Flentje, Michael

    2011-01-15

    Purpose: Single or few arc intensity-modulated arc therapy (IMAT) is intended to be a time saving irradiation method, potentially replacing classical intensity-modulated radiotherapy (IMRT). The aim of this work was to evaluate the quality of different IMAT methods with the potential of fast delivery, which also has the possibility of adapting to the daily shape of the target volume. Methods: A planning study was performed. Novel double and triple IMAT techniques based on the geometrical analysis of the target organ at risk geometry (2-step IMAT) were evaluated. They were compared to step and shoot IMRT reference plans generated using direct machine parameter optimization (DMPO). Volumetric arc (VMAT) plans from commercial preclinical software (SMARTARC) were used as an additional benchmark to classify the quality of the novel techniques. Four cases with concave planning target volumes (PTV) with one dominating organ at risk (OAR), viz., the PTV/OAR combination of the ESTRO Quasimodo phantom, breast/lung, spine metastasis/spinal cord, and prostate/rectum, were used for the study. The composite objective value (COV) and other parameters representing the plan quality were studied. Results: The novel 2-step IMAT techniques with geometry based segment definition were as good as or better than DMPO and were superior to the SMARTARC VMAT techniques. For the spine metastasis, the quality measured by the COV differed only by 3%, whereas the COV of the 2-step IMAT for the other three cases decreased by a factor of 1.4-2.4 with respect to the reference plans. Conclusions: Rotational techniques based on geometrical analysis of the optimization problem (2-step IMAT) provide similar or better plan quality than DMPO or the research version of SMARTARC VMAT variants. The results justify pursuing the goal of fast IMAT adaptation based on 2-step IMAT techniques.

  10. MgCoAl and NiCoAl LDHs synthesized by the hydrothermal urea hydrolysis method: Structural characterization and thermal decomposition

    SciTech Connect

    Chagas, L.H.; De Carvalho, G.S.G.; Do Carmo, W.R.; San Gil, R.A.S.; Chiaro, S.S.X.; Leitão, A.A.; Diniz, R.; De Sena, L.A.; Achete, C.A.

    2015-04-15

    Highlights: • We synthesized MgCoAl and NiCoAl LDHs by the urea hydrolysis method. • Aluminum rich and crystalline materials have been formed. • The calcination of the LDHs generated mixed oxides with high surface areas. - Abstract: Layered double hydroxides (LDHs) with Mg/Co/Al and Ni/Co/Al were synthesized for the first time by the urea hydrolysis method. The experimental conditions promoted aluminum rich and crystalline materials. The formation of LDHs was investigated by powder X-ray diffraction (XRD), chemical analysis, solid state nuclear magnetic resonance with magic angle spinning ({sup 27}Al-MAS-NMR), simultaneous thermogravimetric/differential thermal analysis (TGA/DTA), FTIR spectroscopy, scanning electron microscopy (SEM), and N{sub 2} adsorption–desorption experiments. A single phase corresponding to LDH could be obtained in all the investigated compositions. Thermal calcination of these LDHs at 500 °C resulted in the formation of solid solutions in which Al{sup 3+} was dissolved. All the calcined materials have rock-salt like structures and high surface areas.

  11. A thermal broadening analysis of absorption spectra of the D1/D2/cytochrome b-559 complex in terms of Gaussian decomposition sub-bands.

    PubMed

    Cattaneo, R; Zucchelli, G; Garlaschi, F M; Finzi, L; Jennings, R C

    1995-11-21

    Absorption spectra of the isolated D1/D2/cytochrome b-559 complex have been measured in the temperature range 80-300 K. All spectra were analyzed in terms of a linear combination of Gaussian bands and the thermal broadening data interpreted in terms of a model in which the spectrum of each pigment site is broadened by (a) a homogeneous component due to linear electron-phonon coupling to a low-frequency protein vibration and (b) an inhomogeneous component associated with stochastic fluctuations at each pigment site. In order to obtain a numerically adequate description of the absorption spectra, a minimum number of five sub-bands is required. Further refinement of this sub-band description was achieved by taking into account published data from hole burning and absorption difference spectroscopy. In this way, both a six sub-band description and a seven sub-band description were generated. In arriving at the seven sub-band description, the original five sub-band wavelength positions were essentially unchanged. Thermal broadening analysis of the seven sub-band description yielded data which displayed the closest correspondence with the literature observations. The wavelength positions of the sub-bands were near 661, 667, 670, and 675 nm, with two bands near 680 and 684 nm. The two almost isoenergetic sub-bands near 680 nm, identified as P680 and pheophytin, have optical reorganization energies around 40 and 16 cm-1, respectively. All other sub-bands, identified as accessory pigments, have optical reorganization energies close to 16 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Non-isothermal decomposition kinetics of diosgenin

    NASA Astrophysics Data System (ADS)

    Chen, Fei-xiong; Fu, Li; Feng, Lu; Liu, Chuo-chuo; Ren, Bao-zeng

    2013-10-01

    The thermal stability and kinetics of isothermal decomposition of diosgenin were studied by thermogravimetry (TG) and Differential Scanning Calorimeter (DSC). The activation energy of the thermal decomposition process was determined from the analysis of TG curves by the methods of Flynn-Wall-Ozawa, Doyle, Šatava-Šesták and Kissinger, respectively. The mechanism of thermal decomposition was determined to be Avrami-Erofeev equation ( n = 1/3, n is the reaction order) with integral form G(α) = [-ln(1 - α)]1/3 (α = 0.10-0.80). E a and log A [s-1] were determined to be 44.10 kJ mol-1 and 3.12, respectively. Moreover, the thermodynamics properties of Δ H ≠, Δ S ≠, and Δ G ≠ of this reaction were 38.18 kJ mol-1, -199.76 J mol-1 K-1, and 164.36 kJ mol-1 in the stage of thermal decomposition.

  13. N-((5-chloropyridin-2-yl)carbamothioyl)furan-2-carboxamide and its Co(II), Ni(II) and Cu(II) complexes: Synthesis, characterization, DFT computations, thermal decomposition, antioxidant and antitumor activity

    NASA Astrophysics Data System (ADS)

    Yeşilkaynak, Tuncay; Özpınar, Celal; Emen, Fatih Mehmet; Ateş, Burhan; Kaya, Kerem

    2017-02-01

    N-((5-chloropyridin-2-yl)carbamothioyl)furan-2-carboxamide (HL: C11H8ClN3O2S) and its Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized by elemental analysis, FT-IR,1H NMR and HR-MS methods. The HL was characterized by single crystal X-ray diffraction technique. It crystallizes in the monoclinic system. The HL has the space group P 1 21/c 1, Z = 4, and its unit cell parameters are a = 4.5437(5) Å, b = 22.4550(3) Å, c = 11.8947(14) Å. The ligand coordinates the metal ions as bidentate and thus essentially yields neutral complexes of the [ML2] type. ML2 complex structures were optimized using B97D/TZVP level. Molecular orbitals of both HL ligand were calculated at the same level. Thermal decomposition of the complexes has been investigated by thermogravimetry. The complexes were screened for their anticancer and antioxidant activities. Antioxidant activity of the complexes was determined by using the DPPH and ABTS assays. The anticancer activity of the complexes was studied by using MTT assay in MCF-7 breast cancer cells.

  14. Hydrothermal synthesis, crystal structure, conductivity, and thermal decomposition of [Cu(4,4'-bipy)(H2O)(Mo3O10)].H2O.

    PubMed

    Kong, Zuping; Weng, Linhong; Tan, Dejun; He, Heyong; Zhang, Biao; Kong, Jilie; Yue, Bin

    2004-09-06

    The hydrothermal reaction of (NH(4))(6)Mo(7)O(24).4H(2)O, CuCl(2).2H(2)O, and 4,4'-bipyridine yields bipyridine-ligated copper-trimolybdate monohydrate [Cu(4,4'-bipy)(H(2)O)(Mo(3)O(10))].H(2)O in the monoclinic system with space group of C(2/c) and cell parameters of a = 15.335(2) A, b = 15.535(2) A, c = 15.106(2) A, beta = 101.162(2) degrees, V = 3530.7(9) A(3), and Z = 8. Its structure consists of one-dimensional infinite ([Mo3O10]2-)( infinity ) chains linked through [Cu2(H2O)2(4,4'-bipy)] units. The Mo-O chain contains distorted [MoO(6)] octahedra connected through corner-sharing oxygen atoms into infinite chains along the c direction and each chain is located in the channel formed by four adjacent crossing chains of [Cu(4,4'-bipy)(H2O)](n)(2n+). The crystal shows weak conductivity through Mo-O chain along the c direction and insulating property along either a or b direction. Furthermore, a crystalline bimetallic oxide, CuMo3O10, forms when the title compound undergoes thermal treatment in N(2) atmosphere after the complete removal of the ligands.

  15. Photocatalytic decomposition of selected estrogens and their estrogenic activity by UV-LED irradiated TiO2 immobilized on porous titanium sheets via thermal-chemical oxidation.

    PubMed

    Arlos, Maricor J; Liang, Robert; Hatat-Fraile, Melisa M; Bragg, Leslie M; Zhou, Norman Y; Servos, Mark R; Andrews, Susan A

    2016-11-15

    The removal of endocrine disrupting compounds (EDCs) remains a big challenge in water treatment. Risks associated with these compounds are not clearly defined and it is important that the water industry has additional options to increase the resiliency of water treatment systems. Titanium dioxide (TiO2) has potential applications for the removal of EDCs from water. TiO2 has been immobilized on supports using a variety of synthesis methods to increase its feasibility for water treatment. In this study, we immobilized TiO2 through the thermal-chemical oxidation of porous titania sheets. The efficiency of the material to degrade target EDCs under UV-LED irradiation was examined under a wide range of pH conditions. A yeast-estrogen screen assay was used to complement chemical analysis in assessing removal efficiency. All compounds but 17β-estradiol were degraded and followed a pseudo first-order kinetics at all pH conditions tested, with pH 4 and pH 11 showing the most and the least efficient treatments respectively. In addition, the total estrogenic activity was substantially reduced even with the inefficient degradation of 17β-estradiol. Additional studies will be required to optimize different treatment conditions, UV-LED configurations, and membrane fouling mitigation measures to make this technology a more viable option for water treatment.

  16. STUDIES OF THERMALLY UNSTABLE ACCRETION DISKS AROUND BLACK HOLES WITH ADAPTIVE PSEUDOSPECTRAL DOMAIN DECOMPOSITION METHOD. II. LIMIT-CYCLE BEHAVIOR IN ACCRETION DISKS AROUND KERR BLACK HOLES

    SciTech Connect

    Xue Li; Lu Jufu; Sadowski, Aleksander; Abramowicz, Marek A. E-mail: lujf@xmu.edu.cn

    2011-07-01

    For the first time ever, we derive equations governing the time evolution of fully relativistic slim accretion disks in the Kerr metric and numerically construct their detailed non-stationary models. We discuss applications of these general results to a possible limit-cycle behavior of thermally unstable disks. Our equations and numerical method are applicable in a wide class of possible viscosity prescriptions, but in this paper we use a diffusive form of the 'standard alpha prescription' that assumes that the viscous torque is proportional to the total pressure. In this particular case, we find that the parameters that dominate the limit-cycle properties are the mass-supply rate and the value of the alpha-viscosity parameter. Although the duration of the cycle (or the outburst) does not exhibit any clear dependence on the black hole spin, the maximal outburst luminosity (in the Eddington units) is positively correlated with the spin value. We suggest a simple method for a rough estimate of the black hole spin based on the maximal luminosity and the ratio of outburst to cycle durations. We also discuss a temperature-luminosity relation for the Kerr black hole accretion disk limit cycle. Based on these results, we discuss the limit-cycle behavior observed in microquasar GRS 1915+105. We also extend this study to several non-standard viscosity prescriptions, including a 'delayed heating' prescription recently addressed by the MHD simulations of accretion disks.

  17. 2-Step Maximum Likelihood Channel Estimation for Multicode DS-CDMA with Frequency-Domain Equalization

    NASA Astrophysics Data System (ADS)

    Kojima, Yohei; Takeda, Kazuaki; Adachi, Fumiyuki

    Frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can provide better downlink bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. In this paper, we propose a new 2-step maximum likelihood channel estimation (MLCE) for DS-CDMA with FDE in a very slow frequency-selective fading environment. The 1st step uses the conventional pilot-assisted MMSE-CE and the 2nd step carries out the MLCE using decision feedback from the 1st step. The BER performance improvement achieved by 2-step MLCE over pilot assisted MMSE-CE is confirmed by computer simulation.

  18. Decomposition of Sodium Tetraphenylborate

    SciTech Connect

    Barnes, M.J.

    1998-11-20

    The chemical decomposition of aqueous alkaline solutions of sodium tetraphenylborate (NaTPB) has been investigated. The focus of the investigation is on the determination of additives and/or variables which influence NaTBP decomposition. This document describes work aimed at providing better understanding into the relationship of copper (II), solution temperature, and solution pH to NaTPB stability.

  19. Global optimization using homotopy with 2-step predictor-corrector method

    NASA Astrophysics Data System (ADS)

    Chang, Kerk Lee; Ahmad, Rohanin Bt.

    2014-06-01

    In this research, we suggest a new method for solving global optimization problem by improving Homotopy Optimization with Perturbations and Ensembles (HOPE) method. Our new method, named as Homotopy 2-Step Predictor-corrector Method (HSPM) is based on the intermediate Value Theorem (IVT) coupled with modified Predictor-Corrector Halley method (PCH) for solving global optimization problem. HSPM does not require a good initial guess since it contains the element of homotopy, which is a globally convergent method. This paper discusses the time complexity of the new algorithm, which makes it more efficient than HOPE.

  20. A cyanide-bridged heterometallic coordination polymer constructed from square-planar [Ni(CN)4](2-): synthesis, crystal structure, thermal decomposition, electron paramagnetic resonance (EPR) spectrum and magnetic properties.

    PubMed

    Qin, Ying Lian; Yang, Bin Wu; Wang, Gao Feng; Sun, Hong

    2016-07-01

    Square-planar complexes are commonly formed by transition metal ions having a d(8) electron configuration. Planar cyanometallate anions have been used extensively as design elements in supramolecular coordination systems. In particular, square-planar tetracyanometallate(II) ions, i.e. [M(CN)4](2-) (M(II) = Ni, Pd or Pt), are used as good building blocks for bimetallic Hofmann-type assemblies and their analogues. Square-planar tetracyanonickellate(II) complexes have been extensively developed with N-donor groups as additional co-ligands, but studies of these systems using O-donor ligands are scarce. A new cyanide-bridged Cu(II)-Ni(II) heterometallic compound, poly[[diaquatetra-μ2-cyanido-κ(8)C:N-nickel(II)copper(II)] monohydrate], {[Cu(II)Ni(II)(CN)4(H2O)2]·H2O}n, has been synthesized and characterized by X-ray single-crystal diffraction analyses, vibrational spectroscopy (FT-IR), thermal analysis, electron paramagnetic resonance (EPR) and magnetic moment measurements. The structural analysis revealed that it has a two-dimensional grid-like structure built up of cationic [Cu(H2O)2](2+) and anionic [Ni(CN)4](2-) units connected through bridging cyanide ligands. The overall three-dimensional supramolecular network is expanded by a combination of interlayer O-H...N and intralayer O-H...O hydrogen-bond interactions. The first decomposition reactions take place at 335 K under a static air atmosphere, which illustrates the existence of guest water molecules in the interlayer spaces. The electron paramagnetic resonance (EPR) spectrum confirms that the Cu(II) cation has an axial coordination symmetry and that the unpaired electrons occupy the d(x(2)-y(2)) orbital. In addition, magnetic investigations showed that antiferromagnetic interactions exist in the Cu(II) atoms through the diamagnetic [Ni(CN)4](2-) ion.

  1. Isothermal Decomposition of Hydrogen Peroxide Dihydrate

    NASA Technical Reports Server (NTRS)

    Loeffler, M. J.; Baragiola, R. A.

    2011-01-01

    We present a new method of growing pure solid hydrogen peroxide in an ultra high vacuum environment and apply it to determine thermal stability of the dihydrate compound that forms when water and hydrogen peroxide are mixed at low temperatures. Using infrared spectroscopy and thermogravimetric analysis, we quantified the isothermal decomposition of the metastable dihydrate at 151.6 K. This decomposition occurs by fractional distillation through the preferential sublimation of water, which leads to the formation of pure hydrogen peroxide. The results imply that in an astronomical environment where condensed mixtures of H2O2 and H2O are shielded from radiolytic decomposition and warmed to temperatures where sublimation is significant, highly concentrated or even pure hydrogen peroxide may form.

  2. Dominant modal decomposition method

    NASA Astrophysics Data System (ADS)

    Dombovari, Zoltan

    2017-03-01

    The paper deals with the automatic decomposition of experimental frequency response functions (FRF's) of mechanical structures. The decomposition of FRF's is based on the Green function representation of free vibratory systems. After the determination of the impulse dynamic subspace, the system matrix is formulated and the poles are calculated directly. By means of the corresponding eigenvectors, the contribution of each element of the impulse dynamic subspace is determined and the sufficient decomposition of the corresponding FRF is carried out. With the presented dominant modal decomposition (DMD) method, the mode shapes, the modal participation vectors and the modal scaling factors are identified using the decomposed FRF's. Analytical example is presented along with experimental case studies taken from machine tool industry.

  3. Thermal Decomposition of Nitrated Tributyl Phosphate

    SciTech Connect

    Paddleford, D.F.; Hou, Y.; Barefield, E.K.; Tedder, D.W.; Abdel-Khalik, S.I.

    1995-01-01

    Contact between tributyl phosphate and aqueous solutions of nitric acid and/or heavy metal nitrate salts at elevated temperatures can lead to exothermic reactions of explosive violence. Even though such operations have been routinely performed safely for decades as an intrinsic part of the Purex separation processes, several so-called ``red oil`` explosions are known to have occurred in the United States, Canada, and the former Soviet Union. The most recent red oil explosion occurred at the Tomsk-7 separations facility in Siberia, in April 1993. That explosion destroyed part of the unreinforced masonry walls of the canyon-type building in which the process was housed, and allowed the release of a significant quantity of radioactive material.

  4. Decomposition of Copper (II) Sulfate Pentahydrate: A Sequential Gravimetric Analysis.

    ERIC Educational Resources Information Center

    Harris, Arlo D.; Kalbus, Lee H.

    1979-01-01

    Describes an improved experiment of the thermal dehydration of copper (II) sulfate pentahydrate. The improvements described here are control of the temperature environment and a quantitative study of the decomposition reaction to a thermally stable oxide. Data will suffice to show sequential gravimetric analysis. (Author/SA)

  5. A global HMX decomposition model

    SciTech Connect

    Hobbs, M.L.

    1996-12-01

    HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) decomposes by competing reaction pathways to form various condensed and gas-phase intermediate and final products. Gas formation is related to the development of nonuniform porosity and high specific surface areas prior to ignition in cookoff events. Such thermal damage enhances shock sensitivity and favors self-supported accelerated burning. The extent of HMX decomposition in highly confined cookoff experiments remains a major unsolved experimental and modeling problem. The present work is directed at determination of global HMX kinetics useful for predicting the elapsed time to thermal runaway (ignition) and the extent of decomposition at ignition. Kinetic rate constants for a six step engineering based global mechanism were obtained using gas formation rates measured by Behrens at Sandia National Laboratories with his Simultaneous Modulated Beam Mass Spectrometer (STMBMS) experimental apparatus. The six step global mechanism includes competition between light gas (H[sub 2]Awe, HCN, CO, H[sub 2]CO, NO, N[sub 2]Awe) and heavy gas (C[sub 2]H[sub 6]N[sub 2]Awe and C[sub 4]H[sub 10]N0[sub 2]) formation with zero order sublimation of HMX and the mononitroso analog of HMX (mn-HMX), C[sub 4]H[sub 8]N[sub 8]Awe[sub 7]. The global mechanism was applied to the highly confined, One Dimensional Time to eXplosion (ODTX) experiment and hot cell experiments by suppressing the sublimation of HMX and mn-HMX. An additional gas-phase reaction was also included to account for the gas-phase reaction of N[sub 2]Awe with H[sub 2]CO. Predictions compare adequately to the STMBMS data, ODTX data, and hot cell data. Deficiencies in the model and future directions are discussed.

  6. Structural, magnetic, and electronic properties of iron selenide Fe{sub 6-7}Se{sub 8} nanoparticles obtained by thermal decomposition in high-temperature organic solvents

    SciTech Connect

    Lyubutin, I. S. E-mail: crlin@mail.npue.edu.tw; Funtov, K. O.; Dmitrieva, T. V.; Starchikov, S. S.; Lin, Chun-Rong E-mail: crlin@mail.npue.edu.tw; Siao, Yu-Jhan; Chen, Mei-Li

    2014-07-28

    Iron selenide nanoparticles with the NiAs-like crystal structure were synthesized by thermal decomposition of iron chloride and selenium powder in a high-temperature organic solvent. Depending on the time of the compound processing at 340 °C, the nanocrystals with monoclinic (M)-Fe{sub 3}Se{sub 4} or hexagonal (H)-Fe{sub 7}Se{sub 8} structures as well as a mixture of these two phases can be obtained. The magnetic behavior of the monoclinic and hexagonal phases is very different. The applied-field and temperature dependences of magnetization reveal a complicated transformation between ferrimagnetic (FRM) and antiferromagnetic (AFM) structures, which can be related to the spin rotation process connected with the redistribution of cation vacancies. From XRD and Mössbauer data, the 3c type superstructure of vacancy ordering was found in the hexagonal Fe{sub 7}Se{sub 8}. Redistribution of vacancies in Fe{sub 7}Se{sub 8} from random to ordered leads to the transformation of the magnetic structure from FRM to AFM. The Mössbauer data indicate that vacancies in the monoclinic Fe{sub 3}Se{sub 4} prefer to appear near the Fe{sup 3+} ions and stimulate the magnetic transition with the rotation of the Fe{sup 3+} magnetic moments. Unusually high coercive force H{sub c} was found in both (H) and (M) nanocrystals with the highest (“giant”) value of about 25 kOe in monoclinic Fe{sub 3}Se{sub 4}. This is explained by the strong surface magnetic anisotropy which is essentially larger than the core anisotropy. Such a large coercivity is rare for materials without rare earth or noble metal elements, and the Fe{sub 3}Se{sub 4}-based compounds can be the low-cost, nontoxic alternative materials for advanced magnets. In addition, an unusual effect of “switching” of magnetization in a field of 10 kOe was found in the Fe{sub 3}Se{sub 4} nanoparticles below 280 K, which can be important for applications.

  7. Decomposing Nekrasov decomposition

    NASA Astrophysics Data System (ADS)

    Morozov, A.; Zenkevich, Y.

    2016-02-01

    AGT relations imply that the four-point conformal block admits a decomposition into a sum over pairs of Young diagrams of essentially rational Nekrasov functions — this is immediately seen when conformal block is represented in the form of a matrix model. However, the q-deformation of the same block has a deeper decomposition — into a sum over a quadruple of Young diagrams of a product of four topological vertices. We analyze the interplay between these two decompositions, their properties and their generalization to multi-point conformal blocks. In the latter case we explain how Dotsenko-Fateev all-with-all (star) pair "interaction" is reduced to the quiver model nearest-neighbor (chain) one. We give new identities for q-Selberg averages of pairs of generalized Macdonald polynomials. We also translate the slicing invariance of refined topological strings into the language of conformal blocks and interpret it as abelianization of generalized Macdonald polynomials.

  8. The generalized triangular decomposition

    NASA Astrophysics Data System (ADS)

    Jiang, Yi; Hager, William W.; Li, Jian

    2008-06-01

    Given a complex matrix mathbf{H} , we consider the decomposition mathbf{H} = mathbf{QRP}^* , where mathbf{R} is upper triangular and mathbf{Q} and mathbf{P} have orthonormal columns. Special instances of this decomposition include the singular value decomposition (SVD) and the Schur decomposition where mathbf{R} is an upper triangular matrix with the eigenvalues of mathbf{H} on the diagonal. We show that any diagonal for mathbf{R} can be achieved that satisfies Weyl's multiplicative majorization conditions: prod_{iD1}^k \\vert r_{i}\\vert le prod_{iD1}^k sigma_i, ; ; 1 le k < K, quad prod_{iD1}^K \\vert r_{i}\\vert = prod_{iD1}^K sigma_i, where K is the rank of mathbf{H} , sigma_i is the i -th largest singular value of mathbf{H} , and r_{i} is the i -th largest (in magnitude) diagonal element of mathbf{R} . Given a vector mathbf{r} which satisfies Weyl's conditions, we call the decomposition mathbf{H} = mathbf{QRP}^* , where mathbf{R} is upper triangular with prescribed diagonal mathbf{r} , the generalized triangular decomposition (GTD). A direct (nonrecursive) algorithm is developed for computing the GTD. This algorithm starts with the SVD and applies a series of permutations and Givens rotations to obtain the GTD. The numerical stability of the GTD update step is established. The GTD can be used to optimize the power utilization of a communication channel, while taking into account quality of service requirements for subchannels. Another application of the GTD is to inverse eigenvalue problems where the goal is to construct matrices with prescribed eigenvalues and singular values.

  9. Optimal domain decomposition strategies

    NASA Technical Reports Server (NTRS)

    Yoon, Yonghyun; Soni, Bharat K.

    1995-01-01

    The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.

  10. Hydrazine decomposition and other reactions

    NASA Technical Reports Server (NTRS)

    Armstrong, Warren E. (Inventor); La France, Donald S. (Inventor); Voge, Hervey H. (Inventor)

    1978-01-01

    This invention relates to the catalytic decomposition of hydrazine, catalysts useful for this decomposition and other reactions, and to reactions in hydrogen atmospheres generally using carbon-containing catalysts.

  11. 1-step versus 2-step immobilization of alkaline phosphatase and bone morphogenetic protein-2 onto implant surfaces using polydopamine.

    PubMed

    Nijhuis, Arnold W G; van den Beucken, Jeroen J J P; Boerman, Otto C; Jansen, John A; Leeuwenburgh, Sander C G

    2013-08-01

    Immobilization of biomolecules onto implant surfaces is highly relevant in many areas of biomaterial research. Recently, a 2-step immobilization procedure was developed for the facile conjugation of biomolecules onto various surfaces using self-polymerization of dopamine into polydopamine. In the current study, a 1-step polydopamine-based approach was applied for alkaline phosphatase (ALP) and bone morphogenetic protein-2 (BMP-2) immobilization, and compared to the conventional 2-step polydopamine-based immobilization and plain adsorption. To this end, ALP and BMP-2 were immobilized onto titanium and polytetrafluoroethylene (PTFE) substrates. The absolute quantity and biological activity of immobilized ALP were assessed quantitatively to compare the three types of immobilization. Plain adsorption of both ALP and BMP-2 was inferior to both polydopamine-based immobilization approaches. ALP was successfully immobilized onto titanium and PTFE surfaces via the 1-step approach, and the immobilized ALP retained its enzymatic activity. Using the 1-step approach, the amount of immobilized ALP was increased twofold to threefold compared to the conventional 2-step immobilization process. In contrast, more BMP-2 was immobilized using the conventional 2-step immobilization approach. Retention of ALP and BMP-2 was measured over a period of 4 weeks and was found to be similar for the 1-step and 2-step methods and far superior to the retention of adsorbed biomolecules due to the formation of covalent linkages between catechol moieties and immobilized proteins. The biological behavior of ALP and BMP-2 coatings immobilized using polydopamine (1- and 2-step) as well as adsorption was assessed by culturing rat bone marrow cells, which revealed that the cell responses to the various experimental groups were not statistically different. In conclusion, the 1-step polydopamine-based immobilization method was shown to be more efficient for immobilization of ALP, whereas the conventional 2

  12. On β2 stepped leaders in negative cloud-to-ground lightning

    NASA Astrophysics Data System (ADS)

    Campos, Leandro Z. S.; Saba, Marcelo M. F.; Philip Krider, E.

    2014-06-01

    In their seminal lightning studies using streak cameras, Schonland et al. (1938) identified four negative stepped leader events that they term "β2," a "rather rare variant of the type β leader", and in it, "the second and slower stage of the leader is associated with the appearance of one or more fast dart streamers, which travel rapidly down from the cloud along the previously formed track and cease when they have caught up with the slower leader tip." Seven negative downward leaders that agreed with the description given by Schonland et al. for type β2 were recorded in Tucson, Arizona, USA, and in São José dos Campos, São Paulo, Brazil. All cases were recorded by a high-speed camera operating at 4000 frames per second, and electric field changes were measured for three of them. Their "dart streamers" had speeds between 106 and 107 m s-1, compatible with previous observations of recoil leaders (RLs). Also, during the development of the three cases with correlated electric field changes, it was possible to identify sequences of microsecond-scale pulses preceding the propagation of a dart streamer in the channel. It is proposed that the luminous process that occurs during the development of a type β2 stepped leader is the visible manifestation of one or more RLs that begin inside the cloud and connect to the in-cloud, positive portion of the bipolar, bidirectional leader, and then travel downward to the lower end of the negative stepped leader path.

  13. Multicriteria approximation through decomposition

    SciTech Connect

    Burch, C.; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E.

    1998-06-01

    The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of their technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. Their method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) the authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing; (2) they also show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.

  14. Multicriteria approximation through decomposition

    SciTech Connect

    Burch, C. |; Krumke, S.; Marathe, M.; Phillips, C.; Sundberg, E. |

    1997-12-01

    The authors propose a general technique called solution decomposition to devise approximation algorithms with provable performance guarantees. The technique is applicable to a large class of combinatorial optimization problems that can be formulated as integer linear programs. Two key ingredients of the technique involve finding a decomposition of a fractional solution into a convex combination of feasible integral solutions and devising generic approximation algorithms based on calls to such decompositions as oracles. The technique is closely related to randomized rounding. The method yields as corollaries unified solutions to a number of well studied problems and it provides the first approximation algorithms with provable guarantees for a number of new problems. The particular results obtained in this paper include the following: (1) The authors demonstrate how the technique can be used to provide more understanding of previous results and new algorithms for classical problems such as Multicriteria Spanning Trees, and Suitcase Packing. (2) They show how the ideas can be extended to apply to multicriteria optimization problems, in which they wish to minimize a certain objective function subject to one or more budget constraints. As corollaries they obtain first non-trivial multicriteria approximation algorithms for problems including the k-Hurdle and the Network Inhibition problems.

  15. Pressure Dependent Decomposition Kinetics of the Energetic Material HMX up to 3.6 GPa

    SciTech Connect

    Glascoe, E A; Zaug, J M; Burnham, A K

    2009-05-29

    The effect of pressure on the thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low to moderate pressures (i.e. between ambient pressure and 1 GPa) and decelerates the decomposition at higher pressures. The decomposition acceleration is attributed to pressure enhanced autocatalysis whereas the deceleration at high pressures is attributed pressure inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both {beta} and {delta} phase HMX are sensitive to pressure in the thermally induced decomposition kinetics.

  16. Deformation and Thermal Properties of Energetic Materials.

    DTIC Science & Technology

    1980-12-01

    decomposition of PETN/polymer samples 5 (b) Thermal decomposition of PETN/ Benzoyl peroxide samples ......... 6 (c) Effect of ultra-violet light on... Benzoyl peroxide samples The results of the preceeding section show that the additives tested have very little effect on the thermal decomposition of PETN...nitrate. In order to test this hypothesis, mixtures of benzoyl peroxide and PETN were used in a series of TG experiments. Benzoyl peroxide is an

  17. Tribochemical Decomposition of Light Ionic Hydrides at Room Temperature.

    PubMed

    Nevshupa, Roman; Ares, Jose Ramón; Fernández, Jose Francisco; Del Campo, Adolfo; Roman, Elisa

    2015-07-16

    Tribochemical decomposition of magnesium hydride (MgH2) induced by deformation at room temperature was studied on a micrometric scale, in situ and in real time. During deformation, a near-full depletion of hydrogen in the micrometric affected zone is observed through an instantaneous (t < 1 s) and huge release of hydrogen (3-50 nmol/s). H release is related to a nonthermal decomposition process. After deformation, the remaining hydride is thermally decomposed at room temperature, exhibiting a much slower rate than during deformation. Confocal-microRaman spectroscopy of the mechanically affected zone was used to characterize the decomposition products. Decomposition was enhanced through the formation of the distorted structure of MgH2 with reduced crystal size by mechanical deformation.

  18. In situ analysis of Titan's tholins by Laser 2 steps Desorption Ionisation

    NASA Astrophysics Data System (ADS)

    Benilan, Y.; Carrasco, N.; Cernogora, G.; Gazeau, M.; Mahjoub, A.; Szopa, C.; Schwell, M.

    2013-12-01

    The main objective of the whole project developed in collaboration (LISA/LATMOS) is to provide a better understanding of the chemical composition of Titan aerosols laboratory analogs, called tholins, and thereby of their formation pathways. The tholins are produced in the PAMPRE reactor (French acronyme for Aerosols Microgravity Production by Reactives Plasmas) developed at LATMOS. These tholins are generated in levitation (wall effects are thus limited) in a low pressure radiofrequency plasma. Up to now, the determination of the physical and chemical properties of these tholins was achieved after their collection and ex-situ analysis by several methods. Their bulk composition was then determined but their insoluble part is still unknown. Other studies were performed after the transfer of the soluble part of the aerosols to different analytical instruments. Therefore, possible artifacts could have influenced the results. We present the SMARD (a French acronym for Mass Spectrometry of Aerosols by InfraRed Laser Desorption) program. A challenging issue of our work is to perform the soluble and unsoluble parts of PAMPRE tholins' analysis in real time and in situ. The coupling of the PAMPRE reactor to a unique instrument (Single Particle Laser Ablation Mass Spectrometry) developed at LISA should allow determining in real time and in situ the characteristics (chemical composition together with granulometry) of the nanometric aerosols. The later are introduced in the analytical instrument using an aerodynamic lens device. Their detection and aerodynamic diameter are determined using two continuous diode lasers operating at λ = 403 nm. Then, the L2DI (Laser 2 steps Desorption Ionisation) technique is used in order to access to the chemical composition of individual particles: they are vaporized using a 10 μm CO2 pulsed laser and the gas produced is then ionized by a 248 nm KrF Excimer laser. Finally, the molecular ions are analyzed by a 1 m linear time-of-flight mass

  19. Hydrogen peroxide catalytic decomposition

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2010-01-01

    Nitric oxide in a gaseous stream is converted to nitrogen dioxide using oxidizing species generated through the use of concentrated hydrogen peroxide fed as a monopropellant into a catalyzed thruster assembly. The hydrogen peroxide is preferably stored at stable concentration levels, i.e., approximately 50%-70% by volume, and may be increased in concentration in a continuous process preceding decomposition in the thruster assembly. The exhaust of the thruster assembly, rich in hydroxyl and/or hydroperoxy radicals, may be fed into a stream containing oxidizable components, such as nitric oxide, to facilitate their oxidation.

  20. Mode decomposition evolution equations

    PubMed Central

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2011-01-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  1. Algorithms for the Markov entropy decomposition

    NASA Astrophysics Data System (ADS)

    Ferris, Andrew J.; Poulin, David

    2013-05-01

    The Markov entropy decomposition (MED) is a recently proposed, cluster-based simulation method for finite temperature quantum systems with arbitrary geometry. In this paper, we detail numerical algorithms for performing the required steps of the MED, principally solving a minimization problem with a preconditioned Newton's algorithm, as well as how to extract global susceptibilities and thermal responses. We demonstrate the power of the method with the spin-1/2 XXZ model on the 2D square lattice, including the extraction of critical points and details of each phase. Although the method shares some qualitative similarities with exact diagonalization, we show that the MED is both more accurate and significantly more flexible.

  2. Method for improved decomposition of metal nitrate solutions

    DOEpatents

    Haas, Paul A.; Stines, William B.

    1983-10-11

    A method for co-conversion of aqueous solutions of one or more heavy metal nitrates wherein thermal decomposition within a temperature range of about 300.degree. to 800.degree. C. is carried out in the presence of about 50 to 500% molar concentration of ammonium nitrate to total metal.

  3. Method for improved decomposition of metal nitrate solutions

    DOEpatents

    Haas, P.A.; Stines, W.B.

    1981-01-21

    A method for co-conversion of aqueous solutions of one or more heavy metal nitrates is described, wherein thermal decomposition within a temperature range of about 300 to 800/sup 0/C is carried out in the presence of about 50 to 500% molar concentration of ammonium nitrate to total metal.

  4. Hydrogen iodide decomposition

    DOEpatents

    O'Keefe, Dennis R.; Norman, John H.

    1983-01-01

    Liquid hydrogen iodide is decomposed to form hydrogen and iodine in the presence of water using a soluble catalyst. Decomposition is carried out at a temperature between about 350.degree. K. and about 525.degree. K. and at a corresponding pressure between about 25 and about 300 atmospheres in the presence of an aqueous solution which acts as a carrier for the homogeneous catalyst. Various halides of the platinum group metals, particularly Pd, Rh and Pt, are used, particularly the chlorides and iodides which exhibit good solubility. After separation of the H.sub.2, the stream from the decomposer is countercurrently extracted with nearly dry HI to remove I.sub.2. The wet phase contains most of the catalyst and is recycled directly to the decomposition step. The catalyst in the remaining almost dry HI-I.sub.2 phase is then extracted into a wet phase which is also recycled. The catalyst-free HI-I.sub.2 phase is finally distilled to separate the HI and I.sub.2. The HI is recycled to the reactor; the I.sub.2 is returned to a reactor operating in accordance with the Bunsen equation to create more HI.

  5. Decomposition of Rare Earth Loaded Resin Particles

    SciTech Connect

    Voit, Stewart L; Rawn, Claudia J

    2010-09-01

    resin is made of sulfonic acid functional groups attached to a styrene divinylbenzene copolymer lattice (long chained hydrocarbon). The metal cation binds to the sulfur group, then during thermal decomposition in air the hydrocarbons will form gaseous species leaving behind a spherical metal-oxide particle. Process development for resin applications with radioactive materials is typically performed using surrogates. For americium and curium, a trivalent metal like neodymium can be used. Thermal decomposition of Nd-loaded resin in air has been studied by Hale. Process conditions were established for resin decomposition and the formation of Nd{sub 2}O{sub 3} particles. The intermediate product compounds were described using x-ray diffraction (XRD) and wet chemistry. Leskela and Niinisto studied the decomposition of rare earth (RE) elements and found results consistent with Hale. Picart et al. demonstrated the viability of using a resin loading process for the fabrication of uranium-actinide mixed oxide microspheres for transmutation of minor actinides in a fast reactor. For effective transmutation of actinides, it will be desirable to extend the in-reactor burnup and minimize the number of recycles of used actinide materials. Longer burn times increases the chance of Fuel Clad Chemical or Mechanical Interaction (FCCI, FCMI). Sulfur is suspected of contributing to Irradiation Assisted Stress Corrosion Cracking (IASCC) thus it is necessary to maximize the removal of sulfur during decomposition of the resin. The present effort extends the previous work by quantifying the removal of sulfur during the decomposition process. Neodymium was selected as a surrogate for trivalent actinide metal cations. As described above Nd was dissolved in nitric acid solution then contacted with the AG-50W resin column. After washing the column, the Nd-resin particles are removed and dried. The Nd-resin, seen in Figure 1 prior to decomposition, is ready to be converted to Nd oxide microspheres.

  6. Art of spin decomposition

    SciTech Connect

    Chen Xiangsong; Sun Weimin; Wang Fan; Goldman, T.

    2011-04-01

    We analyze the problem of spin decomposition for an interacting system from a natural perspective of constructing angular-momentum eigenstates. We split, from the total angular-momentum operator, a proper part which can be separately conserved for a stationary state. This part commutes with the total Hamiltonian and thus specifies the quantum angular momentum. We first show how this can be done in a gauge-dependent way, by seeking a specific gauge in which part of the total angular-momentum operator vanishes identically. We then construct a gauge-invariant operator with the desired property. Our analysis clarifies what is the most pertinent choice among the various proposals for decomposing the nucleon spin. A similar analysis is performed for extracting a proper part from the total Hamiltonian to construct energy eigenstates.

  7. The Vector Decomposition Problem

    NASA Astrophysics Data System (ADS)

    Yoshida, Maki; Mitsunari, Shigeo; Fujiwara, Toru

    This paper introduces a new computational problem on a two-dimensional vector space, called the vector decomposition problem (VDP), which is mainly defined for designing cryptosystems using pairings on elliptic curves. We first show a relation between the VDP and the computational Diffie-Hellman problem (CDH). Specifically, we present a sufficient condition for the VDP on a two-dimensional vector space to be at least as hard as the CDH on a one-dimensional subspace. We also present a sufficient condition for the VDP with a fixed basis to have a trapdoor. We then give an example of vector spaces which satisfy both sufficient conditions and on which the CDH is assumed to be hard in previous work. In this sense, the intractability of the VDP is a reasonable assumption as that of the CDH.

  8. Direct Sum Decomposition of Groups

    ERIC Educational Resources Information Center

    Thaheem, A. B.

    2005-01-01

    Direct sum decomposition of Abelian groups appears in almost all textbooks on algebra for undergraduate students. This concept plays an important role in group theory. One simple example of this decomposition is obtained by using the kernel and range of a projection map on an Abelian group. The aim in this pedagogical note is to establish a direct…

  9. The Effect of Body Mass on Outdoor Adult Human Decomposition.

    PubMed

    Roberts, Lindsey G; Spencer, Jessica R; Dabbs, Gretchen R

    2017-02-23

    Forensic taphonomy explores factors impacting human decomposition. This study investigated the effect of body mass on the rate and pattern of adult human decomposition. Nine males and three females aged 49-95 years ranging in mass from 73 to 159 kg who were donated to the Complex for Forensic Anthropology Research between December 2012 and September 2015 were included in this study. Kelvin accumulated degree days (KADD) were used to assess the thermal energy required for subjects to reach several total body score (TBS) thresholds: early decomposition (TBS ≥6.0), TBS ≥12.5, advanced decomposition (TBS ≥19.0), TBS ≥23.0, and skeletonization (TBS ≥27.0). Results indicate no significant correlation between body mass and KADD at any TBS threshold. Body mass accounted for up to 24.0% of variation in decomposition rate depending on stage, and minor differences in decomposition pattern were observed. Body mass likely has a minimal impact on postmortem interval estimation.

  10. Two decoupling methods for non-isothermal DSC results of AIBN decomposition.

    PubMed

    Zhang, Cai-Xing; Lu, Gui-Bin; Chen, Li-Ping; Chen, Wang-Hua; Peng, Min-Jun; Lv, Jia-Yu

    2015-03-21

    During thermal decomposition of azobisisobutyronitrile (AIBN), the endothermic process of phase transition disturbed exothermic decomposition, which brought deformation in its thermal graphs. Therefore, exact kinetic parameters of the decomposition could not be obtained by the existing kinetics analytic models, and the accurate enthalpy data of the decomposition and phase transition were not available. Two methods, i.e., a solvent method and a mathematical method, were introduced in this paper to resolve the coupling phenomenon. In the former method, AIBN was dissolved into aniline to eliminate the endothermic process and obtain curves of the liquid-state decomposition. In the latter method, MATLAB software was employed to get the "pure" exothermic decomposition curve without the influence of phase transition by fitting coupling curves within the section after the transition point and extrapolating to the initial stage of decomposition. Moreover, the kinetic parameters of the "pure" exothermic decomposition of AIBN obtained by the mathematical fitting agreed with the results from the solvent method, verifying the accuracy of the decoupling. The research is of great significance for comprehending the exact characteristics of thermal behaviors and safety parameters of AIBN. It also provides a great help to determine the safe operating temperature and alarm temperature for processes in industry.

  11. Influence of density and environmental factors on decomposition kinetics of amorphous polylactide - Reactive molecular dynamics studies.

    PubMed

    Mlyniec, A; Ekiert, M; Morawska-Chochol, A; Uhl, T

    2016-06-01

    In this work, we investigate the influence of the surrounding environment and the initial density on the decomposition kinetics of polylactide (PLA). The decomposition of the amorphous PLA was investigated by means of reactive molecular dynamics simulations. A computational model simulates the decomposition of PLA polymer inside the bulk, due to the assumed lack of removal of reaction products from the polymer matrix. We tracked the temperature dependency of the water and carbon monoxide production to extract the activation energy of thermal decomposition of PLA. We found that an increased density results in decreased activation energy of decomposition by about 50%. Moreover, initiation of decomposition of the amorphous PLA is followed by a rapid decline in activation energy caused by reaction products which accelerates the hydrolysis of esters. The addition of water molecules decreases initial energy of activation as well as accelerates the decomposition process. Additionally, we have investigated the dependency of density on external loading. Comparison of pressures needed to obtain assumed densities shows that this relationship is bilinear and the slope changes around a density equal to 1.3g/cm(3). The conducted analyses provide an insight into the thermal decomposition process of the amorphous phase of PLA, which is particularly susceptible to decomposition in amorphous and semi-crystalline PLA polymers.

  12. Decomposition of energetic chemicals contaminated with iron or stainless steel.

    PubMed

    Chervin, Sima; Bodman, Glenn T; Barnhart, Richard W

    2006-03-17

    Contamination of chemicals or reaction mixtures with iron or stainless steel is likely to take place during chemical processing. If energetic and thermally unstable chemicals are involved in a manufacturing process, contamination with iron or stainless steel can impact the decomposition characteristics of these chemicals and, subsequently, the safety of the processes, and should be investigated. The goal of this project was to undertake a systematic approach to study the impact of iron or stainless steel contamination on the decomposition characteristics of different chemical classes. Differential scanning calorimetry (DSC) was used to study the decomposition reaction by testing each chemical pure, and in mixtures with iron and stainless steel. The following classes of energetic chemicals were investigated: nitrobenzenes, tetrazoles, hydrazines, hydroxylamines and oximes, sulfonic acid derivatives and monomers. The following non-energetic groups were investigated for contributing effects: halogens, hydroxyls, amines, amides, nitriles, sulfonic acid esters, carbonyl halides and salts of hydrochloric acid. Based on the results obtained, conclusions were drawn regarding the sensitivity of the decomposition reaction to contamination with iron and stainless steel for the chemical classes listed above. It was demonstrated that the most sensitive classes are hydrazines and hydroxylamines/oximes. Contamination of these chemicals with iron or stainless steel not only destabilizes them, leading to decomposition at significantly lower temperatures, but also sometimes causes increased severity of the decomposition. The sensitivity of nitrobenzenes to contamination with iron or stainless steel depended upon the presence of other contributing groups: the presence of such groups as acid chlorides or chlorine/fluorine significantly increased the effect of contamination on decomposition characteristics of nitrobenzenes. The decomposition of sulfonic acid derivatives and tetrazoles

  13. Thin-film methods for examining the decomposition chemistry of explosives

    SciTech Connect

    Erickson, K.L.; Trott, W.M.; Renlund, A.M.

    1993-11-01

    Experimental techniques using thin-film samples and infrared spectroscopy have been developed to examine thermally-induced condensed-phase decomposition chemistry of explosives. Experiments with nitrocellulose (NC) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were done to examine the effects of confining the decomposition proucts so that intimate contact was maintained with the remaining explosive during isothermal decomposition at temperatures below those of the respective DTA exotherms. The NC experiments showed that substantial NC decomposition occurred at 150C and confinement of the decomposition products influenced the decomposition reactions. Some of the mechanisms and reaction rates with confined samples compared favorably with published mechanisms and rates from unconfined samples, while other mechanisms and reaction rates differed. The TATB experiments showed that significant TATB degradation occurred at temperatures as low as 210C, and substantial degradation occurred within 24 hours at 250C which is about 80C below the temperature of the DTA exotherm for TATB.

  14. Decomposition in northern Minnesota peatlands

    SciTech Connect

    Farrish, K.W.

    1985-01-01

    Decomposition in peatlands was investigated in northern Minnesota. Four sites, an ombrotrophic raised bog, an ombrotrophic perched bog and two groundwater minerotrophic fens, were studied. Decomposition rates of peat and paper were estimated using mass-loss techniques. Environmental and substrate factors that were most likely to be responsible for limiting decomposition were monitored. Laboratory incubation experiments complemented the field work. Mass-loss over one year in one of the bogs, ranged from 11 percent in the upper 10 cm of hummocks to 1 percent at 60 to 100 cm depth in hollows. Regression analysis of the data for that bog predicted no mass-loss below 87 cm. Decomposition estimates on an area basis were 2720 and 6460 km/ha yr for the two bogs; 17,000 and 5900 kg/ha yr for the two fens. Environmental factors found to limit decomposition in these peatlands were reducing/anaerobic conditions below the water table and cool peat temperatures. Substrate factors found to limit decomposition were low pH, high content of resistant organics such as lignin, and shortages of available N and K. Greater groundwater influence was found to favor decomposition through raising the pH and perhaps by introducing limited amounts of dissolved oxygen.

  15. Physico-Geometrical Kinetics of Solid-State Reactions in an Undergraduate Thermal Analysis Laboratory

    ERIC Educational Resources Information Center

    Koga, Nobuyoshi; Goshi, Yuri; Yoshikawa, Masahiro; Tatsuoka, Tomoyuki

    2014-01-01

    An undergraduate kinetic experiment of the thermal decomposition of solids by microscopic observation and thermal analysis was developed by investigating a suitable reaction, applicable techniques of thermal analysis and microscopic observation, and a reliable kinetic calculation method. The thermal decomposition of sodium hydrogen carbonate is…

  16. Structural optimization by multilevel decomposition

    NASA Technical Reports Server (NTRS)

    Sobieszczanski-Sobieski, J.; James, B.; Dovi, A.

    1983-01-01

    A method is described for decomposing an optimization problem into a set of subproblems and a coordination problem which preserves coupling between the subproblems. The method is introduced as a special case of multilevel, multidisciplinary system optimization and its algorithm is fully described for two level optimization for structures assembled of finite elements of arbitrary type. Numerical results are given for an example of a framework to show that the decomposition method converges and yields results comparable to those obtained without decomposition. It is pointed out that optimization by decomposition should reduce the design time by allowing groups of engineers, using different computers to work concurrently on the same large problem.

  17. Application of Non-Isothermal Thermogravimetric Method to Interpret the Decomposition Kinetics of , and

    NASA Astrophysics Data System (ADS)

    Pouretedal, H. R.; Ebadpour, R.

    2014-05-01

    The non-isothermal thermogravimetric method was used to study the thermal decomposition of , and at heating rates of (5, 10, 15, and 20) . The activation energy of thermal decomposition reactions was computed by isoconversional methods of Ozawa-Flynn-Wall, Kissinger-Akahiro-Sunose, and Friedman equations. Also, the kinetic triplet of the thermal decomposition of salts was determined by the model-fitting method of the modified Coats-Redfern equation. The activation energies of , and of (293 to 307, 160 to 209, and 192 to 245) , respectively, are obtained by non-isothermal isoconversional methods. The modified Coats and Redfern method showed that the most probable mechanism functions of (model A3: Arami-Erofeev equation) and (model F2: second order) can be used to predict the decomposition mechanisms of , , and , respectively.

  18. AUTONOMOUS GAUSSIAN DECOMPOSITION

    SciTech Connect

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian; Heiles, Carl; Hennebelle, Patrick; Dickey, John

    2015-04-15

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.

  19. Autonomous Gaussian Decomposition

    NASA Astrophysics Data System (ADS)

    Lindner, Robert R.; Vera-Ciro, Carlos; Murray, Claire E.; Stanimirović, Snežana; Babler, Brian; Heiles, Carl; Hennebelle, Patrick; Goss, W. M.; Dickey, John

    2015-04-01

    We present a new algorithm, named Autonomous Gaussian Decomposition (AGD), for automatically decomposing spectra into Gaussian components. AGD uses derivative spectroscopy and machine learning to provide optimized guesses for the number of Gaussian components in the data, and also their locations, widths, and amplitudes. We test AGD and find that it produces results comparable to human-derived solutions on 21 cm absorption spectra from the 21 cm SPectral line Observations of Neutral Gas with the EVLA (21-SPONGE) survey. We use AGD with Monte Carlo methods to derive the H i line completeness as a function of peak optical depth and velocity width for the 21-SPONGE data, and also show that the results of AGD are stable against varying observational noise intensity. The autonomy and computational efficiency of the method over traditional manual Gaussian fits allow for truly unbiased comparisons between observations and simulations, and for the ability to scale up and interpret the very large data volumes from the upcoming Square Kilometer Array and pathfinder telescopes.

  20. Nuclear driven water decomposition plant for hydrogen production

    NASA Technical Reports Server (NTRS)

    Parker, G. H.; Brecher, L. E.; Farbman, G. H.

    1976-01-01

    The conceptual design of a hydrogen production plant using a very-high-temperature nuclear reactor (VHTR) to energize a hybrid electrolytic-thermochemical system for water decomposition has been prepared. A graphite-moderated helium-cooled VHTR is used to produce 1850 F gas for electric power generation and 1600 F process heat for the water-decomposition process which uses sulfur compounds and promises performance superior to normal water electrolysis or other published thermochemical processes. The combined cycle operates at an overall thermal efficiency in excess of 45%, and the overall economics of hydrogen production by this plant have been evaluated predicated on a consistent set of economic ground rules. The conceptual design and evaluation efforts have indicated that development of this type of nuclear-driven water-decomposition plant will permit large-scale economic generation of hydrogen in the 1990s.

  1. Catalyst for sodium chlorate decomposition

    NASA Technical Reports Server (NTRS)

    Wydeven, T.

    1972-01-01

    Production of oxygen by rapid decomposition of cobalt oxide and sodium chlorate mixture is discussed. Cobalt oxide serves as catalyst to accelerate reaction. Temperature conditions and chemical processes involved are described.

  2. Some nonlinear space decomposition algorithms

    SciTech Connect

    Tai, Xue-Cheng; Espedal, M.

    1996-12-31

    Convergence of a space decomposition method is proved for a general convex programming problem. The space decomposition refers to methods that decompose a space into sums of subspaces, which could be a domain decomposition or a multigrid method for partial differential equations. Two algorithms are proposed. Both can be used for linear as well as nonlinear elliptic problems and they reduce to the standard additive and multiplicative Schwarz methods for linear elliptic problems. Two {open_quotes}hybrid{close_quotes} algorithms are also presented. They converge faster than the additive one and have better parallelism than the multiplicative method. Numerical tests with a two level domain decomposition for linear, nonlinear and interface elliptic problems are presented for the proposed algorithms.

  3. Naphthalene and acenaphthene decomposition by electron beam generated plasma application

    SciTech Connect

    Ostapczuk, A.; Hakoda, T.; Shimada, A.; Kojima, T.

    2008-08-15

    The application of non-thermal plasma generated by electron beam (EB) was investigated in laboratory scale to study decomposition of polycyclic aromatic hydrocarbons like naphthalene and acenaphthene in flue gas. PAH compounds were treated by EB with the dose up to 8 kGy in dry and humid base gas mixtures. Experimentally established G-values gained 1.66 and 3.72 mol/100 eV for NL and AC at the dose of 1 kGy. NL and AC removal was observed in dry base gas mixtures showing that the reaction with OH radical is not exclusive pathway to initialize PAH decomposition; however in the presence of water remarkably higher decomposition efficiency was observed. As by-products of NL decomposition were identified compounds containing one aromatic ring and oxygen atoms besides CO and CO{sub 2}. It led to the conclusion that PAH decomposition process in humid flue gas can be regarded as multi-step oxidative de-aromatization analogical to its atmospheric chemistry.

  4. Energy Transfer Dynamics of Formate Decomposition on Cu(110).

    PubMed

    Quan, Jiamei; Kondo, Takahiro; Wang, Guichang; Nakamura, Junji

    2017-03-20

    Energy transfer dynamics of formate (HCOOa ) decomposition on a Cu(110) surface has been studied by measuring the angle-resolved intensity and translational energy distributions of CO2 emitted from the surface in a steady-state reaction of HCOOH and O2 . The angular distribution of CO2 shows a sharp collimation with the direction perpendicular to the surface, as represented by cos(n) θ (n=6). The mean translational energy of CO2 is measured to be as low as 100 meV and is independent of the surface temperature (Ts ). These results clearly indicate that the decomposition of formate is a thermal non-equilibrium process in which a large amount of energy released by the decomposition reaction of formate is transformed into the internal energies of CO2 molecules. The thermal non-equilibrium features observed in the dynamics of formate decomposition support the proposed Eley-Rideal (ER)-type mechanism for formate synthesis on copper catalysts.

  5. Plasma Catalysis of Methane Decomposition in Pulse Microwave Discharge

    NASA Astrophysics Data System (ADS)

    Potapkin, B.; Rusanov, V.; Jivotov, V.; Babaritski, A.; Potechin, S.; Etievant, C.

    1997-10-01

    Investigation of plasma catalysis effects in various chemical reactions, such as SO2 and hydrocarbons oxidation, ammonia and nitrogen oxides synthesis, has been of interest for many decades. Present work describes the first experimental observation and theoretical analysis of plasma catalysis effects in the case of endothermic methane decomposition into molecular hydrogen and carbon black. Process energy requirements are coverd mainly by low potential gas thermal energy while plasma is used for acceleration of chemical reactions via active species generation. The experiments were done as follows: (i) methane was preheated in a conventional heat exchanger up to about 40-65 ^oC where thermal methane decomposition is limited by process kinetics, (ii) methane was passed through a non-equilibrium pulse microwave discharge (9.04 GHz, pulse duration 1 μs). Experiments have shown a strong catalytic effect of plasma on methane decomposition. The degree of conversion after discharge increased drastically, despite gas cooling, because of heat absorption in the methane decomposition reaction. Theoretical analysis of process kinetics and energy balance gave clear evidence of the catalytic effect of plasma under experimental conditions. The estimated chain length was about 300. The possible mechanism of plasma catalysis, the ion-molecular chain Winchester mechanism, is proposed and described.

  6. High Temperature Decomposition of Almandine and Pyrope in Reducing Atmosphere

    NASA Astrophysics Data System (ADS)

    Aparicio, C.; Filip, J.; Mashlan, M.

    2010-07-01

    Thermal decomposition of two garnets of near end-member composition—almandine (Fe2.85Mg0.15)(Al1.99)Si2.99O12 and pyrope (Mg2.22Fe0.47Ca0.33)(Cr0.11Fe0.06Al1.81)Si2.98O12—has been carried out in reducing atmosphere (forming gas: 10% of H2 in N2). High-temperature behavior of both samples was monitored using simultaneous thermogravimetry and differential scanning calorimetry. The decomposition of almandine and pyrope turned out to proceed at slightly different temperatures above 1000 °C. Therefore, two series of samples were prepared based on the results of thermal analysis: almandine heated up to 950 °C, 1070 °C and 1200 °C, and pyrope heated up to 1000 °C, 1100 °C, 1125 °C and 1200 °C. The identification of the decomposition products was performed by X-ray powder diffraction and Mössbauer spectroscopy. The common feature of the decomposition of both garnets is the presence of metallic iron and spinel phase, while the other products include fayalite, cristobalite, and cordierite for almandine; and enstatite and anorthite for pyrope. The formation of this last component was enabled due to Ca content in pyrope.

  7. High Temperature Decomposition of Almandine and Pyrope in Reducing Atmosphere

    SciTech Connect

    Aparicio, C.; Filip, J.; Mashlan, M.

    2010-07-13

    Thermal decomposition of two garnets of near end-member composition--almandine (Fe{sub 2.85}Mg{sub 0.15})(Al{sub 1.99})Si{sub 2.99}O{sub 12} and pyrope (Mg{sub 2.22}Fe{sub 0.47}Ca{sub 0.33})(Cr{sub 0.11}Fe{sub 0.06}Al{sub 1.81})Si{sub 2.98}O{sub 12}--has been carried out in reducing atmosphere (forming gas: 10% of H{sub 2} in N{sub 2}). High-temperature behavior of both samples was monitored using simultaneous thermogravimetry and differential scanning calorimetry. The decomposition of almandine and pyrope turned out to proceed at slightly different temperatures above 1000 degree sign C. Therefore, two series of samples were prepared based on the results of thermal analysis: almandine heated up to 950 deg. C, 1070 deg. C and 1200 deg. C, and pyrope heated up to 1000 deg. C, 1100 deg. C, 1125 deg. C and 1200 deg. C. The identification of the decomposition products was performed by X-ray powder diffraction and Moessbauer spectroscopy. The common feature of the decomposition of both garnets is the presence of metallic iron and spinel phase, while the other products include fayalite, cristobalite, and cordierite for almandine; and enstatite and anorthite for pyrope. The formation of this last component was enabled due to Ca content in pyrope.

  8. Catalytic decomposition of petroleum into natural gas

    SciTech Connect

    Mango, F.D.; Hightower, J.

    1997-12-01

    Petroleum is believed to be unstable in the earth, decomposing to lighter hydrocarbons at temperatures > 150{degrees}C. Oil and gas deposits support this view: gas/oil ratios and methane concentrations tend to increase with depth above 150{degrees}C. Although oil cracking is suggested and receives wide support, laboratory pyrolysis does not give products resembling natural gas. Moreover, it is doubtful that the light hydrocarbons in wet gas (C{sub 2}-C{sub 4}) could decompose over geologic time to dry gas (>95% methane) without catalytic assistance. We now report the catalytic decomposition of crude oil to a gas indistinguishable from natural gas. Like natural gas in deep basins, it becomes progressively enriched in methane: initially 90% (wet gas) to a final composition of 100% methane (dry gas). To our knowledge, the reaction is unprecedented and unexpectedly robust (conversion of oil to gas is 100% in days, 175{degrees}C) with significant implications regarding the stability of petroleum in sedimentary basins. The existence or nonexistence of oil in the deep subsurface may not depend on the thermal stability of hydrocarbons as currently thought. The critical factor could be the presence of transition metal catalysts which destabilize hydrocarbons and promote their decomposition to natural gas.

  9. Inter-year repeatability study of volatile organic compounds from surface decomposition of human analogues.

    PubMed

    Stadler, Sonja; Desaulniers, Jean-Paul; Forbes, Shari L

    2015-05-01

    Decomposition odour and volatile organic compounds (VOCs) have gained considerable attention recently due to their use by insects and scent detection canines to locate remains. However, a comprehensive and accurate profile of decomposition odour is yet to be confirmed. This is, in part, due to the geographical diversity in the studies conducted and the variation in the methodology and compounds being reported. To date, no repeatability studies of decomposition odour have been conducted in the same environment. In order to address this current gap in the scientific literature, this study conducted three replicate trials in order to evaluate the inter-year repeatability of the decomposition VOC profile in a southern Canadian environment. Surface decomposition trials were conducted during the spring and summer months and the VOCs were analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). This study was able to demonstrate that decomposition VOCs are produced consistently during their characteristic stages and that this relationship is maintained under varying environmental factors which influence the rate of decomposition. This consistent production of decomposition VOCs can lead to a better understanding of the mechanisms of soft tissue decomposition and their sources of variation, and it could potentially lead to improved applications of these compounds for the detection of decomposed remains.

  10. A Multiobjective Interval Programming Model for Wind-Hydrothermal Power System Dispatching Using 2-Step Optimization Algorithm

    PubMed Central

    Jihong, Qu

    2014-01-01

    Wind-hydrothermal power system dispatching has received intensive attention in recent years because it can help develop various reasonable plans to schedule the power generation efficiency. But future data such as wind power output and power load would not be accurately predicted and the nonlinear nature involved in the complex multiobjective scheduling model; therefore, to achieve accurate solution to such complex problem is a very difficult task. This paper presents an interval programming model with 2-step optimization algorithm to solve multiobjective dispatching. Initially, we represented the future data into interval numbers and simplified the object function to a linear programming problem to search the feasible and preliminary solutions to construct the Pareto set. Then the simulated annealing method was used to search the optimal solution of initial model. Thorough experimental results suggest that the proposed method performed reasonably well in terms of both operating efficiency and precision. PMID:24895663

  11. A multiobjective interval programming model for wind-hydrothermal power system dispatching using 2-step optimization algorithm.

    PubMed

    Ren, Kun; Jihong, Qu

    2014-01-01

    Wind-hydrothermal power system dispatching has received intensive attention in recent years because it can help develop various reasonable plans to schedule the power generation efficiency. But future data such as wind power output and power load would not be accurately predicted and the nonlinear nature involved in the complex multiobjective scheduling model; therefore, to achieve accurate solution to such complex problem is a very difficult task. This paper presents an interval programming model with 2-step optimization algorithm to solve multiobjective dispatching. Initially, we represented the future data into interval numbers and simplified the object function to a linear programming problem to search the feasible and preliminary solutions to construct the Pareto set. Then the simulated annealing method was used to search the optimal solution of initial model. Thorough experimental results suggest that the proposed method performed reasonably well in terms of both operating efficiency and precision.

  12. Decomposition of silane on tungsten or other materials

    DOEpatents

    Wiesmann, H.J.

    This invention relates to hydrogenated amorphous silicon produced by thermally decomposing silane (SiH/sub 4/) or other gases comprising H and Si, from a W or foil heated to a temperature of about 1400 to 1600/sup 0/C, in a vacuum of about 10-/sup 6/ to 10-/sup 4/ torr. A gaseous mixture is formed of atomic hydrogen and atomic silicon. The gaseous mixture is deposited onto a substrate independent of and outside the source of thermal decomposition. Hydrogenated amorphous silicon is formed. The presence of an ammonia atmosphere in the vacuum chamber enhances the photoconductivity of the hydrogenated amorphous silicon film.

  13. Modeling the Thermal Destruction of Chemical Warfare ...

    EPA Pesticide Factsheets

    Symposium Paper In the event of a terrorist attack with chemical warfare agents (CWAs), large quantities of materials, both indoor and outdoor, may be treated with thermal incineration during the site remediation process. This paper reports on a study to examine the thermal decomposition of surrogate CWAs and formation of decomposition by-products bound in model building materials (in this case, ceiling tile) in a pilot-scale rotary kiln incinerator simulator.

  14. Catalytic and inhibiting effects of lithium peroxide and hydroxide on sodium chlorate decomposition

    SciTech Connect

    Cannon, J.C.; Zhang, Y.

    1995-09-01

    Chemical oxygen generators based on sodium chlorate and lithium perchlorate are used in airplanes, submarines, diving, and mine rescue. Catalytic decomposition of sodium chlorate in the presence of cobalt oxide, lithium peroxide, and lithium hydroxide is studied using thermal gravimetric analysis. Lithium peroxide and hydroxide are both moderately active catalysts for the decomposition of sodium chlorate when used alone, and inhibitors when used with the more active catalyst cobalt oxide.

  15. The ecology of carrion decomposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carrion, or the remains of dead animals, is something that most people would like to avoid. It is visually unpleasant, emits foul odors, and may be the source of numerous pathogens. Decomposition of carrion, however, provides a unique opportunity for scientists to investigate how nutrients cycle t...

  16. Microbial interactions during carrion decomposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This addresses the microbial ecology of carrion decomposition in the age of metagenomics. It describes what is known about the microbial communities on carrion, including a brief synopsis about the communities on other organic matter sources. It provides a description of studies using state-of-the...

  17. Cadaver decomposition in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Carter, David O.; Yellowlees, David; Tibbett, Mark

    2007-01-01

    A dead mammal (i.e. cadaver) is a high quality resource (narrow carbon:nitrogen ratio, high water content) that releases an intense, localised pulse of carbon and nutrients into the soil upon decomposition. Despite the fact that as much as 5,000 kg of cadaver can be introduced to a square kilometre of terrestrial ecosystem each year, cadaver decomposition remains a neglected microsere. Here we review the processes associated with the introduction of cadaver-derived carbon and nutrients into soil from forensic and ecological settings to show that cadaver decomposition can have a greater, albeit localised, effect on belowground ecology than plant and faecal resources. Cadaveric materials are rapidly introduced to belowground floral and faunal communities, which results in the formation of a highly concentrated island of fertility, or cadaver decomposition island (CDI). CDIs are associated with increased soil microbial biomass, microbial activity (C mineralisation) and nematode abundance. Each CDI is an ephemeral natural disturbance that, in addition to releasing energy and nutrients to the wider ecosystem, acts as a hub by receiving these materials in the form of dead insects, exuvia and puparia, faecal matter (from scavengers, grazers and predators) and feathers (from avian scavengers and predators). As such, CDIs contribute to landscape heterogeneity. Furthermore, CDIs are a specialised habitat for a number of flies, beetles and pioneer vegetation, which enhances biodiversity in terrestrial ecosystems.

  18. An analysis of scatter decomposition

    NASA Technical Reports Server (NTRS)

    Nicol, David M.; Saltz, Joel H.

    1990-01-01

    A formal analysis of a powerful mapping technique known as scatter decomposition is presented. Scatter decomposition divides an irregular computational domain into a large number of equal sized pieces, and distributes them modularly among processors. A probabilistic model of workload in one dimension is used to formally explain why, and when scatter decomposition works. The first result is that if correlation in workload is a convex function of distance, then scattering a more finely decomposed domain yields a lower average processor workload variance. The second result shows that if the workload process is stationary Gaussian and the correlation function decreases linearly in distance until becoming zero and then remains zero, scattering a more finely decomposed domain yields a lower expected maximum processor workload. Finally it is shown that if the correlation function decreases linearly across the entire domain, then among all mappings that assign an equal number of domain pieces to each processor, scatter decomposition minimizes the average processor workload variance. The dependence of these results on the assumption of decreasing correlation is illustrated with situations where a coarser granularity actually achieves better load balance.

  19. Kinetic study of non-isothermal decomposition of a composite diasporic-boehmitic bauxite

    NASA Astrophysics Data System (ADS)

    Samouhos, M.; Angelopoulos, P.; Pilatos, G.; Taxiarchou, M.; Papageorgiou, S.

    2016-04-01

    In the current study, the kinetic of the thermal decomposition of a composite diasporic-boehmitic bauxite is investigated under non-isothermal heating conditions by means of thermogravimetric analysis. The calculation of activation energy (Ea) has been performed by various methods and the attained values range from 185000 to 190000 J.mol-1 for conversion rate of 0.5. The first-order kinetic model can adequately be used to describe thermal decomposition of bauxite composite, while the pre-exponential factor value was found to be 2.088*1011 min-1. The calculated activation energy value together with pre-exponential factor and the solid state kinetic model factors enable the simulation of the thermal decomposition under various heating conditions by the implementation of an ordinary differential equation. The calculated values are in satisfactory agreement with the experimental ones.

  20. Diagnosing Diabetic Foot Osteomyelitis: Narrative Review and a Suggested 2-Step Score-Based Diagnostic Pathway for Clinicians

    PubMed Central

    Markanday, Anurag

    2014-01-01

    The diabetic foot infection remains a major cause of morbidity and mortality in many patients and remains a challenging diagnosis for most clinicians. Diagnosis is largely based on clinical signs supplemented by various imaging tests. Magnetic resonance imaging (MRI) is not readily available to many clinicians, and bone biopsy, which is the accepted criterion standard for diagnosis, is rarely performed routinely. This evidence-based review and the proposed diagnostic scoring pathway substratifies the current International Working Group on the Diabetes Foot guidelines for diagnosing diabetic foot osteomyelitis into a convenient 2-step diagnostic pathway for clinicians. This proposed diagnostic approach will need further validation prospectively, but it can serve as a useful diagnostic tool during the initial assessment and management of diabetic foot infections. A MEDLINE search of English-language articles on diabetic foot osteomyelitis published between 1986 and March 2014 was conducted. Additional articles were also identified through a search of references from the retrieved articles, published guidelines, systematic reviews, and meta-analyses. PMID:25734130

  1. Transmission and Accumulation of Nano-TiO2 in a 2-Step Food Chain (Scenedesmus obliquus to Daphnia magna).

    PubMed

    Chen, Jinyuan; Li, Herong; Han, Xiaoqian; Wei, Xiuzhen

    2015-08-01

    The recent increase in nanomaterial usage has led to concerns surrounding its health risks and environmental impact. The food chain is an important pathway for high-trophic-level organisms absorbing and enriching nanomaterials. Our study therefore simulated nanometer titanium dioxide (nano-TiO2) transfer along a 2-step food chain, from the unicellular alga Scenedesmus obliquus to the water flea Daphnia magna. We also explored the effect of sodium dodecyl benzene sulfonate (SDBS) on nano-TiO2 bioavailability. A suspension of 10 mg/L nano-TiO2 was optimally dispersed in aqueous solutions by 5 mg/L SDBS. After 72 h, S. obliquus growth was not significantly affected by 10 mg/L nano-TiO2, 5 mg/L SDBS and their mixed suspension. SDBS not only improved nano-TiO2 stability in water, but also increased its uptake in S. obliquus and enhanced its accumulation in D. magna. Our study suggests that nano-TiO2 is mildly toxic to S. obliquus, and can be transferred along the aquatic food chain with a biomagnification effect.

  2. A MEMS methanol reformer heated by decomposition of hydrogen peroxide.

    PubMed

    Kim, Taegyu; Hwang, Jin Soo; Kwon, Sejin

    2007-07-01

    This paper presents the design, fabrication and evaluation of a micro methanol reformer complete with a heat source. The micro system consists of the steam reforming reactor of methanol, the catalytic decomposition reactor of hydrogen peroxide, and a heat exchanger between the two reactors. In the present study, catalytic decomposition of hydrogen peroxide is used as a process to supply heat to the reforming reactor. The decomposition process of hydrogen peroxide produces water vapor and oxygen as a product that can be used efficiently to operate the reformer/PEMFC system. Cu/ZnO was selected as a catalyst for methanol steam reforming and Pt for the decomposition of hydrogen peroxide. Incipient wetness method was used to load catalysts on a porous support. Catalyst loaded supports were inserted in the cavity made on the glass wafer. The performance of the methanol steam reforming system was measured at various test conditions and the optimum operation condition was sought. At the optimum condition, the hydrogen selectivity was 86.4% and the thermal efficiency was 44.8%. The product gas included 74.1% H(2), 24.5% CO(2) and 1.4% CO and the total volume production rate was 23.5 ml min(-1). This amount of hydrogen can produce 1.5 W of power on a typical PEMFC.

  3. Thermal degradation of InGaN/GaN quantum wells in blue laser diode structure during the epitaxial growth

    NASA Astrophysics Data System (ADS)

    Zhou, Kun; Ikeda, Massao; Liu, Jianping; Li, Zengcheng; Ma, Yi; Gao, Songxin; Ren, Huaijin; Tang, Chun; Sun, Yi; Sun, Qian; Yang, Hui

    2016-01-01

    True blue nitride laser diodes (LDs) are one of the key challenges for epitaxy of nitrides due to the variety of its potential applications. The growth of high temperature p-type layers may cause thermal degradation of the InGaN-based multiple quantum wells (MQWs) active region because of the annealing effect, since thick p-AlGaN layers were introduced as upper optical cladding layer in the LDs. The degradation was found in blue LDs grown on both Si and sapphire substrate. In the degraded LD wafer samples, "Dark" non-radiative MQWs regions were observed by microscopic photoluminescence. Formation of metallic indium precipitates and voids in these regions were confirmed by transmission electron microscope. The thermal degradation is attributed to the decomposition of indium-rich InGaN materials in the MQWs. The indium-rich InGaN materials were supposed to be accumulated at dislocation related V-shaped pits according to the surface morphology by atomic force microscope. To obtain high quality InGaN-based MQWs, one of the four methods can be introduced to eliminate the degradation. A lower thermal budget can suppress the decomposition of indium-rich InGaN clusters by a lower p-cladding layer growth temperature. The use of low threading dislocation density substrates results in low density indium-rich InGaN clusters. The introducing of H2 carrier gas during the quantum barriers growth or a 2-step growth scheme with a higher quantum barrier growth temperature etches off the indium-rich InGaN clusters. The suppression of the thermal degradation in the MQWs makes it possible for lasing of blue laser diode directly grown on Si.

  4. Investigating hydrogel dosimeter decomposition by chemical methods

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin

    2015-01-01

    The chemical oxidative decomposition of leucocrystal violet micelle hydrogel dosimeters was investigated using the reaction of ferrous ions with hydrogen peroxide or sodium bicarbonate with hydrogen peroxide. The second reaction is more effective at dye decomposition in gelatin hydrogels. Additional chemical analysis is required to determine the decomposition products.

  5. Nonlinear mode decomposition: A noise-robust, adaptive decomposition method

    NASA Astrophysics Data System (ADS)

    Iatsenko, Dmytro; McClintock, Peter V. E.; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool—nonlinear mode decomposition (NMD)—which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques—which, together with the adaptive choice of their parameters, make it extremely noise robust—and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  6. Nonlinear mode decomposition: a noise-robust, adaptive decomposition method.

    PubMed

    Iatsenko, Dmytro; McClintock, Peter V E; Stefanovska, Aneta

    2015-09-01

    The signals emanating from complex systems are usually composed of a mixture of different oscillations which, for a reliable analysis, should be separated from each other and from the inevitable background of noise. Here we introduce an adaptive decomposition tool-nonlinear mode decomposition (NMD)-which decomposes a given signal into a set of physically meaningful oscillations for any wave form, simultaneously removing the noise. NMD is based on the powerful combination of time-frequency analysis techniques-which, together with the adaptive choice of their parameters, make it extremely noise robust-and surrogate data tests used to identify interdependent oscillations and to distinguish deterministic from random activity. We illustrate the application of NMD to both simulated and real signals and demonstrate its qualitative and quantitative superiority over other approaches, such as (ensemble) empirical mode decomposition, Karhunen-Loève expansion, and independent component analysis. We point out that NMD is likely to be applicable and useful in many different areas of research, such as geophysics, finance, and the life sciences. The necessary matlab codes for running NMD are freely available for download.

  7. Influence of activated-carbon-supported transition metals on the decomposition of polychlorobiphenyls. Part I: Catalytic decomposition and kinetic analysis.

    PubMed

    Sun, Yifei; Tao, Fei; Liu, Lina; Zeng, Xiaolan; Wang, Wei

    2016-09-01

    In this study, the synergism between activated carbon (AC) as a catalyst support and transition metals (TMs) is used to destroy low concentrations of PCBs. AC-supported TM catalysts were prepared according to two different methods: impregnation and ion exchange. Thermal reactions between 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) and catalysts generated using AC-supported Ni or Cu ion exchange were conducted under a N2 atmosphere and resulted in a decomposition efficiency > 99.0%. Decomposition efficiency of PCB-153, the residual PCB-153 distribution, and the fingerprint characteristics of the decomposition products are investigated. Important findings include: (i) establishing a ranking of TM reactivities with respect to PCB decomposition of: Ni > Cu > Zn > Fe, (ii) PCB degradation reactions proceed via adsorption, reaction, and desorption, (iii) for ion-exchange-type catalysts, the activation energy order was IRNi-C < IRCu-C < IRZn-C < IRFe-C, which matches the order of the catalytic effects of the catalyst.

  8. Decomposition of N2O over particulate matter

    NASA Technical Reports Server (NTRS)

    Rebbert, R. E.; Ausloos, P.

    1978-01-01

    Nitrous oxide is shown to undergo both a thermal and a photochemical decomposition at 296 K when it is adsorbed on various dry sands. The photochemical process occurs with light of wavelengths greater than 280 nm, where gaseous N2O does not absorb. At low pressures (less than 0.1 torr) the half-life for the thermal decomposition of nitrous oxide to nitrogen when placed in contact with about 5 gm of heat-treated Tunisian sand in a one-liter vessel was 350 + or - 35 days. Under certain photolytic conditions this half-life was reduced. The efficiency of the photolytic process for a particular sand depends on the pressure and on the wavelength of light. For Tunisian sand at 1.1 torr and with the full mercury arc, the destruction efficiency is about 0.00002 molecule/incident photon. These results indicate that particulate matter in the troposphere may be responsible for the decomposition of nitrous oxide and hence act as an atmospheric sink for N2O. However, moisture causes a drastic reduction in the number of molecules dissociated per incident photon.

  9. Adiabatic calorimetric decomposition studies of 50 wt.% hydroxylamine/water.

    PubMed

    Cisneros, L O; Rogers, W J; Mannan, M S

    2001-03-19

    Calorimetric data can provide a basis for determining potential hazards in reactions, storage, and transportation of process chemicals. This work provides calorimetric data for the thermal decomposition behavior in air of 50wt.% hydroxylamine/water (HA), both with and without added stabilizers, which was measured in closed cells with an automatic pressure tracking adiabatic calorimeter (APTAC). Among the data provided are onset temperatures, reaction order, activation energies, pressures of noncondensable products, thermal stability at 100 degrees C, and the effect of HA storage time. Discussed also are the catalytic effects of carbon steel, stainless steel, stainless steel with silica coating, inconel, titanium, and titanium with silica coating on the reaction self-heat rates and onset temperatures. In borosilicate glass cells, HA was relatively stable at temperatures up to 133 degrees C, where the HA decomposition self-heat rate reached 0.05 degrees C/min. The added stabilizers appeared to reduce HA decomposition rates in glass cells and at ambient temperatures. The tested metals and metal surfaces coated with silica acted as catalysts to lower the onset temperatures and increase the self-heat rates.

  10. Kinetics of non-isothermal decomposition of cinnamic acid

    NASA Astrophysics Data System (ADS)

    Zhao, Ming-rui; Qi, Zhen-li; Chen, Fei-xiong; Yue, Xia-xin

    2014-07-01

    The thermal stability and kinetics of decomposition of cinnamic acid were investigated by thermogravimetry and differential scanning calorimetry at four heating rates. The activation energies of this process were calculated from analysis of TG curves by methods of Flynn-Wall-Ozawa, Doyle, Distributed Activation Energy Model, Šatava-Šesták and Kissinger, respectively. There are only one stage of thermal decomposition process in TG and two endothermic peaks in DSC. For this decomposition process of cinnamic acid, E and log A[s-1] were determined to be 81.74 kJ mol-1 and 8.67, respectively. The mechanism was Mampel Power law (the reaction order, n = 1), with integral form G(α) = α (α = 0.1-0.9). Moreover, thermodynamic properties of Δ H ≠, Δ S ≠, Δ G ≠ were 77.96 kJ mol-1, -90.71 J mol-1 K-1, 119.41 kJ mol-1.

  11. Anisotropic decomposition of energetic materials

    SciTech Connect

    Pravica, Michael; Quine, Zachary; Romano, Edward; Bajar, Sean; Yulga, Brian; Yang Wenge; Hooks, Daniel

    2007-12-12

    Using a white x-ray synchrotron beam, we have dynamically studied radiation-induced decomposition in single crystalline PETN and TATB. By monitoring the integrated intensity of selected diffraction spots via a CCD x-ray camera as a function of time, we have found that the decomposition rate varies dramatically depending upon the orientation of the crystalline axes relative to polarized x-ray beam and for differing diffracting conditions (spots) within the same crystalline orientation. We suggest that this effect is due to Compton scattering of the polarized x-rays with electron clouds that is dependent upon their relative orientation. This novel effect may yield valuable insight regarding anisotropic detonation sensitivity in energetic materials such as PETN.

  12. Variance decomposition in stochastic simulators

    SciTech Connect

    Le Maître, O. P.; Knio, O. M.; Moraes, A.

    2015-06-28

    This work aims at the development of a mathematical and computational approach that enables quantification of the inherent sources of stochasticity and of the corresponding sensitivities in stochastic simulations of chemical reaction networks. The approach is based on reformulating the system dynamics as being generated by independent standardized Poisson processes. This reformulation affords a straightforward identification of individual realizations for the stochastic dynamics of each reaction channel, and consequently a quantitative characterization of the inherent sources of stochasticity in the system. By relying on the Sobol-Hoeffding decomposition, the reformulation enables us to perform an orthogonal decomposition of the solution variance. Thus, by judiciously exploiting the inherent stochasticity of the system, one is able to quantify the variance-based sensitivities associated with individual reaction channels, as well as the importance of channel interactions. Implementation of the algorithms is illustrated in light of simulations of simplified systems, including the birth-death, Schlögl, and Michaelis-Menten models.

  13. Aflatoxin decomposition in various soils

    SciTech Connect

    Angle, J.S.

    1986-08-01

    The persistence of aflatoxin in the soil environment could potentially result in a number of adverse environmental consequences. To determine the persistence of aflatoxin in soil, /sup 14/C-labeled aflatoxin B1, was added to silt loam, sandy loam, and silty clay loam soils and the subsequent release of /sup 14/CO/sub 2/ was determined. After 120 days of incubation, 8.1% of the original aflatoxin added to the silt loam soil was released as CO/sub 2/. Aflatoxin decomposition in the sandy loam soil proceeded more quickly than the other two soils for the first 20 days of incubation. After this time, the decomposition rate declined and by the end of the study, 4.9% of the aflatoxin was released as CO/sub 2/. Aflatoxin decomposition proceeded most slowly in the silty clay loam soil. Only 1.4% of aflatoxin added to the soil was released as CO/sub 2/ after 120 days incubation. To determine whether aflatoxin was bound to the silty clay loam soil, aflatoxin B1 was added to this soil and incubated for 20 days. The soil was periodically extracted and the aflatoxin species present were determined using thin layer chromatographic (TLC) procedures. After one day of incubation, the degradation products, aflatoxins B2 and G2, were observed. It was also found that much of the aflatoxin extracted from the soil was not mobile with the TLC solvent system used. This indicated that a conjugate may have formed and thus may be responsible for the lack of aflatoxin decomposition.

  14. Phlogopite Decomposition, Water, and Venus

    NASA Technical Reports Server (NTRS)

    Johnson, N. M.; Fegley, B., Jr.

    2005-01-01

    Venus is a hot and dry planet with a surface temperature of 660 to 740 K and 30 parts per million by volume (ppmv) water vapor in its lower atmosphere. In contrast Earth has an average surface temperature of 288 K and 1-4% water vapor in its troposphere. The hot and dry conditions on Venus led many to speculate that hydrous minerals on the surface of Venus would not be there today even though they might have formed in a potentially wetter past. Thermodynamic calculations predict that many hydrous minerals are unstable under current Venusian conditions. Thermodynamics predicts whether a particular mineral is stable or not, but we need experimental data on the decomposition rate of hydrous minerals to determine if they survive on Venus today. Previously, we determined the decomposition rate of the amphibole tremolite, and found that it could exist for billions of years at current surface conditions. Here, we present our initial results on the decomposition of phlogopite mica, another common hydrous mineral on Earth.

  15. Methanethiol decomposition on Ni(100)

    SciTech Connect

    Castro, M.E.; Ahkter, S.; Golchet, A.; White, J.M. ); Sahin, T. )

    1991-01-01

    Static secondary ion mass spectroscopy (SSIMS), temperature programmed desorption (TPD), and Auger electron spectroscopy (AES) were used under ultrahigh vacuum conditions to study the decomposition of CH{sub 3}SH on Ni(100). Only methane, hydrogen, and the parent molecule are observed in TPD. Complete decomposition to C(a), S(a) and desorbing H{sub 2} is the preferred reaction pathway for low exposures, while desorption of methane is observed at higher coverages. Preadsorbed hydrogen promoted methane desorption. Upon adsorption, and for low coverages, SSIMS evidence indicates S-H bond cleavage into CH{sub 3}S and surface hydrogen. S-H bond cleavage is inhibited for high coverages. The TP-SSIMS data are consistent with an activated C-S bond cleavage in CH{sub 3}S, with an activation energy of 8.81 kcal/mol and preexponential factor of 10{sup 6.5}s{sup {minus}1}. The low preexponential factor is taken as indicating a complex decomposition pathway. A mechanism consistent with the observed data is discussed.

  16. Thermochemical decomposition and isomerization of polysilacyclodialkynes and thermochemical and photochemical decomposition of cyclopolysilylketenes

    SciTech Connect

    Altman, Leon Berthold

    1994-05-10

    Kinetic data for elimination of silylene supports formation of a ``tighter`` transition state, indicating a silacyclopropene intermediate. This extends the silacyclopropene mechanism to the cyclicdialkyne system and validates the consistency of the mechanism for silylakynes, in general. Investigation into the other possible silacyclopropene product established the instability of the product. The work with silylketenes proved that an inherent difference exists between reactivity of monosilyl-substituted ketenes and polysilyl-substituted ketenes. Although the mechanism for thermal decomposition of bis(silyl)ketenes can be modified to account for the unexpected silylene elimination products, reasons for the difference are limited to speculation. The photochemistry of silylketenes has not been previously studied, so a model system does not exist for comparison with our polysilylketene work. The photochemical experimentation suggests that the photochemistry and thermochemistry of polysilylketenes is not the same. A more extensive study of the mechanism of the systems covered in this research as well as with monosilyl-substituted systems is needed.

  17. Decomposition of solids accompanied by melting--Bawn kinetics.

    PubMed

    Brown, Michael E; Glass, Beverley D

    2003-03-26

    The book "Chemistry of the Solid State", edited by W.E. Garner more than 50 years ago, contained a chapter (Chapter 10) by C.E.H. Bawn which dealt with the kinetics of the thermal decompositions of solids that are accompanied by some melting. Rate equations were derived and this model has become known as the Bawn model or as "Bawn kinetics". This kinetic model has proved particularly useful in pharmaceutical stability studies. The isothermal curves of extent of decomposition, alpha, against time for this model are sigmoidal and the problems of distinguishing this model from other sigmoidal models (Prout-Tompkins, Avrami-Erofeev) have been examined. Under programmed temperature conditions, distinguishability becomes even more difficult.

  18. Kinetics of HMX and CP Decomposition and Their Extrapolation for Lifetime Assessment

    SciTech Connect

    Burnham, A K; Weese, R K; Andrzejewski, W J

    2004-11-18

    Decomposition kinetics are determined for HMX (nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and CP (2-(5-cyanotetrazalato) pentaammine cobalt (III) perchlorate) separately and together. For high levels of thermal stress, the two materials decompose faster as a mixture than individually. This effect is observed both in high-temperature thermal analysis experiments and in long-term thermal aging experiments. An Arrhenius plot of the 10% level of HMX decomposition by itself from a diverse set of experiments is linear from 120 to 260 C, with an apparent activation energy of 165 kJ/mol. Similar but less extensive thermal analysis data for the mixture suggests a slightly lower activation energy for the mixture, and an analogous extrapolation is consistent with the amount of gas observed in the long-term detonator aging experiments, which is about 30 times greater than expected from HMX by itself for 50 months at 100 C. Even with this acceleration, however, it would take {approx}10,000 years to achieve 10% decomposition at {approx}30 C. Correspondingly, negligible decomposition is predicted by this kinetic model for a few decades aging at temperatures slightly above ambient. This prediction is consistent with additional sealed-tube aging experiments at 100-120 C, which are estimated to have an effective thermal dose greater than that from decades of exposure to temperatures slightly above ambient.

  19. A review of plutonium oxalate decomposition reactions and effects of decomposition temperature on the surface area of the plutonium dioxide product

    NASA Astrophysics Data System (ADS)

    Orr, R. M.; Sims, H. E.; Taylor, R. J.

    2015-10-01

    Plutonium (IV) and (III) ions in nitric acid solution readily form insoluble precipitates with oxalic acid. The plutonium oxalates are then easily thermally decomposed to form plutonium dioxide powder. This simple process forms the basis of current industrial conversion or 'finishing' processes that are used in commercial scale reprocessing plants. It is also widely used in analytical or laboratory scale operations and for waste residues treatment. However, the mechanisms of the thermal decompositions in both air and inert atmospheres have been the subject of various studies over several decades. The nature of intermediate phases is of fundamental interest whilst understanding the evolution of gases at different temperatures is relevant to process control. The thermal decomposition is also used to control a number of powder properties of the PuO2 product that are important to either long term storage or mixed oxide fuel manufacturing. These properties are the surface area, residual carbon impurities and adsorbed volatile species whereas the morphology and particle size distribution are functions of the precipitation process. Available data and experience regarding the thermal and radiation-induced decompositions of plutonium oxalate to oxide are reviewed. The mechanisms of the thermal decompositions are considered with a particular focus on the likely redox chemistry involved. Also, whilst it is well known that the surface area is dependent on calcination temperature, there is a wide variation in the published data and so new correlations have been derived. Better understanding of plutonium (III) and (IV) oxalate decompositions will assist the development of more proliferation resistant actinide co-conversion processes that are needed for advanced reprocessing in future closed nuclear fuel cycles.

  20. An investigation of the Nd{sub 2}O{sub 3}-MoO{sub 3} phase system: Thermal decomposition of Nd{sub 2}Mo{sub 4}O{sub 15} and formation of Nd{sub 6}Mo{sub 10}O{sub 39}

    SciTech Connect

    Barker, Rosemary S.; Evans, Ivana Radosavljevic . E-mail: ivana.radosavljevic@durham.ac.uk

    2006-06-15

    A new neodymium molybdate, Nd{sub 6}Mo{sub 10}O{sub 39}, has been identified in the Nd{sub 2}O{sub 3}-MoO{sub 3} phase system. Nd{sub 6}Mo{sub 10}O{sub 39} appears to be a metastable phase, which does not form directly from a stoichiometric mixture of Nd{sub 2}O{sub 3} and MoO{sub 3} oxides. Instead, it can be obtained by thermal decomposition of Nd{sub 2}Mo{sub 4}O{sub 15}. Nd{sub 2}Mo{sub 4}O{sub 15} usually decomposes into Nd{sub 2}(MoO{sub 4}){sub 3}, and the formation of Nd{sub 6}Mo{sub 10}O{sub 39} critically depends on the heating regime used. The structure of Nd{sub 6}Mo{sub 10}O{sub 39} has been determined by single crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c, with unit cell parameters of a=12.425(1)A, b=19.860(2)A, c=13.882(1)A, {beta}=100.767(2){sup o}, V=3365.2(5)A{sup 3} at 120K. Nd atoms are seven and eight coordinate, and pairs of coordination polyhedra share edges and faces, respectively, to form Nd{sub 2}O{sub 12} and Nd{sub 2}O{sub 13} groups. All Mo atoms are in tetrahedral coordination environments, with some of the tetrahedra sharing corners to form pyromolybdate groups.